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- Gustafsson, Oscar, et al.
(författare)
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Long-wavelength infrared quantum-dot based interband photodetectors
- 2011
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Ingår i: Infrared physics & technology. - : Elsevier BV. - 1350-4495 .- 1879-0275. ; 54:3, s. 287-291
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Tidskriftsartikel (refereegranskat)abstract
- We report on the design and fabrication of (Al)GaAs(Sb)/InAs tensile strained quantum-dot (QD) based detector material for thermal infrared imaging applications in the long-wavelength infrared (LWIR) regime. The detection is based on transitions between confined dot states and continuum states in a type-II band lineup, and we therefore refer to it as a dot-to-bulk (D2B) infrared photodetector with expected benefits including long carrier lifetime due to the type-II band alignment, suppressed Shockley-Read-Hall generation-recombination due to the relatively large-bandgap matrix material, inhibited Auger recombination processes due to the tensile strain and epitaxial simplicity. Metal-organic vapor-phase epitaxy was used to grow multiple (Al)GaAs(Sb) QD layers on InAs substrates at different QD nominal thicknesses, compositions, doping conditions and multilayer periods, and the material was characterized using atomic force and transmission electron microscopy, and Fourier-transform infrared absorption spectroscopy. Dot densities up to 1 x 10(11) cm(-2), 1 x 10(12) cm(-2) and 3 x 10(10) cm(-2) were measured for GaAs, AlGaAs and GaAsSb QDs, respectively. Strong absorption in GaAs, AlGaAs and GaAsSb multilayer QD samples was observed in the wavelength range 6-12 mu m. From the wavelength shift in the spectral absorption for samples with varying QD thickness and composition it is believed that the absorption is due to an intra- valance band transition. From this it is possible to estimate the type-II inter-band transition wavelength, thereby suggesting that (Al)GaAs(Sb) QD/InAs heterostructures are suitable candidates for LWIR detection and imaging.
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- Nyamdorj, R, et al.
(författare)
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Ethnic comparison of the association of undiagnosed diabetes with obesity.
- 2010
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Ingår i: International Journal of Obesity. - : Springer Science and Business Media LLC. - 0307-0565 .- 1476-5497. ; 34:2, s. 332-339
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The aim of the study was to investigate the crude prevalence and estimated probability of undiagnosed diabetes in different ethnic groups, given the same level of obesity. DESIGN AND SUBJECTS: Cross-sectional data from 24 515 men and 29 952 women, aged >or=30 years, and free of previously diagnosed diabetes were included. Baseline body mass index (BMI) and waist circumference were measured. Diabetes was defined according to both fasting and 2-h 75-g glucose criteria. RESULTS: Prevalence of undiagnosed diabetes was the highest in Asian Indians, the lowest in Europeans and intermediate in others, given the same BMI or waist circumference category across the BMI or waist circumference ranges (P<0.001 for all BMI or waist categories). beta-Coefficients corresponding to a 1 s.d. increase in BMI were 0.34/0.28, 0.41/0.43, 0.42/0.61, 0.36/0.59 and 0.33/0.49 for the Asian Indians, Chinese, Japanese, Mauritian Indians and European men/women (homogeneity test: P>0.05 in men and P<0.001 in women), and in waist: 0.31/0.31, 0.30/0.46, 0.22/0.57 and 0.38/0.58 for the Asian Indians, Chinese, Mauritian Indians and Europeans, respectively (homogeneity test: P>0.05 in men and P<0.001 in women). CONCLUSION: Prevalence of undiagnosed diabetes increased with an increasing BMI or waist circumference to a similar degree in men in all ethnic groups but to a lesser degree in Asian Indian women than in others, regardless of the higher prevalence in Asian Indians than in others at the same BMI (or) waist circumference levels.
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- Bannatyne, B A, et al.
(författare)
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Inhibitory inputs to four types of spinocerebellar tract neurons in the cat spinal cord.
- 2012
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Ingår i: Neuroscience. - : Elsevier BV. - 1873-7544 .- 0306-4522. ; 226, s. 253-69
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Tidskriftsartikel (refereegranskat)abstract
- Spinocerebellar tract neurons are inhibited by various sources of input via pathways activated by descending tracts as well as peripheral afferents. Inhibition may be used to modulate transmission of excitatory information forwarded to the cerebellum. However it may also provide information on the degree of inhibition of motoneurons and on the operation of inhibitory premotor neurons. Our aim was to extend previous comparisons of morphological substrates of excitation of spinocerebellar neurons to inhibitory input. Contacts formed by inhibitory axon terminals were characterised as either GABAergic, glycinergic or both GABAergic/glycinergic by using antibodies against vesicular GABA transporter, glutamic acid decarboxylase and gephyrin. Quantitative analysis revealed the presence of much higher proportions of inhibitory contacts when compared with excitatory contacts on spinal border (SB) neurons. However similar proportions of inhibitory and excitatory contacts were associated with ventral spinocerebellar tract (VSCT) and dorsal spinocerebellar tract neurons located in Clarke's column (ccDSCT) and the dorsal horn (dhDSCT). In all of the cells, the majority of inhibitory terminals were glycinergic. The density of contacts was higher on somata and proximal versus distal dendrites of SB and VSCT neurons but more evenly distributed in ccDSCT and dhDSCT neurons. Variations in the density and distribution of inhibitory contacts found in this study may reflect differences in information on inhibitory processes forwarded by subtypes of spinocerebellar tract neurons to the cerebellum.
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- Eliasson, Pernilla, et al.
(författare)
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Hypoxia mediates low cell-cycle activity and increases the proportion of long-term reconstituting hematopoietic stem cells during in vitro culture
- 2010
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Ingår i: Experimental Hematology. - : Elsevier. - 0301-472X .- 1873-2399. ; 38:4, s. 301-310
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Recent evidence suggests that hematopoietic stem cells (HSCs) in the bone marrow (BM) are located in areas where the environment is hypoxic. Although previous studies have demonstrated positive effects by hypoxia, its role in HSC maintenance has not been fully elucidated, neither has the molecular mechanisms been delineated. Here, we have investigated the consequence of in vitro incubation of HSCs in hypoxia prior to transplantation and analyzed the role of hypoxia-inducible factor (HIF)-1 alpha. Materials and Methods. HSC and progenitor populations isolated from mouse BM were cultured in 20% or 1% O-2, and analyzed for effects on cell cycle, expression of cyclin-dependent kinase inhibitors genes, and reconstituting ability to lethally irradiated mice. The involvement of HIF-1 alpha was studied using methods of protein stabilization and gene silencing. Results. When long-term FLT3(-)CD34(-)Lin(-)Sca-1(+)c-Kit(+) (LSK) cells were cultured in hypoxia, cell numbers were significantly reduced in comparison to normoxia. This was due to a decrease in proliferation and more cells accumulating in G(0). Moreover, the proportion of HSCs with long-term engraftment potential was increased. Whereas expression of the cyclin-dependent kinase inhibitor genes p21(cip1), p27(Kip1), and p57(Kip2) increased in LSK cells by hypoxia, only p21(cip1) was upregulated in FLT3(-)CD34(-)LSK cells. We could demonstrate that expression of p27(KiP1) and p57(Kip2) was dependent of HIF-1 alpha. Surprisingly, overexpression of constitutively active HIF-1 alpha or treatment with the HIF stabilizer agent FG-4497 led to a reduction in HSC reconstituting ability. Conclusions. Our results imply that hypoxia, in part via HIF-1 alpha, maintains HSCs by decreasing proliferation and favoring quiescence.
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