bluuebunny/crossref_metadata_2025 huggingface dataset:
Partial Symmetrization of the Photosynthetic Reaction Center
Authors: Robles Steven J. , Breton Jacques , Youvan Douglas C.
Published: October 2006

The bacterial photosynthetic reaction center (RC) is a pigmented intrinsic membrane protein that performs the primary charge separation event of photosynthesis, thereby converting light to chemical energy. The RC pigments are bound primarily by two homologous peptides, the L and M subunits, each containing five transmembrane helices. These α helices and pigments are arranged in an approximate C
2
symmetry and form two possible electron transfer pathways. Only one of these pathways is actually used. In an attempt to identify nonhomologous residues that are responsible for functional differences between the two branches, homologous helical regions that interact extensively with the pigments were genetically symmetrized (that is, exchanged). For example, replacement of the fourth transmembrane helix (D helix) in the M subunit with the homologous helix from the L subunit yields photosynthetically inactive RCs lacking a critical photoactive pigment. Photosynthetic revertants have been isolated in which single amino acid substitutions (intragenic suppressors) compensate for this partial symmetrization.
Site-Specific Cleavage of a Yeast Chromosome by Oligonucleotide-Directed Triple-Helix Formation
Authors: Strobel Scott A. , Dervan Peter B.
Published: October 2006

Oligonucleotides equipped with EDTA⋅Fe can bind specifically to duplex DNA by triple-helix formation and produce double-strand cleavage at binding sites greater than 12 base pairs in size. To demonstrate that oligonucleotide-directed triple-helix formation is a viable chemical approach for the site-specific cleavage of large genomic DNA, an oligonucleotide with EDTA⋅Fe at the 5′ and 3′ ends was targeted to a 20-base pair sequence in the 340-kilobase pair chromosome III of
Saccharomyces cerevisiae
. Double-strand cleavage products of the correct size and location were observed, indicating that the oligonucleotide bound and cleaved the target site among almost 14 megabase pairs of DNA. Because oligonucleotide-directed triple-helix formation has the potential to be a general solution for DNA recognition, this result has implications for physical mapping of chromosomes.
A Cytokinin (Isopentenyl-Adenosyl-Mononucleotide) Linked to Ecdysone in Newly Laid Eggs of
Locusta migratoria
Authors: Tsoupras Georges , Luu Bang , Hoffmann Jules A.
Published: October 2006

Newly laid eggs of the insect
Locusta migratoria

contain high concentrations (50 nanomoles per gram) of an ecdysone conjugate of maternal origin; 3 milligrams of this conjugate were isolated by conventional techniques, and the structure was established by mass spectrometry and
1
H,
13
C, and
31
P nuclear magnetic resonance as the 22

-N

6

-
(isopentenyl)-adenosine monophosphoric ester of ecdysone
.
Treehoppers Transfer Parental Care to Ants: A New Benefit of Mutualism
Authors: Bristow Catherine M.
Published: October 2006

Female treehoppers (
Publilia reticulata
Van Duzee) modify their parental care behavior in the presence of ants. Females with untended young remain with their original brood, but females from ant-tended colonies readily desert their first brood and produce additional clutches. Care by female treehoppers, in the absence of ants, increases the probability that a colony will produce some survivors, but ant attendance greatly increases the number of surviving nymphs.
Insular Erosion, Isostasy, and Subsidence
Authors: Menard H. W.
Published: October 2006

Organic reefs and shore erosion record the intersection of sea level with islands. From this record it is possible to reconstruct the history of vertical movement of the islands and the adjacent deep sea floor, including midplate swells. As judged by coral thickness, islands with barrier reefs sink as though they were on thermally youthful crust regardless of the actual age. Reefless islands do not sink until truncated by erosion. Apparently, thermal subsidence is balanced by isostatic uplift in response to erosion. Barrier reefs prevent wave erosion of encircled volcanoes and capture products of stream erosion so that isostatic uplift is eliminated. Insular shelves widen initially at rates of 0.6 to 1.7 kilometers per million years; the rates decrease with time. Thus the subsidence of islands depends on the size of the island and the presence of reefs, and it may not always be the same as that of the surrounding oceanic crust.
Hemoglobin in a Nonleguminous Plant,
Parasponia
: Possible Genetic Origin and Function in Nitrogen Fixation
Authors: Appleby Cyril A. , Tjepkema John D. , Trinick Michael J.
Published: October 2006

A dimeric hemoglobin was purified from nitrogen-fixing root nodules formed by association of
Rhizobium
with a nonleguminous plant,
Parasponia
. The oxygen dissociation rate constant is probably sufficiently high to allow
Parasponia
hemoglobin to function in a fashion similar to that of leghemoglobin, by oxygen buffering and transport during symbiotic nitrogen fixation. The identification of hemoglobin in a nonlegume raises important questions about the evolution of plant hemoglobin genes.
Building R & D Policy from Strength
Authors: Schmitt Roland W.
Published: October 2006

Many proposals have been made for new initiatives in our nation's research and development system. But before rushing into untried approaches, we need to look to the foundations of the system that has worked so well for us in the past. We have a climate for venture capital that has never been better; the world's greatest research universities; an industrial base that is moving aggressively into high technology, spurred by competition; and a defense effort that can be a major asset to civilian R & D. We should build our future by understanding and using these existing strengths.
Leaf Color Used by Cabbage Root Flies to Distinguish Among Host Plants
Authors: Prokopy Ronald J. , Collier Rosemary H. , Finch Stanley
Published: October 2006

In experiments in which spectrophotometric reflectance patterns of real leaves were mimicked with mixtures of artists' pigments, leaf color was shown to be a character used by cabbage root flies, before landing on leaves, to discriminate among the host plant cultivars radish, green cabbage, and red cabbage. It may be possible to take advantage of factors that affect leaf color, such as epicuticular bloom, pubescence, and masking of chlorophyll by other pigments, to decrease the attraction of certain pest insects to plants.
A Continuum of Sleep and Shallow Torpor in Fasting Doves
Authors: Walker Larry E. , Walker James M. , Palca Joseph W. , Berger Ralph J.
Published: October 2006

Fasting doves entered shallow torpor during nocturnal sleep. Body temperature dropped lower each successive night by 1° to 3° in parallel with diminished rapid-eye-movement sleep until torpor was composed almost entirely of slow-wave sleep at a body temperature of 30° to 32°C. Shallow torpor in doves, as in mammals, thus appears to lie on a metabolic continuum with sleep.
Ages Estimated from a Diffusion Equation Model for Scarp Degradation
Authors: Colman Steven M. , Watson Ken
Published: October 2006

The diffusion equation derived from the continuity equation for hillslopes is applied to scarp erosion in unconsolidated materials. Solutions to this equation allow direct calculation of the product of the rate coefficient and the age of the scarp from measurements of scarp morphology. Where the rate coefficient can be estimated or can be derived from scarps of known age, this method allows direct calculation of unknown ages of scarps.
Patterns of Nitrogen Excretion by Embryonic Softshell Turtles (
Trionyx spiniferus
) Developing in Cleidoic Eggs
Authors: Packard Gary C. , Packard Mary J.
Published: October 2006

Embryonic softshell turtles develop inside eggs exchanging little, if any, liquid water with the nest environment. Despite the consequent restriction on availability of water to support development, embryos convert most of the ammonia released in catabolism of proteins into soluble urea rather than insoluble urate, and thereby commit a portion of their limited reserve of water to serve as solvent for metabolic wastes. This finding is contrary to expectations from prior studies of cleidoic eggs.
Siphonodictidine, a Metabolite of the Burrowing Sponge
Siphonodictyon
sp. That Inhibits Coral Growth
Authors: Sullivan BRIAN , Faulkner D. John , Webb Leith
Published: October 2006

Siphonodictidine is the major secondary metabolite of an undescribed Indo-Pacific sponge
Siphonodictyon
sp. that burrows into living coral heads. The structure of siphonodictidine was determined from spectral data. Laboratory bioassays suggest that siphonodictidine and, by analogy, the siphonodictyals from
S. coralliphagum
are responsible for maintaining zones of dead coral polyps around the oscular chimneys of these sponges.
Gas Emissions and the Eruptions of Mount St. Helens Through 1982
Authors: Casadevall T. , Rose W. , Gerlach T. , Greenland L. P. , Ewert J. , Wunderman R. , Symonds R.
Published: October 2006

The monitoring of gas emissions from Mount St. Helens includes daily airborne measurements of sulfur dioxide in the volcanic plume and monthly sampling of gases from crater fumaroles. The composition of the fumarolic gases has changed slightly since 1980: the water content increased from 90 to 98 percent, and the carbon dioxide concentrations decreased from about 10 to 1 percent. The emission rates of sulfur dioxide and carbon dioxide were at their peak during July and August 1980, decreased rapidly in late 1980, and have remained low and decreased slightly through 1981 and 1982. These patterns suggest steady outgassing of a single batch of magma (with a volume of not less than 0.3 cubic kilometer) to which no significant new magma has been added since mid-1980. The gas data were useful in predicting eruptions in August 1980 and June 1981.
Cigarette Smoke Activates Guanylate Cyclase and Increases Guanosine 3′,5′-Monophosphate in Tissues
Authors: Arnold William P. , Aldred Robert , Murad Ferid
Published: October 2006

The gaseous phase of cigarette smoke induced a 2- to 36-fold increase in the activity of guanylate cyclase in supernatant and particulate fractions from various rat and bovine tissues over basal activity. The characteristics of this phenomenon paralleled those of the activation of guanylate cyclase by nitric oxide, which is a component of tobacco smoke.
Neurotrophic and Neurotoxic Effects of Amyloid β Protein: Reversal by Tachykinin Neuropeptides
Authors: Yankner Bruce A. , Duffy Lawrence K. , Kirschner Daniel A.
Published: October 2006

The amyloid β protein is deposited in the brains of patients with Alzheimer's disease but its pathogenic role is unknown. In culture, the amyloid β protein was neurotrophic to undifferentiated hippocampal neurons at low concentrations and neurotoxic to mature neurons at higher concentrations. In differentiated neurons, amyloid β protein caused dendritic and axonal retraction followed by neuronal death. A portion of the amyloid β protein (amino acids 25 to 35) mediated both the trophic and toxic effects and was homologous to the tachykinin neuropeptide family. The effects of the amyloid β protein were mimicked by tachykinin antagonists and completely reversed by specific tachykinin agonists. Thus, the amyloid β protein could function as a neurotrophic factor for differentiating neurons, but at high concentrations in mature neurons, as in Alzheimer's disease, could cause neuronal degeneration.
Computer Simulations of the Belousov-Zhabotinsky Reaction
Authors: Madore Barry F. , Freedman Wendy L.
Published: October 2006

Morphological features of the two-dimensional Belousov-Zhabotinsky reaction were modeled with an algorithm involving only two simple parameters, one describing the productivity of the reaction on a local scale length and the other characterizing the delay or quiescent time after the localized reaction. Self-organizing wavelike structures, including single- and multiarmed spirals, were most easily generated.
Introduction of Genetic Material into Plant Cells
Authors: Caplan A. , Herrera-Estrella L. , Inzé D. , Van Haute E. , Van Montagu M. , Schell J. , Zambryski P.
Published: October 2006

The tumor-inducing (Ti) plasmid of the soil microorganism
Agrobacterium tumefaciens
is the agent of crown gall disease in dicotyledonous plants. The Ti plasmid contains two regions that are essential for the production of transformed cells. One of these regions, termed transfer DNA, induces tumor formation and is found in all established plant tumor lines; the other, termed the virulence region, is essential for the formation but not the maintenance of tumors. Transfer DNA, which transfers to the plant genomes in a somewhat predictable manner, can be increased in size by the insertion of foreign DNA without its transferring ability being affected. The tumor-causing genes can be removed so that they no longer interfere with normal plant growth and differentiation. This modified Ti plasmid can thus be used as a vector for the transfer of foreign genes into plants.
Studying Scientific Discovery by Computer Simulation
Authors: Bradshaw Gary F. , Langley Patrick W. , Simon Herbert A.
Published: October 2006

BACON is a computer program that simulates some of the important processes of scientific discovery. When provided with data about temperatures before and after two substances are brought into contact, the program infers the concept of specific heat and arrives at Black's law of temperature equilibrium. Comparison of BACON's discovery methods with historical records of Black's work casts light on the relation between data-driven and theory-driven discovery.
Equatorial Undercurrent Disappears During 1982-1983 El Niño
Authors: Firing Eric , Lukas Roger , Sadler James , Wyrtki Klaus
Published: October 2006

The equatorial undercurrent at 159°W decayed during August 1982, partially reversed during September, and rapidly reappeared in January 1983. The virtual disappearance is consistent with the basin-wide adjustment of sea surface slope to the strong westerly winds in the western and central Pacific that caused the 1982-1983 El Niño event.
Native Cellulose: A Composite of Two Distinct Crystalline Forms
Authors: Atalla Rajai H. , VanderHart David L.
Published: October 2006

Multiplicities in the resonances of chemically equivalent carbons, which appear in the solid-state carbon-13 nuclear magnetic resonance spectra of native celluloses, have been examined at high resolution. The patterns of variation are consistent with the existence of two distinct crystalline forms. One form is dominant in bacterial and algal celluloses, whereas the other is dominant in celluloses from higher plants.
Inheritance of Functional Foreign Genes in Plants
Authors: Horsch Robert B. , Fraley Robert T. , Rogers Stephen G. , Sanders Patricia R. , Lloyd Alan , Hoffmann Nancy
Published: October 2006

Morphologically normal plants were regenerated from
Nicotiana plumbaginifolia
cells transformed with an
Agrobacterium tumefaciens
strain containing a tumor-inducing plasmid with a chimeric gene for kanamycin resistance. The presence of the chimeric gene in regenerated plants was demonstrated by Southern hybridization analysis, and its expression in plant tissues was confirmed by the ability of leaf segments to form callus on media containing kanamycin at concentrations that were normally inhibitory. Progeny derived from several transformed plants inherited the foreign gene in a Mendelian manner.
Bismuth Bronze from Machu Picchu, Peru
Authors: Gordon Robert B. , Rutledge John W.
Published: October 2006

The decorative bronze handle of a tumi excavated at the Inca city of Machu Picchu, Peru, contains 18 percent bismuth and appears to be the first known example of the use of bismuth with tin to make bronze. The alloy is not embrittled by the bismuth because the bismuth-rich constituent does not penetrate the grain boundaries of the matrix phase. The use of bismuth facilitates the duplex casting process by which the tumi was made and forms an alloy of unusual color.
Down-regulation of LFA-1 Adhesion Receptors by C-
myc
Oncogene in Human B Lymphoblastoid Cells
Authors: Inghirami Giorgio , Grignani Francesco , Sternas Lars , Lombardi Luigia , Knowles Daniel M. , Dalla-Favera Riccardo
Published: October 2006

The function of the c-
myc
gene and its role in tumorigenesis are poorly understood. In order to elucidate the role of c-
myc
oncogene activation in B cell malignancy, the phenotypic changes caused by the expression of c-
myc
oncogenes in human B lymphoblastoid cells immortalized by Epstein-Barr virus were analyzed. C-
myc
oncogenes caused the down-regulation of lymphocyte function-associated antigen-1 (LFA-1) adhesion molecules (α
L
/ β
2
integrin) and loss of homotypic B cell adhesion in vitro. Down-regulation of LFA-1 occurred by (i) posttranscriptional modulation of LFA-1 α
L
-chain RNA soon after acute c-
myc
induction, and (ii) transcriptional modulation in cells that chronically express c-
myc
oncogenes. Analogous reductions in LFA-1 expression were detectable in Burkitt lymphoma cells carrying activated c-
myc
oncogenes. Since LFA-1 is involved in B cell adhesion to cytotoxic T cells, natural killer cells, and vascular endothelium, these results imply functions for c-
myc
in normal B cell development and lymphomagenesis.
Methylation of an Immediate-Early Inducible Gene as a Mechanism for B Cell Tolerance Induction
Authors: Seyfert Vicki L. , McMahon Steven B. , Glenn William D. , Yellen Amy J. , Sukhatme Vikas P. , Cao Xinmin , Monroe John G.
Published: October 2006

Stage-specific gene regulation is important in determining cell function during development. Immature B cells expressing membrane-bound immunoglobulin M (mIgM) are sensitive to antigen-induced tolerance, whereas mature B cells are activated by antigen. Previous studies have established an association between
Egr-1
gene induction and antigen receptor (mIgM)-mediated activation of mature B cells. Here it is shown that the immature B cell line WEHI-231 and tolerance-sensitive bone marrow-derived B cells do not express
Egr-1
. It is further shown that lack of inducible expression in these cells is due to specific methylation of the
Egr-1
gene. Thus, covalent inactivation of an activation-associated gene may explain tolerance sensitivity at specific stages of B cell development.
A Cytoplasmic Protein Inhibits the GTPase Activity of H-Ras in a Phospholipid-Dependent Manner
Authors: Tsai Men-Hwei , Yu Chun-Li , Stacey Dennis W.
Published: October 2006

A cytoplasmic protein has been identified that inhibits the guanosine triphosphatase (GTPase) activity of bacterially synthesized, cellular H-Ras protein. This GTPase inhibiting protein is able to counteract the activity of GTPase activating protein (GAP), which has been postulated to function as a negative regulator of Ras activity. The potential biological importance of the GTPase inhibiting protein is further supported by its interaction with lipids. Phospholipids produced in cells as a consequence of mitogenic stimulation increase the activity of the GTPase inhibiting protein, as well as inhibit the activity of GAP. The interaction of such lipids with each of these two regulatory proteins would, therefore, tend to increase the biological activity of Ras and stimulate cell proliferation.
Helium-3 Emission Related to Volcanic Activity
Authors: Sano Yuji , Nakamura Yuji , Wakita Hiroshi , Urabe Akiko , Tominaga Takeshi
Published: October 2006

The helium-3/helium-4 ratio in bubbling gases from ten hot springs located around Mount Ontake, an active volcano in central Japan, ranges from 1.71
R
atm
(1.71 times the atmospheric ratio of 1.40 × 10
-6
) to 6.15
R
atm
. The value of the ratio decreases with distance from the central cone of the volcano. Such a tendency may be a characteristic of helium-3 emission in volcanic areas and suggests more primitive helium-3 is carried with fluid flowing through a conduit during volcanic activity.
Ancient Ice Islands in Salt Lakes of the Central Andes
Authors: Hurlbert Stuart H. , Chang Cecily C. Y.
Published: October 2006

Massive blocks of freshwater ice and frozen sediments protrude from shallow, saline lakes in the Andes of southwestern Bolivia and northeastern Chile. These ice islands range up to 1.5 kilometers long, stand up to 7 meters above the water surface, and may extend out tens of meters and more beneath the unfrozen lake sediments. The upper surfaces of the islands are covered with dry white sediments, mostly aragonite or calcite. The ice blocks may have formed by freezing of the fresh pore water of lake sediments during the "little ice age." The largest blocks are melting rapidly because of possibly recent increases in geothermal heat flux through the lake bottom and undercutting by warm saline lake water during the summer.
Trace Elements in Tree Rings: Evidence of Recent and Historical Air Pollution
Authors: Baes C. F. , McLaughlin S. B.
Published: October 2006

Annual growth rings from short-leaf pine trees in the Great Smoky Mountains National Park show suppressed growth and increased iron content between 1863 and 1912, a period of smelting activity and large sulfur dioxide releases at Copperhill, Tennessee, 88 kilometers upwind. Similar growth suppression and increases of iron and other metals were found in rings formed in the past 20 to 25 years, a period when regional fossil fuel combustion emissions increased about 200 percent. Metals concentrations in phloem and cambium are high, but whether they exceed toxic thresholds for these tissues is not known.
Satellite Observations of the 1982-1983 El Niño Along the U.S. Pacific Coast
Authors: Fiedler Paul C.
Published: October 2006

Satellite infrared temperature images illustrate several effects of the 1982-1983 El Niño: warm sea-surface temperatures with the greatest anomalies near the coast, weakened coastal upwelling, and changes in surface circulation patterns. Phytoplankton pigment images from the Coastal Zone Color Scanner indicate reduced productivity during El Niño, apparently related to the weakened coastal upwelling. The satellite images provide direct evidence of mesoscale changes associated with the oceanwide El Niño event.
Strategic Command, Control, Communications, and Intelligence
Authors: Zraket Charles A.
Published: October 2006

Command, control, communications, and intelligence (C
3
I) for nuclear forces are essential elements in the deterrence of nuclear war. The present C
3
I system has vulnerabilities associated with its reliability, survivability, and endurance under attack, thereby weakening deterrence by increasing the ambiguity in our capabilities. Development of a reliable and enduring C
3
I system would reduce this ambiguity. Its reliable, positive control of nuclear forces would give the national leadership more time to assess situations, ensure discriminate retaliation, and improve our ability to manage crises in general. These capabilities could help to stop a war rapidly should one start. A reliable and enduring C
3
I system will be needed for a long time to come, even if a freeze on strategic nuclear forces is accomplished or other arms control successes achieved. Indeed, C
3
I may be the best source today of confidence-building measures to reduce tensions and the threat of nuclear catastrophe.
The Association of Iron and Manganese with Bacteria on Marine Macroparticulate Material
Authors: Cowen James P. , Silver Mary Wilcox
Published: October 2006

Evidence of in situ metal (iron and manganese) deposition onto bacteria associated with rapidly sinking particles in the open ocean is reported. Below 100 meters, bacteria are found with extracellular capsules containing metal precipitates; the frequency of these capsules increases with depth. The capsular metal deposits appear to contribute a major portion of the weakly bound fraction of the particulate iron flux.
Amazon Basin: A System in Equilibrium
Authors: Salati Eneas , Vose Peter B.
Published: October 2006

Despite the very active deforestation of the last decade, the Amazon Basin is still primarily covered with trees and is a system in equilibrium. The Andes form a barrier at the western end of the basin and, coupled with the prevailing easterly winds, ensure an almost unique precipitation and water-recycling regime. On average 50 percent of the precipitation is recycled, and in some areas even more. The soils are poor. Most of the nitrogen and phosphorus is found in the soil, and the remaining nutrient elements are found in the standing biomass. There is some nutrient recycling and little loss from the intact ecosystem, and the small input of nutrients from precipitation maintains a small positive nutrient balance. Continued large-scale deforestation is likely to lead to increased erosion and water runoff with initial flooding in the lower Amazon, together with reduced evapotranspiration and ultimately reduced precipitation. Reduced precipitation in the Amazon could increase the tendency toward continentality and adversely affect climate and the present agriculture in south-central Brazil.
Atmospheric Spectral Imaging
Authors: Torr Marsha R. , Torr D. G.
Published: October 2006

An array of imaging spectrometers flown on the Spacelab 1 mission was capable of providing spectra of the atmospheric emissions over a broad wavelength range from 300 to 12,700 angstroms and acquiring each complete spectrum nearly simultaneously. The instrument was used to make observations on the day side and night side of the earth, looking down in the nadir direction, radially away from the earth, and in various limb-scanning modes. Observations were made looking at various angles to the vehicle velocity vector and during thruster firings and water dumps as well as at times when such events were inhibited. As a result of the mission a data base has been acquired that is valuable for studies of both the upper atmosphere and the shuttle-Spacelab vehicle environment.
Solar Irradiance Observations
Authors: Crommelynck D. , Domingo V.
Published: October 2006

The absolute radiometer on Spacelab 1 was used to obtain solar irradiance observations from space. A number of effects must be taken into account in the data reduction. A provisional value was obtained for the mean solar constant during the observation period (6 to 8 December 1983).
Binary Stars
Authors: Paczyński Bohdan
Published: October 2006

Most stars in the solar neighborhood are either double or multiple systems. They provide a unique opportunity to measure stellar masses and radii and to study many interesting and important phenomena. The best candidates for black holes are compact massive components of two x-ray binaries: Cygnus X-1 and LMC X-3. The binary radio pulsar PSR 1913 + 16 provides the best available evidence for gravitational radiation. Accretion disks and jets observed in close binaries offer a very good testing ground for models of active galactic nuclei and quasars.
Analysis of Obsidian from Moho Cay, Belize: New Evidence on Classic Maya Trade Routes
Authors: Healy Paul F. , McKillop Heather I. , Walsh Bernie
Published: October 2006

Trace element analysis of obsidian artifacts from Moho Cay, Belize, reveals that the obsidian derives primarily from the El Chayal outcrop in highland Guatemala and not from the Ixtepeque source. This is contrary to the widely accepted obsidian trade route model for Classic Maya civilization and suggests that Classic Maya obsidian trade was a more complex economic phenomenon than has been recognized.
Tactics of Acclimation: Morphological Changes of Sponges in an Unpredictable Environment
Authors: Palumbi Stephen R.
Published: October 2006

Reciprocal transplants of genetically identical fragments of intertidal sponges between environments of high and low wave action exhibit great variability in the timing of their responses to environmental change. Sponges quickly begin production of stiffer and stronger tissues in high wave energy environments but delay formation of new, weak tissues in calm habitats. This may be due to the risks of forming wave-intolerant tissue in a temporally variable, unpredictable environment. These results suggest that the evolution of acclimatory control is linked to environmental predictability and concomitantly to risks of acclimatory errors.
Interplanetary Magnetic Field Enhancements and Their Association with the Asteroid 2201 Oljato
Authors: Russell C. T. , Aroian R. , Arghavani M. , Nock K.
Published: October 2006

Comparison of the times of occurrence of a newly discovered type of disturbance in the interplanetary magnetic field at 0.72 astronomical unit with the passage of the small Venus-crossing asteroid, 2201 Oljato, reveals a possible association, but the source of these disturbances appears to be associated with outgassing material in the Oljato orbit some distance behind the asteroid and not with the asteroid itself. This suggested association can account for one quarter of the total number of events seen in eight Venus years.
Temperature Effects on the Rate of Ty Transposition
Authors: Paquin Charlotte E. , Williamson Valerie M.
Published: October 2006

An assay has been developed to measure the rate of transposition of the transposable element Ty in
Saccharomyces cerevisiae
. The assay is based on the altered expression of the glucose-repressible alcohol dehydrogenase gene of yeast upon insertion of a Ty in front of this gene. By this assay the transposition rate of Ty elements was found to increase approximately 100-fold at temperatures lower than 30°C, the optimum growth temperature for
Saccharomyces cerevisiae
.
Temporal Variability of the Antarctic Circumpolar Current Observed from Satellite Altimetry
Authors: Fu Lee-Lueng , Chelton Dudley B.
Published: October 2006

Sea level measurements by the Seasat altimeter were used to study the temporal variability of the Antarctic Circumpolar Current between July and October 1978. Large-scale zonal coherence in the cross-stream sea level difference was observed, indicating a general increase in the surface geostrophic velocity of the current around the Southern Ocean. The result demonstrates the power of satellite altimetry to monitor the variability of large-scale ocean currents.
Multicomponent Polymeric Engineering Materials
Authors: Panar Manuel , Epstein Bennett N.
Published: October 2006

The great advances made in polymeric structural materials over the past decade have led to their replacement of conventional materials in a wide range of uses including high-performance aerospace applications. This shift in choice of materials is based on economic advantages, simplified fabrication, freedom from corrosion, and lower weight. The trend toward use of polymeric materials will grow as the materials science of this new technology is developed. Better insight into such fundamental problems as the mechanisms by which forces are transferred to the polymer molecule, the surface interactions between polymer phases or polymer and fiber, and the molecular processes by which energy is absorbed during fracture will greatly stimulate the development of this field.
Satellite Color Observations of the Phytoplankton Distribution in the Eastern Equatorial Pacific During the 1982-1983. El Niño
Authors: Feldman Gene , Clark Dennis , Halpern David
Published: October 2006

Dramatic changes in the patterns of satellite-derived pigment concentrations around the Galápagos Islands during February and March 1983 are associated with unusual oceanographic conditions observed during the 1982-1983 El Niño. The redistribution of food resources might have contributed to the reproductive failure of seabirds and marine mammals on these islands during this El Niño.
Seismic Verification of a Comprehensive Test Ban
Authors: Hannon W. J.
Published: October 2006

The capabilities of in-country seismic monitoring systems for verifying the absence of underground nuclear explosions are compared against challenges posed by possible clandestine testing schemes. Although analyses indicate that extensive networks of in-country seismic arrays are needed to verify a Comprehensive Test Ban Treaty, such networks cannot ensure that all underground nuclear explosions will be identified. Political and military judgments will determine the level of risk acceptable to each nation.
Glacier Surge Mechanism: 1982-1983 Surge of Variegated Glacier, Alaska
Authors: Kamb Barclay , Raymond C. F. , Harrison W. D. , Engelhardt Hermann , Echelmeyer K. A. , Humphrey N. , Brugman M. M. , Pfeffer T.
Published: October 2006

The hundredfold speedup in glacier motion in a surge of the kind that took place in Variegated Glacier in 1982-1983 is caused by the buildup of high water pressure in the basal passageway system, which is made possible by a fundamental and pervasive change in the geometry and water-transport characteristics of this system. The behavior of the glacier in surge has many remarkable features, which can provide clues to a detailed theory of the surging process. The surge mechanism is akin to a proposed mechanism of overthrust faulting.
Geologic Approach to the Long-Term History of Atmospheric Circulation
Authors: Rea David K. , Leinen Margaret , Janecek Thomas R.
Published: October 2006

Eolian dust preserved in deep-sea pelagic sediments can be used as a proxy indicator of paleoclimate. Analyses of the particle size, composition, and mass accumulation rate of dust grains provide independent evidence of the intensity of atmospheric circulation and the availability of material in the eolian source region. These data provide information on atmospheric circulation and on the climate of the source area at time scales ranging from 10
3
to 10
8
years and have the potential to test computer-generated global circulation models.
High-Resolution Stratigraphy with Strontium Isotopes
Authors: DePaolo Donald J. , Ingram Bonnye L.
Published: October 2006

The isotopic ratio of strontium-87 to strontium-86 shows no detectable variation in present-day ocean water but changes slowly over millions of years. The strontium contained in carbonate shells of marine organisms records the ratio of strontium-87 to strontium-86 of the oceans at the time that the shells form. Sedimentary rocks composed of accumulated fossil carbonate shells can be dated and correlated with the use of high precision measurements of the ratio of strontium-87 to strontium-86 with a resolution that is similar to that of other techniques used in age correlation. This method may prove valuable for many geological, paleontological, paleooceanographic, and geochemical problems.
Ore Metals Through Geologic History
Authors: Meyer Charles
Published: October 2006

The ores of chromite, nickel, copper, and zinc show a wide distribution over geologic time, but those of iron, titanium, lead, uranium, gold, silver, molybdenum, tungsten, and tin are more restricted. Many of the limitations to specific time intervals are probably imposed by the evolving tectonic history of Earth interacting with the effects of the biomass on the evolution of the earth's surface chemistry. Photosynthetic generation of free oxygen and "carbon" contributes significantly to the diversity of redox potentials in both sedimentary and igneous-related processes of ore formation, influencing the selection of metals at the source, during transport, and at the site of ore deposition.
Opiate (Enkephalin) Receptors of Neuroblastoma Cells: Occurrence in Clusters on the Cell Surface
Authors: Hazum Eli , Chang Kwen-Jen , Cuatrecasas Pedro
Published: October 2006

A bioactive, fluorescent derivative of enkephalin, Tyr-D-Ala-Gly-Phe-Leu-Lys-rhodamine, was used to determine the distribution of opiate receptors in living neuroblastoma cells. The receptors appeared in clusters on the cell surface, and no internalization was detected. No specific fluorescence or clusters were observed in the presence of [D-Ala
2
, Leu
5
]enkephalin or at 4°C, and the clusters were much reduced under ionic conditions (that is, with 100 millimolars sodium) that specifically decrease the binding of opiate agonists.
The Sun and Nearby Stars: Microwave Observations at High Resolution
Authors: Kundu Mukul R. , Lang Kenneth R.
Published: October 2006

High-resolution microwave observations are providing new insights into the nature of active regions and eruptions on the sun and nearby stars. The strength, evolution, and structure of magnetic fields in coronal loops can be determined by multiple-wavelength observations with the Very Large Array. Flare models can be tested with Very Large Array snapshot maps, which have angular resolutions of better than 1 second of arc in time periods as short as 10 seconds. Magnetic changes that precede solar eruptions on time scales of tens of minutes involve primarily emerging coronal loops and the interactions of two or more loops. Magnetic reconnection at the interface of two closed loops may accelerate electrons and trigger the release of microwave energy in the coronal parts of the magnetic loops. Nearby main-sequence stars of late spectral type emit slowly varying microwave radiation and stellar microwave bursts that show striking similarities to those of the sun.
Flight of Winter Moths Near 0°C
Authors: Heinrich Bernd , Mommsen Thomas P.
Published: October 2006

Some noctuid winter moths fly at near 0°C by maintaining an elevated (30° to 35°C) thoracic muscle temperature. Geometrid winter moths sustain themselves in free flight at subzero muscle temperatures. However, the temperature characteristics of citrate synthase and pyruvate kinase from both of these different kinds of moths and from a sphinx moth that flies with a muscle temperature of 40°C are nearly identical. Furthermore, mass-specific rates of energy expenditure of both kinds of winter moths are also similar at given thoracic temperature (near 0°C). The geometrids that are able to fly with a thoracic temperature near 0°C do so largely because of unusually low wing-loading, which permits a low energetic cost of flight.
Multis: A New Class of Multiprocessor Computers
Authors: Bell C. Gordon
Published: October 2006

Multis are a new class of computers based on multiple microprocessors. The small size, low cost, and high performance of microprocessors allow the design and construction of computer structures that offer significant advantages in manufacture, price-performance ratio, and reliability over traditional computer families. Currently, commercial multis consist of 4 to 28 modules, which include microprocessors, common memories, and input-output devices, all of which communicate through a single set of wires called a bus. Adding microprocessors together increases the performance of multis in direct proportion to their price and allows multis to offer a performance range that spans that of small minicomputers to mainframe computers. Multis are commercially available for applications ranging from real-time industrial control to transaction processing. Traditional batch, time-sharing, and transaction systems process a number of independent jobs that can be distributed among the microprocessors of a multi with a resulting increased throughput (number of jobs completed per unit of time). Many scientific applications (such as the solving of partial differential equations) and engineering applications (such as the checking of integrated circuit designs) are speeded up by this parallel computation; thus, multis produce results at supercomputer speed but at a fraction of the cost. Multis are likely to be the basis for the next, the fifth, generation of computers—a generation based on parallel processing.
Long-Term Ecosystem Stress: The Effects of Years of Experimental Acidification on a Small Lake
Authors: Schindler D. W. , Mills K. H. , Malley D. F. , Findlay D. L. , Shearer J. A. , Davies I. J. , Turner M. A. , Linsey G. A. , Cruikshank D. R.
Published: October 2006

Experimental acidification of a small lake from an original
p
H value of 6.8 to 5.0 over an 8-year period caused a number of dramatic changes in the lake's food web. Changes in phytoplankton species, cessation of fish reproduction, disappearance of the benthic crustaceans, and appearance of filamentous algae in the littoral zone were consistent with deductions from synoptic surveys of lakes in regions of high acid deposition. Contrary to what had been expected from synoptic surveys, acidification of Lake 223 did not cause decreases in primary production, rates of decomposition, or nutrient concentrations. Key organisms in the food web leading to lake trout, including
Mysis relicta
and
Pimephales promelas
, were eliminated from the lake at
p
H values as high as 5.8, an indication that irreversible stresses on aquatic ecosystems occur earlier in the acidification process than was heretofore believed. These changes are caused by hydrogen ion alone, and not by the secondary effect of aluminum toxicity. Since no species of fish reproduced at
p
H values below 5.4, the lake would become fishless within about a decade on the basis of the natural mortalities of the most long-lived species.
Climate Response Times: Dependence on Climate Sensitivity and Ocean Mixing
Authors: Hansen J. , Russell G. , Lacis A. , Fung I. , Rind D. , Stone P.
Published: October 2006

The factors that determine climate response times were investigated with simple models and scaling statements. The response times are particularly sensitive to (i) the amount that the climate response is amplified by feedbacks and (ii) the representation of ocean mixing. If equilibrium climate sensitivity is 3°C or greater for a doubling of the carbon dioxide concentration, then most of the expected warming attributable to trace gases added to the atmosphere by man probably has not yet occurred. This yet to be realized warming calls into question a policy of "wait and see" regarding the issue of how to deal with increasing atmospheric carbon dioxide and other trace gases.
A 1500-Year Record of Tropical Precipitation in Ice Cores from the Quelccaya Ice Cap, Peru
Authors: Thompson L. G. , Mosley-Thompson E. , Bolzan J. F. , Koci B. R.
Published: October 2006

Two ice cores, covering 1500 years of climatic information, from the summit (5670 meters) of the tropical Quelccaya ice cap, in the Andes of southern Peru, provide information on general environmental conditions including droughts, volcanic activity, moisture sources, temperature, and glacier net balance. The net balance record reconstructed from these cores reflects major precipitation trends for the southern Andes of Peru. These records indicate extended dry periods between 1720 and 1860, 1250 and 1310, and 570 and 610; wet conditions prevailed between 1500 and 1720. Establishing a tropical precipitation record may help explain climatic fluctuations since the tropical evaporation-precipitation cycle is a principal mechanism driving the atmospheric circulation.
Auditory Association Cortex Lesions Impair Auditory Short-Term Memory in Monkeys
Authors: Colombo Michael , D'Amato Michael R. , Rodman Hillary R. , Gross Charles G.
Published: October 2006

Monkeys that were trained to perform auditory and visual short-term memory tasks (delayed matching-to-sample) received lesions of the auditory association cortex in the superior temporal gyrus. Although visual memory was completely unaffected by the lesions, auditory memory was severely impaired. Despite this impairment, all monkeys could discriminate sounds closer in frequency than those used in the auditory memory task. This result suggests that the superior temporal cortex plays a role in auditory processing and retention similar to the role the inferior temporal cortex plays in visual processing and retention.
Laser Resonance Ionization Mass Spectrometry
Authors: Fassett J. D. , Moore L. J. , Travis J. C. , DeVoe J. R.
Published: October 2006

The analysis of inorganic atomic species is greatly facilitated by the coupling of lasers with mass spectrometers. A tunable dye laser, alone or in combination with a pump laser, ionizes atoms by resonant excitation processes; the ions are then analyzed in the mass spectrometer. The laser—mass spectrometer system promises to overcome traditional limits of sensitivity and selectivity and to have diverse applications in analytical chemistry.
The Structure of the Core of the Spiral Wave in the Belousov-Zhabotinskii Reaction
Authors: Müller Stefan C. , Plesser Theo , Hess Benno
Published: October 2006

The quantitative structure of the core of the spiral-shaped traveling wave of chemical activity appearing in a thin excitable layer of the Belousov-Zhabotinskii reaction, in which the oxidation and decarboxylation of malonic acid by bromate ions is catalyzed by ferroin, was analyzed experimentally. Light absorption by ferroin as the reduced reaction catalyst and indicator was measured by means of a video- and computer-based two-dimensional spectrophotometer with 10-micrometer spatial, 2-second temporal, and 256-digital units intensity resolution. The spiral core is a singular site (diameter, 30 micrometers or less) at which intensity modulations due to ferroin-ferriin distributions are at least ten times smaller than in the surrounding area of spiral propagation. Archimedian spirals were fitted to isoconcentration lines.
The Response of Living Cells to Very Weak Electric Fields: the Thermal Noise Limit
Authors: Weaver James C. , Astumian R. Dean
Published: October 2006

A physical model in which cells are considered as possible detectors of very weak periodic electric fields yields a general relation between cell size and both thermally induced fluctuations in membrane potential and the maximum change in membrane potential caused by an applied field. The simplest version of the model provides a broad-band estimate of the smallest applied electric field to which membrane macromolecules can directly respond (about 10
-3
volt per centimeter). Much smaller fields (10
-6
volt per centimeter) can be detected if there is a response in only a narrow band of frequencies or if signal averaging occurs through field-induced variation in the catalytic activity of membrane-associated enzymes. Both extensions of the simplest version remove the apparent violation of the thermal noise limit found in some experiments.
Mini-Mouse: Disruption of the Pygmy Locus in a Transgenic Insertional Mutant
Authors: Xiang Xin , Benson Kathleen F. , Chada Kiran
Published: October 2006

A founder transgenic mouse harbored two different integration patterns of a transgene at the same locus, each of which gave rise to a similar autosomal recessive mutation. Mice of the mutant phenotype were of small stature but had normal levels of growth hormone. The disrupted locus was cloned, and a genetic and molecular analysis showed that the insertional mutants were allelic to a spontaneous mutant, pygmy. The mice should be a useful model for the growth hormone-resistant human dwarf syndromes and could lead to a greater understanding of the pathways involved in growth and development.
A Family of Three Mouse Potassium Channel Genes with Intronless Coding Regions
Authors: Chandy K. George , Williams Calvin B. , Spencer Robert H. , Aguilar Barbara A. , Ghanshani Sanjiv , Tempel Bruce L. , Gutman George A.
Published: October 2006

To understand the molecular mechanisms responsible for generating physiologically diverse potassium channels in mammalian cells, mouse genomic clones have been isolated with a potassium channel complementary DNA, MBK1, that is homologous to the
Drosophila
potassium channel gene,
Shaker
. A family of three closely related potassium channel genes (
MK1
,
MK2
, and
MK3
) that are encoded at distinct genomic loci has been isolated. Sequence analysis reveals that the coding region of each of these three genes exists as a single uninterrupted exon in the mouse genome. This organization precludes the generation of multiple forms of the protein by alternative RNA splicing, a mechanism known to characterize the
Drosophila
potassium channel genes
Shaker
and
Shab
. Thus, mammals may use a different strategy for generating diverse K
+
channels by encoding related genes at multiple distinct genomic loci, each of which produces only a single protein.