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PubMed2004

Molecular dynamics study of the thermal and the density effects on the local and the large-scale motion of polymer melts: scaling properties and dielectric relaxation.

Results from a molecular dynamics simulation of a melt of unentangled polymers are presented. The translational motion, the large-scale and the local reorientation processes of the chains, as well as their relations with the so-called "normal" and "segmental" dielectric relaxation modes are thoroughly investigated in wide temperature and pressure ranges. The thermodynamic states are well fitted by the phenomenological Tait equation of state. A global time-temperature-pressure superposition principle of both the translational and the rotational dynamics is evidenced. The scaling is more robust than the usual Rouse model. The latter provides insight but accurate comparison with the simulation calls for modifications to account for both the local chain stiffness and the nonexponential relaxation. The study addresses the issue whether the temperature or the density is a dominant control parameter of the dynamics or the two quantities give rise to comparable effects. By examining the ratio /alphatau//alphaP between the isochronic and isobaric expansivities, one finds that the temperature is dominant when the dynamics is fast. If the relaxation slows down, the fluctuations of the free volume increase their role and become comparable to those of the thermal energy. Detectable cross-correlation between the "normal-mode" and the "segmental" dielectric relaxations is found and contrasted with the usual assumption of independent modes.

Journal Article↗
PubMed1998

The perception of scale-dependent and scale-independent surface structure from binocular disparity, texture, and shading.

The integration of binocular disparity, shading, and texture was measured for two different aspects of three-dimensional structure: (1) shape index, which is a measure of scale-independent structure, and (2) curvedness, which is a measure of scale-dependent structure. Binocular disparity was found to contribute significantly more to judged shape index than it does to judged curvedness, and shading and texture were both found to contribute more to judged curvedness than to judged shape index. These results demonstrate that different cues do not contribute equally to different aspects of perceived surface structure. This finding suggests that, for the case of linear integration, multiple cues to three-dimensional structure do not combine on the basis of a single type of representation shared by all the 'shape-from-X' processes in the visual system.

Contrast Sensitivity↗
PubMed2005

Subnets of scale-free networks are not scale-free: sampling properties of networks.

Most studies of networks have only looked at small subsets of the true network. Here, we discuss the sampling properties of a network's degree distribution under the most parsimonious sampling scheme. Only if the degree distributions of the network and randomly sampled subnets belong to the same family of probability distributions is it possible to extrapolate from subnet data to properties of the global network. We show that this condition is indeed satisfied for some important classes of networks, notably classical random graphs and exponential random graphs. For scale-free degree distributions, however, this is not the case. Thus, inferences about the scale-free nature of a network may have to be treated with some caution. The work presented here has important implications for the analysis of molecular networks as well as for graph theory and the theory of networks in general.

Journal Article↗
PubMed2001

Interrater reliability of the Physical Self-Maintenance Scale and the Instrumental Activities of Daily Living Scale in a variety of health professional representatives.

This study was performed to assess interrater reliability of the Japanese version of the Physical Self-Maintenance Scale (PSMS) and the Instrumental Activities of Daily Living Scale (IADL), which are simple and efficient assessment instruments of functional abilities in elderly patients. The subjects were 25 consecutive patients with Alzheimer's disease who were outpatients of the Department of Neuropsychiatry in Ehime University School of Medicine and their principal caregivers. One neuropsychiatrist administered the PSMS and IADL, and all sessions were videotaped. Then one clinical psychologist, one public health nurse and one neurologist, and one occupational therapist from another institution, viewed the videotape and performed reassessments. All interrater reliabilities between the neuropsychiatrist and the neurologist, the public health nurse, the clinical psychologist and the occupational therapist were extremely good. Interrater reliability between the public health nurse and the clinical psychologist, between the clinical psychologist and the neurologist and between the public health nurse and the neurologist was also extremely good. The PSMS and IADL showed good interrater reliability between personnel from different disciplines. They are likely to be useful tests for everyday medical consultations and for field research.

Activities of Daily Living↗
PubMed2004

Predicting methadone maintenance treatment outcomes using the Addiction Severity Index and the MMPI-2 Content Scales (Negative Treatment Indicators and Cynism scales).

We studied the ability of the Minnesota Multiphasic Personality Inventory-2 Content Scales (Negative Treatment Indicators [TRT] and Cynicism [CYN]) and the domain scales of the Addiction Severity Index (ASI) in predicting outcome from a methadone maintenance program. Participants were 108 African American males treated in a VA health care outpatient methadone maintenance treatment program and followed for up to 1 year after admission. Dependent variables were 1) length of stay and the percentage of 2) missed medication days, 3) toxicology urine samples free from illicit drugs, 4) full-time employment, 5) attendance at scheduled counseling sessions, and 6) counselor ratings of patient progress. A stepwise linear regression equation indicated that low drug severity scores on the ASI and low scores on percentage of missed medication predicted patients who were clean 1 year later; low scores on the psychological domain of the ASI predicted attendance at counseling sessions; a discriminant function analysis (consisting of percent of missed medication, percentage of clean urines, and ratings of patient progress) successfully predicted patient status (i.e., dropouts vs. "active patients") with 85% accuracy. Although the TRT and CYN were related to some ASI domains, they were not associated with any outcome variable. Results suggest that some ASI scores serve as important indicators of patient progress in methadone maintenance treatment.

Adult↗
PubMed2000

Small-scale Gradients and Large-scale Diffusion of Charged Particles in the Heliospheric Magnetic Field.

We have carried out numerical simulations of the propagation of energetic charged particles in a turbulent magnetic field similar to that observed in the solar wind. If the particles are released impulsively near the Sun, in a region small compared with the field coherence scale (a solar flare, for example), they exhibit characteristic fluctuations in intensity at 1 AU (dropouts) associated with very steep localized gradients. These numerical simulations are quantitatively very similar to recent observations by the Advanced Composition Explorer spacecraft and are the result of the convection of alternatively filled and empty flux tubes past the spacecraft. These fluctuations occur naturally as part of the particle transport in the same field, which results in large-scale cross field diffusion and which has previously been used to study the propagation of corotating interaction region-associated particles to high heliographic latitudes.

Journal Article↗
PubMed1986

Concurrent and predictive validities of the Bayley Motor Scale and the Peabody Developmental Motor Scales.

Concurrent and predictive validities of the Bayley Motor Scale and the Peabody Developmental Motor Scales were examined by administering both tests to 23 full-term and 21 healthy premature infants at 12, 15, and 18 months of age. For both groups, a correlation analysis of age-equivalent scores indicated Bayley scores had good to high correlation with Peabody gross motor scores (range, r = .78 to r = .96) and unacceptable correlation with Peabody fine motor scores (range, r = .20 to r = .57). When results were reported using standardized quotients, mean Bayley quotients for the full-term infant group were significantly higher than Peabody gross motor quotients. Prediction of motor development at 18 months of age was limited (range, r = .25 to r = .60), with the exception of Peabody fine motor scores for the premature infant group (r = .75). This study provides evidence of concurrent validity between Bayley motor and Peabody gross motor age-equivalent scores, and it suggests the need for further testing, using separate assessments of gross motor and fine motor ability, to determine motor development at later ages.

Child Development↗
PubMed1989

The Yale Global Tic Severity Scale: initial testing of a clinician-rated scale of tic severity.

Despite the overt nature of most motor and phonic tic phenomena, the development of valid and reliable scales to rate tic severity has been an elusive goal. The Yale Global Tic Severity Scale (YGTSS) is a new clinical rating instrument that was designed for use in studies of Tourette's syndrome and other tic disorders. The YGTSS provides an evaluation of the number, frequency, intensity, complexity, and interference of motor and phonic symptoms. Data from 105 subjects, aged 5 to 51 years, support the construct, convergent, and discriminant validity of the instrument. These results indicate that the YGTSS is a promising instrument for the assessment of tic severity in children, adolescents and adults.

Adolescent↗
PubMed2006

Test characteristics of the 15-item geriatric depression scale and Hamilton depression rating scale in Parkinson disease.

OBJECTIVE: The objective of this study was to compare the sensitivity, specificity, and diagnostic accuracy of the 15-item Geriatric Depression Scale (GDS-15) and the Hamilton Depression Rating Scale (HDRS) in patients with Parkinson disease (PD). METHOD: A convenience sample of 148 outpatients with idiopathic PD receiving specialty care completed the GDS-15 and were administered the HDRS and Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (SCID) depression module by a research psychiatrist or trained research assistant. Receiver-operating characteristic (ROC) curves were plotted for the GDS-15 and HDRS scores with a SCID diagnosis of a depressive disorder as the state variable. RESULTS: Thirty-two subjects (22%) were diagnosed with a depressive disorder. The discriminant validity of the GDS-15 and HDRS were both high (ROC area under the curve: 0.92 and 0.91, respectively), with greatest dichotomization for the GDS-15 at a cutoff of 4/5 (87% accuracy, 88% sensitivity, 85% specificity) and the HDRS at a cutoff of 9/10 (83% accuracy, 88% sensitivity, 78% specificity). CONCLUSIONS: The GDS-15 performs well as a screening instrument and in distinguishing depressed from nondepressed patients in PD. Its test characteristics are comparable to the HDRS. Because it is a brief instrument and can be self-administered, it is an excellent depression screening tool in this population.

Adult↗
PubMed2003

Pediatric balance scale: a modified version of the berg balance scale for the school-age child with mild to moderate motor impairment.

PURPOSE: The Pediatric Balance Scale (PBS), a modification of Berg's Balance Scale, was developed as a balance measure for school-age children with mild to moderate motor impairments. The purpose of this study was to determine the test-retest and interrater reliability of the PBS. METHODS: To determine test-retest reliability, 20 children (aged five to 15 years) with known balance impairments were tested by one examiner on the PBS. Ten pediatric physical therapists independently scored 10 randomly selected videotaped test sessions. RESULTS: There was no significant difference in total test scores [intraclass correlation coefficient (ICC) model 3,1 = 0.998] or individual items (Kappa Coefficients, k = 0.87 to 1.0; Spearman Rank Correlation Coefficients, r = 0.89 to 1.0) measured by one therapist on two occasions. No significant difference among ratings by different physical therapists was found on the PBS for total test score (ICC 3,1 = 0.997). CONCLUSION: The PBS has been demonstrated to have good test-retest and interrater reliability when used with school-age children with mild to moderate motor impairments.

Journal Article↗
PubMed2002

Shortest paths and load scaling in scale-free trees.

The average node-to-node distance of scale-free graphs depends logarithmically on N, the number of nodes, while the probability distribution function of the distances may take various forms. Here we analyze these by considering mean-field arguments and by mapping the m=1 case of the Barabási-Albert model into a tree with a depth-dependent branching ratio. This shows the origins of the average distance scaling and allows one to demonstrate why the distribution approaches a Gaussian in the limit of N large. The load, the number of the shortest distance paths passing through any node, is discussed in the tree presentation.

Journal Article↗
PubMed2003

Universal finite-size scaling behavior and universal dynamical scaling behavior of absorbing phase transitions with a conserved field.

We analyze numerically three different models exhibiting an absorbing phase transition. We focus on the finite-size scaling as well as the dynamical scaling behavior. An accurate determination of several critical exponents allows one to validate certain hyperscaling relations. Using these hyperscaling relations it is possible to express the avalanche exponents of a self-organized critical system in terms of the ordinary exponents of a continuous absorbing phase transition.

Journal Article↗
PubMed2004

Shortest paths and load scaling in scale-free trees.

Szabó, Alava, and Kertész [Phys. Rev. E 66, 026101 (2002)] considered two questions about the scale-free random tree given by the m=1 case of the Barabási-Albert (BA) model (identical with a random tree model introduced by Szymański in 1987): what is the distribution of the node to node distances, and what is the distribution of node loads, where the load on a node is the number of shortest paths passing through it? They gave heuristic answers to these questions using a "mean-field" approximation, replacing the random tree by a certain fixed tree with carefully chosen branching ratios. By making use of our earlier results on scale-free random graphs, we shall analyze the random tree rigorously, obtaining and proving very precise answers to these questions. We shall show that, after dividing by N (the number of nodes), the load distribution converges to an integer distribution X with Pr(X=c)=2/[(2c+1)(2c+3)], c=0,1,2,..., confirming the asymptotic power law with exponent -2 predicted by Szabó, Alava, and Kertész. For the distribution of node-node distances, we show asymptotic normality, and give a precise form for the (far from normal) large deviation law. We note that the mean-field methods used by Szabó, Alava, and Kertész give very good results for this model.

Journal Article↗
PubMed2006

Inhomogeneous sandpile model: Crossover from multifractal scaling to finite-size scaling.

We study an inhomogeneous sandpile model in which two different toppling rules are defined. For any site only one rule is applied corresponding to either the Bak, Tang, and Wiesenfeld model [P. Bak, C. Tang, and K. Wiesenfeld, Phys. Rev. Lett. 59, 381 (1987)] or the Manna two-state sandpile model [S. S. Manna, J. Phys. A 24, L363 (1991)]. A parameter c is introduced which describes a density of sites which are randomly deployed and where the stochastic Manna rules are applied. The results show that the avalanche area exponent tau a, avalanche size exponent tau s, and capacity fractal dimension Ds depend on the density c. A crossover from multifractal scaling of the Bak, Tang, and Wiesenfeld model (c = 0) to finite-size scaling was found. The critical density c is found to be in the interval 0 < c < 0.01. These results demonstrate that local dynamical rules are important and can change the global properties of the model.

Journal Article↗
PubMed2006

Packet traffic analysis of scale-free networks for large-scale network-on-chip design.

Recent progress in integrated circuit technologies requires precise evaluation between dynamic characteristics and topological architecture design. In this paper, we have investigated the performance evaluation of network-on-chip (NoC) architectures constructed with diverse scale-free network topologies by dynamic packet traffic simulation and theoretical network analysis. Topological differences of scale-free networks are evaluated by the degree-degree correlations that indicate topological tendency between the degree of a node and that of the nearest neighbors. Our simulation results quantitatively show that the NoC architecture constructed with the topology where hubs mostly connect to lower-degree nodes is found to achieve short latency and low packet loss ratio since it can disperse traffic load and avoid the extreme concentration of load on hubs.

Journal Article↗
PubMed2002

Interaction between small-scale zonal flows and large-scale turbulence: a theory for ion transport intermittency in Tokamak plasmas.

Interaction between small-scale zonal flows and large-scale turbulence is investigated. The key mechanism is identified as radially nonlocal mode coupling. Fluctuating energy can be nonlocally transferred from the unstable longer to the stable or damped shorter wavelength region, so that the turbulence spectrum is seriously deformed and deviates from the nonlinear power law structure. Three-dimensional gyrofluid ion-temperature gradient (ITG) turbulence simulations show that an ion transport bursting behavior is consistently linked to the spectral deformity with the causal role of ITG-generated zonal flows in tokamak plasmas.

Journal Article↗
PubMed2002

Weak scale supersymmetry without weak scale supergravity.

It is generally believed that weak scale supersymmetry implies weak scale supergravity, in the sense that the masses of the gravitino and gravitationally coupled moduli have masses below 100 TeV. This Letter presents a realistic framework for supersymmetry breaking in which these masses can be much larger. This solves the cosmological problems of hidden sector models. Supersymmetry breaking is communicated to the visible sector by anomaly-mediated supersymmetry breaking. The framework is compatible with perturbative gauge coupling unification and can be realized either in models of "warped" extra dimensions or in strongly coupled four-dimensional conformal field theories.

Journal Article↗
PubMed2007

Connected shape-size pattern spectra for rotation and scale-invariant classification of gray-scale images.

In this paper, we describe a multiscale and multishape morphological method for pattern-based analysis and classification of gray-scale images using connected operators. Compared with existing methods, which use structuring elements, our method has three advantages. First, in our method, the time needed for computing pattern spectra does not depend on the number of scales or shapes used, i.e., the computation time is independent of the dimensions of the pattern spectrum. Second, size and strict shape attributes can be computed, which we use for the construction of joint 2D shape-size pattern spectra. Third, our method is significantly less sensitive to noise and is rotation-invariant. Although rotation invariance can also be approximated by methods using structuring elements at different angles, this tends to be computationally intensive. The classification performance of these methods is discussed using four image sets: Brodatz, COIL-20, COIL-100, and diatoms. The new method obtains better or equal classification performance to the best competitor with a 5 to 9-fold speed gain.

Algorithms↗