4,239 research outputs found
Buckling of imperfect cylinders under axial compression
Donnell equations, Newton method, and numerical solution applied to buckling of imperfect cylinders under axial compressio
3-manifolds with(out) metrics of nonpositive curvature
In the context of Thurstons geometrisation program we address the question
which compact aspherical 3-manifolds admit Riemannian metrics of nonpositive
curvature. We show that non-geometric Haken manifolds generically, but not
always, admit such metrics. More precisely, we prove that a Haken manifold
with, possibly empty, boundary of zero Euler characteristic admits metrics of
nonpositive curvature if the boundary is non-empty or if at least one atoroidal
component occurs in its canonical topological decomposition. Our arguments are
based on Thurstons Hyperbolisation Theorem. We give examples of closed
graph-manifolds with linear gluing graph and arbitrarily many Seifert
components which do not admit metrics of nonpositive curvature.Comment: 16 page
The Great Big Doorstep Program
Program for the play Great Big Doorstep from New Rochelle College in 1944.https://digitalcommons.usm.maine.edu/giguere-early-life-and-education/1077/thumbnail.jp
A Note on Real Tunneling Geometries
In the Hartle-Hawking ``no boundary'' approach to quantum cosmology, a real
tunneling geometry is a configuration that represents a transition from a
compact Riemannian spacetime to a Lorentzian universe. I complete an earlier
proof that in three spacetime dimensions, such a transition is ``probable,'' in
the sense that the required Riemannian geometry yields a genuine maximum of the
semiclassical wave function.Comment: 5 page
The nature of emotional support and counselling provision for people with sight loss in the United Kingdom
People with sight loss in the United Kingdom are known to have lower levels of emotional wellbeing and to be at higher risk of depression. Consequently ‘having someone to talk to’ is an important priority for people with visual impairment. An on-line survey of the provision of emotional support and counselling for people affected by sight loss across the UK was undertaken. The survey was distributed widely and received 182 responses. There were more services offering ‘emotional support’, in the form of listening and information and advice giving, than offered ‘counselling’. Services were delivered by providers with differing qualifications in a variety of formats. Waiting times were fairly short and clients presented with a wide range of issues. Funding came from a range of sources, but many felt their funding was vulnerable. Conclusions have been drawn about the need for a national standardised framework for the provision of emotional support and counselling services for blind and partially sighted people in the U
Time-Resolved Ultrafast Transient Polarization Spectroscopy to Investigate Nonlinear Processes and Dynamics in Electronically Excited Molecules on the Femtosecond Time Scale
We report a novel experimental technique to investigate ultrafast dynamics in
photoexcited molecules by probing the third-order nonlinear optical
susceptibility. A non-colinear 3-pulse scheme is developed to probe the
ultrafast dynamics of excited electronic states using the optical Kerr effect
by time-resolved polarization spectroscopy. Optical heterodyne and optical
homodyne detection are demonstrated to measure the third-order nonlinear
optical response for the S1 excited state of liquid nitrobenzene, which is
populated by 2-photon absorption of a 780 nm 35 fs excitation pulse.Comment: 12 pages, 4 figures. Changes from previous version: added panel
labels to figures 3-
The Generalized Ricci Flow for 3D Manifolds with One Killing Vector
We consider 3D flow equations inspired by the renormalization group (RG)
equations of string theory with a three dimensional target space. By modifying
the flow equations to include a U(1) gauge field, and adding carefully chosen
De Turck terms, we are able to extend recent 2D results of Bakas to the case of
a 3D Riemannian metric with one Killing vector. In particular, we show that the
RG flow with De Turck terms can be reduced to two equations: the continual Toda
flow solved by Bakas, plus its linearizaton. We find exact solutions which flow
to homogeneous but not always isotropic geometries
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