bluuebunny/crossref_metadata_2025 huggingface dataset:
Chitin‐supplemented Foliar Application of Serratia marcescens GPS 5 Improves Control of Late Leaf Spot Disease of Groundnut by Activating Defence‐related Enzymes
Authors: Kishore G. K. , Pande S. , Podile A. R.
Published: March 2005

Chitinolytic Serratia marcescens GPS 5 and non‐chitinolytic Pseudomonas aeruginosa GSE 18, with and without supplementation of chitin, were tested for their ability to activate defence‐related enzymes in groundnut leaves. Thirty‐day‐old groundnut (cv. TMV 2) plants pretreated with GPS 5 and GSE 18 (with and without supplementation of 1% colloidal chitin) were challenge inoculated after 24 h with Phaeoisariopsis personata, the causal agent of late leaf spot (LLS) disease of groundnut. GPS 5 and GSE 18, applied as a prophylactic spray, reduced the lesion frequency by 23% and 67%, respectively, compared with control. Chitin supplementation had no effect on the control of LLS by GSE 18, unlike GPS 5, which upon chitin supplementation reduced the lesion frequency by 64%, compared with chitin alone. In a time course study the activities of chitinase, β‐1,3‐glucanase, peroxidase and phenylalanine ammonia lyase were determined for the different treatments. There was an enhanced activity of the four defence‐related enzymes with all the bacterial treatments when compared with phosphate buffer and colloidal chitin‐treated controls. In correlation to disease severity in bacterial treatments, chitin‐supplemented GSE 18 was similar to GSE 18, whereas chitin‐supplemented GPS 5 was much more effective than GPS 5, in activation of the defence‐related enzymes. The high levels of enzyme activities following chitin‐supplemented GPS 5 application continued up to the measured 13 days after pathogen inoculation.
Statutory Occupational Health and Safety Workplace Arrangements for the Modern Labour Market
Authors: Johnstone Richard , Quinlan Michael , Walters David
Published: March 2005

Over the past 20 years there has been a significant refashioning of the labour market within Australia and other industrialised countries. This paper examines the implications of the growth of more flexible work arrangements for mechanisms designed to facilitate worker involvement in occupational health and safety at the workplace—a pivotal feature of post-Robens OHS legislation in Australia. It is argued that the growth of subcontracting, casual and home-based work has undermined both coverage and the effectiveness of these provisions, especially in a context where union membership and influence has also been declining. Looking at international experience, the paper examines a number of ways of remedying these deficiencies.
Oil and Water: The Contrasting Anatomies of Resource Conflicts
Authors: Selby Jan
Published: March 2005

It is often said that while many of the twentieth century's wars were fought over oil, those of the twenty-first will be fought over water. This paper seeks to counter this argument, as well as the assumption implicit in it that the two resources engender, or will engender, broadly similar types of conflict. Specifically it argues 1) that within the context of the contemporary global capitalism, oil and water are marked by starkly divergent political economies; 2) that the two resources thus have starkly contrasting impacts upon patterns of state formation; 3) that these factors together militate against the development of violent international water conflicts; and 4) that notwithstanding the above, water is already a significant cause of local violence in many parts of the global South.
EU–Russian Energy Links: A Marriage of Convenience?
Authors: Johnson Debra
Published: March 2005

This article explores issues of energy supply security from the perspective of the EU–Russian energy relationship and of competing foreign energy policy paradigms. Using approaches developed by Peter Rutland within the context of Russia's energy policy towards the CIS and the three pillars of EU energy policy as a starting point, the article concludes that the overall EU–Russian energy relationship can be best explained through a framework of mutual interest and dependency: that is, the EU is becoming increasingly, but not totally, dependent on Russian energy, particularly gas; and Russia is becoming increasingly, but not totally, dependent on European markets. Nevertheless, other paradigms continue to yield useful insights in relation to individual components of the EU–Russian energy relationship.
The local field inside a dielectric gas
Authors: Hynne F.
Published: March 2005

The Clausius–Mossotti relation is systematically in error for molecular gases. The dielectric constant is more adequately described in terms of an effective polarizability, which accounts for the interaction of a molecular dipole with itself through the surrounding molecules. These aspects of the local field problem of dielectric theory are discussed on the basis of a simple macroscopic model due to Onsager and Böttcher. The conclusions drawn from the model have been established by strictly microscopic arguments, however, and we briefly discuss the microscopic representations of the concepts used.
An interdisciplinary science–humanities course
Authors: Dick B. G.
Published: March 2005

A course in the intellectual tradition of the West containing a generous amount of the history of science is described. It has been successfully taught by scientist–humanist teams of two for the last seven years. A selected bibliography of books and articles which have proved to be useful is given.
Exactly solvable three–dimensional scattering problem
Authors: Eftimiu C.
Published: March 2005

Schrödinger’s equation is solved exactly for a potential vanishing outside a prolate spheroid. The potential is then reconstructed from the first Born approximation for the scattering amplitude.
Le Châtelier reciprocal relations and the mechanical analog
Authors: Gilmore Robert
Published: March 2005

Le Châtelier’s principle is discussed carefully in terms of two sets of simple thermodynamic examples. The principle is then formulated quantitatively for general thermodynamic systems. The formulation is in terms of a perturbation-response matrix, the Le Châtelier matrix [L]. Le Châtelier’s principle is contained in the diagonal elements of this matrix, all of which exceed one. These matrix elements describe the response of a system to a perturbation of either its extensive or intensive variables. These response ratios are inverses of each other. The Le Châtelier matrix is symmetric, so that a new set of thermodynamic reciprocal relations is derived. This quantitative formulation is illustrated by a single simple example which includes the original examples and shows the reciprocities among them. The assumptions underlying this new quantitative formulation of Le Châtelier’s principle are general and applicable to a wide variety of nonthermodynamic systems. Le Châtelier’s principle is formulated quantitatively for mechanical systems in static equilibrium, and mechanical examples of this formulation are given.
Space-time symmetries and photon selection rules
Authors: Stedman G. E.
Published: March 2005

The effects of time and space inversion, and also spatial rotation, on photons and their interaction with matter are discussed. Simple analyses are given for spinorial sign reversal effects and for various selection rules on the interaction with matter. Several rules require for their interpretation a judicious combination of arguments from spatial and temporal symmetry operations.
Timing the flight of the projectile in the classical ballistic pendulum experiment
Authors: Peterson F. C.
Published: March 2005

An apparatus has been designed and constructed to measure the time of flight of the projectile fired by the Blackwood pendulum apparatus. Microphones mounted on the pendulum base and on a metal target plate yield signals, which after amplification and shaping by custom designed circuitry, start and stop a commercial digital timer. The purpose, use, and design of these accessories are described.
One-dimensional hydrogen atom and hydrogen molecule ion in momentum space
Authors: Lapidus I. Richard
Published: March 2005

The momentum-space wave functions have been obtained for the one-dimensional hydrogen atom and the symmetric and antisymmetric states of the one-dimensional hydrogen molecule ion with δ-function interactions between the particles. The uncertainty relation has been evaluated as a function of the distance between the nuclei in the molecule ion. For the symmetric state this is finite for the collapsed molecule. For the antisymmetric state the energy is positive for a nuclear separation less than a0=ℏ2/me2 and the uncertainty in the position of the electron is infinite.
An experiment for studying the electrical conductivity and its critical behavior in ferromagnets
Authors: Kamal R. , Sikri S. , Sood B. R.
Published: March 2005

A simple experimental setup is described for studying the critical behavior of electrical conductivity in ferromagnets. It has been used to find the Curie temperature Tc.
A home-made pyranometer for solar experiments
Authors: Zanetti V. , Zecca A.
Published: March 2005

This paper describes the construction and operation of a pyranometer for didactical use. The principle of operation, the performance, and the limitations are described. The didactical relevance of the instrument and the physical facts that can be brought out during its usage and construction are discussed.
An upper-division, introductory biophysics course
Authors: Maltempo Martin M. , Moss Thomas H.
Published: March 2005

A one-semester, introductory biophysics course is described. The course material includes several biophysical topics, most of contemporary research interest, developed from first principles, assuming a background of one year of college physics and one year of college chemistry. A serious effort has been made to choose those accessible topics which would allow for a high degree of continuity in the course. The biophysics of heme proteins is used as a unifying motif to provide continuity over much of the course material.
New method for calculating electric and magnetic fields and forces
Authors: Jefimenko Oleg D.
Published: March 2005

It is shown that for the purpose of electric field calculations, polarized dielectric bodies and real electric charge distributions can be replaced by fictitious ‘‘polarization current’’ distributions. Electric fields can then be calculated by any of the techniques available for calculating magnetic fields, and vice versa. Also electric forces acting on electric charges and dielectrics can be calculated by using the techniques available for calculating magnetic forces on currents. The method is illustrated by examples on calculating electric fields produced by electrets and by examples on calculating forces on dielectric bodies.
Latent heat and low-temperature heat capacity experiment for the general physics laboratory
Authors: Tompson C. W. , White H. W.
Published: March 2005

An experiment to measure the latent heat of vaporization of liquid nitrogen and the average heat capacities at constant pressure of several materials in the temperature range 77–295 K is described. This exercise uses normally available laboratory apparatus and is suitable for the general physics laboratory.
Simultaneity and special relativistic kinematics
Authors: Janis Allen I.
Published: March 2005

Starting with a careful analysis of the thought experiment known as Einstein’s train, it is shown how some basic results of special relativistic kinematics can be understood, both qualitatively and quantitatively, in terms of the relativity of simultaneity.
Dynamics of a tape that unwinds while rolling down an incline
Authors: Calvini P.
Published: March 2005

The problem of a tightly wound tape which unwinds while rolling down an incline is considered. A comparison performed between the elementary solution suggested by a well-known textbook and the solution derived in a proper geometrical scheme shows a difference always exceeding 15% if the time of complete unwinding is concerned. The physical bases for some interesting phenomena such as the ‘‘taking off’’ and the ‘‘uphill’’ rolling of the tape are discussed and the reasonableness of the hypothesis of energy conservation is pointed out.
Particle masses
Authors: Landsberg P. T.
Published: March 2005

The Weinberg relation is discussed in the case of a time dependent gravitational constant. (AIP)
The eastward deflection of a falling object
Authors: Stirling D. R.
Published: March 2005

In the well-known problem of the eastward deflection of a falling object much physical insight is gained by viewing the motion from an inertial frame.
An uncertainty demonstration with electromagnetic waves
Authors: Nunn W. M. , Figueroa M.
Published: March 2005

An experiment is described in which a pulse-modulated electromagnetic signal is simultaneously displayed in the time domain by means of an oscilloscope and in the frequency domain with a spectrum analyzer. The inverse relation between pulse length and spectral-energy density can readily be observed, and an interpretation of the experiment as a demonstration of an uncertainty principle is presented.
Some aspects of the reflection and refraction of an electromagnetic wave at an absorbing surface
Authors: Parmigiani F.
Published: March 2005

It is shown that a limit angle cannot be defined for an electromagnetic wave refracted at a dissipative boundary. Moreover it is pointed out that the equiphase planes of the incident and refracted waves are, in some cases, parallel.
Many-body theory in condensed matter physics
Authors: de Llano Manuel
Published: March 2005

The nonrelativistic, continuous (as opposed to ‘‘spin’’) many-body problem as it relates to condensed matter at absolute zero temperature is reviewed in simple, nontechnical terms, mainly from the standpoint of infinite-order perturbation theory, for physical systems where all the particles have the same mass but which otherwise interact with arbitrary short- or long-range two-body forces.
Near-resonance absorption processes: A model study
Authors: Au C. K. , Aharonov Y.
Published: March 2005

We construct an exactly soluble model in which an otherwise bound system can make transitions to another channel with a continuous energy spectrum to simulate the decay of an excited atom by the emission of photons. We show that the resonance absorption line shape occurs naturally in such a model.
Classical mechanics and the electron spin
Authors: Heslot André
Published: March 2005

It is shown by means of simple techniques how it is possible to describe the electron spin and to predict the correct value for the gyromagnetic ratio within the framework of nonrelativistic classical mechanics. The paper illustrates at an elementary level the relevance of the generator aspect of observables in classical mechanics.
Additional formulas for stimulated atomic transitions
Authors: Siegman A. E.
Published: March 2005

A number of additional formulas for stimulated atomic transitions are presented to supplement the collection of formulas recently assembled by Hilborn [Am. J. Phys. 50, 982–986 (1982)]. Additional topics covered include resonant atoms imbedded in a dielectric medium, the vector and tensor susceptibility properties of atomic transitions, and the often-discussed ‘‘factor of 3.’’
Nuclear physics in Rutherford’s laboratory before the discovery of the neutron
Authors: Badash Lawrence
Published: March 2005

Work by Rutherford and his colleagues led to his nuclear model of the atom (1911), although it took a few years more for him to recognize the significance of this insight. With the understanding that radioactivity is a nuclear phenomenon, one may say that nuclear physics became the major pursuit in Rutherford’s Manchester and Cambridge laboratories. The key to this problem was reported in his 1919 papers on transmutations produced by bombarding nitrogen with alpha particles. Soon, a number of other elements yielded to these projectiles of radioactive decay, but recognition that more energetic particles would be needed to disintegrate heavier elements led to the development of accelerating machines. The search for the neutron, cloud chamber photographs of disintegrations, and exploration of the properties of beta and gamma rays also figured greatly in Rutherford’s attack on the nucleus.
A computerized rotational motion experiment for the introductory physics laboratory
Authors: Peterson F. C. , Williams S. A.
Published: March 2005

Designed for use in a calculus-based introductory physics laboratory, apparatus consisting of a metal disk rotating on a fixed axis has been instrumented with a commercial rotary encoder and a PET microcomputer. The angular velocity of the wheel is continuously monitored and logged by the computer, providing data for detailed study of applied torques, friction, and the collision of the rotating disk with objects dropped upon it.
Ehrenfest theorem for angular displacement
Authors: Kobe Donald H.
Published: March 2005

Because of domain considerations for the z component of the angular momentum operator, the time rate of change of the expectation value of the angular displacement φ is not equal to the expectation value of the angular velocity operator. The angular velocity operator is the angular momentum operator divided by the moment of inertia. Ehrenfest’s theorem is obtained for the time rate of change of the expectation value of cos φ and sin φ.
A critical re-examination of the Aharonov–Bohm effect
Authors: Home D. , Sengupta S.
Published: March 2005

The controversy concerning theoretical treatment of the Aharonov–Bohm (AB) effect is critically investigated. A new approach, taking the time-dependent aspect of this effect into consideration, is proposed which seeks to resolve the prevalent ambiguities. This provides interesting insight into the origin of the AB effect. Some clarifications are also made regarding the experimental verification of this effect.
Experimental observation of ionization waves
Authors: Gibson R. G.
Published: March 2005

Ionization waves are a type of low-frequency plasma oscillation found in dc glow discharges. A conceptual discussion of this wave process is presented and an inexpensive and simple apparatus to observe standing ionization waves is described. Some simple measurements were made and found to agree well with empirical ideas that are discussed.
Coherence time in periodically modulated light beams
Authors: Rebolledo M. A. , López R. J.
Published: March 2005

The study of the coherence properties of modulated light sources is interesting since their utilization has increased considerably. After introducing in an intuitive way the coherence time definition, we present a systematic method for calculating the coherence time of a periodically modulated intensity light beam. The results are applied to two cases: chopped light and pulsed laser light. A comment is made about the results and an experiment to prove the change of coherence properties with the modulation period is described.
Green functions and impurities in harmonic chains
Authors: Prato D. , Condat C. A.
Published: March 2005

The density of vibrational states of harmonic chains is calculated with the Green function formalism. Chains with impurities are considered, and it is explicitly shown how the localized states are built up from the contribution of every lattice site to the density of states. The method can be used, with slight changes, to study the dynamics of a linear ferromagnetic lattice with nearest-neighbor interactions. The procedure employed in this article shows clearly the power and simplicity of the Green function method.
The PET and pendulum: An application of microcomputers to the undergraduate laboratory
Authors: Quist Gregory M.
Published: March 2005

A set of introductory undergraduate experiments designed to illustrate the usefulness of microcomputers for observing and measuring complex physical phenomena is described. A Commodore PET microcomputer is used both as a calculational and data-collecting tool, investigating the motion of a real pendulum. Students at the introductory level are able to investigate and appreciate some relatively complex dynamics without recourse to advanced mathematics.
The physics behind path integrals in quantum mechanics
Authors: Mannheim Philip D.
Published: March 2005

We present a simple pedagogical discussion of the physics of path integrals in nonrelativistic quantum mechanics. Rather than show that the path integral gives the standard results of quantum mechanics, as is usually done in the literature, we instead discuss why it does so. Specifically, we discuss why the phase factor associated with each path is given by the classical action. We construct the path integral using Huygens’ principle. Finally, we show that the existence of many paths is a consequence of the spreading of the quantum-mechanical wave function.
The physics of karate
Authors: Wilk S. R. , McNair R. E. , Feld M. S.
Published: March 2005

This study analyzes physical aspects of a karate strike and its interaction with a target, examining some heretofore unexplored dynamical and biomechanical questions.
Under $100 home computers as laboratory devices
Authors: Wunderlich F. J. , Shaw D. E.
Published: March 2005

The purpose of this article is to alert physics educators to an important new application of inexpensive home computers in the undergraduate laboratory. These computers can be used to establish cost effective yet versatile experimental laboratory stations which directly measure physical parameters and control experiments, as do their more expensive computer counterparts. As specific examples, we illustrate how the computer with minimal circuitry can function as a digital voltmeter and pulse counter.
More on two-dimensional scattering
Authors: Maurone P. A. , Lim T. K.
Published: March 2005

The optical theorem is derived in two dimensions and shown to be consistent with the standard partial wave analysis. [AIP]
Electrostatic energy when dielectrics are present: A general integral approach
Authors: Gauthier N. , Wiederick H. D.
Published: March 2005

A detailed discussion of electric energy storage in the presence of dielectrics is presented. The discussion is general and is aimed at the introductory–intermediate levels, when an integral representation of the laws of electrostatics is more familiar to the student. The case where a discrete set of point charges is slowly transported into the vicinity of an arbitrary dielectric is first considered and then an extension to the continuous distribution is presented. A simple model of atomic polarization is introduced and used to illustrate dielectric nonlinearities and the concept of self-interaction. It is shown that the energy density E⋅D/2 is restricted to the case of linear dielectrics and a novel way of introducing Maxwell’s displacement current term at a more advanced level is suggested as a natural extension of the electrostatic case.
An FFT-based signal processor for 6502 microcomputers
Authors: Pickett R. C. , Lindgren G. E. , Anderson R. K.
Published: March 2005

An apparatus has been developed which enables sophisticated signal processing to be performed on inexpensive microcomputers. The prototyping was accomplished with an AIM-65, but the software is loaded in ROM’s and is completely relocatable (and hence usable with many 6502-based microcomputers). This paper describes the FFT algorithm and the software and hardware developed by the authors, and presents representative test plots of the transform and its inverse, as well as correlation, convolution, power spectrum, and transfer function. Thirty-two-bit data (16 bits real and 16 bits imaginary) are entered, processed in the fixed point, two’s complement mode and output on a digital plotter or oscilloscope. Running time is quite fast for data of this precision (typically 2 s or less for 256-point transforms) enabling nearly real-time processing.
Improved explanation of the electrocardiogram
Authors: Hobbie Russell K.
Published: March 2005

A simple model is presented which is used to calculate the potential outside a nerve or muscle fiber embedded in a uniform conducting medium. The resulting integral is evaluated in the dipole approximation and agrees with equations which have been in the literature for a long time. The result can be used to interpret the electrocardiogram.
Microwave–plasma interaction experiment
Authors: Gilgenbach R. M.
Published: March 2005

A microwave–plasma interaction experiment for laboratory courses is described. The experiment employs a conventional microwave oven to generate breakdown plasmas over a pressure range of 0.02 to 36 Torr in argon. Temporally resolved measurements of forward, reflected, and transmitted microwave power are reported, as well as plasma optical emission measurements. Results indicate a uniform plasma of electron density less than 2×1010 cm−3 can be generated with over 300 W of peak microwave power.
The relativistic classical increase of energy and angular momentum with rotation
Authors: Leonard C. M. L.
Published: March 2005

A body of uniform rest mass may be rotated and its energy in the rotational state clearly exceeds its energy in its rest state. The relativistic classical analysis of the ratio of these energies is carried out for spheres, cylinders, and their shells as a function of one rotational parameter. Given the initial body’s geometry, and the relevant choice for the internal ‘‘holding field,’’ the ratio of the equatorial speed to the light speed is used to characterize the relativistic to nonrelativistic moment of inertia ratio as well as the energy ratio.
Laboratory experiment on the measurement of pyroelectric coefficients
Authors: Morgan Steven H. , Silberman Enrique , Springer John M.
Published: March 2005

This paper describes a simple solid-state physics experiment which allows the determination of the pyroelectric coefficient and spontaneous polarization of a sample from measurements of the pyroelectric charge and pyroelectric current.
Computerized angular position transducer
Authors: Lindgren G. E. , Pickett R. C. , Anderson R. K.
Published: March 2005

A computerized angular position transducer has been developed for introductory laboratory use. The transducer employs a three-phase synchro controller for precisely determining angular position. The computer supplies a precise three-phase signal and also provides processing capability. Data are collected at the three-phase frequency at high resolution. The device appears to be a very useful transducer for physics laboratory experiments involving rotational or vibrational motion.
A particle moving in a homogeneous time-varying force
Authors: Gregório M. A. , de Castro A. S.
Published: March 2005

The problem of a quantum-mechanical particle that moves in a spatially uniform time-varying field of force is solved in the Schrödinger picture. An explanation on the peculiar behavior for the spreading of an initial wave packet is given in terms of the dispersion relation obtained in the analytical solution.
The acoustic radiation force
Authors: Torr G. R.
Published: March 2005

The physical origin of the radiation force exerted by an ultrasonic beam on an absorbing target is explained. It is shown that the force may have two sources—a nonzero time-averaged sound pressure in the ultrasonic beam, and the momentum transported by the beam—but that there is a movement of material out of the ultrasonic beam to prevent a nonzero time-averaged sound pressure from being established. Consequently, the transfer of wave momentum is the sole cause of the force. The assumptions made in evolving this explanation are discussed, and the resulting change in mean density within the ultrasonic beam is considered. It is pointed out that the acoustic radiation force is but one example of a universal phenomenon associated with all forms of wave motion.
Approximate energy levels of bound quantum systems
Authors: Fernández Francisco M. , Castro Eduardo A.
Published: March 2005

A simple approximate method based on variational principles is used to obtain energy eigenvalues for bound quantum systems. It is shown that the approximate eigenvalues satisfy both virial and Hellmann–Feynman theorems. Results obtained by this method are compared with the exact solutions of the Schrödinger equation.
Exactly soluble two-electron atomic model
Authors: Crandall R. , Whitnell R. , Bettega R.
Published: March 2005

For the class of ‘‘heliumlike’’ Hamiltonians, H=− 1/2 ∇21 − 1/2 ∇22 +V(r1)+V(r2)+W(r12), there is a fortuitous choice of (attractive) V and (repulsive) W potentials such that the system admits of exact analytic solution in both classical and quantum pictures. Specifically, harmonic attraction and inverse-cube repulsion forces result in a soluble three-body problem (with infinite nuclear mass). We derive the general classical electron trajectories and give a complete set of eigenfunctions of the Hamiltonian. We indicate how exact expectation values can be obtained and show that best fits to actual helium data require a nonzero repulsive coupling constant. We exhibit an s-state basis subset of wave functions, suitable for application to general problems of atomic and chemical physics.
Resolution of the Schrödinger equation through a simple algebraic technique
Authors: Fernández Francisco M. , Castro Eduardo A.
Published: March 2005

It is shown that the eigenvalues of the simple quantum-mechanical models usually studied in the first courses on Quantum Mechanics can be obtained through a very simple algebraic technique. The N-dimensional hydrogen atom, the N-dimensional isotropic harmonic oscillator, and the Morse oscillator are discussed as illustrative examples.
Some simple considerations on pulse shapes in radiation detectors
Authors: Delaney C. F. G. , Finch E. C.
Published: March 2005

Elementary ideas on pulse shapes from ionization chambers are reviewed. Ramo’s theorem, and a plausible interpretation of it, are discussed and the results applied to semiconductor detectors. The complication of plasma formation is briefly referred to.
Stirling’s formula!
Authors: Mermin N. David
Published: March 2005

Stirling’s approximation to n!  and other estimates, some cruder, some more refined, are developed along surprisingly elementary lines. The aim is to shed some light on why these approximations work so well, for students using them to study entropy and irreversibility in such simple statistical models as might be examined in a general education physics course. At the heart of the argument is an elementary and useful representation of all the corrections to Stirling’s approximation, with which even many experts seem to be unacquainted.
Microwave attenuation in liquid media
Authors: Haranas Yiannis H. , Lonc W. P.
Published: March 2005

A semi-quantitative undergraduate experiment is described which verifies that the attenuation of microwaves propagating in a lossy liquid medium depends both on the distance traveled by the wave in the medium, as well as on the medium’s electric conductivity.
Population dose due to nucleon decay
Authors: Gogolak Carl V. , Miller Kevin M.
Published: March 2005

Assuming a lifetime of 1030 years for nucleons, it is shown that the expected human loss of life expectancy due to nucleon decay is equivalent to that of smoking 10−9 cigarette per year. (AIP)
A remark on principal-value integrals
Authors: Boas Mary L. , Boas R. P.
Published: March 2005

Many physical problems lead to integrals that can be evaluated by contour integration, and sometimes there are poles on the contour. In practice, it usually is appropriate in such cases to express the result as a principal-value integral. Most textbooks treat each problem involving principal values individually by considering an indented contour and taking limits. We want to call the attention of users of the calculus of residues to a theorem which, although known, seems not to be well-known.
Dynamic method to measure the density of water in the vicinity of its maximum
Authors: De Paz Mario , Pilo Miranda , Puppo Giacomo
Published: March 2005

A simple experimental apparatus is described for measurements of water density in the vicinity of 4° C, based upon a dynamic response of water to a temperature gradient.
The two-body problem: A diagrammatic discussion
Authors: Remy F. , Mignard F.
Published: March 2005

The motion of planets and satellites is investigated by considering mainly the velocity vector, rather than the position. We introduce a convenient diagram in the velocity subspace to describe the orbital properties: semi-major axis, eccentricity, pericenter and apocenter distances. Orbital changes resulting from the atmospheric drag or from any sudden modification of the velocity vector are easily inferred from the diagram. Sample applications are presented as well.
On the time-energy uncertainty relation
Authors: Shalitin D.
Published: March 2005

The time-energy uncertainty relation is reviewed and discussed from some elementary aspects. The relation is confirmed for a metastable system by a direct estimate of the uncertainties.
Electron spectroscopy using a Franck–Hertz tube
Authors: Martin A. D. , Quinn P. J.
Published: March 2005

An advanced undergraduate laboratory experiment is described in which a standard two-grid Franck–Hertz tube is used as a combined electron gun, drift space, and retarding potential analyzer. Electron energy spectra with a resolution better than 1 eV are obtained which show some of the energy-loss features characteristic of mercury vapor.
Singular constraints in rigid-body dynamics
Authors: Carroll M. M.
Published: March 2005

The usual assumption on smooth constraint reactions is shown to lead to an inconsistency for a particular problem of plane motion of a rigid body. The singular nature of the problem is illustrated by treating it as the limit of a sequence of well-posed problems.
Experiment in critical phenomena at phase transitions in liquid crystals
Authors: Nicastro A. J.
Published: March 2005

A simple electro-optical experiment is described that allows advanced undergraduates to measure the critical exponent γ. The experiment investigates the electric-field-induced birefringence as a function of temperature at the nematic-isotropic phase transition in liquid crystals. The classical mean-field result that γ=1 is verified.
Identical particle states and operators and the case of two-electron scattering
Authors: Ferrell W. R. , Ritchie R. H. , Ferrell T. L.
Published: March 2005

A simplified notation is introduced for dealing with systems of indistinguishable fermions and bosons. The second-quantized form of system operators is obtained in a simpler manner than is offered ordinarily in textbooks. Details of the calculation of the nonrelativistic M≂ller cross section for scattering of two electrons are given as an example.
On the scattering theory in one dimension
Authors: Kamal A. N.
Published: March 2005

The one-dimensional scattering problem for dissipative media is formulated in terms analogous to the three-dimensional problem. A model simulating dissipative media is used to numerically evaluate the various quantities defined in this paper.
Electron diffraction by macroscopic objects
Authors: Anido G. , Miller D. J.
Published: March 2005

The theoretical results for the diffraction of electrons by a disk and a pair of rectangular slits is derived from the Schrödinger equation using results from time-dependent perturbation theory in both the strong and weak scattering limits. The double-slit ‘‘thought’’ experiment is often used in introductions to quantum mechanics as a demonstration that electrons have wave-like properties. It seems desirable to include a derivation of the result both as an interesting example and also as reassurance that the diffraction of ‘‘matter waves’’ leads to the same results as the diffraction of electromagnetic waves by the same obstacle.
Reply to ‘‘Comment on ‘The eastward deflection of a falling object’ ’’
Authors: Stirling D. R.
Published: March 2005

The apparent discrepancy in the final horizontal velocity viz. 0 and 2ωh=ωgT2 is removed by noting that in my description, the final velocity (relative to the space fixed axes) is V̄=ḡT downwards, which possess the small component V sin θ=Vθ=ωgT2 for θ small, as the required transverse velocity component in the rotated axes.
Entropy
Authors: Andrew Keith
Published: March 2005

Several different conceptualizations of entropy are examined: thermal, probabilistic, quantum-mechanical, information theoretic, black-hole, and chaotic. The unifying nature of entropy in all physical processes and recent cosmological advances are discussed.
Rumors of transcendence in physics
Authors: Pollard William G.
Published: March 2005

There are several hints in physics of a domain of external reality transcendent to three-dimensional space and time. This paper calls attention to several of these intimations of a real world beyond the natural order. Examples are the complex state functions in configuration space of quantum mechanics, the singularity at the birth of the universe, the anthropic principle, the role of chance in evolution, and the unaccountable fruitfulness of mathematics for physics. None of these examples touch on the existence or activity of God, but they do suggest that external reality may be much richer than the natural world which it is the task of physics to describe.
Identical motion in classical and quantum mechanics revisited
Authors: Floyd Edward R.
Published: March 2005

Identical motion for classical and quantum mechanics is re-examined in order to include the effects of energy-dependent potentials in the equations of motion. Only free particles permit such motion.
Study of the slipping of a rolling sphere
Authors: Shaw D. E. , Wunderlich F. J.
Published: March 2005

An experiment is presented that investigates quantitatively the transition of a sphere from rolling with no slipping to a combination of rolling and slipping. Students tend to find their data surprising; however, an application of the laws of rotational dynamics correctly predicts the observed behavior. The experiment is suitable for an introductory mechanics laboratory.
Logarithmic perturbation expansions in nonrelativistic quantum mechanics
Authors: Imbo T. , Sukhatme U.
Published: March 2005

We discuss an alternative method of performing coupling constant perturbation expansions in nonrelativistic quantum mechanics. This method, called logarithmic perturbation theory, yields new expressions for any-order corrections En to an unperturbed bound-state energy which do not involve cumbersome sums over intermediate unperturbed states. In one dimension, these corrections En can be evaluated using a simple explicit form containing a small number of integrals. In more than one dimension the approach is systematic but computations require the solution of well-defined partial differential equations. For order n=2 this equation is identical to that appearing in the method of Dalgarno and Lewis. Numerous illustrative examples are presented.
A simple experiment for studying the transition from order to chaos
Authors: Meissner H. , Schmidt G.
Published: March 2005

A simple experiment is described for the observation of transition from order to chaos in a near Hamiltonian and a strongly dissipative system. The system is a compass needle moving in an oscillating magnetic field. As the field amplitude is increased, period doubling is observed following the Feigenbaum scenario. New modes are also created by tangent bifurcations. The motion in the dissipative case appears to terminate in strange attractor-type chaotic motion.
A modulation transfer function analyzer based on a microcomputer and dynamic ram chip camera
Authors: O’Shea Donald C. , Rakes Alan C.
Published: March 2005

The modulation transfer function of a lens is measured by adapting a commercially available microcomputer-based detector for use in an optics laboratory. The technique and instrumentation for such measurements are described.
Linear flywheel for energy storage
Authors: McCoy Jimmy J.
Published: March 2005

The shape that will allow the maximum kinetic energy to be stored in a linear flywheel is calculated and the advantages of assigning such a problem to an undergraduate advanced mechanics class is discussed.
Black hole radiance and equivalence principle
Authors: Massa Corrado
Published: March 2005

The Hawking formula for the thermal emission of a black hole is derived using a quantum−relativistic effect. (AIP)
A simple model of irreversibility
Authors: Baker Gregory L.
Published: March 2005

One of the most interesting and enduring problems of physics is the reconciliation of time-reversal invariance in mechanics and the time directionality property of the second law of thermodynamics. In this paper a very simple model of a many-body system is given which may be used to illustrate the trend toward equilibrium both in terms of populations, Boltzmann’s H theorem, and fluctuations.
Egg-crate analogy
Authors: Reimann R. J.
Published: March 2005

A simple analogy is made between a crate of eggs and a semiconductor crystal. This permits easy visualization of such semiconductor properties as valence and conduction bands, thermal creation of electron-hole pairs, and doping. In addition, biasing is easily demonstrated along with conduction by majority and minority carriers in the valence and conduction bands.
Exact solvable model of a one-electron diatomic molecule
Authors: Makarewicz Jan
Published: March 2005

A new exact solvable model of a one-electron diatomic molecule is presented. This model takes into account all degrees of freedom of the molecule and determines right hierarchy of molecular energy levels.
What is spin?
Authors: Ohanian Hans C.
Published: March 2005

According to the prevailing belief, the spin of the electron or of some other particle is a mysterious internal angular momentum for which no concrete physical picture is available, and for which there is no classical analog. However, on the basis of an old calculation by Belinfante [Physica 6, 887 (1939)], it can be shown that the spin may be regarded as an angular momentum generated by a circulating flow of energy in the wave field of the electron. Likewise, the magnetic moment may be regarded as generated by a circulating flow of charge in the wave field. This provides an intuitively appealing picture and establishes that neither the spin nor the magnetic moment are ‘‘internal’’—they are not associated with the internal structure of the electron, but rather with the structure of its wave field. Furthermore, a comparison between calculations of angular momentum in the Dirac and electromagnetic fields shows that the spin of the electron is entirely analogous to the angular momentum carried by a classical circularly polarized wave.
Scattering by two-dimensional circular barrier, hard circle, and delta function ring potentials
Authors: Lapidus I. Richard
Published: March 2005

Scattering lengths are obtained for the scattering of particles from two-dimensional circular barrier, hard circle, and delta function ring potentials using classical mechanics and quantum mechanics. These results will be of interest in a quantum mechanics course as a supplement to the discussion of three-dimensional scattering.
Simple electrostatic model of the structural phase transition
Authors: Berezin Alexander A.
Published: March 2005

A purely classical system of four equal point charges q which are free to move over the surface of a sphere is considered. In the equilibrium configuration all charges are located at the vertices of the regular tetrahedron inscribed into the sphere. If a weak uniform electric field E is directed along the z axis, one charge q will move to the position (0,0,R), while three others will form an equilateral inscribed triangle with the plane perpendicular to the field. An increase of the field will distort the tetrahedron [three charges uniformly shift towards the charge at (0,0,R)], keeping the field (z axis) as a C3-symmetry axis. However, when E reaches the ‘‘critical’’ value E0=0.732q/R2, the system abruptly changes its symmetry: For E>E0 the equilibrium (least energy) configuration corresponds to all four charges located symmetrically at the corners of the inscribed square whose plane is perpendicular to E. Consequently, the field will now form a C4-symmetry axis. This jumpwise C3→C4 symmetry change provides a simple classical model for the structural phase transitions when the spontaneous discontinuity arises during a continuous change of one of the intensive variables (in this model the electric field E). Several related open problems which may appear attractive for the modeling on personal computers are also outlined.
Mechanical analog of optical retarders
Authors: Lai H. M. , Leung Lai-Yung , Lee Kwok-Leung , Chik K. P.
Published: March 2005

An anisotropic system, which is composed of only springs and metal balls, is shown to be similar to an optical retarder. A mechanical analog of a half-wave plate is thus constructed and its performance is found in qualitative agreement with the theory. Such a system may serve as a useful demonstration in teaching wave propagation in anisotropic media.
Use of a personal computer in an undergraduate optics laboratory
Authors: Foiles C. L.
Published: March 2005

An eight-channel, 8-bit ADC that plugs into the expansion port of a VIC-20 is described. The use of this ADC/VIC-20 combination in an optics lab is illustrated by a reflection, transmission, and absorption experiment.
The relation between gravitational mass, inertial mass, and velocity
Authors: Tsai Ling
Published: March 2005

This work concerns a ‘‘thought experiment’’ using a balance whose arm length can be varied in order to prove that, within the scope of the special theory of relativity, both inertial mass and gravitational mass of a moving body obey the relationship m=m0/(1−v2/c2)1/2. Therefore, if the inertial mass of a body and its gravitational mass are strictly equal at rest, then they are still equal when the body moves at high velocity. The argument extends Einstein’s principle of equivalence to special relativity.
A simple derivation and an example of Hamiltonian ray propagation
Authors: Molcho Jonathan , Censor Dan
Published: March 2005

The well-known Hamiltonian ray tracing equations are derived in a simple way, using elementary differential operations instead of the calculus of variations approach. A simple example, suitable for classroom demonstration, is given to highlight the use of ray tracing for space and time varying media.
Solar structure without computers
Authors: Clayton Donald D.
Published: March 2005

We derive succinctly the equations of solar structure. We first present models of objects in hydrostatic equilibrium that fail as models of the sun in order to illustrate important physical requirements. Then by arguing physically that the pressure gradient can be matched to the simple function dP/dr=−kre−(r/a)2, we derive a complete analytic representation of the solar interior in terms of a one-parameter family of models. Two different conditions are then used to select the appropriate value of the parameter specifying the best model within the family: (1) the solar luminosity is equated to the thermonuclear power generated near the center and/or (2) the solar luminosity is equated to the radiative diffusion of energy from a central region. The two methods of selecting the parameter agree to within a few percent. The central conditions of the sun are well calculated by these analytic formulas, all without aid of a computer. This is an original treatment, yielding much the best description of the solar center to be found by methods of differential and integral calculus, rendering it an excellent laboratory for applied calculus.
James Clerk Maxwell and religion
Authors: Theerman Paul
Published: March 2005

The evolution of James Clerk Maxwell’s religious beliefs is described. His college-age conversion experience and his membership in the ‘‘Apostles’’ were crucial in his religious development. In his mature statements, Maxwell denied that scientific truth was dependent on religious truth, or the reverse. Nonetheless, scientific conclusions could enrich religious contemplation of God’s actions in nature. Maxwell provided a religious interpretation of the apparent uniformity and eternity of atoms.