A study on the antimicrobial efficacy of RF oxygen plasma and neem extract treated cotton fabrics

The paper deals with a thorough investigation on the antimicrobial activity of RF oxygen plasma and Azadirachtin (neem extract) treated cotton fabric. The hydrophilicity of cotton fabric was found to improve when treated with RF oxygen plasma. The process parameters such as electrode gap, time of exposure and oxygen pressure have been varied to study their effect on improving the hydrophilicity of the cotton fabric. The static immersion test has been carried out to assess the hydrophilicity of the oxygen plasma treated samples and the process parameters were optimized based on these test results. The formation of carbonyl group during surface modification in the plasma treated sample was analysed using FTIR studies. The surface morphology has been studied using SEM micrographs.The antimicrobial activity was imparted to the RF oxygen plasma treated samples using methanolic extract of neem leaves containing Azadirachtin. The antimicrobial activity of these samples has been analysed and compared with the activity of the cotton fabric treated with neem extract alone. The investigation reveals that the surface modification due to RF oxygen plasma was found to increase the hydrophilicity and hence the antimicrobial activity of the cotton fabric when treated with Azadirachtin.     

Adsorption of Chromium (VI) on <Emphasis Type="Italic">Azadirachta Indica</Emphasis> (Neem) Leaf Powder

A novel adsorbent was developed from mature leaves of the Neem tree (Azadirachta Indica) for removing metal ions from water. The adsorbent, in the form of fine powder, was found to be very effective in removing chromium (VI) from aqueous solution. The adsorption was carried out in a batch process taking different concentrations of the metal ion in aqueous solution with variation in adsorbent amount, pH, agitation time and temperature. The suitability of the adsorbent was tested with Langmuir and Freundlich isotherms and with various equilibrium kinetic data. A small amount of the Neem Leaf Powder (NLP) (1.6 g dm^–3) could remove as much as 87% of Cr (VI) in 300 min from a solution of concentration 14.1 mg dm^–3 at 300 K. The optimum range of pH for the adsorption process was 4.5–7.5 and since the natural pH of the Cr (VI) solution was 5.5, no addition of acid or alkali was necessary for achieving maximum adsorption. The adsorption coefficients indicated a high potentiality for the NLP to be used as an adsorbent for removing Cr (VI) from water.     

How good are convex hull algorithms?

A convex polytope P can be specified in two ways: as the convex hull of the vertex set V of P, or as the intersection of the set H of its facet-inducing halfspaces. The vertex enumeration problem is to compute V from H>. The facet enumeration problem is to compute H from V. These two problems are essentially equivalent under point/hyperplane duality. They are among the central computational problems in the theory of polytopes. It is open whether they can be solved in time polynomial in |H| + |V| and the dimension. In this paper we consider the main known classes of algorithms for solving these problems. We argue that they all have at least one of two weaknesses: inability to deal well with “degeneracies”, or, inability to control the sizes of intermediate results. We then introduce families of polytopes that exercise those weaknesses. Roughly speaking, fat-lattice or intricate polytopes cause algorithms with bad degeneracy handling to perform badly; dwarfed polytopes cause algorithms with bad intermediate size control to perform badly. We also present computational experience with trying to solve these problem on these hard polytopes, using various implementations of the main algorithms.     

Geometry and Growth Rate of Frobenius Numbers of Additive Semigroups

Linear combinations x ₁ a ₁ ⋯ x _n a _n of n given natural numbers a _s (with nonnegative integral coefficients x _s ) attain all the integral values, starting from some integer N(a), called the Frobenius number of vector a (provided that the integers a _s have no common divisor, greater than 1). The growth rate of N(a) with the large value of σ = ta ₁ ⋯ a _n depends peculiarly from the direction α of the vector a = σα. The article proves the lower bound of order and the upper bound of order σ ². Both orders are reached from some directions α. The averaging of N(a) along all directions, performed for σ = 7, 19, 41 and 97, provides the values, confirming the rate σ ^p for some p between 3/2 and 2 (for n = 3), excluding neither 3/2 nor 2, for the asymptotic behaviour at large σ. One gets check p ≈ 1, 66 for σ between 100 and 200. These unexpected results, based on some strange relations of the Frobenius numbers to the higher-dimensional continued fractions geometry, lead to many facts of this arithmetic trubulence theory, discussed in this article both as theorems and as conjectures. ^★ Partially supported by RFBR grant 05-01-00104.     

Approximating a real number by a rational number with a limited denominator: A geometric approach

We consider the problem of determining the rational number which best approximates the real number a and such that its denominator belongs to an interval [b,b^′]. There is a related geometric problem consisting in finding the integer point lying in the vertical domain D of the form {(x,y)∈R²∣b≤x≤b^′} such that the straight line passing through the origin and through this point best approximates the straight line L of slope a passing through the origin. The computation of this point is interlinked with the computation of both the convex hulls of the integer points located above and below the straight line L respectively and lying in the vertical domain D. In the literature, many general convex hull algorithms exist, as the gift wrapping algorithm for example. However, we focus on two interesting approaches to compute these convex hulls which are especially appropriated in our special configuration. The first one mainly uses number theory and runs in O(log(b^′)) time. The other is in line with computational geometry as the method proposed in 1999 by Balza-Gomez et al. [H. Balza-Gomez, J.-M. Moreau, D. Michelucci, Convex hull of grid points below a line or a convex curve, in: DGCI ’99: Proceedings of the 8th International Conference on Discrete Geometry for Computer Imagery, Springer, Marne-la-Vallée, France, 1999, pp. 361-374] which runs in O(log(b^′−b)) time. We propose a new method for the computation of these convex hulls which combines number theory and computational geometry. Our method preserves the optimal time complexity and is the first being output sensitive. Indeed, we compute the convex hulls in time linear in their vertex number. Moreover, the resulting algorithm is very simple and so is suitable for implementation.     

Galois hulls of special Goppa codes and related codes with application to EAQECCs

Galois hulls of MDS codes can be applied to construst MDS entanglement-assisted quantum error-correcting codes (EAQECCs). Goppa codes and expurgated Goppa codes (resp., extended Goppa codes) over ${\mathbb{F}}_{q^m}$ are GRS codes (resp., extended GRS codes) when $m=1$. In this paper, we investigate the Galois dual codes of a special kind of Goppa codes and related codes and provide a necessary and sufficient condition for the Galois dual codes of such codes to be Goppa codes and related codes. Then we determine the Galois hulls of the above codes. In particular, we completely characterize Galois LCD, Galois self-orthogonal, Galois dual-containing and Galois self-dual codes among such family of codes. Moreover, we apply the above results to EAQECCs.