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  • Articles  (114,572)
  • Elsevier  (67,825)
  • Springer  (46,747)
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  • 1975-1979  (114,572)
  • Physics  (114,572)
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  • Articles  (114,572)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 28 (1979), S. 11-17 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Mit Hilfe von Radiosondendaten wurde eine Frontalzone, die am 30. März 1977 südlich von Denver, Colorado, verlief, im Detail analysiert. Die Frontalzone zeigte eine Mehrfachstruktur, die auch aus den Verteilungen von O3- und Kondensationskern-Konzentrationen zu ersehen war. Diese Konzentrationen wurden mit dem NCAR Sabreliner vermessen.
    Notes: Summary A detailed analysis of a frontal zone located south of Denver, Colorado, on 30 March, 1977 was made using radiosonde data. This zone revealed a multiple structure which also showed up in the distributions of O3 and condensational nuclei concentrations measured with the Sabre-linear aircraft of the National Center of Atmospheric Research.
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  • 2
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    Meteorology and atmospheric physics 28 (1979), S. 1-10 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Am 29. und 30. März 1977 wurden von einem Sabreliner-Flugzeug aus in einer Frontalzone südlich von Denver in Colorado Ozon und Kondensationskerne gemessen. Das Ozon diente als Tracer für stratosphärische Luft und die Kondensationskerne dienten als Tracer für troposphärische Luft. Sowohl der Langer-Kondensationskernzähler wie auch der Rich-100 Zähler können für Messungen der Kondensationskernkonzentration in der Nähe der Tropopause verwendet werden. Der erstere ist jedoch für niedrige Konzentrationen empfindlicher. Die gemessenen Kerne hatten meist einen größeren Radius als 0,005 μm und bestanden aus tausenden von Molekülen. Die Mesostruktur der Ozon- und Kondensationskernkonzentrationen stimmte gut mit der doppelten Struktur der Frontalzone überein, die aus einer Detailanalyse der Radiosondendaten ersichtlich wurde.
    Notes: Summary Ozone and condensation nuclei were measured on 29 March 1977 (and 30 March GMT) from a Sabreliner in a frontal zone south of Denver, Colorado. The ozone served as a tracer for stratospheric air and the condensation nuclei as a tracer for tropospheric air. Both the Langer condensation nucleus counter and the Rich-100 counter can be used to measure condensation nucleus concentrations in the vicinity of the tropopause. However, the former counter is more sensitive to low concentrations. The nuclei measured were found to be almost entirely larger than 0.005 μm in radius, consisting of thousands of molecules. The mesostructure of the ozone and condensation nucleus concentrations agreed well with a double structure of the frontal zone that became apparent from a detailed analysis of radiosonde data.
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  • 3
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    Meteorology and atmospheric physics 28 (1979), S. 111-112 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
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  • 4
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    Meteorology and atmospheric physics 28 (1979), S. 187-193 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Eine theoretische annähernde Berechnung gibt die Bedingungen an, die für die Bildung der Wellenform eines Frontenprofiles erforderlich sind. Die Wellenform hat Charakteristiken von sekundären und primären Fronten. Aufgrund der systematischen Analyse der Beobachtungsdaten des meteorologischen Stationsnetzes von Jugoslawien wurde gefunden, daß es Wettersituationen gibt, bei denen das Frontenprofil Wellenform hat. Dafür werden zwei Beispiele vorgelegt.
    Notes: Summary One theoretical approach indicates the conditions required for formation of a waveform of the frontal profile. The wave form has characteristics of secondary and primary fronts. On the base of systematic analyse of data from network of meteorological stations over Yugoslavia it is found that there are weather situations when frontal profile is wave shaped. Two examples are presented.
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  • 5
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    Meteorology and atmospheric physics 28 (1979), S. 233-244 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Summary Three examples for non-frontal cloud system are discussed: 1) A cloud system that is created by positive vertical motion as a consequence of vertical wind shear; 2) a cloud system is created by horizontal and vertical temperature and humidity differences; 3) a cloud system is created by positive vorticity values.
    Notes: Zusammenfassung Es werden drei Beispiele nichtfrontaler Bewölkungssysteme diskutiert: 1) Ein Wolkensystem wird durch positive Vertikalbewegung infolge vertikaler Windscherung erzeugt; 2) ein Wolkensystem wird durch horizontale und vertikale Temperatur- und Feuchteunterschiede erzeugt; 3) ein Wolkensystem wird durch zyklonale Vorticity erzeugt.
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  • 6
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    Meteorology and atmospheric physics 28 (1979), S. 195-210 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Von den verschiedenen Termen, welche in den Wärmehaushalt eines Wasservolumens in der Nähe der Meeresoberfläche eingehen und welche Anomalien der Oberflächentemperatur (SST) beeinflussen, scheint die Advektion in den großräumigen Strömungssystemen, vor allem im Westpazifik, einige Bedeutung zu besitzen. Langzeitige Tendenzen in dieser Advektion scheinen zu einem gewissen Grade mit der Schubspannung der Passatwinde des Nordpazifik gekoppelt zu sein. Die Variabilität der Meeresoberflächentemperaturen innerhalb der Zeitspanne von etlichen Monaten scheint entlang der japanischen Küste, zumindest teilweise, von Strömungsmäandern und im offenen Ozean von windschubbeeinflußten Mechanismen kontrolliert zu sein.
    Notes: Summary Among the various terms entering the heat budget of an oceanic volume close to the ocean surface and affecting sea-surface temperature (SST) anomalies, advection in the large current systems appears to be of importance in the West Pacific. Long-term trends in this advection appear to be coupled, to a certain extent, to forcing by zonal wind stress in the North Pacific trade-wind region. Variability of SST on time scales of the order of months off the coast of Japan seems to be governed, at least in part, by current meanders, and in the open ocean by winds-stress operated mechanisms.
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  • 7
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    Meteorology and atmospheric physics 28 (1979), S. 211-232 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Summary In the summer months of 1976 to 1978 the surface energy balance was measured at Obergurgl-Wiese (1960 m a.s.l.) and at Hohe Mut (2560 m a.s.l.) in the Tyrolean Alps. As first result the components of the energy balance at the two stations were analyzed for 8 clear summer days. Microclimate is different at the two stations because of the vegetation (meadow and curvuletum, resp.), because of the location near the bottom of the valley and on a mountain ridge and because of the altitude difference of 600 m. Hourly values of the energy balance components are calculated from radiation measurements, from soil temperatures, and from profiles of air temperature and water vapour using the Bowen ratio method. For the period of positive radiation balance on clear summer days Bowen ratio values of 0.5 to 0.8 are representative for the curvuletum of the Hohe Mut, for the meadow at Obergurgl the values are 0.2 to 0.6. At the two stations the Bowen ratio values increase during summer because vegetation dries up. The diurnal variation of the Bowen ratio is different at the two stations due to vegetation and water balance. In order to check the laws of turbulent transport for applications in mountainous regions, the product of dimensionless wind shear and dimensionless temperature gradient was calculated from wind profile measurements and energy fluxes at the Hohe Mut. The relationship of these parameters to the stability parameters Richardson number and dimensionless height correspond to relations found over homogeneous, level terrain.
    Notes: Zusammenfassung In den Sommermonaten der Jahre 1976 bis 1978 wurden an den Stationen Obergurgl-Wiese (1960 m) und Hohe Mut (2560 m) in den Ötztaler Alpen Wärmehaushaltsmessungen durchgeführt. Als erste Ergebnisse dieser Untersuchungen werden die Komponenten der Energiebilanz an beiden Stationen für je 4 heitere Sommertage 1976 und 1977 analysiert. Unterschiede im Mikroklima beider Stationen werden auf die Vegetation, Bergwiese bzw. Curvuletum der alpinen Grasheide, auf die Lage nahe dem Talboden bzw. auf einem Bergrücken und auf die Höhendifferenz von 600 m zurückgeführt. Die Komponenten der Energiebilanz wurden aus Strahlungsmessungen, aus Profilen der Bodentemperatur und aus Profilmessungen von Lufttemperatur und Dampfdruck über das Bowen-Verhältnis stundenweise berechnet. Für das Curvuletum der Hohen Mut sind an heiteren Sommertagen für die Periode positiver Strahlungsbilanz Bowen-Verhältnisse von 0,5 bis 0,8 repräsentativ, für die Bergwiese Werte von 0,2 bis 0,6. An beiden Stationen kann man am Anstieg des Bowen-Verhältnisses im Laufe der Vegetationsperiode die zunehmende Austrocknung erkennen. Im Tagesgang hingegen verhält sich das Bowen-Verhältnis an den zwei Stationen unterschiedlich, was durch Vegetation und Wasserhaushalt bedingt ist. Um für die Messungen im Hochgebirge die Anwendbarkeit der Gesetze des turbulenten Austausches zu überprüfen, wurde bei labiler Schichtung aus Windprofil und Energieflüssen auf der Hohen Mut das Produkt von dimensionslosem Temperaturgradienten und dimensionsloser Windscherung berechnet. Die Beziehung dieser Größen zu den Stabilitätsparametern Richardson-Zahl und dimensionslose Höhe zeigt an der Hochgebirgsstation einen ähnlichen Verlauf wie an Flachlandstationen.
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  • 8
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    Meteorology and atmospheric physics 28 (1979), S. 271-277 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Summary The drainage behaviour of free water in various snow types is examined in detail. It was found a strong dependence on the grain-size and therefore also on the degree of metamorphism. For the parametern which determines the drainage behaviour results in dependence on the snow structure a range from 1,5 to 4,3. An error analysis of two evaluation methods shows, that it is preferable to obtain the parametern from the course of the measured outflowing water volume rather than from the course of the water flux. The gravity-flow-theory is suitable for describing the drainage process.
    Notes: Zusammenfassung Das Sickerverhalten von freiem Wasser wird in verschiedenen Schneearten näher untersucht. Es zeigt sich eine starke Abhängigkeit von der Korngröße und damit auch vom Grad der Metamorphose. Für den das Sickerverhalten bestimmenden Parametern ergibt sich in Abhängigkeit von der Schneestruktur ein Wertebereich von 1,5≤n≤4,3. Eine Fehleranalyse zu zwei Auswerteverfahren zeigt, daß die Ermittlung dieses Parameters aus dem gemessenen Verlauf des ausrinnenden Wasservolumens der Ermittlung aus dem Verlauf des Flusses vorzuziehen ist. Zur Beschreibung des Sickerverhaltens hat sich die “gravity-flow”-Theorie als geeignet erwiesen.
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  • 9
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    Meteorology and atmospheric physics 28 (1979), S. 305-308 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
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  • 10
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    Meteorology and atmospheric physics 28 (1979), S. 293-299 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Laboratoriums experimente haben gezeigt, daß sich unter besonderen chemischen und physikalischen Bedingungen Mangan aus einer Mn++-angereicherten Lösung von Meereswasser in Form von kolloidalen Micellen absondert. Diese werden, statt zusammen mit dem Lehmmaterial abzuscheiden, davon abgesondert und häufen sich in der Sedimentlösungs-zwischenschicht an. Dies kann eine Erklärung sein für die in der Natur beobachtete Mangankonzentration am Meeresboden gegen die Oberfläche von Sedimentschichten hin. In manchen Fällen können die schwarzen magnetischen Kügelchen (B. M. S.) als Anhäufungskerne für die Fällung von Mangan-Micellen wirken.
    Notes: Summary Laboratory experiments have shown that in particular chemical and physical conditions, manganese separates from a Mn++-enriched solution of seawater in the form of colloidal micelles. These, instead of co-precipitating with the clay matrix, are repelled from it, and accumulate at the sediment solution interface. This may be an explanation of the manganese concentrations observed in nature on the seafloor towards the surface of sediment columns. In some cases, the black magnetic spherules (B. M. S.) might act as aggregation cores for the precipitation of manganes micelles.
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  • 11
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    Meteorology and atmospheric physics 28 (1979), S. 301-304 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Summary Electrical field-strength fluctuations, produced by a person walking in front of an open metal cage, become weaker and almost disappear, if an electric DC-field of about 200 to 1000 V/m is generated within the cage.
    Notes: Zusammenfassung Elektrische Feldstärkeschwankungen, die durch Umhergehen einer Person vor der Öffnung eines Metallkastens erzeugt werden, erscheinen wesentlich schwächer, wenn im Kasten ein elektrisches Gleichfeld von etwa 200 bis 1000 V/m erzeugt wird.
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  • 12
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    Meteorology and atmospheric physics 28 (1979), S. 341-348 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Eine Analyse der Monatsmittel der Gesamtwolkendecke in den Tropen weist die Existenz einer quasibiennalen Oszillation der Gesamtwolkendecke nach. Die Amplitude dieser Oszillation liegt zwischen 1 und 2,5% in den zonalen Anteilen der Gesamtwolkendecke über den äquatorialen und südlichen Breiten. Diese Oszillation wurde auch mit den entsprechenden Oszillationen der stratosphärischen Temperaturen verglichen. Die quasibiennale Oszillation der tropischen Gesamtwolkendecke ist längerzeitigen Schwankungen überlagert, was im Text besprochen wird.
    Notes: Summary An analysis of monthly mean total cloud cover fractions in the tropics showed the existence of a quasi-biennial oscillation in total cloud cover. The amplitude of the oscillation is between 1 and 2.5 percent in zonal total cloud cover fractions, over the equatorial and southern latitudes. This oscillation is also compared with the corresponding oscillations in zonal mean stratospheric temperatures. The QBO in the tropical total cloud cover is superimposed on longer-term fluctuations (trends) which are discussed in the text.
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  • 13
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    Meteorology and atmospheric physics 28 (1979), S. 375-386 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Am 2. November 1977 ist im Gebiet von Athen ein ungewöhnlich starker Regen gefallen. Die gefallene Regenmenge von 165 mm ist die größte seit Beginn der Beobachtungen im Jahre 1871 registrierte Niederschlagsmenge. Nach Darstellung der räumlichen und zeitlichen Verteilung des Regens wird die synoptische Situation beschrieben. Es wird angenommen, daß dieses Ereignis in erster Linie auf den Einfluß des verbauten Gebietes auf eine potentiell instabile Luftmasse zurückzuführen ist und daß das Ergebnis als stadtbedingter Regen bezeichnet werden kann.
    Notes: Summary A spectacularly heavy rainstorm occurred in the Athens area on 2 November 1977. The 165 mm of rain which fell was the heaviest recorded in Athens since records began in 1871. After showing the distribution of the rain spatially and temporally, the synoptic situation is described. It is suggested that the event was due primarily to the influence of the built-up area on a potentially unstable airmass and that the result was an “urban rainstorm”.
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  • 14
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    Meteorology and atmospheric physics 28 (1979), S. 396-396 
    ISSN: 1436-5065
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  • 15
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Es werden Ergebnisse von Messungen der Radon-Aktivität, die während des Monson-77 Beobachtungsprogrammes über der Arabischen See und der Bucht von Bengalen durchgeführt worden sind, dargelegt und zusammen mit Beobachtungsdaten des früheren ISMEX-73 Programmes (Indisch-sowjetisches Monsun-Experiment) diskutiert. Der Radon-Gehalt in der Monsun-Region zeigt beträchtliche Änderungen im Ausmaß von 1 bis 15 pCi pro m3 Luft. Die Werte über der Arabischen See zeigen eine merkliche Zunahme in Breiten um 20°N, die Werte von 8 bis 10 pCi/m3 erreicht, womit auf eine gesteigerte Zufuhr von kontinentaler Luft hingewiesen wird. In niedrigeren Breiten liegen die Werte bei wenigen pCi/m3, was für maritime Luft in den äquatorialen Gebieten charakteristisch ist. Kontinuierliche Messungen an weit voneinander entfernt gelegenen festen Stationen in der Arabischen See ergaben ähnliche Änderungen im Radon-Gehalt. Diese Änderungen scheinen mit Monsunstörungen und ihrer Verlagerung gegen Westen in Verbindung zu stehen, die eine Verminderung des Radon-Gehaltes durch eine Verstärkung der Monsunströmung aus Süden, die nur einen geringen Radon-Gehalt hat, mit sich bringen. In der Bucht von Bengalen zeigen sich niedrigere Radon-Werte während Monsunpausen. Dies könnte darauf zurückzuführen sein, daß während Monsunpausen ein Isobarenverlauf in Nord-Süd-Richtung vorherrscht, wodurch äquatoriale maritime Luft direkt in die Bucht von Bengalen geführt wird, ohne über das Festland von Indien zu kommen.Während des Monsuns kommen die Luftmassen aber erst nach Überstreichen von Indien in die Bucht von Bengalen und haben daher größeren Radon-Gehalt. Nahe der Küste ist der Radon-Gehalt erwartungsgemäß groß.
    Notes: Summary Measurements of Radon activity carried-out during the Monsoon-77 Observational Programme over the Arabian Sea—Bay of Bengal Region are presented and discussed along with the earlier ISMEX-73 data. Levels of radon within the monsoon region show considerable variations in the range of one to fifteen picocuries per cubic meter of air. The levels in the Arabian Sea showed a marked increase at latitudes near-about 20°N, reaching values of eight to ten picocuries per cubic meter, thereby suggesting increased input of continental air. At lower latitudes, the levels are a few picocuries per cubic meter which is characteristics of maritime air from equatorial regions. Continuous measurements at stationary positions in the Arabian sea at widely separated locations show similar variations in radon levels. These variations seem to be connected with monsoon disturbances and their westward movements which reduce radon levels due to the strengthening of the southerly monsoon current having low radon content. In the Bay of Bengal, there is some evidence of lower radon values during “break” monsoon conditions. This could be due to the prevailing pressure pattern during the “breaks” with isobars running in north-south direction resulting in the movement of equatorial maritime air mass directly to the Bay without going over the land mass of India. During strong monsoon conditions, the air mass enters the Bay after travelling over India and consequently has higher randon levels. Near the coast, randon values are high, as is to be expected.
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  • 16
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    Polymer bulletin 1 (1979), S. 665-670 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary It was found that isotactic polymerization of propylene took place over titanium ion-exchanged Y-zeolite without organometallic compounds. The results obtained have led to the conclusions that Ti4+ species as well as Ti3+ species are active for the polymerization and that neither Ti-alkyl bonds nor Cl ligands are necessarily essential for polymerization of propylene.
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  • 17
    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A new azo monomer (2) was synthesized and copolymerized with styrene. The resulting azo copolymer could be used as an initiator for the acrylonitrile polymerisation yielding grafted copolymers. Quantitative treatment of the grafting experiments leads to the conclusion that the intermediate thiyl radicals show less reactivity towards monomers than phenyl radicals.
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  • 18
    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Coordination chain polymers of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), zn(II), and Cd(II) with 5,5-(benzidinebisazo)-8-hydroxyquinoline were synthesized by refluxing a mixture of metal acetate hydrates and ligand (1∶1) in DMSO. From analytical data an empirical formula of ML.2H2O is indicated. Ir spectra reveal coordination through O and N of oxine units, thus forming the polymeric chain; presence of coordinated water is also indicated. Magnetic moments and electronic spectra suggest octahedral geometry around the central metal ion. Besides the presence of 2H2O, TGA shows the order of thermal stability as : Cd∼Zn〉 Mn〉 Co∼Ni∼Cu〉Fe.
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  • 19
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    Polymer bulletin 1 (1979), S. 715-722 
    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Synopsis Several poly(amidine) and poly(guanidine) copolymers and their hydrochloride salts were synthesized by introducing the functional groups into suitable polymers. The properties of the resulting copolymers were investigated by base and acid titration.
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  • 20
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    Polymer bulletin 1 (1979), S. 697-707 
    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A series of PMMA samples of different molecular weights and degrees of copolymerisation have been tested for their crack-healing behavior. Slightly above Tg, a diffusional interpenetration of chain segments takes place. The fracture toughness in the plane of the interpenetrated interface was measured in short- and longtime experiments. After very short penetration times of only 5 min, full material resistance was regained in short-time experiments, whereas the long-time properties were not restored. A qualitative explanation of these effects, based on structural parameters, is given.
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  • 21
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    Polymer bulletin 1 (1979), S. 727-731 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 22
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    Polymer bulletin 1 (1979), S. 723-725 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Divalent metal salts of mono(hydroxyethyl)phthalate (HEP) were considered to be of interest as difunctional ionic monomers and are useful for the preparation of condensation polymers. Recently, Matsuda1 reported the preparation of Ca, Mg and Zn salts of mono-(hydroxyethyl)phthalate and their polymers2–7. He prepared these salts by the reaction of HEP with the respective divalent metal oxides. But so far there was no report on the preparation of Pb2+ and Mn2+ salts of HEP. Since metal dicarboxylates can be obtained by the reaction of organic dibasic acids and metal acetates8, Pb2+ and Mn2+ acetates can similarly react with HEP to give their respective salts at the optimum temperature. We report here the synthesis and characterisation of Pb2+ and Mn2+ salts of mono(hydroxyethyl)-phthalate (HEP).
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  • 23
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    Polymer bulletin 1 (1979), S. 743-748 
    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract PMMA and PC samples were subjected to several cooling rates from the glass transition temperature. Stress-relaxation data, obtained with these samples under strains larger than the yield strain, were not influenced by the cooling rate previously experienced by the material. This shows that after yielding the effect of previous aging is quickly erased; similar indications, drawn from calorimetric measurements, were already available in (11–12).
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  • 24
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    Polymer bulletin 1 (1979), S. 749-753 
    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A new type of polymer support for immobilizing enzymes, a copolymer grafted onto nylon was investigated. Polyacrylamide was used and successfully coupled to β-galactosidase (from yeast and bacteria) using two different methods to give activities of the order of 5 units/g of polymer for the yeast enzyme, and 156 units/g for the E.coli enzyme. Lactose did not affect the yield. The azide method gave better results than the glutaraldehyde method. β-galactosidase coupled enzyme was fairly stable but not as good as the free enzyme. Papain was also coupled to the polyacrylamide grafted nylon using both methods; the glutaraldehyde gave better results with 1.5mg of enzyme being coupled for each gram of polymer.
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    Notes: Summary The present paper describes the terpolymerization involving 2-phenyl-1,3,2-dioxaphospholane, methyl acrylate, and carbon disulfide, which took place without any added initiator in benzonitrile or dimethylformamide. The structure and composition of terpolymer were determined by NMR and IR spectra, as well as by elemental analysis. A reaction scheme proceeding via zwitterion was proposed (Eq. 2–5).
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    Polymer bulletin 1 (1979), S. 253-258 
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    Notes: Summary Poly(vinyl chloride-g-isobutylene) has been synthesized using mildly dehydrochlorinated (NaOH treated) PVC in conjunction with BCl3 coinitiator. Treatment of PVC with NaOH increases initial thermal dehydrochlorination rate and renders the polymer suitable for efficient grafting. Untreated PVC produces negligible grafting.
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    Polymer bulletin 1 (1979), S. 347-354 
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    Notes: Summary The fragmentation of linear polyethylene of high molecular weight, of normal alkanes, and of other nonbranched poly- α- olefins in a pyrolyzer connected with a gas chromatograph was studied previously. From the evaluation of the fragments longer than C11 or than the respective pentamer random decomposition process was suggested for these polymers. This process was described with characteristic cleavage probabilities for the C-C-bonds in the backbone of the chain. It is not possible to apply this simple model to the decomposition of normal alkanes without consideration of the volatilization. An approach to this problem is presented in this paper.
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    Polymer bulletin 1 (1979), S. 397-402 
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    Notes: Summary By means of a new tensile rheometer for polymer melts, stress-strain curves σ(ε) and the elastic recovery εR(ε) of a low density polyethylene melt were measured up to total strains ε=7, i.e. stretch λ=1097, at 150°C and two strain rates, ε=0.03 and 0.1 s−1. Tensile tests up to very high strains e give relevant results only if the test performance is characterized by quality parameters which are defined and given in this paper. The test results show a maximum in a as well as in εR at about ε=5.5. Hence, in the range of ε investigated, a rheologically steady-state of flow does not exist.
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    Polymer bulletin 1 (1979), S. 517-522 
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    Notes: Summary The photochemical and thermal cis-trans isomerization of 4,4 -(diamido)azobenzene derivative built in the polyester segment of a segmented poly(ester urethane) has been investigated. The photoisomerization in bulk proceeds more slowly than in solution and lower fractions of cis-isomers are reached in the photostationary state. The thermal cis-trans isomerization follows first order kinetics in polymers with amorphous soft phase but can only be described by two simultaneous first order processes in annealed samples. This is attributed to restrictions in the chain segmental mobility; it is assumed that the isomerization behaviour reflects different molecular motions in the bulk polymer.
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    Polymer bulletin 1 (1979), S. 523-528 
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    Notes: Summary The kinetic theory of crosslinking by step reactions (Kuchanov 1978) may be extended beyond the gel point, and the structure and amount of sol may be described. For random reactions, the kinetic theory yields results identical with the theory of branching processes based on cascade substitution (Gordon 1962, 1975, Dobson 1965). The extension of the kinetic theory may be employed in order to compare deviations between the two theories expected for the dependent reactivities of functional groups.
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    Polymer bulletin 1 (1979), S. 529-534 
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    Notes: Summary The mechanism of initiation of polymerization of methyl acrylate by di-t-butyl peroxalate at 60°C, has been investigated using 2,2,6,6-tetramethylpiperidine-1-oxyl as a radical trapping agent and isolation of the resulting products. The following processes were identified: Tail addition of t-butoxy radicals to monomer, hydrogen abstraction from the methyl group of the monomer and fragmentation of the t-butoxy radicals to methyl radicals followed by tail addition of these to the methyl acrylate.
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    Polymer bulletin 1 (1979), S. 647-652 
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    Notes: Summary The photostabilizing effect of a hindered piperidine derivative was studied in the photooxidation of polypropylene films by following the formation of carbonyl and hydroperoxide groups, as well as the change of concentration of the stabilizer. This additive — the tetramethylpiperidine sebacate — proved to be more effective than hydroxybenzophenone, hydroxybenztriazole or a sulphur containing nickel complex, since no oxidation products were formed after irradiation with 20O Mlxh dose. Addition of the piperidine derivative together with hydroxybenztriazole or with the organic nickel complex was less effective than with hydroxybenzophenone. In latter case concentration of both stabilizers under irradiation decreased at a slower rate than in the case of separate application. The effect of Cyasorb UV 531 and Tinuvin 770 was additive and the spontaneous rupture of the samples took place only after a long period of irradiation (∼ 250 Mlxh).
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    Polymer bulletin 1 (1979), S. 691-695 
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    Notes: Summary In a second example of the functionalization of soluble polymers the conversion of the hydroxyl groups of poly (oxyethylene) into carboxyl groups is reported. As protected carboxyl component, 4-toluenesulfonyl lactic acid ethyl ester was synthesized and was allowed to react with sodium salt of poly(oxyethylene). Polymer-analogous hydrolysis of the di(lactic acid ethyl ester) poly(oxyethylene) yielded the carboxyl derivative of poly (oxyethylene).
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    Polymer bulletin 1 (1979), S. 671-678 
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    Notes: Summary The use of a Ce (IV)-thiomalic acid (Ce4+-TMA) redox system as an initiator in the polymerization of acrylamide (M) in an aqueous medium has been investigated. The Ce4+ forms a 1∶1 complex with TMA, decomposing through free radical mechanism in an acid medium. From 5 to 15% conversion the rate equation is $$R_p = - \frac{{d[M]}}{{dt}} = k[M]^{3/2} [Ce^{4 + } ]^x [TMA]$$ where Rp is the rate of polymerization and x is 0.5 or 1.0 depending upon the concentration of monomer. The overall energy of activation has been calculated to be 9.12 k cal. deg−1 mol−1(38.12 kJ/mol) in the investigated range of temperature (25°–40°C) the degree of polymerization (P) of the polymer is directly proportional to [M]. The number of average molecular weight of the polymer remains unaffected at lower concentration of Ce4+ and is found to decrease at higher concentrations. In this investigation the kinetics and mechanism of the Ce(IV)-thiomalic acid (TMA) redox system to initiate the polymerization of acrylamide has been studied. Acrylamide (E. Merck) was purified by usual methods. Thiomalic acid and eerie ammonium sulfate were used without purification. All solutions were p repared in twice distilled water. The polymerization procedure adopted was similar to the one used by MISRA et al. [3, 4]. The polymerization was followed by quantitative estimation of the double bonds in acrylamide as described [8]. A small variable induction period was observed perhaps due tothe residual oxygen in the thiol solution. Curves were plotted after eliminating the induction period. The average molecular weights of the p olymers were determined by viscosity measurements at 30°C in an aqueous medium using the relationship of DAINTON et al. [2]. $$[\eta ] 30^\circ = 6.8 x 10^{ - 4} \bar Mn^{0.66} $$ Where [η]=intrinsic viscosity of the polymer solution and ¯Mn=molecular weight of the sample.
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    Polymer bulletin 1 (1979), S. 737-741 
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    Notes: Abstract The method of stress relaxation has been used to study the effect of ketones on polyethylene as it changes with temperature. From the observation of the stress relaxation in polyethylene under ketones and its temperature dependence, the activation energy of penetrant-enhanced relaxation of polyethylene caused by ketones were obtained and the effect of ketones on polyethylene were discussed.
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    Polymer bulletin 1 (1979), S. 755-761 
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    Notes: Summary β-Galactosidase and glucose oxidase have been immobilized on cellulose-polyacrylamide (C-PAM) graft copolymers, using the azide method or through glutaraldehyde. The original (C-PAM) copolymers were prepared via radiation-induced grafting under controlled conditions by both post-irradiation and simultaneous procedures. The optimum conditions for coupling of the copolymers to the enzymes were established as were the levels of activity of the immobilized enzymes. Grafting by the simultaneous route was seen to be more efficient than postirradiation grafting. Indirect evidence of grafting was found from elemental and thermal analysis. Binding of β-galactoside was found to be more successful than that of glucose oxidase. A relationship between the level of immobilized enzyme activity and the extent of grafting in the copolymer was established for the β-galactosidase system.
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    Polymer bulletin 1 (1979), S. 763-770 
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    Notes: Summary The heat of mixing of polyisobutylene with ethylbenzene was measured from 18.2 to 69.2° C with a Tian-Calvet twin micro-calorimeter, and the exchange enthalpy parameter X12 in Flory's theory was estimated. The X12 obtained was discussed also in comparison with the one based on Manzini model. Further combining with osmotic pressure data, temperature dependence of the entropy parameter Q12 was referred.
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    Polymer bulletin 1 (1979), S. 793-799 
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    Notes: Abstract Styrene oxide of different enantiomeric compositions was polymerized in bulk using a potassium alkoxide initiator. A preferential consumption of the enantiomer in excess was observed. The magnitude of this effect depends on the enantiomeric composition of the initial monomer: the more unbalanced is the latter, the stronger is the stereoelection observed. The stereoelective effect was almost completely suppressed by addition of complexing agents such as crown-ethers or cryptands. The observed phenomena are explained in terms of polymer-chain effects.
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    Notes: Summary The change in the scattering pattern of polyisobutylene fibres following rapid stretching was measured using synchrotron radiation. The half-time for the crystallisation process is approximately 50 seconds. Upon release the crystalline portions disappear immediately.
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    Polymer bulletin 1 (1979), S. 845-848 
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    Polymer bulletin 1 (1979), S. 849-856 
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    Notes: Summary The MgCl2 supported TiCl3 catalyst was prepared by grinding the mixture of TiCl3·3Py and MgCl2 in a ball mill. The catalyst was treated either i.vac. at 50–200°C or with alkylaluminum halides to remove the residual pyridine, and propylene polymerization was conducted at 65°C using the resulting catalysts combined with triethylaluminum. The catalyst treated with diethylaluminum chloride showed an extremely high activity for the polymerization.
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    Polymer bulletin 1 (1979), S. 857-864 
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    Notes: Summary The elastic equations of state for 2-component networks are derived from a joint Gaussian distribution function composed of Gaussians for each component. The free energy of elasticity is then applied to the case of uni-directional deformations for compatible systems. The stress-strain equations are shown to be equivalent to those for a single component network except in the case where the macroscopic strain is sufficient to cause the ratio of average chain lengths of the components to change with the strain. The stress-strain equations are developed for both dry and swollen networks.
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    Notes: Summary The concentration dependence of the elasticity modulus (G) of gels produced by heating soybean globulins (SBG) has been investigated in the concentration range C=7.5–58.4%. The tests included constant rate loading and stress relaxation. The experimental results are presented in the form of a modulus reduction parameter b(C)=G(C) / G(C∘), where C∘=15% corresponds to the standard reference state. Whatever the testing conditions, the results are described by a single smooth curve similar, to a constant factor, to the concentration dependence of the equilibrium elasticity modulus of SBG gels. The experimental relationship b (C) agrees with the theoretical concentration dependence of the equilibrium polymer gel modulus according to Hermanns if it is assumed that the gel-point of SBG, Co=6.6 %. Within an order of magnitude this value of Co is consistent with the experimental data. We have to thank the European Branch Director of Central Soya Intern., Inc., Mr.J.F.Casey for kindly providing us defatted soya flour.
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    Polymer bulletin 1 (1979), S. 897-907 
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    Notes: Summary This paper describes new fire-resistant bisphenol A and monoalkyl monoalkaline bis(hydroxy-4 phenyl) alkyl phosphonate copolycarbonates. We show that inclusion of minute quantities (in molar percentages of 0.5 to 1%) of monoalkaline potassium salts of bis(hydroxy-4 phenyl)-alkyl phosphonic acid considerably improves the fire-resistant of the bisphenol A polycarbonate. We obtain oxygen indices of 34 to 35.
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    Polymer bulletin 1 (1979), S. 415-420 
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    Notes: Summary Cyclopentadienylation of PVC with alkaline (NaCPD, LiCPD) and acidic (Me2CPDAl) cyclopentadienylating agents has been investigated. In terms of product quality (absence of discoloration, gelation) Me2 CPDAl was found to be a superior cyclopentadienylating agent than NaCPD and LiCPD.
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    Polymer bulletin 1 (1979), S. 427-431 
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    Notes: Summary In a first example of the functionalization of soluble polymers the conversion of the hydroxyl groups of poly(oxyethylene) into primary amino groups has been studied. Starting from poly(oxyethylene), the preparation of the diphthalimido derivative via the disodium salt is described. Prom this regiospecific functionalized polymer the di(aminoethyl) poly(oxyethylene), which exhibits excellent solubility properties, can be obtained by polymeranalogous hydrazinolysis.
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    Notes: Summary It is shown that the probability for the formation of alternating macromolecules by monomer donor-acceptor complexes can be determined from the microtacticity of the copolymers. If the stereoregularity in the alternating copolymerization is described by the Bernoullian trial two other probabilities concerning the meso-diad formation can be determined by this method. If the stereoregularity is described by the first order Markov chain the transition probabilities can be calculated. Thus a more detailed analysis of the propagation mechanism in alternating copolymerization can be carried out.
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    Polymer bulletin 1 (1979), S. 433-436 
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    Notes: Summary Cationic copolymerination of α-MS and IBVE was successfully carried out using “H2O”/EtAlCl2 initiator system and CH2Cl2 solvent at −50°C. The effect of monomer feed concentration on the copolymer yield and composition was studied. Small concentrations of IBVE had significant effect on the copolymer yield and composition, while that of α-MS had only marginal effect. Tg of the copolymers was linearly dependent on the α-MS content strongly indicating that the copolymerization was of random nature.
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    Polymer bulletin 1 (1979), S. 459-464 
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    Notes: Summary The Stefan-Winkelmann diffusion technique has been used to determine vapor pressures of high boiling point compound-solvents mixtures. Data are reported at a temperature of 67°C for the mixtures polyphenyl ether (6 rings) — benzene and carbowax 1500 — benzene and at a temperature of 100°C for the mixtures polyphenyl ether (6 rings) — toluene and tricresylphosphate-toluene. The range of concentration is only limited by the appearance of a solid phase, and results are in good agreement with those determined by vapor pressure osmometry.
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    Polymer bulletin 1 (1979), S. 469-473 
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    Notes: Summary 1-isopropenyl anthracene was dimerized by reaction with TiCl4 in CH2Cl2 and the structure of the dimer studied by 1H NMR spectroscopy. The spectrum was assigned and is in agreement with simulation. The structure results from the attack of carbocation on carbon 9.
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    Polymer bulletin 1 (1979), S. 475-479 
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    Notes: Summary 9-isopropenyl phenanthrene was dimerized by reaction with TiCl4, in CH2Cl2 and the structure of the dimer studied by 1H NMR spectroscopy. The structure results from the attack of carbocation on carbon 9.
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    Notes: Summary Radical copolymerisation of MMA(r1) and NVC(r2) yields values of the apparent reactivity ratios r1 = 1.80, r2 = 0.06 (benzene) and r1 = 0.57, r2 = 0.75 (methanol) at 55°C. It is suggested that the apparent increase in reactivity of NVC in methanol arises from high local monomer concentrations due to formation of microphases containing the growing copolymer chains in which NVC is preferentially partitioned. Fluorescence emission and u.v. absorption spectra for copolymers prepared in both solvents are identical and consistent with the occurrence of only very short sequences of NVC units.
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    Polymer bulletin 1 (1979), S. 569-573 
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    Notes: Summary The anionic polymerization of δ-valerolactone in tetrahydrofuran with lithium tert-butoxide was found to give a living ring-chain equilibrium system, in which the cyclic oligomers are produced by back-biting degradation from the initially formed linear polymers. The molar cyclization equilibrium constant for the trimer through hexamer decreased in proportion to −2.5 power of the ring size, in accord with the Jacobson-Stockmayer theory.
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    Notes: Synopsis It was confirmed by EPR that 4-amino-2,2,6,6--tetramethylpiperidine-N-oxyl (TEMP-NH2) is cleaved by chymotrypsin from 4-(N-glycyl-L-phenylalanyl)amino −2,2,6,6-tetramethylpiperidine-N-oxyl attached as a substrate with paramagnetic leaving group to the end of side chains of water soluble hydroxypropyl methacrylamide (HPMA) compolymers.
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    Polymer bulletin 1 (1979), S. 599-602 
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    Notes: Summary γ-Ethyl-L-glutamate derivatives having pendant nucleic acid bases, that is, uracil, adenine and theophylline were synthesized. The γ-ethyl-L-glutamate having theophylline moiety was polymerized by using the N-carboxyamino acid anhydride (NCA) method.
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    Polymer bulletin 1 (1979), S. 619-623 
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    Notes: Summary The analytical relationship between the molecular weight averages obtained from an experimental GPC elu tion curve and the true ones is calculated by use of one integration method in order to solve the convolution integral. The knowledge of these relationship signifies an useful tool to carry out critical considerations on the operation of different methods existing for the calculation of the spreading correction and for the elaboration of the calibration function.
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    Polymer bulletin 1 (1979), S. 625-629 
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    Polymer bulletin 1 (1979), S. 653-657 
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    Notes: Summary The polymerization of hexachlorocyclotriphosphazene (trimer) is studied in different solvents. A soluble low molecular weight polymer is obtained when benzene is the solvent, a highly cross-linked polymer when cyclohexane is the solvent, and a mixture of soluble and insoluble polymers results when the solvent is chlorobenzene. The conversion-concentration curve for the trimer shows a dependence of the amount of soluble and insoluble polymer formed on the trimer concentration. No polymerization took place when the solvent was toluene, nitrobenzene or THF, but a reaction between solvent and trimer was detected.
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    Polymer bulletin 1 (1979), S. 659-664 
    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The effect of radiation on the mechanical behaviour of the crosslinked copolymer of maleic anhydride and styrene containing photochromic azo groups was investigated. The analysis of results of the observed photomechanical conversion proved a considerable influence of the thermal effect in addition to the effect of photoisomerization of the photochrome. The interpretation of some photomechanical experiments described earlier may be obscured by a rise in temperature caused by the absorption of radiation.
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    The European physical journal 34 (1979), S. 123-128 
    ISSN: 1434-6036
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    Topics: Physics
    Notes: Abstract We have studied the photoemission properties of liquid, supercooled and crystalline gallium with photon energies up to 6.5 eV. The spectra of the liquid phase are well described by the free electron model, whereas in the solid the density of states is reduced near the Fermi level. The observed changes in the electronic structure at the melting point are explained by the essential change in the ionic short range order.
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    The European physical journal 34 (1979), S. 129-134 
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    Topics: Physics
    Notes: Abstract Copper influences the electrical and optical properties of zinc oxide to a high degree. Previously this has been explained within the frame of a model assuming Cu++ ions to be substitutional for divalent zinc. The observation of additional signals in the Electron Spin Resonance spectrum, however, proved this assumption to be wrong. Satisfying quantitative agreement with experiment is obtained assuming neutral copper atoms at an interstitial site having 3d9 4s2 electron configuration and a2D3/2 ground state. The infrared absorption bands as well as the spin lattice relaxation mechanism give further confirmation of Cu i 0 .
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    The European physical journal 34 (1979), S. 135-140 
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    Notes: Abstract The relation between inner displacement and strain is established and simplified by group theory. Results are given for the diamond structure (C, Ge, Si), cobalt (Co), graphite (C), neodymium (Nd), spinel (MgAl2O4). For these crystals we get an enormous reduction of the number of parameters to be determined by measurement.
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    The European physical journal 34 (1979), S. 141-148 
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    Topics: Physics
    Notes: Abstract The diffusion and drift of an excess plasma in a semiconductor is described with magnetohydrodynamic two-fluid equations including the fluctuating electric field produced by the equilibrium plasma in the sample. Using the weak coupling limit an equation of motion for the mean density of the excess plasma is established with renormalized drift and diffusion coefficients. With the aid of the fluctuation dissipation theorem these coefficients are expressed in terms of the dielectric function and discussed in detail for stable systems. The renormalized diffusion coefficient differs from the bare one by an additional term with thet −3/2-long time dependence. It is shown that this term in addition represents an anomalous diffusion rate proportionalB −1 which overweights the classical ambipolar diffusion for sufficiently strong fields, but decreases with increasing external electric field. The results are compared with experimental data.
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    The European physical journal 34 (1979), S. 149-155 
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    Topics: Physics
    Notes: Abstract Superconducting tunneling was used to obtain the phonon density of statesα 2(ω)F(ω) associated with high frequency localized phonons in (Pb1−x Tl x )0.96In0.04 (0〈x〈0.6), (Pb0.5Tl0.5)0.88In0.12 and (Pb0.70Tl0.15Bi0.15)0.96In0.04.α 2(ω)F (ω) from impurities can be described as three superimposed peaks. One of the peaks appears only when Tl is present. The main peak has the same width in (Pb1−x Tl x )0.96In0.04 as in Pb0.96In0.04, but is much broader in (Pb0.70Tl0.15Bi0.15)0.96In0.04. The electron-phonon couplingα loc 2 of the localized phonons is well below the meanα 2 of the full spectrum for all alloys in general and for (Pb0.70Tl0.15Bi0.15)0.96In0.04 in particular.
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    The European physical journal 34 (1979), S. 165-173 
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    Topics: Physics
    Notes: Abstract The kinetics of particle and energy exchange between gas and surface is treated in analogy to the transport of particles and energy in solutions using Onsager's theory of nonequilibrium thermodynamics. In addition to the coefficients of sticking and thermal accommodation a third kinetic coefficient is introduced describing the coupling of particle and energy transport. This coupling turns out to be particularly important at low temperatures reducing the accommodation coefficient from 2 to 1. The Onsager coefficients are then expressed in terms of the scattering properties of the surface. A simple model is treated to illustrate the general results and to provide estimates for the kinetic coefficients.
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    The European physical journal 35 (1979), S. 207-210 
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    Topics: Physics
    Notes: Abstract An apparently overlooked symmetry of the disordered electron problem is derived. It yields the well-known Ward-identity connecting the one- and two-particle Green's function. This symmetry and the apparent shortrange behaviour of the averaged one-particle Green's function are used to conjecture that the critical behaviour near the mobility edge coincides with that of interacting matrices which have two different eigenvalues of multiplicity zero (due to replicas). As a consequence the exponents of the d.c. conductivity is expected to approach 1 for real matrices and 1/2 for complex matrices as the dimensionality of the system approaches two from above. In two dimensions no metallic conductivity is expected.
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    The European physical journal 35 (1979), S. 277-279 
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    Topics: Physics
    Notes: Abstract We calculate toO(ε=4 −d) the effect of the small ratiow * of the relaxation rates of the order parameter and the entropy on the damping of second sound in the hydrodynamic regime of liquid helium belowT λ . Forw * ≪ 1 we find a partial reduction of the previous discrepancy between theory and experiment on the amplitude of second sound damping.
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    The European physical journal 35 (1979), S. 273-276 
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    Topics: Physics
    Notes: Abstract The hydrogen concentration near to the surface of some typical ultra cold neutron container materials has been measured with theH(11 B, α) 2α reaction. The concentration of 2 – 3 × 1016 H atoms/cm2 is in agreement with results obtained by other methods. Using theoretical neutron scattering cross sections we confirm that at room temperature the experimentally known high UCN reflection loss rate could be caused by the measured concentration of hydrogen. The original hydrogen content has been reduced by ion bombardment to about one tenth of its original value. The redeposition of hydrogen has been studied as a function of the residual pressure. We conclude that it is possible to produce by sputtering container surfaces with hydrogen (and other surface impurity) contents sufficiently low and stable to test directly with UCN whether their losses are mainly due to upscattering on impurities or not.
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    The European physical journal 35 (1979), S. 281-285 
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    Topics: Physics
    Notes: Abstract We define and solve a dynamical real-space renormalization group transformation for the master equation of a kinetic Ising model in one dimension. The exactly solvable model we treat has the dynamical exponentz=2. We show that spin flip rates differing from Glauber's choice may have exponentsz differing from 2. A particular model which hasz=4 is presented.
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    The European physical journal 35 (1979), S. 287-295 
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    Topics: Physics
    Notes: Abstract We consider a cubic crystal with a triply degenerate electronic ground-state in each unit cell (T-state). A linear Jahn-Teller interaction with acoustic phonons is assumed (T-e coupling). Below a critical temperatureT c a tetragonal cooperative ordering is established. If a static crystal field splits the electronic states, an anticrossing of the cooperative excitation branches and the phonons in the smallk-regime is found. The resulting “mixed modes” are calculated (RPA and isotropic Debye model). The dispersion curves are given for specifick-directions and the temperature dependence is discussed.
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    The European physical journal 35 (1979), S. 309-312 
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    Topics: Physics
    Notes: Abstract A treatment of the thermal emission of electrons from deep centers as a collective process is presented. In contrast to the conventional theory our concept leads to a non-exponential approach of the system to a new equilibrium state. Such decays have indeed been observed in our work.
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    The European physical journal 35 (1979), S. 297-308 
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    Topics: Physics
    Notes: Abstract The relation between the time-convolutionless projection operator formalism and the methods developed by Kubo and van Kampen in the context of linear stochastic differential equations is discussed in detail. It is shown how this formalism may be used to develop a systematic procedure for the elimination of “fast variables”. This procedure is applied to the case of a free Brownian particle and to that of a heavily damped Brownian particle in the presence of an external force to obtain a reduced description in terms of the position variable: the results are found to be in complete agreement with the previous works on this problem. The rotational Brownian motion of an asymmetrical top in the presence of an external torque is also considered and an equation for the reduced probability distribution is derived which contains all the previous works on this problem as special cases.
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    The European physical journal 35 (1979), S. 316-316 
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    The European physical journal 35 (1979), S. 317-326 
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    Topics: Physics
    Notes: Abstract The superconducting transition temperature is calculated for a series of representative metals from a selfconsistent LMTO-bandstructure calculation. We carefully avoid any uncontrolled approximations apart from the use of a local exchange-correlation potential and the rigid-ion approximation for the electron-phonon interaction, Our results for V, Nb, Ta, Mo, W, Pd, Pt, Pb clearly indicate that these popular approximations are incapable of reproducing the observed transition temperatures.
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    The European physical journal 35 (1979), S. 391-397 
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    Topics: Physics
    Notes: Abstract Using the recently developed theory of resonant Raman scattering in the presence of strong double frequency fields, the statistical properties of the spontaneously emitted Stokes and Rayleigh radiation are calculated. In particular, the temporal intensity correlations of arbitrary order are evaluated. It is found that they possess the property of factorization in terms of the probabilities for finding the system in the resonant intermediate excited state when the starting state is the given initial state and when the starting state is a particular superposition of the ground and final excited states. The weight-factors in the particular superposition depend on the direction of observation and on the transition dipole-moments. The second-order intensity correlation is shown to have the complete anti-bunching property. The factorization property of the intensity correlations is useful in the calculation of photo-electron counting distributions.
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    The European physical journal 36 (1979), S. 13-21 
    ISSN: 1434-6036
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    Topics: Physics
    Notes: Abstract The variational theory of anharmonic lattice dynamics is applied to the sodium chloride structure. The Coulomb and the inverse-power repulsive pair potential between ions are used. The mean-square displacements (MSDs) at zero pressure for individual ions, i.e., cation and anion, are calculated as a function of temperature without use of any fit parameters. It is shown that the ratio of the MSDs for anion and cation depends strongly on the ionic-radius ratio. The average MSDs are in reasonably good agreement with the experimental data obtained by a Bragg diffraction technique. A discussion is given of the relation between the divergent behavior of the MSDs which we find at some critical temperature and the observed melting point.
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    The European physical journal 36 (1979), S. 1-12 
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    Topics: Physics
    Notes: Abstract The linear heat transport of helium II contained in porous powder samples with mean pore diameters of 1.25µm, 0.17µm and 0.02µm was systematically studied in the temperature range between 0.8 K and 2 K. The effective thermal conductivity was determined by steady-state heat flow measurements and the effective thermal diffusivity by transitory temperature measurements. The experimental results are interpreted by a simple theoretical model. In the framework of this model the linear heat transport consists of two contributions: the laminar flow of the normal fluid (T≳1.4 K) and a diffusion mechanism (T≲1.4 K). At low temperatures (T≲1.2 K) the mean free paths of the elementary excitations of helium II become greater than the pore diameters. In this range, the heat flow is limited by scattering of the elementary excitations with the walls of the pores and can be described by a kinetic model. Good agreement between theory and experiment is obtained in the total temperature range investigated.
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    The European physical journal 36 (1979), S. 37-46 
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    Topics: Physics
    Notes: Abstract We have studied an infinitely narrow band version of the Anderson Hamiltonian. Including a Coulomb repulsion between localized and band states in the mean field approximation, we have been able to describe metal-insulator phase transitions and different properties characteristic of intermediate valence in both phases. These include: non-integer occupation, specific heat, saturating static magnetic succeptibility and dynamical properties such as Mössbauer spectra and spin flip neutron spectra. We discuss for what range of values of the parameters some results can be reproduced by a narrow band version of the Kondo Hamiltonian.
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    The European physical journal 36 (1979), S. 23-35 
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    Topics: Physics
    Notes: Abstract A formalism is presented for the computation of long range as well as short range correlations in the electronic ground state of a solid. It is based on a Local Approach to the correlation problem which was successfully tested before for small molecules. The method connects two approaches to the correlation problem. One is that of the RPA which is often applied in solid state physics and describes the long range aspects of the correlated electronic motions. The other is that of quantum chemistry which tries to calculate to high accuracy the short range part of the correlation problem. The method is variational in nature. The approximations which have been made exclude the application of the present formalism to strongly correlated systems such as valence fluctuating systems.
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    The European physical journal 36 (1979), S. 47-56 
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    Notes: Abstract Superconducting simple cubic Te100−x Au x films (10〈x〈90) were produced by He+-irradiation at low temperatures as well as at room temperature. After low temperature irradiation the as-irradiated disordered samples forx〈60 at % Au are in a semiconducting state which becomes unstable at about 230 K, and then transform into the s.c. superconducting phase. The resistivity of the s.c. phase displays a negative temperature coefficient for residual resistivity values larger than 100 μΩ cm. In comparison to “splat cooled” foils, the s.c. Te—Au phase in the He+-irradiated films is more homogeneous. The observed variation of the transition temperature to the superconducting state with Au content is explained as an interaction of the Fermi-surface with several Bragg-planes.
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    The European physical journal 36 (1979), S. 81-87 
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    Notes: Abstract Theoretical results for the energy distributionP(ε) of atoms scattered by solid surfaces are presented. An exact expression for the first moment (the average energy lossΔε) ofP(ε) is derived involving the force-force correlation of the scattering particle and the susceptibility of the lattice. An approximate result forP(ε) is derived in which the same two quantities occur. The forces are treated statically (i.e. neglecting the response of the lattice) and semiclassically (i.e. neglecting their noncommutativity). Quantum effects of the lattice are taken into account properly. No approximations are made concerning the number of excited phonons. An expression for the reduction of elastic scattering due to inelastic processes (generalized Debye-Waller factor) is found containing the dynamic and finite size effects discussed in the literature.
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    The European physical journal 36 (1979), S. 57-66 
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    Notes: Abstract The pair penetration depth into normal metal films containing various amounts of nonmagnetic or magnetic impurities is determined from the dependence of the critical current density on the normal metal film thickness in superconductor-normal metalsuperconductor junctions.
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    The European physical journal 36 (1979), S. 161-177 
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    Notes: Abstract Ising and Heisenberg magnets with nearest-neighbor ferromagnetic exchangeJ 1 and next-nearest antiferromagnetic exchangeJ 2 and randomly distributed frozen-in nonmagnetic impurities of arbitrary concentration 1−x are studied by several methods: systematic series expansions inx, 1−x and inverse temperature (1/T) as well as Monte Carlo simulation. Depending onR≡J 2/J 1,T andx the model is in paramagnetic, ferromagnetic, antiferromagnetic or spin glass phases. The microscopic magnetic structures of all these phases are investigated and found to be more complicated than usually (e.g., the ferromagnetic state contains spins and clusters either aligned antiparallel or not aligned at all, when “frustration” effects make bonds ineffective). We suggest that the concentrationx c of magnetic ions below which no (anti-)ferromagnetic long range order occurs depends onR continuously, andx c →1 at the multicritical point (R m ,T=0) where the order changes from ferromagnetic to antiferromagnetic. Our results for phase diagram, susceptibility etc. are compared to recent data on the Eu x Sr1−x S system and very good agreement is found.
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    ISSN: 1435-1528
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    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Summary The methods to measure red cell flexibility are reviewed and own investigations reported based on red cell aging as a model for a physiological reduction in red cell flexibility. The measurement of this parameter was performed with whole-blood by means of filtration through filters with a pore diameter of 5 µm. The model of red cell aging and the method used for the measurement of red cell flexibility is suitable as a screening system to evaluate whether chemical compounds influence red cell flexibility. In two series of experiments pentoxifylline in concentrations of 10 µg and 20 µg/ml of blood and theophylline and prednisolone in concentrations of 96.6 µg or 20 µg/ml of blood, respectively, were investigated. For pentoxifylline a dose-dependent increase in red cell flexibility was observed, theophylline and prednisolone did not change this parameter in comparison to the control. The effect of pentoxifylline is probably related to an increase in red cell ATP content. Scanning electron microscopy revealed that this compound does not influence the outer membrane of the red cells.
    Notes: Zusammenfassung Es werden die Möglichkeiten der Messung der Erythrozytenverformbarkeit dargestellt und eigene Untersuchungen mit einer Methode beschrieben, welche die Erythrozytenalterung als Modell für eine physiologische Reduzierung der Erythrozytenverformbarkeit benutzt. Die Messung dieser Größe erfolgt in Vollblut mittels Filtration durch Filter mit Poren von 5 µm. Das Erythrozytenalterungsmodell und die Methode zur Messung der Erythrozytenverformbarkeit eignet sich für die routinemäßige Prüfung, ob chemische Substanzen die Erythrozytenverformbarkeit beeinflussen. In zwei Untersuchungsserien wurden Pentoxifyllin in Konzentrationen von 10 µg und 20 µg/ml Blut sowie Theophyllin in einer Konzentration von 96,6 µg/ml Blut und Prednisolon in einer Konzentration von 20 µg/ml Blut untersucht. Für Pentoxifyllin fand sich eine dosisabhängige Erhöhung der Erythrozytenverformbarkeit, unter Theophyllin und Prednisolon fanden sich keine signifikanten Änderungen gegenüber der Kontrolle. Der Effekt von Pentoxifyllin ist wahrscheinlich in einer Erhöhung des erythrozytären ATP-Gehaltes begründet. Rasterelektronenmikroskopische Untersuchungen zeigen, daß die morphologische Struktur der äußeren Erythrozytenmembran durch Pentoxifyllin nicht beeinflußt wird.
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    Rheologica acta 18 (1979), S. 492-504 
    ISSN: 1435-1528
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    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung In Ergänzung früherer Ergebnisse vonMeißner an einem Polyäthylen niedriger Dichte, die im linearen Bereich der Verformung für die zeitabhängige Dehnviskosität das Dreifache der Scherviskosität ergaben, konnte die Gültigkeit der Beziehung $$\mathop D\limits^ \circ (t) = 1/3\mathop J\limits^ \circ (t)$$ gezeigt werden. $$\mathop D\limits^ \circ (t)$$ und $$\mathop J\limits^ \circ (t)$$ sind die Nachgiebigkeiten in Dehnung und Scherung. Im nichtlinearen Bereich steigtJ(t) mit zunehmender Spannung an, währendD(t) abfällt. Die Zeitabhängigkeit der Viskosität, definiert als der Quotient aus Spannung und Geschwindigkeit des viskosen Deformationsanteils, ist in Scherung und Dehnung ebenfalls unterschiedlich. Die Scherviskosität fällt von dem Wert der Nullviskositätη 0 mit wachsender Scherung auf einen stationären Wert ab, die Dehnviskosität dagegen steigt von 3η 0 auf einen höheren stationären Wert an. Die Temperaturabhängigkeit wurde aus Messungen des stationären Wertes der Dehnviskosität bei konstantgehaltener Zugspannung und aus einer Verschiebung der bei unterschiedlichen Temperaturen, aber konstanten Spannungen gemessenen Nachgiebigkeiten in bezug auf die Zeit bestimmt. Sie ist dieselbe wie in Scherung. Dieses Ergebnis konnte indirekt durch Messungen mit konstanter Dehngeschwindigkeit bestätigt werden. Die reversible Dehnung im stationären Zustand wurde bei konstanter Zugspannung als von der Temperatur unabhängig gefunden.
    Notes: Summary In addition to earlier findings ofMeißner on a low density polyethylene that in the linear range of deformation the time-dependent elongational viscosity is three times the shear viscosity the validity of the relationship $$\mathop D\limits^ \circ (t) = 1/3\mathop J\limits^ \circ (t)$$ could be demonstrated where $$\mathop D\limits^ \circ (t)$$ and $$\mathop J\limits^ \circ (t)$$ describe the compliances in elongation and shear, respectively. In the nonlinear rangeJ(t) was found to increase with stress whereasD(t) decreases. The nonlinear viscosity-time behaviour is different in shear and elongation, too. The shear viscosity obtained by relating the stress to the rate of viscous strain decreases with shear from the zero shear viscosity to its steady-state value. The elongational viscosity goes up with time from 3η 0 to a higher steady-state value. The temperature dependence which was determined by measuring the steady-state elongational viscosities at different constant stresses as a function of temperature and by shifting the tensile creep compliancesD(t) measured at constant stress with respect to time, was found to be exactly the same as in shear. This result could indirectly be verified by some constant stretching rate tests. It was shown experimentally that the recoverable strain in the steady-state is independent of temperature if measured at constant stress.
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    Rheologica acta 18 (1979), S. 545-548 
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    Topics: Chemistry and Pharmacology , Physics
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    Rheologica acta 18 (1979), S. 51-61 
    ISSN: 1435-1528
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    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Summary Dynamic-mechanical and calorimetric measurements on the polymer system phenolic novolac resin (PF) with styrene-butadiene rubber (SBR), natural rubber (NR) and nitrile-butadiene rubber (NBR) have shown that there only is observed an influence of the mixing ratio on the glass-transition of the rubber. For all compositions the position of the glass-transition of the rubber remains unchanged. From a rubber content of 10 weight-% onwards, a soft phase is being formed beside the rigid matrix phase of the resin. The dominating influence of the rubber on the resin is most evident in the region of rubber elasticity. The mechanical properties in this temperature range are vastly influenced by the rubber phase. The results of the torsional pendulum measurements of the resin-rubber blends at room temperature are compared with the prediction of the elastic properties of polymer blends and composite materials.
    Notes: Zusammenfassung Die mechanisch-dynamischen und kalorimetrischen Untersuchungen an den Polymersystemen Phenolnovolakharz mit SBR, NR und NBR haben gezeigt, daß in diesen Mischsystemen nur ein Einfluß des Mischungsverhältnisses auf den Umwandlungsbereich des Kautschuks, dessen Temperaturlage in allen Konzentrationsbereichen unbeeinflußt bleibt, beobachtet werden kann. Ab einer Kautschukkonzentration von 10 Gew.-% im Harz bildet sich neben der kontinuierlichen Harzphase allmählich eine weiche Phase aus. Der Einfluß des Kautschuks auf das Harz zeigt sich am deutlichsten im kautschukelastischen Bereich. Hier werden die mechanischen Eigenschaften weitgehend von der Kautschukphase bestimmt. Die mit dem Torsionsschwingversuch ermittelten Speichermodulwerte der Mischungen werden mit den theoretischen Überlegungen über den Schubmodul von Polymermischungen und Polymerverbunden verglichen.
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    Rheologica acta 18 (1979), S. 86-95 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Summary The viscosity and the first normal-stress difference as a function of the shear rate ( $$\dot \gamma $$ ) were measured for moderately concentrated (70–150 kg/m3) decahydronaphthalene solutions of a polystyrene sample (M = 2 ⋅ 106). The measurements were carried out in a temperature range of 20–80°C. The results of the measurements are discussed, taking into account the earlier developed theory. The number of temporary junctions are changing in the presence of a shear field and imply changes in the partial entropy and enthalpy of formation of a junction. The changes of these thermodynamical functions were evaluated. The values of the partial entropy, corresponding to $$\dot \gamma $$ ⇒ 0 allow to evaluate the number of junctions. These results are in a qualitative accord with results known from the literature. At a certain critical value of $$\dot \gamma $$ the rate of creation of new temporary junctions is getting to become zero and the probability of their rate of decay equals one. This corresponds to the second Newtonian range. These critical values of the shear rate were evaluated. The probability of the rate of dissociation of temporary junctions should be smaller than one for systems forming a network. This could be understood as a criterion of a system under consideration to form a network.
    Notes: Zusammenfassung Die Viskosität und die erste Normalspannungsdifferenz wurden als Funktion des Schergefälles $$\dot \gamma $$ in mäßig konzentierten (70–150 kg/m3) Dekalin-Lösungen einer Polystyrolprobe (M = 2 ⋅ 106) im Temperaturbereich 20–80°C gemessen. Die Ergebnisse wurden anhand früher entwickelter theoretischer Vorstellungen analysiert. Die Entropie und Enthalpiebeiträge bei Änderung der Verknüpfungszahl als Funktion des Schergefälles wurden ausgewertet. Die Ermittlung der partiellen Entropie bei $$\dot \gamma $$ ⇒ 0 liefert eine Möglichkeit, die Zahl der zeitweiligen Verknüpfungsstellen zu berechnen. Die Ergebnisse stehen im qualitativen Einklang mit den aus der Literatur bekannten Daten. Bei einem kritischem $$\dot \gamma $$ -Wert ist die Geschwindigkeit des Einbaus neuer zeitweiliger Verknüpfungspunkte in das Netzwerk gleich Null und die Wahrscheinlichkeit des Zerfalls dieser Verknüpfungen pro Zeiteinheit gleich Eins. Dieser Zustand entspricht dem zweiten newtonschen Bereich. Diese kritischen Werte der Schergeschwindigkeit wurden ermittelt. Für netzwerkbildende Systeme muß die Wahrscheinlichkeit des Zerfalls der Verknüpfungen pro Zeiteinheit kleiner sein als Eins. Dies kann als Kriterium für ein netzwerkbildendes System betrachtet werden.
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  • 90
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    Rheologica acta 18 (1979), S. 104-107 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Summary Results obtained when a viscoelastic liquid is injected into a Newtonian liquid flowing under turbulent conditions in a straight pipe are reported. Especially, the change in pressure drop along the pipe starting at the injection point were measured as a function of total polymer concentration, concentration of the injected liquid and Reynolds number. If the concentration of the injected liquid is higher the solution remains as a “liquid thread” and is conveyed in the centre region of the pipe. Under these conditions a remarkable drag reduction is also observed, though the polymer has not migrated noticeably into layers near the wall.
    Notes: Zusammenfassung Es wird über Experimente berichtet, bei denen eine viskoelastische Flüssigkeit in der Achse einer ausgebildeten turbulenten Rohrströmung eines newtonschen Fluids injiziert wurde. Insbesondere werden Ergebnisse über die Veränderung des Druckabfalls längs des Rohres in Abhängigkeit von der Gesamtkonzentration des Polymers im Rohr, der Konzentration im injizierten Faden und der Reynolds-Zahl mitgeteilt und diskutiert. Bei der Injektion von höher konzentrierten Polymerlösungen tritt eine deutliche Widerstandsverminderung auch dann auf, wenn die Lösung als elastischer Faden im Kernbereich der turbulenten Strömung mitgeführt wird, d. h. das Polymer noch nicht merklich in die wandnahe Schicht hineindiffundiert ist.
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  • 91
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Es wurden die Doppelbrechung und der Orientierungswinkel von Polyox-WSR 301-Lösungen im Konzentrationsbereich 50–1350 ppm bis zu Schergeschwindigkeiten von 8000 s−1 gemessen. Dabei wurden einige ausgeprägte Unterschiede gegenüber normalen flexiblen Polymeren gefunden: (i) ein sehr niedriger Wert des Auslöschwinkels, was auf ein ungewöhnlich hohes Molekulargewicht schließen läßt: (ii) die Unabhängigkeit dieses Winkels von der Konzentration, was von einer Änderung der Flexibilität mit der Konzentration herrührt, wie sie durch die Untersuchung der Konzentrationsabhängigkeit der optischen Anisotropie der Segmente aufgezeigt wird; (iii) die Existenz eines Plateaus in der Konzentrationsabhängigkeit der Streckung beic ≳ 150 ppm, welches auf einen konzentrationsabhängigen reversiblen Assoziationsvorgang hindeutet, der auch durch Messung der reduzierten Viskosität nahegelegt wird.
    Notes: Summary Birefringence and orientation angle of solutions of Polyox WSR 301 in the concentration range of 50 to 1350 ppm have been measured up to 8000 s−1. A few marked differences with ordinary flexible polymers have been evidenced: (i) a very low value of the extinction angle at high shear rate, which could be attributed to an unusually high molecular weight; (ii) the independence of this angle on the concentration, which is due to the variation of the flexibility with the concentration, as shown by the study of the concentration dependence of the segmental optical anisotropy; (iii) the concentration dependence of the elongation shows a plateau value forc ≳ 150 ppm, which may come from a concentration dependent and reversible association process, as shown from reduced viscosity measurements.
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  • 92
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    Rheologica acta 18 (1979), S. 289-296 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Es wird ein neues Gerät beschrieben, das die Bestimmung der Viskosität von Suspensionen mit Teilchen hoher Dichte in niedrig viskosen Flüssigkeiten ermöglicht. Die an Suspensionen von Teilchen mit niedriger Dichte erhaltenen Ergebnisse stimmen gut mit den mittels eines Weissenberg-Rheogoniometers gewonnenen überein, das entweder mit einer Kegel-Platte- oder einer Koaxial-Zylinder-Meßeinrichtung ausgerüstet war. Als ein überraschendes Ergebnis stellt sich heraus, daß die Eilers-Gleichung, zum Zweck der Erfassung der Teilchenform mit Hilfe des Staudinger-Index in bequemer Weise modifiziert, alle experimentellen Daten gut zu korrelieren imstande ist.
    Notes: Summary A new apparatus is presented which allows the determination of the viscosity of suspensions of high density particles in low viscosity media. Results obtained on suspensions of low density particles compare well with those obtained on a Weissenberg Rheogoniometer equipped with a cone-and-plate and a bob-and-cup. Also, a very interesting observation is that the Eilers equation, conveniently modified to take into account the shape of the particles by means of the intrinsic viscosity, can well correlate all the data.
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  • 93
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    Rheologica acta 18 (1979), S. 308-308 
    ISSN: 1435-1528
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    Topics: Chemistry and Pharmacology , Physics
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  • 94
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    Rheologica acta 18 (1979), S. 303-307 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Bei newtonschen Flüssigkeiten weisen die Experimente eine Abweichung vom linearen Zusammenhang zwischen Schubspannung und Schergeschwindigkeit auf. Im Kegel-Platte-Meßsystem ist die Wärmeproduktion durch innere Reibung die wichtigste Ursache der Abweichung. Bei newtonschen Flüssigkeiten, deren dynamische Viskosität sich ungefähr linear mit der Temperatur verändert, ergeben sorgfältig ausgeführte Messungen mit einem Kegel von 10 cm Durchmesser einen linearen Zusammenhang zwischen der Zeit und dem Logarithmus der Temperaturzunahme. Ein aus der Wärmebilanz abgeleitetes Modell vermag dieses Verhalten quantitativ zu beschreiben.
    Notes: Summary At higher shear rates the relation between shear stress and shear rate appears to deviate from the for Newtonian fluids expected linear behaviour. In cone-and-plate rheogoniometry one of the most important causes of that is the effect of viscous heating. Accurate measurements carried out with a 10 cm diameter cone and plate lead to a semi-logarithmic, linear relationship between temperature increase and time for a Newtonian oil which dynamic viscosity varies approximately linearly with time. A simple model based on a heat balance describes this behaviour quantitatively.
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  • 95
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    Rheologica acta 18 (1979), S. 311-322 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Eine inkompressible nicht-newtonsche Flüssigkeit fließt unter der Einwirkung eines gleichförmigen konstanten longitudinalen Druckgradienten durch einen von zwei exzentrischen Kreiszylindern begrenzten Ringspalt. Die Strömung wird als so langsam angenommen, daß das Stoffgesetz einer Rivlin-Ericksen-Flüssigkeit zweiter Ordnung angewandt werden kann. Die von der Flüssigkeit auf die beiden Zylinder ausgeübten resultierenden Kräfte werden berechnet.
    Notes: Summary An incompressible non-Newtonian fluid flows in the annular region between two eccentric circular cylinders under a uniform constant longitudinal pressure gradient. The flow is assumed to be sufficiently slow, so that the second-order Rivlin-Ericksen constitutive equation is applicable. The resultant forces exerted by the fluid on the cylinders are calculated.
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  • 96
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    Rheologica acta 18 (1979), S. 335-338 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Es werden longitudinale Instabilitäten beim Ausströmen aus einem Parallelspalt analysiert. Dabei wird eine Theorie in Ansatz gebracht, welche diese auf die Oberflächenspannung zurückführt. Sie sagt ein Größerwerden der kritischen Wellenlänge mit wachsender Oberflächenspannung, abnehmender Viskosität und zunehmender Spaltweite voraus. Es wird gezeigt, daß dieser Effekt nicht nur, wie früher schon berichtet, in viskoelastischen, sondern auch in newtonschen Flüssigkeiten beobachtet werden kann. Die Theorie sagt weiter voraus, daß derartige longitudinale Instabilitäten nicht beobachtet werden können, solange die mit der halben Spaltweitea gebildete Ohnesorge-Zahl kleiner als 0.945 ausfällt. Schließlich folgt noch, daß die beobachteten Störungen Wellenlängen besitzen, die kleiner als 1,91/a sind.
    Notes: Summary Longitudinal instabilities in exit flow from a slit have been analysed. A theory which shows them to be of surface tension origin has been proposed. It predicts an increase in critical wave length with increasing surface tension, decreasing viscosity, and increasing slit opening. This effect is shown experimentally to be observable in the flow of Newtonian fluids besides the observations in viscoelastic fluids reported previously. The theory predicts that these longitudinal instabilities will not be observed if the Ohnesorge number based on half slit widtha is less than 0.945. Also, the observed disturbances will have wave lengths corresponding to wave numbers less than 1.91/a.
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  • 97
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    Rheologica acta 18 (1979), S. 339-344 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Summary The mathematical effort needed for the description of the strain answer of a viscoelastic material is, in general, very high. Prony-Dirichlet series enable here-with good approximations, where the constants of the series are computed from simple experiments, as for instance creep tests. Possibilities of simulation, based on the mechanical-electrical analogy, as for example the use of passive electrical elements, analog computer circuits or of a process computer, are discussed. Practical examples, obtained with an analog computer for the simulation of material behaviour built in the frame of this work, are presented.
    Notes: Zusammenfassung Der für die Beschreibung der Dehnantwort eines viskoelastischen Körpers benötigte mathematische Aufwand ist im allgemeinen sehr groß. Hierfür ermöglichen Prony-Dirichlet-Reihen gute Approximationen, wobei die Konstanten der Reihen aus einfachen Versuchen, wie z. B. dem Kriechversuch, berechnet werden können. Simulationsmöglichkeiten, die auf der mechanischelektrischen Analogie basieren, wie z. B. der Einsatz passiver elektrischer Bauteile, elektrischer Analogrechnerschaltungen oder eines Prozeßrechners werden diskutiert. Vorgestellt werden praktische Beispiele, die mit Hilfe eines im Rahmen dieser Untersuchung gebauten Analogrechners für Werkstoffsimulation erzielt werden.
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  • 98
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    Rheologica acta 18 (1979), S. 369-373 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Es werden verschiedene neue Meßergebnisse mitgeteilt, die in Scherströmungen an den beiden kommerziellen Polyisobutylen-Typen Vistanex LMMH und L 100 gewonnen worden sind. Außer einigen Messungen unter stationären Bedingungen werden insbesondere Untersuchungen betreffend den Aufbau der Tangentialspannungen nach einer ruckartigen Ingangsetzung der Schergeschwindigkeit sowie deren Abklingen nach Anhalten der stationären Scherströmung durchgeführt. Die Ergebnisse werden zur Prüfung eines rheologischen Stoffgesetzes verwendet, das schon von verschiedenen anderen Autoren untersucht worden ist. Der Vergleich scheint die Eignung des vorgeschlagenen Modells zu bestätigen, wobei dessen einziger Anpassungsparameter sich als unabhängig vom Molekulargewicht erweist.
    Notes: Summary Some new data in shear flow are presented for two commercial polyisobutylene samples, namely Vistanex LMMH and L 100. In particular beyond a few steady state results, the tangential stress build-up after a sudden imposition of a shear rate and the decay after cessation of steady shear flow have been collected. The data are used to further test a constitutive equation already advanced by some of the authors. The comparison seems to confirm the validity of the proposed model, whose single adjustable parameter is shown to be independent of molecular weight.
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  • 99
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Das rheologische Verhalten wäßriger Polymerlösungen von Separan AP-30 und Polyox WSR-301 wird in einem Konzentrationsgebiet von 10–10000 wppm in einem Kegel-Platte-Rheogoniometer untersucht. Der Zusammenhang zwischen Schubspannung und Schergeschwindigkeit wird für niedrige Schergeschwindigkeiten durch eine konzentrationsabhängige Zeitt 0 gekennzeichnet. Für Schergeschwindigkeiten 4000 s−1 〈 $$\dot \gamma $$ 〈 10000 s−1 zeigen beide Polymere ein genähert binghamsches Verhalten, gekennzeichnet durch eine dynamische Viskositätη 0 und eine scheinbare Fließgrenzeτ 0, welche ebenfalls konzentrationsabhängig sind. Die Trägheitskräfte werden für Wasser und einige newtonsche Öle bestimmt. Die Abweichung der experimentellen Ergebnisse vom theoretischen Modell wird durch die Abhängigkeit der Gestalt der Flüssigkeitsoberfläche von der Schergeschwindigkeit erklärt. Um die Werte der ersten Normalspannungsdifferenz zu erhalten, muß man bezüglich der Trägheitskräfte, der Oberflächenspannung und der Auftriebskräfte korrigieren. Die Normalspannungen für Separan AP-30, gemessen für 350 s−1 〈 $$\dot \gamma $$ 〈 3300 s−1, zeigen eine lineare Abhängigkeit von der Schergeschwindigkeit.
    Notes: Summary The rheological behaviour of aqueous solutions of Separan AP-30 and Polyox WSR-301 in a concentration range of 10–10000 wppm is investigated by means of a cone-and-plate rheogoniometer. The relation between the shear stress and the shear rate is for lower shear rates characterized by a timet 0, which is concentration dependent. Both polymers show for 4000 s−1 〈 $$\dot \gamma $$ 〈 10000 s−1 a behaviour similar to that of a Bingham material, characterized by a dynamic viscosityη 0 and an “apparent yield stress”τ 0, which also depend on the concentration. The inertial forces are measured for water and some other Newtonian liquids. An explanation is given why the theoretical model developed for these forces does not match the experimental values; the shape of the liquid surface is shear rate dependent. To obtain the first normal stress difference, we have to correct for these inertial forces, the surface tension and the buoyancy. The normal forces, measured for Separan AP-30, appear to be a linear function of the shear rate for 350 s−1 〈 $$\dot \gamma $$ 〈 3300 s−1.
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  • 100
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    Rheologica acta 18 (1979), S. 429-429 
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
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