Measurements of the density and viscosity of binary mixtures of (hyper-branched polymer,B-H2004 + 1-butanol,or 1-hexanol,or 1-octanol,or methyl tert-butyl ether)

Density and viscosity were determined for binary mixtures of {hyper-branched polymer, Boltorn H2004 (B-H2004) + 1-alcohol (1-butanol, 1-hexanol, and 1-octanol)} at T = (298.15, 308.15, 318.15, 328.15, and 338.15) K and of {B-H2004 + methyl tert-butyl ether (MTBE)} at T = (298.15, 308.15, and 318.15) K and ambient pressure. The temperature dependence of density and viscosity is described by linear regression and by the Vogel–Fucher–Tammann equation, respectively. Excess volumes for the system {B-H2004 + MTBE} are presented as a function of mass fraction. Viscosity deviations were calculated and correlated by the Redlich–Kister polynomial expansions using also the mass fractions. The polynomial correlations describe the variation of viscosity with composition. A qualitative discussion on these quantities in terms of molecular interactions is reported.     

Microorganisms in inorganic chemical analysis

There are innumerable strains of microbes (bacteria, yeast and fungi) that degrade or transform chemicals and compounds into simpler, safer or less toxic substances. These bioprocesses have been used for centuries in the treatment of municipal wastes, in wine, cheese and bread making, and in bioleaching and metal recovery processes. Recent literature shows that microorganisms can be also used as effective sorbents for solid phase extraction procedures. This review reveals that fundamental nonanalytical studies on the parameters and conditions of biosorption processes and on metal–biomass interactions often result in efficient analytical procedures and biotechnological applications. Some selected examples illustrate the latest developments in the biosorption of metals by microbial biomass, which have opened the door to the application of microorganisms to analyte preconcentration, matrix separation and speciation analysis.     

Graph coloring and Graham’s greatest common divisor problem

In this paper we introduce and study two graph coloring problems and relate them to some deep number-theoretic problems. For a fixed positive integer $k$ consider a graph $B_k$ whose vertex set is the set of all positive integers with two vertices $a,b$ joined by an edge whenever the two numbers $a∕gcd(a,b)$ and $b∕gcd(a,b)$ are both at most $k$. We conjecture that the chromatic number of every such graph $B_k$ is equal to $k$. This would generalize the greatest common divisor problem of Graham from 1970; in graph-theoretic terminology it states that the clique number of $B_k$ is equal to $k$. Our conjecture is connected to integer lattice tilings and partial Latin squares completions.     

Dynamical flexibility of damped vibratory clamped-clamped beam in transportation

This work concerns the issue of damped vibratory beam in transportation. Support conditions were defined for clamped-clamped beamlike systems. Structural loads were defined as with unitary amplitude ones up to the used dynamical flexibility definition. Geometric representation of analyzed element is a beam with symmetric cross-section constant on the whole length of the beam. The load assumed as bending one. The beam was fixed onto the rotational disk with the angular velocity treated as transportation velocity. In thesis the dynamical flexibility of analyzed beam was presented and the sample dynamical characteristics were drawn on graphical charts. In derived mathematical model mutual interactions between the damping forces, dynamical flexibilities and angular working velocity were took into consideration. Presented model can be put into use in high speed pumps and turbines as vanes. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Supports of semi-stable probability measures on locally convex spaces

LetE be a locally convex space. Let be an absolutely convexly tight Radom semi-stable probability measure onE with index 1<2 and Lévy measureM. The main result of this paper shows that the closed semigroup generated by the support ofM and the negative of the barycenter ofM restricted to a suitable compact subset ofE is a (closed) linear space ofE, and that the support of is a suitable translate of this linear space. This result complements a few known results concerning the supports of stable and semi-stable probability measures. In particular, it extends an analogous result proved recently for the support of -stable probability measures 1<2 (Ref. 4). Related results concerning the support of Radon semi-stable probability measures onE of index 0<<1 are also discussed.The research of this author was partially supported by AFSOR Grant No. 90-0168The research of this author was supported by KBN Grant, and the University of Tennessee Science Alliance, a State of Tennessee Center of Excellence.     

Modeling the electronic structures of the ground and excited states of the ytterbium atom and the ytterbium dimer: A modern quantum chemistry perspective

We present a comprehensive theoretical study of the electronic structures of the Yb atom and the Yb₂ molecule, respectively, focusing on their ground and lowest-lying electronically excited states. Our study includes various state-of-the-art quantum chemistry methods such as CCSD, CCSD(T), CASPT2 (including spin-orbit coupling), and EOM-CCSD as well as some recently developed pCCD-based approaches and their extensions to target excited states. Specifically, we scan the lowest-lying potential energy surfaces of the Yb₂ dimer and provide a reliable benchmark set of spectroscopic parameters including optimal bond lengths, vibrational frequencies, potential energy depths, and adiabatic excitation energies. Our in-depth analysis unravels the complex nature of the electronic spectrum of Yb₂, which is difficult to model accurately by any conventional quantum chemistry method. Finally, we scrutinize the bi-excited character of the first excited state and its evolution along the potential energy surface.     

Enthalpies of solvation of alkylated uracils in water,nonaqueous and mixed solvents

The enthalpies of solution of uracil and its alkylated derivatives in water, methanol, N,N-dimethylformamide (DMF) and water+DMF mixtures were measured at 25°C. The enthalpies of solvation were determined. The enthalpies of cavity formation, corresponding to the enthalpies of solvent-solvent interactions were calculated and the enthalpies of solute-solvent interactions were obtained. The presence of the alkyl groups was found to have different effects on the enthalpy of interaction depending on the position and size of the substitution. The effect of alkylation at the nonpolar side of the uracil ring was found to arise mostly from the enhancement of the van der Waals interactions. The alkyl substitutions at the polar side resulted also in the removal of the solvent molecules interacting specifically with the polar groups of uracil. The enthalpy of those specific interactions was determined and found to be stronger in methanol and DMF than in water. Enthalpies of solvation in the binary water+DMF solvent were found to depend in a nonlinear way on the solvent composition. The nonlinearities in the water-rich region were found to arise from the decay of the hydrophobic hydration of the solutes with the increasing DMF content. The substitution of two methyl groups caused the uracil molecule to bahave as a predominantly hydrophobic solute. The nonlinearities in the DMF-rich region were found only for those solutes which can form hydrogen bonds with DMF.     

Composite ion exchanger for removal of sodium-24 from mineralizates of biological materials in neutron activation analysis

A composite ion exchanger containing hydrated antimony pentoxide (HAP) in polystyrene-divinylbenzene matrix has been prepared. Its sorption properties with respect to Na, As, Au, Cd, Cu, Ga, Hg, In, K, La, Mn, Mo (Tc), Pd, Pt, Sb, W and Zn have been examined. Sodium is quantitatively retained on the sorbent from 8M HCl solution as well as from a mixture of conc. H₂SO₄+ conc. HNO₃+H₂O (1+1+2). As, W, Cd and Sb are partially retained, while the remaining elements are not retained and can be quantitatively eluted. The composite ion exchanger is stable to oxidizing acid media and it can be directly applied to separation of²⁴Na from mineralizates of neutron-irradiated biological materials.