Showing papers by "Cornell University published in 1998"

Collective dynamics of small-world networks

Abstract: Networks of coupled dynamical systems have been used to model biological oscillators, Josephson junction arrays, excitable media, neural networks, spatial games, genetic control networks and many other self-organizing systems. Ordinarily, the connection topology is assumed to be either completely regular or completely random. But many biological, technological and social networks lie somewhere between these two extremes. Here we explore simple models of networks that can be tuned through this middle ground: regular networks 'rewired' to introduce increasing amounts of disorder. We find that these systems can be highly clustered, like regular lattices, yet have small characteristic path lengths, like random graphs. We call them 'small-world' networks, by analogy with the small-world phenomenon (popularly known as six degrees of separation. The neural network of the worm Caenorhabditis elegans, the power grid of the western United States, and the collaboration graph of film actors are shown to be small-world networks. Models of dynamical systems with small-world coupling display enhanced signal-propagation speed, computational power, and synchronizability. In particular, infectious diseases spread more easily in small-world networks than in regular lattices.

Nonpoint pollution of surface waters with phosphorus and nitrogen

Abstract: Agriculture and urban activities are major sources of phosphorus and nitrogen to aquatic ecosystems. Atmospheric deposition further contributes as a source of N. These nonpoint inputs of nutrients are difficult to measure and regulate because they derive from activities dispersed over wide areas of land and are variable in time due to effects of weather. In aquatic ecosystems, these nutrients cause diverse problems such as toxic algal blooms, loss of oxygen, fish kills, loss of biodiversity (including species important for commerce and recreation), loss of aquatic plant beds and coral reefs, and other problems. Nutrient enrichment seriously degrades aquatic ecosystems and impairs the use of water for drinking, industry, agriculture, recreation, and other purposes. Based on our review of the scientific literature, we are certain that (1) eutrophication is a widespread problem in rivers, lakes, estuaries, and coastal oceans, caused by overenrichment with P and N; (2) nonpoint pollution, a major source of P and N to surface waters of the United States, results primarily from agriculture and urban activity, including industry; (3) inputs of P and N to agriculture in the form of fertilizers exceed outputs in produce in the United States and many other nations; (4) nutrient flows to aquatic ecosystems are directly related to animal stocking densities, and under high livestock densities, manure production exceeds the needs of crops to which the manure is applied; (5) excess fertilization and manure production cause a P surplus to accumulate in soil, some of which is transported to aquatic ecosystems; and (6) excess fertilization and manure production on agricultural lands create surplus N, which is mobile in many soils and often leaches to downstream aquatic ecosystems, and which can also volatilize to the atmosphere, redepositing elsewhere and eventually reaching aquatic ecosystems. If current practices continue, nonpoint pollution of surface waters is virtually certain to increase in the future. Such an outcome is not inevitable, however, because a number of technologies, land use practices, and conservation measures are capable of decreasing the flow of nonpoint P and N into surface waters. From our review of the available scientific information, we are confident that: (1) nonpoint pollution of surface waters with P and N could be reduced by reducing surplus nutrient flows in agricultural systems and processes, reducing agricultural and urban runoff by diverse methods, and reducing N emissions from fossil fuel burning; and (2) eutrophication can be reversed by decreasing input rates of P and N to aquatic ecosystems, but rates of recovery are highly variable among water bodies. Often, the eutrophic state is persistent, and recovery is slow.

Primary Prevention of Acute Coronary Events With Lovastatin in Men and Women With Average Cholesterol Levels: Results of AFCAPS/TexCAPS

Abstract: 0.63; 95% confidence interval [CI], 0.50-0.79;P,.001), myocardial infarction (95 vs 57 myocardial infarctions; RR, 0.60; 95% CI, 0.43-0.83; P = .002), unstable angina (87 vs 60 first unstable angina events; RR, 0.68; 95% CI, 0.49-0.95;P = .02), coronary revascularization procedures (157 vs 106 procedures; RR, 0.67; 95% CI, 0.520.85; P = .001), coronary events (215 vs 163 coronary events; RR, 0.75; 95% CI, 0.61-0.92; P = .006), and cardiovascular events (255 vs 194 cardiovascular events; RR, 0.75; 95% CI, 0.62-0.91; P = .003). Lovastatin (20-40 mg daily) reduced LDL-C by 25% to 2.96 mmol/L (115 mg/dL) and increased HDL-C by 6% to 1.02 mmol/L (39 mg/dL). There were no clinically relevant differences in safety parameters between treatment groups. Conclusions.— Lovastatin reduces the risk for the first acute major coronary event in men and women with average TC and LDL-C levels and below-average HDL-C levels. These findings support the inclusion of HDL-C in risk-factor assessment, confirm the benefit of LDL-C reduction to a target goal, and suggest the need for reassessment of the National Cholesterol Education Program guidelines regarding pharmacological intervention.

A Brief Tutorial on the Development of Measures for Use in Survey Questionnaires

Abstract: The adequate measurement of abstract constructs is perhaps the greatest challenge to understanding the behavior of people in organizations. Problems with the reliability and validity of measures us...

Design of Organic Molecules with Large Two-Photon Absorption Cross Sections

Abstract: A strategy for the design of molecules with large two-photon absorption cross sections, δ, was developed, on the basis of the concept that symmetric charge transfer, from the ends of a conjugated system to the middle, or vice versa, upon excitation is correlated to enhanced values of δ. Synthesized bis(styryl)benzene derivatives with donor-π-donor, donor-acceptor-donor, and acceptor-donor-acceptor structural motifs exhibit exceptionally large values of δ, up to about 400 times that of trans-stilbene. Quantum chemical calculations performed on these molecules indicate that substantial symmetric charge redistribution occurs upon excitation and provide δ values in good agreement with experimental values. The combination of large δ and high fluorescence quantum yield or triplet yield exhibited by molecules developed here offers potential for unprecedented brightness in two-photon fluorescent imaging or enhanced photosensitivity in two-photon sensitization, respectively.

CHOP is implicated in programmed cell death in response to impaired function of the endoplasmic reticulum

Abstract: Cellular stress, particularly in response to toxic and metabolic insults that perturb function of the endoplasmic reticulum (ER stress), is a powerful inducer of the transcription factor CHOP. The role of CHOP in the response of cells to injury associated with ER stress was examined in a murine deficiency model obtained by homologous recombination at the chop gene. Compared with the wild type, mouse embryonic fibroblasts (MEFs) derived from chop -/- animals exhibited significantly less programmed cell death when challenged with agents that perturb ER function. A similar deficit in programmed cells death in response to ER stress was also observed in MEFs that lack CHOP's major dimerization partner, C/EBPbeta, implicating the CHOP-C/EBP pathway in programmed cell death. An animal model for studying the effects of chop on the response to ER stress was developed. It entailed exposing mice with defined chop genotypes to a single sublethal intraperitoneal injection of tunicamycin and resulted in a severe illness characterized by transient renal insufficiency. In chop +/+ and chop +/- mice this was associated with the early expression of CHOP in the proximal tubules followed by the development of a histological picture similar to the human condition known as acute tubular necrosis, a process that resolved by cellular regeneration. In the chop -/- animals, in spite of the severe impairment in renal function, evidence of cellular death in the kidney was reduced compared with the wild type. The proximal tubule epithelium of chop -/- animals exhibited fourfold lower levels of TUNEL-positive cells (a marker for programmed cell death), and significantly less evidence for subsequent regeneration. CHOP therefore has a role in the induction of cell death under conditions associated with malfunction of the ER and may also have a role in cellular regeneration under such circumstances.

On becoming a strategic partner: The role of human resources in gaining competitive advantage

Abstract: Although managers cite human resources as a firm's most important asset, many organizational decisions do not reflect this belief. This article uses the value, rareness, imitability, and organization (VRIO) framework to examine the role that the human resource (HR) function plays in developing a sustainable competitive advantage. Why some popularly cited sources of sustainable competitive advantage are not, and what aspects of a firm's human resources can provide a source of sustainable competitive advantage are discussed. The role of the HR executive as a strategic partner in developing and maintaining competitive advantage within the firm is also examined. © 1998 John Wiley & Sons, Inc.

Electron Capture Dissociation of Multiply Charged Protein Cations. A Nonergodic Process

Abstract: Neutralization-reionization mass spectrometry (MS)1 is of unique value for preparing and characterizing highly reactive and unstable neutral species, such as the intermediate in the dissociative-recombination reaction H3O + ef H2O + H + 6.4 eV.2 Following an earlier suggestion,3 using neutralization accompanying surface-induced dissociation (SID)4 to form an unstable site did not yield new cleavage reactions5 in multiply charged protein cations from electrospray ionization (ESI) with Fourier transform (FT) MS.6 Serendipitously, we now find that one or more charges on such protein cations can be neutralized with low-energy electrons to cause specific cleavage of the amine bond to form c, z products,7 in contrast to the amide cleavage b, y products formed by collisionally activated dissociation (CAD),8 infrared multiphoton (IRMPD)9 and UV10 photodissociation, 70 eV electron impact excitation,11 and SID.5 The b, y products are formed by the lowest energy backbone cleavage of ESI protein ions.6-9 An attempt to cleave stronger bonds using high-energy (6.4 eV) 193 nm photons gave mainly b, y products for 2 kDa protein ions,10 but for 2.8 and 8.6 kDa protein ions12 gave small yields of c, z amine bond cleavage products not previously observed. In this further investigation, extra electrodes were placed outside the ion cell electrodes that trap the positively charged ions. With the outside electrodes at +9 V,13 extensive 193 nm laser irradiation of SWIFT-selected14 (M + 11H)11+ ubiquitin ions (8.6 kDa) only produces b, y, not c, z, ions. However, with the outside electrodes at -1 V, the c, z products are formed along with 10+ molecular ions; unexpectedly, these are mainly (M + 11H)10+• ions (Figure 1d), 1 Da heavier than the (M + 10H)10+ ions formed by ESI (Figure 1c). The 4+ mellitin ion spectrum measured under the same conditions (Figure 1b) similarly contains (M + 4H)3+•, consistent with capture of secondary electrons formed by the 193 nm photons impinging on metal surfaces and trapped by the -1 V electrodes: (M + 4H)4+ + ef (M + 4H)3+•.15 Electrons were produced instead (no laser) by a conventional heated filament source outside the FTMS magnet opposite the ESI source.11 With a 10-5 Torr Ar pulse for ecooling (energy < 0.2 eV; an SF6 pulse lowered the efficiency), the 11+ ions of ubiquitin gave a spectrum that showed c, z cleavage of 50 out of 75 backbone positions; CAD8/IRMPD9 gave b, y cleavage of eight of these positions plus seven others. Cooled electrons plus the 15+ ions of FeIII equine cytochrome c16 produced (Figure 2) c, z fragment ions from cleavages at all but 40 of the 103 possible backbone sites (e.g., N-terminal side of Pro, none; of Ile, Leu, Val, few); CAD produces b, y cleavages (total 19) at eight additional sites. The 21+ apomyoglobin ions (17 kDa) yielded 33 c, z cleavages, but the 34+ ions of bovine carbonic anhydrase (29 kDa) as yet has given only 33+, 32+, and 31+ molecular ions. Electron capture dissociation (ECD)1-3 rationalizes these results. The capture cross section should be proportional to the ionic charge squared, consistent with the minimal secondary fragmentations to produce internal ions and the predominance of cleavages in the central∼70% of the protein chain. Charge values and masses17 of the complementary product ions are consistent with dissociation after ecapture, such as c39/z37 from the 76-residue ubiquitin 11+ ions and c69/z35 from the 104residue cytochrome c 15+ ions. The most favored protonation sites are the side chains of Lys, Arg, and His;18 neutralization to form hypervalent species1-3 at Lys and Arg would account for ions (Figure 2) representing losses of 17, 44, and 59 Da from (M + nH)(n-x)+ (eq 1; neutralization of protonated His gives a more stable radical site).

Learning, Creating, and Using Knowledge: Concept Maps as Facilitative Tools in Schools and Corporations

Abstract: For more than half a century, my students and I have sought to understand why some learners acquire a deep, meaningful understanding of materials studied, whereas others have only a superficial grasp of the information presented. Often the latter kind of student had high school grades and high standardized test scores. What appeared to underlie the differences in these two groups of students was the differences in the way they approached learning of subject matter. Unfortunately, as a graduate student at the University of Minnesota in the 1950’s, the only learning psychology taught was behavioral psychology, and this largely sought to remove meaning from learning experiments, either by using animals, nonsense syllables, paired-word associations, or other material that would not “contaminate” experiments due to the almost idiosyncratic nature of leaner’s meanings of concepts or ideas. I thought then that behavioral psychology had essentially no relevance to human learning of the kind I was interested in. Fortunately for our research group, Ausubel’s assimilation theory of meaningful learning was published in 1963, and this provided a solid theoretical foundation for the work we were interested in doing.

Authoritative sources in a hyperlinked environment

Abstract: The network structure of a hyperlinked environment can be a rich source of information about the content of the environment, provided we have eective means for understanding it. We develop a set of algorithmic tools for extracting information from the link structures of such environments, and report on experiments that demonstrate their eectiveness in a variety of contexts on the World Wide Web. The central issue we address within our framework is the distillation of broad search topics, through the discovery of \authoritative" information sources on such topics. We propose and test an algorithmic formulation of the notion of authority, based on the relationship between a set of relevant authoritative pages and the set of \hub pages" that join them together in the link structure. Our formulation has connections to the eigenvectors of certain matrices associated with the link graph; these connections in turn motivate additional heuristics for link-based analysis.

DIFFUSION IN ORGANIZATIONS AND SOCIAL MOVEMENTS: From Hybrid Corn to Poison Pills

Abstract: There has been rapid growth in the study of diffusion across organizations and social movements in recent years, fueled by interest in institutional arguments and in network and dynamic analysis. This research develops a sociologically grounded account of change emphasizing the channels along which practices flow. Our review focuses on characteristic lines of argument, emphasizing the structural and cultural logic of diffusion processes. We argue for closer theoretical attention to why practices diffuse at different rates and via different pathways in different settings. Three strategies for further development are proposed: broader comparative research designs, closer inspection of the content of social relations between collective actors, and more attention to diffusion industries run by the media and communities of experts.

Robot-aided neurorehabilitation

Abstract: The authors' goal is to apply robotics and automation technology to assist, enhance, quantify, and document neurorehabilitation. This paper reviews a clinical trial involving 20 stroke patients with a prototype robot-aided rehabilitation facility developed at the Massachusetts Institute of Technology, Cambridge, (MIT) and tested at Burke Rehabilitation Hospital, White Plains, NY. It also presents the authors' approach to analyze kinematic data collected in the robot-aided assessment procedure. In particular, they present evidence (1) that robot-aided therapy does not have adverse effects, (2) that patients tolerate the procedure, and (3) that peripheral manipulation of the impaired limb may influence brain recovery. These results are based on standard clinical assessment procedures. The authors also present one approach using kinematic data in a robot-aided assessment procedure.

The Nature of Suffering and the Goals of Medicine

Abstract: The question of suffering and its relation to organic illness has rarely been addressed in the medical literature. This article offers a description of the nature and causes of suffering in patients undergoing medical treatment. A distinction based on clinical observations is made between suffering and physical distress. Suffering is experienced by persons, not merely by bodies, and has its source in challenges that threaten the intactness of the person as a complex social and psychological entity. Suffering can include physical pain but is by no means limited to it. The relief of suffering and the cure of disease must be seen as twin obligations of a medical profession that is truly dedicated to the care of the sick. Physicians' failure to understand the nature of suffering can result in medical intervention that (though technically adequate) not only fails to relieve suffering but becomes a source of suffering itself. (N Engl J Med. 1982; 306:639–45.)

Option Volume and Stock Prices: Evidence on Where Informed Traders Trade

Abstract: This paper investigates the informational role of transactions volume in options markets. We develop an asymmetric information model in which informed traders may trade in option or equity markets. We show conditions under which informed traders trade options, and we investigate the implications of this for the linkage between markets. Our model predicts an important informational role for the volume of particular types of option trades. We empirically test our model's hypotheses with intraday option data. Our main empirical result is that negative and positive option volumes contain information about future stock prices. THE INFORMATION CONTENT of trading activity is a subject of widespread interest. If trades are correlated with private information, then the outcome of the transaction process may portend future movements in price. The extension of trading to different venues or to derivative instruments, however, means that this link between transactions and information need not be easily discernible. If there are alternative markets in which informed traders can profit from their information, then where informed traders choose to trade may have important implications not only for security p:rice movements, but for the behavior of related prices as well. This suggests that transactions in derivative markets may be an important predictor of future security price movements. In this paper we investigate the informational role of transactions volume in options markets. For some readers, this focus may seem puzzling; an option is a derivative security so its price should be dictated unilaterally by the behavior of the stock price. This unidirectional linkage is only true, however, in complete markets; if information is impounded into prices by trading, then the ability of informed traders to transact in options markets mearns

Single-Molecule Vibrational Spectroscopy and Microscopy

Abstract: Vibrational spectra for a single molecule adsorbed on a solid surface have been obtained with a scanning tunneling microscope (STM) Inelastic electron tunneling spectra for an isolated acetylene (C2H2) molecule adsorbed on the copper (100) surface showed an increase in the tunneling conductance at 358 millivolts, resulting from excitation of the C-H stretch mode An isotopic shift to 266 millivolts was observed for deuterated acetylene (C2D2) Vibrational microscopy from spatial imaging of the inelastic tunneling channels yielded additional data to further distinguish and characterize the two isotopes Single-molecule vibrational analysis should lead to better understanding and control of surface chemistry at the atomic level

The simplest walking model: stability, complexity, and scaling.

Abstract: We demonstrate that an irreducibly simple, uncontrolled, two-dimensional, two-link model, vaguely resembling human legs, can walk down a shallow slope, powered only by gravity. This model is the simplest special case of the passive-dynamic models pioneered by McGeer (1990a). It has two rigid massless legs hinged at the hip, a point-mass at the hip, and infinitesimal point-masses at the feet. The feet have plastic (no-slip, no-bounce) collisions with the slope surface, except during forward swinging, when geometric interference (foot scuffing) is ignored. After nondimensionalizing the governing equations, the model has only one free parameter, the ramp slope gamma. This model shows stable walking modes similar to more elaborate models, but allows some use of analytic methods to study its dynamics. The analytic calculations find initial conditions and stability estimates for period-one gait limit cycles. The model exhibits two period-one gait cycles, one of which is stable when 0 < gamma < 0.015 rad. With increasing gamma, stable cycles of higher periods appear, and the walking-like motions apparently become chaotic through a sequence of period doublings. Scaling laws for the model predict that walking speed is proportional to stance angle, stance angle is proportional to gamma 1/3, and that the gravitational power used is proportional to v4 where v is the velocity along the slope.

Long-term effects of nurse home visitation on children's criminal and antisocial behavior: 15-year follow-up of a randomized controlled trial.

Abstract: Context.— A program of home visitation by nurses has been shown to affect the rates of maternal welfare dependence, criminality, problems due to use of substances, and child abuse and neglect. However, the long-term effects of this program on children’s antisocial behavior have not been examined. Objective.— To examine the long-term effects of a program of prenatal and early childhood home visitation by nurses on children’s antisocial behavior. Design.— Fifteen-year follow-up of a randomized trial. Interviews were conducted with the adolescents and their biological mothers or custodial parents. Setting.— Semirural community in New York. Participants.— Between April 1978 and September 1980, 500 consecutive pregnant women with no previous live births were recruited, and 400 were enrolled. A total of 315 adolescent offspring participated in a follow-up study when they were 15 years old; 280 (89%) were born to white mothers, 195 (62%) to unmarried mothers, 151 (48%) to mothers younger than 19 years, and 186 (59%) to mothers from households of low socioeconomic status at the time of registration during pregnancy. Intervention.— Families in the groups that received home visits had an average of 9 (range, 0-16) home visits during pregnancy and 23 (range, 0-59) home visits from birth through the child’s second birthday. The control groups received standard prenatal and well-child care in a clinic. Main Outcome Measures.— Children’s self-reports of running away, arrests, convictions, being sentenced to youth corrections, initiation of sexual intercourse, number of sex partners, and use of illegal substances; school records of suspensions; teachers’ reports of children’s disruptive behavior in school; and parents’ reports of the children’s arrests and behavioral problems related to the children’s use of alcohol and other drugs. Results.— Adolescents born to women who received nurse visits during pregnancy and postnatally and who were unmarried and from households of low socioeconomic status (risk factors for antisocial behavior), in contrast with those in the comparison groups, reported fewer instances (incidence) of running away (0.24 vs 0.60; P = .003), fewer arrests (0.20 vs 0.45; P = .03), fewer convictions and violations of probation (0.09 vs 0.47; P,.001), fewer lifetime sex partners (0.92 vs 2.48; P = .003), fewer cigarettes smoked per day (1.50 vs 2.50; P = .10), and fewer days having consumed alcohol in the last 6 months (1.09 vs 2.49; P = .03). Parents of nurse-visited children reported that their children had fewer behavioral problems related to use of alcohol and other drugs (0.15 vs 0.34; P = .08). There were no program effects on other behavioral problems. Conclusions.— This program of prenatal and early childhood home visitation by nurses can reduce reported serious antisocial behavior and emergent use of substances on the part of adolescents born into high-risk families. JAMA. 1998;280:1238-1244 JUVENILE CRIME is a significant problem in the United States. In 1996, law enforcement agencies made 2.9 million arrests of juveniles (children ,18 years). Moreover, 19% of all arrests and 19% of all violent crime arrests were accounted for by juveniles. Although the number of juvenile Violent Crime Index arrests (ie, for murder, forcible rape, robbery, and aggravated assault) declined in both 1995 and 1996, the rate in 1996 was still 60% higher than the 1987 level. 1

Toward a Unifying Framework for Exploring Fit and Flexibility in Strategic Human Resource Management

Abstract: In this article we present a framework for studying the concepts of fit and flexibility in the field of strategic human resource management (HRM), focusing on HRM practices, employee skills, and employee behaviors, and review past conceptual and empirical work within that framework. We present a model of strategic HRM and use this model to explore the concepts of fit and flexibility as they apply to strategic HRM. After applying the concepts of resource and coordination flexibility to strategic HRM, we discuss the implications of the framework for both the practice of and research on strategic HRM.

Hydraulic lift: consequences of water efflux from the roots of plants.

Abstract: Hydraulic lift is the passive movement of water from roots into soil layers with lower water potential, while other parts of the root system in moister soil layers, usually at depth, are absorbing water. Here, we review the brief history of laboratory and field evidence supporting this phenomenon and discuss some of the consequences of this below-ground behavior for the ecology of plants. Hydraulic lift has been shown in a relatively small number of species (27 species of herbs, grasses, shrubs, and trees), but there is no fundamental reason why it should not be more common as long as active root systems are spanning a gradient in soil water potential (Ψs) and that the resistance to water loss from roots is low. While the majority of documented cases of hydraulic lift in the field are for semiarid and arid land species inhabiting desert and steppe environments, recent studies indicate that hydraulic lift is not restricted to these species or regions. Large quantities of water, amounting to an appreciable fraction of daily transpiration, are lifted at night. This temporary partial rehydration of upper soil layers provides a source of water, along with soil moisture deeper in the profile, for transpiration the following day and, under conditions of high atmospheric demand, can substantially facilitate water movement through the soil-plant-atmosphere system. Release of water into the upper soil layers has been shown to afford the opportunity for neighboring plants to utilize this source of water. Also, because soils tend to dry from the surface downward and nutrients are usually most plentiful in the upper soil layers, lifted water may provide moisture that facilitates favorable biogeochemical conditions for enhancing mineral nutrient availability, microbial processes, and the acquisition of nutrients by roots. Hydraulic lift may also prolong or enhance fine-root activity by keeping them hydrated. Such indirect benefits of hydraulic lift may have been the primary selective force in the evolution of this process. Alternatively, hydraulic lift may simply be the consequence of roots not possessing true rectifying properties (i.e., roots are leaky to water). Finally, the direction of water movement may also be downward or horizontal if the prevailing Ψs gradient so dictates, i.e., inverse, or lateral, hydraulic lift. Such downward movement through the root system may allow growth of roots in otherwise dry soil at depth, permitting the establishment of many phreatophytic species.

Vagus nerve stimulation therapy for partial-onset seizures A randomized active-control trial

Abstract: Objective: The purpose of this multicenter, add-on, double-blind, randomized, active-control study was to compare the efficacy and safety of presumably therapeutic (high) vagus nerve stimulation with less (low) stimulation. Background: Chronic intermittent left vagus nerve stimulation has been shown in animal models and in preliminary clinical trials to suppress the occurrence of seizures. Methods: Patients had at least six partial-onset seizures over 30 days involving complex partial or secondarily generalized seizures. Concurrent antiepileptic drugs were unaltered. After a 3-month baseline, patients were surgically implanted with stimulating leads coiled around the left vagus nerve and connected to an infraclavicular subcutaneous programmable pacemaker-like generator. After randomization, device initiation, and a 2-week ramp-up period, patients were assessed for seizure counts and safety over 3 months. The primary efficacy variable was the percentage change in total seizure frequency compared with baseline. Results: Patients receiving high stimulation (94 patients, ages 13 to 54 years) had an average 28% reduction in total seizure frequency compared with a 15% reduction in the low stimulation group (102 patients, ages 15 to 60 year; p = 0.04). The high-stimulation group also had greater improvements on global evaluation scores, as rated by a blinded interviewer and the patient. High stimulation was associated with more voice alteration and dyspnea. No changes in physiologic indicators of gastric, cardiac, or pulmonary functions occurred. Conclusions: Vagus nerve stimulation is an effective and safe adjunctive treatment for patients with refractory partial-onset seizures. It represents the advent of a new, nonpharmacologic treatment for epilepsy.

Blind equalization using the constant modulus criterion: a review

Abstract: This paper provides a tutorial introduction to the constant modulus (CM) criterion for blind fractionally spaced equalizer (FSE) design via a (stochastic) gradient descent algorithm such as the constant modulus algorithm (CMA). The topical decisions utilized in this tutorial can be used to help catalog the emerging literature on the CM criterion and on the behavior of (stochastic) gradient descent algorithms used to minimize it.

Inferring Web communities from link topology

Abstract: The World Wide Web grows through a decentralized, almost anarchic process, and this has resulted in a large hyperlinked corpus without the kind of logical organization that can be built into more tradit,ionally-created hypermedia. To extract, meaningful structure under such circumstances, we develop a notion of hyperlinked communities on the www t,hrough an analysis of the link topology. By invoking a simple, mathematically clean method for defining and exposing the structure of these communities, we are able to derive a number of themes: The communities can be viewed as containing a core of central, “authoritative” pages linked togh and they exhibit a natural type of hierarchical topic generalization that can be inferred directly from the pat,t,ern of linkage. Our investigation shows that although the process by which users of the Web create pages and links is very difficult to understand at a “local” level, it results in a much greater degree of orderly high-level structure than has typically been assumed.

Differentiation of Monocytes into Dendritic Cells in a Model of Transendothelial Trafficking

Abstract: Essential to the dendritic cell system of antigen-presenting cells are the veiled dendritic cells that traverse afferent lymph to enter lymph nodes, where they initiate immune responses. The origin of veiled cells, which were discovered 20 years ago, is unclear. Monocytes cultured with endothelium differentiated into dendritic cells within 2 days, particularly after phagocytosing particles in subendothelial collagen. These nascent dendritic cells migrated across the endothelium in the ablumenal-to-lumenal direction, as would occur during entry into lymphatics. Monocytes that remained in the subendothelial matrix became macrophages. Therefore, monocytes have two potential fates associated with distinct patterns of migration.

Child Labor: Cause, Consequence, and Cure, with Remarks on International Labor Standards

Abstract: Should child labor be banned outright? Should the World Trade Organization be given the responsibility to discourage child labor using trade sanctions? The answer to this complicated problem depends on the economic milieu, says Basu. At least 120 million of the world's children aged 5 to 14 worked full-time in 1995, most of them under hazardous, unhygienic conditions, for more than 10 hours a day. This is an old problem worldwide but particularly so in Third World countries in recent decades. What has changed, with globalization, is our awareness of these child laborers. (The International Labour Organisation distinguishes between child work, which could include light household chores and could have some learning value, and child labor, a pejorative phrase.) By bringing together the main theoretical ideas, Basu hopes to encourage both more theoretical research and empirical work with a better theoretical foundation. Among other things, Basu observes that: ° The problem is most serious in Africa, where the child-labor participation rate is 26.2 percent. The rate is 12.8 percent in Asia. But since 1950, the trend is a decline in that participation rate worldwide. For most Latin American countries, the decline is notable but less marked than in Asia. In large parts of Africa, including Ethiopia, the problem has been extremely persistent, but even there the trend is downward. ° Child labor has not always been considered evil, and there is no consensus on why it began to decline. In some (not all) countries legislative acts declared it illegal, in some there were rules about compulsory education, and increasing prosperity generally made families less likely to experience poverty if their children weren't working. ° Mandating compulsory education is regarded as more effective than outlawing child labor, because attendance at school is easier to monitor, but some experts believe economic progress is the answer to the problem. The justification for many interventions is that the state is more concerned about the well-being of children than their parents are; Basu believes such an assumption to be wrong when child labor occurs as a mass phenomenon rather than as isolated abuse. Basu argues that, in some economies, the market for labor may exhibit multiple equilibria, with one equilibrium having low adult wage and a high incidence of child labor and another equilibrium exhibiting high adult wage and no child labor. The model is used to provide a framework for analyzing the role of international labor standards. This paper - a product of the Office of the Senior Vice President, Development Economics - is part of a larger effort in the Bank to promote understanding of the causes of child labor. The study was funded by the Bank`s Research Support Budget under the research project Literacy and Child Labor (RPO 683-07). The author may be contacted at kbasu@worldbank.org.

G-protein-coupled receptor of Kaposi's sarcoma-associated herpesvirus is a viral oncogene and angiogenesis activator

Abstract: The Kaposi's sarcoma-associated herpesvirus (KSHV/HHV8) is a gamma-2 herpesvirus that is implicated in the pathogenesis of Kaposi's sarcoma and of primary effusion B-cell lymphomas (PELs). KSHV infects malignant and progenitor cells of Kaposi's sarcoma and PEL, it encodes putative oncogenes and genes that may cause Kaposi's sarcoma pathogenesis by stimulating angiogenesis. The G-protein-coupled receptor encoded by an open reading frame (ORF 74) of KSHV is expressed in Kaposi's sarcoma lesions and in PEL and stimulates signalling pathways linked to cell proliferation in a constitutive (agonist-independent) way. Here we show that signalling by this KSHV G-protein-coupled receptor leads to cell transformation and tumorigenicity, and induces a switch to an angiogenic phenotype mediated by vascular endothelial growth factor, an angiogenesis and Kaposi's-spindle-cell growth factor. We find that this receptor can activate two protein kinases, JNK/SAPK and p38MAPK, by triggering signalling cascades like those induced by inflammatory cytokines that are angiogenesis activators and mitogens for Kaposi's sarcoma cells and B cells. We conclude that the KSHV G-protein-coupled receptor is a viral oncogene that can exploit cell signalling pathways to induce transformation and angiogenesis in KSHV-mediated oncogenesis.