2,892 research outputs found
Hybrid TiO2 Solar Cells Produced from Aerosolized Nanoparticles of Water-Soluble Polythiophene Electron Donor Layer
Hybrid solar cells (HSCs) with water soluble polythiophene sodium poly[2-(3-thienyl)-ethyloxy-4-butylsulfonate] (PTEBS) thin films produced using electrospray deposition (ESD) were fabricated, tested, and modeled and compared to devices produced using conventional spin coating. A single device structure of FTO/TiO2/PTEBS/Au was used to study the effects of ESD of the PTEBS layer on device performance. ESD was found to increase the short circuit current density (Jsc) by a factor of 2 while decreasing the open circuit voltage (Voc) by half compared to spin coated PTEBS films. Comparable efficiencies of 0.009% were achieved from both device construction types. Current-voltage curves were modeled using the characteristic solar cell equation and showed a similar increase in generated photocurrent with an increase by two orders of magnitude in the saturation current in devices from ESD films. Increases in Jsc are attributed to an increase in the interfacial contact area between the TiO2 and PTEBS layers, while decreases in Voc are attributed to incomplete film formation from ESD
Mass production of volume phase holographic gratings for the VIRUS spectrograph array
The Visible Integral-field Replicable Unit Spectrograph (VIRUS) is a baseline
array of 150 copies of a simple, fiber-fed integral field spectrograph that
will be deployed on the Hobby-Eberly Telescope (HET). VIRUS is the first
optical astronomical instrument to be replicated on an industrial scale, and
represents a relatively inexpensive solution for carrying out large-area
spectroscopic surveys, such as the HET Dark Energy Experiment (HETDEX). Each
spectrograph contains a volume phase holographic (VPH) grating with a 138 mm
diameter clear aperture as its dispersing element. The instrument utilizes the
grating in first-order for 350-550 nm. Including witness samples, a suite of
170 VPH gratings has been mass produced for VIRUS. Here, we present the design
of the VIRUS VPH gratings and a discussion of their mass production. We
additionally present the design and functionality of a custom apparatus that
has been used to rapidly test the first-order diffraction efficiency of the
gratings for various discrete wavelengths within the VIRUS spectral range. This
device has been used to perform both in-situ tests to monitor the effects of
adjustments to the production prescription as well as to carry out the final
acceptance tests of the gratings' diffraction efficiency. Finally, we present
the as-built performance results for the entire suite of VPH gratings.Comment: 16 pages, 11 figures, 2 tables. To be published in Proc. SPIE, 2014,
"Advances in Optical and Mechanical Technologies for Telescopes and
Instrumentation", 9151-53. The work presented in this article follows from
arXiv:1207:448
Need for Aeromedical Evacuation High-Level Containment Transport Guidelines
Circumstances exist that call for the aeromedical evacuation high-level containment transport (AE-HLCT) of patients with highly hazardous communicable diseases. A small number of organizations maintain AE-HLCT capabilities, and little is publicly available regarding the practices. The time is ripe for the development of standards and consensus guidelines involving AE-HLCT
Near-Peer Teaching in Radiology Symposia: A Success Story in Residents as Teachers
INTRODUCTION
Peer learning and near-peer teaching have been described in many specialties, less so in Radiology. We present near-peer teaching whereby residents present a series of didactic sessions at the course outset in the form of “symposia” and perform a scholarly activity in the form of teaching. We aim to demonstrate how near-peer teaching in symposia front-loaded within an introductory radiology course can improve medical student satisfaction.
METHOD
A total of 169 students were enrolled over a period of 3 years, 55 before (2017-2018) and 114 (2018-2020) after the introduction of the symposium. Anonymous course evaluations were collected from all students. In addition, 240 fourth-year medical students who also attended symposium lectures received satisfaction surveys in 2019 and 2020.
RESULTS
All (169/169, 100%) students taking the course evaluated it. Overall evaluation scores rose from 8.3/10 to 9.0/10 post-symposia. Among student satisfaction surveys, 89/240 (37%) specifically commented on symposia; 91% (80/89) of those found symposia very or extremely informative. 29/71 (41%) of all residents were able to participate in the symposia, 20/29 in multiple years throughout residency, allowing them to fulfill the Accreditation Council for Graduate Medical Education interpersonal and communication skills core competencies and meet scholarly activity requirements.
CONCLUSION
Near-peer teaching in the form of resident-taught interactive didactics grouped in symposia can have a positive outcome on medical student satisfaction
Linking Remotely Sensed Carbon and Water Use Efficiencies with In Situ Soil Properties
The capacity of terrestrial ecosystems to sequester carbon dioxide (CO2 ) from the atmosphere is expected to be altered by climate change and CO2 fertilization, but this projection is limited by our understanding of how the soil system interacts with plants. Understanding the soil–vegetation interactions is essential to assess the magnitude and response of terrestrial ecosystems to the changing climate. Here, we used soil profile and satellite data to explore the role that soil properties play in regulating water and carbon use by plants. Data obtained for 19 terrestrial ecosystem sites in a warm temperate and humid climate were used to investigate the relationship between remotely sensed data and soil physical and chemical properties. Classification and regression tree results showed that in situ soil carbon isotope (δ 13C), and soil order were significant predictors (r2 = 0.39, mean absolute error (MAE) = 0 of 0.175 gC/KgH2O) of remotely sensed water use efficiency (WUE) based on the Moderate Resolution Imaging Spectroradiometer (MODIS). Soil extractable calcium (Ca), and land cover type were significant predictors of remotely sensed carbon use efficiency (CUE) based on MODIS and Landsat data-(r2 = 0.64–0.78, MAE = 0.04–0.06). We used gross primary productivity (GPP) derived from solar-induced fluorescence (SIF) data, based on the Orbiting Carbon Observatory-2 (OCO-2), to calculate WUE and CUE (referred to as WUESIF and CUESIF, respectively) for our study sites. The regression tree analysis revealed that soil organic matter and soil extractable magnesium (Mg), δ 13C, and soil silt content were the important predictors of both WUESIF (r2 = 0.19, MAE = 0.64 gC/KgH2O) and CUESIF (r2 = 0.45, MAE = 0.1), respectively. Our results revealed the importance of soil extractable Ca, soil carbon (S13C is a facet of soil carbon content), and soil organic matter predicting CUE and WUE. Insights gained from this study highlighted the importance of biotic and abiotic factors regulating plant and soil interactions. These types of data are timely and critical for accurate predictions of how terrestrial ecosystems respond to climate change
Cigarette Smoke Initiates Oxidative Stress-Induced Cellular Phenotypic Modulation Leading to Cerebral Aneurysm Pathogenesis.
OBJECTIVE: Cigarette smoke exposure (CSE) is a risk factor for cerebral aneurysm (CA) formation, but the molecular mechanisms are unclear. Although CSE is known to contribute to excess reactive oxygen species generation, the role of oxidative stress on vascular smooth muscle cell (VSMC) phenotypic modulation and pathogenesis of CAs is unknown. The goal of this study was to investigate whether CSE activates a NOX (NADPH oxidase)-dependent pathway leading to VSMC phenotypic modulation and CA formation and rupture.
APPROACH AND RESULTS: In cultured cerebral VSMCs, CSE increased expression of NOX1 and reactive oxygen species which preceded upregulation of proinflammatory/matrix remodeling genes (MCP-1, MMPs [matrix metalloproteinase], TNF-α, IL-1β, NF-κB, KLF4 [Kruppel-like factor 4]) and downregulation of contractile genes (SM-α-actin [smooth muscle α actin], SM-22α [smooth muscle 22α], SM-MHC [smooth muscle myosin heavy chain]) and myocardin. Inhibition of reactive oxygen species production and knockdown of NOX1 with siRNA or antisense decreased CSE-induced upregulation of NOX1 and inflammatory genes and downregulation of VSMC contractile genes and myocardin. p47phox-/- NOX knockout mice, or pretreatment with the NOX inhibitor, apocynin, significantly decreased CA formation and rupture compared with controls. NOX1 protein and mRNA expression were similar in p47phox-/- mice and those pretreated with apocynin but were elevated in unruptured and ruptured CAs. CSE increased CA formation and rupture, which was diminished with apocynin pretreatment. Similarly, NOX1 protein and mRNA and reactive oxygen species were elevated by CSE, and in unruptured and ruptured CAs.
CONCLUSIONS: CSE initiates oxidative stress-induced phenotypic modulation of VSMCs and CA formation and rupture. These molecular changes implicate oxidative stress in the pathogenesis of CAs and may provide a potential target for future therapeutic strategies
Isolation and characterization of few-layer black phosphorus
Isolation and characterization of mechanically exfoliated black phosphorus
flakes with a thickness down to two single-layers is presented. A modification
of the mechanical exfoliation method, which provides higher yield of atomically
thin flakes than conventional mechanical exfoliation, has been developed. We
present general guidelines to determine the number of layers using optical
microscopy, Raman spectroscopy and transmission electron microscopy in a fast
and reliable way. Moreover, we demonstrate that the exfoliated flakes are
highly crystalline and that they are stable even in free-standing form through
Raman spectroscopy and transmission electron microscopy measurements. A strong
thickness dependence of the band structure is found by density functional
theory calculations. The exciton binding energy, within an effective mass
approximation, is also calculated for different number of layers. Our
computational results for the optical gap are consistent with preliminary
photoluminescence results on thin flakes. Finally, we study the environmental
stability of black phosphorus flakes finding that the flakes are very
hydrophilic and that long term exposure to air moisture etches black phosphorus
away. Nonetheless, we demonstrate that the aging of the flakes is slow enough
to allow fabrication of field-effect transistors with strong ambipolar
behavior. Density functional theory calculations also give us insight into the
water-induced changes of the structural and electronic properties of black
phosphorus.Comment: 11 main figures, 7 supporting figure
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