[en] A thin falling film is well suited to simultaneous heat and mass transfer because of the small thermal resistance through the film and because of the large contact surface achievable at low flow rates. The film enters as a smooth laminar flow and quickly transitions into small-amplitude wavy flow. The waves grown in length and amplitude and are identified as roll waves. This flow regime is termed wavy-laminar flow, and modern heat and mass transfer equipment operate in this complicated transition regime. Research published in open literature has shown the mass flow rate in the rollwaves to be about 10 to 20 times greater than that in the laminar substrate. As the film fully develops, the waves grow in mass and the film substrate thins because fluid is swept from the substrate by the secondary flows of the roll wave. Many studies have been conducted to measure and correlate the film thickness of wavy-laminar flows. Literature data show that Nusselt's theory for smooth laminar flow can over predict the film thickness by as much as 20% for certain wavy-laminar flow conditions. The hydrodynamics of falling films were therefore studied to measure the film thickness of a free-surface falling film and to better understand the parameters that affect the variations of the film thickness. A flow loop was set up for measuring the thickness, wave amplitude,and frequency of a film during hydrodynamic flow. Decreasing the pipe diameter caused the amplitude of the wavy flow to diminish. Measurements monitored from stations along the falling film showed a thinning of film thickness. Fully developed flow required large starting lengths of about 0.5 m. The film thickness increases as the Reynolds number (Re) increases. Increasing the Kapitza number (Ka) causes a decrease in the film thickness. Regression analysis showed that the Re and Ka numbers described the data trends in wavy-laminar flow. Rather than correlating the Re number in discrete ranges of the Ka number as earlier researchers have done, this research made the Ka number an independent regression variable along with the Re number. The correlation explains 96% of the total variation in the data and predicts the experimental data within an absolute average deviation of(+-) 4.0%. The correlation supports the calculation of a fully developed film thickness for wavy-laminar falling films

[en] This paper proposes an experimental split beam apparatus of the Mach-Zehnder type using as a source ultra-cold neutrons to test the ''delayed-choice'' idea. With existing equipment and technology, it is very likely that interferometers using ultra-cold neutrons will be in operation in the very near future. Since these neutrons have such a low velocity (<8m/s), and the proposed interferometer is of appreciable size (--1 meter), the transit time through the apparatus is of the order of tenths of seconds. This would give a longer-lived elementary quantum phenomenon (''great smoky dragon'') than is immediately available in any other way. (author)

[en] In today's words, ''No elementary quantum phenomenon is a phenomenon until it is a registered ('observed', 'indelibly recorded') phenomenon, 'brought to a close' by 'an irreversible act of amplification'. ''In a delayed-choice experiment, one decides which of one or another complementary feature of a phenomenon the observing device will register after the development of the phenomenon is already under way. Several proposals for such experiments are reviewed. When a delayed-choice experiment is conducted at the cosmological level (light coming to the telescope from a distant quasar by two different gravitationally-bent routes), ''one-half of the ghost of a photon'' can be delayed by a month or a year compared to the ''other half''. The circumstance raises an interesting technical question, ''How can one keep one-half the ghost of a photon alive for a year.'' Bohr's phenomenon is discussed as a primordial building element for all of physics. (author)

[en] Recently broadly tunable, coherent VUV radiation down to 111 nm has become available. An experiment is underway using a VUV light source capable of a few μJ per 10 ns pulse to study the spectrum of H in the region of 113 nm. The photon energy of the VUV can be easily tuned and may determine whether the shape resonance has a Fano profile as predicted. A non-relativistic (35 keV), low-emittance H^- beam from the GTA injector at LANL will be used as the ion source. The electrons ejected from the intersecting beams will be analyzed using an electron time-of-flight (TOF) spectrometer. A narrow VUV linewidth allows the width of the Feshbach and shape resonances to be measured to high resolution (∼1 cm^-1). The branching ratios of neutral hydrogen states H(1s), H(2s), H(2p) for each resonance will be calculated by measuring the TOF of the ejected electrons. Of particular interest is the differential of the H(2s) and H(2p) branching ratios, since the product states are nearly degenerate in energy. Simulation of TOF data allows determination of both energy and the angular distribution of the electrons, thus permitting the authors to distinguish all three product states

[en] Purpose. Congenital defects of C2 are rare and can be confused with Hangman's fractures. CT has been advocated as aiding in differentiation between an acute fracture and congenital defects. Methods. We present a case of a 2-year-old recent accident victim, who was erroneously diagnosed by plain film and CT as having a Hangman's fracture. Results. The CT demonstrated an atypical appearance of a congenital defect. Conclusion. This case shows that the radiographic differentiation between a Hangman's fracture and a congenital defect is more difficult than previously described. (orig.)

[en] The structure factors for some liquid rare earth metals (Nd, Dy, Ho, Er and Lu) have been evaluated by means of a high temperature X-ray diffraction technique. The radial distribution functions were calculated by the usual Fourier analysis and were used to estimate interatomic distances and coordination numbers. (author)

[en] We define the simplicial analogues of two concepts from differential topology: the concept of a point on the simplicial manifold and the concept of a tangent space on a simplicial manifold. We derive the simplicial analogues of parallel transport, the covariant derivative, connections, the Riemann curvature tensor, and the Einstein tensor. We construct the extrinsic curvature for a simplicial hypersurface using the simplicial covariant derivative. We discuss the importance of this simplicial extrinsic curvature to the 3+1 Regge-calculus program. It appears to us that the newly developed null-strut lattice is the most natural version of a 3+1 Regge lattice for the construction of extrinsic curvature. (A null-strut lattice is a 3+1 Regge spacetime lattice with TrK = const simplicial hypersurfaces, each connected to its two adjacent hypersurfaces entirely by simplicial light cones built of null struts.) Finally, we test the Regge-calculus version of the extrinsic curvature on a Bianchi type-IX simplicial hypersurface. The calculation agrees with the continuum expression to first order

[en] We present here an application of a new quantization scheme. We quantize the Taub cosmology by quantizing only the anisotropy parameter β and imposing the super-Hamiltonian constraint as an expectation-value equation to recover the relationship between the scale factor Ω and time t. This approach appears to avoid the problem of time

[en] In this paper, we continue from the preceding paper to develop a fully functional Regge calculus geometrodynamic algorithm from the null-strut-calculus construction. The developments discussed include (a) the identification of the Regge calculus analogue of the constraint and evolution equations on the null-strut lattice, (b) a description of the Minkowski solid geometry for the simplicial blocks of the null-strut lattice, (c) a description of the evolution algorithm for the geometrodynamic scheme and an analysis of its consistency, and (d) a presentation of the dynamical degrees of freedom for a simplicial hypersurface and the description of an initial-value prescription. To demonstrate qualitatively this new approach to geometrodynamics, we present the most simple application of null-strut calculus that we know of---the Friedmann cosmology using the three-boundary of a 600-cell simplicial polytope to model the simplicial hypersurface

[en] This paper describes the kinematics of null-strut calculus---a 3+1 Regge calculus approach to general relativity. We show how to model the geometry of spacetime with simplicial spacelike three-geometries (TET's) linked to ''earlier'' and ''later'' momentumlike lattice surfaces (TET^*) entirely by light rays or ''null struts.'' These three-layered lattice spacetime geometries are defined and analyzed using combinatorial formulas for the structure of polytopes. The following paper in this series describes how these three-layered spacetime lattices are used to model spacetimes in full conformity with Einstein's theory of gravity