Strong vacuum polarization and self-damping of e+e− annihilation

If the hadronic contribution to vacuum polarization, which is proportional to the ration of e⁺e^? annihilation into hadrons to that into μ⁺μ^? rises asymptotically as a power $\text{β >}\text{1}\text{2}$ of the squared four-momentum, the ratio $\text{σ}\text{(e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→hadrons)}\text{σ}$ point $\text{(}{}^{\mathrm{\sigma }}\text{point =}\text{(4πα}{}^2\text{)}\text{(3s))}$ is bound to be less than $\text{?}\text{(3}\text{tg}\text{πβ)}\text{(8α)}$ and this limit is approached sooner for higher β. Other models of vacuum polarizations are also considered together with their possible origin and implications.     

Analysis of the 1H NMR spectrum of α-tetralone

An analysis of both the aromatic and aliphatic portions of the ¹H NMR spectrum of α-tetralone has been carried out. Two deuterated derivatives, 2,2-dideuterio- and 4,4-dideuterio-α-tetralone, were prepared to facilitate unambiguous assignment of chemical shifts for the aliphatic protons. The conformation of the 6-membered alicyclic ring of the molecule is defined by the coupling constants among the aliphatic protons. Benzylic coupling was the only detectable long range interaction between the aliphatic and aromatic protons of the molecule. The magnitude and sign of these coupling constants agree with previous calculations of Wasylishen and Schaefer.     

Exact consequences of universality in SU(2) × U(1) gauge models

Exact consequences of universality within SU(2) × U(1) gauge models, with leptons in doublets and singlets, and for arbitrary vacuum expectation values of the Higgs fields, imply an extended Weinberg-Salam structure for leptons, with all neutrinos massless (the inverse statement is obvious). We also discuss approximate universality.     

Structural role of the copper ions in the dinuclear active site of Carcinus aestuarii hemocyanin

In this work we show, by a combination of biochemical and biophysical approaches, that the copper ions bound in the binuclear active site of Carcinus aestuarii hemocyanin play a stabilizing role on the tertiary structure of the protein. Upon removal of copper, the monomeric hemocyanin, but not the hexameric oligomer, undergoes changes at the level of tertiary structure while the secondary structure is almost unaffected. By Small-Angle X-Ray Scattering, supported by gel chromatography measurements, it can be concluded that the apo-monomer, but not the holo form or the hexameric form, undergoes a slow time-dependent oligomerization process.     

Large Deviations Approximations to Distributions of the Total Distance of Compound Random Walks with von Mises Directions

This article considers the planar random walk where the direction taken by each consecutive step follows the von Mises distribution and where the number of steps of the random walk is determined by the class of inhomogeneous birth processes. Saddlepoint approximations to the distribution of the total distance covered by the random walk, i.e. of the length of the resultant vector of the individual steps, are proposed. Specific formulae are derived for the inhomogeneous Poisson process and for processes with linear contagion, which are the binomial and the negative binomial processes. A numerical example confirms the high accuracy of the proposed saddlepoint approximations.     

Diiodobis(diphenyltelluride)mercury(II), [(Ph2Te)2HgI2]

Diiodobis(diphenyltelluride)mercury(II), [(Ph₂Te)₂HgI₂], is formed during the reaction of [(PhTe)₂Hg] with HgI₂ in refluxing THF. The same product can be obtained from a pressure reaction between PhTeI₃ and elemental mercury. The mercury atom is co‐ordinated in a distorted tetrahedral environment with I‐Hg‐I angles of 117?. Long range I···Te contacts of about 3.8 Å link the [(Ph₂Te)₂HgI₂] units to infinite chains along the b axis of the unit cell.     

How to make continuum solvation incredibly fast in a few simple steps: A practical guide to the domain decomposition paradigm for the conductor-like screening model

We illustrate the domain decomposition Conductor-like Screening Model (ddCOSMO) implementation and how to couple it with an existing classical or quantum mechanical (QM) code. We review in detail what input needs to be provided to ddCOSMO and how to assemble it, describe how the ddCOSMO equations are solved and how to process the results to assemble the required quantities, such as Fock matrix contributions for the QM case, or forces for the classical one. Throughout the article, we will make explicit references to the ddCOSMO module, which is an open source, Fortran 90 implementation of ddCOSMO that can be downloaded and distributed under the LGPL license.     

Bromoenterobactins as potent inhibitors of a pathogen-associated, siderophore-modifying C-glycosyltransferase

IroB is a C-glycosyltransferase encoded in the iroA cluster. C-Glucosylation of the bacterial siderophore enterobactin by IroB is a strategy some pathogenic bacteria use to evade the host's innate immunity mediated by lipocalin 2 (Lcn2). Without this modification, enterobactin can be tightly bound by host Lcn2, rendering it ineffective as a siderophore. Therefore, IroB inhibitors could be potential antibiotics against iroA-harboring pathogenic bacteria. We used enterobactin analogues to probe the properties of the active site of IroB and found that enterobactin analogues brominated at the C5 positions of the 2,3-dihydroxybenzoyl rings are potent inhibitors of IroB. This finding could lead to the discovery of effective antibiotics targeting iroA-containing bacteria.     

Equivariant Schubert calculus

We describe T-equivariant Schubert calculus on G(k,n), T being an n-dimensional torus, through derivations on the exterior algebra of a free A-module of rank n, where A is the T-equivariant cohomology of a point. In particular, T-equivariant Pieri’s formulas will be determined, answering a question raised by Lakshmibai, Raghavan and Sankaran (Equivariant Giambelli and determinantal restriction formulas for the Grassmannian, Pure Appl. Math. Quart. 2 (2006), 699–717).