bluuebunny/crossref_metadata_2025 huggingface dataset:
Binding of GAP to Activated PDGF Receptors
Authors: Kazlauskas Andrius , Ellis Christine , Pawson Tony , Cooper Jonathan A.
Published: October 2006

The
ras
proto-oncogene products appear to relay intracellular signals via the Ras guanosine triphosphatase (GTPase) activator protein, GAP. In dog epithelial cells expressing human platelet-derived growth factor (PDGF) receptors, binding of PDGF caused approximately one-tenth of the total GAP molecules to complex with the receptor. Studies with mutant PDGF receptors showed that maximum association required both receptor kinase activity and phosphorylatable tyrosine residues at both the identified sites of receptor autophosphorylation.
Sodium Current-Induced Release of Calcium from Cardiac Sarcoplasmic Reticulum
Authors: Leblanc Normand , Hume Joseph R.
Published: October 2006

The role of sodium-calcium exchange at the sarcolemma in the release of calcium from cardiac sarcoplasmic reticulum was investigated in voltage-clamped, isolated cardiac myocytes. In the absence of calcium entry through voltage-dependent calcium channels, membrane depolarization elicited release of calcium from ryanodine-sensitive internal stores. This process was dependent on sodium entry through tetrodotoxin-sensitive sodium channels. Calcium release under these conditions was also dependent on extracellular calcium concentration, suggesting a calcium-induced trigger release mechanism that involves calcium entry into the cell by sodium-calcium exchange. This sodium current-induced calcium release mechanism may explain, in part, the positive inotropic effects of cardiac glycosides and the negative inotropic effects of a variety of antiarrhythmic drugs that interact with cardiac sodium channels. In response to a transient rise of intracellular sodium, sodium-calcium exchange may promote calcium entry into cardiac cells and trigger sarcoplasmic calcium release during physiologic action potentials.
Identity of Inositol 1,2-Cyclic Phosphate 2-Phosphohydrolase with Lipocortin III
Authors: Ross Theodora S. , Tait Jonathan F. , Majerus Philip W.
Published: October 2006

The amino acid sequences of three fragments of cyanogen bromide-digested human placental inositol 1,2-cyclic phosphate 2-phosphohydrolase, an enzyme of the phosphatidylinositol signaling pathway, are identical to sequences within lipocortin III, a member of a family of homologous calcium- and phospholipid-binding proteins that do not have defined physiological functions. Lipocortin III has also been previously identified as placental anticoagulant protein III (PAP III) and calcimedin 35
α
. Antibodies to PAP III detected PAP III and inositol 1,2-cyclic phosphate 2-phosphohydrolase with identical reactivity on immunoblotting. In addition, inositol 1,2-cyclic phosphate 2-phosphohydrolase was stimulated by the same acidic phospholipids that bind lipocortins.
Ramón
and Maya Ruins: An Ecological, Not an Economic, Relation
Authors: Lambert J. D. H. , Arnason J. T.
Published: October 2006

Economically important trees such as
ramón
have been shown to have a high density in the civic-ceremonial core zone of ancient Maya ruins. The distribution of such trees is probably the result of their requirements for growth and reproduction, which are optimal on the ruins, and not because they are the descendants of trees planted by the Maya aristocracy.
Dispersal by Swarming in a Social Spider
Authors: Lubin Yael D. , Robinson Michael H.
Published: October 2006

Groups of
Achaearanea wau
(Theridiidae) disperse and found new colonies by means of synchronized emigrations of adult and subadult females. Emigrations involve the construction of silk highways from parent colonies to new web sites, synchronized migrations along the highways, and the establishment of daughter colonies. Emigrations of
Achaearanea wau
are similar in timing, group composition, and in some behavior components to swarming of social bees and wasps.
The Sun's Influence on the Earth's Atmosphere and Interplanetary Space
Authors: Evans J. V.
Published: October 2006

The bulk of the sun's radiation is in the visible and infrared. Solar radiation at these wavelengths controls the weather in the lowest levels of the earth's atmosphere. The rate at which this energy is emitted (the so-called solar constant) varies by a few tenths of 1 percent over a time scale of days. Longer period variations may exist, but have yet to be detected. Far more variable are the amounts of energy emitted as ultraviolet, extreme ultraviolet, and x-rays, and in the continuous outflow of ionized solar particles. The latter controls the properties of the space between the earth and the sun as well as those of the earth's magnetosphere. The ultraviolet and particle emissions control the properties of the earth's upper atmosphere, including the global wind circulation and changes therein associated with intense auroral storms. While considerable progress has been made in exploring the solar-terrestrial system since the advent of space research, many problems remain. These include the question of how magnetic energy is converted into ionized particle energy in the sun and in the earth's magnetosphere, the way in which solar and terrestrial magnetic fields join or merge, and how large electric fields are generated and sustained a few thousand kilometers above the earth's poles. Perhaps the most intriguing question concerns the possible relation between solar variability and the earth's weather and climate.
Aircraft Monitoring of Surface Carbon Dioxide Exchange
Authors: Desjardins R. L. , Brach E. J. , Alvo P. , Schuepp P. H.
Published: October 2006

Aircraft-mounted sensors were used to measure the exchange of carbon dioxide above a cornfield, a forest, and a lake under midday conditions. Mean absorption values of 3400, 1200, and 100 milligrams of carbon dioxide per square meter per hour, respectively, are consistent with reported ground-based observations of carbon dioxide flux. Such information, gathered by aircraft, could be used to provide a quantitative evaluation of source and sink distributions of carbon dioxide in the biosphere, to establish a correlation between satellite data and near-surface measurements, and to monitor crop performance.
Deep-Sea Bacteria: Isolation in the Absence of Decompression
Authors: Jannasch Holger W. , Wirsen Carl O. , Taylor Craig D.
Published: October 2006

Sampling and pure culture isolation of deep-sea bacteria without loss of in situ pressure is required in order to determine the viability of decompression-sensitive strains. This was achieved by using a pressure-retaining sterilizable seawater sampling system in connection with a prepressurized hyperbaric isolation chamber. Rates of growth and substrate uptake of the majority of isolates showed highly barotolerant characteristics, while the remainder (4 out of 15) exhibited barophilic characteristics.
How Does the Toad Flip Its Tongue? Test of Two Hypotheses
Authors: Gans Carl , Gorniak Gerard C.
Published: October 2006

Two conflicting hypotheses purport to explain the mechanism generating the lingual flip in frogs. The first suggests that the intrinsic tongue muscles are stiffened, rotate over the symphysis and catapult the soft tissues; the second suggests that the hyoid suddenly moves forward and transfers its momentum to propel the tongue. High-speed cinematography and synchronized electromyography show that the tongue is rotated over the symphysis by a complex of rods formed from stiffened intrinsic tongue muscles. As the flip occurs even when the hyoid is immobilized, the hyoid momentum hypothesis does not apply. The tongue is then propelled by sets of fibers locked into connective tissues. With activation, these become rigid rods that form a muscular ballista.
Lithium: a Modulator of Cyclic AMP-Dependent Events in Lymphocytes?
Authors: Gelfand Erwin W. , Dosch Hans-Michael , Hastings Deborah , Shore Abraham
Published: October 2006

Theophylline, salbutamol, isoproterenol, and dibutyryl cyclic AMP inhibited E-rosette formation by human T lymphocytes and immunoglobulin M secretion from human plaque-forming B cells and augmented T-suppressor cell activity in three patients with agammaglobulinemia. Lithium chloride increased mitogen-induced lymphocyte proliferation and inhibited suppressor cell activity. In the presence of lithium, the effects of all the drugs except dibutyryl cyclic AMP could be prevented. The data suggest a role for lithium in the modulation of cyclic AMP-dependent events in lymphocytes. Its potential role as an inhibitor of suppressor cell activity warrants further attention.
N
-β-Alanyldopamine: Major Role in Insect Cuticle Tanning
Authors: Hopkins Theodore L. , Morgan Thomas D. , Aso Yoichi , Kramer Karl J.
Published: October 2006

N
-β-Alanyldopamine is the major tyrosine metabolite in the hemolymph and cuticle during pupal tanning in the tobacco hornworm,
Manduca sexta
L. Its concentration in hemolymph increases over 800-fold above larval levels by the start of tanning and decreases as the pupal cuticle darkens and hardens. It is a major catechol in species representing several insect orders and is the preferred substrate for pupal cuticular
o
-diphenol oxidase. In insects,
N
-β-alanyldopamine appears to be the main precursor for tanning chemicals at certain developmental stages.
Laboratory Cultivation of
Prochloron
, a Tryptophan Auxotroph
Authors: Patterson Gregory M. L. , Withers Nancy W.
Published: October 2006

Laboratory cultures have been established of the didemnid symbiont
Prochloron
, a unique prokaryotic alga that synthesizes chlorophylls a and b but no phycobilin pigments. Cell division in
Prochloron
cultures occurs under acidic conditions (
p
H 5.5) in the presence of tryptophan. The alga is a naturally occurring tryptophan auxotroph that survives in nature by close association with the host,
Diplosoma similis
. The metabolic dysfunction that renders
Prochloron
auxotrophic may involve only the initial step of the tryptophan biosynthetic pathway.
Binding of SH2 Domains of Phospholipase Cγ1, GAP, and Src to Activated Growth Factor Receptors
Authors: Anderson Deborah , Koch C. Anne , Grey Laura , Ellis Christine , Moran Michael F. , Pawson Tony
Published: October 2006

Phospholipase C
γ
1 (PLC
γ
1) and p21
ras
guanosine triphosphatase (GTPase) activating protein (GAP) bind to and are phosphorylated by activated growth factor receptors. Both PLC
γ
1 and GAP contain two adjacent copies of the noncatalytic Src homology 2 (SH2) domain. The SH2 domains of PLC
γ
1 synthesized individually in bacteria formed high affinity complexes with the epidermal growth factor (EGF)- or platelet derived growth factor (PDGF)-receptors in cell lysates, and bound synergistically to activated receptors when expressed together as one bacterial protein. In vitro complex formation was dependent on prior growth factor stimulation and was competed by intracellular PLC
γ
1. Similar results were obtained for binding of GAP SH2 domains to the PDGF-receptor. The isolated SH2 domains of other signaling proteins, such as p60
src
and Crk, also bound activated PDGF-receptors in vitro. SH2 domains, therefore, provide a common mechanism by which enzymatically diverse regulatory proteins can physically associate with the same activated receptors and thereby couple growth factor stimulation to intracellular signal transduction pathways.
Contributions of Two Types of Calcium Channels to Synaptic Transmission and Plasticity
Authors: Edmonds Brian , Klein Marc , Dale Nicholas , Kandel Eric R.
Published: October 2006

In
Aplysia
sensory and motor neurons in culture, the contributions of the major classes of calcium current can be selectively examined while transmitter release and its modulation are examined. A slowly inactivating, dihydropyridine-sensitive calcium current does not contribute either to normal synaptic transmission or to any of three different forms of plasticity: presynaptic inhibition, homosynaptic depression, and presynaptic facilitation. This current does contribute, however, to a fourth form of plasticity—modulation of transmitter release by tonic depolarization of the sensory neuron. By contrast, a second calcium current, which is rapidly inactivating and dihydropyridine-insensitive, contributes to release elicited by the transient depolarization of an action potential and to the other three forms of plasticity.
Targeting the E1 Replication Protein to the Papillomavirus Origin of Replication by Complex Formation with the E2 Transactivator
Authors: Mohr Ian J. , Clark Robin , Sun Shaw , Androphy Elliot J. , MacPherson Paul , Botchan Michael R.
Published: October 2006

The mechanism by which transcription factors stimulate DNA replication in eukaryotes is unknown. Bovine papillomavirus DNA synthesis requires the products of the viral E1 gene and the transcriptional activator protein encoded by the E2 gene. Experimental data showed that the 68-kilodalton (kD) E1 protein formed a complex with the 48-kD E2 transcription factor. This complex bound specifically to the viral origin of replication, which contains multiple binding sites for E2. Repressor proteins encoded by the E2 open reading frame failed to complex with E1 suggesting that the 162-amino acid region of E2 that participates in transactivation contained critical determinants for interaction with E1. The physical association between a replication protein and a transcription factor suggests that transcriptional activator proteins may function in targeting replication initiator proteins to their respective origins of replication.
Crystal Site Location of Iron and Trace Elements in a Magnesium-Iron Olivine by a New Crystallographic Technique
Authors: Taftø J. , Spence J. C. H.
Published: October 2006

A new crystallographic technique has been developed, which has been applied to the problem of locating the cations in a natural olivine crystal with the composition (Mg
0.90
Fe
0.10
Ni
0.004
Mn
0.002
)
2
SiO
4
. The method uses the variation of characteristic x-ray emission with the direction of an exciting electron beam in an analytical transmission electron microscope. It may be applied to nanometer-sized areas and to concentrations as low as 0.1 atomic percent, is capable of distinguishing neighbors in the periodic table, and does not require external standards. The iron atoms in this crystal are evenly distributed between the two available crystal sites M1 and M2 (49.6 ± 1 percent on M1), whereas the trace elements nickel and manganese occupy the M1 and M2 positions, respectively (97 ± 5 percent nickel on M1 and 1 ± 5 percent manganese on M1).
Microholography of Living Organisms
Authors: Solem Johndale C. , Baldwin George C.
Published: October 2006

By using intense pulsed coherent x-ray sources that are currently under development, it will be possible to obtain magnified three-dimensional images of elementary biological structures in the living state at precisely defined instants. For optimum contrast, sensitivity, and resolution, the hologram should be made with x-rays tuned to a resonance of nitrogen near 0.3 nanometer. Resolution will then be limited mainly by the hydrodynamic expansion that occurs while the necessary number of photons is being registered. Problems of technique are also briefly discussed.
Multichannel Detection in High-Performance Liquid Chromatography
Authors: Miller James C. , George Stephan A. , Willis Barry G.
Published: October 2006

A linear photodiode array has been used as the photodetector element in a new ultraviolet-visible detection system for high-performance liquid chromatography. This array allows simultaneous acquisition of light intensity data at all wavelengths between 190 and 600 nanometers. By use of a computer network concept in the electronics, this detection system can process eight different chromatographic signals simultaneously in real time and acquire spectra manually or automatically. Detector response times are variable and can be as low as 0.040 second, and bandwidth selection is variable from 4 to 400 nanometers. These characteristics permit fast chromatographic techniques and user-selectable signal-to-noise ratio enhancement. Spectra can be acquired in 10 milliseconds, permitting qualitative characterization at several different points on a single peak without destroying chromatographic signal integrity. Examples illustrate applications in fast high-performance liquid chromatography peak purity determination, and postanalysis data reduction.
Crown Gall Disease and Prospects for Genetic Manipulation of Plants
Authors: Ream Lloyd W. , Gordon Milton P.
Published: October 2006

Agrobacterium tumefaciens
incites crown gall tumors when bacterial DNA integrates into plant nuclear DNA. Plant cells can express these integrated bacterial genes. Following insertion of desired genes into bacterial DNA using recombinant DNA techniques, this system permits introduction of these new genes into plant DNA. We discuss the potential for genetic manipulation of plants using
Agrobacterium tumefaciens
and the related organism
Agrobacterium rhizogenes
.
Climatic Fluctuations Due to Deep Ocean Circulation
Authors: Watts Robert G. , Hayder Md. Ehteshamul
Published: October 2006

A simple climate model that includes the effect of deep ocean turnover as a pure time delay exhibits an oscillatory behavior. The deep ocean signal contains frequencies characteristic of both the forcing function and the deep ocean delay.
Correlation of Changes in Gravity, Elevation, and Strain in Southern California
Authors: Jachens Robert C. , Thatcher Wayne , Roberts Carter W. , Stein Ross S.
Published: October 2006

Measurements made once or twice a year from 1977 through 1982 show large correlated changes in gravity, elevation, and strain in several southern California networks. Precise gravity surveys indicate changes of as much as 25 microgals between surveys 6 months apart. Repeated surveys show that annual elevation changes as large as 100 millimeters occur along baselines 40 to 100 kilometers long. Laser-ranging surveys reveal coherent changes in areal strain of 1 to 2 parts per million occurred over much of southern California during 1978 and 1979. Although the precision of these measuring systems has been questioned, the rather good agreement among them suggests that the observed changes reflect true crustal deformation.
Argonne Intense Pulsed Neutron Source Used to Solve the Molecular Structure of a Novel Organometallic Complex
Authors: Schultz Arthur J. , Teller Raymond G. , Beno Mark A. , Williams Jack M. , Brookhart M. , Lamanna W. , Humphrey M. Beth
Published: October 2006

The single-crystal structure of Mn(CO)
3
(C
7
H
11
) is the first to be solved by direct methods based on time-of-flight neutron diffraction data obtained at the Argonne Intense Pulsed Neutron Source. The molecule contains an unusual three-center, two-electron manganese-hydrogen-carbon interaction.
Enchenopa binotata
Complex: Sympatric Speciation?
Authors: Wood T. K. , Guttman S. I.
Published: October 2006

Enchenopa binotata
is a complex of six treehopper species that have diverged along host plant lines. When females were forced to oviposit on "adopted" host plants, few eggs were deposited. Fewer eggs hatched on "adopted" hosts and those that did hatch did so in response to the phenology of the "adopted" host. Mortality of nymphs on "adopted" hosts was substantially higher than on native hosts. These and other data support a sympatric model of speciation through shifts in host plants.
Adaptations for Climbing in North American Multituberculates (Mammalia)
Authors: Jenkins Farish A. , Krause David W.
Published: October 2006

A recently discovered skeleton of
Ptilodus
exhibits several specializations for climbing. A survey of postcranial bones of Cretaceous and early Cenozoic multituberculates from North America reveals similar locomotor specializations. Multituberculates possessed distinctive tarsal adaptations for a range of pedal mobility characteristic of arboreal mammals that descend trees headfirst. The divergent hallux could move independently of the other digits. The long robust tail of
Ptilodus
possessed musculoskeletal features that, among living mammals, are associated with prehensility.
Inelastic Electron Tunneling Spectroscopy
Authors: Khanna S. K. , Lambe John
Published: October 2006

Inelastic electron tunneling spectroscopy is a useful technique for the study of vibrational modes of molecules adsorbed on the surface of oxide layers in a metal-insulator-metal tunnel junction. The technique involves studying the effects of adsorbed molecules on the tunneling spectrum of such junctions. The data give useful information about the structure, bonding, and orientation of adsorbed molecules. One of the major advantages of inelastic electron tunneling spectroscopy is its sensitivity. It is capable of detecting on the order of 10
10
molecules (a fraction of a monolayer) on a 1-square-millimeter junction. It has been successfully used in studies of catalysis, biology, trace impurity detection, and electronic excitations. Because of its high sensitivity, this technique shows great promise in the area of solid-state electronic chemical sensing.
Venus: Global Surface Radio Emissivity
Authors: Ford Peter G. , Pettengill Gordon H.
Published: October 2006

Observations of thermal radio emission from the surface of Venus, made by the Pioneer Venus radar mapper at a wavelength of 17 centimeters, show variations that are dominated by changes in surface emissivity. The regions of lowest emissivity (0.54 ± 0.05 for the highland areas of Aphrodite Terra and Theia Mons) correspond closely to regions of high radar reflectivity reported earlier. These results support the inference of inclusions of material with high electrical conductivity in the surface rock of these areas.
Cell Polarity: Endogenous Ion Currents Precede and Predict Branching in the Water Mold
Achyla
Authors: Kropf Darryl L. , Lupa Mark D. A. , Caldwell John H. , Harold Franklin M.
Published: October 2006

The hyphae of the water mold
Achyla bisexualis
generate electrical currents that enter the growing tips and leave farther back. An inward-moving current also precedes branching and predicts the site of branch emergence; during the branching process, the current at the original tip declines or even reverses transiently without any change in growth rate. The inward current probably acts as an early signal during branch differentiation. The flow of specific ions rather than the flow of electrical charge probably serves to localize growth.
Microfabrication as a Scientific Tool
Authors: Howard R. E. , Liao P. F. , Skocpol W. J. , Jackel L. D. , Craighead H. G.
Published: October 2006

Research in microfabrication not only serves the microelectronics industry but also can provide research tools for studying the behavior of matter at submicrometer dimensions. A variety of techniques including optical, x-ray, and electron beam lithography and reactive ion etching can be used to make structures, devices, and arrays only hundreds of atoms across. Microfabrication techniques have been applied to experiments on surface-enhanced Raman scattering, transport in one-dimensional conductors, and macroscopic quantum tunneling. Recent progress is extending these techniques to scales of less than 100 angstroms.
α-Amanitin Tolerance in Mycophagous
Drosophila
Authors: Jaenike John , Grimaldi David A. , Sluder Ann E. , Greenleaf Arno L.
Published: October 2006

Six species of
Drosophila
were tested for tolerance to the mushroom toxin α-amanitin, a potent inhibitor of RNA polymerase II. Three nonmycophagous species—
D. melanogaster
,
D. immigrans
, and
D. pseudoobscura
—showed very low survival and long development times in the presence of amanitin. Three mycophagous species—
D. putrida
,
D. recens
, and
D. tripunctata
—showed little or no sensitivity. Analysis in vitro indicated that this tolerance is not based on alteration of the molecular structure of RNA polymerase II.
Current Status of Asymmetric Synthesis
Authors: Mosher Harry S. , Morrison James D.
Published: October 2006

In the last 30 years the subject of asymmetric synthesis has grown from a little studied academic niche in organic chemistry to an intensely investigated field of commercial importance and heightened general interest. Impressive advances have been made in several areas, notably catalytic asymmetric homogeneous hydrogenation, catalytic asymmetric epoxidation of allyl alcohols and stereochemical control of carbon-carbon bond-forming reactions. Asymmetric synthesis must now be deliberately considered along with other available methods as a practical strategy for the synthesis of any chiral compound.
Is the Gramicidin A Transmembrane Channel Single-Stranded or Double-Stranded Helix? A Simple Unequivocal Determination
Authors: Urry Dan W. , Trapane Tina L. , Prasad Kari U.
Published: October 2006

Thallium ion-induced carbonyl carbon chemical shifts were compared for all of the L-residue-peptide carbonyl carbons of the gramicidin A transmembrane channel. Molecular structures were deduced by using the argument that helically equivalent and equally proximal carbonyls would exhibit essentially equivalent ion-induced chemical shifts. The transmembrane channel was found to be a head-to-head dimer with the structure of a left-handed, single-stranded β-helix.
Impact of Mass Treatment of Onchocerciasis with Ivermectin on the Transmission of Infection
Authors: Taylor Hugh R. , Pacqué Michel , Muñoz Beatriz , Greene Bruce M.
Published: October 2006

Onchocerciasis is a major blinding disease that, until recently, has been essentially untreatable. Ivermectin is a safe and effective drug for the mass treatment of onchocerciasis and when used on an individual basis, it reduces the ability of the treated person to transmit
Onchocerca volvulus
infection. In the present study, the effect of community-based ivermectin treatment on the degree of transmission within the community was assessed by determining the incidence of new infection in children. Ivermectin was distributed annually on three occasions to the eligible members of a population of approximately 14,000 people living on a rubber plantation in a forest area endemic for onchocerciasis. After 2 years, the prevalence of infection in 5-year-old children decreased by 21%. The annual incidence in an uninfected cohort of children decreased by 35% and, after age-specific adjustment, the reduction in incidence in 7- to 12-year-old children was 45%. Thus, community-based distribution of ivermectin led to a significant reduction in incidence of new infection. These findings suggest that ivermectin can be important in reducing the transmission of onchocerciasis.
Nickel: An Essential Micronutrient for Legumes and Possibly All Higher Plants
Authors: Eskew David L. , Welch Ross M. , Cary Earle E.
Published: October 2006

Soybean plants deprived of nickel accumulated toxic concentrations of urea (2.5 percent) in necrotic lesions on their leaflet tips. This occurred regardless of whether the plants were supplied with inorganic nitrogen or were dependent on nitrogen fixation. Nickel deprivation resulted in delayed nodulation and in a reduction of early growth. Addition of nickel (1 microgram per liter) to the nutrient media prevented urea accumulation, necrosis, and growth reductions. This evidence suggests that nickel is essential for soybeans and possibly for higher plants in general.
Seismic Detection of the Summit Magma Complex of Kilauea Volcano, Hawaii
Authors: Thurber Clifford H.
Published: October 2006

Application of simultaneous inversion of seismic P-wave arrival time data to the investigation of the crust beneath Kilauea Volcano yields a detailed picture of the volcano's heterogeneous structure. Zones of anomalously high seismic velocity are found associated with the volcano's rift zones. A low-velocity zone at shallow depth directly beneath the caldera coincides with an aseismic region interpreted as being the locus of Kilauea's summit magma complex.
The Earth as a Planet: Paradigms and Paradoxes
Authors: Anderson Don L.
Published: October 2006

The independent growth of the various branches of the earth sciences in the past two decades has led to a divergence of geophysical, geochemical, geological, and planetological models for the composition and evolution of a terrestrial planet. Evidence for differentiation and volcanism on small planets and a magma ocean on the moon contrasts with hypotheses for a mostly primitive, still undifferentiated, and homogeneous terrestrial mantle. In comparison with the moon, the earth has an extraordinarily thin crust. The geoid, which should reflect convection in the mantle, is apparently unrelated to the current distribution of continents and oceanic ridges. If the earth is deformable, the whole mantle should wander relative to the axis of rotation, but the implications of this are seldom discussed. The proposal of a mantle rich in olivine violates expectations based on evidence from extraterrestrial sources. These and other paradoxes force a reexamination of some long-held assumptions.
Carbon Monoxide in the Earth's Atmosphere: Increasing Trend
Authors: Khalil M. A. K. , Rasmussen R. A.
Published: October 2006

The results of an analysis of more than 60,000 atmospheric measurements of carbon monoxide taken over 3½ years at Cape Meares, Oregon (45°N, 125°W), indicate that the background concentration of this gas is increasing. The rate of increase, although uncertain, is about 6 percent per year on average. Human activities are the likely cause of a substantial portion of this observed increase; however, because of the short atmospheric lifetime of carbon monoxide and the relatively few years of observations, fluctuations of sources and sinks related to the natural variability of climate may have affected the observed trend. Increased carbon monoxide may deplete tropospheric hydroxyl radicals, slowing down the removal of dozens of man-made and anthropogenic trace gases and thus indirectly affecting the earth's climate and possibly the stratospheric ozone layer.
Laying Eggs in a Neighbor's Nest: Benefit and Cost of Colonial Nesting in Swallows
Authors: Brown Charles R.
Published: October 2006

Intraspecific brood parasitism (laying eggs in another's nest) occurs widely in colonial cliff swallows (Passeriformes: Hirundinidae:
Hirundo pyrrhonota
). In colonies consisting of more than ten nests, up to 24 percent of the nests were sometimes parasitized by colony members. Laying eggs in a conspecific's nest may be a benefit of coloniality for parasitic individuals and simultaneously may represent a cost to host individuals within the same colony.
Computer-Based Instructional Dialogs in Science Courses
Authors: Arons A. B.
Published: October 2006

The personal computer is opening the door to supplemental, essentially tutorial, modes of science instruction that, particularly at introductory levels, can significantly enhance understanding of science and develop abstract reasoning skills. Competently prepared and judiciously utilized materials have the potential to improve the education of science and engineering professionals, elementary and secondary teachers, and, to some degree, the public at large.
Substance P: Evidence for Diverse Roles in Neuronal Function from Cultured Mouse Spinal Neurons
Authors: Vincent Jean-Didier , Barker Jeffery L.
Published: October 2006

Mouse spinal neurons grown in tissue culture were used to examine the membrane mechanisms of action of the peptide substance P. Two functionally distinct actions were observed, one being a rapidly desensitizing excitation, and the other being a dose-dependent, reversible depression of excitatory responses to the putative amino acid neurotransmitter glutamate. These effects on excitability suggest that substance P may play more than one role in intercellular communication in the nervous system.
Microorganisms in the Space Environment
Authors: Horneck G. , Bücker H. , Reitz G. , Requardt H. , Dose K. , Martens K. D. , Mennigmann H. D. , Weber P.
Published: October 2006

Preliminary results of the Spacelab 1 experiment on the response of
Bacillus subtilis
spores to conditions of free space are presented. Exposure to the vacuum of space on the Spacelab pallet reduced viability counts about 50 percent and increased mutation frequencies by a factor of about 10. Interpretation of apparent differences in the photobiological and photochemical data between flight and ground simulation experiments will require more statistical analyses and data from actual fluence measurements.
Marine Lava Cave Fauna: Composition, Biogeography, and Origins
Authors: Iliffe Thomas M. , Wilkens Horst , Parzefall Jakob , Williams Dennis
Published: October 2006

An assemblage of endemic cavernicolous marine invertebrates, including taxa found on both sides of the Atlantic Ocean of great phylogenetic age or with affinities to deep sea organisms, inhabits the Jameos del Agua cave, a sea waterflooded Holocene lava tube cave on Lanzarote in the Canary Islands. This marine cave contains both relicts from Tethyan times, such as an apparently new crustacean family belonging to what had been the monotypic class Remipedia, and relicts of groups that are now common only in the deep sea as well as species that occur outside the cave.
Species Formation Through Punctuated Gradualism in Planktonic Foraminifera
Authors: Malmgren Björn A. , Berggren W. A. , Lohmann G. P.
Published: October 2006

Detailed analysis of evolutionary changes in a 10-million-year long Late Neogene lineage of planktonic foraminifera has revealed a pattern that is not consistent with either the gradualistic or the punctuational model of evolution. The lineage was in stasis over a considerable part of its total duration but underwent relatively rapid, but not geologically instantaneous, gradual morphologic change that did not lead to lineage splitting. The term punctuated gradualism is suggested for this evolutionary modality.
Dynamics of Globular Clusters
Authors: Spitzer Lyman
Published: October 2006

In their attempt to reach kinetic equilibrium, through gravitational encounters between separate stars, globular clusters are driven to destruction, with their cores collapsing and their outer regions expanding. The effects of core collapse, which apparently produces x-ray sources, are not yet fully understood, but white dwarfs and neutron stars, probably in binary systems, are thought to be involved, and possibly black holes as well.
Biomechanics of Mammalian Terrestrial Locomotion
Authors: Biewener Andrew A.
Published: October 2006

Mammalian skeletons experience peak locomotor stresses (force per area) that are 25 to 50% of their failure strength, indicating a safety factor of between two and four. The mechanism by which animals achieve a constant safety factor varies depending on the size of the animal. Over much of their size range (0.1 to 300 kilograms), larger mammals maintain uniform skeletal stress primarily by having a more upright posture, which decreases mass-specific muscle force by increasing muscle mechanical advantage. At greater sizes, increased skeletal allometry and decreased locomotor performance likely maintain stresses constant. At smaller sizes, skeletal stiffness may be more critical than strength. The decrease in mass-specific muscle force in mammals weighing 0.1 to 300 kilogram indicates that peak muscle stresses are also constant and correlates with a decrease in mass-specific energy cost of locomotion. The consistent pattern of locomotor stresses developed in long bones at different speeds and gaits within a species may have important implications for how bones adaptively remodel to changes in stress.
Autonomous Developmental Control of Human Embryonic Globin Gene Switching in Transgenic Mice
Authors: Raich Natacha , Enver Tariq , Nakamoto Betty , Josephson Betty , Papayannopoulou Thalia , Stamatoyannopoulos George
Published: October 2006

The mechanisms by which expression of the β-like globin genes are developmentally regulated are under intense investigation. The temporal control of human embryonic (ε) globin expression was analyzed. A 3.7-kilobase (kb) fragment that contained the entire human ε-globin gene was linked to a 2.5-kb cassette of the locus control region (LCR), and the developmental time of expression of this construct was studied in transgenic mice. The human ε-globin transgene was expressed in yolk sac-derived primitive erythroid cells, but not in fetal liver or bone marrow-derived definitive erythroid cells. The absence of ε gene expression in definitive erythroid cells suggests that the developmental regulation of the ε-globin gene depends only on the presence of the LCR and the ε-globin gene itself (that is, an autonomous negative control mechanism). The autonomy of ε-globin gene developmental control distinguishes it from the competitive mechanism of regulation of γ and β-globin genes, and therefore, suggests that at least two distinct mechanisms function in human hemoglobin switching.
Disruption of the Human SCL Locus by "Illegitimate" V-(D)-J Recombinase Activity
Authors: Aplan Peter D. , Lombardi Donald P. , Ginsberg Ann M. , Cossman Jeffrey , Bertness Virginia L. , Kirsch Ilan R.
Published: October 2006

A fusion complementary DNA in the T cell line HSB-2 elucidates a provocative mechanism for the disruption of the putative hematopoietic transcription factor
SCL
. The fusion cDNA results from an interstitial deletion between a previously unknown locus,
SIL
(
SCL
interrupting locus), and the 5′ untranslated region of
SCL
. Similar to 1;14 translocations, this deletion disrupts the
SCL
5′ regulatory region. This event is probably mediated by V-(D)-J recombinase activity, although neither locus is an immunoglobulin or a T cell receptor. Two other T cell lines, CEM and RPMI 8402, have essentially identical deletions. Thus, in lymphocytes, growth-affecting genes other than immune receptors risk rearrangements.
Tailored Surface Modification by Ion Implantation and Laser Treatment
Authors: Picraux S. T. , Pope L. E.
Published: October 2006

An important trend in materials science is the use of increasingly sophisticated methods to control composition and microstructure during processing. Near-surface modification by ion implantation and laser treatment is one of these new methods for tailoring material properties. Novel materials have been formed which are far from thermodynamic equilibrium and which exhibit unexpected and useful properties. The most extensively studied property changes include modified electrical properties of semiconductors and improved wear, hardness, and corrosion resistance of metals. The high degree of control available with energetic beams allows relations between microstructure and properties to be systematically investigated at the atomic level. This article illustrates how ion and laser beam modification is being applied to advance both the technology and the exploratory science of materials.
Dynamics of Conformational Transitions in Polymers
Authors: Helfand Eugene
Published: October 2006

Conformational transitions in polymers involve large angle rotations about bonds. The process must proceed in a way that does not require gross movements of the macromolecules. The dynamics have been investigated by computer simulation and kinetic theory. The rate-determining step in the transition is found to occur in a mode which is kept local by distortion of nearby parts of the molecule. One especially important type of cooperativity, crank-like counterrotation of second-neighbor bonds, is identified. Experiments which provide evidence about the dynamics of conformational transitions are discussed.
Conducting Organic Materials
Authors: Greene R. L. , Street G. B.
Published: October 2006

Some of the current directions of scientific research on electrically conducting organic solids are reviewed. Both molecular charge transfer salts and polymers are included, with emphasis on the present level of understanding of the novel solid-state properties of these materials in terms of their chemistry and structure. For the charge transfer salts the various types of metal-to-insulator phase transitions which dominate the properties of most of these materials are discussed. Also described are the superconducting and magnetic states which have been found recently. In the case of the polymers the chemistry and physics of the conduction mechanism is examined and contrasted with that of their classical inorganic counterparts.
The Search for Very Low Loss Fiber-Optic Materials
Authors: Lines M. E.
Published: October 2006

Today's fiber-optic communications systems are fused-silica—based fibers for which signals require reamplification every 30 kilometers. Repeaterless long-haul (transcontinental and transoceanic) links can only be envisaged if a new fiber material with intrinsic power losses significantly lower than those of silica can be identified and developed. This article reviews the development of silica-based systems, details the physical mechanisms which produce signal attenuation in fiber materials in general, and identifies that class of materials from which ultralow loss glasses are most likely to be developed in the future.
Relativistic Projectile Fragment Interactions: Anomalons
Authors: Karol Paul J.
Published: October 2006

Interaction mean free paths are calculated for projectile fragments from relativistic heavy-ion interactions in emulsions and plastic. There are important discrepancies between emulsion results and those from other techniques. "Anomalous" secondaries (anomalons) may prove to be interpretable by conventional nuclear physics: short mean free paths may be due to convoys of collinear light fragments from peripheral interactions (for example, with neutrons) or from low-excitation particle-unbound fragments that decay in flight.
Larval Development and Dispersal at Deep-Sea Hydrothermal Vents
Authors: Lutz Richard A. , Jablonski David , Turner Ruth D.
Published: October 2006

Deep-sea hydrothermal vent communities exhibit an array of reproductive strategies. Although a few vent species undergo planktotrophic, high-dispersal modes of development, most exhibit relatively low dispersal, but probably free-swimming nonplanktotrophic development. This predominance of nonplanktotrophy may be largely a reflection of phylogenetic constraints on the vent colonizing taxa; intervent dispersal among these forms may be facilitated by reduced developmental rates in the cold abyssal waters away from the vents. It is proposed that for those vent species with nonplanktotrophic development, larval dispersal is a stepwise process with oceanic ridge axes serving as discrete dispersal corridors.
Courtship Disruption Modifies Mate Choice in a Lek-Breeding Bird
Authors: Trail Pepper W.
Published: October 2006

The aggregation of displaying males in lek-breeding birds is often associated with disruption of courtship and mating but effects of this disruption on mate choice have not been shown. In a 4-year study of
Rupicola rupicola
in Suriname, interference among territorial adult males disrupted 31 percent of all female courtship visits and terminated 32 percent of all matings at a lek where there were an average of 55 territorial males. Disruption in this rain forest species caused females to modify their courtship and mating patterns, and males that used intense and persistent disruption received a disproportionate share of this redirected mate choice.
Volatile Halogenated Organic Compounds Released to Seawater from Temperate Marine Macroalgae
Authors: Gschwend Philip M. , MacFarlane John K. , Newman Kathleen A.
Published: October 2006

Volatile halogenated organic compounds synthesized by various industrial processes are troublesome pollutants because they are persistent in terrestrial ecosystems and because they may be present in sufficient quantities to alter the natural atmospheric cycles of the halogens. Certain of these compounds, including polybromomethanes and several previously unobserved alkyl monohalides and dihalides, appear to be natural products of the marine environment. A variety of temperate marine macroalgae (the brown algae
Ascophyllum nodosum
and
Fucus vesiculosis
, the green algae
Enteromorpha linza
and
Ulva lacta
, and the red alga
Gigartina stellata
) not only contain volatile halogenated organic compounds but also release them to seawater at rates of nanograms to micrograms of each compound per gram of dry algae per day. The macroalgae may be an important source of bromine-containing material released to the atmosphere.
Interspecific Morphogens Regulating Prey-Predator Relationships in Protozoa
Authors: Kuhlmann Hans-Werner , Heckmann Klaus
Published: October 2006

The ciliate
Euplotes octocarinatus
and some close relatives of it are triggered by predator-released substances to undergo morphogenetic changes that inhibit their engulfment. The changes occur within a few hours and do not require cell division. They are perpetuated during reproduction so long as the concentration of the morphogen is maintained. The ability of
Euplotes
to respond to predator-produced signals by a defensive change in cell architecture probably provides an effective mechanism for damping population oscillations of both prey and predators and fosters coexistence. The signal-induced cell transformation merits study for its own sake because of its developmental implications.
Inheritance of Proliferative Breast Disease in Breast Cancer Kindreds
Authors: Skolnick Mark H. , Cannon-Albright Lisa A. , Goldgar David E. , Ward John H. , Marshall C. Jay , Schumann G. Berry , Hogle Hugh , McWhorter William P. , Wright Eileen C. , Tran Thao D. , Bishop D. Timothy , Kushner James P. , Eyre Harmon J.
Published: October 2006

Previous studies have emphasized that genetic susceptibility to breast cancer is rare and is expressed primarily as premenopausal breast cancer, bilateral breast cancer, or both. Proliferative breast disease (PBD) is a significant risk factor for the development of breast cancer and appears to be a precursor lesion. PBD and breast cancer were studied in 103 women from 20 kindreds that were selected for the presence of two first degree relatives with breast cancer and in 31 control women. Physical examination, screening mammography, and four-quadrant fine-needle breast aspirates were performed. Cytologic analysis of breast aspirates revealed PBD in 35% of clinically normal female first degree relatives of breast cancer cases and in 13% of controls. Genetic analysis suggests that genetic susceptibility causes both PBD and breast cancer in these kindreds. This study supports the hypothesis that this susceptibility is responsible for a considerable portion of breast cancer, including unilateral and postmenopausal breast cancer.
Temperature Acclimation: Improved Sustained Swimming Performance in Carp at Low Temperatures
Authors: Rome Lawrence C. , Loughna Paul T. , Goldspink Geoffrey
Published: October 2006

At low temperatures, the reduction in mechanical power output of the aerobic muscle forces cold-blooded animals, such as carp, to recruit their rapidly fatiguing anaerobic fibers at relatively slow swimming speeds. Previous experimental data have suggested that changes in the biochemistry and morphology of the aerobic muscle during cold acclimation might increase its output of mechanical power. The present experiments show that, because of these changes, carp can swim faster at low temperature using only their aerobic muscle, which results in an increase in their sustainable swimming speed. By modifying their musculature, cold-blooded animals can achieve some independence from the effects of seasonal changes in environmental temperature.
Intelligent Tutoring Systems
Authors: Anderson John R. , Boyle C. Franklin , Reiser Brian J.
Published: October 2006

Cognitive psychology, artificial intelligence, and computer technology have advanced to the point where it is feasible to build computer systems that are as effective as intelligent human tutors. Computer tutors based on a set of pedagogical principles derived from the ACT* theory of cognition have been developed for teaching students to do proofs in geometry and to write computer programs in the language LISP.