3,432 research outputs found
Oral History Interview: Mr. and Mrs. S. H. Boland
This interview is one of a series conducted concerning rural life in West Virginia. Mr. and Mrs. Boland have spent most of their lives in Summers County, West Virginia. Mrs. Boland\u27s parents died when she was young, and she and her two older sisters lived together on their farm until they married. Mr. and Mrs. Boland discuss their childhood experiences, education, courting practices, work experiences (Mr. Boland was Hinton fire chief for forty- seven years), the development of their rural district, and life in the country compared to city life.https://mds.marshall.edu/oral_history/1143/thumbnail.jp
Level-Based Analysis of the Population-Based Incremental Learning Algorithm
The Population-Based Incremental Learning (PBIL) algorithm uses a convex
combination of the current model and the empirical model to construct the next
model, which is then sampled to generate offspring. The Univariate Marginal
Distribution Algorithm (UMDA) is a special case of the PBIL, where the current
model is ignored. Dang and Lehre (GECCO 2015) showed that UMDA can optimise
LeadingOnes efficiently. The question still remained open if the PBIL performs
equally well. Here, by applying the level-based theorem in addition to
Dvoretzky--Kiefer--Wolfowitz inequality, we show that the PBIL optimises
function LeadingOnes in expected time for a population size , which matches the bound
of the UMDA. Finally, we show that the result carries over to BinVal, giving
the fist runtime result for the PBIL on the BinVal problem.Comment: To appea
Stochastic Description of a Bistable Frustrated Unit
Mixed positive and negative feedback loops are often found in biological
systems which support oscillations. In this work we consider a prototype of
such systems, which has been recently found at the core of many genetic
circuits showing oscillatory behaviour. Our model consists of two interacting
species A and B, where A activates not only its own production, but also that
of its repressor B. While the self-activation of A leads already to a bistable
unit, the coupling with a negative feedback loop via B makes the unit
frustrated. In the deterministic limit of infinitely many molecules, such a
bistable frustrated unit is known to show excitable and oscillatory dynamics,
depending on the maximum production rate of A which acts as a control
parameter. We study this model in its fully stochastic version and we find
oscillations even for parameters which in the deterministic limit are deeply in
the fixed-point regime. The deeper we go into this regime, the more irregular
these oscillations are, becoming finally random excitations whenever
fluctuations allow the system to overcome the barrier for a large excursion in
phase space. The fluctuations can no longer be fully treated as a perturbation.
The smaller the system size (the number of molecules), the more frequent are
these excitations. Therefore, stochasticity caused by demographic noise makes
this unit even more flexible with respect to its oscillatory behaviour.Comment: 28 pages, 17 figure
Noise induced oscillations in non-equilibrium steady state systems
We consider effect of stochastic sources upon self-organization process being
initiated with creation of the limit cycle. General expressions obtained are
applied to the stochastic Lorenz system to show that departure from equilibrium
steady state can destroy the limit cycle at certain relation between
characteristic scales of temporal variation of principle variables. Noise
induced resonance related to the limit cycle is found to appear if the fastest
variations displays a principle variable, which is coupled with two different
degrees of freedom or more.Comment: 11 pages, 4 figures. Submitted to Physica Script
Observation of twin beam correlations and quadrature entanglement by frequency doubling in a two-port resonator
We demonstrate production of quantum correlated and entangled beams by second
harmonic generation in a nonlinear resonator with two output ports. The output
beams at wavelength 428.5 nm exhibit 0.9 dB of nonclassical intensity
correlations and 0.3 dB of entanglement.Comment: 5 pages, 7 figure
Chromane derivatives from underground parts of Iris tenuifolia and their in vitro antimicrobial, cytotoxicity and antiproliferative evaluation
Phytochemical investigation of the ethanol extract of underground parts of Iris tenuifolia Pall. afforded five new compounds; an unusual macrolide termed moniristenulide (1), 5-methoxy-6,7-methylenedioxy-4-O-2′-cycloflavan (2), 5,7,2′,3′-tetrahydroxyflavanone (3), 5-hydroxy-6,7-dimethoxyisoflavone-2′-O-β-d-glucopyranoside (9), 5,2′,3′-dihydroxy-6,7-dimethoxyisoflavone (10), along with seven known compounds (4–8, 11–12). The structures of all purified compounds were established by analysis of 1D and 2D NMR spectroscopy and HR-ESI-MS. The antimicrobial activity of the compounds 1–3, 5, 9, and 10 was investigated using the agar diffusion method against fungi, Gram-positive and Gram-negative bacteria. In consequence, new compound 3 was found to possess the highest antibacterial activity against Enterococcus faecalis VRE and Mycobacterium vaccae. Cell proliferation and cytotoxicity tests were also applied on all isolated compounds and plant crude extract in vitro with the result of potent inhibitory effect against leukemia cells. In particular, the newly discovered isoflavone 10 was active against both of the leukemia cells K-562 and THP-1 while 4–6 of the flavanone type compounds were active against only THP-1
A New Galactic 6cm Formaldehyde Maser
We report the detection of a new H2CO maser in the massive star forming
region G23.71-0.20 (IRAS 18324-0820), i.e., the fifth region in the Galaxy
where H2CO maser emission has been found. The new H2CO maser is located toward
a compact HII region, and is coincident in velocity and position with 6.7 GHz
methanol masers and with an IR source as revealed by Spitzer/IRAC GLIMPSE data.
The coincidence with an IR source and 6.7 GHz methanol masers suggests that the
maser is in close proximity to an embedded massive protostar. Thus, the
detection of H2CO maser emission toward G23.71-0.20 supports the trend that
H2CO 6cm masers trace molecular material very near young massive stellar
objects.Comment: Accepted for publication in The Astrophysical Journal Letter
An H2CO 6cm Maser Pinpointing a Possible Circumstellar Torus in IRAS18566+0408
We report observations of 6cm, 3.6cm, 1.3cm, and 7mm radio continuum,
conducted with the Very Large Array towards IRAS18566+0408, one of the few
sources known to harbor H2CO 6cm maser emission. Our observations reveal that
the emission is dominated by an ionized jet at cm wavelengths. Spitzer/IRAC
images from GLIMPSE support this interpretation, given the presence of 4.5um
excess emission at approximately the same orientation as the cm continuum. The
7mm emission is dominated by thermal dust from a flattened structure almost
perpendicular to the ionized jet, thus, the 7mm emission appears to trace a
torus associated with a young massive stellar object. The H2CO 6cm maser is
coincident with the center of the torus-like structure. Our observations rule
out radiative pumping via radio continuum as the excitation mechanism for the
H2CO 6cm maser in IRAS18566+0408.Comment: 20 pages, 4 figures, ApJ (in press
The Formaldehyde Masers in Sgr B2: Very Long Baseline Array and Very Large Array Observations
Observations of two of the formaldehyde (H2CO) masers (A and D) in Sgr B2
using the VLBA+Y27 (resolution ~0.01") and the VLA (resolution ~9") are
presented. The VLBA observations show compact sources (<10 milliarcseconds, <80
AU) with brightness temperatures >10^8 K. The maser sources are partially
resolved in the VLBA observations. The flux densities in the VLBA observations
are about 1/2 those of the VLA; and, the linewidths are about 2/3 of the VLA
values. The applicability of a core-halo model for the emission distribution is
demonstrated. Comparison with earlier H2CO absorption observations and with
ammonia (NH3) observations suggests that H2CO masers form in shocked gas.
Comparison of the integrated flux densities in current VLA observations with
those in previous observations indicates that (1) most of the masers have
varied in the past 20 years, and (2) intensity variations are typically less
than a factor of two compared to the 20-year mean. No significant linear or
circular polarization is detected with either instrument.Comment: 20 pages, 3 figures, 5 tables, accepted to Ap
Female Reproductive Performance and Maternal Birth Month: A Comprehensive Meta-Analysis Exploring Multiple Seasonal Mechanisms
Globally, maternal birth season affects fertility later in life. The purpose of this systematic literature review is to comprehensively investigate the birth season and female fertility relationship. Using PubMed, we identified a set of 282 relevant fertility/birth season papers published between 1972 and 2018. We screened all 282 studies and removed 13
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