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.     

Experimental study of phase-step broadening by fringing fields in a three-electrode liquid-crystal cell

The fringing-field broadening of a phase-step profile and its dependence on the thickness of a liquid-crystal (LC) cell were studied in a simple, three-electrode LC cell structure consisting of two lateral electrodes biased with a differential voltage and a third, grounded, electrode placed on the opposite substrate. The results were compared both with an approximate analytical model developed earlier for a fringe-field-broadening kernel and with computer simulations. Good agreement between the experiment and the theoretical as well as the simulation results is shown.     

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.     

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.     

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.