Conformal field theory correlations in the Abelian sandpile mode

We calculate all multipoint correlation functions of all local bond modifications in the two-dimensional Abelian sandpile model, both at the critical point, and in the model with dissipation. The set of local bond modifications includes, as the most physically interesting case, all weakly allowed cluster variables. The correlation functions show that all local bond modifications have scaling dimension two, and can be written as linear combinations of operators in the central charge -2 logarithmic conformal field theory, in agreement with a form conjectured earlier by Mahieu and Ruelle in Phys. Rev. E 64, 066130 (2001). We find closed form expressions for the coefficients of the operators, and describe methods that allow their rapid calculation. We determine the fields associated with adding or removing bonds, both in the bulk, and along open and closed boundaries; some bond defects have scaling dimension two, while others have scaling dimension four. We also determine the corrections to bulk probabilities for local bond modifications near open and closed boundaries.Comment: 13 pages, 5 figures; referee comments incorporated; Accepted by Phys. Rev.

A selected history of expectation bias in physics

The beliefs of physicists can bias their results towards their expectations in a number of ways. We survey a variety of historical cases of expectation bias in observations, experiments, and calculations.Comment: 6 pages, 2 figure

Vacancy diffusion in the triangular lattice dimer model

We study vacancy diffusion on the classical triangular lattice dimer model, sub ject to the kinetic constraint that dimers can only translate, but not rotate. A single vacancy, i.e. a monomer, in an otherwise fully packed lattice, is always localized in a tree-like structure. The distribution of tree sizes is asymptotically exponential and has an average of 8.16 \pm 0.01 sites. A connected pair of monomers has a finite probability of being delocalized. When delocalized, the diffusion of monomers is anomalous:Comment: 15 pages, 27 eps figures. submitted to Physical Review

Higher Order and boundary Scaling Fields in the Abelian Sandpile Model

The Abelian Sandpile Model (ASM) is a paradigm of self-organized criticality (SOC) which is related to $c=-2$ conformal field theory. The conformal fields corresponding to some height clusters have been suggested before. Here we derive the first corrections to such fields, in a field theoretical approach, when the lattice parameter is non-vanishing and consider them in the presence of a boundary.Comment: 7 pages, no figure

PROMOTION OF REPLICATION IN LYMPHOID CELLS BY SPECIFIC THIOLS AND DISULFIDES IN VITRO : EFFECTS ON MOUSE LYMPHOMA CELLS IN COMPARISON WITH SPLENIC LYMPHOCYTES

Numerous lines of mouse lymphoid tumors (13 of 22 tested) showed, with increased sensitivity, a property of normal mouse splenic lymphocytes, the potential for growth promotion in vitro by specific thiols added to standard culture media. For lymphoma L1210 (V), structure activity relationships were examined; 9 of 30 thiols promoted growth; the most active was α-thioglycerol, effective at 0.2 µM. Thiols became oxidized under conditions of tissue culture and had half-lives of less than 8 h. Disulfides of active thiols promoted growth of lymphoma cells. The mitogenic response of splenic lymphocytes to lectins was increased by thiols-disulfides which promoted the growth of lymphoma cells, but the response varied with the mitogen preparation used and under some conditions thiols-disulfides were inhibitory

Orbital-Free Density Functional Theory: Kinetic Potentials and Ab-Initio Local Pseudopotentials

In the density functional (DF) theory of Kohn and Sham, the kinetic energy of the ground state of a system of noninteracting electrons in a general external field is calculated using a set of orbitals. Orbital free methods attempt to calculate this directly from the electron density by approximating the universal but unknown kinetic energy density functional. However simple local approximations are inaccurate and it has proved very difficult to devise generally accurate nonlocal approximations. We focus instead on the kinetic potential, the functional derivative of the kinetic energy DF, which appears in the Euler equation for the electron density. We argue that the kinetic potential is more local and more amenable to simple physically motivated approximations in many relevant cases, and describe two pathways by which the value of the kinetic energy can be efficiently calculated. We propose two nonlocal orbital free kinetic potentials that reduce to known exact forms for both slowly varying and rapidly varying perturbations and also reproduce exact results for the linear response of the density of the homogeneous system to small perturbations. A simple and systematic approach for generating accurate and weak ab-initio local pseudopotentials which produce a smooth slowly varying valence component of the electron density is proposed for use in orbital free DF calculations of molecules and solids. The use of these local pseudopotentials further minimizes the possible errors from the kinetic potentials. Our theory yields results for the total energies and ionization energies of atoms, and for the shell structure in the atomic radial density profiles that are in very good agreement with calculations using the full Kohn-Sham theory.Comment: To be published in Phys. Rev.

The para-substituent effect and pH-dependence of the organometallic Baeyer–Villiger oxidation of rhenium–carbon bonds

We studied the Baeyer–Villiger (BV) type oxidation of phenylrhenium trioxide (PTO) by H2O2 in the aqueous phase using Quantum Mechanics (density functional theory with the M06 functional) focusing on how the solution pH and the para-substituent affect the Gibbs free energy surfaces. For both PTO and MTO (methylrhenium trioxide) cases, we find that for pH > 1 the BV pathway having OH− as the leaving group is lower in energy than the one involving simultaneous protonation of hydroxide. We also find that during this organometallic BV oxidation, the migrating phenyl is a nucleophile so that substituting functional groups in the para-position of phenyl with increased electron-donating character lowers the migration barrier, just as in organic BV reactions. However, this substituent effect also pushes electron density to Re, impeding HOO− coordination and slowing down the reaction. This is in direct contrast to the organic analog, in which para-substitution has an insignificant influence on 1,2-addition of peracids. Due to the competition of the two opposing effects and the dependence of the resting state on pH and concentration, the reaction rate of the organometallic BV oxidation is surprisingly unaffected by para-substitution

Functionalization of Rhenium Aryl Bonds by O-Atom Transfer

Aryltrioxorhenium (ArReO_3) has been demonstrated to show rapid oxy-functionalization upon reaction with O-atom donors, YO, to selectively generate the corresponding phenols in near quantitative yields. (18)^O-Labeling experiments show that the oxygen in the products is exclusively from YO. DFT studies reveal a 10.7 kcal/mol barrier (Ar = Ph) for oxy-functionalization with H_2O_2 via a Baeyer-Villiger type mechanism involving nudeophilic attack of the aryl group on an electrophilic oxygen of YO coordinated to rhenium