Average magnetic susceptibility of rare earth sesquisulfides

Measurements of the average magnetic susceptibility of Nd₂S₃, Gd₂S₃ and Dy₂S₃ are reported over the temperature range 4–300 K. Paramagnetic Gd₂S₃ becomes ferromagnetic below about 30 K. Magnetic ordering in Nd₂S₃ appears to take place near 60 K. Dy₂S₃ appears to remain paramagnetic to the lowest temperatures investigated. Reasonable agreement has been obtained between a calculation using Van Vleck's theory and the data obtained from these Faraday experiments.     

Contribution a l'etude du maximum d'activite globale de chaines radioactives

Radiactive decay chains, composed of two radionuclides have been classified into six different categories. Equations expressing the total activity of the chain were systematically applied to 41 radioisotopes. Conditions necessary to the observation of a maximum activity were determined for every chain. The case of the⁹⁹Mo was studies experimentally, and a maximum of activity was observed with a good concordance with calculated values.      

Discovery of chemical reactions through multidimensional screening

Multidimensional reaction screening of ortho-alkynyl benzaldehydes with a variety of catalysts and reaction partners was conducted in an effort to identify new chemical reactions. Reactions affording unique products were selected for investigation of preliminary scope and limitations.     

Peg solitaire on graphs

There have been several papers on the subject of traditional peg solitaire on different boards. However, in this paper we consider a generalization of the game to arbitrary boards. These boards are treated as graphs in the combinatorial sense. We present necessary and sufficient conditions for the solvability of several well-known families of graphs. In the major result of this paper, we show that the cartesian product of two solvable graphs is likewise solvable. Several related results are also presented. Finally, several open problems related to this study are given.     

Synthesis and reactivity of bicyclo[3.2.1]octanoid-derived cyclopropanes

Photochemical oxa-di-π-methane rearrangement of bicyclo[3.2.1]octanoid scaffolds affords multifunctional, donor-acceptor cyclopropanes. A related photochemical reaction of an iminium ether substrate uncovered an unprecedented aza-di-π-methane rearrangement of a β,γ-unsaturated iminium. Donor-acceptor cyclopropanes have been evaluated as substrates for reactions generating several new chemotypes.     

Contribution a l'etude du maximum d'activite globale de chaines radioactives

The total activity of a radioactive decay chain presents a maximum in many cases, but the maximum can seldom be observed. General equations are developed, which take into account branching ratios, emissions, formation and counting yields. This mathematical model is applicable by analogy to other systems with same kinetics.      

Convergent synthesis of complex diketopiperazines derived from pipecolic acid scaffolds and parallel screening against GPCR targets

A convergent approach to highly functionalized diketopiperazines (DKPs) using enantioenriched pipecolic acids is described. Scandium triflate-catalyzed [4 + 2] aza-annulation was employed to produce stereochemically well-defined building blocks. A resin "catch and release" strategy was devised to convert annulation products to pipecolic acid monomers. Complex diketopiperazines were efficiently assembled utilizing one-pot cyclodimerization of pipecolic acids. Massively parallel screening of the complex DKPs against a panel of molecular targets identified novel ligands for a number of G-protein-coupled receptors (GPCRs).     

Radiological dose assessment of naturally occurring radioactive materials in concrete building materials

Previous studies have shown that the natural radioactivity contained in building materials have significantly influenced the dose rates in dwelling. Exposure to natural radiation in building has been of concerned since almost 80 % of our daily live are spend indoor. Thus, the aim of the study is to assess the radiological risk associated by natural radioactivity in soil based building materials to dwellers. A total of 13 Portland cement, 46 sand and 43 gravel samples obtained from manufacturers or bought directly from local hardware stores in Peninsular of Malaysia were analysed for their radioactivity concentrations. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the studied building materials samples were found to be in the range of 3.7–359.3, 2.0–370.8 and 10.3–1,949.5 Bq kg^?1 respectively. The annual radiation dose rates (μSv year^?1) received by dwellers were evaluated for 1 to 50 years of exposure using Resrad-Build Computer Code based on the activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K found in the studied building material samples. The rooms modelling were based on the changing parameters of concrete wall thickness and the room dimensions. The annual radiation dose rates to dwellers were found to increase annually over a period of 50 years. The concrete thicknesses were found to have significantly influenced the dose rates in building. The self-absorption occurred when the concrete thickness was thicker than 0.4 m. Results of this study shows that the dose rates received by the dwellers of the building are proportional to the size of the room. In general the study concludes that concrete building materials; Portland cements, sands, and gravels in Peninsular of Malaysia does not pose radiological hazard to the building dwellers.