bluuebunny/crossref_metadata_2025 huggingface dataset:
Ecological Aspects of Amphibian Metamorphosis
Authors: Wilbur Henry M. , Collins James P.
Published: October 2006

A synthetic theory of the ecology of amphibian metamorphosis is founded on the observation that the large variation in length of larval period and body size at metamorphosis typical of a particular species of amphibian cannot be directly explained by differences in dates of hatching or egg sizes. It is proposed that as development proceeds, variation in exponential growth coefficients causes a trend from a normal distribution to a skewed distribution of body sizes. The degree of skewing increases and the median of the distribution decreases with increasing initial densities of populations. The relative advantages of the largest members of a cohort may arise from a variety of mechanisms including the production of growth inhibitors, interference competition, and size-selective feeding behavior. These mechanisms result in a nonnormal distribution of competitive ability, a possible source of the density-dependent competition coefficient found in systems with many species.

In our model the ranges of body sizes and dates of metamorphosis are determined by a minimum body size that must be obtained and a maximum body size that will not be exceeded at metamorphosis. Between these two size thresholds the endocrinological initiation of metamorphosis is expected to be related to the recent growth history of the individual larva. Species that exploit uncertain environments will have a wide range of possible sizes at metamorphosis. Species exploiting relatively certain environments will have a narrower range. The evolution of neoteny and direct development logically follow from the application of these ideas to the ecological context of the evolution of amphibian life histories. Species that live in constant aquatic habitats surrounded by hostile environments (desert ponds, caves, high-altitude lakes) may evolve permanent larvae genetically incapable of metamorphosis. Other populations may evolve a facultative metamorphosis such that populations are a mixture of neotenes and terrestrial adults. Direct development results from selection to escape the competition, predation, and environmental uncertainty characteristic of some aquatic habitats and is usually accompanied by parental care. The relation between our ecological model and the physiological mechanisms that initiate metamorphosis can only be suggested and it remains an open problem for developmental biologists.
Engraftment and Development of Human T and B Cells in Mice After Bone Marrow Transplantation
Authors: Lubin Ido , Faktorowich Yifat , Lapidot Tsvee , Gan Yehudit , Eshhar Zelig , Gazit Ephraim , Levite Mia , Reisner Yair
Published: October 2006

A model for human lymphocyte ontogeny has been developed in a normal mouse. Human bone marrow, depleted of mature T and B lymphocytes, and bone marrow from mice with severe combined immunodeficiency were transplanted into lethally irradiated BALB/c mice. Human B and T cells were first detected 2 to 4 months after transplantation and persisted for at least 6 months. Most human thymocytes (30 to 50 percent of total thymocytes) were CD3
+
CD4
+
CD8
+
. Human immunoglobulin was detected in some chimeras, and a human antibody response to dinitrophenol could be generated after primary and secondary immunization.
α-Ketoglutaramate: Increased Concentrations in the Cerebrospinal Fluid of Patients in Hepatic Coma
Authors: Vergara Fernando , Plum Fred , Duffy Thomas E.
Published: October 2006

α-Ketoglutaramate, a deaminated metabolite of glutamine not previously identified in biological tissues, was measured in the cerebrospinal fluid of human subjects and found to be increased three- to tenfold in patients with hepatic coma. When perfused into the cerebral lateral ventricles of rats, α-ketoglutaramate (10 m
M
) depressed the animals' nocturnal locomotor activity, and at higher doses induced circling behavior and myoclonus. The concentration of α-ketoglutaramate in cerebrospinal fluid appears to be a reliable diagnostic indicator of hepatic coma, and its accumulation may contribute to the pathogenesis of this disease.
DNA Synthesis and Mitosis in Well-Differentiated Mammalian Cardiocytes
Authors: Goldstein Margaret A. , Claycomb William C. , Schwartz Arnold
Published: October 2006

Incorporation of [
3
H]thymidine into nuclei of heart cells of 2-day-old rats indicates that neonatal cardiac cells containing well-aligned myofibrils synthesize DNA. In these highly differentiated cells, neither the presence of contractile proteins nor their organization into myofibrils inhibits either DNA synthesis or mitosis.
Carcinogenicity of Methylchrysenes
Authors: Hoffmann Dietrich , Bondinell William E. , Wynder Ernst L.
Published: October 2006

Methylchrysenes are present in tobacco smoke and are suspected to contribute to the tumorigenicity of this inhalant. Chrysene and the six isomeric methylchrysenes were obtained in high purity (> 99.9 percent); they were tested on mouse skin for tumor initiating activity and carcinogenicity. The 3- and 6-methylchrysenes are strong tumor initiators, whereas the other five chrysenes have moderate initiating activity. 5-Methylchrysene is a strong carcinogen; the other chrysenes are inactive or weak carcinogens.
Arachidonic Acid Causes Sudden Death in Rabbits
Authors: Silver Melvin J. , Hoch Willis , Kocsis James J. , Ingerman Carol M. , Smith J. Bryan
Published: October 2006

Injection of sodium arachidonate (1.4 milligrams per kilogram) into the marginal ear veins of rabbits caused death within 3 minutes. Histological examination showed platelet thrombi in the microvasculature of the lungs. Rabbits were protected from the lethal effects of arachidonic acid by pretreatment with aspirin. Fatty acids closely related to arachidonic acid did not cause death.
Long Journey into Tunneling
Authors: Esaki Leo
Published: October 2006

I am, of course, deeply aware of important contributions made by many colleagues and my friends throughout this long journey. The subject of the second section was carried out when I was in Japan and all the rest has been performed in the United States of America. Since my journey into tunneling is still continuing, I do not come to any conclusions in this talk. However, I would like to point out that many high barriers exist in this world: barriers between nations, races, and creeds. Unfortunately, some barriers are thick and strong. But I hope, with determination, we will find a way to tunnel through these barriers easily and freely, to bring the world together so that everyone can share in the legacy of Alfred Nobel.
Auditory Membrane Vibrations: Measurements at Sub-Angstrom Levels by Optical Heterodyne Spectroscopy
Authors: Dragsten Paul R. , Webi Watt W. , Patoi John A. , Capranic Robert R.
Published: October 2006

We describe an optical technique for measurement of mechanical vibrations in the auditory organs of living animals. The technique uses light scattered from the vibrating structure and offers several new advantages. Better than 1 angstrom sensitivity, 10 micrometers spatial resolution, and > 70 decibels dynamic range are achieved. Illustrative measurements of the mechanical response of the tympanic membrane of crickets (
Gryllidae
) are reported.
Comet Kohoutek: Ultraviolet Images and Spectrograms
Authors: Opal C. B. , Carruthers G. R. , Prinz D. K. , Meier R. R.
Published: October 2006

Emissions of atomic oxygen (1304 angstroms), atomic carbon (1657 angstroms), and atomic hydrogen (1216 angstroms) from Comet Kohoutek were observed with ultraviolet cameras carried on a sounding rocket on 8 January 1974. Analysis of the Lyman alpha halo at 1216 angstroms gave an atomic hydrogen production rate of 4.5 × 10
29
atoms per second.
Reverse Transcriptase in Normal Rhesus Monkey Placenta
Authors: Mayer Robert J. , Smith R. Graham , Gallo Robert C.
Published: October 2006

Particles with the morphology of type C virus have been identified from primate placentas by electron microscopy. A reverse transcriptase (RNA-dependent DNA polymerase) was isolated and purified from microsomal pellets of two fresh placentas of rhesus monkeys in the early stages of gestation. This enzyme was biochemically similar yet immunologically distinct from the reverse transcriptases of known tumorigenic type C RNA viruses isolated from primates, but was immunologically related to a reverse transcriptase isolated from a type C virus obtained from normal baboon placenta. These particles may represent endogenous viruses and may function in the transfer of genetic information during embryogenesis.
Inhibition of PDGF β Receptor Signal Transduction by Coexpression of a Truncated Receptor
Authors: Ueno Hikaru , Colbert Heather , Escobedo Jaime A. , Williams Lewis T.
Published: October 2006

A mutated form of the platelet-derived growth factor (PDGF) β receptor lacking most of its cytoplasmic domain was tested for its ability to block wild-type PDGF receptor function. PDGF induced the formation of complexes consisting of wild-type and truncated receptors. Such complexes were defective in autophosphorylation. When truncated receptors were expressed in excess compared to wild-type receptors, stimulation by PDGF of receptor autophosphorylation, association of phosphatidylinositol-3 kinase with the receptor, and calcium mobilization were blocked. Thus, a truncated receptor can inactivate wild-type receptor function by forming ligand-dependent receptor complexes (probably heterodimers) that are incapable of mediating the early steps of signal transduction.
The Spiral Interplanetary Magnetic Field: A Polarity and Sunspot Cycle Variation
Authors: Svalgaard Leif , Wilcox John M.
Published: October 2006

Spacecraft observations near the earth of the average direction of the interplanetary magnetic field during the sunspot maximum year 1968 showed a deviation from the spiral field of Parker's classical description. The included angle between the average field direction when the field polarity was away from the sun and the average direction when the field polarity was toward the sun was 168°, rather than 180° as predicted by Parker. This effect appears to have a sunspot cycle variation.
Human Chromosome 21 Dosage: Effect on the Expression of the Interferon Induced Antiviral State
Authors: Tan Y. H. , Schneider E. L. , Tischfield J. , Epstein C. J. , Ruddle F. H.
Published: October 2006

Human primary skin fibroblasts trisomic for chromosome 13, 18, or 21 and diploid human skin fibroblasts were induced for an antiviral response with human interferon. The cells that were trisomic for chromosome 21 were three to seven times more sensitive to protection by human interferon than the normal diploid or trisomic 18 or 13 fibroblasts. The differential response in trisomic 21 cells is consistent with the known assignment of the human antiviral gene to chromosome 21.
Atmospheric Electrical Detection of Organized Convection
Authors: Markson Ralph
Published: October 2006

Relatively simple atmospheric electrical instrumentation carried on a small aircraft constitutes a flexible and sensitive system for detecting organized convection. Data can be obtained close to the sea surface, and low-velocity flight enhances the spatial resolution. With a slow-flying airplane or powered glider, it may be possible to trace the circulation of individual convection cells and to investigate the trajectory of air which forms cumulus clouds, one of the major unsolved problems in tropical meteorology. Since space charge near the ocean surface was found on some days to be organized on a horizontal scale equivalent to the cumulus cloud scale, this suggests that some of the air which forms maritime cumulus clouds may come from within a few meters of the ocean and that atmospheric electrical instrumentation may have the potential for tracing air from the sea surface to the clouds.

Although the atmospheric electrical instrumentation technique described here cannot be used for direct measurement of air velocity, it may be possible to develop a model that can be used to calculate air velocities from electric field data. Even though with the technique described here it is not possible to make direct measurements of wind velocity, airborne electric field records can provide useful information about convection by delineating patterns in the wind field and structural features of thermals (rising bodies of relatively warm air) and by making possible the remote detection of thermals.

Future plans include attempting to trace interfaces between adjacent roll vortices from the sea surface through the depth of the mixed layer (i) by flying the aircraft parallel to the wind so as to nullify the horizontal electric field (measured between wing-tip probes) while ascending and descending along the interface between adjacent roll vortices and (ii) by measuring vertical and horizontal potential gradient variations at different flight levels.

The sensitivity of atmospheric electrical instrumentation to the top of the mixed layer and structure within it can be used to explore another important problem in boundary layer convection—why convective cloud cover and oceanic rainfall are greater at night than during the day.

Workers in atmospheric electricity have long recognized that their domain is strongly controlled by turbulence in the lower atmosphere, and many have believed that the most effective use of atmospheric electrical techniques to assist meteorological research would be in studying exchange processes. Reiter effectively extended atmospheric electrical studies of boundary layer phenomena through a height range by mounting instruments on cable cars traveling between the valley floor and mountain tops in the Alps. The airborne measurements described here extend this approach. Relating the electrical structure of the atmosphere to its dynamic structure poses an interesting problem which may contribute to our understanding of the atmosphere.
Volcanic Eruptions: Contribution to Magnetism in Deep-Sea Sediments Downwind from the Azores
Authors: Freed W. Kenneth , Watkins Norman D.
Published: October 2006

The mean bulk magnetic susceptibility (χ̅) and the intensity of remanent magnetization (
J̅
) of deep-sea sediments vary systematically, but in an opposite sense, for a distance of 600 kilometers downwind from the Azores. Beyond the distance both
J̅
and χ̅ diminish for at least another 600 kilometers. The dominant type of magnetic particle in the sediments is interpreted to be atmospherically transported volcanic dust.
A Tunneling Spectroscopy Study of Molecular Degradation due to Electron Irradiation
Authors: Hansma Paul K. , Parikh Mihir
Published: October 2006

Electron tunneling spectroscopy has been used to characterize the degradation of β-D-fructose after electron bombardment in a scanning electron microscope. The decrease in intensity of various vibrational bands is correlated with structural changes in the molecule, thereby providing a detailed picture of the degradation process.
Modeling the Ice-Age Climate
Authors: Gates W. Lawrence
Published: October 2006

Using the boundary conditions of sea-surface temperature, ice sheet topography, and surface albedo assembled by CLIMAP for 18,000 B.P., the global ice-age July climate has been simulated with a two-level dynamical atmospheric model. Compared with the simulation for present July climate, the ice age is substantially cooler and drier over the unglaciated continental areas, with the maximum zonal westerlies in the Northern Hemisphere displaced southward in the vicinity of the ice sheets. The simulated changes of surface air temperature agree reasonably well with the estimates available from the analysis of fossil pollen and periglacial data, and are consistent with the simulated changes of other climatic variables. These results are generally supported by independent investigations with simpler models.

In spite of this qualified success, further analysis of both simulated and verification data is needed to establish the details of ice-age climate, especially the precipitation regimes, and to document the role of eddy fluxes in maintaining the heat, momentum, and moisture balances of the ice-age general circulation. New paleoclimatic data bases for both July and January of 18,000 B.P. are being assembled by CLIMAP and will be used in new simulations of the seasonal ice-age climate.
Tropospheric Halogen Gases: Inorganic and Organic Components
Authors: Rahn Kenneth A. , Borys Randolph D. , Duce Robert A.
Published: October 2006

Inorganic and organic components of the gaseous tropospheric halogens chlorine, bromine, and iodine have been simultaneously measured. At four diverse remote locations the organic component contained the bulk of the halogen mass, varied less than the inorganic component, and was comparable in concentration to the independently measured halocarbon component.
Xenon-133: Ambient Activity from Nuclear Power Stations
Authors: Kunz C. O. , Paperiello C. J.
Published: October 2006

The average activity of xenon-133 within and at approximately 100 kilometers from Albany, New York, from April to July 1975 was 2.6 picocuries per cubic meter of air. The source was gaseous effluents from boiling water reactors located in the northeastern United States. Its 5.29-day half-life makes xenon-133 an appropriate isotope to observe for the study of regional and hemispheric dispersion of pollutants.
The Arctic Mirage and the Early North Atlantic
Authors: Sawatzky H. L. , Lehn W. H.
Published: October 2006

The arctic mirage is a phenomenon that is common in higher latitudes. It occurs under conditions of pronounced temperature inversion, which impart to the air a refractive capability that may equal or exceed the curvature of the earth. Manifestations of the arctic mirage, though largely forgotten in modern times, are described in the earliest accounts of North Atlantic discovery.

This interdisciplinary investigation, combining historical induction with scientific observation and analysis, has suggested a new interpretation of historical events. We believe that information gleaned from these mirages was vital to Norse navigation and exploration in the North Atlantic. We further contend that the mirage may furnish a logical basis for the pervasive ancient and medieval concept of the flat or saucer-shaped world.
Determination of Macromolecular Structures from Anomalous Diffraction of Synchrotron Radiation
Authors: Hendrickson Wayne A.
Published: October 2006

Resonance between beams of x-ray waves and electronic transitions from bound atomic orbitals leads to a phenomenon known as anomalous scattering. This effect can be exploited in x-ray crystallographic studies on biological macromolecules by making diffraction measurements at selected wavelengths associated with a particular resonant transition. In this manner the problem of determining the three-dimensional structure of thousands of atoms is reduced to that of initially solving for a few anomalous scattering centers that can then be used as a reference for developing the entire structure. This method of multiwavelength anomalous diffraction has now been applied in a number of structure determinations. Optimal experiments require appropriate synchrotron instrumentation, careful experimental design, and sophisticated analytical procedures. There are rich opportunities for future applications.
Density Maxima in High-Pressure Supercooled Water and Liquid Silicon Dioxide
Authors: Angell C. A. , Kanno H.
Published: October 2006

With glass capillary pressure vessels it has been possible to study the effect of pressure on the temperature of maximum density (TMD) and on the "sharpness" of the density maximum in liquid H
2
O and D
2
O in the important but little-studied supercooled regime. A pressure of 1200 bars produces a 33°C depression of the TMD in these liquids and a considerable reduction in sharpness. Comparison with the rather flat density maximum for liquid SiO
2
supports the notion that the presence or absence of density anomalies in "tetrahedral" liquids depends on the average bridge-bond angle, which is evidently unusually large in water at normal pressure.
Mineral-Produced High-Pressure Striae and Clay Polish: Key Evidence for Nonballistic Transport of Ejecta from Ries Crater
Authors: Chao E. C. T.
Published: October 2006

Recently discovered mineral-produced, deeply incised striae and mirrorlike polish on broken surfaces of limestone fragments from the sedimentary ejecta of the Ries impact crater of southern Germany are described. The striae and polish were produced under high confining pressures during high-velocity nonballistic transport of the ejecta mass within the time span of the cratering event (measured in terms of seconds). The striae on these fragments were produced by scouring by small mineral grains embedded in the surrounding clay matrix, and the polish was formed under the same condition, by movements of relatively fragment-free clay against the fragment surfaces. The occurrence of these striae and polish is key evidence for estimating the distribution and determining the relative importance of nonballistic and ballistic transport of ejecta from the shallow Ries stony meteorite impact crater.
Pluto: Evidence for Methane Frost
Authors: Cruikshank D. P. , Pilcher C. B. , Morrison D.
Published: October 2006

Infrared photometry (1.2 to 2.2 micrometers) of Pluto provides evidence for frozen methane on the surface of the planet. This appears to be the first observational indication of this ice in the solar system. Its presence on Pluto suggests that the planet's albedo (reflectance) may be ≥ 0.4 and that its diameter may be less than that of the moon.
The Spinning Rotation of Ash and Tulip Tree Samaras
Authors: McCutchen C. W.
Published: October 2006

Ash and tulip tree samaras rotate on their long axes as they fall, as well as spin around like maple samaras. They descend faster than would maple samaras of the same size and weight and much faster than would zanonia samaras, but they are very stable, which may explain their evolutionary success.
Plant-Animal Mutualism: Coevolution with Dodo Leads to Near Extinction of Plant
Authors: Temple Stanley A.
Published: October 2006

An endemic sapotaceous treeCalvaria majorfound on the island of Mauritius is nearly extinct because its seeds apparently required passage through the digestive tract of the now-extinct dodoRaphus cucullatusto overcome persistent seed coat dormancy caused by a specially thickened endocarp.
Starvation Kinetics
Authors: Eyring Henry
Published: October 2006

Reactions that take place in shock waves are slow compared to the energy present in the translational degrees of freedom. One explanation for the slow burning in a detonation is that successive surface layers of the solid or liquid must react sequentially. Another mechanism, which can also account for the slowness of reactions in shock waves in gases, is the basis for starvation kinetics: the bond that is breaking must draw its activation energy from a vibrational reservoir in disequilibrium with the translational degrees of freedom of the reacting molecule.
Lunar Crater Giordano Bruno: A.D. 1178 Impact Observations Consistent with Laser Ranging Results
Authors: Calame Odile , Mulholland J. Derral
Published: October 2006

The hypothesis of Hartung, that the impact formation of lunar crater Giordano Bruno (103° east, 36° north) was observed and recorded 800 years ago, is considered in the context of data from the Luna 24 mission and laser range observations. It is concluded that (i) the event would certainly have been visible, and (ii) current determinations of the free libration in longitude in the moon's rotation are consistent with the hypothesis. Such a study cannot prove Hartung's interpretation, but it is nonetheless supportive of it.
Seeing with a New Light: Synchrotron Radiation
Authors: Watson R. E. , Perlman M. L.
Published: October 2006

The special properties of synchrotron light are leading to a rapid increase in its utilization for both research and technology. At wavelengths in the ultraviolet region of the broad spectrum in these beams a number of atomic, molecular, and solid-state spectroscopies are being pursued; soft x-rays are being used for spectroscopy, lithography, microscopy, and topography; at still shorter wavelengths, advantage is taken of scattering properties to probe the structure of matter. Characteristics of synchrotron radiation and of the sources which produce it are described, and some typical investigations and applications are presented to suggest the versatility of these sources.
Size Variation and the Distribution of Hemimetabolous Aquatic Insects: Two Thermal Equilibrium Hypotheses
Authors: Sweeney Bernard W. , Vannote Robin L.
Published: October 2006

Adult body size and fecundity of a number of hemimetabolous aquatic insects depend largely on thermal conditions during the larval period. Small adults and reduced fecundity result when temperatures are either warmed or cooled with respect to more optimal thermal conditions. Temperature apparently affects adult size by altering the larval growth rate and the timing and rate of adult tissue development for each larva. The data suggest a new interpretation for the geographic distribution of aquatic insects.
Chytrid-Like Fossils of Pennsylvanian Age
Authors: Millay M. A. , Taylor T. N.
Published: October 2006

Chytrid-like fungal sporangia are described occurring in saccate pollen grains of Pennsylvanian age. Both endo- and epibiotic sporangia are present, and may exhibit discharge papillae and a coarse rhizomycelium. Sporangial features, choice of substrate, and the presence of a light refractile body in presumed zoospores suggest relationships with the Chytridiales.
Visualization and Transport of Positron Emission from Proton Activation in vivo
Authors: Bennett G. W. , Archambeau J. O. , Archambeau B. E. , Meltzer J. I. , Wingate C. L.
Published: October 2006

Heavy charged particle beams can be widely used for cancer therapy if control in heterogeneous tissue is proved practical. A beam of protons at 200 million electron volts has been visualized in plastic and in a living animal by using an on-line positron camera. The fraction of the activity retained in the radiation site was found to be at least 70 percent of that produced in a dead animal. The sensitivity of the technique was established for a typical geometry.
Marine Snow: Microplankton Habitat and Source of Small-Scale Patchiness in Pelagic Populations
Authors: Silver Mary Wilcox , Shanks Alan L. , Trent Jonathan D.
Published: October 2006

In near-surface waters of the neritic zone, the fragile aggregate material called "marine snow" is enriched by a variety of planktonic organisms and detrital products of plankton. Here marine snow is a source of patchiness and taxonomic diversity for microplankton populations and is a likely food resource and recycling agent for fecal particles.
Surface Science
Authors: Somorjai G. A.
Published: October 2006

During the past 15 years, surfaces have been increasingly studied on the atomic scale. As a result, their atomic structure and composition and the dynamics of gas-surface interactions are much better understood. Modern surface science is beginning to have an impact on many technologies. Techniques are readily available to study solid-vacuum and solid-gas interfaces. Studies of solid-liquid and solid-solid interfaces are difficult and appear to be challenging frontier areas of research. Surface science is at the heart of most research and development problems in energy conversion and storage.
Bees Have Magnetic Remanence
Authors: Gould James L. , Kirschvink J. L. , Deffeyes K. S.
Published: October 2006

Honey bees orient to the earth's magnetic field. This ability may be associated with a region of transversely oriented magnetic material in the front of the abdomen. The magnetic moment apparently develops in the pupal state and persists in the adults.
The Spokane Flood Controversy and the Martian Outflow Channels
Authors: Baker Victor R.
Published: October 2006

In a series of papers published between 1923 and 1932, J Harlen Bretz described an enormous plexus of proglacial stream channels eroded into the loess and basalt of the Columbia Plateau, eastern Washington. He argued that this region, which he called the Channeled Scabland, was the product of a cataclysmic flood, which he called the Spokane flood. Considering the nature and vehemence of the opposition to his hypothesis, which was considered outrageous, its eventual scientific verification constitutes one of the most fascinating episodes in the history of modern science. The discovery of probable catastrophic flood channels on Mars has given new relevance to Bretz's insights.
Fish, Crustaceans, and the Sea Floor Under the Ross Ice Shelf
Authors: Bruchhausen P. M. , Raymond J. A. , Jacobs S. S. , DeVries A. L. , Thorndike E. M. , DeWitt H. H.
Published: October 2006

Baited traps and a camera lowered through the Ross Ice Shelf, Antarctica, at a point 475 kilometers from the open Ross Sea and to 597 meters below sea level revealed the presence of fish, many amphipods, and one isopod. Biological or current markings were not evident on a soft bottom littered with subangular lumps. A fish was caught through a crevasse 80 kilometers from the shelf edge.
Chick Embryonic Skin as a Rapid Organ Culture Assay for Cellular Neoplasia
Authors: Noguchi Philip D. , Johnson Joyce B. , O'Donnell Robert , Petricciani J. C.
Published: October 2006

We used chick embryonic skin (CES) in organ culture to assess the neoplastic potential of a variety of cultured human and nonhuman cell lines. Cells derived from cancer tissues grew in CES and formed tumors in nude mice while cells derived from normal tissues grew in neither system. The CES proved to be more sensitive than the nude mouse when used to assay SV40 transformed human cells; each of four such lines grew in CES while only one of the four lines grew and formed tumors in nude mice. In addition, the patterns of invasion by inoculated cells can be easily studied in the CES. These results suggest that CES in organ culture offers an inexpensive, rapid, and reliable alternative to the nude mouse as a tumorigenicity test.
Different Brain Areas Mediate the Analgesic and Epileptic Properties of Enkephalin
Authors: Frenk Hanan , McCarty Bradford C. , Liebeskind John C.
Published: October 2006

Single injections of 120 micrograms of methionine-enkephalin were made into various midbrain and forebrain structures in the rat. Analgesia was observed after injections into or near the ventral, caudal midbrain periaqueductal gray matter. Seizures and other pathological electroencephalogram (EEG) changes were seen with injections into or near the forebrain dorsomedial nucleus of the thalamus. No animals with midbrain injection sites showed EEG changes, and none with forebrain injection sites were analgesic. These data, taken together with other lines of evidence, suggest that enkephalin-induced analgesia and enkephalin-induced seizures are mediated by opiate receptors that are located in different brain areas and that are pharmacologically different.
Isotope Selectivity of Infrared Laser-Driven Unimolecular Dissociation of a Volatile Uranyl Compound
Authors: Cox D. M. , Hall R. B. , Horsley J. A. , Kramer G. M. , Rabinowitz P. , Kaldor A.
Published: October 2006

Isotope-selective photodissociation of the volatile complex uranyl hexafluoroacetylacetonate ⋅ tetrahydrofuran [UO
2
(hfacac)
2
⋅ THF] has been achieved with both a continuous-wave and a pulsed carbon dioxide laser. The photodissociation was carried out in a low-density molecular beam under collisionless conditions. Transitions of the laser are in resonance with the asymmetric O-U-O stretch of the uranyl moiety, a vibrational mode whose frequency is sensitive to the masses of the uranium and oxygen isotopes. Unimolecular dissociation is observed mass spectrometrically at an extremely low energy fluence, with no evidence of an energy fluence or intensity threshold. The dissociation yield increases nearly linearly with increasing energy fluence. At constant fluence the dissociation yield is independent of contact time between the radiation field and the molecule, indicating that the decomposition is driven by laser energy fluence and not laser intensity. The oxygen and uranium isotope selectivities measured in these experiments are nearly those predicted by the ratio of the linear absorption cross sections for the respective isotopes. Thus, essentially complete selectivity is observed for oxygen isotopes, while a selectivity of only about 1.25 is measured for the uranium isotopes. A model presented to describe these results is based on rapid intramolecular vibrational energy flow from the pumped mode into a limited number of closely coupled modes.
Mayan Urbanism: Impact on a Tropical Karst Environment
Authors: Deevey E. S. , Rice Don S. , Rice Prudence M. , Vaughan H. H. , Brenner Mark , Flannery M. S.
Published: October 2006

From the first millennium B.C. through the 9th-century A.D. Classic Maya collapse, nonurban populations grew exponentially, doubling every 408 years, in the twin-lake (Yaxha-Sacnab) basin that contained the Classic urban center of Yaxha. Pollen data show that forests were essentially cleared by Early Classic time. Sharply accelerated slopewash and colluviation, amplified in the Yaxha subbasin by urban construction, transferred nutrients plus calcareous, silty clay to both lakes. Except for the urban silt, colluvium appearing as lake sediments has a mean total phosphorus concentration close to that of basin soils. From this fact, from abundance and distribution of soil phosphorus, and from continuing post-Maya influxes (80 to 86 milligrams of phosphorus per square meter each year), which have no other apparent source, we conclude that riparian soils are anthrosols and that the mechanism of long-term phosphorus loading in lakes is mass transport of soil. Per capita deliveries of phosphorus match physiological outputs, approximately 0.5 kilogram of phosphorus per capita per year. Smaller apparent deliveries reflect the nonphosphatic composition of urban silt; larger societal outputs, expressing excess phosphorus from deforestation and from food waste and mortuary disposal, are probable but cannot be evaluated from our data. Eutrophication is not demonstrable and was probably impeded, even in less-impacted lakes, by suspended Maya silt. Environmental strain, the product of accelerating agroengineering demand and sequestering of nutrients in colluvium, developed too slowly to act as a servomechanism, damping population growth, at least until Late Classic time.
B1-B2 Transition in Calcium Oxide from Shock-Wave and Diamond-Cell Experiments
Authors: Jeanloz Raymond , Ahrens T. J. , Mao H. K. , Bell P. M.
Published: October 2006

Volume and structural data obtained by shock-wave and diamond-cell techniques demonstrate that calcium oxide transforms from the B1 (sodium chloride type) to the B2 (cesium chloride type) structure at 60 to 70 gigapascals (0.6 to 0.7 megabar) with a volume decrease of 11 percent. The agreement between the shockwave and diamond-cell results independently confirms the ruby-fluorescence pressure scale to about 65 gigapascals. The shock-wave data agree closely with ultrasonic measurements on the B1 phase and also agree satisfactorily with equations of state derived from ab initio calculations. The discovery of this B1-B2 transition is significant in that it allows considerable enrichment of calcium components in the earth's lower mantle, which is consistent with inhomogeneous accretion theories.
Hot Plasma Environment at Jupiter: Voyager 2 Results
Authors: Krimigis S. M. , Armstrong T. P. , Axford W. I. , Bostrom C. O. , Fan C. Y. , Gloeckler G. , Lanzerotti L. J. , Keath E. P. , Zwickl R. D. , Carbary J. F. , Hamilton D. C.
Published: October 2006

Measurements of the hot (electron and ion energies ≳20 and ≳ 28 kiloelectron volts, respectively) plasma environment at Jupiter by the low-energy charged particle (LECP) instrument on Voyager 2 have revealed several new and unusual aspects of the Jovian magnetosphere. The magnetosphere is populated from its outer edge into a distance of at least ∼ 30 Jupiter radii (
R
J
) by a hot (3 × 10
8
to 5 × 10
8
K) multicomponent plasma consisting primarily of hydrogen, oxygen, and sulfur ions. Outside ∼ 30
R
J
the hot plasma exhibits ion densities from ∼ 10
–1
to ∼ 10
–6
per cubic centimeter and energy densities from ∼ 10
–8
to 10
–13
erg per cubic centimeter, suggesting a high β plasma throughout the region. The plasma is flowing in the corotation direction to the edge of the magnetosphere on the dayside, where it is confined by solar wind pressure, and to a distance of ∼ 140 to 160
R
J
on the nightside at ∼ 0300 local time. Beyond ∼ 150
R
J
the hot plasma flow changes into a "magnetospheric wind" blowing away from Jupiter at an angle of ∼ 20° west of the sun-Jupiter line, characterized by a temperature of ∼ 3 × 10
8
K (26 kiloelectron volts), velocities ranging from ∼ 300 to > 1000 kilometers per second, and composition similar to that observed in the inner magnetosphere. The radial profiles of the ratios of oxygen to helium and sulfur to helium (≲ 1 million electron volts per nucleon) monotonically increase toward periapsis, while the carbon to helium ratio stays relatively constant; a significant amount of sodium (Na/O ∼ 0.05) has also been identified. The hydrogen to helium ratio ranges from ∼ 20 just outside the magnetosphere to values up to ∼ 300 inside; the modulation of this ratio suggests a discontinuity in the particle population at ∼ 50 to 60
R
J
. Large fluctuations in energetic particle intensities were observed on the inbound trajectory as the spacecraft approached Ganymede, some of which suggest the presence of a "wake." Five- and 10-hour periodicities were observed in the magnetosphere. Calculations of plasma flow velocities with the use of Compton-Getting formalism imply that plasma is mostly corotating to large radial distances from the planet. Thus the Jovian magnetosphere is confined by a plasma boundary (as was implied by the model of Brice and Ioannidis) rather than a conventional magnetopause. Inside the plasma boundary there exists a discontinuity at ∼ 50 to 60
R
J
; we have named the region inside this discontinuity the "inner plasmasphere."
The Magnetic Field of Saturn: Pioneer 11 Observations
Authors: Acuña Mario H. , Ness Norman F.
Published: October 2006

The intrinsic magnetic field of Saturn measured by the high-field fluxgate magnetometer is much weaker than expected. An analysis of preliminary data combined with the preliminary trajectory yield a model for the main planetary field which is a simple centered dipole of moment 0.20 ± 0.01 gauss-
R
s
3
= 4.3 ± 0.2 × 10
28
gauss-cm
3
(1
R
s
= 1 Saturn radius = 60,000 km). The polarity is opposite that of Earth, and, surprisingly, the tilt is small, within 2° ± 1° of the rotation axis. The equatorial field intensity at the cloud tops is 0.2 gauss, and the polar intensity is 0.56 gauss. The unique moon Titan is expected to be located within the magnetosheath of Saturn or the interplanetary medium about 50 percent of the time because the average subsolar point distance to the magnetosphere is estimated to be 20
R
s
, the orbital distance to Titan.
Sun Compensation by Bees
Authors: Gould James L.
Published: October 2006

In both their navigation and dance communication, bees are able to compensate for the sun's movement. When foragers are prevented from seeing the sun for 2 hours, they compensate by extrapolation, using the sun's rate of movement when last observed. These and other data suggest a time-averaging processing strategy in honey bee orientation.
New Magnetic Alloys
Authors: Chin G. Y.
Published: October 2006

Three notable new developments in magnetic alloys are highlighted. These include rare earth-cobalt permanent magnets with maximum energy products up to 240 kilojoules per cubic meter; chromium-cobalt-iron permanent magnets that have magnetic properties similar to those of the Alnicos, but contain only about half as much cobalt and are sufficiently ductile to be cold-formable; and high-induction grain-oriented silicon steels that exhibit 20 percent less core loss as transformer core materials than conventional oriented grades.
Organometallic Chemistry in Homogeneous Catalysis
Authors: Parshall George W.
Published: October 2006

Many reactions catalyzed by soluble transition metal compounds proceed by way of organometallic intermediates, even though the original catalyst may be a simple salt. This generality is illustrated for three industrial syntheses of acetic acid that use homogeneous catalysts. Some developments in organometallic chemistry that may extend the utility of homogeneous catalysis are photoactivation of catalysts and the recognition of the importance of metallacyclic intermediates.
Investigation of Electron Tunneling Between Cytochrome c Peroxidase and Cytochrome c
Authors: Potasek M. J.
Published: October 2006

The nature of electron transfer between the bound complex cytochrome c and cytochrome c peroxidase has been investigated. Experimental verification of the predicted charge-transfer band provides evidence of electron tunneling as the mechanism of transfer between these molecules in solution at room temperature. The measured transfer distance is ≃ 7 angstroms between heme edges, which results in a distance of ≃ 15 to 20 angstroms between iron atoms.
Retrograde Amnesia Produced by Several Treatments: Evidence for a Common Neurobiological Mechanism
Authors: Gold Paul E. , Sternberg Debra B.
Published: October 2006

This experiment examined the effects on memory of various amnestic treatments in animals earlier treated with the α-adrenergic antagonist phenoxybenzamine (PBZ). Thirty minutes before being trained in a one-trial inhibitory (passive) avoidance task, animals received an injection of PBZ or saline. Immediately after training, each animal received one of the following amnestic treatments: stimulation of the frontal cortex or amygdala, pentylenetetrazol, diethyldithiocarbamate, or cycloheximide. In control animals, each treatment produced retrograde amnesia. However, PBZ-treated animals did not develop amnesia. These findings suggest that there may be a common neurobiological mechanism underlying the amnesias produced by many treatments.
Female Mate Choice in a Neotropical Frog
Authors: Ryan Michael J.
Published: October 2006

Female
Physalaemus pustulosus
choose their mates and are more likely to choose larger males. There is a significant negative correlation between the size of the male and the fundamental frequency of one of the components of its advertisement call. Playback experiments demonstrate that females are capable of choosing larger males by distinguishing among differences in spectral components of the advertisement call.
The Meteorite-Asteroid Connection: The Infrared Spectra of Eucrites, Shergottites, and Vesta
Authors: Feierberg Michael A. , Drake Michael J.
Published: October 2006

Infrared reflectance spectra have been obtained for the meteorites Shergotty and Allan Hills (ALHA) 77005, a unique achondrite apparently related to the shergottites. Comparisons with the reflectance spectra of eucrites and asteroid 4 Vesta indicate that the surface of Vesta is covered with eucrite-like basalts and that, if shergottite-like basalts are present on the surface of Vesta, they must be a minor rock type. The paradox that both the eucrite and shergottite parent bodies should presently exist is examined. The preferred solution is that both eucrites and shergottites are derived from Vesta, and that this asteroid is compositionally and isotopically heterogeneous; however, other possible solutions cannot be ruled out.
Relative Humidity: Important Modifier of Pollutant Uptake by Plants
Authors: McLaughlin S. B. , Taylor G. E.
Published: October 2006

Laboratory measurements of foliar uptake of sulfur dioxide and ozone by red kidney beans demonstrated a strong effect of relative humidity on internal pollutant dose. Foliar uptake was enhanced two- to threefold for sulfur dioxide and three- to fourfold for ozone by an increase in relative humidity from 35 to 75 percent. For the same exposure concentration, vegetation growing in humid areas (such as the eastern United States) may experience a significantly greater internal flux of pollutants than that in more arid regions.
Mutualism Among Sessile Invertebrates: A Mediator of Competition and Predation
Authors: Osman Richard W. , Haugsness Julie Ann
Published: October 2006

Hydroids of the genus
Zanclea
are epizoic on encrusting bryozoans. The bryozoans protect these hydroids with skeletal material.
Zanclea
polyps on the bryozoan
Celleporaria brunnea
sting small predators and adjacent competitors, helping
Celleporaria
to survive and to grow over competing species. This mutualism enables the two species to cover a larger area than they could individually.
Expression of a Zinc Finger Gene in HTLV-I- and HTLV-II-Transformed Cells
Authors: Wright John J. , Gunter Kurt C. , Mitsuya Hiroaki , Irving Steven G. , Kelly Kathleen , Siebenlist Ulrich
Published: October 2006

Gene products encoded by the human T cell leukemia virus (HTLV) types I and II mediate transformation by the transactivation of cellular genes necessary for proliferation, probably including transcriptional regulatory factors. By searching for factors that may control proliferation, a zinc finger gene (225) was identified that was constitutively expressed in all HTLV-I- or HTLV-II-transformed cell lines examined, whereas in normal T cells it was only transiently expressed after mitogenic stimulation. The 225 gene was also constitutively expressed in two HTLV-I-transformed helper T cell clones, but not in the parental cell lines. Thus this putative cellular transcriptional factor, which was abnormally expressed in retrovirus-infected cells, may have a role in transformation.
Planetary Radio Astronomy Observations from Voyager 1 Near Saturn
Authors: Warwick J. W. , Pearce J. B. , Evans D. R. , Carr T. D. , Schauble J. J. , Alexander J. K. , Kaiser M. L. , Desch M. D. , Pedersen M. , Lecacheux A. , Daigne G. , Boischot A. , Barrow C. H.
Published: October 2006

The Voyager 1 planetary radio astronomy experiment detected two distinct kinds of radio emissions from Saturn. The first, Saturn kilometric radiation, is strongly polarized, bursty, tightly correlated with Saturn's rotation, and exhibits complex dynamic spectral features somewhat reminiscent of those in Jupiter's radio emission. It appears in radio frequencies below about 1.2 megahertz. The second kind of radio emission, Saturn electrostatic discharge, is unpolarized, extremely impulsive, loosely correlated with Saturn's rotation, and very broadband, appearing throughout the observing range of the experiment (20.4 kilohertz to 40.2 megahertz). Its sources appear to lie in the planetary rings.
Benthic Storms: Temporal Variability in a Deep-Ocean Nepheloid Layer
Authors: Gardner Wilford D. , Sullivan Lawrence G.
Published: October 2006

Time series measurements of light scattering were made for 2½ months at 20 meters above the bottom in the western North Atlantic. The highest values recorded with the nephelometer exceeded all previous measurements worldwide. Rapid changes indicated a high degree of activity near the sea floor, and some increases may have been related to atmospheric storms.
Exceptionally Strong Near-Bottom Flows on the Continental Rise of Nova Scotia
Authors: Richardson M. J. , Wimbush M. , Mayer L.
Published: October 2006

Recent current velocity measurements across the lower continental rise of Nova Scotia show a deep equatorward flow with speeds (maximum, 73 centimeters per second) among the highest recorded for the deep sea. Silicate measurements indicate that this flow usually consists of southern-source (Antarctic) bottom water. These measurements confirm the existence of a second and deeper western boundary flow that was earlier inferred from geological observations.