1,223 research outputs found
Sensitivity curves for searches for gravitational-wave backgrounds
We propose a graphical representation of detector sensitivity curves for stochastic gravitational-wave backgrounds that takes into account the increase in sensitivity that comes from integrating over frequency in addition to integrating over time. This method is valid for backgrounds that have a power-law spectrum in the analysis band. We call these graphs “power-law integrated curves.” For simplicity, we consider cross-correlation searches for unpolarized and isotropic stochastic backgrounds using two or more detectors. We apply our method to construct power-law integrated sensitivity curves for second-generation ground-based detectors such as Advanced LIGO, space-based detectors such as LISA and the Big Bang Observer, and timing residuals from a pulsar timing array. The code used to produce these plots is available at https://dcc.ligo.org/LIGO-P1300115/public for researchers interested in constructing similar sensitivity curves
Accurate DNA assembly and genome engineering with optimized uracil excision cloning
Simple
and reliable DNA editing by uracil excision (a.k.a. USER
cloning) has been described by several research groups, but the optimal
design of cohesive DNA ends for multigene assembly remains elusive.
Here, we use two model constructs based on expression of <i>gfp</i> and a four-gene pathway that produces β-carotene to optimize
assembly junctions and the uracil excision protocol. By combining
uracil excision cloning with a genomic integration technology, we
demonstrate that up to six DNA fragments can be assembled in a one-tube
reaction for direct genome integration with high accuracy, greatly
facilitating the advanced engineering of robust cell factories
Treatment of calibration uncertainty in multi-baseline cross-correlation searches for gravitational waves
Uncertainty in the calibration of gravitational wave (GW) detector data leads to systematic errors, which must be accounted for in setting limits on the strength of GW signals. When cross-correlation measurements are made using data from a pair of instruments, as in searches for a stochastic GW background, the calibration uncertainties of the individual instruments can be combined into an uncertainty associated with the pair. With the advent of multi-baseline GW observation (e.g., networks consisting of multiple detectors such as the LIGO observatories and Virgo), a more sophisticated treatment is called for. We have described how the correlations between calibration factors associated with different pairs can be taken into account by marginalizing over the uncertainty associated with each instrument
Gravitational waves from Sco X-1: A comparison of search methods and prospects for detection with advanced detectors
The low-mass X-ray binary Scorpius X-1 (Sco X-1) is potentially the most
luminous source of continuous gravitational-wave radiation for interferometers
such as LIGO and Virgo. For low-mass X-ray binaries this radiation would be
sustained by active accretion of matter from its binary companion. With the
Advanced Detector Era fast approaching, work is underway to develop an array of
robust tools for maximizing the science and detection potential of Sco X-1. We
describe the plans and progress of a project designed to compare the numerous
independent search algorithms currently available. We employ a mock-data
challenge in which the search pipelines are tested for their relative
proficiencies in parameter estimation, computational efficiency, robust- ness,
and most importantly, search sensitivity. The mock-data challenge data contains
an ensemble of 50 Scorpius X-1 (Sco X-1) type signals, simulated within a
frequency band of 50-1500 Hz. Simulated detector noise was generated assuming
the expected best strain sensitivity of Advanced LIGO and Advanced VIRGO ( Hz). A distribution of signal amplitudes was then
chosen so as to allow a useful comparison of search methodologies. A factor of
2 in strain separates the quietest detected signal, at
strain, from the torque-balance limit at a spin frequency of 300 Hz, although
this limit could range from (25 Hz) to (750 Hz) depending on the unknown frequency of Sco X-1. With future
improvements to the search algorithms and using advanced detector data, our
expectations for probing below the theoretical torque-balance strain limit are
optimistic.Comment: 33 pages, 11 figure
Linking the rates of neutron star binaries and short gamma-ray bursts
Short gamma-ray bursts are believed to be produced by both binary neutron
star (BNS) and neutron star-black hole (NSBH) mergers. We use current estimates
for the BNS and NSBH merger rates to calculate the fraction of observable short
gamma-ray bursts produced through each channel. This allows us to constrain
merger rates of BNS to ( credible interval), a decrease in the rate
uncertainties from the second LIGO--Virgo Gravitational-Wave Transient Catalog,
GWTC-2. Assuming a top-hat emission profile with a large Lorentz factor, we
constrain the average opening angle of gamma-ray burst jets produced in BNS
mergers to . We also measure the fraction of BNS and NSBH
mergers that produce an observable short gamma-ray burst to be
and , respectively and find that of BNS mergers launch jets (90\% confidence). We forecast constraints for
future gravitational-wave detections given different modelling assumptions,
including the possibility that BNS and NSBH jets are different. With BNS
and NSBH observations, expected within six months of the LIGO-Virgo-KAGRA
network operating at design sensitivity, it will be possible to constrain the
fraction of BNS and NSBH mergers that launch jets with precision. Within
a year of observations, we can determine whether the jets launched in NSBH
mergers have a different structure than those launched in BNS mergers and rule
out whether of binary neutron star mergers launch jets. We
discuss the implications of future constraints on understanding the physics of
short gamma-ray bursts and binary evolution.Comment: Accepted in Physical Review D: 13 pages, 5 figure
Generation of angular-momentum-dominated electron beams from a photoinjector
Various projects under study require an angular-momentum-dominated electron
beam generated by a photoinjector. Some of the proposals directly use the
angular-momentum-dominated beams (e.g. electron cooling of heavy ions), while
others require the beam to be transformed into a flat beam (e.g. possible
electron injectors for light sources and linear colliders). In this paper, we
report our experimental study of an angular-momentum-dominated beam produced in
a photoinjector, addressing the dependencies of angular momentum on initial
conditions. We also briefly discuss the removal of angular momentum. The
results of the experiment, carried out at the Fermilab/NICADD Photoinjector
Laboratory, are found to be in good agreement with theoretical and numerical
models.Comment: 8 pages, 7 figures, submitted to Phys. Rev. ST Accel. Beam
Protostellar collapse: rotation and disk formation
We present some important conclusions from recent calculations pertaining to
the collapse of rotating molecular cloud cores with axial symmetry,
corresponding to evolution of young stellar objects through classes 0 and begin
of class I. Three main issues have been addressed: (1) The typical timescale
for building up a preplanetary disk - once more it turned out that it is of the
order of one free-fall time which is decisively shorter than the widely assumed
timescale related to the so-called 'inside-out collapse'; (2) Redistribution of
angular momentum and the accompanying dissipation of kinetic (rotational)
energy - together these processes govern the mechanical and thermal evolution
of the protostellar core to a large extent; (3) The origin of
calcium-aluminium-rich inclusions (CAIs) - due to the specific pattern of the
accretion flow, material that has undergone substantial chemical and
mineralogical modifications in the hot (exceeding 900 K) interior of the
protostellar core may have a good chance to be advectively transported outward
into the cooler remote parts (beyond 4 AU, say) of the growing disk and to
survive there until it is incorporated into a meteoritic body.Comment: 4 pages, 4 figure
Draft genome sequence and chemical profiling of <i>Fusarium langsethiae</i>, an emerging producer of type A trichothecenes
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