bluuebunny/crossref_metadata_2025 huggingface dataset:
Automatic parameterization of rational curves and surfaces IV: algebraic space curves
Authors: Abhyankar S. S. , Bajaj C. J.
Published: July 2002

For an irreducible algebraic space curve
C
that is implicitly defined as the intersection of two algebraic surfaces,
f
(
x
,
y
,
z
) = 0 and
g
(
x
,
y
,
z
) = 0, there always exists a birational correspondence between the points of
C
and the points of an irreducible plane curve
P
, whose genus is the same as that of
C
. Thus
C
is rational if the genus of
P
is zero. Given an irreducible space curve
C
= (
f
∩
g
), with
f
and
g
not tangent along
C
, we present a method of obtaining a projected irreducible plane curve
P
together with birational maps between the points of
P
and
C
. Together with [4], this method yields an algorithm to compute the genus of
C
, and if the genus is zero, the rational parametric equations for
C
. As a biproduct, this method also yields the implicit and parametric equations of a rational surface
S
containing the space curve
C
.

The birational mappings of implicitly defined space curves find numerous applications in geometric modeling and computer graphics since they provide an efficient way of manipulating curves in space by processing curves in the plane. Additionally, having rational surfaces containing
C
yields a simple way of generating related families of rational space curves.
Scaling up: a research agenda for software engineering
Authors: Computer Science and Technology Board CORPORATE
Published: July 2002

The following excerpts have been gleaned from a report by the Computer Science and Technology Board that summarizes the deliberations of a group of software engineers participating in a CSTB workshop that focused on setting research priorities.
Indefinite and maybe information in relational databases
Authors: Liu Ken-Chih , Sunderraman Rajshekhar
Published: July 2002

This paper extends the relational model to represent indefinite and maybe kinds of incomplete information. A data structure, called an I-table, which is capable of representing indefinite and maybe facts, is introduced. The information content of I-tables is precisely defined, and an operator to remove redundant facts is presented. The relational algebra is then extended in a semantically correct way to operate on I-tables. Queries are posed in the same way as in conventional relational algebra; however, the user may now expect indefinite as well as maybe answers.
EMERGING AND RE-EMERGING INFECTIOUS DISEASES: The Third Epidemiologic Transition
Authors: Barrett Ronald , Kuzawa Christopher W. , McDade Thomas , Armelagos George J.
Published: July 2002

▪ Abstract  We use an expanded framework of multiple epidemiologic transitions to review the issues of re/emerging infection. The first epidemiologic transition was associated with a rise in infectious diseases that accompanied the Neolithic Revolution. The second epidemiologic transition involved the shift from infectious to chronic disease mortality associated with industrialization. The recent resurgence of infectious disease mortality marks a third epidemiologic transition characterized by newly emerging, re- emerging, and antibiotic resistant pathogens in the context of an accelerated globalization of human disease ecologies. These transitions illustrate recurring sociohistorical and ecological themes in human–disease relationships from the Paleolithic Age to the present day.
SELENIUM INHIGHERPLANTS
Authors: Terry N. , Zayed A. M. , de Souza M. P. , Tarun A. S.
Published: July 2002

▪ Abstract  Plants vary considerably in their physiological response to selenium (Se). Some plant species growing on seleniferous soils are Se tolerant and accumulate very high concentrations of Se (Se accumulators), but most plants are Se nonaccumulators and are Se-sensitive. This review summarizes knowledge of the physiology and biochemistry of both types of plants, particularly with regard to Se uptake and transport, biochemical pathways of assimilation, volatilization and incorporation into proteins, and mechanisms of toxicity and tolerance. Molecular approaches are providing new insights into the role of sulfate transporters and sulfur assimilation enzymes in selenate uptake and metabolism, as well as the question of Se essentiality in plants. Recent advances in our understanding of the plant's ability to metabolize Se into volatile Se forms (phytovolatilization) are discussed, along with the application of phytoremediation for the cleanup of Se contaminated environments.
Integration of Signaling Networks that Regulate Dictyostelium Differentiation
Authors: Aubry Laurence , Firtel Richard
Published: July 2002

▪ Abstract  In Dictyostelium amoebae, cell-type differentiation, spatial patterning, and morphogenesis are controlled by a combination of cell-autonomous mechanisms and intercellular signaling. A chemotactic aggregation of ∼105 cells leads to the formation of a multicellular organism. Cell-type differentiation and cell sorting result in a small number of defined cell types organized along an anteroposterior axis. Finally, a mature fruiting body is created by the terminal differentiation of stalk and spore cells. Analysis of the regulatory program demonstrates a role for several molecules, including GSK-3, signal transducers and activators of transcription (STAT) factors, and cAMP-dependent protein kinase (PKA), that control spatial patterning in metazoans. Unexpectedly, two component systems containing histidine kinases and response regulators also play essential roles in controlling Dictyostelium development. This review focuses on the role of cAMP, which functions intracellularly to mediate the activity of PKA, an essential component in aggregation, cell-type specification, and terminal differentiation. Cytoplasmic cAMP levels are controlled through both the regulated activation of adenylyl cyclases and the degradation by a phosphodiesterase containing a two-component system response regulator. Extracellular cAMP regulates G-protein–dependent and –independent pathways to control aggregation as well as the activity of GSK-3 and the transcription factors GBF and STATa during multicellular development. The integration of these pathways with others regulated by the morphogen DIF-1 to control cell fate decisions are discussed.
Recent Advances in Chemical Approaches to the Study of Biological Systems
Authors: Shogren-Knaak Michael A. , Alaimo Peter J. , Shokat Kevan M.
Published: July 2002

▪ Abstract  A number of novel chemical methods for studying biological systems have recently been developed that provide a means of addressing biological questions not easily studied with other techniques. In this review, examples that highlight the development and use of such chemical approaches are discussed. Specifically, strategies for modulating protein activity or protein-protein interactions using small molecules are presented. In addition, methods for generating and utilizing novel biomolecules (proteins, oligonucleotides, oligosaccharides, and second messengers) are examined.
EVOLUTION OF HELPING BEHAVIOR IN COOPERATIVELY BREEDING BIRDS
Authors: Cockburn Andrew
Published: July 2002

▪ Abstract  It has recently been argued that the paradox of helping behavior in birds has been solved ( 73 ). This optimism may be premature. I argue that there is no obvious dichotomy between cooperative societies based on natal philopatry and the formation of extended families, and those formed via recruitment of unrelated individuals into coalitions. Tests of the effect of helping behavior suggest that kinship may have been overemphasized for male helpers but underestimated for females. The first studies applying molecular techniques to resolve genealogy in these societies suggest that reproductive sharing occurs commonly across all types of social organization. Incest avoidance may be an important constraint on sharing in families, but molecular techniques have thus far been inappropriate to assess its importance. The interests of males and female helpers may be quite different because females often have less opportunity to inherit a territory vacancy on the death of the breeder, less opportunity to court mates by helping them, and less opportunity to share reproduction without perturbing the size of the brood. We still have only a weak understanding of sex biases in helping behavior.
MATE CHOICE IN TREE CRICKETS AND THEIR KIN
Authors: Brown W. D.
Published: July 2002

▪ Abstract  Mate choice theory has become a major field of research in behavioral ecology. Tree crickets provide excellent opportunities for studying the diversity and variability of mate choice. The evidence for female mate choice in tree crickets is reviewed, and broad comparisons with other orthopteran groups are made. The evidence shows that female choice may occur during several different stages of mating and may target several different criteria. Song preferences are perhaps dominated by stabilizing preferences for the cues of species recognition, but there is a growing body of evidence for directional preferences based on sensory biases or mate quality. Mate rejection during courtship and forms of postcopulatory choice may favor males, based both on phenotypic quality and on the amount of nutritious courtship gifts they provide, and may differ with the value of mating incentives. Understanding the balance and trade-offs between different forms of mate choice may help in understanding their evolutionary causes.
Ovarian Dynamics and Host Use
Authors: Papaj Daniel R.
Published: July 2002

▪ Abstract  Oviposition behavior in herbivorous and frugivorous insects and parasitoids is dynamic at the level of the individual, responding to variation in host quality and availability. Patterns of variation in egg load in response to host presence and quality suggest that ovarian development also responds to variation in the host environment. Ovarian dynamics are mediated by feedback from oviposition, by host feeding, and by sensory input from the host. The last of these mechanisms, host sensory cuing, is known to occur in three major orders and provides strong evidence that ovarian dynamics are adaptive by design. Conditions favoring host effects on ovarian development include trade-offs between egg production and either survival or dispersal, uncertainty in the host environment, and a correlation in host conditions between the time that oogenesis is initiated and the time that eggs are laid. Some host defenses block ovarian development, suggesting that ovarian dynamics in hostspecific insects should be viewed from a coevolutionary perspective.
Genetic Transformation Systems in Insects
Authors: Atkinson Peter W. , Pinkerton Alexandra C. , O'Brochta David A.
Published: July 2002

▪ Abstract  The past 5 years have witnessed the emergence of techniques that permit the stable genetic transformation of a number of non-drosophilid insect species. These transposable-element-based strategies, together with virus-based techniques that allow the expression of genes to be quickly examined in insects, provide insect scientists with a first generation of genetic tools that can begin to be harnessed to further increase our understanding of gene function and regulation in insects. We review and compare the characteristics of these gene transfer systems and conclude that, although significant progress has been made, these systems still do not meet the requirements of robust genetic tools. We also review risk assessment issues arising from the generation and probable release of genetically engineered insects.
GENE TARGETING AND THE BIOLOGY OF LEARNING AND MEMORY
Authors: Silva Alcino J. , Smith Alan M. , Giese Karl Peter
Published: July 2002

▪ Abstract  The general goal of genetic studies of learning and memory is to develop and test theories that explain the animal's behavior in neuroanatomical, neurophysiological, cellular, and molecular terms. In this review we describe the role that gene targeting and other transgenic techniques have had in the study of mammalian learning and memory. We focus especially on the hippocampus, a brain structure that is thought to be central to the processing and temporary storage of complex information. We also discuss the main issues that confront this young field, as well as our vision for its future.
Shufflons: Multiple Inversion Systems and Integrons
Authors: Komano Teruya
Published: July 2002

▪ Abstract  Conservative site-specific recombination functions to create biological diversity in prokaryotes. Simple site-specific recombination systems consist of two recombination sites and a recombinase gene. The plasmid R64 shufflon contains seven recombination sites, which flank and separate four DNA segments. Site-specific recombinations mediated by the product of the rci gene between any two inverted recombination sites result in the inversion of four DNA segments independently or in groups. The shufflon functions as a biological switch to select one of seven C-terminal segments of the PilV proteins, which is a minor component of R64 thin pilus. The shufflon determines the recipient specificity in liquid matings of plasmid R64. Other multiple inversion systems as well as integrons, which are multiple insertion systems, are also described in this review.
DEVELOPMENT AND MATURATION OF SECONDARY LYMPHOID TISSUES
Authors: Fu Yang-Xin , Chaplin David D.
Published: July 2002

▪ Abstract  The secondary lymphoid tissues are located at strategic sites where foreign antigens can be efficiently brought together with immune system regulatory and effector cells. The organized structure of the secondary lymphoid tissues is thought to enhance the sensitivity of antigen recognition and to support proper regulation of the activation and maturation of the antigen-responsive lymphoid cells. Although a substantial amount is known about the cellular elements that compose the lymphoid and nonlymphoid components of the secondary lymphoid tissues, information concerning the signals that control the development of the tissues and that maintain the organized tissue microenvironment remain undefined. Studies over the past few years have identified lymphotoxin as a critical signaling molecule not only for the organogenesis of secondary lymphoid tissues but for the maintenance of aspects of their microarchitecture as well. Additional signaling molecules that contribute to the formation of normal lymphoid tissue structure are being identified at an accelerating pace. Analyses of mouse strains with congenital defects in different aspects of secondary lymphoid tissue development are beginning to clarify the role of these tissues in immune responses and host defense. This review focuses on studies defining recently identified crucial signals for the biogenesis of secondary lymphoid organs and for the maintenance of their proper microarchitecture. It also discusses new insights into how the structure of these tissues supports effective immune responses.
THE NEW GENERATION HIGH-TEMPERATURE SUPERCONDUCTORS
Authors: Fisk Z. , Sarrao J. L.
Published: July 2002

▪ Abstract  The layered perovskite cuprate materials are a unique class of superconductors with unusual normal-state and superconducting properties. The common physics to all these materials is that of the underlying CuO2 planes. This review provides a survey of and guide to their physical properties as it relates to the superconductivity of this interesting group of conducting oxides.
DIAGNOSIS AND MANAGEMENT OF NONFUNCTIONING PITUITARY TUMORS
Authors: Greenman, M.D Yona , Melmed, M.D Shlomo
Published: July 2002

▪ Abstract  It is now recognized that most clinically nonfunctioning pituitary tumors express gonadotropin hormones or their subunits in vitro, and sometimes in vivo. Many of these tumors are diagnosed by sensitive imaging techniques while patients are still asymptomatic. We outline an overview of the diagnosis and clinical management of these tumors.
Gene Therapy for Adenosine Deaminase Deficiency
Authors: Parkman Robertson , Weinberg Kenneth , Crooks Gay , Nolta Jan , Kapoor Neena , Kohn Donald
Published: July 2002

The clinical gene therapy trials for adenosine deaminase (ADA) deficiency have defined both the potential benefits and the present limitations of gene therapy with hematopoietic stem cells (HSC). Current clinical results indicate that (a) both umbilical cord blood and neonatal bone marrow HSC can be transduced with murine retroviral-based vectors, (b) the transduced HSC can engraft in nonmyeloablated patients, (c) the frequency of HSC transduction/engraftment is low (1/10,000), (d) an in vivo selective advantage can exist for transduced T lymphoid progeny, and (e) the transduced ADA gene is not expressed in nondividing T lymphocytes. Improving the clinical results of gene therapy for ADA deficiency and other genetic diseases involving HSC will require (a) developing new vectors that express the transduced gene in nondividing cells and (b) increasing the frequency of stable HSC transduction.
Nephron-Sparing Surgery for Renal Cell Carcinoma
Authors: Novick Andrew C.
Published: July 2002

▪ Abstract  Nephron-sparing surgery (NSS) provides effective curative therapy for patients with localized renal cell carcinoma. In patients with imperative indications, it represents an alternative to renal replacement therapy. For selected patients with systemic comorbidities that threaten global renal function, NSS preserves unaffected nephrons with excellent cancer-specific survival. Elective partial nephrectomy for patients with a small (≤4 cm), unifocal tumor and a normal contralateral kidney is associated with a low risk (0%–3%) of local recurrence and cancer-specific survival rates of 90%–100%. Comparisons between radical and partial nephrectomy demonstrate equivalent cancer control over five years. Minimally invasive techniques of NSS are feasible but await improved technologies and long-term outcome data before they become fully acceptable treatment options.
THE MOLECULES OF MECHANOSENSATION
Authors: García-Añoveros Jaime , Corey David P.
Published: July 2002

▪ Abstract  Mechanosensation, the transduction of mechanical forces into a cellular electrochemical signal, enables living organisms to detect touch; vibrations, such as sound; accelerations, including gravity; body movements; and changes in cellular volume and shape. Ion channels directly activated by mechanical tension are thought to mediate mechanosensation in many systems. Only one channel has been cloned that is unequivocably mechanically gated: the MscL channel in bacteria. Genetic screens for touch-insensitive nematodes or flies promise to identify the proteins that constitute a mechanosensory apparatus in eukaryotes. In Caenorhabditis elegans, the mec genes thus identified encode molecules for a candidate structure, which includes a “degenerin” channel tethered to specialized extracellular and intracellular structural proteins. In hair cells of the inner ear, evidence suggests that an extracellular tip link pulls on a channel, which attached intracellularly to actin via a tension-regulating myosin 1β. The channel and the tip link have not been cloned. Because degenerins and MscL homologs have not been found outside of nematodes and prokaryotes, respectively, and because intracellular and extracellular accessory structures apparently differ among organs and species, it may be that mechanosensory channel complexes evolved multiple times.
Synaptic Plasticity and Memory: An Evaluation of the Hypothesis
Authors: Martin S. J. , Grimwood P. D. , Morris R. G. M.
Published: July 2002

Changing the strength of connections between neurons is widely assumed to be the mechanism by which memory traces are encoded and stored in the central nervous system. In its most general form, the synaptic plasticity and memory hypothesis states that “activity-dependent synaptic plasticity is induced at appropriate synapses during memory formation and is both necessary and sufficient for the information storage underlying the type of memory mediated by the brain area in which that plasticity is observed.” We outline a set of criteria by which this hypothesis can be judged and describe a range of experimental strategies used to investigate it. We review both classical and newly discovered properties of synaptic plasticity and stress the importance of the neural architecture and synaptic learning rules of the network in which it is embedded. The greater part of the article focuses on types of memory mediated by the hippocampus, amygdala, and cortex. We conclude that a wealth of data supports the notion that synaptic plasticity is necessary for learning and memory, but that little data currently supports the notion of sufficiency.
Contributions of the Medullary Raphe and Ventromedial Reticular Region to Pain Modulation and Other Homeostatic Functions
Authors: Mason Peggy
Published: July 2002

▪ Abstract  The raphe magnus is part of an interrelated region of medullary raphe and ventromedial reticular nuclei that project to all areas of the spinal gray. Activation of raphe and reticular neurons evokes modulatory effects in sensory, autonomic, and motor spinal processes. Two physiological types of nonserotonergic cells are observed in the medullary raphe and are thought to modulate spinal pain processing in opposing directions. Recent evidence suggests that these cells may modulate stimulus-evoked arousal or alerting rather than pain-evoked withdrawals. Nonserotonergic cells are also likely to modulate spinal autonomic and motor circuits involved in thermoregulation and sexual function. Medullary serotonergic cells have state-dependent discharge and are likely to contribute to the modulation of pain processing, thermoregulation, and sexual function in the spinal cord. The medullary raphe and ventromedial reticular region may set sensory, autonomic, and motor spinal circuits into configurations that are appropriate to the current behavioral state.
THECONTINUOUSELECTRONBEAMACCELERATORFACILITY: CEBAF at the Jefferson Laboratory
Authors: Leemann Christoph W. , Douglas David R. , Krafft Geoffrey A.
Published: July 2002

▪ Abstract  The Jefferson Laboratory's superconducting radiofrequency (srf) Continuous Electron Beam Accelerator Facility (CEBAF) provides multi-GeV continuous-wave (cw) beams for experiments at the nuclear and particle physics interface. CEBAF comprises two antiparallel linacs linked by nine recirculation beam lines for up to five passes. By the early 1990s, accelerator installation was proceeding in parallel with commissioning. By the mid-1990s, CEBAF was providing simultaneous beams at different but correlated energies up to 4 GeV to three experimental halls. By 2000, with srf development having raised the average cavity gradient to 7.5 MV/m, energies up to nearly 6 GeV were routine, at 1–150 μA for two halls and 1–100 nA for the other. Also routine are beams of >75% polarization. Physics results have led to new questions about the quark structure of nuclei, and therefore to user demand for a planned 12 GeV upgrade. CEBAF's enabling srf technology is also being applied in other projects.
EXACT CHIRAL SYMMETRY ON THE LATTICE
Authors: Neuberger Herbert
Published: July 2002

▪ Abstract  Developments during the past eight years have refuted the folklore that chiral symmetries cannot be preserved on the lattice. The mechanism that permits chiral symmetry to coexist with the lattice is quite general and may work in nature as well. The reconciliation between chiral symmetry and the lattice is likely to revolutionize the field of numerical QCD.
APPLICATIONS OF MASS ISOTOPOMER ANALYSISTO NUTRITION RESEARCH
Authors: Brunengraber Henri , Kelleher Joanne K. , Des Rosiers Christine
Published: July 2002

▪ Abstract  Investigations into regulating metabolic pathways with stable isotopes have, over the past decade, undergone major development with the use of nuclear magnetic resonance and mass spectrometry in studying labeling patterns of newly synthesized biomolecules. In this review, we concentrate on investigations of mass isotopomer distribution (MID) measured by mass spectrometry. We review the applications of MID to analytical problems, in particular the possibility of amplifying the measurement of low isotopic enrichments by incorporating multiple molecules or atoms of a primary analyte into the molecule of a secondary analyte, the MID of which is assayed. We also review new information on the regulation of intermediary metabolism gathered from the analysis of MID patterns of synthesized compounds. Lastly, we review the applications of MID to the synthesis of polymeric molecules, with emphasis on the validity of these techniques. A number of these techniques are applicable to investigations of nutrient metabolism in health and disease.
TWO-PHOTON–INDUCED FLUORESCENCE
Authors: Callis Patrik R.
Published: July 2002

▪ Abstract  Nonresonant two-photon electronic spectroscopy of polyatomic molecules is reviewed for the period since 1979. Emphasis is placed on studies that expose patterns in the two-photon fluorescence (also ionization, optoacoustic) excitation spectra of aromatic hydrocarbons and the effect of vibrations and substitution, particularly within the framework of pseudoparity rules. A section is devoted to biological molecules and the emerging use of two-photon–induced fluorescence anisotropy. Relevant theoretical results are discussed, with emphasis on quantum chemical predictions of vibronic coupling and substituent effects on two-photon absorptivity and tensor properties of individual molecules. This chapter includes higher-order spectroscopy, and a limited number of three- and four-photon studies are discussed.
Fifty Years in Physical Chemistry: Homage to Mentors, Methods, and Molecules
Authors: Herschbach Dudley
Published: July 2002

A nostalgic account is given of my scientific odyssey, recalling early encounters, some fateful, some just fun, with mentors, methods, and molecules. These include stories of my student years at Stanford, pursuing chemical kinetics with Harold Johnston; graduate study at Harvard, doing molecular spectroscopy with Bright Wilson; and fledgling faculty years at Berkeley, launching molecular beam studies of reaction dynamics. A few vignettes from my “ever after ” era on the Harvard faculty emphasize thematic motivations or methods inviting further exploration. An Appendix provides a concise listing of colleagues in research and the topics we have pursued.
Structures and Dynamics of Molecules on Liquid Beam Surfaces
Authors: Kondow Tamotsu , Mafuné Fumitaka
Published: July 2002

In this review, we describe experimental studies on structures and dynamics of molecules on clean liquid surfaces in a vacuum. These studies use clean-surface preparations in combination with highly sensitive laser-, photoelectron-, and mass-spectroscopic techniques. In particular, we refer to our recent studies on solvation structures and reactions on various solution surfaces using liquid beam–multiphoton ionization–mass spectrometry. These include (a) aggregation of solute molecules on solution surfaces such as formation of solute pairs, clusters, and islands; and (b) chemical reactions induced by photoexcitation and -ionization, such as a nucleophilic reaction of phenyl ketones, polymerization of halo-anilines, and reduction of cations by solvated electrons.
CHOLECYSTOKININ CELLS
Authors: Liddle Rodger A.
Published: July 2002

▪ Abstract  Cholecystokinin (CCK) is an important hormonal regulator of the digestive process. CCK cells are concentrated in the proximal small intestine, and hormone is secreted into the blood upon the ingestion of food. The physiological actions of CCK include stimulation of pancreatic secretion and gallbladder contraction, regulation of gastric emptying, and induction of satiety. Therefore, in a highly coordinated manner, CCK regulates the ingestion, digestion, and absorption of nutrients. CCK is produced by two separate cell types: endocrine cells of the small intestine and various neurons in the gastrointestinal tract and central nervous system. Accordingly, CCK can function as either a hormone or a neuropeptide. This review focuses on the physiology of the CCK cell in the intestine and, in particular, on how the CCK cell is regulated to secrete its hormone product. The effects of ingested nutrients on the CCK cell and the intracellular messenger systems involved in controlling secretion are reviewed. A summary is provided of recent studies examining the electrophysiological properties of CCK cells and newly discovered proteins that act as releasing factors for CCK, which mediate feedback pathways critical for regulated secretion in the intact organism.
TIMING IN THE AUDITORY SYSTEM OF THE BAT
Authors: Covey Ellen , Casseday John H.
Published: July 2002

▪ Abstract  Echolocating bats use audition to guide much of their behavior. As in all vertebrates, their lower brainstem contains a number of parallel auditory pathways that provide excitatory or inhibitory outputs differing in their temporal discharge patterns and latencies. These pathways converge in the auditory midbrain, where many neurons are tuned to biologically important parameters of sound, including signal duration, frequency-modulated sweep direction, and the rate of periodic frequency or amplitude modulations. This tuning to biologically relevant temporal patterns of sound is created through the interplay of the time-delayed excitatory and inhibitory inputs to midbrain neurons. Because the tuning process requires integration over a relatively long time period, the rate at which midbrain auditory neurons respond corresponds to the cadence of sounds rather than their fine structure and may provide an output that is closely matched to the rate at which motor systems operate.
The Impact of the Food Quality Protection Act on the Future of Plant Disease Management
Authors: Ragsdale Nancy N.
Published: July 2002

The Food Quality Protection Act mandates new considerations in pesticide regulatory decisions. Endocrine disruption, determination of the need for an additional safety factor for infants and children, aggregate exposure to each pesticide, and cumulative exposure to pesticides with a common mechanism of toxicity will all become part of the risk assessment process. A reduction in availability of fungicides for many current uses appears to be a likely result of this act. If this occurs, disease management programs, particularly in fruits and vegetables, will be challenged to find alternative approaches. Currently, fungicides play an important role in many production systems. Loss of these valuable pest management tools will contribute to increased costs for producers and consumers, as well as to complex issues facing the structure of agriculture in the United States.
ATTITUDES AND ATTITUDE CHANGE
Authors: Petty Richard E. , Wegener Duane T. , Fabrigar Leandre R.
Published: July 2002

▪ Abstract  We review empirical and conceptual developments over the past four years (1992–1995) on attitudes and persuasion. A voluminous amount of material was produced concerning attitude structure, attitude change, and the consequences of holding attitudes. In the structure area, particular attention is paid to work on attitude accessiblity, ambivalence, and the affective versus cognitive bases of attitudes. In persuasion, our review examines research that has focused on high effort cognitive processes (central route), low effort processes (peripheral route), and the multiple roles by which variables can have an impact on attitudes. Special emphasis is given to work on cognitive dissonance and other biases in message processing, and on the multiple processes by which mood influences evaluations. Work on the consequences of attitudes focuses on the impact of attitudes on behavior and social judgments.
HALYs and QALYs and DALYs, Oh My: Similarities and Differences in Summary Measures of Population Health
Authors: Gold Marthe R. , Stevenson David , Fryback Dennis G.
Published: July 2002

▪ Abstract  Health-adjusted life years (HALYs) are population health measures permitting morbidity and mortality to be simultaneously described within a single number. They are useful for overall estimates of burden of disease, comparisons of the relative impact of specific illnesses and conditions on communities, and in economic analyses. Quality-adjusted life years (QALYs) and disability-adjusted life years (DALYs) are types of HALYs whose original purposes were at variance. Their growing importance and the varied uptake of the methodology by different U.S. and international entities makes it useful to understand their differences as well as their similarities. A brief history of both measures is presented and methods for calculating them are reviewed. Methodological and ethical issues that have been raised in association with HALYs more generally are presented. Finally, we raise concerns about the practice of using different types of HALYs within different decision-making contexts and urge action that builds and clarifies this useful measurement field.
Tuberculosis
Authors: Tiruviluamala Parvathi , Reichman Lee B.
Published: July 2002

▪ Abstract  Tuberculosis is an infectious disease caused by bacteria in the Mycobacterium tuberculosis complex. Of these, the most common species to infect humans is M. tuberculosis. The TB bacillus is an extremely successful human pathogen, infecting two billion persons worldwide; an estimated 2 to 3 million people die from tuberculosis each year. In the United States, TB rates decreased steadily at the rate of 5% per year from 1953 until 1985 when the trend reversed, with the number of TB cases peaking in 1992. Outbreaks of multidrug-resistant TB (MDR TB) were reported, and these cases were documented to be transmitted in nosocomial and congregate settings, including hospitals and prisons. AIDS patients infected with M. tb developed disease rapidly, and case-fatality rates of >80% were noted in those infected with multidrug-resistant M. tb. Intensive intervention, at enormous cost, caused the number of TB cases to decline. This article discusses factors that led to the increase in TB cases, their subsequent decline, and measures needed in the future if TB is to be eliminated in the United States.
Utilization Management: Issues, Effects, and Future Prospects
Authors: Wickizer Thomas M. , Lessler Daniel
Published: July 2002

▪ Abstract  Utilization management encompasses a diverse set of activities designed to influence the use of health care services and thereby constrain health care resource consumption. Utilization management, which has become one of the most widely used cost-containment approaches, has engendered debate and controversy. Physicians have been outspoken critics of utilization management because it has limited their clinical autonomy and has contributed to an intolerable administrative burden. Insurance carriers, managed care plans, and third-party payers have defended the use of utilization management as an imperfect—but necessary—practice that is needed to reduce consumption of unnecessary or inappropriate health care services. This review examines the operation and effects of three widely used utilization management procedures: prospective utilization review, case management, and physician gatekeeping programs. In addition, it explores the future role of utilization management in the health care system and outlines a set of principles that we believe should be used to guide the development of utilization management strategies in the future.
THE SOCIOLOGY OF ENTREPRENEURSHIP
Authors: Thornton Patricia H.
Published: July 2002

▪ Abstract  Recent research on entrepreneurship by sociologists has focused on subsectors of the discipline rather than on entrepreneurship as a class. This review draws insights from diverse literatures to develop a sociological perspective on entrepreneurship as a whole. Until recently, the supply-side perspective, which focuses on the individual traits of entrepreneurs, has been the dominant school of research. Newer work from the demand-side perspective has focused on rates, or the context in which entrepreneurship occurs. This review emphasizes this less developed demand-side perspective—in particular, the influence of firms and markets on how, where, and why new enterprises are founded. I take stock of the differences and separation in the two perspectives and argue that sociological frameworks, an embeddedness perspective, institutional and ecological theory, and multilevel models can be used to integrate the two schools and extend their research implications.
Mechanism of Syncope in Patients With Heart Disease and Negative Electrophysiologic Test
Authors: Menozzi Carlo , Brignole Michele , Garcia-Civera Roberto , Moya Angel , Botto Gianluca , Tercedor Luis , Migliorini Roberta , Navarro Xavier
Published: July 2002

Background

—

In patients with syncope and structural heart disease, syncope is suspected to be attributable to a primary cardiac arrhythmia, but little is known of its mechanism when electrophysiologic study is unremarkable.

Methods and Results

—

We applied an implantable loop recorder in 35 patients with overt heart disease at risk of ventricular arrhythmia, because these were patients with previous myocardial infarction or cardiomyopathy with depressed ejection fraction or nonsustained ventricular tachycardia in whom an electrophysiologic study was unremarkable. During a follow-up of 3 to 15 months, syncope recurred in 6 patients (17%) after a mean of 6±5 months; in 3 patients, the mechanism of syncope was bradycardia with long pauses (sudden-onset AV block in 2 cases and sinus arrest in 1 case); in 1 patient, there was stable sinus tachycardia; and in 2 patients, who had chronic atrial fibrillation, there was an increase in ventricular rate. A total of 23 episodes of presyncope were documented in 8 patients (23%): no rhythm variation or mild tachycardia in 12 cases, paroxysmal atrial fibrillation or atrial tachycardia in 10 cases, and sustained ventricular tachycardia in 1 case. No patient died during the study period nor suffered from injury attributable to syncopal relapse.

Conclusions

—

The patients with unexplained syncope, structural heart disease, and negative electrophysiologic study had a favorable medium-term outcome with no case of death and a low recurrence rate of syncope without related injury. The mechanism of syncope was heterogeneous, and ventricular tachyarrhythmia was unlikely.
Cerebrovascular Disease and Evolution of Depressive Symptoms in the Cardiovascular Health Study
Authors: Steffens David C. , Krishnan K. Ranga Rama , Crump Casey , Burke Gregory L.
Published: July 2002

Background and Purpose

—

Previous studies have reported an association between cerebrovascular disease and depressive symptoms. The Cardiovascular Health Study (CHS) provides an opportunity to examine the relationship between vascular brain pathology seen on neuroimaging and changes in depressive symptoms.

Methods

—

The sample included 3236 CHS participants who had an MRI brain scan. Demographic variables, medical history, functional status, and apolipoprotein E genotype were obtained at baseline. Annual scores on a modified version of the Centers for Epidemiologic Studies Depression (CES-D) scale were obtained initially and up to 7 years subsequently.

Results

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After controlling for important covariates, occurrence of depressive symptoms (defined as modified CES-D score of >7) was associated with small lesions in the basal ganglia, large cortical white-matter lesions, and severe subcortical white-matter grade. Neuroimaging variables did not predict incident depression among those who were nondepressive at the time of MRI. Persistence of depressive symptoms across 2 consecutive time points was associated with small basal ganglia lesions and large cerebral cortical white-matter lesions. Worsening of depression (increase in CES-D score of ≥5) was associated with subcortical white-matter lesions.

Conclusions

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These findings suggest that cerebrovascular disease at baseline is related to depression symptoms over time. Further studies are needed to investigate the differential effects of subcortical white- versus gray-matter lesions on mood.
Financial Interdependence and the State: International Monetary Relations at Century's End
Authors: Andrews David M. , Willett Thomas D.
Published: July 2002

As the twentieth century draws to a close, one can find sharply contrasting views among leading scholars on almost every key issue in positive international political economy. How strong are international as opposed to domestic influences on policy? How important are issues of national security (”high politics”) versus economic considerations(”low politics”)? What role do institutions—international and domestic—play in influencing and constraining the behavior of governments? Why is international cooperation rare but not unheard of? The list goes on and on.
Video Space: A Site for Choreography
Authors: Rosenberg Douglas
Published: July 2002

Since the advent of the film art form, the author finds, cinema and dance have engaged in an al-most unbroken courtship, each appropriating techniques and styles from the object of affec-tion. A hybrid form, video dance, has resulted; its recording me-dium may be thought of as its site. The architecture of this site provides a distinctive context for the critique of dances created for it. The collaborative process nec-essary to realize the potential of video dance is found to require a reconstruction of the dancing body as unencumbered by the re-straints of time and space.
Observations about Music and Decentralized Environments
Authors: Tanzi Dante
Published: July 2002

This paper discusses temporal narratives and musical action, focusing on the decentralization trends in models, means, objects, knowledge and objectives of artistic creation on the Net. In a widespread cognitive environment, diachronic and spatial communication values have to be adapted. The development of linguistic flows, codified according to digital models, leads net users to interact in a different way. In a decentralized environment, many conditions for composing and listening to music may be subordinated to the conception of creative thought as a combination of recursive, connective, and systemic processes, which redefine not only the concept of musical object and sound space, but also that of music itself.
English Expletive Constructions Are Not Infected
Authors: Schütze Carson T.
Published: July 2002

Sobin (1997) proposes an analysis of several “prestige” constructions of English under which they result from grammatical viruses. Counter to his claim, I argue that plural agreement in expletive constructions introduced by there results not from a virus but from the grammar of English, because it lacks signature properties of viruses. I show that the flat agreement seen in expletive constructions with conjoined associates can be explained as a processing effect. I then argue that singular agreement with plural associates represents a second alternative allowed within the grammar.
Extracting the Lowest-Frequency Words: Pitfalls and Possibilities
Authors: Weeber Marc , Vos Rein , Baayen R. Harald
Published: July 2002

In a medical information extraction system, we use common word association techniques to extract side-effect-related terms. Many of these terms have a frequency of less than five. Standard word-association-based applications disregard the lowest-frequency words, and hence disregard useful information. We therefore devised an extraction system for the full word frequency range. This system computes the significance of association by the log-likelihood ratio and Fisher's exact test. The output of the system shows a recurrent, corpus-independent pattern in both recall and the number of significant words. We will explain these patterns by the statistical behavior of the lowest-frequency words. We used Dutch verb-particle combinations as a second and independent collocation extraction application to illustrate the generality of the observed phenomena. We will conclude that a) word-association-based extraction systems can be enhanced by also considering the lowest-frequency words, b) significance levels should not be fixed but adjusted for the optimal window size, c) hapax legomena, words occurring only once, should be disregarded a priori in the statistical analysis, and d) the distribution of the targets to extract should be considered in combination with the extraction method.
Imaging Cognition II: An Empirical Review of 275 PET and fMRI Studies
Authors: Cabeza Roberto , Nyberg Lars
Published: July 2002

Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have been extensively used to explore the functional neuroanatomy of cognitive functions. Here we review 275 PET and fMRI studies of attention (sustained, selective, Stroop, orientation, divided), perception (object, face, space/motion, smell), imagery (object, space/ motion), language (written/spoken word recognition, spoken/ no spoken response), working memory (verbal/numeric, object, spatial, problem solving), semantic memory retrieval (categorization, generation), episodic memory encoding (verbal, object, spatial), episodic memory retrieval (verbal, nonverbal, success, effort, mode, context), priming (perceptual, conceptual), and procedural memory (conditioning, motor, and nonmotor skill learning). To identify consistent activation patterns associated with these cognitive operations, data from 412 contrasts were summarized at the level of cortical Brodmann's areas, insula, thalamus, medial-temporal lobe (including hippocampus), basal ganglia, and cerebellum. For perception and imagery, activation patterns included primary and secondary regions in the dorsal and ventral pathways. For attention and working memory, activations were usually found in prefrontal and parietal regions. For language and semantic memory retrieval, typical regions included left prefrontal and temporal regions. For episodic memory encoding, consistently activated regions included left prefrontal and medial-temporal regions. For episodic memory retrieval, activation patterns included prefrontal, medial-temporal, and posterior midline regions. For priming, deactivations in prefrontal (conceptual) or extrastriate (perceptual) regions were consistently seen. For procedural memory, activations were found in motor as well as in non-motor brain areas. Analysis of regional activations across cognitive domains suggested that several brain regions, including the cerebellum, are engaged by a variety of cognitive challenges. These observations are discussed in relation to functional specialization as well as functional integration.
Dissociations in Processing Past Tense Morphology: Neuropathology and Behavioral Studies
Authors: Tyler Lorraine K. , deMornay-Davies Paul , Anokhina Rebekah , Longworth Catherine , Randall Billi , Marslen-Wilson William D.
Published: July 2002

Neuropsychological research showing that the regular (“jump–jumped”) and irregular (“drive/drove”) past tense inflectional morphology can dissociate following brain damage has been important in testing claims about the cognitive and neural status of linguistic rules. These dissociations have been interpreted as evidence for two different computational systems—a rule-based system underlying the processing of regulars and the irregulars being individually listed in the mental lexicon. In contrast, connectionist accounts claim that these dissociations can be modeled within a single system. Combining behavioral data from patients with detailed information about their neuropathology can, in principle, provide strong constraints on accounts of the past tense. In this study, we tested five nonfluent aphasic patients, all of whom had extensive left hemisphere (LH) damage involving the left inferior frontal gyrus and underlying structures, and four patients with semantic deficits following herpes simplex encephalitis (HSE) who had extensive damage to the inferior temporal cortex. These patients were tested in experiments probing past tense processing. In a large priming study, the nonfluent patients showed no priming for the regular past tense but significant priming for the irregulars (whereas controls show priming for both). In contrast, the HSE patients showed significantly impaired performance for the irregulars in an elicitation task. These patterns of behavioral data and neuropathology suggest that two separable but interdependent systems underlie processing of the regular and irregular past tense.