Ranges of interaction inp\bar p scattering at low energies

Thep¯ p cross sections at low energies are analysed in the framework of the optical model. It is shown that the annihilation range is closely related to the size of the proton as measured in electromagnetic and hadronic interactions. At larger distances thep¯ p interaction has the similar character as the NN one.     

X-ray characterization of La−Sr−Cu−O system

The high-temperature (38 K) superconducting La–Sr–Cu–O sample was investigated by X-ray diffractometry with diffracted beam monochromator. Four phases were identified. It is possible that the interaction between two of them can influence the superconducting properties of the sample. The EPMA analysis revealed the precipitates enriched by Sr up to 97%. The compositions of the matrix and the area with excess of Cu were estimated. The correlations between X-ray diffraction and EPMA results are discussed.     

Synthesis and characterization of amphiphilic fullerenes and their Langmuir-Blodgett films

We report here the synthesis and characterization of three amphiphilic fullerene derivatives and their Langmuir-Blodgett thin films. Two of the C(60) amphiphiles are mono-derivatives with a long alkyl chain terminated with either -COOH (2) or NH(2) (3) as the hydrophilic headgroup, and the third one (5) is designed to bear the same NH(2) group as 3 but with 10 additional hydrophobic alkyl chains grafted on the C(60) sphere (Scheme 1). These amphiphiles form stable, ordered monolayers at the air-water interface. The molecular packing at the air-water interface and the mean area per molecule are determined by pressure isotherms at room temperature. Hysteresis of pressure isotherms of side chain C(60) (5) shows complete reversibility upon compression and decompression, which suggests that side chains on the C(60) sphere inhibit formation of aggregates at the air-water interface. Comparative studies of all three amphiphiles allow us to better determine the interaction between C(60)'s and their self-assembly kinetics at the air-water interface. Monolayers of monoderivatized amphiphiles (2 and 3) were transferred successfully onto quartz substrates as Z-type multilayered Langmuir-Blodgett films, and monolayers of 5 were transferred as Y-type films. Detailed characterization of the multilayer films (Z-type deposition) prepared from amine-terminated C(60) (3) using X-ray and neutron reflectometry reveals staggering of C(60) spheres and a head-to-head (Y-type) structure presumably due to flipping and reattaching of C(60) amphiphiles to the previous underlying C(60) layer.     

Synthesis, surface modifications, and size-sorting of mixed nickel-zinc ferrite colloidal magnetic nanoparticles

We report on the spontaneous covalent growth of monomolecular adlayers on mixed nickel-zinc nanoferrite colloidal suspensions (ferrofluids). Synthesized nanoparticles were subjected to surface modification by means of acid chloride chemistry, leading to the formation of covalent bonds between the hydroxy groups at the nanoparticle surface and the acid chloride molecules. This procedure can be easily tailored to allow for the formation of adlayers containing both hydrophobic and hydrophilic regions stacked at predetermined distances from the magnetic core, and also providing the nanoferrites with functional carboxy groups capable of further modifications with, for example, drug molecules. Here, fluorophore aminopyrene molecules were bound to such modified nanoferrites through amide bonds. We also used the same chemistry to modify the surface with covalently bound long-chain palmitoyl moieties, and for comparison we also modified the nanoferrite surface by simple adsorption of oleic acid. Both procedures made the surface highly hydrophobic. These hydrophobic colloids were subsequently spread on an aqueous surface to form Langmuir monolayers with different characteristics. Moreover, since uniformity of size is crucial in a number of applications, we propose an efficient way of sorting the magnetic nanoparticles by size in their colloidal suspension. The suspension is centrifuged at increasing rotational speed and the fractions are collected after each run. The mean size of nanoferrite in each fraction was measured by the powder X-ray diffraction (PXRD) technique.     

Local dielectric spectroscopy of near-surface glassy polymer dynamics

A noncontact scanning probe microscopy method was used to probe local near-surface dielectric susceptibility and dielectric relaxation in polyvinyl acetate near the glass transition. Dielectric spectra were measured from 10(-4) to 10(2) Hz as a function of temperature. The measurements probed a 20 nm thick layer below the free surface of a bulk film. A significant change in the fragility index and moderate narrowing of the distribution of relaxation times were found in the near-surface layer. In contrast to results for ultrathin films confined on or between metallic electrodes, no reduction in the dielectric strength was found, inconsistent with the immobilization of slower modes.     

Deuterium isotope effects on 13C NMR chemical shifts of some α-(2-hydroxyaryl)-N-phenylnitrones (Schiff base N-oxides)

The deuterium isotope effect on the ¹³C NMR chemical shifts of some α-2-hydroxyaryl-N-phenylnitrones (Schiff base N-oxides) was studied. The existence of an intramolecular hydrogen bond with the proton localized on the phenolic oxygen atom was evidenced. Exceptionally large isotope effects ΔC-2(D) and ΔC-α(D) suggest that the substitution of the proton of the OH group by deuterium leads to a weakening of the hydrogen bond and some conformational changes in the molecule. This conclusion was drawn on the basis of a comparison of the deuterium isotope effects of Schiff base N-oxides and parent Schiff bases. Copyright © 2001 John Wiley & Sons, Ltd.     

Designing 1D grating for extraordinary optical transmission for TM polarization

Due to their high brightness at resonance, 1D metallo-dielectric transmission gratings have been proposed as useful in a number of applications including Scanning Near-field Optical Microscopy (SNOM), flat-panel displays, spatial light modulators and optoelectronic devices. In this article, using the Fabry–Perot resonance condition and numerical optimization, we demonstrate a design methodology of 1D grating structure that provides resonance at a desired wavelength for Transverse Magnetic (TM) polarization. Depending on grating and substrate materials and target applications under consideration, our method provides optimum grating parameters, i.e. slit width, grating period and thickness adaptively. Application specific requirements such as the bandwidth around a resonance can be adjusted by setting appropriate constraint functions. Simulations results from modal analysis show that resonances are achieved at wavelengths for which grating parameters have been optimized.     

Remarks on Effect Algebras

Erik M. Alfsen and Frederic W. Shultz had recently developed the characterisation of state spaces of operator algebras. It established full equivalence (in the mathematical sense) between the Heisenberg and the Schr?dinger picture, i.e. given a physical system we are able to construct its state space out of its observables as well as to construct algebra of observables from its state space. As an underlying mathematical structure they used the theory of duality of ordered linear spaces and obtained results are valid for various types of operator algebras (namely C ^*, von Neumann, JB and JBW algebras). Here, we show that the language they developed also admits a representation of an effect algebra.     

On Quantum Correlations and Positive Maps

We present a discussion on local quantum correlations and their relations with entanglement. We prove that a vanishing coefficient of quantum correlations implies separability. The new results on locally decomposable maps which we obtain in the course of the proof also seem to be of independent interest.     

Sample path large deviations for a family of long-range dependent traffic and associated queue length processes

We consider the long-range dependent cumulative traffic generated by the superposition of constant rate fluid sources having exponentially distributed inter start times and Pareto distributed durations with finite mean and infinite variance. We prove a sample path large deviation principle when the session start time intensity is increased and the processes are centered and scaled appropriately. Properties of the rate function are investigated. We derive a sample path large deviation principle for a related family of stationary queue length processes. The large deviation approximation of the steady-state queue length distribution is compared with the corresponding empirical distribution obtained by a computer simulation. MSC 2000 Classifications: Primary 60F10; Secondary 60K25, 68M20, 90B22