54,986 research outputs found
Fiber Based Multiple-Access Optical Frequency Dissemination
We demonstrate a fiber based multiple-access optical frequency dissemination
scheme. Without using any additional laser sources, we reproduce the stable
disseminated frequency at an arbitrary point of fiber link. Relative frequency
stability of 3E10^{-16}/s and 4E10^{-18}/10^4s is obtained. A branching fiber
network for highly-precision synchronization of optical frequency is made
possible by this method and its applications are discussed.Comment: 5 pages, 3 figure
Techniques of replica symmetry breaking and the storage problem of the McCulloch-Pitts neuron
In this article the framework for Parisi's spontaneous replica symmetry
breaking is reviewed, and subsequently applied to the example of the
statistical mechanical description of the storage properties of a
McCulloch-Pitts neuron. The technical details are reviewed extensively, with
regard to the wide range of systems where the method may be applied. Parisi's
partial differential equation and related differential equations are discussed,
and a Green function technique introduced for the calculation of replica
averages, the key to determining the averages of physical quantities. The
ensuing graph rules involve only tree graphs, as appropriate for a
mean-field-like model. The lowest order Ward-Takahashi identity is recovered
analytically and is shown to lead to the Goldstone modes in continuous replica
symmetry breaking phases. The need for a replica symmetry breaking theory in
the storage problem of the neuron has arisen due to the thermodynamical
instability of formerly given solutions. Variational forms for the neuron's
free energy are derived in terms of the order parameter function x(q), for
different prior distribution of synapses. Analytically in the high temperature
limit and numerically in generic cases various phases are identified, among
them one similar to the Parisi phase in the Sherrington-Kirkpatrick model.
Extensive quantities like the error per pattern change slightly with respect to
the known unstable solutions, but there is a significant difference in the
distribution of non-extensive quantities like the synaptic overlaps and the
pattern storage stability parameter. A simulation result is also reviewed and
compared to the prediction of the theory.Comment: 103 Latex pages (with REVTeX 3.0), including 15 figures (ps, epsi,
eepic), accepted for Physics Report
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Bioinspired Multifunctional Anti-icing Hydrogel
The recent anti-icing strategies in the state of the art mainly focused on three aspects: inhibiting ice nucleation, preventing ice propagation, and decreasing ice adhesion strength. However, it is has proved difficult to prevent ice nucleation and propagation while decreasing adhesion simultaneously, due to their highly distinct, even contradictory design principles. In nature, anti-freeze proteins (AFPs) offer a prime example of multifunctional integrated anti-icing materials that excel in all three key aspects of the anti-icing process simultaneously by tuning the structures and dynamics of interfacial water. Here, inspired by biological AFPs, we successfully created a multifunctional anti-icing material based on polydimethylsiloxane-grafted polyelectrolyte hydrogel that can tackle all three aspects of the anti-icing process simultaneously. The simplicity, mechanical durability, and versatility of these smooth hydrogel surfaces make it a promising option for a wide range of anti-icing applications
Risk analysis of viral diseases in infected pig farms during the lockdown period in China, January to May 2020
Biosecurity plays a critical role in preventing and controlling the introduction and spread of infectious diseases. The COVID-19 pandemic in China triggered a nationwide lockdown policy which reduced most of the daily activities of people, but the pig industry was encouraged to ensure the pork supply. An investigation of biosecurity practices in intensive pig farms across several provinces in China was conducted in June 2020 via questionnaire to evaluate the factors that may pose viral diseases risk to the farms during the lockdown period from January to May 2020. A total of 50 farms in 12 provinces of China were engaged. Fourteen of them were classified as positive farms since at least one viral disease was presented during this period, including porcine reproductive and respiratory syndrome (seven farms), porcine epidemic diarrhea (three farms), and pseudorabies (one farm). The other three farms only reported their disease positive status but refused to release disease names. The overall farm level prevalence of viral disease was 28.0% (95%CI: 16.3–42.5%). A logistic regression model was built to identify risk/protective factors for farm positivity. In the multivariable logistic regression model, the risk factor of dead pig ‘removal by the others’ (OR = 8.0, 95%CI: 1.5, 43.5) was found to be significantly associated with viral disease positivity. On-farm incineration pits are highly recommended to be the administered for the harmless treatment of dead pigs. This is not only crucial for controlling the transmission of viral diseases but also plays a key role in reducing activity in the illegal dead meat business. According to previous studies, factors such as adapting an all-in-all-out system, on-farm incineration pits, and requiring workers to wash their hands regularly would reduce the risk of virus transmission, even though these factors did not show significance in our study. The results of our study could help to design better surveillance strategies in China and other countries
The Properties of H{\alpha} Emission-Line Galaxies at z = 2.24
Using deep narrow-band and -band imaging data obtained with
CFHT/WIRCam, we identify a sample of 56 H emission-line galaxies (ELGs)
at with the 5 depths of and (AB)
over 383 arcmin area in the ECDFS. A detailed analysis is carried out
with existing multi-wavelength data in this field. Three of the 56 H
ELGs are detected in Chandra 4 Ms X-ray observation and two of them are
classified as AGNs. The rest-frame UV and optical morphologies revealed by
HST/ACS and WFC3 deep images show that nearly half of the H ELGs are
either merging systems or with a close companion, indicating that the
merging/interacting processes play a key role in regulating star formation at
cosmic epoch z=2-3; About 14% are too faint to be resolved in the rest-frame UV
morphology due to high dust extinction. We estimate dust extinction from SEDs.
We find that dust extinction is generally correlated with H luminosity
and stellar mass (SM). Our results suggest that H ELGs are
representative of star-forming galaxies (SFGs). Applying extinction correction
for individual objects, we examine the intrinsic H luminosity function
(LF) at , obtaining a best-fit Schechter function characterized by a
faint-end slope of . This is shallower than the typical slope of
in previous works based on constant extinction correction.
We demonstrate that this difference is mainly due to the different extinction
corrections. The proper extinction correction is thus key to recovering the
intrinsic LF as the extinction globally increases with H luminosity.
Moreover, we find that our H LF mirrors the SM function of SFGs at the
same cosmic epoch. This finding indeed reflects the tight correlation between
SFR and SM for the SFGs, i.e., the so-called main sequence.Comment: 15 pages, 12 figures, 2 tables, Received 2013 October 11; accepted
2014 February 13; published 2014 March 18 by Ap
Conductively-cooled, high-energy, single-frequency diode pumped slab laser for space applications
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