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  • 1
    facet.materialart.
    Unknown
    German Medical Science; Düsseldorf, Köln
    In:  68. Jahrestagung der Deutschen Gesellschaft für Unfallchirurgie, 90. Tagung der Deutschen Gesellschaft für Orthopädie und Orthopädische Chirurgie und 45. Tagung des Berufsverbandes der Fachärzte für Orthopädie; 20041019-20041023; Berlin; DOC04dguH12-2004 /20041019/
    Publication Date: 2004-10-20
    Keywords: ddc: 610
    Language: German
    Type: conferenceObject
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  • 2
    ISSN: 0168-1176
    Keywords: negative thermal ion mass spectrometry ; secondary ion mass spectrometry ; sputter-induced resonance ionization mass spectrometry. ; thermal ion mass spectrometry
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1431-4630
    Keywords: Key words d-Amino acids ; Chemical markers ; Acetic fermentation ; Aceto balsamico ; Authenticity control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Twenty-five vinegars were examined quantitatively for their content of free amino acid (AA) enantiomers using chiral gas chromatography/mass spectrometry. Vinegars manufactured from grape must contained l-proline (l-Pro) as the major AA. Balsamic vinegars (aceto balsamico di Modena), with one exception, contained the highest amounts of l-AAs (861–2000 mg l–1) as well as d-AAs (46–361 mg l–1). The amounts of d-Pro and d-alanine (d-Ala) increased in the course of maturation. Sherry vinegars had a AA pattern similar to that of balsamic vinegars but with much lower amounts: concentrations of l-AAs were 244 mg l–1 and 456 mg l–1 and of d-AAs were 18 mg l–1 and 19 mg l–1. The l-AA content of cider vinegars was very low (34 mg l–1 and 44 mg l–1) and only traces of d-AAs (〈2 mg l–1) were found. In spirit vinegars few d-AAs and low amounts of most l-AAs were detected, with the exception of l-glutamic acid (l-Glu) (210–847 mg l–1), probably added as a flavour enhancer. The AA content of spirit vinegars blended with wine vinegar was influenced by the portion of wine vinegar added. Rice vinegars had concentrations of l-AAs from as low as 36 mg l–1 to as high as 6860 mg l–1, and the concentrations of d-AAs ranged from 6 mg l–1 to 531 mg l–1. All vinegars declared as "produced by microbial fermentation" contained d-Ala, d-aspartic acid, and d-Glu as typical bacterial markers. From the data it is concluded that chiral AA analysis can be used to distinguish among fermented and synthetic vinegars and to identify raw materials used for their production. In particular, the amount of d-Pro can be used as proof of the maturation process of balsamic vinegar.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1431-4630
    Keywords: Key words Amino acid epimerization ; Infant formulae ; Food proteins ; Hydroxyproline stereoisomers ; Gas chromatography-mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Aqueous solutions (5 g/100 ml) of commercial preparations of (a) an enzymatic partial hydrolysate of gelatin and (b) type A gelatin were subjected to threefold heating to boiling in a domestic microwave oven at 750 W and to conventional heating. Then samples were totally hydrolyzed (6 M hydrochloric acid, 110  °C, 24 h) and investigated for the presence of eight possible stereoisomers of 3- and 4-hydroxyproline (Hyp) using capillary gas chromatography. Amino acids were analyzed as N(O)-trifluoroacetyl 2-propyl esters on Chirasil-l-Val and detected by selected ion monitoring mass spectrometry. Blanks of (a) and (b) were analyzed in parallel. Relative amounts of 5.0±0.2% cis-4-d-Hyp were generated from native trans-4-l-Hyp as a result of total hydrolysis in all samples and independent of previous treatment. Notably, neither cis-3-l-Hyp nor cis-4-l-Hyp could be detected in either of the gelatin samples. Thus a report on the generation of antifibrotic and therefore potentially hazardous cis-3-l-Hyp and cis-4-l-Hyp from protein-bonded native trans-3-l-Hyp and trans-4-l-Hyp on microwave heating of infant formulae could not be confirmed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 32 (2005), S. 0 
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: summary  The aim of this in vitro study was to determine the thermal mechanical properties of veneering composites after polymerization with the appropriate polymerization device. Fracture tests were performed to investigate the effect on fixed partial dentures (FPDs).Dynamic mechanical thermal analysis was used to determine the temperature-dependent mechanical properties. To approximate the clinical situation, the fracture resistance of three-unit metal-based FPDs with different composite veneering was investigated after a simulated 5-year oral wearing period. The restorations were made of a high gold alloy and veneered with three different composites. To determine the influence of fabrication, one composite was used in a light-polymerizing and a heat/pressure-curing version and, in addition, a newly developed heat protection paste was used. After a 5-year simulation period, the fracture resistance was determined.The storage modulus varied between 14268 N mm−2 (Belleglass) and 6616 N mm−2 (Sinfony). Adoro showed no significant differences between light curing (9155 N mm−2) and heat curing (8184 N mm−2) variations. The Adoro-veneering with the heat protection paste showed the highest median fracture strength (1700 N), followed by Adoro LC (1555 N), Belleglass (1051 N), Adoro HP (1150 N) and Sinfony (909 N). The most common failure type occurring in all FPDs was a cracking of the composite, exposing the metal framework. All FPDs showed stress cracking of the composite. The heat protection paste seemed to reduce the crack formation after fabrication and increased the fracture resistance of the composite veneering. Stress cracking after thermal cycling and mechanical loading affected all composites, but all veneered three-unit alloy FPDs showed a fracture resistance sufficient for posterior application.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1431-4630
    Keywords: Key words Collagen ; D-Amino acids ; Hydroxyproline stereoisomers ; Racemisation ; Food proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Using capillary gas chromatography on chiral stationary phases total hydrolysates of gelatins were investigated for their amounts of D-amino acids (D-AAs). Gelatins of different quality and origin were analysed including gelatin-containing final products like candies and meat products. In gelatins manufactured by stepwise extraction (first to fifth extract) with water of increasing temperature (ca. 55–95°C) amounts of 2.7–4.8% of D-aspartic acid (D-Asp) were determined in extracts obtained at ≤ 85°C. The amounts D-Asp were as high as 28.1% in fifth extracts obtained at 95°C (data corrected for 4.3% of D-Asp determined in native collagen as a result of acid-induced epimerisation of L-Asp during total hydrolysis). Epimerisation of aspartyl or asparaginyl residues of proteins in general on heating in water is assumed to proceed via formation of aspartyl succinimide, tautomerisation and release of D-Asp on total hydrolysis. The other AA residues of gelatin showed only a slight increase of epimerisation with increasing thermal treatment. Furthermore, amounts of 3–4% of cis-4-D-hydroxyproline, formed from native trans-4-L-hydroxyproline in collagen on hydrolysis, were detected in total hydrolysates of all gelatins.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of the clamped dielectric constant on mixed single crystals of Rb1-x(NH4)xH2PO4,x=0.35, are reported up to 11 GHz. Between 24 and 60 K, the dielectric dispersion can be fitted to a Cole-Cole relaxation, the parameters of which indicate a temperature-dependent distribution of relaxation times consistent with Vogel-Fulcher freezing. Both the audio and the microwave measurements can be scaled up to ≊ 100 MHz, with a freezing temperature ofT o≅8.4 K. In the GHz range, a relaxation process in addition to the low-frequency freezing mode contributes to the dielectric response.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The dielectric response and the Raman spectra of single crystals of deuterated betaine phosphate are studied around the antiferroelectric phase transition. The dielectric data between 10 MHz and 11 GHz can be explained on the basis of a simple Debye-relaxation with a critical slowing-down of the relaxation rate on approachingT C . Using the Cole-Davidson form of the dielectric function we succeeded in fitting the data in the whole frequency range from 10 MHz to 11 GHz and from 64–400 GHz over a temperature range from 145–280 K. Raman spectra clearly indicate that the doubling of the unit cell does not take place at the antiferroelectric transition temperature, but some degrees below.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of the dielectric permittivity around the ferroelectric transition of betaine arsenate and around the antiferroelectric one of deuterated betaine arsenate reveal relaxation-type dispersions in the upper MHz-region. The data analysis points to two mechanisms which contribute to the low temperature phase transitions of these crystals. In case of betaine phosphate Raman-spectra demonstrate that besides the antiferroelectric transition at 86 K a second structural transition exists at 81 K. Both transitions correlate with dielectric anomalies and the unit cell doubles at 81 K.
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  • 10
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The dielectric behavior of highly deuterated betaine arsenate in the frequency range up to 11 GHz is described by a Cole-Davidson relaxation. The characteristic dynamics show a critical slowing down near the para-antiferroelectric phase transition. The temperature dependence of the dielectric constant is analyzed in terms of a pseudo-one-dimensional Ising model. Evidence is given for a dependence of antiferroelectric coupling on deuteration which can explain the change from a ferro- to an antiferroelectric ordering on deuteration. Measurements of the dielectric relaxation under a dc bias field parallel to the critical axis elucidate the unusual phase transition behavior at low temperatures. A multicritical point appears in theE-T-phase diagram. Frustration effects due to competing ferro- and antiferroelectric interactions are not seen.
    Type of Medium: Electronic Resource
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