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41.
For two methods commonly used to achieve canonical-ensemble sampling in a molecular-dynamics simulation, the Langevin thermostat and the Andersen [H. C. Andersen, J. Chem. Phys. 72, 2384 (1980)] thermostat, we observe, as have others, synchronization of initially independent trajectories in the same potential basin when the same random number sequence is employed. For the first time, we derive the time dependence of this synchronization for a harmonic well and show that the rate of synchronization is proportional to the thermostat coupling strength at weak coupling and inversely proportional at strong coupling with a peak in between. Explanations for the synchronization and the coupling dependence are given for both thermostats. Observation of the effect for a realistic 97-atom system indicates that this phenomenon is quite general. We discuss some of the implications of this effect and propose that it can be exploited to develop new simulation techniques. We give three examples: efficient thermalization (a concept which was also noted by Fahy and Hamann [S. Fahy and D. R. Hamann, Phys. Rev. Lett. 69, 761 (1992)]), time-parallelization of a trajectory in an infrequent-event system, and detecting transitions in an infrequent-event system. 相似文献
42.
43.
Nicolae Anghel 《Proceedings of the American Mathematical Society》1996,124(11):3555-3561
In this paper we address the problem of generic vanishing for (negative) harmonic spinors of Dirac operators coupled with variable metric connections.
44.
Tiberiu Freniu Ana-Maria Rusu Michaela Ponta Sorin D. Anghel E. A. Cordos 《Fresenius' Journal of Analytical Chemistry》1996,355(3-4):254-255
A low to medium power radiofrequency capacitively coupled plasma is characterized as spectral source for atomic emission. The signal to background ratio and the limits of detection were determined for 19 elements as a function of the plasma torch geometry and the observation point. 相似文献
45.
We report herein the synthesis of cytotoxic cyanobactin, Wewakazole B through an efficient solution-phase approach. The key steps of the synthesis are the macrocyclic lactamization of linear dodecapeptide and construction of two hexapeptides with three different substituted oxazole rings. 相似文献
46.
47.
This paper presents both a numerical and analytical study in connection with the steady boundary layer flow and heat transfer
induced by a moving permeable semi-infinite flat plate in a parallel free stream. Both the velocities of the flat plate and
the free stream are proportional to x
1/3. The surface temperature is assumed to be constant. The governing partial differential equations are converted into ordinary
differential equations by a new similarity transformation. Numerical results for the flow and heat transfer characteristics
are obtained for various values of the moving parameter, transpiration parameter and the Prandtl number. Approximate analytical
solutions are also obtained when the suction or injection parameter is very large. It is found that dual solutions exist for
the case when the fluid and the plate move in the opposite directions. 相似文献
48.
49.
Corina Duda-Seiman T. Vlase Gabriela Vlase Rodica Cinca Mariana Anghel N. Doca 《Journal of Thermal Analysis and Calorimetry》2011,105(3):851-858
Verapamil is a phenyl-alchil-amine type pharmaceutical largely used as a specific calcium antagonist. Knowledge of drug-excipient
compatibility represents an important phase in development of different dosage forms. Hyphenated techniques are versatile
for obtaining such necessary information’s. The TG/DTG/DTA curves were obtained in air at different heating rates and in nitrogen.
The IR spectra of pure compound and its char at 400 °C (by U-ATR technique) and the IR identification of Evolved Gasses allowed
some discussions on the thermally induced events. In the solid dosage forms verapamil was mixed with talc, magnesium stearate,
starch, and cellulose, and the corresponding thermoanalytical curves were compared with that one of pure I. No physical or
chemical interactions were observed till 250 °C. A kinetic analysis was performed for TG step of verapamil between 250 and
350 °C. The data at four heating rates (7, 10, 12, 15 °C min−1) were processed on a strategy using at last three different kinetic methods. For these, the NPK method seems to be less speculative,
allowing an objective determination of the kinetic parameters. 相似文献
50.
S.D. Anghel 《Journal of Electrostatics》2013,71(2):155-158
A new kind of electrically isolated flat spiral electrode for generating homogeneous atmospheric pressure plasmas is proposed. A sinusoidal voltage (5 kVpk–pk, 48 kHz) has been applied to the electrode. The high voltage is generated with a dc supply voltage of only 4 V, based on the electrical characteristics of a resonant circuit. Plasma was generated in closed spaces in helium with air impurities, with or without using a second grounded electrode. The gas temperature was of around 324 K and the plasma was tested for the paperboard hydrophilicity and transparent film for printer wettability modifications. 相似文献