3,562 research outputs found
Light-to-light readout system of the CMS electromagnetic calorimeter
For the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) at CERN, an 80,000-crystal electromagnetic calorimeter will measure electron and photon energies with high precision over a dynamic range of roughly 16 bits. The readout electronics will be located directly behind the crystals, and must survive a total dose of up to 2×104 Gy along with 5×1013 n/cm 2. A readout chain consisting of a custom wide-range acquisition circuit, commercial ADC and custom optical link for each crystal is presently under construction. An overview of the design is presented, with emphasis on the large-scale fiber communication syste
Two-dimensional AMR simulations of colliding flows
Colliding flows are a commonly used scenario for the formation of molecular
clouds in numerical simulations. Due to the thermal instability of the warm
neutral medium, turbulence is produced by cooling. We carry out a
two-dimensional numerical study of such colliding flows in order to test
whether statistical properties inferred from adaptive mesh refinement (AMR)
simulations are robust with respect to the applied refinement criteria. We
compare probability density functions of various quantities as well as the
clump statistics and fractal dimension of the density fields in AMR simulations
to a static-grid simulation. The static grid with 2048^2 cells matches the
resolution of the most refined subgrids in the AMR simulations. The density
statistics is reproduced fairly well by AMR. Refinement criteria based on the
cooling time or the turbulence intensity appear to be superior to the standard
technique of refinement by overdensity. Nevertheless, substantial differences
in the flow structure become apparent. In general, it is difficult to separate
numerical effects from genuine physical processes in AMR simulations.Comment: 6 pages, 6 figures, submitted to A&
The Shocking Properties of Supersonic Flows: Dependence of the Thermal Overstability on M, alpha, and T_c/T_0
We investigate the Mach number dependence of the radiative overstability of
shocks. We find that the stability of radiative shocks increases with
decreasing Mach number, with the result that M=2 shocks require cooling
exponents < -1.2 to be overstable. The frequency of oscillation of the
fundamental mode has a strong Mach number dependence. We find that feedback
between the cooling region and the cold dense layer (CDL) further downstream is
a function of Mach number, with stronger feedback and oscillation of the
boundary between the CDL and the cooling region occuring at lower Mach numbers.
This feedback can be quantified in terms of the reflection coefficient of sound
waves. An interesting finding is that the stability properties of low Mach
number shocks can be dramatically altered if the shocked gas is able to cool to
temperatures less than the pre-shock value, and it is probable that low Mach
number astrophysical shocks will be overstable in a variety of situations. The
results of this work are relevant to astrophysical shocks with low Mach
numbers, such as supernova remnants (SNRs) immersed in a hot interstellar
medium (e.g., within a starburst region), and shocks in molecular clouds, where
time-dependent chemistry can lead to overstability. (Abridged)Comment: 12 pages, 12 figures, accepted by A&
Photoevaporating flows from the cometary knots in the Helix nebula (NGC 7293)
We explain the Ha emission of the cometary knots in the Helix Nebula (NGC
7293) with an analytical model that describes the emission of the head of the
globules as a photoevaporated flow produced by the incident ionizing radiation
of the central star.We compare these models with the Ha emission obtained from
the HST archival images of the Helix Nebula. From a comparison of the Ha
emission with the predictions of the analytical model we obtain a rate of
ionizing photons from the central star of about 5e45 s^-1, which is consistent
with estimates based on the total Hb flux of the nebula. We also model the
tails of the cometary knots as a photoevaporated wind from a neutral shadow
region produced by the diffuse ionizing photon field of the nebula. A
comparison with the HST images allows us to obtain a direct determination of
the value of the diffuse ionizing flux. We compare the ratio of diffuse to
direct stellar flux as a function of radius inside an HII region with those
obtained from the observational data through the analytical tail and head wind
model. The agreement of this model with the values determined from the
observations of the knots is excellent.Comment: 9 pages, 5 figures, accepted for publication in Ap
Weak Lensing from Space I: Instrumentation and Survey Strategy
A wide field space-based imaging telescope is necessary to fully exploit the
technique of observing dark matter via weak gravitational lensing. This first
paper in a three part series outlines the survey strategies and relevant
instrumental parameters for such a mission. As a concrete example of hardware
design, we consider the proposed Supernova/Acceleration Probe (SNAP). Using
SNAP engineering models, we quantify the major contributions to this
telescope's Point Spread Function (PSF). These PSF contributions are relevant
to any similar wide field space telescope. We further show that the PSF of SNAP
or a similar telescope will be smaller than current ground-based PSFs, and more
isotropic and stable over time than the PSF of the Hubble Space Telescope. We
outline survey strategies for two different regimes - a ``wide'' 300 square
degree survey and a ``deep'' 15 square degree survey that will accomplish
various weak lensing goals including statistical studies and dark matter
mapping.Comment: 25 pages, 8 figures, 1 table, replaced with Published Versio
Supernova / Acceleration Probe: A Satellite Experiment to Study the Nature of the Dark Energy
The Supernova / Acceleration Probe (SNAP) is a proposed space-based
experiment designed to study the dark energy and alternative explanations of
the acceleration of the Universe's expansion by performing a series of
complementary systematics-controlled measurements. We describe a
self-consistent reference mission design for building a Type Ia supernova
Hubble diagram and for performing a wide-area weak gravitational lensing study.
A 2-m wide-field telescope feeds a focal plane consisting of a 0.7
square-degree imager tiled with equal areas of optical CCDs and near infrared
sensors, and a high-efficiency low-resolution integral field spectrograph. The
SNAP mission will obtain high-signal-to-noise calibrated light-curves and
spectra for several thousand supernovae at redshifts between z=0.1 and 1.7. A
wide-field survey covering one thousand square degrees resolves ~100 galaxies
per square arcminute. If we assume we live in a cosmological-constant-dominated
Universe, the matter density, dark energy density, and flatness of space can
all be measured with SNAP supernova and weak-lensing measurements to a
systematics-limited accuracy of 1%. For a flat universe, the
density-to-pressure ratio of dark energy can be similarly measured to 5% for
the present value w0 and ~0.1 for the time variation w'. The large survey area,
depth, spatial resolution, time-sampling, and nine-band optical to NIR
photometry will support additional independent and/or complementary dark-energy
measurement approaches as well as a broad range of auxiliary science programs.
(Abridged)Comment: 40 pages, 18 figures, submitted to PASP, http://snap.lbl.go
Efficacy and safety of oral methazolamide in patients with type 2 diabetes: A 24-week, placebo-controlled, double-blind study
OBJECTIVE To evaluate the safety and efficacy of methazolamide as a potential therapy for type 2 diabetes. RESEARCH DESIGN AND METHODS This double-blind, placebo-controlled study randomized 76 patients to oral methazolamide (40 mg b.i.d.) or placebo for 24 weeks. The primary efficacy end point for methazolamide treatment was a placebo-corrected reduction in HbA1c from baseline after 24 weeks (ΔHbA1c). RESULTS Mean ± SD baseline HbA1c was 7.1 ± 0.7% (54 ± 5 mmol/mol; n = 37) and 7.4 ± 0.6% (57 ± 5 mmol/mol; n = 39) in the methazolamide and placebo groups, respectively. Methazolamide treatment was associated with a ΔHbA1c of –0.39% (95% CI –0.82, 0.04; P < 0.05) (–4.3 mmol/mol [–9.0, 0.4]), an increase in the proportion of patients achieving HbA1c ≤6.5% (48 mmol/mol) from 8 to 33%, a rapid reduction in alanine aminotransferase (∼10 units/L), and weight loss (2%) in metformin-cotreated patients. CONCLUSIONS Methazolamide is the archetype for a new intervention in type 2 diabetes with clinical benefits beyond glucose control
Técnica do Inseto Estéril (TIE): nova tecnologia para o controle de moscas-das-frutas no Brasil; Projeto Piloto Livramento de Nossa Senhora.
Neste trabalho, relatam-se os resultados do “Projeto Piloto para Uso de Moscamed Estéril em Livramento de Nossa Senhora”, no Sudoeste da Bahia. O projeto teve como objetivo testar a efi ciência da linhagem “Viena 8” de C. capitata, nas condições do semi-árido do Nordeste do Brasil, bem como a logística de transporte e de liberação massal em campo, como uma ação pró-ativa às atividades da Bio-fábrica Moscamed Brasil
Inpatient COVID-19 mortality has reduced over time: Results from an observational cohort
BACKGROUND: The Covid-19 pandemic in the United Kingdom has seen two waves; the first starting in March 2020 and the second in late October 2020. It is not known whether outcomes for those admitted with severe Covid were different in the first and second waves. METHODS: The study population comprised all patients admitted to a 1,500-bed London Hospital Trust between March 2020 and March 2021, who tested positive for Covid-19 by PCR within 3-days of admissions. Primary outcome was death within 28-days of admission. Socio-demographics (age, sex, ethnicity), hypertension, diabetes, obesity, baseline physiological observations, CRP, neutrophil, chest x-ray abnormality, remdesivir and dexamethasone were incorporated as co-variates. Proportional subhazards models compared mortality risk between wave 1 and wave 2. Cox-proportional hazard model with propensity score adjustment were used to compare mortality in patients prescribed remdesivir and dexamethasone. RESULTS: There were 3,949 COVID-19 admissions, 3,195 hospital discharges and 733 deaths. There were notable differences in age, ethnicity, comorbidities, and admission disease severity between wave 1 and wave 2. Twenty-eight-day mortality was higher during wave 1 (26.1% versus 13.1%). Mortality risk adjusted for co-variates was significantly lower in wave 2 compared to wave 1 [adjSHR 0.49 (0.37, 0.65) p<0.001]. Analysis of treatment impact did not show statistically different effects of remdesivir [HR 0.84 (95%CI 0.65, 1.08), p = 0.17] or dexamethasone [HR 0.97 (95%CI 0.70, 1.35) p = 0.87]. CONCLUSION: There has been substantial improvements in COVID-19 mortality in the second wave, even accounting for demographics, comorbidity, and disease severity. Neither dexamethasone nor remdesivir appeared to be key explanatory factors, although there may be unmeasured confounding present
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