Eu activation in beta-Ga_2O_3 MOVPE thin films by ion implantation

In this work, we have established the effects of Eu implantation and annealing on beta-Ga_2O_3 thin films grown by metal organic vapor phase epitaxy (MOVPE) on sapphire substrate. The study is based on the combined information from structural and optical techniques: X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), cathodoluminescence (CL), photoluminescence (PL), and photoluminescence excitation (PLE). The thin films were implanted with a fluence of 1 x 10^15 Eu.cm^-2 and annealed at 900 degrees C. Neither significant changes in peak width or position nor additional peaks related to Eu complexes were detected in the XRD 2 theta-omega scans. RBS results and SRIM simulation are in good agreement, revealing that no Eu diffusion to the surface occurs during annealing. For the used implantation/annealing conditions, the Eu ion penetration depth reached similar to 130 nm, with a maximum concentration at similar to 50 nm. Furthermore, CL and PL/PLE results evidenced the optical activation of the Eu^3+ in the beta-Ga_2O_3 host. The detailed study of the Eu^3+ intra-4f shell transitions revealed that at least one active site is created by the Eu implantation/annealing in beta-Ga_2O_3 thin films grown on sapphire. Independently of the beta-Ga_2O_3 film thickness, well controlled optical activation of implanted Eu was achieved

Asteroids' physical models from combined dense and sparse photometry and scaling of the YORP effect by the observed obliquity distribution

The larger number of models of asteroid shapes and their rotational states derived by the lightcurve inversion give us better insight into both the nature of individual objects and the whole asteroid population. With a larger statistical sample we can study the physical properties of asteroid populations, such as main-belt asteroids or individual asteroid families, in more detail. Shape models can also be used in combination with other types of observational data (IR, adaptive optics images, stellar occultations), e.g., to determine sizes and thermal properties. We use all available photometric data of asteroids to derive their physical models by the lightcurve inversion method and compare the observed pole latitude distributions of all asteroids with known convex shape models with the simulated pole latitude distributions. We used classical dense photometric lightcurves from several sources and sparse-in-time photometry from the U.S. Naval Observatory in Flagstaff, Catalina Sky Survey, and La Palma surveys (IAU codes 689, 703, 950) in the lightcurve inversion method to determine asteroid convex models and their rotational states. We also extended a simple dynamical model for the spin evolution of asteroids used in our previous paper. We present 119 new asteroid models derived from combined dense and sparse-in-time photometry. We discuss the reliability of asteroid shape models derived only from Catalina Sky Survey data (IAU code 703) and present 20 such models. By using different values for a scaling parameter cYORP (corresponds to the magnitude of the YORP momentum) in the dynamical model for the spin evolution and by comparing synthetics and observed pole-latitude distributions, we were able to constrain the typical values of the cYORP parameter as between 0.05 and 0.6.Comment: Accepted for publication in A&A, January 15, 201

Antimicrobial resistance (AMR) nanomachines: mechanisms for fluoroquinolone and glycopeptide recognition, efflux and/or deactivation

In this review, we discuss mechanisms of resistance identified in bacterial agents Staphylococcus aureus and the enterococci towards two priority classes of antibiotics—the fluoroquinolones and the glycopeptides. Members of both classes interact with a number of components in the cells of these bacteria, so the cellular targets are also considered. Fluoroquinolone resistance mechanisms include efflux pumps (MepA, NorA, NorB, NorC, MdeA, LmrS or SdrM in S. aureus and EfmA or EfrAB in the enterococci) for removal of fluoroquinolone from the intracellular environment of bacterial cells and/or protection of the gyrase and topoisomerase IV target sites in Enterococcus faecalis by Qnr-like proteins. Expression of efflux systems is regulated by GntR-like (S. aureus NorG), MarR-like (MgrA, MepR) regulators or a two-component signal transduction system (TCS) (S. aureus ArlSR). Resistance to the glycopeptide antibiotic teicoplanin occurs via efflux regulated by the TcaR regulator in S. aureus. Resistance to vancomycin occurs through modification of the D-Ala-D-Ala target in the cell wall peptidoglycan and removal of high affinity precursors, or by target protection via cell wall thickening. Of the six Van resistance types (VanA-E, VanG), the VanA resistance type is considered in this review, including its regulation by the VanSR TCS. We describe the recent application of biophysical approaches such as the hydrodynamic technique of analytical ultracentrifugation and circular dichroism spectroscopy to identify the possible molecular effector of the VanS receptor that activates expression of the Van resistance genes; both approaches demonstrated that vancomycin interacts with VanS, suggesting that vancomycin itself (or vancomycin with an accessory factor) may be an effector of vancomycin resistance. With 16 and 19 proteins or protein complexes involved in fluoroquinolone and glycopeptide resistances, respectively, and the complexities of bacterial sensing mechanisms that trigger and regulate a wide variety of possible resistance mechanisms, we propose that these antimicrobial resistance mechanisms might be considered complex ‘nanomachines’ that drive survival of bacterial cells in antibiotic environments

Revisiting the 2014-15 Disneyland measles outbreak and its influence on pediatric vaccinations

The 2014–15 Disneyland measles outbreak that began at the California theme park in December 2014 sparked an international conversation regarding measles, vaccine hesitancy, and vaccine policies. The outbreak capped a year with the highest number of measles cases reported in two decades and came amidst increasing trends in nonmedical vaccine exemptions in California and elsewhere. Because of its sensational story line and spread among unvaccinated populations, the outbreak received a high level of media coverage that focused on vaccine hesitancy as a primary driver of the outbreak. This media coverage and the ostensible public support for vaccines that followed led some to hypothesize that the outbreak might have a “Disneyland effect,” or a positive influence on the uptake of pediatric measles vaccine. This article reviews the facts of the outbreak and its context, and explores the evidence for the Disneyland outbreak causing an influence on U.S. pediatric vaccine-related beliefs and behaviors

Structural characterization of Cu2SnS3 and Cu2 Sn,Ge S3 compounds

Cu2SnS3 CTS and Cu2Sn0.83Ge0.17S3 CTGS compounds were successfully prepared by a powder technology using a combination of mechanical alloying MA and spark plasma sintering SPS . Structural, compositional and optical properties were studied. A true alloy with composition similar to the starting constituents was formed after 2 h of MA at 400 rpm. Subsequently, SPS was performed at 600 C for 5 min under a pressure of 50 MPa. The Cu Sn Ge composition ratios of the MA and SPS materials, determined by wavelength dispersive X ray spectroscopy, are in the range of 1.84 1.94. Rietveld refinements of the powder X ray diffraction data show a good agreement with the monoclinic crystal structure already for the MA materials. No structural changes were observed after SPS. Raman measurements coincide with XRD results in the identification of the characteristic peaks from phonon vibrational modes of monoclinic CTS phase. Band gaps between 1.24 eV and 1.34 eV were determined by diffuse reflectance for the mechanically alloyed and sintered sample

Exploring the impact of the New York State repeal of nonmedical vaccination exemptions on student enrollment, absenteeism, and school workload: Perspectives from a survey of school administrators

In June 2019, New York State (NYS) adopted Senate Bill 2994A eliminating nonmedical vaccine exemptions from school entry laws. Since student noncompliance with the law required school exclusion, we sought to evaluate the law’s effects on student enrollment and absenteeism, and school workloads related to its implementation. In November 2019, we sent an electronic survey to NYS (excluding New York City) schools. Due to the COVID-19 pandemic, outreach was curtailed in March 2020 with 525 (14%) of 3,759 eligible schools responding. To account for non-response, results were analyzed using inverse probability weighting. After weighting, 39% (95% CI: 34%, 44%) of schools reported enrollment changes and 31% (95% CI: 26%, 36%) of schools reported absenteeism related to the law. In addition, 95% (95% CI: 93%, 98%) of schools reported holding meetings and/or preparing correspondence about the law, spending a mean of 14 (95% CI: 11, 18) hours on these communication efforts. Schools in the highest pre-mandate nonmedical exemption tertile (vs. lowest) were more likely to report enrollment and absenteeism changes, and higher workloads. While our results should be interpreted with caution, changes in student enrollment, absenteeism, and school workloads may represent important considerations for policymakers planning similar legislation.</p

Early and natural embryonic death in Lagostomus maximus: Association with the uterine glands, vasculature, and musculature

The uterus is an organ with great plasticity due to the morphological and physiological changes it experiences during the estrous cycle and pregnancy. In mammals, pregnancy requires diverse sex hormones, growth factors and cytokines, among others, for promoting uterine remodeling to favor implantation, placentation, and embryo/fetus survival and growth. The hystricognathi rodent Lagostomus maximus (plains viscacha) has a high rate of embryonic resorption. The cranial and middle implants are reabsorbed 25–35 days after intercourse while the caudal embryos continue with their development until two precocial offspring are born. So far, no uterine studies of non-pregnant L. maximus females were performed to determine the possible existence of variations in the organ that could be related to the differential survival of the implants. We used ultrasonography, as well as morphological, morphometric, histochemical, lectinhistochemical, and immunohistochemical methods to study differences in the uterine glands (area), vasculature (area), and musculature (thickness) along the uterine horns in non-pregnant females. Along the uterus, all these structures were in more advanced developmental condition in the caudal region as compared to more anterior positions. These regional variations could be decisive in explaining the reason why only caudal implantations come to term. In contrast, no differences in the in the luminal and glandular epithelial cells, nor in the degree of cell proliferation and apoptosis, and hormonal receptor staining were found. These parameters could be related to implantation along the uterine horns, but not to the differential survival of the implants.Fil: Acuña, Francisco. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Barbeito, Claudio Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; ArgentinaFil: Portiansky, Enrique Leo. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Cátedra de Patología General Veterinaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Ranea, Guadalupe. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; ArgentinaFil: Nishida, Fabian. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Cátedra de Patología General Veterinaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Miglino, María A.. Universidade de Sao Paulo; BrasilFil: Flamini, Mirta Alicia. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentin

Loss of the Martian atmosphere to space: Present-day loss rates determined from MAVEN observations and integrated loss through time

Observations of the Mars upper atmosphere made from the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft have been used to determine the loss rates of gas from the upper atmosphere to space for a complete Mars year (16 Nov 2014 – 3 Oct 2016). Loss rates for H and O are sufficient to remove ∼2–3 kg/s to space. By itself, this loss would be significant over the history of the planet. In addition, loss rates would have been greater early in history due to the enhanced solar EUV and more-active Sun. Integrated loss, based on current processes whose escape rates in the past are adjusted according to expected solar evolution, would have been as much as 0.8 bar CO2 or 23 m global equivalent layer of H2O; these losses are likely to be lower limits due to the nature of the extrapolation of loss rates to the earliest times. Combined with the lack of surface or subsurface reservoirs for CO2 that could hold remnants of an early, thick atmosphere, these results suggest that loss of gas to space has been the dominant process responsible for changing the climate of Mars from an early, warmer environment to the cold, dry one that we see today