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Sökning: WFRF:(Richmond Michael)

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1.
  • Birney, Ewan, et al. (författare)
  • Identification and analysis of functional elements in 1% of the human genome by the ENCODE pilot project
  • 2007
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 447:7146, s. 799-816
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the generation and analysis of functional data from multiple, diverse experiments performed on a targeted 1% of the human genome as part of the pilot phase of the ENCODE Project. These data have been further integrated and augmented by a number of evolutionary and computational analyses. Together, our results advance the collective knowledge about human genome function in several major areas. First, our studies provide convincing evidence that the genome is pervasively transcribed, such that the majority of its bases can be found in primary transcripts, including non-protein-coding transcripts, and those that extensively overlap one another. Second, systematic examination of transcriptional regulation has yielded new understanding about transcription start sites, including their relationship to specific regulatory sequences and features of chromatin accessibility and histone modification. Third, a more sophisticated view of chromatin structure has emerged, including its inter-relationship with DNA replication and transcriptional regulation. Finally, integration of these new sources of information, in particular with respect to mammalian evolution based on inter- and intra-species sequence comparisons, has yielded new mechanistic and evolutionary insights concerning the functional landscape of the human genome. Together, these studies are defining a path for pursuit of a more comprehensive characterization of human genome function.
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2.
  • van Kuilenburg, Andre B. P., et al. (författare)
  • Glutaminase Deficiency Caused by Short Tandem Repeat Expansion in GLS
  • 2019
  • Ingår i: New England Journal of Medicine. - 0028-4793 .- 1533-4406. ; 380:15, s. 1433-1441
  • Tidskriftsartikel (refereegranskat)abstract
    • We report an inborn error of metabolism caused by an expansion of a GCA-repeat tract in the 5′ untranslated region of the gene encoding glutaminase (GLS) that was identified through detailed clinical and biochemical phenotyping, combined with whole-genome sequencing. The expansion was observed in three unrelated patients who presented with an early-onset delay in overall development, progressive ataxia, and elevated levels of glutamine. In addition to ataxia, one patient also showed cerebellar atrophy. The expansion was associated with a relative deficiency of GLS messenger RNA transcribed from the expanded allele, which probably resulted from repeat-mediated chromatin changes upstream of the GLS repeat. Our discovery underscores the importance of careful examination of regions of the genome that are typically excluded from or poorly captured by exome sequencing.
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3.
  • Zhou, Wei, et al. (författare)
  • Global Biobank Meta-analysis Initiative : Powering genetic discovery across human disease
  • 2022
  • Ingår i: Cell Genomics. - : Elsevier. - 2666-979X. ; 2:10
  • Tidskriftsartikel (refereegranskat)abstract
    • Biobanks facilitate genome-wide association studies (GWASs), which have mapped genomic loci across a range of human diseases and traits. However, most biobanks are primarily composed of individuals of European ancestry. We introduce the Global Biobank Meta-analysis Initiative (GBMI)-a collaborative network of 23 biobanks from 4 continents representing more than 2.2 million consented individuals with genetic data linked to electronic health records. GBMI meta-analyzes summary statistics from GWASs generated using harmonized genotypes and phenotypes from member biobanks for 14 exemplar diseases and endpoints. This strategy validates that GWASs conducted in diverse biobanks can be integrated despite heterogeneity in case definitions, recruitment strategies, and baseline characteristics. This collaborative effort improves GWAS power for diseases, benefits understudied diseases, and improves risk prediction while also enabling the nomination of disease genes and drug candidates by incorporating gene and protein expression data and providing insight into the underlying biology of human diseases and traits.
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4.
  • Beaumont, Robin N, et al. (författare)
  • Genome-wide association study of offspring birth weight in 86,577 women identifies five novel loci and highlights maternal genetic effects that are independent of fetal genetics.
  • 2018
  • Ingår i: Human molecular genetics. - : Oxford University Press (OUP). - 1460-2083 .- 1460-2083 .- 0964-6906. ; 27:4, s. 742-756
  • Tidskriftsartikel (refereegranskat)abstract
    • Genome-wide association studies (GWAS) of birth weight have focused on fetal genetics, while relatively little is known about the role of maternal genetic variation. We aimed to identify maternal genetic variants associated with birth weight that could highlight potentially relevant maternal determinants of fetal growth. We meta-analysed data on up to 8.7 million SNPs in up to 86,577 women of European descent from the Early Growth Genetics (EGG) Consortium and the UK Biobank. We used structural equation modelling (SEM) and analyses of mother-child pairs to quantify the separate maternal and fetal genetic effects. Maternal SNPs at 10 loci (MTNR1B, HMGA2, SH2B3, KCNAB1, L3MBTL3, GCK, EBF1, TCF7L2, ACTL9, CYP3A7) were associated with offspring birth weight at P<5x10-8. In SEM analyses, at least 7 of the 10 associations were consistent with effects of the maternal genotype acting via the intrauterine environment, rather than via effects of shared alleles with the fetus. Variants, or correlated proxies, at many of the loci had been previously associated with adult traits, including fasting glucose (MTNR1B, GCK and TCF7L2) and sex hormone levels (CYP3A7), and one (EBF1) with gestational duration. The identified associations indicate genetic effects on maternal glucose, cytochrome P450 activity and gestational duration, and potentially on maternal blood pressure and immune function, are relevant for fetal growth. Further characterization of these associations in mechanistic and causal analyses will enhance understanding of the potentially modifiable maternal determinants of fetal growth, with the goal of reducing the morbidity and mortality associated with low and high birth weights.
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5.
  • Nounu, Aayah, et al. (författare)
  • A combined proteomics and mendelian randomization approach to investigate the effects of aspirin-targeted proteins on colorectal cancer
  • 2021
  • Ingår i: Cancer Epidemiology, Biomarkers and Prevention. - : Elsevier. - 1055-9965 .- 1538-7755. ; 30:3, s. 564-575
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Evidence for aspirin’s chemopreventative properties on colorectal cancer (CRC) is substantial, but its mechanism of action is not well-understood. We combined a proteomic approach with Mendelian randomization (MR) to identify possible new aspirin targets that decrease CRC risk.Methods: Human colorectal adenoma cells (RG/C2) were treated with aspirin (24 hours) and a stable isotope labeling with amino acids in cell culture (SILAC) based proteomics approach identified altered protein expression. Protein quantitative trait loci (pQTLs) from INTERVAL (N ¼ 3,301) and expression QTLs (eQTLs) from the eQTLGen Consortium (N ¼ 31,684) were used as genetic proxies for protein and mRNA expression levels. Two-sample MR of mRNA/protein expression on CRC risk was performed using eQTL/pQTL data combined with CRC genetic summary data from the Colon Cancer Family Registry (CCFR), Colorectal Transdisciplinary (CORECT), Genetics and Epidemiology of Colorectal Cancer (GECCO) consortia and UK Biobank (55,168 cases and 65,160 controls).Results: Altered expression was detected for 125/5886 proteins. Of these, aspirin decreased MCM6, RRM2, and ARFIP2 expression, and MR analysis showed that a standard deviation increase in mRNA/protein expression was associated with increased CRC risk (OR: 1.08, 95% CI, 1.03–1.13; OR: 3.33, 95% CI, 2.46–4.50; and OR: 1.15, 95% CI, 1.02–1.29, respectively).Conclusions: MCM6 and RRM2 are involved in DNA repair whereby reduced expression may lead to increased DNA aberrations and ultimately cancer cell death, whereas ARFIP2 is involved in actin cytoskeletal regulation, indicating a possible role in aspirin’s reduction of metastasis.Impact: Our approach has shown how laboratory experiments and population-based approaches can combine to identify aspirin-targeted proteins possibly affecting CRC risk.
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6.
  • Nounu, Aayah, et al. (författare)
  • Salicylic Acid and Risk of Colorectal Cancer : A Two-Sample Mendelian Randomization Study
  • 2021
  • Ingår i: Nutrients. - : MDPI. - 2072-6643. ; 13:11
  • Tidskriftsartikel (refereegranskat)abstract
    • Salicylic acid (SA) has observationally been shown to decrease colorectal cancer (CRC) risk. Aspirin (acetylsalicylic acid, that rapidly deacetylates to SA) is an effective primary and secondary chemopreventive agent. Through a Mendelian randomization (MR) approach, we aimed to address whether levels of SA affected CRC risk, stratifying by aspirin use. A two-sample MR analysis was performed using GWAS summary statistics of SA (INTERVAL and EPIC-Norfolk, N = 14,149) and CRC (CCFR, CORECT, GECCO and UK Biobank, 55,168 cases and 65,160 controls). The DACHS study (4410 cases and 3441 controls) was used for replication and stratification of aspirin-use. SNPs proxying SA were selected via three methods: (1) functional SNPs that influence the activity of aspirin-metabolising enzymes; (2) pathway SNPs present in enzymes' coding regions; and (3) genome-wide significant SNPs. We found no association between functional SNPs and SA levels. The pathway and genome-wide SNPs showed no association between SA and CRC risk (OR: 1.03, 95% CI: 0.84-1.27 and OR: 1.08, 95% CI: 0.86-1.34, respectively). Results remained unchanged upon aspirin use stratification. We found little evidence to suggest that an SD increase in genetically predicted SA protects against CRC risk in the general population and upon stratification by aspirin use.
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7.
  • Wahl, Simone, et al. (författare)
  • Epigenome-wide association study of body mass index, and the adverse outcomes of adiposity
  • 2017
  • Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 541:7635, s. 81-
  • Tidskriftsartikel (refereegranskat)abstract
    • Approximately 1.5 billion people worldwide are overweight or affected by obesity, and are at risk of developing type (2) diabetes, cardiovascular disease and related metabolic and inflammatory disturbances(1,2). Although the mechanisms linking adiposity to associated clinical conditions are poorly understood, recent studies suggest that adiposity may influence DNA methylation(3-6), a key regulator of gene expression and molecular phenotype(7). Here we use epigenome-wide association to show that body mass index (BMI; a key measure of adiposity) is associated with widespread changes in DNA methylation (187 genetic loci with P < 1 x 10(-7), range P = 9.2 x 10(-8) to 6.0 x 10(-46); n = 10,261 samples). Genetic association analyses demonstrate that the alterations in DNA methylation are predominantly the consequence of adiposity, rather than the cause. We find that methylation loci are enriched for functional genomic features in multiple tissues (P < 0.05), and show that sentinel methylation markers identify gene expression signatures at 38 loci (P < 9.0 x 10(-6), range P = 5.5 x 10(-6) to 6.1 x 10(-35), n = 1,785 samples). The methylation loci identify genes involved in lipid and lipoprotein metabolism, substrate transport and inflammatory pathways. Finally, we show that the disturbances in DNA methylation predict future development of type 2 diabetes (relative risk per 1 standard deviation increase in methylation risk score: 2.3 (2.07-2.56); P = 1.1 x 10(-54)). Our results provide new insights into the biologic pathways influenced by adiposity, and may enable development of new strategies for prediction and prevention of type 2 diabetes and other adverse clinical consequences of obesity.
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8.
  • Young, William J., et al. (författare)
  • Genetic analyses of the electrocardiographic QT interval and its components identify additional loci and pathways
  • 2022
  • Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 13
  • Tidskriftsartikel (refereegranskat)abstract
    • The QT interval is a heritable electrocardiographic measure associated with arrhythmia risk when prolonged. Here, the authors used a series of genetic analyses to identify genetic loci, pathways, therapeutic targets, and relationships with cardiovascular disease. The QT interval is an electrocardiographic measure representing the sum of ventricular depolarization and repolarization, estimated by QRS duration and JT interval, respectively. QT interval abnormalities are associated with potentially fatal ventricular arrhythmia. Using genome-wide multi-ancestry analyses (>250,000 individuals) we identify 177, 156 and 121 independent loci for QT, JT and QRS, respectively, including a male-specific X-chromosome locus. Using gene-based rare-variant methods, we identify associations with Mendelian disease genes. Enrichments are observed in established pathways for QT and JT, and previously unreported genes indicated in insulin-receptor signalling and cardiac energy metabolism. In contrast for QRS, connective tissue components and processes for cell growth and extracellular matrix interactions are significantly enriched. We demonstrate polygenic risk score associations with atrial fibrillation, conduction disease and sudden cardiac death. Prioritization of druggable genes highlight potential therapeutic targets for arrhythmia. Together, these results substantially advance our understanding of the genetic architecture of ventricular depolarization and repolarization.
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9.
  • Niemi, MEK, et al. (författare)
  • 2021
  • swepub:Mat__t
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10.
  • Abdel-Magied, Ahmed, et al. (författare)
  • Diastereomeric control of enantioselectivity: evidence for metal cluster catalysis.
  • 2014
  • Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X. ; 50:57, s. 7705-7708
  • Tidskriftsartikel (refereegranskat)abstract
    • Enantioselective hydrogenation of tiglic acid effected by diastereomers of the general formula [(μ-H)2Ru3(μ3-S)(CO)7(μ-P-P*)] (P-P* = chiral Walphos diphosphine ligand) strongly supports catalysis by intact Ru3 clusters. A catalytic mechanism involving Ru3 clusters has been established by DFT calculations.
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11.
  • Abdel-Magied, Ahmed F., et al. (författare)
  • Asymmetric hydrogenation of an α-unsaturated carboxylic acid catalyzed by intact chiral transition metal carbonyl clusters-diastereomeric control of enantioselectivity
  • 2020
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:14, s. 4244-4256
  • Tidskriftsartikel (refereegranskat)abstract
    • Twenty clusters of the general formula [(μ-H)2Ru3(μ3-S)(CO)7(μ-P-P∗)] (P-P∗ = chiral diphosphine of the ferrocene-based Walphos or Josiphos families) have been synthesised and characterised. The clusters have been tested as catalysts for asymmetric hydrogenation of tiglic acid [trans-2-methyl-2-butenoic acid]. The observed enantioselectivities and conversion rates strongly support catalysis by intact Ru3 clusters. A catalytic mechanism involving an active Ru3 catalyst generated by CO loss from [(μ-H)2Ru3(μ3-S)(CO)7(μ-P-P∗)] has been investigated by DFT calculations.
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12.
  • Campbell, Heather, et al. (författare)
  • COSMOLOGY WITH PHOTOMETRICALLY CLASSIFIED TYPE Ia SUPERNOVAE FROM THE SDSS-II SUPERNOVA SURVEY
  • 2013
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 763:2, s. 88-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the cosmological analysis of 752 photometrically classified Type Ia Supernovae (SNe Ia) obtained from the full Sloan Digital Sky Survey II (SDSS-II) Supernova (SN) Survey, supplemented with host-galaxy spectroscopy from the SDSS-III Baryon Oscillation Spectroscopic Survey. Our photometric-classification method is based on the SN classification technique of Sako et al., aided by host-galaxy redshifts (0.05 < z < 0.55). SuperNova ANAlysis simulations of our methodology estimate that we have an SN Ia classification efficiency of 70.8%, with only 3.9% contamination from core-collapse (non-Ia) SNe. We demonstrate that this level of contamination has no effect on our cosmological constraints. We quantify and correct for our selection effects (e. g., Malmquist bias) using simulations. When fitting to a flat.CDM cosmological model, we find that our photometric sample alone gives Omega(m) = 0.24(-0.05)(+0.07) (statistical errors only). If we relax the constraint on flatness, then our sample provides competitive joint statistical constraints on Omega(m) and Omega(Lambda), comparable to those derived from the spectroscopically confirmed Three-year Supernova Legacy Survey (SNLS3). Using only our data, the statistics-only result favors an accelerating universe at 99.96% confidence. Assuming a constant wCDM cosmological model, and combining with H-0, cosmic microwave background, and luminous red galaxy data, we obtain w = -0.96(-0.10)(+0.10), Omega(m) = 0.29(-0.02)(+0.02), and Omega(k) = 0.00(-0.02)(+0.03)(statistical errors only), which is competitive with similar spectroscopically confirmed SNe Ia analyses. Overall this comparison is reassuring, considering the lower redshift leverage of the SDSS-II SN sample (z < 0.55) and the lack of spectroscopic confirmation used herein. These results demonstrate the potential of photometrically classified SN Ia samples in improving cosmological constraints.
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13.
  • Contreras, Milena, et al. (författare)
  • Internet-delivered guided self-help Acceptance and Commitment Therapy for family carers of people with dementia (iACT4CARERS) : a qualitative study of carer views and acceptability
  • 2022
  • Ingår i: International Journal of Qualitative Studies on Health and Well-being. - : Taylor & Francis Group. - 1748-2623 .- 1748-2631. ; 17:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: To explore carers' views and acceptability of internet-delivered, therapist-guided, self-help Acceptance and Commitment Therapy (ACT) for family carers of people with dementia (iACT4CARERS).Methods: A qualitative approach with semi-structured interviews was employed with family carers (N = 23) taking part in a feasibility study of iACT4CARERS. The interviews were audio-recorded, transcribed and analysed using thematic analysis.Results: Four overarching themes were identified: 1) usefulness and relevance of the content of the sessions, 2) sense of connectedness, 3) the impact of the intervention on participants and 4) acceptability of the online delivery. Positive carer experiences and intervention acceptability were facilitated by learning helpful ACT skills, perceiving the content of the session as relatable to the carers' needs, feeling connected to other carers and the therapist during the intervention, noticing the benefits of the intervention and the user-friendliness of the online platform. Recommendations for a full-scale trial were identified, such as the inclusion of some "face-to-face" interactions (e.g., via video call) between carers and therapists to facilitate a bidirectional interaction and the provision of an additional aide-memoire to improve the learning experiences.Conclusion: Overall, the intervention was acceptable to the family carers. The proposed recommendations should be considered in a full-scale trial.
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14.
  • Contreras, Milena, et al. (författare)
  • Therapists' perceptions and acceptability of providing internet-delivered guided self-help acceptance and commitment therapy (ACT) for family carers of people with dementia (iACT4CARERS) : a qualitative study
  • 2021
  • Ingår i: The Cognitive Behaviour Therapist. - : Cambridge University Press. - 1754-470X. ; 14
  • Tidskriftsartikel (refereegranskat)abstract
    • This study aimed to explore therapists' perceptions and acceptability of providing internet-delivered, therapist-guided, self-help acceptance and commitment therapy (ACT) for family carers of people with dementia (iACT4CARERS). To achieve this, a qualitative approach with semi-structured interviews was employed with eight novice therapists recruited from primary and secondary care services taking part in a feasibility study of iACT4CARERS. The interviews were audio-recorded, transcribed, and analysed using thematic analysis. Four over-arching themes were identified: (1) positive attitudes towards the intervention, (2) therapists' workload, (3) therapists' confidence to perform their role, and (4) connecting with family carers in a virtual context. Theme 1 included seeing their involvement as an opportunity for personal growth and perceiving benefits to the family carers, which contributed to greater acceptability. Theme 2 reflected that while workload and the user-friendliness of the online platform were highly acceptable among the therapists, there were also time-consuming cases that increased therapists' burden. Theme 3 revealed that practical resources provided during the training, continued supervision, and opportunities to learn from other therapists, increased therapist confidence and facilitated greater acceptability. Finally, Theme 4 highlighted that improving the connection between therapists and carers was critical in a virtual context and strategies to improve the therapist-carer relationship were recommended. The implementation of iACT4CARERS was largely acceptable for the therapists involved in the trial. Ways to strengthen the therapeutic relationship in the virtual context and practical strategies to deal with common problems may enhance therapist experience and delivery in a full-scale effectiveness trial.
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15.
  • Davis, Tamara M., et al. (författare)
  • The Effect of Peculiar Velocities on Supernova Cosmology
  • 2011
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 741, s. 67-
  • Tidskriftsartikel (refereegranskat)abstract
    • We analyze the effect that peculiar velocities have on the cosmological inferences we make using luminosity distance indicators, such as Type Ia supernovae. In particular we study the corrections required to account for (1) our own motion, (2) correlations in galaxy motions, and (3) a possible local under- or overdensity. For all of these effects we present a case study showing the impact on the cosmology derived by the Sloan Digital Sky Survey-II Supernova Survey (SDSS-II SN Survey). Correcting supernova (SN) redshifts for the cosmic microwave background (CMB) dipole slightly overcorrects nearby SNe that share some of our local motion. We show that while neglecting the CMB dipole would cause a shift in the derived equation of state of Δw ~ 0.04 (at fixed Ω m ), the additional local-motion correction is currently negligible (Δw <~ 0.01). We then demonstrate a covariance-matrix approach to statistically account for correlated peculiar velocities. This down-weights nearby SNe and effectively acts as a graduated version of the usual sharp low-redshift cut. Neglecting coherent velocities in the current sample causes a systematic shift of Δw ~ 0.02. This will therefore have to be considered carefully when future surveys aim for percent-level accuracy and we recommend our statistical approach to down-weighting peculiar velocities as a more robust option than a sharp low-redshift cut.
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16.
  • Fairfield, Heather, et al. (författare)
  • Mutation discovery in mice by whole exome sequencing
  • 2011
  • Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1465-6906 .- 1474-760X. ; 12:9, s. R86-
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the development and optimization of reagents for in-solution, hybridization-based capture of the mouse exome. By validating this approach in a multiple inbred strains and in novel mutant strains, we show that whole exome sequencing is a robust approach for discovery of putative mutations, irrespective of strain background. We found strong candidate mutations for the majority of mutant exomes sequenced, including new models of orofacial clefting, urogenital dysmorphology, kyphosis and autoimmune hepatitis.
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17.
  • Ghosh, Shishir, et al. (författare)
  • Electrocatalytic proton reduction by thiolate-capped triiron clusters [Fe3(CO)9(μ3-SR)(μ-H)] (R = iPr, tBu)
  • 2018
  • Ingår i: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693. ; 480, s. 47-53
  • Tidskriftsartikel (refereegranskat)abstract
    • The redox behaviour and electrocatalytic proton reduction ability of the thiolate-capped triiron clusters [Fe3(CO)9(μ3-SR)(μ-H)] (1, R = iPr; 2, R = tBu) have been investigated. In CH2Cl2, both show a quasi-reversible reduction and an irreversible oxidation. The thiol substituent has a significant influence on their reduction potentials (E1/2 = −1.24 V for 1 and E1/2 = −1.40 V for 2 vs. Fc+/Fc) but less impact on oxidation potentials (E1/2 = 0.99 V for 1 and E1/2 = 0.93 V for 2 vs. Fc+/Fc). Reduction is quasi-reversible and DFT studies reveal that this is due to scission of an iron-iron bond. While the clusters are not protonated by CF3CO2H or HBF4·Et2O, they can catalyse proton reduction of these acids at their corresponding reduction potentials following an ECEC mechanism.
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18.
  • Ghosh, Shishir, et al. (författare)
  • Hydrogenase biomimetics with redox-active ligands : Electrocatalytic proton reduction by [Fe2(CO)4(κ2-diamine)(μ-edt)] (diamine = 2,2′-bipy, 1,10-phen)
  • 2016
  • Ingår i: Polyhedron. - : Elsevier BV. - 0277-5387. ; 116, s. 127-135
  • Tidskriftsartikel (refereegranskat)abstract
    • Diiron complexes bearing redox active diamine ligands have been studied as models of the active site of [FeFe]-hydrogenases. Heating [Fe2(CO)6(μ-edt)] (edt = 1,2-ethanedithiolate) with 2,2′-bipyridine (2,2′-bipy) or 1,10-phenanthroline (1,10-phen) in MeCN in the presence of Me3NO leads to the formation of [Fe2(CO)4(κ2-2,2′-bipy)(μ-edt)] (1-edt) and [Fe2(CO)4(κ2-1,10-phen)(μ-edt)] (2-edt), respectively, in moderate yields. In the solid state the diamine resides in dibasal sites, while both dibasal and apical–basal isomers are present in solution. Both stereoisomers protonate readily upon addition of strong acids. Cyclic voltammetry in MeCN shows that both complexes undergo irreversible oxidation and reduction, proposed to be a one- and two-electron process, respectively. The structures of neutral 2-edt and its corresponding one- and two-electron reduced species have been investigated by DFT calculations. In 2-edt−the added electron occupies a predominantly ligand-based orbital, and the iron–iron bond is maintained, being only slightly elongated. Addition of the second electron affords an open-shell triplet dianion where the second electron populates an Fe–Fe σ*antibonding orbital, resulting in effective scission of the iron–iron bond. The triplet state lies 4.2 kcal mol−1lower in energy than the closed-shell singlet dianion whose HOMO correlates nicely with the LUMO of the neutral species 2-edt. Electrocatalytic proton reduction by both complexes has been studied in MeCN using CF3CO2H as the proton source. These catalysis studies reveal that while at high acid concentrations the active catalytic species is [Fe2(CO)4(μ-H)(κ2-diamine)(μ-edt)]+, at low acid concentrations the two complexes follow different catalytic mechanisms being associated with differences in their relative rates of protonation.
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19.
  • Hossain, Kamal, et al. (författare)
  • Oxygen atom transfer catalysis by dioxidomolybdenum(VI) complexes of pyridyl aminophenolate ligands
  • 2021
  • Ingår i: Polyhedron. - : Elsevier BV. - 0277-5387. ; 205
  • Tidskriftsartikel (refereegranskat)abstract
    • A series of new cationic dioxidomolybdenum(VI) complexes [MoO2(Ln)]PF6 (2–5) with the tripodal tetradentate pyridyl aminophenolate ligands HL2-HL5 have been synthesized and characterized. Ligands HL2-HL4 carry substituents in the 4-position of the phenolate ring, viz. Cl, Br and NO2, respectively, whereas the ligand HL5, N-(2-hydroxy-3,5-di-tert-butylbenzyl)-N,N-bis(2-pyridylmethyl)amine, is a derivative of 3,5-di-tert-butylsalicylaldehyde. X-ray crystal structures of complexes 2, 3 and 5 reveal that they have a distorted octahedral geometry with the bonding parameters around the metal centres being practically similar. Stoichiometric oxygen atom transfer (OAT) properties of 5 with PPh3 were investigated using UV–Vis, 31P NMR and mass spectrometry. In CH2Cl2 solution, a dimeric Mo(V) complex [(µ-O){MoO(L5)}2](PF6)2 6 was formed while in methanol solution an air-sensitive Mo(IV) complex [MoO(OCH3)(L5)] 7 was obtained. The solid-state structure of the µ-oxo bridged dimer 6 was determined by X-ray diffraction. Complex 7 is unstable under ambient conditions and capable of reducing DMSO, thus showing reactivity analogous to that of DMSO reductases. Similarly, the OAT reactions of complexes 2–4 also resulted in the formation of dimeric Mo(V) and unsaturated monomeric Mo(IV) complexes that are analogous to complexes 6 and 7. Catalytic OAT at 25 °C could also be observed, using complexes 1–5 as catalysts for oxidation of PPh3 in deuterated dimethylsulfoxide (DMSO‑d6), which functioned both as a solvent and oxidant. All complexes were also tested as catalysts for sulfoxidation of methyl-p-tolylsulfide and epoxidation of various alkene substrates with tert-butyl hydroperoxide (TBHP) as an oxidant. Complex 1 did not exhibit any sulfoxidation activity under the conditions used, while 2–5 catalyzed the sulfoxidation of methyl-p-tolylsulfide. Only complexes 2 and 3, with ligands containing halide substituents, exhibited good to moderate activity for epoxidation of all alkene substrates studied, and, in general, good activity for all molybdenum(VI) catalysts was only exhibited when cis-cyclooctene was used as a substrate. No complex catalysed epoxidation of cis-cyclooctene when an aqueous solution of H2O2 was used as potential oxidant.
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20.
  • Hossain, Kamal, et al. (författare)
  • Syntheses and catalytic oxotransfer actiVIties of oxo molybdenum(VI) complexes of a new aminoalcohol phenolate ligand
  • 2017
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 46:21, s. 7051-7060
  • Tidskriftsartikel (refereegranskat)abstract
    • The new aminoalcohol phenol 2,4-di-tert-butyl-6-(((2-hydroxy-2-phenylethyl)amino)methyl)phenol (H2L) was prepared by a facile solvent-free synthesis and used as a tridentate ligand for new cis-dioxomolybdenum(vi)(L) complexes. In the presence of a coordinating solvent (DMSO, MeOH, pyridine), the complexes crystallise as monomeric solvent adducts while in the absence of such molecules, a trimer with asymmetric MoO→Mo bridges crystallises. The complexes can catalyse epoxidation of cis-cyclooctene and sulfoxidation of methyl-p-tolylsulfide, using tert-butyl hydroperoxide as oxidant.
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21.
  • Hossain, Kamal, et al. (författare)
  • Synthesis of [Ru-3(CO)(9)(mu-dppf){P(C4H3E)(3)}] (E = O, S) and thermally induced cyclometalation to form [(mu-H)Ru-3(CO)(7)(mu-dppf){mu(3)-( C4H3E)(2)P(C4H2E)}] (dppf=1,1 '-bis(diphenylphosphino) ferrocene)
  • 2014
  • Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 760, s. 231-239
  • Tidskriftsartikel (refereegranskat)abstract
    • The new clusters [Ru-3(CO)(9)(mu-dppf){P(C4H3E)(3)}] (1, E = O; 2, E = S) have been prepared from the Me3NO-induced decarbonylation of [Ru-3(CO)(10)(mu-dppf)] in the presence of PFu(3) (E = O) and PTh3 (E = S), respectively. Upon thermolysis in benzene, the major products are the cyclometalated clusters [(mu-H) Ru-3(CO)(7)(mu-dppf){mu(3)-(C4H3E)(2)P(C4H2E)}] (3, E - O; 4, E - S). This thermolytic behavior is in marked contrast to that previously noted for the analogous bis(diphenylphosphino) methane (dppm) complexes [Ru-3(CO)(9)(mu-dppm){P(C4H3E)(3)}], in which both carbon-hydrogen and carbon-phosphorus bond activation yields furyne- and thiophyne-capped clusters. The crystal structures of 1, 3 and 4 are presented and reveal that phosphine migration has occurred during the transformation of 1,2 into 3,4, respectively. The possible relation of the observed reactivity to the relative flexibilities of the diphosphine ligands is discussed. Density functional calculations have been performed on the model cluster [Ru-3(CO)(9)(mu-Me-4-dppf){ P(C4H3O)(3)]}], and these data are discussed relative to the ground-state energy differences extant between the different isomeric forms of this cluster. The dynamic NMR behavior displayed by the metalated thienyl ring in cluster 4 has also been investigated by computational methods, and the free energy of activation for the "windshield wiper" motion of the activated thienyl moiety determined. (C) 2013 Elsevier B.V. All rights reserved.
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22.
  • Hossain, Md Kamal, et al. (författare)
  • Cis- and trans molybdenum oxo complexes of a prochiral tetradentate aminophenolate ligand : Synthesis, characterization and oxotransfer activity
  • 2020
  • Ingår i: Polyhedron. - : Elsevier BV. - 0277-5387. ; 178
  • Tidskriftsartikel (refereegranskat)abstract
    • Reaction of [MoO2Cl2(dmso)2] with the tetradentate O2N2 donor ligand papy [H2papy = N-(2-hydroxybenzyl)-N-(2-picolyl)glycine] leads to formation of the dioxomolybdenum(VI) complex [MoO2(papy)] (1) as a mixture of cis and trans isomers. Recrystallization from methanol furnishes solid cis-1, whereas the use of a dichloromethane-hexane mixture allows for the isolation of the trans-1 isomer. Both isomers have been structurally characterized by X-ray crystallography and the energy difference between the isomeric pair has been investigated by electronic structure calculations. Optimization of two configurational isomers in the gas phase predicts the trans isomer to lie 2.5 kcal/mol lower in energy (ΔG) than the cis isomer, which is inconsistent with the solution NMR data in d3-MeCN that exhibit a Keq of ca. 3 at 298 K for the trans ⇌ cis equilibrium. The DFT-computed energy difference is significantly improved (Keq = 5.4) by the inclusion of the MeCN solvent using the polarization continuum model (PCM). Density functional calculations reveal that the isomerization proceeds via a Ray-Dutt twist mechanism with a barrier of 14.5 kcal/mol, which is in accordance with the 1H NMR spectral data and the rapid equilibration of these isomers in solution. The catalytic reactivity of [MoO2(papy)] in the epoxidation of cis-cyclooctene is described, as well as its ability to effect oxo transfer from DMSO to PPh3.
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23.
  • Hossain, Md Kamal, et al. (författare)
  • Oxidovanadium(V) complexes with tridentate hydrazone ligands as oxygen atom transfer catalysts
  • 2024
  • Ingår i: Polyhedron. - 0277-5387. ; 258
  • Tidskriftsartikel (refereegranskat)abstract
    • Four isostructural oxovanadium(V) complexes with hydrazone ligands have been synthesised, characterised, and evaluated as epoxidation and sulfoxidation catalysts. The reactions between [VO(acac)2] (acac– = acetylacetonate) and H2Ln (n = 1–4), precursors for monoanionic tridentate hydrazone ligands, afford complexes formulated as [VO(Ln)(bzh)·MeOH] (1–4) when bidentate benzohydroxamic acid (Hbzh) is included as a co-ligand. Single crystal X-ray structure analyses showed that complexes 1–3 have a distorted octahedral coordination geometry with an O5N coordination environment. Cyclic voltammetry showed that all complexes undergo two quasi-irreversible reduction peaks and a single irreversible oxidation peak. The bonding in 1 has been investigated by electronic structure calculations, and these data are discussed with respect to the electrochemical results. Complexes 1–4 were tested as catalysts for the epoxidation of cis-cyclooctene at 50 °C and sulfoxidation of methyl-p-tolylsulfide at room temperature using tert-butyl hydroperoxide (tBuOOH) and aqueous H2O2 as the terminal oxidants.
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24.
  • Hrovat, David A., et al. (författare)
  • DFT Investigation of the Mechanism of Phosphine-Thioether Isomerization in the Triosmium Cluster Os-3(CO)(10)(Ph2PCH2CH2SMe): Migratory Preference for the Formation of an Edge-Bridged Thioether versus a Phosphine Moiety
  • 2012
  • Ingår i: Organometallics. - : American Chemical Society (ACS). - 1520-6041 .- 0276-7333. ; 31:18, s. 6608-6613
  • Tidskriftsartikel (refereegranskat)abstract
    • The rearrangement of the phosphine-thioether ligand in 1,2-(P-eq,S-eq)-Os-3(CO)(10)(Ph2PCH2CH2SMe) to 1,1-(P-eq,S-ax)-Os-3(CO)(10)(Ph2PCH2CH2SMe) was investigated by electronic structure calculations. The chelated isomer lies 2.5 kcal/mol lower in energy than its bridged counterpart, and the barrier computed for the mechanism is in agreement with the results from our earlier experimental study. Phosphine-thioether isomerization occurs via three distinct steps that involve the migration of the CO and SMe groups in a plane that is perpendicular to the trimetallic core. One of the intermediates on the reaction surface corresponds to the 50e cluster Os-3(CO)(9)(mu-CO)(mu-Ph2PCH2CH2SMe), whose edge-bridging thioether moiety functions as a 4e donor ligand. Alternative mechanisms involving ligand dissociation/association and merry-go-round sequences are energetically prohibitive.
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25.
  • Kessler, Richard, et al. (författare)
  • First-Year Sloan Digital Sky Survey-II Supernova Results : Hubble Diagram and Cosmological Parameters
  • 2009
  • Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 185:1, s. 32-84
  • Tidskriftsartikel (refereegranskat)abstract
    • We present measurements of the Hubble diagram for 103 Type Ia supernovae (SNe) with redshifts 0.04 < z < 0.42, discovered during the first season (Fall 2005) of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. These data fill in the redshift "desert" between low- and high-redshift SN Ia surveys. Within the framework of the MLCS2K2 light-curve fitting method, we use the SDSS-II SN sample to infer the mean reddening parameter for host galaxies, RV = 2.18 ± 0.14stat ± 0.48syst, and find that the intrinsic distribution of host-galaxy extinction is well fitted by an exponential function, P(AV ) = exp(-AV /τV), with τV = 0.334 ± 0.088 mag. We combine the SDSS-II measurements with new distance estimates for published SN data from the ESSENCE survey, the Supernova Legacy Survey (SNLS), the Hubble Space Telescope (HST), and a compilation of Nearby SN Ia measurements. A new feature in our analysis is the use of detailed Monte Carlo simulations of all surveys to account for selection biases, including those from spectroscopic targeting. Combining the SN Hubble diagram with measurements of baryon acoustic oscillations from the SDSS Luminous Red Galaxy sample and with cosmic microwave background temperature anisotropy measurements from the Wilkinson Microwave Anisotropy Probe, we estimate the cosmological parameters w and ΩM, assuming a spatially flat cosmological model (FwCDM) with constant dark energy equation of state parameter, w. We also consider constraints upon ΩM and ΩΛ for a cosmological constant model (ΛCDM) with w = -1 and non-zero spatial curvature. For the FwCDM model and the combined sample of 288 SNe Ia, we find w = -0.76 ± 0.07(stat) ± 0.11(syst), ΩM = 0.307 ± 0.019(stat) ± 0.023(syst) using MLCS2K2 and w = -0.96 ± 0.06(stat) ± 0.12(syst), ΩM = 0.265 ± 0.016(stat) ± 0.025(syst) using the SALT-II fitter. We trace the discrepancy between these results to a difference in the rest-frame UV model combined with a different luminosity correction from color variations; these differences mostly affect the distance estimates for the SNLS and HST SNe. We present detailed discussions of systematic errors for both light-curve methods and find that they both show data-model discrepancies in rest-frame U band. For the SALT-II approach, we also see strong evidence for redshift-dependence of the color-luminosity parameter (β). Restricting the analysis to the 136 SNe Ia in the Nearby+SDSS-II samples, we find much better agreement between the two analysis methods but with larger uncertainties: w = -0.92 ± 0.13(stat)+0.10 -0.33(syst) for MLCS2K2 and w = -0.92 ± 0.11(stat)+0.07 -0.15 (syst) for SALT-II.
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26.
  • Kishita, Naoko, et al. (författare)
  • Internet-delivered guided self-help acceptance and commitment therapy for family carers of people with dementia (iACT4CARERS) : a feasibility study
  • 2022
  • Ingår i: Aging & Mental Health. - : Taylor & Francis. - 1360-7863 .- 1364-6915. ; 26:10, s. 1933-1941
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: The feasibility of research into internet-delivered guided self-help Acceptance and Commitment Therapy (ACT) for family carers of people with dementia is not known. This study assessed this in an uncontrolled feasibility study.Method: Family carers of people with dementia with mild to moderate anxiety or depression were recruited from primary and secondary healthcare services in the UK. Participants were offered eight, guided, self-help online ACT sessions adapted for the needs of family carers of people with dementia with optional online peer support groups. Pre-defined primary indicators of success included recruitment of 30 eligible carers over 6 months and ≥70% completing at least two online sessions.Results: Thirty-three participants (110% of the target sample) were recruited over 6 months and 30 participants (91%) completed two or more sessions, and thus both indicators of success were met. Further, 70% of participants completed seven or all eight sessions, and 27% of participants were lost to follow-up, but none of the reasons for early withdrawal were related to the intervention.Conclusion: This study supports the feasibility, including recruitment and treatment completion. A full-scale trial to assess the clinical- and cost-effectiveness of the intervention including its long-term effects is warranted.
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27.
  • Li, Chuanshuai, et al. (författare)
  • Electron Transfer Mediated by Iron Carbonyl Clusters Enhance Light-Driven Hydrogen Evolution in Water by Quantum Dots
  • 2020
  • Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 13:12, s. 3252-3260
  • Tidskriftsartikel (refereegranskat)abstract
    • Photocatalytic water splitting has become a promising strategy for converting solar energy into clean and carbon-neutral solar fuels in a low-cost and environmentally benign way. Hydrogen gas is such a potential solar fuel/energy carrier. In a classical artificial photosynthetic system, a photosensitizer is generally associated with a co-catalyst to convert photogenerated charge into (a) chemical bond(s). In the present study, assemblies consisting of CdSe quantum dots that are coupled with one of two molecular complexes/catalysts, that is, [Fe2S2(CO)6] or [Fe3Te2(CO)9], using an interface-directed approach, have been tested as catalytic systems for hydrogen production in aqueous solution/organic solution. In the presence of ascorbic acid as a sacrificial electron donor and proton source, these assemblies exhibit enhanced activities for the rate of hydrogen production under visible light irradiation for 8 h in aqueous solution at pH 4.0 with up to 110 μmol of H2 per mg of assembly, almost 8.5 times that of pure CdSe quantum dots under the same conditions. Transient absorption and time-resolved photoluminescence spectroscopies have been used to investigate the charge carrier transfer dynamics in the quantum dot/iron carbonyl cluster assemblies. The spectroscopic results indicate that effective electron transfer from the molecular iron complex to the valence band of the excited CdSe quantum dots significantly inhibits the recombination of photogenerated charge carriers, boosting the photocatalytic activity for hydrogen generation; that is, the iron clusters function as effective intermediaries for electron transfer from the sacrificial electron donor to the valence band of the quantum dots.
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28.
  • Mansoor, Rashid, et al. (författare)
  • Haematological consequences of acute uncomplicated falciparum malaria : a WorldWide Antimalarial Resistance Network pooled analysis of individual patient data
  • 2022
  • Ingår i: BMC Medicine. - : Springer Nature. - 1741-7015. ; 20:1
  • Tidskriftsartikel (refereegranskat)abstract
    • BackgroundPlasmodium falciparum malaria is associated with anaemia-related morbidity, attributable to host, parasite and drug factors. We quantified the haematological response following treatment of uncomplicated P. falciparum malaria to identify the factors associated with malarial anaemia.MethodsIndividual patient data from eligible antimalarial efficacy studies of uncomplicated P. falciparum malaria, available through the WorldWide Antimalarial Resistance Network data repository prior to August 2015, were pooled using standardised methodology. The haematological response over time was quantified using a multivariable linear mixed effects model with nonlinear terms for time, and the model was then used to estimate the mean haemoglobin at day of nadir and day 7. Multivariable logistic regression quantified risk factors for moderately severe anaemia (haemoglobin < 7 g/dL) at day 0, day 3 and day 7 as well as a fractional fall >= 25% at day 3 and day 7.ResultsA total of 70,226 patients, recruited into 200 studies between 1991 and 2013, were included in the analysis: 50,859 (72.4%) enrolled in Africa, 18,451 (26.3%) in Asia and 916 (1.3%) in South America. The median haemoglobin concentration at presentation was 9.9 g/dL (range 5.0-19.7 g/dL) in Africa, 11.6 g/dL (range 5.0-20.0 g/dL) in Asia and 12.3 g/dL (range 6.9-17.9 g/dL) in South America. Moderately severe anaemia (Hb < 7g/dl) was present in 8.4% (4284/50,859) of patients from Africa, 3.3% (606/18,451) from Asia and 0.1% (1/916) from South America. The nadir haemoglobin occurred on day 2 post treatment with a mean fall from baseline of 0.57 g/dL in Africa and 1.13 g/dL in Asia. Independent risk factors for moderately severe anaemia on day 7, in both Africa and Asia, included moderately severe anaemia at baseline (adjusted odds ratio (AOR) = 16.10 and AOR = 23.00, respectively), young age (age < 1 compared to >= 12 years AOR = 12.81 and AOR = 6.79, respectively), high parasitaemia (AOR = 1.78 and AOR = 1.58, respectively) and delayed parasite clearance (AOR = 2.44 and AOR = 2.59, respectively). In Asia, patients treated with an artemisinin-based regimen were at significantly greater risk of moderately severe anaemia on day 7 compared to those treated with a non-artemisinin-based regimen (AOR = 2.06 [95%CI 1.39-3.05], p < 0.001).ConclusionsIn patients with uncomplicated P. falciparum malaria, the nadir haemoglobin occurs 2 days after starting treatment. Although artemisinin-based treatments increase the rate of parasite clearance, in Asia they are associated with a greater risk of anaemia during recovery.
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29.
  • Mitra, Mainak, et al. (författare)
  • An investigation of steric influence on the reactivity of FeV(O)(OH) tautomers in stereospecific C-H hydroxylation
  • 2023
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 52:12, s. 3596-3609
  • Tidskriftsartikel (refereegranskat)abstract
    • Two new tetradentate N4 ligands (LN4), LN4 = Me2,Me2PyzTACN (1-(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)-4,7-dimethyl-1,4,7-triazacyclononane) and Me2,MeImTACN (1-((1-methyl-1H-imidazol-1-yl)methyl)-4,7-dimethyl-1,4,7-triazacyclononane) have been synthesized and their corresponding Fe(ii) complexes [FeII(Me2,Me2PyzTACN)(CF3SO3)2], 1Pz, and [FeII(Me2,MeImTACN)(CF3SO3)2], 1Im, have been prepared and characterized. Complexes 1Pz and 1Im catalyse the hydroxylation of C-H bonds of alkanes with excellent efficiencies, using hydrogen peroxide as oxidant. The high H/D kinetic isotope effect values for C-H hydroxylation, large normalized tertiary/secondary C-H (C3/C2) bond selectivities in adamantane oxidation, and high degrees of stereoretention in the oxidation of cis-1,2-dimethylcyclohexane are indicative of metal-based oxidation processes. The complexes also catalyse the oxidation of cyclooctene to form its corresponding epoxide and syn-diol. For 1Pz the epoxide is the main product, while for the analogous complex 1Im the syn-diol predominates. The active oxidant is proposed to be an [(LN4)FeV(O)(OH)]2+ species (2Pz, LN4 = Me2,Me2PyzTACN and 2Im, LN4 = Me2,MeImTACN) which may exist in two tautomeric forms related by a proton shift between the oxo and hydroxo ligands. Isotope labelling experiments show that the oxygen atom in the hydroxylated products originates from both water and hydrogen peroxide, and labelling experiments involving oxygen atom transfer to sterically bulky substrates provide indirect information on the steric influence exerted by the two ligands in the relative reactivities of the two hypervalent iron tautomers. Based on these labelling studies, the steric influence exerted by each of the ligands towards the relative reactivity of the oxo ligands of the corresponding pair of Fe(v)(O)(OH) tautomers can be derived. Furthermore, this steric influence can be gauged relative to related complexes/ligands.
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30.
  • Mitra, Mainak, et al. (författare)
  • Catalytic C-H oxidations by nonheme mononuclear Fe(II) complexes of two pentadentate ligands: Evidence for an Fe(IV) oxo intermediate
  • 2017
  • Ingår i: Journal of Molecular Catalysis A: Chemical. - : Elsevier BV. - 1381-1169. ; 426, s. 350-356
  • Tidskriftsartikel (refereegranskat)abstract
    • The oxidation reactions of alkanes with hydrogen peroxide and peracids (peracetic acid (PAA) and m-chloroperoxybenzoic acid (mCPBA)) catalysed by two Fe(II) complexes of pentadentate {N5}-donor ligands have been investigated. Kinetic isotope effect experiments and the use of other mechanistic probes have also been performed. While the total yields of oxidized products are similar regardless of oxidant (e.g. 30–39% for oxidation of cyclohexane), the observed alcohol/ketone ratios and kinetic isotope effects differ significantly with different oxidants. Catalytic reactions in H2O2 medium are consistent with the involvement of hydroxyl radicals in the Csingle bondH bond cleavage step, and resultant low kinetic isotope effect values. On the other hand, catalytic reactions performed using peracid media indicate the involvement of an oxidant different from the hydroxyl radical. For these reactions, the kinetic isotope effect values are relatively high (within a range of 4.2–5.1) and the C3/C2 selectivity parameters in adamantane oxidation are greater than 11, thereby excluding the presence of hydroxyl radicals in the Csingle bondH bond cleavage step. A low spin Fe(III)-OOH species has been detected in the H2O2-based catalytic system by UV/Vis, mass spectrometry and EPR spectroscopy, while an Fe(IV)-oxo species is postulated to be the active oxidant in the peracid-based catalytic systems. Computational studies on the Csingle bondH oxidation mechanism reveal that while the hydroxyl radical is mainly responsible for the H-atom abstraction in the H2O2-based catalytic system, it is the Fe(IV)-oxo species that abstracts the H-atom from the substrate in the peracid-based catalytic systems, in agreement with the experimental observations.
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31.
  • Mitra, Mainak, et al. (författare)
  • Nonheme Fe(IV) Oxo Complexes of Two New Pentadentate Ligands and Their Hydrogen-Atom and Oxygen-Atom Transfer Reactions
  • 2015
  • Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 54:15, s. 7152-7164
  • Tidskriftsartikel (refereegranskat)abstract
    • Two new pentadentate {N5} donor ligands based on the N4Py (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) framework have been synthesized, viz. [N-(1-methyl-2-benzimidazolyl)methyl-N-(2-pyridyl)methyl-N-(bis-2-pyridyl methyl)amine] (L1) and [N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2-pyridylmethyl)amine] (L2), where one or two pyridyl arms of N4Py have been replaced by corresponding (N-methyl)benzimidazolyl-containing arms. The complexes [FeII(CH3CN)(L)]2+ (L = L1 (1); L2 (2)) were synthesized, and reaction of these ferrous complexes with iodosylbenzene led to the formation of the ferryl complexes [FeIV(O)(L)]2+ (L = L1 (3); L2 (4)), which were characterized by UV–vis spectroscopy, high resolution mass spectrometry, and Mössbauer spectroscopy. Complexes 3 and 4 are relatively stable with half-lives at room temperature of 40 h (L = L1) and 2.5 h (L = L2). The redox potentials of 1 and 2, as well as the visible spectra of 3 and 4, indicate that the ligand field weakens as ligand pyridyl substituents are progressively substituted by (N-methyl)benzimidazolyl moieties. The reactivities of 3 and 4 in hydrogen-atom transfer (HAT) and oxygen-atom transfer (OAT) reactions show that both complexes exhibit enhanced reactivities when compared to the analogous N4Py complex ([FeIV(O)(N4Py)]2+), and that the normalized HAT rates increase by approximately 1 order of magnitude for each replacement of a pyridyl moiety; i.e., [FeIV(O)(L2)]2+ exhibits the highest rates. The second-order HAT rate constants can be directly related to the substrate C–H bond dissociation energies. Computational modeling of the HAT reactions indicates that the reaction proceeds via a high spin transition state.
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32.
  • Morokuma, Tomoki, et al. (författare)
  • Kiso Supernova Survey (KISS) : Survey strategy
  • 2014
  • Ingår i: Nippon Tenmon Gakkai obun kenkyu hokoku. - : Oxford University Press (OUP). - 0004-6264. ; 66:6
  • Tidskriftsartikel (refereegranskat)abstract
    • lThe Kiso Supernova Survey (KISS) is a high-cadence optical wide-field supernova (SN) survey. The primary goal of the survey is to catch the very early light of a SN, during the shock breakout phase. Detection of SN shock breakouts combined with multi-band photometry obtained with other facilities would provide detailed physical information on the progenitor stars of SNe. The survey is performed using a 2 degrees.2 x 2 degrees.2 field-of-view instrument on the 1.05-m Kiso Schmidt telescope, the Kiso Wide Field Camera (KWFC). We take a 3-min exposure in g-band once every hour in our survey, reaching magnitude g similar to 20-21. About 100 nights of telescope time per year have been spent on the survey since 2012 April. The number of the shock breakout detections is estimated to be of the order of 1 during our three-year project. This paper summarizes the KISS project including the KWFC observing setup, the survey strategy, the data reduction system, and CBET-reported SNe discovered so far by KISS.
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33.
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34.
  • Persson, Roger, et al. (författare)
  • Synthesis, Characterization, and Dynamic Behaviour of Triosmium Clusters Containing the Tridentate Ligand {Ph2PCH2CH2}2S (PSP)
  • 2013
  • Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1099-0682 .- 1434-1948. ; :13, s. 2447-2459
  • Tidskriftsartikel (refereegranskat)abstract
    • Reaction of [Os3(CO)11(NCMe)] with bis-diphenylphosphanylethylene sulfide, {Ph2PCH2CH2}2S (PSP), leads to the formation of [Os3(CO)11(PSP)] and [{Os3(CO)11}2(-PSP)] in good yield. Similarly, treatment of [Os3(CO)10(NCMe)2] with PSP affords the cluster [Os3(CO)10(-PSP)], in which the two phosphanes of the PSP ligand coordinate to different osmium atoms of the same triosmium unit. Reaction of [Os3(CO)11(PSP)] with [Os3(CO)10(NCMe)2] yields the compound 1,2-[{Os3(CO)11}(3-PSP){Os3(CO)10}] in which the thioether moiety and one of the phosphane groups of the PSP ligand are coordinated equatorially to the {Os3(CO)10} subunit. The cluster 1,2-[{Os3(CO)11}(3-PSP){Os3(CO)10}] is also formed when [Os3(CO)11(PSP)] is oxidatively decarbonylated by reaction with trimethylamine N-oxide. The metastable cluster 1,2-[{Os3(CO)11}(3-PSP){Os3(CO)10}] undergoes slow isomerisation at room temperature to form 1,1-[{Os3(CO)11}(3-PSP){Os3(CO)10}] in which the thioether and phosphane moieties coordinate in a chelating mode to one of the {Os3(CO)10} subunits with the thioether moiety in an axial position. The dynamic behaviour of these clusters has been investigated by variable-temperature 13C{1H} and 13P{1H} NMR spectroscopy. The solid-state structures of [{Os3(CO)11}2(-PSP)] and [Os3(CO)10(-PSP)] are reported.
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35.
  • Raha, Arun K., et al. (författare)
  • A comparative study of the reactivity of the lightly stabilized cluster [Os-3(CO)(8){mu(3)-Ph2PCH2P(Ph)C6H4}(mu-H)] towards tri(2-thienyl)-, tri(2-furyl)- and triphenyl-phosphine
  • 2014
  • Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 751, s. 399-411
  • Tidskriftsartikel (refereegranskat)abstract
    • Reactions of the lightly stabilized triosmium cluster [Os-3(CO)(8){mu(3)-Ph2PCH2P(Ph)C6H4}(mu-H)] with tri(2-thienyl)phosphine (PTh3) and tri(2-furyl)phosphine (PFu(3)) are described and compared to analogous reactions with PPh3. At room temperature, a number of products are isolated: [Os-3(CO)(10)(mu-dppm)] from CO addition, [Os-3(CO)(8)(PR3){mu(3)-Ph2PCH2P(Ph)C6H4}(mu-H)] from phosphine addition, [Os-3(CO)(9)(PR3)(mu-dppm)] from phosphine and CO addition and [Os-3(CO)(8)(PR3)(2)(mu-dppm)] from addition of two equivalents of phosphine. The latter are shown by NMR and X-ray diffraction to exist as 1,2-isomers, whereby one phosphine is bound to the non-dppm-substituted center and the second shares an osmium atom with one end of the diphosphine. Heating 1,2-[Os-3(CO)(8)(PTh3)(2)(mu-dppm)] at 100 degrees C results in its clean isomerization to the 1,1-isomer in which both monodentate phosphines are located on the same osmium atom. Prolonged heating of [Os-3(CO)(8)(PR3)(2)(mu-dppm)] (R = Th, Ph) at 110 degrees C gives [Os-3(CO)(9)(PR3)(mu-dppm)] and the new lightly stabilized clusters [Os-3(CO)(7)(PR3){mu(3)-Ph2PCH2P(Ph)C6H4}(mu-H)], the latter being formed by loss of phosphine and CO with concurrent metalation of a phenyl ring. Heating [Os-3(CO)(8)(PFu(3))(2)(mu-dppm)] at 110 degrees C gives [Os-3(CO)(9)(PFu(3))(mu-dppm)] together with the carbon-phosphorus bond cleavage products [Os-3(CO)(7)(mu-PFu(2))(mu(3)-eta(2)-C4H2O)(mu-H)(mu-dppm)] and [Os-3(CO)(7)(mu-PFu(2))(mu(3)-eta(2)-C6H3CH3)(mu-H)(mu-dppm)]. All new compounds were characterized by analytical and spectroscopic techniques together with single crystal X-ray diffraction analysis of nine clusters. Density functional theory (DFT) calculations have been carried out on isomers of [Os-3(CO)(8)(PR3)(2)(mu-dppm)] in order to understand the observed isomer ratios. (C) 2013 Elsevier B.V. All rights reserved.
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36.
  • Rahaman, Ahibur, et al. (författare)
  • Bioinspired Hydrogenase Models: The Mixed-Valence Triiron Complex [Fe3(CO)7(μ-edt)2] and Phosphine Derivatives [Fe3(CO)7-x (PPh3) x (μ-edt)2] (x = 1, 2) and [Fe3(CO)5(κ(2)-diphosphine)(μ-edt)2] as Proton Reduction Catalysts.
  • 2014
  • Ingår i: Organometallics. - : American Chemical Society (ACS). - 1520-6041 .- 0276-7333. ; 33:6, s. 1356-1366
  • Tidskriftsartikel (refereegranskat)abstract
    • The mixed-valence triiron complexes [Fe3(CO)7-x (PPh3) x (μ-edt)2] (x = 0-2; edt = SCH2CH2S) and [Fe3(CO)5(κ(2)-diphosphine)(μ-edt)2] (diphosphine = dppv, dppe, dppb, dppn) have been prepared and structurally characterized. All adopt an anti arrangement of the dithiolate bridges, and PPh3 substitution occurs at the apical positions of the outer iron atoms, while the diphosphine complexes exist only in the dibasal form in both the solid state and solution. The carbonyl on the central iron atom is semibridging, and this leads to a rotated structure between the bridged diiron center. IR studies reveal that all complexes are inert to protonation by HBF4·Et2O, but addition of acid to the pentacarbonyl complexes results in one-electron oxidation to yield the moderately stable cations [Fe3(CO)5(PPh3)2(μ-edt)2](+) and [Fe3(CO)5(κ(2)-diphosphine)(μ-edt)2](+), species which also result upon oxidation by [Cp2Fe][PF6]. The electrochemistry of the formally Fe(I)-Fe(II)-Fe(I) complexes has been investigated. Each undergoes a quasi-reversible oxidation, the potential of which is sensitive to phosphine substitution, generally occurring between 0.15 and 0.50 V, although [Fe3(CO)5(PPh3)2(μ-edt)2] is oxidized at -0.05 V. Reduction of all complexes is irreversible and is again sensitive to phosphine substitution, varying between -1.47 V for [Fe3(CO)7(μ-edt)2] and around -1.7 V for phosphine-substituted complexes. In their one-electron-reduced states, all complexes are catalysts for the reduction of protons to hydrogen, the catalytic overpotential being increased upon successive phosphine substitution. In comparison to the diiron complex [Fe2(CO)6(μ-edt)], [Fe3(CO)7(μ-edt)2] catalyzes proton reduction at 0.36 V less negative potentials. Electronic structure calculations have been carried out in order to fully elucidate the nature of the oxidation and reduction processes. In all complexes, the HOMO comprises an iron-iron bonding orbital localized between the two iron atoms not ligated by the semibridging carbonyl, while the LUMO is highly delocalized in nature and is antibonding between both pairs of iron atoms but also contains an antibonding dithiolate interaction.
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37.
  • Rahaman, Ahibur, et al. (författare)
  • Chalcogenide-capped triiron clusters [Fe3(CO)9(μ3-E)2], [Fe3(CO)7(μ3-CO)(μ3-E)(μ-dppm)] and [Fe3(CO)7(μ3-E)2(μ-dppm)] (E = S, Se) as proton-reduction catalysts
  • 2019
  • Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 880, s. 213-222
  • Tidskriftsartikel (refereegranskat)abstract
    • Chalcogenide-capped triiron clusters [Fe3(CO)7(μ3-CO)(μ3-E)(μ-dppm)] and [Fe3(CO)7(μ3-E)2(μ-dppm)] (E = S, Se) have been examined as proton-reduction catalysts. Protonation studies show that [Fe3(CO)9(μ3-E)2] are unaffected by strong acids. Mono-capped [Fe3(CO)7(μ3-CO)(μ3-E)(μ-dppm)] react with HBF4.Et2O but changes in IR spectra are attributed to BF3 binding to the face-capping carbonyl, while bicapped [Fe3(CO)7(μ3-E)2(μ-dppm)] are protonated but in a process that is not catalytically important. DFT calculations are presented to support these protonation studies. Cyclic voltammetry shows that [Fe3(CO)9(μ3-Se)2] exhibits two reduction waves, and upon addition of strong acids, proton-reduction occurs at a range of potentials. Mono-chalcogenide clusters [Fe3(CO)7(μ3-CO)(μ3-E)(μ-dppm)] (E = S, Se) exhibit proton-reduction at ca. -1.85 (E = S) and -1.62 V (E = Se) in the presence of p-toluene sulfonic acid (p-TsOH). Bicapped [Fe3(CO)7(μ3-E)2(μ-dppm)] undergo quasi-reversible reductions at -1.55 (E = S) and -1.45 V (E = Se) and reduce p-TsOH to hydrogen but protonated species do not appear to be catalytically important. Current uptake is seen at the first reduction potential in each case, showing that [Fe3(CO)7(μ3-E)2(μ-dppm)]- are catalytically active but a far greater response is seen at ca. -1.9 V being tentatively associated with reduction of [H2Fe3(CO)7(μ3-E)2(μ-dppm)]+. In general, selenide clusters are reduced at slightly lower potentials than sulfide analogues and show slightly higher current uptake under comparable conditions.
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38.
  • Rahaman, Ahibur, et al. (författare)
  • Electrocatalytic proton-reduction behaviour of telluride-capped triiron clusters : tuning of overpotentials and stabilization of redox states relative to lighter chalcogenide analogues
  • 2020
  • Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:21, s. 7133-7143
  • Tidskriftsartikel (refereegranskat)abstract
    • Reaction of [Fe3(CO)9(µ3-Te)2] (1) with the corresponding phosphine has been used to prepare the phosphine-substituted tellurium-capped triiron clusters [Fe3(CO)9(µ3-Te)2(PPh3)] (2), [Fe3(CO)8(µ3-Te)2(PPh3)] (3) and [Fe3(CO)7(µ3-Te)2(µ-R2PXPR2)] (X = CH2, R = Ph (4), Cy (5); X = NPri, R = Ph (6)). The directly related cluster [Fe3(CO)7(µ3-CO)(µ3-Te)(µ-dppm)] (7) was isolated from the reaction of [Fe3(CO)10(µ-Ph2PCH2PPh2)] with elemental tellurium. The electrochemistry of these new clusters has been probed by cyclic voltammetry, and selected complexes have been tested as proton reduction catalysts. Each 50-electron dicapped cluster exhibits two reductive processes; the first has good chemical reversibility in all cases but the reversibility of the second is dependent upon the nature of the supporting ligands. For the parent cluster1and the diphosphine derivatives4-5this second reduction is reversible, but for the PPh3complex3it is irreversible, possibly as a result of CO or phosphine loss. The nature of the reduced products of1has been probed by DFT calculations. Upon addition of one electron, an elongation of one of the Fe-Te bonding interactions is found, while the addition of the second electron affords an open-shell triplet which is more stable by 8.8 kcal mol-1than the closed-shell singlet dianion and has two elongated Fe-Te bonds. The phosphine-substituted clusters also exhibit oxidation chemistry but with poor reversibility in all cases. Since the reduction potentials for the tellurium-capped clusters occur at more positive potentials than for the sulfur and selenium analogues, and the redox processes also show better reversibility than for the S/Se analogues, the tellurium-capped clusters1and3-5have been examined as proton reduction catalysts. In the presence ofp-toluenesulfonic acid (TsOH) or trifluoroacetic acid (TFA), these clusters reduce protons to H2at both their first and second reduction potentials. Electron uptake at the second reduction potential is far greater than the first, suggesting that the open-shell triplet dianions are efficient catalysts. As expected, the catalytic overpotential increases upon successive phosphine substitution but so does the current response. A mechanistic scheme that takes the roles of the supporting ligands on the preferred route(s) to H2production and release into account is presented.
  •  
39.
  • Rahaman, Ahibur, et al. (författare)
  • Proton reduction by phosphinidene-capped triiron clusters
  • 2021
  • Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 943
  • Tidskriftsartikel (refereegranskat)abstract
    • Bis(phosphinidene)-capped triiron carbonyl clusters, including electron rich derivatives formed by substitution with chelating diphosphines, have been prepared and examined as proton reduction catalysts. Treatment of the known cluster [Fe3(CO)9(µ3-PPh)2] (1) with various diphosphines in refluxing THF (for 5, refluxing toluene) afforded the new clusters [Fe3(CO)7(µ3-PPh)2(κ2-dppb)] (2), [Fe3(CO)7(µ3-PPh)2(κ2-dppv)] (3), [Fe3(CO)7(µ3-PPh)2(κ2-dppe)] (4) and [Fe3(CO)7(µ3-PPh)2(µ-κ2-dppf)] (5) in moderate yields, together with small amounts of the corresponding [Fe3(CO)8(µ3-PPh)2(κ1-Ph2PxPPh2)] cluster (x = -C4H6-, -C2H2-, -C2H4-, -C3H6-, -C5H4FeC5H4-). The molecular structures of complexes 3 and 5 have been established by X-ray crystallography. Complexes 1–5 have been examined as proton reduction catalysts in the presence of p-toluenesulfonic acid (p-TsOH) in CH2Cl2. Cluster 1 exhibits two one-electron quasi-reversible reduction waves at –1.39 V (ΔE = 195 mV) and at –1.66 V (ΔE = 168 mV; potentials vs. Fc+/Fc). Upon addition of p-TsOH the unsubstituted cluster 1 shows a first catalytic wave at –1.57 V and two further proton reduction processes at –1.75 and –2.29 V, each with a good current response. The diphosphine-substituted derivatives of 1 are reduced at more negative potentials than the parent cluster 1. Clusters 2–4 each exhibit an oxidation at ca. +0.1 V and a reduction at ca. –1.6 V; for 4 conversion to a redox active successor species is seen upon both oxidation and reduction. Clusters 2–4 show catalytic waves in the presence of p-TsOH, with cluster 4 exhibiting the highest relative catalytic current (icat/i0 ≈ 57) in the presence of acid, albeit at a new third reduction process not observed for 2 and 3. Addition of the dppf ligand to the parent diphosphinidene cluster 1 gave cluster 5 which exhibited a single reduction process at –1.95 V and three oxidation processes, all at positive values as compared to 2–4. Cluster 5 showed only weak catalytic activity for proton reduction with p-TsOH. The bonding in 4 was investigated by DFT calculations, and the nature of the radical anion and dianion is discussed with respect to the electrochemical data.
  •  
40.
  • Rahaman, Ahibur, et al. (författare)
  • Synthesis and molecular structures of the 52-electron triiron telluride clusters [Fe3(CO)8(μ3-Te)2(κ2-diphosphine)] - Electrochemical properties and activity as proton reduction catalysts
  • 2018
  • Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 867, s. 381-390
  • Tidskriftsartikel (refereegranskat)abstract
    • Heating the 50-electron cluster [Fe3(CO)9 (μ3-Te)2] (1) with the diphosphines Ph2P-R-PPh2 [R = -CH2CH2- (dppe), Z-CH=CH- (dppv), 1,2-C6H4 (dppb), -CH2CH2CH2- (dpp), ferrocenyl (dppf), naphthalenyl (dppbn)] in benzene affords the 52-electron diphosphine-containing tellurium-capped triiron clusters [Fe3(CO)8 (μ3-Te)2 (κ2-diphosphine)] (diphosphine = dppe, dppv, dppb, dpp, dppf, dppnd) (2–7) in moderate yields, resulting from both phosphine addition and carbonyl loss. With 1,2-bis(diphenylphosphino)benzene (dppb) a second product is the cubane cluster [Fe4(CO)10(μ3-Te)4 (κ2-dppb)] (8). Cyclic voltammetry measurements on 2–7 reveal that all clusters show irreversible reductive behaviour at ca. −1.85 V with a series of associated small back oxidation waves, suggesting that reduction leads to significant structural change but that this can be reversed chemically. Oxidation occurs at relatively low potentials and is diphosphine-dependent. The first oxidation appears at ca. +0.35 V for 2–6 with a small degree of reversibility but is as low as +0.14 V for the bis(diphenylphosphino)naphthalene derivative 7 and in some cases is followed by further closely-spaced oxidation. Addition of [Cp2Fe][PF6] to 2–7 results in the formation of new clusters formulated as [Fe3(CO)8(μ3-Te)2(κ2-diphosphine)]+, with their IR spectra suggesting oxidation at the diiron centre. This is supported by computational studies (DFT) of the bis(diphenylphosphino)propane cluster 5 showing that the HOMO is the Fe–Fe σ-bonding orbital, while the LUMO is centered on the diphosphine-substituted iron atom and has significant Fe–Te σ∗-anti-bonding character consistent with the irreversible nature of the reduction. Complexes 2–7 have been examined as proton reduction catalysts in the presence of para-toluenesulfonic acid (TsOH). All are active at their first reduction potential, with a second catalytic process being observed at slightly higher potentials. While their overall electrocatalytic behaviour is similar to that noted for [Fe2(CO)6{μ-E(CH2)3E}] (E = S, Se, Te), the DFT results suggest that as the added electron is localised on the unique iron atom. The mechanistic aspects of hydrogen formation are likely to be quite different from the more widely studied diiron models.
  •  
41.
  • Richmond, Erinn K., et al. (författare)
  • A diverse suite of pharmaceuticals contaminates stream and riparian food webs
  • 2018
  • Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 9
  • Tidskriftsartikel (refereegranskat)abstract
    • A multitude of biologically active pharmaceuticals contaminate surface waters globally, yet their presence in aquatic food webs remain largely unknown. Here, we show that over 60 pharmaceutical compounds can be detected in aquatic invertebrates and riparian spiders in six streams near Melbourne, Australia. Similar concentrations in aquatic invertebrate larvae and riparian predators suggest direct trophic transfer via emerging adult insects to riparian predators that consume them. As representative vertebrate predators feeding on aquatic invertebrates, platypus and brown trout could consume some drug classes such as antidepressants at as much as one-half of a recommended therapeutic dose for humans based on their estimated prey consumption rates, yet the consequences for fish and wildlife of this chronic exposure are unknown. Overall, this work highlights the potential exposure of aquatic and riparian biota to a diverse array of pharmaceuticals, resulting in exposures to some drugs that are comparable to human dosages.
  •  
42.
  • Sako, Masao, et al. (författare)
  • The Data Release of the Sloan Digital Sky Survey-II Supernova Survey
  • 2018
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 130:988
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper describes the data release of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey conducted between 2005 and 2007. Light curves, spectra, classifications, and ancillary data are presented for 10,258 variable and transient sources discovered through repeat ugriz imaging of SDSS Stripe 82, a 300 deg(2) area along the celestial equator. This data release is comprised of all transient sources brighter than r similar or equal to 22.5 mag with no history of variability prior to 2004. Dedicated spectroscopic observations were performed on a subset of 889 transients, as well as spectra for thousands of transient host galaxies using the SDSS-III BOSS spectrographs. Photometric classifications are provided for the candidates with good multi-color light curves that were not observed spectroscopically, using host galaxy redshift information when available. From these observations, 4607 transients are either spectroscopically confirmed, or likely to be, supernovae, making this the largest sample of supernova candidates ever compiled. We present a new method for SN host-galaxy identification and derive host-galaxy properties including stellar masses, star formation rates, and the average stellar population ages from our SDSS multi-band photometry. We derive SALT2 distance moduli for a total of 1364 SN. Ia with spectroscopic redshifts as well as photometric redshifts for a further 624 purely photometric SN. Ia candidates. Using the spectroscopically confirmed subset of the three-year SDSS-II SN. Ia sample and assuming a flat.CDM cosmology, we determine Omega(M) = 0.315 +/- 0.093 (statistical error only) and detect a non-zero cosmological constant at 5.7 sigma.
  •  
43.
  •  
44.
  • Sukalo, Maja, et al. (författare)
  • Mutations in the Human UBR1 Gene and the Associated Phenotypic Spectrum
  • 2014
  • Ingår i: Human Mutation. - : Hindawi Limited. - 1059-7794 .- 1098-1004. ; 35:5, s. 521-531
  • Tidskriftsartikel (refereegranskat)abstract
    • Johanson-Blizzard syndrome (JBS) is a rare, autosomal recessive disorder characterized by exocrine pancreatic insufficiency, typical facial features, dental anomalies, hypothyroidism, sensorineural hearing loss, scalp defects, urogenital and anorectal anomalies, short stature, and cognitive impairment of variable degree. This syndrome is caused by a defect of the E3 ubiquitin ligase UBR1, which is part of the proteolytic N-end rule pathway. Herein, we review previously reported (n=29) and a total of 31 novel UBR1 mutations in relation to the associated phenotype in patients from 50 unrelated families. Mutation types include nonsense, frameshift, splice site, missense, and small in-frame deletions consistent with the hypothesis that loss of UBR1 protein function is the molecular basis of JBS. There is an association of missense mutations and small in-frame deletions with milder physical abnormalities and a normal intellectual capacity, thus suggesting that at least some of these may represent hypomorphic UBR1 alleles. The review of clinical data of a large number of molecularly confirmed JBS cases allows us to define minimal clinical criteria for the diagnosis of JBS. For all previously reported and novel UBR1 mutations together with their clinical data, a mutation database has been established at LOVD.
  •  
45.
  • Tanaka, Masaomi, et al. (författare)
  • DISCOVERY OF DRAMATIC OPTICAL VARIABILITY IN SDSS J1100+4421 : A PECULIAR RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXY?
  • 2014
  • Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 793:2, s. L26-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present our discovery of dramatic variability in SDSS J1100+4421 by the high-cadence transient survey Kiso Supernova Survey. The source brightened in the optical by at least a factor of three within about half a day. Spectroscopic observations suggest that this object is likely a narrow-line Seyfert 1 galaxy (NLS1) at z = 0.840, however, with unusually strong narrow emission lines. The estimated black hole mass of similar to 10(7) M-circle dot implies bolometric nuclear luminosity close to the Eddington limit. SDSS J1100+4421 is also extremely radio-loud, with a radio loudness parameter of R similar or equal to 4 x 10(2)-3 x 10(3), which implies the presence of relativistic jets. Rapid and large-amplitude optical variability of the target, reminiscent of that found in a few radio- and gamma-ray-loud NLS1s, is therefore produced most likely in a blazar-like core. The 1.4 GHz radio image of the source shows an extended structure with a linear size of about 100 kpc. If SDSS J1100+4421 is a genuine NLS1, as suggested here, this radio structure would then be the largest ever discovered in this type of active galaxies.
  •  
46.
  • Taylor, Matt, et al. (författare)
  • THE CORE COLLAPSE SUPERNOVA RATE FROM THE SDSS-II SUPERNOVA SURVEY
  • 2014
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 792:2, s. 135-
  • Tidskriftsartikel (refereegranskat)abstract
    • We use the Sloan Digital Sky Survey II Supernova Survey (SDSS-II SNS) data to measure the volumetric core collapse supernova (CCSN) rate in the redshift range (0.03 < z < 0.09). Using a sample of 89 CCSN, we find a volume-averaged rate of 1.06 +/- 0.19 x 10(-4)((h/0.7)(3)/(yr Mpc(3))) at a mean redshift of 0.072 +/- 0.009. We measure the CCSN luminosity function from the data and consider the implications on the star formation history.
  •  
47.
  • Tyrrell, Jessica, et al. (författare)
  • Genetic Evidence for Causal Relationships Between Maternal Obesity-Related Traits and Birth Weight.
  • 2016
  • Ingår i: JAMA. - : American Medical Association (AMA). - 1538-3598 .- 0098-7484. ; 315:11, s. 1129-40
  • Tidskriftsartikel (refereegranskat)abstract
    • Neonates born to overweight or obese women are larger and at higher risk of birth complications. Many maternal obesity-related traits are observationally associated with birth weight, but the causal nature of these associations is uncertain.To test for genetic evidence of causal associations of maternal body mass index (BMI) and related traits with birth weight.Mendelian randomization to test whether maternal BMI and obesity-related traits are potentially causally related to offspring birth weight. Data from 30,487 women in 18 studies were analyzed. Participants were of European ancestry from population- or community-based studies in Europe, North America, or Australia and were part of the Early Growth Genetics Consortium. Live, term, singleton offspring born between 1929 and 2013 were included.Genetic scores for BMI, fasting glucose level, type 2 diabetes, systolic blood pressure (SBP), triglyceride level, high-density lipoprotein cholesterol (HDL-C) level, vitamin D status, and adiponectin level.Offspring birth weight from 18 studies.Among the 30,487 newborns the mean birth weight in the various cohorts ranged from 3325 g to 3679 g. The maternal genetic score for BMI was associated with a 2-g (95% CI, 0 to 3 g) higher offspring birth weight per maternal BMI-raising allele (P=.008). The maternal genetic scores for fasting glucose and SBP were also associated with birth weight with effect sizes of 8 g (95% CI, 6 to 10 g) per glucose-raising allele (P=7×10(-14)) and -4 g (95% CI, -6 to -2 g) per SBP-raising allele (P=1×10(-5)), respectively. A 1-SD (≈4 points) genetically higher maternal BMI was associated with a 55-g higher offspring birth weight (95% CI, 17 to 93 g). A 1-SD (≈7.2 mg/dL) genetically higher maternal fasting glucose concentration was associated with 114-g higher offspring birth weight (95% CI, 80 to 147 g). However, a 1-SD (≈10 mm Hg) genetically higher maternal SBP was associated with a 208-g lower offspring birth weight (95% CI, -394 to -21 g). For BMI and fasting glucose, genetic associations were consistent with the observational associations, but for systolic blood pressure, the genetic and observational associations were in opposite directions.In this mendelian randomization study, genetically elevated maternal BMI and blood glucose levels were potentially causally associated with higher offspring birth weight, whereas genetically elevated maternal SBP was potentially causally related to lower birth weight. If replicated, these findings may have implications for counseling and managing pregnancies to avoid adverse weight-related birth outcomes.
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48.
  • Uddin, Md Miaz, et al. (författare)
  • Thermal transformations of tris(2-thienyl)phosphine (PTh3) at low-valent ruthenium cluster centers : Part I. Carbon-hydrogen, carbon-phosphorus and carbon-sulfur bond activation yielding Ru3(CO)8L{μ-Th2P(C4H2S)}(μ-H) (L = CO, PTh3), Ru3(CO)7(μ-PTh2)2(μ3-η2-C4H2S), Ru4(CO)9(μ-CO)2(μ4-η2-C4H2S)(μ4-PTh) and Ru5(CO)11(μ-PTh2)(μ4-η4-C4H3)(μ4-S)
  • 2016
  • Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 812, s. 197-206
  • Tidskriftsartikel (refereegranskat)abstract
    • Reaction of Ru3(CO)12 with tris(2-thienyl)phosphine (PTh3) in CH2Cl2 at room temperature or in THF in the presence of a catalytic amount of Na[Ph2CO] furnishes the carbonyl substitution products Ru3(CO)11(PTh3) (1), Ru3(CO)10(PTh3)2 (2), and Ru3(CO)9(PTh3)3 (3). Heating 1 in toluene affords the cyclometalated cluster Ru3(CO)9{μ-Th2P(C4H2S)}(μ-H) (4) resulting from carbonyl loss and carbon-hydrogen bond activation, and both 4 and the substituted derivative Ru3(CO)8{μ-Th2P(C4H2S)}(PTh3)(μ-H) (5) resulted from the direct reaction of Ru3(CO)12 and PTh3 at 110 °C in toluene. Interestingly, thermolysis of 2 in benzene at 80 °C affords 5 together with phosphido-bridged Ru3(CO)7(μ-PTh2)2(μ3-η2-C4H2S) (6) resulting from both phosphorus-carbon and carbon-hydrogen bond activation of coordinated PTh3 ligand(s). Cluster 6 is the only product of the thermolysis of 2 in toluene. Heating cyclometalated 4 with Ru3(CO)12 in toluene at 110 °C yielded the tetranuclear phosphinidine cluster, Ru4(CO)9(μ-CO)2(μ4-η2-C4H2S)(μ4-PTh) (7), resulting from carbon-phosphorus bond scission, together with the pentaruthenium sulfide cluster, Ru5(CO)11(μ-PTh2)(μ4-η4-C4H3)(μ4-S) (8), in which sulfur is extruded from a thiophene ring. All the new compounds were characterized by elemental analysis, mass spectrometry, IR and NMR spectroscopy, and by single crystal X-ray diffraction analysis in case of clusters 4, 6, 7, and 8. Cluster 4 consists of a triangular ruthenium framework containing a μ3-Th2P(C4H2S) ligand, while 6 consists of a ruthenium triangle containing η2-μ3-thiophyne ligand and two edge-bridging PTh2 ligands. Cluster 7 exhibits a distorted square arrangement of ruthenium atoms that are capped on one side by a μ4-phosphinidene ligand and on the other by a 4e donating μ4-η2-C4H2S ligand. The structure of 8 represents a rare example of a pentaruthenium wing-tip bridged-butterfly skeleton capped by μ4-S and μ4-η4-C4H3 ligands. The compounds 4, 6, 7, and 8 have been examined by density functional theory (DFT), and the lowest energy structure computed coincides with the X-ray diffraction structure. The hemilabile nature of the activated thienyl ligand in 4 and 6 has also been computationally investigated.
  •  
49.
  • Wynberg, Elke, et al. (författare)
  • Variability in white blood cell count during uncomplicated malaria and implications for parasite density estimation : a WorldWide Antimalarial Resistance Network individual patient data meta-analysis
  • 2023
  • Ingår i: Malaria Journal. - : Springer Nature. - 1475-2875. ; 22
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: The World Health Organization (WHO) recommends that when peripheral malarial parasitaemia is quantified by thick film microscopy, an actual white blood cell (WBC) count from a concurrently collected blood sample is used in calculations. However, in resource-limited settings an assumed WBC count is often used instead. The aim of this study was to describe the variability in WBC count during acute uncomplicated malaria, and estimate the impact of using an assumed value of WBC on estimates of parasite density and clearance.Methods: Uncomplicated malaria drug efficacy studies that measured WBC count were selected from the WorldWide Antimalarial Resistance Network data repository for an individual patient data meta-analysis of WBC counts. Regression models with random intercepts for study-site were used to assess WBC count variability at presentation and during follow-up. Inflation factors for parasitaemia density, and clearance estimates were calculated for methods using assumed WBC counts (8000 cells/mu L and age-stratified values) using estimates derived from the measured WBC value as reference.Results: Eighty-four studies enrolling 27,656 patients with clinically uncomplicated malaria were included. Geometric mean WBC counts (x 1000 cells/mu L) in age groups < 1, 1-4, 5-14 and >= 15 years were 10.5, 8.3, 7.1, 5.7 and 7.5, 7.0, 6.5, 6.0 for individuals with falciparum (n = 24,978) and vivax (n = 2678) malaria, respectively. At presentation, higher WBC counts were seen among patients with higher parasitaemia, severe anaemia and, for individuals with vivax malaria, in regions with shorter regional relapse periodicity. Among falciparum malaria patients, using an assumed WBC count of 8000 cells/mu L resulted in parasite density underestimation by a median (IQR) of 26% (4-41%) in infants < 1 year old but an overestimation by 50% (16-91%) in adults aged = 15 years. Use of age-stratified assumed WBC values removed systematic bias but did not improve precision of parasitaemia estimation. Imprecision of parasite clearance estimates was only affected by the within-patient WBC variability over time, and remained < 10% for 79% of patients.Conclusions: Using an assumed WBC value for parasite density estimation from a thick smear may lead to underdiagnosis of hyperparasitaemia and could adversely affect clinical management; but does not result in clinically consequential inaccuracies in the estimation of the prevalence of prolonged parasite clearance and artemisinin resistance.
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