An empirical many-body potential energy function constructed from pair-interactions

A new empirical potential energy function (PEF) is proposed, which is formed from pair-interactions only, and containes the many-body contributions. The PEF satisfies bulk cohesive energy and bulk stability condition. The PEF is parameterized for copper, silver, and gold elements in fcc crystal structure. The elastic constantsC ₁₁ andC ₁₂ and the bulk modulus of the elements are calculated, and the structural stability and energetics of microclusters containing 3 to 7 atoms of the same elements are investigated.     

Piston-effect-induced thermal oscillations at the Rayleigh-Bénard threshold in supercritical 3He

We perform a Navier-Stokes numerical simulation of the transient Rayleigh-Bénard convection onset in nearly supercritical 3He in the exact conditions in experiments performed by Kogan, Murphy, and Meyer [Phys. Rev. Lett. 82, 4635 (1999)]Phys. Rev. E 63, 056310 (2001)]]. We find an interpretation of the observed unexpected temperature oscillations at the convection onset in terms of the piston effect. This is our first result towards the exploration of the whole instability diagram as recently mapped in those experiments.     

Numerical modeling of the impact pressure in a compressible liquid medium: application to the slap phase of the locomotion of a basilisk lizard

The forces acting on a solid body just at the time of impact on the surface of a medium with very low compressibility, such as water, can be quantified at acoustic time scales. This is necessary in wide range of applications varying from large-scale ship designs to the walking or running mechanisms of small creatures such as the basilisk lizard. In order to characterize such forces, a numerical model is developed in this study and is validated using analytical expressions of pressure as a function of the speed of sound-wave propagation in water. The computational results not only accurately match the analytical values but are also able to effectively capture the propagation of acoustic waves in water. The model is further applied to a case study wherein the impact impulse required by the basilisk lizard to assist in its walking on the water surface is evaluated. The numerical results are found to be in agreement with the closest available experimental data. The model and approach are thus proposed to evaluate impact forces for wide range of applications.     

On two‐liquid AC electroosmotic system for thin films

Lab‐on‐chip devices employ EOF for transportation and mixing of liquids. However, when a steady (DC) electric field is applied to the liquids, there are undesirable effects such as degradation of sample, electrolysis, bubble formation, etc. due to large magnitude of electric potential required to generate the flow. These effects can be averted by using a time‐periodic or AC electric field. Transport and mixing of nonconductive liquids remain a problem even with this technique. In the present study, a two‐liquid system bounded by two rigid plates, which act as substrates, is considered. The potential distribution is derived by assuming a Boltzmann charge distribution and using the Debye–Hückel linearization. Analytical solution of this time‐periodic system shows some effects of viscosity ratio and permittivity ratio on the velocity profile. Interfacial electrostatics is also found to play a significant role in deciding velocity gradients at the interface. High frequency of the applied electric field is observed to generate an approximately static velocity profile away from the Electric Double Layer (EDL).     

Determination of atenolol in human urine by gas chromatography-mass spectrometry method

A sensitive and efficient method was developed for the determination of atenolol in human urine by gas chromatography-mass spectrometry (GC-MS). Atenolol and metoprolol (internal standard, IS) were extracted from human urine with a mixture of chloroform and butanol at basic pH with liquid-liquid extraction. The extracts were derivatized with N-Methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) and analyzed by GC-MS using a capillary column. The standard curve was linear (r = 0.99) over the concentration range of 50-750 ng/mL. Intra- and inter-day precision, expressed as the relative standard deviation were less than 5.0%, and accuracy (relative error) was better than 7.0%. The analytical recovery of atenolol from human urine has averaged 91%. The limit of quantification was 50 ng/mL. Also, the method was successfully applied to a patient with hypertension who had been given an oral tablet of 50 mg atenolol.     

Electroosmotic flow of ultrathin liquid films and their stability

The Debye-Huckel approximation is generalized to the case of two-phase flows. A one-dimensional steady solution describing electroosmotic flow is found, and, for the first time, its linear stability is investigated analytically.     

A Bohr-Mottelson model of nuclei at finite temperature

Starting from Boltzmann-Langevin equation and performing a fluid dynamical reduction, a system of coupled Langevin equations is derived for a multipolar velocity field. This system is then applied to monopole andβ-,γ-quadrupole resonances, making a link between microscopic approaches and phenomenological macroscopic ones.     

Long-range correlations in Boltzmann-Langevin model

The average phase-space density described by the Boltzmann-Langevin model can largely deviate from the one provided by the Boltzmann-Uhling-Uhlenbeck model, due to the non-linear evolution of density fluctuations. This aspect is investigated for long-wavelength, small density fluctuations in the framework of a memory incorporated Boltzmann-Langevin model. It is shown that the correlations associated with density fluctuations yield a collision term describing coupling between the collective vibrations and the single-particle degrees of freedom, which may play an important role in damping of collective motion in both the stable and unstable regions.