bluuebunny/crossref_metadata_2025 huggingface dataset:
Resource letter: AHRS-1: Atoms in high Rydberg states
Authors: Dunning F. B.
Published: March 2005

A dramatic increase in studies of atoms in high Rydberg states has occurred in recent years. This increase derives in part from their many unusual physical properties and in part from recent technological advances, including the development of tunable dye lasers. This Resource Letter provides a guide to experimental work in this area and to the physics of Rydberg atoms. The letter E after an entry identifies introductory material or papers that can be readily understood by readers with no specialized knowledge of the field. The letter I indicates articles of a somewhat more specialized nature and the letter A identifies specialized papers written at an advanced level. An asterisk (*) indicates those articles to be included in an accompanying reprint book.
A novel method of solving two-dimensional electrostatic potential problems
Authors: Dasgupta Basab B.
Published: March 2005

A novel method of solving a certain class of two-dimensional electrostatic potential problems is developed by exploiting their analogy with magnetostatic problems.
Atomic level order as function of angular momentum
Authors: Grosse H. , Pflug A.
Published: March 2005

A recently derived theorem for potential models is used to discuss the order of atomic energy levels for a single electron in the field of a nucleus surrounded by a closed electronic shell. Neglecting exchange energies, we can prove the observed increase of these levels as a function of angular momentum. The usual textbook explanation for the level order is seen to be not conclusive.
The initial knowledge state of college physics students
Authors: Halloun Ibrahim Abou , Hestenes David
Published: March 2005

An instrument to assess the basic knowledge state of students taking a first course in physics has been designed and validated. Measurements with the instrument show that the student’s initial qualitative, common sense beliefs about motion and causes has a large effect on performance in physics, but conventional instruction induces only a small change in those beliefs.
Common sense concepts about motion
Authors: Halloun Ibrahim Abou , Hestenes David
Published: March 2005

Common sense beliefs of college students about motion and its causes are surveyed and analyzed. A taxonomy of common sense concepts which conflict with Newtonian theory is developed as a guide to instruction.
Running Crooke’s radiometer backwards
Authors: Crawford Frank S.
Published: March 2005

It is pointed out that the direction in which a Crooke’s radiometer rotates can be controlled by changing the temperature of its surroundings. (AIP)
Kinematics of the Compact Disc/Digital Audio system
Authors: McKelvey J. P.
Published: March 2005

The kinematics of the recently introduced Compact Disc/Digital Audio system is investigated. Experimentally, it is demonstrated that the nominally constant linear velocity of scanning actually varies by as much as 15% during playback. This variation gives rise to an easily observable departure from the conventional kinematics of tape recording, wherein this velocity is held strictly constant. A modified scheme of kinematics is introduced, which describes all observable aspects of the kinematic behavior of the CD system in close accord with experimental results. The measurements and calculations exhibit certain interesting and important features of rotational kinematics, illuminate some little-known aspects of the behavior of the CD system, and form the basis of an informative and up-to-date experiment in intermediate mechanics.
The axioms underlying Maxwell’s electromagnetic equations
Authors: Walker G. B.
Published: March 2005

An attempt is made to identify the axiomatic natural laws contained in Maxwell’s equations. It is proposed that the dual to the Faraday law be accepted as axiomatic and given the name the Maxwell law. An argument is presented to show that the magnetic effect of a current is a consequence of that law.
Temperature variation of modulus of rigidity and internal friction: An experiment with torsional oscillator
Authors: Shanker Gauri , Gupta V. K. , Saraf B. , Sharma N. K.
Published: March 2005

An experiment is described for studying the frequency response of a thin metallic rod clamped at one end and loaded at the other, when forced to execute torsional oscillations. The width of resonance, although sharp, is studied in detail by a specially designed function generator. The specimen can be heated and the internal friction of the specimen metal is studied as a function of temperature by measuring the width of resonance. The comparison of the measured values of internal friction with the theoretical estimates based upon various models available is rather involved and not done here. However, as an undergraduate experiment the student can be successfully baptized to the intricacy of the study of solids and their mechanical and thermal behaviors.
U.S. population dynamics
Authors: Bartlett Albert A. , Conklin Richard L.
Published: March 2005

Interesting results can be derived by applying to the population of the U.S. the elementary concepts of the kinematics and Newtonian dynamics of an ensemble of particles. The average speed of Americans (≊0.7 m/s) is found by using data from standard statistical sources to estimate the total distance traveled each year by the entire population of the U.S. The interesting dynamics follow from an analysis of the motion of the center of population (center of mass) whose latitude and longitude are published for each decennial census since the year 1790. The most recent average velocity of Americans (1970–1980) is 2.7×10−4 m/s; 26° S of W. The most recent average acceleration (1965–1975) is 3.9×10−13 m/s2; 33° S of W. The elementary analysis yields quantitative values of a number of interesting parameters that characterize the dynamic population of the U.S.
Fresnel diffraction by a circular aperture
Authors: Burch D. S.
Published: March 2005

The Fresnel–Kirchhoff theory is used to derive formulas which permit rapid calculation by personal computer of the radial distribution of irradiance in a Fresnel diffraction pattern behind a circular aperture illuminated by a plane wave. An experiment to measure the radial distribution of irradiance is described. The experimental results are in good, but not complete, agreement with the theory.
Eigenvectors of the electromagnetic field tensor and relativistic charged-particle motions
Authors: Dumais Jean-François
Published: March 2005

Eigenvectors and eigenvalues of the electromagnetic field tensor are found with use of a special representation of the electromagnetic field tensor. These are then used to describe, in any frame, the relativistic motion of a charged particle in an arbitrary spatially uniform and static electromagnetic field.
Cardboard star finder
Authors: Holverson E. L.
Published: March 2005

An inexpensive star finder which is accurate enough to be used by science majors and simple enough to be used by nonscience majors will be described. Experiments described consist of measurement of the right ascension and angle of declination of celestial objects; the path of the moon on the celestial sphere; the sidereal period of the moon; and measurement of large distances by the method of parallax. A summary of the experimental results obtained by nonscience majors using the star finder will be compared with accepted values.
The lightning-rod fallacy
Authors: Price Richard H. , Crowley Ronald J.
Published: March 2005

It is accepted generally that the electric field strength on the surface of an isolated charged conductor is greatest where the surface curvature is greatest. We show here that there is, in fact, no relationship between these two maxima and that, in general, they are located at different points on the surface. Two classes of analytic examples are offered: one using conformal mapping techniques and the other involving small perturbations of a conducting spherical surface.
Fourier series experiment for the undergraduate physics laboratory
Authors: Lambert R. K. , O’Driscoll R. C.
Published: March 2005

An experiment is described in which students manually sample a given periodic waveform, then use the discrete Fourier transform to perform harmonic analysis of this waveform. The waveform is then reconstructed using a waveform synthesizer which is described here. The synthesizer has controls for amplitude and phase on each of eight harmonically related frequencies. By choosing different sampling frequencies the effects of aliasing can be seen.
Speed dependence of the efficiency of heat engines
Authors: Spence R. D. , Harrison Michael J.
Published: March 2005

We have studied the efficiency and power output of a simple model of an irreversible heat engine as a function of cyclic operating frequency. The model adopted is defined by a reversibly cycled working substance coupled to heat source and sink by thermally conducting walls. The maximum operating frequency corresponding to zero external power output is associated with the traversal of a limit cycle in the working substance. Closed form expressions for the maximum operating frequencies are derived for the special cases of isothermal and polytropic limit cycles.
Photoelectric effect for the one-dimensional hydrogen atom with a δ-function interaction
Authors: Postma B. J.
Published: March 2005

A one-dimensional hydrogen atom with a δ-function interaction potential is considered in a weak external harmonically oscillating electromagnetic field. The photoelectric effect is treated in first-order perturbation theory. The total cross section σ(ω) is calculated and expressed in terms of the imaginary part of the frequency-dependent complex polarizability.
Energy in a one-dimensional small amplitude mechanical wave
Authors: Mathews W. N.
Published: March 2005

We present a discussion of the energy associated with a one-dimensional mechanical wave which has a small amplitude but is otherwise general. We consider the kinetic energy only briefly because the standard treatments are adequate. However, our treatment of the potential energy is substantially more general and complete than the treatments which appear in introductory and intermediate undergraduate level physics textbooks. Specifically, we present three different derivations of the potential energy density associated with a one-dimensional, small amplitude mechanical wave. The first is based on the ‘‘virtual displacement’’ concept. The second is based on the ideas of stress and strain as they are generally used in dealing with the macroscopic elastic properties of matter. The third is based on the principle of conservation of energy, and also leads to an expression for the energy flux of the wave. We also present an intuitive and physical discussion based on the analogy between our system and a spring.
Extreme values problems in mechanics without calculus
Authors: Mak Se-yuen
Published: March 2005

The use of a noncalculus technique (imposing the condition that physically meaningful roots of a quadratic equation must be real) to obtain the maximum or minimum value of some variable of interest is found appropriate for a class of mechanics problems. Three examples are illustrated. An overall review of other possible cases is listed.
Improvements in the demonstration of the hysteresis loops of ferromagnetic materials
Authors: Meng Yunchi , Liang Zhujian
Published: March 2005

An improved apparatus has been developed for demonstrating the hysteresis loops of ferromagnetic materials. Using a Hall probe, a storage oscilloscope, and specially designed circuitry one can in effect plot the initial magnetization curve and the hysteresis loop of a sample point by point, either manually or automatically. Under manual control, the apparatus can also be used to demonstrate minor hysteresis loops of the sample. These minor loops are related to the concepts of permeability μ, incremental permeability μΔ and reversible permeability μr.
A critical examination of the Abraham–Lorentz equation for a radiating charged particle
Authors: Jiménez J. L. , Campos I.
Published: March 2005

This is a discussion of the conceptual problems that have muddled the equation of motion for a radiating charged particle for a long time. An effort is made to pinpoint the weak parts of the usual arguments on this topic. The problems found range from doubts on the applicability of the classical electrodynamics of Maxwell and Lorentz to the problem at hand, to the inapplicability of certain perturbation techniques once the general theory has been tentatively accepted. Hopefully this will raise interest on these challenging problems, whose importance goes beyond the classical domain.
Rotating discontinuity of the bowed string using computer graphics
Authors: Brown Judith C.
Published: March 2005

Starting from Helmholtz’ observations on the time dependence of the motion of a point on a bowed string, the Fourier series for this experimental curve is obtained. By comparing this to the general time-dependent Fourier series for a string fixed at both ends, a general expression for the displacement of the bowed string as a function of position and time is derived. Using computer graphics facilities this function is plotted versus position 12 times during a period. The same is done for the velocity on the string. Finally, the velocity as a function of time for five different positions on the string is plotted.
Interesting results for rolling and slipping
Authors: Capell K.
Published: March 2005

Rolling with slipping of a uniform rigid body of revolution on a rough horizontal or inclined plane in two-dimensional motion is a standard problem in elementary dynamics; in such motion each cross section of the body of revolution remains parallel to a fixed vertical plane that is taken to contain the line of greatest slope in the case of motion on an inclined plane. Consider similar two-dimensional motion inside a fixed cylinder with general, rather than circular, cross-sectional curve C. This much more difficult problem is considerably simplified if there is no gravity force. The translational and rotational velocities of the body are then found to depend only on the change in direction of the tangent to the curve C up to the current point of contact during the motion and not on the curve itself.
An operator solution for the hydrogen atom with application to the momentum representation
Authors: de Lange O. L. , Raab R. E.
Published: March 2005

The radial form of Hylleraas’ equation for the hydrogen atom, Λl‖El〉=4ℏ4a−2‖El〉 (a=Bohr radius), is considered and it is shown that the operator Λl can be factorized. Hence ladder operators P±l are derived that are linear in the position operator r and are nonlinear functions of the momentum operator p. It is proven that P±l‖El〉 =2ℏ2a−1[1+(l+ (1)/(2) ± (1)/(2) )2 ×(2Mℏ−2a2E)]1/2‖E,l±1〉. In the momentum representation of wave mechanics the solutions to these equations are the radial momentum-space wavefunctions for the hydrogen atom. Thus a simple method of calculating these wavefunctions is obtained. The results complement the familiar operator solution for the hydrogen atom that is based on factorization of the radial Hamiltonian and yields operators that are linear in p and are nonlinear functions of r.
Determination of gravitational acceleration using a rubber ball
Authors: Guercio G. , Zanetti V.
Published: March 2005

A rubber ball, with a 4.9-cm diameter and 64-g mass, is dropped from a certain height h to bounce onto the floor, and the time between the first bounce and the nth bounce is measured. In the first version this time is taken by a digital stopwatch with one centisecond resolution, and in the second version, by an integrated-circuit timer with 1-ms resolution, triggered by a microphone. Considering the formula h=(1/2)gt2 and the coefficient of restitution of energy in the collision of the ball against the floor, the acceleration of gravity g may be determined to 2%–3% in the first version and to better than 1% in the second one. The experiment opens many problems, i.e., about the time of contact, the internal vibrational energy of the ball, and the dependence of the elastic properties of the rubber on the temperature.
A relativistic mass tensor with geometric interpretation
Authors: Rockower Edward B.
Published: March 2005

We derive a relativistic mass tensor (dyadic or matrix) whose origin and properties have a direct geometric interpretation in terms of projection operators related to the particle’s world line and local inertial frame in Minkowski space, yet whose eigenvalues are simply the longitudinal (ml) and the transverse (mt) mass. Writing the noncovariant equations of motion (EOM) for a point particle in terms of this mass tensor bridges the gap between the compact but sterile form of the Lorentz covariant EOM and the usual (‘‘unwieldy’’) noncovariant EOM in which ml and mt appear. General expressions for 3- and 4-space mass (inverse mass) tensors are presented in terms of the system Lagrangian (Hamiltonian).
Neutron irradiation of a NaI(Tl) crystal
Authors: Rhode J. I.
Published: March 2005

A series of measurements of nuclear beta and gamma radiation arising in neutron irradiation of a NaI(Tl) crystal is described. These measurements, which employ equipment items available in many advanced undergraduate physics laboratories, permit identification of prominent low-energy prompt gamma radiations produced in the I127(n,γ)I128 reaction as well as certain other radiations interpreted as arising in deexcitation of states in I127 excited by inelastic neutron scattering. In addition, a good determination of the Q value for beta-minus decay of I128 to Xe128 can be made, and the K capture branching to the Te128 ground state can be determined.
Whatever happened to Maxwell?
Authors: Hood C. Gregory
Published: March 2005

Our teaching of electromagnetism at the noncalculus level, whether in high school or college, should be based upon Maxwell’s equations, just as we customarily base our discussions of mechanics upon Newton’s second law of motion. Both the second law and Maxwell’s equations are differential equations; but each has an algebraic representation which is fruitful in many applications. An algebraic formulation of Maxwell’s equations is presented, along with some suggestions for teaching Maxwell’s equations ab initio based upon experiences accrued at Newton South since the 83/84 academic year.
Two laboratory experiments involving the homopolar generator
Authors: Eagleton R. D.
Published: March 2005

In these experiments numerical integration is used to verify Faraday’s law of induction for the case of an open-circuit homopolar generator. The computed emfs are compared with experimentally measured values.
A simple rainbow hologram for college optics laboratory project
Authors: Chen Hsuan , Pastor Ricardo
Published: March 2005

We describe a simple one-step optical recording geometry for the fabrication of a white light transmission hologram. The arrangement is a modified Leith–Upatnieks off-axis holographic configuration that yields a wide-field, deep-scene rainbow hologram. Detailed recording layout of the hologram and the experimental results are also included.
‘‘Diagonalization’’ of a compound Atwood machine
Authors: Crawford Frank S.
Published: March 2005

We consider a simple Atwood machine consisting of a massless frictionless pulley no. 0 supporting two masses m1 and m2 connected by a massless flexible string. We show that the string that supports massless pulley no. 0 ‘‘thinks’’ it is simply supporting a mass m0, with m0=4m1m2/(m1+m2). This result, together with Einstein’s equivalence principle, allows us to solve easily those compound Atwood machines created by replacing one or both of m1 and m2 in machine no. 0 by an Atwood machine. We may then replacing the masses in these new machines by machines, etc. The complete solution can be written down immediately, without solving simultaneous equations. Finally we give the effective mass of an Atwood machine whose pulley has nonzero mass and moment of inertia.
A numerical alternative to the traditional treatment of the propagation of uncertainty
Authors: Titus William J.
Published: March 2005

This article presents a numerical alternative for treating the propagation of uncertainty in a function that depends on random experimental variables. With the help of microcomputers, this technique can be used by students at all levels in a college physics curriculum and is particularly useful when there are a large number of such calculations to do or the function involved is complicated due to the number of variables present or the explicit functional form. The numerical procedure can even be used with a function that cannot be expressed analytically, but is given instead in the form of a table or graph. Finally, the technique does not require knowledge of partial differentiation or multivariable Taylor series expansions in contrast to the traditional treatment of the propagation of uncertainty.
Fermi–Dirac and Bose–Einstein distributions and the interaction of light with matter
Authors: Zitter R. N. , Hilborn Robert C.
Published: March 2005

Einstein’s treatment of stimulated emission, spontaneous emission, and absorption yields the Planck distribution law for photons if the ‘‘atoms’’ with which the photons interact are described by the Boltzmann distribution. We show that the Planck law is also obtained when the photons interact with matter that is described by either Fermi–Dirac or Bose–Einstein distributions.
The rattle in the cradle
Authors: Aničin B. A.
Published: March 2005

The history of science has known for quite some time that Newton’s very first concept of centripetal force is derived from a simple model of a particle bouncing elastically in a polygonal path from a circular constraint. Fully described by Isaac Newton himself in his ‘‘Principia’’ 300 years ago, the model does not seem to have caused any response in physics courses or textbooks.
Quantum mechanics of a chargeless spinning particle in a periodic magnetic field: A simple, soluble system
Authors: Calvo Miguel
Published: March 2005

The Schrödinger equation for a spin- 1/2 neutral particle with a magnetic dipole moment interacting with a helical periodic magnetic field of arbitrary strength and period is solved exactly. The solution is easily obtained by exploiting the symmetries of the Hamiltonian and it is expressed in terms of elementary functions. Several interesting physical aspects of the solution emerge. The behavior of the spin, the group velocity, and the effective mass tensor are obtained, yielding some novel and nontrivial results. Because of the mathematical simplicity, this problem is particularly suitable for an elementary graduate course in quantum mechanics.
Analog simulation of interacting diatomic molecules on two-dimensional lattices
Authors: Jin C. , Van Bladel K. H. , Edwards C. M. , Brookeman J. R. , Sullivan N. S.
Published: March 2005

A table-top demonstration model which simulates the orientational ordering of diatomic molecules on two-dimensional lattices is described. Fundamental ideas and phenomena concerning collective excitations (libron waves) and the effects of disorder on frustrated systems are illustrated by means of simple demonstrations.
Toward a modeling theory of physics instruction
Authors: Hestenes David
Published: March 2005

An analysis of the conceptual structure of physics identifies essential factual and procedural knowledge which is not explicitly formulated and taught in physics courses. It leads to the conclusion that mathematical modeling of the physical world should be the central theme of physics instruction. There are reasons to believe that traditional methods for teaching physics are inefficient and substantial improvements in instruction can be achieved by a vigorous program of pedagogical research and development.
Duality rotations and relativistic charged-particle motions
Authors: Salingaros Nikos
Published: March 2005

This paper establishes a connection between duality rotations of the electromagnetic field and the relativistic motion of a charged particle. The connection is a mathematical one, yet it helps to make the physics of charged-particle motions transparent. Explicit forms for the relativistic velocity and the gyration angle in a constant field are given. The result for the gyration angle in both electric and magnetic constant fields is not widely known, and is discussed at some length.
Derivation of energy expressions in the Rayleigh–Schrödinger perturbation theory
Authors: Naqvi K. Razi
Published: March 2005

It is shown that repeated differentiation, with respect to the perturbation parameter λ, of the equation 〈ψm (λ)‖H0+λV‖ψn(λ)〉 =En(λ)δmn, and methodical application of the closure relation ∑‖ψn〉〈ψn‖=1, provide a painless technique for deriving the energy corrections in the Rayleigh–Schrödinger perturbation theory. The procedure is compared with one based on solving the secular equation D(E)=0, where D is the determinant whose elements are 〈ψi‖H0+V‖ψj〉−Eδij.
Explaining the orbital velocity of an Earth satellite
Authors: Crawford Frank S.
Published: March 2005

A very nontechnical explanation is given for the mechanics of placing a satellite in orbit. (AIP)
Science and society test X: Energy conservation
Authors: Hafemeister David
Published: March 2005

United States energy consumption has remained essentially constant at about 80 exajoules/year (75 quads/year) since the oil embargo of 1973–1974, while the GNP in constant dollars has increased by about 30%. This article will discuss the physics behind some of these improvements in end-use efficiency in such areas as: (i) buildings (scaling laws, ‘‘free-heat,’’ superinsulated houses, thermal storage in large buildings, off-peak cooling), (ii) solar energy (passive, photovoltaics), (iii) utility load management (‘‘smart meters,’’ capital recovery fees, voltage control), (iv) appliances (life-cycle costs, refrigerators), and (v) lighting (isotopic enhancement).
Quantum action-angle-variable analysis of basic systems
Authors: Leacock Robert A. , Padgett Michael J.
Published: March 2005

Quantum action-angle variables are used to describe and analyze a number of familiar systems. For a given system, the quantum canonical transformation from the old coordinates, e.g., linear or polar, to the new coordinates, action-angle variables, is found by generalizing the corresponding classical transformation using a method based upon the correspondence principle, the Hermiticity and canonical nature of the old coordinates, and the requirement that the Hamiltonian be independent of the quantum angle variable. The bound-state energy levels and other important system properties follow immediately from the canonical transformation. Harmonic oscillators of various dimensions and the three-dimensional angular momentum system are used as illustrations; these illustrations provide interesting alternatives to the usual quantum treatments.
Graphical methods in geometric and Gaussian optics
Authors: Wiggins T. A. , Herman R. M.
Published: March 2005

Graphical methods showing the relationships among object and image positions, focal length and magnification for geometric optics are extended to the use of Newtonian variables. By defining similar quantities for Gaussian beams, we develop graphical methods to describe the relationships among the parameters specifying Gaussian beams. Examples are included.
Quantum strings
Authors: Fogleman Guy
Published: March 2005

The theory of the classical string and the method of canonical quantization are reviewed. The nonrelativistic string is then quantized using the canonical quantization procedure. A number of properties of quantized strings, such as quantized normal modes of vibration and ground state fluctuations, are discussed. The quantized nonrelativistic string is compared to quantized fields and to the strings in the recent superstring theories. The theory of relativistic strings is reviewed.
Elementary derivation of the law of equipartition of energy
Authors: Crawford Frank S.
Published: March 2005

In a freshman physics course the classical law of equipartition of energy is usually stated without proof, because its usual derivation assumes knowledge of the Maxwell–Boltzmann distribution function, which is not always included in a first course. Here, instead, is a nonrigorous but plausible derivation based on simple mechanical models. It does not use the distribution function and it shows roughly how long it takes to reach thermal equilibrium.
Slinky whistlers
Authors: Crawford Frank S.
Published: March 2005

Delightful sounds, produced in simple experiments, agree with an elementary theoretical analysis.
The total probability current and the quantum period
Authors: Lévy-Leblond Jean-Marc
Published: March 2005

Starting from the standard current density of probability for a quantum particle in a potential V(r), the total probability current in a stationary state is considered and investigated. Its physical interpretation leads to a natural definition of the time period for such a quantum stationary state. A simple and elegant formula relates the total current to the energy level of the state. This formula is shown to be consistent with the Correspondence Principle. The results are applied to the hydrogen atom and the harmonic oscillator.
On the molecular distribution of a hard-sphere gas
Authors: Güémez J. , Velasco S.
Published: March 2005

Given a gas of N0 hard-sphere molecules in a vessel of volume V0, one shows in a simple way that the probability WN0(N,V,V0) that N molecules are located in a subvolume V of V0 is given by the hypergeometric distribution. One shows that this distribution can be written as the product of the binomial distribution, which characterizes the ideal gas, and a factor which takes into account the size of the molecules. In the limit of low densities, one checks in two cases of practical interest that the derived distribution presents slight deviations from the corresponding ideal behavior.
Classical limit of the path-integral formulation of quantum mechanics in terms of the density matrix
Authors: Ajanapon Pimon
Published: March 2005

Instead of regarding the classical limit as the limit ℏ→0, an alternative view based on the physical interpretation of the elements of the density matrix is proposed. The derivation of the classical limit of quantum mechanics is carried out in two stages. First, the statistical classical limit is derived, and then, with an appropriate initial condition, the deterministic classical limit is obtained. The derivation hinges on the use of the Feynman path-integral formulation of quantum mechanics in terms of the density matrix. It is shown that deterministic (Hamilton’s or Newton’s) classical mehanics is not the classical limit of Schrödinger’s wave mechanics. The classical limit of Schrödinger’s wave mechanics is only statistical and corresponds to the classical Liouville equation. In order to obtain the deterministic classical limit, it is necessary to start out initially with a quantum mechanical mixture.
Computer-assisted teaching of optics
Authors: Chen Xiangxi , Huang Jacob , Loh Eddie
Published: March 2005

This article introduces ideas for the teaching of an undergraduate optics course using personal computers. It covers five topics with three on geometric optics and two on physical optics. They are (1) image formation of spherical mirrors, (2) spherical aberration of a lens, (3) chromatic aberration of lenses, (4) computer generated hologram, and (5) Fourier transforms and information processing.
Simple experiments in chaotic dynamics
Authors: Briggs Keith
Published: March 2005

Five simple nonlinear physical systems exhibiting chaotic dynamics are described. They are specifically designed for demonstration purposes to illustrate the ideas of period doubling, subharmonics, noisy periodicity, and intermittent and continuous chaos.
Newton and comets
Authors: Bork Alfred
Published: March 2005

The publication of Isaac Newton’s ‘‘notions about motion’’ 300 years ago was a major moment in the history of science. In the period just before 1687 Newton’s correspondence was much concerned with comets. In this period two bright comets were seen. These comets appear to have been a major stimulation to Newton’s work on mechanics.
Hsp90 Protein in Fission Yeast Swo1p and UCS Protein Rng3p Facilitate Myosin II Assembly and Function
Authors: Mishra Mithilesh , D'souza Ventris M. , Chang Kai Chen , Huang Yinyi , Balasubramanian Mohan K.
Published: March 2005

The F-actin-based molecular motor myosin II is involved in a variety of cellular processes such as muscle contraction, cell motility, and cytokinesis. In recent years, a family of myosin II-specific cochaperones of the UCS family has been identified from work with yeasts, fungi, worms, and humans. Biochemical analyses have shown that a complex of Hsp90 and the
Caenorhabditis elegans
UCS domain protein UNC-45 prevent myosin head aggregation, thereby allowing it to assume a proper structure. Here we demonstrate that a temperature-sensitive mutant of the fission yeast Hsp90 (Swo1p),
swo1-w1
, is defective in actomyosin ring assembly at the restrictive temperature. Two alleles of
swo1
,
swo1-w1
and
swo1-26
, showed synthetic lethality with a specific mutant allele of the fission yeast type II myosin head,
myo2-E1
, but not with two other mutant alleles of
myo2
or with mutations affecting 14 other genes important for cytokinesis.
swo1-w1
also showed a strong genetic interaction with
rng3-65
, a gene encoding a mutation in the fission yeast UCS domain protein Rng3p, which has previously been shown to be important for myosin II assembly. A similar deleterious effect was found when
myo2-E1
,
swo1-w1
, and
rng3-65
were pharmacologically treated with geldanamycin to partially inhibit Hsp90 function. Interestingly, Swo1p-green fluorescent protein is detected at the improperly assembled actomyosin rings in
myo2-E1
but not in a wild-type strain. Yeast two-hybrid and coimmunoprecipitation analyses verified interactions between Rng3p and the myosin head domain as well as interactions between Rng3p and Swo1p. Our analyses of Myo2p, Swo1p, and the UCS domain protein Rng3p establish that Swo1p and Rng3p collaborate in vivo to modulate myosin II function.
Initiation of Protein Synthesis in Bacteria
Authors: Laursen Brian Søgaard , Sørensen Hans Peter , Mortensen Kim Kusk , Sperling-Petersen Hans Uffe
Published: March 2005

Valuable information on translation initiation is available from biochemical data and recently solved structures. We present a detailed description of current knowledge about the structure, function, and interactions of the individual components involved in bacterial translation initiation. The first section describes the ribosomal features relevant to the initiation process. Subsequent sections describe the structure, function, and interactions of the mRNA, the initiator tRNA, and the initiation factors IF1, IF2, and IF3. Finally, we provide an overview of mechanisms of regulation of the translation initiation event. Translation occurs on ribonucleoprotein complexes called ribosomes. The ribosome is composed of a large subunit and a small subunit that hold the activities of peptidyltransfer and decode the triplet code of the mRNA, respectively. Translation initiation is promoted by IF1, IF2, and IF3, which mediate base pairing of the initiator tRNA anticodon to the mRNA initiation codon located in the ribosomal P-site. The mechanism of translation initiation differs for canonical and leaderless mRNAs, since the latter is dependent on the relative level of the initiation factors. Regulation of translation occurs primarily in the initiation phase. Secondary structures at the mRNA ribosomal binding site (RBS) inhibit translation initiation. The accessibility of the RBS is regulated by temperature and binding of small metabolites, proteins, or antisense RNAs. The future challenge is to obtain atomic-resolution structures of complete initiation complexes in order to understand the mechanism of translation initiation in molecular detail.
Neonatal maternal separation enhances dopamine D2-receptor and tyrosine hydroxylase mRNA expression levels in carotid body of rats
Authors: Kinkead Richard , Joseph Vincent , Lajeunesse Yves , Bairam Aida
Published: March 2005

Adult male (but not female) rats previously subjected to neonatal maternal separation (NMS) are hypertensive and show a significant increase (25%) in their hypoxic ventilatory response. To begin investigating the mechanisms involved in this gender-specific disruption in cardiorespiratory regulation, we tested the hypothesis that NMS alters the expression of dopamine D2-receptors and tyrosine hydroxylase mRNA in 3 peripheral organs involved in cardio respiratory regulation: the carotid bodies, superior cervical ganglia, and adrenals. Pups subjected to NMS were placed in a temperature- and humidity-controlled incubator 3 h per day for 10 consecutive days (P3–P12). Control pups were undisturbed. Once they reached adulthood (8–10 weeks), male and female rats were anesthetised. The carotid bodies, superior cervical ganglia, and adrenals were harvested for semi-quantitative analyses of dopamine D2-receptors and tyrosine hydroxylase mRNA expression using reverse transcription-polymerase chain reaction (carotid bodies only) and Northern blot. In the carotid bodies, comparison of densitometric analyses showed that NMS enhanced tyrosine hydroxylase mRNA expression in male, but not female, rats. Neonatal maternal separation increased dopamine D2-receptor mRNA expression also, but the effect was not gender specific. No changes in mRNA expression related to dopaminergic neurotransmission were observed in superior cervical ganglia or the adrenals. These results indicate that subsequent mechanistic investigations should focus on the carotid bodies, as enhancement of dopaminergic neurotransmission within this organ likely contributes to the gender-specific effects of NMS on cardiorespiratory regulation.Key words: control of breathing, plasticity, neonatal stress.
Chronic obstructive pulmonary disease: a novel risk factor for cardiovascular disease
Authors: Sin Don D , Man S.F Paul
Published: March 2005

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of morbidity and mortality in Canada and elsewhere. It affects 5% of all adult Canadians and is the fourth leading cause of death. Interestingly, the leading causes of hospitalizations and mortality among COPD patients are cardiovascular events. In the Lung Health Study, over 5 800 patients with mild to moderate COPD were studied. Forty-two to 48% of all hospitalizations that occurred over the study's 5-year follow-up period were related to cardiovascular complications. Various population-based studies suggest that independent of smoking, age, and gender, COPD increases the risk of cardiovascular morbidity and mortality twofold. Alarmingly, some bronchodilators, which are commonly used to treat symptoms in COPD, may increase the risk of cardiovascular morbidity and even mortality among COPD patients. In this paper, we discuss the epidemiologic evidence linking COPD and cardiovascular events as well as the potential mechanism(s) which may be responsible for this association.Key words: COPD, FEV1, cardiovascular events, C-reactive protein.
Radiation-induced strain differences in mouse alveolar inflammatory cell apoptosis
Authors: O'Brien Thomas J , Létuvé Séverine , Haston Christina K
Published: March 2005

Whole-thorax irradiation results in the development of the diffuse inflammatory response alveolitis in C3H/HeJ (C3H) mice and a milder alveolitis with fibrosis in C57BL/6J (B6) mice. In this study, we investigate if this mouse strain difference in response to radiation is due to differences in lung inflammatory cell apoptosis. Mice of the C3H and B6 strains were given a radiation dose of 18 Gy to the thorax and the animals were sacrificed at 11 or 18 weeks following exposure or when they were moribund. Active caspase-3 staining was used to identify apoptotic cells in the alveolar space of histological lung sections from the mice. The apoptotic index of B6 mice was greater than that of C3H mice at 11 weeks postirradiation (17.8% of airspace cells vs. 7.8%, p = 0.028) and in mice sacrificed because of illness (27.3% vs. 14.4%, p = 0.036). No C3H mice survived to the later time point. The inflammatory cells undergoing apoptosis in the mouse lungs were morphologically consistent with alveolar macrophages. We conclude that a difference in inflammatory cell apoptosis may contribute to the disparate pulmonary radiation response of these mouse strains.Key words: mouse, lung, radiation, apoptosis, fibrosis, caspase-3.
A new Apicomplexa-specific protein kinase family : multiple members in Plasmodium falciparum, all with an export signature
Authors: Schneider Achim G , Mercereau-Puijalon Odile
Published: March 2005

Background

Malaria caused by protozoan parasites of the genus Plasmodium spp. is a major health burden in tropical countries. The development of new control tools, including vaccines and drugs, is urgently needed. The availability of genome sequences from several malaria parasite species provides a basis on which to identify new potential intervention targets. Database mining for orthologs to the Plasmodium falciparum trophozoite protein R45, a vaccine candidate, led us identify a new gene family.

Results

Orthologs to the P. falciparum trophozoite protein R45 were detected exclusively in protozoan parasites of the phylum Apicomplexa, including several Plasmodium spp., Toxoplasma gondii and Cryptosporidium parvum. All family members are hybrid genes with a conserved C-terminal protein kinase domain of a novel type, recently called FIKK kinase, associated with a non conserved N-terminal region without any known functional signature. While a single copy gene was detected in most species, considerable gene expansion was observed in P. falciparum and its closest phylogenic relative P. reichenowi, with 20 and six copies, respectively, each with a distinct N-terminal domain. Based on full length protein sequence, pairs of orthologs were observed in closely related species, such as P. berghei and P.y. yoelii, P. vivax and P. knowlesi, or P. reichenowi and P. falciparum. All 20 P. falciparum paralogs possess a canonical Plasmodium export element downstream of a signal / anchor sequence required for exportation outside the parasitophorous vacuole. This is consistent with the reported association of the trophozoite protein R45, the only paralog characterised to date, with the infected red blood cell membrane. Interestingly, most genes are located in the subtelomeric region of chromosomes, in association with other multigene families contributing to the remodelling of the infected red blood cell membrane, in particular the ring erythrocyte surface antigen multigene family.

Conclusion

This Apicomplexan-specific gene family was called R45-FIKK kinase. The family hallmark is a kinase domain with unusual characteristics, raising the possibility of designing drug or vaccine strategies targeting this domain. The characteristics of the P. falciparum family suggest a role in remodelling the infected cell and as such possibly contribute to the particular virulence of this species.
Full Haplotype-Mismatched Hematopoietic Stem-Cell Transplantation: A Phase II Study in Patients With Acute Leukemia at High Risk of Relapse
Authors: Aversa Franco , Terenzi Adelmo , Tabilio Antonio , Falzetti Franca , Carotti Alessandra , Ballanti Stelvio , Felicini Rita , Falcinelli Flavio , Velardi Andrea , Ruggeri Loredana , Aloisi Teresa , Saab Jean Pierre , Santucci Antonella , Perruccio Katia , Martelli Maria Paola , Mecucci Cristina , Reisner Yair , Martelli Massimo F.
Published: March 2005

Purpose

Establishment of hematopoietic stem-cell (HSC) transplantation from mismatched relatives is feasible for patients with acute leukemia. As our original method of graft processing was unsuitable for large-scale clinical studies, we use automated devices for CD34+ cell purification.

Patients and Methods

Sixty-seven patients with acute myeloid leukemia (AML; 19 complete remission [CR] 1, 14 CR 2, nine CR > 2, 25 in relapse) and 37 with acute lymphoid leukemia (ALL; 14 CR 1, eight CR 2, two CR > 2, 13 in relapse) were conditioned with total-body irradiation, thiotepa, fludarabine, and antithymocyte globulin. Peripheral-blood progenitor cells were mobilized with recombinant human granulocyte colony-stimulating factor and depleted of T-cells using CD34+ cell immunoselection. No post-transplantation graft-versus-host disease (GvHD) prophylaxis was administered.

Results

Primary engraftment was achieved in 94 of 101 assessable patients. Six of the seven patients who rejected the primary graft, engrafted after a second transplantation. Overall, 100 of 101 patients engrafted. Acute GvHD developed in eight of 100 patients, and chronic GvHD, in five of 70 assessable patients. Thirty-eight patients died of nonleukemic causes. Relapse occurred in nine of 66 patients receiving transplantation in remission and in 17 of 38 receiving transplantation in relapse. Median follow-up of the 40 patients who survived event-free was 22 months (range, 1 to 65 months). Event-free survival (± standard deviation) rate was 48% ± 8% and 46% ± 10%, respectively, for the 42 AML and 24 ALL patients receiving transplantation in remission.

Conclusion

Our transplantation procedure provides reliable, reproducible CD34+ cell purification, high engraftment rates, and prevention of GvHD. The mismatched-related transplant emerges as a viable, alternative source of stem cells for acute leukemia patients without matched donors and/or those who urgently need transplantation.
Mechanisms underlying phonotactic steering in the cricketGryllus bimaculatusrevealed with a fast trackball system
Authors: Hedwig B. , Poulet J. F. A.
Published: March 2005

Phonotactic steering behaviour of the cricket G. bimaculatus was analysed with a new highly sensitive trackball system providing a spatial and temporal resolution of 127 μm and 0.3 ms, respectively. Orientation to artificial calling songs started at 45 dB SPL, it increased up to 75 dB SPL and then saturated. When exposed to two identical patterns of different intensity, crickets significantly steered towards the louder sound pattern,whenever the intensity difference was greater than 1 dB. Bilateral latency differences in sound presentation did not always cause clear orientation towards the leading side. The overall walking direction depended on the number of sound pulses perceived from the left or right side with the animals turning towards the side providing the larger number of pulses. The recordings demonstrated rapid changes in walking direction performed even during a chirp. These rapid steering responses occurred with a latency of 55–60 ms, well before the central nervous system had time to evaluate the temporal structure of a whole chirp. When every other sound pulse was presented from opposite directions, the crickets followed the temporal pattern of sound presentation and rapidly steered towards the left and right side. Steering towards individual sound pulses does not agree with the proposal that crickets analyse the quality of sound patterns and then steer towards the better pattern. Rather, these experiments suggest that fast steering to single sound pulses determines the lateral deviation of the animals and that complex auditory orientation emerges from this simple mechanism of auditory steering.