Phase Space Models for Stochastic Nonlinear Parabolic Waves: Wave Spread and Singularity

We derive several kinetic equations to model the large scale, low Fresnel number behavior of the nonlinear Schrodinger (NLS) equation with a rapidly fluctuating random potential. There are three types of kinetic equations the longitudinal, the transverse and the longitudinal with friction. For these nonlinear kinetic equations we address two problems: the rate of dispersion and the singularity formation. For the problem of dispersion, we show that the kinetic equations of the longitudinal type produce the cubic-in-time law, that the transverse type produce the quadratic-in-time law and that the one with friction produces the linear-in-time law for the variance prior to any singularity. For the problem of singularity, we show that the singularity and blow-up conditions in the transverse case remain the same as those for the homogeneous NLS equation with critical or supercritical self-focusing nonlinearity, but they have changed in the longitudinal case and in the frictional case due to the evolution of the Hamiltonian

Inverse Scattering and Acousto-Optic Imaging

We propose a tomographic method to reconstruct the optical properties of a highly-scattering medium from incoherent acousto-optic measurements. The method is based on the solution to an inverse problem for the diffusion equation and makes use of the principle of interior control of boundary measurements by an external wave field.Comment: 10 page

Radiation- and Phonon-Bottleneck-Induced Tunneling in the Fe8 Single-Molecule Magnet

We measure magnetization changes in a single crystal of the single-molecule magnet Fe8 when exposed to intense, short (<20 $\mu$s) pulses of microwave radiation resonant with the m = 10 to 9 transition. We find that radiation induces a phonon bottleneck in the system with a time scale of ~5 $\mu$s. The phonon bottleneck, in turn, drives the spin dynamics, allowing observation of thermally assisted resonant tunneling between spin states at the 100-ns time scale. Detailed numerical simulations quantitatively reproduce the data and yield a spin-phonon relaxation time of T1 ~ 40 ns.Comment: 6 RevTeX pages, including 4 EPS figures, version accepted for publicatio

An Improved IOC-ω Technique: Part V - Ionization Potentials & Heats of Formation of Some Organic Molecules

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An Improved IOC-ω Technique: Oxidation & Reduction Potentials & Charge Transfer Energies of Some Conjugated Hydrocarbons

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Measurement of Magnetization Dynamics in Single-Molecule Magnets Induced by Pulsed Millimeter-Wave Radiation

We describe an experiment aimed at measuring the spin dynamics of the Fe8 single-molecule magnet in the presence of pulsed microwave radiation. In earlier work, heating was observed after a 0.2-ms pulse of intense radiation, indicating that the spin system and the lattice were out of thermal equilibrium at millisecond time scale [Bal et al., Europhys. Lett. 71, 110 (2005)]. In the current work, an inductive pick-up loop is used to probe the photon-induced magnetization dynamics between only two levels of the spin system at much shorter time scales (from ns to us). The relaxation time for the magnetization, induced by a pulse of radiation, is found to be on the order of 10 us.Comment: 3 RevTeX pages, including 3 eps figures. The paper will appear in the Journal of Applied Physics as MMM'05 conference proceeding

Les effets pléiotropes d’un inhibiteur réversible de récepteurs P2Y12

RésuméLe cangrelor actif par voie injectable a été le premier inhibiteur réversible des récepteurs P2Y12, et maintenant, le ticagrelor, premier inhibiteur réversible actif par voie orale, ouvre une ère nouvelle dans l’inhibition de la voie de l’ADP: en effet, ils n’ont ni la même pharmacocinétique ni la même pharmacodynamie que les inhibiteurs irréversibles que sont les métabolites actifs des thiénopyridines auxquels nous étions accoutumés. La molécule agit par sa concentration plasmatique et non par son affinité pour son récepteur. L’activité de la molécule va donc pouvoir se porter:-sur des sites P2Y12 extra-plaquettaires qui n’étaient que peu ou pas accessibles aux inhibiteurs irréversibles, et ainsi dévoiler au niveau vasculaire des effets vasodilatateurs;-sur des sites récepteurs transporteurs de moindre affinité. C’est ainsi que le ticagrélor inhibe l’« erythrocyte equilibrative nucleoside transporter », transporteur situé à la membrane des globules rouges et responsable de l’incorporation rapide et active de l’adénosine dans les globules. L’inhibition de l’ENT induit une accumulation d’adénosine avec toute une série d’effets possibles, « les effets adénosine », qui peuvent potentiellement renforcer l’effet primaire: l’adénosine a une activité directe d’anti-agrégant plaquettaire et pas seulement inhibitrice de l’agrégation plaquettaire; l’adénosine a des effets vasculaires: vasodilatateurs mais aussi de pré- et de post-conditionnement en protection contre l’ischémie-reperfusion, et des effets anti-inflammatoires au niveau local. Mais c’est aussi cet effet adénosine qui peut expliquer certains effets secondaires notés lors des études avec le ticagrélor (dyspnée, augmentation des taux plasmatiques d’acide urique et de créatinine, bradycardie en particulier). L’observation que ces patients présentant ces effets secondaires tirent un bénéfice même supérieur du traitement est un argument fort pour indiquer que l’effet adénosine participe de manière significative au bénéfice global net du traitement par le ticagrélor.SummaryCangrelor, administered intravenously, was the first reversible inhibitor of P2Y12 receptors. More recently, ticagrelor is the first oral reversible inhibitor of P2Y12 receptors. These drugs act through their extracellular concentration, in contrast to thienopyridines, which act through irreversible binding of their active metabolite to P2Y12 receptors. These drugs also differ in terms of their pharmacokinetics, pharmacodynamics and modes of action (direct vs indirect). Besides inhibition of platelet P2Y12 receptors, ticagrelor also acts on P2Y12 receptors of other cells. These receptors are much less accessible to the high affinity and short plasma survival of the active metabolites of thienopyridines. At the vascular level, inhibition of P2Y12 receptors on smooth muscle cells prevents vasoconstriction induced by adenosine diphosphate. Ticagrelor also inhibits the erythrocyte equilibrative nucleoside transporter (ENT) (which is responsible for the rapid and active incorporation of adenosine into erythrocytes), and therefore leads to extra-cellular adenosine accumulation. Adenosine, a potent cellular mediator responsible for the ‘adenosine effects’of ticagrelor, can reinforce the primary effect of ticagrelor (adenosine has a direct inhibitory effect on platelet activation/aggregation and is not only an inhibitor of the ADP pathway of platelet activation/aggregation). Adenosine exerts multiple vascular effects – vasodilatation and protection against ischaemic – reperfusion lesions (pre-conditioning and post-conditioning effects) – and these effects can explain some of the secondary effects observed during clinical studies in patients receiving ticagrelor (dyspnoea, increase in plasma concentrations of uric acid and creatinine, bradycardia). The observation that patients affected by such side-effects benefit to a greater extent than patients who do not, provides substance to the argument that the adenosine effect of ticagrelor is significantly implicated in the net global benefit of treatment in patients with acute coronary syndromes

Interpretable Multivariate Time Series Forecasting with Temporal Attention Convolutional Neural Networks

Data in time series format, such as biological signals from medical sensors or machine signals from sensors in industrial environments are rich sources of information that can give crucial insights on the present and future condition of a person or machine. The task of predicting future values of time series has been initially approached with simple machine learning methods, and lately with deep learning. Two models that have shown good performance in this task are the temporal convolutional network and the attention module. However, despite the promising results of deep learning methods, their black-box nature makes them unsuitable for real-world applications where the predictions need to be explainable in order to be trusted. In this paper we propose an architecture comprised of a temporal convolutional network with an attention mechanism that makes predictions while presenting the timesteps of the input that were most influential for future outputs. We apply it on two datasets and we show that we gain interpretability without degrading the accuracy compared to the original temporal convolutional models. We then go one step further and we combine our configuration with various machine learning methods on top, creating a pipeline that achieves interpretability both across timesteps and input features. We use it to forecast a different variable from one of the above datasets and we study how the accuracy is affected compared to the original black-box approach