bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-Energy Hot Plasma and Particles in Saturn's Magnetosphere
Authors: Krimigis S. M. , Armstrong T. P. , Axford W. I. , Bostrom C. O. , Gloeckler G. , Keath E. P. , Lanzerotti L. J. , Carbary J. F. , Hamilton D. C. , Roelof E. C.
Published: October 2006

The low-energy charged particle instrument on Voyager 2 measured low-energy electrons and ions (energies ≳ 22 and ≳ 28 kiloelectron volts, respectively) in Saturn's magnetosphere. The magnetosphere structure and particle population were modified from those observed during the Voyager 1 encounter in November 1980 but in a manner consistent with the same global morphology. Major results include the following. (i) A region containing an extremely hot ( ∼ 30 to 50 kiloelectron volts) plasma was identified and extends from the orbit of Tethys outward past the orbit of Rhea. (ii) The low-energy ion mantle found by Voyager 1 to extend ∼ 7 Saturn radii inside the dayside magnetosphere was again observed on Voyager 2, but it was considerably hotter ( ∼ 30 kiloelectron volts), and there was an indication of a cooler ( < 20 kiloelectron volts) ion mantle on the nightside. (iii) At energies ≳ 200 kiloelectron volts per nucleon, H, H
2
, and H
3
(molecular hydrogen), helium, carbon, and oxygen are important constituents in the Saturnian magnetosphere. The presence of both H
2
and H
3
suggests that the Saturnian ionosphere feeds plasma into the magnetosphere, but relative abundances of the energetic helium, carbon, and oxygen ions are consistent with a solar wind origin. (iv) Low-energy ( ∼ 22 to ∼ 60 kiloelectron volts) electron flux enhancements observed between the
L
shells of Rhea and Tethys by Voyager 2 on the dayside were absent during the Voyager 1 encounter. (v) Persistent asymmetric pitch-angle distributions of electrons of 60 to 200 kiloelectron volts occur in the outer magnetosphere in conjunction with the hot ion plasma torus. (vi) The spacecraft passed within ∼ 1.1° in longitude of the Tethys flux tube outbound and observed it to be empty of energetic ions and electrons; the microsignature of Enceladus inbound was also observed. (vii) There are large fluxes of electrons of ∼ 1.5 million electron volts and smaller fluxes of electrons of ∼ 10 million electron volts and of protons ≳ 54 million electron volts inside the orbits of Enceladus and Mimas; all were sharply peaked perpendicular to the local magnetic field. (viii) In general, observed satellite absorption signatures were not located at positions predicted on the basis of dipole magnetic field models.
Carbonyl Sulfide and Carbon Disulfide from the Eruptions of Mount St. Helens
Authors: Rasmussen R. A. , Khalil M. A. K. , Dalluge R. W. , Penkett S. A. , Jones B.
Published: October 2006

Ash from the massive 18 May 1980 eruption of Mount St. Helens readily gave off large amounts of carbonyl sulfide and carbon disulfide gases at room temperature. These findings suggest that the sulfur that enhances the Junge sulfate layer in the stratosphere after volcanic eruptions could be carried directly to the upper atmosphere as carbonyl sulfide and carbon disulfide adsorbed on ash particles from major volcanic eruptions.
The UNIX Operating System: A Model for Software Design
Authors: Kernighan Brian W. , Morgan Samuel P.
Published: October 2006

The UNIX operating system, a general-purpose time-sharing system, has, without marketing, advertising, or technical support, become widely used by universities and scientific research establishments. It is the de facto standard of comparison for such systems and has spawned a small industry of suppliers of UNIX variants and look-alikes. This article attempts to uncover the reasons for its success and to draw some lessons for the future of operating systems.
Asbestos: Scientific Developments and Implications for Public Policy
Authors: Mossman B. T. , Bignon J. , Corn M. , Seaton A. , Gee J. B. L.
Published: October 2006

Asbestos is a commercial term for a group of fibrous minerals often associated with the development of pulmonary interstitial fibrosis (asbestosis), lung cancer, and malignant mesothelioma in occupationally exposed individuals. The pathogenicity of different forms of asbestos varies—long, thin amphibole fibers are most pathogenic, particularly in the induction of mesothelioma. Available data do not support the concept that low-level exposure to asbestos is a health hazard in buildings and schools. The concentration of asbestos fibers in air, type of asbestos, and size of fibers must be considered in evaluation of potential health risks.
Mutual Flocculation of Algae and Clay: Evidence and Implications
Authors: Avnimelech Yoram , Troeger Bill W. , Reed Lester W.
Published: October 2006

Algae-clay aggregates were formed when algal and clay suspensions were mixed in the presence of an electrolyte. The maximum ratio of clay to algae in the aggregates was 1.7, 0.2, and 0.03 milligrams of clay per milligram of algae (wet weight) for
Anabaena
,
Chlamydomonas
, and
Chlorella
sp., respectively. The aggregates formed at Ca
2+
concentrations higher than 5 × 10
–4
M
or Na
+
concentrations higher than 2 × 10
–2
M
. The mutualf flocculation and subsequent sedimentation have many practical and ecological implications for bodies of water.
Surface Spectroscopies with Synchrotron Radiation
Authors: Smith N. V. , Woodruff D. P.
Published: October 2006

A variety of photoelectron spectroscopies using synchrotron radiation have been devised to study solid surfaces. Measurements of the energies and angular distributions of electrons photoemitted from valence levels yield detailed information on surface electronic states and the chemical bonding of adsorbed atoms and molecules. Core level studies yield surface atom positions and molecular orientations. Some highlights of recent research are presented here. The capabilities of the techniques will be extended by the forthcoming generation of new storage rings dedicated to the production of synchrotron radiation.
Homeothermic Response to Reduced Ambient Temperature in a Scarab Beetle
Authors: Morgan K. R. , Bartholomew G. A.
Published: October 2006

Elephant beetles (
Megasoma elephas
; Scarabaeidae) weighing from 10 to 35 grams, respond homeothermically when ambient temperature is reduced below about 20°C in the laboratory. This metabolic response is not associated with locomotion or any other overt activity. Warming is initiated when the body temperature reaches an apparent set point of 20° to 22°C. Unlike the case for euthermic birds and mammals, energy metabolism and body temperature in these beetles are conspicuously oscillatory, with a given cycle in oxygen consumption peaking before the corresponding cycle in body temperature.
Localization of an Elevated Sound Source by the Green Tree Frog
Authors: Gerhardt H. Carl , Rheinlaender Jürgen
Published: October 2006

Female green tree frogs readily localized an elevated sound source. Prior to hopping on sticks that formed a three-dimensional grid, females usually scanned laterally with their heads elevated after first scanning in the normal, nonelevated fashion. Unlike mammals and owls, frogs lack external anatomical features specialized for resolving vertical and horizontal components of source direction.
Carbon Dioxide and Climate: The Importance of Realistic Geography in Estimating the Transient Temperature Response
Authors: Thompson Starley L. , Schneider Stephen H.
Published: October 2006

Results obtained from a detailed air-sea-ice climate model for an instantaneous increase in the atmospheric carbon dioxide content are used to estimate the transient surface temperature response for several time-dependent carbon dioxide increase scenarios. The inclusion of realistic variations of land fraction and ocean mixing with latitude is found to limit the applicability of steady-state simulations as approximate guides to the actual time-dependent temperature response, particularly when the regional response is considered.
Direct Determination of Ionic Solvation from Neutron Diffraction
Authors: Narten A. H. , Hahn R. L.
Published: October 2006

Much information on ionic solvation in electrolyte solutions has been inferred from macroscopic thermodynamic and transport properties and from spectroscopy. These ion-water interactions can now be probed directly and unambiguously by neutron diffraction. Such measurements have been done with neodymium trichloride solutions in heavy water that are identical in every respect except the isotopic state of the neodymium ions; these experiments yield in a straightforward manner the distribution of oxygen and deuterium atoms from the water molecules in the first hydration sphere of the neodymium ion. Each ion is surrounded by 8.6 oxygen atoms at a distance of 2.48 angstroms and 16.7 deuterium atoms at 3.13 angstroms indicating a well-defined first hydration sphere of water molecules, the deuterium atoms pointing away from the cation.
Norwalk Virus Genome Cloning and Characterization
Authors: Jiang Xi , Graham David Y. , Wang Kening , Estes Mary K.
Published: October 2006

Major epidemic outbreaks of acute gastroenteritis result from infections with Norwalk or Norwalk-like viruses. Virus purified from stool specimens of volunteers experimentally infected with Norwalk virus was used to construct recombinant complementary DNA (cDNA) and derive clones representing most of the viral genome. The specificity of the clones was shown by their hybridization with post- (but not pre-) infection stool samples from volunteers infected with Norwalk virus and with purified Norwalk virus. A correlation was observed between the appearance of hybridization signals in stool samples and clinical symptoms of acute gastroenteritis in volunteers. Hybridization assays between overlapping clones, restriction enzyme analyses, and partial nucleotide sequence information of the clones indicated that Norwalk virus contains a single-stranded RNA genome of positive sense, with a polyadenylated tail at the 3′ end and a size of at least 7.5 kilobases. A consensus amino acid sequence motif typical of viral RNA-dependent RNA polymerases was identified in one of the Norwalk virus clones. The availability of Norwalk-specific cDNA and the new sequence information of the viral genome should permit the development of sensitive diagnostic assays and studies of the molecular biology of the virus.
Calanoid Copepods, Feeding Currents, and the Role of Gravity
Authors: Strickler J. Rudi
Published: October 2006

Feeding currents of free-swimming calanoid copepods, observed through an expanded krypton laser beam and a back-focus dark-field optical system, show that these planktonic animals generate a double shear field to help in detecting food. The interrelation between flow field, perception of food items, and body orientation explains why these animals are generally negatively buoyant.
Beryllium-10 in Australasian Tektites: Evidence for a Sedimentary Precursor
Authors: Pal D. K. , Tuniz C. , Moniot R. K. , Kruse T. H. , Herzog G. F.
Published: October 2006

Each of seven Australasian tektites contains about 1 × 10
8
atoms of beryllium-10 (half-life, 1.53 × 10
6
years) per gram. Cosmic-ray bombardment of the australites cannot have produced the measured amounts of beryllium-10 either at the earth's surface or in space. The beryllium-10 contents of these australites are consistent with a sedimentary precursor that adsorbed from precipitation beryllium-10 produced in the atmosphere. The sediments must have spent several thousand years at the earth's surface within a few million years of the tektite-producing event.
Management of High-Level Waste Repository Siting
Authors: Hill Douglas , Pierce Barbara L. , Metz William C. , Rowe Michael D. , Haefele Edwin T. , Bryant F. Carlene , Tuthill Edwin J.
Published: October 2006

The selection of sites to store high-level radioactive waste will require more than technical decisions; an acceptable site must gain widespread public support. Ad hoc approaches have recently served as a stimulus to overcome institutional inertia in radioactive waste management, as exemplified by the Interagency Review Group and the State Planning Council for Radioactive Waste Management, but ad hoc approaches have not characteristically succeeded in resolving intense conflicts. Acceptable sites can best be established through traditional processes of legal and scientific advocacy, and their ultimate legitimacy will depend on the proper use of established democratic processes.
Pressure Enhancement of Ion Mobilities in Liquid Silicates from Computer Simulation Studies to 800 Kilobars
Authors: Angell C. A. , Cheeseman P. A. , Tamaddon S.
Published: October 2006

Ion dynamics computer simulation methods show that for many liquid silicates, like silica itself, the component diffusion coefficients show anomalous pressure dependences. This implies that their viscosities have negative pressure dependences. Overall, there is an interesting degree of analogy between the fundamental binary solutions of geochemistry and the aqueous solutions of common experience; however, due to the stronger bonding in silicate systems, the anomalies are much more persistent. Diffusivity maxima occur at pressures of 200 to 300 kilobars and are correlated with a prevalence of fivefold coordination of silicon ions. The relevance of these findings to planetary dynamics and thermophysical modeling problems is briefly considered.
Initial Analysis of OSTA-1 Ocean Color Experiment Imagery
Authors: Kim Hongsuk H. , Hart William D. , van der Piepen Heinz
Published: October 2006

Ocean images were obtained at three widely separated locations on the earth as part of NASA's ocean color experiment. Digital computer enhancement and band-ratioing techniques were applied to radiometrically corrected spectral data to emphasize patterns of chlorophyll distribution and, in one case, of bottom topography. The chlorophyll pattern in the Yellow Sea between China and Korea was evident in a scene produced from shuttle orbit 24. The effects of the discharge from the Yangtze and other rivers were also observed. Two scenes from orbits 30 and 32 revealed the movement of patches of plankton in the Gulf of Cádiz. Geometric corrections of these images permitted ocean current velocities in the vicinity to be deduced. The variability in water depth over the Grand Bahama Bank was estimated by using the blue-green channel of the instrument. The very clear water conditions in the area caused bottom-reflected sunlight to produce a sensor signal that was inversely related to the depth of the water.
Chemical Reactions of Anions in the Gas Phase
Authors: DePuy Charles H. , Grabowski Joseph J. , Bierbaum Veronica M.
Published: October 2006

Anions of many types, both organic and inorganic, familiar and exotic, can be generated in the gas phase by rational chemical synthesis in a flowing afterglow apparatus. Once formed, the rates, products, and mechanisms of their reactions with neutral species of all kinds can be studied, not only at room temperature but at higher energies in a drift field. These completely unsolvated ions undergo a large number of reactions that are analogous to those they undergo in solution, as well as some that are less familiar. New types of ions, for which there are no counterparts in solution, can be produced and their chemical reactions explored.
A New Greenland Deep Ice Core
Authors: Dansgaard W. , Clausen H. B. , Gundestrup N. , Hammer C. U. , Johnsen S. F. , Kristinsdottir P. M. , Reeh N.
Published: October 2006

The polar ice sheets are rich sources of information on past atmospheric conditions, including paleoclimates. A new deep ice core has been drilled in south Greenland. Comparison of the oxygen isotopic profile with that from Camp Century and with a deep-sea foraminifera record indicates that the new core reaches back to about 90,000 years before present in a continuous sequence. The details in the Wisconsin part of the ice core records seem to be climatically significant, and the general trends reveal all of the relevant Emiliani stages recorded in deep-sea cores. The redated Camp Century record suggests a dramatic termination of the Eem/Sangamon interglacial.
Regional Localization of the Gene for Human Phosphoribosylpyrophosphate Synthetase on the X Chromosome
Authors: Becker Michael A. , Yen Richard C. K. , Itkin Pamela , Goss Stephen J. , Seegmiller J. Edwin , Bakay Bohdan
Published: October 2006

Sixty-eight independent hybrid clones were isolated after irradiated normal human lymphocytes were fused with Chinese hamster fibroblasts lacking hypoxanthine-guanine phosphoribosyltransferase activity. The cells were grown under selective conditions requiring retention of the X chromosome-linked locus for human hypoxanthine-guanine phosphoribosyltransferase. The frequency and patterns of cotransference of human phosphoribosylpyrophosphate synthetase with the selected marker and with additional X-linked enzymatic markers confirm X linkage of the structural gene for human phosphoribosylpyrophosphate synthetase and support assignment of this gene to a position on the long arm of the X, between the loci for α-galactosidase and hypoxanthine-guanine phosphoribosyltransferase.
Amino Acid Sequence Homology Between Histone H5 and Murine Leukemia Virus Phosphoprotein p12
Authors: Henderson Louis E. , Gilden Raymond V. , Oroszlan Stephen
Published: October 2006

The amino terminal acid sequences of several mouse leukemia virus phosphoproteins (p12) show definite homology with the amino terminal conserved region of H5 histones, the phosphorylated nuclear proteins of nucleated erythrocytes. Differences in the amino acid compositions of the two groups of proteins seem to rule out the possibility that they evolved from a single common ancestral gene. The finding of sequence homology between viral p12's and cellular histones, however, is consistent with evolution of retrovirus structural proteins by a process of differentiation from preexisting cellular genes. The conserved primary and secondary structure at the amino terminal region, common to both groups of proteins, may be related to their common function of nucleic acid binding modulated by phosphorylation.
Single-Cell Proteins
Authors: Litchfield John H.
Published: October 2006

Both photosynthetic and nonphotosynthetic microorganisms, grown on various carbon and energy sources, are used in fermentation processes for the production of single-cell proteins. Commercial-scale production has been limited to two algal processes, one bacterial process, and several yeast and fungal processes. High capital and operating costs and the need for extensive nutritional and toxicological assessments have limited the development and commercialization of new processes. Any increase in commercial-scale production appears to be limited to those regions of the world where low-cost carbon and energy sources are available and conventional animal feedstuff proteins, such as soybean meal or fish meal, are in short supply.
Controlled Stimulation of Magnetospheric Electrons by Radio Waves: Experimental Model for Lightning Effects
Authors: Goldberg R. A. , Curtis S. A. , Barcus J. R. , Siefring C. L. , Kelley M. C.
Published: October 2006

Magnetospheric electrons precipitated by ground-based coded very low frequency radio transmissions have been detected by rocket measurement of bremsstrahlung x-rays, caused by impact of the electrons with the upper atmosphere. The direct correlations obtained between the very low frequency signals and the x-rays demonstrate the limits of sensitivity required and indicate that this remote sensing technique would be useful for future study of very low frequency effects induced by single lightning strokes.
Science and Technology in Mexico: Toward Self-Determination
Authors: Flores Edmundo
Published: October 2006

During the last decade Mexico has moved progressively to develop and naturalize its scientific and technological capabilities, a decision requiring long-term government investment in education and research. The areas in which Mexico's National Council of Science and Technology selected to focus a national development program include the following: scholarships for middle- as well as high-level researchers and technicians; indicative programs to support research and basic or new industries in fields such as energy, electronics, metalworking, and agronomy; a government-industry shared risk program; research centers, many located in the provinces; and international scientific agreements. The translation of scientific classics and contemporary publications into Spanish and their widespread dissemination in Mexico have received special attention as has the dissemination of Mexico's work worldwide.
Crop Germplasm Conservation and Developing Countries
Authors: Plucknett D. L. , Smith N. J. H. , Williams J. T. , Anishetty N. Murthi
Published: October 2006

Loss of the genetic diversity of some of the world's crops has accelerated in recent decades, with many crops becoming increasingly susceptible to diseases, pests, and environmental stresses. A global network of gene banks has therefore been established to provide plant breeders with the genetic resources necessary for developing more resistant crops that will enable farmers to maintain high yields. Most of these gene banks now store the germplasm of only the major crops such as cereals, potatoes, and grain legumes. Cultivated varieties of these crops are conserved as well as wild species that might otherwise become extinct. Tropical cash crops such as bananas and coconuts are also important food crops in many Third World countries, and more effort needs to be made to conserve the germplasm of these crops as well as of other important plants such as plantation crops, medicinal herbs, and fruit and timber trees.
Carbon Dioxide Exchange Between Air and Seawater: No Evidence for Rate Catalysis
Authors: Goldman Joel C. , Dennett Mark R.
Published: October 2006

It has been suggested that enzymatic catalysis plays a major role in regulating the mass transport of carbon dioxide from the atmosphere into the oceans. Evidence for this mechanism was not found in a series of gas exchange experiments in which the gas transfer rate coefficients for samples obtained from various natural seawaters, with and without the addition of carbonic anhydrase, were compared with those from artificial seawater. Wind-induced turbulence appears to be the major factor controlling the ocean's response to anthropogenic increases in atmospheric carbon dioxide.
Breathing Gas Mixtures Different from Air: An Adaptation for Survival Under the Ice of a Facultative Air-Breathing Fish
Authors: Magnuson John J. , Keller John W. , Beckel Annamarie L. , Gallepp George W.
Published: October 2006

Gaseous respiration by central mudminnows (
Umbra limi
), particularly their use of bubbles composed of gas mixtures other than air, may have evolved as an adaptation to the oxygen-depleted, carbon dioxide-rich water of winterkill lakes. Under simulated winterkill conditions, mudminnows frequently engulfed gaseous bubbles. Use of bubbles was not related to varying methane or nitrogen content (0 to 80 percent) when all bubbles contained 20 percent oxygen. When the oxygen content of bubbles varied (0 to 20 percent), fish visited bubbles randomly but remained longer and took fewer "breaths" at bubbles with high oxygen content. High temperature (16° to 34°C) and low
p
H (6.8 to 4.5) did not stimulate increased air-breathing when dissolved oxygen was sufficient.
Mutants of
Rhizobium japonicum
with Increased Hydrogenase Activity
Authors: Merberg David , Maier Robert J.
Published: October 2006

Some strains of
Rhizobium japonicum
can use hydrogen as an energy source for growth under microaerophilic conditions. Mutant strains have been selected that use hydrogen in the presence of high partial pressures of oxygen. The mutants contain more hydrogenase than the parent strain, both as free-living cells and as bacteroids in nitrogen-fixing soybean root nodules.
Early Tertiary Age of Pitchstone in the Northern Black Hills, South Dakota
Authors: Redden Jack A. , Obradovich John D. , Naeser Charles W. , Zartman Robert E. , Norton James J.
Published: October 2006

A block of pitchstone in the northern Black Hills, South Dakota, is Paleocene in age, according to potassium-argon dating of biotite and fission-track dating of zircon in the sample. These data invalidate published suggestions that the age is much younger. The pitchstone is not extrusive in its present position but instead is in a volcanic pipe with other fragments that came downward from as much as 1100 meters above the modern surface.
The Quantized Hall Effect
Authors: Stormer H. L. , Tsui D. C.
Published: October 2006

Quantization of the Hall effect is one of the most surprising discoveries in recent experimental solid-state research. At low temperatures and high magnetic fields the ratio of the Hall voltage to the electric current in a two-dimensional system is quantized in units of
h/e
2
, where
h
is Planck's constant and
e
is the electronic charge. Concomitantly, the electrical resistance of the specimen drops to values far below the resistances of the best normal metals.
Reverse Diel Vertical Migration: An Escape from Invertebrate Predators
Authors: Ohman Mark D. , Frost Bruce W. , Cohen Edward B.
Published: October 2006

The marine copepod
Pseudocalanus
sp. exhibits an unusual reverse diel vertical migration in Dabob Bay, Washington, concurrently with a normal vertical migration by nocturnal invertebrate predators. Reduced spatial overlap with predators appears to decrease mortality rate of adult female
Pseudocalanus
. A life table analysis suggests that the demographic disadvantage associated with daily migration across a thermal gradient can be overcome if mortality is reduced by as little as 16 percent.
Systematic Evolution of Ligands by Exponential Enrichment: RNA Ligands to Bacteriophage T4 DNA Polymerase
Authors: Tuerk Craig , Gold Larry
Published: October 2006

High-affinity nucleic acid ligands for a protein were isolated by a procedure that depends on alternate cycles of ligand selection from pools of variant sequences and amplification of the bound species. Multiple rounds exponentially enrich the population for the highest affinity species that can be clonally isolated and characterized. In particular one eight-base region of an RNA that interacts with the T4 DNA polymerase was chosen and randomized. Two different sequences were selected by this procedure from the calculated pool of 65,536 species. One is the wild-type sequence found in the bacteriophage mRNA; one is varied from wild type at four positions. The binding constants of these two RNA's to T4 DNA polymerase are equivalent. These protocols with minimal modification can yield high-affinity ligands for any protein that binds nucleic acids as part of its function; high-affinity ligands could conceivably be developed for any target molecule.
Regulation of Activity of a Transcriptional Anti-Rerminator in
E. coli
by Phosphorylation in Vivo
Authors: Amster-Choder Orna , Wright Andrew
Published: October 2006

Expression of the
bgl
operon of
Escherichia coli
is regulated in vitro by phosphorylation and dephosphorylation of a positive regulatory protein, BglG, which functions in its nonphosphorylated state as a transcriptional antiterminator. The degree of phosphorylation of BglG in vivo was shown to be dependent on the cellular levels of BglF protein, which is both the BglG kinase and phosphatase. The degree of phosphorylation of BglG also depended on the presence or absence of a β-glucoside, the inducer of operon expression. Addition of inducer to cells in growth medium resulted in rapid dephosphorylation of phosphorylated BglG. The
bgl
operon is thus regulated by a sensory system that modulates gene expression by protein phosphorylation and dephosphorylation in response to the external levels of inducer.
Cell Proliferation in Carcinogenesis
Authors: Cohen Samuel M. , Ellwein Leon B.
Published: October 2006

Chemicals that induce cancer at high doses in animal bioassays often fail to fit the traditional characterization of genotoxins. Many of these nongenotoxic compounds (such as sodium saccharin) have in common the property that they increase cell proliferation in the target organ. A biologically based, computerized description of carcinogenesis was used to show that the increase in cell proliferation can account for the carcinogenicity of nongenotoxic compounds. The carcinogenic dose-response relationship for genotoxic chemicals (such as 2-acetylaminofluorene) was also due in part to increased cell proliferation. Mechanistic information is required for determination of the existence of a threshold for the proliferative (and carcinogenic) response of nongenotoxic chemicals and the estimation of risk for human exposure.
Electrostatic and Steric Contributions to Regulation at the Active Site of Isocitrate Dehydrogenase
Authors: Dean Anthony M. , Koshland Daniel E.
Published: October 2006

The isocitrate dehydrogenase of
Escherichia coli
is regulated by covalent modification at the active site rather than, as expected, at an allosteric site. As a means of evaluating the mechanism of regulation, the kinetics of the substrate, 2
R
,3
S
-isocitrate, and a substrate analog, 2
R
-malate, were compared for the native, phosphorylated, and mutant enzymes. Phosphorylation decreases activity by more than a factor of 10
6
for the true substrate, but causes minor changes in the activity of the substrate analog. The kinetic results indicate that electrostatic repulsion and steric hindrance between the phosphoryl moiety and the γ carboxyl group of 2
R
,3
S
-isocitrate are the major causes of the inactivation, with a lesser contribution from the loss of a hydrogen bond.
Is Titan Wet or Dry?
Authors: Eshleman Von R. , Lindal Gunnar F. , Tyler G. Leonard
Published: October 2006

Titan's dense and cold nitrogen atmosphere contains a small amount of methane under conditions at least approaching those at which one or both constituents would condense. The possibility of methane and nitrogen rain clouds and global methane oceans has been discussed widely. From specific features of radio occultation and other Voyager results, however, it is concluded that nitrogen does not condense on Titan and that Titan has neither global methane oceans nor a global cloud of liquid methane droplets. Certain results indirectly support the conjecture that methane does not condense at any location. However, other considerations favor a methane ice haze high in the troposphere, and liquid and solid methane might exist on the surface and as low clouds at polar latitudes.
Sulfur Diagenesis in Everglades Peat and Origin of Pyrite in Coal
Authors: Altschuler Z. S. , Schnepfe M. M. , Silber C. C. , Simon F. O.
Published: October 2006

The pattern of sulfur transformation in peat across the Everglades basin indicates that pyrite formation in organic-rich swamps depends on the use of organic oxysulfur compounds in dissimilatory respiration by sulfur-reducing bacteria. This paragenesis explains the primary distribution of sulfur compounds in low-sulfur coals and possibly in most coals and many organic-rich soils and sediments. It also accounts for the occurrence of framboidal pyrite bound in fossil tissue in coal and sediments.
Scientific Freedom, National Security, and the First Amendment
Authors: Ferguson James R.
Published: October 2006

The Supreme Court may soon be asked to decide an important issue of First Amendment law arising from the government's efforts to restrict the dissemination of "militarily critical" technological knowledge. To resolve the issue, the Court will first determine whether technological knowledge qualifies for a full measure of protection under the free-speech clause of the First Amendment. The Court will then address the government's stated justification for restricting the contested information. This inquiry will evaluate both the gravity of the asserted danger to national security and the likelihood of its occurrence.
Martian Gases in an Antarctic Meteorite?
Authors: Bogard D. D. , Johnson P.
Published: October 2006

Significant abundances of trapped argon, krypton, and xenon have been measured in shock-altered phases of the achondritic meteorite Elephant Moraine 79001 from Antarctica. The relative elemental abundances, the high ratios of argon-40 to argon-36 (≥ 2000), and the high ratios of xenon-129 to xenon-132 (≥ 2.0) of the trapped gas more closely resemble Viking data for the martian atmosphere than data for noble gas components typically found in meteorites. These findings support earlier suggestions, made on the basis of geochemical evidence, that shergottites and related rare meteorites may have originated from the planet Mars.
Alluvial-River Response to Neotectonic Deformation in Louisiana and Mississippi
Authors: Burnett A. W. , Schumm S. A.
Published: October 2006

Repeat geodetic surveys show uplift of the Monroe and Wiggins anticlines in Louisiana and Mississippi. There are deformed Quaternary terraces, which indicate long-term deformation in the valleys of the alluvial rivers that cross these structures, and there are floodplain and channel convexities that provide evidence of modern deformation. In addition, the channels show significant variations of morphology (sinuosity, gradient, and depth) and behavior appropriate to reaches of increased and decreased valley slope. These alluvial rivers are adjusting to modern deformation and their adjustment confirms two geodetic leveling anomalies.
Rates of Hydrothermal Reactions
Authors: Wood Bernard J. , Walther John V.
Published: October 2006

The rates of reactions of silicates and aqueous fluids follow zero-order kinetics controlled by the reacting surface area with the rate constant given by the equation: log
k
≏ -2900/
T
-6.85, where
T
is temperature and where
k
has the unit's gram-atoms of oxygen per square centimeter per second. This expression appears to hold for all silicates and for reactions involving dissolution, fluid production, or solid-solid transformations in the presence of a fluid of moderate to high
p
H.
A Paleozoic Pangaea
Authors: Boucot A. J. , Gray Jane
Published: October 2006

Paleozoic paleogeographies should be consistent with all available, reliable data. However, comparison of three different Devonian paleogeographies that are based largely or wholly on the data of remanent magnetism show them to be inconsistent in many regards. When these three paleogeographies are provided with possible ocean surface current circulation patterns, and have added to them lithofacies and biogeographic data, they also are shown to be inconsistent with such data. A pangaeic reconstruction positioned in the Southern Hemisphere permits the lithofacies and biogeographical data to be reconciled in a plausible manner.
Iridium Enrichment in Airborne Particles from Kilauea Volcano: January 1983
Authors: Zoller William H. , Parrington Josef R. , Phelan Kotra Janet M.
Published: October 2006

Airborne particulate matter from the January 1983 eruption of Kilauea volcano was inadvertently collected on air filters at Mauna Loa Observatory at a sampling station used to observe particles in global circulation. Analyses of affected samples revealed unusually large concentrations of selenium, arsenic, indium, gold, and sulfur, as expected for volcanic emissions. Strikingly large concentrations of iridium were also observed, the ratio of iridium to aluminum being 17,000 times its value in Hawaiian basalt. Since iridium enrichments have not previously been observed in volcanic emissions, the results for Kilauea suggest that it is part of an unusual volcanic system which may be fed by magma from the mantle. The iridium enrichment appears to be linked with the high fluorine content of the volcanic gases, which suggests that the iridium is released as a volatile IrF
6
.
Structural and Bonding Changes in Cesium Iodide at High Pressures
Authors: Knittle Elise , Jeanloz Raymond
Published: October 2006

Cesium iodide, a simple ionic salt at low pressures, undergoes a second-order transformation at 40 gigapascals (400 kilobars) from the cubic B2 (cesium chloride-type) structure to the body-centered tetragonal structure. Also, the energy gap between valence and conduction bands decreases from 6.4 electron volts at zero pressure to about 1.7 electron volts at 60 gigapascals, transforming cesium iodide from a highly ionic compound to a semiconductor. The structural transition increases the rate at which the band gap closes, and an extrapolation suggests that cesium iodide becomes metallic near (or somewhat above) 100 gigapascals. Similar changes in bonding character are likely to occur in other alkali halides at pressures above 100 gigapascals.
Infinite Resources: The Ultimate Strategy
Authors: Goeller H. E. , Zucker A.
Published: October 2006

By projecting global population growth and demand for nonrenewable materials over the next century, it appears unlikely that the world will run short of any element before about 2050. This provides considerable time to develop new technology to economically exploit lower grade and alternative ores to bring some 30 elements into essentially infinite supply, and to use these elements in developing substitutes to satisfy the requirements of modern civilized societies.
Preservation of Membranes in Anhydrobiotic Organisms: The Role of Trehalose
Authors: Crowe John H. , Crowe Lois M. , Chapman Dennis
Published: October 2006

Trehalose is a nonreducing disaccharide of glucose commonly found at high concentrations in anhydrobiotic organisms. In the presence of trehalose, dry dipalmitoyl phosphatidylcholine (DPPC) had a transition temperature similar to that of the fully hydrated lipid, whereas DPPC dried without trehalose had a transition temperature about 30 degrees Kelvin higher. Results obtained with infrared spectroscopy indicate that trehalose and DPPC interact by hydrogen bonding between the OH groups in the carbohydrate and the polar head groups of DPPC. These and previous results show that this hydrogen bonding alters the spacing of the polar head groups and may thereby decrease van der Waals interactions in the hydrocarbon chains of the DPPC. This interaction between trehalose and DPPC is specific to trehalose. Hence this specificity may be an important factor in the ability of this molecule to stabilize dry membranes in anhydrobiotic organisms.
Polymerized Surfactant Vesicles: Novel Membrane Mimetic Systems
Authors: Fendler Janos H.
Published: October 2006

Vesicles formed from dialkyl surfactants containing vinyl, methacrylate, diacetylene, isocyano, and styrene groups have been stabilized by polymerization across their bilayers of head groups. Polymerized vesicles have shelf lives of many months and controllable permeabilities and sizes. The kinetics of surfactant vesicle photopolymerization have been determined, and the mechanism of photopolymerization has been discussed as a two-dimensional surface process. Polymerized surfactant vesicles concentrate reagents in their aqueous interiors, in bilayers, and in their inner or outer surfaces. This, in turn, leads to altered reaction rates and sites. Polymerized surfactant vesicles also provide a good media for the generation, in situ, of small, uniform, and efficient colloidal catalysts.
Quasars and Gravitational Lenses
Authors: Turner Edwin L.
Published: October 2006

Despite the expenditure of large amounts of telescope time and other resources, most of the fundamental questions concerning quasi-stellar objects (quasars) remain unanswered. A complex phenomenology of radio, infrared, optical, and x-ray properties has accumulated but has not yielded even a satisfactory classification system. The large red shifts (distances) of quasars make them very valuable tools for studying cosmology and the properties of intervening matter in the Universe through observations of absorption lines and gravitational lenses.
Control of Colonial Hydroid Macrofouling by Free-Field Ultrasonic Radiation
Authors: Burton Dennis T. , Richardson Leonard B. , Taylor Robert J.
Published: October 2006

Free-field ultrasonic radiation inhibited the feeding of the macrofouling hydroid
Garveia franciscana
by causing tentacle contraction at the sonic degasification threshold. Within the frequency range of 250 to 2000 kilohertz, the threshold sound intensity (sonic degasification threshold) that caused tentacle contraction was directly proportional to frequency, with the minimum observed being 0.6 watt per square centimeter at 250 kilohertz. A pulse length of 0.2 second and interpulse period of 102 seconds gave the lowest average power required to produce tentacle contraction at a peak pulse sound intensity of 6.2 watts per square centimeter with a frequency of 250 kilohertz. Twenty-four hour exposures to the sound regime caused destruction of the hydranths and regression of tissue in the stolons.
Congruent Paleomagnetic and Archeomagnetic Records from the Western United States: A.D. 750 to 1450
Authors: Verosub Kenneth L. , Mehringer Peter J.
Published: October 2006

Two independently dated, high-resolution paleomagnetic records, one lacustrine and one archeological, record the passage across western North America of the same nondipole feature of the geomagnetic field during the time interval from A.D. 750 to 1450. Although these sequences indicate that correlation between paleomagnetic and archeomagnetic records is feasible under certain conditions, differences between the records underscore the difficulty of dating accurately an archeological site by correlation of a single archeomagnetic direction with a secular variation curve.
Cultured Cells of White Pine Show Genetic Resistance to Axenic Blister Rust Hyphae
Authors: Diner Alex M. , Mott Ralph L. , Amerson Henry V.
Published: October 2006

Hypersensitive resistance to axenically cultured
Cronartium ribicola
was displayed by subcultured callus of
Pinus lambertiana
. Cellular resistance to a destructive rust disease can now be studied at the macromolecular level through use of cloned cells of both host and pathogen in a system amenable to emerging recombinant DNA technology.
Windows on a New Cosmology
Authors: Lake George
Published: October 2006

The standard Big Bang cosmology requires very special initial conditions: (i) an excess of matter over antimatter, (ii) delicate tuning of the expansion rate at an early time to produce the long-lived Universe we see today, and (iii) a conspiracy among parts of the Universe out of causal contact to produce the currently observed degree of homogeneity. New theories that unify the strong and electroweak interactions may remove the necessity of specifying these conditions as initial data by introducing an inherent matter-antimatter asymmetry in physical laws and changing the early dynamic history of the Universe.
Transient Expression of Homologous Genes in
Drosophila
Cells
Authors: Morganelli Christine M. , Berger Edward M.
Published: October 2006

A cloned
Drosophila
heat shock protein 22 gene was transfected into two independently established
Drosophila
cell lines. Each line carried a different heat shock protein 22 allele, distinguishable by electrophoresis of the protein. The transfected gene was not expressed at 25°C but could be induced at 36°C. In one line, two heat shock protein 22 electromorphs were synthesized.
Uranium Power and Horizontal Proliferation of Nuclear Weapons
Authors: Starr Chauncey
Published: October 2006

Only a few nonnuclear weapons states with uranium-fueled power plants have kept the weapons option open, and none has evidenced activities intended for diverting fissionable material from its civilian system. Analysis of alternative strategies shows that acquisition of nuclear weapons material would probably depend on military production facilities rather than diversion. Horizontal proliferation is primarily a political issue and is related only marginally to uranium power development. Restrictions of the Nuclear Non-Proliferation Act on the supply of equipment and fuel by the United States appear to have induced, in some nonnuclear weapons states, the building of small-scale facilities that can be modified for production of weapons material. More attention should be given to the international political, economic, and military factors that persuade such states to abjure nuclear weapons.
Variations in the Rotation of the Earth
Authors: Carter W. E. , Robertson D. S. , Pettey J. E. , Tapley B. D. , Schutz B. E. , Eanes R. J. , Lufeng Miao
Published: October 2006

Variations in the earth's rotation (UT1) and length of day have been tracked at the submillisecond level by astronomical radio interferometry and laser ranging to the LAGEOS satellite. Three years of regular measurements reveal complex patterns of variations including UT1 fluctuations as large as 5 milliseconds in a few weeks. Comparison of the observed changes in length of day with variations in the global atmospheric angular momentum indicates that the dominant cause of changes in the earth's spin rate, on time scales from a week to several years, is the exchange of angular momentum between the atmosphere and the mantle. The unusually intense El Niño of 1982-1983 was marked by a strong peak in the length of day.
Growth Stasis and Limited Shell Calcification in Larvae of
Cymatium parthenopeum
During Trans-Atlantic Transport
Authors: Pechenik Jan A. , Scheltema Rudolf S. , Eyster Linda S.
Published: October 2006

Larvae of the shallow-water marine gastropod
Cymatium parthenopeum
show no appreciable shell calcification and no demonstrable growth as they disperse across the Atlantic Ocean. Evidence of what appears to be physiological specialization for prolonged delay of metamorphosis was found in larvae of this prosobranch gastropod.
Diurnal Variation of Stratospheric Chlorine Monoxide: A Critical Test of Chlorine Chemistry in the Ozone Layer
Authors: Solomon P. M. , de Zafra R. , Parrish A. , Barrett J. W.
Published: October 2006

This article reports measurements of the column density of stratospheric chlorine monoxide and presents a complete diurnal record of its variation (with 2-hour resolution) obtained from ground-based observations of a millimeter-wave spectral line at 278 gigahertz. Observations were carried out during October and December 1982 from Mauna Kea, Hawaii. The results reported here indicate that the mixing ratio and column density of chlorine monoxide above 30 kilometers during the daytime are ∼20 percent lower than model predictions based on 2.1 parts per billion of total stratospheric chlorine. The observed day-to-night variation of chlorine monoxide is, however, in good agreement with recent model predictions, confirms the existence of a nighttime reservoir for chlorine, and verifies the predicted general rate of its storage and retrieval. From this evidence, it appears that the chlorine chemistry above 30 kilometers is close to being understood in current stratospheric models. Models based on this chemistry and measured reaction rates predict a reduction in the total stratospheric ozone content in the range of 3 to 5 percent in the final steady state for an otherwise unperturbed atmosphere, although the percentage decrease in the upper stratosphere is much higher.
Acetolactate Synthase Is the Site of Action of Two Sulfonylurea Herbicides in Higher Plants
Authors: Chaleff R. S. , Mauvais C. J.
Published: October 2006

Biochemical and genetic studies of a tobacco mutant resistant to the herbicides chlorsulfuron and sulfometuron methyl have demonstrated that these sulfonylurea herbicides inhibit acetolactate synthase, the first enzyme specific to the branched chain amino acid biosynthetic pathway. Resistance of this mutant is accomplished by production of a form of the enzyme that is insensitive to inhibition by the two herbicides.
[
3
H]GABA Binding in Brains from Huntington's Chorea Patients: Altered Regulation by Phospholipids?
Authors: Lloyd Kenneth G. , Davidson Lynne
Published: October 2006

Binding sites for tritium-labeled γ-aminobutyric acid (GABA) in cerebellar cortex of Huntington's chorea patients have an increased affinity but unaltered maximum capacity as compared to binding sites in tissue from control patients. A similar binding pattern is produced in control membranes by treatment with Triton X-100, phospholipase C, or glycerophosphoethanolamine. Thus, it is likely that phospholipids or their metabolites regulate the accessibility of the GABA binding site and that this regulation is abnormal in Huntington's chorea.