bluuebunny/crossref_metadata_2025_split huggingface dataset:
Blocks—a new datatype for SNOBOL4
Authors: Gimpel James F. 
Published: July 2002

A new datatype, called a block, has been implemented for SNOBOL4. A block is a three-dimensional aggregate of characters in the form of a right parallelepiped, best thought of as a three-dimensional extension to a string. (The third dimension is used for overstriking.) Blocks may be printed, concatenated in any of three dimensions, and merged on the basis of program-defined connection points. Some blocks adapt in size and shape to their environment.
Blocks and their operations are mainly used for composing printable output. A variety of graphical problems (including flowcharting, bargraphs, logic diagrams, mathematical-equation formation, and text justification and preparation) have been programmed on a printer in what appears to be an easy and natural way. In addition to these somewhat specialized applications, blocks appear to be a good general purpose device-independent output formation mechanism especially suitable for nonnumerical work.
The concept of a block is largely language independent. That is, blocks require little in the way of specialized syntax and could readily be absorbed into the external structure of most programming languages.
An algorithm for the construction of bounded-context parsers
Authors: Loeckx Jacques 
Published: July 2002

An algorithm is described which accepts an arbitrary context-free grammar and constructs a bounded-context parser for it whenever such a parser exists.
In the first part of the paper the definition of a context-free grammar and the working of a bounded-context parser are recalled. The notion of reduction class for a context-free grammar is then introduced and its connection with the structure of a bounded-context parser is indicated. Next, pushdown automata which generate the different reduction classes of a context-free grammar are defined. Finally, the algorithm is described; it essentially carries out an exhaustive study of all possible runs of the pushdown automata generating the reduction classes.
In the second part, the utility of the algorithm is discussed in the light of the experience gained from its use in compiler design. The algorithm is claimed to be particularly useful in the simultaneous design of a language and a compiler for it.
A method for comparing the internal operating speeds of computers
Authors: Raichelson Eugene , Collins George 
Published: July 2002

First, a table of frequencies of various types of operations is prepared based on experience in similar applications or, perhaps, on actual counts if these are available. Table 1 shows such a frequency table. Next, the total weighted execution time for a given operation type is obtained by multiplying the time required for the operation by the frequency count. Finally, an “average” operation time is calculated by summing overall operation types and dividing by the sum of the frequency counts. Table 2 shows the computation for the IBM 7090.
Table 3 shows a comparison of average and relative speeds for several current computers for the particular application using the IBM 7090 as a reference base.
An executive system implemented as a finite-state automaton
Authors: Heistand Roy E. 
Published: July 2002

The 473L command and control system used by the Air Force permits many operators to access large data files through the use of a computer. The man-machine interface is satisfied by several communication consoles from which operators may enter queries and view replies. A data link permits remote stations to send messages, status reports and inventories directly to the computer. The information received over the online data link is used to update the data files which are stored on disk.
The 473L programming system is divided into an Executive Control Program and five components with different processing priorities. These priorities permit the system to be most sensitive to the console inputs and permit the operators at all the consoles to time share the central processor. The Executive Control Program provides for the orderly transitions of control among the programming system components. The major emphasis of the paper is on the technique of using the definition of a finite-state automaton for organizing the Executive Control Program.
The organization of structured files
Authors: Dzubak B. J. , Warburton C. R. 
Published: July 2002

A data file is an integral part of a data processing system. In many systems, the selection of an organization for the data within the file can be critical to the system's operating efficiency.
This paper provides the systems designer with an information source which describes ten techniques that may be employed for organizing structured data.
The characteristics of the organizations described are application independent, thus providing the designer with a reference which allows him to limit the number of file organizations he must consider for his system.
Communications design for Co-oP: a group decision support system
Authors: Bui Tung X. , Jarke Matthias 
Published: July 2002

Decision Support Systems (DSSs), computer-based systems intended to assist managers in preparing and analyzing decisions, have been single-user systems for most of the past decade. Only recently has DSS research begun to study the implications of the fact that most complex managerial decisions involve multiple decision makers and analysts. A number of tools for facilitating group decisions have been proposed under the label Group Decision Support Systems (GDSSs).
One of the most important functions of a GDSS is to provide problem-oriented services for communication among decision makers. On the basis of an analysis of the communication requirements in various group decision settings, this paper presents an architecture for defining and enforcing dynamic application-level protocols that organize decision group interaction. The architecture has been implemented on a network of personal computers in Co-oP, a GDSS for cooperative group decision making based on interactive, multiple-criteria decision methods.
Likelihood ratio gradient estimation for stochastic systems
Authors: Glynn Peter W. 
Published: July 2002

Consider a computer system having a CPU that feeds jobs to two input/output (I/O) devices having different speeds. Let θ be the fraction of jobs routed to the first I/O device, so that 1 - θ is the fraction routed to the second. Suppose that α = α(θ) is the steady-sate amount of time that a job spends in the system. Given that θ is a decision variable, a designer might wish to minimize α(θ) over θ. Since α(·) is typically difficult to evaluate analytically, Monte Carlo optimization is an attractive methodology. By analogy with deterministic mathematical programming, efficient Monte Carlo gradient estimation is an important ingredient of simulation-based optimization algorithms. As a consequence, gradient estimation has recently attracted considerable attention in the simulation community. It is our goal, in this article, to describe one efficient method for estimating gradients in the Monte Carlo setting, namely the likelihood ratio method (also known as the efficient score method). This technique has been previously described (in less general settings than those developed in this article) in [6, 16, 18, 21]. An alternative gradient estimation procedure is infinitesimal perturbation analysis; see [11, 12] for an introduction. While it is typically more difficult to apply to a given application than the likelihood ratio technique of interest here, it often turns out to be statistically more accurate.
In this article, we first describe two important problems which motivate our study of efficient gradient estimation algorithms. Next, we will present the likelihood ratio gradient estimator in a general setting in which the essential idea is most transparent. The section that follows then specializes the estimator to discrete-time stochastic processes. We derive likelihood-ratio-gradient estimators for both time-homogeneous and non-time homogeneous discrete-time Markov chains. Later, we discuss likelihood ratio gradient estimation in continuous time. As examples of our analysis, we present the gradient estimators for time-homogeneous continuous-time Markov chains; non-time homogeneous continuous-time Markov chains; semi-Markov processes; and generalized semi-Markov processes. (The analysis throughout these sections assumes the performance measure that defines α(θ) corresponds to a terminating simulation.) Finally, we conclude the article with a brief discussion of the basic issues that arise in extending the likelihood ratio gradient estimator to steady-state performance measures.
STRUCTURE, FUNCTION AND REGULATION OF THE VACUOLAR (H+)-ATPase
Authors: Stevens Tom H. , Forgac Michael 
Published: July 2002

▪ Abstract  The vacuolar (H+)-ATPases (or V-ATPases) function in the acidification of intracellular compartments in eukaryotic cells. The V-ATPases are multisubunit complexes composed of two functional domains. The peripheral V1 domain, a 500-kDa complex responsible for ATP hydrolysis, contains at least eight different subunits of molecular weight 70-13 (subunits A-H). The integral V0 domain, a 250-kDa complex, functions in proton translocation and contains at least five different subunits of molecular weight 100-17 (subunits a-d). Biochemical and genetic analysis has been used to identify subunits and residues involved in nucleotide binding and hydrolysis, proton translocation, and coupling of these activities. Several mechanisms have been implicated in the regulation of vacuolar acidification in vivo, including control of pump density, regulation of assembly of V1 and V0 domains, disulfide bond formation, activator or inhibitor proteins, and regulation of counterion conductance. Recent information concerning targeting and regulation of V-ATPases has also been obtained.
Embryo-Derived Stem Cells: Of Mice and Men
Authors: Smith Austin G. 
Published: July 2002

▪ Abstract  Mouse embryonic stem cells are continuous cell lines derived directly from the fetal founder tissue of the preimplantation embryo. They can be expanded in culture while retaining the functional attributes of pluripotent early embryo cells. In particular, they can participate fully in fetal development when reintroduced into the embryo. The capacity for multilineage differentiation is reproduced in culture where embryonic stem cells can produce a wide range of well-defined cell types. This has stimulated interest in the isolation of analogous cells of human origin. Such human pluripotent stem cells could constitute a renewable source of more differentiated cells that could be employed to replace diseased or damaged tissue by cellular transplantation. In this review, the relationships between mouse embryonic stem cells, resident pluripotent cells in the embryo, and human embryo-derived cell lines are evaluated, and the prospects and challenges of embryo stem cell research are considered. This review is dedicated to Rosa Beddington FRS, a great developmental biologist, a wonderful colleague, and an inspirational advocate of human stem cell research.
Therapy of Carotid Arteriosclerosis
Authors: Barnett H.J.M. 
Published: July 2002

Carotid arteriosclerotic disease is the most readily treatable type of lesion leading to stroke. Its management involves lowering those risk factors over which the patient has control. Patients should regulate hypertension, quit smoking, seek medical attention for treatable cardiac abnormalities, and take steps to reduce increased blood lipids. For symptomatic carotid disease, regardless of whether surgery is offered, platelet inhibitors are obligatory. The recommended dose is 650 mg aspirin per day (or up to 1300 mg, if tolerated). For patients whose symptoms continue despite aspirin therapy or who are aspirin intolerant, ticlopidine is the only recommended platelet inhibitor. Cerebral arterial bypass surgery is not an effective treatment for carotid arteriosclerosis. Carotid endarterectomy helps patients with ≥ 70% stenosis as determined by strict arteriographic measurements. We do not yet have sufficient data to determine whether endarterectomy would benefit patients with lower levels of carotid stenosis or asymptomatic patients with any degree of stenosis.
CYPRESS CANKER: A Pandemic in Progress
Authors: Graniti Antonio 
Published: July 2002

▪ Abstract  Over the past 70 years a destructive blight of Cupressus macrocarpa and other Cupressaceae, caused by Seiridium cardinale, has spread worldwide from California, devastating forests, plantations, and ornamental cypresses. The epidemic has been particularly severe in the Mediterranean region, on C. sempervirens. A similar destructive blight induced by Lepteutypa cupressi, which caused serious losses to Monterey cypresses in East Africa in the 1940s, has now also spread to distant continents, albeit to a lesser extent. There is yet a third wave of canker disease induced by S. unicorne, although this is a milder type. This review deals with problems related to identification of the pathogens, their taxonomy, pathogenesis and role of fungal toxins, and early screening of cypress clones or hybrids for resistance to the pathogens and tolerance to their toxins.
Auditory Cortex Accesses Phonological Categories: An MEG Mismatch Study
Authors: Phillips Colin , Pellathy Thomas , Marantz Alec , Yellin Elron , Wexler Kenneth , Poeppel David , McGinnis Martha , Roberts Timothy 
Published: July 2002

Abstract
The studies presented here use an adapted oddball paradigm to show evidence that representations of discrete phonological categories are available to the human auditory cortex. Brain activity was recorded using a 37-channel biomagnetometer while eight subjects listened passively to synthetic speech sounds. In the phonological condition, which contrasted stimuli from an acoustic /dæ/-/tæ/ continuum, a magnetic mismatch field (MMF) was elicited in a sequence of stimuli in which phonological categories occurred in a many-to-one ratio, but no acoustic many-to-one ratio was present. In order to isolate the contribution of phonological categories to the MMF responses, the acoustic parameter of voice onset time, which distinguished standard and deviant stimuli, was also varied within the standard and deviant categories. No MMF was elicited in the acoustic condition, in which the acoustic distribution of stimuli was identical to the first experiment, but the many-to-one distribution of phonological categories was removed. The design of these studies makes it possible to demonstrate the all-or-nothing property of phonological category membership. This approach contrasts with a number of previous studies of phonetic perception using the mismatch paradigm, which have demonstrated the graded property of enhanced acoustic discrimination at or near phonetic category boundaries.
Age-Related Differences in Neural Activity during Item and Temporal-Order Memory Retrieval: A Positron Emission Tomography Study
Authors: Cabeza Roberto , Anderson Nicole D. , Houle Sylvain , Mangels Jennifer A. , Nyberg Lars 
Published: July 2002

AbstractPositron emission tomography (PET) was used to investigate the hypothesis that older adults' difficulties with temporal-order memory are related to deficits in frontal function. Young (mean 24.7 years) and old (mean 68.6 years) participants studied a list of words, and were then scanned while retrieving information about what words were in the list (item retrieval) or when they occurred within the list (temporal-order retrieval). There were three main results. First, whereas the younger adults engaged right prefrontal regions more during temporal-order retrieval than during item retrieval, the older adults did not. This result is consistent with the hypothesis that context memory deficits in older adults are due to frontal dysfunction. Second, ventromedial temporal activity during item memory was relatively unaffected by aging. This finding concurs with evidence that item memory is relatively preserved in old adults and with the notion that medial temporal regions are involved in automatic retrieval operations. Finally, replicating the result of a previous study (Cabeza, R., Grady, C. L, Nyberg, L., McIntosh, A. R., Tulving, E., Kapur, S., Jennings, J. M., Houle, S., & Craik, F. I. M., 1997), the old adults showed weaker activations than the young adults in the right prefrontal cortex but stronger activations in the left prefrontal cortex. The age-related increase in left prefrontal activity may be interpreted as compensatory. Taken together, the results suggest that age-related changes in brain activity are rather process- and region-specific, and that they involve increases as well as decreases in neural activity.
Failed Suppression of Direct Visuomotor Activation in Parkinson's Disease
Authors: Praamstra P. , Plat F. M. 
Published: July 2002

Abstract
The response times in choice-reaction tasks are faster when the relative spatial positions of stimulus and response match than when they do not match, even when the spatial relation is irrelevant to response choice. This spatial stimulus—response (S-R) compatibility effect (i.e., the Simon effect) is attributed in part to the automatic activation of spatially corresponding responses, which need to be suppressed when the spatial location of stimulus and correct response do not correspond. The present study tested patients with Parkinson's disease and healthy control subjects in a spatial S-R compatibility task in order to investigate whether basal ganglia dysfunction in Parkinson's disease leads to disinhibition of direct visuomotor activation. High-density event-related brain potential recordings were used to chart the cortical activity accompanying attentional orientation and response selection. Response time measures demonstrated a failure to inhibit automatic response activation in Parkinson patients, which was revealed by taking into account a sequence-dependent modulation of the Simon effect. Event-related potential (ERP) recordings demonstrated that visuospatial orientation to target stimuli was accompanied by signal-locked activity above motor areas of the cortex, with similar latencies but an enhanced amplitude in patients compared to control subjects. The results suggest that inhibitory modulation of automatic, stimulus-driven, visuomotor activation occurs after the initial sensory activation of motor cortical areas. The failed inhibition in Parkinson's disease appears therefore related to a disturbance in processes that prevent early attention-related visuomotor activation, within motor areas, from actually evoking a response.
Parallel Cortico-Basal Ganglia Mechanisms for Acquisition and Execution of Visuomotor Sequences—A Computational Approach
Authors: Nakahara Hiroyuki , Doya Kenji , Hikosaka Okihide 
Published: July 2002

Abstract
Experimental studies have suggested that many brain areas, including the basal ganglia (BG), contribute to procedural learning. Focusing on the basal ganglia-thalamo-cortical (BG-TC) system, we propose a computational model to explain how different brain areas work together in procedural learning. The BG-TC system is composed of multiple separate loop circuits. According to our model, two separate BG-TC loops learn a visuomotor sequence concurrently but using different coordinates, one visual, and the other motor. The visual loop includes the dorsolateral prefrontal (DLPF) cortex and the anterior part of the BG, while the motor loop includes the supplementary motor area (SMA) and the posterior BG. The concurrent learning in these loops is based on reinforcement signals carried by dopaminergic (DA) neurons that project divergently to the anterior (“visual”) and posterior (“motor”) parts of the striatum. It is expected, however, that the visual loop learns a sequence faster than the motor loop due to their different coordinates. The difference in learning speed may lead to inconsistent outputs from the visual and motor loops, and this problem is solved by a mechanism called a “coordinator,” which adjusts the contribution of the visual and motor loops to a final motor output. The coordinator is assumed to be in the presupplementary motor area (pre-SMA). We hypothesize that the visual and motor loops, with the help of the coordinator, achieve both the quick acquisition of novel sequences and the robust execution of well-learned sequences. A computational model based on the hypothesis is examined in a series of computer simulations, referring to the results of the 2 × 5 task experiments that have been used on both monkeys and humans. We found that the dual mechanism with the coordinator was superior to the single (visual or motor) mechanism. The model replicated the following essential features of the experimental results: (1) the time course of learning, (2) the effect of opposite hand use, (3) the effect of sequence reversal, and (4) the effects of localized brain inactivations. Our model may account for a common feature of procedural learning: A spatial sequence of discrete actions (subserved by the visual loop) is gradually replaced by a robust motor skill (subserved by the motor loop).
Functional Anatomy of Perceptual and Semantic Processing for Odors
Authors: Royet Jean-P. , Koenig Olivier , Gregoire Marie-C. , Cinotti Luc , Lavenne Frank , Bars Didier Le , Costes Nicolas , Vigouroux Michel , Farget Vincent , Sicard Gilles , Holley André , Mauguière François , Comar Dominique , Froment Jean-C. 
Published: July 2002

Abstract
The functional anatomy of perceptual and semantic processings for odors was studied using positron emission tomography (PET). The first experiment was a pretest in which 71 normal subjects were asked to rate 185 odorants in terms of intensity, familiarity, hedonicity, and comestibility and to name the odorants. This pretest was necessary to select the most appropriate stimuli for the different cognitive tasks of the second experiment. The second one was a PET experiment in which 15 normal subjects were scanned using the water bolus method to measure regional cerebral blood flow (rCBF) during the performance in three conditions. In the first (perceptual) condition, subjects were asked to judge whether an odor was familiar or not. In the second (semantic) condition, subjects had to decide whether an odor corresponded to a comestible item or not. In the third (detection) condition, subjects had to judge whether the perceived stimulus was made of an odor or was just air. It was hypothetized that the three tasks were hierarchically organized from a superficial detection level to a deep semantic level. Odorants were presented with an air-flow olfactometer, which allowed the stimulations to be synchronized with breathing. Subtraction of activation images obtained between familiarity and control judgments revealed that familiarity judgments were mainly associated with the activity of the right orbito-frontal area, the subcallosal gyrus, the left inferior frontal gyrus, the left superior frontal gyrus, and the anterior cingulate (Brodmann's areas 11, 25, 47, 9, and 32, respectively). The comestibility minus familiarity comparison showed that comestibility judgments selectively activated the primary visual areas. In contrast, a decrease in rCBF was observed in these same visual areas for familiarity judgments and in the orbitofrontal area for comestibility judgments. These results suggest that orbito-frontal and visual regions interact in odor processing in a complementary way, depending on the task requirements.