cssi/SciSciGPT-SciSciNet huggingface dataset:
Fetal brain tissue transplant techniques: A cautionary note

Abstract The fact that embryonic brain tissue can be successfully transplanted into damaged brain of adult laboratory animals has many interesting and exciting implications for basic and clinical neuroscience. However, problems involving the degeneration of multiple brain systems in most neuro-denegerative diseases will likely limit the clinical usefulness of this technique. Furthermore, the question of whether aged or diseased brain can serve as a viable host organ has not been fully addressed. On the other hand, greater utility may exist in cases involving focal brain lesions. This may be particularly true in conditions not dependent upon complete or perfect re-innervation, and which may benefit more from the delivery of high concentrations of endogenous tropic factors. Of course, whether fetal tissue transplantation represents the most effective means of accomplishing this remains an issue for future study.
Ignition of hydrogen and oxygen in counterflow at high pressures

Ignition of hydrogen and oxygen in the “third limit” was studied in counterflow for both premixed and nonpremixed systems with activation energy asymptotics. The results of the analysis were then compared to numerical calculations for further verification of the findings. In the analysis, simplifications to the chemical mechanism were formally derived, and criteria determining the accuracy of these simplifications were identified. It was demonstrated that the chemical steady-state approximations of O and OH are accurate for a wide range of conditions, while the steady-state approximations of H and HO2 were both found to be inaccurate in certain regimes. Using these approximations, a reduced mechanism was derived and used to explain the ignition behavior of H2 and O2. It is shown that, for both the preximed and nonpremixed configurations, ignition occurs through the effect of heat release on the Arrhenius term of reaction 15, H2O2+M→2OH+M, and expressions were derived that are able to qualitatively predict the relationship between the pressure, temperature, and strain rate at ignition. The difference in ignition temperature between the premixed and nonpremixed configurations is associated with the effect of reactions between H and HO2. For the premixed case, the rate of destruction of H through H+O2+M→HO2+M is much slower due to the lower concentration of O2 in the reaction zone, thus reactions between H and HO2 play a greater role in the ignition process.
Overview of Quantum Wires for Optical Devices

Techniques for fabricating semiconductor quantum wires continue to proliferate and improve, yielding shrinking dimensions and clearer evidence for the sought after quantum confinement effects. However, practical application of quantum wires in optical devices requires that stringent demands must be fulfilled. It is not obvious how soon this will occur. This talk will discuss basic concepts involved in potential optical devices utilizing quantum wires, and how they relate to the goal of achieving practical devices.
Synthesis, structural characterization and dynamic behavior of Group 12 metals containing the sterically hindered ligand [N( t -Bu)CH( t -Bu)CHN- t -Bu] −

Abstract The reaction of two molar equivalents of the alkyl-substituted (E)-4-lithio-1,4-diazabut-1-ene, Li[μ-N(t-Bu)CH(t-Bu)CHN-t-Bu], with zinc dichloride, cadmium dibromide, or mercury dibromide in diethyl ether yields zinc M{[μ-N(t-Bu)CH(t-Bu)CHN-t-Bu][N(t-Bu)CH(t-Bu)CHN-t-Bu]}, [M=Zn (1)], cadmium M[μ-N(t-Bu)CH(t-Bu)CHN-t-Bu]2, [M=Cd (2)], or mercury M{[μ-N(t-Bu)CH(t-Bu)CHN-t-Bu][N(t-Bu)CH(t-Bu)CHN-t-Bu]} [M=Hg (3)], respectively, as colorless crystals. In the solid state, the central metal of 2 possesses a coordination number of four; compounds 1 and 3 display the rather unusual coordination number of three.
The electronic structure of crystalline solids and photoemission spectroscopy: From Einstein to high temperature superconductors

Abstract Band Theory has contributed immensely to our society. Without it we would never have understood semiconductors. Lacking that, the Information Revolution we are presently enjoying would never have occurred. However, is Band Theory sufficient to satisfactorily describe the electronic structure as well as the excitation spectra of all crystalline solids? Do other potential technological revolutions depend on the answer to the primary question? We will restrict our discussion of this question to results from photoemission spectroscopy (PES). PES was formally developed as an experimental technique starting about 1957. However, one can look upon Einstein's and Millikan's photoemission evidence for the photon as the first use of PES. A key physical problem in all photoemission is momentum conservation. The excited electron usually increases its momentum by much more than the momentum lost by the photon it absorbs; thus, there must be coupling to a third body (the crystalline lattice) which recoils in the excitation and in this way conserves momentum. A considerable portion of this paper is dedicated to examining the band theory question and its relation to the nature of the spatial and electronic structure of the photoemitting solid. Examples are given of cases where Band Theory may be insufficient to describe the excitation spectra and, perhaps, electron structure of large classes of crystalline materials. This paper is arranged roughly in a historic manner. It first examines the Einstein's photoemission predictions and shows why for almost four decades this early work established photoemission as only a surface phenomena. The work leading to the realization that bulk photoemission is usually dominant rather than surface photoemission is sketched out. Included is a section showing that if the dominant optical selection rules of Band Theory had applied, Einstein would have been proven wrong in his photoemission predictions. The development of what we now formally call photoemission spectroscopy (PES) starting in the late fifties is outlined. One element in this is the early attempts to use PES to test the limits of Band Theory. Finally, the PES results from a most interesting high temperature superconductor are examined. Here, the question of band theory is central and will be examined using PES studies which are among the most advanced.
A rat model for combined Trypanosoma cruzi and Pneumocystis carinii infection.

Abstract Dexamethasone treated rats inoculated with Trypanosoma cruzi developed acute parasitemia. In addition, these animals concomitantly developed severe Pneumocystis carinii pneumonia (PCP) and died after 4 weeks of immunosuppression (100%). However, immunocompetent (untreated) rats inoculated with T. cruzi did not acquire P. carinii and recovered from T. cruzi infection. Rats immunosuppressed, but not inoculated with T. cruzi, developed only PCP and died 5–6 weeks later (93%). In contrast, immunocompetent or immunocompromized IRC mice infected with T. cruzi all died of acute parasitemia in only 8–12 days with no detectable PCP infection. In conclusion, rats immunosuppressed and T. cruzi inoculated can serve as a MOPPS model for a single drug evaluation. In addition, T. cruzi infection independently does not provoke P. carinii pneumonia in this model. Finally, patients with Chagas» disease treated with corticosteroids may be at risk for PCP and should be considered for chemoprophylaxis.
Macroreticular copolymer bound analogs of phenylmercuric chloride, phenyllithium, and phenyldi--butyltin chloride

Abstract Macroreticular copolymers of styrene and 20% divinylbenzene were functionalized with resin-bound analogs of phenylmercuric chloride, phenyllithium, and phenyldi- n -butyltin chloride at levels lower than 0.05 meq per gram of resin. Resino-phenylmercuric chloride was formed by the reaction of mercuric trifluoroacetate with the resin followed by trifluoroacetate -- chloride exchange. Resino-phenyllithium was formed by the action of n -butyllithium on resino-phenylmercuric chloride and also by direct lithiation using the tetramethylethylenediamine complex of n -butyllithium. Resino-phenyllithium reacted with di- n -butyltin dichloride to form resino-phenyldi- n -butyltin chloride. In this case, relatively large quantities of resino-phenyltri- n -butyltin are also produced as a result of n -butyllithium adsorbed on the reacting polymer.
Competition and Coordination in a Two-Channel Supply Chain

We study competition and coordination in a supply chain in which a single supplier both operates a direct channel and sells its product through multiple differentiated retailers. We study analytically the supply chain with symmetric retailers and find that the supplier prefers to have as many retailers as possible in the market, even if the retailers' equilibrium retail price is lower than that of the supplier, and even if the number of retailers and their cost or market advantage prevent sales through the direct channel. We find that the two-channel supply chain may be subject to inefficiencies not present in the single-channel supply chain. We show that several contracts known to coordinate a single-channel supply chain do not coordinate the two-channel supply chain; thus we propose a linear quantity discount contract and demonstrate its ability to perfectly coordinate the two-channel supply chain with symmetric retailers. We provide some analytical results for the supply chain with asymmetric retailers and propose an efficient solution approach for finding the equilibrium. We find numerically that the supplier still benefits from having more retailers in the market and that linear quantity discount contracts can mitigate supply chain inefficiency, though they no longer achieve perfect coordination.
Use of totally carbon-based preservatives to improve the performance of naturally durable woods

Abstract Demand for naturally durable timbers has encouraged the development of more aggressively managed plantation of species such as teak ( Tectona grandis ) or California coast redwood ( Sequioa sempervirens ). A number of reports suggest that heartwood from some plantation-grown species tends to be less durable than that from naturally grown materials. Developing methods for improving the durability of these species will be important for maintaining their markets. One approach is to supplement the natural durability with colorless organic wood preservatives. In this report, the decay resistance of teak, redwood, and western red cedar sapwood and heartwood samples with and without supplemental treatment with didecyldimethylammonium chloride (DDAC) or 4,5-dichloro-2- N -octyl-4-isothiazolin-3-one (DCOI) was compared with samples treated with alkaline copper quaternary compound (ACQ) and untreated samples. All samples were exposed in a ground proximity test in Hawaii, and the degree of decay was visually assessed every 6 months over a 36-month period. The ACQ treatment generally provided the most protection, but its green color could negatively affect public acceptance of the materials. DDAC and DCOI both improved performance in most sapwood materials, but their effects on heartwood were less clear and a longer evaluation period will be required to determine the benefits of treating heartwood of these species.
Adaptive Video Streaming for Wireless Networks With Multiple Users and Helpers

We consider the design of a scheduling policy for video streaming in a wireless network formed by several users and helpers (e.g., base stations). In such networks, any user is typically in the range of multiple helpers. Hence, an efficient policy should allow the users to dynamically select the helper nodes to download from and determine adaptively the quality level of the requested video segment. In order to obtain a tractable formulation, we follow a “divide and conquer” approach. First, we formulate a network utility maximization (NUM) problem where the network utility function is a concave and component-wise nondecreasing function of the time-averaged users' requested video quality index, and maximization is subject to the stability of all queues in the system. Second, we solve the NUM problem by using a Lyapunov drift plus penalty approach, obtaining a dynamic adaptive scheme that decomposes into two building blocks: 1) adaptive video quality and helper selection (run at the user nodes); and 2) dynamic allocation of the helper-to-user transmission rates (run at the help nodes). Our solution provably achieves NUM optimality in a strong per-sample path sense (i.e., without assumptions of stationarity and ergodicity). Third, we observe that, since all queues in the system are stable, all requested video chunks shall be eventually delivered. Fourth, in order to translate the requested video quality into the effective video quality at the user playback, it is necessary that the chunks are delivered within their playback deadline. This requires that the largest delay among all queues at the helpers serving any given user is less than the pre-buffering time of that user at its streaming session startup phase. In order to achieve this condition with high probability, we propose an effective and decentralized (albeit heuristic) scheme to adaptively calculate the pre-buffering and re-buffering time at each user. In this way, the system is forced to work in the “smooth streaming regime,” i.e., in the regime of very small playback buffer underrun rate. Through simulations, we evaluate the performance of the proposed algorithm under realistic assumptions of a network with densely deployed helper and user nodes, including user mobility, variable bit-rate video coding, and users joining or leaving the system at arbitrary times.
Evidence for the role of alveolar epithelial gp60 in active transalveolar albumin transport in the rat lung.

The alveolar epithelium represents the rate-limiting barrier to solute and fluid transport between the pulmonary capillary lumen and distal air spaces (Schneeberger & Karnovsky, 1971; Gorin et al. 1979; Berthiaume et al. 1989). The liquid in contact with the respiratory surface of alveoli is restricted to a thin layer of epithelial lining fluid (ELF). Type I alveolar epithelial cells regulate the ELF composition and volume, which in turn is important for the maintenance of low alveolar surface tension and efficient gas exchange. Relative to blood plasma, this fluid contains lower Na+ and higher K+ concentrations resulting from the activity of a Na+-K+ ionic pump in the basolateral epithelial membrane (Basset et al. 1987; Goodman et al. 1987; Valeyre et al. 1991; Rutschman et al. 1993; Saumon & Basset, 1993) and from passive Na+ transport through apical Na+ channels (Matalon & O'Brodovich, 1999). The protein concentration in ELF is also found to be lower than that of plasma by a factor of 4 or more depending on the species investigated and methodology employed (Peterson et al. 1990; Peterson et al. 1993; Pusch et al. 1997). Such a steep protein concentration gradient implies the existence of an active transport process for plasma proteins. In this regard, some investigators have recognized the existence of a monensin- and nocodazole-sensitive protein uptake pathway in alveolar epithelium of intact mammalian lungs (Hastings et al. 1994; Wangensteen et al. 1996); however, the quantitative importance of such uptake for overall alveolar protein clearance remains unclear (see review by Folkesson et al. 1996). Active transport of protein molecules across endothelial cells was shown, in some instances, to occur by a receptor-mediated process (Vasile et al. 1983; Ghitescu et al. 1986; Descamps et al. 1996). In the pulmonary microvascular endothelium, albumin bound with high specificity to the 60 kDa albumin-binding glycoprotein (gp60 or albondin) and was shown to activate albumin transcytosis through the endothelium (Schnitzer et al. 1988; Schnitzer, 1992; Tiruppathi et al. 1996; Minshall et al. 2000). Cross-linking of gp60 with an anti-gp60 antibody stimulated endocytosis (as measured by fluorescent styryl pyridinium probes) and albumin uptake (quantified with radiolabelled albumin) in cultured endothelial cells (Tiruppathi et al. 1997; Niles & Malik, 1999; Minshall et al. 2000). As a transcellular albumin transport pathway may also be present in alveolar epithelial cells (Kim et al. 1985), the purpose of the present study was to characterize the albumin clearance mechanism of the alveolar epithelium with particular reference to the possible role of gp60 in regulating albumin transport in the intact lung.
Bounded-observation Kalman filtering of correlation in multivariate neural recordings

A persistent question in multivariate neural signal processing is how best to characterize the statistical association between brain regions known as functional connectivity. Of the many metrics available for determining such association, the standard Pearson correlation coefficient (i.e., the zero-lag cross-correlation) remains widely used, particularly in neuroimaging. Generally, the cross-correlation is computed over an entire trial or recording session, with the assumption of within-trial stationarity. Increasingly, however, the length and complexity of neural data requires characterizing transient effects and/or non-stationarity in the temporal evolution of the correlation. That is, to estimate dynamics in the association between brain regions. Here, we present a simple, data-driven Kalman filter-based approach to tracking correlation dynamics. The filter explicitly accounts for the bounded nature of correlation measurements through the inclusion of a Fisher transform in the measurement equation. An output linearization facilitates a straightforward implementation of the standard recursive filter equations, including admittance of covariance identification via an autoregressive least squares method. We demonstrate the efficacy and utility of the approach in an example of multivariate neural functional magnetic resonance imaging data.
Functional integration of microRNAs into oncogenic and tumor suppressor pathways

A large body of evidence has documented abnormal microRNA (miRNA) expression patterns in diverse human malignancies. Given that miRNA expression is tightly regulated during development and cellular differentiation, aberrant miRNA expression in cancer cells is likely to be in part a consequence of the loss of normal cellular identity that accompanies malignant transformation. Nevertheless, it is now clear that miRNAs function as critical effectors of several canonical oncogenic and tumor suppressor pathways, including those controlled by Myc and p53. Gain- and loss-of-function of these factors in cancer cells contributes to miRNA dysregulation, directly influencing neoplastic phenotypes including cellular proliferation and apoptosis.
Surface electrostatic effects in oligonucleotide microarrays: control and optimization of binding thermodynamics.

We present a theoretical thermodynamic framework for the design of more efficient oligonucleotide microarrays. A general thermodynamic relation is derived to describe the electrostatic surface effects on the binding of the assayed biomolecule to a surface-tethered molecular probe. The relation is applied to analyze how the nucleic acid target, the oligonuleotide probe, and their DNA duplex electrostatic interactions with the surface affect the hybridization on DNA arrays. Taking advantage of a closed form exact solution of the linear Poisson-Boltzmann equation for a charged ion-penetrable sphere in electrolyte solution interacting with a plane wall, we study the effects of the surface and solution conditions. Binding free energy is found as a function of the surface material, dielectric or metal, the surface charge density, linker molecule length, temperature, and added salt content. The charge or electric potential of the dielectric or metal surface, respectively, is shown to dominate the hybridization, especially at low added salt or short linker length. We predict that substantial enhancement of sensitivity, selectivity, and reliability of microarrays can be achieved by control of the surface conditions. As examples, we discuss how to overcome two limitations of current technologies: nonequal sensitivity of the probes with different GC and AT bases content, and poor match/mismatch discrimination. In addition, we suggest the design of microarray conditions where the tested nucleic acid is unfolded, thus making possible the screening of a larger sequence with single nucleotide resolution. These promising findings are discussed and further experimental tests suggested.
A corrected likelihood ratio statistic for the multivariate regression model with antedependent errors

This paper addresses the problem of inference for the antedependence model (Gabriel, 1961, 1962). Antedependence can be formulated as an autoregressive process of general order which is non-stationary in time. Its primary application is in the analysis of repeated measurements data, that is, data consisting of independent replicates of relatively short time series. Our focus is on testing a general linear hypothesis in the context of a multivariate regression model with multivariate normal antedependent errors. Although the relevant likelihood ratio statistic was first presented by Gabriel (1961), the distribution of this statistics has not yet been derived. We present this derivation and show how this result leads to a simple correction factor to improve the x2 approximation of the likelihood ratio statistic.
Multi‐satellite measurements of the substorm injection region

Measurements of energetic particles obtained with a set of three geosynchronous satellites (1977-007, 1981-025, and 1982-019) are used to investigate the substorm injection region and particle drifts for an event on Feb. 3, 1983. A technique has been developed which allows remote sensing of the boundaries of the substorm injection region and the injection time by using measured energy dispersion and modeling particle drifts within the semi-empirical magnetospheric field model of Tsyganenko and Usmanov [1982]. The injection region for this event was found to span 90° around local midnight. The presence of spacecraft on either side of the injection region limit possible errors. Good agreement between long and short drift paths is found for ions while electron measurements give less reliable results.
The information age and agricultural entomology

Bishop Museum, Box 19, 000-A, Honolulu, Hawaii, 96817 USA e-mail: Scottm@bishop.bishop.hawaii.org Prevention and resolution of agricultural entomology problems relies on current and accurate information, part of the overall information on biological diversity. The popular news media provide daily examples of how the information age is rapidly revolutioniz- ing the way information is compiled, managed, and distributed. But what does the infor- mation age mean to agricultural entomology? What lies beyond CD-ROM? Within a few years, farmers in many countries will be able to call up a knowledge base on biological diversity, identify their pest organism, and see what is known about it. Using this same system, they could communicate with farmers in other regions who are struggling with the same pest, or interact with an international research team working on the problem. How will these farmers progress from having no access to telephones to having access to a biodiversity knowledge base? The technologies to provide these services are rapidly be- coming available on a world scale. While these technologies present tremendous oppor- tunities, they also present challenges to the traditional systems of compiling, archiving, and distributing information. Problems Some of the major problems preventing local identifications and systematics research in tropical countries include scarcity of correctly identified reference collections; scattered type and voucher specimens and taxonomic literature, not easily accessible because of physical location, lack of indexing, and language; or inadequacy of communication (Hawksworth & Ritchie, 1993; Miller, in press); and, in some countries, a lack of trained personnel. Solutions Emerging technology, such as distributed networks, can cut through some of these problems, and empower local users to resolve their own problems, as well as to facilitate training. Distributed networks provide each user with a fully functional system able to work independently and the ability to use data from other members of the network. For example, an end user could be simultaneously connected to specimen databases at several herbaria. The system can be designed to make the user feel that he/she is only using one database (e.g., the process of accessing multiple databases is transparent). Internet, the concatenation of networks around the world using TCP/IP commtinica- tions protocols, provides a vehicle for such services (Krol, 1992). Along with mail and file transfer, Internet allows fully interactive communications at great speed and accuracy. Where teleconununications infrastructure is not yet suitable for full Internet, other systems that do not provide interactive access (e.g., store and forward systems) are still useful. There are over 1,500,000 host computers connected to Internet, serving an estimated 15 million individual users-and doubling annually. By mid-1993, 55 countries had opera- Correspondence is encouraged and should be addressed to the Editors.
Can residents learn to be good doctors without harming patients

One of Dr. Richard Vilter's former residents mustered his courage, approached Dr. Vilter and asked "Dr. Vilter, you are such a marvelous clinician. To what do you attribute your success?" Vilter replied "Good judgment." The questioner thought for a moment and, not completely satisfied with the response, asked, "But Dr. Vilter, to what do you attribute your good judgment?" Vilter replied: "Experience." Still not satisfied, the questioner pursued it one step further. "But Dr. Vilter, how does one gain experience?" Vilter's response: "Bad judgment." 1 .
William Gibson's Paternity Test

Contemporary culture views DNA through a strange temporal logic: on the one hand, technologies of DNA identification and sequencing testify to fundamental transformations in the way we understand biology, anthropology, law, and medicine—we live in "the DNA age"; and on the other, these technologies have revealed as much about the past as they have about the present or future, gesturing backwards to scenes of conception, crime, and evolutionary branching. The essay shows how this double temporal logic operates within William Gibson's electronic poem Agrippa. It concludes that the poem's stanzas form a metaphorical DNA fingerprint that reveals Gibson's life to be, paradoxically, a novel repetition of his father's and grandfather's lives.
Lead poisoning and brain tumors in children: a report of 2 cases.

Lead poisoning and subclinical body lead elevations have become increasingly widespread findings in children, not only in the inner cities but in the suburbs and rural areas as well. This paper reports on 2 institutionalized children with elevated urinary lead levels who subsequently developed astrocytomas. Lead toxicity may play a role in causing mental retardation, hyperactivity, and more subtle neuropsychological dysfunction in children. It has been shown to have a direct toxic effect on neurons, causing astrocytic proliferation in humans and central nervous system neoplasms in rats.
Deposition of Ag ions and neutral atoms on ZnSe(100): Influence of interface morphology on Schottky-barrier formation.

Ag overlayers were grown on ZnSe(100) by thermal evaporation and by a new approach using partially ionized beams. For the latter, \ensuremath{\sim}4% of the atoms were ionized and accelerated to an energy of 300--400 eV, thus making it possible to vary the amount of surface disruption. Interface evolution was monitored with photoemission and low-energy electron diffraction. No disruption of the ZnSe surface was found for thermal evaporation, and three-dimensional growth was observed. For ion deposition, three-dimensional growth was again observed, but there was clear evidence of substrate disruption. Parallel measurements of band-bending changes show that the barrier height is the same to within 100 meV for neutral-atom and ion deposition, despite differences in interface morphology.
Critiquing the city, envisioning the country: Shen Congwen’s urban fiction

The essay studies Shen Congwen’s urban fictions in the literary contexts of his native-soil fiction and contemporary urban fiction by the Shanghai school in modern Chinese literature. It argues that Shen Congwen’s urban and rural writings demonstrate a profound irony: his perception of the disappearing rural idyllic and his panoramic representation are achieved through a modern sensibility as well as his disenchantment with the city, while his urban imagining/representation betrays an agrarianist distrust of the city, part of an age-old anti-urban Confucian thinking. His ambivalent attitude towards modernity also betrays a sense of loss in terms of his historical position regarding how to understand fundamental changes of his time as epitomized by the city. Nevertheless, Shen’s urban fiction has registered the initial efforts in modern Chinese literature in coming to grips of the modern city as it was emerging from its traditional form to become the locus of modernity and site of fundamental socioeconomic and cultural transformation.
Perturbation analysis of communication networks with feedback control using stochastic hybrid models

Abstract Communication networks may be abstracted through Stochastic Fluid Models (SFM) with the node dynamics described by switched flow equations as various events take place, thus giving rise to hybrid automaton models with stochastic transitions. The inclusion of feedback mechanisms complicates these dynamics. In a tandem setting, a typical feedback mechanism is the control of a node processing rate as a threshold-based function of the downstream node’s buffer level. We consider the problem of controlling the threshold parameters so as to optimize performance metrics involving average workload and packet loss and show how Infinitesimal Perturbation Analysis (IPA) can be used to analyze congestion propagation through a network and develop gradient estimators of such metrics.
Sex differences in children's discrepant perceptions of peer acceptance

Abstract Sex differences in children's play patterns during middle childhood are thought to promote greater awareness of social acceptance among girls compared with boys. The present study posited that girls are more discerning of peer acceptance than are boys; however, these sex differences were predicted to vary depending on how discrepant perceptions were assessed (i.e., inaccuracy versus bias). Additional differences were expected if children perceived acceptance by same- versus opposite-sex peers. Participants were 912 third through fifth graders (420 girls and 492 boys). Consistent with predictions, boys were more inaccurate than girls, but only for perceived acceptance by same-sex peers. As expected, girls were more negatively biased than boys, but only for perceived acceptance by opposite-sex peers. Results did not support the hypothesis that boys have more positively biased perceptions of peer acceptance than girls. Overall, these findings raise important issues regarding the evaluation of children's discrepant self-perceptions of peer acceptance.
Limit Theorem on the Self-Normalized Range for Weakly and Strongly Dependent Process

R is a range and Q a self-normalized range. For certain r.f. X(t), one can select the weight function A(d; Q), so that (in some sense) the d ~ limit of either Q (d)/A (d; Q) or Q (e ~ d)/A (e* d; Q) is nondegenerate; if so, A (d; Q) is the key factor in a new statistical technique, called R/S analysis. The theorems in this paper describe some aspects that have already been founded fully upon theorems (easy to prove but unexpected) concerning weak convergence of certain r.f., while the conjectures relate to other aspects of R/S analysis that still rely, at this stage, upon properties suggested by heuristics and by computer simulation. For iid processes satisfying E X 2 < ~:), or attracted to a stable process of exponent ~, it is shown that A = l /~ independently of a. For processes that are weakly dependent (e.g., Markov or autoregressive) one still has A = v/d. Conversely, whenever A = V ~, the r.f. X (t) will be said to have a finite R/S memory. On the other hand, if X(t) are the finite increments of a proper fractional Brownian m o t i o n defined as the fractional integral of order H 0 . 5 : ~ 0 of ordinary Brownian m o t i o n o n e has A = d n. This X(t) is strongly d e p e n d e n t rather than strongly m i x i n g a n d it can be said to have an infinite memory. Conversely, whenever A#]//d, the r.f. X(t) will be said to have an infinite R/S memory. When A = d n L(d), with H ~ 0.5 and
RecQ Helicase Stimulates Both DNA Catenation and Changes in DNA Topology by Topoisomerase III

Together, RecQ helicase and topoisomerase III (Topo III) of Escherichia coli comprise a potent DNA strand passage activity that can catenate covalently closed DNA (Harmon, F. G., DiGate, R. J., and Kowalczykowski, S. C. (1999) Mol. Cell 3, 611-620). Here we directly assessed the structure of the catenated DNA species formed by RecQ helicase and Topo III using atomic force microscopy. The images show complex catenated DNA species involving crossovers between multiple double-stranded DNA molecules that are consistent with full catenanes. E. coli single-stranded DNA-binding protein significantly stimulated both the topoisomerase activity of Topo III alone and the DNA strand passage activity of RecQ helicase and Topo III. Titration data suggest that an intermediate of the RecQ helicase unwinding process, perhaps a RecQ helicase-DNA fork, is the target for Topo III action. Catenated DNA is the predominant product under conditions of molecular crowding; however, we also discovered that RecQ helicase and single-stranded DNA-binding protein greatly stimulated the intramolecular strand passage ("supercoiling") activity of Topo III, as revealed by changes in the linking number of uncatenated DNA. Together our results demonstrate that RecQ helicase and Topo III function together to comprise a potent and concerted single-strand DNA passage activity that can mediate both catenation-decatenation processes and changes in DNA topology.
Revisiting McCallum's Border Puzzle

The “border effect” in international trade refers to a situation in which there is higher volume of trade within a country compared with the volume of trade across the country's borders. Although t...
Layered representations for vision and video

Human vision, machine vision, and image coding, each demand representations that are useful and efficient. The best-established techniques today are based on low-level processing. Future systems for image analysis and image coding will increasingly use image representations that involve such concepts as surfaces, lighting, transparency, etc. These representations fall in the domain of "mid-level" vision, and there is accumulating evidence of their importance in human vision. By representing images with these more sophisticated vocabularies we can increase the flexibility and efficiency of our vision and image coding systems. We are developing systems that decompose image sequences into overlapping layers, rather like the "cels" used by a traditional animator. These layers are ordered in depth, sliding over one another and being combined according to the rules of transparency and occlusion. Using the layered representation we can achieve greatly improved motion analysis and image segmentation. By applying layers to image coding we can achieve data compression far better than MPEG, and achieve frame-rate independence as a side benefit. Moreover, the image sequence is decomposed in a meaningful way, which allows flexible image editing and access.
The Response of Custodial Care Networks to the Needs of Custodial Grandparents and their Adult Children: A Framework Based on Four Caregiving Situations

ABSTRACT The quality of the relationship between custodial grandparents or kin caregivers and the biological parent may have an affect on the ability of kin care or, “grandfamilies,” to obtain help from social and educational services, including child welfare, and to provide a safe living arrangement for the child. The custodial care network consists of the biological parent, custodial grandparent(s), friends, other relatives, educational institutions, and social service organizations. The authors of this paper present a theoretical framework for assessing and addressing the ability of the custodial care network to help children in custodial care homes. Using questions that have been posed by custodial grandparents in a statewide, “relatives as parents program,” in West Virginia, as evidence of need for information and assistance, the framework addresses four custodial care situations and makes suggestions for family preparation as well as resource development by social service and educational personnel. ...
An expanded multilocus phylogeny does not resolve morphological species within the small-spored Alternaria species complex

Small-spored Alternaria species are a taxo- nomically challenging group of fungi with few morphological or molecular characters that allow unambiguous discrimination among taxa. The pro- tein-coding genes most commonly employed in fungal systematics are invariant among these taxa, so noncoding, anonymous regions of the genome were developed to assess evolutionary relationships among these organisms. Nineteen sequence-characterized amplified regions (SCAR) were screened for phylo- genetic utility by comparing sequences among refer- ence isolates of small-spored Alternaria species. Five of nineteen loci were consistently amplifiable and had sufficient phylogenetic signal. Phylogenetic analyses were performed with 150 small-spored Alternaria isolates using sequence data from an endopolygalac- turonase gene and two anonymous loci. Associations among phylogenetic lineage, morphological classifi- cation, geography and host were evaluated for use as practical taxonomic characters. Samples included isolates from citrus in Florida, pistachio in California, desert plants in Arizona, walnuts in France/Italy and apples in South Africa. No associations were found between host or geographic associations and phylo- genetic lineage, indicating that these characters were not useful for cladistic classification of small-spored Alternaria. Similarly strict congruence between mor- phology and phylogenetic lineage was not found among isolates grouped morphologically with A. alternata or A. tenuissima. In contrast 34 isolates grouped morphologically with A. arborescens fell into discrete clades for all datasets. Although 5-9 well supported clades were evident among isolates, it is currently unclear if these clades should be considered phylogenetic species or emerging evolutionary line-
In-situ nanomechanical studies of carbon nanotube bundles

Hybrid carbon nanotubes represent a distinctive platform for nanoresonator-based detection of fundamental phenomena and the development of multifunctional sensors. The resonant mechanical properties of single-walled carbon nanotube bundles are reported. Resonant frequencies ranging from 0.2 to 9 MHz were observed. Quality factors of resonances varied from 77 to 800. An experimental effective bundle Young's modulus of E*=76/spl plusmn/4 GPa is extracted. Onset of nonlinear response was observed at large oscillations. Electron beam-induced structural changes were also observed. We discuss these data with respect to reported literature values and structural issues intrinsic to the system.
Impact of Preoperative Staging and Chemoradiation Versus Postoperative Chemoradiation on Outcome in Patients With Rectal Cancer: A Decision Analysis

Background: Although radical resection and postoperative chemoradiation have been the standard therapy for patients with rectal cancer, preoperative staging by local imaging and chemoradiation are widely used. We used a decision analysis to compare the two strategies for rectal cancer management. Methods: We developed a decision model to compare survival outcomes after postoperative chemoradiation versus preoperative staging and chemoradiation in patients aged 70 years with resectable rectal cancer. In the postoperative chemoradiation strategy, patients undergo radical resection and receive postoperative chemoradiation. In the preoperative staging and chemoradiation strategy, patients with locally advanced cancer receive preoperative chemoradiation and radical resection, whereas those with amenable localized tumors undergo local excision. The cohorts of patients were entered into a Markov model incorporating age-adjusted and disease-specific mortality. Outcomes were evaluated by modeling 5-year disease-specific survival for preoperative chemoradiation as less than, equal to, or greater than that of postoperative chemoradiation. Base‐case probabilities were derived from published data; the Surveillance, Epidemiology, and End Results (SEER) Program database; and U.S. Life Tables. One-way and two-way sensitivity analyses were performed. The outcome measures were life expectancy and quality-adjusted life expectancy. Results: Life expectancy and quality-adjusted life expectancy were 9.72 and 8.72 years, respectively, in the postoperative chemoradiation strategy. In the preoperative staging and chemoradiation strategy, life expectancy was 9.36, 9.72, and 10.09 years and quality-adjusted life expectancy was 8.71, 9.04, and 9.37 years when 5-year disease-specific survival was less than, equal to, or greater than that of postoperative chemoradiation, respectively. The decision model was sensitive to differences in the long-term toxicity of pre- and postoperative chemoradiation. When the 5-year disease-specific survival for patients after pre- or postoperative chemoradiation was equal, the decision model was sensitive to surgical mortality and to the probability of residual lymph node disease after local excision. Conclusion: If efficacy and toxicity after preoperative chemoradiation are equal to or better than that after postoperative chemoradiation in patients with locally advanced rectal cancer, then preoperative staging to select patients appropriate for preoperative chemoradiation is beneficial. [J Natl Cancer Inst 2004;96:191‐201]
A Mucin-type O-Glycosyltransferase Modulates Cell Adhesion during Drosophila Development

Cell-cell and cell-matrix adhesion are crucial during many stages of eukaryotic development. Here, we provide the first example that mucin-type O-linked glycosylation is involved in a developmentally regulated cell adhesion event in Drosophila melanogaster. Mutations in one member of the evolutionarily conserved family of enzymes that initiates O-linked glycosylation alter epithelial cell adhesion in the Drosophila wing blade. A transposon insertion mutation in pgant3 or RNA interference to pgant3 resulted in blistered wings, a phenotype characteristic of genes involved in integrin-mediated cell interactions. Expression of wild type pgant3 in the mutant background rescued the wing blistering phenotype, whereas expression of another family member (pgant35A) did not, revealing a unique requirement for pgant3. pgant3 mutants displayed reduced O-glycosylation along the basal surface of larval wing imaginal discs, which was restored with wild type pgant3 expression, suggesting that reduced glycosylation of basal proteins is responsible for disruption of adhesion in the adult wing blade. Glycosylation reactions demonstrated that PGANT3 glycosylates certain extracellular matrix (ECM) proteins. Immunoprecipitation experiments revealed that PGANT3 glycosylates tiggrin, an ECM protein known to bind integrin. We propose that this glycosyltransferase is uniquely responsible for glycosylating tiggrin in the wing disc, thus modulating proper cell adhesion through integrin-ECM interactions. This study provides the first evidence for the role of O-glycosylation in a developmentally regulated, integrin-mediated, cell adhesion event and reveals a novel player in wing blade formation during Drosophila development.
Rhinovirus 3C protease precursors 3CD and 3CD' localize to the nuclei of infected cells.

Human rhinovirus (HRV) 3C protease (3Cpro) plays several important roles in the virus replication cycle. This enzyme cleaves the viral polyprotein at discrete sites to produce mature viral proteins and also inhibits cellular RNA transcription. It is not clear, however, whether the observed transcriptional shutoff activities are due to 3Cpro itself or to 3Cpro-containing precursors, and where 3Cpro exerts its effects within infected cells. To address these questions HeLa cells were infected with HRV-16, stained with polyclonal antibodies directed against 3Cpro and then analysed by laser confocal microscopy. Proteins containing 3Cpro accumulated in nuclei 2–4 h post-infection, and progressively increased in the cytoplasm. Analyses of subcellular extracts demonstrated that 3CD′, a minor component among 3Cpro precursors, gave rise to the earliest 3Cpro nuclear signals. Mature 3Cpro and another 3Cpro precursor, 3CD, were also detected in the nucleus, cytoplasm and perinuclear membrane fractions 4 h post-infection. Transfecting cells with 3Cpro, 3CD precursor and 3CDΔ371 (with deletion of 371 aa at the carboxyl terminus of 3D) demonstrated that the nucleolar localization signal was near the amino terminus of 3D. In addition, 3Cpro precursors were found to co-localize in nuclei with the transcription factor OCT-1 and the nucleolar chaperone B23. Finally, it was demonstrated that HRV-16 3Cpro, 3CD and 3CDΔ371 could cleave OCT-1. Collectively, these findings suggest that HRV 3CD′ and/or 3CD are specifically localized to the nucleoli of infected cells during the early stage of infection, and contribute to the inhibition of cellular RNA transcription via a proteolytic mechanism.
The Soul of Evolution

Stephen Jay Gould. Evolution and Human Equality. Cambridge, Mass.: Insight Video, 875 Main Street, Cambridge, Mass. 02139. Available in VHS, BETA I, II; Running Time: 42 minutes; $200.
Urinary and Anal Incontinence in African American Teenaged Gravidas during Pregnancy and the Puerperium

Study Objective: To determine the prevalence of urinary and anal incontinence during pregnancy and im- mediately postpartum in a convenience sample of African American teenaged women in an urban setting and to assess for an association between this incontinence and obstetrical risk factors. Methods: 74 African American adolescents, ages 14e19, participated in the study. During third trimester prenatal visits and at 6 weeks postpartum, participants com- pleted the Wexner Continence Grading Scale and Urogeni- tal Distress Inventory Short Form (UDI-6). Chart abstraction was conducted for other relevant history. Results: Seventy-eight percent (58/74) of the adolescents were followed for the duration of the study; 22% were lost to follow-up. Incontinence was defined by a positive re- sponse on either questionnaire, irrespective of severity. In the third trimester, 44% of patients complained of urinary urge incontinence and 43% of stress incontinence; 12% complained of fecal and 41% of flatal incontinence. At six weeks postpartum, only 9% complained of urge incon- tinence and 5% of stress symptoms. Similarly, fecal incon- tinence decreased to 4% and flatal incontinence to 9%. Postpartum, the rate of flatal incontinence in the women who underwent instrumental deliveries was significantly increased when compared to those who had a spontaneous vaginal delivery or cesarean section (OR 12, P 5 0.04). Conclusion: Urinary and anal incontinence is present in this convenience sample of pregnant African American teenagers and should be addressed during pregnancy and the puerperium. Instrumental delivery significantly increased the risk of flatal incontinence postpartum in this population.