524 research outputs found
Rotational state-changing collisions between N and Rb at low energies
We present a theoretical study of rotationally elastic and inelastic
collisions between molecular nitrogen ions and Rb atoms in the sub-Kelvin
temperature regime prevalent in ion-atom hybrid trapping experiments. The cross
sections for rotational excitation and de-excitation collisions were calculated
using quantum-scattering methods on ab-initio potential energy surfaces for the
energetically lowest singlet electronic channel of the system. We find that the
rotationally inelastic collision rates are at least an order of magnitude
smaller than the charge-exchange rates found in this system, rendering
inelastic processes a minor channel under the conditions of typical hybrid
trapping experiments.Comment: 6 pages, 5 figures, Computational study of rotational state changing
collision
Cascade Failure in a Phase Model of Power Grids
We propose a phase model to study cascade failure in power grids composed of
generators and loads. If the power demand is below a critical value, the model
system of power grids maintains the standard frequency by feedback control. On
the other hand, if the power demand exceeds the critical value, an electric
failure occurs via step out (loss of synchronization) or voltage collapse. The
two failures are incorporated as two removal rules of generator nodes and load
nodes. We perform direct numerical simulation of the phase model on a
scale-free network and compare the results with a mean-field approximation.Comment: 7 pages, 2 figure
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In situ Raman spectroscopy on silicon nanowire anodes integrated in lithium ion batteries
Rapid decay of silicon anodes during lithiation poses a significant challenge in application of silicon as an anode material in lithium ion batteries. In situ Raman spectroscopy is a powerful method to study the relationship between structural and electrochemical data during electrode cycling and to allow the observation of amorphous as well as liquid and transient species in a battery cell. Herein, we present in situ Raman spectroscopy on high capacity electrode using uncoated and carbon-coated silicon nanowires during first lithiation and delithiation cycle in an optimized lithium ion battery setup and complement the results with operando X-ray reflection diffraction measurements. During lithiation, we were able to detect a new Raman signal at 1859 cm−1 especially on uncoated silicon nanowires. The detailed in situ Raman measurement of the first lithiation/delithiation cycle allowed to differentiate between morphology changes of the electrode as well as interphase formation from electrolyte components
Multipliers for p-Bessel sequences in Banach spaces
Multipliers have been recently introduced as operators for Bessel sequences
and frames in Hilbert spaces. These operators are defined by a fixed
multiplication pattern (the symbol) which is inserted between the analysis and
synthesis operators. In this paper, we will generalize the concept of Bessel
multipliers for p-Bessel and p-Riesz sequences in Banach spaces. It will be
shown that bounded symbols lead to bounded operators. Symbols converging to
zero induce compact operators. Furthermore, we will give sufficient conditions
for multipliers to be nuclear operators. Finally, we will show the continuous
dependency of the multipliers on their parameters.Comment: 17 page
On Metric Dimension of Functigraphs
The \emph{metric dimension} of a graph , denoted by , is the
minimum number of vertices such that each vertex is uniquely determined by its
distances to the chosen vertices. Let and be disjoint copies of a
graph and let be a function. Then a
\emph{functigraph} has the vertex set
and the edge set . We study how
metric dimension behaves in passing from to by first showing that
, if is a connected graph of order
and is any function. We further investigate the metric dimension of
functigraphs on complete graphs and on cycles.Comment: 10 pages, 7 figure
Neuroanatomic Correlates of Female Sexual Dysfunction in Multiple Sclerosis
OBJECTIVE:
This study intended to determine associations between alterations of female sexual arousal as well as vaginal lubrication and the site of cerebral multiple sclerosis (MS) lesions.
METHODS:
In 44 women with MS (mean age: 36.5 ± 9.9 years), we assessed their medical history and evaluated sexual function using the Female Sexual Function Index scores for arousal and vaginal lubrication. We determined potential confounding factors of sexual dysfunction: age; disease duration; physical disability; depression; bladder or urinary dysfunction; and total volume of cerebral lesions. Arousal and lubrication scores were correlated with one another and with potential confounding factors. Cerebral MS lesions were recorded on imaging scans. A voxel-based lesion symptom mapping (VLSM) analysis adjusted for confounding variables was performed correlating cerebral sites of MS lesions with arousal and lubrication scores.
RESULTS:
Decreased arousal scores correlated with decreased lubrication scores; decreased lubrication scores were associated with bladder or urinary symptoms. Arousal and lubrication scores were not associated with any other variables. Multivariate VLSM analysis, including arousal and lubrication scores as covariables of interest, showed right occipital lesions associated with impaired arousal and left insular lesions associated with decreased lubrication. Impaired lubrication remained associated with left insular lesions after adjustment for bladder or urinary dysfunction.
INTERPRETATION:
Our data indicate that impaired female sexual arousal is associated with MS lesions in the occipital region, integrating visual information and modulating attention toward visual input. Impaired lubrication correlated with lesions in the left insular region, contributing to mapping and generating visceral arousal states
Current status and future perspectives of lithium metal batteries
With the lithium-ion technology approaching its intrinsic limit with graphite-based anodes, Li metal is recently receiving renewed interest from the battery community as potential high capacity anode for next-generation rechargeable batteries. In this focus paper, we review the main advances in this field since the first attempts in the mid-1970s. Strategies for enabling reversible cycling and avoiding dendrite growth are thoroughly discussed, including specific applications in all-solid-state (inorganic and polymeric), Lithium–Sulfur (Li–S) and Lithium-O2 (air) batteries. A particular attention is paid to recent developments of these battery technologies and their current state with respect to the 2030 targets of the EU Integrated Strategic Energy Technology Plan (SET-Plan) Action 7
Dynamics of fully coupled rotators with unimodal and bimodal frequency distribution
We analyze the synchronization transition of a globally coupled network of N
phase oscillators with inertia (rotators) whose natural frequencies are
unimodally or bimodally distributed. In the unimodal case, the system exhibits
a discontinuous hysteretic transition from an incoherent to a partially
synchronized (PS) state. For sufficiently large inertia, the system reveals the
coexistence of a PS state and of a standing wave (SW) solution. In the bimodal
case, the hysteretic synchronization transition involves several states.
Namely, the system becomes coherent passing through traveling waves (TWs), SWs
and finally arriving to a PS regime. The transition to the PS state from the SW
occurs always at the same coupling, independently of the system size, while its
value increases linearly with the inertia. On the other hand the critical
coupling required to observe TWs and SWs increases with N suggesting that in
the thermodynamic limit the transition from incoherence to PS will occur
without any intermediate states. Finally a linear stability analysis reveals
that the system is hysteretic not only at the level of macroscopic indicators,
but also microscopically as verified by measuring the maximal Lyapunov
exponent.Comment: 22 pages, 11 figures, contribution for the book: Control of
Self-Organizing Nonlinear Systems, Springer Series in Energetics, eds E.
Schoell, S.H.L. Klapp, P. Hoeve
Deep learning for brain metastasis detection and segmentation in longitudinal MRI data
Brain metastases occur frequently in patients with metastatic cancer. Early
and accurate detection of brain metastases is very essential for treatment
planning and prognosis in radiation therapy. To improve brain metastasis
detection performance with deep learning, a custom detection loss called
volume-level sensitivity-specificity (VSS) is proposed, which rates individual
metastasis detection sensitivity and specificity in (sub-)volume levels. As
sensitivity and precision are always a trade-off in a metastasis level, either
a high sensitivity or a high precision can be achieved by adjusting the weights
in the VSS loss without decline in dice score coefficient for segmented
metastases. To reduce metastasis-like structures being detected as false
positive metastases, a temporal prior volume is proposed as an additional input
of DeepMedic. The modified network is called DeepMedic+ for distinction. Our
proposed VSS loss improves the sensitivity of brain metastasis detection for
DeepMedic, increasing the sensitivity from 85.3% to 97.5%. Alternatively, it
improves the precision from 69.1% to 98.7%. Comparing DeepMedic+ with DeepMedic
with the same VSS loss, 44.4% of the false positive metastases are reduced in
the high sensitivity model and the precision reaches 99.6% for the high
specificity model. The mean dice coefficient for all metastases is about 0.81.
With the ensemble of the high sensitivity and high specificity models, on
average only 1.5 false positive metastases per patient needs further check,
while the majority of true positive metastases are confirmed. The ensemble
learning is able to distinguish high confidence true positive metastases from
metastases candidates that require special expert review or further follow-up,
being particularly well-fit to the requirements of expert support in real
clinical practice.Comment: Implementation is available to public at
https://github.com/YixingHuang/DeepMedicPlu
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