Etude des volumes specifiques partiels de polystyrenes-modeles—Influence de la masse moleculaire et de la nature des groupements terminaux

It is well known that the apparent specific volume η₂ of a polymer may be expressed by the following relationship: $\text{η}{}_2\text{= η}{}_{\mathrm{m}}\text{+ K/}\text{M}{}_{\mathrm{n}}$ where M?_n is the number-average molecular weight of the polymer, η_m the specific volume of the infinite polymer, and K a constant. We have shown that this relationship is valid for low molecular weight polystyrenes ($\text{M}{}_{\mathrm{n}}\text{< 4·10}{}^4$) with different end-groups, independently of the nature of the solvent. The K values (and variations with the solvent and with the nature of the end-groups) may be predicted through simple calculations proposed here. We conclude that η_m does not represent the specific volume of the infinite polymer, since we observe a rapid decrease of η₂ for increasing M (when $\text{M}{}_{\mathrm{n}}\text{< 4·10}{}^4$). The decrease is much greater than expected from the relationship $\text{η}{}_2\text{= ? (1/}\text{M}\text{)}$.     

Analyse conformationnelle theorique des complexes acide-base de lewis: III. Une approche semi-empirique (méthode CNDO/2) des geométries et de l'analyse conformationnelle du borazane et de ses dérives perfluoré

The optimized geometries and theoretical data from conformational analysis cf borazane and its perfluoro derivatives are investigated within the framework of the CNDO/2 approximation. The effect that fluorination has on the geometrical and electronic parameters of the investigated series of compounds is pointed out and the authors offer an explanation for the anomalous behaviour of H₃N.BF₃. Furthermore, it is shown that the assumption of tetragonal hybridization for the N and B atoms of any borazane is incorrect if the F₃N molecule is used as the Lewis base.     

Cyclophosphazenes and Relatives as Anticancer Drugs

Abstract

Aziridinocyclophosphazenes N₃P₃Az₆ (code name MYKO 63), N₄P₄Az₈ (code name MYKO 83) and relatives constituted the first generation of anticancer drugs whose efficiency on several rodent neoplasms was made conspicuous in a quantitative manner from 1976 to 1978 both in our Laboratory and by EORTC Screening Pharmacology Groups¹. MYKO 63 appeared at that time as a promising drug for industrial development owing to its wide spectrum of activity and its very low mutagenicity². However, this hope failed as a consequence of a cumulative toxicity which occurs upon heavy polyinjections schedules. In other words, MYKO 63 exhibits an uncomfortable kinetics of action on the tumor - and, consequently, of excretion - presumably due (it was our assumption) to a too high chemical stability of the molecule.     

Synthesis of Annelated Phospholes through Intramolecular C?H Activation by Monovalent Phosphorus

Electrophilic terminal phosphinidene complexes [Ar‐Ar‐P‐W(CO)₅] (Ar‐Ar: biaryl or an analogue thereof) undergo a spontaneous insertion of the phosphorus atom into the vicinal C H bonds to give annelated phospholes. Twelve examples are described, including biphenyl, thienyl, pyrrolyl, and benzofuryl groups as biaryl moieties. The activation energy of the insertion reaction is quite low (about 2 kcal mol⁻¹).     

Unconventional Approaches to Hydrogen Sorption Reactions: Non-Thermal and Non-Straightforward Thermally Driven Methods

In the last decades, a broad family of hydrides have attracted attention as prospective hydrogen storage materials of very high gravimetric and volumetric capacity, fast H₂-sorption kinetics, environmental friendliness and economical affordability. However, constraints due to their high activation energies of the different H₂-sorption steps and the Gibbs energy of their reaction with H₂ has led to the need of high thermal energy to drive H₂ uptake and release. High heat leads to significant degradation effects (recrystallization, phase segregation, nanoparticles agglomeration…) of the hydrides. In this context, this short review aims to summarize alternative non-thermal methods and non-straightforward thermally driven methods to overcome the previous constraints. The phenomenology lying behind these methods, i. e. tribological activation, sonication, and electromagnetic radiation, and the effect of these processes on hydrogen sorption properties of hydrides are described. These non-usual approaches could boost the capability of the next generation of solid-hydride materials for hydrogen conversion in energy sector, in mobile devices and as hydrogen reservoirs.     

On the mechanics of fishscale structures

Biological and manmade structures often share the same specifications and design constraints: structural support, lightweight or protection against specific threats. In this context, the structure of fishscales, consisting of small rigid plates growing out of the skin of a majority of fish species, are characterized by a large variety of shape, size and properties in order to achieve particular functions. The present study introduces a basic two-dimensional micromechanical model that permits to establish a correlation between the flexural response of a scaled skin and the nature of its underlying structure, including both geometric and material aspects. The model is used to predict trends in the structure’s response and illustrates the fact that the scale design, arrangement and properties can be tailored to achieve a wide spectrum of response. In particular, fishscale structure possesses an inherent strain-stiffening response that can be suppressed or magnified by certain structural features. This particularity, shared by most biological materials, ensures that the structure provides both a structural and protective support for the animal.     

A Preparative Synthesis of 1-Amino-3-hydroxypropylphosphonic Acid (Phosphonic Analogue of Homoserine)

A novel procedure for the preparation of the phosphonic analogue of homoserine is described starting from the commercially available 4-acetoxy-azetidin-2-one.     

Automated self-organising vehicles for Barclays Cycle Hire

Self-organisation is a distributed and asynchronous process in which global pattern or behaviour emerge from local components of the system. Neither central control nor external intervention is necessary during this process. Self-organising systems are adaptive and robust, which are appealing properties from a design and engineering point of view. In this paper, we present an innovative self-organisation approach for a dynamic vehicle routing problem, the Barclay Cycle Hire truck dispatch. In addition, we introduce an evolutionary algorithm capable of automatically configuring the “self-organising trucks”. Experimental results show the evolutionary algorithm improves the overall fitness of the self-organising trucks; and we observe global emergent behaviour in the way trucks self-organise.