We present and characterize a narrow-linewidth external-cavity diode laser at 2 μm, and show that it represents a low-cost, high-performance alternative to fiber lasers for research into 2 μm ...photonic technologies for next-generation gravitational-wave detectors. A linewidth of 20 kHz for a 10 ms integration time was measured without any active stabilization, with frequency noise of ∼ 15 Hz/Hz between 3 kHz and 100 kHz. This performance is suitable for the generation of quantum squeezed light, and we measure intensity noise comparable to that of master oscillators used in current gravitational wave interferometers. The laser wavelength is tunable over a 120 nm range, and both the frequency and intensity can be modulated at up to 10 MHz by modulating the diode current. These features also make it suitable for other emerging applications in the 2 μm wavelength region including gas sensing, optical communications and LIDAR.
Designs for future gravitational wave detection facilities feature silicon test masses at cryogenic temperatures to reduce thermal noise and thermally induced aberrations. Designers call for ...operation at 123 K or close to 18 K to exploit the vanishing thermal expansion of crystalline silicon. The amount of absorbed heat that can be radiatively removed from the test masses is limited at these temperatures, forcing complex cooling scenarios to be considered, including conduction through suspension wires. This is particularly relevant for the kilohertz class of detectors that aim for extremely high circulating power, i.e., roughly a factor 20 more than the world record at the time of writing, to reduce quantum noise. We explore the impact of raising the test mass temperature and show that a dedicated kilohertz-band cryogenic instrument can do so without significant sensitivity penalty, thereby boosting the radiative cooling rate and allowing higher power operation with simpler suspensions. We also explore the implications of operating cryogenic broadband detectors at elevated temperatures. The work presented here was instrumental in the development of the Neutron Star Extreme Matter Observatory kilohertz-band gravitational wave detector design concept.
With the spread of the human immunodeficiency virus in the early 1980s, cryptosporidiosis was regarded as an AIDS-defining disease. As an opportunistic pathogen, the intestinal parasite ...Cryptosporidium parvum became an important cause of chronic diarrhoea, leading to high morbidity and mortality in immunocompromised patients. To date, no effective chemotherapy is available. With the introduction of protease inhibitors (PIs) in highly active antiretroviral therapy (HAART), the incidence of cryptosporidiosis in AIDS patients has declined substantially in western countries. We have therefore tested the effect of five PIs used in HAART on the excystation, invasion and development of the parasite in a cell culture system. The human ileocaecal adenocarcinoma cell line HCT-8 served as a host cell. None of the substances had an effect on the excystation rate, and only nelfinavir moderately, but statistically significantly, inhibited the host cell invasion over a period of 2 h. There were more pronounced inhibitory effects when PIs were present over the total time of intracellular development (48 h). Indinavir, nelfinavir and ritonavir inhibited parasite development significantly. The inhibitory effect was increased when the aminoglycoside paromomycin was combined with the PIs indinavir, ritonavir, and to a lesser extent saquinavir, compared to the PIs alone.
The barium meal with plain X-ray films of the small intestine has for decades been the undisputed gold standard in imaging of the small intestine. More recently, X-rays and fluoroscopy with an ...overall accuracy of 73% have been replaced by multislice computed tomography (MSCT) or modern magnetic resonance imaging (MRI). Ultrasound is suitable for the orienting investigation of the small intestine in the context of general abdominal sonography as well as for dedicated examinations with a sensitivity of 67-96% and a specificity up to 97%. The endoscopic examinations of the small bowel, such as video capsule endoscopy and double-balloon enteroscopy are expensive and time-consuming techniques, which provide valuable information in special indications. Other than with the stomach or colon, the diagnostics of primary small intestine tumors plays a relatively subordinate role due to the low incidence of 3-5% of all gastrointestinal (GI) neoplasms but with a high sensitivity of 84% and a specificity of up to 97% for computed tomography (CT) and MRI. Predominant questions are those concerning ileus or the diagnostics of passage disturbances after preceding operations, to depict bowel obstructions, adhesions or the involvement of the small bowel in peritoneal carcinomatosis. The sensitivity per lesion in the initial evaluation of Crohn's disease (CD) is 47-68% for capsule endoscopy, 43% for MRI and 21% for CT enterography. In cases of known CD, the sensitivity is 70% for capsule endoscopy and 79% for MRI. A further indication is the evaluation of acute or occult gastrointestinal bleeding.
In this paper we present the results of the first low frequency all-sky search of continuous gravitational wave signals conducted on Virgo VSR2 and VSR4 data. The starting point was a set of short ...fast Fourier transforms, of length 8192 s, built from the calibrated strain data. On each data set a number of candidates has been selected, using the FrequencyHough transform in an incoherent step. Only coincident candidates among VSR2 and VSR4 have been examined in order to strongly reduce the false alarm probability, and the most significant candidates have been selected. The criteria we have used for candidate selection and for the coincidence step greatly reduce the harmful effect of large instrumental artifacts. Our upper limits on signal strain show an improvement of up to a factor of ~2 with respect to the results of previous all-sky searches at frequencies below 80 Hz.
We report results of a wideband search for periodic gravitational waves from isolated neutron stars within the Orion spur towards both the inner and outer regions of our Galaxy. As gravitational ...waves interact very weakly with matter, the search is unimpeded by dust and concentrations of stars. One search disk (A) is 6.87degrees in diameter and centered on 20 super(h) 10 super(m) 54.71 super(s)+ 33degrees33'25.29'', and the other (B) is 7.45degrees in diameter and centered on 8 super(h) 35 super(m) 20.61 super(s)-46degrees49'25.15 1''. We explored the frequency range of 50-1500 Hz and frequency derivative from 0 to -5x10 super(-9)Hz/s. A multistage, loosely coherent search program allowed probing more deeply than before in these two regions, while increasing coherence length with every stage. Rigorous follow-up parameters have winnowed the initial coincidence set to only 70 candidates, to be examined manually. None of those 70 candidates proved to be consistent with an isolated gravitational-wave emitter, and 95% confidence level upper limits were placed on continuous-wave strain amplitudes. Near 169 Hz we achieve our lowest 95% C.L. upper limit on the worst-case linearly polarized strain amplitude h sub(0) of 6.3x10 super(-25), while at the high end of our frequency range we achieve a worst-case upper limit of 3.4x10 super(-24) for all polarizations and sky locations.
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