Electrochemical reduction of indigo in fixed and fluidized beds of graphite granules

Reducing agents required in the dyeing process for vat and sulfur dyes cannot be recycled and lead to problematic waste products. The electrochemical reduction of indigo on a fixed bed cathode consisting of graphite granules has been investigated by spectrophotometric experiments in laboratory cells. Experiments yield information about the kinetics and show the possibility of this process for production of water soluble leuco indigo, which offers environmental benefits. The influence of noble metals deposited on the granules and of different pretreatment methods of the graphite is demonstrated. In addition, the immobilization of quinoid molecules on the graphite surface has been investigate

Direct electrochemical reduction of indigo: process optimization and scale-up in a flow cell

Reducing agents required in the dyeing process for vat and sulfur dyes cannot be recycled, and lead to problematic waste products. Therefore, modern economical and ecological requirements are not fulfilled. The industrial feasibility of the direct electrochemical reduction of indigo as a novel method has been determined and a preliminary optimization of electrolytic conditions was performed using a laboratory-scale flow-cell system. The role of current density, pH, temperature and the rate of mass transport are discussed. The influence of particle size reduction by the application of ultrasound is critically considere

Mechanical and SEM analysis of artificial comet nucleus samples

Since 1987 experiments dealing with comet nucleus phenomena have been carried out in the DFVLR space simulation chambers. The main objective of these experiments is a better understanding of thermal behavior, surface phenomena and especially the gas dust interaction. As a function of different sample compositions and exposure to solar irradiation (xenon-bulbs) crusts of different hardness and thickness were measured. The measuring device consists of a motor driven pressure foot (5 mm diameter), which is pressed into the sample. The applied compressive force is electronically monitored. The microstructure of the crust and dust residuals is investigated by scanning electron microscopy (SEM) techniques. Stress-depth profiles of an unirradiated and an irradiated model comet are given

Modifications of comet materials by the sublimation process: Results from simulation experiments

An active comet like comet Halley loses by sublimation a surface layer of the order of 1 m thickness per perihelion passage. In situ measurements show that water ice is the main constituent which contributes to the gas emission although even more volatile species (CO, NH3, CH4, CO2 etc.) have been identified. Dust particles which were embedded in the ices are carried by the sublimating gases. Measurements of the chemical composition of cometary grains indicate that they are composed of silicates of approximate chondritic composition and refractory carbonaceous material. Comet simulation experiments show that significant modifications of cometary materials occur due to sublimation process in near surface layers which have to be taken into account in order to derive the original state of the material

The silence of self-knowledge

Gareth Evans famously affirmed an explanatory connection between answering the question whether p and knowing whether one believes that p. This is commonly interpreted in terms of the idea that judging that p constitutes an adequate basis for the belief that one believes that p. This paper formulates and defends an alternative, more modest interpretation, which develops from the suggestion that one can know that one believes that p in judging that p

Effect of varying material anisotropy on critical current anistropy in vicinal YBa2_2Cu3_3O7−δ_{7-\delta} thin films

The high $T_{c}$ cuprate superconductors are noted for their anisotropic layered structure, certain of these materials indeed tend toward the limit of a Lawrence-Doniach superconductor. However, YBa$_2$Cu$_3$O$_{7-\delta}$ has a smaller anisotropy than would be expected from its interlayer spacing. This is due to the cuprate chains in the structure. To investigate the influence of the chain oxygen on transport properties critical current versus applied field angle measurements were performed on fully oxygenated and de-oxygenated YBa$_2$Cu$_3$O$_{7-\delta}$ thin films and optimally oxygenated Y$_{0.75}$Ca$_{0.2}$Ba$_2$Cu$_3$O$_{7-\delta}$ thin films. The films were grown on 10$^{\circ}$ mis-cut SrTiO$_3$ substrates to enable the intrinsic vortex channelling effect to be observed. The form of the vortex channelling minimum observed in field angle dependent critical current studies on the films was seen to depend on film oxygenation. The vortex channelling effect is dependent on a angular dependent cross-over to a string-pancake flux line lattice. The results obtained appear to be consistent with the prediction of Blatter et al. [Rev. Mod. Phys., 66 (4): 1125 (1994)] that increased superconducting anisotropy leads to the kinked string-pancake lattice existing over a smaller angular range.Comment: To be submitted to AP

Fractalization of Torus Revisited as a Strange Nonchaotic Attractor

Fractalization of torus and its transition to chaos in a quasi-periodically forced logistic map is re-investigated in relation with a strange nonchaotic attractor, with the aid of functional equation for the invariant curve. Existence of fractal torus in an interval in parameter space is confirmed by the length and the number of extrema of the torus attractor, as well as the Fourier mode analysis. Mechanisms of the onset of fractal torus and the transition to chaos are studied in connection with the intermittency.Comment: Latex file ( figures will be sent electronically upon request):submitted to Phys.Rev. E (1996

DERMATOFITOSIS. ETIOLOGIA Y SUSCEPTIBILIDAD ANTIFUNGICA “IN VITRO” EN TRES CENTROS HOSPITALARIOS DE SANTIAGO (CHILE)

Con el objetivo de determinar la frecuencia de dermatofitos en lesiones sospechosas de micosis y evaluar su susceptibilidad “in vitro” frente a Clotrimazol (CLZ), Itraconazol (ITZ), Griseofulvina (GRI), Fluconazol(FCZ) y Terbinafina (TBF), se recolectaron 175 muestras (piel, pelo y uñas ) y datos epidemiológicos de cada paciente. El diagnóstico micológico se realizó mediante: un examen directo con KOH al 20% y cultivo en agar Sabouraud y Lactrimel, incubados a 25º y 37º por 21días. La susceptibilidad “in vitro” se realizó por el método de microdilución en caldo según recomendaciones NCCLS (documento M38-P), determinándose CIM 50 y CIM90.El examen directo fue positivo en e l 73,7% (n=129) de las muestras y el cultivo en 66,3% (n=116), aumentando a un 80,6% (n=141) al usar ambas técnicas. Los agentes aislados correspondieron a Trichophytonrubrum (81%), T. mentagrophytes(14,7%) y Microsporum canis (4,3%). En 110 cepas, la CIM50 para FCZ fue 0,25 μg/mL y 0,03 μg/mL para GRI, ITZ, CLZ y TBF. La CIM90 de FCZ fue 2,0 μg/mL, 0,12 μg/mL para ITZ y 0,06 μg/mL para CLZ, GRI y TBF.En general, los antifúngicos probados fueron activos frente a las cepas aisladas, excepto 2 cepas que mostraron CIM elevadas para ITZ.