p53 protein accumulation and response to adjuvant chemotherapy in premenopausal women with node-negative early breast cancer

Although beta-sheets represent a sizable fraction of the secondary structure found in proteins, the forces guiding the formation of beta-sheets are still not well understood. Here we examine the folding of a small, all beta-sheet protein, the E. coli major cold shock protein CspA, using both equilibrium and kinetic methods. The equilibrium denaturation of CspA is reversible and displays a single transition between folded and unfolded states. The kinetic traces of the unfolding and refolding of CspA studied by stopped-flow fluorescence spectroscopy are monoexponential and thus also consistent with a two-state model. In the absence of denaturant, CspA refolds very fast with a time constant of 5 ms. The unfolding of CspA is also rapid, and at urea concentrations above the denaturation midpoint, the rate of unfolding is largely independent of urea concentration. This suggests that the transition state ensemble more closely resembles the native state in terms of solvent accessibility than the denatured state. Based on the model of a compact transition state and on an unusual structural feature of CspA, a solvent-exposed cluster of aromatic side chains, we propose a novel folding mechanism for CspA. We have also investigated the possible complications that may arise from attaching polyhistidine affinity tags to the carboxy and amino termini of CspA.     

Decomposition du methane sur le carbone aux tres hautes temperatures et sous basses pressions

The decomposition of methane on pyrocarbon as deposited in the course of the reaction has been investigated at high temperatures (1000–2000°C) and low pressures ( 10⁻² Torr). Experiments have been carried out with electrically heated filaments made of amorphous, pyrolytic or graphitic carbon. Rates of decomposition are calculated from rates of molecular hydrogen formation. Results are very different from those reported previously about the decompositions of ethylene, acetylene, propadiene and benzene on the same substrates.

1. (1) Electron microscope observations never showed any evidence of pyrocarbon deposition (Fig. 4). However some indications do not exclude this possibility in the deep pores of the Acheson graphite.

2. (2) Electrical resistivity measurements confirm the smallness—or even the complete absence—of any pyrocarbon deposition (Fig. 5).

3. (3) Even after many series of ten hours reaction time, the kinetics of methane decomposition are still strongly dependent upon the type of sample. This fact supports also the conclusion that pyrocarbon deposition is absent (in contrast, the pyrocarbon deposited in similar experiments using unsaturated hydrocarbons makes all types of samples tend progressively to a standard chemical behavior).

4. (4) On smooth pyrocarbon surfaces, methane decomposition is hardly detectable; collision yields are of the order 10⁻⁷ (as compared to 10⁻⁴ for unsaturated hydrocarbons, Fig. 6). But with porous samples—especially Acheson graphite—appreciable decomposition occurs; the kinetics show then many similarities with those reported previously for unsaturated hydrocarbons decompositions: especially the reactivity of the carbon surface is temperature and pressure dependent (Figs. 1–3).

The peculiar behavior of methane is explained in terms of chemical reactivity: unlike unsaturated hydrocarbons, methane does not undergo weakly activated chemisorption on the active sites of the carbon surface, and decomposition may then only occur after thermal accommodation of the gas molecules.

Résumé

On étudie la décomposition du méthane sous basses pressions ( 10⁻² Torr) et à hautes températures (1000–2000°C) sur le carbone qui se forme durant la réaction. Les résultats obtenus sont très différents de ceux acquis antérieurement dans des expériences similaires menées avec l'éthylène, l'acétylène, l'aliène et le benzène.

1. (1) Les observations à l'oeil nu et au microscope électronique n'ont jamais permis de déceler un changement de la surface du filament de carbone de départ qui puisse être imputé à un dépôt de carbone pyrolytique. Cependant certains indices n'excluent pas la possibilité d'un tel dépôt dans les anfractuosités profondes des graphites Acheson.

2. (2) Les mesures de résistivité électrique de l'échantillon de carbone ont confirmé l'insignifiance—ou l'inexistence—d'un dépôt de carbone.

3. (3) Même après une dizaine d'heures de réaction la cinétique de la décomposition du méthane varie beaucoup selon le type de filament de départ, preuve supplémentaire que le dépôt de carbone pyrolytique est quasi inexistant (en opérant pareillement avec les hydrocarbures insaturés, le dépôt de carbone pyrolytique uniformise rapidement tous les échantillons et unifie leur comportement chimique).

4. (4) Avec les échantillons à texture fermée et à surface lisse une décomposition du méthane est à peine décelable (rendement de choc 10⁻⁷ contre 10⁻⁴ pour les hydrocarbures insaturés). Avec les échantillons poreux—notamment les graphites Acheson—une décomposition mesurable a lieu: la cinétique s'apparente alors à celles observées avec les hydrocarbures saturés sur des surfaces de carbone lisses, c'est-à-dire qu'elle est révélatrice d'une réactivité de la surface du carbone variable avec la température et la pression.

On interprète le comportement singulier du méthane en terme de réactivité chimique: le méthane, contrairement aux hydrocarbures insaturés ne donne pas lieu à une adsorption très peu activée à la surface du carbone. Sa chimisorption, et par conséquent sa décomposition nécessitent une accommo- dation thermique beaucoup plus complète que dans le cas des hydrocarbures insaturés.     

Caractérisation thermophysique et mécanique de briques de terre stabilisées en vue de l'isolation thermique de bâtiment

Résumé Cet article présente une étude expérimentale portant sur la caractérisation de matériaux locaux utilisés dans l'isolation thermique des batiments. Ces matériaux sont des briques de terre compressées et stabilisées au ciment. La conductivité thermique et la chaleur spécifique de matériaux à base de latérite incorporant de la pouzzolane et de la sciure de bois a été déterminée. Les résultats montrent que les blocs en latérite + pouzzolane ou en latérite + sciure de bois sont meilleurs isolants thermiques que les blocs en latérite simple. Cependant, ces matériaux composites utilisés pour l'enveloppe du batiment doivent avoir des résistances mécaniques suffisantes pour être utilisés dans la construction. La mesure des propriétés mécaniques telles que la résistance à la compression et la résistance à la traction a montré un faible écart entre les résistances des trois types de matériaux étudiés. Les résistances en traction de la latérite et de la latérite + pouzzolane sont voisines et environ deux fois plus élevées que celle de la latérite + sciure de bois. Ces résultats permettent de préciser les conditions d'utilisation optimale de ces matériaux pour l'enveloppe du batiment.

---

Thermophysical and mechanical characterization of stabilized clay bricks for building thermal insulation

An experimental study was carried out in order to determine the properties of local materials used for building thermal insulation. Cement stabilised compressed clay bricks were tested. The thermal conductivity and specific heat of laterite based materials incorporating pouzzolane or sawdust was determined. The experimental results showed that pouzzolane + laterite bricks or sawdust + laterite bricks give better thermal insulation than simple laterite bricks. However, these composite materials used for building shielding must present sufficient mechanical strength to the suitable for constructions. The measurement of mechanical properties such as compressive strength and tensile strength showed little difference between the strength of the three studied materials. The tensile strengths of the laterite and the laterite + pouzzolane bricks were similar. They were about two times that of the laterite + sawdust bricks. The obtained thermal and mechanical results permit to specify the optimal use conditions of the tested materials.

---

     

Highly efficient pilot biopiles for on-site fertilization treatment of diesel oil-contaminated sub-Antarctic soil

In order to determine the efficiency of on-site bioremediation of diesel contaminated subAntarctic soils, a pilot biopiles study was initiated in January 2006 with a selected soil of The Grande Terre (Kerguelen Archipelago, 69° 42′E–49° 19′S). Each 4 kg biopile received 180 g of diesel fuel and several of them were submitted to different treatments. All biopiles were sampled on a regular basis over a one-year period. A highly efficient biodegradation was observed in all piles. Analytical results show that less than 7% of total petroleum hydrocarbons (TPH) remained after one year in biopiles not treated with fertilizers. This proportion decreases to less than 0.2% in biopiles treated with fish compost. These biopiles revealed to be 100 times more efficient than previously reported in situ bioremediation study conducted under similar weather conditions with the same concentrations of similar fertilizers. After one year, a significantly larger amount of polycyclic aromatic hydrocarbons (PAH) was present in fertilized biopiles without a physical treatment compared to ventilated or agitated ones. Although biopiles were highly efficient to reduce TPH concentrations well below the target concentration of 100 ppm, a residual toxicity determined with Microtox assay was observed in a number of biopiles treated with fish compost.     

Adhesion of Campylobacter jejuni and Mycobacterium avium onto polyethylene terephtalate (PET) used for bottled waters

Adhesion of the bacteria Campylobacter jejuni and Mycobacterium avium onto polyethylene terephtalate (PET), a polymer widely used within the bottled water industry was measured in two different groundwater solutions. From this, it was found that whilst the percentage cell adhesion for a given strain did not change between groundwater types, substantial variation was obtained between the two bacterial species tested: M. avium (10-30% adhered cells) and C. jejuni (1-2%) and no major variations were measured as a function of groundwater composition for a given strain. To explain this, the interfacial electro-hydrodynamic properties of the bacteria were investigated by microelectrophoresis, with the resultant data analysed on the basis of electrokinetic theory for soft biocolloidal particles. The results obtained showed that M. avium carries a significant volume charge density and that its peripheral layer exhibits limited hydrodynamic flow permeation compared to that of C. jejuni. It was also demonstrated that steric hindrance to flow penetration and the degree of hydrophobicity within/of the outer bacterial interface are larger for M. avium cells. In line with this, the larger amount of M. avium cells deposited onto PET substrates as compared to that of C. jejuni can be explained by hydrophobic attraction and chemical binding between hydrophobic PET and outer soft surface layer of the bacteria. Hydrophobicity of PET was addressed by combining contact angle analyses and force spectroscopy using CH₃-terminated AFM tip.     

Effects of calcium nitrate and triisopropanolamine on the setting and strength evolution of Portland cement pastes

The purpose of this work is to study the effect of using some admixtures such as calcium nitrate and triisopropanolamine on the setting and hardening process of cement pastes at 20°C temperature. Tests were performed on specimens cast from various mixtures prepared with two types of cements. The results indicate that calcium nitrate alone acts as a setting accelerator, but has relatively little beneficial effect on the long term period development of mechanical resistances. Regardless of the cement type used, triisopropanolamine used alone performed well as a hardening accelerator at all ages. The combined addition of calcium nitrate and triisopropanolamine produced at very early age significant and promising results with respect to both setting and hardening acceleration. Continuous compressive strength increase was observed with time.     

Evolution of T-shaped gate lithography for compound semiconductors field-effect transistors

T-shaped gate formation is a major processing step in the fabrication of high-performance FET-based III-V devices. Traditional bilayer or trilayer E-beam lithography methods using PMMA/(PMMA&PMAA) copolymers are high-cost options which also lack the required critical dimension control for manufacturing. Lithography methods that use only a single layer of PMMA for the formation of T-shaped gate stem, and routine I-line resist lithography for the tee-top, i.e., hybrid T-shaped gates, have been developed and extensively used in manufacturing. This approach has also been extended to the fabrication of deep submicron T-shaped gates using all I-line optical lithography. Both chemical shrinks and chromeless phase-shift resolution enhancement techniques have been investigated.     

Influence des charges sur le comportement mécanique d'un joint collé cisaillé en traction

Résumé Le comportement mécanique d'un joint collé cisaillé en traction dépend de nombreux facteurs tant mécaniques que géométriques. Parmi tous ces paramètres, nous nous sommes proposés d'étudier, tout particulièrement, l'influence des charges sur la tenue d'un collage ainsi que leur r?le sur la microfissuration d'un joint. Après avoir caractérisé la nature minéralogique des charges vulgaires et renfor?antes, nous déterminons les contraintes radiales et tangentielles dans la matrice et dans l'inclusion aux points les plus sollicités mécaniquement. La comparaison avec l'état des contraintes autour d'un trou circulaire nous permet, alors, de déterminer un diamètre limite en-de?à duquel les charges ne jouent plus aucun r?le dans la rupture du film d'adhésif.

---

Summary In the course of study of the influence of fillers on the mechanical behaviour of a glued joint, the author was first led to characterize them by spectroscopic analysis and scanning microscopy. These fillers of essentially mineral origin can be classified as common fillers (chalk, calcite, kaolin ...) and reinforcing fillers (aluminia, titanium oxide, ferrous oxide). Roughly spherical in shape, they may reach a diameter of 15 μm, whereas the maximum pore size is close to 20 μm. In a second phase of research, the author determined the radial and tangential stresses in the matrix and in the inclusion at places in the joint under the greatest mechanical stress by a uniform plane field of compressive stresses. The calculation is based on the Mauskhelisvili formulae and shows that the radial and tangential stresses (σ _r andσ _θ respectively) in the matrix are fairly equal and maximum at points M₂ and M ₂ ^′ -extremities of the diameter of the circular load, in the direction of monoaxial loading p. The values ofσ _r andσ _θ are 1.45 and 0.45 respectively whatever the type of reinforcing filler. At M₁ and M ₁ ^′ these stresses are nil (M₁ and M ₁ ^′ are the extremities of the diameter perpendicular to M₂M ₂ ^′ ). In the circular inclusion for the same type of filler, the stress tensor is reduced to a compressive stress of 1,45 p at M₁, M ₁ ^′ , M₂ and M ₂ ^′ . Using these results as a basis and applying the Isha? fracture criterion, the authors show that the onset of microcraking at points M₂ and M ₂ ^′ in the joints occurs for a value of p equal to two thirds of the tensile elastic limit of the resin. By approaching this value of limit load of a circular hole, it is possible to determine a 7μm limit diameter for an inclusion beyond which the filler plays no role in the microcracking of the glued joint. Finally, the authors show that a common fillter fractures well before the onset of microcracking in the matrix. The singularity then behaves like a circular hole under increasing uniform compressive stress p.