bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrogele: Verwendungsmöglichkeiten und thermodynamische Eigenschaften
Authors: Thiel Joachim , Maurer Gerd , Prausnitz John M.
Published: December 2004

Hydrogels are crosslinked macromolecules in which at least part of the network consists of hydrophilic groups. Hydrogels are widespread in nature; for example, plant and animal tissues consist mainly of hydrogels. They are becoming increasingly important in chemical engineering, e. g. as ion excahngers, in gel chromatography, and for dewatering. Hydrogels swell or shrink in aqueous solutions. Such swelling equilibria are the basis for most of their applications. This article surveys the applications and also the swelling behaviour of hydrogels. It covers both the termodynamic principles and methods for correlation of experimentally determined swelling equilibria for nonionic and ionic hydrogels. The swelling of a hydrogel results from the interplay of intermolecular interactions in aqueous, partly ionic polymer solutions on the one hand and elastic properties of polymeric networks on the other. It ist therefore hardly surprising that it is presently impossible to quantitatively predict phase equilibria and the swelling behaviour of such hydrogels from a few basic data. However, it is possible to describe the swelling of hydrogels with straightforward approaches reported in the literature if a number of the parameters of these approaches are adapted to experimentally determined swelling data.
Reaktorintegrierter Umweltschutz in der chemischen Produktion
Authors: Zlokarnik Marko
Published: December 2004

In the series of environmental protection measures avoidance‐utilisation‐disposal the greatest priority in the chemical industry is given to the first, particularly since it is the chemical reaction which predetermines the nature and extent of subsequent work‐up steps and the environmental burden. This reactor‐integrated environmental protection leads to a process reappraisal which is divided into searches for alternative synthetic routes, reactants, reaction media, and catalysts. However, one of the principal tasks concerns reexamination of the thermodynamics and kinetics, not only to ensure optimised concentration and temperature control but also to examine the possibility of integrating separation operations during the course of reaction with the aim of shifting equilibria.
Wärmeaustauscher aus nichtmetallischen Werkstoffen, insbesondere für korrosive Medien und Rauchgase
Authors: Suhr Ludwig
Published: December 2004

Corrosion‐resistant heat exchangers made of plastics can open up a new field of heat recovery from power station exhaust gases, even below the dew point of sulphuric acid. This article reports about plant constructed and experience gained. In addition: special heat exchanger geometries for increasing power generation efficiency and avoiding acid aerosols are also presented.
Berechnung und Modellierung komplexer Phasen‐ und Reaktionsgleichgewichte in wäßrigen Elektrolytlösungen
Authors: Luckas Michael
Published: December 2004

In many natural and industrial processes the thermodynamic properties of aqueous electrolyte solutions play an important role. Systems of interest are frequently characterized by a large number of components and possible reactions. Due to low solubility, some reaction products precipitate as solids. The thermodynamic modelling therefore implies the computation of simultaneous phase and chemical equilibria. The minimization of the Gibbs free energy and the K‐value method are powerful algorithms for numerical computation and permit the simulation of complex electrolyte systems. The behaviour of the liquid solution has to be described by suitable activity coefficient models.
Wiederaufladbare Zink/Luftsauerstoff‐Batterien
Authors: Haas Otto , Müller Stefan , Wiesener Klaus
Published: December 2004

Thanks to their high specific energy content, their cost‐favourable materials, and their good environmental compatibility, zinc/atmospheric oxygen batteries are of interest as energy source for electrotraction. Rechargeable zinc/atmospheric oxygen batteries are particularly suitable for this application. Use of atmospheric oxygen as reactant requires a semi‐open construction with stringent demands on the materials of the interface. The state of the art of variants of this battery type and the principal components (air‐diffusion electrode, zinc electrode, electrolyte) are presented in detail and discussed in this review article.
Optimierung verfahrenstechnischer Prozesse
Authors: Keil Frerich J. , Keil F. J.
Published: December 2004

Methoden der Optimierung werden in der Verfahrenstechnik häfig angewandt. Parameteridentifikation oder die Optimierung von Anlagenverschaltungen sind nur zwei Beispiele. Es werden Methoden der linearen und nichtlinearen Programmierung mit und ohne Nebenbedingung dargestellt, wobei eine Beschränkung auf in der Praxis besonders bewährte und verbreitete Verfahren erfolgt. Probleme der globalen Optimierung werden besprochen. Von den heuristischen Algorithmen wird die Linnhoff‐Pinch‐Methode erwähnt. Abschließend werden einige Anwendungen der Optimierung in der Verfahrenstechnik dargestellt.
Simulierte Gegenstromchromatographie – eine effiziente Technik zur Herstellung optisch aktiver Verbindungen im industriellen Maßstab
Authors: Schulte Michael , Kinkel Joachim N. , Nicoud Roger‐Marc , Charton Frédéric
Published: December 2004

Seit der Einführung stabiler chiraler stationärer Phasen (CSP) für die Hochleistungsflüssigchromatographie (HPLC) wird die präparative Chromatographie mehr und mehr als ein effizientes Verfahren zur Herstellung enantiomerenreiner Verbindungen im industriellen Maßstab angesehen. Die aus der Natur der klassischen Chromatographie resultierende Diskontinuität des Verfahrens, verlangt die Umwandlung des Prozesses in einen kontinuierlichen Betrieb. Fine intelligente Lösung dieses Problems ist mit der simulierten Gegenstrom‐chromatographie (SMB) gelungen. Diese ermöglicht die kontinuierliche Trennung eines Gemisches in zwei Komponenten mit hoher Reinheit und hoher Ausbeute. Zudem werden im Vergleich zur klassischen Chromatographie große Einsparungen an mobiler und stationärer Phase erzielt. Durch die Komplexität des Verfahrens bedingt, ist eine Simulation der chromatographischen Bedingungen erforderlich. Es werden das Prinzip des Verfahrens, die technischen Ausgestaltungen der Anlagen und das Verfahren zur Ermittlung der Betriebsparameter vorgestellt. An einem Beispiel wird ein Vergleich zwischen verschiedenen chromatographischen Verfahren durchgeführt.
Optimierungsstrategien für Batchreaktoren
Authors: Uhlemann Jens , Garcia Valérie , Cabassud Michel , Casamatta Gilbert
Published: December 2004

The successful development of a new fine chemical always comprises the selection of a synthesis process including the appropriate reactants, solvents, catalysts and so on. The operating strategy ‐ i.e. the operating conditions ‐ of the synthesis has to be established in order to obtain optimum quality. The present paper reviews the optimization strategies for batch reactors in fine chemical industries.
Tomographisches Messen der relativen Phasenanteile in zweiphasigen Strömungen fluider Phasen
Authors: Reinecke Nicolas , Boddem Martin , Petritsch Georg , Mewes Dieter
Published: December 2004

A new tomographic process measures the spatial phase fractions in slug flow and possesses high positional and temporal resolution. The measuring method is based on the electrical conductivity of the flowing fluids, which is measured between numerous parallel wires. The individual measurements are directly proportional to the relative liquid content. With the aid of an iterative reconstruction procedure they permit calculation of the phase fractions. The quality of reconstruction is improved by consideration of a priori knowledge. The temporal resolution is 0.009 s and the spatial resolution less than 0.1% of the flow cross‐section.
Extraktion – ein historischer Rückblick
Authors: Blass Eckhart , Liebl Thomas , Häberl Michael
Published: December 2004

The extraction of plants with the aid of water is one of the oldest techniques known to humankind for obtaining aromatic principles and medicaments from these sources. Extraction vessels excavated in Mesopotamia can be dated back to around 3500 BC, and Sumerian clay tablets describing the preparation of medicaments which were found in the same region date from around 2100 BC. The Greek and Roman civilisations of antiquity inherited extraction together with other skills from their predecessors, and this knowledge was passed on to Christendom by Arabian scholars. Europe of the Middle Ages saw the development of pharmacy, medicine, and mining, as well as the sugar industry, all of which made active use of extraction with a wide range of solvents. Whereas technological applications of extraction were thus steadily increasing prior to the industrial revolution, the equipment used underwent hardly any changes up the end of the 18th century. It was only in the 19th century that active development of equipment, materials, and modes of operation started, while successful combination of theory and practice and treatment of extraction by the methods of engineering science had to wait until the 20th century. This article reports about equipment, solvents, and extraction processes up to the beginning of the present century, and places then in a political and sociological context.
Multifunktionale Reaktoren
Authors: Hoffmann Ulrich , Sundmacher Kai
Published: December 2004

In multifunctional reactors chemical and physical unit operations are carried out simultaneously. Traditionally chemical reaction engineering considers mass and heat transfer processes in combination with chemical reactions. However, the term multifunctional reactor points to an extended and more detailed view of process integration. By application of these reactors it is possible to save investment and/or operating costs, to meet environmentally relevant limits or to improve process safety. Mechanical and thermal unit operations are especially good candidates for integration with a chemical reaction step. In this contribution selected multifunctional reactors are presented, which were either adopted from the literature or are the subject of the authors' own research activities.
Rechnergestützte Problemlösungsstrategien in der mechanischen Flüssigkeits‐abtrennung
Authors: Uhlemann Jens
Published: December 2004

The decision‐making process in an expert group involved in solid‐liquid separations cannot be covered by a monolithic methodology or software. The analysis of typical problem‐solving processes shows the experts' knowledge requirements and turnover. According to the proposal in the present paper, these requirements are covered by a three‐tier computer‐based knowledge supply comprising databases, simulation programs and hypertexts. Software details of a typical simulation program for continuous vacuum filtration on belt filters are presented. In addition, a hypertext‐based electronic handbook on equipment scale‐up and design is described. This handbook represents an easy‐to‐use reference manual for empirical knowledge in the expert group. The above‐mentioned tools enhance work quality and efficiency in the expert group; knowledge is pre‐served and easily accessible. The tools allow rapid training of newcomers. In a crossfunctional team effort, the solid‐liquid separation expert can provide rapidly well‐founded informations.
Technische Konzepte zum Recycling von Homogenkatalysatoren
Authors: Behr Arno
Published: December 2004

Techical Concepts for the Recycling of Homogeneous Catalysts. Homogeneous transition metal catalysis will only be used by industry if almost complete recycling of the expensive catalyst is guaranteed. This can be realized by using the liquid‐liquid two phase technique in which the catalyst stays in one liquid phase and the products in another. This contribution gives a general survey of this technique and different ideas for its technical realization.
Einsatz von Membrantrennverfahren in der chemischen Industrie
Authors: Knauf Rüdiger , Meyer‐Blumenroth Ulrich , Semel Joachim
Published: December 2004

Membran Processes in the Chemical IndustryIn the chemical industry (less so in the pharmaceutical industry), membrane technology is still at an early stage of acceptance. However, in this field too, it is gaining increasing importance as an innovative, reliable and, first and foremost, cost‐effective alternative to conventional processes. This trend is evidenced by a variety of new plants which have been installed in recent years, and also by the rapidly growing interest in this technology shown by production and design departments. This article gives an overview of the industrial importance of membrane processes in chemical and pharmaceutical production and also presents some typical examples of applications in this field by describing plants which have already been installed and are now in production.
Auslegung, Betrieb und ökonomische Betrachtung chromatographischer Trennprozesse
Authors: Strube Jochen , Schmidttraub Henner , Schulte Michael
Published: December 2004

Design, Operation, and Economics of Chromatographic SeperationsDue to increasing demands on pure products, there is a rapid growth of interest in chromatographic techniques. Those techniques are able to separate even compounds with small differences in their physico‐chemical properties. Continuous processes, e.g. simulated moving bed (SMB) chromatography, are a new field of growing interest for the production of pure pharmaceuticals and fine chemicals. These complex procedures cannot be optimized by a strategy based on trial and error. Therefore, rigorous modeling and efficient simulation/optimization techniques have to be used. This article presents an overview showing the advantages and disadvantages of different modeling approaches in theory and in practical applications to technical chromatographic separations.
Dioxine – Eine Aufgabe für die Umwelttechnik
Authors: Köser Heinz
Published: December 2004

Dioxins – Task for Environmental Engineering Two decades of the environmental history of dioxins, i.e. of PCCDs and PCDFs, are examined, with the main emphasis being placed on developments in Germany. After a brief consideration of the important, environmentally relevant properties of dioxins, interest is focussed on the course of the Seveso incident of 1976. The environmental effects of dioxins observed in Seveso received global publicity. In the following years our knowledge of the analysis and toxicology of this group of substances greatly improved and the production of dioxins in the aromatics sector of the chemical industry was drastically reduced. In the 1980s, discussions concentrated on the formation of dioxins in waste incineration. The results obtained during this period led to the present situation in which waste incineration is no longer a significant source of dioxin emission in Germany. The greatest known source of dioxins in Germany is in the metallurgical industry. By the year 2000 this dioxin source will also have been largely eliminated.
Modellierung und effektive numerische Simulation von chromatographischen Trennprozessen im SMB‐Betrieb
Authors: Klatt Karsten‐Ulrich
Published: December 2004

Modeling and Efficient Computational Simulation of Simulated Moving Bed Chromatographic Separation Processes.

Chromatographic separation processes provide a powerful tool for the separation of mixtures in which the components have different adsorption affinities, especially when high purities are required. In this area, simulated moving bed (SMB) technology is becoming an important technique for large‐scale continuous chromatographic separation processes since it provides the advantages of a continuous countercurrent operation while avoiding the technical problem of a true moving bed. Because of the complex dynamics of the process, the choice of the optimal operation parameters and the control of the process in order to keep the product specifications at any time is not straightforward. For this challenging task, a reliable dynamic model of the process is necessary which is accurate enough as well as efficient enough in order to permit its online use for model based control. The purpose of this contribution is to review the state of the art in dynamic modeling of SMB chromatographic separation processes, highlighting new trends and results in the design of computationally effective simulation models suitable for online applications.
Dislocation cell structures in melt‐grown semiconductor compound crystals
Authors: Rudolph P.
Published: December 2004

The phenomenon of dislocation patterning during melt growth of III‐V, II‐VI and IV‐VI semiconductor crystals is discussed. The paper is focused on the formation of cellular structures driven by the growth inherent thermo‐mechanical stress. Of particular interest is the scaling of relations between cells size, dislocation density and acting shear stress. Among the materials there are characteristic similarities but also significant variations of the cell genesis. After the related compound specifics are discussed possible measures for retardation of cell patterning during growth are demonstrated. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic X‐ray scattering and the example of the investigation ofRCu2compounds (R= rare earth)
Authors: Schneidewind A. , Kreyssig A. , Loewenhaupt M.
Published: December 2004

For the investigation of magnetic structures, neutron scattering is the established standard method. Much experience and experimental know‐how encourage approaching complex problems as well. On the other hand, since the beginning of the nineties the magnetic X‐ray scattering methods (MXS) have been applied as complementary tools to the magnetic neutron scattering (MNS). We present the application of different aspects of magnetic X‐ray scattering onRCu2compounds as an example of its complementary nature to neutron scattering in the investigation of magnetism and discuss particular details of the magnetic X‐ray scattering. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Small angle X‐ray transmission characterisation of nanometer‐sized Pt‐clusters in a ceramic thin film on metal substrate
Authors: Müller J. , Löthman P. , Meyer D.C.
Published: December 2004

Nanometer‐sized platinum embedded in a ceramic matrix on metal substrate was investigated by small angle X‐ray scattering (SAXS). The influence of heat treatment on cluster size was also studied with the same method. Although the sample was as thick as 0.25 mm the measurement could be carried out successfully in transmission mode with a slit‐collimation based SAXS camera and a conventional X‐ray tube. The influences of sample geometry on experimental data were corrected numerically; the algorithm used is described in detail. Assuming spherical geometry of the platinum clusters, and that the overall system is monodisperse and diluted, the characteristic radius obeys the Guinier approximation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ergänzungsprodukte für Mauerwerk
Authors: Schubert Peter
Published: December 2004

Wandbauteile im Wohnungsbau werden zu über 80 % in Mauerwerk ausgeführt. Aber auch für öffentliche Bauten, Industrie‐ und Bürobauten wird Mauerwerk angewendet. Durch die Vielzahl der verfügbaren Mauerstein‐Mauermörtel‐Kombinationen und verschiedene Wandkonstruktionen kann eine optimale Auswahl für den jeweiligen Anwendungsfall erfolgen. Zur funktionsgerechten Fertigstellung von Wandbauteilen aus Mauerwerk einschließlich der Auflagerung bzw. Anbindung von anschließenden Bauteilen sind ergänzende Bauteile bzw. Verbindungselemente erforderlich. Auch heute noch werden die notwendigen Ergänzungen in anderen Baustoffen – i. w. in Beton ausgeführt. Dies kann zu Unverträglichkeiten mit dem Baustoff Mauerwerk aber auch mit auf Mauerwerk angepaßten “Ausbaubaustoffen” – wie z. B. Innen‐ und Außenputz – führen. Werden Ringanker oder Ringbalken in Beton hergestellt, so können aus der Verformungsunverträglichkeit zu Mauerwerk schädliche Risse entstehen.

Derartige Nachteile und die damit verbundenen Probleme lassen sich vermeiden, wenn die seit Jahren verfügbaren mauerwerkgerechten Ergänzungsbaustoffe bzw.‐bauteile, im Folgenden Ergänzungsprodukte genannt, angewendet werden. Diese Stoffe und Produkte sind speziell für Mauerwerkbauteile entwickelt und angepaßt worden, sind rationell einsetzbar und haben sich seit langem bewährt.

Nachfolgend wird eine Übersicht über die wesentlichen derartigen Ergänzungsprodukte sowie eine daran anschließende beispielhafte Produktinformation der verschiedenen Hersteller gegeben.
Further variations of smoke density with heat flux
Authors: Edgerley P. G. , Pettett K.
Published: December 2004

The heat flux in the NBS smoke chamber has been varied from 1.0 to 5.0 W cm−2 in 0.5 W cm−2 steps for some fifteen natural and synthetic materials. These experiments confirm the results given in previous papers for a smaller heat flux range, namely that smoke density varies ove4r the temperature/heat flux range. The extended range studied ensured that a much higher proportion of the materials reached a heat flux at which ignition occurred. As before at this and higher heat fluxes, the experiments were repeated in the flaming mode to ensure better reproducibility. With a few exceptions the general shape of the specific optical density/heat flux plot was similar, with a steep rise to a peak and then a corresponding drop to a low value at high fluxes. At 5 W cm−2the drop had not been reached in some cases, but it is assumed to occur later by inference from earlier work on a smaller‐scale apparatus at high temperatures. Complex materials can give unusual plots during the transition from pyrolysis to combustion. This is true of certain polymers containing fire retardant when the pyrolysis of the additive can have a separate effect.
Assessment of toxic hazards of smoke: Toxicological potency and intoxication rate thresholds
Authors: Hartzell G. E. , Packham S. C. , Switzer W. G.
Published: December 2004

Smoke toxicity test methods which determine only lethal toxicological potency under ‘worst case’ conditions do not satisfactorily address the critical issue of relative hazard, including time‐to‐escape and tenability limits resulting from the fire performance of materials under comparable conditions. Since threats to escape from a fire are largely time‐dependent, toxic insults produced by burning materials should also be considered as rate processes. Assessment of time thresholds exhibited by burning materials under test conditions to effect performance impairment (incapacitation) of an animal model would appear to be more relevant than lethal toxicological potencies in estimating probability of successful escape from fires. A model is advanced in which intoxication rate thresholds for materials are obtained using a rodent exposure test method. Concentration‐time curves, obtained from experimentally derived concentration‐time‐response surfaces, are the basis for estimating rate thresholds which are distinctively different for each material and which vary as a function of test conditions. it is this performance impairment response surface which is potentially a key to the modeling of toxic hazards of smoke in perspective with other hazards presented by fire.
Application of test results to analysis and control of fire growth hazards
Authors: Thomas P. H.
Published: December 2004

Some examples of the application of fire tests to hazard and risk assessment and some of the problems to be encountered are described. Reference is made to theoretical studies designed to show how to obtain basic data on material properties from ignitability and flame spread tests, and recent correlations of the rate of heat release required to cause flashover are presented. Progress in predicting fire growth from theory for certain idealized conditions will increasingly condition the choice of which processes shall be the subject of tests.
The extinction of hydrocarbon flames based on the heat‐absorption processes which occur in them
Authors: Ewing Curtis T. , Hughes J. Thomas , Carhart Homer W.
Published: December 2004

An empirical relation has been developed which correlates and predicts the fire‐suppression effectiveness of a wide variety of gaseous, liquid and solid agents. The flame‐extinguishment model is based on the premise that extinction is dominated by heat‐absorption processes and that a flame is extinguished when sufficient heat has been removed by the extinguishant to reduce the temperature to a limit value. This limit value. This limit is the minimum temperature at which the effective rate of the combustion reactions is sufficient to maintain flamepropagation, and it depends in a predictable way on the properties of the suppressant and flame system. The heat‐balance equation describing this is derived in two stages. In the first, a preliminary equation is obtained by considering only those substances which are thermally stable and act only as heat‐capacity sinks. In the second, the equation is generalized by consideration of all endothermic reaction sinks, e.g. vaporization, dissociation and decomposition. The general equation correlates most of the extinction data found in the literature. The results suggest that for most substances the extinguishing capacity is related to heat‐extraction data found in the literature. The results suggest that for most substances the extinguishing capacity is related to heat‐extraction and that many of the effects previously attributed to chemical mechanisms may be thermodynamic in nature rather than kinetic.
Rate of heat release by oxygen consumption in an open test arrangement
Authors: Svensson I. Gunilla , Östman Birgit A.‐L.
Published: December 2004

Equipment has been developed for measuring the rate of heat release from building materials in an open test arrangement. The method is based on an oxygen consumption technique. A vertical sample is placed under an open hood in which the combustion gases and a certain amount of air are collected. The decrease in oxygen concentration and the mass flow of the gases are measured in the exhaust duct. The rate of heat release is then calculated. The equipment has been calibrated with good agreement between input and measured effects. The total response time for the system is 10s. The method has been used for testing building materials at radiation intensities up to 5W Cm−2. It is able to distinguish between different board materials, and the repeatability is good, The paper describes the equipment, including the weighing of a burning sample and the selection of test condition. Smoke and gas analysis can be added when desirable. Some test results with building materials are also presented.
Assessment of smoke density with a helium–neon laser
Authors: Clark Ferrers R. S.
Published: December 2004

Smoke‐obscuration of monochromatic (0.632μm) light helium‐neon lasers and of broad‐band continuum light a hot tungsten filament is reported. The effect of forward‐scattered light is evaluated for the monochromatic source, and the degree to which the Bouguer law is obeyed for a non‐monochromatic source is discussed. Practical experience with both small‐scall and fire experiments is described.
A summary of the NBS literature reviews on the chemical nature and toxicity of the pyrolysis and combustion products from seven plastics: Acrylonitrile–butadiene–styrenes (ABS), nylons, polyesters, polyethylenes, polystyrenes, poly(vinyl chlorides) and rigid polyurethane foams
Authors: Levin Barbara C.
Published: December 2004

A series of literature reviews was undertaken by the National Bureau of Standards to examine the toxicity and chemistry of the effluents produced when seven plastics were decomposed under various thermal and atmospheric condition. These plastics are: acrylonitrile–butadiene–styrenes, nylons, polyesters, polyethylenes, polystyrenes, poly(vinyl chlorides) and rigid polyurethane foams. The English‐language literature on each of these was reviewed and published as a separate report of the National Bureau of Standards. Over 400 different thermal decomposition products, many common to more than one plastic, were identified. The toxicity of most of these individual products is products, many common to more than one plastic, were identified. The toxicity of most of these individual products is unknown and an assessment of the toxicity of the multitude of possible combinations is not feasible at this time. Therefore a variety of bioassay toxicity protocols have been used to assess the toxicity of the gaseous atmospheres generated by the thermal decomposition of these plastics. In general, these seven plastics did not produce unusually or extremely toxic pyrolysis or combustion products when compared with those of other synthetic or natural materials. In a few cases involving additives, toxic products of concern were produced.
Effects of additives on fire properties of polyethylene
Authors: Christopher A. J.
Published: December 2004

Low‐density polyethylene, with and without an antimony–bromine synergistic fire retardant or aluminium hydroxide, was subjected to standard fire tests and to experiments which determined the smoke and harmful fumes emitted on overheating. Both additives improved most fire properties but the fire retardant increased the smoke generated by intense radiant heat. The onset of smoke, flammable gas, carbon monoxide and acids was generally delayed by the additives. The total amounts and maximum values of these volatiles were lessened. Sample weight and form affect the results of these experiments. Observations during heating show that the additives reduce spreading of the melt, thus reducing the surface area available for oxidation.
Means of escape ‐ 1988. How close are we to modelling egress from buildings in fire?
Authors: Kendik Ezel
Published: December 2004

During the last twenty years a number design methods for calculating the movement of people in buildings have been developed. This presentation briefly reviews some of these modelling efforts. Furthermore, it discusses some aspects of the pedestrian movement and addresses an egress model based on the data provided by Predtechenskii and Milinski. This model is applicable to the evacuation of multi‐storey buildings via staircases and predicts the flow movement in terms of time with regard to the building's layout and the interdependencies between adjacent egress way on this model, written in GWBasic language for any IBM‐compatible personal computer. The program is built up as a dialogue between the user and the computer, where the escape route configurations (the width and the length of each section) as well as the number of the persons are put gradually during the course of the computation. The program enables the user to change the dimensions of the building's means of escape and the occupant load easily and work out the influence of the variation on the complete circulation system. Recently, the program also calculates the flow movement under decreased visibility conditions on smoke filled escape routes based on japanese measurements about the walking speed of pedestrians in fire smoke.
Defining the thermal environment in fire tests
Authors: Keltner N. R. , Moya J. L.
Published: December 2004

The ability of engineered systems to withstand a fire environment is usually demonstrated by test. Iterative design and experimentation historically has been used to develop these engineered systems. To optimize the engineered system, in instances where the cost of the prototype is high, the process of iterative redesign and testing may be infeasible. Consequently, in such instances it is desirable to predict the thermal performance of the engineered system analytically. In order to predict the thermal performance of the engineered system the thermal insult the test environment provides to a test unit must be quantified. To quantify the thermal insult, both temperature and heat flux measurements are necessary. However, as will be discussed, one of the major difficulties associated with conducting any type of fire test is making accurate measurements in both the fire and on the test unit. This paper discusses a number of measurement techniques. Due to the potential for errors in the measurements, the uncertainty in the measured parameters is emphasized.
Fire‐gas hazards in rail traffic
Authors: Prager F. H. , Cabos H.‐P.
Published: December 2004

A review is given of the various national requirements and test procedures concerning testing and classification of smoke produced in the case of a fire in rolling stock. A comparison of the various test methods is made using the relevant available literature. The toxic potency philosophy of SC3 ‘Toxic Hazard in Fire’ from ISO TC92 is used to provide a concept for assessing the possible smoke hazard in the case of a fire.
The flammability of polyacrylonitrile and its copolymers III. Effect of flame retardants
Authors: Hall Michael E. , Zhang Jun , Richard Horrocks A.
Published: December 2004

This paper extends previously reported work 1,2 and describes the influence that a range of selected flame retardants have on the burning behaviour and pyrolyses of homo‐and copolymers of acrylonitrile. Various inorganic and organic phosphorus and nitrogen‐ or sulphur‐containing, halogen‐containing (in the absence and presence of halogen or antimony (III) oxide) and nitrogen‐containing flame retardants and red phosphorus were studied using LOI, TGA, DSC and residual char measuring techniques. Flame retardancy relates directly to char‐forming tendency for all retardants and their ability to reduce the dominance of flammable volatiles formed during the first stage of acrylic polymer pyrolysis. Ammonium phosphates are particularly effective flame retardants for the selected copolymers. Possible mechanisms of retardant activity are discussed, including the char‐forming tendency of antimony–bromine combiniations.
The use of partial least squares (PLS) in quantitative FTIR: Determination of gas concentrations in smoke gases of burning textiles
Authors: Pottel Hans
Published: December 2004

Fourier transform infrared spectroscopy ca be used for on‐line smoke gas analysis of burning textile materials for several gases simultaneously. The technique is sensitive enough for the determination of the concentrations of compounds like H2O, CO2, Co, NO, NO2, SO2, C3H4O, HCI, HBr, HCN and HF. Quantitative analysis is, however, sometimes difficult to perform due to spectral interferences of two or more components. Simple mathematical techniques based on the direct relation between concentration and peak height or peak height or peak area then becomes impossible since they cannot be completely assigned to one component. Spectral subtraction can then be used but the results are sometimes unsatisfactory. Alternative techniques, like Partial Least Squares (PLS), Provide excellent possibilities to overcome the problems due to overlapping spectral features, without making use of spectral concentrations of different compounds in smoke gases. The use of PLS as a tool to overcome the problem of interfering of different compounds in smoke gases. The use of PLS as a tool to overcome the problem of interfering components is demonstrated by application to the overlapping spectral bands of H2O/CO2 and of H2O/NO. PLS calibration curves for other interfering components can be constructed in an analogous way.
Specific processing of the bacterial β‐lactamase precursor in Saccharomyces cerevisiae
Authors: Roggenkamp Rainer , Hoppe Jürgen , Hollenberg Cornelis P.
Published: December 2004

Synthesis and processing of the bacterial enzyme β‐lactamase (E.C. 3.5. 2.6) were studied in Saccharomyces cerevisiae. The 2‐μm DNA vector pADH040‐2 containing the yeast ADH1 promoter fused to the bacterial gene was used in order to obtain enhanced synthesis of the bacterial protein in yeast transformants. Both precursor and mature β‐lactamase were shown to be present in yeast cells, the precursor being the major product. The mature enzyme was purified about 500‐fold over crude extracts to apparent homogeneity and thus represents nearly 0.2% of the total yeast protein. No difference in specific activity and molecular weight could be observed when compared with the authentic β‐lactamase from Escherichia coli. Specificity of the processing of β‐lactamase in yeast cells was verified by partial amino acid sequence analysis demonstrating the removal of the signal peptide at the correct position.
Oxygen‐dependent microbicidal systems of phagocytes and host defense against intracellular protozoa
Authors: Locksley Richard M. , Klebanoff Seymour J.
Published: December 2004

The role of oxygen‐dependent microbicidal systems of leukocytes in the host defense against the major nonerythrocytic intracellular protozoa which infect man—Toxoplasma gondii, Trypanosoma cruzi, and the Leishmania species—is reviewed. The hydrogen peroxide‐halide‐peroxidase microbicidal system is uniformly cidal to these organisms in vitro. Peroxidase‐independent oxygen product(s) toxicity is more variable. Studies to date indicate that phagocytes which contain granule peroxidase and which have the capacity to generate a vigorous respiratory burst; eg, neutrophils and monocytes, possess substantial activity against these protozoa. The absence of granule peroxidase together with the markedly attenuated respiratory burst of resident macrophages leaves these cells with a severe microbicidal defect. These protozoa can enter resident macrophages in the absence of antibody and survive and replicate within the intracellular environment. Enhancement of the antiparasite activity of resident macrophages can be accomplished either by activation of these cells by exposure to sensitized T‐cell products, or by the introduction of exogenous peroxidase into the vacuole. Other factors influencing the ability of protozoa to survive intracellularly include the capacity of these organisms to avoid effective triggering of the macrophage respiratory burst and the levels of endogenous scavengers of oxygen products within the parasite.
Radioiodination studies of the envelopes from Xenopus laevis eggs
Authors: Nishihara Tatsuro , Gerton George L. , Hedrick Jerry L.
Published: December 2004

To investigate the molecular basis of the observed morphological and biological characteristics of coelomic egg envelopes (CE), vitelline envelopes (VE), and fertilization envelopes (FE) of Xenopus laevis eggs, envelopes were radioiodinated under a variety of conditions: in situ, isolated and intact, or solubilized. The distribution of 125I in envelope components was analyzed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. Each envelope type displayed unique profiles when iodinated in the intact state. A major constituent of VE, the 41,500 molecular weight component, was not labeled in the intact state, although the corresponding component of CE was heavily labeled. After dissociation of the envelope by guanidine‐HCl or sodium dodecyl sulfate, all of the components could be radioiodinated. However, when the envelopes (VE and FE) were dissolved by heating and subsequently radioiodinated by lactoperoxidase, the resulting radioactivity profile was similar to that of the intact envelopes, suggesting that in the heat‐dissolved envelope, the individual components retain similar structural relations as in the intact envelope. Quantitative but not qualitative differences were found between the inner and outer aspects of VE and FE. The significance of these findings is discussed in relation to what is known about the morphological, biological, and molecular properties of the envelopes.
Nuclear protein changes following N,N‐dimethylformamide (DMF)‐induced maturation
Authors: Kimball P. M. , Hixon Sharon
Published: December 2004

A human colonic carcinoma cell line was exposed to a nontoxic concentration of N,N‐dimethylformamide (DMF) for 2 wk. Nuclear proteins were isolated from control and treated cells and compared by sodium dodecyl sulfate (SDS) electrophoresis. Qualitative and quantitative differences were observed. Metabolic labeling with tritiated leucine demonstrated qualitative variation between control and treated cells.
Primary photochemistry in the facultative green photosynthetic bacterium Chloroflexus aurantiacus
Authors: Blankenship Robert E. , Feick Reiner , Bruce Barry D. , Kirmaier Christine , Holten Dewey , Fuller R. Clinton
Published: December 2004

The mechanism of primary photochemistry has been investigated in purified cytoplasmic membranes and isolated reaction centers of Chloroflexus aurantiacus. Redox titrations on the cytoplasmic membranes indicate that the midpoint redox potential of P870, the primary electron donor bacteriochlorophyll, is +362 mV. An early electron acceptor, presumably menaquinone has Em 8.1 = −50 mV, and a tightly bound photooxidizable cytochrome c554 has Em 8.1 = +245 mV. The isolated reaction center has a bacteriochlorophyll to bacteriopheophytin ratio of 0.94:1. A two‐quinone acceptor system is present, and is inhibited by o‐phenanthroline. Picosecond transient absorption and kinetic measurements indicate the bacteriopheophytin and bacteriochlorophyll form an earlier electron acceptor complex.
Comparison of the expression‐linked extra copy (ELC) and basic copy (BC) genes of a trypanosome surface antigen
Authors: Donelson John E. , Murphy William J. , Brentano Steven T. , Rice‐Ficht Allison C. , Cain George D.
Published: December 2004

A recombinant clone of an expression‐linked extra copy (ELC) gene of a trypanosome‐variable surface glycoprotein was sequenced. In addition the sequences of the corresponding cDNA and portions of the two basic copy genes were determined. Comparison of these sequences reveals that the 5′ boundary of the ELC‐transposed segment (2.2 kb) occurs within a repetitive sequence about 700 bp upstream from the start codon of the coding sequence. This sequence does not contain internal symmetries and is not homologous with the repetitive sequence at the 3′ boundary. The first 35 nucleotides of the cDNA are different than the corresponding ELC sequence and presumably were transcribed from another genomic location. A restriction fragment containing predominantly sequences outside of the 5′ boundary hybridizes to a Pst I fragment whose length is variable in different trypanosome clones. This hybridization pattern is similar to that observed using probes for surface glycoprotein genes that are expressed via the nonduplication‐associatcd (NDA) mechanism rather than the ELC mechanism. This indicates that there is a sequence correlation between these two DNA rearrangement mechanism.
Sorting and recycling of cell surface receptors and endocytosed ligands: The asialoglycoprotein and transferrin receptors
Authors: Ciechanover Aaron , Schwartz Alan L. , Lodish Harvey F.
Published: December 2004

With few exceptions, receptor‐mediated endocytosis of specific ligands is mediated through clustering of receptor‐ligand complexes in coated pits on the cell surface, followed by internalizalion of the complex into endocytic vesicles. During this process, ligand‐receptor dissociation occurs, most probably in a low pH prelysosomal compartment. In most cases the ligand is ultimately directed to the lysosomes, wherein it is degraded, while the receptor recycles to the cell surface.

We have studied the kinetics of internalization and recycling of both the asialoglycoprotein receptor and the transferrin receptor in a human hepatoma cell line. By employing both biochemical and morphological/immunocytochemical approaches, we have gained some insight into the complex mechanisms which govern receptor recycling as well as ligand sorting and targeting. We can, in particular, explain why transferrin is exocytosed intact from the cells, while asialoglycoprotcins are degraded in lysosomes. We have also localized the intra‐cellular site at which endocylosed receptor and ligand dissociate.
Fluorescence decay kinetics of chlorophyll in photosynthetic membranes
Authors: Karukstis Kerry K. , Sauer Kenneth
Published: December 2004

The absorption of light by the pigments of photosynthetic organisms results in electronic excitation that provides the energy to drive the energy‐storing light reactions. A small fraction of this excitation gives rise to fluorescence emission, which serves as a sensitive probe of the energetics and kinetics of the excited states. The wavelength dependence of the excitation and emission spectra can be used to characterize the nature of the absorbing and fluorescing molecules and to monitor the process of sensitization of the excitation transfer from one pigment to another. This excitation transfer process can also be followed by the progressive depolarization of the emitted radiation. Using time‐resolved fluorescence rise and decay kinetics, measurements of these processes can now be characterized to as short as a few picoseconds. Typically, excitation transfer among the antenna or light harvesting pigments occurs within 100 psec, whereupon the excitation has reached a photosynthetic reaction center capable of initiating electron transport. When this trap is functional and capable of charge separation, the fluorescence intensity is quenched and only rapidly decaying kinetic components resulting from the loss of excitation in transit in the antenna pigment bed are observed. When the reaction centers are blocked or saturated by high light intensities, the photochemical quenching is relieved, the fluorescence intensity rises several fold, and an additional slower decay component appears and eventually dominates the decay kinetics. This slower (1‐2 nsec) decay results from initial charge separation followed by recombination in the blocked reaction centers and repopulation of the excited electronic state, leading' to a rapid delayed fluorescence component that is the origin of variable fluorescence. Recent growth in the literature in this area is reviewed here, with an emphasis on new information obtained on excitation transfer, trapping, and communication between different portions of the photosynthetic membranes.
Differential protein insertion into developing photosynthetic membrane Regions of Rhodopseudomonas sphaeroides
Authors: Inamine Gordon S. , Reilly Patricia A. , Niederman Robert A.
Published: December 2004

Previous studies have suggested that much of the B800‐850 light‐harvesting bacteriochlorophyll a‐protein complex is inserted directly into the intracytoplasmic photosynthetic membrane of Rhodopseudomonas sphaeroides. In contrast, the B875 light‐harvesting and reaction center complexes are assembled preferentially at peripheral sites of photosynthetic membrane growth initiation. The basis for this apparent site‐specific polypeptide insertion was examined during the inhibition of RNA and protein syntheses. The pulse labeling of polypeptides at the membrane growth initiation sites was significantly less sensitive to inhibition by rifampicin, chloramphenicol, or kasugamycin than in the intfacytoplasmic or outer membranes. This suggests increased stability for the translation machinery at these membrane invagination sites. Similar differential effects in polypeptide insertion were observed during inhibition of bacteriochlorophyll synthesis through deprival of δ‐aminolevulinate to R sphaeroides mutant H‐5, which requires this porphyrin precursor. The pulse‐labeling patterns observed during the inhibition of both RNA and pigment syntheses were consistent with the uncoupling of polypeptide insertion into the membrane invagination sites from their growth and maturation into intracytoplasmic membranes.