bluuebunny/crossref_metadata_2025 huggingface dataset:
No Major Schizophrenia Locus Detected on Chromosome 1q in a Large Multicenter Sample
Authors: Levinson Douglas F. , Holmans Peter A. , Laurent Claudine , Riley Brien , Pulver Ann E. , Gejman Pablo V. , Schwab Sibylle G. , Williams Nigel M. , Owen Michael J. , Wildenauer Dieter B. , Sanders Alan R. , Nestadt Gerald , Mowry Bryan J. , Wormley Brandon , Bauché Stéphanie , Soubigou Stéphane , Ribble Robert , Nertney Deborah A. , Liang Kung Yee , Martinolich Laura , Maier Wolfgang , Norton Nadine , Williams Hywel , Albus Margot , Carpenter Eric B. , deMarchi Nicola , Ewen-White Kelly R. , Walsh Dermot , Jay Maurice , Deleuze Jean-François , O'Neill F. Anthony , Papadimitriou George , Weilbaecher Ann , Lerer Bernard , O'Donovan Michael C. , Dikeos Dimitris , Silverman Jeremy M. , Kendler Kenneth S. , Mallet Jacques , Crowe Raymond R. , Walters Marilyn
Published: July 2002

Reports of substantial evidence for genetic linkage of schizophrenia to chromosome 1q were evaluated by genotyping 16 DNA markers across 107 centimorgans of this chromosome in a multicenter sample of 779 informative schizophrenia pedigrees. No significant evidence was observed for such linkage, nor for heterogeneity in allele sharing among the eight individual samples. Separate analyses of European-origin families, recessive models of inheritance, and families with larger numbers of affected cases also failed to produce significant evidence for linkage. If schizophrenia susceptibility genes are present on chromosome 1q, their population-wide genetic effects are likely to be small.
Two-Photon Imaging of Lymphocyte Motility and Antigen Response in Intact Lymph Node
Authors: Miller Mark J. , Wei Sindy H. , Parker Ian , Cahalan Michael D.
Published: July 2002

Lymphocyte motility is vital for trafficking within lymphoid organs and for initiating contact with antigen-presenting cells. Visualization of these processes has previously been limited to in vitro systems. We describe the use of two-photon laser microscopy to image the dynamic behavior of individual living lymphocytes deep within intact lymph nodes. In their native environment, T cells achieved peak velocities of more than 25 micrometers per minute, displaying a motility coefficient that is five to six times that of B cells. Antigenic challenge changed T cell trajectories from random walks to “swarms” and stable clusters. Real-time two-photon imaging reveals lymphocyte behaviors that are fundamental to the initiation of the immune response.
Direct Cortical Control of 3D Neuroprosthetic Devices
Authors: Taylor Dawn M. , Tillery Stephen I. Helms , Schwartz Andrew B.
Published: July 2002

Three-dimensional (3D) movement of neuroprosthetic devices can be controlled by the activity of cortical neurons when appropriate algorithms are used to decode intended movement in real time. Previous studies assumed that neurons maintain fixed tuning properties, and the studies used subjects who were unaware of the movements predicted by their recorded units. In this study, subjects had real-time visual feedback of their brain-controlled trajectories. Cell tuning properties changed when used for brain-controlled movements. By using control algorithms that track these changes, subjects made long sequences of 3D movements using far fewer cortical units than expected. Daily practice improved movement accuracy and the directional tuning of these units.
Soil Fertility and Biodiversity in Organic Farming
Authors: Maeder Paul , Fliessbach Andreas , Dubois David , Gunst Lucie , Fried Padruot , Niggli Urs
Published: July 2002

An understanding of agroecosystems is key to determining effective farming systems. Here we report results from a 21-year study of agronomic and ecological performance of biodynamic, bioorganic, and conventional farming systems in Central Europe. We found crop yields to be 20% lower in the organic systems, although input of fertilizer and energy was reduced by 34 to 53% and pesticide input by 97%. Enhanced soil fertility and higher biodiversity found in organic plots may render these systems less dependent on external inputs.
Activation of Endothelial Cell Protease Activated Receptor 1 by the Protein C Pathway
Authors: Riewald Matthias , Petrovan Ramona J. , Donner Aaron , Mueller Barbara M. , Ruf Wolfram
Published: July 2002

The coagulant and inflammatory exacerbation in sepsis is counterbalanced by the protective protein C (PC) pathway. Activated PC (APC) was shown to use the endothelial cell PC receptor (EPCR) as a coreceptor for cleavage of protease activated receptor 1 (PAR1) on endothelial cells. Gene profiling demonstrated that PAR1 signaling could account for all APC-induced protective genes, including the immunomodulatory monocyte chemoattractant protein-1 (MCP-1), which was selectively induced by activation of PAR1, but not PAR2. Thus, the prototypical thrombin receptor is the target for EPCR-dependent APC signaling, suggesting a role for this receptor cascade in protection from sepsis.
Galileo Plasma Wave Observations in the Io Plasma Torus and Near Io
Authors: Gurnett D. A. , Kurth W. S. , Roux A. , Bolton S. J. , Kennel C. F.
Published: July 2002

The Galileo plasma wave instrument detected jovian radio emissions, narrowband upper hybrid waves, and whistler-mode emissions during the inbound pass through the Io torus. The upper hybrid waves provided an accurate profile of electron density through the Io torus and in the vicinity of Io. These measurements show that the torus density has increased by about a factor of 2 since the Voyager 1 flyby in 1979. A well-defined peak in the electron density was observed in the wake of Io, with densities as high as about 4 × 10
4
per cubic centimeter.
Hyperresponsive B Cells in CD22-Deficient Mice
Authors: O'Keefe Theresa L. , Williams Gareth T. , Davies Sarah L. , Neuberger Michael S.
Published: July 2002

CD22 is a surface glycoprotein of B lymphocytes that is rapidly phosphorylated on cytoplasmic tyrosines after antigen receptor cross-linking. Splenic B cells from mice with a disrupted CD22 gene were found to be hyperresponsive to receptor signaling: Heightened calcium fluxes and cell proliferation were obtained at lower ligand concentrations. The mice gave an augmented immune response, had an expanded peritoneal B-1 cell population, and contained increased serum titers of autoantibody. Thus, CD22 is a negative regulator of antigen receptor signaling whose onset of expression at the mature B cell stage may serve to raise the antigen concentration threshold required for B cell triggering.
Molecular Chaperone Machines: Chaperone Activities of the Cyclophilin Cyp-40 and the Steroid Aporeceptor-Associated Protein p23
Authors: Freeman Brian C. , Toft David O. , Morimoto Richard I.
Published: July 2002

Molecular chaperones are essential proteins that participate in the regulation of steroid receptors in eukaryotes. The steroid aporeceptor complex contains the molecular chaperones Hsp90 and Hsp70, p48, the cyclophilin Cyp-40, and the associated proteins p23 and p60. In vitro folding assays showed that Cyp-40 and p23 functioned as molecular chaperones in a manner similar to that of Hsp90 or Hsp70. Although neither Cyp-40 nor p23 could completely refold an unfolded substrate, both proteins interacted with the substrate to maintain a nonnative folding-competent intermediate. Thus, the steroid aporeceptor complexes have multiple chaperone components that maintain substrates in an intermediate folded state.
Copper-Catalyzed Oxidation of Alcohols to Aldehydes and Ketones: An Efficient, Aerobic Alternative
Authors: Markó István E. , Giles Paul R. , Tsukazaki Masao , Brown Stephen M. , Urch Chistopher J.
Published: July 2002

An efficient, copper-based catalyst has been discovered that oxidizes a wide range of alcohols into aldehydes and ketones under mild conditions. This catalytic system utilizes oxygen or air as the ultimate, stoichiometric oxidant, producing water as the only by-product.
Biotechnology: The Genomics Gamble
Authors: Cohen Jon
Published: July 2002

Drug companies, biotechs, and Wall Street investors are putting their money down on efforts to unlock the secrets of human DNA. But when will genomics deliver on its promise of next-generation drugs and treatments?

RELATED WEB SITES:

http://www.ornl.gov/sci/techresources/Human_Genome/home.html
A U.S. government-maintained Web page for news, policy guidelines, and ethics discussions centered on the international Human Genome Project.

http://www3.techstocks.com/~wsapi/investor/stocktalk-10
A private site where small investors chat, often with scant insight, about a wide variety of biotech stocks.

http://www.tradesmart.com/rumor/
The Biotech Rumor Mill, a gossip zone about biotech companies, much of it anonymous. (See the
site review
in Science's Next Wave.)

http://www.recap.com/
Recombinant Capital, a San Francisco consulting group directed by Mark Edwards. With detailed analytical information on biotech companies, their capitalization, and past press releases.

http://www.sec.gov/cgi-bin/srch-edgar
The U.S. Securities and Exchange Commission's search engine for looking up recent disclosures filed by public companies.
Recharge in Volcanic Systems: Evidence from Isotope Profiles of Phenocrysts
Authors: Davidson Jon P. , Tepley Frank J.
Published: July 2002

Strontium isotope ratios measured from core to rim across plagioclase feldspar crystals can be used to monitor changes in the isotope composition of the magma from which they grew. In samples from three magma systems from convergent margin volcanoes, sudden changes in major element composition, petrographic features, and strontium isotope composition were found to correspond to discrete magmatic events, most likely repeated recharge of more mafic magma with lower ratios of strontium-87 to strontium-86 into a crustally contaminated magma.
Prevention of Lysosomal Storage in Tay-Sachs Mice Treated with
N
-Butyldeoxynojirimycin
Authors: Platt Frances M. , Neises Gabrielle R. , Reinkensmeier Gabriele , Townsend Mandy J. , Perry V. Hugh , Proia Richard L. , Winchester Bryan , Dwek Raymond A. , Butters Terry D.
Published: July 2002

The glycosphingolipid (GSL) lysosomal storage diseases result from the inheritance of defects in the genes encoding the enzymes required for catabolism of GSLs within lysosomes. A strategy for the treatment of these diseases, based on an inhibitor of GSL biosynthesis
N
-butyldeoxynojirimycin, was evaluated in a mouse model of Tay-Sachs disease. When Tay-Sachs mice were treated with
N
-butyldeoxynojirimycin, the accumulation of G
M2
in the brain was prevented, with the number of storage neurons and the quantity of ganglioside stored per cell markedly reduced. Thus, limiting the biosynthesis of the substrate (G
M2
) for the defective enzyme (β-hexosaminidase A) prevents GSL accumulation and the neuropathology associated with its lysosomal storage.
Low-Mass Pre-Main Sequence Stars and Their X-ray Emission
Authors: Neuhäuser Ralph
Published: July 2002

To investigate the formation and early evolution of stars, astronomers study the x-ray emission of T Tauri stars, which are young, solar-mass stars called pre–main sequence stars. Two Earth-orbiting x-ray satellites, the Röntgen X-ray Satellite (ROSAT) and the Advanced Satellite for Cosmology and Astrophysics (ASCA), have discovered x-ray emission from young protostars, called Class I objects. Many T Tauri stars were detected as x-ray sources by ROSAT. X-ray luminosity functions and correlations with other stellar parameters can be studied and used to investigate the x-ray emission mechanism. From the ROSAT data hundreds of T Tauri stars have been discovered, some of which are located outside regions of ongoing star formation. Stellar x-rays also irradiate circumstellar disks, regions where planets may form, so x-ray emission data from T Tauri stars may also be used to investigate the formation of planets.
A Role for Ecotones in Generating Rainforest Biodiversity
Authors: Smith Thomas B. , Wayne Robert K. , Girman Derek J. , Bruford Michael W.
Published: July 2002

Gene flow and morphological divergence were measured among 12 populations of a common species of rainforest passerine. Populations in the forest and the ecotone (the transition zone between the African rainforest and savanna) are morphologically divergent, despite high gene flow, and morphological differences between habitats are as large as those found between related species. In contrast to past theories of rainforest speciation, which emphasize geographic isolation, these results suggest that natural selection may play an important role in generating rainforest biodiversity. Because ecotone habitats may be a source of evolutionary novelty, greater attention should be paid to their conservation in order to preserve the processes that may be important to maintain rainforest diversity.
The Influence of Island Area on Ecosystem Properties
Authors: Wardle David A. , Zackrisson Olle , Hörnberg Greger , Gallet Christiane
Published: July 2002

Island area is frequently a major determinant of the species composition of biological communities; community structure, in turn, often has important effects on ecosystem-level properties. Fifty islands of varying area were selected in an archipelago in the northern Swedish boreal forest zone, in which larger islands burn more frequently than smaller ones through wildfire arising from lightning strike, thus inducing a significant relationship between island area and plant species composition. This relationship was found to be a major factor in determining several ecosystem-level properties of these islands, including standing biomass, plant litter decomposition, nitrogen mineralization, terrestrial carbon partitioning, humus accumulation, and plant nitrogen acquisition.
Generation of Coherent X-rays in the Water Window Using 5-Femtosecond Laser Pulses
Authors: Spielmann Ch. , Burnett N. H. , Sartania S. , Koppitsch R. , Schnürer M. , Kan C. , Lenzner M. , Wobrauschek P. , Krausz F.
Published: July 2002

Coherent extreme-ultraviolet radiation extending to wavelengths below the carbon K edge at 4.37 nanometers (nm) has been generated at a repetition rate of 1 kilohertz by focusing 5-femtosecond near-infrared (780 nm) laser pulses into a helium gas jet. The incident light field performs just a few oscillations, which results in the emission of an x-ray supercontinuum rather than discrete harmonics. Owing to the extremely short rise time of the driving pulses, neutral atoms can be exposed to high fields before they are depleted by ionization. As a result, the observed x-ray radiation extends well into the water window and is delivered in a well-collimated beam (divergence less than 1 milliradian). The high repetition rate and spatial coherence result in a brightness of about 5 × 10
8
photons per square millimeter per square milliradian per second in a 1-percent bandwidth at 4.37 nm, the carbon edge of the water window. The compact laboratory system holds promise as a source for biological holography and nonlinear optics in the x-ray regime.
Recent Advances in Chemoprevention of Cancer
Authors: Hong Waun Ki , Sporn Michael B.
Published: July 2002

Chemoprevention is the use of pharmacologic or natural agents that inhibit the development of invasive cancer either by blocking the DNA damage that initiates carcinogenesis or by arresting or reversing the progression of premalignant cells in which such damage has already occurred. Recent advances in our understanding of the mechanisms of carcinogenesis have led to the synthesis of new drugs that can inhibit tumor development in experimental animals by selective action on specific molecular targets, such as the estrogen, androgen, and retinoid receptors or inducible cyclooxygenase. Several of these agents (including tamoxifen, 13-
cis
-retinoic acid, retinyl palmitate, and an acyclic retinoid) are clinically effective in preventing the development of cancer, particularly in patients who are at high risk for developing second primary tumors after surgical removal of the initial tumor.
Growth of SiO
2
at Room Temperature with the Use of Catalyzed Sequential Half-Reactions
Authors: Klaus Jason W. , Sneh Ofer , George Steven M.
Published: July 2002

Films of silicon dioxide (SiO
2
) were deposited at room temperature by means of catalyzed binary reaction sequence chemistry. The binary reaction SiCl
4
+ 2H
2
O → SiO
2
+ 4HCl was separated into SiCl
4
and H
2
O half-reactions, and the half-reactions were then performed in an ABAB … sequence and catalyzed with pyridine. The pyridine catalyst lowered the deposition temperature from >600 to 300 kelvin and reduced the reactant flux required for complete reactions from ∼10
9
to ∼10
4
Langmuirs. Growth rates of ∼2.1 angstroms per AB reaction cycle were obtained at room temperature for reactant pressures of 15 millitorr and 60-second exposure times with 200 millitorr of pyridine. This catalytic technique may be general and should facilitate the chemical vapor deposition of other oxide and nitride materials.
Femtosecond Dynamics of Electron Localization at Interfaces
Authors: Ge N.-H. , Wong C. M. , Lingle R. L. , McNeill J. D. , Gaffney K. J. , Harris C. B.
Published: July 2002

The dynamics of two-dimensional small-polaron formation at ultrathin alkane layers on a silver(111) surface have been studied with femtosecond time- and angle-resolved two-photon photoemission spectroscopy. Optical excitation creates interfacial electrons in quasi-free states for motion parallel to the interface. These initially delocalized electrons self-trap as small polarons in a localized state within a few hundred femtoseconds. The localized electrons then decay back to the metal within picoseconds by tunneling through the adlayer potential barrier. The energy dependence of the self-trapping rate has been measured and modeled with a theory analogous to electron transfer theory. This analysis determines the inter- and intramolecular vibrational modes of the overlayer responsible for self-trapping as well as the relaxation energy of the overlayer molecular lattice. These results for a model interface contribute to the fundamental picture of electron behavior in weakly bonded solids and can lead to better understanding of carrier dynamics in many different systems, including organic light-emitting diodes.
Resilient Quantum Computation
Authors: Knill Emanuel , Laflamme Raymond , Zurek Wojciech H.
Published: July 2002

Practical realization of quantum computers will require overcoming decoherence and operational errors, which lead to problems that are more severe than in classical computation. It is shown that arbitrarily accurate quantum computation is possible provided that the error per operation is below a threshold value.
Conjugative Transfer by the Virulence System of
Legionella pneumophila
Authors: Vogel Joseph. P. , Andrews Helene L. , Wong Swee Kee , Isberg Ralph R.
Published: July 2002

Legionella pneumophila
, the causative agent of Legionnaires' pneumonia, replicates within alveolar macrophages by preventing phagosome-lysosome fusion. Here, a large number of mutants called
dot
(defective for organelle trafficking) that were unable to replicate intracellularly because of an inability of the bacteria to alter the endocytic pathway of macrophages were isolated. The
dot
virulence genes encoded a large putative membrane complex that functioned as a secretion system that was able to transfer plasmid DNA from one cell to another.
Gastrointestinal Tract as a Major Site of CD4
+
T Cell Depletion and Viral Replication in SIV Infection
Authors: Veazey Ronald S. , DeMaria MaryAnn , Chalifoux Laura V. , Shvetz Daniel E. , Pauley Douglas R. , Knight Heather L. , Rosenzweig Michael , Johnson R. Paul , Desrosiers Ronald C. , Lackner Andrew A.
Published: July 2002

Human and simian immunodeficiency virus (HIV and SIV) replicate optimally in activated memory CD4
+
T cells, a cell type that is abundant in the intestine. SIV infection of rhesus monkeys resulted in profound and selective depletion of CD4
+
T cells in the intestine within days of infection, before any such changes in peripheral lymphoid tissues. The loss of CD4
+
T cells in the intestine occurred coincident with productive infection of large numbers of mononuclear cells at this site. The intestine appears to be a major target for SIV replication and the major site of CD4
+
T cell loss in early SIV infection.
Plutonium-Fission Xenon Found in Earth's Mantle
Authors: Kunz Joachim , Staudacher Thomas , Allègre Claude J.
Published: July 2002

Data from mid-ocean ridge basalt glasses indicate that the short-lived radionuclide plutonium-244 that was present during an early stage of the development of the solar system is responsible for roughly 30 percent of the fissiogenic xenon excesses in the interior of Earth today. The rest of the fissiogenic xenon can be ascribed to the spontaneous fission of still live uranium-238. This result, in combination with the refined determination of xenon-129 excesses from extinct iodine-129, implies that the accretion of Earth was finished roughly 50 million to 70 million years after solar system formation and that the atmosphere was formed by mantle degassing.
Bloodstream- Versus Tick-Associated Variants of a Relapsing Fever Bacterium
Authors: Schwan Tom G. , Hinnebusch B. Joseph
Published: July 2002

The relapsing fever spirochete,
Borrelia hermsii
, alternates infections between a mammal and a tick vector. Whether the spirochete changes phenotypically in the different hosts was examined by allowing the tick vector
Ornithodoros hermsi
to feed on mice infected with serotype 7 or serotype 8 of
B. hermsii.
Upon infection of ticks, the spirochetal serotype-specific variable major proteins (Vmps) 7 and 8 became undetectable and were replaced by Vmp33. This switch from a bloodstream- to tick-associated phenotype could be induced in culture by a decrease in temperature. After tick-bite transmission back to mice, the process was reversed and the spirochetes resumed expression of the same Vmp present in the previous infectious blood meal.
Gating of CaMKII by cAMP-Regulated Protein Phosphatase Activity During LTP
Authors: Blitzer Robert D. , Connor John H. , Brown George P. , Wong Tony , Shenolikar Shirish , Iyengar Ravi , Landau Emmanuel M.
Published: July 2002

Long-term potentiation (LTP) at the Schaffer collateral–CA1 synapse involves interacting signaling components, including calcium (Ca
2+
)/calmodulin–dependent protein kinase II (CaMKII) and cyclic adenosine monophosphate (cAMP) pathways. Postsynaptic injection of thiophosphorylated inhibitor-1 protein, a specific inhibitor of protein phosphatase–1 (PP1), substituted for cAMP pathway activation in LTP. Stimulation that induced LTP triggered cAMP-dependent phosphorylation of endogenous inhibitor-1 and a decrease in PP1 activity. This stimulation also increased phosphorylation of CaMKII at Thr
286
and Ca
2+
-independent CaMKII activity in a cAMP-dependent manner. The blockade of LTP by a CaMKII inhibitor was not overcome by thiophosphorylated inhibitor-1. Thus, the cAMP pathway uses PP1 to gate CaMKII signaling in LTP.
Cholinergic Switching Within Neocortical Inhibitory Networks
Authors: Xiang Zixiu , Huguenard John R. , Prince David A.
Published: July 2002

Differential actions of acetylcholine on the excitability of two subtypes of interneurons in layer V of the rat visual cortex were examined. Acetylcholine excited low-threshold spike (LTS) cells through nicotinic receptors, whereas it elicited hyperpolarization in fast spiking (FS) cells through muscarinic receptors. Axons of LTS cells were mainly distributed vertically to upper layers, and those of FS cells were primarily confined to layer V. Thus, cortical cholinergic activation may reduce some forms of intralaminar inhibition, promote intracolumnar inhibition, and change the direction of information flow within cortical circuits.
Determinants of Kinesin Motor Polarity
Authors: Endow Sharyn A. , Waligora Kimberly W.
Published: July 2002

The kinesin motor protein family members move along microtubules with characteristic polarity. Chimeric motors containing the stalk and neck of the minus-end-directed motor, Ncd, fused to the motor domain of plus-end-directed kinesin were analyzed. The Ncd stalk and neck reversed kinesin motor polarity, but mutation of the Ncd neck reverted the chimeric motor to plus-end movement. Thus, residues or regions contributing to motor polarity must be present in both the Ncd neck and the kinesin motor core. The neck-motor junction was critical for Ncd minus-end movement; attachment of the neck to the stalk may also play a role.
Prevention of Cardiac Hypertrophy in Mice by Calcineurin Inhibition
Authors: Sussman Mark A. , Lim Hae W. , Gude Natalie , Taigen Tyler , Olson Eric N. , Robbins Jeffrey , Colbert Melissa C. , Gualberto Antonio , Wieczorek David F. , Molkentin Jeffery D.
Published: July 2002

Hypertrophic cardiomyopathy (HCM) is an inherited form of heart disease that affects 1 in 500 individuals. Here it is shown that calcineurin, a calcium-regulated phosphatase, plays a critical role in the pathogenesis of HCM. Administration of the calcineurin inhibitors cyclosporin and FK506 prevented disease in mice that were genetically predisposed to develop HCM as a result of aberrant expression of tropomodulin, myosin light chain–2, or fetal β-tropomyosin in the heart. Cyclosporin had a similar effect in a rat model of pressure-overload hypertrophy. These results suggest that calcineurin inhibitors merit investigation as potential therapeutics for certain forms of human heart disease.
Oxygen Reservoirs in the Early Solar Nebula Inferred from an Allende CAI
Authors: Young Edward D. , Russell Sara S.
Published: July 2002

Ultraviolet laser microprobe analyses of a calcium-aluminum–rich inclusion (CAI) from the Allende meteorite suggest that a line with a slope of exactly 1.00 on a plot of δ
17
O against δ
18
O represents the primitive oxygen isotope reservoir of the early solar nebula. Most meteorites are enriched in
17
O and
18
O relative to this line, and their oxygen isotope ratios can be explained by mass fractionation or isotope exchange initiating from the primitive reservoir. These data establish a link between the oxygen isotopic composition of the abundant ordinary chondrites and the primitive
16
O-rich component of CAIs.
Pressure-Induced Landau-Type Transition in Stishovite
Authors: Andrault Denis , Fiquet Guillaume , Guyot François , Hanfland Michael
Published: July 2002

A Rietveld structural analysis of stishovite, with angle-dispersive x-ray diffraction synchrotron source at the European Synchrotron Radiation Facility, confirmed a CaCl
2
form of stishovite distortion at 54 ± 1 gigapascals but confirmed no further phase transformation up to 120 gigapascals. The deviatoric stress that is usually encountered at such pressures was relaxed after yttrium-aluminum-garnet–laser heating. A single Birch-Murnaghan equation of state fits volumes of stishovite and a CaCl
2
form, showing that the tetragonal distortion occurs without a substantial change in volume. At the 54-gigapascal transition, the pressure-induced lattice modifications were similar to those found in a Landau-type temperature-induced transition. It is proposed that, above the transition pressure, the critical temperature increases above 300 kelvin, so that the lower entropy form becomes stable.
Presolar Corundum and Spinel in Ordinary Chondrites: Origins from AGB Stars and a Supernova
Authors: Choi Byeon-Gak , Huss Gary R. , Wasserburg G. J. , Gallino Roberto
Published: July 2002

On the basis of anomalous isotopic compositions of oxygen and magnesium, 14 oxide grains from two primitive meteorites (Bishunpur and Semarkona) have been identified as circumstellar condensates. One corundum grain has a high18O/16O ratio and isotopic compositions of magnesium, calcium, and titanium that are compatible with a formation in ejecta of a type II supernova that was about 15 times the mass of the sun. The other grains have oxygen, magnesium, and titanium compositions that are consistent with a formation around asymptotic giant branch (AGB) stars with a range of mass and initial composition. The large range of aluminum/magnesium in circumstellar corundum and spinel is considered to reflect various stages of back-reaction between condensed corundum and gaseous magnesium in cooling stellar ejecta.
Mass-Independent Isotope Effects in Planetary Atmospheres and the Early Solar System
Authors: Thiemens Mark H.
Published: July 2002

A class of isotope effects that alters isotope ratios on a mass-independent basis provides a tool for studying a wide range of processes in atmospheres of Earth and other planets as well as early processes in the solar nebula. The mechanism for the effect remains uncertain. Mass-independent isotopic compositions have been observed in O3, CO2, N2O, and CO in Earth's atmosphere and in carbonate from a martian meteorite, which suggests a role for mass-independent processes in the atmosphere of Mars. Observed mass-independent meteoritic oxygen and sulfur isotopic compositions may derive from chemical processes in the presolar nebula, and their distributions could provide insight into early solar system evolution.
16O Excesses in Olivine Inclusions in Yamato-86009 and Murchison Chondrites and Their Relation to CAIs
Authors: Hiyagon Hajime , Hashimoto Akihiko
Published: July 2002

In situ ion microprobe analyses of oxygen isotopes in Yamato-86009 and Murchison chondrites show that they contain abundant olivine-rich inclusions that have large oxygen-16 (16O) excesses, similar to those in spinel grains in calcium-aluminium–rich inclusions in Allende and other carbonaceous chondrites. The existence of16O-enriched olivine-rich inclusions suggests that oxygen isotopic anomalies were more extensive in the early solar system than was previously thought and that their origin may be attributed to a nebular chemical process rather than to an unidentified16O-rich carrier of presolar origin.
Degradation Mechanism of Small Molecule-Based Organic Light-Emitting Devices
Authors: Aziz Hany , Popovic Zoran D. , Hu Nan-Xing , Hor Ah-Mee , Xu Gu
Published: July 2002

Studies on the long-term degradation of organic light-emitting devices (OLEDs) based on tris(8-hydroxyquinoline) aluminum (AlQ3), the most widely used electroluminescent molecule, reveal that injection of holes in AlQ3is the main cause of device degradation. The transport of holes into AlQ3caused a decrease in its fluorescence quantum efficiency, thus showing that cationic AlQ3species are unstable and that their degradation products are fluorescence quenchers. These findings explain the success of different approaches to stabilizing OLEDs, such as doping of the hole transport layer, introducing a buffer layer at the hole-injecting contact, and using mixed emitting layers of hole and electron transporting molecules.
High-Resolution Holocene Environmental Changes in the Thar Desert, Northwestern India
Authors: Enzel Y. , Ely L. L. , Mishra S. , Ramesh R. , Amit R. , Lazar B. , Rajaguru S. N. , Baker V. R. , Sandler A.
Published: July 2002

Sediments from Lunkaransar dry lake in northwestern India reveal regional water table and lake level fluctuations over decades to centuries during the Holocene that are attributed to changes in the southwestern Indian monsoon rains. The lake levels were very shallow and fluctuated often in the early Holocene and then rose abruptly around 6300 carbon-14 years before the present (
14
C yr B.P.). The lake completely desiccated around 4800
14
C yr B.P. The end of this 1500-year wet period coincided with a period of intense dune destabilization. The major Harrapan-Indus civilization began and flourished in this region 1000 years after desiccation of the lake during arid climate and was not synchronous with the lacustral phase.
Silica Sol as a Nanoglue: Flexible Synthesis of Composite Aerogels
Authors: Morris Catherine A. , Anderson Michele L. , Stroud Rhonda M. , Merzbacher Celia I. , Rolison Debra R.
Published: July 2002

Low-density nanoscale mesoporous composites may be readily synthesized by adding a colloidal or dispersed solid to an about-to-gel silica sol. The silica sol can “glue” a range of chemically and physically diverse particles into the three-dimensional silica network formed upon gelation. If the composite gel is supercritically dried so as to maintain the high porosity of the wet gel, a composite aerogel is formed in which the nanoscopic surface and bulk properties of each component are retained in the solid composite. The volume fraction of the second solid can be varied above or below a percolation threshold to tune the transport properties of the composite aerogel and thereby design nanoscale materials for chemical, electronic, and optical applications.
Adsorbed Layers and the Origin of Static Friction
Authors: He Gang , Müser Martin H. , Robbins Mark O.
Published: July 2002

Analytic results and experiments in ultrahigh vacuum indicate that the static friction between two clean crystalline surfaces should almost always vanish, yet macroscopic objects always exhibit static friction. A simple and general explanation for the prevalence of static friction is proposed. “Third bodies,” such as small hydrocarbon molecules, adsorb on any surface exposed to air and can arrange to lock two contacting surfaces together. The resulting static friction is consistent with experimental behavior, including Amontons' laws.
Identification of a Vertebrate Sister-Chromatid Separation Inhibitor Involved in Transformation and Tumorigenesis
Authors: Zou Hui , McGarry Thomas J. , Bernal Teresita , Kirschner Marc W.
Published: July 2002

A vertebrate securin (vSecurin) was identified on the basis of its biochemical analogy to the Pds1p protein of budding yeast and the Cut2p protein of fission yeast. The vSecurin protein bound to a vertebrate homolog of yeast separins Esp1p and Cut1p and was degraded by proteolysis mediated by an anaphase-promoting complex in a manner dependent on a destruction motif. Furthermore, expression of a stableXenopussecurin mutant protein blocked sister-chromatid separation but did not block the embryonic cell cycle. The vSecurin proteins share extensive sequence similarity with each other but show no sequence similarity to either of their yeast counterparts. Human securin is identical to the product of the gene called pituitary tumor-transforming gene (PTTG), which is overexpressed in some tumors and exhibits transforming activity in NIH 3T3 cells. The oncogenic nature of increased expression of vSecurin may result from chromosome gain or loss, produced by errors in chromatid separation.
Historical Genetics: The Parentage of Chardonnay, Gamay, and Other Wine Grapes of Northeastern France
Authors: Bowers John , Boursiquot Jean-Michel , This Patrice , Chu Kieu , Johansson Henrik , Meredith Carole
Published: July 2002

The origins of the classic European wine grapes (
Vitis vinifera
) have been the subject of much speculation. In a search for parental relationships, microsatellite loci were analyzed in more than 300 grape cultivars. Sixteen wine grapes that have long been grown in northeastern France, including ‘Chardonnay’, ‘Gamay noir’, ‘Aligoté’, and ‘Melon’, have microsatellite genotypes consistent with their being the progeny of a single pair of parents, ‘Pinot’ and ‘Gouais blanc’, both of which were widespread in this region in the Middle Ages. Parentage analysis at 32 microsatellite loci provides statistical support for these relationships.
Shape Representations and Visual Guidance of Saccadic Eye Movements
Authors: Moore Tirin
Published: July 2002

One hallmark of primate vision is that the direction of gaze is constantly shifting to position objects of interest appropriately on the fovea, where visual acuity is greatest. This process must involve the close cooperation of oculomotor and visual recognition mechanisms because visual details must be translated into specific motor commands. This paper describes the correspondence between the presaccadic activity of V4 neurons and the degree of visual guidance of saccadic eye movements to objects of different form. The results suggest that neurons that participate in coding visual stimuli are also involved in guiding the eyes to prominent features of objects.
Primordial Noble Gases from Earth's Mantle: Identification of a Primitive Volatile Component
Authors: Caffee M. W. , Hudson G. B. , Velsko C. , Huss G. R. , Alexander E. C. , Chivas A. R.
Published: July 2002

Carbon dioxide well gases in Colorado, New Mexico, and South Australia show excesses of
124–128
Xe correlated with
129
I-derived
129
Xe and
20
Ne/
22
Ne ratios that are higher than the atmospheric
20
Ne/
22
Ne ratio. The xenon isotopic data indicate the presence of a solarlike component deep within Earth. The presence of this component in crustal and upper mantle reservoirs may be explained by a steady-state transport of noble gases from the lower mantle, which still retains much of its juvenile volatile inventory. These measurements also indicate that the mantle source of these noble gases in the carbon dioxide well gases cannot be the source of Earth's present atmosphere. The variations observed in
129
Xe/
130
Xe between solar wind xenon, Earth's atmosphere, and mantle samples may be generated by variations of iodine/xenon in terrestrial reservoirs, as opposed to rapid early degassing.
Anaerobic Microbes: Oxygen Detoxification Without Superoxide Dismutase
Authors: Jenney Francis E. , Verhagen Marc F. J. M. , Cui Xiaoyuan , Adams Michael W. W.
Published: July 2002

Superoxide reductase from the hyperthermophilic anaerobe
Pyrococcus furiosus
uses electrons from reduced nicotinamide adenine dinucleotide phosphate, by way of rubredoxin and an oxidoreductase, to reduce superoxide to hydrogen peroxide, which is then reduced to water by peroxidases. Unlike superoxide dismutase, the enzyme that protects aerobes from the toxic effects of oxygen, SOR does not catalyze the production of oxygen from superoxide and therefore confers a selective advantage on anaerobes. Superoxide reductase and associated proteins are catalytically active 80°C below the optimum growth temperature (100°C) of
P. furiosus
, conditions under which the organism is likely to be exposed to oxygen.
A Systems Perspective on Early Olfactory Coding
Authors: Laurent Gilles
Published: July 2002

This review critically examines neuronal coding strategies and how they might apply to olfactory processing. Basic notions such as identity, spatial, temporal, and correlation codes are defined and different perspectives are brought to the study of neural codes. Odors as physical stimuli and their processing by the early olfactory system, one or two synapses away from the receptors, are discussed. Finally, the concept of lateral inhibition, as usually understood and applied to odor coding by mitral (or equivalent) cells, is challenged and extended to a broader context, possibly more appropriate for olfactory processing.
Opposite Patterns of Synchrony in Sympatric Disease Metapopulations
Authors: Rohani Pejman , Earn David J. D. , Grenfell Bryan T.
Published: July 2002

Measles epidemics in UK cities, which were regular and highly synchronous before vaccination, are known to have become irregular and spatially uncorrelated in the vaccine era. Whooping cough shows the reverse pattern, namely a shift from spatial incoherence and irregularity before vaccination to regular, synchronous epidemics afterward. Models show that these patterns can arise from disease-specific responses to dynamical noise. This analysis has implications for vaccination strategies and illustrates the power of comparative dynamical studies of sympatric metapopulations.
Plant Diversity and Productivity Experiments in European Grasslands
Authors: Hector A. , Schmid B. , Beierkuhnlein C. , Caldeira M. C. , Diemer M. , Dimitrakopoulos P. G. , Finn J. A. , Freitas H. , Giller P. S. , Good J. , Harris R. , Högberg P. , Huss-Danell K. , Joshi J. , Jumpponen A. , Körner C. , Leadley P. W. , Loreau M. , Minns A. , Mulder C. P. H. , O'Donovan G. , Otway S. J. , Pereira J. S. , Prinz A. , Read D. J. , Scherer-Lorenzen M. , Schulze E.-D. , Siamantziouras A.-S. D. , Spehn E. M. , Terry A. C. , Troumbis A. Y. , Woodward F. I. , Yachi S. , Lawton J. H.
Published: July 2002

At eight European field sites, the impact of loss of plant diversity on primary productivity was simulated by synthesizing grassland communities with different numbers of plant species. Results differed in detail at each location, but there was an overall log-linear reduction of average aboveground biomass with loss of species. For a given number of species, communities with fewer functional groups were less productive. These diversity effects occurred along with differences associated with species composition and geographic location
.
Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool.
Global Measurements of Stratospheric Mountain Waves from Space
Authors: Eckermann Stephen D. , Preusse and Peter
Published: July 2002

Temperatures acquired by the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) during shuttle mission STS-66 have provided measurements of stratospheric mountain waves from space. Large-amplitude, long-wavelength mountain waves at heights of 15 to 30 kilometers above the southern Andes Mountains were observed and characterized, with vigorous wave breaking inferred above 30 kilometers. Mountain waves also occurred throughout the stratosphere (15 to 45 kilometers) over a broad mountainous region of central Eurasia. The global distribution of mountain wave activity accords well with predictions from a mountain wave model. The findings demonstrate that satellites can provide the global data needed to improve mountain wave parameterizations and hence global climate and forecast models.
Mechanical Rotation of the c Subunit Oligomer in ATP Synthase (F
0
F
1
): Direct Observation
Authors: Sambongi Yoshihiro , Iko Yuko , Tanabe Mikio , Omote Hiroshi , Iwamoto-Kihara Atsuko , Ueda Ikuo , Yanagida Toshio , Wada Yoh , Futai Masamitsu
Published: July 2002

F
0
F
1
, found in mitochondria or bacterial membranes, synthesizes adenosine 5′-triphosphate (ATP) coupling with an electrochemical proton gradient and also reversibly hydrolyzes ATP to form the gradient. An actin filament connected to a c subunit oligomer of F
0
was able to rotate by using the energy of ATP hydrolysis. The rotary torque produced by the c subunit oligomer reached about 40 piconewton-nanometers, which is similar to that generated by the γ subunit in the F
1
motor. These results suggest that the γ and c subunits rotate together during ATP hydrolysis and synthesis. Thus, coupled rotation may be essential for energy coupling between proton transport through F
0
and ATP hydrolysis or synthesis in F
1
.
Chemokines and Cell Migration in Secondary Lymphoid Organs
Authors: Cyster Jason G.
Published: July 2002

As few as one in 100,000 B and T lymphocytes are specific for a single protein antigen, such as tetanus toxin, yet these cells must come together if an antibody response is to occur. Bringing antigen-presenting cells and rare antigen-specific B and T lymphocytes into physical contact is a principal function of secondary lymphoid organs. In the last few years, details have begun to emerge on the cues that guide cell movements inside lymphoid organs, and a central role for the chemokine family of molecules has been uncovered. Here, current understanding of the roles played by chemokines in the functional biology of secondary lymphoid organs will be reviewed.
Direct Observation of Dynamical Heterogeneities in Colloidal Hard-Sphere Suspensions
Authors: Kegel Willem K. , van Blaaderen and Alfons
Published: July 2002

The real-space dynamics in a model system of colloidal hard spheres was studied by means of time-resolved fluorescence confocal scanning microscopy. Direct experimental evidence for the presence of dynamical heterogeneities in a dense liquid was obtained from an analysis of particle trajectories in two-dimensional slices of the bulk sample. These heterogeneities manifest themselves as a non-Gaussian probability distribution of particle displacements and also affect the onset of long-time diffusive behavior.
Rapid Evolution of a Geographic Cline in Size in an Introduced Fly
Authors: Huey Raymond B. , Gilchrist George W. , Carlson Margen L. , Berrigan David , Serra § Luı́s
Published: July 2002

The introduction and rapid spread of
Drosophila subobscura
in the New World two decades ago provide an opportunity to determine the predictability and rate of evolution of a geographic cline. In ancestral Old World populations, wing length increases clinally with latitude. In North American populations, no wing length cline was detected one decade after the introduction. After two decades, however, a cline has evolved and largely converged on the ancestral cline. The rate of morphological evolution on a continental scale is very fast, relative even to rates measured within local populations. Nevertheless, different wing sections dominate the New versus Old World clines. Thus, the evolution of geographic variation in wing length has been predictable, but the means by which the cline is achieved is contingent.
A Tale of Two Futures: HIV and Antiretroviral Therapy in San Francisco
Authors: Blower S. M. , Gershengorn H. B. , Grant R. M.
Published: July 2002

The effect of antiretroviral therapy (ART) in preventing human immunodeficiency virus (HIV) infections and averting acquired immunodeficiency syndrome (AIDS) deaths in the San Francisco gay community over the next 10 years was predicted. A transmission model was coupled with a statistical approach that enabled inclusion of a high degree of uncertainty in the potential treatment effects of ART (in terms of infectivity and survival), increase in risky behavior, and rate of emergence of drug resistance. Increasing the usage of ART in San Francisco would decrease the AIDS death rate and could substantially reduce the incidence rate.
Two-Dimensional Electronic Excitations in Self-Assembled Conjugated Polymer Nanocrystals
Authors: Österbacka R. , An C. P. , Jiang X. M. , Vardeny Z. V.
Published: July 2002

Several spectroscopic methods were applied to study the characteristic properties of the electronic excitations in thin films of regioregular and regiorandom polythiophene polymers. In the regioregular polymers, which form two-dimensional lamellar structures, increased interchain coupling strongly influences the traditional one-dimensional electronic properties of the polymer chains. The photogenerated charge excitations (polarons) show two-dimensional delocalization that results in a relatively small polaronic energy, multiple absorption bands in the gap where the lowest energy band becomes dominant, and associated infrared active vibrations with reverse absorption bands caused by electron-vibration interferences. The relatively weak absorption bands of the delocalized polaron in the visible and near-infrared spectral ranges may help to achieve laser action in nanocrystalline polymer devices using current injection.
Ethanol-Induced Apoptotic Neurodegeneration and Fetal Alcohol Syndrome
Authors: Ikonomidou Chrysanthy , Bittigau Petra , Ishimaru Masahiko J. , Wozniak David F. , Koch Christian , Genz Kerstin , Price Madelon T. , Stefovska Vanya , Hörster Friederike , Tenkova Tanya , Dikranian Krikor , Olney John W.
Published: July 2002

The deleterious effects of ethanol on the developing human brain are poorly understood. Here it is reported that ethanol, acting by a dual mechanism [blockade of
N
-methyl-
d
-aspartate (NMDA) glutamate receptors and excessive activation of GABA
A
receptors], triggers widespread apoptotic neurodegeneration in the developing rat forebrain. Vulnerability coincides with the period of synaptogenesis, which in humans extends from the sixth month of gestation to several years after birth. During this period, transient ethanol exposure can delete millions of neurons from the developing brain. This can explain the reduced brain mass and neurobehavioral disturbances associated with human fetal alcohol syndrome.