A parabolic reflector with asymmetric low sidelobes

A technique for generating low sidelobes on one side of the main lobe for a parabolic reflector antenna is presented. The reflector system that generates such an asymmetric sidelobe pattern consists of a central parabola with two sections of offset parabolas situated at the top and bottom of the central parabola. By adjusting the positions and dimensions of the side reflectors, considerable suppression of the first few sidelobes can be obtained. Further, by similar adjustments it is possible to achieve suppression of sidelobes on both sides of the main beam, though this suppression is relatively less. The technique, though explained in detail with reference to a cylindrical geometry, is extended for a paraboloid of revolution. The analysis program utilized for the optimization of the side reflectors is based on physical optics current integration.     

Successively pulse plated cadmium selenide films and their photoelectrochemical behaviour

In successive pulse plating, the pulse deposition is repeated after a definite duration of plating preceded by a mild cleaning of the electrode and with a fresh deposition bath for the same duration. In this study, CdSe films were deposited on Ti substrates by successive pulse plating from a bath containing CdSO₄ and SeO₂ at a current density of 80 mA cm⁻² and a duty cycle of 3·3% for a duration of 30 min. The films heat-treated to 550°C for 20 min in argon atmosphere, were polycrystalline with a hexagonal structure. At an illumination of 60 mW cm⁻², a conversion efficiency of 4·5% for the photoetched film and 1·7% for the chemically etched one were determined.     

Glomerular permeability: in vivo tracer studies with polyanionic and polycationic ferritins

The influence of molecular charge on glomerular permeability to the globular ferritin molecule in vivo was investigated. Mice (Charles River CD strain) and rats (Munich-Wistar strain) were injected intravenously either with native anionic ferritin or various cationized derivatives with different isoelectric points (pI) and the kidneys were examined by electron microscopy. Native anionic ferritin was almost completely restricted from entry into the glomerular filter at the level of the endothelium and subendothelial layer of the glomerular basement membrane (GBM). Cationized derivatives penetrated the filter in increasing amounts depending on the pI of the tracer. Regardless of charge, all molecules that filtered through the lamina densa of the GBM and reached the subepithelial layer were completely restricted from entry into the urinary space at the level of filtration slits and appeared in phagosomes present in podocytes. Reduction of arterial pressure of cessation of renal blood flow did not influence the movement of ferritin molecules into the GBM. The results are consonant with physiological studies indicating charge dependent restriction of polyanion transport by the mammalian glomerulus. These tracer studies, in conjunction with cytochemical and biochemical evidence for the presence of polyanionic glycoproteins in the glomerular filter, suggest that glomerular restriction of plasma proteins occurs in part by a process similar to that which exludes negatively charged macromolecules in polyanionic gel systems.     

Estimation of body fat in rats by whole-body counting

A method for determining body fat in vivo in rats by whole-body counting of 40K is described. The technique utilizes a Nuclear Chicago Corporation TOBOR system with 5-in thallium-activated sodium iodide crystals. To test the method a regression equation was developed using the 40K counts and body weight of young adult rats weighing 333-788 g; the results were compared with those obtained from the gravimetric determination of fat in the carcass. The correlation coefficient between the two methods was 0.945.     

Urethane coatings based on aldehyde oils

A series of polyol acetals of aldehyde oils was prepared by an acetal interchange reaction between dimethyl and tetramethyl acetals of aldehyde oils derived by the reductive ozonolysis of linseed and soybean oils. The acetals interchanged with pentaerythritol, trimethylol propane and glycerol contained the equivalent of .93 and 1.88 aldehyde groups per oil molecule. The polyol acetals were reacted with toluene diisocyanate in an NCO/OH of 2. These products were tested as film formers. Curing was by two reactions, namely oxidation polymerization of the residual unsaturation in the oil and moisture curing of the unreacted isocyanate group. Good quality films were formed. Presented at the AOCS-AACC Meeting, Washington, D.C., March, 1968.     

Defect centres and thermoluminescence in CaSO4:Dy,Ag phosphor

The defect centres formed in the TL phosphor CaSO4:Dy,Ag are studied using the technique of Electron Spin Resonance. The Ag co-doped phosphor exhibits three glow peaks around 130, 220 and 375 degrees C in contrast with the two glow peaks observed in the CaSO4:Dy phosphor at 130 and 220 degrees C at a gamma ray dose of 1Gy. ESR studies show that the additional peak at 375 degrees C correlates with a Ag2+ centre formed due to gamma irradiation and observable only below -170 degrees C. The Ag2+ centre is characterised by an axial g-tensor with principal values g(parallel) = 2.38 and g(perpendicular) = 2.41. ESR studies further indicate that the precursor to a centre observable at low temperature (-170 degrees C) appears to act as the recombination centre for the TL peak at 375 degrees C; this radical is characterised by the g-values g(parallel) = 2.0023 and g(perpendicular) = 2.0038 and is assigned to SO3- radical. It is observed that there is more incorporation of Ag in the CaSO4:Dy system as compared with that in pure CaSO4 system.     

Cognitive Radio Dynamic Access Techniques

The ever growing demand for wireless services has placed enormous burden on valuable resources such as spectral bandwidth. This has resulted in a major rethinking in resource allocation policies culminating in an explosion of research activity in the field of Cognitive Radio (CR) towards optimum resource usage. In this tutorial paper the physical layer design and transmission techniques for CR in the context of efficient spectrum utilization are discussed. Spectrum sensing as the key element of CR awareness is described. Orthogonal frequency division multiplexing (OFDM) as a spectrally efficient modulation scheme is discussed and the rationale for its use in the CR system is explained. Spectrum pooling for efficient use of spectrum is studied and the role of adaptive OFDM techniques in this method is highlighted. Wavelet basis function as a replacement of Fourier transform in OFDM is evaluated. MIMO system as an added value to the CR performance is described. Adaptive Waveform and beamforming as alternative techniques in CR are reviewed.

Development and quality evaluation of cooked buffalo tripe rolls

Cooked buffalo tripe rolls (BTRs) were prepared from a combination of buffalo tripe (75%) and buffalo meat (25%) by using mincing (M-BTR) and blade tenderization (BT-BTR). They were stored at 4 ± 1 °C and studied for various physico-chemical, sensory and microbial qualities. Significantly (P < 0.01) higher pH, shear force value, diameter shrinkage and fat percentage were observed in M-BTR and BT-BTR than control product (100% minced buffalo meat). The product yield and drip loss percentage were significantly (P < 0.01) lower in BT-BTR, whereas drip loss percentage was significantly higher in M-BTR compared to controls and BT-BTR. No significant change was noticed in protein and moisture content between the different products. All physico-chemical parameters and sensory evaluation scores of M-BTR were comparable with control. Significant (P < 0.01) increases were noticed in pH, moisture content, thiobarbituric acid and tyrosine values with increasing storage period, whereas the extract release volume decreased significantly. All microbial counts and sensory evaluation scores were within the acceptable limits until 15 days of storage at 4 ± 1 °C in low-density polyethylene pouches stored aerobically.