21,573 research outputs found
Characterization of High Temperature Optocoupler for Power Electronic Systems
High-temperature devices have been rapidly increas due to the implementation of new technologies like silicon carbide, high-temperature ceramic, and others. Functionality under elevated temperatures can reduce signal integrity reducing the reliability of power electronic systems. This study presents an ongoing research effort to develop a high-temperature package for optocouplers to operate at higher temperature compared with commercial devices. Low temperature co-fired ceramic (LTCC) was used as the substrate. Bare die commercial LED and photodetectors were attached to the substrate and tested for functionality. Preliminary results show enhanced performance at elevated temperatures compared to a commercial optocoupler device
Abundance Analyses of Field RV Stars, V: DS Aquarii, UY Arae, TW Camelopardis, BT Librae, U Moncerotis, TT Ophiuchi, and RV Tauri
Abundance analyses are presented and discussed for eight RV Tauri variables.
The RV B star UY Ara shows the abundance anomalies seen in other RV B stars,
namely elements that condense into grains at high temperature are underabundant
but elements of low condensation temperature are much less underabundant. This
pattern is ascribed to a separation of dust from gas with accretion of gas but
not dust by the atmosphere. Abundances for two RV C stars with earlier results
for other RV C stars show that these intrinsically metal-poor stars do not show
effects of dust-gas separation. Analyses of five RV A stars show that these
cooler stars are very largely unaffected by dust-gas separation. It is proposed
that the deeper convective envelope of cooler stars dilutes anomalies resulting
from dust-gas separation - the dusty wind off the RV Tauri variable or a dusty
circumbinary disk - are reviewed and observational tests are suggested.Comment: 42 pages, 6 figures, 8 tables, this may be listed as ApJ in pres
Global constraints on anomalous triple gauge couplings in effective field theory approach
We present a combined analysis of LHC Higgs data (signal strengths) together
with LEP-2 WW production measurements. To characterize possible deviations from
the Standard Model (SM) predictions, we employ the framework of an Effective
Field Theory (EFT) where the SM is extended by higher-dimensional operators
suppressed by the mass scale of new physics . The analysis is
performed consistently at the order in the EFT expansion keeping
all the relevant operators. While the two data sets suffer from flat
directions, together they impose stringent model-independent constraints on the
anomalous triple gauge couplings. As a side product, we provide the results of
the combined fit in different EFT bases.Comment: 7 pages. v2: References and clarifications adde
454 screening of individual MHC variation in an endemic island passerine
Genes of the major histocompatibility complex (MHC) code for receptors that are central to the adaptive immune response of vertebrates. These genes are therefore important genetic markers with which to study adaptive genetic variation in the wild. Next-generation sequencing (NGS) has increasingly been used in the last decade to genotype the MHC. However, NGS methods are highly prone to sequencing errors, and although several methodologies have been proposed to deal with this, until recently there have been no standard guidelines for the validation of putative MHC alleles. In this study, we used the 454 NGS platform to screen MHC class I exon 3 variation in a population of the island endemic Berthelot’s pipit (Anthus berthelotii). We were able to characterise MHC genotypes across 309 individuals with high levels of repeatability. We were also able to determine alleles that had low amplification efficiencies, whose identification within individuals may thus be less reliable. At the population level we found lower levels of MHC diversity in Berthelot’s pipit than in its widespread continental sister species the tawny pipit (Anthus campestris), and observed trans-species polymorphism. Using the sequence data, we identified signatures of gene conversion and evidence of maintenance of functionally divergent alleles in Berthelot’s pipit. We also detected positive selection at 10 codons. The present study therefore shows that we have an efficient method for screening individual MHC variation across large datasets in Berthelot’s pipit, and provides data that can be used in future studies investigating spatio-temporal patterns and scales of selection on the MHC
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