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Biomedical subjects

M E Warren

Publications and source records attributed to M E Warren.

11 recordsLinked to original sources
PubMed2006

Containerless measurements of thermophysical properties of Zr54Ti8Cu20Al10Ni8.

High-temperature measurement and study of reactive materials can be difficult with conventional processing methods because contamination from the measuring apparatus and container walls can adversely affect measurements. Containerless processing techniques can be employed to isolate samples from their environment, reducing contamination. Benefits of containerless processing include reduction in heterogeneous nucleation sites, which in turn delays the onset of solidification and allows the study of meta-stable undercooled phases. However, property measurements must use noncontact methods as well. Fortunately, several optical-based methods have been developed and successfully employed to measure thermophysical properties, including surface tension, viscosity, density, and thermal expansion. Combining these techniques with the electrostatic levitator (ESL) located at the NASA Marshall Space Flight Center (MSFC) has resulted in an excellent facility to perform containerless material studies which support microgravity flight projects. Currently, studies of the thermophysical properties of liquid quasi-crystal forming and related alloys ranging from superheated to deeply undercooled states are being done with this facility in support of the NASA-funded flight project Quasi-crystalline Undercooled Alloys for Space Investigation (QUASI). While the primary purpose of these measurements is to support planned flight experiments, they are also a desirable resource for future manufacturing considerations and for fundamental insight in the physics of icosahedral ordering in liquids and solids. Presented here is an overview of the contactless measuring methods for surface tension, viscosity, density, and thermal expansion applied to Zr54Ti8Cu20Al10Ni8, for the superheated and meta-stable undercooled liquid phases, in support of QUASI.

Journal Article↗
PubMed2000

Tandem mass spectrometric analysis of aspergillus niger pectin methylesterase: mode of action on fully methyl-esterified oligogalacturonates.

The substrate specificity and the mode of action of Aspergillus niger pectin methylesterase (PME) was determined using both fully methyl-esterified oligogalacturonates with degrees of polymerization (DP) 2-6 and chemically synthesized monomethyl trigalacturonates. The enzymic activity on the different substrates and a preliminary characterization of the reaction products were performed by using high-performance anion-exchange chromatography at neutral pH. Electrospray ionization tandem MS (ESI-MS/MS) was used to localize the methyl esters on the (18)O-labelled reaction products during the course of the enzymic reaction. A. niger PME is able to hydrolyse the methyl esters of fully methyl-esterified oligogalacturonates with DP 2, and preferentially hydrolyses the methyl esters located on the internal galacturonate residues, followed by hydrolysis of the methyl esters towards the reducing end. This PME is unable to hydrolyse the methyl ester of the galacturonate moiety at the non-reducing end.

Aspergillus niger↗
PubMed1998

On-probe solid-phase extraction/MALDI-MS using ion-pairing interactions for the cleanup of peptides and proteins.

Samples originating from biological sources often contain a complex mixture of inorganic salts, buffers, chaotropic agents, surfactants/detergents, preservatives, and other solubilizing agents. However, the presence of these contaminants virtually ensures the failure of any subsequent analysis of the sample by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Sample cleanup procedures, therefore, must be performed prior to MALDI-MS analysis. This paper reports a probe-surface derivatization method that greatly simplifies this sample preparation process. MALDI probes possessing self-assembled monolayers (SAMs) terminated with ionic functional groups can rapidly extract peptides/proteins via ionic interactions from < or = 1-microL volumes of sample solutions placed directly on their surface. We have found that MALDI probes modified in this manner are a practical solution for analyzing very small volumes of peptide/protein solutions contaminated with high levels of inorganic salts, buffers, detergents, chaotropic agents, and other solubilizing agents.

Indicators and Reagents↗
PubMed1994

Medicare Transaction System: platform for change.

This article provides an overview of the Medicare Transaction System (MTS), a Health Care Financing Administration (HCFA)-wide initiative to be implemented starting in 1997 which will develop a national, standard, integrated, government-owned, contractor-operated Medicare claims processing system that will meet the challenges confronting Medicare over the next 2 decades. The authors discuss MTS goals and objectives, major features, how it will work, standardization efforts being undertaken in support of the initiative, contracting efforts involved, and project status.

Centers for Medicare and Medicaid Services, U.S.↗
PubMed1993

Case report: thrombosis of the inferior vena cava--an unusual presentation of protein C deficiency.

In children, venous thrombosis is uncommon and this is true particularly for one of the inferior vena cava. Recurrent superficial venous thrombosis is a well-recognized presenting symptom of Protein C deficiency but thrombosis of the inferior vena cava as the initial manifestation of this condition has only rarely been reported. We present a case of a 13-year-old boy in whom the first indication of Protein C deficiency was an isolated thrombosis in the intra-hepatic inferior vena cava noted on a routine ultrasound examination.

Adolescent↗
PubMed1991

Motor variables correlated with the hand-to-mouth maneuver in stroke patients.

This study investigated the relationship between each of three independent variables and the completion of the hand-to-mouth maneuver in 23 hemiparetic stroke patients. The independent variables were elbow-extensor muscle tone (graded using the Modified Ashworth Scale); active elbow-flexion range-of-motion deficit measured without the influence of gravity; and elbow-flexion strength measured without the influence of gravity with a hand-held dynamometer. The hand-to-mouth maneuver was graded according to the degree of completion using a three-level ordinal scale. Spearman (rs) correlations demonstrated a significant relationship between the extent of completion of the hand-to-mouth maneuver and both the active elbow-flexion-range deficit (rs = -.853) and the elbow-flexor muscle force (rs = .829). The correlation of the maneuver with elbow-extensor muscle tone (rs = -.063) was not significant, but the relationship may have been influenced by the fact that only a minority of subjects had elevated tone, and that elevation was minimal. The result suggest that both active-movement deficits and muscle strength may be important to upper extremity function.

Arm↗
PubMed1979

Detection of mutagens in the urine of rats following topical application of hair dyes.

Mutagens were detected in the urine of rats following topical application of two commercial oxidative-type hair dye preparations. The test system used was induction of back mutation with the bacterial tester strain TA1538, a histidine-dependent mutant of Salmonella typhimurium. Various quantities of dye were applied to the shortened hair on the backs of the test animals. The dye was allowed to remain on the hair for 20 min after application and was then removed by shampooing and thorough rinsing. Maximal levels of mutagenic activity occurred with urine collected during first 24 h following dye application, and a dose--response was observed when increasing volumes of mutagenic urine were tested. Mutagens were detected in rat urine after intraperitoneal injection, and also after topical application of 4-nitro-o-phenylenediamine, one of the constituents of the hair-dye preparations.

Administration, Topical↗