bluuebunny/crossref_metadata_2025 huggingface dataset:
Toxicity of a Furanocoumarin to Armyworms: A Case of Biosynthetic Escape from Insect Herbivores
Authors: Berenbaum May
Published: October 2006

When the linear furanocoumarin xanthotoxin, found in many plants of the families Rutaceae and Umbelliferae, was administered to larvae of
Spodoptera eridania
a generalist insect herbivore, it displayed toxic properties lacking in its biosynthetic precursor umbelliferone. Reduced toxicity observed in the absence of ultraviolet light is consistent with the known mechanism of photoinactivation of DNA by furanocoumarins through ultraviolet-catalyzed cross-linkage of strands. Thus, the ability of a plant to convert umbelliferone to linear furanocoumarins appears to confer broader protection against insect herbivores.
Time, Structure, and Fluctuations
Authors: Prigogine Ilya
Published: October 2006

Fundamental conceptual problems that arise from the macroscopic and microscopic aspects of the second law of thermodynamics are considered. It is shown that nonequilibrium may become a source of order and that irreversible processes may lead to a new type of dynamic states of matter called "dissipative structures." The thermodynamic theory of such structures is outlined. A microscopic definition of irreversible processes is given, and a transformation theory is developed that allows one to introduce nonunitary equations of motion that explicitly display irreversibility and approach to thermodynamic equilibrium. The work of the group at the University of Brussels in these fields is briefly reviewed. In this new development of theoretical chemistry and physics, it is likely that thermodynamic concepts will play an ever-increasing role.
Microgeographic Prediction of Polygyny in the Lark Bunting
Authors: Pleszczynska Wanda K.
Published: October 2006

Field experiments on breeding populations of lark buntings (
Calamospiza melanocorys
) in South Dakota support the hypothesis that polygyny is promoted by a high variance in quality among male territories. Among these birds protection of the nest site from solar radiation is the major indicator of quality: nestling survival was significantly correlated with nest-site cover, and experimental increase of shading resulted in higher reproductive success. Males with superior territories attracted two mates, whereas those with poor territories failed to attract any. Secondary females had fledging success at least equal to that of contemporaneous monogamous pairs. On the sole basis of a shading score for each territory, the mating status of males (polygynous, monogamous, or bachelor) was predicted accurately in new areas of Colorado and North Dakota before females arrived.
Nothomyrmecia macrops
: A Living-Fossil Ant Rediscovered
Authors: Taylor Robert W.
Published: October 2006

The Australian
Nothomyrmecia macrops
is the most primitive living ant. Until recently rediscovered, it was known only from two 46-year-old specimens, both workers. All developmental stages and adult castes are now known. Adults have stridulatory organs placed ventrally, between abdominal sternites III (with plectrum) and IV (with stridulitrum), differing from all other Hymenoptera, where these organs are dorsal. The chromosome number is the highest recorded for Hymenoptera (2
n
= 92). Virgin queens are brachypterous. Other anatomical and behavioral features are reviewed. Most are primitive for ants, many being shared with
Myrmecia
, another primitive Australian genus. Fundamental differences in abdominal structure place
Myrmecia
near the base of the poneroid phylad of ant subfamilies, while
Nothomyrmecia
is a primitive formicoid.
Regional Implications of Triassic or Jurassic Age for Basalt and Sedimentary Red Beds in the South Carolina Coastal Plain
Authors: Gohn Gregory S. , Gottfried David , Lanphere Marvin A. , Higgins Brenda B.
Published: October 2006

Whole rock potassium-argon ages for samples of subsurface basalt recovered near Charleston, South Carolina, are interpreted to indicate a Triassic or Jurassic age for the basalt and underlying sedimentary red beds. This age is consistent with existing evidence indicating that an early Mesozoic basin is present in the subsurface of a large part of the coastal plain of South Carolina, Georgia, Florida, and Alabama.
Biohybrid Artificial Pancreas: Long-Term Implantation Studies in Diabetic, Pancreatectomized Dogs
Authors: Sullivan Susan J. , Maki Takashi , Borland Kermit M. , Mahoney Michele D. , Solomon Barry A. , Muller Thomas E. , Monaco Anthony P. , Chick William L.
Published: October 2006

Diabetic complications such as neuropathy, retinopathy, and renal and cardiovascular disease continue to pose major health risks for diabetic patients. Consequently, much effort has focused on approaches that could replace conventional insulin therapy and provide more precise regulation of blood glucose levels. The biohybrid perfused artificial pancreas was designed to incorporate islet tissue and a selectively permeable membrane that isolates this tissue from the immune system of the recipient. Biohybrid pancreas devices containing canine islet allografts were implanted in ten pancreatectomized dogs requiring 18 to 32 units of injected insulin daily. These implants resulted in good control of fasting glucose levels in six of these animals without further exogenous insulin for periods of up to 5 months.
Postmating Reproductive Isolation in
Pseudophryne
and the Evolutionary Significance of Hybrid Zones
Authors: Woodruff David S.
Published: October 2006

Hybrid zones involving
Pseudophryne
(Anura: Leptodactylidae) provide direct evidence for the operation of postmating reproductive isolating mechanisms in animals in a natural situation. Significant introgression is prevented by hybrid inviability but there is no evidence for the reinforcement of premating isolating mechanisms. These parapatric hybrid zones are of unknown etiology, but are interpreted as being relatively old and persistent.
Electron Temperatures and Densities in the Venus Ionosphere: Pioneer Venus Orbiter Electron Temperature Probe Results
Authors: Brace L. H. , Theis R. F. , Krehbiel J. P. , Nagy A. F. , Donahue T. M. , McElroy M. B. , Pedersen A.
Published: October 2006

Altitude profiles of electron temperature and density in the ionosphere of Venus have been obtained by the Pioneer Venus orbiter electron temperature probe. Elevated temperatures observed at times of low solar wind flux exhibit height profiles that are consistent with a model in which less than 5 percent of the solar wind energy is deposited at the ionopause and is conducted downward through an unmagnetized ionosphere to the region below 200 kilometers where electron cooling to the neutral atmosphere proceeds rapidly. When solar wind fluxes are higher, the electron temperatures and densities are highly structured and the ionopause moves to lower altitudes. The ionopause height in the late afternoon sector observed thus far varies so widely from day to day that any height variation with solar zenith angle is not apparent in the observations. In the neighborhood of the ionopause, measurements of plasma temperatures and densities and magnetic field strength indicate that an induced magnetic barrier plays an important role in the pressure transfer between the solar wind and the ionosphere. The bow shock is marked by a distinct increase in electron current collected by the instrument, a feature that provides a convenient identification of the bow shock location.
Red-Absorbing Visual Pigment of Butterflies
Authors: Bernard Gary D.
Published: October 2006

Noninvasive photochemical and physiological experiments with intact butterflies of 17 species showed that nine species have a rhodopsin absorbing maximally at 610 nanometers, contained in retinular cells that are maximally sensitive at 610 nanometers. This is the longest-wavelength visual pigment known for an invertebrate. Eight species of butterflies lack the 610-nanometers rhodopsin. All species possess a rhodopsin absorbing maximally in the green region of the spectrum.
Tropopause Detection by Partial Specular Reflection with Very-High-Frequency Radar
Authors: Gage K. S. , Green J. L.
Published: October 2006

The tropopause can be detected and its altitude determined routinely with the use of meter-wavelength, very-high-frequency radar. At meter wavelengths and at vertical incidence, the tropopause is revealed by partial specular reflection from stable atmospheric layers. The echoes received at vertical incidence as a result of partial specular reflection are greatly enhanced over echoes received at oblique incidence arising from turbulent scatter. Very-high-frequency radars utilizing partial specular reflection promise a major advance in the remote sensing of the atmosphere.
Climatic Ice Core Records from the Tropical Quelccaya Ice Cap
Authors: Thompson Lonnie G. , Hastenrath Stefan , Arnao Benjamín Morales
Published: October 2006

The Quelccaya Ice Cap in the easternmost glaciated mountain chain of the Peruvian Andes has been studied in four recent field seasons. Ice cores to a depth of 15 meters have been retrieved at the summit dome (elevation, 5650 meters) and two other locations and used for microparticle, isotope, and beta radioactivity measurements. A concurrent study of the present climate and the heat and mass budgets is being made to permit a paleoclimatic interpretation of deep core records. The results indicate the need for a revision of the isotope "thermometry" for application in the tropics. However, the seasonality of the beta radioactivity, microparticle content, and isotope ratios offers the prospect of a mass balance chronology. This is important in that precipitation is believed to be a more indicative paleoclimatic parameter than temperature in the tropics.
Methane Efflux from Lake Sediments Through Water Lilies
Authors: Dacey J. W. H. , Klug M. J.
Published: October 2006

During winter, when water lilies have no surface leaves, the gases in the rhizome lacunae approach equilibrium with the gases of the sediment water. The resulting increase of internal pressure is manifested by the sustained streams of bubbles (up to 37 percent methane and 6 percent carbon dioxide) that escape when emerging leaves are torn in the spring. Methane continues to enter the roots and rhizome during summer, rapidly moves up the petioles, and passes out through the emergent leaves into the atmosphere.
Tree Dispersion, Abundance, and Diversity in a Tropical Dry Forest
Authors: Hubbell Stephen P.
Published: October 2006

Patterns of tree abundance and dispersion in a tropical deciduous (dry) forest are summarized. The generalization that tropical trees have spaced adults did not hold. All species were either clumped or randomly dispersed, with rare species more clumped than common species. Breeding system was unrelated to species abundance or dispersion, but clumping was related to mode of seed dispersal. Juvenile densities decreased approximately exponentially away from adults. Rare species gave evidence of poor reproductive performance compared with their performance when common in nearby forests. Patterns of relative species abundance in the dry forest are compared with patterns in other forests, and are explained by a simple stochastic model based on random-walk immigration and extinction set in motion by periodic community disturbance.
Genetic Self-Incompatibility in
Oenothera
subsect
Euoenothera
Authors: Stubbe Wilfried , Raven Peter H.
Published: October 2006

Although it has been postulated that genetic self-incompatibility was involved in the origin of complex heterozygotes in
Oenothera
subsect
Euoenothera
, it has not been detected in any species of this well-studied group. It is now reported for populations of
Oenothera grandiflora
from west central Alabama, and should be sought in other populations of this species, which has been in cultivation for nearly two centuries.
Effects of Raw Materials on Biface Manufacture
Authors: Jones Peter Rasmussen
Published: October 2006

It has been suggested that the degree of refinement of trimming seen on Lower Paleolithic bifaces reflects the level of technical sophistication of the toolmaker. This has been tested by a series of experiments carried out at Olduvai Gorge, Tanzania, and related to some of the archeological assemblages there. It is concluded that advanced ideas and increased mastery over raw materials do not necessarily result in stone tools that are more refined in appearance.
Mortality of the Monarch Butterfly (
Danaus plexippus
L.): Avian Predation at Five Overwintering Sites in Mexico
Authors: Calvert William H. , Hedrick Lee E. , Brower Lincoln P.
Published: October 2006

Analyses of predated butterflies on the forest floor at five monarch overwintering sites in Mexico and observations of birds foraging in mixed flocks indicate that individual birds of several species have learned to penetrate the monarch's cardenolide-based chemical defense. Predation is inversely proportional to colony size and appears to be one evolutionary explanation of the dense aggregations.
Extreme Ultraviolet Observations from Voyager 1 Encounter with Jupiter
Authors: Broadfoot A. L. , Belton M. J. S. , Takacs P. Z. , Sandel B. R. , Shemansky D. E. , Holberg J. B. , Ajello J. M. , Atreya S. K. , Donahue T. M. , Moos H. W. , Bertaux J. L. , Blamont J. E. , Strobel D. F. , McConnell J. C. , Dalgarno A. , Goody R. , McElroy M. B.
Published: October 2006

Observations of the optical extreme ultraviolet spectrum of the Jupiter planetary system during the Voyager 1 encounter have revealed previously undetected physical processes of significant proportions. Bright emission lines of S III, S IV, and O III indicating an electron temperature of 10
5
K have been identified in preliminary analyses of the Io plasma torus spectrum. Strong auroral atomic and molecular hydrogen emissions have been observed in the polar regions of Jupiter near magnetic field lines that map the torus into the atmosphere of Jupiter. The observed resonance scattering of solar hydrogen Lyman α by the atmosphere of Jupiter and the solar occultation experiment suggest a hot thermosphere (≥ 1000 K) with a large atomic hydrogen abundance. A stellar occultation by Ganymede indicates that its atmosphere is at most an exosphere.
Voyager 1 Planetary Radio Astronomy Observations Near Jupiter
Authors: Warwick J. W. , Pearce J. B. , Riddle A. C. , Alexander J. K. , Desch M. D. , Kaiser M. L. , Thieman J. R. , Carr T. D. , Gulkis S. , Boischot A. , Harvey C. C. , Pedersen B. M.
Published: October 2006

We report results from the first low-frequency radio receiver to be transported into the Jupiter magnetosphere. We obtained dramatic new information, both because Voyager was near or in Jupiter's radio emission sources and also because it was outside the relatively dense solar wind plasma of the inner solar system. Extensive radio spectral arcs, from above 30 to about 1 megahertz, occurred in patterns correlated with planetary longitude. A newly discovered kilometric wavelength radio source may relate to the plasma torus near Io's orbit. In situ wave resonances near closest approach define an electron density profile along the Voyager trajectory and form the basis for a map of the torus. Detailed studies are in progress and are outlined briefly.
Motor Nerve Sprouting and Acetylcholine Receptors
Authors: Pestronk Alan , Drachman Daniel B.
Published: October 2006

Sprouting of motor nerve terminals was evoked by functional denervation of skeletal muscles brought about by presynaptic blockade or disuse. The amount of sprouting, determined by morphometric measurement, was correlated with the level of extrajunctional acetylcholine receptors. Sprouting was inhibited by blockade of acetylcholine receptors with α-bungarotoxin. Extrajunctional acetylcholine receptors may play an important role in eliciting motor nerve terminal sprouting.
Composition and Structure of the Venus Atmosphere: Results from Pioneer Venus
Authors: Hoffman J. H. , Hodges R. R. , McElroy M. B. , Donahue T. M. , Kolpin M.
Published: October 2006

Results from the Pioneer Venus sounder probe neutral mass spectrometer indicate that there is no difference in the isotopic ratios of carbon and oxygen between Venus and Earth to within ± 5 percent. The mixing ratio of nitrogen is 3.5
+3
-2
percent with an isotopic ratio within 20 percent of that of Earth. The ratio of argon-36 to argon-40 is 85 percent, and the ratio of argon-38 to argon-36 is 20 percent. The mixing ratios of argon-36 and argon-40 are approximately 40 and 50 parts per million, respectively, with an error of about a factor of 2 (mainly toward a lesser amount) resulting from uncertainty in the response of the ion pump to rare gases. Hydrogen chloride cannot account for more than a few percent of the 36 mass peak, and therefore the large excess of primordial argon is a reasonable conclusion. The ratio of neon-20 to argon-36 of 0.5 ± 0.3 is definitely terrestrial in character rather than solar. These results indicate that there is a large excess of all primordial noble gases on Venus relative to Earth. There appears to be a considerably higher abundance of sulfur compounds below 20 kilometers than in or above the main cloud layer. The 32 and 60 mass peaks show a sharp increase below 22 kilometers, indicating the possible production of sulfur and carbon oxysulfide (COS) at the expense of sulfur dioxide.
Ultraviolet Night Airglow of Venus
Authors: Stewart A. Ian , Barth Charles A.
Published: October 2006

The night airglow spectrum of Venus in the ultraviolet is dominated by the
v
′ = 0 progressions of the gamma and delta bands of nitric oxide. The bands are produced by two-body radiative recombination of nitrogen and oxygen atoms. Since the source of these atoms is in the dayside thermosphere, the night airglow is a tracer of the day-to-night thermospheric circulation. The airglow is brightest at equatorial latitudes, and at longitudes on the morning side of the antisolar meridian.
Stable Isotopes in a Mollusk Shell: Detection of Upwelling Events
Authors: Killingley J. S. , Berger W. H.
Published: October 2006

The California mussel
Mytilus californianus
records with high fidelity annual temperature variations of nearshore waters in the oxygen isotope composition of its shell. The onset and termination of upwelling events (and metabolic activity) are recorded in the associated carbon isotope signal, and the magnitude and timing of upwelling can be estimated. The method has implications for studying the history of upwelling and the life history of living and fossil mollusks and for analyzing shell midden deposits.
Management of Multispecies Fisheries
Authors: May Robert M. , Beddington John R. , Clark Colin W. , Holt Sidney J. , Laws Richard M.
Published: October 2006

With the overexploitation of many conventional fish stocks, and growing interest in harvesting new kinds of food from the sea, there is increasing need for managers of fisheries to take account of interactions among species. In particular, as Antarctic krill-fishing industries grow, there is a need to agree upon sound principles for managing the Southern Ocean ecosystem. Using simple models, we discuss the way multispecies food webs respond to the harvesting of species at different trophic levels. These biological and economic insights are applied to a discussion of fisheries in the Southern Ocean and the North Sea and to enunciate some general principles for harvesting in multispecies systems.
Solid State Electrodes for High Energy Batteries
Authors: Murphy D. W. , Christian P. A.
Published: October 2006

A new class of electrode materials for high energy density, rechargeable batteries based on topochemical reactions of lithium and transition metal compounds is evolving. The physical and structural properties relevant to the ability of transition metal oxides with framework structures to topochemically incorporate lithium are discussed. Perovskite-related structures are particularly attractive hosts for lithium.
Sea-Level Lowering During the Illinoian Glaciation: Evidence from a Bahama "Blue Hole"
Authors: Gascoyne M. , Benjamin G. J. , Schwarcz H. P. , Ford D. C.
Published: October 2006

Stalagmites have been recovered from 45 meters below sea level in an underwater karstic cave ("blue hole") near Andros Island in the Bahamas. Uranium series ages, corrected for contamination of the sample by young marine carbonate replacements, show that the speleothem was deposited between 160,000 and 139,000 years before the present. This period corresponds to the Illinoian glacial event and demonstrates that sea level must have been lowered by at least 42 meters (allowing for subsidence) from its present position during this time.
Nest Guard Replacement in the Antarctic Fish
Harpagifer bispinis
: Possible Altruistic Behavior
Authors: Daniels Robert A.
Published: October 2006

Nesting biology of the Antarctic plunder fish,
Harpagifer bispinis
(Schneider), was examined at Arthur Harbor, Antarctic Peninsula, during the austral winter, 1975. Females prepare nest sites, spawn, and guard the eggs for 4 to 5 months, the longest guarded incubation period reported for any fish species. If this guard is removed, it is soon replaced by a conspecific, usually male. If the second guard is removed, a third replaces it. Guards are essential to ensure nest survival. Selfish or parental acts or acts of kinship or reciprocity do not adequately explain guard replacement. The act may be altruistic.
The Genome of Simian Virus 40
Authors: Reddy V. B. , Thimmappaya B. , Dhar R. , Subramanian K. N. , Zain B. S. , Pan J. , Ghosh P. K. , Celma M. L. , Weissman S. M.
Published: October 2006

The nucleotide sequence of SV40 DNA was determined, and the sequence was correlated with known genes of the virus and with the structure of viral messenger RNA's. There is a limited overlap of the coding regions for structural proteins and a complex pattern of leader sequences at the 5′ end of late messenger RNA. The sequence of the early region is consistent with recent proposals that the large early polypeptide of SV40 is encoded in noncontiguous segments of DNA.
Different Actions of Anticonvulsant and Anesthetic Barbiturates Revealed by Use of Cultured Mammalian Neurons
Authors: Macdonald Robert L. , Barker Jeffery L.
Published: October 2006

Barbiturate anesthetics, but not anticonvulsants, abolish the spontaneous activity of cultured spinal cord neurons; directly increase membrane conductance, an effect which is suppressed by the γ-aminobutyric acid (GABA) antagonists picrotoxin and penicillin; and are more potent than anticonvulsants in augmenting GABA and depressing glutamate responses. Barbiturate anticonvulsants abolish picrotoxin-induced convulsive activity. These results indicate qualitative and quantitative differences between anesthetic and anticonvulsant barbiturates, which may explain their different clinical effects.
Magnetic Field Studies at Jupiter by Voyager 2: Preliminary Results
Authors: Ness Norman F. , Acuna Mario H. , Lepping Ronald P. , Burlaga Leonard F. , Behannon Kenneth W. , Neubauer Fritz M.
Published: October 2006

Data from the Goddard Space Flight Center magnetometers on Voyager 2 have yielded on inbound trajectory observations of multiple crossings of the bow shock and magnetosphere near the Jupiter-sun line at radial distances of 99 to 66 Jupiter radii (
R
J
) and 72 to 62
R
J
, respectively. While outbound at a local hour angle of 0300, these distances increase appreciably so that at the time of writing only the magnetopause has been observed between 160 and 185
R
J
. These results and the magnetic field geometry confirm the earlier conclusion from Voyager I studies that Jupiter has an enormous magnetic tail, approximately 300 to 400
R
J
in diameter, trailing behind the planet with respect to the supersonic flow of the solar wind. Additional observations of the distortion of the inner magnetosphere by a concentrated plasma show a spatial merging of the equatorial magnetodisk current with the current sheet in the magnetic tail. The spacecraft passed within 62,000 kilometers of Ganymede (radius = 2,635 kilometers) and observed characteristic fluctuations interpreted tentatively as being due to disturbances arising from the interaction of the Jovian magnetosphere with Ganymede.
Coal Science: Basic Research Opportunities
Authors: Gorbaty Martin L. , Wright Franklin J. , Lyon Richard K. , Long Robert B. , Schlosberg Richard H. , Baset Zeinab , Liotta Ronald , Silbernagel Bernard G. , Neskora Dan R.
Published: October 2006

More fundamental knowledge of coal (knowledge of its structure and its behavior during conversion processes) is essential before we can generate new technologies necessary for the efficient use of coal in the future. Herein are suggested specific basic research opportunities in the areas of coal characterization, gasification, combustion, and liquefaction, along with an assessment of the impact such research programs could have. Critical characterization needs include qualitative and quantitative determination of the chemical forms of carbon, oxygen, nitrogen, and sulfur and reliable methods for the measurement of surface area, pore volume, and weight-average molecular weights. Mechanistic studies aimed at increasing understanding of the thermal breakdown of the functionalities in coal, the behavior of coal in the presence of molecular and donor hydrogen environments, and carbon gasification and hydrocarbon synthesis reactions starting from carbon monoxide and hydrogen will lay the scientific foundation for the development of new processes for converting coal into clean usable fuels and chemicals.
Relatedness and Inbreeding Avoidance: Counterploys in the Communally Nesting Acorn Woodpecker
Authors: Koenig Walter D. , Pitelka Frank A.
Published: October 2006

Acorn woodpeckers (
Melanerpes formicivorus
) live in family groups within which more than one female may lay eggs communally in a single nest. Communally nesting females are usually closely related and share evenly in nesting activities. Although birds of either sex may breed in their natal territory, reproductive inhibition of offspring by the presence of their parent of the opposite sex and dispersal by unisexual sibling units ensure that inbreeding between close relatives is rare.
A corticosteroid Receptor in Neuronal Membranes
Authors: Orchinik Miles , Murray Thomas F. , Moore Frank L.
Published: October 2006

Steroids may rapidly alter neuronal function and behavior through poorly characterized, direct actions on neuronal membranes. The membrane-bound receptors mediating these behavioral responses have not been identified. [
3
H]Corticosterone labels a population of specific, high-affinity recognition sites (dissociation constant = 0.51 nanomolar) in synaptic membranes from an amphibian brain. These binding sites were localized by receptor autoradiography in the neuropil, outside the regions of perikarya. The affinities of corticoids for this [
3
H]corticosterone binding site were linearly related to their potencies in rapidly suppressing male reproductive behavior. Thus, it appears that brain membranes contain a corticosteroid receptor that could participate in the regulation of behavior.
Reconstruction and Future Trends of the AIDS Epidemic in the United States
Authors: Brookmeyer Ron
Published: October 2006

There has been considerable uncertainty in estimates of past and current human immunodeficiency virus (HIV) infection rates in the United States. Statistical estimates of historical infection rates can be obtained from acquired immunodeficiency syndrome (AIDS) incidence data and the incubation period. However, this approach is subject to a number of sources of uncertainty and two other approaches, epidemic models of HIV transmission and surveys of HIV prevalence, are used to corroborate and refine the statistical estimates. Analyses suggest the HIV infection rate in the United States grew rapidly in the early 1980s, peaked in the mid-1980s, and subsequently declined markedly. Due both to the decline in the underlying infection rate and to the development of effective therapies that may delay AIDS diagnosis, overall AIDS incidence may plateau during the next 5 years. However, the number of individuals with advanced HIV disease without a diagnosis of AIDS who could potentially benefit from therapy is expected to increase 40% by 1995 as infected individuals progress to more advanced stages of HIV disease. Thus, although the overall HIV infection rate has declined, the demands on the U.S. health care system for treatment and care of HIV-infected individuals remain enormous.
Folate Conjugase: Two Separate Activities in Human Jejunum
Authors: Reisenauer Ann M. , Krumdieck Carlos L. , Halsted Charles H.
Published: October 2006

Previous perfusion studies of the human jejunum suggested that conjugated folate is hydrolyzed on the mucosal surface. The techniques of cell fractionation and DEAE and gel chromatography led to the identification of two separate folate conjugase activities in human jejunal mucosa: one membrane-bound and concentrated in the brush border, the other soluble and intracellular. These enzyme activities exhibit different
p
H optima, molecular weights, and inhibition characteristics. Folate conjugase in the brush border may accomplish the initial digestion of dietary pteroylpolyglutamates.
Saturn's Magnetosphere, Rings, and Inner Satellites
Authors: Van Allen J. A. , Thomsen M. F. , Randall B. A. , Rairden R. L. , Grosskreutz C. L.
Published: October 2006

Our 31 August to 5 September 1979 observations together with those of the other Pioneer 11 investigators provide the first credible discovery of the magnetosphere of Saturn and many detailed characteristics thereof. In physical dimensions and energetic charged particle population, Saturn's magnetosphere is intermediate between those of Earth and Jupiter. In terms of planetary radii, the scale of Saturn's magnetosphere more nearly resembles that of Earth and there is much less inflation by entrapped plasma than in the case at Jupiter. The orbit of Titan lies in the outer fringes of the magnetosphere. Particle angular distributions on the inbound leg of the trajectory (sunward side) have a complex pattern but are everywhere consistent with a dipolar magnetic field approximately perpendicular to the planet's equator. On the outbound leg (dawnside) there are marked departures from this situation outside of 7 Saturn radii (
R
s
), suggesting an equatorial current sheet having both longitudinal and radial components. The particulate rings and inner satellites have a profound effect on the distribution of energetic particles. We find (i) clear absorption signatures of Dione and Mimas; (ii) a broad absorption region encompassing the orbital radii of Tethys and Enceladus but probably attributable, at least in part, to plasma physical effects; (iii) no evidence for Janus (1966 S 1) (S 10) at or near 2.66
R
s
; (iv) a satellite of diameter ≳ 170 kilometers at 2.534
R
s
(1979 S 2), probably the same object as that detected optically by Pioneer 11 (1979 S 1) and previously by groundbased telescopes (1966 S 2) (S 11); (v) a satellite of comparable diameter at 2.343
R
s
(1979 S 5); (vi) confirmation of the F ring between 2.336 and 2.371
R
s
; (vii) confirmation of the Pioneer division between 2.292 and 2.336
R
s
; (viii) a suspected satellite at 2.82
R
s
(1979 S 3); (ix) no clear evidence for the E ring though its influence may be obscured by stronger effects; and (x) the outer radius of the A ring at 2.292
R
s
. Inside of 2.292
R
s
there is a virtually total absence of magnetospheric particles and a marked reduction in cosmic-ray intensity. All distances are in units of the adopted equatorial radius of Saturn, 60,000 kilometers.
Sound Playback Experiments with Southern Right Whales (
Eubalaena australis
)
Authors: Clark Christopher W. , Clark Jane M.
Published: October 2006

A variety of sound recordings were played to southern right whales. Whales approached the loudspeaker and made frequent sounds in response to recordings of other southern right whales, but swam away and made relatively few sounds in response to playbacks of water noise, 200-hertz tones, and humpback whale sounds. Thus it appears that southern right whales can differentiate between conspecific sounds and other sounds.
Multiple Daily Amphetamine Administration: Behavioral and Neurochemical Alterations
Authors: Segal David S. , Weinberger Susan B. , Cahill Jerome , McCunney Stanley J.
Published: October 2006

In rats, multiple daily amphetamine injections (2.5 milligrams per kilogram of body weight, injected subcutaneously every 4 hours for 5 days) resulted in a progressive augmentation in response, characterized by a more rapid onset and an increased magnitude of stereotypy. By contrast, offset times of both the stereotypy and the poststereotypy hyperactivity periods were markedly shortened. When the animals were retested with the same dose of amphetamine 8 days after the long-term treatment was discontinued, the time of offset of the stereotypy and hyperactivity phases had recovered to values found with short-term amphetamine treatment, whereas the more rapid onset of stereotypy persisted. Brain monoamine and amphetamine concentrations and tyrosine hydroxylase activity were determined in comparably treated rats at times corresponding to the behavioral observations. The behavioral data indicate that enhanced responsiveness to amphetamine following its repeated administration may contribute to the development of amphetamine psychosis.
Saturn's Luminosity and Magnetism
Authors: Stevenson D. J.
Published: October 2006

The Pioneer 11 results for Saturn's large heat output, small magnetic field, and near-axisymmetry of the field may all be explained by an interior model in which the helium is undergoing phase separation and is nonuniformly distributed. Substantial depletion of helium from the atmosphere is predicted.
Metallic Glasses
Authors: Gilman John J.
Published: October 2006

The novel internal structures of metallic glasses lead to exceptional strength, corrosion resistance, and ease of magnetization. Combined with low manufacturing costs, these properties make glassy ribbons attractive for many applications. These materials also have scientific fascination because their compositions, structures, and properties have unexpected features.
III-V Compounds and Alloys: An Update
Authors: Woodall Jerry M.
Published: October 2006

The III-V compounds and alloys have been studied for three decades. Until recently, these materials have been commercialized for only a few specialized optoelectronic devices and microwave devices. Advances in thin-film epitaxy techniques, such as liquid phase epitaxy and chemical vapor deposition, are now providing the ability to form good quality lattice-matched heterojunctions with III-V materials. New optoelectronic devices, such as room-temperature continuous-wave injection lasers, have already resulted. This newfound ability may also affect the field of high-speed integrated circuits.
Initiation of Sulfate Activation: A Variation in C
4
Photosynthesis Plants
Authors: Gerwick B. C. , Ku S. B. , Black C. C.
Published: October 2006

In leaves of plants with C
4
photosynthesis, sulfur assimilation is initiated in bundle sheath cells whereas carbon and nitrogen assimilation are initiated in mesophyll cells. The activation of sulfate by adenosine triphosphate sulfurylase in leaves of C
4
plants occurs in chloroplasts of bundle sheath cells and is effected by two isozymes of approximately equal activities that accounted for 95 to 100 percent of the total leaf activity.
A Major Meteorite Impact on the Earth 65 Million Years Ago: Evidence from the Cretaceous-Tertiary Boundary Clay
Authors: Ganapathy R.
Published: October 2006

Evidence for a major meteorite impact on the earth 65 million years ago is shown by the presence of meteoritic debris in the "fish clay" from Denmark representing the Cretaceous-Tertiary boundary. Noble metals (iridium, osmium, gold, platinum, rhenium, ruthenium, palladium, nickel, and cobalt), which are sensitive indicators of meteorites and are normally depleted on the terrestrial surface by factors of 10
4
to 10
2
relative to cosmic abundances, are enriched in this boundary clay by factors of 5 to 100 over the expected abundances. With the exception of rhenium, all the enriched noble metals in the clay are present in cosmic proportions, indicating that the impacting celestial body had not undergone gross chemical differentiation. The major extinction of life on the earth at the end of the Cretaceous Period may be related to the meteorite impact.
Episodic Ice-Free Arctic Ocean in Pliocene and Pleistocene Time: Calcareous Nannofossil Evidence
Authors: Worsley Thomas R. , Herman Yvonne
Published: October 2006

Today's ice cover (2 to 4 meters thick) over the Arctic Ocean provides a shadow that prevents coccolithophorids (photosynthetic, planktonic algae) from living there. Sparse, low-diversity, but indigenous coccolith assemblages in late Pliocene to mid-Pleistocene (but not Holocene) sediments imply deep penetrating warm currents or an ice-free Arctic Ocean, or both, as those layers were being deposited.
Rupture Zones of Great Earthquakes in the Alaska-Aleutian Arc, 1784 to 1980
Authors: Sykes Lynn R. , Kisslinger Jerome B. , House Leigh , Davies John N. , Jacob Klaus H.
Published: October 2006

Historical documents indicate that great earthquakes ruptured at least a 500-kilometer-long segment of the plate boundary near the Alaska Peninsula in 1788 and 1847. At least half of a major seismic gap in the Shumagin Islands ruptured during those shocks but has not experienced a great earthquake for at least 77 years. Large shocks along this and other plate boundaries occur in bursts followed by several decades during which there is very little energy release.
Chemical Species in Fly Ash from Coal-Burning Power Plants
Authors: Hulett L. D. , Weinberger A. J. , Northcutt K. J. , Ferguson Marian
Published: October 2006

Fly ash specimens from four power plants in the Tennessee Valley Authority system have been separated into three matrices: glass, mullite-quartz, and magnetic spinel. Chemical species of trace elements are defined to a large extent by the matrices that contain them. The magnetic component of fly ash is ferrite. The mullite-quartz phase is relatively pure and can be recovered as a resource.
A Promoter That Drives Transgene Expression in Cerebellar Purkinje and Retinal Bipolar Neurons
Authors: Oberdick John , Smeyne Richard J. , Mann Jeff R. , Zackson Saul , Morgan James I.
Published: October 2006

A genomic clone encoding the Purkinje cell-specific L7 protein has been isolated and utilized to drive the expression of β-galactosidase in mice. Three independent transgenic lines, germ line transformed with an L7-β-galactosidase fusion gene, exhibit β-galactosidase expression in both cerebellar Purkinje cells and retinal bipolar neurons. This distribution is the same as that previously determined for the L7 protein by immunohistochemistry. The transgenic murine lines can be used to obtain populations of marked Purkinje and bipolar neurons. Similar L7 promoter constructs can be used to express other foreign genes specifically in these two classes of neurons.
Siliceous Microfossils from the Lower Cambrian of Northwest Canada: Possible Source for Biogenic Chert
Authors: Allison Carol Wagner
Published: October 2006

Round to oval, scalelike siliceous microstructures from cherts in Cambrian limestones of the western Yukon Territory suggest affinity with chrysophycean algae. At least six morphotypes present include porous forms with single branching processes and nonporous oval, ringlike forms. Partially dissolved specimens may indicate a contribution to contemporaneous or early diagenetic chert formation.
The Origin of Man
Authors: Lovejoy C. Owen
Published: October 2006

Five characters separate man from other hominoids—a large neocortex, bipedality, reduced anterior dentition with molar dominance, material culture, and unique sexual and reproductive behavior. Evidence provided by the fossil record, primate behavior, and demographic analysis shows that the traditional view that early human evolution was a direct consequence of brain expansion and material culture is incorrect, and that the unique sexual and reproductive behavior of man may be the sine qua non of human origin.
Volcanic Origin of the Eruptive Plumes on Io
Authors: Cook A. F. , Shoemaker E. M. , Smith B. A. , Danielson G. E. , Johnson T. V. , Synnott S. P.
Published: October 2006

A quadruple long exposure of Io in eclipse exhibits faint auroral emission from the eruptive plumes. No luminous spots in the vents, predicted by Gold, were observed. Heat from the interior of Io appears to be the predominant source of energy in the plumes.
Protease Nexin-II(amyloid β-protein Precursor): a Platelet α-Granule Protein
Authors: Van Nostrand William E. , Schmaier Alvin H. , Farrow Jeffrey S. , Cunningham Dennis D.
Published: October 2006

Protease nexin-II (PN-II) [amyloid β-protein precursor (APP)] and the amyloid β-protein are major constituents of neuritic plaques and cerebrovascular deposits in individuals with Alzheimer's disease and Down syndrome. Both the brain and the circulation have been implicated as sources of these molecules, although they have not been detected in blood. Human platelets have now been found to contain relatively large amounts of PN-II/APP. Platelet PN-II/APP was localized in platelet α-granules and was secreted upon platelet activation. Because PN-II/APP is a potent protease inhibitor and possesses growth factor activity, these results implicate PN-II/APP in wound repair. In certain disease states, alterations in platelet release and processing and clearance of PN-II/APP and its derived fragments could lead to pathological accumulation of these proteins.
Platelet Coagulation Factor XI
a
-Inhibitor, a Form of Alzheimer Amyloid Precursor Protein
Authors: Smith Raymond P. , Higuchi Darryl A. , Broze George J.
Published: October 2006

An inhibitor of coagulation factor XI
a
was purified from serum-free conditioned medium of HepG2 liver cells. Platelets stimulated with thrombin or calcium ionophore (A23187) secrete a protein functionally and immunologically identical to the inhibitor, implying a role for this inhibitor in hemostasis. Analysis of the amino-terminal amino acid sequence and immunologic reactivity showed the inhibitor to be a truncated form of the Alzheimer's amyloid precursor protein that contains a Kunitz-type serine protease inhibitor domain and at least a portion of the amyloid β protein. It inhibits factor XI
a
and trypsin with a
K
i
of 450 ± 50 pM and 20 ± 10 pM, respectively. Heparin (1 unit/ml) did not significantly effect inhibition of trypsin, but inhibition of XI
a
was 15 times greater (
K
i
= 25 ± 15 pM) in the presence of heparin.
Comparison of Two Forms of Long-Term Potentiation in Single Hippocampal Neurons
Authors: Zalutsky Robert A. , Nicoll Roger A.
Published: October 2006

In invertebrate nervous systems, some long-lasting increases in synaptic efficacy result from changes in the presynaptic cell. In the vertebrate nervous system, the best understood long-lasting change in synaptic strength is long-term potentiation (LTP) in the CA1 region of the hippocampus. Here the process is initiated postsynaptically, but the site of the persistent change is unresolved. Single CA3 hippocampal pyramidal cells receive excitatory inputs from associational-commissural fibers and from the mossy fibers of dentate granule cells and both pathways exhibit LTP. Although the induction of associational-commissural LTP requires in the postsynaptic cell
N
-methyl-D-aspartate (NMDA) receptor activation, membrane depolarization, and a rise in calcium, mossy fiber LTP does not. Paired-pulse facilitation, which is an index of increased transmitter release, is unaltered during associational-commissural LTP but is reduced during mossy fiber LTP. Thus, both the induction and the persistent change may be presynaptic in mossy fiber LTP but not in associational-commissural LTP.
Plasma Waves Near Saturn: Initial Results from Voyager 1
Authors: Gurnett D. A. , Kurth W. S. , Scarf F. L.
Published: October 2006

The Voyager 1 plasma wave instrument detected many familiar types of plasma waves during the encounter with Saturn, including ion-acoustic waves and electron plasma oscillations upstream of the bow shock, an intense burst of electrostatic noise at the shock, and chorus, hiss, electrostatic electron cyclotron waves, and upper hybrid resonance emissions in the inner magnetosphere. A clocklike Saturn rotational control of low-frequency radio emissions was observed, and evidence was obtained of possible control by the moon Dione. Strong plasma wave emissions were detected at the Titan encounter indicating the presence of a turbulent sheath extending around Titan, and upper hybrid resonance measurements of the electron density show the existence of a dense plume of plasma being carried downstream of Titan by the interaction with the rapidly rotating magnetosphere of Saturn.
Alternative Male Strategies: Genetic Differences in Crickets
Authors: Cade William H.
Published: October 2006

Male field crickets,
Gryllus integer
, call and attract mates, or they silently intercept females attracted to calling males. Selection experiments demonstrate that the duration of nightly calling has an important genetic component. Mean calling times in high and low lines were significantly different and had realized heritabilities of 0.50 and 0.53, respectively. Selection can operate in such a way that each of the alternative forms of male reproductive behavior is associated with a specific genetic substrate. This has not yet been shown for other species in which males adopt contrasting modes of mating behavior.
Dolphin Vocalization Mechanisms
Authors: Mackay R. Stuart , Liaw H. M.
Published: October 2006

Although humans have difficulty whistling when in a habitat that is more than 20 meters underwater, dolphins can make certain sounds at great depths through a related mechanism. Other dolphin sounds, such as clicks and complex buzzes, are produced by vibrations of the tissue of the nasal plugs, apparently without the use of the larynx; in these instances, the air sacs act as reservoirs. This was determined from studies of
Tursiops truncatus
and
Delphinus delphis
with harmless ultrasonic beams projected noninvasively to determine movements of the air sacs.
Increased Reproductive Effort with Age in the California Gull
(Larus californicus)
Authors: Pugesek Bruce H.
Published: October 2006

Comparisons of reproductive behaviors of three age classes of California gulls demonstrate that reproductive effort increases with age in this seabird. These findings contradict the assumption that increased reproductive success with age results from increased experience and social status and demonstrate that selection for increased reproductive effort can occur in long-lived species.
Salt Glands in the Tongue of the Estuarine Crocodile
Crocodylus porosus
Authors: Taplin Laurence E. , Grigg Gordon C.
Published: October 2006

The apparent absence of salt glands in marine and estuarine Crocodilia has long been a puzzle. However, we have identified glands in the tongue of
Crocodylus porosus
which exude a concentrated secretion of sodium chloride. The glands are similar in ultrastructure to other reptilian salt glands and undoubtedly play a major role in electrolyte regulation.
Historical Nile Floods and Their Implications for Climatic Change
Authors: Hassan Fekri A.
Published: October 2006

Analysis of Nile flood stages from A.D. 640 to 1921 reveals major episodes of low Nile discharge during the years 930 to 1070 and 1180 to 1350 and major episodes of high Nile floods during 1070 to 1180 and 1350 to 1470. Examination of Nile flood maxima and minima and comparison with water levels in Lake Chad reveal a correlation between high Nile discharge and greater rainfall in equatorial East Africa. There is also apparently a correlation between low Nile discharge and cold climate in Europe.
Infant Carrying by Male Chacma Baboons
Authors: Busse Curt , Hamilton William J.
Published: October 2006

Male chacma baboons,
Papio ursinus
, carry their offspring during confrontations with higher ranking immigrant males, who are a threat to the infants' lives. The infants sometimes initiate these confrontations by approaching and provoking immigrant males when protective males are close by. Mothers rarely interfere during these interactions.