2,588 research outputs found
Detecting transient gravitational waves in non-Gaussian noise with partially redundant analysis methods
There is a broad class of astrophysical sources that produce detectable,
transient, gravitational waves. Some searches for transient gravitational waves
are tailored to known features of these sources. Other searches make few
assumptions about the sources. Typically events are observable with multiple
search techniques. This work describes how to combine the results of searches
that are not independent, treating each search as a classifier for a given
event. This will be shown to improve the overall sensitivity to
gravitational-wave events while directly addressing the problem of consistent
interpretation of multiple trials.Comment: 11 pages, 5 figure
Likelihood-ratio ranking of gravitational-wave candidates in a non-Gaussian background
We describe a general approach to detection of transient gravitational-wave
signals in the presence of non-Gaussian background noise. We prove that under
quite general conditions, the ratio of the likelihood of observed data to
contain a signal to the likelihood of it being a noise fluctuation provides
optimal ranking for the candidate events found in an experiment. The
likelihood-ratio ranking allows us to combine different kinds of data into a
single analysis. We apply the general framework to the problem of unifying the
results of independent experiments and the problem of accounting for
non-Gaussian artifacts in the searches for gravitational waves from compact
binary coalescence in LIGO data. We show analytically and confirm through
simulations that in both cases the likelihood ratio statistic results in an
improved analysis.Comment: 10 pages, 6 figure
Repulsive bimodal atomic force microscopy on polymers
Bimodal atomic force microscopy can provide high-resolution images of polymers. In the bimodal operation mode, two eigenmodes of the cantilever are driven simultaneously. When examining polymers, an effective mechanical contact is often required between the tip and the sample to obtain compositional contrast, so particular emphasis was placed on the repulsive regime of dynamic force microscopy. We thus investigated bimodal imaging on a polystyrene-block-polybutadiene diblock copolymer surface and on polystyrene. The attractive operation regime was only stable when the amplitude of the second eigenmode was kept small compared to the amplitude of the fundamental mode. To clarify the influence of the higher eigenmode oscillation on the image quality, the amplitude ratio of both modes was systematically varied. Fourier analysis of the time series recorded during imaging showed frequency mixing. However, these spurious signals were at least two orders of magnitude smaller than the first two fundamental eigenmodes. Thus, repulsive bimodal imaging of polymer surfaces yields a good signal quality for amplitude ratios smaller than A 01/A 02 = 10:1 without affecting the topography feedback. © 2012 Gigler et al; licensee Beilstein-Institut.This work was financially supported by the European Commission (FORCETOOL, NMP4-CT-2004-013684) and the Excellence Cluster “Nanosystems Initiative Munich> (NIM).Peer Reviewe
Just Enough: An Introduction
The concept of ‘enough’ is highly polysemous and in its diverse invocations is always already value-laden and political. The introduction traces current articulations of ‘enough’ and argues that these need to be placed within a historical and comparative context that highlights the often hidden multiplicity of its cultural and political resonance. ‘Enough’ is often malleable and changing in relation to new desires, technologies or values. Drawing on the chapters in this volume, the concept of ‘enough’ is suggested to be more complex than quantitative measures can resolve. These various case studies also prompt critical thought about the politics of sufficiency more broadly and which pose important questions for sustainability proponents
Electrical Manipulation of Telecom Color Centers in Silicon
Silicon color centers have recently emerged as promising candidates for
commercial quantum technology, yet their interaction with electric fields has
yet to be investigated. In this paper, we demonstrate electrical manipulation
of telecom silicon color centers by fabricating lateral electrical diodes with
an integrated G center ensemble in a commercial silicon on insulator wafer. The
ensemble optical response is characterized under application of a
reverse-biased DC electric field, observing both 100% modulation of
fluorescence signal, and wavelength redshift of approximately 1.4 GHz/V above a
threshold voltage. Finally, we use G center fluorescence to directly image the
electric field distribution within the devices, obtaining insight into the
spatial and voltage-dependent variation of the junction depletion region and
the associated mediating effects on the ensemble. Strong correlation between
emitter-field coupling and generated photocurrent is observed. Our
demonstration enables electrical control and stabilization of semiconductor
quantum emitters
Prospects for radical emissions reduction through behaviour and lifestyle change
Over the past two decades, scholars and practitioners across the social sciences, in policy and beyond have proposed, trialled and developed a wide range of theoretical and practical approaches designed to bring about changes in behaviours and lifestyles that contribute to climate change. With the exception of the establishment of a small number of iconic behaviours such as recycling, it has however proved extremely difficult to bring about meaningful transformations in personal greenhouse gas emissions at either the individual or societal level, with multiple reviews now pointing to the limited efficacy of current approaches. We argue that the majority of approaches designed to achieve mitigation have been constrained by the need to operate within prevailing social scientific, economic and political orthodoxies which have precluded the possibility of non-marginal change. In this paper we ask what a truly radical approach to reducing personal emissions would look like from social science perspectives which challenge the unstated assumptions severely limiting action to date, and which explore new alternatives for change. We emphasise the difficulties likely to impede the instituting of genuinely radical societal change regarding climate change mitigation, whilst proposing ways that the ground could be prepared for such a transformation to take place
Searching for a Stochastic Background of Gravitational Waves with LIGO
The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed
the fourth science run, S4, with significantly improved interferometer
sensitivities with respect to previous runs. Using data acquired during this
science run, we place a limit on the amplitude of a stochastic background of
gravitational waves. For a frequency independent spectrum, the new limit is
. This is currently the most sensitive
result in the frequency range 51-150 Hz, with a factor of 13 improvement over
the previous LIGO result. We discuss complementarity of the new result with
other constraints on a stochastic background of gravitational waves, and we
investigate implications of the new result for different models of this
background.Comment: 37 pages, 16 figure
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV
The t t-bar production cross section (sigma[t t-bar]) is measured in
proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS
experiment, corresponding to an integrated luminosity of 2.3 inverse
femtobarns. The measurement is performed in events with two leptons (electrons
or muons) in the final state, at least two jets identified as jets originating
from b quarks, and the presence of an imbalance in transverse momentum. The
measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/-
2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction
of the standard model.Comment: Replaced with published version. Included journal reference and DO
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