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Articles 31 - 34 of 34

Full-Text Articles in Life Sciences

Air Sampling With Solid Phase Microextraction, Jacek A. Koziel, Fabio Augusto, Janusz Pawliszyn Jan 2001

Air Sampling With Solid Phase Microextraction, Jacek A. Koziel, Fabio Augusto, Janusz Pawliszyn

Jacek A. Koziel

Solid phase microextraction (SPME) presents many advantages over conventional analytical methods by combining sampling, pre-concentration and direct transfer of the VOCs into a standard gas chromatography (GC) system. Since its introduction SPME has been applied to the sampling and analysis of environmental samples including airborne VOCs and particulates. The first part of this paper presents theory of air sampling with SPME and an overview of the a few current methods for quantitative air sampling and VOC determination with SPME using grab (‘instantaneous”) and time-weighted average (TWA) modes. The second part of this paper is focused on the recent development of ...


Trophic Gradient Analysis Of Lake Powell: The 1994 Utah State University Aquatic Ecology Laboratory Analyses, Wayne Wurtsbaugh, Megan Barker, Ron Brunson, David Fogle, Scott Hawxhurst, Chad Mellison, Lis Phillips, Felipe Queiroz, Daniel Zamecnik Jan 1994

Trophic Gradient Analysis Of Lake Powell: The 1994 Utah State University Aquatic Ecology Laboratory Analyses, Wayne Wurtsbaugh, Megan Barker, Ron Brunson, David Fogle, Scott Hawxhurst, Chad Mellison, Lis Phillips, Felipe Queiroz, Daniel Zamecnik

Wayne A. Wurtsbaugh

From 9-11 April, 1994, the Aquatic Ecology Laboratory Class (FW462) of Utah State University sampled the upper reaches of Lake Powell to assess if a trophic gradient existed. We °ampled physical and chemical parameters (temperature, oxygen, conductivity, and total phosphorus), phytoplankton chlorophyll a, littoral and pelagic zooplankton biomass and composition, littoral and profundal benthic invertebrates, and fish abundance measured in the littoral zone (gill nets) and the pelagic zone (hydroacoustics). Data was collected along the upper 50 miles of the reservoir between Bullfrog and the Hite marina near the Colorado River inflow.

Our field trip was done just prior to ...


A Trophic Gradient Analysis Of Lake Powell During Spring Runnoff 1992, Wayne Wurtsbaugh, Clyde Lay, Darren Carlise, Corey Huxol, Craig Schaugaard, Beau Clements, David Beauchamp Jan 1992

A Trophic Gradient Analysis Of Lake Powell During Spring Runnoff 1992, Wayne Wurtsbaugh, Clyde Lay, Darren Carlise, Corey Huxol, Craig Schaugaard, Beau Clements, David Beauchamp

Wayne A. Wurtsbaugh

Between 26 April and 2 May 1992, students in a utah state university aquatic ecology class visited Lake Powell to do a study of trophic gradients of the reservoir. The main axis of the reservoir was surveyed, as well as less detailed analyses of Moki and Escalante Canyons. The work was conducted in collaboration with personnel from the u.s. Bureau of Reclamation headed by Bill Vernieu, and from the u.s. Geological Survey (Dick Marzolf). Some of their data appear in the physical-chemical section of this report.Each student was responsible for compiling a report on one of the ...


An Analysis Of The Limonin And Naringin Content Of Grapefruit Juice Samples Collected From Florida State Test Houses, Richard L. Mansell, Cecilia Mcintosh, Susan E. Vest Dec 1982

An Analysis Of The Limonin And Naringin Content Of Grapefruit Juice Samples Collected From Florida State Test Houses, Richard L. Mansell, Cecilia Mcintosh, Susan E. Vest

Cecilia A. McIntosh

An analysis of the limonin and naringin content of 6685 grapefruit juice samples (representing approximately 6% of all grapefruit harvested) collected from three Florida State Test Houses showed that there were statistically significant differences between the Test Houses.  There also was a statistically significant difference in the concentration of these compounds in the juice from the different cultivars of fruit sampled.  Average limonin and naringin concentrations in the juice remained fairly constant through the beginning of the season until a freeze occurred in early 1981.  Juice obtained from fruit harvested after this freeze contained decreasing amounts of limonin and increasing ...