18,656 research outputs found
Measuring test mass acceleration noise in space-based gravitational wave astronomy
The basic constituent of interferometric gravitational wave detectors -- the
test mass to test mass interferometric link -- behaves as a differential
dynamometer measuring effective differential forces, comprising an integrated
measure of gravity curvature, inertial effects, as well as non-gravitational
spurious forces. This last contribution is going to be characterised by the
LISA Pathfinder mission, a technology precursor of future space-borne detectors
like eLISA. Changing the perspective from displacement to acceleration can
benefit the data analysis of LISA Pathfinder and future detectors. The response
in differential acceleration to gravitational waves is derived for a
space-based detector's interferometric link. The acceleration formalism can
also be integrated into time delay interferometry by building up the
unequal-arm Michelson differential acceleration combination. The differential
acceleration is nominally insensitive to the system free evolution dominating
the slow displacement dynamics of low-frequency detectors. Working with
acceleration also provides an effective way to subtract measured signals acting
as systematics, including the actuation forces. Because of the strong
similarity with the equations of motion, the optimal subtraction of systematic
signals, known within some amplitude and time shift, with the focus on
measuring the noise provides an effective way to solve the problem and
marginalise over nuisance parameters. The -statistic, in
widespread use throughout the gravitation waves community, is included in the
method and suitably generalised to marginalise over linear parameters and noise
at the same time. The method is applied to LPF simulator data and, thanks to
its generality, can also be applied to the data reduction and analysis of
future gravitational wave detectors.Comment: 10 pages, 3 figures, 1 tabl
Parallax and Distance Estimates for Fourteen Cataclysmic Variable Stars
I used the 2.4 m Hiltner telescope at MDM Observatory in an attempt to
measure trigonometric parallaxes for 14 cataclysmic variable stars. Techniques
are described in detail. In the best cases the parallax uncertainties are below
1 mas, and significant parallaxes are found for most of the program stars. A
Bayesian method which combines the parallaxes together with proper motions and
absolute magnitude constraints is developed and used to derive distance
estimates and confidence intervals. The most precise distance derived here is
for WZ Sge, for which I find 43.3 (+1.6, -1.5) pc. Six Luyten Half-Second stars
with previous precise parallax measurements were re-measured to test the
techniques, and good agreement is found.Comment: 33 pages, 3 figures. Astronomical Journal, accepte
The Luminosity and Redshift Distributions of Short-Duration GRB
Using the BATSE peak flux distribution we rederive the short GRBs luminosity
function and compare it with the observed redshift distribution of long bursts.
We show that both distributions are compatible with the assumption that short
as well as long bursts follow the star formation rate. In this case the
difference between the two observed distributions can be interpreted as arising
mostly from differences in the detector's sensitivity to long and short bursts,
while the local rate of short bursts is 0.1 h_70^3 Gpc^-3 yr^-1 . We also
consider the possibility that short GRBs may be associated with binary neutron
star mergers and estimate the effect of the merging time delay on the
luminosity function and redshift distribution. We find that in this case the
local rate of short GRBs is ~0.8 h_70^3 Gpc^-3 yr^-1. Assuming that all binary
merging systems lead to short GRBs, we find a typical jet opening angle of
1.6^oComment: 7 pages, 5 figures. to be published in Astronomy and Astrophysic
SUMOylation of Rad52-Rad59 synergistically change the outcome of mitotic recombination
Homologous recombination (HR) is essential for maintenance of genome stability through double-strand break (DSB) repair, but at the same time HR can lead to loss of heterozygosity and uncontrolled recombination can be genotoxic. The post-translational modification by SUMO (small ubiquitin-like modifier) has been shown to modulate recombination, but the exact mechanism of this regulation remains unclear. Here we show that SUMOylation stabilizes the interaction between the recombination mediator Rad52 and its paralogue Rad59 in Saccharomyces cerevisiae. Although Rad59 SUMOylation is not required for survival after genotoxic stress, it affects the outcome of recombination to promote conservative DNA repair. In some genetic assays, Rad52 and Rad59 SUMOylation act synergistically. Collectively, our data indicate that the described SUMO modifications affect the balance between conservative and non-conservative mechanisms of HR
Catching Card Counters
The casino industry has been researched through a variety of disciplines including psychological gambling habits, technological advances, business strategies, and mathematical simulations. In the vast number of studies that have been conducted, there are few scholarly articles that focus on the specific aspect of card counting. The majority of games in the casino are designed to favor the “house”. This study focuses on the game of blackjack, in which players using a card counting strategy can tip the odds in their favor. A computer simulation was used to model the betting strategy of a card counter who would bet methodically. Conversely, the unpredictable betting strategy of a “normal” gambler was gathered through observations of over one thousands hands of blackjack. The comparison of the two led to deviations in behavior and betting habits. An understanding of these differences will provide a casino with additional information to catch card counters at the table
Inferring transmission fitness advantage of SARS-CoV-2 variants of concern from wastewater samples using digital PCR, Switzerland, December 2020 through March 2021
BackgroundThroughout the COVID-19 pandemic, SARS-CoV-2 genetic variants of concern (VOCs) have repeatedly and independently arisen. VOCs are characterised by increased transmissibility, increased virulence or reduced neutralisation by antibodies obtained from prior infection or vaccination. Tracking the introduction and transmission of VOCs relies on sequencing, typically whole genome sequencing of clinical samples. Wastewater surveillance is increasingly used to track the introduction and spread of SARS-CoV-2 variants through sequencing approaches.AimHere, we adapt and apply a rapid, high-throughput method for detection and quantification of the relative frequency of two deletions characteristic of the Alpha, Beta, and Gamma VOCs in wastewater.MethodsWe developed drop-off RT-dPCR assays and an associated statistical approach implemented in the R package WWdPCR to analyse temporal dynamics of SARS-CoV-2 signature mutations (spike Δ69-70 and ORF1a Δ3675-3677) in wastewater and quantify transmission fitness advantage of the Alpha VOC.ResultsBased on analysis of Zurich wastewater samples, the estimated transmission fitness advantage of SARS-CoV-2 Alpha based on the spike Δ69-70 was 0.34 (95% confidence interval (CI): 0.30-0.39) and based on ORF1a Δ3675-3677 was 0.53 (95% CI: 0.49-0.57), aligning with the transmission fitness advantage of Alpha estimated by clinical sample sequencing in the surrounding canton of 0.49 (95% CI: 0.38-0.61).ConclusionDigital PCR assays targeting signature mutations in wastewater offer near real-time monitoring of SARS-CoV-2 VOCs and potentially earlier detection and inference on transmission fitness advantage than clinical sequencing. Keywords: B.1.1.7; SARS-CoV-2; digital PCR; drop-off assays; transmission fitness
Quantum metrology with nonclassical states of atomic ensembles
Quantum technologies exploit entanglement to revolutionize computing,
measurements, and communications. This has stimulated the research in different
areas of physics to engineer and manipulate fragile many-particle entangled
states. Progress has been particularly rapid for atoms. Thanks to the large and
tunable nonlinearities and the well developed techniques for trapping,
controlling and counting, many groundbreaking experiments have demonstrated the
generation of entangled states of trapped ions, cold and ultracold gases of
neutral atoms. Moreover, atoms can couple strongly to external forces and light
fields, which makes them ideal for ultra-precise sensing and time keeping. All
these factors call for generating non-classical atomic states designed for
phase estimation in atomic clocks and atom interferometers, exploiting
many-body entanglement to increase the sensitivity of precision measurements.
The goal of this article is to review and illustrate the theory and the
experiments with atomic ensembles that have demonstrated many-particle
entanglement and quantum-enhanced metrology.Comment: 76 pages, 40 figures, 1 table, 603 references. Some figures bitmapped
at 300 dpi to reduce file siz
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