Scroll-wave dynamics in the presence of ionic and conduction inhomogeneities in an anatomically realistic mathematical model for the pig heart

Nonlinear waves of the reaction–diffusion (RD) type occur in many biophysical systems, including the heart, where they initiate cardiac contraction. Such waves can form vortices called scroll waves, which result in the onset of life-threatening cardiac arrhythmias. The dynamics of scroll waves is affected by the presence of inhomogeneities, which, in a very general way, can be of (i) ionic type; i.e., they affect the reaction part, or (ii) conduction type, i.e., they affect the diffusion part of an RD-equation. We demonstrate, for the first time, by using a state-of-the-art, anatomically realistic model of the pig heart, how differences in the geometrical and biophysical nature of such inhomogeneities can influence scroll-wave dynamics in different ways. Our study reveals that conduction-type inhomogeneities become increasingly important at small length scales, i.e., in the case of multiple, randomly distributed, obstacles in space at the cellular scale (0.2–0.4 mm). Such configurations can lead to scroll-wave break up. In contrast, ionic inhomogeneities affect scroll-wave dynamics significantly at large length scales, when these inhomogeneities are localized in space at the tissue level (5–10 mm). In such configurations, these inhomogeneities can attract scroll waves, by pinning them to the heterogeneity, or lead to scroll-wave breakup.     

A new polymer supported packing material as a substitute of hydroxylapatite: Purification of Topoisomerases

Summary Hydroxylapatite (HA), a form of calcium phosphate, finds extensive usages in the fractionation and purification of proteins, enzymes and nucleic acids. However, commercial HA preparations for liquid chromatography (LC) differ from many other LC packing materials in that the former is not polymer supported. We have now developed a substitute packing material which uses Fractosil 200 as the polymer support. Other polymer supports can also be similarly used. Being Fractosil 200 supported, this Hydroxylapatite Substitute (HAS) matrix can be employed for open column LC as well as for HPLC purposes. Although the exact chemical nature of HAS is different from the conventional HA, HAS mimicks the functions of the latter support. Due to the high’ binding capacity of HA many DNA binding proteins have been partially purified on this support. In the present work HAS has been successfully used in the partial purification of Topoisomerase I and II from wheat germ. Dedicated to Professor Hartmut Seliger on his 50th birthday.     

Electro-chromatography in the separation of ions : Part III. Separation of silver group metals

The migration sequences of silver group ions Ag⁺, Hg₂⁺², Pb⁺²and Ti⁺ have been studied in a number of complex-forming electrolytes. Based on the migration sequences, the ions in a mixture can be separated into distinct zones using a decinormal solution of sodium chloride, potassium chloride or potassium cyanide as the electrolyte. The sequence is Hg — Ag— Pb—Ti, while in KCN at pH 7.0 the sequence becomes Ag—Hg—Pb—Ti.     

Isolation of a new two-dimensional honeycomb carbonato-bridged copper(II) complex exhibiting long-range ferromagnetic ordering

Atmospheric CO2 fixation by an aqueous solution containing Cu(ClO4)2.6H2O and 4-aminopyridine (4-apy) yields a novel example of a two-dimensional mu3-CO3 bridged copper(II) complex {[Cu(4-apy)2]3(mu3-CO3)2(ClO4)2.(1/2)CH3OH}n that has been characterized by IR, UV and X-ray crystallography; preliminary magnetic measurements show that complex exhibits long-range ordered ferromagnetic coupling.     

Studies on the characteristics of the isomers of hexachlorocyclohexane (HCCH) by thermogravimetry

A new method of determination of HCCH isomers by thermogravimetry is described. The thermal changes of the isomers, the decomposition characteristics and the parameters for identification are discussed.

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Zusammenfassung Eine neue Methode der Bestimmung von HCCH-Isomeren durch Thermogravimetrie wird beschrieben. Die thermischen Änderungen der Isomere, die Zersetzungscharakteristika und die Identifizierungsparameter werden erörtert.

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Résumé On décrit une nouvelle méthode de détermination des isomères HCCH par thermogravimétrie. On discute les modifications thermiques des isomères, les caractéristiques de décomposition et les paramètres d'identification.

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We are grateful to Dr. B. L. Amla, Director of this Institute, for his encoragement, and to Shri Hanumantha Rao Judav for his assistance.     

Analysis of chromatic dispersion effect on coherent optical CPFSK system and performance improvement with the use of combinations of various optical fibers

The performance of a coherent optical continuous-phase frequency shift keying (CPFSK) system is evaluated theoretically including the combined effect of fiber chromatic dispersion, non-zero laser line width and receiver noises. The system limitations imposed by chromatic dispersion and laser phase noise are depicted. The system performance can be improved by shifting the zero-dispersion wavelength to the operating wavelength of the system and this shifting can be achieved efficiently by using a suitable combination of different types of optical fibers. Dispersion shifting characteristics are demonstrated using four kinds of fibers, namely: standard single-mode fiber (SMF), dispersion shifted fiber (DSF), dispersion compensated fiber (DCF) and large core fiber (LCF). The effect of dispersion shifting on the system performance is evaluated in terms of transmission distance and bit rate.     

Vibration characteristics of a power tiller

The vibration characteristics of a power tiller (two-wheel tractor) were studied. Tests were conducted at 1000, 1200, 1400, 1600, 1800, 2000, and 2200 rpm engine speeds in a stationary condition, and at 1000, 1200, 1400, 1600, and 1800 rpm engine speeds during transportation and tillage. Tests during tillage operation were conducted in the Bangkok clay soil. For the measurement of vibration, three semiconductor strain-gauge-type accelerometers, capable of sensing vibration signals in three mutually perpendicular directions, i.e. horizontal, lateral and vertical modes at the same time, were used. Vibration characteristics of the power tiller were found to be quite complex. In general, it was observed that, in any working condition, due to an increase in engine speed of the power tiller, the acceleration and frequency of vibration increased. At the same operating speed and test condition, the intensity of the vibration was the highest in the vertical mode and the lowest in the lateral mode. The maximum vibration intensities were observed during second plowing and the lowest vibration intensities were when stationary on an off-road surface. The vibration intensities, when compared to the ISO standard 2631, were found to exceed the standard during field operations.     

Observation of magnetic domains in undoped ZnO grains at room temperature

The present study reports the room temperature ferromagnetism in undoped ZnO thin films grown by PVD method. The 500 nm film with small (90 nm) ZnO grains possess isolated magnetic domains with coercivity of 520 Oe. However, long range magnetic ordering with smaller coercivity of 230 Oe is observed for 1000 nm film. The long range ordering is caused by the reduction in domain wall pinning effect due to the presence of bigger (270 nm) ZnO grains. PL measurements show that these grains are semiconducting in nature. Results presented here suggest that oxygen vacancies at the surface may be responsible for the observed ferromagnetism.     

Efficient delivery of Cre-recombinase to neurons in vivo and stable transduction of neurons using adeno-associated and lentiviral vectors

Background

As development proceeds the human embryo attains an ever more complex three dimensional (3D) structure. Analyzing the gene expression patterns that underlie these changes and interpreting their significance depends on identifying the anatomical structures to which they map and following these patterns in developing 3D structures over time. The difficulty of this task greatly increases as more gene expression patterns are added, particularly in organs with complex 3D structures such as the brain. Optical Projection Tomography (OPT) is a new technology which has been developed for rapidly generating digital 3D models of intact specimens. We have assessed the resolution of unstained neuronal structures within a Carnegie Stage (CS)17 OPT model and tested its use as a framework onto which anatomical structures can be defined and gene expression data mapped.

Results

Resolution of the OPT models was assessed by comparison of digital sections with physical sections stained, either with haematoxylin and eosin (H&E) or by immunocytochemistry for GAP43 or PAX6, to identify specific anatomical features. Despite the 3D models being of unstained tissue, peripheral nervous system structures from the trigeminal ganglion (~300 μm by ~150 μm) to the rootlets of cranial nerve XII (~20 μm in diameter) were clearly identifiable, as were structures in the developing neural tube such as the zona limitans intrathalamica (core is ~30 μm thick). Fourteen anatomical domains have been identified and visualised within the CS17 model. Two 3D gene expression domains, known to be defined by Pax6 expression in the mouse, were clearly visible when PAX6 data from 2D sections were mapped to the CS17 model. The feasibility of applying the OPT technology to all stages from CS12 to CS23, which encompasses the major period of organogenesis for the human developing central nervous system, was successfully demonstrated.

Conclusion

In the CS17 model considerable detail is visible within the developing nervous system at a minimum resolution of ~20 μm and 3D anatomical and gene expression domains can be defined and visualised successfully. The OPT models and accompanying technologies for manipulating them provide a powerful approach to visualising and analysing gene expression and morphology during early human brain development.     

Baryon-strangeness correlations: a diagnostic of strongly interacting matter

The correlation between baryon number and strangeness elucidates the nature of strongly interacting matter, such as that formed transiently in high-energy nuclear collisions. This diagnostic can be extracted theoretically from lattice QCD calculations and experimentally from event-by-event fluctuations. The analysis of present lattice results above the critical temperature severely limits the presence of qq bound states, thus supporting a picture of independent (quasi)quarks.