bluuebunny/crossref_metadata_2025 huggingface dataset:
Reactive ion beam etching of GaAs and related compounds in an inductively coupled plasma of Cl2–Ar mixture
Authors: Hahn Y. B. , Lee J. W. , Vawter G. A. , Shul R. J. , Abernathy C. R. , Hays D. C. , Lambers E. S. , Pearton S. J.
Published: July 2002

Reactive ion beam etching (RIBE) of GaAs, GaP, AlGaAs, and GaSb was performed in a Cl2–Ar mixture using an inductively coupled plasma source. The etch rates and yields were strongly affected by ion energy and substrate temperature. The RIBE was dominated by ion-assisted etching at <600 eV and by physical sputtering beyond 600 eV. The temperature dependence of the etch rates revealed three different regimes, depending on the substrate temperature: (1) sputtering-etch limited, (2) products-desorption limited, and (3) mass-transfer limited regions. GaSb showed the overall highest etch rates, while GaAs and AlGaAs were etched at the same rates. The etched features showed extremely smooth morphologies with anisotropic sidewalls.
Pulsed metal ion source by triggerless shunting arc discharge
Authors: Yukimura Ken , Isono Ryota , Monguchi Toshihide , Yoshioka Kenji , Masamune Sadao
Published: July 2002

The shunting arc is an arc discharge that is self-ignited in a low pressure gas without any trigger source. Possible application of the shunting arc to a pulsed ion source for plasma based ion implantation will be discussed. A 35 mm long titanium (Ti) wire 0.05 mm in diameter is heated by means of pulsed current from a 20 μF capacitor (1.5–3.0 kV) in an argon environment with pressure from 2.7 to 1300 Pa. Arc ignition was indicated by an abrupt decrease of the wire voltage accompanied by an abrupt increase of the arc current. Ultraviolet light spectroscopy has shown that a plasma containing Ti ions and neutrals is produced by means of the arc discharge. The maximum arc current is about 2.1 kA with arc voltage of 200–300 V. The wire temperature is estimated at about 1500 K, well below the melting point of Ti. The wire therefore remains in a solid phase during the arc discharge so that the wire can be used repeatedly. Ions are extracted from the plasma by a 5 kV, 10 μs negative high voltage pulse applied to a target. Shunting arc ignition using materials other than Ti will also be discussed.
Fabrication of microdiamond array and electrical characterization of individual diamond microcrystals based on scanning probe microscopy
Authors: Sugimura Hiroyuki , Ushiyama Kazuya , Sato Yoshiki , Takai Osamu , Sakamoto Yukihiro , Takaya Matsufumi , Nakagiri Nobuyuki
Published: July 2002

A microdiamond array, in which 2500 diamond microparticles 2 μm in diameter were precisely arranged in a μm scale, was fabricated by site-selective plasma chemical vapor deposition (CVD). Diamond was synthesized on a Pt substrate covered with a SiO2 layer 0.2 μm in thickness on which, using photolithographic processes, holes of 2×2 μm2 were fabricated in order to expose the Pt surface at the bottom of each hole. Diamond microparticles grew selectively on these Pt sites based on the great difference between the nucleation densities of diamond on Pt and SiO2 surfaces. At the initial stage of this site-selective CVD, the diamond growth was confined in the hole, and accordingly, a plate-like shaped diamond microparticle was formed. Using an electrically conductive probe for atomic force microscopy, the electrical conductivity of each plate-like diamond particle was measured while simultaneously acquiring a topographic image of the particles. The diamond particle consisted of multiple grains and their conductivity was not homogeneous. The central regions of the grains were less conductive than their edge regions. The grain boundaries were as nonconductive as the surrounding SiO2 region.
Microstructure of concentric ring patterns on Ta/Si(100)
Authors: Sheng H. Y. , Fujita D. , Dong Z. C. , Okamoto H. , Ohgi T. , Nejoh H.
Published: July 2002

We observed concentric ring patterns on a Ta film deposited on Si(100) after thermal treatments of annealing at 900 °C for 24 h, followed by flashing at 1300 °C for a few seconds in an ultrahigh vacuum. The diameters of the ring pattern range from a few tens of micrometers to several hundred micrometers. Atomic force microscopy studies indicate a height of about 100 nm for the rings. Auger electron spectroscopy analyses show that the TaSi2 layer is formed on the Si surface during heating and that the silicide layer is about four times thicker than the as-deposited Ta film.
Fabrication of dielectric hollow submicrometric pipes
Authors: Soares Leandro L. , Cescato Lucila , Cruz Nilson C. , de Moraes Mário B.
Published: July 2002

A simple technique to obtain an array of hollow submicrometric titanium oxide pipes is described. Initially, a submicrometric structure is formed in a positive photoresist by holographic exposure, followed by the deposition of the titanium oxide film and the removal of the photoresist by an appropriate solvent. These structures may be useful as waveguides for x-ray and neutron capillary optics.
High resolution phosphor screening method for full-color field emission display applications
Authors: Jang J. E. , Gwak J.-H. , Jin Y. W. , Lee S. J. , Park S. H. , Jung J. E. , Lee N. S. , Kim J. M.
Published: July 2002

A polyvinyl alcohol-slurry screening technology of phosphors was studied for field emission displays with a resolution up to supervideo graphics adapter. Phosphor lines were successfully patterned as narrow as 25 μm on 6 in. glass substrates. Process conditions such as spin coating speeds, exposure time, and shadow mask layout for photolithography were related to thickness and line resolutions of phosphor. Luminance characteristics of phosphors were optimized in terms of firing processes. For ZnS:Cu, Al, ZnS:Ag, Cl, and Y2O3:Eu phosphors, the firing temperature was optimized to be 400 °C. The nitrogen ambient during the cooling process improves the stability of phosphor surface.
A Multispecies Overkill Simulation of the End-Pleistocene Megafaunal Mass Extinction
Authors: Alroy John
Published: July 2002

A computer simulation of North American end-Pleistocene human and large herbivore population dynamics correctly predicts the extinction or survival of 32 out of 41 prey species. Slow human population growth rates, random hunting, and low maximum hunting effort are assumed; additional parameters are based on published values. Predictions are close to observed values for overall extinction rates, human population densities, game consumption rates, and the temporal overlap of humans and extinct species. Results are robust to variation in unconstrained parameters. This fully mechanistic model accounts for megafaunal extinction without invoking climate change and secondary ecological effects.
Sea Level Change Through the Last Glacial Cycle
Authors: Lambeck Kurt , Chappell John
Published: July 2002

Sea level change during the Quaternary is primarily a consequence of the cyclic growth and decay of ice sheets, resulting in a complex spatial and temporal pattern. Observations of this variability provide constraints on the timing, rates, and magnitudes of the changes in ice mass during a glacial cycle, as well as more limited information on the distribution of ice between the major ice sheets at any time. Observations of glacially induced sea level changes also provide information on the response of the mantle to surface loading on time scales of 10
3
to 10
5
years. Regional analyses indicate that the earth-response function is depth dependent as well as spatially variable. Comprehensive models of sea level change enable the migration of coastlines to be predicted during glacial cycles, including the anthropologically important period from about 60,000 to 20,000 years ago.
A 14,000-Year Oxygen Isotope Record from Diatom Silica in Two Alpine Lakes on Mt. Kenya
Authors: Barker P. A. , Street-Perrott F. A. , Leng M. J. , Greenwood P. B. , Swain D. L. , Perrott R. A. , Telford R. J. , Ficken K. J.
Published: July 2002

Oxygen isotopes are sensitive tracers of climate change in tropical regions. Abrupt shifts of up to 18 per mil in the oxygen isotope ratio of diatom silica have been found in a 14,000-year record from two alpine lakes on Mt. Kenya. Interpretation of tropical-montane isotope records is controversial, especially concerning the relative roles of precipitation and temperature. Here, we argue that Holocene variations in δ
18
O are better explained by lake moisture balance than by temperature-induced fractionation. Episodes of heavy convective precipitation dated ∼11,100 to 8600, 6700 to 5600, 2900 to 1900, and <1300 years before the present were linked to enhanced soil erosion, neoglacial ice advances, and forest expansion on Mt. Kenya.
Crystal Structure of the Ribosome at 5.5 Å Resolution
Authors: Yusupov Marat M. , Yusupova Gulnara Zh. , Baucom Albion , Lieberman Kate , Earnest Thomas N. , Cate J. H. D. , Noller Harry F.
Published: July 2002

We describe the crystal structure of the complete
Thermus thermophilus
70
S
ribosome containing bound messenger RNA and transfer RNAs (tRNAs) at 5.5 angstrom resolution. All of the 16
S
, 23
S
, and 5
S
ribosomal RNA (rRNA) chains, the A-, P-, and E-site tRNAs, and most of the ribosomal proteins can be fitted to the electron density map. The core of the interface between the 30
S
small subunit and the 50
S
large subunit, where the tRNA substrates are bound, is dominated by RNA, with proteins located mainly at the periphery, consistent with ribosomal function being based on rRNA. In each of the three tRNA binding sites, the ribosome contacts all of the major elements of tRNA, providing an explanation for the conservation of tRNA structure. The tRNAs are closely juxtaposed with the intersubunit bridges, in a way that suggests coupling of the 20 to 50 angstrom movements associated with tRNA translocation with intersubunit movement.
Recognition of Cognate Transfer RNA by the 30
S
Ribosomal Subunit
Authors: Ogle James M. , Brodersen Ditlev E. , Clemons William M. , Tarry Michael J. , Carter Andrew P. , Ramakrishnan V.
Published: July 2002

Crystal structures of the 30
S
ribosomal subunit in complex with messenger RNA and cognate transfer RNA in the A site, both in the presence and absence of the antibiotic paromomycin, have been solved at between 3.1 and 3.3 angstroms resolution. Cognate transfer RNA (tRNA) binding induces global domain movements of the 30
S
subunit and changes in the conformation of the universally conserved and essential bases A1492, A1493, and G530 of 16
S
RNA. These bases interact intimately with the minor groove of the first two base pairs between the codon and anticodon, thus sensing Watson-Crick base-pairing geometry and discriminating against near-cognate tRNA. The third, or “wobble,” position of the codon is free to accommodate certain noncanonical base pairs. By partially inducing these structural changes, paromomycin facilitates binding of near-cognate tRNAs.
Migratory Movements, Depth Preferences, and Thermal Biology of Atlantic Bluefin Tuna
Authors: Block Barbara A. , Dewar Heidi , Blackwell Susanna B. , Williams Thomas D. , Prince Eric D. , Farwell Charles J. , Boustany Andre , Teo Steven L. H. , Seitz Andrew , Walli Andreas , Fudge Douglas
Published: July 2002

The deployment of electronic data storage tags that are surgically implanted or satellite-linked provides marine researchers with new ways to examine the movements, environmental preferences, and physiology of pelagic vertebrates. We report the results obtained from tagging of Atlantic bluefin tuna with implantable archival and pop-up satellite archival tags. The electronic tagging data provide insights into the seasonal movements and environmental preferences of this species. Bluefin tuna dive to depths of >1000 meters and maintain a warm body temperature. Western-tagged bluefin tuna make trans-Atlantic migrations and they frequent spawning grounds in the Gulf of Mexico and eastern Mediterranean. These data are critical for the future management and conservation of bluefin tuna in the Atlantic.
Carbon Nanotube Single-Electron Transistors at Room Temperature
Authors: Postma Henk W. Ch. , Teepen Tijs , Yao Zhen , Grifoni Milena , Dekker Cees
Published: July 2002

Room-temperature single-electron transistors are realized within individual metallic single-wall carbon nanotube molecules. The devices feature a short (down to ∼20 nanometers) nanotube section that is created by inducing local barriers into the tube with an atomic force microscope. Coulomb charging is observed at room temperature, with an addition energy of 120 millielectron volts, which substantially exceeds the thermal energy. At low temperatures, we resolve the quantum energy levels corresponding to the small island. We observe unconventional power-law dependencies in the measured transport properties for which we suggest a resonant tunneling Luttinger-liquid mechanism.
Freshwater Forcing of Abrupt Climate Change During the Last Glaciation
Authors: Clark Peter U. , Marshall Shawn J. , Clarke Garry K. C. , Hostetler Steven W. , Licciardi Joseph M. , Teller James T.
Published: July 2002

Large millennial-scale fluctuations of the southern margin of the North American Laurentide Ice Sheet occurred during the last deglaciation, when the margin was located between about 43° and 49°N. Fluctuations of the ice margin triggered episodic increases in the flux of freshwater to the North Atlantic by rerouting continental runoff from the Mississippi River drainage to the Hudson or St. Lawrence Rivers. We found that periods of increased freshwater flow to the North Atlantic occurred at the same time as reductions in the formation of North Atlantic Deep Water, thus providing a mechanism for observed climate variability that may be generally characteristic of times of intermediate global ice volume.
The Ground State of the Ventral Appendage in
Drosophila
Authors: Casares Fernando , Mann Richard S.
Published: July 2002

In
Drosophila melanogaster
, the antennae, legs, genitalia, and analia make up a serially homologous set of ventral appendages that depend on different selector genes for their unique identities. The diversity among these structures implies that there is a common ground state that selector genes modify to generate these different appendage morphologies. Here we show that the ventral appendage that forms in the absence of selector gene activity is leglike but consists of only two segments along its proximo-distal axis: a proximal segment and a distal tarsus. These results raise the possibility that, during evolution, leglike appendages could have developed without selector gene activity.
Role of the Isthmus and FGFs in Resolving the Paradox of Neural Crest Plasticity and Prepatterning
Authors: Trainor Paul A. , Ariza-McNaughton Linda , Krumlauf Robb
Published: July 2002

Cranial neural crest cells generate the distinctive bone and connective tissues in the vertebrate head. Classical models of craniofacial development argue that the neural crest is prepatterned or preprogrammed to make specific head structures before its migration from the neural tube. In contrast, recent studies in several vertebrates have provided evidence for plasticity in patterning neural crest populations. Using tissue transposition and molecular analyses in avian embryos, we reconcile these findings by demonstrating that classical manipulation experiments, which form the basis of the prepatterning model, involved transplantation of a local signaling center, the isthmic organizer. FGF8 signaling from the isthmus alters
Hoxa2
expression and consequently branchial arch patterning, demonstrating that neural crest cells are patterned by environmental signals.
Predictability of the UK Variant Creutzfeldt-Jakob Disease Epidemic
Authors: d'Aignaux Jerome N. Huillard , Cousens Simon N. , Smith Peter G.
Published: July 2002

Back-calculation analysis of the variant Creutzfeldt-Jakob disease epidemic in the United Kingdom is used to estimate the number of infected individuals and future disease incidence. The model assumes a hazard of infection proportional to the incidence of bovine spongiform encephalopathy in the United Kingdom and accounts for precautionary control measures and very wide ranges of incubation periods. The model indicates that current case data are compatible with numbers of infections ranging from a few hundred to several millions. In the latter case, the model suggests that the mean incubation period must be well beyond the human life-span, resulting in disease epidemics of at most several thousand cases.
Anatolian Tree Rings and a New Chronology for the East Mediterranean Bronze-Iron Ages
Authors: Manning Sturt W. , Kromer Bernd , Kuniholm Peter Ian , Newton Maryanne W.
Published: July 2002

We report an extensive program of high-precision radiocarbon dating to establish the best date for a floating 1599-year Anatolian tree ring chronology that spans the later third millennium B.C. through the earlier first millennium B.C. This chronology is directly associated with a number of key sites and ancient personages. A previously suggested dating is withdrawn and is replaced by a robust new date fix 22 (+4 or –7) years earlier. These new radiocarbon wiggle-matched dates offer a unique independent resource for establishing the precise chronology of the ancient Near East and Aegean and help resolve, among others, a long-standing debate in favor of the so-called Middle Mesopotamian chronology.
Germline Transmission and Tissue-Specific Expression of Transgenes Delivered by Lentiviral Vectors
Authors: Lois Carlos , Hong Elizabeth J. , Pease Shirley , Brown Eric J. , Baltimore David
Published: July 2002

Single-cell mouse embryos were infected in vitro with recombinant lentiviral vectors to generate transgenic mice carrying the green fluorescent protein (GFP) gene driven by a ubiquitously expressing promoter
.
Eighty percent of founder mice carried at least one copy of the transgene, and 90% of these expressed GFP at high levels. Progeny inherited the transgene(s) and displayed green fluorescence. Mice generated using lentiviral vectors with muscle-specific and T lymphocyte–specific promoters expressed high levels of GFP only in the appropriate cell types. We have also generated transgenic rats that express GFP at high levels, suggesting that this technique can be used to produce other transgenic animal species.
Stromal Effects on Mammary Gland Development and Breast Cancer
Authors: Wiseman Bryony S. , Werb Zena
Published: July 2002

Breast cancer manifests itself in the mammary epithelium, yet there is a growing recognition that mammary stromal cells also play an important role in tumorigenesis. During its developmental cycle, the mammary gland displays many of the properties associated with breast cancer, and many of the stromal factors necessary for mammary development also promote or protect against breast cancer. Here we review our present knowledge of the specific factors and cell types that contribute to epithelial-stromal crosstalk during mammary development. To find cures for diseases like breast cancer that rely on epithelial-stromal crosstalk, we must understand how these different cell types communicate with each other.
Amacrine-Signaled Loss of Intrinsic Axon Growth Ability by Retinal Ganglion Cells
Authors: Goldberg Jeffrey L. , Klassen Matthew P. , Hua Ying , Barres Ben A.
Published: July 2002

The central nervous system (CNS) loses the ability to regenerate early during development, but it is not known why. The retina has long served as a simple model system for study of CNS regeneration. Here we show that amacrine cells signal neonatal rat retinal ganglion cells (RGCs) to undergo a profound and apparently irreversible loss of intrinsic axon growth ability. Concurrently, retinal maturation triggers RGCs to greatly increase their dendritic growth ability. These results suggest that adult CNS neurons fail to regenerate not only because of CNS glial inhibition but also because of a loss of intrinsic axon growth ability.
Large-Scale Transcriptional Activity in Chromosomes 21 and 22
Authors: Kapranov Philipp , Cawley Simon E. , Drenkow Jorg , Bekiranov Stefan , Strausberg Robert L. , Fodor Stephen P. A. , Gingeras Thomas R.
Published: July 2002

The sequences of the human chromosomes 21 and 22 indicate that there are approximately 770 well-characterized and predicted genes. In this study, empirically derived maps identifying active areas of RNA transcription on these chromosomes have been constructed with the use of cytosolic polyadenylated RNA obtained from 11 human cell lines. Oligonucleotide arrays containing probes spaced on average every 35 base pairs along these chromosomes were used. When compared with the sequence annotations available for these chromosomes, it is noted that as much as an order of magnitude more of the genomic sequence is transcribed than accounted for by the predicted and characterized exons.
Identity and Search in Social Networks
Authors: Watts Duncan J. , Dodds Peter Sheridan , Newman M. E. J.
Published: July 2002

Social networks have the surprising property of being “searchable”: Ordinary people are capable of directing messages through their network of acquaintances to reach a specific but distant target person in only a few steps. We present a model that offers an explanation of social network searchability in terms of recognizable personal identities: sets of characteristics measured along a number of social dimensions. Our model defines a class of searchable networks and a method for searching them that may be applicable to many network search problems, including the location of data files in peer-to-peer networks, pages on the World Wide Web, and information in distributed databases.
NIH Works to Rekindle Old Flame
Authors: Lawler Andrew
Published: July 2002

Officials at the National Institutes of Health (NIH) thought they had a good thing going a decade ago when they received federal permission to form partnerships with industry. But a bitter battle over a now-removed fair pricing clause left leading pharmaceutical companies with little stomach for new agreements with the government's premier biomedical institution, and the program has foundered.
New Funding Helps MITI Reform Labs
Authors: Normile Dennis
Published: July 2002

Tsukuba, Japan--The 15 national labs that are part of Japan's Agency of Industrial Science and Technology make its parent organization, the Ministry of International Trade and Industry (MITI), an important player in the country's research enterprise. Thanks to a big infusion of government funds, those labs are also setting the pace for much-needed reforms in how scientists are hired and grants are awarded, changes that Japan's national universities have been reluctant to make. The new policies are part of a broader campaign to improve the quality of science in Japan.
Knowing the Earth's Biodiversity: Challenges for the Infrastructure of Systematic Biology
Authors: Blackmore Stephen
Published: July 2002

In the wake of the Rio Convention on Biological Diversity, much attention has centered on our poor current state of knowledge about the diversity of life on Earth. This Policy Forum reviews the challenges that confront the systematic biology community. Whereas new collection-based institutes are being established in several tropical collections, resources are failing for many long-established centers of excellence. Given the exciting prospect of exploring Mars for life, it is too easy to forget the urgent need to discover and understand effectively the diversity of life on our own planet.
Animal-Free Experiments
Authors: Roush Wade
Published: July 2002

How do you find out how a chemical affects biological tissue without testing it on a live animal? Researchers are coming up with a range of solutions, from using two-celled embryos as test agents, to predicting aspects of a compound's toxicity on the basis of its molecular structure.
Congress: Tough Races and New Faces
Authors: Lawler Andrew
Published: July 2002

Retirements and the possible defeat of several incumbents will lead to new chairs of several congressional panels that oversee federal science programs. For lobbyists, that means spreading the word about research to a new audience of legislators
Swift Justice Salvages Reputations
Authors: Kaiser Jocelyn
Published: July 2002

A recent study of scientists who have faced misconduct charges suggests that even those who have been cleared often suffer professional damage.
Grad Students Press for Right to Strike
Authors: Holden Constance
Published: July 2002

Graduate students at the University of California campuses and Yale University are pressing for the right to unionize. They say they need to organize to counter ever-heavier teaching loads and stagnant salaries.
Discovering High-Affinity Ligands for Proteins: SAR by NMR
Authors: Shuker Suzanne B. , Hajduk Philip J. , Meadows Robert P. , Fesik Stephen W.
Published: July 2002

A nuclear magnetic resonance (NMR)-based method is described in which small organic molecules that bind to proximal subsites of a protein are identified, optimized, and linked together to produce high-affinity ligands. The approach is called “SAR by NMR” because structure-activity relationships (SAR) are obtained from NMR. With this technique, compounds with nanomolar affinities for the FK506 binding protein were rapidly discovered by tethering two ligands with micromolar affinities. The method reduces the amount of chemical synthesis and time required for the discovery of high-affinity ligands and appears particularly useful in target-directed drug research.
Large-Scale Synthesis of Aligned Carbon Nanotubes
Authors: Li W. Z. , Xie S. S. , Qian L. X. , Chang B. H. , Zou B. S. , Zhou W. Y. , Zhao R. A. , Wang G.
Published: July 2002

Large-scale synthesis of aligned carbon nanotubes was achieved by using a method based on chemical vapor deposition catalyzed by iron nanoparticles embedded in mesoporous silica. Scanning electron microscope images show that the nanotubes are approximately perpendicular to the surface of the silica and form an aligned array of isolated tubes with spacings between the tubes of about 100 nanometers. The tubes are up to about 50 micrometers long and well graphitized. The growth direction of the nanotubes may be controlled by the pores from which the nanotubes grow.
Tumor-Killer Made; How Does It Work?
Authors: Service Robert F.
Published: July 2002

Two groups have synthesized a bacterial compound known as Epothilone A, which kills cultured tumor cells in a manner similar to taxol, thwarting their ability to divide. The achievement will let chemists alter the compound's structure and possibly improve its properties.
Femtosecond Dynamics of Excited-State Evolution in [Ru(bpy)
3
]
2+
Authors: Damrauer Niels H. , Cerullo Giulio , Yeh Alvin , Boussie Thomas R. , Shank Charles V. , McCusker James K.
Published: July 2002

Time-resolved absorption spectroscopy on the femtosecond time scale has been used to monitor the earliest events associated with excited-state relaxation in tris-(2,2′-bipyridine)ruthenium(II). The data reveal dynamics associated with the temporal evolution of the Franck-Condon state to the lowest energy excited state of this molecule. The process is essentially complete in ∼300 femtoseconds after the initial excitation. This result is discussed with regard to reformulating long-held notions about excited-state relaxation, as well as its implication for the importance of non-equilibrium excited-state processes in understanding and designing molecular-based electron transfer, artificial photosynthetic, and photovoltaic assemblies in which compounds of this class are currently playing a key role.
The Inverse Association Between Tuberculin Responses and Atopic Disorder
Authors: Shirakawa Taro , Enomoto Tadao , Shimazu Shin-ichiro , Hopkin Julian M.
Published: July 2002

Human immune responses are heterogeneous and may involve antagonism between T helper (T
H
) lymphocyte subsets and their cytokines. Atopy is characterized by immediate immunoglobulin E (IgE)-mediated hypersensitivity to agents such as dust mites and pollen, and it underlies the increasingly prevalent disorder asthma. Among Japanese schoolchildren, there was a strong inverse association between delayed hypersensitivity to
Mycobacterium tuberculosis
and atopy. Positive tuberculin responses predicted a lower incidence of asthma, lower serum IgE levels, and cytokine profiles biased toward T
H
1 type. Exposure and response to
M. tuberculosis
may, by modification of immune profiles, inhibit atopic disorder.
Common Neural Substrates for the Addictive Properties of Nicotine and Cocaine
Authors: Pich Emilio Merlo , Pagliusi Sonia R. , Tessari Michela , Talabot-Ayer Dominique , van Huijsduijnen Rob Hooft , Chiamulera Christian
Published: July 2002

Regional brain activation was assessed by mapping of Fos-related protein expression in rats trained to self-administration of intravenous nicotine and cocaine. Both drugs produced specific overlapping patterns of activation in the shell and the core of the nucleus accumbens, medial prefrontal cortex, and medial caudate areas, but not in the amygdala. Thus, the reinforcing properties of cocaine and nicotine map on selected structures of the terminal fields of the mesocorticolimbic dopamine system, supporting the idea that common substrates for these addictive drugs exist.
Japan's ‘Super’ Site Confirms Deficit
Authors: Glanz James
Published: July 2002

CHICAGO
—The world's largest neutrino detector, a 50,000-metric-ton water tank in a Japanese mine, has begun to collect enough data to satisfy an international audience of astronomers trying to explain why there are fewer of these particles than predicted by current theories of matter. Along the way, researchers hope to learn much more about the energy spectrum of these elusive cosmic messengers.
The Media's Love Affair With AIDS Research: Hope vs. Hype
Authors: Cohen Jon
Published: July 2002

Popular magazines have been trumpeting the power of new drug cocktails to defeat the AIDS virus. But can the new therapies really fulfill popular expectations? Researchers fear a backlash against medical science if the impact of the drugs wanes.
Putting a Quantum Computer to Work in a Cup of Coffee
Authors: Taubes Gary
Published: July 2002

A quantum computer, tapping into the quantum weirdness of the microscopic world, could in theory collapse calculations that would take billions of years on mundane supercomputers into a few seconds. Experimentally, though, quantum computers have been daunting. Now two groups of researchers have come up with a way to realize at least some of that potential by applying nuclear magnetic resonance—a standard technique in medical imaging and chemical analysis—to a liquid as simple as coffee (see Research Article on
p. 350
). By flipping, coupling, and reading out the spins of individual nuclei in the coffee, the strategy can turn it into a quantum logic gate and even a quantum integrated circuit.
Consumer Versus Resource Control in Freshwater Pelagic Food Webs
Authors: Brett Michael T. , Goldman Charles R.
Published: July 2002

Models predict that food-web structure is regulated by both consumers and resources, and the strength of this control is dependent on trophic position and food-web length. To test these hypotheses, a meta-analysis was conducted of 11 fish (consumer)-by-nutrient (resource) factorial plankton community experiments. As predicted, zooplankton biomass was under strong consumer control but was weakly stimulated by nutrient additions; phytoplankton biomass was under strong resource control with moderate control by fish. However, the phytoplankton and zooplankton responses to nutrient additions did not follow theoretical predictions based on the number of trophic levels in the food web.
$1.6 Million Fraud Award Overturned
Authors: Kaiser Jocelyn
Published: July 2002

Universities are breathing a sigh of relief after a federal appeals court last week threw out a lower court's award of $1.6 million in a case brought by a graduate student who had claimed that the University of Alabama, Birmingham, defrauded the government by wrongly accepting grant money for work she had done
The ‘Gallo Case’: Popovic Strikes Back
Authors: Kaiser Jocelyn
Published: July 2002

Cell biologist Mikulas Popovic, who was cleared of scientific misconduct by an appeals board in 1993, has filed a $5 million lawsuit against the United States and one of its employees, fraud investigator Suzanne Hadley, for pursuing a “baseless” investigation that caused him “severe emotional stress” and resulted in his “de facto forced exile from science for 4 years.” On 31 January, the government submitted its formal response to the suit, arguing that it should be dismissed on technical grounds.
A Mapmaker That Was Nearly Lost
Authors: Watson Andrew
Published: July 2002

After a perfect launch on 8 August 1989, one of the European satellite Hipparcos's onboard motors failed, and the satellite ended up in a highly elliptical rather than a geostationary orbit. Mission controllers managed to save the situation by rewriting software and enlisting the help of additional ground stations, and the satellite survived 4 years, enough to gather a full set of data. However, astronomers still had to endure 3 years of data processing before getting their hands on a single piece of data.
Trapped Buckyball Turns Up the Amp
Authors: Hellemans Alexander
Published: July 2002

Using a scanning tunneling microscope (STM)—the probe with an atom-fine tip—a pair of European researchers made the accidental discovery that if you squeeze a soccer-ball-shaped fullerene molecule of 60 carbon atoms, its electrical resistance changes. The pair then constructed a circuit, incorporating the STM, which uses a single “buckyball” as an electromechanical amplifier.
How to Play Platonic Billiards
Authors: Cipra Barry
Published: July 2002

SAN DIEGO
—Minnesota Fats has some mathematical competition. With a little help from a computer, a mathematician has demonstrated some amazing three-dimensional shots for a cue ball bouncing around inside three equal-sided, or Platonic, solids—the eight-sided octahedron, the 12-sided dodecahedron, and the 20-sided icosahedron. Each shot hits each side of the pertinent solid and returns to its exact starting point and direction of travel.
Brown Dwarfs: A Possible Missing Link Between Stars and Planets
Authors: Kulkarni S. R.
Published: July 2002

Brown dwarfs are objects with masses between that of stars and planets. Postulated some three decades ago, they remained elusive until recently. Unlike stars, these objects have no sustained energy source and cool as they age. One such cool brown dwarf has been discovered as a companion to a nearby star. The spectrum of this object is similar to that of Jupiter. Single brown dwarfs have been detected in stellar nurseries. Ongoing and planned efforts, from both ground and space, will enable astronomers to decisively determine the population of these elusive and dim objects.
The Role of Antibody Concentration and Avidity in Antiviral Protection
Authors: Bachmann M. F. , Kalinke U. , Althage A. , Freer G. , Burkhart C. , Roost H.-P. , Aguet M. , Hengartner H. , Zinkernagel R. M.
Published: July 2002

Neutralizing antibodies are necessary and sufficient for protection against infection with vesicular stomatitis virus (VSV). The in vitro neutralization capacities and in vivo protective capacities of a panel of immunoglobulin G monoclonal antibodies to the glycoprotein of VSV were evaluated. In vitro, neutralizing activity correlated with avidity and with neutralization rate constant, a measure of on-rate. However, in vivo, protection was independent of immunoglobulin subclass, avidity, neutralization rate constant, and in vitro neutralizing activity; above a minimal avidity threshold, protection depended simply on a minimum serum concentration. These two biologically defined thresholds of antibody specificity offer hope for the development of adoptive therapy with neutralizing antibodies.
Biotic Survivors
Authors: Lazcano Antonio
Published: July 2002

Evolution of Hydrothermal Ecosystems on Earth (and Mars?).
GREGORY R. BOCK and JAMIE A. GOODE, Eds. Wiley, New York, 1996. xii, 334 pp., illus. $84.95 or £55. ISBN 0-471-96509-x. Ciba Foundation Symposium 202. From a symposium, London, Jan. 1996.
Evolution Step by Step
Authors: Endler John A.
Published: July 2002

Selection.
The Mechanism of Evolution. GRAHAM BELL. Chapman and Hall, New York, 1996. xxvi, 699 pp., illus. $75 or £55. ISBN 0-412-05521-x.

The Basics of Selection.
GRAHAM BELL. Chapman and Hall, New York, 1996. xxii, 378 pp., illus. Paper, $37.50 or £24.99. ISBN 0-412-05531-7. Briefer edition of Selection: The Mechanism of Evolution.
Extensible Collagen in Mussel Byssus: A Natural Block Copolymer
Authors: Coyne Kathryn J. , Qin Xiao-Xia , Waite J. Herbert
Published: July 2002

To adhere to solid surfaces, marine mussels produce byssal threads, each of which is a stiff tether at one end and a shock absorber with 160 percent extensibility at the other end. The elastic extensibility of proximal byssus is extraordinary given its construction of collagen and the limited extension (less than 10 percent) of most collagenous materials. From the complementary DNA, we deduced that the primary structure of a collagenous protein (preCol-P) predominating in the extensible proximal portion of the threads encodes an unprecedented natural block copolymer with three major domain types: a central collagen domain, flanking elastic domains, and histidine-rich terminal domains. The elastic domains have sequence motifs that strongly resemble those of elastin and the amorphous glycine-rich regions of spider silk fibroins. Byssal thread extensibility may be imparted by the elastic domains of preCol-P.
An Ongoing Debate
Authors: Hall Wayne
Published: July 2002

Marijuana Myths, Marijuana Fact. A Review of the Scientific Evidence.
LYNN ZIMMER and JOHN P. MORGAN. Lindesmith Center, New York, 1997. xvi, 245 pp. Paper, $12.95. ISBN 0-9641568-4-9.
A Biographical Bandwagon
Authors: Howard Don
Published: July 2002

Albert Einstein.
A Biography. ALBRECHT FÖLSING. Viking, New York, 1997. xiv, 882 pp. + plates. $34.95 or C$45. ISBN 0-670-85545-6. Translated from the German edition (Frankfurt am Main, 1993) by Ewald Osers.

Einstein.
A Life. DENIS BRIAN. Wiley, New York, 1996. xvi, 509 pp. + plates. $30, ISBN 0-471-11459-6; paper, $19.95 or C$27.95, ISBN 0-471-19362-3.
daf-16
: An HNF-3/forkhead Family Member That Can Function to Double the Life-Span of
Caenorhabditis elegans
Authors: Lin Kui , Dorman Jennie B. , Rodan Aylin , Kenyon Cynthia
Published: July 2002

The wild-type
Caenorhabditis elegans
nematode ages rapidly, undergoing development, senescence, and death in less than 3 weeks. In contrast, mutants with reduced activity of the gene
daf-2,
a homolog of the insulin and insulin-like growth factor receptors, age more slowly than normal and live more than twice as long. These mutants are active and fully fertile and have normal metabolic rates. The life-span extension caused by
daf-2
mutations requires the activity of the gene
daf-16. daf-16
appears to play a unique role in life-span regulation and encodes a member of the hepatocyte nuclear factor 3 (HNF-3)/forkhead family of transcriptional regulators. In humans, insulin down-regulates the expression of certain genes by antagonizing the activity of HNF-3, raising the possibility that aspects of this regulatory system have been conserved.
A Naturalist of Note
Authors: Taylor Kenneth L.
Published: July 2002

Buffon.
A Life in Natural History. JACQUES ROGER. Cornell University Press, Ithaca, NY, 1997. xviii, 492 pp., illus. $49.95 or £39.50. ISBN 0-8014-2918-8. Cornell History of Science. Translated from the French edition (1989) by Sarah Lucille Bonnefoi. L. Pearce Williams, translation editor.
A Pulsar, the Heliosphere, and Pioneer 10: Probable Mimicking of a Planet of PSR B1257+12 by Solar Rotation
Authors: Scherer Klaus , Fichtner Horst , Anderson John D. , Lau Eunice L.
Published: July 2002

Doppler data generated with the Pioneer 10 spacecraft's radio carrier wave between 1987 and 1995 show a 25.3-day periodicity which is related to the solar rotation. The timing data of the pulsar PSR B1257+12 also show a periodicity of 25.34 days, which has been explained as a signature of the pulsar's barycentric motion in response to the existence of a small moon-like object. However, because PSR B1257+12 is located close to the ecliptic and because the timing variations are in the range of microseconds, it is likely that the pulsar signal is affected by the same mechanism acting on the Pioneer 10 Doppler data. Hence, the hypothesized inner planet around PSR B1257+12 is probably an artifact of the heliosphere.
Atomic and Macroscopic Reaction Rates of a Surface-Catalyzed Reaction
Authors: Wintterlin J. , Völkening S. , Janssens T. V. W. , Zambelli T. , Ertl G.
Published: July 2002

The catalytic oxidation of carbon monoxide (CO) on a platinum (111) surface was studied by scanning tunneling microscopy. The adsorbed oxygen atoms and CO molecules were imaged with atomic resolution, and their reactions to carbon dioxide (CO
2
) were monitored as functions of time. The results allowed the formulation of a rate law that takes the distribution of the reactants in separate domains into account. From temperature-dependent measurements, the kinetic parameters were obtained. Their values agree well with data from macroscopic measurements. In this way, a kinetic description of a chemical reaction was achieved that is based solely on the statistics of the underlying atomic processes.
An Architect of Science
Authors: Aspray William
Published: July 2002

Endless Frontier.
Vannevar Bush, Engineer of the American Century. G. PASCAL ZACHARY. Free Press (Simon and Schuster), New York, 1997. viii, 518 pp. + plates. $32.50 or C$43. ISBN 0-684-82821-9.
Also Noteworthy
Authors: Kelner Katrina
Published: July 2002

On the Surface of Things.
Images of the Extraordinary in Science. F. FRANKEL and G. M. WHITESIDES. Chronicle Books, San Francisco, 1997. 160 pp., illus. Paper, $22.95. ISBN 0-8118-1394-0.
A Massive Terraced Village Complex in Chihuahua, Mexico, 3000 Years Before Present
Authors: Hard Robert J. , Roney John R.
Published: July 2002

Cerro Juanaqueña is a residential complex with 8 kilometers of terrace walls in northwestern Mexico that was occupied at ∼3000 calendar years before present based on radiocarbon dates on maize (
Zea mays
L
.
). Most other similar sized terrace complex sites that have been found date to ∼1000 years before present. Cerro Juanaqueña was contemporaneous with 10 other sites in the southwestern United States that have yielded 18 of the earliest maize or squash radiocarbon dates yet, and it is by far the largest and most complex site. The archaeological evidence from this site, combined with other recent data, implies that highly variable combinations of population aggregation, agricultural dependence, and degrees of sedentism were present during the time maize was being introduced into the American Southwest.
Water Ordering Landscapes
Authors: Tsonis Anastasios A.
Published: July 2002

Fractal River Basins
. Chance and Self-Organization. IGNACIO RODRIGUEZ-ITURBE and ANDREA RINALDO. Cambridge University Press, New York, 1997. xvi, 547 pp., illus. $100 or £70. ISBN 0-521-47398-5.
Forty Years in the Conceptual Wilderness
Authors: Sandler Merton
Published: July 2002

The Antidepressant Era
. DAVID HEALY. Harvard University Press, Cambridge, MA, 1998. xii, 317 pp., illus. $39.95. ISBN 0-674-03957-2.
Locating Sustainability
Authors: Norton Bryan G.
Published: July 2002

Taking Complexity Seriously
. Policy Analysis, Triangulation and Sustainable Development. EMERY ROE. Kluwer, Boston, 1997. xii, 138 pp., illus. $98.50, NLG 215, or £65. ISBN 0-7923-8058-4.
A National Tissue Bank to Track HIV Eradication and Immune Reconstitution
Authors: Cavert Winston , Haase Ashley T.
Published: July 2002

Understanding of HIV reservoirs that can complicate and confound current approaches to antiretroviral therapy will require better resources than are currently available. Cavert and Haase propose the creation of tissue banks from HIV-positive individuals who have died from other causes such as accidents or trauma. They estimate that it might be possible to collect tissues from 10 to 30 individuals over a 2-year period at a cost of $1 million per year.
Limitations of a Molecular Clock Applied to Considerations of the Origin of HIV-1
Authors: Korber Bette , Theiler James , Wolinsky Steven
Published: July 2002

A recent report has provided information that helps to determine the age of a common viral ancestor of the AIDS epidemic. Korber
et al
. examine the strengths as well as limitations of molecular clock analysis and the implications of the findings for planning vaccines and forecasting the future of the epidemic.
Unexpected Effects
Authors: Sternberg Esther M.
Published: July 2002

The Powerful Placebo.
From Ancient Priest to Modern Physician. ARTHUR K. SHAPIRO and ELAINE SHAPIRO. Johns Hopkins University Press, Baltimore, 1997. xiv, 282 pp. $39.95. ISBN 0-8018-5569-1.
Contingency and Convergence
Authors: Foote Mike
Published: July 2002

The Crucible of Creation.
The Burgess Shale and the Rise of Animals. SIMON CONWAY MORRIS. Oxford University Press, Oxford, 1998. xxxiv, 242 pp., illus. $30. ISBN 0-19-850256-7.
C, N, and Noble Gas Isotopes in Grain Size Separates of Presolar Diamonds from Efremovka
Authors: Verchovsky A. B. , Fisenko A. V. , Semjonova L. F. , Wright I. P. , Lee M. R. , Pillinger C. T.
Published: July 2002

Nanometer-size presolar diamonds from the Efremovka CV3 chondrite were physically separated into several grain size fractions by ultracentrifugation. The coarsest size fraction is the most enriched in carbon-12; the others have broadly similar carbon isotopic compositions. Measurement of noble gases shows that their concentration decreases with decreasing grain size. This effect is attributed to ion implantation. Such an episode could occur in the envelope of a supernova that produced the diamonds, or in interstellar space; in either case, ions with energies above a certain threshold pass completely through the smaller diamond grains without being captured. Concentrations of nitrogen show only minor variations with grain size, indicating a different mechanism of incorporation into the diamonds.
Building Memories: Remembering and Forgetting of Verbal Experiences as Predicted by Brain Activity
Authors: Wagner Anthony D. , Schacter Daniel L. , Rotte Michael , Koutstaal Wilma , Maril Anat , Dale Anders M. , Rosen Bruce R. , Buckner Randy L.
Published: July 2002

A fundamental question about human memory is why some experiences are remembered whereas others are forgotten. Brain activation during word encoding was measured using blocked and event-related functional magnetic resonance imaging to examine how neural activation differs for subsequently remembered and subsequently forgotten experiences. Results revealed that the ability to later remember a verbal experience is predicted by the magnitude of activation in left prefrontal and temporal cortices during that experience. These findings provide direct evidence that left prefrontal and temporal regions jointly promote memory formation for verbalizable events.
Photofragment Helicity Caused by Matter-Wave Interference from Multiple Dissociative States
Authors: Rakitzis T. Peter , Kandel S. Alex , Alexander Andrew J. , Kim Zee Hwan , Zare Richard N.
Published: July 2002

Isolated diatomic molecules of iodine monochloride (ICl) were photodissociated by a beam of linearly polarized light, and the resulting ground-state Cl atom photofragments were detected by a method that is sensitive to the handedness (helicity) of the electronic angular momentum. It was found that this helicity oscillates between “topspin” and “backspin” as a function of the wavelength of the dissociating light. The helicity originates solely from the (de Broglie) matter-wave interference of multiple dissociating pathways of the electronic excited states of ICl. These measurements can be related to the identity and to the detailed shapes of the dissociating pathways, thus demonstrating that it is possible to probe repulsive states by spectroscopic means.