bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparative Study of Distributed Learning Environments on Learning Outcomes
Authors: Alavi Maryam , Marakas George M. , Yoo Youngjin
Published: November 2005

Advances in information and communication technologies have fueled rapid growth in the popularity of technology-supported distributed learning (DL). Many educational institutions, both academic and corporate, have undertaken initiatives that leverage the myriad of available DL technologies. Despite their rapid growth in popularity, however, alternative technologies for DL are seldom systematically evaluated for learning efficacy. Considering the increasing range of information and communication technologies available for the development of DL environments, we believe it is paramount for studies to compare the relative learning outcomes of various technologies.

In this research, we employed a quasi-experimental field study approach to investigate the relative learning effectiveness of two collaborative DL environments in the context of an executive development program. We also adopted a framework of hierarchical characteristics of group support system (GSS) technologies, outlined by DeSanctis and Gallupe (1987), as the basis for characterizing the two DL environments.

One DL environment employed a simple e-mail and listserv capability while the other used a sophisticated GSS (herein referred to as Beta system). Interestingly, the learning outcome of the e-mail environment was higher than the learning outcome of the more sophisticated GSS environment. The post-hoc analysis of the electronic messages indicated that the students in groups using the e-mail system exchanged a higher percentage of messages related to the learning task. The Beta system users exchanged a higher level of technology sense-making messages. No significant difference was observed in the students' satisfaction with the learning process under the two DL environments.
Potential Research Space in MIS: A Framework for Envisioning and Evaluating Research Replication, Extension, and Generation
Authors: Berthon Pierre , Pitt Leyland , Ewing Michael , Carr Christopher L.
Published: November 2005

Replications are an important component of scientific method in that they convert tentative belief to accepted knowledge. Given the espoused importance of replications to the extraction of knowledge from research, there is surprisingly little evidence of its practice or discussion of its importance in the management information systems literature. In this article we develop a framework within which to systematize the conceptualization of replications; we review and illustrate how some key information systems research fits into the framework and examine the factors that influence the selection of a research strategy. Our framework includes a conceptualization of the relationship among replication, extension, and generation in IS research. The concept of “research space” is defined and a framework is developed that delineates eight possible research strategies. Finally, the benefits of our framework to salient stakeholders in the research process are outlined.
Research Report: Intrafirm Resource Allocation with Asymmetric Information and Negative Externalities
Authors: Nadiminti Raja , Mukhopadhyay Tridas , Kriebel Charles H.
Published: November 2005

We examine the intrafirm resource allocation problem with the following characteristics. The resource exhibits negative externalities, and the benefit of using the resource is known only to the user department and not to top management or other user departments. In addition, the consumption of the resource depends upon the choice of the mechanism for allocating the resource. For this problem, we derive a two-stage mechanism, and show that this proposed mechanism leads to optimal allocation.
A Fast Cross-Entropy Method for Estimating Buffer Overflows in Queueing Networks
Authors: de Boer P. T. , Kroese D. P. , Rubinstein R. Y.
Published: November 2005

In this paper, we propose a fast adaptive importance sampling method for the efficient simulation of buffer overflow probabilities in queueing networks. The method comprises three stages. First, we estimate the minimum cross-entropy tilting parameter for a small buffer level; next, we use this as a starting value for the estimation of the optimal tilting parameter for the actual (large) buffer level. Finally, the tilting parameter just found is used to estimate the overflow probability of interest. We study various properties of the method in more detail for the M/M/1 queue and conjecture that similar properties also hold for quite general queueing networks. Numerical results support this conjecture and demonstrate the high efficiency of the proposed algorithm.
Random Walks and Sustained Competitive Advantage
Authors: Denrell Jerker
Published: November 2005

Strategy is concerned with sustained interfirm profitability differences. Observations of such sustained differences are often attributed to unobserved systematic a priori differences in firm characteristics. This paper shows that sustained interfirm profitability differences may be very likely even if there are no a priori differences among firms. As a result of the phenomenon of long leads in random walks, even a random resource accumulation process is likely to produce persistent resource heterogeneity and sustained interfirm profitability differences. A Cournot model in which costs follow a random walk shows that such a process could produce evidence of substantial persistence of profitability. The results suggest that persistent profitability does not necessarily provide strong evidence for systematic a priori differences among firms. Nevertheless, since the phenomenon of long leads is highly unrepresentative of intuitive notions of random sequences, such evidence may still be persuasive.
Pricing and Priority Auctions in Queueing Systems with a Generalized Delay Cost Structure
Authors: Afèche Philipp , Mendelson Haim
Published: November 2005

This paper studies alternative price-service mechanisms for a provider that serves customers whose delay cost depends on their service valuations. We propose a generalized delay cost structure that augments the standard additive model with a multiplicative component, capturing the interdependence between delay cost and values. We derive and compare the revenue-maximizing and socially optimal equilibria under uniform pricing, preemptive, and nonpreemptive priority auctions with an admission price. We find that the delay cost structure has a paramount effect on system behavior. The classical result that the revenue-maximizing admission price is higher and the utilization lower than is socially optimal can be reversed under our generalized structure, and we identify the conditions driving this reversal under each mechanism. We show that the conditional bid equilibria are unique and induce the socially optimal allocations. The auctions yield gains in system net value and provider profit over uniform pricing, which are dramatically larger for the preemptive mechanism. Both auctions perform better under multiplicative compared to additive delay costs. The highest-value customers always gain under the preemptive, but may lose under the nonpreemptive auction. The lowest-value customers always gain in either auction.
Modeling Daily Arrivals to a Telephone Call Center
Authors: Avramidis Athanassios N. , Deslauriers Alexandre , L'Ecuyer Pierre
Published: November 2005

We develop stochastic models of time-dependent arrivals, with focus on the application to call centers. Our models reproduce three essential features of call center arrivals observed in recent empirical studies: a variance larger than the mean for the number of arrivals in any given time interval, a time-varying arrival intensity over the course of a day, and nonzero correlation between the arrival counts in different periods within the same day. For each of the new models, we characterize the joint distribution of the vector of arrival counts, with particular focus on characterizing how the new models are more flexible than standard or previously proposed models. We report empirical results from a study on arrival data from a real-life call center, including the essential features of the arrival process, the goodness of fit of the estimated models, and the sensitivity of various simulated performance measures of the call center to the choice of arrival process model.
Valuation of Commodity-Based Swing Options
Authors: Jaillet Patrick , Ronn Ehud I. , Tompaidis Stathis
Published: November 2005

In the energy markets, in particular the electricity and natural gas markets, many contracts incorporate flexibility-of-delivery options known as “swing” or “take-or-pay” options. Subject to daily as well as periodic constraints, these contracts permit the option holder to repeatedly exercise the right to receive greater or smaller amounts of energy. We extract market information from forward prices and volatilities and build a pricing framework for swing options based on a one-factor mean-reverting stochastic process for energy prices that explicitly incorporates seasonal effects. We present a numerical scheme for the valuation of swing options calibrated for the case of natural gas.
50th Anniversary Article: Stochastic Simulation Research in Management Science
Authors: Nelson Barry L.
Published: November 2005

When the simulation department of Management Science was created in 1978 it ushered in an era of significant methodological advances in stochastic simulation. However, the foundation for the field—not just the work that has been published in Management Science—was provided by two papers published long before simulation had its own department in the journal. We will review the seminal papers of Conway, Johnson, and Maxwell (1959) and Conway (1963), and then trace their impact through eight award-winning papers that appeared much later in Management Science.
Eliminating Public Knowledge Biases in Information-Aggregation Mechanisms
Authors: Chen Kay-Yut , Fine Leslie R. , Huberman Bernardo A.
Published: November 2005

We present a novel methodology for identifying public knowledge and eliminating the biases it creates when aggregating information in small group settings. A two-stage mechanism consisting of an information market and a coordination game is used to reveal and adjust for individuals' public information. A nonlinear aggregation of their decisions then allows for the calculation of the probability of the future outcome of an uncertain event, which can then be compared to both the objective probability of its occurrence and the performance of the market as a whole. Experiments show that this nonlinear aggregation mechanism outperforms both the imperfect market and the best of the participants.
Markov Perfect Equilibrium Advertising Strategies of Lanchester Duopoly Model: A Technical Note
Authors: Jarrar Ramla , Martín-Herrán Guiomar , Zaccour Georges
Published: November 2005

We propose a numerical approach to compute stationary Markov perfect Nash equilibrium advertising strategies of the Lanchester model. The algorithm can be implemented using a standard mathematical package, and, importantly, it does not require that the players discount their future earnings at a zero rate, an assumption that has been made in the literature.
Migration from a Mitogenic Niche Promotes Cell-Cycle Exit
Authors: Choi Yoojin , Borghesani Paul R. , Chan Jennifer A. , Segal Rosalind A.
Published: November 2005

During development, neural precursors proliferate in one location and migrate to the residence of their mature function. The transition from a proliferative stage to a migratory stage is a critical juncture; errors in this process may result in tumor formation, mental retardation, or epilepsy. This transition could be the result of a simple sequential process in which precursors exit the cell cycle and then begin to migrate or a dynamically regulated process in which migration away from a mitogenic niche induces precursors to exit the cell cycle. Here, we show, usingin vivoandin vitroapproaches, that granule cell precursors proliferate when they are exposed to the microenvironment of the external granule cell layer (EGL) and exit the cell cycle as a result of migrating away from this environment.In vivo, granule cell precursors that remain in the EGL because of impaired migration continue to proliferate in the mitogenic niche of the EGL.In vitro, granule cell precursors that are introduced into an organotypic cerebellar slice proliferate preferentially in the EGL. We identify Sonic Hedgehog as a critical component of the EGL mitogenic niche. Together, these data indicate that migration away from a mitogenic niche promotes transition from a proliferative to a nonproliferative, migratory stage.
Kinetics and Spontaneous Open Probability Conferred by the ϵ Subunit of the GABAAReceptor
Authors: Wagner David A. , Goldschen-Ohm Marcel P. , Hales Tim G. , Jones Mathew V.
Published: November 2005

GABAAreceptors mediate synaptic and extrasynaptic inhibition. Native receptors consist of α and β subunits, which are required for function, and another “modulatory” subunit, for example, γ, δ, or ϵ. Of these, the ϵ subunit has the most restricted distribution, confers resistance to neurosteroid and anesthetic modulation, and causes spontaneous channel opening. Little is known, however, about how ϵ affects receptor kinetics, which in turn shape responses to both ambient and synaptic GABA exposure. Here, we expressed human α2β1, α2β1γ2, or α2β1ϵ subunit combinations in human embryonic kidney 293 cells and used rapid solution exchange to study receptor kinetics in outside-out patches. The ϵ subunit greatly slowed deactivation and recovery after brief GABA pulses. During long, saturating GABA pulses, the rate of desensitization was slower for α2β1ϵ and α2β1γ2 than for α2β1. However, in α2β1ϵ, the final extent of desensitization was large compared with that of α2β1γ2. Responses in α2β1ϵ, but not the others, were often followed by an “overshoot” above the baseline, suggesting that a fraction of channels are spontaneously open and are transiently silenced by receptor activation and subsequent desensitization. The baseline current and associated noise were reduced by picrotoxin, revealing that ϵ-containing channels are open ∼4% of the time in the absence of GABA. These results suggest that, if ϵ-containing receptors are expressed at synapses, the synaptic currents would be long-lasting but may rundown quickly under high-frequency activation. In addition, silencing of spontaneous openings by desensitization raises the possibility that tonic inhibition mediated by ϵ-containing receptors may be regulated by phasic inhibition.
Gephyrin Regulates the Cell Surface Dynamics of Synaptic GABAAReceptors
Authors: Jacob Tija C. , Bogdanov Yury D. , Magnus Christopher , Saliba Richard S. , Kittler Josef T. , Haydon Philip G. , Moss Stephen J.
Published: November 2005

The efficacy of fast synaptic inhibition is critically dependent on the accumulation of GABAAreceptors at inhibitory synapses, a process that remains poorly understood. Here, we examined the dynamics of cell surface GABAAreceptors using receptor subunits modified with N-terminal extracellular ecliptic pHluorin reporters. In hippocampal neurons, GABAAreceptors incorporating pHluorin-tagged subunits were found to be clustered at synaptic sites and also expressed as diffuse extrasynaptic staining. By combining FRAP (fluorescence recovery after photobleaching) measurements with live imaging of FM4-64-labeled active presynaptic terminals, it was evident that clustered synaptic receptors exhibit significantly lower rates of mobility at the cell surface compared with their extrasynaptic counterparts. To examine the basis of this confinement, we used RNAi to inhibit the expression of gephyrin, a protein shown to regulate the accumulation of GABAAreceptors at synaptic sites. However, whether gephyrin acts to control the actual formation of receptor clusters, their stability, or is simply a global regulator of receptor cell surface number remains unknown. Inhibiting gephyrin expression did not modify the total number of GABAAreceptors expressed on the neuronal cell surface but significantly decreased the number of receptor clusters. Live imaging revealed that clusters that formed in the absence of gephyrin were significantly more mobile compared with those in control neurons. Together, our results demonstrate that synaptic GABAAreceptors have lower levels of lateral mobility compared with their extrasynaptic counterparts, and suggest a specific role for gephyrin in reducing the diffusion of GABAAreceptors, facilitating their accumulation at inhibitory synapses.
Dopamine Modulation of State-Dependent Endocannabinoid Release and Long-Term Depression in the Striatum
Authors: Kreitzer Anatol C. , Malenka Robert C.
Published: November 2005

Endocannabinoids are important mediators of short- and long-term synaptic plasticity, but the mechanisms of endocannabinoid release have not been studied extensively outside the hippocampus and cerebellum. Here, we examined the mechanisms of endocannabinoid-mediated long-term depression (eCB-LTD) in the dorsal striatum, a brain region critical for motor control and reinforcement learning. Unlike other cell types, strong depolarization of medium spiny neurons was not sufficient to yield detectable endocannabinoid release. However, when paired with postsynaptic depolarization sufficient to activate L-type calcium channels, activation of postsynaptic metabotropic glutamate receptors (mGluRs), either by high-frequency tetanic stimulation or an agonist, induced eCB-LTD. Pairing bursts of afferent stimulation with brief subthreshold membrane depolarizations that mimicked down-state to up-state transitions also induced eCB-LTD, which not only required activation of mGluRs and L-type calcium channels but also was bidirectionally modulated by dopamine D2receptors. Consistent with network models, these results demonstrate that dopamine regulates the induction of a Hebbian form of long-term synaptic plasticity in the striatum. However, this gating of plasticity by dopamine is accomplished via an unexpected mechanism involving the regulation of mGluR-dependent endocannabinoid release.
Silencing Primary Dystonia: Lentiviral-Mediated RNA Interference Therapy for DYT1 Dystonia
Authors: Gonzalez-Alegre Pedro , Bode Nicole , Davidson Beverly L. , Paulson Henry L.
Published: November 2005

DYT1 is the most common inherited dystonia. Currently, there are no preventive or curative therapies for this dominantly inherited disease. DYT1 dystonia is caused by a common three-nucleotide deletion in theTOR1Agene that eliminates a glutamic acid residue from the protein torsinA. Recent studies suggest that torsinA carrying the disease-linked mutation, torsinA(ΔE) acts through a dominant-negative effect by recruiting wild-type torsinA [torsinA(wt)] into oligomeric structures in the nuclear envelope. Therefore, suppressing torsinA(ΔE) expression through RNA interference (RNAi) could restore the normal function of torsinA(wt), representing a potentially effective therapy regardless of the biological role of torsinA. Here, we have generated short hairpin RNAs (shRNAs) that mediate allele-specific suppression of torsinA(ΔE) and rescue cells from its dominant-negative effect, restoring the normal distribution of torsinA(wt). In addition, delivery of this shRNA by a recombinant feline immunodeficiency virus effectively silenced torsinA(ΔE) in a neural model of the disease. We further establish the feasibility of this viral-mediated RNAi approach by demonstrating significant suppression of endogenous torsinA in mammalian neurons. Finally, this silencing of torsinA is achieved without triggering an interferon response. These results support the potential use of viral-mediated RNAi as a therapy for DYT1 dystonia and establish the basis for preclinical testing in animal models of the disease.
Neural Activity in Macaque Parietal Cortex Reflects Temporal Integration of Visual Motion Signals during Perceptual Decision Making
Authors: Huk Alexander C. , Shadlen Michael N.
Published: November 2005

Decision-making often requires the accumulation and maintenance of evidence over time. Although the neural signals underlying sensory processing have been studied extensively, little is known about how the brain accrues and holds these sensory signals to guide later actions. Previous work has suggested that neural activity in the lateral intraparietal area (LIP) of the monkey brain reflects the formation of perceptual decisions in a random dot direction-discrimination task in which monkeys communicate their decisions with eye-movement responses. We tested the hypothesis that decision-related neural activity in LIP represents the time integral of the momentary motion “evidence.” By briefly perturbing the strength of the visual motion stimulus during the formation of perceptual decisions, we tested whether this LIP activity reflected a persistent, integrated “memory” of these brief sensory events. We found that the responses of LIP neurons reflected substantial temporal integration. Brief pulses had persistent effects on both the monkeys' choices and the responses of neurons in LIP, lasting up to 800 ms after appearance. These results demonstrate that LIP is involved in neural time integration underlying the accumulation of evidence in this task. Additional analyses suggest that decision-related LIP responses, as well as behavioral choices and reaction times, can be explained by near-perfect time integration that stops when a criterion amount of evidence has been accumulated. Temporal integration may be a fundamental computation underlying higher cognitive functions that are dissociated from immediate sensory inputs or motor outputs.
Triploid and Diploid Rainbow Trout Do Not Differ in Their Stress Response to Transportation
Authors: Leggatt Rosalind A , Scheer Ken W , Afonso Luis O B , Iwama George K
Published: November 2005

We examined the neuroendocrine and cellular stress responses of diploid and triploid rainbow trout Oncorhynchus mykiss to transportation. Juvenile diploid and triploid rainbow trout (28 and 26 g/fish average weight, respectively) were stocked at 100 g/L in replicate 70-L tanks and subjected to transportation for an 8-h period. Subsequent levels of plasma cortisol and glucose and of cellular hepatic glutathione (GSH) and heat shock protein 70 (Hsp70) were similar between ploidy groups, indicating that triploid fish respond to transportation in much the same way as diploid fish. A stationary treatment was also included that involved confinement of experimental fish in similar tanks without transport to determine to what extent high-density containment contributed to the stress response in the absence of the noise and vibration of transport. Unexpectedly, fish in the stationary treatment had significantly higher plasma cortisol and glucose levels than the transported fish; however, this might be attributable to a confounding effect of hyperoxia, as oxygen levels fluctuated between 150% and 460% saturation in the stationary tank, while those in the transported tank remained within 100–200% saturation. We suggest that when long stops are necessary while transporting fish, water agitators be used to preclude the additional stress of excessive gas saturation. This may be particularly important for triploid fish, which had lower hepatic GSH levels than diploid fish as well as a low level of mortality in the stationary treatment, unlike the diploid fish.
The Effects of Whirling Disease on Growth and Survival of Snake River Cutthroat and Colorado River Rainbow Trout Fingerlings
Authors: Sipher Cory R. , Bergersen Eric P.
Published: November 2005

Two sizes of fingerling Snake River cutthroat trout Oncorhynchus clarkii behnkei and Colorado River rainbow trout O. mykiss were raised at hatcheries testing negative for Myxobolus cerebralis and stocked into the Dolores and Cache la Poudre rivers from 1999 to 2001. Populations were resampled over a 2-year period to determine which species and size combination had the highest growth and survival rates. Fish were tested for M. cerebralis via polymerase chain reaction and pepsin−trypsin digest analyses. Growth and survival rates between the species and size groups were not significantly different in either river. In the Dolores River, annual survival for both species and sizes of fish combined ranged from 0.063 to 0.12. In the Cache la Poudre River, survival for both sizes of rainbow trout was 0.004; survival for cutthroat trout ranged from 0.182 to 0.53. Larger fish had higher growth rates than smaller fish, and cutthroat trout had higher rates than similar sizes of rainbow trout. In both rivers, a higher percentage of the rainbow trout sample was infected than in the cutthroat trout sample. Rainbow trout also had a higher mean number of spores per head than cutthroat trout, and small rainbow trout had higher spore counts than large rainbow trout. Survival rates for cutthroat trout in the Cache la Poudre River were the highest of any of the groups, suggesting a difference that is biologically significant. Raising fingerlings to sizes greater than 100 mm can improve poststocking survival. If rainbow trout are stocked into contaminated waters, raising fingerlings to a larger size does not appear to improve growth or survival rates. Stocking rainbow trout in the spring could maximize growth rates but will expose fish to greater triactinomyxon densities, resulting in higher intensities of infection.
Evaluation of Cell Culture Methods for Detection of Largemouth Bass Virus
Authors: McClenahan Shasta D. , Beck Benjamin H. , Grizzle John M.
Published: November 2005

Largemouth bass virus (LMBV), a recently discovered iridovirus found in the eastern United States, is usually detected by isolation in cell culture. Although LMBV will replicate in several cell lines, optimal cell culture methods for the detection of this virus have not been determined. We tested inoculation method, adsorption time, incubation temperature, and various cell lines to determine the conditions that would provide the most sensitive cell culture assay for LMBV. The optimal inoculation procedure tested was to remove the culture medium from the culture well before the addition of the inoculum, and the optimal adsorption procedure tested was to allow the virus to adsorb for 40 min while the plates were on an orbital shaker. Following inoculation, incubation at 30°C resulted in a higher number of viral plaques than incubation at 25°C or 32°C. Four cell lines (bluegill fry (BF-2), fathead minnow (FHM), epithelioma papulosum cyprini, and channel catfish ovary cells) inoculated with LMBV had similar susceptibility to infection. Similar percentages of LMBV-positive samples were detected in BF-2 and FHM cell cultures inoculated with homogenized organ samples from largemouth bass Micropterus salmoides; however, the use of two cell lines increased the number of infected samples discovered. A blind passage also increased the number of positive samples detected in cell culture. Subcultivation to confirm virus-positive samples was useful for reducing false-positive results.
Assessment of Recent Habitat Conditions of Eastern Oyster Crassostrea virginica Bars in Mesohaline Chesapeake Bay
Authors: Smith G. F. , Bruce D. G. , Roach E. B. , Hansen A. , Newell R. I. E. , McManus A. M.
Published: November 2005

Eastern oysters Crassostrea virginica in Chesapeake Bay, USA, have been subjected to intense harvest pressure since about 1850 and to disease epizootics since the 1950s. Combined, these processes have degraded the once extensive eastern oyster bottom; the remaining oyster shells, which are required as substrate for successful larval oyster settlement, are thus rendered increasingly susceptible to siltation. Between 1999 and 2001, we used an acoustic seabed classification system and underwater videography to assess oyster habitat conditions throughout Maryland's portion of Chesapeake Bay relative to eastern oyster recruitment and habitat restoration activities. We performed 16 surveys that covered a total of 39 km2 of bottom that were classified in 1911 as supporting productive oyster populations. Over 90% of this area has degraded from productive oyster bottom to mud, sand, or heavily sedimented oyster shell. Seventy percent of the locations we identified as containing unsedimented shell came from within the approximately 90 km2 of oyster bottom that had been subject to the management activity of spreading large volumes of shell at some time between 1960 and 1999. However, video observations of 49 of these locations that had been replenished with shell at various times indicated that any improvements in oyster habitat were short lived, as interstitial spaces in spread shell became highly sedimented after an average period of 5.5 years (n = 49; SE = 1.03). We conclude that the majority of oyster bottom in Maryland is extremely degraded and that no reasonable increase in the scale of present management practices will reverse this habitat decline.
Análisis de errores en las relativas
Authors: Di Tullio Ángela , Suñer Avelina
Published: November 2005

The relativization devices of a language can be hierarchized according to case codification on the basis of linguistic typology, diachrony and acquisition studies. Yet, such a scale is sensitive to the variation between spoken and written language. In Spanish, the canonical relative, proper of the written language, fills a clause internal slot of the relative. Spoken language, however, drastically reduces morphosyntactic marking (as shown, e.g., by the depronominalization of the relative marker and by quesuismo), while at the same time simplifying the semantic compatibility relations with the antecedent (extending, e.g., the use of donde ‘where’).

We propose to analyze native speakers’ and language learners’ errors, including those stemming from hypercorrection, in order to find out which are the prevailing relativization strategies. The tension between grammatical economy and communicative efficiency explains the fluctuation between simplification, on the one hand, characterized by the loss of prepositions and by the use of marked relative forms (e.g. cuyo ‘whose’), and on the other, the recovery of information, e.g. through the use of resumptive pronouns. Special attention will be paid to the so-called “subordinate subject relative attraction”, which privileges clause-internal concordance relations.
Teacher Feedback
Authors: Leong Ping Alvin , Pin Pin Vera Tay , Wee Samuel , Hwee Nah Heng
Published: November 2005

This article reports on the findings of an investigative study on teacher feedback at a lower-secondary class in a Singaporean school. Involving an observation of the writing lessons and interviews with several respondents, the study reveals a misfit between desired and actual feedback The potential for such mismatches becomes greater if the writing lesson is set rigidly as a unilateral transfer of knowledge from teacher to student This study argues that the writing lesson should not be viewed as a mere pedagogic event but as a social event as well, allowing room for teacher-student interaction and the provision of personal, substantiated feedback In such an environment, students are guided to discover writing as a process of finding and structuring ideas, and the responsibility that comes with searching for a way to express them (GAGE 1986:25),
Writing Processes of EFL Students in argumentative Essays
Authors: Mahfoudhi Abdessatar
Published: November 2005

The paper reports on a case study of the writing processes and products of Tunisian EFL university students in an argumentative essay. The data came from (i) audio-taped think-aloud protocols followed by immediate retrospective comments, (ii) experts' comments and grades on the subjects' products, and (iii) a questionnaire administered to the students. Results of the process analysis, using an adapted version of the coding scheme used by A. RAIMES (1985;1987), corroborated by the questionnaire fmdings, showed that students wrote fluently and concerned themselves more with meaning than with granunatical correctness. However, they planned very little, rarely made notes before writing, and rarely rewrote. They faced difficulties especially in fmding the appropriate word and in organizing their ideas. At the local level, products showed inaccurate use of mechanics and granunar. At a more global level, most essays lacked clear thesis statement, substantial support of claims, adequate transitions, and hedged statements. The product problems were partially attributed to little planning, notemaking, and revising. The process strategies were themselves related to writing habits for which the classroom and the exam settings are partly responsible.
Improving EFL learners' pragmatic awareness
Authors: Doğançay-Aktuna Seran
Published: November 2005

This paper overviews the ways in which EFL learners' pragmatic awareness can be developed in language classrooms through focused instruction and practice. It argues that effective communication requires awareness of the conventions governing language use and attention to the characteristics of the context and the interlocutors, besides linguistic resources. The main claim is that even though some pragmatics data that is based on native speaker norms might not provide relevant models for learners of English as a foreign or international language, these learners still need to become aware of crosscultural variation in norms of language use and learn how to consider social and contextual factors surrounding effective communication. After defining pragmatic competence and transfer, the paper discusses possible ways for integrating pragmatic consciousness-raising into language teaching and the problems involved in this endeavour. It then describes a course designed to raise pragmatic awareness in advanced level EFL learners as part of their TEFL training program. The underlying principles, materials and sample activities of the course are presented and learners' reaction to the course is discussed.
Bottom‐up trophic cascades and material transfer in terrestrial food webs
Authors: Kagata Hideki , Ohgushi Takayuki
Published: November 2005

In contrast to top‐down trophic cascades, few reviews have appeared of bottom‐up trophic cascades. We review the recent development of research on bottom‐up cascades in terrestrial food webs, focusing on tritrophic systems consisting of plants, herbivorous insects, and natural enemies, and attempt to integrate bottom‐up cascade and material transfer among trophic levels. Bottom‐up cascades are frequently reported in various tritrophic systems, and are important to determine community structure, population dynamics, and individual performance of higher trophic levels. In addition, we highlight several features of bottom‐up cascades. Accumulation or dilution of plant nutritional and defensive materials by herbivorous insects provides a mechanistic base for several bottom‐up cascades. Such a stoichiometric approach has the potential to improve our understanding of bottom‐up cascading effects in terrestrial food webs. We suggest a future direction for research by integration of bottom‐up cascades and material transfer among trophic levels.
Prolonged Operative Time Correlates with Increased Infection Rate after Total Knee Arthroplasty
Authors: Peersman G. , Laskin R. , Davis J. , Peterson M. G. E. , Richart T.
Published: November 2005

Risk stratification has proven to be a useful tool in surgical site infection prevention. The duration of the surgical procedure has been recommended for use in surgical site infection (SSI) risk stratification (Infect Control Hosp Epidemiol 20:247–248, 1999). A retrospective analysis of 6489 patients who underwent total knee replacement (TKR) between 1993 and 1999 assessed the association between the duration of the surgical procedure and the risk of postoperative infection. One hundred thirteen infected patients were matched with 236 controls, and nominal variables were statistically processed. Patients without infections ( n = 236) had surgery durations of 94 ± 28 min, and patients with infection ( n = 104) had durations of 127 ± 45 min ( p < 0.001). Operation time has positive correlations with weight ( r = 0.3, p < 0.001), body mass index ( r = 0.3, p < 0.001), and the total number of comorbidities ( r = 0.2, p < 0.001; n = 340). The results confirm that the duration of the surgical procedure can be used as a risk predictor for SSI in TKR.
Rat limbal epithelial side population cells exhibit a distinct expression of stem cell markers that are lacking in side population cells from the central cornea
Authors: Umemoto Terumasa , Yamato Masayuki , Nishida Kohji , Kohno Chinatsu , Yang Joseph , Tano Yasuo , Okano Teruo
Published: November 2005

The side population (SP) phenotype is shared by stem cells in various tissues and species. Here we demonstrate SP cells with Hoechst dye efflux were surprisingly collected from the epithelia of both the rat limbus and central cornea, unlike in human and rabbit eyes. Our results show that rat limbal SP cells have a significantly higher expression of the stem cell markers ABCG2, nestin, and notch 1, compared to central corneal SP cells. Immunohistochemistry also revealed that ABCG2 and the epithelial stem/progenitor cell marker p63 were expressed only in basal limbal epithelial cells. These results demonstrate that ABCG2 expression is closely linked to the stem cell phenotype of SP cells.
FM1–43 measurements of local exocytotic events in rat melanotrophs
Authors: Sikdar S.K. , Kreft M. , Pangrsic T. , Grilc S. , Zorec R.
Published: November 2005

We have explored the existence of fusion‐ and secretion‐competent sites on the plasma membrane of peptide secreting rat pituitary melanotrophs at rest, and following stimulation with glutamate. We monitored changes in fluorescence of FM1–43, a styryl dye which labels plasma membrane. The results show spontaneous local increases in FM1–43 reporting changes in membrane surface area due to cumulative exocytosis. Addition of glutamate, further increased the occurrence of these events. Statistical analysis of local FM1–43 fluorescence changes suggests that this is due to the recruitment of inactive exocytotic domains and due to the stimulation of already active exocytotic domains.
The Arg473Cys‐neuroligin‐1 mutation modulates NMDA mediated synaptic transmission and receptor distribution in hippocampal neurons
Authors: Khosravani Houman , Altier Christophe , Zamponi Gerald W. , Colicos Michael A.
Published: November 2005

Synapses mediate communication between neurons, thus playing a fundamental role in information processing in the CNS. Neuroligins form a family of heterophilic synaptic cell adhesion molecules, and neuroligin 1 (NL1) has been shown to be involved in the formation of excitatory synapses and have been suggested to associate indirectly with NMDA receptors by common binding to PSD95. A mutation in neuroligin 3 (Arg451Cys‐NL3, human sequence numbering) identified in autistic patients is associated with altered spine density and has reduced binding capacity for its presynaptic partner β‐neurexin. Here, we investigated the role of NL1 and the homologous NL1 mutation Arg473Cys‐NL1 (R473C‐NL1) in excitatory synaptic transmission and NMDA receptor distribution. We demonstrate that R473C‐NL1, when expressed in cultured hippocampal neurons, can induce a dramatic increase in NMDA current amplitude and that this change is accompanied by NMDA receptor clustering in the postsynaptic cell.
Structure of a halophilic nucleoside diphosphate kinase from Halobacterium salinarum
Authors: Besir Hüseyin , Zeth Kornelius , Bracher Andreas , Heider Ursula , Ishibashi Matsujiro , Tokunaga Masao , Oesterhelt Dieter
Published: November 2005

Nucleoside diphosphate kinase from the halophilic archaeon Halobacterium salinarum was crystallized in a free state and a substrate‐bound form with CDP. The structures were solved to a resolution of 2.35 and 2.2 Å, respectively. Crystals with the apo‐form were obtained with His6‐tagged enzyme, whereas the untagged form was used for co‐crystallization with the nucleotide. Crosslinking under different salt and pH conditions revealed a stronger oligomerization tendency for the tagged protein at low and high salt concentrations. The influence of the His6‐tag on the halophilic nature of the enzyme is discussed on the basis of the observed structural properties.
What factor drives the fibrillogenic association of β‐sheets?
Authors: Fernández Ariel
Published: November 2005

The identification of the driving factor for fibril formation is paramount to understand the molecular basis of amyloidogenic disease. Recently, an atomic‐detail structure of a fibrillogenic aggregate was reported and revealed a tight packing of β‐sheets. However, there is not a single pair‐wise interaction of significance between the β‐sheets, no hydrogen bond and no hydrophobic interaction. Instead, there is extensive burial of polar groups at the interface. These observations lead to the question: What factor drives the association of β‐sheets? This issue is addressed by combining all‐atom molecular dynamics with an implicit‐solvent analysis. The driving force for the association arises from the mechanical equivalent of the dehydration propensity of pre‐formed intra‐sheet hydrogen bonds and dipole–dipole interactions.
Catalytic properties of the bifunctional soybean β‐glucan‐binding protein, a member of family 81 glycoside hydrolases
Authors: Fliegmann Judith , Montel Emilie , Djulić Alma , Cottaz Sylvain , Driguez Hugues , Ebel Jürgen
Published: November 2005

The β‐glucan‐binding protein (GBP) of soybean (Glycine max L.) has been shown to contain two different activities. As part of the plasma membrane‐localized pathogen receptor complex, it binds a microbial cell wall elicitor, triggering the activation of defence responses. Additionally, the GBP is able to hydrolyze β‐1,3‐glucans, as present in the cell walls of potential pathogens. The substrate specificity, the mode of action, and the stereochemistry of the catalysis have been elucidated. This defines for the first time the inverting mode of the catalytic mechanism of glycoside hydrolases belonging to family 81.
Endotoxin recognition: In fish or not in fish?
Authors: Iliev Dimitar B. , Roach Jared C. , Mackenzie Simon , Planas Josep V. , Goetz Frederick W.
Published: November 2005

The interaction between pathogens and their multicellular hosts is initiated by activation of pathogen recognition receptors (PRRs). These receptors, that include most notably members of the toll‐like receptor (TLR) family, recognize specific pathogen‐associated molecular patterns (PAMPs). TLR4 is a central part of the receptor complex that is involved in the activation of the immune system by lipopolysaccharide (LPS) through the specific recognition of its endotoxic moiety (Lipid A). This is a critical event that is essential for the immune response to Gram‐negative bacteria as well as the etiology of endotoxic shock. Interestingly, compared to mammals, fish are resistant to endotoxic shock. This in vivo resistance concurs with in vitro studies demonstrating significantly lowered sensitivity of fish leukocytes to LPS activation. Further, our in vitro analyses demonstrate that in trout mononuclear phagocytes, LPS fails to induce antiviral genes, an event that occurs downstream of TLR4 and is required for the development of endotoxic shock. Finally, an in silico approach that includes mining of different piscine genomic and EST databases, reveals the presence in fish of all of the major TLR signaling elements except for the molecules specifically involved in TLR4‐mediated endotoxin recognition and signaling in mammals. Collectively, our analysis questions the existence of TLR4‐mediated cellular responses to LPS in fish. We further speculate that other receptors, in particular beta‐2 integrins, may play a primary role in the activation of piscine leukocytes by LPS.
A semiautomatic task-oriented programming system for sensor-controlled robotised small-batch and one-off manufacturing
Authors: Cederberg Per , Olsson Magnus , Bolmsjö Gunnar
Published: November 2005

A task-oriented system structure has been developed. In normal industrial robot programming, the path is created and the process is based on the path. Here a process-focused method is proposed, where a task can be split in sub-tasks, one for each part of the process with similar process-characteristics. By carefully encapsulating the information needed to execute a sub-task, this component can be re-used whenever the actual sub-task occurs. Applications using system design do not change between simulation and actual shop floor runs and the system allows a mix of real- and simulated components during simulation and run-time.
Implementation of a hexapod mobile robot with a fuzzy controller
Authors: Kern Makoto , Woo Peng-Yung
Published: November 2005

Fuzzy logic has features that are particular attractive in light of the problems posed by autonomous robot navigation. Fuzzy logic allows us to model different types of uncertainty and imprecision. In this paper, the implementation of a hexapod mobile robot with a fuzzy controller navigating in unknown environments is presented. The robot, MKIII, interprets input sensor data through the comparison of values in its fuzzy rule base and moves accordingly to avoid obstacles. Results of trial run experiments are presented.
An effective approach for dynamic analysis of rovers
Authors: Meghdari A. , Karimi R. , Pishkenari H. N. , Gaskarimahalle A. L. , Mahboobi S. H.
Published: November 2005

In this paper a novel approach to dynamic formulation of rovers has been presented. The complexity of these multi-body systems especially on rough terrain, challenged us to use the Kane's method which has been preferred to others in these cases. As an example, symbolic equations of a six-wheeled rover, named CEDRA Rescue Robot which uses a shrimp like mechanism, have been derived and a simulation of forward and inverse dynamics has been presented. Due to the clear form of equations, each term defines a physical meaning which represents the effect of each parameter, resulting in a frame-work for performance comparison of rovers. Although the method has been described for a 2-D non-slipping case, it is also very useful for dimensional and dynamical optimization, high speed motion analysis, and checking various control algorithms. Furthermore, it can be extended to 3-D cases and other complicated mechanisms and rovers while conserving its inherent benefits and adding to the ease of handling nonholonomic constraints.
Position and impedance force control of tele-operated master-slave robot hand system
Authors: Shao Hui , Nonami Kenzo , Wojtara Tytus
Published: November 2005

The paper developed a robust position tracking scheme with a neuro-fuzzy inverse model velocity controller of a tele-operated master-slave robot hand system for demining. And by using impedance force control and a two-posture recognition Neural Network (NN) a smooth grasping and releasing action is realized.
Dynamics and model-based control for mobile modular manipulators
Authors: Liu Yugang , Li Yangmin
Published: November 2005

The dynamic modeling and trajectory following issues are addressed for mobile modular manipulators. Simulations are performed to validate the proposed algorithms.
Control of a robot manipulator and pendubot system using artificial neural networks
Authors: Constantin Joseph , Nasr Chaïban , Hamad Denis
Published: November 2005

The paper introduces artificial neural networks for the conventional control of robotic systems for better tracking performance. Different advanced dynamic control techniques are explained and a new second order recursive algorithm has been developed to tune the weights of the neural network. The problem of real-time control of a Pendubot system in difficult situations has been addressed. Examples, such as positioning and balancing structures, are presented and performances are compared to a conventional PD controller.