bluuebunny/crossref_metadata_2025 huggingface dataset:
Identity Elements for Specific Aminoacylation of Yeast tRNA
Asp
by Cognate Aspartyl-tRNASynthetase
Authors: Pütz Joern , Puglisi Joseph D. , Florentz Catherine , Giegé Richard
Published: October 2006

The nucleotides crucial for the specific aminoacylation of yeast tRNA
Asp
by its cognate synthetase have been identified. Steady-state aminoacylation kinetics of unmodified tRNA transcripts indicate that G34, U35, C36, and G73 are important determinants of tRNA
Asp
identity. Mutations at these positions result in a large decrease (19- to 530-fold) of the kinetic specificity constant (ratio of the catalytic rate constant
k
cat
and the Michaelis constant
K
m
) for aspartylation relative to wild-type tRNA
Asp
. Mutation to G10-C25 within the D-stem reduced
k
cat
/
K
m
eightfold. This fifth mutation probably indirectly affects the presentation of the highly conserved G10 nucleotide to the synthetase. A yeast tRNA
Phe
was converted into an efficient substrate for aspartyl-tRNA synthetase through introduction of the five identity elements. The identity nucleotides are located in regions of tight interaction between tRNA and synthetase as shown in the crystal structure of the complex and suggest sites of base-specific contacts.
Pioneer Venus Results: An Overview
Authors: Donahue T. M.
Published: October 2006

A summary is presented of the scientific results obtained during the first 120 days of the Pioneer Venus orbiter mission and produced by analysis of multiprobe data as of about 1 April 1979. The summary is essentially a guide to the material presented in the reports devoted to Pioneer Venus results in this issue of
Science
.
Laboratory Corroboration of the Pioneer Venus Gas Chromatograph Analyses
Authors: Oyama V. I. , Carle G. C. , Woeller F. , Pollack J. B.
Published: October 2006

Laboratory simulation and tests of the inlet sampling system and columns of the Pioneer Venus gas chromatograph show that the sensitivity to argon is not diminished after the column regeneration step, argon isotopes are not separated, oxygen and sulfur dioxide are not produced in the inlet sampling system from sulfur trioxide, and sulfur trioxide is not formed from sulfur dioxide and oxygen. Comparisons of the volatile inventory of Venus and Earth imply similar efficiencies of early outgassing but a lower efficiency for later outgassing in the case of Venus. The high oxidation state of the Venus atmosphere in the region of cloud formation may prohibit the generation of elemental sulfur particles.
Temperature, Cloud Structure, and Dynamics of Venus Middle Atmosphere by Infrared Remote Sensing from Pioneer Orbiter
Authors: Taylor F. W. , Diner D. J. , Elson L. S. , McCleese D. J. , Martonchik J. V. , Delderfield J. , Bradley S. P. , Schofield J. T. , Gille J. C. , Coffey M. T.
Published: October 2006

Further results from the Venus orbiter radiometric temperature experiment (VORTEX) on the Pioneer orbiter are presented. These are used to characterize the three-dimensional temperature field, the cloud structure, and the dynamics of the 60- to 130-kilometer altitude region of the Venus atmosphere. One of the new discoveries is a "dipole" structure at high latitudes, with two hot spots rotating around the pole, surrounded by banks of cold cloud.
Nature of the Ultraviolet Absorber in the Venus Clouds: Inferences Based on Pioneer Venus Data
Authors: Pollack James B. , Ragent Boris , Boese Robert , Tomasko Martin G. , Blamont Jacques , Knollenberg Robert G. , Esposito Larry W. , Stewart A. Ian , Travis Lawrence
Published: October 2006

Several photometric measurements of Venus made from the Pioneer Venus orbiter and probes indicate that solar near-ultraviolet radiation is being absorbed throughout much of the main cloud region, but little above the clouds or within the first one or two optical depths. Radiative transfer calculations were carried out to simulate both Pioneer Venus and ground-based data for a number of proposed cloud compositions. This comparison rules out models invoking nitrogen dioxide, meteoritic material, and volatile metals as the source of the ultraviolet absorption. Models involving either small (∼1 micrometer) or large (∼10 micrometers) sulfur particles have some serious difficulties, while ones invoking sulfur dioxide gas appear to be promising.
Samarium-Neodymium Systematics in Kimberlites and in the Minerals of Garnet Lherzolite Inclusions
Authors: Basu Asish R. , Tatsumoto Mitsunobu
Published: October 2006

The initial ratios of neodymium-143 to neodymium-144 in kimberlites ranging in age between 90 × 10
6
to 1300 × 10
6
years from South Africa, India, and the United States are different from the corresponding ratios in the minerals of peridotite inclusions in the kimberlites but are identical to the ratios in the basaltic achondrite Juvinas at the times of emplacement of the respective kimberlite pipes. This correlation between the kimberlites and Juvinas, which represents the bulk chondritic earth in rare-earth elements, strongly indicates that the kimberlite's source in the mantle is chondritic in rare-earth elements and relatively primeval in composition.
Remote Detection of Biological Stresses in Plants with Infrared Thermometry
Authors: Pinter P. J. , Stanghellini M. E. , Reginato R. J. , Idso S. B. , Jenkins A. D. , Jackson R. D.
Published: October 2006

Green leaves of mature sugar beets infected with
Pythium aphanidermatum
and cotton infected with
Phymatotrichum omnivorum
had midday radiant leaf temperatures 3° to 5°C warmer than adjacent plants with no sign of disease. The temperature difference persisted under varying conditions of soil moisture and could be used to detect biological stress imposed by these soilborne root-rotting fungi.
Earthquake-Caused Landslides: A Major Disturbance to Tropical Forests
Authors: Garwood Nancy C. , Janos David P. , Brokaw Nicholas
Published: October 2006

Earthquakes occasionally denude large areas of tropical forest: for example, 54 square kilometers in Panama in 1976 and 130 square kilometers in New Guinea in 1935. Earthquake rates in New Guinea, but not in Panama, are sufficiently high so that substantial areas of disturbed, nonclimax forest may accumulate. In New Guinea, earthquake-caused landslides are as important as tree falls in the disturbance regime.
Gravitational Lens of the Sun: Its Potential for Observations and Communications over Interstellar Distances
Authors: Eshleman Von R.
Published: October 2006

The gravitational field of the sun acts as a spherical lens to magnify the intensity of radiation from a distant source along a semi-infinite focal line. A spacecraft anywhere on that line in principle could observe, eavesdrop, and communicate over interstellar distances, using equipment comparable in size and power with what is now used for interplanetary distances. If one neglects coronal effects, the maximum magnification factor for coherent radiation is inversely proportional to the wavelength, being 100 million at 1 millimeter. The principal difficulties are that the nearest point on the focal half-line is about 550 times the sun-earth distance, separate spacecraft would be needed to work with each stellar system of interest, and the solar corona would severely limit the intensity of coherent radiation while also restricting operations to relatively short wavelengths.
West Antarctic Ice Sheet: Present-Day Thinning and Holocene Retreat of the Margins
Authors: Thomas Robert H.
Published: October 2006

Retreat of the margins of the West Antarctic ice sheet associated with rising sea level during the last 15,000 years is the main cause for the thinning of the ice sheet by approximately 300 meters. The West Antarctic ice sheet during the late Wisconsin was at least 30 percent wider than it is today, and Holocene retreat of its margins has added about 6 meters to the world sea level.
Keeping a Cool Head: Honeybee Thermoregulation
Authors: Heinrich Bernd
Published: October 2006

At high ambient temperatures, honeybees regulate head temperature by evaporative cooling of regurgitated honeycrop contents. Thoracic temperature is secondarily stabilized as heat flows from thorax to head by means of passive conduction and physiological facilitation resulting from accelerated blood flow. The mechanism permits flight at the extraordinarily high ambient temperature of 46°C without overheating the head and thorax despite prodigious amounts of heat produced as a by-product of flight metabolism. In contrast, at low ambient temperatures, thoracic rather than head temperature is regulated; no liquid is regurgitated, and the head is heated passively by conduction both in flight and while stationary.
Sociobiology of Bank Swallows: Reproductive Strategy of the Male
Authors: Beecher Michael D. , Beecher inger Mornestam
Published: October 2006

Male bank swallows pursue a mixed reproductive strategy. As previously documented, they form monogamous pair bonds with females with whom they will share parental duties of nest-building, incubation, and feeding of the young. In addition, however, they routinely seek promiscuous copulations with other females, both before and after pair-bonding.
Cytochrome c Oxidase as the Receptor Molecule for Chemoaccumulation (Chemotaxis) of
Euglena
Toward Oxygen
Authors: Miller S. , Diehn B.
Published: October 2006

Chemoaccumulation of
Euglena gracilis
toward oxygen was selectively inhibited, without concomitant effects on cell motility, by cyanide (10
-6
to 10
-4
molar) and carbon monoxide (5 × 10
-5
to 5 × 10
-4
molar). Above these concentrations, motility of the cell was impaired and the chemosensory response was inhibited. Azide did not affect chemoaccumulation even at 5 × 10
-3
molar. It is concluded that cytochrome a
3
serves as the chemoreceptor molecule for oxygen-mediated behavioral responses in
Euglena
.
Collagenase Immunolocalization in Cultures of Rheumatoid Synovial Cells
Authors: Woolley David E. , Harris Edward D. , Mainardi Carlo L. , Brinckerhoff Constance E.
Published: October 2006

Cultures of rheumatoid synovial cells that have been enzymatically dissociated and are adherent to a culture vessel are morphologically heterogeneous. When these cells are cultured on a collagenous substrate for 2 to 6 days at 37°C in serum-free medium, they produce collagenase. A monospecific antibody to human collagenase has localized the enzyme extracellularly around cytoplasmic extensions of dendritic cells and intracellularly within a few macrophage-like and fibroblast-like cells.
High-Grade Fuels from Biomass Farming: Potentials and Constraints
Authors: Weisz Paul B. , Marshall John F.
Published: October 2006

The key parameters controlling the productivity and the cost of net high-grade fuel from a system for biomass agriculture and conversion are analyzed. Performance depends sensitively on a "symbiotic" interaction between agronomy and technology. The conditions for obtaining net productivity and costs are explored for U.S. grain alcohol as a reference point. Currently practiced technology consumes more high-grade fuel than it generates. Some potentials and constraints for future systems, including use of other plant species and conversion systems, are explored.
Radar Measurement of the Upper Atmosphere
Authors: Walker James C. G.
Published: October 2006

In the last two decades large radars have proved to be powerful instruments for the measurement of the properties of the upper atmosphere. These radars were used initially to measure properties of the ionosphere by the Thomson scattering technique at heights above 100 kilometers. Careful interpretation of the power and spectrum of radar echoes yielded data on electron and ion densities and temperatures as well as on bulk motion of the ionospheric plasma, all as functions of height and time. More recent developments have made it possible to measure wind speeds and the structure of turbulence in the stratosphere and mesosphere at altitudes below 100 kilometers.
Fiber, Food, Fuel, and Fungal Symbionts
Authors: Ruehle John L. , Marx Donald H.
Published: October 2006

Virtually all plants of economic importance form mycorrhizae. These absorbing organs of higher plants result from a symbiotic union of beneficial soil fungi and feeder roots. In forestry, the manipulation of fungal symbionts ecologically adapted to the planting site can increase survival and growth of forest trees, particularly on adverse sites. Vesicular-arbuscular mycorrhizae, which occur not only on many trees but also on most cultivated crops, are undoubtedly more important to world food crops. Imperatives for mycorrhizal research in forestry and agriculture are (i) the development of mass inoculum of mycorrhizal fungi, (ii) the interdisciplinary coordination with soil management, plant breeding, cultivation practices, and pest control to ensure maximum survival and development of fungal symbionts in the soil, and (iii) the institution of nursery and field tests to determine the circumstances in which mycorrhizae benefit plant growth in forestry and agri-ecosystems.
Heterogeneous Atmospheric Reactions: Sulfuric Acid Aerosols as Tropospheric Sinks
Authors: Baldwin Alan C. , Golden David M.
Published: October 2006

The collisional reaction probabilities of several atmospheric species on bulk sulfuric acid surfaces indicate that heterogeneous processes may be important in tropospheric chemistry.
Solid Electrolyte Behavior of NaMgF
3
: Geophysical Implications
Authors: O'Keeffe M. , Bovin J.-O.
Published: October 2006

In the solid state, NaMgF
3
transforms smoothly with temperature into a solid electrolyte phase; the conductivity is 130 siemens per meter just below the melting point. The isostructural compound MgSiO
3
should behave similarly under conditions obtaining in the earth's lower mantle, and so it is expected that the electrical conductivity in that region is ionic rather than electronic.
Electrical Origin of the Outbursts on Io
Authors: Gold Thomas
Published: October 2006

The outbursts seen on Jupiter's satellite Io have been described as volcanic eruptions. They may instead be the result of large electric currents flowing through hot spots on Io and causing evaporation of surface materials. A strictly periodic behavior would then be expected.
New Experimental Data on Atmospheric Propagation
Authors: Shannon R. R. , Ceccon C. , Smith W. S. , Metheny W. , Philbrick R.
Published: October 2006

An experiment has been performed to measure directly the effect of atmospheric turbulence on spherical wave propagation of light on a vertical path. The results permit determination of the magnitude of the effect at a variety of locations and under different conditions. Agreement is found with the functional form predicted by the inertial theory of turbulence. General agreement is found with scattering data obtained by a low-frequency radar and with predictions of some turbulence profile models. The results also demonstrate some reasons for poor agreement with time integrating sensors.
Working Women Scientists and Engineers
Authors: Vetter Betty M.
Published: October 2006

About 80 percent of women trained in science or engineering are in the labor force, but many are employed outside of their fields. Most who withdraw from the labor force do so temporarily, and about half do not take a career break even when they have small children. Factors affecting labor force participation are student status, highest degree level, parental status and age of children, and field of degree. Employment opportunities are restricted in some fields, and women have higher unemployment rates and lower earnings than men. Some policy changes would improve opportunities for women, and better data are needed to monitor their participation in science and technology.
Direct Measurement of Solar Luminosity Variation
Authors: Willson R. C. , Duncan C. H. , Geist J.
Published: October 2006

Two rocket flights of an absolute pyrheliometer, separated by 30 months, indicate an increase in solar luminosity (solar constant) of 0.4 percent. The significance of this result is considered in light of the instrument performance during the rocket flights and of pre- and postflight intercomparisons with independently maintained pyrheliometers. There is a high probability that the measured difference is real. Additional observations are required to determine whether the difference results from random fluctuations in solar luminosity, a nonrandom change of short duration, or a sustained change that has climatological significance.
Power Plant Cooling Systems: Policy Alternatives
Authors: Reynolds John Z.
Published: October 2006

Policies and pressures emanating from the 1972 Amendments to the Federal Water Pollution Control Act favor the installation of cooling towers, or closed-cycle cooling systems, in power plants. An assessment of the relative risks of alternative cooling system designs indicates that, in general, adverse environmental effects associated with cooling towers are more certain, are of larger scale, and are more likely to be irreversible than impacts associated with once-through cooling systems and cooling reservoirs. Adverse environmental effects associated with once-through cooling and cooling reservoirs are largely amenable to mitigation in the context of resource management principles. These factors, together with the greater costs associated with cooling towers, indicate that wherever the feasibility is demonstrated and there is minimal risk to aquatic ecosystems, once-through cooling systems or cooling reservoirs should be preferred.
Symbolic Communication Between Two Pigeons,
(Columba livia domestica)
Authors: Epstein Robert , Lanza Robert P. , Skinner B. F.
Published: October 2006

Through the use of learned symbols, a pigeon accurately communicated information about hidden colors to another pigeon. Each verbal exchange was initiated with a spontaneous request for information. The two pigeons engaged in a sustained and natural conversation without human intervention.
Accreting Neutron Stars, Black Holes, and Degenerate Dwarf Stars
Authors: Pines David
Published: October 2006

During the past 8 years, extended temporal and broadband spectroscopic studies carried out by x-ray astronomical satellites have led to the identification of specific compact x-ray sources as accreting neutron stars, black holes, and degenerate dwarf stars in close binary systems. Such sources provide a unique opportunity to study matter under extreme conditions not accessible in the terrestrial laboratory. Quantitative theoretical models have been developed which demonstrate that detailed studies of these sources will lead to a greatly increased understanding of dense and superdense hadron matter, hadron superfluidity, high-temperature plasma in superstrong magnetic fields, and physical processes in strong gravitational fields. Through a combination of theory and observation such studies will make possible the determination of the mass, radius, magnetic field, and structure of neutron stars and degenerate dwarf stars and the identification of further candidate black holes, and will contribute appreciably to our understanding of the physics of accretion by compact astronomical objects.
Electricity Generation Choices for the Near Term
Authors: Bodansky David
Published: October 2006

Electricity demand is expected to increase during the next few decades, especially if it is accepted that the primary goal of energy conservation is to reduce oil consumption. Although the renewable resources in principle have unlimited potential, it is not clear that they can make a major contribution to electricity expansion within the 20th century. Coal and nuclear power are the practical alternatives. The adverse effects of nuclear power probably remain less than those of coal, despite the impact of the Three Mile Island accident. It is important to explore and exploit all options, especially the endangered nuclear option.
The Potential for Grass-Fed Livestock: Resource Constraints
Authors: Pimentel David , Oltenacu P. A. , Nesheim M. C. , Krummel John , Allen M. S. , Chick Sterling
Published: October 2006

Using pasture and grazed forest-range for a system of producing livestock by feeding grass alone reduces the inputs of energy about 60 percent and land resources about 8 percent, but also reduces by about half the production of animal protein in the United States. Under a system in which only grass was fed, livestock would be restricted to beef, milk, and lamb production. The amount of grain fed to U.S. livestock is about 135 million tons (metric) or about ten times the amount consumed by the U.S. population.
Cryptic Self-Fertilization in the Malpighiaceae
Authors: Anderson William R.
Published: October 2006

Some Malpighiaceae produce minute cleistogamous flowers in addition to showy chasmogamous flowers. Standard techniques fail to reveal how the cleistogamous flowers achieve self-fertilization. Fluorescence in longitudinal sections shows that the pollen germinates inside the indehiscent anther. The pollen tubes then grow down through the filament, into the receptacle, up into the carpels, and into the nucellar beak of the ovule.
A Simple Description of the 3 K Cosmic Microwave Background
Authors: Henry Paul S.
Published: October 2006

An intuitive model for the expansion of the universe is developed in which special relativity is used to describe events seen by a hypothetical observer in a Lorentz frame of reference. The cosmic microwave background photons he sees are the red-shifted remnants of hot photons emitted from the matter flying rapidly away from him. This special relativistic model, also called the Milne model, represents the extreme case of a Friedmann (general relativistic) universe in the limit of vanishingly small density of matter. The special relativistic model approximates an open universe (one that expands forever) with increasing accuracy as time evolves.
Hektor: The Largest Highly Elongated Asteroid
Authors: Hartmann William K. , Cruikshank Dale P.
Published: October 2006

New observations of Trojan asteroid 624, Hektor, in April 1979 establish that the high amplitude of the rotational light curve of this object is caused by its elongated shape and not by patches of dark and light albedo on opposing hemispheres. These observations confirm that Hektor is a very unusual object and are consistent with the hypothesis that it may be a compound asteroid formed when two Trojans of comparable size fell together—a rare fossilized example of a planetary accretion process.
Detrital Nonprotein Amino Acids Are the Key to Rapid Growth of
Tilapia
in Lake Valencia, Venezuela
Authors: Bowen Stephen H.
Published: October 2006

The detritivorous cichlid
Sarotherodon mossambicus
grows rapidly on a low-protein diet by assimilating detrital nonprotein amino acids. Differences in the quantity of detrital amino acids in different lakes may account for the variable success of
S. mossambicus
introductions around the world.
Strong Stellar Winds
Authors: Conti Peter S. , McCray Richard
Published: October 2006

The hottest and most luminous stars lose a substantial fraction of their mass in strong stellar winds. These winds not only affect the evolution of the star, they also carve huge expanding cavities in the surrounding interstellar medium, possibly affecting star formation. The winds are probably driven by radiation pressure, but uncertainties persist in their theoretical description. Strong x-ray sources associated with a few of these hot stars may be used to probe the stellar winds. The nature of the weak x-ray sources recently observed to be associated with many of these stars is uncertain. It is suggested that roughly 10 percent of the luminous hot stars may have as companions neutron stars or black holes orbiting within the stellar winds.
A Federalist Strategy for Nuclear Waste Management
Authors: Lee Kai N.
Published: October 2006

The federal government plans to rely on a policy of "consultation and concurrence" with state governments in developing nuclear waste repositories. The weaknesses of the concurrence approach are analyzed, and an alternative institutional framework for locating a waste repository is proposed: a siting jury that provides representation for state and local interests, while maintaining a high level of technical review. The proposal could be tested in the siting of away-from-reactor storage facilities for spent nuclear fuel.
Photovoltaic Materials
Authors: Perez-Albuerne Evelio A. , Tyan Yuan-Sheng
Published: October 2006

Solid-state photovoltaic cells are feasible devices for converting solar energy directly to electricity. Recent cost reductions have spurred an incipient industry, but further advances in materials science and technology are needed before photovoltaic cells can compete with other sources for the supply of large amounts of energy. In this article energy loss mechanisms in solid-state photovoltaic cells are examined and related to materials properties. Various systems under development are reviewed which illustrate some key concepts, opportunities, and problems of this most promising emerging technology. Areas where contributions from innovative materials research would have a significant effect are also indicated.
Nickel Carbonyl: Decomposition in Air and Related Kinetic Studies
Authors: Stedman D. H. , Hikade D. A. , Pearson R. , Yalvac E. D.
Published: October 2006

Nickel carbonyl [Ni(CO)
4
] is a toxic gas used in the manufacture of metallic nickel which has been shown to be carcinogenic and teratogenic in laboratory studies. Its decomposition in air proceeds at a rate that is strongly dependent on the concentration of carbon monoxide (CO). In the absence of CO, the lifetime in air at 296°K and at atmospheric pressure is 60 ± 5 seconds. A mechanism consisting of equilibrium unimolecular decomposition to Ni(CO)
3
and CO, followed by reaction of the Ni(CO)
3
with molecular oxygen, is consistent with the observations.
Red Cochineal Dye (Carminic Acid): Its Role in Nature
Authors: Eisner Thomas , Nowicki Stephen , Goetz Michael , Meinwald Jerrold
Published: October 2006

Carminic acid, the well-known red dyestuff from cochineal insects (
Dactylopius
spp.), is a potent feeding deterrent to ants. This deterrency may be indicative of the natural function of the compound, which may have evolved in cochineals as a chemical weapon against predation. The behavior of an unusual predator is described—the carnivorous caterpillar of a pyralid moth (
Laetilia coccidivora
)— which is undeterred by carminic acid and feeds on cochineals. The animal has the remarkable habit of utilizing the ingested carminic acid for defensive purposes of its own.
Higher Order Structure of Simian Virus 40 Chromatin
Authors: Müller Ulrike , Zentgraf Hanswalter , Eicken Ingrid , Keller Walter
Published: October 2006

Simian virus 40 nucleoprotein complexes undergo an ionic strength-dependent structural transition. At moderate ionic strength they contain histone H1 as well as the nucleosomal histones and have a compact conformation with globular subunits 190 angstroms in diameter. At high ionic strength histone H1 is released, and the structure unfolds into chains with an average of 24 nucleosomes. The extended viral chromatin converts to the compact form by the addition of histone H1. Transcriptionally active simian virus 40 chromatin undergoes the same structural transitions. The higher order structure of viral chromatin may be analogous to the compact state of cellular chromatin fibers observed at physiological ionic strength.
A Global and Long-Range Picture of Energy Developments
Authors: Häfele Wolf
Published: October 2006

Most studies of energy supply and demand ignore either global inter-dependence or the long time spans necessary to adjust to new energy sources. The International Institute for Applied Systems Analysis has therefore studied on a global scale, for seven major world regions, the balance between energy supply and demand for the next 50 years. Reported here are the results for two benchmark scenarios. In the "low" scenario world energy consumption increases from today's 8.2 terawatt-year per year to 22 terawatt-year per year in 2030; in the "high" scenario, consumption increases to 35 terawatt-year per year. The study showed that time will be the limiting constraint in adapting the energy supply infrastructure to changing resource availability; resources will be available until the second half of the next century, but a strong shift will be required to low-grade fossil fuels such as shale oil and tar sands. Each scenario studied indicated increased environmental problems associated with increased use of fossil fuels, and potential geopolitical problems associated with the world distribution of resources.
The Earth and Planetary Sciences
Authors: Wetherill George W. , Drake Charles L.
Published: October 2006

During the last two decades the earth sciences community has become persuaded that the earth is a dynamic body; an engine driven by its internal heat. The major surface manifestation of this dynamism has been fragmentation of the earth's outer shell and subsequent relative horizontal movement of the pieces on a large scale. The driving force is convection within the earth, but much remains to be learned about the nature of the convection and the composition of the earth's interior. The other terrestrial planets show evidence of once having been hot, but their surfaces suggest long-term stability and lack evidence of continuing convection.
Saturn's E Ring Revisited
Authors: Feibelman A. W. , Klinglesmith D. A.
Published: October 2006

Saturn's E ring is revealed by image processing of direct photographs of the 1966 edge-on presentation of the planet's ring plane. Two different techniques were used: scanning with an image quantizer operated in the derivative mode and computer-enhanced background subtraction from digitized images.
Genesis of Petroleum Hydrocarbons in Marine Sediments
Authors: Hunt John M. , Whelan Jean K. , Huc Alain Y.
Published: October 2006

Distribution patterns of isopentane and normal pentane in marine sediments show a reversal in slope at a subsurface temperature of about 90°C. The data indicate that three types of reactions are involved in pentane formation: (i) biological origin at the sediment surface, (ii) low-temperature (< 90°C) chemical reactions yielding predominately secondary carbon structures, and (iii) high-temperature (> 90°C) cracking reactions at great depth yielding predominately straight carbon chains.
Development of the Subsurface Currents of the Northern Somali Current Gyre from March to July 1979
Authors: Schott F. , Quadfasel D. R.
Published: October 2006

Measurements from March to July 1979 by current meters moored between the shelf and the deep sea from 5° to 8°N show that there was shallow (< 150-meter) coastward and northward circulation between 6° and 8°N long before the onset of the southwest monsoon. After the onset, a powerful coastward flow developed offshore around 6°N, branching into northward and southward flows at the continental rise while the current deepened to more than 250 meters. There seemed to be a separate circulation on the shelf with some counterflow to offshore. All current records show that there were strong fluctuations with periods of 3 to 6 days.
Juvocimenes: Potent Juvenile Hormone Mimics from Sweet Basil
Authors: v W. S. , Nishida R.
Published: October 2006

Two compounds with highly potent juvenile hormone activity were isolated and identified from the oil of sweet basil,
Ocimum basilicum
L., Labiatae.
Serial Female Sex Changes After Simultaneous Removal of Males from Social Groups of a Coral Reef Fish
Authors: Shapiro Douglas Y.
Published: October 2006

The simultaneous removal of three to nine males from large social groups of
Anthias squamipinnis
led to close to a one-to-one replacement of the removed males by sex-reversing females. The females changed sex serially within each group with a mean interval between successive onset times of 1.9 days. The timing of sex change is thus not independent for each fish but is influenced by the events surrounding other sex reversals within the group.
Signals for Food: Reinforcers or Informants?
Authors: Cherfas Jeremy Jon
Published: October 2006

Ring doves pecked one of two keys for food. Pecks at the chosen key then stopped being reinforced, and the signals that normally preceded food were either present or absent. In the presence of signals for food, the dove switched to the second key more quickly. When only one key was used, the same signals acted, as expected, to keep the bird pecking the extinguished key.
Managing State Energy Conservation Programs: The Minnesota Experience
Authors: Hirst Eric , Armstrong John R.
Published: October 2006

In fiscal year 1980, the Department of Energy awarded grants for state energy conservation programs that totaled more than $400 million; the proposed figure for fiscal year 1981 is almost $600 million. Many states provide additional funds to implement conservation programs. This suggests that state governments play a major role in delivering conservation services to their citizens and are key agents in the nation's conservation efforts. This article discusses the energy conservation activities and responsibilities of one state energy office, the Minnesota Energy Agency, and the obstacles and constraints it faces in delivering its services. Suggestions are presented for resolving these difficulties and for improving the efficiency with which the agency manages its programs.
Brightness Temperatures of Saturn's Disk and Rings at 400 and 700 Micrometers
Authors: Whitcomb S. E. , Hildebrand R. H. , Keene Jocelyn
Published: October 2006

Saturn was observed in two broad submillimeter photometric bands with the rings nearly edge-on. The observed brightness temperatures fall below the predictions of atmospheric models constructed from data at shorter wavelengths, indicating the presence of an opacity source besides pressure-broadened hydrogen lines in the submillimeter region. In combination with earlier measurements at larger inclination angles, these results yield a 400-micrometer brightness temperature for the rings of ∼75 K.
Solar Neutrino Production of Long-Lived Isotopes and Secular Variations in the Sun
Authors: Haxton W. C. , Cowan G. A.
Published: October 2006

Long-lived isotopes produced in the earth's crust by solar neutrinos may provide a method of probing secular variations in the rate of energy production in the sun's core. Only one isotope, calcium-41, appears to be suitable from the dual standpoints of reliable nuclear physics and manageable backgrounds. The proposed measurement also may be interesting in view of recent evidence for neutrino oscillations.
Resource Concentration and Herbivory in Oak Forests
Authors: Futuyma Douglas J. , Wasserman Steven S.
Published: October 2006

Larvae of the fall cankerworm (
Alsophila pometaria
), a polyphagous defoliator of canopy trees, hatch at the time of budbreak of scarlet oak (
Quercus coccinea
), about 10 days before budbreak of white oak (
Quercus alba
). Thus the
Alsophila
population was dense in a site dominated by scarlet oaks and defoliated the scattered white oaks when they came into leaf. In a site dominated by white oaks, the
Alsophila
population was sparse and chiefly attacked scattered scarlet oak. Thus in each stand, the rarer species of tree suffered greater herbivory, in contrast to the more commonly reported observation that herbivore attack on a plant species increases with density.
Cellulose Metabolism by the Flagellate
Trichonympha
from a Termite Is Independent of Endosymbiotic Bacteria
Authors: Yamin Michael A.
Published: October 2006

Continuous axenic cultures were established of
Trichonympha sphaerica
, a cellulose-digesting symbiotic protozoon in the gut of a termite. The cultured flagellates harbored no endosymbiotic bacteria and metabolized cellulose to acetate, carbon dioxide, and hydrogen. Thus, the cellulolytic activity of this flagellate is an inherent property and is not dependent on endosymbiotic bacteria.
Diatoms as Hydrographic Tracers: Example from Bering Sea Sediments
Authors: Sancetta Constance
Published: October 2006

Variations in the distribution of diatom species in surface sediments mirror distinct hydrographic regimes on the Bering shelf. Spring salinity fronts divide the water column into four zones with different vertical structures and different productivity patterns. Four assemblages of diatoms can be distinguished in sediments underlying the zones.
Extinctions and Introductions in the New Zealand Avifauna: Cause and Effect?
Authors: Diamond Jared M. , Veitch C. Richard
Published: October 2006

New Zealand, like many other islands, has suffered extinctions of native species and successful introductions of exotic species. It has been uncertain whether the introductions caused the extinctions or whether the extinctions permitted the introductions. On New Zealand's Hauraki Gulf islands, which are unusual in their near lack of introduced mammalian predators and complete lack of mammalian browsers, exotic bird species abundant in mainland New Zealand forest and reaching these islands are virtually absent from unmodified forest. Exotic bird species disappeared from Cuvier Island's forest after elimination of mammalian predators and browsers. Hence extinctions of native species were not due to competition from introduced species but to other factors (such as mammalian predators and habitat alteration). Only after decimation of native species and forest alteration by browsing mammals could exotic birds invade forest.
Energy Supply Interruptions and National Security
Authors: Alm Alvin L.
Published: October 2006

Vulnerability to oil supply interruptions poses serious threats to the U.S. economy and the life-style of its citizens. The Iranian cutbacks in 1979 resulted in price increases of 120 percent in 1 year and gasoline lines across the country. Creation and use of ample public and private stocks could moderate price increases after another interruption and prevent disruption of supplies. Use of the marketplace to allocate shortages, coupled with rebates to cushion blows to the economy and hardship to individuals, would be eminently more efficient than government allocation programs. International cooperation, through coordination of stock buildup and withdrawal, could mitigate the damage from oil disruptions among all the Western nations.
Presynaptic Alpha-Receptor Subsensitivity After Long-Term Antidepressant Treatment
Authors: Crews Fulton T. , Smith Charles B.
Published: October 2006

After 3 weeks of twice-daily administration of desipramine to rats, the frequency-response curve for field stimulation of adrenergic neurons in isolated left atrial strips was shifted markedly to the left and the efflux of [
3
H]norepinephrine was enhanced greatly. After 1 day of treatment, only slight shifts in the frequency-response curve and small increases in [
3
H]norepinephrine efflux occurred although inhibition of [
3
H]norepinephrine uptake was already maximal, and phenoxybenzamine caused a further shift to the left in the frequency-response curve similar to that which occurred after 3 weeks of desipramine treatment alone. A gradual decrease in the sensitivity of the presynaptic α receptor would explain the delay in the onset of the clinical effect of the tricyclic antidepressants.
Threads in the Hagfish Slime Gland Thread Cells: Organization, Biochemical Features, and Length
Authors: Downing Stephen W. , Spitzer Robert H. , Salo Wilmar L. , Downing J. Scott , Saidel Leo J. , Koch Elizabeth A.
Published: October 2006

Scanning electron microscopy in conjunction with cell isolation procedures revealed details of the packing of threads in hagfish slime gland thread cells. Biochemical studies indicate that the thread is largely composed of a protein subunit with a molecular weight of 63,500. Mathematical calculations suggest that the thread may attain lengths of 60 centimeters or more.
"Self-Awareness" in the Pigeon
Authors: Epstei Robert , Lanza Robert P. , Skinner B. F.
Published: October 2006

Each of three pigeons used a mirror to locate a spot on its body which it could not see directly. Although similar behavior in primates has been attributed to a self-concept or other cognitive process, the present example suggests an account in terms of environmental events.
Microparticle Concentration Variations Linked with Climatic Change: Evidence from Polar Ice Cores
Authors: Thompson L. G. , Mosley-Thompson E.
Published: October 2006

The microparticle concentrations in three deep ice cores reveal a substantial increase in the concentration of insoluble particles in the global atmosphere during the latter part of the last major glaciation. The ratio of the average particle concentration in the late glacial strata to that in the Holocene strata is 6/1 for the core from Dome C, Antarctica, 3/1 for the core from Byrd Station, Antarctica, and 12/1 for the core from Camp Century, Greenland. Whether this temporal correlation between increased atmospheric particle load and the lower surface temperatures is directly causal is unknown; however, the variations in these two parameters must be satisfactorily resolved in any successful hypothesis that addresses the causes of climatic change.
Gulf Stream Cold-Core Rings: Their Physics, Chemistry, and Biology
Authors:   The Ring Group
Published: October 2006

Cyclonic Gulf Stream rings are energetic eddies in the warm Sargasso Sea consisting of a ring of Gulf Stream water surrounding a core of cold Slope Water. Initially a ring core has the characteristics of the Slope Water; it is rich in plants, animals, and nutrients. As a ring decays the Slope Water properties of its core are gradually replaced by those of the Sargasso Sea, where standing crops of plants, animals, and nutrients generally are low. Although the decay rate suggests a rather long lifetime (2 to 4 years), the usual death of a ring comes when it rejoins the Gulf Stream after 6 to 12 months.
Soldier Determination in Ants: New Role for Juvenile Hormone
Authors: Wheeler Diana E. , Nijhout H. Frederik
Published: October 2006

Topical application of juvenile hormone analog induces soldier development in the ant
Pheidole bicarinata
. Soldier induction takes place if the juvenile hormone analog is present during a period of sensitivity that occurs during the last larval instar. Control of worker dimorphism seems to be accomplished through control of timing of metamorphosis. The smallest size at which metamorphosis can be initiated is shifted upward from 1.2 to 1.7 millimeters by exposure to the juvenile hormone analog during the sensitive period.
Man-Made Radionuclides Confirm Rapid Burial of Kepone in James River Sediments
Authors: Cutshall Norman H. , Larsen Ingvar L. , Nichols Maynard M.
Published: October 2006

Profiles of man-made radionuclides in sediment cores from the James River estuary confirm the rapid burial of the pesticide Kepone. The greatest deposition of Kepone has occurred in zones characterized by very high sedimentation rates, 10 to 20 centimeters per year. Since sediment is the major Kepone reservoir, rapid burial probably reduces the exposure of organisms to further contamination. Disturbance caused by hurricanes or dredging, however, could return highly contaminated sediment to the surface although this sediment would be diluted with less contaminated particles.
Initial Effects of Ashfall from Mount St. Helens on Vegetation in Eastern Washington and Adjacent Idaho
Authors: Mack Richard N.
Published: October 2006

Extensive plant damage from the 18 May 1980 eruption of Mount St. Helens was largely restricted to acaulescent and prostrate dicot species in the ashfall area east of the Cascade Range (more than 150 kilometers from the vent)
Veratrum californicum
a large monocot, displayed widespread stem death through mechanical overloading of the plant's clasping leaves. The ash surface in this area presents new opportunities for both seeds and seed predators.
Phonon Optics and Phonon Propagation in Semiconductors
Authors: Narayanaamurti V.
Published: October 2006

Recent experiments involving the propagation of extremely high frequency, short-wavelength acoustic phonons in semiconductors are described. Such phonons, which play an important role in thermal energy transport and nonradiative recombination processes, can be used as sensitive microscopic probes of electronic, defect, and interface states. Experiments on phonon transmission through epitaxially grown bulk material as well as thin-film superlattice structures in the semiconductor gallium arsenide are described. Such thin-film periodic structures can be used to build frequency-selective phonon filters and reflectors, which can in turn be used to manipulate phonon diagnostic beams in technologically important materials.
Calcium-Bearing Objects Elicit Shell Selection Behavior in a Hermit Crab
Authors: Mesce Karen Anne
Published: October 2006

Hermit crabs explore empty gastropod shells by touching, rolling, and probing them before choosing one for a home. This component of shell selection behavior was examined in
Pagurus hirsutiusculus hirsutiusculus
(Dana) with binary choice tests between natural shells and accurate replicas of the shells with different chemical compositions. The results show that calcium emanating from the surface of shells is responsible for the behavior. Sensitivity to calcium may be a factor that enables the hermit crab to locate partially buried shells and discriminate empty shells from ones housing living gastropods or from small pebbles.
A T Cell-Specific Transcriptional Enhancer within the Human T Cell Receptor δ Locus
Authors: Redondo Juan Miguel , Hata Shingo , Brocklehurst Cathy , Krangel Michael S.
Published: October 2006

The T cell antigen receptor (TCR) δ gene is located within the TCRα locus. A T cell-specific transcriptional enhancer, distinct from the TCRα enhancer, has been identified within the J
δ
3-C
δ
intron of the human T cell receptor δ gene. This enhancer activates transcription from the V
δ
1 and V
δ
3 promoters as well as from heterologous promoters. Enhancer activity has been localized to a 250-bp region that contains multiple binding sites for nuclear proteins. Thus, transcriptional control of the TCRδ and TCRα genes is mediated by distinct regulatory elements.
Association of Human Papillomavirus Types 16 and 18 E6 Proteins with p53
Authors: Werness Bruce A. , Levine Arnold J. , Howley Peter M.
Published: October 2006

Human papillomavirus type 16 (HPV-16) is a DNA tumor virus that is associated with human anogenital cancers and encodes two transforming proteins, E6 and E7. The E7 protein has been shown to bind to the retinoblastoma tumor suppressor gene product, pRB. This study shows that the E6 protein of HPV-16 is capable of binding to the cellular p53 protein. The ability of the E6 proteins from different human papillomaviruses to form complexes with p53 was assayed and found to correlate with the in vivo clinical behavior and the in vitro transforming activity of these different papillomaviruses. The wild-type p53 protein has tumor suppressor properties and has also been found in association with large T antigen and the E1B 55-kilodalton protein in cells transformed by SV40 and by adenovirus type 5, respectively, providing further evidence that the human papillomaviruses, the adenoviruses, and SV40 may effect similar cellular pathways in transformation.
RNA Polymerase II Transcription Blocked by
Escherichia coli Lac
Repressor
Authors: Deuschle Ulrich , Hipskind Robert A. , Bujard Hermann
Published: October 2006

A reversible block to RNA polymerase II transcriptional elongation has been created with a
lac
operator sequence in the intron of the SV40 large T-antigen gene. When this transcription unit is injected into rabbit kidney cells expressing
Escherichia coli
lac
repressor, T-antigen expression is reduced. This effect is not observed in cells lacking repressor or in the absence of the operator, and it is reversed by an inducer of the
lac
operon, namely isopropyl thiogalactoside (IPTG). In an extract of HeLa nuclei supplemented with
lac
repressor, this and similar constructs give rise to shortened transcripts that map to the 5′ boundary of the repressor-operator complex. These shorter RNAs are also sensitive to IPTG induction. This model system shows that a protein-DNA complex can block the passage of RNA polymerase II, and offers some insight into the control of eukaryotic gene expression during transcription elongation, a phenomenon observed in a variety of systems.