Simple expressions for performance parameters of complex filters, with applications to super-Gaussian phase filters

To study the three-dimensional (3-D) behavior produced by complex filters, we have extended the expressions for the axial and the transverse gain to the case in which the best image plane is not near the paraxial focus. Super-Gaussian phase filters are proposed to control the 3-D image response of an optical system. Super-Gaussian phase filters depend on several parameters that modify the shape of the phase filter, producing tunable control of the 3-D response of the optical system. The filters are capable of producing a wide range of optical effects: transverse superresolution with high depth of focus, 3-D superresolution, and transverse apodization with different axial responses.     

Analytic relations between localizable entanglement and string correlations in spin systems

We study the relation between the recently defined localizable entanglement and generalized correlations in quantum spin systems. Differently from the current belief, the localizable entanglement is always given by the average of a generalized string. Using symmetry arguments we show that in most spin-1/2 and spin-1 systems the localizable entanglement reduces to the spin-spin or string correlations, respectively. We prove that a general class of spin-1 systems, which includes the Heisenberg model, can be used as a perfect quantum channel. These conclusions are obtained in analytic form and confirm some results found previously on numerical grounds.     

Analysis of Frequency Selective Surfaces at Millimeter Wave Band Using the Hertz Vector Potential Method

In this work, the Hertz vector potential method was used to obtain the dyadic Greens function components for frequency selective surfaces (FSS) on an anisotropic layer. The considered structures are composed by periodic arrays of conducting crossed dipole and rectangular patch elements. Results of reflected power were obtained by using the moment method. Curves for the reflected power versus frequency are presented as function of the structural parameters, assuming x, y, and z orientation for the optical axis in the anisotropic substrate.     

The use of 2-2-thiazolylazo-p-cresol to minimize the interference of Ni and Cu for the bismuth determination in alloys by hydride generation atomic absorption spectrometry

Thiazolylazo p-cresol (TAC) was studied as a masking agent for the determination of Bi in rich Ni and Cu alloys by hydride generation atomic absorption spectrometry (HGAAS). In the presence of TAC, Bi/Ni and Bi/Cu ratios up to 1:160 000 and 1:16 000, respectively, were found to be tolerable. No buffering was necessary once the masking agent was effective even in very acid medium. Limits of detection at the low mug g(-1) range were reached and the accuracy of the procedure was confirmed by the good concordance between found and certified values in the analysis of certified reference materials (CRM).     

Lifetime of levels belonging to the 3p54p configuration of Ar(I)

The lifetimes of nine levels of Ar(I) belonging to the 3p⁵4p configuration have been measured by the delayed coincidence method, with errors in the range from 4 to 7%. The results are compared with other experimental values and with theoretical calculations using jK coupling and intermediate coupling. From cascade components of the 4p levels, decay lifetime values for some levels belonging to the 3p⁵3d and 3p⁵5s configurations have been inferred.     

Estimation of the optical properties of seawater from measurements of exit radiance

An inverse analysis for simultaneous estimation of the radiation phase function, single scattering albedo and optical thickness in natural waters, from the knowledge of the exit radiance measurements, is presented. A forward and an inverse model are utilized in our analysis. The forward model uses an analytical discrete-ordinates method for solving the radiative transfer equation and the inverse model contains an algorithm for least-squares estimation that is iteratively solved for retrieving the desired optical properties. The experimental data are simulated with synthetic data corrupted with noise. The results show that the optical properties, with the exception of the optical thickness, can be recovered with high accuracy, even for data with up to 10% noise.     

Transition probabilities of 4p−nd(n = 4, 5, 6, 7) lines of Ar(I)

Relative transition probabilities for 120 lines belonging to the 4p-nd(n = 4, 5, 6, 7) transition arrays of Ar(I) have been determined from emission-intensity measurements. Lifetime data for the 4d levels were used to obtain absolute transition probabilities. We have obtained 32 transition probabilities for 4p?4d lines. Because of the lack of data on 5p?4d transition probabilities, calculations were performed on jK coupling. Our experimental values are compared with experimental and theoretical data given by other authors.     

Emission cross sections of the second positive and first negative systems of N2 and N+2 excited by electron impact

Cross sections have been measured for emission of the 2nd positive system of N₂ and the 1st negative system of N⁺₂ by electron excitation. The electron energy ranged from the threshold to 400 eV. To obtain absolute values, comparison with the emission cross section of the 5¹S He level has been used.The results for the (0, 2) band of the 2nd positive system and for the (0, 1) band of the 1st negative system are (2.87 ± 0.40) × 10^-18 and (5.35 ± 0.5) × 10^-18cm², respectively, at the peak. The cross sections are given for 23 bands of the 1st negative systems.Use of the (0, 1) band of the 1st negative system is proposed for reference in obtaining absolute values.     

Evaluation of immunoaffinity chromatography for isolating human lipoproteins containing apolipoprotein B

Because of high specificity, immunoaffinity chromatography is the most suitable procedure for the isolation of lipoprotein (LP) particles defined by their apolipoprotein (Apo) composition. The purpose of the present study was to describe immunosorber methodology and its application to the isolation of ApoB-containing lipoproteins from either plasma or isolated lipoprotein density classes. The exploration of various coupling procedures demonstrated that immunosorbers of highest capacity were obtained by cyanogen bromide activation of Sepharose. Among various dissociating agents tested, 3 M sodium thiocyanate was found to be the most effective desorbent for bound lipoproteins. Studies on the non-specific binding of serum albumin to several different immunosorbers showed a negligible retention (1.9%) of albumin. Good recoveries (80-98%) were obtained with all apolipoproteins tested with both anti-ApoA-I and anti-LP-B immunosorbers. By using the optimal experimental conditions, it was shown that the ApoB-containing lipoproteins retained by immunosorbers with antibodies to LP-B had chemical, physical and immunological properties similar, if not identical, to those of their corresponding parent density classes. The application of an alternative immunoaffinity chromatography procedure with serially connected immunosorbers with antibodies to apolipoproteins other than ApoB resulted in the isolation of LP-B, a lipoprotein containing ApoB as its sole protein constitutent. LP-B had chemical and physical properties very similar to those of subclass 2 of low-density lipoproteins (density 1.019-1.063 g/ml, flotation coefficient 0-12). Based on these studies, we suggest that immunoaffinity chromatography in combination with microanalytical procedures for quantification of lipids and apolipoproteins offers a powerful tool for the isolation and functional characterization of lipoprotein particles defined by their apolipoprotein composition.