9,206 research outputs found
Stability of the proton-to-electron mass ratio
We report a limit on the fractional temporal variation of the
proton-to-electron mass ratio as, obtained by comparing the frequency of a
rovibrational transition in SF6 with the fundamental hyperfine transition in
Cs. The SF6 transition was accessed using a CO2 laser to interrogate spatial
2-photon Ramsey fringes. The atomic transition was accessed using a primary
standard controlled with a Cs fountain. This result is direct and model-free
Measurement of Synchrotron x-ray energies and line shapes using diffraction markers
Standard reference markers for accurate, reproducible synchrotron x-ray energies are obtained using a three Si crystal spectrometer. The first two crystals are in the monochromator and the third is used to obtain diffraction markers which monitor the energy. Then for any value of the glancing angle on the reference Si crystal the energy for the (333) diffraction must occur at 3/4 that of the (444) and 3/5 of that for the (555). This establishes for the first time an absolute synchrotron energy scale. Higher-order diffractions are used to determine excitation line profiles. We conclude that the use of reference diffractions is necessary to measure reproducible x-ray energies and to analyze the incident photons\u27 line profile. The detection of diffractions near the edge of measurement and near the Cu edge will provide a fast secondary standard which will allow comparison of edge data between different laboratories. The diffraction profiles will allow the proper analysis of spectral line widths
Magnetic Lensing near Ultramagnetized Neutron Stars
Extremely strong magnetic fields change the vacuum index of refraction. This
induces a lensing effect that is not unlike the lensing phenomenon in strong
gravitational fields. The main difference between the two is the polarization
dependency of the magnetic lensing, a behaviour that induces a handful of
interesting effects. The main prediction is that the thermal emission of
neutron stars with extremely strong magnetic fields is polarized - up to a few
percent for the largest fields known. This potentially allows a direct method
for measuring their magnetic fields.Comment: To appear in MNRAS, 12 pages, 9 figure
General Relativistic Contributions in Transformation Optics
One potentially realistic specification for devices designed with
transformation optics is that they operate with high precision in curved
space-time, such as Earth orbit. This raises the question of what, if any, role
does space-time curvature play in determining transformation media?
Transformation optics has been based on a three-vector representation of
Maxwell's equations in flat Minkowski space-time. I discuss a completely
covariant, manifestly four-dimensional approach that enables transformations in
arbitrary space-times, and demonstrate this approach for stable circular orbits
in the spherically symmetric Schwarzschild geometry. Finally, I estimate the
magnitude of curvature induced contributions to satellite-borne transformation
media in Earth orbit and comment on the level of precision required for
metamaterial fabrication before such contributions become important.Comment: 14 pages, 3 figures. Latest version has expanded analysis,
corresponds to published versio
The role of novel Rydberg-valence behaviour in the non-adiabatic dynamics of tertiary aliphatic amines
Time-resolved photoelectron imaging was used to study non-adiabatic relaxation dynamics in N,N-dimethylisopropylamine, N,N-dimethylpropylamine and N-methylpyrrolidine following excitation at 200 nm.</p
Negotiating daughterhood and strangerhood: retrospective accounts of serial migration
Most considerations of daughtering and mothering take for granted that the subjectivities of mothers and daughters are negotiated in contexts of physical proximity throughout daughtersâ childhoods. Yet many mothers and daughters spend periods separated from each other, sometimes across national borders. Globally, an increasing number of children experience life in transnational families.
This paper examines the retrospective narratives of four women who were serial migrants as children (whose parents migrated before they did) . It focuses on their accounts of the reunion with their mothers and how these fit with the ways in which they construct their mother-daughter relationships. We take a psychosocial approach by using a psychoanalytically-informed reading of these narratives to acknowledge the complexities of the attachments produced in the context of migration and to attend to the multi-layered psychodynamics of the resulting relationships. The paper argues that serial migration positioned many of the daughters in a conflictual emotional landscape from which they had to negotiate âstrangerhoodâ in the context of sadness at leaving people to whom they were attached in order to join their mothers (or parents). As a result, many were resistant to being positioned as daughters, doing daughtering and being mothered in their new homes
Born-Oppenheimer Approximation near Level Crossing
We consider the Born-Oppenheimer problem near conical intersection in two
dimensions. For energies close to the crossing energy we describe the wave
function near an isotropic crossing and show that it is related to generalized
hypergeometric functions 0F3. This function is to a conical intersection what
the Airy function is to a classical turning point. As an application we
calculate the anomalous Zeeman shift of vibrational levels near a crossing.Comment: 8 pages, 1 figure, Lette
E.P. Thompson and cultural sociology: questions of poetics, capitalism and the commons
There is currently a need for cultural sociology to readdress the work of humanistic and cultural Marxism. While more recently much of this work has been dismissed the appearance of more radical social movements and the on-going crisis of neoliberalism suggests that it still has much to tell us. In this respect, this article seeks to readdress the writing of historian E.P.Thompson arguing that his work on the class based and other social movements, poetics, critique of positivism and economic reason, utopia and work on the idea of the commons all has much to offer more contemporary scholarship. While the article recognises that the cultural Marxism of figures like Thompson can-not simply be resurrected it does continue to offer a number of critical insights lacking from other traditions within cultural sociology. By readdressing the internal complexity of Thompsonâs writing the argumentative strategy of this article suggests that cultural sociology needs to move beyond more simplistic understandings of cultural Marxism and more carefully explore what it has to offer
Thermodynamics of a black hole in a cavity
We present a unified thermodynamical description of the configurations
consisting on self-gravitating radiation with or without a black hole. We
compute the thermal fluctuations and evaluate where will they induce a
transition from metastable configurations towards stable ones. We show that the
probability of finding such a transition is exponentially small. This indicates
that, in a sequence of quasi equilibrium configurations, the system will remain
in the metastable states till it approaches very closely the critical point
beyond which no metastable configuration exists. Near that point, we relate the
divergence of the local temperature fluctuations to the approach of the
instability of the whole system, thereby generalizing the usual fluctuations
analysis in the cases where long range forces are present. When angular
momentum is added to the cavity, the above picture is slightly modified.
Nevertheless, at high angular momentum, the black hole loses most of its mass
before it reaches the critical point at which it evaporates completely.Comment: 27 pages, latex file, contains 3 figures available on request at
[email protected]
A review of clinical decision-making: Models and current research
Aims and objectives: The aim of this paper was to review the current literature with respect to clinical decision-making models and the educational application of models to clinical practice. This was achieved by exploring the function and related research of the three available models of clinical decision making: information processing model, the intuitive-humanist model and the clinical decision making model.
Background: Clinical decision-making is a unique process that involves the interplay between knowledge of pre-existing pathological conditions, explicit patient information, nursing care and experiential learning. Historically, two models of clinical decision making are recognised from the literature; the information processing model and the intuitive-humanist model. The usefulness and application of both models has been examined in relation the provision of nursing care and care related outcomes. More recently a third model of clinical decision making has been proposed. This new multidimensional model contains elements of the information processing model but also examines patient specific elements that are necessary for cue and pattern recognition.
Design: Literature review
Methods: Evaluation of the literature generated from MEDLINE, CINAHL, OVID, PUBMED and EBESCO systems and the Internet from 1980 â November 2005
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