70 research outputs found
Microwave Inter-Connections and Switching by means of Carbon Nano-tubes
In this work, carbon nanotube (CNT) based
interconnections and switches will be reviewed,
discussing the possibility to use nanotubes as potential
building blocks for signal routing in microwave
networks. In particular, theoretical design of coplanar
waveguide (CPW), microâstrip singleâpoleâsingleâthrow
(SPST) and singleâpoleâdoubleâthrow (SPDT) devices has
been performed to predict the electrical performances of
CNTâbased RF switching configurations. Actually, by
using the semiconductorâconductor transition obtained
by properly biasing the CNTs, an isolation better than 30
dB can be obtained between the ON and OFF states of the
switch for very wide bandwidth applications. This
happens owing to the shape deformation and consequent
change in the bandâgap due to the external pressure
caused by the electric field. Stateâofâart for other
switching techniques based on CNTs and their use for RF
nanoâinterconnections is also discussed, together with
current issues in measurement techniques
Two-Dimensional Spectroscopy of Photospheric Shear Flows in a Small delta Spot
In recent high-resolution observations of complex active regions,
long-lasting and well-defined regions of strong flows were identified in major
flares and associated with bright kernels of visible, near-infrared, and X-ray
radiation. These flows, which occurred in the proximity of the magnetic neutral
line, significantly contributed to the generation of magnetic shear. Signatures
of these shear flows are strongly curved penumbral filaments, which are almost
tangential to sunspot umbrae rather than exhibiting the typical radial
filamentary structure. Solar active region NOAA 10756 was a moderately complex,
beta-delta sunspot group, which provided an opportunity to extend previous
studies of such shear flows to quieter settings. We conclude that shear flows
are a common phenomenon in complex active regions and delta spots. However,
they are not necessarily a prerequisite condition for flaring. Indeed, in the
present observations, the photospheric shear flows along the magnetic neutral
line are not related to any change of the local magnetic shear. We present
high-resolution observations of NOAA 10756 obtained with the 65-cm vacuum
reflector at Big Bear Solar Observatory (BBSO). Time series of
speckle-reconstructed white-light images and two-dimensional spectroscopic data
were combined to study the temporal evolution of the three-dimensional vector
flow field in the beta-delta sunspot group. An hour-long data set of consistent
high quality was obtained, which had a cadence of better than 30 seconds and
sub-arcsecond spatial resolution.Comment: 23 pages, 6 gray-scale figures, 4 color figures, 2 tables, submitted
to Solar Physic
Observational Constraints on Chaplygin Quartessence: Background Results
We derive the constraints set by several experiments on the quartessence
Chaplygin model (QCM). In this scenario, a single fluid component drives the
Universe from a nonrelativistic matter-dominated phase to an accelerated
expansion phase behaving, first, like dark matter and in a more recent epoch
like dark energy. We consider current data from SNIa experiments, statistics of
gravitational lensing, FR IIb radio galaxies, and x-ray gas mass fraction in
galaxy clusters. We investigate the constraints from this data set on flat
Chaplygin quartessence cosmologies. The observables considered here are
dependent essentially on the background geometry, and not on the specific form
of the QCM fluctuations. We obtain the confidence region on the two parameters
of the model from a combined analysis of all the above tests. We find that the
best-fit occurs close to the CDM limit (). The standard
Chaplygin quartessence () is also allowed by the data, but only at
the level.Comment: Replaced to match the published version, references update
Early- Onset Stroke and Vasculopathy Associated with Mutations in ADA2
Adenosine deaminase 2 (ADA2) is an enzyme involved in purine metabolism and a growth factor that influences the development of endothelial cells and leukocytes. This study shows that defects in ADA2 cause recurrent fevers, vascular pathologic features, and mild immunodeficiency. Patients with autoinflammatory disease sometimes present with clinical findings that encompass multiple organ systems.(1) Three unrelated children presented to the National Institutes of Health (NIH) Clinical Center with intermittent fevers, recurrent lacunar strokes, elevated levels of acute-phase reactants, livedoid rash, hepatosplenomegaly, and hypogammaglobulinemia. Collectively, these findings do not easily fit with any of the known inherited autoinflammatory diseases. Hereditary or acquired vascular disorders can have protean manifestations yet be caused by mutations in a single gene. Diseases such as the Aicardi-Goutieres syndrome,(2),(3) polypoidal choroidal vasculopathy,(4) sickle cell anemia,(5) livedoid vasculopathy,(6) and the small-vessel vasculitides(7),(8) are examples of systemic ...</p
Structure and Dynamics of Breaking Foams
Experimental results are presented for the relaxation of a two dimensional soap foam in which wall breakage is initiated through gentle warming of the foam cell. Significantly different phenomenology from the relaxation of nonbreaking foams is observed. At a critical "break time," which depends on the temperature ramping rate and initial conditions, a large scale mechanical cascade of wall rupture sets in, leading to a rapid disintegration of the foam. In the cascade regime, whose behavior is essentially independent of the ramping rate, a dynamical scaling behavior, associated with the distribution of cell edge lengths, is proposed
Dialogue Manager for a NLIDB for Solving the Semantic Ellipsis Problem in Query Formulation
The Discounted Economic Stock of Money with VAR Forecasting
Monetary aggregation, Divisia money aggregate, Economic stock of money, User cost of money, Currency equivalent index, Bayesian vector autoregression, Asymmetric vector autoregression, E41, G12, C43, C22, E5,
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