ALBERT

Description / Table of Contents: Summary α-keratose isolated from wool was fractionated by gelchromatography under optimum conditions — using Sephadex G 75 in 5 m columns and mild alkaline-buffered solutions of theα-keratose. Theα-keratose was separated into three main parts: a very heterogeneous component calledα KA protein, a very small fraction namedα KB1-protein and a pure proteinα 2KB (6% of total wool). After rechromatography of theα KB2-fraction the molecular weight of the protein was estimated to be 8300. Analysis of the N-terminal endgroups showed that theα KB2-protein contains the same N-terminal amino acids as wool; but there is only one C-terminal amino acid (tyrosine). A very high content of tyrosine, phenylalanine and glycine was found by amino acid analysis of theα KB2-protein.

Description / Table of Contents: Zusammenfassung Die freie Oberflächenenergie von Polyäthylenkristallen wurde aus der Auflösungstemperatur der Kristalle in dem Lösungsmittel, aus dem sie gebildet wurden, über thermodynamische Betrachtungen abgeschätzt. Aus der Größe der freien Oberflächenenergie und der Dichte der Einkristalle wurde die in der vorhergehenden Veröffentlichung angegebene Folgerung bestätigt, daß die Oberfläche um so regelmäßiger ausgebildet wird, je größer der thermodynamische Wechselwirkungsparameter und das Molvolumen des Lösungsmittels sind.

Description / Table of Contents: Zusammenfassung Zur Bestimmung der Oberflächen-OH-Gruppen im Knochenmineral, welches als unreiner Hydroxyl-apatit beschrieben werden kann, wurde Lithium-Aluminiumhydrid in Diglymelösung verwendet. Die Menge der OH-Gruppen wurde aus der entwickelten Wasserstoffmenge berechnet. Ein Vergleich der auf diesem Wege ermittelten Menge an OH-Gruppen mit der aus der spezifischen Oberfläche (BET N2-Adsorption) und der Kristallstruktur errechneten zeigt ein Defizit von mehr als 50%. Zur Deutung werden mehrere Möglichkeiten diskutiert. Die Annahme, daß echte Fehlstellen für die Oberflächen-OH-Gruppen vorliegen, wird bevorzugt.

Description / Table of Contents: Zusammenfassung Die komplexe Dielektrizitätskonstante von trockenem Rhinozeros Horn wurde über ein Frequenzintervall von 10−6 bis 10+6 Hz und ein Temperaturintervall von −14 °C bis 125 °C gemessen. Trockene Wolle wurde ebenfalls geprüft, aber nur für ein Frequenzintervall von 10−2 bis 106 Hz. Die Resultate lassen sich auf Grund der 6 gefundenen Absorptionsgebiete, ihres Verhaltens und der Aktivierungsenergien erklären. Der Vergleich mit den mechanischen und dielektrischen Eigenschaften der Polyamide wurde angestellt.

Description / Table of Contents: Summary A description is given of the measurement of the velocity of dissolution with the help of an interference microscope. A swollen surface layer of constant thickness determines the rate of this stationary process. The mutual (D) and the intrinsic diffusion coefficient of the solvent (dlm) can be determined throughout the whole range of concentrations.D shows a maximum and DLM a monotonous increase with the volume fraction of the solvent. The influence of the size of the solvent molecule is investigated with the help of a series of esters with increasing paraffin sceleton. The interdependence of thermodynamic and kinetic quality of a solvent on the swollen surface layer is shown schematically. The poorest solvent methylacetate exhibits a new type of dissolution: The surface layer with partial miscibility. It is described in detail.

Description / Table of Contents: Summary From the theories of light scattering of colloidal spheres (Mie, Zimm andDandliker) a method was derived, which allows the determination of the diameter and the refractive index of spherical particles by measuring specific turbidity and refractive index increment. The method requires only small experimental equipment and is simple in measurement and evaluation. In order to test the method experimentally, the particle diameters of different latices (homo- and copolymers) were measured and compared with the corresponding measurements obtained from ultracentrifugation and electron microscopy. The results are in good agreement.

Description / Table of Contents: Zusammenfassung Viele anorganische kristalline Substanzen sind polymer, meist nach ihrer chemischen Struktur dreidimensionale Netzwerke. Die anorganischen Polymeren, die nicht dreidimensional sind, verdienen besondere Beachtung, da sie ungewöhnliche mechanische Eigenschaften erwarten lassen. Polymerer Schwefel, linear im Bau, ist innerhalb eines sehr schmalen Temperaturbereichs elastisch. Cadmiumjodid, ein Flächenpolymeres, kann leicht gespalten werden und bildet dabei Lamellen so dünn wie 40 mikrons. Das Verhalten der Blättchen auf Zug sollte der Matrizen-Mathematik vonWeissenberg entsprechen, obgleich dies noch nicht demonstriert wurde. Goldjodid (AuI), beschrieben als ein lineares Polymeres, ist tatsächlich nicht linear. Die Au-I-Au-I-Zick-zacks, gebildet durch chemische Bindung, sind zu Ebenen metallisch miteinander gebundener Goldatome verknüpft, so daß das Ganze ein zweidimensionales Netzwerk darstellt. Die beobachteten mechanischen Eigenschaften sind mit dieser Struktur konsistent.

Description / Table of Contents: Zusammenfassung Entsprechend der Hypothese, daßlose Schlaufen in dieengen Schleifen an der Oberfläche von Polyäthylen-Einkristallen, und zwar abhängig von den Kristallisationsbedingungen, eingelagert sind, werden die Dichtemessungen mit einer Pyknometermethode ähnlich der früher beschriebenen [Phil. Mag.8, 1203 (1963)] an Einkristallen an sorgfältig fraktioniertem Polyäthylen (PÄ) von verschiedenen Molekulargewichten wiederholt. Die Dichten werden in Abhängigkeit von Polymerkonzentration, Kristallisationstemperatur und Lösungsmittel bestimmt. Nahezu alle Proben geben Werte sehr nahe der kristallographischen Dichte 1,00, übereinstimmend mit den früheren Ergebnissen. Jedoch für die höchste MG-Fraktion (¯M v =150000) ergeben sich etwas kleinere Werte. Das ist nicht nur konsistent mit der obigen Hypothese, sondern auch mit Beobachtungen im Elektronenmikroskop, daß diese Fraktion nicht mehr Kristalle mit so wohldefinierten Prismenflächen und Sektoren wie die anderen gibt, Eine Abhängigkeit der Dichte von Konzentration, Kristallisationstemperatur und Lösungsmittel konnte innerhalb der experimentellen Genauigkeit nicht ermittelt werden. InfrarotAnalysen gemäßKoenig undWitenhafer zeigten andererseits einen systematichen Gang für das Verhältnis der Absorption zweier Banden, dem gauche-Methylen zukommend, mit MG und Konzentration entsprechend der obigen Hypothese. Unter Anwendung der Technik vonPalmer undCobbold, mit der Lamellenkristalle nach Behandlung von festem PÄ mit rauchender Salpetersäure extrahiert wurden, wurden darüberhinaus die Falten der Einkristalle abgelöst. Die Zahl der Kohlenstoffatome in den Schlaufen wurde aus dem Gewichtsverlust und den MG-Werten nach der Behanlung abgeschätzt, in Kombination mit Röntgenkleinwinkelstreuung an den Ausgangskristallen und chemischer Analyse der Elemente in den nach Behandlung verbliebenen Kristallen. Obgleich diese Methode den Anteil an Oberflächenschicht zu hoch erscheinen läßt, ergeben die Experimente eine mehr als 90%ige Kristallinität der Einkristalle. Alle diese Resultate unterstützen die These des Modells mit engen Schlaufen. Immerhin könnte durchaus eine kleine Zahl weiter Schlaufen, abhängig von den Kristallisationsbedingungen, den regulären engen Faltungen überlagert sein.

Description / Table of Contents: Summary For the determination of specific surfaces and microporosities the dynamic method with constant terminal voltage is used. An empirical equation is given which is useful to describe the experimental system. This is a very time consuming step. A derivation of an equation valid for the general case, using all experimental parameters as variables is possible if the following conditions are met: feeding with constant current and constant temperature of the walls of the heat conductivity detector. The experimental parameters, with the help of the equation, give the amount of gas and the evaluation of the maximum sensitivity. There is a difference for small sources between the theoretical model and the experiment due to diffusion. The coordination of the two experimental signals can be given with high accuracy by employing an approximation. Therefore the standardisation of the complete experimental system is reduced to three measurements.

Description / Table of Contents: Summary The chemical structure of the free radicals in irradiated polyethylenoxide is investigated by means of EPR. Other EPR experiments, measurements of oxygen consumption and IR experiments show, that the oxidation of irradiated polyethyleneoxide follows a radical chain reaction; in the course of this chain reaction every step leads to the cleavage of a CO bond which is stabilized by the formation of aldehyd end groups. From quantitative analysis of the IR experiments and of viscosimetric measurements of the molecular weight results finally, that the oxidative degradation of irradiated polyethyleneoxide is caused by the cleavages which are formed during the chain reaction. A model for the kinetic of the chain reaction is developed which describes the experimental results.

Description / Table of Contents: Zusammenfassung Die Koagulation eines handelsüblichen Styrol-Butadien-Latex durch Elektrolyte wurde eingehend untersucht. Bei 1-, 2- und 3-wertigen Gegenionen zeigt der Vergleich mit Silberhalogenid-Solen weitgehende Ähnlichkeit in den kolloidchemischen Eigenschaften. Aus Trübungsmessungen in den Anfangsstadien der Koagulation und aus Elektrophoresemessungen bei verschiedenem Gehalt an Elektrolyt wurden dieHamaker- Konstante, dasSternsche Potential, die Oberflächenladung und die Entfernung derScherungsfiäche von der Sternschicht abgeleitet.

Description / Table of Contents: Summary The oxidation of irradiated polypropylene follows a radical chain reaction. A model for this reaction is discussed, which was originally developed for polyethyleneoxide. It leads to an equation, which describes the oxygen consumption of irradiated samples as a function of the decrease of the radical concentration. The experimental results follow this equation also for polypropylene. An earlier calculation is shown to be the first order approximation of the new equation.

Description / Table of Contents: Summary Poly-p-xylylene crystallizes from some solvents into two single crystal forms, rectangular and hexagonal. These two single crystals show different X-ray and electron diffraction patterns, respectively. By X-ray measurements it was found that these two single crystals correspond toα- undβ-crystal forms, which were observed with bulk materials byBrown andFarthing. It was also found that these morphological forms depend on the crystallization-conditions, especially on crystallization-solvents. The annealing effects and the transformation fromα- toβ-form were studied by X-ray diffraction and differential thermal analysis.

Description / Table of Contents: Zusammenfassung Es wurde die Wechselwirkung einer Anzahl von ionischen oberflächenaktiven Agentien mit menschlichen roten Blutkörperchen untersucht, um die Geschwindigkeit zu messen, mit welcher die oberflächenaktive Substanz die roten Zellen zerreißt. Die Ergebnisse stimmen mit der Hypothese überein, daß die oberflächenaktive Substanz primär eine monomolekulare Lipidschicht durchdringt und sie dadurch zum Zerfall bringt. Die mit der Hämolyse Hand in Hand gehenden Enthalpieänderungen liegen schätzungsweise bei −2×104 bis −5×104 Joule pro Mol oberflächenaktiver Substanz.

Description / Table of Contents: Summary Some water-insoluble copolymers of polyvinylalcohol-acetate are solubilized transparently in aqueous solutions of non-ionic surfactants. From viscosity measurements it is concluded that the copolymer chains, which areshrunken in water, are uncoiled in the aqueous non-ionic surfactant solutions. Clouding points of the aqueous polymer solutions are increased by addition of the non-ionic surfactants, but the effect is less remarkable than by ionic surfactants, especially at higher temperatures. The mixed solution of a hydrophobic copolymer and a non-ionic surfactant has a solubilisation power which is different from that of the surfactant alone. These phenomena are explained by binding of the non-ionic surfactants to the hydrophobic parts of the copolymers, i. e., by the complex formation.

Description / Table of Contents: Summary The specific heat of some commercially available samples of polyvinyl chloride (suspension PVC, emulsion PVC, high impact PVC, and a copolymerisate of vinylchloride and vinylacetate) was measured in the temperature range from 20 (or −50) to 140 °C, using an adiabatic calorimeter. Special attention was paid to the influence of thermal history of the samples. Investigations of annealed samples gave simple curves with a steep slope in the glass transition range, in agreement with the results of other authors. Measurements with samples quenched in ice water showed specific heat curves with a minimum at the beginning of the glass transition range caused by enthalpy relaxation. Above the glass transition range crystallization occurred accompanied by heat effects of about −1,3 cal/g (exothermal). From this the fraction of crystalline PVC was estimated to be about 3%. The melting point of the PVC crystallites as determined by differential thermal analysis was 156 or 170 °C. With high impact PVC the melting of traces of polyethylene was observed between 102 and 125 °C. The glass transition temperatures as determined by calorimetry agreed with those determined by dilatometric measurements, provided thermal pretreatment being equal in both cases.

Description / Table of Contents: Summary The thermal conductivity of 6-, 6.6-, 6.10-polyamid,Penton and polyoxyethylene was measured in the temperature range from −175°C to +140°C by a quasi-stationary method. For the polyamids the thermal conductivity increases with increasing crystallinity and increasing content of water. The thermal conductivity of the amorphous and the crystalline phase was calculated on the basis of a two-phase model. For the thermal conductivity of the amorphous phase we obtained a dependence on temperture, which is typical for amorphous polymers, with a flat maximum in the glass transition range. This maximum is shifted to lower temperatures with increasing content of water like the α-maxima of the mechanical damping. The thermal conductivity of the crystalline phase λ k decreases with increasing temperature analogous to the thermal conductivity of low molecular crystals in accordance with the relation 1/λ k =a+bT;a andb are constants. The thermal conductivity ofPenton decreases with increasing temperature. AT −8°C we found a flat maximum the position of which is according to the dilatometrically determined glass transition temperature of the amorphous regions. Polyoxyethylene shows likewise a decrease of thermal conductivity with increasing temperature. The maximum, however, which lies at about −60°C, cannot only be attributed to glass transition phenomena in the amorphous regions because of the high degree of crystallinity. Presumably also displacements in the crystalline regions are involved. It is remarkable, too, that in this case the specific heat does not indicate any transitions (31).

Description / Table of Contents: Zusammenfassung Zwei optisch aktive organische Säuren wurden aus D- und L-Alanin synthetisiert und ihr Bindungsverhalten an Rinder-Serum-Albumin geprüft. In der Untersuchung fanden wir, daß die D-Form der Verbindungen, die an das Albumin gebunden werden, sich stärker anlagern als die L-Form innerhalb eines pH-Bereichs von 5,0 bis 8,0. Im pH-Gebiet 4,0 jedoch konnten wir keinen Unterschied zwischen dem Verhalten der beiden optischen Isomeren feststellen. Die spektralen Untersuchungen lassen schließen, daß die D-Form fester mit dem Albumin verbunden ist als die L-Form.

Description / Table of Contents: Summary By precipitation of Al-hydroxide geles and dehydration of bayerite it is shown that the formation of a large surface area of γ-Al2O3 depends at least on an intermediate formation of böhmite. The rate of crystallization of böhmite influences significantly the formation of the surface area of γ-Al2O3. The incorporation of Ca-ions causes a thermal stabilization of the crystal lattice as well as the surface area of γ-Al2O3. From the formation of spinels and from spectroscopic investigations, resp., it can be concluded that Ca is incorporated in γ-Al2O3 at tetrahedral lattice sites. The incorporation of CO2 in Al-hydroxide geles delays the crystallization and stabilises the surface area of the dehydration products at higher temperatures. By means of IR-measurements it was shown that CO2 is incorporated at first as a basic carbonate while at higher temperatures CO2 was identified.

Description / Table of Contents: Summary The surface chemistry of solids is described using three examples. On the diamond surface, hydrogen, fluorine und chlorine are chemisorbed in quantities which correspond to ca. one third of the estimated number of “dangling bonds” of surface atoms. All free valences are saturated with oxygen at 420°. The chemisorbed oxygen is bound to a large extent in carbonyl groups and ether-like structures. The surface chemistry of silica is determined by the reactions of Si−OH groups. Typical reactions are described. Titania (anatase) exhibits more ionic character. There are OH groups on its surface, too, which react partly acidic and partly basic. The influence of the surface coverage on the adsorption and wetting behavior of solids is shown.

Description / Table of Contents: Zusammenfassung Optisch schwarze Kohlenwasserstoff-Filme werden unter wäßrigem Medium aus Lösungen von Isosorbidestern, Phospholipiden und Phospholipiden+Cholesterol inn-Decane gebildet. Die Dicke dieser Filme ist aus optischen und elektrischen Eigenschaften bekannt, aber die Bestimmung ihrer molekularen Zusammensetzung enthält Schwierigkeiten. Vorliegende Mitteilung prüft und wendet Methoden an, die auf Oberflächenspannungsmessungen beruhen. Für Filme, die durch lösliche Moleküle stabilisiert sind, können wir direkt oder indirekt dieGibsschen Adsorptionsisothermen anwenden. Für Filme, die durch unlösliche Moleküle (solche wie einige Phospholipide) stabilisiert sind, ist eine andere Näherung möglich. Die Zusammensetzungen der schwarzen Filme, bestimmt durch diese Methode, werden angegeben.

Description / Table of Contents: Summary Aqueous solutions of iodine complexes with starch, different samples of amylose or amylopectin show an induced positive Cotton effect in the region of the absorption maximum. The rotatory power and the extinction at 660 and 445 mμ depends upon iodine amylose ratio. The optical of some complexes increases with time, whereas the absorption remains constant. Experimental conditions which change the structure of the channel complexe (heating, addition of salts, solvents, urea or detergents) influence the induced Cotton effect.

Description / Table of Contents: Summary The stabilization of TiO2 Rutil-suspensions by electrical repulsion may be described by the termQ/r, called the reduced electrical charge. In solution of polyester there are two mechanisms of stabilization of dispersed TiO2-Rutil, stabilization by electrical repulsion and stabilization by adsorbed layers of polyester. Which of both mechanisms is occurring depends on the chemical constitution of the polyester and the polyester concentration.

Description / Table of Contents: Summary The methods of gel permeation chromatography (GPC) are mentioned and a flow diagram is shown to explain the function of an analytical gelchromatograph. The mechanism of separation is discussed. The resolution power of gel columns is defined and equations for its evaluation are shown. For a narrow molecular weight distribution it is necessary to elemeninate the dispersion in order to bring the results of elution chromatography and GPC to agree with one another.

Description / Table of Contents: Summary “Structure-rheology” is the structure investigation with the help of rheological methods. For concentrated solutions, it makes possible the characterization of the state at rest by means of both a viscosity and a shear modulus pertinent to the entanglement network at rest. For streaming solutions, a portion of the network is disrupted, and both viscosity and elasticity of the stationary streaming solution are lowered. By combining measurements of viscosity and viscoelasticity at very small shear rates and in the prestationary state, with measurements at finite, large shear rates, the mentioned characteristic figures can be determined. They allow the characterization of a certain concentrated solution for a fixed state of flow. Extrapolation of the values to zero concentration yields the data of the isolated macromolecules, and thereby provides to connection with investigations of highly diluted solutions.

Description / Table of Contents: Summary Semicontinuous emulsion polymerization of styrene and methyl acrylate with a feed of either monomer or monomer emulsion has been investigated. Using monomer feed, water, emulsifier, initiator, and part of the monomer are charged into the reaction vessel, the remaining monomer is fed with constant feeding rateR z after the start of the polymerization. In the process with emulsion feed an aliquot part of the whole batch is charged, the rest is fed continuously as a monomer emulsion. Feeding rate and initial charge were varied, reaction rateR p, degree of polymerization $$\bar P_\eta $$ , number of latex particlesN, and particles size distribution were measured. With both monomersR p and $$\bar P_\eta $$ are independent ofR z as long asR z is large enough to maintain the saturation value of monomer concentration [M] in the latex particles. If [M] falls below this value a steady state is reached as well with monomer feed as with emulsion feed,R p equalsR z and $$\bar P_\eta $$ increased with increasingR z. Taking theSmith-Ewart theory as a basis for calculation, the propagation rate constantk p was determined for both monomers in the steady state. Emulsion feed produces less, i. e. larger particles than monomer feed or batch polymerization, the overall charge being kept constant. Emulsion feed gives a narrower particle size distribution, and the initial rate of polymerization andN are proportional to the initial charge, if formation of new latex particles during the emulsion feed can be avoided. If not, particle size distribution is broadened and can eventually become even broader than with the other two methods.

Description / Table of Contents: Summary Changes of state of the perfect gas are compared with those ones of a perfect rubber with the help of thermodynamics. There are characteristic differences between the two systems during isothermic reversible processes due to the different functions of state. There only exist analogous effects if the perfect systems are closed systems and if they are running from a restricted thermodynamic equilibrium state into a newequilibrium state (Gay-Lussac-Thmoson-experiment). Particularly for a not isoenergetic network the temperature of the closed system should be changed after free shrinking. The temperature change can be related to the conformation changes in the network urged by the shrinking process. Deformation of networks with finite velocities as a irreversible process should also reveal temperature changes in the sample. These temperature changes can be related to the whole work being done during the deformation process.

Description / Table of Contents: Zusammenfassung Es wurden Silberhalogeniddispersionen mit Trübung- und Lichtstreuungsmessungen untersucht, die aus Gelatinelösungen in Gegenwart bzw. Abwesenheit von Adenin als Hemmstoff und von Thiosulfat als Sensibilisator hergestellt worden waren. Adenin hemmt das Kristallwachstum gleichmäßig, während die Sensibilisatorwirkung des Thiosulfats in einer vorübergehenden Hemmung liegt. Infolge der gemeinsamen Wirkung von Adenin und Thiosulfat während der Reifeprozesse, die zu stark polydispersen Systemen führte, kann man aus Trübungsmessungen völlig irreführende Ergebnisse erhalten. Die Arbeit hebt hervor, daß Folgerungen aus Trübungsmessungen in Hinblick auf die photographische Aktivität der Gelatine zu Fehlschlüssen führen können.

Description / Table of Contents: Summary It is shown that the dependence of the intrinsic dielectric strength on the volume, the time and the relaxation time of the molecular processes which was deduced formerly by using the model of a polymer with distributed free volume, can be obtained by applying the theory of extreme values, without ressorting to a model. By expressing the relaxation time as a function of temperature, the temperature dependence of the dielectric strength is obtained. The dependence found in this way is similar to that found experimentally.

Description / Table of Contents: Zusammenfassung In der Trübungstechnik für die Molekulargewichts-analyse von Polymeren wird die Ausfällung des Polymeren (Entmischung) durch die Zugabe eines Fällungsmittels zu einer sehr verdünnten Polymerlösung herbeigeführt; in diesmaligem Artikel ist eine Modifikation dieser Technik vorgeschlagen, bei welcher die Ausfällung durch die Abkühlung einer solchen Lösung herbeigeführt ist. Die Modifikation hat die praktischen Vorteile, daß durch weniger notwendig gewordenes Rühren die Stabilität der Polymersuspension erhöht wird; daß das Volumen des Systems im wesentlichen unverändert bleibt; daß es kaum möglich ist, daß hier Veränderungen in der Trübung des Systems erscheinen, nachdem das ganze Polymer ausgefällt wurde, wie bei der normalen Trübungstitration; und daß es viel leichter sein würde, die Reversibilität der Ausfällung zu untersuchen als in solchen Titrationen. Es hat auch den Vorteil vom theoretischen Standpunkt aus, daß mit monodispersem Polymer und einer Einzelflüssigkeit als Medium, worin das Polymer zuerst gelöst wurde, das System eine binäre Flüssigkeitsmischung wird. DieFlory-Hugginsschen Gleichungen wurden angewendet bei dem Fall von solchen monodispersen Polymer bei niedriger Konzentration in einem Einzelflüssigkeitsmedium, und die Ausfällungstemperaturen wurden zahlenmäßig kalkuliert und graphisch dargestellt für die Reihenfolge: Molekulargewichte von 104 bis 106; Volumfraktionen des Polymeren in der Lösung von 10−2 bis 10−9; und Werte für ψ (Entropieveränderungsparameter der Verdünnung) von 0,5, 1,0 und 1,5. Die Behandlung zeigt, daß die Idealtemperatur Θ der wichtige Parameter ist in der Entscheidung, ob das Polymer sich völlig in der obersten Grenze der experimentellen Temperaturen auflöst, und der andere Parameter ψ ist wichtig in der Entscheidung, ob alles in der untersten Grenze der Temperaturen dann ausgefällt ist. Diese zwei Konditionen sind diejenigen, die erfüllt werden müssen, wenn das Medium geeignet sein soll für die Enthüllung der totalen Molekulargewichtsverteilung eines breitverteilten Polymeren. In der nachherigen Lichtstreuungsbehandlung der Trübung der Teilchensuspension, die durch die Entmischung erzeugt ist, ist darauf aufmerksam gemacht, daß diese Teilchen sphärisch sind (da die Errechnung der Entmischungsbehandlung diese immer als mit dem Medium gequollen anzeigt) und, bezüglich deren Zusammensetzung und relativen Nähe der Brechungs-exponenten von Polymer und Medium, werden diese Teilchen einen sogar noch näheren Brechungsexponenten zu der übrigen Lösung haben. Unter diesen Umständen reduzieren sich die komplexenMieschen Verwandtschaften für Teilchen von willkürlicher Größe zu einer einfachen Art, entdeckt vonvan de Hulst; diese Art ist am aggregierenden System angewendet, für welches gezeigt ist, daß während die Aggregation fortschreitet, die Trübung, τ, erzeugt von einer bestimmten Anzahl ausgefällten Polymeren, durch den maximalen Wert durchgehen wird: $$\tau _{\max } = 2.7\pi \left| {n_2 - n_1 } \right|(\varphi _2 )_i /\lambda _0 ,$$ wennn 1 undn 2 die Brechungsexponenten von reinem Medium und reinem Polymer sind, (ϕ 2) i die durchschnittliche Volumfraktion des ausgefällten Polymer, undλ 0 die Vakuum-Wellenlänge des einfallenden Lichtes. Die Wichtigkeit dieser Beschreibung liegt im Beweis der direkten Proportionalität zwischenτ max und der allgemeinen Polymerkonzentrierung und ihrer Abhängigkeit von vier leicht zugänglichen Parametern ohne Berücksichtigung der Größe der Teilchen oder deren Zusammensetzung. Die theoretische Behandlung in diesem ersten Teil ist unter Berücksichtigung der Zeitskala der Aggregation anhand vonSmoluchowski erschlossen und einer Besprechung der grundsätzlichen Kriteria für die Auswahl geeigneter Media, besonders bezüglich der Wahl von Medien von niedrigen Brechungsexponenten, um die Trübung zu erhöhen, erzeugt durch einen angegebenen Betrag ausgefällter Polymeren.

Description / Table of Contents: Zusammenfassung Die Adsorptionskinetik an Phasengrenzflächen wird im allgemeinen durch die Diffusion der grenzflächenaktiven Stoffe an die Grenzfläche und durch Adsorptions-Desorptionsvorgänge der an die Grenzfläche herandiffundierten Moleküle bestimmt. Unter ausgewählten experimentellen Bedingungen wird einer der beiden Prozesse dominant. In Teil I der Arbeit wird die diffusionsbestimmte Adsorptionskinetik von Steroiden an Öl/Wasser-Grenzflächen durch Messung von Grenzflächenspannungen in Abhängigkeit von der Zeit untersucht. Im Teil II der Arbeit wird am Beispiel des unpolaren 5 α-Androstans gezeigt, daß hier die Adsorptionsgeschwindigkeit durch eine Aktiverungsschwelle beim Übertritt des Androstans aus der Lösung an die Öl/Wasser-Grenzfläche bestimmt wird. Zur Auswertung wird die Zustandsgleichung für Grenzflächenfilme herangezogen.

Description / Table of Contents: Summary Bounds are obtained on the stresses that can develop at an arbitrary section of a structure (such as a continuous beam, or a rigid frame) by anelastic strains of unknown distribution but bounded magnitudes. Examples of a continuous beam with two equal spans, and a portal frame are worked out in detail to illustrate the procedure.

Description / Table of Contents: Summary The subject matter of this paper is a pilot study of the feasibility of active shock isolation. Whereas conventional shock isolation systems use passive elements such as springs and dashpots, this study is concerned with investigating the advantages of using active elements, e. g., servo or force generators, in addition to passive elements. In actuality the excitation function of the isolating system is not known. The case considered here is a one-degree-of-freedom system, where the complete input is known, and the objective is to find a control to optimize the active isolator performance and compare it with an optimally tuned linear passive isolator. The maesure of performance is the ratio of the magnitudes of the maximum absolute acceleration of the protected equipment to the maximum acceleration of the shock-excited environment. Two numerical methods of solution, dynamic and linear programming, are considered and their relative merits assessed.

Description / Table of Contents: Summary With the aid of complex stress-functions, the state of stress and strain in the infinite plate and half-plate is calculated in general with regard to arbitrary force and displacement singularities (dislocation). The six fundamental singularities (force and dislocation singularity with each two components, moment and expansive force) and also higher singularities are considered. As well as the dislocation all other singularities may also act at the boundary. By integration along lines or over areas, any state of stress, including incompatible and thermoelastic states, can be represented.

Description / Table of Contents: Summary A theory of two-dimensional non-uniform flow U(y) = ae cy +be −cy past profiles is developed. For elliptical profiles exact solutions by series expansions are given. For profiles with small camber and thickness, an analogue to the Riegels method is derived. Numerical examples show the accuracy of this approximation and the influence of the shear-parameter on the interesting aerodynamic quantities.

Description / Table of Contents: Summary By means of complex stress functions the state of stress and strain in plates with notches or holes is calculated with regard to force and dislocation singularities.

Description / Table of Contents: Summary The range of validity of the singularity method of the lifting surface theory for incompressible flow is extended to include the leading edge of wings, an area of study till now not fully completed. Some refinements and improvements of the physical and mathematical content of the lifting-surface theory are proposed. Computed results for wings with four different plan-forms are given.

Description / Table of Contents: Summary The accuracy of P. D. Lux's scheme for numerically solving nonlinear hyperbolic systems of partial differential equations has been tested with regard to instationary compressible fluid flow. Two modifications of the original scheme are given, which considerably increase the speed of convergence, one of them optimizing the calculation with regard to the eventually wide range of values of the ratio Δt/Δx.

Description / Table of Contents: Summary Vertical and torsional vibrations of a non-linear stratiform soil are studied using a uniaxial model. An example is presented showing the influence of the non-linear effects on frequency and amplitude response.

Description / Table of Contents: Übersicht Es wird ein Verfahren beschrieben, das den rationellen Entwurf von Auftriebskörpern für den Reiseflug im Machzahlbereich zwischen 4 und 7 gestattet. Die Möglichkeit, reibungsfreie Strömungen um solche Körper exakt zu berechnen, beruht auf der Tatsache, daß man Strömungsflächen in rotationssymmetrischen Strömungen nach bestimmten Regeln durch feste Flächen ersetzen kann. Es zeigt sich, daß diese Methode genügend Spielraum läßt, um Flugkörper mit gewünschter Verteilung von Auftrieb und Volumen zu konstruieren. Es wird außerdem gezeigt, daß sich dieses Verfahren auch so weiter entwickeln läßt, daß der Auftriebs-Wirkungsgrad untersucht und zu einem gewissen Grade auch optimiert werden kann.

Description / Table of Contents: Summary The stability of twisted columns is investigated for a load consisting of a continuously distributed force of constant direction along the column and a single force of constant direction at the ends of the column. The numerical procedure and typical results are given for the determination of critical buckling loads in the elastic and the plastic region.

Description / Table of Contents: Summary General solutions of the heat conduction equation are obtained analytically in a rigid, finite body of arbitrary shape and composed of an arbitrary number of isotropic components in imperfect thermal contact. The solutions for the unsteady temperature distributions incorporate arbitrary heat sources and initial conditions, and time-dependent boundary conditions. Various forms of the solutions are given and the reduction of the general problem to simpler ones is indicated.

Description / Table of Contents: Summary A two-dimensional solution expressed in finite terms is given to the problem of the extension of two anisotropic semi-infinite plates, which have different elastic properties and are bonded to each other along a finite number of straight-line segments on their boundaries. The method of solution is based on the reduction to a type of dual nonhomogeneousHilbert problems for two functions. To explain the effect of anisotropy on the stresses near the common edge, numerical computations are carried out for the case where two semi-infinite plates bonded along a single segment are subjected to some special loading conditions. Stress distributions on this common edge and isochromatic lines in its neighborhood are shown in several figures.

Description / Table of Contents: Summary An elastic isotropic inhomogenous half-space is replaced by a uniaxial cylinder-symmetrical model showing equivalent behavior under torsional vibrations. This can be achieved by determining the corresponding moment of inertiaJ(z) characterizing the dispersion-free model for prescribed shear modulusG(z). Twist ϕ(z) and amplitude Φ(z) under torsional vibrations of a base-plate on an inhomogeneous half-space are calculated and determination of soil parameters from experimental data is discussed.

Description / Table of Contents: Summary The well-known solutions ofPrandtl's indentation problem (Fig. 1) for the rigid-plastic half-plane are discussed. From the viewpoint of limit analysis they all supply the same collapse load, but they are incomplete insofar as the stress fields established byPrandtl, Hill, Prager andHodge Jr. are defined only in the immediate vicinity of the punch. In this paper an admissible stable continuation of the stress field into the entire half-plane is given. In this way the collapse load of the above mentioned authors becomes firmly established.

Description / Table of Contents: Summary The author undertakes an analysis of the effect of compaction of a cylindrical vibrator on surrounding loose material. After explaining the basic data of the vibrator and the material necessary for mathematical description of the problem and the required assumptions, the problem is dealt with according to the theory of waves. The result allows a description of the oscillation of the vibrator, the energy required by the vibrator and partly transmitted to the material as well as the stresses occuring in the material. If main shearing stresses are calculated from the results, they will give an indication how far away from the vibrator compaction might be anticipated.

Description / Table of Contents: Summary A resumé of the finite element idealisation and matrix displacement analysis of a structure is presented. The stiffness matrix of a tetrachedra element, within which the stresses and strains vary linearly is then developed, emphasis being placed on the use of natural deformation modes. Using this element, two examples of arch dams are analysed and some typical results presented graphically.

Description / Table of Contents: Summary The formation of a shock wave by the gradual steepening of an acceleration wave in plane motion or in motion with cylindrical or spherical symmetry is studied for a gas which undergoes an arbitrary number of thermodynamic relaxation processes. The thermodynamic state of the relaxing gas is described implicitly by introducing additional independent thermodynamic variables together with relaxation equations for these variables. The conservation of mass and momentum leads to relations for the propagation of acceleration discontinuities. Combined with the thermodynamic equations these relations yield an expression for the variation with time of the amplitude of an acceleration wave. This in turn leads to a condition for shock wave formation. The results are generalizations of a result given byBürger for the time of formation of a plane shock wave. They are, moreover, in formal agreement with results given byVarley et al. for acceleration waves in viscoelastic materials with fading memory for which the thermodynamic equations of state are given explicitly in form of functionals.

Description / Table of Contents: Summary The biharmonic differential equation with prescribed boundary conditions on two opposite edges is established using difference expression obtained from five-term matrix equations. A complete solution to this special category of matrix equations consists of an inhomogeneous and homogeneous part, which are obtained as a sum of products of eigenvalues, eigenvectors and free constants. Equations to determine the free constants in the homogeneous solution result from the boundary conditions of the two other opposite edges. Eigenvalues and eigenvectors for a clamped strip are given.

Description / Table of Contents: Übersicht Der A-P Algorithmus wurde ursprünglich zur Eigenreduktion reellsymmetrischer Matrizen aufgestellt; er wurde jedoch in den letzten Jahren auf normalisierbare reelle und komplexe Matrizen erweitert. Beträchtliche Erfahrungen mit der Methode bei der Bestimmung der Eigenschwingungsformen und der Knickformen komplizierter Tragwerke haben gezeigt, daß sie ein wirksames Hilfsmittel für Computerrechnungen ist. insbesondere in Verbindung mit der von Argyris entwickelten Matrizenmethode [1, 2, 3]. Neuere Forschungen über Schwingungsprobleme mit nicht-proportionaler Dämpfung bestätigen, daß die Methode auch auf diesem Gebiet sehr wertvoll ist. Es wird hier die Erweiterung dieses Problems behandelt, um aerodynamische Dämpfungs- und Steifigkeitskräfte zu berücksichtigen, wobei auf die Untersuchung der dynamischen Stabilität eines gesamten Flugzeuges mittels der antisymmetrischen Frei-Frei-Schwingungsformen Bezug genommen wird.

Description / Table of Contents: Übersicht In der vorliegenden Arbeit wird das hydroelastische Problem des Schwappens von flüssigem Treibstoff in einem kreiszylindrischen Tank mit starrer Wand und ebenem, flexiblem Boden untersucht. Die Flüssigkeit wird als reibungsfrei, homogen und inkompressibel, der Boden als gespannte Membran angenommen. Eine Näherungslösung wird angegeben und numerische Rechnungen werden diskutiert. Die erhaltenen Resultate zeigen gute Übereinstimmung mit experimentellen Befunden anderer Autoren.

Description / Table of Contents: Summary This paper deals first with the equations of motion of a conductive, homogeneous and isotropic elastic body subjected not only to externally applied mass forces and surface forces, but also to a uniform magnetic field, in which an induced magnetic field is generated. On the assumption that the electrical conductivity is infinite, the problem of motion is reduced to the consideration of a single differential vector equation in which the displacement of a point in the elastic body is the only unknown. The conditions that must be satisfied at the surface are then considered. Using the generalised formula of Kirchhoff, formulas expressing the Cartesian components of the displacement, the cubic dilatation and the rotation components are established by means of the so-called fundamental elements.

Description / Table of Contents: Summary This paper expounds researches done by the author and others on the theory of the diffusion of neutrons in a moderating medium from the point of view of “phenomenological theory” and of “transport integro-differential equations”. In particular the transformational methods with a rigorous analysis for the case of “slab-geometry” are considered.

Description / Table of Contents: Summary After a few basic remarks on continuous media mechanics, equations of unsteady laminar flow for non-newtonian incompressible fluids are written; a solution for a particular plane flow (with zero hydraulic slope) is carried out, supposing that the components of the stress tensor T are polynomials in the components of the deformation rate tensor F. In particular if we adopt a cubic law, we recognize a second viscosity coefficient, which may be a positive or negative number; a way is then suggested for finding experimentally both viscosity coefficients of the fluid; a simple numerical example is also given.

Description / Table of Contents: Summary The nature of a material is in large part described by its symmetry group. It is proposed to extend this concept to a more general type of symmetry transformation, and the use of such an extension is illustrated by using it to define several classes of materials and presenting the corresponding representation theorems.

Description / Table of Contents: Summary The behavior of the beam-soil system is examined within the scope of the bilateral schematization of ideal elastoplastic bodies, in the following work stages; the expression for the limit load is supplied for each stage: -elastic beam in an elastoplastic medium -elastoplastic beam in an elastic medium -beam and soil in an elastoplastic condition. Two peculiar features of the problem are highlighted:1) the “plastic hinge migration” phenomenon, due to the elastic unloading of the material, and2) the successive propagation of plastification in the soil which, being related to the displacement of the hinges in the beam, leads to the identification of the collapse mechanism of the systme.

Description / Table of Contents: Summary In analogy with the well-known Shanley's column model, a model has been devised to illustrate the buckling behaviour of three-hinged arches in the inelastic range. A bilinear stress-strain relationship has been assumed in the deformable elements. As in the case of the compressed strut, a wholesegment of bifurcation is found, and load values analogous to thetangent modulus (Shanley) andreduced modulus (Kàrmàn) loads can be defined. An example of load-displacement curves is fully developed.

Description / Table of Contents: Summary The thermodynamic foundations of a theory of permanent deformations are considered: in the axioms, an appropriate definition of free enthalpy plays an essential rôle. Our developments are parallel (but in a certain sense dual) to those which occur in a theory of viscoelastic materials, due to Coleman and Noll.

Description / Table of Contents: Summary The diffraction of a plane wave incident on an isolated breakwater is here studied: the exact solution of the problem is briefly reported and a general method involving energies is used to determine comparative importance of the terms of the series which appear in the solution, which becomes of much greater facility in use in practical problems. Numerical calculations have been carried out for twelve different cases, with the wavelength of the incident wave comparable to the length of the breakwater. Results are graphically shown in a set of tables.

Description / Table of Contents: Summary The search for the deviation from the linear elastic, of the response of a nonlinear discrete structure to given loads, is formulated for various classes of cases. All the problems considered are shown to be reducible to a single mathematical model: the quadratic program with sign constraints only. The Kubn-Tucker theorem for quadratic programming directly supplies the appropriate extremum principles, for which some physical interpretations are proposed. Other results of quadratic programming theory prove to be useful in the discussion of the structural problems considered.

Description / Table of Contents: Summary Equilibrium equations for orthotropic media are written taking the displacement components as unknowns; these equations are integrated with operational methods by separation of the variables. The unknown quantities are six « initial funcitons » that is, displacements and their partial derivatives with respect toz, calculated on the planez=0. Following a method of structural mechanics, the cases of symmetrical and nonsymmetrical loading of plate, namely compression and flexion, are considered separately. The separation of the variables allows us to resolve in two successive stages the problem of the boundary conditions: the Cauchy conditions on the surfacesz=± h become differential equations to which we associate the condition on the cylindrical surface. The process leads to a symbolic solution of the problem from which we construct the resolvent equations in the form of power series of operators. If terms of a higher order are retained in these equations, a more accurate theory is obtained; it is shown that if only the first term is assumed, the equation for the ortho tropic plate in the Kirchhoff-Love sense is obtained. The method is applied in order to resolve a problem numerically; the results are compared with those deduced by the usual theory.

Description / Table of Contents: Summary In the Hamiltonian formulation of relativistic theory of gravitation the gravitational field at a given time is defined on a spacelike hypersurface of Riemannian space-time by six gravitational potentials and as many conjugate momenta. The former characterize the metric of the hypersurface and it is shown that the momenta are constructed tensorially only with the two fundamental tensors of the hypersurface since Dirac's velocities are equated with the components of the second fundamental tensor. Invariants of the two fundamental tensors, geometrically interpretable, can then be introduced into the Hamiltonian. It is at once clear from the Gauss and Codazzi equations, relating the two fundamental tensors of a hypersurface that the four secondary constraints, which the conjugate dynamical variables satisfy, are equivalent to four Einstein gravitational equations.

Description / Table of Contents: Summary An elastoplastic beam-column model with one degree of freedom subjected statically to an on-center or off-center axial compressive force is considered. Its dynamic behavior in the elastoplastic range, resulting from a transverse periodic acting force in resonance with the structure in the elastic range, is examined. The principal features are highlighted by a phase plane study.

Description / Table of Contents: Summary Two model struts subject to an axial force and to radiant heat parallel to the axis are studied dynamically. The elastic and thermal deformations of the strut are “lumped” in one or two cells; the heat absorbed by each cell and the consequential thermal deformation depend on its rotation. Thermal inertia is neglected, while a viscous damping is introduced. The possible exchange of energy between the strut and the surrounding world leads to a non-conservative mechanical problem. The stability of equilibrium of the original strut position is investigated by the kinetic method, and the zones of stability (bounded perturbed motion), static instability (divergent motion) and dynamic instability (flutter) are found and plotted in some cases, in function of axial load and radiant heat intensity.

Description / Table of Contents: Summary For shells generated by translation of an arbitrary profile Λ along an arc of finite rise and large chord, as compared with the dimensions of Λ, an elastic theory is developed on three-dimensional basis by the method of parametric expansions.