414 research outputs found
Nondestructive Evaluation of Flaw Criticality in Graphite-Epoxy Laminates
An analytical and experimental study is conducted to determine criticality of interlaminar disbands by NDE methods. Criticality of such flaws in a shear environment (action of shear near support) is defined in terms of crack propagation and is analyzed by principles and methods of fracture mechanics. Growth of disbands under cyclic loading is also being studied. Fajlure under compressive loading in presence of a disband is defined in terms of buckling and an elastic stability analysis is utilized for assessing criticality. Analytical predictions are compared with experimental results in both cases
Failure Mode Predictions in the Compressive Response of Laminated Composites
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106434/1/AIAA2013-1724.pd
Cardioprotection by systemic dosing of thymosin beta four following ischemic myocardial injury
Thymosin beta 4 (TĪ²4) was previously shown to reduce infarct size and improve contractile performance in chronic myocardial ischemic injury via two phases of action: an acute phase, just after injury, when TĪ²4 preserves ischemic myocardium via antiapoptotic or anti-inflammatory mechanisms; and a chronic phase, when TĪ²4 activates the growth of vascular or cardiac progenitor cells. In order to differentiate between the effects of TĪ²4 during the acute and during the chronic phases, and also in order to obtain detailed hemodynamic and biomarker data on the effects of TĪ²4 treatment suitable for use in clinical studies, we tested TĪ²4 in a rat model of chronic myocardial ischemia using two dosing regimens: short term dosing (TĪ²4 administered only during the first 3 days following injury), and long term dosing (TĪ²4 administered during the first 3 days following injury and also every third day until the end of the study). TĪ²4 administered throughout the study reduced infarct size and resulted in significant improvements in hemodynamic performance; however, chamber volumes and ejection fractions were not significantly improved. TĪ²4 administered only during the first 3 days following injury tended to reduce infarct size, chamber volumes and improve hemodynamic performance. Plasma biomarkers of myocyte injury were significantly reduced by TĪ²4 treatment during the acute injury period, and plasma ANP levels were significantly reduced in both dosing groups. Surprisingly, neither acute nor chronic TĪ²4 treatment significantly increased blood vessel density in peri-infarct regions. These results suggest the following: repeated dosing may be required to achieve clinically measureable improvements in cardiac function post-myocardial infarction (MI); improvement in cardiac function may be observed in the absence of a high degree of angiogenesis; and that plasma biomarkers of cardiac function and myocardial injury are sensitive pharmacodynamic biomarkers of the effects of TĪ²4
Double-slit interference pattern from single-slit screen and its gravitational analogues
The double slit experiment (DSE) is known as an important cornerstone in the
foundations of physical theories such as Quantum Mechanics and Special
Relativity. A large number of different variants of it were designed and
performed over the years. We perform and discuss here a new verion with the
somewhat unexpected results of obtaining interference pattern from single-slit
screen. This outcome, which shows that the routes of the photons through the
array were changed, leads one to discuss it, using the equivalence principle,
in terms of geodesics mechanics. We show using either the Brill's version of
the canonical formulation of general relativity or the linearized version of it
that one may find corresponding and analogous situations in the framework of
general relativity.Comment: 51 pages, 12 Figures five of them contain two subfigures and thus the
number of figures is 17, 1 Table. Some minor changes introduced, especially,
in the reference
The band-gap structure and the singular character of the bounded large array of potential barriers
The bounded one dimensional multibarrier potential shows signs of chaos,
phase transition and a transmission probability of unity for certain values of
its total length and the ratio of total interval to total width. Like
the infinite Kronig-Penney system, which is arranged along the whole spatial
region, the bounded multibarrier potential has a band-gap structure in its
energy spectrum. But unlike the Kronig-Penney system, in which the gaps
disappear for large energies, these gaps do not disappear for certain values of
and . The energy is discontinuous even in parts of the spectrum with no
gaps at all. These results imply that the energy spectrum of the bounded
multibarrier system is singular.Comment: 22 pages, 7 PS figures, former text removed and a new one inserte
The Interaction of Failure Modes in the Compression Response and Failure of Laminated Composites
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97075/1/AIAA2012-1895.pd
Christian Higher Education in Europe: A Historical Overview
The history of Christian higher education in Europe may be analyzed in terms of seven eras. From their medieval origins in scholasticism and the practical needs of students and rulers, universities passed through Renaissance humanism to a period of decay, yet remained substantially Christian in intent. The Enlightenment exercised a partially secularizing influence, and the neohumanist reaction against it also tended to dilute the faith. The recent era of the late 20th and early 21st centuries has been associated with the rise of postmodernism and the involvement of the state in the quest for relevance. A Christian response to contemporary circumstances is to engage with the cultural currents of the present day and, in drawing on the thought of John Henry Newman and Sir Walter Moberly, to ensure the integration of Christianity into higher education so that discussion of ultimate questions is informed by the Christian faith
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