257 research outputs found
Gravitational wave burst vetoes in the LIGO S2 and S3 data analyses
The LIGO detectors collected about 4 months of data in 2003-2004 during two
science runs, S2 and S3. Several environmental and auxiliary channels that
monitor the instruments' physical environment and overall interferometric
operation were analyzed in order to establish the quality of the data as well
as the presence of transients of non-astrophysical origin. This analysis
allowed better understanding of the noise character of the instruments and the
establishment of correlations between transients in these channels and the one
recording the gravitational wave strain. In this way vetoes for spurious burst
were identified. We present the methodology we followed in this analysis and
the results from the S2 and S3 veto analysis within the context of the search
for gravitational wave bursts.Comment: 9 pages, 4 figures, submitted to Classical and Quantum Gravity for
the special issue of the GWDAW9 Proceeding
Tailoring the thermal conductivity of rubber nanocomposites by inorganic systems: Opportunities and challenges for their application in tires formulation
The development of effective thermally conductive rubber nanocomposites for heat management represents a tricky point for several modern technologies, ranging from electronic devices to the tire industry. Since rubber materials generally exhibit poor thermal transfer, the addition of high loadings of different carbon‐based or inorganic thermally conductive fillers is mandatory to achieve satisfactory heat dissipation performance. However, this dramatically alters the mechanical behavior of the final materials, representing a real limitation to their application. Moreover, upon fillers’ incorporation into the polymer matrix, interfacial thermal resistance arises due to differences between the phonon spectra and scattering at the hybrid interface between the phases. Thus, a suitable filler functionalization is required to avoid discontinuities in the thermal transfer. In this challenging scenario, the present review aims at summarizing the most recent efforts to improve the thermal conductivity of rubber nanocomposites by exploiting, in particular, inorganic and hybrid filler systems, focusing on those that may guarantee a viable transfer of lab-scale formulations to technological applicable solutions. The intrinsic relationship among the filler’s loading, structure, morphology, and interfacial features and the heat transfer in the rubber matrix will be explored in depth, with the ambition of providing some methodological tools for a more profitable design of thermally conductive rubber nanocomposites, especially those for the formulation of tires
Localizing the cross-links distribution in elastomeric composites by tailoring the morphology of the curing activator
The localization of the rubber vulcanization reaction close to the silica filler surface was investigated in isoprene rubber composites (IR NCs): the main goal was to highlight the role of curing agents’ dispersion and filler surface features on the spatial propagation of the rubber cross-links and the resulting mechanical behavior of the material. The study was realized by tailoring the morphology of the curing activator, i.e. by vulcanizing IR NCs with Zn@SiO2 double function filler, composed of Zn(II) single sites anchored on SiO2 filler, in comparison to silica filled IR NCs vulcanized with microcrystalline ZnO (m-ZnO). The microscopic cross-links distribution was measured by Transmission Electron Microscopy for network visualization (NVTEM) and Time Domain Nuclear Magnetic Resonance (TD-NMR). Besides the NCs mechanical behavior was characterized both at small strain and at fracture. In the presence of Zn@SiO2, higher cross-link density in proximity to SiO2 particles was evidenced, which gradually spreads from the filler surface to the bulk, induced by localization of the Zn(II) centers. IR NCs with Zn@SiO2 resulted stiffer (+45%) and with a lower fracture toughness (less than one third), compared to m-ZnO based NCs, which shows a quite homogeneous structure of the rubber cross-links network. The results highlighted the correlation between the composites structural features and their macroscopic behavior, paving the way to modulating the mechanical properties of elastomeric materials by tuning the nature of the curing agents
Robust vetoes for gravitational-wave burst triggers using known instrumental couplings
The search for signatures of transient, unmodelled gravitational-wave (GW)
bursts in the data of ground-based interferometric detectors typically uses
`excess-power' search methods. One of the most challenging problems in the
burst-data-analysis is to distinguish between actual GW bursts and spurious
noise transients that trigger the detection algorithms. In this paper, we
present a unique and robust strategy to `veto' the instrumental glitches. This
method makes use of the phenomenological understanding of the coupling of
different detector sub-systems to the main detector output. The main idea
behind this method is that the noise at the detector output (channel H) can be
projected into two orthogonal directions in the Fourier space -- along, and
orthogonal to, the direction in which the noise in an instrumental channel X
would couple into H. If a noise transient in the detector output originates
from channel X, it leaves the statistics of the noise-component of H orthogonal
to X unchanged, which can be verified by a statistical hypothesis testing. This
strategy is demonstrated by doing software injections in simulated Gaussian
noise. We also formulate a less-rigorous, but computationally inexpensive
alternative to the above method. Here, the parameters of the triggers in
channel X are compared to the parameters of the triggers in channel H to see
whether a trigger in channel H can be `explained' by a trigger in channel X and
the measured transfer function.Comment: 14 Pages, 8 Figures, To appear in Class. Quantum Gra
Plans for the LIGO-TAMA Joint Search for Gravitational Wave Bursts
We describe the plans for a joint search for unmodelled gravitational wave
bursts being carried out by the LIGO and TAMA collaborations using data
collected during February-April 2003. We take a conservative approach to
detection, requiring candidate gravitational wave bursts to be seen in
coincidence by all four interferometers. We focus on some of the complications
of performing this coincidence analysis, in particular the effects of the
different alignments and noise spectra of the interferometers.Comment: Proceedings of the 8th Gravitational Wave Data Analysis Workshop,
Milwaukee, WI, USA. 10 pages, 3 figures, documentclass ``iopart'
Searching for prompt signatures of nearby core-collapse supernovae by a joint analysis of neutrino and gravitational-wave data
We discuss the science motivations and prospects for a joint analysis of
gravitational-wave (GW) and low-energy neutrino data to search for prompt
signals from nearby supernovae (SNe). Both gravitational-wave and low-energy
neutrinos are expected to be produced in the innermost region of a
core-collapse supernova, and a search for coincident signals would probe the
processes which power a supernova explosion. It is estimated that the current
generation of neutrino and gravitational-wave detectors would be sensitive to
Galactic core-collapse supernovae, and would also be able to detect
electromagnetically dark SNe. A joint GW-neutrino search would enable
improvements to searches by way of lower detection thresholds, larger distance
range, better live-time coverage by a network of GW and neutrino detectors, and
increased significance of candidate detections. A close collaboration between
the GW and neutrino communities for such a search will thus go far toward
realizing a much sought-after astrophysics goal of detecting the next nearby
supernova.Comment: 10 pages, 3 figures. To appear in Class. Quantum Gra
The LSC Glitch Group : Monitoring Noise Transients during the fifth LIGO Science Run
The LIGO Scientific Collaboration (LSC) glitch group is part of the LIGO
detector characterization effort. It consists of data analysts and detector
experts who, during and after science runs, collaborate for a better
understanding of noise transients in the detectors. Goals of the glitch group
during the fifth LIGO science run (S5) included (1) offline assessment of the
detector data quality, with focus on noise transients, (2) veto recommendations
for astrophysical analysis and (3) feedback to the commissioning team on
anomalies seen in gravitational wave and auxiliary data channels. Other
activities included the study of auto-correlation of triggers from burst
searches, stationarity of the detector noise and veto studies. The group
identified causes for several noise transients that triggered false alarms in
the gravitational wave searches; the times of such transients were identified
and vetoed from the data generating the LSC astrophysical results.Comment: 9 pages, 8 figures, Contribution to 12th Gravitational Wave Data
Analysis Workshop. Changes in response to referee comments. Accepted for
publication in CQ
The Borexino detector at the Laboratori Nazionali del Gran Sasso
Borexino, a large volume detector for low energy neutrino spectroscopy, is
currently running underground at the Laboratori Nazionali del Gran Sasso,
Italy. The main goal of the experiment is the real-time measurement of sub MeV
solar neutrinos, and particularly of the mono energetic (862 keV) Be7 electron
capture neutrinos, via neutrino-electron scattering in an ultra-pure liquid
scintillator. This paper is mostly devoted to the description of the detector
structure, the photomultipliers, the electronics, and the trigger and
calibration systems. The real performance of the detector, which always meets,
and sometimes exceeds, design expectations, is also shown. Some important
aspects of the Borexino project, i.e. the fluid handling plants, the
purification techniques and the filling procedures, are not covered in this
paper and are, or will be, published elsewhere (see Introduction and
Bibliography).Comment: 37 pages, 43 figures, to be submitted to NI
New results on solar neutrino fluxes from 192 days of Borexino data
We report the direct measurement of the ^7Be solar neutrino signal rate
performed with the Borexino detector at the Laboratori Nazionali del Gran
Sasso. The interaction rate of the 0.862 MeV ^7Be neutrinos is
49+-3(stat)+-4(syst) counts/(day * 100ton). The hypothesis of no oscillation
for ^7Be solar neutrinos is inconsistent with our measurement at the 4sigma
level. Our result is the first direct measurement of the survival probability
for solar nu_e in the transition region between matter-enhanced and
vacuum-driven oscillations. The measurement improves the experimental
determination of the flux of ^7Be, pp, and CNO solar nu_e, and the limit on the
magnetic moment of neutrinos
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