Kalpana Singh

ANALYSIS OF A COAXIAL WAVEGUIDE CORRUGATED WITH WEDGE-SHAPED RADIAL VANES CONSIDERING AZIMUTHAL HARMONIC EFFECTS

The analysis was developed for a coaxial waveguide for two configurations — one in which the central conductor is corrugated in axial slot-wedges, with ridge-wedges between them, and the other in which the outer conductor is provided with radial metal vane-wedges. Azimuthal harmonics were considered in the structure regions, the effects of which were ignored in earlier published analyses based on the surface impedance model to replace the interface between the two structure regions by a homogeneous reactive surface. For both the structure configurations, one and the same form of the dispersion relation with proper interpretation of the symbol for the radius of the ridge/vane was obtained. The dispersion relation obtained by the present analysis was validated against that obtained by other analytical methods reported in the literature. The shape of the dispersion characteristics is found uncontrollable by the structure parameters, and therefore the structure cannot be used for broadbanding a gyro-TWT. However, the plot of the eigenvalue versus the ratio of the outer conductor to ridge/vane radii strongly depended on the ridge/vane parameters. Thus the structure with its cross section tapered and ridge/groove parameters optimized has the potential for providing mode rarefaction in high-power, over-sized, over-moded gyrotrons.

Analysis of a corrugated coaxial waveguide resonator for mode rarefaction in a gyrotron

The analysis of a coaxial waveguide resonator with its central conductor corrugated with wedge-shaped slots, considering space harmonic effects due to slot periodicity, was used to study the problem of mode competition in a gyrotron. A more positive slope of the plot of the eigenvalue versus the ratio of the waveguide wall to outer slot radii (coaxial parameter) for the desired mode, typically, TE/sub 8,4/ as compared to the corresponding slopes for the competing modes formed a basis for the study of mode separation. Considering the aspect of mode separation on the basis of the relative slopes of the eigenvalue plot and that of mode degeneracy, a tradeoff was made to select the slot depth at a value intermediate between the values corresponding to the narrow and deeper slots. For the slot depth parameter selected, one may find the coaxial parameter, around which to taper the structure cross section, for mode separation on the basis of relative slopes of the eigenvalue plot, avoiding, at the same time, the region of the mode degeneracy. The analysis and interpretation of results for mode separation with reference to the typical mode TE/sub 8,4/ chosen is extendible to higher modes as well, which was exemplified with reference to the typical higher order TE/sub 12,4/ and TE/sub 27,11/ modes.

Gr/gr deletions on Y-chromosome correlate with male infertility: an original study, meta-analyses, and trial sequential analyses.

We analyzed the AZFc region of the Y-chromosome for complete (b2/b4) and distinct partial deletions (gr/gr, b1/b3, b2/b3) in 822 infertile and 225 proven fertile men. We observed complete AZFc deletions in 0.97% and partial deletions in 6.20% of the cases. Among partial deletions, the frequency of gr/gr deletions was the highest (5.84%). The comparison of partial deletion data between cases and controls suggested a significant association of the gr/gr deletions with infertility (P = 0.0004); however, the other partial deletions did not correlate with infertility. In cohort analysis, men with gr/gr deletions had a relatively poor sperm count (54.20 ± 57.45 million/ml) in comparison to those without deletions (72.49 ± 60.06), though the difference was not statistically significant (p = 0.071). Meta-analysis also suggested that gr/gr deletions are significantly associated with male infertility risk (OR = 1.821, 95% CI = 1.39–2.37, p = 0.000). We also performed trial sequential analyses that strengthened the evidence for an overall significant association of gr/gr deletions with the risk of male infertility. Another meta-analysis suggested a significant association of the gr/gr deletions with low sperm count. In conclusion, the gr/gr deletions show a strong correlation with male infertility risk and low sperm count, particularly in the Caucasian populations.

Association of the IL1RN Gene VNTR Polymorphism with Human Male Infertility

Interleukin-1 (IL-1) is a regulatory cytokine that plays an important role in the maintenance of the immune environment of the testis, regulation of junction dynamics and cell differentiation during spermatogenesis. Members of the IL-1 family are pleiotropic cytokines that are involved in inflammation, immunoregulation and other homeostatic functions in the body. IL-1α, IL-1β, and the IL-1 receptor antagonistic molecule (IL-1 Ra) are expressed in the testis under normal homeostasis and they further increase upon infection/inflammation. In the present study we have examined the association of Variable Number Tandem Repeats (VNTR) polymorphism of the Interleukin-1 receptor antagonist gene (IL1RN) with human male infertility. The case-control study comprised of two groups: 331 idiopathic infertile patients and 358 fertile healthy men. The study indicates risk of IL1RN2 variant with male infertility (OR: 1.43, CI: 1.1546 to 1.7804, P = 0.001). To our best knowledge, this is the first report that links IL1RN VNTR polymorphism with human male infertility.

Simulation of whistler mode propagation for low latitude stations

Representing lightning discharge current source by a Dirac delta function, Maxwell’s equations are solved to derive the expression for wave-electric field as a function of frequency and distance including the effect of interparticle collisions. The exact time-dependence of the propagating non-monochromatic signal for the realistic magnetospheric model is computed for low latitude stations (in India). The computation is extended for the wave propagating through different regions of the magnetosphere and results are compared with the measured data. Points of agreements and differences are illuminated.

Excitation of electromagnetic waves by a current source in the inhomogeneous lossy magnetoplasma

The excitation of nonmonochromatic signals by source current and their longitudinal propagation in an inhomogeneous magnetoplasma is studied. Three types of excitation source current are considered for the study. The inhomogeneity of magneto-ionic medium is taken with respect to the variation in plasma density and strength of the magnetic field. The effect of interparticle collisions on the amplitude of the signal is studied. Properties of the excited signals are discussed in different frequency ranges in terms of charge per unit length of the excitation source and the distance of propagation of the signal.

Association of the gonadotrophin‐regulated testicular RNA helicase gene polymorphism with human male infertility

Gonadotrophin‐regulated testicular RNA helicase (GRTH) plays an important role in RNA functions including nuclear transcription, pre‐mRNA splicing and it regulates the translation of specific genes required for the progression of spermatogenesis. In this study, we analysed the association of GRTH gene IVS6+55G/T and c.852C/T polymorphisms with human male infertility. The study showed c.852 T allele was associated with an increased risk of male infertility (OR: 3.16, P = 0.008), whereas IVS6+55G/T allele conferred no risk. In Indian population, this is the first report on association of GRTH gene SNP polymorphism and male infertility and it underscores the significance of GRTH genotypes in modulating the risk of male infertility.