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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 584-586 (June 2008), p. 405-410 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A tungsten heavy alloy (92%W, Ni-Co matrix) is subjected to severe plastic deformation(SPD) by high pressure torsion (HPT) at room temperature up to equivalent strains of 0.7, 5.3, 10.7and 14.3. The microstructure and the mechanical properties are investigated by cylindricalcompression samples at quasi-static and dynamic loading. The harder spherical W particles arehomogeneously deformed within the softer matrix, becoming ellipsoidal at medium strains andbanded at high strains without shear localization or fracture. Results of quasi-static loading showthat the strength is approaching a limiting value at strains of ~10. At this strain for the matrix a grainsize of ~80 nm and for W a cell size of ~250 nm was observed, suggesting strain concentration onthe matrix. The initial yield stress of 945 MPa for the coarse-grained condition is increased therebyto an ultimate value of 3500 MPa, while a peak stress of ~3600 MPa is reached. Such remarkablystrength has never been reported before for pure W or W-based composites. The strain hardeningcapacity as well as the strain rate sensitivity is reduced drastically, promoting the early formation of(adiabatic) shear bands
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1600-0501
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The aim of this investigation was to evaluate the effect of a new calcium hydroxide suspension (Osteoinductal®) on the healing process of endosseous dental implants after placement. The material, composed of 25% calcium hydroxide, 25% Oleum pedum tauri and 50% vaselinum album, was developed with the intention to accelerate and to increase the mineralized bone to implant contact during the healing phase. Eight adult beagle dogs were used in this study. Prior to the beginning of the study the dogs had all mandibular premolars extracted. After the extraction sites had healed for 3 months. implant osteotomies were performed. On one side of the mandible Osteoinductal® was applied into the osteotomies before placement of the implants, whereas the other side did not receive Osteoinductal®. A total of 48 implants were placed with two losses during the entire study period. Two dogs were sacrificed 1 week, 2 weeks, 4 weeks and 3 months after implant placement. The specimens were evaluated histologically and histomorphometrically. In the histological evaluation an intense inflammatory reaction towards the calcium hydroxide suspension was found leading to a destruction of the bone surrounding the implants after 1 and 2 weeks. A giant cell reaction against the test material was visible at 4 weeks. At 3 months no inflammatory and no giant cell reaction could be depicted in the test group. The mean direct bone to implant contact or inflammatory tissue to implant contact showed no differences between test and control group for 1 and 2 weeks. Although statistically not significant, there was a clinical significant difference in the mineralized bone to implant contact between test and control group for the last two timepoints (i.e. 4-week specimens: test group 2.3±0.9%, control group 26% 11.1%; 3-month specimens: test group 10.5±12.7%, control group 60.7±13.7%). This study indicates that the use of the calcium hydroxide suspension Osteoinductal® has a detrimental effect on wound healing and osseointegration of dental imolants and cannot be 1 recommended for use with dental implants.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1615-6692
    Keywords: Key Words Acute myocardial infarction ; Primary angioplasty ; Reperfusion therapy ; Clinical practice ; Schlüsselwörter Akuter Myokardinfarkt ; Primärdilatation ; Thrombolyse ; Klinische Praxis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Aus der Gruppe von Patienten mit einem akuten Myokardinfarkt lassen sich einzelne Subgruppen definieren, die von einer akuten Koronarintervention profitieren können. Werden solche Patienten von Krankenhäusern ohne die Möglichkeit zur Durchführung von Koronardilatationen aufgenommen, könnten sie anschließend zu einer Intervention verlegt werden. Die gegenwärtige klinische Praxis an nicht inter-ventionellen Krankenhäusern ist jedoch bisher nicht untersucht worden. Wir werteten die gepoolten Daten der beiden deutschen Herzinfarktregister MITRA (= Maximale Individuelle Therapie beim Akuten Myokardinfarkt) und MIR (= Myokardinfarkt-Register) aus. Die Möglichkeit zur Koronarintervention war bei 221 der 271 teilnehmenden Kliniken (81,5%) nicht gegeben. Von den 14 487 Patienten mit einem akuten Myokardinfarkt, die von diesen Kliniken eingeschlossen wurden, erhielten 50,1% (7 259/14 487) eine Thrombolyse in der aufnehmenden Klinik, und 3,6% (523/14 487) wurden zu einer Akutintervention verlegt. Von den verlegten Patienten wurden 55,3% (289/523) mittels Primärdilatation und 44,7% (234/523) mittels einer Kombination aus Thrombolyse und Dilatation behandelt. Der Anteil der verlegten Patienten an der Gesamtheit aller an den nicht interventionellen Krankenhäusern eingeschlossenen Herzinfarktpatienten stieg von 1,1% im Jahr 1994 auf 5,5% in 1998 (p für Trend = 0,001). 104 Krankenhäuser (47,1%) verlegten zu keiner Zeit der Erhebung Patienten zur Akutintervention. Patienten, die zur Primärdilatation verlegt wurden (289 Patienten), verglichen wir mit Patienten, die mittels Thrombolyse an dem Aufnahmekrankenhaus behandelt wurden (7 259 Patienten). Eine logistische Regressionsanalyse ergab für die folgenden Variablen eine unabh&ängige Assoziation mit der Verlegung zur Primärdilatation: das Vorliegen von Kontraindikationen zur Thrombolyse (OR = 17,9), ein nicht diagnostisches Erst-EKG (OR = 4,0), eine Prähospitalzeit über sechs Stunden (OR = 2,5), ein unbekannter Infarktbeginn (OR = 2,0) und das Vorliegen eines Vorderwandinfarkts (OR = 1,6). Das Vorliegen einer Herzinsuffizienz bei der Aufnahme war der einzige unabhängige Prädiktor, einen Patienten nicht zur Primärdilatation zu verlegen (OR = 0,40). In Deutschland verlegten zur Zeit der Erhebung nur 47,1% der Krankenhäuser ohne die Möglichkeit der Koronarintervention Patienten mit einem akuten Myokardinfarkt zur Primär- oder Akutdilation. Der Anteil an verlegten Patienten stieg von 1,1% im Jahr 1994 auf 5,5% in 1998. Das Vorliegen von Kontraindikationen zur Thrombolyse war der wichtigste Prädiktor, Herzinfarktpatienten zur Primärdilatation zu verlegen.
    Notes: Abstract In patients with acute myocardial infarction (AMI) admitted at hospitals without angioplasty facilities there are some subgroups of patients which seem to profit from a transfer to primary or acute angioplasty. However, current clinical practice at such hospitals is unknown. We analyzed the pooled data of the german acute myocardial infarction registries MITRA and the MIR. Angioplasty was not available at 221/271 hospitals (81.5%). Out of 14,487 patients with acute myocardial infarction admitted to these hospitals, 50.1% (7,259/14,487) received thrombolysis at the initial hospital and 3.6% (523/14,487) were transferred. Out of the transferred patients, 55.3% (289/523) were treated with primary angioplasty and 44.7% (234/523) received a combination of thrombolysis and angioplasty. The proportion of transferred patients increased from 1.1% in 1994 to 5.5% in 1998 (p for trend = 0.001). One hundred and four hospitals (47.1%) never transferred patients. Patients transferred for primary angioplasty (289 patients) were compared to patients treated with thrombolysis at the initial hospitals (7,259 patients). Multivariate analysis showed the following independent predictors for transfer of patients for primary angioplasty: contraindications for thrombolysis (OR = 17.9), a non-diagnostic first ECG (OR = 4.0), pre-hospital delay ≥ 6 hours (OR = 2.5), unknown symptom onset of the acute myocardial infarction (OR = 2.0) and anterior wall acute myocardial infarction (OR = 1.6). Heart failure at admission was the only dependent predictor not to transfer patients (OR = 0.40). In Germany only 47.1% of hospitals without angioplasty facilities transfer patients with acute myocardial infarction to primary or acute angioplasty. The proportion of transferred patients increased from 1.1% in 1994 to 5.5% in 1998. Contraindications for thrombolysis were the strongest predictor to transfer patients to primary angioplasty.
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  • 4
    Publication Date: 2022-07-19
    Description: We demonstrate, based on data derived from computed tomography, that integrating 2D and 3D morphological data of ammonoid shells represent an important new approach to disentangle the palaeobiology of ammonoids. Characterization of ammonite morphology has long been constrained to 2D data and only a few studies collect ontogenetic data in 180° steps. We combine this traditional approach with 3D data collected from high-resolution nano-computed tomography. For this approach, ontogenetic morphological data of the hollow shell of a juvenile ammonite Kosmoceras (Jurassic, Callovian) is collected. 2D data is collected in 10° steps and show significant changes in shell morphology. Preserved hollow spines show multiple mineralized membranes never reported before, representing temporal changes of the ammonoid mantle tissue. 3D data show that chamber volumes do not always increase exponentially, as was generally assumed, but may represent a proxy for life events, e.g. stress phases. Furthermore, chamber volume cannot be simply derived from septal spacing in forms comparable to Kosmoceras. Vogel numbers, a 3D parameter for chamber shape, of Kosmoceras are similar to other ammonoids (Arnsbergites, Amauroceras) and modern cephalopods (Nautilus, Spirula). Two methods to virtually document the suture line ontogeny, used to document phylogenetic relationships of larger taxonomic entities, were applied for the first time and seem a promising alternative to hand drawings. The curvature of the chamber surfaces increases during ontogeny due to increasing strength of ornamentation and septal complexity. As increasing curvature may allow for faster handling of cameral liquid, it could compensate for decreasing SA/V ratios through ontogeny.
    Language: English
    Type: article , doc-type:article
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