| 1. |
- Blumenau, A.T., et al.
(författare)
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The effect of charge on kink migration at 90° partial dislocations in SiC
- 2005
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 202:5, s. 877-882
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Tidskriftsartikel (refereegranskat)abstract
- SiC bipolar devices show a degradation under forward-biased operation which has been linked with a recombination enhanced motion of one of the two glide dislocations having either Si or C core atoms. We have carried out calculations of the core structures and dynamics of partial dislocations in 3C and 2H-SiC using the density functional based codes DFTB and AIMPRO. After in earlier theoretical work we reported on the structure, energetics and electronic activity of both of the Shockley partials, and on the formation and migration barriers of kinks, in this work we present first results on the effect of charge on the disloction kinks. The calculations give insights into the device degradation mechanism.
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| 2. |
- Goss, J.P., et al.
(författare)
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Planar interstitial aggregates in Si
- 2002
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 14:48, s. 12843-12853
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Tidskriftsartikel (refereegranskat)abstract
- Self-interstitials in silicon aggregate to form rod-like defects aligned along [110] directions and inhabiting either {111} or {113} crystallographic planes. These systems are known to be electrically and optically active. We present the results of first-principles calculations on the structure and energetics for candidate structures contained within the {113}, {111} and {001} planes and compare the results with experiment.
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| 3. |
- Strosberg, J., et al.
(författare)
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Phase 3 Trial of Lu-177-Dotatate for Midgut Neuroendocrine Tumors
- 2017
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Ingår i: New England Journal of Medicine. - 0028-4793 .- 1533-4406. ; 376:2, s. 125-135
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND Patients with advanced midgut neuroendocrine tumors who have had disease progression during first-line somatostatin analogue therapy have limited therapeutic options. This randomized, controlled trial evaluated the efficacy and safety of lutetium-177 (Lu-177)-Dotatate in patients with advanced, progressive, somatostatin-receptor-positive midgut neuroendocrine tumors. METHODS We randomly assigned 229 patients who had well-differentiated, metastatic midgut neuroendocrine tumors to receive either Lu-177-Dotatate (116 patients) at a dose of 7.4 GBq every 8 weeks (four intravenous infusions, plus best supportive care including octreotide long-acting repeatable [LAR] administered intramuscularly at a dose of 30 mg) (Lu-177-Dotatate group) or octreotide LAR alone (113 patients) administered intramuscularly at a dose of 60 mg every 4 weeks (control group). The primary end point was progression-free survival. Secondary end points included the objective response rate, overall survival, safety, and the side-effect profile. The final analysis of overall survival will be conducted in the future as specified in the protocol; a prespecified interim analysis of overall survival was conducted and is reported here. RESULTS At the data-cutoff date for the primary analysis, the estimated rate of progression-free survival at month 20 was 65.2% (95% confidence interval [CI], 50.0 to 76.8) in the Lu-177-Dotatate group and 10.8% (95% CI, 3.5 to 23.0) in the control group. The response rate was 18% in the Lu-177-Dotatate group versus 3% in the control group (P<0.001). In the planned interim analysis of overall survival, 14 deaths occurred in the Lu-177-Dotatate group and 26 in the control group (P = 0.004). Grade 3 or 4 neutropenia, thrombocytopenia, and lymphopenia occurred in 1%, 2%, and 9%, respectively, of patients in the Lu-177-Dotatate group as compared with no patients in the control group, with no evidence of renal toxic effects during the observed time frame. CONCLUSIONS Treatment with Lu-177-Dotatate resulted in markedly longer progression-free survival and a significantly higher response rate than high-dose octreotide LAR among patients with advanced midgut neuroendocrine tumors. Preliminary evidence of an overall survival benefit was seen in an interim analysis; confirmation will be required in the planned final analysis. Clinically significant myelosuppression occurred in less than 10% of patients in the Lu-177-Dotatate group. (Funded by Advanced Accelerator Applications; NETTER-1 ClinicalTrials. gov number, NCT01578239; EudraCT number 2011-005049-11.)
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| 4. |
- Ashwin, M.J., et al.
(författare)
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The bonding of CAs acceptors in InxGa1-xAs grown by chemical beam epitaxy using carbon tetrabromide as the source of carbon
- 1996
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 80:12, s. 6754-6760
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Tidskriftsartikel (refereegranskat)abstract
- InxGa1-xAs layers (0≤x≤0.37) doped with carbon (>1020 cm-3) were grown on semi-insulating GaAs substrates by chemical beam epitaxy using carbon tetrabromide (CBr4) as the dopant source. Hall measurements imply that all of the carbon was present as CAs for values x up to 0.15. The C acceptors were passivated by exposing samples to a radio frequency hydrogen plasma for periods of up to 6 h. The nearest-neighbor bonding configurations of CAs were investigated by studying the nondegenerate antisymmetric hydrogen stretch mode (A-1 symmetry) and the symmetric XH mode (A+1 symmetry) of the H-CAs pairs using IR absorption and Raman scattering, respectively. Observed modes at 2635 and 450 cm-1 had been assigned to passivated Ga4CAs clusters. New modes at 2550 and 430 cm-1 increased in strength with increasing values of x and are assigned to passivated InGa3CAs clusters. These results were compared with ab initio local density functional theory. Modes due to AlInGaCAs clusters were detected in samples containing grown in Al and In. These results demonstrate that for InGaAs, CBr4 is an efficient C doping source since both In-CAs bonds as well as Ga-CAs bonds are formed, whereas there is no evidence for the formation of In-CAs bonds in samples doped with C derived from trimethylgallium or solid sources
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| 5. |
- Beye, M., et al.
(författare)
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Selective Ultrafast Probing of Transient Hot Chemisorbed and Precursor States of CO on Ru(0001)
- 2013
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 110:18
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the femtosecond dynamics following optical laser excitation of CO adsorbed on a Ru surface by monitoring changes in the occupied and unoccupied electronic structure using ultrafast soft x-ray absorption and emission. We recently reported [M. Dell'Angela et al. Science 339, 1302 (2013)] a phonon-mediated transition into a weakly adsorbed precursor state occurring on a time scale of >2 ps prior to desorption. Here we focus on processes within the first picosecond after laser excitation and show that the metal-adsorbate coordination is initially increased due to hot-electron-driven vibrational excitations. This process is faster than, but occurs in parallel with, the transition into the precursor state. With resonant x-ray emission spectroscopy, we probe each of these states selectively and determine the respective transient populations depending on optical laser fluence. Ab initio molecular dynamics simulations of CO adsorbed on Ru(0001) were performed at 1500 and 3000 K providing insight into the desorption process.
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| 6. |
- Blumenau, A.T., et al.
(författare)
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Basal plane partial dislocations in silicon carbide
- 2003
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 340, s. 160-164
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Tidskriftsartikel (refereegranskat)abstract
- Under operating conditions (forward bias) bipolar 4H- and 6H-SiC devices are known to degrade rapidly through stacking fault formation and expansion in the basal plane. It has been suggested that a recombination-enhanced dislocation glide (REDG) mechanism allows the bordering Shockley partial dislocations to overcome their barrier to glide motion and thus results in the observed stacking fault growth. In this work, we investigate the structure and properties of the participating Shockley partials by means of density functional-based atomistic calculations. Their glide motion is modelled in a process involving the formation and subsequent migration of kinks. This in combination with an analysis of the electronic structure of the partials allows an identification of those types which will be affected by the REDG mechanism.
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| 7. |
- Blumenau, A.T., et al.
(författare)
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Density functional based modelling of 30° partial dislocations in SiC
- 2004
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Ingår i: Proceedings of the 10th International Conference on Silicon Carbide and Related Materials, ICSCRM 2003. - Stafa-Zuerich : Trans Tech Publications Inc.. - 0878499431 ; , s. 453-456
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Konferensbidrag (refereegranskat)abstract
- Experiment has shown that 4H- and 6H-SiC pin diodes degrade rapidly during forward biased operation. This degradation is accompanied by the formation and expansion of stacking faults in the basal plane. It is believed that the observed rapid stacking fault growth is due to a recombination-enhanced dislocation glide (REDG) mechanism at the bordering partial dislocations. In our work we investigate the structure and properties of basal plane 30° Shockley partials in SiC by means of density functional based calculations. Barriers to their glide motion, and thus the expansion of the accompanying stacking fault is modelled in a process involving the formation and subsequent migration of kinks in the dislocation. In combination with an analysis of the electronic structure of the partials and stacking faults, this allows an identification of those types of partials which will be affected by the REDG mechanism in this model.
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| 8. |
- Blumenau, A. T., et al.
(författare)
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Dislocation related photoluminescence in silicon
- 2001
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 87:18
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Tidskriftsartikel (refereegranskat)abstract
- Dislocation related photoluminescence in Si and SiGe is attributed to stable interstitial clusters bound to 60° dislocations. Density functional based total energy calculations in Si give binding energies between 1.5 and 3.6 eV for I3 and I4 clusters with 90° and 30° partials. They possess donor levels around Ev+0.4 eV which are consistent with deep level transient spectroscopic studies on p-Si. It is further suggested that the clusters would act as the obstacles to the movement of dislocations which may have been observed in recent transmission electron microscopy studies.
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| 9. |
- Blumenau, A.T., et al.
(författare)
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Dislocations in hexagonal and cubic GaN
- 2000
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 12, s. 10223-10233
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Tidskriftsartikel (refereegranskat)abstract
- The structure and electronic activity of several types of dislocations in both hexagonal and cubic GaN are calculated using first-principles methods. Most of the stoichiometric dislocations investigated in hexagonal GaN do not induce deep acceptor states and thus cannot be responsible for the yellow luminescence. However, it is shown that electrically active point defects, in particular gallium vacancies and oxygen-related defect complexes, can be trapped at the stress field of the dislocations and may be responsible for this luminescence. For cubic GaN, we find the ideal stoichiometric 60° dislocation to be electrically active and the glide set to be more stable than the shuffle. The dissociation of the latter is considered
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| 10. |
- Blumenau, A.T., et al.
(författare)
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Optical bands related to dislocations in Si
- 2000
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 12:49, s. 10123-10129
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Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations are used to investigate the interaction of self-interstitial aggregates with the 90° partial dislocation in Si. We find that I4 is bound to the line with an energy of around 3 eV. The defect causes deep levels to appear in the band gap and optical transitions between these levels may account for the luminescent bands relating to plastically deformed Si.
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| 11. |
- Blumenau, A.T., et al.
(författare)
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Straight and kinked 90° partial dislocations in diamond and 3C-SiC
- 2002
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 14:48, s. 12741-12747
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Tidskriftsartikel (refereegranskat)abstract
- Density-functional based calculations are used to investigate low energy core structures of 90° partial dislocations in diamond and 3C-SiC. In both materials dislocation glide is analysed in terms of kink formation and migration and the fundamental steps to kink migration are investigated. We find the C terminated core structure in SiC to be more mobile than the Si core. However, the Si partial is electrically active and this opens the possibility of recombination-enhanced glide under ionizing conditions or an enhanced mobility in doped material.
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| 12. |
- Blumenau, A.T., et al.
(författare)
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Structure and motion of basal dislocations in silicon carbide
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 68:17, s. 174108-1
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Tidskriftsartikel (refereegranskat)abstract
- 30° and 90° Shockley partial dislocations lying in {111} and basal planes of cubic and hexagonal silicon carbide, respectively, are investigated theoretically. Density-functional-based tight-binding total-energy calculations are used to determine the core structure and energetics of the dislocations. In a second step their electronic structure is investigated using a pseudopotential method with a Gaussian basis set. Finally, the thermal activation barriers to glide motion of 30° and 90° Shockley partials are calculated in terms of a process involving the formation and migration of kinks along the dislocation line. The mechanism for enhanced dislocation movement observed under current injection conditions in bipolar silicon carbide devices is discussed.
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| 13. |
- Coutens, A., et al.
(författare)
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The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid in the interstellar medium
- 2016
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 590
-
Tidskriftsartikel (refereegranskat)abstract
- Formamide (NH2CHO) has previously been detected in several star-forming regions and is thought to be a precursor for different prebiotic molecules. Its formation mechanism is still debated, however. Observations of formamide, related species, and their isopotologues may provide useful clues to the chemical pathways leading to their formation. The Protostellar Interferometric Line Survey (PILS) represents an unbiased, high angular resolution and sensitivity spectral survey of the low-mass protostellar binary IRAS 16293-2422 with the Atacama Large Millimeter/submillimeter Array (ALMA). For the first time, we detect the three singly deuterated forms of NH2CHO (NH2CDO, cis-and trans-NHDCHO), as well as DNCO towards the component B of this binary source. The images reveal that the different isotopologues are all present in the same region. Based on observations of the 13C isotopologues of formamide and a standard 12C/13C ratio, the deuterium fractionation is found to be similar for the three different forms with a value of about 2%. The DNCO/HNCO ratio is also comparable to the D/H ratio of formamide (~1%). These results are in agreement with the hypothesis that NH2CHO and HNCO are chemically related through grain-surface formation.
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| 14. |
- Dell'Angela, M., et al.
(författare)
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Real-Time Observation of Surface Bond Breaking with an X-ray Laser
- 2013
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 339:6125, s. 1302-1305
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Tidskriftsartikel (refereegranskat)abstract
- We used the Linac Coherent Light Source free-electron x-ray laser to probe the electronic structure of CO molecules as their chemisorption state on Ru(0001) changes upon exciting the substrate by using a femtosecond optical laser pulse. We observed electronic structure changes that are consistent with a weakening of the CO interaction with the substrate but without notable desorption. A large fraction of the molecules (30%) was trapped in a transient precursor state that would precede desorption. We calculated the free energy of the molecule as a function of the desorption reaction coordinate using density functional theory, including van der Waals interactions. Two distinct adsorption wells-chemisorbed and precursor state separated by an entropy barrier-explain the anomalously high prefactors often observed in desorption of molecules from metals.
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| 15. |
- Drakvik, E., et al.
(författare)
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Statement on advancing the assessment of chemical mixtures and their risks for human health and the environment
- 2020
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Ingår i: Environment International. - : Elsevier BV. - 0160-4120 .- 1873-6750. ; 134
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Tidskriftsartikel (refereegranskat)abstract
- The number of anthropogenic chemicals, manufactured, by-products, metabolites and abiotically formed transformation products, counts to hundreds of thousands, at present. Thus, humans and wildlife are exposed to complex mixtures, never one chemical at a time and rarely with only one dominating effect. Hence there is an urgent need to develop strategies on how exposure to multiple hazardous chemicals and the combination of their effects can be assessed. A workshop, “Advancing the Assessment of Chemical Mixtures and their Risks for Human Health and the Environment” was organized in May 2018 together with Joint Research Center in Ispra, EU-funded research projects and Commission Services and relevant EU agencies. This forum for researchers and policy-makers was created to discuss and identify gaps in risk assessment and governance of chemical mixtures as well as to discuss state of the art science and future research needs. Based on the presentations and discussions at this workshop we want to bring forward the following Key Messages: • We are at a turning point: multiple exposures and their combined effects require better management to protect public health and the environment from hazardous chemical mixtures. • Regulatory initiatives should be launched to investigate the opportunities for all relevant regulatory frameworks to include prospective mixture risk assessment and consider combined exposures to (real-life) chemical mixtures to humans and wildlife, across sectors. • Precautionary approaches and intermediate measures (e.g. Mixture Assessment Factor) can already be applied, although, definitive mixture risk assessments cannot be routinely conducted due to significant knowledge and data gaps. • A European strategy needs to be set, through stakeholder engagement, for the governance of combined exposure to multiple chemicals and mixtures. The strategy would include research aimed at scientific advancement in mechanistic understanding and modelling techniques, as well as research to address regulatory and policy needs. Without such a clear strategy, specific objectives and common priorities, research, and policies to address mixtures will likely remain scattered and insufficient. © 2019 The Authors
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| 16. |
- Eberlein, T.A.G., et al.
(författare)
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Effect of charge on the movement of dislocations in SiC
- 2006
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 88:8, s. 82113-
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Tidskriftsartikel (refereegranskat)abstract
- SiC bipolar devices show a degradation under forward-biased operation which has been linked with a current induced motion of one of the two glide dislocations having either Si or C core atoms. We have carried out calculations of the core structures and dynamics of partial dislocations in 3C and 2H-SiC. In this work we present results on the effect of charge on the dislocation kinks. The calculations show that silicon kinks have a deep filled band above the valence band and the trapping of holes into this band permits motion at room temperature.
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| 17. |
- Eberlein, T.A.G., et al.
(författare)
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Movement and pinning of dislocations in SiC
- 2007
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Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - : Wiley. - 1610-1634 .- 1610-1642. ; 4:8, s. 2923-2928
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Tidskriftsartikel (refereegranskat)abstract
- SiC bipolar devices show a degradation under forward-biased operation due to the formation and rapid propagation of stacking faults in the active region of the device. It is believed that the observed rapid stacking fault growth is due to a recombination-enhanced dislocation glide (REDG) mechanism at the bordering partial dislocations having either Si or C core atoms. We investigated the effect of charge on the dislocation kinks and found that only silicon kinks have a deep filled band above the valence band. Trapping of holes into this band permits dislocation glide at room temperature. This mechanism is distinct from REDG as it requires only holes to be trapped at a Si partial and not in addition electrons in stacking fault states. We furthermore looked at the pinning of dislocations by nitrogen and boron and found a strong pinning of the C core by N and of the Si core by B.
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| 18. |
- Fayolle, E. C., et al.
(författare)
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Protostellar and cometary detections of organohalogens
- 2017
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Ingår i: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 1:10, s. 703-708
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Tidskriftsartikel (refereegranskat)abstract
- Organohalogens, a class of molecules that contain at least one halogen atom bonded to carbon, are abundant on the Earth where they are mainly produced through industrial and biological processes(1). Consequently, they have been proposed as biomarkers in the search for life on exoplanets(2). Simple halogen hydrides have been detected in interstellar sources and in comets, but the presence and possible incorporation of more complex halogen-containing molecules such as organohalogens into planet-forming regions is uncertain(3,4). Here we report the interstellar detection of two isotopologues of the organohalogen CH3Cl and put some constraints on CH3F in the gas surrounding the low-mass protostar IRAS 16293-2422, using the Atacama Large Millimeter/submillimeter Array (ALMA). We also find CH3Cl in the coma of comet 67P/Churyumov-Gerasimenko (67P/C-G) by using the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument. The detections reveal an efficient pre-planetary formation pathway of organohalogens. Cometary impacts may deliver these species to young planets and should thus be included as a potential abiotical production source when interpreting future organohalogen detections in atmospheres of rocky planets.
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| 19. |
- Goss, J.P., et al.
(författare)
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Electrical and optical properties of rod-like defects in silicon
- 2004
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 85:20, s. 4633-4635
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Tidskriftsartikel (refereegranskat)abstract
- Self-interstitials in silicon can aggregate to form rod-like defects (RLDs) having both electrical and optical activity. We carry out local density functional calculations for both {113} and {111} RLDs to determine their structures and electrical activity. We find that small {113} RLDs are more stable than {111} RLDs but this reverses for larger defects. We attribute the electrical activity of {113} RLDs found in deep level transient spectroscopy studies with the bounding dislocations and the 0.903 eV photoluminescence to vacancy point defects lying on the habit plane.
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| 20. |
- Itel, F., et al.
(författare)
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CO2 permeability of cell membranes is regulated by membrane cholesterol and protein gas channels
- 2012
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Ingår i: Faseb Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 26:12, s. 5182-5191
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Tidskriftsartikel (refereegranskat)abstract
- Recent observations that some membrane proteins act as gas channels seem surprising in view of the classical concept that membranes generally are highly permeable to gases. Here, we study the gas permeability of membranes for the case of CO2, using a previously established mass spectrometric technique. We first show that biological membranes lacking protein gas channels but containing normal amounts of cholesterol (30-50 mol% of total lipid), e.g., MDCK and tsA201 cells, in fact possess an unexpectedly low CO2 permeability (PCO2) of similar to 0.01 cm/s, which is 2 orders of magnitude lower than the PCO2 of pure planar phospholipid bilayers (similar to 1 cm/s). Phospholipid vesicles enriched with similar amounts of cholesterol also exhibit PCO2 approximate to 0.01 cm/s, identifying cholesterol as the major determinant of membrane PCO2. This is confirmed by the demonstration that MDCK cells depleted of or enriched with membrane cholesterol show dramatic increases or decreases in PCO2, respectively. We demonstrate, furthermore, that reconstitution of human AQP-1 into cholesterol-containing vesicles, as well as expression of human AQP-1 in MDCK cells, leads to drastic increases in PCO2, indicating that gas channels are of high functional significance for gas transfer across membranes of low intrinsic gas permeability.-Itel, F., Al-Samir, S., Oberg, F., Chami, M., Kumar, M., Supuran, C. T., Deen, P. M. T., Meier, W., Hedfalk, K., Gros, G., Endeward, V. CO2 permeability of cell membranes is regulated by membrane cholesterol and protein gas channels. FASEB J. 26, 5182-5191 (2012). www.fasebj.org
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| 21. |
- Jorgensen, J. K., et al.
(författare)
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The ALMA Protostellar Interferometric Line Survey (PILS) First results from an unbiased submillimeter wavelength line survey of the Class 0 protostellar binary IRAS 16293-2422 with ALMA
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 595, s. Art no A117-
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Tidskriftsartikel (refereegranskat)abstract
- Context. The inner regions of the envelopes surrounding young protostars are characterized by a complex chemistry, with prebiotic molecules present on the scales where protoplanetary disks eventually may form. The Atacama Large Millimeter/submillimeter Array (ALMA) provides an unprecedented view of these regions zooming in on solar system scales of nearby protostars and mapping the emission from rare species. Aims. The goal is to introduce a systematic survey, the Protostellar Interferometric Line Survey (PILS), of the chemical complexity of one of the nearby astrochemical templates, the Class 0 protostellar binary IRAS 16293 2422, using ALMA in order to understand the origin of the complex molecules formed in its vicinity. In addition to presenting the overall survey, the analysis in this paper focuses on new results for the prebiotic molecule glycolaldehyde, its isomers, and rarer isotopologues and other related molecules. Methods. An unbiased spectral survey of IRAS 16293 2422 covering the full frequency range from 329 to 363 GHz (0.8 mm) has been obtained with ALMA, in addition to a few targeted observations at 3.0 and 1.3 mm. The data consist of full maps of the protostellar binary system with an angular resolution of 0.5 '' (60 AU diameter), a spectral resolution of 0.2 km s(-1), and a sensitivity of 4-5 mJy beam(-1) km s(-1), which is approximately two orders of magnitude better than any previous studies. Results. More than 10 000 features are detected toward one component in the protostellar binary, corresponding to an average line density of approximately one line per 3 km s(-1). Glycolaldehyde; its isomers, methyl formate and acetic acid; and its reduced alcohol, ethylene glycol, are clearly detected and their emission well-modeled with an excitation temperature of 300 K. For ethylene glycol both lowest state conformers, aGg' and gGg', are detected, the latter for the first time in the interstellar medium (ISM). The abundance of glycolaldehyde is comparable to or slightly larger than that of ethylene glycol. In comparison to the Galactic Center these two species are over-abundant relative to methanol, possibly an indication of formation of the species at low temperatures in CO-rich ices during the infall of the material toward the central protostar. Both C-13 and the deuterated isotopologues of glycolaldehyde are detected, also for the first time ever in the ISM. For the deuterated species, a D/H ratio of approximate to 5% is found with no differences between the deuteration in the different functional groups of glycolaldehyde, in contrast to previous estimates for methanol and recent suggestions of significant equilibration between water and-OH functional groups at high temperatures. Measurements of the C-13-species lead to a C-12:C-13 ratio of approximate to 30, lower than the typical ISM value. This low ratio may reflect an enhancement of (CO)-C-13 in the ice due to either ion-molecule reactions in the gas before freeze-out or to differences in the temperatures where (CO)-C-12 and (CO)-C-13 ices sublimate. Conclusions. The results reinforce the importance of low-temperature grain surface chemistry for the formation of prebiotic molecules seen here in the gas after sublimation of the entire ice mantle. Systematic surveys of the molecules thought to be chemically related, as well as the accurate measurements of their isotopic composition, hold strong promise for understanding the origin of prebiotic molecules in the earliest stages of young stars.
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| 22. |
- Lykke, J. M., et al.
(författare)
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The ALMA-PILS survey: First detections of ethylene oxide, acetone and propanal toward the low-mass protostar IRAS 16293-2422
- 2017
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 597, s. A53-
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Tidskriftsartikel (refereegranskat)abstract
- Context. One of the open questions in astrochemistry is how complex organic and prebiotic molecules are formed. The unsurpassed sensitivity of the Atacama Large Millimeter/submillimeter Array (ALMA) takes the quest for discovering molecules in the warm and dense gas surrounding young stars to the next level. Aims. Our aim is to start the process of compiling an inventory of oxygen-bearing complex organic molecules toward the solar-type Class 0 protostellar binary IRAS 16293-2422 from an unbiased spectral survey with ALMA, Protostellar Interferometric Line Survey (PILS). Here we focus on the new detections of ethylene oxide (c-C2H4O), acetone (CH3COCH3), and propanal (C2H5CHO). Methods. With ALMA, we surveyed the spectral range from 329 to 363 GHz at 0.5? (60 AU diameter) resolution. Using a simple model for the molecular emission in local thermodynamical equilibrium, the excitation temperatures and column densities of each species were constrained. Results. We successfully detect propanal (44 lines), ethylene oxide (20 lines) and acetone (186 lines) toward one component of the protostellar binary, IRAS 16293B. The high resolution maps demonstrate that the emission for all investigated species originates from the compact central region close to the protostar. This, along with a derived common excitation temperature of Tex ? 125 K, is consistent with a coexistence of these molecules in the same gas. Conclusions. The observations mark the first detections of acetone, propanal and ethylene oxide toward a low-mass protostar. The relative abundance ratios of the two sets of isomers, a CH3COCH3/C2H5CHO ratio of 8 and a CH3CHO/c-C2H4O ratio of 12, are comparable to previous observations toward high-mass protostars. The majority of observed abundance ratios from these results as well as those measured toward high-mass protostars are up to an order of magnitude above the predictions from chemical models. This may reflect either missing reactions or uncertain rates in the chemical networks. The physical conditions, such as temperatures or densities, used in the models, may not be applicable to solar-type protostars either.
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| 23. |
- Noresson, A. L., et al.
(författare)
-
Designing interactions by control of protein-ligand complex conformation : Tuning arginine-arene interaction geometry for enhanced electrostatic protein-ligand interactions
- 2018
-
Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 9:4, s. 1014-1021
-
Tidskriftsartikel (refereegranskat)abstract
- We investigated galectin-3 binding to 3-benzamido-2-O-sulfo-galactoside and -thiodigalactoside ligands using a combination of site-specific mutagenesis, X-ray crystallography, computational approaches, and binding thermodynamics measurements. The results reveal a conformational variability in a surface-exposed arginine (R144) side chain in response to different aromatic C3-substituents of bound galactoside-based ligands. Fluorinated C3-benzamido substituents induced a shift in the side-chain conformation of R144 to allow for an entropically favored electrostatic interaction between its guanidine group and the 2-O-sulfate of the ligand. By contrast, binding of ligands with non-fluorinated substituents did not trigger a conformational change of R144. Hence, a sulfate-arginine electrostatic interaction can be tuned by the choice of ligand C3-benzamido structures to favor specific interaction modes and geometries. These results have important general implications for ligand design, as the proper choice of arginine-aromatic interacting partners opens up for ligand-controlled protein conformation that in turn may be systematically exploited in ligand design.
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| 24. |
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| 25. |
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| 26. |
- Wagner, J, et al.
(författare)
-
Di-Carbon defects in annealed highly carbon doped GaAs
- 1997
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 78:1, s. 74-77
-
Tidskriftsartikel (refereegranskat)abstract
- Formation of bonded dicarbon C-C centers is deduced from the observation of Raman lines at 1742, 1708, and 1674 cm -1 in GaAs codoped with 12C and 13C after annealing at 850 °C with concomitant loss of vibrational scattering from CAs. The frequencies agree with results of ab initio theory for a C-C split interstitial (deep donor) formed by the trapping of a mobile interstitial C (displaced CAs) atom by an undisplaced CAs acceptor. Other mechanisms of carrier loss are inferred since a weaker Raman triplet is detected at 1859, 1824, and 1788 cm -1 from a different C-C complex.
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| 27. |
- Walsh, Kyle M., et al.
(författare)
-
A pilot genome-wide association study shows genomic variants enriched in the non-tumor cells of patients with well-differentiated neuroendocrine tumors of the ileum
- 2011
-
Ingår i: Endocrine-Related Cancer. - 1351-0088 .- 1479-6821. ; 18:1, s. 171-180
-
Tidskriftsartikel (refereegranskat)abstract
- Genetic studies of midgut carcinoid cancer have exclusively focused on genomic changes of the tumor cells. We investigated the role of constitutional genetic polymorphisms in predisposing individuals to ileal carcinoids. In all, 239 cases and 110 controls were collected from three institutions: the Uppsala University Hospital; the Dana-Farber Cancer Institute; and the MD Anderson Cancer Center, and were genotyped using microarrays assaying >300 000 single nucleotide polymorphisms. Association with rs2208059 in KIF16B approached statistical significance (Mantel-Haenszel odds ratio=2.42, P=4.16×10−7) at a Bonferroni-corrected level (<1.62×10−7). Using two computational algorithms, four copy-number variants (CNVs) were identified in multiple cases that were absent in study controls and markedly less frequent in ∼1500 population-based controls. Of these four constitutional CNVs identified in blood-derived DNA, a 40 kb heterozygous deletion in Chr18q22.1 corresponded with a region frequently showing loss of heterozygosity (LOH) in ileal carcinoid tumor cells based on our meta-analysis of previously published cytogenetic studies (69.7% LOH, 95% confidence interval=60.0–77.9%). We analyzed the constitutional 40 kb deletion on chr18 in our study samples with a real-time quantitative PCR assay; 14/226 cases (6.19%) and 2/97 controls (2.06%) carried the CNV, although the exact boundaries of each deletion have not been determined. Given the small sample size, our findings warrant an independent cohort for a replication study. Owing to the rarity of this disease, we believe these results will provide a valuable resource for future work on this serious condition by allowing others to make efficient use of their samples in targeted studies.
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| 28. |
- Öberg, Henrik, et al.
(författare)
-
Optical laser-induced CO desorption from Ru(0001) monitored with a free-electron X-ray laser : DFT prediction and X-ray confirmation of a precursor state
- 2015
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 640, s. 80-88
-
Tidskriftsartikel (refereegranskat)abstract
- We present density functional theory modeling of time-resolved optical pump/X-ray spectroscopic probe data of CO desorption from Ru(0001). The BEEF van der Waals functional predicts a weakly bound state as a precursor to desorption. The optical pump leads to a near-instantaneous (<100 fs) increase of the electronic temperature to nearly 7000 K. The temperature evolution and energy transfer between electrons, substrate phonons and adsorbate is described by the two-temperature model and found to equilibrate on a timescale of a few picoseconds to an elevated local temperature of similar to 2000K. Estimating the free energy based on the computed potential of mean force along the desorption path, we find an entropic barrier to desorption (and by time-reversal also to adsorption). This entropic barrier separates the chemisorbed and precursor states, and becomes significant at the elevated temperature of the experiment (similar to 1.4 eV at 2000 K). Experimental pump-probe X-ray absorption/X-ray emission spectroscopy indicates population of a precursor state to desorption upon laser-excitation of the system (Dell'Angela et al., 2013). Computing spectra along the desorption path confirms the picture of a weakly bound transient state arising from ultrafast heating of the metal substrate.
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| 29. |
- Agirre, J. A., et al.
(författare)
-
The VALU3S ECSEL project : Verification and validation of automated systems safety and security
- 2021
-
Ingår i: Microprocessors and microsystems. - : Elsevier BV. - 0141-9331 .- 1872-9436. ; 87, s. 104349-
-
Tidskriftsartikel (refereegranskat)abstract
- Manufacturers of automated systems and their components have been allocating an enormous amount of time and effort in R&D activities, which led to the availability of prototypes demonstrating new capabilities as well as the introduction of such systems to the market within different domains. Manufacturers need to make sure that the systems function in the intended way and according to specifications. This is not a trivial task as system complexity rises dramatically the more integrated and interconnected these systems become with the addition of automated functionality and features to them. This effort translates into an overhead on the V&V (verification and validation) process making it time-consuming and costly. In this paper, we present VALU3S, an ECSEL JU (joint undertaking) project that aims to evaluate the state-of-the-art V&V methods and tools, and design a multi-domain framework to create a clear structure around the components and elements needed to conduct the V&V process. The main expected benefit of the framework is to reduce time and cost needed to verify and validate automated systems with respect to safety, cyber-security, and privacy requirements. This is done through identification and classification of evaluation methods, tools, environments and concepts for V&V of automated systems with respect to the mentioned requirements. VALU3S will provide guidelines to the V&V community including engineers and researchers on how the V&V of automated systems could be improved considering the cost, time and effort of conducting V&V processes. To this end, VALU3S brings together a consortium with partners from 10 different countries, amounting to a mix of 25 industrial partners, 6 leading research institutes, and 10 universities to reach the project goal.
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| 30. |
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| 31. |
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| 32. |
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| 33. |
- Ask, Per, 1950-, et al.
(författare)
-
ECG Electrodes : A Study of Electrical and Mechanical Long-term Properties
- 1979
-
Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 23:2, s. 189-206
-
Tidskriftsartikel (refereegranskat)abstract
- The long-term properties of commercially available ECG-electrodes were studied by investigating the parameters: polarization potential, electrical impedance, adhesion, and skin reactions during a period of 7 days. As expected, the most stable polarization potentials were obtained for Ag/AgCl electrodes. Certain simple disposable electrodes showed large polarization potential variations. The most stable electrode impedance was obtained for disposable electrodes with stable adhesion and equipped with an electrode cup or similar. Unchanged adhesion and mechanical properties during the test period were shown by the disposable electrodes with a large self-adhesive collar.
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| 34. |
- Asklund, Helen, 1975-, et al.
(författare)
-
Hur meriterade lärare kan samverka för kollegial pedagogisk utveckling : Exemplet Mata inte studenten
- 2024
-
Konferensbidrag (refereegranskat)abstract
- Vad skulle hända om du som lärare slutade att mata studenterna med information om vad och hur de ska lära sig? Den frågan ligger till grund för det kollegiala utvecklingsprojekt som vi, en grupp meriterade och excellenta lärare vid Mittuniversitetet, har genomfört i form av antologin Mata inte studenterna. Med antologiprojektet som utgångspunkt är vårt syfte att dels reflektera över vår kollegiala skrivprocess, dels bidra till den nationella diskussionen om meriterade lärares roll. Vi vill därför lyfta frågor om hur vi gått tillväga, vilka resurser som behövs för att få till stånd ett kollegialt skrivprojekt och eventuella vinster på individuell, kollegial och organisatorisk nivå - alltså de nivåer som är centrala för det akademiska lärarskapet och som meriterade lärare förväntas bidra till att utveckla. Med samtalet riktar vi oss därmed till en bred målgrupp - såväl meriterade lärare som alla med intresse för kollegiala samverkansformer. Rundabordssamtalet inleds med en presentation av vår kollektiva skrivprocess. Boken är resultatet av en idé från ett skrivinternat arrangerat av Nätverket för meriterade lärare på vårt lärosäte. Startpunkten var en diskussion om “spoon-fed students" och hur vi som lärare kan arbeta för ett mer aktivt lärande. Vi beslöt att dela med oss av våra tidigare erfarenheter i ett antologiprojekt. I rundabordssamtalet belyser vi drivkrafter och utmaningar från vår skrivprocess (jmf Fjellström & Wester, 2019) genom att lyfta våra lärdomar. I vidare mening vill vi reflektera över det akademiska lärarskapet och vad som krävs för att det ska fungera. Därefter följer gruppsamtal med erfarenhetsutbyte och diskussion om vilka resurser och strukturer som behövs för pedagogisk utveckling på olika nivåer. Ett sista steg är en kritisk metadiskussion om meriterade lärares roll och den typ av utvecklingsarbete vi bedrivit. Sessionen avslutas med en gemensam summering och dokumenteras i en padlet. Genom samtalet vill vi synliggöra behovet av att gå bortom den egna undervisningspraktiken och möjliggöra ett aktivt kollegialt kunskapsutbyte. Därigenom förstärks i slutändan det akademiska lärarskapet där lärare “kontinuerligt och systematiskt reflekterar över, utforskar och utvecklar den egna pedagogiska praktiken och dess inverkan på studenters lärande” (Bolander Laksov & Scheja, 2020,s.29).Referenser:Bolander Laksov, K., & Scheja, M. (2020). Akademiskt lärarskap. Stockholm: SULF.Fjellström, M. & Wester, M. (2019). Universitetslärares skrivande om och för sin undervisning.Högreutbildning, 9(1), s. 20-33.
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| 35. |
- Avdic, Una, et al.
(författare)
-
Immune profile in blood following non-convulsive epileptic seizures in rats
- 2019
-
Ingår i: Frontiers in Neurology. - : Frontiers Media SA. - 1664-2295. ; 10:JUL
-
Tidskriftsartikel (refereegranskat)abstract
- Non-convulsive status epilepticus (NCSE) is a prolonged epileptic seizure with subtle symptoms that may delay clinical diagnosis. Emerging experimental evidence shows brain pathology and epilepsy development following NCSE. New diagnostic/prognostic tools are therefore needed for earlier and better stratification of treatment. Here we examined whether NCSE initiates a peripheral immune response in blood serum from rats that experienced electrically-induced NCSE. ELISA analysis showed an acute transient increase in serum protein levels including interleukin-6 6 h post-NCSE, similar to the immune reaction in the brain. At 4 weeks post-NCSE, when 75% of rats subjected to NCSE had also developed spontaneous seizures, several immune proteins were altered. In particular, markers associated with microglia, macrophages and antigen presenting cells, such as CD68, MHCII, and galectin-3, were increased and the T-cell marker CD4 was decreased in serum compared to both non-stimulated controls and NCSE rats without spontaneous seizures, without correlation to interictal epileptiform activity. Analyses of serum following intracerebral injection of lipopolysaccharide (LPS) showed an acute increase in interleukin-6, but at 4 weeks unaltered levels of MHCII and galectin-3, an increase in CD8 and CD11b and a decrease in CD68. None of the increased serum protein levels after NCSE or LPS could be confirmed in spleen tissue. Our data identifies the possibility to detect peripheral changes in serum protein levels following NCSE, which may be related to the development of subsequent spontaneous seizures.
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| 36. |
- Bakoush, Omran, et al.
(författare)
-
Effect of diabetes mellitus on the recovery of changes in renal functions and glomerular permeability following reversible 24-hour unilateral ureteral obstruction
- 2018
-
Ingår i: Journal of Diabetes. - : Wiley. - 1753-0393 .- 1753-0407.
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Following reversal of short periods of ureteral obstruction (UO), glomerular and tubular renal dysfunction recovers with time. Diabetes mellitus (DM) affects glomerular function; thus, the ability of diabetic kidneys to recover from UO may be impaired. This study investigated the effects of long-term DM on the recovery of glomerular and tubular function, as well as permeability of the glomerular filtration barrier (GFB), after unilateral UO (UUO) reversal. Methods: Diabetes mellitus was induced in Wistar rats by intraperitoneal streptozotocin. All diabetic and age-matched control rats underwent reversible 24-hour left UUO. The renal function of both kidneys was measured using clearance techniques 3 hours and 7 and 30 days after UUO reversal. Glomerular permeability was assessed by measuring the glomerular sieving coefficients for fluorescein isothiocyanate-conjugated Ficoll (molecular radius: 20-90 Å). Results: Unilateral UO induced transient changes in the size selectivity of GFB small pores. However, the size selectivity function of large pores had not returned to baseline even 30 days after UUO reversal. Diabetes mellitus caused exaggerated early alterations in glomerular hemodynamic and tubular function, as well as size selectivity dysfunction of both small and large pores. At 30 days after UUO reversal, despite glomerular hemodynamic and tubular function and the size selectivity of small pores returning to normal in both diabetic and non-diabetic rats, the residual size selectivity dysfunction of large pores was more severe in diabetic rats. Conclusion: Unilateral UO caused long-term dysfunction in the size selectivity of large pores of the GFB. In addition, DM significantly exaggerated this dysfunction, indicating a more ominous outcome in diabetic kidneys following UUO.
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| 37. |
- Bangert, U., et al.
(författare)
-
Electron energy loss spectroscopic studies of brown diamonds
- 2006
-
Ingår i: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 86:29-31, s. 4757-4779
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate both experimentally and theoretically, low-loss electron energy losses in brown type IIa monocrystalline diamonds both before and after high-temperature, high-pressure anneals which remove the brown colouration. We find additional losses within and near the band edge for brown diamond which are significantly reduced after treatment. The additional losses are not associated with dislocations. Graphitic inclusions are detected by EELS as well as TEM studies for some brown diamonds before treatment. These lead to pronounced subgap absorption. However, all brown diamonds exhibit additional losses which are due to point defects lying in the regions between dislocations. First principles theoretical modelling shows that common dislocations are not responsible for the brown colouration but a -bonded vacancy disk lying on {111} planes gives broad bands lying in the diamond band gap, possesses an optical absorption spectrum similar to that of brown diamond, and leads to additional electron energy losses in the band edge region. These and similar defects are suggested to be responsible for the brown colouration. Mechanisms are proposed for their formation and removal.
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| 38. |
- Blumenau, AT, et al.
(författare)
-
Dislocation structures in diamond : density-functional based modelling and high-resolution electron microscopy
- 2004
-
Ingår i: Defect and Diffusion Forum. - Zürich : Trans Tech Publications. - 1012-0386 .- 1662-9507. ; 226-228, s. 11-30
-
Tidskriftsartikel (refereegranskat)abstract
- The core structures of perfect 60 and edge dislocations in diamond are investigated atomistically in a density-functional based tight-binding approach, and their dissociation is discussed both in terms of structure and energy. Furthermore, high resolution electron microscopy is performed on dislocation cores in high-temperature, high-pressure annealed natural brown diamond, and HRTEM image simulation allows a comparison of theoretically predicted and experimentally observed structures.
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| 39. |
- Brännström, Jonas, et al.
(författare)
-
The initial evaluation of an Internet-based support system for audiologists and first-time hearing aid clients
- 2016
-
Ingår i: Internet Interventions. - : Elsevier BV. - 2214-7829. ; 4, s. 82-91
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: Audiologists provide professional contact and support between appointments to clients with hearing impairment using telephone and e-mail, but more advanced and flexible technological platforms are also possible. The present study aimed to evaluate the clinical application of an Internet-based support system for audiologists and their first-time hearing aid clients. Design: An Internet-based support system developed by Månsson et al. (2013) for psychologists and their clients was adapted for audiologic purposes. Three audiologic clinics in Sweden tested the support system with their clients. Study sample: Twenty-three clients managed by four audiologists used and evaluated the support system. In addition, five of the clients and all four audiologists were interviewed and their responses were analyzed using content analysis. Results: The clients and the audiologists reported positive experiences and overall satisfaction but audiologists reported that the support system did not address the needs of all clients. More positive experiences and greater satisfaction with the support system were associated with reductions on self-reported consequences of hearing loss and positive hearing aids outcomes. Conclusions: An Internet-based support system can be used in audiologic rehabilitation. Both audiologists and clients recognized the system's potential value to offer an online support to the provision of audiologic services.
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| 40. |
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| 41. |
- Brännström, Jonas, et al.
(författare)
-
The Process of Developing an Internet-Based Support System for Audiologists and First-Time Hearing Aid Clients
- 2015
-
Ingår i: American Journal of Audiology. - : American Speech-Language-Hearing Association. - 1059-0889 .- 1558-9137. ; 24:3, s. 320-324
-
Tidskriftsartikel (refereegranskat)abstract
- Background: In audiologic practice, complementary information sources and access to the clinician between appointments improve information retention and facilitate adjustment behaviors. An Internet-based support system is a novel way to support information sharing and clinician access. Purpose: This research forum article describes the process of developing an Internet-based support system for audiologists and their first-time hearing aid clients. Method: The iterative development process, including revisions by 4 research audiologists and 4 clinical audiologists, is described. The final system is exemplified. Conclusion: An Internet-based support system was successfully developed for audiologic practice.
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| 42. |
- Caporale, N., et al.
(författare)
-
From cohorts to molecules: Adverse impacts of endocrine disrupting mixtures
- 2022
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 375:6582
-
Tidskriftsartikel (refereegranskat)abstract
- Convergent evidence associates exposure to endocrine disrupting chemicals (EDCs) with major human diseases, even at regulation-compliant concentrations. This might be because humans are exposed to EDC mixtures, whereas chemical regulation is based on a risk assessment of individual compounds. Here, we developed a mixture-centered risk assessment strategy that integrates epidemiological and experimental evidence. We identified that exposure to an EDC mixture in early pregnancy is associated with language delay in offspring. At human-relevant concentrations, this mixture disrupted hormone-regulated and disease-relevant regulatory networks in human brain organoids and in the model organisms Xenopus leavis and Danio rerio, as well as behavioral responses. Reinterrogating epidemiological data, we found that up to 54% of the children had prenatal exposures above experimentally derived levels of concern, reaching, for the upper decile compared with the lowest decile of exposure, a 3.3 times higher risk of language delay. © 2022 American Association for the Advancement of Science. All rights reserved.
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| 43. |
- Carvalho, A., et al.
(författare)
-
Identification of the local vibrational modes of small nitrogen clusters in dilute GaAsN
- 2007
-
Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 401-402, s. 339-342
-
Tidskriftsartikel (refereegranskat)abstract
- Ultra-high-resolution infra-red local vibrational mode (IR LVM) spectroscopy measurements together with density-functional calculations have been used to identify the signatures of close substitutional nitrogen (NAs) pairs in GaAs1 - x Nx alloys with concentrations of x < 0.025. We show that the presence of sub-peaks close to the NAs absorption band can be attributed to nitrogen pairs up to fourth neighbor position. Additionally, we suggest that the nitrogen pairs which give rise to the deepest levels below the conduction band edge are the first to be removed upon annealing
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| 44. |
- Carvalho, Alexandra T.G., et al.
(författare)
-
Electronic and optical properties of chlorinated silicon nanoparticles
- 2013
-
Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 13:2, s. 1039-1042
-
Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations are used to investigate the structure, electronic and optical properties of silicon nanocystals with chlorine-passivated surface. The nanocrystals considered were approximately spherical, with diameters between 1.5 and 3.0 nm. We show that the nanocrystals with chlorinated surface have a smaller bandgap, lower optical absorption threshold, and greater ionization energy and electron affinity than hydrogenated silicon nanocrystals of the same size
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| 45. |
- Carvalho, Alexandra T.G., et al.
(författare)
-
Increased electronic coupling in silicon nanocrystal networks doped with F4-TCNQ
- 2013
-
Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 13:2, s. 1035-1038
-
Tidskriftsartikel (refereegranskat)abstract
- The modification of the electronic structure of silicon nanocrystals using an organic dopant, 2,3,5,6- tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4-TCNQ), is investigated using first-principles calculations. It is shown that physisorbed F4-TCNQ molecules have the effect of oxidizing the nanocrystal, attracting the charge density towards the F 4-TCNQ-nanocrystal interface, and decreasing the excitation energy of the system. In periodic F4-TCNQ/nanocrystal superlattices, F 4-TCNQ is suggested to enhance exciton separation, and in the presence of free holes, to serve as a bridge for electron/hole transfer between adjacent nanocrystals.
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| 46. |
- Collins, Patrick M., et al.
(författare)
-
Taloside Inhibitors of Galectin-1 and Galectin-3
- 2012
-
Ingår i: Chemical Biology and Drug Design. - : Wiley. - 1747-0285 .- 1747-0277. ; 79:3, s. 339-346
-
Tidskriftsartikel (refereegranskat)abstract
- Galectin-1 and galectin-3 have roles in cancer and inflammation. Galectin-1 has recently emerged as a significant protein produced by tumour cells to promote tumour development, angiogenesis and metastasis and consequently represents an important target to inhibit. The design of inhibitors targeting the carbohydrate recognition domain that is known to recognize galactose is an important approach in the fight against cancer. Based on the analysis of crystal structures, we pursued the concept that if the galactose was replaced with talose (the C2 epimer of galactose) as a scaffold, then O2 substituents would be directed closer to the protein surface and provide opportunity to design inhibitors that are more specific towards particular galectins. Our elucidation of X-ray crystal structures of two of our synthesized talosides in complex with galectin-1 and galectin-3 provides the first atomic information on the interactions of galectins, and indeed any protein, with talosides. These results have enabled a structure-based rationale for the specificity differences shown by galectin-1 and galectin-3 towards these talosides and demonstrate new opportunities for further exploitation as specific inhibitors of galectins.
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| 47. |
- Dahlgren, Markus K, et al.
(författare)
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Synthesis of 2-(2-Aminopyrimidine)-2,2-difluoroethanols as Potential Bioisosters of Salicylidene Acylhydrazides
- 2010
-
Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 15:6, s. 4207-12
-
Tidskriftsartikel (refereegranskat)abstract
- Salicylidene acylhydrazides are inhibitors of type III secretion in several Gramnegative pathogens. To further develop the salicylidene acylhydrazides, scaffold hopping was applied to replace the core fragment of the compounds. The novel 2-(2-aminopyrimidine)-2,2-difluoroethanol scaffold was identified as a possible analog to thesalicylidene acylhydrazide core structure. The synthesis of a library of 2-(2-aminopyrimidine)-2,2-difluoro-ethanols is described in this paper.
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| 48. |
- Eberlein, T.A.G., et al.
(författare)
-
Alphabet luminescence lines in 4H-SiC
- 2002
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 65:18
-
Tidskriftsartikel (refereegranskat)abstract
- First-principles density functional calculations are used to investigate antisite pairs in 4H-SiC. We show that they are likely to be formed in close proximity under ionizing conditions, and they possess a donor level and thermal stability consistent with the series of 40 photoluminescent lines called the alphabet lines. Moreover, the gap vibrational mode of the silicon antisite defect is close to a phonon replica of the b1 line and possesses a weak isotopic shift with 13C in agreement with observation.
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| 49. |
- Eberlein, T.A.G., et al.
(författare)
-
Density functional theory calculation of the DI optical center in SiC
- 2006
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 74:14, s. 144106-1
-
Tidskriftsartikel (refereegranskat)abstract
- The DI center is a prominent defect which is detected in as-grown or irradiated SiC. It is unusual in that its intensity grows with heat treatments and survives anneals of 1700 °C. It has been assigned recently to either a close-by antisite pair or to the close-by antisite pair adjacent to a carbon antisite. We show here using local density functional calculations that these defects are not stable enough to account for DI. Instead, we assign DI to an isolated Si antisite and the four forms of the close-by antisite pair in 4H-SiC to the a, b, c, and d members of the alphabet series. The assignments allow us to understand the concentration of DI following growth, the recombination enhanced destruction of these alphabet defects and the annealing behavior of the remaining members of the series.
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| 50. |
- Eberlein, T.A.G., et al.
(författare)
-
Grown-in and radiation-induced defects in 4H-SiC
- 2005
-
Ingår i: Semiconductor defect engineering. - Warrendale, Pa : Materials Research Society. - 1558998179 ; , s. 3-13
-
Konferensbidrag (refereegranskat)abstract
- SiC is a material that seems ideal for high-power, high frequency and high temperature electronic devices. It does not suffer from large reverse recovery inefficiencies typical for silicon when switching. In contrast to silicon. SiC is however difficult to dope by diffusion, and instead ion-implantation is used to achieve selective area doping. The drawback of this technique is that irradiating the crystal with dopant atoms creates a great, deal of lattice damage including vacancies, interstitials, antisites and impurity-radiation defect complexes. Although many of the point defects can be eliminated through thermal annealing, some however, e.g. the photoluminescence (PL) D1 and DLTS Z1/Z2 centers in 4H-SiC, are stable to high temperatures. In this polytype, D1 and the related alphabet lines are the most prominent PL signals. The latter can be seen directly after low energy irradiation while D1 usually dominates the PL spectrum of implanted and irradiated SiC after annealing. Not only implantation but also rapid growth of SiC by CVD methods leads to a deterioration in quality with an increase in electrically active grown in defects. Among these, the Z1/Z2 defects are dominant in n-type 4H-SiC. as well as material that has been exposed to radiation. We use first principles density functional calculations to investigate defect models for the above mentioned defects in 4H-SiC and relate their electrical and optical activity to experiments
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