bluuebunny/crossref_metadata_2025 huggingface dataset:
Depolarization Without Calcium Can Release γ-Aminobutyric Acid from a Retinal Neuron
Authors: Schwartz Eric A.
Published: October 2006

Calcium influx is often an essential intermediate step for the release of neurotransmitter. However, some retinal neurons appear to release transmitter by a mechanism that does not require calcium influx. It was uncertain whether depolarization released calcium from an intracellular store or released transmitter by a mechanism that does not require calcium. The possibility that voltage, and not calcium, can regulate the release of transmitter was studied with pairs of solitary retinal neurons. Horizontal and bipolar cells were isolated from fish retinas and juxtaposed in culture. Communication between them was studied with electrophysiological methods. A horizontal cell released its neurotransmitter, γ-aminobutyric acid, when depolarized during conditions that buffered the internal calcium concentration and prohibited calcium entry. The speed and amount of material released were sufficient for a contribution to synaptic transmission.
Synaptic Reorganization in the Hippocampus Induced by Abnormal Functional Activity
Authors: Sutula Thomas , He Xiao-Xian , Cavazos Jose , Scott Grayson
Published: October 2006

Abnormal functional activity induces long-lasting physiological alterations in neural pathways that may play a role in the development of epilepsy. The cellular mechanisms of these alterations are not well understood. One hypothesis is that abnormal activity causes structural reorganization of neural pathways and promotes epileptogenesis. This report provides morphological evidence that synchronous perforant path activation and kindling of limbic pathways induce axonal growth and synaptic reorganization in the hippocampus, in the absence of overt morphological damage. The results show a previously unrecognized anatomic plasticity associated with synchronous activity and development of epileptic seizures in neural pathways.
Spectral Reflectance Properties of Hydrocarbons: Remote-Sensing Implications
Authors: Cloutis Edward A.
Published: October 2006

The spectral reflectance properties of bituminous tar sands were examined in the wavelength range from 0.35 to 2.6 micrometers. Unique absorption features due to all the major phases, except quartz, appear in the spectra. The intensities of the absorption features correlate with the abundances of the various phases. The results of this study have applications to the remote sensing of many terrestrial and extraterrestrial targets because of potential similarities between tar sand and other hydrocarbon occurrences. For example, it is found that highly polymerized hydrocarbons are a plausible constituent of the dark material on one of Saturn's satellites, Iapetus.
Experiments on Hydraulic Jumps in Turbidity Currents Near a Canyon-Fan Transition
Authors: Garcia Marcelo , Parker Gary
Published: October 2006

The point at which a submarine canyon debouches on its associated abyssal fan is generally characterized by a drop in channel slope. Turbidity currents of the kind responsible for the genesis of the canyon and fan should display an internal hydraulic jump near the slope transition. No direct field observations of any such jump appear, however, to have been made. Experiments on the nature of the jump and the resulting sedimentary deposits indicate that the thickness of the deposits just downstream of the jump tends to increase as the ratio of bed shear velocity immediately behind the jump to particle fall velocity decreases.
Aerosols, Cloud Microphysics, and Fractional Cloudiness
Authors: Albrecht Bruce A.
Published: October 2006

Increases in aerosol concentrations over the oceans may increase the amount of low-level cloudiness through a reduction in drizzle—a process that regulates the liquid-water content and the energetics of shallow marine clouds. The resulting increase in the global albedo would be in addition to the increase due to enhancement in reflectivity associated with a decrease in droplet size and would contribute to a cooling of the earth's surface.
Cell and Environment Interactions in Tumor Microregions: The Multicell Spheroid Model
Authors: Sutherland Robert M.
Published: October 2006

Abnormal vascularization of malignant tumors is associated with the development of microregions of heterogeneous cells and environments. Experimental models such as multicell spheroids and a variety of new techniques are being used to determine the characteristics of these microregions and to study the interactions of the cells and microenvironments. The special cellular microecology of tumors influences responsiveness to therapeutic agents and has implications for future directions in cancer research.
The Early Radiation and Relationships of the Major Arthropod Groups
Authors: Briggs Derek E. G. , Fortey Richard A.
Published: October 2006

Cambrian arthropods are now well known, but there has been little agreement on how they contribute to an understanding of arthropod phylogeny. Fossils have either been lumped together as "trilobitomorphs" or, more recently, have been the subject of speculation invoking a multiple polyphyletic origin of arthropods. Cladistic analysis of characters of Cambrian and living representatives (excluding Uniramia) shows that trilobites and chelicerates are relatively advanced compared with 'crustaceans,' and there are doubts whether the latter constitute a natural group. An undue emphasis on singular autapomorphies of problematic fossils has obscured these relationships in the past. "Trilobitomorphs" were simply an artificial taxon based on shared primitive characters. The arthropods that evolved during the Cambrian radiation show no more apparent morphological diversity than do the living groups. The evidence of well-preserved problematica is critical to understanding the nature of this radiation and the affinities of the groups that remain today.
Holocene—Late Pleistocene Climatic Ice Core Records from Qinghai-Tibetan Plateau
Authors: Thompson L. G. , Mosley-Thompson E. , Davis M. E. , Bolzan J. F. , Dai J. , Klein L. , Yao T. , Wu X. , Xie Z. , Gundestrup N.
Published: October 2006

Three ice cores to bedrock from the Dunde ice cap on the north-central Qinghai-Tibetan Plateau of China provide a detailed record of Holocene and Wisconsin-Würm late glacial stage (LGS) climate changes in the subtropics. The records reveal that LGS conditions were apparently colder, wetter, and dustier than Holocene conditions. The LGS part of the cores is characterized by more negative δ
18
O ratios, increased dust content, decreased soluble aerosol concentrations, and reduced ice crystal sizes than the Holocene part. These changes occurred rapidly ∼10,000 years ago. In addition, the last 60 years were apparently one of the warmest periods in the entire record, equalling levels of the Holocene maximum between 6000 and 8000 years ago.
The Origins of Ceramic Technology at Dolni Věstonice, Czechoslovakia
Authors: Vandiver Pamela B. , Soffer Olga , Klima Bohuslav , Svoboda JiŘi
Published: October 2006

A typology was established for more than 5000 ceramic artifacts at Dolni Vestonice, Czechoslovakia. Conjectured methods of manufacture were confirmed by radiography. The compositions and mineralogy of the artifacts were identical to those of the local soil, loess. A firing temperature range of 500° to 800°C was measured and compared with those of hearths and kilns. The mechanism of sintering was impurity-initiated, liquid-phase sintering. Many fracture sections show evidence of thermal shock, although thermal expansion of the loess is low. The making, firing, and sometimes exploding of the figurines may have been the prime function of the ceramics at this site rather than being manufactured as permanent, portable objects.
Predator-Induced Life-History Shifts in a Freshwater Snail
Authors: Crowl Todd A. , Covich Alan P.
Published: October 2006

The snail
Physella virgata virgata,
a widely distributed freshwater pulmonate, was observed to change its life-history characteristics in the presence of the crayfish
Orconectes virilis
in spring-fed Oklahoma streams. These changes were apparently initiated by a water-borne cue released when crayfish fed on conspecific snails. In the presence of the cue, snails exhibited rapid growth rates and little reproduction until they reached a size of about 10 mm after 8 months. In the absence of the cue, snails typically grew to about 4 mm (3.5 months) and then began reproduction. The chemically inducible shift indicates that the life histories of these snails are phenotypically plastic. By increasing the variance associated with size and age of maturity, prey may increase the likelihood of coexisting with seasonal predators.
Orientational Dielectric Relaxation of Collisionless Molecules
Authors: Farley Francis W. , McClelland Gary M.
Published: October 2006

The generation of the orientation component of the polarization of matter in an electric field has previously been thought to require interaction of molecules with their neighbors. It is demonstrated that, even in the absence of collisions between neighboring molecules, hot isolated polyatomic molecules can reorient in response to an external field, thereby giving rise to the orientation component of polarization. This reorientation occurs through the interaction of rotation with molecular vibrations, which provides a heat bath to establish thermal rotational equilibrium. This effect is demonstrated for
o
-difluorobenzene,
o
-dichlorobenzene, and
p
-chlorotoluene, with an inhomogeneous electric field used to deflect molecular beams of these molecules.
Scanning Tunneling Microscopy of Nucleic Acids
Authors: Lee Gil , Arscott Patricia G. , Bloomfield Victor A. , Evans D. Fennell
Published: October 2006

The scanning tunneling microscope (STM) has been used to measure properties of poly(rA)⋅poly(rU) and DNA, such as helical pitch, half-period oscillations that were interpreted as the alternation between the major and minor grooves, and interhelical spacing. Average pitches were measured by two-dimensional Fourier transforms and by topographic profiles along the fiber axes. Values were typically 7 percent less than standard dimensions of A-form RNA and B-form DNA fibers. This result is compatible with the mild dehydration that occurred under air-drying conditions. More extensive dehydration typically led to 19 percent shrinkage. Analysis of specific regions allowed local variations in helical pitch as small as 1 angstrom to be detected, thus demonstrating that the STM can visualize functionally significant modulations of nucleic acid structure.
High-Resolution Epitope Mapping of hGH-Receptor Interactions by Alanine-Scanning Mutagenesis
Authors: Cunningham Brian C. , Wells James A.
Published: October 2006

A strategy, called alanine-scanning mutagenesis, was used to identify specific side chains in human growth hormone (hGH) that strongly modulate binding to the hGH receptor cloned from human liver. Single alanine mutations (62 in total) were introduced at every residue contained within the three discontinuous segments of hGH (residues 2 to 19, 54 to 74, and 167 to 191) that have been implicated in receptor recognition. The alanine scan revealed a cluster of a dozen large side chains that when mutated to alanine each showed more than a four times lower binding affinity to the hGH receptor. Many of these residues that promote binding to the hGH receptor are altered in homologs of hGH (such as placental lactogens and prolactins) that do not bind tightly to the hGH receptor. The overall folding of these mutant proteins was indistinguishable from that of the wild-type hGH, as determined by strong cross-reactivities with seven different conformationally sensitive monoclonal antibodies. The alanine scan also identified at least one side chain, Glu
174
, that hindered binding because when it was mutated to alanine the receptor affinity increased by more than a factor of four.
Identification of the Cystic Fibrosis Gene: Cloning and Characterization of Complementary DNA
Authors: Riordan John R. , Rommens Johanna M. , Kerem Bat-Sheva , Alon Noa , Rozmahel Richard , Grzelczak Zbyszko , Zielenski Julian , Lok Si , Plavsic Natasa , Chou Jia-Ling , Drumm Mitchell L. , Iannuzzi Michael C. , Collins Francis S. , Tsui Lap-Chee
Published: October 2006

Overlapping complementary DNA clones were isolated from epithelial cell libraries with a genomic DNA segment containing a portion of the putative cystic fibrosis (CF) locus, which is on chromosome 7. Transcripts, approximately 6500 nucleotides in size, were detectable in the tissues affected in patients with CF. The predicted protein consists of two similar motifs, each with (i) a domain having properties consistent with membrane association and (ii) a domain believed to be involved in ATP (adenosine triphosphate) binding. A deletion of three base pairs that results in the omission of a phenylalanine residue at the center of the first predicted nucleotide-binding domain was detected in CF patients.
Ultrahigh-Pressure Melting of Lead: A Multidisciplinary Study
Authors: Godwal B. K. , Meade Charles , Jeanloz Raymond , Garcia Alberto , Liu Amy Y. , Cohen Marvin L.
Published: October 2006

Measurements of the melting temperature of lead, carried out to pressures of 1 megabar (10
11
pascal) and temperatures near 4000 kelvin by means of a laser-heated diamond cell, are in excellent agreement with the results of previous shock-wave experiments. The data are analyzed by means of first principles quantum mechanical calculations, and the agreement documents the reliability of current experimental and theoretical techniques for studies of melting at ultrahigh pressures. These studies have potentially wide-ranging applications, from planetary science to condensed matter physics.
Coral-Bryozoan Mutualism: Structural Innovation and Greater Resource Exploitation
Authors: McKinney Frank K. , Broadhead Thomas W. , Gibson Michael A.
Published: October 2006

Shell-encrusting species of the coral
Aulopora
and the bryozoan
Leioclema
changed ecological guilds and escaped limits imposed by substrate size through mutualistic intergrowth during the Early Devonian. Where colonies of these species intergrew, they produced upright, arborescent masses consisting of sparsely branched uniserial
Aulopora
sp. entirely covered, except for calyx openings, by a thin encrustation of
Leioclema
sp. These intergrowths appear to constitute a mutualistic association with benefits including escape from limited space on the substratum into a higher tier of suspension feeders, as well as more modules per colony. Such mutualism between benthic modular competitors may have developed more readily than associations between solitary competitors.
Biomimetic Total Synthesis of
Proto
-Daphniphylline
Authors: Piettre Serge , Heathcock Clayton H.
Published: October 2006

Proto
-daphniphylline, the imputed biogenetic parent of the
Daphniphyllum
alkaloids, has been assembled in a biogenetically styled laboratory synthesis in which a pentacyclization process is the fundamental synthetic stratagem. This extraordinary transformation involves the formation of six σ-bonds under the influence of three elementary reagents—potassium hydroxide, ammonia, and acetic acid. The facility of the process adds credibility to the previous speculation that a similar process is an important step in the biosynthesis of the
Daphniphyllum
alkaloids.
Synthesis of Phytoalexins in Sorghum as a Site-Specific Response to Fungal Ingress
Authors: Snyder Beth A. , Nicholson Ralph L.
Published: October 2006

Sorghum produces phytoalexins that are 3-deoxyanthocyanidin flavonoids. The compounds inhibit the growth of phytopathogenic fungi in vitro. The phytoalexins appear to be synthesized in subcellular inclusions within a host epidermal cell that is about to be penetrated by a fungus. This site-restricted synthesis suggests that the phytoalexin response occurs initially in the first cells that come under fungal attack and is not simply a response of cells that surround the original infection site.
A Thiosulfate Shunt in the Sulfur Cycle of Marine Sediments
Authors: Jørgensen Bo Barker
Published: October 2006

The oxidation of sulfide, generated by bacterial sulfate reduction, is a key process in the biogeochemistry of marine sediments, yet the pathways and oxidants are poorly known. By the use of
35
S-tracer studies of the S cycle in marine and freshwater sediments, a novel shunt function of thiosulfate (S
2
O
3
2-
) was identified. The S
2
O
3
2-
constituted 68 to 78 percent of the immediate HS
-
-oxidation products and was concurrently (i) reduced back to HS
-
, (ii) oxidized to SO
4
2-
, and (iii) disproportionated to HS
-
+ SO
4
2-
. The small thiosulfate pool is thus involved in a dynamic HS
-
- S
2
O
3
2-
cycle in anoxic sediments. The disproportionation of thiosulfate may help account for the large difference in isotopic composition (
34
S/
32
S) of sulfate and sulfides in sediments and sedimentary rocks.
Hind Limbs of Eocene
Basilosaurus:
Evidence of Feet in Whales
Authors: Gingerich Philip D. , Smith B. Holly , Simons Elwyn L.
Published: October 2006

New specimens of middle Eocene
Basilosaurus isis
from Egypt include the first functional pelvic limb and foot bones known in Cetacea. These are important in corroborating the intermediate evolutionary position of archaeocetes between generalized Paleocene land mammals that used hind limbs in locomotion and Oligocene-to-Recent whales that lack functional pelvic limbs. The foot is paraxonic, consistent with derivation from mesonychid Condylarthra. Hind limbs of
Basilosaurus
are interpreted as copulatory guides.
Optical Matter: Crystallization and Binding in Intense Optical Fields
Authors: Burns Michael M. , Fournier Jean-Marc , Golovchenko Jene A.
Published: October 2006

Properly fashioned electromagnetic fields coupled to microscopic dielectric objects can be used to create arrays of extended crystalline and noncrystalline structures. Organization can be achieved in two ways: In the first, dielectric matter is transported in direct response to the externally applied standing wave optical fields. In the second, the external optical fields induce interactions between dielectric objects that can also result in the creation of complex structures. In either case, these new ordered structures, whose existence depends on the presence of both light and polarizable matter, are referred to as
optical matter
.
In Situ Interfacial Mass Detection with Piezoelectric Transducers
Authors: Ward Michael D. , Buttry Daniel A.
Published: October 2006

The converse piezoelectric effect, in which an electric field applied across a piezoelectric material induces a stress in that material, has spurred many recent developments in mass measurement techniques. These methods commonly rely on the changes in the vibrational resonant frequency of piezoelectric quartz oscillators that result from changes in mass on the surface of the oscillator. The dependence of frequency on mass has been exploited extensively for mass measurements in vacuum or gas phase, for example, thickness monitors for thin-film preparation and sensors for chemical agents. Advances in piezoelectric methodology in the last decade now allow dynamic measurements of minute mass changes (< 10
-9
grams per square centimeter) at surfaces, thin films, and electrode interfaces in liquid media as well. Mass measurements associated with a diverse collection of interfacial processes can be readily performed, including chemical and biological sensors, reactions catalyzed by enzymes immobilized on surfaces, electron transfer at and ion exchange in thin polymer films, and doping reactions of conducting polymers.
Spreading of Liquids on Highly Curved Surfaces
Authors: Quéré David , di Meglio Jean-Marc , Brochard-Wyart Françoise
Published: October 2006

Because of surface tension, liquid films coating fibers or the insides of capillary tubes are usually unstable and break up into a periodic array of droplets. However, if these films are very thin (of thickness in the range of tens of angstroms), they can be stabilized by long-range van der Waals forces. A simple method for making such wetting films consists of slowly drawing the fiber out of a bath of liquid; the thickness of the film is then measured using a method based on gas chromatography. If these liquid films are thick, and are forced to flow, they may then not break up: the instability becomes "saturated."
Atmospheric Carbon Dioxide Levels Over Phanerozoic Time
Authors: Berner Robert A.
Published: October 2006

A new model has been constructed for calculating the level of atmospheric CO
2
during the past 570 million years. A series of successive steady states for CO
2
is used in order to calculate CO
2
level from a feedback function for the weathering of silicate minerals. Processes considered are: sedimentary burial of organic matter and carbonates; continental weathering of silicates, carbonates, and organic matter; and volcanic and metamorphic degassing of CO
2
. Sediment burial rates are calculated with the use of an isotope mass-balance model and carbon isotopic data on ancient seawater. Weathering rates are calculated from estimates of past changes in continental land area, mean elevation, and river runoff combined with estimates of the effects of the evolution of vascular land plants. Past degassing rates are estimated from changes in the rate of generation of sea floor and the shift of carbonate deposition from platforms to the deep sea. The model results indicate that CO
2
levels were high during the Mesozoic and early Paleozoic and low during the Permo-Carboniferous and late Cenozoic. These results correspond to independently deduced Phanerozoic paleoclimates and support the notion that the atmospheric CO
2
greenhouse mechanism is a major control on climate over very long time scales.
Rapid Determination of the Critical Temperature in Simulated Annealing Inversion
Authors: Basu Atanu , Frazer L. Neil
Published: October 2006

Knowledge of the critical temperature,
T
*
, the temperature at which a phase change occurs, greatly improves the efficiency of simulated annealing when used for optimization or inversion. A numerical method of accurately determining
T
*
in a relatively short computation time has been developed. This method is used to recover the seismic soundspeed profile from wavefield data, a problem in which cycle skipping causes many local minima of the energy function and the averaging of the medium by finite length waves results in many states with similar energies. Computations indicate that it is cost-effective to spend about 80 percent of the computing budget looking for
T
*
instead of annealing, and that in the course of finding
T
*
many states with energies near the global minimum will also be found. The a posteriori probability distribution of the solution has been constructed from trial solutions generated at
T
*
.
Mechanism of Interleukin-2 Signaling: Mediation of Different Outcomes by a Single Receptor and Transduction Pathway
Authors: Tigges Michael A. , Casey Leslie S. , Koshland Marian Elliott
Published: October 2006

The T cell lymphokine, interleukin-2 (IL-2), plays a pivotal role in an immune response by stimulating antigen-activated B lymphocytes to progress through the cell cycle and to differentiate into antibody-secreting cells. An IL-2 inducible B lymphoma line, in which the growth and differentiation responses are uncoupled, provides a model system for dissecting the signaling mechanisms operating in each response. This system was used to show that both signals are initiated by IL-2 binding to a single, unifunctional receptor complex. Moreover, both signals are transduced by a pathway that does not involve any known second messenger system and that can be blocked by a second T cell lymphokine, interleukin 4. These findings suggest that the pleiotrophic effects of IL-2 are determined by different translations of the signal in the nucleus.
Structure of Recombinant Human Renin, a Target for Cardiovascular-Active Drugs, at 2.5 Å Resolution
Authors: Sielecki Anna R. , Hayakawa Koto , Fujinaga Masao , Murphy Michael E. P. , Fraser Marie , Muir Alastair K. , Carilli Cynthia T. , Lewicki John A. , Baxter John D. , James Michael N. G.
Published: October 2006

The x-ray crystal structure of recombinant human renin has been determined. Molecular dynamics techniques that included crystallographic data as a restraint were used to improve an initial model based on porcine pepsinogen. The present agreement factor for data from 8.0 to 2.5 angstroms (Å) is 0.236. Some of the surface loops are poorly determined, and these disordered regions border a 30 Å wide solvent channel. Comparison of renin with other aspartyl proteinases shows that, although the structural cores and active sites are highly conserved, surface residues, some of which are critical for specificity, vary greatly (up to 10 Å). Knowledge of the actual structure, as opposed to the use of models based on related enzymes, should facilitate the design of renin inhibitors.
G
olf
: an Olfactory Neuron Specific-G Protein Involved in Odorant Signal Transduction
Authors: Jones David T. , Reed Randall R.
Published: October 2006

Biochemical and electrophysiological studies suggest that odorants induce responses in olfactory sensory neurons via an adenylate cyclase cascade mediated by a G protein. An olfactory-specific guanosine triphosphate (GTP)-binding protein α subunit has now been characterized and evidence is presented suggesting that this G protein, termed G
olf
, mediates olfaction. Messenger RNA that encodes G
olfα
is expressed in olfactory neuroephithelium but not in six other tissues tested. Moreover, within the olfactory epithelium, G
olfα
appears to be expressed only by the sensory neurons. Specific antisera were used to localize G
olfα
protein to the sensory apparatus of the receptor neurons. G
olfα
shares extensive amino acid identity (88 percent) with the stimulatory G protein, G
sα
. The expression of G
olfα
in S49 cyc
-
kin
-
cells, a line deficient in endogenous stimulatory G proteins, demonstrates its capacity to stimulate adenylate cyclase in a heterologous system.
Chaotic Motion of Europa and Ganymede and the Ganymede-Callisto Dichotomy
Authors: Tittemore William C.
Published: October 2006

Europa and Ganymede may have undergone an episode of chaotic motion before the establishment of the current Laplace resonance involving the three inner Galilean satellites. During this episode, the orbital eccentricities of both satellites may have increased dramatically. As a result, the mechanical stresses due to tidal deformation of the satellites' icy lithospheres may have been large enough to result in extensive fracturing, and tidal heating may have melted water ice in the mantles of both satellites, triggering the geological activity that has modified their surfaces since the heavy cratering period. The tidal effects on Ganymede during this episode provide an explanation of the dichotomy between it and Callisto, which have similar bulk properties but very different geological histories.
Human Origins
Authors: Simons Elwyn L.
Published: October 2006

New discoveries combine to indicate that all the major steps in human evolution took place in Africa. Skeletal analysis of oldest human forbears around 3 million years ago reveal many anatomical similarities to African Great Apes. These and biochemical resemblances indicate a common ancestry for humans and apes, perhaps only a few million years earlier. Enlarged knowledge through recent recovery of skeletons of several successive stages in the line leading to modern peoples shows that many attributes or skills by which we define humanity arose much more recently in time than heretofore believed.
Constraints on the Diameter and Albedo of 2060 Chiron
Authors: Sykes Mark V. , Walker Russell G.
Published: October 2006

Asteroid 2060 Chiron is the largest known object exhibiting cometary activity. Radiometric observations made in 1983 from a ground-based telescope and the Infrared Astronomical Satellite are used to examine the limits on Chiron's diameter and albedo. It is argued that Chiron's surface temperature distribution at that time is best described by an "isothermal latitude" or "rapid-rotator" model. Consequently, Chiron has a maximum diameter of 372 kilometers and a minimum geometric albedo of 2.7%. This is much bigger and darker than previous estimates, and suggests that gravity may play a significant role in the evolution of gas and dust emissions. It is also found that for large obliquities, surface temperatures can vary dramatically on time scales of a decade, and that such geometry may play a critical role in explaining Chiron's observed photometric behavior since its discovery in 1977.
Auger Electron Angular Distributions from Surfaces: Direct Comparison with Isoenergetic Photoelectrons
Authors: Terminello Louis J. , Barton John J.
Published: October 2006

Angular distribution patterns of Auger electrons and of photoelectrons from a Cu (001) surface were measured at the same electron kinetic energy. These measurements reveal that the low kinetic energy angular distributions for Cu Auger electrons and Cu 3
p
3/2
photoelectrons differ substantially. This direct comparison between the photoelectron and Auger electron angular distributions demonstrates that, in some circumstances, the Auger process produces a complicated source wave whose nature must be explored before Auger angular distributions can be used for surface structure analysis.
Mite-Plant Associations from the Eocene of Southern Australia
Authors: O'Dowd Dennis J. , Brew Christine R. , Christophel David C. , Norton Roy A.
Published: October 2006

Acarodomatia or "mite houses" are located on leaves of many present-day angiosperms and are inhabited by mites that may maintain leaf hygiene. Eocene deposits in southern Australia have yielded acarodomatia on fossil leaves of Elaeocarpaceae and Lauraceae and also contain oribatid mites with close affinities to those that inhabit the acarodomatia of the closest living relatives of the fossil plant taxa. The data indicate that mite-plant associations may have been widespread in southern Australia 40 million years ago.
Development of Diapiric Structures in the Upper Mantle Due to Phase Transitions
Authors: Liu M. , Yuen D. A. , Zhao W. , Honda S.
Published: October 2006

Solid-state phase transitions in time-dependent mantle convection can induce diapiric flows in the upper mantle. When a deep mantle plume rises toward phase boundaries in the upper mantle, the changes in the local thermal buoyancy, local heat capacity, and latent heat associated with the phase change at a depth of 670 kilometers tend to pinch off the plume head from the feeding stem and form a diapir. This mechanism may explain episodic hot spot volcanism. The nature of the multiple phase boundaries at the boundary between the upper and lower mantle may control the fate of deep mantle plumes, allowing hot plumes to go through and retarding the tepid ones.
The Mutations in Ashkenazi Jews with Adult G
M2
Gangliosidosis, the Adult Form of Tay-Sachs Disease
Authors: Navon Ruth , Proia Richard L.
Published: October 2006

The adult form of Tay-Sachs disease, adult G
M2
gangliosidosis, is an autosomal recessive disorder that results from mutations in the α chain of β-hexosaminidase A. This disorder, like infantile Tay-Sachs disease, is more frequent in the Ashkenazi Jewish population. A point mutation in the α-chain gene was identified that results in the substitution of Gly
269
with Ser in eight Ashkenazi adult G
M2
gangliosidosis patients from five different families. This amino acid substitution was shown to depress drastically the catalytic activity of the α chain after expression in COS-1 cells. All of these patients proved to be compound heterozygotes of the allele with the Gly to Ser change and one of the two Ashkenazi infantile Tay-Sachs alleles. These findings will aid in the diagnosis and understanding of β-hexosaminidase A deficiency disorders.
Isolation of a cDNA cLone Derived from a Blood-Borne Non-A, Non-B Viral Hepatitis Genome
Authors: Choo Qui-Lim , Kuo George , Weiner Amy J. , Overby Lacy R. , Bradley Daniel W. , Houghton Michael
Published: October 2006

A random-primed complementary DNA library was constructed from plasma containing the uncharacterized non-A, non-B hepatitis (NANBH) agent and screened with serum from a patient diagnosed with NANBH. A complementary DNA clone was isolated that was shown to encode an antigen associated specifically with NANBH infections. This clone is not derived from host DNA but from an RNA molecule present in NANBH infections that consists of at least 10,000 nucleotides and that is positive-stranded with respect to the encoded NANBH antigen. These data indicate that this clone is derived from the genome of the NANBH agent and are consistent with the agent being similar to the togaviridae or flaviviridae. This molecular approach should be of great value in the isolation and characterization of other unidentified infectious agents.
Immunologic Tolerance: Collaboration Between Antigen and Lymphokines
Authors: Nossal G. J. V.
Published: October 2006

Immunologic tolerance is the process whereby limits are placed on the degree to which lymphocytes respond to an animal's inherent antigens. It is a quantitative rather than an absolute term, as some autoantibody formation is common. Contrary to early hopes, it is not due to some single, simple causative mechanism confined to early developmental stages of the fetal immune system. Rather, self-tolerance results from a variety of complementary mechanisms and feedback loops in the immune system and is thus best seen as part of the general process of immunoregulation.
Elimination of Two Reef-Building Hydrocorals Following the 1982-83 El Niño Warming Event
Authors: Glynn P. W. , de Weerdt W. H.
Published: October 2006

One probable extinction and one range reduction of eastern Pacific reef-building hydrocoral (
Millepora
) species mark the first documented cases of species eliminations resulting from the worldwide 1980s coral reef bleaching events. Two of 12 Panamanian coral species were eliminated suddenly from their former ranges by prolonged high sea temperatures during the 1982-83 El Niño-Southern Oscillation event. Three conditions contributed to their demise: high sensitivity to sea warming, populations confined to a small geographic area, and bathymetric restriction to the euphotic zone (≤20 meters depth) where El Niño sea warming had its greatest effect.
Fallout of Pyroclastic Debris from Submarine Volcanic Eruptions
Authors: Cashman Katharine V. , Fiske Richard S.
Published: October 2006

Volcanic fallout deposits on land, being widespread and accessible for study, have received much attention and have revealed a great deal about subaerial eruption mechanisms. In contrast, virtually nothing is known about equivalent deposits produced by submarine volcanoes, despite the probable abundance of such material in today's oceans and in accreted volcanic arc terrains. Many submarine deposits may form by the fallout of debris to the sea floor downcurrent from the umbrella region of submarine eruption columns. Experiments on water-saturated pumice and pieces of rock (lithics) show that particles settling to the sea floor at terminal velocities of 10 to 50 centimeters per second will display conspicuous bimodality of particle diameters: pieces of pumice may be five to ten times as large as codeposited lithic fragments. Similar material, erupted into the air and deposited on land, displays less well-developed bimodality; pumice diameters are generally two to three times as large as associated lithics. Submarine fallout deposits are therefore distinctive and may be used to indicate a subaqueous origin for some of the great thicknesses of nonfossiliferous volcanic debris contained in ancient volcanic terrains worldwide whose environment of deposition has been uncertain.
Germline Transmission of Exogenous Genes in the Chicken
Authors: Bosselman Robert A. , Hsu Rou-Yin , Boggs Tina , Hu Sylvia , Bruszewski Joan , Ou Susan , Kozar Lee , Martin Frank , Green Cal , Jacobsen Frederick , Nicolson Margery , Schultz Joseph A. , Semon Kenneth M. , Rishell William , Stewart R. Gregory
Published: October 2006

Difficulties associated with in vitro manipulation and culture of the early chicken embryo have restricted generation of transgenic chickens to approaches that use replication-competent retroviruses. The need to produce transgenic chickens in the absence of replicating virus prompted development of a new method of gene transfer into the chicken. Microinjection of the replication-defective reticuloendotheliosis virus (REV) vector ME111 beneath unincubated chicken embryo blastoderms results in infection of germline stem cells. This vector contains genetic information exogenous to the chicken genome, including both the herpes simplex virus type 1 thymidine kinase gene and the Tn5 neomycin phosphotransferase gene. About 8 percent of male birds hatched from injected embryos contained vector DNA in their semen. All four positive males tested passed vector sequences onto their progeny. Analysis of G
1
offspring showed that gonads of G
0
male birds were mosaic with respect to insertion of vector provirus. Thus, primordial germ cells present in the unincubated chicken embryo blastoderm are susceptible to infection by defective REV vectors.
On the Social Science Contribution to Governmental Decision-Making
Authors: CHELIMSKY ELEANOR
Published: October 2006

It is often said that a major impediment to effective government is the lack of research knowledge underlying the development, implementation, and assessment of federal policies and programs. An examination is made here of the causes of (i) some continuing failures in integrating research information with decision-making and (ii) some notable successes of the past two decades in matching research capabilities with policy needs. Six recommendations are made to facilitate and further the progress that has recently been achieved.
Synorogenic Collapse: A Perspective from the Middle Crust, the Proterozoic Grenville Orogen
Authors: Mezger K. , van der Pluijm B. A. , Essene E. J. , Halliday A. N.
Published: October 2006

Structural, petrological, and geochronological studies of the middle to late Proterozoic Grenville orogen in Ontario, Canada, indicate that a major extensional fault developed synchronously with late thrusting. This fault zone was initiated during peak metamorphism and extended into the crust to depths of at least 25 kilometers. The temporal and spatial relations among faulting, metamorphism, and regional compression indicate that synorogenic collapse initiated because the crust exceeded the maximum physiographic height and thickness that could be supported by its rheology. Comparison of Grenville with recent Himalayan orogenic activity suggests that during Proterozoic times physiographic height, crustal thickness, and crustal strength were similar to modern conditions in orogenic belts.
Magma Generation on Mars: Amounts, Rates, and Comparisons with Earth, Moon, and Venus
Authors: Greeley Ronald , Schneid Byron D.
Published: October 2006

Total extrusive and intrusive magma generated on Mars over the last ∼3.8 billion years is estimated at 654 × 10
6
cubic kilometers, or 0.17 cubic kilometers per year (km
3
/yr), substantially less than rates for Earth (26 to 34 km
3
/yr) and Venus (less than 20 km
3
/yr) but much more than for the Moon (0.025 km
3
/yr). When scaled to Earth's mass the martian rate is much smaller than that for Earth or Venus and slightly smaller than for the Moon.
Oxygen Radicals in Influenza-Induced Pathogenesis and Treatment with Pyran Polymer-Conjugated SOD
Authors: Oda Tatsuya , Akaike Takaaki , Hamamoto Takayoshi , Suzuki Fujio , Hirano Takashi , Maeda Hiroshi
Published: October 2006

The pathogenicity of influenza virus infection in the mice involves, at least in part, overreaction of the immune responses of the host rather than a direct effect of virus multiplication. Xanthine oxidase, which is responsible for the generation of oxygen free radicals, was elevated in serum and lung tissue of mice infected with influenza virus. To test the theory that oxygen-free radicals are involved in pathogenesis, free radicals were removed by injecting superoxide dismutase (SOD), a specific superoxide radical scavenger, which was conjugated with a pyran copolymer. The conjugate protected mice against a potentially lethal influenza virus infection if administered 5 to 8 days after infection. These findings indicate that oxygen radicals are important in the pathogenesis of influenza virus infection, and that a polymer-conjugated SOD has therapeutic potential for this virus infection and other diseases associated with free radicals.
Isolation of Single-Copy Human Genes from a Library of Yeast Artificial Chromosome Clones
Authors: Brownstein Bernard H. , Silverman Gary A. , Little Randall D. , Burke David T. , Korsmeyer Stanley J. , Schlessinger David , Olson Maynard V.
Published: October 2006

A recently developed cloning system based on the propagation of large DNA molecules as linear, artificial chromosomes in the yeast
Saccharomyces cerevisiae
provides a potential method of cloning the entire human genome in segments of several hundred kilobase pairs. Most applications of this system will require the ability to recover specific sequences from libraries of yeast artificial chromosome clones and to propagate these sequences in yeast without alterations. Two single-copy genes have now been cloned from a library of yeast artificial chromosome clones that was prepared from total human DNA. Multiple, independent isolates were obtained of the genes encoding factor IX and plasminogen activator inhibitor type 2. The clones, which ranged in size from 60 to 650 kilobases, were stable on prolonged propagation in yeast and appear to contain faithful replicas of human DNA.
5-Bromo-2′-Deoxyuridine Blocks Myogenesis by Extinguishing Expression of MyoD1
Authors: Tapscott Stephen J. , Lassar Andrew B. , Davis Robert L. , Weintraub Harold
Published: October 2006

The pyrimidine analog 5-bromodeoxyuridine (BUdR) competes with thymidine for incorporation into DNA. Substitution of BUdR for thymidine does not significantly affect cell viability but does block cell differentiation in many different lineages. BUdR substitution in a mouse myoblast line blocked myogenic differentiation and extinguished the expression of the myogenic determination gene MyoD1. Forced expression of MyoD1 from a transfected expression vector in a BUdR-substituted myoblast overcame the block to differentiation imposed by BUdR. Activation of BUdR-substituted muscle structural genes and apparently normal differentiation were observed in transfected myoblasts. This shows that BUdR blocks myogenesis at the level of a myogenic regulatory gene, possibly MyoD1, not by directly inhibiting the activation of muscle structural genes. It is consistent with the idea that BUdR selectively blocks a class of regulatory genes, each member of which is important for the development of a different cell lineage.
Observation of Single-Electron Charging in Double-Barrier Heterostructures
Authors: Su Bo , Goldman V. J. , Cunningham J. E.
Published: October 2006

Incremental single-electron charging of size-quantized states has been observed in the well in submicrometer double-barrier resonant tunneling devices. In order to distinguish between the effects of size quantization and the single-electron charging, the heterostructure material was grown asymmetrical so that one barrier is substantially less transparent than the other. In the voltage polarity such that the emitter barrier is more transparent than the collector barrier, electrons accumulate in the well; incremental electron occupation of the well is accompanied by Coulomb blockade, which leads to sharp steps of the tunneling current. In the opposite voltage polarity the emitter barrier is less transparent than the collector barrier and the tunneling current reflects resonant tunneling through size-quantized well states.
Electrical Transport Properties of Undoped CVD Diamond Films
Authors: Pan L. S. , Pianetta P. , Kania D. R. , Han S. , Landen O. L. , Ager J. W. , Landstrass M.
Published: October 2006

Polycrystalline diamond films synthesized by microwave-assisted chemical vapor deposition (MACVD) were examined with transient photoconductivity, and two fundamental electrical transport properties, the carrier mobility and lifetime, were measured. The highest mobility measured is 50 centimeters squared per volt per second at low initial carrier densities (<10
15
per cubic centimeter). Electron-hole scattering causes the carrier mobility to decrease at higher carrier densities. Although not measured directly, the carrier lifetime was inferred to be 40 picoseconds. The average drift length of the carriers is smaller than the average grain size and appears to be limited by defects within the grains. The carrier mobility in the MACVD films is higher than values measured in lower quality dc-plasma films but is much smaller than that of single-crystal natural diamond.
Neutrophil Mac-1 and MEL-14 Adhesion Proteins Inversely Regulated by Chemotactic Factors
Authors: Kishimoto Takashi Kei , Jutila Mark A. , Berg Ellen Lakey , Butcher Eugene C.
Published: October 2006

The neutrophil Mac-1 and gp100
MEL-14
adhesion proteins are involved in neutrophil extravasation during inflammation. Both the expression and activity of Mac-1 are greatly increased after neutrophil activation. In contrast, neutrophils shed gp100
MEL-14
from the cell surface within 4 minutes after activation with chemotactic factors or phorbol esters, releasing a 96-kilodalton fragment of the antigen into the supernatant. Immunohistology showed that gp100
MEL-14
was downregulated on neutrophils that had extravasated into inflamed tissue. The gp100
MEL-14
adhesion protein may participate in the binding of unactivated neutrophils to the endothelium; rapid shedding of gp100
MEL-14
may prevent extravasation into and damage of normal tissues by activated neutrophils.
Mantle Plumes and Continental Tectonics
Authors: Hill R. I. , Campbell I. H. , Davies G. F. , Griffiths R. W.
Published: October 2006

Mantle plumes and plate tectonics, the result of two distinct modes of convection within the Earth, operate largely independently. Although plumes are secondary in terms of heat transport, they have probably played an important role in continental geology. A new plume starts with a large spherical head that can cause uplift and flood basalt volcanism, and may be responsible for regional-scale metamorphism or crustal melting and varying amounts of crustal extension. Plume heads are followed by narrow tails that give rise to the familiar hot-spot tracks. The cumulative effect of processes associated with tail volcanism may also significantly affect continental crust.
Energy Sources: A Realistic Outlook
Authors: Starr Chauncey , Searl Milton F. , Alpert Sy
Published: October 2006

Projections to the middle of the next century indicate that unabated historical global energy trends would lead to an annual global energy demand about four times present levels, primarily due to population and economic growth. But extensive global conservation and energy-efficient systems might reduce this value by half. The cumulative effect of the coming half century's use may strain the world's low-cost resources, particularly oil. The future fuel mix is further complicated by the environmental thrust to reduce the global use of carbon-based fuels. The interaction of the principal factors influencing future energy resource and technology options are projected.