A simplified computational procedure for the analysis of planar arrays

A simplified procedure for inverting the mutual impedance matrix of a uniform-spaced planar array of dipoles is presented. It relies on the special features of this matrix being symmetric block-Toeplitz and having a nilpotent off-diagonal part. Active radiation impedances and voltage standing-wave ratio (VSWR) values are then evaluated for various element positions and scan angles. The array-element patterns and far-field radiation patterns are then derived. Some specific examples are given to exhibit the significant reduction in computational effort. It is concluded that this method may be generalized to the analysis of higher order excitation modes and to nonuniform spaced arrays.     

Comments on “An exact formulation for the vector potential ofa cylindrical antenna with uniformly distributed current and arbitraryradius” [and reply]

The paper written by Werner (see ibid, vol.41, no.8, p.1009-1018, 1993) relies on the technique and results that were developed by Overfelt (1987). At the time, I submitted a comment regarding that method (see. Gera, ibid. p.584, 1990). It seems that this comment applies here. Werner replies that the exact expressions for the generalised exponential integral are mathematically correct in the form that they appear in the paper, as demonstrated by the results shown. There are actually several equivalent forms which exist for these expansions     

Synthesis and stability of 3-nitro-2-pyridinesulfenyl chloride (NpysCl)

3-Nitro-2-pyridinesulfenyl chloride (NpysCl) is the starting material for the synthesis of N-, O- and S-Npys-protected amino acids. Two efficient, novel synthetic routes to NpysCl are described. The stability of NpysCl was determined in a variety of solvents, with and without base, to determine the most suitable solvent and base for the synthesis of N-Npys amino acids. The syntheses of Npys-Ala and Boc-Lys(Npys) tert-butylammonium salt are also described.     

Resistance of HER2/neu-overexpressing tumor targets to lymphokine-activated-killer-cell-mediated lysis: evidence for deficiency of binding and post-binding events

HER2/neu-overexpressing tumor cell lines are relatively resistant to lymphokine-activated killer (LAK) cell cytotoxicity when compared to HER2/neu-nonexpressing lines. HER2/neu+ targets were also resistant to binding by LAK large granular lymphocytes (LGL) as shown by visualization at the single-cell level, a target monolayer binding assay and in "cold" target inhibition experiments. HER2/neu+ LAK-resistant ovarian cell lines demonstrated an absence of ICAM-1 expression while expression of LFA-3, N-CAM, laminin and beta 1 integrins was comparable to that of HER2/neu- targets. In contrast, the HER2/neu+ breast cell line, SKBR-3, which was also resistant to lysis and binding by LAK LGL, demonstrated normal expression of ICAM-1. Anti-ICAM-1 antibodies blocked binding and lysis of HER2/neu- carcinoma targets by LAK cells, further supporting the notion that lack of ICAM-1 expression on HER2/neu+ cells contributes to their resistance. The modest binding and lysis of HER2/neu+ targets by LAK cells was significantly inhibited by anti-LFA-1 antibodies, suggesting the existence of another counter-receptor for LFA-1 on HER2/neu+ targets. The following also supported deficiencies in post-binding events when HER2/neu+ cells resisted the lytic activity of LAK cells: (a) when the relative resistance to effector cell binding was overcome by exogenous lectin. HER2/neu+ cell lines were still resistant to LAK cytolysis, and (b) HER2/neu+ targets were resistant to perforin-containing granule extracts obtained from the CTLL-R8 cytotoxic lymphocyte cell line. These results indicate that deficiency in effector binding as well as post-binding events contributes to the resistance of HER2/neu-overexpressing tumor targets to LAK-cell-mediated lysis.     

Lattice Boltzmann Simulation of Natural Convection in a Differentially Heated Square Enclosure Containing Heat Generating Low‐Prandtl Number Fluid

Lattice Boltzmann simulations were conducted for the free convective flow of a low‐Prandtl number (Pr = 0.0321) fluid with internal heat generation in a square enclosure having adiabatic top and bottom walls and isothermal side walls. The problem of free convection with volumetric heat source has represented itself in connection with advanced engineering applications, such as water‐cooled lithium–lead breeder blankets for nuclear fusion reactors and liquid metal sources of spallation neutrons for subcritical fission systems. A single relaxation time (SRT) thermal lattice Boltzmann method (LBM) was employed. While applying SRT, a D2Q9 model was used to simulate the flow field and temperature field. Results have been obtained for various Rayleigh numbers characterizing internal and external heating from 10³ to 10⁶. Flow and temperature fields in terms of stream function and isotherms in the enclosure were predicted for these cases. The temperature of the fluid in the enclosure was found higher than the heated wall temperature at high values of internal Rayleigh numbers. The internal heat generation affected the rate of heat transfer significantly as two convection loops are observed in the enclosure. The average Nusselt number at the heated and cold wall was determined for all the cases.     

Process analytical technology for cheese manufacture

Recent research on the development and application of process analytical technology (PAT) for cheese manufacture is reviewed in this article. PAT is a framework for innovative process manufacturing and quality assurance, which has been widely investigated for dairy processing applications, where particular processing challenges arise due to the variations in the physiochemical properties of milk. Cheese manufacturers are increasingly considering the adoption of a PAT approach to facilitate manufacture of cheese with enhanced product quality, safety and process efficiency. However, to date adoption of PAT in the dairy industry has been limited due to challenges associated with development and validation of calibration models, instrument variability, sanitary design and compatibility with processing environments. New technical developments in PAT tools, advances in chemometric modelling, robust data management tools and improved understanding of critical product and process parameters will facilitate further adoption of a PAT approach in cheese manufacture.     

State Nullification by Memoryless Output Feedback

We examine linear single-input single-output finite-dimensional systems. It is shown that a continuous time controllable and observable system can be nullified utilizing periodic sampling of the output with time-varying linear feedback. Almost any sampling rate can be used. The result relies on a characterization of linear output feedback nullification of discrete time observable and controllable systems. An algorithm for the nullification and an estimate on the time in which the algorithm is concluded are provided.Research supported by grants from the Israel Science Foundation and from the Information Society Technologies Programme of the European Commission.(Incumbent of the Hettie H. Heineman Professorial Chair in Mathematics).     

European competition law, the new e-communications framework, and the consumer in the information society: more than a virtual position?

Free and open competition benefits consumers. The consumer may ultimately benefit from a wider range of products and more competitive prices if workable competition on the information technology market has been safeguarded. However, consumers will lose the benefits of competition if firms engage in anti-competitive practices, such as arrangements on prices, market sharing and allocation of customers. Firms must also be prevented from abusing their dominant position on the market. Abuse could arise if unfair prices or unfair trading conditions are imposed. The main goal of the EC competition regulation is to achieve a system that ensures effective competition on the internal market to improve the position of the consumer. However, a consumer who actively seeks protection under the current competition rules may end up frustrated. In general, ex ante regulation appears to be a better instrument for safeguarding consumer interests. The framework of the new electronic communication directives, which must be implemented in national legislation on 25 July 2003 at the latest, indexes ex ante regulation but is largely based on a competition law analysis. Clear obligations can be imposed to safeguard the interests of the consumer in the information society. These obligations not only relate to Internet access, but also to transparency in consumer contracts, affordable prices and dispute settlement.