235 research outputs found
Gamma-ray Bursts: Light on the distant Universe
Observations of a long-lasting Gamma-ray burst, one that has the brightest
optical counterpart yet discovered, challenge theoretical understanding of
these bursts but may enhance their usefulness as cosmic probes.Comment: News and Views article for Nature (Sept. 11, 2008
Dwarf Galaxy Formation Was Suppressed By Cosmic Reionization
A large number of faint galaxies, born less than a billion years after the
big bang, have recently been discovered. The fluctuations in the distribution
of these galaxies contributed to a scatter in the ionization fraction of cosmic
hydrogen on scales of tens of Mpc, as observed along the lines of sight to the
earliest known quasars. Theoretical simulations predict that the formation of
dwarf galaxies should have been suppressed after cosmic hydrogen was reionized,
leading to a drop in the cosmic star formation rate. Here we present evidence
for this suppression. We show that the post-reionization galaxies which
produced most of the ionizing radiation at a redshift z~5.5, must have had a
mass in excess of ~10^{10.6+/-0.4} solar masses or else the aforementioned
scatter would have been smaller than observed. This limiting mass is two orders
of magnitude larger than the galaxy mass that is thought to have dominated the
reionization of cosmic hydrogen (~10^8 solar masses). We predict that future
surveys with space-based infrared telescopes will detect a population of
smaller galaxies that reionized the Universe at an earlier time, prior to the
epoch of dwarf galaxy suppression.Comment: 19 pages, 3 figures. Accepted for publication in Nature; press
embargo until publishe
Mutual Information Decay Curves and Hyper-Parameter Grid Search Design for Recurrent Neural Architectures
We present an approach to design the grid searches for hyper-parameter
optimization for recurrent neural architectures. The basis for this approach is
the use of mutual information to analyze long distance dependencies (LDDs)
within a dataset. We also report a set of experiments that demonstrate how
using this approach, we obtain state-of-the-art results for DilatedRNNs across
a range of benchmark datasets.Comment: Published at the 27th International Conference on Neural Information
Processing, ICONIP 2020, Bangkok, Thailand, November 18-22, 2020. arXiv admin
note: text overlap with arXiv:1810.0296
Streaming Algorithm for Euler Characteristic Curves of Multidimensional Images
We present an efficient algorithm to compute Euler characteristic curves of
gray scale images of arbitrary dimension. In various applications the Euler
characteristic curve is used as a descriptor of an image.
Our algorithm is the first streaming algorithm for Euler characteristic
curves. The usage of streaming removes the necessity to store the entire image
in RAM. Experiments show that our implementation handles terabyte scale images
on commodity hardware. Due to lock-free parallelism, it scales well with the
number of processor cores. Our software---CHUNKYEuler---is available as open
source on Bitbucket.
Additionally, we put the concept of the Euler characteristic curve in the
wider context of computational topology. In particular, we explain the
connection with persistence diagrams
1H, 13C and 15N resonance assignments of the Calmodulin-Munc13-1 peptide complex
Ca2+-Calmodulin binding to the variable N-terminal region of the diacylglycerol/phorbol ester-binding UNC13/Munc13 family of proteins modulates the short-term synaptic plasticity characteristics in neurons. Here, we report the sequential backbone and side chain resonance assignment of the Ca2+-Calmodulin/Munc13-1458–492 peptide complex at pH 6.8 and 35°C (BMRB No. 15470)
Structure in the early afterglow lightcurve of the gamma-ray burst of 29 March 2003
Gamma-ray bursts (GRBs) are energetic explosions that for 0.01--100 s are the
brightest gamma-ray sources in the sky. Observations of the early evolution of
afterglows we expected to provide clues about the nature of the bursts, but
their rapid fading has hampered such studies; some recent rapid localizations
of bursts have improved the situation. Here we report on an early detection of
the very bright afterglow of the burst of 29 March 2003 (GRB030329). Our data
show that, even early in the aferglow phase, the light curve shows unexpectedly
complicated structures superimposed on the fading background.Comment: 8 pages, 1 figure, To appear in Nature June 19 issue. For the access
to the data in the paper, see
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/GRB/grb030329/GRB030329_information
.htm
Radio Remnants of Compact Binary Mergers - the Electromagnetic Signal that will follow the Gravitational Waves
The question "what is the observable electromagnetic (EM) signature of a
compact binary merger?" is an intriguing one with crucial consequences to the
quest for gravitational waves (GW). Compact binary mergers are prime sources of
GW, targeted by current and next generation detectors. Numerical simulations
have demonstrated that these mergers eject energetic sub-relativistic (or even
relativistic) outflows. This is certainly the case if the mergers produce short
GRBs, but even if not, significant outflows are expected. The interaction of
such outflows with the surround matter inevitably leads to a long lasting radio
signal. We calculate the expected signal from these outflows (our calculations
are also applicable to short GRB orphan afterglows) and we discuss their
detectability. We show that the optimal search for such signal should,
conveniently, take place around 1.4 GHz. Realistic estimates of the outflow
parameters yield signals of a few hundred Jy, lasting a few weeks, from
sources at the detection horizon of advanced GW detectors. Followup radio
observations, triggered by GW detection, could reveal the radio remnant even
under unfavorable conditions. Upcoming all sky surveys can detect a few dozen,
and possibly even thousands, merger remnants at any give time, thereby
providing robust merger rate estimates even before the advanced GW detectors
become operational. In fact, the radio transient RT 19870422 fits well the
overall properties predicted by our model and we suggest that its most probable
origin is a compact binary merger radio remnant
Dynamic in vitro measurement of patellar movement after total knee arthroplasty: an in vitro study
BACKGROUND: Changing the kinematic behaviour of patellar movement could be one of the reasons for anterior knee pain after implantation of a total knee arthroplasty (TKA). The aim of the current study was to measure the potential influence on patellar kinematics of patellar resurfacing during TKA. METHODS: Patellar movement before and after TKA with and without patellar resurfacing was measured under dynamic conditions in an in vitro cadaver simulation. Physiologic Musculus quadriceps forces were applied to five physiologic human knee specimens undergoing simulated isokinetic extension motions, patellar movement was measured using an ultrasonic measurement system. Thereafter, the Interax(® )I.S.A.-prosthesis system was implanted without and with resurfacing the patella, and patellar movement was again measured. RESULTS: The physiologic patella center moved on a semilunar path up to 6.4 mm (SD 6.4 mm) medially during extension. After TKA, the unresurfaced patella showed significantly less medial translation (p = 0.04) than the resurfaced patella. Subsequent resurfacing of the patella then resulted in a return to mediolateral positioning of the patella similar to the physiological case, whereas the resurfaced patella tilted up to twice as much as physiologic. CONCLUSION: The results of this study suggest that resurfacing of the patella during TKA can result in a restoration of the physiologic mediolateral shift of the patellofemoral joint while angulation of the patella remains unphysiologic
Brugia malayi Excreted/Secreted Proteins at the Host/Parasite Interface: Stage- and Gender-Specific Proteomic Profiling
Relatively little is known about the filarial proteins that interact with the human host. Although the filarial genome has recently been completed, protein profiles have been limited to only a few recombinants or purified proteins of interest. Here, we describe a large-scale proteomic analysis using microcapillary reverse-phase liquid chromatography-tandem-mass spectrometry to identify the excretory-secretory (ES) products of the L3, L3 to L4 molting ES, adult male, adult female, and microfilarial stages of the filarial parasite Brugia malayi. The analysis of the ES products from adult male, adult female, microfilariae (Mf), L3, and molting L3 larvae identified 852 proteins. Annotation suggests that the functional and component distribution was very similar across each of the stages studied; however, the Mf contributed a higher proportion to the total number of identified proteins than the other stages. Of the 852 proteins identified in the ES, only 229 had previous confirmatory expressed sequence tags (ESTs) in the available databases. Moreover, this analysis was able to confirm the presence of 274 “hypothetical” proteins inferred from gene prediction algorithms applied to the B. malayi (Bm) genome. Not surprisingly, the majority (160/274) of these “hypothetical” proteins were predicted to be secreted by Signal IP and/or SecretomeP 2.0 analysis. Of major interest is the abundance of previously characterized immunomodulatory proteins such as ES-62 (leucyl aminopeptidase), MIF-1, SERPIN, glutathione peroxidase, and galectin in the ES of microfilariae (and Mf-containing adult females) compared to the adult males. In addition, searching the ES protein spectra against the Wolbachia database resulted in the identification of 90 Wolbachia-specific proteins, most of which were metabolic enzymes that have not been shown to be immunogenic. This proteomic analysis extends our knowledge of the ES and provides insight into the host–parasite interaction
Polymicrobial Nature of Chronic Diabetic Foot Ulcer Biofilm Infections Determined Using Bacterial Tag Encoded FLX Amplicon Pyrosequencing (bTEFAP)
Diabetic extremity ulcers are associated with chronic infections. Such ulcer infections are too often followed by amputation because there is little or no understanding of the ecology of such infections or how to control or eliminate this type of chronic infection. A primary impediment to the healing of chronic wounds is biofilm phenotype infections. Diabetic foot ulcers are the most common, disabling, and costly complications of diabetes. Here we seek to derive a better understanding of the polymicrobial nature of chronic diabetic extremity ulcer infections. spp. and against difficult to culture bacteria such as anaerobes. While PCR methods also have bias, further work is now needed in comparing traditional culture results to high-resolution molecular diagnostic methods such as bTEFAP
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