bluuebunny/crossref_metadata_2025 huggingface dataset:
Midwestern Holocene Paleoenvironments Revealed by Floodplain Deposits in Northeastern Iowa
Authors: Chumbley C. A. , Baker R. G. , Bettis E. A.
Published: October 2006

Pollen analysis of pond deposits in the upper reaches of a stream from northeastern Iowa, an area beyond the last glacial margin, provides a nearly complete record of vegetational changes during the last 12.5 thousand years. Sixty-one radiocarbon dates provide good chronological control. Spruce forest was replaced by deciduous forest before 9.1 thousand years ago, followed by prairie from 5.4 to 3.5 thousand years ago, and oak savanna from 3.5 thousand years ago until presettlement times. The prairie invasion was nearly 3 thousand years later here than at other sites in Iowa and Minnesota, documenting a late Holocene, rather than an early-middle Holocene, period of maximum warmth and dryness for the southern part of the upper Midwest.
Evolution of the Northern Santa Cruz Mountains by Advection of Crust Past a San Andreas Fault Bend
Authors: Anderson Robert S.
Published: October 2006

The late Quaternary marine terraces near Santa Cruz, California, reflect uplift associated with the nearby restraining bend on the San Andreas fault. Excellent correspondence of the coseismic vertical displacement field caused by the 17 October 1989 magnitude 7.1 Loma Prieta earthquake and the present elevations of these terraces allows calculation of maximum long-term uplift rates 1 to 2 kilometers west of the San Andreas fault of 0.8 millimeters per year. Over several million years, this uplift, in concert with the right lateral translation of the resulting topography, and with continual attack by geomorphic processes, can account for the general topography of the northern Santa Cruz Mountains.
Quaternary Deepwater Paleoceanography
Authors: Boyle Edward A.
Published: October 2006

During the past decade, geochemical paleoceanographers have begun to explore the changes in the circulation of the deep ocean that occurred during the glacial-interglacial cycles of the earth's recent history. The deep ocean was significantly colder during the glacial maximum. The distributions of biologically utilized elements (such as carbon and phosphorus) were significantly different as well; higher concentrations of these elements occurred in the deep (>2500 meters depth) North Atlantic, and lower concentrations occurred in the upper (<2500 meters depth) waters of the North Atlantic and possibly in all of the major ocean basins. In contrast, relatively subtle changes have been observed in the radiocarbon ages of deep waters. Slow deepwater changes are statistically linked to variations in the earth's orbit, but rapid changes in deepwater circulation also have occurred. Deepwater chemistry and circulation changes may control the variability in atmospheric CO
2
levels that have been documented from studies of air bubbles in polar ice cores.
Endogenous Reproductive Rhythms in a Tropical Bird
Authors: Gwinner Eberhard , Dittami John
Published: October 2006

Like other tropical birds, African stonechats breeding at the equator reproduce once a year during the main rainy season and subsequently carry out a complete molt. These two activities are controlled by endogenous circannual mechanisms: in stonechats held in constant conditions of photoperiod and temperature, a rhythm of gonadal size and molt persisted for up to 7.5 years, which would be a lifetime for free-living conspecifics. The fact that the period of these rhythms deviated from 12 months demonstrates their true endogenous nature. The results represent the longest circannual reproductive rhythm yet documented and suggest that circannual mechanisms may be of particular importance for reproductive timing in tropical organisms.
Sexual Role Reversal in Mate-Finding Strategies of the Cabbage Looper Moth
Authors: Landolt Peter J. , Heath Robert R.
Published: October 2006

The mate-finding behavior of the cabbage looper moth
Trichoplusia ni
(Lepidoptera: Noctuidae) includes both female- and male-produced sex pheromones used in distinct mate-finding strategies. Both sexes release multicomponent pheromones attractive to the opposite sex. Male pheromone is comprised of
d
-linalool,
m
-cresol, and
p
-cresol released from abdominal hair pencils. Males exposed to host plant odor or to the female sex pheromone (
Z
)-7-dodecen-1-ol acetate are more attractive to females, suggesting stimulation of male pheromone release.
Time-Resolved X-Ray Diffraction Study of Solid Combustion Reactions
Authors: Wong Joe , Larson E. M. , Holt J. B. , Waide P. A. , Rupp B. , Frahm R.
Published: October 2006

Real-time synchrotron diffraction has been used to monitor the phase transformations of highly exothermic, fast self-propagating solid combustion reactions on a subsecond time scale down to 100 milliseconds and in some instances to 10 milliseconds. Three systems were investigated: Ti + C → TiC; Ti + C + xNi → TiC + Ni-Ti alloy; and Al + Ni → AlNi. In all three reactions, the first step was the melting of the metal reactants. Formation of TiC in the first two reactions was completed within 400 milliseconds of the melting of the Ti metal, indicating that the formation of TiC took place during the passage of the combustion wave front. In the Al + Ni reaction, however, passage of the wave front was followed by the appearance and disappearance of at least one intermediate in the afterburn region. The final AlNi was formed some 5 seconds later and exhibited a delayed appearance of the (210) reflection, which tends to support a phase transformation from a disordered AlNi phase at high temperature to an ordered CsCl structure some 20 seconds later. This new experimental approach can be used to study the chemical dynamics of high-temperature solid-state phenomena and to provide the needed database to test various models for solid combustion.
Magnetic Confinement Fusion
Authors: Furth H. P.
Published: October 2006

Fusion plasmas with reactorlike temperatures have been confined in magnetic-field configurations of the tokamak type. The measured rate of heat leakage from these plasmas is sufficiently small to be compatible with the requirements of a full-sized fusion power reactor. Improvements in other aspects of reactor performance are still needed, however, and the high cost of reactor-development steps has become an obstacle on the path to practical fusion power.
Epitaxial and Smooth Films of
a
-Axis YBa
2
Cu
3
O
7
Authors: Eom C. B. , Marshall A. F. , Laderman S. S. , Jacowitz R. D. , Geballe T. H.
Published: October 2006

YBa
2
Cu
3
O
7
films have been grown epitaxially on SrTiO
3
(100) and LaAlO
3
(100) substrates with nearly pure
a
-axis orientation and with transition temperature
T
c
(
R
= 0) of 85 K. A unique feature of these films is their smooth surface. These smooth surfaces enable the growth of short-period superlattices with well-defined modulations. The films are untwinned and the grains grow with their
c
-axis along one of two perpendicular directions on the substrate ([100] or [010]). The fabrication of sandwich-type Josephson junctions with good characteristics may now be possible because unlike
c
-axis—oriented films, the superconducting coherence length of these smooth films is appreciably large perpendicular to their surfaces.
Treatment with Tin Prevents the Development of Hypertension in Spontaneously Hypertensive Rats
Authors: Sacerdoti David , Escalante Bruno , Abraham Nader G. , McGiff John C. , Levere Richard D. , Schwartzman Michal L.
Published: October 2006

Cytochrome P-450-dependent metabolites of arachidonic acid (AA) increased in the kidneys of young, spontaneously hypertensive rats (SHRs) during the period of rapid elevation of blood pressure (BP) but not in adult SHRs or in Wistar Kyoto rats (WKYs) with normal BP. Treatment of SHRs and WKYs with stannous chloride (SnCl
2
), which selectively depletes renal cytochrome P-450, restored BP to normal, coincident with a natriuresis, in young but not in adult SHRs and did not affect either BP or sodium excretion in WKYs. Depletion of renal cytochrome P-450 was associated with decreased generation of these AA metabolites only in young SHRs. The antihypertensive effect of SnCl
2
in young SHRs was greatly reduced by prevention of its cytochrome P-450-depleting action.
An Ultraviolet-Sensitive RNA Structural Element in a Viroid-Like Domain of the Hepatitis Delta Virus
Authors: Branch Andrea D. , Benenfeld Bonnie J. , Baroudy Bahige M. , Wells Frances V. , Gerin John L. , Robertson Hugh D.
Published: October 2006

The RNA genome of the hepatitis delta virus (HDV) appears to be made up of two parts: a small domain with a high degree of sequence conservation and structural features likely to promote replication; plus a second, larger domain that is less conserved and encodes the delta antigen. This report focuses on one of the several sets of data that have led to the proposal of this model: the existence of a novel structural element in HDV genomic RNA. This structural element lies within the highly conserved domain of HDV RNA and may be related to the local tertiary structure previously mapped to the central conserved region of the plant viroid genome. Both elements occur in regions with no apparent coding capacity and are distinctively responsive to ultraviolet (UV) light. Transcripts containing partial and full-length genomic sequences of HDV readily undergo a UV-induced crosslinking reaction, which establishes a covalent bond between two noncontiguous segments. By locking two segments of the overall structure into place, this crosslink has permitted the unbranched, rodlike model of HDV RNA to be examined and confirmed in the portion of the RNA analyzed. The clustering of the novel tertiary structure and the recently discovered self-cleavage sites into a highly conserved, but apparently noncoding, portion of the genome defines a viroid-like domain in HDV RNA and raises questions about the possible events leading up to the association of free-living RNAs with messenger RNAs and other RNA molecules.
Reversible Cleavage and Ligation of Hepatitis Delta Virus RNA
Authors: Wu Huey-Nan , Lai Michael M. C.
Published: October 2006

A 148-nucleotide subfragment of hepatitis delta virus RNA was shown to undergo cleavage and ligation reversibly. The direction of the reaction is determined by the presence or absence of Mg
2+
ions, with the presence of Mg
2+
favoring the cleavage reaction. Ligation requires specific conformation of the RNA molecules involved and occurs only between two cleaved RNA fragments that are still held together by hydrogen bonds. The ligation reaction occurs rapidly on removal of Mg
2+
by EDTA. This represents a new class of RNA enzymes.
A Family of Putative Potassium Channel Genes in
Drosophila
Authors: Butler Alice , Wei Aguan , Baker Keith , Salkoff Lawrence
Published: October 2006

Mutant flies in which the gene coding for the
Shaker
potassium channel is deleted still have potassium currents similar to those coded by the
Shaker
gene. This suggests the presence of a family of
Shaker
-like genes in
Drosophila
. By using a
Shaker
complementary DNA probe and low-stringency hybridization, three additional family members have now been isolated,
Shab
,
Shaw
, and
Shal
. The
Shaker
family genes are not clustered in the genome. The deduced proteins of
Shab
,
Shaw
, and
Shal
have high homology to the
Shaker
protein; the sequence identity of the integral membrane portions is greater than 50 percent. These genes are organized similarly to
Shaker
in that only a single homology domain containing six presumed membrane-spanning segments common to all voltage-gated ion channels is coded by each messenger RNA. Thus, potassium channel diversity could result from an extended gene family, as well as from alternate splicing of the
Shaker
primary transcript.
Recombinant Gene Expression in Vivo Within Endothelial Cells of the Arterial Wall
Authors: Nabel Elizabeth G. , Plautz Gregory , Boyce Frederick M. , Stanley James C. , Nabel Gary J.
Published: October 2006

A technique for the transfer of endothelial cells and expression of recombinant genes in vivo could allow the introduction of proteins of therapeutic value in the management of cardiovascular diseases. Porcine endothelial cells expressing recombinant β-galactosidase from a murine amphotropic retroviral vector were introduced with a catheter into denuded iliofemoral arteries of syngeneic animals. Arterial segments explanted 2 to 4 weeks later contained endothelial cells expressing β-galactosidase, an indication that they were successfully implanted on the vessel wall.
Reversible Root Tip Rotation in
Arabidopsis
Seedlings Induced by Obstacle-Touching Stimulus
Authors: Okada Kiyotaka , Shimura Yoshiro
Published: October 2006

In soil, downwardly growing plant roots frequently alter their growth direction to escape obstacles that lie in their paths. This response has been analyzed with a simple system that provides a constant obstacle-touching stimulus to root tips of young seedlings of
Arabidopsis thaliana
. On the surface of agar plates, which were set at an angle of 45° to the vertical, the roots exhibit a wavy growth pattern that is caused by periodic reversion of rotation of the root tip. A set of mutants with abnormal wavy growth was used to demonstrate that at least six genes are involved in this stimulus-response interaction.
Temperature and Thermal Emissivity of the Surface of Neptune's Satellite Triton
Authors: Nelson Robert M. , Smythe William D. , Wallis Brad D. , Horn Linda J. , Lane Arthur L. , Mayo Marvin J.
Published: October 2006

Analysis of the preliminary results from the Voyager mission to the Neptune system has provided the scientific community with several methods by which the temperature of Neptune's satellite Triton may be determined. If the 37.5 K surface temperature reported by several Voyager investigations is correct, then the photometry reported by the imaging experiment on Voyager requires that Triton's surface have a remarkably low emissivity. Such a low emissivity is not required in order to explain the photometry from the photopolarimeter experiment on Voyager. A low emissivity would be inconsistent with Triton having a rough surface at the ∼100-μm scale as might be expected given the active renewal processes which appear to dominate Triton's surface.
The Origin of Crustacean Biramous Appendages and the Evolution of Arthropoda
Authors: Emerson Michael J. , Schram Frederick R.
Published: October 2006

The evolution of biramous appendages in crustaceans is central to the debate on the origin of the arthropods. It is proposed that the biramous limb evolved through the basal fusion of adjacent pairs of ancestrally uniramous appendages. As a result, the existing system of homology, in which uniramous and biramous appendages are considered equivalent, may be invalid. Similarly, the homology of individual body segments between uniramians, such as insects and myriapods, and arthropod groups with biramous limbs is also called into question. Two uniramian segments, or a diplosegment, may be homologous to a single body segment in biramous groups.
The Texas Cytoplasm of Maize: Cytoplasmic Male Sterility and Disease Susceptibility
Authors: Levings Charles S.
Published: October 2006

The Texas cytoplasm of maize carries two cytoplasmically inherited traits, male sterility and disease susceptibility, which have been of great interest both for basic research and plant breeding. The two traits are inseparable and are associated with an unusual mitochondrial gene, T-
urf13
, which encodes a 13-kilodalton polypeptide (URF13). An interaction between fungal toxins and URF13, which results in permeabilization of the inner mitochondrial membrane, accounts for the specific susceptibility to the fungal pathogens.
Melting of Diamond at High Pressure
Authors: Galli Giulia , Martin Richard M. , Car Roberto , Parrinello Michele
Published: October 2006

Melting of diamond at high pressure and the properties of liquid carbon at pressures greater than 1 megabar were investigated with a first-principles molecular dynamics technique. The results indicate an increase of the diamond melting temperature with pressure, which is opposite to the behavior of silicon and germanium. This is contrary to long-held assumptions, but agrees with recent experiments, and has important implications for geology and astrophysics. As is the case for the solid phase of carbon at low temperature, which changes greatly with pressure from graphite to diamond, the structural and bonding properties of liquid carbon vary strongly with pressure.
Synapsins: Mosaics of Shared and Individual Domains in a Family of Synaptic Vesicle Phosphoproteins
Authors: Südhof Thomas C. , Czernik Andrew J. , Kao Hung-Teh , Takei Kohji , Johnston Patricia A. , Horiuchi Atsuko , Kanazir Selma D. , Wagner Michael A. , Perin Mark S. , De Camilli Pietro , Greengard Paul
Published: October 2006

Synapsins are neuronal phosphoproteins that coat synaptic vesicles, bind to the cytoskeleton, and are believed to function in the regulation of neurotransmitter release. Molecular cloning reveals that the synapsins comprise a family of four homologous proteins whose messenger RNA's are generated by differential splicing of transcripts from two genes. Each synapsin is a mosaic composed of homologous amino-terminal domains common to all synapsins and different combinations of distinct carboxyl-terminal domains. Immunocytochemical studies demonstrate that all four synapsins are widely distributed in nerve terminals, but that their relative amounts vary among different kinds of synapses. The structural diversity and differential distribution of the four synapsins suggest common and different roles of each in the integration of distinct signal transduction pathways that modulate neurotransmitter release in various types of neurons.
The Dynamics of the Stratospheric Polar Vortex and Its Relation to Springtime Ozone Depletions
Authors: Schoeberl Mark R. , Hartmann Dennis L.
Published: October 2006

Dramatic springtime depletions of ozone in polar regions require that polar stratospheric air has a high degree of dynamical isolation and extremely cold temperatures necessary for the formation of polar stratospheric clouds. Both of these conditions are produced within the stratospheric winter polar vortex. Recent aircraft missions have provided new information about the structure of polar vortices during winter and their relation to polar ozone depletions. The aircraft data show that gradients of potential vorticity and the concentration of conservative trace species are large at the transition from mid-latitude to polar air. The presence of such sharp gradients at the boundary of polar air implies that the inward mixing of heat and constituents is strongly inhibited and that the perturbed polar stratospheric chemistry associated with the ozone hole is isolated from the rest of the stratosphere until the vortex breaks up in late spring. The overall size of the polar vortex thus limits the maximum areal coverage of the annual polar ozone depletions. Because it appears that this limit has not been reached for the Antarctic depletions, the possibility of future increases in the size of the Antarctic ozone hole is left open. In the Northern Hemisphere, the smaller vortex and the more restricted region of cold temperatures suggest that this region has a smaller theoretical maximum for column ozone depletion, about 40 percent of the currently observed change in the Antarctic ozone column in spring.
Atomic-Resolution Electrochemistry with the Atomic Force Microscope: Copper Deposition on Gold
Authors: Manne S. , Hansma P. K. , Massie J. , Elings V. B. , Gewirth A. A.
Published: October 2006

The atomic force microscope (AFM) was used to image an electrode surface at atomic resolution while the electrode was under potential control in a fluid electrolyte. A new level of subtlety was observed for each step of a complete electrochemical cycle that started with an Au(111) surface onto which bulk Cu was electrodeposited. The Cu was stripped down to an underpotential-deposited monolayer and finally returned to a bare Au(111) surface. The images revealed that the underpotential-deposited monolayer has different structures in different electrolytes. Specifically, for a perchloric acid electrolyte the Cu atoms are in a close-packed lattice with a spacing of 0.29 ± 0.02 nanometer (nm). For a sulfate electrolyte they are in a more open lattice with a spacing of 0.49 ± 0.02 nm. As the deposited Cu layer grew thicker, the Cu atoms converged to a (111)-oriented layer with a lattice spacing of 0.26 ± 0.02 nm for both electrolytes. A terrace pattern was observed during dissolution of bulk Cu. Images were obtained of an atomically resolved Cu monolayer in one region and an atomically resolved Au substrate in another in which a 30° rotation of the Cu monolayer lattice from the Au lattice is clearly visible.
Recent Trends in Fertility and Nuptiality in China
Authors: Coale Ansley J. , Feng Wang , Riley Nancy E. , De Lin Fu
Published: October 2006

The State Family Planning Commission of China has conducted two large-scale fertility surveys, in 1982 and 1988, covering sample households containing 1 million and 2 million persons, respectively. These surveys obtained lifetime histories, including age at first marriage and at each birth for female members of the households from ages 15 to 67 in the first survey and from 15 to 57 in the second. The data provide detailed information on the extraordinary decline in the rate of childbearing in China (by 60% from 1970 to 1980). Because rising age at marriage played a significant role in this decline, the effect of changes in the pattern of entry into marriage on childbearing since 1980 was examined. There was a sharp increase in overall fertility (the total fertility rate) from 1980 to 1982; after falling to slightly below the 1980 level in 1985, the rate rose in 1985 and 1986 to well above that of 1980. A major factor in this arrested and partially reversed decline was a boom in marriage that followed a relaxation in 1980 of locally administered restrictions on marriage before the officially designated desirable age. In fact, the total fertility rate of married women (summed over duration of marriage rather than age) averaged much lower in the mid-1980s than in 1980. The summary rate of bearing second children increased markedly in the 1980s when calculated by age of women, but declined when calculated by duration of marriage, given the inflated number of recently married women.
Exact Solution of Large Asymmetric Traveling Salesman Problems
Authors: Miller Donald L. , Pekny Joseph F.
Published: October 2006

The traveling salesman problem is one of a class of difficult problems in combinatorial optimization that is representative of a large number of important scientific and engineering problems. A survey is given of recent applications and methods for solving large problems. In addition, an algorithm for the exact solution of the asymmetric traveling salesman problem is presented along with computational results for several classes of problems. The results show that the algorithm performs remarkably well for some classes of problems, determining an optimal solution even for problems with large numbers of cities, yet for other classes, even small problems thwart determination of a provably optimal solution.
Baddeleyite-Type High-Pressure Phase of TiO
2
Authors: Sato H. , Endo S. , Sugiyama M. , Kikegawa T. , Shimomura O. , Kusaba K.
Published: October 2006

A high-pressure phase of TiO
2
, which had been observed by shock-wave experiments and remained unresolved, has been studied by in situ x-ray diffraction. The single phase was formed at 20 gigapascals and 770°C with the use of sintered-diamond multianvils; it has the same structure as baddeleyite, the stable phase of ZrO
2
at ambient conditions. The coordination number of Ti increases from six to seven across the rutile to baddeleyite transition, and the volume is reduced by approximately 9 percent.
Nylon Production: An Unknown Source of Atmospheric Nitrous Oxide
Authors: Thiemens Mark H. , Trogler William C.
Published: October 2006

Nitrous oxide in the earth's atmosphere contributes to catalytic stratospheric ozone destruction and is also a greenhouse gas component. A precise budgetary accounting of N
2
O sources has remained elusive, and there is an apparent lack of source identification. One source of N
2
O is as a by-product in the manufacture of nylon, specifically in the preparation of adipic acid. Characterization of the reaction N
2
O stoichiometry and its isotopic composition with a simulated industrial adipic acid synthesis indicates that because of high rates of global adipic acid production, this N
2
O may account for ∼10 percent of the increase observed for atmospheric N
2
O.
The Current Situation in Mexican Immigration
Authors: Vernez Georges , Ronfeldt David
Published: October 2006

By 1988, the Mexican-origin population of the United States had grown to 12.1 million, largely from recent, sharp increases in immigration. The policy concerns raised by this phenomenon have been influenced by some perceptions that available research contradicts. Today most Mexican immigrants come to stay, about half are female, and they have increasingly less schooling compared to the native-born population and other immigrants. Nationally, they do not cause adverse economic effects for native-born workers and, across generations, their language and political assimilation is proceeding well. They put greater demands on education than on other public services. However, the Mexican-origin population affects the economy and public services more and differently in the areas where it is concentrated, primarily in the western United States and large urban areas. Further, the recent legalization of 2.3 million Mexican immigrants can be expected to increase the demand on public services, especially in those areas.
Fuel Ethanol from Cellulosic Biomass
Authors: Lynd Lee R. , Cushman Janet H. , Nichols Roberta J. , Wyman Charles E.
Published: October 2006

Ethanol produced from cellulosic biomass is examined as a large-scale transportation fuel. Desirable features include ethanol's fuel properties as well as benefits with respect to urban air quality, global climate change, balance of trade, and energy security. Energy balance, feedstock supply, and environmental impact considerations are not seen as significant barriers to the widespread use of fuel ethanol derived from cellulosic biomass. Conversion economics is the key obstacle to be overcome. In light of past progress and future prospects for research-driven improvements, a cost-competitive process appears possible in a decade.
Some of the Tough Decisions Required by a National Health Plan
Authors: Russell Louise B.
Published: October 2006

The goals of providing coverage for everyone in the United States and controlling the growth in national health expenditures require difficult decisions about what medical services to provide. Currently accepted practices vary enormously in the amount of health they produce for a given expenditure. Studies of the health effects of several major interventions in relation to their costs—Pap smears, mammography, coronary care units, bypass surgery, and cholesterol reduction—indicate the kinds of choices to be made.
The Cholinergic Neuronal Differentiation Factor from Heart Cells Is Identical to Leukemia Inhibitory Factor
Authors: Yamamori Tetsuo , Fukada Keiko , Aebersold Ruedi , Korsching Sigrun , Fann Ming-Ji , Patterson Paul H.
Published: October 2006

A protein secreted by cultured rat heart cells can direct the choice of neurotransmitter phenotype made by cultured rat sympathetic neurons. Structural analysis and biological assays demonstrated that this protein is identical to a protein that regulates the growth and differentiation of embryonic stem cells and myeloid cells, and that stimulates bone remodeling and acute-phase protein synthesis in hepatocytes. This protein has been termed D factor, DIA, DIF, DRF, HSFIII, and LIF. Thus, this cytokine, like IL-6 and TGFβ, regulates growth and differentiation in the embryo and in the adult in many tissues, now including the nervous system.
Deep-Focus Earthquakes and Recycling of Water into the Earth's Mantle
Authors: Meade Charles , Jeanloz Raymond
Published: October 2006

For more than 50 years, observations of earthquakes to depths of 100 to 650 kilometers inside Earth have been enigmatic: at these depths, rocks are expected to deform by ductile flow rather than brittle fracturing or frictional sliding on fault surfaces. Laboratory experiments and detailed calculations of the pressures and temperatures in seismically active subduction zones indicate that this deep-focus seismicity could originate from dehydration and high-pressure structural instabilities occurring in the hydrated part of the lithosphere that sinks into the upper mantle. Thus, seismologists may be mapping the recirculation of water from the oceans back into the deep interior of our planet.
Are Prescription Drug Prices High?
Authors: Vagelos P. Roy
Published: October 2006

The U.S. pharmaceutical industry has been criticized because its products are perceived to be too expensive, yet prescription medicines remain the least expensive form of therapy. At this time, we are experiencing a dramatic increase in the risks and costs of pharmaceutical research and development (R&D). An example may be seen in the R&D history of lovastatin. The U.S. pharmaceutical industry continues to lead the world in the discovery and development of important new medicines because it assumes greater financial risk and invests more of its sales dollar in R&D than virtually any other industry. Where such a risk is posed, there must continue to be the potential for profits. Pharmaceutical companies must set responsible prices, must keep price increases down, and must help improve access to important medicines.
A Room-Temperature Molecular/Organic-Based Magnet
Authors: Manriquez Juan M. , Yee Gordon T. , McLean R. Scott , Epstein Arthur J. , Miller Joel S.
Published: October 2006

The reaction of bis(benzene)vanadium with tetracyanoethylene, TCNE, affords an insoluble amorphous black solid that exhibits field-dependent magnetization and hysteresis at room temperature. The critical temperature could not be estimated as it exceeds 350 kelvin, the thermal decomposition temperature of the sample. The empirical composition of the reported material is V(TCNE)

x

⋅
y
(CH
2
Cl
2
) with
x
∼ 2 and
y
∼ 1/2. On the basis of the available magnetic and infrared data, three-dimensional antiferromagnetic exchange of the donor and acceptor spins resulting in ferrimagnetic behavior appears to be the mode of magnetic coupling.
Vβ-Specific Stimulation of Human T Cells by Staphylococcal Toxins
Authors: Kappler John , Kotzin Brian , Herron Lynne , Gelfand Erwin W. , Bigler Robert D. , Boylston Arthur , Carrel Stefan , Posnett David N. , Choi Yongwon , Marrack Philippa
Published: October 2006

The staphylococcal toxins are responsible for a number of diseases in man and other animals. Many of them have also long been known to be powerful T cell stimulants. They do not, however, stimulate all T cells. On the contrary, each toxin reacts with human T cells bearing particular Vβ sequences as part of their receptors for major histocompatibility complex protein-associated antigen. The specificity of these toxins for Vβs puts them in the recently described class of superantigens and may account for the differential sensitivity of different individuals to the toxic effects of these proteins.
Nonlinear Optical Materials
Authors: Eaton David F.
Published: October 2006

The current state of materials development in nonlinear optics is summarized, and the promise of these materials is critically evaluated. Properties and important materials constants of current commercial materials and of new, promising, inorganic and organic molecular and polymeric materials with potential in second- and third-order nonlinear optical applications are presented.
Impact-Induced Cleaving and Melting of Alkali-Halide Nanocrystals
Authors: Beck Rainer D. , St. John Pamela , Homer Margie L. , Whetten Robert L.
Published: October 2006

Impact of nanocrystalline alkali-halide clusters against solid surfaces causes them to fission exclusively into low surface-energy fragments. In time-of-flight scattering experiments, this process appears at an impact energy so low that it must result from a single-step cleavage of the nanocrystal along low surface-energy cleavage planes. At higher energies (more than 1 electron volt per atom), a crossover occurs to an entirely different behavior—evaporative cascades that proceed irrespective of the structure-energetic properties of the fragments. These cascades, and the approximately linear scaling of the crossover energy with cluster size, are characteristic of impact-induced transformation of the cluster to a molten state. Collision with the high-rigidity surface of silicon gives a substantially greater cleavage probability than the soft basal-plane surface of graphite.
A Polypeptide from Tomato Leaves Induces Wound-Inducible Proteinase Inhibitor Proteins
Authors: Pearce Gregory , Strydom Daniel , Johnson Scott , Ryan Clarence A.
Published: October 2006

Defensive genes in plants can be activated by several different types of nonpeptide signaling molecules. An endogenous polypeptide, consisting of 18 amino acids, was isolated from tomato leaves and was able at very low concentrations to induce the synthesis of two wound-inducible proteinase inhibitor proteins when supplied to young tomato plants. The sequence of the polypeptide was determined, and an identical polypeptide was synthesized that possessed full inducing activity. These data establish that a polypeptide factor can initiate signal transduction to regulate the synthesis of defensive proteins in plant tissues.
Imaging Powders with the Atomic Force Microscope: From Biominerals to Commercial Materials
Authors: Friedbacher Gernot , Hansma Paul K. , Ramli Emannuel , Stucky Galen D.
Published: October 2006

Atomically resolved images of pressed powder samples have been obtained with the atomic force microscope (AFM). The technique was successful in resolving the particle, domain, and atomic structure of pismo clam (
Tivela stultorum
) and sea urchin (
Strongylocentrotus purpuratus
) shells and of commercially available calcium carbonate (CaCO
3
) and strontium carbonate (SrCO
3
) powders. Grinding and subsequent pressing of the shells did not destroy the microstructure of these materials. The atomic-resolution imaging capabilities of AFM can be applied to polycrystalline samples by means of pressing powders with a grain size as small as 50 micrometers. These results illustrate that the AFM is a promising tool for material science and the study of biomineralization.
Molecular Origin of Io's Fast Sodium
Authors: Schneider Nicholas M. , Trauger John T. , Wilson Jody K. , Brown David I. , Evans Robin W. , Shemansky Donald E.
Published: October 2006

Neutral sodium emissions encircling Jupiter exhibit an intricate and variable structure that is well matched by a simple loss process from Io's atmosphere. These observations imply that fast neutral sodium is created locally in the Io plasma torus, both near Io and as much as 8 hours downstream. Sodium-bearing molecules may be present in Io's upper atmosphere, where they are ionized by the plasma torus and swept downstream. The molecular ions dissociate and dissociatively recombine on a short time scale, releasing neutral fragments into escape trajectories from Jupiter. This theory explains a diverse set of sodium observations, and it implies that molecular reactions (particularly electron impact ionization and dissociation) are important at the top of Io's atmosphere.
Generation of a Large Combinatorial Library of the Immunoglobulin Repertoire in Phage Lambda
Authors: Huse William D. , Sastry Lakshmi , Iverson Sheila A. , Kang Angray S. , Alting-Mees Michelle , Burton Dennis R. , Benkovic Stephen J. , Lerner Richard A.
Published: October 2006

A novel bacteriophage lambda vector system was used to express in
Escherichia coli
a combinatorial library of Fab fragments of the mouse antibody repertoire. The system allows rapid and easy identification of monoclonal Fab fragments in a form suitable for genetic manipulation. It was possible to generate, in 2 weeks, large numbers of monoclonal Fab fragments against a transition state analog hapten. The methods described may supersede present-day hybridoma technology and facilitate the production of catalytic and other antibodies.
Autocrine Induction of Collagenase by Serum Amyloid A-Like and β
2
-Microglobulin-Like Proteins
Authors: Brinckerhoff Constance E. , Mitchell Teresa I. , Karmilowicz Michael J. , Kluve-Beckerman Barbara , Benson Merrill D.
Published: October 2006

Two autocrine proteins of 14 and 12 kilodaltons that induce the synthesis of rabbit fibroblast collagenase were identified. The proteins were purified from serum-free culture medium taken from rabbit synovial fibroblasts stimulated with phorbol myristate acetate. The amino-terminal sequences of the 14- and 12-kilodalton species were ∼60 to 80 percent homologous with serum amyloid A and β
2
microglobulin, respectively. The polyacrylamide gel-eluted proteins retained the ability to induce collagenase synthesis in rabbit and human fibroblasts. These autocrine proteins may provide a means to modulate collagenase synthesis in normal remodeling as well as in inflammation and disease states.
Modulation of Calcium Channels in Cardiac and Neuronal Cells by an Endogenous Peptide
Authors: Callewaert Geert , Hanbauer Ingeborg , Morad Martin
Published: October 2006

Calcium channels mediate the generation of action potentials, pacemaking, excitation-contraction coupling, and secretion and signal integration in muscle, secretory, and neuronal cells. The physiological regulation of the L-type calcium channel is thought to be mediated primarily by guanine nucleotide-binding proteins (G proteins). A low molecular weight endogenous peptide has been isolated and purified from rat brain. This peptide regulates up and down the cardiac and neuronal calcium channels, respectively. In cardiac myocytes, the peptide-induced enhancement of the L-type calcium current had a slow onset (half-time ≈75 seconds), occurred via a G protein-independent mechanism, and could not be inhibited by α
1
-adrenergic, β-adrenergic, or angiotensin II blockers. In neuronal cells, on the other hand, the negative effect had a rapid onset (half-time <500 milliseconds) and was observed on both T-type and L-type calcium channels.
Splice Variants of the α Subunit of the G Protein G
s
Activate Both Adenylyl Cyclase and Calcium Channels
Authors: Mattera Rafael , Graziano Michael P. , Yatani Atsuko , Zhou Zhimin , Graf Rolf , Codina Juan , Birnbaumer Lutz , Gilman Alfred G. , Brown Arthur M.
Published: October 2006

Signal transducing guanine nucleotide binding (G) proteins are heterotrimers with different α subunits that confer specificity for interactions with receptors and effectors. Eight to ten such G proteins couple a large number of receptors for hormones and neurotransmitters to at least eight different effectors. Although one G protein can interact with several receptors, a given G protein was thought to interact with but one effector. The recent finding that voltage-gated calcium channels are stimulated by purified G
s
, which stimulates adenylyl cyclase, challenged this concept. However, purified G
s
may have four distinct α-subunit polypeptides, produced by alternative splicing of messenger RNA. By using recombinant DNA techniques, three of the splice variants were synthesized in
Escherichia coli
and each variant was shown to stimulate both adenylyl cyclase and calcium channels. Thus, a single G protein α subunit may regulate more than one effector function.
Stretch-Inactivated Ion Channels Coexist with Stretch-Activated Ion Channels
Authors: Morris Catherine E. , Sigurdson Wade J.
Published: October 2006

Stretch-activated ion channels of animal, plant, bacterial, and fungal cells are implicated in mechanotransduction and osmoregulation. A new class of channel has now been described that is stretch-inactivated. These channels occur in neurons, where they coexist with stretch-activated channels. Both channels are potassium selective. The differing stretch sensitivities of the two channels minimize potassium conductance over an intermediate range of tension, with the consequence that, over this same range, voltage-gated calcium channels are most readily opened. Thus, by setting the relation between membrane tension and transmembrane calcium fluxes, stretch-sensitive potassium channels may participate in the control of calcium-dependent motility in differentiating, regenerating, or migrating neurons.
Expression of a Cloned Rat Brain Potassium Channel in
Xenopus
Oocytes
Authors: Christie MacDonald J. , Adelman John P. , Douglass James , North R. Alan
Published: October 2006

Potassium channels are ubiquitous membrane proteins with essential roles in nervous tissue, but little is known about the relation between their function and their molecular structure. A complementary DNA library was made from rat hippocampus, and a complementary DNA clone (RBK-1) was isolated. The predicted sequence of the 495-amino acid protein is homologous to potassium channel proteins encoded by the
Shaker
locus of
Drosophila
and differs by only three amino acids from the expected product of a mouse clone MBK-1. Messenger RNA transcribed from RBK-1 in vitro directed the expression of potassium channels when it was injected into
Xenopus
oocytes. The potassium current through the expressed channels resembles both the transient (or A) and the delayed rectifier currents reported in mammalian neurons and is sensitive to both 4-aminopyridine and tetraethylammonium.
Liquids at Large Negative Pressures: Water at the Homogeneous Nucleation Limit
Authors: Zheng Q. , Durben D. J. , Wolf G. H. , Angell C. A.
Published: October 2006

An isochoric cooling method for obtaining unprecedented tensions on liquids was used to determine the homogeneous nucleation limit for stretching of water at a variety of water densities. At densities in the range 0.55 to 0.68 gram per milliliter (g/ml), the data agree with the homogeneous nucleation temperatures measured by Skripov for superheated water at positive pressures. At densities between 0.68 and 0.93 g/ml, cavitation occurred only at negative pressures (that is, under tension). The cavitation tensions measured were in excellent agreement with those predicted by Fisher's 1948 vapor nucleation theory. A maximum tension of 140 megapascals (=1400 bars) was reached at 42°C, which lies on an extrapolation of the line of isobaric density maxima. At higher densities, cavitation of droplets that survived heterogeneous nucleation failed to occur at all unless provoked, at much lower temperatures, by freezing. This observation confirms the existence of a density maximum at 42°C and –140 megapascals and hence greatly strengthens the basis for Speedy's conjecture of a reentrant spinodal for water.
Major Role of the Cyanobacterium
Trichodesmium
in Nutrient Cycling in the North Atlantic Ocean
Authors: Carpenter Edward J. , Romans Kristen
Published: October 2006

The diazotrophic cyanobacterium
Trichodesmium
is a large (about 0.5 by 3 millimeters) phytoplankter that is common in tropical open-ocean waters. Measurements of abundance, plus a review of earlier observations, indicate that it, rather than the picophytoplankton, is the most important primary producer (about 165 milligrams of carbon per square meter per day) in the tropical North Atlantic Ocean. Furthermore, nitrogen fixation by
Trichodesmium
introduces the largest fraction of new nitrogen to the euphotic zone, approximately 30 milligrams of nitrogen per square meter per day, a value exceeding the estimated flux of nitrate across the thermocline. Inclusion of this organism, plus the abundant diazotrophic endosymbiont
Richelia intracellularis
that is present in some large diatoms, in biogeochemical studies of carbon and nitrogen may help explain the disparity between various methods of measuring productivity in the oligotrophic ocean. Carbon and nitrogen fixation by these large phytoplankters also introduces a new paradigm in the biogeochemistry of these elements in the sea.
Raman Studies of Alkali-Metal Doped A

x

C
60
Films (A = Na, K, Rb, and Cs;
x
= 0, 3, and 6)
Authors: Duclos S. J. , Haddon R. C. , Glarum S. , Hebard A. F.
Published: October 2006

The room temperature Raman spectra of the intramolecular modes between 100 cm
–1
and 2000 cm
–1
are reported for alkali-metal doped A

x

C
60
films. For A = K, Rb, and Cs, phase separation is observed with the spectra of C
60
, K
3
C
60
, K
6
C
60
, Rb
3
C
60
, Rb
6
C
60
, and Cs
6
C
60
phases reported. The
x
= 3 phases show only three Raman active modes: two of

A
g

symmetry and only the lowest frequency

H
g

mode. The other

H
g

modes regain intensity in the
x
= 6 films, with several mode splittings observed. For A = Na, such phase separation is not clearly observed, and reduced mode shifts are interpreted as due to incomplete charge transfer in these films.
A Pertussis Toxin-Sensitive G Protein in Hippocampal Long-Term Potentiation
Authors: Goh Joanne W. , Pennefather Peter S.
Published: October 2006

High-frequency (tetanic) stimulation of presynaptic nerve tracts in the hippocampal region of the brain can lead to long-term synaptic potentiation (LTP). Pertussis toxin prevented the development of tetanus-induced LTP in the stratum radiatum-CA1 synaptic system of rat hippocampal slices, indicating that a guanosine triphosphate-binding protein (G protein) may be required for the initiation of LTP. This G protein may be located at a site distinct from the postsynaptic neuron (that is, in presynaptic terminals or glial cells) since maximal activation of CA1 neuronal G proteins by intracellular injection of guanosine-5′-
O
-(3-thiotriphosphate), a nonhydrolyzable analog of guanosine 5′-triphosphate, did not occlude LTP.
Purification and Complementary DNA Cloning of a Receptor for Basic Fibroblast Growth Factor
Authors: Lee Pauline L. , Johnson Daniel E. , Cousens Lawrence S. , Fried Victor A. , Williams Lewis T.
Published: October 2006

Basic fibroblast growth factor (bFGF) participates in many processes including early developmental events, angiogenesis, wound healing, and maintenance of neuronal cell viability. A 130-kilodalton protein was isolated on the basis of its ability to specifically bind to bFGF. A complementary DNA clone was isolated with an oligonucleotide probe corresponding to determined amino acid sequences of tryptic peptide fragments of the purified protein. The putative bFGF receptor encoded by this complementary DNA is a transmembrane protein that contains three extracellular immunoglobulin-like domains, an unusual acidic region, and an intracellular tyrosine kinase domain. These domains are arranged in a pattern that is different from that of any growth factor receptor described.
Human Diabetes Associated with a Mutation in the Tyrosine Kinase Domain of the Insulin Receptor
Authors: Odawara Masato , Kadowaki Takashi , Yamamoto Ritsuko , Shibasaki Yoshikazu , Tobe Kazuyuki , Accili Domenico , Bevins Charles , Mikami Yuhei , Matsuura Nobuo , Akanuma Yasuo , Takaku Fumimaro , Taylor Simeon I. , Kasuga Masato
Published: October 2006

Insulin receptor complementary DNA has been cloned from an insulin-resistant individual whose receptors have impaired tyrosine protein kinase activity. One of this individual's alleles has a mutation in which valine is substituted for Gly
996
, the third glycine in the conserved Gly-X-Gly-X-X-Gly motif in the putative binding site for adenosine triphosphate. Expression of the mutant receptor by transfection into Chinese hamster ovary cells confirmed that the mutation impairs tyrosine kinase activity.