4,237 research outputs found
Calibration of the LIGO displacement actuators via laser frequency modulation
We present a frequency modulation technique for calibration of the
displacement actuators of the LIGO 4-km-long interferometric gravitational-wave
detectors. With the interferometer locked in a single-arm configuration, we
modulate the frequency of the laser light, creating an effective length
variation that we calibrate by measuring the amplitude of the frequency
modulation. By simultaneously driving the voice coil actuators that control the
length of the arm cavity, we calibrate the voice coil actuation coefficient
with an estimated 1-sigma uncertainty of less than one percent. This technique
enables a force-free, single-step actuator calibration using a displacement
fiducial that is fundamentally different from those employed in other
calibration methods.Comment: 10 pages, 5 figures, submitted to Classical and Quantum Gravit
Phase ordering and shape deformation of two-phase membranes
Within a coupled-field Ginzburg-Landau model we study analytically phase
separation and accompanying shape deformation on a two-phase elastic membrane
in simple geometries such as cylinders, spheres and tori. Using an exact
periodic domain wall solution we solve for the shape and phase ordering field,
and estimate the degree of deformation of the membrane. The results are
pertinent to a preferential phase separation in regions of differing curvature
on a variety of vesicles.Comment: 4 pages, submitted to PR
Simulation of Blast Waves with Headwind
The blast wave resulting from an explosion was simulated to provide guidance for models estimating risks for human spacecraft flight. Simulations included effects of headwind on blast propagation, Blasts were modelled as an initial value problem with a uniform high energy sphere expanding into an ambient field. Both still air and cases with headwind were calculated
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
OH Satellite Line Masers and an AGN Candidate in M82
We report the detection of OH satellite line masers at 1720 MHz and 1612 MHz
from the nuclear region of the starburst galaxy M82. The observations were
aimed at detecting 1720 MHz maser emission from the known radio emitting SNR in
the nuclear region. At 1720 MHz we detect six features above the 5-sigma limit
set by noise, four in emission and two in absorption. Three of the emission
features appear closely associated with known discrete continuum radio sources,
and one of the absorption features is precisely coincident with the discrete
continuum source 44.01+59.6. The latter source also exhibits strong 1612 MHz
emission at the same velocity. No other 1612 MHz features were detected. All of
the 1720 MHz emission features are consistent with masers pumped by collisions
with molecular hydrogen at densities between 10^3 cm^{-3} and 10^5 cm^{-3}, and
T_k between 50 K and 250 K. The absorption and emission associated with the two
satellite lines in 44.01+59.6, together with other evidence, points to the
possibility that this source is the AGN in M82.Comment: accepted ApJ
Can personality predict foreign language classroom emotions? The devil’s in the detail
Personality has been identified as a possible antecedent to emotions experienced in the foreign language (FL) classroom. However, contrasting results and differing personality models have resulted in ambiguous findings. This study set out to delve deeper into the role of personality as a predictor of FL emotions through a series of increasingly restrictive statistical models on a sample of n=246 FL learners. The relationships between personality – operationalised as global and lower-order factors in the Five Factor Model – and the FL emotions of Foreign Language Enjoyment, Anxiety, and Boredom were examined. The global factors of Neuroticism, Extraversion, and Conscientiousness, and the lower-order factors of Trust, Dutifulness, and Cheerfulness were significant predictors of FL emotions. However, the complexity of personality as a predictor variable is demonstrated in the intricacy of the results and as such the inclusion of personality in explanatory models of FL emotions ought to be approached with caution
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