Bearing Fatigue Life Tests of Two Advanced Base Oils for Space Applications Under Vacuum and Atmospheric Environments

Four series of rolling-element bearing fatigue tests were conducted with 51104 size thrust ball bearings with three balls made from SUJ2 (AISI 52100) steel lubricated with two advanced synthetic base oils used for space applications. The test lubricants were perfluoropolyether (PFPE) and multiply alkyated cyclopentane (MAC). Each oil was tested with bearings under vacuum and atmospheric environments. The bearings were tested at a maximum Hertzian stress of 4 GPa on the inner and outer races. The outer race was rotated at a speed of 250 rpm. A pool lubrication system was used. Fresh lubricant was used for each test bearing. Testing in vacuum conditions was at 5 × 10^?2 Pa. The test oils were analyzed to determine whether changes occurred as a result of operating in air and in a vacuum. In a vacuum environment, the PFPE 815Z oil exhibited a longer fatigue life than the MAC 2001A oil. However, in an air environment, the MAC 2001A oil had a longer L₁₀ fatigue life than the PFPE 815Z oil. The fatigue life tests of PFPE 815Z oil in vacuum resulted in a longer L₁₀ life than when tested in an air environment. In an air environment, hydrogen fluoride was generated in the bearing tests with the PFPE 815Z oils. Under vacuum conditions, hydrogen fluoride was not generated with the PFPE 815Z oil, resulting in longer bearing fatigue lives. The fatigue life tests of MAC 2001A oil in a vacuum resulted in shorter L₁₀ fatigue life than in an air environment. The shorter life was attributed to the lower elastohydrodynamic oil film formation with the MAC 2001A oil because of a higher operating temperature and decomposition of the oil in vacuum.     

Novel Detection of Nasty Bugs,Prevention Is Better than Cure

Hospital-acquired infections (HAIs) are a growing concern around the world. They contribute to increasing mortality and morbidity rates and are an economic threat. All hospital patients have the potential to contract an HAI, but those with weakened or inferior immune systems are at highest risk. Most hospital patients will contract at least one HAI, but many will contract multiple ones. Bacteria are the most common cause of HAIs and contribute to 80–90% of all HAIs, with Staphylococcus aureus, Clostridium difficile, Escherichia coli, Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae accounting for the majority. Each of these bacteria are highly resistant to antibiotics and can produce a protective film, known as a biofilm, to further prevent their eradication. It has been shown that by detecting and eradicating bacteria in the environment, infection rates can be reduced. The current methods for detecting bacteria are time consuming, non-specific, and prone to false negatives or false positives. Aptamer-based biosensors have demonstrated specific, time-efficient and simple detection, highlighting the likelihood that they could be used in a similar way to detect HAI-causing bacteria.     

Structure activity relationships of monocyte chemoattractant proteins in complex with a blocking antibody

Monocyte chemoattractant proteins (MCPs) are cytokines that direct immune cells bearing appropriate receptors to sites of inflammation or injury and are therefore attractive therapeutic targets for inhibitory molecules. 11K2 is a blocking mouse monoclonal antibody active against several human and murine MCPs. A 2.5 A structure of the Fab fragment of this antibody in complex with human MCP-1 has been solved. The Fab blocks CCR2 receptor binding to MCP-1 through an adjacent but distinct binding site. The orientation of the Fab indicates that a single MCP-1 dimer will bind two 11K2 antibodies. Several key residues on the antibody and on human MCPs were predicted to be involved in antibody selectivity. Mutational analysis of these residues confirms their involvement in the antibody-chemokine interaction. In addition to mutations that decreased or disrupted binding, one antibody mutation resulted in a 70-fold increase in affinity for human MCP-2. A key residue missing in human MCP-3, a chemokine not recognized by the antibody, was identified and engineering the preferred residue into the chemokine conferred binding to the antibody.     

Occurrence,Characterization, and Antimicrobial Susceptibility of Salmonella enterica in Slaughtered Pigs in Sardinia

The aim of this study was to determine Salmonella occurrence in slaughtered finishing pigs and piglets and in slaughterhouse environment in order to characterize the isolates with phenotypical (antimicrobial testing) and molecular (PFGE, MLVA) methods. Nine slaughterhouses located in Sardinia were visited. Six hundred and eight samples collected from 106 pigs and 108 environmental samples were collected and analyzed. Salmonella was isolated in 65 of 504 (12.9%) samples from finishing pigs, with an occurrence of 15.1% in colon content, 12.7% in lymph nodes and liver, and 11.1% in carcass surface samples. Salmonella was never detected in piglets. The combined results of serotyping and PFGE showed a possible self‐contamination in 71.5% of Salmonella positive carcasses of lymph nodes and/or colon content carriers, pointing out the role of healthy pigs for carcass contamination. A significantly higher (P < 0.05) occurrence was detected in finishing pigs of EC countries origin (23%) than in pigs of local farms (8%). Salmonella was also detected in 3.7% of environmental samples. The most prevalent serovar was S. Anatum, followed by S. Rissen, S. Derby, and monophasic S. Typhimurium. Resistance to at least 3 antimicrobial was observed in 97.1% of strains and 7 different patterns of multiple resistance were identified. The most common resistance was detected against sulphonamide compounds. A strict slaughterhouse application of hygiene standards is essential to control the risk of Salmonella contamination.     

Construction of phase diagram up to 2 GPa and 200°C for thermo‐reversible gel lubricants by diamond anvil cell

The objective of this research was to make the phase diagram up to 2.0 GPa and 200°C of thermo‐reversible gel lubricants (TR Gel‐Lube) using diamond anvil cell (DAC). TR Gel‐Lube consisted of base fluid and gelling agent. The most important characteristic of TR Gel‐Lube is the reversible change of its physical state. The DAC is able to concerning visual observation of the sol/gel and liquid/viscoelastic–solid transition at high pressure and high temperature. DAC enables the visual observation of the photoelastic effect in order to generate local principal stress difference under the compression field for liquid/viscoelastic‐solid transition of base oil poly‐α‐olefin. The direct observation for sol/gel transition of TR Gel‐Lube at high pressure was also made possible. The phase diagram corresponding to transition from liquid to viscoelastic solid for base oil poly‐α‐olefin and sol to gel for TR Gel‐Lube was made by using DAC. Copyright © 2009 John Wiley & Sons, Ltd.     

Kinetics feasibility study of alcohol sulfate esterification reactions in tropospheric aerosols

Sulfate esters have recently been identified in the secondary organic aerosol (SOA) formed in the photooxidation of biogenic hydrocarbons both in laboratory and under ambient atmospheric conditions. In the present study, the kinetics feasibility of direct reactions between alcohols and sulfuric acid to form sulfate esters in aerosol particles is explored. Nuclear magnetic resonance methods were used to monitor the bulk reaction kinetics of sulfate esterification reactions for a number of simple alcohols. The experiments were carried out at various sulfuric acid concentrations and a range of temperatures in order to estimate the rate constants of such reactions in aerosols under the previously studied laboratory conditions and under ambient atmospheric conditions. The measured rate constants did not depend greatly on the identity of the reactant alcohol, but increased strongly as a function of the sulfuric acid concentration, as predicted by excess acidity theory. Because of the strong temperature dependence of the rate constants for the direct reaction of alcohols with sulfuric acid, it appears that these reactions are kinetically infeasible for low temperature upper tropospheric sulfuric aerosols. For lower tropospheric SOA, it appears that the aerosol acidity is rarely high enough such that these reactions are likely to be responsible for the presence of sulfate esters in SOA.     

Persistence in children's reading behavior as a function of N length and attribution retraining.

In an investigation using 30 children (Grades 5-7) who were experiencing reading difficulties, procedures involving partial reinforcement and attribution retraining were assessed in terms of their relative effectiveness in developing reading persistence. Two levels of a partial reinforcement variable, termed N length (the number of successive failures prior to success), were factorially combined with the presence or absence of attribution retraining. A 5th condition received success-only training. These manipulations occurred in the context of a reading task presented on 3 successive days. A posttest measure of persistence revealed that the number of difficult sentences attempted by the Ss was increased jointly by both independent variables. However, Ss receiving success-only training or partial reinforcement with nonsuccessive failure (N lengths of 1), without the benefit of attribution retraining, did not show improvement from pretest to posttest. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the formation of fibrous capsule and fluid space around machined and porous blood plasma clot coated titanium

Machined and machined submicron porous titanium, with and without a thin blood plasma coating (100 nm), were implanted for 7 or 28 days in subcutaneous pockets on the back of the rat. After explantation the specimens were analyzed by light microscopy with respect to thickness of the fibrous capsule, the fluid space width between implants and fibrous capsule, and formation of blood vessels. The results at 7 days indicate a thinnest fluid space for the plasma clot coated porous titanium surface, and the spaces vanished at the light microscopic level after 28 days outside all the analyzed surfaces. The thickness of the fibrous capsule increased outside the different surfaces at 7-28 days, and in this respect no significant differences were observed between the different surfaces at any time. Analysis of neovascularization showed that the number of vessels and proportion of vessels in the fibrous capsule increased with time at all surfaces, except machined Ti where the number instead decreased from 7 to 28 days. The average distance between the blood vessels and the fluid space increased with time for all types of surfaces. The results in the present study indicate that the healing process around titanium can be modulated by porosity and thin pre-prepared plasma coatings.     

SMA: A Self-Monitored Adaptive Cache Warm-Up Scheme for Microprocessor Simulation

This paper presents an adaptive technique for warming up caches in sampled microprocessor simulation. The simulator monitors the warm-up process of the caches and decides when the caches are warmed up based on simple heuristics. This mechanism allows the warm up length to be adaptive to cache sizes and benchmark variability characteristics. With only half or one-third of the average warm-up length of previous methods, the proposed Self-Monitored Adaptive (SMA) warm-up technique achieves CPI results very similar to previous methods. On average SMA exhibits only 0.2% warm-up error in CPI. For simulating small caches, the SMA technique can reduce the warm-up overhead by an order of magnitude compared to previous techniques. Finally, SMA gives the user some indicator of warm-up error at the end of the cycle-accurate simulation that helps the user to gauge the accuracy of the warm-up.