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- ItemGravitational lensing in astronomy(Berlin : Springer, 1998) Wambsganss, J.Deflection of light by gravity was predicted by General Relativity and observationally confirmed in 1919. In the following decades, various aspects of the gravitational lens effect were explored theoretically. Among them were: the possibility of multiple or ring-like images of background sources, the use of lensing as a gravitational telescope on very faint and distant objects, and the possibility of determining Hubble's constant with lensing. It is only relatively recently, (after the discovery of the first doubly imaged quasar in 1979), that gravitational lensing has became an observational science. Today lensing is a booming part of astrophysics. In addition to multiply-imaged quasars, a number of other aspects of lensing have been discovered: For example, giant luminous arcs, quasar microlensing, Einstein rings, galactic microlensing events, arclets, and weak gravitational lensing. At present, literally hundreds of individual gravitational lens phenomena are known. Although still in its childhood, lensing has established itself as a very useful astrophysical tool with some remarkable successes. It has contributed significant new results in areas as different as the cosmological distance scale, the large scale matter distribution in the universe, mass and mass distribution of galaxy clusters, the physics of quasars, dark matter in galaxy halos, and galaxy structure. Looking at these successes in the recent past we predict an even more luminous future for gravitational lensing.
- ItemCoherent motion of low frequency vibrations in ultrafast excited state proton transfer(Routledge : Taylor and Francis Inc., 1999) Pfeiffer, M.; Chudoba, C.; Lau, A.; Lenz, K.; Elsaesser, T.Photoexcitation of internal proton transfer in the tinuvin molecule causes the excitation of some low frequency vibrational modes which oscillate with high amplitudes in a coherent manner over 700 fs. Such effect is observed for the first time applying two color pump/probe measurement with 25 fs pulses. Based on resonance Raman spectra a normal coordinate analysis of the modes is performed. It is shown that the nuclear movement given by the normal vibration of one of the modes serves to open up a barrierfree proton transfer path.
- ItemResonance Raman and optical dephasing study of HITCI(Routledge : Taylor and Francis Inc., 1999) Kummrow, A.; Ashworth, S.H.; Lenz, K.Line shape analysis based on resonance Raman spectra of HITCI is used to determine the details of the vibrational part of the line broadening function. Forced Light Scattering with 20 fs pulses from a Ti: sapphire laser measured optical dephasing probing with an Ar+ laser. The observed response is well described by the line broadening function derived from the fluorescence line shape.
- Itemstress generation modulus as a counterpart of the stress relaxation modulus(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Brückner, Rolf; Hessenkemper, Heiko; Habeck, Andreas; Yue, YuanzhengIn order to measure the time dependence of the stress relaxation modulus, E, a stress-strain deformation has to precede which induces a stress within the viscoelastic sample from which the sample relaxes. The generation of stress is characterized by a strain rate-dependent and relaxation rate-dependent portion which exhibits a maximum value, E_max, which is called "stress generation modulus". E_max was called the "maximum stress relaxation modulus" in earlier papers. Meanwhile, however, it turned out that a better verbal distinction should be made in future by the new term "stress generation modulus" because E_max is about one order of magnitude larger than E.
- ItemAdvanced oxygen burner for the glass industry(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Legiret, Thierry; Philippe, Louis; Tsiava, Remi; Marié, Bruno[no abstract available]
- ItemThermodynamic calculations of chemical solubilities of gases in oxide melts and glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Pelton, Arthur D.The Reddy-Blander thermodynamic model for calculating sulfide solubilities in oxide melts and glasses has been modified and extended to predict a priori solubilities of sulfide, sulfate, phosphate, carbonate and halides in multicomponent oxide melts and glasses, from a knowledge of the thermodynamic activities of the basic component oxides (SiO₂, Na₂O, K₂O, CaO, etc.), in most cases with no adjustable parameters. Agreement with measured solubilities is within or nearly within experimental uncertainties over wide ranges of composition in two-, three-, four- and five-component melts and glasses. Particularly good agreement is obtained for the dissolution of sulfur, SO₂ and SO₃ as sulfate. The oxide activities used in the computations are calculated from a database of model parameters obtained by optimizing thermodynamic and phase equilibrium data for oxide Systems. Sulfide, sulfate, phosphate, carbonate and halides as solutes have now been included in this database. Software for Gibbs energy minimization with automatic access to this and other databases permits the calculation of solubilides in multicomponent oxide melts and glasses in equilibrium with other phases such as gases, molten salts, solids and metals, and can be useful to model evaporation processes and bubble formation.
- ItemKonventionell beheizte Glasschmelzöfen für die Hohl- und Flachglasherstellung im deutschsprachigen Raum - Ergebnisse einer HVG-Umfrage - Teil 1. Beheizung, bauliche Merkmale, Schmelzleistung(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Fleischmann, Bernhard[no abstract available]
- ItemIn-situ investigations of sintering and crystallization of lithium aluminosilicate glass-ceramics(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Zimemr, José; Raether, Friedrich; Müller, GerdThe sintering and crystalhzation behaviour of a Li₂O-Al₂O₃-SiO₂ glass powder containing TiO₂ and ZrO₂ was investigated by the in-situ measuring methods of high-temperature dilatometry, high-temperature X-ray diffractometry and differential thermal analysis at heating rates between 0.5 a n d 20 K/min. By comparing the results of the different methods the shrinkage could be explained as an overlap of sintering and crystallization processes. When increasing the heating rate, the sintering and crystallization processes are separated mor e sharply, so that higher final densities of the sintered samples can be achieved.
- ItemUV-VIS spectroscopic investigations of amber glass at high temperatures(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Müller, Matthias; Rüssel, Christian; Claußen, OlafThe absorption spectra of iron-containing glasses and an amber glass were recorded in the temperature ränge of 25 to 700 °C. Α shift of the UV absorption edge towards lower wave numbers with increasing temperature was found. The amount of the shift depends on the Fe³⁺ concentration. Here, the UV absorption edge may superimpose or even cover up the absorption bands of colouring ions with increasing temperatures. For an amber glass sample, with increasing temperature, the intensity of the absorption bands of the amber chromophore decreases slightly. However, above 550 °C the decomposition of the chromophore is observed. All changes are reversible when temperature is decreased again. The decomposition of the chromophore and the attributed temperature ränge are in agreement with thermodynamic calculations.
- ItemDetermination of the composition of glass, glass-ceramics and glass raw materials with Laser-ICP-MS(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Strubel, Christine; Meckel, Lothar; Effenberger, RuthΑ mass-spectrometric method with an inductively coupled plasma as an ion source (ICP-MS) is presented which uses an excimer laser for direct ablation of solid material. The oxide compositions of a television screen glass, a glass-ceramic and a quartz powder analyzed by LA-ICP-MS are given and compared with data obtained by wet chemical analysis. Fundamental processes of the technique are described and advantages and disadvantages for the analysis of glass are discussed.