Search Results - (Author, Cooperation:T. Seeger)

2013-02-22

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Aging/genetics/pathology/*physiology ; Animals ; Apoptosis ; DNA Damage ; Fibrosis/genetics/pathology ; Gene Deletion ; *Gene Expression Regulation ; Gene Knockout Techniques ; Genetic Therapy ; Heart/*physiology ; Mice ; Mice, Inbred C57BL ; MicroRNAs/*genetics/metabolism ; Myocardial Infarction/genetics/pathology/therapy ; Myocardium/cytology/*metabolism/pathology ; Myocytes, Cardiac/cytology/metabolism/pathology ; Substrate Specificity ; Telomere/genetics/metabolism

2018-05-04

American Society of Hematology (ASH)

0006-4971

1528-0020

Biology

Medicine

Myeloid Neoplasia

1077-3118

AIP Digital Archive

Physics

We demonstrate a new technique for measuring the desorption products as a function of time during ultrafast laser-induced desorption. Measurements of the evaporation of Ga atoms and desorption of surface oxides from picosecond laser-heated GaAs are presented.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Arrays of aligned nanotubes of large diameter (100–250 nm) are synthesized by pyrolyzing a jet (spray) solution of Fe(C5H5)2 and C6H6 in an Ar atmosphere at relatively low temperatures (850 °C). The tubular structures consist of highly crystalline nested graphene cylinders (〈200 concentric tubes) with tips that are usually open. Raman studies confirm the high degree of perfection of these "thick" structures. Tube diameter, degree of alignment, and crystallinity can be controlled by varying the Ar flow rate and the Fe:C ratio within the precursor solution. Based on these observations a possible growth mechanism is suggested. This low cost route for the synthesis of carbon nanotubes is advantageous due to the absence of H2 as a carrier gas and the low pyrolytic temperature. © 2000 American Institute of Physics.

Electronic Resource

1460-2695

Blackwell Publishing Journal Backfiles 1879-2005

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Electronic Resource

1460-2695

Blackwell Publishing Journal Backfiles 1879-2005

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Opening and closure of short cracks has been examined experimentally using small strain gauges fixed to unnotched specimens very close to short fatigue cracks. The results of completely reversed tension-compression constant amplitude tests are that crack opening stresses decrease with increasing stress amplitude and that crack closure occurs at nearly the same strain as crack opening. In variable amplitude loading the crack is subjected to a low crack opening level resulting from larger cycles. Based on the results of this experimental investigation some simple approximation formulas are proposed with which decrease as well as increase of crack opening levels can be described. Using these formulas it is possible to compute crack opening strains for any load sequence. The findings of the investigations have been merged to build an algorithm for the prediction of fatigue lives to initiation of cracks of technical sizes in case of variable amplitude loading. The improvement in accuracy of life predictions compared to results of an existing damage accumulation concept is demonstrated for two materials and two load sequences.

Electronic Resource

1460-2695

Blackwell Publishing Journal Backfiles 1879-2005

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Electronic Resource

1460-2695

Blackwell Publishing Journal Backfiles 1879-2005

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Abstract— The opening and closure behaviour of surface, corner and through-thickness cracks in thin notched plates of FeE460 (Kt= 2.5) and A15086 (Kt= 3.4) was experimentally studied. The cracks were initiated and examined under uniaxial fully reversed constant amplitude and two-step loading. Crack opening load values were measured during crack growth in notch sections with a nonuniform stress distribution using small strain gauges glued to the specimen surface, very close to the crack tip. The results represent a comprehensive set of experimental data for crack opening load values in dependence on crack lengths a, c and load level including the influence of overloads and covering all types of cracks. The results indicate uniform relationships between crack opening load levels and all crack types. Crack opening and closure occur at nearly the same strain level, which depends on the applied load level. The crack opening load values measured at large notched specimens differ from those measured at similar smaller specimens because of the different local stress gradients.

Electronic Resource

1460-2695

Blackwell Publishing Journal Backfiles 1879-2005

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Abstract— An analytical procedure for the prediction of opening load levels for cracks growing from notches is presented, and estimates are made using experimental crack opening load data. The procedure is based on McClung's original procedure for estimating the local elastic-plastic stress—strain situation at the point of a hypothetical crack tip in a notched but uncracked body. A crack opening stress value for a crack in an urmotched body under the same stress—strain condition is then predicted. The corresponding opening load level for the crack stress-strain configuration in the notched but uncracked body is then predicted with a simple backward calculation. For the evaluation of the elastic-plastic stress distribution, simple analytical relationships, such as Neuber's rule, are used. Estimation of the crack opening stress level is performed using various crack opening stress formulae reported in the literature for cracks in unnotched specimens under a uniform stress distribution. The accuracy of all the investigated crack opening stress formulae within the scope of the presented procedure is checked, and discussed in detail using experimental data sets for opening load levels of comer cracks and through-thickness cracks in notched specimens of FeE460 and A15086. The predicted results using Newman's crack opening stress formulae, simply modified in respect to the definition of the flow stress, have been identified to be qualitatively and quantitatively consistent with the trends observed in experimental crack opening data.

Electronic Resource

1460-2695

Blackwell Publishing Journal Backfiles 1879-2005

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

In this contribution the results of an experimental investigation into the fatigue crack growth of welded tube-to-plate specimens of steel StE 460 under bending, torsion, and combined in-phase and out-of-phase bending/torsion loading are presented. The tests were performed at stress ratios of R = −1 and R = 0. The residual stresses were reduced by thermal stress relief. The fatigue crack development is compared with the prediction on the crack growth rates of Paris. Individual stress intensity factors for the semielliptical surface cracks in the tube-flange specimens are approximated on a weight function analogy using the published solutions of other workers.

Electronic Resource

1460-2695

Blackwell Publishing Journal Backfiles 1879-2005

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Abstract— Based on fracture mechanics a model has been developed for predicting the fatigue lifetime to initiate a crack of technical size (2a∼ .5mm) in engineering components under multiaxial-proportional loading. Using material data determined for uniaxial loading, the model describes and evaluates the elasto-plastic multiaxial notch stresses and strains using the effective range of the J-integral, ΔJeff, as a crack tip parameter. Mean stresses, load sequence effects and various modes of crack propagation due to variable amplitude loading with individual multiaxiality ratios can be explicitly considered. The prediction accuracy of the model is demonstrated using experimental fatigue life data determined with unnotched specimens of FeE460 and A15083 for proportional fully-reversed constant and variable amplitude loading with various multiaxiality ratios.

Electronic Resource

0031-9422

Bartramia pomiformis ; Bartramiaceae ; Musci ; ^1H NMR. ; ^1^3C NMR ; anhydro-bartramiaflavone ; bartramiafiavone ; biflavonoids

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Electronic Resource

0022-3956

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Medicine

Electronic Resource

0031-9422

2,3-dihydro-3',3-biapigenin ; 3',3 - biapigenin ; 3',3-binaringenin ; Brachytheciaceae ; Homalothecium lutescens ; Musci ; biflavonoids.

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Electronic Resource

1573-2673

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Electronic Resource

1573-2673

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Electronic Resource

1573-2673

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Electronic Resource

0933-5137

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Fatigue Life Estimation for Surface Strengthened Specimens Based on Local Elastic-Plastic Stresses and StrainsModels are proposed for an engineering approach to the fatigue life calculation for surface-strengthened components. Input data for the calculation can be obtained from total strain controlled tests on polished specimens under constant amplitude loading, measurements of local hardness and residual stresses and in special cases from finite element analysis. For two different combinations of surface-strengthening procedure and base material fatigue tests were carried out on smooth and notched specimens under axial loading. Numerical and experimental results are compared.

Es werden Modelle für eine ingenieurmäßige Lebensdauerberechnung randschichtverfestigter Bauteile beschrieben. Totaldehnungskontrollierte Einstufenversuche an unbehandelten Proben, Härte und Eigenspannungsmessungen sowie in bestimmten Fällen auch FE-Analysen dienen zur Bestimmung der Eingabedaten für die Rechenmodelle. Für zwei verschiedene Kombinationen von Randschichtverfestigungsverfahren und Grundwerkstoff wurden Schwingfestigkeitsversuche an ungekerbten und gekerbten axial belasteten Proben durchgeführt. Berechnungs- und Versuchsergebnisse werden gegenübergestellt.

17 Ill.

Electronic Resource

0933-5137

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

On some recent crack initiation life prediction procedures for cyclic loaded members based on local material behaviourA critical review of some recently suggested procedures is given. Distinction is made between the procedure according to the basic scheme and the modified procedures. The first one is based on three fundamentals - Load-Notch Strain Relation, - Stress-Strain Law of the Material, - Damage and Failure of the Material. The modified procedures additionally take into account the cyclic behavior of the member. The modified procedures additionally take into account the cyclic behavior of the member. The three fundamentals are described, especially the two latter concerning material behavior. The transferability of this behavior as investigated by means of smooth specimens to that of the notch root element is discussed briefly. The various procedures are explained and the quality of their modifications is reviewed. Finally possible improvements of the three fundamentals and of the transferability are pointed out. Modifications should only be made within those fundamentals, where results of the calculation according to the basic scheme deviate from experimental results. In order to find the deviations, each fundamental must be checked separately.

Es wird ein kritischer Überblick über die derzeit bekannten neueren Berechnungsverfahren gegeben. Unterschieden wird zwischen dem Verfahren nach dem Grundschema und den modifizierten Verfahren. Das erstere arbeitet auf der Grundlage der drei Bausteine - „Gesetzmäßigkeit für den Zusammenhang zwischen äußerer Belastung und Kerbgrundbeanspruchung“, - „zyklisches Spannungs- Dehnungsverhalten des Werkstoffes“ und - „Schädigung und Versagen des Werkstoffes“. Die modifizierten Verfahren verwenden zusätzlich Kenntnisse über das zyklische Bauteilverhalten. Zunächst werden die drei Bausteine, insbesondere die beiden letzten, die das Werkstoffverhalten betreffen, eingehend beschrieben. Danach wird die Frage nach der Übertragbarkeit des an glatten Proben ermittelten Werkstoffverhaltens auf das Verhalten des Kerbgrundelementes erörtert. Die Berechnungsverfahren werden erläutert und bewertet. Zum Abschluß werden Verbesserungsmöglichkeiten aufgezeigt, die die drei Bausteine sowie die Übertragbarkeit betreffen. Es wird gefordert, daß bei den modifizierten Verfahren die Modifikationen nur in den Bausteinen vorgenommen werden, in denen bei der Rechnung nach dem Grundschema Fehler entstehen. Der Nachweis solcher Fehler muß durch die Überprüfung der einzelnen Bausteine erbracht werden.

10 Ill.

Electronic Resource

0933-5137

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Evaluation of Recent Models for Short Fatigue CracksIn the present study some new procedures for the evaluation of the propagation behavior of small cracks at notches which were originally proposed by T. H. Topper et al. and by K. J. Miller et al. are considered. They are presented in a manner that they can immediately be used for practical applications. The basis of the procedures and their ranges in application are considered and they are compared to conventional fracture mechanics analyses.In a second part of the study still existing limitations in the physical basis of the procedures are outlined and some aspects regarding the extension of the range in application of the procedures to variable amplitude loading histories are given.

In der vorliegenden Arbeit werden neuere im Schrifttum mitgeteilte Methoden (Verfahren nach T. H. Topper u. Mitarbeiter und nach K. J. Miller und Mitarbeiter) zur Beschreibung des Ausbreitungsverhaltens kleiner Risse an Kerben betrachtet und in der Weise aufbereitet, daß sie unmittelbar in der Praxis anwendbar sind. Es erfolgt eine ausführliche Darstellung der Grundlagen und des Anwendungsbereichs der Methoden, ferner ein Vergleich mit konventionellen Lösungsansätzen auf der Grundlage der linear-elastischen Bruchmechanik (LEFM).Anschließend werden die derzeit noch bestehenden Beschränkungen in den physikalischen Grundlagen der betrachteten Methoden angegeben. Es werden Weiterentwicklungsschwerpunkte im Hinblick auf die allgemeine Anwendung der Methoden auf Betriebsfestigkeitsprobleme aufgezeigt.

16 Ill.

Electronic Resource