Film Forming Behavior of Greases Under Starved and Fully Flooded EHL Conditions

Improving knowledge on the film forming behavior of greases is essential to be able to develop efficient greases. This article examines how operating conditions (e.g., temperature, lubrication condition [fully flooded/starved]) and base oil viscosity influence the film forming properties of greases by comparing the behavior of two lithium-based greases and their respective base oils in rolling point contact. It is found that the onset and degree of starvation is controlled by speed (u) × viscosity (ν)/load (W) factor (uν/W) and temperature and that low uν/W values promote entrainment of thickener into contact. Thus, grease with low base oil viscosity shows significant thickener entrainment in the low speed region compared to the one with high base oil viscosity, which leads to the formation of thickener-rich viscous material during extended running with the low base oil viscosity grease. The results suggest that the shape of the film thickness versus speed curve is viscosity and uν/W range dependent. Furthermore, for the test conditions used in this study, grease-lubricated contacts appear to shift from the initial fully flooded condition to starved condition over a prolonged running of 2 h. The results from this study concur with those reported in the literature that fully flooded oil elastohydrodynamic lubrication (EHL) theory or film thickness cannot be directly applied or taken as a guideline in grease-lubricated contacts.     

A Unitary Analysis of some Voltage and Current Mode Linear Circuits

This paper presents a systematic and unitary analysis of a large class of current and voltage mode circuits based on a series-shunt-like configuration. Four possible OA types are considered for the basic amplifier. The amplifiers have voltage and current input signals and voltage and current outputs. The analysis method is based on the separation of the circuit signal graph in two different paths, one that controls the gain and the other that controls the bandwidth.     

TAAR1 Expression in Human Macrophages and Brain Tissue: A Potential Novel Facet of MS Neuroinflammation

TAAR1 is a neuroregulator with emerging evidence suggesting a role in immunomodulation. Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system. Here, we investigate TAAR1 expression in human primary monocytes, peripherally-derived macrophages, and MS brain tissue. RT-qPCR was used to assess TAAR1 levels in MS monocytes. Using a previously validated anti-human TAAR1 antibody and fluorescence microscopy, TAAR1 protein was visualized in lipopolysaccharide-stimulated or basal human macrophages, as well as macrophage/microglia populations surrounding, bordering, and within a mixed active/inactive MS lesion. In vivo, TAAR1 mRNA expression was significantly lower in MS monocytes compared to age- and sex-matched healthy controls. In vitro, TAAR1 protein showed a predominant nuclear localization in quiescent/control macrophages with a shift to a diffuse intracellular distribution following lipopolysaccharide-induced activation. In brain tissue, TAAR1 protein was predominantly expressed in macrophages/microglia within the border region of mixed active/inactive MS lesions. Considering that TAAR1-mediated anti-inflammatory effects have been previously reported, decreased mRNA in MS patients suggests possible pathophysiologic relevance. A shift in TAAR1 localization following pro-inflammatory activation suggests its function is altered in pro-inflammatory states, while TAAR1-expressing macrophages/microglia bordering an MS lesion supports TAAR1 as a novel pharmacological target in cells directly implicated in MS neuroinflammation.     

Conjugated linoleic acid isomer concentrations in milk from high‐ and low‐input management dairy systems

BACKGROUND: Different conjugated linoleic acid (CLA) isomers are known to have contrasting physiology or health effects and there is growing evidence that the profile of natural isomers in milk is influenced by the production system. This survey is the first to compare feeding regimes and concentrations of 14 CLA isomers in milk from three production systems in the UK. RESULTS: Total CLA and seven isomers (including C18:2 c9t11 which comprised > 80% of total) were significantly higher in milk from both organically certified and non‐certified low input (LI) systems compared with milk from conventional high input farms. Sampling date also affected concentrations of total CLA and nine isomers; being lowest in March and highest in August. Seasonal differences were greater in milk from LI herds, thought to be due to changes in herbage and/or stage of lactation. Multivariate analysis showed a strong positive relationship between several CLA isomers and increasing levels of fresh forage in the diet. CONCLUSIONS: These results add to the evidence on how management adjustment may improve the profile of CLA isomers in milk fat, although animal or human intervention studies are required to identify the effects of consuming milk with different CLA levels and isomer profiles on human health. Copyright © 2009 Society of Chemical Industry     

Highly luminescent europium and terbium complexes based on succinimide and N-hydroxysuccinimide

The preparation of two highly luminescent europium(III) and terbium(III) complexes with succinimide(SI) and N-hydroxysuccinimide(NHSI) were reported,which were further investigated through elemental chemical analysis,thermal analysis,FT-IR,powder X-ray diffraction,SEM and fluorescence spectroscopy.Data collected through these analysis revealed the formation of the Eu(III) and Tb(III) complexes with the above mentioned ligands at a metal to ligand(M:L) molar ratio of 1:3.Interesting conclusions regarding the efficient sensitization through the coordination site of the lanthanide luminescent centers were retained from the photoluminescent spectra investigation.Strong luminescence emission was observed in case of Eu(III)-SI and Tb(III)-NHSI complexes while the corresponding Eu(III)-NHSI and Tb(III)-SI complexes exhibited no photo luminescent properties.Newly obtained luminescent lanthanide complexes may be of particular interest for various applications in optoelectronics.     

Biodiesel production using enzymatic transesterification - Current state and perspectives

Biodiesel has attracted considerable interest in recent years as an alternative, biodegradable and nonpolluting transportation fuel. Conventional alkaline process for biodiesel production are energy-consuming and generate undesirable by-products such as soaps, that make difficult the separation and purification of biodiesel.Particular attention has been dedicated to the use of lipases as biocatalysts for biodiesel production due to their favorable conversion rate obtained in gentle conditions and relatively simple downstream processing steps for the purification of biodiesel and by-products. However, comparatively to conventional chemical processes, the major obstacles for enzymatic production of biodiesel remain the cost of lipases, the relatively slower reaction rate and lipases inactivation caused by methanol and glycerol.This review evaluates the current status and perspectives for enzymatic biodiesel production and indicates the key operational variables that influence lipase activity and stability together with the technological solutions for industrial implementation of enzymatic process.     

Investigation of the resilient behavior of granular base materials with simple test apparatus

In many developing countries, where resources are at premium, thin asphalt layers or chip seals are widely used to provide a durable all weather pavement surfacing. In such pavements the role of granular layers is very important in the general performance of the structure. Pavement designs in these countries are empirical in nature and rely on simple input parameters like California Bearing Ratio (CBR) values. Although widely applicable the traditional CBR test does not provide the mechanical properties such as resilient and permanent deformation characteristics of granular road materials. This paper documents the characterization technique developed to determine the mechanical behavior of granular (sub-) base materials based on CBR test using repeated load cycles. The confining pressure developed in the complex CBR stress state is estimated using strain gauges. Finite Element analysis has been attempted to model the repeated load CBR (RL-CBR) and derive an equivalent resilient modulus. Furthermore, a large scale cyclic load triaxial test was carried out on coarse unbound granular materials (UGMs) to validate the result of the RL-CBR. The RL-CBR test reasonably estimates the resilient modulus of UGMs which can be used as an input in mechanistic pavement design analysis in the absence of triaxial testing facilities.     

Empirical correlations for the solubility of pressurant gases in cryogenic propellants

We have analyzed data published by others reporting the solubility of helium in liquid hydrogen, oxygen, and methane, and of nitrogen in liquid oxygen, to develop empirical correlations for the mole fraction of these pressurant gases in the liquid phase as a function of temperature and pressure. The data, compiled and provided by NIST, are from a variety of sources and covers a large range of liquid temperatures and pressures. The correlations were developed to yield accurate estimates of the mole fraction of the pressurant gas in the cryogenic liquid at temperature and pressures of interest to the propulsion community, yet the correlations developed are applicable over a much wider range. The mole fraction solubility of helium in all these liquids is less than 0.3% at the temperatures and pressures used in propulsion systems. When nitrogen is used as a pressurant for liquid oxygen, substantial contamination can result, though the diffusion into the liquid is slow.