bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical Studies of the Energetics and Dynamics of Chemical Reactions
Authors: Dunning Thom H. , Harding Lawrence B. , Wagner Albert F. , Schatz George C. , Bowman Joel M.
Published: October 2006

Computational studies of basic chemical processes not only provide numbers for comparison with experiment or for use in modeling complex chemical phenomena such as combustion, but also provide insight into the fundamental factors that govern molecular structure and change which cannot be obtained from experiment alone. We summarize the results of three case studies, on HCO, OH + H
2
, and O + C
2
H
2
, which illustrate the range of problems that can be addressed by using modern theoretical techniques. In all cases, the potential energy surfaces were characterized by using ab initio electronic structure methods. Collisions between molecules leading to reaction or energy transfer were described with quantum dynamical methods (HCO), classical trajectory techniques (HCO and OH + H
2
), and statistical methods (HCO, OH + H
2
, and O + C
2
H
2
). We can anticipate dramatic increases in the scope of this work as new generations of computers are introduced and as new chemistry software is developed to exploit these computers.
U.S. Competitiveness: Beyond the Trade Deficit
Authors: Hatsopoulos George N. , Krugman Paul R. , Summers Lawrence H.
Published: October 2006

Large trade deficits and the corresponding increase in U.S. international indebtedness have raised concerns about the long-run competitiveness of the United States. But being competitive requires more than balance in our foreign trade; it requires an improving standard of living. The long-term U.S. competitive problem is largely caused by low saving rates, high costs of capital, and the resulting inadequate level of both visible and invisible investment. As long as the U.S. national saving rate remains far below that of all our major competitor nations, there is little chance for restoring America's international economic position.
Acoustical Detection of High-Density Krill Demersal Layers in the Submarine Canyons off Georges Bank
Authors: Greene C. H. , Wiebe P. H. , Burczynski J. , Youngbluth M. J.
Published: October 2006

High-density demersal layers of krill have been detected in the submarine canyons off Georges Bank by means of a high-frequency, dual-beam bioacoustical technique. Krill densities in these demersal layers were observed to be two to three orders of magnitude greater than the highest densities observed in water-column scattering layers. Such abundances may help explain the unusually high squid and demersal fish production estimates attributed to the Georges Bank ecosystem.
RH 5849, a Nonsteroidal Ecdysone Agonist: Effects on Larval Lepidoptera
Authors: Wing Keith D. , Slawecki Richard A. , Carlson Glenn R.
Published: October 2006

The ecdysone agonist RH 5849 (1,2-dibenzoyl-1-
tert
-butylhydrazine) causes the premature initiation of molting at all stages of larval development of the tobacco hornworm,
Manduca sexta
. This phenomenon occurs without an increase in the endogenous ecdysone (20-hydroxyecdysone) titers. RH 5849 likewise provokes the initiation of molting in larval abdomens in the absence of a source of endogenous hormone. Although substantially less active than 20-hydroxyecdysone in vitro, RH 5849 was 30 to >670 times as active as the authentic molting hormone in bioassays with isolated larval abdomens or intact hornworms. This reversal in potency can be attributed to the superior transport properties and metabolic stability of RH 5849 relative to 20-hydroxyecdysone. Thus RH 5849 and its analogs are relatively persistent ecdysone agonists that halt feeding in larval lepidoptera by forcing an ultimately lethal, developmentally premature molt.
Synthesis of Buried Oxide and Silicide Layers with Ion Beams
Authors: White Alice E. , Short K. T.
Published: October 2006

Ion implantation, because it is inherently a strongly nonequilibrium process, can add a new dimension to materials studies. A large variety of chemical elements may be readily introduced into a target substrate by ion bombardment at concentrations considerably greater than the normal solid solubilities. In addition, the interaction of the accelerated ions with the target produces lattice defects. Both effects have been studied extensively in experiments directed at understanding the mechanisms of formation of buried oxide and silicide layers in silicon with high-dose ion implantation. These layers have properties that are difficult to attain with conventional techniques.
Energy Loss Mechanisms of Superconductors Used in Alternating-Current Power Transmission Systems
Authors: Forsyth E. B.
Published: October 2006

The intrinsic hysteretic loss of superconductors carrying alternating current has been derived from simple models and verified experimentally. In practical cable designs the losses are increased by surface roughness, conductor configuration, and added metallic components. When possible applications by electric utility companies are being considered, such losses are only one of many factors that must be adjusted in an optimization that produces the lowest cost (including both capital and operating expenses) during the lifetime of the system.
Estimates of Mass and Angular Momentum in the Oort Cloud
Authors: Marochnik Leonid S. , Mukhin Lev M. , Sagdeev Roald Z.
Published: October 2006

Estimates can be made of unseen mass (in the form of cometary nuclei) at the heliocentric distances between 3 × 10
3
and 2 × 10
4
astronomical units (AU) under the assumptions (i) that the Oort cloud is a rarefied halo surrounding the core (dense, inner cometary cloud) and (ii) that the mass and albedo of comet Halley is typical for comets both in the core and the Oort cloud populations. The mass appears to be approximately 0.03 solar masses, with angular momentum of the order of 10
52
to 10
53
g-cm
2
/s. This mass is of the order of the total mass of the planetary system before the loss of volatiles. This leads to an estimate of a mass
M
o
≃ 100
M
⊕
(where
M
⊕
is the mass of Earth) concentrated in the Oort cloud (
r
> 2 × 10
4
AU) with an angular momentum that may exceed the present angular momentum of the whole planetary system by one order of magnitude. The present angular momentum of the Oort cloud appears to be of the same order as the total angular momentum of the planetary system before the loss of volatiles.
Artificial Airglow Excited by High-Power Radio Waves
Authors: Bernhardt P. A. , Duncan L. M. , Tepley C. A.
Published: October 2006

High-power electromagnetic waves beamed into the ionosphere from ground-based transmitters illuminate the night sky with enhanced airglow. The recent development of a new intensified, charge coupled-device imager made it possible to record optical emissions during ionospheric heating. Clouds of enhanced airglow are associated with large-scale plasma density cavities that are generated by the heater beam. Trapping and focusing of electromagnetic waves in these cavities produces accelerated electrons that collisionally excite oxygen atoms, which emit light at visible wavelengths. Convection of plasma across magnetic field lines is the primary source for horizontal motion of the cavities and the airglow enhancements. During ionospheric heating experiments, quasi-cyclic formation, convection, dissipation and reappearance of the cavities comprise a major source of long-term variability in plasma densities during ionospheric heating experiments.
Dynamics of a Second-Order Phase Transition: P1̅ to I1̅ Phase Transition in Anorthite, CaAl
2
Si
2
O
8
Authors: Ghose Subrata , Van Tendeloo G. , Amelinckx S.
Published: October 2006

Electron microscopic study of the reversible P1̅ to I1̅ phase transition in anorthite (transition temperature
T
c
= 516 Kelvin) shows that the antiphase boundaries (APBs) with the displacement vector R = 1/2[111] become unstable at
T
c
, and numerous small APB loops are formed. These interfaces are highly mobile, and their vibration frequency increases strongly with temperature. These observations suggest that close to
T
c
, breathing-motion—type lattice vibrations of the framework cause the two different configurations around the calcium atoms, which are related by a translation of R ≈ 1/2[111], to interchange dynamically through an intermediate I1̅ configuration. The high-temperature I1̅ structure is interpreted as a statistical-dynamic average of highly mobile antiphase domains of primitive anorthite.
Tyr
527
Is Phosphorylated in pp60

c-
src

: Implications for Regulation
Authors: Cooper Jonathan A. , Gould Kathleen L. , Cartwright Christine A. , Hunter Tony
Published: October 2006

The Rous sarcoma virus oncogene product, pp60

v-
src

, transforms cultured fibroblasts but its corresponding proto-oncogene product, pp60

c-
src

, does not. Both proteins are known to be protein-tyrosine kinases. Published results suggest that the kinase activity of pp60

c-
src

is inhibited relative to that of pp60

v-
src

, due perhaps to phosphorylation of a tyrosine in pp60

c-
src

that is not phosphorylated in pp60

v-
src

. In this study, it was observed that the tyrosine phosphorylated in pp60

c-
src

is Tyr
527
, six residues from the COOH-terminus of the protein. The region of pp60

c-
src

from residue 515 to the COOH-terminus, including Tyr
527
, has been replaced with a different sequence in pp60

v-
src

. Thus, the increase in transforming ability and kinase activity that occurred in the genesis of pp60

v-
src

may have resulted from the loss of a tyrosine involved in negative regulation.
Lysinoalanine: Presence in Foods and Food Ingredients
Authors: Sternberg M. , Kim C. Y. , Schwende F. J.
Published: October 2006

Lysinoalanine, N
ε
-(DL-2-amino-2-carboxyethyl)-L-lysine, an unusual amino acid implicated as a renal toxic factor in rats, has been found in proteins of home-cooked and commercial foods and ingredients. Although it has been reported to occur in both edible and nonfood proteins only after alkali treatment, it has now been identified in food proteins that had not been subjected to alkali. Lysinoalanine is generated in a variety of proteins when heated under nonalkaline conditions.
Existence of High Abundance Antiproliferative mRNA's in Senescent Human Diploid Fibroblasts
Authors: Lumpkin C. K. , McClung J. Keith , Pereira-Smith Olivia M. , Smith James R.
Published: October 2006

Polyadenylated RNA isolated from senescent human diploid fibroblasts (HDF) inhibited DNA synthesis in proliferation-competent cells after microinjection, whereas polyadenylated RNA from young HDF had no inhibitory effect. Polyadenylated RNA from young cells made quiescent by removal of serum growth factors had a slight inhibitory effect on DNA synthesis. The abundance level of inhibitor messenger RNA (mRNA) from senescent cells was estimated at 0.8 and that of quiescent cells at 0.005 percent. These results demonstrate the existence of one or more antiproliferative mRNA's in nonproliferating normal human cells; these RNA's code for factors that either work antagonistically to initiators of DNA synthesis or regulate the expression of the initiators in some way. The abundance level of the inhibitory mRNA in senescent cells indicates the feasibility of developing a complementary DNA probe that will be useful in studying cell cycle control mechanisms.
Calcium and Sodium Channels in Spontaneously Contracting Vascular Muscle Cells
Authors: Sturek Michael , Hermsmeyer Kent
Published: October 2006

Electrophysiological recordings of inward currents from whole cells showed that vascular muscle cells have one type of sodium channel and two types of calcium channels. One of the calcium channels, the transient calcium channel, was activated by small depolarizations but then rapidly inactivated. It was equally permeable to calcium and barium and was blocked by cadmium, but not by tetrodotoxin. The other type, the sustained calcium channel, was activated by larger depolarizations, but inactivated very little; it was more permeable to barium than calcium. The sustained calcium channel was more sensitive to block by cadmium than the transient channel, but also was not blocked by tetrodotoxin. The sodium channel inactivated 15 times more rapidly than the transient calcium channel and at more negative voltages. This sodium channel, which is unusual because it is only blocked by a very high (60 μ
M
) tetrodotoxin concentration but not by cadmium, is the first to be characterized in vascular muscle, and together with the two calcium channels, provides a basis for different patterns of excitation in vascular muscles.
Atom Counting at Surfaces
Authors: Pappas David L. , Hrubowchak David M. , Ervin Matthew H. , Winograd Nicholas
Published: October 2006

Multiphoton resonance ionization has been combined with energetic ion bombardment to examine dopant concentrations of indium on the surface of silicon. The results yield a linear relation between the indium concentration and the known bulk values and a detection limit of 9 parts per trillion, at a mass resolution exceeding 160. This measurement, which surpasses the limits of any previous surface analysis by a factor of 100, has been made possible with an experimental configuration that optimizes sampling and detection efficiency while reducing background noise to virtually zero. During the analysis, submonolayer quantities of the surface are removed, so that as few as 180 surface atoms may be counted.
Take Your Choice: Ice Ages, Quakes, or Impacts
Authors: Kerr Richard A.
Published: October 2006

If you are looking for a coherent, tidily packaged program, do not bother with the meetings of the American Geophysics Union. Its name suggests at least certain constraints, but in practice there are almost none. This past December's meeting was typical: it included anything natural and nonliving within the gravitational influence of the sun. For good measure the marine biology of the American Society of Limnology and Oceanography was thrown in as well. Here are some selections.
Is the Stock Market Efficient?
Authors: Malkiel Burton G.
Published: October 2006

A stock market is said to be efficient if it accurately reflects all relevant information in determining security prices. Critics have asserted that share prices are far too volatile to be explained by changes in objective economic events—the October 1987 crash being a case in point. Although the evidence is not unambiguous, reports of the death of the efficient market hypothesis appear premature.
Honeyguides and Honey Gatherers: Interspecific Communication in a Symbiotic Relationship
Authors: Isack H. A. , Reyer H.-U.
Published: October 2006

In many parts of Africa, people searching for honey are led to bees' nests by the greater honeyguide (
Indicator indicator
Sparrman). The Boran people of Kenya claim that they can deduce the direction and the distance to the nest as well as their own arrival at the nest from the bird's flight pattern, perching height, and calls. Analyses of the behavior of guiding birds confirmed these claims.
Hexagonal Domain-Like Charge Density Wave Phase of TaS
2
Determined by Scanning Tunneling Microscopy
Authors: Wu Xian Liang , Lieber Charles M.
Published: October 2006

The structure of the room-temperature charge density wave (CDW) phase in octahedrally coordinated tantalum disulfide, 1T-TaS
2
, has been a controversial issue for over 15 years. Large-scale scanning tunneling microscope images of the intralayer structure of this phase exhibit a domain-like pattern defined by a variation in the maximum CDW amplitude. The circular domains, consisting of high-amplitude CDWs, are arranged in a regular hexagonal lattice (period 73 ± 3 angstroms) that is rotated relative to the CDWs. In addition, from the analysis of atomic resolution images it was determined that there is a well-defined phase shift between the CDWs in adjacent domains, and that within a domain the CDW superlattice is commensurate with the atomic lattice. These results provide evidence for the hexagonal discommensurate CDW phase in 1T-TaS
2
and also suggest an explanation for the long-standing controversy concerning the structure of this phase.
Thirty Thousand Years of Human Colonization in Tasmania: New Pleistocene Dates
Authors: Cosgrove Richard
Published: October 2006

Basal dates of 30,420 years before present (BP) from a limestone cave in the Florentine River valley and 30,840 BP from a sandstone rockshelter in the Shannon River valley on the edge of the central Tasmanian highlands indicate colonization of Tasmania 8,000 years earlier than previously thought. These data indicate that people arrived before the Bassian Bridge was exposed about 23,000 years ago and support evidence that Tasmania and Australia may have been connected intermittently during the past 50,000 years. The dates support earlier suggestions that the Tasmanian inland was an important focus for systematic occupation and exploitation by human groups and dispel a belief that the Aboriginal economy 30,000 years ago was based on littoral, lacustral, and riverine resources. The absence of megafauna at both sites points to their extinction by 30,000 years ago in Tasmania. The people inhabiting Tasmania at this time, together with those at Monte Verde in Chile, were the most southerly humans on Earth.
CD8
+
Lymphocytes Can Control HIV Infection in Vitro by Suppressing Virus Replication
Authors: Walker Christopher M. , Moody Dewey J. , Stites Daniel P. , Levy Jay A.
Published: October 2006

Lymphocytes bearing the CD8 marker were shown to suppress replication of human immunodeficiency virus (HIV) in peripheral blood mononuclear cells. The effect was dose-dependent and most apparent with autologous lymphocytes; it did not appear to be mediated by a cytotoxic response. This suppression of HIV replication could be demonstrated by the addition of CD8
+
cells at the initiation of virus production as well as after several weeks of virus replication by cultured cells. The observations suggest a potential approach to therapy in which autologous CD8 lymphocytes could be administered to individuals to inhibit HIV replication and perhaps progression of disease.
Light Reflection Models for Computer Graphics
Authors: Greenberg Donald P.
Published: October 2006

During the past 20 years, computer graphic techniques for simulating the reflection of light have progressed so that today images of photorealistic quality can be produced. Early algorithms considered direct lighting only, but global illumination phenomena with indirect lighting, surface interreflections, and shadows can now be modeled with ray tracing, radiosity, and Monte Carlo simulations. This article describes the historical development of computer graphic algorithms for light reflection and pictorially illustrates what will be commonly available in the near future.
Contribution of Ultraviolet Irradiance Variations to Changes in the Sun's Total Irradiance
Authors: Lean J.
Published: October 2006

The sun's total irradiance decreased from 1980 to mid-1985, remained approximately constant until mid-1987, and has recently begun to increase. This time interval covered the decrease in solar activity from the maximum of solar cycle 21 to solar minimum and the onset of cycle 22. The sun's ultraviolet irradiance also decreased during the descending phase of cycle 21 and, like the total irradiance, is now increasing concurrently with the increase in cycle 22 activity. Although only 1 percent of the sun's energy is emitted at ultraviolet wavelengths between 200 and 300 nanometers, the decrease in this radiation from 1 July 1981 to 30 June 1985 accounted for 19 percent of the decrease in the total irradiance over the same period.
Blockade of "NMDA" Receptors Disrupts Experience-Dependent Plasticity of Kitten Striate Cortex
Authors: Kleinschmidt Andreas , Bear Mark F. , Singer Wolf
Published: October 2006

Intracortical infusion of the "
N
-methyl-D-aspartate" (NMDA) receptor blocker D,L-2-amino-5-phosphonovaleric acid (APV) renders kitten striate cortex resistant to the effects of monocular deprivation. In addition, 1 week of continuous APV treatment (50 nanomoles per hour) produces a striking loss of orientation selectivity in area 17. These data support the hypothesis that crucial variables for the expression of activity-dependent synaptic modifications are a critical level of postsynaptic activation and calcium entry through ion channels linked to NMDA receptors.
Dominant Role of N-Type Ca
2+
Channels in Evoked Release of Norepinephrine from Sympathetic Neurons
Authors: Hirning Lane D. , Fox Aaron P. , McCleskey Edwin W. , Olivera Baldomero M. , Thayer Stanley A. , Miller Richard J. , Tsien Richard W.
Published: October 2006

Multiple types of calcium channels have been found in neurons, but uncertainty remains about which ones are involved in stimulus-secretion coupling. Two types of calcium channels in rat sympathetic neurons were described, and their relative importance in controlling norepinephrine release was analyzed. N-type and L-type calcium channels differed in voltage dependence, unitary barium conductance, and pharmacology. Nitrendipine inhibited activity of L-type channels but not N-type channels. Potassium-evoked norepinephrine release was markedly reduced by cadmium and the conesnail peptide toxin ω-
Conus geographus
toxin VIA, agents that block both N- and L-type channels, but was little affected by nitrendipine at concentrations that strongly reduce calcium influx, as measured by fura-2. Thus N-type calcium channels play a dominant role in the depolarization-evoked release of norepinephrine.
IgG from Patients with Lambert-Eaton Syndrome Blocks Voltage-Dependent Calcium Channels
Authors: Kim Yong I. , Neher Erwin
Published: October 2006

Lambert-Eaton syndrome, an autoimmune disorder frequently associated with small-cell carcinoma of the lung, is characterized by impaired evoked release of acetylcholine from the motor nerve terminal. Immunoglobulin G (IgG) antibodies from patients with the syndrome, applied to bovine adrenal chromaffin cells, reduced the voltage-dependent calcium channel currents by about 40 percent. When calcium was administered directly into the cytoplasm, however, the IgG-treated cells exhibited normal exocytotic secretion, as assayed by membrane capacitance measurement. Measurement with the fluorescent calcium indicator fura-2 indicated that the IgG treatment reduced potassium-stimulated increase in free intracellular calcium concentration. The pathogenic IgG modified neither kinetics of calcium channel activation nor elementary channel activity, suggesting that a reduction in the number of functional calcium channels underlies the IgG-induced effect. Therefore, Lambert-Eaton syndrome IgG reacts with voltage-dependent calcium channels and blocks their function, a phenomenon that can account for the presynaptic impairment characteristic of this disorder.
Attraction of the Parasitic Mite
Varroa
to the Drone Larvae of Honey Bees by Simple Aliphatic Esters
Authors: Le Conte Yves , Arnold Gérard , Trouiller Jérôme , Masson Claudine , Chappe Bertrand , Ourisson Guy
Published: October 2006

An important parasitic threat to honey bees, the mite
Varroa jacobsoni,
is attracted to its major prey, drone larvae, by methyl and ethyl esters of straight-chain fatty acids, in particular methyl palmitate. These esters were extracted from drone larvae with
n
-hexane and were identified by gas chromatography-mass spectrometry. Their behavioral effect was evaluated with the use of a four-arm airflow olfactometer.
A Rotationally Resolved Fluorescence Excitation Spectrum of
all-trans
-1,4-Diphenyl-1,3-butadiene
Authors: Pfanstiel J. F. , Champagne B. B. , Majewski W. A. , Plusquellic D. F. , Pratt D. W.
Published: October 2006

Band 1 in the jet-cooled one-photon S
1
← S
0
fluorescence excitation spectrum of
all-trans
-1,4-diphenyl-1,3-butadiene has been rotationally resolved with a molecular beam laser spectrometer. Both the orientation of the optical transition moment and the rotational constants of the two vibronic levels have been measured. The molecule shows no evidence of being significantly distorted from a
C

2
h

geometry when it is low in the vibrational manifolds of either of the two electronic states.
Silicon Coordination and Speciation Changes in a Silicate Liquid at High Pressures
Authors: Xue Xianyu , Kanzaki Masami , Trønnes Reidar G. , Stebbins Jonathan F.
Published: October 2006

Coordination and local geometry around Si cations in silicate liquids are of primary importance in controlling the chemical and physical properties of magmas. Pressure-induced changes from fourfold to sixfold coordination of Si in silicate glass samples quenched from liquids has been detected with
29
Si magic-angle spinning nuclear magnetic resonance spectrometry. Samples of Na
2
Si
2
O
5
glass quenched from 8 gigapascals and 1500°C contained about 1.5 percent octahedral Si, which was demonstrably part of a homogeneous, amorphous phase. The dominant tetrahedral Si speciation in these glasses became disproportionated to a more random distribution of bridging and nonbridging oxygens with increasing pressure.
Circadian System Controlling Release of Sperm in the Insect Testes
Authors: Giebultowicz J. M. , Riemann J. G. , Raina A. K. , Ridgway R. L.
Published: October 2006

Release of mature sperm from the testis into seminal ducts of the gypsy moth exhibits a circadian rhythm. The rhythm of sperm release was shown to persist in vitro, in isolated complexes of testis and seminal ducts cultured in light-dark cycles or in constant darkness. The phase of the rhythm was also reset in vitro by exposure to shifted light-dark cycles. Therefore, the testis—seminal ducts complex from the gypsy moth is photosensitive and contains a circadian pacemaker, which controls the rhythm of sperm movement. This finding extends the range of structures in multicellular organisms that are known to contain circadian oscillators and provides a new model system in which circadian mechanisms may be studied.
History of Meteorites from the Moon Collected in Antarctica
Authors: Eugster O.
Published: October 2006

In large asteroidal or cometary impacts on the moon, lunar surface material can be ejected with escape velocities. A few of these rocks were captured by Earth and were recently collected on the Antarctic ice. The records of noble gas isotopes and of cosmic ray—produced radionuclides in five of these meteorites reveal that they originated from at least two different impact craters on the moon. The chemical composition indicates that the impact sites were probably far from the Apollo and Luna landing sites. The duration of the moon-Earth transfer for three meteorites, which belong to the same fall event on Earth, lasted 5 to 11 million years, in contrast to a duration of less than 300,000 years for the two other meteorites. From the activities of cosmic ray—produced radionuclides, the date of fall onto the Antarctic ice sheet is calculated as 70,000 to 170,000 years ago.
An
E. coli
Promoter That Regulates Transcription by DNA Superhelix-Induced Cruciform Extrusion
Authors: Horwitz Marshall S. Z. , Loeb Lawrence A.
Published: October 2006

DNA can form structures other than the Watson-Crick double helix. The potential contributions to gene regulation from one such structure have been investigated by assembling a promoter capable of adopting cruciform base-pairing. Transcription from this promoter by RNA polymerase in vitro was repressed as the cruciform was extruded by increasing negative DNA supercoiling. Transcription in vivo was induced as supercoiling was relaxed by growth in conditions that inhibit DNA gyrase. A DNA conformational change is therefore capable of regulating the initiation of transcription.
Pertussis Toxin S1 Mutant with Reduced Enzyme Activity and a Conserved Protective Epitope
Authors: Burnette W. Neal , Cieplak Witold , Mar Vernon L. , Kaljot Kaarel T. , Sato Hiroko , Keith Jerry M.
Published: October 2006

Pertussis toxin (PTX) is a major virulence factor in whooping cough and can elicit protective antibodies. Amino acid residues 8 to 15 of PTX subunit S1 are important for the adenosine diphosphate-ribosyltransferase activity associated with the pathobiological effects of PTX. Furthermore, this region contains at least a portion of an epitope that elicits both toxin-neutralizing and protective antibody responses in mice. The gene encoding the S1 subunit was subjected to site-specific mutagenesis in this critical region. A mutant containing a single amino acid substitution (Arg
9
→Lys) had reduced enzymatic activity (approximately 0.02% of control) while retaining the protective epitope. This analog S1 molecule may provide the basis for a genetically detoxified PTX with potential for use as a component of an acellular vaccine against whooping cough.
Hormonal and Genetic Control of Behavioral Integration in Honey Bee Colonies
Authors: Robinson Gene E. , Page Robert E. , Strambi Colette , Strambi Alain
Published: October 2006

The ability of insect colonies to adjust the division of labor among workers in response to changing environmental and colony conditions, coupled with research showing genetic effects on the division of labor in honey bee colonies, led to an investigation of the role of genetics and the environment in the integration of worker behavior. Measurements of juvenile hormone (JH) titers and allozyme analyses of worker honey bees suggest that two processes are involved in colony-level regulation of division of labor: (i) plasticity in age-dependent behavior is a consequence of modulation of JH titers by extrinsic factors, and (ii) stimuli that can affect JH titers and age-dependent behavior do elicit variable responses among genetically distinct subpopulations of workers within a colony. These results provide a new perspective on the developmental plasticity of insect colonies and support the emerging view that colony genetic structure affects behavioral organization.
Inclusion Systems of Organic Molecules in Restacked Single-Layer Molybdenum Disulfide
Authors: Divigalpitiya W. M. R. , Frindt R. F. , Morrison S. R.
Published: October 2006

Novel materials have been obtained by restacking single-layer molybdenum disulfide (MoS
2
) with organic molecules included between the layers. A large variety of organic molecules can be included between layers of MoS
2
and other transition-metal dichalcogenides. The films with the included organics are formed at the interface between an aqueous suspension of the MoS
2
and a water-immiscible organic liquid. The organic molecules are not necessarily electron donors. A highly oriented, conducting film of restacked MoS
2
containing ferrocene is presented as an example.
Styles of Volcanism on Venus: New Arecibo High Resolution Radar Data
Authors: Campbell Donald B. , Head James W. , Senske David A. , Fisher Paul C. , Hine Alice A. , Harmon John K.
Published: October 2006

Arecibo high-resolution (1.5 to 2 km) radar data of Venus for the area extending from Beta Regio to western Eisila Regio provide strong evidence that the mountains in Beta and Eisila Regiones and plains in and adjacent to Guinevere Planitia are of volcanic origin. Recognized styles of volcanism include large volcanic edifices on the Beta and Eisila rises related to regional structural trends, plains with multiple source vents and a mottled appearance due to the ponding of volcanic flows, and plains with bright features surrounded by extensive quasi-circular radar-dark halos. The high density of volcanic vents in the plains suggests that heat loss by abundant and widely distributed plains volcanism may be more significant than previously recognized. The low density of impact craters greater than 15 km in diameter in this region compared to the average density for the higher northern latitudes suggests that the plains have a younger age.
Natural and Artificially Initiated Lightning
Authors: Uman Martin A. , Krider E. Philip
Published: October 2006

Recent research on lightning has been motivated, in part, by the desire to prevent spectacular accidents, such as occurred in 1969 during the launch of Apollo 12 and in 1987 during the launch of Atlas-Centaur 67, and by the need to protect advanced ground-based and airborne systems that utilize low voltage, solid-state electronics. The present understanding of both natural and artificially initiated (triggered) lightning is reviewed, and suggestions are given for future research that can improve our understanding both of the physics of lightning and the parameters that are important for protection.
Phyllosilicate Absorption Features in Main-Belt and Outer-Belt Asteroid Reflectance Spectra
Authors: Vilas Faith , Gaffey Michael J.
Published: October 2006

Absorption features having depths up to 5% are identified in high-quality, high-resolution reflectance spectra of 16 dark asteroids in the main belt and in the Cybele and Hilda groups. Analogs among the CM2 carbonaceous chondrite meteorites exist for some of these asteroids, suggesting that these absorptions are due to iron oxides in phyllosilicates formed on the asteroidal surfaces by aqueous alteration processes. Spectra of ten additional asteroids, located beyond the outer edge of the main belt, show no discernible absorption features, suggesting that aqueous alteration did not always operate at these heliocentric distances.
Structure of a Three-Dimensional, Microporous Molybdenum Phosphate with Large Cavities
Authors: Haushalter Robert C. , Strohmaier Karl G. , Lai Frank W.
Published: October 2006

The synthesis, single-crystal x-ray structural characterization, and sorption properties of a microporous molybdenum phosphate, (Me
4
N)
1.3
(H
3
O)
0.7
[Mo
4
O
8
(PO
4
)
2
] ⋅ 2H
2
O (Me, methyl), are presented. The three-dimensional framework is built up from Mo
4
O
8
4+
cubes and PO
4
3-
tetrahedra that are connected in such a way that large, cation-filled voids are generated; these voids constitute 25% of the volume of the solid. Absorption isotherms for water show the completely reversible uptake of 4 to 5 percent by weight water into the micropores of this compound, which corresponds to 10 to 12 percent by volume.
Quantifying the Information Content of Lattice Images
Authors: Ourmazd A. , Taylor D. W. , Bode M. , Kim Y.
Published: October 2006

Quantitative information may be extracted from local areas of images that consist of one or more types of unit cell. Fourier-space analysis, real-space intensity analysis, and real-space vector pattern recognition are discussed. The pattern recognition approach efficiently exploits the available information by representing the intensity distribution within each unit cell of the image as a multidimensional vector. Thus, the amount and the effect of noise present are determined, statistically significant features are identified, and quantitative comparisons are made with model images. In the case of chemical lattice images, the position of a vector can be directly related to the atomic composition of the unit cell it represents, allowing quantitative chemical mapping of materials at near-atomic sensitivity and resolution. More generally, the vector approach allows the efficient and quantitative extraction of information from images, which consist of mosaics of unit cells.
Precision Lattice-Parameter Determination of (Mg,Fe)SiO
3
Tetragonal Garnets
Authors: Matsubara Rie , Toraya Hideo , Tanaka Satoshi , Sawamoto Hiroshi
Published: October 2006

The tetragonal garnet (Mg,Fe)SiO
3
is a high-pressure phase of pyroxene that is thought to be a major constituent of the earth's upper mantle. Its crystal structure is similar to that of cubic garnet, but it is slightly distorted to tetragonal symmetry so that its x-ray powder diffraction pattern shows a very small line splitting. A suite of tetragonal garnets with different compositions in the MgSiO
3
-rich portion of the MgSiO
3
-FeSiO
3
system was synthesized at about 20 gigapascals and 2000°C. The lattice parameters
a
and
c
of quenched samples were determined by whole-powder-pattern decomposition analysis of Fe Kα x-ray powder diffraction data, which has the capacity to resolve to a high degree heavily overlapping reflections. It was found that the lattice parameters can be obtained from the following equations;
a
(in angstroms) = 11.516 + 0.088
x
and
c
(in angstroms) = 11.428 + 0.157
x
, where
x
, the mole fraction of FeSiO
3
, is 0.0 ≤
x
≤ 0.2.
A Wave Dynamical Interpretation of Saturn's Polar Hexagon
Authors: Allison M. , Godfrey D. A. , Beebe R. F.
Published: October 2006

The hexagonal, pole-centered cloud feature in Saturn's northern atmosphere, as revealed in Voyager close-encounter imaging mosaics, may be interpreted as a stationary Rossby wave. The wave is embedded within a sharply peaked eastward jet (of 100 meters per second) and appears to be perturbed by at least one anticyclonic oval vortex immediately to the south. The effectively exact observational determination of the horizontal wave number and phase speed, applied to a simple model dispersion relation, suggests that the wave is vertically trapped and provides a diagnostic template for further modeling of the deep atmospheric stratification.
Mapping Neuronal Inputs to REM Sleep Induction Sites with Carbachol-Fluorescent Microspheres
Authors: Quattrochi James J. , Mamelak Adam N. , Madison Roger D. , Macklis Jeffrey D. , Hobson J. Allan
Published: October 2006

The cholinergic agonist carbachol was conjugated to latex microspheres that were fluorescently labeled with rhodamine and used as neuroanatomical probes that show little diffusion from their injection site and retrogradely label neurons projecting to the injection site. Microinjection of this pharmacologically active probe into the gigantocellular field of the cat pontine brain stem caused the awake cats to fall into rapid eye movement (REM) sleep indistinguishable from that produced by free carbachol. Three-dimensional computer reconstruction of the retrogradely labeled neurons revealed a widely distributed neuronal network in the pontine tegmentum. These pharmacologically active microspheres permit a new precision in the characterization and mapping of neurons associated with the control of behavioral state and of other cholinergic networks.
Vascular Permeability Factor, an Endothelial Cell Mitogen Related to PDGF
Authors: Keck Pamela J. , Hauser Scott D. , Krivi Gwen , Sanzo Kim , Warren Thomas , Feder Joseph , Connolly Daniel T.
Published: October 2006

Vascular permeability factor (VPF) is a 40-kilodalton disulfide-linked dimeric glycoprotein that is active in increasing blood vessel permeability, endothelial cell growth, and angiogenesis. These properties suggest that the expression of VPF by tumor cells could contribute to the increased neovascularization and vessel permeability that are associated with tumor vasculature. The cDNA sequence of VPF from human U937 cells was shown to code for a 189-amino acid polypeptide that is similar in structure to the B chain of platelet-derived growth factor (PDGF-B) and other PDGF-B-related proteins. The overall identity with PDGF-B is 18%. However, all eight of the cysteines in PDGF-B were found to be conserved in human VPF, an indication that the folding of the two proteins is probably similar. Clusters of basic amino acids in the COOH-terminal halves of human VPF and PDGF-B are also prevalent. Thus, VPF appears to be related to the PDGF/v-
sis
family of proteins.
Radar Images of Asteroid 1989 PB
Authors: Ostro Steven J. , Chandler John F. , Hine Alice A. , Rosema Keith D. , Shapiro Irwin I. , Yeomans Donald K.
Published: October 2006

Radar observations of the near-Earth asteroid 1989 PB, made shortly after its optical discovery, yield a sequence of delay-Doppler images that reveal it to consist of two distinct lobes that appear to be in contact. It seems likely that the two lobes once were separate and that they collided to produce the current "contact-binary" configuration.
Immunodeficiency and Clonal Growth of Target Cells Induced by Helper-Free Defective Retrovirus
Authors: Huang Ming , Simard Carole , Jolicoeur Paul
Published: October 2006

The murine acquired immunodeficiency syndrome is induced by a defective retrovirus. To study the role of virus replication in this disease, helper-free stocks of defective Duplan virus were produced. These stocks were highly pathogenic in absence of detectable replicating murine leukemia viruses (MuLVs) other than xenotropic MuLV. They induced expansion of the infected cell population (over 1000-fold), and this cell expansion was oligoclonal in origin and, most likely, arose through cell division. These results suggest that this defective virus is oncogenic, inducing a primary neoplasia associated with an acquired immunodeficiency syndrome as a paraneoplastic syndrome. These data emphasize the need to determine whether virus replication is necessary for the progression of other immunodeficiency diseases, including acquired immunodeficiency syndrome, and whether these diseases also represent paraneoplastic syndromes.
Theoretical and Experimental Rate Constants for Two Isotopic Modifications of the Reaction H + H
2
Authors: Michael Joe V. , Fisher J. Robert , Bowman Joel M. , Sun Qiyan
Published: October 2006

Theoretical rate constants for two isotopic modifications of the simplest possible chemical reaction, namely, H + D
2
→ HD + D and D + H
2
→ HD + H, are presented. Experimental results, which have previously been obtained in the higher temperature regime by a shock tube technique, are combined with lower temperature results to give an experimental determination of the rate behavior over the large temperature range ∼200 to 2000 K. It is now possible to assess the accuracy of ab initio potential energy surface calculations and to judge theoretical chemical kinetic methods.
Theories of Bargaining Delays
Authors: Kennan John , Wilson Robert
Published: October 2006

Contract negotiations over wages are sometimes accompanied by strikes; similarly in legal contexts, settlements of damage claims may require lengthy negotiations. These and other costly delays in resolving disputes are the subject of the studies described in this article. Formulations in terms of game theory indicate that procedural features can allow delays, but the main cause may be informational disparities between the parties. Several models are described and related to data about strikes.
Simple Dynamical Models of Neptune's Great Dark Spot
Authors: Polvani L. M. , Wisdom J. , DeJong E. , Ingersoll A. P.
Published: October 2006

The large amplitude oscillations of the shape of Neptune's Great Dark Spot are well reproduced by simple dynamical models of an isolated vortex embedded in a background shear flow. From the time series of the aspect ratio and inclination of the vortex values are estimated for the background shear and the mean vorticity of the Great Dark Spot, and a lower bound is placed on the value of the Rossby deformation radius. These models imply the existence of a planetary-scale zone of deterministic chaotic advection in the atmosphere of Neptune.
Activation of an Excluded Immunoglobulin Allele in a Human B Lymphoma Cell Line
Authors: Berinstein Neil , Levy Shoshana , Levy Ronald
Published: October 2006

Mature B cells that express surface immunoglobulin (Ig) are usually committed to their original Ig product. It was shown that such a cell can replace its light chain by rearranging and expressing a new light chain from the other allele. Anti-idiotype antibodies were used to isolate idiotypic variants from a surface IgM
+
λ
+
human B cell tumor line. The variants expressed a new λ light chain. Both the original and the new λ transcripts were present in the variant cells, but only the new one was expressed as a protein on the cell surface. Therefore, although the cell exhibited allelic exclusion and had only one Ig receptor at a time, the commitment to a particular light chain gene was reversible.
Functionally Distinct NF-κB Binding Sites in the Immunoglobulin κ and IL-2 Receptor α Chain Genes
Authors: Cross Sharon L. , Halden Nancy F. , Lenardo Michael J. , Leonard Warren J.
Published: October 2006

The interleukin-2 receptor alpha (IL-2Rα) chain gene contains a sequence similar to the immunoglobulin (Ig) kappa (κ) enhancer NF-κB binding site. This site, which is bound by the nuclear protein, NF-κB, is critical for Ig κ gene expression. The major T cell nuclear factor that binds to the IL-2Rα site in vitro appears indistinguishable from NF-κB. NF-κB binds to IL-2Rα and κ sequences with similar affinities; however, only the κ site potently activates transcription from heterologous promoters. Thus, high-affinity NF-κB binding in vitro cannot be equated with transcriptional activation in vivo. Mutation of the NF-κB binding site in the context of an IL-2Rα promoter construct markedly diminished promoter activity in human T cell lymphotropic virus type I (HTLV-I)-transformed MT-2 cells but not in phorbol myristate acetate-stimulated Jurkat T cells.
Voyager Disk-Integrated Photometry of Triton
Authors: Hillier J. , Helfenstein P. , Verbiscer A. , Veverka J. , Brown R. H. , Goguen J. , Johnson T. V.
Published: October 2006

Hapke's photometric model has been combined with a plane-parallel thin atmospheric haze model to describe Voyager whole-disk observations of Triton, in the violet (0.41 μm), blue (0.48 μm), and green (0.56 μm) wavelength bands, in order to obtain estimates of Triton's geometric albedo, phase integral, and Bond albedo. Phase angle coverage in these filters ranging from ∼12° to 159° was obtained by combining narrow- and wide-angle camera images. An upturn in the data at the highest phase angles observed can be explained by including scattering in a thin atmospheric haze layer with optical depths systematically decreasing with wavelength from ∼0.06 in the violet to 0.03 for the green filter data. The geometric albedo, phase integral, and spherical albedo of Triton in each filter corresponding to our best fit Hapke parameters yield an estimated Bond albedo of 0.82 ± 0.05. If the 14-μbar N
2
atmosphere detected by Voyager is in vapor equilibrium with the surface (therefore implying a surface temperature of 37.5 K), our Bond albedo implies a surface emissivity of 0.59 ± 0.16.
Ice Nucleation by Alcohols Arranged in Monolayers at the Surface of Water Drops
Authors: Gavish Michal , Popovitz-Biro Ronit , Lahav Meir , Leiserowitz Leslie
Published: October 2006

Monolayers of aliphatic long-chain alcohols induced nucleation of ice at temperatures approaching 0°C, in contrast with water-soluble alcohols, which are effective antifreeze agents. The corresponding fatty acids, or alcohols with bulky hydrophobic groups, induce freezing at temperatures as much as 12°C lower. The freezing point induced by the amphiphilic alcohols was sensitive not only to surface area per molecule but, for the aliphatic series (C

n

H

2n
+ 1

OH), to chain length and parity. The freezing point for chains with
n
odd reached an asymptotic temperature of 0°C for an upper value of
n
= 31; for
n
even the freezing point reached a plateau of -8°C for
n
in the upper range of 22 to 30. The higher freezing point induced by the aliphatic alcohols is due to formation of ordered clusters in the uncompressed state as detected by grazing incidence synchrotron x-ray diffraction measurements. The diffraction data indicate a close lattice match with the
ab
layer of hexagonal ice.
Astrophysics and Cosmology Closing in on Neutrino Masses
Authors: Dar Arnon
Published: October 2006

Massive neutrinos are expected in most grand unified theories that attempt to unify the strong and electroweak interactions. So far, heroic laboratory experiments have yielded only upper bounds on the masses of the elusive neutrinos. These bounds, however, are not very restrictive and cannot even exclude the possibility that the dark matter in the universe consists of neutrinos. The astrophysical and cosmological bounds on the masses of the muon and tau neutrinos,
m

ν
μ

and
m

ν
τ

, which already are much more restrictive than the laboratory bounds, and the laboratory bound on the mass of the electron neutrino,
m

ν
c

, can be improved significantly by future astrophysical and cosmological observations that perhaps will pin down the neutrino masses. Indeed, the recent results from the solar neutrino experiments combined with the seesaw mechanism for generating neutrino masses suggest that
m

ν
c

∼ 10
-8
electron volts,
m

ν
μ

∼ 10
-3
electron volts, and
m

ν
τ

∼ 10 electron volts, which can be tested in the near future by solar neutrino and accelerator experiments.