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  • 1
    ISSN: 1572-8900
    Schlagwort(e): Poly(3-hydroxybutyrate) ; ring-opening polymerization ; syndiotactic ; syndioregularity ; crystallization ; thermal properties ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik , Maschinenbau
    Notizen: Abstract Predominantly syndiotactic poly(β-hydroxybutyrate), syn-PHB, of variable syndioregularity (syndyad fractions 0.59, 0.62, 0.64, and 0.71) and molecular weight was prepared by the dibutyltin dimethoxide catalyzed ring opening of racemicβ-butyrolactone (BL). The crystallization behavior of the syn-PHB polymers was investigated by DSC and X-ray diffraction analyses. DSC of films after melting and annealing showed at least one, and often two distinct melting transitions occuring over a broad (often ∼ 40°C) temperature range. These results indicate that syn-PHB chain segments of variable syndioregularity form crystalline regions with very different thermodynamic stabilities. Maximum degrees of crystallinity for melt annealed 0.64- and 0.71-syn-PHB was observed at an annealing temperature (T c ) of 30°C. AtT c values at 45°C and higher, crystallization of relatively lower syndioregular chain segments was apparently excluded to variable degrees dependent onT c and sample syndiotactic dyad content. After crystallization of syn-PHB samples at elevated temperatures, ambient temperature annealing resulted in an observed lower temperature melting transition at ∼ 50°C. This result showed little to no dependence on syn-PHB syndio-regularity andT c . Both solution precipitated 0.62-syn-PHB and 0.71-syn-PHB have WAXS patterns with poorly resolved crystalline reflections superimposed on amorphous haloes indicating low levels of crystallinity (17% and 25%, respectively) and poorly formed crystals. Isothermal crystallization monitored by DSC showed that the syn- and natural origin PHB showed fastest crystallization rates at temperatures between ∼ 50°C and 70°C and 60°C and 90°C, respectively. From the dependence of the higher melting transition onT c it was determined that the equilibrium melting temperatures for 0.62-syn-PHB (M n =83,700 g/mol) and a 0.64-syn-PHB (M n =11,900 g/mol) were ∼ 157 and 154°C, respectively. An Avrami analysis of syn-PHB yielded results similar to that found for natural origin PHB indicating that crystal growth occurs by a two-dimensional mechanism.
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 37 (1996), S. 41-46 
    ISSN: 1572-879X
    Schlagwort(e): fuel cell ; supported electrocatalysts ; X-ray diffraction ; electron microscopy ; alloy structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Carbon supported alloy electrocatalysts based on Pt, Cu and Fe (atomic ratios Pt∶Cu∶Fe=2∶1∶1 and 6∶1∶1) are prepared at various alloying temperatures and are characterized by XRD and TEM techniques. Powder XRD analyses show that Pt6CuFe clusters form a face-centered cubic structure (AuCu3 type), while Pt2CuFe clusters form an ordered alloy with a facecentered tetragonal structure (AuCu type) at higher temperature than 700
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 31 (1995), S. 37-45 
    ISSN: 1572-879X
    Schlagwort(e): Pd/γ-Al2O3 ; neopentane conversion ; X-ray diffraction ; Pd-Al formation ; isomerization selectivity ; effect of residual chlorine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract X-ray diffraction showed that during high temperature reduction at 600°C, chlorine-free Pd/γ-Al2O3 undergoes partial transformation to a Pd-Al alloy, which confirms results of other studies [9]. This evolution appears to have a large effect on the catalytic behaviour in the reaction of neopentane with hydrogen: the selectivity towards isomerization increases from 〈20 up to ∼80%. At the same time, the activation energy drops from ∼ 60 to ∼ 22 kcal/mol. These changes can be reversed by oxidation at 500°C followed by reduction at 300°C. The presence of residual chlorine (ex-PdCl2 precursor) appears to inhibit the Pd induced reduction of Al2O3 leading to Pd-Al alloy formation.
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  • 4
    ISSN: 1572-879X
    Schlagwort(e): methanol oxidation ; conversion to formaldehyde ; silver ; surface oxygen ; STM ; IMR-MS ; adsorption-induced restructuring ; atomic structure ; texture ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Electrolytic silver was investigated as partial oxidation catalyst for the conversion of methanol to formaldehyde. Using the mass spectrometric technique as on-line detector the relation between feed composition and temperature was determined allowing us to conclude that two simultaneous reaction pathways operate under steady state conditions. The microstructure was analysed by XRD and STM. A pronounced restructuring of the surface on the mesoscopic scale was detected. The atomic structure of the γ oxygen phase was determined on the (111) face of facets grown during reaction. The two reaction pathways find their counterparts in two distinctly different surface microstructures providing different geometries for the respective active sites. After prolonged time on stream the high surface mobility of the silver atoms removes all mesoscopic restructuring without changing the conversion characteristics. The observed restructuring is thus considered as a frozen large scale image of the continuously changing surface under reaction conditions.
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  • 5
    ISSN: 1572-8935
    Schlagwort(e): Liquid crystalline ; Side chain ; Copolysiloxane polymers ; Mesomorphic behavior ; Smectic phase ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Abstract The syntheses and characterizations of poly [4-allyloxy-benzoic acid [4′-(2-methoxy) ethoxy] biphenyl]-4-yl ester-co-4-allyloxy-[(4-cyano)-4′-phenyl] carboxyl benzoate ester (poly [(MS3BDBE1)-co-(MCN)]x/y) (where x/y represents the molar ratio of the two structural units on the side chain) were performed in this study. The molar compositions of the structural units on the copolymers side chain were characterized by1H NMR. The transition temperatures, mesophase texture, and layer spacing (dl) of the polysiloxane polymers and copolymers were determined by differential scanning calorimetry (DSC), polarized optical microscopy, and X-ray diffraction patterns. The effects of the molar composition in the copolymers on the mesophase texture, transition temperatures, enthalpy/entropy change of mesophase/isotropic transition, dl of these copolymers were also discussed.
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  • 6
    ISSN: 1572-8927
    Schlagwort(e): Manganese chloride ; cobalt chloride ; nickel chloride ; X-ray diffraction ; saturated solution ; structure of complex ; growth unit
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract As a part of our studies on crystallization processes of electrolytes, the structure of aqueous solutions of MCl2 (M = Mn, Co, Ni) equilibrated with hydrate crystals, MCl2 · mH2O (m = 6, 4, 2), was investigated by means of X-ray diffraction at 25, 40, 55, and 70°C. The complexes formed in MnCl2 solutions, were found to be mixed–ligand chloroaqua octahedral complexes of M2+ ions with the Mn—O and Mn—Cl distances of about 220 and 251 pm, respectively. The average number of Mn—Cl and Mn—O interactions increased from 1.2 to 1.9 and decreased from 4.8 to 4.1, respectively, with changing MnCl2 solutions from Mn25 (MnCl2 solution at 25°C) to Mn70 (MnCl2 solution at 70°C). In the octahedral species of Co2+, the Co—O and Co—Cl distances were found to be about 211 and 240 pm, respectively. With an increase in the saturated concentration by changing temperature from 25 to 70°C, the average coordination number of the Co—Cl contact per Co2+ increased from 0.5 to 1.2, and the average number of Co—O interactions decreased from 5.5 to 4.8. The structural analysis was carried out by taking into consideration the existence of the tetrahedral species in the solutions saturated at 40, 55, and 70°C, on the assumption of the existence of [CoCl4]2−. The Co—Cl distance was found to be 228 pm, while the number of Co—Cl interactions in the [CoCl4] complex was calculated to be 3.7 by the least-squares calculations. The Ni—O and Ni—Cl distances were estimated to be about 206 and 237 pm, respectively. The frequency factor n of the Ni—O and Ni—Cl interactions decreased monotonously from 5.6 to 5.0 and increased from 0.4 to 1.0, respectively, with increasing NiCl2 concentration. The n values of the Co—Cl and Ni—Cl interactions of the octahedral complexes increased sharply with concentration at higher concentrations. Comparing structures of the complexes in the saturated solutions and the hydrate crystals of these metal ions, we discussed a role of the complexing species on crystallization of the hydrates.
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of polymer research 5 (1998), S. 77-84 
    ISSN: 1572-8935
    Schlagwort(e): Block copolyetheresters ; Poly(trimethylene 2,6-naphthalenedicarboxylate) ; Segments ; Thermal transitions ; X-ray diffraction ; Thermal stimulated current
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Abstract Block copolyetheresters with hard segments of poly(trimethylene 2,6-naphthalenedicarboxylate) and soft segments of poly(tetramethylene oxide) were prepared by melt polycondensation of dimethyl 2,6-naphthalenedicarboxylate, 1,3-propanediol and poly(tetramethylene ether)glycol (PTMEG) of molecular weights of 650, 1000 and 2000. The block copolyetheresters were characterized by FTIR, 1H NMR, DSC, X-ray diffraction, TSC (thermal stimulated current), DMA and TGA. It was found that the thermal transitions were dependent on the composition. As the charge molar ratio of PTMEG to dimethyl 2,6-naphthalenedicarboxylate, x, increased, the Tm and ΔHm of the polyester segments decreased, which has been also confirmed by the X-ray diffraction data. The polyether segments of the block copolyetheresters derived from PTMEG2000 could crystallize after cooling, but those of the block copolyetheresters derived from PTMEG1000 and PTMEG650 could not crystallize. The DSC, TSC and DMA results show consistent Tg data of the polyether segments. Based on the shift in Tg of the polyether segments, the amorphous parts of the polyether segments and the amorphous parts of the polyester segments were immiscible for the block copolyetheresters derived from PTMEG2000, but became partially miscible for the block copolyetheresters derived from PTMEG1000 and PTMEG650. The TGA results indicated that composition had little effect on thermal degradation under nitrogen.
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  • 8
    ISSN: 1572-8935
    Schlagwort(e): Liquid crystalline ; Side chain ; Copolysiloxane polymers ; X-ray diffraction ; Differential scanning calorimeter ; Bi-layer structures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Abstract The syntheses and characterizations of copolymers (poly [(MS3BDBE3)-co-(MCN)]x,y) (where x/y represents the molar ratio of the two structural units on the side chain) were accomplished in this study. Differential scanning calorimeter (DSC) was used to determine the transition temperatures, enthalpy changes and entropy changes of the mesophase phase. The layer spacings (d1) in the mesophases of the homo-and co-polysiloxanes were determined by an X-ray diffractometer equipped with a temperature-controlling Pt hot stage. From DSC thermal data and X-ray diffraction analysis, we found both mixed and double bilayer smectic C mesophases at lower MCN concentrations and a mixed and bilayer smectic A mesophases at higher MCN concentrations. The microstructures of the copolymers poly [(MS3BDBE3)-co-(MCN)]x/y are different from those of the copolymers poly [(MS3BDBE1)-co-(MCN)]x,y reported previously. Mesophase and layer spacing of the copolymer are dependent on the MCN concentration in the copolymer. Incorporation of MCN into the copolymer increases the entropy change, which is the result of a loss of positional order contributed by conformational or orientational disorder.
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of polymer research 6 (1999), S. 51-58 
    ISSN: 1572-8935
    Schlagwort(e): Aromatic polyimides ; X-ray diffraction ; Molecular mechanics modeling ; Crystal unit cell ; Correlation length ; Paracrystalline distortion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Abstract X-ray diffraction and molecular mechanics modeling have been used to investigate the structures of aromatic polyimides. The polyimides are synthesized by the reaction of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (PFMB), 3,3′-dimethyl-4,4′-diaminobiphenyl or o-tolidine (OTOL) and 2,2′-dimethyl-4,4′-diaminobiphenyl (DMB). PFMB, OTOL and DMB contain the same biphenyl structure, but the pendent groups are different or are at different positions. In the present paper, we describe the effect of pendent groups on the crystal structure and the drawability for these polymers. The crystal structures are triclinic unit cell with a=17.49 Å, b=19.94 Å, c=20.43 Å, α=40.7°, β=74.5° and γ=79.4° for homopoly(BPDA-OTOL) and triclinic unit cell with a=16.46 Å, b=9.60 Å, c=40.6 Å, α=90°, β=46°, and γ=79.4° for homopoly(BPDA-DMB). The homopoly(BPDA-OTOL) fibers can be drawn into ×2. Higher draw ratio of homopoly(BPDA-OTOL) fibers were not obtained because of thermal degradation. The other two homopolymers can be drawn from ×2 upto ×10. The increasing draw ratios are accompanied with a decrease of paracrystalline distortion and an increase of correlation length as well as degree of orientation. These are probably due to the presence of more flexible polymer chains of homopoly(BPDA-PFMB) and homopoly(BPDA-DMB), which increase the perfection of polymer chain arrangements during drawing.
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  • 10
    ISSN: 1572-8935
    Schlagwort(e): Liquid side chain crystalline copolysiloxane polymers ; Microstructure ; X-ray diffraction ; Differential scanning calorimetry ; Solid state NMR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Abstract This manuscript proposes a packing arrangement model for a co-mesogenic sidechain liquid crystalline copolysiloxane polymer copoly[4-allyloxy-benzoic acid [4′-2-(2-methoxyethoxy) ethoxy] biphenyl]-4-y1 ester-co-4-allyloxy-[(4-cyano)-4′-phenyl] carboxyl benzoate ester (copoly [(MS3BDBE2)-co-(MCN)]x/y depending on the relative molar composition of each mesogen. From the analysis of the thermal data, X-ray diffraction data, and solid state NMR spin-lattice relaxation (T1ρ H) data, we have found two side chain molecules in the mesophase layer coming from the same or a different polymer backbone. They are presumed to be mixed and form a bilayer smectic C mesophase at lower MCN concentrations as well as at higher MCN concentrations.
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  • 11
    ISSN: 1572-9028
    Schlagwort(e): MCM-41 ; mesoporous ; X-ray absorption spectroscopy ; X-ray diffraction ; hetero-element substitution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract MCM-41 type mesoporous silicas have been prepared in which one or more of the following elements are accommodated in framework sites: titanium, iron, chromium, vanadium, manganese, boron and aluminium. XRD and FTIR are used as aids to characterisation, which is achieved chiefly — and to a degree that arrives at valence states, bond lengths and coordination numbers of the metal ion — by X-ray absorption spectroscopy (XAS). Ti-containing MCM-41, as well as the Fe-, V- and Cr-containing variants, yield self-consistent, XAS-based, structural data of the respective metal-ion sites. Some of these (especially those containing Ti) are exceptionally good catalysts for the selective oxidation of large organic molecules such as limonene and norbornene.
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  • 12
    ISSN: 1434-4475
    Schlagwort(e): Hydrogen bonding ; 2-Hydroxy(di(thio))benzoic acid ; IR spectra ; NMR spectra ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Röntgenstrukturdaten von 2-Hydroxythiobenzoesäure (T=200 K;P21/a;a=14.903(5) Å,b=5.203(3) Å,c=9.114(6) Å, β=92.40(4)°;Z=4;R=0.049) und 2-Hydroxydithiobenzoesäure (T=297 K;P21/a;a=14.416(3) Å,b=13.447(3) Å,c=3.947(1) Å, β=90.96(2)°;Z=4;R=0.047) werden berichtet. In 2-Hydroxythiobenzoesäure sind jeweils zwei Moleküle über S-H...O=C Wasserstoffbrückenbindungen zu zyklischen Dimeren verbunden, in Analogie zum Assoziationsmuster von 2-Hydroxybenzoesäure. In 2-Hydroxydithiobenzoesäure sind die Moleküle hingegen über S-H...O(H)-C Wasserstoffbrückenbindungen zu Ketten verknüpft. Festkörper-IR-, und Lösungs-IR-und NMR-spektroskopische Daten von 2-Hydroxybenzoesäure, 2-Hydroxythiobenzoesäure und 2-Hydroxydithiobenzoesäure werden gegenübergestellt. Die wesentlichen Charakteristika der intramolekular assoziierten phenolischen O-H Gruppen der drei Titelverbindungen sind $$\bar v_{OH} = 3230, 3120, 2750 cm^{--1} $$ für die Festkörper sowie $$\bar v_{OH} = 3210, 3185, 2945 cm^{--1} $$ und δOH=10.21, 10.53, 12.20 ppm für Lösungen (CCl4 bzw. CCl4:CDCl3=5:1).
    Notizen: Summary X-ray structural data are reported for 2-hydroxythiobenzoic acid (T=200 K;P21/a;a=14.903(5) Å,b=5.203(3) Å,c=9.114(6) Å, β=92.40(4)°;Z=4;R=0.049) and 2-hydroxydithiobenzoic acid (T=297 K;P21/a;a=14.416(3) Å,b=13.447(3) Å,c=3.947(1) Å, β=90.96(2)°;Z=4;R=0.047). In 2-hydroxythiobenzoic acid, each two molecules form cyclic dimersvia S-H...O=C hydrogen bonds, analogous to the association pattern of 2-hydroxybenzoic acid. In 2-hydroxydithiobenzoic acid, the molecules are linked to chains by S-H...O(H)-C hydrogen bonds. Solid state IR, and solution IR and NMR spectroscopic data of 2-hydroxybenzoic acid, 2-hydroxythiobenzoic acid, and 2-hydroxydithiobenzoic acid are summarized. The main characteristics of the intramolecularly associated phenolic O-H groups of the three title compounds are $$\bar v_{OH} = 3230, 3120, 2750 cm^{--1} $$ for the solids, $$\bar v_{OH} = 3210, 3185, 2945 cm^{--1} $$ for solutions (CCl4), and δOH=10.21, 10.53, 12.20 ppm for solutions (CCl4:CDCl3=5:1).
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 40 (1996), S. 167-173 
    ISSN: 1572-879X
    Schlagwort(e): sulfated zirconia ; platinum ; X-ray diffraction ; Pt-Zr alloy ; zirconia alloy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Platinum is present in a metallic state following activation in air at 725
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solid state electrochemistry 3 (1999), S. 97-103 
    ISSN: 1433-0768
    Schlagwort(e): Key words Lithium battery ; Anode ; Amorphous tin composite oxides ; X-ray diffraction ; Infrared spectroscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Tin-based composite oxide materials have received considerable attention as potential anode materials for rechargeable lithium batteries. In this contribution we present the results of our investigations of the SnOB2O3P2O5 system. We have investigated its electrochemical properties and especially its cycling performance. A focus of our interest was to explain the structural changes which occur during lithium cycling and their strong dependence on the preparation method. A part of the SnO component was converted into a very stable metallic phase. In addition, a decrease was observed in capacity owing to the formation of isolated and inactive tin grains. We also report on structural changes in the B2O3P2O5 matrix.
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Microchimica acta 125 (1997), S. 25-31 
    ISSN: 1436-5073
    Schlagwort(e): AlGeSi-alloys ; X-ray diffraction ; analytical transmission electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract AlGeSi-alloys of different composition were cast by a melt spin device to ribbons of 40 μm thickness. The ribbons melt near 500 °C and should be well suited for brazing of high strength Al-alloys. Because of the existence of metastable phases, these ribbons are brittle in the rapidly solidified state, but increasingly ductile and cuttable after an appropriate annealing between 200 and 400 °C. The thermally induced phase transformations are revealed by the hightemperature X-ray diffractograph as well as, with help of a heating sample holder, by the analytical transmission electron microscope (TEM). The identification of elements and phases is performed by X-ray Bragg reflexes and of electron diffraction (ED) patterns, whereby the latter can be associated to single microstructure details in the sub-μm range. Moreover, the distribution of the elements can be seen on distribution maps “din the light” of characteristic X-ray spectral lines. The observed microstructure of as-quenched AlGe45 with 2 or 4 mass-% Si was of similar appearence but more refined as in the AlGe45 alloy. It consists of α-Al primary crystals surrounded by an eutectic mixture of α-Al and two metastable intermetallic AlGe(Si) phases. Si was observed exclusively within these metastable phases. During an appropriate tempering the metastable phases transform into the equilibrium phases α-Al and β-Ge(Si). For this decomposition the temperature is decreased by alloying with Si.
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  • 16
    ISSN: 1436-5073
    Schlagwort(e): alumina scales ; spallation ; stress measurement ; X-ray diffraction ; Raman spectroscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The effect of silicon and titanium on the spallation resistance of alumina scales grown on NiCrAlY-type alloys has been investigated. For this purpose cyclic oxidation experiments on model alloys with different additions of silicon or titanium were carried out at temperatures between 950 and 1100 °C. Selected samples were analysed by X-ray stress evaluation (XSE) after various times of oxidation. It was found that the compressive stresses measured at ambient temperature increase with increasing time and are affected by the presence of silicon. The XSE results were used to calibrate laser Raman spectroscopy (LRS) for strain measurement. Then, the suitability of Raman spectroscopy for stress measurement at higher temperatures was evaluated.
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Microchimica acta 125 (1997), S. 349-353 
    ISSN: 1436-5073
    Schlagwort(e): microstructure ; MoSx films ; X-ray diffraction ; TEM
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The influence of process parameters on the formation of microstructure of magnetron-sputtered MoSx-films on silicon wafers was investigated. The MoSx-films were analyzed by means of X-ray diffraction and TEM. The prepared MoSx-films show a microstructure in dimension of some nm without any prefered orientation or texture. The X-ray diffraction measurements indicate clearly differences in the structure for various preparation conditions. Simulations provided a first structural model for the description of the MoSx-films. The MoSx-films consist of two-dimensional nanocrystals and noncrystallographic randomly packed (001) planes. Transitions between these structural states and intermediate states determine the microstructure depending on the preparation conditions.
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Monatshefte für Chemie 126 (1995), S. 61-66 
    ISSN: 1434-4475
    Schlagwort(e): Crystal structure ; Hexafluorostannate hexahydrate ; Hydrogen bonding ; IR spectra ; Raman spectra ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Kristallstrukturen von CoSnF6·6H2O (rhomboedrisch; R{ie61-3}-C 3i 2 ;a=9.735(7) Å,c=10.095(7) Å, γ=120°;Z=3;R=0.047) und von NiSnF6·6H2O (rhomboedrisch; R{ie61-4}-C 3i 2 ;a=9.697(1)Å,c=10.021(1)Å, γ=120°;Z=3;R=0.038) wurden mittels Röntgen-Einkristalldaten (beiT=300 K) bestimmt. Die beiden Verbindungen sind isostrukturell zu FeSnF6·6H2O. IR- und Raman-Spektren vonMSnF6·6H2O (M=Fe, Co, Ni) wurden von Proben mit unterschiedlichem Deuterierungsgrad gemessen (beiT=300 und 75 K). Bei allen drei Verbindungen findet man für isotopenverdünnte HDO Moleküle zwei nur geringfügig unterschiedliche $$\bar v$$ (OD)-Valenzfrequenzen und eine $$\bar v$$ (HDO)-Deformationsfrequenz, was mit der Existenz von nur einer Art von Wassermolekülen mit zwei verschiedenen, aber doch sehr ähnlichen O ... F Wasserstoffbrückenbindungen übereinstimmt.
    Notizen: Summary Single crystal X-ray structural data (atT=300 K) are reported for CoSnF6·6H2O (rhombohedral; R{ie61-1}-C 3i 2 ;a=9.735(7) Å,c=10.095(7) Å, γ=120°;Z=3;R=0.047) and for NiSnF6· 6H2O (rhombohedral; R{ie61-2}-C 3i 2 ;a=9.697(1)Å,c=10.021(1)Å, γ=120°;Z=3;R=0.038). The two compounds are isostructural to FeSnF6·6H2O. IR and Raman spectroscopic data (atT=300 and 75 K) are reported for hydrated and for partially deuterated samples ofMSnF6·6H2O (M=Fe, Co, Ni). Two rather similar $$\bar v$$ (OD) stretching frequencies and one $$\bar v$$ (HDO) bending frequency of isotopically dilute HDO molecules are observed for either of the three compounds, which is consistent with one crystallographically distinct water molecule forming two different, but rather similar O ... F hydrogen bonds.
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Physics and chemistry of minerals 26 (1999), S. 206-211 
    ISSN: 1432-2021
    Schlagwort(e): Key words Iron ; Fe ; Si alloy ; X-ray diffraction ; Equation of state ; Thermoelasticity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: Abstract  We have carried out an in situ synchrotron X-ray diffraction study on iron and an iron-silicon alloy Fe0.91Si0.09 at simultaneously high pressure and temperature. Unit-cell volumes, measured up to 8.9 GPa and 773 K on the bcc phases of iron and Fe0.91Si0.09, are analyzed using the Birch-Murnaghan equation of state and thermal pressure approach of Anderson. Equation of state parameters on iron are found to be in agreement with results of previous studies. For both iron and Fe0.91Si0.09, thermal pressures show strong dependence on volume; the (∂KT/∂T)V values are considerably larger than those previously reported for other solids. The present results, in combination with our previous results on ɛ-FeSi, suggest a small dependency of the room-temperature bulk modulus upon the silicon content, less than 0.3 GPa for 1 wt.% silicon. We also find that substitution of silicon in iron would not appreciably change the thermoelastic properties of iron-rich Fe−Si alloys. If this behavior persists over large pressure and temperature ranges, the relative density contrast between iron and iron-rich Fe−Si alloys at conditions of the outer core of the Earth could be close to that measured at ambient conditions, i.e., 0.6% for 1 wt.% Si.
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Physics and chemistry of minerals 26 (1999), S. 644-648 
    ISSN: 1432-2021
    Schlagwort(e): Key words MnO ; CdO ; rock-salt monoxides ; X-ray diffraction ; equation of state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: Abstract Room-temperature volume measurements up to 8.1 GPa reveal that rock-salt structured MnO and CdO have identical compressibility in the pressure range studied. In the plot of bulk modulus vs unit-cell volume, CdO plots well above the trend of the 3d transition metal monoxides, a behavior that deviates from empirical predictions of constant K 0 V 0. The present observations are in favor of our earlier suggestion that, for isostructural solids, the empirically predicted bulk modulus-volume relationship may be limited to their subsets that share the same valence electron character (i.e., s vs 3d vs 4d). For cations forming transition metal monoxides, variations of Pauling electronegativity with ionic radius show differences that are qualitatively similar to the observed trends of bulk modulus, suggesting that bond covalency differences may contribute to the different behaviors between the 3d and 4d transition metal monoxides.
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1545-1565 
    ISSN: 1572-8943
    Schlagwort(e): cocoa butter ; fat crystallization ; DSC ; fat polymorphism ; fat structure ; fats ; lard ; milk fat ; triacylglycerols ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal behavior of three ural fats (displaying very different composition), cocoa butter (CB)2, lard, and a stearin obtained from anhydrous milk-fat (AMF) fractionation, were studied by both DSC and X-ray diffraction as a function of temperature (XRDT). To perform temperature explorations between −30
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 53 (1998), S. 467-475 
    ISSN: 1572-8943
    Schlagwort(e): cesium acetate ; intercalation ; kaolinite ; mass spectrometry ; potassium acetate ; Raman microscopy ; thermal analysis ; urea ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal behaviour of ordered kaolinites from Hungary and Australia intercalated with potassium acetate, cesium acetate and urea has been investigated by simultaneous TG-DTG-DTA, TG-MS, Raman microscopy and XRD. Remarkable changes in the thermal decomposition pattern of the intercalates were obtained as a function of the nature of the intercalating re-agents. Replacing the potassium cation to cesium leads to a change in the OH environments resulting in a more complicated dehydroxylation pattern. The urea intercalates can be decomposed completely without dehydroxylating the mineral, although further treatments are necessary to restore the original d-spacing.
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 57 (1999), S. 559-567 
    ISSN: 1572-8943
    Schlagwort(e): calciumsulphate hemihydrate ; differential thermal analysis ; hydrothermal treatment ; infrared analysis ; selenite ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Selenite was boiled in KCl solutions of different concentrations at the respective boiling temperatures and atmospheric pressure. The products were subjected to X-ray diffraction analysis, qualitative infrared analysis, differential thermal analysis and microscopic examination. The product obtained in 1.0 M KCl solution was the β-form of calcium sulphate hemihydrate (α-CaSO4·0.5H2O). In more concentrated KCl solution (1.5, 2.0, 2.5, 3.0, 3.5 or 4.0 M), the α-form of calcium sulphate hemihydrate (α-CaSO4·0.5H2O) was formed, and a reaction took place between KCl and CaSO4, which gave a double salt: potassium pentacalcium sulphate monohydrate (K2SO4·5CaSO4·H2O).
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 57 (1999), S. 631-642 
    ISSN: 1572-8943
    Schlagwort(e): DSC ; fluorocarbon chain ; polymerizability ; polymorphic behaviors ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The molecular aggregation of acrylic and methacrylic acid esters containing long-fluorocarbon chains: 2-(perfluoroalkyl)ethyl acrylate (FFnEA) and 2-(perfluoroalkyl)ethyl methacrylate (FFnEMA) (F(CF2)nCH2CH2OCOC(X)=CH2, where X=H, CH3 and n=6, 8, 10) was investigated by differential scanning calorimetry (DSC) and temperature controlled X-ray powder diffraction measurement. These compounds exhibited some characteristic polymorphic behaviors depending on the length of fluorocarbon chain and the α-position methyl group. The solid-state polymerization by γ-ray irradiation was studied for these compounds in the various crystal forms. In the solid-state polymerization, highest polymerizability was observed in the crystal form that exists in the highest temperature region for each compound.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 363-368 
    ISSN: 1572-8943
    Schlagwort(e): DSC ; lipid ; phase behaviour ; synchrotron radiation ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The phase behaviour and phase stability of lipids are of importance in an understanding of the biological functions of cell membranes. Among a variety of physical techniques employed to study the phase behaviour and structural properties of polar lipids, differential scanning calorimetry and X-ray diffraction have proved to be successful and are the most frequently used methods. Applications involving a combination of the two techniques, particularly when synchrotron radiation is used as the light source of X-ray diffraction, are reviewed in this article.
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  • 26
    ISSN: 1572-9001
    Schlagwort(e): Phosphaalkanes ; molecular structure ; electronic structure ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Peculiarities of the molecular and electronic structure of P- and C-halogen-substituted phosphaalkenes have been considered on the basis of results of X-ray diffraction studies and quantumchemical calculations. Introduction of an electronegative halogen atom is shown to have an insignificant effect on the intramolecular bond angle distribution, whereas the influence on the P=C bond length is noticeable. Thus, in P-substituted phosphaalkenes it substantially increases the polarization of the P=C bond (which causes its noticeable shortening). In C-substituted phosphaalkenes the effect of halogen atoms is less pronounced: decreasing the P=C bond polarization leads only to its slight elongation. In addition, a considerable elongation of the phosphorus-halogen bond in comparison with three-coordination phosphorus compounds is a peculiarity of the molecular structure of P-halogen-substituted phosphaalkenes.
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 429-435 
    ISSN: 1572-8943
    Schlagwort(e): DSC ; nickel sulphide ; TG ; toughened glass ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Nickel sulphide (NiS) was characterised using X-ray diffraction, thermal gravimetric analysis (TG) and differential scanning calorimetry (DSC). The 'as received' Millerite, stoichiometric NiS, observed to be slightly nickel deficient, was found to readily decompose in a nitrogen atmosphere at elevated temperatures (450°C max.) to the sulphur deficient Godlevskite, Ni7S6. DSC and X-ray measurements demonstrated that the high temperature form of the Godlevskite was readily stabilised at room temperature. The kinetics of the α-β re-transformation in Godlevskite were then investigated using DSC and were observed to be first order.
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 27-37 
    ISSN: 1572-8943
    Schlagwort(e): antimony oxides ; antimony(III) oxide hydroxide nitrate ; thermal decomposition ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal decomposition of the only known antimony nitrate antimony(III) oxide hydroxide nitrate Sb4O4(OH)2(NO3)2, whose synthesis routes were reviewed and optimized was followed by TG-DTA under an argon flow, from room temperature up to 750°C. Chemical analysis (for hydrogen and nitrogen) performed on samples treated at different temperatures showed that an amorphous oxide hydroxide nitrate appeared first at 175°C, and decomposed into an amorphous oxide nitrate above 500°C. Above 700°C, Sb6O13 and traces of α-Sb2O4 crystallized.
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 151-162 
    ISSN: 1572-8943
    Schlagwort(e): equilibrium of solubility ; phosphogypsum ; thermal analysis ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The aim of the study was to investigate the solubility properties of the phosphogypsum a sideproduct of phosphor industry. Phase diagrams of potassium, calcium, hydrogen phosphates, sulphates and water are presented in order to determine equilibrium of solubility. Solid phases were investigated by X-ray diffraction, IR spectrometry and thermal analysis (DTG-DTA).
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 503-514 
    ISSN: 1572-8943
    Schlagwort(e): cyclodextrins ; IR spectroscopy ; thermal analysis ; Tolperisone-HCl ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Solid inclusion complexes of TolperisoneHCl with five various cyclodextrins were prepared by kneading and spray drying. The complex formation between the drug and the cyclodextrins were proven using thermoanalytical methods, X-ray diffraction, IR spectroscopy. The results of the solid state investigations were supported by the liquid phase investigations, such solubility and parition constant measurements and stability constant determination. Among all cyclodextrins used the β- and γ-CD-s were found to be the best complexing agents.
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 115-121 
    ISSN: 1572-8943
    Schlagwort(e): comb-like polymer ; DSC ; fluorocarbon chain ; side-chain crystallization ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thermal properties of acrylate and methacrylate monomers containing long-fluorocarbon chains (H(CF2)nCH2OCOCH=CH2, (FnA) and H(CF2)nCH2OCOC(CH3)=CH2, (FnMA), wheren=6, 8, 10) and their comb-like polymers have been investigated by differential scanning calorimeter (DSC) and X-ray diffraction. The comb-like polymers (PF10A and PF10MA) with sufficiently long-fluorocarbon chains showed a simple melting and crystallizing behavior. For the fusion of PF10A in 1st heating, enthalpy change δH f was 18 kJ mol−1 and entropy change δS f was 45 J K−1 mol−1, while for PF10MA the values δH f and δSf were 5.3 kJ mol−1 and 14 J K−1 mol−1, respectively. Melted PF8A crystallized slowly, whereas PF8MA with same fluorocarbon chain and also both of PF6A and PF6MA with shorter fluorocarbon chains can hardly crystallize by the aggregation of side-chains. Effects of the length of side-chain and the flexibility of main chain on the side-chain crystallization of comb-like polymers are clear. Crystallization process of the methacrylate monomers was sensitively affected by the scanning rate of DSC measurement and the length of fluorocarbon chains.
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1113-1132 
    ISSN: 1572-8943
    Schlagwort(e): chiral molecule ; conformational disorder and motion ; crystal ; DSC ; heat capacity ; γ-gauche effect ; glass ; glass transition ; melting transition ; molecular mechanics computations ; tetra[methyleneoxycarbonyl (2,4,4-trimethyl) pentyl] methane ; solid state13C NMR ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The symmetric neopolyol ester tetra[methyleneoxycarbonyl(2,4,4-trirnethyl)pentyl]methane (MOCPM) has been studied by variable-temperature solid-state13C NMR and X-ray powder diffraction and compared to molecular mechanics calculations of the molecular structure. Between melting and glass transition temperatures the material is semicrystalline, consisting of two conformationally and motionally distinguishable phases. The more mobile phase is liquid-like and is, thus attributed to an amorphous phase (≈16%). The branches of the molecules in the crystal exhibit two conformationally distinguishable behaviors. In one, the branches are well ordered (≈56%), in the other, the branches are conformationally disordered (≈28%). Different branches of the same molecule may show different conformational order. This unique character of the rigid phase is the reason for the deficit of the entropy of fusion observed earlier by DSC. In the melt, solid state NMR can identify two bonds that are rotationally immobile, even though the molecules as a whole have liquid-like mobility. This partial rigidity of the branches accounts quantitatively for the observed increase in heat capacity at the glass transition. The reason for this unique behavior of MOCPM, a small molecule, is the existence of one chiral centers in each of the four arms of the molecule. A statistical model assuming that at least two of the chiral centers must fit into the order of the crystal can explain the crystallization behavior and would require 12.5% amorphous phase, 28.1% conformational disorder, and 59.4% crystallinity, close to the observed maximum perfection.
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1421-1435 
    ISSN: 1572-8943
    Schlagwort(e): bentonitic clay ; IR spectroscopy ; thermal analyses ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Egyptian bentonitic clays from Qasr El-Sagha, Wadi El-Rayan, Kom Oshim and the Cairo — Alexandria desert road were studied thermally (TG, DTG and DTA) and structurally (XRD and IR). The clay fraction consisted mainly of montmorillonite, kaolinite and some illite. Gypsum, quartz and calcite were also identified. It was found that the Na-to Ca-montmorillonite ratio increases in the following sequence: Qasr El-Sagha〈Wadi El-Rayan〈Kom Oshim〈Cairo-Alexandria desert road. There is a marked concentration of gypsum, the highest amount occurring in the bentonite from Qasr El-Sagha, and the least in that from the Cairo — Alexandria desert road. Calcite was mainly found in Kom Oshim, with a very small amount from the Cairo — Alexandria desert road. Magnesium is more abundant than iron in the octahedral layer and increases in the following sequence: Cairo — Alexandria desert road〈Kom Oshim〈Wadi El-Rayan〈Qasr El-Sagha.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1025-1037 
    ISSN: 1572-8943
    Schlagwort(e): crystallographic evaluation ; evaluation with difference procedure ; kinetics ; Rietveld refinement ; X-ray diffraction ; temperature resolved
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Time and temperature resolved X-ray diffraction was used for thermal analysis. Series of diffraction patterns were measured, while the samples are heated/cooled stepwise or isothermally with freely selectable temperature programs. The method was applied for the investigation of the phase transitions of ammonium nitrate and HMX (1,3,5,7-tetranitro-1,3,5,7-tetraaza-cyclooctane), when the identification of phases was required. Its capability in the field of kinetics is demonstrated with the isothermal investigation of the solid state reaction of ammonium nitrate with copper oxide and the non-isothermal investigation of the high temperature corrosion of nickel, which was performed by means of a difference procedure. For obtaining structural details peak fitting and Rietveld refinement were applied for the investigation of ammonium nitrate and HMX.
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1197-1205 
    ISSN: 1572-8943
    Schlagwort(e): Bi2O3-PbO system ; DTA-TG ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The scientific interest for the Bi2O3-PbO system has increased due to the importance of the PbO in the high-T c superconducting phase formation in the Bi2O3-SrO-CaO-CuO system. Also Bi2O3-PbO system contains compounds with some specific semiconductor and dielectric properties and Bi2O3-based solid solutions are well known as high oxygen ion conductors. Previously, several low melting defined compounds have been identified in the system: 6Bi2O3·PbO; 3Bi2O3·2PbO; 4Bi2O3·5PbO; 4Bi2O3·6PbO and Bi2O3·3PbO. This work deals with the phase formation and thermal stability of these compounds. Under non-isothermal conditions, in all mixtures regardless of the Bi2O3/PbO ratio, the compound 6Bi2O3·PbO is preferentially formed, followed by the compound 4Bi2O3·5PbO. The formation of the compound 4Bi2O3·6PbO was not confirmed while the formation of the compound Bi2O3 3PbO occurs through a complex mechanism which includes an intermediate step in which a solid solution with the litharge structure was identified. Under isothermal conditions in the same temperature range the tendency to form the stoichiometric compounds increases. All compounds form, decompose and melt at temperatures between 530–780°C.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 50 (1997), S. 401-407 
    ISSN: 1572-8943
    Schlagwort(e): bismuth cuprates ; DTA-DTG ; oxygen partial pressure ; X-ray diffraction ; zirconia sensor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The oxygen exchange between the condensed phase(s) and the gas phase was studied as a function of temperature for superconducting phases of the system (Bi,Pb)-Sr-Ca-Cu-O. An oxygen probe apparatus allowed confirmation that the variation in oxygen composition in the Pb2212 and Pb2223 superconducting phases is a reversible phenomenon on heating and cooling. It was demonstrated that the mass loss of both phases, for the 905 and 980°C isotherms, was due to the oxygen composition variation and to PbO loss (this latter phenomenon begin irreversible).
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 52 (1998), S. 903-914 
    ISSN: 1572-8943
    Schlagwort(e): Bi2Sr2CaCu2Oy〉 ; DSC ; electrophoretically deposited superconducting coatings ; high-temperature superconductors ; magnetic measurements ; Raman spectroscopy ; X-ray diffraction ; YBa2Cu3O7-x
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The optimum calcination and sintering conditions for the preparation of the desired phases with the proper stoichiometry of the bulk high-temperature superconductors YBa2Cu3O7-x (YBCO) and Bi2Sr2CaCu2Oy〉 (BSCCO) were investigated by differential scanning calorimetry. DSC analysis on the corresponding superconducting coatings, electrophoretically deposited, indicated that the sintering and annealing procedure was suitable for the production of stable, strong and adherent coatings. X-ray diffraction analysis, Raman spectroscopy and magnetic measurements confirmed the improved properties of the superconducting powders and coatings obtained.
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 53 (1998), S. 547-558 
    ISSN: 1572-8943
    Schlagwort(e): cation exchange ; montmorillonite ; thermogravimetry ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Various cation-exchanged montmorillonites (Li+, Na+, Ba2+, Mg2+, Ca2+, Mn2+, Co2+, Cu2+, Ag+, Cd2+, Hg2+, Al3+, Pb2+ and NH4+) were prepared from calcium montmorillonite and their properties were studied by means of X-ray diffraction and thermal analysis. The two methods give information on the cation exchange in the interlayer space only. X-ray diffraction studies at room temperature are mainly suitable for estimation of the exchange of cations of different valencies. At 500°C, when the structure is completely collapsed, the d value of montmorillonite depends on the non-hydrated ionic radius of the interlayer cation, but the measurement interval is limited for fine interpretation. The thermoanalytical method is suitable for a better distinction of different exchangeable cations of higher hydration energy on the basis of the DTG or DDTG curve.
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Plasma chemistry and plasma processing 16 (1996), S. 209-225 
    ISSN: 1572-8986
    Schlagwort(e): Atomic oxygen ; erosion ; plasma ; atomic beam facility ; zirconium complex ; weight loss ; optical photography ; profilometry ; diffuse reflectance spectroscopy ; total transmittance spectroscopy ; scanning electron microscopy ; wavelength dispersive X-ray spectroscopy ; X-ray diffraction ; X-ray photoelectron spectroscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Glassy residues of the complex bis(N,N′-disalicylidene-1,2-phenylenediamino)zirconium(IV), Zr(dsp)2, on glass slides were exposed to atomic oxygen in a plasma asher or an atomic beam facility for various amounts of lime in order to study the erosion process, determine the rate of erosion, and learn the chemical identity of the residue. The exposed films were characterized by weight loss, optical photography, profilometry, diffuse reflectance and total transmittance spectroscopy, scanning electron microscopy (SEM) with wavelength dispersive X-ray spectrometry (WDS), X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). Results indicate that these films erode much more slowly polyimide (Kapton™) film under identical conditions, that the erosion is very nonuniform, and that zirconium dioxide is the predominant product after extended exposure. This complex is currently being evaluated as a polymer additive.
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Journal of sol gel science and technology 11 (1998), S. 289-298 
    ISSN: 1573-4846
    Schlagwort(e): Ag/SiO2 ; Cu/SiO2 and Ag-Cu/SiO2 nanocomposite films ; sol-gel ; annealing atmospheres ; clusters growth by thermal annealing ; optical absorption ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In a program on the development of metal nanoclusters in sol-gel derived thin films, attempts were made to synthesize pure and mixed metal clusters, control the cluster size and increase the volume fract f the clusters. Thus, Ag, Cu and Ag-Cu nanoclusters were prepared in silica films using dip- and spin-coating techniques. The annealing of Ag/SiO2 films in different atmospheres (air, argon and 5% H2-95% N2 gas) caused modifications of Ag nanoclusters resulting in changes in their surface plasmon resonance (SPR) peak positions. The Cu and Ag-Cu codoped films were annealed in reducing atmosphere (5% H2-95% N2 gas). In order to prepare Cu nanoclusters of different sizes, the concentrations of Cu in Cu/SiO2 composite films were varied from 8 to 30 mol% and annealed at 800°C for different times for growth. The size of the Cu nanoclusters was measured from the half band width of Cu SPR peak (appearing within 570–557 nm range) and X-ray diffraction. In this way Cu-nanoclusters of size ranges from about 3.5 to 10 nm (average diameters) were prepared . The Ag-Cu nanocluster-containing silica films show the existence of both Ag and Cu SPR peaks with some blue shifting in comparison with to their pure analogues depending on the Ag:Cu ratio.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Journal of sol gel science and technology 8 (1997), S. 437-442 
    ISSN: 1573-4846
    Schlagwort(e): sol-gel hydrotalcites ; X-ray diffraction ; aluminum precursors ; hydrotalcites Mg/Al ratio ; mixed metal hydroxides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Sol-Gel Hydrotalcites were synthesized using magnesium ethoxide and variable aluminum sources: aluminum acetilacetonate, aluminum chloride, aluminum nitrate and aluminum sulfate; in all cases, the gelation was done at pH 10. X-ray diffraction studies show that the crystallinity depends on the aluminum precursor used. The crystallinity was found in the order aluminum acetylcetonate 〉 aluminum chloride 〉 aluminum nitrate 〉 aluminum sulfate. The precursor determines the sintering behavior as well.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Journal of sol gel science and technology 8 (1997), S. 437-442 
    ISSN: 1573-4846
    Schlagwort(e): sol-gel hydrotalcites ; X-ray diffraction ; aluminum precursors ; hydrotalcites Mg/Al ratio ; mixed metal hydroxides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Sol-Gel Hydrotalcites were synthesized using magnesium ethoxide and variable aluminum sources: aluminum acetilacetonate, aluminum chloride, aluminum nitrate and aluminum sulfate; in all cases, the gelation was done at pH 10. X-ray diffraction studies show that the crystallinity depends on the aluminum precursor used. The crystallinity was found in the order aluminum acetylcetonate〉aluminum chloride〉aluminum nitrate〉aluminum sulfate. The precursor determines the sintering behavior as well.
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Journal of sol gel science and technology 6 (1996), S. 257-262 
    ISSN: 1573-4846
    Schlagwort(e): FTIR spectroscopy ; X-ray diffraction ; bond length ; hydrolysis ; doping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Nb doped silica was prepared by the sol-gel method. The experimental variables were the pH (acidic and basic) and the Nb concentration (1.0–10.0 wt.%). The samples were calcined at 300°C and 600°C and analyzed by XRD, and FTIR. The TGA and DTA of the gels were also performed. From the XRD results the radial distribution function allowed us to establish the existence of the Si−O−Nb bond in the powders.
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Physics and chemistry of minerals 26 (1999), S. 257-263 
    ISSN: 1432-2021
    Schlagwort(e): Key words Acetamide ; DRIFT spectroscopy ; Intercalation ; Hydrogen bonding ; Kaolinite ; Raman spectroscopy ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: Abstract  Upon intercalation of both ordered (low defect) and disordered (high defect) kaolinites with acetamide, two types of interaction are observed. Firstly, hydrogen bonding between the NH2 groups of the acetamide with the siloxane oxygens is formed, as evidenced by the formation of two new bands at 3400 and 3509 cm–1. Secondly, the appearance of additional bands at ∼3600 cm–1 in both the infrared and Raman spectra of the acetamide intercalates is attributed to a second type of hydrogen bonding by the interaction of the C=O group and the inner surface hydroxyls. Changes in the intensity of the hydroxyl deformation modes in the 895 to 940 cm–1 region are attributed to the changes in the hydrogen bonding of the kaolinite surfaces. It is proposed that the hydrogen bonding between the adjacent kaolinite layers is replaced with hydrogen bonding between both kaolinite surfaces and the acetamide molecule. Changes in the molecular structure of acetamide are observed upon intercalation. The amide 1 band is lost and replaced with a well-defined NH2 deformation vibration. The loss of the amide 1 band is attributed the hydrogen bond formation between the amide hydrogens and the siloxane surface. The bands of the C=O group at 1680 and 1740 cm–1 become a single band at 1680 cm–1. The amide 2 band remains unchanged. The lack of intensity of the 1740 cm–1 band is attributed to the formation of hydrogen bonding between the inner surface hydroxyl groups and the carbonyl group.
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Physics and chemistry of minerals 26 (1999), S. 406-414 
    ISSN: 1432-2021
    Schlagwort(e): Key words Lawsonite ; Equation of state ; X-ray diffraction ; High-pressure ; High-temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: Abstract  A pressure-volume-temperature data set has been obtained for lawsonite [CaAl2Si2O7(OH)2.H2O], using synchrotron X-ray diffraction and an externally heated diamond anvil cell. Unit-cell volumes were measured to 9.4 GPa and 767 K by angle dispersive X-ray diffraction using imaging plates. Phase changes were not observed within this pressure-temperature range, and lawsonite compressed almost isotropically at constant temperature. The P-V-T data have been analyzed using a Birch- Murnaghan equation of state and a linear equation of state expressed as β=–1/V0 (∂V/∂P) T . At room temperature, the derived equation of state parameters are: K 0=124.1 (18) GPa K'0 set to 4) and β–1=142.0(24) GPa, respectively. Our results are intermediate between previously reported measurements. The high-temperature data show that the incompressibility of lawsonite decreases with increasing temperature to ∼500 K and then increases above. Hence, the second order temperature derivative of the bulk modulus is taken into account in the equation of state; a fit of the volume data yields K 0=123.9(18) GPa, (∂K/∂T)P=–0.111(3) GPa K–1, (∂2 K/∂T 2)P=0.28(6) 10–3 GPa K–2, α0=3.1(2) 10–5 K–1, assuming K'0=4.
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Physics and chemistry of minerals 26 (1999), S. 419-424 
    ISSN: 1432-2021
    Schlagwort(e): Key words Iron ; Fe-Si alloys ; X-ray diffraction ; Phase transformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: Abstract In situ X-ray diffraction experiments at high pressure were carried out up to 8.9 GPa and 1100 °C to study phase transformations of iron and two iron-silicon alloys Fe0.91Si0.09 and Fe0.83Si0.17. For iron, the transformation from the bcc phase to the fcc phase was observed at pressures 3.8–8.2 GPa and temperatures that are consistent with previous in situ X-ray diffraction studies. Reversal of the transformation of iron was found to be sensitive to temperature; hysteresis of the transformation increased from 25 °C at 3.8 GPa to 100 °C at 7.0 GPa, primarily because the bcc-fcc phase boundary has a negative Clayperon slope. In the binary system Fe-Si, the observations of the present study indicate that the ferrite (bcc phase)-stabilizing behavior of silicon persists at high pressures and that the maximum solubility of silicon in the fcc phase increases with increasing pressure: (1) the transformation from the bcc phase to the fcc phase was observed in Fe0.91Si0.09 at 6.0, 7.4 and 8.9 GPa and the temperatures measured at the onset of the transformations were 300 °C higher than those in iron at similar pressures, (2) the transformation rate in Fe0.91Si0.09 was extremely sluggish compared to that of iron, and (3) the bcc-fcc phase transformation was not observed in Fe0.91Si0.09 at 4.7 GPa up to 1000 °C and in Fe0.83Si0.17 at 8.2 GPa and 1100 °C.
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  • 47
    ISSN: 1432-2021
    Schlagwort(e): Key words Majorite garnet ; X-ray diffraction ; PVT observation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: Abstract The high-pressure and temperature equation of state of majorite solid solution, Mj0.8Py0.2, was determined up to 23 GPa and 773 K with energy-dispersive synchrotron X-ray diffraction at high pressure and high temperature using the single- and double-stage configurations of the multianvil apparatuses, MAX80 and 90. The X-ray diffraction data of the majorite sample were analyzed using the WPPD (whole-powder-pattern decomposition) method to obtain the lattice parameters. A least-squares fitting using the third-order Birch-Murnaghan equation of state yields the isothermal bulk modulus, K T0  = 156 GPa, its pressure derivative, K′ = 4.4(±0.3), and temperature derivative (∂K T /∂T) P = −1.9(±0.3)× 10−2 GPa/K, assuming that the thermal expansion coefficient is similar to that of pyrope-almandine solid solution.
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  • 48
    ISSN: 1573-4986
    Schlagwort(e): Salivary mucin (MUC7) ; O-glycosylation ; APP segments ; tandem repeat ; (glyco)peptide synthesis ; crystallization ; X-ray diffraction ; poly-L-proline type conformation ; aa, amino acid ; MUC7, human salivary mucin ; APP, Ala-Pro-Pro, Boc-Ala-Pro-Pro-OBzl ; Boc, Nα-t-butyloxycarbonyl ; Bzl, benzyl ; CD, circular dichroism ; e.s.ds, estimated standard deviations ; Fmoc, Nα-fluorenylmethoxycarbonyl ; Fuc, fucose ; Gal, galactose ; GalNAc, N-acetylgalactosamine ; MALDI, matrix assisted laser desorptionionization ; PPI, poly-L-proline type I conformation ; PPII, poly-L-proline type II conformation ; NeuAc, sialic acid ; SPPS, solid-phase peptide synthesis ; SSCP, secondary structure content prediction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Human salivary mucin (MUC7) is characterized by a single polypeptide chain of 357 aa. Detailed analysis of the derived MUC7 peptide sequence reveals five distinct regions or domains: (1) an N-terminal basic, histatin-like domain which has a leucine-zipper segment, (2) a moderately glycosylated domain, (3) six heavily glycosylated tandem repeats each consisting of 23 aa, (4) another heavily glycosylated MUC1- and MUC2-like domain, and (5) a C-terminal leucine-zipper segment. Chemical analysis and semi-empirical prediction algorithms for O-glycosylation suggested that 86/105 (83%) Ser/Thr residues were O-glycosylated with the majority located in the tandem repeats. The high (∼25%) proline content of MUC7 including 19 diproline segments suggested the presence of polyproline type structures. CD studies of natural and synthetic diproline-rich peptides and glycopeptides indicated that polyproline type structures do play a significant role in the conformational dynamics of MUC7. In addition, crystal structure analysis of a synthetic diproline segment (Boc-Ala-Pro-OBzl) revealed a polyproline type II extended structure. Collectively, the data indicate that the polyproline type II structure, dispersed throughout the tandem repeats, may impart a stiffening of the backbone and could act in consort with the glycosylated segments to keep MUC7 in a semi-rigid, rod shaped conformation resembling a ‘bottle-brush’ model.
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Pharmacy world & science 18 (1996), S. 56-62 
    ISSN: 1573-739X
    Schlagwort(e): Computer graphics ; Databases ; Drug design ; Molecular conformation ; Nuclear magnetic resonance ; Receptors ; Structure-activity relationship ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Structure-based ligand design is a technique that is used in the initial stages of a drug development programme. The role of various computational methods in the characterization of the chemical properties and behaviour of molecular systems is discussed. The determination of the three-dimensional properties of small molecules and macromolecular receptor structures is a core activity in the efforts towards a better understanding of structure-activity relationships.
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  • 50
    ISSN: 1573-4935
    Schlagwort(e): Membrane insertion ; membrane junctions ; mitochondria ; cytochrome c oxidase ; p25 ; peptide-lipid interaction ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The structural effect of the presequence of cytochrome oxidase subunit IV (p25) on multilamellar liposomes with different lipid compositions has been investigated using X-ray diffraction and electron microscopy. The presequence causes the disordering of the liposomes containing negatively charged lipids, without destabilizing the bilayer structure or destroying the multilamellar nature of the liposomes. In the systems containing only zwitterionic lipids, a small increase in the d-spacing (lamellar stacking spacing) is observed without any disorder effect suggesting a weaker interaction of the peptide and lipid. Circular Dichroism measurements of the peptide, in the presence and absence of the different lipid systems studied, show that the secondary structure of the peptide is modulated by the lipid environment. Considerable amounts of α-helix in the presequence is only observed in the systems containing negatively charged lipids. These are the same systems for which the disordering effect is observed with X-ray diffraction. It is proposed that p25 disorders the bilayer stacking by corrugating the membranes. The results are discussed in terms of the relevance of the specific lipid properties (e.g., electric charge and ability to form inverted phases) in determining how the peptide interacts with the lipid and affects its structural organization. It is suggested that the lipid properties relevant for the disordering effect induced by the peptide are the same as those involved in the formation of contact sites between mitochondrial membranes during the import of nuclear coded proteins.
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  • 51
    ISSN: 1573-904X
    Schlagwort(e): iobitridol ; proteinase ; hydrophobic shielding ; contrast agent ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. The concept of Hydrophilic Sphere Stabilization, or Hydrophobic Shielding, has been postulated in the synthesis of biocompatible contrast agents in vascular imaging. To improve the safety of these polyiodinated agents, interactions with protein hydrophobic sites in biomacromolecules should be kept as low as possible. In order to evaluate the level of interactions with proteins, we have selected the serine proteinase Elastase, in presence of Iobitridol (Xenetix®), as a model. Methods. The complex between Iobitridol and Pancreatic Porcine Elastase was investigated by X-ray diffraction techniques, on saturated monocrystals, using the synchrotron radiation at 0.98Å. Results. In contrast to Iohexol, which displays several interactions including one in the active site, Iobitridol is unable to interact directly with elastase. Only one partially occupied site is found in between two molecules of the crystal packing. Conclusions. The validation of the 'hydrophobic shielding' concept, which was at the origin of the design of the Iobitridol molecule, has been proven to be an essential feature in minimizing in vivo protein interactions.
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 275 (1997), S. 617-626 
    ISSN: 1435-1536
    Schlagwort(e): Key words High-modulus polypropylene fibre ; polymer blend ; manufacturing process ; X-ray diffraction ; tensile properties ; fibre structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract  The tensile behavior of fibres, spun from a blend of small percentage of plastic grade poly-propylene with fibre grade poly-propylene, was studied in relation to their structure. The spinning and drawing process was optimized in order to increase the elastic moduli of produced filament yarns. By such optimization of the process a tenacity of 0.7 GPa, an elastic modulus of 14.8 GPa and a dynamic modulus of 19 GPa were attained. From diffuse small-angle X-ray scattering the presence of voids, up to 11.5%, was established. Voidness of the fibrillar structure was confirmed with electron micrographs. In spite of the rather drastic changes in morphology the mechanical properties of high void fibrillar structures are good, indicating that the load bearing units of the filament have maintained their integrity. The improved mechanical behavior of highly drawn fibres spun from 10/90 plastic/fibre grade polymer blend is related to higher crystalline and above all to higher amorphous orientation.
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  • 53
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 277 (1999), S. 1220-1223 
    ISSN: 1435-1536
    Schlagwort(e): Key words Nonaqueous liquid crystals ; Hexagonal and lamellar phase ; Gel phase ; X-ray diffraction ; Calorimetry ; Phase diagram
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Two mixtures of the binary system K-behenate/glycerol, x KC22 = 0.30 and 0.50 (x = mole fraction), have been investigated as a function of temperature using small- and wide-angle X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The binary phase diagram based on texture observations using polarizing optical microscopy was confirmed. XRD and DSC measurements provided concordant results with respect to the range of the phase regions in the phase diagram. Only differences between the DSC curves for rising and falling temperatures were detected. The recorded XRD and DSC data of the liquid crystals and gel phases observed are also in agreement with previously reported investigations on K-soap/glycerol. The C ⇆ G and G ⇆ Lα phase transitions correlate with a sharp shift in the d value of the first small-angle reflection. The G phase is characterized by a split of the first small-angle reflections. Also, the position and shape of the wide-angle reflections change and the peak intensity is reduced.
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  • 54
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 23 (1995), S. 35-39 
    ISSN: 1573-1111
    Schlagwort(e): β-Cyclodextrin (β-CD) ; acaricide ; dimethylformamide (DMF) ; spectrophotometry ; X-ray diffraction ; GLC
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Many synthetic pesticides (herbicides, insecticides, fungicides etc.) can be complexed with cyclodextrins. The inclusion complexes of acaricides such as Fenson, Chlorfenson and Genite were prepared. The formation of inclusion complexes was established by UV and X-ray diffraction techniques. The host-to-guest ratio was determined by UV spectral and GLC methods.
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 34 (1999), S. 19-29 
    ISSN: 1573-1111
    Schlagwort(e): analgesic ; p-bromoacetanilide ; cyclodextrin ; inclusion complex ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The preparation and X-ray crystal structure of a 1 : 1 complex between β-cyclodextrin (β-CD) and the analgesic p-bromoacetanilide are reported. Thermogravimetric and UV spectrophotometric analyses of single crystals grown from an aqueous solution containing host and guest in 1 : 1 molar ratio yielded the composition β-CD ċ p-bromoacetanilide ċ$ 13.5H2O. Crystals of the complex are triclinic, space group P1, with a = 15.197(3), b = 15.613(2), c = 15.743(4) Å, α = 87.16(2), β = 98.29(2), γ = 103.39(1)° and Z = 2 crystallographically independent complex units per unit cell. The β-CD molecules form head-to-head dimers which pack in the channel-mode. Each dimer contains two guest molecules whose acetylamino substituents are located at the dimer interface while the bromine atoms protrude from the β-CD primary faces. The acetyl residues of both guest molecules were found to be disordered but the X-ray data permitted
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  • 56
    ISSN: 1435-1536
    Schlagwort(e): Key words Lyotropic liquid crystals ; X-ray diffraction ; Calorimetry ; Gel phase ; K-myristinate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Samples from the three selected concentrations x KC14 = 0.25,0.37, and 0.50 of the K-myristinate/glycerol (KC14/Gl) binary system have been investigated by means of small- and wide-angle X-ray diffraction measurements as well as differential scanning calorimetry (DSC) measurements as a function of temperature. The results are – The G1 gel phase, contained in the preliminary phase diagram according to Dörfler and Senst [(1993) Colloid Polym Sci 271: 173], is nonexistent. – The same applies of the isotropic phase in the preliminary phase diagram according to Dörfler and Senst. Initially an isotropic or a cubic phase was assumed based on polarized microscopy texture observations. X-ray diffraction and DSC measurements provided no indication for their existence. – Due to the nonexistence of the G1 and isotropic phases the preliminary phase diagram of the KC14/Gl binary system had to be corrected. The region of the lamellar phase extends over a wider region. – X-ray diffraction and DSC measurements provided concordant results, which were further confirmed by electron microscopic investigation. Differences in phase-transition points from DSC data obtained for rising and falling temperatures have been observed. – The crystalline-to-gel phase transition correlates with a sharp shift in the d value of the first small-angle reflex. – The gel phase is accompanied by a distinct splitting of the first small-angle reflexes. The wide-angle reflexes show rearrangement and reduced intensity. – Similar to the crystalline-to-gel phase transition, the gel-to-lamellar phase transition is accompanied by a sharp change in the d values.
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 275 (1997), S. 1088-1092 
    ISSN: 1435-1536
    Schlagwort(e): Key words Semi-crystalline polymers ; X-ray diffraction ; necking ; phase transformation ; molecular mechanisms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract  The plastic deformation of syndiotactic polypropylene (sPP) bulk samples has been investigated. A structural comparison of the initial states before and after plastic deformation by necking is carried out by X-ray diffraction observations. Independent of the initial states (amorphous, semi-crystalline with different crystal phases), only the planar all-trans crystal form of sPP is present in the deformed samples after necking. Form these results, molecular mechanisms of the plastic deformation in the neck zone of semi-crystalline polymers will be discussed.
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 277 (1999), S. 340-346 
    ISSN: 1435-1536
    Schlagwort(e): Key words Chirality ; Clay organocomplexes ; Intercalation ; Nanophase reactors ; Binary liquid mixtures ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Chiral phenylethyl alkylammonium montmorillonites were prepared by ion exchange of Na montmorillonite (from Wyoming). The structure of chiral montmorillonite organocomplexes was studied in the dry state by X-ray diffraction, IR spectroscopy and 13C cross-polarized MAS NMR and after swelling by X-ray diffraction. The phenylethylammonium ions are intercalated in montmorillonite in a monolayer structure, while higher derivatives containing alkyl chains with lengths of n c=10−16 take up a bilayer orientation. The hydrophobized clay mineral is readily dispersed in organic solvents, for example in ethanol, toluene and their binary mixtures. Due to selective adsorption, the liquids penetrate into the interlamellar space under significant interlayer expansion producing a great variety of alkyl chain orientations within the interlamellar space, depending on the length of alkyl chains and on the mixture composition. Such interlamellar spaces are possible chiral nanoreactors with adjustable volume and may be prospectively utilized for shape-selective catalytic reactions and the production of enantiomers.
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 277 (1999), S. 1104-1108 
    ISSN: 1435-1536
    Schlagwort(e): Key words Nonaqueous lyotropic liquid crystals ; X-ray diffraction ; Calorimetry ; Gel phase ; K-palmitate ; Phase diagram
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Three mole fractions of the binary system K-palmitate/glycerol (KC16/Gl) xKC16 = 0.30, 0.37 and 0.50 have been investigated as a function of temperature by small- and wide-angle X-ray diffraction investigations and differential scanning calorimetry (DSC) measurements. The existence of a gel-like region, named G1 in the preliminary binary phase diagram [4], could not be confirmed. Consequently, a corrected version of the phase diagram of the KC16/Gl system is established. According to this corrected phase diagram at low K-palmitate concentrations, xKC16 〈 0.25, the transitions crystalline phase (C) ⇆ hexagonal phase, chains fluid (Hα) ⇆ isotropic, micellar phase (S) occur with rising temperature. At xKC16 〉 0.25 the transitions C ⇆ gel phase (G) ⇆ lamellar phase, chains fluid (Lα) were observed. X-ray diffraction and DSC measurements provided concordant results. Only differences in the phase transition temperatures from DSC curves obtained at rising and falling temperatures were observed. The phase transitions C ⇆ G, G ⇆ Lα and G ⇆ Hα correlate with a sharp shift in the d value of the first small-angle reflection. The occurrence of the G phase is accompanied by a distinct split of the first small-angle reflections. Simultaneously, the wide-angle reflections change and the peak intensity is reduced.
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 277 (1999), S. 1109-1114 
    ISSN: 1435-1536
    Schlagwort(e): Key words Nonaqueous liquid crystals ; Gel phase ; X-ray diffraction ; Calorimetry ; K-stearate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The K-stearate/glycerol (KC18/Gl) binary system was studied at mole fractions of stearate of x KC18 = 0.10, 0.25, 0.30 and 0.50. Small- and wide-angle X-ray diffraction (XRD) measurements were combined with differential scanning calorimetry (DSC) measurements at different temperatures. The investigations were intended to verify the previously published phase diagram and were targeted at the confirmation of the gel-like (G1) phase and the isotropic (I) phase. The XRD and DSC measurements lead to the conclusion that the G1 phase as well as the I phase, the existence of which had been proposed from texture observations, do in fact not exist. Consequently, a correction of the preliminary phase diagram is given. This corrected phase diagram reveals the crystalline phase (C) ⇆ gel phase (G) ⇆ hexagonal phase (Hα) ⇆ isotropic, micellar phase phase transitions for low KC18 concentrations of x KC18 = 0.15–0.3 and the C ⇆ G ⇆ lamellar phase (Lα) phase transitions for concentrations about or higher than x KC18 = 0.35. The C, G, Lα and Hα phases have been further characterized by structural parameters (characteristic d values) as a function of temperature. The phase transitions C ⇆ G, G ⇆ Lα and G ⇆ Hα correlate with sharp shifts in the d value of the first small-angle reflections.
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 105 (1997), S. 224-227 
    ISSN: 1435-1536
    Schlagwort(e): Zwitterionic surfactants ; vesicles ; lamellar phase ; X-ray diffraction ; dispersion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract New double-chain zwitterionic surfactants were shown to undergo spontaneous dispersion as vesicles in water by means of simple dilution of the lamellar phase. The molecular parameters of relevance were investigated in a systematic study of the structure of the lamellar phase and of the ability of spontaneous formation of vesicles in a series of homologous zwitterionic surfactants. Thus, the double-chain zwitterionic surfactants which occupies a small interfacial area per molecule in spite of the large size of their hydrophilic headgroup can form spontaneous vesicles. In this case, the bending modulus ¯k of the surfactant film is strongly negative and the short-range repulsive interactions between hydrophilic groups protruding from the surfactant films into water allow a large swelling of the lamellar phase, and are the origin of the colloidal stability of the vesicles dispersion.
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 52 (1998), S. 697-703 
    ISSN: 1572-8943
    Schlagwort(e): DSC ; novolac resin ; thermogravimetry ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal stability of p-cresol novolac resin was studied by means of DSC, X-ray diffraction, thermogravimetry and SEC investigations. After 30 thermal cycles in which the same sample was heated, cooled and heated again, without attainment of the temperature of degradation at any time in the experiment, important structural modifications are observed. At the end of the experiments, the resin, which is initially highly crystalline, exhibits all the characteristics of a semi-crystalline material.
    Materialart: Digitale Medien
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 125-130 
    ISSN: 1572-8943
    Schlagwort(e): Bi2O3-PbO-CaO system ; DTA ; solid-state reactions ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Following our previous research, this work is dedicated to the study of phase formation in the subsolidus domain of the Bi2O3-PbO-CaO system. Former investigations performed by DTA/TGA and XRD have pointed out that under non-isothermal conditions only the formation of binary compounds occurs. Under such conditions these compounds could be non-equilibrium phases. In order to establish the conditions of formation of equilibrium phases, a study of the Bi2O3-PbO-CaO system, in isothermal conditions, was carried out. The results obtained in isothermal conditions have confirmed the presence of Bi2O3-rich solid solutions and Ca2PbO4 as main equilibrium phases. An attempt to represent the phase relations of the mentioned system at 700°C should be equally mentioned.
    Materialart: Digitale Medien
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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 57 (1999), S. 193-202 
    ISSN: 1572-8943
    Schlagwort(e): barium strontium fluorohalides ; DTA ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract We have studied the solid-liquid equilibrium of the system Sr1−yBayFCl1−xBrx using DTA and X-ray diffraction techniques. The entire composition range in this system yields solid solutions which crystallize in the PbFCl (Matlockite) structure type. The melting points of the entire composition range have been parametrized (within 5°C rms error) using a biquadratic fit of the available data obtained by experiment and from the literature.
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  • 65
    ISSN: 1572-9001
    Schlagwort(e): X-ray diffraction ; Mössbauer spectroscopy ; μ-oxo-bis(trichloro-iron(III))
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The crystal and molecular structure of (BzlMe3N) 2 + [Fe2OCl6]2- has been determined. The asymmetric unit contains two benzyltrimethylammonium cations and two half μ-oxo-bis(trichloro-iron(III)) anions. The bridging μ-oxygen atoms of these anions are located over crystallographic symmetry elements. Therefore, the two anions resulting from the symmetry operations correspond to two different conformers presenting “angular” and “linear” dispositions of the Fe-O-Fe bond angle. Mössbauer spectrum consists of two asymmetric lines that are adequately simulated by two equally populated quadrupole doublets associated with the two iron sites.
    Materialart: Digitale Medien
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Structural chemistry 8 (1997), S. 149-154 
    ISSN: 1572-9001
    Schlagwort(e): Epoxide group ; hydrogen bonding ; hydrogen bonding to epoxide groups ; cyclooctane conformation ; X-ray diffraction ; cis-2,3-epoxycyclooctanol ; crystal structure determination ; cis-2,3-epoxycy-clooctanol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Hydrogen bonding and the electron-withdrawing or electron-donating characteristics of substituent groups that are neighboring to epoxide groups can affect the reactivity of the epoxide ring. The crystal structure ofcis-2,3-epoxycyclooctanol has been determined as a saturated eight-membered ring compound in which a hydroxyl group is attached to the C(1) atom that is adjacent to a 2,3-fused epoxy ring. The findings are that the longer epoxide C-O bond (and hence the one expected to be more readily broken) is the one farther from the hydroxyl group [1.462(1) å versus 1.447(1) å] and that the optimal hydrogen bonding is to an adjacent molecule radier than within the molecule. The shortest C-C bond is that of the epoxide group; the bond adjacent to it (on the side farther from the hydroxyl group) is the next shortest.
    Materialart: Digitale Medien
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 131-143 
    ISSN: 1573-1111
    Schlagwort(e): Hydroxypropyl α-, β-, or γ-cyclodextrin ; naproxen ; amorphous naproxen/hydroxypropylcyclodextrin blends ; inclusion complexes ; crystallinity ; dissolution rate ; thermodynamic parameters ; molecular modelling ; thermal analysis ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Solid combinations of naproxen with amorphous hydroxypropyl derivatives of α-, β-, and γ-cyclodextrin with an average substitution degree per anhydroglucose unit of 0.6 were investigated for thermal behaviour (differential scanning calorimetry), drug crystallinity (X-ray diffractometry), and dissolution rate (dispersed amount and rotating disc methods). Phase-solubility analysis and computer-aided molecular modelling were carried out to study the inclusion complexation of naproxen with hydroxypropyl cyclodextrins. The cavity size of the host is a selective factor for the solubilizing effect, complexing ability, and dissolution rate enhancement on naproxen, hydroxypropyl β-cyclodextrin being markedly the most effective derivative. No relationship was found between the decrease in crystallinity of the drug dispersed in the amorphous carrier matrix and the geometrical features of the cyclodextrin macrocycle.
    Materialart: Digitale Medien
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  • 68
    ISSN: 1573-3904
    Schlagwort(e): homo-β-Amino acids ; β-Amino acid residue ; X-ray diffraction ; Crystal structure ; Solid-state conformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract An N- and C-protected derivative of homo-β-leucine, Fmoc-homo-β-(S)-leucine methyl ester, synthesized from the corresponding proteinogenic parent α-amino acid in enantiopure form has been fully characterized in the solid state by X-ray diffraction analysis. The crystal conformation of this new residue indicates an extended conformation for this homo-β-residue, with the ϕ torsion angle being more constrained than the µ and ψ angles.
    Materialart: Digitale Medien
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  • 69
    Digitale Medien
    Digitale Medien
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 213-218 
    ISSN: 1573-3904
    Schlagwort(e): α/310-Helix〉 ; Nitroxide amino acid ; Peptide conformation ; X-ray diffraction ; α-Tetrasubstituted amino acids ; Trichogin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract An X-ray diffraction analysis of the [Fmoc0,TOAC4,8, Leu-OMe11] analogue of thelipopeptaibol antibiotic trichogin A IV shows that the undecapeptide isfolded in a right-handed, mixed α/310-helix. The helicalmolecules are connected in a head-to-tail arrangement along the b-axisthrough C=O···H-N intermolecular H-bonding. Thispacking mode generates a hydrophobic cavity where the FmocNα-protecting groups are accommodated. The distances andangles between the nitroxide groups of the two TOAC residues, separated byone turn of the α-helix, have been determined.
    Materialart: Digitale Medien
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  • 70
    Digitale Medien
    Digitale Medien
    Springer
    International journal of peptide research and therapeutics 2 (1995), S. 187-189 
    ISSN: 1573-3904
    Schlagwort(e): β-turns ; Cα-tetrasubstituted α-amino acids ; Conformational restrictions ; Peptide conformation ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary X-ray diffraction analyses have provided detailed structural information on the 310-helices of (i) pBrBz-d-(αMe)Phe-(Aib)2-d-(αMe)Phe-Aib-OtBu and Ac-(Aib)2-l-Lys(Bz)-(Aib)2-l-Lys(Bz)-(Aib)2-NHMe as suitable templates for molecular recognition studies, and (ii) pBrBz-TOAC-(l-Ala)2-TOAC-l-Ala-NHtBu as an appropriate spacer for an ESR study of side chain to side chain interactions. In addition, in Ac-TOAC-(Aib)2-l-Trp-Aib-OMe, forming a 310-helix, the TOAC residue plays the role of an effective quencher of the fluorescence of the tryptophan residue located one turn apart.
    Materialart: Digitale Medien
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  • 71
    Digitale Medien
    Digitale Medien
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 415-422 
    ISSN: 1573-3904
    Schlagwort(e): Pseudopeptide ; Turn mimic ; Vinylogous peptides ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A Z- or E-ethenyl group has been inserted between the α-carbon andthe carboxyl group of the proline residue by stereoselective Hornersynthesis. The resulting vinylogous amino acid has been coupled with aminocompounds by classical methods, and model amino acid derivatives anddipeptides containing a Z- or E-CH=CMe group have been investigated insolution by 1H-NMR and IR spectroscopy, and in the solid stateby X-ray diffraction. The E-ethenyl group gives rise to an openconformation and the Z-conformer to a folded structure with anintramolecular hydrogen bond closing a nine-membered pseudocycle.
    Materialart: Digitale Medien
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  • 72
    ISSN: 1573-3904
    Schlagwort(e): homo-β-Amino acids ; β-Amino acid residue ; X-ray diffraction ; Crystal structure ; Solid-state conformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An N- and C-protected derivative ofhomo-β-leucine, Fmoc-homo-β-(S)-leucine methyl ester, synthesized from the corresponding proteinogenic parent α-amino acid in enantiopure form has been fully characterized in the solid state by X-ray diffraction analysis. The crystal conformation of this new residue indicates and extended conformation for thishomo-β-residue, with the ϕ torsion angle being more constrained than the μ and ψ angles.
    Materialart: Digitale Medien
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  • 73
    Digitale Medien
    Digitale Medien
    Springer
    International journal of peptide research and therapeutics 5 (1998), S. 337-340 
    ISSN: 1573-3904
    Schlagwort(e): enkephalin ; neuropeptide ; pharmacophore ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Since the discovery and isolation of the endogenous opioid peptides Leu- and Met-enkephalin, structural studies have been focused on deducing the bioactive conformation of the peptide ligands. Theoretically, linear peptides can have many different backbone conformations, yet early X-ray studies on enkephalin and its analogues showed only two different backbone conformations: extended and single β-bend. More recent reports include a third conformation for Leu-enkephalin and constrained opioid peptides from two ‘new’ classes (i.e. cyclic and ‘all-aromatic’ peptides). In this report the relationship between solid-state X-ray structure and opioid peptide activity is examined. The N-terminal amine nitrogen and the two aromatic rings have previously been identified as structural features important to the biological activity of opioid peptides. From X-ray studies we find that the distances between the centroids of the aromatic rings, and between the N-terminal amine nitrogen and the centroid of the phenylalanine ring, vary over a large range. There is a discernible relationship, however, between the separation of the two rings and their orientation that correlates with activity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 74
    Digitale Medien
    Digitale Medien
    Springer
    International journal of peptide research and therapeutics 2 (1995), S. 239-242 
    ISSN: 1573-3904
    Schlagwort(e): Pseudopeptide ; Triphosgene ; Beta-turn ; NMR ; FT-IR ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary For the sake of improving synthetic methods and evaluating the conformational perturbation induced by the substitution of AzAsx for the Asx residue in the cognate dipeptide R-CO-Asx-Pro-NHR′, we prepared the AzAsx-dipeptide sequence by making use of the crystalline triphosgene. This reagent allows, in situ and under very mild experimental conditions, both the carbonylation and the activation of the properly substituted and N-protected hydrazine before coupling with the proline partner. With regard to conformational behaviour, the azadipeptide sequence displays a β-fold, unlike the cognate dipeptide which adopts an Asx-turn.
    Materialart: Digitale Medien
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  • 75
    Digitale Medien
    Digitale Medien
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 213-218 
    ISSN: 1573-3904
    Schlagwort(e): α/310-Helix ; Nitroxide amino acid ; Peptide conformation ; X-ray diffraction ; α-Tetrasubstituted amino acids ; Trichogin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An X-ray diffraction analysis of the [Fmoc0, TOAC4,8, Leu-OMe11]analogue of the lipopeptaibol antibiotic trichogin A Iv shows that the undecapeptide is folded in a right-handed, mixed α/310-helix. The helical molecules are connected in a head-to-tail arrangement along the b-axis through C=O...H-N intermolecular H-bonding. This packing mode generates a hydrophobic cavity where the Fmoc Nα-protecting groups are accommodated. The distances and angles between the nitroxide groups of the two TOAC residues, separated by one turn of the α-helix, have been determined.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 415-422 
    ISSN: 1573-3904
    Schlagwort(e): Pseudopeptide ; Turn mimic ; Vinylogous peptides ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A Z-orE-ethenyl group has been inserted between the α-carbon and the carboxyl group of the proline residue by stereoselective Horner synthesis. The resulting vinylogous amino acid has been coupled with amino compounds by classical methods, and model amino acid derivatives and dipeptides containing a Z-orE-CH=CMe group have been investigated in solution by1H-NMR and IR spectroscopy, and in the solid state by X-ray diffraction. TheE-ethenyl group gives rise to an open conformation and the Z-conformer to a folded structure with an intramolecular hydrogen bond closing a ninemembered pseudocycle.
    Materialart: Digitale Medien
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    International journal of peptide research and therapeutics 5 (1998), S. 337-340 
    ISSN: 1573-3904
    Schlagwort(e): enkephalin ; neuropeptide ; pharmacophore ; X-ray diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Since the discovery and isolation of the endogenous opioid peptides Leu- and Met-enkephalin, structural studies have been focused on deducing the bioactive conformation of the peptide ligands. Theoretically, linear peptides can have many different backbone conformations, yet early, X-ray studies on enkephalin and its analogues showed only two different backbone conformations: extended and single β-bend. More recent reports include a third conformation for Leu-enkephalin and constrained opioid peptides from two ‘new’ classes (i.e. cyclic and ‘allaromatic’ peptides). In this report the relationship between solid-state X-ray structure and opioid peptide activity is examined. The N-terminal amine nitrogen and the two aromatic rings have previously been identified as structural features important to the biological activity of opioid peptides. From X-ray studies we find that the distances between the centroids of the aromatic rings, and between the N-terminal amine nitrogen and the centroid of the phenylalanine ring, vary over a large range. There is a discernible relationship, however, between the separation of the two rings and their orientation that correlates with activity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 44 (1995), S. 2064-2067 
    ISSN: 1573-9171
    Schlagwort(e): carbon adsorbents ; X-ray diffraction ; microcrystallites ; micropores ; adsorption ; water vapor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A correlation of adsorption and X-ray data for a series of both initial and modified active carbons (AC) was performed. The AC were modified by thermal treatment and progressive activation. A linear correlation between the sizes of crystallites and micropore widths of AC was established. It was shown that the adsorption of water vapor results in an increase in the parameterL aof crystallites of active carbons.
    Materialart: Digitale Medien
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