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PubMed2001

Transport tensors in perfectly aligned low-density fluids: self-diffusion and thermal conductivity.

The modified Taxman equation for the kinetic theory of low-density fluids composed of rigid aspherical molecules possessing internal degrees of freedom is generalized to obtain the transport tensors in a fluid of aligned molecules. The theory takes care of the shape of the particles exactly but the solution has been obtained only for the case of perfectly aligned hard spheroids within the framework of the first Sonine polynomial approximation. The expressions for the thermal-conductivity components have been obtained for the first time whereas the self-diffusion components obtained here turn out to be exactly the same as those derived by Kumar and Masters [Mol. Phys. 81, 491 (1994)] through the solution of the Lorentz-Boltzmann equation. All our expressions yield correct results in the hard-sphere limit.

Journal Article↗
PubMed2003

Evaluation of immature granulocyte counts by the XE-IG master: upgraded software for the XE-2100 automated hematology analyzer.

We evaluated an automated immature granulocyte (IG) count in the peripheral blood with the XE-IG Master (Sysmex Corporation). The XE-IG Master is the upgraded software package for the XE-2100 automated hematology analyzer. Reproducibility tests demonstrated a mean coefficient of variation of 7.02% for the IG percentage (IG%) and 6.93% for the absolute IG count. Correlations of the IG counts were assessed in two ways. A flow cytometric IG count using CD11b, CD16, and CD45 monoclonal antibodies and a manual differential count were used as reference methods. The regression equation and the correlation coefficient of the IG% for the flow cytometric reference count versus results with the XE-IG Master were: y = 0.91x + 0.10; r = 0.96. For the comparison with the manual differential count of promyelocytes, myelocytes, and metamyelocytes, the regression equation and correlation coefficient were: y = 0.81x + 1.27; r = 0.78. Samples were found to be stable up to 48 hours both at room temperature and when refrigerated. We investigated the clinical significance of the IG count as a new marker of acute inflammation. In this preliminary study, most samples with a high IG count had positive values for C-reactive protein and the erythrocyte sedimentation rate (positive sample rates were 84.0% and 95.0%, respectively) despite neutrophil counts within the normal range. Elevated IG counts correlated most closely with CD64 expression on polymorphonuclear cells and less so with the concentration of interleukin 6. Compared with other available inflammation markers, the IG count is rapidly generated with each full blood count at no extra cost and with no delay in sample analysis.

Acute Disease↗
PubMed2000

Characterisation by drop tensiometry and by ellipsometry of the adsorption layer formed at the air/champagne wine interface.

A foam ring composed of small bubbles on the surface of a champagne glass is one of its hallmarks. The equilibrium state of that ring is linked with the rate of formation and of disappearance of bubbles. The stability of bubbles is usually ascribed to the occurrence and to the properties of an adsorption layer formed at the gas/liquid interface. Our goal is to characterise such an adsorption layer at the gas/wine interface in order to understand its role in bubble stability. Alcohol in wine lowers the surface tension to 49 mN/m. The adsorption of other molecules may cause a further decrease of 2 mN/m. Such a situation makes the study of adsorption by surface tension measurement inaccurate. To overcome this problem, we have diluted the wine four times with water before its surface tension measurement by pendant drop shape analysis. In these conditions, ethanol lowers the surface tension to 64 mN/m and the adsorption of other molecules of the wine can be monitored over 6-8 mN/m. The usual behaviour of such a diluted wine is a lowering of the surface tension during at least 20 min after drop formation. Since the role of macromolecules on the foaming properties of wine had been previously observed, we have chosen to evaluate the effect of this fraction of the wine molecules on its surface properties. Thus, wines were ultrafiltrated on a membrane with a 10000 molecular mass cut-off. The ultrafiltrate (UF) does not show any decrease of its surface tension over a 20-min period while the ultraconcentrate (UC) has a kinetics similar to that of unfiltered wine. Mixtures of UF and UC have behaviours intermediate between those of these products. A technological treatment of the wine with bentonite, believed to lower the content of macromolecules, yields a wine similar to UF. The effect of ultrafiltration was also analysed by spectroscopic ellipsometry. UF has a spectrum similar to that of a water/alcohol mixture with the same ethanol content and its ellipticity is stable during at least 20 min. On the contrary, wine or UC show spectra with the features of an adsorption layer and those characteristics increase during more than 20 min. Two varieties of vine were compared: 'Chardonnay' and 'Pinot noir'. The former is known to have better foaming properties than the latter. Its surface properties measured in this study are also more pronounced than those of Pinot noir. However, the representation of the dilational modulus against the surface pressure (which, in some instances, may be a mathematical transformation of the state equation) puts all the samples (wines, UF and UC of each) on the same master curve, a fact in favour of a common nature for all the adsorption layers. It can be concluded that surface properties of champagne wines are mostly determined by ethanol and by macromolecules with a molecular mass larger than 10000. Moreover, the adsorption layers seem to have the same nature, irrespective of the vine variety and of the concentration ratio of the wine.

Adsorption↗
PubMed2006

Semiconservative quasispecies equations for polysomic genomes: the haploid case.

This paper develops the semiconservative quasispecies equations for genomes consisting of an arbitrary number of chromosomes. We assume that the chromosomes are distinguishable, so that we are effectively considering haploid genomes. We derive the quasispecies equations under the assumption of arbitrary lesion repair efficiency, and consider the cases of both random and immortal strand chromosome segregation. We solve the model in the limit of infinite sequence length for the case of the static single fitness peak landscape, where the master genome has a first-order growth rate constant of k>1, and all other genomes have a first-order growth rate constant of 1. If we assume that each chromosome can tolerate an arbitrary number of lesions, so that only one master copy of the strands is necessary for a functional chromosome, then for random chromosome segregation we obtain an equilibrium mean fitness of [equation in text] below the error catastrophe, while for immortal strand co-segregation we obtain kappa (t=infinity)=k[e(-mu(1-lambda/2))+e(-mulambda/2)-1] (N denotes the number of chromosomes, lambda denotes the lesion repair efficiency, and mu is identical with epsilonL, where epsilon is the per base-pair mismatch probability, and L is the total genome length). It follows that immortal strand co-segregation leads to significantly better preservation of the master genome than random segregation when lesion repair is imperfect. Based on this result, we conjecture that certain classes of tumor cells exhibit immortal strand co-segregation.

Animals↗
PubMed2005

Developmental changes in mental arithmetic: evidence for increased functional specialization in the left inferior parietal cortex.

Arithmetic reasoning is arguably one of the most important cognitive skills a child must master. Here we examine neurodevelopmental changes in mental arithmetic. Subjects (ages 8-19 years) viewed arithmetic equations and were asked to judge whether the results were correct or incorrect. During two-operand addition or subtraction trials, for which accuracy was comparable across age, older subjects showed greater activation in the left parietal cortex, along the supramarginal gyrus and adjoining anterior intra-parietal sulcus as well as the left lateral occipital temporal cortex. These age-related changes were not associated with alterations in gray matter density, and provide novel evidence for increased functional maturation with age. By contrast, younger subjects showed greater activation in the prefrontal cortex, including the dorsolateral and ventrolateral prefrontal cortex and the anterior cingulate cortex, suggesting that they require comparatively more working memory and attentional resources to achieve similar levels of mental arithmetic performance. Younger subjects also showed greater activation of the hippocampus and dorsal basal ganglia, reflecting the greater demands placed on both declarative and procedural memory systems. Our findings provide evidence for a process of increased functional specialization of the left inferior parietal cortex in mental arithmetic, a process that is accompanied by decreased dependence on memory and attentional resources with development.

Adaptation, Physiological↗
PubMed2002

Nature of the divergence in low shear viscosity of colloidal hard-sphere dispersions.

Measurements of the low-shear viscosity eta(o) with a Zimm-Crothers viscometer for dispersions of colloidal hard spheres are reported as a function of volume fraction phi up to 0.56. Nonequilibrium theories based on solutions to the two-particle Smoluchoski equation or ideal mode coupling approximations do not capture the divergence. However, the nonhydrodynamic contribution to the relative viscosity Deltaeta(o) is correlated over a wide range of volume fractions by the Doolittle and Adam-Gibbs equations, indicating an exponential divergence at phi(m)=0.625+/-0.015. The data extend the previously proposed master curve, providing a test for improved theories for the many-body thermodynamic and hydrodynamic interactions that determine the viscosity of hard-sphere dispersions.

Journal Article↗
PubMed2001

Replication and mutation on neutral networks.

Folding of RNA sequences into secondary structures is viewed as a map that assigns a uniquely defined base pairing pattern to every sequence. The mapping is non-invertible since many sequences fold into the same minimum free energy (secondary) structure or shape. The pre-images of this map, called neutral networks, are uniquely associated with the shapes and vice versa. Random graph theory is used to construct networks in sequence space which are suitable models for neutral networks. The theory of molecular quasispecies has been applied to replication and mutation on single-peak fitness landscapes. This concept is extended by considering evolution on degenerate multi-peak landscapes which originate from neutral networks by assuming that one particular shape is fitter than all the others. On such a single-shape landscape the superior fitness value is assigned to all sequences belonging to the master shape. All other shapes are lumped together and their fitness values are averaged in a way that is reminiscent of mean field theory. Replication and mutation on neutral networks are modeled by phenomenological rate equations as well as by a stochastic birth-and-death model. In analogy to the error threshold in sequence space the phenotypic error threshold separates two scenarios: (i) a stationary (fittest) master shape surrounded by closely related shapes and (ii) populations drifting through shape space by a diffusion-like process. The error classes of the quasispecies model are replaced by distance classes between the master shape and the other structures. Analytical results are derived for single-shape landscapes, in particular, simple expressions are obtained for the mean fraction of master shapes in a population and for phenotypic error thresholds. The analytical results are complemented by data obtained from computer simulation of the underlying stochastic processes. The predictions of the phenomenological approach on the single-shape landscape are very well reproduced by replication and mutation kinetics of tRNA(phe). Simulation of the stochastic process at a resolution of individual distance classes yields data which are in excellent agreement with the results derived from the birth-and-death model.

Base Pairing↗
PubMed2005

Evaluation of sliding friction and contact mechanics of elastomers based on dynamic-mechanical analysis.

The paper presents a combined experimental and theoretical approach to the understanding of hysteresis and adhesion contributions to rubber friction on dry and lubricated rough surfaces. Based on a proper analysis of the temperature- and frequency-dependent behaviors of nonlinear viscoelastic materials such as filler reinforced elastomer materials, master curves for the viscoelastic moduli are constructed. It is shown that the classical williams-Landel-Ferry equation cannot be applied in its simple form, but needs the introduction of an energy term describing the temperature dependency of glassy polymer bridges, which transmit the forces within flocculated filler clusters. The activation energy for carbon black and silica-filled elastomers is compared based on two different evaluation methods. The obtained dynamic data are shown to be related to a different friction behavior of elastomers regarding the two filler systems. Theoretical predictions of the stationary frictional behavior of the systems are in fair agreement with the experimental friction data at low sliding velocities. It is found that the formulated adhesion plays a dominant role on rough dry surfaces within this range of velocities.

Journal Article↗
PubMedDate not supplied

Color comparison of two shade guides.

PURPOSE: The aim of this study was to analyze color parameters and color compatibility of two randomly chosen Vita shade guides, as well as to propose possible clinical guidelines. MATERIALS AND METHODS: Data were recorded using a colorimeter set to standard illuminant source C and the CIE L*a*b* system. A custom adapter system, which allowed a measuring area at the middle third of the tabs, was produced. Each of 42 tabs was recorded one time each on three different days. Color distribution was examined in diagrams whose coordinates were L*a*b* and L*C*H degree color coordinate pairs. Color coordinate ranges and coverage error were examined using the corresponding equations and statistical methods. RESULTS: The method repeatability was approximately delta E* = 0.1. Color difference ranges of Vitapan Classical and Vitapan 3D Master were 14.3 and 19.2, respectively. Color coordinate ranges of Vitapan Classical were as follows: delta L* = 12.8; delta a* = 1.7; delta b* = 9.0; delta C* = 9.0; and delta H degree = 7.4. Corresponding values for Vitapan 3D Master were delta L* = 15.3; delta a* = 3.4; delta b* = 16.3; delta C* = 16.6; and delta H degree = 10.5. Coverage error of Vitapan 3D Master to Vitapan Classical was 1.4 +/- 0.6, while vice versa it was 2.0 +/- 1.5. CONCLUSION: Compared to Vitapan Classical, chromaticity ranges of Vitapan 3D Master were extended in the desired directions: hue was extended toward yellow-red, and saturation was extended toward more saturated tabs. Compared to Vitapan Classical, Vitapan 3D Master tabs were more uniformly spaced. The examined shade guides were found to be color compatible.

Color↗
PubMed2000

Sentinel lymphadenectomy in node negative breast cancer.

SLND, regardless of method, can precisely predict the status of the axillary lymph nodes. Despite differences in technique, the consistent results support the sentinel node hypothesis in breast cancer. The procedure is well tolerated, and staging can be achieved accurately with minimal morbidity. SLND is a minimally-invasive procedure that provides tissue for the pathologist that represents the site most likely to harbor metastases. If a negative sentinel node is removed at SLND, it equates to truly node-negative breast cancer in almost all cases when done by experienced surgeons familiar with the technique. SLND can be mastered by surgeons at several institutions, but requires appropriate training to learn the technique. The team involved in SLND, which consists of the surgeon, pathologist and nuclear medicine physician, must determine its own false negative rate for the procedure, which requires a concomitant ALND so that accuracy is validated. Multicenter randomized clinical trials from the American College of Surgeons and NSABP are in progress, which will evaluate in general, although with different randomization schemes, the outcome of patients who have SLND alone compared to those who have ALND. Before ALND is completely abandoned, these trials must be completed so that the role of SLND in the management of all patients with early breast cancer is fully defined.

Axilla↗
PubMed2005

Splitting the dynamics of large biochemical interaction networks.

This article is inscribed in the general motivation of understanding the dynamics on biochemical networks including metabolic and genetic interactions. Our approach is continuous modeling by differential equations. We address the problem of the huge size of those systems. We present a mathematical tool for reducing the size of the model, master-slave synchronization, and fit it to the biochemical context.

Algorithms↗
PubMed2006

Parallelization of the integral equation formulation of the polarizable continuum model for higher-order response functions.

We present a parallel implementation of the integral equation formalism of the polarizable continuum model for Hartree-Fock and density functional theory calculations of energies and linear, quadratic, and cubic response functions. The contributions to the free energy of the solute due to the polarizable continuum have been implemented using a master-slave approach with load balancing to ensure good scalability also on parallel machines with a slow interconnect. We demonstrate the good scaling behavior of the code through calculations of Hartree-Fock energies and linear, quadratic, and cubic response function for a modest-sized sample molecule. We also explore the behavior of the parallelization of the integral equation formulation of the polarizable continuum model code when used in conjunction with a recent scheme for the storage of two-electron integrals in the memory of the different slaves in order to achieve superlinear scaling in the parallel calculations.

Journal Article↗
PubMed2006

Fractional calculus applied to the analysis of spectral electrical conductivity of clay-water system.

The analysis of the low-frequency conductivity spectra of the clay-water mixtures is presented. The frequency dependence of the conductivity is shown to follow the power-law with the exponent n=0.67 before reaching the frequency-independent part. When scaled with the value of the frequency-independent part of the spectrum the conductivity spectra for samples at different water content values are shown to fit to a single master curve. It is argued that the observed conductivity dispersion is a consequence of the anomalously diffusing ions in the clay-water system. The fractional Langevin equation is then used to describe the stochastic dynamics of the single ion. The results indicate that the experimentally observed dielectric properties originate in anomalous ion transport in clay-water system characterized with time-dependent diffusion coefficient.

Diffusion↗
PubMed2004

Higher virial coefficients of four and five dimensional hard hyperspheres.

The seventh and eighth virial coefficients for hard hyperspheres are calculated by Monte Carlo techniques. It is found that B(7)/B(2) (6)=0.001 43+/-0.000 13 and 0.000 44+/-0.000 12 in four and five dimensions, respectively, and that B(8)/B(2) (7)=0.000 414+/-0.000 20 in four dimensions. These values are used to investigate various proposed equations of state. Comparisons against the molecular dynamics calculations of Luban and Michels show that their proposed semiempirical form is excellent at higher densities. Moreover, we confirm Santos observation in five dimensions that a suitable linear combination of the Percus-Yevick compressibility and virial equations of state fits the molecular dynamics data nearly as well as any other proposed form.

Journal Article↗
PubMed1979

Rapid computation of diagnostic X-ray bremsstrahlung spectra.

A method is described for rapid and accurate computation of diagnostic x-ray spectra. Accuracy limitations of Kramers' equation are overcome by providing intensity correction factors derived from published measured data. Use of a parameter based on the energy of the Kramers spectrum intensity peak permits deriving master factor curves which are remarkably independent of kVp, waveform and filtration. Computed and measured spectra generally agree to better than +/- 1 keV for beams generated at 100 kVp and below. Possible application of the method to higher energy diagnostic beams is discussed.

Mathematics↗
PubMed2006

A control scheme for stable force-reflecting teleoperation over IP networks.

The problem of force-reflecting teleoperation over Internet protocol networks is addressed. The existence of time-varying communication delay and the possibility of data losses are taken into consideration. Since significant data loss may result in discontinuity of the reference trajectory transmitted through the communication channel, the proposed control scheme includes a filter that provides a smooth approximation of a possibly discontinuous reference trajectory. The stability of the overall system is guaranteed by a version of the input-to-output stable small-gain theorem for functional differential equations. If the communication delay in the forward channel is an "approximately smooth" function of time, the proposed scheme guarantees that the slave manipulator tracks the delayed trajectory of the master within a prescribed small error.

Algorithms↗
PubMed2000

Viscoelastic properties of pectin--co-solute mixtures at iso-free-volume states.

Small-deformation oscillatory measurements were performed on pectin-sucrose-glucose syrup systems at a total level of solids of 81%, with the polysaccharide content being fixed at levels of industrial use (1%). The experimental temperature range was between 50 and - 50 degrees C. Analysis of the temperature dependence of viscoelastic processes by the equation of Williams, Landel, and Ferry provides values of fractional free volume for the temperatures covering the glass transition region. The shift factors used in the conversion of mechanical spectra into master curves were normalised at suitably different temperatures so that their temperature dependence becomes coincident. The treatment implies an iso-free-volume state and relates to changes in the monomeric friction coefficient with increasing levels of intermolecular interactions in the mixture. A free-volume related glass transition temperature was defined and manipulated markedly by introducing pectin of variable degrees of esterification to the sucrose-glucose syrup system.

Chemical Phenomena↗