Cross-stream migration of flexible molecules in a nanochannel

Molecular dynamics simulations are used to examine the cross-stream chain migration phenomenon in dilute polymer solutions that are flowing in nanochannels. In particular, both uniform planar shear (Couette) and pressure driven (Poiseuille) flows of a dilute polymer solution are studied using a bead-spring representation of polymer chains and a coarse grained model for the solvent. Our results show that three mechanisms govern the migration of deformable molecules in a nanochannel: (1) chain-wall hydrodynamic interactions, (2) thermal diffusion, and (3) gradient in chain mobility. These results are discussed in the context of recent experimental, numerical and theoretical work.     

Soft mode analysis and ferroelectric transition in spherical nanoparticles

We address the dielectric behavior in a free standing spherical particle using the phenomenological Landau theory. Considering the equations of motion and small perturbation against uniform polarization, we obtain the size driven ferroelectricity. The size driven polarization is shown to diverge at a new correlation length which turns out to be the extrapolation length. Mode analysis in such systems is carried out and it is found that the size driven ferroelectricity is associated with a soft mode which takes a minimum value at the new transition temperature similar to that of the bulk system. We suggested that such a mode can be tested in Raman measurement.     

Reduction of homomorphisms mod p and algebraicity

Let A be an abelian variety over a number field K. Let φ be an endomorphism of A(K) into itself which reduces modulo v for almost all finite places v of K. The question we discuss in this paper is whether φ arises from an endomorphism of the abelian variety A. We answer this question in the affirmative for many cases. The question is inspired by a work of C. Corrales and R. Schoof, and uses a recent work of Larsen. We also look at the analogue of this question for linear algebraic groups.     

Local identities involving Jacobi elliptic functions

We derive a number of local identities involving Jacobi elliptic functions and use them to obtain several new results. First, we present an alternative, simpler derivation of the cyclic identities discovered by us recently, along with an extension to several new cyclic identities. Second, we obtain a generalization to cyclic identities in which successive terms have a multiplicative phase factor exp(2iπ/s), wheres is any integer. Third, we systematize the local identities by deriving four local ‘master identities’ analogous to the master identities for the cyclic sums discussed by us previously. Fourth, we point out that many of the local identities can be thought of as exact discretizations of standard non-linear differential equations satisfied by the Jacobi elliptic functions. Finally, we obtain explicit answers for a number of definite integrals and simpler forms for several indefinite integrals involving Jacobi elliptic functions.     

Preparation and study of silver added La0.67Ca0.33MnO3 film

La_0.67Ca_0.33MnO₃ (LCMO) and Ag admixed La_0.67Ca_0.33MnO₃ (Ag-LCMO) polycrystalline films have been prepared on SrTiO₃ single crystal (100) substrates by ultrasonic spray pyrolysis technique. These films are characterized using XRD, SEM, and temperature dependence of resistivity (ρ-T) and ac susceptibility (χ-T). The films are having cubic structure with lattice parameters as 3.890 and 3.885 Å for LCMO and Ag-LCMO films, respectively. The peek in ρ-T curve (T_p) and the ferromagnetic transition temperature (T_C) for the Ag-LCMO film is higher than that of LCMO film. The stability of both the films was tested by repeated measurements of its characteristics over a period of one week after several thermal cycling from room temperature to 77 K. In the LCMO film, the peak in the ρ-T curve (T_p) is found to shift towards lower value and conduction noise of the film increases in the subsequent measurements. In the case of Ag-LCMO the value of T_p, T_C and conduction noise of the film did not change even after several measurements. Silver segregating at the grain boundaries in Ag-LCMO polycrystalline film seems to be responsible for improving the characteristics of Ag-LCMO films.     

mga Genosensor for Early Detection of Human Rheumatic Heart Disease

The 5′ amino-labeled DNA probe complementary to mga gene of Streptococcus pyogenes was immobilized on carboxylated multiwall carbon nanotubes electrode and hybridized with 0.1–100 ng/6 μl single-stranded genomic DNA (ssG-DNA) of S. pyogenes from throat swab of suspected rheumatic heart disease (RHD) patients. Electrochemical response was measured by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance (EI). The sensitivity of the sensor was 106.03?(μA/cm²)/ng and limit of detection (LOD) was found 0.014 ng/6 μl with regression coefficient (R ²) of 0.921 using DPV. The genosensor was characterized by FTIR and SEM, and electrode was found stable for 6 months on storage at 4 °C with 5–6 % loss in initial DPV current. mga genosensor is the first report on RHD sensor which can save life of several suspected patients by early diagnosis in 30 min.     

Biochemical Basis of Mercury Remediation and Bioaccumulation by Enterobacter sp. EMB21

The aims of this study were to isolate metal bioaccumulating bacterial strains and to study their applications in removal of environmental problematic heavy metals like mercury. Five bacterial strains belonging to genera Enterobacter, Bacillus, and Pseudomonas were isolated from oil-spilled soil. Among these, one of the strains Enterobacter sp. EMB21 showed mercury bioaccumulation inside the cells simultaneous to its bioremediation. The bioaccumulation of remediated mercury was confirmed by transmission electron microscopy and energy dispersive X-ray. The mercury-resistant loci in the Enterobacter sp. EMB21 cells were plasmid-mediated as confirmed by transformation of mercury-sensitive Escherichia coli DH5α by Enterobacter sp. EMB21 plasmid. Effect of different culture parameters viz-a-viz inoculum size, pH, carbon, and nitrogen source revealed that alkaline pH and presence of dextrose and yeast extract favored better remediation. The results indicated the usefulness of Enterobacter sp. EMB21 for the effective remediation of mercury in bioaccumulated form. The Enterobacter sp. EMB21 seems promising for heavy metal remediation wherein the remediated metal can be trapped inside the cells. The process can further be developed for the synthesis of valuable high-end functional alloy, nanoparticles, or metal conjugates from the metal being remediated.     

Protein-Coated Microcrystals of Pseudomonas aeruginosa PseA lipase

Highly active Pseudomonas aeruginosa lipase protein-coated microcrystals (PAL PCMC) have been prepared by immobilization of protein onto K₂SO₄ as excipient solid support carrier and n-propanol as precipitating solvent. Transmission electron micrographs confirmed the formation of PAL PCMC. These PCMC were found to be a catalytically more active and stable preparation for p-nitrophenyl palmitate hydrolysis in n-heptane, compared to free lipase. The V _max, K _m, and temperature optimum for PAL PCMC increased from 0.49 to 5.66 nmol min^?1 mg^?1, 589 to 679.8 mmol, and 40°C to 45°C, respectively. These were thermally more stable with 4.65, 2.56, and 1.24-fold improvement in half lives at 45°C, 55°C, and 60°C compared to free P. aeruginosa PseA lipase. Their catalytic efficiency was enhanced by tenfold over that of free enzyme. PAL PCMC offer a simple and effective technique for obtaining stable and efficient lipase preparation for biocatalysis in nonaqueous medium.     

Preparation and low field magnetoresistance of double layered manganite La1.4Ca1.6Mn2O7

Double layered manganite of La_1.4Ca_1.6Mn₂O₇ (DLCMO) was prepared using solid state reaction method and had a metal-insulator transition temperature (T_MI) of 125 K. The short range 2D-feerromagnetic ordering (T_C2) starts growing when T<168 K and it gets converted into 3D-ferromagnetic ordering (T_C1) at 114 K. Low field magnetoresistance (MR) behaviour of the DLCMO was investigated and compared with an infinite layered manganite La_0.7Ca_0.3MnO₃ (LCMO). For DLCMO, in the temperature range between T_C1 and T_C2, the MR showed a gradual increase with the magnetic field. The observed MR and R-T behaviour of double layered manganite for T_C1<T<T_C2 has been explained in the frame work of the two phase model [ferromagnetic (FM) domains and paramagnetic (PM) regions] and percolative behaviour of transport in FM-PM mixture.