Human hydration level monitoring using embedded piezoresistive microcantilever sensors.

Embedded piezoresistive microcantilever (EPM) sensors were used to measure osmolality changes in both saliva mimic solutions and true human saliva. Osmolality changes in human saliva or urine may prove to be reliable, simple, and easy to measure markers for tracking human hydration levels. EPM sensors used in these experiments show good response to osmolality changes in both NaCl-based saliva mimic solutions and to human saliva. The addition of zero-point offset correction to EPM sensors allows for tracking of saliva osmolality changes with high accuracy. Also, the same EPM sensors exhibit a large enough range of osmolality response to make them potentially suitable for urine or blood serum osmolality monitoring.

Scanning force microscopy studies of the colonization and growth of A. ferrooxidans on the surface of pyrite minerals.

We have used the technique of scanning force microscopy (SFM) for studying the interaction of the bacteria A. ferrooxidans with the surface of the mineral pyrite. These bacteria are important to study with regard to acidification of streams and the environmental impact of such acidification. A. ferrooxidans cells readily colonize the pyrite surface, forming a tight mineral seal between the cell and the pyrite substrate. These bacteria subsequently may grow under pH neutral conditions, biooxidizing the underlying pyrite; this process creates etch pits in the pyrite. On average, these etch pits are 1.2 microns in lateral dimension and approximately 220 nm deep.

Hydration level monitoring using embedded piezoresistive microcantilever sensors.

A new MEMS based sensor technology, embedded piezoresistive microcantilever (EPM) sensors, may be useful in the real-time monitoring of hydration levels in athletes or other individuals whose activities may result in dehydration. In these devices, organic polymers or functionalized polymeric materials respond to osmolality changes in a person's saliva by expanding or contracting volumetrically. These volumetric changes are measured by tiny piezoresistive microcantilevers embedded in the polymeric material. In this report, we have tested a prototype device utilizing UV crosslinked poly(vinyl acetate) as the active sensing material. This device was able to reliably respond to 1% changes in sodium chloride concentration in solution or alternately to 1% changes in relative humidity.

Investigation of the antigen antibody reaction between anti-bovine serum albumin (a-BSA) and bovine serum albumin (BSA) using piezoresistive microcantilever based sensors.

A new microsensor application based on piezoresistive microcantilever technology has been used to study the interaction of anti-bovine serum albumin (a-BSA) with bovine serum albumin (BSA). A thin layer of BSA attached to a glass slide was used as the active sensing layer for the detection of a-BSA in solution. This design produced a large, consistent cantilever deflection when exposed to the analyte. In this system, the cantilever deflection is measured as a simple resistance change in the piezoresistive channel within the cantilever. In a second set of experiments, 3:1 BSA:PEO protein/polymer blended substrates were used as the active sensing layer for the detection of a-BSA in an aerosol delivery. A distinct signature for the analyte, separate from the water vapor carrier, is obtained for this system.

Exploring the structure of a hydrogen cyanide polymer by electron spin resonance and scanning force microscopy.

Aqueous solutions of potassium cyanide and ammonium hydroxide are known to yield a heterogeneous cyanide polymer, containing paramagnetic sites and biologically significant substructures including polypeptides. Here, such solutions were used to prepare various samples of polymer for study by X-band and W-band electron spin resonance (ESR), scanning electron microscopy (SEM), and scanning force microscopy (SFM). Elemental composition of a typical sample of the polymer was C-35.2%, N-38.47%, 0-14.51%, and H-4.13%, exposing the polymer to 6M HCl hydrolyzed portions of the polymer and released glycine and traces of other amino acids. The X-band ESR spectra consist of a single slightly asymmetric line centered at g = 2.003; spin concentration measurements made at X-band using a nitroxide radical standard yield approximate radical concentrations of 10(18) spins/gm. W-band ESR indicates the presence of a single rhombic paramagnetic site with g(x) = 2.0025, g(y) = 2.0030, and g(z) = 2.0048 and the possibility of small 14N hyperfine splittings. The ESR spin echo studies yield a longitudinal relaxation time, Tl of 75 microS and a short-phase memory relaxation time, Tm, of about 300 nS. Scanning electron microscopy studies of the polymer show that it is made of ellipsoidal particles about one micron in size. The particles tend to clump together when suspended in aqueous solution. The particles disperse and dissolve in dimethyl sulfoxide (DMSO); when these solutions dry on microscope slides, optical microscopy shows a branched island morphology for the polymer. This morphology is reminiscent of snowflakes and is identified as dendritic. Phase contrast SFM of the dendritic arms show a striking segregation and ordering of various components of the polymer. Paramagnetic sites are conserved in the series of steps leading to dendritic structures.

Analysis of peptides synthesized in the presence of SAz-1 montmorillonite and Cu(2+) exchanged hectorite.

We have investigated the synthesis of oligopeptides containing glycine and tyrosine in the presence of the clay minerals montmorillonite (non-exchanged, SAz-1) and Cu(2+) exchanged hectorite. In both cases, homopolymers of the two amino acids are formed, as are mixed peptides. In the case of Cu(2+) hectorite, mixed oligopeptides up to trimers are detected in small amounts. For montmorillonite, heterogeneous oligopeptides up to hexamers are detected. Our experiments indicate montmorillonite is more effective in promoting oligopeptide formation than Cu(2+) hectorite. Analysis of the oligopeptide sequences formed on the montmorillonite surfaces indicates preferential synthesis of certain Gly-Tyr sequences over others.

The interaction of biological molecules with clay minerals: a scanning force microscopy study.

We have used the technique of scanning force microscopy (SFM) to investigate the reaction of both amino acids and activated nucleotides in the presence of the clay mineral Cu(II)-exchanged hectorite. Using simulated prebiotic heating and wetting cycles, we have shown that the clay mineral acts to adsorb, concentrate, and subsequently catalyze the polymerization of these biological monomers into short peptides and oligonucleotides. The presence of the Cu(II) cations within the clay intergallery regions, and at surface step edges and cracks, is crucial for the observed reactions to occur. Clay minerals such as hectorite may have thus played an important role in the evolution of biologically viable molecules on the prebiotic earth.

Site-specific prebiotic oligomerization reactions of glycine on the surface of hectorite.

Condensation reactions of the amino acid glycine on the surface of Cu(II)-exchanged hectorite are investigated using the technique of scanning force microscopy. Prebiotic conditions are simulated using alternate wetting and heating cycles. Concentration, immobilization, and subsequent polymerization resulting in glycine oligomers are seen to occur primarily at step edges or faults in the topmost layer. Condensation reactions also occur within tiny micropores or defects in the topmost layer. These reactions are facilitated by the availability of intergallery metal cations at the step edges or pores in the surface region.

Psychiatric stigma in the military.

There is potential for the stigma of mental health care to directly affect an active duty member's career. The authors are aware of cases in which fear of adverse career consequences has led service members to avoid needed mental health care. In order to investigate the legitimacy of this fear, the authors surveyed 252 USN and USMC commanding and executive officers concerning their attitudes about service members who had received mental health and other services; 138 responded. Overall the responses were neutral and there were relatively few negative evaluations of service members who had received services. Military health care providers should take an active role in diminishing the stigma of mental illness, and in allaying fears of adverse career consequences for seeking care.

Shifts of dependency in the resolution of folie à deux.

We have presented a case of folie à deux in which the wife was the primary (dominant) partner and the husband the secondary (submissive) partner. The husband's symptoms seemed to have resolved as his dependency shifted from his wife back to his mother. Treatment is recommended by deliberately shifting dependencies only when there is advantage in doing so. For most patients, the aim should be independence.

The Medical Association of Georgia's Impaired Physicians Program. Review of the first 1000 physicians: analysis of specialty.

Risk factors for the disease of chemical dependence, or addiction to alcohol and/or drugs, for physicians have not been clearly defined. Yet chemical dependence is believed to be a leading occupational hazard for physicians. This study compares the specialties of a population of physicians assessed for the presence of impairment (study group, N = 1000) with the distribution of specialties for all US physicians. Only 21 of the total were found to be free of impairment from chemical dependence or psychiatric disease, while 920 physicians (92.0%) had a primary diagnosis of chemical dependence, and 59 (5.9%) had a major psychiatric illness. Anesthesia and family and general practice were found to be overrepresented in the population under study, as compared with all US physicians. There were significant differences between the study group and all US physicians with respect to age, sex, and practice activity status. The authors urge these apparent high-risk specialties, as well as the medical profession itself, to develop control or prevention strategies that will reduce risk for chemical dependence through education, early identification, intervention, and treatment of those individuals with the disease.