Chemical and structural characterization of bacterially-derived casein peptides that impair milk clotting

Milk-clotting parameters are highly affected by hydrolysis of casein. Previously, it was shown that products of the hydrolysis of casein impair milk clotting, affecting both clotting time and curd firmness. One of these fractions is of particular interest since it is produced exclusively by enzymes of Streptococcus dysgalactiae. The present study aims to further investigate the chemical and structural properties of this fraction in an attempt to understand its influence on milk clotting. Preparations of this fraction, obtained from either S. dysgalactiae-infected glands or ex vivo inoculations with the same bacteria, were found to be identical. Mass spectrometry and Edman degradation analyses indicate that it comprises primarily β-CN^83–209, generated by cleavage at a Val-Val peptide bond, presumably by bacterial thermolysin- or elastin-like proteases. A model offering a putative mechanism for interference with milk-clotting parameters through production of this fraction is presented.     

Thermal inactivation of Escherichia coli in camel milk

Camels subsist and produce milk in desert pastures not utilized by other domesticated herbivores. Developing the camel milk industry can improve the economy of desert inhabitants. To comply with sanitary ordinances, camel milk is pasteurized by procedures specified for bovine milk. It is widely accepted that milk composition might affect bacterial thermal death time (TDT). Camel and bovine milks markedly differ in their chemical composition, yet data regarding TDT values of bacteria in camel milk is missing. As a first step toward developing specific heat treatments appropriate for camel milk, TDT curves of Escherichia coli in artificially contaminated camel and cow milks have been compared. Heating the milks to temperatures ranging from 58 to 65 degrees C yields similar thermal death curves and derived D- and z-values. These findings suggest that, in this temperature range, E. coli might behave similarly in bovine and camel milk. Additional TDT studies of various pathogenic species in camel milk are required before establishing pasteurization conditions of camel milk.     

Towards a First Vertical Prototyping of an Extremely Fine-Grained Parallel Programming Approach

Explicit multithreading (XMT) is a parallel programming approach for exploiting on-chip parallelism. XMT introduces a computational framework with (1) a simple programming style that relies on fine-grained PRAM-style algorithms; (2) hardware support for low-overhead parallel threads, scalable load balancing, and efficient synchronization. The missing link between the algorithmic-programming level and the architecture level is provided by the first prototype XMT compiler. This paper also takes this new opportunity to evaluate the overall effectiveness of the interaction between the programming model and the hardware, and enhance its performance where needed, incorporating new optimizations into the XMT compiler. We present a wide range of applications, which written in XMT obtain significant speedups relative to the best serial programs. We show that XMT is especially useful for more advanced applications with dynamic, irregular access patterns, where for regular computations we demonstrate performance gains that scale up to much higher levels than have been demonstrated before for on-chip systems.     

Finding Euler tours in parallel

The problem of finding Euler tours in directed and undirected Euler graphs is considered. O(log |V|) time algorithms are given using a linear number of processors on a concurrent-read concurrent-write parallel RAM.     

Fringing-field effect in liquid-crystal beam-steering devices: an approximate analytical model

An approximate analytical model was developed that links the fringing-field broadening of the phase profile of a liquid-crystal (LC) beam-steering device, and the resulting diffraction efficiency, to the physical parameters of the device including the cell thickness as well as the dielectric, optical, and geometrical constants of the device. The analysis includes a full solution of the Laplace equation for the LC device in which the broadening of the initial voltage profile into an effective voltage-drop profile, due to the fringing-field effect, is derived. It is shown that within the linear approximation used, the broadening of the phase profile is identical to the broadening of the effective voltage profile in the presence of the fringing field. On the basis of this model, the resulting broadening kernel of the phase profile is found to be proportional to the LC cell thickness. These results are found to be in an excellent agreement with high-precision computer simulations performed on the LC beam-steering structure, thereby validating this approximate linear model.     

Alternating current Josephson effect and resonant superconducting transport through vibrating Nb nanowires

In 1962, Josephson made a celebrated prediction: when a constant voltage is applied across a thin insulator separating two superconductors, it will generate an oscillating current. These oscillations are ubiquitous in superconducting weak links of various geometries, and analogues have been found in other macroscopic quantum systems, such as superfluids and gaseous Bose-Einstein condensates. The interplay between the oscillating current and external microwave radiation of matching frequency (Shapiro steps) or with internal electrodynamic resonances (Fiske effect) appear as changes in the current-voltage characteristics of superconducting tunnel junctions and provide further insight into the phenomenon. Here, we report measurements and theoretical studies suggesting that Josephson current oscillations interact with atomic-scale mechanical motion as well. We formed a niobium dimer nanowire that acts as a weak link between two superconducting (bulk) niobium electrodes. We find features in the differential conductance through the dimer which we believe correspond to excitations of the dimer vibrational modes by Josephson oscillations and support our results with theoretical simulations.     

An experimental investigation of the effects of workpiece and grinding parameters on minimum quantity lubrication—MQL grinding

Coolant is a term generally used to describe grinding fluids used for cooling and lubricating in grinding process. The main purposes of a grinding fluid can be categorized into lubrication, cooling, transportation of chips, cleaning of the grinding wheel and minimizing the corrosion. On the other hand, grinding fluids have negative influences on the working environment in terms of the health of the machine operator, pollution and the possibility of explosion (for oil). Furthermore, the cost of the grinding fluid, filtering and waste disposal of the metal working fluids is even higher than the tool cost and constitutes a great part of the total cost. Additionally, grinding fluids can not effectively penetrate into the contact zone, are health hazard and their consumption must be restricted. Generally, compared to other machining processes, grinding involves high specific energy. Major fraction of this energy is changed into heat, which makes harmful effect on the surface quality as well as the tool wear. Since there is no coolant lubricant to transfer the heat from the contact zone in dry grinding, surface damages are not preventable. Alternatives to current practices are getting more serious consideration in response to environmental and operational cost pressures. One attractive alternative is the minimum quantity lubrication (MQL) grinding or the near dry grinding (NDG). In near dry grinding an air–oil mixture called an aerosol is fed into the wheel-work contact zone. Compared to dry grinding, MQL grinding substantially enhances cutting performance in terms of increasing wheel life and improving the quality of the ground parts. In this research, the influences of workpiece hardness and grinding parameters including wheel speed, feed rate and depth of cut have been studied on the basis of the grinding forces and surface quality properties to develop optimum grinding performances such as cooling, lubrication, high ecological and environmental safety.     

Elevated concentrate-to-forage ratio in dairy cow rations is associated with a shift in the diameter of milk fat globules and remodeling of their membranes

We examined the effects of concentrate-to-forage ratio in dairy cow rations on milk-fat composition, with a specific focus on the structure of milk fat globules (MFG). Twenty-four Holstein cows, 153 d in milk, were assigned to 2 dietary treatments in a crossover design study. Treatments were (1) high-concentrate (65%), low-forage (35%; HCLF) diet and (2) low-concentrate (35%), high-forage (65%; LCHF) diet. The mean diameter of the MFG; plasma concentrations of insulin, glucose, and nonesterified fatty acids (FA); and the composition and concentrations of milk FA and polar lipids were determined. Concentrations of insulin were 56% higher, and those of nonesterified FA 46% lower, in the HCLF than in the LCHF diet. The milk yield was 8.5 kg/d higher and yields of fat, protein, and lactose were 180, 350, and 403 g/d higher, respectively, in the HCLF versus LCHF diet. Milk FA composition differed between treatments, with 1.5 and 1.0 percentage units higher saturated and polyunsaturated FA concentrations, respectively, in the HCLF versus LCHF diet. Mean MFG diameter tended to be smaller (0.2 μm) in the HCLF diet than in the LCHF diet, associated with increased daily phospholipids yield (34%), lower phosphatidylserine and higher phosphatidylcholine concentrations. In conclusion, the decreased milk and fat yields in the LCHF diet were associated with remodeling of the MFG membrane and with the secretion of larger MFG. Membrane remodeling of the mammary epithelium membranes seems to play a role in regulating MFG size.     

Evaluating the ductility and shear behaviour of carbon fibre reinforced polymer and glass fibre reinforced polymer reinforced concrete columns

Brittle shear failure in short reinforced concrete (RC) columns has been identified as one of the most dangerous failure modes that may cause collapse of bridges, based on research findings and damage reconnaissance of past earthquakes. Using ABAQUS software, the effect of carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP) on retrofitting of existing circular RC columns, and also enhancing of shear strength have been studied. Five types of concrete columns were studied in the ‘as built’ condition to investigate the shear failure mode of columns. These columns were assessed again after being retrofitted by using CFRP and GFRP. Based on findings of this research, the effect of CFRP jackets on improving the shear behaviour of column is more than that of GFRP jackets, while GFRP jackets are more effective than CFRP jackets, regarding their contribution in increasing the column ductility. Therefore, these FRP composites can be utilized in different conditions, according to column demand for increasing the ductility or shear strength. Copyright © 2010 John Wiley & Sons, Ltd.