bluuebunny/crossref_metadata_2025 huggingface dataset:
Galileo and optical illusion
Authors: Parker Gary D.
Published: March 2005

Galileo’s earliest telescopic measurements are of sufficient quality that their detailed analysis yields scientifically interesting and pedagogically useful results. An optical illusion strongly influences Galileo’s observations of Jupiter’s moons, as published in the Starry Messenger. A simple procedure identifies individual satellites with sufficient reliability to demonstrate that Galileo regularly underestimated satellite brightness and overestimated elongation when a satellite was very close to Jupiter. The probability of underestimation is a monotonically decreasing function of separation angle, both for Galileo and for viewers of a laboratory simulation of the Jupiter ‘‘starfield’’ viewed by Galileo. Analysis of Galileo’s records and a simple simulation experiment appropriate to undergraduate courses clarify the scientific problems facing Galileo in interpreting his observations.
Electromagnetic radiation from a kicked sheet of charge
Authors: Peters P. C.
Published: March 2005

The plane-wave electromagnetic fields for a kicked sheet of charge are found and then compared with the fields obtained by superimposing the radiation fields of the individual charges in the plane. Unlike the case of the oscillating sheet of charge discussed in The Feynman Lectures on Physics, Vol. I [R. P. Feynman et al. (Addison-Wesley, Reading, MA, 1963)], the plane-wave fields of the kicked sheet differ from the fields obtained by superposition of the individual radiation fields. The resolution of this problem requires consideration of relativistic effects even though the velocity of the sheet after the kick may be as small as desired. The relation between the solution for the kicked sheet and solution for the oscillating sheet is discussed, and it is shown how the two solutions are consistent if all contributions to the fields are taken into account.
A mechanical model exhibiting a tricritical point
Authors: Sivardière Jean
Published: March 2005

It is shown that a generalized Alben model with a Van der Waals gas exhibits a critical line and a tricritical point as the intermolecular interaction parameter of the gas is varied. The whole phase diagram is discussed: It agrees with the Griffiths picture of a symmetrical tricritical point.
Exact solvable three-dimensional models of many-body systems
Authors: Makarewicz Jan
Published: March 2005

This paper presents new realistic models of many-body systems. They provide a good insight into the dynamics of such systems as many-electron atoms, diatomic molecules, and various van der Waals complexes. These models can be used as excellent illustrations of the important topics of atomic and molecular physics.
General relativity, black holes, and cosmology: A course for nonscientists
Authors: Roman Thomas A.
Published: March 2005

An approach toward teaching the conceptual framework of general relativity and its consequences to nonscience students is presented. The basis for our discussion is a successful course offered as a general honors seminar at the University of Hartford. Specific teaching suggestions are made regarding the explanations of certain key points and sample exam questions are provided.
Worldwide radioactivity from a nuclear war
Authors: Broyles A. A.
Published: March 2005

Formulas are derived for calculating the amount of worldwide fallout that can be expected from a nuclear war.
On the radiation from point charges
Authors: Haus H. A.
Published: March 2005

An alternative derivation of the radiation field of a point charge is presented. It starts with the Fourier components of the current produced by the moving charge. The electric field is found from the vector wave equation. Each step in the integration permits physical interpretation. The retarded time appears very naturally in this derivation. The interpretation of the present derivation is that a charge at constant velocity v̄(‖v̄‖<c) does not radiate, not because it is unaccelerated, but because it has no Fourier components synchronous with waves traveling at the speed of light. Of course, Cherenkov radiation in a medium, in which the velocity of electromagnetic propagation is less than c, is the classic example of radiation by a charge moving at constant velocity.
Note on a ‘‘Class of Lorentz-invariant theories of gravitation’’ [E.G. Harris, Am. J. Phys. 4
9, 1051 (1981)]
Authors: Leubner C.
Published: March 2005

It is pointed out that Harris’ paper on gravitation suffers from an inproper choice of Lagrangian. (AIP)
Radial expectation values for central force problems and the Feynman–Hellman theorem
Authors: Valk H. S.
Published: March 2005

The Feynman–Hellmann theorem is employed to derive simple expressions for the expectation values of particular powers of the radial coordinate for a class of central or hypercentral force problems. The results are applied to the Kratzer, the modified oscillator, and the hyperspherical oscillator potentials.
Supersymmetry in quantum mechanics
Authors: Haymaker Richard W. , Rau A. R. P.
Published: March 2005

We give some illustrations and interpretations of supersymmetry in quantum mechanics in simple models. We show that the value of 2 for the g factor of the electron expresses the presence of supersymmetry in the Hamiltonian for an electron in a uniform magnetic field. The problem is considered both in the Schrödinger and Dirac formulations. We also show that the radial Coulomb problem with orbital angular momentum l, nuclear charge Z, and principal quantum number n, is supersymmetrically linked to the similar problem with charge Z(1−1/n) and quantum number n−1. Thereby the dependence of Coulomb energies only on the combination Z/n is seen as a manifestation of the supersymmetry in the radial Coulomb problem. Other examples of supersymmetry we consider are the Morse potential, the three-dimensional isotropic oscillator, the states of the helium atom and those of the hydrogen atom in an extremely strong magnetic field.
The unrestrained brachistochrone
Authors: Stork David G. , Yang Ju-xing , Stover Chris
Published: March 2005

The unrestrained brachistochrone problem is to find the path of a frictionless track between two horizontally separated points along which a block with an initial velocity will travel in the shortest time. The track lies in a uniform gravitational field and must be horizontal at its beginning and its end. Furthermore, the block must slide along the track like a block on an inclined plane and it must remain in contact with the track at all times. Although the problem is well posed, the nature of the unusual constraints makes it quite difficult to solve using standard variational techniques, such as those of Euler and Lagrange. We present a solution that avoids explicit reliance on such techniques.
Ghost’s shadows and superluminal occultations
Authors: Meyer-Vernet N.
Published: March 2005

The field intensity behind a moving (nonrelativistic) occulting object has a rather counterintuitive behavior at sufficiently large distance: finite transit time effects yield two simultaneous shadow paths on a plane, which separate from each other with superluminal velocity.
Magnetic field of an infinite current-carrying ribbon
Authors: Gauthier N.
Published: March 2005

Simple analytic expressions are developed for the magnetic field due to an infinitely long current-carrying ribbon of finite width. These expressions are evaluated explicitly for the cases of a flat ribbon, a parallel-plate inductor, a hollow rectangular wire, and a hollow circular wire. The results can be used to discuss the behavior of the magnetic field distribution near the edge of a conductor.
ICBM vulnerability: Calculations, predictions, and error bars
Authors: Hobson Art
Published: March 2005

The theory of intercontinental ballistic missile (ICBM) silo vulnerability is reviewed, and the present and probable future (mid-1990s) vulnerability of US silos is analyzed. The analysis emphasizes methodology, sources of information, and uncertainties. US ICBMs might still be survivable today but they will certainly be vulnerable to ICBM attack, and perhaps even to submarine-launched ballistic missile attack, by the mid-1990s. These calculations are presented not only for their immediate importance but also to introduce other physicists to some of the quantitative methods that can be used to analyze international security topics.
A simple relativistic paradox about electrostatic energy
Authors: Rindler Wolfgang , Denur Jack
Published: March 2005

A charged parallel-plate vacuum capacitor moves uniformly through an inertial frame. Its field energy alone does not transform according to the familiar law ‘‘energy=γ× rest energy.’’ However, when the stresses in the supports are taken into account, the entire system does satisfy this relation.
What really happens in the Franck–Hertz experiment with mercury?
Authors: Hanne G. F.
Published: March 2005

Recent studies using spin-polarized electrons have revealed the role that various interactions play in inelastic collisions of slow electrons with complex atoms. It has been shown that electron exchange and resonances (temporarily negative compound ion states) strongly influence the excitation cross sections of the first excited states of mercury very close to excitation thresholds. The particular result obtained in the Franck–Hertz experiment is determined by the magnitude of the excitation cross sections involved and depends on the geometrical design of the tube.
Electrostatic fields in inhomogeneous dielectrics
Authors: McKelvey J. P.
Published: March 2005

Conditions under which simple, closed-form solutions to the electrostatic field equations in linear inhomogeneous dielectrics can be obtained are investigated. It is shown that such solutions can be found in general orthogonal coordinates (q1,q2,q3), in which equipotential surfaces are given by constant values of the axial q1 coordinate, whenever the permittivity can be expressed as ε(q1,q2,q3)=ε0(h1/h2h3)f(q1) g(q2,q3). In this formula, h1,h2, and h3 are arc length factors, while f(q1) and g(q2,q3) are essentially arbitrary functions of the coordinates. These solutions have the property that the E and D fields have components only in the axial q1 direction. Explicit formulas for field, displacement, polarization, potential, capacitance, etc. are obtained in terms of the generalized coordinates and the functions f and g. These expressions encompass virtually all the ‘‘workable’’ capacitor problems posed in standard texts. In the case of Cartesian coordinates where x is the axial coordinate, the conditions for closed-form solutions of this type reduce to ε=ε0 f(x)g(y,z), where f(x) and g(y,z) are arbitrary functions, and it is found that Ex depends only on x, while Dx depends only upon y and z. Effects arising from the presence of volume distributions of free charge are investigated, and it is found that their presence severely restricts the conditions under which simple solutions may exist. The methods used, and the results obtained, are applicable to structures such as capacitors, superlattices, optical fibers, inhomogeneous thin films, semiconductor heterojunctions, etc.
A simple example related to the time-reversal paradox
Authors: Luke Jon C.
Published: March 2005

An example is given of a reversible, deterministic system in which unexpected and seemingly irreversible behavior occurs. The system is simple enough so that states can be counted explicitly and the behavior can be clearly understood as nonparadoxical.
Comment on ‘‘The strange polarization of the classical atom’’ [Am. J. Phys. 5
5, 906 (1987)]
Authors: Biedenharn L. C. , Brown Lowell S. , Solem J. C.
Published: March 2005

There has been much interest recently, both experimentally and theoretically, in ‘‘Rydberg atoms’’—atoms with large principal quantum number n. A classical treatment of the associated Coulomb field problem describes most of the features of these atoms. Using classical mechanics, Solem1 recently showed the existence of an interesting, counterintuitive effect for an atom in a weak uniform electric field: The response of the electron was orthogonal to the direction of the applied field. This effect was shown both analytically by the method of variation of parameters and numerically by direct integration of the equations of motion. Such a basic effect in a simple system should, however, admit an elementary derivation. This we provide here.
Kinetic energy and chemical bonding
Authors: Harcourt Richard D.
Published: March 2005

The Ruedenberg theory is used to ananyze the covalent bonding of hydrogen molecules and molecular ions. (AIP)
Progressive fluid deformation in low Reynolds number flow past a falling cylinder
Authors: Weijermars Ruud
Published: March 2005

A new laboratory technique is outlined by which the flow of a very viscous fluid can be made visible and finite strains and fluid rotations in the flow can be measured. The technique involves the emplacement of a pattern of grid lines in a plane through the fluid before the flow begins. The grid lines are in fact formed by placing an ‘‘unfixed’’ photocopy in contact with a surface of the fluid, thereby transferring carbon particles from the photocopying paper on to the fluid, and then bringing that surface of the fluid into contact with another similar volume of fluid. The carbon particles are therefore embedded within the working volume of fluid. Use of the technique, and some of the results that can be obtained, are demonstrated by the example of flow about a falling cylinder.
On cooling tea and coffee
Authors: Rees W. G. , Viney C.
Published: March 2005

Factors influencing the rate of cooling of hot coffee and tea have been investigated theoretically and studied experimentally using deliberately ‘‘domestic’’ apparatus. It is demonstrated that black coffee cools faster than white coffee under the same conditions. Under most (but not all) circumstances, if coffee is required to be as hot as possible several minutes after its preparation, any milk or cream should be added immediately, rather than just before drinking.
Elastic scattering by a paraboloid of revolution
Authors: Evans James
Published: March 2005

The differential cross section for scattering by a perfectly elastic, impenetrable paraboloid of revolution is obtained. The angular dependence is identical to that for Rutherford scattering. It follows that Rutherford scattering of particles of a particular energy is equivalent to scattering from a particular paraboloid of revolution.
Coupled oscillations of a ball and a curved-track pendulum
Authors: Benenson R. E , Marsh B. B.
Published: March 2005

The curious motion of a quarter-circle track suspended as a pendulum in which a ball bearing moves back and forth is analyzed using Lagrangian mechanics.
Electric energy and forces in the presence of boundary conditions
Authors: Pomer F.
Published: March 2005

Energy and forces in boundary value problems of electrostatics are considered. It is well known that when boundary conditions can be simulated by electrical images, care must be taken in evaluating forces from energy. In this article, it is shown how the energy has to be corrected, in the general case, in order to be used as a force potential. Physical meaning of this correction is analyzed.
A method for evaluating two-spin correlations of a one-dimensional Ising model
Authors: Tejero C. F.
Published: March 2005

A novel method for evaluating two-spin correlations of a one-dimensional Ising model is described. The method is based on an algebraic technique motivated by renormalization group theory and adapted for presentation in a graduate statistical physics course.
An adiabatic reversible process
Authors: Rechtman Raul
Published: March 2005

It is argued that an adiabatic reversible process is a subtle thermodynamical concept. It is then shown how such a process may be constructed for the special case of an ideal gas enclosed in a rigid cylinder surrounded by adiabatic walls fitted with a piston that slides without friction.
The new physics—Physical or mathematical science?
Authors: Oldershaw Robert L.
Published: March 2005

As creators of the new physics have proposed increasingly abstract descriptions of nature, the ‘‘testability’’ of their theoretical constructs has markedly declined. While the current problems are not different in kind from those characterizing other eras in the evolution of physics, they do appear to be substantially different in degree from past experience. This situation, exacerbated by an incongruously strong confidence in the standard paradigms of particle physics and cosmology, is a cause for concern.
A real-time demonstration of the depth dependence of pressure in a liquid
Authors: Fox John N. , Eddy Jerry K. , Gaggini Norman W.
Published: March 2005

A demonstration experiment is described that employs a computer interface to make a real-time plot of the pressure in a liquid as a function of depth. When two immiscible fluids are used the change in density across the fluid interface can be demonstrated. Data are presented for the case of water floating on carbon tetrachloride.
Conductance fluctuations in loops of gold
Authors: Washburn S.
Published: March 2005

The magnetoresistance of small wires and loops is described. At low temperatures, the electrons retain quantum mechanical phase coherence for distances of a micron or so, which is the size scale over which the measurements are made. The random interference of the electron wavefunctions appears as random fluctuations in the magnetoresistance, and in loops, the Aharonov–Bohm effect causes periodic oscillations. The resistance varies randomly with the Fermi energy of the electrons, with the voltage across the sample, and with any transverse voltages applied by external gates. The nonlocal character of the wavefunction leads to resistance fluctuations in configurations where classical physics predicts null results. Throughout the discussion the physics is explained for those new to the field.
A general method for differentiation of vectors in orthogonal systems of coordinates
Authors: Koo W. K. , Liew Y. C.
Published: March 2005

A general matrix method for differentiating unit vectors in an arbitrary orthogonal system of coordinates is given. The spatial and time derivatives of any vectors can then be obtained by differentiating the vector that has been expressed in terms of a product of a component row matrix and a unit vector column matrix, and then recombining the resultant matrices. Some examples are given to illustrate its use.
Historical contributions of the medical profession to physics
Authors: Spradley Joseph L.
Published: March 2005

About a dozen scientists who have made important contributions in the history of physics are identified as physicians or as having a scientific education that included medical school. Their relationship to the medical profession and their contributions to physics are briefly summarized. Both the strengths and weaknesses of a background in medicine are considered in relation to research and discovery in physics.
Realism and/or physics
Authors: Adler Carl G.
Published: March 2005

A recent editorial [John S. Rigden, ‘‘... to see it as it is ... to know it as it isn’t ...,’’ Am. J. Phys. 54, 397 (1986)] has suggested that physics as it is commonly practiced may be basically an antirealist science. At the same time, it can be observed that the current practitioners of biology and chemistry are usually strongly realist in their orientation. A case study in support of the general position of the editorial is presented. In addition, a possible reason for the difference in the philosophical perspective of physics and biology/chemistry is also examined.
A simple solution for the Dirac hydrogenlike atom
Authors: de Lange O. L.
Published: March 2005

Transformed, radial Dirac–Coulomb equations are solved for bound-state energy eigenvalues and coordinate-space eigenfunctions by a method Schrödinger used for the nonrelativistic case. The calculations use first-order differential operators and are simpler to perform than in the nonrelativistic limit because of a normalization property of the transformed Dirac eigenfunctions.
Reversing relative displacement in rolling fluids
Authors: Nickas G. D.
Published: March 2005

The theoretical behavior of various viscous fluids confined to cylinders rolling down an incline is analyzed. The moments of inertia of cylinder and fluid and the viscosity of the fluid, in a cylindrically symmetric laminar flow, determine the rolled distance as a function of time. In a multisystem race down the incline, as unusual double passing or double reversal in relative displacement is predicted by the dynamical solutions. Possible reasons for this behavior are discussed on the basis of ‘‘spin-up’’ times and energy transfer.
Field mapping: Computer calculation and analytical approximation
Authors: Gillis P. , Bailly J.-L. , Henri V. P. , Peto S.
Published: March 2005

A procedure for the calculation of the magnetic field generated by various coils is explained and compared to a 1902 approximation by Lyle. This approximation consists of substituting two single loops for a coil with a finite rectangular section. Both methods (exact and approximate) are applied in the case of two magnets used in the design of a nuclear magnetic relaxometer; the agreement between them is quite satisfactory, so that Lyle’s approximation can be used even off-axis, outside the region for which it was established.
Uniqueness of solutions to Helmholtz’s equation with linear boundary conditions
Authors: Kannenberg L.
Published: March 2005

This article presents a compact demonstration that a general linear boundary condition uniquely specifies the solution to Helmholtz’s equation in a finite volume. The Dirichlet and Neumann electrostatic boundary value problems appear as two special cases of the general problem.
On the effect of finite closure time of switches in electrical circuits with fast transient behavior
Authors: Bruzzone H. , Kelly H. , Moreno C.
Published: March 2005

The effect of finite closure time of switches in fast transient electrical circuits is presented. A simple theoretical model to predict the influence of the switching action is developed, yielding a good description of the measured behavior.
Photogates: An instrument evaluation
Authors: Mosca Eugene P. , Ertel John P.
Published: March 2005

The effective length of a flag executing photogate transit varies from photogate to photogate. It also varies with the position in the gap where it crosses the beam, and with the speed of the flag. Measurements were made using 23 photogates (the PASCO model 9204 and its newly updated version, the model 9204A). The flags were 11.66-mm-diam cylinders. The effective length of these flags was found to vary from photogate to photogate by up to 20%; vary with gap position by up to 8%; decrease by about 0.2% per meter/second with flag speed. Measurements and analysis are presented along with suggestions for minimizing systematic errors when using photogates in the laboratory.
A thermometer based on Archimedes’ principle
Authors: Nickas George D.
Published: March 2005

The theory is given for a thermometer whose thermometric property is the response of neutrally buoyant objects to the temperature-dependent density of a fluid. It is found that such a device would require very careful adherence to accurate density measurements of the responding elements.
Synthesis of the Planck and Bohr formulations of the correspondence principle
Authors: Hassoun Ghazi Q. , Kobe Donald H.
Published: March 2005

Planck formulated the correspondence principle between quantum and classical mechanics as the limit in which the Planck constant h goes to zero. Bohr formulated the correspondence principle to be the limit of large quantum numbers. For three common quantum mechanical systems it is shown that in order for eigenvalues of quantum mechanical observables to have meaningful classical limits, it is necessary to take the double limit as both the Planck constant goes to zero and the quantum number goes to infinity, subject to the constraint that their product is equal to an appropriate classical action. This synthesis of the Bohr and Planck formulations of the correspondence principle is also used to show that the quantum mechanical transition frequency between adjacent levels approaches the corresponding classical frequency. The features these systems have in common in their classical limit are explained by general considerations of the classical limit of the Schrödinger equation.
Elementary calculation of soil damping depth
Authors: Robson R. E.
Published: March 2005

An important problem in biophysics, calculation of the damping depth in relation to penetration of temperature ‘‘waves’’ through soil, is solved by adopting an approximate method of solving Fourier’s partial differential equation. The method illustrates a way in which students of physics majoring in life sciences, with limited mathematical experience, can come to terms with quantitative analysis of problems that would otherwise be beyond the scope of usual courses.
A model for undergraduate physics major outcomes objectives
Authors: Taylor G. R. , Erwin T. Dary
Published: March 2005

Concern with assessment of student outcomes of undergraduate physics major programs is rapidly rising. The Southern Association of Colleges and Schools and many other regional and state organizations are requiring explicit outcomes assessment in the accrediting process. The first step in this assessment process for major programs is the establishment of student outcomes objectives. A model and set of physics outcomes (educational) objectives that were developed by the faculty in the Physics Department at James Madison University are presented.
Scattering by spherically symmetric and nonspherically symmetric potentials
Authors: Ziegler Alfred
Published: March 2005

The usual presentation of scattering in standard quantum mechanics texts—based on the scattering phase shift δl —is neither very enlightening nor does it lend itself readily to generalization to nonspherically symmetric potentials. The presentation given in this article avoids these drawbacks by being both more general and more transparent.
Laplace vectors for the harmonic oscillator
Authors: Sivardière Jean
Published: March 2005

The two invariant Laplace vectors for the two-dimensional harmonic oscillator are derived from an elementary point of view. They are used to determine the equation of the orbit, and the orientation of the orbit from the initial conditions of the motion.
A propeller-driven glider for the student air track
Authors: Melton B. F.
Published: March 2005

A propeller-driven attachment for accelerating gliders on the student air track has been constructed and tested. The dc propeller motor is controlled by a switching-mode regulator circuit powered by a single 9-V dry cell battery. Constant forces in the range 0.05–0.15 N are readily obtainable. Spark paper measurements of position versus time on a 5-m air track, at velocities up to 1.2 m/s, yielded results that could be satisfactorily explained by assuming a constant accelerating force and a small damping force proportional to the square of the velocity. The results of several experiments that demonstrate the usefulness of the device for classroom lecture demonstrations are reported.
Angular momentum of a charge–monopole pair
Authors: Brownstein K. R.
Published: March 2005

The angular momentum of a static electric charge–magnetic monopole is, in SI units, L=(eg/4π) â. Here, e and g are their respective strengths and â is a unit vector along the line from the electric charge to the magnetic pole. A simple derivation is presented of this well-known result. The derivation makes use of vector (and tensor) analysis; no actual integrations involving the electromagnetic field are involved.
Redesigning courses and textbooks for the twenty-first century
Authors: Aubrecht Gordon J.
Published: March 2005

There is evidence that a confluence of pressures to change the current physics syllabus is building from many sources. Texts for science and engineering students do not usually have much contemporary physics content. There is a need to update textbooks to include areas of current interest in physics research, to include important facets of 20th-century physics that have gone virtually unnoticed in the present generation of physics textbooks. The consequence of additions of topics must be restructuring of the physics curriculum and may lead to corresponding deletions among topics presently discussed.
An analysis of two unusual reflection caustics
Authors: Lock James A. , Woodruff Judith R.
Published: March 2005

A reflection caustic consisting of an x or a cross surrounded by a circle was observed using two different reflector geometries. Double-glazed insulating windows that have become bowed, and circularly symmetric cookie trays and cake covers possessing two different curvatures at different distances from the symmetry axis, produce similar caustics when plane waves are incident far off-axis. For the case of the insulating windows, it was found that the concavely bowed outer pane produced the x portion of the caustic and the convexly bowed inner pane produced the circle portion. For the case of the circularly symmetric reflectors, the x and circle portions of the caustic were found to be produced by the regions of greater and lesser curvature, respectively. These results were verified by numerical spot diagram calculations for each of the reflector geometries.
Geometrical interpretation of the simultaneous diagonalization of two quadratic forms
Authors: Aravind P. K.
Published: March 2005

The theory of small oscillations, when cast in matrix form, leads to an eigenvalue problem involving the simultaneous diagonalization of two real symmetric matrices. While a geometrical interpretation of this process exists, its visualization is generally hampered by the multidimensional nature of the coordinate transformations involved. I consider a model problem with just two degrees of freedom for which the coordinate transformations become planar and therefore easily visualizable. A set of plane diagrams is provided showing how the diagonalization is achieved for the model problem considered.
A theorem on elastic collisions between ideal rigid bodies
Authors: Crawford Frank S.
Published: March 2005

In an elastic collision between two rigid bodies of arbitrary shape, the component of relative velocity of the impact points along the impulse direction is exactly reversed. The two relative velocity components perpendicular to the impulse direction are usually changed in a nonsimple manner, as for collisions between smooth ellipsoids, but are sometimes simply not changed at all, as for a collision between smooth spheres, or do not exist, as for a collision between an ideal superball and a flat surface.
Spherical acoustic resonators in the undergraduate laboratory
Authors: Bretz Michael , Shapiro M. L. , Moldover M. R.
Published: March 2005

A spherical acoustic resonator is reported that measures the speed of sound in gases with very high accuracy using comparatively simple instrumentation. The resonator can be used to illustrate, in a quantitative fashion, the temperature and pressure dependence of the speed of sound, the effects of thermal conductivity, and the splitting of nearly degenerate modes.
Teaching software construction to physicists
Authors: Carlson Edward H.
Published: March 2005

An ‘‘invisible issue’’ has arisen while teaching numerical and simulation methods applied to physics—training students to write clear and reliable programs. Appropriate elements are extracted from the field of software engineering and applied to the special problems that face students, faculty, and researchers who write computer programs for doing physics.
The dynamics of a falling chain: II
Authors: Calkin M. G.
Published: March 2005

The motion of a chain initially hanging symmetrically over a smooth horizontal peg is discussed, and an error in the usual solution is corrected. The motion of the chain after it leaves the peg is also considered.
A geometrical approach to sums of uniform random variables
Authors: Denardo Bruce , Larraza Andrés
Published: March 2005

Sums of independent random variables that have uniform probability densities are considered. With elementary geometry, the probability density is determined for the cases of two, three, and four variables and applications to the teaching of error analysis are discussed. The solution for the general case of any number of variables is geometrically motivated and this solution is discussed.
Radiation thermodynamics with applications to lasing and fluorescent cooling
Authors: Mungan Carl E.
Published: March 2005

Laser cooling of bulk matter uses thermally assisted fluorescence to convert heat into light and can be interpreted as an optically pumped laser running in reverse. Optical pumping in such devices drives the level populations out of equilibrium. Nonthermal radiative energy transfers are thereby central to the operation of both lasers and luminescent coolers. A thermodynamic treatment of their limiting efficiencies requires a careful development of the entropy and effective temperatures of radiation, valid for the entire range of light from the blackbody to the ideal laser limiting cases. In particular, the distinct meaning and utility of the brightness and flux temperatures should be borne in mind. Numerical examples help illustrate these concepts at a level suitable for undergraduate physics majors.
Divergent Host Responses during Primary Simian Immunodeficiency Virus SIVsm Infection of Natural Sooty Mangabey and Nonnatural Rhesus Macaque Hosts
Authors: Silvestri Guido , Fedanov Andrew , Germon Stephanie , Kozyr Natalia , Kaiser William J. , Garber David A. , McClure Harold , Feinberg Mark B. , Staprans Silvija I.
Published: March 2005

To understand how natural sooty mangabey hosts avoid AIDS despite high levels of simian immunodeficiency virus (SIV) SIVsm replication, we inoculated mangabeys and nonnatural rhesus macaque hosts with an identical inoculum of uncloned SIVsm. The unpassaged virus established infection with high-level viral replication in both macaques and mangabeys. A species-specific, divergent immune response to SIV was evident from the first days of infection and maintained in the chronic phase, with macaques showing immediate and persistent T-cell proliferation, whereas mangabeys displayed little T-cell proliferation, suggesting subdued cellular immune responses to SIV. Importantly, only macaques developed CD4+-T-cell depletion and AIDS, thus indicating that in mangabeys limited immune activation is a key mechanism to avoid immunodeficiency despite high levels of SIVsm replication. These studies demonstrate that it is the host response to infection, rather than properties inherent to the virus itself, that causes immunodeficiency in SIV-infected nonhuman primates.
Dynamic Fluorescent Imaging of Human Immunodeficiency Virus Type 1 Gag in Live Cells by Biarsenical Labeling
Authors: Rudner Lynnie , Nydegger Sascha , Coren Lori V. , Nagashima Kunio , Thali Markus , Ott David E.
Published: March 2005

Human immunodeficiency virus type 1 (HIV-1) Gag is the primary structural protein of the virus and is sufficient for particle formation. We utilized the recently developed biarsenical-labeling method to dynamically observe HIV-1 Gag within live cells by adding a tetracysteine tag (C-C-P-G-C-C) to the C terminus of Gag in both Pr55
Gag
expression and full-length proviral constructs. Membrane-permeable biarsenical compounds FlAsH and ReAsH covalently bond to this tetracysteine sequence and specifically fluoresce, effectively labeling Gag in the cell. Biarsenical labeling readily and specifically detected a tetracysteine-tagged HIV-1 Gag protein (Gag-TC) in HeLa, Mel JuSo, and Jurkat T cells by deconvolution fluorescence microscopy. Gag-TC was localized primarily at or near the plasma membrane in all cell types examined. Fluorescent two-color analysis of Gag-TC in HeLa cells revealed that nascent Gag was present mostly at the plasma membrane in distinct regions. Intracellular imaging of a Gag-TC myristylation mutant observed a diffuse signal throughout the cell, consistent with the role of myristylation in Gag localization to the plasma membrane. In contrast, mutation of the L-domain core sequence did not appreciably alter the localization of Gag, suggesting that the PTAP L domain functions at the site of budding rather than as a targeting signal. Taken together, our results show that Gag concentrates in specific plasma membrane areas rapidly after translation and demonstrate the utility of biarsenical labeling for visualizing the dynamic localization of Gag.
Vesicular Stomatitis Viruses Expressing Wild-Type or Mutant M Proteins Activate Apoptosis through Distinct Pathways
Authors: Gaddy Daniel F. , Lyles Douglas S.
Published: March 2005

Vesicular stomatitis virus (VSV) induces apoptosis by at least two mechanisms. The viral matrix (M) protein induces apoptosis via the mitochondrial pathway due to the inhibition of host gene expression. However, in some cell types, the inhibition of host gene expression by VSV expressing wild-type (wt) M protein delays VSV-induced apoptosis, indicating that another mechanism is involved. In support of this, the recombinant M51R-M (rM51R-M) virus, expressing a mutant M protein that is defective in its ability to inhibit host gene expression, induces apoptosis much more rapidly in L929 cells than do viruses expressing wt M protein. Here, we determine the caspase pathways by which the rM51R-M virus induces apoptosis. An analysis of caspase activity, using fluorometric caspase assays and Western blots, indicated that each of the main initiator caspases, caspase-8, caspase-9, and caspase-12, were activated during infection with the rM51R-M virus. The overexpression of Bcl-2, an inhibitor of the mitochondrial pathway, or MAGE-3, an inhibitor of caspase-12 activation, did not delay apoptosis induction in rM51R-M virus-infected L929 cells. However, an inhibitor of caspase-8 activity significantly delayed apoptosis induction. Furthermore, the inhibition of caspase-8 activity prevented the activation of caspase-9, suggesting that caspase-9 is activated by cross talk with caspase-8. These data indicate that VSV expressing the mutant M protein induces apoptosis via the death receptor apoptotic pathway, a mechanism distinct from that induced by VSV expressing the wt M protein.
Epstein-Barr Virus with the Latent Infection Nuclear Antigen 3B Completely Deleted Is Still Competent for B-Cell Growth Transformation In Vitro
Authors: Chen Adrienne , DiVisconte Matthew , Jiang Xiaoqun , Quink Carol , Wang Fred
Published: March 2005

The Epstein-Barr virus (EBV) nuclear antigen 3B (EBNA-3B) is considered nonessential for EBV-mediated B-cell growth transformation in vitro based on three virus isolates with EBNA-3B mutations. Two of these isolates could potentially express truncated EBNA-3B products, and, similarly, we now show that the third isolate, IB4, has a point mutation and in-frame deletion of 263 amino acids. In order to test whether a virus with EBNA-3B completely deleted can immortalize B-cell growth, we first cloned the EBV genome as a bacterial artificial chromosome (BAC) and showed that the BAC-derived virus was B-cell immortalization competent. Deletion of the entire EBNA-3B open reading frame from the EBV BAC had no adverse impact on growth of EBV-immortalized B cells, providing formal proof that EBNA-3B is not essential for EBV-mediated B-cell growth transformation in vitro.
Modulation of Protective Immunity, Eosinophilia, and Cytokine Responses by Selective Mutagenesis of a Recombinant G Protein Vaccine against Respiratory Syncytial Virus
Authors: Huang Yan , Anderson Robert
Published: March 2005

Using anEscherichia coli-grown plasmid vector encoding a fragment of thioredoxin (Trx) fused to a central region (amino acids 128 to 229) of the respiratory syncytial virus (RSV) (Long strain) G protein, we employed site-directed mutagenesis to investigate the importance of selected amino acids to vaccine efficacy. Mice were immunized with a total of 10 wild-type or mutant Trx-G proteins and challenged intranasally with RSV. Striking differences in the induction of RSV G-protein-specific antibodies, protection against RSV challenge, cytokine RNA responses, and induction of RSV-associated eosinophilic inflammation were observed among the mutant proteins examined. Taken together, the results identify a critical role for specific amino acids in the induction of protective immunity and priming for eosinophilia against RSV.
Risk of breast cancer after miscarriage or induced abortion: a Scottish record linkage case-control study
Authors: Brewster David H , Stockton Diane L , Dobbie Richard , Bull Diana , Beral Valerie
Published: March 2005

Study objective:To assess the risk of breast cancer in patients with a previous history of miscarriage or induced abortion.

Design:Case-control study relating “exposure” to outcome by linkage of national hospital discharge and maternity records, the national cancer registry, and death records.

Setting:Scotland.

Participants:Miscarriage analysis—2828 women with breast cancer and 9781 matched controls; induced abortion analysis—2833 women with breast cancer and 9888 matched controls.

Main results:After stratification for age at diagnosis, parity, and age at first birth, the odds ratio (95% confidence intervals) of breast cancer was 1.02 (0.88 to 1.18) in women with a previous miscarriage, and 0.80 (0.72 to 0.89) in women with a previous induced abortion. Further adjustments for age at bilateral oophorectomy, socioeconomic status (based on small area of residence), and health board area of residence had only minor effects on these odds ratios.

Conclusion:These data do not support the hypothesis that miscarriage or induced abortion represent substantive risk factors for the future development of breast cancer.
Arsenic mobilization from waste piles of the El Terronal mine,Asturias, Spain
Authors: Loredo J. , Ordóñez A. , Baldo C. , García-Iglesias J.
Published: March 2005

Arsenic is associated with Hg in the mercury deposits of the Asturias region of northern Spain. Until 1974, the mines of La Peña and El Terronal exploited an ore deposit located in the valley of the San Tirso River (Mieres district). At this site, a great volume of waste material from mining and metallurgical works have been stock-piled for years, constituting a spoil heap of about 20 000 m
2
in area. Total As concentrations in representative samples of waste materials on the surface of the spoil heap reach a maximum value of 72 153 mg kg
−1
and an average value of 15 967 mg kg
−1
; analysis of deeper samples (trenches on the spoil heap) exceed 99 999 mg kg
−1
. The total flow of polluted water from its circulation through the spoil heap is estimated at 3465 m
3
a
−1
. Weathering processes facilitate the dissolution and leaching of As and heavy metals in the ore and waste material. Arsenic contents in surface waters (San Tirso River) immediately downstream of the spoil heap reach 7.9 mg l
−1
. The impact on the area, reflected by elevated concentrations of As in adjacent soils, biota and surface/underground waters, is discussed.
Nitrogen budget of the Mobile–Alabama River System watershed
Authors: Carey Anne E. , Nezat Carmen A. , Pennock Jonathan R. , Jones Tracy , Lyons W. Berry
Published: March 2005

We have determined the nitrogen mass balance for the Mobile–Alabama River System (MARS) for two years of different hydrologic regimes (i.e. low flow
vs.
high flow). The maximum riverine export of N from the watershed is only 7%, suggesting relatively high retention and/or losses of N by denitrification within the watershed. Previous investigations of other watersheds within the USA demonstrate export percentages of
c.
20–25%. Our calculations indicate that during a high flow year such as 1990,
c
. 13% of the new N introduced to the watershed annually is lost within the riverine system either through diatom uptake or denitrification. Another 4% is lost to the groundwater while 25–38% is sequestered by the terrestrial biomass (i.e. crop production and forest growth). Thus, as much as 51% of the N input to the landscape in the MARS is unaccounted for. We believe the location of this ‘missing’ N is probably within the soil, or the N has been lost through denitrification within the terrestrial ecosystem. The relatively low N yield from the MARS suggests that the watershed is not as saturated with respect to N as are many other U.S. drainages.
Estimating sampling errors for major and trace elements in geological materials using a propagation of variance approach
Authors: Stanley Clifford R.
Published: March 2005

Sampling errors produced when geological materials (rocks, soils, tills, drainage sediments) are collected have been estimated empirically using variance decomposition methods or theoretically using Poisson or binomial statistics. Unfortunately, historical distribution-based approaches assume that the element of interest occurs in only one mineral. Although this may be true in some cases, most major oxide and many trace elements reside in more than one mineral in most geological materials. As a result, historical distribution-based approaches do not estimate sampling errors correctly.

An alternative theoretical approach to sampling error estimation is proposed that employs both Poisson and hypergeometric statistics, depending on whether the elements of interest reside in rare or common grains. It is intended for use in advance of sampling to ensure that samples in a survey will be colleted in sufficient size to achieve a desired level of sampling precision. This method requires estimates of the proportions, sizes and compositions of the minerals making up the geological material, and thus is based on information readily available from a few (orientation) samples of the material to be sampled.

This approach accommodates cases where more than one mineral contains an element of interest. It involves first estimating the sampling error for the minerals present in the geological material. Then, the mineral sampling errors are used to make estimates of the sampling error of all elements within these minerals simultaneously using a simple propagation of variance approach. An EXCEL spreadsheet is provided that undertakes the relevant calculations, and this can be adapted to consider any suite of minerals and elements in geological materials.