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941.
Muncipinto G Kaya T Wilson JA Kumagai N Clemons PA Schreiber SL 《Organic letters》2010,12(22):5230-5233
A short and modular synthetic pathway using intramolecular 1,3-dipolar cycloaddition reactions and yielding functionalized isoxazoles, isoxazolines, and isoxazolidines is described. The change in shape of previous compounds and those in this study is quantified and compared using principal moment-of-inertia shape analysis. 相似文献
942.
Marta Moraschi Giovanni Giulietti Federico Giove Manuela Guardati Girolamo Garreffa Nicola Modugno Claudio Colonnese Bruno Maraviglia 《Magnetic resonance imaging》2010
Parkinson's disease is a neurological disorder associated with the disfunction of dopaminergic pathways of the basal ganglia, mainly resulting in a progressive alteration in the execution of voluntary movements. We present a functional magnetic resonance imaging (fMRI) study on cortical activations during simple motor task performance, in six early–stage hemiparkinsonian patients and seven healthy volunteers. We acquired data in three sessions, during which subjects performed the task with right or left hand, or bimanually. We observed consistent bilateral activations in cingulate cortex and dorsolateral prefrontal cortex of Parkinsonian subjects during the execution of the task with the affected hand. In addition, patients showed both larger and stronger activations in motor cortex of the affected hemisphere with respect to the healthy hemisphere. Compared with the control group, patients showed a hyperactivation of the dorsolateral prefrontal cortex of the affected hemisphere. We concluded that a presymptomatic reorganization of the motor system is likely to occur in Parkinson's disease at earlier stages than previously hypothesized. Moreover, our results support fMRI as a sensitive technique for revealing the initial involvement of motor cortex areas at the debut of this degenerative disorder. 相似文献
943.
944.
Giovanni Bellettini Matteo Novaga Giandomenico Orlandi 《Physica D: Nonlinear Phenomena》2010,239(6):335-339
We consider the sharp interface limit ?→0+ of the semilinear wave equation in R1+n, where takes values in Rk, k=1,2, and W is a double-well potential if k=1 and vanishes on the unit circle and is positive elsewhere if k=2. For fixed ?>0 we find some special solutions, constructed around minimal surfaces in Rn. In the general case, under some additional assumptions, we show that the solutions converge to a Radon measure supported on a time-like k-codimensional minimal submanifold of the Minkowski space-time. This result holds also after the appearance of singularities, and enforces the observation made by J. Neu that this semilinear equation can be regarded as an approximation of the Born-Infeld equation. 相似文献
945.
Sophie Chausson Richard Retoux Jean-Michel Rueff Loïc Le Pluart Pierre-Jean Madec Paul-Alain Jaffres Giovanni Camino 《Macromolecular Symposia》2011,301(1):40-45
Summary: We report herein a study performed on a layered titanoniobate KTiNbO5 modified by octadecylamine to evaluate the fire retardancy properties of this novel hybrid nanofiller dispersed in PA12 and LLDPE, by polymer melt intercalation. The nanocomposites have been characterized using Electron Microscopy techniques to evaluate the degree of exfoliation and the morphologies. Thermogravimetric analyses and cone calorimeter tests have been carried out to assess the fire retardant performances. 相似文献
946.
Hypergraph decomposition and secret sharing 总被引:1,自引:0,他引:1
Giovanni Di Crescenzo 《Discrete Applied Mathematics》2009,157(5):928-946
A secret sharing scheme is a protocol by which a dealer distributes a secret among a set of participants in such a way that only qualified sets of them can reconstruct the value of the secret whereas any non-qualified subset of participants obtain no information at all about the value of the secret. Secret sharing schemes have always played a very important role for cryptographic applications and in the construction of higher level cryptographic primitives and protocols.In this paper we investigate the construction of efficient secret sharing schemes by using a technique called hypergraph decomposition, extending in a non-trivial way the previously studied graph decomposition techniques. A major advantage of hypergraph decomposition is that it applies to any access structure, rather than only structures representable as graphs. As a consequence, the application of this technique allows us to obtain secret sharing schemes for several classes of access structures (such as hyperpaths, hypercycles, hyperstars and acyclic hypergraphs) with improved efficiency over previous results. Specifically, for these access structures, we present secret sharing schemes that achieve optimal information rate. Moreover, with respect to the average information rate, our schemes improve on previously known ones.In the course of the formulation of the hypergraph decomposition technique, we also obtain an elementary characterization of the ideal access structures among the hyperstars, which is of independent interest. 相似文献
947.
948.
A simple and cost-effective laboratory-made liquid junction interface was used for coupling of CE with MS. In this device the capillary column and the spray tip were positioned in the electrode vessel containing appropriate spray liquid. The electrospray potential was applied on the electrode inside the liquid junction. A stable electrospray was produced at nanoliter per minute flow rates generated in the emitter tip without using an external pump. This arrangement provided high durability of the spray tip and independent optimization of the CE separation (use of coated capillaries) and ESI conditions. CE-MS analysis of mixtures of drugs, peptides, tryptic digests of proteins and biological fluids was optimized with respect to the effects of the distance between the separation capillary and electrospray tip and pressure applied on the liquid junction. The sensitivity of the system, in terms of the LOD (base peak monitoring) was below 10 ng/mL for the beta-blocker drugs and below 200 ng/mL for peptide analysis. 相似文献
949.
950.
High-performance liquid chromatography determination of phenyllactic acid in MRS broth 总被引:1,自引:0,他引:1
Phenyllactic acid (PLA) is an organic acid produced by some strains of lactic acid bacteria (LAB) and concentrations higher than 7.5 mg/ml inhibit growth of moulds and yeasts. Since PLA can be used to select LAB, a rapid, simple and cheap method for its determination is desirable. Typical methods for its analysis in broth are time-consuming, analytically complicated, and have poor recoveries. Herein we propose a simple and rapid method that does not require extraction, but only microfiltration of broth before injection in HPLC. The improved chromatographic conditions allow separation and quantification of PLA with a recovery of 98.7%. The method is highly reproducible with an intraday repeatability of the total peak area of 2.00%, while an interday repeatability of 2.69%. 相似文献