Generalized probability model for estimating the proportion of the female population at different levels of fertility based on census sampling from a mixed population

The present exercise is an attempt to generalize a probability model referring to the waiting time distribution for conception in a mixed group of fecund females with two varying levels of fecundity, based on a census sample truncated at time T =t from the date of resumption of fecundity following an earlier conception (Biswas, 1975, Sankhya, Series B, 37, Part III). The generalization is made in two aspects, viz. instead of fixed conception rates, time-dependent rates decreasing with the age of the woman have been used. Additionally, unlike the model of Biswas (1975) consisting of two different fecund groups, three different levels of fecundity have been taken into consideration in this paper. Estimates of the proportion of fecund females over time, viz. π_i(t) (i = 1, 2, 3) are attempted by the method of maximum likelihood on the basis of a census sample truncated at time T = t under the generalized set up.     

The origin of striations on the surface of iron–zinc coated steel sheet produced by hot-dip galvannealing

Dark striations are often observed on the surface of iron–zinc coated steel sheet annealed immediately after hot-dip galvanizing (galvanneal). The striations can be explained on the basis of the differential formation of an iron–aluminium barrier layer at the steel-bath interface during galvanizing. The contact of a submerged, grooved sink roll in the galvanizing bath with the steel sheet causes variations in the iron–aluminium barrier layer at the interface. A more coherent layer is formed in the areas where there is no contact i.e., the grooved areas on the sink roll. The growth of the iron–zinc coating under a higher local aluminium concentration during subsequent annealing leads to a pitted surface in those groove areas, and creates the appearance of dark striations on the surface of the coated sheet. The aluminium content of the galvanizing bath is a key factor in determining the extent of the non-uniformity imposed by the contact with the sink roll. Consequently the striations can be reduced by lowering the aluminium content of the galvanizing bath. This revised version was published online in November 2006 with corrections to the Cover Date.     

EVALUATION OF PCR AND DNA HYBRIDIZATION PROTOCOLS FOR DETECTION OF VIABLE ENTEROTOXIGENIC CLOSTRIDIUM PERFRINGENS IN IRRADIATED BEEF

The sensitivity of DNA hybridization and polymerase chain reaction (PCR), was evaluated in irradiated cooked and raw beef samples. A membrane-based colony hybridization assay and a PCR protocol, both with specificity for the enterotoxin A gene of Clostridium perfringens, were compared with viable plate counts. The results of the colony hybridization procedure were in agreement with viable plate counts for detection and enumeration of enterotoxigenic C. perfringens. The PCR procedure combined a 4 h enrichment followed by a nucleic acid extraction step and assessed the amplification of 183 and 750 base pair enterotoxin gene targets. Detection of C. perfringens by PCR did not show a reliable correlation with viable plate counts or the colony hybridization assay . C. perfringens killed by irradiation were not detected by the plate count or colony hybridization methods; however, killed cells were detected with the PCR technique. By relying on the growth of viable cells for detection and/or enumeration, the colony hybridization and plate count methods provided a direct correlation with the presence of viable bacteria .; Accepted for Publication August 6, 1997     

Decentralized linear quadratic power system stabilizers for multi-machine power systems

Linear quadratic stabilizers are well-known for their superior control capabilities when compared to the conventional lead?Clag power system stabilizers. However, they have not seen much of practical importance as the state variables are generally not measurable; especially the generator rotor angle measurement is not available in most of the power plants. Full state feedback controllers require feedback of other machine states in a multi-machine power system and necessitate block diagonal structure constraints for decentralized implementation. This paper investigates the design of Linear Quadratic Power System Stabilizers using a recently proposed modified Heffron?CPhillip??s model. This model is derived by taking the secondary bus voltage of the step-up transformer as reference instead of the infinite bus. The state variables of this model can be obtained by local measurements. This model allows a coordinated linear quadratic control design in multi machine systems. The performance of the proposed controller has been evaluated on two widely used multi-machine power systems, 4 generator 10 bus and 10 generator 39 bus systems. It has been observed that the performance of the proposed controller is superior to that of the conventional Power System Stabilizers (PSS) over a wide range of operating and system conditions.     

Protective effect of aqueous suspension of dried latex of <i>Calotropis procera</i> against oxidative stress and renal damage in diabetic rats

Calotropis species have been used in the traditional medicinal system for the treatment of diseases of the liver and abdomen. In view of the antioxidant and anti-hyperglycemic properties of an aqueous suspension obtained from the dried latex of Calotropis procera, the present study was carried out to evaluate its efficacy in affording protection against alloxan induced changes in rat kidney. A single intraperitoneal injection of alloxan (150 mg/kg) in rats produced hyperglycemia within 3 days and altered kidney functions over a period of 90 days. Daily oral administration of the aqueous suspension (100 and 400 mg/kg) in diabetic rats produced anti-hyperglycemic effect that was comparable to that of glibenclamide (10 mg/kg). Unlike glibenclamide, the aqueous suspension did not increase the serum insulin levels in diabetic rats. However, it produced a marked reduction in the levels of urinary glucose and protein and normalized the renal tissue levels of thiobarbituric acid-reactive substances (TBARS) and glutathione (GSH) in diabetic rats and the effect was comparable to that of glibenclamide. The protection afforded by the aqueous suspension was also evident from the histological analysis of the renal tissue. Our study shows that by exhibiting antioxidant and anti-hyperglycemic property the aqueous suspension of dried latex of C. procera affords protection against the complications associated with diabetes.     

Radiation and canonical sources in uniaxial dielectric media

The three-dimensional electric Green function for uniaxial dielectric media has been given by Chen (1973, 1983) Here we give the magnetic Green's function, whose form suggests that magnetic field formulations may be more tractable than electric field formulations. Using the electric and the magnetic Green's functions, canonical sources for the independent generation of the ordinary and the extraordinary fields are also obtaned.     

Competing risk theory approach to the nature of the outcome of conception

An attempt has been made to obtain the probabilities of pregnancy termination by live birth, still birth and abortion, in any particular order, assuming that the termination of pregnancy is associated with three competing ‘risks’, i.e. live birth, still birth and abortion, which need not necessarily operate at the same point of time. A probability model has been constructed to obtain the conditional probability of live birth/still birth/abortion given that the previous pregnancy has been terminated by a particular one of the three. The correlation coefficient between the outcomes of two particular consecutive pregnancy terminations, viz. live birth and reproductive wastage (which includes both abortion and still birth), has also been obtained. Given data pertaining to sample correlation coefficients between the nature of consecutive orders of the outcomes of conception from first to sixth, an exercise has been undertaken to estimate parameters relating to the ‘hazard’ rates of live births, still birth and abortion. The exercise further enables one to test the well-known demographic hypothesis that reproductive wastages follow each other in succession over consecutive orders of the outcomes of conception.     

Robustness of the partitions in grouping multi-item inventories

A recent work obtained closed-form solutions to the.problem of optimally grouping a multi-item inventory into subgroups with a common order cycle per group, when the distribution by value of the inventory could be described by a Pareto function. This paper studies the sensitivity of the optimal subgroup boundaries so obtained. Closed-form expressions have been developed to find intervals for the subgroup boundaries for any given level of suboptimality. Graphs have been provided to aid the user in selecting a cost-effective level of aggregation and choosing appropriate subgroup boundaries for a whole range of inventory distributions. The results of sensitivity analyses demonstrate the availability of flexibility in the partition boundaries and the cost-effectiveness of any stock control system through three groups, and thus also provide a theoretical support to the intuitive ABC system of classifying the items.     

Plane waves and canonical sources in a gyroelectromagnetic uniaxial medium

A characteristic of a gyroelectromagnetic uniaxial medium is that its permittivity and permeability tensors have the same preferred axis. Dyadic analysis is used to obtain expressions for plane waves in such a medium, and their characteristics are explored. Conditions for incidental and pathological unirefringence are identified; and expressions for time-averaged Poynting vectors and time-averaged energy densities are obtained. Canonical sources for this medium are also identified.     

Microstructure and microhardness of AA1050/TiC surface composite fabricated using friction stir processing

Friction stir processing (FSP) has been developed by several researchers to produce an upper surface modification of metallic materials. The fabrication of TiC particulate (~2? $\upmu $ m) reinforced aluminum matrix composite (AMC) using FSP is studied in this paper. The measured content of TiC powders were compacted into a groove of 0.5?mm × 5.5?mm. A single pass FSP was carried out using a tool rotational speed of 1600?rpm, processing speed of 60?mm/min and axial force of 10?kN. A tool made of HCHCr steel, oil hardened to 62 HRC, having a cylindrical profile was used in this study. The microstructure and microhardness of the fabricated AMC were analysed. Scanning Electron Microscope (SEM) micrographs revealed a uniform distribution of TiC particles which were well-bonded to the matrix alloy. The hardness of the AMC increased by 45% higher than that of the matrix alloy.