| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
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| 3. |
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| 4. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 9. |
- Abolfathi, Bela, et al.
(författare)
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The Fourteenth Data Release of the Sloan Digital Sky Survey : First Spectroscopic Data from the Extended Baryon Oscillation Spectroscopic Survey and from the Second Phase of the Apache Point Observatory Galactic Evolution Experiment
- 2018
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Ingår i: Astrophysical Journal Supplement Series. - : IOP Publishing Ltd. - 0067-0049 .- 1538-4365. ; 235:2
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Tidskriftsartikel (refereegranskat)abstract
- The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since 2014 July. This paper describes the second data release from this phase, and the 14th from SDSS overall (making this Data Release Fourteen or DR14). This release makes the data taken by SDSS-IV in its first two years of operation (2014-2016 July) public. Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey; the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data-driven machine-learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from the SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS web site (www.sdss.org) has been updated for this release and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020 and will be followed by SDSS-V.
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- Huusko, Johanna M, et al.
(författare)
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Whole exome sequencing reveals HSPA1L as a genetic risk factor for spontaneous preterm birth.
- 2018
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Ingår i: PLoS genetics. - : Public Library of Science (PLoS). - 1553-7404. ; 14:7
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Tidskriftsartikel (refereegranskat)abstract
- Preterm birth is a leading cause of morbidity and mortality in infants. Genetic and environmental factors play a role in the susceptibility to preterm birth, but despite many investigations, the genetic basis for preterm birth remain largely unknown. Our objective was to identify rare, possibly damaging, nucleotide variants in mothers from families with recurrent spontaneous preterm births (SPTB). DNA samples from 17 Finnish mothers who delivered at least one infant preterm were subjected to whole exome sequencing. All mothers were of northern Finnish origin and were from seven multiplex families. Additional replication samples of European origin consisted of 93 Danish sister pairs (and two sister triads), all with a history of a preterm delivery. Rare exonic variants (frequency <1%) were analyzed to identify genes and pathways likely to affect SPTB susceptibility. We identified rare, possibly damaging, variants in genes that were common to multiple affected individuals. The glucocorticoid receptor signaling pathway was the most significant (p<1.7e-8) with genes containing these variants in a subgroup of ten Finnish mothers, each having had 2-4 SPTBs. This pathway was replicated among the Danish sister pairs. A gene in this pathway, heat shock protein family A (Hsp70) member 1 like (HSPA1L), contains two likely damaging missense alleles that were found in four different Finnish families. One of the variants (rs34620296) had a higher frequency in cases compared to controls (0.0025 vs. 0.0010, p = 0.002) in a large preterm birth genome-wide association study (GWAS) consisting of mothers of general European ancestry. Sister pairs in replication samples also shared rare, likely damaging HSPA1L variants. Furthermore, in silico analysis predicted an additional phosphorylation site generated by rs34620296 that could potentially affect chaperone activity or HSPA1L protein stability. Finally, in vitro functional experiment showed a link between HSPA1L activity and decidualization. In conclusion, rare, likely damaging, variants in HSPA1L were observed in multiple families with recurrent SPTB.
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| 14. |
- Mishra, A, et al.
(författare)
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Diminishing benefits of urban living for children and adolescents' growth and development
- 2023
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 615:7954, s. 874-883
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Tidskriftsartikel (refereegranskat)abstract
- Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified.
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| 15. |
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| 16. |
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| 17. |
- Taddei, C, et al.
(författare)
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Repositioning of the global epicentre of non-optimal cholesterol
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 582:7810, s. 73-
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Tidskriftsartikel (refereegranskat)abstract
- High blood cholesterol is typically considered a feature of wealthy western countries1,2. However, dietary and behavioural determinants of blood cholesterol are changing rapidly throughout the world3 and countries are using lipid-lowering medications at varying rates. These changes can have distinct effects on the levels of high-density lipoprotein (HDL) cholesterol and non-HDL cholesterol, which have different effects on human health4,5. However, the trends of HDL and non-HDL cholesterol levels over time have not been previously reported in a global analysis. Here we pooled 1,127 population-based studies that measured blood lipids in 102.6 million individuals aged 18 years and older to estimate trends from 1980 to 2018 in mean total, non-HDL and HDL cholesterol levels for 200 countries. Globally, there was little change in total or non-HDL cholesterol from 1980 to 2018. This was a net effect of increases in low- and middle-income countries, especially in east and southeast Asia, and decreases in high-income western countries, especially those in northwestern Europe, and in central and eastern Europe. As a result, countries with the highest level of non-HDL cholesterol—which is a marker of cardiovascular risk—changed from those in western Europe such as Belgium, Finland, Greenland, Iceland, Norway, Sweden, Switzerland and Malta in 1980 to those in Asia and the Pacific, such as Tokelau, Malaysia, The Philippines and Thailand. In 2017, high non-HDL cholesterol was responsible for an estimated 3.9 million (95% credible interval 3.7 million–4.2 million) worldwide deaths, half of which occurred in east, southeast and south Asia. The global repositioning of lipid-related risk, with non-optimal cholesterol shifting from a distinct feature of high-income countries in northwestern Europe, north America and Australasia to one that affects countries in east and southeast Asia and Oceania should motivate the use of population-based policies and personal interventions to improve nutrition and enhance access to treatment throughout the world.
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| 18. |
- Zhang, Guojie, et al.
(författare)
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Comparative genomics reveals insights into avian genome evolution and adaptation
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 346:6215, s. 1311-1320
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Tidskriftsartikel (refereegranskat)abstract
- Birds are the most species-rich class of tetrapod vertebrates and have wide relevance across many research fields. We explored bird macroevolution using full genomes from 48 avian species representing all major extant clades. The avian genome is principally characterized by its constrained size, which predominantly arose because of lineage-specific erosion of repetitive elements, large segmental deletions, and gene loss. Avian genomes furthermore show a remarkably high degree of evolutionary stasis at the levels of nucleotide sequence, gene synteny, and chromosomal structure. Despite this pattern of conservation, we detected many non-neutral evolutionary changes in protein-coding genes and noncoding regions. These analyses reveal that pan-avian genomic diversity covaries with adaptations to different lifestyles and convergent evolution of traits.
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| 19. |
- Bixby, H., et al.
(författare)
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Rising rural body-mass index is the main driver of the global obesity epidemic in adults
- 2019
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 569:7755, s. 260-4
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Tidskriftsartikel (refereegranskat)abstract
- Body-mass index (BMI) has increased steadily in most countries in parallel with a rise in the proportion of the population who live in cities(.)(1,2) This has led to a widely reported view that urbanization is one of the most important drivers of the global rise in obesity(3-6). Here we use 2,009 population-based studies, with measurements of height and weight in more than 112 million adults, to report national, regional and global trends in mean BMI segregated by place of residence (a rural or urban area) from 1985 to 2017. We show that, contrary to the dominant paradigm, more than 55% of the global rise in mean BMI from 1985 to 2017-and more than 80% in some low- and middle-income regions-was due to increases in BMI in rural areas. This large contribution stems from the fact that, with the exception of women in sub-Saharan Africa, BMI is increasing at the same rate or faster in rural areas than in cities in low- and middle-income regions. These trends have in turn resulted in a closing-and in some countries reversal-of the gap in BMI between urban and rural areas in low- and middle-income countries, especially for women. In high-income and industrialized countries, we noted a persistently higher rural BMI, especially for women. There is an urgent need for an integrated approach to rural nutrition that enhances financial and physical access to healthy foods, to avoid replacing the rural undernutrition disadvantage in poor countries with a more general malnutrition disadvantage that entails excessive consumption of low-quality calories.
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| 20. |
- Blanton, Michael R., et al.
(författare)
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Sloan Digital Sky Survey IV : Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
- 2017
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Ingår i: Astronomical Journal. - : IOP Publishing Ltd. - 0004-6256 .- 1538-3881. ; 154:1
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Tidskriftsartikel (refereegranskat)abstract
- We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and. high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median z similar to 0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between z similar to 0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs. and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5 m Sloan Foundation Telescope at the. Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5 m du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in 2016 July.
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| 21. |
- Chen, Zhiqiang, et al.
(författare)
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Accuracy of genomic selection for growth and wood quality traits in two control-pollinated progeny trials using exome capture as the genotyping platform in Norway spruce
- 2018
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Ingår i: BMC Genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 19
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundGenomic selection (GS) can increase genetic gain by reducing the length of breeding cycle in forest trees. Here we genotyped 1370 control-pollinated progeny trees from 128 full-sib families in Norway spruce (Picea abies (L.) Karst.), using exome capture as genotyping platform. We used 116,765 high-quality SNPs to develop genomic prediction models for tree height and wood quality traits. We assessed the impact of different genomic prediction methods, genotype-by-environment interaction (GxE), genetic composition, size of the training and validation set, relatedness, and number of SNPs on accuracy and predictive ability (PA) of GS.ResultsUsing G matrix slightly altered heritability estimates relative to pedigree-based method. GS accuracies were about 11-14% lower than those based on pedigree-based selection. The efficiency of GS per year varied from 1.71 to 1.78, compared to that of the pedigree-based model if breeding cycle length was halved using GS. Height GS accuracy decreased to more than 30% while using one site as training for GS prediction and using this model to predict the second site, indicating that GxE for tree height should be accommodated in model fitting. Using a half-sib family structure instead of full-sib structure led to a significant reduction in GS accuracy and PA. The full-sib family structure needed only 750 markers to reach similar accuracy and PA, as compared to 100,000 markers required for the half-sib family, indicating that maintaining the high relatedness in the model improves accuracy and PA. Using 4000-8000 markers in full-sib family structure was sufficient to obtain GS model accuracy and PA for tree height and wood quality traits, almost equivalent to that obtained with all markers.ConclusionsThe study indicates that GS would be efficient in reducing generation time of breeding cycle in conifer tree breeding program that requires long-term progeny testing. The sufficient number of trees within-family (16 for growth and 12 for wood quality traits) and number of SNPs (8000) are required for GS with full-sib family relationship. GS methods had little impact on GS efficiency for growth and wood quality traits. GS model should incorporate GxE effect when a strong GxE is detected.
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| 22. |
- Christiansen, Line I., et al.
(författare)
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Insulin-Like Growth Factor-1 Supplementation Promotes Brain Maturation in Preterm Pigs
- 2023
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Ingår i: eNeuro. - 2373-2822. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- Very preterm infants show low levels of insulin-like growth factor-1 (IGF-1), which is associated with postnatal growth restriction and poor neurologic outcomes. It remains unknown whether supplemental IGF-1 may stimulate neurode-velopment in preterm neonates. Using cesarean-delivered preterm pigs as a model of preterm infants, we investi-gated the effects of supplemental IGF-1 on motor function and on regional and cellular brain development. Pigs were treated with 2.25 mg/kg/d recombinant human IGF-1/IGF binding protein-3 complex from birth until day 5 or 9 before the collection of brain samples for quantitative immunohistochemistry (IHC), RNA sequencing, and quantitative PCR analyses. Brain protein synthesis was measured using in vivo labeling with [2H5] phenylalanine. We showed that the IGF-1 receptor was widely distributed in the brain and largely coexisted with immature neurons. Region-spe-cific quantification of IHC labeling showed that IGF-1 treatment promoted neuronal differentiation, increased subcorti-cal myelination, and attenuated synaptogenesis in a region-dependent and time-dependent manner. The expression levels of genes involved in neuronal and oligodendrocyte maturation, and angiogenic and transport functions were al-tered, reflecting enhanced brain maturation in response to IGF-1 treatment. Cerebellar protein synthesis was increased by 19% at day 5 and 14% at day 9 after IGF-1 treatment. Treatment had no effect on Iba1+ microglia or regional brain weights and did not affect motor development or the expression of genes related to IGF-1 signaling. In conclusion, the data show that supplemental IGF-1 promotes brain maturation in newborn preterm pigs. The results provide further support for IGF-1 supplementation therapy in the early postnatal period in preterm infants.
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| 23. |
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| 24. |
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| 25. |
- Feigin, Valery L., et al.
(författare)
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Global, regional, and national burden of neurological disorders, 1990–2016 : a systematic analysis for the Global Burden of Disease Study 2016
- 2019
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Ingår i: Lancet Neurology. - : Elsevier. - 1474-4422 .- 1474-4465. ; 18:5, s. 459-480
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Tidskriftsartikel (refereegranskat)abstract
- Background: Neurological disorders are increasingly recognised as major causes of death and disability worldwide. The aim of this analysis from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2016 is to provide the most comprehensive and up-to-date estimates of the global, regional, and national burden from neurological disorders.Methods: We estimated prevalence, incidence, deaths, and disability-adjusted life-years (DALYs; the sum of years of life lost [YLLs] and years lived with disability [YLDs]) by age and sex for 15 neurological disorder categories (tetanus, meningitis, encephalitis, stroke, brain and other CNS cancers, traumatic brain injury, spinal cord injury, Alzheimer's disease and other dementias, Parkinson's disease, multiple sclerosis, motor neuron diseases, idiopathic epilepsy, migraine, tension-type headache, and a residual category for other less common neurological disorders) in 195 countries from 1990 to 2016. DisMod-MR 2.1, a Bayesian meta-regression tool, was the main method of estimation of prevalence and incidence, and the Cause of Death Ensemble model (CODEm) was used for mortality estimation. We quantified the contribution of 84 risks and combinations of risk to the disease estimates for the 15 neurological disorder categories using the GBD comparative risk assessment approach.Findings: Globally, in 2016, neurological disorders were the leading cause of DALYs (276 million [95% UI 247–308]) and second leading cause of deaths (9·0 million [8·8–9·4]). The absolute number of deaths and DALYs from all neurological disorders combined increased (deaths by 39% [34–44] and DALYs by 15% [9–21]) whereas their age-standardised rates decreased (deaths by 28% [26–30] and DALYs by 27% [24–31]) between 1990 and 2016. The only neurological disorders that had a decrease in rates and absolute numbers of deaths and DALYs were tetanus, meningitis, and encephalitis. The four largest contributors of neurological DALYs were stroke (42·2% [38·6–46·1]), migraine (16·3% [11·7–20·8]), Alzheimer's and other dementias (10·4% [9·0–12·1]), and meningitis (7·9% [6·6–10·4]). For the combined neurological disorders, age-standardised DALY rates were significantly higher in males than in females (male-to-female ratio 1·12 [1·05–1·20]), but migraine, multiple sclerosis, and tension-type headache were more common and caused more burden in females, with male-to-female ratios of less than 0·7. The 84 risks quantified in GBD explain less than 10% of neurological disorder DALY burdens, except stroke, for which 88·8% (86·5–90·9) of DALYs are attributable to risk factors, and to a lesser extent Alzheimer's disease and other dementias (22·3% [11·8–35·1] of DALYs are risk attributable) and idiopathic epilepsy (14·1% [10·8–17·5] of DALYs are risk attributable).Interpretation: Globally, the burden of neurological disorders, as measured by the absolute number of DALYs, continues to increase. As populations are growing and ageing, and the prevalence of major disabling neurological disorders steeply increases with age, governments will face increasing demand for treatment, rehabilitation, and support services for neurological disorders. The scarcity of established modifiable risks for most of the neurological burden demonstrates that new knowledge is required to develop effective prevention and treatment strategies.Funding: Bill & Melinda Gates Foundation.
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| 26. |
- Forsman, Bo, et al.
(författare)
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Shear properties of fragmented rock masses : model tests and theories
- 1989
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Ingår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts. - : Elsevier BV. - 0148-9062 .- 1879-2073. ; 26:1, s. 25-36
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Tidskriftsartikel (refereegranskat)abstract
- In material handling, such as loading and gravity flow, shear strength is one of the most important physical properties. This work deals with important factors influencing the shear strength of fragmented rock in order to give a better theoretical background for developing rock loading techniques.Shear tests were performed on three types of fragmented rock mass samples to investigate the parameters particle size and distribution, moisture content and compaction of the material.From the standpoint of deformation energy, a shear strength envelope equation has been deducted for loose rock material. A comparison has been made between the results calculated with this equation and Coulomb's equation.The results obtained for each investigated parameter include the relation between shear force and shear displacement during constant normal force, the volume change, the deformation energy change and the internal friction angle.
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| 27. |
- Fu, Pan, et al.
(författare)
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Metasurface Enabled On-Chip Generation and Manipulation of Vector Beams from Vertical Cavity Surface-Emitting Lasers
- 2023
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Metasurface polarization optics that consist of 2D array of birefringent nano-antennas have proven remarkable capabilities to generate and manipulate vectorial fields with subwavelength resolution and high efficiency. Integrating this new type of metasurface with the standard vertical cavity surface-emitting laser (VCSEL) platform enables an ultracompact and powerful solution to control both phase and polarization properties of the laser on a chip, which allows to structure a VCSEL into vector beams with on-demand wavefronts. Here, this concept is demonstrated by directly generating versatile vector beams from commercially available VCSELs through on-chip integration of high-index dielectric metasurfaces. Experimentally, the versatility of the approach for the development of vectorial VCSELs are validated by implementing a variety of functionalities, including directional emission of multibeam with specified polarizations, vectorial holographic display, and vector vortex beams generations. Notably, the proposed vectorial VCSELs integrated with a single layer of beam shaping metasurface bypass the requirements of multiple cascaded optical components, and thus have the potential to promote the advancements of ultracompact, lightweight, and scalable vector beams sources, enriching and expanding the applications of VCSELs in optical communications, laser manipulation and processing, information encryption, and quantum optics.
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| 28. |
- Jiang, Pan, et al.
(författare)
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Toward well-defined colloidal particles : Efficient fractionation of lignin by a multi-solvent strategy
- 2024
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Ingår i: International Journal of Biological Macromolecules. - 0141-8130 .- 1879-0003. ; 254:3
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Tidskriftsartikel (refereegranskat)abstract
- Colloidal lignin particles (CLPs) have sparked various intriguing insights toward bio-polymeric materials and triggered many lignin-featured innovative applications. Here, we report a multi-solvent sequential fractionation methodology integrating green solvents of acetone, 1-butanol, and ethanol to fractionate industrial lignin for CLPs fabrication. Through a rationally designed fractionation strategy, multigrade lignin fractions with variable hydroxyl group contents, molecular weights, and high purity were obtained without altering their original chemical structures. CLPs with well-defined morphology, narrow size distribution, excellent thermal stability, and long-term colloidal stability can be obtained by rational selection of lignin fractions. We further elucidated that trace elements (S, N) were reorganized onto the near-surface area of CLPs from lignin fractions during the formation process in the form of -SO42− and -NH2. This work provides a sustainable and efficient strategy for refining industrial lignin into high-quality fractions and an in-depth insight into the CLPs formation process, holding great promise for enriching the existing libraries of colloidal materials.
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| 29. |
- Li, Longkun, et al.
(författare)
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Altered expression of calcium-activated K and Cl channels in detrusor overactivity of rats with partial bladder outflow obstruction
- 2008
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Ingår i: BJU International. - 1464-4096 .- 1464-410X. ; 101:12, s. 1588-1594
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate the activity of large- and small-conductance calcium-activated potassium channels (BKCa, SKCa) and calcium-activated chloride channels (ClCa) in detrusor overactivity (DO) cells after partial bladder outlet obstruction (PBOO) in rats. MATERIALS AND METHODS Thirteen female Wistar rats with DO caused by PBOO were studied simultaneously with eight sham-operated rats. The expression of KCa and ClCa channels was assessed by reverse transcription-polymerase chain reaction, and the function of the two groups compared. RESULTS In the DO cells the expression of BKCa, SKCa2 and SKCa3 was lower, and that of ClCa channels higher, than in the control group cells. Using confocal laser scanning microscopic analysis, the function of BKCa and SKCa channels was suppressed, and that of ClCa channels was enhanced in DO group cells. KCa and ClCa effectors altered the cell membrane potentials more significantly in the DO cells than in the control cells, indicating a decrease in KCa and an increase in ClCa in DO group in either iso- or hypo-osmolar medium. Moreover, the change in BKCa, SKCa and ClCa channel activators in DO cells showed a more excitable state in hypo-osmolar medium than in iso-osmolar medium. CONCLUSION In DO myocytes after PBOO, the expression and function of KCa channels were decreased, and those of ClCa channels increased. These changes all provoke greater cell excitability, and could partly account for the DO.
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| 30. |
- Li, Yanying, et al.
(författare)
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A D-peptide ligand of neuropeptide Y receptor Y-1 serves as nanocarrier traversing of the blood brain barrier and targets glioma
- 2022
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Ingår i: Nano Today. - : Elsevier. - 1748-0132 .- 1878-044X. ; 44
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Tidskriftsartikel (refereegranskat)abstract
- Diseases of the central nervous system (CNS) are challenging for drug treatment because the blood-brain barrier (BBB) restricts entry of drugs into the brain tissue. Therefore, strategies for drug transport across the BBB are an important component in development of CNS drug therapies. Here, a D-amino acid ligand of the neuropeptide Y (NPY) receptor Y1 is described, (D)[Asn(28), Pro(30), Trp(32)]-DNPY (25-36) (termed DAPT), with 2.5 times higher number of hydrogen bonds interacting with the receptor, based on docking into a structural model, than the corresponding peptide with standard L-amino acids (LAPT). Using in vitro BBB models, in vivo healthy mice with intact BBB, and U87-MG orthotopic tumor-bearing mice, we demonstrate that DAPT exhibits significantly higher ability than LAPT to serve as nanocarrier across the BBB and specifically targets gliomas. Using DAPT nanomicelles loaded with IRDye780, it was possible to achieve excellent photothermal therapeutic and photoacoustic cancer imaging. Thus, this study demonstrates the importance of ligand stability and affinity in Y1 receptor-mediated transcytosis and paves the way for versatile brain tumor imaging and therapy using nanomicelles.
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| 31. |
- Li, Yanying, et al.
(författare)
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A D-Y Shaped Neuropeptide Y Mimetic Peptide-Dye Self-Assembly with Maximal Emission Beyond 1300 nm and Glioma Mitochondrial Activity Modulation
- 2024
-
Ingår i: Small. - : John Wiley & Sons. - 1613-6810 .- 1613-6829. ; 20:13
-
Tidskriftsartikel (refereegranskat)abstract
- Neuropeptide Y (NPY), as one of the most abundant neuropeptides known, is widely distributed in the central and peripheral nervous system. However, most of the reported NPY-mimetic peptides are hard to cross the blood-brain barrier, target glioma mitochondria, and achieve self-assembly nanostructure in situ. Here, based on the α-helix structure of the novel chiral NPY-mimetic peptides D/LNPY(14), a Y-shaped peptide is designed with the sequences that can be recognized by enterokinase and achieved nanofibers conversion in glioma cell mitochondria. Coupling the Y-shaped NPY-mimetic peptide with the NIR-II fluorophore IR1048, a red-shifting of the fluorescence spectrum beyond 1300 nm is achieved through self-assembly. After the self-assembly in glioma mitochondria, the formed nanofibers can promote intracellular mitochondrial ROS production and extend the NIR-II fluorescence imaging time to at least 7 days in vivo. This work for the first time endows the self-assembly of α-helical-based chiral NPY-mimetic peptides, providing a novel strategy for glioma subcellular regulation enhanced antitumor treatment guided by NIR-II fluorescence imaging.
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| 32. |
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| 33. |
- Lind, Lars, et al.
(författare)
-
Heterogeneous contributions of change in population distribution of body mass index to change in obesity and underweight NCD Risk Factor Collaboration (NCD-RisC)
- 2021
-
Ingår i: eLife. - : eLife Sciences Publications Ltd. - 2050-084X. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions.
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| 34. |
- Liu, Zhigang, et al.
(författare)
-
Gut microbiota mediates intermittent-fasting alleviation of diabetes-induced cognitive impairment
- 2020
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 11:1, s. 855-
-
Tidskriftsartikel (refereegranskat)abstract
- Cognitive decline is one of the complications of type 2 diabetes (T2D). Intermittent fasting (IF) is a promising dietary intervention for alleviating T2D symptoms, but its protective effect on diabetes-driven cognitive dysfunction remains elusive. Here, we find that a 28-day IF regimen for diabetic mice improves behavioral impairment via a microbiota-metabolites-brain axis: IF enhances mitochondrial biogenesis and energy metabolism gene expression in hippocampus, re-structures the gut microbiota, and improves microbial metabolites that are related to cognitive function. Moreover, strong connections are observed between IF affected genes, microbiota and metabolites, as assessed by integrative modelling. Removing gut microbiota with antibiotics partly abolishes the neuroprotective effects of IF. Administration of 3-indolepropionic acid, serotonin, short chain fatty acids or tauroursodeoxycholic acid shows a similar effect to IF in terms of improving cognitive function. Together, our study purports the microbiota-metabolites-brain axis as a mechanism that can enable therapeutic strategies against metabolism-implicated cognitive pathophysiologies.
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| 35. |
- Lozano, Rafael, et al.
(författare)
-
Measuring progress from 1990 to 2017 and projecting attainment to 2030 of the health-related Sustainable Development Goals for 195 countries and territories: a systematic analysis for the Global Burden of Disease Study 2017
- 2018
-
Ingår i: The Lancet. - : Elsevier. - 1474-547X .- 0140-6736. ; 392:10159, s. 2091-2138
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Efforts to establish the 2015 baseline and monitor early implementation of the UN Sustainable Development Goals (SDGs) highlight both great potential for and threats to improving health by 2030. To fully deliver on the SDG aim of “leaving no one behind”, it is increasingly important to examine the health-related SDGs beyond national-level estimates. As part of the Global Burden of Diseases, Injuries, and Risk Factors Study 2017 (GBD 2017), we measured progress on 41 of 52 health-related SDG indicators and estimated the health-related SDG index for 195 countries and territories for the period 1990–2017, projected indicators to 2030, and analysed global attainment. Methods: We measured progress on 41 health-related SDG indicators from 1990 to 2017, an increase of four indicators since GBD 2016 (new indicators were health worker density, sexual violence by non-intimate partners, population census status, and prevalence of physical and sexual violence [reported separately]). We also improved the measurement of several previously reported indicators. We constructed national-level estimates and, for a subset of health-related SDGs, examined indicator-level differences by sex and Socio-demographic Index (SDI) quintile. We also did subnational assessments of performance for selected countries. To construct the health-related SDG index, we transformed the value for each indicator on a scale of 0–100, with 0 as the 2·5th percentile and 100 as the 97·5th percentile of 1000 draws calculated from 1990 to 2030, and took the geometric mean of the scaled indicators by target. To generate projections through 2030, we used a forecasting framework that drew estimates from the broader GBD study and used weighted averages of indicator-specific and country-specific annualised rates of change from 1990 to 2017 to inform future estimates. We assessed attainment of indicators with defined targets in two ways: first, using mean values projected for 2030, and then using the probability of attainment in 2030 calculated from 1000 draws. We also did a global attainment analysis of the feasibility of attaining SDG targets on the basis of past trends. Using 2015 global averages of indicators with defined SDG targets, we calculated the global annualised rates of change required from 2015 to 2030 to meet these targets, and then identified in what percentiles the required global annualised rates of change fell in the distribution of country-level rates of change from 1990 to 2015. We took the mean of these global percentile values across indicators and applied the past rate of change at this mean global percentile to all health-related SDG indicators, irrespective of target definition, to estimate the equivalent 2030 global average value and percentage change from 2015 to 2030 for each indicator. Findings: The global median health-related SDG index in 2017 was 59·4 (IQR 35·4–67·3), ranging from a low of 11·6 (95% uncertainty interval 9·6–14·0) to a high of 84·9 (83·1–86·7). SDG index values in countries assessed at the subnational level varied substantially, particularly in China and India, although scores in Japan and the UK were more homogeneous. Indicators also varied by SDI quintile and sex, with males having worse outcomes than females for non-communicable disease (NCD) mortality, alcohol use, and smoking, among others. Most countries were projected to have a higher health-related SDG index in 2030 than in 2017, while country-level probabilities of attainment by 2030 varied widely by indicator. Under-5 mortality, neonatal mortality, maternal mortality ratio, and malaria indicators had the most countries with at least 95% probability of target attainment. Other indicators, including NCD mortality and suicide mortality, had no countries projected to meet corresponding SDG targets on the basis of projected mean values for 2030 but showed some probability of attainment by 2030. For some indicators, including child malnutrition, several infectious diseases, and most violence measures, the annualised rates of change required to meet SDG targets far exceeded the pace of progress achieved by any country in the recent past. We found that applying the mean global annualised rate of change to indicators without defined targets would equate to about 19% and 22% reductions in global smoking and alcohol consumption, respectively; a 47% decline in adolescent birth rates; and a more than 85% increase in health worker density per 1000 population by 2030. Interpretation: The GBD study offers a unique, robust platform for monitoring the health-related SDGs across demographic and geographic dimensions. Our findings underscore the importance of increased collection and analysis of disaggregated data and highlight where more deliberate design or targeting of interventions could accelerate progress in attaining the SDGs. Current projections show that many health-related SDG indicators, NCDs, NCD-related risks, and violence-related indicators will require a concerted shift away from what might have driven past gains—curative interventions in the case of NCDs—towards multisectoral, prevention-oriented policy action and investments to achieve SDG aims. Notably, several targets, if they are to be met by 2030, demand a pace of progress that no country has achieved in the recent past. The future is fundamentally uncertain, and no model can fully predict what breakthroughs or events might alter the course of the SDGs. What is clear is that our actions—or inaction—today will ultimately dictate how close the world, collectively, can get to leaving no one behind by 2030.
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| 36. |
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| 37. |
- Olika, B., et al.
(författare)
-
Numerical simulation and industrial investigation on the melt stratification phenomena in ladles holding molten steel
- 1996
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Ingår i: Scandinavian journal of metallurgy. - 0371-0459 .- 1600-0692. ; 25:1, s. 18-26
-
Tidskriftsartikel (refereegranskat)abstract
- The melt stratification phenomenon, which results from the natural convection in ladles holding molten steel, is of fundamental importance for the temperature control in the continuous casting process. The progressively increasing stress on the quality of continuously cast products necessitates much tighter tundish temperature control, which in turn will require a more precise definition of the extent of melt temperature stratification in ladles. For this reason, ladle melt stratification phenomena were studied both by numerical simulations, using the PHOENICS package, and by plant measurements at SSAB Tunnplat AB's steelworks in Lulea. The parameters studied in the numerical simulations were the fluid flow velocity field, the temperature distribution field, ladle initial heat content and height to diameter ratio of ladles. One of the important boundary conditions that was used in these numerical simulations was the time and geometry-dependent heat loss rate through the ladle walls, which is the major cause of the natural convection. This transient boundary condition was obtained from the temperature simulation model TempSim. Steel temperatures measured at different positions along the ladle height are compared in the paper with results from the numerical calculations. The possibility of expressing the stratification with a simple formula was discussed. However, to propose this model for industrial use, experimental verification with prolonged holding time is needed.
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| 38. |
- Olika, Bekele, et al.
(författare)
-
Numerical simulation and industrial investigation on the melt stratification phenomena in ladles holding molten steel
- 1995
-
Ingår i: Scaninject VII. - : MEFOS. ; , s. 361-384
-
Konferensbidrag (refereegranskat)abstract
- The melt stratification phenomenon, which results from the natural convection in ladles holding molten steel, is of fundamental importance for the temperature control in the continuous casting process. The progressively increasing stress on the quality of continuously cast products necessitates much tighter tundish temperature control, which in turn will require a more precise definition of the extent of melt temperature stratification in ladles. For this reason, ladle melt stratification phenomena were studied both by numerical simulations, using the PHOENICS package, and by plant measurements at SSAB Tunnplat AB's steelworks in Lulea. The parameters studied in the numerical simulations were the fluid flow velocity field, the temperature distribution field, ladle initial heat content and height to diameter ratio of ladles. One of the important boundary conditions that was used in these numerical simulations was the time and geometry-dependent heat loss rate through the ladle walls, which is the major cause of the natural convection. This transient boundary condition was obtained from the temperature simulation model TempSim. Steel temperatures measured at different positions along the ladle height are in the paper compared with results from the numerical calculations. The possibility to express the stratification with a simple formula was discussed. However, to propose this model for industrial use, experimental verification with prolonged holding time is needed.
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| 39. |
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| 40. |
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| 41. |
- Pan, Jinshan, 1962-, et al.
(författare)
-
Tafel slopes used in monitoring of copper corrosion in a bentonite/groundwater environment
- 2005
-
Ingår i: Corrosion Science. - : Elsevier. - 0010-938X .- 1879-0496. ; 47:12, s. 3267-3279
-
Tidskriftsartikel (refereegranskat)abstract
- The harmonic analysis, the polarization resistance, and the noise resistance methods have been applied in an effort to monitor corrosion of pure copper in a bentonite/groundwater environment with commercially available equipment. Without the need to use a reference electrode, the first method supplies not only an estimate of the corrosion rate, but also estimates of Tafel slopes required by the other methods. The recorded corrosion rate is overestimated but to a varying degree. While the recorded corrosion rates for the first two methods give quite similar values far below 3 lm/year, the electrochemical noise resistance method gives considerably higher values.
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| 42. |
- Pan, Yuhua, et al.
(författare)
-
Development and experimental verification of a model for simulation of the fluid dynamics in a 105t steel ladle before and during casting
- 1999
-
Ingår i: 82nd Steelmaking conference proceedings. - Warrendale, Pa : Iron and Steel Society. - 1886362335 ; , s. 405-416
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a three-dimensional numerical model simulating fluid flow, heat transfer and concentration distribution in 105t steel ladles before and during casting. The model was developed by combined implementation of a numerical simulation package, TEMPSIM, and a computational fluid dynamics (CFD) simulation package, PHOENICS. In this study, TEMPSIM was used to calculate the heat transfer in ladle linings and predict the heat losses from the steel melt to the linings which are transient and sensitive to ladle configurations. These data were used as input into PHOENICS for CFD modeling of fluid flow and heat transfer as well as transport of six tracer elements in steel bath in the ladle. The modeling results were compared with concentrations measured in an industrial experiment where six tracer elements were added at different positions in the ladle and at different times before and during casting. With the use of this model, the stratification phenomenon and the effect of drainage flow, as well as the behavior of added tracer elements, in the steel ladle during the casting period, were described and discussed.
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| 43. |
- Pan, Yuhua, et al.
(författare)
-
Numerical analysis on the similarity between steel ladles and hot-water models regarding natural convection phenomena
- 2002
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 42:1, s. 53-62
-
Tidskriftsartikel (refereegranskat)abstract
- The similarity between steel ladles and hot-water models regarding natural convection phenomena has been systematically analysed through examination of the numerical solutions of turbulent Navier-Stokes partial differential equations governing the phenomena in question. The numerical solutions have been obtained by using a computational fluid dynamics (CFD) simulation method. Key similarity criteria for nonisothermal physical modelling of steel ladles with hot-water models have been derived. Accordingly, appropriate conditions fulfilling the above criteria, such as model size, water temperature, time scale factor and the scale factor of boundary heat loss fluxes, have been proposed and discussed. As a result, water models with geometry scales between 1/5 and 1/3 and using hot-water of temperature higher than 45 deg C are appropriate for simulating natural convection phenomena in steel ladles.
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| 44. |
- Pan, Yuhua, et al.
(författare)
-
Numerical studies on the parameters influencing steel ladle heat loss rate, thermal stratification during holding and steel stream temperature during teeming
- 2003
-
Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 32:2, s. 71-85
-
Tidskriftsartikel (refereegranskat)abstract
- Numerical experiments were performed on fluid flow and heat transfer in 107-tonne steel ladles by 3-step implementations of numerical models. In the first step, a 1-dimensional numerical model was used to predict heat conduction fluxes through the ladle wall, bottom and top slag layer. In the second step, by means of computational fluid dynamics (CFD) modelling and employing the predicted heat loss fluxes as thermal boundary conditions, a 2-dimensional CFD model was applied to simulate natural convection in steel ladles during the holding period before teeming. In the third step, a 3-dimensional CFD model was implemented to further simulate fluid dynamics in the same ladles with drainage flows during teeming. Using these mathematical numerical models, the bulk cooling rate of the steel melt, the extent of thermal stratification during holding and the steel stream temperature during teeming were investigated for 2 types of 107-tonne steel ladles lined, respectively, with alumina and spinel in walls. In these investigations, the following 4 parameters were considered: (i)ladle lining inside surface (hot-face) temperature before tapping, (ii)top slag layer thickness, (iii) holding time and (iv) teeming rate. An important result of these investigations is that the concerned parameters all significantly influence the steel stream temperature during teeming, and the differences in teeming stream temperatures among different ladles, caused by these parameters, can be up to 20 deg C, which may be essential to temperature control in tundishes during continuous casting.
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| 45. |
- Pan, Yuhua, et al.
(författare)
-
Physical and mathematical modelling of thermal stratification phenomena in steel ladles
- 2002
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 42:6, s. 614-623
-
Tidskriftsartikel (refereegranskat)abstract
- A 1/4-scale hot-water model of industrial 107-tonne steel ladles was established in the laboratory. With this physical model, thermal stratification phenomena due to natural convection in steel ladles during the holding period before casting were investigated. By controlling the cooling intensity of the water model to correspond to the heat loss rate of steel ladles, which is governed by dimensionless numbers Fr and beta Delta T, temperature distributions in the water model can simulate those in the steel ladles. Consequently, the temperature profile in the hot-water bath in the model can be used to deduce the thermal stratification phenomena in liquid steel bath in the ladles. In addition, mathematical simulations on fluid flow and heat transfer both in the water model and in the prototype steel ladle were performed using a computational fluid dynamics (CFD) numerical method. The CFD model was validated against temperatures measured in the water model. Comparisons between mathematically simulated temperature profiles in the prototype steel ladle and those physically simulated by scaling-up the measured temperature profiles in the water model showed a good agreement. Therefore, it can be concluded that, as long as accurate heat loss information is known, it is feasible to use a 1/4-scale water model to non-isothermally simulate fluid flow and heat transfer in steel ladles during the holding period before casting.
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| 46. |
- Pecunia, Vincenzo, et al.
(författare)
-
Roadmap on energy harvesting materials
- 2023
-
Ingår i: Journal of Physics. - : IOP Publishing. - 2515-7639. ; 6:4
-
Tidskriftsartikel (refereegranskat)abstract
- Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere.
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| 47. |
- Rosborg, Bo, et al.
(författare)
-
An electrochemical impedance spectroscopy study of copper in a bentonite/saline groundwater environment
- 2008
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 53:25, s. 7556-7564
-
Tidskriftsartikel (refereegranskat)abstract
- Pure copper samples have been exposed for 6 years in a bentonite test parcel in the Aspo Hard Rock Laboratory, which offers a realistic environment for the conditions that will prevail in a deep repository for high-level radioactive waste disposal in Sweden. After retrieval of the test parcel, a bentonite test package containing the samples was placed in a container and sealed with a thick layer of paraffin, and later on new copper and platinum samples were installed. An electrochemical impedance spectroscopy study has been performed on the pre-exposed and new copper samples for different durations in the retrieved test package. The impedance spectra for copper in the bentonite/saline groundwater environment change considerably with time of exposure. The change is more pronounced at higher than at lower frequencies. It is presumed that the corrosion resistance of pure copper in this environment mainly depends on a thin protective cuprite film that forms readily, and on a thick porous outer corrosion product layer (mainly cuprite) that develops slowly and partly intermixes with the bentonite. The impedance data revealed that both the inner and the outer corrosion product layer were involved in the impairment and the recovery of the corrosion resistance when the copper interface was disturbed during retrieval of the bentonite test package.
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| 48. |
- Rosborg, Bo, et al.
(författare)
-
Electrochemical impedance spectroscopy of pure copper exposed in bentonite under oxic conditions
- 2011
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 56:23, s. 7862-7870
-
Tidskriftsartikel (refereegranskat)abstract
- The corrosion rate of pure copper has been followed by thin electrical resistance (ER) sensors placed in a test package containing an oxic bentonite/saline groundwater environment at room temperature for a period of more than three years. Potential measurements have verified oxic conditions in the test package. A series of electrochemical impedance spectroscopy (EIS) measurements has also been performed on the ER sensors and results from one of the sensors are presented. The impedance spectra for copper in the oxic bentonite/saline groundwater environment changed considerably with time of exposure. The impedance increased over the whole frequency range. Three methods were applied to estimate the corrosion rate from the EIS spectra. The EIS measurements have revealed decreasing but measurable corrosion rates all through the exposure period. The former reveals a desired behaviour of copper in the environment. After three-year exposure the estimated corrosion rate from the EIS measurements fell in the range 0.4-0.7 mu m/year, which is somewhat lower than the value of 1.0 p,mu m/year, obtained from the ER measurements. Gravimetric data from six years exposure in the Aspo Hard Rock Laboratory showed an average corrosion rate of 0.5 mu m/year. The corrosion resistance of copper is improved by the presence of bentonite.
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| 49. |
- Rosborg, Bo, et al.
(författare)
-
Real-time monitoring of copper corrosion at the Äspö HRL
- 2004
-
Konferensbidrag (refereegranskat)abstract
- In Sweden the principal strategy for high-level radioactive waste disposal is to enclose the spent nuclear fuel in tightly sealed copper canisters that are embedded in bentonite clay about 500 m down in the Swedish bed-rock. Initially, a limited amount of air will be left in a repository after emplacement. The entrapped oxygen will be consumed through reactions with minerals in the rock and the bentonite and also through microbial activity. After the oxygen has been consumed in the repository, after a few hundred years at the very most, corrosion will be controlled completely by the supply of dissolved sulphide to the canister. The present work concerns the oxic period after emplacement. The main hypothesis is that the average corrosion rate of the canister under oxic conditions will be less than 7 μm/year, and that pitting will only be possible under these conditions. The Äspö Hard Rock Laboratory offers a realistic environment for different experiments and tests under the conditions that will prevail in a deep repository. Real-time monitoring of copper corrosion is presently performed with polarization resistance, harmonic distortion analysis and electrochemical noise techniques. The first two techniques are used to derive information regarding the general corrosion rate and the third to derive information regarding localized corrosion. In order to support these measurements at Äspö, laboratory work is also performed at the Royal Institute of Technology in Stockholm using the very same corrosion monitoring equipment and also other equipment and techniques. Copper coupons are also exposed at Äspö. Results from the work at Äspö and in Stockholm are presented with an emphasis on the gained information concerning localized corrosion. The recorded corrosion rates at Äspö are well below the value given above, and the recorded localization factors are interpreted as indicating only a slight tendency to local attack.
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| 50. |
- Rosborg, Bo, et al.
(författare)
-
The corrosion rate of copper in a test parcel at the Äspö Hard Rock Laboratory
- 2004
-
Ingår i: Mater Res Soc Symp Proc. ; , s. 489-494
-
Konferensbidrag (refereegranskat)abstract
- Cylindrical copper electrodes have been installed in a test parcel at the Äspö Hard Rock Laboratory and real-time corrosion monitoring was initiated in May 2001. The test parcel was emplaced on October 29, 1999, and will be retrieved in 2004. The three electrodes, each of about 100 cm 2 surface area, are installed in bentonite block 36, where the temperature is about 24°C. The corrosion monitoring is performed with linear polarization resistance (LPR), harmonic distortion analysis (HDA) and electrochemical noise techniques. A value on the Stern-Geary coefficient is required to calculate the corrosion rate from the measured LPR data. A default value of 10.3 mV has been used, but an actual value can in fact be obtained from the HDA. The corrosion rate will be overestimated if the frequency of the voltage perturbation for the LPR measurements is not low enough. Electrode impedance measurements have been performed to verify this. Two and a half year after emplacement the recorded corrosion rate of copper in the above bentonite block amounts to about 2.2 μm per year (using a default value of 10.3 mV for the Stern-Geary coefficient and a 0.01 Hz voltage perturbation frequency). The actual corrosion rate is estimated to less than 0.7 μm per year (considering a measured Stern-Geary coefficient of 6.5 mV and the findings from the electrode impedance measurements).
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