17,894 research outputs found
Modelling of hydrological response to climate change in glacierized Central Asian catchments
The arid lowlands of Central Asia are highly dependent on the water supplied by the Tien Shan mountains. Snow and ice storage make large contributions to current runoff, particularly in summer. Two runoff models with different temporal resolutions, HBV-ETH and OEZ, were applied in three glaciated catchments of the Tien Shan mountains. Scenario runs were produced for a climate change caused by the doubling of atmospheric CO2 as predicted by the GISS global circulation model and assuming a 50% reduction of glaciation extent, as well as a complete loss of glaciation. Agreement of the results was best for runs based on 50% glaciation loss, where both models predict an increase in spring and summer runoff compared to current levels. Scenarios for complete loss of glaciation predict an increase in spring runoff levels, followed by lower runoff levels for July and August. Model predictions differ concerning the degree of reduction of late summer runoff. These scenarios are sensitive to model simulation of basin precipitation, as well as to reduction of glaciation extent
Acrylamide Production Using Encapsulated Nitrile Hydratase from \u3cem\u3ePseudonocardia thermophila\u3c/em\u3e in a Sol–gel Matrix
The cobalt-type nitrile hydratase from Pseudonocardia thermophila JCM 3095 (PtNHase) was successfully encapsulated in tetramethyl orthosilicate sol–gel matrices to produce a PtNHase:sol–gel biomaterial. The PtNHase:sol–gel biomaterial catalyzed the conversion of 600 mM acrylonitrile to acrylamide in 60 min at 35 °C with a yields of \u3e90%. Treatment of the biomaterial with proteases confirmed that the catalytic activity is due to the encapsulated enzyme and not surface bound NHase. The biomaterial retained 50% of its activity after being used for a total of 13 consecutive reactions for the conversion of acrylonitrile to acrylamide. The thermostability and long-term storage of the PtNHase:sol–gel are substantially improved compared to the soluble NHase. Additionally, the biomaterial is significantly more stable at high concentrations of methanol (50% and 70%, v/v) as a co-solvent for the hydration of acrylonitrile than native PtNHase. These data indicate that PtNHase:sol–gel biomaterials can be used to develop new synthetic avenues involving nitriles as starting materials given that the conversion of the nitrile moiety to the corresponding amide occurs under mild temperature and pH conditions
Low-Temperature Orientation Dependence of Step Stiffness on {111} Surfaces
For hexagonal nets, descriptive of {111} fcc surfaces, we derive from
combinatoric arguments a simple, low-temperature formula for the orientation
dependence of the surface step line tension and stiffness, as well as the
leading correction, based on the Ising model with nearest-neighbor (NN)
interactions. Our formula agrees well with experimental data for both Ag and
Cu{111} surfaces, indicating that NN-interactions alone can account for the
data in these cases (in contrast to results for Cu{001}). Experimentally
significant corollaries of the low-temperature derivation show that the step
line tension cannot be extracted from the stiffness and that with plausible
assumptions the low-temperature stiffness should have 6-fold symmetry, in
contrast to the 3-fold symmetry of the crystal shape. We examine Zia's exact
implicit solution in detail, using numerical methods for general orientations
and deriving many analytic results including explicit solutions in the two
high-symmetry directions. From these exact results we rederive our simple
result and explore subtle behavior near close-packed directions. To account for
the 3-fold symmetry in a lattice gas model, we invoke a novel
orientation-dependent trio interaction and examine its consequences.Comment: 11 pages, 8 figure
Exploiting graph neural networks to perform finite-difference time-domain based optical simulations
Morphological stability of electromigration-driven vacancy islands
The electromigration-induced shape evolution of two-dimensional vacancy
islands on a crystal surface is studied using a continuum approach. We consider
the regime where mass transport is restricted to terrace diffusion in the
interior of the island. In the limit of fast attachment/detachment kinetics a
circle translating at constant velocity is a stationary solution of the
problem. In contrast to earlier work [O. Pierre-Louis and T.L. Einstein, Phys.
Rev. B 62, 13697 (2000)] we show that the circular solution remains linearly
stable for arbitrarily large driving forces. The numerical solution of the full
nonlinear problem nevertheless reveals a fingering instability at the trailing
end of the island, which develops from finite amplitude perturbations and
eventually leads to pinch-off. Relaxing the condition of instantaneous
attachment/detachment kinetics, we obtain non-circular elongated stationary
shapes in an analytic approximation which compares favorably to the full
numerical solution.Comment: 12 page
Reducing decoherence of the confined exciton state in a quantum dot by pulse-sequence control
We study the phonon-induced dephasing of the exciton state in a quantum dot
excited by a sequence of ultra-short pulses. We show that the multiple-pulse
control leads to a considerable improvement of the coherence of the optically
excited state. For a fixed control time window, the optimized pulsed control
often leads to a higher degree of coherence than the control by a smooth single
Gaussian pulse. The reduction of dephasing is considerable already for 2-3
pulses.Comment: Final version (moderate changes
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Similar representations of emotions across faces and voices
Emotions are a vital component of social communication, carried across a range of modalities and via
different perceptual signals such as specific muscle contractions in the face and in the upper
respiratory system. Previous studies have found that emotion recognition impairments after brain
damage depend on the modality of presentation: recognition from faces may be impaired whilst
recognition from voices remains preserved, and vice versa. On the other hand, there is also evidence
for shared neural activation during emotion processing in both modalities. In a behavioural study, we
investigated whether there are shared representations in the recognition of emotions from faces and
voices. We used a within-subjects design in which participants rated the intensity of facial expressions
and non-verbal vocalisations for each of the six basic emotion labels. For each participant and each
modality, we then computed a representation matrix with the intensity ratings of each emotion. These
matrices allowed us to examine the patterns of confusions between emotions and to characterise the
representations of emotions within each modality. We then compared the representations across
modalities by computing the correlations of the representation matrices across faces and voices. We
found highly correlated matrices across modalities, which suggest similar representations of emotions
across faces and voices. We also showed that these results could not be explained by commonalities
between low-level visual and acoustic properties of the stimuli. We thus propose that there are similar
or shared coding mechanisms for emotions which may act independently of modality, despite their
distinct perceptual inputs.This research was supported by an ESRC 1+3 PhD studentship to Lisa Kuhn (ES/I90042X/1)
The new HiVIS spectropolarimeter and spectropolarimetric calibration of the AEOS telescope
We designed, built, and calibrated a new spectropolarimeter for the HiVIS
spectrograph (R 12000-49000) on the AEOS telescope. We also did a polarization
calibration of the telescope and instrument. We will introduce the design and
use of the spectropolarimeter as well as a new data reduction package we have
developed, then discuss the polarization calibration of the spectropolarimeter
and the AEOS telescope. We used observations of unpolarized standard stars at
many pointings to measure the telescope induced polarization and compare it
with a Zemax model. The telescope induces polarization of 1-6% with a strong
variation with wavelength and pointing, consistent with the altitude and
azimuth variation expected. We then used scattered sunlight as a linearly
polarized source to measure the telescopes spectropolarimetric response to
linearly polarized light. We then made an all-sky map of the telescope's
polarization response to calibrate future spectropolarimetry.Comment: PASP 118, June 200
Anomalous crossover between thermal and shot noise in macroscopic diffusive conductors
We predict the existence of an anomalous crossover between thermal and shot
noise in macroscopic diffusive conductors. We first show that, besides thermal
noise, these systems may also exhibit shot noise due to fluctuations of the
total number of carriers in the system. Then we show that at increasing
currents the crossover between the two noise behaviors is anomalous, in the
sense that the low frequency current spectral density displays a region with a
superlinear dependence on the current up to a cubic law. The anomaly is due to
the non-trivial coupling in the presence of the long range Coulomb interaction
among the three time scales relevant to the phenomenon, namely, diffusion,
transit and dielectric relaxation time.Comment: 4 pages, 2 figure
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