Non-linear elastic effects in phase field crystal and amplitude equations: Comparison to ab initio simulations of bcc metals and graphene

We investigate non-linear elastic deformations in the phase field crystal model and derived amplitude equations formulations. Two sources of non-linearity are found, one of them based on geometric non-linearity expressed through a finite strain tensor. It reflects the Eulerian structure of the continuum models and correctly describes the strain dependence of the stiffness. In general, the relevant strain tensor is related to the left Cauchy-Green deformation tensor. In isotropic one- and two-dimensional situations the elastic energy can be expressed equivalently through the right deformation tensor. The predicted isotropic low temperature non-linear elastic effects are directly related to the Birch-Murnaghan equation of state with bulk modulus derivative $K'=4$ for bcc. A two-dimensional generalization suggests $K'_{2D}=5$. These predictions are in agreement with ab initio results for large strain bulk deformations of various bcc elements and graphene. Physical non-linearity arises if the strain dependence of the density wave amplitudes is taken into account and leads to elastic weakening. For anisotropic deformations the magnitudes of the amplitudes depend on their relative orientation to the applied strain.Comment: 16 page

Beyond the local approximation to exchange and correlation: the role of the Laplacian of the density in the energy density of Si

We model the exchange-correlation (XC) energy density of the Si crystal and atom as calculated by variational Monte Carlo (VMC) methods with a gradient analysis beyond the local density approximation (LDA). We find the Laplacian of the density to be an excellent predictor of the discrepancy between VMC and LDA energy densities in each system. A simple Laplacian-based correction to the LDA energy density is developed by means of a least square fit to the VMC XC energy density for the crystal, which fits the homogeneous electron gas and Si atom without further effort.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let

About the Dirac Equation with a δ\delta potential

An elementary treatment of the Dirac Equation in the presence of a three-dimensional spherically symmetric $\delta (r-r_0)$-potential is presented. We show how to handle the matching conditions in the configuration space, and discuss the occurrence of supercritical effects.Comment: 8 pages, 1 postscript figure, Latex, Revise

Protein and Long-Chain n-3 Polyunsaturated Fatty Acids Recovered from Herring Brines upon Flocculation and Flotation─A Case Study

A novel integrated process for recovery of protein-enriched biomasses from 5% presalting brines and spice brines of herring (Clupea harengus) was investigated by combining carrageenan- and/or acid-driven flocculation (F) plus dissolved air flotation (DAF). The F-DAF technique with carrageenan resulted in protein and lipid recoveries from 5% presalting brine of 78 and 38%, respectively. Without flocculation or with only acidification, protein and lipid recoveries in DAF were only 13 and 10%, respectively. Low protein and lipid recoveries, 8-12 and 1.8-8.2%, respectively, were also obtained when spice brine was subjected to only acidification and DAF. The protein content in dry biomasses from 5% presalting brine and spice brine was 36-43 and 13-16%, respectively. The corresponding lipid levels were 23-31 and 9-18%, respectively, with ash levels of 11-20 and 38-45%, respectively. Biomass proteins contained ≤45% essential amino acids, and the lipids had ≤16% long-chain n-3 polyunsaturated fatty acids. Freeze-dried spice brine biomasses were characterized by anchovy- and spice-related sensory attributes. 5% presalting brine biomasses were connected to fish and seafood attributes and showed gel forming capacity. The outlined F-DAF recovery system can thus recover both nutrients and interesting flavors from the herring process waters, which are currently lost from the food chain

Influence of hydration status on changes in plasma cortisol, leukocytes and antigen-stimulated cytokine production by whole blood culture following prolonged exercise.

Elevated antigen-stimulated anti-inflammatory cytokine production appears to be a risk factor for upper respiratory tract illness in athletes. The purpose of this study was to determine the effects of prolonged exercise and hydration on antigen-stimulated cytokine production. Twelve healthy males cycled for 120min at 60% O2 max on two occasions, either euhydrated or moderately hypohydrated (induced by fluid restriction for 24 h). Blood samples were collected before and after exercise and following 2 h recovery for determination of cell counts, plasma cortisol, and in vitro antigen-stimulated cytokine production by whole blood culture. Fluid restriction resulted in mean body mass loss of 1.3% and 3.9% before and after exercise, respectively. Exercise elicited a significant leukocytosis and elevated plasma cortisol, with no differences between trials. IL-6 production was significantly reduced 2 h postexercise ( < 0.05), while IL-10 production was elevated postexercise ( < 0.05). IFN- and IL-2 production tended to decrease postexercise. No significant effect of hydration status was observed for the measured variables. Prolonged exercise appears to result in augmented anti-inflammatory cytokine release in response to antigen challenge, possibly coupled with acute suppression of proinflammatory cytokine production, corresponding with studies using mitogen or endotoxin as stimulant. Moderate hypohydration does not appear to influence these changes

The influence of hydration status during prolonged endurance exercise on salivary antimicrobial proteins

Purpose: Antimicrobial proteins (AMPs) in saliva including secretory immunoglobulin A (SIgA), lactoferrin (SLac) and lysozyme (SLys) are important in host defence against oral and respiratory infections. This study investigated the effects of hydration status on saliva AMP responses to endurance exercise. Methods: Using a randomized design, 10 healthy male participants (age 23 ± 4 years, (Formula presented.) 56.8 ± 6.5 ml/kg/min) completed 2 h cycling at 60 % (Formula presented.) in states of euhydration (EH) or dehydration (DH) induced by 24 h fluid restriction. Unstimulated saliva samples were collected before, during, immediately post-exercise and each hour for 3 h recovery. Results: Fluid restriction resulted in a 1.5 ± 0.5 % loss of body mass from baseline and a 4.3 ± 0.7 % loss immediately post-exercise. Pre-exercise urine osmolality was higher in DH than EH and overall, saliva flow rate was reduced in DH compared with EH (p < 0.05). Baseline SIgA secretion rates were not different between conditions; however, exercise induced a significant increase in SIgA concentration in DH (161 ± 134 to 309 ± 271 mg/L) which remained elevated throughout 3 h recovery. SLac secretion rates increased from pre- to post-exercise in both conditions which remained elevated in DH only. Overall, SLac concentrations were higher in DH than EH. Pre-exercise SLys concentrations were lower in DH compared with EH (1.6 ± 2.0 vs. 5.5 ± 6.7 mg/L). Post-exercise SLys concentrations remained elevated in DH but returned to pre-exercise levels by 1 h post-exercise in EH. Conclusions: Exercise in DH caused a reduction in saliva flow rate yet induced greater secretion rates of SLac and higher concentrations of SIgA and SLys. Thus, DH does not impair saliva AMP responses to endurance exercise