2,841 research outputs found
Measurement of the Charge Collection Efficiency after Heavy Non-Uniform Irradiation in BaBar Silicon Detectors
We have investigated the depletion voltage changes, the leakage current
increase and the charge collection efficiency of a silicon microstrip detector
identical to those used in the inner layers of the BaBar Silicon Vertex Tracker
(SVT) after heavy non-uniform irradiation. A full SVT module with the front-end
electronics connected has been irradiated with a 0.9 GeV electron beam up to a
peak fluence of 3.5 x 10^14 e^-/cm^2, well beyond the level causing substrate
type inversion. We irradiated one of the two sensors composing the module with
a non-uniform profile with sigma=1.4 mm that simulates the conditions
encountered in the BaBar experiment by the modules intersecting the horizontal
machine plane. The position dependence of the charge collection properties and
the depletion voltage have been investigated in detail using a 1060 nm LED and
an innovative measuring technique based only on the digital output of the chip.Comment: 7 pages, 13 figures. Presented at the 2004 IEEE Nuclear Science
Symposium, October 18-21, Rome, Italy. Accepted for publication by IEEE
Transactions on Nuclear Scienc
Spiky oscillations in NF-kB signalling
The NF-kB signalling system is involved in a variety of cellular processes
including immune response, inflammation, and apoptosis. Recent experiments have
found oscillations in the nuclear-cytoplasmic translocation of the NF-kB
transcription factor. How the cell uses the oscillations to differentiate input
conditions and send specific signals to downstream genes is an open problem. We
shed light on this issue by examining the small core network driving the
oscillations, which, we show, is designed to produce periodic spikes in nuclear
NF-kB concentration. The oscillations can be used to regulate downstream genes
in a variety of ways. In particular, we show that genes to whose operator sites
NF-kB binds and dissociates fast can respond very sensitively to changes in the
input signal, with effective Hill coefficients in excess of 20.Comment: 11 pages, 13 figure
A VIRTUAL CRANKSHAFT THIGH MODEL TO ESTIMATE TIBIAL-FEMORAL TRANSVERSE PLANE KINEMATICS
Sports injuries often require a thorough evaluation of the knee that includes transverse plane measurements, which are difficult to measure accurately using motion capture. We have developed a method to estimate thigh position modelling the lower limb as a modified slider-crank mechanism. Our model does not rely on cutaneous thigh markers; its motion is defined by a functionally determined hip joint center and constrained distally to the tibial plateau. Motion capture was used to acquire normal gait and countermovement jump data from three unimpaired subjects. The transverse plane translations and rotation along with frontal plane rotation estimated by our model were shown to be reflective of those reported in literature. Our slider-crank model of the pelvis-femur-tibia complex has been demonstrated to perform well in both low and high impact motions
Human metapneumovirus establishes persistent infection in lung microvascular endothelial cells and primes a th2-skewed immune response
Human metapneumovirus (HMPV) is a major cause of lower respiratory tract infections. HMPV infection has been hypothesized to alter dendritic cell (DC) immune response; however, many questions regarding HMPV pathogenesis within the infected lung remain unanswered. Here, we show that HMPV productively infects human lung microvascular endothelial cells (L-HMVECs). The release of infectious virus occurs for up to more than 30 days of culture without producing overt cytopathic effects and medium derived from persistently HMPV-infected L-HMVECs (secretome) induced monocyte-derived DCs to prime naïve CD4 T-cells toward a Th2 phenotype. Moreover, we demonstrated that infected secretomes trigger DCs to up-regulate OX40L expression and OX40L neutralization abolished the pro-Th2 effect that is induced by HMPV-secretome. We clarified secretome from HMPV by size exclusion and ultracentrifugation with the aim to characterize the role of viral particles in the observed pro-Th2 effect. In both cases, the percentage of IL-4-producing cells and expression of OX40L returned at basal levels. Finally, we showed that HMPV, per se, could reproduce the ability of secretome to prime pro-Th2 DCs. These results suggest that HMPV, persistently released by L-HMVECs, might take part in the development of a skewed, pro-Th2 lung microenvironment
Nanoscale phase-engineering of thermal transport with a Josephson heat modulator
Macroscopic quantum phase coherence has one of its pivotal expressions in the
Josephson effect [1], which manifests itself both in charge [2] and energy
transport [3-5]. The ability to master the amount of heat transferred through
two tunnel-coupled superconductors by tuning their phase difference is the core
of coherent caloritronics [4-6], and is expected to be a key tool in a number
of nanoscience fields, including solid state cooling [7], thermal isolation [8,
9], radiation detection [7], quantum information [10, 11] and thermal logic
[12]. Here we show the realization of the first balanced Josephson heat
modulator [13] designed to offer full control at the nanoscale over the
phase-coherent component of thermal currents. Our device provides
magnetic-flux-dependent temperature modulations up to 40 mK in amplitude with a
maximum of the flux-to-temperature transfer coefficient reaching 200 mK per
flux quantum at a bath temperature of 25 mK. Foremost, it demonstrates the
exact correspondence in the phase-engineering of charge and heat currents,
breaking ground for advanced caloritronic nanodevices such as thermal splitters
[14], heat pumps [15] and time-dependent electronic engines [16-19].Comment: 6+ pages, 4 color figure
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