8,137 research outputs found
Guyasuta: Warrior, Estate, and Home to Boy Scouts
For nearly a century, Camp Guyasuta has been “an ideal place for Boy Scouts to live out their Handbook, to dream and be inspired and become good Americans.” Situated on roughly 130 acres in a deep valley between Aspinwall and Sharpsburg, Guyasuta is the primary camp for the Boy Scouts of America (BSA) in the newly formed Laurel Highlands Council. But before Guyasuta was established in 1918, the land was home to multiple generations of a prominent Pittsburgh family. It also served as the burial ground for a famous Native American. It has hosted lively parties, protected wildlife as a sanctuary, and was the center of a contentious battle between the mighty Pennsylvania Railroad and a “silver-haired old woman.
Topological censorship for Kaluza-Klein space-times
The standard topological censorship theorems require asymptotic hypotheses
which are too restrictive for several situations of interest. In this paper we
prove a version of topological censorship under significantly weaker
conditions, compatible e.g. with solutions with Kaluza-Klein asymptotic
behavior. In particular we prove simple connectedness of the quotient of the
domain of outer communications by the group of symmetries for models which are
asymptotically flat, or asymptotically anti-de Sitter, in a Kaluza-Klein sense.
This allows one, e.g., to define the twist potentials needed for the reduction
of the field equations in uniqueness theorems. Finally, the methods used to
prove the above are used to show that weakly trapped compact surfaces cannot be
seen from Scri.Comment: minor correction
Superconformal Technicolor
In supersymmetric theories with a strong conformal sector, soft supersymmetry
breaking at the TeV scale naturally gives rise to confinement and chiral
symmetry breaking at the same scale. We investigate models where such a sector
dynamically breaks electroweak symmetry. We consider two scenarios, one where
the strong dynamics induces vacuum expectation values for elementary Higgs
fields, and another where the strong dynamics is solely responsible for
electroweak symmetry breaking. In both cases there is no fine tuning required
to explain the absence of a Higgs boson below the LEP bound, solving the
supersymmetry naturalness problem. A good precision electroweak fit can be
obtained, and quark and lepton masses are generated without flavor-changing
neutral currents. Electroweak symmetry breaking may be dominated either by the
elementary Higgs bosons or by the strong dynamics. In addition to standard
superymmetry collider signals, these models predict production of multiple
heavy standard model particles (t, W, Z, and b) from decays of resonances in
the strong sector.Comment: 4 pages; v2: minor changes, references adde
Erosion-corrosion behaviour of Zirconia WC-6Co, WC-6Ni and SS316
The current study investigates a ceramic, two cermets and a metal under solid-liquid impingement with 3.5% NaCl and 150mg/l hydraulic fracturing sand at two extreme angles of impact, 90° and 20°. The materials tested were Zirconia, sintered WC-6Co, sintered WC-6Ni and SS316. Each material was exposed to a testing regime using re-circulating impinging jet apparatus with a velocity of 19m/s and one hour duration. The electrochemical properties of the materials were investigated in-situ through anodic and cathodic polarisation and application of cathodic protection. Post experimental analysis of the degraded surface was completed using Scanning Electron Microscopy (SEM) and Optical 3D Imaging. Zirconia exhibited a brittle response to erosion-corrosion testing with the mass loss at 90° being fifty times greater than the negligible mass loss at 20°. WC-6Co and WC-6Ni both outperformed SS316 under all solid-liquid impingement erosion-corrosion testing regimes. WC-6Ni exhibited slightly better erosion-corrosion resistance over WC-6Co at both 90° and 20°. SS316 had the best corrosion resistance and showed passivation during anodic polarisations in solid-liquid impingement conditions. The nickel binder increased the corrosion resistance of WC-6Ni over WC-6Co. Cathodic protection was successfully applied on sintered WC-6Co and SS316 isolating the key components of erosion-corrosion
The Cosmic Censor Forbids Naked Topology
For any asymptotically flat spacetime with a suitable causal structure
obeying (a weak form of) Penrose's cosmic censorship conjecture and satisfying
conditions guaranteeing focusing of complete null geodesics, we prove that
active topological censorship holds. We do not assume global hyperbolicity, and
therefore make no use of Cauchy surfaces and their topology. Instead, we
replace this with two underlying assumptions concerning the causal structure:
that no compact set can signal to arbitrarily small neighbourhoods of spatial
infinity (``-avoidance''), and that no future incomplete null geodesic is
visible from future null infinity. We show that these and the focusing
condition together imply that the domain of outer communications is simply
connected. Furthermore, we prove lemmas which have as a consequence that if a
future incomplete null geodesic were visible from infinity, then given our
-avoidance assumption, it would also be visible from points of spacetime
that can communicate with infinity, and so would signify a true naked
singularity.Comment: To appear in CQG, this improved version contains minor revisions to
incorporate referee's suggestions. Two revised references. Plain TeX, 12
page
On the Gannon-Lee Singularity Theorem in Higher Dimensions
The Gannon-Lee singularity theorems give well-known restrictions on the
spatial topology of singularity-free (i.e., nonspacelike geodesically
complete), globally hyperbolic spacetimes. In this paper, we revisit these
classic results in the light of recent developments, especially the failure in
higher dimensions of a celebrated theorem by Hawking on the topology of black
hole horizons. The global hyperbolicity requirement is weakened, and we expand
the scope of the main results to allow for the richer variety of spatial
topologies which are likely to occur in higher-dimensional spacetimes.Comment: 13 pages, no figures, to appear in Class. Quantum Gra
Standing on the Shoulders of Giants: The Cleft Palate-Craniofacial Journal (1964-1989)Electronic Archive
Current research and clinical practice in cleft palate and craniofacial disorders “stands on the shoulders of giants” who came before us. To enable thirty years of seminal research articles to become digitally available to a worldwide community of students, scholars, and clinicians, a collaboration was forged in 2004 between University of Pittsburgh’s Digital Research Library (DRL) and ACPA, (with the agreement of Allen Press), to create an electronic archive of the first thirty years of the Cleft Palate Craniofacial Journal . The work was performed pro bono, by all parties
Artificial neural network prediction of weld distortion rectification using a travelling induction coil
An experimental investigation has been carried out to determine the applicability of an induction heating process with a travelling induction coil for the rectification of angular welding distortion. The results obtained from experimentation have been used to create artificial neural network models with the ability to predict the welding induced distortion and the distortion rectification achieved using a travelling induction coil. The experimental results have shown the ability to reduce the angular distortion for 8 mm and 10 mm thick DH36 steel plate and effectively eliminate the distortion on 6 mm thick plate. Results for 6 mm plate also show the existence of a critical induction coil travel speed at which maximum corrective bending occurs. Artificial neural networks have demonstrated the ability to predict the final distortion of the plate after both welding and induction heating. The models have also been used as a tool to determine the optimum speed to minimise the resulting distortion of steel plate after being subjected to both welding and induction heating processes
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