bluuebunny/crossref_metadata_2025 huggingface dataset:
The Modification of an Estuary
Authors: Nichols Frederic H. , Cloern James E. , Luoma Samuel N. , Peterson David H.
Published: October 2006

The San Francisco Bay estuary has been rapidly modified by human activity. Diking and filling of most of its wetlands have eliminated habitats for fish and waterfowl; the introduction of exotic species has transformed the composition of its aquatic communities; reduction of freshwater inflow by more than half has changed the dynamics of its plant and animal communities; and wastes have contaminated its sediments and organisms. Continued disposal of toxic wastes, the probable further reduction in freshwater inflow, and the possible synergy between the two provide the potential for further alteration of the estuary's water quality and biotic communities.
Sea-Air Partitioning of Mercury in the Equatorial Pacific Ocean
Authors: Kim Jonathan P. , Fitzgerald William F.
Published: October 2006

The partitioning of gaseous mercury between the atmosphere and surface waters was determined in the equatorial Pacific Ocean. The highest concentrations of dissolved gaseous mercury occurred in cooler, nutrient-rich waters that characterize equatorial upwelling and increased biological productivity at the sea surface. The surface waters were supersaturated with respect to elemental mercury; a significant flux of elemental mercury to the atmosphere is predicted for the equatorial Pacific. When normalized to primary production on a global basis, the ocean effluxes of mercury may rival anthropogenic emissions of mercury to the atmosphere.
Overview of VEGA Venus Balloon in Situ Meteorological Measurements
Authors: Sagdeev R. Z. , Linkin V. M. , Kerzhanovich V. V. , Lipatov A. N. , Shurupov A. A. , Blamont J. E. , Crisp D. , Ingersoll A. P. , Elson L. S. , Preston R. A. , Hildebrand C. E. , Ragent B. , Seiff A. , Young R. E. , Petit G. , Boloh L. , Alexandrov Yu. N. , Armand N. A. , Bakitko R. V. , Selivanov A. S.
Published: October 2006

The VEGA balloons made in situ measurements of pressure, temperature, vertical wind velocity, ambient light, frequency of lightning, and cloud particle backscatter. Both balloons encountered highly variable atmospheric conditions, with periods of intense vertical winds occurring sporadically throughout their flights. Downward winds as large as 3.5 meters per second occasionally forced the balloons to descend as much as 2.5 kilometers below their equilibrium float altitudes. Large variations, in pressure, temperature, ambient light level, and cloud particle backscatter (VEGA-1 only) correlated well during these excursions, indicating that these properties were strong functions of altitude in those parts of the middle cloud layer sampled by the balloons.
Autolytic Processing of Dimeric Plant Virus Satellite RNA
Authors: Prody Gerry A. , Bakos John T. , Buzayan Jamal M. , Schneider Irving R. , Bruening George
Published: October 2006

Associated with some plant viruses are small satellite RNA's that depend on the plant virus to provide protective coat protein and presumably at least some of the proteins necessary for satellite RNA replication. Multimeric forms of the satellite RNA of tobacco ringspot virus are probable in vivo precursors of the monomeric satellite RNA. Evidence is presented for the in vitro autolytic processing of dimeric and trimeric forms of this satellite RNA. The reaction generates biologically active monomeric satellite RNA, apparently is reversible to form dimeric RNA from monomeric RNA, and does not require an enzyme for its catalysis.
Requirement for Activin a and Transforming Growth Factor--β1 Pro-Regions in Homodimer Assembly
Authors: Gray Alane M. , Mason Anthony J.
Published: October 2006

Many proteins are initially synthesized as part of a large precursor. The role of the pro-region in the biosynthesis of transforming growth factor-β1 (TGF-β1) and activin A, two structurally related disulfide-linked homodimers synthesized as large precursors, was studied. Vectors that expressed either the pro-region or the mature regions of these molecules were used in complementation experiments, only when the pro-region was coexpressed with the mature region did intracellular dimerization and secretion of biologically active homodimers occur. The pro-regions of activin A and TGF-β1, therefore, aid the folding, disulfide bond formation, and export of their respective homodimers.
Observations of Energetic Ions from Comet Giacobini-Zinner
Authors: Hynds R. J. , Cowley S. W. H. , Sanderson T. R. , Wenzel K.-P. , Van Rooijen J. J.
Published: October 2006

During the encounter with comet Giacobini-Zinner, the energetic particle anisotropy spectrometer on the International Cometary Explorer spacecraft observed large fluxes of energetic ions, believed to result principally from ionization of the cometary atmosphere followed by pickup and acceleration by the ambient flow of the solar wind. These heavy cometary ions were observed from approximately 1 day before closest approach to about 2½ days afterward. Three regimes of differing ion characteristics have been identified. An outer region with a scale of ∼10
6
kilometers contains variable fluxes of antisolar-streaming pick-up ions in the undisturbed solar wind. In the middle region, of ∼10
5
kilometers, fluxes have less large-scale variability and broader angular and energy distributions. This region is separated from the outer zone by a sharp transition. The inner region has a scale of ∼10
4
kilometers and is characterized by reduced fluxes and complex angular distributions.
Sex Differences in Economic Well-Being
Authors: Fuchs Victor R.
Published: October 2006

Despite large structural changes in the economy and major antidiscrimination legislation, the economic well-being of women in comparison with that of men did not improve between 1959 and 1983. The women to men ratio of money income almost doubled, but women had less leisure while men had more, an increase in the proportion of adults not married made more women dependent on their own income, and women's share of financial responsibility for children rose. The net result for women's access to goods, services, and leisure in comparison with that of men ranged from a decrease of 15 percent to an increase of 4 percent, depending on assumptions about income sharing within households.
Basic Research and Economic Health: The Coming Challenge
Authors: Bloch Erich
Published: October 2006

The United States faces an international economic challenge that can best be met with a renewed emphasis on the basic science and engineering that underlies new technology. For 20 years, however, the nation has not invested adequately in the science and engineering base, with the result that we have too few young people entering science and engineering programs and inadequate facilities and equipment in the nation's universities. We need a fresh infusion of resources into the universities, together with a new emphasis on cooperative efforts between universities and industry. The engineering research centers recently established by the National Science Foundation are an example of how we should proceed.
A Mid-Brunhes Climatic Event: Long-Term Changes in Global Atmosphere and Ocean Circulation
Authors: Jansen J. H. F. , Kuijpers A. , Troelstra S. R.
Published: October 2006

A long-term climatic change 4.0 × 10
5
to 3.0 × 10
5
years ago is recorded in deep-sea sediments of the Angola and Canary basins in the eastern Atlantic Ocean. In the Angola Basin (Southern Hemisphere) the climatic signal shows a transition to more humid ("interglacial") conditions in equatorial Africa, and in the Canary Basin (Northern Hemisphere) to more "glacial" oceanic conditions. This trend is confirmed by comparison with all well-documented marine and continental records from various latitudes available; in the Northern Hemisphere, in the Atlantic north of 20°N, climate merged into more "glacial" conditions and in equatorial regions and in the Southern Hemisphere to more "interglacial" conditions. The data point to a more northern position of early Brunhes oceanic fronts and to an intensified atmosphere and ocean surface circulation in the Southern Hemisphere during that time, probably accompanied by a more zonal circulation in the Northern Hemisphere. The mid-Brunhes climatic change may have been forced by the orbital eccentricity cycle of 4.13 × 10
5
years.
Archaeopteryx
Is Not a Forgery
Authors: Charig Alan J. , Greenaway Frank , Milner Angela C. , Walker Cyril A. , Whybrow Peter J.
Published: October 2006

Archaeopteryx lithographica
might be regarded as the most important zoological species known, fossil or recent. Its importance lies not in that its transitional nature is unique—there are many such transitional forms at all taxonomic levels—but in the fact that it is an obvious and comprehensible example of organic evolution. There have been recent allegations that the feather impressions on
Archaeopteryx
are a forgery. In this report, proof of authenticity is provided by exactly matching hairline cracks and dendrites on the feathered areas of the opposing slabs, which show the absence of the artificial cement layer into which modern feathers could have been pressed by a forger.
Gradual Dinosaur Extinction and Simultaneous Ungulate Radiation in the Hell Creek Formation
Authors: Sloan Robert E. , Rigby J. Keith , Van Valen Leigh M. , Gabriel Diane
Published: October 2006

Dinosaur extinction in Montana, Alberta, and Wyoming was a gradual process that began 7 million years before the end of the Cretaceous and accelerated rapidly in the final 0.3 million years of the Cretaceous, during the interval of apparent competition from rapidly evolving immigrating ungulates. This interval involves rapid reduction in both diversity and population density of dinosaurs. The last dinosaurs known are from a channel that contains teeth of Mantuan mammals, seven species of dinosaurs, and Paleocene pollen. The top of this channel is 1.3 meters above the likely position of the iridium anomaly, the Cretaceous/Tertiary boundary.
Bacterioplankton: A Sink for Carbon in a Coastal Marine Plankton Community
Authors: Ducklow Hugh W. , Purdie Duncan A. , Williams Peter J. LeB. , Davies John M.
Published: October 2006

Recent determinations of high production rates (up to 30 percent of primary production in surface waters) implicate free-living marine bacterioplankton as a link in a "microbial loop" that supplements phytoplankton as food for herbivores. An enclosed water column of 300 cubic meters was used to test the microbial loop hypothesis by following the fate of carbon-14—labeled bacterioplankton for over 50 days. Only 2 percent of the label initially fixed from carbon-14—labeled glucose by bacteria was present in larger organisms after 13 days, at which time about 20 percent of the total label added remained in the particulate fraction. Most of the label appeared to pass directly from particles smaller than 1 micrometer (heterotrophic bacterioplankton and some bacteriovores) to respired labeled carbon dioxide or to regenerated dissolved organic carbon-14. Secondary (and, by implication, primary) production by organisms smaller than 1 micrometer may not be an important food source in marine food chains. Bacterioplankton can be a sink for carbon in planktonic food webs and may serve principally as agents of nutrient regeneration rather than as food.
Oxidation Fronts in Pelagic Sediments: Diagenetic Formation of Metal-Rich Layers
Authors: Wilson T. R. S. , Thomson J. , Hydes D. J. , Colley S. , Culkin F. , Sørensen J.
Published: October 2006

The periodic deposition of distal turbidites at a site on the Madeira Abyssal Plain causes the development of a nonsteady-state diagenetic system in which an oxidation front migrates downward into the sediment. Data presented here show that iron, manganese, and particulate organic carbon are oxidized at this front by oxidants (molecular oxygen and nitrate) diffusing from above. A numerical model of systems of this type predicts the formation of iron-rich layers under certain nonsteady-state conditions. The layers predicted by the model are closely comparable in thickness and general morphology to iron-rich layers found in certain ocean sediments, the origin of which has been until now unexplained.
Two-Photon Laser Scanning Fluorescence Microscopy
Authors: Denk Winfried , Strickler James H. , Webb Watt W.
Published: October 2006

Molecular excitation by the simultaneous absorption of two photons provides intrinsic three-dimensional resolution in laser scanning fluorescence microscopy. The excitation of fluorophores having single-photon absorption in the ultraviolet with a stream of strongly focused subpicosecond pulses of red laser light has made possible fluorescence images of living cells and other microscopic objects. The fluorescence emission increased quadratically with the excitation intensity so that fluorescence and photobleaching were confined to the vicinity of the focal plane as expected for cooperative two-photon excitation. This technique also provides unprecedented capabilities for three-dimensional, spatially resolved photochemistry, particularly photolytic release of caged effector molecules.
A Class I Antigen, HLA-G, Expressed in Human Trophoblasts
Authors: Kovats Susan , Main Elliott K. , Librach Clifford , Stubblebine Marcia , Fisher Susan J. , DeMars Robert
Published: October 2006

The α chain of the human histocompatibility antigen HLA-G was identified as an array of five 37- to 39-kilodalton isoforms by the use of two-dimensional gel electrophoresis. Both cell-associated and secreted HLA-G antigens are prominent in first trimester villous cytotrophoblasts and are greatly reduced in third trimester cytotrophoblasts. Allelic variation was not detected, an indication that HLA-G is not obviously polymorphic in cytotrophoblasts. Among the following choriocarcinoma cell lines studied, HLA-G is expressed in JEG but not in Jar or BeWo. Expression of endogenous HLA-G genes has not been found in normal lymphoid cells. Thus, HLA-G is subject to both cell type-specific and developmental regulation and is expressed in early gestation human cytotrophoblasts.
The Voyager 2 Encounter with the Uranian System
Authors: Stone E. C. , Miner E. D.
Published: October 2006

An overview of the Voyager 2 encounter with Uranus is presented, including a brief discussion of the trajectory and the planned observations as well as the highlights of the results described in the 11 companion papers.
Voyager 2 in the Uranian System: Imaging Science Results
Authors: Smith B. A. , Soderblom L. A. , Beebe R. , Bliss D. , Boyce J. M. , Brahic A. , Briggs G. A. , Brown R. H. , Collins S. A. , Cook A. F. , Croft S. K. , Cuzzi J. N. , Danielson G. E. , Davies M. E. , Dowling T. E. , Godfrey D. , Hansen C. J. , Harris C. , Hunt G. E. , Ingersoll A. P. , Johnson T. V. , Krauss R. J. , Masursky H. , Morrison D. , Owen T. , Plescia J. B. , Pollack J. B. , Porco C. C. , Rages K. , Sagan C. , Shoemaker E. M. , Sromovsky L. A. , Stoker C. , Strom R. G. , Suomi V. E. , Synnott S. P. , Terrile R. J. , Thomas P. , Thompson W. R. , Veverka J.
Published: October 2006

Voyager 2 images of the southern hemisphere of Uranus indicate that submicrometersize haze particles and particles of a methane condensation cloud produce faint patterns in the atmosphere. The alignment of the cloud bands is similar to that of bands on Jupiter and Saturn, but the zonal winds are nearly opposite. At mid-latitudes (-70° to -27°), where winds were measured, the atmosphere rotates faster than the magnetic field; however, the rotation rate of the atmosphere decreases toward the equator, so that the two probably corotate at about -20°. Voyager images confirm the extremely low albedo of the ring particles. High phase angle images reveal on the order of 10
2
new ringlike features of very low optical depth and relatively high dust abundance interspersed within the main rings, as well as a broad, diffuse, low optical depth ring just inside the main ring system. Nine of the newly discovered small satellites (40 to 165 kilometers in diameter) orbit between the rings and Miranda; the tenth is within the ring system. Two of these small objects may gravitationally confine the ε ring. Oberon and Umbriel have heavily cratered surfaces resembling the ancient cratered highlands of Earth's moon, although Umbriel is almost completely covered with uniform dark material, which perhaps indicates some ongoing process. Titania and Ariel show crater populations different from those on Oberon and Umbriel; these were probably generated by collisions with debris confined to their orbits. Titania and Ariel also show many extensional fault systems; Ariel shows strong evidence for the presence of extrusive material. About half of Miranda's surface is relatively bland, old, cratered terrain. The remainder comprises three large regions of younger terrain, each rectangular to ovoid in plan, that display complex sets of parallel and intersecting scarps and ridges as well as numerous outcrops of bright and dark materials, perhaps suggesting some exotic composition.
Ultraviolet Spectrometer Observations of Uranus
Authors: Broadfoot A. L. , Herbert F. , Holberg J. B. , Hunten D. M. , Kumar S. , Sandel B. R. , Shemansky D. E. , Smith G. R. , Yelle R. V. , Strobel D. F. , Moos H. W. , Donahue T. M. , Atreya S. K. , Bertaux J. L. , Blamont J. E. , McConnell J. C. , Dessler A. J. , Linick S. , Springer R.
Published: October 2006

Data from solar and stellar occultations of Uranus indicate a temperature of about 750 kelvins in the upper levels of the atmosphere (composed mostly of atomic and molecular hydrogen) and define the distributions of methane and acetylene in the lower levels. The ultraviolet spectrum of the sunlit hemisphere is dominated by emissions from atomic and molecular hydrogen, which are known as electroglow emissions. The energy source for these emissions is unknown, but the spectrum implies excitation by low-energy electrons (modeled with a 3-electron-volt Maxwellian energy distribution). The major energy sink for the electrons is dissociation of molecular hydrogen, producing hydrogen atoms at a rate of 10
29
per second. Approximately half the atoms have energies higher than the escape energy. The high temperature of the atmosphere, the small size of Uranus, and the number density of hydrogen atoms in the thermosphere imply an extensive thermal hydrogen corona that reduces the orbital lifetime of ring particles and biases the size distribution toward larger particles. This corona is augmented by the nonthermal hydrogen atoms associated with the electroglow. An aurora near the magnetic pole in the dark hemisphere arises from excitation of molecular hydrogen at the level where its vertical column abundance is about 10
20
per square centimeter with input power comparable to that of the sunlit electroglow (approximately 2 × 10
11
watts). An initial estimate of the acetylene volume mixing ratio, as judged from measurements of the far ultraviolet albedo, is about 2 × 10
-7
at a vertical column abundance of molecular hydrogen of 10
23
per square centimeter (pressure, approximately 0.3 millibar). Carbon emissions from the Uranian atmosphere were also detected.
Conodont Survival and Low Iridium Abundances Across the Permian-Triassic Boundary in South China
Authors: Clark David L. , Cheng-Yuan Wang , Orth Charles J. , Gilmore James S.
Published: October 2006

The Permian-Triassic sedimentary sequence of China includes one of the most complete and fossiliferous Paleozoic-Mesozoic boundaries known. Closely spaced sampling across the boundary, which is an important extinction event for most organisms, has produced good conodont faunas that show little diversity change. A drop in conodont abundance is the only apparent response to the extinction event. A low concentration of iridium in the boundary clay (0.002 part per billion ± 20 percent), as well as in samples immediately below and above, that range from 0.004 to 0.034 part per billion do not support the proposal of an extraterrestrial impact event at this boundary in China.
Lightning Strike Fusion: Extreme Reduction and Metal-Silicate Liquid Immiscibility
Authors: Essene E. J. , Fisher D. C.
Published: October 2006

A glassy fulgurite, formed recently on a morainal ridge in southeastern Michigan, contains micrometer- to centimeter-sized metallic globules rich in native silicon, which unmixed from a silica-rich liquid. The unusual character of these globules and their potential for elucidating conditions of fulgurite formation prompted further study. Thermodynamic calculations indicate that temperatures in excess of 2000 K and reducing conditions approaching those of the SiO
2
-Si buffer were needed to form the coexisting metallic and silicate liquids. The phases produced are among the most highly reduced naturally occurring materials known. Some occurrences of other highly reduced minerals may also be due to lightning strike reduction. Extreme reduction and volatilization may also occur during high-temperature events such as lightning strikes in presolar nebulae and impacts of extraterrestrial bodies. As a result of scavenging of platinum-group elements by highly reduced metallic liquids, geochemical anomalies associated with the Cretaceous-Tertiary boundary may have a significant terrestrial component even if produced through bolide impact.
What Has Happened to Productivity Growth?
Authors: Baily Martin Neil
Published: October 2006

The collapse of U.S. productivity growth is the most severe and persistent of recent economic problems. Unless there is an increase in growth, American living standards will remain stagnant and problems such as the budget deficit will plaque policy-makers. Why has this happened? Among the important reasons are a failure to innovate, changing demographics, and disruptions to the economy, including oil price increases and inflation.
Changing Climate: Geothermal Evidence from Permafrost in the Alaskan Arctic
Authors: Lachenbruch Arthur H. , Marshall B. Vaughn
Published: October 2006

Temperature profiles measured in permafrost in northernmost Alaska usually have anomalous curvature in the upper 100 meters or so. When analyzed by heat-conduction theory, the profiles indicate a variable but widespread secular warming of the permafrost surface, generally in the range of 2 to 4 Celsius degrees during the last few decades to a century. Although details of the climatic change cannot be resolved with existing data, there is little doubt of its general magnitude and timing; alternative explanations are limited by the fact that heat transfer in cold permafrost is exclusively by conduction. Since models of greenhouse warming predict climatic change will be greatest in the Arctic and might already be in progress, it is prudent to attempt to understand the rapidly changing thermal regime in this region.
Vertical Nitrate Fluxes in the Oligotrophic Ocean
Authors: Lewis Marlon R. , Hebert David , Harrison W. Glen , Platt Trevor , Oakey Neil S.
Published: October 2006

The vertical flux of nitrate across the thermocline in the upper ocean imposes a rigorous constraint on the rate of export of organic carbon from the surface layer of the sea. This export is the primary means by which the oceans can serve as a sink for atmospheric carbon dioxide. For the oligotrophic open ocean regions, which make up more than 75% of the world's ocean, the rate of export is currently uncertain by an order of magnitude. For most of the year, the vertical flux of nitrate is that due to vertical turbulent transport of deep water rich in nitrate into the relatively impoverished surface layer. Direct measurements of rates of turbulent kinetic energy dissipation, coupled with highly resolved vertical profiles of nitrate and density in the oligotrophic eastern Atlantic showed that the rate of transport, averaged over 2 weeks, was 0.14 (0.002 to 0.89, 95% confidence interval) millimole of nitrate per square meter per day and was statistically no different from the integrated rate of nitrate uptake as measured by incorporation of15N-labeled nitrate. The stoichiometrically equivalent loss of carbon from the upper ocean, which is the relevant quantity for the carbon dioxide and climate question, is then fixed at 0.90 (0.01 to 5.70) millimole of carbon per square meter per day. These rates are much lower than recent estimates based on in situ changes in oxygen over annual scales; they are consistent with a biologically unproductive oligotrophic ocean.
Development of a More Market-Oriented Economy in China
Authors: Chow Gregory C.
Published: October 2006

Before 1978 in China, the economic institutions for agriculture and industry operated essentially under a centrally planned system. The reasons for a change toward a more market-oriented economy and the key elements of economic reform are discussed. Today the major issues being deliberated by the leading economic officials include reform of the price system, the administrative structure of state-owned enterprises, the banking system and macroeconomic control mechanisms, and foreign trade and investment.
Synthesis and Equation of State of (Mg,Fe) SiO
3
Perovskite to Over 100 Gigapascals
Authors: Knittle Elise , Jeanloz Raymond
Published: October 2006

Silicate perovskite of composition (Mg
0.88
Fe
0.12
)SiO
3
has been synthesized in a laser-heated diamond-anvil cell to a pressure of 127 gigapascals at temperatures exceeding 2000 K. The perovskite phase was identified and its unit-cell dimensions measured by in situ x-ray diffraction at elevated pressure and room temperature. An analysis of these data yields the first high-precision equation of state for this mineral, with values of the zero-pressure isothermal bulk modulus and its pressure derivative being
K

0
T

= 266 ± 6 gigapascals and
K
′

0
T

= 3.9 ± 0.4. In addition, the orthorhombic distortion of the silicate-perovskite structure away from ideal cubic symmetry remains constant with pressure: the lattice parameter ratios are
b/a
= 1.032 ± 0.002 and
c/a
= 1.444 ± 0.006. These results, which prove that silicate perovskite is stable to ultrahigh pressures, demonstrate that perovskite can exist throughout the pressure range of the lower mantle and that it is therefore likely to be the most abundant mineral in Earth.
Global Images of the Earth's Interior
Authors: Dziewonski Adam M. , Woodhouse John H.
Published: October 2006

The three-dimensional maps of the earth's interior now span regions from the bottom of the crust to the inner core of the earth. Although a wealth of new information on the dynamics of the earth has been discovered, the inner core offers the greatest surprise: it appears to be anisotropic with the axis of symmetry aligned with the axis of rotation.
The Melting Curve of Iron to 250 Gigapascals: A Constraint on the Temperature at Earth's Center
Authors: Williams Quentin , Jeanloz Raymond , Bass Jay , Svendsen Bob , Ahrens Thomas J.
Published: October 2006

The melting curve of iron, the primary constituent of Earth's core, has been measured to pressures of 250 gigapascals with a combination of static and dynamic techniques. The melting temperature of iron at the pressure of the core-mantle boundary (136 gigapascals) is 4800 ± 200 K. whereas at the inner core-outer core boundary (330 gigapascals), it is 7600 ± 500 K. Corrected for melting point depression resulting from the presence of impurities, a melting temperature for iron-rich alloy of 6600 K at the inner core-outer core boundary and a maximum temperature of 6900 K at Earth's center are inferred. This latter value is the first experimental upper bound on the temperature at Earth's center, and these results imply that the temperature of the lower mantle is significantly less than that of the outer core.
Decision-Making in the Presence of Risk
Authors: Machina Mark J.
Published: October 2006

Proposed in the 18th century by Cramer and Bernoulli and formally axiomatized in the 20th century by von Neumann and Morgenstern and others, the expected utility model has long been the dominant framework for the analysis of decision-making under risk. A growing body of experimental evidence, however, indicates that individuals systematically violate the key behavioral assumption of this model, the so-called independence axiom. This has led to the development and analysis of nonexpected utility models of decision-making. Although recent work in this area has shown that the analytical results of expected utility theory are more robust than previously supposed, other important issues remain unresolved.
Gene Transfer in Cereals
Authors: Cocking Edward C. , Davey Michael R.
Published: October 2006

Until recently, gene transfer in plants was achieved only by sexual hybridization. Now, in addition, plant genetic manipulation, with the use of both recombinant DNA and protoplast fusion technology, is being applied to an increasing range of plants. The soil bacterium
Agrobacterium tumefaciens
, with its associated plasmid, is used as a vector for introducing DNA into the genomes of dicotyledonous plants, but it has not proved suitable for cereals. Instead, the direct uptake of plasmid DNA into cereal protoplasts is being used for the transformation of cells in rice, wheat, and maize. Transformation efficiencies, in some cases, are becoming comparable to those obtained in dicotyledons with
Agrobacterium
In rice it is now possible to regenerate efficiently whole plants from protoplasts, and this capability may soon be extended to the other cereals. By means of direct interaction of cereal protoplasts with plasmids, coupled with improved procedures for the regeneration of plants from their protoplasts, gene transfer in the cereals is becoming established at the frontiers of recombinant DNA technology.
Precipitation Fluctuations over Northern Hemisphere Land Areas Since the Mid-19th Century
Authors: Bradley R. S. , Diaz H. F. , Eischeid J. K. , Jones P. D. , Kelly P. M. , Goodess C. M.
Published: October 2006

An extensive array of measurements extending back to the mid-19th century was used to investigate large-scale changes in precipitation over Northern Hemisphere land areas. Significant increases in mid-latitude precipitation and concurrent decreases in low-latitude precipitation have occurred over the last 30 to 40 years. Although these large-scale trends are consistent with general circulation model projections of precipitation changes associated with doubled concentrations of atmospheric carbon dioxide, they should be viewed as defining large-scale natural climatic variability. Additional work to refine regional variations and address potential network inhomogeneities is needed. This study attempts to show secular precipitation fluctuations over hemispheric- and continental-scale areas of the Northern Hemisphere.
Laser Techniques in High-Pressure Geophysics
Authors: Hemley R. J. , Bell P. M. , Mao H. K.
Published: October 2006

Laser techniques in conjunction with the diamond-anvil cell can be used to study high-pressure properties of materials important to a wide range of problems in earth and planetary science. Spontaneous Raman scattering of crystalline and amorphous solids at high pressure demonstrates that dramatic changes in structure and bonding occur on compression. High-pressure Brillouin scattering is sensitive to the pressure variations of single-crystal elastic moduli and acoustic velocities. Laser heating techniques with the diamond-anvil cell can be used to study phase transitions, including melting, under deep-earth conditions. Finally, laser-induced ruby fluorescence has been essential for the development of techniques for generating the maximum pressures now possible with the diamond-anvil cell, and currently provides a calibrated in situ measure of pressure well above 100 gigapascals.
Oxygen Isotopes in Refractory Stratospheric Dust Particles: Proof of Extraterrestrial Origin
Authors: McKeegan Kevin D.
Published: October 2006

The oxygen and magnesium isotopic compositions of five individual particles that were collected from the stratosphere and that bear refractory minerals were measured by secondary ion mass spectrometry. Four of the particles exhibit excesses of oxygen-16 similar to those observed in anhydrous mineral phases of carbonaceous chondrites and thus are extraterrestrial. The oxygen and magnesium isotopic abundances of one corundum-rich particle are consistent with a terrestrial origin. Magnesium in the four extraterrestrial particles is isotopically normal. It is unlikely that these particles are derived from carbonaceous chondrites and thus such particles probably represent a new type of collected extraterrestrial material.
Acantharian Fluxes and Strontium to Chlorinity Ratios in the North Pacific Ocean
Authors: Bernstein R. E. , Betzer P. R. , Feely R. A. , Byrne R. H. , Lamb M. F. , Michaels A. F.
Published: October 2006

Data on particulate strontium sulfate fluxes and strontium to chlorinity ratios were compared to provide insights into the strontium cycle of the North Pacific. Free-drifting sediment traps were used to derive large particle fluxes between depths of 100 and 3500 meters in the eastern and western North Pacific Ocean. Flux data revealed substantial quantities of acantharian skeletons and cysts (both made of strontium sulfate) settling through the upper kilometer of the water column. The greatest fluxes of celestite were detected at 400 meters. Minimal to nondetectable fluxes noted at and below 900 meters provide evidence that by this horizon, the majority of acantharian specimens had dissolved, thereby contributing to the pool of dissolved strontium. Growth and subsequent dissolution of acantharians in the upper kilometer are qualitatively consistent with the well-developed minimum and maximum strontium to chlorinity ratios that are consistently noted in these waters. These fluxes of particulate strontium and model calculations for fluxes of dissolved strontium indicate that acantharians play an important role in the ocean's strontium budget.
Electromagnetic Stabilization of Weakly Conducting Fluids
Authors: Ivory Cornelius F. , Gobie William A. , Beckwith James B. , Hergenrother Robert , Malec Michael
Published: October 2006

Classical hydromagnetic theory predicts that the flow of dilute aqueous electrolyte in a slit can be stabilized by application of a strong, transverse magnetic field. However, recent experiments indicate that stabilization can be achieved with the use of a much weaker field in the presence of a small lateral current. A revised theory describes how the magnetic and electric fields interact to eliminate natural convection.
Real-Time Landslide Warning During Heavy Rainfall
Authors: Keefer David K. , Wilson Raymond C. , Mark Robert K. , Brabb Earl E. , Brown William M. , Ellen Stephen D. , Harp Edwin L. , Wieczorek Gerald F. , Alger Christopher S. , Zatkin Robert S.
Published: October 2006

A real-time system for issuing warnings of landslides during major storms is being developed for the San Francisco Bay region, California. The system is based on empirical and theoretical relations between rainfall and landslide initiation, geologic determination of areas susceptible to landslides, real-time monitoring of a regional network of telemetering rain gages, and National Weather Service precipitation forecasts. This system was used to issue warnings during the storms of 12 to 21 February 1986, which produced 800 millimeters of rainfall in the region. Although analysis after the storms suggests that modifications and additional developments are needed, the system successfully predicted the times of major landslide events. It could be used as a prototype for systems in other landslide-prone regions.
Atmospheric Trends in Methylchloroform and the Global Average for the Hydroxyl Radical
Authors: Prinn R. , Cunnold D. , Rasmussen R. , Simmonds P. , Alyea F. , Crawford A. , Fraser P. , Rosen R.
Published: October 2006

Frequent atmospheric measurements of the anthropogenic compound methylchloroform that were made between 1978 and 1985 indicate that this species is continuing to increase significantly around the world. Reaction with the major atmospheric oxidant, the hydroxyl radical (OH), is the principal sink for this species. The observed mean trends for methylchloroform are 4.8, 5.4, 6.4, and 6.9 percent per year at Aldrigole (Ireland) and Cape Meares (Oregon), Ragged Point (Barbados), Point Matatula (American Samoa), and Cape Grim (Tasmania), respectively, from July 1978 to June 1985. These measured trends, combined with knowledge of industrial emissions, were used in an optimal estimation inversion scheme to deduce a globally averaged methylchloroform atmospheric lifetime of 6.3 (+ 1.2, -0.9) years (1σ uncertainty) and a globally averaged tropospheric hydroxyl radical concentration of (
7.7
± 1.4) × 10
5
radicals per cubic centimeter (1σ uncertainty). These 7 years of gas chromatographic measurements, which comprise about 60,000 individual calibrated real-time air analyses, provide the most accurate estimates yet of the trends and lifetime of methylchloroform and of the global average for tropospheric hydroxyl radical levels. Accurate determination of hydroxyl radical levels is crucial to understanding global atmospheric chemical cycles and trends in the levels of trace gases such as methane.
Interhemispheric Transfer of Plasticity in the Cerebral Cortex
Authors: Calford Michael B. , Tweedale Rowan
Published: October 2006

Each half of the body surface is represented topographically in the contralateral cerebral hemisphere. Physiological data are presented showing that homotopic regions of primary somatosensory cortex are linked such that plasticity induced in one hemisphere, in the form of receptive field expansion brought about by a small peripheral denervation, is immediately mirrored in the other hemisphere. Neurons which display the plasticity show no responsiveness to stimulation of the ipsilateral body surface. This suggests that the pathways and mechanisms mediating this transfer are specific to the role of maintaining balance, or integration, between corresponding cortical fields.
Evolution of Polygonal Fracture Patterns in Lava Flows
Authors: Aydin Atilla , DeGraff James M.
Published: October 2006

Cooling-induced fractures, also known as columnar joints, divide basaltic lava flows into prismatic columns with polygonal cross sections. The regularity and symmetry of the fracture patterns have long fascinated naturalists. In view of the recent selection of two candidate nuclear waste sites in areas where polygonally fractured volcanic rocks are located, a better understanding of the fracture patterns is required. Field data indicate that the tetragonal networks at flow surfaces evolve systematically to hexagonal networks as the joints grow inward during solidification of lava. This evolution occurs by the gradual change of most orthogonal intersections to nonorthogonal intersections of about 120 degrees. The surface features and intersection geometries of columnar joints show that joint segments at any given level form sequentially yet harmoniously.
Life Histories, Blood Revenge, and Warfare in a Tribal Population
Authors: Chagnon Napoleon A.
Published: October 2006

Blood revenge is one of the most commonly cited causes of violence and warfare in tribal societies, yet it is largely ignored in recent anthropological theories of primitive warfare. A theory of tribal violence is presented showing how homicide, revenge, kinship obligations, and warfare are linked and why reproductive variables must be included in explanations of tribal violence and warfare. Studies of the Yanomamö Indians of Amazonas during the past 23 years show that 44 percent of males estimated to be 25 or older have participated in the killing of someone, that approximately 30 percent of adult male deaths are due to violence, and that nearly 70 percent of all adults over an estimated 40 years of age have lost a close genetic relative due to violence. Demographic data indicate that men who have killed have more wives and offspring than men who have not killed.
Activation of Extrastriate and Frontal Cortical Areas by Visual Words and Word-Like Stimuli
Authors: Petersen Steven E. , Fox Peter T. , Snyder Abraham Z. , Raichle Marcus E.
Published: October 2006

Visual presentation of words activates extrastriate regions of the occipital lobes of the brain. When analyzed by positron emission tomography (PET), certain areas in the left, medial extrastriate visual cortex were activated by visually presented pseudowords that obey English spelling rules, as well as by actual words. These areas were not activated by nonsense strings of letters or letter-like forms. Thus visual word form computations are based on learned distinctions between words and nonwords. In addition, during passive presentation of words, but not pseudowords, activation occurred in a left frontal area that is related to semantic processing. These findings support distinctions made in cognitive psychology and computational modeling between high-level visual and semantic computations on single words and describe the anatomy that may underlie these distinctions.
Adaptability of the U.S. Industrial Relations System
Authors: Kochan Thomas A.
Published: October 2006

An industrial relations system describes the basic values, laws, institutions, and organizational practices that govern employment relationships. To be effective, an industrial relations system must be well matched to its economic and social environment and able to meet the strategic needs of employers, the workforce, and the larger society. The current state of American industrial relations is assessed against these criteria. The general proposition advanced is that the U.S. system of industrial relations that grew out of the New Deal labor legislation of the 1930s performed effectively from the 1940s through the 1960s. Pressures for change on the system began to build through the 1970s because of changes in the economic and technological environment and in the strategic behavior and needs of the parties. These pressures erupted in the early 1980s to produce a period of experimentation and fundamental change in union-management relations. The critical question in industrial relations today is whether the process of adaptation will be sustained and expanded to cover a broader range of employment relationships.
The Greenhouse Theory of Climate Change: A Test by an Inadvertent Global Experiment
Authors: Ramanathan V.
Published: October 2006

Since the dawn of the industrial era, the atmospheric concentrations of several radiatively active gases have been increasing as a result of human activities. The radiative heating from this inadvertent experiment has driven the climate system out of equilibrium with the incoming solar energy. According to the greenhouse theory of climate change, the climate system will be restored to equilibrium by a warming of the surface-troposphere system and a cooling of the stratosphere. The predicted changes, during the next few decades, could far exceed natural climate variations in historical times. Hence, the greenhouse theory of climate change has reached the crucial stage of verification. Surface warming as large as that predicted by models would be unprecedented during an interglacial period such as the present. The theory, its scope for verification, and the emerging complexities of the climate feedback mechanisms are discussed.
Supernova 1987A!
Authors: Woosley S. E. , Phillips M. M.
Published: October 2006

Light from the brightest supernova in almost 400 years arrived at Earth on 23 February 1987. Although located 160,000 light years away in a satellite galaxy of our own known as the Large Magellanic Cloud, this supernova's relative proximity compared to all others that have been observed in modern times has allowed observations, which were never possible before, to be made from space, from detectors on the ground and carried by balloons and airplanes, and from neutrino detectors deep underground. What emerges is a greater understanding of one of the most violent events in the universe, the death of a massive star. For the most part, theoretical expectations have been borne out, but some major surprises have made the event all the more fascinating.
Anatomy of a Conformational Change: Hinged "Lid" Motion of the Triosephosphate Isomerase Loop
Authors: Joseph Diane , Petsko Gregory A. , Karplus Martin
Published: October 2006

Triosephosphate isomerase (TIM) is used as a model system for the study of how a localized conformational change in a protein structure is produced and related to enzyme reactivity. An 11-residue loop region moves more than 7 angstroms and closes over the active site when substrate binds. The loop acts like a "lid" in that it moves rigidly and is attached by two hinges to the remainder of the protein. The nature of the motion appears to be built into the loop by conserved residues; the hinge regions, in contrast, are not conserved. Results of molecular dynamics calculations confirm the structural analysis and suggest a possible ligand-induced mechanism for loop closure.
Rationale for Development of a Synthetic Vaccine Against
Plasmodium falciparum
Malaria
Authors: Zavala Fidel , Tam James P. , Hollingdale Michael R. , Cochrane Allan H. , Quakyi Isabella , Nussenzweig Ruth S. , Nussenzweig Victor
Published: October 2006

Protective immunity against malaria can be obtained by vaccination with irradiated sporozoites. The protective antigens known as circumsporozoite (CS) proteins, are polypeptides that cover the surface membrane of the parasite. The CS proteins contain species-specific immunodominant epitopes formed by tandem repeated sequences of amino acids. Here it is shown that the dominant epitope of
Plasmodium falciparum
is contained in the synthetic dodecapeptide Asn-Ala-Asn-Pro-Asn-Ala-Asn-Pro-Asn-Ala-Asn-Pro or (NANP)
3
. Monoclonal antibodies and most or all polyclonal human antibodies to the sporozoites react with (NANP)
3
, and polyclonal antibodies raised against the synthetic peptide (NANP)
3
react with the surface of the parasite and neutralize its infectivity. Since (NANP)
3
repeats are present in CS proteins of
P. falciparum
from many parts of the world, this epitope is a logical target for vaccine development.
Neurotrophic Factors
Authors: Thoenen Hans , Edgar David
Published: October 2006

In addition to nerve growth factor (NGF), many proteins present in soluble tissue extracts and in the extracellular matrix influence the survival and development of cultured neurons. The structure, synthesis, and mechanism of action of NGF as a neurotrophic factor are considered along with the experiments on the new putative trophic molecules.
Uromodulin: A Unique 85-Kilodalton Immunosuppressive Glycoprotein Isolated from Urine of Pregnant Women
Authors: Muchmore Andrew V. , Decker Jean M.
Published: October 2006

Crude fractions of urine from pregnant women are immunosuppressive in vitro. An 85-kilodalton immunosuppressive glycoprotein purified to homogeneity from such urine inhibited in vitro assays of human T-cell and monocyte activity at concentrations of 10
-9
to 10
-11
molar. This material was nontoxic and blocked early events required for normal T-cell proliferation in vitro. On the basis of its tissue source and its in vitro activity, the name "uromodulin" is proposed for this glycoprotein.
Fractal Reaction Kinetics
Authors: Kopelman Raoul
Published: October 2006

Classical reaction kinetics has been found to be unsatisfactory when the reactants are spatially constrained on the microscopic level by either walls, phase boundaries, or force fields. Recently discovered theories of heterogeneous reaction kinetics have dramatic consequences, such as fractal orders for elementary reactions, self-ordering and self-unmixing of reactants, and rate coefficients with temporal "memories." The new theories were needed to explain the results of experiments and supercomputer simulations of reactions that were confined to low dimensions or fractal dimensions or both. Among the practical examples of "fractal-like kinetics" are chemical reactions in pores of membranes, excitation trapping in molecular aggregates, exciton fusion in composite materials, and charge recombination in colloids and clouds.