Comparison of UTD and UAT in axially symmetric reflectors

Radiation patterns of focus-fed axially symmetric reflector antennas are determined by using the uniform geometrical theory of diffraction (UTD) and the uniform asymptotic theory (UAT). The calculations are based on a computer program, which can determine the radiation pattern of any conic-section-generated reflector with arbitrary eccentricity. Comparison of the radiation patterns inE- andH-planes shows that the UTD and UAT yield similar results and the differences between the two are insignificant from engineering point of view.     

Dynamic Behavior of a Spin- 1 Ising Model. I. Relaxation of Order Parameters and the “Flatness” Property of Metastable States

The dynamic behavior of a spin-1 Ising system with arbitrary bilinear and biquadratic pair interactions is studied by using the path probability method, and approaches of the system toward the stable or metastable equilibrium states according to the ratio of interaction parameters and rate constants are presented. In particular, we investigate the relaxation of the order parameters for temperatures less than, equal to, and greater than the second-order and first-order phase transitions. From this investigation, the “flatness” property of metastable states is seen explicitly. We also show how a system freezes in a metastable state as well as how it escapes from one metastable state to the other.     

Characteristics of a circular patch microstrip antenna on uniaxially anisotropic substrate

Resonant characteristics of a circular patch microstrip antenna on the uniaxially anisotropic substrate are determined via spectral domain analysis. Green's functions of the structure in Hankel transform domain are determined by using Hertz vector formulation. The variations in the resonant characteristics depending on the replacement of the isotropic substrate with the uniaxially anisotropic one are analyzed for different permittivity tensor element cases. The results of the study indicate that resonant frequency and bandwidth characteristics of the antenna can be considerably changed due to proper selection of substrate anisotropy ratio and other structural parameters. Depending on the arrived results, operational performance of the antenna will be improved in future studies.     

Electron Spin Polarization and Time-Resolved Electron Paramagnetic Resonance: Applications to the Paradigms of Molecular and Supramolecular Photochemistry

Most molecular and supramolecular organic photochemical reactions involve paramagnetic reactive intermediates (such as molecular triplet states, triplet radical pairs, and free radicals). In a number of cases these species are created with "anomalous" spin populations which are far from thermal equilibrium. Such paramagnetic species are said to be "spin polarized" and may be observed directly by time-resolved electron paramagnetic resonance (TREPR). The TREPR technique can be applied to exploit spin polarization, which, in addition to providing an enormous signal to noise enhancement, also reveals the mechanisms involved in photochemical reactions. TREPR spectroscopy provides a means of tracking the reaction of radicals with molecules and the nonreactive interactions of radicals with other radicals in real time. The latter interactions provide a systematic investigation of supramolecular interactions of geminate radicals in micelles.     

A new proposed model of aldose reductase enzyme inhibition on the basis of an artificial intelligence approach: A computer automated structure evaluation (case) study

A large number of inhibitors of aldose reductase enzyme were submitted to the CASE (computer automated structure evaluation) program in order to ascertain the topological features relevant to activity. On the basis of the twenty-six biophores (activating fragments) and one biophobe (inactivating fragment), a new proposed interaction model was suggested for an aldose reductase enzyme with the chemical inhibitors. The critical relationship between enzyme inhibition and the structure of inhibitors is believed to depend on the relative positions of subordinate regions within the inhibitor structure.     

Optimizing control of simulated moving beds--experimental implementation

The operation of simulated moving beds (SMBs) at their optimal operating conditions is difficult and not robust. Therefore, it is common practice to operate SMB units far from their economic optimum in order to tolerate uncertainties in the system and minimize the effect of disturbances. Recently, we have proposed an on-line optimization based SMB control scheme that allows to exploit the full economic potential of SMB technology. The goal of this work is two-fold. Firstly, to experimentally evaluate and demonstrate the capability of the controller to optimize and operate the SMB units, thus delivering the products with maximum productivity and minimum solvent consumption. Secondly, to show the suitability of the controller even using a minimum of system information, thus making the detailed isotherm measurements redundant and saving time in the separation design phase. This paper reports and discusses the first experimental implementation of the control concept on a high purity separation of nucleosides (uridine, guanosine) with an eight-column four-section SMB where the species to be separated are retained on the source 30RPC stationary phase according to a linear isotherm.     

DNA sensing on glassy carbon electrodes by using hemin as the electrochemical hybridization label

The electrochemical behavior of hemin, an iron complex of porphyrin, on binding to DNA at a glassy carbon electrode (GCE) and in solution, is described. Hemin, which interacts with covalently immobilized calf thymus DNA, was detected by use of a bare GCE, a double-stranded DNA-modified GCE (dsDNA-modified GCE), and a single-stranded DNA-modified GCE (ssDNA-modified GCE), in combination with differential pulse voltammetry (DPV). The structural conformation of DNA was determined from changes in the voltammetric signals acquired on reduction of hemin. As a result of its large steric structure and anionic substitution on its porphyrin plane, hemin intercalates between the base pairs of dsDNA. A scan-rate study for hemin and the dsDNA-hemin complex were also performed to determine the electrochemical behavior of the complex. The partition coefficient was obtained from the peak currents measured when different concentrations of hemin were in the presence of dsDNA. By observing the oxidation signals of guanine, damage to DNA after reaction with hemin at the GCE surface was also detected. The electrochemical detection of hybridization between the covalently immobilized probe and its target sequence was detected by use of hemin. These results demonstrate the use of DNA biosensors in conjunction with hemin for electrochemical detection of hybridization and damage to DNA.