Propensities and conditional probabilities

The present paper deals with the objection that Paul Humphreys raised against the propensity interpretation of probability - “Humphreys’ paradox”. An update on existing solutions is offered, and it is concluded that none of them is completely satisfactory in view of Humphreys’ 2004 rejoinder. Positively, an original solution is formulated and discussed.     

Programmed Multiple C-H Bond Functionalization of the Privileged 4-hydroxyquinoline Template

The introduction of substituents on bare heterocyclic scaffolds can selectively be achieved by directed C−H functionalization. However, such methods have only occasionally been used, in an iterative manner, to decorate various positions of a medicinal scaffold to build chemical libraries. We herein report the multiple, site selective, metal-catalyzed C−H functionalization of a “programmed” 4-hydroxyquinoline. This medicinally privileged template indeed possesses multiple reactive sites for diversity-oriented functionalization, of which four were targeted. The C-2 and C-8 decorations were directed by an N-oxide, before taking benefit of an O-carbamoyl protection at C-4 to perform a Fries rearrangement and install a carboxamide at C-3. This also released the carbonyl group of 4-quinolones, the ultimate directing group to functionalize position 5. Our study highlights the power of multiple C−H functionalization to generate diversity in a biologically relevant library, after showing its strong antimalarial potential.     

Ligand trans-effect: using an old concept as a novel approach to bis(dipolar) NLO-phores

In plane parallel arrangement and enhancement of NLO-activity are observed upon coordination of heteroditopic dipoles containing a phosphole ring on square-planar d8-palladium centre.     

New stereoselective reaction of methylglyoxal with 2-aminopyridine and adenine derivatives: formation of imino acid-nucleic base derivatives in water under mild conditions

A remarkable stereoselective reaction of methylglyoxal with 2-aminopyridine, the nucleic base adenine and adenine nucleosides leads in good yield to heterocycles of a new family in water under mild conditions and should be of interest in the understanding of the biological effects of methylglyoxal which is toxic, mutagenic and involved in diabetic complications.     

Stress relaxation in styrene-butadiene-styrene block copolymers containing unattached linear polybutadiene and styrene-butadiene diblocks

Stress relaxation has been studied in networks of styrene-butadiene-styrene triblock copolymers with spherical styrene domain structure containing 0.10 weight fraction of unattached linear polybutadiene (M_w = 389,000) or styrene-butadiene diblocks with very long butadiene segments (M = 225,000 or 510,000). The stretch ratio (uniaxial extension) was usually 1.15 and the temperature ranged from ?20 to +20°C. The contribution of the linear polybutadiene species to relaxation was essentially the same in two triblock networks with very different butadiene block lengths, as expected if the configurational rearrangements are dominated by reptation. In the diblock-triblock mixtures, in which the diblock butadiene segments are free at one end but anchored at the other and therefore incapable of reptation, there was no contribution to relaxation from the dangling butadiene segments of the diblock component; this would be expected if there are no relaxation mechanisms alternative to reptation for these very long semiattached species within the experimental time scale.     

Balance equation formulation and memory effects in retarded high field semiconductor transport

The role of the finite, non-zero collision duration in high electric fields is examined for its effect on transient and overshoot response of carrier velocity and energy. A quantum kinetic equation approach is used to develop modifications of the balance equations obtained in a drifted Maxwellian approach for treating high-field transport. These result in corrections which require convolution integrals to be evaluated on the short-time scale.     

On the existence and detection of Bloch oscillations in superlattices

While many predicted superlattice behaviors depend on the presence of Bloch oscillations, the existence of such oscillations remains problematical. Here, we consider procedures by which their existence within a superlattice could be detected. We first set upper and lower bounds on the necessary fields. We then demonstrate that while a negative differential mobility is expected, no resonant peak occurs in this mobility at the Bloch frequency. However, we provide two ways of directly observing Bloch oscillations. In the first, we note the existence of structures in the dc velocity-field characteristic when an externally applied RF field has a frequency which is harmonically related to the Bloch frequency. The second approach is to measure the velocity fluctuation noise spectra, which should have a peak at the field-tunable Bloch frequency.     

Cytotoxic effect and electrophysiological activity of S-irniine, a synthesised isomer of the natural R-irniine, on human MRC-5 fibroblasts

Numerous original alkaloids are present in tubers of Arisarum vulgare Targ. a species belonging to the Araceae family known in Morocco for its toxicity. Some previous works deal with the activity of these natural compounds as R-irniine. As the enantioselective total synthesis of irniine has been realised, the R- and S-forms were obtained and this last one could be tested. Thus, a study of the cytotoxicity and the electrophysiological activity of S-irniine was carried out on human MRC-5 fibroblasts. A cytotoxic effect of S-irniine at 40 microg/mL was detected on MRC-5 fibroblasts. An electrophysiological study was also carried out on the MRC-5 cells by using the patch-clamp technique and no effect of this compound at this concentration on the outward potassium current of MRC-5 fibroblasts was observed. Thus, this study showed, as it was for R-irniine, that the cytotoxicity of S-irniine was not explained by an effect on the potassium currents.