1,395 research outputs found
Quantization and Training of Neural Networks for Efficient Integer-Arithmetic-Only Inference
The rising popularity of intelligent mobile devices and the daunting
computational cost of deep learning-based models call for efficient and
accurate on-device inference schemes. We propose a quantization scheme that
allows inference to be carried out using integer-only arithmetic, which can be
implemented more efficiently than floating point inference on commonly
available integer-only hardware. We also co-design a training procedure to
preserve end-to-end model accuracy post quantization. As a result, the proposed
quantization scheme improves the tradeoff between accuracy and on-device
latency. The improvements are significant even on MobileNets, a model family
known for run-time efficiency, and are demonstrated in ImageNet classification
and COCO detection on popular CPUs.Comment: 14 pages, 12 figure
Confined run-and-tumble model with boundary aggregation: long time behavior and convergence to the confined Fokker-Planck model
The motile micro-organisms such as E. coli, sperm, or some seaweed are
usually modelled by self-propelled particles that move with the run-and-tumble
process. Individual-based stochastic models are usually employed to model the
aggregation phenomenon at the boundary, which is an active research field that
has attracted a lot of biologists and biophysicists. Self-propelled particles
at the microscale have complex behaviors, while characteristics at the
population level are more important for practical applications but rely on
individual behaviors. Kinetic PDE models that describe the time evolution of
the probability density distribution of the motile micro-organisms are widely
used. However, how to impose the appropriate boundary conditions that take into
account the boundary aggregation phenomena is rarely studied. In this paper, we
propose the boundary conditions for a 2D confined run-and-tumble model (CRTM)
for self-propelled particle populations moving between two parallel plates with
a run-and-tumble process. The proposed model satisfies the relative entropy
inequality and thus long-time convergence. We establish the relation between
CRTM and the confined Fokker-Planck model (CFPM) studied in [22]. We prove
theoretically that when the tumble is highly forward peaked and frequent
enough, CRTM converges asymptotically to the CFPM. A numerical comparison of
the CRTM with aggregation and CFPM is given. The time evolution of both the
deterministic PDE model and individual-based stochastic simulations are
displayed, which match each other well.Comment: 30 pages, 8 figure
Impact des méthodes de résolution du contact sur le comportement mécanique des structures
Le contact mécanique présente les non-linéarités les plus difficiles à prendre en compte. Selon les cas d'étude, certaines méthodes de résolution sont plus adaptées que d'autres. De même, l'amortissement est introduit dans les codes de calcul sous différentes formes. On présente la formulation analytique de ces méthodes et on analysera les résultats issus de l'étude de sensibilité pour identifier la méthode donnant les résultats les plus robustes
Susceptibility to ATP depletion of primary proximal tubular cell cultures derived from mice lacking either the alpha1 or the alpha2 isoform of the catalytic domain of AMPK.
International audienceBACKGROUND: The purpose of this study was to determine whether AMPK influences the survival of primary cultures of mouse proximal tubular (MPT) cells subjected to metabolic stress. Previous studies, using an immortalized MPT cell line, suggest that AMPK is activated during metabolic stress, and ameliorates stress-induced apoptosis of these cells. METHODS: Primary MPT cells were cultured from AMPK knockout (KO) mice lacking either the alpha1 or the alpha2 isoform of the catalytic domain of AMPK. MPT cells were subjected to ATP depletion using antimycin A. RESULTS: Surprisingly, there was no difference in the amount of death induced by metabolic stress of MPT cells from either type of AMPK KO mice compared to its WT control. Moreover, inhibition of the activity of the alpha1 isoform in primary MPT cells from alpha2-/- mice (pharmacologically, via compound C) or inhibition of the alpha2 isoform in primary MPT cells from alpha1-/- mice (molecularly, via knockdown) both decreased cell viability equivalently in response to metabolic stress. The explanation for this unexpected result appears to be an adaptive increase in expression of the non-deleted alphaisoform. As a consequence, total As a consequence-domain expression (i.e. alpha1 + alpha2), is comparable in kidney cortex and in cultured MPT cells derived from either type of KO mouse versus its WT control. Importantly, each alphaisoform appears able to compensate fully for the absence of the other, with respect to both the phosphorylation of downstream targets of AMPK and the amelioration of stress-induced cell death. CONCLUSIONS: These findings not only confirm the importance of AMPK as a pro-survival kinase in MPT cells during metabolic stress, but also show, for the first time, that each of the two alpha-isoforms can substitute for the other in MPT cells from AMPK KO mice with regard to amelioration of stress-induced loss of cell viability
Differentiating the Cognitive Profile of Schizophrenia from That of Alzheimer Disease and Depression in Late Life
To compare the cognitive profile of older patients with schizophrenia to those with other neuropsychiatric disorders assessed in a hospital-based memory clinic.Demographic, clinical, and cognitive data of all patients referred to the memory clinic at the Centre for Addiction and Mental Health between April 1, 2006 and August 15, 2008 were reviewed. We then identified four groups of older patients with: (1) late-life schizophrenia (LLS) and no dementia or depression (DEP); (2) Alzheimer's disease (AD); (3) DEP and no dementia or LLS; (4) normal cognition (NC) and no DEP or LLS.The four groups did not differ in demographic data except that patients with AD were about 12 years older than those with LLS. However, they differed on cognitive tests even after controlling for age. Patients with LLS were impaired on most cognitive tests in comparison with patients with NC but not on recalling newly learned verbal information at a short delay. They experienced equivalent performance on learning new verbal information in comparison with patients with AD, but better performance on all other tests of memory, including the ability to recall newly learned verbal information. Finally, they were more impaired than patients with DEP in overall memory.Patients with LLS have a different cognitive profile than patients with AD or DEP. Particularly, memory impairment in LLS seems to be more pronounced in learning than recall. These findings suggest that cognitive and psychosocial interventions designed to compensate for learning deficits may be beneficial in LLS
Theory of Luminescence Spectra of High-Density Electron-Hole Systems: Crossover from Excitonic Bose-Einstein Condenstation to Electron-Hole BCS State
We present a unified theory of luminescence spectra for highly excited
semiconductors, which is applicable both to the electron-hole BCS state and to
the exciton Bose-Einstein condensate. The crossover behavior between
electron-hole BCS state and exciton Bose-Einstein condensate clearly manifests
itself in the calculated luminescence spectra. The analysis is based on the
Bethe-Salpeter equation combined with the generalized
random-phase-approximation, which enables us to consider the multiple Coulomb
scattering and the quantum fluctuation associated with the center-of-mass
motion of electron-hole pairs. In the crossover regime, the calculated spectra
are essentially different from results obtained by the BCS-like mean-field
theory and the interacting Boson model. In particular, it is found that the
broad spectrum, arising from the recombination of electron-hole BCS state,
splits into the P- and P_2-luminescence bands with decreasing the particle
density. The dependence of these bands on the carrier density is in good
agreement with experiments for highly excited semiconductors.Comment: 9 pages, 4 figures, To appear in Solid State Communication
Thermal history modeling of the H chondrite parent body
The cooling histories of individual meteorites can be empirically
reconstructed by using ages from different radioisotopic chronometers with
distinct closure temperatures. For a group of meteorites derived from a single
parent body such data permit the reconstruction of the cooling history and
properties of that body. Particularly suited are H chondrites because precise
radiometric ages over a wide range of closure temperatures are available. A
thermal evolution model for the H chondrite parent body is constructed by using
all H chondrites for which at least three different radiometric ages are
available. Several key parameters determining the thermal evolution of the H
chondrite parent body and the unknown burial depths of the H chondrites are
varied until an optimal fit is obtained. The fit is performed by an 'evolution
algorithm'. Empirical data for eight samples are used for which radiometric
ages are available for at least three different closure temperatures. A set of
parameters for the H chondrite parent body is found that yields excellent
agreement (within error bounds) between the thermal evolution model and
empirical data of six of the examined eight chondrites. The new thermal model
constrains the radius and formation time of the H chondrite parent body
(possibly (6) Hebe), the initial burial depths of the individual H chondrites,
the average surface temperature of the body, the average initial porosity of
the material the body accreted from, and the initial 60Fe content of the H
chondrite parent body.Comment: 16 pages, 7 figure
A modelling approach towards Epidermal homoeostasis control
In order to grasp the features arising from cellular discreteness and
individuality, in large parts of cell tissue modelling agent-based models are
favoured. The subclass of off-lattice models allows for a physical motivation
of the intercellular interaction rules. We apply an improved version of a
previously introduced off-lattice agent-based model to the steady-state flow
equilibrium of skin. The dynamics of cells is determined by conservative and
drag forces,supplemented with delta-correlated random forces. Cellular
adjacency is detected by a weighted Delaunay triangulation. The cell cycle time
of keratinocytes is controlled by a diffusible substance provided by the
dermis. Its concentration is calculated from a diffusion equation with
time-dependent boundary conditions and varying diffusion coefficients. The
dynamics of a nutrient is also taken into account by a reaction-diffusion
equation. It turns out that the analysed control mechanism suffices to explain
several characteristics of epidermal homoeostasis formation. In addition, we
examine the question of how {\em in silico} melanoma with decreased basal
adhesion manage to persist within the steady-state flow-equilibrium of the
skin.Interestingly, even for melanocyte cell cycle times being substantially
shorter than for keratinocytes, tiny stochastic effects can lead to completely
different outcomes. The results demonstrate that the understanding of initial
states of tumour growth can profit significantly from the application of
off-lattice agent-based models in computer simulations.Comment: 23 pages, 7 figures, 1 table; version that is to appear in Journal of
Theoretical Biolog
Many-body theory of pump-probe spectra for highly excited semiconductors
We present a unified theory for pump-probe spectra in highly excited
semiconductors, which is applicable throughout the whole density regime
including the high-density electron-hole BCS state and the low-density
excitonic Bose-Einstein condensate (BEC). The analysis is based on the BCS-like
pairing theory combined with the Bethe-Salpeter (BS) equation, which first
enables us to incorporate the state-filling effect, the band-gap
renormalization and the strong/weak electron-hole pair correlations in a
unified manner. We show that the electron-hole BCS state is distinctly
stabilized by the intense pump-light, and this result strongly suggests that
the macroscopic quantum state can be observed under the strong photoexcitation.
The calculated spectra considerably deviate from results given by the BCS-like
mean field theory and the simple BS equation without electron-hole pair
correlation especially in the intermediate density states between the
electron-hole BCS state and the excitonic BEC state. In particular, we find the
sharp stimulated emission and absorption lines which originate from the optical
transition accompanied by the collective phase fluctuation mode in the
electron-hole BCS state. From the pump-probe spectral viewpoint, we show that
this fluctuation mode changes to the exciton mode with decreasing carrier
densityComment: RevTeX 11 pages, 10 figures. To appear in Phys.Rev.B1
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