Pseudo-steady-state solutions for solidification in a wedge

Polubarinova-Kochina's analytical differential equation methodis used to determine the pseudo-steady-state solution to problemsinvolving the freezing (solidification) of wedges of liquidwhich are initially at their fusion temperature. In particular,we consider four distinct problems for wedges which are: freezingwith the same constant boundary temperature, freezing with thesame constant boundary heat fluxes, freezing with distinct constantboundary temperatures and freezing with distinct constant fluxesat the boundaries. For the last two problems, a Heun's differentialequation with an unknown singularity is derived, which in bothcases admits a particularly elegant simple solution for thespecial case when the wedge angle is . The moving boundariesobtained are shown pictorially.     

An Adamantyl Amino Acid Containing Gramicidin S Analogue with Broad Spectrum Antibacterial Activity and Reduced Hemolytic Activity

The cyclic cationic antimicrobial peptide gramicidin S (GS) is an effective topical antibacterial agent that is toxic for human red blood cells (hemolysis). Herein, we present a series of amphiphilic derivatives of GS with either two or four positive charges and characteristics ranging between very polar and very hydrophobic. Screening of this series of peptide derivatives identified a compound that combines effective antibacterial activity with virtually no toxicity within the same concentration range. This peptide acts against both Gram‐negative and Gram‐positive bacteria, including several MRSA strains, and represents an interesting lead for the development of a broadly applicable antibiotic.     

Boltzmann power laws

In this paper we propose a model based on the Boltzmann distribution as a mechanism for generating power laws, Boltzmann Power Laws (BPL). Some of these power laws are studied and compared to popular power laws such as ‘1/f’ noise and self-organized criticality (SOC). We will show how, in some cases, these BPLs reproduce behaviors similar to the finite size scaling (FSS) scenario, which is typical of SOC.     

Plasmon spectroscopy of metallic nanoparticles above flat dielectric substrates

We numerically analyze the spectral properties of localized plasmon resonances in metal nanoparticles when these are above a dielectric substrate. This analysis is performed as a function of the various parameters involved in the problem (relative optical properties, particle-substrate separation, angle of incidence, etc.). It can be shown that from the spectral behavior of the resonance in the far field, information about particle near-field interactions can be obtained.     

Monitoring small defects on surface microstructures through backscattering measurements

The detection and characterization of small defects on particles or structures of a size comparable with the incident wavelength and located on flat substrates is numerically analyzed. For metallic scattering systems, calculations based on the extinction theorem of physical optics show that geometrical information about a small Gaussian defect can be obtained by partially integrating the backscattering patterns.     

Differential non-destructive image current detection in a fourier transform quadrupole ion trap

Dual-detector differential non-destructive Fourier transform detection in a quadrupole ion trap is shown to improve signal intensity and reduce noise compared with spectra recorded using a single detector. A larger area detector in each end-cap electrode is machined to fit its hyperbolic shape and so minimize field imperfections on the z-axis. Argon, acetophenone and bromobenzene spectra were recorded to allow a comparison between single- and dual-detector (differential) modes of detection and to demonstrate the improvement achieved with differential detection. Copyright 1999 John Wiley & Sons, Ltd.     

Application of the polar decomposition to light scattering particle systems

We have applied the polar decomposition theorem (PDT) to the scattering matrix of simple systems such as an isolated sphere, either metallic or dielectric. The discrete dipole approximation (DDA) method has been used as an intermediate tool to calculate these matrices. We show how the parameters introduced by the PDT for describing the scattering by a single sphere can be easily interpreted. It is also shown that the PDT provides us with an alternative frame to conventional Mueller matrix analysis, by characterizing the systems by means of a group of independent parameters representing magnitudes of simple (virtual) elements. This step is necessary in order to translate other complex system matrices into manageable information.