bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk Within Reason
Authors: Zeckhauser Richard J. , Viscusi W. Kip
Published: October 2006

Advances in low-level risk detection threaten to engulf us with information. Regulators typically respond to each newly highlighted risk, whether painstakingly uncovered through scientific investigation or divulged with fanfare by the media, on an ad hoc basis. This response makes it hard to relate disparate risks to the overall risk level and impedes intelligent risk reduction, which must consider the costs and benefits involved. Efficient risk management requires decisions not only about what to regulate and how stringently, but also about the appropriate division of labor among the agents influencing risks. These agents include individuals, whose potential contributions too often are overlooked, corporations, and government.
Corrosion of Electronic Materials and Devices
Authors: Comizzoli R. B. , Frankenthal R. P. , Milner P. C. , Sinclair J. D.
Published: October 2006

Electronic materials and devices corrode in the same ways as automobiles, bridges, and pipelines, but their typically small dimensions make them orders of magnitude more susceptible to corrosion failure. As elsewhere, the corrosion involves interactions with the environment. Under control, these interactions can be put to use, as in the formation of protective and functional oxide films for superconducting devices. Otherwise, they cause damage, as in the electrolytic dissolution of conductors, even gold, in the presence of humidity and ionic contamination from atmospheric particles and gases. Preventing corrosion entails identifying the damaging interactions and excluding species that allow them to occur.
Seabed Materials
Authors: Broadus James M.
Published: October 2006

A large catalog of materials has been proposed as potential seabed resources, and some seabed materials such as hydrocarbons and tin already contribute to the world's economy. Scientific advances have increased our knowledge of other seabed prospects, but realization of their potential will be determined by their relative economic accessibility compared to rival resources on land. Examination of existing stocks of conventional resources, and of the economic process by which new resources are added, suggests that most potential sources of seabed materials will not be exploited in the near future. Strategic behavior in seabed materials development, however, implies that investment in exploration and R&D could proceed on a larger scale and at a more rapid pace than might be expected solely on the basis of apparent commercial potential.
Alpha-Decay—Induced Fracturing in Zircon: The Transition from the Crystalline to the Metamict State
Authors: Chakoumakos Bryan C. , Murakami Takashi , Lumpkin Gregory R. , Ewing Rodney C.
Published: October 2006

A natural single crystal of zircon, ZrSiO
4,
from Sri Lanka exhibited zonation due to alpha-decay damage. The zones vary in thickness on a scale from one to hundreds of micrometers. The uranium and thorium concentrations vary from zone to zone such that the alpha-decay dose is between 0.2 × 10
16
and 0.8 × 10
16
alpha-events per milligram (0.15 to 0.60 displacement per atom). The transition from the crystalline to the aperiodic metamict state occurs over this dose range. Differential expansion of individual layers due to variations in their alpha-decay dose caused a systematic pattern of fractures that do not propagate across aperiodic layers. High-resolution transmission electron microscopy revealed a systematic change in the microstructure from a periodic atomic array to an aperiodic array with increasing alpha-decay dose. At doses greater than 0.8 × 10
16
alpha-events per milligram there is no evidence for long-range order. This type of damage will accumulate in actinide-bearing, ceramic nuclear waste forms. The systematic pattern of fractures would occur in crystalline phases that are zoned with respect to actinide radionuclides.
Millisecond Pulsar PSR 1937+21: A Highly Stable Clock
Authors: Rawley L. A. , Taylor J. H. , Davis M. M. , Allan D. W.
Published: October 2006

The stable rotation and sharp radio pulses of PSR 1937+21 make this pulsar a clock whose long-term frequency stability approaches and may exceed that of the best atomic clocks. Improvements in measurement techniques now permit pulse arrival times to be determined in 1 hour at the Arecibo radio telescope with uncertainties of about 300 nanoseconds relative to atomic time. Measurements taken approximately every 2 weeks since November 1982 yield estimates of fractional frequency stability that continue to improve with increasing averaging time. The pulsar's frequency stability is at least as good as 6 × 10
-14
for averaging times longer than 4 months, and over the longest intervals the measurements appear to be limited by the stability of the reference atomic clocks. The data yield a firm upper limit of 7 × 10
-36
gram per cubic centimeter for the energy density of a cosmic background of gravitational radiation at frequencies of about 0.23 cycle per year. This limit corresponds to approximately 4 × 10
-7
of the density required to close the universe.
Spacelab-2 Plasma Depletion Experiments for Ionospheric and Radio Astronomical Studies
Authors: Mendillo M. , Baumgardner J. , Allen D. P. , Foster J. , Holt J. , Ellis G. R. A. , Klekociuk A. , Reber G.
Published: October 2006

The Spacelab-2 Plasma Depletion Experiments were a series of studies to examine shuttle-induced perturbations in the ionosphere and their application to ground-based radio astronomy. The space shuttle Challenger fired its orbital maneuvering subsystem engines on 30 July and 5 August 1985, releasing large amounts of exhaust molecules (water, hydrogen, and carbon dioxide) that caused the electrons and ions in Earth's upper atmosphere to chemically recombine, thereby creating so-called "ionospheric holes." Two burns conducted over New England produced ionospheric peak depletions ranging from 25 to 50 percent, affected the ionosphere over a 200-kilometer altitude range, and covered 1° to 2° of latitude. Optical emissions associated with the hole spanned an area of several hundred thousand square kilometers. A third burn was conducted over a low-frequency radio observatory in Hobart, Australia, to create an "artificial window" for ground-based observations at frequencies normally below the natural ionospheric cutoff (penetration) frequency. The Hobart experiment succeeded in making high-resolution observations at 1.7 megahertz through the induced ionospheric hole.
American Historical Archeology: Methods and Results
Authors: Deetz James
Published: October 2006

For historical archeology to be effective, research methods must be employed that ensure that both archeological and historical data be synthesized in a constructive manner. An example from Flowerdew Hundred, a Virginia plantation, illustrates such an approach. Collections from eighteen sites (1619 to 1720) were studied and dated by the inside bore diameters of pipestem fragments from clay smoking pipes. The sites grouped into three distinct categories, each with a different date. The latest group of sites (1680 to 1720) contained Colono ware, a slave produced pottery; none of the earlier sites did, although there were blacks at Flowerdew Hundred as early as 1619. On the basis of studies of probate data and other primary historical sources, it is suggested that this pattern of Colono ware occurrence is due to a change in the social and residential status of blacks during the century and that only when they lived separately from the masters did they make this type of pottery.
De Novo Design, Expression, and Characterization of Felix: a Four-Helix Bundle Protein of Native-Like Sequence
Authors: Hecht Michael H. , Richardson Jane S. , Richardson David C. , Ogden Richard C.
Published: October 2006

The protein Felix was designed de novo to fold into an antiparallel four-helix bundle of specific topology. Its sequence of 79 amino acid residues is not homologous to any known protein sequence, but is "native-like" in that it is nonrepetitive and contains 19 of the 20 naturally occurring amino acids. Felix has been expressed from a synthetic gene cloned in
Escherichia coli
, and the protein has been purified to homogeneity. Physical characterization of the purified protein indicates that Felix (i) is monomeric in solution, (ii) is predominantly α-helical, (iii) contains a designed intramolecular disulfide bond linking the first and fourth helices, and (iv) buries its single tryptophan in an apolar environment and probably in close proximity with the disulfide bond. These physical properties rule out several alternative structures and indicate that Felix indeed folds into approximately the designed three-dimensional structure.
NKR-P1, a Signal Transduction Molecule on Natural Killer Cells
Authors: Giorda Roberto , Rudert William A. , Vavassori Carla , Chambers William H. , Hiserodt John C. , Trucco Massimo
Published: October 2006

Natural killer (NK) cells are a subpopulation of large granular lymphocytes characterized by densely staining azurophilic granules. NK cells are able to recognize and lyse various virally infected or neoplastic target cells without previous sensitization or major histocompatibility complex restriction. A 60-kD disulfide-linked dimer, highly expressed on NK cells, was found capable of mediating transmembrane signaling. The gene encoding this signal transduction molecule was cloned and its nucleotide sequence determined. The encoded protein showed significant homology with a number of lectin-related membrane proteins that share receptor characteristics. This protein may function as a receptor able to selectively trigger NK cell activity.
'Ain Ghazal: A Major Neolithic Settlement in Central Jordan
Authors: Simmons Alan H. , Köhler-Rollefson Ilse , Rollefson Gary O. , Mandel Rolfe , Kafafi Zeidan
Published: October 2006

'Ain Ghazal, an archeological site located on the outskirts of Amman, Jordan, is one of the largest early villages known in the Near East. The site dates to the Neolithic period, during which mankind made one of its most significant advances, the adoption of domestic plants and animals as primary subsistence sources. Recent excavations at 'Ain Ghazal have augmented considerably current knowledge of several aspects of the Neolithic. Of particular interest has been the documentation of a continuous, or near continuous, occupation from early through late Neolithic components, and a concomitant dramatic economic shift. This shift was from a broad subsistence base relying on a variety of both wild and domestic plants and animals, to an economic strategy reflecting an apparent emphasis on pastoralism.
Stratospheric Response to Trace Gas Perturbations: Changes in Ozone and Temperature Distributions
Authors: Brasseur Guy , Hitchman Matthew H.
Published: October 2006

The stratospheric concentration of trace gases released in the atmosphere as a result of human activities is increasing at a rate of 5 to 8 percent per year in the case of the chlorofluorocarbons (CFCs), 1 percent per year in the case of methane (CH
4
), and 0.25 percent per year in the case of nitrous oxide (N
2
O). The amount of carbon dioxide (CO
2
) is expected to double before the end of the 21st century. Even if the production of the CFCs remains limited according to the protocol for the protection of the ozone layer signed in September 1987 in Montreal, the abundance of active chlorine (2 parts per billion by volume in the early 1980s) is expected to reach 6 to 7 parts per billion by volume by 2050. The impact of these increases on stratospheric temperature and ozone was investigated with a two-dimensional numerical model. The model includes interactive radiation, wave and mean flow dynamics, and 40 trace species. An increase in CFCs caused ozone depletion in the model, with the largest losses near the stratopause and, in the vertical mean, at high latitudes. Increased CO
2
caused ozone amounts to increase through cooling, with the largest increases again near 45 kilometers and at high latitudes. This CO
2
-induced poleward increase reduced the CFC-induced poleward decrease. Poleward and downward ozone transport played a major role in determining the latitudinal variation in column ozone changes.
Mutations of the Adenylyl Cyclase Gene that Block RAS Function in
Saccharomyces cerevisiae
Authors: Field Jeffrey , Xu Hao-Peng , Michaeli Tamar , Ballester Roymarie , Sass Philip , Wigler Michael , Colicelli John
Published: October 2006

The interaction between RAS proteins and adenylyl cyclase was studied by using dominant interfering mutations of adenylyl cyclase from the yeast
Saccharomyces cerevisiae
. RAS proteins activate adenylyl cyclase in this organism. A plasmid expressing a catalytically inactive adenylyl cyclase was found to interfere dominantly with this activation. The interfering region mapped to the leucine-rich repeat region of adenylyl cyclase, which is homologous to domains present in several other proteins and is thought to participate in protein-protein interactions.
Molecular Switch for Signal Transduction: Structural Differences Between Active and Inactive Forms of Protooncogenic
ras
Proteins
Authors: Milburn Michael V. , Tong Liang , deVos Abraham M. , Brünger Axel , Yamaizumi Ziro , Nishimura Susumu , Kim Sung-Hou
Published: October 2006

Ras
proteins participate as a molecular switch in the early steps of the signal transduction pathway that is associated with cell growth and differentiation. When the protein is in its GTP complexed form it is active in signal transduction, whereas it is inactive in its GDP complexed form. A comparison of eight three-dimensional structures of
ras
proteins in four different crystal lattices, five with a nonhydrolyzable GTP analog and three with GDP, reveals that the "on" and "off" states of the switch are distinguished by conformational differences that span a length of more than 40 Å, and are induced by the γ-phosphate. The most significant differences are localized in two regions: residues 30 to 38 (the switch I region) in the second loop and residues 60 to 76 (the switch II region) consisting of the fourth loop and the short α-helix that follows the loop. Both regions are highly exposed and form a continuous strip on the molecular surface most likely to be the recognition sites for the effector and receptor molecule(or molecules). The conformational differences also provide a structural basis for understanding the biological and biochemical changes of the proteins due to oncogenic mutations, autophosphorylation, and GTP hydrolysis, and for understanding the interactions with other proteins.
Enhanced Immunogenicity of the Pre-S Region of Hepatitis B Surface Antigen
Authors: Milich David R. , Thornton George B. , Neurath A. Robert , Kent Steven B. , Michel Marie-Louise , Tiollais Pierre , Chisari Francis V.
Published: October 2006

The 55 codons upstream of the gene sequence encoding the hepatitis B surface antigen (HBsAg) are called the pre-S(2) region. It has been proposed that polypeptides of high molecular weight that contain the pre-S(2) region should be included in future hepatitis B virus (HBV) vaccines. The pre-S(2) region and the S gene product [25 kilodalton (kD)] together compose a polypeptide of high molecular weight (33 kD). As an initial attempt to determine the relevance of the 33-kD polypeptide to development of an HBV vaccine, the murine immune response to pre-S(2)-encoded determinants as compared to S-encoded determinants on the same polypeptide was examined. The results indicate (i) the pre-S(2) region is significantly more immunogenic than the S region of HBsAg, (ii) the 26 amino acid residues at the NH2-terminus of the 33-kD polypeptide represent a dominant antibody binding site on the pre-S(2) region, (iii) the immune response to the pre-S(2) region is regulated by H-2-linked genes distinct from those that regulate the response to the S region, and (iv) immunization of an S region nonresponder strain with HBV envelope particles that contain both the pre-S(2) and S regions can circumvent nonresponsiveness to the S region.
Bulk Superconductivity up to 122 K in the Tl-Pb-Sr-Ca-Cu-O System
Authors: Subramanian M. A. , Torardi c. c. , Gopalakrishnan J. , Gai P. L. , Calabrese J. C. , Askew T. R. , Flippen R. B. , Sleight A. W.
Published: October 2006

New high-temperature superconductors based on oxides of thallium and copper, but not containing barium, have been prepared. A transition temperature (
T
c
) of about 85 K is found for (Tl
0.5
Pb
0.5
) Sr
2
CaCu
2
O
7
whereas (Tl
0.5
Pb
0.5
)Sr
2
Ca
2
Cu
3
O
9
has a
T
c
of about 120 K. Both materials possess tetragonal symmetry with
a
= 3.80 Å,
c
= 12.05 Å for (Tl
0.5
Pb
0.5
)Sr
2
CaCu
2
O
7
, and
a
= 3.81 Å,
c
= 15.23 Å for (Tl
0.5
Pb
0.5
)Sr
2
Ca
2
Cu
3
O
9
. A structure refinement of the latter phase has been carried out with single-crystal x-ray diffraction data.
Growing Up in Poor Neighborhoods: How Much Does It Matter?
Authors: Mayer Susan E. , Jencks Christopher
Published: October 2006

This article is a review of research on how much the life chances of children are affected by the socioeconomic and racial mix of their schools and neighborhoods. The social mix of a high school has little effect on students' chances of attending college or on white students' academic achievement. Evidence about the effect of the socioeconomic mix of schools or neighborhoods on achievement of elementary school students, on graduation rates of high school students, on teenage crime, and on early labor market experience is weak. Growing up in poor neighborhoods seems to increase black teenage pregnancy rates.
The Relation Between Major Histocompatibility Complex (MHC) Restriction and the Capacity of Ia to Bind Immunogenic Peptides
Authors: Buus Soren , Sette Alessandro , Colon Sonia M. , Miles Craig , Grey Howard M.
Published: October 2006

The capacity of purified I-A
d
, I-E
d
, I-A
k
, and I-E
k
to bind to protein derived peptides that have been previously reported to be T cell immunogens has been examined. For each of the 12 peptides studied strong binding to the relevant Ia restriction element was observed. All the peptides bound more than one Ia molecule; however, for 11 of 12 peptides, the dominant binding was to the restriction element, whereas in one instance the dominant binding was to a nonrestriction element. When the peptides were used to inhibit the presentation of antigen by prefixed accessory cells to T cells, an excellent correlation was found between the capacity of a peptide to inhibit the binding of an antigen to purified Ia and the capacity of the peptide to inhibit accessory cell presentation of the antigen. Thus, the binding of peptide to purified Ia is immunologically relevant, and Ia seems to be the only saturable molecule on the surface of the accessory cell involved in antigen presentation. Inhibition analysis also indicated that all peptides restricted to a particular Ia molecule competitively inhibited one another, suggesting that each Ia restriction element has a single binding site for antigen. Cross-linking of labeled peptides to Ia followed by electrophoretic analysis and autoradiography suggested that this single binding site is made up of portions of both α and β chains of Ia.
Genetically Engineering Plants for Crop Improvement
Authors: Gasser Charles S. , Fraley Robert T.
Published: October 2006

Dramatic progress has been made in the development of gene transfer systems for higher plants. The ability to introduce foreign genes into plant cells and tissues and to regenerate viable, fertile plants has allowed for explosive expansion of our understanding of plant biology and has provided an unparalleled opportunity to modify and improve crop plants. Genetic engineering of plants offers significant potential for seed, agrichemical, food processing, specialty chemical, and pharmaceutical industries to develop new products and manufacturing processes. The extent to which genetically engineered plants will have an impact on key industries will be determined both by continued technical progress and by issues such as regulatory approval, proprietary protection, and public perception.
Multipotent Precursors Can Give Rise to All Major Cell Types of the Frog Retina
Authors: Wetts Richard , Fraser Scott E.
Published: October 2006

A prospective lineage analysis was performed to determine the variety of cell types that could be formed by individual precursor cells of the developing frog retina. Fluorescent dextran was iontophoretically injected into single cells of the embryonic optic vesicle. After further development of the embryo, labeled descendants were observed in all three layers of the larval retina. Furthermore, different clones were composed of various combinations of all major cell types, including the glial Müller cells. Hence, single optic vesicle cells have the potential to form any type of retinal cell, suggesting that the interactions that specify the differentiation pathway of retinal cells must occur late in development.
Neptune's Story
Authors: Goldreich P. , Murray N. , Longaretti P. Y. , Banfield D.
Published: October 2006

It is conjectured that Triton was captured from a heliocentric orbit as the result of a collision with what was then one of Neptune's regular satellites. The immediate post-capture orbit was highly eccentric with a semimajor axis
a
∼10
3
R
N
and a periapse distance
r
p
that oscillated periodically above a minimum value of about 5
R
N
. Dissipation due to tides raised by Neptune in Triton caused Triton's orbit to evolve to its present state in ≲10
9
years. For much of this time Triton was almost entirely molten. While its orbit was evolving, Triton cannibalized most of the regular satellites of Neptune and also perturbed Nereid, thus accounting for that satellite's highly eccentric and inclined orbit. The only regular satellites of Neptune that survived were those that formed well within 5
R
N
and they move on inclined orbits as the result of chaotic perturbations forced by Triton. Neptune's arcs are confined around the corotation resonances of one of these inner satellites. The widths and lengths of the arcs imply that the satellite's radius is at least 30/(sin
i
)
2/3
kilometers for
i
≲ 1, where
i
is the angle of inclination.
Hot Plasma and Energetic Particles in Neptune's Magnetosphere
Authors: Krimigis S. M. , Armstrong T. P. , Axford W. I. , Bostrom C. O. , Cheng A. F. , Gloeckler G. , Hamilton D. C. , Keath E. P. , Lanzerotti L. J. , Mauk B. H. , Van Allen J. A.
Published: October 2006

The low-energy charged particle (LECP) instrument on Voyager 2 measured within the magnetosphere of Neptune energetic electrons (22 kiloelectron volts ≲
E
≲ 20 megaelectron volts) and ions (28 keV ≲
E
≲ 150 MeV) in several energy channels, including compositional information at higher (≳0.5 MeV per nucleon) energies, using an array of solid-state detectors in various configurations. The results obtained so far may be summarized as follows: (i) A variety of intensity, spectral, and anisotropy features suggest that the satellite Triton is important in controlling the outer regions of the Neptunian magnetosphere. These features include the absence of higher energy (≳150 keV) ions or electrons outside 14.4
R
N
(where
R
N
= radius of Neptune), a relative peak in the spectral index of low-energy electrons at Triton's radial distance, and a change of the proton spectrum from a power law with γ ≳ 3.8 outside, to a hot Maxwellian (
kT
≃ 55 keV) inside the satellite's orbit. (ii) Intensities decrease sharply at all energies near the time of closest approach, the decreases being most extended in time at the highest energies, reminiscent of a spacecraft's traversal of Earth's polar regions at low altitudes; simultaneously, several spikes of spectrally soft electrons and protons were seen (power input ≈ 5 × 10
-4
ergs cm
-2
s
-1
) suggestive of auroral processes at Neptune. (iii) Composition measurements revealed the presence of H, H
2
, and He
4
, with relative abundances of 1300:1:0.1, suggesting a Neptunian ionospheric source for the trapped particle population. (iv) Plasma pressures at
E
≳ 28 keV are maximum at the magnetic equator with β ≈ 0.2, suggestive of a relatively empty magnetosphere, similar to that of Uranus. (v) A potential signature of satellite 1989N1 was seen, both inbound and outbound; other possible signatures of the moons and rings are evident in the data but cannot be positively identified in the absence of an accurate magnetic-field model close to the planet. Other results indude the absence of upstream ion increases or energetic neutrals [particle intensity (
j
) < 2.8 × 10
-3
cm
-2
s
-1
keV
-1
near 35 keV, at ∼40
R
N
] implying an upper limit to the volume-averaged atomic H density at
R
≲ 6
R
N
of ≲ 20 cm
-3
; and an estimate of the rate of darkening of methane ice at the location of 1989N1 ranging from ∼10
5
years (1-micrometer depth) to ∼2 × 10
6
years (10-micrometers depth). Finally, the electron fluxes at the orbit of Triton represent a power input of ∼10
9
W into its atmosphere, apparently accounting for the observed ultraviolet auroral emission; by contrast, the precipitating electron (>22 keV) input on Neptune is ∼3 × 10
7
W, surprisingly small when compared to energy input into the atmosphere of Jupiter, Saturn, and Uranus.
Air Ventilation by Recoil Aspiration in Polypterid Fishes
Authors: Brainerd Elizabeth L. , Liem Karel F. , Samper Cristián T.
Published: October 2006

High-speed x-ray cine films synchronized with intra-pleuroperitoneal pressure measurements show that polypterid fishes aspiration breathe by the deformation and recoil of their bony-scaled integument. Paleozoic amphibians arose from ancient air-breathing fishes and retained piscine bony scales in V-shaped rows along the belly. These scales resemble those of modern polypterid fishes and may have contributed to inhalation by elastic recoil. The discovery that polypterid fishes breathe by recoil aspiration is the first evidence for aspiration breathing in any lower vertebrate. The use of recoil aspiration by polypterids shows that elastic storage in a stiff body wall can contribute to inhalation in animals with limited capacity for active aspiration.
Allometric Scaling in the Earliest Fossil Bird,
Archaeopteryx lithographica
Authors: Houck Marilyn A. , Gauthier Jacques A. , Strauss Richard E.
Published: October 2006

Archaeopteryx
is almost universally considered a primitive bird. Debate persists, however, about the taxonomic assignment of the six skeletal fossils. Allometric scaling of osteological data shows that all specimens are consistent with a single growth series. The absence of certain bone fusions suggests that no specimen is full-grown. Allometric patterns, as compared to growth gradients of other dinosaurs, extant ectotherms, and extant endotherms, suggest that
Archaeopteryx
was likely a homeothermic endotherm with rapid growth and precocial abilities for running and flying. Multivariate allometric models offer a significant potential for interpreting ontogenetic patterns and phylogenetic trends in the fossil record.
Learning Curves in Manufacturing
Authors: Argote Linda , Epple Dennis
Published: October 2006

Large increases in productivity are typically realized as organizations gain experience in production. These "learning curves" have been found in many organizations. Organizations vary considerably in the rates at which they learn. Some organizations show remarkable productivity gains, whereas others show little or no learning. Reasons for the variation observed in organizational learning curves include organizational "forgetting," employee turnover, transfer of knowledge from other products and other organizations, and economies of scale.
Direct Coupling of Marine Invertebrate Spawning with Phytoplankton Blooms
Authors: Starr Michel , Himmelman John H. , Therriault Jean-Claude
Published: October 2006

Spawning of green sea urchins and blue mussels may be triggered by a heat-stable metabolite released by various species of phytoplankton. Mussels require a higher phytoplankton density for a maximum response than urchins, perhaps because mussels are exposed to higher concentrations of phytoplankton as a result of their filtering activity. Phytoplankton as a spawning cue appears to integrate numerous physical and biotic factors indicating favorable conditions for larval growth and survival. Evolution of similar direct coupling of the larval phase with phytoplankton blooms may be common among marine invertebrates.
Atmospheric Dynamics of the Outer Planets
Authors: Ingersoll Andrew P.
Published: October 2006

Despite major differences in the solar and internal energy inputs, the atmospheres of the four Jovian planets all exhibit latitudinal banding and high-speed jet streams. Neptune and Saturn are the windiest planets, Jupiter is the most active, and Uranus is a tipped-over version of the others. Large oval storm systems exhibit complicated time-dependent behavior that can be simulated in numerical models and laboratory experiments. The largest storm system, the Great Red Spot of Jupiter, has survived for more than 300 years in a chaotic shear zone where smaller structures appear and dissipate every few days. Future space missions will add to our understanding of small-scale processes, chemical composition, and vertical structure. Theoretical hypotheses about the interiors provide input for fluid dynamical models that reproduce many observed features of the winds, temperatures, and cloud patterns. In one set of models the winds are confined to the thin layer where clouds form. In other models, the winds extend deep into the planetary fluid interiors. Hypotheses will be tested further as observations and theories become more exact and detailed comparisons are made.
Ultradeep (Greater Than 300 Kilometers), Ultramafic Upper Mantle Xenoliths
Authors: Haggerty Stephen E. , Sautter Violaine
Published: October 2006

Geophysical discontinuities in Earth's upper mantle and experimental data predict the structural transformation of pyroxene to garnet and the solid-state dissolution of pyroxene into garnet with increasing depth. These predictions are indirectly verified by omphacitic pyroxene exsolution in pyropic garnet-bearing xenoliths from a diamondiferous kimberlite. Conditions for silicon in octahedral sites in the original garnets are met at pressures greater than 130 kilobars, placing the origin of these xenoliths at depths of 300 to 400 kilometers. These ultradeep xenoliths support the theory that the 400-km seismic discontinuity is marked by a transition from peridotite to eclogite.
Cosmogenic Chlorine-36 Chronology for Glacial Deposits at Bloody Canyon, Eastern Sierra Nevada
Authors: Phillips Fred M. , Zreda Marek G. , Smith Stewart S. , Elmore David , Kubik Peter W. , Sharma Pankaj
Published: October 2006

Deposits from mountain glaciers provide an important record of Quaternary climatic fluctuations but have proved difficult to date directly. A chronology has been obtained for glacial deposits at Bloody Canyon, California, by measurement of the accumulation of chlorine-36 produced by cosmic rays in boulders exposed on moraine crests. The accumulation of chlorine-36 indicates that episodes of glaciation occurred at about 21, 24, 65, 115, 145, and 200 ka (thousand years ago). Although the timing of the glaciations correlates well with peaks of global ice volume inferred from the marine oxygen isotope record, the relative magnitudes differ markedly. The lengths of the moraines dating from 115 ka and 65 ka show that the early glacial episodes were more extensive than those during the later Wisconsin and indicate that the transition from interglacial to full glacial conditions was rapid.
Transgenic Mice with I-A on Islet Cells Are Normoglycemic But Immunologically Intolerant
Authors: Böhme J. , Haskins K. , Stecha P. , van Ewijk W. , LeMeur M. , Gerlinger P. , Benoist C. , Mathis D.
Published: October 2006

Insulin-dependent diabetes mellitus (IDDM) is caused by a specific loss of the insulin-producing beta cells from pancreatic Langerhans islets. It has been proposed that aberrant expression of major histocompatibility complex (MHC) class II molecules on these cells could be a triggering factor for their autoimmune destruction. This proposal was tested in transgenic mice that express allogeneic or syngeneic class II molecules on the surface of islet cells at a level comparable with that normally found on resting B lymphocytes. These animals do not develop diabetes, nor is lymphocyte infiltration of the islets observed. This immunological inactivity does not result from tolerance to the "foreign" class II molecules.
Intercalation of Sea Urchin Proteins in Calcite: Study of a Crystalline Composite Material
Authors: Berman Amir , Addadi Lia , Kvick Åke , Leiserowitz Leslie , Nelson Mitch , Weiner Stephen
Published: October 2006

Sea urchin skeletal elements are composed of single crystals of calcite. Unlike their synthetic counterparts, these crystals do not have well-developed cleavage and are consequently much more resistant to fracture. This phenomenon is due in part to the presence of acidic glycoproteins occluded within the crystals. By means of x-ray diffraction with synchrotron radiation, it is shown that the presence of the protein in synthetic calcite only slightly decreases the coherence length but significantly increases the angular spread of perfect domains of the crystals. In biogenic calcite, the coherence length is 1/3 to 1/4 as much as that in synthetic calcite and the angular spread is 20 to 50 times as wide. It is proposed that the presence of macromolecules concentrated at mosaic boundaries that are oblique to cleavage planes is responsible for the change in fracture properties. These results may be important in the material sciences, because of the unusual nature of this material, namely, a composite based on the controlled intercalation of macromolecules inside single-crystal lattices.
Rapid Changes in the Range Limits of Scots Pine 4000 Years Ago
Authors: Gear Annabel J. , Huntley Brian
Published: October 2006

Paleoecological data provide estimates of response rates to past climate changes. Fossil
Pinus sylvestris
stumps in far northern Scotland demonstrate former presence of pine trees where conventional pollen evidence of pine forests is lacking. Radiocarbon, dendrochronological, and fine temporal-resolution palynological data show that pine forests were present for about four centuries some 4000 years ago; the forests expanded and then retreated rapidly some 70 to 80 kilometers. Despite the rapidity of this response to climate change, it occurred at rates slower by an order of magnitude than those necessary to maintain equilibrium with forecast climate changes attributed to the greenhouse effect.
Living Polymerization Methods
Authors: Webster Owen W.
Published: October 2006

Living polymerization techniques can be used to achieve a high degree of control over polymer chain architecture. Examples of the type of polymers that can be synthesized include block copolymers, comb-shaped polymers, multiarmed polymers, ladder polymers, and cyclic polymers. This control of structure, in turn, results in polymers with widely diverse physical properties, even though they are made from readily available low-cost monomers.
Why Gases Dissolve in Liquids
Authors: Pollack Gerald L.
Published: October 2006

The thermodynamics and statistical mechanics of solubility are fairly well understood. It is still very difficult, however, to make quantitative predictions of solubility for real systems from first principles. The purposes of this article are to present the results of solubility experiments in some prototype solute-solvent systems, to show how far they may be understood from molecular first principles, and to discuss some of the things that are still missing. The main systems used as examples have the inert gas xenon as solute and some simple organic liquids as solvents.
Strain Measurements and the Potential for a Great Subduction Earthquake Off the Coast of Washington
Authors: Savage J. C. , Lisowski M.
Published: October 2006

Geodetic measurements of deformation in northwestern Washington indicate that strain is accumulating at a rate close to that predicted by a model of the Cascadia subduction zone in which the plate interface underlying the continental slope and outer continental shelf is currently locked but the remainder of the interface slips continuously. Presumably this locked segment will eventually rupture in a great thrust earthquake with a down-dip extent greater than 100 kilometers.
Folding and Unbinding Transitions in Tethered Membranes
Authors: Abraham Farid F. , Kardar Mehran
Published: October 2006

Molecular dynamics simulations of tethered membranes indicate that an attraction between the monomers leads to a well-defined sequence of folding transitions with decreasing temperature. With insights gained from Landau theory and simulations of bimembranes, the folding transitions are found to be intimately linked to the unbinding of membranes. Finite-size effects, mainly due to the loss of entropy from edge fluctuations, play an important role in hindering folding transitions.
Interpretation of Snow-Climate Feedback as Produced by 17 General Circulation Models
Authors: Cess R. D. , Potter G. L. , Zhang M.-H. , Blanchet J.-P. , Chalita S. , Colman R. , Dazlich D. A. , Del Genio A. D. , Dymnikov V. , Galin V. , Jerrett D. , Keup E. , Lacis A. A. , Le Treut H. , Liang X.-Z. , Mahfouf J.-F. , McAvaney B. J. , Meleshko V. P. , Mitchell J. F. B. , Morcrette J.-J. , Norris P. M. , Randall D. A. , Rikus L. , Roeckner E. , Royer J.-F. , Schlese U. , Sheinin D. A. , Slingo J. M. , Sokolov A. S. , Taylor K. E. , Washington W. M. , Wetherald R. T. , Yagai I.
Published: October 2006

Snow feedback is expected to amplify global warming caused by increasing concentrations of atmospheric greenhouse gases. The conventional explanation is that a warmer Earth will have less snow cover, resulting in a darker planet that absorbs more solar radiation. An intercomparison of 17 general circulation models, for which perturbations of sea surface temperature were used as a surrogate climate change, suggests that this explanation is overly simplistic. The results instead indicate that additional amplification or moderation may be caused both by cloud interactions and longwave radiation. One measure of this net effect of snow feedback was found to differ markedly among the 17 climate models, ranging from weak negative feedback in some models to strong positive feedback in others.
Allerød—Younger Dryas Lake Temperatures from Midge Fossils in Atlantic Canada
Authors: Walker Ian R. , Mott Robert J. , Smol John P.
Published: October 2006

Remains of freshwater midges are abundant in lake sediments, and their species distributions are closely related to the surface-water temperature of lakes; their distributions thus provide a powerful tool for paleoclimatology. The distribution of species in a core from Splan Pond in Atlantic Canada indicates that there were abrupt transitions in late-glacial temperatures between warm and cold states. The transitions are correlative with the well-known warm Allerød and cold Younger Dryas events in Europe. These data thus confirm the inference from palynological data that these events affected regions on both sides of the Atlantic.
Transneuronal Transfer of Herpes Virus from Peripheral Nerves to Cortex and Brainstem
Authors: Ugolini G. , Kuypers H. G. J. M. , Strick P. L.
Published: October 2006

The transneuronal transfer of neurotropic viruses may represent an effective tool for tracing chains of connected neurons because replication of virus in the recipient neurons after transfer amplifies the "tracer signal." Herpes simplex virus type 1 was transferred transneuronally from forelimb and hindlimb nerves of rats to the cortical and brainstem neurons that project to the spinal enlargements to which the nerves receiving injections are connected. This transneuronal transfer of herpes simplex virus type 1 from peripheral nerves has the potential to be used to identify neurons in the brain that are related transsynaptically to different nerves and muscles.
Selection for Precise Chromosomal Targeting of a Dominant Marker by Homologous Recombination
Authors: Dorin Julia R. , Inglis John D. , Porteous David J.
Published: October 2006

The antibiotic resistance gene neomycin phosphotransferase (
neo
) has been precisely targeted to a chromosomal region close to the cystic fibrosis (CF) locus on chromosome 7. The chromosomal target was the expressed SV40 array integrated at chromosome 7, band q31-q35 in a human-mouse hybrid cell line that contains chromosome 7 as the only human component. Stringent selection for
neo
expression by homologous recombination (3 of 11 correctly targeted) was achieved by fusing the SV40 large T antigen gene, in frame, to
neo
in a promoterless construct, such that G418 resistance depended on endogenous promoter function and read-through transcription. Chromosome-mediated gene transfer (CMGT) with G418 selection was then used generate mouse hybrids that carried the targeted locus intact, but retained only a fragment of human chromosome 7. This gene targeting strategy will access new regions of the human (or other mammalian) genome, create precise mutations efficiently by gene disruption, and potentially restore normal gene function by mutation correction.
A Multiubiquitin Chain Is Confined to Specific Lysine in a Targeted Short-Lived Protein
Authors: Chau Vincent , Tobias John W. , Bachmair Andreas , Marriott David , Ecker David J. , Gonda David K. , Varshavsky Alexander
Published: October 2006

The ubiquitin-dependent degradation of a test protein β-galactosidase (βgal) is preceded by ubiquitination of βgal. The many (from 1 to more than 20) ubiquitin moieties attached to a molecule of βgal occur as an ordered chain of branched ubiquitin-ubiquitin conjugates in which the carboxyl-terminal Gly
76
of one ubiquitin is joined to the internal Lys
48
of an adjacent ubiquitin. This multiubiquitin chain is linked to one of two specific Lys residues in βgal. These same Lys residues have been identified by molecular genetic analysis as components of the amino-terminal degradation signal in βgal. The experiments with ubiquitin mutated at its Lys
48
residue indicate that the multiubiquitin chain in a targeted protein is essential for the degradation of the protein.
Superconductivity at 45 K in Rb/Tl Codoped C
60
and C
60
/C
70
Mixtures
Authors: Iqbal Zafar , Baughman Ray H. , Ramakrishna B. L. , Khare Sandeep , Murthy N. Sanjeeva , Bornemann Hans J. , Morris Donald E.
Published: October 2006

The appearance of superconductivity at relatively high temperatures in alkali metal—doped C
60
fullerene provides the challenge to both understand the nature and origin of the superconductivity and to determine the upper limit of the superconducting transition temperature (
T
c
). Towards the latter goal, it is shown that doping with potassium-thallium and rubidium-thallium alloys in the 400 to 430°C temperature range increases the
T
c
of C
60
/C
70
mixtures to 25.6 K and above 45 K, respectively. Similar increases in
T
c
were also observed upon analogous doping of pure C
60
. Partial substitution of potassium with thallium in interstitial sites between C
60
molecules is suggested by larger observed unit cell parameters than for the K
3
C
60
and K
4
C
60
phases. Contrary to previous results for C
60
doped with different alkali metals, such expansion does not alone account for the changes in critical temperature.
Long-Term History of Chesapeake Bay Anoxia
Authors: Cooper Sherri R. , Brush Grace S.
Published: October 2006

Stratigraphic records from four sediment cores collected along a transect across the Chesapeake Bay near the mouth of the Choptank River were used to reconstruct a 2000-year history of anoxia and eutrophication in the Chesapeake Bay. Variations in pollen, diatoms, concentration of organic carbon, nitrogen, sulfur, acid-soluble iron, and an estimate of the degree of pyritization of iron indicate that sedimentation rates, anoxic conditions and eutrophication have increased in the Chesapeake Bay since the time of European settlement.
Diffusive Isotopic Contamination of Mafic Magma by Coexisting Silicic Liquid in the Muskox Intrusion
Authors: Stewart Brian W. , DePaolo Donald J.
Published: October 2006

Shifts in
87
Sr/
86
Sr and
143
Nd/
144
Nd ratios measured in cumulates from the upper levels of the Muskox mafic intrusion indicate that isotopic and bulk chemical exchange were decoupled across a mafic-silicic liquid interface during crystallization of the intrusion. Modeling of diffusive exchange between liquid layers demonstrates that isotopic compositions of silicate liquids in layered magma chambers may be strongly affected by this process on time scales of 10
3
to 10
4
years. Diffusive contamination can be used to place constraints on the physical processes and time scales of magmatic systems.
A Liver-Specific Enhancer in the Core Promoter Region of Human Hepatitis B Virus
Authors: Yee Jiing-Kuan
Published: October 2006

An 88-base pair fragment in the core promoter of the human hepatitis B virus (HBV) contains a functional promoter and a strong liver-specific enhancer. This enhancer functions in human hepatoma cells, where it is much more active than the previously described HBV enhancer in stimulating expression of the linked bacterial chloramphenicol acetyltransferase gene expressed from heterologous promoters. Studies of the role of this enhancer-promoter in HBV may help to clarify mechanisms of gene expression in cells infected with HBV and the role of the virus in the pathogenesis of hepatitis and hepatocellular carcinoma.
Crossover Reactions Between Synthetic Replicators Yield Active and Inactive Recombinants
Authors: Feng Qing , Park Tae Kyo , Rebek Julius
Published: October 2006

Self-replicating molecules can be synthesized through the covalent linkage of two complementary subunits to give a self-complementary structure. Complementarity refers to sizes, shapes, and the weak intermolecular forces involved in molecular recognition between the two subunits. In order to provide a model system for evolution at the molecular level, "crossover" or recombination experiments were staged with synthetic replicators. These reactions gave rise to new structural types. The ability (or inability) of the new recombinants to catalyze their own formation is shown to be a consequence of their molecular shapes.
Calmodulin Trapping by Calcium-Calmodulin-Dependent Protein Kinase
Authors: Meyer Tobias , Hanson Phyllis I. , Stryer Lubert , Schulman Howard
Published: October 2006

Multifunctional calcium-calmodulin-dependent protein kinase (CaM kinase) transduces transient elevations in intracellular calcium into changes in the phosphorylation state and activity of target proteins. By fluorescence emission anisotropy, the affinity of CaM kinase for dansylated calmodulin was measured and found to increase 1000 times after autophosphorylation of the threonine at position 286 of the protein. Autophosphorylation markedly slowed the release of bound calcium-calmodulin; the release time increased from less than a second to several hundred seconds. In essence, calmodulin is trapped by autophosphorylation. The shift in affinity does not occur in a site-directed mutant in which threonine at position 286 has been replaced by a non-phosphorylatable amino acid. These experiments demonstrate the existence of a new state in which calmodulin is bound to CaM kinase even though the concentration of calcium is basal. Calmodulin trapping provides for molecular potentiation of calcium transients and may enable detection of their frequency.
Luminescent Color Image Generation on Porous Silicon
Authors: Doan Vincent V. , Sailor Michael J.
Published: October 2006

Black and white images were projected onto
n
-type silicon (100) wafers during a photoelectrochemical etch to produce a color image that photoluminesces. The photoluminescence originates from a thin layer of luminescent porous silicon that is produced in the photoetch, and the colors that appear in the etched image arise from thin-film optical interference. A diffraction grating was also photoetched into the substrate, demonstrating simultaneous encoding of a gray-scale image into thin-film interference, luminescence, and diffraction phenomena.