Gas-phase acidities and O-H bond dissociation enthalpies of phenol, 3-methylphenol, 2,4,6-trimethylphenol, and ethanoic acid

Energy-resolved, competitive threshold collision-induced dissociation (TCID) methods are used to measure the gas-phase acidities of phenol, 3-methylphenol, 2,4,6-trimethylphenol, and ethanoic acid relative to hydrogen cyanide, hydrogen sulfide, and the hydroperoxyl radical using guided ion beam tandem mass spectrometry. The gas-phase acidities of Delta(acid)H298(C6H5OH) = 1456 +/- 4 kJ/mol, Delta(acid)H298(3-CH3C6H4OH) = 1457 +/- 5 kJ/mol, Delta(acid)H298(2,4,6-(CH3)3C6H2OH) = 1456 +/- 4 kJ/mol, and Delta(acid)H298(CH3COOH) = 1457 +/- 6 kJ/mol are determined. The O-H bond dissociation enthalpy of D298(C6H5O-H) = 361 +/- 4 kJ/mol is derived using the previously published experimental electron affinity for C6H5O, and thermochemical values for the other species are reported. A comparison of the new TCID values with both experimental and theoretical values from the literature is presented.     

A localized specific interaction alters the unfolding pathways of structural homologues

Reductive unfolding studies of proteins are designed to provide information about intramolecular interactions that govern the formation (and stabilization) of the native state and about folding/unfolding pathways. By mutating Tyr92 to G, A, or L in the model protein, bovine pancreatic ribonuclease A, and through analysis of temperature factors and molecular dynamics simulations of the crystal structures of these mutants, it is demonstrated that the markedly different reductive unfolding rates and pathways of ribonuclease A and its structural homologue onconase can be attributed to a single, localized, ring-stacking interaction between Tyr92 and Pro93 in the bovine variant. The fortuitous location of this specific stabilizing interaction in a disulfide-bond-containing loop region of ribonuclease A results in the localized modulation of protein dynamics that, in turn, enhances the susceptibility of the disulfide bond to reduction leading to an alteration in the reductive unfolding behavior of the homologues. These results have important implications for folding studies involving topological determinants to obtain folding/unfolding rates and pathways, for protein structure-function prediction through fold recognition, and for predicting proteolytic cleavage sites.     

On Smooth Maps with Finitely Many Critical Points: Addendum

The paper is an addendum to D. Andrica and L. Funar, ‘Onsmooth maps with finitely many critical points’, J. LondonMath. Soc. (2) 69 (2004) 783–800.     

Measurement of natural radioactivity and radiation hazards for some natural and artificial building materials available in Romania

As building materials are known to be the second source regarding high radon concentrations, it is very important to determine the amounts of natural radionuclides from every building material in use. In the present study the most frequently used Romanian natural (sand, gypsum, limestone) and artificial (portland cement, lime, clinker, electrofilter powder, fly ash, cement-lime plaster mortar, cement plaster mortar) building materials were analyzed. The absorbed dose rate and the annual effective dose equivalent rate for people living in dwelling buildings made of these building materials under investigation were also calculated. The analysis was performed with gamma-ray spectrometry, with two hyper-pure germanium detectors. The activity concentrations of natural radionuclides were in the ranges: 5.2–511.8 Bq kg^?1 for ²²⁶Ra; 0.6–92.6 Bq kg^?1 for ²³²Th and <1–1,720.7 Bq kg^?1 for ⁴⁰K, respectively. The radium equivalent activity in the fifty-one (51) samples varied from 9 to 603 Bq kg^?1. By calculating all the radioactivity indices (Ra_eq, H _ext, I _α, I _yr) it was found that all the building materials under investigation can be used to erect dwelling buildings. Except for sample SA6, SA7 and SA11 among the natural building materials and sample SG1, SG2, FAH1, CLM1, CM1 among the artificial building materials that are considered hazardous materials when are used in large quantities.     

Crosslinked QA‐PEI nanoparticles: synthesis reproducibility,chemical modifications,and stability study

Quaternary ammonium polyethylenimine (QA‐PEI) nanoparticles were synthesized by PEI crosslinking and alkylation with octyliodide followed by quaternization by methyl iodide. The present study focuses on the reproducibility of particles formation with respect to particle size, positive charge, oxidative, thermal stability and antibacterial activity. The QA‐PEI‐based nanoparticles with particle size in the range of 160–190 nm were synthesized in high reproducibility and showed high chemical stability against environmental changes including exposure to different oxidizers and storage conditions. QA‐PEI nanoparticles incorporated in dental restorative resin composites at 2% w/w demonstrated strong antibacterial activity. Copyright © 2013 John Wiley & Sons, Ltd.     

Variational formulation for the stationary fractional advection dispersion equation

In this article a theoretical framework for the Galerkin finite element approximation to the steady state fractional advection dispersion equation is presented. Appropriate fractional derivative spaces are defined and shown to be equivalent to the usual fractional dimension Sobolev spaces H^s. Existence and uniqueness results are proven, and error estimates for the Galerkin approximation derived. Numerical results are included that confirm the theoretical estimates. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2005     

Characterization of the shape stability for nonlinear elliptic problems

We characterize all geometric perturbations of an open set, for which the solution of a nonlinear elliptic PDE of p-Laplacian type with Dirichlet boundary condition is stable in the L^∞-norm. The necessary and sufficient conditions are jointly expressed by a geometric property associated to the γp-convergence.If the dimension N of the space satisfies N−1<p?N and if the number of the connected components of the complements of the moving domains are uniformly bounded, a simple characterization of the uniform convergence can be derived in a purely geometric frame, in terms of the Hausdorff complementary convergence. Several examples are presented.     

Do Optimal Shapes Exist?

This paper surveys the talk given by the author at the “Seminario Matematico e Fisico di Milano” in November 2006. It deals with the existence question for shape optimization problems associated to the Dirichlet Laplacian. Existence of solutions is seen from both geometrical and functional (γ-convergence) point of view and is discussed in relationship with the optimality conditions and numerical algorithms. Several examples are given concerning isoperimetric inequalities for eigenvalues and shape control problems. Received: August 2007     

On the number of edge disjoint cliques in graphs of given size

In this paper, we prove that any graph ofn vertices andt _r–1(n)+m edges, wheret _r–1(n) is the Turán number, contains (1–o(1)m edge disjointK _r'sifm=o(n ²). Furthermore, we determine the maximumm such that every graph ofn vertices andt _r–1(n)+m edges containsm edge disjointK _r's ifn is sufficiently large.Research partially supported by Hungarian National Foundation for Scientific Research Grant no. 1812.