Studies on adsorption of guar gum onto biotite mica

The interaction of guar gum with biotite mica has been investigated through adsorption, flotation and electrokinetic measurements. The adsorption densities of guar gum increase with increase of pH and the isotherms exhibit Langmuirian behaviour. Pretreatment of mica with a complexing agent such as EDTA results in a decrease in the adsorption density, highlighting the contribution of metal ions to the adsorption process. An increase in the surface face-to-edge ratio lends to an increase in the adsorption density. The flotation recoveries decrease as a function of pH, complementing the adsorption results. However, polymer depressant ability is reduced in the case of EDTA treated mica, consequent to reduction of metallic sites. Electrokinetic measurements portray conformational rearrangements of macromolecules with the loading, resulting in the shift of the shear plane, further away from the interface. Dissolution experiments indicate release of metal ions from mica, while co-precipitation tests confirm polymer-metal ion interaction in the bulk solution. The adsorption process is governed by hydrogen bonding as well as chemical interaction between guar gum and the surface metal hydroxide groups of mica. (C) 1997 Published by Elsevier Science Ltd.

Novel Mn-doped chalcopyrites

Heavily Mn-doped II-VI-V-2 semiconductors, such as CdGeP2 and ZnGeP2 have been prepared by depositing Mn on single crystalline substrate at nearly 400 T in an ultra high vacuum chamber. Well-defined ferromagnetic hysteresis with a saturation behavior appears in the magnetization curve up to above room temperature. The chemical states of the ZDGeP(2):Mn interface has been clarified by a careful in situ photoemission spectroscopy. The as-prepared surface consists of Ge-rich, metallic Mn compound. In and below the sub-surface region, dilute divalent Mn species as precursors of the DMS phase exist. No MnP phase was observed at any stage of the depth profile. Theoretical band-calculation suggests that the system with vacancies (Cd, V-c, Mn)GeP2 or a non-stoichiometric (Cd, Ge, Mn)GeP2 are ferromagnetic and energetically stable although ferromagnetism is not stable in a stoichiometric compound (Cd, Mn)GeP2. (C) 2003 Elsevier Ltd. All rights reserved.

Probing the mobility of lithium in LISICON: Li+/H+ exchange studies in Li2ZnGeO4 and Li2+2xZn1-xGeO4

We investigated Li+/H+ exchange in the lithium ion conductors (LISICONS) [ Li2+2xZn1-xGeO4; x = 0.5 ( I) and x = 0.75 (II)] and their parent, gamma-Li2ZnGeO4. Facile exchange of approximately 2x lithium ions per formula unit occurs with both the LISICONS in dilute acetic acid, while the parent material does not exhibit an obvious Li+/H+ exchange under the same conditions. The results can be understood in terms of lithium ion distribution in the crystal structures: the parent Li2ZnGeO4, where all the lithium ions form part of the tetrahedral framework structure, does not exhibit a ready Li+/H+ exchange; LISICONS, where lithium ions are distributed between framework ( tetrahedral) and nonframework sites, undergo a facile Li+/H+ exchange of the nonframework site lithium ions. Accordingly, Li+/H+ exchange in dilute aqueous acetic acid provides a convenient probe to distinguish between the mobile and the immobile lithium ions in lithium ion conductors.

Anomalous X-ray scattering study of local structures in the superionic conducting glass (AgBr)0.4 (Ag2O)0.3 (GeO2)0.3

The local structural information in the near-neighbor region of superionic conducting glass (AgBr)0.4(Ag2O)0.3(GeO2)0.3 has been estimated from the anomalous X-ray scattering (AXS) measurements using Ge and Br K absorption edges. The possible atomic arrangements in the near-neighbor region of this glass were obtained by coupling the results with the least-squares variational method so as to reproduce two differential intensity profiles for Ge and Br as well as the ordinary scattering profile. The coordination number of oxygen around Ge is found to be 3.6 at a distance of 0.176 nm, suggesting the GeO4 tetrahedral unit as the probable structural entity in this glass. Moreover, the coordination number of Ag around Br is estimated as 6.3 at a distance of 0.284 nm, suggesting an arrangement similar to that in crystalline AgBr.

Room temperature magnetic quantum cellular automata

All computers process information electronically. A processing method based on magnetism is reported here, in which networks of interacting submicrometer magnetic dots are used to perform logic operations and propagate information at room temperature. The logic states are signaled by the magnetization direction of the single-domain magnetic dots; the dots couple to their nearest neighbors through magnetostatic interactions. Magnetic solitons carry information through the networks, and an applied oscillating magnetic field feeds energy into the system and serves as a clock. These networks offer a several thousandfold increase in integration density and a hundredfold reduction in power dissipation over current microelectronic technology.

Evolution induced catastrophe in a nonlinear dynamical model of material failure

In order to study the failure of disordered materials, the ensemble evolution of a nonlinear chain model was examined by using a stochastic slice sampling method. The following results were obtained. (1) Sample-specific behavior, i.e. evolutions are different from sample to sample in some cases under the same macroscopic conditions, is observed for various load-sharing rules except in the globally mean field theory. The evolution according to the cluster load-sharing rule, which reflects the interaction between broken clusters, cannot be predicted by a simple criterion from the initial damage pattern and even then is most complicated. (2) A binary failure probability, its transitional region, where globally stable (GS) modes and evolution-induced catastrophic (EIC) modes coexist, and the corresponding scaling laws are fundamental to the failure. There is a sensitive zone in the vicinity of the boundary between the GS and EIC regions in phase space, where a slight stochastic increment in damage can trigger a radical transition from GS to EIC. (3) The distribution of strength is obtained from the binary failure probability. This, like sample-specificity, originates from a trans-scale sensitivity linking meso-scopic and macroscopic phenomena. (4) Strong fluctuations in stress distribution different from that of GS modes may be assumed as a precursor of evolution-induced catastrophe (EIC).

Prevalencia de vacas gestadas sacrificadas en el Matadero PROINCASA Tipitapa, Managua en el periodo de Diciembre 2008 a Junio 2009

El presente estudio se realizó con el objetivo de Generar información útil para determinar el impacto económico del sacrificio de hembras gestantes en el Matadero PROINCASA, Tipitapa, Managua, Nicaragua. Se realizó un estudio observacional de tipo transversal que mide la prevalencia de vacas gestadas sacrificadas en el matadero PROINCASA, Tipitapa, Managua, y por eso suelen denominarse estudios de prevalencia. Se tomaron todas las hembras sacrificadas en el matadero desde Diciembre 2008 a Junio 2009. Obteniéndose los siguientes resultados, De un total de 7,977 animales sacrificados de ambos sexos, correspondió a hembras un 89% y de estas la prevalencia de gestantes fue del 44%. Del total de vacas gestantes sacrificadas, el 44% se encontraban en tiempo de gestación de 0 a 3 meses, el 33% se encontraban en tiempo de gestación de 3 a 6 meses y el 23% se encontraban en tiempo de gestación de 7 a 9 meses. Las patologías encontradas fueron Quistes Ováricos, Cervix Quebrada, Infantilismo, Maceración Fetal, Cervicitis y Piometra por orden de importancia. Se deja de percibir la cantidad de $7,635,964 dólares americanos, por sacrificar hembras gestantes y disminución del hato nacional de 15,293 animales.

Flow Characteristics of Non-Polar Organic Liquids with Small Molecules in a Microchannel

用去离子水及有机液体在内径约为25μm的石英圆管内进行了流量特性实验.液体分子量范围为18～160,动力黏性系数的范围为0.5～1 mPa.s.实验雷诺数范围为Re<8.所用有机液体为:四氯化碳、乙基苯及环己烷都是非极性液体,其分子结构尺度小于1 nm.实验结果表明,在定常层流条件下,圆管内的液体流量与两端压力差成正比,其压力-流量关系仍符合经典的Hagen-Poiseuille流动.这说明非极性小分子有机液体在本实验所用微米尺度管道中其流动规律仍符合连续介质假设.鉴于微尺度流动实验的特殊性,文中还介绍了微流动实验装置,分析了微尺度流动测量误差来源及提高测量精度的措施.

Efecto de la distancia de siembra en el rendimiento de dos variedades de tabaco (Nicotiana tabacum L.) burley

Durante el ciclo agrícola 1993-1994, en la localidad de Estelí, se realizó un experimento para determinar el efecto de tres distancias de siembra (0.51 m x 1.0 m, 0.56 m x 1.0 m y 0.61 m x 1.0 m) sobre los rendimientos en cantidad y calidad de dos variedades de tabaco (Nicotiana tabacum L.) Burley KY-17 y Burley TN-90. Se empleó un diseño experimental de Bloques al Azar con arreglo combinatorio bifactorial. Los resultados obtenidos no demostraron diferencias significativas en los rendimientos por unidad de área (kg/ha) ni de calidad entre las dos variedades de tabaco y las diferentes distancias de siembra estudiadas. Se logró determinar una relación directa entre el rendimiento en peso seco por unidad de área y el aumento de la densidad poblacional como producto de las distancias de siembra entre planta y planta. La mejor relación beneficio/costo se estableció con la interacción Burley TN-90 con estructura de siembra 0.51 m x 1.0 m.

Effects of surface roughness on airframe noise

The generation of sound by turbulent boundary layer flow at low Mach number over a rough wall is investigated by applying the theoretical model which describes the scattering of the turbulence near field into sound by roughness elements. Attention is focused on the numerical method to approximately quantify the absolute level of the roughness noise radiated to far field. Empirical models for the source statistics are obtained by scaling smooth-wall data through increased skin friction velocity and boundary layer thickness for the rough surface. Numerical integration is performed to determine the roughness noise, and it reproduces the spectral characteristics of the available empirical formula and experimental data. Experiments are conducted to measure the radiated sound from two rough plates in an open jet by four 1/2'' free-field condenser microphones. The measured noise spectra of the rough plates are above that of a smooth plate in 1-2.5 kHz frequency and exhibits encouraging agreement with the predicted spectra. Also, a phased microphone array is utilized to localize the sound source, and it confirms that the rough plates generate higher source strengthes in this frequency range. A parametric study illustrates that the roughness height and roughness density significantly affect the far-field radiated roughness noise with the roughness height having the dominant effect. The estimates of the roughness noise for a Boeing 757 sized aircraft wing show that in high frequency region the sound radiated from surface roughness may exceed that from the trailing edge, and higher overall sound pressure levels for the roughness noise are also observed.

El ciclo ceremonial de la batalla de La Higueruela (1431)

Resumen: La batalla de La Higueruela (1431) fue el éxito militar más importante en la frontera granadina de Juan II de Castilla. Más allá del hecho militar, este acontecimiento fue una ocasión para el desarrollo de varias ceremonias de la realeza. El estudio de estas ceremonias ofrece un interesante reflejo de las relaciones políticas dentro de la corte castellana.

Competitive adsorption between bovine serum albumin and collagen observed by atomic force microscope

Atomic force microscopy (AFM) was used to study the competitive adsorption between bovine serum albumin (BSA) and type I collagen on hydrophilic and hydrophobic silicon wafers. BSA showed a grain shape and the type I collagen displayed fibril-like molecules with relatively homogeneous height and width, characterized with clear twisting (helical formation). These AFM images illustrated that quite a lot of type I collagen appeared in the adsorption layer on hydrophilic surface in a competitive adsorption state, but the adsorption of BSA was more preponderant than that of type I collagen on hydrophobic silicon wafer surface. The experiments showed that the influence of BSA on type I collagen adsorption on hydrophilic surface was less than that on hydrophobic surface.

Alguns comentários sobre alterações da lei nº 10.267/01

Consultoria Legislativa - Área VI - Direito Agrário e Política Fundiária.