bluuebunny/crossref_metadata_2025 huggingface dataset:
Astronomical Imaging with Infrared Array Detectors
Authors: Gatley Ian , Depoy D. L. , Fowler A. M.
Published: October 2006

History shows that progress in astronomy often stems directly from technological innovation and that each portion of the electromagnetic spectrum offers unique insights into the nature of the universe. Most recently, the widespread availability of infrared-sensitive two-dimensional array detectors has led to dramatic improvements in the capabilities of conventional ground-based observatories. The impact of this new technology on our understanding of a wide variety of phenomena is illustrated here by infrared pictures of star-forming regions, of nebulae produced by the late stages of stellar evolution, of the nucleus of our own galaxy (the Milky Way), and of activity in other galaxies.
HTLV-III
gag
Protein Is Processed in Yeast Cells by the Virus
pol
-Protease
Authors: Kramer R. A. , Schaber M. D. , Skalka A. M. , Ganguly K. , Wong-Staal F. , Reddy E. P.
Published: October 2006

The
gag
-
pol
gene of HTLV-III (human T-lymphotropic virus), the virus linked to AIDS (acquired immune deficiency syndrome), was expressed in yeast, and processing of the
gag
precursor into proteins of the same size as those in the virion was observed. Processing of the
gag
gene in yeast cells mimics the process that naturally occurs in mammalian cells during maturation of virions. Therefore it was possible to perform mutational analysis of the virus genome to localize the gene that codes for the protease function to the amino terminal coding region of the
pol
gene. Since this region overlaps the
gag
gene, it is likely that ribosomal frameshifting occurs from
gag
to
pol
. Antibodies in all of the AIDS patients' sera tested recognized the yeast synthesized
gag
proteins, although the sera showed differences in relative reactivity to the individual
gag
proteins and the precursor. This yeast system should be valuable not only for production of viral proteins for diagnostic or vaccine purposes but also for analysis of the genetics and biochemistry of viral gene functions—parameters that are difficult to study otherwise with this virus.
Cloning of a cDNA for a T Cell-Specific Serine Protease from a Cytotoxic T Lymphocyte
Authors: Gershenfeld Howard K. , Weissman Irving L.
Published: October 2006

A new serine protease was encoded by a clone isolated from a murine cytotoxic T-lymphocyte complementary DNA library by an RNA-hybridization competition protocol. Complementary transcripts were detected in cytotoxic T lymphocytes, spleen cells from nude mice, a rat natural killer cell leukemia, and in two of eight T-helper clones (both cytotoxic), but not in normal mouse kidney, liver, spleen, or thymus, nor in several tested T- and B-cell tumors. T-cell activation with concanavalin A plus interleukin-2 induced spleen cells to express this gene with kinetics correlating with the acquisition of cytolytic capacity. The nucleotide sequence of this gene encoded an amino acid sequence of approximately 25,700 daltons, with 25 to 35 percent identity to members of the serine protease family. The active site "charge-relay" residues (His
57
, Asp
102
, and Ser
195
of the chymotrypsin numbering system) are conserved, as well as the trypsin-specific Asp (position 189 in trypsin). A Southern blot analysis indicated that this gene is conserved in humans, mouse, and chicken. This serine protease may have a role in lymphocyte lysis and a "lytic cascade."
The Ninth Component of Complement and the Pore-Forming Protein (Perforin 1) from Cytotoxic T Cells: Structural, Immunological, and Functional Similarities
Authors: Young John Ding-E , Cohn Zanvil A. , Podack Eckhard R.
Published: October 2006

The ninth component of complement (C9) and the pore-forming protein (PFP or perforin) from cytotoxic T lymphocytes polymerize to tubular lesions having an internal diameter of 100 Å and 160 Å, respectively, when bound to lipid bilayers. Polymerized C9, assembled by slow spontaneous or rapid Zn
2+
-induced polymerization, and polyperforin, which is assembled only in the presence of Ca
2+
, constitute large aqueous pores that are stable, nonselective for solutes, and insensitive to changes of membrane potential. Monospecific polyclonal antibodies to purified C9 and PFP show cross-reactivity, suggesting structural homology between the two molecules. The structural and functional homologies between these two killer molecules imply an active role for pore formation during cell lysis.
40
Ar-
39
Ar Dating of the Manson Impact Structure: A Cretaceous-Tertiary Boundary Crater Candidate
Authors: Kunk M. J. , Izett G. A. , Haugerud R. A. , Sutter J. F.
Published: October 2006

The mineralogy of shocked mineral and lithic grains in the Cretaceous-Tertiary (K-T) boundary claystone worldwide is most consistent with a bolide impact on a continent. Both the concentrations and sizes of these shocked grains are greatest in the western interior of North America. These data suggest that the Manson impact structure in north-central Iowa is a viable candidate for the K-T boundary impact event. Argon-40–argon-39 age spectrum dating of shocked microcline from the crystalline central uplift of the Manson impact structure indicates that there was severe argon-40 loss at 65.7 ± 1.0 million years ago, an age that is indistinguishable from that of the K-T boundary, within the limits of analytical precision.
Toward Protein Tertiary Structure Recognition by Means of Associative Memory Hamiltonians
Authors: Friedrichs Mark S. , Wolynes Peter G.
Published: October 2006

The statistical mechanics of associative memories and spin glasses suggests ways to design Hamiltonians for protein folding. An associative memory Hamiltonian based on hydrophobicity patterns is shown to have a large capacity for recall and to be capable of recognizing tertiary structure for moderately variant sequences.
Photoemission Spectroscopy of the High-Temperature Superconductivity Gap
Authors: Margaritondo G. , Huber D. L. , Olson C. G.
Published: October 2006

Superconductivity is related to the presence of a narrow forbidden gap in the spectrum of the possible energies for the electrons in the material. These "superconductivity gaps" have traditionally been studied with tunneling and infrared absorption experiments. A third, powerful technique has been made possible by the discovery of high-transition temperature materials: the direct observation of the gap in photoemission spectra. The data analysis requires a careful reconsideration of the standard Einstein-Fermi model of the photoelectric effect. The conclusions are surprisingly simple and offer an alternate way to measure superconductivity gaps. This approach can also be used to study the directional properties of the gap, phenomena related to the coherence length, and possible departures from Fermi-liquid behavior.
Voyager Planetary Radio Astronomy at Neptune
Authors: Warwick James W. , Evans David R. , Peltzer Gerard R. , Peltzer Robert G. , Romig Joseph H. , Sawyer Constance B. , Riddle Anthony C. , Schweitzer Andrea E. , Desch Michael D. , Kaiser Michael L. , Farrell William M. , Carr Thomas D. , de Pater Imke , Staelin David H. , Gulkis Samuel , Poynter Robert L. , Boischot André , Genova Françoise , Leblanc Yolande , Lecacheux Alain , Pedersen Bent M. , Zarka Philippe
Published: October 2006

Detection of very intense short radio bursts from Neptune was possible as early as 30 days before closest approach and at least 22 days after closest approach. The bursts lay at frequencies in the range 100 to 1300 kilohertz, were narrowband and strongly polarized, and presumably originated in southern polar regions of the planet. Episodes of smooth emissions in the frequency range from 20 to 865 kilohertz were detected during an interval of at least 10 days around closest approach. The bursts and the smooth emissions can be described in terms of rotation in a period of 16.11 ± 0.05 hours. The bursts came at regular intervals throughout the encounter, including episodes both before and after closest approach. The smooth emissions showed a half-cycle phase shift between the five episodes before and after closest approach. This experiment detected the foreshock of Neptune's magnetosphere and the impacts of dust at the times of ring-plane crossings and also near the time of closest approach. Finally, there is no evidence for Neptunian electrostatic discharges.
Structure and Function of Human Amphiregulin: A Member of the Epidermal Growth Factor Family
Authors: Shoyab Mohammed , Plowman Gregory D. , McDonald Vicki L. , Bradley J. Garrett , Todaro George J.
Published: October 2006

The complete amino acid sequence of amphiregulin, a bifunctional cell growth modulator, was determined. The truncated form contains 78 amino acids, whereas a larger form of amphiregulin contains six additional amino acids at the amino-terminal end. The amino-terminal half of amphiregulin is extremely hydrophilic and contains unusually high numbers of lysine, arginine, and asparagine residues. The carboxyl-terminal half of amphiregulin (residues 46 to 84) exhibits striking homology to the epidermal growth factor (EGF) family of proteins. Amphiregulin binds to the EGF receptor but not as well as EGF does. Amphiregulin fully supplants the requirement for EGF or transforming growth factor-α in murine keratinocyte growth, but it is a much weaker growth stimulator in other cell systems.
Scales and Effects of Fluid Flow in the Upper Crust
Authors: Cathles Lawrence M.
Published: October 2006

Two of the most important agents of geological change, solar energy and internal heat from the mantle, meet and battle for dominance in propelling aqueous and related fluids in the earth's upper crust. Which prevails and how they interact are subjects of active research. Recent work has demonstrated that both agents can propel fluids over nearly continental-scale distances in a fashion that influences a host of important geological processes and leaves a record in chemical alteration, mineral deposits, and hydrocarbon resources.
Developmental Arrest During Larval Life and Life-Span Extension in a Marine Mollusc
Authors: Miller S. E. , Hadfield M. G.
Published: October 2006

The length of larval life in the nudibranchPhestilia sibogaeis determined by a chance encounter with a specific metamorphic stimulus associated with the post-larval benthic habitat. A developmental hiatus begins at the onset of larval metamorphic competence and ends at metamorphosis; aging is suspended during this hiatus. Because the duration of post-larval life is unaffected by the duration of larval life, total life-span varies with the length of the larval period. Developmental control of the timing of expression of life-history stages is an important factor regulating aging and senescence in animals with complex life cycles.
Oral Cocaine: Plasma Concentrations and Central Effects
Authors: Van Dyke C. , Jatlow P. , Ungerer J. , Barash P. G. , Byck R.
Published: October 2006

Cocaine (2.0 milligrams per kilogram) given by the oral route is at least as effective as the same dose given intranasally. Cocaine is not detected in the plasma until 30 minutes after oral administration, but peak plasma concentrations are similar after both routes. The subjective "highs" in man are greater after oral than after intranasal administration.
Seeing Phenomena in Flatland: Studies of Monolayers by Fluorescence Microscopy
Authors: Knobler Charles M.
Published: October 2006

Monolayers formed at the interface between air and water can be seen with fluorescence microscopy. This allows the phase behavior of these monolayers to be determined by direct observation and opens up the possibility of following the kinetics of phase transformations in two-dimensional systems. Some unexpected morphologies have been discovered that provide information about the nature of monolayer phases and have connections to pattern formation in other systems.
The DNA Binding Domain of the Rat Liver Nuclear Protein C/EBP Is Bipartite
Authors: Landschulz William H. , Johnson Peter F. , McKnight Steven L.
Published: October 2006

C/EBP is a rat liver nuclear protein capable of sequence-specific interaction with DNA. The DNA sequences to which C/EBP binds in vitro have been implicated in the control of messenger RNA synthesis. It has therefore been predicted that C/EBP will play a role in regulating gene expression in mammalian cells. The region of the C/EBP polypeptide required for direct interaction with DNA has been identified and shown to bear amino acid sequence relatedness with the product of the
myc
,
fos
, and
jun
proto-oncogenes. The arrangement of these related amino acid sequences led to the prediction of a new structural motif, termed the "leucine zipper," that plays a role in facilitating sequence-specific interaction between protein and DNA. Experimental tests now provide support for the leucine zipper hypothesis.
Transient Particle Acceleration Associated with Solar Flares
Authors: Chupp E. L.
Published: October 2006

Understanding how individual charged particles can be accelerated to extreme energies (10
20
electron volts), remains a foremost problem in astrophysics. Within our solar system, the active sun is capable of producing, on a short time scale, ions with energies higher than 25 gigaelectron volts. Satellite and ground-based observation over the past 30 years have greatly increased our knowledge of the properties of transient bursts of energetic particles emitted from the sun in association with solar flares, but a real understanding of the solar flare particle acceleration process requires greatly refined experimental data. On the practical side, it is also imperative that this problem be solved if man is to venture, for long periods of time, beyond the protective umbrella of Earth's magnetic field, which excludes much of the biologically damaging solar energetic particles. It is only through an understanding of the basic acceleration problem that we can expect to be able to predict the occurrence of a solar flare with lethal solar radiations. For our knowledge of these effects to advance, a new space mission dedicated to studying the high-energy aspects of solar flares at high spatial and energy resolution will be required.
Scattering and Recoiling Spectrometry: An Ion's Eye View of Surface Structure
Authors: Rabalais J. Wayne
Published: October 2006

Recent developments in ion-scattering spectrometry have led to a surface crystallography that is sensitive to all elements, including hydrogen. Time-of-flight techniques for the detection of atoms scattered and recoiled from surfaces in simple collision sequences, together with calculations of shadowing and blocking cones, can be used to make direct measurements of interatomic spacings and adsorption sites within an accuracy of ≲0.1 angstrom. Time-of-flight detection of both neutrals and ions provides the high sensitivity necessary for nondestructive analysis. Structures are determined by monitoring the angular anisotropies in the scattered primary and recoiled target atom flux. Such surface and adsorption site determinations find application in such fields as catalysis, thin film growth, and interfaces.
Deuterium on Venus: Observations From Earth
Authors: de Bergh Catherine , Bézard Bruno , Owen Tobias , Crisp David , Maillard Jean-Pierre , Lutz Barry L.
Published: October 2006

Absorption lines of HDO and H
2
O have been detected in a 0.23-wave number resolution spectrum of the dark side of Venus in the interval 2.34 to 2.43 micrometers, where the atmosphere is sounded in the altitude range from 32 to 42 kilometers (8 to 3 bars). The resulting value of the deuterium-to-hydrogen ratio (D/H) is 120 ± 40 times the telluric ratio, providing unequivocal confirmation of in situ Pioneer Venus mass spectrometer measurements that were in apparent conflict with an upper limit set from International Ultraviolet Explorer spectra. The 100-fold enrichment of the D/H ratio on Venus compared to Earth is thus a fundamental constraint on models for its atmospheric evolution.
Thymic Requirement for Clonal Deletion During T Cell Development
Authors: Fry Alicia M. , Jones Lori A. , Kruisbeek Ada M. , Matis Louis A.
Published: October 2006

During T cell differentiation, self tolerance is established in part by the deletion of self-reactive T cells within the thymus (negative selection). The presence of T cell receptor (TCR)-αβ
+
T cells in older athymic (nu/nu) mice indicates that some T cells can also mature without thymic influence. Therefore, to determine whether the thymus is required for negative selection, TCR V
β
expression was compared in athymic nu/nu mice and their congenic normal littermates. T cells expressing V
β
3 proteins are specific for minor lymphocyte stimulatory (Mls
c
) determinants and are deleted intrathymically due to self tolerance in Mls
c+
mouse strains. Here it is shown that V
β
3
+
T cells are deleted in Mls
c+
BALB/c nu/+ mice, but not in their BALB/c nu/nu littermates. Thus, the thymus is required for clonal deletion during T cell development.
Organic Superconductors—New Benchmarks
Authors: Williams Jack M. , Schultz Arthur J. , Geiser Urs , Carlson K. Douglas , Kini Aravinda M. , Wang H. Gau , Kwok Wai-Kwong , Whangbo Myung-Hwan , Schirber James E.
Published: October 2006

Recent advances in the design and synthesis of organic synthetic metals have yielded materials that have the highest superconducting transition temperatures (
T
c
≈ 13 kelvin) reported for these systems. These materials have crystal structures consisting of alternating layers of organic donor molecules and inorganic anions. Organic superconductors have various electronic and magnetic properties and crystal structures that are similar to those of the inorganic copper oxide superconductors (which have high
T
c
values); these similarities include highly anisotropic conductivities, critical fields, and short coherence lengths. The largest number of organic superconductors, including those with the highest
T
c
values, are charge-transfer salts derived from the electron donor molecule BEDT-TTF or ET [bis(ethylenedithio)-tetrathiafulvalene]. The synthesis and crystal structures of these salts are discussed; their electrical, magnetic, and band electronic structure properties and their many similarities to the copper oxide superconductors are treated as well.
Sporozoite Vaccine Induces Genetically Restricted T Cell Elimination of Malaria from Hepatocytes
Authors: Hoffman Stephen L. , Isenbarger Daniel , Long Gary W. , Sedegah Martha , Szarfman Ana , Waters Leslie , Hollingdale Michael R. , van der Meide Peter H. , Finbloom David S. , Ballou W. Ripley
Published: October 2006

The target of the CD8
+
T cell-dependent immunity that protects mice immunized with irradiation-attenuated malaria sporozoites has not been established. Immune BALB/c mice were shown to develop malaria-specific, CD8+ T cell-dependent inflammatory infiltrates in their livers after challenge with
Plasmodium berghei
sporozoites. Spleen cells from immune BALB/c and C57BL/6 mice eliminated hepatocytes infected with the liver stage of
P. berghei
in vitro. The activity against infected hepatocytes is not inhibited by antibodies to interferon-γ and is not present in culture supernatants. It is genetically restricted, an indication that malaria antigens on the hepatocyte surface are recognized by immune T effector cells. Subunit vaccine development will require identification of the antigens recognized by these T cells and a method of immunization that induces such immunity.
Resource Constraints in Petroleum Production Potential
Authors: Masters C. D. , Root D. H. , Attanasi E. D.
Published: October 2006

Geologic reasons indicate that the dominant position of the Middle East as a source of conventional petroleum will not be changed by new discoveries elsewhere. The share of world crude oil production coming from the Middle East could increase, within 10 to 20 years, to exceed 50 percent, under even modest increases in world consumption. Nonconventional resources of oil exist in large quantities, but because of their low production rates they can at best only mitigate extant trends. Increased production of natural gas outside the United States, however, offers an opportunity for geographically diversified energy supplies in the near future.
Instruction-Level Parallel Processing
Authors: Fisher Joseph A. , Rau Ramakrishna
Published: October 2006

The performance of microprocessors has increased steadily over the past 20 years at a rate of about 50% per year. This is the cumulative result of architectural improvements as well as increases in circuit speed. Moreover, this improvement has been obtained in a transparent fashion, that is, without requiring programmers to rethink their algorithms and programs, thereby enabling the tremendous proliferation of computers that we see today. To continue this performance growth, microprocessor designers have incorporated instruction-level parallelism (ILP) into new designs. ILP utilizes the parallel execution of the lowest level computer operations—adds, multiplies, loads, and so on—to increase performance transparently. The use of ILP promises to make possible, within the next few years, microprocessors whose performance is many times that of a CRAY-1S. This article provides an overview of ILP, with an emphasis on ILP architectures—superscalar, VLIW, and dataflow processors—and the compiler techniques necessary to make ILP work well.
Expression of Functional Nerve Growth Factor Receptors After Gene Transfer
Authors: Hempstead Barbara L. , Schleifer Leonard S. , Chao Moses V.
Published: October 2006

Nerve growth factor (NGF) interacts with both high affinity (
K
d
= 10
-10
-10
-11
M
) and low affinity (
K
d
= 10
-8
-10
-9
M
) receptors; the binding of NGF to the high affinity receptor is correlated with biological actions of NGF. To determine whether a single NGF binding protein is common to both forms of the receptor, a full-length receptor cDNA was introduced in the NR18 cell line, an NGF receptor-deficient variant of the PC12 pheochromocytoma cell line. The transformant displayed (i) both high and low affinity receptors detectable by receptor binding; (ii) an affinity cross-linking pattern with
125
I-labeled NGF similar to that of the parent PC12 cell line; and (iii) biological responsiveness to NGF as assayed by induction of c-
fos
transcription. These findings support the hypothesis that a single binding protein is common to both forms of the NGF receptor and suggest that an additional protein is required to produce the high affinity form of the NGF receptor.
Smart Computer-Assisted Markets
Authors: McCabe Kevin A. , Rassenti Stephen J. , Smith Vernon L.
Published: October 2006

The deregulation movement has motivated the experimental study of auction markets designed for interdependent network industries such as natural gas pipelines or electric power systems. Decentralized agents submit bids to buy commodity and offers to sell transportation and commodity to a computerized dispatch center. Computer algorithms determine prices and allocations that maximize the gains from exchange in the system relative to the submitted bids and offers. The problem is important, because traditionally the scale and coordination economies in such industries were thought to require regulation. Laboratory experiments are used to study feasibility, limitations, incentives, and performance of proposed market designs for deregulation, providing motivation for new theory.
Polar Orientation of Dyes in Robust Multilayers by Zirconium Phosphate-Phosphonate Interlayers
Authors: Katz H. E. , Scheller G. , Putvinski T. M. , Schilling M. L. , Wilson W. L. , Chidsey C. E. D.
Published: October 2006

Polar orientation of molecules in solids leads to materials with potentially useful properties such as nonlinear optical and electrooptical activity, electrochromism, and pyroelectricity. A simple self-assembly procedure for preparing such materials is introduced that yields multiple polar dye monolayers on solid surfaces joined by zirconium phosphate-phosphonate interlayers. Second harmonic generation (SHG) shows that the multilayers have polar order that does not decrease with increasing numbers (up to a large number) of monolayers in the film. The inorganic interlayers, as determined by SHG, impart excellent orientational stability to the dye molecules, with the onset of orientational randomization above 150°C.
Selective Amplification And Cloning Of Four New Members Of The G Protein-coupled Receptor Family
Authors: Libert Frédérick , Parmentier Marc , Lefort Anne , Dinsart Christiane , Van Sande Jacqueline , Maenhaut Carine , Simons Marie-Jeanne , Dumont Jacques E. , Vassart Gilbert
Published: October 2006

An approach based on the polymerase chain reaction has been devised to clone new members of the family of genes encoding guanosine triphosphate-binding protein (G protein)-coupled receptors. Degenerate primers corresponding to consensus sequences of the third and sixth transmembrane segments of available receptors were used to selectively amplify and clone members of this gene family from thyroid complementary DNA. Clones encoding three known receptors and four new putative receptors were obtained. Sequence comparisons established that the new genes belong to the G protein-coupled receptor family. Close structural similarity was observed between one of the putative receptors and the 5HT1a receptor. Two other molecules displayed common sequence characteristics, suggesting that they are members of a new subfamily of receptors with a very short nonglycosylated (extracellular) amino-terminal extension.
Transfer of a Protein Encoded by a Single Nucleus to Nearby Nuclei in Multinucleated Myotubes
Authors: Ralston Evelyn , Hall Zach W.
Published: October 2006

Specialized regions of muscle fibers may result from differential gene expression within a single fiber. In order to investigate the range of action of individual nuclei in multinucleated myotubes, C2 myoblasts were transfected to obtain stable cell lines that express a reporter protein that is targeted to the nucleus. Hybrid myotubes were then formed containing one or a few transfected nuclei as well as a large number of nuclei from the parental strain. In order to determine how far the products of a single nucleus extend, transfected nuclei were labeled with [
3
H]thymidine before fusion and the myotubes were stained to identify the reporter protein. In such myotubes the fusion protein was not confined to its nucleus of origin, but was restricted to nearby nuclei.
Control of Gene Expression by Artificial Introns in
Saccharomyces cerevisiae
Authors: Yoshimatsu Tadanori , Nagawa Fumikiyo
Published: October 2006

Artificial yeast introns that show cold-sensitive splicing have been constructed. These conditional introns can be inserted into a target gene as an "intron cassette" without disrupting the coding information, allowing expression of the gene to be cold sensitive. Insertion of these intron cassettes rendered the yeast
URA3
gene cold sensitive in its expression. The advantage of this intron-mediated control system is that any gene can be converted to a controllable gene by simple insertion of an intron.
Degradation of Proteins with Acetylated Amino Termini by the Ubiquitin System
Authors: Mayer Arie , Siegel Ned R. , Schwartz Alan L. , Ciechanover Aaron
Published: October 2006

A free NH
2
-terminal group has been previously shown to be an obligatory signal for recognition and subsequent degradation of proteins in a partially fractionated and reconstituted ubiquitin proteolytic system. Naturally occurring proteins with acetylated NH
2
-termini—most cellular proteins fall in this category—were not degraded by this system. Other studies have suggested that the identity of the NH
2
-terminal residue is important in determining the metabolic stability of a protein in vivo (N-end rule). Whole reticulocyte lysate and antibodies directed against the ubiquitin-activating enzyme (E1) have now been used to show that such acetylated proteins are degraded in a ubiquitin-dependent mode. Although fractionation of lysate does not affect its proteolytic activity toward substrates with free NH
2
-termini, it completely abolishes the activity toward the blocked substrates, indicating that an important component of the system was either removed or inactivated during fractionation. An NH
2
-terminal "unblocking" activity that removes the blocking group, thus exposing a free NH
2
-terminus for recognition according to the N-end rule, does not seem to participate in this pathway. Incubation of whole lysate with labeled histone H2A results in the formation of multiple ubiquitin conjugates. In contrast, the fractionated system is devoid of any significant conjugating activity. These results suggest that a novel conjugating enzyme (possibly a ubiquitin-protein ligase) may be responsible for the degradation of these acetylated proteins by recognizing structural features of the substrate that are downstream and distinct from the NH
2
-terminal residue.
Role of Prostaglandins and cAMP in the Secretory Effects of Cholera Toxin
Authors: Peterson Johnny W. , Ochoa Laura G.
Published: October 2006

The role of adenosine 3′,5′-monophosphate (cAMP) and prostaglandins in the pathogenesis of experimental cholera was evaluated. Fluid accumulated in the rabbit intestinal loop model after 16 hours of incubation with cholera toxin, prostaglandin E
1
, or prostaglandin E
2
, but not with membrane-permeable derivatives of cAMP or forskolin. Dibutyryl cAMP triggered a small, transient intestinal fluid accumulation response by 4.5 hours; however, the fluid was completely absorbed by 9 hours. After exposure of intestinal loops to cholera toxin, prostaglandin E was released into the intestinal lumen in a concentration-dependent manner independent of cAMP. Thus, not only cAMP, but also prostaglandins may regulate water and electrolyte secretion in cholera.
Quantum Conversion and Image Detection by a Bacteriorhodopsin-Based Artificial Photoreceptor
Authors: Miyasaka Tsutomu , Koyama Koichi , Itoh Isamu
Published: October 2006

A thin film (50 to 500 angstroms thick) comprising fragments of bacteriorhodopsin (bR)-containing purple membrane was formed on an SnO
2
conductive electrode by the Langmuir-Blodgett method. The film was put into contact with a thin, aqueous electrolyte gel to construct an electrochemical sandwich-type photocell with a junction structure SnO
2
/bR/electrolyte/Au electrode. Under visible light irradiation, the bR-based photocell produced an efficient rectified photocurrent that proved to have unique differential responsivity to light intensity, which is characteristic of in vivo biological photoreceptors. An artificial photoreceptor comprising a pixel network of the bR photocell was fabricated in an attempt to study image-detecting and processing abilities of bR.
Duplication, Deletion, and Polymorphism in the Sex-Determining Region of the Mouse Y Chromosome
Authors: Mardon Graeme , Mosher Rebecca , Disteche Christine M , Nishioka Yutaka , McLaren Anne , Page David C.
Published: October 2006

The
ZFY
gene in the sex-determining region of the human Y chromosome encodes a "zinc-finger" protein that may be the testis-determining factor,
TDF
. Although the Y chromosomes of most placental mammals carry a single homolog of
ZFY
, the mouse Y chromosome has two homologs, both in the sex-determining (
Sxr
) region.
Zfy-1
alone may suffice to determine maleness;
Zfy-2
is dispensable, as it was deleted in an
Sxr
variant that retains sex-determining function but has lost other genes. Both loci mapped near the centromere of the mouse Y chromosome. The Y chromosomes of the subspecies
Mus musculus musculus
and
M. m. domesticus
were distinguishable by a
Zfy-1
restriction fragment polymorphism, which can be used to study their differing interactions with autosomal sex-determining genes.
The Reversal and Splitting of Waves in an Excitable Medium Caused by an Electrical Field
Authors: Sevčíková Hana , Marek Milos , Müller Stefan C.
Published: October 2006

The reversal and splitting of traveling concentration waves was observed in a one-dimensional Belousov-Zhabotinski reaction medium under the influence of low-intensity electric field gradients (∼10 V per centimeter). The wave reversal and splitting were strongly correlated with a characteristic transformation of the shape of both the wave front and the refractory tail of a wave in the local field gradient. The secondary role of generated hydrodynamic flow on wave transformation was also investigated.
Large Enhancement in Oxygen Mobility in the Superconductors RBa
2
Cu
3
O
7
with Increasing Rare-Earth Size
Authors: Tallon J. L. , Mellander B. -E.
Published: October 2006

Ultrasonic composite oscillator measurements of the mechanical relaxation in RBa
2
Cu
3
O
7–δ
arising from oxygen hopping in the basal chain layer show enhancements in oxygen mobility of 20, 50, and 100 times for R = gadolinium, neodymium, and lanthanum, respectively, above that for R = yttrium. The use of the larger rare earths offers a practical solution to the major problem of slow oxygen diffusion in single crystals and bulk, dense material for wires and melt-textured monolithic bodies.
Identification of Human Glucocorticoid Receptor Complementary DNA Clones by Epitope Selection
Authors: Weinberger Cary , Hollenberg Stanley M. , Ong Estelita S. , Harmon Jeffrey M. , Brower Steven T. , Cidlowski John , Thompson E. Brad , Rosenfeld Michael G. , Evans Ronald M.
Published: October 2006

Steroid hormones regulate cellular differentiation and physiologic functions predominantly through gene transcription. Regulation is achieved by the interaction of specific steroid receptor proteins and target genes. Expression cloning techniques were used to select human glucocorticoid receptor complementary DNA clones in order to define the mechanism by which the receptor exerts its transcriptional control. Immobilized fusion proteins from individual clones were used to select epitope-specific antibody which was subsequently eluted and identified by binding to protein blots of cellular extracts. Three cross-hybridizing clones containing inserts expressing antigenic determinants of the human glucocorticoid receptor were isolated.
Terrestrial Soft-Bodied Protists and Other Microorganisms in Triassic Amber
Authors: Poinar George O. , Waggoner Benjamin M. , Bauer Ulf-Christian
Published: October 2006

Protozoa, cyanobacteria, sheathed algae, sheathed fungi, germinating pollen or spores, and fungal spores have been found in amber 220 to 230 million years old. Many of these microorganisms can be assigned to present-day groups. This discovery of terrestrial, soft-bodied protists that can be referred to modern groups indicates that morphological evolution is very gradual in many protists and that both structural and probably functional stasis extend back at least to the Upper Triassic period.
Radiative Climate Forcing by the Mount Pinatubo Eruption
Authors: Minnis P. , Harrison E. F. , Stowe L. L. , Gibson G. G. , Denn F. M. , Doelling D. R. , Smith W. L.
Published: October 2006

Radiative flux anomalies derived from the National Aeronautics and Space Administration (NASA) spaceborne Earth Radiation Budget Experiment were used to determine the volcanic radiative forcing that followed the eruption of Mount Pinatubo in June 1991. They are the first unambiguous, direct measurements of large-scale volcanic forcing. The volcanic aerosols caused a strong cooling effect immediately; the amount of cooling increased through September 1991 as shortwave forcing increased relative to the longwave forcing. The primary effects of the aerosols were a direct increase in albedo over mostly clear areas and both direct and indirect increases in the albedo of cloudy areas.
C
60
H
2
: Synthesis of the Simplest C
60
Hydrocarbon Derivative
Authors: Henderson Craig C. , Cahill Paul A.
Published: October 2006

The reaction of C
60
with BH
3
: tetrahydrofuran in toluene followed by hydrolysis yielded C
60
H
2
. This product was separated by high-performance liquid chromatography and characterized as the addition product of H
2
to a 6,6-ring fusion (1a1b isomer). The
1
H nuclear magnetic resonance (NMR) spectrum of the product remained a sharp singlet between –80° and +100°C, which suggests a static structure on the NMR time scale. Hydrolysis of the proposed borane addition product with acetic acid-
d
1
or D
2
O yielded C
60
HD, and its
3
J
HD
coupling constant is consistent with vicinal addition. The observation of a single C
60
H
2
isomer is in complete agreement with earlier calculations that indicated that at most 2 of the 23 possible isomers of C
60
would be observable at equilibrium at room temperature. These results suggest that organoborane chemistry may be applied to further functionalization of fullerenes.
In-Plane Structure of the Liquid-Vapor Interface of an Alloy: A Grazing Incidence X-ray Diffraction Study of Bismuth:Gallium
Authors: Flom Erik B. , Li Mengyang , Acero Anibal , Maskil Nissan , Rice Stuart A.
Published: October 2006

The liquid-vapor interface of a bismuth-gallium mixture (0.2 percent bismuth and 99.8 percent gallium) at 36°C has been studied by grazing incidence x-ray diffraction. The data show, in agreement with thermodynamic arguments, that bismuth is heavily concentrated in the liquid-vapor interface. The x-ray diffraction data are interpreted with the assistance of a simple model that represents the interface as a partial monolayer of bismuth. This analysis leads to the conclusion that the bismuth concentration in the interface is about 80 percent, that there is no significant mixing of gallium and bismuth in the interface, and that the structure function of the interfacial bismuth is like that of supercooled bulk liquid bismuth.
Copernicus: A Regional Probe of the Lunar Interior
Authors: Pinet Patrick C. , Chevrel Serge D. , Martin Patrick
Published: October 2006

Earth-based telescopic spectral imaging techniques were used to document the spatial distribution of crater materials within the large lunar crater Copernicus at the subkilometer scale on the basis of spectral ultraviolet—visible—near-infrared characteristics. The proposed spectral mixing analysis leads to a first-order mapping of the impact melt material within the crater. Olivine was detected not only within the three central peaks but also along a significant portion of the crater rim. Consideration of an olivine-bearing end-member in the mixing model emphasizes the overall morphological pattern of the rim and wall terraces in the associated fraction image. The identification of widely exposed olivine units supports the idea that the lower crust and possibly the lunar mantle itself are regionally at shallow depth.
Beach Cusps as Self-Organized Patterns
Authors: Werner B. T. , Fink T. M.
Published: October 2006

Computer simulations of flow and sediment transport in the swash zone on a beach demonstrate that a model that couples local flow acceleration and alongshore surface gradient is sufficient to produce uniformly spaced beach cusps. The characteristics of the simulated cusps and the conditions under which they form are in reasonable agreement with observations of natural cusps. The self-organization mechanism in the model is incompatible with an accepted model in which standing alongshore waves drive the regular pattern of erosion and deposition that gives rise to beach cusps. Because the models make similar predictions, it is concluded that currently available observational data are insufficient for discrimination between them.
Diversity and Extinction of Tropical American Mollusks and Emergence of the Isthmus of Panama
Authors: Jackson Jeremy B. C. , Jung Peter , Coates Anthony G. , Collins Laurel S.
Published: October 2006

The gradual closure of the Panamanian seaway and the resulting environmental change stimulated an increase in Caribbean molluscan diversity rather than the mass extinction hypothesized previously on the basis of inadequate data. Upheaval of molluscan faunas did occur suddenly throughout tropical America at the end of the Pliocene as a result of more subtle, unknown causes. There is no necessary correlation between the magnitude of regional shifts in abiotic conditions and the subsequent biological response.
A Detailed Map of the 660-Kilometer Discontinuity Beneath the Izu-Bonin Subduction Zone
Authors: Wicks Charles W. , Richards Mark A.
Published: October 2006

Dynamical processes in the Earth's mantle, such as cold downwelling at subduction zones, cause deformations of the solid-state phase change that produces a seismic discontinuity near a depth of 660 kilometers. Observations of short-period, shear-to-compressional wave conversions produced at the discontinuity yield a detailed map of deformation beneath the Izu-Bonin subduction zone. The discontinuity is depressed by about 60 kilometers beneath the coldest part of the subducted slab, with a deformation profile consistent with the expected thermal signature of the slab, the experimentally determined Clapeyron slope of the phase transition, and the regional tectonic history.
Mechanism and Dynamics of Ion Transfer Across a Liquid-Liquid Interface
Authors: Benjamin llan
Published: October 2006

A detailed molecular model for ion transfer across the interface between water and 1,2-dichloroethane provides insight into the mechanism of the transfer across the interface between two immiscible liquids. Extensive molecular dynamics computer simulations underscore the roles of surface roughness and capillary distortions in this process, demonstrate that ion transfer is an activated rather than a simple diffusive process, and provide a test for the applicability of theoretical models.
Cross-Shelf Sediment Transport by an Anticyclonic Eddy Off Northern California
Authors: Washburn Libe , Swenson Mark S. , Largier John L. , Kosro P. Michael , Ramp Steven R.
Published: October 2006

A combination of satellite imagery, shipboard profiles, drifter tracks, and moored current observations reveals that an anticyclonic eddy off the coast of northern California transported plumes of suspended sediments from the continental shelf into the deep ocean. The horizontal scale of the eddy was about 90 kilometers, and the eddy remained over the continental shelf and slope for about 2 months during the summer of 1988. The total mass of sediments transported by the eddy was of order 105 metric tons. Mesoscale eddies are recurrent features in this region and occur frequently in eastern boundary currents. These results provide direct evidence that eddies export sediments from continental shelves.
Radio Emission from the Heliopause Triggered by an Interplanetary Shock
Authors: Gurnett D. A. , Kurth W. S. , Allendorf S. C. , Poynter R. L.
Published: October 2006

A strong heliospheric radio emission event has been detected by Voyagers 1 and 2 in the frequency range of 2 to 3 kilohertz. This event started in July 1992 and is believed to have been generated at or near the heliopause by an interplanetary shock that originated during a period of intense solar activity in late May and early June 1991. This shock produced large plasma disturbances and decreases in cosmic ray intensity at Earth, Pioneers 10 and 11, and Voyagers 1 and 2. The average propagation speed estimated from these effects is 600 to 800 kilometers per second. After correction for the expected decrease in the shock speed in the outer heliosphere, the distance to the heliopause is estimated to be between 116 and 177 astronomical units.
Enhanced C
2
Yields from Methane Oxidative Coupling by Means of a Separative Chemical Reactor
Authors: Tonkovich Anna Lee , Carr Robert W. , Aris Rutherford
Published: October 2006

Of the processes for converting natural gas into a more useful chemical feedstock, the oxidative coupling of methane to form ethane and ethylene (C
2
) has perhaps been the most intensively investigated in recent years, but it has proved extremely difficult to obtain C
2
yields in excess of 20 to 25%. Methane oxidative coupling was carried out in a separative chemical reactor that simulated a countercurrent chromatographic moving-bed. This reaction gives 65% methane conversion, 80% C
2
selectivity, and a C
2
yield slightly better than 50% with Sm
2
O
3
catalyst at ∼1000 K.
Closely Approaching the Silylium Ion (R
3
Si
+
)
Authors: Reed Christopher A. , Xie Zuowei , Bau Robert , Benesi Alan
Published: October 2006

The crystal structure of the tri-isopropyl silyl species,
i
-Pr
3
Si(Br
6
-CB
11
H
6
), where the brominated carborane Br
6
-CB
11
H
6
–
is perhaps the least nucleophilic anion presently known, has revealed the highest degree of silylium cation character (R
3
Si
+
) yet observed. The average C—Si—C angle is 117°, only 3° short of the planarity expected of a pure silylium ion (120°). This value compares to 114° recently reported for a toluene-solvated silyl cation, [Et
3
Si(toluene)]
+
by Lambert and co-workers. The greater silylium ion character of
i
-Pr
3
Si(Br
6
-CB
11
H
6
) versus [
i
-Pr
3
Si(toluene)]
+
is also reflected in the larger downfield shift of the silicon-29 nuclear magnetic resonance, 109.8 versus ≤94.0 parts per million. The unusual bonding of toluene to R
3
Si
+
in Lambert's compound is reinterpreted as a significant covalent π interaction.
Induction of Mesoderm by a Viral Oncogene in Early
Xenopus
Embryos
Authors: Whitman Malcolm , Melton D. A.
Published: October 2006

During frog embryogenesis, mesoderm is specified in the equatorial region of the early embryo by a signal from the vegetal hemisphere. Prospective ectodermal cells dissected from the animal hemisphere can be respecified to form mesodermal tissues by recombination with vegetal tissue or by treatment with any of several polypeptide growth factors or growth factor-like molecules. Together with the discovery that several developmental mutations in
Drosophila
are in genes with significant homology to mammalian mitogens and oncogenes, these observations suggest that early developmental signals may use similar transduction pathways to mitogenic signals characterized in cultured mammalian cells. Whether mesoderm can be induced by activation of intracellular signal transduction pathways implicated in mitogenesis and oncogenesis has been investigated with the viral oncogene polyoma middle T. Microinjection of middle T messenger RNA into early embryos results in the respecification of isolated prospective ectodermal tissue to form characteristic mesodermal structures. Middle T in frog blastomeres appears to associate with cellular activities similar to those observed in polyoma-transformed mouse cells, and transformation-defective middle T mutants fail to induce mesoderm. These results suggest that early inductive signals and mitogenic and oncogenic stimuli may share common signal transduction pathways.
Contributions of Bird Studies to Biology
Authors: Konishi Masakazu , Emlen Stephen T. , Ricklefs Robert E. , Wingfield John C.
Published: October 2006

Birds are widely distributed, highly diversified, and exhibit behavior and social organizations equal in complexity to mammals, yet they are generally more conspicuous and approachable in natural environments. These attributes make birds excellent subjects in many areas of biological research. The topics in which studies on birds have figured prominently include the mechanisms of species formation, the regulation of the distribution and abundance of animals, the effects of the environment on behavior and physiology, the biological and evolutionary significance of variations in social organizations, the encoding of information in animal communication, the sensory basis for migration and navigation, the effects of hormones on nerve cells and behavior, the ontogeny of brain and behavior, and the structure and function of the vertebrate brain. The outstanding record of avian research suggests that birds will continue to provide important models for developing and testing new ideas in various fields of biology.