A Simple and Efficient Procedure for Oxidation of Sulfides to Sulfoxides on Hydrated Silica Gel with Ceric Ammonium Nitrate (Can) In Methylene Chloride

A simple, fast and efficient procedure for oxidation of sulfides to the corresponding sulfoxides with CAN mediated by hydrated silica gel in methylene chloride has been developed. To our knowledge, this is the first example of oxidation of sulfides with CAN in a non-aqueous media.     

Symmetry and singularity properties of a system of ordinary differential equations arising in the analysis of the nonlinear telegraph equations

We investigate the symmetry and similarity properties of a system of equations arising in the analysis of the nonlinear telegraph equations. The system of two equations can be decoupled and integrated. Although one of equations is linear in one of the dependent variables, we are able to perform successfully a singularity analysis. We are able to interpret the results of the singularity analysis in terms of the possibility of the existence of a subsidiary solution.     

Radio-frequency probe for 1H decoupled 31P MRS of the head and neck region.

For optimal performance of 31P MRS at 1.5 Tesla, the use of a double resonant probe is essential to enable the application of 1H decoupling and Nuclear Overhauser Enhancement. This note describes the design, evaluation and safety validation of a versatile and compact probe optimized for 1H decoupled 31P MRS studies of tumors close to the surface of the body, in particular the head and neck region.     

Sexual Harassment In Chemistry Classrooms: Three Students' Experiences

Issues of sexual bias and harassment are serious ones for all educators, but perhaps are of the greatest concern for science educators due to the serious underrepresentation of women in scientific fields. Female students are receiving both overt and covert messages from many directions that are turning them away from choices that might lead to science careers, and many of these messages come directly from their science teachers. Sexual harassment is a new and uncharted issue for society in general and educators specifically. This article deals with sexual bias and harassment behaviors of teachers that potentially impede the success and participation of female students in science.     

Mercury in organic chemistry. 20. Alkylation of organomercurials via organocopper reagents

Aryl-, alkenyl-, and alkylmercurials readily cross-couple with primary and secondary alkyl- and alkenylcuprate reagents to provide the first truly general method for the alkylation of a wide variety of organomercurials.     

Exponential Smoothing with an Adaptive Response Rate

A modification is proposed to forecasting systems employing exponential smoothing whereby the response rate is varied and made to depend on the value of a tracking signal. In a simple system, this is equivalent to varying α the smoothing constant according to the extent to which biased forecasts are being obtained. Such a system is shown to react much faster to, for example, step changes whilst still retaining the facility to filter out random noise.     

An integrable SIS model

We provide a demonstration of the integrability of a classical model of an infectious disease which neither kills nor induces autoimmunity by means of the Painlevé analysis and use the Lie theory of transformation groups to present an explicit solution.     

Solid angles 5. Chiral molecules and the case of face selectivity

In this paper we present the analytical algorithm to calculate the solid angle of a collection of spheres in a hemisphere and quadrant. The methodology is a reliable and useful measure of partial steric congestion and can readily be applied to chiral and pro-chiral molecules. This algorithm lays the foundation for the application of a steric measure to the prediction of diastereomeric and enantiomeric excess.     

Kinetic and electrochemical study of nitrile adducts of tetrachloro-bis (1,2-bis(diphenylphosphine)methane)dirhenium(II)

Summary The addition of two nitrile ligands to the complex Re₂Cl₄-(dppm)₂ (dppm= 1,2-bis(diphenylphosphine)methane)in CH₂Cl₂ solution has been investigated electrochemically. Upon addition of one equivalent of nitrile NCR (R = aromatic or aliphatic group) to the CH₂Cl₂/0.1m tetra-N-butylammonium hexafluorophosphate (TBAH) solution, Re₂Cl₄(dppm)₂(NCR) is formed immediately, without dissociation of chloride; electrochemical investigation indicates this nitrile addition is reversible upon oxidation of the dirhenium complex. On addition of two or more equivalents of nitrile, a slow ligand substitution takes place with addition of a second nitrile and concomitant loss of a chloride ion to form [Re₂Cl₃-(dppm)₂(NCR)₂]⁺. The rate of addition of nitrile to Re₂Cl₄(dppm)₂(NCR) appears to depend on the electrondonating or electron-withdrawing abilities of the ligand. The change from monoadduct to diadduct was followed with differential pulse voltammetry for various concentrations of added nitrile. The addition was found to be first order in nitrile.     

Intravascular delivery of hyperpolarized129Xenon forin vivo MRI

The nuclear polarization of¹²⁹Xe and³He can be enhanced by several orders of magnitude by using optical pumping techniques, thus allowing NMR detection of xenon and helium in very low concentrations. The benefits of optically enhanced magnetic resonance (MR) are already exploited in MR imaging of the lungs using optically polarized³He. The high solubility of xenon in blood and lipids suggests a variety ofin vivo MR applications, for instance perfusion measurements or functional MR studies. This article reviews some current work directed towards delivery of optically polarized xenon forin vivo MR applications.