bluuebunny/crossref_metadata_2025 huggingface dataset:
Qualification of spreading resistance probe operations
Authors: Clarysse T. , Vandervorst W.
Published: July 2002

This article discusses the preliminary results obtained from an extensive spreading resistance probe (SRP) intercomparison conducted between 21 international laboratories with different levels of expertise both in the U.S. and in eight European countries. In the first phase, identical raw SRP model data and model calibration curves were sent around for six different structures. The carrier and resistivity profiles obtained from many different versions of software packages from three different manufacturers were analyzed. The observed variations are mainly dominated by radius variations and differences in applied mobility models. In the second phase, an extensive round robin was organized, involving the measurement of 22 separate samples including submicron source/drain and well implants and an ultrashallow sub-100 nm, 20 keV As implant. All samples were initially characterized by secondary ion mass spectrometry and four point probe mappings. The SRP repeatability and reproducibility for dose, sheet resistance, and junction depth obtained from a statistical analysis as defined by the International ISO 5725 standard are discussed as well as basic operational parameters such as bevel surface roughness, probe penetration, and bevel angle accuracy. All results indicate that there is a need for better international standardization of SRP operations.
Silicon nanopillars formed with gold colloidal particle masking
Authors: Lewis P. A. , Ahmed H. , Sato T.
Published: July 2002

Silicon nanopillars were fabricated by a novel natural lithography technique utilizing a gold colloidal particle monolayer as an etch mask. Using SiCl4 based reactive ion etching (RIE), silicon nanopillars with high density and uniformity in height and shape were obtained with 15 and 10 nm diam gold colloidal particles. The uniform pillars obtained from the 15 nm colloidal gold etch mask were subsequently sharpened to less than 5 nm diam tips by oxidation. 5 nm diam colloids were used to obtain nonuniform 5 nm diam pillars directly by RIE, but with 2 nm colloids the limit of pillar formation was reached. The pillars were also fabricated in selected areas by lithographic patterning of the substrate.
Mask electron modeling for Coulomb interaction by mask-scattered electrons in electron-beam projection lithography
Authors: Yamashita Hiroshi , Wen Victor S. H. , Neureuther Andrew R. , Nomura Eiichi
Published: July 2002

A rigorous statistical Coulomb interaction simulator that can take into account mask electrons was developed. In electron-beam (EB) projection lithography, many electrons incident to an absorber or a scatterer pass through the EB mask. These mask electrons, however, have not been considered in a simulation of Coulomb interaction. In a novel simulation approach, an assessment has been made of the effects of mask electrons on image quality and flare due to electron–electron interactions. The statistical electron–electron interactions from mask electrons under various conditions are simulated by injecting them into a simulation domain and using the fast multipole accelerated method to rigorously follow all interactions as a function of time. It was found that mask electrons contribute to the trajectory displacement effect and increase the number of deviated electrons in the pattern area by four to five times when the accelerating voltage is 125 kV, the beam current density is 0.1 A/cm2, the mask thickness is 10 μm, and the electron transmittance is 95%.
Comparison of negative resists for 100 nm electron-beam direct write and mask making applications
Authors: Nordquist K. J. , Resnick D. J. , Ainley E. S.
Published: July 2002

A new negative tone, chemically amplified deep ultraviolet resist, Shipley UVN-2, and a negative electron-beam (e-beam) resist, Sumitomo NEB-22A5, have been investigated for use in direct write and mask fabrication applications. The Sumitomo NEB-22A5 material has shown superior high resolution capabilities with excellent exposure latitude for both isolated and line/space features. Line and space gratings and isolated lines of 100 nm were resolved in a 400 nm film of NEB-22 using a 40 kV e-beam exposure tool. UVN-2 resist has shown resolution down to 150 nm line/space features with excellent etch selectivity and postexposure bake critical dimension control. Both resists perform well with respect to delay stability before and after exposure. This article will discuss the process development of the two resists and compare the performance characteristics including resolution, exposure latitude, linearity, and etch selectivity in various chemistries. Effects relating to pre-exposure and postexposure bake delay will also be considered because of the susceptibility of many chemically amplified resists to contaminants in the air. Finally, the application of these resists for both direct write and advanced mask making applications will be discussed.
Analysis of a micromachine based vacuum pump on a chip actuated by the thermal transpiration effect
Authors: Young Robert M.
Published: July 2002

A novel technique to create a vacuum pump on an integrated circuit chip is presented. This pump consists of small tubes operating in the free molecular flow regime, connected to larger, although still miniature, viscous flow chambers. The gas is alternately heated and cooled as it traverses these tubes and chambers, the thermal transpiration effect creating a mass flow and compression in each stage. The pump has no moving parts, eliminating wear and particulate generation and increasing reliability, also the power required is low, in the milliwatt range, permitting battery power for portability; no valves are required; and the pump is silent, with no noise being generated. An analysis is given for sizing the dimensions of the free molecular tubes and the continuum cells. Two examples are provided for a vacuum pump compressing from 3 up to 152 Torr at flow rates of 2E-4 and 2E-3 sccm, the latter case having the connecting tubes in transition (Knudsen number of 1). These parameters are appropriate for the first roughing pump of a “mass spectrometer on a chip” gas sensor.
Native oxides and regrowth on III–N surfaces
Authors: Gupta V. K. , Wamsley C. C. , Koch M. W. , Wicks G. W.
Published: July 2002

The characteristics of native oxides on epitaxially grown III–N materials, particularly GaN and AlN, were studied using reflection high-energy electron diffraction (RHEED) and photoluminescence (PL) spectroscopy. RHEED observations show no sign of the formation of native oxides on III–N surfaces by air exposure, contrary to the III–As surfaces which readily oxidize upon exposure to air. One result of this behavior is that high-quality regrowth is possible on air-exposed III–N surfaces. Two GaN samples were grown on top of AlN buffer layers using molecular beam epitaxy, one sample was grown continuously while the other had an air-exposed interface in the AlN buffer. PL studies show that the luminescence properties of GaN layers in both samples are comparable and that material quality is not degraded due to the air exposure of the AlN buffer.
Band offsets for ultrathin SiO2 and Si3N4 films on Si(111) and Si(100) from photoemission spectroscopy
Authors: Keister J. W. , Rowe J. E. , Kolodziej J. J. , Niimi H. , Madey T. E. , Lucovsky G.
Published: July 2002

High resolution soft x-ray photoelectron spectroscopy with synchrotron radiation is used to study the interfaces of SiO2/Si(111), SiO2/Si(100), Si(111)/Si3N4, and SiO2/Si3N4 for device-quality ultrathin gate oxides and nitrides. The thin oxides and nitrides were grown by remote plasma deposition at a temperature of 300 °C. Aftergrowth samples were further processed by rapid thermal annealing for 30 s at various temperatures from 700 to 950 °C. The Si(111)/Si3N4 samples were air exposed and formed a thin ∼6 Å SiO2 layer with a Si(2p) core-level shift of 3.9 eV, thus allowing us to study both the Si(111)/Si3N4 and SiO2/Si3N4 interfaces with a single type of sample. We obtain band offsets of 4.54±0.06 eV for SiO2/Si(111) and 4.35±0.06 eV for SiO2/Si(100) with film thicknesses in the range 8–12 Å. The Si(111)/Si3N4 nitrides show 1.78±0.09 eV valence-band offset for 15–21 Å films. This value agrees using the additivity relationship with our independent photoemission measurements of the nitride–oxide valence-band offset of 2.66±0.14 eV. However, we measure a substantially larger SiO2/Si3N4 ΔEV value of 3.05 eV for thicker (∼60 Å) films, and this indicates substantial differences in core-hole screening for films of different thickness due to additional silicon substrate screening in the thinner (15–21 Å) films.
Practical aspects of solid source molecular beam epitaxial growth of phosphorus-containing films
Authors: Hoke W. E. , Lemonias P. J.
Published: July 2002

The growth of phosphide films by solid source molecular beam epitaxy presents challenges in regard to safety, oxygen contamination, and disposal of residual phosphorus. Upon venting the growth chamber after phosphide growth, phosphine concentrations greater than the permissible exposure limit were measured inside the chamber due to the reaction of moisture with residual red phosphorus deposits on the chamber walls. Another product of the reaction is hydrated phosphorus oxides that can degrade subsequently grown aluminum-containing films. Procedures were developed to safely vent the growth chamber as well as to minimize oxygen contamination of phosphide and arsenide films. Contamination in the phosphide films was also caused by significant concentrations of oxygen in the bulk of the starting phosphorus ingot. The contamination was greatly reduced by lowering the phosphorus cracker temperature. A mechanism involving volatile phosphorus trioxide, P4O6, is proposed to qualitatively explain the effect of cracker temperature on oxygen contamination. Due to incomplete cracking of sublimed elemental phosphorus, deposits of flammable white phosphorus were created in the chamber. Procedures were developed to safely remove the white phosphorus from the machine and convert it into a nontoxic form for easy disposal.
Fabrication of patterned media for high density magnetic storage
Authors: Ross C. A. , Smith Henry I. , Savas T. , Schattenburg M. , Farhoud M. , Hwang M. , Walsh M. , Abraham M. C. , Ram R. J.
Published: July 2002

Arrays of discrete, lithographically patterned magnetic elements have been proposed as a new generation of ultrahigh density patterned magnetic storage media. Interferometric lithography has been used to make prototype arrays over large areas with periods of 100–200 nm. Arrays of magnetic pillars, pyramids, and dots have been made by electrodeposition, evaporation and liftoff, and etching processes, and the magnetic properties of the particles and their mutual interactions have been measured.
Dielectric characteristics of a metal–insulator–metal capacitor using plasma-enhanced chemical vapor deposited silicon nitride films
Authors: Maeda Masahiko , Yamamoto Ei-ichi , Ohfuji Shin-ichi , Itsumi Manabu
Published: July 2002

Dielectric characteristics of a metal–insulator–metal (MIM) capacitor using plasma-enhanced chemical vapor deposited thin silicon nitride films have been evaluated. The capacitance values of the MIM capacitors are in proportion to the area of capacitors and in inverse proportion to the thickness of silicon nitride films. The breakdown strength of silicon nitride films with thicknesses of less than 0.2 μm decreases because of the concentration of electrical fields at hillocks induced on the aluminum surface. However, about 3 MV/cm is obtained in the silicon nitride films with thicknesses of 0.1 μm. The dielectric losses of the MIM capacitors are low enough up to the gigahertz regions.
Nanometer-scale data storage on 3-phenyl-1-ureidonitrile thin film using scanning tunneling microscopy
Authors: Shi D. X. , Ma L. P. , Xie S. S. , Pang S. J.
Published: July 2002

We present nanometer-scale date storage on 3-phenyl-1-ureidonitrile thin film using scanning tunneling microscopy (STM). This monomer film can become polymerized when a voltage pulse is applied between the STM tip and the substrate. The affected region changes from being electrically resistant to electrically conductive along the direction of the polymeric molecular chain. The recorded mark of the data occurs in the region, and is 0.8 nm. We have obtained recorded marks arranged regularly as 6×8 arrays. A possible chemical mechanism of this data storage would be the phase transition from the monomer state to the polymeric state. The small marks are very stable.
Hunting the Metaphor
Authors: Brenner Sydney
Published: July 2002

Cracking the Genome
Inside the Race to Unlock Human DNA. Kevin Davies. Free Press, New York, 2001. 320 pp. $25. ISBN 0-7432-0479-4.
Released in the UK as
The Sequence
Inside the Race for the Human Genome. Weidenfeld and Nicholson, London, 2001. 320 pp. £20. ISBN 0-297-64698-2.

This lively, accessible, and even-handed account describes the efforts to sequence the human genome from the early plans of the mid-1980s to the White House announcement of June 2000. Davies weaves together stories of the science, technologies, politics, and personalities that contributed to the Human Genome Project, Venter's shotgun approach, and the intense competition that developed between them.
Cytokine-Specific Transcriptional Regulation Through an IL-5Rα Interacting Protein
Authors: Geijsen Niels , Uings Iain J. , Pals Cornelieke , Armstrong John , McKinnon Murray , Raaijmakers Jan A. M. , Lammers Jan-Willem J. , Koenderman Leo , Coffer Paul J.
Published: July 2002

Cytokine receptors consist of multiple subunits, which are often shared between different receptors, resulting in the functional redundancy sometimes observed between cytokines. The interleukin 5 (IL-5) receptor consists of an IL-5–specific α-subunit (IL-5Rα) and a signal-transducing β-subunit (βc) shared with the IL-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors. In this study, we sought to find a role for the cytoplasmic domain of IL-5Rα. We show that syntenin, a protein containing PSD-95/Discs large/zO-1 (PDZ) domains, associates with the cytoplasmic tail of the IL-5Rα. Syntenin was found to directly associate with the transcription factor Sox4. Association of syntenin with IL-5Rα was required for IL-5–mediated activation of Sox4. These studies identify a mechanism of transcriptional activation by cytokine-specific receptor subunits.
An Optical Clock Based on a Single Trapped
199
Hg
+
Ion
Authors: Diddams S. A. , Udem Th. , Bergquist J. C. , Curtis E. A. , Drullinger R. E. , Hollberg L. , Itano W. M. , Lee W. D. , Oates C. W. , Vogel K. R. , Wineland D. J.
Published: July 2002

Microwave atomic clocks have been the de facto standards for precision time and frequency metrology over the past 50 years, finding widespread use in basic scientific studies, communications, and navigation. However, with its higher operating frequency, an atomic clock based on an optical transition can be much more stable. We demonstrate an all-optical atomic clock referenced to the 1.064-petahertz transition of a single trapped
199
Hg
+
ion. A clockwork based on a mode-locked femtosecond laser provides output pulses at a 1-gigahertz rate that are phase-coherently locked to the optical frequency. By comparison to a laser-cooled calcium optical standard, an upper limit for the fractional frequency instability of 7 × 10
−15
is measured in 1 second of averaging—a value substantially better than that of the world's best microwave atomic clocks.
Role of the Nonsense-Mediated Decay Factor hUpf3 in the Splicing-Dependent Exon-Exon Junction Complex
Authors: Kim V. Narry , Kataoka Naoyuki , Dreyfuss Gideon
Published: July 2002

Nonsense-mediated messenger RNA (mRNA) decay, or NMD, is a critical process of selective degradation of mRNAs that contain premature stop codons. NMD depends on both pre-mRNA splicing and translation, and it requires recognition of the position of stop codons relative to exon-exon junctions. A key factor in NMD is hUpf3, a mostly nuclear protein that shuttles between the nucleus and cytoplasm and interacts specifically with spliced mRNAs. We found that hUpf3 interacts with Y14, a component of post-splicing mRNA-protein (mRNP) complexes, and that hUpf3 is enriched in Y14-containing mRNP complexes. The mRNA export factors Aly/REF and TAP are also associated with nuclear hUpf3, indicating that hUpf3 is in mRNP complexes that are poised for nuclear export. Like Y14 and Aly/REF, hUpf3 binds to spliced mRNAs specifically (∼20 nucleotides) upstream of exon-exon junctions. The splicing-dependent binding of hUpf3 to mRNAs before export, as part of the complex that assembles near exon-exon junctions, allows it to serve as a link between splicing and NMD in the cytoplasm.
Indication of Global Deforestation at the Cretaceous-Tertiary Boundary by New Zealand Fern Spike
Authors: Vajda Vivi , Raine J. Ian , Hollis Christopher J.
Published: July 2002

The devastating effect on terrestrial plant communities of a bolide impact at the Cretaceous-Tertiary boundary is shown in fossil pollen and spore assemblages by a diverse flora being abruptly replaced by one dominated by a few species of fern. Well documented in North America, this fern spike signals widespread deforestation due to an impact winter or massive wildfires. A Southern Hemisphere record of a fern spike, together with a large iridium anomaly, indicates that the devastation was truly global. Recovery of New Zealand plant communities followed a pattern consistent with major climatic perturbations occurring after an impact winter that was possibly preceded by global wildfires.
Nonequilibrium Diversity Dynamics of the Lesser Antillean Avifauna
Authors: Ricklefs Robert E. , Bermingham Eldredge
Published: July 2002

MacArthur and Wilson's model of island diversity predicts an increase in the number of species until colonization and extinction are balanced at a long-term steady state. We appraise this model on an evolutionary time scale by molecular phylogenetic analysis of the colonization of the Lesser Antilles by small land birds. The pattern of accumulation of species with time, estimated by genetic divergence between island and source lineages, rejects a homogeneous model of colonization and extinction. Rather, our results suggest an abrupt, roughly 10-fold increase in colonization rate or a 90% mass extinction event 0.55 to 0.75 million years ago.
Cell Proliferation Without Neurogenesis in Adult Primate Neocortex
Authors: Kornack David R. , Rakic Pasko
Published: July 2002

A recent assertion that new neurons are continually added to the neocortex of adult macaque monkeys has profound implications for understanding the cellular mechanisms of higher cognitive functions. Here we searched for neurogenesis in adult macaques by using immunofluorescent triple labeling for the DNA-replication indicator, bromodeoxyuridine (BrdU), and neuronal and glial cell markers. Although numerous BrdU-labeled cells were distributed throughout the cerebral wall, including the neocortex, these were identified as nonneuronal cells; evidence for newly generated neurons was limited to the hippocampus and olfactory bulb. Thus, our results do not substantiate the claim of neurogenesis in normal adult primate neocortex.
Direct Determination of the Timing of Sea Level Change During Termination II
Authors: Gallup Christina D. , Cheng H. , Taylor F. W. , Edwards R. L.
Published: July 2002

An outcrop within the last interglacial terrace on Barbados contains corals that grew during the penultimate deglaciation, or Termination II. We used combined
230
Th and
231
Pa dating to determine that they grew 135.8 ± 0.8 thousand years ago, indicating that sea level was 18 ± 3 meters below present sea level at the time. This suggests that sea level had risen to within 20% of its peak last-interglacial value by 136 thousand years ago, in conflict with Milankovitch theory predictions. Orbital forcing may have played a role in the deglaciation, as may have isostatic adjustments due to large ice sheets. Other corals in the same outcrop grew during oxygen isotope (δ
18
O) substage 6e, indicating that sea level was 38 ± 5 meters below present sea level, about 168.0 thousand years ago. When compared to the δ
18
O signal in the benthic V19-30/V19-28 record at that time, the coral data extend to the previous glacial cycle the conclusion that deep-water temperatures were colder during glacial periods.
Control of the Selectivity of the Aquaporin Water Channel Family by Global Orientational Tuning
Authors: Tajkhorshid Emad , Nollert Peter , Jensen Morten Ø. , Miercke Larry J. W. , O'Connell Joseph , Stroud Robert M. , Schulten Klaus
Published: July 2002

Aquaporins are transmembrane channels found in cell membranes of all life forms. We examine their apparently paradoxical property, facilitation of efficient permeation of water while excluding protons, which is of critical importance to preserving the electrochemical potential across the cell membrane. We have determined the structure of the
Escherichia coli
aquaglyceroporin GlpF with bound water, in native (2.7 angstroms) and in W48F/F200T mutant (2.1 angstroms) forms, and carried out 12-nanosecond molecular dynamics simulations that define the spatial and temporal probability distribution and orientation of a single file of seven to nine water molecules inside the channel. Two conserved asparagines force a central water molecule to serve strictly as a hydrogen bond donor to its neighboring water molecules. Assisted by the electrostatic potential generated by two half-membrane spanning loops, this dictates opposite orientations of water molecules in the two halves of the channel, and thus prevents the formation of a “proton wire,” while permitting rapid water diffusion. Both simulations and observations revealed a more regular distribution of channel water and an increased water permeability for the W48F/F200T mutant.
Bile Acid Secreted by Male Sea Lamprey That Acts as a Sex Pheromone
Authors: Li Weiming , Scott Alexander P. , Siefkes Michael J. , Yan Honggao , Liu Qin , Yun Sang-Seon , Gage Douglas A.
Published: July 2002

We show that reproductively mature male sea lampreys release a bile acid that acts as a potent sex pheromone, inducing preference and searching behavior in ovulated female lampreys. The secreted bile acid 7α,12α,24-trihydroxy-5α-cholan-3-one 24-sulfate was released in much higher amounts relative to known vertebrate steroid pheromones and may be secreted through the gills. Hence, the male of this fish species signals both its reproductive status and location to females by secreting a pheromone that can act over long distances.
Multicolor and Electron Microscopic Imaging of Connexin Trafficking
Authors: Gaietta Guido , Deerinck Thomas J. , Adams Stephen R. , Bouwer James , Tour Oded , Laird Dale W. , Sosinsky Gina E. , Tsien Roger Y. , Ellisman Mark H.
Published: July 2002

Recombinant proteins containing tetracysteine tags can be successively labeled in living cells with different colors of biarsenical fluorophores so that older and younger protein molecules can be sharply distinguished by both fluorescence and electron microscopy. Here we used this approach to show that newly synthesized connexin43 was transported predominantly in 100- to 150-nanometer vesicles to the plasma membrane and incorporated at the periphery of existing gap junctions, whereas older connexins were removed from the center of the plaques into pleiomorphic vesicles of widely varying sizes. Selective imaging by correlated optical and electron microscopy of protein molecules of known ages will clarify fundamental processes of protein trafficking in situ.
Autosomal Dominant Mutations Affecting X Inactivation Choice in the Mouse
Authors: Percec Ivona , Plenge Robert M. , Nadeau Joseph H. , Bartolomei Marisa S. , Willard Huntington F.
Published: July 2002

X chromosome inactivation is the silencing mechanism eutherian mammals use to equalize the expression of X-linked genes between males and females early in embryonic development. In the mouse, genetic control of inactivation requires elements within the X inactivation center (
Xic
) on the X chromosome that influence the choice of which X chromosome is to be inactivated in individual cells. It has long been posited that unidentified autosomal factors are essential to the process. We have used chemical mutagenesis in the mouse to identify specific factors involved in X inactivation and report two genetically distinct autosomal mutations with dominant effects on X chromosome choice early in embryogenesis.
California Bans Affirmative Action
Authors: Barinaga Marcia
Published: July 2002

By passing Proposition 209, California voters outlawed affirmative action at state-funded universities--a move predicted to shrink the already-small pool of minority students in science.
Complexities in the Treatment of Autoimmune Disease
Authors: McFarland Henry F.
Published: July 2002

Excitement has been high in the immunological community, as animal and human studies have suggested that autoimmune diseases can be prevented or inhibited by treatment with the offending endogenous antigen. But two cautionary reports in
Science
(
p. 2054
and
p. 1707
) indicate that under some circumstances oral or parental treatment with antigen can exacerbate the autoimmune attack. In his Perspective, McFarland summarizes these new results and explains the great complexity of the immune system that they imply.
Clinton Picks Peña to Lead Energy
Authors: Lawler Andrew
Published: July 2002

Ethnic politics won out over experience in the energy field as President Bill Clinton late last month picked Transportation Secretary Federico Peña to lead the Department of Energy, completing his roster of science and technology appointments.
Navigating Shrinking Financial Seas
Authors: Morell Virginia
Published: July 2002

Ashland, Oregon—Deep-sea oceanography was once supported by several different agencies, but the National Science Foundation (NSF) now finds itself funding the lion's share of research in everything from the geochemistry of deep-sea vents to the development of new undersea robotic craft. Last month, NSF's Marine Geology and Geosciences program invited about 40 marine researchers to a gloves-off workshop to discuss future directions. They got an emotional response. Researchers offered ideas ranging from more interdisciplinary research to better public relations, but if there was one single theme it was this: hard choices lie ahead.
The Many Faces of WAS Protein
Authors: Featherstone Carol
Published: July 2002

For many years, immunologists have puzzled over how a single gene mutation can cause the diverse symptoms of Wiskott-Aldrich syndrome, a rare hereditary disease characterized by symptoms ranging from a severely compromised immune system to bleeding and cancer. Recent studies of WASp, protein produced by the gene at fault in WAS, are helping to solve that mystery, and at the same time are pointing to some intriguing new connections between the cell's internal communication pathways.
Hedging Bets on Hard Problems
Authors: Seife Charles
Published: July 2002

Solving certain problems in computer science is a gamble: There's no way to know in advance how long an algorithm will take to yield an answer. In this issue (see
page 51
), a group of researchers presents a technique for bettering the odds by imitating Wall Street: splitting the computer's investment among a “portfolio” of different programs in the hope that one of them will get lucky.
Pig-Human Transplants Barred for Now
Authors: Williams Nigel
Published: July 2002

LONDON
—A report by a panel of British government advisers gave an amber light last week for research into the transplantation of pig organs into humans. The panel agreed that the procedure was ethically acceptable but ruled out clinical trials until further research has shown that such transplants are safe and that patients will benefit.
Science and the Protection of Endangered Species
Authors: Pulliam H. Ronald , Babbitt Bruce
Published: July 2002

A report by Dobson
et al
. (
p. 550
) in this week's issue of
Science
brings together data from many sources on the distribution of endemic plants and animals in the United States and identifies three “hot spots” that contain a particularly high number of endangered species. Hawaii, California, and Florida contain concentrations of endangered organisms. In their Perspective, Pulliam and Interior Secretary Babbitt describe how these data can be profitably used in improving the fate of endangered species and making policy decisions.
Regulation of NF-κB by Cyclin-Dependent Kinases Associated with the p300 Coactivator
Authors: Perkins Neil D. , Felzien Lisa K. , Betts Jonathan C. , Leung Kwanyee , Beach David H. , Nabel Gary J.
Published: July 2002

The nuclear factor κB (NF-κB) transcription factor is responsive to specific cytokines and stress and is often activated in association with cell damage and growth arrest in eukaryotes. NF-κB is a heterodimeric protein, typically composed of 50- and 65-kilodalton subunits of the Rel family, of which RelA(p65) stimulates transcription of diverse genes. Specific cyclin-dependent kinases (CDKs) were found to regulate transcriptional activation by NF-κB through interactions with the coactivator p300. The transcriptional activation domain of RelA(p65) interacted with an amino-terminal region of p300 distinct from a carboxyl-terminal region of p300 required for binding to the cyclin E-Cdk2 complex. The CDK inhibitor p21 or a dominant negative Cdk2, which inhibited p300-associated cyclin E-Cdk2 activity, stimulated κB-dependent gene expression, which was also enhanced by expression of p300 in the presence of p21. The interaction of NF-κB and CDKs through the p300 and CBP coactivators provides a mechanism for the coordination of transcriptional activation with cell cycle progression.
First Atom Laser Shoots Pulses of Coherent Matter
Authors: Taubes Gary
Published: July 2002

The word laser has taken on a new meaning: a beam of atoms marching in quantum lockstep, like the photons of a light laser. Two years ago, physicists achieved the crucial starting point for an atom laser, which could aid everything from atomic clocks to chipmaking, when they created an exotic brew of atoms all merged in a single quantum state. Now, a group at the Massachusetts Institute of Technology reports in this issue (
p. 637
) that they have shaped this “Bose-Einstein condensate” into pulses, each one a single, coherent “matter wave.”
Disposing of Plutonium
Authors: Ewing Rodney C. , Lutze Werner , Steinberg Meyer
Published: July 2002

Wolfgang K. H. Panofsky has recently written (Letters, 3 Jan.,
p. 11
) in support of the decision by the Department of Energy (DOE) to “pursue two technologies for disposing of excess military plutonium.” He describes the technologies as (i) the “throw away” vitrification into glass logs option, and (ii) the “burn-up” in a mixed oxide fuel option. This does not seem to be an accurate or complete description of the Administration's two options. It is correct that one option is to burn up the surplus plutonium as mixed oxide fuel, with subsequent disposal of the spent fuel in a geologic repository. However, the other option is not restricted to vitrification, but includes immobilization of plutonium in “glass or ceramic material” (
1
).

The “ceramic” option includes the possibility of developing durable, crystalline materials for disposing of dangerous, long-lived, fissile materials, particularly if DOE decides to immobilize all of the surplus plutonium. The National Research Council's committee (chaired by Panofsky) which assessed the options for disposing of plutonium gave the ceramic option only cursory consideration (
2
). However, research on ceramics as waste forms already has a long history (
3
). The disposal of fissile materials with long half-lives may well benefit from strategies that capitalize on the benefits of using highly durable materials that can retain both the fissile nuclides and the required neutron absorbers for hundreds of millions of years (
4
).
Grizzly Habitat
Authors: Shilling Fraser
Published: July 2002

The grizzlies described in Bernice Weuthrich's article (News & Comment, 25 Oct.,
p 493
) are hardly “wayward.” They are exploring their natural habitat. The “grazing land” they have chosen to forage on is national forest— agency-managed land of many uses, including (one hopes) habitat for threatened wild mammals. The biggest threat to survival facing large predators such as grizzlies in the United States today is not hunting or poaching, loss of prey, or habitat fragmentation. It is the politically driven approach to their “conservation” through pressure applied to agencies such as the U.S. Fish and Wildlife Service and the U.S. Forest Service.

It is high time for biologists to advocate the protection and restoration of endangered species and their habitat using ecological criteria, rather than criteria related to political pressure. Otherwise, these species will go extinct
Mixed Reviews for Habitat Plan
Authors: Kling Jim
Published: July 2002

Federal and state officials signed a land-management agreement last week to protect a host of species, including the infamous northern spotted owl, in Washington state's forests. The plan has drawn a lot of criticism, however, and not just from disgruntled loggers. Some biologists question the plan's ecological underpinnings
Dusty Roads of the Cosmos Lure New Explorers
Authors: Glanz James
Published: July 2002

TORONTO
—Astronomers, like householders, have never cared much for dust. But cosmic dust is gaining new respect, as astronomers study the interplay of dust and light in interstellar space. At an American Astronomical Society meeting here last month, that was the theme of presentations ranging from how dust in the Milky Way creates a giant Polaroid filter for starlight to how gravitational “magnifying glasses” in clusters of stars could be burning away dust.
Homage to an Itinerant Master
Authors: Mackenzie Dana
Published: July 2002

SAN DIEGO
—The mathematics community paid tribute at a meeting here last month to one of its legendary figures: Paul Erdös, who died last September. Erdös is considered the most prolific mathematician ever, yet he had no permanent home and no formal job after 1954—only a vast succession of collaborators and a gift for problems that opened productive new areas of research.
Biotechnology: How Many Genes Are There?
Authors: Cohen Jon
Published: July 2002

More than a century after Austrian monk Gregor Mendel first detailed how genetic material was passed from one generation to the next, researchers still don't know how many genes we're all walking around with. Expert estimates range from 60,000 to 150,000.
Spat Over Intellectual Property Threatens Canadian Networks
Authors: Kondro Wayne
Published: July 2002

OTTAWA
—The Canadian government, like its neighbor to the south, has been trying to forge stronger links between the nation's private companies and universities. But a new report on one such program warns that these efforts could falter unless universities relax their grip on technologies with commercial potential. One research manager in the middle of disputes over intellectual property rights calls the issue a “ticking time bomb.”
U.S., Russia to Study Radiation Effects
Authors: Marshall Eliot
Published: July 2002

On 11 February, officials from the United States and Russia announced the signing of a memorandum to launch half a dozen new, in-depth studies of the effects of radiation on people living along the Techa River in Russia. The area was heavily contaminated in the 1940s and 1950s by a nuclear-weapons facility, and the studies should provide valuable data on long-term exposure. But there's a catch: Both partners are short of cash.
Listening to Pele
Authors: Vergniolle Sylvie
Published: July 2002

Some volcanoes erupt explosively, with magma rapidly expelled as a hot jet of gas. The processes by which the magma is converted into the hot jet are still poorly understood. As discussed in the Perspective by Vergniolle, recent research reported by Morrissey and Chouet in the same issue (p.
1290
) may shed light on these violent events. Data obtained with a network of microbarographs, or pressure sensors, can be used to estimate the pressure of the exiting gas jet.
APC-Mediated Proteolysis of Ase1 and the Morphogenesis of the Mitotic Spindle
Authors: Juang Yue-Li , Huang James , Peters Jan-Michael , McLaughlin Margaret E. , Tai Chin-Yin , Pellman David
Published: July 2002

The molecular mechanisms that link cell-cycle controls to the mitotic apparatus are poorly understood. A component of the
Saccharomyces cerevisiae
spindle, Ase1, was observed to undergo cell cycle-specific degradation mediated by the cyclosome, or anaphase promoting complex (APC). Ase1 was degraded when cells exited from mitosis and entered G
1
. Inappropriate expression of stable Ase1 during G
1
produced a spindle defect that is sensed by the spindle assembly checkpoint. In addition, loss of
ASE1
function destabilized telophase spindles, and expression of a nondegradable Ase1 mutant delayed spindle disassembly. APC-mediated proteolysis therefore appears to regulate both spindle assembly and disassembly.
Panel Hopes to Splice Pieces of U.S. Research Network
Authors: Mervis Jeffrey
Published: July 2002

Connectivity is a hot topic these days, with a new White House effort on networking poised to expand the capacity of existing federal high-speed networks and join with a university-based effort to improve campus links. The goal is to design the next information superhighway.
Science Slides to Bottom of Schedule
Authors: Lawler Andrew
Published: July 2002

U.S. and Russian officials are bickering over whether the first pieces of the international space station will be launched this year or next. But whatever they decide, don't expect much science to be done on the $30 billion orbiting laboratory until after the turn of the century.
Why the West Stands Tall
Authors: Kerr Richard A.
Published: July 2002

From Denver, the “Mile-High City,” to California's Sierra Nevada, the American West stands high above sea level. For years, geologists thought that a thick, buoyant continental crust raised the West's spectacular scenery, but new geophysical surveys suggest that the forces holding up many Western mountains and plateaus come from much deeper, in Earth's mantle.
HOX Gene Links Limb, Genital Defects
Authors: Dickman Steven
Published: July 2002

The HOX gene family has helped to unlock the intricacies of development in animals from flies to mammals, but its role in humans has been a mystery. Now the second human HOX gene mutation has been found in a Michigan family. It causes abnormalities in both limbs and genitals—and raises some intriguing evolutionary ideas.
Introduction
Authors: Chin Gilbert J. , Marx Jean
Published: July 2002

T
hree hundred years ago, the French philosopher René Descartes gained immortality with his pronouncement, “I think, therefore I am.” Today, a disparate band of researchers—physicians, psychologists, and neurobiologists—is asking the next question: How do we think? This special issue of Science surveys how they are trying to provide an answer by fusing the perspectives of their formerly separate disciplines.

In her Article,
N. C. Andreasen
discusses approaches to understanding schizophrenia as a dysfunction of specific cognitive systems, such as those for working memory and consciousness. The normal underpinnings of working memory and consciousness are also coming to light, as two stories in the Special News Section make clear. (For interactive demonstrations of behavioral paradigms used to study working memory, reconstructive memory, and visual-spatial attention, see J. D. Cohen's Web site at
http://psyscope.psy.cmu.edu/cogdemos/welcome.html
) In another Article,
W. Schultz
and his colleagues examine the neural basis of animals' ability to predict future events, an essential survival skill for finding food and mates and avoiding danger. They report that neurophysiological studies of primates, buttressed by computer modeling of neuronal behavior, have revealed the importance of a particular set of dopamine-releasing neurons.

The final pair of Articles describes two efforts to tackle that peculiarly human attribute—language.
M. S. Seidenberg
reviews the classic paradigm of Noam Chomsky that focuses on innate capabilities for language acquisition and processing, then suggests an alternative based on connectionist theories that attempt to explain learning as alterations in neuronal networks. And
A. Prince and P. Smolensky
review how optimization, a formal organizing principle derived from neural computation, can characterize grammar as a hierarchy of linguistic constraints. The satisfaction of a single set of constraints appears to resolve well-known inconsistencies between listening and speaking abilities when learning language.
Cognitive Neuroscience: Working Memory Linked to Intelligence
Authors: Wickelgren Ingrid
Published: July 2002

People often think of intelligence as quickness of thought or propensity for flashes of insight. But a variety of evidence suggests that such indicators of intelligence as language comprehension and problem-solving ability may instead depend on the ability to juggle lots of possibilities in the mind—that is, on working memory.
Mammalian Cloning Debate Heats Up
Authors: Marshall Eliot
Published: July 2002

The hubbub over the cloning of Dolly, a Scottish mountain sheep, continued without letup last week. In Senate hearings and at a meeting of the National Bioethics Advisory Commission, experts, including Dolly's “father,” Ian Wilmut of the Roslin Institute in Edinburgh, Scotland, and nonexperts alike offered opinions on how the cloning technique might change the way humans reproduce and whether human cloning should be made illegal.
Staying Off Beaten Track Puts LED Researcher a Step Ahead
Authors: Normile Dennis
Published: July 2002

ANAN, JAPAN
—The inventor of the world's first bright blue light-emitting diode (LED) and leader in the race to commercialize a blue laser is an easygoing researcher far off the beaten technology track in Japan. But Shuji Nakamura of Nichia Chemical Industries Ltd. is all business when it comes to science.
Gamma-Ray Source in Distant Universe?
Authors: Schilling Govert , Biggin Susan
Published: July 2002

Over the last 30 years, space-based detectors have picked up hundreds of gamma-ray flashes, but astronomers disagree about what might be producing them and even where they come from. Now a burst source may have been revealed. Just hours after astronomers had narrowed down the position of a burst, a Dutch group pointed a telescope at the site and spotted a dim galaxy in the far reaches of the universe.
Thanks to a Parasite, Asexual Reproduction Catches On
Authors: Enserink Martin
Published: July 2002

Can you catch a new kind of sex life? Wasps can, according to new research on the speciation patterns of one family of asexually reproducing wasps and its bacterial parasite,
Wolbachia. Wolbachia
live in their hosts' egg cells and alter reproduction. And if a wasp picks up a
Wolbachia
infection from another wasp, it may be forever doomed to an asexual state.
HAARP Facility in Alaska
Authors: Gordon William E.
Published: July 2002

With respect to the News & Comment article “Ionosphere research lab sparks fears in Alaska” by Lisa Busch (
21 Feb., p. 1060
), I would like to make two points.

First, the anti-HAARP (High-Frequency Active Auroral Research Program) activists overestimated the power of the Gakona, Alaska, facility by a factor of more than a million and then used statements in patents (
1
) to fuel speculations on the part of the public about possible effects such as weather manipulations, mind warping, and communication disruptions. This incorrect information has been refuted in hearings in the Alaska legislature, in a video prepared by Senator Frank H. Murkowski (R-AK) for airing in Alaska, and at open-house sessions at the site for interested visitors.

Second, the Gakona site is now intended to be a world-class facility for studying the upper atmosphere, although the function has evolved from an over-the-horizon radar (never constructed), to a high-frequency facility (under construction) to generate ELF (Extremely Low Frequency) radio waves in the ionosphere, to a major center for upper atmosphere studies using a variety of diagnostics (some in place) with a powerful incoherent scatter radar (ISR) as the core instrument (to be constructed). The core instrument will join with existing ISRs at Svalbard and Tromsø in Norway; Sondrestrom, Greenland; and Boston, Massachusetts, and with the proposed ISR at Resolute Bay, Canada, to form an Arctic network of radars to observe virtually the whole Polar Cap and to track disturbances produced by solar inputs in the form of waves and particles. The network will be a remarkable additon to the tools available to the atmospheric science community with applications to space weather, Arctic and satellite communications, and electric power-grid problems.

In the early days of the Arecibo Observatory in Puerto Rico there were concerns expressed about the facility, but these have long since been replaced by satisfaction with the scientific outcomes and the benefits to the local economy. The residents of Alaska will find similar benefits.
International Support for Natural History Museums
Authors: Budiman Arie , Burley John , Peake John , West Judy
Published: July 2002

An article by Nigel Williams (News & Comment,
27 Sept., p. 1792
) and a Policy Forum by Stephen Blackmore (
4 Oct., p. 63
) raise three issues: (i) How can the biodiversity information associated with natural history museum collections be made available to a wider range of users? (ii) How can international support and funding for this activity be increased? and (iii) Do we need a new international organization, responsible for coordination and strategic planning, to facilitate these two objectives?

Multilateral and bilateral international funding agencies have already demonstrated a willingness to fund systematic collections and biodiversity information systems, in the context of “demand driven” projects that have close links to users, lead to clearly identifiable outputs, and can be achieved in discrete time-frames. Present examples include the Indonesian Biodiversity Collections Project, a 5-year international program to strengthen the institutional capacity of the national herbarium (Herbarium Bogoriense) and the national zoological museum (Museum Zoologicum Bogoriense), under the Research and Development Center for Biology of the Indonesian Institute of Sciences. This project is funded in part by a $7.2-million grant from the Global Environment Facility Trust Fund under the supervision of the World Bank. Closely associated with this project is the Indonesian Biodiversity Conservation Project, which includes $14 million in grant aid from the government of Japan to construct a new, custom-built museum to rehouse the zoology collections.

The urgent need for these projects was first identified in the Biodiversity Action Plan for Indonesia. The Government of Indonesia has since reaffirmed this goal as a national priority and provided substantial counterpart funding.

Careful consideration should be given to how these and other projects are being implemented before the systematics community develops proposals to create new international organizations for the promotion of natural history collections or new financial instruments to facilitate access to information held in these collections.
Is ‘Good Wood’ Bad for Forests?
Authors: McRae Michael
Published: July 2002

Conservation biologists have long believed that the way to save rain forests and the wealth of species inhabiting them is to harvest their trees in a sustainable manner. But that notion has been challenged recently by two researchers who contend that, in some cases, sustainable management can be bad for forests, biodiversity, and loggers. Their heretical prescription for saving at least some rain forests is to permit loggers to cut the most valuable species, and then place the forest off limits to commercial logging. Critics counter that their viewpoint is naïve and damaging to rain-forest conservation.