Crystal Structure and Molecular Conformational Studies of Allyl 6-Amino-5-cyano-4-(4-fluorophenyl)-2-methyl-4H-pyran-3-carboxylate

Crystallography Reports - The allyl 6-amino-5-cyano-4-(4-fluorophenyl)-2-methyl-4H-pyran-3-carboxylate, C17H15FN2O3, compound adopts a triclinic crystal system with the sp. gr. $$P\bar {1}$$, Z =...     

On the Existence of XOR-Based Codes for Private Information Retrieval with Private Side Information

We consider the problem of Private Information Retrieval with Private Side Information (PIR-PSI), wherein the privacy of the demand and the side information are jointly preserved. Although the capacity of the PIR-PSI setting is known, we observe that the underlying capacity-achieving code construction uses Maximum Distance Separable (MDS) codes therefore contributing to high computational complexity when retrieving the demand. Pointing at this drawback of MDS-based PIR-PSI codes, we propose XOR-based PIR-PSI codes for a simple yet non-trivial setting of two non-colluding databases and two side information files at the user. Although our codes offer substantial reduction in complexity when compared to MDS-based codes, the code-rate marginally falls short of the capacity of the PIR-PSI setting. Nevertheless, we show that our code-rate is strictly higher than that of XOR-based codes for PIR with no side information. As a result, our codes can be useful when privately downloading a file especially after having downloaded a few other messages privately from the same database at an earlier time-instant.     

Analytical expressions for polar magnetoptics in magnetic multilayers

This paper is a comprehensive study of different formalisms used to simulate polar magneto-optical (MO) effects in multilayers. A development of the 4 × 4 matrix calculation to first order in off-diagonal elements of the permittivity tensor gives original analytical expressions. They allow to express the MO effects in multilayers as a sum of contributions from individual layers. Each contribution consists of two components assigned to the interface and propagation effects. The explicit expressions for multilayers containing up to seven layers, together with those obtained in the frame of an ultrathin layer approximation, are shown to be useful both in a qualitative comprehension and in quantitative simulations of the experimental MO Kerr spectra of a wide variety of ultrathin magnetic structures. They can be used to separate the different contributions arising from the interfaces due to intermixing or spin polarization (including interface roughness) as well as to simulate magnetically coupled multilayers. As an example, the analytical expression is provided for a system consisting of two ultrathin films separated by a non-magnetic spacer and deposited on a non-magnetic substrate. The capabilities of the analytical expressions are demonstrated on MO spectroscopy in a broad spectral range of some well characterized ultrathin magnetic structures. This work has been partially supported by HCM programme “Magnetic properties of novel ultrathin films” (project number ERBCIPDCT940622), NATO Grant “High Technology” (LG931415) and Grant Agency of Czech Republic (# 202/97/1180 and # 202/00/0761).     

Fluorescence Methods to Probe Nanometer-Scale Organization of Molecules in Living Cell Membranes

The ability to study the structure and function of cell membranes and membrane components is fundamental to understanding cellular processes. This requires the use of methods which are capable of resolving structures at nanometer-scale resolution in living cells. In this review we survey fluorescence imaging methodologies capable of nanometer-scale resolution. We then critically examine specific biological applications of these methods, in the context of understanding membrane protein conformation and dynamics, intracellular signaling, organization of lipid rafts, and cell surface topology.     

Photoelectrochemistry of indium hexacyanoferrate–titania composite films

The voltammetric and electrochromic behavior of two types of indium(III) hexacyanoferrate(II/III) (InHCF) films, potentiodynamically grown either on polycrystalline Au or on tin-doped indium oxide (ITO) support electrodes, are described. A new spectral feature was seen at ca. 475 nm for the InHCF films grown on Au under extended potential window (EPW) conditions, in addition to the dominant 420 nm feature described by previous authors. The 420 nm band is the sole electrochromic feature in films grown under restricted potential window (RPW) conditions. The InHCF films were also grown in the presence of TiO₂ particles in the deposition bath. The resultant InHCF–TiO₂ composite films showed distinctly different photoelectrochemical responses for the EPW and the RPW counterparts. X-ray phoelectron spectroscopy data showed a higher TiO₂ particle uptake for the EPW films relative to their RPW counterparts, under otherwise identical growth conditions. A second film configuration built up by InHCF derivatization of a pre-formed In–TiO₂ film, yielded decidedly inferior photoresponses. Mechanistic reasons for this are presented as is evidence for the dominance of two distinct forms of InHCF under the EPW growth conditions.     

Evanescently coupled resonance in surface plasmon enhanced transmission

The optical transmission through subwavelength holes in metal films can be enhanced by several orders of magnitude by enabling interaction of the incident light with independent surface plasmon (SP) modes on either side of the film. Here, we show that this transmission is boosted by an additional factor of 10 when the energies of the SP modes on both sides are matched. These results, confirmed by a three-dimensional theoretical analysis, give a totally new understanding of the phenomenon of SP enhanced transmission. It is found that the holes behave like subwavelength cavities for the evanescent waves coupling the SPs on either side of the film. In this unusual device, the reflection at either end of the cavity is provided by the SP modes which act as frequency dependent mirrors.     

Magnetization and spin echo studies in compositionally modulated CoNb and Co films

The ⁵⁹Co spin echo signal frequency of a compositionally modulated CoNb sample with Co sublayer as thin as 14 Å is the same as that of a Co film but the low frequency tail becomes more pronounced as this thickness decreases. Increasing Nb layer thickness reduces the signal intensity.