bluuebunny/crossref_metadata_2025 huggingface dataset:
Colligative Properties of Simple Solutions
Authors: Andrews Frank C.
Published: October 2006

Vapor pressure lowering, osmotic pressure, boiling point elevation, and freezing point depression are all related quantitatively to the decrease in μ
1
soln
upon the addition of solute in forming a solution. In any equilibrium system, regardless of whether it is in a gravitational field or whether it contains walls, semipermeable membranes, phase transitions, or solutes, all equilibria are maintained locally, in the small region of the equilibrium, by the equality of μ
1
soln
. If there are several subsystems in a gravitational field, at any fixed height, μ

i

will have the same value in each subsystem into which substance
i
can get, and μ

i

+

M
i
gh

is constant throughout the entire system.

In a solution, there is no mechanism by which solvent and solute molecules could sustain different pressures. Both the solvent and solute are always under identical pressures in a region of solution, namely, the pressure of the solution in that region. Since nature does not know which component we call the solvent and which the solute, equations should be symmetric in the two (acknowledging that the nonvolatile component, if any, is commonly chosen to be solute).

Simple molecular pictures illustrate what is happening to cause pressure (positive or negative) in liquids, vapor pressure of liquids, and the various colligative properties of solutions. The only effect of solute involved in these properties is that it dilutes the solvent, with the resulting increase in
S
and decrease in μ
1
soln
.

Water can be driven passively up a tree to enormous heights by the difference between its chemical potential in the roots and the ambient air. There is nothing mysterious about the molecular bases for any of these phenomena. Biologists can use the well-understood pictures of these phenomena with confidence to study what is happening in the complicated living systems they consider.
Comet West and the Scattering Function of Cometary Dust
Authors: Ney Edward P. , Merrill K. M.
Published: October 2006

Observations of Comet West (1975n) at wavelengths from 0.5 to 18 microns and at a variety of scattering angles are used to infer the scattering phase function for the cometary dust. This function is strongly peaked in the forward direction. The form of the function indicates that the particles are dielectric grains with radii of approximately 1 micron. Abrupt increases in the intrinsic brightness of the coma (both in scattered sunlight and in thermal emission) are consistent with the projected times of comet fragmentation.
Martian North Pole Summer Temperatures: Dirty Water Ice
Authors: Kieffer Hugh H. , Chase Stillman C. , Martin Terry Z. , Miner Ellis D. , Palluconi Frank Don
Published: October 2006

Broadband thermal and reflectance observations of the martian north polar region in late summer yield temperatures for the residual polar cap near 205 K with albedos near 43 percent. The residual cap and several outlying smaller deposits are water ice with included dirt; there is no evidence for any permanent carbon dioxide polar cap.
Control of Granulocytes and Macrophages: Molecular, Cellular, and Clinical Aspects
Authors: Metcalf Donald
Published: October 2006

The production and functional activity of two important white blood cells, the granulocytes and macrophages, are regulated mainly by a group of glycoprotein colony-stimulating factors. The colony-stimulating factors have been mass-produced with recombinant technology and are now proving of value in preventing or suppressing infections in a variety of individuals with subnormal or defective formation of blood cells.
Functional Mapping of the Human Visual Cortex by Magnetic Resonance Imaging
Authors: Belliveau J. W. , Kennedy D. N. , McKinstry R. C. , Buchbinder B. R. , Weisskoff R. M. , Cohen M. S. , Vevea J. M. , Brady T. J. , Rosen B. R.
Published: October 2006

Knowledge of regional cerebral hemodynamics has widespread application for both physiological research and clinical assessment because of the well-established interrelation between physiological function, energy metabolism, and localized blood supply. A magnetic resonance technique was developed for quantitative imaging of cerebral hemodynamics, allowing for measurement of regional cerebral blood volume during resting and activated cognitive states. This technique was used to generate the first functional magnetic resonance maps of human task activation, by using a visual stimulus paradigm. During photic stimulation, localized increases in blood volume (32 ± 10 percent,
n
= 7 subjects) were detected in the primary visual cortex. Center-of-mass coordinates and linear extents of brain activation within the plane of the calcarine fissure are reported.
Structure of a Legume Lectin with an Ordered N-Linked Carbohydrate in Complex with Lactose
Authors: Shaanan Boaz , Lis Halina , Sharon Nathan
Published: October 2006

The three-dimensional structure of the lactose complex of the
Erythrina corallodendron
lectin (EcorL), a dimer of N-glycosylated subunits, was determined crystallographically and refined at 2.0 angstrom resolution to an
R
value of 0.19. The tertiary structure of the subunit is similar to that of other legume lectins, but interference by the bulky N-linked heptasaccharide, which is exceptionally well ordered in the crystal, forces the EcorL dimer into a drastically different quaternary structure. Only the galactose moiety of the lactose ligand resides within the combining site. The galactose moiety is oriented differently from ligands in the mannose-glucose specific legume lectins and is held by hydrophobic interactions with Ala
88
, Tyr
106
, Phe
131
, and Ala
218
and by seven hydrogen bonds, four of which are to the conserved Asp
89
, Asn
133
, and NH of Gly
107
. The specificity of legume lectins toward the different C-4 epimers appears to be associated with extensive variations in the outline of the variable parts of the binding sites.
Prediction of a Crystallization Pathway for Z-DNA Hexanucleotides
Authors: Ho P. Shing , Kagawa Todd F. , Tseng Kaihan , Schroth Gary P. , Zhou Guangwen
Published: October 2006

Crystallization of macromolecules for structural studies has long been a hit-or-miss process. The crystallization of hexanucleotides as Z-DNA was studied, and it was shown that the cation concentration for crystal formation could be predicted from solvation free energy (SFE) calculations. Solution studies on the conformation and solubilities of the hexanucleotides showed that a critical concentration of the DNA in the Z-conformation must be present in solution to effect crystallization. The SFE calculations therefore predict the propensity of the hexanucleotides to adopt the left-handed conformation and the driving force required to reach this critical concentration relative to the intrinsic solubility of Z-DNA for crystallization.
Structures of Free and Inhibited Human Secretory Phospholipase A
2
from Inflammatory Exudate
Authors: Scott David L. , White Steven P. , Browning Jeffrey L. , Rosa Joseph J. , Gelb Michael H. , Sigler Paul B.
Published: October 2006

Phospholipase A
2
(PLA
2
) participates in a wide range of cellular processes including inflammation and transmembrane signaling. A human nonpancreatic secretory PLA
2
(hnps-PLA
2
) has been identified that is found in high concentrations in the synovial fluid of patients with rheumatoid arthritis and in the plasma of patients with septic shock. This enzyme is secreted from certain cell types in response to the proinflammatory cytokines, tumor necrosis factor or interleukin-1. The crystal structures of the calcium-bound form of this enzyme have been determined at physiological pH both in the presence [2.1 angstrom (Å) resolution] and absence (2.2 Å resolution) of a transition-state analogue. Although the critical features that suggest the chemistry of catalysis are identical to those inferred from the crystal structures of other extracellular PLA
2
s, the shape of the hydrophobic channel of hnps-PLA
2
is uniquely modulated by substrate binding.
Hypotensive Activity of Fibroblast Growth Factor
Authors: Cuevas Pedro , Carceller Fernando , Ortega Sagrario , Zazo Mercedes , Nieto Ignacio , Giménez-Gallego Guillermo
Published: October 2006

Acidic and basic fibroblast growth factors (FGFs) are members of a family of proteins that are broad-spectrum mitogens, have diverse hormone-like activities, and function in tumorigenesis. FGF's ability to raise the concentration of intracellular calcium ion suggests that FGF could induce the synthesis of endothelium-derived relaxing factor (EDRF) and consequently vasodilation. Systemic administration of FGF decreased arterial blood pressure. This effect was mediated by EDRF and by adenosine triphosphate-sensitive potassium ion channels. The hypotensive effect of FGF was segregated from its mitogenic activity by protein engineering. These results extend the range of FGF autocrine activities and potential therapeutic applications, emphasize the role of endothelium as an arterial blood pressure—regulating organ, and provide insight on the structural basis of FGF functions.
Molecular Self-Assembly and Nanochemistry: a Chemical Strategy for the Synthesis of Nanostructures
Authors: Whitesides George M. , Mathias John P. , Seto Christopher T.
Published: October 2006

Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10
2
nanometers (with molecular weights of 10
4
to 10
10
daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.
Structural Basis for the Activation of Glycogen Phosphorylase b by Adenosine Monophosphate
Authors: Sprang Stephen R. , Withers Stephen G. , Goldsmith Elizabeth J. , Fletterick Robert J. , Madsen Neil B.
Published: October 2006

The three-dimensional structure of the activated state of glycogen phosphorylase (GP) as induced by adenosine monophosphate (AMP) has been determined from crystals of pyridoxalpyrophosphoryl-GP. The same quaternary changes relative to the inactive conformation as those induced by phosphorylation are induced by AMP, although the two regulatory signals function through different local structural mechanisms. Moreover, previous descriptions of the phosphorylase active state have been extended by demonstrating that, on activation, the amino- and carboxyl-terminal domains of GP rotate apart by 5°, thereby increasing access of substrates to the catalytic site. The structure also reveals previously unobserved interactions with the nucleotide that accounts for the specificity of the nucleotide binding site for AMP in preference to inosine monophosphate.
The N-End Rule in Bacteria
Authors: Tobias John W. , Shrader Thomas E. , Rocap Gabrielle , Varshavsky Alexander
Published: October 2006

The N-end rule relates the in vivo half-life of a protein to the identity of its amino-terminal residue. Distinct versions of the N-end rule operate in all eukaryotes examined. It is shown that the bacterium
Escherichia coli
also has the N-end rule pathway. Amino-terminal arginine, lysine, leucine, phenylalanine, tyrosine, and tryptophan confer 2-minute half-lives on a test protein; the other amino-terminal residues confer greater than 10-hour half-lives on the same protein. Amino-terminal arginine and lysine are secondary destabilizing residues in
E. coli
because their activity depends on their conjugation to the primary destabilizing residues leucine or phenylalanine by leucine, phenylalanine-transfer RNA-protein transferase. The adenosine triphosphate-dependent protease Clp (Ti) is required for the degradation of N-end rule substrates in
E. coli
.
Shoreline Forms and Shoreline Dynamics
Authors: Dolan Robert , Hayden Bruce , Heywood Jeffrey , Vincent Linwood
Published: October 2006

Atlantic coast barrier-island shorelines are sinuous in plan view, with curvatures ranging in size from cusps to capes. The orientation of shoreline segments within the larger of these sinuous features (10 to 15 kilometers between apexes) is significantly related to shoreline dynamics.
Mining the Apollo and Amor Asteroids
Authors: O'Leary Brian
Published: October 2006

Earth-approaching asteroids could provide raw materials for space manufacturing. For certain asteroids the total energy per unit mass for the transfer of asteroidal resources to a manufacturing site in high Earth orbit is comparable to that for lunar materials. For logistical reasons the cost may be many times less. Optical studies suggest that these asteroids have compositions corresponding to those of carbonaceous and ordinary chondrites, with some containing large quantities of iron and nickel; others are thought to contain carbon, nitrogen, and hydrogen, elements that appear to be lacking on the moon. The prospect that several new candidate asteroids will be discovered over the next few years increases the likelihood that a variety of asteroidal resource materials can be retrieved on low-energy missions.
Ovarian Dynamics in Heliconiine Butterflies: Programmed Senescence versus Eternal Youth
Authors: Dunlap-Pianka Helen , Boggs Carol L. , Gilbert Lawrence E.
Published: October 2006

New oocytes are generated throughout long lives in butterflies of the genus
Heliconius,
which as adults feed on amino acids from pollen. In
Dryas julia,
a related heliconiine that feeds only on nectar and is relatively short-lived, the original oocyte supply is eventually depleted. Such divergent ovarian dynamics in closely related organisms are significant in terms of both their evolutionary basis and their physiological controls.
Identification of the Female Japanese Beetle Sex Pheromone: Inhibition of Male Response by an Enantiomer
Authors: Tumlinson J. H. , Klein M. G. , Doolittle R. E. , Ladd T. L. , Proveaux A. T.
Published: October 2006

(
Z
)- 5-(1-Decenyl)dihydro-2(3
H
)-furanone, isolated from virgin female Japanese beetles (
Popillia japonica
) attracted males of the species infield bioassays. However, the synthesized racemic mixture of this compound did not attract male Japanese beetles. The
Z
and
E
isomers and the saturated analog of both enantiomers of this compound were synthesized stereospecifically. Pure synthetic (
R
,
Z
)-5-(1-decenyl)dihydro-2(3
H
)-furanone was competitive with live females and with the pheromone isolated from live females in attracting males. Male response was strongly inhibited by small amounts of the
S
,
Z
isomer. Although the
E
isomer and the saturated analog of the pheromone are present in the material obtained from females, the role of these compounds in mediating the insect's behavior is unclear.
Immunological Resolution of a Diploid-Tetraploid Species Complex of Tree Frogs
Authors: Maxson Linda , Pepper Ellendee , Maxson R. D.
Published: October 2006

Micro-complement fixation studies of eastern and western populations of the North American tree frog
Hyla chrysoscelis
reveal they have been genetically isolated for about 4 million years. Immunological comparisons of populations of the cryptic tetraploid
Hyla versicolor
indicate a recent origin, from hybridization between eastern and western
H. chrysoscelis
.
Long Waves in the Eastern Equatorial Pacific Ocean: A View from a Geostationary Satellite
Authors: Legeckis Richard
Published: October 2006

During 1975, westward-moving long waves with a period of about 25 days and a wavelength of 1000 kilometers were observed at a sea surface temperature front in the equatorial Pacific on infrared images obtained by a geostationary environmental satellite system. The absence of these waves during 1976, and the above-average equatorial sea surface temperatures during 1976, may be related to a decrease in the southeasterly trade winds during that year.
Thermoluminescent Determination of Prehistoric Heat Treatment of Chert Artifacts
Authors: Melcher C. L. , Zimmerman D. W.
Published: October 2006

In recent years archeologists have become interested in the extent to which prehistoric peoples heat-treated chert prior to shaping it into tools. Thermoluminescent determination of the radiation dose accumulated by an artifact since it was formed or last heated provides a simple, reliable test for such heat treatment. This test can be applied to single artifacts without the need for raw source material for comparison. Results on 25 artifacts from four sites indicate that, for many chert sources, color and luster are not useful indicators of heat treatment by prehistoric peoples.
Recognition by Human V
γ
9/V
δ
2 T Cells of a GroEL Homolog on Daudi Burkitt's Lymphoma Cells
Authors: Fisch Paul , Malkovsky Miroslav , Kovats Susan , Sturm Els , Braakman Erik , Klein Bruce S. , Voss Stephan D. , Morrissey Lawrence W. , DeMars Robert , Welch William J. , Bolhuis Reinder L. H. , Sondel Paul M.
Published: October 2006

All human γδ T cells coexpressing the products of the variable (V) region T cell receptor (TCR) gene segments V
γ
9 and V
δ
2 recognize antigens from some mycobacterial extracts and Daudi cells. Exogenous and endogenous ligands on the cell surface, homologous to the groEL heat shock family, induced reactivities that resembled superantigen responses in this major subset of human peripheral blood γδ T cells. Stimulation of human V
γ
9/V
δ
2 T cells is not restricted by human leukocyte antigens (HLA), including nonpolymorphic β
2
-microglobulin (β
2
M)-associated class Ib molecules. These data may be important for understanding the role of γδ T cells in autoimmunity and in responses to microorganisms and tumors.
High Pressures on Small Areas
Authors: Ruoff A. L. , Wanagel J.
Published: October 2006

Small diamond indentors with spherical tips were pressed against a polished diamond flat. Pressures were calculated from Hertz contact theory. Very high pressures were achieved on small areas.
Anaerobiosis and a Theory of Growth Line Formation
Authors: Lutz Richard A. , Rhoads Donald C.
Published: October 2006

Microstructural growth increments within the shells of numerous Recent and fossil molluscs are interpreted as reflections of alternating periods of shell deposition and dissolution, occurring during aerobic and anaerobic respiration, respectively. The acidic end products of anaerobic metabolism are neutralized by calcium carbonate from the shell, leaving a relatively insoluble organic residue at the mantle-shell interface. With the return of oxygenated conditions and resumption of aerobic respiration, this organic material is reincorporated within the shell. Inasmuch as metabolic changes are often synchronized with lunar or solar cycles (or both), we are led to the nearly paradoxical conclusion that, as a result of shell destructive processes, a relatively complete and detailed record of both short- and long-term growth is often preserved within the molluscan exoskeleton. Analyses of relationships between ambient oxygen concentrations and shell
structural types
may eventually prove useful, in paleoecological studies, for determination of dissolved oxygen gradients in Phanerozoic marine environments.
Generation of Calcium Oscillations in Fibroblasts by Positive Feedback Between Calcium and IP
3
Authors: Harootunian Alec T.. , Kao Joseph P. Y.. , Paranjape Suman. , Tsien Roger Y..
Published: October 2006

A wide variety of nonexcitable cells generate repetitive transient increases in cytosolic calcium ion concentration ([Ca
2+
]
i
) when stimulated with agonists that engage the phosphoinositide signalling pathway. Current theories regarding the mechanisms of oscillation disagree on whether Ca
2+
inhibits or stimulates its own release from internal stores and whether inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DG) also undergo oscillations linked to the Ca
2+
spikes. In this study, Ca
2+
was found to stimulate its own release in REF52 fibroblasts primed by mitogens plus depolarization. However, unlike Ca
2+
release in muscle and nerve cells, this amplification was insensitive to caffeine or ryanodine and required hormone receptor occupancy and functional IP3 receptors. Oscillations in [Ca
2+
]
i
were accompanied by oscillations in IP3 concentration but did not require functional protein kinase C. Therefore, the dominant feedback mechanism in this cell type appears to be Ca
2+
stimulation of phospholipase C once this enzyme has been activated by hormone receptors.
Visualizing the Higher Order Folding of a Catalytic RNA Molecule
Authors: Celander Daniel W. , Cech Thomas R.
Published: October 2006

The higher order folding process of the catalytic RNA derived from the self-splicing intron of
Tetrahymena thermophila
was monitored with the use of Fe(II)-EDTA-induced free radical chemistry. The overall tertiary structure of the RNA molecule forms cooperatively with the uptake of at least three magnesium ions. Local folding transitions display different metal ion dependencies, suggesting that the RNA tertiary structure assembles through a specific folding intermediate before the catalytic core is formed. Enzymatic activity, assayed with an RNA substrate that is complementary to the catalytic RNA active site, coincides with the cooperative structural transition. The higher order RNA foldings produced by Mg(II), Ca(II), and Sr(II) are similar; however, only the Mg(II)-stabilized RNA is catalytically active. Thus, these results directly demonstrate that divalent metal ions participate in general folding of the ribozyme tertiary structure, and further indicate a more specific involvement of Mg(II) in catalysis.
Choline Administration: Modification of the Central Actions of Atropine
Authors: Wecker Lynn , Dettbarn Wolf-D. , Schmidt Dennis E.
Published: October 2006

The anticholinergic agent atropine decreases acetylcholine concentrations and increases high-affinity choline uptake in cortical and hippocampal regions of rat brain. Administration of choline 1 hour before atropine prevents both of these atropine-induced alterations. These findings suggest that alterations in acetylcholine precursor availability may modify the effects of centrally active anticholinergic agents.
Methyl Chloroform: Impact on Stratospheric Ozone
Authors: McConnell J. C. , Schiff H. I.
Published: October 2006

Regulations to limit the use of trichloroethylene as a degreasing solvent have led to an increased use of the more photochemically inert solvent methyl chloroform as a substitute. Model calculations show that about 15 percent of the methyl chloroform released into the atmosphere will reach the stratosphere. Time scenarios based on past production figures and reasonable projections for future release rates lead to a steady-state ozone depletion due to this solvent about 20 percent as large as those resulting from the continuous release of chlorofluoromethanes at 1973 rates.
Brachiopods: Biomechanical Interdependences Governing Their Origin and Phylogeny
Authors: Gutmann W. F. , Vogel K. , Zorn H.
Published: October 2006

The adaptive advantage of epibenthic articulate brachiopods over inarticulate forms resulted from a modification of the mechanics of shell opening from an indirect hydraulic system to a direct muscular one. As a consequence, the articulate brachiopods were able to reduce the complex muscular system of the ancestral inarticulates, freeing two-thirds of the space within the shell for enlargement of the feeding apparatus. The original hydraulic mechanism of the inarticulate brachiopods most likely evolved from the hydrostatic skeleton of metameric lower invertebrates, probably polychaete-like annelids, as shown by a biomechanical analysis. The transitional stages between such annelids and inarticulate brachiopods are presented and explained as adaptive improvements in body construction.
Pollen Abortion in T Cytoplasmic Male-Sterile Corn (
Zea mays
): A Suggested Mechanism
Authors: Warmke H. E. , Lee Sheu-Ling Janet
Published: October 2006

A rapid replication of mitochondria (20- to 40-fold increase) occurs between the precallose and tetrad stages in the tapetum of N and T corn (
Zea mays
) anthers, followed by mitochondrial, tapetal, and pollen breakdown in T anthers. It is suggested that the altered DNA in T mitochondria may malfunction under these stress conditions.
Scanning Electron Microscope Study of Early Lichen Synthesis
Authors: Ahmadjian Vernon , Jacobs Jerome B. , Russell Lorraine A.
Published: October 2006

In the early stages of cellular interaction between the symbionts of
Lecidea albocaerulescens
, the phycobiont produced an extracellular sheath which bound to it hyphae of the mycobiont. Such a sheath may be a means by which the symbionts recognize each other. Hyphae of the mycobiont formed flattened appressoria as they grew over the algal cells and in this way secured the autotrophic population necessary for the development of a lichen thallus.
Peptide Processing and Targeting in the Neuronal Secretory Pathway
Authors: Jung Linda J. , Scheller Richard H.
Published: October 2006

The abdominal ganglion of the marine mollusk
Aplysia
contains a pair of identified neuronal clusters, the bag cells, which control egg laying by means of a number of unique regulatory mechanisms. Each neuron in the bag cell clusters synthesizes several peptides derived from a single prohormone and packages them into separate vesicles. These vesicles are then differentially localized in specific neuronal processes, thus segregating peptides destined for autocrine and hormonal release sites. Therefore in this system, protein trafficking through the secretory pathway organizes multiple peptide neurochemical messengers to efficiently regulate simple behaviors.
Multiple Representations of Pain in Human Cerebral Cortex
Authors: Talbot Jeanne D. , Marrett Sean , Evans Alan C. , Meyer Ernst , Bushnell M. Catherine , Duncan Gary H.
Published: October 2006

The representation of pain in the cerebral cortex is less well understood than that of any other sensory system. However, with the use of magnetic resonance imaging and positron emission tomography in humans, it has now been demonstrated that painful heat causes significant activation of the contralateral anterior cingulate, secondary somatosensory, and primary somatosensory cortices. This contrasts with the predominant activation of primary somatosensory cortex caused by vibrotactile stimuli in similar experiments. Furthermore, the unilateral cingulate activation indicates that this forebrain area, thought to regulate emotions, contains an unexpectedly specific representation of pain.
Mantle Uplifted Block in the Western Indian Ocean
Authors: Bonatti Enrico , Hamlyn Paul R.
Published: October 2006

An anomalous topographic high located close to the intersection of the Owen Fracture Zone with the Mid-Indian Ridge exposes exclusively ultramafic rocks for a thickness of more than 2 kilometers. The rocks, consisting of partly serpentinized spinel lherzolites, with minor harzburgites and dunites, display protogranular to porphyroclastic fabrics, but no cumulate textures. The chemistry of olivine, ortho- and clinopyroxene, and spinel crystals suggests that the rocks originated at a depth of at least 25 kilometers in the oceanic lithosphere and were partially reequilibrated and recrystallized during subsequent upwelling. Thus, field, textural, and mineral chemistry data indicate the presence of an uplifted block of upper mantle. The considerable vertical uplift can be explained by a two-stage process: mantle upwelling in the axial zone of plate accretion, followed by vertical tectonic uplift along the fracture zone. The rate of uplift in the fracture zone was of the order of 1 millimeter per year.
The Environment Today
Authors: Train Russell E.
Published: October 2006

While considerable progress has been made in dealing with air and water pollution, the earth's natural systems seem in difficulty. Scientific knowledge of environmental matters remains inadequate. A massive effort to promote solar energy and a national commitment to energy conservation are needed. The Clean Air Act has important implications for economic growth, and the Environmental Protection Agency should emphasize flexibility of administration, decentralization, and close cooperation with state and local governments. Expanded use of coal presents major uncertainties in human health and atmospheric effects. Increasing emphasis on chemical pollutants requires better societal perception of risks and benefits. New efforts to avoid confrontation on environmental issues are promising. Finally, the protection of life in all its diversity is today's urgent environmental challenge.
Carbon Isotopic Evidence for Different Feeding Patterns in Two Hyrax Species Occupying the Same Habitat
Authors: DeNiro Michael J. , Epstein Samuel
Published: October 2006

The carbon-13/carbon-12 ratios of the carbonate and collagen fractions of bone of the sympatric hyrax species
Procavia johnstoni
and
Heterohyrax brucei
indicate that the former obtains most of its diet by grazing while the latter is primarily a browser. The carbon-13/carbon-12 ratios of these fractions in fossil bone will record information about diet if they have not been altered during diagenesis.
Mitochondrial Heredity: A Determinant in the Toxic Response of Maize to the Insecticide Methomyl
Authors: Koeppe David E. , Cox Julie K. , Malone Carl P.
Published: October 2006

Mitochondria isolated from etiolated Texas male-sterile (TMS) cytoplasm maize (
Zea mays L.
) seedlings were adversely affected by methomyl (Lannate, 90 wettable powder), while those isolated from normal-fertile seedlings were not. In a manner analogous to that reported for
Bipolaris
(Helminthosporium)
maydis
(race T) toxin, experiments with TMS mitochondria showed that 1 to 3 millimolar methomyl inhibited the state 4 oxidation rate of combined malate and pyruvate while stimulating that of succinate or exogenous reduced nicotinamide adenine dinucleotide. Similar concentrations of methomyl effected an inhibition of phosphorylation, an increase in the percentage of transmittance of light through mitochondrial suspensions, and a decrease in the density of the mitochondrial matrix. Methomyl (15 millimolar) had little effect on the physiological activity or ultrastructure of isolated normal-fertile mitochondria. These observations provide the opportunity to specifically assess the homogeneity, or lack of it, of a cytoplasmic heritable characteristic in a widely divergent group of higher plants.
Dynamic Tracking of Cardiac Vulnerability by Complex Demodulation of the T Wave
Authors: Nearing Bruce D. , Huang Alice H. , Verrier Richard L.
Published: October 2006

A link is found between T wave alternans and vulnerability to ventricular fibrillation, and a new approach is provided for quantification of susceptibility to malignant arrhythmias. Complex demodulation reveals that alternation of the electrocardiogram is concentrated during the first half of the T wave, coinciding with the vulnerable period of the cardiac cycle. During myocardial ischemia and reperfusion, there are marked increases in the degree of T wave alternans that parallel the established time course of changes in vulnerability. The influence of the sympathetic nervous system in arrhythmogenesis is also accurately detected. Ultimately, complex demodulation of the electrocardiogram could provide a technique for identification and management of individuals at risk for sudden cardiac death.
Microstructure of Agglomerated Suspended Sediments in Northern Chesapeake Bay Estuary
Authors: Zabawa Christopher F.
Published: October 2006

Suspended sediments in the turbidity maximum of Chesapeake Bay include composite particles which contain platy mineral grains, arranged both in pellets (attributable to fecal pelletization) and in networks of angular configuration (attributable to electrochemical flocculation and coagulation).
Copper in Aerosol Particles Produced by the Ocean
Authors: Cattell Frank C. R. , Scott William D.
Published: October 2006

Measurements of particulate copper in the atmosphere near the island of Tasmania indicate that the ocean is a source of atmospheric copper. A biogenic agent may be responsible for the approximately 20,000-fold enrichment of copper during aerosol production from the ocean.
At the Crossroads of Chemistry and Immunology: Catalytic Antibodies
Authors: Lerner Richard A. , Benkovic Stephen J. , Schultz Peter G.
Published: October 2006

Immunochemistry has historically focused on the nature of antigenicity and antibody-antigen recognition. However, in the last 5 years, the field of immunochemistry has taken a new direction. With the aid of mechanistic and synthetic chemistry, the vast network of molecules and cells of the immune system has been tapped to produce antibodies with a new function—catalytic antibodies. Because antibodies can be generated that selectively bind almost any molecule of interest, this new technology offers the potential to tailor-make highly selective catalysts for applications in biology, chemistry, and medicine. In addition, catalytic antibodies provide fundamental insight into important aspects of biological catalysis, including the importance of transition-state stabilization, proximity effects, general acid and base catalysts, electrophilic and nucleophilic catalysis, and strain.
Modular Organization of Genes Required for Complex Polyketide Biosynthesis
Authors: Donadio Stefano , Staver Michael J. , McAlpine James B. , Swanson Susan J. , Katz Leonard
Published: October 2006

In
Saccharopolyspora erythraea
, the genes that govern synthesis of the polyketide portion of the macrolide antibiotic erythromycin are organized in six repeated units that encode fatty acid synthase (FAS)-like activities. Each repeated unit is designated a module, and two modules are contained in a single open reading frame. A model for the synthesis of this complex polyketide is proposed, where each module encodes a functional synthase unit and each synthase unit participates specifically in one of the six FAS-like elongation steps required for formation of the polyketide. In addition, genetic organization and biochemical order of events appear to be colinear. Evidence for the model is provided by construction of a selected mutant and by isolation of a polyketide of predicted structure.
An Unexpectedly Efficient Catalytic Antibody Operating by Ping-Pong and Induced Fit Mechanisms
Authors: Wirsching Peter , Ashley Jon A. , Benkovic Stephen J. , Janda Kim D. , Lerner Richard A.
Published: October 2006

A transition state analogue was used to produce a mouse antibody that catalyzes transesterification in water. The antibody behaves as a highly efficient catalyst with a covalent intermediate and the characteristic of induced fit. While some features of the catalytic pathway were programmed when the hapten was designed and reflect favorable substrate-antibody interactions, other features are a manifestation of the chemical potential of antibody diversity. The fact that antibodies recapitulate mechanisms and pathways previously thought to be a characteristic of highly evolved enzymes suggests that once an appropriate binding cavity is achieved, reaction pathways commensurate with the intrinsic chemical potential of proteins ensue.
Pyrite: Its Rapid Formation in a Salt Marsh and Its Importance in Ecosystem Metabolism
Authors: Howarth Robert W.
Published: October 2006

Pyrite formation in salt-marsh peat occurs more rapidly than is generally thought for any natural system. Pyrite is the major end product of sulfate reduction, and sulfate reduction is the major form of respiration in the salt-marsh ecosystem. When the rapid formation of pyrite is ignored, the rates of sulfate reduction and ecosystem respiration may be grossly underestimated.
Fission Power: An Evolutionary Strategy
Authors: Feiveson Harold A. , von Hippel Frank , Williams Robert H.
Published: October 2006

Motivated by concerns about the difficulty of safeguarding the large flows of plutonium in a breeder reactor fuel cycle, we explore the resource and economic implications of a strategy in which there is no nuclear weapons-usable material in fresh reactor fuel. The strategy involves the deployment of already developed types of advanced converter reactors which, unlike the breeder, can be operated effectively on proliferation-resistant once-through fuel cycles. Advanced converter reactors could be much more uranium-efficient on once-through fuel cycles than current systems and therefore could compete economically with breeders up to very high uranium prices. If necessary, the uranium requirements of an advanced converter reactor system could be reduced much further with the recycling of isotopically denatured uranium, but any commitment to a closed fuel cycle would be unnecessary for many decades.
Clouds of Venus: Particle Size Distribution Measurements
Authors: Knollenberg Robert G. , Hunten D. M.
Published: October 2006

Data from the Pioneer Venus cloud particle size spectrometer experiment has revealed the Venus cloud system to be a complicated mixture of particles of various chemical composition distinguishable by their multimodal size distributions. The appearance, disappearance, growth, and decay of certain size modes has aided the preliminary identification of both sulfuric acid and free sulfur cloud regions. The discovery of large particles > 30 micrometers, significant particle mass loading, and size spectral features suggest that precipitation is likely produced; a peculiar aerosol structure beneath the lowest cloud layer could be residue from a recent shower.
Fixation of Nitrogen in the Prebiotic Atmosphere
Authors: Yung Y. L. , McElroy M. B.
Published: October 2006

Reactions between nitrogen and water in the air surrounding lightning discharges can provide an important source of nitric oxide even under conditions where oxygen is a minor atmospheric constituent. Estimates are given for the associated source of soluble nitrite and nitrate. It is shown that lightning and subsequent atmospheric chemistry can provide a source of nitrate for the primitive ocean as large as 10
6
tons of nitrogen per year, sufficient to fill the ocean to its present level of nitrate in less than 10
6
years.
Molybdenum Disulfide in the Poorly Crystalline "Rag" Structure
Authors: Chianelli R. R. , Prestridge E. B. , Pecoraro T. A. , DeNeufville J. P.
Published: October 2006

Molybdenum disulfide has been prepared in an unusual poorly crystalline form, termed the "rag" structure, consisting of several stacked but highly folded and disordered S-Mo-S layers. This previously unknown structure demonstrates the flexible and macromolecular nature of the layered transition metal dichalcogenides. The determination of this structure provides a basis for understanding its highly broadened x-ray diffraction pattern and relatively low surface area, and is a starting point for optimizing the catalytic and surface properties of molybdenum disulfide.
Possible Mechanism for Pressurized-Liquid Tank Explosions or BLEVE's
Authors: Reid Robert C.
Published: October 2006

The hypothesis is made that rapid depressurization of hot, saturated liquids may result in an explosion. The temperature of the hot liquid must, however, be above the superheat limit temperature at 1 atmosphere, and the drop in tank pressure must be very rapid. Two examples of large-scale pressure-letdown explosions are cited and possible preventative measures suggested.
Warmth of the Subpolar North Atlantic Ocean During Northern Hemisphere Ice-Sheet Growth
Authors: Ruddiman W. F. , McIntyre A.
Published: October 2006

Two 10,000-year periods of Northern Hemisphere continental ice-sheet growth stand out prominently within the last full interglacial-to-glacial cycle. During the first half of each rapid ice-growth phase, the subpolar North Atlantic from 40°N to 60°N maintained warm sea-surface temperatures comparable to those of today's ocean. The juxtaposition at latitudes 50°N to 60°N of an "interglacial" ocean alongside a "glacial" land mass, particularly along eastern North America, is regarded as an optimal configuration for delivering moisture to the growing ice sheets.
Strontium-Calcium Thermometry in Coral Skeletons
Authors: Smith S. V. , Buddemeier R. W. , Redalje R. C. , Houck J. E.
Published: October 2006

The strontium to calcium ratio of skeletal aragonite in three genera of reef-building corals varies as a simple function of temperature and the strontium to calcium ratio of the incubation water. The strontium/calcium distribution coefficients of coral aragonite apparently differ from the corresponding coefficient of inorganically precipitated aragonite. With some care, coral skeletons can be used as recording thermometers.
The Jupiter System Through the Eyes of Voyager 1
Authors: Smith Bradford A. , Soderblom Laurence A. , Johnson Torrence V. , Ingersoll Andrew P. , Collins Stewart A. , Shoemaker Eugene M. , Hunt G. E. , Masursky Harold , Carr Michael H. , Davies Merton E. , Cook Allan F. , Boyce Joseph , Danielson G. Edward , Owen Tobias , Sagan Carl , Beebe Reta F. , Veverka Joseph , Strom Robert G. , McCauley John F. , Morrison David , Briggs Geoffrey A. , Suomi Verner E.
Published: October 2006

The cameras aboard Voyager 1 have provided a closeup view of the Jupiter system, revealing heretofore unknown characteristics and phenomena associated with the planet's atmosphere and the surfaces of its five major satellites. On Jupiter itself, atmospheric motions—the interaction of cloud systems—display complex vorticity. On its dark side, lightning and auroras are observed. A ring was discovered surrounding Jupiter. The satellite surfaces display dramatic differences including extensive active volcanism on Io, complex tectonism on Ganymede and possibly Europa, and flattened remnants of enormous impact features on Callisto.
Photochemical Air Pollution in the Northeast United States
Authors: Cleveland William S. , Graedel T. E.
Published: October 2006

Statistical analyses of meteorological and contaminant data and chemical kinetic modeling demonstrate that (i) the concentrations of ozone in the New Jersey-New York City metropolitan area are regional in character; (ii) ozone concentrations in Connecticut are increased by approximately 20 percent as a consequence of primary emissions in the New Jersey-New York City metropolitan region and subsequent transport; and (iii) the concentrations of a variety of products of smog chemistry in the New Jersey area are markedly increased by an increase in NO emissions, but are minimally affected by a change in hydrocarbon emissions.
Lymphocyte Function of Michigan Dairy Farmers Exposed to Polybrominated Biphenyls
Authors: Bekesi J. George , Holland James F. , Anderson Henry A. , Fischbein Alf S. , Rom William , Wolff Mary S. , Selikoff Irving J.
Published: October 2006

Michigan dairy farm residents ate farm products containing polybrominated biphenyls (PBB's) after the accidental contamination of animal feed with the chemical in that state in 1973. The circulating blood lymphocytes of these residents show significant changes. Abnormalities include decreases in the numbers and percentages of peripheral blood lymphocytes that form rosettes with either sheep erythrocytes alone or with sheep erythrocytes sensitized with antibody and complement, increases in lymphocytes with no detectable surface markers ("null" cells), and altered responses to tests designed to evaluate functional integrity of the cells. There appears to be no consistent correlation between the concentration of PBB's in the plasma and the altered lymphocytes. Studies showed that in Wisconsin dairy farm residents and healthy individuals in the New York area who were not exposed to PBB's there were no such abnormalities.
Dopamine Activation of an Orphan of the Steroid Receptor Superfamily
Authors: Power Ronan F. , Lydon John P. , Conneely Orla M. , O'Malley Bert W.
Published: October 2006

The chicken ovalbumin upstream promoter transcription factor (COUP-TF) is a member of the steroid receptor superfamily and participates in the regulation of several genes. While a number of functions have been ascribed to COUP-TF, no ligand or activator molecule has been identified, and thus it is classified as one of a group of orphan receptors. Activation of COUP-TF by physiological concentrations of the neurotransmitter dopamine was observed in transient transfection assays. Treatment of transfected cells with the dopamine receptor agonist α-ergocryptine also activated COUP-dependent expression of a reporter gene. COUP-TF that contained a deletion in the COOH-terminal domain was not activated by these compounds. These observations suggest that dopamine may be a physiological activator of COUP-TF.
Generation of Torsional and Vertical Eye Position Signals by the Interstitial Nucleus of Cajal
Authors: Crawford J. D. , Cadera W. , Vilis T.
Published: October 2006

The neural integrator, which converts eye velocity signals into position signals, is central to oculomotor theory. Similar integrators are probably necessary in any neural system that changes and maintains muscular tension. The integrator for horizontal eye position is in the pons, but the locations of the vertical and torsional integrators have not been clearly defined. Recording three-dimensional eye movements in alert monkeys during microstimulation and pharmacological inactivation of midbrain sites showed that the interstitial nucleus of Cajal generates both the torsional and vertical eye position signals. Up and down signals are linked with clockwise signals in the right brain and counterclockwise signals in the left brain. This three-dimensional coordinate system achieves orthogonality and bilateral symmetry without redundancy and optimizes energy efficiency for horizontal visual scanning.
Venus: Preliminary Topographic and Surface Imaging Results from the Pioneer Orbiter
Authors: Pettengill Gordon H. , Ford Peter G. , Brown Walter E. , Kaula William M. , Masursky Harold , Eliason Eric , McGill George E.
Published: October 2006

Three large Venus surface features, identified previously in images obtained from Earth-based radar observations, are shown by the Pioneer Venus radar mapper to be elevated 5 to 10 kilometers above the surrounding terrain. Two of these features, one bright and the other dark, lie adjacent to each other astride the 65°N parallel between longitudes 310°E and 10°E. The combined region forms a huge tectonically uplifted plateau, surmounted by radar-bright ridges that may have either a volcanic or tectonic origin. The third feature, located at 30°N, 283°E, is radar-bright and may consist of volcanic material extruded along a fault zone. A first radar-scattering image, compiled from data obtained by the mapper in its imaging mode, shows a region north of the equator; several circular depressions seen in this area may result from meteoritic impact.
Tidal Vertical Migration: An Endogenous Rhythm in Estuarine Crab Larvae
Authors: Cronin Thomas W. , Forward Richard B.
Published: October 2006

Field-caught larvae of the estuarine crab
Rhithropanopeus harrisii
have a tidal rhythm of vertical migration when maintained in constant conditions. Laboratory-reared larvae do not show this rhythm. Endogenous tidal vertical migrations aid the retention of these planktonic larvae in estuaries near the parent populations.
Learning in Normal and Mutant
Drosophila
Larvae
Authors: Aceves-Piña Efrain O. , Quinn William G.
Published: October 2006

Adult
Drosophila melanogaster
have previously been conditioned with shock to avoid various odors. In these experiments, larvae also sensed airborne odorants, responded to electric shock, and learned. Larval behavior paralleled adult behavior for (i) a mutant, smellblind, which failed to respond to odorants; (ii) three mutants, dunce, turnip, and cabbage, which were deficient in olfactory learning ability; and (iii) a mutant heterozygote, turnip/+, which learned but also forgot rapidly.