bluuebunny/crossref_metadata_2025 huggingface dataset:
Dinosaurs on the North Slope, Alaska: High Latitude, Latest Cretaceous Environments
Authors: Brouwers Elisabeth M. , Clemens William A. , Spicer Robert A. , Ager Thomas A. , Carter L. David , Sliter William V.
Published: October 2006

Abundant skeletal remains demonstrate that lambeosaurine hadrosaurid, tyrannosaurid, and troodontid dinosaurs lived on the Alaskan North Slope during late Campanian—early Maestrichtian time (about 66 to 76 million years ago) in a deltaic environment dominated by herbaceous vegetation. The high ground terrestrial plant community was a mild- to cold-temperate forest composed of coniferous and broad leaf trees. The high paleolatitude (about 70° to 85° North) implies extreme seasonal variation in solar insolation, temperature, and herbivore food supply. Great distances of migration to contemporaneous evergreen floras and the presence of both juvenile and adult hadrosaurs suggest that they remained at high latitudes year-round. This challenges the hypothesis that short-term periods of darkness and temperature decrease resulting from a bolide impact caused dinosaurian extinction.
Stimulation of Phospholipase C-γ1 Membrane Association by Epidermal Growth Factor
Authors: Todderud Gordon , Wahl Matthew I. , Rhee Sue Goo , Carpenter Graham
Published: October 2006

Epidermal growth factor (EGF) treatment of A-431 epidermoid carcinoma cells elicited a redistribution of phospholipase C-γ1 (PLC-γ1) from a predominantly cytosolic localization to membrane fractions. The temporal coincidence of this redistribution with EGF stimulation of inositol phosphate formation and EGF increased phosphorylation of PLC-γ1 suggests that the membrane association of PLC-γ1 is a significant event in second messenger transduction.
X-ray Photographs of a Solar Active Region with a Multilayer Telescope at Normal Incidence
Authors: Underwood J. H. , Bruner M. E. , Haisch B. M. , Brown W. A. , Acton L. W.
Published: October 2006

An astronomical photograph was obtained with a multilayer x-ray telescope. A 4-centimeter tungsten-carbon multilayer mirror was flown as part of an experimental solar rocket payload, and successful images were taken of the sun at normal incidence at a wavelength of 44 angstroms. Coronal Si-XII emission from an active region was recorded on film; as expected, the structure is very similar to that observed at O-VIII wavelengths by the Solar Maximum Mission flat crystal spectrometer at the same time. The small, simple optical system used in this experiment appears to have achieved a resolution of 5 to 10 arc seconds.
Was Venus Wet? Deuterium Reconsidered
Authors: Grinspoon David H.
Published: October 2006

The ratio of deuterium to hydrogen on Venus has been accepted as proof of a wetter, more Earth-like past on that planet. However, the present-day water abundance and the nonthermal hydrogen escape flux on Venus imply that hydrogen is in a steady state and that a hydrogen source, most likely cometary infall, is present. An alternative interpretation of the D/H ratio is offered, in which the measured value is consistent with a steady-state evolution over the age of the solar system. No past water excess is required to explain the isotopic data.
Target-Dependent Structural Changes Accompanying Long-Term Synaptic Facilitation in
Aplysia
Neurons
Authors: Glanzman David L. , Kandel Eric R. , Schacher Samuel
Published: October 2006

The mechanisms underlying structural changes that accompany learning and memory have been difficult to investigate in the intact nervous system. In order to make these changes more accessible for experimental analysis, dissociated cell culture and low-light-level video microscopy were used to examine
Aplysia
sensory neurons in the presence or absence of their target cells. Repeated applications of serotonin, a facilitating transmitter important in behavioral dishabituation and sensitization, produced growth of the sensory neurons that paralleled the long-term enhancement of synaptic strength. This growth required the presence of the postsynaptic motor neuron. Thus, both the structural changes and the synaptic facilitation of
Aplysia
sensorimotor synapses accompanying long-term behavioral sensitization can be produced in vitro by applying a single facilitating transmitter repeatedly. These structural changes depend on an interaction of the presynaptic neuron with an appropriate postsynaptic target.
Continuing Worldwide Increase in Tropospheric Methane, 1978 to 1987
Authors: Blake Donald R. , Rowland F. Sherwood
Published: October 2006

The average worldwide tropospheric mixing ratio of methane has increased by 11% from 1.52 parts per million by volume (ppmv) in January 1978 to 1.684 ppmv in September 1987, for an increment of 0.016 ± 0.001 ppmv per year. Within the limits of our measurements, the global tropospheric mixing ratio for methane over the past decade is consistent either with a linear growth rate of 0.016 ± 0.001 ppmv per year or with a slight lessening of the rate of growth over the past 5 years. No indications were found of an effect of the El Niño-Southern Oscillation-El Chichon events of 1982-83 on total global methane, although severe reductions were reported in the Pacific Northwest during that time period. The growth in tropospheric methane may have increased the water concentration in the stratosphere by as much as 28% since the 1940s and 45% over the past two centuries and thus could have increased the mass of precipitable water available for formation of polar stratospheric clouds.
Stereoscopic Depth Discrimination in the Visual Cortex: Neurons Ideally Suited as Disparity Detectors
Authors: Ohzawa Izumi , DeAngelis Gregory C. , Freeman Ralph D.
Published: October 2006

The possibility has been explored that a subset of physiologically identifiable cells in the visual cortex is especially suited for the processing of stereoscopic depth information. First, characteristics of a disparity detector that would be useful for such processing were outlined. Then, a method was devised by which detailed binocular response data were obtained from cortical cells. In addition, a model of the disparity detector was developed that includes a plausible hierarchical arrangement of cortical cells. Data from the cells compare well with the requirements for the archetypal disparity detector and are in excellent agreement with the predictions of the model. These results demonstrate that a specific type of cortical neuron exhibits the desired characteristics of a disparity detector.
Single-Stranded DNA Binding Protein Encoded by the
virE
Locus of
Agrobacterium tumefaciens
Authors: Citovsky Vitaly , De Vos Guido , Zambryski Patricia
Published: October 2006

The transfer process of T (transfer)-DNA of
Agrobacterium tumefaciens
is activated after the induction of the expression of the Ti plasmid virulence (
vir
) loci by plant signal molecules such as acetosyringone. The
vir
gene products then act to generate a free transferable single-stranded copy of the T-DNA, designated the T-strand. Although some
vir
proteins are responsible for the synthesis of the T-strand, others may mediate T-strand transfer to plant cells as part of a DNA-protein complex. Here, a novel
69
-kilodalton
vir
-specific single-stranded DNA binding protein is identified in
Agrobacterium
harboring a nopaline-type Ti plasmid. This protein binds single-stranded but not double-stranded DNA regardless of nucleotide sequence composition. The molecular size of the
vir
-specific single-stranded DNA binding protein and its relative abundance in acetosyringone-induced
Agrobacterium
suggested that it might be the product of the
virE
locus; molecular cloning and expression of the
virE
region in
Escherichia coli
confirmed this prediction.
Spectrum Line Intensity as a Surrogate for Solar Irradiance Variations
Authors: Livingston W. C. , Wallace L. , White O. R.
Published: October 2006

Active Cavity Radiometer Irradiance Monitor (ACRIM) solar constant measurements from 1980 to 1986 are compared with ground-based, irradiance spectrophotometry of selected Fraunhofer lines. Both data sets were identically sampled and smoothed with an 85-day running mean, and the ACRIM total solar irradiance (
S
) values were corrected for sunspot blocking (
S
c
). The strength of the mid-photospheric manganese 539.4-nanometer line tracks almost perfectly with ACRIM
S
c
, Other spectral features formed high in the photosphere and chromosphere also track well. These comparisons independently confirm the variability in the ACRIM
S
c
, signal, indicate that the source of irradiance is faculae, and indicate that ACRIM
S
c
, follows the 11-year activity cycle.
Organization of Ion Channels in the Myelinated Nerve Fiber
Authors: Waxman Stephen G. , Ritchie J. Murdoch
Published: October 2006

The functional organization of the mammalian myelinated nerve fiber is complex and elegant. In contrast to nonmyelinated axons, whose membranes have a relatively uniform structure, the mammalian myelinated axon exhibits a high degree of regional specialization that extends to the location of voltage-dependent ion channels within the axon membrane. Sodium and potassium channels are segregated into complementary membrane domains, with a distribution reflecting that of the overlying Schwann or glial cells. This complexity of organization has important implications for physiology and pathophysiology, particularly with respect to the development of myelinated fibers.
Sequence Homology Between Certain Viral Proteins and Proteins Related to Encephalomyelitis and Neuritis
Authors: Jahnke Ulrike , Fischer Edmond H. , Alvord Ellsworth C.
Published: October 2006

Post-infectious or post-vaccinal demyelinating encephalomyelitis and neuritis may be due to immunological cross-reactions evoked by specific viral antigenic determinants (epitopes) that are homologous to regions in the target myelins of the central and peripheral nervous systems. Such homologies have been found by computer searches in which decapeptides in two human myelin proteins were compared with proteins of viruses known to infect humans. These viruses include measles, Epstein-Barr, influenza A and B, and others that cause upper respiratory infections. Several regions identified in myelin basic protein and P
2
protein can be related to experimental allergic encephalomyelitis or neuritis in laboratory animals.
The Discovery of Crown Ethers
Authors: Pedersen Charles J.
Published: October 2006

The discovery of the crown ethers stemmed from efforts to control the catalytic activity of vanadium and copper by complexation with multidentate ligands. The first crown ether, 2,3,11,12-dibenzo-1,4,7,10,13,16-hexaoxacyclo-octadeca-2,11-diene, was obtained in 0.4% yield during an attempt to prepare a phenolic ligand from catechol and bis(2-chloroethyl)ether. This compound, which complexed with the sodium cation, was the first compound known to display such activity and became known as dibenzo-18-crown-6, an 18-atom heterocycle containing 6 oxygen atoms. Some 60 related compounds were made involving heterocyclic rings containing 12 to 60 atoms including 4 and 10 oxygen atoms. There are optimum polyether ring sizes for the different alkali metal cations: 15 to 18 for sodium, 18 for potassium, and 18 to 21 for cesium. Complexes having polyether to cation ratios of 1:1, 3:2, and 2:1 were prepared. Solubilization of inorganic salts in aprotic solvents, especially by saturated crown ethers, was demonstrated.
Expression of the Rous Sarcoma Virus
pol
Gene by Ribosomal Frameshifting
Authors: Jacks Tyler , Varmus Harold E.
Published: October 2006

The
pol
gene of Rous sarcoma virus is positioned downstream of the
gag
gene in a different, briefly overlapping reading frame; nevertheless, the primary translation product of
pol
is a
gag-pol
fusion protein. Two mechanisms, ribosomal frameshifting and RNA splicing, have been considered to explain this phenomenon. The frameshifting model is supported by synthesis of both
gag
protein and
gag-pol
fusion protein in a cell-free mammalian translation system programmed by a single RNA species that was synthesized from cloned viral DNA with a bacteriophage RNA polymerase. Under these conditions, the ratio of the
gag
protein to the fusion protein (about 20 to 1) is similar to that previously observed in infected cells, the frameshifting is specific for the
gag-pol
junction, and it is unaffected by large deletions in
gag
. In addition, synthesis of the fusion protein is ten times less efficient in an Escherichia coli cell-free translation system and cannot be explained by transcriptional errors or in vitro modification of the RNA. Ribosomal frameshifting may affect production of other proteins in higher eukaryotes, including proteins encoded by several retroviruses and transposable elements.
Characterization of Highly Immunogenic p66/p51 as the Reverse Transcriptase of HTLV-III/LAV
Authors: di Marzo Veronese Fulvia , Copeland Terry D. , DeVico Anthony L. , Rahman Rukhsana , Oroszlan Stephen , Gallo Robert C. , Sarngadharan M. G.
Published: October 2006

Approximately 80 percent of all human sera that react with antigens of HTLV-III, the etiologic agent of the acquired immune deficiency syndrome (AIDS), recognize protein bands at 66 and 51 kilodaltons. A mouse hybridoma was produced that was specific to these proteins. Repeated cloning of the hybridoma did not separate the two reactivities. The p66/p51 was purified from HTLV-III lysates by immunoaffinity chromatography and subjected to NH2-terminal Edman degradation. Single amino acid residues were obtained in 17 successive degradation cycles. The sequence determined was a perfect translation of the nucleotide sequence of a portion of the HTLV-III
pol
gene. The purified p66/51 had reverse transcriptase activity and the monoclonal immunoglobulin G specifically removed the enzyme activity from crude viral extract as well as purified enzyme.
Laser Femtochemistry
Authors: Zewail Ahmed H.
Published: October 2006

Femtochemistry is concerned with the very act of the molecular motion that brings about chemistry, chemical bond breaking, or bond formation on the femtosecond (10
-15
second) time scale. With lasers it is now possible to record snapshots of chemical reactions with sub-angstrom resolution. This strobing of the transition-state region between reagents and products provides real time observations that are fundamental to understanding the dynamics of the chemical bond.
Reproductive Tract Lesions in Male Mice Exposed Prenatally to Diethylstilbestrol
Authors: McLachlan J. A. , Newbold R. R. , Bullock B.
Published: October 2006

Sixty percent of the male offspring from pregnant mice treated with diethylstilbestrol during gestation were sterile. The affected animals had gonadal changes which included intra-abdominal or fibrotic testes, or both. Additionally, nodular masses in the ampullary region of the reproductive tract were observed in 6 of 24 animals; one of these appeared to be preneoplastic.
Large-Scale Cell Culture in Biotechnology
Authors: Arathoon W. R. , Birch J. R.
Published: October 2006

The purpose of this article is to review the current state of large-scale cell culture in terms of its applications, problems, and potential. Because of the commercial and proprietary nature of most large-scale cell culture processes, this review does not contain many detailed scientific results although an attempt is made to address some key issues and findings. Much of this summary deals with processes having an established, commercial track record but some attention is given to more recent innovations with interesting potential applications. Reference is made to plant cell culture but the main emphasis is on mammalian cells.
Replacement of Liver Function in Rats by Transplantation of Microcarrier-Attached Hepatocytes
Authors: Demetriou Achilles A. , Whiting James F. , Feldman David , Levenson Stanley M. , Chowdhury Namita Roy , Moscioni Albert D. , Kram Michael , Chowdhury Jayanta Roy
Published: October 2006

Isolated hepatocytes, harvested from normal rat livers by portal vein collagenase perfusion, can be attached to collagen-coated dextran microcarriers and transplanted by intraperitoneal injection into rats. Survival and function of the transplanted hepatocytes have been demonstrated in mutant rats lacking bilirubin-uridine diphosphate glucuronosyltransferase activity (Gunn strain) and rats with inherited lack of plasma albumin (Nagase analbuminemia rat strain). This simple technique promises to be useful in the treatment of acute liver failure in humans.
Altered K
+
Channel Expression in Abnormal T Lymphocytes from Mice with the
lpr
Gene Mutation
Authors: Chandy K. George , DeCoursey Thomas E. , Fischbach Michael , Talal Norman , Cahalan Michael D. , Gupta Sudhir
Published: October 2006

The observation that voltage-dependent K
+
channels are required for activation of human T lymphocytes suggests that pathological conditions involving abnormal mitogen responses might be reflected in ion channel abnormalities. Gigaohm seal techniques were used to study T cells from MRL/MpJ-
lpr
/
lpr
mice; these mice develop generalized lymphoproliferation of functionally and phenotypically abnormal T cells and a disease resembling human systemic lupus erythematosus. The number and predominant type of K
+
channels in T cells from these mice differ dramatically from those in T cells from control strains and a congenic strain lacking the
lpr
gene locus. Thus an abnormal pattern of ion channel expression has now been associated with a genetic defect in cells of the immune system.
The Effects of Enriched Carbon Dioxide Atmospheres on Plant—Insect Herbivore Interactions
Authors: Fajer Eric D. , Bowers M. Deane , Bazzaz Fakhri A.
Published: October 2006

Little is known about the effects of enriched CO
2
atmospheres, which may exist in the next century, on natural plant—insect herbivore interactions. Larvae of a specialist insect herbivore,
Junonia coenia
(Lepidoptera: Nymphalidae), were reared on one of its host plants,
Plantago lanceolata
(Plantaginaceae), grown in either current low (350 parts per million) or high (700 ppm) CO
2
environments. Those larvae raised on high-CO
2
foliage grew more slowly and experienced greater mortality, especially in early instars, than those raised on low-CO
2
foliage. Poor larval performance on high-CO
2
foliage was probably due to the reduced foliar water and nitrogen concentrations of those plants and not to changes in the concentration of the defensive compounds, iridoid glycosides. Adult pupal weight and female fecundity were not affected by the CO
2
environment of the host plant. These results indicate that interactions between plants and herbivorous insects will be modified under the predicted CO
2
conditions of the 21st century.
Diversity of Alpha-Fetoprotein Gene Expression in Mice Is Generated by a Combination of Separate Enhancer Elements
Authors: Hammer Robert E. , Krumlauf Robb , Camper Sally A. , Brinster Ralph L. , Tilghman Shirley M.
Published: October 2006

The 5′ flanking region of the mouse alpha-fetoprotein (AFP) gene contains a tissue-specific promoter and three upstream regulatory elements that behave as classical enhancers. At least one of these enhancers is now shown to be required for the tissue-specific expression of the AFP gene when it is introduced into the mouse genome by microinjection of cloned DNA fragments into fertilized eggs. Each enhancer can direct expression in the appropriate tissues, the visceral endoderm of the yolk sac, the fetal liver, and the gastrointestinal tract, but each exerts different influence in these three tissues. These differences may explain the tissue-specific diversity in the levels of expression characteristic of the AFP gene. The postnatal repression of transcription of the AFP gene in both liver and gut, as well as the reinitiation of its transcription during liver regeneration, is mimicked by the introduced gene when it is linked to the enhancer domains together or singly. Thus, the DNA sequence elements responsible for directing the activation of AFP transcription, its repression, and reinduction are contained in a limited segment of DNA within or 5′ to the gene (or both) and are operative in the absence of the closely linked albumin gene.
Regulated Genes in Transgenic Plants
Authors: Benfey Philip N. , Chua Nam-Hai
Published: October 2006

Transgenic plants are an effective system for the study of regulated gene expression. Developmental control of expression can be monitored by assaying different tissues or by assaying a plant at different developmental stages. Analysis of the petunia 5-enolpyruvylshikimate-3-phosphate synthase gene, which is highly expressed in flowers, allowed identification of an upstream region that confers tissue-specific and developmentally regulated expression. The cell specificity of expression in floral tissues has been defined by histochemical localization. This expression is contrasted to that of the 35
S
promoter of cauliflower mosaic virus, a nominally constitutive promoter that shows a definite specificity of expression in floral tissues. Moreover, this expression differs in transgenic hosts of different species.
Bacterial Motility: Membrane Topology of the
Escherichia coli
MotB Protein
Authors: Chun Sang Yearn , Parkinson John S.
Published: October 2006

The MotB protein of
Escherichia coli
is an essential component of the force generators that couple proton movement across the cytoplasmic membrane to rotation of the flagellar motors. The membrane topology of MotB was examined to explore the possibility that it might form a proton channel. MotB-alkaline phosphatase fusion proteins were constructed to identify likely periplasmic domains of the MotB molecule. Fusions distal to a putative membrane-spanning segment near the amino terminus of MotB exhibited alkaline phosphatase activity, indicating that an extensive carboxyl-terminal portion of MotB may be located on the periplasmic side of the membrane. Protease treatment of MotB in spheroplasts confirmed this view. The simple transmembrane organization of MotB is difficult to reconcile with a role as a proton conductor.
Origin and Evolution of Outer Solar System Atmospheres
Authors: Lunine J. I.
Published: October 2006

The atmospheres of bodies in the outer solar system are distinct in composition from those of the inner planets and provide a complementary set of clues to the origin of the solar system. This article reviews current understanding of the origin and evolution of these atmospheres on the basis of abundances of key molecular species. The systematic enrichment of methane and deuterated species from Jupiter to Neptune is consistent with formation models in which significant infall of icy and rocky planetesimals accompanies the formation of giant planets. The atmosphere of the Saturnian satellite Titan has been strongly modified by photochemistry and interaction with the surface over 4.5 billion years; the combined knowledge of this moon's bulk density and estimates of the composition of the surface and atmosphere provide some constraints on this body's formation. Neptune's satellite Triton is a poorly known object for which it is hoped that substantial information will be gleaned from the Voyager 2 encounter in August 1989. The mean density of the Pluto-Charon system is well known and suggests an origin in the rather water-poor solar nebula. The recent occultation of a star by Pluto provides evidence that carbon monoxide, in addition to methane, may be present in its atmosphere.
A 48-Million-Year-Old Aphid—Host Plant Association and Complex Life Cycle: Biogeographic Evidence
Authors: Moran Nancy A.
Published: October 2006

Biogeographical and paleobotanical evidence suggests that the aphid subtribe Melaphidina has been associated with its sumac host plant since the early Eocene when these plants were continuously distributed across the Bering land bridge. Transfer experiments indicate that the American species,
Melaphis rhois
, shows an unusual complex life cycle, similar to that known in Chinese melaphidines, with some generations feeding on mosses as alternate host plants. As with the association with sumac, this complex life cycle may have been established in the melaphidine lineage before the southward retreat of sumac from Alaska 48 million years ago. This example suggests that the interactions and life histories shown by modern populations may be determined, in large part, by evolutionary commitments made in the distant past.
Management Accounting for Advanced Technological Environments
Authors: Kaplan Robert S.
Published: October 2006

Management accounting systems designed decades ago no longer provide timely, relevant information for companies in today's highly competitive environment. New operational control and performance measurement systems are recognizing the importance of direct measurements of quality, manufacturing lead times, flexibility, and customer responsiveness, as well as more accurate measures of the actual costs of consumed resources. Activity-based cost systems can assign the costs of indirect and support resources to the specific products and activities that benefit from these resources. Both operational control and activity-based systems represent new opportunities for improved managerial information in complex, technologically advanced environments.
Three-Dimensional Optical Storage Memory
Authors: Parthenopoulos Dimitri A. , Rentzepis Peter M.
Published: October 2006

A novel three-dimensional (3-D) optical memory device is presented that allows fast random access of the information and extremely high bit densities. This device is based on two-photon writing, reading, and erasing of the information in a photochromic material embedded in a polymer matrix. Absorption and emission data show that two-photon writing and reading of information is feasible. The advantages and properties of such a 3-D optical memory are discussed.
Malondialdehyde-Altered Protein Occurs in Atheroma of Watanabe Heritable Hyperlipidemic Rabbits
Authors: Haberland Margaret E. , Fong Dora , Cheng Lorna
Published: October 2006

It has been proposed that chemically reactive lipids released during lipid peroxidation convert low density lipoprotein (LDL), the major carrier of plasma cholesterol, to an abnormal form and that receptor-mediated clearance of this altered LDL produces cholesteryl ester deposition in macrophage-derived foam cells of atheroma. Immunocytochemical analyses now reveal the presence of protein modified by malondialdehyde, a peroxidative end product, which colocalizes with the extracellular deposition of apolipoprotein B-100 protein of LDL in atheroma from Watanabe heritable hyperlipidemic rabbits. These findings provide direct evidence for the existence in vivo of protein modified by a physiological product of lipid peroxidation within arterial lesions.
GABA
A
-Receptor Function in Hippocampal Cells Is Maintained by Phosphorylation Factors
Authors: Stelzer Armin , Kay Alan R. , Wong Robert K. S.
Published: October 2006

Gamma aminobutyric acid (GABA) mediates fast synaptic inhibition in the central nervous system by activating the chloride-permeable GABA
A
channel. The GABA
A
conductance progressively diminishes with time when the intracellular contents of hippocampal neurons are perfused with a minimal intracellular medium. This "run down" of the GABA-activated conductance can be prevented by the inclusion of magnesium adenosine triphosphate and calcium buffer in the intracellular medium. The amount of chloride conductance that can be activated by GABA is determined by competition between a calcium-dependent process that reduces the conductance and a phosphorylation process that maintains the conductance.
Giant Radiation-Induced Color Halos in Quartz: Solution to a Riddle
Authors: Odom A. Leroy , Rink William J.
Published: October 2006

The radii of radiation-induced color halos (RICHs) surrounding radioactive mineral inclusions in mica generally correspond closely to the calculated range of common uranogenic and thorogenic alpha particles in mica. Many exceptions are known, however, and these variants have led investigators to some rather exotic interpretations. Three RICHs found in quartz are identified as aluminum hole-trapping centers. Whereas the inner radii of these RICHs closely match the predicted range of the most energetic common alphas (39 micrometers), the color centers observed extend to 100 micrometers. Migration of valence-band holes down a radiation-induced charge potential might account for enigmatic RICHs. Such RICHs provide natural experiments in ultraslow charge diffusion.
First Plasma Wave Observations at Neptune
Authors: Gurnett D. A. , Kurth W. S. , Poynter R. L. , Granroth L. J. , Cairns I. H. , Macek W. M. , Moses S. L. , Coroniti F. V. , Kennel C. F. , Barbosa D. D.
Published: October 2006

The Voyager 2 plasma wave instrument detected many familiar plasma waves during the encounter with Neptune, including electron plasma oscillations in the solar wind upstream of the bow shock, electrostatic turbulence at the bow shock, and chorus, hiss, electron cyclotron waves, and upper hybrid resonance waves in the inner magnetosphere. Low-frequency radio emissions, believed to be generated by mode conversion from the upper hybrid resonance emissions, were also observed propagating outward in a disklike beam along the magnetic equatorial plane. At the two ring plane crossings many small micrometer-sized dust particles were detected striking the spacecraft. The maximum impact rates were about 280 impacts per second at the inbound ring plane crossing, and about 110 impacts per second at the outbound ring plane crossing. Most of the particles are concentrated in a dense disk, about 1000 kilometers thick, centered on the equatorial plane. However, a broader, more tenuous distribution also extends many tens of thousands of kilometers from the equatorial plane, including over the northern polar region.
Experimentally Induced Visual Projections into Auditory Thalamus and Cortex
Authors: Sur Mriganka , Garraghty Preston E. , Roe Anna W.
Published: October 2006

Retinal cells have been induced to project into the medial geniculate nucleus, the principal auditory thalamic nucleus, in newborn ferrets by reduction of targets of retinal axons in one hemisphere and creation of alternative terminal space for these fibers in the auditory thalamus. Many cells in the medial geniculate nucleus are then visually driven, have large receptive fields, and receive input from retinal ganglion cells with small somata and slow conduction velocities. Visual cells with long conduction latencies and large contralateral receptive fields can also be recorded in primary auditory cortex. Some visual cells in auditory cortex are direction selective or have oriented receptive fields that resemble those of complex cells in primary visual cortex. Thus, functional visual projections can be routed into nonvisual structures in higher mammals, suggesting that the modality of a sensory thalamic nucleus or cortical area may be specified by its inputs during development.
Signal Peptide for Protein Secretion Directing Glycophospholipid Membrane Anchor Attachment
Authors: Caras Ingrid W. , Weddell Gregory N.
Published: October 2006

Decay accelerating factor (DAF) is anchored to the plasma membrane by a glycophospholipid (GPI) membrane anchor covalently attached to the COOH-terminus of the protein. A hydrophobic domain located at the COOH-terminus is required for anchor attachment; DAF molecules lacking this domain are secreted. Replacement of the COOH-terminal hydrophobic domain with a signal peptide that normally functions in membrane translocation, or with a random hydrophobic sequence, results in efficient and correct processing, producing GPI-anchored DAF on the cell surface. The structural requirements for GPI anchor attachment and for membrane translocation are therefore similar, presumably depending on overall hydrophobicity rather than specific sequences.
Mountains and Arid Climates of Middle Latitudes
Authors: Manabe S. , Broccoli A. J.
Published: October 2006

Simulations from a global climate model with and without orography have been used to investigate the role of mountains in maintaining extensive arid climates in middle latitudes of the Northern Hemisphere. Dry climates similar to those observed were simulated over central Asia and western interior North America in the experiment with mountains, whereas relatively moist climates were simulated in these areas in the absence of orography. The experiments suggest that these interior regions are dry because general subsidence and relatively infrequent storm development occur upstream of orographically induced stationary wave troughs. Downstream of these troughs, precipitation-bearing storms develop frequently in association with strong jet streams. In contrast, both atmospheric circulation and precipitation were more zonally symmetric in the experiment without mountains. In addition, orography reduces the moisture transport into the continental interiors from nearby oceanic sources. The relative soil wetness of these regions in the experiment without mountains is consistent with paleoclimatic evidence of less aridity during the late Tertiary, before substantial uplift of the Rocky Mountains and Tibetan Plateau is believed to have occurred.
An Empirical Model of Total Solar Irradiance Variation Between 1874 and 1988
Authors: Foukal P. , Lean J.
Published: October 2006

An empirical model of variations in the total solar irradiance caused by observed changes in photospheric magnetic activity between 1874 and 1988 is presented. The model provides a remarkably good representation of the irradiance variations observed by satellite-borne radiometers between 1980 and 1988. It suggests that the mean total irradiance has been rising steadily since about 1945, with the largest peak so far at about 1980 and another large peak expected during the current solar cycle 22. But it is doubtful whether even this rise can contribute significantly to global warming, unless the temperature increase of about 0.02°C that it produces in current energy balance models seriously underestimates the sensitivity of climate to solar irradiance changes.
Painting the Phase Space Portrait of an Integrable Dynamical System
Authors: Coffey Shannon , Deprit André , Deprit Etienne , Healy Liam
Published: October 2006

For an integrable dynamical system with one degree of freedom, "painting" the integral over the phase space proves to be very effective for uncovering the global flow down to minute details. Applied to the main problem in artificial satellite theory, for instance, the technique reveals an intricate configuration of equilibria and bifurcations when the polar component of the angular momentum approaches zero.
Interferon-α But Not AZT Suppresses HIV Expression in Chronically Infected Cell Lines
Authors: Poli Guido , Orenstein Jan M. , Kinter Audrey , Folks Thomas M. , Fauci Anthony S.
Published: October 2006

Promonocytic (U1) and T lymphocytic (ACH-2) cell lines chronically infected with human immunodeficiency virus type 1 (HIV-1) constitutively express low levels of virus, but expression can be induced by phorbol esters and cytokines. Whereas ACH-2 cells produce infectious virions, U1 cells produce defective, noninfectious particles. Although 3′-azido-3′-deoxythimidine (AZT) prevented acute HIV infection of susceptible cells, it did not prevent the induction of HIV expression in the infected cell lines. In contrast, interferon alpha (IFN-α) inhibited the release of reverse transcriptase and viral antigens into the culture supernatant after phorbol ester stimulation of both cell lines. Further, IFN-α suppressed the production or release (or both) of whole HIV virions, but had no effect on the amount of cell-associated viral proteins. Also, after phorbol ester stimulation of ACH-2 cells, IFN-α reduced the number of infectious viral particles secreted into the culture supernatant, but had no effect on the infectivity of cell-associated virus. These findings lend support to the combined use of antiviral agents that have action at both the early (AZT) and the late (IFN-α) stages of HIV replication.
Vascular Endothelial Growth Factor Is a Secreted Angiogenic Mitogen
Authors: Leung David W. , Cachianes George , Kuang Wun-Jing , Goeddel David V. , Ferrara Napoleone
Published: October 2006

Vascular endothelial growth factor (VEGF) was purified from media conditioned by bovine pituitary folliculostellate cells (FC). VEGF is a heparin-binding growth factor specific for vascular endothelial cells that is able to induce angiogenesis in vivo. Complementary DNA clones for bovine and human VEGF were isolated from cDNA libraries prepared from FC and HL60 leukemia cells, respectively. These cDNAs encode hydrophilic proteins with sequences related to those of the A and B chains of platelet-derived growth factor. DNA sequencing suggests the existence of several molecular species of VEGF. VEGFs are secreted proteins, in contrast to other endothelial cell mitogens such as acidic or basic fibroblast growth factors and platelet-derived endothelial cell growth factor. Human 293 cells transfected with an expression vector containing a bovine or human VEGF cDNA insert secrete an endothelial cell mitogen that behaves like native VEGF.
The Z Boson
Authors: Chanowitz Michael S.
Published: October 2006

The discovery of the Z boson 7 years ago verified a key prediction of the unified theory of electromagnetic and weak forces. Today an experimental program is beginning at two electron-positron colliders to study the properties of the Z particle in great detail. The data accumulated will subject the unified theory to more rigorous tests and will probe with great sensitivity for new physics not encompassed by the existing standard model of the elementary particles and forces. Questions under study include the number of quark and lepton families, the mass of the still undiscovered top quark, and the search for the still unknown fifth force of nature required by the theory to generate the masses of the elementary particles.
Memory Glass: An Amorphous Material Formed from AlPO
4
Authors: Kruger M. B. , Jeanloz Raymond
Published: October 2006

A glass exhibiting structural memory has been produced through the compression of a single crystal of AlPO
4
berlinite to 18 gigapascals at 300 kelvin. The unique and extraordinary characteristic of this glass is that upon decompression below 5 gigapascals, it transforms back into a single crystal with the same orientation as the starting crystal. This glass has a "memory" of the previous crystallographic orientation of the crystal from which it forms.
Hole Density Dependence of the Critical Temperature and Coupling Constant in the Cuprate Superconductors
Authors: Whangbo M.-H. , Torardi C. C.
Published: October 2006

A bond valence sum (BVS) analysis was performed for the p-type cuprate superconductors. The superconducting critical temperature
T
c
versus in-plane Cu-O BVS correlation for copper is grouped into classes and subclasses. Only within a class or subclass for which the nonelectronic effect is constant does the variation of the in-plane Cu-O BVS reflect the corresponding change in the hole density
n
H
of the CuO
2
layers. This study strongly suggests that the
T
c
for every class or subclass of the superconductors is an inverted parabolic function of
n
H
, and so is the coupling constant λ for Cooper pair formation.
The Interdiffusion of Polymers
Authors: Klein Jacob
Published: October 2006

In contrast to interdiffusion in simple liquids, interdiffusion of polymeric chains is dominated by their intertanglement and their large size. These properties profoundly reduce both the molecular mobilities and the role of entropy in driving the mixing. The resulting diffusional processes have only recently been studied. Such studies reveal a wide spectrum of behavior ranging from accelerated interdiffusion (for strongly compatible chains) to its suppression below the critical point for phase separation. Effects that are still poorly understood include the initial disposition at interfaces of the chains' ends (through which diffusion proceeds by reptation) and the need for cooperative motion, which can strongly magnify local friction.
Effects of Climatic Warming on Lakes of the Central Boreal Forest
Authors: Schindler D. W. , Beaty K. G. , Fee E. J. , Cruikshank D. R. , DeBruyn E. R. , Findlay D. L. , Linsey G. A. , Shearer J. A. , Stainton M. P. , Turner M. A.
Published: October 2006

Twenty years of climatic, hydrologic, and ecological records for the Experimental Lakes Area of northwestern Ontario show that air and lake temperatures have increased by 2°C and the length of the ice-free season has increased by 3 weeks. Higher than normal evaporation and lower than average precipitation have decreased rates of water renewal in lakes. Concentrations of most chemicals have increased in both lakes and streams because of decreased water renewal and forest fires in the catchments. In Lake 239, populations and diversity of phytoplankton also increased, but primary production showed no consistent trend. Increased wind velocities, increased transparency, and increased exposure to wind of lakes in burned catchments caused thermoclines to deepen. As a result, summer habitats for cold stenothermic organisms like lake trout and opposum shrimp decreased. Our observations may provide a preview of the effects of increased greenhouse warming on boreal lakes.
In Vivo Activity Against HIV and Favorable Toxicity Profile of 2′,3′-Dideoxyinosine
Authors: Yarchoan Robert , Mitsuya Hiroaki , Thomas Rose V. , Pluda James M. , Hartman Neil R. , Perno Carlo-Federico , Marczyk Kathy S. , Allain Jean-Pierre , Johns David G. , Broder Samuel
Published: October 2006

The purine analog 2′,3′-dideoxyinosine (ddI), which has anti-retroviral activity in vitro was administered for up to 42 weeks to 26 patients with acquired immunodeficiency syndrome (AIDS) or severe AIDS-related complex (ARC). Ten of these individuals were AZT-intolerant. Eight dose regimens were studied. The drug was orally bioavailable and penetrated into the cerebrospinal fluid (CSF). Comparatively little evidence of an effect against human immunodeficiency virus (HIV) was seen at the lowest four doses. However, patients in the four highest dose groups (ddI at 1.6 milligrams per kilogram intravenously and then ≥ 3.2 milligrams per kilogram orally at least every 12 hours or higher) had increases in their circulating CD4
+
T cells (P < 0.0005), increased CD4/CD8 T cell ratios (P < 0.01), and, where evaluable, more than an 80% decrease in serum HIV p24 antigen (P < 0.05). The patients also had evidence of improved immunologic function, had reduced viremic symptomatology, and gained a mean of 1.6 kilogram with these comparatively infrequent dosing schedules (every 8 or 12 hours). The most notable adverse effects directly attributable to ddI administration at the doses used in this study included increases in serum uric acid (due to hypoxanthine release) and mild headaches and insomnia. These results suggest that serious short-term toxicity at therapeutic doses is not an inherent feature in the profile of agents with clinical anti-HIV activity. Further controlled studies to define the safety and efficacy of this agent may be worth considering.
Mapping the
Drosophila
Genome with Yeast Artificial Chromosomes
Authors: Garza Dan , Ajioka James W. , Burke David T. , Hartl Daniel L.
Published: October 2006

The ability to clone large fragments of DNA in yeast artificial chromosomes (YAC's) has created the possibility of obtaining global physical maps of complex genomes. For this application to be feasible, most sequences in complex genomes must be able to be cloned in YAC's, and most clones must be genetically stable and colinear with the genomic sequences from which they originated (that is, not liable to undergo rearrangement). These requirements have been met with a YAC library containing DNA fragments from
Drosophila melanogaster
ranging in size up to several hundred kilobase pairs. Preliminary characterization of the
Drosophila
YAC library was carried out by in situ hybridization of random clones and analysis of clones containing known sequences. The results suggest that most euchromatic sequences can be cloned. The library also contains clones in which the inserted DNA is derived from the centromeric heterochromatin. The locations of 58 clones collectively representing about 8 percent of the euchromatic genome are presented.
Laser Method for Synthesis and Processing of Continuous Diamond Films on Nondiamond Substrates
Authors: Narayan J. , Godbole V. P. , White C. W.
Published: October 2006

A laser method based upon carbon ion implantation and pulsed laser melting of copper has been used to produce continuous diamond thin film. Carbon ions were implanted with ion energies in the range of 60 to 120 keV, and doses of 1.0 × 10
18
to 2.0 × 10
18
ions cm
-2
. The ion-implanted specimens were treated with nanosecond excimer laser pulses with the following parameters: energy density, 3.0 to 5.0 J cm
-2
; wavelength, 0.308 μm; pulse width, 45 nanoseconds. The specimens were characterized with scanning electron microscopy (SEM), x-ray diffraction, Rutherford backscattering/ion channeling, Auger, and Raman spectroscopy. The macroscopic Raman spectra contained a strong peak at 1332 cm
-1
with full width at half maximum of 5 cm
-1
, which is very close to the quality of the spectra obtained from single-crystal diamond. The selected area electron diffraction patterns and imaging confirmed the films to be defect-free single crystal over large areas of up to several square micrometers with no grain boundaries. Low voltage SEM imaging of surface features indicated the film to be continuous with presence of growth steps.
Activation of γδ T Cells in the Primary Immune Response to
Mycobacterium tuberculosis
Authors: Janis Eric M. , Kaufmann Stefan H. E. , Schwartz Ronald H. , Pardoll Drew M.
Published: October 2006

Although the immunologic role of T cells bearing the conventional αβ T cell receptor (TCR) has been well characterized, little is known about the function of the population of T cells bearing the γδ TCR. Therefore, the role of γδ T cells in the immune response to
Mycobacterium tuberculosis
(MT) was investigated. The number of TCR γδ cells in the draining lymph nodes of mice immunized with MT was greatly increased in comparison with the number of TCR αβ cells. Three biochemically distinct γδ TCRs were detected. Analyses of cell cycle, of interleukin-2 receptor expression, and of interleukin-2 responsiveness showed that a large proportion of the γδ T cells were activated in vivo. TCR γδ cells responded to solubilized MT antigens in vitro but, in contrast to MT-specific αβ T cells, the response of γδ T cells to MT did not require major histocompatability complex class II recognition. These results provide an example of antigen-specific activation of γδ T cells in vivo and indicate that γδ T cells may have a distinct role in generating a primary immune response to certain microorganisms.
Genetic Engineering of Filamentous Fungi
Authors: Timberlake William E. , Marshall Margaret A.
Published: October 2006

Filamentous fungi are important in medicine, industry, agriculture, and basic biological research. For example, some fungal species are pathogenic to humans, whereas others produce β-lactam antibiotics (penicillin and cephalosporin). Industrial strains produce large amounts of enzymes, such as glucosamylose and proteases, and low molecular weight compounds, such as citric acid. The largest and most economically important group of plant pathogens are fungi. Several fungal species have biological properties and genetic systems that make them ideally suited for basic biological research. Recently developed techniques for genetic engineering of filamentous fungi make it possible to alter their detrimental and beneficial activities in novel ways.