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Final Report for the SEED Project: ''Inexpensive Chemresistor Sensors for Real Time Ground Water Contamination Measurement''

Description: This report details some proof-of-principle experiments we conducted under a small, one year ($100K) grant from the Strategic Environmental Research and Development Program (SERDP) under the SERDP Exploratory Development (SEED) effort. Our chemiresistor technology had been developed over the last few years for detecting volatile organic compounds (VOCs) in the air, but these sensors had never been used to detect VOCs in water. In this project we tried several different configurations of the chemiresistors to find the best method for water detection. To test the effect of direct immersion of the (non-water soluble) chemiresistors in contaminated water, we constructed a fixture that allowed liquid water to pass over the chemiresistor polymer without touching the electrical leads used to measure the electrical resistance of the chemiresistor. In subsequent experiments we designed and fabricated probes that protected the chemiresistor and electronics behind GORE-TEX{reg_sign} membranes that allowed the vapor from the VOCs and the water to reach a submerged chemiresistor without allowing the liquids to touch the chemiresistor. We also designed a vapor flow-through system that allowed the headspace vapor from contaminated water to be forced past a dry chemiresistor array. All the methods demonstrated that VOCs in a high enough concentration in water can be detected by chemiresistors, but the last method of vapor phase exposure to a dry chemiresistor gave the fastest and most repeatable measurements of contamination. Answers to questions posed by SERDP reviewers subsequent to a presentation of this material are contained in the appendix.
Date: April 1, 2002
Creator: HUGHES, ROBERT C.; DAVIS, CHAD E. & THOMAS, MICHAEL L.
Partner: UNT Libraries Government Documents Department

The impact of solution agglomeration on the deposition of self-assembled monolayers

Description: Self-assembled monolayers (SAMS) are commonly produced by immersing substrates in organic solutions containing trichlorosilane coupling agents. Unfortunately, such deposition solutions can also form alternate structures including inverse micelles and lamellar phases. The formation of alternate phases is one reason for the sensitivity of SAM depositions to factors such as the water content of the deposition solvent. If such phases are present, the performance of thin films used for applications such as minimization of friction and stiction in micromachines can be seriously compromised. Inverse micelle formation has been studied in detail for depositions involve 1H-, 1H-, 2H-, 2H-perfluorodecyltrichlorosilane (FDTS) in isooctane. Nuclear magnetic resonance experiments have been used to monitor the kinetics of hydrolysis and condensation reactions between water and FDTS. Light scattering experiments show that when hydrolyzed FDTS concentrations reach a critical concentration, there is a burst of nucleation to form high concentrations of spherical agglomerates. Atomic force microscopy results show that the agglomerates then deposit on substrate surfaces. Deposition conditions leading to monolayer formation involve using deposition times that are short relative to the induction time for agglomeration. After deposition, inverse micelles can be converted into lamellar or monolayer structures with appropriate heat treatments if surface concentrations are relatively low.
Date: April 17, 2000
Creator: BUNKER,BRUCE C.; CARPICK,ROBERT W.; ASSINK,ROGER A.; THOMAS,MICHAEL L.; HANKINS,MATTHEW G.; VOIGT,JAMES A. et al.
Partner: UNT Libraries Government Documents Department

Minimization of Childhood Maltreatment Is Common and Consequential: Results from a Large, Multinational Sample Using the Childhood Trauma Questionnaire

Description: This article discusses a study to investigate 3 aspects of minimization, as defined by the Childhood Trauma Questionnaire's (CTQ) Minimization-Denial (MD) scale: 1) its prevalence; 2) its latent structure; and finally 3) whether minimization moderates the CTQ's discriminative validity in terms of distinguishing between psychiatric patients and community volunteers.
Date: January 27, 2016
Creator: MacDonald, Kai; Thomas, Michael L.; Sciolla, Andres F.; Schneider, Beacher; Pappas, Katherine; Bleijenberg, Gijs et al.
Partner: UNT College of Arts and Sciences