Equivalent thermo-mechanical parameters for perfect crystals

Thermo-elastic behavior of perfect single crystal is considered. The crystal is represented as a set of interacting particles (atoms). The approach for determination of equivalent continuum values for the discrete system is proposed. Averaging of equations of particles' motion and long wave approximation are used in order to make link between the discrete system and equivalent continuum. Basic balance equations for equivalent continuum are derived from microscopic equations. Macroscopic values such as Piola and Cauchy stress tensors and heat flux are represented via microscopic parameters. Connection between the heat flux and temperature is discussed. Equation of state in Mie-Gruneisen form connecting Cauchy stress tensor with deformation gradient and thermal energy is obtained from microscopic considerations.Comment: To be published in proceedings of IUTAM Simposium on "Vibration Analysis of Structures with Uncertainties", 2009; 14 pages

Relativistic treatment of harmonics from impurity systems in quantum wires

Within a one particle approximation of the Dirac equation we investigate a defect system in a quantum wire. We demonstrate that by minimally coupling a laser field of frequency omega to such an impurity system, one may generate harmonics of multiples of the driving frequency. In a multiple defect system one may employ the distance between the defects in order to tune the cut-off frequency.Comment: 9 pages Latex, 8 eps figures, section added, numerics improve

Reduced contextually induced muscle thermogenesis in rats with calorie restriction and lower aerobic fitness but not monogenic obesity

We have previously identified predator odor as a potent stimulus activating thermogenesis in skeletal muscle in rats. As this may prove relevant for energy balance and weight loss, the current study investigated whether skeletal muscle thermogenesis was altered with negative energy balance, obesity propensity seen in association with low intrinsic aerobic fitness, and monogenic obesity. First, weight loss subsequent to three weeks of 50% calorie restriction suppressed the muscle thermogenic response to predator odor. Next, we compared rats bred based on artificial selection for intrinsic aerobic fitness—high- and low-capacity runners (HCR, LCR)—that display robust leanness and obesity propensity, respectively. Aerobically fit HCR showed enhanced predator odor-induced muscle thermogenesis relative to the less-fit LCR. This contrasted with the profound monogenic obesity displayed by rats homozygous for a loss of function mutation in Melanocortin 4 receptor (Mc4rK314X/K314X rats), which showed no discernable deficit in thermogenesis. Taken together, these data imply that body size or obesity per se are not associated with deficient muscle thermogenesis. Rather, the physiological phenotype associated with polygenic obesity propensity may encompass pleiotropic mechanisms in the thermogenic pathway. Adaptive thermogenesis associated with weight loss also likely alters muscle thermogenic mechanisms.</p

Screening polymeric ionic liquids for chromatography-based purification of bacteriophage M13

M13 bacteriophage is a key instrument in phage display applications, as well as a possible antibacterial therapeutic agent due to its highly restrictive bacterial pathogenesis, and other applications. The traditional phage purification process is usually achieved by gradient ultracentrifugation or a combination of precipitation, centrifugation and microfiltration. These approaches easily lead to long process times, high operational costs, phage aggregation and consequent product loss (approximately 60%). This work is thus focused on an alternative potential large-scale process to achieve high yield and purity while minimizing the operational costs. Electrostatic-based separation processes are also common biomolecules purification techniques. Although anion exchange chromatography has been used before to purify several viral particles, this technique has been poorly reported for the purification of M13 phage. In a recent work, our group has demonstrated the use of a predominant anion exchange process, where a polymeric ionic liquid (PIL) was used as an alternative separation matrix for M13 bacteriophage. In this work, a variety of system parameters was studied, including chemical structure of the cation and the anion, the crosslinker nature and its concentration, either in batch adsorption/elution or chromatographic operation mode. The PIL-based chromatographic operation mode revealed to be a suitable separation process for M13 from directly filtered E. coli supernatant, reaching over 70% M13 recovery and 4.6 purification factor in a single step. To our knowledge, this is the first time that PILs have been reported as separation agents for bioproducts from complex mixtures.publishe

The Effect of Shear on Phase-Ordering Dynamics with Order-Parameter-Dependent Mobility: The Large-n Limit

The effect of shear on the ordering-kinetics of a conserved order-parameter system with O(n) symmetry and order-parameter-dependent mobility \Gamma({\vec\phi}) \propto (1- {\vec\phi} ^2/n)^\alpha is studied analytically within the large-n limit. In the late stage, the structure factor becomes anisotropic and exhibits multiscaling behavior with characteristic length scales (t^{2\alpha+5}/\ln t)^{1/2(\alpha+2)} in the flow direction and (t/\ln t)^{1/2(\alpha+2)} in directions perpendicular to the flow. As in the \alpha=0 case, the structure factor in the shear-flow plane has two parallel ridges.Comment: 6 pages, 2 figure