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  • 1
    Digitale Medien
    Digitale Medien
    Pulse broadening in a Ne–CuBr–Zn laser system by optical resonance pumping (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 1859-1861 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A Zn atom is employed as the light source for optical resonance pumping to a high lying energy level of the Cu atom, thereby depopulating both the Cu lower laser level and enhancing the upper laser level via cascading decays that is carried out simultaneously. The width of the lasing pulse broadened by 220% and the peak value increased by 180%. The cascading decay route was clarified by observing the fluorescence lines, λ=675.1, 793.5, and 809.0 nm, thereby specifying five levels of excitation loop. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1458074
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  • 2
    Digitale Medien
    Digitale Medien
    Effect of mixing method on rheological properties of alginate impression materials (2002)
    Oxford UK : Blackwell Science Ltd
    Journal of oral rehabilitation 29 (2002), S. 0 
    Details
    ISSN: 1365-2842
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The apparent viscosity of alginate impression paste prepared by three mixing methods (hand-mixing technique (HM), semiautomatic instrument (SM) and automatic mixing instrument (AM)), and the gel strength and surface depression of the respective set materials were measured. The materials used were eight commercially available products mixed at a temperature of 23 ± 0.5 °C and allowed to set. The AM had a high mixing speed, which reduced the working time 4.4–31.5%, compared with HM. This was the result of an increase in paste temperature during mixing. In the case of impression materials mixed with the AM, the gel strength and the surface depression at the gel fracture increased significantly, in accordance with Fisher's protected least significant difference (PLSD) analysis. This phenomenon is caused by a decrease of air bubbles in the set material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2842.2002.00726.x
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  • 3
    Digitale Medien
    Digitale Medien
    Effect of light intensity on linear shrinkage of photo-activated composite resins during setting (2005)
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 32 (2005), S. 0 
    Details
    ISSN: 1365-2842
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: summary  The purpose of this investigation was to examine the effects of light intensity on linear shrinkage of photo-activated composite resins during setting. The materials used were four commercially available photo-activated composite resins. Three light-irradiation instruments were selected and prepared so as to obtain four light intensities (200, 480, 800 and 1600 mW cm−2). The linear shrinkage during setting was examined 10 min after light irradiation using a trial balance plastometer, and the specimen thickness was 2·0 mm for all materials. The depth of cure was examined according to the test method described in the International Organization for Standardization (ISO/FDIS 4049: 2000(E)). In measuring the linear shrinkage 60 s from the start of light irradiation for 10 s, there was a significant correlation (r = 0·89–0·94) between the amount of linear shrinkage and the light intensity: an increase in light intensity produced a greater linear shrinkage. Furthermore, there was a significant correlation (r = 0·92–1·0) between the linear shrinkage and the irradiation time: an increase in irradiation time resulted in a greater linear shrinkage. Values of the depth of cure ranged from 1·69 to 3·75 mm.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2842.2004.01363.x
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  • 4
    Digitale Medien
    Digitale Medien
    Physical and mechanical properties of PMMA resins containing γ-methacryloxypropyltrimethoxysilane (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 31 (2004), S. 0 
    Details
    ISSN: 1365-2842
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: summary  The polymethylmethacrylate (PMMA) resins containing γ-methacryloxypropyltrimethoxysilane (γ -MPS) of 0, 2, 4, 6, 10, 15, 20 and 30 mo1%, added to methylmethacrylate, were prepared using a monomer–polymer technique and stored in air or water at 37 ± 0·5 °C for 28 days. The flexural strength and flexural modulus of the PMMA resins containing γ -MPS of 20 and 30 mo1% were significantly smaller than those containing 2–6 mo1% and the same statements were true for the adhesive strength to porcelain tooth. However, its value of adhesive strength to Co–Cr alloy was remarkably less than to porcelain tooth. By contrast, there was no significant difference among the Knoop hardness of the PMMA resins examined. On the other hand, the thermal expansion had an increasing tendency with an increase of a γ -MPS content. The dynamic shear modulus within a temperature measured (20–140 °C) decreased s1ightly as the γ -MPS content of the PMMA resins increased, and the peak temperature of mechanical loss tangent also tended to decrease. These results indicated that the PMMA resin containing γ -MPS of 6 mol% was the best composition from the standpoint of an excellent adhesive strength against porcelain, although its water absorption was 1·9 times that of PMMA.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2842.2004.01043.x
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  • 5
    Digitale Medien
    Digitale Medien
    Bending strength and depth of cure of light-cured composite resins irradiated using filters that simulate enamel (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 31 (2004), S. 0 
    Details
    ISSN: 1365-2842
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: summary  This study evaluates the light-attenuating effects of enamel on the properties of light-cured restorative resins using simple experimental filters. Three filters were designed to replicate the light transmittance characteristics of 0·5, 1·0 and 1·5 mm thick human enamel. The bending strength, depth of cure, and levels of residual monomer for 12 shades of three commercial light-cured composite resins were examined. These resins were cured either using direct irradiation from a light source or irradiation through one of the filters. For all materials, the bending strength and depth of cure of specimens irradiated through a filter were lower and the levels of residual monomer were higher than those found in specimens irradiated directly. The results indicate that the light-attenuating effect of enamel reduces the polymerization efficiency, resulting in poorer mechanical properties of light-cured composite resins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2842.2004.01025.x
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  • 6
    Digitale Medien
    Digitale Medien
    Effect of ethanol on the hardness and relaxation modulus of experimental photo-activated soft lining materials stored in aqueous solutions (2002)
    Oxford UK : Blackwell Science Ltd
    Journal of oral rehabilitation 29 (2002), S. 0 
    Details
    ISSN: 1365-2842
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Summary We studied changes in the hardness, relaxation modulus {Er(t)}, and weight change ratio (Wc) of experimental photo-activated acrylic soft lining materials (EPLs) stored in three aqueous solutions [distilled water (DW), physiological saline solution (PS), and artificial saliva (AS)] at 37 °C for 8 weeks. The hardness of the EPLs increased markedly during the first 4 days of storage, and subsequently changed little. The greatest hardness occurred in the EPL specimen containing the largest amount of ethanol (Et). The relaxation modulus {Er(8)} of the EPLs ranged from 1·35 to 1·66 MPa immediately before storage, and from 1·43 to 2·21 MPa after an 8-week immersion. Like hardness, the increase in {Er(t)} was greatest when the EPL contained large amounts of Et. The Wc ranged from 0·118 to 0·661% after storage for 8 weeks, and increased most for the EPL specimen containing the smallest amount of Et. Furthermore, 3–7 days after the start of immersion many hollows were observed in the surface of specimens with a high Et content. The results indicate that Wc and hollow formation are sensitive to the Et content of the EPL, and that Et content is closely tied to the change in hardness and relaxation modulus with time.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2842.2002.00873.x
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  • 7
    Digitale Medien
    Digitale Medien
    Viscoelastic properties of denture base resins obtained by underwater test (2000)
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 27 (2000), S. 0 
    Details
    ISSN: 1365-2842
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The viscoelastic properties of denture base polymers, such as poly(methylmethacrylate) (PMMA), polycarbonate (PC), polysulfone (PSF) and polyethersulfone (PES) which have been used in current clinical dentistry were investigated. In addition, water absorption, diffusion coefficient of water into material, cubical expansion, specific volume and residual monomer were also determined. From the results of this study, the viscoelastic behaviours of the denture base polymers in water have been discussed. The relaxation modulus (Er(5)) which was calculated using a stress at 5 s from the start of measurement for the specimen which reached an equilibrium moisture content (wet specimen), decreased from 23·1 to 25·5% compared with that of PMMA stored in a desiccator (37 °C) for 1 week (dry specimen). In contrast, this decreasing ratio was 7·0 to 10·0% for PC, PSF and PES. It is suggested that this phenomenon is caused by the increase of specific volume (cm3/g) with water absorption in each material. The water absorption of the PMMA group was relatively large in comparison with other material and was 1·81–1·85%. This value was within the range from 0·38 to 1·74% for PC, PSF and PES. The diffusion coefficients of water for PC, PSF and PES increased by approximately 1·5–2·7 times that of PMMA. Furthermore, the coefficient of cubical expansion of the wet specimen was larger than that of the dry specimen. The increasing ratio was 1·03–1·10 times for the PMMA group and 1·18–2·38 times for PC, PSF and PES. The variation of Er(5) of the PMMA group with temperature in water was larger than those of PC, PSF and PES.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2842.2000.00545.x
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  • 8
    Digitale Medien
    Digitale Medien
    Effect of photo-irradiation on hardness of soft lining materials for denture base (2002)
    Oxford UK : Blackwell Science Ltd
    Journal of oral rehabilitation 29 (2002), S. 0 
    Details
    ISSN: 1365-2842
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Nine photo-activated acrylic-type (EPL) soft lining materials were produced experimentally to examine their durability. The purpose of this study was to investigate the effect of photo-irradiation on the hardness of experimental soft lining materials. The hardness (Hex) of the nine EPLs was increased 4·3–170·1% by exposing them to light. The effect of irradiation on the Hex of the EPLs was remarkable when the material contained much ethylmethacrylate, together with smaller amounts of di-n-butyl phthalate. Moreover, the Hex tended to increase for EPLs in which the liquid portion contained less di-n-butyl phthalate or more ethanol (Et). The weight change ratio (Wc) was greater for EPL specimens containing less Et. The Wcs ranged from 0·118 to 0·661% after 8 weeks. These results showed that the Hexs of six of the EPLs were approximately equal to those of four commercially available soft lining materials, and these six EPLs may have properties favouring their use in clinical dentistry.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2842.2002.00868.x
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  • 9
    Digitale Medien
    Digitale Medien
    Dynamic viscoelastic properties of commercial glass-fibre reinforced resin used for crowns and bridges (2002)
    Oxford UK : Blackwell Science Ltd
    Journal of oral rehabilitation 29 (2002), S. 0 
    Details
    ISSN: 1365-2842
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Summary In order to investigate the thermal stability, the physical and mechanical, and dynamic viscoelastic properties of glass-fibre reinforced composite materials were measured. The G′ of the seven materials examined was within 5˙20 ± 14˙55 and 4˙50–14˙35 GPa for dry and wet specimens in air at 37 °C, respectively, and decreased with increasing temperature. The G′ values of dry specimens decreased by 7˙74–15˙4% when heated to 60 °C. The value of tan δ ranged from 0˙0102 to 0˙0295 and from 0·0181 to 0·0406 for dry and wet specimens in air at 37 °C, respectively. The coefficient of linear thermal expansion between 30 and 60 °C ranged from 0˙557 to 3˙95 × 10–5/°C. Moreover, the filler content ranged from 56˙36 to 88˙87 wt%. These results showed that the magnitudes of G′, tan δ, and the coefficient of linear thermal expansion and water absorption depend on the inorganic filler or glass-fibre content; i.e. the amount of resin matrix. Moreover, for all the materials examined, the G′ values were thermostable in the temperature range encountered in the oral cavity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2842.2002.00887.x
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  • 10
    Digitale Medien
    Digitale Medien
    Neuromagnetic assessment of epileptogenicity in cerebral arteriovenous malformation (2000)
    Springer
    Neurosurgical review 23 (2000), S. 206-212 
    Details
    ISSN: 1437-2320
    Schlagwort(e): Keywords Arteriovenous malformation ; Magnetoencephalography ; Magnetic source imaging ; Electrocorticography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Magnetoencephalographic (MEG) activities were recorded in five patients with cerebral arteriovenous malformation (AVM) who presented with epilepsy and no clinical history of intracranial hemorrhage, using a 37-channel DC superconducting quantum interference device (SQUID) system. While scalp-recorded electroencephalograms (EEG) failed to reveal paroxysmal discharge, MEGs demonstrated localized high frequency magnetic activity (HFMA). Magnetic source imaging (MSI) depicted the accumulation of equivalent current dipole (ECD) originating from HFMA around the nidus, and the ECD localization agreed well with spike localization on intraoperative electrocorticography (ECoG). These areas corresponded with the areas of hypoperfusion on single photon emission tomography and the intraoperative laser Doppler flow meter. We discussed the application of MEG in estimating interictal paroxysmal activity sources in patients with AVM and addressed the questions of its reliability and validity in source localization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00011956
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