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Articles 1 - 19 of 19

Full-Text Articles in Life Sciences

Probing The Intermolecular Hydrogen Bonding Of Water Molecules At The Ccl4/Water Interface In The Presence Of Charges Soluble Surfactant, D. E. Gragson, G. L. Richmond Dec 1997

Probing The Intermolecular Hydrogen Bonding Of Water Molecules At The Ccl4/Water Interface In The Presence Of Charges Soluble Surfactant, D. E. Gragson, G. L. Richmond

Chemistry and Biochemistry

The molecular structure and hydrogen bonding of water molecules at the CCl4/water interface in the presence of a charged soluble surfactant has been explored in this study using vibrational sum frequency generation. By examining OH stretching modes that are highly sensitive to the local hydrogen bonding environment it is found that water molecules at the CCl4/water interface both in the presence and absence of a charged soluble surfactant are predominantly in a tetrahedral arrangement much like the structure ofice. Isotopic dilution studies have been employed to further characterize this icelike interfacial structure. Ablueshift ofapproximately120 cm-1 ...


Review Of Sexual Selection: Mate Choice And Courtship In Nature By James L. Gould And Carol Grant Gould, Marlene Zuk, Gita R. Kolluru, Kurt A. Mckean Dec 1997

Review Of Sexual Selection: Mate Choice And Courtship In Nature By James L. Gould And Carol Grant Gould, Marlene Zuk, Gita R. Kolluru, Kurt A. Mckean

Biological Sciences

No abstract provided.


Sources Of Variability In The Column Photosynthetic Cross Section For Antarctic Coastal Waters, Mark A. Moline, Herve Claustre, Barbara B. Prezelin Nov 1997

Sources Of Variability In The Column Photosynthetic Cross Section For Antarctic Coastal Waters, Mark A. Moline, Herve Claustre, Barbara B. Prezelin

Biological Sciences

Using a highly resolved Long Term Ecological Research (LTER) database collected near Palmer Station, Antarctica, from 1991 to 1994, the variability in the column photosynthetic cross section (ψ*, m2 g Chl a -1) was analyzed. The relationship between the daily integrated primary production rates versus the product of surface irradiance (QPAR(0*)) and the integrated chlorophyll content (down to 0.1% QPAR(0*)) gave a ψ* value of 0.0695 m 2 g Chl a-1 (r2 = 0.85, p 2 g Chl a-1) with extreme values extending over a fiftyfold range (0.009-0.488 ...


Tree Root Response To Circling Root Barriers, Laurence R. Costello, Clyde L. Elmore, Scott J. Steinmaus Nov 1997

Tree Root Response To Circling Root Barriers, Laurence R. Costello, Clyde L. Elmore, Scott J. Steinmaus

Biological Sciences

Root system size and distribution were measured for Raywood ash (Fraxinus oxycarpa 'Raywood') and Lombardy poplar (Populus nigra 'Italica') planted with and without circling root barriers. Trees with circling barriers had fewer numbers of roots than controls (no barriers), but mean root diameters were similar. Root depth 30 cm outside barriers was greater for trees with barriers, but at 90 and 150 cm away, depth was equivalent to controls. Roots tended to grow toward the soil surface after growing under the barriers. No consistent differences in root response to any of the four types of barriers tested were found for ...


Liquid-Liquid Immiscibility In Lipid Monolayers, John P. Hagen, Harden M. Mcconnell Oct 1997

Liquid-Liquid Immiscibility In Lipid Monolayers, John P. Hagen, Harden M. Mcconnell

Chemistry and Biochemistry

Some binary lipid mixtures form coexisting liquid phases when spread at the air/water interface. This work describes the pressure–composition phase diagrams of binary mixtures of four unsaturated phosphatidylcholines with dihydrocholesterol. These four binary mixtures have critical compositions of approximately fifty mole percent, and average critical exponents of 0.25±0.07. The data can also be approximated by a regular solution thermodynamic model, yielding parameters for the non-ideality of these mixtures.


Dry Weight Production And Nitrogen Efficiency Traits In Kentucky Bluegrass Cultivars In Nutrient Solution And Soil, Anthony F. Bertauski, John M. Swiader, David J. Wehner Sep 1997

Dry Weight Production And Nitrogen Efficiency Traits In Kentucky Bluegrass Cultivars In Nutrient Solution And Soil, Anthony F. Bertauski, John M. Swiader, David J. Wehner

Office of the Dean (CAFES) Scholarship

Because of the importance of such factors as appearance and vigor in turf management, genetic selection of Kentucky bluegrass (Poa pratensis L.) is often conducted at high levels of N application. This process can mask potential differences between genotypes in N efficiency, especially under low N levels. The case is also made that because soil is the medium in which plant selections ultimately must perform, cultivar screening for N efficiency in solution culture should relate to results in soil. This study was conducted to evaluate N-utilization efficiency (NUE – mg plant dry matter mg-1 plant N) in six bluegrass cultivars ...


Isolation, Characterization, And Diversity Of Microorganisms From Amber, Raúl J. Cano Jul 1997

Isolation, Characterization, And Diversity Of Microorganisms From Amber, Raúl J. Cano

Biological Sciences

Retrieval of viable bacteria from fossil material dating from the Oligocene back to the Miocene opens the opportunity to study the evolution of prokaryotes through the evolution of their DNA, their physiology, and their ecology. This unique system in which ancient organisms and their genes may be compared directly, rather than by inference, with modern homologues is without precedent. Clearly, however, confirmation of the fossil origin of such isolates must be made in a manner that would allay reasonable skepticism. Present approaches of verification of authenticity of fossil DNA are either arbitrary or potentially unconvincing, because of their dependence on ...


Dietary Iron And Recurrence Of Colorectal Adenomas, Marilyn Tseng, Robert S. Sandler, E. Robert Greenberg, Jack S. Mandel, Robert W. Haile, John A. Baron Jun 1997

Dietary Iron And Recurrence Of Colorectal Adenomas, Marilyn Tseng, Robert S. Sandler, E. Robert Greenberg, Jack S. Mandel, Robert W. Haile, John A. Baron

Kinesiology

Previous research suggests that iron acts as a prooxidant to increase the risk of colorectal neoplasia. This study examined effects of dietary intake of iron on colorectal adenoma recurrence using data from an antioxidant clinical trial. All subjects were free of polyps at study entry but had at least one adenoma removed within the 3 months before enrollment. Follow-up colonoseopies were conducted after 1 and 4 years. Patients who developed one or more adenomatous polyps between years 1 and 4 were classified as cases; all others were controls. Dietary iron intake at baseline and at the end of the study ...


Communicating The Role Of Science In Managing Giant Sequoia Groves, Douglas D. Piirto, Robert R. Rogers, Mary C. Bethke May 1997

Communicating The Role Of Science In Managing Giant Sequoia Groves, Douglas D. Piirto, Robert R. Rogers, Mary C. Bethke

Natural Resources Management and Environmental Sciences

Management of giant sequoia groves has been and continues to be a hotly debated issue. The debate has reached Congress, with all parties seeking resolution as to what constitutes an ecologically and publicly acceptable management approach. Determining the correct management approach and communicating that approach to the general public is the crux of the problem. Emerging concepts and principles of forest ecosystem management may provide a mechanism to seek resolution of these management problems related to giant sequoia. The Memorandum of Understanding between the members of the recently formed Giant Sequoia Ecology Cooperative provided the impetus for the development of ...


Comparison Of Sampling Methods Used To Estimate Spider (Araneae) Species Abundance And Composition In Grape Vineyards, Michael J. Costello, Kent M. Daane Apr 1997

Comparison Of Sampling Methods Used To Estimate Spider (Araneae) Species Abundance And Composition In Grape Vineyards, Michael J. Costello, Kent M. Daane

Horticulture and Crop Science

The effectiveness of 3 methods for sampling spiders in grape vineyards was tested. The sampling methods were as follows: (1) a drop-cloth method in which spiders were dislodged from a 5.1-m2 area of grapevine onto a drop cloth, (2) a funnel method in which spiders were dislodged into a 0.74-m2 funnel, and (3) a D-vac method in which 50 sections of grapevine (30-cm sections, total area of 5.4 m2) were suctioned with a gasoline-powered vacuum. Data from all sampling methods were adjusted for area sampled and compared with an absolute control, in which foliage from an entire ...


Using Impedance For Mechanical Conditioning Of Tomato Transplants To Control Excessive Stem Elongation, Lauren C. Garner, Thomas Björkman Mar 1997

Using Impedance For Mechanical Conditioning Of Tomato Transplants To Control Excessive Stem Elongation, Lauren C. Garner, Thomas Björkman

Horticulture and Crop Science

Mechanical stimulation is known to control excessive stem elongation in highdensity tomato (Lycopersicon esculentum Mill.) transplants. Mechanical stimulation using physical impedance provided height control equivalent to that obtained using brushing. Low-cost materials can be used to apply the impedance. Mylar film in a plastic frame was equivalent to expensive acrylic sheets in its effect on plant height (40 mm shorter than nontreated, a 40% reduction in the elongation rate during the treatment period), stem diameter (18% thicker), and biomass (14% lighter) when they applied a pressure of 66 N·m-2• Stem elongation was not reduced ifless pressure was applied (25 ...


Brushing Pansy (Viola Tricolor L.) Transplants: A Flexible, Effective Method For Controlling Plant Size, Lauren C. Garner, F. A. Langton Feb 1997

Brushing Pansy (Viola Tricolor L.) Transplants: A Flexible, Effective Method For Controlling Plant Size, Lauren C. Garner, F. A. Langton

Horticulture and Crop Science

Though brushing is an effective method for controlling excessive elongation in many species, its adoption by the commercial plug transplant industry will depend on the ease and flexibility of its application. Brushing was applied to pansy (Viola tricolor L.) seedlings growing at a density of 1500 plants m-2 by daily stroking with 20/20 gauge netting. In dose response experiments, final petiole length appeared to approach a lower asymptote as number of brush strokes increased, and the number of strokes required to give near full reduction in length increased under environmental conditions favouring extension growth. Ten or 20 daily ...


Molecular Engineering Of Side-Chain Liquid Crystalline Polymers By Living Polymerizations, Coleen Pugh, Alan L. Kiste Jan 1997

Molecular Engineering Of Side-Chain Liquid Crystalline Polymers By Living Polymerizations, Coleen Pugh, Alan L. Kiste

Chemistry and Biochemistry

“Living” anionic, cationic, metalloporphyrin and ring-opening metathesis polymerizations have been used to prepare well-defined side-chain liquid crystalline homopolymers, block and graft copolymers and statistical copolymers. This paper analyzes their successes and failures by reviewing the mechanistic aspects and experimental conditions of each type of polymerization, and identifies other classes of mesogenic monomers that could be polymerized in a controlled manner in the future. The emerging structure/property relationships are then identified using well-defined SCLCPs in which only one structural feature is varied while all others remain constant.

The thermal transitions of liquid crystalline polymethacrylates, polynorbomenes and poly(viny1 ether)s ...


Behavior Of Female Eretmocerus Sp. Nr. Californicus Howard (Aphelinidae: Hymenoptera) Attacking Bemisa Argentifolii Bellows And Perring (Aleyrodidae: Homoptera) On Two Native Californian Weeds, David H. Headrick, Thomas S. Bellows, Jr., Thomas M. Perring Jan 1997

Behavior Of Female Eretmocerus Sp. Nr. Californicus Howard (Aphelinidae: Hymenoptera) Attacking Bemisa Argentifolii Bellows And Perring (Aleyrodidae: Homoptera) On Two Native Californian Weeds, David H. Headrick, Thomas S. Bellows, Jr., Thomas M. Perring

Horticulture and Crop Science

Searching and ovipositional behaviors by female Eretmocems sp. nr. californicus Howard on Bemisia argentifolii Bellows and Perring infesting velvetleaf, Abutilon theophrasti Medic. (Malavaceae), and telegraph weed, Heterotheca grandiflora Nutt. (Asteraceae), were quantified. Adult female behaviors were described and quantified for E. sp. nr. californicus to establish a behavioral time budget analysis. Females departed from leaves of A. theophrasti in 83.3% of the trials, and of those that remained and searched for hosts, walking speeds averaged 0.29 mm/s. Females departed from the leaves of H. grandiflora in 44.4% of the trials, and those remaining readily searched for ...


Review Of A Manual Of California Vegetation By J. Sawyer & T. Keeler-Wolf, David J. Keil Jan 1997

Review Of A Manual Of California Vegetation By J. Sawyer & T. Keeler-Wolf, David J. Keil

Biological Sciences

No abstract provided.


Palmer Lter: Stable Interannual Successional Patterns Of Phytoplankton Communities In The Coastal Waters Off Palmer Station, Antarctica, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield Jan 1997

Palmer Lter: Stable Interannual Successional Patterns Of Phytoplankton Communities In The Coastal Waters Off Palmer Station, Antarctica, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield

Biological Sciences

No abstract provided.


Instar Susceptibility Of The Monarch Butterfly (Danaus Plexippus) To The Neogregarine Parasite, Ophryocystis Elektroscirrha, Kingston L. H. Leong, Michael A. Yoshimura, H. K. Kaya, H. Williams Jan 1997

Instar Susceptibility Of The Monarch Butterfly (Danaus Plexippus) To The Neogregarine Parasite, Ophryocystis Elektroscirrha, Kingston L. H. Leong, Michael A. Yoshimura, H. K. Kaya, H. Williams

Biological Sciences

The susceptibility of the monarch butterfly (Danaus plexippus) larvae to the neogregarine parasite, Ophryocystis elektroscirrha, was tested in the laboratory. Spore loads recovered from infected monarch butterflies were directly related to the inoculum level, larval stage of the host, and spore age. There was a linear relationship between spores ingested by first instar larvae and spore concentration. Larvae feeding on leaves treated with 0, 50, 500, 5000, or 50,000 spores averaged 0, 0, 193, 457, or 1,255 spores, respectively, on the abdomens of the adult butterflies. When first, third, and fifth instar larvae were given 14.5 spores ...


Shortfin Mako, Isurus Oxyrinchus, Impaled By Blue Marlin, Makaira Nigricans (Teleostei: Istiophoridae), Harry L. Fierstine, Gregor M. Cailliet, Julie A. Neer Jan 1997

Shortfin Mako, Isurus Oxyrinchus, Impaled By Blue Marlin, Makaira Nigricans (Teleostei: Istiophoridae), Harry L. Fierstine, Gregor M. Cailliet, Julie A. Neer

Biological Sciences

No abstract provided.


An Atlantic Blue Marlin, Makaira Nigricans, Impaled By Two Species Of Billfishes (Teleostei:Istiophoridae), Harry L. Fierstine Jan 1997

An Atlantic Blue Marlin, Makaira Nigricans, Impaled By Two Species Of Billfishes (Teleostei:Istiophoridae), Harry L. Fierstine

Biological Sciences

Billfishes (Istiophoridae and Xiphiidae) are notorious for driving their rostra into animate and inanimate objects, a behavior usually resulting in transverse fracture of the bill and leaving the distal segment embedded (Gudger, 1940; Frazier et aI., 1994). Some billfishes recover from this loss because there are records ofapparently healthy fish with missing rostra (Frazier et aI., 1994). Generally only one rostral fragment is found in each object, but multiple stabbings have been reported. For example, fragments of three swordfish bills were discovered in a whale during flensing (Jonsgard, 1962), several "marlin" spears were found impaled in bales of rubber that ...