Showing papers on "Active surface published in 1995"

Microprecipitation of nanoparticulate pharmaceutical agents using surface active material derived from similar pharmaceutical agents

Abstract: This invention describes the preparation of nanoparticulate pharmaceutical agent dispersion via a process that comprises the dissolution of the said pharmaceutical agent in an alkaline solution and then neutralizing the said solution with an acid in the presence of suitable surface-modifying, surface-active agents to form a fine particle dispersion of the said pharmaceutical agent. A combination of surface active surface modifying agents comprising a nonionic surface active substance and an anionic surface active material having a chemical structure which is at least on a molecular basis 75% similar to the pharmaceutical agent is used. This process is preferably followed by steps of diafiltration clean-up of the dispersion and then concentration of it to a desired level. This process of dispersion preparation leads to microcrystalline particles of Z-average diameters smaller than 400 nm as measured by photon correlation spectroscopy. Various modifications of precipitation schemes are described, many of which are suitable for large-scale manufacture of these agent dispersions.

Surface modified bimetallic catalysts: preparation, characterization, and applications

Abstract: The basic principles of the preparation of surface modified catalysts, the problems of characterization of the metals, and models describing their active surface are considered. The characteristics of surface transformations and the distribution of modifying elements are defined by the ratio of reactivity/diffusivity under the conditions of the surface modification. The state of the metals (Ni, Pd, Cr, Si, Sn) is characterized by using electron spectroscopy for chemical analysis, laser microprobe analysis, extended X-ray absorption fine structure, Mossbauer spectroscopy as well as magnetization and chemisorption. The high activity, selectivity, and tolerance to common poisons are demonstrated for catalysts based on supported nickel and palladium in hydrogenation and dehydrogenation reactions.

Stable blister free flexible graphite and method

Abstract: A stable blister free flexible graphite is formed in accordance with the present invention by performing two chemical reactions including a first step of high temperature heat treatment which converts the active carbon surface from hydrophilic to hydrophobic and generates active surface sites and a second step of exposing the heat treated graphite to a stabilizing reagent for stabilizing the active sites generated by the first step of high temperature heat treatment.

Electronically shielded solid state charged particle detector

Abstract: An electronically shielded solid state charged particle detector system having enhanced radio frequency interference immunity includes a detector housing with a detector entrance opening for receiving the charged particles. A charged particle detector having an active surface is disposed within the housing. The active surface faces toward the detector entrance opening for providing electrical signals representative of the received charged particles when the received charged particles are applied to the active surface. A conductive layer is disposed upon the active surface. In a preferred embodiment, a nonconductive layer is disposed between the conductive layer and the active surface. The conductive layer is electrically coupled to the detector housing to provide a substantially continuous conductive electrical shield surrounding the active surface. The inner surface of the detector housing is supplemented with a radio frequency absorbing material such as ferrite.

Hydrogenation of nitrotoluenes controlled by the electrochemical potential of the catalyst

Abstract: The hydrogenation of 2-nitrotoluene, 2,4-dinitrotoluene and 2,4,6-trinitrotoluene on Pd/C, Pt/C and Ni/SiO2 catalysts was investigated in a liquid phase batch reactor at pressures between 0.4 and 2.5 MPa. The reaction was controlled by regulating the substrate supply in such a way that the electrochemical potential of the catalyst and, consequently, the surface concentration of active hydrogen was kept at a constant level. The observed hydrogenation rate dependence on the concentration of active surface hydrogen shows that the hydrogen activation is at least one of the rate determining steps. Additionally, controlling the reaction by the potential of the catalyst allows one to prevent dangerous feed concentrations and fast deactivation, too.

Edge die bond semiconductor package

Abstract: An edge die bond semiconductor package including a semiconductor die having an active major surface and a mounting edge substantially orthogonal to the active surface, a base having a mounting surface, and material affixing the mounting edge of the semiconductor die to the mounting surface of the base.

Mercury thread electrode

Abstract: An improved mercury electrode for electrochemical analysis is formed by a small diameter thread of liquid mercury contained within an inert tube which, at one point along its length, has an short, fixed length of thin walled tubular semipermeable membrane surrounding and forming the electrodes' active surface in order to prevent or reduce fouling of the surface while allowing the mercury thread to be advanced through the membrane to expose a fresh active surface whenever desired.

Active centers on the surface of thermoactivated silica. Their reactivity toward organoaluminum compounds

Abstract: Interaction between organoaluminum compounds (triethylaluminum, ethoxydiethylaluminum, and diethoxyethylaluminum) and the surface of silica activated at various temperatures (200–800 °C) was studied by IR spectroscopy, mass spectrometry, and quantum chemistry. Formation of structural silanon defects on the surface of silica activated at 800 °C was considered. It was established that the fraction of terminal silanol groups involved in the interaction with organoaluminum compounds on the surface of silica thermoactivated above 600 °C is low, and siloxane bonds and structural surface defects play a determining role. The thermodynamic favorability of coordination of organoaluminum compounds on these active surface centers is shown. The structure and routes of decomposition of aluminum-containing surface intermediates were studied.

Simulation of the effect of fractional dimension on tin-oxide-based gas sensors

Abstract: The effect of the fractional dimension of a tin-oxide surface on the sensing mechanism is studied by means of Monte Carlo simulation in the case of CO. The dimension of the active surface has been found to be connected to both the sensitivity and the recovery rate of sensor resistance after CO removal. A method of producing fractal surfaces with different dimensions is presented. Experimentally observed large recovery times are explained on the basis of a small fractal dimension. On the other hand, the observed instabilities of tin-oxide-based thick-film gas sensors are explained by considering the change of surface dimension caused by local reduction of tin oxide in the presence of CO.

Distance and speed measuring apparatus

Abstract: PURPOSE:To achieve a smaller size and a lower cost of the apparatus by performing a fast modulation of a semiconductor laser part alone with a low output integrated with a light amplifier part. CONSTITUTION:An n-Al0.5Ga0.5As clad layer 2, a multi-weight well active layer 3, p-Al0.5Ga0.5As clad layer 4 and p-GaAs contact layer 5 are laminated sequentially, parts of the layers 4 and 5 are etched to let the n-GaAs block layer 8 grow and subsequently. a p-Al0.5Ga0.5As buried layer 9 and a p-GAs cap layer 10 are formed to reduce a series resistance. Then. after an Au electrode 11 is formed on both sides of a wafer and a surface 13 vertical to an active surface is formed on a boundary of a dry etched layer 12 to integrate a laser part and an amplifier part. With such an arrangement, a laser part with a low output requiring a pulse driving can be driven easily with a short pulse by a drive current of 100-200mA or and the amplifying of a light pulse generated with the amplifier part facilitates the obtaining of a high output pulse of several watt.

Polygonal mirror, device and method for its production

Abstract: The invention relates to a polygonal mirror which comprises mirror segments which are cemented in a defined manner on the outer surface of a carrier, are positioned at an angle relative to each other and in each case have a cementing surface and an active surface. The polygonal mirror is characterised in that the carrier (4) has the design of a circular cylinder, at least one outer circular ring (19) of a cover surface (13) of the carrier (4) being positioned at a defined angle relative to the outer surface (18) of the carrier (4), in that the mirror segments (3) have, on their inner side which forms the cementing surface (9), a radius (r2) which is larger than the radius (r1) of the outer surface (18) by the width of a cementing gap, in that the active surface (10) of each mirror segment (3) is divided, in the direction of the outer circumferential diameter, into a first partial surface which is an interference surface (17), and into a second partial surface which is a mirror surface (16), and in that the interference surface (17) of each mirror segment (3) is aligned relative to an aligning surface (11) on a side surface of the mirror segment (3) at an angle which is identical for all mirror segments (3) of the polygonal mirror. The invention further relates to a device and a method for producing the polygonal mirror.

A method for air purification

Abstract: A process for purifying gaseous hydrocarbon emissions-containing air in a Abluftleitkanal, wherein the Abluftleitkanal comprises several successive in the flow direction the following sections, wherein the exhaust air in a first section of the air duct to UV radiation with a wavelength of preferably 254 nm to excite the hydrocarbons to higher energy levels and a wavelength of preferably 185 nm to the formation of ozone, molecular oxygen and radicals from the ozone and partial oxidation of the hydrocarbon molecules is exposed in the gas phase, wherein a catalytic oxidation of the hydrocarbon molecules is effected on the active surface of a catalyst in a subsequent second section, wherein the hydrocarbon molecules adsorbed, then oxidised on the active surface by the additionally formed ozone and from the surface of the catalyst in the form of H wherein a control device is provided, which in dependence of the measured values ​​of spaced Abluftleitkanal sensors that detect the concentration of harmful substances, ...

Recording-reading magnetic head.

Abstract: not available for EP0380624Abstract of corresponding document: EP0350412A device made of magnetic material comprises a sintered magnetic material (1) in contact with an active surface of the device (which may be the active surface of a magnetic head). The device also includes a bonding layer (2), for example of silica, and a carbon layer (3). Application: magnetic recording heads, reading, and recording media.

Analysis of uncontrollable errors on the performance of a large segmented active surface reflector antenna for millimeter wavelengths

Abstract: Active surface telescopes have become a practical design choice for large reflector systems in which the main optical surface is replaced by a segmented surface with a control system for maintaining a perfect shape. The authors focus on one of the most interesting problems associated with this type of ground-based large active surface radio telescope. This is the effect produced by uncontrollable errors due to gravitational deformation of the antenna structure, and which the active surface control system is unable to compensate for. The impact of these errors must be carefully assessed. First, the authors present a study of the effects of random lateral displacements and uncontrollable rotations of the segments with respect to the nominal position for the purpose of comparison with systematic errors. Second, based on the results of deformation analysis of the antenna structures under gravitational load, the authors assess the effects on the LMT (Large Millimeter Telescope) antenna performance. An analysis of these systematic errors is presented in terms of antenna efficiency and radiation patterns, as a function of elevation.

Surface Modified Bimetallic Catalysts: Preparation, Characterization, and Applications

Abstract: The basic principles of the preparation of surface modified catalysts, the problems of characterization of the metals, and models describing their active surface are considered. The characteristics of surface transformations and the distribution of modifying elements are defined by the ratio of reactivity/diffusivity under the conditions of the surface modification. The state of the metals (Ni, Pd, Cr, Si, Sn) is characterized by using electron spectroscopy for chemical analysis, laser microprobe analysis, extended X-ray absorption fine structure, Mossbauer spectroscopy as well as magnetization and chemisorption. The high activity, selectivity, and tolerance to common poisons are demonstrated for catalysts based on supported nickel and palladium in hydrogenation and dehydrogenation reactions.