Current sheet formation and nonideal behavior at three-dimensional magnetic null points

The nature of the evolution of the magnetic field, and of current sheet formation, at three-dimensional (3D) magnetic null points is investigated. A kinematic example is presented which demonstrates that for certain evolutions of a 3D null (specifically those for which the ratios of the null point eigenvalues are time-dependent) there is no possible choice of boundary conditions which renders the evolution of the field at the null ideal. Resistive MHD simulations are described which demonstrate that such evolutions are generic. A 3D null is subjected to boundary driving by shearing motions, and it is shown that a current sheet localised at the null is formed. The qualitative and quantitative properties of the current sheet are discussed. Accompanying the sheet development is the growth of a localised parallel electric field, one of the signatures of magnetic reconnection. Finally, the relevance of the results to a recent theory of turbulent reconnection is discussed.Comment: to appear in Phys. Plasmas. A version with higher quality figures can be found at http://www.maths.dundee.ac.uk/~dpontin/ In this replacement version, typos have been corrected, and in addition references and some further discussion adde

Dynamic phase transition in the conversion of B-DNA to Z-DNA

The long time dynamics of the conformational transition from B-DNA to Z-DNA is shown to undergo a dynamic phase transition. We obtained the dynamic phase diagram for the stability of the front separating B and Z. The instability in this front results in two split fronts moving with different velocities. Hence, depending on the system parameters a denatured state may develop dynamically eventhough it is thermodynamically forbidden. This resolves the current controversies on the transition mechanism of the B-DNA to Z-DNA.Comment: 5 pages, 4 figures. New version with correction of typos, new references, minor modifications in Fig 2, 3. To appear in EP

Current sheets at three-dimensional magnetic nulls:effect of compressibility

The nature of current sheet formation in the vicinity of three-dimensional (3D) magnetic null points is investigated. The particular focus is upon the effect of the compressibility of the plasma on the qualitative and quantitative properties of the current sheet. An initially potential 3D null is subjected to shearing perturbations, as in a previous paper [Pontin et al., Phys. Plasmas, in press (2007)]. It is found that as the incompressible limit is approached, the collapse of the null point is suppressed, and an approximately planar current sheet aligned to the fan plane is present instead. This is the case regardless of whether the spine or fan of the null is sheared. Both the peak current and peak reconnection rate are reduced. The results have a bearing on previous analytical solutions for steady-state reconnection in incompressible plasmas, implying that fan current sheet solutions are dynamically accessible, while spine current sheet solutions are not.Comment: to appear in Physics of Plasmas. This version contains updated figures and references, additional discussion, and typos are fixed. This is the second in a series of papers - the first of which (by the same authors) is located at astro-ph/0701462. A version with higher quality figures can be found at http://www.maths.dundee.ac.uk/~dpontin

Scaling of fluctuation for Directed polymers with random interaction

Using a finite size scaling form for reunion probability, we show numerically the existence of a binding-unbinding transition for Directed polymers with random interaction. The cases studied are (A1) two chains in 1+1 dimensions, (A2) two chains in 2+1 dimensions and (B) three chains in 1+1 dimensions. A similar finite size scaling form for fluctuation establishes a disorder induced transition with identical exponents for cases A2 and B. The length scale exponents in all the three cases are in agreement with previous exact renormalization group results.Comment: Revtex, 4 postscript figures available on request (email: [email protected]); To appear in J. Phys. A Letter

Antimicrobial activity of the essential oil of Cestrum diurnum (L.) (Solanales: Solanaceae)

Cestrum diurnum (Solanaceae: Solanales) is a single or multistemmed shrub that is also known as Day Jasmine. The essential oil of the mature leaves of C. diurnum was analyzed by GLC and GLC-MS and altogether 14 components were detected. The main constituents were palmitic acid (27.62%), stearic acid (4.62%) and oleic acid (3.06%). The essential oil of mature leaves of C. diurnum were evaluated for antimicrobial activity against pathogenic strains of Gram positive (Staphylococcus aureus, Bacillus subtilis) and Gram negative (Escherichia Coli, Pseudomonas aeruginosa) bacteria. The oil showed strong in vitro activity against P. aeruginosa and S. aureus.African Journal of Biotechnology Vol. 4 (4), pp. 371-374, 200

Microbiological examination of milk in Tarakeswar, India with special reference to coliforms

A study was carried out to assess the milk quality in Tarakeswar, India with special reference to coliforms. By standard plate count (SPC) method, out of ten raw milk samples, the microbial colonies were found to be high in six samples and the colony content was low in rest four samples. Inpasteurized milk samples, the colonies were low in seven samples and high in three samples. The methylene blue test performed for raw milk samples showed that out of ten samples, the five samples were poor, two samples were fair, two samples were good and only one sample was found to be anexcellent. Out of ten pasteurized samples, nine samples were of good quality and one was found to be excellent. Bacterial colony was found to be opaque and metallic sheen in colour prepared from five raw milk samples, and by biochemical characterization it was identified as Escherichia col

Theory of tricriticality for miscut surfaces

We propose a theory for the observed tricriticality in the orientational phase diagram of Si(113) misoriented towards [001]. The systems seems to be at or close to a very special point for long range interactions.Comment: Revtex, 1 ps figur

Integrated Classifier: A Tool for Microarray Analysis

Microarray technology has been developed and applied in different biological context, especially for the purpose of monitoring the expression levels of thousands of genes simultaneously. In this regard, analysis of such data requires sophisticated computational tools. Hence, we confined ourselves to propose a tool for the analysis of microarray data. For this purpose, a feature selection scheme is integrated with the classical supervised classifiers like Support Vector Machine, K-Nearest Neighbor, Decision Tree and Naive Bayes, separately to improve the classification performance, named as Integrated Classifiers. Here feature selection scheme generates bootstrap samples that are used to create diverse and informative features using Principal Component Analysis. Thereafter, such features are multiplied with the original data in order create training and testing data for the classifiers. Final classification results are obtained on test data by computing posterior probability. The performance of the proposed integrated classifiers with respect to their conventional classifiers is demonstrated on 12 microarray datasets. The results show that the integrated classifiers boost the performance up to 25.90% for a dataset, while the average performance gain is 9.74%, over the conventional classifiers. The superiority of the results has also been established through statistical significance test