Oceans and electrical power (part I)

What could replace our exhausting fossil fuels? The nuclear solution has generated considerable controversy and land opposition. Atomic fusion is by no means close to implementation; direct solarenergy is abundant, but its conversion at an acceptable cost has not been as yet developed. Geothermal energy has been tapped, but it is only locally available and is non‐renewable. In the first of this two‐part paper, alternative ocean‐sources of energy are reviewed, some of which hold reasonable promise, like bioconversion and salinity differentials; and others, like thermal exchange, are suitable for immediate harnessing.     

Defects in carbon nanotubes

Carbon nanotubes are quasi one-dimensional nanostructures with unique eletrical prroperties that make them prime candidates for molecular electronics, which is certainly a most promising direction in nanotechnology. Early theoretical works predicted that the electronic properties of "ideal" carbon nanotubes depend on their diameter and chirality. However, carbon nanotubes are probably not as perfect as they were once thought to be. Defects such as pentagons, heptagons, vacancies, or dopant are found to modify drastically the electronic properties of these nanosystems. Irradiation processes can lead to interesting, highly defective nanostructures and also to the coalescence of nanotubes within a rope. The introduction of defects in the carbon network is thus an interesting way to tailor its intrinsic properties, to create new potential nanodevices. The aim of the present Acount is to investigate theoretically the effects of different types of defects on the electronic properties of carbon nanotubes, and to propose new potential applications in nanoelectronics.     

Electronic, thermal and mechanical properties of carbon nanotubes

A review of the electronic, thermal and mechanical properties of nanotubes is presented, with particular reference to properties that differ from those of the bulk counterparts and to potential applications that might result from the special structure and properties of nanotubes. Both experimental and theoretical aspects of these topics are reviewed.     

Mask‐free Localized Grafting of Organic Polymers at the Micrometer or Submicrometer Scale on Composite Conductors or Semiconductor Substrates

This work presents a new one‐step process enabling the mask‐free localized functionalization by organic polymers of the conducting or semiconducting parts of composite surfaces at the micrometer and submicrometer scale. The functionalization is carried out via cathodic electrografting of suitable precursors of composite cathodes, which gives an insulating polymer film strongly grafted to selected parts of the composite electrodes and guarantees that the resolution is that of the pre‐existing pattern, even when the whole surface is dipped into the reaction medium. The presumed mechanism is based on a regioselective extraction of electrons from the composite surface according to its apparent local work function in solution.     

Reorganization of Wells–Dawson Heteropoly Compounds During the Oxygen Assisted Catalytic Reaction of 2-butanol: Effect of the Oxido-Reduction Strength of the Working Conditions

The reorganization of a Wells–Dawson heteropoly compound during the oxygen assisted catalytic reaction of 2-butanol appears to be dictated by the oxido-reduction strength of the working conditions. Indeed, the oxido-reduction strength is a tool to smoothly induce the rearrangement of the Wells–Dawson compound and to stabilize a particular intermediate species, formed in situ, with most desired enhanced performances in selective oxidation processes. It thus appears clearly that the O₂:2-butanol ratio of 5 allows to keep the selectivity in methyl-ethyl-ketone stable with time-on-stream. This feed seems to be a good compromise compared both to more reducing or oxidizing working conditions.     

Pollution problems give the earth a chance

Electric narrow gauge railroads near highways are torn up to provide space for exhaust‐spewing buses. New apartments and hotels are added to seaside resorts to increase the amount of unfiltered sewage in the sea. Venice and Bruges discharge untreated human faeces into the canals sailed by oblivious tourists, while Europe heralds with joy the era of the plastic container but no new dumps.

Totally ignorant of the environmental disaster to which America just awoke, other countries seem to be determined to emulate the United States in a headlong rush to destruction.

“Give Earth a chance”, is the author's cry. The author does not wish to be a prophet of doom, but evidence produced by scientists of repute points to the urgent need to sacrifice some of the aspects of the “easy life”, to reduce industrial pollution, to restrict demands for energy, and to control the population explosion. The alternative is an unhabitable Earth or a substandard geoecosystem housing a debilitated humanity.     

Structural and dimensional stabilities of tin-bismuth fusible cores

Eutectic tin-bismuth alloys, used as fusible cores for high polymer injection moulding, were studied in order to identify structural and dimensional modifications during ageing at temperatures ranging from 4 to 110°C. Optical and scanning electron microscopies together with X-ray diffraction were used to observe the coarsening of the eutectic structure and to plot an isothermal transformation diagram. Thermal cycles around the eutectic temperature promoted the dissociation of the eutectic structure into light tin dendrites at the top of the ingots and heavy bismuth crystals at the bottom. Differential scanning calorimetry and thermomechanical analysis were performed to observe possible phase transformations.     

A two scale anisotropic damage model accounting for initial stresses in microcracked materials

In a recent study [15], we proposed a class of isotropic damage models which account for initial stresses. The present paper extends this approach to anisotropic damage due to growth of an arbitrarily penny-shaped microcracks system. The basic principle of the upscaling technique in the presence of initial stress is first recalled. Then, we derive a closed-form expression of the elastic energy potential corresponding to a system of arbitrarily oriented microcracks. It is shown that the coupling between initial stresses and damage is strongly dependent of the microcracks density and orientation. Predictions of the proposed model are illustrated through the investigation of the influence of initial stresses on the material response under non monotonous loading paths. Finally, by considering a particular distribution of microcracks orientation, described by a second order damage tensor, it is shown that the model is a generalization of the macroscopic damage model of Halm and Dragon [9], for which a physically-based interpretation is then proposed.