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Articles 1801 - 1830 of 2038

Full-Text Articles in Life Sciences

Evaluation Of Commercial Adjuncts For Use In Cheese Ripening: 2. Ripening Aspects And Flavor Development In Cheese Curd Slurries Prepared With Adjunct Lactobacilli, S. A. Madkor, M. El-Soda, P. S. Tong Jan 1999

Evaluation Of Commercial Adjuncts For Use In Cheese Ripening: 2. Ripening Aspects And Flavor Development In Cheese Curd Slurries Prepared With Adjunct Lactobacilli, S. A. Madkor, M. El-Soda, P. S. Tong

Dairy Science

No abstract provided.

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Food Choices For The 21st Century, Louise Berner, Nancy Childs, Constance Geiger, Carl Keen, Janet King, Janet Mcdonald, Sanford Miller, Suzanne Murphy, Harold Schmitz, Anne Shaw, Phil Tong, Connie Weaver Jan 1999

Food Choices For The 21st Century, Louise Berner, Nancy Childs, Constance Geiger, Carl Keen, Janet King, Janet Mcdonald, Sanford Miller, Suzanne Murphy, Harold Schmitz, Anne Shaw, Phil Tong, Connie Weaver

Dairy Science

In December 1997, a coalition of health professional with a wide range of expertise in science, government, education, marketing and communications, convened to discuss the challenges and implications of food choices for the 21st Century. Taking the newly published Dietary Reference Intakes (DRIs) as a framework and starting point, the members of the coalition explored how health professionals can individualize dietary recommendation to help guide people in their food choices.

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Dietary Intake And Gallbladder Disease: A Review, Marilyn Tseng, James E. Everhart, Robert S. Sandler Jan 1999

Dietary Intake And Gallbladder Disease: A Review, Marilyn Tseng, James E. Everhart, Robert S. Sandler

Kinesiology and Public Health

Objective: Dietary intake has long been looked upon as a potentially modifiable risk factor for gallbladder disease (GBD), here defined as either having gallstones or having had surgery for gallstones. This paper reviews the epidemiological evidence for an association between dietary intake and GBD, focusing on six dietary factors that have received the most attention in studies in this area: energy intake, fatty acids, cholesterol, carbohydrates and fibre, calcium and alcohol. The objectives of this review are to evaluate the potential usefulness of altering the diet to prevent GBD and to consider future research in this area. Design: We reviewed …

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Nitrogen Utilization Efficiency Of Creeping Bentgrass Genotypes, Y. Kuo, David J. Wehner, T. W. Fermanian, John M. Swiader Jan 1999

Nitrogen Utilization Efficiency Of Creeping Bentgrass Genotypes, Y. Kuo, David J. Wehner, T. W. Fermanian, John M. Swiader

Office of the Dean (CAFES) Scholarship

A greenhouse study was conducted in a hydroponic system to determine the nitrogen (N) utilization efficiency (NUE) of 14 creeping bentgrass cultivars. There were significant differences among cultivars in plant tissue dry weight, tissue N content, root absorption efficiency (RAE), and NUE. Considering all plant tissue (whole plant), 'Penncross' accumulated the highest N accompanied with the highest whole plant dry weight (WPDW), while 'Allure' accumulated the lowest total Nand WPDW than all the other cultivars. The proportion of WPDW and total N partitioned to shoots was higher than partitioned to roots in each cultivar. On a whole plant basis, 'Regent' …

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Nitrogen Utilization In Creeping Bentgrass, Y. Kuo, T. W. Fermanian, David J. Wehner Jan 1999

Nitrogen Utilization In Creeping Bentgrass, Y. Kuo, T. W. Fermanian, David J. Wehner

Office of the Dean (CAFES) Scholarship

N utilization, including plant dry weight (DW) production, total N and nitrate N (NO3-N) content accumulation, N utilization efficiency (NUE), root absorption efficiency (RAE), reduced N accumulation, and nitrate assimilation capacity (NAC) were determined for creeping bentgrass cultivars grown in hydroponic culture. Possible mechanisms affecting N utilization including nitrate reductase activity (NRA) and root morphology were also examined. Four cultivars, selected from an initial screening of creeping bentgrasses were grown under both low and high levels of N in a flowing solution culture system. The relationship between NUE and plant growth for two different creeping bentgrass cultivars was …

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Ontogenies Of Phototactic Behavior And Metamorphic Competence In Larvae Of Three Species Of Bugula (Bryozoa), Dean E. Wendt, Robert M. Woollacott Jan 1999

Ontogenies Of Phototactic Behavior And Metamorphic Competence In Larvae Of Three Species Of Bugula (Bryozoa), Dean E. Wendt, Robert M. Woollacott

Biological Sciences

The free swimming larvae of many marine invertebrates actively respond to light. Light cues can be used to regulate position in the water column and to facilitate encountering sites suitable for metamorphosis. We examined the ontogeny of larval phototaxis and the ontogeny of metamorphic competency in larvae from three congeneric species of bryozoans. Larvae of Bugula neritina are positively phototactic on emergence from the brood chamber, whereas larvae of B. simplex and B. stolonifera appear initially photoneutral when populations of larvae are examined. Larvae of all three species become photonegative with time. Temporally coincident with this change to negative phototaxis …

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Response To Dietary Dilution In An Omnivorous Freshwater Turtle: Implications For Ontogenetic Dietary Shifts, Shannon J. Mccauley, Karen A. Bjorndal Jan 1999

Response To Dietary Dilution In An Omnivorous Freshwater Turtle: Implications For Ontogenetic Dietary Shifts, Shannon J. Mccauley, Karen A. Bjorndal

Biological Sciences

Several species of freshwater turtles in the family Emydidae undergo an ontogenetic dietary shift; as juvenile turtles mature, they change from a primarily carnivorous to a primarily herbivorous diet. It has been hypothesized that this shift results from an unfavorable ratio of gut capacity to metabolic rate that prevents small reptiles from processing adequate volumes of plant material to meet their energetic demands. Effects of dietary dilution on intake were evaluated in two size classes of red-eared sliders (Trachemys scripta elegans) to test whether small reptiles have a lower capacity to compensate for low-quality diets through increased intake …

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Determining The Source Of Individuals: Multilocus Genotyping In Nonequilibrium Population Genetics, Neil Davies, Francis X. Villablanca, George K. Roderick Jan 1999

Determining The Source Of Individuals: Multilocus Genotyping In Nonequilibrium Population Genetics, Neil Davies, Francis X. Villablanca, George K. Roderick

Biological Sciences

Recently founded populations represent an enormous challenge for genetic analysis: new populations are often genetically impoverished, making it hard to find sufficiently variable markers, and what little variation is present tends to be ancestral, rendering phylogenetic methods inappropriate. Recently, novel genetic markers and new statistical analyses have made multilocus genotyping an invaluable tool in the fledgling field of nonequilibrium population genetics. Such advances are not of mere academic interest but address questions of great economic, medical and conservation significance.

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Sex Can Be Dangerous: Acoustically-Orienting Parasitoids On Field Crickets (Orthoptera: Gryllidae), Gita R. Kolluru Dec 1998

Sex Can Be Dangerous: Acoustically-Orienting Parasitoids On Field Crickets (Orthoptera: Gryllidae), Gita R. Kolluru

Biological Sciences

The Orthopterists' Society generously awarded me grants in 1995 and 1997 to conduct research on Teleogryllus oceanicus (Orthoptera: Gryllidae) on the Big Island of Hawaii. Here I report results to date from fieldwork conducted in the past few years.

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Exploitations Of Sexual Signals By Predators And Parasitoids, Marlene Zuk, Gita R. Kolluru Dec 1998

Exploitations Of Sexual Signals By Predators And Parasitoids, Marlene Zuk, Gita R. Kolluru

Biological Sciences

Signals used to attract mates are often conspicuous to predators and parasites, and their evolution via sexual selection is expected to be opposed by viability selection. Many secondary sexual traits may represent a compromise between attractiveness and avoidance of detection. Although such signal exploitation appears to be widespread, most examples come from species that use acoustic or olfactory mating signals, and relatively few cases of visual signal exploitation can be substantiated. Because males are usually the signaling sex, they are more at risk from predators or parasitoids that locate prey or hosts by sexual signals; this differential selection on the …

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Photosynthetic Parameters And Empirical Modeling Of Primary Production: A Case Study On The Antarctic Peninsula Shelf, Mark A. Moline, Oscar Schofield, Nicolas P. Boucher Nov 1998

Photosynthetic Parameters And Empirical Modeling Of Primary Production: A Case Study On The Antarctic Peninsula Shelf, Mark A. Moline, Oscar Schofield, Nicolas P. Boucher

Biological Sciences

Eight hundred photosynthesis-irradiance relationships were determined in the shelf waters adjacent to Palmer Station, Antarctica during the spring/summer periods of 1991–94. Biomass specific maximum photosynthetic rate, PBmax, and the light limited photosynthetic efficiency, αB, were poorly correlated to the physical forcing and nutrient regimes at the sampling stations. The two photosynthetic parameters, however, did strongly covary indicating the minimum irradiance required to saturate photosynthesis, Ik, was relatively constant in this highly variable environment. The variability in Ik could partially be attributed to both depth in the water column and time of the …

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Rostral-Caudal Variation In Troponin T And Parvalbumin Correlates With Differences In Relaxation Rates Of Cod Axial Muscle, Tierney M. Thys, Jason M. Blank, Fred H. Schachat Nov 1998

Rostral-Caudal Variation In Troponin T And Parvalbumin Correlates With Differences In Relaxation Rates Of Cod Axial Muscle, Tierney M. Thys, Jason M. Blank, Fred H. Schachat

Biological Sciences

Relaxation rate is an important determinant of axial muscle power production during the oscillatory contractions of undulatory locomotion. Recently, significant differences have been reported in the relaxation rates of rostral versus caudal white muscle fibers of the Atlantic cod Gadus morhua L. The present study investigates the biochemical correlates of this rostral-caudal physiological variation. Using denaturing gel electrophoresis, a series of fresh muscle samples from the dorsal epaxial muscle region was analyzed and several differences were detected. First, a gradual shift occurs in the expression of two troponin T isoforms along the length of the body. Second, rostral muscles were …

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Metamorphis Is Not A New Beginning, Jan A. Pechenik, Dean E. Wendt, Jeremiah N. Jarrett Nov 1998

Metamorphis Is Not A New Beginning, Jan A. Pechenik, Dean E. Wendt, Jeremiah N. Jarrett

Biological Sciences

No abstract provided.

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Sequence Analysis Of Bacterial Dna In The Colon Of An Andean Mummy, Massimo Ubaldi, Stefania Luciani, Isolina Marota, Gino Fornaciari, Raul J. Cano, Franco Rollo Nov 1998

Sequence Analysis Of Bacterial Dna In The Colon Of An Andean Mummy, Massimo Ubaldi, Stefania Luciani, Isolina Marota, Gino Fornaciari, Raul J. Cano, Franco Rollo

Biological Sciences

We have isolated DNA from 14 tissue samples from the internal organs of an Andean human mummy (10th–11th century A.D.) and have checked the persistence of the original human and bacterial templates using the following main approaches: 1) amino acid racemization test; 2) quantification of mitochondrial DNA copy number; 3) survey of bacterial DNA in the different organs; 4) sequence analysis of bacterial amplicons of different lengths. The results demonstrate that both the original human DNA and the DNA of the bacteria of the mummy gut are preserved. In particular, sequence analysis of two (respectively 100 and 196 bp in …

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Effect Of Larval Swimming Duration On Growth And Reproduction Of Bugula Neritina (Bryozoa) Under Field Conditions, Dean E. Wendt Oct 1998

Effect Of Larval Swimming Duration On Growth And Reproduction Of Bugula Neritina (Bryozoa) Under Field Conditions, Dean E. Wendt

Biological Sciences

A growing body of evidence indicates that even subtle events occurring during one portion of an animal's life cycle can have detrimental, and in some cases, lasting effects on later stages. Using a laboratory-field transplant design, postmetamorphic costs associated with the duration of larval swimming were investigated in the bryozoan Bugula neritina. Larvae were induced to metamorphose in the laboratory after swimming for either less than 1 h or between 23 and 24 h; colonies that developed from these two groups of larvae are referred to hereafter as "1-h colonies" and "24-h colonies," respectively. After completing metamorphosis, individuals were …

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Can Cover Crops Reduce Leafhopper Abundance In Vineyards?, Kent M. Daane, Michael J. Costello Sep 1998

Can Cover Crops Reduce Leafhopper Abundance In Vineyards?, Kent M. Daane, Michael J. Costello

Horticulture and Crop Science

In 3 of 4 vineyards we studied, late-season leafhopper density was lower on vines in cover cropped plots than in plots with no cover crops. However, the level of leafhopper reduction (about 15%) was rarely economically important and the mechanisms leading to reduction were not clear. For example, there were few differences in the number of leaf hopper predators or parasitoids on the vines in cover cropped versus no cover plots. However, there were significant between-treatment differences in vine growth. Plots with seasonwide maintenance of a cover crop and resident grasses had a reduction in vine vigor. Lower vine vigor …

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Whey Protein Edible Film Structures Determined By Atomic Force Microscope, L.E. Lent, L. S. Vanasupa, P. S. Tong Sep 1998

Whey Protein Edible Film Structures Determined By Atomic Force Microscope, L.E. Lent, L. S. Vanasupa, P. S. Tong

Dairy Science

Atomic force microscopy was used to study edible films produced from whey proteins. The films were imaged under ambient conditions with no special sample preparation. Low resolution imaging of areas from 10 μm to 150 μm on a side was performed in the contact mode. Higher resolution scans of 350 nm to 2,700 nm required use of the noncontact imaging mode. Features about the same size as the primary protein in whey, beta-lactoglobulin (7 nm), were identified in the film samples. Molecular aggregates in the range of 1 μm, reported in other studies using transmission electron microscopy of whey protein …

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Rapid Detection Of Listeria Monocytogenes In Dairy Samples Utilizing A Pcr-Based Fluorogenic 5′ Nuclease Assay, T. Cox, C. Frazier, J. Tuttle, S. Flood, L. Yagi, C. T. Yamashiro, R. Behari, C. Paszko, R. J. Cano Sep 1998

Rapid Detection Of Listeria Monocytogenes In Dairy Samples Utilizing A Pcr-Based Fluorogenic 5′ Nuclease Assay, T. Cox, C. Frazier, J. Tuttle, S. Flood, L. Yagi, C. T. Yamashiro, R. Behari, C. Paszko, R. J. Cano

Biological Sciences

The presence of Listeria monocytogenes as a dairy food contaminant is a lethal threat to dairy industrialists; therefore, products tainted with L. monocytogenes must be quickly detected and removed from production. This fluorogenic PCR-based assay was developed to rapidly detect L. monocytogenes contamination in dairy samples before a final product is distributed. The detection method employed uses a PCR primer pair and a fluorogenic TaqMan probe which bind to a region of a virulence determinant gene specific to L. monocytogenes. As the DNA target is amplified, the 5′ nuclease activity of Taq DNA polymerase hydrolyzes the internal fluorogenic probe …

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Is Population Genetics Mired In The Past?, Andrew J. Bohonak, Neil Davies, George K. Roderick, Francis X. Villablanca Sep 1998

Is Population Genetics Mired In The Past?, Andrew J. Bohonak, Neil Davies, George K. Roderick, Francis X. Villablanca

Biological Sciences

No abstract provided.

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Identification Of A Functional Homolog Of The Yeast Copper Homeostasis Gene Atx1 From Arabidopsis, Edward Himelblau, Helena Mria, Su-Ju Lin, Valeria Cizewski Culotta, Lola Penarrubia, Richard M. Amasino Aug 1998

Identification Of A Functional Homolog Of The Yeast Copper Homeostasis Gene Atx1 From Arabidopsis, Edward Himelblau, Helena Mria, Su-Ju Lin, Valeria Cizewski Culotta, Lola Penarrubia, Richard M. Amasino

Biological Sciences

A cDNA clone encoding a homolog of the yeast (Saccharomyces cerevisiae) gene Anti-oxidant 1 (ATX1) has been identified from Arabidopsis. This gene, referred to as Copper CHaperone (CCH), encodes a protein that is 36% identical to the amino acid sequence of ATX1 and has a 48-amino acid extension at the C-terminal end, which is absent from ATX1 homologs identified in animals. ATX1-deficient yeast (atx1) displayed a loss of high-affinity iron uptake. Expression of CCH in the atx1 strain restored high-affinity iron uptake, demonstrating that CCH is a functional homolog of ATX1 …

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Genetic Admixture And Gallbladder Disease In Mexican Americans, Marilyn Tseng, Robert C. Williams, Kurt R. Maurer, Moses S. Schanfield, William C. Knowler, James E. Everhart Jul 1998

Genetic Admixture And Gallbladder Disease In Mexican Americans, Marilyn Tseng, Robert C. Williams, Kurt R. Maurer, Moses S. Schanfield, William C. Knowler, James E. Everhart

Kinesiology and Public Health

Gallbladder disease is a common source of morbidity in the Mexican American population. Genetic heritage has been proposed as a possible contributor, but evidence for this is limited. Because gallbladder disease has been associated with Native American heritage, genetic admixture may serve as a useful proxy for genetic susceptibility to the disease in epidemiologic studies. The objective of our study was to examine thepossibility that gallbladder disease is associated with greater Native American admixture in Mexican Americans. This study used data from the Hispanic Health and Nutrition Examination Survey and was based on 1,145 Mexican Americans who underwent gallbladder ultrasonography …

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Invasion Genetics Of The Mediterranean Fruit Fly: Variation In Multiple Nuclear Introns, F. X. Villablanca, G. K. Roderick, S. R. Palumbi May 1998

Invasion Genetics Of The Mediterranean Fruit Fly: Variation In Multiple Nuclear Introns, F. X. Villablanca, G. K. Roderick, S. R. Palumbi

Biological Sciences

Biological invasions generally start from low initial population sizes, leading to reduced genetic variation in nuclear and especially mitochondrial DNA. Consequently, genetic approaches for the study of invasion history and population structure are difficult. An extreme example is the Mediterranean fruit fly, Ceratitis capitata (Medfly), for which successive invasions during this century have resulted in a loss of 60% of ancestral genetic variation in isozymes and 75% of variation in mitochondrial DNA. Using Medflies as an example, we present a new approach to invasion genetics that measures DNA sequence variation within introns from multiple nuclear loci. These loci are so …

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Staphylococcus Succi Nus Sp. Nov., Isolated From Dominican Amber, L. H. Lambert, T. Cox, K. Mitchell, R. A. Rosselló-Mora, C. Del Cueto, D. E. Dodge, P. Orkand, R. J. Cano Apr 1998

Staphylococcus Succi Nus Sp. Nov., Isolated From Dominican Amber, L. H. Lambert, T. Cox, K. Mitchell, R. A. Rosselló-Mora, C. Del Cueto, D. E. Dodge, P. Orkand, R. J. Cano

Biological Sciences

Two bacterial isolates, designated AMG-D1Tand AMG-D2, were recovered from 25-35-million-year-old Dominican amber. AMG-D1Tand AMG-D2 biochemically most closely resemble Staphylococcus xylosus; they differ physiologically from other staphylococci. Fatty acid analysis and comparisons with extensive databases were unable to show relatedness to any specific taxon. Moreover, AMG-D1Tand AMG-D2 contain tuberculostearic acid and meso-diaminopimelic acid, characteristic of the G+C-rich coryneform bacteria, as opposed to L-lysine characteristic of staphylococci. AMG-D1Tand AMG-D2 have a G+C ratio of 35 mol%. Phylogenetic analysis with the 16S rRNA gene indicated that AMG-D1Tand AMG-D2 were most closely …

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The Biology Of Nonfrugivorous Tephritid Fruit Flies, David H. Headrick, Richard D. Goeden Jan 1998

The Biology Of Nonfrugivorous Tephritid Fruit Flies, David H. Headrick, Richard D. Goeden

Horticulture and Crop Science

This review is the first comprehensive treatment of the biology of nonfrugivorous fruit flies of the family Tephritidae. Feeding habits of destructive and useful species, morphology of immature stages, and hypotheses regarding structural homology and the evolutionary biology of nonfrugivorous tephritids are reviewed, including zoogeography and theories involving resource heterogeneity, guild structure, resource partitioning, resource utilization, facultative niche exploitation, extrinsic and intrinsic factors, host associations, seasonal distribution and phenology, aggregative and circumnatal life history strategies, voltinism, diapause, aestivation, oviposition site, clutch size, and supernumerary oviposition.

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Influence Of Ground Cover On Spider Populations In A Table Grape Vineyard, Michael J. Costello, Kent M. Daane Jan 1998

Influence Of Ground Cover On Spider Populations In A Table Grape Vineyard, Michael J. Costello, Kent M. Daane

Horticulture and Crop Science

1. Cover crops and/or resident ground vegetation have been used in California vineyards to increase the number of predators and decrease the number of pestiferous herbivores. The most common resident predators in vineyards are spiders (Araneae). Several observational studies suggest that the addition of cover crops results in an increase in spider density and a decrease in insect pest densities. 2. To test experimentally the effects of cover crops and/or resident ground vegetation (hereafter collectively referred to as ground cover) on spider populations, a 3-year study was undertaken in a commercial vineyard. Large, replicated plots were established with and without …

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Alcohol, Hormones, And Postmenopausal Women, Matthew P. Longnecker, Marilyn Tseng Jan 1998

Alcohol, Hormones, And Postmenopausal Women, Matthew P. Longnecker, Marilyn Tseng

Kinesiology and Public Health

Many women take supplemental estrogens after menopause, a practice called hormone replacement therapy (HRT). Moderate alcohol consumption may increase estrogen levels in women receiving HRT, potentially affecting their risk for various adverse health effects. Two recent studies, however, provide no strong evidence for an effect of alcohol on hormones in postmenopausal women. The possible association between alcohol consumption and risk of cancer of the breast does not appear to be mediated by estrogens. Both estrogens and moderate alcohol consumption have been associated with a decreased risk for cardiovascular disease; however, alcohol’s beneficial effect on heart disease does not appear to …

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Terminal Restriction Fragment Patterns (Trfps), A Rapid, Pcr-Based Method For The Comparison Of Complex Bacterial Communities, Brian G. Clement, Lucia E. Kehl, Kristin L. Debord, Christopher L. Kitts Jan 1998

Terminal Restriction Fragment Patterns (Trfps), A Rapid, Pcr-Based Method For The Comparison Of Complex Bacterial Communities, Brian G. Clement, Lucia E. Kehl, Kristin L. Debord, Christopher L. Kitts

Biological Sciences

Microbial populations in complex environmental samples are difficult to characterize; current techniques are incomplete and time consuming. We investigated a polymerase chain reaction (PCR)-based method for rapidly comparing bacterial communities independent of culture or cloning. Community 16S rRNA genes were amplified and fluorescently labeled by PCR. The labeled products were digested by a restriction enzyme and the labeled, terminal restriction fragments (TRFs) were separated by electrophoresis and detected by laser-induced fluorescence on an automated gene sequencer. PCR parameters were optimized using an in vitro model community of known organisms. Community comparisons were made between deer fecal pellets, petroleum hydrocarbon-contaminated sands …

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Impact Of Temperature Acclimation On Photosynthesis In The Toxic Red-Tide Dinoflagellate Alexandrium Fundyense (Ca28), Oscar Schofield, Joseph Grzymski, Mark A. Moline, Raffael J.M. Jovine Jan 1998

Impact Of Temperature Acclimation On Photosynthesis In The Toxic Red-Tide Dinoflagellate Alexandrium Fundyense (Ca28), Oscar Schofield, Joseph Grzymski, Mark A. Moline, Raffael J.M. Jovine

Biological Sciences

This study assessed the impact of temperature on the photosynthetic activity in the dinoflagellate Alexandrium fundyense (Ca28) for cultures grown at 75 µmol photons m–2 s–1 over a range of temperatures. Increasing light intensity under static temperatures caused a 5-fold decrease in the maximum quantum yield for photosystern II (PSII) (FvlFm) Carbon fixation rates mirrored high-light depressions in (FvlFm). Cells in the presence of streptomycin showed an 83% recovery in (FvlFm); therefore, only a minor proportion of the decline in (FvlFm)was attributable …

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Photoadaptive Response During The Development Of A Coastal Antarctic Diatom Bloom And Relationship To Water Column Stability, Mark A. Moline Jan 1998

Photoadaptive Response During The Development Of A Coastal Antarctic Diatom Bloom And Relationship To Water Column Stability, Mark A. Moline

Biological Sciences

The ratio of the xanthophyll pigments diadinoxanthin and diatoxanthin to chlorophyll a [(DD + DT): Chl a] was used as a photoadaptive index during the development of a large Antarctic diatom bloom. This index was found to track fluctuations in the incident solar irradiance and the in situ light field over a 3-order-magnitude change in the water column biomass. Depth profiles of the (DD + DT): Chl a ratio showed that the upper mixed layer, assessed by physical data, was in fact stable over the course of the month. Diel experiments conducted over the same period showed a delayed …

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Vibrational Sum Frequency Spectroscopy Of Surfactants And Phospholipids Monolayers At Liquid-Liquid Interfaces, B. L. Smiley, R. A. Walker, D. E. Gragson, T. E. Hannon, G. L. Richmond Jan 1998

Vibrational Sum Frequency Spectroscopy Of Surfactants And Phospholipids Monolayers At Liquid-Liquid Interfaces, B. L. Smiley, R. A. Walker, D. E. Gragson, T. E. Hannon, G. L. Richmond

Chemistry and Biochemistry

Work from our laboratory on vibrational sum frequency spectroscopic investigations of molecular ordering at the carbon tetrachloride-water interface is reviewed. Simple charged surfactants adsorbed at the liquid-liquid interface are seen to induce alignment of interfacial water molecules to a degree which is dependent on the induced surface potential. Saturation of water molecule alignment occurs at a surfactant surface concentration corresponding to a calculated surface potential of approximately 160 mV. In complementary studies, the relative degree of hydrocarbon chain ordering within monolayers of symmetric phosphatidylcholines of different chain lengths is inferred by the relative signal contributions of the methyl and methylene …

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