Investigating the possibility of increasing cooling air flow in a hydrogenerator rotor fan

Journal of Thermal Analysis and Calorimetry - The possibility of increasing cooling airflow inside a hydrogenerator rotor fan is investigated. The rotor fan has a heat dissipation problem and it is...     

Vesicle deformations by clusters of transmembrane proteins

We carry out a coarse-grained molecular dynamics simulation of phospholipid vesicles with transmembrane proteins. We measure the mean and Gaussian curvatures of our protein-embedded vesicles and quantitatively show how protein clusters change the shapes of their host vesicles. The effects of depletion force and vesiculation on protein clustering are also investigated. By increasing the protein concentration, clusters are fragmented to smaller bundles, which are then redistributed to form more symmetric structures corresponding to lower bending energies. Big clusters and highly aspherical vesicles cannot be formed when the fraction of protein to lipid molecules is large.     

The C*-algebra of the N-dimensional harmonic oscillator

In this paper we study the Fredholm thoery of a C*-algebraOl of o-order pseudo-differential operators on L²(ⁿ). IfK denotes the ideal of all compact operators of L², the algebraOl will be generated by (i) the idealK, (ii) a function algebra CS(ⁿ) and (iii) by the bounded operators x_j, D_j, j=1,...,n, = H^–1/2, H=1+¦x¦²–. We show thatOl/K is a commutative C*-algebra with identity and obtain its Gelfany space M. This provides Fredholm criterion and index formula for a graded algebra of partial differential operators including all oeprators with polynomial coefficients. We also give Fredholm criterion and index formula for systems of such operators.     

A systematic determination of diffusion coefficients of trace elements in open and restricted diffusive layers used by the diffusive gradients in a thin film technique

A systematic comparison of the diffusion coefficients of cations (Al, Cd, Co, Cu, Mn, Ni, Pb, Zn) and oxyanions (Al, As, Mo, Sb, V, W) in open (ODL) and restricted (RDL) diffusive layers used by the DGT technique was undertaken. Diffusion coefficients were measured using both the diffusion cell (D_cell) method at pH 4.00 and the DGT time-series (D_DGT) method at pH 4.01 and 7.04 (pH 8.30 was used instead of 7.04 for Al) using the Chelex-Metsorb mixed binding layer. The performance of Chelex-Metsorb as a new DGT binding layer for Al uptake was also evaluated for the first time. Reasonable agreement was observed between D_cell and D_DGT measurements for both ODL and RDL, except for V and W. The ratios of D_cell/D_DGT for V of 0.44 and 0.39, and for W of 0.66 and 0.63 with ODL and RDL respectively, were much lower due to the formation of a high proportion of polyoxometalate species at the higher concentrations required with the D_cell measurements. This is the first time that D values have been reported for several oxyanions using RDL. Except for Al at pH 8.30 with ODL, all D_DGT measurements were retarded relative to diffusion coefficients in water (D_W) for both diffusive hydrogels. Diffusion in RDL was further retarded compared with ODL, for all elements (0.66–0.78) with both methods. However, the degree of retardation observed changed for cations and anions at each pH. At pH 7.04 cations had a slightly higher D_DGT and oxyanions had a slightly lower D_DGT than at pH 4.01 for both ODL and RDL. It is proposed that this is due to partial formation of acrylic acid functional groups (pK_a ≈4.5), which would be fully deprotonated at pH 7.04 (negative) and mostly protonated at pH 4.01 (neutral). As Al changes from being cationic at pH 4.01 to anionic at pH 8.30 the results were more complex.     

Polymerization in submonolayers of styrene monomer adsorbed from its vapor phase

The surface coverage of porous glass (PD = 500 Å) by styrene adsorbed from its vapor (0.1–6 torr) was studied in a vacuum electrobalance. The adsorption isotherm of the monomer was analyzed by the BET method, and a full monolayer coverage was found to form at a relative pressure of 0.11, weighing 6 mg per gram of glass. Polymerization in submonolayers of adsorbed styrene was initiated by thermal decomposition of predeposited BPO and found to continue until all initiator decomposed, sample cooled, or vapor removed, hence allowing a controlled film thickness. The films were extracted in THF and analyzed by computerized GPC. Molecular weights were in the range 18000–69000. These were related to the rates of polymerization by the usual statistical correlations.     

Synthesis of aliphatic polyesters containing tetracyanoquinodimethane units by low-temperature polycondensation reactions

The low-temperature solution polycondensation reaction between 1,4-bis-(2′-hydroxy-ethoxy)benzene and adipyl chloride has been studied in N,N-dimethylacetamide. The effect of temperature, concentration, and reaction time on the percent yield and product viscosity has been determined. Optimum conditions were established for the preparation of high molecular weight products and then applied to the synthesis of novel tetracyanoquinodimethane polyesters. Products were characterized by gel permeation chromatography.     

Oxidation of thioanisole by peroxomolybdate in assemblies of cetylpyridinium chloride and methyltri-n-octylammonium chloride

Methyltri-n-octylammonium chloride (Aliquat 336) is sparingly soluble in water but is readily soluble with a 2-fold excess of micellized cetylpyridinium chloride (CPyCl), and the mixtures show breaks in plots of surface tension or electrolytic conductance against concentration indicative of a critical micelle concentration slightly lower than that of CPyCl. Micellization markedly increases 35Cl and 14N NMR line widths of CPyCl, but addition of NaCl reduces the 35Cl line width and addition of Aliquat increases it. Mixing Aliquat and CPyCl has little effect on their 14N line widths. Ion pairing in alcohol mixtures also increases 35Cl line widths. In water these mixed assemblies behave similarly to micelles of CPyCl as regards effects on rates and equilibria of interconversion of tri- and tetraperoxomolybdate ions, and oxidation of thioanisole by the latter, although it is slightly slower than in micelles of CPyCl. Despite differences in the hydrophobic regions, and relationships between amphiphilic structures and morphologies of association colloids, assemblies of CPyCl and Aliquat behave very much like CPyCl micelles in their physical properties and effects upon reactivity. Geometrical optimization indicates that Aliquat can adopt conformations that allow intercalation with CPyCl micelles.     

Embeddings of minimal non-abelian p-groups

By a quasi-permutation matrix we mean a square matrix over the complex field C with non-negative integral trace. For a given finite group G, let p(G) denote the minimal degree of a faithful representation of G by permutation matrices, and let c(G) denote the minimal degree of a faithful representation of G by quasi-permutation matrices. See [4]. It is easy to see that c(G) is a lower bound for p(G). Behravesh [H. Behravesh, The minimal degree of a faithful quasi-permutation representation of an abelian group, Glasg. Math. J. 39 (1) (1997) 51-57] determined c(G) for every finite abelian group G and also [H. Behravesh, Quasi-permutation representations of p-groups of class 2, J. Lond. Math. Soc. (2) 55 (2) (1997) 251-260] gave the algorithm of c(G) for each finite group G. In this paper, we first improve this algorithm and then determine c(G) and p(G) for an arbitrary minimal non-abelian p-group G.