100ps time resolution with thin silicon pixel detectors and a SiGe HBT amplifier

A 100um thick silicon detector with 1mm2 pad readout optimized for sub-nanosecond time resolution has been developed and tested. Coupled to a purposely developed amplifier based on SiGe HBT technology, this detector was characterized at the H8 beam line at the CERN SPS. An excellent time resolution of (106+-1)ps for silicon detectors was measured with minimum ionizing particles

Impaired Cleavage of Preproinsulin Signal Peptide Linked to Autosomal-Dominant Diabetes

Recently, missense mutations upstream of preproinsulin’s signal peptide (SP) cleavage site were reported to cause mutant INS gene-induced diabetes of youth (MIDY). Our objective was to understand the molecular pathogenesis using metabolic labeling and assays of proinsulin export and insulin and C-peptide production to examine the earliest events of insulin biosynthesis, highlighting molecular mechanisms underlying β-cell failure plus a novel strategy that might ameliorate the MIDY syndrome. We find that whereas preproinsulin-A(SP23)S is efficiently cleaved, producing authentic proinsulin and insulin, preproinsulin-A(SP24)D is inefficiently cleaved at an improper site, producing two subpopulations of molecules. Both show impaired oxidative folding and are retained in the endoplasmic reticulum (ER). Preproinsulin-A(SP24)D also blocks ER exit of coexpressed wild-type proinsulin, accounting for its dominant-negative behavior. Upon increased expression of ER–oxidoreductin-1, preproinsulin-A(SP24)D remains blocked but oxidative folding of wild-type proinsulin improves, accelerating its ER export and increasing wild-type insulin production. We conclude that the efficiency of SP cleavage is linked to the oxidation of (pre)proinsulin. In turn, impaired (pre)proinsulin oxidation affects ER export of the mutant as well as that of coexpressed wild-type proinsulin. Improving oxidative folding of wild-type proinsulin may provide a feasible way to rescue insulin production in patients with MIDY

Enhanced interlayer neutral excitons and trions in trilayer van der Waals heterostructures

Vertically stacked van der Waals heterostructures constitute a promising platform for providing tailored band alignment with enhanced excitonic systems. Here we report observations of neutral and charged interlayer excitons in trilayer WSe2-MoSe2-WSe2 van der Waals heterostructures and their dynamics. The addition of a WSe2 layer in the trilayer leads to significantly higher photoluminescence quantum yields and tunable spectral resonance compared to its bilayer heterostructures at cryogenic temperatures. The observed enhancement in the photoluminescence quantum yield is due to significantly larger electron-hole overlap and higher light absorbance in the trilayer heterostructure, supported via first-principle pseudopotential calculations based on spin-polarized density functional theory. We further uncover the temperature- and power-dependence, as well as time-resolved photoluminescence of the trilayer heterostructure interlayer neutral excitons and trions. Our study elucidates the prospects of manipulating light emission from interlayer excitons and designing atomic heterostructures from first-principles for optoelectronics.Comment: 25 pages, 5 figures(Maintext). 9 pages, 7 figures(Supplementary Information). - Accepted for publication in npg: 2D materials and applications and reformatted to its standard. - Updated co-authors and references. - Title and abstract are modified for clarity. - Errors have been corrected, npg: 2D materials and applications (2018

Piercing Through Highly Obscured and Compton-thick AGNs in the Chandra Deep Fields: I. X-ray Spectral and Long-term Variability Analyses

We present a detailed X-ray spectral analysis of 1152 AGNs selected in the Chandra Deep Fields (CDFs), in order to identify highly obscured AGNs ($N_{\rm H} > 10^{23}\ \rm cm^{-2}$). By fitting spectra with physical models, 436 (38%) sources with $L_{\rm X} > 10^{42}\ \rm erg\ s^{-1}$ are confirmed to be highly obscured, including 102 Compton-thick (CT) candidates. We propose a new hardness-ratio measure of the obscuration level which can be used to select highly obscured AGN candidates. The completeness and accuracy of applying this method to our AGNs are 88% and 80%, respectively. The observed logN-logS relation favors cosmic X-ray background models that predict moderate (i.e., between optimistic and pessimistic) CT number counts. 19% (6/31) of our highly obscured AGNs that have optical classifications are labeled as broad-line AGNs, suggesting that, at least for part of the AGN population, the heavy X-ray obscuration is largely a line-of-sight effect, i.e., some high-column-density clouds on various scales (but not necessarily a dust-enshrouded torus) along our sightline may obscure the compact X-ray emitter. After correcting for several observational biases, we obtain the intrinsic NH distribution and its evolution. The CT-to-highly-obscured fraction is roughly 52% and is consistent with no evident redshift evolution. We also perform long-term (~17 years in the observed frame) variability analyses for 31 sources with the largest number of counts available. Among them, 17 sources show flux variabilities: 31% (5/17) are caused by the change of NH, 53% (9/17) are caused by the intrinsic luminosity variability, 6% (1/17) are driven by both effects, and 2 are not classified due to large spectral fitting errors.Comment: 32 pages, 21 figures, 9 tables, accepted for publication in Ap

Relation between land cover and landslide susceptibility in Val d'Aran, Pyrenees (Spain): historical aspects, present situation and forward prediction

The effects of land use and land cover (LULC) dynamics on landslide susceptibility are not fully understood. This study evaluates the influence of LULC on landslide susceptibility and assesses the historic and future LULC changes in a high mountain region. A detailed inventory map showing the distribution of landslides was prepared based on the 2013 episode in Val d'Aran, Pyrenees (Spain). This inventory showed that LULC clearly affected landslide susceptibility. Both the number of landslides and the landslide density triggered in grassland and meadow was highest (52% and 2.0 landslides/km2). In contrast, the landslide density in areas covered by forest and shrubs was much lower (15% and 0.4 landslides/km2, and 23% and 1.7 landslides/km2, respectively). Historical changes of LULC between 1946 and 2013 were determined by comparing aerial photographs. The results indicated that the forest and shrub areas increased by 68 and 65%, respectively; whereas grassland and scree areas decreased by 33 and 52%. Urban area also increased by 532%, especially between 1990 and 2001. Future LULC was predicted until 2097 using TerrSet software. The results showed that the forest area and urban area increased by 57 and 43%, severally; while shrubs, grassland and scree area decreased by 28, 46 and 78%, respectively. Heuristic and deterministic models were applied to create susceptibility maps, which classified the study area into four susceptibility degrees from very low to high. The maps were validated by the 2013 landslide dataset and showed satisfactory results using receiver operating characteristics curves and density graph method. Then, susceptibility maps until 2097 were calculated by the heuristic model and results revealed that landslide susceptibility will decrease by 48% for high-susceptible areas. In contrast, the areas of very-low susceptibility degree will increase 95%, while medium and low-susceptible areas will be more or less constant. This study only includes the effect of future LULC changes on the landslide susceptibility and does not analyze the future impacts of climate changes and the variation of rainfall conditions. Nevertheless, the results may be used as support for land management guidelines to reduce the risk of slope instabilities.Postprint (author's final draft

UV-Ozone reactor with modified high pressure mercury vapor lamp for surface treatment of transparent conductive oxides used in electroluminescent polymeric devices

An UV-Ozone reactor was developed with an ignition tube extracted into HID mercury lamp used to irradiation on zinc oxide (ZnO) and fluorinated tin oxide (FTO) films for PLEDs devices. Different exposures times were used. In contact angle measurements revealed better results for ZnO and FTO by 15 and 5 min, respectively. In Diffuse Reflectance Infra-red Fourier Transformed (DRIFT) spectroscopy allowed the observation of water, hydrocarbon and carbon dioxide adsorbed on the untreated TCO surfaces. After the UV-Ozone treatment the contaminants were significantly reduced or eliminated and the PLEDs devices decreased threshold voltages in comparison with respectively untreated TCOs

Inefficient Translocation of Preproinsulin Contributes to Pancreatic β Cell Failure and Late-onset Diabetes

Among the defects in the early events of insulin biosynthesis, proinsulin misfolding and endoplasmic reticulum (ER) stress have drawn increasing attention as causes of β cell failure. However, no studies have yet addressed potential defects at the cytosolic entry point of preproinsulin into the secretory pathway. Here, we provide the first evidence that inefficient translocation of preproinsulin (caused by loss of a positive charge in the n region of its signal sequence) contributes to β cell failure and diabetes. Specifically, we find that, after targeting to the ER membrane, preproinsulin signal peptide (SP) mutants associated with autosomal dominant late-onset diabetes fail to be fully translocated across the ER membrane. The newly synthesized, untranslocated preproinsulin remains strongly associated with the ER membrane, exposing its proinsulin moiety to the cytosol. Rather than accumulating in the ER and inducing ER stress, untranslocated preproinsulin accumulates in a juxtanuclear compartment distinct from the Golgi complex, induces the expression of heat shock protein 70 (HSP70), and promotes β cell death. Restoring an N-terminal positive charge to the mutant preproinsulin SP significantly improves the translocation defect. These findings not only reveal a novel molecular pathogenesis of β cell failure and diabetes but also provide the first evidence of the physiological and pathological significance of the SP n region positive charge of secretory proteins

Quantum Optics and Photonics

Contains reports on nine research projects.National Science Foundation (Grant PHY82-10369)Joint Services Electronics Program (Contract DAAG29-83-K-0003)U.S. Air Force - Office of Scientific Research (Contract F49620-82-C-0091)Litton Guidance and Control SystemNational Science Foundation (Grant PHY82-10369