9,704 research outputs found
An optimised scalable synthesis of H2O@C60and a new synthesis of H2@C60
New high-yielding synthetic routes to the small-molecule endofullerenes H2O@C60, D2O@C60 and H2@C60 are described. The use of high temperatures and pressures for the endohedral molecule incorporation are avoided. A new partial closure step using PPh3, and final suturing using a novel Diels–Alder/retro-Diels–Alder sequence are amongst the advances reported
The homotopy invariance of the string topology loop product and string bracket
Let M be a closed, oriented, n -manifold, and LM its free loop space.
Chas and Sullivan defined a commutative algebra structure in the homology of
LM, and a Lie algebra structure in its equivariant homology. These structures
are known as the string topology loop product and string bracket, respectively.
In this paper we prove that these structures are homotopy invariants in the
following sense.
Let f : M_1 \to M_2 be a homotopy equivalence of closed, oriented n
-manifolds. Then the induced equivalence, Lf : LM_1 \to LM_2 induces a ring
isomorphism in homology, and an isomorphism of Lie algebras in equivariant
homology. The analogous statement also holds true for any generalized homology
theory h_* that supports an orientation of the M_i 's.Comment: 21 pages, 2 figures final version published in Journal of Topolog
An investigation into the effects of social network strength and stress level on cardiovascular responses in colleges students
The present study investigated the effects of strength of social network on physiological stress during a cognitive task. Participants were randomly assigned to a timed or untimed word search task. The dependent variables were heart rate and participants\u27 perceptions of the difficulty of their word search task. Participants in the high stress condition reported performing significantly worse on the word search task than those in the low stress condition. Participants perceived the task to be less difficult when in the high social network group as compared to the low social network group. While there were no significant findings for the heart rate measure, there was an interesting pattern. For the high stress condition, participants with a low social network had slightly higher heart rates than participants with a high social network
Fault tolerant architectures for integrated aircraft electronics systems
Work into possible architectures for future flight control computer systems is described. Ada for Fault-Tolerant Systems, the NETS Network Error-Tolerant System architecture, and voting in asynchronous systems are covered
Fault tolerant architectures for integrated aircraft electronics systems, task 2
The architectural basis for an advanced fault tolerant on-board computer to succeed the current generation of fault tolerant computers is examined. The network error tolerant system architecture is studied with particular attention to intercluster configurations and communication protocols, and to refined reliability estimates. The diagnosis of faults, so that appropriate choices for reconfiguration can be made is discussed. The analysis relates particularly to the recognition of transient faults in a system with tasks at many levels of priority. The demand driven data-flow architecture, which appears to have possible application in fault tolerant systems is described and work investigating the feasibility of automatic generation of aircraft flight control programs from abstract specifications is reported
ELSA: An Integrated, Semi-Automated Nebular Abundance Package
We present ELSA, a new modular software package, written in C, to analyze and
manage spectroscopic data from emission-line objects. In addition to
calculating plasma diagnostics and abundances from nebular emission lines, the
software provides a number of convenient features including the ability to
ingest logs produced by IRAF's splot task, to semi-automatically merge spectra
in different wavelength ranges, and to automatically generate various data
tables in machine-readable or LaTeX format. ELSA features a highly
sophisticated interstellar reddening correction scheme that takes into account
temperature and density effects as well as He II contamination of the hydrogen
Balmer lines. Abundance calculations are performed using a 5-level atom
approximation with recent atomic data, based on R. Henry's ABUN program.
Improvements planned in the near future include use of a three-region
ionization model, similar to IRAF's nebular package, error propagation, and the
addition of ultraviolet and infrared line analysis capability. Detailed
documentation for all aspects of ELSA are available at
http://www.williams.edu/Astronomy/research/PN .Comment: 2 pages, contributed paper, IAU Symp. 234, Planetary Nebulae in Our
Galaxy and Beyon
Understanding and managing three-dimensional/four-dimensional model implementations at the project team level
This paper introduces an extant, theoretical, social-psychological model that explains the sense-making processes of project managers confronted with a new technology to improve our understanding of project-based innovation processes. The model represents the interlinked processes through which project managers decide to implement new technologies on their projects according to the outcomes of these sense-making processes. The paper validates the model against observations gathered in four case studies of technology implementation on construction projects. Doing so, it assesses the general usefulness of the model to explain the success of technology implementation dynamics in project teams. The paper also derives a number of management suggestions from the model: for example, project managers should focus squarely on the immediate benefits of the technology in improving work processes on the project instead of focusing on long-term strategic firm or industry benefits
Phase space spinor amplitudes for spin 1/2 systems
The concept of phase space amplitudes for systems with continuous degrees of
freedom is generalized to finite-dimensional spin systems. Complex amplitudes
are obtained on both a sphere and a finite lattice, in each case enabling a
more fundamental description of pure spin states than that previously given by
Wigner functions. In each case the Wigner function can be expressed as the star
product of the amplitude and its conjugate, so providing a generalized Born
interpretation of amplitudes that emphasizes their more fundamental status. The
ordinary product of the amplitude and its conjugate produces a (generalized)
spin Husimi function. The case of spin-\half is treated in detail, and it is
shown that phase space amplitudes on the sphere transform correctly as spinors
under under rotations, despite their expression in terms of spherical
harmonics. Spin amplitudes on a lattice are also found to transform as spinors.
Applications are given to the phase space description of state superposition,
and to the evolution in phase space of the state of a spin-\half magnetic
dipole in a time-dependent magnetic field.Comment: 19 pages, added new results, fixed typo
Embedding, compression and fiberwise homotopy theory
Given Poincare spaces M and X, we study the possibility of compressing
embeddings of M x I in X x I down to embeddings of M in X. This results in a
new approach to embedding in the metastable range both in the smooth and
Poincare duality categories.Comment: Published by Algebraic and Geometric Topology at
http://www.maths.warwick.ac.uk/agt/AGTVol2/agt-2-15.abs.htm
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