2,131 research outputs found

    Integral mean estimates for the polar derivative of a polynomial

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    Let P(z) P(z) be a polynomial of degree n n having all zeros in ∣z∣≤k|z|\leq k where k≤1,k\leq 1, then it was proved by Dewan \textit{et al} that for every real or complex number α\alpha with ∣α∣≥k|\alpha|\geq k and each r≥0r\geq 0 n(∣α∣−k){∫02π∣P(eiθ)∣rdθ}1r≤{∫02π∣1+keiθ∣rdθ}1rMax∣z∣=1∣DαP(z)∣. n(|\alpha|-k)\left\{\int\limits_{0}^{2\pi}\left|P\left(e^{i\theta}\right)\right|^r d\theta\right\}^{\frac{1}{r}}\leq\left\{\int\limits_{0}^{2\pi}\left|1+ke^{i\theta}\right|^r d\theta\right\}^{\frac{1}{r}}\underset{|z|=1}{Max}|D_\alpha P(z)|. \indent In this paper, we shall present a refinement and generalization of above result and also extend it to the class of polynomials P(z)=anzn+∑ν=μnan−νzn−ν,P(z)=a_nz^n+\sum_{\nu=\mu}^{n}a_{n-\nu}z^{n-\nu}, 1≤μ≤n,1\leq\mu\leq n, having all its zeros in ∣z∣≤k|z|\leq k where k≤1k\leq 1 and thereby obtain certain generalizations of above and many other known results.Comment: 8 page

    Studies on resistance and associated fitness costs in Lepidoptera to Bacillus thuringiensis toxins

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    Microbial insecticides derived from the common soil bacterium Bacillus thuringiensis (Bt) have become increasingly important for pest management, particularly in Bt (GM) crops. In addition to crystal (Cry) proteins produced during the spore stage, vegetative insecticidal proteins (VIP) produced during vegetative growth are of current interest for use with Cry toxins in GM crops. In this thesis, the effects of Bt toxins on two target lepidopteran pest species, the bollworm, Heliothis virescens, and the diamondback moth, Plutella xylostella, are described. Cross-resistance to non-Bt insecticides was not found in populations of H. virescens (Vip3A-Sel WF06) and P. xylostella (Cry1Ac-Sel Karak) resistant to Vip3A and Cry1Ac respectively. While the synergist piperonyl butoxide (PBO), an inhibitor of microsomal mono-oxygenases and esterases, did not enhance the toxicity of Vip3A in Vip3A-Sel H. virescens and PBO and the esterase inhibitor DEF did not enhance the toxicity of Cry1Ac in P. xylostella Cry1Ac-Sel Karak. Selection studies with PBO on a population of P. xylostella (SERD4) with a history of developing resistance and cross-resistance to insecticides failed to result in resistance to PBO after selection for 20 generations. Electrophoresis studies indicated the presence of an extra esterase band in Vip3A-Sel compared with unselected H. virescens but there is no evidence that it is related to resistance. Binding experiments suggested that the labelling reaction may have inactivated the binding sites of Vip3Aa and evidence of specific binding of Vip3A toxin to midgut epithelial membranes of unselected H. virescens could not be obtained. Treatment of H. virescens (WFO6, unselected) and P. xylostella (Karak, unselected) with a sub-lethal concentration of Vip3A was found to increase larval and pupal development time and pupal weight, reduce survival (neonate larvae to adult emergence) and mating pair success, increase fecundity and reduce egg viability and the intrinsic rate of population increase (rm). Various fitness costs were found to be associated with resistance in Vip3A-Sel H. virescens and some fitness costs were shown to be temperature dependent: survival (egg to adult), mating pair success, production of viable progeny, egg viability and fecundity, and rm of Vip3A resistant insects being lower at sub-optimal culture temperatures compared with unselected insects. Vip3A resistant larvae were also found to be more susceptible to entomopathogenic nematodes, and had a lower flight muscle ratio, and a greater level of fluctuating asymmetry of morphological traits compared with unselected insects. The work is discussed with particular reference to resistance management strategies for Vip toxins

    Inter-city Variation in Prices

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    In this paper we have constructed a relative cost of living index for 32 cities/towns of Pakistan using latest available prices to understand the extent of current differences in cost of living across cities and also to compare changes in relative cost of living since 1999 [Pasha and Pasha (2002)]. The index values reveal significant differences in cost of living across Pakistan and especially across provinces with prices significantly higher in Balochistan (overall) and NWFP (for wheat). When regressed against various explanatory variables, the variation in cost of living appears to be determined by the population in cubic form (reaching a minimum for a city size of 2.1 million) and the provincial affiliation of cities. The index also reveals that relative to 1999, the economy as a whole appears to have become less integrated as the difference in prices across cities is much greater than in 1999. However, cities in Sindh due to their close proximity to the port have become less expensive because of the increased share of imports in consumption. The findings of this paper have very important implications for public policy with respect to transfer payments to relieve poverty, urban development, inter-provincial trade and transport and allocation of development funds among provinces.Regional Economics Measurement, Regional Economic Activity, Growth, Development, and Changes
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