Recrystallization of HDPE in HDPE/iPP quenched films

Epitaxial crystallization behavior of HDPE/iPP double layers under quenching and annealing conditions has been studied by means of transmission electron microscopy (TEM). The results obtained from bright field TEM observations indicate that in the as-quenched state the HDPE that is in direct contact with the surface of the oriented iPP substrate recrystallizes in the form of oriented crystallites dispersed on the iPP substrate. The electron diffraction results show that besides the two normally observed epitaxial orientations between HDPE and iPP, there is also a special orientation with [001](HDPE)parallel to[001](iPP). The HDPE which is in contact with the clean surface of a glass slide crystallizes in small lamellae with random orientation. In the boundary region, the epitaxially crystallized HDPE small lamellae stop right on the boundary of the oriented iPP film. If the quenched samples are annealed at 128 degrees C (below T-m of HDPE) for 2 h, the small HDPE crystals grow to thick lamellae in both areas. But only the epitaxial orientation of HDPE with [001](HDPE)parallel to[101](iPP) has been observed.

A Note on Ordinally Equivalent Pareto Surfaces

Assuming at least three individuals and some regularity conditions, we construct a set S* of Pareto surfaces which is an ordinal basis of the set S of all surfaces: every surface in S is ordinally equivalent to some surface in S* and all surfaces in S* are ordinally distinct.

Perception de la vitesse : les bases psychophysiques et neuronales

David Katz a fait l’observation que le mouvement entre la peau et l’objet est aussi important pour le sens du toucher que la lumière l’est pour la vision. Un stimulus tactile déplacé sur la peau active toutes les afférences cutanées. Les signaux résultants sont très complexes, covariant avec différents facteurs dont la vitesse, mais aussi la texture, la forme et la force. Cette thèse explore la capacité des humains à estimer la vitesse et la rugosité de surfaces en mouvements. Les bases neuronales de la vitesse tactile sont aussi étudiées en effectuant des enregistrements unitaires dans le cortex somatosensoriel primaire (S1) du singe éveillé. Dans la première expérience, nous avons montré que les sujets peuvent estimer la vitesse tactile (gamme de vitesses, 30 à 105 mm/s) de surfaces déplacées sous le doigt, et ceci sans indice de durée. Mais la structure des surfaces était essentielle (difficulté à estimer la vitesse d’une surface lisse). Les caractéristiques physiques des surfaces avaient une influence sur l’intensité subjective de la vitesse. La surface plus rugueuse (8 mm d’espacement entre les points en relief) semblait se déplacer 15% plus lentement que les surfaces moins rugueuses (de 2 et 3 mm d’espacement), pour les surfaces périodiques et non périodiques (rangées de points vs disposition aléatoire). L’effet de la texture sur la vitesse peut être réduit en un continuum monotonique quand les estimés sont normalisés avec l’espacement et présentés en fonction de la fréquence temporelle (vitesse/espacement). L'absence de changement des estimés de vitesse entre les surfaces périodiques et non périodiques suggère que les estimés de rugosité devraient aussi être indépendants de la disposition des points. Dans la deuxième expérience, et tel que prévu, une équivalence perceptuelle entre les deux séries de surfaces est obtenue quand les estimés de la rugosité sont exprimés en fonction de l'espacement moyen entre les points en relief, dans le sens de l'exploration. La troisième expérience consistait à rechercher des neurones du S1 qui pourraient expliquer l’intensité subjective de la vitesse tactile. L’hypothèse est que les neurones impliqués devraient être sensibles à la vitesse tactile (40 à 105 mm/s) et à l’espacement des points (2 à 8 mm) mais être indépendants de leur disposition (périodique vs non périodique). De plus, il est attendu que la fonction neurométrique (fréquence de décharge/espacement en fonction de la fréquence temporelle) montre une augmentation monotonique. Une grande proportion des cellules était sensible à la vitesse (76/119), et 82% d’entres elles étaient aussi sensibles à la texture. La sensibilité à la vitesse a été observée dans les trois aires du S1 (3b, 1 et 2). La grande majorité de cellules sensibles à la vitesse, 94%, avait une relation monotonique entre leur décharge et la fréquence temporelle, tel qu’attendu, et ce surtout dans les aires 1 et 2. Ces neurones pourraient donc expliquer la capacité des sujets à estimer la vitesse tactile de surfaces texturées.

The Perception of Subjective Surfaces

It is proposed that subjective contours are an artifact of the perception of natural three-dimensional surfaces. A recent theory of surface interpolation implies that "subjective surfaces" are constructed in the visual system by interpolation between three-dimensional values arising from interpretation of a variety of surface cues. We show that subjective surfaces can take any form, including singly and doubly curved surfaces, as well as the commonly discussed fronto-parallel planes. In addition, it is necessary in the context of computational vision to make explicit the discontinuities, both in depth and in surface orientation, in the surfaces constructed by interpolation. It is proposed that subjective surfaces and subjective contours are demonstrated. The role played by figure completion and enhanced brightness contrast in the determination of subjective surfaces is discussed. All considerations of surface perception apply equally to subjective surfaces.

Vegetative and reproductive morphology of Kallymenia patens (Kallymeniaceae, Rhodophyta) in the Mediterranean Sea

Reproductive morphology of the Mediterranean red alga Kallymenia patens is described for the first time, confirming its position in the genus. K. patens is characterized by a non-procarpic female reproductive apparatus, carpogonial branch systems consisting of supporting cells bearing both three-celled carpogonial branches and subsidiary cells that lack a hypogynous cell and carpogonium; fusion cells develop numerous connecting filaments, and tetrasporangia are scattered over the thallus and are probably cruciately divided. Old fertile spathulate specimens of K. patens are morphologically similar to K. spathulata, but they can be distinguished by the length of spathulated proliferations (up to 0.6 cm and 6 cm, respectively), the length of inner cortical cells (up to 70 and 30 μm, respectively), and the gonimoblast location (in proliferations from the perennial part of the blade and over all the thallus surface, respectively)

Análisis de la situación actual y propuesta de mejoramiento en el plan de negocio de la empresa CIRO ROBERTO MORENO S. EN C.S – “Minas Peñitas“

CIRO ROBERTO MORENO S. EN C.S – “Minas Peñitas”. Es una empresa en el sector minero energético. Este sector se ha caracterizado en Colombia como uno de los más importantes de inigualable crecimiento y con un gran potencial, ya que no solo le trae grandes beneficios a la economía del país, sino que es un sector distinguido por generar grandes niveles de empleo. De este modo CIRO ROBERTO MORENO S. EN C.S – “Minas Peñitas” tiene grandes oportunidades de crecimiento y perdurabilidad, pero debe tener en cuenta que tiene que estar preparada y en las mejores condiciones en todos los aspectos posibles. El propósito del presente trabajo de análisis de la empresa CIRO ROBERTO MORENO S. EN C.S – “Minas Peñitas” es de identificar la forma cómo se desarrollan todas las actividades de la empresa y así determinar el desempeño de estas, para identificar las fortalezas y debilidades presentes, para establecer un plan de mejoramiento en todas las actividades de la cadena de valor y por lo tanto en el plan de negocio de la compañía. La meta de este trabajo no solo fue analizar la situación de la empresa, sino también mostrar las condiciones de la minería de carbón y su comportamiento a nivel mundial y nacional, datos que no se tienen muy claros por parte de empresa y por lo tanto no se le ha dado la suficiente importancia a esta clase de información para beneficio de la misma; sin embargo de acuerdo a las mejoras propuestas en las falencias encontradas en los temas de comunicación y manejo de información en la empresa se espera que si CIRO ROBERTO MORENO S. EN C.S – “Minas Peñitas” considere aplicarlas de la mejor forma, lo cual le traerá grandes beneficios y cumplir con la visión establecida por la empresa.

Administración en la cadena de suministro y su relación con el desempeño de las PYME del sector agroindustrial

En la actualidad las organizaciones están en búsqueda de una mejora continua, esto lleva a que las empresas hagan una revisión de estrategias que permitan alcanzar una posición de líderes en los diferentes sectores en los que se desempeñan. Una de las estrategias para lograr un alto posicionamiento en las nuevas empresas es la adecuada gestión que hacen de la cadena de suministro. El sector agroindustrial tiene un amplia cadena de suministro desde la obtención de materias primas hasta la llegada al cliente final, por su gran magnitud requiere de una adecuada administración de procesos que permitan ser eficaces y eficientes para alcanzar logros propuestos, aprovechar los recursos limitados con los que cuentan para su cumplimiento y, por último, la capacidad propia para la transformación de sus recursos. Para lograr que las empresas obtengan ventajas competitivas, es necesario que los distintos eslabones de la cadena de suministros cuenten con una capacidad de interacción que les permita, tanto agilizar como asegurar el éxito durante la incorporación de los nuevos productos en el mercado. Por medio de esta investigación se busca esclarecer y analizar la importancia de la administración en la cadena de suministro y la relación con el desempeño, basándose en las Pymes del sector agroindustrial. La intención es evaluar la información de diversos autores quienes han hablado de la relación que existe entre la cadena de suministro y su desempeño, teniendo en cuenta variables como el sector agroindustrial y las Pymes.

Dissociation of water on oxygen-covered Rh{111}

The adsorption of water and coadsorption with oxygen on Rh{111} under ultrahigh vacuum conditions was studied using synchrotron-based photoemission and photoabsorption spectroscopy. Water adsorbs intact on the clean surface at temperatures below 154 K. Irradiation with x-rays, however, induces fast dissociation and the formation of a mixed OH+H(2)O layer indicating that the partially dissociated layer is thermodynamically more stable. Coadsorption of water and oxygen at a coverage below 0.3 monolayers has a similar effect, leading to the formation of a hydrogen-bonded network of water and hydroxyl molecules at a ratio of 3:2. The partially dissociated layers are more stable than chemisorbed intact water with the maximum desorption temperatures up to 30 K higher. For higher oxygen coverage, up to 0.5 monolayers, water does not dissociate and an intact water species is observed above 160 K, which is characterized by an O 1s binding energy 0.6 eV higher than that of chemisorbed water and a high desorption temperature similar to the partially dissociated layer. The extra stabilization is most likely due to hydrogen bonds with atomic oxygen.

Water adsorption on O-covered Ru{0001}: coverage-dependent change from dissociation to molecular adsorption

When water is coadsorbed with oxygen at coverages above 0.25ML an intact water species is observed in high resolution X-ray photoelectron spectroscopy up to 220 K, which is significantly more stable than intact water on the clean surface. The presence of this species causes a shift in the O 1s binding energy of the pre-adsorbed oxygen, which indicates the formation of hydrogen bonds between the two adsorbates. Low coverages of oxygen induce partial dissociation and recombinative desorption in the same temperature range, which illustrates that desorption temperatures alone cannot be used to determine whether water is molecularly intact or not.

The structure of the mixed OH+H2O overlayer on Pt{111}

The structure of the mixed p(3x3)-(3OH+3H(2)O) phase on Pt{111} has been investigated by low-energy electron diffraction-IV structure analysis. The OH+H2O overlayer consists of hexagonal rings of coplanar oxygen atoms interlinked by hydrogen bonds. Lateral shifts of the O atoms away from atop sites result in different O-O separations and hexagons with only large separations (2.81 and 3.02 angstrom) linked by hexagons with alternating separations of 2.49 and 2.81/3.02 A. This unusual pattern is consistent with a hydrogen-bonded network in which water is adsorbed in cyclic rings separated by OH in a p(3x3) structure. The topmost two layers of the Pt atoms relax inwards with respect to the clean surface and both show vertical buckling of up to 0.06 angstrom. In addition, significant shifts away from the lateral bulk positions have been found for the second layer of Pt atoms. (C) 2005 American Institute of Physics.

Low-temperature partial dissociation of water on Cu(110)

The low-temperature reactivity of water (D2O) adsorbed on clean and oxygen pre-covered Cu(1 1 0) was studied using high resolution X-ray photoelectron spectroscopy (HRXPS) and low energy electron diffraction (LEED). On the clean surface partial dissociation to hydroxyl was observed already at 95 K. Upon annealing to 220 K hydrogen bonded water-hydroxyl chains are formed. Upon further annealing water desorbs leaving behind a layer of hydroxyl, most of which desorbs recombinatively eventually. With pre-adsorbed oxygen water reacts to hydroxyl lifting the added-row reconstruction even below 225 K. Upon annealing this adsorbate layer passes through essentially the same stages as without pre-adsorbed oxygen.

Coverage-dependent molecular tilt of carbon monoxide chemisorbed on Pt{110}: A combined LEED and DFT structural analysis

The adsorption of carbon monoxide on the Pt{110} surface at coverages of 0.5 ML and 1.0 ML was investigated using quantitative low-energy electron diffraction (LEED IV) and density-functional theory (DFT). At 0.5 ML CO lifts the reconstruction of the clean surface but does not form an ordered overlayer. At the saturation coverage, 1.0 ML, a well-ordered p(2×1) superstructure with glide line symmetry is formed. It was confirmed that the CO molecules adsorb on top of the Pt atoms in the top-most substrate layer with the molecular axes tilted by ±22° with respect to the surface normal in alternating directions away from the close packed rows of Pt atoms. This is accompanied by significant lateral shifts of 0.55 Å away from the atop sites in the same direction as the tilt. The top-most substrate layer relaxes inwards by −4% with respect to the bulk-terminated atom positions, while the consecutive layers only show minor relaxations. Despite the lack of long-range order in the 0.5 ML CO layer it was possible to determine key structural parameters by LEED IV using only the intensities of the integer-order spots. At this coverage CO also adsorbs on atop sites with the molecular axis closer to the surface normal (b10°). The average substrate relaxations in each layer are similar for both coverages and consistent with DFT calculations performed for a variety of ordered structures with coverages of 1.0 ML and 0.5 ML.

Coverage-dependent structural evolution in the interaction of NO2 with Au{111}

We have used low-temperature STM, together with DFT calculations incorporating the effects of dispersion forces, to study from a structural point of view the interaction of NO2 with Au{111} surfaces. NO2 adsorbs molecularly on Au{111} at 80 K, initially as small, disordered clusters at the elbows of the type-x reconstruction lines of the clean-surface herringbone reconstruction, and then as larger, ordered islands on the fcc regions. Within the islands, the NO2 molecules define a (√3 × 2)rect. superlattice, for which we evaluate structural models. By around 0.25 ML coverage, the herringbone reconstruction has been lifted, accompanied by the formation of Au nanoclusters, and the islands have coalesced. At this stage, essentially the whole surface is covered with an overlayer consisting predominantly of domains of the (√3 × 2)rect. structure, but also containing less wellordered regions. With further exposure, the degree of disorder in the overlayer increases; saturation occurs close to 0.43 ML.

Analysis of phosphorus use efficiency traits in Coffea genotypes reveals Coffea arabica and Coffea canephora have contrasting phosphorus uptake and utilization efficiencies

Background and Aims: Phosphate (Pi) is one of the most limiting nutrients for agricultural production in Brazilian soils due to low soil Pi concentrations and rapid fixation of fertilizer Pi by adsorption to oxidic minerals and/or precipitation by iron and aluminum ions. The objectives of this study were to quantify phosphorus (P) uptake and use efficiency in cultivars of the species Coffea arabica L. and Coffea canephora L., and group them in terms of efficiency and response to Pi availability. Methods: Plants of 21 cultivars of C. arabica and four cultivars of C. canephora were grown under contrasting soil Pi availabilities. Biomass accumulation, tissue P concentration and accumulation and efficiency indices for P use were measured. Key Results: Coffee plant growth was significantly reduced under low Pi availability, and P concentration was higher in cultivars of C. canephora. The young leaves accumulated more P than any other tissue. The cultivars of C. canephora had a higher root/shoot ratio and were significantly more efficient in P uptake, while the cultivars of C. arabica were more efficient in P utilization. Agronomic P use efficiency varied among coffee cultivars and E16 Shoa, E22 Sidamo, Iêmen and Acaiá cultivars were classified as the most efficient and responsive to Pi supply. A positive correlation between P uptake efficiency and root to shoot ratio was observed across all cultivars at low Pi supply. These data identify Coffea genotypes better adapted to low soil Pi availabilities, and the traits that contribute to improved P uptake and use efficiency. These data could be used to select current genotypes with improved P uptake or utilization efficiencies for use on soils with low Pi availability and also provide potential breeding material and targets for breeding new cultivars better adapted to the low Pi status of Brazilian soils. This could ultimately reduce the use of Pi fertilizers in tropical soils, and contribute to more sustainable coffee production.

Chemical bonding and composition of silicon nitride films prepared by inductively coupled plasma chemical vapor deposition

Thin silicon nitride films were prepared at 350 degrees C by inductively coupled plasma chemical vapor deposition on Si(100) substrates under different NH(3)/SiH(4) or N(2)/SiH(4) gas mixture. The chemical composition and bonding structure of the deposited films were investigated as a function of the process parameters, such as the gas flow ratio NH(3)/SiH(4) or N(2)/SiH(4) and the RF power, using X-ray photoelectron spectroscopy (XPS). The gas flow ratio was 1.4, 4.3, 7.2 or 9.5 and the RF power, 50 or 100 W. Decomposition results of Si 2p XPS spectra indicated the presence of bulk Si, under-stoichiometric nitride, stoichiometric nitride Si(3)N(4), oxynitride SiN(x)O(y), and stoichiometric oxide SiO(2), and the amounts of these compounds were strongly influenced by the two process parameters. These results were consistent with those obtained from N 1s XPS spectra. The chemical composition ratio N/Si in the film increased with increasing the gas flow ratio until the gas flow ratio reached 4.3, reflecting the high reactivity of nitrogen, and stayed almost constant for further increase in gas flow ratio, the excess nitrogen being rejected from the growing film. A considerable and unexpected incorporation of contaminant oxygen and carbon into the depositing film was observed and attributed to their high chemical reactivity. (C) 2010 Elsevier B.V. All rights reserved.