bluuebunny/crossref_metadata_2025 huggingface dataset:
Ti/TiN coatings for microfabricated cantilevers used in atomic force microscopy
Authors: Wiederhold K. P. , Yamaguchi Y. , Ayala A. , Matheaus M. , Gutierrez C. J. , Galloway H. C.
Published: July 2002

We report the successful sputter coating of microfabricated silicon cantilever and tip assemblies with high-quality titanium/titanium nitride (Ti/TiN) thin films using a technique that will be available to many researchers. We demonstrate that the use of pulsed mode reactive dc magnetron sputtering, adequate thermal budget, and careful control of a titanium seed layer were the key elements for producing usable coated cantilevers. This coating material takes advantage of the excellent adhesive properties of Ti with silicon and silicon oxide and the intrinsically hard and conductive properties of TiN. Hence, these coated cantilever and tip assemblies have promising advantages over standard cantilever and tip assemblies for many demanding atomic force microscopy applications. We were able to fabricate Ti/TiN coatings with negligible stress-induced bending of the delicate cantilevers. Tests to assess the performance of the Ti/TiN coatings were done on the tip assemblies and on sputter-coated blanket films on thermally oxidized silicon to obtain a measure of the film resistivity and thickness.
Role of passivation etch polymers in interfacial delamination for polymeric low-k dielectrics
Authors: Breen M. R. , Foster C. M. , Bass S. , Lee J. J. , Mlynko W.
Published: July 2002

For copper/low-dielectric constant (low-k) interconnects, delamination at the dielectric-barrier metal interface has been studied. In particular, the role of deposited etch polymers used for sidewall passivation on the integrity of this interface has been examined. We found that etch polymers were deposited on the flat (horizontal) surfaces used as low-k masks. Fluorinated polymeric etch residues of approximately 10–20 Å in thickness were detected using time-of-flight secondary ion mass spectroscopy and Auger electron spectroscopy. Although these etch residues resulted primarily from the etch sidewall passivation process, no detectable residue was found on the sidewalls themselves. The presence of the polymeric residue was found to compromise the integrity of the dielectric-barrier metal interface. Removal of the residue could be accomplished through either sputtering or by a concluding O2 plasma flash step during etch. Using these techniques, significant improvement in dielectric-barrier metal interfacial integrity could be obtained.
Fragmented Formative Story
Authors: O'Neill Hugh
Published: July 2002

Origin of the Earth and Moon
. R. M. Canup and K. Righter, Eds. University of Arizona Press, Tucson, in collaboration with Lunar and Planetary Institute, Houston, 2000. 571 pp. $50. ISBN 0-8165-2073-9.

The contributors to this volume, which grew out of a December 1998 conference, discuss experimental results, theoretical analyses, and computational modeling related to the early history of the Earth-Moon system.
Role of the Stratospheric Polar Freezing Belt in Denitrification
Authors: Tabazadeh A. , Jensen E. J. , Toon O. B. , Drdla K. , Schoeberl M. R.
Published: July 2002

Homogeneous freezing of nitric acid hydrate particles can produce a polar freezing belt in either hemisphere that can cause denitrification. Computed denitrification profiles for one Antarctic and two Arctic cold winters are presented. The vertical range over which denitrification occurs is normally quite deep in the Antarctic but limited in the Arctic. A 4 kelvin decrease in the temperature of the Arctic stratosphere due to anthropogenic and/or natural effects can trigger the occurrence of widespread severe denitrification. Ozone loss is amplified in a denitrified stratosphere, so the effects of falling temperatures in promoting denitrification must be considered in assessment studies of ozone recovery trends.
Music of the Spheres
Authors: Visser Matt
Published: July 2002

Einstein's Unfinished Symphony
Listening to the Sounds of Space-Time. Marcia Bartusiak. Joseph Henry, Washington, DC, 2000. 263 pp. $24.95. ISBN 0-309-06987-4.

Bartusiak provides engaging portraits of the theorists and experimenters involved in the search for gravity waves and a carefully researched summary of their achievements and prospects.
Elementary, My Dear Chimpanzee
Authors: Hauser Marc D.
Published: July 2002

Folk Physics for Apes
The Chimpanzee's Theory of How the World Works. Daniel J. Povinelli. Oxford University Press, Oxford, 2000. 407 pp. $85. ISBN 0-19-857220-4.

Povinelli argues that a chimpanzee's understanding of the physical world is radically different from our own; our reviewer finds this conclusion undermined by serious problems with the design and interpretation of the experiments that form the framework for the book.
Fermi Surface Nesting and Nanoscale Fluctuating Charge/Orbital Ordering in Colossal Magnetoresistive Oxides
Authors: Chuang Y.-D. , Gromko A. D. , Dessau D. S. , Kimura T. , Tokura Y.
Published: July 2002

We used high-resolution angle-resolved photoemission spectroscopy to reveal the Fermi surface and key transport parameters of the metallic state of the layered colossal magnetoresistive oxide La
1.2
Sr
1.8
Mn
2
O
7
. With these parameters, the calculated in-plane conductivity is nearly one order of magnitude larger than the measured direct current conductivity. This discrepancy can be accounted for by including the pseudogap, which removes at least 90% of the spectral weight at the Fermi energy. Key to the pseudogap and to many other properties are the parallel straight Fermi surface sections, which are highly susceptible to nesting instabilities. These nesting instabilities produce nanoscale fluctuating charge/orbital modulations, which cooperate with Jahn-Teller distortions and compete with the electron itinerancy favored by double exchange.
We Are Made of Starstuff
Authors: Hogan Craig J.
Published: July 2002

The Magic Furnace
The Search for the Origins of Atoms. Marcus Chown. Oxford University Press, New York, 2001. 240 pp. $25. ISBN 0-19-514305-1.

Writing for nonspecialists, Chowan presents the stories of the birth of atoms in the Big Bang and stellar evolution and sketches the history of research into both processes.
Writing About the Unseen
Authors: Berry Andrew
Published: July 2002

Chance in the House of Fate
A Natural History of Heredity. Jennifer Ackerman. Houghton Mifflin, New York, 2001. 268 pp. $25. ISBN 0-618-08287-5.

Ackerman applies her skills at nature writing to a consideration of heredity that is focused on the microscopic world of molecular biology.
Explaining Exuberant Diversification
Authors: Meyer Axel
Published: July 2002

The Ecology of Adaptive Radiation
. Dolph Schluter. Oxford University Press, New York, 2000. 296 pp. Price $85, £49.50. ISBN 0-19-850523-X. Paper, $34.95, £24.95. ISBN 0-19-850522-1.

In an illuminating discussion that suggests new ways of looking at one of the central concepts of evolutionary biology, Schluter examines the last half century of progress toward identifying the mechanisms responsible for generating ecological and phenotypic diversity within rapidly multiplying lineages.
Nota Bene: The Webs We Weave
Authors: Voss David
Published: July 2002

The Once and Future Web
Worlds Woven by the Telegraph and Internet.
a play by Jerry James
. May and June 2001,. National Library of . Medicine, Bethesda, MD.

The Once and Future Web
.
Michael Sappol and Hunter Crowther-Heyck, Curators
. National Library of Medicine, Bethesda, MD.
www.nlm.nih.gov/onceandfutureweb

This exhibit on information technology explores parallels between the global communication networks of the telegraph and the Internet.
Why We Must Worry
Authors: Raven Peter
Published: July 2002

The World According to Pimm
A Scientist Audits the Earth. Stuart L. Pimm. McGraw Hill, New York, 2001. 303 pp. $24.95. ISBN 0-07-137490-6.

In this slim, highly readable book, Pimm draws on his research experiences around the world to provide a vivid, detailed, and well documented account of our relation to our environment.
An Eastern View of Apes and Monkeys
Authors: Boysen Sarah
Published: July 2002

Primate Origins of Human Cognition and Behavior
. T. Matsuzawa, Ed. Springer, Tokyo, 2001. 599 pp. $129, €119, ¥9,500. ISBN 4-431-70290-3.

In a volume that highlights Japanese contributions to primatology, Matsuzawa and his colleagues explore a broad range of topics from the fields of behavioral ecology, psychology, and cognitive science.
Tales Told by Loops, Whorls, and Ridges
Authors: Jackall Robert
Published: July 2002

Suspect Identities
A History of Fingerprinting and Criminal Identification. Simon A. Cole. Harvard University Press, Cambridge, MA, 2001. 381 pp. $35, £23.95. ISBN 0-674-00455-8.

Cole offers a critical examination of how the fingerprints came to be seen as a trustworthy technique for identifying individuals and how the craft of interpreting them became a cornerstone of forensics science.
Construction and Analysis of a Human-Chimpanzee Comparative Clone Map
Authors: Fujiyama Asao , Watanabe Hidemi , Toyoda Atsushi , Taylor Todd D. , Itoh Takehiko , Tsai Shih-Feng , Park Hong-Seog , Yaspo Marie-Laure , Lehrach Hans , Chen Zhu , Fu Gang , Saitou Naruya , Osoegawa Kazutoyo , de Jong Pieter J. , Suto Yumiko , Hattori Masahira , Sakaki Yoshiyuki
Published: July 2002

The recently released human genome sequences provide us with reference data to conduct comparative genomic research on primates, which will be important to understand what genetic information makes us human. Here we present a first-generation human-chimpanzee comparative genome map and its initial analysis. The map was constructed through paired alignment of 77,461 chimpanzee bacterial artificial chromosome end sequences with publicly available human genome sequences. We detected candidate positions, including two clusters on human chromosome 21 that suggest large, nonrandom regions of difference between the two genomes.
Changes in Life Across Many Temporal Scales
Authors: Bambach Richard
Published: July 2002

Evolutionary Patterns
Growth, Form, and Tempo in the Fossil Record. Jeremy B. C. Jackson, Scott Lidgard, and Frank K. McKinney, Eds. University of Chicago Press, Chicago, 2001. 415 pp. $85, £54. ISBN 0-226-38930-8. Paper, $30, £19. ISBN 0-226-38931-6.

Exploring topics such as modes of development, tempos of speciation and extinction, and macroevolutionary trends, the contributors illustrate the many insights the fossil record offers to our understanding of life and its history.
Some of the Truth
Authors: Polkinghorne John
Published: July 2002

Religion Explained
The Evolutionary Origins of Religious Thought. Pascal Boyer. Basic Books, New York, 2001. 383 pp. $27.50. ISBN 0-465-00695-7.

Boyer argues that evolutionary psychology provides the framework for answering the question of why humans have religion. Our reviewer notes that this reductionistic approach addresses only one level of a many-layered subject.
Images of Inhumanism
Authors: Cokinos Christopher
Published: July 2002

The Selected Poetry of Robinson Jeffers
. Tim Hunt, Ed. Stanford University Press, Stanford, CA, 2001. 774 pp. $75. ISBN 0-8047-3890-4. Paper, $24.95. ISBN 0-8047-4108-5.

This new collection samples both the lengthy story-poems that supported Jeffers's national reputation between the world wars and the short lyric poems on nature that gained him a posthumous following among environmentalists. Our reviewer concludes that these shorter works establish Jeffers as the preeminent American poet of nature, ecology, and science.
Do We Need Species Concepts?
Authors: Shaw Kerry L.
Published: July 2002

Genes, Categories, and Species
The Evolutionary and Cognitive Causes of the Species Problem. Jody Hey. Oxford University Press, New York, 2001. 235 pp. $45, £34.95. ISBN 0-19-514477-5.

Hey argues that attempts to craft a simple, universal definition of species are doomed because one term cannot capture all of the complexities of evolutionary divergence.
Relying on Manna from Heaven?
Authors: Grubb Michael
Published: July 2002

The Skeptical Environmentalist
Measuring the Real State of the World. Bjørn Lomborg. Cambridge University Press, Cambridge, 2001. 539 pp. $69.95, £47.50. ISBN 0-521-80447-7. Paper, $27.95, £17.95. ISBN 0-521-01068-3.

Lomborg marshals a large amount of data to argue that the important aspects of the environment are improving, that technology will solve the remaining problems, and that we therefore should not turn to governmental policy to improve the state of the world. But his rather selective use of the literature and his failure to examine possible links between previous legislation and the improvements he emphasizes undermine the claims the author and many commentators have made for the book.
Interconnected Stories of Brain Rhythms
Authors: Buzsáki György
Published: July 2002

The Intact and Sliced Brain
. Mircea Steriade. MIT Press, Cambridge, MA, 2001. 382 pp. $55, £37.95. ISBN 0-262-19456-2.

Steriade combines a summary of his several decades of research on the forebrain with discussions of the background and context of other studies on the dynamic function of the cerebral cortex.
Framing the Evidence
Authors: Fara Patricia
Published: July 2002

Secret Knowledge
Rediscovering the Lost Techniques of the Old Masters. David Hockney. Thames and Hudson, London, 2001. 296 pp. £35, ISBN 0-500-23785-9. Viking Studio, New York. $60, C$87. ISBN 0-670-03026-0.

Hockney marshals visual and textual evidence for his claim that pictures became far more realistic in the 15th century because major artists used lenses and mirrors to project images onto paper or canvas.
Magnetic Resonant Mode in the Single-Layer High-Temperature Superconductor Tl
2
Ba
2
CuO
6+δ
Authors: He H. , Bourges P. , Sidis Y. , Ulrich C. , Regnault L. P. , Pailhès S. , Berzigiarova N. S. , Kolesnikov N. N. , Keimer B.
Published: July 2002

An unusual spin excitation mode observed by neutron scattering has inspired numerous theoretical studies of the interplay between charged quasiparticles and collective spin excitations in the copper oxide high-temperature superconductors. The mode has, thus far, only been observed in materials with crystal structures consisting of copper oxide bilayers, and it is absent in the single-layer compound La

2−
x

Sr

x

CuO
4+δ
. Neutron-scattering data now show that the mode is present in Tl
2
Ba
2
CuO
6+δ
, a single-layer compound with a superconducting transition temperature of ∼90 kelvin, demonstrating that it is a generic feature of the copper oxide superconductors, independent of the layer sequence. This restricts the theoretical models for the origin of the resonant mode and its role in the mechanism of high-temperature superconductivity.
The Childless Father of Eugenics
Authors: Bynum W. F.
Published: July 2002

A Life of Sir Francis Galton
From African Exploration to the Birth of Eugenics. Nicholas Wright Gillham. Oxford University Press, New York, 2001. 428 pp. $35, £22.50. ISBN 0-19-514365-5.

Galton's role in the founding of eugenics has overshadowed his substantial contributions to a wide range of fields, including the discovery of anticyclones, pioneering work on fingerprinting, the invention of regression and correlation analysis, and the application of pedigree analysis and twin studies to human heredity. These topics are among the many examined in Gillham's fascinating biography, which aims to place Galton in the context of his times.
Metasomatic Origin of Quartz-Pyroxene Rock, Akilia, Greenland, and Implications for Earth's Earliest Life
Authors: Fedo Christopher M. , Whitehouse Martin J.
Published: July 2002

A quartz-pyroxene rock interpreted as a banded iron formation (BIF) from the island of Akilia, southwest Greenland, contains
13
C-depleted graphite that has been claimed as evidence for the oldest (>3850 million years ago) life on Earth. Field relationships on Akilia document multiple intense deformation events that have resulted in parallel transposition of Early Archean rocks and significant boudinage, the tails of which commonly form the banding in the quartz-pyroxene rock. Geochemical data possess distinct characteristics consistent with an ultramafic igneous, not BIF, protolith for this lithology and the adjacent schists. Later metasomatic silica and iron introduction have merely resulted in a rock that superficially resembles a BIF. An ultramafic igneous origin invalidates claims that the carbon isotopic composition of graphite inclusions represents evidence for life at the time of crystallization.
Feynman's Path-Integral Approach for Intense-Laser-Atom Interactions
Authors: Salières P. , Carré B. , Le Déroff L. , Grasbon F. , Paulus G. G. , Walther H. , Kopold R. , Becker W. , Milošević D. B. , Sanpera A. , Lewenstein M.
Published: July 2002

Atoms interacting with intense laser fields can emit electrons and photons of very high energies. An intuitive and quantitative explanation of these highly nonlinear processes can be found in terms of a generalization of classical Newtonian particle trajectories, the so-called quantum orbits. Very few quantum orbits are necessary to reproduce the experimental results. These orbits are clearly identified, thus opening the way for an efficient control as well as previously unknown applications of these processes.
Do-It-Yourself Supercomputers
Authors: Taubes Gary
Published: July 2002

For the last several years, the new wave of supercomputers has consisted of clusters of workstations. Make way for piles of PCs. Demonstration machines built of 16 Pentium Pro chips and costing no more than $60,000 can run over a billion operations a second (gigaflops)—a realm of processing speed formerly open only to workstation-based supercomputers costing several hundred thousand dollars or more.
eIF4G--A Multipurpose Ribosome Adapter?
Authors: Hentze Matthias W.
Published: July 2002

Messenger RNAs are translated into protein—a complex enterprise. Now, in work from a number of laboratories, one small adapter protein is shown to be a central player in several variations on the process. In his Perspective, Hentze describes how eIF4G serves as an adapter that binds the small ribosome subunit to the messenger RNA, working in different ways when the message has a
7
mG cap at its 5
'
end or a polyadenylated tail at its 3
'
end.
Transformation in Garnet from Orthorhombic Perovskite to LiNbO
3
Phase on Release of Pressure
Authors: Funamori Nobumasa , Yagi Takehiko , Miyajima Nobuyoshi , Fujino Kiyoshi
Published: July 2002

High-pressure in situ x-ray diffraction and transmission electron microscopy on quenched samples show that natural garnet transforms to orthorhombic perovskite (and minor coexisting phases) containing increasing amounts of aluminum with increasing pressure. This suggests that the perovskite is the dominant host mineral for aluminum in Earth's lower mantle. Orthorhombic perovskite is quenched from ∼35 gigapascals but, because of the increased aluminum content, transforms to the LiNbO
3
structure upon quenching from ∼60 gigapascals.
An Fe
2
IV
O
2
Diamond Core Structure for the Key Intermediate Q of Methane Monooxygenase
Authors: Shu Lijin , Nesheim Jeremy C. , Kauffmann Karl , Münck Eckard , Lipscomb John D. , Que Lawrence
Published: July 2002

A new paradigm for oxygen activation is required for enzymes such as methane monooxygenase (MMO), for which catalysis depends on a nonheme diiron center instead of the more familiar Fe-porphyrin cofactor. On the basis of precedents from synthetic diiron complexes, a high-valent Fe
2
(μ-O)
2
diamond core has been proposed as the key oxidizing species for MMO and other nonheme diiron enzymes such as ribonucleotide reductase and fatty acid desaturase. The presence of a single short Fe-O bond (1.77 angstroms) per Fe atom and an Fe-Fe distance of 2.46 angstroms in MMO reaction intermediate Q, obtained from extended x-ray absorption fine structure and Mössbauer analysis, provides spectroscopic evidence that the diiron center in Q has an Fe
2
IV
O
2
diamond core.
Transgenic Corn Ban Sparks a Furor
Authors: Balter Michael
Published: July 2002

PARIS
—Axel Kahn, one of France's leading geneticists, has quit as president of the nation's Biomolecular Engineering Commission, which regulates the use of genetically altered organisms, after a government decision to prohibit cultivation of transgenic corn in France. The government's action came exactly 1 week after it had approved transgenic corn for consumption by humans and animals, and 2 months after the European Commission gave the green light to its commercialization in Europe, largely at the insistence of France.
Polarization-Enhanced NMR Spectroscopy of Biomolecules in Frozen Solution
Authors: Hall Dennis A. , Maus Douglas C. , Gerfen Gary J. , Inati Souheil J. , Becerra Lino R. , Dahlquist Frederick W. , Griffin Robert G.
Published: July 2002

Large dynamic nuclear polarization signal enhancements (up to a factor of 100) were obtained in the solid-state magic-angle spinning nuclear magnetic resonance (NMR) spectra of arginine and the protein T4 lysozyme in frozen glycerol-water solutions with the use of dynamic nuclear polarization. Polarization was transferred from the unpaired electrons of nitroxide free radicals to nuclear spins through microwave irradiation near the electron paramagnetic resonance frequency. This approach may be a generally applicable signal enhancement scheme for the high-resolution solid-state NMR spectroscopy of biomolecules.
Size Variation in Middle Pleistocene Humans
Authors: Arsuaga J. L. , Carretero J. M. , Lorenzo C. , Gracia A. , Martı́nez I. , Bermúdez de Castro J. M. , Carbonell E.
Published: July 2002

It has been suggested that European Middle Pleistocene humans, Neandertals, and prehistoric modern humans had a greater sexual dimorphism than modern humans. Analysis of body size variation and cranial capacity variation in the large sample from the Sima de los Huesos site in Spain showed instead that the sexual dimorphism is comparable in Middle Pleistocene and modern populations.
Volatile Compounds in Archaeological Plant Remains and the Maillard Reaction During Decay of Organic Matter
Authors: Evershed Richard P. , Bland Helen A. , van Bergen Pim F. , Carter James F. , Horton Mark C. , Rowley-Conwy Peter A.
Published: July 2002

Archaeological plant remains from excavations at Qasr Ibrı̂m, Egypt, preserve volatile decay products trapped within internal networks of structural and storage macromolecules. These volatile components can be linked to specific degradative reactions occurring during the long-term burial of organic matter. Abundant alkyl pyrazines are characteristic by-products of the Maillard (or browning) reaction of proteins and carbohydrates and provide evidence for the reaction occurring in buried organic matter.
Inhibition of Phosphatases and Increased Ca
2+
Channel Activity by Inositol Hexakisphosphate
Authors: Larsson Olof , Barker Christopher J. , Sjöholm Åke , Carlqvist Håkan , Michell Robert H. , Bertorello Alejandro , Nilsson Thomas , Honkanen Richard E. , Mayr Georg W. , Zwiller Jean , Berggren Per-Olof
Published: July 2002

Inositol hexakisphosphate (InsP
6
), the dominant inositol phosphate in insulin-secreting pancreatic β cells, inhibited the serine-threonine protein phosphatases type 1, type 2A, and type 3 in a concentration-dependent manner. The activity of voltage-gated L-type calcium channels is increased in cells treated with inhibitors of serine-threonine protein phosphatases. Thus, the increased calcium channel activity obtained in the presence of InsP
6
might result from the inhibition of phosphatase activity. Glucose elicited a transient increase in InsP
6
concentration, which indicates that this inositol polyphosphate may modulate calcium influx over the plasma membrane and serve as a signal in the pancreatic β cell stimulus-secretion coupling.
Requirement for V
α
14 NKT Cells in IL-12-Mediated Rejection of Tumors
Authors: Cui Junqing , Shin Tahiro , Kawano Tetsu , Sato Hiroshi , Kondo Eisuke , Toura Isao , Kaneko Yoshikatsu , Koseki Haruhiko , Kanno Masamoto , Taniguchi Masaru
Published: July 2002

A lymphocyte subpopulation, the V
α
14 natural killer T (NKT) cells, expresses both NK1.1 and a single invariant T cell receptor encoded by the V
α
14 and J
α
281 gene segments. Mice with a deletion of the J
α
281 gene segment were found to exclusively lack this subpopulation. The V
α
14 NKT cell–deficient mice could no longer mediate the interleukin-12 (IL-12)–induced rejection of tumors. Although the antitumor effect of IL-12 was thought to be mediated through natural killer cells and T cells, V
α
14 NKT cells were found to be an essential target of IL-12, and they mediated their cytotoxicity by an NK-like effector mechanism after activation with IL-12.
Elucidation of the Chain Conformation in a Glassy Polyester, PET, by Two-Dimensional NMR
Authors: Schmidt-Rohr K. , Hu W. , Zumbulyadis N.
Published: July 2002

The chain conformation of glassy poly(ethylene terephthalate) (PET) was characterized by two-dimensional double-quantum nuclear magnetic resonance (NMR). In amorphous carbon-13–labeled PET, the statistics of the O–
13
CH
2
–
13
CH
2
–O torsion angle were determined, on the basis of the distinct shapes of the two-dimensional NMR patterns of trans and gauche conformations. In crystalline PET, the trans content is 100 percent, but in the amorphous PET it is only 14 percent (±5 percent). An average gauche torsion angle of 70 degrees (±9 degrees) was obtained. Implications for materials properties of polyesters are discussed.
High Selectivities to Ethylene by Partial Oxidation of Ethane
Authors: Bodke A. S. , Olschki D. A. , Schmidt L. D. , Ranzi E.
Published: July 2002

At least 85 percent selectivity to ethylene at greater than 70 percent conversion can be obtained by partial oxidation of ethane by adding large amounts of H
2
to the reaction mixture and using a platinum-tin catalyst operating at 950°C with a contact time of ∼10
−3
seconds. This system almost totally shuts off the reactions that form undesired CO and CO
2
, which fall from 20 percent without H
2
to 5 percent when H
2
is added. Although a 2/1 H
2
/O
2
mixture should be explosive at high temperatures, no flames or explosions occur in the presence of ethane. The successive reactions on the catalyst generate more H
2
than used in the feed, so with recycle no additional H
2
would be needed. These results are unexpected because ethylene is a nonequilibrium product and entropy considerations argue that all reaction channels open at high temperatures so the products should approach equilibrium, which predicts only a few percent ethylene. This process is promising for the replacement of steam cracking in the production of ethylene.
Evidence for Quantum Critical Behavior in the Optimally Doped Cuprate Bi
2
Sr
2
CaCu
2
O
8+δ
Authors: Valla T. , Fedorov A. V. , Johnson P. D. , Wells B. O. , Hulbert S. L. , Li Q. , Gu G. D. , Koshizuka N.
Published: July 2002

The photoemission line shapes of the optimally doped cuprate Bi
2
Sr
2
CaCu
2
O
8+δ
were studied in the direction of a node in the superconducting order parameter by means of very high resolution photoemission spectroscopy. The peak width or inverse lifetime of the excitation displays a linear temperature dependence, independent of binding energy, for small energies, and a linear energy dependence, independent of temperature, for large binding energies. This behavior is unaffected by the superconducting transition, which is an indication that the nodal states play no role in the superconductivity. Temperature-dependent scaling suggests that the system displays quantum critical behavior.
Gate-Controlled Superconducting Proximity Effect in Carbon Nanotubes
Authors: Morpurgo A. F. , Kong J. , Marcus C. M. , Dai H.
Published: July 2002

The superconducting proximity effect in single-walled carbon nanotubes connected to niobium electrodes was controlled with the use of nearby gates that tune the niobium-nanotube transparency. At 4.2 kelvin, when the transparency was tuned to be high, a dip in the low-bias differential resistance was observed, indicating a proximity effect mediated by Andreev reflection. When the transparency was tuned to be low, signatures of Andreev reflection disappeared and only tunneling conduction was observed. Below ∼4 kelvin, a narrow peak in differential resistance around zero bias appeared superimposed on the Andreev dip, probably as a result of electron-electron interaction competing with the proximity effect.
All-Inorganic Field Effect Transistors Fabricated by Printing
Authors: Ridley Brent A. , Nivi Babak , Jacobson Joseph M.
Published: July 2002

A solution of cadmium selenide nanocrystals was used to print inorganic thin-film transistors with field effect mobilities up to 1 square centimeter per volt second. This mobility is an order of magnitude larger than those reported for printed organic transistors. A field effect was achieved by developing a synthesis that yielded discretely sized nanocrystals less than 2 nanometers in size, which were free of intimately bound organic capping groups. The resulting nanocrystal solution exhibited low-temperature grain growth, which formed single crystal areas encompassing hundreds of nanocrystals. This process suggests a route to inexpensive, all-printed, high-quality inorganic logic on plastic substrates.
Formation of Cyclic Water Hexamer in Liquid Helium: The Smallest Piece of Ice
Authors: Nauta K. , Miller R. E.
Published: July 2002

The cyclic water hexamer, a higher energy isomer than the cage structure previously characterized in the gas phase, was formed in liquid helium droplets and studied with infrared spectroscopy. This isomer is formed selectively as a result of unique cluster growth processes in liquid helium. The experimental results indicate that the cyclic hexamer is formed by insertion of water molecules into smaller preformed cyclic complexes and that the rapid quenching provided by the liquid helium inhibits its rearrangement to the more stable cage structure.
Illusions in Reasoning About Consistency
Authors: Johnson-Laird P. N. , Legrenzi Paolo , Girotto Vittorio , Legrenzi Maria S.
Published: July 2002

Reasoners succumb to predictable illusions in evaluating whether sets of assertions are consistent. We report two studies of this computationally intractable task of “satisfiability.” The results show that as the number of possibilities compatible with the assertions increases, the difficulty of the task increases, and that reasoners represent what is true according to assertions, not what is false. This procedure avoids overloading memory, but it yields illusions of consistency and of inconsistency. These illusions modify our picture of human rationality.
Raman Spectroscopy of Iron to 152 Gigapascals: Implications for Earth's Inner Core
Authors: Merkel Sébastien , Goncharov Alexander F. , Mao Ho-kwang , Gillet Philippe , Hemley Russell J.
Published: July 2002

Raman spectra of hexagonal close-packed iron (
ɛ
-Fe) have been measured from 15 to 152 gigapascals by using diamond-anvil cells with ultrapure synthetic diamond anvils. The results give a Grüneisen parameter γ
0
= 1.68 (±0.20) and
q
= 0.7 (±0.5). Phenomenological modeling shows that the Raman-active mode can be approximately correlated with an acoustic phonon and thus provides direct information about the high-pressure elastic properties of iron, which have been controversial. In particular, the
C
44
elastic modulus is found to be lower than previous determinations. This leads to changes of about 35% at core pressures for shear wave anisotropies.
Impacts of a Global Climate Cycle on Population Dynamics of a Migratory Songbird
Authors: Sillett T. Scott , Holmes Richard T. , Sherry Thomas W.
Published: July 2002

Progress toward understanding factors that limit abundances of migratory birds, including climate change, has been difficult because these species move between diverse locations, often on different continents. For black-throated blue warblers (
Dendroica caerulescens
), demographic rates in both tropical winter quarters and north temperate breeding grounds varied with fluctuations in the El Niño Southern Oscillation. Adult survival and fecundity were lower in El Niño years and higher in La Niña years. Fecundity, in turn, was positively correlated with subsequent recruitment of new individuals into winter and breeding populations. These findings demonstrate that migratory birds can be affected by shifts in global climate patterns and emphasize the need to know how events throughout the annual cycle interact to determine population size.
A Single-Molecule Study of RNA Catalysis and Folding
Authors: Zhuang Xiaowei , Bartley Laura E. , Babcock Hazen P. , Russell Rick , Ha Taekjip , Herschlag Daniel , Chu Steven
Published: July 2002

Using fluorescence microscopy, we studied the catalysis by and folding of individual
Tetrahymena thermophila
ribozyme molecules . The dye-labeled and surface-immobilized ribozymes used were shown to be functionally indistinguishable from the unmodified free ribozyme in solution. A reversible local folding step in which a duplex docks and undocks from the ribozyme core was observed directly in single-molecule time trajectories, allowing the determination of the rate constants and characterization of the transition state. A rarely populated docked state, not measurable by ensemble methods, was observed. In the overall folding process, intermediate folding states and multiple folding pathways were observed. In addition to observing previously established folding pathways, a pathway with an observed folding rate constant of 1 per second was discovered. These results establish single-molecule fluorescence as a powerful tool for examining RNA folding.
Abolition and Reversal of Strain Differences in Behavioral Responses to Drugs of Abuse After a Brief Experience
Authors: Cabib Simona , Orsini Cristina , Moal Michel Le , Piazza Pier Vincenzo
Published: July 2002

Inbred strains of mice are largely used to identify the genetic basis of normal and pathological behaviors. This report demonstrates that a moderate period of food shortage, an ecologically common experience, can reverse or abolish strain differences in behavioral responses to the abused psychostimulant amphetamine. The period of food shortage occurred when the animals were mature and was terminated before the administration of amphetamine. Strain differences in behavior appear highly dependent on environmental experiences. Consequently, to identify biological determinants of behavior, an integrated approach considering the interaction between environmental and genetic factors needs to be used.
Enhanced Room-Temperature Geometric Magnetoresistance in Inhomogeneous Narrow-Gap Semiconductors
Authors: Solin S. A. , Thio Tineke , Hines D. R. , Heremans J. J.
Published: July 2002

A symmetric van der Pauw disk of homogeneous nonmagnetic indium antimonide with an embedded concentric gold inhomogeneity is found to exhibit room-temperature geometric magnetoresistance as high as 100, 9100, and 750,000 percent at magnetic fields of 0.05, 0.25, and 4.0 teslas, respectively. For inhomogeneities of sufficiently large diameter relative to that of the surrounding disk, the resistance is field-independent up to an onset field above which it increases rapidly. These results can be understood in terms of the field-dependent deflection of current around the inhomogeneity.
NEAR at Eros: Imaging and Spectral Results
Authors: Veverka J. , Robinson M. , Thomas P. , Murchie S. , Bell J. F. , Izenberg N. , Chapman C. , Harch A. , Bell M. , Carcich B. , Cheng A. , Clark B. , Domingue D. , Dunham D. , Farquhar R. , Gaffey M. J. , Hawkins E. , Joseph J. , Kirk R. , Li H. , Lucey P. , Malin M. , Martin P. , McFadden L. , Merline W. J. , Miller J. K. , Owen W. M. , Peterson C. , Prockter L. , Warren J. , Wellnitz D. , Williams B. G. , Yeomans D. K.
Published: July 2002

Eros is a very elongated (34 kilometers by 11 kilometers by 11 kilometers) asteroid, most of the surface of which is saturated with craters smaller than 1 kilometer in diameter. The largest crater is 5.5 kilometers across, but there is a 10-kilometer saddle-like depression with attributes of a large degraded crater. Surface lineations, both grooves and ridges, are prominent on Eros; some probably exploit planes of weakness produced by collisions on Eros and/or its parent body. Ejecta blocks (30 to 100 meters across) are abundant but not uniformly distributed over the surface. Albedo variations are restricted to the inner walls of certain craters and may be related to downslope movement of regolith. On scales of 200 meters to 1 kilometer, Eros is more bland in terms of color variations than Gaspra or Ida. Spectra (800 to 2500 nanometers) are consistent with an ordinary chondrite composition for which the measured mean density of 2.67 ± 0.1 grams per cubic centimeter implies internal porosities ranging from about 10 to 30 percent.
The Kondo Effect in the Unitary Limit
Authors: van der Wiel W. G. , Franceschi S. De , Fujisawa T. , Elzerman J. M. , Tarucha S. , Kouwenhoven L. P.
Published: July 2002

We observe a strong Kondo effect in a semiconductor quantum dot when a small magnetic field is applied. The Coulomb blockade for electron tunneling is overcome completely by the Kondo effect, and the conductance reaches the unitary limit value. We compare the experimental Kondo temperature with the theoretical predictions for the spin-½ Anderson impurity model. Excellent agreement is found throughout the Kondo regime. Phase coherence is preserved when a Kondo quantum dot is included in one of the arms of an Aharonov-Bohm ring structure, and the phase behavior differs from previous results on a non-Kondo dot.
Plasma Membrane Compartmentalization in Yeast by Messenger RNA Transport and a Septin Diffusion Barrier
Authors: Takizawa Peter A. , DeRisi Joseph L. , Wilhelm James E. , Vale Ronald D.
Published: July 2002

Asymmetric localization of proteins plays a key role in many cellular processes, including cell polarity and cell fate determination. Using DNA microarray analysis, we identified a plasma membrane protein-encoding mRNA (IST2) that is transported to the bud tip by an actomyosin-based process. mRNA localization created a higher concentration of
IST2
protein in the bud compared with that of the mother cell, and this asymmetry was maintained by a septin-mediated membrane diffusion barrier at the mother-bud neck. These results indicate that yeast creates distinct plasma membrane compartments, as has been described in neurons and epithelial cells.
Quantum Superposition of Macroscopic Persistent-Current States
Authors: van der Wal Caspar H. , ter Haar A. C. J. , Wilhelm F. K. , Schouten R. N. , Harmans C. J. P. M. , Orlando T. P. , Lloyd Seth , Mooij J. E.
Published: July 2002

Microwave spectroscopy experiments have been performed on two quantum levels of a macroscopic superconducting loop with three Josephson junctions. Level repulsion of the ground state and first excited state is found where two classical persistent-current states with opposite polarity are degenerate, indicating symmetric and antisymmetric quantum superpositions of macroscopic states. The two classical states have persistent currents of 0.5 microampere and correspond to the center-of-mass motion of millions of Cooper pairs.
Replication Dynamics of the Yeast Genome
Authors: Raghuraman M. K. , Winzeler Elizabeth A. , Collingwood David , Hunt Sonia , Wodicka Lisa , Conway Andrew , Lockhart David J. , Davis Ronald W. , Brewer Bonita J. , Fangman Walton L.
Published: July 2002

Oligonucleotide microarrays were used to map the detailed topography of chromosome replication in the budding yeast
Saccharomyces cerevisiae
. The times of replication of thousands of sites across the genome were determined by hybridizing replicated and unreplicated DNAs, isolated at different times in S phase, to the microarrays. Origin activations take place continuously throughout S phase but with most firings near mid–S phase. Rates of replication fork movement vary greatly from region to region in the genome. The two ends of each of the 16 chromosomes are highly correlated in their times of replication. This microarray approach is readily applicable to other organisms, including humans.
Role of the Neurotransmitter Reuptake-Blocking Activity of Antidepressants in Reversing Chloroquine Resistance In Vitro in
Plasmodium falciparum
Authors: Taylor Dale , Walden Jason C. , Robins Ashley H. , Smith Peter J.
Published: July 2002

Since the discovery of the chloroquine (CQ) resistance reversal properties of several different, structurally unrelated classes of compounds, including antidepressants, the way is again open to employ the aminoquinoline drugs to combat malaria effectively. In this study, CQ sensitivity was restored to varying extents in vitro in the CQ-resistant
Plasmodium falciparum
strain RSA11 by using the antidepressants amitriptyline, citalopram, oxaprotiline, and nomifensine. The 50% inhibitory concentrations (IC
50
) of CQ were reduced from 360 to as low as 11 nM when antidepressants were present. These particular antidepressants are highly specific for blocking the ATP-binding cassette transport protein-mediated reuptake of different neurotransmitters at the synaptic level. This study was aimed at determining the extent to which the neurotransmitter reuptake-blocking properties of these antidepressants play a role in the reversal process. None of the compounds or CQ-antidepressant combinations tested had innate antimalarial activity. No chemosensitizer or combination showed an increased CQ accumulation or significant shift in the IC
50
in the CQ-sensitive clone D10. Of the compounds tested, citalopram, a highly specific serotonin reuptake blocker, produced the largest shift observed in the IC
50
for the resistant isolate RSA11. No particular class of antidepressant was found to be better than any other at restoring CQ sensitivity. We conclude that the resistance-reversing properties of these compounds do not correlate with their activities as reuptake blockers.
Cloning and Nucleotide Sequence of the DNA Gyrase (
gyrA
) Gene from
Mycoplasma hominis
and Characterization of Quinolone-Resistant Mutants Selected In Vitro with Trovafloxacin
Authors: Bébéar C. M. , Grau O. , Charron A. , Renaudin H. , Gruson D. , Bébéar C.
Published: July 2002

We report the cloning and characterization of the
gyrA
gene of the
Mycoplasma hominis
DNA gyrase, which was previously shown to be associated with quinolone resistance in this organism. The 2,733-bp
gyrA
gene encodes a protein of 911 amino acids with a calculated molecular mass of 102.5 kDa. As expected,
M. hominis
GyrA exhibits higher homology with the GyrA subunits of the gram-positive bacteria
Clostridium acetobutylicum
,
Bacillus subtilis
,
Streptococcus pneumoniae
, and
Staphylococcus aureus
than with its
Escherichia coli
counterpart. Knowing the entire sequence of the
gyrA
gene of
M. hominis
could be very useful for confirming the role of the GyrA subunit in fluoroquinolone resistance. Twenty-nine mutants of
M. hominis
were selected stepwise for resistance to trovafloxacin, a new potent fluoroquinolone, and their
gyrA
,
gyrB
,
parC
, and
parE
quinolone resistance-determining regions were characterized. Three rounds of selection yielded 3 first-step, 12 second-step, and 14 third-step mutants. The first-step mutants harbored a single substitution, Glu460→Lys (
E. coli
coordinates), in ParE. GyrA changes, Ser83→Leu, Glu87→Lys, and Ala119→Glu or Val, were found only in the second round of selection. At the third step, additional substitutions, at ParC Ser80, Ser81, and Glu84 and ParE Leu440, associated with high-level resistance to fluoroquinolones, appeared. Thus, high-level resistance to trovafloxacin required three steps and was associated with alterations in both fluoroquinolone targets. According to these genetic data, in
M. hominis
, as in
Staphylococcus aureus
and
Streptococcus pneumoniae
, topoisomerase IV seems to be the primary target of trovafloxacin.
Pentamidine Inhibition of Group I Intron Splicing in
Candida albicans
Correlates with Growth Inhibition
Authors: Miletti Karl E. , Leibowitz Michael J.
Published: July 2002

We previously demonstrated that pentamidine, which has been clinically used against
Pneumocystis carinii
, inhibits in vitro a group I intron ribozyme from that organism. Another fungal pathogen,
Candida albicans
, also harbors a group I intron ribozyme (Ca.LSU) in the essential rRNA genes in almost half of the clinical isolates analyzed. To determine whether pentamidine inhibits Ca.LSU in vitro and in cells, phylogenetically closely related intron-containing (4-1) and intronless (62-1) strains were studied. Splicing in vitro of the Ca.LSU group I intron ribozyme was completely inhibited by pentamidine at 200 μM. On rich glucose medium, the intron-containing strain was more sensitive to growth inhibition by pentamidine than was the intronless strain, as measured by disk or broth microdilution assays. On rich glycerol medium, they were equally susceptible to pentamidine. At pentamidine levels selectively inhibiting the intron-containing strain (1 μM) in glucose liquid cultures, inhibition of splicing and rRNA maturation was detected by quantitative reverse transcription-PCR within 1 min with a 10- to 15-fold accumulation of precursor rRNA. No comparable effect was seen in the intronless strain. These results correlate the cellular splicing inhibition of Ca.LSU with the growth inhibition of strain 4-1 harboring Ca.LSU. Broth microdilution assays of 13
Candida
strains showed that intron-containing strains were generally more susceptible to pentamidine than the intronless strains. Our data suggest that ribozymes found in pathogenic microorganisms but absent in mammals may be targets for antimicrobial therapy.
In Vitro Comparison of Terbinafine and Itraconazole against
Penicillium marneffei
Authors: McGinnis Michael R. , Nordoff Nicole G. , Ryder Neil S. , Nunn Gary B.
Published: July 2002

We evaluated terbinafine and itraconazole against 30 isolates of
Penicillium marneffei
using a modification of the National Committee for Clinical Laboratory Standards broth macrodilution MIC testing protocol for yeasts. The minimal fungicidal concentration (MFC) was determined by plating 100 μl from each MIC drug dilution having no growth onto Sabouraud glucose agar incubated at 30°C. The MFC was the dilution at which growth was absent at 72 h of incubation. The MICs, in micrograms per milliliter, were as follows: terbinafine, 0.03 to 1.0 (geometric mean titer, 0.09); itraconazole, 0.03 to 0.5 (geometric mean titer, 0.04). The MFCs, in micrograms per milliliter, were as follows: terbinafine, 0.03 to 8 (geometric mean titer, 2.60); itraconazole, 0.03 to 8 (geometric mean titer, 2.45). Primary fungicidal activity (MFC within 2 dilutions of MIC) was observed with terbinafine in eight isolates and with itraconazole in four isolates. The data indicate that terbinafine is active against
P. marneffei
in vitro and may have a previously unrealized role in the management of infections caused by this fungus.
Studies of the Novel Ketolide ABT-773: Transport, Binding to Ribosomes, and Inhibition of Protein Synthesis in
Streptococcus pneumoniae
Authors: Capobianco John O. , Cao ZhenSheng , Shortridge Virginia D. , Ma ZhenKun , Flamm Robert K. , Zhong Ping
Published: July 2002

Macrolide resistance in
Streptococcus pneumoniae
has been associated with two main mechanisms: target modification by Erm methyltransferases and efflux by macrolide pumps. The ketolide ABT-773, which has a 3-keto group and no
l
-cladinose sugar, represents a new class of drugs with in vitro activity against a variety of resistant bacteria. Several approaches were undertaken to understand how ABT-773 was able to defeat resistance mechanisms. We demonstrated tighter ribosome binding of ABT-773 than erythromycin. We also showed that ABT-773 (i) accumulated in macrolide-sensitive
S. pneumoniae
at a higher rate than erythromycin, (ii) was able to bind with methylated ribosomes, though at lower affinities than with wild-type ribosomes, and (iii) accumulated in
S. pneumoniae
strains with the efflux-resistant phenotype.