1,892 research outputs found
A Microcalorimeter and Bolometer Model
The standard non-equilibrium theory of noise in ideal bolometers and
microcalorimeters fails to predict the performance of real devices due to
additional effects that become important at low temperature. In this paper we
extend the theory to include the most important of these effects, and find that
the performance of microcalorimeters operating at 60 mK can be quantitatively
predicted. We give a simple method for doing the necessary calculations,
borrowing the block diagram formalism from electronic control theory.Comment: 20 pages, 15 figure
Lithium Experiment on Solar Neutrinos to Weight the CNO Cycle
The measurement of the flux of beryllium neutrinos with the accuracy of about
10% and CNO neutrinos with the accuracy 30% will enable to find the flux of
pp-neutrinos in the source with the accuracy better than 1% using the
luminosity constraint. The future experiments on \nu e- scattering will enable
to measure with very good accuracy the flux of beryllium and pp-neutrinos on
the Earth. The ratio of the flux of pp-neutrinos on the Earth and in the source
will enable to find with very good accuracy a mixing angle theta solar. Lithium
detector has high sensitivity to CNO neutrinos and can find the contribution of
CNO cycle to the energy generated in the Sun. This will be a stringent test of
the theory of stellar evolution and combined with other experiments will
provide a precise determination of the flux of pp-neutrinos in the source and a
mixing angle theta solar. The work on the development of the technology of
lithium experiment is now in progress.Comment: Minor corrections, one reference added, 11 pages, 2 figures, talk
given at NANP 2003, Dubna, Russia, June 200
Prevalence of Baker's cyst in patients with knee pain: an ultrasonographic study
The objectives of this study are to investigate the prevalence of Baker's cyst (BC) in patients with knee pain, and to assess the correlation between BC and severity of osteophytes and joint effusion. A retrospective study was conducted on a group of patients with knee pain referred to our outpatient clinic for ultrasonography of the knee between January 2010 and February 2011. Patients underwent an ultrasonographic exam of the knees to assess the presence of marginal femorotibial osteophytosis, joint effusion and BC. A dichotomous score was assigned to each item (1 present, 0 absent) and severity of US signs of osteoarthritis and joint effusion were also graded semiquantitatively. Collected data were processed using logistic regression analysis to evaluate the correlation between degree of osteophytosis and joint effusion and BC. Patients affected by inflammatory joint conditions or with history of joint surgery or recent trauma were excluded. A total of 399 patients with knee pain were studied (299 women), in the age range 18-89 years (mean 56.2, SD 16.3 years). 293 patients (73.4%) showed sonographic features of osteoarthritis and 251 (62.9%) joint effusion. BC was found in 102 patients (25.8%) together with a positive association with sonographic features of osteoarthritis and joint effusion. Our data show a prevalence of BC of 25.8% in a population of patients with knee pain, and suggest that BC is positively related to osteoarthritis and joint effusion. Ultrasonographic examination of knee is worthwhile in patients with painful osteoarthritis or evidence of effusion
Observed Limits on Charge Exchange Contributions to the Diffuse X-ray Background
We present a high resolution spectrum of the diffuse X-ray background from
0.1 to 1 keV for a ~1 region of the sky centered at l=90, b=+60 using a
36-pixel array of microcalorimeters flown on a sounding rocket. With an energy
resolution of 11 eV FWHM below 1 keV, the spectrum's observed line ratios help
separate charge exchange contributions originating within the heliosphere from
thermal emission of hot gas in the interstellar medium. The X-ray sensitivity
below 1 keV was reduced by about a factor of four from contamination that
occurred early in the flight, limiting the significance of the results. The
observed centroid of helium-like O VII is 568+2-3 eV at 90% confidence. Since
the centroid expected for thermal emission is 568.4 eV while for charge
exchange is 564.2 eV, thermal emission appears to dominate for this line
complex, consistent with much of the high-latitude O VII emission originating
in 2-3 x 10^6 K gas in the Galactic halo. On the other hand, the observed ratio
of C VI Ly gamma to Ly alpha is 0.3+-0.2. The expected ratios are 0.04 for
thermal emission and 0.24 for charge exchange, indicating that charge exchange
must contribute strongly to this line and therefore potentially to the rest of
the ROSAT R12 band usually associated with 10^6 K emission from the Local Hot
Bubble. The limited statistics of this experiment and systematic uncertainties
due to the contamination require only >32% thermal emission for O VII and >20%
from charge exchange for C VI at the 90% confidence level. An experimental gold
coating on the silicon substrate of the array greatly reduced extraneous
signals induced on nearby pixels from cosmic rays passing through the
substrate, reducing the triggered event rate by a factor of 15 from a previous
flight of the instrument.Comment: 14 pages, 7 figures, to be published in Ap
Testing the neutrality of matter by acoustic means in a spherical resonator
New measurements to test the neutrality of matter by acoustic means are
reported. The apparatus is based on a spherical capacitor filled with gaseous
SF excited by an oscillating electric field. The apparatus has been
calibrated measuring the electric polarizability. Assuming charge conservation
in the decay of the neutron, the experiment gives a limit of
for the electron-proton charge
difference, the same limit holding for the charge of the neutron. Previous
measurements are critically reviewed and found incorrect: the present result is
the best limit obtained with this technique
Scintillating properties of frozen new liquid scintillators
The light emission from scintillators which are liquid at room temperature was studied in the interval between ~C and ~C, where the phase transition from liquid to solid takes place. The light yield measured at ~C is about twice as much as that observed at ~C. By cooling the scintillator from ~C to ~C and then heating it from ~C to ~C, the light yield varies in steps at well defined temperatures, which are different for the cooling and heating processes. These hysteresis phenomena appear to be related to the solvent rather than to the dopant. The decay time of scintillation light was measured at ~C and ~C. Whilst at room temperature most of the light is emitted with a decay time of 6--8 ns, at ~C a slower component, with a decay time of 25--35 ns, becomes important
Normalizing glycosphingolipids restores function in CD4+ T cells from lupus patients
Patients with the autoimmune rheumatic disease systemic lupus erythematosus (SLE) have multiple defects in lymphocyte signaling and function that contribute to disease pathogenesis. Such defects could be attributed to alterations in metabolic processes, including abnormal control of lipid biosynthesis pathways. Here, we reveal that CD4+ T cells from SLE patients displayed an altered profile of lipid raft–associated glycosphingolipids (GSLs) compared with that of healthy controls. In particular, lactosylceramide, globotriaosylceramide (Gb3), and monosialotetrahexosylganglioside (GM1) levels were markedly increased. Elevated GSLs in SLE patients were associated with increased expression of liver X receptor β (LXRβ), a nuclear receptor that controls cellular lipid metabolism and trafficking and influences acquired immune responses. Stimulation of CD4+ T cells isolated from healthy donors with synthetic and endogenous LXR agonists promoted GSL expression, which was blocked by an LXR antagonist. Increased GSL expression in CD4+ T cells was associated with intracellular accumulation and accelerated trafficking of GSL, reminiscent of cells from patients with glycolipid storage diseases. Inhibition of GSL biosynthesis in vitro with a clinically approved inhibitor (N-butyldeoxynojirimycin) normalized GSL metabolism, corrected CD4+ T cell signaling and functional defects, and decreased anti-dsDNA antibody production by autologous B cells in SLE patients. Our data demonstrate that lipid metabolism defects contribute to SLE pathogenesis and suggest that targeting GSL biosynthesis restores T cell function in SLE
DXL: a sounding rocket mission for the study of solar wind charge exchange and local hot bubble X-ray emission
The Diffuse X-rays from the Local galaxy (DXL) mission is an approved
sounding rocket project with a first launch scheduled around December 2012. Its
goal is to identify and separate the X-ray emission generated by solar wind
charge exchange from that of the local hot bubble to improve our understanding
of both. With 1,000 cm2 proportional counters and grasp of about 10 cm2 sr both
in the 1/4 and 3/4 keV bands, DXL will achieve in a 5-minute flight what cannot
be achieved by current and future X-ray satellites.Comment: 15 Pages, 5 figures. Accepted for publication on Experimental
Astronom
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