1,171 research outputs found
Ebola Virus Localization in the Macaque Reproductive Tract during Acute Ebola Virus Disease.
Sexual transmission of Ebola virus (EBOV) has been demonstrated more than a year after recovery from the acute phase of Ebola virus disease (EVD). The mechanisms underlying EBOV persistence and sexual transmission are not currently understood. Using the acute macaque model of EVD, we hypothesized EBOV would infect the reproductive tissues and sought to localize the infection in these tissues using immunohistochemistry and transmission electron microscopy. In four female and eight male macaques that succumbed to EVD between 6 and 9 days after EBOV challenge, we demonstrate widespread EBOV infection of the interstitial tissues and endothelium in the ovary, uterus, testis, seminal vesicle, epididymis, and prostate gland, with minimal associated tissue immune response or organ pathology. Given the widespread involvement of EBOV in the reproductive tracts of both male and female macaques, it is reasonable to surmise that our understanding of the mechanisms underlying sexual transmission of EVD and persistence of EBOV in immune-privileged sites would be facilitated by the development of a nonhuman primate model in which the macaques survived past the acute stage into convalescence
Fullerene-based molecular nanobridges: A first-principles study
Building upon traditional quantum chemistry calculations, we have implemented
an {\em ab-initio} method to study the electrical transport in nanocontacts. We
illustrate our technique calculating the conductance of C molecules
connected in various ways to Al electrodes characterized at the atomic level.
Central to a correct estimate of the electrical current is a precise knowledge
of the local charge transfer between molecule and metal which, in turn,
guarantees the correct positioning of the Fermi level with respect to the
molecular orbitals. Contrary to our expectations, ballistic transport seems to
occur in this system.Comment: 4 pages in two-column forma
Exploring tandem ruthenium-catalyzed hydrogen transfer and SNAr chemistry
A hydrogen-transfer strategy for the catalytic functionalization of benzylic alcohols via electronic arene activation, accessing a diverse range of bespoke diaryl ethers and aryl amines in excellent isolated yields (38 examples, 70% average yield), is reported. Taking advantage of the hydrogen-transfer approach, the oxidation level of the functionalized products can be selected by judicious choice of simple and inexpensive additives
Applied Plasma Research
Contains reports on three research projects.National Science Foundation (Grant GK-18185)M. I. T. Lincoln Laboratory Purchase Order No. CC-55
Auditory and tactile gap discrimination by observers with normal and impaired hearing
Temporal processing ability for the senses of hearing and touch was examined through the measurement of gap-duration discrimination thresholds (GDDTs) employing the same low-frequency sinusoidal stimuli in both modalities. GDDTs were measured in three groups of observers (normal-hearing, hearing-impaired, and normal-hearing with simulated hearing loss) covering an age range of 21–69 yr. GDDTs for a baseline gap of 6 ms were measured for four different combinations of 100-ms leading and trailing markers (250–250, 250–400, 400–250, and 400–400 Hz). Auditory measurements were obtained for monaural presentation over headphones and tactile measurements were obtained using sinusoidal vibrations presented to the left middle finger. The auditory GDDTs of the hearing-impaired listeners, which were larger than those of the normal-hearing observers, were well-reproduced in the listeners with simulated loss. The magnitude of the GDDT was generally independent of modality and showed effects of age in both modalities. The use of different-frequency compared to same-frequency markers led to a greater deterioration in auditory GDDTs compared to tactile GDDTs and may reflect differences in bandwidth properties between the two sensory systems.National Institute on Deafness and Other Communication Disorders (U.S.) (Grant R01 DC000117
Hamiltonian thermodynamics of the Reissner-Nordstr\"om-anti-de Sitter black hole
We consider the Hamiltonian dynamics and thermodynamics of spherically
symmetric Einstein-Maxwell spacetimes with a negative cosmological constant. We
impose boundary conditions that enforce every classical solution to be an
exterior region of a Reissner-Nordstr\"om-anti-de Sitter black hole with a
nondegenerate Killing horizon, with the spacelike hypersurfaces extending from
the horizon bifurcation two-sphere to the asymptotically anti-de Sitter
infinity. The constraints are simplified by a canonical transformation, which
generalizes that given by Kucha\v{r} in the spherically symmetric vacuum
Einstein theory, and the theory is reduced to its true dynamical degrees of
freedom. After quantization, the grand partition function of a thermodynamical
grand canonical ensemble is obtained by analytically continuing the Lorentzian
time evolution operator to imaginary time and taking the trace. A~similar
analysis under slightly modified boundary conditions leads to the partition
function of a thermodynamical canonical ensemble. The thermodynamics in each
ensemble is analyzed, and the conditions that the (grand) partition function be
dominated by a classical Euclidean black hole solution are found. When these
conditions are satisfied, we recover in particular the Bekenstein-Hawking
entropy. The limit of a vanishing cosmological constant is briefly discussed.
(This paper is dedicated to Karel Kucha\v{r} on the occasion of his sixtieth
birthday.)Comment: 34 pages, REVTeX v3.0. (Minor corrections and presentational
revisions; added references.
Electrostatic potential profiles of molecular conductors
The electrostatic potential across a short ballistic molecular conductor
depends sensitively on the geometry of its environment, and can affect its
conduction significantly by influencing its energy levels and wave functions.
We illustrate some of the issues involved by evaluating the potential profiles
for a conducting gold wire and an aromatic phenyl dithiol molecule in various
geometries. The potential profile is obtained by solving Poisson's equation
with boundary conditions set by the contact electrochemical potentials and
coupling the result self-consistently with a nonequilibrium Green's function
(NEGF) formulation of transport. The overall shape of the potential profile
(ramp vs. flat) depends on the feasibility of transverse screening of electric
fields. Accordingly, the screening is better for a thick wire, a multiwalled
nanotube or a close-packed self-assembled monolayer (SAM), in comparison to a
thin wire, a single-walled nanotube or an isolated molecular conductor. The
electrostatic potential further governs the alignment or misalignment of
intramolecular levels, which can strongly influence the molecular I-V
characteristic. An external gate voltage can modify the overall potential
profile, changing the current-voltage (I-V) characteristic from a resonant
conducting to a saturating one. The degree of saturation and gate modulation
depends on the metal-induced-gap states (MIGS) and on the electrostatic gate
control parameter set by the ratio of the gate oxide thickness to the channel
length.Comment: to be published in Phys. Rev. B 69, No.3, 0353XX (2004
A first-principles approach to electrical transport in atomic-scale nanostructures
We present a first-principles numerical implementation of Landauer formalism
for electrical transport in nanostructures characterized down to the atomic
level. The novelty and interest of our method lies essentially on two facts.
First of all, it makes use of the versatile Gaussian98 code, which is widely
used within the quantum chemistry community. Secondly, it incorporates the
semi-infinite electrodes in a very generic and efficient way by means of Bethe
lattices. We name this method the Gaussian Embedded Cluster Method (GECM). In
order to make contact with other proposed implementations, we illustrate our
technique by calculating the conductance in some well-studied systems such as
metallic (Al and Au) nanocontacts and C-atom chains connected to metallic (Al
and Au) electrodes. In the case of Al nanocontacts the conductance turns out to
be quite dependent on the detailed atomic arrangement. On the contrary, the
conductance in Au nanocontacts presents quite universal features. In the case
of C chains, where the self-consistency guarantees the local charge transfer
and the correct alignment of the molecular and electrode levels, we find that
the conductance oscillates with the number of atoms in the chain regardless of
the type of electrode. However, for short chains and Al electrodes the even-odd
periodicity is reversed at equilibrium bond distances.Comment: 14 pages, two-column format, submitted to PR
Loss of Cytokine-STAT5 Signaling in the CNS and Pituitary Gland Alters Energy Balance and Leads to Obesity
Signal transducers and activators of transcription (STATs) are critical components of cytokine signaling pathways. STAT5A and STAT5B (STAT5), the most promiscuous members of this family, are highly expressed in specific populations of hypothalamic neurons in regions known to mediate the actions of cytokines in the regulation of energy balance. To test the hypothesis that STAT5 signaling is essential to energy homeostasis, we used Cre-mediated recombination to delete the Stat5 locus in the CNS. Mutant males and females developed severe obesity with hyperphagia, impaired thermal regulation in response to cold, hyperleptinemia and insulin resistance. Furthermore, central administration of GM-CSF mediated the nuclear accumulation of STAT5 in hypothalamic neurons and reduced food intake in control but not in mutant mice. These results demonstrate that STAT5 mediates energy homeostasis in response to endogenous cytokines such as GM-CSF
Measurement of Atmospheric Neutrino Oscillations with the ANTARES Neutrino Telescope
The data taken with the ANTARES neutrino telescope from 2007 to 2010, a total
live time of 863 days, are used to measure the oscillation parameters of
atmospheric neutrinos. Muon tracks are reconstructed with energies as low as 20
GeV. Neutrino oscillations will cause a suppression of vertical upgoing muon
neutrinos of such energies crossing the Earth. The parameters determining the
oscillation of atmospheric neutrinos are extracted by fitting the event rate as
a function of the ratio of the estimated neutrino energy and reconstructed
flight path through the Earth. Measurement contours of the oscillation
parameters in a two-flavour approximation are derived. Assuming maximum mixing,
a mass difference of eV is
obtained, in good agreement with the world average value.Comment: 9 pages, 5 figure
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