Search

An Au/Cu 2 ZnSnS 4 (CZTS)/n-GaN heterojunction (HJ) is fabricated with a CZTS interlayer and probed its chemical states, structural, electrical and frequency-dependent characteristics by XPS, TEM, I - V and C - V measurements. XPS and TEM results confirmed that the CZTS films are formed on the n-GaN surface. The band gap of deposited CZTS film is found to be 1.55 eV. The electrical properties of HJ correlated with the Au/n-GaN Schottky junction (SJ). The Au/CZTS/n-GaN HJ reveals a good rectification nature with high barrier height (0.82 eV) compared to the Au/n-GaN SJ (0.69 eV), which suggests the barrier height is influenced by the CZTS interlayer. The barrier height values assessed by I - V , Cheung’s and Norde functions are closely matched with one other, thus the methods used here are reliable and valid. The extracted interface state density ( N SS ) of Au/CZTS/n-GaN HJ is lower compared to the Au/n-GaN SJ that suggests the CZTS interlayer plays an important role in the reduction of N SS . Moreover, the capacitance-frequency ( C - f ) and conductance-frequency ( G -f) characteristics of SJ and HJ are measured in the range of 1 kHz–1 MHz, and found that the capacitance and conductance strappingly dependent on frequency. It is found that the N SS estimated from C - f and G - f characteristics is lower compared to those estimated from I - V characteristics. Analysis confirmed that Poole-Frenkel emission dominates the reverse leakage current in both SJ and HJ, probably related to the structural defects and trap levels in the CZTS interlayer. [ABSTRACT FROM AUTHOR]

The induction of small heat shock proteins (sHsp) is observed under various stress conditions to protect the cells and organisms from adverse events including diabetes. Diabetic cardiomyopathy is a common complication of diabetes. Therefore, in this study, we investigated the expression of sHsp under chronic hyperglycemic conditions in rat heart. Hyperglycemia was induced in WNIN rats by intraperitoneal injection of streptozotocin and maintained for a period of 12 weeks. Expression of sHsp, phosphorylation and translocation of phosphoforms of Hsp27 and αB-crystallin (αBC) from cytosolic fraction to cytoskeletal fraction was analyzed. While the expression of MKBP, HspB3, αBC was found to be increased in diabetic heart, expression of Hsp20 was decreased. Chronic hyperglycemia further induced phosphorylation of αBC at S59, S45, Hsp27 at S82, p38MAPK and p44/42MAPK. However, pS59-αBC and pS82-Hsp27 were translocated from detergent-soluble to detergent-insoluble fraction under hyperglycemic conditions. Furthermore, the interaction of pS82-Hsp27 and pS59-αBC with desmin was increased under hyperglycemia. However, the interaction of αBC and pS59-αBC with Bax was impaired by chronic hyperglycemia. These results suggest up regulation of sHsp (MKBP, HspB3 and αBC), phosphorylation and translocation of Hsp27 and αBC to striated sarcomeres and impaired interaction of αBC and pS59-αBC with Bax under chronic hyperglycemia. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effects of annealing on electrical and structural properties of W/p-InP SBD are studied. [•] Maximum barrier height is achieved on W/p-InP SBD upon annealing at 300°C. [•] Interface state density decreases with increasing annealing temperature up to 300°C. [•] W–P interfacial phases are responsible for increase in barrier height after annealing at 300°C. [•] Overall surface morphology of the SBD did not change significantly at elevated temperatures. [ABSTRACT FROM AUTHOR]

Highlights: [•] Temperature dependent electrical characteristics of Se/n-GaN SBD have been investigated. [•] The estimated ϕbo and n are found to be 0.46eV and 3.83 to 0.92eV and 1.29 at 400K. [•] The I–V characteristics of Se/n-GaN SBD have revealed the existence of a double GD. [•] The interface state density (Nss ) is found to be decreased with an increasing temperature. [•] The reverse-bias leakage current mechanism of Se/n-GaN SBD is investigated. [Copyright &y& Elsevier]

Highlights: [•] I–V and C–V characteristics of Er Schottky contacts to p-InP. [•] Discrepancy between barrier heights estimated from I–V and C–V measurements. [•] Optimum annealing temperature for the Er/p-InP Schottky diode is 200°C. [•] Variation of barrier heights caused by the formation of interfacial phases at Er/p-InP interface. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes a two-stage feedforward neural network (FFNN) based approach for modeling fundamental frequency (F 0) values of a sequence of syllables. In this study, (i) linguistic constraints represented by positional, contextual and phonological features, (ii) production constraints represented by articulatory features and (iii) linguistic relevance tilt parameters are proposed for predicting intonation patterns. In the first stage, tilt parameters are predicted using linguistic and production constraints. In the second stage, F 0 values of the syllables are predicted using the tilt parameters predicted from the first stage, and basic linguistic and production constraints. The prediction performance of the neural network models is evaluated using objective measures such as average prediction error (μ), standard deviation (σ) and linear correlation coefficient (γ X,Y ). The prediction accuracy of the proposed two-stage FFNN model is compared with other statistical models such as Classification and Regression Tree (CART) and Linear Regression (LR) models. The prediction accuracy of the intonation models is also analyzed by conducting listening tests to evaluate the quality of synthesized speech obtained after incorporation of intonation models into the baseline system. From the evaluation, it is observed that prediction accuracy is better for two-stage FFNN models, compared to the other models. [Copyright &y& Elsevier]

Abstract: We have investigated the current transport mechanisms in Ru/Pd/n-GaN Schottky barrier diodes in the temperature range 105–405K. The calculated barrier height and ideality factor are 0.27eV and 3.93 at 105K, and 0.75eV and 1.29 at 405K respectively, and it is observed that barrier height (Φbo) decreases and the ideality factor (n) increases with decreasing temperature. The apparent barrier height and the ideality factor derived by using thermionic emission theory are found to be strongly temperature dependent. This behavior has been interpreted based on the assumption of a Gaussian distribution of barrier heights due to barrier height inhomogeneities that prevail at the metal–semiconductor interface. The linearity of the apparent barrier height versus 1/2kT plot yields a mean barrier height () of 0.89eV and a standard deviation (σ o) of 111mV. A modified versus 1000/T plot gives (T =0) and A ∗ as 0.87eV and 21.25A/cm2 K2, respectively without using the temperature coefficient of the barrier heights. The interface state densities extracted for the Ru/Pd/n-GaN Schottky diode are in the range of 9.38×1013 to 1.06×1012 eV−1 cm−2 in the band gap below conduction band from E C-0.14 to E C-0.66eV. Deep level transient spectroscopy (DLTS) results showed that the two deep level defects are observed in as-grown sample (E 1 and E 2) which have activation energies of E 1 =0.54eV and E 2 =0.68eV, suggest that E 2 level is most probably associated with N Ga-related defect. [Copyright &y& Elsevier]

Abstract: The current–voltage (–) and capacitance–voltage (–) characteristics of Ni/Au/n-InP (111) Schottky contacts have been studied in the temperature range 210–420 K in steps of 30 K. The forward – characteristics are analyzed on the basis of thermionic emission (TE) theory assuming a Gaussian distribution of the barrier heights (BHs). The estimated Schottky barrier height (SBH) of an Ni/Au Schottky contact is in the region of 0.38 eV (–), 0.93 eV (–) at 210 K and 0.70 eV (–), 0.73 eV (–) at 420 K, respectively. The calculated ideality factor of an Ni/Au Schottky barrier diode (SBD) varies from 3.25 at 210 K to 1.99 at 420 K. It has been observed that the ideality factor decreases while the zero-bias BH increases with increasing temperature. This behavior has been interpreted by the assumption of a Gaussian distribution of BHs due to barrier inhomogeneities that prevail at the metal–semiconductor interface. The zero-bias BH versus plot has been drawn to obtain evidence of the Gaussian distribution of the BHs. The mean value of obtained is 1.01 eV, with standard deviation . From the modified Richardson plot, the mean BH is 0.97 eV and the Richardson constant () is 4.507 A cm−2 K−2, which is close to the theoretical value of 9.4 A cm−2 K−2. The discrepancy between SBHs obtained from the – and – measurements is also explained. The experimentally observed value of 5.235 meV agrees very well with the theoretically calculated value of . [ABSTRACT FROM AUTHOR]

Small heat shock proteins (sHsps) are a family of proteins. Some are induced in response to multiple stimuli and others are constitutively expressed. They are involved in fundamental cellular processes, including protein folding, apoptosis, and maintenance of cytoskeletal integrity. Hyperglycemia created during diabetes leads to neuronal derangements in the brain. In this study, we investigated the impact of chronic hyperglycemia on the expression of sHsps and heat shock transcription factors (HSFs), solubility and aggregation of sHsps and amyloidogenic proteins, and their role in neuronal apoptosis in a diabetic rat model. Diabetes was induced in Sprague–Dawley rats with streptozotocin and hyperglycemia was maintained for 16 weeks. Expressions of sHsps and HSFs were analyzed by qRT-PCR and immunoblotting in the cerebral cortex. Solubility of sHsps and amyloidogenic proteins, including α-synuclein and Tau, was analyzed by the detergent soluble assay. Neuronal cell death was analyzed by TUNEL staining and apoptotic markers. The interaction of sHsps with amyloidogenic proteins and Bax was assessed using co-immunoprecipitation. Hyperglycemia decreased Hsp27 and HSF1, and increased αBC, Hsp22, and HSF4 levels at transcript and protein levels. Diabetes induced the aggregation of αBC, Hsp22, α-synuclein, and pTau, as their levels were higher in the insoluble fraction. Additionally, diabetes impaired the interaction of αBC with α-synuclein and pTau. Furthermore, diabetes reduced the interaction of αBC with Bax, which may possibly contribute to neuronal apoptosis. Together, these results indicate that chronic hyperglycemia induces differential responses of sHsps by altering their expression, solubility, interaction, and roles in apoptosis. • Diabetes significantly increased the levels of αB-crystallin (αBC), Hsp22, HSF4 while decreased the Hsp27 and HSF1. • Diabetes induced the aggregation of αBC, Hsp22, α-synuclein, pTau by reducing their solubility. • Diabetes impaired the interaction of αBC with α-synuclein, and pTau. • Diabetes increased the neuronal apoptosis and reduced the interaction of αBC with Bax. [ABSTRACT FROM AUTHOR]

Examines the development of preference for baby-featured teddy bears in young children to assess who is driving the evolution of the toy. Matching of sign stimuli that release nurturant behavior; Paradox of theory suggesting that young children exhibit a preference for objects that afford nurturing when they themselves require intensive nurture.

A series of benzo[ d ]imidazo[2,1- b ]thiazole-chalcone conjugates ( 5a-aa ) were designed, synthesized and evaluated for their cytotoxic potency against a panel of human cancer cell lines like lung (A-549), breast (MDA MB-231), prostrate (DU-145) and colon cancer (HT-29). Preliminary results revealed that some of these conjugates like 5d and 5u exhibited significant antiproliferative effect against human breast cancer (MDA MB-231) with IC 50 values of 1.3 and 1.2 µM respectively. To investigate the mechanistic aspects underlying the activity, the detailed biological studies of these promising conjugates ( 5d and 5u ) were carried out on the MDA MB-231 cancer cells. Flow cytometric analysis revealed that these conjugates induce cell-cycle arrest in the G2/M phase. The tubulin polymerization assay suggests that these conjugates effectively inhibit microtubule assembly. In addition, morphological changes, reactive oxygen species (ROS) detection by 2′, 7′–dichlorofluorescin diacetate (DCFDA) and annexin V–FITC/PI assays indicate that 5d and 5u induces apoptosis. Furthermore, in silico computational studies, including molecular docking studies have been carried out to rationalise the binding modes of these conjugates with the tubulin protein. [ABSTRACT FROM AUTHOR]

The electrical properties and carrier transport mechanism of vanadium (V) Schottky contacts on p-type GaN have been investigated. The electrical characteristics are analyzed by using current–voltage–temperature, turn-on voltage–temperature and series resistance–temperature in the temperature range of 280–400 K. An exponential decrease in the experimental series resistance ( R S ) and increase in the ideality factor ( n ), Schottky barrier height (SBH) with decrease in the temperature is observed. The characteristic temperature ( T 0 ) resulting from the Norde’s function is compared with those from the Cheung’s functions, and it is observed that there is good agreement between the T 0 values from both methods. Experimental results reveal that the thermal coefficient ( K j ) is −1.0 mV/K at ⩾280 K. The effective SBH is determined to be 1.88 ± 0.2 eV, which is in good agreement with the theoretical value. The feasible carrier transport mechanism of V/p-GaN Schottky diode is discussed based on the thermally decreased energy band gap of p-type GaN layers, thermally increased deep-level acceptor and increased further activated shallow-level acceptor. [ABSTRACT FROM AUTHOR]

A Ru/V/n-InP Schottky barrier diode (SBD) is fabricated and investigated its electrical and structural properties as a function of annealing temperature. Measurements showed that the barrier height (BH) of the as-deposited Ru/V/n-InP SBD is found to be 0.83 eV ( I – V ) and 1.03 eV ( C – V ). Experimental results indicate that the SBD with high BH and low ideality factors (0.87 eV ( I – V ), 1.20 eV ( C – V ), and 1.12) can be achieved after annealing at 400 °C for 1 min in N 2 atmosphere. Further, it is observed that the BH slightly decreases to 0.85 eV ( I – V ) and 1.09 eV ( C – V ) upon annealing at 500 °C. The BH, ideality factor and series resistance are also determined by Cheung’s functions and Norde method. Further, the energy distribution of interface state density of Ru/V/n-InP SBD is calculated from the forward bias I – V characteristics as a function of annealing temperature. It is found that the interface state density decreases upon annealing at 400 °C and then slightly increases after annealing at 500 °C. The AES and XRD results revealed that the formation of indium phases at the Ru/V/n-InP interface could be the reason for the increase of BH upon annealing at 400 °C. The formation of phosphide phases at the interface may be the cause for the decrease of BH after annealing at 500 °C. The overall surface morphology of Ru/V Schottky contacts is considerably smooth at elevated temperatures. [ABSTRACT FROM AUTHOR]

Signaling via the phosphatidylinositol-3 kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) is crucial for divergent physiological processes including transcription, translation, cell-cycle progression and apoptosis. The aim of work was to elucidate the anti-cancer effect of celastrol and the signal transduction pathways involved. Cytotoxic effect of celastrol was assessed by MTT assay on human triple negative breast cancer cells (TNBCs) and compared with that of MCF-7. Apoptosis induction was determined by AO/EtBr staining, mitochondrial membrane potential by JC-1, Annexin binding assays and modulation of apoptotic proteins and its effect on PI3K/Akt/mTOR pathway by western blotting. Celastrol induced apoptosis in TNBC cells, were supported by DNA fragmentation, caspase-3 activation and PARP cleavage. Meanwhile, celastrol triggered reactive oxygen species production with collapse of mitochondrial membrane potential, down-regulation of Bcl-2 and up-regulation of Bax expression. Celastrol effectively decreased PI3K 110α/85α enzyme activity, phosphorylation of Akt ser473 and p70S6K1 and 4E-BP1. Although insulin treatment increased the phosphorylation of Akt ser473 , p70S6K1, 4E-BP1, celastrol abolished the insulin mediated phosphorylation. It clearly indicates that celastrol acts through PI3k/Akt/mTOR axis. We also found that celastrol inhibited the Akt/GSK3β and Akt/NFkB survival pathway. PI3K/Akt/mTOR inhibitor, PF-04691502 and mTOR inhibitor rapamycin enhanced the apoptosis-inducing effect of celastrol. These data demonstrated that celastrol induces apoptosis in TNBC cells and indicated that apoptosis might be mediated through mitochondrial dysfunction and PI3K/Akt signaling pathway. [ABSTRACT FROM AUTHOR]

A variety of geologic landforms and features are observed within quadrangle Av-13 Tuccia in the southern hemisphere of Vesta. The quadrangle covers parts of the highland Vestalia Terra as well as the floors of the large Rheasilvia and Veneneia impact basins, which results in a substantial elevation difference of more than 40 km between the northern and the southern portions of the quadrangle. Measurements of crater size–frequency distributions within and surrounding the Rheasilvia basin indicate that gravity-driven mass wasting in the interior of the basin has been important, and that the basin has a more ancient formation age than would be expected from the crater density on the basin floor alone. Subsequent to its formation, Rheasilvia was superimposed by several mid-sized impact craters. The most prominent craters are Tuccia, Eusebia, Vibidia, Galeria, and Antonia, whose geology and formation ages are investigated in detail in this work. These impact structures provide a variety of morphologies indicating different sorts of subsequent impact-related or gravity-driven mass wasting processes. Understanding the geologic history of the relatively young craters in the Rheasilvia basin is important in order to understand the even more degraded craters in other regions of Vesta. [ABSTRACT FROM AUTHOR]

The electrical characteristics of a Pt/n-type Ge Schottky diode with a pyronine-B (PYR-B) interlayer prepared by spin coating was investigated by current–voltage ( I – V ) and capacitance–voltage ( C – V ) measurements. It was observed that the barrier height of Pt/PYR-B/n-type Ge (0.65 eV) was higher than that of the conventional Pt/n-type Ge Schottky diode (0.58 eV). This is attributed to the fact that the organic interlayer increases the effective barrier height by influencing the space-charge region of Ge. The introduction of the PYR-B interlayer led to a reduction of the interface state density in the Pt Schottky contact to n-type Ge. The electric field dependence of the reverse leakage current revealed that Schottky emission and Poole–Frenkel emission mechanisms dominated the reverse current in the Pt/n-type Ge and Pt/PYR-B/n-type Ge Schottky diodes, respectively. [ABSTRACT FROM AUTHOR]

Highlights: [•] C–f and G–f characteristics of Ir/n-InGaN SBDs are studied at different temperatures. [•] The N ss and τ of the Ir/n-InGaN SBD are determined from C–f characteristics. [•] N ss show a decrease with bias from the bottom of the CB towards the mid gap at various temperatures. [•] Results reveal that the values of relaxation time τ are higher towards the low temperature. [ABSTRACT FROM AUTHOR]

Abstract: Human adenoviruses cause a significant number of acute respiratory, enteric and ocular infections, however they have also served as useful model systems for uncovering fundamental aspects of cell and molecular biology. In addition, replication-defective forms of adenovirus are being used in gene transfer and vaccine clinical trials. Over the past decade, steady advances in structural biology techniques have helped reveal important insights into the earliest events in the adenovirus life cycle as well as virus interactions with components of the host immune system. This review highlights the continuing use of structure-based approaches to uncover the molecular features of adenovirus–host interactions. [Copyright &y& Elsevier]

Abstract: The current–voltage measurements of Pd/Pt/n-InP Schottky barrier diodes were carried out in the temperature range of 230–410 K. The current–voltage characteristics show an abnormal decrease of apparent barrier height and increase of ideality factor at low temperatures. The nonlinearity in the Richardson plot and strong dependence of barrier height and ideality factor on temperature indicates the spatial inhomogeneity in the interface. The series resistance estimated from the forward current–voltage characteristics is strongly temperature-dependent and the series resistance is decreased with an increase in temperature. A versus plot was drawn to obtain the mean barrier height ( ()) and the standard deviation () at zero bias which was found to be 0.97 eV, 151 meV respectively. The effective Richardson constant (3.85 A cm−2 K−2) obtained from the modified Richardson plot is closer to the theoretical value (9.4 A cm−2 K−2). The temperature-dependent behavior of the Pd/Pt Schottky contact has been interpreted by the assumption of a Gaussian distribution of barrier heights due to barrier inhomogeneities at the metal–semiconductor interfaces. [Copyright &y& Elsevier]

The near-stoichiometric amount of bases is used both in laboratory and industry in Wadsworth–Emmons (WE) reactions, since the by-product, (EtO)2P(O)OH, formed in the reaction neutralizes the base into an inert salt. A strategy to design, develop, and evolve the recyclable Mg–Al–hydrotalcite–O tBu (HT–O tBu) by the interaction of KO tBu with the calcined hydrotalcite that transforms a well-defined stoichiometric WE reaction into a catalytic one in an effort to minimize the quantum of effluents released and reduce the cost of the process is described here. HT–O tBu is found to be an efficient solid base for WE reactions for the simple synthesis of α,β-unsaturated esters and nitriles for the first time. The HT–O tBu, composed of various ratios of Mg/Al (i.e., 2, 2.5, and 3) and different contents of tBuO− (Mg/Al:3), and their precursors were prepared and well characterized to draw a correlation between structure and reactivity of the hydrotalcites in WE reactions. [Copyright &y& Elsevier]

Highlights • Spectra for more than 1000 near-Earth objects (NEOs) are presented and analyzed. • NEOs originate from specific regions in the main asteroid belt, according to type. • Meteorites linked to NEO classes show specific escape regions from the main belt. • Distinct spectral trends are found for surface alteration by radiation and impacts. • Altered surfaces become refreshed by planetary encounters and other processes. Abstract Advancing technology in near-infrared instrumentation and dedicated planetary telescope facilities have enabled nearly two decades of reconnoitering the spectral properties for near-Earth objects (NEOs). We report measured spectral properties for more than 1000 NEOs, representing >5% of the currently discovered population. Thermal flux detected below 2.5 µm allows us to make albedo estimates for nearly 50 objects, including two comets. Additional spectral data are reported for more than 350 Mars-crossing asteroids. Most of these measurements were achieved through a collaboration between researchers at the Massachusetts Institute of Technology and the University of Hawaii, with full cooperation of the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. We call this project the MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS; myth-neos). While MITHNEOS has continuously released all spectral data for immediate use by the scientific community, our objectives for this paper are to: (1) detail the methods and limits of the survey data, (2) formally present a compilation of results including their taxonomic classification within a single internally consistent framework, (3) perform a preliminary analysis on the overall population characteristics with a concentration toward deducing key physical processes and identifying their source region for escaping the main belt. Augmenting our newly published measurements are the previously published results from the broad NEO community, including many results graciously shared by colleagues prior to formal publication. With this collective data set, we find the near-Earth population matches the diversity of the main-belt, with all main-belt taxonomic classes represented in our sample. Potentially hazardous asteroids (PHAs) as well as the subset of mission accessible asteroids (ΔV ≤ 7 km/s) both appear to be a representative mix of the overall NEO population, consistent with strong dynamical mixing for the population that interacts most closely with Earth. Mars crossers, however, are less diverse and appear to more closely match the inner belt population from where they have more recently diffused. The fractional distributions of major taxonomic classes (60% S, 20% C, 20% other) appear remarkably constant over two orders of magnitude in size (10 km to 100 m), which is eight orders of magnitude in mass, though we note unaccounted bias effects enter into our statistics below about 500 m. Given the range of surface ages, including possible refreshment by planetary encounters, we are able to identify a very specific space weathering vector tracing the transition from Q- to Sq- to S-types that follows the natural dispersion for asteroid spectra mapped into principal component space. We also are able to interpret a shock darkening vector that may account for some objects having featureless spectra. Space weathering effects for C-types are complex; these results are described separately by Lantz, Binzel, DeMeo. (2018, Icarus 302, 10–17). Independent correlation of dynamical models with taxonomic classes map the escape zones for NEOs to main-belt regions consistent with well established heliocentric compositional gradients. We push beyond taxonomy to interpret our visible plus near-infrared spectra in terms of the olivine and pyroxene mineralogy consistent with the H, L, and LL classes of ordinary chondrites meteorites. Correlating meteorite interpretations with dynamical escape region models shows a preference for LL chondrites to arrive from the ν 6 resonance and H chondrites to have a preferential signature from the mid-belt region (3:1 resonance). L chondrites show some preference toward the outer belt, but not at a significant level. We define a Space Weathering Parameter as a continuous variable and find evidence for step-wise changes in space weathering properties across different planet crossing zones in the inner solar system. Overall we hypothesize the relative roles of planetary encounters, YORP spin-up, and thermal cycling across the inner solar system. [ABSTRACT FROM AUTHOR]

The temperature-dependent current-voltage ( I-V ) characteristics of permalloy (Ni 0.8 Fe 0.2 ) Schottky contacts to n-type GaN have been investigated. Magnetization measurements revealed the ferromagnetic behavior of Ni 0.8 Fe 0.2 film on n-type GaN. The Schottky barrier parameters, such as the barrier height and ideality factor, determined by thermionic emission depended on the measurement temperature, suggesting the presence of lateral inhomogeneity in the Schottky barrier. The experimental data modified by the thermionic emission model along with a Gaussian distribution of the barrier heights indicated the presence of a double Gaussian barrier distribution in the Ni 0.8 Fe 0.2 /n-type GaN Schottky contact. The mean barrier heights and standard deviations for each Gaussian distribution were 0.84 & 1.32 eV and 0.10 & 0.17 eV over temperature range of 125–200 K and 225–400 K, respectively. The noise spectral density of the current fluctuations measured as a function of frequency ( f ) at room temperature followed a 1/ f γ dependence with a γ value close to unity, irrespective of the applied forward bias. The 1/ f- type noise was attributed to the barrier inhomogeneity existing at the Ni 0.8 Fe 0.2 /n-type GaN Schottky interface as revealed from the temperature-dependent I – V characteristics. [ABSTRACT FROM AUTHOR]

Several carbonaceous chondrites (CCs) display evidence of aqueous and thermal alteration. However, the process of thermal alteration is not fully understood. To investigate the spectral variations caused by thermal alteration, we heated powders of CM2 CCs Murchison and Jbilet Winselwan, as well as a simulant Murchison mixture (WMM) and its end members. Heating was conducted up to 1200 °C, in 100 °C increments under a purified nitrogen environment. We also compared the findings of our study with results of previous heating experiments conducted on CCs to better understand the effect differing conditions have on the spectral properties observed. Formation of Fe3+ oxyhydroxides and the decomposition of serpentine due to heating are confirmed by both reflectance and X-ray diffraction (XRD) data. Fe3+ oxyhydroxides features such as a steep slope in between 350 to ∼700 nm, and an ∼850 nm feature can be seen starting at ∼300 and 400 °C, respectively. The serpentine-associated features start to decompose at ∼700 °C and disappear by ∼900 °C. Spectra >1000 °C are generally dark and featureless and above this temperature, mafic silicate absorption bands begin to appear. Our results show that heating-induced spectral variations are evident, and the nature of these changes depends on various parameters including temperature, experimental conditions, duration of heating, sample grain size, as well as mineralogical changes accompanying heating, and heterogeneity between CCs. • CM2 Murchison and Jbilet Winselwan and analogues were subject to heating experiments to temperatures up to 1200 °C. • Several spectral metrics were identified to characterize the spectral properties of the samples. • Temperature and environmental conditions are the most dominant factors controlling the observed spectral variations. • Other factors include differences in grain size, mineralogy, and the duration of heating. • Spectral variations are also caused by the heterogeneity between carbonaceous chondrites. [ABSTRACT FROM AUTHOR]

Au-CuPc nanocomposite films were prepared by simultaneous evaporation of Au and CuPc with various Au and CuPc concentrations. Microstructural analysis of Au-CuPc films revealed elongated Au cluster formation from isolated Au nanoclusters with increasing Au concentration associated with coalescence of Au clusters. Au-CuPc films with different compositions were employed as interlayer in Al/n-Si Schottky diode. Barrier height and series resistance of the Al/n-Si Schottky diode with Au-CuPc interlayer decreased with increasing Au concentration. This could be associated with the enhancement of electron tunneling between neighboring clusters due to decrease in spacing of Au clusters and formation of conducting paths through the composite material. Interface state density of the Al/n-Si Schottky diode with Au-CuPc interlayer increased with increasing Au concentration. This might be because the inclusion of metal decreases the crystallinity and crystal size of the polymer matrix accompanied by the formation of local defect sites at the places of metal nucleation. [ABSTRACT FROM AUTHOR]

Au/Ba 0.6 Sr 0.4 TiO 3 (BST)/n-InP metal/insulator/semiconductor (MIS) Schottky diodes have been analyzed by current-voltage ( I-V ) and capacitance-voltage ( C-V ) measurements. The surface morphology of the BST films on InP is fairly smooth. The Au/BST/n-InP MIS Schottky diode shows better rectification ratio and low leakage current compared to the conventional Au/n-InP metal-semiconductor (MS) Schottky diode. Higher barrier height is achieved for the MIS Schottky diode compared to the MS Schottky diode. The Norde and Cheung's methods are employed to determine the barrier height, ideality factor and series resistance. The interface state density ( N SS ) is determined from the forward bias I-V data for both the MS and MIS Schottky diodes. Results reveal that the N SS of the MIS Schottky diode is lower than that of the MS Schottky diode. The Poole-Frenkel emission is found dominating the reverse current in both Au/n-InP MS and Au/BST/n-InP MIS Schottky diodes, indicating the presence of structural defects and trap levels in the dielectric film. [ABSTRACT FROM AUTHOR]

Analysis of data from the Dawn mission shows that the Pinaria region of Vesta spanning a portion of the rim of the Rheasilvia basin is bright and anhydrous. Reflectance spectra, absorption band centers, and their variations, cover the range of pyroxenes from diogenite-rich to howardite and eucrite compositions, with no evidence of olivine in this region. By examining band centers and depths of the floor, walls and rims of six major craters in the region, we find a lane of diogenite-rich material next to howardite–eucrite material that does not follow the local topography. The source of this material is not clear and is probably ejecta from post-Rheasilvia impacts. Material of a howardite–eucrite composition originating from beyond the Rheasilvia basin is evident on the western edge of the region. Overall, the Pinaria region exposes the complete range of basaltic achondrite parent body material, with little evidence of contamination of non-basaltic achondrite material. With both high reflectance and low abundance of hydrated material, this region of Vesta may be considered the “Pinaria desert”. [ABSTRACT FROM AUTHOR]

The effects of annealing temperature on the electrical, structural and surface morphological properties of Ru/Ti/ n -InP Schottky diode have been investigated. Calculations showed that the Schottky barrier height (SBH) and ideality factor n of the as-deposited Ru/Ti/ n -InP Schottky diode are 0.82 eV ( I – V )/1.00 eV ( C – V ) and 1.19, respectively. However, it is observed that the SBH of Ru/Ti/ n -InP Schottky diode decreases upon annealing at 200 °C, 300 °C and 400 °C. Cheung’s and Norde method are also employed to calculate the SBH, ideality factor and series resistance of the Ru/Ti/ n -InP Schottky diode as a function of annealing temperature. Experimental results reveal that the SBH and series resistance of the Ru/Ti/ n -InP Schottky diode decreases upon annealing temperatures. The energy distribution of interface state density ( N ss ) is determined for the Ru/Ti/ n -InP Schottky diode at different annealing temperatures. The X-ray diffraction studies revealed that the formation of phosphide phases at the Ru/Ti/ n -InP interface may be the cause for the decrease of SBH upon annealing temperature. The AFM results indicated that there is no significant degradation in the surface morphology of the Ru/Ti Schottky contacts at elevated annealing temperatures. [ABSTRACT FROM AUTHOR]

The howardite, eucrite and diogenite (HED) meteorites are genetically related and represent the most voluminous group of achondrites. They are the closest analog materials to Vesta and V-type asteroids. Many of these meteorites were the focus of intense petrologic and visible to near infrared spectral studies. As ground-based and orbital observations of basaltic asteroids have increased, an improved understanding of HEDs is needed. For this study, we investigated 24 HED samples, mainly new finds from Northwest Africa (NWA). Visible to near infrared (up to 2.5 μm) spectral measurements under varying illumination and observation geometries were acquired for 4 samples. Phase reddening and bluing (i.e., increase and decrease in spectral slope) is observed for the visible slope as phase angle increase. Monotonic phase reddening can occur for the near infrared slope as phase angle increase. Non-systematic changes with phase angle are found for the Band Area Ratio parameter. At phase angles higher than ∼60°, the decrease of reflectance and decrease of pyroxene bands depth are undistinguishable from admixture of low albedo material to HED samples. To assess the precision of empirical equations relating spectral properties and composition, the pyroxenes, feldspar, and olivine chemistry of the samples was determined. Using previous calibrations, systematic overestimations of the ferrosilite (Fs) and wollastonite (Wo) contents are found, especially in the 15–40 Fs range. To overcome such discrepancies, a new set of empirical equations is proposed. For an application of the new calibration, we selected two compositional end-member areas on Vesta on the basis of their iron content. For the iron-poor terrain we found an average pyroxene composition of Fs 30 Wo 5 and for the iron-rich terrain an average of Fs 47 Wo 14 . [ABSTRACT FROM AUTHOR]

Reflectance spectra of many asteroids and other Solar System bodies are commonly reported as “featureless”. Here, we show that weak but consistently detectable absorption bands are observable in 200–2500 nm spectra of the Tagish Lake meteorite, a likely compositional and spectral analogue for low-albedo, “spectrally-featureless” asteroids. Tagish Lake presents a rare opportunity to study multiple lithologies within a single meteorite. Reflectance spectra of Tagish Lake display significant variation between different lithologies. The spectral variations are due in part to mineralogical variations between different Tagish Lake lithologies. Ultraviolet reflectance spectra (200–400 nm), few of which have been reported in the literature to date, reveal albedo and spectral ratio variations as a function of mineralogy. Similarly visible–near infrared reflectance spectra reveal variations in albedo, spectral slope, and the presence of weak absorption features that persist across different lithologies and can be attributed to various phases present in Tagish Lake. These observations demonstrate that significant spectral variability may exist between different lithologies of Tagish Lake, which may affect the interpretation of potential source body spectra. It is also important to consider the spectral variability within the meteorite before excluding compositional links between possible parent bodies in the main belt and Tagish Lake. Tagish Lake materials may also be spectral–compositional analogues for materials on the surfaces of other dark asteroids, including some that are targets of upcoming spacecraft missions. Tagish Lake has been proposed as a spectral match for ‘ultra-primitive’ D or P-type asteroids, and the variability reported here may be reflected in spatially or rotationally-resolved spectra of possible Tagish Lake parent bodies and source objects in the Near-Earth Asteroid population. A search for objects with spectra similar to Tagish Lake has been carried out among the Near-Earth Asteroids. We have identified three possible spectral matches, the best of which are Asteroids (326732) 2003 HB6, and (17274) 2000 LC16. [ABSTRACT FROM AUTHOR]

We produced a geologic map of the Av-9 Numisia quadrangle of asteroid Vesta using Dawn spacecraft data to serve as a tool to understand the geologic relations of surface features in this region. These features include the plateau Vestalia Terra, a hill named Brumalia Tholus, and an unusual “dark ribbon” material crossing the majority of the map area. Stratigraphic relations suggest that Vestalia Terra is one of the oldest features on Vesta, despite a model crater age date similar to that of much of the surface of the asteroid. Cornelia, Numisia and Drusilla craters reveal bright and dark material in their walls, and both Cornelia and Numisia have smooth and pitted terrains on their floors suggestive of the release of volatiles during or shortly after the impacts that formed these craters. Cornelia, Fabia and Teia craters have extensive bright ejecta lobes. While diogenitic material has been identified in association with the bright Teia and Fabia ejecta, hydroxyl has been detected in the dark material within Cornelia, Numisia and Drusilla. Three large pit crater chains appear in the map area, with an orientation similar to the equatorial troughs that cut the majority of Vesta. Analysis of these features has led to several interpretations of the geological history of the region. Vestalia Terra appears to be mechanically stronger than the rest of Vesta. Brumalia Tholus may be the surface representation of a dike-fed laccolith. The dark ribbon feature is proposed to represent a long-runout ejecta flow from Drusilla crater. [ABSTRACT FROM AUTHOR]

Highlights: [•] The 4–6μm region reflectance spectra of 13 HED meteorites were studied. [•] They exhibit absorption bands in this region due to Si–(Al–)O overtones. [•] The position of these bands can be related to their major minerals. [•] These bands appear in all HED spectra, from fine-grained powders to slabs. [ABSTRACT FROM AUTHOR]

Abstract: The effect of annealing temperature on interface properties of iridium/ruthenium (Ir/Ru) Schottky contacts on n-type InGaN have been investigated by current–voltage (I–V), capacitance–voltage (C–V), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) techniques. An as-deposited Ru/Ir/n-InGaN Schottky diode exhibits a barrier height of 0.61eV (I–V) and 0.79eV (C–V), which increases to 0.71eV (I–V) and 0.96eV (C–V) after annealing at 200°C. A maximum barrier height of 0.73eV (I–V) and 1.02eV (C–V) is achieved for the Ir/Ru Schottky contacts after annealing at 300°C. Further, it is observed that the Schottky barrier height slightly decreases upon annealing at temperatures of 400°C and 500°C and the obtained values are 0.68eV (I–V), 0.93eV (C–V) and 0.66eV (I–V), 0.86eV (C–V), respectively. The Norde and Cheung’s methods are used to extract the barrier height (Φb ), ideality factor (n) and series resistance (R s). The interface state density is also determined by Terman’s method. According to the above results, the optimum annealing temperature for Ru/Ir/n-InGaN Schottky diode is 300°C. Based on the AES and XRD analysis, the formation of gallide phases at the Ru/Ir/n-InGaN interface could be the reason for the increase of Schottky barrier heights upon annealing temperatures. It is noted that overall surface morphology of Ir/Ru Schottky contacts is reasonably smooth even after annealing at 500°C as observed from AFM results. [Copyright &y& Elsevier]

Abstract: We have studied the spectral reflectance properties of the CM2 xenolith-bearing howardite PRA 04401, intimate and areal mixtures of a eucrite (Millbillillie) and a CM2 chondrite (Murchison), and a mineralogically diverse suite of 12 HED meteorites. The main goal is to ascertain whether the presence of CM2-type material can be discriminated from grain size variations in HEDs. This project was motivated by the presence of CM2 material in a number of howardites. This study is of high relevance to Vesta because of the detection of low-albedo features on its surface by the Framing Camera (FC) aboard NASA’s Dawn spacecraft. The addition of CM2 material and increasing HED grain size both lead to decreasing overall albedo. However these two processes can be recognized by how they affect pyroxene band depths and shapes and, to a lesser extent, band widths. Pyroxene band depths and widths decrease with increasing CM2 abundance and increase with increasing HED grain size, as do various FC reflectance ratios. HED pyroxene absorption bands appear to reach saturation when grain size is in the region of 60–170μm, with band I saturating at smaller grain sizes than band II. Band I centers are largely insensitive to CM2 abundances or HED grain size variations, while Band II center positions increase by up to 40nm with increasing CM2 abundance, and vary non-systematically by up to 22nm as a function of grain size. The variation with CM2 abundance is probably due to the red-sloped nature of the CM2 spectrum and the broad and shallow nature of the pyroxene band II absorption. Band area ratios show less consistent behavior, likely due to CM2-induced slope changes in the mixtures and band saturation effects in the HEDs. Because HED pyroxene is so strongly featured, CM2 abundances must be well in excess of 80wt.% to allow for the appearance of their much weaker CM2 phyllosilicate absorption bands. CM2 material may also cause a reddening of spectral slope and a shifting of pyroxene band minima to shorter wavelengths, although CM2 chondrites can exhibit a range of spectral slopes. The presence of submicron opaques (specifically chromite) in HED pyroxenes can lead to large variations in all spectral parameters. Discriminating the spectrum-altering effects of CM2 material from HED grain size variations is possible, with the confidence in the interpretation increasing as a larger range of spectral parameters are applied to the analysis. [Copyright &y& Elsevier]

Abstract: Suppression of wing fate and specification of haltere fate in Drosophila by the homeotic gene Ultrabithorax is a classical example of Hox regulation of serial homology (Lewis, E.B. 1978. Nature 276, 565–570) and has served as a paradigm for understanding homeotic gene function. We have used DNA microarray analyses to identify potential targets of Ultrabithorax function during haltere specification. Expression patterns of 18 validated target genes and functional analyses of a subset of these genes suggest that down-regulation of both anterior–posterior and dorso-ventral signaling is critical for haltere fate specification. This is further confirmed by the observation that combined over-expression of Decapentaplegic and Vestigial is sufficient to override the effect of Ubx and cause dramatic haltere-to-wing transformations. Our results also demonstrate that analysis of the differential development of wing and haltere is a good assay system to identify novel regulators of key signaling pathways. [Copyright &y& Elsevier]

Obesity is a global health problem associated with several diseases including ocular complications. Earlier we reported progressive retinal degeneration because of obesity in a spontaneous obese rat (WNIN/Ob) model. In the current study, we examined the molecular mechanisms leading to retinal degeneration in WNIN/Ob rat. Sorbitol was estimated by the fluorometric method in the retina of WNIN/Ob rats at different age (3-, 6- and 12- months), along with their respective lean rats. Immunoblotting was performed in the retina to assess the status of the insulin signaling pathway, ER stress and cellular stress (p38MAPK and ERK1/2). Human SK-N-SH cells were treated with 0.5 and 1.0 M sorbitol for 30 min to study insulin signaling, ER stress, and cellular stress. TUNEL assay was done to measure apoptosis. The retinal function in the rats was determined by electroretinogram. A gradual but significantly higher intracellular sorbitol accumulation was observed in the retina of obese rats from 3- to 12-months. The cellular osmotic stress has activated the insulin signaling mechanism without activating AKT and also triggered ER stress. Both the stresses activated the ERK and p38MAPK signaling causing apoptosis in the retina leading to retinal degeneration. Retinal dysfunction was confirmed by altered scotopic and photopic electroretinogram responses. These in vivo results were mimicked in SK-N-SH cells when exposed to sorbitol in vitro. These results suggest cellular stress due to sorbitol accumulation impairing the ER function, thereby leading to progressive retinal degeneration under obese conditions. • Retinal disorders are the new addition to the mounting list of obesity associated diseases. • Retinal function is impaired in WNIN/Ob rats as indicated by electroretinogram. • Intracellular sorbitol accumulation activated proximal insulin signaling mediators but not AKT. • MAPKs that are negative regulators of insulin signaling are elevated in the retina. • Sorbitol induces ER stress and thereby apoptosis in the retina of obese rats. [ABSTRACT FROM AUTHOR]