523 research outputs found
1,2-Bis[5-(2,2′-dicyanovinyl)-2-n-pentyl-3-thienyl]-3,3,4,4,5,5-hexafluorocyclopent-1-ene: a new photochromic diarylethene compound
The title compound, C31H26F6N4S2, is a new photochromic dithienylethene with dicyanovinyl subsitituents. In the crystal structure, the molecule adopts a photoactive antiparallel conformation, with two n-pentyl groups located on opposite sides of the cyclopentene ring. The cyclopentene ring assumes an envelope conformation. The distance between the two reactive C atoms on the thiophene rings is 3.834 (7) Å. One of the n-pentyl groups is disordered over two positions; the site occupancy factors are ca 0.7 and 0.3
A Monte Carlo Bayesian Search for the Plausible Source of the Telescope Array Hotspot
The Telescope Array (TA) collaboration has reported a hotspot of 19
ultrahigh-energy cosmic rays (UHECRs). Using a universal model with one source
and energy-dependent magnetic deflections, we show that the distribution of the
TA hotspot events is consistent with a single source hypothesis, although
multiple sources cannot be ruled out. The chance probability of this
distribution arising from a homogeneous distribution is . We describe a
Monte Carlo Bayesian (MCB) inference approach, which can be used to derive
parameters of the magnetic fields as well as the source coordinates, and we
apply this method to the TA hotspot data, inferring the location of the likely
source. We discuss possible applications of the same approach to future data.Comment: 7 pages, 5 figures, accepted by Physical Review
A possible Macronova in the late afterglow of the `long-short' burst GRB 060614
Long-duration ( s) -ray bursts that are believed to originate
from the death of massive stars are expected to be accompanied by supernovae.
GRB 060614, that lasted 102 s, lacks a supernova-like emission down to very
stringent limits and its physical origin is still debated. Here we report the
discovery of near-infrared bump that is significantly above the regular
decaying afterglow. This red bump is inconsistent with even the weakest known
supernova. However, it can arise from a Li-Paczy\'{n}ski macronova the
radioactive decay of debris following a compact binary merger. If this
interpretation is correct GRB 060614 arose from a compact binary merger rather
than from the death of a massive star and it was a site of a significant
production of heavy r-process elements. The significant ejected mass favors a
black hole-neutron star merger but a double neutron star merger cannot be ruled
out.Comment: Minor revision; The version published in Nature Communication
3-(4-{3,3,4,4,5,5-Hexafluoro-2-[5-(3-methoxyphenyl)-2-methyl-3-thienyl]cyclopent-1-enyl}-5-methyl-2-thienyl)benzonitrile
The title compound, C29H19F6NOS2, is a new unsymmetrical photochromic diarylethene derivative with different meta-phenyl substituents. The distance between the two reactive (i.e. can be irradiated to form a new chemical bond) C atoms is 3.501 (4) Å; the dihedral angles between the mean plane of the main central cyclopentene ring and the thiophene rings are 47.7 (5) and 45.1 (2)°, and those between the thiophene rings and the adjacent benzene rings are 29.4 (2) and 28.4 (3)°. The three C atoms and the F atoms of hexafuorocyclopentene ring are disordered over two positions, with site-occupancy factors of 0.751 (4) and 0.249 (4)
Silicon nitride metalenses for unpolarized high-NA visible imaging
As one of nanoscale planar structures, metasurface has shown excellent
superiorities on manipulating light intensity, phase and/or polarization with
specially designed nanoposts pattern. It allows to miniature a bulky optical
lens into the chip-size metalens with wavelength-order thickness, playing an
unprecedented role in visible imaging systems (e.g. ultrawide-angle lens and
telephoto). However, a CMOS-compatible metalens has yet to be achieved in the
visible region due to the limitation on material properties such as
transmission and compatibility. Here, we experimentally demonstrate a divergent
metalens based on silicon nitride platform with large numerical aperture
(NA~0.98) and high transmission (~0.8) for unpolarized visible light,
fabricated by a 695-nm-thick hexagonal silicon nitride array with a minimum
space of 42 nm between adjacent nanoposts. Nearly diffraction-limit virtual
focus spots are achieved within the visible region. Such metalens enables to
shrink objects into a micro-scale size field of view as small as a single-mode
fiber core. Furthermore, a macroscopic metalens with 1-cm-diameter is also
realized including over half billion nanoposts, showing a potential application
of wide viewing-angle functionality. Thanks to the high-transmission and
CMOS-compatibility of silicon nitride, our findings may open a new door for the
miniaturization of optical lenses in the fields of optical fibers,
microendoscopes, smart phones, aerial cameras, beam shaping, and other
integrated on-chip devices.Comment: 16 pages, 7 figure
MiRFinder: an improved approach and software implementation for genome-wide fast microRNA precursor scans
Background: MicroRNAs (miRNAs) are recognized as one of the most important families of noncoding RNAs that serve as important sequence-specific post-transcriptional regulators of gene expression. Identification of miRNAs is an important requirement for understanding the mechanisms of post-transcriptional regulation. Hundreds of miRNAs have been identified by direct cloning and computational approaches in several species. However, there are still many miRNAs that remain to be identified due to lack of either sequence features or robust algorithms to efficiently identify them. Results: We have evaluated features valuable for pre-miRNA prediction, such as the local secondary structure differences of the stem region of miRNA and non-miRNA hairpins. We have also established correlations between different types of mutations and the secondary structures of pre-miRNAs. Utilizing these features and combining some improvements of the current premiRNA prediction methods, we implemented a computational learning method SVM (support vector machine) to build a high throughput and good performance computational pre-miRNA prediction tool called MiRFinder. The tool was designed for genome-wise, pair-wise sequences from two related species. The method built into the tool consisted of two major steps: 1) genome wide search for hairpin candidates and 2) exclusion of the non-robust structures based on analysis of 18 parameters by the SVM method. Results from applying the tool for chicken/human and D. melanogaster/D. pseudoobscura pair-wise genome alignments showed that the tool can be used for genome wide pre-miRNA predictions. Conclusion: The MiRFinder can be a good alternative to current miRNA discovery software. This tool is available at http://www.bioinformatics.org/mirfinder/
Genome-Wide Association Study Identifies Loci for Body Composition and Structural Soundness Traits in Pigs
Background
The recent completion of the swine genome sequencing project and development of a high density porcine SNP array has made genome-wide association (GWA) studies feasible in pigs. Methodology/Principal Findings
Using Illumina\u27s PorcineSNP60 BeadChip, we performed a pilot GWA study in 820 commercial female pigs phenotyped for backfat, loin muscle area, body conformation in addition to feet and leg (FL) structural soundness traits. A total of 51,385 SNPs were jointly fitted using Bayesian techniques as random effects in a mixture model that assumed a known large proportion (99.5%) of SNPs had zero effect. SNP annotations were implemented through the Sus scrofa Build 9 available from pig Ensembl. We discovered a number of candidate chromosomal regions, and some of them corresponded to QTL regions previously reported. We not only have identified some well-known candidate genes for the traits of interest, such as MC4R (for backfat) and IGF2 (for loin muscle area), but also obtained novel promising genes, including CHCHD3 (for backfat), BMP2 (for loin muscle area, body size and several FL structure traits), and some HOXA family genes (for overall leg action). The candidate regions responsible for body conformation and FL structure soundness did not overlap greatly which implied that these traits were controlled by different genes. Functional clustering analyses classified the genes into categories related to bone and cartilage development, muscle growth and development or the insulin pathway suggesting the traits are regulated by common pathways or gene networks that exert roles at different spatial and temporal stages. Conclusions/Significance
This study is one of the earliest GWA reports on important quantitative traits in pigs, and the findings will contribute to the further biological function analysis of the identified candidate genes and potential utilization of them in marker assisted selection
An analytic derivation of the empirical correlations of gamma-ray bursts
Empirical correlations between various key parameters have been extensively
explored ever since the discovery of gamma-ray bursts (GRBs) and have been
widely used as standard candles to probe the Universe. The Amati relation and
the Yonetoku relation are two good examples, which have been paid special
attention to. The former reflects the connection between the peak photon energy
(Ep) and the isotropic -ray energy release (Eiso), while the latter
links Ep with the isotropic peak luminosity (Lp), both in the form of a power
law function. Most GRBs are found to well follow these correlations, but a
theoretical interpretation is still lacking. Meanwhile, there are also some
obvious outliers, which may be off-axis GRBs and may follow different
correlations as compared with the on-axis ones. Here we present a simple
analytical derivation for the Amati relation and the Yonetoku relation in the
framework of the standard fireball model, the correctness of which are then
confirmed by numerical simulations. The off-axis Amati relation and Yonetoku
relation are also derived, which differ from the corresponding on-axis relation
markedly. Our results reveal the intrinsic physics lying behind the radiation
processes of GRBs, and highlight the importance of viewing angle in the
empirical correlations of GRBs.Comment: 20 pages, 7 figures, 2 tables. Submitted to A&
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