bluuebunny/crossref_metadata_2025 huggingface dataset:
Botanical and Geological Significance of Potassium-Argon Dates from the Juan Fernández Islands
Authors: Stuessy Tod F. , Foland K. A. , Sutter John F. , Sanders Roger W. , Silva O. Mario
Published: October 2006

Potassium-argon dating of five basalts from the three main islands of the Juan Fernández (or Robinson Crusoe) Islands of Chile in the southeastern Pacific gives ages of 1.01 ± 0.12 and 2.44 ± 0.14 million years for Masafuera, 3.79 ± 0.20 and 4.23 ± 0.16 for Masatierra, and 5.8 ± 2.1 for Santa Clara. These ages are much younger than that of the underlying oceanic plate and are consistent with the origin of the island-seamount chain from a mantle hot spot beneath the eastward moving Nazca plate. The young age for the archipelago suggests that speciation within endemic genera has occurred within the past 4 to 5 million years. Endemic genera of apparently more ancient origins, such as
Lactoris
and
Thyrsopteris
, have apparently dispersed to the islands and survive refugially.
Marangoni Convection in Space Microgravity Environments
Authors: Napolitano L. G.
Published: October 2006

Thermally induced surface-driven convection (thermal Marangoni convection) was investigated in the Spacelab 1 microgravity environment. The configuration studied is related to the floating-zone technique used for crystal growth.
Variation Among Floral Visitors in Pollination Ability: A Precondition for Mutualism Specialization
Authors: Schemske Douglas W. , Horvitz Carol C.
Published: October 2006

The unusual floral biology of a neotropical herb provided an opportunity to determine that floral visitors varied significantly in their ability to effect fruit-set. Pollination efficiency and visitation frequency varied among Hymenoptera (five taxa), which were responsible for 99 percent of all fruits set. Lepidoptera (four taxa) were common visitors but poor pollinators. These results indicate that flower visitors vary in their beneficial effects on plants, fulfilling one of the primary conditions required for the specialization of plants on pollinators.
Central Pacific Seabirds and the El Niño Southern Oscillation: 1982 to 1983 Perspectives
Authors: Schreiber Ralph W. , Schreiber Elizabeth Anne
Published: October 2006

The breeding chronology and reproductive attempts of the seabird community on Christmas Island in the central Pacific Ocean (2°N, 157°W) were interrupted by the 1982-1983 El Niño Southern Oscillation. The resultant reproductive failure and disappearance of the entire seabird community of this equatorial atoll represents the most dramatic interruption on record of a seabird community located distant from coastal upwelling. Our data indicate the effect that the abiotic and biotic aspects of a global atmospheric-oceanic anomaly have on marine birds. The 1982-1983 El Niño Southern Oscillation provides an example of selective pressures and a natural experiment in the study of vertebrate population dynamics.
X-ray Absorption Spectroscopic Investigation of Sulfur Sites in Coal: Organic Sulfur Identification
Authors: Spiro C. L. , Wong J. , Lytle F. W. , Greegor R. B. , Maylotte D. H. , Lamson S. H.
Published: October 2006

High-resolution x-ray absorption spectroscopy was used to probe the chemical and structural environments of sulfur in coal. Measurement of the sulfur Kedge spectra down to 2472.0 electron volts under nonvacuum conditions was made possible in an all-helium path, and a Stern-Heald type ion chamber was used for fluorescence detection. For a number of selected sulfur-containing minerals and organic model compounds, results show that near-edge spectral features are diagnostic for sulfur in specific organic moieties such as thiols, disulfides, and various heterocyclics, as well as in mineral sulfide and sulfate phases. The spectrum of a model system containing 35 percent iron pyrite and 65 percent benzothiophene was found to match the observed spectral features of a bituminous coal from the eastern United States.
Chenopodium
as a Prehistoric Domesticate in Eastern North America: Evidence from Russell Cave, Alabama
Authors: Smith Bruce D.
Published: October 2006

Approximately 50,000 carbonized fruits of the species
Chenopodium berlandieri
recovered from Russell Cave, Alabama, and dating to 1975 ± 55 before the present, exhibit a set of interrelated morphological characteristics reflecting domestication (thin testa, truncate margin, rectanguloid fruit cross section, ligulate cotyledons, and increased internal fruit volume). These morphological characteristics establish the presence of a domestic variety of
Chenopodium
in the eastern United States by 2000 years ago.
Solar
p
-Mode Eigenfrequencies Are Decreased by Turbulent Convection
Authors: Brown Timothy M.
Published: October 2006

Average solar
p
-mode eigenfrequencies are decreased by large fluctuating velocity fields in the upper convection zone. This effect is greatest for modes with large horizontal wave numbers and frequencies. It is large enough to affect estimates of the depth of the convection zone and may carry useful information about the structure of solar convective turbulence.
Amino-Terminal Amino Acid Sequence of the Silkworm Prothoracicotropic Hormone: Homology with Insulin
Authors: Nagasawa Hiromichi , Kataoka Hiroshi , Isogai Akira , Tamura Saburo , Suzuki Akinori , Ishizaki Hironori , Mizoguchi Akira , Fujiwara Yuko , Suzuki Atsushi
Published: October 2006

Three molecular forms of prothoracicotropic hormone were isolated from the head of the adult silkworm,
Bombyx mori
, and the amino acid sequence of 19 amino acid residues in the amino terminus of these prothoracicotropic hormones was determined. These residues exhibit significant homology with insulin and insulin-like growth factors.
Discovery of Nuclear Tracks in Interplanetary Dust
Authors: Bradley J. P. , Brownlee D. E. , Fraundorf P.
Published: October 2006

Nuclear tracks have been identified in interplanetary dust particles (IDP's) collected from the stratosphere. The presence of tracks unambiguously confirms the extraterrestrial nature of IDP's, and the high track densities (10
10
to 10
11
per square centimeter) suggest an exposure age of approximately 10
4
years within the inner solar system. Tracks also provide an upper temperature limit for the heating of IDP's during atmospheric entry, thereby making it possible to distinguish between pristine and thermally modified micrometeorites.
Florida Current: Seasonal and Interannual Variability
Authors: Schott Friedrich , Zantopp Rainer
Published: October 2006

Annual and interannual variations in the Florida Current, Caribbean, and subtropical Atlantic are investigated with the use of historical sea level differences and wind field data. Observational and model evidence suggests that the seasonal transport cycle of the Florida Current is locally forced, either upstream in the Caribbean or downstream over topography. Although at seasonal and shorter periods sea level or bottom pressure fluctuations on the left side of the Florida Current contribute almost all of the variance of sea level difference across the Florida Straits and hence transport, this relation does not seem to apply at interannual time scales. Using results from the Subtropical Atlantic Climate Studies, it is estimated from historical sea level data that interannual transport fluctuations of the Florida Current are only of order 1 × 10
6
cubic meters per second. Interannual fluctuations in the 2- to 3-year period range in the Florida Straits seem to be correlated with sea level differences across the Caribbean and the subtropical Atlantic but not with Sverdrup transport fluctuations in the subtropical Atlantic.
African Land-Cover Classification Using Satellite Data
Authors: Tucker Compton J. , Townshend John R.G. , Goff Thomas E.
Published: October 2006

Data from the advanced very-high-resolution radiometer sensor on the National Oceanic and Atmospheric Administration's operational series of meteorological satellites were used to classify land cover and monitor vegetation dynamics for Africa over a 19-month period. There was a correspondence between seasonal variations in the density and extent of green-leaf vegetation and the patterns of rainfall associated with the movement of the Intertropical Convergence Zone. Regional variations, such as the 1983 drought in the Sahel of western Africa, were observed. Integration of the weekly satellite data with respect to time for a 12-month period produced a remotely sensed estimate of primary production based upon the density and duration of green-leaf biomass. Eight of the 21-day composited data sets covering an 11-month period were used to produce a general land-cover classification that corresponded well with those of existing maps.
Kaitoku Seamount and the Mystery Cloud of 9 April 1984
Authors: Walker Daniel A. , McCreery Charles S. , Oliveira Firmin J.
Published: October 2006

On 9 April 1984, commercial airlines enroute from Tokyo, Japan, to Anchorage, Alaska, reported an unusual mushroom-shaped cloud at about 38.5°N, 146.0°E. On 8 and 9 April the intensity of volcanism from Kaitoku Seamount (26.0°N, 140.8°E), as indicated by T-phase recordings on an array of ocean bottom hydrophones, reached a maximum level and then declined rapidly. An examination was made of the possible relation of the cloud to eruptions of Kaitoku through an analysis of pilot depositions, satellite photos, wind charts, signal strengths and spectra of known man-made underwater explosions, as well as ascent rates of volcanic plumes and cumulonimbus clouds.
Early Neolithic Horsebean from Yiftah'el, Israel
Authors: Kislev Mordechai E.
Published: October 2006

Charred seeds of horsebean (
Vicia faba
L.) from the seventh millennium B.C. that were found at Yiftah'el, Israel, push back the known use of this vetch by about 2000 years. Horsebean should be included in the ensemble of legumes grown by some early Neolithic people. The site, situated near the southwest outlet of Biq'at Bet Netofa, lies in a valley with heavy soil suitable for growing contemporary cultivars of horsebean. The still unknown wild ancestor of the horsebean may have originated in similar habitats in the Levant.
Taphonomy and Herd Structure of the Extinct Irish Elk,
Megaloceros giganteus
Authors: Barnosky Anthony D.
Published: October 2006

Fossils of the late Pleistocene elk
Megaloceros giganteus
from Ballybetagh bog, near Dublin, Ireland, indicate that males segregated from females during winters. The segregation implies seasonal rutting and polygynous mating and is consistent with the idea that large antlers functioned for social display. Within male groups, winterkill was the chief cause of death and was highest among juveniles and small adults with small antlers. There is no evidence to support the popular conception that heavy antlers caused animals to drown or become mired.
Metal Oxide Chemistry in Solution: The Early Transition Metal Polyoxoanions
Authors: Day Victor W. , Klemperer Walter G.
Published: October 2006

Many of the early transition elements form large polynuclear metal-oxygen anions containing up to 200 atoms or more. Although these polyoxoanions have been investigated for more than a century, detailed studies of structure and reactivity were not possible until the development of modern x-ray crystallographic and nuclear magnetic resonance spectroscopic techniques. Systematic studies of small polyoxoanions in inert, aprotic solvents have clarified many of the principles governing their structure and reactivity, and also have made possible the preparation of entirely new types of covalent derivatives such as CH
2
Mo
4
O
15
H
3-
, C
5
H
5
TiMo
5
O
18
3-
, and (OC)
3
Mn(Nb
2
W
4
O
19
)
3-
. Since most early transition metal polyoxoanions have structures based on close-packed oxygen arrays containing interstitial metal centers, their chemistry offers a rare opportunity to study chemical transformations in detail on well-defined metal oxide surfaces.
Torsional Oscillations of the Sun
Authors: Snodgrass Herschel B. , Howard Robert
Published: October 2006

The sun's differential rotation has a cyclic pattern of change that is tightly correlated with the sunspot, or magnetic activity, cycle. This pattern can be described as a torsional oscillation, in which the solar rotation is periodically sped up or slowed down in certain zones of latitude while elsewhere the rotation remains essentially steady. The zones of anomalous rotation move on the sun in wavelike fashion, keeping pace with and flanking the zones of magnetic activity. It is uncertain whether this torsional oscillation is a globally coherent ringing of the sun or whether it is a local pattern caused by and causing local changes in the magnetic fields. In either case, it may be an important link in the connection between the rotation and the cycle that is widely believed to exist but is not yet understood.
Phytoplankton Blooming Off the U.S. East Coast: A Satellite Description
Authors: Brown O. B. , Evans R. H. , Brown J. W. , Gordon H. R. , Smith R. C. , Baker K. S.
Published: October 2006

A "bloom" of near-surface phytoplankton occurs in the Atlantic Slope region of the western Atlantic Ocean off the U.S. East Coast in the spring. Satellite time series of sea-surface temperature and phytoplankton pigment concentration, derived from measurements of the National Oceanic and Atmospheric Administration NOAA-7 Advanced Very-High-Resolution Radiometer and the National Aeronautics and Space Administration Nimbus-7 Coastal Zone Color Scanner, respectively, give information on the spatial extent and temporal development of such a bloom for a 28-day period in April through May 1982. The phytoplankton concentration of the slope area is comparable to that of the Atlantic Shelf. Total primary productivity of the slope during this period is equivalent to that of the shelf. The primary productivity within a warm-core ring and in the Gulf Stream system is less by a factor of 2.
A Peptide Sequence Confers Retention and Rapid Degradation in the Endoplasmic Reticulum
Authors: Bonifacino Juan S. , Suzuki Carolyn K. , Klausner Richard D.
Published: October 2006

A nonlysosomal pathway exists for the degradation of newly synthesized proteins retained within the endoplasmic reticulum (ER). This pathway is extremely selective: whereas some proteins are rapidly degraded, others survive for long periods in the ER. The question of whether this selectivity is due to the presence within the sensitive proteins of definable peptide sequences that are sufficient to target them for degradation has been addressed. Deletion of a carboxyl-terminal sequence, comprising the transmembrane domain and short cytoplasmic tail of the α chain of the T cell antigen receptor (TCR-α), prevented the rapid degradation of this polypeptide. Fusion of this carboxyl-terminal sequence to the extracellular domain of the Tac antigen, a protein that is normally transported to the cell surface where it survives long-term, resulted in the retention and rapid degradation of the chimeric protein in the ER. Additional mutagenesis revealed that the transmembrane domain of TCR-α alone was sufficient to cause degradation within the ER. This degradation was not a direct consequence of retention in the ER, as blocking transport of newly synthesized proteins out of the ER with brefeldin A did not lead to degradation of the normal Tac antigen. It is proposed that a 23-amino acid sequence, comprising the transmembrane domain of TCR-α, contains information that determines targeting for degradation within the ER system.
Target Control of Collateral Extension and Directional Axon Growth in the Mammalian Brain
Authors: Heffner Christopher D. , Lumsden Andrew G. S. , O'Leary Dennis D. M.
Published: October 2006

Individual neurons in the brain send their axons over considerable distances to multiple targets, but the mechanisms governing this process are unresolved. An amenable system for studying axon outgrowth, branching, and target selection is the mammalian corticopontine projection. This major connection develops from parent corticospinal axons that have already grown past the pons, by a delayed interstitial budding of collateral branches that then grow directly into their target, the basilar pons. When cocultured with explants of developing cortex in three-dimensional collagen matrices, the basilar pons elicits the formation and directional growth of cortical axon collaterals across the intervening matrix. This effect appears to be target-specific and selectively influences neurons in the appropriate cortical layer. These in vitro findings provide evidence that the basilar pons becomes innervated by controlling at a distance the budding and directed ingrowth of cortical axon collaterals through the release of a diffusible, chemotropic molecule.
Crystal Axes in Recent and Fossil Adult Echinoids Indicate Trophic Mode in Larval Development
Authors: Emlet Richard B.
Published: October 2006

The type of larval development in echinoids (
Phylum Echinodermata
) was found to determine crystal patterns in adult apical skeletal plates. This relation between larvae and adults will allow fossil species to be examined to determine the effects of developmental mode on evolutionary patterns, such as species longevity and speciation rate. Independent tests of hypotheses of such patterns now shown among fossil mollusks with and without feeding larvae can thus be performed.
Expanded HIV-1 Cellular Tropism by Phenotypic Mixing with Murine Endogenous Retroviruses
Authors: Lusso Paolo , Veronese Fulvia di Marzo , Ensoli Barbara , Franchini Genoveffa , Jemma Cristina , DeRocco Susan E. , Kalyanaraman V. S. , Gallo Robert C.
Published: October 2006

In view of the current interest in in vivo murine models for acquired immunodeficiency syndrome (AIDS), the interaction between human immunodeficiency virus type 1 (HIV-1) and endogenous murine leukemia virus (MuLV)-related retroviruses was investigated with a human leukemic T cell line (PF-382
x
) that acquired xenotropic MuLV (X-MuLV) after in vivo passage in immunosuppressed mice. Despite similar levels of membrane CD4 expression and HIV-1
125
I-labeled gp120 binding, a dramatic acceleration in the time course of HIV-1 infection was observed in PF-382
x
compared to its X-MuLV-negative counterpart (PF-382). Moreover, PF-382 cells coinfected by X-MuLV and HIV-1 generated a progeny of phenotypically mixed viral particles, enabling HIV-1 to productively infect a panel of CD4
-
human cells, including B lymphoid cells and purified normal peripheral blood CD4
-
/CD8
+
T lymphocytes. Mixed viral phenotypes were also produced by human CD4
+
T cells coinfected with an amphotropic MuLV-related retrovirus (A-MuLV) and HIV-1. These data show that endogenous MuLV acquired by human cells transplanted into mice can significantly interact with HIV-1, thereby inducing important alterations of HIV-1 biological properties.
Tissue-Specific Cell Lineages Originate in the Gastrula of the Zebrafish
Authors: Kimmel Charles B. , Warga Rachel M.
Published: October 2006

In the zebrafish, cells of a clone derived from a single blastomere migrate away from one another during gastrulation. Later in development their descendants are usually found scattered within several different types of tissues of embryo. The divisions and migrations of individual cells were monitored during early development, revealing that in most cases the lineal descendants of single cells present at gastrula stage exclusively populate only single tissues, and may have stereotyped positional relationships within these tissues. Thus the gastrula stage is the first stage when heritable restrictions in cell type might arise in the zebrafish.
Lasing Droplets: Highlighting the Liquid-Air Interface by Laser Emission
Authors: Qian Shi-Xiong , Snow Judith B. , Tzeng Huey-Ming , Chang Richard K.
Published: October 2006

When dye-doped ethanol droplets are irradiated with an intense pulsed laser beam, the resulting laser emission from individual droplets highlights the liquid-air interface. Photographs of the lasing droplets in the micrometer size range taken in a single 10-nanosecond laser pulse clearly show the dynamic changes in droplet size, shape, and orientation.
Oregon Subduction Zone: Venting, Fauna, and Carbonates
Authors: Kulm L. D. , Suess E. , Moore J. C. , Carson B. , Lewis B. T. , Ritger S. D. , Kadko D. C. , Thornburg T. M. , Embley R. W. , Rugh W. D. , Massoth G. J. , Langseth M. G. , Cochrane G. R. , Scamman R. L.
Published: October 2006

Transects of the submersible
Alvin
across rock outcrops in the Oregon subduction zone have furnished information on the structural and stratigraphic framework of this accretionary complex. Communities of clams and tube worms, and authigenic carbonate mineral precipitates, are associated with venting sites of cool fluids located on a fault-bend anticline at a water depth of 2036 meters. The distribution of animals and carbonates suggests up-dip migration of fluids from both shallow and deep sources along permeable strata or fault zones within these clastic deposits. Methane is enriched in the water column over one vent site, and carbonate minerals and animal tissues are highly enriched in carbon-12. The animals use methane as an energy and food source in symbiosis with microorganisms. Oxidized methane is also the carbon source for the authigenic carbonates that cement the sediments of the accretionary complex. The animal communities and carbonates observed in the Oregon subduction zone occur in strata as old as 2.0 million years and provide criteria for identifying other localities where modern and ancient accreted deposits have vented methane, hydrocarbons, and other nutrient-bearing fluids.
Cost of Space-Based Laser Ballistic Missile Defense
Authors: Field George , Spergel David
Published: October 2006

Orbiting platforms carrying infrared lasers have been proposed as weapons forming the first tier of a ballistic missile defense system under the President's Strategic Defense Initiative. As each laser platform can destroy a limited number of missiles, one of several methods of countering such a system is to increase the number of offensive missiles. Hence it is important to know whether the cost-exchange ratio, defined as the ratio of the cost to the defense of destroying a missile to the cost to the offense of deploying an additional missile, is greater or less than 1. Although the technology to be used in a ballistic missile defense system is still extremely uncertain, it is useful to examine methods for calculating the cost-exchange ratio. As an example, the cost of an orbiting infrared laser ballistic missile defense system employed against intercontinental ballistic missiles launched simultaneously from a small area is compared to the cost of additional offensive missiles. If one adopts lower limits to the costs for the defense and upper limits to the costs for the offense, the cost-exchange ratio comes out substantially greater than 1. If these estimates are confirmed, such a ballistic missile defense system would be unable to maintain its effectiveness at less cost than it would take to proliferate the ballistic missiles necessary to overcome it and would therefore not satisfy the President's requirements for an effective strategic defense. Although the method is illustrated by applying it to a space-based infrared laser system, it should be straightforward to apply it to other proposed systems.
Elementary Particle Physics and the Superconducting Super Collider
Authors: Quigg Chris , Schwitters Roy F.
Published: October 2006

The present status and future prospects of elementary particle physics are reviewed, and some of the scientific questions that motivate the construction of a major new accelerator complex in the United States are summarized.
Geometrical Aspects of Sorted Patterned Ground in Recurrently Frozen Soil
Authors: Gleason Kevin J. , Krantz William B. , Caine Nelson , George John H. , Gunn Robert D.
Published: October 2006

A model for sorted patterned ground shows that some types arise from density-driven Rayleigh free convection that occurs during thawing of water-saturated recurrently frozen soils. The regularly spaced convection cells result in an uneven melting of the underlying ice front. Frost action causes stones to be upthrusted and to form in a pattern on the ground surface that mirrors the corrugation in the underlying ice front. The implications of the water circulation direction in the cells on the sorting process are considered.
Distribution of and Feeding by the Copepod
Pseudocalanus
Under Fast Ice During the Arctic Spring
Authors: Conover R. J. , Herman A. W. , Prinsenberg S. J. , Harris L. R.
Published: October 2006

The arctic copepod
Pseudocalanus
can be highly aggregated in the first few centimeters under landfast ice during spring in concentrations up to 10
6
per cubic meter. Chlorophyll-derived pigments in the water, the abundance of animals, and their gut pigment index show fluctuations that may be tidally related. Short-term grazing experiments performed at -1.7°C, in which ice algae was used as food, yielded feeding rates comparable to the highest known for the genus. Arctic
Pseudocalanus
seem to feed opportunistically near the ice-water interface, either directly on the attached epontic (under ice) algae or as it erodes from the ice.
Cultivation of the
Drosophila
Sex-Ratio Spiroplasma
Authors: Hackett Kevin J. , Lynn Dwight E. , Williamson David L. , Ginsberg Annette S. , Whitcomb Robert F.
Published: October 2006

Uncultivable for more than 25 years, the sex-ratio spiroplasma of
Drosophila willistoni
grew in a tissue culture medium (H-2) containing an embryo-derived lepidopteran cell line (IPLB-TN-R
2
). After adaptation, it grew in a cell-free H-2 medium. This success demonstrates the usefulness of cell culture systems for cultivation of fastidious microorganisms and facilitates study of the sex-ratio trait in
Drosophila.
Diffuse-Double Layer at a Membrane-Aqueous Interface Measured with X-Ray Standing Waves
Authors: Bedzyk Michael J. , Bommarito G. Mark , Caffrey Martin , Penner Thomas L.
Published: October 2006

The ion distribution in an electrolyte solution in contact with a charged polymerized phospholipid membrane was directly measured with long-period x-ray standing waves. The 27-angstrom-thick lipid monolayer was supported on a tungsten/silicon mirror. X-ray standing waves were generated above the mirror surface by total external reflection of a 9.8-kiloelectron volt x-ray beam from a synchrotron undulator. The membrane surface, which contained negatively charged phosphate headgroups, was bathed in a dilute ZnCl
2
solution. The concentration of Zn
2+
in the condensed layer at the membrane surface and the Zn
2+
distribution in the diffuse layer were measured as a function of headgroup charge. The Debye length of the diffuse layer varied between 3 and 58 angstroms. The results qualitatively agree with the Gouy-Chapman-Stern model.
Multiple-Quantum Nuclear Magnetic Resonance Spectroscopy
Authors: Munowitz M. , Pines A.
Published: October 2006

A nuclear magnetic resonance (NMR) event is popularly viewed as the flip of a single spin in a magnetic field, stimulated by the absorption or emission of only one quantum of radio-frequency energy. Nevertheless, resonances between nuclear spin states that differ by more than one unit in the Zeeman quantum number also can be induced in systems of coupled spins by suitably designed sequences of radio-frequency pulses. Pairs of states excited in this way oscillate coherently at the frequencies of the corresponding multiple-quantum transitions and produce a response that may be monitored indirectly in a two-dimensional time-domain experiment. The pattern of multiple-quantum excitation and response, influenced largely by the concerted interactions of groups of coupled nuclei, simplifies the NMR spectrum in some instances and provides significant new information in others. Applications of multiple-quantum NMR extend to problems in many different areas, ranging from studies of the structure and function of proteins and nucleic acids in solution to investigations of the arrangements of atoms in amorphous semiconductors. The specific spectroscopic techniques are varied as well and include methods designed, for example, to simplify spectral analysis for liquids and liquid crystals, eliminate inhomogeneous broadening, study interatomic connectivity in liquid-state molecules, identify clusters of atoms in solids, enhance the spatial resolution in solid-state imaging experiments, and probe correlated molecular motions.
Equatorial Pacific Seismic Reflectors as Indicators of Global Oceanographic Events
Authors: Mayer Larry A. , Shipley Thomas H. , Winterer Edward L.
Published: October 2006

The origin of a series of regionally correlatable seismic horizons in the Neogene sediments of the central equatorial Pacific is examined through seismic modeling and the detailed analyses of stratigraphic and physical property relationships in Deep Sea Drilling Project cores. These regionally traceable reflectors are synchronous; the younger reflectors are the direct result of carbonate dissolution events, the older ones of stratigraphically selective diagenetic processes. The changes in ocean chemistry associated with these events appear to be linked to global reorganizations of surface and bottom-water circulation patterns, the most dramatic of which are associated with reorganizations of North Atlantic bottom waters. These deepwater seismic horizons appear to correlate with the major events on the "relative sea-level" curve of Vail
et al.
for the Neogene.
Dynamic Atomic-Level Rearrangements in Small Gold Particles
Authors: Smith David J. , Petford-Long Amanda K. , Wallenberg L. R. , Bovin J.-O.
Published: October 2006

Small metal particles (<5 nanometers), which are widely used in catalysis, have physical and chemical properties that are markedly different from those of the bulk metal. The differences are related to crystal structure, and it is therefore significant that structural rearrangements in small particles have been observed in real time by using high-resolution electron microscopy. A detailed investigation at the atomic level has been made of the factors affecting the dynamic activity of small gold crystals that are supported on thin films of amorphous carbon, silicon, and germanium. The rate of activity depends mainly on the current density of the incident electron beam and the degree of contact of the particle with the substrate, but this rate decreases rapidly as the particle size is increased. The activity of the particles is very similar on either carbon or silicon, but it is generally less marked on germanium because of increased contact between the particle and the substrate. The electron beam effectively heats the particles, and it appears that their dynamic behavior depends on their thermal contact with the substrate.
Catalytic Hydration of Terminal Alkenes to Primary Alcohols
Authors: Jensen Craig M. , Trogler William C.
Published: October 2006

Direct catalytic hydration of terminal alkenes to primary alcohols would be an inexpensive route to industrially useful alcohols and a convenient synthetic route for the synthesis of terminal alcohols in general. The reaction betweentrans-PtHCl(PMe3)2(where Me = CH3) and sodium hydroxide in a one-to-one mixture of water and 1-hexene yields a species that, at 60°C and in the presence of the phasetransfer catalyst benzyltriethylammonium chloride, catalyzes selective hydration of 1-hexene ton-hexanol at a rate of 6.9 ± 0.2 turnovers per hour. Hydration of 1-dodecene ton-dodecanol occurs at a rate of 8.3 ± 0.4 turnovers per hour at 100°C. Deuterium labeling experiments withtrans-PtDCl(PMe3)2show that hydration involves reductive elimination of a C—H bond. At low hydroxide concentrations (<8 equivalents), hydration of the water-soluble olefin 3-butene-1-ol to 1,4-butanediol exhibited a first-order dependence on hydroxide concentration for loss of catalytic activity. This suggests that hydroxide attacks the coordinated alkene slowly. At high hydroxide concentrations, the rate of catalysis was hydroxide-independent and first order in alkene. Substitution of coordinated water (k1= 9.3 ± 0.5 × 10-3liters per mol per second) appears to be limiting under these conditions.
Coastal Uplift and Mortality of Intertidal Organisms Caused by the September 1985 Mexico Earthquakes
Authors: Bodin Paul , Klinger Terrie
Published: October 2006

Coastal uplift associated with the great Mexican earthquake of 19 September 1985 and its principal aftershock produced widespread mortality of intertidal organisms along the coast of the states of Michoacán and Guerrero, Mexico. Measurements of the vertical extent of mortality at ten sites provided estimates of the magnitude of the vertical component of deformation along the coast. Within the affected area, uplift ranged from about 12 centimeters to about 1 meter, and no subsidence was observed. The observations are consistent with models of the tectonic deformation that results from buried slip on a shallow-dipping underthrust fault.
Oceanic Dimethylsulfide: Production During Zooplankton Grazing on Phytoplankton
Authors: Dacey John W. H. , Wakeham Stuart G.
Published: October 2006

About half the biogenic sulfur flux to the earth's atmosphere each year arises from the oceans. Dimethylsulfide (DMS), which constitutes about 90% of this marine sulfur flux, is presumed to originate from the decomposition of dimethylsulfoniopropionate produced by marine organisms, particularly phytoplankton. The rate of DMS release by phytoplankton is greatly increased when the phytoplankton are subjected to grazing by zooplankton. DMS production associated with such grazing may be the major mechanism of DMS production in many marine settings.
Slip Deficit on the San Andreas Fault at Parkfield, California, as Revealed by Inversion of Geodetic Data
Authors: Segall Paul , Harris Ruth
Published: October 2006

A network of geodetic lines spanning the San Andreas fault near the rupture zone of the 1966 Parkfield, California, earthquake (magnitude
M
= 6) has been repeatedly surveyed since 1959. In the study reported here the average rates of line-length change since 1966 were inverted to determine the distribution of interseismic slip rate on the fault. These results indicate that the Parkfield rupture surface has not slipped significantly since 1966. Comparison of the geodetically determined seismic moment of the 1966 earthquake with the interseismic slip-deficit rate suggests that the strain released by the latest shock will most likely be restored between 1984 and 1989, although this may not occur until 1995. These results lend independent support to the earlier forecast of an
M
= 6 earthquake near Parkfield within 5 years of 1988.
The Proterozoic Ophiolite Problem, Continental Emergence, and the Venus Connection
Authors: Moores E. M.
Published: October 2006

To account for the lack of preservation of ophiolites (fragments of oceanic crust and mantle) in old orogenic belts (age 1000 to 2500 million years), a hypothesis proposes that the magmatic oceanic crust formed during sea-floor spreading was thicker during the cited time interval. This thickening led to reduced contrast between the elevation of continental and oceanic regions and to greater average flooding of the continents. The resultant distribution of elevation may have resembled modern Venus more than modern Earth.
Life Cycle, Individual Thrift, and the Wealth of Nations
Authors: Modigliani Franco
Published: October 2006

One theory of the determinants of individual and national thrift has come to be known as the life cycle hypothesis of saving. The state of the art on the eve of the formulation of the hypothesis some 30 years ago is reviewed. Then the theoretical foundations of the model in its original formulation and later amendment are set forth, calling attention to various implications, some distinctive to it and some counterintuitive. A number of crucial empirical tests, both at the individual and the aggregate level, are presented as well as some applications of the life cycle hypothesis of saving to current policy issues.
Outward-Dipping Ring-Fault Structure at Rabaul Caldera as Shown by Earthquake Locations
Authors: Mori Jim , McKee Chris
Published: October 2006

The locations of a large number of earthquakes recorded at Rabaul caldera in Papua New Guinea from late 1983 to mid-1985 have produced a picture of this active caldera's structural boundary. The earthquake epicenters form an elliptical annulus about 10 kilometers long by 4 kilometers wide, centered in the southern part of the Rabaul volcanic complex. A set of events with well-constrained depth determinations shows a ring-fault structure that extends from the surface to a depth of about 4 kilometers and slopes steeply outward from the center of the caldera. This is the first geophysical data set that clearly outlines the orientation of an active caldera's bounding faults. This orientation, however, conflicts with the configuration of many other calderas and is not in keeping with currently preferred models of caldera formation.
Covalent Group IV Atomic Clusters
Authors: Brown W. L. , Freeman R. R. , Raghavachari Krishnan , Schlüter M.
Published: October 2006

Atomic clusters containing from two to several hundred atoms offer the possibility of studying the transition from molecules to crystalline solids. The covalent group IV elements carbon, silicon, and germanium are now being examined with this long-range objective. These elements are particularly interesting because of the very different character of their crystalline solids and because they are intermediate between metals and insulators in the nature of their bonding. Small mass-selected atom cluster ions are formed by pulsed laser techniques and identified by time-of-flight methods. Laser photoexcitation is used to study the relative stability of these clusters and their modes of fragmentation. These modes for C
n
+
clusters, which tend to fragment with a characteristic loss of a neutral C
3
, are found to be different from the modes for Si
n
+
and Ge
n
+
clusters, which tend to fragment to "magic" clusters such as Si
4
+
, Si
6
+
and Si
10
+
. These experimental results can be accounted for by recent theoretical calculations of the ground-state structure and stability of small silicon and carbon clusters. Several theoretical approaches give consistent results, showing that small silicon clusters are compact and different from small fragments of the bulk crystal. Calculations show that carbon clusters change from linear structures toward cyclic structures as the cluster size increases, but with significant odd-even differences.
The Art and Science of Microstructural Control
Authors: Spaepen Frans
Published: October 2006

A historical perspective on the development of physical metallurgy is presented. Two recent advances in the control of microstructure, rapid solidification and artificial multilayers, are discussed. Rapid solidification has produced metallic glasses and metastable crystalline systems, and has led to important technological and scientific discoveries. The synthesis of artificial multilayers by direct deposition represents the ultimate control of such microstructures.
Functional Box-Counting and Multiple Elliptical Dimensions in Rain
Authors: Lovejoy S. , Schertzer D. , Tsonis A. A.
Published: October 2006

Many physical systems that have interacting structures that span wide ranges in size involve substantial scale invariant (or scaling) subranges. In these regimes, the large and small scales are related by an operation that involves only the scale ratio. The system has no intrinsic characteristic size. In the atmosphere gravity causes differential stratification, so that the scale change involves new elliptical dimensions (
d
el
). Fields that are extremely variable, such as rain, involve multiple scaling and dimensions that characterize the increasingly intense regions. Elliptical dimensional sampling and functional box-counting have been used to analyze radar rain data to obtain both the multiple dimensions of the rain field and the estimate
d
el
= 2.22 ± 0.07.
Flunarizine Protects Neurons from Death After Axotomy or NGF Deprivation
Authors: Rich Keith M. , Hollowell James P.
Published: October 2006

Systemically administered flunarizine enhanced neuronal survival in lumbar sensory ganglia in newborn rats after axotomy. Flunarizine-treated rats lost 71 percent fewer neurons than the untreated control rats at the end of 1 week. In cell culture, flunarizine at 30 to 40 μM also prevented neuronal death in nerve growth factor-dependent embryonic sensory and sympathetic neurons after the abrupt withdrawal of neurotrophic support. The drug may cause this effect by acting at an intracellular site, one distinct from its blockade of voltage-dependent calcium channels.
First Record of Giant Anteater (Xenarthra, Myrmecophagidae) in North America
Authors: Shaw Christopher A. , McDonald H. Gregory
Published: October 2006

A right metacarpal III represents the first North American record of the giant anteater (
Myrmecophaga tridactyla
). Recovered in northwestern Sonora, Mexico, with a rich vertebrate fauna of early Pleistocene (Irvingtonian) age, it belongs to a cohort of large mammals that dispersed from South America to North America along a savanna corridor. Presumably habitat and climatic changes have subsequently driven this mammalian family more than 3000 kilometers back into Central America from its former expansion into temperate North America.
Calcium-41 Concentration in Terrestrial Materials: Prospects for Dating of Pleistocene Samples
Authors: Henning W. , Bell W. A. , Billquist P. J. , Glagola B. G. , Kutschera W. , Liu Z. , Lucas H. F. , Paul M. , Rehm K. E. , Yntema J. L.
Published: October 2006

Calcium-41 has been suggested as a new tool for radiometric dating in the range of 10
5
to 10
6
years. The concentration of cosmogenic calcium-41 in natural samples of terrestrial origin has now been determined by high-sensitivity accelerator mass spectrometry after pre-enrichment in calcium-41 with an isotope separator. Ratios of calcium-41 to total calcium between 2 × 10
-14
and 3 × 10
-15
were measured for samples of contemporary bovine bone and from limestone deposits. Some prospects for the use of calcium-41 for dating Middle and Late Pleistocene bone and for other geophysical applications are discussed.
Managing the Soils of Sub-Saharan Africa
Authors: Lal Rattan
Published: October 2006

Many constraints to intensive food-crop production in tropical Africa are related to tropical soils. Improved technologies are available for different ecological regions. Important technological innovations include manual land clearing, mulch farming, conservation tillage and tiedridges, agroforestry, cover crops, mixed- and relay-cropping, and early sowing for improved and sustained productivity. Irrigation, animal traction or draft animals, and the use of chemical fertilizers are also important. Much of the agrarian stagnation in Africa is caused by neglect and misuse of the most basic of all resources, the soil. In fact, the root cause of the perpetual famine can be traced to the misuse of soil and water resources and issues related to their misuse. Substantial increases in food production are possible if the proven technologies can be effectively transferred and implemented. Priorities lie in both short-term development projects and in initiating long-term research to understand soil and water resources and how to manage them. The agrarian research must address the issue of improving the welfare of resource-poor farmers.
Statistical Short-Term Earthquake Prediction
Authors: Kagan Y. Y. , Knopoff L.
Published: October 2006

A statistical procedure, derived from a theoretical model of fracture growth, is used to identify a foreshock sequence while it is in progress. As a predictor, the procedure reduces the average uncertainty in the rate of occurrence for a future strong earthquake by a factor of more than 1000 when compared with the Poisson rate of occurrence. About one-third of all main shocks with local magnitude greater than or equal to 4.0 in central California can be predicted in this way, starting from a 7-year database that has a lower magnitude cutoff of 1.5. The time scale of such predictions is of the order of a few hours to a few days for foreshocks in the magnitude range from 2.0 to 5.0.
Modern Turtle Origins: The Oldest Known Cryptodire
Authors: Gaffney Eugene S. , Hutchison J. Howard , Jenkins Farish A. , Meeker Lorraine J.
Published: October 2006

The discovery of a turtle in the Early Jurassic (185 million years before present) Kayenta Formation of northeastern Arizona provides significant evidence about the origin of modern turtles. This new taxon possesses many of the primitive features expected in the hypothetical common ancestor of pleurodires and cryptodires, the two groups of modern turtles. It is identified as the oldest known cryptodire because of the presence of a distinctive cryptodiran jaw mechanism consisting of a trochlea over the otic chamber that redirects the line of action of the adductor muscle. Aquatic habits appear to have developed very early in turtle evolution.
Kayentachelys
extends the known record of cryptodires back at least 45 million years and documents a very early stage in the evolution of modern turtles.
Wadi Howar: Paleoclimatic Evidence from an Extinct River System in the Southeastern Sahara
Authors: Pachur H.-J. , Kröpelin S.
Published: October 2006

Field research into the climatic history and shifting of the East Saharan desert has furnished evidence that during Quaternary time the present extremely arid western part of Upper Nubia (northern Sudan) was temporarily linked to the Nile by way of a hitherto unknown 400 kilometer long tributary. From about 9500 to 4500 years ago, lower Wadi Howar flowed through an environment characterized by numerous ground water outlets and freshwater lakes. Savanna fauna and cattle-herders occupied this region, which today receives at most 25 millimeters of rainfall per year. At that period the southern edge of the eastern Sahara was some 500 kilometers further north than today and ground water resources were recharged for the last time.
Ultrahigh-Power Semiconductor Diode Laser Arrays
Authors: Cross Peter S. , Harnagel Gary L. , Streifer William , Scifres Donald R. , Welch David F.
Published: October 2006

The power available from transistor-sized semiconductor diode lasers has increased rapidly in recent years, more than doubling every year. Continuous outputs of several watts and pulsed powers in the kilowatt range with 50 percent overall efficiency are now possible with these compact devices. These developments may signal the start of a technological advancement in optics comparable to the solid-state revolution in electronics 20 years ago.
Fission-Track Dating of Haughton Astrobleme and Included Biota, Devon Island, Canada
Authors: Omar Gomaa , Johnson Kirk R. , Hickey Leo J. , Robertson P. Blyth , Dawson Mary R. , Barnosky Cathy W.
Published: October 2006

Haughton Astrobleme is a major extraterrestrial impact structure located on Devon Island in the Canadian Arctic Archipelago, Northwest Territories. Apatite grains separated from shocked Precambrian gneiss contained in a polymict breccia from the center of the astrobleme yielded a fission-track date of 22.4 million ± 1.4 million years before the present or early Miocene (Aquitanian). This provides a date for the impact event and an upper limit on the age of crater-filling lake sediments and a flora and vertebrate fauna occurring in them. A geologically precise date for these fossils provides an important biostratigraphic reference point for interpreting the biotic evolution of the Arctic.