A spatial covariance model with a single wave effect and a finite range

We propose a new spatial covariance model with a single wave effect and a finite range. The construction of this model is based on a radial kernel composed of two concentric spheres and the finite range enables us to obtain an exact simulation from the circulant embedding method. This model responds to the lack of efficient covariance functions to model patterns characterized by concentration areas surrounded by gaps. We compare the single wave model to other existing hole effect models such as the Bessel model, the damped cosine model and the cardinal sine model.     

Acid Catalyzed Cyclization of Bis Silyl Diacylhydrazines: A New 1, 3, 4-Oxadiazole Synthesis

Diacylhydrazines are converted in good yields into 1,3,4-oxadiazoles with dichlorodimethyl-silane and trifluoromethane sulfonic acid.     

Disilylated Compounds as Precursors of Heterocycles: A New and Easy Oxadiazole Synthesis

Silyl diacylhydtazines have been synthesized. When they are treated with 3 slight amount of a uariety of catalyst (nucleophiles, F, true or Lewis acids, Pd, Pt.), 1,3,4-oxadiazoles are obtained. This cyclization can be performed in one step by using hexamethyldisilazane or dimethyldichlorosilane as the silylation agent.     

Block copolymers based on 2‐vinyl‐4,4‐dimethyl‐5‐oxazolone by RAFT polymerization: Experimental and computational studies

The ability of 2‐vinyl‐4,4‐dimethyl‐5‐oxazolone (VDM), a highly reactive functional monomer, to produce block copolymers by reversible addition fragmentation chain transfer (RAFT) sequential polymerization with methyl acrylate (MA), styrene (S), and methyl methacrylate (MMA) was investigated using cumyl dithiobenzoate (CDB) and 2‐cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agents. The results show that PS‐b‐PVDM and PMA‐b‐PVDM well‐defined block copolymers can be prepared either by polymerization of VDM from PS‐ and PMA‐macroCTAs, respectively, or polymerization of S and MA from a PVDM‐macroCTA. In contrast, PMMA‐b‐PVDM block copolymers with controlled molecular weight and low polydispersity can only be obtained by using PMMA as the macroCTA. Ab initio calculations confirm the experimental studies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

A high throughput dried DMSO Log D lipophilicity measurement based on 96-well shake-flask and atmospheric pressure photoionization mass spectrometry detection

A rapid throughput octanol–water lipophilicity measurement based on 96-well shake-flask and LC/UV/APPI/MS is described. The method utilizes central liquid storage where compounds are stored as 10 mM solutions in dimethyl sulfoxide (DMSO). The DMSO is subsequently removed to generate solid like material used for Log D measurement. The removal of DMSO minimizes the concern for potential DMSO cosolvent effect on the measured value. Sample preparation is automated using a liquid handling workstation with 96-well pipetter. Both octanol and buffer phases are quantified using state of the art ultra-high pressure HPLC coupled with a superficially diffused core reversed-phase column and an atmospheric pressure photo ionization mass spectrometer. The throughput of the method is two days for a batch of 96 compounds. The method has been validated using 72 literature compounds with diverse ionization and Log D values ranging from −2 to +6. The observed coefficient of determination r² is 0.9973.