bluuebunny/crossref_metadata_2025 huggingface dataset:
Martian Valleys: Morphology, Distribution, Age, and Origin
Authors: Pieri David C.
Published: October 2006

Branching valley networks throughout the heavily cratered terrain of Mars exhibit no compelling evidence for formation by rainfall-fed erosion. The networks are diffuse and inefficient, with irregular tributary junction angles and large, undissected intervalley areas. Rather, the deeply entrenched canyons, with blunt amphitheater terminations, cliff-bench wall topography, lack of evidence of interior erosion by flow, and clear structural control, suggest headward extension by basal sapping. The size-frequency distributions of impact craters in these valleys and in the heavily cratered terrain that surrounds them are statistically indistinguishable, suggesting that valley formation has not occurred on Mars for billions of years.
Trisodium Phosphonoformate, a New Antiviral Compound
Authors: Helgstrand E. , Eriksson B. , Johansson N. G. , Lannerö B. , Larsson A. , Misiorny A. , Norén J. O. , Sjöberg B. , Stenberg K. , Stening G. , Stridh S. , Öberg B. , Alenius S . , Philipson L.
Published: October 2006

Trisodium phosphonoformate selectively inhibits cell-free DNA polymerase activity induced by herpesvirus. The new inhibitor has an antiviral effect on herpes simplex virus types 1 and 2, pseudorables virus, and infectious bovine rhinotracheitis virus in cell culture. It has a good therapeutic activity against cutaneous herpes simplex virus infection in guinea pigs.
Genetic Analysis of Histone H4: Essential Role of Lysines Subject to Reversible Acetylation
Authors: Megee Paul C. , Morgan Brian A. , Mittman Barbara A. , Smith M. Mitchell
Published: October 2006

The nucleosome is the fundamental unit of assembly of the chromosome and reversible modifications of the histones have been suggested to be important in many aspects of nucleosome function. The structure-function relations of the amino-terminal domain of yeast histone H4 were examined by the creation of directed point mutations. The four lysines subject to reversible acetylation were essential for histone function as the substitution of arginine or asparagine at these four positions was lethal. No single lysine residue was completely essential since arginine substitutions at each position were viable, although several of these mutants were slower in completing DNA replication. The simultaneous substitution of glutamine for the four lysine residues was viable but conferred several phenotypes including mating sterility, slow progression through the G
2
/M period of the division cycle, and temperature-sensitive growth, as well as a prolonged period of DNA replication. These results provide genetic proof for the roles of the H4 amino-terminal domain lysines in gene expression, replication, and nuclear division.
Tumor Resistance to Alkylating Agents Conferred by Mechanisms Operative Only in Vivo
Authors: Teicher Beverly A. , Herman Terence S. , Holden Sylvia A. , Wang Yenyun , Pfeffer M. Raphael , Crawford James W. , Frei Emil
Published: October 2006

EMT-6 murine mammary tumors were made resistant to
cis
-diamminedichloroplatinum (II) (CDDP), carboplatin, cyclophosphamide (CTX), or thiotepa in vivo by treatment of tumor-bearing animals with the drug during a 6-month period. In spite of high levels of in vivo resistance, no significant resistance was observed when the cells from these tumors were exposed to the drugs in vitro. The pharmacokinetics of CDDP and CTX were altered in animals bearing the respective resistant tumors. The resistance of all tumor lines except for the EMT-6/thiotepa decreased during 3 to 6 months in vivo passage in the absence of drugs. These results indicate that very high levels of resistance to anticancer drugs can develop through mechanisms that are expressed only in vivo.
Organic Farming in the Corn Belt
Authors: Lockeretz William , Shearer Georgia , Kohl Daniel H.
Published: October 2006

A small minority of farmers in the Midwest produces crops on a commercial scale without using modern fertilizers and pesticides. On the basis of a 5-year study, it appears that these farmers have more in common with the majority of farmers in the region than with certain stereotypes of organic farmers. Their farming practices (other than chemical use), the size and labor requirements of their farms, and the production and profitability they achieve differ from those of conventional farmers by considerably less than might be expected on the basis of the fundamental importance of chemicals in modern agricultural production. Compared to conventional methods, organic methods consume less fossil energy and cause less soil erosion, but have mixed effects on soil nutrient status and grain protein content.
Petroleum Drilling and Production in the United States: Yield per Effort and Net Energy Analysis
Authors: Hall Charles A. S. , Cleveland Cutler J.
Published: October 2006

For the past three decades the quantity of petroleum (both oil and oil plus gas) found per foot of drilling effort in the United States for any given year can be expressed as a secular decrease of about 2 percent per year combined with an inverse function of drilling effort for that year. Extrapolation of energy costs and gains from petroleum drilling and extraction indicates that drilling for domestic petroleum could cease to be a net source of energy by about 2004 at low drilling rates and by 2000 or sooner at high drilling rates, and that the net yield will be less at higher drilling rates.
Measurements of the Imaginary Part of the Refractive Index Between 300 and 700 Nanometers for Mount St. Helens Ash
Authors: Patterson E. M.
Published: October 2006

The absorption properties, expressed as a wavelength-dependent imaginary index of refraction, of the Mount St. Helens ash from the 18 May 1980 eruption were measured between 300 and 700 nanometers by diffuse reflectance techniques. The measurements were made for both surface and stratospheric samples. The stratospheric samples show imaginary index values that decrease from approximately 0.01 to 0.02 at 300 nanometers to about 0.0015 at 700 nanometers. The surface samples show less wavelength variation in imaginary refractive index over this spectral range.
Marine Macrophytes as a Global Carbon Sink
Authors: Smith S. V.
Published: October 2006

Marine macrophyte biomass production, burial, oxidation, calcium carbonate dissolution, and metabolically accelerated diffusion of carbon dioxide across the air-sea interface may combine to sequester at least 10
9
tons of carbon per year in the ocean. This carbon sink may partially account for discrepancies in extant global carbon budgets.
Turbulent Vertical Transport due to Thin Intermittent Mixing Layers in the Stratosphere and Other Stable Fluids
Authors: Dewan Edmond M.
Published: October 2006

Pollution effects in the stratosphere and the ocean are exacerbated by buoyant stability. Turbulence in such media is confined to thin layers. To estimate vertical transport by such turbulence, one can view the situation as nature's way of simulating the finite-difference diffusion equation. This analogy finally yields a diffusivity parameter which is valid for this extremely inhomogeneous case.
Strong Interactions in Supported-Metal Catalysts
Authors: Tauster S. J. , Fung S. C. , Baker R. T. K. , Horsley J. A.
Published: October 2006

Many commercially important catalysts consist of small metal particles dispersed on inorganic oxide surfaces. Although in most cases there is no significant interaction between the metal and the support, strong bonding can be demonstrated in a recently discovered class of supported-metal catalysts. These cases typically involve group VIII metals dispersed on transition metal oxides whose surfaces can be reduced to form cations with lower valences. Spectroscopic measurements indicate that an electron is transferred from the cation (such as Ti
3+
or Nb
4+
) to the metal particle. This, in turn, leads to profound changes in the catalytic and chemisorption properties and the morphology of the metal particles.
In Vivo Receptor-Mediated Phosphorylation of a G Protein in
Dictyostelium
Authors: Gundersen Robert E. , Devreotes Peter N.
Published: October 2006

Extracellular adenosine 3′,5′-monophosphate (cAMP) serves multiple roles in
Dictyostelium
development, acting as a chemoattractant, a cell-cell signaling molecule, and an inducer of differentiation. The
Dictyostelium
G-protein α subunit Gα2 appears to be the major transducer linking the surface cAMP receptor to these intracellular responses. On stimulation of cells with cAMP, Gα2 is phosphorylated on one or more serine residues, resulting in an alteration of its electrophoretic mobility. Phosphorylation of Gα2 is triggered by increased occupancy of the surface cAMP receptor and is rapid and transient, coinciding with the time course of activation of physiological responses.
Eicosapentaenoic and Arachidonic Acids from
Phytophthora infestans
Elicit Fungitoxic Sesquiterpenes in the Potato
Authors: Bostock Richard M. , Kuc Joseph A. , Laine Roger A.
Published: October 2006

Mycelial extracts from
Phytophthora infestans
caused necrosis and elicited the accumulation of antimicrobial stress metabolites in potato tubers. A portion of the material with elicitor activity could be extracted from the mycelium by a mixture of chloroform and methanol. The most active elicitors of stress metabolites in these extracts were eicosapentaenoic and arachidonic acids. These fatty acids were found in either free or esterified form in all active fractions of the mycelial extracts .
Pheromonal Control of Dealation and Oogenesis in Virgin Queen Fire Ants
Authors: Fletcher David J. C. , Blum Murray S.
Published: October 2006

In the fire ant
Solenopsis invicta
, sexually mature virgin females are prevented from shedding their wings and becoming functional egg layers by the presence of the mated queen. Experimental data suggest that this inhibitory effect results from the action of a relatively nonvolatile primer pheromone (or pheromones) produced by the mated queen and distributed by the workers. Target ants are both virgin queens and workers.
Low-Energy Charged Particles in Saturn's Magnetosphere: Results from Voyager 1
Authors: Krimigis S. M. , Armstrong T. P. , Axford W. I. , Bostrom C. O. , Gloeckler G. , Keath E. P. , Lanzerotti L. J. , Carbary J. F. , Hamilton D. C. , Roelof E. C.
Published: October 2006

The low-energy charged particle instrument on Voyager 1 measured low-energy electrons and ions (energies ≥ 26 and ≥ 40 kiloelectron volts, respectively) in Saturn's magnetosphere. The first-order ion anisotropies on the dayside are generally in the corotation direction with the amplitude decreasing with decreasing distance to the planet. The ion pitch-angle distributions generally peak at 90°, whereas the electron distributions tend to have field-aligned bidirectional maxima outside the
L
shell of Rhea. A large decrease in particle fluxes is seen near the
L
shell of Titan, while selective particle absorption (least affecting the lowest energy ions) is observed at the
L
shells of Rhea, Dione, and Tethys. The phase space density of ions with values of the first invariant in the range ∼ 300 to 1000 million electron volts per gauss is consistent with a source in the outer magnetosphere. The ion population at higher energies (≥ 200 kiloelectron volts per nucleon) consists primarily of protons, molecular hydrogen, and helium. Spectra of all ion species exhibit an energy cutoff at energies ≳ 2 million electron volts. The proton-to-helium ratio at equal energy per nucleon is larger (up to ∼ 5 × 10
3
) than seen in other magnetospheres and is consistent with a local (nonsolar wind) proton source. In contrast to the magnetospheres of Jupiter and Earth, there are no lobe regions essentially devoid of particles in Saturn's nighttime magnetosphere. Electron pitch-angle distributions are generally bidirectional and field-aligned, indicating closed field lines at high latitudes. Ions in this region are generally moving toward Saturn, while in the magnetosheath they exhibit strong antisunward streaming which is inconsistent with purely convective flows. Fluxes of magnetospheric ions downstream from the bow shock are present over distances ≥ 200 Saturn radii from the planet. Novel features identified in the Saturnian magnetosphere include a mantle of low-energy particles extending inward from the dayside magnetopause to ∼ 17 Saturn radii, at least two intensity dropouts occurring ∼ 11 hours apart in the nighttime magnetosphere, and a pervasive population of energetic molecular hydrogen.
Insects as Selective Agents on Plant Vegetative Morphology: Egg Mimicry Reduces Egg Laying by Butterflies
Authors: Williams Kathy S. , Gilbert Lawrence E.
Published: October 2006

Experiments show that
Heliconius
butterflies are less likely to oviposit on host plants that possess eggs or egglike plant structures. These egg mimics are an unambiguous example of a plant trait evolved in response to a host-restricted group of insect herbivores.
Tectonics and Evolution of Venus
Authors: Phillips R. J. , Kaula W. M. , McGill G. E. , Malin M. C.
Published: October 2006

The global tectonics of Venus differs significantly from that of Earth, most markedly in that the surface is covered predominately by gently rolling terrain; there apparently are no features like ocean rises; the gravity is positively correlated with topography at all wavelengths; and the few highlands are estimated to be supported or compensated at a depth of approximately 100 kilometers. The surface of Venus appears to be covered mainly by an ancient crust, the high surface temperature making subduction difficult. It seems likely that well over 1 billion years ago water was destabilized at the surface and, soon after, plate tectonics ceased. The highlands appear to be actively supported, presumably as manifestations of long-enduring hot spots.
Erosion of Galilean Satellite Surfaces by Jovian Magnetosphere Particles
Authors: Johnson R. E. , Lanzerotti L. J. , Brown W. L. , Armstrong T. P.
Published: October 2006

The Galilean satellites of Jupiter—Io (J1), Europa (J2), Ganymede (J3), and Callisto (J4)—are embedded in the intense ion and electron fluxes of the Jovian magnetosphere. The effect of these particles on the icy surfaces of the outer three satellites depends on the fluxes and the efficiency of the sputtering of water ice by such particles. Recent laboratory measurements provided data on the erosion of water ice by energetic particles and showed that it occurs much faster than would be expected from normal sputtering theory. The Voyager spacecraft encounters with Jupiter provided the first measurements of ion fluxes (energies ≳ 30 kiloelectron volts) in the vicinity of the Galilean satellites. Using the laboratory sputtering data together with particle measurements from the Voyager 1 low-energy charged particle experiment, the effects of erosion on the surfaces of J2 to J4 are estimated. It is shown that the surface of Europa could be eroded by as much as 100 meters over an eon (10
9
years). Column densities of water vapor that could be produced around the three satellites from particle bombardment of their surfaces are also calculated, and the sources and losses of oxygen in the gravitationally bound gas produced by sputtering or sublimation are estimated.
Dictyota dichotoma
(Phaeophyceae): Identification of the Sperm Attractant
Authors: Müller D. G. , Gassmann G. , Boland W. , Marner F. , Jaenicke L.
Published: October 2006

Freshly released eggs of the marine brown alga
Dictyota dichotoma
secrete a substance that attracts spermatozoids. This compound has been identified as
n
-butyl-cyclohepta-2,5-diene. It is closely related to attractants in several other brown algae and confirms that a relation exists between phylogeny and attractant compounds.
Fly Ash-Derived Strontium as an Index to Monitor Deposition from Coal-Fired Power Plants
Authors: Straughan I. R. , Elseewi A. A. , Page A. L. , Kaplan I. R. , Hurst R. W. , Davis T. E.
Published: October 2006

The combustion of western U.S. coals releases significant amounts of strontium, which is relatively enriched in the fine particles of fly ash. Fly ash-derived strontium is readily absorbed by agronomic and native plant species when incorporated in soil. The strontium-87 to strontium-86 ratios of fly ash and soils were significantly different, but similar ratios were found in fly ash and plants treated with fly ash. A technique for measuring and monitoring deposition from coal-fired power plants is inferred from the enhanced plant uptake of fly ash strontium and the similarity in the isotopic ratios of fly ash and treated plants.
Magnetotactic Bacteria at the Geomagnetic Equator
Authors: Frankel R. B. , Blakemore R. P. , Torres de Araujo F. F. , Esquivel D. M. S. , Danon J.
Published: October 2006

Magnetotactic bacteria are present in fresh water and marine sediments of Fortaleza, Brazil, situated close to the geomagnetic equator. Both South-seeking and North-seeking bacteria are present in roughly equal numbers in the same samples. This observation is consistent with the hypothesis that the vertical component of the geomagnetic field selects the predominant polarity type among magnetotactic bacteria in natural environments.
The Environmental Crisis: Quantifying Geosphere Interactions
Authors: Fyfe W. S.
Published: October 2006

Because of increasing population, human activity has become a dominant process modifying the continents and their environment. Understanding the new environmental stresses includes studies of interface processes on all scales. The present scientific effort is inadequate and is not providing the data necessary for rational decision-making in critical areas, such as global energy production, land use, and resource development.
Prehistoric Raised-Field Agriculture in the Maya Lowlands
Authors: Turner B. L. , Harrison Peter D.
Published: October 2006

The ground patterns found in Pulitrouser Swamp, northern Belize, are vestiges of raised and channelized fields, types of wetland cultivation used by the ancient Maya. This form of hydraulic cultivation was apparently employed sometime between 200 B.C. and A.D. 850. The environment of the swamp, the fields and canals, and one nearby settlement, Kokeal, are described. The evidence indicates that the large number of well-defined ground patterns reported in other areas in the central Maya lowlands are probably vestiges of Maya wetland cultivation.
Chemical Signatures for Superheavy Elementary Particles
Authors: Cahn Robert N. , Glashow Sheldon L.
Published: October 2006

Models of unified fundamental interactions suggest the existence of many particles in the mass range 10 × 10
9
to 100 × 10
12
electron volts. Among these may be charged particles, X
±
, that are stable or nearly so. The X
+,
s would form superheavy hydrogen, while the X
–,
s would bind to nuclei. Chemical isolation of naturally occurring technetium, promethium, actinium, protactinium, neptunium, or americium would indicate the presence of superheavy particles in the forms RuX
–
, SmX
–
,
232
ThX
–
,
235,236,238
UX
–
,
244
PuX
–
, or
247
CmX
–
. Other substances worth searching for include superheavy elements with the chemical properties of boron, fluorine, manganese, beryllium, scandium, vanadium, lithium, neon, and thallium.
The Permeability of Plant Cell Walls as Measured by Gel Filtration Chromatography
Authors: Tepfer Mark , Taylor Iain E. P.
Published: October 2006

The permeability of plant cell walls to macromolecules may limit the ability of enzymes to alter the biochemical and physical properties of the wall. Proteins of molecular weight up to 60,000 can permeate a substantial portion of the cell wall. Measurements of wall permeability in which cells are exposed to hypertonic solutions of macromolecules may seriously underestimate wall permeability.
Disease Resistance: Incorporation into Sexually Incompatible Somatic Hybrids of the Genus
Nicotiana
Authors: Evans David A. , Flick Christopher E. , Jensen Roy A.
Published: October 2006

Somatic hybrid plants of
Nicotiana nesophila
and
N. stocktonii
with
N. tabacum
(cultivated tobacco) were produced by protoplast fusion. These combinations cannot be achieved with conventional sexual hybridization, yet are important in that the wild
Nicotiana
species are resistant to numerous diseases. Hybridity was verified by chromosome number, isoenzyme analysis, morphological characteristics, and genetic behavior. Local lesion-type resistance to tobacco mosaic virus has been observed in leaves of these somatic hybrid plants.
Kimmswick: A Clovis-Mastodon Association in Eastern Missouri
Authors: Graham Russell W. , Haynes C. Vance , Johnson Donald Lee , Kay Marvin
Published: October 2006

Stone tools characteristic of the Clovis culture have been found in direct association with bones of the American mastodon at Kimmswick, Missouri. The vertebrate fauna from Clovis components suggests a deciduous woodland and meadow habitat. Such an environmental reconstruction provides a new perspective for Clovis adaptations and the ecological tolerances of
Mammut americanum
.
A Gel Partition Model for Organic Desorption from a Pond Sediment
Authors: Freeman David H. , Cheung Leticia S.
Published: October 2006

Adsorption at the water-sediment interface has been correlated with the organic carbon content of natural sediment samples and with water-octanol partitioning equilibria. In deriving a new model for sorption in sediment, it is assumed that adsorption is due to humin-kerogen polymers associated with the clay component in the sediment. The model includes solubility parameter theory applied to solute-gel-liquid interactions and a theory of the liquid-polymer interactions that control gel swelling. Partially swollen gels are expected to exhibit impeded diffusion. These concepts are able to explain observations of limited desorption of certain organic compounds from natural sediments and soil minerals. Experiments were performed in which extractive solvents flowed through a liquid chromatographic column packed with dried estuarine and pond sediment samples and the effluent was analyzed for a test lipophilic compound, di(2-ethylhexyl) phthalate. The model predicts that the maximum desorption rate and the maximum extent of gel swelling should coincide and, conversely, that the desorption rate should be diffusion-limited if the polymer gel is only partially swollen. The conditions for maximum desorption and for diffusion-limited desorption were both observed experimentally.
Honey Bee Orientation: A Backup System for Cloudy Days
Authors: Dyer Fred C. , Gould James L.
Published: October 2006

On cloudy days, honey bees are known to navigate to familiar food sources and orient their dances accurately. This capacity could be based on a magnetic compass sense, an ability to perceive the sun or patterns of polarized light through the clouds, or on the bees' memory of the diurnal course of the sun with respect to local landmarks. Experiments pitting these alternatives against one another demonstrate that the navigational backup system of bees is based on memory.
Olfactory Recognition: A Simple Memory System
Authors: Brennan Peter , Kaba Hideto , Keverne Eric B.
Published: October 2006

Mice have an olfactory (pheromone) recognition memory located at the first relay in the sensory system. It is acquired with one-trial learning, contingent upon norepinephrine activation at mating, and lasts for several weeks. The mechanism involves Hebbian (association-dependent) changes in synaptic efficacy at dendrodendritic synapses in the accessory olfactory bulb. As a result of this memory, males made familiar by mating are recognized by the females, thereby mitigating pregnancy block. Such a memory function is biologically important to the female, as it is required to sustain pregnancy in the presence of her stud male's odors.
Pulmonary Blood Plasma Filtration in Reptiles: A "Wet" Vertebrate Lung?
Authors: Burggren Warren W.
Published: October 2006

The net loss of plasma from blood into tissues within the ventilated reptile lung is 10 to 20 times greater than that in mammalian lungs. When blood flow is reduced during breathholding by reptiles, the plasma loss stops, and a net reabsorption of fluid from the tissues occurs. Fluid movement dynamics and the relative "dryness" of the lung of reptiles and mammals thus differ in several important respects and reflect the more variable cardiovascular performance of reptiles.
Spray Aiming in Bombardier Beetles: Jet Deflection by the Coanda Effect
Authors: Eisner Thomas , Aneshansley Daniel J.
Published: October 2006

Bombardier beetles of the carabid subfamily Paussinae have a pair of flanges, diagnostic for the group, that project outward from the sides of the body. Behind each flange is a gland opening, from which the beetles discharge a hot, quinone-containing secretion when disturbed. The flanges are curved and grooved and serve as launching guides for anteriorly aimed ejections of secretion. Jets of fluid, on emergence from the gland openings, follow the curvature of the flanges and are thereby bent sharply in their trajectory and directed forward. The phenomenon is illustrative of the Coanda effect, widely applicable in engineering and responsible for the familiar tendency of liquids to curve around spouts and down the front of containers when being poured.
Helpers: Effects of Experimental Removal on Reproductive Success
Authors: Brown Jerram L. , Brown Esther R. , Brown Sheryl D. , Dow Douglas D.
Published: October 2006

Experimental removal of helpers from a communal bird population decreased the reproductive success of the reduced units. By controlling for variables that are potentially correlated with both reproductive success and unit size, this experiment establishes that helpers contribute significantly to their indirect fitness.
Infrared Observations of the Saturnian System from Voyager 2
Authors: Hanel R. , Conrath B. , Flasar F. M. , Kunde V. , Maguire W. , Pearl J. , Pirraglia J. , Samuelson R. , Cruikshank D. , Gautier D. , Gierasch P. , Horn L. , Ponnamperuma C.
Published: October 2006

During the passage of Voyager 2 through the Saturn system, infrared spectral and radiometric data were obtained for Saturn, Titan, Enceladus, Tethys, Iapetus, and the rings. Combined Voyager 1 and Voyager 2 observations of temperatures in the upper troposphere of Saturn indicate a seasonal asymmetry between the northern and southern hemispheres, with superposed small-scale meridional gradients. Comparison of high spatial resolution data from the two hemispheres poleward of 60° latitude suggests an approximate symmetry in the small-scale structure, consistent with the extension of a symmetric system of zonal jets into the polar regions. Longitudinal variations of 1 to 2 K are observed. Disk- averaged infrared spectra of Titan show little change over the 9-month interval between Voyager encounters. By combining Voyager 2 temperature measurements with ground-based geometric albedo determinations, phase integrals of 0.91 ± 0.13 and 0.89 ± 0.09 were derived for Tethys and Enceladus, respectively. The subsolar point temperature of dark material on Iapetus must exceed 110 K. Temperatures (and infrared optical depths) for the A and C rings and for the Cassini division are 69 ± 1 K (0.40 ± 0.05), 85 ± 1 K (0.10 ± 0.03), and 85 ± 2 K (0.07 ± 0.04), respectively.
Computer Networks: Prospects for Scientists
Authors: Newell Allen , Sproull Robert F.
Published: October 2006

Computer networks are an integral part of the rapid expansion of computing. Their emergence depends both on evolving communication technologies, such as packet-switching and satellites, and on diverse experiments and innovations in the software tools that exploit communications. The tools provide computer users with facilities such as electronic mail, access to remote computers, and electronic bulletin boards. Scientists can both adapt and extend tools to meet the communication needs of their work, and several networks are developing to serve particular scientific communities.
The High-Velocity Core of the Western Boundary Undercurrent at the Base of the U.S. Continental Rise
Authors: Bulfinch Douglas L. , Ledbetter Michael T. , Ellwood Brooks B. , Balsam William L.
Published: October 2006

The Western Boundary Undercurrent is a high-velocity, contour-following bottom current that flows southwesterly on the U.S. Atlantic continental margin. A high-velocity core of the Western Boundary Undercurrent is delineated by an analysis of underlying sediments, which are characterized by coarse particle sizes and efficiently aligned magnetic grains in a zone from 4440 meters at the base of the rise to 5200 meters on the adjacent abyssal plain.
Graphical Presentation of Results from Scientific Computer Models
Authors: Graedel T. E. , McGill R.
Published: October 2006

The graphical presentation of the results of complex computer model calculations is frequently as important as the computation, since it is generally through such presentations that the modeler and the modeler's audience derive the maximum amount of information. In this article graphical techniques for presenting multidimensional model results are reviewed and examples are given of the most useful forms of presentation. Color graphics is used increasingly for the presentation of model results, and three types of color displays are discussed here: the chromatic plot, the binary chromatic plot, and the ternary chromatic plot. Their use is illustrated with examples from computer modeling of air quality in the urban atmosphere.
Human Sickle Hemoglobin in Transgenic Mice
Authors: Ryan Thomas M. , Townes Tim M. , Reilly Michael P. , Asakura Toshio , Palmiter Richard D. , Brinster Ralph L. , Behringer Richard R.
Published: October 2006

DNA molecules that contain the human α- and β
s
-globin genes inserted downstream of erythroid-specific, deoxyribonuclease I super-hypersensitive sites were coinjected into fertilized mouse eggs and a transgenic mouse line was established that synthesizes human sickle hemoglobin (Hb S). These animals were bred to β-thalassemic mice to reduce endogenous mouse globin levels. When erythrocytes from these mice were deoxygenated, greater than 90 percent of the cells displayed the same characteristic sickled shapes as erythrocytes from humans with sickle cell disease. Compared to controls the mice have decreased hematocrits, elevated reticulocyte counts, lower hemoglobin concentrations, and splenomegaly, which are all indications of the anemia associated with human sickle cell disease.
Functional Properties of Rat Brain Sodium Channels Expressed in a Somatic Cell Line
Authors: Scheuer Todd , Auld Vanessa J. , Boyd Shelley , Offord James , Dunn Robert , Catterall William A.
Published: October 2006

Transfection of Chinese hamster ovary cells with complementary DNA encoding the R
IIA
sodium channel α subunit from rat brain led to expression of functional sodium channels with the rapid, voltage-dependent activation and inactivation characteristic of sodium channels in brain neurons. The sodium currents mediated by these transfected channels were inhibited by tetrodotoxin, persistently activated by veratridine, and prolonged by
Leiurus
α-scorpion toxin, indicating that neurotoxin receptor sites 1 through 3 were present in functional form. The R
IIA
sodium channel α subunit cDNA alone is sufficient for stable expression of functional sodium channels with the expected kinetic and pharmacological properties in mammalian somatic cells.
The Actin-Binding Protein Profilin Binds to PIP
2
and Inhibits Its Hydrolysis by Phospholipase C
Authors: Goldschmidt-Clermont Pascal J. , Machesky Laura M. , Baldassare Joseph J. , Pollard Thomas D.
Published: October 2006

Profilin is generally thought to regulate actin polymerization, but the observation that acidic phospholipids dissociate the complex of profilin and actin raised the possibility that profilin might also regulate lipid metabolism. Profilin isolated from platelets binds with high affinity to small clusters of phosphatidylinositol 4,5-bisphosphate (PIP
2
) molecules in micelles and also in bilayers with other phospholipids. The molar ratio of the complex of profilin with PIP
2
is 1:7 in micelles of pure PIP
2
and 1:5 in bilayers composed largely of other phospholipids. Profilin competes efficiently with platelet cytosolic phosphoinositide-specific phospholipase C for interaction with the PIP
2
substrate and thereby inhibits PIP
2
hydrolysis by this enzyme. The cellular concentrations and binding characteristics of these molecules are consistent with profilin being a negative regulator of the phosphoinositide signaling pathway in addition to its established function as an inhibitor of actin polymerization.
The Relationship Between Charge Movements Associated with
I
Ca
and
I
Na-Ca
in Cardiac Myocyte
Authors: Bridge John H. B. , Smolley John R. , Spitzer Kenneth W.
Published: October 2006

Ventricular myocytes exhibit a nifedipine-sensitive inward calcium current (
I
Ca
) and contracture when they are voltage clamped from -40 to 0 millivolt in the presence of caffeine and in the absence of extracellular sodium. However, upon repolarization they fail to relax because neither the sarcoplasmic reticulum nor the sodium-calcium exchange can reduce intracellular calcium. Sudden application of extracellular sodium during the contracture (but after repolarization) causes immediate relaxation and activates a transient inward sodium-calcium exchange current (
I
Na-Ca
), whose peak slightly precedes mechanical relaxation. The total charge carried by the nifedipine-sensitive
I
Ca
is twice the total charge carried by the transient inward
I
Na-Ca
. Assuming an exchange stoichiometry of three sodium to one calcium, these results indicate that all the calcium entering the cell during the initial depolarization is extruded by the sodium-calcium exchange.
Behavioral Sequences During Dominance Hierarchy Formation in Chickens
Authors: Chase Ivan D.
Published: October 2006

Dominance hierarchies near linearity (containing mostly transitive and few intransitive triads) are common in many species. Analysis of the possible sequences for forming dominance relationships shows that two ensure transitivity, and two others produce either transitive or intransitive triads. Experiments with chickens show that in groups of three and four they most often use the two sequences that ensure transitivity and thus linear hierarchies. Examination of such sequences may help explain the formation of near linear hierarchies in other species.
Transfer of Fermentative Microbes Between Generations in a Herbivorous Lizard
Authors: Troyer Katherine
Published: October 2006

Iguana iguana
is herbivorous throughout life and utilizes a microbial fermentation system in the elaborated hindgut to break down plant cell walls. Iguanas reared in captivity grew more slowly than wild hatchlings and failed to develop the same complex populations of fermentative microbes. Captive hatchlings fed fresh fecal material from an adult iguana acquired the complex microflora and grew as rapidly as wild hatchlings. In the field, hatchlings actively associated with adults during the first weeks of life and obtained the complex microflora during this time. Acquisition of the fermentative microflora by neonatal iguanas apparently requires direct contact with older conspecifics.
Upwelling of Hydrothermal Solutions Through Ridge Flank Sediments Shown by Pore Water Profiles
Authors: Maris Cynthia R. P. , Bender Michael L.
Published: October 2006

High calcium ion and low magnesium ion concentrations in sediment pore waters in cores from the Galápagos Mounds Hydrothermal Field on the flank of the Galápagos Spreading Center are believed to be due to a calcium-magnesium exchange reaction between circulating seawater and basement basalt. The nonlinearity of the calcium ion and magnesium ion gradients indicates that these discharging hydrothermal solutions on the ridge flank are upwelling at the rate of about 1 centimeter per year through the pelagic sediments of the Mounds Field and at about 20 centimeters per year through the hydrothermal mounds themselves.
The Mount St. Helens Volcanic Eruption of 18 May 1980: Large Short-Term Surface Temperature Effects
Authors: Robock Alan , Mass Clifford
Published: October 2006

The surface temperature effects of the 18 May 1980 eruption of Mount St. Helens Volcano were examined for 1 day immediately after the eruption; 24-hour temperature differences and Model Output Statistics errors as well as the detailed temporal evolution of surface temperature at selected stations were used. During the daytime hours immediately after the eruption, the temperature was suppressed by the volcanic plume by as much as 8°C. That night, low-level volcanic dust produced temperature enhancements of up to 8°C. These effects quickly diminished the next day as the volcanic dust cloud dissipated and moved toward the east. The net local effect of the eruption appears to be warming, in contrast to cooling which might be expected over climatic time scales.
Probing the Structure of the Deep Continental Crust
Authors: Oliver Jack
Published: October 2006

Old, buried, deformed, crystalline rocks apparently make up most of the 40-kilometer-thick continental crust. This part of the earth is poorly explored and constitutes a major frontier of modern earth science. Two techniques, seismic reflection profiling and drilling, which were developed by industry for other purposes, offer special potential for such exploration. Seismic profiling of the deep crust by COCORP (the Consortium for Continental Reflection Profiling) has already produced important information, including evidence for extensive thin-skinned thrusting of older rocks over a continental margin as the corresponding ocean basin closed. Deep drilling of crystalline rocks of the continents for scientific purposes is so far relatively unexploited in the United States but is already being carried on elsewhere. In general, big science is likely to become more important in basic geology as this frontier is explored.
Ion Beam Spectroscopy of Solids and Surfaces
Authors: Garrison Barbara J. , Winograd Nicholas
Published: October 2006

Ion beams are important new probes for characterizing the chemistry and structure of a wide variety of materials. When beams of particles with energies of ∼ 1000 electron volts are used, as in secondary ion mass spectrometry, it is possible to detect ions ejected from the top layer of the material with sensitivities well below the picogram level. A number of theoretical developments now permit analysis of the geometry of adsorbed atoms and molecules on surfaces from the angular distributions of the ejected particles. Much surface chemical information can also be deduced from ejected molecular cluster ions. In addition, the observation of clusters with weights up to nearly 20,000 atomic mass units promises to expand applications of mass spectrometry to the analysis of biomolecules and the sequencing of proteins.
Amazon Basin Soils: Management for Continuous Crop Production
Authors: Sanchez Pedro A. , Bandy Dale E. , Villachica J. Hugo , Nicholaides John J.
Published: October 2006

Technology has been developed which permits continuous production of annual crops in some of the acid, infertile soils of the Amazon Basin. Studies in Yurimaguas, Peru, show that three grain crops can be produced annually with appropriate fertilizer inputs. Twenty-one crops have been harvested during the past 8½ years in the same field, with an average annual production of 7.8 tons of grain per hectare. Soil properties are improving with continuous cultivation. The technology has been validated by local farmers, who normally practice shifting cultivation. Economic interpretations indicate large increases in annual family farm income and a high return on the investment of chemical inputs. Other promising land use alternatives include low-input crop production systems, paddy rice production in fertile alluvial soils, and pastures or agroforestry in rolling areas. Stable, continuous food crop production is an attractive alternative to shifting cultivation in humid tropical regions experiencing severe demographic pressures. For each hectare of land managed in a highly productive manner, there may be less need for clearing additional tropical forests to meet food demands.
Carbyne Forms of Carbon: Do They Exist?
Authors: Smith P. P. K. , Buseck Peter R.
Published: October 2006

Almost 15 years have passed since carbynes entered the literature as new forms of elemental carbon. They recently attracted attention as possible interstellar dust constituents and as carriers of presolar noble gases in meteorites. Their existence and that of the related mineral chaoite are questioned, and a reevaluation of previous data is suggested.
Tephra from the 1979 Soufriere Explosive Eruption
Authors: Sigurdsson Haraldur
Published: October 2006

The explosive phase of the 1979 Soufriere eruption produced 37.5 × 10
6
cubic meters (dense-rock equivalent) of tephra, consisting of about 40 percent juvenile basaltic andesite and 60 percent of a nonjuvenile component derived from the fragmentation of the 1971-1972 lava island during phreatomagmatic explosions. The unusually fine grain size, poor sorting, and bimodality of the land deposit are attributed to particle aggregation and the formation of accretionary lapilli in a wet eruption column.
Geostationary Satellite Observations of the April 1979 Soufriere Eruptions
Authors: Krueger Arthur F.
Published: October 2006

Infrared images from the geostationary satellite SMS-1 were used to study the growth of the eight major eruptions of Soufriere, St. Vincent, during April 1979. These eruptions differed considerably in growth and intensity, the most intense being that of 17 April which formed an ash cloud of 96,000 square kilometers in 4 hours. The weakest eruption formed a cloud of only 16,000 square kilometers.
Stratospheric Aerosol Effects from Soufriere Volcano as Measured by the SAGE Satellite System
Authors: McCormick M. Patrick , Kent G. S. , Yue G. K. , Cunnold D. M.
Published: October 2006

During its April 1979 eruption series, Soufriere Volcano produced two major stratospheric plumes that the SAGE (Stratospheric Aerosol and Gas Experiment) satellite system tracked to West Africa and the North Atlantic Ocean. The total mass of these plumes, whose movement and dispersion are in agreement with those deduced from meteorological data and dispersion theory, was less than 0.5 percent of the global stratospheric aerosol burden; no significant temperature or climate perturbation is therefore expected.
PDGF-Induced Activation of Phospholipase C Is Not Required for Induction of DNA Synthesis
Authors: Hill Timothy D. , Dean Nicholas M. , Mordan Lawrence J. , Lau Alan F. , Kanemitsu Martha Y. , Boynton Alton L.
Published: October 2006

Platelet-derived growth factor (PDGF) induction of DNA synthesis is believed to involve activation of phospholipase C (PLC) and subsequent accumulation of inositol 1,4,5-trisphosphate [I(1,4,5)P
3
], increase in intracellular Ca
2+
, activation of protein kinase C (PKC), and receptor down regulation. Generation of these events is triggered by the tyrosine protein kinase (TPK) activity of the PDGF receptor. The TPK inhibitor genistein blocked PDGF induction of these events, including DNA synthesis, with the exception of receptor down regulation. PDGF-induced phosphotyrosine phosphorylations, including receptor autophosphorylation, were inhibited by genistein. Removal of genistein and PDGF resulted in DNA synthesis without the occurrence of PLC activation. These findings indicate that these early events, with the exception of receptor down regulation, are not necessary for PDGF-induced DNA synthesis.
Inhibition of GTPase Activating Protein Stimulation of Ras-p21 GTPase by the K
rev
-1 Gene Product
Authors: Frech Matthias , John Jacob , Pizon Veronique , Chardin Pierre , Tavitian Armand , Clark Robin , McCormick Frank , Wittinghofer Alfred
Published: October 2006

K
rev
-1 is known to suppress transformation by
ras
. However, the mechanism of the suppression is unclear. The protein product of K
rev
-1, Rap1A-p21, is identical to Ras-p21 proteins in the region where interaction with guanosine triphosphatase (GTPase) activating protein (GAP) is believed to occur. Therefore, the ability of GAP to interact with Rap1A-p21 was tested. Rap1A-p21 was not activated by GAP but bound tightly to GAP and was an effective competitive inhibitor of GAP-mediated Ras-GTPase activity. Binding of GAP to Rap1A-p21 was strictly guanosine triphosphate (GTP)-dependent. The ability of Rap1A-p21 to bind tightly to GAP may account for K
rev
-1 suppression of transformation by
ras
. This may occur by preventing interaction of GAP with Ras-p21 or with other cellular proteins necessary for GAP-mediated Ras GTPase activity.
A G Protein Mutant That Inhibits Thrombin and Purinergic Receptor Activation of Phospholipase A
2
Authors: Gupta Sunil K. , Diez Emilio , Heasley Lynn E. , Osawa Shoji , Johnson Gary L.
Published: October 2006

The stimulation of phospholipase A
2
by thrombin and type 2 (P
2
)-purinergic receptor agonists in Chinese hamster ovary cells is mediated by the G protein G
i
. To delineate α chain regulatory regions responsible for control of phospholipase A
2
, chimeric cDNAs were constructed in which different lengths of the α subunit of G
s
(α
s
) were replaced with the corresponding sequence of the G
i
α subunit (α
i2
). When a carboxyl-terminal chimera α
s-i(38)
, which has the last 38 amino acids of α
s
substituted with the last 36 residues of α
i2
, was expressed in Chinese hamster ovary cells, the receptor-stimulated phospholipase A
2
activity was inhibited, although the chimera could still activate adenylyl cyclase. Thus, α
s-i(38)
is an active α
s
, but also a dominant negative α
i
molecule, indicating that the last 36 amino acids of α
i2
are a critical domain for G protein regulation of phospholipase A
2
activity.
Failure to Phosphorylate the Retinoblastoma Gene Product in Senescent Human Fibroblasts
Authors: Stein Gretchen H. , Beeson Mary , Gordon Lena
Published: October 2006

Heterokaryon studies suggest that senescent and quiescent human diploid fibroblasts (HDF) contain a common inhibitor of entry into S phase. DNA synthesis can be induced in senescent and quiescent HDF by fusing them with cells containing DNA viral oncogenes such as SV40 T antigen, adenovirus E1A, or human papillomavirus E7. Both senescent and quiescent HDF contained the unphosphorylated form (p110
Rb
) of the retinoblastoma protein, a putative inhibitor of proliferation. After serum stimulation, senescent HDF did not phosphorylate p110
Rb
and did not enter S phase, whereas quiescent HDF phosphorylated p110
Rb
and entered S phase. These findings, combined with the observations that T antigen, E1A, and E7 form complexes with, and presumably inactivate, unphosphorylated p110
Rb
, suggest that failure to phosphorylate p110
Rb
may be an immediate cause of failure to enter S phase in senescent HDF.
An Insertion in the Human Thyrotropin Receptor Critical for High Affinity Hormone Binding
Authors: Wadsworth Harry L. , Chazenbalk Gregorio D. , Nagayama Yuji , Russo Diego , Rapoport Basil
Published: October 2006

Thyrotropin (TSH), luteinizing hormone (LH), and chorionic gonadotropin (CG) are structurally related glycoprotein hormones, which bind to receptors that share a high degree of sequence similarity. However, comparison of the primary amino acid sequences of the TSH and LH-CG receptors reveals two unique insertions of 8 and 50 amino acids in the extracellular domain of the TSH receptor. The functional significance of these insertions were determined by site-directed mutagenesis. Deletion of the 50-amino acid tract (residues 317 to 366) had no effect on TSH binding or on TSH and thyroid-stimulating immunoglobulin (TSI) biological activities. In contrast, either deletion or substitution of the eight-amino acid region (residues 38 to 45) abolished these activities. This eight-amino acid tract near the amino terminus of the TSH receptor appears to be an important site of interaction for both TSH and TSI.