Can the Local Energy-Momentum Conservation Laws be Derived Solely from Field Equations?

The vanishing of the divergence of the matter stress-energy tensor for General Relativity is a particular case of a general identity, which follows from the covariance of the matter Lagrangian in much the same way as (generalized) Bianchi identities follow from the covariance of the purely gravitational Lagrangian. This identity, holding for any covariant theory of gravitating matter, relates the divergence of the stress tensor with a combination of the field equations and their derivatives. One could thus wonder if, according to a recent suggestion [1], the energy-momentum tensor for gravitating fields can be computed through a suitable rearrangement of the matter field equations, without relying on the variational definition. We show that this can be done only in particular cases, while in general it leads to ambiguities and possibly to wrong results. Moreover, in nontrivial cases the computations turn out to be more difficult than the standard variational technique.     

Detailed mechanism of squalene epoxidase inhibition by terbinafine

Squalene epoxidase (SE) is a key flavin adenine dinucleotide (FAD)-dependent enzyme of ergosterol and cholesterol biosynthetic pathways and an attractive potential target for drugs used to inhibit the growth of pathogenic fungi or to lower cholesterol level. Although many studies on allylamine drugs activity have been published during the last 30 years, up until now no detailed mechanism of the squalene epoxidase inhibition has been presented. Our study brings such a model at atomic resolution in the case of yeast Saccharomyces cerevisiae . Presented data resulting from modeling studies are in excellent agreement with experimental findings. A fully atomic three-dimensional (3D) model of squalene epoxidase (EC 1.14.99.7) from S. cerevisiae was built with the help of 3D-Jury approach and further screened based on data known from mutation experiments leading to terbinafine resistance. Docking studies followed by molecular dynamics simulations and quantum interaction energy calculations [MP2/6-31G(d)] resulted in the identification of the terbinafine-squalene epoxidase mode of interaction. In the energetically most likely orientation of terbinafine its interaction energy with the protein is ca. 120 kJ/mol. In the favorable position the terbinafine lipophilic moiety is located vertically inside the squalene epoxidase binding pocket with the tert-butyl group oriented toward its center. Such a position results in the SE conformational changes and prevents the natural substrate from being able to bind to the enzyme's active site. That would explain the noncompetitive manner of SE inhibition. We found that the strongest interaction between terbinafine and SE stems from hydrogen bonding between hydrogen-bond donors, hydroxyl group of Tyr90 and amine nitrogen atom of terbinafine. Moreover, strong attractive interactions were recorded for amino acids whose mutations resulted in terbinafine resistance. Our results, elucidating at a molecular level the mode of terbinafine inhibitory activity, can be utilized in designing more potent or selective antifungal drugs or even medicines lowering cholesterol in humans.     

Independence results for variants of sharply bounded induction

The theory , axiomatized by the induction scheme for sharply bounded formulae in Buss’ original language of bounded arithmetic (with ⌊x/2⌋ but not ⌊x/2^y⌋), has recently been unconditionally separated from full bounded arithmetic S₂. The method used to prove the separation is reminiscent of those known from the study of open induction.We make the connection to open induction explicit, showing that models of can be built using a “nonstandard variant” of Wilkie’s well-known technique for building models of IOpen. This makes it possible to transfer many results and methods from open to sharply bounded induction with relative ease.We provide two applications: (i) the Shepherdson model of IOpen can be embedded into a model of , which immediately implies some independence results for ; (ii) extended by an axiom which roughly states that every number has a least 1 bit in its binary notation, while significantly stronger than plain , does not prove the infinity of primes.     

1H, 13C, 195Pt and 15N NMR structural correlations in Pd(II) and Pt(II) chloride complexes with various alkyl and aryl derivatives of 2,2'-bipyridine and 1,10-phenanthroline

(1)H, (13)C, (195)Pt and (15)N NMR studies of platinide(II) (M = Pd, Pt) chloride complexes with such alkyl and aryl derivatives of 2,2'-bipyridine and 1,10-phenanthroline as LL = 6,6'-dimethyl-bpy, 5,5'-dimethyl-bpy, 4,4'-di-tert-butyl-bpy, 2,9-dimethyl-phen, 2,9-dimethyl-4,7-diphenyl-phen, 3,4,7,8-tetramethyl-phen, having the general [M(LL)Cl(2)] formula were performed and the respective chemical shifts (δ(1H), δ(13C), δ(195Pt), δ(15N)) reported. (1)H high-frequency coordination shifts (Δ(coord)(1H) = δ(complex)(1H)-δ(ligand)(1H)) mostly pronounced for nitrogen-adjacent protons and methyl groups in the nearest adjacency of nitrogen, as well as (15)N low-frequency coordination shifts (Δ(coord)(15H) = δ(complex)(15H)-δ(ligand)(15H)) were discussed in relation to the molecular structures.     

Variational formulations for transmission problems of the electromagnetic field

The subject of this article is a review of all possible transmission problems for electromagnetic phenomena. In particular, we study the case of a perfect dielectric and a perfect conductor via a (formal) limit with conductivity approaching zero or infinity and discuss the expected regularity of the involved unknowns. Finally, we formulate equivalent variational formulations for each considered problem.     

DFT calculations of structures, 13C NMR chemical shifts,and Raman RBM mode of simple models of small‐diameter zigzag (4,0) carboxylated single‐walled carbon nanotubes

Linearly conjugated benzene rings (acenes), belt‐shaped molecules (cyclic acenes), and models of single‐walled carbon nanotubes (SWCNTs) with one carboxylic group at the open end were fully optimized at the B3LYP/6‐31G* level of theory. These models were selected to obtain some insight into the nuclear isotropic changes resulting from systematically increasing the basic building units of open‐tip‐monocarboxylated SWCNTs. In addition, the position of radial breathing mode (RBM), empirically correlated with the SWCNT diameter, was directly related with the radius of model cyclic acene rings. A regular convergence of selected structural, NMR, and Raman parameters with the molecular system size increase was observed, and a simple two‐parameter mathematical formula enabled their estimation in infinity. The predicted ¹³C NMR chemical shifts of carbon atoms close to the substituted rim of carboxylated models of zigzag (4,0) SWCNTs differed significantly from the pristine nanotubes. Copyright © 2012 John Wiley & Sons, Ltd.     

The concept of the trichotomy of motivating factors in the workplace

Central European Journal of Operations Research - The paper presents key issues related to motivation in the workplace and its methodological aspects, giving special attention to an analysis of the...     

Quinolinesulfonamides: Interaction between bovine serum albumin,molecular docking analysis,and antiproliferative activity against human breast carcinoma cells

The complex formation of bovine serum albumin (BSA) with library of all seven regioisomeric quinolinesulfonamides (QSAs) under physiological condition is studied in this paper. The fluorescence quenching mechanism of BSA by QSAs was discussed and the association constants, as well as the number of binding sites, were calculated. In addition, a molecular docking study of the tested sulfamoylquinolines on the active site of serum albumin is performed. The experimental data and molecular docking studies reveal that sulfamoylquinolines bind in the large hydrophobic cavity of subdomain IB, and in the hydrophobic pockets of BSA subdomains IIA and IIIA by hydrophobic interactions with tryptophanyl (Trp-213) and tyrosyl residues. Moreover, the antiproliferative activity of QSAs against two human breast cancer cell lines (human adenocarcinoma (MCF-7) and human ductal carcinoma (MDA-MB-231)) and a human normal fibroblast is also studied in this paper. The antiproliferative activity of the tested QSAs was comparable to those of cisplatin. The returned data indicate that some of the tested quinolinesulfamoyl derivatives display significant cytotoxic activity.     

Alkyl methylphosphonic acids,the degradation products of organophosphorous CWA — preparation and direct quantitative GC-FID analysis

Seven alkyl methylphosphonic acids, products of hydrolytic degradation of organophosphorus chemical warfare agents, were obtained with a high purity (mostly above 98%), with the aim of being applyed as future certified reference materials. Ethyl (EMPA), isopropyl (IMPA), pinacolyl (PMPA), butyl (BUMPA), isobutyl (IBUMPA), cyclohexyl (CHMPA) and 2-ethylhexyl (EHMPA) monoesters of MPA were synthesized and characterized by MS EI, FTIR and NMR (¹H, ¹³C, ³¹P), TLC, as well as GC and GC-MS after derivatization. The conditions for a direct quantitative GC FID analysis on CP-FFAP CB column of non-derivatized alkyl methylphosphonic acids were developed. This is the first successful attempt of a directed GC analysis of free alkyl phosphonic acids. Their chemical purity was determined and limit of quantification (LOQ) values for some of them were evaluated for the GC-FID method.