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  • Springer  (49)
  • 1995-1999  (34)
  • 1980-1984  (15)
  • 1
    Electronic Resource
    Electronic Resource
    Anion incorporation and its effect on the dielectric constant and growth rate of zirconium oxides (1996)
    Springer
    Journal of applied electrochemistry 26 (1996), S. 1037-1043 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Mechanically polished zirconium electrodes were potentiodynamically polarized in phosphate buffer solutions of various pH values and in 0.5 lvl NaOH. The results show that the shape of the I-E curves is independent of the solution pH. At relatively low scan rates, oxygen gas evolution was observed. The oxide film thickness was calculated from the values of the charge consumed in the anodic process assuming 100% current efficiency for oxide formation below oxygen evolution (lower values for the current efficiency are assumed for potentials above oxygen evolution). Capacitance measurements, together with the calculated oxide thickness, were used to estimate values for the dielectric constant of the oxide. Two different values of the dielectric constant were obtained for the oxides formed in the range of potential below and above oxygen evolution. Also, higher dielectric constant values were obtained with increasing solution pH. Anion incorporation was assumed to increase the conductivity of the oxide films and, hence, decrease the dielectric constant. A two-layer structure is proposed for the anodically formed oxide on zirconium in aqueous solutions; an anion-free layer near the metal and an outer layer containing the incorporated anions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242198
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  • 2
    Electronic Resource
    Electronic Resource
    Infrared observations of beta Cephei and delta Scuti stars (1983)
    Springer
    Astrophysics and space science 92 (1983), S. 173-176 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have made near-infrared photometric observations of nine β-Cephei and eight δ-Scuti stars inJ, H, andK bands. The observed fluxes are in good agreement with those expected according to their spectral types. We conclude that these stars do not have any anomalous emission in these near-infrared bands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00653597
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of 5-methylisocytidine derivatives (1996)
    Springer
    Monatshefte für Chemie 127 (1996), S. 455-459 
    Details
    ISSN: 1434-4475
    Keywords: Herpes simplex virus ; Human immunodeficiency virus ; Isocytidines ; N2-alkyl-5-methyl ; Nucleosides ; convergent synthesis of ; 2-Thiouridine ; 5,S2-dimethyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung N2-substituierte 5-Methylisocytidin-Derivate wurden ausgehend von S2-Methyl-2-thiothymidin entweder durch direkte Substitution der Methylthiogruppe durch eine Aminogruppe und anschließende Kondensation mit 1,2,3,5-tetra-O-Acetyl-β-D-ribofuranose zum acetylierten Nucleosid oder umgekehrt durch Synthese eines acetylierten 5,S2-Dimethyl-2-thiouridins und nachfolgende Behandlung mit dem entsprechenden Amin hergestellt.
    Notes: Summary N2-Substituted 5-methylisocytidine derivatives were synthesized from S2-methyl-2-thiothymine either by direct substitution of the methylthio group by an amino group and subsequent condensation with 1,2,3,5-tetra-O-acetyl-β-D-ribofuranose to give the acetylated nucleoside or by the opposite sequence first preparing an acetylated 5,S2-dimethyl-2-thiouridine followed by treatment with the appropriate amine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00810888
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of 2-O-ethyl analogues of 3′-azido- and 3′-fluoro-2′,3′-dideoxyuridines and evaluation of their biological activity against HIV (1995)
    Springer
    Monatshefte für Chemie 126 (1995), S. 811-817 
    Details
    ISSN: 1434-4475
    Keywords: Nucleosides ; convergent synthesis of ; Uridines, 2-O-ethyl ; Uridines, 2′,3′-dideoxy-3′-fluoro ; AZT analogues ; Human immunodeficiency virus ; Herpes simplex virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung 2-O-Ethyluracil und 2-O-Ethylthymin wurden mit 1,1,1,3,3,3-Hexamethyldisilazan silyliert und in Gegenwart vonTMS-triflat mit 2,3-Dideoxy-3-fluoro-D-erythro-pentofuranosid, 3-Azido-2,3-dideoxy-D-erythro-pentofuranosid und 2,3-Dideoxy-3-phthalimido-β-D-erythro-pentofuranosederivaten zu den entsprechenden 2-O-Ethyl-Nucleosiden umgesetzt. Entfernung der Schutzgruppe mit gesättigter methanolischer Ammoniaklösung lieferte 2′,3′-Dideoxy-3′-fluor-2-O-ethyluridin; 3′-Azido-2′,3′-dideoxy-3-O-ethyl-uridin wurde durch Entschützung mit Tetrabutylammoniumfluorid in Tetrahydrofuran erhalten. 3′-Amino-2′,3′-dideoxy-3-O-ethyl-uridin konnte nur durch Behandeln des entsprechenden 3′-Azido-Nucleosids mit Triphenylphosphin in Pyridin hergestellt werden. 3′-Deoxy-2-O-ethyl-3′-fluor-thymidin (6b) zeigt geringe Aktivität gegenüber HIV-1.
    Notes: Summary 2-O-Ethyluracil and 2-O-ethylthymine were silylated with 1,1,1,3,3,3-hexamethyldisilazane and condensed in the presence ofTMS triflate with 2,3-dideoxy-3-fluoro-D-erythro-pentofuranoside, 3-azido-2,3-dideoxy-D-erythro-pentofuranoside, and 2,3-dideoxy-3-phthalimido-β-D-erythro-pentofuranose derivatives to give the corresponding 2-O-ethyl nucleosides. Deprotection with saturated methanolic ammonia afforded the 2′,3′-dideoxy-3′-fluoro-2-O-ethyluridines, whereas 3′-azido-2′,3′-dideoxy-3-O-ethyluridine was obtained by deprotection with tetrabutylammonium fluoride in tetrahydrofuran. 3′-Amino-2′,3′-dideoxy-3-O-ethyluridine could be obtained only by treatment of the corresponding 3′-azido nucleoside with triphenylphosphine in pyridine. 3′-Deoxy-2-O-ethyl-3′-fluorothymidine (6b) showed moderate activity against HIV-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807175
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  • 5
    Electronic Resource
    Electronic Resource
    Petrogenesis of the Wadi Dib alkaline ring complex, Eastern Desert of Egypt (1999)
    Springer
    Mineralogy and petrology 65 (1999), S. 249-275 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Der Wadi Dib-Komplex ist die älteste bekannte Ringstruktur im ägyptischen Teil des Panafrikanischen Orogengürtels. Rb-Sr Isotopendaten von sieben Proben ergeben ein vendisches Alter von 578±16 Ma and ein initiales87Sr/86Sr-Verhältnis von 0,7048±0,0010. Der magmatische Komplex besitzt einen Durchmesser von 2 km und hat am Schnittpunkt zweier Störungen innerhalb panafrikanischer Granodiorite Platz genommen. Er weist eine konzentrische Zonierung mit mehreren syenitischen äußeren Ringen, einem vorwiegend trachytischen mittleren Ring und einem quarzsyenitischen inneren Ring mit einem granitischen Kern auf; die relativen Alter der Gesteine nehmen vom Rand zurn Kern hin ab. Mineralogische and chemische Charakteristika sind die von Intraplatten- (A-Typ-) Komplexen. Haupt- and Spurenelementmuster weisen auf eine ko-magmatische Entstehung hin, zeigen aber eine Entwicklung in drei Stadien mit mehreren magmatischen Pulsen auf. Charakteristika der Elememverteilungen sind wenig systematische Änderung in den älteren Lithologien, aber ein gerichteter Entwicklungstrend in den späten, quarzführenden Lithologien. Wir schließen, daß ein alkali-basaltisches Magma in ein tiefes oder mittleres Niveau der jungen panafrikanischen Kruste intrudierte. Differentiation erfolgte im wesentlichen durch fraktionierte Kristallisation von Olivin, Klinopyroxen, Plagioklas und Apatit. Während später Entwicklungsstadien gab es vermutlich begrenzte Assimilation von Inselbogen-Kruste. Die Platznahme erfolgte entlang von Ringbrüchen in einem subvulkanischen Stockwerk und war vermutlich mit der Bildung einer Caldera während der Platznahme der trachytischen Lithologien verbunden. Der anorogene Charakter der magmatischen Folge zeigt an, daß die panafrikanische Kruste Nordost-Afrikas zur Zeit der Platznahme der alkalischen Intrusion bereits konsolidiert war.
    Notes: Summary The Wadi Dib magmatic complex is the oldest known alkaline ring complex in the Egyptian part of the Pan-African orogenic belt. Rb-Sr isotope data for seven samples suggest a Vendian age of 578±16 Ma, and a87Sr/86Sr initial ratio of 0.7048±0.0010. The igneous complex has a diameter of 2 km and was emplaced within granodioritic Pan-African host rocks at the intersection of two faults. It shows distinct concentric compositional zoning with several syenitic outer ring sheets, a mainly trachytic intermediate ring sheet, and a quartz syenite inner ring sheet with a granitic core; relative ages decrease from margin to core. The mineralogical and chemical features are characteristic of within-plate (A-type) magmatic complexes. Major and trace element patterns underline the co-magmatic origin of the suite but indicate three stages of evolution with several pulses of emplacement. A common feature of element distribution patterns is the small systematic change in the early lithologies, but a distinct evolution trend in the late quartz-bearing rocks. We propose that an alkali-basaltic parent magma was emplaced within deep or middle levels of the juvenile Pan-African crust. Differentiation mainly occurred by fractional crystallization of olivine, clinopyroxene, plagioclase, and apatite. During the late stages of evolution, limited assimilation of island-arc magmatic rocks may have occurred. Emplacement took place along ring fractures at a subvolcanic level and was probably related with formation of a caldera during emplacement of the trachytic lithologies. The anorogenic character of the magmatic suite indicates consolidation of the Pan-African crust of NE Africa at the time of emplacement of the alkaline body.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01161963
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  • 6
    Electronic Resource
    Electronic Resource
    On the modelling of abrasive waterjet cutting (1996)
    Springer
    The international journal of advanced manufacturing technology 12 (1996), S. 255-265 
    Details
    ISSN: 1433-3015
    Keywords: Abrasive waterjet technology ; Erosion ; Machining processes ; Material cutting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Abrasive waterjet cutting operates by the impingement of a high-velocity abrasive-laden waterjet against the workpiece. The jet is formed by mixing abrasive particles with high-velocity water in mixing tubes and is forced through a tiny sapphire orifice. The accelerated jet exiting the nozzle travels at more than twice the speed of sound and cuts as it passes through the workpiece. This cutting process is being developed as a net-shape and near-net-shape machining process for cutting many metals and hard-to-machine materials. The narrow kerf produced by the stream results in neither delimitation nor stresses along the cutting path. This new technology offers significant advantages over traditional processes for its ability to cut through most sections of dense or hard materials without the need for secondary machining, to produce contours, and to be integrated into computer-controlled systems. The abrasive waterjet cutting process involves a large number of process and material parameters which are related to the waterjet, the abrasive particles, and workpiece material. Those parameters are expected to effect the material removal rates and the depth of cut. The purpose of the present work is to propose a model which is capable of predicting the maximum depth of cut for different types of materials using different process parameters. A comparison of the results of the proposed model and the models reported in the literature is introduced along with a discussion of the limitations of those models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01239612
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis of 3′-deoxy-3′-fluoro and -3′-amino nucleosides from 2-methylthiopyrimidin-4(1H)-ones (1996)
    Springer
    Monatshefte für Chemie 127 (1996), S. 979-988 
    Details
    ISSN: 1434-4475
    Keywords: Nucleosides, convergent synthesis of ; Nucleosides, 2′,3′-dideoxy-3′-fluoro ; Nucleosides, 2′,3′-dideoxy-3′-amino ; 2-Methylthiopyridin-4(1H)-one nucleosides ; Human immunodeficiency virus ; Herpes simplex virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Methyl-2,3-didesoxy-3-fluoro-5-O-(4-phenylbenzoyl)-β-D-erythro-pentofuranosid (3) und 1,5-di-O-Acetyl-2,3-didesoxy-3-phthalimido-β-D-erythro-pentofuranose (12) wurden in Gegenwart von Trimethylsilyltriflat als Katalysator mit den silylierten 2-Methylthiopyridin-4(1H)-onen2a, b zu den entsprechenden Nucleosiden5–6 und13 kondensiert. Bei diesen Reaktionen tritt als Nebenreaktion eine Öffnung der endocyclischen C-O — Bindung auf, sodaß auch die acyclischen Nucleoside4a, b gebildet werden. Die 3′-Fluoronucleoside wurden mit NH3/MeOH entschützt, die 3′-Phthalimidonucleoside mit Methylamin in Ethanol. Letztere Reaktion resultierte in eine gleichzeitigen Substitution der Pyrimidineinheit unter Austausch der Methylthiogruppe. Das 2-Methylthioanalogon zu 3′-Desoxy-3′-fluorthymidin zeigt mäßige Aktivität gegen HIV-1.
    Notes: Summary Methyl 2,3-dideoxy-3-fluoro-5-O-(4-phenylbenzoyl)-β-D-erythro-pentofuranoside (3) as well as 1,5-di-O-acetyl-2,3-dideoxy-3-phthalimodo-β-D-erythro-pentofuranose (12) were condensed with silylated 2-methylthiopyridin-4(1H)-ones2a, b in the presence of trimethylsilyl triflate as a catalyst to produce the corresponding nucleosides5, 6, 13. In these reactions, an endocyclic cleavage of C-O in3 took place; therefore, acyclic nucleosides4a, b were also formed. All 3′-fluoro nucleosides were deprotected with NH3/MeOH; the 3′-phthalimido nucleosides were deprotected with methylamine in ethanol. The latter method resulted in a concomitant substitution reaction in the pyrimidine moiety with replacement of the methylthio group. The 2-methylthio analogue of 3′-deoxy-3′-fluorothylmidine showed moderate activity against HIV-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807039
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  • 8
    Electronic Resource
    Electronic Resource
    Structural and optical properties of ZnSe x Te1−-x solid solutions in thin-film form (1996)
    Springer
    Applied physics 63 (1996), S. 81-86 
    Details
    ISSN: 1432-0630
    Keywords: 78.20.-e ; 81.15.-z
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Solid solutions of ZnSe x Te1−x (0. 1 ≤x ≤ 1) were synthesized by vacuum fusion of stoichiometric proportions of ZnSe and ZnTe. X-ray diffraction data revealed that they have polycrystalline cubic zinc-blende structure. The calculated unit cell lattice constant (a) for the different compositions in powder form vary linearly, with molecular fractionx following Vegard's law:a(x) = 6.165 – 0.485x. Thin films of ZnSe x Te1−x (0.1 ≤x ≤ 1) solid solutions deposited onto glass or quartz substrates by thermal evaporation in a vacuum of 10−4 Pa were found to be polycrystalline with a preferred (1 1 1) orientation. The obtained data were confirmed by electron diffraction. The optical studies showed that ZnSe x Te1−x polycrystalline films of different compositions have two direct transitions with corresponding energy gapsE g andE g +Δ so The variations in bothE g andE g +Δ so, withx indicate that ZnSe x Te1−x solid solution belongs to an amalgamation-type following quadratic equations with bowing parameters 1.251 and 1.275, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01579749
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  • 9
    Electronic Resource
    Electronic Resource
    Structural and optical properties of ZnSe x Te 1-x solid solutions in thin-film form (1996)
    Springer
    Applied physics 63 (1996), S. 81-86 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 78.20. ; e; 81.15. ; z
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  Solid solutions of ZnSe x Te 1-x (0.1≤x≤1) were synthesized by vacuum fusion of stoichiometric proportions of ZnSe and ZnTe. X-ray diffraction data revealed that they have polycrystalline cubic zinc blende structure. The calculated unit cell lattice constant (a) for the different compositions in powder form vary linearly, with molecular fraction x following Vegard’s law: a(x)=6.165−0.485x. Thin films of ZnSe x Te 1-x (0.1≤x≤1) solid solutions deposited onto glass or quartz substrates by thermal evaporation in a vacuum of 10-4 Pa were found to be polycrystalline with a preferred (1 1 1) orientation. The obtained data were confirmed by electron diffraction. The optical studies showed that ZnSe x Te 1-x polycrystalline films of different compositions have two direct transitions with corresponding energy gaps E g and E g+ΔSO The variations in both E g and E g+ΔSO with x indicate that ZnSe x Te 1-x solid solution belongs to an amalgamation-type following quadratic equations with bowing parameters 1.251 and 1.275, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050355
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  • 10
    Electronic Resource
    Electronic Resource
    Relative stability of f.c.c. and b.c.c. structures for model systems at high temperatures (1984)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 4 (1984), S. 357-381 
    Details
    ISSN: 0392-6737
    Keywords: Phase equilibria, phase transitions, and critical points of specific substances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto La differenza di energia libera, entropia e volume tra strutture cubiche a facce eentrate e a corpo centrato sono valutate, per cristalli modello di gas rari e metalli alcalini, con il metodo delle distribuzioni sovrapposte. Nella regione di validità della meccanica classica si predice la stabilità delle fasi osservate per le sostanze reali anche in accordo con i risultati di precedenti studi di simulazione della nucleazione del cristallo dalla fase liquida e di transformazioni polimorfe. Inoltre si predice in questo modo l'esistenza di una fase stabile di struttura cubica a corpo centrato per i solidi di Lennard-Jones, mentre non ci si aspetta una fase di struttura cubica a facce centrate per i metalli alcalini sotto pressione. Si mostra inoltre la possibilità di effettuare il calcolo della barriera di energia libera che impedisce le trasformazioni cristalline con spostamento lungo una traiettoria prefissata nello spazio delle configurazioni.
    Abstract: Резюоме Оцениваются разлцчия свободных энергий, энтропий и объемов между гранецентрированными иобъемоцентрированными кубическми структурами для модельнын редких газов и щелочно-галоидных криисталлоб используя метод перекрывающихся распределений. Предсказываются устойчивые фазы в соответствии с поведением реальных материалов в областях справедливости классической механики и в сочласии с результатами предыдущих динамических рассмотрений зарождения кристаллов из расплава иполиморфных образований. Предсказывается существование устойчивой ВВС фазы при высоких давлениях и температурах для твердых тел Леннарда-Джонса, тогда как не ожидается устойчивой FCC фазы при высоком давлении для модельных Rb и Cs систем. Мы также показываем возможность проведения вычислений барьеров свободной энергии для кристаллических превраений вдоль предсказанной траектории в конфигурацонном пространстве.
    Notes: Summary Free-energy, entropy and volume differences between face-centered and body-centered cubic structures have been evaluated for model rare gas and alkali metal crystals by using the method of overlapping distributions. Stable phases are predicted in agreement with the behaviour of real materials in the regions of validity of classical mechanics and in agreement with the results of previous dynamical-simulation studies of crystal nucleation from the melt and of polymorphic transformations. The existence of a stable b.c.c. phase at high pressure and temperatures is predicted in this way for Lennard-Jones solids, while no high-pressure f.c.c. phase is expected for model Rb and Cs systems. We also show the possibility of making calculations of free-energy barriers to displacive crystalline transformations along a prescribed trajectory in configuration space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02451294
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