The GEO 600 status Grote, H
Classical and quantum gravity,
04/2010, Volume:
27, Issue:
8
Journal Article, Conference Proceeding
Peer reviewed
Open access
The British--German gravitational wave detector GEO 600 has concluded a long observational period called Astrowatch, which lasted from November 2007 to July 2009. Together with the LIGO-H2 detector, ...GEO 600 was kept observing, while other detectors of the world-wide network of laser-interferometers like LIGO(L1 and H1) and Virgo were upgraded. A fraction of the time during the astrowatch period was set apart for noise investigations and experiments preparing future upgrades. Even with these investigations GEO 600 reached an observation time of 86.0% of the overall time, such that a total of 522 days worth of data were collected. The average sensitivity was roughly a factor of 2 lower than that of the LIGO-H2 detector for frequencies above 500 Hz. In July 2009 GEO 600 has started an upgrade program called GEO-HF. Within this program we aim at improving the sensitivity by a number of sequential upgrades, like tuned signal recycling, DC readout, output mode-cleaning, injection of squeezed vacuum states and the increase of circulating light power. Tuned signal recycling and DC readout have already been implemented and can be operated robustly, due to a new technique associated with the automatic alignment system.
In this work, we present the first experimental upper limits on the presence of stochastic gravitational waves in a frequency band with frequencies above 1 THz. We exclude gravitational waves in the ...frequency bands from
2.7
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14
×
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14
Hz and
5
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12
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Hz down to a characteristic amplitude of
h
c
min
≈
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26
and
h
c
min
≈
5
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28
at 95% confidence level, respectively. To obtain these results, we used data from existing facilities that have been constructed and operated with the aim of detecting weakly interacting slim particles, pointing out that these facilities are also sensitive to gravitational waves by graviton to photon conversion in the presence of a magnetic field. The principle applies to all experiments of this kind, with prospects of constraining (or detecting), for example, gravitational waves from light primordial black-hole evaporation in the early universe.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We report on the first long-term application of squeezed vacuum states of light to improve the shot-noise-limited sensitivity of a gravitational-wave observatory. In particular, squeezed vacuum was ...applied to the German-British detector GEO 600 during a period of three months from June to August 2011, when GEO 600 was performing an observational run together with the French-Italian Virgo detector. In a second period, the squeezing application continued for about 11 months from November 2011 to October 2012. During this time, squeezed vacuum was applied for 90.2% (205.2 days total) of the time that science-quality data were acquired with GEO 600. A sensitivity increase from squeezed vacuum application was observed broadband above 400 Hz. The time average of gain in sensitivity was 26% (2.0 dB), determined in the frequency band from 3.7 to 4.0 kHz. This corresponds to a factor of 2 increase in the observed volume of the Universe for sources in the kHz region (e.g., supernovae, magnetars). We introduce three new techniques to enable the long-term application of squeezed light, and show that the glitch rate of the detector did not increase from squeezing application. Squeezed vacuum states of light have arrived as a permanent application, capable of increasing the astrophysical reach of gravitational-wave detectors.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Dark matter may induce apparent temporal variations in the physical “constants”, including the electromagnetic fine-structure constant and fermion masses. In particular, a coherently oscillating ...classical dark-matter field may induce apparent oscillations of physical constants in time, while the passage of macroscopic dark-matter objects (such as topological defects) may induce apparent transient variations in the physical constants. In this paper, we point out several new signatures of the aforementioned types of dark matter that can arise due to the geometric asymmetry created by the beam-splitter in a two-arm laser interferometer. These new signatures include dark-matter-induced time-varying size changes of a freely suspended beam-splitter and associated time-varying shifts of the main reflecting surface of the beam-splitter that splits and recombines the laser beam, as well as time-varying refractive-index changes in the freely suspended beam-splitter and time-varying size changes of freely suspended arm mirrors. We demonstrate that existing ground-based experiments already have sufficient sensitivity using existing data to probe extensive regions of the unconstrained parameter space in models involving oscillating scalar dark-matter fields and domain walls composed of scalar fields. In the case of oscillating dark-matter fields, Michelson interferometers—in particular, the GEO 600 detector—are especially sensitive. The sensitivity of Fabry-Perot-Michelson interferometers, including LIGO, VIRGO, and KAGRA, to oscillating dark-matter fields can be significantly increased by making the thicknesses of the freely suspended Fabry-Perot arm mirrors different in the two arms. Not-too-distantly separated laser interferometers can benefit from cross-correlation measurements in searches for effects of spatially coherent dark-matter fields. In addition to broadband searches for oscillating dark-matter fields, we also discuss how small-scale Michelson interferometers, such as the Fermilab holometer, could be used to perform resonant narrowband searches for oscillating dark-matter fields with enhanced sensitivity to dark matter. Finally, we discuss the possibility of using future space-based detectors, such as LISA, to search for dark matter via time-varying size changes of and time-varying forces exerted on freely floating test masses.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM, UPUK
Abstract
Theories of quantum gravity based on the holographic principle predict the existence of quantum fluctuations of distance measurements that accumulate and exhibit correlations over ...macroscopic distances. This paper models an expected signal due to this phenomenology, and details the design and estimated sensitivity of co-located twin table-top 3D interferometers being built to measure or constrain it. The experiment is estimated to be sensitive to displacements
∼
1
0
−
19
m
/
H
z
in a frequency band between 1 and 250 MHz, surpassing previous experiments and enabling the possible observation of quantum gravity phenomena. The experiment will also be sensitive to MHz gravitational waves and various dark matter candidates.
The world-wide network of km-scale laser interferometers is aiming at the detection of gravitational waves of astrophysical origin. The second generation of these instruments, called advanced ...detectors has been, or is in the process of being completed, and a first observational run with the Advanced LIGO interferometers has been performed late in 2015. The basic functionality of advanced detectors is discussed, along with specific features and status updates of the individual projects.
The German-British laser-interferometric gravitational wave detector GEO 600 is in its 14th year of operation since its first lock in 2001. After GEO 600 participated in science runs with other ...first-generation detectors, a program known as GEO-HF began in 2009. The goal was to improve the detector sensitivity at high frequencies, around 1 kHz and above,with technologically advanced yet minimally invasive upgrades. Simultaneously, the detector would record science quality data in between commissioning activities. As of early 2014, all of the planned upgrades have been carried out and sensitivity improvements of up to a factor of four at the high-frequency end of the observation band have been achieved. Besides science data collection, an experimental program is ongoing with the goal to further improve the sensitivity and evaluate future detector technologies. We summarize the results of the GEO-HF program to date and discuss its successes and challenges.
The aim of the study was to characterize the interendothelial junctions in tumor microvessels of five cases of human glioblastoma multiforme. In addition to morphological analysis, tumors were ...screened for the expression of junctional proteins, such as occludin, claudin-1, ZO-1 and catenins. The expression of the tight junction protein claudin-1 was lost in the majority of tumor microvessels, whereas claudin-5 and occludin were significantly down-regulated only in hyperplastic vessels. As shown by freeze-fracture analysis, under the conditions of tumor growth tight junction particles of endothelial cells were almost exclusively associated with the exocytoplasmic fracture face, providing evidence for a switch of the particles from the protoplasmic to the external leaflet of the endothelial membrane. These results suggest a relationship between claudin-1 suppression and the alteration of tight junction morphology, which is likely to correlate with the increase of endothelial permeability. Underlining the undifferentiated state of tumor microvessels, plakoglobin, a crucial protein for mature endothelial junctions, was not detectable in most microvessels, whereas beta-catenin was abundantly labeled. In this context, it is of particular interest that the majority of microvascular pericytes were negative for alpha-smooth muscle actin, which is a marker of differentiated pericytes, although pericytes were frequently found in electron micrographs. In conclusion, the data suggest that the increase in microvascular permeability in human gliomas, contributing to the clinically severe symptoms of brain edema, is a result of a dysregulation of junctional proteins.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
Background
The coronavirus pandemic, in particular the introduction of masks, presented a huge challenge for the UK’s D/deaf community, many of whom rely on visual cues in lipreading and ...sign language. This particularly affected D/deaf healthcare professionals (HCPs), who faced significant communication challenges at work due to the lack of transparent masks or other reasonable adjustments.
Aims
To determine the impact that a lack of transparent masks and reasonable adjustments had on communication, confidence at work and well-being among D/deaf HCPs during the coronavirus pandemic.
Methods
A survey was sent to all members of the ‘UK Deaf Healthcare Professionals Group’ on Facebook, the ‘Healthcare Professionals with Hearing Loss’ listserver and promoted on Social Media.
Results
Eighty-three responses were received. Nine (11%) individuals had access to transparent masks. Over three-quarters of respondents reported feeling anxious and fearful of making a mistake due to communication difficulties. Fourteen (17%) were removed from clinical roles due to a lack of reasonable adjustments. One-third felt they would need to consider an alternative career if improvements were not made. Seventy-eight per cent felt the communication needs of D/deaf HCPs had not been met during the pandemic.
Conclusions
D/deaf HCPs felt left behind, isolated and frustrated by a lack of transparent masks and reasonable adjustments to meet their communication needs. Loss of experienced, qualified HCPs has a significant economic and workforce impact, particularly during a pandemic. Urgent action is needed to ensure D/deaf HCPs are provided with the workplace support required under the Equality Act (2010).
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