bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE PIN GROUPS IN PHYSICS: C, P AND T
Authors: BERG MARCUS , DeWITT-MORETTE CÉCILE , GWO SHANGJR , KRAMER ERIC 
Published: July 2002

A simple, but not widely known, mathematical fact concerning the coverings of the full Lorentz group sheds light on parity and time reversal transformations of fermions. Whereas there is, up to an isomorphism, only one Spin group which double covers the orientation preserving Lorentz group, there are two essentially different groups, called Pin groups, which cover the full Lorentz group. Pin(1, 3) is to O(1, 3) what Spin(1, 3) is to SO(1, 3). The existence of two Pin groups offers a classification of fermions based on their properties under space or time reversal finer than the classification based on their properties under orientation preserving Lorentz transformations — provided one can design experiments that distinguish the two types of fermions. Many promising experimental setups give, for one reason or another, identical results for both types of fermions. These negative results are reported here because they are instructive. Two notable positive results show that the existence of two Pin groups is relevant to physics: • In a neutrinoless double beta decay, the neutrino emitted and reabsorbed in the course of the interaction can only be described in terms of Pin(3, 1). • If a space is topologically nontrivial, the vacuum expectation values of Fermi currents defined on this space can be totally different when described in terms of Pin(1, 3) and Pin(3, 1). Possibly more important than the two above predictions, the Pin groups provide a simple framework for the study of fermions; it makes possible clear definitions of intrinsic parities and time reversal; it clarifies colloquial, but literally meaningless, statements. Given the difference between the Pin group and the Spin group it is useful to distinguish their representations, as groups of transformations on "pinors" and 'spinors", respectively. The Pin(1, 3) and Pin(3, 1) fermions are twin-like particles whose behaviors differ only under space or time reversal. A section on Pin groups in arbitrary spacetime dimensions is included.
SYNTHESIS OF NANOMETER-SIZED (BI)METALLIC CLUSTERS WITH A NUCLEAR REACTOR
Authors: DOUDNA C. M. , HUND J. F. , BERTINO M. F. 
Published: July 2002

Mono- and heteronuclear clusters were synthesized by irradiating with gamma rays from a nuclear reactor aqueous solutions containing ionic precursors. Ag, Au/Ag and Ag/Pd clusters were produced and characterized by optical absorption and transmission electron microscopy measurements. Electron diffraction measurements show that the clusters have a crystalline fcc structure. Ag and Au/Ag clusters have a lattice parameter which coincides with the bulk. In the case of Ag/Pd clusters, a homogeneous alloy is formed whose lattice parameter closely follows Vegard's law. The cluster size distribution is in the nanometer range, although coalescence processes lead often to large aggregates. Optical absorption spectra are in agreement with previously reported results, when the presence of large aggregates is taken into account.
AN EMPIRICAL RELATION FOR CRITICAL LOAD OF DLC COATINGS PREPARED ON SILICON SUBSTRATES
Authors: Sheeja D. , Tay B. K. , Lau S. P. , Leong K. W. , Lee C. H. 
Published: July 2002

The adhesion, of a coating to the underlying substrate, in terms of critical load (using scratch test) is complex and is a function of many parameters such as coating thickness, interfacial stress, coefficient of friction, intermixing, hardness, structural parameters, etc. The present study examines the relationship of critical load to other properties such as film thickness, compressive stress, coefficient of friction, etc. of diamond-like carbon coatings prepared under floating condition (no substrate bias), on silicon substrates. The results show that the compressive stress increases with increasing thickness. However, the adhesive strength in terms of critical load increases with increasing the film thickness up to a certain value and then it decreases. The decrease in critical load with thickness of the films is due to the dominant effect of compressive stress. In order to obtain the parameters that affect the adhesion, a factor analysis has been carried out on the experimental data using SPSS — a statistical software package. Thickness, stress, and critical load emerged as one of the factors and hence it suggests that thickness and stress are two primary parameters that affect adhesion. None of the parameters of Raman study were emerged in the factor analysis along with critical load and thickness. This suggests that the variation of the sp3-bonded carbon with thickness is relatively small and that may not have any direct impact on the adhesion. In this case, stress shows a strong linear relationship with thickness. Moreover, it is not an operational parameter. Hence inclusion of stress in the model becomes unnecessary. Therefore, an empirical relation has been obtained for critical load as a function of thickness.
LANGUAGE AND COHERENT NEURAL AMPLIFICATION IN HIERARCHICAL SYSTEMS: RENORMALIZATION AND THE DUAL INFORMATION SOURCE OF A GENERALIZED SPATIOTEMPORAL STOCHASTIC RESONANCE
Authors: WALLACE RODRICK 
Published: July 2002

A growing body of work suggests an important unifying perspective in the study of stochastic resonance: Examining the "prehistory probability density" of the ensemble of pathways by which a system approaches the trigger of the nonlinear oscillator. This view, in the context of the Shannon–McMillan Theorem of information theory, leads to a draconian simplification of the complex of "signal," "noise" and oscillator in terms of a single object, an ergodic information source dual to a certain class of resonances. For "spatial" stochastic resonator arrays, in the most general sense, the Shannon–McMillan Theorem further provides an analogy between the Shannon uncertainty of the dual information source and the free energy density of a physical system which allows imposition of real-space renormalization to give essential results in a straightforward manner. We find in particular threshold behavior in the onset of an epileptiform spatiotemporal coherence, and a likely usefulness of tuned spatial arrays for the detection of very subtle pattern. These simplifications may provide, in addition, a natural context for discussing hierarchical structure in neural systems. In sum, we attempt to bring stochastic resonance into the contemporary framework of applied mathematics which has begun to unify the study of fluctuations, statistical mechanics and information theory. Our critical generalization lies in the transfer of renormalization methods from statistical mechanics to information theory, via a parametization of source uncertainty.
DEVELOPMENT OF WIRELESS EMBEDDED SYSTEMS USING COMPONENT BASED SOFTWARE
Authors: YANG STEPHEN J. H. , TSAI JEFFREY J. P. , CHEN IRENE 
Published: July 2002

Many mobile and wireless devices are connecting to the Internet nowadays, among them, mobile phones and PDAs are the most popular ones. Thus, in this paper, we will focus on how to develop embedded software running on the two devices by using design patterns and Java based software components. Notably, some components may be used directly in an embedded software system, whereas most components must be specialized prior to reuse. Developers have to identify the variation points on these components. In order to develop a reusable embedded software system, we will identify several variation points with some variants, and introduce some useful design patterns for implementing variation points. Consequently, we can customize an embedded software system just through attaching variants on corresponding variation point in our system. The design patterns we are using are property container, strategy, decorator, and model-view-controller. The component technology we are using is J2ME. J2ME is a specification focused on the development of mobile applications. It provides a similar environment as standard Java environment. J2ME's components programming includes the Spotlet programming for PDA, and the MIDlet programming for Java phone. In addition, along with the XML, J2ME can also provide the XMIDlet programming for dynamic downloading and execution of XML-based applications for PDA and Java phones.
Scapho-Trapezio-Trapezoid Arthrodesis.
Authors: Kaines Andrew , Chissell Hugh , Hayes Michael , Saies Andrew 
Published: July 2002

Scapho-trapezio-trapezoid (STT) arthrodesis is a relatively common procedure performed for severe STT arthritis, scapholunate instability and Kienböck's disease. Twenty-eight of 31 patients who had undergone this procedure were reviewed at a mean of 65 months following surgery (range 24 to 97 months). Four patients underwent wrist arthrodesis; two for failed STT fusion; and two for uncontrolled pain related to pre-existing carpal osteoarthritis. Ninety-two percent of patients who had a successful STT arthrodesis achieved good or excellent pain relief and 79% were satisfied with the results of surgery. Pain relief was best in patients with a pre-operative diagnosis of STT arthritis. Wrist range of motion and strength were well preserved. No patients developed isolated arthrosis in the radiocarpal, intercarpal or adjacent joints. STT provides excellent pain relief with an acceptable reduction in grip strength and range of motion. However, the benefits of this procedure must be balanced against the potentially serious postoperative complications and the possibility of arthrosis.
Algorithm 720: An algorithm for adaptive cubature over a collection of 3-dimensional simplices
Authors: Berntsen Jarle , Cools Ronald , Espelid Terje O. 
Published: July 2002

An adaptive algorithm for computing an approximation to the integral of each element in a vector of functions over a 3-dimensional region covered by simplices is presented. The algorithm is encoded in FORTRAN 77.
Locally, a cubature formula of degree 8 with 43 points is used to approximate an integral. The local error estimate is based on the same evaluation points. The error estimation procedure tries to decide whether the approximation for each function has asymptotic behavior, and different actions are taken depending on that decision.
The simplex with the largest error is subdivided into 8 simplices. The local procedure is then applied to each new region. This procedure is repeated until convergence.
Neural Activation During Response Competition
Authors: Hazeltine Eliot , Poldrack Russell , Gabrieli John D. E. 
Published: July 2002

Abstract
The flanker task, introduced by Eriksen and Eriksen [Eriksen, B. A., & Eriksen, C. W. (1974). Effects of noise letters upon the identification of a target letter in a nonsearch task. Perception & Psychophysics, 16, 143-149], provides a means to selectively manipulate the presence or absence of response competition while keeping other task demands constant. We measured brain activity using functional magnetic resonance imaging (fMRI) during performance of the flanker task. In accordance with previous behavioral studies, trials in which the flanking stimuli indicated a different response than the central stimulus were performed significantly more slowly than trials in which all the stimuli indicated the same response. This reaction time effect was accompanied by increases in activity in four regions: the right ventrolateral prefrontal cortex, the supplementary motor area, the left superior parietal lobe, and the left anterior parietal cortex. The increases were not due to changes in stimulus complexity or the need to overcome previously learned associations between stimuli and responses. Correspondences between this study and other experiments manipulating response interference suggest that the frontal foci may be related to response inhibition processes whereas the posterior foci may be related to the activation of representations of the inappropriate responses.
Activity in Human Frontal Cortex Associated with Spatial Working Memory and Saccadic Behavior
Authors: Postle Bradley R. , Berger Jeffrey S. , Taich Alexander M. , D'Esposito Mark 
Published: July 2002

AbstractWe examined, with event-related fMRI, two hypotheses about the organization of human working memory function in frontal cortex: (1) that a region immediately anterior to the frontal eye fields (FEF) (superior frontal cortex, SFC) is specialized for spatial working memory (Courtney, et al., 1998); and (2) that dorsolateral prefrontal cortex (PFC) plays a privileged role in the manipulation of spatial stimuli held in working memory (Owen, et al., 1996; Petrides 1994). Our delayed-response task featured 2-D arrays of irregularly arranged squares that were highlighted serially in a random sequence. The Forward Memory condition required maintenance of the spatio-temporal sequence, the Manipulate Memory condition required reordering this sequence into a new spatially defined order, the Guided Saccade condition required saccades to highlighted squares in the array, but no memory, and the Free Saccade condition required self-paced, horizontal saccades. The comparison of fMRI signal intensity associated with 2-D saccade generation (Guided Saccades) versus fMRI signal intensity associated with the delay period of the working memorials condition revealed no evidence for greater working memory-related activity than saccade-related activity in SFC in any individual subject, nor at the level of the group, and greater 2-D saccade than delay-period activity in three of five subjects. These results fail to support the hypothesis that spatial working memory-related activity is represented preferentially in a region of SFC anterior to the FEF (Courtney, et al., 1998). The comparison of maintenance versus manipulation of spatio-temporal information in working memory revealed significantly greater activity associated with the latter in dorsolateral PFC, but not in ventrolateral PFC or in SFC. These results suggest that the delay-related function of SFC is limited to the maintenance of spatial information, and that this region does not support the nonmnemonic executive control functions supported by dorsolateral PFC. These results also indicate that the preferential recruitment of dorsolateral PFC for the manipulation of information held in working memory applies to tasks employing spatial stimuli, as well as to tasks employing verbal stimuli (D'Esposito, et al., 1999); Petrides et al., 1993; Postle et al., 1999).
Dynamic Diaschisis: Anatomically Remote and Context-Sensitive Human Brain Lesions
Authors: Price C. J. , Warburton E. A. , Moore C. J. , Frackowiak R. S. J. , Friston K. J. 
Published: July 2002

Abstract
Functional neuroimaging was used to investigate how lesions to the Broca's area impair neuronal responses in remote undamaged cortical regions. Four patients with speech output problems, but relatively preserved comprehension, were scanned while viewing words relative to consonant letter strings. In normal subjects, this results in left lateralized activation in the posterior inferior frontal, middle temporal, and posterior inferior temporal cortices. Each patient activated normally in the middle temporal region but abnormally in the damaged posterior inferior frontal cortex and the undamaged posterior inferior temporal cortex. In the damaged frontal region, activity was insensitive to the presence of words but in the undamaged posterior inferior temporal region, activity decreased in the presence of words rather than increasing as it did in the normal individuals. The reversal of responses in the left posterior inferior temporal region illustrate the context-sensitive nature of the abnormality and that failure to activate the left posterior temporal region could not simply be accounted for by insufficient demands on the underlying function. We propose that, in normal individuals, visual word presentation changes the effective connectivity among reading areas and, in patients, posterior temporal responses are abnormal when they depend upon inputs from the damaged inferior frontal cortex. Our results serve to introduce the concept of dynamic diaschisis; the anatomically remote and context-sensitive effects of focal brain lesions. Dynamic diaschisis reveals abnormalities of functional integration that may have profound implications for neuropsychological inference, functional anatomy and, vicariously, cognitive rehabilitation.
Vase or Face? A Neural Correlate of Shape-Selective Grouping Processes in the Human Brain
Authors: Hasson Uri , Hendler Talma , Bashat Dafna Ben , Malach Rafael 
Published: July 2002

Abstract
Recent neuroimaging studies have described a differential activation pattern associated with specific object images (e.g., face-related and building-related activation) in human occipito-temporal cortex. However, it is as yet unclear to what extent this selectivity is due to differences in the statistics of local object features present in the different object categories, and to what extent it reflects holistic grouping processes operating across the entire object image. To resolve this question it is essential to use images in which identical sets of local features elicit the perception of different object categories. The classic Rubin vase-face illusion provides an excellent experimental set to test this question. In the illusion, the same local contours lead to the perception of different objects (vase or face). Here we employed a modified Rubin vase-face illusion to explore to what extent the activation in face-related regions is attributable to the presence of local face features, or is due to a more holistic grouping process that involves the entire face figure. Biasing cues (gratings and color) were used to control the perceptual state of the observer. We found enhanced activation in face-related regions during the “face profile” perceptual state compared to the “vase” perceptual state. Control images ruled out the involvement of the biasing cues in the effect. Thus, object-selective activation in human face-related regions entails global grouping processes that go beyond the local processing of stimulus features.
Motor Learning of Compatible and Incompatible Visuomotor Maps
Authors: Grafton Scott T. , Salidis Joanna , Willingham Daniel B. 
Published: July 2002

Abstract
Brain imaging studies demonstrate increasing activity in limb motor areas during early motor skill learning, consistent with functional reorganization occurring at the motor output level. Nevertheless, behavioral studies reveal that visually guided skills can also be learned with respect to target location or possibly eye movements. The current experiments examined motor learning under compatible and incompatible perceptual/motor conditions to identify brain areas involved in different perceptual-motor transformations. Subjects tracked a continuously moving target with a joystick-controlled cursor. The target moved in a repeating sequence embedded within random movements to block sequence awareness. Psychophysical studies of behavioral transfer from incompatible (joystick and cursor moving in opposite directions) to compatible tracking established that incompatible learning was occurring with respect to target location. Positron emission tomography (PET) functional imaging of compatible learning identified increasing activity throughout the precentral gyrus, maximal in the arm area. Incompatible learning also led to increasing activity in the precentral gyrus, maximal in the putative frontal eye fields. When the incompatible task was switched to a compatible response and the previously learned sequence was reintroduced, there was an increase in arm motor cortex. The results show that learning-related increases of brain activity are dynamic, with recruitment of multiple motor output areas, contingent on task demands. Visually guided motor sequences can be linked to either oculomotor or arm motor areas. Rather than identifying changes of motor output maps, the data from imaging experiments may better reflect modulation of inputs to multiple motor areas.
The Attentional Role of the Left Parietal Cortex: The Distinct Lateralization and Localization of Motor Attention in the Human Brain
Authors: Rushworth Matthew F. S. , Krams Michael , Passingham Richard E. 
Published: July 2002

AbstractIt is widely agreed that visuospatial orienting attention depends on a network of frontal and parietal areas in the right hemisphere. It is thought that the visuospatial orienting role of the right parietal lobe is related to its role in the production of overt eye movements. The experiments reported here test the possibility that other parietal regions may be important for directing attention in relation to response modalities other than eye movement. Specifically, we used positron emission tomography (PET) to test the hypothesis that a ‘left’ parietal area, the supramarginal gyrus, is important for attention in relation to limb movements (Rushworth et al., 1997; Rushworth, Ellison, & Walsh, in press). We have referred to this process as ‘motor attention’ to distinguish it from orienting attention. In one condition subjects spent most of the scanning period covertly attending to ‘left’ hand movements that they were about to make. Activity in this first condition was compared with a second condition with identical stimuli and movement responses but lacking motor attention periods. Comparison of the conditions revealed that motor attention related activity was almost exclusively restricted to the ‘left’ hemisphere despite the fact that subjects only ever made ipsilateral, left-hand responses. Left parietal activity was prominent in this comparison, within the parietal lobe the critical region for motor attention was the supramarginal gyrus and the adjacent anterior intraparietal sulcus (AIP), a region anterior to the posterior parietal cortex identified with orienting attention. In a second part of the experiment we compared a condition in which subjects covertly rehearsed verbal responses with a condition in which they made verbal responses immediately without rehearsal. A comparison of the two conditions revealed verbal rehearsal-related activity in several anterior left hemisphere areas including Broca's area. The lack of verbal rehearsal-related activity in the left supra-marginal gyrus confirms that this area plays a direct role in motor attention that cannot be attributed to any strategy of verbal mediation. The results also provide evidence concerning the importance of ventral premotor (PMv) and Broca's area in motor attention and language processes.
Synaesthetic Photisms Influence Visual Perception
Authors: Smilek Daniel , Dixon Mike J. , Cudahy Cera , Merikle Philip M. 
Published: July 2002

Abstract
When C, a digit-color synaesthete, views black digits, she reports that each digit elicits a highly specific color (a photism), which is experienced as though the color was externally projected onto the digit. We evaluated this claim by assessing whether C's photisms influenced her ability to perceive visually presented digits. C identified and localized target digits presented against backgrounds that were either congruent or incongruent with the color of her photism for the digits. The results showed that C was poorer at identifying and localizing digits on congruent than incongruent trials. Such differences in performance between congruent and incongruent trials were not found with nonsynaesthete control participants. These results suggest that C's colored photisms influence her perception of black digits. We propose a model in which color information influences the perception of digits through reentrant pathways in the visual system.