Dr. William J. Rogers Profile

Dr. William J. Rogers

at Texas A&M Univ

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Proceedings Article | 3 June 2010 Paper

Microscopic examination on cytological changes in Allium cepa and shift in phytoplankton population at different doses of Atrazine

Nabarun Ghosh, Kristen Finger, Samantha Usnick, William Rogers, A. B. Das, Don Smith

Proceedings Volume 7729, 77291W (2010) https://doi.org/10.1117/12.853238

KEYWORDS: Bridges, Microscopes, Microscopy, Statistical analysis, Agriculture, Luminescence, Molecular bridges, Bioalcohols, Organisms, Tissues

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Atrazine is a wide-range herbicide. For over 50 years, atrazine has been used as a selective broadleaf herbicide in many capacities, from pre-plant to pre-emergence to post-emergence, depending on the crop and application. Currently, 96% of all atrazine used is for commercial applications in fields for the control of broadleaf and grassy weeds in crops such as sorghum, corn, sugarcane, pineapple and for the control of undesirable weeds in rangeland. Many panhandle wells have also detected atrazine in samples taken. The concern for the public is the long-term effect of atrazine with its increasing popularity, and the impact on public health. We investigated the effect of different concentrations of atrazine on Allium cepa (onion), a standard plant test system. We established a control with the Allium bulbs grown on hydroponics culture. Varying concentrations of atrazine was used on the standard plant test system, Allium cepa grown hydroponically. The mitotic indices varied and with higher doses, we observed various chromosomal abnormalities including sticky bridges, early and late separations, and lag chromosomes with higher doses of treatments. In the second part of the experiment, 0.1ppb, 1ppb, 10ppb, and 100ppb concentrations of atrazine were applied to established phytoplankton cultures from the Lake Tanglewood, Texas. Study with a Sedgwick-Rafter counter, a BX-40 Olympus microscope with DP-70 camera revealed a gradual shift in the phytoplankton community from obligatory to facultative autotroph and finally to a parasitic planktonic community. This explains the periodic fish kill in the lakes after applications of atrazine in crop fields.

Proceedings Article | 18 May 2006 Paper

Detection of explosives using heated microcantilever sensors

Ian Nelson, Debjyoti Banerjee, William Rogers, M. Sam Mannan

Proceedings Volume 6223, 62230O (2006) https://doi.org/10.1117/12.666339

KEYWORDS: Sensors, Explosives, Explosives detection, Mercury, Adsorption, Control systems, Coating, Nanolithography, Silicon, Silicon carbide

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The objective of this study is to develop a portable micro-sensor platform for real-time detection of energetic materials (e.g., explosives) over a wide range of vapor pressures. The bending response of an electrically heated microcantilever thermal bi-morph array is used for specific detection of combustible substances using their calorimetric properties. Chemical reactions on the surface induce stress on a micro-cantilever which affects the bending and is measured in real-time using an optical apparatus. The threshold value of actuation current is found to provide a unique signature for identifying equilibrium concentration of iso-propyl alcohol, acetone and gasoline vapors at room temperature. The threshold current is found to scale with the vapor pressure of the volatile species and the ignition temperature. This shows that the sensors can be used for specific detection of different types of combustible materials. The sensor array can be used to detect, identify and monitor volatile combustible species in real time (response time in milliseconds) with the capability for redundancy checks and the ability to eliminate false positive/ false-negative results. The sensor is capable of remote monitoring on a continuous basis for indoor and outdoor applications - which protects the operator of the sensor instrument from explosive effects. The sensor design permits detection at a nominal distance away from the source without coming in contact with the contaminated surface. The sensor capability can be enhanced by specifically coating the micro-cantilever surfaces (e.g. using Dip Pen Nanolithography techniques) and can be integrated into a portable detection platform or instrument.

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