bluuebunny/crossref_metadata_2025 huggingface dataset:
The division of the Martian eccentricity from Hipparchos to Kepler: A history of the approximations to Kepler motion
Authors: Evans James
Published: March 2005

Any planetary theory with pretensions of quantitative validity must grapple with the inequality of movement due to Kepler motion. This was so in antiquity no less than today. The technical details of six historically important planetary models are discussed. The relationships of the models to one another and to the real motions of the planets are examined with simple geometrical techniques. The discussion centers on the history of the attempts to provide a model for the motion of Mars.
Rescue from falling into a black hole
Authors: Hammond Richard T.
Published: March 2005

According to a distant observer, an object falling toward a black hole never quite reaches the event horizon. The question then arises, how long can an observer wait before rescuing the falling object. This article discusses this question.
A study of barrier penetration in quantum mechanics
Authors: Chalk Jeff D.
Published: March 2005

The Schrödinger equation is solved for the truncated Gaussian potential barrier using a power series solution and a general expression is obtained for the transmission coefficient. For this potential barrier, computer calculations show only a trace of the oscillatory behavior that characterizes the penetration of a rectangular barrier. The oscillations diminish rapidly as the discontinuity in the potential function approaches zero. The results indicate that it is the unrealistic discontinuities in potential models that cause such oscillatory behavior.
A simple facility for the teaching of plasma dynamics and plasma nuclear fusion
Authors: Lee S. , Tou T. Y. , Moo S. P. , Eissa M. A. , Gholap A. V. , Kwek K. H. , Mulyodrono S. , Smith A. J. , Suryadi  , Usada W. , Zakaullah M.
Published: March 2005

A small plasma focus (3.3 kJ) is designed from the viewpoint of simplicity, reliability, and cost effectiveness to act as a source of pulsed high-density plasmas. The simplicity of the device and associated diagnostics coupled with its rich variety of plasma phenomena makes this device ideal for the teaching of plasma nuclear fusion particularly for developing countries where such facilities are at present rarely available. Six sets of the device have been constructed and tested in various gases with better than 95% reliability and reproducibility in various plasma phenomena including neutron production of 0.5–1.0×108 per discharge when operated in 3-Torr deuterium. The design principles, procedures, and parameters are discussed and test results shown.
On the physical reality of the isotropic speed of light
Authors: Brehme Robert W.
Published: March 2005

It was suggested by Einstein and later greatly elaborated on by others that the methods used to synchronize distant clocks are a matter of convention. The standard method, in which it is assumed that the speed of light is isotropic, obviously yields an isotropic light speed when such clocks are involved in determining the speed of light. Another method, in which clocks travel symmetrically but otherwise arbitrarily in opposite directions, may also be used to synchronize distant clocks. This method establishes whether or not the clocks are synchronized in a physically significant way in the sense that it allows a distinction to be made between a contrived anisotropic light speed and an anisotropic speed that is physically significant or real. Specifically, a contrived anisotropic light speed results in laws of physics that are not symmetric, whereas a true anisotropic light speed does not affect the symmetry of physical laws. Furthermore, when invariance in the speed of light is imposed, the invariant interval may be identified with the lapse of proper time in the case in which anisotropy is contrived. But, in the case of true anisotropy, this identification is not possible. Experiment reveals that, on the basis of symmetry in physical law, any anisotropy in the speed of light is contrived and not physically significant.
Ether and the one-way speed of light
Authors: Ungar Abraham
Published: March 2005

Thinking about nature seems, not surprisingly, to invite thought experiments. The aim of this article is to shed light (and dark) on two recently proposed thought experiments to detect one-way velocities. It is shown that these thought experiments fare like a naive thought experiment to detect absolute velocities relative to the ether.
An acoustic laboratory experiment to determine the coefficient of mutual diffusion of gases
Authors: Ashkenazi S. , Polturak E.
Published: March 2005

The variation of the speed of sound in a binary mixture of gases with the relative concentration of the constituents can be used to determine the mutual diffusion of one gas into another. An experimental setup is described that uses acoustics to measure the diffusion coefficient. The experiment is suitable for illustrating some basic topics in introductory statistical mechanics.
The use of a moving-coil galvanometer to demonstrate free and forced vibrations
Authors: Main Iain G.
Published: March 2005

A suspended moving-coil galvanometer is the basis of a simple system for demonstrating free and forced vibrations over a representative range of damping conditions. With the aid of closed-circuit television, both amplitude and phase information are conveyed visually.
Transverse electromagnetic standing waves with E∥B
Authors: Zaghloul H. , Buckmaster H. A.
Published: March 2005

This article examines the conditions under which transverse electromagnetic (TEM) waves exist in a sourceless medium. It shows that TEM waves can be classified according to whether their Poynting vector is identically zero or nonzero. The former are nonpropagating TEM standing waves with E∥B and the latter are TEM traveling and standing waves with E⊥B and E∥/B. The general condition under which TEM standing waves with E∥B exist is derived. Mathematical examples of these standing waves are given. An experimental configuration to realize one of these examples is proposed. The behavior of these waves under Lorentz transformations is discussed and it is shown that these waves are lightlike and that their fields lead to well-defined Lorentz invariants. It is hoped that this article will encourage electrodynamics course instructors to include a discussion of E∥B TEM standing waves.
Lowest modes of a bottle
Authors: Crawford Frank S.
Published: March 2005

Helmholtz’s model predicts correctly the frequency of the lowest mode of a bottle. A simple generalization of Helmholtz’s model correctly predicts this mode and also the next few modes—‘‘flute modes’’—of flasks with long uniform necks but arbitrarily shaped bodies. Wine bottles have additional low-frequency ‘‘cavity modes’’ that require a further easy generalization. For a bottle with slowly varying cross section an additional generalization can be made that retains the one-dimensional (1-D) character of the previous models and gives results that are in good agreement with experiment for the lowest mode—the ‘‘diametral mode’’—of a hollow sphere. For higher modes of a sphere, the 1-D model is inadequate and must be discarded in favor of exact solutions of the 3-D wave equation.
Acoustically induced square law forces and some speculations about gravitation
Authors: Apfel Robert E.
Published: March 2005

The goal of this article is twofold: (1) To review and clarify a derivation of the force between two objects in an acoustic field, demonstrating the circumstances under which this force takes a special form—an inverse-square-law behavior like that of gravitational attraction; and (2) to carry this analogy to gravitational forces, speculating (in perhaps an outlandish manner) that so-called mock gravity (from radiation pressure) is the source of real gravitational forces—that is, that this force arises from the response of bodies to a reverberating field of gravity waves perhaps produced in the big bang.
The ‘‘faster than gravity’’ demonstration revisited
Authors: Theron W. F. D.
Published: March 2005

The initial acceleration of a rigid rod rotating around one end, and the time required for the rod to fall onto a horizontal table, is compared with the acceleration and falling time of a free particle originally placed on the rod. The conditions under which the rod falls faster than the particle are established. Three cases are identified. The third case, in which the particle catches up with the rod, has not, to the author’s knowledge, been published previously.
Gravomagnetism in special relativity
Authors: Kolbenstvedt H.
Published: March 2005

The existence of a gravomagnetic field from a uniformly moving mass is predicted from special relativity and gravitational time dilation. Except for a factor of one-half, the field is identical to the field following from the linearized theory of gravitation.
Symmetric Fresnel equations: An energy conservation approach
Authors: Zia R. K. P.
Published: March 2005

The Fresnel equations, governing the relative amplitudes of the reflected and transmitted waves at a plane interface, are usually written in terms of only electric fields. The lengthy expressions for the two polarizations appear quite different. A simplified approach, based on energy conservation, is presented. Involving both electric and magnetic fields, the equations for the two polarizations now appear symmetric. The emergence of the magnetic analog of the Brewster angle is naturally expected.
Visual observation of a voltage distribution
Authors: Sparks P. D. , Pierce R. M.
Published: March 2005

The color of the light emitted from a metal–metal oxide–metal tunnel junction is determined primarily by the voltage drop across the tunneling barrier. This voltage drop will vary from point to point in a real light-emitting tunnel junction as a result of the finite resistance of the metal films. Consequently, the color of the emitted light will also vary from point to point. The observation of the color distribution provides a visual demonstration of the voltage gradient caused by Ohmic losses in the metallic films.
A numerical investigation of the classical motion of a particle in time-dependent magnetic fields
Authors: O’Neill Ed , Garner J.
Published: March 2005

Newton’s second law is solved numerically for the trajectory of a single charged particle moving in a time-dependent spatially uniform magnetic field. The charge is restricted to a plane. Numerical results are given corresponding to several choices of time dependence of the field including a randomly fluctuating field. The induced electric field accompanying the time-varying magnetic field is included in the equation of motion. Comments are made on the possible significance of these results to actual physical systems.
Can a projection method of obtaining equations of motion compete with Lagrange’s equations?
Authors: Scott Dan
Published: March 2005

An alternative technique for deriving the differential equations of motion for problems in classical mechanics is presented. This approach can be used to derive all the same equations of motion that can be derived by use of Lagrange’s equations. Advantages of this method are its ease of derivation, its intuitive nature, the physical insights it gives, and the fact that it is somewhat more general than Lagrange’s equations. In order to properly illustrate the use of the method, several examples are shown.
Moments of probability distribution, wavefunctions, and their derivatives at the origin of N-dimensional central potentials
Authors: Ray Aparna , Mahata Kalyaneswari , Ray Pritam P.
Published: March 2005

Generalized virial theorems are developed for central potentials in an N-dimensional space. The virial relations are then used to find the various spatial moments of the probability distribution, wavefunctions, and their derivatives at the origin of Coulomb and isotropic harmonic oscillator potentials in N dimension.
Angular momentum conservation in double star orbits: A laboratory exercise
Authors: Weitenbeck Anthony J.
Published: March 2005

Kepler’s second law, which is a geometrical statement of conservation of angular momentum, is true for double star orbits. Since this can be shown using tabulated and plotted observational data and simple measuring devices it can be done as an exercise by students in introductory astronomy or physics courses.
A light-beam data recorder for determination of the gravitational constant: Anomalous driven oscillations of a gravitation torsion balance
Authors: D’Anci A. M. , Armentrout C. E.
Published: March 2005

A 10-in. potentiometric strip-chart recorder with a broken slidewire is rehabilitated by adding a phototransistor to the pen pointer and a simple circuit supplying error voltage to the null amplifier. The usually important signal input circuits and reference voltage supply are not needed. The modified recorder pointer follows the light beam reflected onto the chart from a gravitational balance to produce an exact timed tracing of balance deflections. A simple addition provides automatic resetting of the pointer after beam interruption or power failure. Thus gravitational constant experiments are made much more accessible to undergraduates. The modified recorder also has other uses. But, most unexpectedly, it revealed consistent repetitive anomalous driven oscillations of the balance that are not related to its normal damped motion.
A mechanical resonance experiment with fluid dynamic undercurrents
Authors: Greenhow R. C.
Published: March 2005

An experimental arrangement suitable for the undergraduate laboratory is described that permits the quantitative study, at several different levels of sophistication, of forced, damped, simple harmonic motion in a mechanical system. The system comprises a spring supporting a ball that oscillates in an oil dashpot. The chief experimental innovation is an optical transducer that allows the oscillations to be observed on an oscilloscope screen. Values of oil viscosities deduced from the measured damping factors reveal large discrepancies that are resolved by a fuller consideration of the fluid dynamics of the damping media. Transverse viscous waves are launched that enhance the effective velocity sheer. The increase in effective inertia of the ball resulting from the fluid displaced is also readily observed. These effects are easily allowed for by the application of simple correction factors, thus allowing observation of all the major resonance phenomena in a quantitative manner.
Interference reflection demonstrated on a lumped L
C-transmission line
Authors: Janssen H. J. , Beerden L. , Flerackers E. L. M.
Published: March 2005

A lumped-element LC-transmission line is used to demonstrate interference reflection. In order to make the analysis easier, the line was connected to a microcomputer. The interference structures corresponding to (i) dielectric mirrors and (ii) Bragg reflectors have been examined. The voltage standing wave patterns are shown and the reflection coefficient as a function of the frequency is discussed.
Some experiments on x-ray fluorescence for the student laboratory
Authors: Dasgupta Mahananda , Sharma B. K. , Ahuja B. L. , Mohammad Farid M.
Published: March 2005

In this article some undergraduate laboratory experiments based on x-ray fluorescence are described. The characteristic x rays have been induced by irradiating the samples with 59.54-keV gamma rays from an 241Am radioisotope and analyzed with a planar Ge detector. Typical results from student experiments are presented. Variation of the fluorescence x-ray intensity with thickness has been studied for Ag and AgBr samples. These data are then used to determine absorption coefficients for AgKα x rays in the two samples and relative concentration of Ag and Br in the AgBr sample. Some comments on the quantitative analysis from x-ray fluorescence are also made.
Noether’s theorem in discrete classical mechanics
Authors: Bobillo-Ares Nilo
Published: March 2005

A derivation of Noether’s theorem in discrete classical mechanics from the invariance properties of the action is given. This derivation closely parallels the one given in classical field theory and emphasizes the fact that the involved symmetry transformations act on paths rather than on space and time points. Several illustrative examples are also presented.
A benevolent nonlinear system: The dynamically shifted oscillator
Authors: Thomsen John. S.
Published: March 2005

Hartmann has given an analysis of the dynamically shifted oscillator; this system is characterized by a restoring force k[x+x0 sign(x)], where sign(x)=x/‖x‖. He obtained an exact solution for free oscillations in terms of a Fourier series. This problem is reexamined and an alternative exact (piecewise) solution is given. The analysis is then extended to include a cosinusoidal forcing term. Exact solutions are given for three cases: (a) ω>ω0; (b) ω<ω0; (c) ω=ω0, where ω0 is the linear resonant frequency. Response curves are plotted and compared with those for the ‘‘hard spring’’ Duffing equation. While the system is simple enough to permit exact solutions in terms of elementary functions, it exhibits a number of characteristically nonlinear features; these include multiple-valued solutions, hysteresis effects, and amplitude jumps.
A simple look at the Kepler motion
Authors: Sivardière Jean
Published: March 2005

A large number of properties of the Kepler motion can be derived from Kepler’s three laws using only elementary geometry and kinematics.
Coulomb and Fermi holes in a two-electron model atom
Authors: Makarewicz Jan
Published: March 2005

The limitations of the independent particle model in describing electron motion in an atom are shown. To this end, an exact solvable model of a two-electron atom is studied. The way the interelectron interaction splits the atomic energy levels is shown. Both Coulomb and spin correlations are analyzed and Coulomb and Fermi holes are illustrated.
Ideal water waves via instantaneous action at a distance
Authors: Crawford Frank S.
Published: March 2005

An elementary derivation is given of the kinematics and dynamics of small amplitude sinusoidal water waves in deep water, using, for the kinematics, a ‘‘Green’s function integral’’ approach having intuitive appeal. At first, the usual simplifying assumption of incompressible water is made and the standard results are obtained. Then the approach is found to lend itself to the calculation of small corrections due to finite compressibility.
Wind energy as a solar-driven heat engine: A thermodynamic approach
Authors: Gordon J. M. , Zarmi Y.
Published: March 2005

An upper bound on annual average energy in the Earth’s winds is calculated via the formalism of finite-time thermodynamics. The Earth’s atmosphere is viewed as the working fluid of a heat engine where the heat input is solar radiation, the heat rejection is to the surrounding universe, and the work output is the energy in the Earth’s winds. The upper bound for the annual average power in the Earth’s winds is found to be 17 W/m2, which can be contrasted with the actual estimated annual average wind power of 7 W/m2. Our thermodynamic model also predicts the average extreme temperatures of the Earth’s atmosphere and can be applied to wind systems on other planets.
A correction for spring mass in the ubiquitous centripetal force experiment of freshman physics
Authors: Wildey Robert L.
Published: March 2005

A widely deployed experiment in freshman physics tests the hypothesis that the magnitude of the central force that accomplishes uniform circular motion is mv2/r (equivalently mrω2). This is accomplished by using a spring rotating about one end as the central force applied to a vertically hanging bob of known mass, tracking a circle of measured radius, at a speed deduced by counting revolutions over time. The spring force is independently measured by determining the gravitational force that produces the same degree of extension of the spring. Because the inertia of the spring is unimportant to the latter measurement, but does matter in the dynamical phase of the experiment, an error is introduced. Students have always been admonished to neglect the effects of the mass of the spring; however, typical parameters used in this experiment imply an error greater than 1%, which exceeds the probable error of which the experiment is capable.
Simple demonstration of superconductivity in YBa2Cu3O7
Authors: Brown G. C. , Rasure J. O. , Morrison W. A.
Published: March 2005

A simple four-point probe using pressure contacts is used to demonstrate the zero resistivity property of superconducting YBa2Cu3O7 and the superconducting–normal-state transition as a function of temperature.
Interesting features of relativistic and nonrelativistic quantal bound states in one, two, and three dimensions
Authors: Sahu B. , Khan M. Z.Rahman , Shastry C. S. , Dey B. , Phatak S. C.
Published: March 2005

Various aspects of critically bound quantal ground states close to the threshold in one, two, and three dimensions are examined in nonrelativistic quantum mechanics using attractive square-well and delta-function potentials. The mathematical and physical reasons are presented for the nonoccurrence of the bound state in the case of three dimensions and its occurrence in one and two dimensions for infinitesimally small strengths and ranges of the potential. Also analyzed is the condition for critical binding in relativistic quantum mechanics using the Klein–Gordon equation in one, two, and three dimensions. Corresponding features for the case of the Dirac equation in one and three dimensions are briefly discussed.
Using a Smart-pulley Atwood machine to study rocket motion
Authors: Greenwood M. Stautberg , Bernett R. , Benavides M. , Granger S. , Plass R. , Walters S.
Published: March 2005

The Atwood machine consisted of a funnel partly filled with water on one side and a fixed mass of 400 g on the other side. The ‘‘rocket’’ begins to ascend when the acceleration is momentarily zero. This occurs when the total mass of the rocket is slightly larger than 400 g due to the rocket’s thrust. As the wheel of Pasco’s Smart pulley rotates, signals are sent to the Apple computer and the software generates tables and graphs of position, speed, and acceleration as a function of time. Also presented is a numerical differentiation scheme that greatly reduces the scatter in the experimental data for the acceleration. The data are compared with theory, assuming that dm/dt is constant. The value of dm/dt necessary to fit the data is compared with that found by measuring the flow rate from the funnel directly. Excellent agreement is obtained for the two values of dm/dt.
The complex operator method of the hydrogen atom
Authors: Jiang Xundong
Published: March 2005

Frequently the hydrogen atom eigenvalue problem is analytically solved by solving a radial wave equation for a particle in a Coulomb field. In this article, complex coordinates are introduced, and an expression for the energy levels of the hydrogen atom is obtained by means of the algebraic solution of operators. The form of this solution is in accord with that of the analytical solution.
Absorption spectrum of iodine vapor—An experiment
Authors: George Simon , Krishnamurthy N.
Published: March 2005

The absorption spectrum of iodine was photographed in the visible region using a 3.4-m Ebert plane-grating spectrograph. An evacuated glass envelope containing a small amount of iodine was used as the absorption cell while a tungsten filament lamp served as the continuous source. A number of band heads were identified and these measurements led to the determination of the dissociation limit, the dissociation energy, the force constant, and the fundamental vibrational frequency of the iodine molecule. Such an experiment will provide the physics major with an introduction to molecular spectra and, in light of the discovery of molecular lasers, it is recommended that such an experiment be included in the undergraduate physics curriculum.
The empirical foundation of classical dynamics
Authors: Desloge Edward A.
Published: March 2005

Two formulations of the empirical principles on which classical dynamics is founded are presented and compared. The first is based on the law of conservation of momentum and gives initial priority to the concept of mass. The second is based on Newton’s laws and gives initial priority to the concept of force. On the basis of a variety of criteria the first formulation is shown to be superior to the second.
Energy density and stress: A new approach to teaching electromagnetism
Authors: Herrmann F.
Published: March 2005

By introducing the electromagnetic field in the customary way, ideas are promoted that do not correspond to those of contemporary physics: on the one hand, ideas that stem from pre-Maxwellian times when interactions were still conceived as actions at a distance and, on the other hand, ideas that can be understood only from the point of view that the electromagnetic field is carried by a medium. A part of a course in electromagnetism is sketched in which, from the beginning, the electromagnetic field is presented as a system in its own right and the local quantities energy density and stress are put into the foreground. In this way, justice is done to the views of modern physics and, moreover, the field becomes conceptually simpler.
Magnetic field of a long wire in a static background gravitational field: A classroom exercise in general relativity
Authors: De Fatima A. Da Silva M. , Da Silveira Filho Otton T. , Souza J. A.
Published: March 2005

A general expression is found for the magnetic field generated by a long rectilinear current placed in a static background gravitational field. Then it is applied to the case of uniform, Schwarzschild, general Reissner–Nordstrom and ‘‘charge-equal-to-mass’’ Reissner–Nordstrom background metrics. All the calculations are very simple and can easily be done in the classroom.
Charts of modulus and phase of the S matrix
Authors: Sesma J.
Published: March 2005

The possibility is suggested of using charts of modulus and phase of the S matrix to illustrate lessons on nonrelativistic scattering in quantum mechanics courses. Special attention is paid to the existence of resonances and to Levinson’s theorem on the number of bound states.
Electric field and radiation by a pointlike source moving in an isotropic medium
Authors: Bornatici M. , Spada M.
Published: March 2005

The electric field in space and time of a source moving in a lossless, isotropic, and dispersive medium is obtained from the inhomogeneous wave equation combined with the charge continuity equation. The Fourier transform method is employed together with the theory of functions of complex variables to express the causality condition. The existence of two retarded times is pointed out for the case of a pointlike source moving in a nondispersive medium faster than the propagation velocity of the electromagnetic field. The Čerenkov as well as the polarization radiation is obtained for a dispersive isotropic medium.
Linear least-squares fits with errors in both coordinates
Authors: Reed B. Cameron
Published: March 2005

York’s solution to the problem of linear least-squares fits with errors in both coordinates [D. York, Can. J. Phys. 44, 1079 (1966)] is shown to be exact and not subject to the erroneous results that attempts to modify standard least-squares algorithms can produce. Detailed examples of the use of York’s method are given; a fortran implementation suitable for use on personal computers is available to interested parties.
A pendulum with adjustable trends in the period
Authors: Peters R. D. , Shepherd J. A.
Published: March 2005

A precision ‘‘simple’’ pendulum can be made nearly isochronous (without driving) at amplitudes of the order of a few degrees. This is accomplished by means of a leaky vacuum chamber for the pendulum. The declining period from amplitude decay can be opposed by means of a pressure increase. By careful initialization, the period can be held constant to better than 50 μs over 10 min.
What nature knows about solving equations of motion
Authors: Ares-de-Parga G. , Rosales M. A.
Published: March 2005

The problem of representing an equation of motion by means of an integro-differential equation and a series is analyzed and the results are used to clarify a recent controversy on the equation of motion for classical charged particles.
Measurement of the gravitational constant without torsion
Authors: Saulnier Michael S. , Frisch David
Published: March 2005

A Cavendish torsion balance is modified to measure the force of gravity easily enough to be used in an introductory teaching laboratory. The balance is suspended by a wire of very small restoring torque, so that for small displacements the linear accelerations of the test masses are measured directly. Representative results shown here give G=(6.65±0.09)×10−8 dyn cm2/g2, and in 1/rn give n=2.1±0.1.
Exercises in the synthesis of electrical impedances
Authors: Collier Robert L.
Published: March 2005

Two general circuits are developed for the synthesis of user-variable electrical impedances. One circuit permits user-variable enlargement of any existing impedance without affecting its phase characteristics. This circuit facilitates such devices as floating capacitors and inductors which are continuously variable over wide ranges. The other circuit permits simulation of user-variable floating impedances whose phase and frequency characteristics are widely subject to design objectives. In addition to all conventional impedance functions, it poses access to an infinite set of alternatives for the simulation of resistance and reactance functions of frequency. Included is a theoretical approach for predicting parasitic impedances reported in earlier works on similar devices known as gyrators.
Time-reversal invariance in multiple collisions between coupled masses
Authors: Crawford Frank S.
Published: March 2005

The time evolution of two mechanical oscillators coupled by a spring can (but need not) exhibit an instant t=2t′ when the initial conditions at t=0 have been exactly restored. When that is the case, then at t=t′ energy and momentum have been exchanged exactly as in an elastic collision between two free particles, and the evolution of the system from t=t′ to 2t′ is related to that from 0 to t′ by time-reversal invariance. A similar ‘‘simulation of elastic scattering’’ at t=t′ can occur for two free particles coupled via collisions with an intermediary mass that bounces back and forth between the two particles provided the intermediary is left at rest at t=t′. Examined here is the time evolution of the exchange of momentum and energy for these two examples, determining the values of the coupling spring constant (or mass value) of the intermediating spring (or mass) needed to simulate single elastic scattering between free particles, and looking at the manifestation of time-reversal invariance.
Crawford’s technique applied to laser cooling and equipartition
Authors: Menon V. J. , Agrawal D. C.
Published: March 2005

Crawford’s method of analyzing sequential two-body collisions is applied to the phenomenon of laser cooling and to the equipartition of energy in the case of radiation–atom interaction.
Historical parallels in science and culture
Authors: Spradley Joseph L.
Published: March 2005

A historical framework for relating science and culture is developed and illustrated. In each of four periods in the history of western civilization, the basic scientific concepts most characteristic of that period are summairzed and then correlated with relevant attempts at philosophical synthesis. These science-related syntheses then provide the basis for showing the interaction between science and society by comparing them with social ideals and cultural trends most evident in each period.
Chaos versus predictability in formulating national strategic security policy
Authors: Saperstein Alvin M. , Mayer-Kress Gottfried
Published: March 2005

The relation between chaos and predictability in deterministic theories, as developed and used in physical models, is also useful in studying important nonphysical problems such as that of international security. In the latter case, the well-known transition from laminar to turbulent flow is a heuristic analogy to the transition from cold to hot war. A simplified procurement model for the Strategic Defense Initiative (SDI) is presented, which can be used to determine the outcome of various deployment modes. A specific outcome, even if desirable from the point of view of a transition from an offensive to a defensive strategy, may represent a dangerous crisis instability—conducive to the outbreak of war—if it occurs in the model’s chaotic regime. Some numerical examples of the various possibilities are given.
Some simple experimental studies using a passive cavity coupled to a He–Ne laser cavity for practice in a quantum electronics laboratory
Authors: Podoleanu Adrian Gh. , Popescu Ion M.
Published: March 2005

Some quantum optics experiments about self-locking and mode-locking operation, optical bistable operation, and low-absorption monitoring are described using a versatile, inexpensive experimental setup. These experiments are easy to implement with a He–Ne laser coupled to a passive cavity to which a few simple devices have been added.
Heterogeneity of a Fluorescent Tegument Component in Single Pseudorabies Virus Virions and Enveloped Axonal Assemblies
Authors: del Rio T. , Ch'ng T. H. , Flood E. A. , Gross S. P. , Enquist L. W.
Published: March 2005

The molecular mechanisms responsible for long-distance, directional spread of alphaherpesvirus infections via axons of infected neurons are poorly understood. We describe the use of red and green fluorescent protein (GFP) fusions to capsid and tegument components, respectively, to visualize purified, single extracellular virions and axonal assemblies after pseudorabies virus (PRV) infection of cultured neurons. We observed heterogeneity in GFP fluorescence when GFP was fused to the tegument component VP22 in both single extracellular virions and discrete puncta in infected axons. This heterogeneity was observed in the presence or absence of a capsid structure detected by a fusion of monomeric red fluorescent protein to VP26. The similarity of the heterogeneous distribution of these fluorescent protein fusions in both purified virions and in axons suggested that tegument-capsid assembly and axonal targeting of viral components are linked. One possibility was that the assembly of extracellular and axonal particles containing the dually fluorescent fusion proteins occurred by the same process in the cell body. We tested this hypothesis by treating infected cultured neurons with brefeldin A, a potent inhibitor of herpesvirus maturation and secretion. Brefeldin A treatment disrupted the neuronal secretory pathway, affected fluorescent capsid and tegument transport in the cell body, and blocked subsequent entry into axons of capsid and tegument proteins. Electron microscopy demonstrated that in the absence of brefeldin A treatment, enveloped capsids entered axons, but in the presence of the inhibitor, unenveloped capsids accumulated in the cell body. These results support an assembly process in which PRV capsids acquire a membrane in the cell body prior to axonal entry and subsequent transport.
The Minor Capsid Protein L2 Contributes to Two Steps in the Human Papillomavirus Type 31 Life Cycle
Authors: Holmgren Sigrid C. , Patterson Nicole A. , Ozbun Michelle A. , Lambert Paul F.
Published: March 2005

Prior studies, which have relied upon the use of pseudovirions generated in heterologous cell types, have led to sometimes conflicting conclusions regarding the role of the minor capsid protein of papillomaviruses, L2, in the viral life cycle. In this study we carry out analyses with true virus particles assembled in the natural host cell to assess L2's role in the viral infectious life cycle. For these studies we used the organotypic (raft) culture system to recapitulate the full viral life cycle of the high-risk human papillomavirus HPV31, which was either wild type or mutant for L2. After transfection, the L2 mutant HPV31 genome was able to establish itself as a nuclear plasmid in proliferating populations of poorly differentiated (basal-like) human keratinocytes and to amplify its genome to high copy number, support late viral gene expression, and cause formation of virus particles in human keratinocytes that had been induced to undergo terminal differentiation. These results indicate that aspects of both the nonproductive and productive phases of the viral life cycle occur normally in the absence of functional L2. However, upon the analysis of the virus particles generated, we found an approximate 10-fold reduction in the amount of viral DNA encapsidated into L2-deficient virions. Furthermore, there was an over-100-fold reduction in the infectivity of L2-deficient virus. Because the latter deficiency cannot be accounted for solely by the 10-fold decrease in encapsidation, we conclude that L2 contributes to at least two steps in the production of infectious virus.
Circumventing Tolerance to the Prion Protein (PrP): Vaccination with PrP-Displaying Retrovirus Particles Induces Humoral Immune Responses against the Native Form of Cellular PrP
Authors: Nikles Daphne , Bach Patricia , Boller Klaus , Merten Christoph A. , Montrasio Fabio , Heppner Frank L. , Aguzzi Adriano , Cichutek Klaus , Kalinke Ulrich , Buchholz Christian J.
Published: March 2005

Passive immunization with antibodies directed against the cellular form of the prion protein (PrP
C
) can protect against prion disease. However, active immunization with recombinant prion protein has so far failed to induce antibodies directed against native PrP
C
expressed on the cell surface. To develop an antiprion vaccine, a retroviral display system presenting either the full-length mouse PrP (PrP209) or the C-terminal 111 amino acids (PrP111) fused to the transmembrane domain of the platelet-derived growth factor receptor was established. Western blot analysis and immunogold electron microscopy of the retroviral display particles revealed successful incorporation of the fusion proteins into the particle membrane. Interestingly, retroviral particles displaying PrP111 (PrP
D111
retroparticles) showed higher incorporation efficiencies than those displaying PrP209. Already 7 days after intravenous injection of PrP
D111
retroparticles, PrP
C
-deficient mice (
Prnp
o/o
) showed high immunoglobulin M (IgM) and IgG titers specifically binding the native PrP
C
molecule as expressed on the surface of T cells isolated from PrP
C
-overexpressing transgenic mice. More importantly, heterozygous
Prnp
+/o
mice and also wild-type mice showed PrP
C
-specific IgM and IgG antibodies upon vaccination with PrP
D111
retroparticles, albeit at considerably lower levels. Bacterially expressed recombinant PrP, in contrast, was unable to evoke IgG antibodies recognizing native PrP
C
in wild-type mice. Thus, our data show that PrP or parts thereof can be functionally displayed on retroviral particles and that immunization with PrP retroparticles may serve as a novel promising strategy for vaccination against transmissible spongiform encephalitis.
Role of Receptor-Mediated Endocytosis in the Formation of Vaccinia Virus Extracellular Enveloped Particles
Authors: Husain Matloob , Moss Bernard
Published: March 2005

Infectious intracellular mature vaccinia virus particles are wrapped by cisternae, which may arise from trans-Golgi or early endosomal membranes, and are transported along microtubules to the plasma membrane where exocytosis occurs. We used EH21, a dominant-negative form of Eps15 that is an essential component of clathrin-coated pits, to investigate the extent and importance of endocytosis of viral envelope proteins from the cell surface. Several recombinant vaccinia viruses that inducibly or constitutively express an enhanced green fluorescent protein (GFP)-EH21 fusion protein were constructed. Expression of GFP-EH21 blocked uptake of transferrin, a marker for clathrin-mediated endocytosis, as well as association of adaptor protein-2 with clathrin-coated pits. When GFP-EH21 was expressed, there were increased amounts of viral envelope proteins, including A33, A36, B5, and F13, in the plasma membrane, and their internalization was inhibited. Wrapping of virions appeared to be qualitatively unaffected as judged by electron microscopy, a finding consistent with a primary trans-Golgi origin of the cisternae. However, GFP-EH21 expression caused a 50% reduction in released enveloped virions, decreased formation of satellite plaques, and delayed virus spread, indicating an important role for receptor-mediated endocytosis. Due to dynamic interconnection between endocytic and exocytic pathways, viral proteins recovered from the plasma membrane could be used by trans-Golgi or endosomal cisternae to form new viral envelopes. Adherence of enveloped virions to unrecycled viral proteins on the cell surface may also contribute to decreased virus release in the presence of GFP-EH21. In addition to a salvage function, the retrieval of viral proteins from the cell surface may reduce immune recognition.
Isolation and Characterization of Avian Influenza Viruses, Including Highly Pathogenic H5N1, from Poultry in Live Bird Markets in Hanoi, Vietnam, in 2001
Authors: Nguyen Doan C. , Uyeki Timothy M. , Jadhao Samadhan , Maines Taronna , Shaw Michael , Matsuoka Yumiko , Smith Catherine , Rowe Thomas , Lu Xiuhua , Hall Henrietta , Xu Xiyan , Balish Amanda , Klimov Alexander , Tumpey Terrence M. , Swayne David E. , Huynh Lien P. T. , Nghiem Ha K. , Nguyen Hanh H. T. , Hoang Long T. , Cox Nancy J. , Katz Jacqueline M.
Published: March 2005

Since 1997, outbreaks of highly pathogenic (HP) H5N1 and circulation of H9N2 viruses among domestic poultry in Asia have posed a threat to public health. To better understand the extent of transmission of avian influenza viruses (AIV) to humans in Asia, we conducted a cross-sectional virologic study in live bird markets (LBM) in Hanoi, Vietnam, in October 2001. Specimens from 189 birds and 18 environmental samples were collected at 10 LBM. Four influenza A viruses of the H4N6 (
n
= 1), H5N2 (
n
= 1), and H9N3 (
n
= 2) subtypes were isolated from healthy ducks for an isolation frequency of over 30% from this species. Two H5N1 viruses were isolated from healthy geese. The hemagglutinin (HA) genes of these H5N1 viruses possessed multiple basic amino acid motifs at the cleavage site, were HP for experimentally infected chickens, and were thus characterized as HP AIV. These HA genes shared high amino acid identities with genes of other H5N1 viruses isolated in Asia during this period, but they were genetically distinct from those of H5N1 viruses isolated from poultry and humans in Vietnam during the early 2004 outbreaks. These viruses were not highly virulent for experimentally infected ducks, mice, or ferrets. These results establish that HP H5N1 viruses with properties similar to viruses isolated in Hong Kong and mainland China circulated in Vietnam as early as 2001, suggest a common source for H5N1 viruses circulating in these Asian countries, and provide a framework to better understand the recent widespread emergence of HP H5N1 viruses in Asia.
Amino Acid Preferences for a Critical Substrate Binding Subsite of Retroviral Proteases in Type 1 Cleavage Sites
Authors: Bagossi Péter , Sperka Tamás , Fehér Anita , Kádas János , Zahuczky Gábor , Miklóssy Gabriella , Boross Péter , Tözsér József
Published: March 2005

The specificities of the proteases of 11 retroviruses representing each of the seven genera of the family
Retroviridae
were studied using a series of oligopeptides with amino acid substitutions in the P2 position of a naturally occurring type 1 cleavage site (Val-Ser-Gln-Asn-Tyr↓Pro-Ile-Val-Gln; the arrow indicates the site of cleavage) in human immunodeficiency virus type 1 (HIV-1). This position was previously found to be one of the most critical in determining the substrate specificity differences of retroviral proteases. Specificities at this position were compared for HIV-1, HIV-2, equine infectious anemia virus, avian myeloblastosis virus, Mason-Pfizer monkey virus, mouse mammary tumor virus, Moloney murine leukemia virus, human T-cell leukemia virus type 1, bovine leukemia virus, human foamy virus, and walleye dermal sarcoma virus proteases. Three types of P2 preferences were observed: a subgroup of proteases preferred small hydrophobic side chains (Ala and Cys), and another subgroup preferred large hydrophobic residues (Ile and Leu), while the protease of HIV-1 preferred an Asn residue. The specificity distinctions among the proteases correlated well with the phylogenetic tree of retroviruses prepared solely based on the protease sequences. Molecular models for all of the proteases studied were built, and they were used to interpret the results. While size complementarities appear to be the main specificity-determining features of the S2 subsite of retroviral proteases, electrostatic contributions may play a role only in the case of HIV proteases. In most cases the P2 residues of naturally occurring type 1 cleavage site sequences of the studied proteases agreed well with the observed P2 preferences.
Role of a Cytotoxic-T-Lymphocyte Epitope-Defined, AlternativegagOpen Reading Frame in the Pathogenesis of a Murine Retrovirus-Induced Immunodeficiency Syndrome
Authors: Gaur Arti , Green William R.
Published: March 2005

LP-BM5 murine leukemia virus-infected C57BL/6 mice develop profound immunodeficiency and B-cell lymphomas. The LP-BM5 complex contains a mixture of defective (BM5def) and replication-competent helper viruses among which BM5def is the primary causative agent of disease. The BM5def primary open reading frame (ORF1) encodes the singlegagprecursor protein (Pr60gag). Our lab has recently demonstrated that a novel immunodominant cytotoxic-T-lymphocyte (CTL) epitope (SYNTGRFPPL) is expressed from a +1-nucleotide translational open reading frame of BM5def during the course of normal retrovirus expression. The SYNTGRFPPL CTL epitope may be generated from either of two initiation methionines present, ORF2a or ORF2b, located downstream of the ORF1 initiation site. This study investigates the role(s) of the alternative ORF2-derivedgagprotein(s) of BM5def in viral pathogenesis. We have examined the disease-inducing capabilities of mutant viruses in which the translational potential of either the initiating ORF2a or ORF2b AUG has been disrupted. Although these mutated viruses are capable of wild-type ORF1 expression, they are unable to induce disease. Our data strongly suggest the existence of a novel ORF2 product(s) that is required for LP-BM5-induced pathogenesis and have potentially broad implications for other retroviral diseases.