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  • Articles  (256)
  • Polymer and Materials Science  (132)
  • Electronic structure and strongly correlated systems  (124)
  • Air temperature at 10 m height; Air temperature at 2 m height; Anemometer; AWI_Meteo; AWIPEV; AWIPEV_based; BARO; Barometer; DATE/TIME; HEIGHT above ground; Humidity, relative; HYGRO; Hygrometer; Meteorological Long-Term Observations @ AWI; Monitoring station; MONS; NYA; Ny-Ålesund; Ny-Ålesund, Spitsbergen; PYRA; Pyranometer; Short-wave downward radiation, 525 - 3000 nm; Short-wave downward radiation, 696 - 3000 nm; Station pressure; Sunshine duration; Thermometer; Total Ultraviolet Radiometer (TUVR), Eppley; Ultraviolet radiation; Wind direction at 10 m height; Wind direction at 2 m height; Wind speed at 10 m height; Wind speed at 2 m height
  • Physics  (256)
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  • Articles  (256)
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  • 1
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 2
    Publication Date: 2011-05-11
    Description: Author(s): Andreas Holzner, Andreas Weichselbaum, Ian P. McCulloch, Ulrich Schollwöck, and Jan von Delft We show that recursively generated Chebyshev expansions offer numerically efficient representations for calculating zero-temperature spectral functions of one-dimensional lattice models using matrix product state (MPS) methods. The main features of this Chebyshev matrix product state (CheMPS) approa... [Phys. Rev. B 83, 195115] Published Tue May 10, 2011
    Keywords: Electronic structure and strongly correlated systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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  • 3
    Publication Date: 2018-08-08
    Description: Author(s): Mehdi Biderang, Andreas Leonhardt, Nimisha Raghuvanshi, Andreas P. Schnyder, and Alireza Akbari We consider a two-orbital tight-binding model defined on a layered three-dimensional hexagonal lattice to investigate the properties of topological nodal lines and their associated drumhead surface states. We examine these surface states in centrosymmetric systems, where the bulk nodal lines are of ... [Phys. Rev. B 98, 075115] Published Tue Aug 07, 2018
    Keywords: Electronic structure and strongly correlated systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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  • 4
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: An Proben aus Polypropylen, die bei sehr unterschiedlichen Einstellungen von Spritzgußmaschinen und Extrudern hergestellt wurden, stellten sich deutliche Abhängigkeiten des Alterungsverhaltens von den thermischen und mechanischen Produktionsparametern ein, die nicht durch unterschiedliche Schmelzetemperaturen bedingt sind. Insbesondere kann ausgesagt werden, daß bei Spritzguß eine hähere Scherbelastung und damit stärkere Orientierungen -eine stärkere Veränderung der Eigenspannungen hervorrufen-einen früheren Glanzabfall und-eine geringere Initialzeit bis zur Rißbildung bewirken.Bei Extrusion fiihrt eine geringere Abkühlgeschwindigkeit und damit ein gröberes Gefüge zu -einer stärkeren Veränderung der Eigenspannungen-einem friiheren und ausgeprägteren Glanzverlust-sowie zu einem früheren Abfall der Reißdehnungen.Unbekannt ist, -ob diese Wirkungen auch bei anderen Thermoplasten als PP auftreten-ob sie auch bei stabilisierten Systemen in relativ gleichem Umfange auftreten-und ob es sich lohnt, die beobachteten Effekte ggf. durch ge zielte Maschineneinstellungen auszunutzen.Auf jeden Fall sollten auf diesem Gebiet weitere Arbeiten durchge-führt werden.
    Notes: Specimens of unmodified polypropylene have been manufactured using extreme adjustings of injection moulding machines and extruders. After artificial weathering, distinct relations of ageing processes to thermal and mechanical production parameters were found, which are not influenced by different melting temperatures. It can be started in particular, that during injection moulding a larger shear stress (resulting in more distinct orientation) results in -a greater change in residual stresses-an earlier gloss reduction-a shorter initial period before cracking.During extrusion a lower cooling rate (resulting in a coarser structure) leads to -a greater change in residual stresses-an earlier and more distinct gloss reduction-an earlier loss of ultimate strain.It remains unknown, whether -these relationships will be similar with other thermoplastic materials than PP-these relationships appear to the same relative extend with stabilized systems-it may be advantageous, to use the observed effects by adjusting the injection moulding and extrusion machines in a special way.It seems to be significant to do more research work in this field.
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  • 5
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The tensio-active properties of different types of diesters can be used to synthesize two-dimensional model networks at the interface between oil and water. We have systematically studied rubber-elastic, glass-like and transient membrances which are stabilized and crosslinked by physical or chemical contacts.The adsorption process of the monomeric diesters was investigated by measuring the interfacial tension at the boundary between oil and water. The experimental results can be interpreted on the basis of the “Szyskowski”- equation which holds for monomolecular films under ideal conditions. From the measured values of the interfacial tension it is possible to determine the surface concentration. The polymerization process occurs through radical-reactions which can be initiated by UV-irradiation.We have systematically studied the kinetics of surface gelation by measuring the two-dimensional shear modulus as a function of the reaction time. The experimental results can be interpreted in the framework of simple reaction mechanisms. The quantitative analysis of the experimental data allows to evaluate many details of the photo-reaction as the free radical concentration. the number of linear chains and the rate constant of the cross-linking process.The two-dimensional sol-gel transition can easily be described in the framework of percolation theories which were proposed by Stauffer and de Gennes. According to these models, one expects to find a steep increase in the elastic modulus after passing the gel point. The two-dimensional percolation exponent, determined in our experiments, agrees very well with the calculated result of 4/3. This holds for rubber-elastic and glass-like membranes.Rubber-elastic, cross-linked films exhibit interesting features, which can be explained by simple models. The shear modulus depends upon the surface concentration of elastically effective chains. The interfacial polymerization is not restricted to flat surfaces, and the corresponding films can be used for the stabilization of different types of emulsions. Oil droplets which are surrounded by cross-linked membranes, from simple systems which exhibit interesting properties of biological cells. The microcapsules can, for instance, be used in order to simulate blood flow in living vessels. We have measured the deformation process and the aggregation behavior of these microcapsules in Couette flow under a microscope, and we have investigated the influence of the membrane elasticity on the flow behavior of these emulsions. The data, thus obtained, can be compared with the particle behavior of rigid spheres and deformable liquid drops. The rheological properties of these artificial cells are useful to get a clearer picture of the complicated flow processes which occur in biological systems.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 211 (1993), S. 141-155 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die after-glow Plasmapolymerisation wird als neues Verfahren zur Herstellung polymerer Schichten aus ungesättigten Monomeren vorgestellt. Als Monomeres wird ein optisch aktiver Acrylsäureester verwendet. Die Abscheidekinetik wird durch Variation von Monomerfluß, Fluß und Art des Hilfsgases (He, Ne, Ar, Kr) Abstand zwischen Plasma und Substrat, Druck und nomineller Plasmaleistung untersucht. Die erhaltenen Polymeren sind optisch aktiv und lassen sich mittels IR_Spektroskopie nicht von den in Masse polymerisierten Analoga unterscheiden. Die Polymeren sind meist vernetzt und damit unlöslich. NMR-Spektren von Löslichen Proben zeigen, daß es sich um atktische Polymere handelt. Die after-glow Plasmapolymerisation verläuft über einen radikalischen Kettenwachstumsmechanismus. Membranchichten aus den erhaltenen Polymeren sind in der Lage, Racemate zu trennen.
    Notes: After-glow plasma polymerization is described as a new method to prepare polymeric layers from unsaturated monomers. An optically active acrylic monomer is used in this investigation. The deposition rates are given as functions of plasma power, pressure, distance between plasma and deposition zone, flux and kind of auxiliary gas (He, Ne, Ar, Kr) and of monomer flux. The polymers prepared are optically active, the IR spectra comply with those of polymers synthesized in bulk. Mostly the polymers prepared by after-glow plasma polymerization are cross-linked and therefore insoluble. NMR spectra of soluble samples show that the polymers are atactic. After-glow plasma polymerization occurs by a radical chain growth mechanism. Membranes made from these polymers are able to separate racemates.
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  • 7
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch Polykondensation aliphatischer Dicarbonsäuren wie Bernsteinsäure, Iminodiessigsäure und Ethylendiamintetraessigsäure (die als difunktionelles Monomeres reagierte) mit Diaminen wie Diethylentriamin, l, 2-Bis(3-aminopropylamino)ethan und den beiden löslichkeitsverbesserenden Polyethylenoxid-Derivaten α,ω-Bis(2-aminopropyl)polyethylenglykol800 (Jeffamine ED-900) und α,ω-Bis-(2-aminopropyl)- poly-ethylenglykol 1900 (Jeffamine ED-2001) wurden hydrophile Polyamide mit Aminooder Carboxygruppen in ihren Wiederholungseinheiten hergestellt, die zur Ankopplung physiologisch aktiver Substanzen geeignet sind. Die Reaktionen wurden in Polyphosphorsäure im optimalen Temperaturbereich von 150- 165°C durchgefuhrt. Die Produktpolymeren wurden durch Dialyse wäßriger Lösungen fraktioniert und durch Gefriertrocknung isoliert. Die Ausbeuten, die von 1% bis nahe 40% reichten, zeigen für das fluchtige Diethylentriamin unter diesen Bedingungen eine geringe Tendenz zur Polykondensation und eine mittelmanige Reaktionsneigung fur die thermolabilen Jeffamine-Reaktanden, während für das Bis(aminopropylamino)ethan eine zufriedenstellende Polykondensationsbereitschaft gefunden wurde. Die mikroanalytisch und spektroskopisch charakterisierten Polyamide verfügen über eine  -  für biomedizinische Anwendungen wichtige  -  ausreichende Wasserlöslichkeit. Die inhärenten Viskositäten in diesem Medium liegen im Bereich von 5 - 15 ml g-1. Die Nutzung dieser Polymeren zur Verankerung von Medikamenten wird Gegenstand weiterer Veröffentlichungen sein.
    Notes: Hydrophilic polyamides containing amino or carboxyl groups in the repeat units suitable for drug binding are synthesized by polycondensation of aliphatic dicarboxylic acids, including succinic acid, iminodiacetic acid, and ethylenediaminetetraacetic acid (reacting as a difunctional monomer in these polymerizations), with diamines, such as diethylenetriamine, 1,2-bis(3-aminopropylamino)ethane, and the two hydrosolubilizing poly(ethylene oxide) derivatives, α,ω-bis(2-aminopropyl)poly(ethylene glycol) 800 (Jeffamine ED-900) and α,ω-bis(2-aminopropyl)poly(ethylene glycol) 1900 (Jeffamine ED-2001). The reactions are conducted in polyphosphoric acid medium at the optimal temperature range of 150-165°C. The product polymers, fractionated by aqueous-phase dialysis in 12000-14000 molecular-mass cut-off membrane tubing, are isolated by freeze-drying. Yield data, ranging from 1% to nearly 40% for the material so fractionated, indicate low propensity for polycondensation under these conditions for the volatile diethylenetriamine monomer, and only moderately better performance for the thermally labile Jeffamines, yet satisfactory polymerization behaviour for the bis(aminopropylamino)ethane. The microanalytically and spectroscopically characterized polyamides fulfil the biomedically important requirement of solubility in water; inherent viscosities in this medium are in the approximate range of 5-15 ml · g-1. The drug-anchoring capabilities of these polymers will be the subject of forthcoming publications.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 238 (1996), S. 177-189 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß von CO2-Laserstrahlung auf die Oberflächeneigenschaften eines Epoxid-Laminierharzes (wärmebeständig bis 120°C) für kohlefaserverstärkte Kunststoffe (CFK) wird untersucht. Infrarot- und XPS-Spektroskopie zeigen, daß die Hydroxygruppen des Harzes unter Bildung von Doppelbindungen eliminiert werden. In Kohlendioxidatmosphäre werden tiefer liegende Teile des Harzes modifiziert als bei der Behandlung in Luft. Eine Steigerung der Reproduzierbarkeit der Klebfestigkeit des verwendeten CFK auf Basis des untersuchten Harzes ist nur bei gleichzeitiger Verringerung der Klebfestigkeit selbst möglich. Beim Einsatz eines heißhärtenden Klebstoffes kann kein Einfluß der Laserbehandlung auf die Klebfestigkeit festgestellt werden.
    Notes: The influence of CO2 laser radiation on the surface properties of a lamination resin (temperature resistant up to 120°C) which is used for carbon fibre-reinforced plastics (CFRP) is examined. It is shown by XPS and infrared spectroscopy that the hydroxy groups of the resin are eliminated by the laser radiation. Using a carbon dioxide atmosphere, also deeper parts of the resin are influenced compared to the treatment in air. The reproducibility of the bond strength is higher for the laser-treated samples than for untreated samples if a room temperature-curing adhesive is used, but the bond strength itself is lower. Laser treatment shows no influence at all if a hot-curing adhesive is used.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 241 (1996), S. 175-190 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The influence of submicron mineral additives on the rheological properties of polyamide 6 was investigated. Usually, after incorporation of increasing amounts of commercial fillers in the polymer matrix (particle sizes in micron range), the viscosity is continuously increased when applying low shear rates due to higher friction in the sliding planes.After intensive dispersion of submicron additives in ethylene glycol by using polyethyleneimine as a cation-active dispersing agent, agglomerate-free dispersions of all investigated additives were realized.Under standard conditions, the ethylene glycol/additive slurries were incorporated in the PA 6-matrix by using a twin screw extruder equipped with a vacuum degassing stillhead to remove excessive glycol immediately. The expected effects characterized by improved intramolecular sliding behaviour were found in different extents for TiO2, Al2O3, SiO2, clay and talcum. However, submicronized CaCO3 already restricted the intramolecular sliding in concentration ranges below 1 wt.-%.The analogous effect failed to appear when the same powdery additives were incorporated in the polyamide 6-matrix by twin screw extrusion.
    Notes: Der Einfluß submikroner mineralischer Additive auf die rheologischen Eigenschaften von Polyamid 6 (PA 6) wurde untersucht. Üblicherweise steigt bei niedriger Schergeschwindigkeit die Viskosität nach der Einarbeitung zunehmender Mengen kommerzieller Füllstoffe (Mikronbereich der Korngrößen) stetig an, weil die Reibung in den Gleitschichten zunimmt.Nach intensiver Dispergierung submikroner Additive in Ethylenglykol unter Zusatz von Polyethylenimin als kationaktivem Dispergierhilfsmittel wurde eine agglomeratfreie Dispergierung aller untersuchten Additive erreicht. Unter Standardbedingungen wurden die glykolischen Suspensionen mit Hilfe eines Doppelschneckenextruders in die PA 6-Matrix eingearbeitet, dabei mittels einer Entgasungsstufe sofort der Glykolüberschuß entfernt. Die erwarteten Effekte verbesserten intramolekularen Gleitens zeigten sich in unterschiedlicher Höhe bei TiO2, Al2O3, SiO2, Kaolin und Talkum. CaCO3 dagegen schränkte auch im Submikronbereich das intramolekulare Gleiten schon in Konzentrationen unter 1 Gew.-% deutlich ein. Bei der Einarbeitung pulverförmiger Additive mittels eines Doppelschneckenextruders direkt in die PA 6-Matrix wurden analoge Effekte nicht erreicht.
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  • 10
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: It could be shown by a detailed 1H-NMR-study of suitable model compounds that also in the isolated dissolved molecule of N-phenylphthalimide the nitrogen atom is subject of a stationary sp2-hybridization with strong planar geometry of the three σ-bonds. From this molecular structure it can be concluded, that the polyimide of pyromellitic acid, poly(pyromellitdiimido-4,4′-biphenylylene) (4), must have a strictly linear rod-like structure of the whole macromolecule.
    Notes: Anhand geeigneter Modellverbindungen konnte 1H-NMR-spektroskopisch nachgewiesen werden, daß sich auch am isolierten, gelösten Molekül des N-Phenylphthalimids eine zeitlich stationäre sp2-Hybridisierung mit ebener Anordnung der drei vom Stickstoff ausgehenden σ-Bindungen einstellt. Diese Bindungsverhältnisse haben für das Polyimid der Pyromellithsäure, Poly(pyromellithdiimido-4,4′-biphenylylen) (4), eine streng lineare, stäbchenförmige Struktur des Makromoleküls zur Folge.
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