443 research outputs found
Stress Distribution in Porcelain-Fused-to-Gold Crowns and Preparations Constructed with Photoelastic Plastics
Composite models representing porcelain-fused-to-gold restorations were constructed from photoelastic plastics. Better stress distributions resulted when the porcelain-gold joint was as far as feasible from the loading site, a bulk of gold was present on the lingual shoulder, and the porcelain-gold joint at the shoulder was 30° from the horizontal.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66999/2/10.1177_00220345710500053101.pd
A New Composite Restorative Based on a Hydrophobic Matrix
A hydrophobic restorative composite based on a fluorocarbon analog of an alkyl methacrylate and a bisphenol adduct was formulated into a one-paste system, which polymerized in the presence of blue light. Physical, mechanical, and water-related properties were determined. High contact angles and low water sorption were shown by the experimental composite. Capillary penetration of oral fluids around restorations, therefore, could be prevented in the presence of this highly hydrophobic surface. The physical and mechanical properties of the experimental composite were either comparable to or somewhat less favorable than commercial Bis-GMA composites.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67042/2/10.1177_00220345790580100401.pd
Yukawa couplings in intersecting D-brane models
We compute the Yukawa couplings among chiral fields in toroidal Type II
compactifications with wrapping D6-branes intersecting at angles. Those models
can yield realistic standard model spectrum living at the intersections. The
Yukawa couplings depend both on the Kahler and open string moduli but not on
the complex structure. They arise from worldsheet instanton corrections and are
found to be given by products of complex Jacobi theta functions with
characteristics. The Yukawa couplings for a particular intersecting brane
configuration yielding the chiral spectrum of the MSSM are computed as an
example. We also show how our methods can be extended to compute Yukawa
couplings on certain classes of elliptically fibered CY manifolds which are
mirror to complex cones over del Pezzo surfaces. We find that the Yukawa
couplings in intersecting D6-brane models have a mathematical interpretation in
the context of homological mirror symmetry. In particular, the computation of
such Yukawa couplings is related to the construction of Fukaya's category in a
generic symplectic manifold.Comment: 47 pages, using JHEP3.cls, 11 figures. Typos and other minor
corrections. References adde
Limit on Tau Neutrino Mass from
From a data sample of 29058
decays observed in the CLEO detector we derive a 95% confidence upper limit on
the tau neutrino mass of 28 MeV.Comment: 17 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Observation of hard scattering in photoproduction events with a large rapidity gap at HERA
Events with a large rapidity gap and total transverse energy greater than 5
GeV have been observed in quasi-real photoproduction at HERA with the ZEUS
detector. The distribution of these events as a function of the
centre of mass energy is consistent with diffractive scattering. For total
transverse energies above 12 GeV, the hadronic final states show predominantly
a two-jet structure with each jet having a transverse energy greater than 4
GeV. For the two-jet events, little energy flow is found outside the jets. This
observation is consistent with the hard scattering of a quasi-real photon with
a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil
Ergonomics and sustainability: Towards and embrace of complexity and emergence
Technology offers a promising route to a sustainable future, and ergonomics can serve a vital role. The argument of this article is that the lasting success of sustainability initiatives in ergonomics hinges on an examination of ergonomics' own epistemology and ethics. The epistemology of ergonomics is fundamentally empiricist and positivist. This places practical constraints on its ability to address important issues such as sustainability, emergence and complexity. The implicit ethical position of ergonomics is one of neutrality, and its positivist epistemology generally puts value-laden questions outside the parameters of what it sees as scientific practice. We argue, by contrast, that a discipline that deals with both technology and human beings cannot avoid engaging with questions of complexity and emergence and seeking innovative ways of addressing these issues.No Full Tex
The roles of the formal and informal sectors in the provision of effective science education
For many years, formal school science education has been criticised by students, teachers, parents and employers throughout the world. This article presents an argument that a greater collaboration between the formal and the informal sector could address some of these criticisms. The causes for concern about formal science education are summarised and the major approaches being taken to address them are outlined. The contributions that the informal sector currently makes to science education are identified. It is suggested that the provision of an effective science education entails an enhanced complementarity between the two sectors. Finally, there is a brief discussion of the collaboration and communication still needed if this is to be effective
- …