| 1. |
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| 2. |
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| 3. |
- Budde, M., et al.
(författare)
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Identification of the hydrogen-saturated self-interstitials in silicon and germanium
- 1998
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 57:18, s. 4397-4412
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Tidskriftsartikel (refereegranskat)abstract
- Silicon and germanium single crystals are implanted with protons. The infrared-absorption spectra of the samples contain sharp absorption lines due to the excitation of hydrogen-related local vibrational modes. The lines at 743.1, 748.0, 1986.5, and 1989.4 cm-1 in silicon and at 700.3, 705.5, 1881.8, and 1883.5 cm-1 in germanium originate from the same defect in the two materials. Measurements on samples coimplanted with protons and deuterons show that the defect contains two equivalent hydrogen atoms. Uniaxial stress measurements are carried out and a detailed analysis of the results is presented. It is shown that the defect has monoclinic-II symmetry, and the orientations of the Si-H and Ge-H bonds of the defect are determined. Ab initio local-density-functional theory is used to calculate the structure and local vibrational modes of the self-interstitial binding one and two hydrogen atoms in silicon and germanium together with the structure of the self-interstitial itself. The observed properties of the defect are in excellent agreement with those calculated for the self-interstitial binding two hydrogen atoms.
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| 4. |
- Budde, M., et al.
(författare)
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The hydrogen-saturated self-interstitial in silicon and germanium
- 1997
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Ingår i: Defects in semiconductors. - : Trans Tech Publications Inc.. ; , s. 35-40
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Konferensbidrag (refereegranskat)abstract
- Infrared absorption spectroscopy is used to study H-related point defects in H+-implanted Si (Si:H) and Ge (Ge:H). The absorption lines at 743.1, 748.0, 1986.5 and 1989.4 cm-1 in Si:H and at 700.3, 705.5, 1881.8 and 1883.5 cm-1 in Ge:H are shown to originate from the same defect containing two equivalent H atoms. Uniaxial stress experiments show that the defects have monoclinic-II symmetry, and the orientations of the two Si-H or Ge-H bonds are determined. The structure and the local vibrational modes of the self-interstitial binding two H atoms (IH2) are calculated with LDF cluster theory. The symmetry, bond-orientations and isotopic frequency-shifts calculated for IH2 are in excellent agreement with those observed for the 743.1-, 748.0-, 1986.5- and 1989.4-cm-1 modes in Si:H and for the 700.3-, 705.5-, 1881.8- and 1883.5-cm-1 modes in Ge:H.
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| 5. |
- Coomer, B.J., et al.
(författare)
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Vacancy-hydrogen complexes in germanium
- 1998
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Ingår i: E-MRS Meeting. - : European Materials Research Society.
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Konferensbidrag (refereegranskat)abstract
- Local-density-functional pseudopotential theory is used to investigate the structural, electronic and vibrational properties of vacancy-hydrogen complexes in germanium. The results are compared with recent infrared absorption data from proton and deuteron implanted Ge. The acceptor and donor levels of the VH defects are derived semi-empirically from the relaxed structures
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| 6. |
- Coomer, B.J., et al.
(författare)
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Vacancy-hydrogen complexes in germanium
- 1999
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Ingår i: Materials Science & Engineering. - 0921-5107 .- 1873-4944. ; 58:1-2, s. 36-38
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Tidskriftsartikel (refereegranskat)abstract
- Local-density-functional pseudopotential theory is used to investigate the structural, electronic and vibrational properties of vacancy-hydrogen complexes in germanium. The results are compared with recent infrared absorption data from proton and deuteron implanted Ge. The acceptor and donor levels of the VHn defects are derived semi-empirically from the relaxed structures
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| 7. |
- Hoffmann, L., et al.
(författare)
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Substitutional carbon in Si1-xGex
- 1999
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 60:19, s. 13573-13581
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Tidskriftsartikel (refereegranskat)abstract
- Local vibrational modes of carbon impurities in relaxed Si1-xGex have been studied with infrared absorption spectroscopy in the composition range 0.05≤x≤0.50. Carbon modes with frequencies in the range 512-600 cm-1 are observed in 13C+-implanted Si1-xGex after annealing at 550°C. Measurements on samples coimplanted with 12C+ and 13C+ show that these modes originate from defects containing a single carbon atom and from the variation of the mode frequencies with composition x, the modes are assigned to substitutional carbon in Si1-xGex. Based on the frequencies obtained from a simple vibrational model, the observed modes are assigned to specific combinations of the four Si and Ge neighbors to the carbon. The intensities of the modes indicate that the combination of the four neighbors deviates from a random distribution. Ab initio local-density-functional cluster theory has been applied to calculate the structure and the local mode frequencies of substitutional carbon with n Ge and 4-n Si neighbors in a Si and a Ge cluster. The calculated frequencies are ∼9% higher than those observed, but the ordering and the splitting of the mode frequencies agree with our assignments.
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| 8. |
- Joseph, A, et al.
(författare)
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Metabolic features of cancer cells impact immunosurveillance
- 2021
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Ingår i: Journal for immunotherapy of cancer. - : BMJ. - 2051-1426. ; 9:6
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Tidskriftsartikel (refereegranskat)abstract
- Tumors rewire their metabolism to achieve robust anabolism and resistance against therapeutic interventions like cisplatin treatment. For example, a prolonged exposure to cisplatin causes downregulation of pyridoxal kinase (PDXK), the enzyme that generates the active vitamin B6, and upregulation of poly ADP-ribose (PAR) polymerase-1 (PARP1) activity that requires a supply of nicotinamide (vitamin B3) adenine dinucleotide. We investigated the impact of the levels of PDXK and PAR on the local immunosurveillance (ie, density of the antigen presenting cells and adaptive immune response by CD8 T lymphocytes) in two different tumor types.MethodsTumors from patients with locally advanced cervical carcinoma (LACC) and non-small cell lung cancer (NSCLC) were stained for PAR, PDXK, dendritic cell lysosomal associated membrane glycoprotein (DC-LAMP) and CD8 T cell infiltration. Their correlations and prognostic impact were assessed. Cisplatin-resistant NSCLC cell clones isolated from Lewis-lung cancer (LLC) cells were evaluated for PAR levels by immunoblot. Parental (PARlow) and cisplatin-resistant (PARhigh) clones were subcutaneously injected into the flank of C57BL/6 mice. Tumors were harvested to evaluate their immune infiltration by flow cytometry.ResultsThe infiltration of tumors by CD8 T and DC-LAMP+ cells was associated with a favorable overall survival in patients with LACC (p=0.006 and p=0.008, respectively) and NSCLC (p<0.001 for both CD8 T and DC-LAMP cells). We observed a positive correlation between PDXK expression and the infiltration by DC-LAMP (R=0.44, p=0.02 in LACC, R=0.14, p=0.057 in NSCLC), and a negative correlation between PAR levels and CD8 T lymphocytes (R=−0.39, p=0.034 in LACC, R=−0.18, p=0.017 in NSCLC). PARP1 is constitutively hyperactivated in cisplatin-resistant LLC cells manifesting elevated intracellular levels of poly(ADP-ribosyl)ated proteins (PARhigh). Tumors formed by such cancer cells injected into immunocompetent mice were scarcely infiltrated by CD8 T (p=0.028) and antigen presenting cells (p=0.086).ConclusionsOncometabolic features can impact local immunosurveillance, providing new functional links between cisplatin resistance and therapeutic failure.
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| 9. |
- Leary, P., et al.
(författare)
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Interstitial carbon-hydrogen defects in silicon
- 1997
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Ingår i: Defects in semiconductors. - : Trans Tech Publications Inc.. ; , s. 265-270
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Konferensbidrag (refereegranskat)abstract
- Interstitial carbon, in contrast with substitutional carbon, forms defects with hydrogen which are both electrically active and stable to high temperatures. Ab initio cluster calculations show that the most primitive defect, CiH, diffuses very rapidly and is expected to complex with many other impurities notably C, H and O. We describe here the structure and properties of Ci,nHm defects where n and m are less than 3. The most stable defects of the type CiCsHm have very different structures when m = 0 and when m > 0. In the former case, the C-C bond is metastable and only C-Si-C bonds are formed. However in the second case, the presence of a H atom stabilises the C-C bond. These results are supported by experiment. We show that the vibrational modes of the Cs-CiH defect are close to those observed for the T-photoluminescent centre and this defect is passivated when complexed with a further H atom. This defect then provides the first example of a fully characterised carbon centre containing a C-C bond.
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| 10. |
- Charakida, M., et al.
(författare)
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Endothelial dysfunction in childhood infection
- 2005
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Ingår i: Circulation. - 1524-4539. ; 111:13, s. 1660-5
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Atherosclerosis begins in early life, and endothelial dysfunction is recognized as a key initiating event in the development of atherosclerosis. Although infection has been implicated in endothelial dysfunction and atherogenesis, the impact of acute common childhood infections on the vascular endothelium is unknown. METHODS AND RESULTS: We studied 600 children aged 10 years drawn from the Avon Longitudinal Study of Parents and Children. The children were divided into 3 groups: those with current acute infection (AI; n=135; 73 boys and 62 girls); a convalescent group with infection in the past 2 weeks (n=166; 78 boys and 88 girls), and a healthy control group (n=299; 131 boys and 168 girls). Endothelial function was determined in all subjects by high-resolution ultrasound to measure brachial artery flow-mediated dilation (FMD) and was expressed as the percentage change in diameter from baseline after reactive hyperemia. FMD was repeated in 40 children in the AI group and 50 in the control group after a mean interval of 1 year. FMD was lower in both the AI group (6.3+/-2.7%, mean+/-SD) and the convalescent group (8.1+/-3.1%) than in the control group (9.7+/-2.5%; P<0.001 for both). The observed differences in FMD remained after adjustment for potential confounding variables. At the repeat visit, FMD was unchanged in controls (P=0.85) but improved in the AI group (P<0.001). CONCLUSIONS: Acute infection in childhood is associated with impaired endothelium-dependent vasodilation. These findings support a potential role for previously unsuspected extrinsic inflammatory stimuli in the pathogenesis of early atherosclerosis.
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| 11. |
- Dawson, George J., et al.
(författare)
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Prevalence studies of GB virus-C infection using reverse transcriptase-polymerase chain reaction
- 1996
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Ingår i: Journal of Medical Virology. - 1096-9071. ; 50:1, s. 97-103
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Tidskriftsartikel (refereegranskat)abstract
- Among the three recently described GB viruses (GBV-A, GBV-B, and GBV-C), only GBV-C has been linked to cryptogenic hepatitis in man. Because of the limited utility of currently available research tests to determine antibody response to GBV-C proteins, the prevalence of GBV-C RNA in human sera was studied using reverse transcription-polymerase chain reaction (RT-PCR). The prevalence of GBV-C is higher among volunteer blood donors with elevated serum alanine aminotransferase (ALT) levels (3.9%) than among volunteer blood donors with normal ALT levels (0.8%). Higher rates were also noted among commercial blood donors (12.9%) and intravenous drug users (16.0%). GBV-C was frequently detected in residents of West Africa, where the prevalence was > 10% in most age groups. Approximately 20% of patients diagnosed with either acute or chronic hepatitis C virus (HCV) were found to be positive for GBV-C RNA. In addition, GBV-C RNA sequences were detected in individuals diagnosed with non-A-E hepatitis, with clinical courses ranging from mild disease to fulminant hepatitis. Fourteen of sixteen subjects with or without clinically apparent hepatitis were positive for GBV-C RNA more than 1 year after the initial positive result.
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| 12. |
- Hoffman, Lindsey M., et al.
(författare)
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Clinical, Radiologic, Pathologic, and Molecular Characteristics of Long-Term Survivors of Diffuse Intrinsic Pontine Glioma (DIPG) : A Collaborative Report From the International and European Society for Pediatric Oncology DIPG Registries
- 2018
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Ingår i: Journal of Clinical Oncology. - : AMER SOC CLINICAL ONCOLOGY. - 0732-183X .- 1527-7755. ; 36:19, s. 1963-1972
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Tidskriftsartikel (refereegranskat)abstract
- PurposeDiffuse intrinsic pontine glioma (DIPG) is a brainstem malignancy with a median survival of < 1 year. The International and European Society for Pediatric Oncology DIPG Registries collaborated to compare clinical, radiologic, and histomolecular characteristics between short-term survivors (STSs) and long-term survivors (LTSs).Materials and MethodsData abstracted from registry databases included patients from North America, Australia, Germany, Austria, Switzerland, the Netherlands, Italy, France, the United Kingdom, and Croatia.ResultsAmong 1,130 pediatric and young adults with radiographically confirmed DIPG, 122 (11%) were excluded. Of the 1,008 remaining patients, 101 (10%) were LTSs (survival 2 years). Median survival time was 11 months (interquartile range, 7.5 to 16 months), and 1-, 2-, 3-, 4-, and 5-year survival rates were 42.3% (95% CI, 38.1% to 44.1%), 9.6% (95% CI, 7.8% to 11.3%), 4.3% (95% CI, 3.2% to 5.8%), 3.2% (95% CI, 2.4% to 4.6%), and 2.2% (95% CI, 1.4% to 3.4%), respectively. LTSs, compared with STSs, more commonly presented at age < 3 or > 10 years (11% v 3% and 33% v 23%, respectively; P < .001) and with longer symptom duration (P < .001). STSs, compared with LTSs, more commonly presented with cranial nerve palsy (83% v 73%, respectively; P = .008), ring enhancement (38% v 23%, respectively; P = .007), necrosis (42% v 26%, respectively; P = .009), and extrapontine extension (92% v 86%, respectively; P = .04). LTSs more commonly received systemic therapy at diagnosis (88% v 75% for STSs; P = .005). Biopsies and autopsies were performed in 299 patients (30%) and 77 patients (10%), respectively; 181 tumors (48%) were molecularly characterized. LTSs were more likely to harbor a HIST1H3B mutation (odds ratio, 1.28; 95% CI, 1.1 to 1.5; P = .002).ConclusionWe report clinical, radiologic, and molecular factors that correlate with survival in children and young adults with DIPG, which are important for risk stratification in future clinical trials.
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| 13. |
- Hoffmann, L., et al.
(författare)
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Substitutional carbon in Ge and Si1-xGex
- 1997
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Ingår i: Defects in semiconductors. - : Trans Tech Publications Inc.. ; , s. 97-102
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Konferensbidrag (refereegranskat)abstract
- In the present work, carbon is implanted into monocrystalline Ge and into relaxed epitaxial MBE-grown Si1-xGex. The samples are studied with infrared absorption spectroscopy along with ion-channeling studies on the Ge samples. Finally, ab-initio local density functional cluster theory is applied to calculate the structure and the local vibrational modes of substitutional carbon, Cs, in Ge. After implantation of 12C+ in Ge at room temperature and subsequent annealing at 350°C, a sharp absorption line is observed at 531 cm-1. By isotope substitution, it is concluded that the 531 cm-1 line represents a local vibrational mode of a single carbon atom. From ion-channeling measurements on samples annealed at 450°C, it is found that 31±3 % of the carbon atoms are located at substitutional sites. The population of the substitutional site and the intensity of the 531 cm-1 mode have identical annealing behavior and it is concluded that the 531 cm-1 mode is the three-dimensional T2 stretch mode of Cs in Ge. The calculated frequency and isotope shift for this mode are in good agreement with the observations. In Si0.65Ge0.35, two broad absorption lines are observed at ∼551 and ∼592 cm-1 after implantation of 12C+ and subsequent annealing at 550°C. From measurements on samples implanted with 13C+ and coimplanted with 12C+ and 13C+ we conclude that these lines represent local vibrational modes of defects containing a single carbon atom. In 13C+ implanted Si1-xGex samples that contain 15 to 50 % Ge a number of modes are observed in a frequency range from ∼510 to ∼610 cm-1, i.e., in the range of Cs in Ge and in Si. From the experimental findings it is concluded that substitutional carbon in Si1-xGex binds to both Si and Ge.
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| 14. |
- Hoffmann, L., et al.
(författare)
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Substitutional carbon in germanium
- 1997
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 55:17, s. 11167-11173
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Tidskriftsartikel (refereegranskat)abstract
- Carbon impurities implanted into single-crystalline germanium are studied with infrared absorption spectroscopy and ion channeling. After implantation of 12C+ at room temperature and subsequent annealing at 350 °C, a sharp infrared absorption line is observed at 531 cm-1. When 12C+ is substituted by 13C+, the line shifts down in frequency to 512 cm-1 and co-implantation of 12C+ and 13C+ does not give rise to additional lines. Therefore, the 531-cm-1 line represents a local vibrational mode of a defect containing a single carbon atom. Channeling measurements are carried out around the 〈100〉, 〈110〉, and 〈111〉 axes in 12C+-implanted samples annealed at 450 °C. The analysis of the data shows that 31±3 % of the carbon atoms are located at substitutional sites, while the remaining carbon atoms appear to be located randomly. The population of the substitutional site and the intensity of the 531-cm-1 mode have identical temperature dependencies. It is concluded that the 531-cm-1 mode is the three-dimensional T2 stretch mode of substitutional carbon. The effective charge of the mode is determined to be (3.4±0.5)e.mAb initio local density functional cluster theory is applied to calculate the structure and the local vibrational modes of substitutional carbon in germanium. The calculated frequencies and isotope shifts for the T2 stretch mode are in good agreement with the observations.
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| 15. |
- Hughes, C, et al.
(författare)
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An evaluation of current services available for people diagnosed with head and neck cancer in the UK (2009-2010).
- 2012
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Ingår i: Clinical Oncology. - 0936-6555 .- 1433-2981. ; 24:10, s. e187-92
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: To evaluate current care and service provision for people with head and neck cancer in the UK.MATERIALS AND METHODS: Self-report questionnaires for cancer networks, clinical leads of oncology units and leads for multidisciplinary teams (MDTs) were designed. These questionnaires were based on a previous survey. Questionnaires were sent out between 2009 and 2010.RESULTS: Questionnaires were received from all networks (n = 37), most oncology units (48 of 53) and most MDTs (51 of 63). Care for people with head and neck cancer is increasingly being provided by a centralised MDT. The membership of these teams varies; facilities available for team meetings are fit for purpose in most cases. MDTs are meeting frequently (weekly meetings in 96%) and discussing on average 18 cases at each meeting (95% confidence interval 15-21 cases). Most oncologists have access to all common anti-cancer drugs and most have access to all forms of radiotherapy. Intensity-modulated radiotherapy is not yet available in some oncology units (28%). A small number of units have only one oncologist (13%). Despite audit and research being part of the rationale for MDT working, regular discussion of morbidity and mortality is unusual (40%) and use of a database to record decisions is not universal. Only seven centres record decisions into the Data for Head and Neck Oncology database. Reported recruitment to studies is generally low (<2% of cases enrolled in studies in 62%).CONCLUSIONS: Head and neck cancer care is increasingly provided through a centralised MDT. Increased resources and further changes in practice are required to implement current National Health Service cancer policy. Teams need to improve recording of their decision-making, discuss morbidity and mortality and support recruitment to clinical studies.
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| 16. |
- Johnson, Katherine, et al.
(författare)
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Increased serum miR-193a-5p during non-alcoholic fatty liver disease progression : Diagnostic and mechanistic relevance
- 2022
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Ingår i: JHEP Reports. - : Elsevier. - 2589-5559. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- Background & Aims: Serum microRNA (miRNA) levels are known to change in non-alcoholic fatty liver disease (NAFLD) and may serve as useful biomarkers. This study aimed to profile miRNAs comprehensively at all NAFLD stages.Methods: We profiled 2,083 serum miRNAs in a discovery cohort (183 cases with NAFLD representing the complete NAFLD spectrum and 10 population controls). miRNA libraries generated by HTG EdgeSeq were sequenced by Illumina NextSeq. Selected serum miRNAs were profiled in 372 additional cases with NAFLD and 15 population controls by quantitative reverse transcriptase PCR.Results: Levels of 275 miRNAs differed between cases and population controls. Fewer differences were seen within individual NAFLD stages, but miR-193a-5p consistently showed increased levels in all comparisons. Relative to NAFL/non-alcoholic steatohepatitis (NASH) with mild fibrosis (stage 0/1), 3 miRNAs (miR-193a-5p, miR-378d, and miR378d) were increased in cases with NASH and clinically significant fibrosis (stages 2-4), 7 (miR193a-5p, miR-378d, miR-378e, miR-320b, miR-320c, miR-320d, and miR-320e) increased in cases with NAFLD activity score (NAS) 5-8 compared with lower NAS, and 3 (miR-193a-5p, miR-378d, and miR-378e) increased but 1 (miR-19b-3p) decreased in steatosis, activity, and fibrosis (SAF) activity score 2-4 compared with lower SAF activity. The significant findings for miR-193a-5p were replicated in the additional cohort with NAFLD. Studies in Hep G2 cells showed that following palmitic acid treatment, miR-193a-5p expression decreased significantly. Gene targets for miR-193a-5p were investigated in liver RNAseq data for a case subgroup (n = 80); liver GPX8 levels correlated positively with serum miR-193a-5p.Conclusions: Serum miR-193a-5p levels correlate strongly with NAFLD activity grade and fibrosis stage. MiR-193a-5p may have a role in the hepatic response to oxidative stress and is a potential clinically tractable circulating biomarker for progressive NAFLD.Lay summary: MicroRNAs (miRNAs) are small pieces of nucleic acid that may turn expression of genes on or off. These molecules can be detected in the blood circulation, and their levels in blood may change in liver disease including non-alcoholic fatty liver disease (NAFLD). To see if we could detect specific miRNA associated with advanced stages of NAFLD, we carried out miRNA sequencing in a group of 183 patients with NAFLD of varying severity together with 10 population controls. We found that a number of miRNAs showed changes, mainly increases, in serum levels but that 1 particular miRNA miR-193a-5p consistently increased. We confirmed this increase in a second group of cases with NAFLD. Measuring this miRNA in a blood sample may be a useful way to determine whether a patient has advanced NAFLD without an invasive liver biopsy.
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| 17. |
- Leary, P, et al.
(författare)
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Dynamic properties of interstitial carbon and carbon-carbon pair defects in silicon
- 1997
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 55:4, s. 2188-2194
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Tidskriftsartikel (refereegranskat)abstract
- Interstitial carbon, Ci, defects in Si exhibit a number of unexplained features. The Ci defect in the neutral charge state gives rise to two almost degenerate vibrational modes at 920 and 931 cm-1 whose 2:1 absorption intensity ratio naturally suggests a trigonal defect in conflict with uniaxial stress measurements. The dicarbon, Cs-Ci, defect is bistable, and the energy difference between its A and B forms is surprisingly small even though the bonding is very different. In the B form appropriate to the neutral charge state, a silicon interstitial is believed to be located near a bond-centered site between two Cs atoms. This must give rise to vibrational modes which involve the motion of both C atoms in apparent conflict with the results of photoluminescence experiments. We use an ab initio local density functional cluster method, AIMPRO, to calculate the structure and vibrational modes of these defects and find that the ratio of the absorption intensities of the local modes of Ci is in reasonable agreement with experiment even though the structure of the defect is not trigonal. We also show that modes in the vicinity of those detected by photoluminescence for the B form of the dicarbon center involve independent movements of the two C atoms. Finally, the trends in the relative energies of the A and B forms in three charge states are investigated.
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| 18. |
- Leary, P., et al.
(författare)
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Interaction of hydrogen with substitutional and interstitial carbon defects in silicon
- 1998
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 57:7, s. 3887-3889
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Tidskriftsartikel (refereegranskat)abstract
- An ab initio cluster method is used to investigate substitutional, Cs, and interstitial, Ci, carbon defects in silicon complexed with hydrogen. We find that the binding energy of neutral H with Cs is 1.01 eV, and that the defect is bistable. In the positive and neutral charge states H lies near the center of a C-Si bond, and is antibonded to C in the negative charge state. A second H atom can be trapped in a H2* defect. H forms stronger bonds with interstitial Ci. In the Ci-H defect, the binding energy of H is 2.8 eV, and two low-energy structures have almost degenerate energies. These consist of a bond-centered Si-(Ci-H)-Si defect and a 〈100〉-oriented Ci-Si split interstitial with H bonded to Ci. The calculated barrier for conversion between the two stable structures is very low, ∼0.3 eV, implying that the defect migrates rapidly, and readily reacts with other defects or impurities present. Two possible reactions are considered: the first is with another H and the second with Cs. The defect is completely passivated in the former while the stable form of the latter consists of a 〈100〉 C-C dicarbon interstitial, where one radical is passivated by H. The calculated symmetry and the local vibrational modes are in excellent agreement with those experimentally observed for the T photoluminescent center. Finally, a further reaction involving the T center and a second H atom is considered, and is found to lead to the elimination of electrical activity.
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| 19. |
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| 20. |
- Safonov, A N, et al.
(författare)
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Interstitial-carbon hydrogen interaction in silicon
- 1996
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 77:23, s. 4812-4815
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Tidskriftsartikel (refereegranskat)abstract
- The T-line luminescence system is created in Si by annealing at 400-600 °C. Shifts and splitting of the spectral features with 13C and D isotope substitution identify the presence of two C atoms and one H atom in the center. Uniaxial stress and magnetic field measurements show that the T center has monoclinic I symmetry and possesses an acceptor ( -/0) level at 0.2 eV below the conduction band. Ab initio cluster calculations lead to a structure in which an interstitial C-H defect binds with a substitutional C atom. The calculated vibrational modes are in good agreement with those observed.
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| 21. |
- Toreti, A, et al.
(författare)
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Narrowing uncertainties in the effects of elevated CO2 on crops
- 2020
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Ingår i: Nature Food. - : Springer Science and Business Media LLC. - 2662-1355. ; 1, s. 775-782
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Tidskriftsartikel (refereegranskat)abstract
- Plant responses to rising atmospheric carbon dioxide (CO2) concentrations, together with projected variations in temperature and precipitation will determine future agricultural production. Estimates of the impacts of climate change on agriculture provide essential information to design effective adaptation strategies, and develop sustainable food systems. Here, we review the current experimental evidence and crop models on the effects of elevated CO2 concentrations. Recent concerted efforts have narrowed the uncertainties in CO2-induced crop responses so that climate change impact simulations omitting CO2 can now be eliminated. To address remaining knowledge gaps and uncertainties in estimating the effects of elevated CO2 and climate change on crops, future research should expand experiments on more crop species under a wider range of growing conditions, improve the representation of responses to climate extremes in crop models, and simulate additional crop physiological processes related to nutritional quality.
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| 22. |
- Wood, Laura D, et al.
(författare)
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The genomic landscapes of human breast and colorectal cancers.
- 2007
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 318:5853, s. 1108-1113
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Tidskriftsartikel (refereegranskat)abstract
- Human cancer is caused by the accumulation of mutations in oncogenes and tumor suppressor genes. To catalog the genetic changes that occur during tumorigenesis, we isolated DNA from 11 breast and 11 colorectal tumors and determined the sequences of the genes in the Reference Sequence database in these samples. Based on analysis of exons representing 20,857 transcripts from 18,191 genes, we conclude that the genomic landscapes of breast and colorectal cancers are composed of a handful of commonly mutated gene "mountains" and a much larger number of gene "hills" that are mutated at low frequency. We describe statistical and bioinformatic tools that may help identify mutations with a role in tumorigenesis. These results have implications for understanding the nature and heterogeneity of human cancers and for using personal genomics for tumor diagnosis and therapy.
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