bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid Changes in Tree Leaf Chemistry Induced by Damage: Evidence for Communication Between Plants
Authors: Baldwin Ian T. , Schultz Jack C.
Published: October 2006

Potted poplar ramets showed increased concentrations and rates of synthesis of phenolic compounds within 52 hours of having 7 percent of their leaf area removed by tearing, as did undamaged plants sharing the same enclosure. Damaged sugar maple seedlings responded in a manner similar to that of the damaged poplars. Nearby undamaged maples had increased levels of phenolics and hydrolyzable and condensed tannin within 36 hours, but exhibited no change in rates of synthesis. An airborne cue originating in damaged tissues may stimulate biochemical changes in neighboring plants that could influence the feeding and growth of phytophagous insects.
New Methods of Drug Delivery
Authors: Langer Robert
Published: October 2006

Conventional forms of drug administration generally rely on pills, eye drops, ointments, and intravenous solutions. Recently, a number of novel drug delivery approaches have been developed. These approaches include drug modification by chemical means, drug entrapment in small vesicles that are injected into the bloodstream, and drug entrapment within pumps or polymeric materials that are placed in desired bodily compartments (for example, the eye or beneath the skin). These techniques have already led to delivery systems that improve human health, and continued research may revolutionize the way many drugs are delivered.
Extension of the Life-Span of Human Endothelial Cells by an Interleukin-1αAntisense Oligomer
Authors: Maier Jeanette A. M. , Voulalas Pamela , Roeder David , Maciag Thomas
Published: October 2006

The proliferative potential of human diploid endothelial cells is finite, and cellular senescence in vitro is accompanied by the failure of the endothelial cell to respond to exogenous growth factors. Senescent human endothelial cells were shown to contain high amounts of the transcript for the cytokine interleukin-1α (IL-1α), a potent inhibitor of endothelial cell proliferation in vitro. In contrast, transformed human endothelial cells did not contain detectable IL-1α messenger RNA. Treatment of human endothelial cell populations with an antisense oligodeoxynucleotide to the human IL-1α transcript prevented cell senescence and extended the proliferative lifespan of the cells in vitro. Removal of the IL-1α antisense oligomer resulted in the generation of the senescent phenotype and loss of proliferative potential. These data suggest that human endothelial cell senescence in vitro is a dynamic process regulated by the potential intracellular activity of IL-1α.
Functional Magnetic Resonance Imaging in Medicine and Physiology
Authors: Moonen Chrit T. W. , van Zijl Peter C. M. , Frank Joseph A. , Le Bihan Denis , Becker Edwin D.
Published: October 2006

Magnetic resonance imaging (MRI) is a well-established diagnostic tool that provides detailed information about macroscopic structure and anatomy. Recent advances in MRI allow the noninvasive spatial evaluation of various biophysical and biochemical processes in living systems. Specifically, the motion of water can be measured in processes such as vascular flow, capillary flow, diffusion, and exchange. In addition, the concentrations of various metabolites can be determined for the assessment of regional regulation of metabolism. Examples are given that demonstrate the use of functional MRI for clinical and research purposes. This development adds a new dimension to the application of magnetic resonance to medicine and physiology.
Sleep and Estivation (Shallow Torpor): Continuous Processes of Energy Conservation
Authors: Walker James M. , Garber Ann , Berger Ralph J. , Heller H. C.
Published: October 2006

Estivation (shallow torpor) in the round-tailed ground squirrel (
Citellus tereticaudus
) is entered through electrophysiologically defined states of sleep. Rapid-eye-movement sleep diminishes as body temperature falls in such a way that, at a body temperature of 26° to 28°C, torpor is characterized by almost continuous slow-wave sleep isomorphic with that observed at euthermic body temperatures.
New Burgess Shale Fossil Sites Reveal Middle Cambrian Faunal Complex
Authors: Collins Desmond , Briggs Derek , Morris Simon Conway
Published: October 2006

Soft-bodied and lightly sclerotized Burgess shale fossils have been found at more than a dozen new localities in an area extending for 20 kilometers along the front of the Cathedral Escarpment in the Middle Cambrian Stephen Formation of the Canadian Rockies. Five different fossil assemblages from four stratigraphic levels have been recognized. These assemblages represent distinct penecontemporaneous marine communities that together make up a normal fore-reef faunal complex.
Osmium-187/Osmium-186 in Manganese Nodules and the Cretaceous-Tertiary Boundary
Authors: Luck J. M. , Turekian K. K.
Published: October 2006

As a result of the radioactive decay of rhenium-187 (4.6 × 10
10
years) the osmium-187/osmium-186 ratio changes in planetary systems as a function of time and the rhenium-187/osmium-186 ratio. For a value of the rhenium-187/osmium-186 ratio of about 3.2, typical of meteorites and the earth's mantle, the present-day osmium-187/osmium-186 ratio is about 1. The earth's continental crust has an estimated rhenium-187/osmium-186 ratio of about 400, so that for a mean age of the continent of 2 × 10
9
years, a present-day osmium-187/osmium-186 ratio of about 10 is expected. Marine manganese nodules show values (6 to 8.4) compatible with this expectation if allowance for a 25 percent mantle osmium supply to the oceans is allowed. The Cretaceous-Tertiary boundary iridium-rich layer in the marine section at Stevns Klint, Denmark, yields an osmium-187/osmium-186 ratio of 1.65, and the one in a continental section in the Raton Basin, Colorado, is 1.29. The simplest explanation is that these represent osmium imprints of predominantly meteoritic origin.
El Chichón: Composition of Plume Gases and Particles
Authors: Phelan Kotra Janet , Finnegan David L. , Zoller William H. , Hart Mark A. , Moyers Jarvis L.
Published: October 2006

Aircraft measurements were made of trace gases, atmospheric particles, and condensed acid volatiles in the plume of El Chichón volcano, Chiapas, Mexico, in November 1982. Hydrogen sulfide was the primary gaseous sulfur species in the plume at the time of collection. Concentrations of 28 elements were determined by neutron activation analysis of particulate material from the plume. Rates of trace element emission to the atmosphere for each species were estimated by normalization to the simultaneously determined total sulfur emission rate. The volatile elements sulfur, chlorine, arsenic, selenium, bromine, antimony, iodine, tungsten, and mercury were enriched relative to bulk pyroclastic material by factors of 60 to 20,000. Arsenic, antimony, and selenium were associated predominantly with small (≤ 3 micrometer) particles. Calcium and sodium were present almost exclusively on larger particles and aluminum and manganese were bimodally distributed. Ashladen particulate material injected into the stratosphere during the early violent eruptions was enriched by factors of 10 to 30 relative to ash in some of the same elements observed in the quiescent plume.
Meteorological Aspects of the El Niño/Southern Oscillation
Authors: Rasmusson Eugene M. , Wallace John M.
Published: October 2006

The single most prominent signal in year-to-year climate variability is the Southern Oscillation, which is associated with fluctuations in atmospheric pressure at sea level in the tropics, monsoon rainfall, and wintertime circulation over North America and other parts of the extratropics. Although meteorologists have known about the Southern Oscillation for more than a half-century, its relation to the oceanic El Niño phenomenon was not recognized until the late 1960's, and a theoretical understanding of these relations has begun to emerge only during the past few years. The past 18 months have been characterized by what is probably the most pronounced and certainly the best-documented El Niño/Southern Oscillation episode of the past century. In this review meteorological aspects of the time history of the 1982-1983 episode are described and compared with a composite based on six previous events between 1950 and 1975, and the impact of these new observations on theoretical interpretations of the event is discussed.
Molecular Basis of Herbicide Resistance in Plants in
Amaranthus hybridus
Authors: Hirschberg Joseph , McIntosh Lee
Published: October 2006

Resistance of different species of weeds to
s
-triazines, a commonly used class of herbicides, has been shown to involve a change in the binding affinity of the herbicide to a chloroplast polypeptide of 32,000 daltons. A single amino acid difference in this 32,000-dalton protein appears to be responsible for resistance to the herbicide in
Amaranthus hybridus
.
Communal Nursing in Mexican Free-Tailed Bat Maternity Colonies
Authors: McCracken Gary F.
Published: October 2006

Examination of genotypes of female-pup nursing pairs taken from large maternity colonies of the Mexican free-tailed bat in Texas demonstrates that nursing is nonrandom and selective along genetic (kinship) lines. This is contrary to previous reports that nursing in these colonies is indiscriminate. Although nursing is nonrandom, an estimated 17 percent of the females sampled were nursing pups that could not be their offspring. This "nonparental" nursing is an apparent result of the difficulties females face in consistently relocating and selectively nursing their own pups within these enormous colonies.
Geologic Framework of Nonmarine Cretaceous-Tertiary Boundary Sites, Raton Basin, New Mexico and Colorado
Authors: Pillmore C. L. , Tschudy R. H. , Orth C. J. , Gilmore J. S. , Knight J. D.
Published: October 2006

Iridium concentrations are anomalously high at the palynological Cretaceous-Tertiary boundary in fluvial sedimentary rocks of the lower part of the Raton Formation at several localities in the Raton Basin of New Mexico and Colorado. The iridium anomaly is associated with a thin bed of kaolinitic claystone in a discontinuous carbonaceous shale and coal sequence.
A Thermodynamic Scale for the Helix-Forming Tendencies of the Commonly Occurring Amino Acids
Authors: O'Neil Karyn T. , DeGrado William F.
Published: October 2006

Amino acids have distinct conformational preferences that influence the stabilities of protein secondary and tertiary structures. The relative thermodynamic stabilities of each of the 20 commonly occurring amino acids in the α-helical versus random coil states have been determined through the design of a peptide that forms a noncovalent α-helical dimer, which is in equilibrium with a randomly coiled monomeric state. The α helices in the dimer contain a single solvent-exposed site that is surrounded by small, neutral amino acid side chains. Each of the commonly occurring amino acids was substituted into this guest site, and the resulting equilibrium constants for the monomer-dimer equilibrium were determined to provide a list of free energy difference (ΔΔ
G
°) values.
Precipitation of Sulfide Ores and Organic Matter: Sulfate Reactions at Pine Point, Canada
Authors: Powell Trevor G. , MacQueen Roger W.
Published: October 2006

Bitumen is a common associate of carbonate-hosted lead-zinc deposits. On the Pine Point lead-zinc property, Northwest Territories, Canada, there are two forms of bitumen. Unaltered bitumens have atomic hydrogen/carbon ratios of about 1.4, sulfur contents of about 7.8 percent, and sulfur isotope ratios (δ
34
S) of approximately +4.6 per mil. Altered bitumens occur in proximity to sulfide ore bodies and white sparry dolomite. Their hydrogen/carbon ratios are about 1.02, the sulfur contents average 22 percent, and the δ
34
S values are about +12.4 per mil. These data indicate that some bitumen has participated in the thermochemical reduction of sulfate to produce hydrogen sulfide required to precipitate the ores. Mass balance considerations show that the amount and degree of alteration of bitumen is more than adequate to account for the reduced sulfur species (lead, zinc, and iron sulfides) deposited at Pine Point. These reactions may provide an important means of generating the large volumes of sulfide necessary to precipitate ore bodies in carbonate rocks.
Early Land Animals in North America: Evidence from Devonian Age Arthropods from Gilboa, New York
Authors: Shear William A. , Bonamo Patricia M. , Grierson James D. , Rolfe W. D. Ian , Smith Edward Laidlaw , Norton Roy A.
Published: October 2006

A new fossil site near Gilboa, New York, is one of only three where fossils of terrestrial arthropods of Devonian age have been found. The new Gilboan fauna is younger than the other two but richer in taxa. Fragmentary remains and nearly whole specimens assigned to Eurypterida, Arachnida (Trigonotarbida, Araneae, Amblypygi, and Acari), Chilopoda [Craterostigmatomorpha(?) and Scuterigeromorpha(?)], and tentatively to Insecta (Archaeognatha) have been found. The centipedes and possible insects may represent the earliest records known for these groups.
Ancient Bisexual Flowers
Authors: Basinger James F. , Dilcher David L.
Published: October 2006

Fossil flowers discovered in 94-million-year-old clays of the Dakota Formation in Nebraska are among the earliest known demonstrably bisexual flowers. The flowers are of medium size and have pentamerous whorls of clearly differentiated floral parts, petals alternate with the sepals, short stamens are borne opposite the petals, the carpels are fused, and a receptacular disk is present. The pollen is small and tricolporate. These flowers appear to be well adapted to insect pollination. The numerous floral features and pollen characters provide sufficient diagnostic data to assess its systematic position. No extant order accommodates the features of this flower and it shares some features of various extant orders. The classification of flowering plants and our understanding of their evolution must be influenced by the fossilized remains of ancient flowers.
Single-Crystal Elastic Properties of the Modified Spinel (Beta) Phase of Magnesium Orthosilicate
Authors: Sawamoto Hiroshi , Weidner Donald J. , Sasaki Satoshi , Kumazawa Mineo
Published: October 2006

The single-crystal elastic moduli of the modified spinel structure (beta phase) of magnesium orthosilicate (Mg
2
SiO
4
) have been measured by Brillouin spectroscopy under ambient conditions. Single crystals with dimensions up to 500 micrometers were grown at 22 gigapascals and 2000°C over a period of 1 hour. Growth of crystals larger than 100 micrometers was achieved only when the pressure was within 5 percent of the pressure of the phase boundary separating the beta- and gamma-phase stability fields. A comparison of the elastic properties of the modified spinel phase with those of the olivine phase suggests that the 400-kilometer seismic discontinuity in the earth's mantle can be described by a mantle with 40 percent olivine. These results confirm that the 400-kilometer discontinuity can be due to the transition from olivine to modified spinel. The amount of olivine that must be present is less than that in a pyrolite model, although the results do not exclude pyrolite as a possible mantle model.
Diet-Induced Hypercholesterolemia in Mice: Prevention by Overexpression of LDL Receptors
Authors: Yokode Masayuki , Hammer Robert E. , Ishibashi Shun , Brown Michael S. , Goldstein Joseph L.
Published: October 2006

The current studies were designed to determine whether chronic overexpression of low density lipoprotein (LDL) receptors in the liver would protect mice from the increase in plasma LDL-cholesterol that is induced by high-fat diets. A line of transgenic mice was studied that express the human LDL receptor gene in the liver under control of the transferrin promoter. When fed a diet containing cholesterol, saturated fat, and bile acids for 3 weeks, the transgenic mice, in contrast to normal mice, did not develop a detectable increase in plasma LDL. The current data indicate that unregulated overexpression of LDL receptors can protect against diet-induced hypercholesterolemia in mice.
Technological Trends in Automobiles
Authors: Horton Emmett J. , Compton W. Dale
Published: October 2006

Current technological trends in the automotive industry reflect many diverse disciplines. Electronics and microprocessors, new engine transmission concepts, composite and ceramic materials, and computer-aided design and manufacture will combine to make possible the creation of advanced automobiles offering outstanding quality, fuel economy, and performance. A projected "average" vehicle of the 1990's is described to illustrate the application of these new concepts.
Favositid Tabulates: Evidence for Poriferan Affinity
Authors: Kaźmierczak Józef
Published: October 2006

Calcitic pseudomorphs of desma-like siliceous spicules found in the calcareous skeleton of a Devonian thamnoporid support the proposal of poriferan origin of at least some favositid Tabulata. These favositids arose from a group of Ordovician lithistid demosponges that adapted to toxic calcium excess in shallow, tropical marine environments by developing calicoblasts within the pinacoderm, supplementing their primary siliceous spicular skeletons with basally secreted calcium carbonate. They are tentatively recognized as an order of the subclass Sclerospongiae (class Demospongiae).
Increasing Atmospheric Carbon Dioxide: Tree Ring Evidence for Growth Enhancement in Natural Vegetation
Authors: LaMarche Valmore C. , Graybill Donald A. , Fritts Harold C. , Rose Martin R.
Published: October 2006

A response of plant growth to increased atmospheric carbon dioxide, which has been anticipated from laboratory data, may now have been detected in the annual rings of subalpine conifers growing in the western United States. Experimental evidence shows that carbon dioxide can be an important limiting factor in the growth of plants in this high-altitude environment. The greatly increased tree growth rates observed since the mid-19th century exceed those expected from climatic trends but are consistent in magnitude with global trends in carbon dioxide, especially in recent decades. If correctly interpreted, these findings have important implications for climate studies involving tree ring observations and for models of the global carbon dioxide budget.
Disruption of the Terrestrial Plant Ecosystem at the Cretaceous-Tertiary Boundary, Western Interior
Authors: Tschudy R. H. , Pillmore C. L. , Orth C. J. , Gilmore J. S. , Knight J. D.
Published: October 2006

The palynologically defined Cretaceous-Tertiary boundary in the western interior of North America occurs at the top of an iridium-rich clay layer. The boundary is characterized by the abrupt disappearance of certain pollen species, immediately followed by a pronounced, geologically brief change in the ratio of fern spores to angiosperm pollen. The occurrence of these changes at two widely separated sites implies continentwide disruption of the terrestrial ecosystem, probably caused by a major catastrophic event at the end of the period.
The Concept of Probability in Safety Assessments of Technological Systems
Authors: Apostolakis George
Published: October 2006

Safety assessments of technological systems, such as nuclear power plants, chemical process facilities, and hazardous waste repositories, require the investigation of the occurrence and consequences of rare events. The subjectivistic (Bayesian) theory of probability is the appropriate framework within which expert opinions, which are essential to the quantification process, can be combined with experimental results and statistical observations to produce quantitative measures of the risks from these systems. A distinction is made between uncertainties in physical models and state-of-knowledge uncertainties about the parameters and assumptions of these models. The proper role of past and future relative frequencies and several issues associated with elicitation and use of expert opinions are discussed.
The Precursor of the Cretaceous-Tertiary Boundary Clays at Stevns Klint, Denmark, and DSDP Hole 465A
Authors: Kastner M. , Asaro F. , Michel H. V. , Alvarez W. , Alvarez L. W.
Published: October 2006

Results of detailed mineralogical, chemical, and oxygen isotope analyses of the clay minerals and zeolites from two Cretaceous-Tertiary (K/T) boundary regions, Stevns Klint, Denmark, and Deep Sea Drilling Project (DSDP) Hole 465A in the north central Pacific Ocean, are presented. In the central part of the Stevns Klint K/T boundary layer, the only clay mineral detected by x-ray diffraction is a pure smectite with > 95 percent expandable layers. No detrital clay minerals or quartz were observed in the clay size fraction in these beds, whereas the clay minerals above and below the boundary layer are illite and mixed-layer smectite-illite of detrital origin as well as quartz. The mineralogical purity of the clay fraction, the presence of smectite only at the boundary, and the δ
18
O value of the smectite (27.2 ± 0.2 per mil) suggest that it formed in situ by alteration of glass. Formation from impact rather than from volcanic glass is supported by its major element chemistry. The high content of iridium and other siderophile elements is not due to the cessation of calcium carbonate deposition and resulting slow sedimentation rates. At DSDP Hole 465A, the principal clay mineral in the boundary zone (80 to 143 centimeters) is a mixed-layer smectite-illite with ≥90 percent expandable layers, accompanied by some detrital quartz and small amounts of a euhedral authigenic zeolite (clinoptilolite). The mixed-layer smectite-illite from the interval 118 to 120 centimeters in the zone of high iridium abundance has a very low rare earth element content; the negative cerium anomaly indicates formation in the marine environment. This conclusion is corroborated by the δ
18
O value of this clay mineral (27.1 ± 0.2 per mil). Thus, this mixed-layer smectite-illite formed possibly from the same glass as the K/T boundary smectite at Stevns Klint, Denmark.
Deposit from a Giant Wave on the Island of Lanai, Hawaii
Authors: Moore James G. , Moore George W.
Published: October 2006

Limestone-bearing gravel, the newly named Hulopoe Gravel, blankets the coastal slopes on Lanai. The deposit, which reaches a maximum altitude of 326 meters, formerly was believed to have been deposited along several different ancient marine strandlines, but dated submerged coral reefs and tide-gauge measurements indicate that the southeastern Hawaiian Islands sink so fast that former worldwide high stands of the sea now lie beneath local sea level. Evidence indicates that the Hulopoe Gravel and similar deposits on nearby islands were deposited during the Pleistocene by a giant wave generated by a submarine landslide on a sea scarp south of Lanai.
Geological Rhythms and Cometary Impacts
Authors: Rampino Michael R. , Stothers Richard B.
Published: October 2006

Time-series analysis reveals two dominant, stable long-term periodicities approximately equal to 33 ± 3 and 260 ± 25 million years in the known series of geological and biological upheavals during the Phanerozoic Eon. Because the cycles of these episodes agree in period and phase with the cycles of impact cratering on Earth, these results suggest that periodic comet impacts strongly influence global tectonism and biological evolution. These two periodicities could arise from interactions of the solar system with interstellar clouds as the solar system moves cyclically through the Galaxy.
Geologic Evidence for Recurrent Moderate to Large Earthquakes Near Charleston, South Carolina
Authors: Obermeier Stephen F. , Gohn Gregory S. , Weems Robert E. , Gelinas Robert L. , Rubin Meyer
Published: October 2006

Multiple generations of earthquake-induced sand blows in Quaternary sediments and soils near Charleston, South Carolina, are evidence of recurrent moderate to large earthquakes in that area. The large 1886 earthquake, the only historic earthquake known to have produced sand blows at Charleston, probably caused the youngest observed blows. Older (late Quaternary) sand blows in the Charleston area indicate at least two prehistoric earthquakes with shaking severities comparable to the 1886 event.
Supramolecular Chemistry: Receptors, Catalysts, and Carriers
Authors: Lehn Jean-Marie
Published: October 2006

Supramolecular chemistry is the study of the structures and functions of the supermolecules that result from binding substrates to molecular receptors. Macropolycyclic receptors and coreceptors have been designed that form cryptate inclusion complexes and display molecular recognition towards spherical, tetrahedral, and linear substrates of various kinds (metal cations, inorganic anions, and organic or biological cations or anions). Anion binding has led to the development of anion coordination chemistry. Metalloreceptors simultaneously bind organic molecules and metal ions; speleands combine polar and nonpolar binding subunits. Receptors bearing reactive functional groups may act as molecular reagents or catalysts, performing a chemical transformation on the bound substrates (by such reactions as hydrogen transfer, ester cleavage, and protoadenosinetriphosphatase and protokinase activities). Receptors fitted with lipophilic groups can operate as molecular carriers, translocating bound species through a membrane; this transport can be coupled to chemical potentials (proton and redox gradients).
Monoclonal Antibodies Against the Aster Yellows Agent
Authors: Lin Chan-Pin , Chen Tseh An
Published: October 2006

Hybridoma clones secreting specific monoclonal antibodies against the aster yellows agent, a mycoplasma-like organism, were produced by using partially purified salivary gland preparations from infected leafhopper vectors as the immunogen. After 3947 hybridomas from 20 independent fusions were screened for specific antibody against the aster yellows agent, two table clones were obtained. With these monoclonal antibodies the aster yellows agent in diseased lettuce, periwinkles, and inoculative insects was specifically identified by enzyme-linked immunosorbent assay. The aster yellows agent was serologically differentiated from the mycoplasma-like organisms associated with ash yellows, loofah witches'-broom, paulownia witches'-broom, sweet potato witches'-broom, peanut rosette, maize bushy stunt, and elm phloem necrosis.
A Mechanism for Social Selection and Successful Altruism
Authors: Simon Herbert A.
Published: October 2006

Within the framework of neo-Darwinism, with its focus on fitness, it has been hard to account for altruism, behavior that reduces the fitness of the altruist but increases average fitness in society. Many population biologists argue that, except for altruism to close relatives, human behavior that appears to be altruistic amounts to reciprocal altruism, behavior undertaken with an expectation of reciprocation, hence incurring no net cost to fitness. Herein is proposed a simple and robust mechanism, based on human docility and bounded rationality, that can account for the evolutionary success of genuinely altruistic behavior. Because docility-receptivity to social influence-contributes greatly to fitness in the human species, it will be positively selected. As a consequence, society can impose a "tax" on the gross benefits gained by individuals from docility by inducing docile individuals to engage in altruistic behaviors. Limits on rationality in the face of environmental complexity prevent the individual from avoiding this "tax." An upper bound is imposed on altruism by the condition that there must remain a net fitness advantage for docile behavior after the cost to the individual of altruism has been deducted.
Male Reproductive Parasitism: A Factor in the Africanization of European Honey-Bee Populations
Authors: Rinderer Thomas E. , Hellmich Richard L. , Danka Robert G. , Collins Anita M.
Published: October 2006

Africanized drone honey bees (
Apis mellifera
) migrate into European honey-bee colonies in large numbers, but Africanized colonies only rarely host drones from other colonies. This migration leads to a strong mating advantage for Africanized bees since it both inhibits European drone production and enhances Africanized drone production.
Coral Community Reproductive Patterns: Red Sea Versus the Great Barrier Reef
Authors: Shlesinger Y. , Loya Y.
Published: October 2006

In contrast to many corals of the Great Barrier Reef, Australia, which are synchronous multispecific spawners, the abundant coral species in the northern Red Sea, Israel, exhibit temporal reproductive isolation. Spawning dates of 12 of the 13 Red Sea species followed lunar periodicity and were consistent throughout 3 years of study. Spawning periods of all species occurred in different seasons, different months, or different lunar phases within the same month. The high abundance of the corals studied at Eilat may be due in part to the advantages gained through not having overlapping spawning periods and settlement times.
Mechanisms Controlling Phosphorus Retention Capacity in Freshwater Wetlands
Authors: Richardson Curtis J.
Published: October 2006

Freshwater wetland ecosystems do not effectively conserve phosphorus in the way that terrestrial ecosystems do. The phosphorus retention capacity varies greatly among bogs, fens, and swamps and is concomitant with the amorphous acid oxalate-extractable aluminum and iron content in the soil. However, the phosphorus adsorption potential in wetland ecosystems may be predicted solely from the extractable aluminum content of the soil. Wetlands tested as wastewater filtration systems became phosphorus-saturated in a few years, with the export of excessive quantities of phosphate.
Aluminum Mobilization in an Acidic Headwater Stream: Temporal Variation and Mineral Dissolution Disequilibria
Authors: Hooper Richard P. , Shoemaker Christine A.
Published: October 2006

Intensive sampling was performed along an elevational gradient in a headwater stream during snowmelt and storm events to study the chemical response of the stream to acidic inputs. Aluminum is an important constituent because of its toxicity to some fish species. The results indicate that aluminum concentrations during this period were not in equilibrium with a readily formed mineral phase, as has been assumed, and that the increase in aluminum concentration due to episodic depressions in
p
H lessened during the snowmelt. It is hypothesized that this temporal variation is caused by the depletion of a slowly forming, labile pool of aluminum in the soil.
Discovery of Sodium in the Atmosphere of Mercury
Authors: Potter Andrew , Morgan Thomas
Published: October 2006

The spectrum of Mercury at the Fraunhofer sodium D lines shows strong emission features that are attributed to resonant scattering of sunlight from sodium vapor in the atmosphere of the planet. The total column abundance of sodium was estimated to be 8.1 × 10
11
atoms per square centimeter, which corresponds to a surface density at the subsolar point of about 1.5 × 10
5
atoms per cubic centimeter. The most abundant atmospheric species found by the Mariner 10 mission to Mercury was helium, with a surface density of 4.5 × 10
3
atoms per cubic centimeter. It now appears that sodium vapor is a major constituent of Mercury's atmosphere.
Molybdenum Availability, Nitrogen Limitation, and Phytoplankton Growth in Natural Waters
Authors: Howarth Robert W. , Cole Jonathan J.
Published: October 2006

Sulfate inhibits molybdate assimilation by phytoplankton, making molybdate less available in seawater than it is in freshwater. As a result, nitrogen fixation and nitrate assimilation, both processes that require molybdenum, may require a greater expenditure of energy in seawater than in freshwater. This may explain in part why coastal marine ecosystems are usually nitrogen limited whereas lakes usually are not. Experimentally increasing the ratio of sulfate to molybdate (i) inhibits molybdate uptake, (ii) slows nitrogen fixation rates, and (iii) slows the growth of organisms that use nitrate as their nitrogen source.
Geochemical Exploration for Petroleum
Authors: Horvitz Leo
Published: October 2006

Geochemical methods used in exploring for oil and natural gas are based on the premise that hydrocarbons migrate upward from subsurface petroleum accumulations and produce anomalous patterns near the surface. Geochemical exploration techniques are both direct or indirect. Direct techniques require analysis of microquantities of hydrocarbons that occur in the free state in the soil interstices or that are adsorbed on the fine-grained portions of the soil. Indirect geochemical methods are based on the detection, in near-surface soils or in vegetation, of inorganic alteration products that result from upward migration of hydrocarbons.
Graphical Perception and Graphical Methods for Analyzing Scientific Data
Authors: Cleveland William S. , McGill Robert
Published: October 2006

Graphical perception is the visual decoding of the quantitative and qualitative information encoded on graphs. Recent investigations have uncovered basic principles of human graphical perception that have important implications for the display of data. The computer graphics revolution has stimulated the invention of many graphical methods for analyzing and presenting scientific data, such as box plots, two-tiered error bars, scatterplot smoothing, dot charts, and graphing on a log base 2 scale.
Chronology of Guitarrero Cave, Peru
Authors: Lynch Thomas F. , Gillespie R. , Gowlett John A. J. , Hedges R. E. M.
Published: October 2006

Dating by accelerator mass spectrometry of wooden artifacts, cord, and charcoal samples from Guitarrero Cave, Peru, supports the antiquity of South America's earliest textiles and other perishable remains. The new dates are consistent with those obtained from disintegration counters and leave little doubt about the integrity of the lower Preceramic layers and their early cultivars. Re-evaluation of the mode of deposition suggests that most of the remains resulted from short-term use of the cave in the eighth millennium B.C., with a possible brief human visit as early as 12,560 years ago.
Episodic Rifting of Phanerozoic Rocks in the Victoria Land Basin, Western Ross Sea, Antarctica
Authors: Cooper Alan K. , Davey F. J.
Published: October 2006

Multichannel seismic-reflection data show that the Victoria Land basin, unlike other sedimentary basins in the Ross Sea, includes a rift-depression 15 to 25 kilometers wide that parallels the Transantarctic Mountains and contains up to 12 kilometers of possible Paleozoic to Holocene age sedimentary rocks. An unconformity separates the previously identified Cenozoic sedimentary section from the underlying strata of possible Mesozoic and Paleozoic age. Late Cenozoic volcanic rocks intrude into the entire section along the eastern flank of the basin. The Victoria Land basin is probably part of a more extensive rift system that has been active episodically since Paleozoic time. Inferred rifting and basin subsidence during Mesozoic and Cenozoic time may be associated with regional crustal extension and uplift of the nearby Transantarctic Mountains.
Identification of a Chromosome 18q Gene that Is Altered in Colorectal Cancers
Authors: Fearon Eric R. , Cho Kathleen R. , Nigro Janice M. , Kern Scott E. , Simons Jonathan W. , Ruppert J. Michael , Hamilton  , Preisinger Antonette C. , Thomas Giles , Kinzler Kenneth W. , Vogelstein Bert
Published: October 2006

Allelic deletions involving chromosome 18q occur in more than 70 percent of colorectal cancers. Such deletions are thought to signal the existence of a tumor suppressor gene in the affected region, but until now a candidate suppressor gene on this chromosomal arm had not been identified. A contiguous stretch of DNA comprising 370 kilobase pairs (kb) has now been cloned from a region of chromosome 18q suspected to reside near this gene. Potential exons in the 370-kb region were defined by human-rodent sequence identities, and the expression of potential exons was assessed by an "exon-connection" strategy based on the polymerase chain reaction. Expressed exons were used as probes for cDNA screening to obtain clones that encoded a portion of a gene termed DCC; this cDNA was encoded by at least eight exons within the 370-kb genomic region. The predicted amino acid sequence of the cDNA specified a protein with sequence similarity to neural cell adhesion molecules and other related cell surface glycoproteins. While the DCC gene was expressed in most normal tissues, including colonic mucosa, its expression was greatly reduced or absent in most colorectal carcinomas tested. Somatic mutations within the DCC gene observed in colorectal cancers included a homozygous deletion of the 5′ end of the gene, a point mutation within one of the introns, and ten examples of DNA insertions within a 0.17-kb fragment immediately downstream of one of the exons. The DCC gene may play a role in the pathogenesis of human colorectal neoplasia, perhaps through alteration of the normal cell-cell interactions controlling growth.
Nodal Modulation of the Lunar Semidiurnal Tide in the Bay of Fundy and Gulf of Maine
Authors: Ku L.-F. , Greenberg D. A. , Garrett C. J. R. , Dobson F. W.
Published: October 2006

Observations, numerical modeling, and theoretical calculations show how the 18.6-year modulation of the main lunar semidiurnal tide in the Bay of Fundy and Gulf of Maine is reduced from its astronomical value of 3.7 percent to 2.4 percent by the effects of friction and resonance. The agreement of the three approaches increases confidence in model predictions of widespread changes in the tidal regime resulting from development of tidal power.
What Makes a Good Computer Device?
Authors: Keyes Robert W.
Published: October 2006

Numerous development projects aimed at replacing the silicon technology that dominates computer logic with a faster alternative have been conducted throughout the past 25 years. None has succeeded. The alternatives are usually based on a device that switches very rapidly, and they neglect many other requirements of computer logic. In this article the essential physical factors that account for the success of transistors in digital applications are identified, as are the factors that are absent in proposed alternative devices.
Resource Availability and Plant Antiherbivore Defense
Authors: Coley Phyllis D. , Bryant John P. , Chapin F. Stuart
Published: October 2006

The degree of herbivory and the effectiveness of defenses varies widely among plant species. Resource availability in the environment is proposed as the major determinant of both the amount and type of plant defense. When resources are limited, plants with inherently slow growth are favored over those with fast growth rates; slow rates in turn favor large investments in antiherbivore defenses. Leaf lifetime, also determined by resource availability, affects the relative advantages of defenses with different turnover rates. Relative limitation of different resources also constrains the types of defenses. The proposals are compared with other theories on the evolution of plant defenses.
Human Intelligence: The Model Is the Message
Authors: Sternberg Robert J.
Published: October 2006

Theories of intelligence, and some of the research testing them, are designed to answer three basic questions about intelligence: (i) What is the relation of intelligence to the internal world of the individual? (ii) What is the relation of intelligence to the external world of the individual? (iii) What is the relation of intelligence to experience? Various models of the mind underlying the theories have been proposed; the strengths and limitations of these models are assessed. A theory that addresses all three questions simultaneously is the triarchic theory.
Transplanted Suprachiasmatic Nucleus Determines Circadian Period
Authors: Ralph Martin R. , Foster Russell G. , Davis Fred C. , Menaker Michael
Published: October 2006

The pacemaker role of the suprachiasmatic nucleus in a mammalian circadian system was tested by neural transplantation by using a mutant strain of hamster that shows a short circadian period. Small neural grafts from the suprachiasmatic region restored circadian rhythms to arrhythmic animals whose own nucleus had been ablated. The restored rhythms always exhibited the period of the donor genotype regardless of the direction of the transplant or genotype of the host. The basic period of the overt circadian rhythm therefore is determined by cells of the suprachiasmatic region.
Diet-Induced Head Allometry Among Foliage-Chewing Insects and Its Importance for Graminivores
Authors: Bernays E. A.
Published: October 2006

Individuals of the grass-feeding caterpillar of
Pseudaletia unipuncta
, reared from hatching on hard grass, had head masses twice as great as those of caterpillars fed soft artificial diet, even though the larvae reached the same body mass. Larvae reared on soft wheat seedlings had intermediate head masses. Thus muscular effort increases muscular development in an insect, which in turn has a dramatic morphogenetic effect on head size. Size differences in the head capsules, with the correlated differences in mandibular power, have a direct effect on the ability of the insects to ingest hard foods rapidly: larger heads are adaptive for dealing with hard grasses.
Transition Between Frictional Slip and Ductile Flow for Halite Shear Zones at Room Temperature
Authors: Shimamoto Toshihiko
Published: October 2006

A complete transition from frictional slip to ductile shearing flow upon decreasing velocity (or slip rate) or increasing confining pressure is documented for a thin layer of halite undergoing large shearing deformation. The results indicate that the logarithmic law for steady-state friction with a negative velocity dependence breaks down when friction becomes nearly equal to the shear resistance required for ductile flow and that the law changes into a flow law in shear upon further decrease in velocity. The friction-velocity relation is crucial in stability analyses of fault motion, and the results are important for earthquake and state-of-stress problems, especially in the application of laboratory data to the slow average motion of natural faults and to the behavior of deep faults along which ductile deformation becomes increasingly predominant.
Reduction in Summer Soil Wetness Induced by an Increase in Atmospheric Carbon Dioxide
Authors: Manabe S. , Wetherald R. T.
Published: October 2006

The geographical distribution of the change in soil wetness in response to an increase in atmospheric carbon dioxide was investigated by using a mathematical model of climate. Responding to the increase in carbon dioxide, soil moisture in the model would be reduced in summer over extensive regions of the middle and high latitudes, such as the North American Great Plains, western Europe, northern Canada, and Siberia. These results were obtained from the model with predicted cloud cover and are qualitatively similar to the results from several numerical experiments conducted earlier with prescribed cloud cover.
Accretion Rate of Extraterrestrial Matter: Iridium Deposited 33 to 67 Million Years Ago
Authors: Kyte Frank T. , Wasson John T.
Published: October 2006

Iridium measured in 149 samples of a continuous 9-meter section of Pacific abyssal clay covering the time span 33 to 67 million years ago shows a well-defined peak only at the Cretaceous/Tertiary boundary. In the rest of the section iridium ranges from a minimum concentration near 0.35 nanograms per gram in the Paleocene to a maximum near 1.7 in the Eocene; between 63 and 33 million years ago the mean iridium accumulation rate is approximately 13 nanograms per square centimeter per million years. Correction for terrestrial iridium leads to an extraterrestrial flux of 9 ± 3 nanograms of iridium per square centimeter per million years, and an estimated annual global influx of 78 billion grams of chondritic matter, consistent with recent estimates of the influx of dust, meteorites, and crater-producing bodies with masses ranging from 10
-13
to 10
18
grams. Combining the recent flux of objects ranging in mass from 10
6
to 10
7
grams with the flux of 10
14
- to 10
15
-gram objects indicates that the number of objects is equal to 0.54 divided by the radius (in kilometers) to the 2.1 power. Periodic comet showers should increase the cometary iridium flux by a factor of 200 to 600 on a time scale of 1 to 3 million years; the predicted iridium maxima (more than 30 times background) are not present in the intervals associated with the Cretaceous/Tertiary boundary or the tektite-producing late Eocene events.
Reorganization of Retinotopic Cortical Maps in Adult Mammals After Lesions of the Retina
Authors: Kaas Jon H. , Krubitzer Leah A. , Chino Yuzo M. , Langston Andy L. , Polley Edward H. , Blair Norman
Published: October 2006

The organization of the visual cortex has been considered to be highly stable in adult mammals. However, 5° to 10° lesions of the retina in the contralateral eye markedly altered the systematic representations of the retina in primary and secondary visual cortex when matched inputs from the ipsilateral eye were also removed. Cortical neurons that normally have receptive fields in the lesioned region of the retina acquired new receptive fields in portions of the retina surrounding the lesions. The capacity for such changes may be important for normal adjustments of sensory systems to environmental contingencies and for recoveries from brain damage.
Iridium Abundances Across the Ordovician-Silurian Stratotype
Authors: Wilde Pat , Berry William B. N. , Quinby-Hunt Mary S. , Orth Charles J. , Quintana Leonard R. , Gilmore James S.
Published: October 2006

Chemostratigraphic analyses in the Ordovician-Silurian boundary stratotype section, bracketing a major extinction event in the graptolitic shale section at Dob's Linn, Scotland, show persistently high iridium concentrations of 0.050 to 0.250 parts per billion. There is no iridium concentration spike in the boundary interval or elsewhere in the 13 graptolite zones examined encompassing about 20 million years. Iridium correlated with chromium, both elements showing a gradual decrease with time into the middle part of the Lower Silurian. The chromium-iridium ratio averages about 10
6
. Paleogeographic and geologic reconstructions coupled with the occurrence of ophiolites and other deep crustal rocks in the source area suggest that the high iridium and chromium concentrations observed in the shales result from terrestrial erosion of exposed upper mantle ultramafic rocks rather than from a cataclysmic extraterrestrial event.
Cambrian River Terraces and Ridgetops in Central Australia: Oldest Persisting Landforms?
Authors: Stewart A. J. , Blake D. H. , Ollier C. D.
Published: October 2006

Fluvial sediments in paleovaileys cut in the Ashburton surface of the Davenport province of central Australia form terrace remnants that appear to retain their original depositional tops and have probably existed as subaerial landforms since their inception. Marine fossils in sediments conformable with the fluvial sediments near the southeast margin of the province give a Cambrian age for the terraces; the Ashburton surface forming the ridgetops between the paleovalleys is Cambrian or older.
Strong Ground Motion from the Michoacan, Mexico, Earthquake
Authors: Anderson J. G. , Bodin P. , Brune J. N. , Prince J. , Singh S. K. , Quaas R. , Onate M.
Published: October 2006

The network of strong motion accelerographs in Mexico includes instruments that were installed, under an international cooperative research program, in sites selected for the high potential of a large earthquake. The 19 September 1985 earthquake (magnitude 8.1) occurred in a seismic gap where an earthquake was expected. As a result, there is an excellent description of the ground motions that caused the disaster.