Preparation of quaternized dimethylaminoethylmethacrylate grafted nonwoven fabric for the removal of phosphate

Dimethylaminoethylmethacrylate (DMAEMA) grafted polyethylene/polypropylene (PE/PP) nonwoven fabric was prepared by radiation-induced graft polymerization. Grafting conditions were optimized and about 150% DMAEMA grafted samples were used for further experiments. DMAEMA graft chains were later quaternized with dimethyl sulphate for the removal of phosphate ions. Adsorption experiments were conducted with quaternized DMAEMA grafted fabric for phosphate removal at low (0.5–25 ppm) and high phosphate concentrations (50–1000 ppm). Adsorbed phosphate amounts at pH 7 were found to be 63 mg phosphate/g polymer and 512 mg phosphate/g polymer for low (25 ppm) and high phosphate concentrations (1000 ppm) respectively showing the efficiency of the adsorbent material in removing phosphate. The pH effect on phosphate adsorption showed that the quaternized DMAEMA grafted nonwoven fabric can adsorb phosphate over a wide pH range (5.00–9.00) indicating that adsorbent material can effectively remove different forms of phosphate ions, namely H₂PO₄^?, HPO₄^2? and PO₄^3? in aqueous solution at this pH range where the species exist. Competitive adsorption experiments were also carried out with two concentration levels at pH 7 to investigate the effect of competing ions. Phosphate adsorption on quaternized DMAEMA grafted nonwoven fabric was found to be higher than the other competing ions at two concentration levels. At high concentration level, the adsorption order was phosphate>nitrite>bromide>sulphate>nitrate whereas at low concentration level, the order was phosphate?sulphate>bromide>nitrite>nitrate.     

Effect of G/M ratio on the radiation-induced degradation of sodium alginate

Radiation-induced degradation of sodium alginate (NaAlg) having different G/M ratios was investigated. NaAlg samples were irradiated with gamma rays in air at ambient temperature in the solid state at low dose rate. Change in their molecular weights was followed by size exclusion chromatography (SEC). Changes in their rheological properties and viscosity values as a function of temperature, shear rate and irradiation dose were also determined. Chain scission yields, G(S), and degradation rates were calculated. It was observed that G/M ratio was an important factor controlling the G(S) and degradation rate of sodium alginate.     

A Highly Efficient Chelating Polymer for the Adsorption of Uranyl and Vanadyl Ions at Low Concentrations

A new polymer containing double amidoxime groups per repeating unit was synthesized to enhance the metal ion uptake capacity. The adsorption properties of this new polymeric adsorbent, amidoximated poly(N,N-dipropionitrile acrylamide), for U(VI), V(V), Cu(II), Co(II) and Ni(II) ions were investigated by batch and flow-through processes at very low concentration levels (ppb). The chelating polymer showed high adsorption capacity for uranyl as well as vanadyl ions. In selectivity studies from a mixture of metal ions in aqueous solutions, the adsorbent showed high selectivity for uranyl and vanadyl ions in the following order: U(VI) > V(V) Co(II) = Cu(II) Ni(II) as determined by calculating the distribution coefficients D, of corresponding ions. The adsorption of uranyl and vanadyl ions from natural seawater by the new adsorbent was also examined in flow through mode.     

The effect of external stimuli on the Bovine Serum Albumin adsorption capacity of poly(acrylamide/maleic acid) hydrogels prepared by gamma rays

The effects of external stimuli such as pH of the buffer solution, ionic strength, temperature and the amount of poly-electrolyte monomer in the hydrogel system on the Bovine Serum Albumin (BSA) adsorption capacity of poly(acrylamide/maleic acid) [P(AAm/MA)] hydrogels were investigated. Poly-electrolyte P(AAm/MA) hydrogels with varying compositions were prepared by irradiating acrylamide/maleic acid/water mixtures with γ rays at ambient temperature. Langmuir type adsorption isotherms were observed for all prepared hydrogels. Increase of ionic strength of the buffer solution from 0.01 to 0.1 mol dm⁻³ decreased the adsorption capacity of hydrogels and zero adsorption was observed in the presence of 0.1 mol dm⁻³ Na⁺ and Ca²⁺ ion in the adsorption medium. The adsorption capacity of hydrogels was found to increase from 0 to 120 mg BSA/g dry gel, by changing external stimuli and hydrogel composition.     

Removal of phosphate using copper-loaded polymeric ligand exchanger prepared by radiation grafting of polypropylene/polyethylene (PP/PE) nonwoven fabric

A novel polymeric ligand exchanger (PLE) was prepared for the removal of phosphate ions from water. 2,2′-dipyridylamine (DPA), a bidentate ligand forming compound with high coordination capacity with a variety of metal ions was bound to glycidyl methacrylate (GMA) grafted polypropylene/polyethylene (PP/PE) nonwoven fabric synthesized by radiation-induced grafting technique. DPA attachment on epoxy ring of GMA units was tested in different solvents, i.e. methanol, ethanol, dioxane and dimethylsulfoxide (DMSO). The highest amount of modification was achieved in dioxane. In order to prepare the corresponding PLE for the removal of phosphate, DPA-immobilized fabric was loaded with Cu(II) ions. Phosphate adsorption experiments were performed in batch mode at different pH (5–9) and phosphate concentrations. The fabric was found to be effective for the removal of phosphate ions. At every stage of preparation and use, the nonwoven fabric was characterized by thermal (i.e. DSC and TGA) and spectroscopic (FTIR) methods. Competitive adsorption experiments were also carried out using two solutions with different concentration levels at pH 7 to see the effect of competing ions. Phosphate adsorption was found to be effective and selective from solutions having trace amounts of competitive anions. It is expected that the novel PLE synthesized can be used for the removal of phosphate ions in low concentrations over a large range of pH.     

Super magic strength of a graph

By G(p, q) we denote a graph having p vertices and q edges, by V and E the vertex set and edge set of G respectively. A graph G(p, q) is said to have an edge magic labeling (valuation) with the constant (magic number) c(f) if there exists a one-to-one and onto function f: V ∪ E → {1, 2, …., p + q} such that f(u)+f(v)+f(uv) = c(f) for all uv ∈ E. An edge magic labeling f of G is called a super magic labeling if f(E) ={1, 2, …., q}. In this paper the concepts of the super magic and super magic strength of a graph are introduced. The super magic strength (sms) of a graph G is defined as the minimum of all constants c′(f) where the minimum is taken over all super magic labeling of G and is denoted by sms(G). This minimum is defined only if the graph has at least one such super magic labeling. In this paper, the super magic strength of some well known graphs P _2n , P _2n+1, K _1,n , B _n,n , < K _1,n : 2 >, P _n ² and (2 _{n + 1})P ₂, C _n and W _n are obtained, where P _n is a path on n vertices, K _1,n is a star graph on n+1 vertices, n-bistar B _n,n is the graph obtained from two copies of K _1,n by joining the centres of two copies of K _1,n by an edge e, if e is subdivided then B _n,n becomes < K _1,n : 2 >, (2 _{n + 1}) P ₂ is 2 _{n + 1} disjoint copies of P ₂, P _n ² is a square graph of P _n . C _n is a cycle on n vertices and W _n = C _n + K ₁ is wheel on n + 1 vertices.     

Intrinsic Compiler Support for Interval Arithmetic

Interval arithmetic provides an efficient method for monitoring errors in numerical computations and for solving problems that cannot be efficiently solved with floating-point arithmetic. To support interval arithmetic, several software tools have been developed including interval arithmetic libraries, extended scientific programming languages, and interval-enhanced compilers. The main disadvantage of these software tools is their speed, since interval operations are implemented using function calls. In this paper, compiler support for interval arithmetic is investigated. In particular, the performance benefits of having the compiler inline interval operations to eliminate function call overhead is researched. Interval operations are inlined with the GNU gcc compiler and the performance of interval arithmetic is evaluated on a superscalar architecture. To implement interval operations with compiler support, the compiler produces sequences of instructions that use existing floating point hardware. Simulation results show that the compiler implementation of interval arithmetic is approximately 4 to 5 times faster than a functionally equivalent interval arithmetic software implementation with function call overhead and approximately 1.2 to 1.5 times slower than a dedicated interval arithmetic hardware implementation.     

Radiation of waves from a spherical shell accelerating in an acoustic medium

A thin, elastic and ring-stiffened spherical shell accelerates in an acoustic medium which is inviscid, irrotational and compressible. The transient response of the fluid-shell system is studied numerically. The effect of the translation of the center of mass of the shell on the radiated fluid pressure is discussed. Two acceleration functions with the same shape but different durations are used in the analysis. The propagation of the radiated pressure along the wet surface of the shell and along the radial co-ordinate is presented.     

The compactness of adaptive routing tables

The compactness of a routing table is a complexity measure of the memory space needed to store the routing table on a network whose nodes have been labelled by a consecutive range of integers. It is defined as the smallest integer k such that, in every node u, every set of labels of destinations having the same output in the table of u can be represented as the union of k intervals of consecutive labels. While many works studied the compactness of deterministic routing tables, few of them tackled the adaptive case when the output of the table, for each entry, must contain a fixed number α of routing directions. We prove that every n-node network supports shortest path routing tables of compactness at most n/α for an adaptiveness parameter α, whereas we show a lower bound of n/α^O(1).     

On Line Graphs with Crossing Number 1

In this paper we deduce a necessary and sufficient condition for a line grah to have crossing number 1. In addition, we prove that the line graph of any nonplanar graph has crossing number greater than 2.