bluuebunny/crossref_metadata_2025 huggingface dataset:
Irregular Recurrence of Large Earthquakes Along the San Andreas Fault: Evidence from Trees
Authors: Jacoby Gordon C. , Sheppard Paul R. , Sieh Kerry E.
Published: October 2006

Old trees growing along the San Andreas fault near Wrightwood, California, record in their annual ring-width patterns the effects of a major earthquake in the fall or winter of 1812 to 1813. Paleoseismic data and historical information indicate that this event was the "San Juan Capistrano" earthquake of 8 December 1812, with a magnitude of 7.5. The discovery that at least 12 kilometers of the Mojave segment of the San Andreas fault ruptured in 1812, only 44 years before the great January 1857 rupture, demonstrates that intervals between large earthquakes on this part of the fault are highly variable. This variability increases the uncertainty of forecasting destructive earthquakes on the basis of past behavior and accentuates the need for a more fundamental knowledge of San Andreas fault dynamics.
Desiccation of the Aral Sea: A Water Management Disaster in the Soviet Union
Authors: Micklin Philip P.
Published: October 2006

The Aral Sea in the Soviet Union, formerly the world's fourth largest lake in area, is disappearing. Between 1960 and 1987, its level dropped nearly 13 meters, and its area decreased by 40 percent. Recession has resulted from reduced inflow caused primarily by withdrawals of water for irrigation. Severe environmental problems have resulted. The sea could dry to a residual brine lake. Local water use is being improved and schemes to save parts of the sea have been proposed. Nevertheless, preservation of the Aral may require implementation of the controversial project to divert water from western Siberia into the Aral Sea basin.
Oceanic Primary Production: Estimation by Remote Sensing at Local and Regional Scales
Authors: Platt Trevor , Sathyendranath Shubha
Published: October 2006

Satellites provide the only avenue by which marine primary production can be studied at ocean-basin scales. With maps of chlorophyll distribution derived from remotely sensed data on ocean color as input, deduction of a suitable algorithm for primary production is a problem in applied plant physiology. An algorithm is proposed that combines a spectral and angular model of submarine light with a model of the spectral response of algal photosynthesis. To apply the algorithm at large horizontal scale, a dynamic biogeography is needed for the physiological rate parameters and the biological structure of the water column. Fieldwork to obtain this type of data should be undertaken so that the use of satellite data in modern biological oceanography may be optimized.
Defense Strategies Against Hypoxia and Hypothermia
Authors: Hochachka P. W.
Published: October 2006

Because aerobic metabolic rates decrease in hypoxia-sensitive cells under oxygen-limiting conditions, the demand for glucose or glycogen for anaerobic glycolysis may rise drastically as a means of making up for the energetic shortfall. However, ion and electrical potentials typically cannot be sustained because of energy insufficiency and high membrane permeabilities; therefore metabolic and membrane functions in effect become decoupled. In hypoxia-tolerant animals, these problems are resolved through a number of biochemical and physiological mechanisms; of these (i) metabolic arrest and (ii) stabilized membrane functions are the most effective strategies for extending tolerance to hypoxia. Metabolic arrest is achieved by means of a reversed or negative Pasteur effect (reduced or unchanging glycolytic flux at reduced O
2
availability); and coupling of metabolic and membrane function is achievable, in spite of the lower energy turnover rates, by maintaining membranes of low permeability (probably via reduced densities of ion-specific channels). The possibility of combining metabolic arrest with channel arrest has been recognized as an intervention strategy. To date, the success of this strategy has been minimal, mainly because depression of metabolism through cold is the usual arrest mechanism used, and hypothermia in itself perturbs controlled cell function in most endotherms.
A Parathyroid Hormone-Like Protein from Cultured Human Keratinocytes
Authors: Merendino J. J. , Insogna K. L. , Milstone L. M. , Broadus A. E. , Stewart A. F.
Published: October 2006

Parathyroid hormone-like factors have been found in extracts of tumors associated with humoral hypercalcemia of malignancy, many of which are of squamous epithelial origin. Cultured, nonmalignant human keratinocytes were examined for the production of similar factors. Keratinocyte-conditioned medium from ten cultures stimulated the production of cyclic adenosine monophosphate in clonally derived rat osteosarcoma cells sensitive to parathyroid hormone. Bovine [Nle
8,18
, Tyr
34
]PTH-(3-34)NH
2
, a competitive inhibitor of parathyroid hormone, stopped the adenylate cyclase production stimulated by keratinocyte-conditioned medium, but antisera to parathyroid hormone had no effect on such adenylate cyclase activity. The active component of keratinocyte-conditioned medium has a molecular weight exceeding that of native parathyroid hormone. These characteristics are shared by the parathyroid hormone receptor agonists associated with humoral hypercalcemia of malignancy, which suggests that normal human keratinocytes may produce a factor related to that produced by malignant tumors associated with humoral hypercalcemia of malignancy.
Catastrophic Landslide Deposits in the Karakoram Himalaya
Authors: Hewitt Kenneth
Published: October 2006

In July 1986, three catastrophic landslides deposited about 20 × 106cubic meters of debris on Bualtar Glacier in the Karakoram Himalaya. A sudden acceleration and superficial breakup of the glacier provided an opportunity to examine the fresh deposits in depth. Beneath a surface layer of large boulders, finer materials, mainly sand and silt, made up half of the total volume. The fine materials were formed during the rock avalanche from mostly intact, massive rock of the source zone. Velocity estimates suggest that this disaggregation occurred in less than 2 minutes. Coarse materials remained in bands of uniform lithology, but the fine materials had diffused throughout the landslides. A small amount of carbonate appears to have been calcined by frictional heating, presumably at the base of the initial sliding masses. These observations are relevant to understanding the mechanisms of catastrophic landslides. Other nearby rock avalanche deposits indicate that landslides are an important geomorphic process in the area and that they pose a continuing risk to human activity.
Earthquake-Caused Coastal Uplift and Its Effects on Rocky Intertidal Kelp Communities
Authors: Castilla Juan Carlos
Published: October 2006

The coastal uplift (approximately 40 to 60 centimeters) associated with the Chilean earthquake of 3 March 1985 caused extensive mortality of intertidal organisms at the Estación Costera de Investigaciones Marinas, Las Cruces. The kelp belt of the laminarian
Lessonia nigrescens
was particularly affected. Most of the primary space liberated at the upper border of this belt was invaded by species of barnacles, which showed an opportunistic colonization strategy. Drastic modifications in the environment such as coastal uplift, subsidence, or the effects of the El Niño phenomenon are characteristic of the southern Pacific. Modifications in the marine ecosystem that generate catastrophic and widespread mortalities of intertidal organisms can affect species composition, diversity, or local biogeography.
Probing C
60
Authors: Curl Robert F. , Smalley Richard E.
Published: October 2006

Experiments involving the laser vaporization of graphite have indicated that one particular cluster of carbon, C
60
, is preeminently stable; this special stability may be evidence that C
60
can readily take the form of a hollow truncated icosahedron (a sort of molecular soccerball). If true, this structure for C
60
would be the first example of a spherical aromatic molecule. In fact, because of symmetry properties unique to the number 60, it may be the most perfectly spherical, edgeless molecule possible. Its rapid formation in condensing carbon vapors and its extreme chemical and photophysical stability may have far-reaching implications in a number of areas, particularly combustion science and astrophysics. For these reasons C
60
and other clusters of carbon have continued to be the subject of intense research. This article provides a short review of the many new experimental probes of the properties of C
60
and related carbon dusters.
Self-Organization, Transformity, and Information
Authors: Odum Howard T.
Published: October 2006

Ecosystems and other self-organizing systems develop system designs and mathematics that reinforce energy use, characteristically with alternate pulsing of production and consumption, increasingly recognized as the new paradigm. Insights from the energetics of ecological food chains suggest the need to redefine work, distinguishing kinds of energy with a new quantity, the
transformity
(energy of one type required per unit of another). Transformities may be used as an energy-scaling factor for the hierarchies of the universe including information. Solar transformities in the biosphere, expressed as solar emjoules per joule, range from one for solar insolation to trillions for categories of shared information. Resource contributions multiplied by their transformities provide a scientifically based value system for human service, environmental mitigation, foreign trade equity, public policy alternatives, and economic vitality.
X-Ray Scattering Studies of Aligned, Stacked Surfactant Membranes
Authors: Sirota Eric B. , Smith Gregory S. , Safinya Cyrus R. , Plano Robert J. , Clark Noel A.
Published: October 2006

X-ray scattering studies were performed to understand the structure and correlations in the lamellar phases of thick, freely suspended films of (i) the hydrated phospholipid dimyristoylphosphotidylcholine (DMPC) and (ii) the ternary system consisting of the surfactant sodium dodecyl sulfate (SDS), cosurfactant (pentanol), and water. The films were drawn in a temperature- and humidity-controlled environment, where the layers were oriented to within 0.1°. In the DMPC system, this made it possible to directly observe the orientation of the P
β′
modulation and to identify phase L
β′
as three distinct phases distinguished by the direction of chain tilt with respect to the lattice. In the L
α
phase of the ternary system, power law behavior of the (0,0,L) structure factor arising from the algebraic decay of layer correlations was observed in single crystals.
Calcium Channels in Planar Lipid Bilayers: Insights into Mechanisms of Ion Permeation and Gating
Authors: Rosenberg Robert L. , Hess Peter , Reeves John P. , Smilowitz Henry , Tsien Richard W.
Published: October 2006

Electrophysiological recordings were used to analyze single calcium channels in planar lipid bilayers after membranes from bovine cardiac sarcolemmal vesicles had been incorporated into the bilayer. In these cell-free conditions, channels in the bilayer showed unitary barium or calcium conductances, gating kinetics, and pharmacological responses that were similar to dihydropyridine-sensitive calcium channels in intact cells. The open channel current varied in a nonlinear manner with voltage under asymmetric (that is, physiological) ionic conditions. However, with identical solutions on both sides of the bilayer, the current-voltage relation was linear. In matched experiments, calcium channels from skeletal muscle T-tubules differed significantly from cardiac calcium channels in their conductance properties and gating kinetics.
Recombinant Human Granulocyte Colony-Stimulating Factor: Effects on Normal and Leukemic Myeloid Cells
Authors: Souza Lawrence M. , Boone Thomas C. , Gabrilove Janice , Lai Por H. , Zsebo Krisztina M. , Murdock Douglas C , Chazin Vicki R. , Bruszewski Joan , Lu Hsieng , Chen Kenneth K. , Barendt Jean , Platzer Erich , Moore Malcolm A. S. , Mertelsmann Roland , Welte Karl
Published: October 2006

Experiments were conducted to isolate and characterize the gene and gene product of a human hematopoietic colony-stimulating factor with pluripotent biological activities. This factor has the ability to induce differentiation of a murine myelomonocytic leukemia cell line WEHI-3B(D
+
) and cells from patients with newly diagnosed acute nonlymphocytic leukemia (ANLL). A complementary DNA copy of the gene encoding a pluripotent human granulocyte colony-stimulating factor (hG-CSF) was cloned and expressed in
Escherichia coli
. The recombinant form of hG-CSF is capable of supporting neutrophil proliferation in a CFU-GM assay. In addition, recombinant hG-CSF can support early erythroid colonies and mixed colony formation. Competitive binding studies done with
125
I-labeled hG-CSF and cell samples from two patients with newly diagnosed human leukemias as well as WEHI-3B(D
+
) cells showed that one of the human leukemias (ANLL, classified as M4) and the WEHI-3B(D
+
) cells have receptors for hG-CSF. Furthermore, the murine WEHI-3B(D
+
) cells and human leukemic cells classified as M2, M3, and M4 were induced by recombinant hG-CSF to undergo terminal differentiation to macrophages and granulocytes. The secreted form of the protein produced by the bladder carcinoma cell line 5637 was found to be
O
-glycosylated and to have a molecular weight of 19,600.
An Apical-Membrane Chloride Channel in Human Tracheal Epithelium
Authors: Welsh Michael J.
Published: October 2006

The mechanism of chloride transport by airway epithelia has been of substantial interest because airway and sweat gland-duct epithelia are chloride-impermeable in cystic fibrosis. The decreased chloride permeability prevents normal secretion by the airway epithelium, thereby interfering with mucociliary clearance and contributing to the morbidity and mortality of the disease. Because chloride secretion depends on and is regulated by chloride conductance in the apical cell membrane, the patch-clamp technique was used to directly examine single-channel currents in primary cultures of human tracheal epithelium. The cells contained an anion-selective channel that was not strongly voltage-gated or regulated by calcium in cell-free patches. The channel was also blocked by analogs of carboxylic acid that decrease apical chloride conductance in intact epithelia. When attached to the cell, the channel was activated by isoproterenol, although the channel was also observed to open spontaneously. However, in some cases, the channel was only observed after the patch was excised from the cell. These results suggest that this channel is responsible for the apical chloride conductance in airway epithelia.
Three-Dimensional Structure of an Antigen-Antibody Complex at 2.8 Å Resolution
Authors: Amit A. G. , Mariuzza R. A. , Phillips S. E. V. , Poljak R. J.
Published: October 2006

The 2.8 Å resolution three-dimensional structure of a complex between an antigen (lysozyme) and the Fab fragment from a monoclonal antibody against lysozyme has been determined and refined by x-ray crystallographic techniques. No conformational changes can be observed in the tertiary structure of lysozyme compared with that determined in native crystalline forms. The quaternary structure of Fab is that of an extended conformation. The antibody combining site is a rather flat surface with protuberances and depressions formed by its amino acid side chains. The antigen-antibody interface is tightly packed, with 16 lysozyme and 17 antibody residues making close contacts. The antigen contacting residues belong to two stretches of the lysozyme polypeptide chain: residues 18 to 27 and 116 to 129. All the complementarity-determining regions and two residues outside hypervariable positions of the antibody make contact with the antigen. Most of these contacts (10 residues out of 17) are made by the heavy chain, and in particular by its third complementarity-determining region. Antigen variability and antibody specificity and affinity are discussed on the basis of the determined structure.
Ecological Effects of a Major Oil Spill on Panamanian Coastal Marine Communities
Authors: Jackson J. B. C. , Cubit J. D. , Keller B. D. , Batista V. , Burns K. , Caffey H. M. , Caldwell R. L. , Garrity S. D. , Getter C. D. , Gonzalez C. , Guzman H. M. , Kaufmann K. W. , Knap A. H. , Levings S. C. , Marshall M. J. , Steger R. , Thompson R. C. , Weil E.
Published: October 2006

In 1986 more than 8 million liters of crude oil spilled into a complex region of mangroves, seagrasses, and coral reefs just east of the Caribbean entrance to the Panama Canal. This was the largest recorded spill into coastal habitats in the tropical Americas. Many populations of plants and animals in both oiled and unoiled sites had been studied previously, thereby providing an unprecedented measure of ecological variation before the spill. Documentation of the spread of oil and its biological effects begun immediately. Intertidal mangroves, algae, and associated invertebrates were covered by oil and died soon after. More surprisingly, there was also extensive mortality of shallow subtidal reef corals and infauna of seagrass beds. After 1.5 years only some organisms in areas exposed to the open sea have recovered.
Composition of the Earth
Authors: Anderson Don L.
Published: October 2006

New estimates of solar composition, compared to earlier measurements, are enriched in Fe and Ca relative to Mg, Al, and Si. The Fe/Si and Ca/Al atomic ratios are 30 to 40 percent higher than chondritic values. These changes necessitate a revision in the cosmic abundances and in the composition of the nebula from which the planets accreted (which have been based on chondritic values). These new values imply that the mantle could contain about 15 weight percent FeO and more CaMgSi
2
O
6
than has been supposed. Geophysical data are consistent with a dense, FeO-rich lower mantle and a CaMgSi
2
O
6
(diopside)-rich transition region. FeO contents of 13 to 18 weight percent appear to be typical of the mantles of bodies in the inner solar system. The oldest komatiites (high-temperature MgO-rich magmas) have a similar chemistry to the derived mantle. These results favor a chemically zoned mantle.
Rhenium-Osmium Isotope Systematics of Carbonaceous Chondrites
Authors: Walker R. J. , Morgan J. W.
Published: October 2006

Rhenium and osmium concentrations and Os isotopic compositions of eight carbonaceous chondrites, one LL3 ordinary chondrite, and two iron meteorites were determined by resonance ionization mass spectrometry. Iron meteorite
187
Re/
186
Os and
187
Os/
186
Os ratios plot on the previously determined iron meteorite isochron, but most chondrite data plot 1 to 2 percent above this meteorite isochron. This suggests either that irons have significantly younger Re-Os closure ages than chondrites or that chondrites were formed from precursor materials with different chemical histories from the precursors of irons. Some samples of Semarkona (LL3) and Murray (C2M) meteorites plot 4 to 6 percent above the iron meteorite isochron, well above the field delineated by other chondrites. Murray may have lost Re by aqueous leaching during its preterrestrial history. Semarkona could have experienced a similar loss of Re, but only slight aqueous alteration is evident in the meteorite. Therefore, the isotopic composition of Semarkona could reflect assembly of isotopically heterogeneous components subsequent to 4.55 billion years ago or Os isotopic heterogeneities in the primordial solar nebula.
Stishovite at the Cretaceous-Tertiary Boundary, Raton, New Mexico
Authors: McHone John F. , Nieman Ronald A. , Lewis Charles F. , Yates Ann M.
Published: October 2006

Stishovite, a dense phase of silica, has become widely accepted as an indicator of terrestrial impact events. Stishovite occurs at several impact structures but has not been found at volcanic sites. Solid-state silicon-29 magic-angle spinning nuclear magnetic resonance (silicon-29 MAS NMR) and X-ray diffraction of samples from the Cretaceous-Tertiary boundary layer at Raton, New Mexico, indicate that stishovite occurs in crystalline mineral grains. Stishovite was indicated by a single, sharp resonance with a chemical shift value of -191.3 ppm, characteristic of silicon in octahedral coordination, that disappeared after heating the sample at 850° Celsius for 30 minutes. An X-ray diffraction pattern of HF residuals from the unheated sample displayed more than 120 peaks, most of which correspond to quartz, zircon, rutile, and anatase. Eight unambiguous weak to moderate reflections could be ascribed to
d
-spacings characteristic of stishovite.
Plate Tectonics 2.5 Billion Years Ago: Evidence at Kolar, South India
Authors: Krogstad E. J. , Balakrishnan S. , Mukhopadhyay D. K. , Rajamani V. , Hanson G. N.
Published: October 2006

The Archean Kolar Schist Belt, south India, is a suture zone where two gneiss terranes and at least two amphibolite terranes with distinct histories were accreted. Amphibolites from the eastern and western sides of the schist belt have distinct incompatible element and isotopic characteristics suggesting that their volcanic protoliths were derived from different mantle sources. The amphibolite and gneiss terranes were juxtaposed by horizontal compression and shearing between 2530 and 2420 million years ago (Ma) along a zone marked by the Kolar Schist Belt. This history of accretion of discrete crustal terranes resembles those of Phanerozoic convergent margins and thus suggests that plate tectonics operated on Earth by 2500 Ma.
Polar Solvent Dynamics and Electron-Transfer Reactions
Authors: Maroncelli Mark , MacInnis Jean , Fleming Graham R.
Published: October 2006

Polar solvents often exert a dramatic influence on reactions in solution. Equilibrium aspects of this influence involve differential solvation of reactants compared to the transition state that lead to alteration of the free-energy barrier to reaction. Such effects are well known, and often give rise changes in reaction rates of many orders of magnitude. Less well understood are effects arising from non-equilibrium, dynamical aspects of solvation. During the course of reaction, charge is rapidly redistributed among reactants. How the reaction couples to its solvent environment depends critically on how fast the solvent can respond to these changes in reactant charge distribution. In this article the dynamics of solvation in polar liquids and the influence of this dynamics on electron-transfer reactions are discussed. A molecular picture suggests that polar solvation occurs on multiple time scales as a result of the involvement of different types of solvent motion. A hierarchy of models from a homogeneous continuum model to one incorporating molecular aspects of solvation, combined with computer simulations, gives insight into the underlying dynamics. Experimental measures of solvation dynamics from picosecond and subpicosecond time-dependent Stokes shift studies are compared with the predictions of theoretical models. The implication of these results for electron-transfer reactions in solution are then briefly considered.
Preferred Microtubules for Vesicle Transport in Lobster Axons
Authors: Miller Robert H. , Lasek Raymond J. , Katz Michael J.
Published: October 2006

The hypothesis that transported vesicles are preferentially associated with a subclass of microtubules has been tested in lobster axons. A cold block was used to collect moving vesicles in these axons; this treatment caused the vesicles to accumulate in files along some of the microtubules. Quantitative analysis of the number of vesicles associated with microtubule segments indicated that lobster axons have two distinct populations of microtubules—transport microtubules that are the preferred substrates for vesicle transport and architectural microtubules that contribute to axonal structure.
Angiogenic Factors
Authors: Folkman Judah , Klagsbrun Michael
Published: October 2006

Within the past 2 years, several angiogenic factors have been fully purified, their amino acid sequences determined, and their genes cloned. These polypeptides include acidic and basic fibroblast growth factor, angiogenin, and transforming growth factors α and β. Other less well characterized angiogenesis factors have also been isolated, some of which are lipids. This article traces the discovery of the angiogenic factors and describes their possible significance in understanding growth regulation of the vascular system. When evaluated according to their putative targets, they appear to fall into two groups: (i) those that act directly on vascular endothelial cells to stimulate locomotion or mitosis, and (ii) those that act indirectly by mobilizing host cells (for example, macrophages) to release endothelial growth factors. In addition to their presence in tumors undergoing neovascularization, the same angiogenic peptides are found in many normal tissues where neovascularization is not occurring. This suggests that physiological expression of angiogenic factors is tightly regulated. In addition to the persistent angiogenesis induced by tumors, it now appears that a variety of nonneoplastic diseases, previously thought to be unrelated, can be considered as "angiogenic diseases" because they are dominated by the pathologic growth of capillary blood vessels.
Long-Term Sensitization in
Aplysia
: Biophysical Correlates in Tail Sensory Neurons
Authors: Scholz Kenneth P. , Byrne John H.
Published: October 2006

A fundamental problem in the cellular analysis of learning and memory is the identification of the neuronal substrates of long-term information storage and their relation to short-term cellular alterations. In this report, biophysical correlates of long-term sensitization of a simple withdrawal reflex in the mollusc
Aplysia
were examined. A voltage-clamp analysis of the sensory neurons that control the reflex, 24 hours after sensitization training, revealed a significant reduction in net outward current. The results indicate that one mechanism for the storage of long-term sensitization is the regulation of membrane currents that influence the characteristics of the action potential and the excitability of individual neurons. The results also provide insights into the relation between short- and long-term sensitization in that the biophysical loci involved in the storage of long-term sensitization appear similar to those involved in short-term sensitization.
Why Nature Chose Phosphates
Authors: Westheimer F. H.
Published: October 2006

Phosphate esters and anhydrides dominate the living world but are seldom used as intermediates by organic chemists. Phosphoric acid is specially adapted for its role in nucleic acids because it can link two nucleotides and still ionize; the resulting negative charge serves both to stabilize the diesters against hydrolysis and to retain the molecules within a lipid membrane. A similar explanation for stability and retention also holds for phosphates that are intermediary metabolites and for phosphates that serve as energy sources. Phosphates with multiple negative charges can react by way of the monomeric metaphosphate ion PO
3
-
as an intermediate. No other residue appears to fulfill the multiple roles of phosphate in biochemistry. Stable, negatively charged phosphates react under catalysis by enzymes; organic chemists, who can only rarely use enzymatic catalysis for their reactions, need more highly reactive intermediates than phosphates.
Detection of C
5
in the Circumstellar Shell of IRC+10216
Authors: Bernath Peter F. , Hinkle Kenneth H. , Keady John J.
Published: October 2006

The C
5
molecule has been identified in the infrared spectrum of the prototypical obscured carbon star, IRC+10216. In addition to their astrophysical importance, pure carbon chain molecules such as C
5
are of interest in the chemistry of flames and propellants.
Experimental Research on Jury Decision-Making
Authors: MacCoun Robert J.
Published: October 2006

Because trial juries deliberate in secrecy, legal debates about jury functioning have relied heavily on anecdote and speculation. In recent years, investigators have begun to challenge many common assumptions about jury behavior. An important tool in this effort has been the mock jury experiment, in which research participants are randomly assigned to alternative trial conditions and asked to reach a verdict in a simulated case. Researchers have used mock jury experiments to test hypotheses about causal influences on jury behavior and to develop theoretical models of the jury deliberation process.
Accelerated Healing of Incisional Wounds in Rats Induced by Transforming Growth Factor-β
Authors: Mustoe Thomas A. , Pierce Glenn F. , Thomason Arlen , Gramates Peggy , Sporn Michael B. , Deuel Thomas F.
Published: October 2006

The role of polypeptide growth factors in the processes of inflammation and repair was investigated by analyzing the influence of transforming growth factor-β (TGF-β), applied directly to linear incisions made through rat dorsal skin. A dose-dependent, direct stimulatory effect of a single application of TGF-β on the breaking strength of healing incisional wounds was demonstrated. An increase in maximum wound strength of 220 percent of control was observed at 5 days; the healing rate was accelerated by approximately 3 days for at least 14 days after production of the wound and application of TGF-β. These increases in wound strength were accompanied by an increased influx of mononuclear cells and fibroblasts and by marked increases in collagen deposition at the site of application of TGF-β. TGF-β is thus a potent pharmacologic agent that can accelerate wound healing in rats.
Primer-Directed Enzymatic Amplification of DNA with a Thermostable DNA Polymerase
Authors: Saiki Randall K. , Gelfand David H. , Stoffel Susanne , Scharf Stephen J. , Higuchi Russell , Horn Glenn T. , Mullis Kary B. , Erlich Henry A.
Published: October 2006

A thermostable DNA polymerase was used in an in vitro DNA amplification procedure, the polymerase chain reaction. The enzyme, isolated from
Thermus aquaticus
, greatly simplifies the procedure and, by enabling the amplification reaction to be performed at higher temperatures, significantly improves the specificity, yield, sensitivity, and length of products that can be amplified. Single-copy genomic sequences were amplified by a factor of more than 10 million with very high specificity, and DNA segments up to 2000 base pairs were readily amplified. In addition, the method was used to amplify and detect a target DNA molecule present only once in a sample of 10
5
cells.
Subset-Specific Expression of Potassium Channels in Developing Murine T Lymphocytes
Authors: Lewis Richard S. , Cahalan Michael D.
Published: October 2006

Ion channels were studied in four major subsets of developing murine thymocytes by using patch-clamp recording and cell-surface staining techniques. The expression of three types of voltage-gated potassium channels in thymocytes varies consistently with the cell′s developmental state and functional class as defined by cell-surface markers. One class of potassium channel (type
n
) predominates in immature thymocyte subsets as well as in mature-phenotype CD4
+
CD8
-
thymocytes (precursors to helper T lymphocytes), and the average surface density of this channel type correlates with the extent of cell proliferation. Two additional types of potassium channels (types
n
′ and
l
) are found in the mature CD4
-
CD8
+
thymocyte subset that contains precursors to cytotoxic and suppressor T cells. The subset-specific expression of type
n
′ and
l
potassium channels suggests their use as additional cell-surface markers with which to identify precursors to the cytotoxic suppressor T cell lineage.
Translocation as a Species Conservation Tool: Status and Strategy
Authors: Griffith Brad , Scott J. Michael , Carpenter James W. , Reed Christine
Published: October 2006

Surveys of recent (1973 to 1986) intentional releases of native birds and mammals to the wild in Australia, Canada, Hawaii, New Zealand, and the United States were conducted to document current activities, identify factors associated with success, and suggest guidelines for enhancing future work. Nearly 700 translocations were conducted each year. Native game species constituted 90 percent of translocations and were more successful (86 percent) than were translocations of threatened, endangered, or sensitive species (46 percent). Knowledge of habitat quality, location of release area within the species range, number of animals released, program length, and reproductive traits allowed correct classification of 81 percent of observed translocations as successful or not.
Gravitational Lens Optics
Authors: Blandford R. D. , Kochanek C. S. , Kovner Israel , Narayan Ramesh
Published: October 2006

Several instances of multiple imaging of cosmologically distant sources by intervening galaxies and galaxy clusters have been discovered over the past decade. These "gravitational lenses" have distinctive optical properties. Pointlike sources such as quasars generally produce two or four images when lensed, whereas extended sources such as galaxies produce spectacular arcs and rings. The salient features of most of the observations can be reproduced with the use of simple elliptical lens models that approximate the lenses made by ellipsoidal mass distributions such as are common in the universe. In addition to illustrating simple optics in operation on a cosmological scale, multiple images and arcs provide useful probes of the lensing galaxies and clusters. Also, gravitational lenses can make magnified images of cosmologically distant sources and may eventually furnish important cosmographic data such as the Hubble constant.
Prediction of New Low Compressibility Solids
Authors: Liu Amy Y. , Cohen Marvin L.
Published: October 2006

An empirical model and an ab initio calculation of the bulk moduli for covalent solids are used to suggest possible new hard materials. The empirical model indicates that hypothetical covalent solids formed between carbon and nitrogen are good candidates for extreme hardness. A prototype system is chosen and a first principles pseudopotential total energy calculation on the system is performed. The results are consistent with the empirical model and show that materials like the prototype can have bulk moduli comparable to or greater than diamond. It may be possible to synthesize such materials in the laboratory.
One Fifth of the Nation's Children: Why Are They Poor?
Authors: Bane Mary Jo , Ellwood David T.
Published: October 2006

Despite 20 years of concern about poverty, the most recent census figures show that 20 percent of children in the United States live in families with incomes below the poverty line. In understanding why, it is important to recognize the reasons for poverty among children in both two-parent working poor families and single-parent families. Examination of the evidence suggests that family poverty basically reflects the economic and social changes that affect most United States families.
Origin of Ancient Potash Evaporites: Clues from the Modern Nonmarine Qaidam Basin of Western China
Authors: Lowenstein Tim K. , Spencer Ronald J. , Pengxi Zhang
Published: October 2006

Modern potash salt deposits and associated brines of the Qaidam Basin, western China, demonstrate that some anomalous marine evaporites may have formed from nonmarine brines instead of seawater. Qaidam Basin brines are derived from meteoric river inflow mixed with small amounts of CaCl spring inflow similar in composition to many saline formation waters and hydrothermal brines. Evaporation of spring-enriched inflow yields a predicted mineral sequence including carnallite, bischofite, and tachyhydrite that is identical to several anomalous marine evaporites. Other mixtures of river and spring inflow produce the salt assemblage expected from evaporation of seawater.
A Chitin-Binding Lectin from Stinging Nettle Rhizomes with Antifungal Properties
Authors: Broekaert Willem F. , Van Parijs Jan , Leyns Frederik , Joos Henk , Peumans Willy J.
Published: October 2006

Rhizomes of stinging nettle contain a small-sized lectin that exhibits binding specificity toward chitin. This lectin inhibits growth of several phytopathogenic and saprophytic chitin-containing fungi in vitro. The antifungal action of the nettle lectin differs from the action of chitinases, which are a ubiquitous class of antifungal plant proteins. Moreover, the nettle lectin acts synergistically with chitinase in inhibiting fungal growth. The nettle lectin may be a promising candidate for possible applications in the genetic engineering of disease-resistant crops.
Reshaping Human Antibodies: Grafting an Antilysozyme Activity
Authors: Verhoeyen Martine , Milstein Cesar , Winter Greg
Published: October 2006

The production of therapeutic human monoclonal antibodies by hybridoma technology has proved difficult, and this has prompted the "humanizing" of mouse monoclonal antibodies by recombinant DNA techniques. It was shown previously that the binding site for a small hapten could be grafted from the heavy-chain variable domain of a mouse antibody to that of a human myeloma protein by transplanting the hypervariable loops. It is now shown that a large binding site for a protein antigen (lysozyme) can also be transplanted from mouse to human heavy chain. The success of such constructions may be facilitated by an induced-fit mechanism.
Changing the Identity of a tRNA by Introducing a G-U Wobble Pair Near the 3′ Acceptor End
Authors: McClain William H. , Foss K.
Published: October 2006

Although the genetic code for protein was established in the 1960's, the basis for amino acid identity of transfer RNA (tRNA) has remained unknown. To investigate the identity of a tRNA, the nucleotides at three computer-identified positions in tRNA
Phe
(phenylalanine tRNA) were replaced with the corresponding nucleotides from tRNA
Ala
(alanine tRNA). The identity of the resulting tRNA, when examined as an amber suppressor in
Escherichia coli
, was that of tRNA
Ala
.
Iron-Responsive Elements: Regulatory RNA Sequences That Control mRNA Levels and Translation
Authors: Casey John L. , Hentze Matthias W. , Koeller David M. , Caughman S. Wright , Rouault Tracey A. , Klausner Richard D. , Harford Joe B.
Published: October 2006

The biosynthetic rates for both the transferrin receptor (TfR) and ferritin are regulated by iron. An iron-responsive element (IRE) in the 5′ untranslated portion of the ferritin messenger RNA (mRNA) mediates iron-dependent control of its translation. In this report the 3′ untranslated region of the mRNA for the human TfR was shown to be necessary and sufficient for iron-dependent control of mRNA levels. Deletion studies identified a 678-nucleotide fragment of the TfR complementary DNA that is critical for this iron regulation. Five potential stem-loops that resemble the ferritin IRE are contained within the region critical for TfR regulation. Each of two of the five TfR elements was independently inserted into the 5′ untranslated region of an indicator gene transcript. In this location they conferred iron regulation of translation. Thus, an mRNA element has been implicated in the mediation of distinct regulatory phenomena dependent on the context of the element within the transcript.
Burgess Shale Faunas and the Cambrian Explosion
Authors: Morris S. Conway
Published: October 2006

Soft-bodied marine faunas from the Lower and Middle Cambrian, exemplified by the Burgess Shale of British Columbia, are a key component in understanding the major adaptive radiations at the beginning of the Phanerozoic ("Cambrian explosion"). These faunas have a widespread distribution, and many taxa have pronounced longevity. Among the components appear to be survivors of the preceding Ediacaran assemblages and a suite of bizarre forms that give unexpected insights into morphological diversification. Microevolutionary processes, however, seem adequate to account for this radiation, and the macroevolutionary patterns that set the seal on Phanerozoic life are contingent on random extinctions. They weeded out the morphological spectrum and permitted rediversification among surviving clades. Although the predictability of which clades will play in successive acts of the Phanerozoic theater is low, at least the outlines of the underlying ecological plot are already clear from the opening of the drama.
Angiosperm Diversification and Paleolatitudinal Gradients in Cretaceous Floristic Diversity
Authors: Crane Peter R. , Lidgard Scott
Published: October 2006

The latitudinally diachronous appearance of angiosperm pollen during the Cretaceous is well documented, but the subsequent diversification and accompanying significant changes in floristic dominance have not been assessed quantitatively for a wide range of paleolatitudes. Trend surfaces fitted to within-palynoflora diversity data from 1125 pollen and spore assemblages show that angiosperms first become floristically prominent in low paleolatitude areas (∼20°N to 20°S). Non-magnoliid dicotyledons show a similar but slightly delayed pattern of increase and are the principal component of angiosperm diversity from all areas sampled. Monocotyledons and magnoliid dicotyledons are significant primarily in low to middle paleolatitude palynofloras (∼50°N to 20°S) during the latest Cretaceous. As angiosperms become increasingly prevalent the importance of most non-angiosperm taxa either decreases or remains unchanged. The only apparent exception is a striking increase in gnetalean diversity concurrent with the initial angiosperm diversification at low paleolatitudes.
Mapping the Universe
Authors: Geller Margaret J. , Huchra John P.
Published: October 2006

Maps of the galaxy distribution in the nearby universe reveal large coherent structures. The extent of the largest features is limited only by the size of the survey. Voids with a density typically 20 percent of the mean and with diameters of 5000 km s
-1
are present in every survey large enough to contain them. Many galaxies lie in thin sheet-like structures. The largest sheet detected so far is the "Great Wall" with a minimum extent of 60
h
-1
Mpc × 170
h
-1
Mpc, where
h
is the Hubble constant in units of 100 km s
-1
Mpc
-1
. The frequent occurrence of these structures is one of several serious challenges to our current understanding of the origin and evolution of the large-scale distribution of matter in the universe.
Ultrafast Dynamics at Semiconductor and Metal Surfaces
Authors: Bokor J.
Published: October 2006

A variety of important dynamical phenomena at metal and semiconductor surfaces are now being investigated with the use of new ultrafast measurement techniques involving lasers and nonlinear optics. Understanding of the rates and mechanisms for relaxation of optical excitations of the surface itself as well as those of adsorbates on the surface is providing new insight into surface chemistry, surface phase transitions, and surface recombination of charge carriers in semiconductors.
Direct and Remote Sensing Observations of the Effects of Ships on Clouds
Authors: Radke Lawrence F. , Coakley James A. , King Michael D.
Published: October 2006

Under certain conditions ships can affect the structure of shallow layer clouds. Simultaneous observations of two ship track signatures in stratus clouds from a satellite and in situ from an aircraft show that in the ship tracks the droplet sizes were reduced and total concentrations of both droplets and particles were substantially increased from those in adjacent clouds. In situ measurements of the upwelling radiance within the ship tracks was significantly enhanced at visible wavelengths, whereas radiance at 2.2 micrometers was significantly reduced. Cloud reflectivity along the tracks was enhanced at 0.63 and 3.7 micrometers. These observations support the contention that ship track signatures in clouds are produced primarily by particles emitted from ships.
Ferroelectric Memories
Authors: Scott James F. , Paz de Araujo Carlos A.
Published: October 2006

In the past year it has become possible to fabricate ferroelectric thin-film memories onto standard silicon integrated circuits that combine very high speed (30-nanosecond read/erase/rewrite operation), 5-volt standard silicon logic levels, very high density (2 by 2 micrometer cell size), complete nonvolatility (no standby power required), and extreme radiation hardness. These ferroelectric random-access memories are expected to replace magnetic core memory, magnetic bubble memory systems, and electrically erasable read-only memory for many applications. The switching kinetics of these films, 100 to 300 nanometers thick, are now well understood, with switching times that fit an activation field dependence that scales applied field and temperature. Earlier problems of fatigue and retention failure are also now understood and have been improved to acceptable levels.
Infrared Observations of the Neptunian System
Authors: Conrath B. , Flasar F. M. , Hanel R. , Kunde V. , Maguire W. , Pearl J. , Pirraglia J. , Samuelson R. , Gierasch P. , Weir A. , Bezard B. , Gautier D. , Cruikshank D. , Horn L. , Springer R. , Shaffer W.
Published: October 2006

The infrared interferometer spectrometer on Voyager 2 obtained thermal emission spectra of Neptune with a spectral resolution of 4.3 cm-1. Measurements of reflected solar radiation were also obtained with a broadband radiometer sensitive in the visible and near infrared. Analysis of the strong C2H2emission feature at 729 cm-1suggests an acetylene mole fraction in the range between 9 × 10-8and 9 × 10-7. Vertical temperature profiles were derived between 30 and 1000 millibars at 70° and 42°S and 30°N. Temperature maps of the planet between 80°S and 30°N were obtained for two atmospheric layers, one in the lower stratosphere between 30 and 120 millibars and the other in the troposphere between 300 and 1000 millibars. Zonal mean temperatures obtained from these maps and from latitude scans indicate a relatively warm pole and equator with cooler mid-latitudes. This is qualitatively similar to the behavior found on Uranus even though the obliquities and internal heat fluxes of the two planets are markedly different. Comparison of winds derived from images with the vertical wind shear calculated from the temperature field indicates a general decay of wind speed with height, a phenomenon also observed on the other three giant planets. Strong, wavelike longitudinal thermal structure is found, some of which appears to be associated with the Great Dark Spot. An intense, localized cold region is seen in the lower stratosphere, which does not appear to be correlated with any visible feature. A preliminary estimate of the effective temperature of the planet yields a value of 59.3 ± 1.0 kelvins. Measurements of Triton provide an estimate of the daytime surface temperature of 38+3-4kelvins.
A Pituitary
N
-Acetylgalactosamine Transferase That Specifically Recognizes Glycoprotein Hormones
Authors: Smith Peter L. , Baenziger Jacques U.
Published: October 2006

The glycoprotein hormones lutropin (LH) and follitropin (FSH), which have common α-subunits but hormone-specific β-subunits, are both synthesized in the gonadotroph. However, they bear Asn-linked oligosaccharides that differ in structure. Those on LH terminate with the sequence SO
4
-4GalNAcβ1→4GlcNAcβ1→2Manα, whereas those on FSH terminate with the sequence sialic acidα-Galβ1→4GlcNAcβ1→2Manα. A GalNAc-transferase was identified in bovine pituitary membranes that recognizes features of the α-subunit peptide and adds GalNAc to its oligosaccharides with an apparent Michaelis constant of 25 micromolar. The different patterns of glycosylation for LH and FSH indicate that access to the protein recognition marker on the α-subunit is modulated by the associated β-subunit. The tightly regulated synthesis of sulfated and sialylated oligosaccharides on the pituitary glycoprotein hormones suggests these oligosaccharides have an important biological role.