Modelling of orthogonal cutting processes with the method of smoothed particle hydrodynamics

In the last decades, mesh-free methods for simulating various cutting processes have been used very widely as they can eliminate numerical problems in the simulation of material failure and large plastic deformations. This paper deals with the results from modelling the orthogonal cutting of AISI 1045 steel using smoothed particle hydrodynamics (SPH) method. Moreover, it is determined how the parameters of the SPH solver such as initial smoothing length, initial particle density and coefficient for the timestep increase affect the prediction error for the values of cutting force and chip compression ratio as well as computing time. The optimum values of the SPH solver parameters are determined by minimising an objective function. The best balance between the prediction error of machining variables and computing time is achieved for an initial particle density of 40 μm and a coefficient for the timestep increase of 0.4.     

An Improved Method for Determining Medium- and Long-Chain FAMEs Using Gas Chromatography

The existing protocols for analyzing fatty acid methyl esters (FAMEs) using a one-step acetyl chloride (AC) catalyzed transesterification and extraction procedure cannot accurately determine the medium- and long-chain fatty acids simultaneously in clinical (enteral, parenteral) formulations. For example: (1) addition of AC at room temperature generates an exothermic reaction that often results in loss of sample and possible injury to the analyst; (2) certain polyunsaturated fatty acids (PUFAs) are less stable at elevated temperatures during the transesterification and contribute to the over-estimation of the C16:0 and C18:1 fatty acids; and (3) the flame-ionization detector (FID) response varies depending on the carbon chain length of the fatty acids, that consequently impacts the underestimation of medium-chain fatty acid (C6–C10) recoveries. To overcome these deficiencies and accurately determine FAMEs, we have developed an improved one-step transesterification method that employs the addition of AC in tubes kept on a dry ice bath, the transesterification at room temperature, and the data analysis using relative response factors. Using this modified protocol, we determined the fatty acid composition of lipid emulsions (Omegaven^® and Lipidem^®) on a Shimadzu GC2010 gas chromatography (GC) system using a capillary GC column (Zebron ZB-WAX plus, 30 m, 0.25 mm ID, 0.25 μm). Our data suggest that the improved method can be easily used to accurately determine fatty acids (C6–C24) in functional foods and lipid emulsions.     

A new membrane bioreactor generation for wastewater treatment application: Strategy of membrane aeration management by sequencing aeration cycles

Polymem is developing in the past few years a new membrane bioreactor concept using external module membranes. The membranes are hollow fibers. They are housed in carters and work in outside/in filtration mode. Permanent air scouring is provided at the bottom of the module to control the accumulation of sludge on the membrane surface. In other words, the membrane carters look like bubble columns with hollow fiber membranes inside.The main advantages of this concept are the easy maintenance of the external modules; the total independence of the bioreactor from the membrane filtration part, which facilitates plant retrofitting and upgrading; the high membrane compacity (up to 500 m²/m3), and better efficiency of membrane air scouring thanks to a dedicated coarse bubbles aeration system inside the module vessel.The first part of this paper deals with the quantification of the specific aeration demand of the system. Aeration demand was compared to conventional MBR systems. The study shows that with this optimised geometry of module concept, the aeration flow rate is lowered compared with conventional processes.In the second part of this paper, an optimisation of the aeration demand was carried out by sequencing the cycle of aeration by incorporating a syncope in the aeration. Ratios of the time-on and time-off from 1/2 to 1/5 were tested for various instantaneous aeration flow rates. Impacts on both short term fouling and long term fouling were evaluated and quantified in terms of permeability decrease. The advantages of the location of the membrane in an external cylindrical carter have been demonstrated in terms of operating cost savings with a reduction of specific aeration demand for membranes scouring at 100 to 250 Nl/h m², which is half the classical consumption of the submerged MBR today.     

Effect of Heat Treatment of Molten Bi2O3 Containing 22 mol % SiO2 on the State of the Metastable δ*-Phase Forming during Solidification

Inorganic Materials - We have studied the effect of isothermal holding of a melt containing 78 mol % Bi2O3 and 22 mol % SiO2 and various melt cooling schedules on the morphology, microstructure,...     

Parenteral Lipid Emulsions in Guinea Pigs Differentially Influence Plasma and Tissue Levels of Fatty Acids,Squalene, Cholesterol,and Phytosterols

Lipid emulsions are made by mixing vegetable and/or fish oils with egg yolk and contain different types and amounts of fatty acids and sterols. This study assessed the effects of oral diet, soybean oil (SO)-, fish oil (FO)-, a mixture of olive and soybean oil (OOSO)-, and a mixture of fish, olive, coconut, and soybean oil (FOCS)-based emulsions on plasma triacylglycerols and plasma and tissue fatty acid and sterol content following acute and chronic intravenous administration in the guinea pig. Upon acute administration, peak triacylglycerols were highest with SO and lowest with OOSO. Upon chronic administration, the plasma triglyceride levels did not increase in any group over that of the controls. Fatty acid levels varied greatly between organs of animals on the control diets and organs of animals following acute or chronic lipid administration. Squalene levels increased in plasma following acute administration of OOSO, but plasma squalene levels were similar to control in all emulsion groups following chronic administration. Total plasma phytosterol levels were increased in the SO, OOSO, and FOCS groups following both acute and chronic infusions, whereas phytosterols were not increased following FO infusion. Total phytosterol levels were higher in liver, lung, kidney and adipose tissue following SO and OOSO. Levels were not increased in tissues after FO and FOCS infusion. These results indicate that fatty acid and sterol contents vary greatly among organs and that no one tissue reflects the fatty acid or sterol composition of other tissues, suggesting that different organs regulate these compounds differently.     

Tocopherol and tocotrienol homologs in parenteral lipid emulsions

Parenteral lipid emulsions, which are made of oils from plant and fish sources, contain different types of tocopherols and tocotrienols (vitamin E homologs). The amount and types of vitamin E homologs in various lipid emulsions vary considerably and are not completely known. The objective of this analysis was to develop a quantitative method to determine levels of all vitamin E homologs in various lipid emulsions. An HPLC system was used to measure vitamin E homologs using a Pinnacle DB Silica normal phase column and an isocratic, n‐hexane:1,4 dioxane (98:2) mobile phase. An optimized protocol was used to report vitamin E homolog concentrations in soybean oil‐based (Intralipid®, Ivelip®, Lipofundin^® N, Liposyn^® III, and Liposyn^® II), medium‐ and long‐chain fatty acid‐based (Lipofundin^® , MCT and Structolipid®), olive oil‐based (ClinOleic® ), and fish oil‐based (Omegaven®) and mixture of these oils‐based (SMOFlipid®, Lipidem®) commercial parenteral lipid emulsions. Total content of all vitamin E homologs varied greatly between different emulsions, ranging from 57.9 to 383.9 µg/mL. Tocopherols (α, β, γ, δ) were the predominant vitamin E homologs for all emulsions, with tocotrienol content < 0.3%. In all of the soybean emulsions, except for Lipofundin® N, the predominant vitamin E homolog was γ‐tocopherol, which ranged from 57–156 µg/mL. ClinOleic® predominantly contained α‐tocopherol (32 µg/mL), whereas α‐tocopherol content in Omegaven® was higher than most of the other lipid emulsions (230 µg/mL). Practical applications: The information on the types and quantity of vitamin E homologs in various lipid emulsions will be extremely useful to physicians and healthcare personnel in selecting appropriate lipid emulsions that are exclusively used in patients with inadequate gastrointestinal function, including hospitalized and critically ill patients. Some emulsions may require vitamin E supplementation in order to meet minimal human requirements. Vitamin E homologs (tocopherols and tocotrienols) contain a chromanol ring and a hydrophobic side chain.     

Spatial and seasonal variations in phytoplankton community structure in alkaline–saline Lake Nakuru,Kenya

Spatial and seasonal variations of phytoplankton, expressed in terms of species composition, cell density, biovolumes and biomass, collected at 10 sampling sites in alkaline–saline Lake Nakuru, Kenya, were investigated monthly from March 2004 to February 2005, in relation to selected physical and chemical water quality parameters. A total of eight species, belonging to five genera and three classes, were recorded. The Cyanophyceae comprised the bulk of the phytoplankton, followed by Euglenophyceae, while Bacillariophyceae were the least abundant. Arthrospira fusiformis was the most dominant species, in terms of density, among the Cyanophyceae, while Euglena spp. and Navicula elkabs dominated the Euglenophyceae and Bacillariophyceae density, respectively. Seasonal variations in phytoplankton species composition, density and biomass were significant (P < 0.05) with minimum cell density and biomass occurring during the dry season, and being maximum following the end of the two rainy seasons from May to November 2004, suggesting the possible influence of various environmental factors on the lake. Sampling sites located close to the inlets of inflowing rivers exhibited significantly (P < 0.05) higher phytoplankton cell density and biomass than those by the inshore sites. Soluble reactive phosphorus, ammonia‐nitrogen, conductivity and total alkalinity accounted for most of the variations in the cell densities of phytoplankton species.     

Preliminary typology designed for treatment matching of driving-while-intoxicated offenders.

A typology of 156 convicted driving-while-intoxicated (DWI) offenders was developed using cluster analysis and external validation procedures. The typology was derived from 4 variables (alcohol dependence severity, psychiatric severity, bad-driving index, and social instability) selected to maximize the feasibility of performing treatment matching with DWI offenders. Five clusters that suggested specific treatment matching opportunities were identified. The largest, Cluster 4 (31% of cases), showed a low problem profile. However, a moderate-severity group (Cluster 1), a high-risk driver group (Cluster 2), and 2 high problem-severity groups (Clusters 3 and 5) were also found. Clusters 3 and 5 had high levels of alcohol dependence and psychiatric symptoms but differed significantly on social instability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Permissive underfeeding

Dietary manipulation may influence outcome after infection and injury by altering production of inflammatory mediators and disease activity. Restricted nutrient intake may have beneficial effects on life-span, development of degenerative disease, autoimmune processes, renal injury, susceptibility to infection, and survival rate after infection. Nutritional therapies that serve to maximize nitrogen balance may adversely affect the host response to injury, especially when given in excess of energy and protein needs. The optimal calorie/protein intake during different phases of critical illness remains to be established. However, a short period of restricted intake may be beneficial.