6,685 research outputs found
Application of a low order panel method to complex three-dimensional internal flow problems
An evaluation of the ability of a low order panel method to predict complex three-dimensional internal flow fields was made. The computer code VSAERO was used as a basis for the evaluation. Guidelines for modeling internal flow geometries were determined and the effects of varying the boundary conditions and the use of numerical approximations on the solutions accuracy were studied. Several test cases were run and the results were compared with theoretical or experimental results. Modeling an internal flow geometry as a closed box with normal velocities specified on an inlet and exit face provided accurate results and gave the user control over the boundary conditions. The values of the boundary conditions greatly influenced the amount of leakage an internal flow geometry suffered and could be adjusted to eliminate leakage. The use of the far-field approximation to reduce computation time influenced the accuracy of a solution and was coupled with the values of the boundary conditions needed to eliminate leakage. The error induced in the influence coefficients by using the far-field approximation was found to be dependent on the type of influence coefficient, the far-field radius, and the aspect ratio of the panels
Delayed-choice quantum eraser for the undergraduate laboratory
In a delayed-choice quantum eraser, interference fringes are obtained by
erasing which-way information after the interfering particle has already been
irreversibly detected. Following an introductory review of delayed-choice
experiments and quantum erasure, we describe the experimental realization of an
optical delayed-choice quantum eraser, suitable for advanced undergraduates,
based on polarization-entangled pairs of single photons. In our experiment, the
delay of the erasure is implemented using two different setups. The first setup
employs an arrangement of mirrors to increase the optical path length of the
photons carrying which-way information. In the second setup, we use fiber-optic
cables to elongate the path of these photons after their passage through the
polarization analyzer but prior to their arrival at the detector. We compare
our results to data obtained in the absence of a delay and find excellent
agreement. This shows that the timing of the erasure is irrelevant, as also
predicted by quantum mechanics. The experiment can serve as a valuable
pedagogical tool for conveying the fundamentals of quantum mechanics.Comment: 13 pages, 5 figures, identical to published versio
Cardiovascular MRI in clinical trials: expanded applications through novel surrogate endpoints
Recent advances in cardiovascular magnetic resonance (CMR) now allow the accurate and reproducible measurement of many aspects of cardiac and vascular structure and function, with prognostic data emerging for several key imaging biomarkers. These biomarkers are increasingly used in the evaluation of new drugs, devices and lifestyle modifications for the prevention and treatment of cardiovascular disease. This review outlines a conceptual framework for the application of imaging biomarkers to clinical trials, highlights several important CMR techniques which are in use in randomised studies, and reviews certain aspects of trial design, conduct and interpretation in relation to the use of CMR
Observation of the quantum paradox of separation of a single photon from one of its properties
We report an experimental realization of the quantum paradox of the
separation of a single photon from one of its properties (the so-called
"quantum Cheshire cat"). We use a modified Sagnac interferometer with displaced
paths to produce appropriately pre- and postselected states of heralded single
photons. Weak measurements of photon presence and circular polarization are
performed in each arm of the interferometer by introducing weak absorbers and
small polarization rotations and analyzing changes in the postselected signal.
The absorber is found to have an appreciable effect only in one arm of the
interferometer, while the polarization rotation significantly affects the
signal only when performed in the other arm. We carry out both sequential and
simultaneous weak measurements and find good agreement between measured and
predicted weak values. In the language of Aharonov et al. and in the sense of
the ensemble averages described by weak values, the experiment establishes the
separation of a particle from one its properties during the passage through the
interferometer.Comment: 9 pages, 4 figures, identical to published versio
The Paraldor Project
Paraldor is an experiment in bringing the power of categorical languages to
lattice QCD computations. Our target language is Aldor, which allows the
capture of the mathematical structure of physics directly in the structure of
the code using the concepts of categories, domains and their
inter-relationships in a way which is not otherwise possible with current
popular languages such as Fortran, C, C++ or Java. By writing high level
physics code portably in Aldor, and implementing switchable machine dependent
high performance back-ends in C or assembler, we gain all the power of
categorical languages such as modularity, portability, readability and
efficiency.Comment: 4 pages, 2 figures, Lattice 2002 conference proceeding
Pioneer Anomaly and the Helicity-Rotation Coupling
The modification of the Doppler effect due to the coupling of the helicity of
the radiation with the rotation of the source/receiver is considered in the
case of the Pioneer 10/11 spacecraft. We explain why the Pioneer anomaly is not
influenced by the helicity-rotation coupling.Comment: LaTeX file, 1 figure, 6 pages, v2: note and figure added at the end
of the paper, to be published in Phys. Lett.
Recommended from our members
Re-evaluation of the first synthetic estrogen, 1-keto-1,2,3,4-tetrahydrophenanthrene, and bisphenol A, using both the ovariectomised rat model used in 1933 and additional assays
1-Keto-1,2,3,4-tetrahydrophenanthrene (THP-1) was reported by Cook et al in 1933 as the first synthetic estrogen. Estrogenic activity was assessed by the induction of vaginal cornification in ovariectomised rats. The corresponding 4-isomer (THP-4) was shown to be inactive. Both chemicals have been re-synthesised and assessed for hormonal activity. Each chemical bound weakly and to the same extent to isolated estrogen receptors, but only at high concentrations. However, they each lacked estrogenic or anti-estrogenic activity when evaluated in vitro using a yeast hER assay, and both failed to induce vaginal cornification or uterotrophic effects in ovariectomised rats. THP-1, and to a lesser extent THP-4, were shown to possess weak androgenic and anti-androgenic activity in vitro when evaluated using an hAR yeast assay. Estrogenic activity for bisphenol A (BPA) was subsequently demonstrated by Dodds and Lawson (1936) using the same ovariectomised rat protocol, and this activity has been confirmed and supplemented by positive uterotrophic effects for BPA in the same bioassays.
The present results illustrate the complexity of deriving conclusions regarding the hormonal activities of chemicals. First, some activities observed in isolated hormonal receptor binding assays may not be expressed in functional hormonal assays. This indicates the need for functional hormonal assays in any screening programme. Second, that activities observed for a chemical in one hormonal assay may not be reflected in related hormonal assays. This indicates the need to define assay protocols with some precision when incorporating them into screening batteries. Finally, that some literature reports of hormonal activity for chemicals may not be capable of independent confirmation under apparently identical conditions of test. This illustrates the need to use lists of hormonally active chemicals with car
Fear and Trembling at the Court: Dimensions of Understanding in the Supreme Court\u27s Religion Jurisprudence
Amine-terminated nanoparticle films: pattern deposition by a simple nanostencilling technique and stability studies under X-ray irradiation
Exploring the surface chemistry of nanopatterned amine-terminated nanoparticle films.</p
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