Multiple passive element enriched photoacoustic computed tomography

Recently, we presented a method using laser-induced ultrasound from an external absorber (passive element) to image the ultrasound transmission parameters of an object under photoacoustic tomographic investigation. The method suffers from long measurement times due to the requirement for a large number of views and consequently physical projections around the object. Here we propose and validate an approach that permits a multitude of views to be obtained within a limited projection scenario. The approach uses a plurality of spatially distributed external absorbers in the path of the light, that results in multiple laser-induced ultrasound sources to interrogate the object from a number of angles. This reduces the required number of rotation angles or physical projections around the object, permitting a considerable reduction in imaging time without significant degradation in image quality. The approach brings the concept of hybrid imaging of ultrasound transmission parameters together with photoacoustic imaging, into the realm of practical application.     

Synthesis of Specifically Fluorinated Methyl β-Glycosides of (1→6)-β-D-Galactooligosaccharides II. Methyl 4-Deoxy-4-fluoro-6-O-(β-D-galactopyranosyl)-β-D-galactopyranoside

Abstract

Condensation of methyl 2,3-di-O-benzyl-4-deoxy-4-fluoro-β-D-galactopyranoside with 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl bromide in the presence of mercuric cyanide in benzene afforded, in excellent yield, the β-linked product. Its deblocking, effected by hydrogenolytic cleavage of the benzyl groups followed by deacecylation or, alternatively, via a pathway where the sequence of the deblocking reactions was reversed, gave crystalline title disaccharide 10. The structures of the compounds involved in the synthesis were confirmed by C NMR spectroscopy.     

High temperature liquid chromatography hyphenated with ESI-MS and ICP-MS detection for the structural characterization and quantification of halogen containing drug metabolites

In this paper we describe the hyphenation of high temperature liquid chromatography with ICP-MS and ESI-MS for the characterization of halogen containing drug metabolites. The use of temperature gradients up to 200°C enabled the separation of metabolites with low organic modifier content. This specific property allowed the use of detection methods that suffer from (significant) changes in analyte response factors as a function of the organic modifier content such as ICP-MS. Metabolites of two kinase inhibitors (SB-203580-Iodo and MAPK inhibitor VIII) produced by bacterial cytochrome P450 BM3 mutants and human liver microsomes were identified based on high resolution MS(n) data. Quantification was done using their normalized and elemental specific response in the ICP-MS. The importance of these kinds of quantification strategies is stressed by the observation that the difference of the position of one oxygen atom in a structure can greatly affect its response in ESI-MS and UV detection.     

Dichloro{N‐[3‐(η5‐cyclopentadienyl)propyl]‐4‐toluenesulfonamido‐κ2N,O}titanium(IV)

The title compound, [Ti(C₁₅H₁₇NO₂S)Cl₂], has a Ti atom bound to the N and O atoms of a p‐toluene­sulfon­amide ligand, which is tethered by a three‐carbon chain to a η⁵‐cyclo­penta­dienyl group. The distorted square‐pyramidal geometry is completed by two Cl atoms. The Ti—N bond length of 2.0375 (13) Å is longer than that in related compounds, the N atom having asymmetric trigonal–planar geometry. Conformational strain relief is noted when compared with ethyl‐tethered compounds.     

Mechanism of Pd(NHC)-catalyzed transfer hydrogenation of alkynes

The transfer semihydrogenation of alkynes to (Z)-alkenes shows excellent chemo- and stereoselectivity when using a zerovalent palladium(NHC)(maleic anhydride)-complex as precatalyst and triethylammonium formate as hydrogen donor. Studies on the kinetics under reaction conditions showed a broken positive order in substrate and first order in catalyst and hydrogen donor. Deuterium-labeling studies on the hydrogen donor showed that both hydrogens of formic acid display a primary kinetic isotope effect, indicating that proton and hydride transfers are separate rate-determining steps. By monitoring the reaction with NMR, we observed the presence of a coordinated formate anion and found that part of the maleic anhydride remains coordinated during the reaction. From these observations, we propose a mechanism in which hydrogen transfer from coordinated formate anion to zerovalent palladium(NHC)(MA)(alkyne)-complex is followed by migratory insertion of hydride, after which the product alkene is liberated by proton transfer from the triethylammonium cation. The explanation for the high selectivity observed lies in the competition between strongly coordinating solvent and alkyne for a Pd(alkene)-intermediate.     

Equicontinuous families of Markov operators in view of asymptotic stability

The relation between the equicontinuity – the so-called e-property – and the stability of Markov operators is studied. In particular, it is shown that any asymptotically stable Markov operator with an invariant measure such that the interior of its support is non-empty satisfies the e-property.     

A parameterized extended shift-splitting preconditioner for nonsymmetric saddle point problems

In this article, a parameterized extended shift-splitting (PESS) method and its induced preconditioner are given for solving nonsingular and nonsymmetric saddle point problems with nonsymmetric positive definite (1,1) part. The convergence analysis of the $PESS$ iteration method is discussed. The distribution of eigenvalues of the preconditioned matrix is provided. A number of experiments are given to verify the efficiency of the $PESS$ method for solving nonsymmetric saddle-point problems.