267 research outputs found
New thermocouple-based microwave/millimeter-wave power sensor MMIC techniques in GaAs
We describe a new RF and microwave power sensor monolithic microwave integrated circuit design. The circuit incorporates a number of advances over existing designs. These include a III–V epitaxial structure optimized for sensitivity, the figure-of-merit applicable to the optimization, a mechanism for in-built detection of load ageing and damage to extend calibration intervals, and a novel symmetrical structure to linearize the high-power end of the scale
Effects of Air Entrainment on Fluid Transients in Pumping Systems
In pumping installations, fluid transient computations are necessary to achieve safety, efficiency and
economy in design and operation. In some systems, where air content and air entrainment exist, such
computations become highly inaccurate when constant wave speed is assumed. In this paper, a numerical
model and a computational procedure have been developed to investigate the effects of air entrainment on
the pressure transient in pumping systems. Free gas in the fluid and cavitation at the fluid vapour pressure
were modeled in the form of variable wave speed model, which was numerically solved by the method of
characteristics. This model was tested for the case of pump trips due to power failures. The pressure
transient results obtained by this variable wave speed model were analyzed and compared with those results
obtained by constant wave speed model and with the experimental results of other investigators
Polarimetric Properties of Flux-Ropes and Sheared Arcades in Coronal Prominence Cavities
The coronal magnetic field is the primary driver of solar dynamic events.
Linear and circular polarization signals of certain infrared coronal emission
lines contain information about the magnetic field, and to access this
information, either a forward or an inversion method must be used. We study
three coronal magnetic configurations that are applicable to polar-crown
filament cavities by doing forward calculations to produce synthetic
polarization data. We analyze these forward data to determine the
distinguishing characteristics of each model. We conclude that it is possible
to distinguish between cylindrical flux ropes, spheromak flux ropes, and
sheared arcades using coronal polarization measurements. If one of these models
is found to be consistent with observational measurements, it will mean
positive identification of the magnetic morphology that surrounds certain
quiescent filaments, which will lead to a greater understanding of how they
form and why they erupt.Comment: 22 pages, 8 figures, Solar Physics topical issue: Coronal Magnetis
18F-fluorodeoxyglucose positron emission tomography as a window into human dengue pathophysiology.
In mouse models of dengue virus (DENV) infection, 18F-FDG PET is able to sensitively detect tissue-specific sites of inflammation and disease activity, as well as track therapeutic response to anti- DENV agents. However, the use of 18F-FDG PET to study the pathogenesis of inflammation and disease activity in DENV infection in humans, has not been clinically validated. Here we report the 18F-FDG PET imaging results of two patients during the febrile phase of acute DENV infection, paired with serial serum viral load, NS1 and proinflammatory cytokine measurements. Our findings demonstrate that 18F-FDG PET is able to sensitively detect and quantify organ-specific inflammation in the lymph nodes and spleen, in classic acute dengue fever. This raises the potential for 18F-FDG PET to be used as a research tool that may provide further insights into disease pathogenesis
Modeling the Subsurface Structure of Sunspots
While sunspots are easily observed at the solar surface, determining their
subsurface structure is not trivial. There are two main hypotheses for the
subsurface structure of sunspots: the monolithic model and the cluster model.
Local helioseismology is the only means by which we can investigate
subphotospheric structure. However, as current linear inversion techniques do
not yet allow helioseismology to probe the internal structure with sufficient
confidence to distinguish between the monolith and cluster models, the
development of physically realistic sunspot models are a priority for
helioseismologists. This is because they are not only important indicators of
the variety of physical effects that may influence helioseismic inferences in
active regions, but they also enable detailed assessments of the validity of
helioseismic interpretations through numerical forward modeling. In this paper,
we provide a critical review of the existing sunspot models and an overview of
numerical methods employed to model wave propagation through model sunspots. We
then carry out an helioseismic analysis of the sunspot in Active Region 9787
and address the serious inconsistencies uncovered by
\citeauthor{gizonetal2009}~(\citeyear{gizonetal2009,gizonetal2009a}). We find
that this sunspot is most probably associated with a shallow, positive
wave-speed perturbation (unlike the traditional two-layer model) and that
travel-time measurements are consistent with a horizontal outflow in the
surrounding moat.Comment: 73 pages, 19 figures, accepted by Solar Physic
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV
Isolated photon production is measured in proton-proton and lead-lead
collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the
pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80
GeV with the CMS detector at the LHC. The measured ET spectra are found to be
in good agreement with next-to-leading-order perturbative QCD predictions. The
ratio of PbPb to pp isolated photon ET-differential yields, scaled by the
number of incoherent nucleon-nucleon collisions, is consistent with unity for
all PbPb reaction centralities.Comment: Submitted to Physics Letters
Flavor Production in Pb(160AGeV) on Pb Collisions: Effect of Color Ropes and Hadronic Rescattering
Collective interactions in the preequilibrium quark matter and hadronic
resonance gas stage of ultrarelativistic nucleus-nucleus collisions are studied
in the framework of the the transport theoretical approach RQMD. The paper
reviews string fusion into color ropes and hadronic rescattering which serve as
models for these interactions. Hadron production in central Pb(160AGeV) on Pb
collisions has been calculated. The changes of the final flavor composition are
more pronounced than in previous RQMD studies of light ion induced reactions at
200AGeV. The ratio of created quark pairs /(+) is
enhanced by a factor of 2.4 in comparison to results. Color rope formation
increases the initially produced antibaryons to 3 times the value in the `NN
mode', but only one quarter of the produced antibaryons survives because of
subsequent strong absorption. The differences in the final particle composition
for Pb on Pb collisions compared to S induced reactions are attributed to the
hadronic resonance gas stage which is baryon-richer and lasts longer.Comment: 60 pages + 11 postscript figures (uuencoded and included
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