The single-particle microbeam facility at CEA-Saclay

Low dose and non-targeted effect studies continue to attract the attention of a growing number of radiobiologists. Experimental setups based on light ion microbeams constitute a tool of choice for this kind of investigations. However, a careful attention must be given to experimental conditions, as setup-induced stress levels should be well below those induced by the irradiation itself. Here, we present the current status of the single-particle microbeam facility that has been developed these last years at the nuclear microprobe of Saclay. The driving idea was to build a facility in which local irradiation studies are performed in an environment close to cellular biology standards. This facility includes unique features, such as (i) a compact setup that allows easy access and vertical irradiation mode, (ii) a collimated beam that can be mechanically positioned under the desired cells at a very fast speed, avoiding the requirement of a focusing element and (iii) a controlled environment (temperature, CO₂, humidity) that allows performing of very long term experiments on cultured cells.Fluorescent techniques are implemented and permit in situ monitoring of cellular responses to irradiations.Several radiobiological studies are already underway and this will be illustrated with recent results regarding DNA damage and reactive oxygen species signaling time courses following targeted irradiations.     

Atomistic study of structural, elastic, electronic and thermal properties of perovskites Ba(Ti,Zr,Nb)O3

The full-potential linearized augmented plane waves (FP-LAPW) method based the on density functional theory (DFT) using the generalized gradient approximation (GGA) is applied to study the structural, mechanical, and electronic properties of BaTiO₃, BaZrO₃, and BaNbO₃ cubic perovskites. The quasi-harmonic Debye model, by means of total energy versus volume calculations obtained with the FP-LAPW method, is applied to study the thermal and vibrational effects. Predicted temperature and pressure effects on the structural parameters, thermal expansions, heat capacities, and Debye temperatures are determined from the non-equilibrium Gibbs functions.     

Deletion mapping in breast tumor cell lines points to two distinct tumor-suppressor genes in the 1p32-pter region, one of deleted regions (1p36.2) being located within the consensus region of LOH in neuroblastoma

The nucleotide sequence of the cry11Bb1 gene from Bacillus thuringiensis subsp. medellin was determined. The corresponding protein has a deduced molecular mass of 88.2 kDa, and is 60.9% and 83% identical to the proteins Cry11Aa1 and Cry11Ba1, respectively. The Cry11Bb1 protein contains five repetitive blocks of 16 amino acids at the C terminal part. It is highly toxic to first instar laboratory reared Aedes aegypti, Anopheles albimanus and Culex quinquefasciatus larvae.     

Evidence of sequential lift in growth of aligned multiwalled carbon nanotube multilayers

We synthesized aligned multiwalled carbon nanotube multilayers by aerosol-assisted catalytic chemical vapor deposition through sequential injections of aerosols containing both carbon and catalyst precursors. Each sequence was traced by a specific duration or precursor mixture, with the carbon source being possibly enriched in (13)C isotope labels. We discovered that any sequence involved the growth of a new layer on the substrate surface, under any pre-existing one by lifting it up, giving definitive evidence of a base-growth mechanism.     

Theoretical study of structural,electronic and optical properties of novel ternary alloys $$\hbox {MgO}_{1-{x}}{\hbox {Se}}_{{x}}$$ ($$x =$$x= 0.25, 0.50 and 0.75)

We report on the investigation of the structural, electronic, and optical properties of binary compounds (MgO and MgSe) and their ternary \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\) (\(x=0.25, 0.5, 0.75\)) alloys within the density functional theory based on the full-potential linearized augmented plane wave method as implemented in the WIEN2k code. We have used the revised Perdew–Burke–Ernzerhof generalized gradient approximation (GGA-PBEsol) to calculate the structural properties and analyze the effect of the Se composition on the lattice constant and the bulk modulus of \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\). The calculated electronic properties by employing the GGA-PBEsol and TB-mBJ approaches show that \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\) alloys have a direct band gap \(\Gamma \)–\(\Gamma \) for \(x = 0, 0.25, 0.5\) and 0.75, suggesting the possibility of their use in the long wavelength optoelectronic applications. The optical properties such as the real and imaginary parts of the dielectric function, the refractive index, and the reflectivity of \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\) are computed by using the accurate TB-mBJ potential. The wide band gaps larger than 3.1 eV mean that \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\) alloys can be used in the applications of the ultraviolet region of the spectrum. Our data for all studied bowing parameters of \(\hbox {MgO}_{1-{x}}\hbox {Se}_{x}\) may serve as references for future experimental studies.     

Preparation and Aqueous Properties of Starch‐grafted Polyacrylamide Copolymers

In the present work, starch‐grafted polyacrylamide copolymers were prepared and their rheological properties, either in water or in water‐based muds, were investigated. The advantages in using starches as substrates to prepare additives which are suited for improving stability and the rheological properties of water‐based muds, lie in their low cost, and their lower biodegradability than native starches. Thus, various copolymer series were prepared by free‐radically grafting acrylamide (AM) onto starch using ceric ammonium sulphate (CAS) as initiator. It is shown that the intrinsic viscosity and the molecular weight of the grafted starches are controlled by the initiator and monomer concentrations. Furthermore, to predict the behaviour of the samples under oil‐well conditions, the aqueous solution properties of the copolymers such as water solubility, viscosity, shear rate, were determined as function of temperature, salt concentration and type, and aging time. The knowledge of these properties is a prerequisite for the use of the copolymers in drilling fluids. The data indicate that starch‐grafted polyacrylamide copolymers as compared to the non‐modified starch, behave as shear‐thinning, are salt resistant, and their rheological properties are stable with time. The grafted starches as prepared above were also added to water‐based mud and the rheological properties of the resulting muds were determined under oil‐well conditions. Grafted starches, having high AM contents, are more efficient in decreasing the filtrate volume, and increasing the plastic viscosity of the muds, when compared to PAC‐L, a modified cellulosic polymer used in the filtration control of most water‐based muds. Such improvements in the rheological properties of the muds were found to result from the behaviour and/or properties of the grafted starches in water.     

Parallel sparse linear solver with GMRES method using minimization techniques of communications for GPU clusters

In this paper, we aim at exploiting the power computing of a graphics processing unit (GPU) cluster for solving large sparse linear systems. We implement the parallel algorithm of the generalized minimal residual iterative method using the Compute Unified Device Architecture programming language and the MPI parallel environment. The experiments show that a GPU cluster is more efficient than a CPU cluster. In order to optimize the performances, we use a compressed storage format for the sparse vectors and the hypergraph partitioning. These solutions improve the spatial and temporal localization of the shared data between the computing nodes of the GPU cluster.     

The G-group heuristic for single machine lot scheduling

This paper develops a heuristic procedure for generating feasible solutions for the single-machine, multi-product, infinite-horizon, lot scheduling problem. This problem occurs in several practical situations, for example, in metal stamping factories, on appliance assembly lines, in the beverage blending and bottling industries, in paint production and on motor car assembly lines. The proposed heuristic divides the N products into G groups and the products belonging to the same group are produced in the same cyclical pattern. Thus the problem of scheduling N independent products is reduced to that of scheduling G groups of products. Since G is much less than N, the problem is made simpler. The proposed heuristics has two main advantages: implementation facility and effectiveness. Computer codes are available for several mini and micro computers. The effectiveness is demonstrated by two tests. First, we solved the six problems originally solved by Elmaghraby (1978 a). Obviously, the results based on only six problems, cannot be generalized. Second, the G-group heuristic, as well as five other heuristics, was applied to 270 random computer-generated problems. The results show that it performed better.