How Oxygen Exposure Improves the Back Contact and Performance of Antimony Selenide Solar Cells.

The improvement of antimony selenide solar cells by short-term air exposure is explained using complementary cell and material studies. We demonstrate that exposure to air yields a relative efficiency improvement of n-type Sb2Se3 solar cells of ca. 10% by oxidation of the back surface and a reduction in the back contact barrier height (measured by J-V-T) from 320 to 280 meV. X-ray photoelectron spectroscopy (XPS) measurements of the back surface reveal that during 5 days in air, Sb2O3 content at the sample surface increased by 27%, leaving a more Se-rich Sb2Se3 film along with a 4% increase in elemental Se. Conversely, exposure to 5 days of vacuum resulted in a loss of Se from the Sb2Se3 film, which increased the back contact barrier height to 370 meV. Inclusion of a thermally evaporated thin film of Sb2O3 and Se at the back of the Sb2Se3 absorber achieved a peak solar cell efficiency of 5.87%. These results demonstrate the importance of a Se-rich back surface for high-efficiency devices and the positive effects of an ultrathin antimony oxide layer. This study reveals a possible role of back contact etching in exposing a beneficial back surface and provides a route to increasing device efficiency.

Modular Design via Multiple Anion Chemistry of the High Mobility van der Waals Semiconductor Bi4O4SeCl2.

Making new van der Waals materials with electronic or magnetic functionality is a chemical design challenge for the development of two-dimensional nanoelectronic and energy conversion devices. We present the synthesis and properties of the van der Waals material Bi4O4SeCl2, which is a 1:1 superlattice of the structural units present in the van der Waals insulator BiOCl and the three-dimensionally connected semiconductor Bi2O2Se. The presence of three anions gives the new structure both the bridging selenide anion sites that connect pairs of Bi2O2 layers in Bi2O2Se and the terminal chloride sites that produce the van der Waals gap in BiOCl. This retains the electronic properties of Bi2O2Se while reducing the dimensionality of the bonding network connecting the Bi2O2Se units to allow exfoliation of Bi4O4SeCl2 to 1.4 nm height. The superlattice structure is stabilized by the configurational entropy of anion disorder across the terminal and bridging sites. The reduction in connective dimensionality with retention of electronic functionality stems from the expanded anion compositional diversity.

A CO2 -Tolerant Perovskite Oxide with High Oxide Ion and Electronic Conductivity.

Mixed ionic-electronic conductors (MIECs) that display high oxide ion conductivity (σo ) and electronic conductivity (σe ) constitute an important family of electrocatalysts for a variety of applications including fuel cells and oxygen separation membranes. Often MIECs exhibit sufficient σe but inadequate σo . It has been a long-standing challenge to develop MIECs with both high σo and stability under device operation conditions. For example, the well-known perovskite oxide Ba0.5 Sr0.5 Co0.8 Fe0.2 O3- δ (BSCF) exhibits exceptional σo and electrocatalytic activity. The reactivity of BSCF with CO2 , however, limits its use in practical applications. Here, the perovskite oxide Bi0.15 Sr0.85 Co0.8 Fe0.2 O3- δ (BiSCF) is shown to exhibit not only exceptional bulk transport properties, with a σo among the highest for known MIECs, but also high CO2 tolerance. When used as an oxygen separation membrane, BiSCF displays high oxygen permeability comparable to that of BSCF and much higher stability under CO2 . The combination of high oxide transport properties and CO2 tolerance in a single-phase MIEC gives BiSCF a significant advantage over existing MIECs for practical applications.

Low-Temperature Wafer-Scale Deposition of Continuous 2D SnS2 Films.

Semiconducting 2D materials, such as SnS2 , hold immense potential for many applications ranging from electronics to catalysis. However, deposition of few-layer SnS2 films has remained a great challenge. Herein, continuous wafer-scale 2D SnS2 films with accurately controlled thickness (2 to 10 monolayers) are realized by combining a new atomic layer deposition process with low-temperature (250 °C) postdeposition annealing. Uniform coating of large-area and 3D substrates is demonstrated owing to the unique self-limiting growth mechanism of atomic layer deposition. Detailed characterization confirms the 1T-type crystal structure and composition, smoothness, and continuity of the SnS2 films. A two-stage deposition process is also introduced to improve the texture of the films. Successful deposition of continuous, high-quality SnS2 films at low temperatures constitutes a crucial step toward various applications of 2D semiconductors.

Enteric coronavirus infection in adult horses.

A new enteric virus of adult horses, equine coronavirus (ECoV), has recently been recognized. It is associated with fever, lethargy, anorexia, and less frequently, colic and diarrhea. This enteric virus is transmitted via the feco-oral route and horses become infected by ingesting fecally contaminated feed and water. Various outbreaks have been reported since 2010 from Japan, Europe and the USA. While the clinical signs are fairly non-specific, lymphopenia and neutropenia are often seen. Specific diagnosis is made by the detection of ECoV in feces by either quantitative real-time PCR, electron microscopy or antigen-capture ELISA. Supportive treatment is usually required, as most infections are self-limiting. However, rare complications, such as endotoxemia, septicemia and hyperammonemia-associated encephalopathy, have been reported, and have been related to the loss of barrier function at the intestinal mucosa. This review article will focus on the latest information pertaining to the virus, epidemiology, clinical signs, diagnosis, pathology, treatment and prevention of ECoV infection in adult horses.

Bi4O4Cu1.7Se2.7Cl0.3: Intergrowth of BiOCuSe and Bi2O2Se Stabilized by the Addition of a Third Anion.

Layered two-anion compounds are of interest for their diverse electronic properties. The modular nature of their layered structures offers opportunities for the construction of complex stackings used to introduce or tune functionality, but the accessible layer combinations are limited by the crystal chemistries of the available anions. We present a layered three-anion material, Bi4O4Cu1.7Se2.7Cl0.3, which adopts a new structure type composed of alternately stacked BiOCuSe and Bi2O2Se-like units. This structure is accessed by inclusion of three chemically distinct anions, which are accommodated by aliovalently substituted Bi2O2Se0.7Cl0.3 blocks coupled to Cu-deficient Bi2O2Cu1.7Se2 blocks, producing a formal charge modulation along the stacking direction. The hypothetical parent phase Bi4O4Cu2Se3 is unstable with respect to its charge-neutral stoichiometric building blocks. The complex layer stacking confers excellent thermal properties upon Bi4O4Cu1.7Se2.7Cl0.3: a room-temperature thermal conductivity (κ) of 0.4(1) W/mK was measured on a pellet with preferred crystallite orientation along the stacking axis, with perpendicular measurement indicating it is also highly anisotropic. This κ value lies in the ultralow regime and is smaller than those of both BiOCuSe and Bi2O2Se. Bi4O4Cu1.7Se2.7Cl0.3 behaves like a charge-balanced semiconductor with a narrow band gap. The chemical diversity offered by the additional anion allows the integration of two common structural units in a single phase by the simultaneous and coupled creation of charge-balancing defects in each of the units.

Equine coronavirus: An emerging enteric virus of adult horses.

Equine coronavirus (ECoV) is an emerging virus associated clinically and epidemiologically with fever, depression, anorexia and less frequently colic and diarrhoea in adult horses. Sporadic cases and outbreaks have been reported with increased frequency since 2010 from Japan, the USA and more recently from Europe. A faeco-oral transmission route is suspected and clinical or asymptomatic infected horses appear to be responsible for direct and indirect transmission of ECoV. A presumptive clinical diagnosis of ECoV infection may be suggested by clinical presentation, haematological abnormalities such as leucopenia due to lymphopenia and/or neutropenia. Confirmation of ECoV infection is provided by specific ECoV nucleic acid detection in faeces by quantitative PCR (qPCR) or demonstration of coronavirus antigen by immunohistochemistry or electron microscopy in intestinal biopsy material obtained ante or post mortem. The disease is generally self-limiting and horses typically recover with symptomatic supportive care. Complications associated with disruption of the gastrointestinal barrier have been reported in some infected horses and include endotoxaemia, septicaemia and hyperammonaemia-associated encephalopathy. Although specific immunoprophylactic measures have been shown to be effective in disease prevention for closely-related coronaviruses such as bovine coronavirus (BCoV), such strategies have yet not been investigated for horses and disease prevention is limited to basic biosecurity protocols. This article reviews current knowledge concerning the aetiology, epidemiology, clinical signs, diagnosis, pathology, treatment and prevention of ECoV infection in adult horses.

Radiographic scoring lacks predictive value in inflammatory airway disease.

REASONS FOR PERFORMING STUDY: Diagnosis of inflammatory airway disease (IAD) currently rests upon the results of bronchoalveolar lavage (BAL) cytology, lung function testing and histamine bronchoprovocation (HBP), none of which provides direct information about structural change in the lung. HYPOTHESIS: That thoracic radiography might better portray structural change in the lungs and therefore offer a good clinical assessment of IAD. METHODS: A radiographic scoring system was developed to assess the extent of bronchial and interstitial pattern on thoracic radiographs in the dorsocaudal, dorsocranial and caudoventral regions in 16 control horses and 33 horses with IAD. Mean scores were compared to ascertain whether thoracic radiographs could distinguish between the 2 groups. In order to determine whether independent observers reliably scored radiographs similarly, an inter-rater reliability score was employed for each radiographic observation. Correlations between radiographic scores, BAL cytology, lung function testing using the forced oscillatory technique and HBP were examined. RESULTS: Inter-rater reliability was only moderate. Radiographic scoring demonstrated no differences between the 2 groups. There were no correlations among BAL cytology, lung function testing, HBP and radiographic scores. CONCLUSIONS AND POTENTIAL RELEVANCE: Thoracic radiographs are a low-yield diagnostic modality in horses with a clinical history compatible with IAD. In the absence of clinical evidence of more extensive, infectious disease, thoracic radiographs neither refine nor improve diagnosis of IAD, but increase diagnostic costs.

Molecular ordering in isonicotinic acid on rutile TiO2(110) investigated with valence band photoemission.

The adsorption of isonicotinic acid on rutile TiO(2)(110) has been investigated using synchrotron-based valence band photoemission. Structural ordering in multilayer films of the molecules is found to give rise to a strong angular dependence in the valence band intensities when measured using linearly polarized radiation. Molecular ordering in this case is proposed to be induced by intermolecular hydrogen bonding which is found to be highly dependent upon the deposition rate of the isonicotinic acid. Through comparison of the experimental data with density functional calculated valence band spectra of hydrogen-bonded isonicotinic acid molecules, we can account for the angular dependence in terms of the spatial distribution of the molecular orbitals.

Bronchoscopic volume reduction: a safe and effective alternative to surgical therapy for emphysema.

Lung volume reduction surgery (LVRS), the removal of damaged, hyperexpanded lung, has been shown to improve respiratory function in many patients with end-stage emphysema. We report the results of an animal study using a new transbronchoscopic alternative to LVRS in which a washout solution and fibrin-based glue are used to collapse, seal, and scar target regions of abnormal lung. Twelve sheep had static and dynamic lung functions measured at baseline. Emphysema was produced by inhaled papain (7,000 U/wk x 4 wk), resulting in a significant increase of lung volumes, compliance, and airway resistance. The animals were then divided into three treatment groups of four animals, and underwent surgical volume reduction (SVR), bronchoscopic volume reduction (BVR), or bronchoscopy alone (Sham-BVR). Response to each intervention was assessed 8 to 12 wk after treatment by measuring lung function and examining lung tissue. BVR and SVR groups responded with significant and similar decreases in TLC and residual volume (RV). Tissue examination demonstrated that BVR caused collapse of the lung with focal scarring in 11 of 20 target territories (55% success rate). Three of the 11 target zones developed sterile abscesses. Postprocedure complications were less frequent with BVR than with SVR. This pilot study suggests that lung volume reduction can be achieved in animals without surgery using a bronchoscopic approach and a novel fibrin-based glue system. BVR has the potential for simplifying volume reduction, extending indications, and reducing morbidity, mortality, and costs in humans.