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- ItemSporadic Ca and Ca+ layers at mid-latitudes: Simultaneous observations and implications for their formation(München : European Geopyhsical Union, 2001) Gerding, M.; Alpers, M.; Höffner, J.; von Zahn, U.We report on the observations of 188 sporadic layers of either Ca atoms and/or Ca ions that we have observed during 112 nights of lidar soundings of Ca, and 58 nights of Ca+ soundings, at Kühlungsborn, Germany (54° N, 12° E). The Ca+ soundings have been performed simultaneously and in a common volume with the Ca soundings by two separate lidars. Correlations between sporadic neutral and ionized metal layers are demonstrated through four case studies. A systematic study of the variations of occurrence of sporadic Ca and Ca+ layers reveals that neutral and ionized Ca layers are not as closely correlated as expected earlier: (a) The altitude distribution shows the simultaneous occurrence of both sporadic Ca and Ca+ layers to be most likely only in the narrow altitude range between 90 and 95 km. Above that region, in the lower thermosphere, the sporadic ion layers are much more frequent than atom layers. Below 90 km only very few sporadic layers have been observed; (b) The seasonal variation of sporadic Ca layers exhibits a minimum of occurrence in summer, while sporadic Ca+ layers do not show a significant seasonal variation (only the dense Ca+ layers appear to have a maximum in summer). At mid-latitudes sporadic Ca layers are more frequent than sporadic layers of other atmospheric metals like Na or K. For the explanation of our observations new formation mechanisms are discussed.
- ItemOn the longitudinal structure of the transient day-to-day variation of the semidiurnal tide in the mid-latitude lower thermosphere - I. Winter season(München : European Geopyhsical Union, 2001) Merzlyakov, E.G.; Portnyagin, Yu.I.; Jacobi, C.; Mitchell, N.J.; Muller, H.G.; Manson, A.H.; Fachrutdinova, A.N.; Singer, W.; Hoffmann, P.The longitudinal structure of the day-to-day variations of semidiurnal tide amplitudes is analysed based on coordinated mesosphere/lower thermosphere wind measurements at several stations during three winter campaigns. Possible excitation sources of these variations are discussed. Special attention is given to a nonlinear interaction between the semidiurnal tide and the day-to-day mean wind variations. Data processing includes the S-transform analysis which takes into account transient behaviour of secondary waves. It is shown that strong tidal modulations appear during a stratospheric warming and may be caused by aperiodic mean wind variations during this event.
- ItemThree years of routine Raman lidar measurements of tropospheric aerosols: Backscattering, extinction, and residual layer height(Göttingen : Copernicus GmbH, 2002) Schneider, J.; Eixmann, R.We have performed a three-year series of routine lidar measurements at preselected times. The measurements were performed between 1 December 1997, and 30 November 2000, at Kühlungsborn, Germany (54°07′N, 11°46′E). Using a Rayleigh/Mie/Raman lidar system, we measured the aerosol backscatter coefficients at three wavelengths and the extinction coefficient at one wavelength. The present data analysis focuses on after-sunset Raman measurements obtained on cloud-free days. Aerosol backscatter profiles are available for altitudes above 100 m, while the majority of the extinction measurements has been restricted to heights above the residual layer. The residual layer shows an annual cycle with its maximum height in summer (2000 m) and minimum height in winter (850 m). The backscatter coefficients in the residual layer were found to be about 10 times higher than above. The mean aerosol optical depth above the residual layer and below 5 km is 0.3(±1.0) × 10-2 in summer, and 1.5(±1.0) × 10-2 in winter, which almost is negligible compared to values measured in during daytime in the planetary boundary layer. A cluster analysis of the backward trajectories yielded two major directions of air mass origin above the residual layer and 4 major directions inside. A marked difference between the aerosol properties dependent on the air mass origin could be found for air masses originating from the west and travelling at high wind speeds. Comparing the measured spectral dependence of the backscatter coefficients with data from the Global Aerosol Data Set, we found a general agreement, but only a few conclusions with respect to the aerosol type could be drawn due to the high variability of the measured backscatter coefficients.
- ItemOberflächenmorphologie von Arzneistoffpartikeln - Ein optisch evaluierbares Kriterium für die Auflösungsgeschwindigkeit(München : Elsevier, Urban & Fischer , 2002) Diebold, Steffen M.Für die Auflösungsgeschwindigkeit von schwer wasserlöslichen Arzneistoffpartikeln spielt die Hydrodynamik an den Partikel-Oberflächen eine große Rolle. Diese ist ihrerseits beeinflußt von der Geometrie und der Oberflächenmorphologie der Partikel. In dieser Arbeit wurde gezeigt, dass sich zur Charakterisierung dieser Parameter die Rasterelektronenmikroskopie (SEM) auch für die Untersuchung von Arzneistoffen gut eignet. Am Beispiel von Felodipin-Kristallen wurde nachgewiesen, dass reale Arzneistoffpulver auch an scheinbar „glatten“ Oberflächen Protrusionen, Kanten und Kavitäten aufweisen. Deren Größenordnungen lassen sich mit Hilfe der Elektronenmikroskopie abschätzen. Die Oberflächenmorphologie von Arzneistoffpartikeln ist ein Kriterium für die Auflösungsgeschwindigkeit oral verabreichter Arzneistoffe. Die Rasterelektronenmikroskopie leistet dabei wertvolle Dienste zur Charakterisierung der Oberflächen von Arzneistoffpartikeln.
- ItemZerstörungskennlinien für Verbundsicherheitsglasscheiben(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Mayrhofer, Christoph; Kranzer, CarolineFür die Bewertung des Tragverhaltens von Bauteilen bei Explosionsereignissen sind sogenannte „Druck-Impuls-Diagramme" erforderlich. Diese geben in Abhängigkeit vom Druck und dem Impuls der Belastung an, für welche Wertepaare Zerstörung eintritt und welchen Belastungswerten das betrachtete Bauteil standhält. Derartige Zerstörungskennlinien sind am Fraunhofer EMI für eine Vielzahl von Werkstoffen entwickelt worden. Den Zerstörungskennlinien liegt das Rechenmodell des Ein-Massen-Schwingers zugrunde. Voraussetzungen für seine Anwendbarkeit sind Biegetragmechanismen, Bruch- bzw. Zerstörungskriterien (z.B. Grenzdurchbiegung) und die Kenntnis des statischen Last-Verformungsverhaltens. Untersuchungen ergaben, daß Verbundsicherheitsglasscheiben die Voraussetzungen für die Erstellung von Zerstörungskennlinien erfüllen. Es wird eine Näherungsmethode zur Erfassung des statischen Tragverformungsverhaltens unter Berücksichtigung von Membranspannungszuständen dargestellt. Am Beispiel anderer Werkstoffe wird die prinzipielle Vorgehensweise erläutert, da für Verbundsicherheitsscheiben bisher noch keine Bruchkriterien zur Verfügung stehen.
- ItemCollaborative study into the analysis of total selenium and selenium valence states in glass - a general method by hydride generation atomic absorption spectrometry and photometry : Report of the International Commission on Glass (ICG) Technical Committee 2 "Chemical Durability and Analysis"(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Guadagnino, Emanuel; Çorumluoğlu, OrhanWhilst the determination of total selenium in glass is of great relevance to environmental purposes, the measurement of the oxidation states of selenium which may arise under different redox conditions may contribute to clarify the mechanisms of colour formation. In the proposed method, the determination of total selenium is carried out by hydride generation atomic absorption spectrometry (HGAAS) on three different glasses covering the range of selenium content between 10 and 130 mg/kg of glass. To prevent losses during the decomposition step, selenium is converted into a nonvolatile form as selenate (Se6+). When the sample is decomposed, the HCl Solution (c(HC1) = 10 mol/l) is made and selenium is pre-reduced to Se4+ by heating for 2 h at 80 °C. The determination of selenium oxidation states requires a stepwise approach. The measurement of Se0 is based on its insolubility in HF. After the sample is decomposed, Se0 is filtered off, dissolved from the filter with a HBr-Br2 mixture and finally measured by HGAAS. Se4+ and Se6+ are recovered in the filtrate of the same sample and determined together after conversion of Se4+ into Se6+. Se4+ is determined in the same filtrate by photometry with o-phenylenediamine (OPDA).
- ItemPostmortem analyses of salvaged conventional silica bricks from glass production furnaces(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Wereszczak, Andrew; Wang, Hsin; Karakus, Musa; Curtis, Warren; Aume, Victor; VerDow, DennisThe microstructure, phase content, and thermal conductivity of salvaged conventional silica bricks from float glass and TV-panel glass production furnaces were examined as a function of position through the brick, and compared with the original, unaltered brick materials. The silica brick from the float glass furnace was in service for approximately 10 years while that for the TV-panel glass furnace was for approximately 6 1/2 years. The microstructure and phase content in both salvaged bricks showed gradients, from tridymite at the bricks' cold-face ends, to cristobalite at their hot-face end even though both bricks were an initial mixture of tridymite and cristobalite to begin with. The thermal conductivity of both bricks had increased as a consequence of these phase and microstructural changes. Α thermal analysis model predicted that such changes would result in an increase in the bricks' cold-face temperature and heat content during service. The initially-produced temperature gradients and environment caused microstructural changes in the silica brick; however, the cause-and-effect relationship between temperature/environment and microstructural changes in the brick likely became mutually reversible once the microstructural changes initiated and the thermal conductivity of the brick started to change as a consequence.
- ItemDevelopment of organic-inorganic coatings for strength-preserving of glass bottles(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Mennig, Martin; Gier, Andreas; Anschütz, Dieter; Schmidt, HelmutAn amino-epoxy-silane based coating system (GAMAL) for glass surfaces was developed, which can efficiently protect bottles from the damages of a bottling plant. Testing bottles with a ramp pressure tester show an identical value of about (40 ± 4) bar for conventionally hot- and cold-end coated bottles and bottles coated with the developed organic-inorganic composite (GAMAL) system. After already 2 min of wet line-simulation testing, all species of a conventionally coated probe fall short of the critical limit of 16 bar, whereas bottles coated with GAMAL (thickness about 7 µm) show a value of (21 ± 3) bar. Coating is possible by dip and spray applicadon on cold or hot (80 °C) substrates, the coating is cured at 120 °C for 5 to 10 min. Additional functions such as colour or UV protection can be added easily, without reduction of the protection potential. The low content of carbon (about 0.5 g per 1 l soft drink bottle) should not disturb the recycling process of such coated bottles.
- ItemMicrowave-assisted digestion of ceramic frits for boron and lithium determination by inductively coupled plasma spectrometry (ICP-OES)(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Barba, Antonio; Gazulla, M. Fernanda; Gómez, M. Pilar; Jarque, Juan Carlos; Mestre, SergioBoron and lithium are two elements commonly found in the chemical composition of ceramic frits. They are usually determined by volumetric titration and atomic absorption spectrometry, respectively, after melting the ceramic frit by high-temperature alkaline fusion and dissolving the melt in acid medium. This dissolution procedure is long and tedious, and does not enable determining both elements simultaneously. An alternative ceramic frit dissolution procedure based on microwave-assisted digestion in acid medium has been proposed, which allows jointly determining boron and lithium by inductively coupled plasma-optical emission spectrometry. This procedure is rapid and reproducible, and the results are independent of frit chemical composition.
- ItemMatrix algebra method for deriving oxide factors and its relationship to the principle of least squares(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Rawson, HaroldMultiple regression analysis of glass property-composition data involves the derivadon of 'normal equations', one for each oxide factor. The number of these is, in general, much smaller than the number of initial equations, which, for each composition, relate the property to the glass composition. The normal equations are readily derived by a matrix multiplication process. It is shown, by the use of a simple numerical example, that the method minimizes the sum of squares of the residuals in the initial set of equations. The method is used to derive oxide factors for calculating thermal expansion coefficients of glasses in a number of systems. Good agreement between calculated and measured expansion coefficients was obtained, the best being for a large group of alkaline earth aluminoborosilicate glasses, data for which is given in a recent patent. For oxides of both group I and group II elements, there is a linear dependence of the oxide factor on z/a, where z is the valency and a is the cation-oxygen distance. The method and results are compared with earlier work.