High-quality spin-on glass-based oxide as a matrix for embedding HfO<Subscript>2</Subscript> nanoparticles for metal-oxide-semiconductor capacitors

By using a low cost, simple, and reproducible spin-coating method, thin films of SOG (spin-on-glass)-based oxides with electrical characteristics resembling those of a dry thermal oxide have been obtained. The superior electrical characteristics of Metal-Oxide-Semiconductor (MOS) capacitors based on SOG-oxides come from both (1) reducing the organic content of the SOG solutions after dilution with deionized water and (2) passivation of the silicon surface by a thin chemical oxide. Fourier transform infrared spectroscopy analysis shows that the organic content in H₂O-diluted SOG-oxides is reduced compared to undiluted SOG after N₂ annealing. In addition, by chemically embedding HfO₂ nanoparticles (np-HfO₂) to these SOG-based oxides, an effective increase in the accumulation capacitance of MOS capacitors is observed and this is related to the increase in the final dielectric constant of the resulting oxide after annealing so that potential use of SOG as a glass matrix for embedding HfO₂ nanoparticles and produce higher-k oxide materials is demonstrated.     

Optomechanics with silicon nanowires by harnessing confined electromagnetic modes

The optomechanical coupling that emerges in an optical cavity in which one of the mirrors is a mechanical resonator has allowed sub-Kelvin cooling with the prospect of observing quantum phenomena and self-sustained oscillators with very high spectral purity. Both applications clearly benefit from the use of the smallest possible mechanical resonator. Unfortunately, the optomechanical coupling largely decays when the size of the mechanical system is below the light wavelength. Here, we propose to exploit the optical resonances associated to the light confinement in subwavelength structures to circumvent this limitation, efficiently extending optomechanics to nanoscale objects. We demonstrate this mechanism with suspended silicon nanowires. We are able to optically cool the mechanical vibration of the nanowires from room temperature to 30-40 K or to obtain regenerative mechanical oscillation with a frequency stability of about one part per million. The reported optomechanical phenomena can be exploited for developing cost-optimized mass sensors with sensitivities in the zeptogram range.     

Composition-dependent properties of polyethylene/Kaolin composites Part II Thermoelastic behaviour of blow-moulded samples

Samples of the blow-moulding grade HDPE filled with Kaolin were characterized by wide-angle X-ray scattering, microhardness and stretching calorimetry techniques. It is shown that crystallinity of the polymer matrix in the filled samples remains essentially the same as that in the neat polymer regardless of the filler content. The thermoelastic behaviour of all samples below the apparent yield point * is quantitatively described by classical equations for elastic solids. The thermoelastic parameters of the boundary interphase (BI) are discussed in terms of predictions of the step-by-step averaging approach. The experimental values of the internal energy increment in the inelastic strain interval for unfilled and filled samples are analyzed in the light of the filler debonding processes in the latter.     

Methodological approaches to supply chain design1

This paper reviews methodological approaches to the design (or redesign) of the supply chain (SC), including comprehensive approaches (proposals concerning the entire process of designing the SC) and those that deal with four specific aspects of the process (definition of the SC objectives, reverse SC, finance, and generation and use of scenarios) that have a decisive influence on the whole design of the SC. The comprehensive approaches include those based on typologies of products, markets and SCs and those that propose a succession of the stages to follow through the design process. The discussion shows that the use of typologies is not adequate to face SC design and that the methods proposing a succession of stages may suit, provided that they are developed and presented in a manner appropriate to their use for practitioners. The discussion leads also to suggest several research lines.     

Viscoelastic relaxations in poly(dimethylphenyl methacrylates)

Summary Dynamic mechanical properties of poly(dimethylphenyl methacrylátes) were studied considering the different positions of the methyl groups on the phenyl ring. In all cases a clear relaxation can be observed which is associated to the polymer glass transition temperature (Tg). Nevertheless, at lower temperatures, viscoelastic activity is negligible. A correlation between the steric hindrance due to the methyl groups and the temperature at which the relaxation is detected, was established.     

On the dynamic mechanical behavior of poly(methyl methacrylate) reinforced with Kevlar fibers

The dynamic mechanical relaxation behavior of poly(methyl methacrylate) reinforced by continuous parallel Kevlar-49 fibers is investigated here on samples with several fiber volume fractions. The shifts in the temperature of the main relaxation of the matrix are interpreted according to free volume considerations and with the help of a thermomechanical block model. The dependence of the storage and loss moduli both on temperature and fiber content found experimentally can be reproduced by the model. It is not necessary to rely on the existence of an interphase to account for the modifications evidenced by the spectrum of the matrix, which can be explained on the basis of the two phase model.     

Dielectric relaxation in chlorinated polyethylene–polypropylene copolymers

Dielectric relaxation measurements were carried out on eight chlorinated polyethylene–polypropylene (PEPP) copolymers in the range of temperatures covering the main dielectric absorption. Chlorination of PEPP is expected to change the dynamic dielectric properties gradually with increasing amount of chlorine in the polymer chains. Thus, in the present study, increasing degrees of chlorination give a clear shift of the glass transition temperature towards higher values, except in the range between 40 and 51% chlorine, where an anomalous behaviour was observed. The same tendency is also observed in the relaxation strength (Δϵ). The value of Δϵ has been estimated by using a nonlinear squares regression program (LEVM6) to calculate the parameters of the Havriliak–Negami empirical equation. It appears reasonable to assume that the anomalous behaviour observed can be attributed to a compensation of the dipolar moments of chlorine groups in the macromolecules.     

Temperature dependence of microhardness and structure of ferroelectric copolymers of vinylidene fluoride

Measurement of the microhardness (H) and X-ray investigation of melt-crystallized random copolymers of vinylidene fluoride with trifluorethylene containing 60 to 80 mol% VF₂ were carried out as a function of temperature. The results show that (i) at a given temperatureH rapidly increases with VF₂ content; (ii) the Curie transition was found to involve an inflection point in the exponential temperature dependence of hardness; and (iii) at the Curie temperature (T _c) the ferroelectric crystals undergo reversibly a solid-state transformation, followed by the microhardness, to a non-polar (paraelectric) state showing a faster hardness decrease with increasing temperature aboveT _c. Changes inH with VF₂ content and temperature are discussed in the light of the lattice spacings of the ferro- and paraelectric phases and crystallinity values. The application of a relationship to account for correlations between mechanical properties and microstructure is considered.     

Overexpression of a constitutively active form of phosphatidylinositol 3-kinase is sufficient to promote Glut 4 translocation in adipocytes

Insulin stimulates glucose transport in its target cells by recruiting the glucose transporter Glut 4 from an intracellular compartment to the cell surface. Previous studies have indicated that phosphatidylinositol 3-kinase (PI 3-kinase) is a necessary step in this insulin action. We have investigated whether PI 3-kinase activation is sufficient to promote Glut 4 translocation in transiently transfected adipocytes. Rat adipose cells were cotransfected with expression vectors that allowed transient expression of epitope-tagged Glut 4 and a constitutively active form of PI 3-kinase (p110*). The expression of p110* induced the appearance of epitope-tagged Glut 4 at the cell surface at a level similar to that obtained after insulin treatment, whereas a kinase-dead version of p110* had no effect. The p110* effect was observed over a wide range of the transfected cDNA. When subcellular fractionation of adipocytes was performed, p110* was found, similar to the endogenous PI 3-kinase, enriched in the low density microsomal compartment, which also contains the Glut 4 vesicles. This could suggest that a specific localization of PI 3-kinase in this compartment is required for the action on Glut 4. The observations made with PI 3-kinase are in contrast with those seen with the MAP kinase cascade. Indeed, a constitutively active form of MAP kinase kinase had no effect on Glut 4 translocation in basal conditions. At the highest degree of expression, the constitutively active form of MAP kinase kinase slightly inhibited the insulin stimulation of Glut 4 translocation. Taken together, our results indicate that Glut 4 translocation can be efficiently promoted by an active form of PI 3-kinase but not by the activation of the MAP kinase pathway.