Rotational diffusion of an ionic solute in polymorphic environments of a block copolymer: influence of interfacial friction on solute rotation

In an attempt to understand the role of interfacial friction on solute rotation, fluorescence anisotropy decays of a cationic solute, rhodamine 110, have been measured in polymorphic environments of a triblock copolymer, (PEO)20-(PPO)70-(PEO)20 (P123) (PEO = poly(ethylene oxide), PPO = poly(propylene oxide)). It has been noticed that even though rhodamine 110 is located in the interfacial region of the micelles, sol-gel transition does not significantly influence its rotation. Micelle-micelle entanglement, which is responsible for gelation, persists even in the micellar solution phase, perhaps to a lesser degree, and this entanglement is responsible for the observed behavior. This hypothesis has been substantiated by undertaking concentration-dependent studies in which it is shown that the reorientation time of the solute increases with an increase in the micellar concentration. In the case of reverse micelles, it has been observed that an enhancement in the water content facilitates solute rotation, which has been rationalized on the basis of solute migration from the hydrated poly(ethylene oxide) region to the poly(ethylene oxide)-water interface within the core.     

Rotational diffusion of ionic and neutral solutes in mixed micelles: effect of surfactant to block copolymer mole ratio on solute rotation

Rotational diffusion of an ionic solute rhodamine 110 and a neutral solute 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DMDPP) has been investigated in aqueous mixtures of cetyltrimethylammonium chloride (CTAC) and poly(ethylene oxide)20-poly(propylene oxide)70-poly(ethylene oxide)20 (P123). The purpose of this work is to understand how an increase in the mole ratio of surfactant to block copolymer from low to high influences the dynamics of ionic and neutral solute molecules. The variation in the mole ratio of CTAC to P123 from low to high has resulted in a drastic increase in the average reorientation time of rhodamine 110. In contrast, an exactly opposite trend has been noticed in the case of DMDPP. In the low mole ratio regime, rhodamine 110 and DMDPP are located at the interface and palisade layer, respectively, of P123 micelle-CTAC complexes. On the other hand, in the high mole ratio regime, both the probes are located in the Stern layer of CTAC-P123 complexes. The enhancement in the average reorientation time of rhodamine 110 with an increase in the mole ratio of surfactant to block copolymer has been rationalized on the basis of formation of rhodamine 110-Cl ion pair, which in turn associates with the cationic head groups of CTAC-P123 complexes. The observed decrease in the average reorientation time of DMDPP with an increase in the mole ratio of CTAC to P123 is a consequence of lower microviscosity of the Stern layer of CTAC-P123 complexes compared to the palisade layer of P123 micelle-CTAC complexes.     

A Modified Proximity Approach in the Fusion of Heavy Ions

By using a suitable set of the surface energy coefficient, nuclear radius, and universal function, the original proximity potential 1977 is modified. The overestimate of the data by 4% reported in the literature is significantly reduced. Our modified proximity potential reproduces the experimental data nicely compared to its older versions.     

Coherence of an optically illuminated single nuclear spin qubit

We investigate the coherence properties of individual nuclear spin quantum bits in diamond [Dutt, Science 316, 1312 (2007)10.1126/science.1139831] when a proximal electronic spin associated with a nitrogen-vacancy (N-V) center is being interrogated by optical radiation. The resulting nuclear spin dynamics are governed by time-dependent hyperfine interaction associated with rapid electronic transitions, which can be described by a spin-fluctuator model. We show that due to a process analogous to motional averaging in nuclear magnetic resonance, the nuclear spin coherence can be preserved after a large number of optical excitation cycles. Our theoretical analysis is in good agreement with experimental results. It indicates a novel approach that could potentially isolate the nuclear spin system completely from the electronic environment.     

Die quantitative Bestimmung von Triglyceriden mit Hilfe der Gaschromatographie

Ohne Zusammenfassung     

Rotational diffusion of a nonpolar and a dipolar solute in 1-butyl-3-methylimidazolium hexafluorophosphate and glycerol: interplay of size effects and specific interactions

Temperature dependent rotational diffusion of a nonpolar solute, 9-phenylanthracene (9-PA), and a dipolar solute, rhodamine 110 (R110), has been examined in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim(+)][PF(6) (-)]) and in a conventional solvent, glycerol. This study has been undertaken to explore how parameters such as solvent size and free volume influence solute rotation in the case of a nonpolar solute, 9-PA. To understand the role of specific solute-solvent interactions, similar measurements have been performed with a dipolar analogue, R110. It has been observed that the viscosity normalized reorientation times of 9-PA are longer by a factor of 1.4-1.6 in glycerol compared to those in [bmim(+)][PF(6) (-)]. While the most commonly used Stokes-Einstein-Debye hydrodynamic theory is not successful in explaining this experimental observation, Gierer-Wirtz and Dote-Kivelson-Schwartz quasihydrodynamic theories could rationalize this trend, albeit in a qualitative manner. Rotational diffusion of R110, on the other hand, follows an exactly opposite trend compared to 9-PA. The normalized reorientation times of R110 are longer by a factor of 1.3-1.4 in [bmim(+)][PF(6) (-)] compared to glycerol, which is due to the formation of stronger solute-solvent hydrogen bonds between the positively charged R110 and the ionic liquid.     

Experimental implementation of local adiabatic evolution algorithms by an NMR quantum information processor

Quantum adiabatic algorithm is a method of solving computational problems by evolving the ground state of a slowly varying Hamiltonian. The technique uses evolution of the ground state of a slowly varying Hamiltonian to reach the required output state. In some cases, such as the adiabatic versions of Grover's search algorithm and Deutsch-Jozsa algorithm, applying the global adiabatic evolution yields a complexity similar to their classical algorithms. However, using the local adiabatic evolution, the algorithms given by J. Roland and N.J. Cerf for Grover's search [J. Roland, N.J. Cerf, Quantum search by local adiabatic evolution, Phys. Rev. A 65 (2002) 042308] and by Saurya Das, Randy Kobes, and Gabor Kunstatter for the Deutsch-Jozsa algorithm [S. Das, R. Kobes, G. Kunstatter, Adiabatic quantum computation and Deutsh's algorithm, Phys. Rev. A 65 (2002) 062301], yield a complexity of order N (where N=2(n) and n is the number of qubits). In this paper, we report the experimental implementation of these local adiabatic evolution algorithms on a 2-qubit quantum information processor, by Nuclear Magnetic Resonance.     

Fabrication and Characterization of Cysteine-Functionalized Zinc Oxide Nanoparticles for Enzyme Immobilization

A green approach is reported for the synthesis of cysteine-functionalized zinc oxide nanoparticles using potato extract as a nontoxic and economical reducing agent. The cysteine-functionalized nanoparticles were used as a support for enzyme immobilization. The structural morphology, crystallinity, and surface functionalization were characterized by scanning electron microscopy, X-ray diffraction, and infrared spectroscopy, respectively. Spherical nanoparticles from 150 to 200?nm were used to evaluate the immobilization efficiency for urease through covalent attachment on the glutaraldehyde-activated amino group of cysteine. In comparison to the unmodified nanoparticles, 62.9% enzyme loading with 72.45% of enzyme specific activity was recovered which was 56% higher than on bare zinc oxide nanoparticles. The point of addition of cysteine during the nanoparticle synthesis had a direct effect on the immobilization efficiency. The immobilized enzyme-specific activity was reduced to 34.32% when cysteine was added following the nanoparticle synthesis. With a facile synthesis procedure and significant immobilization efficiency, cysteine-functionalized zinc oxide nanoparticles were shown to be suitable for various clinical and industrial applications.     

Sorption behavior of metal ions on thiourea-impregnated silica gel G and alumina stationary phases in aqueous HCl and acetone—HCl media: Quantitative separation of Pb2+ and Hg2+ from other metal ions

JPC – Journal of Planar Chromatography – Modern TLC - The sorption behavior of a number of metal ions was investigated on thiourea-impregnated silica gel G and alumina layers with...     

Amperometric titrations using the tubular graphite electrode. Development of an automatic technique

The tubular geometry of the electrode, by virtue of which the electrode can permit continuous analysis of electroactive solutions, has been made use of in developing an automatic technique for carrying out amperometric titrations, the tubular graphite electrode acting as an indicator electrode. A correlation, describing the time required for the completion of a particular titration in terms of relevant parameters such as the concentrations of the titrant and the titration solutions, volumetric flow rate of the titrant/titration solution and the total volume of the titration solution, has been derived theoretically and verified experimentally. Knowing the time required for the completion of a particular titration from the titration curve recorded automatically, the concentration of the titration solution can be easily calculated.