bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Materials
Authors: Glass A. M.
Published: October 2006

Optical technologies are becoming increasingly important in areas that were traditionally the domain of electronics. This trend is likely to continue into the foreseeable future with optics and electronics being integral, mutually compatible components of systems for consumer markets, industry, and defense. The basis of this progress is the development of materials that have the required purity, physical properties, and optical quality; glass fibers for optical transmission, semiconductors for lasers and detectors, and nonlinear materials for optical switching are examples. In this article, some of the materials of choice for a variety of applications are described and the frontiers of materials research for new areas of opportunity are discussed. Particular emphasis is placed on optical materials for the transmission and processing of information.
Superconductivity at 40 K in the Oxygen-Defect Perovskites La

2-
x

Sr

x

CuO

4-
y
Authors: Tarascon J. M. , Greene L. H. , McKinnon W. R. , Hull G. W. , Geballe T. H.
Published: October 2006

Structural, magnetic, and electronic properties of compounds in the series La

2-
x

Sr

x

CuO

4-
y

for 0.05 ≤
x
≤ 1.1, with Δ
x
= 0.025, were studied. Resistance, susceptibility, Meissner, and shielding measurements have revealed superconductivity among several members of the series. For
x
= 0.15, the transition temperature
T
c
, measured at the midpoint of the resistive transition, is a maximum at 39.3 K with a width of 2 K. At other compositions the transition is broader and occurs at a lower temperature. Annealing the
x
= 0.15 sample in oxygen at 500°C increases
T
c
to 40.3 K, while annealing at the same temperature under vacuum suppresses the superconductivity. These changes in oxygen content and
T
c
are reversible.
A Tephritid Fly Mimics the Territorial Displays of Its Jumping Spider Predators
Authors: Greene Erick , Orsak Larry J. , Whitman Douglas W.
Published: October 2006

The tephritid fly
Zonosemata vittigera
(Coquillett) has a leg-like pattern on its wings and a wing-waving display that together mimic the agonistic territorial displays of jumping spiders (Salticidae).
Zonosemata
flies initiate this display when stalked by jumping spiders, causing the spiders to display back and retreat. Wing transplant experiments showed that both the wing pattern and wing-waving displays are necessary for effective mimicry:
Zonosemata
flies with transplanted house fly wings and house flies with transplanted
Zonosemata
wings were attacked by jumping spiders. Similar experiments showed that this mimicry does not protect
Zonosemata
against nonsalticid predators. This is a novel form of sign stimulus mimicry that may occur more generally.
An Oxygen Key to the New Superconductors
Authors: Robinson Arthur L.
Published: October 2006

First it was the physicists, then the chemists, and most recently the materials scientists and ceramists who have hastily included in their annual meetings symposia on the new high-temperature, ceramic superconductors. Below are briefings from the 1987 Spring Meeting of the Materials Research Society (MRS) that was held in Anaheim, California, from 21 to 24 April, 1 week before the American Ceramics Society's conclave in Pittsburgh.

With the initial wave of euphoria now past, the atmosphere in Anaheim was decidedly more professional than that of the now fabled ""Woodstock of Physics"" that was part of the American Physical Society's March Meeting in New York City only 5 weeks before. Nonetheless, perhaps 1500 materials researchers listened to 69 scheduled papers and several late walk-ons that were crammed into a 2-day symposium. With a martial strictness, cochairs Michael Schlüter of AT&T Bell Laboratories and Donald Gubser of the Naval Research Laboratory kept the talks to the allotted 10 minutes each.

Except for an impassioned presentation by Juei-Teng Chen of Wayne State University, who sought to convince listeners that a group there had seen dear signs of superconductivity at 240 K, which is ambient temperature during a cold night on the northern plains, no significant indications of room-temperature superconductivity were reported. The most skeptical view was that of Theodore Geballe of Stanford University, who suggested that some of the unreproducible signs seen in several laboratories could be due to something other than superconductivity, as similar effects disappeared in Stanford samples with repeated cycling between room and liquid-nitrogen temperature.

If there was one theme at the symposium, it was that oxygen is the key to the family of rare-earth-based ceramic materials now in hand that remain superconducting up to about 100 K.
Magnetic Properties of Hydrothermally Recrystallized Magnetite Crystals
Authors: Heider Franz , Dunlop David J. , Sugiura Naoji
Published: October 2006

The discrepancy between the magnetic hysteresis properties of magnetite crystals that are precipitated from solution (<0.3 micrometer) and of crushed sifted grains (>0.3 micrometer) is not an inherent property of magnetite but is caused by the highly stressed state of crushed material and by adhering finer fragments. The size trends of magnetic properties exhibited by submicrometer-size precipitated grains continue in the size range from 1 micrometer to 1 millimeter in a set of hydrothermally recrystallized magnetite crystals. Coercive forces of these narrowly sized crystals follow a power law over a wide size range (0.1 micrometer to 1 millimeter) as predicted by theory. Dislocation etch pits show similar dislocation densities for hydrothermally grown (3 × 10
10
meter
-2
) and natural (1 × 10
10
meter
-2
) magnetite crystals. Hysteresis parameters of hydrothermally grown crystals are similar to those of natural crystals but are about one-fifth of those for crushed grains.
Scientific Basis of Modern Weather Prediction
Authors: Tribbia Joseph J. , Anthes Richard A.
Published: October 2006

A review of the scientific principles and computational methods used in modern weather prediction is presented. The history of research in this area shows that researchers attempting to improve weather prediction have advanced all of meteorology. The numerical models developed for weather prediction are today an integral component of meteorological data analysis and are used in simulating past and present climates and in assessing the potential for future climate changes. Related disciplines, such as oceanography, computational fluid dynamics, and mathematics, have also reaped benefits from this effort, which is currently being extended to studies at smaller spatial and longer temporal scales.
The Discovery of a Class of High-Temperature Superconductors
Authors: Müller K. Alex , Bednorz J. Georg
Published: October 2006

The exceptional interest in the new class of oxide superconductors and the importance of these materials are discussed together with the concepts that led to their discovery. The discovery itself and its early confirmation are summarized, including the work until the beginning of 1987. The observation of a superconductive glass state in percolative samples is also discussed.
Heritability at the Species Level: Analysis of Geographic Ranges of Cretaceous Mollusks
Authors: Jablonski David
Published: October 2006

Geographic range has been regarded as a property of species rather than of individuals and thus as a potential factor in macroevolutionary processes. Species durations in Late Cretaceous mollusks exhibit statistically significant positive relationships with geographic range, and the attainment of a typical frequency distribution of geographic ranges in the cohort of species that originated just before the end-Cretaceous extinction indicates that species duration is the dependent variable. The strong relation between geographic ranges in pairs of closely related species indicates that the trait is, in effect, heritable at the species level. The significant heritabilities strengthen claims for processes of evolution by species-level selection, and for differential survivorship of organismic-level traits owing to extinction and origination processes operating at higher levels.
Chaos, Strange Attractors, and Fractal Basin Boundaries in Nonlinear Dynamics
Authors: Grebogi Celso , Ott Edward , Yorke James A.
Published: October 2006

Recently research has shown that many simple nonlinear deterministic systems can behave in an apparently unpredictable and chaotic manner. This realization has broad implications for many fields of science. Basic developments in the field of chaotic dynamics of dissipative systems are reviewed in this article. Topics covered include strange attractors, how chaos comes about with variation of a system parameter, universality, fractal basin boundaries and their effect on predictability, and applications to physical systems.
Mechanism of the Body-Centered Cubic—Hexagonal Close-Packed Phase Transition in Iron
Authors: Bassett W. A. , Huang E.
Published: October 2006

The transition from body-centered cubic to hexagonal close-packed phase in iron has been studied in a diamond anvil cell with synchrotron radiation. The hexagonal close-packed phase, when it first appears, has a ratio of lattice parameters that is significantly larger than normal. This is attributed to a displacive mechanism that causes a distortion of the hexagonal close-packed structure in a body-centered cubic matrix. The hexagonal close-packed phase adjacent to a boundary with the body-centered cubic phase is stretched in the
c
direction and compressed in the
a
direction when it first forms.
Fluvial Perturbance in the Western Amazon Basin: Regulation by Long-Term Sub-Andean Tectonics
Authors: Räsänen Matti E. , SALO JUKKA S. , KALLIOLA RISTO J.
Published: October 2006

Haffer's refuge theory proposes that during the arid climatic phases of the late Pleistocene, tropical lowland forests of Amazonia were reduced to isolated patches contributing to the high species richness of the present-day forest. The theory was developed because no obvious historic or modern geomorphic isolation barriers were recorded in Amazonia. Analyses of radar images combined with stratigraphical data show that in the basinal forelands of the tectonically active Andes the geological setting causes long-term fluvial perturbance. This leads to a temporally structured highly complex mosaic of fossil and present floodplains. These dynamics have been present with varying activity and geographic range during the Tertiary and Quaternary, providing site-turnover that has not been recognized by the biogeographic tradition of the Amazon basin.
Stimulation of Heterotrophic Microplankton Production by Resuspended Marine Sediments
Authors: Wainright Sam C.
Published: October 2006

Resuspended material experimentally derived from natural marine sediments and added to dark microcosms containing natural seawater stimulated the suspended microheterotrophs (bacteria and protozoa) to attain 2.6 times the biovolume of controls after 32 hours. Free bacteria benefited most from the stimulus, both numerically and volumetrically. Attached suspended bacteria also increased in number during the first 64 hours of the experiment; particles remaining in suspension became more densely packed with bacteria. This increased microbial production may be an important source of high-quality biomass for consumers in the nearshore zone, depending on the frequency, duration, and intensity of resuspension events in a given region.
Global Trends in Total Ozone
Authors: Bowman Kenneth P.
Published: October 2006

Satellite ozone data from the Total Ozone Mapping Spectrometer from 1979 through 1986 show that recent decreases of total ozone have not been confined to the Antarctic spring season (the Antarctic ozone hole), but are global in extent. The losses are about twice the estimated uncertainty in the satellite data. The decreases are largest in middle and high latitudes and occur in all seasons of the year. The decreases for this 8-year period are comparable in magnitude to the increases observed during the 1960s. Southern Hemisphere values from 1986 are generally greater than those from 1985.
Enzymatic Oxidation of Cholesterol Aggregates in Supercritical Carbon Dioxide
Authors: Randolph T. W. , Clark D. S. , Blanch H. W. , Prausnitz J. M.
Published: October 2006

Fundamental studies of enzyme-solvent interactions can be conducted with supercritical fluids because small changes in pressure or temperature may bring about great changes in the properties of a single solvent near its critical point. Cholesterol oxidase is active in supercritical carbon dioxide and supercritical carbon dioxide-cosolvent mixtures. Variations in solvent power caused by pressure changes or by the addition of dopants affected the rate of enzymatic oxidation of cholesterol by altering the structure of cholesterol aggregates.
Diode Laser—Pumped Solid-State Lasers
Authors: Byer Robert L.
Published: October 2006

Diode laser—pumped solid-state lasers are efficient, compact, all solid-state sources of coherent optical radiation. Major advances in solid-state laser technology have historically been preceded by advances in pumping technology. The helical flash lamps used to pump early ruby lasers were superseded by the linear flash lamp and arc lamp now used to pump neodymium-doped yttrium-aluminum-garnet lasers. The latest advance in pumping technology is the diode laser. Diode laser—pumped neodymium lasers have operated at greater than 10 percent electrical to optical efficiency in a single spatial mode and with linewidths of less than 10 kilohertz. The high spectral power brightness of these lasers has allowed frequency extension by harmonic generation in nonlinear crystals, which has led to green and blue sources of coherent radiation. Diode laser pumping has also been used with ions other than neodymium to produce wavelengths from 946 to 2010 nanometers. In addition, Q-switched operation with kilowatt peak powers and mode-locked operation with 10-picosecond pulse widths have been demonstrated. Progress in diode lasers and diode laser arrays promises all solid-state lasers in which the flash lamp is replaced by diode lasers for average power levels in excess of tens of watts and at a price that is competitive with flash lamp—pumped laser systems. Power levels exceeding 1 kilowatt appear possible within the next 5 years. Potential applications of diode laser—pumped solid-state lasers include coherent radar, global sensing from satellites, medical uses, micromachining, and miniature visible sources for digital optical storage.
Spectroscopic Evidence for Pressure-Induced Coordination Changes in Silicate Glasses and Melts
Authors: Williams Quentin , Jeanloz Raymond
Published: October 2006

Infrared spectra demonstrate that at pressures above 20 gigapascals and room temperature the regular tetrahedral coordination of oxygen around both silicon and aluminum ions is severely disrupted in SiO
2
, CaMgSi
2
O
6
, and CaAlSi
2
O
8
composition glasses. The spectra are consistent with gradual, pressure-induced increases in the coordination numbers of silicon and aluminum. A variety of coordination environments, from sixfold to fourfold, appears to be present at pressures as high as about 40 gigapascals. This apparent change in coordination is not quenchable at room temperature: on decompression, the glasses return to tetrahedral coordination. This continuous and reversible coordination change in amorphous silicates explains the lack of observation of coordination changes in silicate glasses quenched from high pressure, the shallow melting slopes observed for mantle silicates at high pressures, and the possible presence of neutrally buoyant magmas deep within the terrestrial planets.
Cooperative Hunting Harris' Hawks (Parabuteo unicinctus)
Authors: Bednarz James C.
Published: October 2006

Coordinated hunting by several individuals directed toward the capture and sharing of one large prey animal has been documented convincingly only for a few mammalian carnivores. In New Mexico, Harris' hawks formed hunting parties of two to six individuals in the nonbreeding season. This behavior improved capture success and the average energy available per individual and enabled hawks to dispatch prey larger than themselves. These patterns suggest that cooperation is important to understanding the evolution of complex social behavior in higher vertebrates and, specifically, that benefits derived from team hunting are a key factor in the social living of Harris' hawks.
Molecular/Organic Ferromagnets
Authors: Miller Joel S. , Epstein Arthur J. , Reiff William M.
Published: October 2006

Some molecular/organic solids comprised of linear chains of alternating metallocenium donors (D) and cyanocarbon acceptors (A) with spin state
S
= 1/2 (⋅⋅⋅D⋅
+
A⋅
-
D⋅
+
A⋅
-
⋅⋅⋅) exhibit cooperative magnetic phenomena, that is, ferro-, antiferro-, ferri-, and metamagnetism. For [Fe
III
(C
5
Me
5
)
2
]⋅
+
[TCNE]
-
⋅ (Me = methyl; TCNE = tetracyanoethylene), bulk ferromagnetic behavior is observed below the Curie temperature of 4.8 K. A model of configuration mixing of the lowest charge-transfer excited state with the ground state was developed to understand the magnetic coupling as a function of electron configuration and direction of charge transfer. This model predicts that ferromagnetic coupling requires stable radicals with a non-half-filled degenerate valence orbital and a charge-transfer excited state with the same spin multiplicity that mixes with the ground state. Ferromagnetic coupling must dominate in all directions to achieve a bulk ferromagnet. Thus, the primary, secondary, and tertiary structures are crucial considerations for the design of molecular/organic ferromagnets.
The Nature of the Interior of Uranus Based on Studies of Planetary Ices at High Dynamic Pressure
Authors: Nellis W. J. , Hamilton D. C. , Holmes N. C. , Radousky H. B. , Ree F. H. , Mitchell A. C. , Nicol M.
Published: October 2006

Data from the Voyager II spacecraft showed that Uranus has a large magnetic field with geometry similar to an offset tilted dipole. To interpret the origin of the magnetic field, measurements were made of electrical conductivity and equation-of-state data of the planetary "ices" ammonia, methane, and "synthetic Uranus" at shock pressures and temperatures up to 75 gigapascals and 5000 K. These pressures and temperatures correspond to conditions at the depths at which the surface magnetic field is generated. Above 40 gigapascals the conductivities of synthetic Uranus, water, and ammonia plateau at about 20 (ohm-cm)
-1
, providing an upper limit for the electrical conductivity used in kinematic or dynamo calculations. The nature of materials at the extreme conditions in the interior is discussed.
Specific Expression of a Tyrosine Kinase Gene,
blk
, in B Lymphoid Cells
Authors: Dymecki Susan M. , Niederhuber John E. , Desiderio Stephen V.
Published: October 2006

Several pathways of transmembrane signaling in lymphocytes involve protein-tyrosine phosphorylation. With the exception of p56

lck

, a tyrosine kinase specific to T lymphoid cells that associates with the T cell transmembrane proteins CD4 and CD8, the kinases that function in these pathways are unknown. A murine lymphocyte complementary DNA that represents a new member of the
src
family has now been isolated and characterized. This complementary DNA, termed
blk
(for B lymphoid kinase), specifies a polypeptide of 55 kilodaltons that is related to, but distinct from, previously identified retroviral or cellular tyrosine kinases. The protein encoded by
blk
exhibits tyrosine kinase activity when expressed in bacterial cells. In the mouse and among cell lines,
blk
is specifically expressed in the B cell lineage. The tyrosine kinase encoded by
blk
may function in a signal transduction pathway that is restricted to B lymphoid cells.
A Potent GAL4 Derivative Activates Transcription at a Distance in Vitro
Authors: Carey Michael , Leatherwood Janet , Ptashne Mark
Published: October 2006

Transcription of a typical eukaryotic gene by RNA polymerase II is activated by proteins bound to sites found near the beginning of the gene as well as to sites, called enhancers, located a great distance from the gene. According to one view, the primary difference between an activator that can work at a large distance and one that cannot is that the former bears a particularly strong activating region; the stronger the activating region, the more readily the activator interacts with its target bound near the transcriptional start site, with the intervening DNA looping out to accommodate the reaction. One alternative view is that the effect of proteins bound to enhancers might require some special aspect of cellular or chromosome structure. Consistent with the first view, an activator bearing an unusually potent activating region can stimulate transcription of a mammalian gene in a HeLa nuclear extract when bound as far as 1.3 kilobase pairs upstream or 320 base pairs downstream of the transcriptional start site.
Translation Initiation and Ribosomal Biogenesis: Involvement of a Putative rRNA Helicase and RPL46
Authors: Sachs A. B. , Davis R. W.
Published: October 2006

Cold-sensitive mutations in the
SPB
genes (
spb1-spb7
) of
Saccharomyces cerevisiae
suppress the inhibition of translation initiation resulting from deletion of the poly(A)-binding protein gene (
PAB1
). The SPB4 protein belongs to a family of adenosine triphosphate (ATP)-dependent RNA helicases. The aberrant production of 25
S
ribosomal RNA (rRNA) occurring in
spb4-1
mutants or the deletion of SPB2 (RPL46) permits the deletion of
PAB1
. These data suggest that mutations affecting different steps of 60
S
subunit formation can allow PAB-independent translation, and they indicate that further characterization of the
spb
mutations could lend insight into the biogenesis of the ribosome.
Prostacyclin Synthesis Induced in Vascular Cells by Interleukin-1
Authors: Rossi Vincenzo , Breviario Ferruccio , Ghezzi Pietro , Dejana Elisabetta , Mantovani Alberto
Published: October 2006

Supernatants from cultures of human monocytes that had been stimulated with endotoxin or silica induced the synthesis of prostacyclin in endothelial and smooth muscle cells. The lymphokine mediating these effects on the cells of the blood vessel wall was identified as interleukin-1; interferons and interleukin-2 were inactive. Interleukin-1-induced prostacyclin synthesis represents a new aspect of the interaction between the immune system (as well as other tissues) and the vessel wall and may serve as a basis for the development of new strategies in antithrombotic therapy.
Velocity of Sound and Equations of State for Methanol and Ethanol in a Diamond-Anvil Cell
Authors: Brown J. M. , Slutsky L. J. , Nelson K. A. , Cheng L.-T.
Published: October 2006

The adaptability of laser-induced phonon spectroscopy to the determination of acoustic velocity and the equation of state in the diamond-anvil high-pressure cell is demonstrated. The technique provides a robust method for measurements at high pressure in both solids and liquids so that important problems in high-pressure elasticity and the earth sciences are now tractable. The velocity of sound and the density of methanol at 25°C have been measured up to a pressure of 6.8 gigapascals. These results imply a higher density (by approximately 5 percent) for liquid methanol above 2.5 gigapascals than that given in existing compilations. The adiabatic bulk modulus increases by a factor of 50 at a maximum compression of 1.8. The thermodynamic Grüneisen parameters of methanol and ethanol both increase with increasing pressure, in contrast to the behavior of most solids.
On the Prediction of the El Niño of 1986-1987
Authors: Barnett T. , Graham N. , Cane M. , Zebiak S. , Dolan S. , O'Brien J. , Legler D.
Published: October 2006

Three different classes of numerical models successfully predicted the occurrence of the El Niño of 1986-87 at lead times of 3 to 9 months. Although the magnitude and timing of predicted ocean surface temperatures were not perfect, these results suggest that routine prediction of moderate to large El Niño events is feasible. The key to the success of the models lies in recognizing or simulating the low-frequency, large-scale changes in the tropical ocean-atmosphere system that give rise to El Niño events.
Discovery of Sodium and Potassium Vapor in the Atmosphere of the Moon
Authors: Potter A. E. , Morgan T. H.
Published: October 2006

Spectra of the region just above the bright limb of the Moon show weak emission features that are attributed to resonant scattering of sunlight from sodium and potassium vapor in the lunar atmosphere. The maximum omnidirectional emission flux above the bright limb is 3.8 ± 0.4 kilorayleighs for sodium and 1.8 ± 0.4 kilorayleighs for potassium. The zenith column densities above the subsolar point are estimated to be 8 ± 3 × 10
8
atoms cm
-2
for sodium and 1.4 ± 0.3 × 10
8
atoms cm
-2
for potassium. Corresponding surface densities are 67 ± 12 atoms cm
-3
and 15 ± 3 atoms cm
-3
, respectively. The scale height for the sodium atmosphere is 120 ± 42 kilometers, and for potassium 90 ± 20 kilometers, which implies that the effective temperature of the sodium and potassium is close to the lunar surface temperature. The sodium density at the south polar region was found to be similar to that at the subsolar point, indicating widespread distribution of sodium vapor over the lunar surface. The ratio of the density of sodium to the density of potassium is (6 ± 3) to 1, which is close to the sodium to potassium ratio in the lunar surface, suggesting that the atmosphere originates from the vaporization of surface minerals.
A Cineradiographic Analysis of Bird Flight: The Wishbone in Starlings Is a Spring
Authors: Jenkins Farish A. , Dial Kenneth P. , Goslow G. E.
Published: October 2006

High-speed x-ray movies of European starlings flying in a wind tunnel provide detailed documentation of avian skeletal movements during flapping flight. The U-shaped furcula (or "wishbone," which represents the fused clavicles) bends laterally during downstroke and recoils during upstroke; these movements may facilitate inflation and deflation of the clavicular air sac. Sternal movements are also coupled with wingbeat, ascending and retracting on downstroke and descending and protracting on upstroke in an approximately elliptical pathway. The coupled actions of the sternum and furcula appear to be part of a respiratory cycling mechanism between the lungs and air sacs.
Restoration by Calmodulin of a Ca
2+
-Dependent K
+
Current Missing in a Mutant of
Paramecium
Authors: Hinrichsen Robert D. , Burgess-Cassler Anthony , Soltvedt Brook Chase , Hennessey Todd , Kung Ching
Published: October 2006

A combination of genetics, biochemistry, and biophysics was used to show that calmodulin is involved in the regulation of an ion channel. Calmodulin restored the Ca
2+
-dependent K
2+
current in
pantophobiac
, a mutant in
Paramecium
that lacks this current. The restoration of the current occurred within 2 hours after the injection of 1 picogram of wild-type calmodulin into the mutant. The current remained for approximately 30 hours before the mutant phenotype returned. The injection of calmodulin isolated from
pantophobiac
had no effect. These results imply that calmodulin is required for the function or regulation of the Ca
2+
-dependent K
2+
current in
Paramecium
.
Transforming Growth Factor-α: a More Potent Angiogenic Mediator than Epidermal Growth Factor
Authors: Schreiber Alain B. , Winkler Marjorie E. , Derynck Rik
Published: October 2006

Transforming growth factor-α (TGF-α) and epidermal growth factor (EGF) are structurally related peptides. Purified human TGF-α produced in
Escherichia coli
and pure natural mouse EGF were compared for their ability to bind to target cells in vitro and to promote angiogenesis in the hamster cheek pouch bioassay. Both polypeptides were found to bind in vitro to several target cells, including endothelial cells, and to stimulate their DNA synthesis in an equipotent fashion. In vivo, however, TGF-α was more potent than EGF in promoting angiogenesis and, because TGF-α is known to be secreted by a variety of human tumors, it is suggested that this growth factor may contribute to tumor-induced angiogenesis.
Acid Deposition: Unraveling a Regional Phenomenon
Authors: Schwartz Stephen E.
Published: October 2006

Because sources of sulfur and nitrogen oxides distributed broadly across eastern North America have greatly overlapping zones of influence, it is difficult to determine detailed relations between emissions and the resulting acid deposition. Although substantial progress has been made in the past decade in understanding the pertinent atmospheric processes and in describing them in numerical models, because of the complexities of these processes and the wide range of the time and space scales involved, credible source-receptor relations for regional-scale acid deposition are not yet at hand. Consequently, near-term strategies for reducing acid deposition should be based on considerations other than detailed atmospheric source-receptor relations, but with confidence that regional deposition will be reduced equivalently to any reduction in regional emissions.
Upper Jurassic Dinosaur Egg from Utah
Authors: Hirsch Karl F. , Stadtman Kenneth L. , Miller Wade E. , Madsen James H.
Published: October 2006

The Upper Jurassic egg described here is the first known egg from the 100-million-year gap in the fossil record between Lower Jurassic (South Africa) and upper Lower Cretaceous (Utah). The discovery of the egg, which was found mixed in with thousands of dinosaur bones rather than in a nest, the pathological multilayering of the eggshell as found in modern and fossil reptilians, and the pliable condition of the eggshell at the time of burial indicate an oviducal retention of the egg at the time of burial.
Mapping the Main Immunogenic Region and Toxin-Binding Site of the Nicotinic Acetylcholine Receptor
Authors: Barkas T. , Mauron A. , Roth B. , Alliod C. , Tzartos S. J. , Ballivet M.
Published: October 2006

The α-chain of the nicotinic acetylcholine receptor carries the binding sites both for cholinergic ligands and for most experimentally induced or naturally occurring antibodies to the native receptor. By means of expression cloning in
Escherichia coli
, fusion proteins were derived from specific fragments of a complementary DNA encoding the mouse α-chain, allowing the mapping of the toxin-binding site to residues 160-216 and the main immunogenic region to residues 6-85. This approach permits the independent study of different functional domains of a complex receptor molecule and should be generally applicable to other proteins for which complementary DNA clones are available.
Cloning of Complementary DNA for GAP-43, a Neuronal Growth-Related Protein
Authors: Karns Larry R. , Ng Shi-Chung , Freeman John A. , Fishman Mark C.
Published: October 2006

GAP-43 is one of a small subset of cellular proteins selectively transported by a neuron to its terminals. Its enrichment in growth cones and its increased levels in developing or regenerating neurons suggest that it has an important role in neurite growth. A complementary DNA (cDNA) that encodes rat GAP-43 has been isolated to study its structural characteristics and regulation. The predicted molecular size is 24 kilodaltons, although its migration in SDS-polyacrylamide gels is anomalously retarded. Expression of GAP-43 is limited to the nervous system, where its levels are highest during periods of neurite outgrowth. Nerve growth factor or adenosine 3′,5′-monophosphate induction of neurites from PC12 cells is accompanied by increased GAP-43 expression. GAP-43 RNA is easily detectable, although at diminished levels, in the adult rat nervous system. This regulation of GAP-43 is concordant with a role in growth-related processes of the neuron, processes that may continue in the mature animal.
Rewarding Performance That Is Hard to Measure: The Private Nonprofit Sector
Authors: Weisbrod Burton A.
Published: October 2006

The private nonprofit form of institutions is large and growing. Its role in a mixed economy is the subject of this article. Nonprofits differ from private enterprises primarily in the constraints on them. The key element is that nonprofits may not distribute profits to anyone associated with the organization, a restriction that is in sharp contrast to the freedom that private firms have to reward owners and managers for generating profit. The theoretical case that such a constraint can be useful when consumers are poorly informed is examined. Also, the available empirical evidence on differences in behavior between nonprofit and for-profit organizations is presented.
Neuronal pp60

c-
src

Contains a Six-Amino Acid Insertion Relative to Its Non-Neuronal Counterpart
Authors: Martinez Ricardo , Mathey-Prevot Bernard , Bernards André , Baltimore David
Published: October 2006

Neuronal cells express a pp60

c-
src

variant that displays an altered electrophoretic mobility and a different V8 peptide pattern relative to pp60

c-
src

expressed in tissues of non-neuronal origin. To determine whether the neuronal form of pp60

c-
src

is encoded by a brain-specific messenger RNA, a mouse brain complementary DNA (cDNA) library was screened with a chicken c-
src
probe and a 3.8-kilobase c-
src
cDNA clone was isolated. This clone encodes a 60-kilodalton protein that differs from chicken or human pp60

c-
src

primarily in having six extra amino acids (Arg-Lys-Val-Asp-Val-Arg) within the NH
2
-terminal 16 kilodaltons of the molecule. S1 nuclease protection analysis confirmed that brain c-
src
RNA contains an 18-nucleotide insertion at the position of the extra six amino acids. This insertion occurs at a position that corresponds to a splice junction in the chicken and human c-
src
genes. The isolated c-
src
cDNA clone encodes a protein that displays an identical V8 peptide pattern to that observed in pp60

c-
src

isolated from tissues of neuronal origin.
Nuclear Reassembly Excludes Large Macromolecules
Authors: Swanson Joel A. , McNeil Paul L.
Published: October 2006

Interphase nucleus and cytoplasm are distinct compartments, whose soluble macromolecular contents mix when the nuclear envelope disassembles at mitosis. To determine how their interphase identities are reestablished, fibroblasts were loaded with fluorescent dextrans and then allowed to divide. Large dextrans (molecular weight of 40,000 or more) were excluded from condensed mitotic chromosomes and from newly formed, postmitotic interphase nuclei. Therefore, postmitotic reassembly of the nucleus as a compartment distinct from cytoplasm occurs by exclusion not only of organelles but also of soluble macromolecules. This might occur by exclusion of macromolecules from condensed chromatin throughout mitosis and completion of nuclear envelope assembly before nuclear expansion.
Microtubule Gelation-Contraction: Essential Components and Relation to Slow Axonal Transport
Authors: Weisenberg Richard C. , Flynn James , Gao Baochong , Awodi Shuaibu , Skee Frank , Goodman Steven R. , Riederer Beat M.
Published: October 2006

Preparations of microtubule proteins isolated by assembly and disassembly undergo gelation-contraction after addition of adenosine triphosphate (ATP). A particulate fraction from these preparations that is required, along with purified tubulin, to produce ATP-dependent microtubule gelation-contraction in vitro has been isolated. The particulates exhibited microtubule-stimulated adenosine triphosphatase activity and moved slowly (about 1 micrometer per minute) along microtubule walls in the presence of ATP. The particulates contained tubulin, neurofilament, and spectrin polypeptides. The composition, solubility, and motility of the particulates are consistent with those of slow component a of axonal transport.
Signal for Attachment of a Phospholipid Membrane Anchor in Decay Accelerating Factor
Authors: Caras Ingrid W. , Weddell Gregory N. , Davitz Michael A. , Nussenzweig Victor , Martin David W.
Published: October 2006

Decay accelerating factor (DAF) belongs to a novel group of membrane proteins anchored to the cell surface by a glycophospholipid membrane anchor that is covalently attached to the carboxyl terminus of the protein. The last 37 amino acids of membrane DAF, when fused to the carboxyl terminus of a secreted protein, are sufficient to target the fusion protein to the plasma membrane by means of a glycophospholipid anchor. This approach provides a novel means of targeting proteins to the cell-surface membrane.
Voltage-Sensitive Calcium Channels in Normal and Transformed 3T3 Fibroblasts
Authors: Chen Chinfei , Corbley Michael J. , Roberts Thomas M. , Hess Peter
Published: October 2006

Patch clamp recordings of whole-cell and single channel currents revealed the presence of two voltage-sensitive calcium channel types in the membrane of 3T3 fibroblasts. The two calcium channel types were identified by their unitary properties and pharmacological sensitivities. Both calcium channel types were present in all control 3T3 cells, but one type was selectively suppressed in 3T3 cells that had been transformed by activated c-H-
ras
, EJ-
ras
, v-
fms
, or polyoma middle T oncogenes. The presence of voltage-sensitive calcium channels in these nonexcitable cells and the control of their functional expression by transforming oncogenes raises questions about their role in the control of calcium-sensitive processes such as cell motility, cytoskeletal organization, and cell growth.
Magnetic Flux Transport on the Sun
Authors: Wang Y. -M. , Nash A. G. , Sheeley N. R.
Published: October 2006

Although most of the magnetic flux observed on the sun originates in the low-latitude sunspot belts, this flux is gradually dispersed over a much wider range of latitudes by supergranular convective motions and meridional circulation. Numerical simulations show how these transport processes interact over the 11-year sunspot cycle to produce a strong "topknot" polar field, whose existence near sunspot minimum is suggested by the observed strength of the interplanetary magnetic field and by the observed areal extent of polar coronal holes. The required rates of diffusion and flow are consistent with the decay rates of active regions and with the rotational properties of the large-scale solar magnetic field.
Rate of Formation of the ClO Dimer in the Polar Stratosphere: Implications for Ozone Loss
Authors: Sander Stanley P. , Friedl Randall R. , Yung Yuk L.
Published: October 2006

The gas-phase recombination of chlorine monoxide (ClO) has been investigated under the conditions of pressure and temperature that prevail in the Antarctic stratosphere during the period of maximum ozone (O
3
) disappearance. Measured rate constants are less than one-half as great as the previously accepted values. One-dimensional model calculations based on the new rate data indicate that currently accepted chemical mechanisms can quantitatively account for the observed O
3
losses in late spring (17 September to 7 October). A qualitative assessment indicates that the existing mechanisms can only account for at most one-half of the measured O
3
depletion in the early spring (28 August to 17 September), indicating that there may be additional catalytic cycles, besides those currently recognized, that destroy O
3
.
Pre-Mesozoic Palinspastic Reconstruction of the Eastern Great Basin (Western United States)
Authors: Levy Marjorie , Christie-Blick Nicholas
Published: October 2006

The Great Basin of the western United States has proven important for studies of Proterozoic and Paleozoic geology [2500 to 245 million years ago (Ma)] and has been central to the development of ideas about the mechanics of crustal shortening and extension. An understanding of the deformational history of this region during Mesozoic and Cenozoic time (245 Ma to the present) is required for palinspastic reconstruction of now isolated exposures of older geology in order to place these in an appropriate regional geographic context. Considerable advances in unraveling both the crustal shortening that took place during Mesozoic to early Cenozoic time (especially from about 150 to 50 Ma) and the extension of the past 37 million years have shown that earlier reconstructions need to be revised significantly. A new reconstruction is developed for rocks of middle Proterozoic to Early Cambrian age based on evidence that total shortening by generally east-vergent thrusts and folds was at least 104 to 135 kilometers and that the Great Basin as a whole accommodated ∼250 kilometers of extension in the direction 287° ± 12° between the Colorado Plateau and the Sierra Nevada. Extension is assumed to be equivalent at all latitudes because available paleomagnetic evidence suggests that the Sierra Nevada experienced little or no rotation with respect to the extension direction since the late Mesozoic. An estimate of the uncertainty in the amount of extension obtained from geological and paleomagnetic uncertainties increases northward from ±56 kilometers at 36°30′N to
-87
+108
kilometers at 40°N. On the basis of the reconstruction, the original width of the preserved part of the late Proterozoic and Early Cambrian basin was about 150 to 300 kilometers, about 60 percent of the present width, and the basin was oriented slightly more north-south with respect to present-day coordinates.
Duchenne Muscular Dystrophy Gene Expression in Normal and Diseased Human Muscle
Authors: Scott M. Oronzi , Sylvester J. E. , Heiman-Patterson T. , Shi Y.-J. , Fieles W. , Stedman H. , Burghes A. , Ray P. , Worton R. , Fischbeck K. H.
Published: October 2006

A probe for the 5′ end of the Duchenne muscular dystrophy (DMD) gene was used to study expression of the gene in normal human muscle, myogenic cell cultures, and muscle from patients with DMD. Expression was found in RNA from normal fetal muscle, adult cardiac and skeletal muscle, and cultured muscle after myoblast fusion. In DMD muscle, expression of this portion of the gene was also revealed by in situ RNA hybridization, particularly in regenerating muscle fibers.
HIV-1 Reverse Transcriptase Is a Target for Cytotoxic T Lymphocytes in Infected Individuals
Authors: Walker Bruce D. , Flexner Charles , Paradis Timothy J. , Fuller Thomas C. , Hirsch Martin S. , Schooley Robert T. , Moss Bernard
Published: October 2006

Characterization of the host immune response to human immunodeficiency virus type 1 (HIV-1) is critical to the rational design of an effective AIDS vaccine. In this study, cytotoxic T lymphocytes (CTL) specific for HIV-1 reverse transcriptase (RNA-dependent DNA polymerase) were found in blood samples from HIV-1-infected individuals. CTL targets were prepared by immortalizing B cells from ten seropositive and six seronegative individuals, and then infecting these cells with recombinant vaccinia viruses containing HIV-1 genes. CTL directed against autologous B lymphoblasts expressing HIV-1 reverse transcriptase were detected in fresh blood samples from eight HIV-1 seropositive subjects, but in no seronegative controls. The effector cells were identified as major histocompatibility complex-restricted CD3+CD8+ lymphocytes. Because the HIV-1
pol
gene is highly conserved among different isolates and generates both humoral and cellular immune responses, it bears consideration for inclusion in a candidate AIDS vaccine.
Amiloride Selectively Blocks the Low Threshold (T) Calcium Channel
Authors: Tang Cha-Min , Presser Fernando , Morad Martin
Published: October 2006

More than one type of voltage-gated calcium channel has been identified in muscle cells and neurons. Many specific organic and inorganic blockers of the conventional, slowly inactivating high threshold (L) calcium channel have been reported. No specific blockers of the low threshold (T) channel have been as yet identified. Amiloride, a potassium sparing diuretic, has now been shown to selectively block the low threshold calcium channel in mouse neuroblastoma and chick dorsal root ganglion neurons. The selective blockade of the T-type calcium channel will allow identification of this channel in different tissues and characterization of its specific physiological role.
Sustained Dendritic Gradients of Ca
2+
Induced by Excitatory Amino Acids in CA1 Hippocampal Neurons
Authors: Connor John A. , Wadman Wytse J. , Hockberger Philip E. , Wong Robert K. S.
Published: October 2006

Spatially resolved measurements of intracellular free calcium and of the changes produced by excitatory amino acids were made in neurons isolated from adult mammalian brain. Extremely long-lasting (minutes) Ca
2+
gradients were induced in the apical dendrites of hippocampal CA1 neurons after brief (1 to 3 seconds), local application of either glutamate or
N
-methyl-D-aspartate (NMDA). These gradients reflect the continuous flux of Ca
2+
into the dendrite. The sustained gradients, but not the immediate transient response to the agonists, were prevented by prior treatment with the protein kinase C inhibitor sphingosine. Expression of the long-lasting Ca
2+
gradients generally required a priming or conditioning stimulus with the excitatory agonist. The findings demonstrate a coupling between NMDA receptor activation and long-lasting intracellular Ca
2+
elevation that could contribute to certain use-dependent modifications of synaptic responses in hippocampal CA1 neurons.
DNA and RNA Sequence Determination Based on Phosphorothioate Chemistry
Authors: Gish Gerald , Eckstein Fritz
Published: October 2006

The difference in reactivity between phosphate and phosphorothioate diesters is the basis of a chemical degradation scheme for the sequencing of DNA and RNA. The phosphorothioate groups are incorporated into the nucleic acid in four separate enzymatic reactions, with three of the natural nucleoside triphosphates and one α-thiotriphosphate in each reaction. Selective strand cleavage is achieved through alkylation to form the hydrolytically labile phosphorothioate triester. As an example, the sequence analysis is presented of M13 phage DNA and of RNA prepared by transcription with SP6 RNA polymerase.
Synaptic Transmission Between Dissociated Adult Mammalian Neurons and Attached Synaptic Boutons
Authors: Drewe John A. , Childs Gwendolyn V. , Kunze Diana L.
Published: October 2006

In most studies of synaptic currents in mammalian central neurons, preparations have been used in which synaptic currents are recorded at some distance from the synapse itself. This procedure introduces problems in interpretation of the kinetics and voltage-dependent properties of the synaptic current. These problems have now been overcome by the development of a preparation in which presynaptic vesicle-containing boutons have been coisolated with the soma of individual neurons, thus providing the opportunity to study synaptic currents under conditions of both adequate voltage control and internal ionic perfusion. Spontaneous synaptic currents mediated by γ-aminobutyric acid and excitatory amino acids were recorded from neurons isolated from a mammalian medial solitary tract nucleus. Calcium- and depolarization-dependent spontaneous currents of several to hundreds of picoamperes occurred with rapid rise times of 0.8 to 3 milliseconds and decays at least ten times as long.
Recent Developments in Analytical Chromatography
Authors: Novotny Milos V.
Published: October 2006

Capillary gas chromatography (GC) is rapidly reaching a state of maturity. Recent advances in GC include new highly selective and stable open-tubular columns, capillary sampling techniques, and element-sensitive (plasma) detectors. An impressive growth of modern liquid chromatography continues with an emphasis on the separation of biopolymers, new silica-based and stable polymeric packings, microcolumn techniques, electroosmotically driven separations, and ultrasensitive detection. Supercritical fluid chromatography has gained considerable attention primarily because of its distinctive detection capabilities. Novel combinations of chromatographic techniques with each other, or with spectroscopic methods, continue to be explored.