Speciation of bound and free metals evaluated for lobster digestive gland extracts

A simple method is described for the speciation of metalions in biological extracts with a short desalting gel-filtration column. The system was optimized for the eluent and gel type to provide accurate free metal ion levels and minimum processing times. The four separation media studied were Sephadex G25, Bio-Gel P-6DG, controlled pore glass CPG40, and Fractogel HW40F. The best medium was the Fractogel HW40F because it was not compressible and allowed a pump to be used to obtain uniform flow rates. The eluent was 0.10 M ammonium acetate/0.01 M citric acid adjusted to pH 7.0. This eluent minimized ion/gel interactions and gave a lower salt content relative to other possible eluents. The separation time was 10 min per sample per metal ion of interest. The detection limits relative to the mass of wet tissue for the column/flame spectrometer system were 0.80 μg g^?1, 0.80 μg g^?1, and 1.6 μg g^?1 for zinc, cadmium and copper, respectively. The method is evaluated for a lobster digestive gland extract; the methodology should be applicable to other systems containing nonlabile metal species.     

A digital real-time lidar data recording,processing and display system

Application of laser radars to meteorological programs has been limited by the absence of suitable data recording, processing and display techniques. This paper discusses a digital data system that provides the means of performing real-time analysis and display of lidar data. The system is constructed of commercially available components and makes optimum use of available software. Application of the system to the real-time viewing of cirrus cloud structure and inference of cloud density is presented. A review of previously used lidar data handling techniques is also presented.Development of this system was supported by the United States Air Force, Space and Missiles Systems Organization.     

Extending the language of DNA molecular recognition by polyamides: unexpected influence of imidazole and pyrrole arrangement on binding affinity and specificity

Pyrrole (Py) and imidazole (Im) polyamides can be designed to target specific DNA sequences. The effect that the pyrrole and imidazole arrangement, plus DNA sequence, have on sequence specificity and binding affinity has been investigated using DNA melting (DeltaT(M)), circular dichroism (CD), and surface plasmon resonance (SPR) studies. SPR results obtained from a complete set of triheterocyclic polyamides show a dramatic difference in the affinity of f-ImPyIm for its cognate DNA (K(eq) = 1.9 x 10(8) M(-1)) and f-PyPyIm for its cognate DNA (K(eq) = 5.9 x 10(5) M(-1)), which could not have been anticipated prior to characterization of these compounds. Moreover, f-ImPyIm has a 10-fold greater affinity for CGCG than distamycin A has for its cognate, AATT. To understand this difference, the triamide dimers are divided into two structural groupings: central and terminal pairings. The four possible central pairings show decreasing selectivity and affinity for their respective cognate sequences: -ImPy > -PyPy- > -PyIm- approximately -ImIm-. These results extend the language of current design motifs for polyamide sequence recognition to include the use of "words" for recognizing two adjacent base pairs, rather than "letters" for binding to single base pairs. Thus, polyamides designed to target Watson-Crick base pairs should utilize the strength of -ImPy- and -PyPy- central pairings. The f/Im and f/Py terminal groups yielded no advantage for their respective C/G or T/A base pairs. The exception is with the -ImPy- central pairing, for which f/Im has a 10-fold greater affinity for C/G than f/Py has for T/A.     

Preconditioned iterative methods for coupled discretizations of fluid flow problems

Computational fluid dynamics, where simulations require largecomputation times, is one of the areas of application of highperformance computing. Schemes such as the SIMPLE (semi-implicitmethod for pressure-linked equations) algorithm are often usedto solve the discrete Navier-Stokes equations. Generally theseschemes take a short time per iteration but require a largenumber of iterations. For simple geometries (or coarser grids)the overall CPU time is small. However, for finer grids or morecomplex geometries the increase in the number of iterationsmay be a drawback and the decoupling of the differential equationsinvolved implies a slow convergence of rotationally dominatedproblems that can be very time consuming for realistic applications.So we analyze here another approach, DIRECTO, that solves theequations in a coupled way. With recent advances in hardwaretechnology and software design, it became possible to solvecoupled Navier-Stokes systems, which are more robust but implyincreasing computational requirements (both in terms of memoryand CPU time). Two approaches are described here (band blockLU factorization and preconditioned GMRES) for the linear solverrequired by the DIRECTO algorithm that solves the fluid flowequations as a coupled system. Comparisons of the effectivenessof incomplete factorization preconditioners applied to the GMRES(generalized minimum residual) method are shown. Some numericalresults are presented showing that it is possible to minimizeconsiderably the CPU time of the coupled approach so that itcan be faster than the decoupled one.     

Mie scattering techniques for air pollution measurement with lasers

Lidar (laser radar) techniques of remotely observing atmospheric particulates have obvious relevance to air pollution. After briefly noting the capability of lidar in a semiquantitative role for monitoring spatial and temporal variations of particulate concentration attention is directed to the problems of evaluating lidar observations quantitatively in terms of such physically meaningful parameters as the turbidity, opacity or particulate mass concentration of smoke plumes or the ambient atmosphere. Solutions based on Mie scattering theory are illustrated with examples from (1) hazy atmospheres (2) smoke plumes and (3) controlled aerosols in a test chamber. While noting that the role of lidar in research applications in air pollution is well established, its routine operational use is seen to be dependent upon further experimental and technological development. Its potential for monitoring ambient air quality and emission sources is stressed.     

Preparation, structural analysis and dielectric properties of Bi x La1−x FeO3 perovskite

Rare earth element substituted bismuth ferrites (BiFeO₃) are of enormous importance as magnetoelectric materials. The polycrystalline samples of Bi _x La_1−x FeO₃ (x=0, 0.2, 0.4, 0.6, 0.8) were prepared by solid-state reaction using standard ceramic method. The single-phase formation of these compounds was confirmed by X-ray diffraction (XRD) studies. The samples with x=0, 0.2, 0.4, 0.6 are found to be orthorhombic while the sample with x=0.8 is triclinic. The dielectric constant (ε′) and dissipation factor (tan δ) were measured in the frequency range 100 Hz to 1 MHz at room temperature and as a function of temperature at certain fixed frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz). All the samples showed dielectric dispersion. The dielectric constant with temperature shows a broad peak; the peak temperature shifts with frequency which reflects the relaxor-type behavior. The peak above 600 K in the measured temperature range corresponds to antiferromagnetic ordering temperature (Néel temperature). The broadness of the peak changes with composition. The ac conductivity as well as ε′ are found to be maximum for the sample x=0.2 at room temperature.     

Design of Steel-Composite Multirim Cylindrical Flywheels Manufactured by Winding with High Tensioning and in situ Curing. 2. Numerical Analysis

The possibility of using forced winding coupled with in situ curing to increase the energy storage capacity of hybrid steel-composite cylindrical flywheels is estimated and analyzed. Stress states for given loading conditions in two- and three-layered compound cylinders made from steel and four different types of unidirectional composites are calculated. For each of these combinations, optimum dimensions and the energy storage capacity of the flywheels are found.__________Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 3, pp. 351–372, May–June, 2005.     

Design of Steel-Composite Multirim Cylindrical Flywheels Manufactured by Winding with High Tensioning and <Emphasis Type="Italic">in situ</Emphasis> Curing. 1. Basic Relations

The possibility of using force winding coupled with in situ curing to increase the energy storage capacity of hybrid steel-composite cylindrical flywheels is estimated and analyzed. Relations describing the rotational, thermal, and winding stresses are considered and discussed. These relations are used for a numerical analysis of the stress state and energy capacity of hybrid flywheels in the second part of the paper.__________Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 2, pp. 203–224, March–April, 2005.