bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of a thin-resist process for KrF imaging to 130 nm device fabrication
Authors: Azuma Tsukasa , Chiba Kenji , Kawamura Daisuke , Miyoshi Seiro , Ozaki Tohru , Kageyama Hiroyoshi
Published: July 2002

A practical bilayer bottom antireflective coating (BARC) process, consisting of an upper conventional organic film and a lower amorphous-Si blackout film, is introduced to realize highly antireflective performance and efficient pattern-transfer performance simultaneously. The application of a thin-resist process for KrF imaging to 130 nm device fabrication is also investigated including a practical pattern-transfer process, especially in the gate layer and the metal-wiring layer. It is demonstrated that no standing-wave effects in the resist are observed due to the effective bilayer BARC structure; furthermore, the resist patterns, which are 215 nm thick, are successfully transferred to the substrates in the gate layer and the metal-wiring layer. Finally, experimental and simulation results suggest that the thin-resist process, in combination with the practical bilayer BARC process using KrF imaging featuring a numerical aperture of 0.68 and a partial coherency of 0.75 with a 2/3 annular aperture, could guarantee the early stage of 1 Gb dynamic random access memory device fabrication.
Rapid Electron Tunneling Through Oligophenylenevinylene Bridges
Authors: Sikes Hadley D. , Smalley John F. , Dudek Stephen P. , Cook Andrew R. , Newton Marshall D. , Chidsey Christopher E. D. , Feldberg Stephen W.
Published: July 2002

We measured rate constants of thermal, interfacial electron transfer through oligophenylenevinylene bridges between a gold electrode and a tethered redox species in contact with an aqueous electrolyte using the indirect laser-induced temperature jump technique. Analysis of the distance dependence indicates that, unlike other bridges studied to date, the rate constants are not limited by electronic coupling for bridges up to 28 angstroms long. The energy levels of the bridges relative to those of the redox species rule out hopping through the bridge. We conclude that, out to 28 angstroms, the transfer is limited by structural reorganization and that electron tunneling occurs in less than 20 picoseconds, suggesting that oligophenylenevinylene bridges could be useful for wiring molecular electronic elements.
Observation of Magnetic Hysteresis at the Nanometer Scale by Spin-Polarized Scanning Tunneling Spectroscopy
Authors: Pietzsch O. , Kubetzka A. , Bode M. , Wiesendanger R.
Published: July 2002

Using spin-polarized scanning tunneling microscopy in an external magnetic field, we have observed magnetic hysteresis on a nanometer scale in an ultrathin ferromagnetic film. An array of iron nanowires, being two atomic layers thick, was grown on a stepped tungsten (110) substrate. The microscopic sources of hysteresis in this system—domain wall motion, domain creation, and annihilation—were observed with nanometer spatial resolution. A residual domain 6.5 nanometers by 5 nanometers in size has been found which is inherently stable in saturation fields. Its stability is the consequence of a 360° spin rotation. With magnetic memory bit sizes approaching the superparamagnetic limit with sub–10 nanometer characteristic lengths, the understanding of the basic physical phenomena at this scale is of fundamental importance.
Gene Families from the
Arabidopsis thaliana
Pollen Coat Proteome
Authors: Mayfield Jacob A. , Fiebig Aretha , Johnstone Sarah E. , Preuss Daphne
Published: July 2002

The pollen extracellular matrix contains proteins mediating species specificity and components needed for efficient pollination. We identified all proteins >10 kilodaltons in the
Arabidopsis
pollen coating and showed that most of the corresponding genes reside in two genomic clusters. One cluster encodes six lipases, whereas the other contains six lipid-binding oleosin genes, including
GRP17
, a gene that promotes efficient pollination. Individual oleosins exhibit extensive divergence between ecotypes, but the entire cluster remains intact. Analysis of the syntenic region in
Brassica oleracea
revealed even greater divergence, but a similar clustering of the genes. Such allelic flexibility may promote speciation in plants.
Rapid Increase in Clusters of Presynaptic Proteins at Onset of Long-Lasting Potentiation
Authors: Antonova Irina , Arancio Ottavio , Trillat Anne-Cecile , Wang Hong-Gang , Zablow Leonard , Udo Hiroshi , Kandel Eric R. , Hawkins Robert D.
Published: July 2002

A change in the efficiency of synaptic communication between neurons is thought to underlie learning. Consistent with recent studies of such changes, we find that long-lasting potentiation of synaptic transmission between cultured hippocampal neurons is accompanied by an increase in the number of clusters of postsynaptic glutamate receptors containing the subunit GluR1. In addition, potentiation is accompanied by a rapid and long-lasting increase in the number of clusters of the presynaptic protein synaptophysin and the number of sites at which synaptophysin and GluR1 are colocalized. These results suggest that potentiation involves rapid coordinate changes in the distribution of proteins in the presynaptic neuron as well as the postsynaptic neuron.
Bose-Einstein Condensation of Potassium Atoms by Sympathetic Cooling
Authors: Modugno G. , Ferrari G. , Roati G. , Brecha R. J. , Simoni A. , Inguscio M.
Published: July 2002

We report on the Bose-Einstein condensation of potassium atoms, whereby quantum degeneracy is achieved by sympathetic cooling with evaporatively cooled rubidium. Because of the rapid thermalization of the two different atoms, the efficiency of the cooling process is high. The ability to achieve condensation by sympathetic cooling with a different species may provide a route to the production of degenerate systems with a larger choice of components.
Organic Molecules Acting as Templates on Metal Surfaces
Authors: Rosei F. , Schunack M. , Jiang P. , Gourdon A. , Lægsgaard E. , Stensgaard I. , Joachim C. , Besenbacher F.
Published: July 2002

The electronic connection of single molecules to nanoelectrodes on a surface is a basic, unsolved problem in the emerging field of molecular nanoelectronics. By means of variable temperature scanning tunneling microscopy, we show that an organic molecule (C
90
H
98
), known as the Lander, can cause the rearrangement of atoms on a Cu(110) surface. These molecules act as templates accommodating metal atoms at the step edges of the copper substrate, forming metallic nanostructures (0.75 nanometers wide and 1.85 nanometers long) that are adapted to the dimensions of the molecule.
Mutant Mice and Worms Help Solve Mysteries of Olfaction
Authors: Barinaga Marcia
Published: July 2002

How do olfactory neurons signal the brain when they detect an odor? Two sets of mutant animals have shown that a crucial trigger is the intracellular messenger molecule cyclic AMP, which floods olfactory neurons when they are stimulated, opening ion channels and setting off action potentials that convey the signal to the brain.
PIN: An Associated Protein Inhibitor of Neuronal Nitric Oxide Synthase
Authors: Jaffrey Samie R. , Snyder Solomon H.
Published: July 2002

The neurotransmitter functions of nitric oxide are dependent on dynamic regulation of its biosynthetic enzyme, neuronal nitric oxide synthase (nNOS). By means of a yeast two-hybrid screen, a 10-kilodalton protein was identified that physically interacts with and inhibits the activity of nNOS. This inhibitor, designated PIN, appears to be one of the most conserved proteins in nature, showing 92 percent amino acid identity with the nematode and rat homologs. Binding of PIN destabilizes the nNOS dimer, a conformation necessary for activity. These results suggest that PIN may regulate numerous biological processes through its effects on nitric oxide synthase activity.
Selling Darwinism in a Citadel of Social Science
Authors: Williams Nigel
Published: July 2002

London—In one of Britain's most prestigious institutes for the social sciences, the London School of Economics, a pioneering evolutionary biologist is opening her colleagues' eyes to a Darwinian view of human behavior.
Alterations in Synaptic Strength Preceding Axon Withdrawal
Authors: Colman H. , Nabekura J. , Lichtman J. W.
Published: July 2002

Permanent removal of axonal input to postsynaptic cells helps shape the pattern of neuronal connections in response to experience, but the process is poorly understood. Intracellular recording from newborn and adult mouse muscle fibers temporarily innervated by two axons showed an increasing disparity in the synaptic strengths of the two inputs before one was eliminated. The connection that survived gained strength by increasing the amount of neurotransmitter released (quantal content), whereas the input that was subsequently removed became progressively weaker, because of a reduction in quantal content and a reduction in quantal efficacy associated with reduced postsynaptic receptor density. Once the synaptic strengths of two inputs began to diverge, complete axonal withdrawal of the weaker input occurred within 1 to 2 days. These experiments provide a link between experience-driven changes in synaptic strength and long-term changes in connectivity in the mammalian nervous system.
Peer Review Lands Safely in Russia
Authors: Allakhverdov Andrey , Lawler Andrew
Published: July 2002

MOSCOW
—Most Western grant programs in the former Soviet Union now insist on collaborative research and Western-style peer review rather than the old, hierarchical style of Soviet funding. Getting used to the competitive ways of the West is tough for some researchers, but Western officials see it as part of their mission to teach them: not only to improve their chances of carryingout successful collaborations with other nations but also to improve the quality of Russian science.
Bracing for a Biological Nightmare
Authors: Marshall Eliot
Published: July 2002

Leaders of the Defense Advanced Research Projects Agency's new biology program say they made biological countermeasures a high priority after the Aum Shinrikyo religious group attacked passengers on Tokyo's subway trains with nerve gas in 1995 and after it was revealed that Iraq's military built an extensive bioweapons stockpile in the late 1980s.
Researchers Seek New Weapon Against the Flu
Authors: Service Robert F.
Published: July 2002

There may be a magic bullet after all, at least when it comes to the flu. Scientists announced last week that they have developed a new compound that may ward off the flu by halting the spread of influenza viruses in the mucous membranes of the nose and lungs. Public health experts caution, however, that even if the new compound, which so far has been tested only in animals, proves to be safe and effective, it shouldn't eclipse current vaccination programs.
Organelle Genomes--Going, Going, Gone
Authors: Palmer Jeffrey D.
Published: July 2002

The organelles of eukaryotic cells—chloroplasts and mitochondria—first arose as engulfed symbionts with their own genomes. They subsequently lost most of their genes to the nucleus, retaining a few that could not be transferred. In his Perspective, Palmer discusses recent evidence that suggests that another organelle, the hydrogenosome, is a highly modified mitochondrion that has lost all of its genetic material.
Big Bucks for New Equipment
Authors: Kondro Wayne
Published: July 2002

OTTAWA
—Universities across the country are applauding a new program that could generate $1.5 billion in new research equipment and facilities, even as the government continues to trim funding for individual research grants.
Do We Want More Kids, or Fewer, Richer Kids?
Authors: Kaiser Jocelyn
Published: July 2002

SEATTLE
—At the annual meeting of the American Association for the Advancement of Science here, behavioral ecologist Monique Borgerhoff Mulder of the University of California, Davis, presented new data suggesting a key to the evolutionary puzzle of why, as societies get richer, individuals have fewer children, rather than trying to pass on their genes by having more. The answer: They are more successful at passing on their genes if they maximize not their total number of children but the amount of resources, or wealth, they pass along to each child.

See last week's issue (
Science
, 21 February,
p.1061
) for coverage of early sessions on
global R&D funding
and
submarine vents
.
Cloning Sparks Calls for New Laws
Authors: Williams Nigel
Published: July 2002

The news of the first successful cloning of an adult mammal has sent ethical shock waves around the world. As a result, in many countries, officials and even some scientists are calling for new or strengthened legislation to outlaw human cloning, although at this early date, no concrete measures have been proposed.
One Species or Two (or Three)?
Authors: Tangley Laura
Published: July 2002

Recent studies of elephant DNA suggest that forest and savanna elephants, generally thought of as separate subspecies, may, in fact, be entirely different species.
Unresolvable Endings--Defective Telomeres and Failed Separation
Authors: Hawley R. Scott
Published: July 2002

Telomeres, usually consisting of repetitive sequences and proteins bound to them, form the ends of all chromosomes, where they protect against unwanted shortening during DNA replication and cell division. The Perspective by Hawley discusses two reports, one by Kirk
et al
. (
p. 1478
) of this week's issue and the other in press at
Genes and Development
, that point to a surprising new function for telomeres in the separation of the ends of the chromosomes during cell division.
Biology Departments Restructure
Authors: Roush Wade
Published: July 2002

A wave of reorganization is striking U.S. biology departments, and many are splitting according to level of study—molecules versus ecosystems. But there's also a growing backlash against this trend, as some researchers argue that the hottest topics in biology encompass several levels.
Court Invalidates Expert Panel Report
Authors: Kaiser Jocelyn
Published: July 2002

Three U.S. activist groups last week won a court victory when a judge agreed that because a National Academy of Sciences panel formed to study the National Ignition Facility—a $1.1 billion laser-fusion project—had operated behind closed doors, the Department of Energy, which commissioned the report, could not use its findings. This decision suggest that the much-cherished confidentiality of academy panels may be a thing of the past.
New Institute Seen as Brains Behind Big Boost in Spending
Authors: Normile Dennis
Published: July 2002

TOKYO
—A new $61 million Brain Science Institute at the Institute of Physical and Chemical Research is the centerpiece for an ambitious program to boost Japan's international profile in neuroscience and to better coordinate efforts at home.
Labs Take Aim at Rapid-Fire Lasers for Fusion Power
Authors: Weiss Peter
Published: July 2002

LIVERMORE, CALIFORNIA
—Laser researchers at Lawrence Livermore National Laboratory here and at the Naval Research Laboratory in Washington, D.C., are setting out to challenge the view that lasers can't live up to the demands of an inertial-confinement fusion power plant. Such a plant would have to blast a pellet of fuel with powerful beams many times a second‐a pace thousands of times faster than existing lasers can manage. New laser technology, however, could change all that.
Climate Warms a Bit for NASA Mission
Authors: Lawler Andrew
Published: July 2002

Congressional opponents of NASA's ambitious Mission to Planet Earth (MTPE) appear to be softening their criticism of the multibillion-dollar program, in part because of changes being made to satisfy the concerns of legislators and scientists. The result likely will be smaller spacecraft and a data-management system more closely tailored to the needs of researchers.
France Distributes Iodine Near Reactors
Authors: Balter Michael
Published: July 2002

PARIS
—French Health Minister Hervé Gaymard has announced that local authorities will begin distributing potassium iodide tablets to everyone living within 10 kilometers of 24 nuclear installations. In the event of a nuclear accident, the residents would take the tablets to block the uptake of radioactive iodine isotopes, byproducts of nuclear fission that could cause thyroid cancer. The decision in France has sparked considerable interest among radiation scientists in other countries, particularly the United States, where stable iodine is not generally made available to the public.
Tax Law Halts Western Grant Payments
Authors: Stone Richard
Published: July 2002

The old adage about the inevitability of death and taxes has taken on new meaning in Ukraine: A new tax law could spell death for dozens of scientific projects. Several Western organizations have suspended grant payments to members of this country's scientific elite, citing a law that apparently will siphon 20% from each grant. The law could undermine vital support for Ukrainian labs doing world-class science.
Canada Reaches Out to NASA
Authors: Kondro Wayne
Published: July 2002

OTTAWA
—Three years after Canada decided it could not afford to do science on the international space station, officials are hoping to broker a deal with NASA that would reopen the facility's labs to the nation's research community in exchange for making an essential piece of hardware. But some Canadian space scientists warn that, even if NASA lets them aboard, the arrangement won't do them any good until the government finds enough money to fund their ideas.
Baltimore's Newest Tourist Attraction—Scientists
Authors: Olson Steve
Published: July 2002

BALTIMORE
—Tourists visiting this city's revamped Inner Harbor will soon have a new attraction to check out: working scientists. The $160 million Columbus Center, which opens 3 May, combines a sophisticated research facility with a science museum. But some observers wonder whether this marriage of lab and museum will be a happy one. Researchers already have become embroiled in disputes over the design of the building and exhibits. And many are struggling to work out how to play a dual role as scientist and interpreter of science to the public.
A Gut Reaction--Lymphoepithelial Communication in the Intestine
Authors: Shanahan Fergus
Published: July 2002

The vast epithelial lining of the gut has its own branch of the immune system to protect the body from invasion. In his Perspective, Shanahan describes the components of this system—the intestinal epithelial cells and intraepithelial lymphocytes—and a new local paracrine network among them, mediated by thyrotropin-releasing hormone and thyroid-stimulating hormone and reported in this issue on p.
1937
(Wang
et al
.)
Mammography: NCI Reverses One Expert Panel, Sides With Another
Authors: Taubes Gary
Published: July 2002

The National Cancer Institute (NCI) recommended last week that women in their forties should get mammograms every 1 to 2 years. The announcement came just 5 days after the American Cancer Society stated first that it favored yearly mammograms for 40-something women. This apparent harmony, however, masks a highly contentious debate in which different groups of scientists have come to different conclusions about the same set of data. And the debate has been tainted by political pressure from the U.S. Congress, which has put many of the researchers involved in a highly uncomfortable position.
Muscular Dystrophy: Backup Gene May Help Muscles Help Themselves
Authors: Roush Wade
Published: July 2002

Mammalian DNA contains redundant genes that might, in a pinch, be capable of standing in for their counterparts. Now, scientists are trying to use one of those genes to treat a currently incurable human genetic disease: Duchenne type muscular dystrophy. Each year, about 21,000 boys worldwide are born with a genetic defect that renders them incapable of making a key muscle-strengthening protein called dystrophin. Recent work in mice suggests that it may be possible to correct this defect by enticing muscle cells to make more of a very similar protein, called utrophin.
Molecular Biology: Counterfeit Chromosomes for Humans
Authors: Roush Wade
Published: July 2002

Researchers at Case Western Reserve University and Athersys Inc., both in Cleveland, report constructing the first wholly synthetic, self-replicating, human “microchromosomes,” which are one-fifth to one-tenth the size of normal human chromosomes. Although the team hasn't yet found an efficient way of transplanting microchromosomes’ self-assembling components into new cells--a crucial step before researchers can exploit them fully--human artificial chromosomes could eventually be used to study chromosomal functions and to ferry “repair genes” into target cells in gene therapy.
Differential Regulation of HIV-1 Fusion Cofactor Expression by CD28 Costimulation of CD4
+
T Cells
Authors: Carroll Richard G. , Riley James L. , Levine Bruce L. , Feng Yu , Kaushal Sumesh , Ritchey David W. , Bernstein Wendy , Weislow Owen S. , Brown Charles R. , Berger Edward A. , June Carl H. , St. Louis Daniel C.
Published: July 2002

Activation of CD4
+
T lymphocytes from human immunodeficiency virus–type 1 (HIV-1)–infected donors with immobilized antibodies to CD3 and CD28 induces a virus-resistant state. This effect is specific for macrophage-tropic HIV-1. Transcripts encoding CXCR4/Fusin, the fusion cofactor used by T cell line–tropic isolates, were abundant in CD3/CD28-stimulated cells, but transcripts encoding CCR5, the fusion cofactor used by macrophage-tropic viruses, were not detectable. Thus, CD3/CD28 costimulation induces an HIV-1–resistant phenotype similar to that seen in some highly exposed and HIV-uninfected individuals.
Surface Composition of Kuiper Belt Object 1993SC
Authors: Brown Robert H. , Cruikshank Dale P. , Pendleton Yvonne , Veeder Glenn J.
Published: July 2002

The 1.42- to 2.40-micrometer spectrum of Kuiper belt object 1993SC was measured at the Keck Observatory in October 1996. It shows a strongly red continuum reflectance and several prominent infrared absorption features. The strongest absorptions in 1993SC’s spectrum occur near 1.62, 1.79, 1.95, 2.20, and 2.32 micrometers in wavelength. Features near the same wavelengths in the spectra of Pluto and Neptune’s satellite Triton are due to CH
4
on their surfaces, suggesting the presence of a simple hydrocarbon ice such as CH
4
, C
2
H
6
, C
2
H
4
, or C
2
H
2
on 1993SC. In addition, the red continuum reflectance of 1993SC suggests the presence of more complex hydrocarbons.
Bimolecular Exon Ligation by the Human Spliceosome
Authors: Anderson Karin , Moore Melissa J.
Published: July 2002

Intron excision is an essential step in eukaryotic gene expression, but the molecular mechanisms by which the spliceosome accurately identifies splice sites in nuclear precursors to messenger RNAs (pre-mRNAs) are not well understood. A bimolecular assay for the second step of splicing has now revealed that exon ligation by the human spliceosome does not require covalent attachment of a 3′ splice site to the branch site. Furthermore, accurate definition of the 3′ splice site in this system is independent of either a covalently attached polypyrimidine tract or specific 3′ exon sequences. Rather, in this system 3′ splice site selection apparently occurs with a 5′ → 3′ directionality.
Precursor-Directed Biosynthesis of Erythromycin Analogs by an Engineered Polyketide Synthase
Authors: Jacobsen John R. , Hutchinson C. Richard , Cane David E. , Khosla Chaitan
Published: July 2002

A genetic block was introduced in the first condensation step of the polyketide biosynthetic pathway that leads to the formation of 6-deoxyerythronolide B (6-dEB), the macrocyclic precursor of erythromycin. Exogenous addition of designed synthetic molecules to small-scale cultures of this null mutant resulted in highly selective multimilligram production of unnatural polyketides, including aromatic and ring-expanded variants of 6-dEB. Unexpected incorporation patterns were observed, illustrating the catalytic versatility of modular polyketide synthases. Further processing of some of these scaffolds by postpolyketide enzymes of the erythromycin pathway resulted in the generation of novel antibacterials with in vitro potency comparable to that of their natural counterparts.
Aquatic Nonconformists
Authors: Burggren Warren W.
Published: July 2002

Air-Breathing Fishes.
Evolution, Diversity, and Adaptation. JEFFREY B. GRAHAM. Academic Press, San Diego, 1997. xii, 299 pp., illus. $79.95 or £55. ISBN 0-12-294860-2.
In Situ Activation Pattern of
Drosophila
EGF Receptor Pathway During Development
Authors: Gabay Limor , Seger Rony , Shilo Ben-Zion
Published: July 2002

Signaling cascades triggered by receptor tyrosine kinases (RTKs) participate in diverse developmental processes. The active state of these signaling pathways was monitored by examination of the in situ distribution of the active, dual phosphorylated form of mitogen-activated protein kinase (ERK) with a specific monoclonal antibody. Detection of the active state of the
Drosophila
epidermal growth factor receptor (DER) pathway allowed the visualization of gradients and boundaries of receptor activation, assessment of the distribution of activating ligands, and analysis of interplay with the inhibitory ligand Argos. This in situ approach can be used to monitor other receptor-triggered pathways in a wide range of organisms.
Molecular Errata
Authors: Loeb Lawrence A.
Published: July 2002

Correcting the Blueprint of Life.
An Historical Account of the Discovery of DNA Repair Mechanisms. ERROL C. FRIEDBERG. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1997. xiv, 210 pp., illus. $49. ISBN 0-87969-507-2.
The Serpent World
Authors: Shine Richard
Published: July 2002

Snakes.
The Evolution of Mystery in Nature. HARRY W. GREENE. Photographs by Michael and Patricia Fogden. University of California Press, Berkeley, 1997. xiv, 351 pp., illus. $45 or £35. ISBN 0-520-20014-4.
Repair of Adult Rat Corticospinal Tract by Transplants of Olfactory Ensheathing Cells
Authors: Li Ying , Field Pauline M. , Raisman Geoffrey
Published: July 2002

The upper cervical corticospinal tract was transected on one side in adult rats. A suspension of ensheathing cells cultured from adult rat olfactory bulb was injected into the lesion site. This induced unbranched, elongative growth of the cut corticospinal axons. The axons grew through the transplant and continued to regenerate into the denervated caudal host tract. Rats with complete transections and no transplanted cells did not use the forepaw on the lesioned side for directed reaching. Rats in which the transplanted cells had formed a continuous bridge across the lesion exhibited directed forepaw reaching on the lesioned side.*
NEAR's Flyby of 253 Mathilde: Images of a C Asteroid
Authors: Veverka J. , Thomas P. , Harch A. , Clark B. , Bell J. F. , Carcich B. , Joseph J. , Chapman C. , Merline W. , Robinson M. , Malin M. , McFadden L. A. , Murchie S. , Hawkins S. E. , Farquhar R. , Izenberg N. , Cheng A.
Published: July 2002

On 27 June 1997, the Near Earth Asteroid Rendezvous (NEAR) spacecraft flew within 1212 kilometers of asteroid 253 Mathilde. Mathilde is an irregular, heavily cratered body measuring 66 kilometers by 48 kilometers by 46 kilometers. The asteroid's surface is dark (estimated albedo between 0.035 and 0.050) and similar in color to some CM carbonaceous chondrites. No albedo or color variations were detected. The volume derived from the images and the mass from Doppler tracking of the spacecraft yield a mean density of 1.3 ± 0.2 grams per cubic centimeter, about half that of CM chondrites, indicating a porous interior structure.
Superfluidity Within a Small Helium-4 Cluster: The Microscopic Andronikashvili Experiment
Authors: Grebenev Slava , Toennies J. Peter , Vilesov Andrei F.
Published: July 2002

The infrared spectrum of single oxygen carbon sulfide (OCS) molecules was measured inside large superfluid pure helium-4 droplets and nonsuperfluid pure helium-3 droplets, both consisting of about 10
4
atoms. In the helium-4 droplets, sharp rotational lines were observed, whereas in helium-3 only a broad peak was found. This difference is interpreted as evidence that the narrow rotational lines, which imply free rotations, are a microscopic manifestation of superfluidity. Upon addition of 60 helium-4 atoms to the pure helium-3 droplets, the same sharp rotational lines were found; it appears that 60 is the minimum number needed for superfluidity.
Inhibitory Function of p21
Cip1/WAF1
in Differentiation of Primary Mouse Keratinocytes Independent of Cell Cycle Control
Authors: Di Cunto Ferdinando , Topley Gabrielle , Calautti Enzo , Hsiao Jimmy , Ong Lydia , Seth Prem K. , Dotto G. Paolo
Published: July 2002

The cyclin-dependent kinase inhibitor p21
Cip1/WAF1
has been implicated as an inducer of differentiation. However, although expression of p21 is increased in postmitotic cells immediately adjacent to the proliferative compartment, its expression is decreased in cells further along the differentiation program. Expression of the p21 protein was decreased in terminally differentiated primary keratinocytes of mice, and this occurred by a proteasome-dependent pathway. Forced expression of p21 in these cells inhibited the expression of markers of terminal differentiation at both the protein and messenger RNA levels. These inhibitory effects on differentiation were not observed with a carboxyl-terminal truncation mutant or with the unrelated cyclin-dependent kinase inhibitor p16
INK4a
, although all these molecules exerted similar inhibition of cell growth. These findings reveal an inhibitory role of p21 in the late stages of differentiation that does not result from the effects of p21 on the cell cycle.
Noggin, Cartilage Morphogenesis, and Joint Formation in the Mammalian Skeleton
Authors: Brunet Lisa J. , McMahon Jill A. , McMahon Andrew P. , Harland Richard M.
Published: July 2002

Noggin is a bone morphogenetic protein (BMP) antagonist expressed in Spemann's organizer. Murine Noggin is expressed in condensing cartilage and immature chondrocytes, as are many BMPs. In mice lacking Noggin, cartilage condensations initiated normally but developed hyperplasia, and initiation of joint development failed as measured by the expression of growth and differentiation factor–5. The maturation of cartilage and Hoxd expression were unaffected. Excess BMP activity in the absence of Noggin antagonism may enhance the recruitment of cells into cartilage, resulting in oversized growth plates; chondrocytes are also refractory to joint-inducing positional cues.
Order at the End
Authors: Shmaefsky Brian
Published: July 2002

Endnote 3.0
. by Niles and Associates. Berkeley, CA. $299. Phone: 510-559-8592,
www.niles.com
Into Jurassic Air
Authors: Swartz Sharon
Published: July 2002

Taking Wing:
Archaeopteryx
and the Evolution of Bird Flight.
By Pat Shipman
. Simon and Schuster, New York, 1998. 336 pp. illus. $25 or C$35. ISBN 0-684-81131-6.
Spatial Organization of Transcription Elongation Complex in
Escherichia coli
Authors: Nudler Evgeny , Gusarov Ivan , Avetissova Ekaterina , Kozlov Maxim , Goldfarb Alex
Published: July 2002

During RNA synthesis in the ternary elongation complex, RNA polymerase enzyme holds nucleic acids in three contiguous sites: the double-stranded DNA-binding site (DBS) ahead of the transcription bubble, the RNA-DNA heteroduplex-binding site (HBS), and the RNA-binding site (RBS) upstream of HBS. Photochemical cross-linking allowed mapping of the DNA and RNA contacts to specific positions on the amino acid sequence. Unexpectedly, the same protein regions were found to participate in both DBS and RBS. Thus, DNA entry and RNA exit occur close together in the RNA polymerase molecule, suggesting that the three sites constitute a single unit. The results explain how RNA in the integrated unit RBS–HBS–DBS may stabilize the ternary complex, whereas a hairpin in RNA result in its dissociation.
Role of Phosphorylation in Regulation of the Assembly of Endocytic Coat Complexes
Authors: Slepnev Vladimir I. , Ochoa Gian-Carlo , Butler Margaret H. , Grabs Detlev , Camilli Pietro De
Published: July 2002

Clathrin-mediated endocytosis involves cycles of assembly and disassembly of clathrin coat components and their accessory proteins. Dephosphorylation of rat brain extract was shown to promote the assembly of dynamin 1, synaptojanin 1, and amphiphysin into complexes that also included clathrin and AP-2. Phosphorylation of dynamin 1 and synaptojanin 1 inhibited their binding to amphiphysin, whereas phosphorylation of amphiphysin inhibited its binding to AP-2 and clathrin. Thus, phosphorylation regulates the association and dissociation cycle of the clathrin-based endocytic machinery, and calcium-dependent dephosphorylation of endocytic proteins could prepare nerve terminals for a burst of endocytosis.
Rescued Account of a Vanished People
Authors: Politis Gustavo
Published: July 2002

Chronicle of the Guayaki Indians
. Pierre Clastres. Translated by Paul Auster. Zone Books, New York, 1998. 352 pp. $25.50, £21.95. ISBN 0-942299-77-9. Paper, Faber and Faber, London. 253 pp. £9.99. ISBN 0-571-19398-6.

Chronicle
is the French political anthropologist's account of his first fieldwork, two years in the early 1960s spent with a small, now vanished, group inhabiting the Paraguayan rainforest. Clastres provides illuminating descriptions of a lost culture, transactions between cultures, and the practice of anthropology. The translation, by novelist Paul Auster, captures the original's freshness, sense of humor, and intellectual insight.
The New "Great Work"
Authors: Wain-Hobson Simon
Published: July 2002

Retroviruses
. John M. Coffin, Stephen H. Hughes, and Harold E. Varmus, Eds. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1998. 859 pp. $180. ISBN 0-87969-497-1.

A benchmark reference written for the research community, with individual contributions intended to be independent and accessible in any order. Early chapters provide resolutely molecular descriptions of retrovirus structure, function, and replication; later ones consider pathogenesis, immune responses, and other aspects of the relationships between retroviruses and their hosts.
A Wondrous and Poetic Spectrum
Authors: Vest Charles M.
Published: July 2002

Unweaving the Rainbow
Science, Delusion and the Appetite for Wonder. Richard Dawkins. Houghton Mifflin, New York, 1998. 351 pp. $26. ISBN 0-395-88382-2.

In this assessment of what science is (and is not), Dawkins' tapestry includes strands on the wonder and fascination of science, poetry within science, his continuing jousts with Gould, genes as selfish cooperators, and the importance of coevolution in a variety of contexts.
True Stories of An Imaginary Number
Authors: Katz Victor J.
Published: July 2002

An Imaginary Tale
The Story of ÷-1. Paul J. Nahin. Princeton University Press, Princeton, NJ, 1998. 277 pp. $24.95, £18.95. ISBN 0-691-02795-1.

Nahin provides an outstanding integration of the history of imaginary numbers and a lot of interesting mathematics, much of which will be new to college mathematics majors or to professional scientists and engineers.
Ordered Mesoporous Polymers of Tunable Pore Size from Colloidal Silica Templates
Authors: Johnson Stacy A. , Ollivier Patricia J. , Mallouk Thomas E.
Published: July 2002

Ordered mesoporous polymers have been prepared by replication of colloidal crystals made from silica spheres 35 nanometers in diameter. The pores in the colloidal crystals were filled with divinylbenzene (DVB), ethyleneglycol dimethacrylate (EDMA), or a mixture of the two. Polymerization and subsequent dissolution of the silica template leaves a polycrystalline network of interconnected pores. When mixtures of DVB and EDMA are used, the pore size of the polymer replicas can be varied continuously between 35 and 15 nanometers because the polymer shrinks when the silica template is removed.
Reversible Conversion of Monomeric Human Prion Protein Between Native and Fibrilogenic Conformations
Authors: Jackson G. S. , Hosszu L. L. P. , Power A. , Hill A. F. , Kenney J. , Saibil H. , Craven C. J. , Waltho J. P. , Clarke A. R. , Collinge J.
Published: July 2002

Prion propagation involves the conversion of cellular prion protein (PrP
C
) into a disease-specific isomer, PrP
Sc
, shifting from a predominantly α-helical to β-sheet structure. Here, conditions were established in which recombinant human PrP could switch between the native α conformation, characteristic of PrP
C
, and a compact, highly soluble, monomeric form rich in β structure. The soluble β form (β-PrP) exhibited partial resistance to proteinase K digestion, characteristic of PrP
Sc
, and was a direct precursor of fibrillar structures closely similar to those isolated from diseased brains. The conversion of PrP
C
to β-PrP in suitable cellular compartments, and its subsequent stabilization by intermolecular association, provide a molecular mechanism for prion propagation.
Pressure-Induced Solid Carbonates from Molecular CO
2
by Computer Simulation
Authors: Serra S. , Cavazzoni C. , Chiarotti G. L. , Scandolo S. , Tosatti E.
Published: July 2002

A combination of ab initio molecular dynamic simulations and fully relaxed total energy calculations is used to predict that molecular CO
2
should transform to nonmolecular carbonate phases based on CO
4
tetrahedra at pressures in the range of 35 to 60 gigapascals. The simulation suggests a variety of competing phases, with a more facile transformation of the molecular phase at high temperatures. Thermodynamically, the most stable carbonate phase at high pressure is predicted to be isostructural to SiO
2
α-quartz (low quartz). A class of carbonates, involving special arrangements of CO
4
tetrahedra, is found to be more stable than all the other silica-like polymorphs.
The Future of the Fossil Record
Authors: Jablonski David
Published: July 2002

The fossil record provides a powerful basis for analyzing the controlling factors and impact of biological evolution over a wide range of temporal and spatial scales and in the context of an evolving Earth. An increasingly interdisciplinary paleontology has begun to formulate the next generation of questions, drawing on a wealth of new data, and on methodological advances ranging from high-resolution geochronology to simulation of morphological evolution. Key issues related to evolutionary biology include the biotic and physical factors that govern biodiversity dynamics, the developmental and ecological basis for the nonrandom introduction of evolutionary innovations in time and space, rules of biotic response to environmental perturbations, and the dynamic feedbacks between life and the Earth's surface processes. The sensitivity of evolutionary processes to rates, magnitudes, and spatial scales of change in the physical and biotic environment will be important in all these areas.
Plant Functional Genomics
Authors: Somerville Chris , Somerville Shauna
Published: July 2002

Nucleotide sequencing of the
Arabidopsis
genome is nearing completion, sequencing of the rice genome has begun, and large amounts of expressed sequence tag information are being obtained for many other plants. There are many opportunities to use this wealth of sequence information to accelerate progress toward a comprehensive understanding of the genetic mechanisms that control plant growth and development and responses to the environment.
Eutrophication, Fisheries, and Consumer-Resource Dynamics in Marine Pelagic Ecosystems
Authors: Micheli Fiorenza
Published: July 2002

Anthropogenic nutrient enrichment and fishing influence marine ecosystems worldwide by altering resource availability and food-web structure. Meta-analyses of 47 marine mesocosm experiments manipulating nutrients and consumers, and of time series data of nutrients, plankton, and fishes from 20 natural marine systems, revealed that nutrients generally enhance phytoplankton biomass and carnivores depress herbivore biomass. However, resource and consumer effects attenuate through marine pelagic food webs, resulting in a weak coupling between phytoplankton and herbivores. Despite substantial physical and biological variability in marine pelagic ecosystems, alterations of resource availability and consumers result in general patterns of community change.
Precisely Localized LTD in the Neocortex Revealed by Infrared-Guided Laser Stimulation
Authors: Dodt H.-U. , Eder M. , Frick A. , Zieglgänsberger W.
Published: July 2002

In a direct approach to elucidate the origin of long-term depression (LTD), glutamate was applied onto dendrites of neurons in rat neocortical slices. An infrared-guided laser stimulation was used to release glutamate from caged glutamate in the focal spot of an ultraviolet laser. A burst of light flashes caused an LTD-like depression of glutamate receptor responses, which was highly confined to the region of “tetanic” stimulation (<10 micrometers). A similar depression of glutamate receptor responses was observed during LTD of synaptic transmission. A spatially highly specific postsynaptic mechanism can account for the LTD induced by glutamate release.
Requirement of Yeast
SGS1
and
SRS2
Genes for Replication and Transcription
Authors: Lee Sung-Keun , Johnson Robert E. , Yu Sung-Lim , Prakash Louise , Prakash Satya
Published: July 2002

The
SGS1
gene of the yeast
Saccharomyces cerevisiae
encodes a DNA helicase with homology to the human Bloom's syndrome gene
BLM
and the Werner's syndrome gene
WRN
. The
SRS2
gene of yeast also encodes a DNA helicase. Simultaneous deletion of
SGS1
and
SRS2
is lethal in yeast. Here, using a conditional mutation of
SGS1
, it is shown that DNA replication and RNA polymerase I transcription are drastically inhibited in the
srs2
Δ
sgs1-ts
strain at the restrictive temperature. Thus,
SGS1
and
SRS2
function in DNA replication and RNA polymerase I transcription. These functions may contribute to the various defects observed in Werner's and Bloom's syndromes.
Ultrafast Mid-Infrared Response of YBa
2
Cu
3
O
7-δ
Authors: Kaindl R. A. , Woerner M. , Elsaesser T. , Smith D. C. , Ryan J. F. , Farnan G. A. , McCurry M. P. , Walmsley D. G.
Published: July 2002

Optical spectra of high-transition-temperature superconductors in the mid-infrared display a gap of in-plane conductivity whose role for superconductivity remains unresolved. Femtosecond measurements of the mid-infrared reflectivity of YBa
2
Cu
3
O
7-δ
after nonequilibrium optical excitation are used to demonstrate the ultrafast fill-in of this gap and reveal two gap constituents: a picosecond recovery of the superconducting condensate in underdoped and optimally doped material and, in underdoped YBa
2
Cu
3
O
7-δ
, an additional subpicosecond component related to pseudogap correlations. The temperature-dependent amplitudes of both contributions correlate with the antiferromagnetic 41-millielectronvolt peak in neutron scattering, supporting the coupling between charges and spin excitations.
Pif1p Helicase, a Catalytic Inhibitor of Telomerase in Yeast
Authors: Zhou J.-Q. , Monson E. K. , Teng S.-C. , Schulz V. P. , Zakian V. A.
Published: July 2002

Mutations in the yeast
Saccharomyces cerevisiae PIF1
gene, which encodes a 5′-to-3′ DNA helicase, cause telomere lengthening and a large increase in the formation rate of new telomeres. Here, we show that Pif1p acts by inhibiting telomerase rather than telomere-telomere recombination, and this inhibition requires the helicase activity of Pif1p. Overexpression of enzymatically active Pif1p causes telomere shortening. Thus, Pif1p is a catalytic inhibitor of telomerase-mediated telomere lengthening. Because Pif1p is associated with telomeric DNA in vivo, its effects on telomeres are likely direct. Pif1p-like helicases are found in diverse organisms, including humans. We propose that Pif1p-mediated inhibition of telomerase promotes genetic stability by suppressing telomerase-mediated healing of double-strand breaks.
Change in the Probability for Earthquakes in Southern California Due to the Landers Magnitude 7.3 Earthquake
Authors: Wyss Max , Wiemer Stefan
Published: July 2002

The Landers earthquake in June 1992 redistributed stress in southern California, shutting off the production of small earthquakes in some regions while increasing the seismicity in neighboring regions, up to the present. This earthquake also changed the ratio of small to large events in favor of more small earthquakes within about 100 kilometers of the epicenter. This implies that the probabilistic estimate for future earthquakes in southern California changed because of the Landers earthquake. The location of the strongest increase in probability for large earthquakes in southern California was the volume that subsequently produced the largest slip in the magnitude 7.1 Hector Mine earthquake of October 1999.
Glycopeptide Susceptibility Profiles of
Staphylococcus haemolyticus
Bloodstream Isolates
Authors: Biavasco Francesca , Vignaroli Carla , Lazzarini Raffaella , Varaldo Pietro E.
Published: July 2002

Twelve clinical strains of
Staphylococcus haemolyticus
(eight methicillin resistant and three methicillin susceptible), isolated from blood cultures between 1982 and 1997, were investigated for teicoplanin and vancomycin susceptibility profiles. On the basis of conventional MIC tests and breakpoints, four isolates were susceptible (MICs, 1 to 8 μg/ml) and eight were resistant (MICs, 32 to 64 μg/ml) to teicoplanin while all were susceptible to vancomycin (MICs, 1 to 2 μg/ml). All four strains for which the conventional teicoplanin MICs were within the range of susceptibility expressed heterogeneous resistance to teicoplanin and homogeneous vancomycin susceptibility. Of the eight strains for which the conventional teicoplanin MICs were within the range of resistance, six expressed heterogeneous and two expressed homogeneous teicoplanin resistance while seven showed heterogeneous vancomycin resistance profiles (with subpopulations growing on 8 μg of the drug per ml at frequencies of ≥10
−6
for six strains and 10
−7
for one) and one demonstrated homogeneous vancomycin susceptibility. Of six bloodstream isolates of other staphylococcal species (
S. aureus
,
S. epidermidis
, and
S. simulans
), for all of which the conventional teicoplanin MICs were ≥4 μg/ml and the vancomycin MICs were ≤2 μg/ml, none exhibited heterogeneous susceptibility profiles for teicoplanin while three showed homogeneous and three showed heterogeneous susceptibility profiles for vancomycin (with subpopulations growing on 8 μg of the drug per ml found for only one strain). The results of this study indicate that a heterogeneous response to glycopeptides is a common feature of
S. haemolyticus
isolates and suggest that susceptibility to glycopeptides as determined by conventional MIC tests may not be predictive of the outcome of glycopeptide therapy.
Genetic Characterization of
vanG
, a Novel Vancomycin Resistance Locus of
Enterococcus faecalis
Authors: McKessar Stuart J. , Berry Anne M. , Bell Jan M. , Turnidge John D. , Paton James C.
Published: July 2002

Enterococcus faecalis
strain WCH9 displays a moderate level of resistance to vancomycin (MIC = 16 μg/ml) and full susceptibility to teicoplanin but is negative by PCR analysis using primers specific for all known enterococcal vancomycin resistance genotypes (
vanA
,
vanB
,
vanC
,
vanD
, and
vanE
). We have isolated and sequenced a novel putative vancomycin resistance locus (designated
vanG
), which contains seven open reading frames, from this strain. These are organized differently from those of all the other enterococcal
van
loci, and, furthermore, the individual
vanG
gene products exhibit less than 50% amino acid sequence identity to other
van
gene products.