Evaluation of the acetate buffer attack of a sequential extraction scheme for marine particulate metal speciation studies by scanning electron microscopy with energy dispersive X-ray analysis

Scanning electron microscopy, with energy dispersive X-ray analysis (SEM-EDX), has been used to evaluate and possibly optimize, the first step (acetate buffer attack for exchangeable and carbonatic fractions) of a sequential selective extraction scheme. The extraction has been performed on two different particulates, a certified reference plankton and a real marine suspended particulate, using an increased acetate concentration and various solid/extractant ratios. SEM-EDX has been performed on the non treated particulates and on the residues after the attack, and the results related to the spectroscopic analyses of the extracts, allowed us to verify that even if efficiency has been optimized, the procedure still suffers of a lack of selectivity. Nevertheless, SEM data were helpful to put forward some interesting speciation hypothesis, that would have been certainly different, and probably wrong, if based on analyses of the extracts only.     

Metallation reactions. XXXIV. Synthesis of 2‐(1‐hydroxy‐1‐arylethyl)‐1,3‐benzoxathiol‐3‐oxide derivatives

The reaction of benzoxathiole‐3‐oxide with lithiumdiisopropylamide in tetrahydrofuran gave an anion, which was reacted with various aryl‐methyl‐ketones to give 2‐(1‐hydroxy‐1‐arylethyl)‐1,3‐benzoxathiol‐3‐oxide derivatives. The reaction was carried out in different temperature conditions: at ‐88 °C the trans addition stereoisomers to the sulfoxide oxygen atom were the main products.     

Internal energy content of n-butylbenzene, bromobenzene, iodobenzene and aniline molecular ions generated by two-photon ionization at 266 nm. A photodissociation study

A technique to investigate photodissociation kinetics on a nanosecond time scale has been devised for molecular ions generated by multiphoton ionization (MPI) using mass-analyzed ion kinetic energy spectrometry. The branching ratio or rate constant has been determined for the photodissociation of the n-butylbenzene, bromobenzene, iodobenzene, and aniline molecular ions generated by MPI at 266 nm. The ion internal energies have been estimated by comparing the measured kinetic data with the previous energy dependence data. The analysis has shown that only those molecular ions generated by two-photon ionization contribute to the photodissociation signals. Around half of the available energy has been found to remain as molecular ion internal energy in the two-photon ionization process. Copyright 1999 John Wiley & Sons, Ltd.     

Local and global solutions for some parabolic nonlocal problems

We study local and global existence of solutions for some semilinear parabolic initial boundary value problems with autonomous nonlinearities having a “Newtonian” nonlocal term.     

Simultaneous diastereo- and enantioseparation of farnesoid X receptor (FXR) agonists with a quinine carbamate-based chiral stationary phase

In the frame of a project aimed at finding non-steroidal farnesoid X receptor (FXR) agonists, we identified 4-(2,4-dimethoxyphenyl)-3,6-dimethyl-1-(2-tolyl)-4,8-dihydro-1H-pyrazole[3,4-e][1,4]thiazepin-7-one (1) as a hit endowed with FXR activity. Most of the compounds synthesised during the hit-to-lead optimisation work were characterised by the presence of two chiral centres and were therefore obtained as mixtures of anti(±)- and syn(±)-diastereoisomers. A restricted sub-set of species harboured with a carboxylic acid group on the distal phenyl ring of the biphenyl (a(±)5 (A1) and s(±)5 (S1)) or the phenoxyphenyl (a(±)6 (A2) and s(±)6 (S2)) moiety at C-4 position of the pyrazole[3,4-e][1,4]thiazepin-7-one core, resulted in suitable diastereo- and enantioresolution with a quinine (QN) carbamate-derived chiral stationary phase (CSP). Differently from the compounds usually analysed with QN-based CSPs, the couples A1/S1 and A2/S2 were atypical selectands, in which the two chiral carbon atoms reside at a remote position with respect to the carboxylic function, the main “point of attack” to the CSP. We produced evidence that the scarcely employed normal-phase (NP) eluent systems represent the elective choice for achieving the simultaneous diastereo- and enantioseparation of this class of compounds over the usually preferred reversed-phase (RP) and polar-organic (PO) modes of elution. Indeed, after the optimisation of the eluent composition, NP conditions allowed to obtain profitable enantioselectivity profiles, along with excellent diastereoselectivity levels (α(A1)?=?1.07, R _S(A1)?=?1.15; α(S1)?=?1.09, R _S(S1)?=?1.47; α(A2)?=?1.08, R _S(A2)?=?1.31; and α(S2)?=?1.06, R _S(S2)?=?1.18). The optimised NP methods are suitable for simultaneously providing information on the diastereo- and enantiopurity of the investigated compounds.

The neuroblast and angioblast chemotaxic factor SDF-1 (CXCL12) expression is briefly up regulated by reactive astrocytes in brain following neonatal hypoxic-ischemic injury

Background  

Stromal cell-derived factor 1 (SDF-1 or CXCL12) is chemotaxic for CXCR4 expressing bone marrow-derived cells. It functions in brain embryonic development and in response to ischemic injury in helping guide neuroblast migration and vasculogenesis. In experimental adult stroke models SDF-1 is expressed perivascularly in the injured region up to 30 days after the injury, suggesting it could be a therapeutic target for tissue repair strategies. We hypothesized that SDF-1 would be expressed in similar temporal and spatial patterns following hypoxic-ischemic (HI) injury in neonatal brain.     

Approximating call-scheduling makespan in all-optical networks

We study the problem of routing and scheduling requests of limited durations in all-optical networks with restrictions on the number of available wavelengths on each link. The task is servicing the requests, assigning each of them a route from source to destination, a starting time and a wavelength with the goal of minimizing the overall time needed to serve all requests. We study the relationship between this problem and minimum path coloring and we show how to exploit known results on path coloring to derive approximation scheduling algorithms for meshes, trees and nearly-Eulerian, uniformly high-diameter graphs. We also propose different approximation algorithms for stars, trees and in trees of rings.