bluuebunny/crossref_metadata_2025 huggingface dataset:
Designing a Bloom filter for differential file access
Authors: Gremillion Lee L.
Published: July 2002

The use of a differential file for a database update can yield integrity and performance benefits, but it can also present problems in providing current data to subsequent accessing transactions. A mechanism known as a Bloom filter can solve these problems by preventing most unnecessary searches of the differential file. Here, the design process for a Bloom filter for an on-line student database is described, and it is shown that a very effective filter can be constructed with a modest expenditure of system resources.
On improving the worst case running time of the Boyer-Moore string matching algorithm
Authors: Galil Zvi
Published: July 2002

It is shown how to modify the Boyer-Moore string matching algorithm so that its worst case running time is linear even when multiple occurrences of the pattern are present in the text.
Pseudoinversus and conjugate gradients
Authors: Hestenes Magnus R.
Published: July 2002

This paper is devoted to the study of connections between pseudoinverses of matrices and conjugate gradients and conjugate direction routines.
Cubic splines on uniform meshes
Authors: Nilson E. N.
Published: July 2002

A very simple procedure is presented for constructing cubic splines, periodic or nonperiodic, on uniform meshes. Arcs of two cubics suffice to construct a basis of cardinal splines. An algorithm is given which requires only minimal storage and computation and permits easy trade-off of one against the other.
Mathematical model for a documentation system
Authors: Kent Allen
Published: July 2002

The Center is currently engaged in a number of theoretical and basic research investigations which are expected to lead to the formulation of a theory of documentation and of searching strategy. A basic program is leading to the development of a mathematical model for a documentation system. Work is proceeding (1) on a comprehensive investigation of the properties of aggregates and systems of messages in order to arrive at a general theory of “measure” for documentation systems, (2) on an analysis of the algebra that is imposed on the message complex, and (3) on a detailed study of the concept of mapping in documentation.
ADAM (Attrition Damage Assessment Model
Authors: Batchelder B. A.
Published: July 2002

ADAM is a computer routine designed to do a Monte Carlo simulation of a one-sided air battle. ADAM requires as input plans for bombing missions (including targets) the initial condition of defense installations (missile sites, radar sites, and fighter bases) and bomber bases, and parameters determining aircraft characteristics and weapon effectiveness. Time is broken into short intervals (15 minutes as presently coded), and during each time interval ADAM carries out the action called for by the plans and computes the consequences, thus setting up a new set of conditions for the next time period. During this cycle the functions performed include: (1) flight following—the movement of aircraft is directed in accordance with the route specifications; fuel consumption, altitude, and distance traveled are computed; airborne operations such as refueling, air release of deception devices, the dropping of bombs, and communication of mission results are carried out; (2) attrition—radar detection of bombers and attacks by fighters and missiles are simulated; (3) targeting—designated ground zeros for bombs dropped over target are selected and the amount of information obtained by reconnaissance missions is determined; (4) damage—blast damage to bomber bases and defense installations is computed, as well as their restricted operation as a result of radioactive fallout from ground bursts. The output from ADAM consists of the final status of bomber bases and defense installations, a time history of all bombing missions, counters (these include such quantities as the number of aircraft killed by missiles or fighters, the number of bases and defense installations destroyed or rendered inoperable because of radiation), the actual ground zeros (from bomb drops at target points or attrited bombers), and the fighter engagements. A strike of 312 bombers against 71 bomber bases and 1158 defense installations takes about 15 minutes of 704 time.
What is a code?
Authors: Patterson G. W.
Published: July 2002

The etymology of the word
code
is most interesting. It seems evident that in its original form it has reference to the paginated format of a book as distinguished from the earlier scrolls. Books with leaves fastened together at a common edge were apparently used in Roman times to record compilations of laws, and this is the basis for the original meanings of
code
, as a systematic collection, compilation, or formulation of laws, principles, rules or regulations.
Computer pattern recognition techniques: electrocardiographic diagnosis
Authors: Stark Lawrence , Okajima Mitsuharu , Whipple Gerald H.
Published: July 2002

The use of programmed digital computers as general pattern classification and recognition devices is one phase of the current lively interest in artificial intelligence. It is important to choose a class of signals which is, at present, undergoing a good deal of visual inspection by trained people for the purpose of pattern recognition. In this way comparisons between machine and human performance may be obtained. A practical result also serves as additional motivation. Clinical electrocardiograms make up such a class of signals.

The approach to the problem presented here centers upon the use of multiple adaptive matched filters that classify normalized signals. The present report gives some of the background for the application of this method.
Topological sorting of large networks
Authors: Kahn A. B.
Published: July 2002

Topological Sorting is a procedure required for many problems involving analysis of networks. An example of one such problem is PERT. The present paper presents a very general method for obtaining topological order. It permits treatment of larger networks than can be handled on present procedures and achieves this with greater efficiency. Although the procedure can be adapted to any machine, it is discussed in terms of the 7090. A PERT network of 30,000 activities can be ordered in less than one hour of machine time.

The method was developed as a byproduct of procedure needed by Westinghouse, Baltimore. It has not been programmed and at present there are no plans to implement it. In regard to the techniques described, Westinghouse's present and anticipated needs are completely served by the Lockheed program, which is in current use.
A model of multimedia information retrieval
Authors: Meghini Carlo , Sebastiani Fabrizio , Straccia Umberto
Published: July 2002

Research on multimedia information retrieval (MIR) has recently witnessed a booming interest. A prominent feature of this research trend is its simultaneous but independent materialization within several fields of computer science. The resulting richness of paradigms, methods and systems may, on the long run, result in a fragmentation of efforts and slow down progress. The primary goal of this study is to promote an integration of methods and techniques for MIR by contributing a conceptual model that encompasses in a unified and coherent perspective the many efforts that are being produced under the label of MIR. The model offers a retrieval capability that spans two media, text and images, but also several dimensions: form, content and structure. In this way, it reconciles similarity-based methods with semantics-based ones, providing the guidelines for the design of systems that are able to provide a generalized multimedia retrieval service, in which the existing forms of retrieval not only coexist, but can be combined in any desired manner. The model is formulated in terms of a fuzzy description logic, which plays a twofold role: (1) it directly models semantics-based retrieval, and (2) it offers an ideal framework for the integration of the multimedia and multidimensional aspects of retrieval mentioned above. The model also accounts for relevance feedback in both text and image retrieval, integrating known techniques for taking into account user judgments. The implementation of the model is addressed by presenting a decomposition technique that reduces query evaluation to the processing of simpler requests, each of which can be solved by means of widely known methods for text and image retrieval, and semantic processing. A prototype for multidimensional image retrieval is presented that shows this decomposition technique at work in a significant case.
A unified approach to approximating resource allocation and scheduling
Authors: Bar-Noy Amotz , Bar-Yehuda Reuven , Freund Ari , (Seffi) Naor Joseph , Schieber Baruch
Published: July 2002

We present a general framework for solving resource allocation and scheduling problems. Given a resource of fixed size, we present algorithms that approximate the maximum throughput or the minimum loss by a constant factor. Our approximation factors apply to many problems, among which are: (i) real-time scheduling of jobs on parallel machines, (ii) bandwidth allocation for sessions between two endpoints, (iii) general caching, (iv) dynamic storage allocation, and (v) bandwidth allocation on optical line and ring topologies. For some of these problems we provide the first constant factor approximation algorithm. Our algorithms are simple and efficient and are based on the local-ratio technique. We note that they can equivalently be interpreted within the primal-dual schema.
Building a distributed full-text index for the web
Authors: Melink Sergey , Raghavan Sriram , Yang Beverly , Garcia-Molina Hector
Published: July 2002

We identify crucial design issues in building a distributed inverted index for a large collection of Web pages. We introduce a novel pipelining technique for structuring the core index-building system that substantially reduces the index construction time. We also propose a storage scheme for creating and managing inverted files using an embedded database system. We suggest and compare different strategies for collecting global statistics from distributed inverted indexes. Finally, we present performance results from experiments on a testbed distributed Web indexing system that we have implemented.
On the algebraic and geometric foundations of computer graphics
Authors: Goldman Ron
Published: July 2002

Today's computer graphics is ostensibly based upon insights from projective geometry and computations on homogeneous coordinates. Paradoxically, however, projective spaces and homogeneous coordinates are incompatible with much of the algebra and a good deal of the geometry currently in actual use in computer graphics. To bridge this gulf between theory and practice, Grassmann spaces are proposed here as an alternative to projective spaces. We establish that unlike projective spaces, Grassmann spaces do support all the algebra and geometry needed for contemporary computer graphics. We then go on to explain how to exploit this algebra and geometry for a variety of applications, both old and new, including the graphics pipeline, shading algorithms, texture maps, and overcrown surfaces.
Reliable scheduling in a TMR database system
Authors: Pittelli Frank M. , Garcia-Molina Hector
Published: July 2002

A Triple Modular Redundant (TMR) system achieves high reliability by replicating data and all processing at three independent nodes. When TMR is used for database processing all nonfaulty computers must execute the same sequence of transactions, and this is ensured by a collection of processes known as
schedulers
. In this paper we study the implementation of efficient schedulers through analysis of various enhancements such as null transactions and message batching. The schedulers have been implemented in an experimental TMR system and the evaluation results are presented here.
Linda in context
Authors: Carriero Nicholas , Gelernter David
Published: July 2002

How can a system that differs sharply from all currently fashionable approaches score any kind of success? Here's how.
Crisis and aftermath
Authors: Spafford E. H.
Published: July 2002

Last November the Internet was infected with a worm program that eventually spread to thousands of machines, disrupting normal activities and Internet connectivity for many days. The following article examines just how this worm operated.
Four paradigms of information systems development
Authors: Hirschheim Rudy , Klein Heinz K.
Published: July 2002

Developing computer-based information systems necessarily involves making a number of implicit and explicit assumptions. The authors examine four different approaches to information systems development.
Finding minimum-cost circulations by canceling negative cycles
Authors: Goldberg Andrew V. , Tarjan Robert E.
Published: July 2002

A classical algorithm for finding a minimum-cost circulation consists of repeatedly finding a residual cycle of negative cost and
canceling
it by pushing enough flow around the cycle to saturate an arc. We show that a judicious choice of cycles for canceling leads to a polynomial bound on the number of iterations in this algorithm. This gives a very simple strongly polynomial algorithm that uses no scaling. A variant of the algorithm that uses dynamic trees runs in Ο(
nm
(log
n
)min{log(
nC
),
m
log
n
}) time on a network of
n
vertices,
m
arcs, and arc costs of maximum absolute value
C
. This bound is comparable to those of the fastest previously known algorithms.
Multidimensional icons
Authors: Henry Tyson R. , Hudson Scott E.
Published: July 2002

Background: Direct manipulation interfaces, such as the Macintosh desktop, often represent objects with icons [l, 41. For example, text files are represented by icons. Selection of the icon invokes an editor to view the file it represents, thus the icon not only represents the text file but also represents a text editor used to view the text file. Each type of object is viewed by using a specific program. Diagram objects, for example, require a graphical editor to view. In a typical iconic interface, icons represent a single view of an object.

While the single-view single-icon model has proven very intuitive and easy to use, some objects have more than one logical view [2]. Program code can be viewed as text by using a text editor, or it can be viewed as program code by a compiler. The machine code that corresponds to the program code can be thought of as another view, thus the execution of a program can be thought of as another view of program code. This paper describes a mechanism for grouping a set of icons that depict several views of a single object into one multidimensional icon.

Multidimensional icons group sets of icons, each describing a unique view of an object, into a single entity. The individual icons are projected onto the sides of a simulated cube. There are two distinct advantages to using a cube instead of displaying all the icons in a menu. The first advantage is that since cubes are very familiar objects, it is a natural mental model to think of the faces of a cube as views of the entire cube—views of the actual object. The second advantage is that by allowing rotation of the cube, several icons representing views of an object are accessible using only a fraction of the screen space required to display all the icons.
COMPARTMENTATION OF PROTEINS IN THE ENDOMEMBRANE SYSTEM OF PLANT CELLS
Authors: Okita Thomas W. , Rogers John C.
Published: July 2002

▪ Abstract  This review focuses on four interrelated processes in the plant endomembrane system: compartmentation of proteins in subdomains of the endoplasmic reticulum, mechanisms that determine whether storage proteins are retained within the ER lumen or transported out, the origin and function of biochemically distinct vacuoles or prevacuolar organelles, and the cellular processes by which proteins are sorted to vacuolar compartments. We postulate that ER-localized protein bodies are formed by a series of orderly events of protein synthesis, protein concentration, and protein assembly in subdomains of the ER. Protein concentration, which facilitates protein-to-protein interactions and subsequent protein assembly, may be achieved by the interactions with chaperones and by the localization of storage protein mRNAs. We also describe recent developments on the coexistence of two biochemically distinguishable vacuolar compartments, the possible direct role of the ER in vacuole biogenesis, and proposed mechanisms for transport of proteins from the ER or Golgi apparatus to the vacuole.
CHLAMYDOMONAS AS A MODEL ORGANISM
Authors: Harris Elizabeth H
Published: July 2002

▪ Abstract  The unicellular green alga Chlamydomonas offers a simple life cycle, easy isolation of mutants, and a growing array of tools and techniques for molecular genetic studies. Among the principal areas of current investigation using this model system are flagellar structure and function, genetics of basal bodies (centrioles), chloroplast biogenesis, photosynthesis, light perception, cell-cell recognition, and cell cycle control. A genome project has begun with compilation of expressed sequence tag data and gene expression studies and will lead to a complete genome sequence. Resources available to the research community include wild-type and mutant strains, plasmid constructs for transformation studies, and a comprehensive on-line database.
Tolerance and Specificity of Polyketide Synthases
Authors: Khosla Chaitan , Gokhale Rajesh S. , Jacobsen John R. , Cane David E.
Published: July 2002

▪ Abstract  Polyketide synthases catalyze the assembly of complex natural products from simple precursors such as propionyl-CoA and methylmalonyl-CoA in a biosynthetic process that closely parallels fatty acid biosynthesis. Like fatty acids, polyketides are assembled by successive decarboxylative condensations of simple precursors. But whereas the intermediates in fatty acid biosynthesis are fully reduced to generate unfunctionalized alkyl chains, the intermediates in polyketide biosynthesis may be only partially processed, giving rise to complex patterns of functional groups. Additional complexity arises from the use of different starter and chain extension substrates, the generation of chiral centers, and further functional group modifications, such as cyclizations. The structural and functional modularity of these multienzyme systems has raised the possibility that polyketide biosynthetic pathways might be rationally reprogrammed by combinatorial manipulation. An essential prerequisite for harnessing this biosynthetic potential is a better understanding of the molecular recognition features of polyketide synthases. Within this decade, a variety of genetic, biochemical, and chemical investigations have yielded insights into the tolerance and specificity of several architecturally different polyketide synthases. The results of these studies, together with their implications for biosynthetic engineering, are summarized in this review.
Tissue Engineering: Orthopedic Applications
Authors: Laurencin C. T. , Ambrosio A. M. A. , Borden M. D. , Cooper J. A.
Published: July 2002

▪ Abstract  Because of an aging population and increased occurrence of sports-related injuries, musculoskeletal disorders have become one of the major health concerns in the United States. Current treatments, although fairly successful, do not provide the optimum therapy. These treatments typically rely on donor tissues obtained either from the patient or from another source. The former raises the issue of supply, whereas the latter poses the risk of rejection and disease transfer. This has prompted orthopedic surgeons and scientists to look for viable alternatives. In recent years, tissue engineering has gained increasing support as a method to treat orthopedic disorders. Because it uses principles of engineering, biology, and chemistry, tissue engineering may provide a more effective approach to the treatment of musculoskeletal disorders than traditional methods. This chapter presents a review of current methods and new tissue-engineering techniques for the treatment of disorders affecting bone, ligament, and cartilage.
Two-Photon Excitation Fluorescence Microscopy
Authors: So Peter T. C. , Dong Chen Y. , Masters Barry R. , Berland Keith M.
Published: July 2002

▪ Abstract  Two-photon fluorescence microscopy is one of the most important recent inventions in biological imaging. This technology enables noninvasive study of biological specimens in three dimensions with submicrometer resolution. Two-photon excitation of fluorophores results from the simultaneous absorption of two photons. This excitation process has a number of unique advantages, such as reduced specimen photodamage and enhanced penetration depth. It also produces higher-contrast images and is a novel method to trigger localized photochemical reactions. Two-photon microscopy continues to find an increasing number of applications in biology and medicine.
Biochemical Pathways of Caspase Activation During Apoptosis
Authors: Budihardjo Imawati , Oliver Holt , Lutter Michael , Luo Xu , Wang Xiaodong
Published: July 2002

▪ Abstract  Caspase activation plays a central role in the execution of apoptosis. The key components of the biochemical pathways of caspase activation have been recently elucidated. In this review, we focus on the two most well-studied pathways of caspase activation: the cell surface death receptor pathway and the mitochondria-initiated pathway. In the cell surface death receptor pathway, activation of caspase-8 following its recruitment to the death-inducing signaling complex (DISC) is the critical event that transmits the death signal. This event is regulated at several different levels by various viral and mammalian proteins. Activated caspase-8 can activate downstream caspases by direct cleavage or indirectly by cleaving Bid and inducing cytochrome c release from the mitochondria.

In the mitochondrial-initiated pathway, caspase activation is triggered by the formation of a multimeric Apaf-1/cytochrome c complex that is fully functional in recruiting and activating procaspase-9. Activated caspase-9 will then cleave and activate downstream caspases such as caspase-3, -6, and -7. This pathway is regulated at several steps, including the release of cytochrome c from the mitochondria, the binding and hydrolysis of dATP/ATP by Apaf-1, and the inhibition of caspase activation by the proteins that belong to the inhibitors of apoptosis (IAP).
Regulation of Nuclear Localization: A Key to a Door
Authors: Kaffman Arie , O'Shea Erin K.
Published: July 2002

▪ Abstract  Information can be transferred between the nucleus and the cytoplasm by translocating macromolecules across the nuclear envelope. Communication of extracellular or intracellular changes to the nucleus frequently leads to a transcriptional response that allows cells to survive in a continuously changing environment. Eukaryotic cells have evolved ways to regulate this movement of macromolecules between the cytoplasm and the nucleus such that the transfer of information occurs only under conditions in which a transcriptional response is required. This review focuses on the ways in which cells regulate movement of proteins across the nuclear envelope and the significance of this regulation for controlling diverse biological processes.
SUMO—Nonclassical Ubiquitin
Authors: Melchior Frauke
Published: July 2002

▪ Abstract  SUMO (small ubiquitin-related modifier) is the best-characterized member of a growing family of ubiquitin-related proteins. It resembles ubiquitin in its structure, its ability to be ligated to other proteins, as well as in the mechanism of ligation. However, in contrast to ubiquitination—often the first step on a one-way road to protein degradation—SUMOlation does not seem to mark proteins for degradation. In fact, SUMO may even function as an antagonist of ubiquitin in the degradation of selected proteins. While most SUMO targets are still at large, available data provide compelling evidence for a role of SUMO in the regulation of protein-protein interactions and/or subcellular localization.
THE CAUSES AND CONSEQUENCES OF PARTICULATE AIR POLLUTION IN URBAN INDIA: A Synthesis of the Science
Authors: Kandlikar Milind , Ramachandran Gurumurthy
Published: July 2002

▪ Abstract  Indian megacities are among the most polluted in the world. Air concentrations of a number of air pollutants are much higher than levels recommended by the World Health Organization. In this paper, we focus on Mumbai and Delhi to characterize salient issues in health risks from particulate air (PM10) pollution in Indian cities. We perform a synthesis of the literature for all elements of the causal chain of health risks—sources, exposure, and health effects—and provide estimates of source strengths, exposure levels, and health risks from air pollution in Indian cities. We also analyze the factors that lead to uncertainty in these quantities and provide an overall assessment of the state of scientific knowledge on air pollution in urban India.
EVOLUTION OF ARTHROPOD SILKS
Authors: Craig Catherine L.
Published: July 2002

▪ Abstract  Silks belong to the class of molecules called structural proteins. The ability to produce silk proteins has evolved multiple times in the arthropods, and silk secreting glands have evolved via two different pathways. The comparative data and phylogenetic analyses in this review suggest that the silk-secreting systems of spiders and insects are homologous and linked to the crural gland (origin of systemic pathway to silk production) and cuticular secretions (origin of surficial pathway to silk production) of an onychophoran-like ancestor. The evolution of silk secreting organs via a surficial pathway is possible in adult and larval hexapods, regardless of their developmental mode. Silk secretion via a systemic pathway is possible in either adult or larval hexapods, but only larval insects have dedicated silk producing glands. Spiders, however, have evolved silk producing systems via both systemic pathway and surficial pathways, and a single individual retains both throughout its lifespan. Early in the evolution of spiders, silk glands were undifferentiated, suggesting that the number of silk secreting glands of any individual was related to the spider's energetic need to produce large quantities of protein. However, the complex silk-producing systems that characterize the aerial web–building spiders and the diverse types of proteins they produce suggest that their silks reflect the diverse and increasing number of ways in which spiders use them. Because the muscular and innervated spinnerets and spigots of spiders allow them to control fiber functional properties, silk proteins represent an avenue through which animal behavior may directly affect the molecular properties of a protein.
CORE-ANNULAR FLOWS
Authors: Joseph D. D. , Bai R. , Chen K. P. , Renardy Y. Y.
Published: July 2002

▪ Abstract  This paper gives an overview of the issues posed by the science and technology of transporting heavy oils in a sheath of lubricating water. It touches on measures of energy efficiency, industrial experience, fouling, stability, models of levitation, and future directions.
GENETIC ANALYSIS OF BACTERIOPHAGE-ENCODED COCHAPERONINS
Authors: Ang Debbie , Keppel France , Klein Gracjana , Richardson Alexandra , Georgopoulos Costa
Published: July 2002

▪ Abstract  Early genetic studies identified the Escherichia coli groES and groEL genes because mutations in them blocked the growth of bacteriophages λ and T4. Subsequent genetic and biochemical analyses have shown that GroES and GroEL constitute a chaperonin machine, absolutely essential for E. coli growth, because it is needed for the correct folding of many of its proteins. In spite of very little sequence identity to GroES, the bacteriophage T4-encoded Gp31 protein and the bacteriophage RB49-encoded CocO protein are bona fide GroEL cochaperonins, even capable of substituting for GroES in E. coli growth. A major functional distinction is that only Gp31 and CocO can assist GroEL in the correct folding of Gp23, the major bacteriophage capsid protein. Conserved structural features between CocO and Gp31, which are absent from GroES, highlight their potential importance in specific cochaperonin function.
THE ROLE OF THE IKAROS GENE IN LYMPHOCYTE DEVELOPMENT AND HOMEOSTASIS
Authors: Georgopoulos Katia , Winandy Susan , Avitahl Nicole
Published: July 2002

▪ Abstract  The Ikaros gene, which encodes a family of hemopoietic-specific zinc finger proteins, is described as a central regulator of lymphocyte differentiation. During fetal development, it is required at the earliest stage of T cell and B cell specification. In the adult, however, lymphoid lineages rely on Ikaros at distinct phases of their development. Its activity is essential for the generation of B cell but not of T cell precursors, although the differentiation of the latter is not normal. A significant increase in CD4 thymocytes and their immediate precursors is detected, and because these cells lack markers that correlate with positive selection, a deregulation in their maturation process is suggested. Furthermore, Ikaros-null thymocytes hyperproliferate in response to T cell receptor (TCR) signaling; within days after their appearance in the thymus, clonally expanding populations are detected. Deregulated TCR-mediated responses and the fast kinetics of tumor development in these mutant thymocytes implicate Ikaros as a central tumor suppressor gene for the T cell lineage. In addition, lack of natural killer cells and selective defects in γδ T cells and dendritic antigen-presenting cells point to Ikaros as an essential factor for the establishment of early branchpoints of the T cell pathway. The dominant interference activity of Ikaros isoforms unable to bind DNA and their effects in lymphocyte development suggest that Ikaros works in concert with other factors. The role of Aiolos, a lymphoid-restricted and structurally related gene, in lymphoid differentiation is discussed. A model is proposed that defines Ikaros as the backbone of a complex regulatory protein network that controls cell fate decisions and regulates homeostasis in the hemo-lymphoid system. Changes in this regulatory network may reflect differentiation and proliferation adjustments made in hemo-lymphoid progenitors and precursors as they give rise to the cells of our immune system.
TRANSIENT DIFFUSION OF BERYLLIUM AND SILICON IN GALLIUM ARSENIDE
Authors: Haddara Yaser M. , Bravman John C.
Published: July 2002

▪ Abstract  Transient diffusion is an increasingly important phenomenon as thermal budgets for real processes decrease and diffusion during sample growth becomes more important. To fully characterize dopant diffusion in gallium arsenide, an understanding must be developed of the dominant atomistic processes for a given dopant, as well as the sources of transient effects under a given set of experimental conditions. Theoretical, experimental, and simulation results were obtained to understand transient diffusivities of beryllium and silicon in grown-in and implanted samples. In implanted samples, by understanding implant damage and modeling the evolution of point defect populations, the observed transient effects can be explained. Such phenomena cannot account for the time-dependent diffusivity observed when the dopant is introduced during molecular beam epitaxial growth. Transient diffusivities for grown-in beryllium were investigated and explained by modeling the evolution of point defect populations as they increase beyond their equilibrium levels at the growth temperature to achieve equilibrium at the anneal temperature.
TREATMENT OF OSTEOPOROSIS
Authors: Prestwood, M.D Karen M. , Pilbeam, M.D Carol C. , Raisz, M.D Lawrence G.
Published: July 2002

▪ Abstract  Osteoporosis is a common disorder affecting the health of many adults. Strategies for fracture prevention include optimization of peak bone mass and prevention of bone loss at menopause and with aging. Genetic, nutritional, and life-style factors influence peak bone mass and may be used to focus preventive efforts. Once peak bone mass is reached, increased bone resorption may be the major pathogenetic factor. Calcium plus vitamin D, estrogen replacement therapy, calcitonin, and etidronate are agents currently available for treatment of osteoporosis; they act by inhibiting bone resorption. The failure of bone formation to keep pace with bone resorption also contributes to bone loss. Fluoride and intermittent parathyroid hormone therapy increase bone formation; however, more data are needed to determine efficacy. Insulin-like growth factors, transforming growth factor-β (TGF-β), and bone morphogenetic proteins may stimulate bone formation, but they have not yet been tested clinically. New approaches to treatment of osteoporosis will emerge as our understanding of the pathogenesis increases.
Oxygen Respiration by Desulfovibrio Species
Authors: Cypionka Heribert
Published: July 2002

▪ Abstract  Throughout the first 90 years after their discovery, sulfate-reducing bacteria were thought to be strict anaerobes. During the last 15 years, however, it has turned out that they have manifold properties that enable them to cope with oxygen. Sulfate-reducing bacteria not only survive oxygen exposure for at least days, but many of them even reduce oxygen to water. This process can be a true respiration process when it is coupled to energy conservation. Various oxygen-reducing systems are present in Desulfovibrio species. In Desulfovibrio vulgaris and Desulfovibrio desulfuricans, oxygen reduction was coupled to proton translocation and ATP conservation. In these species, the periplasmic fraction, which contains hydrogenase and cytochrome c3, was found to catalyze oxygen reduction with high rates. In Desulfovibrio gigas, a cytoplasmic rubredoxin oxidase was identified as an oxygen-reducing terminal oxidase. Generally, the same substrates as with sulfate are oxidized with oxygen. As additional electron donors, reduced sulfur compounds can be oxidized to sulfate. Sulfate-reducing bacteria are thus able to catalyze all reactions of a complete sulfur cycle. Despite a high respiration rate and energy coupling, aerobic growth of pure cultures is poor or absent. Instead, the respiration capacity appears to have a protective function. High numbers of sulfate-reducing bacteria are present in the oxic zones and near the oxic-anoxic boundaries of sediments and in stratified water bodies, microbial mats and termite guts. Community structure analyses and microbiological studies have shown that the populations in those zones are especially adapted to oxygen. How dissimilatory sulfate reduction can occur in the presence of oxygen is still enigmatic, because in pure culture oxygen blocks sulfate reduction. Behavioral responses to oxygen include aggregation, migration to anoxic zones, and aerotaxis. The latter leads to band formation in oxygen-containing zones at concentrations of ≤20% air saturation.
Prion Diseases of Humans and Animals: Their Causes and Molecular Basis
Authors: Collinge John
Published: July 2002

▪ Abstract  Prion diseases are transmissible neurodegenerative conditions that include Creutzfeldt-Jakob disease (CJD) in humans and bovine spongiform encephalopathy (BSE) and scrapie in animals. Prions appear to be composed principally or entirely of abnormal isoforms of a host-encoded glycoprotein, prion protein. Prion propagation involves recruitment of host cellular prion protein, composed primarily of α-helical structure, into a disease specific isoform rich in β-sheet structure. The existence of multiple prion strains has been difficult to explain in terms of a protein-only infections agent, but recent studies suggest that strain specific phenotypes can be encoded by different prion protein conformations and glycosylation patterns. The ability of a protein to encode phenotypic information has important biological implications. The appearance of a novel human prion disease, variant CJD, and the clear experimental evidence that it is caused by exposure to BSE has highlighted the need to understand the molecular basis of prion propagation, pathogenesis, and the barriers limiting intermammalian transmission. It is unclear if a large epidemic of variant CJD will occur in the years ahead.
PPARγANDGLUCOSEHOMEOSTASIS
Authors: Picard Frédéric , Auwerx Johan
Published: July 2002

▪ Abstract  Peroxisome proliferator-activated receptor gamma (PPARγ) is a nuclear receptor involved in the control of metabolism. Research on PPARγ is oriented towards understanding its role in insulin sensitization, which was inspired by the discovery that antidiabetic agents, the thiazolidinediones, were agonists for PPARγ. PPARγ stimulation improves glucose tolerance and insulin sensitivity in type 2 diabetic patients and in animal models of insulin resistance through mechanisms that are incompletely understood. Upon activation, PPARγ heterodimerizes with retinoid X receptor, recruits specific cofactors, and binds to responsive DNA elements, thereby stimulating the transcription of target genes. Because PPARγ is highly enriched in adipose tissue and because of its major role in adipocyte differentiation, it is thought that the effects of PPARγ in adipose tissue are crucial to explain its role in insulin sensitization, but recent studies have highlighted the contribution of other tissues as well. Although relatively potent for their insulin-sensitizing action, currently marketed PPARγ activators have some important undesirable side effects. These concerns led to the discovery of new ligands with potent antidiabetic properties but devoid of certain of these side effects. Data from human genetic studies and from PPARγ heterozygous knockout mice indicate that a reduction in PPARγ activity could paradoxically improve insulin sensitivity. These findings suggest that modulation of PPARγ activity by partial agonists or compounds that affect cofactor recruitment might hold promise for the treatment of insulin resistance.
Interactions Between Monoamines, Glutamate, and GABA in Schizophrenia: New Evidence
Authors: Carlsson Arvid , Waters Nicholas , Holm-Waters Susanna , Tedroff Joakim , Nilsson Marie , Carlsson Maria L.
Published: July 2002

In spite of its proven heuristic value, the dopamine hypothesis of schizophrenia is now yielding to a multifactorial view, in which the other monoamines as well as glutamate and GABA are included, with a focus on neurotransmitter interactions in complex neurocircuits. The primary lesion(s) in schizophrenia does not necessarily involve any of these neurotransmitters directly but could deal with a more general defect, such as a faulty connectivity of developmental origin. Nevertheless, a precise identification of neurotransmitter aberrations in schizophrenia will probably provide clues for a better understanding of the disease and for the development of new treatment and prevention strategies.
Cellular Responses to DNA Damage
Authors: Norbury Chris J , Hickson Ian D
Published: July 2002

Cells are constantly under threat from the cytotoxic and mutagenic effects of DNA damaging agents. These agents can either be exogenous or formed within cells. Environmental DNA-damaging agents include UV light and ionizing radiation, as well as a variety of chemicals encountered in foodstuffs, or as air- and water-borne agents. Endogenous damaging agents include methylating species and the reactive oxygen species that arise during respiration. Although diverse responses are elicited in cells following DNA damage, this review focuses on three aspects: DNA repair mechanisms, cell cycle checkpoints, and apoptosis. Because the areas of nucleotide excision repair and mismatch repair have been covered extensively in recent reviews ( 1 , 2 , 3 , 4 , 5 , 6 ), we restrict our coverage of the DNA repair field to base excision repair and DNA double-strand break repair.
Endothelin System: The Double-Edged Sword in Health and Disease
Authors: Kedzierski Rafal M , Yanagisawa Masashi
Published: July 2002

The endothelin system consists of two G-protein-coupled receptors, three peptide ligands, and two activating peptidases. Its pharmacological complexity is reflected by the diverse expression pattern of endothelin system components, which have a variety of physiological and pathophysiological roles. In the vessels, the endothelin system has a basal vasoconstricting role and participates in the development of diseases such as hypertension, atherosclerosis, and vasospasm after subarachnoid hemorrhage. In the heart, the endothelin system affects inotropy and chronotropy, and it mediates cardiac hypertrophy and remodeling in congestive heart failure. In the lungs, the endothelin system regulates the tone of airways and blood vessels, and it is involved in the development of pulmonary hypertension. In the kidney, it controls water and sodium excretion and acid-base balance, and it participates in acute and chronic renal failure. In the brain, the endothelin system modulates cardiorespiratory centers and the release of hormones. More advanced functional analysis of the endothelin system awaits not only additional pharmacological studies using highly specific endothelin antagonists but also the generation of genetically altered rodent models with conditional loss-of-function and gain-of-function manipulations.
STARK SPECTROSCOPY: Applications in Chemistry, Biology, and Materials Science
Authors: Bublitz Gerold U. , Boxer Steven G.
Published: July 2002

▪ Abstract  Stark spectroscopy has been applied to a wide range of molecular systems and materials. A generally useful method for obtaining electronic and vibrational Stark spectra that does not require sophisticated equipment is described. By working with frozen glasses it is possible to study nearly any molecular system, including ions and proteins. Quantitative analysis of the spectra provides information on the change in dipole moment and polarizability associated with a transition. The change in dipole moment reflects the degree of charge separation for a transition, a quantity of interest to a variety of fields. The polarizability change describes the sensitivity of a transition to an electrostatic field such as that found in a protein or an ordered synthetic material. Applications to donor-acceptor polyenes, transition metal complexes (metal-to-ligand and metal-to-metal mixed valence transitions), and nonphotosynthetic biological systems are reviewed.
TIME-RESOLVED PHOTOELECTRON SPECTROSCOPY OF MOLECULES AND CLUSTERS
Authors: Neumark Daniel M
Published: July 2002

▪ Abstract  Time-resolved photoelectron spectroscopy (TRPES) has become a powerful new tool in studying the dynamics of molecules and clusters. It has been applied to processes ranging from energy flow in electronically excited states of molecules to electron solvation dynamics in clusters. This review covers experimental and theoretical aspects of TRPES, focusing on studies of neutral and negatively charged species.
Citrus Blight and Other Diseases of Recalcitrant Etiology
Authors: Derrick K. S. , Timmer L. W.
Published: July 2002

Several economically important diseases of unknown or recently determined cause are reviewed. Citrus blight (CB), first described over 100 years ago, was shown in 1984 to be transmitted by root-graft inoculations; the cause remains unknown and is controversial. Based on graft transmission, it is considered to be an infectious agent by some; others suggest that the cause of CB is abiotic. Citrus variegated chlorosis, although probably long present in Argentina, where it was considered to be a variant of CB, was identified as a specific disease and shown to be caused by a strain of Xylella fastidiosa after if reached epidemic levels in Brazil in 1987. Citrus psorosis, described in 1933 as the first virus disease of citrus, is perhaps one of the last to be characterized. In 1988, it was shown to be caused by a very unusual virus. The cause of lettuce big vein appears to be a viruslike agent that is transmitted by a soilborne fungus. Double-stranded RNAs were associated with the disease, suggesting it may be caused by an unidentified RNA virus. Rio Grande gummosis, dry rot root, peach tree short life, and some replant diseases may be diseases of complex etiology. Various microorganisms have been isolated from trees with these diseases, but the diseases may be attributable in part to environmental factors. Determination of the cause of these diseases of complex etiology has proven difficult, in part, because they affect only mature trees.
HOWCONCEPTUALPROBLEMSMIGRATE: Rational Choice, Interpretation, and the Hazards of Pluralism
Authors: Johnson James
Published: July 2002

▪ Abstract  When they assess competing theories, political scientists typically rely almost exclusively and rather naively on criteria of empirical performance. They have correspondingly little to say about conceptual problems and seem generally unaware of the extent to which their assessments of empirical performance are parasitic on conceptual commitments. This blind spot, in turn, hinders their ability both to persuasively conduct and critically assess substantive research. I call attention to the importance and complexity of conceptual problems for ongoing social and political research. As a vehicle for this argument, I examine and criticize recent attempts to integrate interpretive and rational choice theories in hopes of improving our understanding of how culture and politics intersect. I argue that these efforts are plagued by important, mostly unrecognized conceptual problems that, in turn, subvert their explicitly stated explanatory objectives. I also show, in light of this same example, how conceptual problems unintentionally can frustrate laudable pluralist aspirations. This essay illustrates why, if we take conceptual problems seriously, calls for methodological and theoretical pluralism are significantly more demanding than they often appear.
Attention and Performance
Authors: Pashler Harold , Johnston James C. , Ruthruff Eric
Published: July 2002

▪ Abstract  Recent progress in the study of attention and performance is discussed, focusing on the nature of attentional control and the effects of practice. Generally speaking, the effects of mental set are proving more pervasive than was previously suspected, whereas automaticity is proving less robust. Stimulus attributes (e.g. onsets, transients) thought to have a “wired-in” ability to capture attention automatically have been shown to capture attention only as a consequence of voluntarily adopted task sets. Recent research suggests that practice does not have as dramatic effects as is commonly believed. While it may turn out that some mental operations are automatized in the strongest sense, this may be uncommon. Recent work on task switching is also described; optimal engagement in a task set is proving to be intimately tied to learning operations triggered by the actual performance of a new task, not merely the anticipation of such performance.
Rationality
Authors: Shafir Eldar , LeBoeuf Robyn A.
Published: July 2002

▪ Abstract  This chapter reviews selected findings in research on reasoning, judgment, and choice and considers the systematic ways in which people violate basic requirements of the corresponding normative analyses. Recent objections to the empirical findings are then considered; these objections question the findings' relevance to assumptions about rationality. These objections address the adequacy of the tasks used in the aforementioned research and the appropriateness of the critical interpretation of participants' responses, as well as the justifiability of some of the theoretical assumptions made by experimenters. The objections are each found not to seriously impinge on the general conclusion that people often violate tenets of rationality in inadvisable ways. In the process, relevant psychological constructs, ranging from cognitive ability and need for cognition, to dual process theories and the role of incentives, are discussed. It is proposed that the rationality critique is compelling and rightfully gaining influence in the social sciences in general.