bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature and Precipitation Estimates Through the Last Glacial Cycle from Clear Lake, California, Pollen Data
Authors: Adam David P. , West G. James
Published: October 2006

Modern pollen surface samples from six lake and marsh sites in the northern California Coast Ranges establish a linear relation between elevation and the oak/(oak + pine) pollen ratio. Modern temperature and precipitation lapse rates were used to convert variations in the pollen ratio into temperature and precipitation changes. Pollen data from two cores from Clear Lake, Lake County, California, spanning the past 40,000 and 130,000 years were used to estimate temperature and precipitation changes through the last full glacial cycle. The maximum glacial cooling is estimated to be 7° to 8° C; the last full interglacial period was about 1.5° C warmer than the Holocene, and a mid-Holocene interval was warmer than the present. The estimated precipitation changes are probably less reliable than the estimated temperature changes.
Removal of Uranium(VI) from Solution by Fungal Biomass and Fungal Wall-Related Biopolymers
Authors: Galun M. , Keller P. , Malki D. , Feldstein H. , Galun E. , Siegel S. M. , Siegel B. Z.
Published: October 2006

Penicillium digitatum
mycelium can accumulate uranium from aqueous solutions of uranyl chloride. Azide present during the uptake tests does not inhibit the process. Killing the fungal biomass in boiling water or by treatment with alcohols, dimethyl sulfoxide, or potassium hydroxide increases the uptake capability to about 10,000 parts per million (dry weight). Formaldehyde killing does not enhance the uranium uptake. The inference that wall-binding sites were involved led to the testing of uranium uptake by chitin, cellulose, and cellulose derivatives in microcolumns. All were active, especially chitin.
Ammonium-Nitrogen in Green River Formation Oil Shale
Authors: Cooper James E. , Evans W. Scot
Published: October 2006

It has been assumed that all of the nitrogen in oil shale from the Green River Formation is present as organic nitrogen and that the nitrogen in spent shale from retorting is present in the char or coke. In fact, from 41 to 84 percent of the nitrogen is present as ammonium fixed within silicate minerals in five samples of raw oil shale and between 46 and 69 percent of the nitrogen is similarly fixed in two samples of spent shale. Both organic nitrogen and fixed ammonium-nitrogen are lost during retorting by the Fischer assay procedure; the loss of organic nitrogen is greater.
Comparing Brains
Authors: Harvey Paul H. , Krebs John R.
Published: October 2006

Some animals have larger brains than others, but it is not yet known why. Species differences in life-style, including dietary habits and patterns of development of the young, are associated with variation in brain weight, independently of the effects of body weight and evolutionary history. Taken together with behavioral and neuroanatomical analyses, these studies begin to suggest the evolutionary pressures that favor different sized brains and brain components.
Optimization by Simulated Annealing
Authors: Kirkpatrick S. , Gelatt C. D. , Vecchi M. P.
Published: October 2006

There is a deep and useful connection between statistical mechanics (the behavior of systems with many degrees of freedom in thermal equilibrium at a finite temperature) and multivariate or combinatorial optimization (finding the minimum of a given function depending on many parameters). A detailed analogy with annealing in solids provides a framework for optimization of the properties of very large and complex systems. This connection to statistical mechanics exposes new information and provides an unfamiliar perspective on traditional optimization problems and methods.
Variability of Antarctic Sea Ice: and Changes in Carbon Dioxide
Authors: Zwally H. Jay , Parkinson C. L. , Comiso J. C.
Published: October 2006

A definitive long-term decrease in the extent of antarctic sea ice is not detectable from 9 years (1973 to 1981) of year-round satellite observations and limited prior data. Regional interannual variability is large, with sea ice decreasing in some regions while increasing in others. A significant decrease in overall ice extent during the mid-1970's, previously suggested to reflect warming induced by carbon dioxide, has not been maintained. In particular, the extent of ice in the Weddell Sea region has rebounded after a large decrease concurrent with a major oceanographic anomaly, the Weddell polynya. Over the 9 years, the trends are nearly the same in all seasons, but for periods of 3 to 5 years, greater winter ice maxima are associated with lesser summer ice minima. The decrease of the mid-1970's was preceded by an increase in ice extent from 1966 to 1972, further indicating the presence of cyclical components of variation that obscure any long-term trends that might be caused by a warming induced by carbon dioxide.
The Tunguska Explosion of 1908: Discovery of Meteoritic Debris near the Explosion Site and at the South Pole
Authors: Ganapathy Ramachandran
Published: October 2006

Submillimeter-sized metallic spheres extracted from soil in the Tunguska region of central Siberia contain noble metals in cosmic proportions. The trace element composition and geographical distribution of these spheres suggest that they are from the 30 June 1908 Tunguska explosion and not meteoritic ablation products falling continuously on the earth. Debris from this explosion was also discovered in a South Pole ice core; this discovery indicates that the Tunguska object exploded in the atmosphere with subsequent stratospheric injection and transport of the debris. The celestial body that exploded over Tunguska weighed more than 7 million tons, was more than 0.16 kilometer in diameter, and may well have been a stony meteorite. This discovery offers a new precision time marker in polar ice strata for the year 1909. The steady-state influx of cosmic matter at the South Pole is estimated to be 1.8 × 10
–8
grams per square centimeter per year, which corresponds to a global influx of 4 × 10
5
tons per year.
Sighting of El Chichón Sulfur Dioxide Clouds with the Nimbus 7 Total Ozone Mapping Spectrometer
Authors: Krueger Arlin J.
Published: October 2006

The eruptions of El Chichón volcano on 28 March and 3 and 4 April 1982 were observed by the Nimbus 7 total ozone mapping spectrometer due to strong absorption by volcanic gases at the shortest wavelengths of the spectrometer (312.5 and 317.5 nanometers). These ultraviolet pictures permit a measurement of the volume, dispersion, and drift of volcanic gas clouds. The tropospheric clouds were rapidly dispersed in westerly winds while persistent stratospheric clouds drifted in easterly winds at speeds up to 13 meters per second. The spectral reflectance is consistent with sulfur dioxide absorption and rules out carbon disulfide as a major constituent. A preliminary estimate of the mass of sulfur dioxide deposited in the stratosphere by the large eruptions on 3 and 4 April is 3.3 × 10
6
tons. Prior estimates of volcanic cloud volume were based on extrapolation of locally measured sulfur dioxide concentrations.
Evidence of Changes in Protease Sensitivity and Subunit Exchange Rate on DNA Binding by C/EBP
Authors: Shuman Jon D. , Vinson Charles R. , McKnight Steven L.
Published: October 2006

The transcription factor C/EBP uses a bipartite structural motif to bind DNA. Two protein chains dimerize through a set of amphipathic α helices termed the leucine zipper. Highly basic polypeptide regions emerge from the zipper to form a linked set of DNA contact surfaces. In the recently proposed a "scissors grip" model, the paired set of basic regions begin DNA contact at a central point and track in opposite directions along the major groove, forming a molecular clamp around DNA. This model predicts that C/EBP must undertake significant changes in protein conformation as it binds and releases DNA. The basic region of ligand-free C/EBP is highly sensitive to protease digestion. Pronounced resistance to proteolysis occurred when C/EBP associated with its specific DNA substrate. Sequencing of discrete proteolytic fragments showed that prominent sites for proteolysis occur at two junction points predicted by the "scissors grip" model. One junction corresponds to the cleft where the basic regions emerge from the leucine zipper. The other corresponds to a localized nonhelical segment that has been hypothesized to contain an N-cap and facilitate the sharp angulation necessary for the basic region to track continuously in the major groove of DNA.
Testosterone Reduces Refractory Period of Stria Terminalis Neurons in the Rat Brain
Authors: Kendrick K. M. , Drewett R. F.
Published: October 2006

The absolute refractory period of neurons projecting from the corticomedial amygdala to the medial preoptic-anterior hypothalamic junction in rats was significantly increased by castration (from 1.01 to 1.61 milliseconds) and decreased again by testosterone (from 1.48 to 0.97 millisecond). Corticomedial amygdala neurons which projected to the capsule of the ventromedial nucleus of the hypothalamus were unaffected. These results demonstrate a specific, direct neuronal effect of testosterone.
Molecular Genetics of the Bithorax Complex in
Drosophila melanogaster
Authors: Bender Welcome , Akam Michael , Karch François , Beachy Philip A. , Peifer Mark , Spierer Pierre , Lewis E. B. , Hogness David S.
Published: October 2006

The bithorax complex in
Drosophila melanogaster
is a cluster of homeotic genes that specify developmental pathways for many of the body segments of the fly. The DNA of the bithorax complex has been isolated, and a region of 195,000 base pairs that covers the left half of the complex is described here. The lesions associated with many of the bithorax complex mutants have been identified, and most are due to DNA rearrangements. Most of the spontaneous mutants have insertions of a particular mobile element named "gypsy." This element affects the functions of sequences removed from the site of insertion. Mutant lesions for a given phenotypic class are distributed over large DNA distances of up to 73,000 base pairs.
Oceans on Titan?
Authors: Flasar F. M.
Published: October 2006

If global oceans of methane exist on Titan, the atmosphere above them must be within 2 percent of saturation. The two Voyager radio occultation soundings, made at low latitudes, probably occurred over land, since they imply a relative humidity ≲ 70 percent near the surface. Oceans might exist at other low-latitude locations if the zonal wind velocities in the lowest 3 kilometers are ≤ 4 centimeters per second.
Intraspecific Deception by Bluffing: A Defense Strategy of Newly Molted Stomatopods (Arthropoda: Crustacea)
Authors: Steger Rick , Caldwell Roy L.
Published: October 2006

After molting, stomatopods can be evicted easily from home cavities by conspecifics because these marine crustaceans lose temporarily their body armor and the use of their raptorial appendages. Some newly molted stomatopods defend their cavities with a meral spread display, a signal correlated with attack when used by animals between molts. The use of the meral spread display actually increases after molting. Since new molts cannot fight, their use of meral spread appears to be a bluff.
Lignin-Degrading Enzyme from the Hymenomycete
Phanerochaete chrysosporium
Burds
Authors: Tien Ming , Kirk T. Kent
Published: October 2006

The extracellular fluid of ligninolytic cultures of the wood-decomposing basidiomycete
Phanerochaete chrysosporium
Burds. contains an enzyme that degrades lignin substructure model compounds as well as spruce and birch lignins. It has a molecular size of 42,000 daltons and requires hydrogen peroxide for activity.
Facing Quantum Mechanical Reality
Authors: Rohrlich Fritz
Published: October 2006

Two recent precision experiments provide conclusive evidence against any local hidden variables theory and in favor of standard quantum mechanics. Therefore the epistemology and the ontology of quantum mechanics must now be taken more seriously than ever before. The consequences of the standard interpretation of quantum mechanics are summarized in nontechnical language. The implications of the finiteness of Planck's constant (
h
> 0) for the quantum world are as strange as the implications of the finiteness of the speed of light (
c
< ∞) for space and time in relativity theory. Both lead to realities beyond our common experience that cannot be rejected.
Structural Characterization of a Partly Folded Apomyoglobin Intermediate
Authors: Hughson Frederick M. , Wright Peter E. , Baldwin Robert L.
Published: October 2006

To understand why proteins adopt particular three-dimensional structures, it is important to elucidate the hierarchy of interactions that stabilize the native state. Proteins in partly folded states can be used to dissect protein organizational hierarchies. A partly folded apomyoglobin intermediate has now been characterized structurally by trapping slowly exchanging peptide NH protons and analyzing them by two-dimensional
1
H-NMR (nuclear magnetic resonance). Protons in the A, G, and H helix regions are protected from exchange, while protons in the B and E helix regions exchange freely. On the basis of these results and the three-dimensional structure of native myoglobin, a structural model is presented for the partly folded intermediate in which a compact subdomain retains structure while the remainder of the protein is essentially unfolded.
Sources of Human Psychological Differences: The Minnesota Study of Twins Reared Apart
Authors: Bouchard Thomas J. , Lykken David T. , McGue Matthew , Segal Nancy L. , Tellegen Auke
Published: October 2006

Since 1979, a continuing study of monozygotic and dizygotic twins, separated in infancy and reared apart, has subjected more than 100 sets of reared-apart twins or triplets to a week of intensive psychological and physiological assessment. Like the prior, smaller studies of monozygotic twins reared apart, about 70% of the variance in IQ was found to be associated with genetic variation. On multiple measures of personality and temperament, occupational and leisure-time interests, and social attitudes, monozygotic twins reared apart are about as similar as are monozygotic twins reared together. These findings extend and support those from numerous other twin, family, and adoption studies. It is a plausible hypothesis that genetic differences affect psychological differences largely indirectly, by influencing the effective environment of the developing child. This evidence for the strong heritability of most psychological traits, sensibly construed, does not detract from the value or importance of parenting, education, and other propaedeutic interventions.
Rates of Evolution: Effects of Time and Temporal Scaling
Authors: Gingerich Philip D.
Published: October 2006

Rates of morphological evolution documented in laboratory selection experiments, historical colonization events, and the fossil record are inversely related to the interval of time over which they are measured. This inverse relationship is an artifact of comparing a narrow range of morphological variation over a wide range of time intervals, and it is also a product of time averaging. Rates measured over different intervals of time must be scaled against interval length before they can be compared.
Early Eutrophication in the Lower Great Lakes:
Authors: Schelske Claire L. , Stoermer Eugene F. , Conley Daniel J. , Robbins John A. , Glover Rebecca M.
Published: October 2006

New evidence from studies of biogenic silica and diatoms in sediment cores indicates that eutrophication in the lower Great Lakes resulted from nutrient enrichment associated with early settlement and forest clearance. Diatom production peaked from 1820 to 1850 in Lake Ontario, at about 1880 in Lake Erie, but not until 1970 in Lake Michigan. This is the first reported sediment record of the silica-depletion sequence for the Great Lakes.
Three Mars Years: Viking Lander 1 Imaging Observations
Authors: Arvidson Raymond E. , Guinness Edward A. , Moore Henry J. , Tillman James , Wall Stephen D.
Published: October 2006

The Mutch Memorial Station (Viking Lander 1) on Mars acquired imaging and meteorological data over a period of 2245 martian days (3:3 martian years). This article discusses the deposition and erosion of thin deposits (ten to hundreds of micrometers) of bright red dust associated with global dust storms, and the removal of centimeter amounts of material in selected areas during a dust storm late in the third winter. Atmospheric pressure data acquired during the period of intense erosion imply that baroclinic disturbances and strong diurnal solar tidal heating combined to produce strong winds. Erosion occurred principally in areas where soil cohesion was reduced by earlier surface sampler activities. Except for redistribution of thin layers of materials, the surface appears to be remarkably stable, perhaps because of cohesion of the undisturbed surface material.
Chesapeake Bay Anoxia: Origin, Development, and Significance
Authors: Officer Charles B. , Biggs Robert B. , Taft Jay L. , Cronin L. Eugene , Tyler Mary A. , Boynton Walter R.
Published: October 2006

Anoxia occurs annually in deeper waters of the central portion of the Chesapeake Bay and presently extends from Baltimore to the mouth of the Potomac estuary. This condition, which encompasses some 5 billion cubic meters of water and lasts from May to September, is the result of increased stratification of the water column in early spring, with consequent curtailment of reoxygenation of the bottom waters across the halocline, and benthic decay of organic detritus accumulated from plankton blooms of the previous summer and fall. The Chesapeake Bay anoxia appears to have had significant ecological effects on many marine species, including several of economic importance.
Elemental Tracers of Distant Regional Pollution Aerosols
Authors: Rahn Kenneth A. , Lowenthal Douglas H.
Published: October 2006

A seven-element tracer system shows that regional pollution aerosols of both North America and Europe have characteristic signatures that can be followed into remote areas up to several thousand kilometers downwind. In aerosols of mixed origin, regional contributions to the tracer elements can be resolved by least-squares procedures. After transport of several hundred kilometers, secondary sulfate can also be apportioned satisfactorily. Regional elemental tracers thus offer a way to determine the sources of pollution aerosol in important areas such as the northeastern United States, Scandinavia, and the Arctic.
Activation of Alkanes with Organotransition Metal Complexes
Authors: Bergman Robert G.
Published: October 2006

Alkanes, although plentiful enough to be considered for use as feedstocks in large-scale chemical processes, are so unreactive that relatively few chemical reagents have been developed to convert them to molecules having useful functional groups. However, a recently synthesized iridium (Ir) complex successfully converts alkanes into hydridoalkylmetal complexes (M + R-H → R-M-H). This is a dihydride having the formula Cp*(L)IrH
2
, where Cp* and L are abbreviations for the ligands (CH
3
)
5
C
5
and (CH
3
)
3
P, respectively. Irradiation with ultraviolet light causes the dihydride to lose H
2
, generating the reactive intermediate Cp*IrL. This intermediate reacts rapidly with C-H bonds in every molecule so far tested (including alkanes) and leads to hydridoalkyliridium complexes Cp*(L)Ir(R)(H). Evidence has been obtained that this C-H insertion, or oxidative addition, reaction proceeds through a simple three-center transition state and does not involve organic free radicals as intermediates. Thus the intermediate Cp*IrL reacts most rapidly with C-H bonds having relatively high bond energies, such as those at primary carbon centers, in small organic rings, and in aromatic rings. This contrasts directly with the type of hydrogen-abstraction selectivity that is characteristic of organic radicals. The hydridoalkyliridium products of the insertion reactions can be converted into functionalized organic molecules—alkyl halides—by treatment with mercuric chloride followed by halogens. Expulsion (reductive elimination) of the hydrocarbon from the hydridoalkyliridium complexes can be induced by Lewis acids or heat, regenerating the reactive intermediate Cp*IrL. Oxidative addition of the corresponding rhodium complexes Cp*RhL to alkane C-H bonds has also been observed, although the products formed in this case are much less stable and undergo reductive elimination at -20°C. These and other recent observations provide an incentive for reexamining the factors that have been assumed to control the rate of reaction of transition metal complexes with C-H bonds—notably the need for electron-rich metals and the proximity of reacting centers.
End-Cretaceous Brachiopod Extinctions in the Chalk of Denmark
Authors: Surlyk Finn , Johansen Marianne Bagge
Published: October 2006

The results of a detailed study of the brachiopods of the most complete Cretaceous-Tertiary boundary in Denmark, Nye Kløv, show an extinction pattern for this marine invertebrate group compatible with that reported for pelagic foraminifera and coccoliths and with the impact scenario. The extinction is abrupt, coinciding with the Maastrichtian-Danian boundary. There is no warning in the form of decreasing density, decreasing diversity, or early extinction of specialized groups. The basal few meters of the Danian are almost devoid of brachiopods, and a Danian brachiopod fauna starts almost as abruptly as the Maastrichtian fauna disappeared. The new fauna is similar to the Maastrichtian as regards density and diversity, and at maximum six species are common to both stages. The northwest European Maastrichtian chalk is composed mainly of the remains of coccoliths and pelagic foraminifera. The mass extinction of these groups led to a total cessation of chalk production. The chalk is overlain by a thin clay bed deposited partly under anoxic conditions. This combination of anoxia and clay deposition coupled with a cessation of productivity led to the extinction of specialized groups such as the chalk brachiopods. The surviving species included forms that could survive in well-aerated shallow marine waters on substrates other than chalk.
Mass Spawning in Tropical Reef Corals
Authors: Harrison Peter L. , Babcock Russell C. , Bull Gordon D. , Oliver James K. , Wallace Carden C. , Willis Bette L.
Published: October 2006

Synchronous multispecific spawning by a total of 32 coral species occurred a few nights after late spring full moons in 1981 and 1982 at three locations on the Great Barrier Reef, Australia. The data invalidate the generalization that most corals have internally fertilized, brooded planula larvae. In every species observed, gametes were released; external fertilization and development then followed. The developmental rates of externally fertilized eggs and longevities of planulae indicate that planulae may be dispersed between reefs.
Cerebral Cortical Microfluorometry at Isosbestic Wavelengths for Correction of Vascular Artifact
Authors: Kramer Richard S. , Pearlstein Robert D.
Published: October 2006

Microfluorometric measurements of cerebral cortical mitochondrial respiration in vivo are obscured by hemodynamic and oximetric artifacts. Isosbestic fluorometry provides appropriate correction for these vascular phenomena and permits simultaneous evaluation of mitochondrial nicotinamide adenine dinucleotide redox state, microcirculatory volume, and hemoglobin oxygenation.
Reduction of a Larval Herring Population by Jellyfish Predator
Authors: Möller Heino
Published: October 2006

The scyphomedusa
Aurelia aurita
consumes large amounts of yolk-sac herring larvae in Kiel Fjord. The decline of the larval herring population in late spring coincides with a major population growth of the jellyfish. The size of the larval herring population seems to be more significantly affected by the size of the predator stock than by the size of the parental herring stock.
Mineralogic Evidence for an Impact Event at the Cretaceous-Tertiary Boundary
Authors: Bohor B. F. , Foord E. E. , Modreski P. J. , Triplehorn D. M.
Published: October 2006

A thin claystone layer found in nonmarine rocks at the palynological Cretaceous-Tertiary boundary in eastern Montana contains an anomalously high value of iridium. The nonclay fraction is mostly quartz with minor feldspar, and some of these grains display planar features. These planar features are related to specific crystallographic directions in the quartz lattice. The shocked quartz grains also exhibit asterism and have lowered refractive indices. All these mineralogical features are characteristic of shock metamorphism and are compelling evidence that the shocked grains are the product of a high velocity impact between a large extraterrestrial body and the earth. The shocked minerals represent silicic target material injected into the stratosphere by the impact of the projectile.
Common Elements and Interconnections
Authors: Harrison Anna J.
Published: October 2006

The major concepts addressed in this article are the synergistic nature of science, engineering, and technology; the benefits and burdens of technology; the resolution of societal issues; and the roles of scientists and engineers in the resolution of societal issues.
Modeling Long-Term Fluctuations in Fish Stocks
Authors: Steele John H. , Henderson Eric W.
Published: October 2006

Many pelagic fish stocks change rapidly in abundance, with intervening periods of about 50 years. The physical environment does not display such abrupt changes but has a variance that increases with time. A simple population model with multiple equilibrium states exhibited the observed behavior when subjected to this type of stochastic variability. The periodicity exhibited by the model is of the same order as the observations. Thus the assumption by fisheries management of a natural persistence in stocks is questionable.
Binding of the Wilms' Tumor Locus Zinc Finger Protein to the EGR-1 Consensus Sequence
Authors: Rauscher Frank J. , Morris Jennifer F. , Tournay Olivia E. , Cook Donna M. , Curran Tom
Published: October 2006

The Wilms' tumor locus (WTL) at 11p13 contains a gene that encodes a zinc finger-containing protein that has characteristics of a DNA-binding protein. However, binding of this protein to DNA in a sequence-specific manner has not been demonstrated. A synthetic gene was constructed that contained the zinc finger region, and the protein was expressed in
Escherichia coli
. The recombinant protein was used to identify a specific DNA binding site from a pool of degenerate oligonucleotides. The binding sites obtained were similar to the sequence recognized by the early growth response-1 (EGR-1) gene product, a zinc finger-containing protein that is induced by mitogenic stimuli. A mutation in the zinc finger region of the protein originally identified in a Wilms' tumor patient abolished its DNA-binding activity. These results suggest that the WTL protein may act at the DNA binding site of a growth factor-inducible gene and that loss of DNA-binding activity contributes to the tumorigenic process.
Chronic Zinc Deficiency Alters Neuronal Function of Hippocampal Mossy Fibers
Authors: Hesse Gary W.
Published: October 2006

Low-frequency stimulation of hippocampal mossy fiber axons in zinc-deficient adult rats produced synaptic responses that declined in amplitude with successive stimuli. This response decrement is abnormal and suggests that the heavy deposits of zinc in mossy fiber boutons are important for synaptic transmission.
Mechanisms of Nitrogen Retention in Forest Ecosystems: A Field Experiment
Authors: Vitousek Peter M. , Matson Pamela A.
Published: October 2006

Intensive forest management led to elevated losses of nitrogen from a recently harvested loblolly pine plantation in North Carolina. Measurements of nitrogen-15 retention in the field demonstrated that microbial uptake of nitrogen during the decomposition of residual organic material was the most important process retaining nitrogen. Management practices that remove this material cause increased losses of nitrogen to aquatic ecosystems and the atmosphere.
Sex Ratio of Sea Turtles: Seasonal Changes
Authors: Mrosovsky N. , Hopkins-Murphy Sally R. , Richardson James I.
Published: October 2006

Sex ratios of hatchling loggerhead turtles
Caretta caretta
taken from South Carolina and Georgia ranged from no females in nests laid in late May to 80 percent females in those laid in early July; the sex ratio decreased to 10 percent females in nests laid in early August. These seasonal changes are consistent with the role of temperature in directing sexual differentiation in various reptiles. The data have implications for understanding the demography of sea turtles and for their conservation.
Flotation of the Bivalve
Corbicula fluminea
as a Means of Dispersal
Authors: Prezant Robert S. , Chalermwat Kashane
Published: October 2006

Small specimens of the Asiatic bivalve
Corbicula
c.f.
fluminea
(Müller) secrete long mucous threads through their exhalent siphons that act as draglines to buoy the animal into a water column. These mucous strands, secreted in response to water current stimuli, are produced by dense accumulations of ctenidial mucocytes and may help in the downstream or interstream dispersal of this rapidly spreading exotic clam.
Metalorganic Chemical Vapor Deposition of III-V Semiconductors
Authors: Dupuis R. D.
Published: October 2006

Metalorganic chemical vapor deposition (MOCVD) is a process in which two or more metalorganic chemicals (for instance, trimethylgallium) or one or more metalorganic sources and one or more hydride sources (for instance, arsine, AsH
3
) are used to form the corresponding intermetallic crystalline solid solution. MOCVD materials technology is a vapor-phase growth process that is becoming widely used to study the basic physics of novel materials and to grow complex semiconductor device structures for new optoelectronic and photonic systems. The MOCVD process is described and some of the device applications and results that have been realized with it are reviewed, with particular emphasis on the III-V compound semiconductors.
Ductile Ordered Intermetallic Alloys
Authors: Liu C. T. , Stiegler J. O.
Published: October 2006

Many ordered intermetallic alloys have attractive high-temperature properties; however, low ductility and brittle fracture limit their use for structural applications. The embrittlement in these alloys is mainly caused by an insufficient number of slip systems (bulk brittleness) and poor grain-boundary cohesion. Recent studies have shown that the ductility and fabricability of ordered intermetallics can be substantially improved by alloying processes and control of microstructural features through rapid solidification and thermomechanical treatments. These results demonstrate that the brittleness problem associated with ordered intermetallics can be overcome by using physical metallurgical principles. Application of these principles will be illustrated by results on Ni
3
Al and Ni
3
V-Co
3
V-Fe
3
V. The potential for developing these alloys as a new class of high-temperature structural materials is discussed.
Theoretical Chemistry Comes Alive: Full Partner with Experiment
Authors: Goddard William A.
Published: October 2006

During the last decade, advances in computational techniques and in the extraction of chemically useful concepts from electronic wave functions have put theorists into the mainstream of chemistry. Some recent examples of the prediction of spectroscopic quantities and the elucidation of catalytic processes for homogeneous and heterogeneous reactions from theoretical calculations are used to illustrate how theory and experiment are now full partners in chemical research. It is expected that during the next decade the thrust of theoretical chemistry will be to combine the knowledge of fundamental chemical steps and fundamental interactions with advances in chemical dynamics and irreversible statistical mechanics and in computer technology to produce simulations of chemical systems with competing reactions taking place simultaneously at various reaction sites. The promise of such simulation is illustrated by a study of the enzyme thermolysin.
Bacterial 5-Nucleotidase in Aquatic Ecosystems: A Novel Mechanism of Phosphorus Regeneration
Authors: Ammerman James W. , Azam Farooq
Published: October 2006

Zooplankton excretion and algal alkaline phosphatase are presumed to be responsible for phosphorus recycling in aquatic ecosystems; the role of bacteria has been unclear. High levels of bacterial cell-surface 5′-nucleotidase were discovered in samples of picoplankton from California coastal waters. 5′-Nucleotidase rapidly generated orthophosphate from 5′-nucleotide added in nanomolar amounts and could supply half the orthophosphate required by plankton. Unlike alkaline phosphatase, 5′-nucleotidase was not inhibited by orthophosphate at any concentration found in aquatic environments. Initial results indicate even greater 5′-nucleotidase activity in fresh water (Lake Hodges, California) and brackish water (Baltic). Release and uptake of orthophosphate were tightly coupled.
Cloning and Expression of a Developmentally Regulated Protein That Induces Mitogenic and Neurite Outgrowth Activity
Authors: Li Yue-Sheng , Milner Peter G. , Chauhan Anil K. , Watson Mark A. , Hoffman Ruth M. , Kodner Charles M. , Milbrandt Jeffrey , Deuel Thomas F
Published: October 2006

A heparin binding mitogenic protein isolated from bovine uterus shares NH
2
-terminal amino acid sequence with a protein isolated from newborn rat brain. The cDNA's of the bovine, human, and rat genes have been isolated and encode extraordinarily conserved proteins unrelated to known growth or neurotrophic factors, although identity of nearly 50 percent has been found with the predicted sequence of a retinoic acid induced transcript in differentiating mouse embryonal carcinoma cells. Lysates of COS-7 cells transiently expressing this protein were mitogenic for NRK cells and initiated neurite outgrowth from mixed cultures of embryonic rat brain cells. RNA transcripts encoding this protein were widely distributed in tissues and were developmentally regulated. This protein, previously designated as heparin binding growth factor (HBGF)-8, is now renamed pleiotrophin (PTN) to reflect its diverse activities. PTN may be the first member of a family of developmentally regulated cytokines.
New Physicians: A Natural Experiment in Market Organization
Authors: Roth Alvin E.
Published: October 2006

The National Resident Matching Program is a centralized clearinghouse through which new medical graduates in the United States obtain their first positions. The history of this market, from the market failures that the centralized system was designed to address, to the present, is discussed, and a hypothesis about the behavior of such markets is presented. New evidence is then presented from a set of similar centralized markets in the United Kingdom. Because some of these latter markets have failed, while others have succeeded, they provide a natural experiment that permits the hypothesis to be tested. The new evidence also suggests directions in which modifications of existing procedures might be considered.
Acetylcholine Binding by a Synthetic Receptor: Implications for Biological Recognition
Authors: Dougherty Dennis A. , Stauffer David A.
Published: October 2006

The neurotransmitter acetylcholine (ACh) is bound with 50-micromolar affinity by a completely synthetic receptor (host) comprising primarily aromatic rings. The host provided an overall hydrophobic binding site, but one that could recognize the positive charge of the quaternary ammonium group of ACh through a stabilizing interaction with the electron-rich π systems of the aromatic rings (cation-π interaction). Similar interactions may be involved in biological recognition of ACh and other choline derivatives.
Crystal Structure of Cobra-Venom Phospholipase A
2
in a Complex with a Transition-State Analogue
Authors: White Steven P. , Scott David L. , Otwinowski Zbyszek , Gelb Michael H. , Sigler Paul B.
Published: October 2006

The crystal structure of a complex between a phosphonate transition-state analogue and the phospholipase A
2
(PLA
2
) from
Naja naja atra
venom has been solved and refined to a resolution of 2.0 angstroms. The identical stereochemistry of the two complexes that comprise the crystal's asymmetric unit indicates both the manner in which the transition state is stabilized and how the hydrophobic fatty acyl chains of the substrate are accommodated by the enzyme during interfacial catalysis. The critical features that suggest the chemistry of binding and catalysis are the same as those seen in the crystal structure of a similar complex formed with the evolutionarily distant bee-venom PLA
2
.
Expression, Glycosylation, and Secretion of an
Aspergillus
Glucoamylase by
Saccharomyces cerevisiae
Authors: Innis M. A. , Holland M. J. , McCabe P. C. , Cole G. E. , Wittman V. P. , Tal R. , Watt K. W.K. , Gelfand D. H. , Holland J. P. , Meade J. H.
Published: October 2006

A strain of
Saccharomyces cerevisiae
capable of simultaneous hydrolysis and fermentation of highly polymerized starch oligosaccharides was constructed. The
Aspergillus awamori
glucoamylase enzyme, form GAI, was expressed in
Saccharomyces cerevisiae
by means of the promoter and termination regions from a yeast enolase gene. Yeast transformed with plasmids containing an intron-free recombinant glucoamylase gene efficiently secreted glucoamylase into the medium, permitting growth of the transformants on starch as the sole carbon source. The natural leader sequence of the precursor of glucoamylase (preglucoamylase) was processed correctly by yeast, and the secreted enzyme was glycosylated through both
N
- and
O
-linkages at levels comparable to the native
Aspergillus
enzyme. The data provide evidence for the utility of yeast as an organism for the production, glycosylation, and secretion of heterologous proteins.
Role of Fault Bends in the Initiation and Termination of Earthquake Rupture
Authors: King Geoffrey , Nábělek John
Published: October 2006

Rupture in individual earthquakes apparently is limited to regions between bends in faults. This is illustrated for eight events that have occurred since 1966. A model based on geometric concepts describes why this is so and clarifies earlier ideas of "asperities" and "barriers" used to explain earthquake initiation and termination processes. Because of their importance in the rupture process, bend zones should be monitored for precursory effects.
Imaging Spectrometry for Earth Remote Sensing
Authors: Goetz Alexander F. H. , Vane Gregg , Solomon Jerry E. , Rock Barrett N.
Published: October 2006

Imaging spectrometry, a new technique for the remote sensing of the earth, is now technically feasible from aircraft and spacecraft. The initial results show that remote, direct identification of surface materials on a picture-element basis can be accomplished by proper sampling of absorption features in the reflectance spectrum. The airborne and spaceborne sensors are capable of acquiring images simultaneously in 100 to 200 contiguous spectral bands. The ability to acquire laboratory-like spectra remotely is a major advance in remote sensing capability. Concomitant advances in computer technology for the reduction and storage of such potentially massive data sets are at hand, and new analytic techniques are being developed to extract the full information content of the data. The emphasis on the deterministic approach to multispectral data analysis as opposed to the statistical approaches used in the past should stimulate the development of new digital image-processing methodologies.
The Sociogenesis of Insect Colonies
Authors: Wilson Edward O.
Published: October 2006

Studies on the social insects (ants, bees, wasps, and termites) have focused increasingly on sociogenesis, the process by which colony members undergo changes in caste, behavior, and physical location incident to colonial development. Caste is determined in individuals largely by environmental cues that trigger a sequence of progressive physiological restrictions. Individual determination, which is socially mediated, yields an age-size frequency distribution of the worker population that enhances survival and reproduction of the colony as a whole, typically at the expense of individuals. This "adaptive demography" varies in a predictable manner according to the species and size of the colony. The demography is richly augmented by behavioral pacemaking on the part of certain castes and programmed changes in the physical position of colony members according to age and size. Much of what has been observed in these three colony-level traits (adaptive demography, pacemaking, and positional effects) can be interpreted as the product of ritualization of dominance and other forms of selfish behavior that is still found in the more primitive insect societies. Some of the processes can also be usefully compared with morphogenesis at the levels of cells and tissues.
Smoke Production from Multiple Nuclear Explosions in Nonurban Areas
Authors: Small R. D. , Bush B. W.
Published: October 2006

The amount of smoke that may be produced by wildland or rural fires as a consequence of a large-scale nuclear exchange is estimated. The calculation is based on a compilation of rural military facilities, identified from a wide variety of unclassified sources, together with data on their geographic positions, surrounding vegetation (fuel), and weather conditions. The ignition area (corrected for fuel moisture) and the amount of fire spread are used to calculate the smoke production. The results show a substantially lower estimated smoke production (from wildland fires) than in earlier "nuclear winter" studies. The amount varies seasonally and at its peak is less by an order of magnitude than the estimated threshold level necessary for a major attenuation of solar radiation.
Geomicrobiology of Deep-Sea Hydrothermal Vents
Authors: Jannasch Holger W. , Mottl Michael J.
Published: October 2006

During the cycling of seawater through the earth's crust along the mid-ocean ridge system, geothermal energy is transferred into chemical energy in the form of reduced inorganic compounds. These compounds are derived from the reaction of seawater with crustal rocks at high temperatures and are emitted from warm (≤25°C) and hot (∼350°C) submarine vents at depths of 2000 to 3000 meters. Chemolithotrophic bacteria use these reduced chemical species as sources of energy for the reduction of carbon dioxide (assimilation) to organic carbon. These bacteria form the base of the food chain, which permits copious populations of certain specifically adapted invertebrates to grow in the immediate vicinity of the vents. Such highly prolific, although narrowly localized, deep-sea communities are thus maintained primarily by terrestrial rather than by solar energy. Reduced sulfur compounds appear to represent the major electron donors for aerobic microbial metabolism, but methane-, hydrogen-, iron-, and manganese-oxidizing bacteria have also been found. Methanogenic, sulfur-respiring, and extremely thermophilic isolates carry out anaerobic chemosynthesis. Bacteria grow most abundantly in the shallow crust where upwelling hot, reducing hydrothermal fluid mixes with downwelling cold, oxygenated seawater. The predominant production of biomass, however, is the result of symbiotic associations between chemolithotrophic bacteria and certain invertebrates, which have also been found as fossils in Cretaceous sulfide ores of ophiolite deposits.
Increase of Atmospheric Methane Recorded in Antarctic Ice Core
Authors: Stauffer B. , Fischer G. , Neftel A. , Oeschger H.
Published: October 2006

Air entrapped in bubbles of cold ice has essentially the same composition as that of the atmosphere at the time of bubble formation. Measurements of the methane concentration in air extracted by two different methods from ice samples from Siple Station in western Antarctica allow the reconstruction of the history of the increase of the atmospheric methane during the past 200 years.
High-Resolution Mapping of Human Chromosome 11 by in Situ Hybridization with Cosmid Clones
Authors: Lichter Peter , Tang Chieh-Ju Chang , Call Katherine , Hermanson Gary , Evans Glen A. , Housman David , Ward David C.
Published: October 2006

Cosmid clones containing human DNA inserts have been mapped on chromosome 11 by fluorescence in situ hybridization under conditions that suppress signal from repetitive DNA sequences. Thirteen known genes, one chromosome 11-specific DNA repeat, and 36 random clones were analyzed. High-resolution mapping was facilitated by using digital imaging microscopy and by analyzing extended (prometaphase) chromosomes. The map coordinates established by in situ hybridization showed a one to one correspondence with those determined by Southern (DNA) blot analysis of hybrid cell lines containing fragments of chromosome 11. Furthermore, by hybridizing three or more cosmids simultaneously, gene order on the chromosome could be established unequivocally. These results demonstrate the feasibility of rapidly producing high-resolution maps of human chromosomes by in situ hybridization.
Production of 2-Keto-L-Gulonate, an Intermediate in L-Ascorbate Synthesis, by a Genetically Modified
Erwinia herbicola
Authors: Anderson Stephen , Marks Cara Berman , Lazarus Robert , Miller Jeffrey , Stafford Kevin , Seymour Jana , Light David , Rastetter William , Estell David
Published: October 2006

A new metabolic pathway has been created in the microorganism
Erwinia herbicola
that gives it the ability to produce 2-keto-L-gulonic acid, an important intermediate in the synthesis of L-ascorbic acid. Initially, a
Corynebacterium
enzyme that could stereoselectively reduce 2,5-diketo-D-gluconic acid to 2-keto-L-gulonic acid was identified and purified. DNA probes based on amino acid sequence information from 2,5-diketo-D-gluconic acid reductase were then used to isolate the gene for this enzyme from a
Corynebacterium
genomic library. The 2,5-diketo-D-gluconic acid reductase coding region was fused to the
Escherichia coli
trp promoter and a synthetic ribosome binding site and was then introduced into
E. herbicola
on a multicopy plasmid.
Erwinia herbicola
naturally produces 2,5-diketo-D-gluconic acid via glucose oxidation, and when recombinant cells expressing the plasmid-encoded reductase were grown in the presence of glucose, 2-keto-L-gulonic acid was made and released into the culture medium. The data demonstrate the feasibility of creating novel in vivo routes for the synthesis of important specialty chemicals by combining useful metabolic traits from diverse sources in a single organism.
Dust Devils on Mars
Authors: Thomas Peter , Gierasch Peter J.
Published: October 2006

Columnar, cone-shaped, and funnel-shaped clouds rising 1 to 6 kilometers above the surface of Mars have been identified in Viking Orbiter images. They are interpreted as dust devils, confirming predictions of their occurrence on Mars and giving evidence of a specific form of dust entrainment.
Phytochelatins: The Principal Heavy-Metal Complexing Peptides of Higher Plants
Authors: Grill Erwin , Winnacker Ernst-L. , Zenk Meinhart H.
Published: October 2006

A set of novel heavy-metal complexing peptides was isolated from plant cell suspension cultures; the structure of the peptides was established as (γ-glutamic acid-cysteine)
n
-glycine (
n
= 3 to 7). These peptides appear upon induction of plant cells with heavy metals and represent the principal metal-binding activities in the cells. The name phytochelatin is proposed for this new class of natural products.