High electrocatalytic oxidation of folic acid at carbon paste electrode bulk modified with iron nanoparticle-decorated multiwalled carbon nanotubes and its application in food and pharmaceutical analysis

Ionics - A simple and rapid method was employed for the modification of carbon paste electrode with iron nanoparticle-decorated multiwalled carbon nanotubes (MCPE/Fe-MWCNTs). The synergistic effect...     

First order linear partial differential equations with discontinuous coefficients

Summary Si dà un teorema di esistenza e di unicità di soluzione generalizzata per il problema di Cauchy relativo all'equazione . Le ipotesi fatte sui coefficienti a_i(t, x) permettono discontinuità di tipo molto generale, purchè sia soddisfatta una certa «condizione di trasversalità» tra le caratteristiche dell'equazione e le discontinuità del campo di vettori che le definisce.     

ESR and XRD investigation of effects induced by gamma radiation on PVA-TiO2 membranes

The effects of gamma radiation on the local structure of PVA membranes containing TiO₂ were investigated by ESR and XRD methods. An intense ESR signal is observed after irradiation at 16 KGy dose. This signal appears only for irradiated samples and it is associated with the breaking of the polymeric chain, followed by local reorganization of the polymeric segments and the apparition of the unpaired electrons and free radicals. The intensity of the signal decreases with the concentration of TiO₂, indicating a shielding effect of the dopand. That the modification of local order of the polymeric chains has been modified after irradiation is confirmed by XRD method.     

Investigation on hexamethyldisilazane vapor treatment of plasma-damaged nanoporous organosilicate films

Hexamethyldisilazane (HMDS) vapor treatment of plasma-damaged nanoporous organosilicate thin films has been studied as a function of treatment temperature in this work. Although, the HMDS vapor treatment facilitated incorporation of methyl (CH₃) groups subsequent to the removal of free hydroxyl (OH) groups in the damaged films at treatment temperature as low as 55 °C, the bonded OH groups were not removed. More significantly, detailed analysis of the results reveals that HMDS vapor modified only the surface of the plasma-damaged samples and not the entire film as expected. This is attributed to the formation of a thin solid layer on the surface, which effectively prevents penetration of HMDS vapors into the bulk. The Fourier transform-infrared (FT-IR) absorption and dielectric constant measurements confirm that the vapor treatment assists only partial curing of the plasma-damaged films. Alternative processes of curing the films with HMDS dissolved in supercritical carbon dioxide (SCCO₂) as a medium of reaction in static and pulsed modes were also attempted and the results are presented in this paper.     

All-optical measurement-based quantum-information processing in quantum dots

Parity measurements on qubits can generate the entanglement resource necessary for scalable quantum computation. Here we describe a method for fast optical parity measurements on electron spin qubits within coupled quantum dots. The measurement scheme, which can be realized with existing technology, consists of the optical excitation of excitonic states followed by monitored relaxation. Conditional on the observation of a photon, the system is projected into the odd/even-parity subspaces. Our model incorporates all the primary sources of error, including detector inefficiency, effects of spatial separation and nonresonance of the dots, and also unwanted excitations. Through an analytical treatment we establish that the scheme is robust to such effects. Two applications are presented: a realization of a controlled-NOT gate, and a technique for growing large scale graph states.     

Electronic spin precession and interferometry from spin-orbital entanglement in a double quantum dot

A double quantum dot inserted in parallel between two metallic leads can entangle the electron spin with the orbital (dot index) degree of freedom. An Aharonov-Bohm orbital phase can be transferred to the spinor wave function, providing a geometrical control of the spin precession around a fixed magnetic field. A fully coherent behavior occurs in a mixed orbital-spin Kondo regime. Evidence for the spin precession can be obtained, either using spin-polarized metallic leads or by placing the double dot in one branch of a metallic loop.     

Hyper-Raman scattering from vitreous boron oxide: coherent enhancement of the boson peak

Hyper-Raman scattering spectra of vitreous B(2)O(3) are compared to Raman scattering ones. Particular attention is given to the low-frequency boson peak which relates to out-of-plane rigid librations of planar structural units, mostly boroxols. While the Raman strength can be accounted for by the motions of single units, the hyper-Raman signal exhibits a unequaled enhancement due to coherent librations of several boroxols. This important distinction is explained by the different symmetry properties of the polarizability and hyperpolarizability tensors of the structural units.     

Observation of Optical Second Harmonic Generation in Wet-Spun Films of Na-DNA

The observation of optical second harmonic generation (SHG) from wetspun films of Na-DNA is reported. The SHG signal is stronger at a relative humidity of 92% (corresponding to the B conformation of Na-DNA) than at low humidity of -33% (corresponding to a disordered conformation of Na-DNA). The strength of the SHG signal is also dependent on the orientation of the incident laser beam polarization with respect to the DNA helical axes.     

Operators with singular continuous spectrum,VII. Examples with borderline time decay

We construct one-dimensional potentialsV(x) so that if onL ²(), thenH has purely singular spectrum; but for a dense setD, D implies that |,e ^-itH |C |t|^-1/2 ln(|t|) for t>2. This implies the spectral measures have Hausdorff dimension one and also, following an idea of Malozemov-Molchanov, provides counterexamples to the direct extension of the theorem of Simon-Spencer on one-dimensional infinity high barriers.This material is based upon work supported by the National Science Foundation under Grant No. DMS-9401491. The Government has certain rights in this material.