Polyethylene stibinite phosphate esters: Novel flame-retardant plasticizers for PVC

A new series of multielement flame-retardant plasticizers containing polyethylene stibinite phosphate esters have been prepared by bulk polymerization from ethylene glycol with various antimony (III) aryloxydichlorides and arylphosphorodichloridates possessing various combinations of substituent [Cl,Br,NO2]. All the polymers are pink-coloured viscous fluids. They were characterized by inherent viscosity, density, IR, H-1, C-13 and P-31 NMR spectroscopy. The thermal behaviour of the polymers was compared by thermogravimetric analysis and correlated with their structures. The flammability studies were carried out by the limiting oxygen index test. The polymers containing P, Sb, N and Pr elements in their backbone show superior thermal-and flame-retardant characteristics than the other polymers. A comparative study was carried out with one of the synthesized polymers as a polymeric flame-retardant additive to plasticized PVC. The results showed improved LOI and mechanical properties to that of the conventional flame-retardant additive composition. (C) 1997 Elsevier Science Ltd.

Metal-insulator transition in a degenerate Hubbard model

We have studied the metal-insulator transition at integer fillings in a triply degenerate Hubbard model using the Lanczos method. The critical Coulomb interaction strength U-c, is found to depend strongly on the band filling, with U-c similar to root 3 W (W is the bandwidth) at half filling for this case with threefold degeneracy. We discuss the implications of our results on metal-insulator transitions in strongly correlated systems in general, and on the unusual electronic ground state of the alkali-metal-doped fullerenes, in particular. [S0163-1829(99)11003-8].

Magnetically tunable nonlinear current-voltage characteristics in oxygen deficient manganite perovskites

(La0.667Ca0.333Mn1-xMO3-delta)-O-x (M = Mg, Li or Re) exhibit insulating behaviour and nonlinear current-voltage (J-E) relationship with voltage-limiting characteristics at temperatures below the ferromagnetic transition (T-c). The high current region is set in at field strengths <60 V/cm. Nonlinearity exponent, alpha in the relation J = kE(alpha) increases inversely with temperature. In presence of an external magnetic field, the J-E curves show higher current density at lower field strengths. Microstructural studies indicate that there is no segregation of secondary phases in the grain boundary regions. There is remarkable changes in p(T) as well as J-E curves with the grain size. Annealing studies in lower p(O2) atmospheres indicate that there is significant out-diffusion of oxygen ions through the grain boundary layer (GBL) regions creating oxygen vacancies in the GBL regions. The concentration of Mn4+ ions is lowered at the GBL due to oxygen vacancies, reducing the probability of hopping and resulting in insulating behaviour. Therefore an insulating barrier is introduced between two conducting grains and the carrier motion between the grains is inhibited. Thus below T-c, where sufficient increase in resistivity is observed the conduction may be arising as a result of spin dependent tunneling across the barrier. External electric field lowers the barrier height and establishes carrier transport across the barrier. Above certain field strength, barrier height diminishes significantly and thereby allowing large number of carriers for conduction, giving rise to highly nonlinear conductivity. (C) 2002 Elsevier Science B.V. All rights reserved.

Hydrolysis of Ammonia Borane as a Hydrogen Source: Fundamental Issues and Potential Solutions Towards Implementation

In todays era of energy crisis and global warming, hydrogen has been projected as a sustainable alternative to depleting CO2-emitting fossil fuels. However, its deployment as an energy source is impeded by many issues, one of the most important being storage. Chemical hydrogen storage materials, in particular B?N compounds such as ammonia borane, with a potential storage capacity of 19.6 wt?% H2 and 0.145 kg?H?2?L-1, have been intensively studied from the standpoint of addressing the storage issues. Ammonia borane undergoes dehydrogenation through hydrolysis at room temperature in the presence of a catalyst, but its practical implementation is hindered by several problems affecting all of the chemical compounds in the reaction scheme, including ammonia borane, water, borate byproducts, and hydrogen. In this Minireview, we exhaustively survey the state of the art, discuss the fundamental problems, and, where applicable, propose solutions with the prospect of technological applications.

Functional analysis of ultra high information rates conveyed by rat vibrissal primary afferents

Sensory receptors determine the type and the quantity of information available for perception. Here, we quantified and characterized the information transferred by primary afferents in the rat whisker system using neural system identification. Quantification of ``how much'' information is conveyed by primary afferents, using the direct method (DM), a classical information theoretic tool, revealed that primary afferents transfer huge amounts of information (up to 529 bits/s). Information theoretic analysis of instantaneous spike-triggered kinematic stimulus features was used to gain functional insight on ``what'' is coded by primary afferents. Amongst the kinematic variables tested-position, velocity, and acceleration-primary afferent spikes encoded velocity best. The other two variables contributed to information transfer, but only if combined with velocity. We further revealed three additional characteristics that play a role in information transfer by primary afferents. Firstly, primary afferent spikes show preference for well separated multiple stimuli (i.e., well separated sets of combinations of the three instantaneous kinematic variables). Secondly, neurons are sensitive to short strips of the stimulus trajectory (up to 10 ms pre-spike time), and thirdly, they show spike patterns (precise doublet and triplet spiking). In order to deal with these complexities, we used a flexible probabilistic neuron model fitting mixtures of Gaussians to the spike triggered stimulus distributions, which quantitatively captured the contribution of the mentioned features and allowed us to achieve a full functional analysis of the total information rate indicated by the DM. We found that instantaneous position, velocity, and acceleration explained about 50% of the total information rate. Adding a 10 ms pre-spike interval of stimulus trajectory achieved 80-90%. The final 10-20% were found to be due to non-linear coding by spike bursts.

Fish distribution dynamics in the Aghanashini estuary of Uttara Kannada, west coast of India

Fish diversity (77 species) in the Aghanashini River estuary of the Indian west coast is linked to variable salinity conditions and zones I, II and III for high, medium and low salinity respectively. Zone I, the junction between Arabian Sea and the estuary, had all species in yearly succession due to freshwater conditions in monsoon to high salinity in pre-monsoon. The medium (zone II) and low (zone III) salinity mid and upstream portions had maximum of 67 and 39 fish species respectively. Maintenance of natural salinity regimes in estuary, among other ecological factors, is critical for its fish diversity.

Orientation Selection and Microstructural Evolution in Directionally Solidified Tb0.3Dy0.7Fe1.95

Tb0.3Dy0.7Fe1.95 alloy was directionally solidified by using a modified Bridgman technique at a wide range of growth rates of 5 to 100 cm/h. The directionally grown samples exhibited plane front solidification morphology up to a growth rate of 90 cm/h. Typical island banding feature was observed closer to the chilled end, which eventually gave rise to irregular peritectic coupled growth (PCG). The PCG gained prominence with an increase in the growth rate. The texture study revealed formation of strong aOE (c) 311 > texture in a lower growth rate regime, aOE (c) 110 > and ``rotated aOE (c) 110 > aEuroe in an intermediate growth regime, and aOE (c) 112 > in a higher growth rate regime. In-depth analysis of the atomic configuration of a solid-liquid interface revealed that the growth texture is influenced by the kinetics of atomic attachment to the solid-liquid interface, which is intimately related to a planar packing fraction and an atomic stacking sequence of the interfacial plane. The mechanism proposed in this article is novel and will be useful in addressing the orientation selection mechanism of topologically closed packed intermetallic systems. The samples grown at a higher growth rate exhibit larger magnetostriction (lambda) and d lambda/dH owing to the absence of pro-peritectic (Tb,Dy)Fe-3 and formation of aOE (c) 112 > texture, which lies closer to the easy magnetization direction (EMD).

表面张力效应对空间和地面合金凝固行为的影响

为揭示空间微重力条件下合金的凝固特性，分别于1990年及1996年两次利用我国返回式科学试验卫星，研究了Al-Al_3Ni,Al_RE等共晶和Al-Bi偏晶合金的空间凝固行为。文章结合流体物理理论和两次卫星搭载的实验结果，着重讨论了合金中的表面张力梯度驱动对流和熔滴的Marangonic迁移现象及其在偏晶合金地面生产中的应用。

Squeeze-film Effects in MEMS Devices with Perforated Plates for Small Amplitude Vibration

Squeeze-film effects of perforated plates for small amplitude vibration are analyzed through modified Reynolds equation (MRE). The analytical analysis reckons in most important influential factors: compressibility of the air, border effects, and the resistance caused by vertical air flow passing through perforated holes. It is found that consideration of air compressibility is necessary for high operating frequency and small ratio of the plate width to the attenuation length. The analytical results presented in this paper agree with ANSYS simulation results better than that under the air incompressibility assumption. The analytical analysis can be used to estimate the squeeze-film effects causing damping and stiffness added to the system. Since the value of Reynolds number involved in this paper is low (< 1), inertial effects are neglected.

Manejo del picudo negro (Cosmopolites sordidus Germar) aplicando el hongo (Beauveria bassiana Bals.,) en el cultivo del plátano

Se estableció un experimento de campo en el cultivo del plátano (Musa paradisiaca L.) en la localidad de Las Crucitas, Niquinohomo, Nicaragua, en la que se probaron diferentes momentos de aplicación de Beauveria bassiana Bals. En los meses de junio, agosto y octubre, donde se disminuyeron las poblaciones de adulto de picudo negro del plátano (Cosmopites sordidus Germar), estos resultados en los dos años de trabajo también muestran que realizándose de manera sistemática las aplicaciones del hongo, la población resultó ser mas baja en el segundo año. Con respecto a las variables número de plantas caídas, en el segundo año fue menor que en el primer año, mientras que se encontraron mayor número de galerias en los cormos provocados por las larvas de picudo. Sin embargo, se muestreo el suelo para determinar la presencia de nématodos, encontrándose que estos eran la principal causa de la caída de las plantas. Para las variables de la cosecha se encontró diferencias numéricas con relación al segundo año de inicio de la aplicación de los tratamientos, puesto que la tendencia es aumentar los valores de algunos parámetros aunque no se observa claramente el efecto de los tratamientos en particular.

Comportamiento agronómico de dos cultivares clonales de quequisque (Xanthosoma sagittifolium (L) schott), en condiciones de Yolaina, Nueva Guinea, primera 2000-2001

Con el objetivo de caracterizar agronómicamente dos genotipos de quequisque (Xanthosoma sagittiolium (L) Schott), se estableció un ensayo en condiciones de campo de Yolaina, municipio de Nueva Guinea, en época de primera del 7 junio del 2000 al 23 de marzo del 2001 se evaluó las variables morfológicas, fenológicas, de rendimiento y la presencia de enfermedades (virus) en los cultivares Masaya (My) y Nueva Guinea (NG). Se utilizó un diseño de bloque completos al azar (BCA), con 4 bloques y 2 tratamiento por bloque. La parcela experimental estuvo conformada por 6 surcos, con una longitud de 12 m. La distancia de siembra de 1m entre surco y 0.60 m entre planta para un total de 20 plantas por surco y 240 plantas por parcela, para un total de 960 plantas en el ensayo. El área total del experimento fue de 729m2, el área de tratamiento de 144m2 y los dos surcos centrales representaron la parcela útil, sin incluir las primeras 5 plantas en ambos extremos. Las variables evaluadas fueron: altura de planta (cm), área foliar (cm 2), número de hojas, número de hijos y grosor de pseudotallo (cm), de rendimiento: número de cormelos por planta, peso de cormelos totales por planta (g), peso promedio de cormelo (g), largo de cormelo (cm) y diámetro de cormelo (cm). Los eventos morfológicos velocidad de brotación y momento de cosecha: presencia de enfermedades (DMV). A las medias de los datos se les realizó un ANDEVA y separación de medias con la prueba de rangos múltiples de Duncan. Indicando que los cultivares presentaron diferencias estadísticas entre ellas en las variables morfológicas habiendo obtenido el genotipo My los mayores valores en: altura de planta con (70.3 cm), área foliar con (1,540 cm2), número de hojas con (3.79), grosor de pseudotallo por planta (1,540 cm) y para el número de brotes el genotipo NG obtuvo los mayores valores con (0.172). En los componentes de rendimiento el genotipo NG reportó los mayores valores: número de cormelo por planta (3.84), peso de cormelo por planta (464.8 g), largo de cormelo (12.34 cm) y el genotipo My reportó los mayores valores en diámetro de cormelo con (5.19 cm) y peso promedio (130.5 g). Se realizaron 3 conteos visuales de la presencia del virus. Se encontró tendencia a aumentar y disminuir el porcentaje de plantas con presencia del DMV con el aumento de los días después de la siembra. El genotipo My reportó un máximo de (27.7%) y NG (25.3%) a los 76 dds. En los eventos fenológicos la velocidad de brotación y la traslocación temprana de nutrientes (número de hojas (3.56), reducción del área foliar (1,085) y la presencia de cormelos con las yemas apicales y axilares brotadas (41.73%) y con presencia de raíces en crecimiento con (78.26%) al momento de la cosecha, con esto se demostró que el cultivar NG fue más precoz que el My.

Properties of a-C:H films deposited from a methane electron cyclotron wave resonant plasma

An electron cyclotron wave resonant methane plasma discharge was used for the high rate deposition of hydrogenated amorphous carbon (a-C:H). Deposition rates of up to ∼400 Å/min were obtained over substrates up to 2.5 in. in diameter with a film thickness uniformity of ∼±10%. The deposited films were characterised in terms of their mass density, sp3 and hydrogen contents, C-H bonding, intrinsic stress, scratch resistance and friction properties. The deposited films possessed an average sp3 content, mass density and refractive index of ∼58%, 1.76 g/cm3 and 2.035 respectively.Mechanical characterisation indicated that the films possessed very low steady-state coefficients of friction (ca. 0.06) and a moderate shear strength of ∼141 MPa. Nano-indentation measurements also indicated a hardness and elastic modulus of ∼16.1 and 160 GPa respectively. The critical loads required to induce coating failure were also observed to increase with ion energy as a consequence of the increase in degree of ion mixing at the interface. Furthermore, coating failure under scratch test conditions was observed to take place via fracture within the silicon substrate itself, rather than either in the coating or at the film/substrate interface. © 2003 Elsevier B.V. All rights reserved.

Aplicabilidade da teoria do desvio de poder no controle da constitucionalidade de atos legislativos : contornos, limites e superação pela teoria dos princípios

Consultoria Legislativa - Área VIII - Área de Direito Administrativo e de Administração Pública.