883 research outputs found
Non-verbal sound processing in the primary progressive aphasias
Little is known about the processing of non-verbal sounds in the primary progressive aphasias. Here, we investigated the processing of complex non-verbal sounds in detail, in a consecutive series of 20 patients with primary progressive aphasia [12 with progressive non-fluent aphasia; eight with semantic dementia]. We designed a novel experimental neuropsychological battery to probe complex sound processing at early perceptual, apperceptive and semantic levels, using within-modality response procedures that minimized other cognitive demands and matching tests in the visual modality. Patients with primary progressive aphasia had deficits of non-verbal sound analysis compared with healthy age-matched individuals. Deficits of auditory early perceptual analysis were more common in progressive non-fluent aphasia, deficits of apperceptive processing occurred in both progressive non-fluent aphasia and semantic dementia, and deficits of semantic processing also occurred in both syndromes, but were relatively modality specific in progressive non-fluent aphasia and part of a more severe generic semantic deficit in semantic dementia. Patients with progressive non-fluent aphasia were more likely to show severe auditory than visual deficits as compared to patients with semantic dementia. These findings argue for the existence of core disorders of complex non-verbal sound perception and recognition in primary progressive aphasia and specific disorders at perceptual and semantic levels of cortical auditory processing in progressive non-fluent aphasia and semantic dementia, respectively
Local Anisotropy of Fluids using Minkowski Tensors
Statistics of the free volume available to individual particles have
previously been studied for simple and complex fluids, granular matter,
amorphous solids, and structural glasses. Minkowski tensors provide a set of
shape measures that are based on strong mathematical theorems and easily
computed for polygonal and polyhedral bodies such as free volume cells (Voronoi
cells). They characterize the local structure beyond the two-point correlation
function and are suitable to define indices of
local anisotropy. Here, we analyze the statistics of Minkowski tensors for
configurations of simple liquid models, including the ideal gas (Poisson point
process), the hard disks and hard spheres ensemble, and the Lennard-Jones
fluid. We show that Minkowski tensors provide a robust characterization of
local anisotropy, which ranges from for vapor
phases to for ordered solids. We find that for fluids,
local anisotropy decreases monotonously with increasing free volume and
randomness of particle positions. Furthermore, the local anisotropy indices
are sensitive to structural transitions in these simple
fluids, as has been previously shown in granular systems for the transition
from loose to jammed bead packs
Nonmonotonic Decay of Nonequilibrium Polariton Condensate in Direct-Gap Semiconductors
Time evolution of a nonequilibrium polariton condensate has been studied in
the framework of a microscopic approach. It has been shown that due to
polariton-polariton scattering a significant condensate depletion takes place
in a comparatively short time interval. The condensate decay occurs in the form
of multiple echo signals. Distribution-function dynamics of noncondensate
polaritons have been investigated. It has been shown that at the initial stage
of evolution the distribution function has the form of a bell. Then
oscillations arise in the contour of the distribution function, which further
transform into small chaotic ripples. The appearance of a short-wavelength wing
of the distribution function has been demonstrated. We have pointed out the
enhancement and then partial extinction of the sharp extra peak arising within
the time interval characterized by small values of polariton condensate density
and its relatively slow changes.Comment: 20 pages, LaTeX 2.09; in press in PR
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A monolithically integrated silicon modulator with a 10 Gb/s 5 V pp or 5.6 V pp driver in 0.25 μm SiGe:C BiCMOS
This paper presents as a novelty a fully monolithically integrated 10 Gb/s silicon modulator consisting of an electrical driver plus optical phase modulator in 0.25 μm SiGe:C BiCMOS technology on one chip, where instead of a SOI CMOS process (only MOS transistors) a SiGe BiCMOS process (MOS transistors and fast SiGe bipolar transistors) is implemented. The fastest bipolar transistors in the BiCMOS product line used have a transit frequency of f t ≈ 120 GHz and a collector-emitter breakdown voltage of BV CE0 = 2.2 V (IHP SG25H3). The main focus of this paper will be given to the electronic drivers, where two driver variants are implemented in the test chips. Circuit descriptions and simulations, which treat the influences of noise and bond wires, are presented. Measurements at separate test chips for the drivers show that the integrated driver variant one has a low power consumption in the range of 0.66 to 0.68 W but a high gain of S 21 = 37 dB. From the large signal point of view this driver delivers an inverted as well as a non-inverted output data signal between 0 and 2.5 V (5 V pp differential). Driver variant one is supplied with 2.5 V and with 3.5 V. Bit-error-ratio (BER) measurements resulted in a BER better than 10 −12 for voltage differences of the input data stream down to 50 mV pp . Driver variant two, which is an adapted version of driver variant one, is supplied with 2.5 and 4.2 V, consumes 0.83 to 0.87 W, delivers a differential data signal with 5.6 V pp at the output and has a gain of S 21 = 40 dB. The chip of the fully integrated modulator occupies an area of 12.3 mm 2 due to the photonic components. Measurements with a 240 mV pp electrical input data stream, 1.25 V input common-mode voltage and for an optical input wavelength of 1540 nm resulted in an extinction ratio of 3.3 dB for 1 mm long RF phase shifters in each modulator arm driven by driver variant one and a DC tuning voltage of 1.2 V. The extinction ratio was 8.4 dB at a DC tuning voltage of 7 V for a device with 2 mm long RF phase shifters in each arm and driver variant two
Modeling the effects of litter stoichiometry and soil mineral N availability on soil organic matter formation using CENTURY-CUE (v1.0)
Microbial decomposition of plant litter is a crucial process for the land
carbon (C) cycle, as it directly controls the partitioning of litter C
between CO2 released to the atmosphere versus the formation of new
soil organic matter (SOM). Land surface models used to study the C cycle
rarely considered flexibility in the decomposer C use efficiency
(CUEd) defined by the fraction of decomposed litter C that is
retained as SOM (as opposed to be respired). In this study, we adapted a
conceptual formulation of CUEd based on assumption that litter
decomposers optimally adjust their CUEd as a function of litter
substrate C to nitrogen (N) stoichiometry to maximize their growth rates.
This formulation was incorporated into the widely used
CENTURY soil biogeochemical
model and evaluated based on data from laboratory litter incubation
experiments. Results indicated that the CENTURY model with new
CUEd formulation was able to reproduce differences in respiration
rate of litter with contrasting C : N ratios and under different levels of
mineral N availability, whereas the default model with fixed CUEd
could not. Using the model with flexible CUEd, we also
illustrated that litter quality affected the long-term SOM formation. Litter
with a small C : N ratio tended to form a larger SOM pool than litter with
larger C : N ratios, as it could be more efficiently incorporated into SOM
by microorganisms. This study provided a simple but effective formulation to
quantify the effect of varying litter quality (N content) on SOM formation
across temporal scales. Optimality theory appears to be suitable to predict
complex processes of litter decomposition into soil C and to quantify how
plant residues and manure can be harnessed to improve soil C sequestration
for climate mitigation.</p
Momentum-resolved superconducting gap in the bulk of BaKFeAs from combined ARPES and SR measurements
Here we present a calculation of the temperature-dependent London penetration
depth, , in BaKFeAs (BKFA) on the basis of
the electronic band structure [1,2] and momentum-dependent superconducting gap
[3] extracted from angle-resolved photoemission spectroscopy (ARPES) data. The
results are compared to the direct measurements of by muon spin
rotation (SR) [4]. The value of , calculated with \emph{no}
adjustable parameters, equals 270 nm, while the directly measured one is 320
nm; the temperature dependence is also easily reproduced. Such
agreement between the two completely different approaches allows us to conclude
that ARPES studies of BKFA are bulk-representative. Our review of the available
experimental studies of the superconducting gap in the new iron-based
superconductors in general allows us to state that all hole-doped of them bear
two nearly isotropic gaps with coupling constants and
Size Dependence of Current Spin Polarization Through Superconductor/Ferromagnet Nanocontacts
The spin polarization P of the transport current through the interface
between superconducting Al and ferromagnetic Fe is determined by means of
Andreev reflection at nanostructured point contacts. We observe a systematic
decrease of P with decreasing contact resistance. Our data provide evidence for
the reduction of P by spin-orbit scattering and thus establish a link between
density-of-states and transport spin polarizations.Comment: 4 pages, 4 figures, accepted for publication in Phys. Rev. Let
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