bluuebunny/crossref_metadata_2025 huggingface dataset:
Dental Cutting with Diamond Burs: Heavy‐Handed or Light‐Touch?
Authors: Siegel Sharon Crane , Fraunhofer Joseph Anthony
Published: March 2005

Purpose

The cutting efficiency of diamond dental burs using different handpiece loads was evaluated against simulated enamel, a machinable glass ceramic (Macor).

Materials and Methods

An ultra‐high‐speed dental handpiece was mounted in a frictionless bearing so that the pressure applied at the contact interface between the dental bur and the cutting substrate was controlled. One type of coarse‐ and two types of medium‐grit diamond burs were studied. Handpiece loads of 44,91.5, and 183 g were applied at the bur/Macor interface, and cutting efficiency was determined as the amount of Macor removed in ten 30‐second‐duration cuts that were 4 mm in length. The data were analyzed by one‐way ANOVA and a post‐hoc Scheffé test at an a priori α= 0.05.

Results

Cutting efficiency depended on both the diamond grit of the bur and the load applied to the handpiece.

Conclusion

The pressure used by most dentists, about 100 g at the bur tip, appears to be optimal for medium‐grit burs. If the pressure applied to the handpiece is markedly increased, there was no increase in cutting efficiency for medium‐grit burs. In contrast, an increased handpiece pressure raises the cutting efficiency of coarse‐grit burs but the effect of this enhanced rate of cutting on the pulpal tissues is uncertain. Cutting efficiency also appeared to be dependent on debris accumulation between the diamond chips.
Classification System for Complete Edentulism
Authors: McGarry Thomas J. , Nimmo Arthur , Skiba James F. , Ahlstrom Robert H. , Smith Christopher R. , Koumjian Jack H.
Published: March 2005

The American College of Prosthodontists has developed a classification system for complete edentulism based on diagnostic findings. These guidelines may help practitioners determine appropriate treatments for their patients. Four categories are defined, ranging from Class I to Class IV, with Class I representing an uncomplicated clinical situation and a Class IV patient representing the most complex and higher‐risk situation. Each class is differentiated by specific diagnostic criteria. This system is designed for use by dental professionals who are involved in the diagnosis of patients requiring treatment for complete edentulism. Potential benefits of the system include: 1) better patient care, 2) improved professional communication, 3) more appropriate insurance reimbursement, 4) a better screening tool to assist dental school admission clinics, and 5) standardized criteria for outcomes assessment.
A Technique to Replicate Soft Tissues Around Fixed Restoration Pontics on Working Casts
Authors: Chee Winston W. L. , Cho George C. , Ikoma Michelle M. , Arcidiacono Alessandro
Published: March 2005

When missing maxillary incisors are replaced, the patient's primary concern is usually esthetics. Depending on the patient's smile line and the display of the incisors, the esthetic zone may extend to the entire clinical crown and include the surrounding soft tissue. For these patients, the appearance and form of the soft tissue at the base of the pontics is as critical as the esthetics of the incisal edges of the restoration. A technique is presented to precisely transfer the soft tissue morphology of the pontic area to the working cast. This modified master cast allows the laboratory technician to fabricate restorations that will harmonize precisely with the soft tissues of the patient.
The Esthetic Width in Fixed Prosthodontics
Authors: Magne Pascal , Magne Michel , Belser Urs
Published: March 2005

With the evolution of adhesive dentistry and the increasing use of porcelain veneers, single‐unit crowns generally are restricted to the replacement of pre‐existing full‐coverage crowns and the restoration of nonvital and/or severely damaged teeth. Porcelain‐fused‐to‐metal restorations are still widely used to generate single‐unit crowns and fixed partial dentures. Collarless metal‐ceramic restorations represent the most successful evolution among efforts to meet maximum esthetic requirements using porcelain‐fused‐to‐metal restorations. Extended metal frameworks and opaque aluminous ceramic cores are associated with unpleasant optical effects in the soft tissues surrounding such restorations. This problem is particularly evident in the presence of the upper lip, which can generate an “umbrella effect” characterized by gray marginal gingivae and dark interdental papillae. Based on the concept of the biologic width, a systematic approach is proposed for the elaboration of an “esthetic width,” including: 1) positioning of preparation margins; 2) reduction of the metal framework; and (c) appropriate marginal design of porcelain‐fused‐to‐metal restorations. Strategic features of pontics and a specific interdental design are suggested to compensate for deficient anatomical features of the soft tissue and the edentulous ridge.
A Soldering Index for Cement‐Retained Implant Restorations
Authors: Dario Lawrence J.
Published: March 2005

Recent advances in implant abutment interface design purport to offer more repeatable, accurate abutment connection. Improved circumferential indexing of the abutments along with a decrease in micromovement may result in a more predictable fit of cement‐retained implant prostheses through a simple variation of soldering technique. A technique for developing a more accurate soldering relationship is described.
Using a Facsimile (Fax) as an Aid for Communication in Maxillectomy Planning Between the Prosthodontist and Surgeon
Authors: Cheng Ansgar C. , Lee Linda , Wee Alvin G. , Morrison David
Published: March 2005

Preoperative communication between the prosthodontist and surgeon is required for properly planning the surgical prostheses that are often indicated for maxillectomy patients. When geography or long distances preclude face‐to‐face consultation, electronic means of correspondence are necessary to minimize delays in the fabrication of surgical prostheses. This article presents a time‐efficient procedure for facilitation of the necessary communication between the prosthodontist and surgeon before maxillectomy surgical procedures.
Long‐Term Reliability of Semiadjustable Articulator Interchangeability
Authors: Price Richard B. T. , Mansfield W. Michael
Published: March 2005

Purpose

Interchangeability between articulators allows mounted casts to be accurately transferred from one articulator to another. The purpose of this study was to evaluate the interchangeability of Whip‐Mix model #2240 articulators (Whip‐Mix Corporation, Louisville, KY) that had been in clinical use for between 1 and 6 years.

Materials and Methods

Forty‐six Whip‐Mix model #2240 articulators that had been in clinical use by students, practitioners, or laboratory technicians for between 1 and 6 years were evaluated for interchangeability using the Whip‐Mix #2245 check system. The horizontal tolerance of the check system was 94 μm. The articulators were also evaluated in the vertical dimension at four locations around the check system cylinders using 26‐μm shimstock. Vertical discrepancies between the cylinders were recorded as the thickness of 0, 1, 2, or more than 2 pieces of shimstock.

Results

Thirty‐eight of the articulators (83%) passed the test for interchangeability. These articulators were interchangeable with other Whip‐Mix model #2240 articulators fabricated over a 5½‐year period (December 1990 to August 1996). In the vertical dimension, most articulators had discrepancies 26 μm. Three articulators (6.5%) had vertical discrepancies greater than 52 μm.

Conclusions

(1) Eighty‐three percent of Whip‐Mix model #2240 articulators that had been in clinical use for between 1 and 6 years remained interchangeable within a tolerance of 94 μm in the horizontal dimension. (2) Only three articulators in this study (6.5%) had a vertical discrepancy at any location between the cylinders greater than 52 μm. (3) The model #2240 articulator has the potential to remain interchangeable during clinical use.
Effect of Toothbrushing on Elemental Release from Dental Casting Alloys
Authors: Wataha John C. , Lockwood Petra E. , Frazier Kevin B. , Khajotia Sharukh S.
Published: March 2005

Purpose

This study assessed the effect of toothbrushing on the elemental release from common dental casting alloys.

Materials and Methods

A Au‐Pt high‐noble alloy, a Au‐Pd high‐noble alloy, a Pd‐Cu‐Ga noble alloy, and a Ni‐Cr base‐metal alloy were placed into a biological medium for 1 week to allow equilibration of elemental release, then brushed for 30 minutes at 90 strokes/min under 200 g of force with a soft toothbrush. The brushing was performed in neutral saline or lactic acid at pH 4 with or without toothpaste. The alloys were then transferred back into a biological medium for 1 week. Atomic absorption spectroscopy was used to measure the mass lost from each alloy during and in the week after brushing. Mass loss was expressed as micrograms per square centimeter of alloy surface, and the various brushing conditions were compared by analysis of variance and Tukey multiple comparison intervals (α= 0.05).

Results

During brushing, element release increased significantly over nonbrushed controls for all alloys except the Ni‐Cr. Toothpastes, acidic solutions, or combinations of these conditions with toothbrushing further enhanced elemental release, but Ni release from the Ni‐Cr alloy increased the most (30‐fold). In the week after brushing, brushing alone increased elemental release only from the Ni‐Cr alloy. However, toothpastes and acidic solutions increased elemental release for all alloys significantly, except for the Au‐Pd alloy. In general, elemental release during brushing was far greater than in the week after brushing.

Conclusions

Under the conditions of this study, toothbrushing increased the elemental release from dental casting alloys.
Conservative treatment for root fracture located very close to gingiva
Authors: Rintaro Terata , Kiyotaka Minami , Minoru Kubota
Published: March 2005

Abstract –  When a root fracture is located very close to the gingiva, the chance of healing with calcified tissue is poorest. Therefore, a preferable treatment is usually thought to be the removal of the coronal fragment and subsequent orthodontic or surgical extrusion of remaining apical fragment. This case report describes conservative treatment for root fracture located very close to the gingiva. The treatment of root fracture was by repositioning and fixation. A 7‐years follow‐up showed healing with calcified tissue and pulp canal obliteration.
RELATIONSHIPS BETWEEN PRIMARY PLANT CELL WALL ARCHITECTURE AND MECHANICAL PROPERTIES FOR ONION BULB SCALE EPIDERMAL CELLS
Authors: HEPWORTH DAVID G. , BRUCE DAVID M.
Published: March 2005

This article investigates onion epidermal tissue (Allium cepa) using a combination of mechanical testing, microscopy and modeling and relates tissue mechanical properties to the known structure of the cell walls. Onion epidermal tissue has a simple, regular structure of elongated cells, which have been used to enable the contributions to mechanical properties of cell walls and of higher order structures to be separated and analyzed. Two models of wall behavior were used to explore how Poisson's ratio of cell walls parallel to the plane of the epidermal surface may vary with applied strain. In the first model, cellulose microfibrils can be reorientated in an unrestricted way with the result that the cell wall volume decreases. In the second model the volume of the cell wall remains constant, which controls the reorientation of microfibrils, hence the Poisson's ratio. Measurements made from uniaxially stretched cells show that the data most closely fits model I, therefore, it is concluded that the bulk of the matrix has little influence on the observed mechanical properties (at a test rate of 1 mm/min), allowing cellulose microfibrils to reorient through the matrix in an unrestricted way during uniaxial tests. In its mechanical attributes the primary cell wall resembles more a knitted cloth than a semisolid composite material. When biaxial stretching is applied to tissue, so that there is no re‐orientation of microfibrils, the cell wall material is still able to reach surprisingly large elastic strains of up to 12.5% and no plastic deformation was recorded. Current theory suggests that cellulose microfibrils can stretch elastically by a maximum of 7%, therefore further work is required to identify mechanisms that could account for the extra elastic strain.
RELATIVE IMPORTANCE OF COHESION AND ADHESION FOR SENSORY STICKINESS OF SEMISOLID FOODS
Authors: DUNNEWIND B. , JANSSEN A.M. , VAN VLIET T. , WEENEN H.
Published: March 2005

Sensory stickiness (sticky mouthfeel) was hypothesized to result from the viscoelastic and adhesive properties of a foodstuff. The objective of the present study was to investigate the relative importance of these two properties. Measurements consisted of compression – decompression cycles on a texture analyzer, with product, type of surface, the presence or absence of saliva and compression regime as variables. Products included commercial mayonnaises, custard desserts and warm sauces, varying in apparent viscosity (at shear rate of 10 s

−1

) between 0.3 and 18.3 Pa.s. Fairly good models were obtained, predicting sensory stickiness with R2 = 0.85–0.92. The predictive value of the mathematical models did not increase when the surface characteristics approached those of the human tongue (use of porcine lingual mucosa). Different surfaces or the use of saliva resulted in differences in the absolute values of the parameters, but their relative values when comparing different products did not change. The parameters appearing in the predictive models represented product characteristics only. The type of surface was not an important factor in determining differences in sensory stickiness between these samples. For the products used in this study, adhesion was large enough to prevent detachment of the sample from the surfaces, i.e., adhesion was not limiting. Variations in perceived stickiness could be explained with R2 = 0.86, based on only two product characteristics: consistency and ‘long behavior’ (the extent to which necking occurs during decompression). This was better than the correlation between sensory stickiness and apparent viscosity (R2 = 0.77),  confirming  the relevance of ‘long behavior’ for sensory stickiness.
RELATIONSHIP BETWEEN WATER ACTIVITY AND CRISPNESS OF EXTRUDED RICE CRISPS
Authors: HEIDENREICH STEPHAN , JAROS DORIS , ROHM HARALD , ZIEMS ANNETTE
Published: March 2005

Extruded rice crisps were adjusted to water activities in the range of 0.05–0.65, and texture measurements were carried out by single compression or compression of a layer of 10 specimens. Sensory crispness ranking was performed by a panel familiar with texture evaluation. Several parameters were derived from the force/displacement curves, and a crispness indicator was calculated on the basis of the relationship between the texture parameters and water activity. This crispness indicator showed best correspondence sensory results, especially when layer compression was performed.
Material Properties of the Human Lumbar Facet Joint Capsule
Authors: Little Jesse S. , Khalsa Partap S.
Published: March 2005

The human facet joint capsule is one of the structures in the lumbar spine that constrains motions of vertebrae during global spine loading (e.g., physiological flexion). Computational models of the spine have not been able to include accurate nonlinear and viscoelastic material properties, as they have not previously been measured. Capsules were tested using a uniaxial ramp-hold protocol or a haversine displacement protocol using a commercially available materials testing device. Plane strain was measured optically. Capsules were tested both parallel and perpendicular to the dominant orientation of the collagen fibers in the capsules. Viscoelastic material properties were determined. Parallel to the dominant orientation of the collagen fibers, the complex modulus of elasticity was E*=1.63MPa, with a storage modulus of E′=1.25MPa and a loss modulus of: E″=0.39MPa. The mean stress relaxation rates for static and dynamic loading were best fit with first-order polynomials: Bε=0.1110ε−0.0733 and Bε=−0.1249ε+0.0190, respectively. Perpendicular to the collagen fiber orientation, the viscous and elastic secant moduli were 1.81 and 1.00 MPa, respectively. The mean stress relaxation rate for static loading was best fit with a first-order polynomial: Bε=−0.04ε−0.06. Capsule strength parallel and perpendicular to collagen fiber orientation was 1.90 and 0.95 MPa, respectively, and extensibility was 0.65 and 0.60, respectively. Poisson’s ratio parallel and perpendicular to fiber orientation was 0.299 and 0.488, respectively. The elasticity moduli were nonlinear and anisotropic, and capsule strength was larger aligned parallel to the collagen fibers. The phase lag between stress and strain increased with haversine frequency, but the storage modulus remained large relative to the complex modulus. The stress relaxation rate was strain dependent parallel to the collagen fibers, but was strain independent perpendicularly.
Single-Step Stereolithography of Complex Anatomical Models for Optical Flow Measurements
Authors: de Ze´licourt, Diane , Pekkan, Kerem , Kitajima, Hiroumi , Frakes, and David , Yoganathan Ajit P.
Published: March 2005

Transparent stereolithographic rapid prototyping (RP) technology has already demonstrated in literature to be a practical model construction tool for optical flow measurements such as digital particle image velocimetry (DPIV), laser doppler velocimetry (LDV), and flow visualization. Here, we employ recently available transparent RP resins and eliminate time-consuming casting and chemical curing steps from the traditional approach. This note details our methodology with relevant material properties and highlights its advantages. Stereolithographic model printing with our procedure is now a direct single-step process, enabling faster geometric replication of complex computational fluid dynamics (CFD) models for exact experimental validation studies. This methodology is specifically applied to the in vitro flow modeling of patient-specific total cavopulmonary connection (TCPC) morphologies. The effect of RP machining grooves, surface quality, and hydrodynamic performance measurements as compared with the smooth glass models are also quantified.
The letters between Titius and Bonnet and the Titius–Bode law of planetary distances
Authors: Nieto Michael Martin
Published: March 2005

Titius first published the law of planetary distances as an insertion into the main text of his German translation of Bonnet’s Contemplation de la Nature. Recently studied letters between Titius and Bonnet show that it was at Bonnet’s request that the second edition of the translation had this law (and other insertions) separated out as translator’s notes. It was this second edition that Bode read, taking the law as his own.
Waves and targets: Generalizations and specifics
Authors: Morse Philip
Published: March 2005

A large variety of phenomena in physics involves the interaction between a wave and a reacting target immersed in the wave. Light impinging on a fog particle, a sound wave scattered from an elastic object, a radar wave striking a metal target, an electron wave interacting with an atom; all are examples of this sort of event. In each case, the wave produces reactions in the target that modify the wave. Comparison between theoretical calculation and physical observation of the modified wave makes it possible to determine many of the properties of the target. In all but a few simple examples the interaction between wave and target is complex enough so that theoretical calculations, to be compared with observations, involve considerable mathematical difficulties. Even where the theory is well understood, most solutions devolve into a series of successive approximations or else a massive computer operation, in either case making it difficult to relate the observations with the internal mechanism of the target. Also, if the solution is approximate, there will exist a degree of uncertainty as to what the measurements imply regarding the structural parameters of the target. There is thus a certain utility in finding an example of wave–target interaction which is complex enough to illustrate many of its characteristics and yet simple enough so an exact solution of the theoretical model can be found. One also can cite less pretentious reasons for playing around with a problem of this sort. To anyone with even a minor theoretical bent there is a certain fascination in exploring a physical problem that can be solved exactly, in terms of known functions. Classical dynamics has many such, and a fair number of us have spent pleasant hours exploring some of them; seeing what happens when one or another of the parameters is enlarged or made to vanish; getting a feel for the physical meaning of the terms in the solution and thence reaching a more complete understanding of the physical system simulated by the equations. The fascination is heightened if the equations have a modicum of complexity and if they represent a not too idealized, real system. There are few such systems made up of waves and a reacting target, particularly if the target has multiple resonances. Hence it seems worthwhile to examine such a system in some detail, both for the satisfaction of working it out and in the hope that the resulting understanding will help us grasp the finer details of the behavior of other wave–target systems.
Mie scattering
Authors: Drake R. M. , Gordon J. E.
Published: March 2005

We describe a light scattering apparatus in which the detection electronics are interfaced to a microcomputer. We report experimental results obtained with the apparatus on the scattering of 0.6328-μm laser light from dilute water suspensions of polystyrene latex spheres with diameters of 2 and 5 μm. Experimental results are compared with theoretical scattering curves obtained from a simple, yet reasonably good, approximation of Mie scattering theory.
The temporary capture of light by a dielectric film
Authors: Lock James A.
Published: March 2005

When a wave packet of light passes through a dielectric film it is found that at a transmission maximum, the group velocity of the light wave packet within the film attains its minimum value. Similarly, at a transmission minimum, it is found that the group velocity of the light wave packet within the film attains its maximum value. The measurability of this effect is also discussed.
Computer-aided experiments with the damped harmonic oscillator
Authors: McInerney M. F.
Published: March 2005

Two types of damped harmonic motion are considered: motion that has damping terms proportional to the speed and the square of the speed and motion with damping that is constant and proportional to the square of the speed. These equations are solved analytically within the averaging approximation for small angle oscillations. Unknown coefficients in the equations of motion are then found by comparing their solutions with experimental data. Finally, the derived coefficients are used numerically to find values for θ̇n0, the angular speed of the pendulum at the lowest point of its (n+1)th swing, for a large release angle. The numerical solutions are compared with experimental results to validate the derived coefficients in the equation of motion.
Young’s experiment with polarized light: Properties and applications
Authors: Andrés P. , Pons A. , Ojeda-Castañeda J.
Published: March 2005

We discuss in a simpler manner, several properties of the fringes obtained if Young’s experiment is performed with polarized light. These properties are applied to implement three contemporary experiments of optical image processing: weighted addition and subtraction of two images, contrast reversal, and pseudocolor encoding of gray level information.
Simple alpha particle detector
Authors: Klein A. G. , Caspar M. J. , Nicola A.
Published: March 2005

An alpha detector that can be used in a lecture hall is described. The device is a spark counter consisting of a length of 4−mil wire. (AIP)
Queueing: A different model for physics
Authors: Baker Gregory L.
Published: March 2005

The analogy of simple queueing models with physical, two-level systems is described. Time-dependent and steady-state queues are used to model radioactive decay and spin systems, respectively. The queue model for the spin system is seen to predict (1) the average population difference between the energy levels when a small periodic magnetic field is applied, (2) the relative standard deviation of the populations, and (3) an expression for the minimum width of the associated spectral line.
On the fiftieth anniversary of major discoveries at the Cavendish Laboratory
Authors: Sargent B. W.
Published: March 2005

This paper begins with some recollections of the Cavendish Laboratory of the University of Cambridge in the years 1928–30, which just preceded the discovery of the neutron and other major discoveries there in 1932–33. It then goes on to describe new developments in experimental techniques for accelerating, detecting, and counting charged particles such as protons and α particles in the Cavendish Laboratory which made possible the major discoveries by Chadwick, Blackett, and Cockcroft and Walton in 1932–33. The scintillation method was superseded by the linear amplifier and scale-of-two counter. Other experimental techniques described here include the original proportional counter, the cloud chamber triggered by coincident pulses in two Geiger–Müller counters for the detection of cosmic rays, and a 700-kV voltage multiplier for the first transmutations by artificially accelerated hydrogen ions. Pioneer measurements on pair production of γ rays and annihilation radiation are discussed in terms of Dirac’s relativistic theory of the electron.
Einstein–Podolsky–Rosen paradox and reality of individual physical properties
Authors: Paul H.
Published: March 2005

A slightly modified two-photon-cascade experiment of the Einstein–Podolsky–Rosen type is discussed. It allows one of two observers to select photons either according to linear or to circular polarization properties. Hence one and the same photon can be integrated, at will, either in an ensemble with linear polarization or an ensemble with circular polarization. This shows that polarization properties cannot generally be ascribed to individual photons in an unambiguous manner, in contradiction to the classical reality concept.
Simple electronic circuit for the demonstration of chaotic phenomena
Authors: Mishina T. , Kohmoto T. , Hashi T.
Published: March 2005

This paper describes an electronic circuit which is very versatile for the demonstration and examination of chaotic phenomena. A coupled logistic equation is taken as a basis and typical features of chaotic phenomena such as successive bifurcations leading to chaotic regimes and so on can easily be seen on an oscilloscope by adjusting variable resistors.
The anthropic principle
Authors: Rosen Joe
Published: March 2005

The anthropic principle states that the fact of existence of intelligent beings may be a valid explanation of why the universe and laws of physics are as they are. The origin and some of the deeper implications of the principle are investigated. The discussion involves considerations of physics and metaphysics, unified schemes and holism, the nature of physical explanation, realism and idealism, and symmetry.
Collision between two balls accompanied by deformation: A qualitative approach to Hertz’s theory
Authors: Leroy Bernard
Published: March 2005

When real balls collide they suffer deformation. Though the theory of collision accompanied by elastic deformation has been developed by H. Hertz a long time ago, it is rarely accounted for in elementary courses because of its mathematical intricacies. It is shown that an order-of-magnitude approach is nevertheless possible, and that the essentials of Hertz’s results can be obtained without recourse to complicated calculations.
Determining the temperature-dependent characteristic temperature of beryllium from electrical resistance measurements
Authors: Listerman Thomas W. , Zhou Xiao-Li
Published: March 2005

We have developed an intermediate-level laboratory experiment to determine the temperature- dependent characteristic temperature of beryllium. The apparatus used to measure the resistance of a beryllium wire sample between liquid nitrogen and room temperatures was simple. The characteristic temperatures obtained from these data using the Block–Grüneisen model are in reasonable agreement with literature values obtained from resistivity and heat capacity experiments. The experiment introduced students to cryogenic and computer data analysis techniques and forced them to extend their knowledge of the theory of electrical resistance and of characteristic temperatures.
Normal modes and dispersion relations in a beaded string: An experiment for an undergraduate laboratory
Authors: Shanker Gauri , Gupta V. K. , Sharma N. K. , Khandelwal D. P.
Published: March 2005

Normal modes and dispersion relations are studied in a beaded string by forming stationary waves. Thin copper wire, with brass beads mounted on it, works as a one-dimensional medium possessing a granular structure. The beaded string carrying a sinusoidal current is forced to oscillate under the action of an external magnetic field. Various normal modes are conveniently excited and the observed ω vs k relationship agrees well with the theoretical predictions. Simplicity of the apparatus, tractibility of the mathematical analysis, and the correspondence between theoretical predictions and measurements make the experiment suitable for an undergraduate laboratory.
Laboratory study of the cosmic-ray muon lifetime
Authors: Ward T. , Barker M. , Breeden J. , Komisarcik K. , Pickar M. , Wark D. , Wiggins J.
Published: March 2005

The cosmic-ray muon lifetime was measured with a variety of counters designed to study both the free and μ− capture lifetimes. The data were obtained using scintillation detectors and a lead glass detector. These data show the dependence of μ− capture on the atomic number of the chemical element in the detector. The Z dependence of the weak interaction capture process is discussed in terms of the familiar Fermi (ΔJ=0) and Gamow–Teller (ΔJ=1) decays. This experiment was designed for use in advanced undergraduate physics laboratories.
Fiber-optic analogies with mechanics
Authors: Black Richard J. , Ankiewicz Adrian
Published: March 2005

We provide a new unified formalism for the analogy between fiber-optics and mechanics. It is based on the scalar theory of light for an optical fiber with length-independent refractive index, and the mechanics of a particle in a time-independent potential. Illustrative examples such as tunneling and precession are given. We also mention the conceptual analogies that arise when we include (i) polarization and (ii) length or time-dependent variations. This should prove useful both in teaching and as a bridge between research areas.
Vortex flow and maximum principles
Authors: Lugt Hans J.
Published: March 2005

Maximum principles of partial differential equations can give information on general properties of vortices and vorticity fields and the corresponding pressure and temperature fields independently of the solutions proper. They also reveal fundamental differences between two- and three-dimensional motions and peculiar flow properties in limiting cases: In steady two-dimensional viscous flows a maximum principle for the vorticity-transport equation exists and its consequences are discussed. Steady concentrated vortices with an extremum of vorticity occur only in the three-dimensional nonlinear case, and in linear slow motion vortices exhibit peculiar properties. In unsteady flows local extrema of vorticity are possible, even in two-dimensional flows. In all cases studied, the Navier–Stokes equation in the form of the vorticity-transport equation is used as the basic equation for incompressible homogeneous fluid flows.
Simple laboratory demonstration of the Doppler shift of laser light
Authors: Nichols T. D. , Harrison D. C. , Alpert S. S.
Published: March 2005

The edge of a smoothly rotating turntable was used as a reflecting surface in a Michelson interferometer configuration to demonstrate the Doppler effect on laser light. Attached to the edge of the turntable was reflective tape which greatly enhanced the backscattered light. Spectrum analysis of the detected signal indicated that all of the signal and noise components were contained in a frequency range of about 15% of the central Doppler frequency. As a quantitative test of the method, the wavelength of the laser source, known to be 633 nm, was measured to be (612±43) nm using an oscilloscope as the output device and (634±12) nm using a spectrum analyzer for the output. All components that were used with the exception of the spectrum analyzer are commonly available items. The techniques described in this paper provide a quantitative demonstration of the Doppler effect of light and overcome the usual problems caused by motional instabilities associated with the moving mirror.
Active interpretation of the Lorentz ‘‘boosts’’ as a physical explanation of different time rates
Authors: Bohm D. , Hiley B. J.
Published: March 2005

The purely passive interpretation of the Lorentz transformation does not explain why an accelerated system actually has a changed time rate (e.g., as in the case of the twins’ paradox). This has made the theory in some ways rather difficult to understand. In this paper, we propose an active interpretation of the Lorentz transformation or ‘‘boost,’’ and show that it leads to a simple and clear explanation of how and why time rates change. Thus the meaning of the theory is clarified and made more evident.
Forced harmonic oscillator: A path integral approach
Authors: Holstein Barry R.
Published: March 2005

The problem of the harmonic oscillator driven by an external force is explored using path integral techniques. The qualitative features of the solution are demonstrated.
The hydrogen atom as a Morse oscillator
Authors: Lee Soo-Y.
Published: March 2005

In its radial motion, the electron in the hydrogen atom can be pictured as oscillating about the Bohr orbits under Morse potentials. For each principal quantum number n, there corresponds a Morse oscillator with n bound states—one for each allowed value of the angular momentum quantum number l. The equilibrium positions of the Morse oscillators are exactly the Bohr orbits.
Quantum persistence and classical probability
Authors: Woo C. H.
Published: March 2005

A quantum system may be contained when classically one expects it to disperse. Simple examples are given to illustrate that classical probabilistic considerations may be still valid if reflections are taken into account. The possible relevance of this phenomenon to the decay of a ‘‘false vacuum’’ is briefly commented on.
Converging beam optical Fourier transforms
Authors: Puang-ngern Srisuda , Almeida Silverio P.
Published: March 2005

The classical, most often used, system for performing the optical Fourier transform is by using parallel coherent beam illumination. Lenses used in this method can become quite costly. In this paper we present results obtained using converging beam illumination which is suitable for many applications and is less expensive than the parallel beam method. The input objects for which the Fourier transforms were made are transparencies of snowflakes.
Looking into Chapman’s homer: The physics of judging a fly ball
Authors: Brancazio Peter J.
Published: March 2005

How does a baseball player learn to judge a fly ball? An experienced outfielder, observing the initial stages of flight, can predict the landing point rapidly and accurately. In 1968, S. Chapman [Am. J. Phys. 36, 868 (1968)] proposed that an outfielder unconsciously uses trigonometry to determine the landing point. However, Chapman assumed incorrectly that the effects of aerodynamic drag could be ignored. The trajectory of a baseball is shown to be affected significantly by air resistance, so that the specific trigonometric factor cited by Chapman cannot provide useful cues to the fielder. In evaluating potentially useful cues, we take note not only of aerodynamic drag, but also of the specific neurophysiological processes used for the detection of distance and motion. This study shows that the angular acceleration of the fielder’s line of sight to the ball provides the strongest initial cue to the location of the eventual landing point. This suggests that the fielder’s vestibular system, responding to the acceleration of the fielder’s head as he observes the initial stages of flight, may play a key role in the judgment process.
The hydrogenic atom and the periodic table of the elements in two spatial dimensions
Authors: Asturias Francisco J. , Aragón Sergio R.
Published: March 2005

A linear variational method was used to determine the energy eigenvalues of the Schrödinger equation for the hydrogenic atom in two space dimensions (2-D) using the correct logarithmic potential. The basis set consisted of scaled wave functions of the 2-D isotropic harmonic oscillator. The secular equations were solved by a tridiagonalization method and a nonlinear scale parameter was chosen to minimize each energy level individually. Approximate wave functions and energies accurate to four decimal places were obtained for up to five excited states of s, p, d, f, and g orbitals. The values presented here are compared to previous calculations. Additionally, the Thomas–Fermi model was used to study the electronic structure of two-dimensional multi-electron atoms. The results obtained in the calculation, combined with the observations about 2-D hydrogenic systems, are used to predict the structure of the periodic table of the elements. With available electronic configurations, valences are assigned and the 2-D elements are tentatively identified with their three-dimensional analogs. With the results presented here, the basis of 2-D chemistry is more firmly established, and interesting comparisons can be made with the three-dimensional case.
Comment on ‘‘Electrostatic images by multipole expansion’’
Authors: Ferrell Thomas L.
Published: March 2005

It is pointed out that there can be no point charge image in a dielectric sphere, contrary to a previous calculation. (AIP)
Is length contraction really paradoxical?
Authors: Sastry G. P.
Published: March 2005

A thought experiment is proposed in which a moving conducting shuttle encounters a gap between two conducting rails connected at one end through a bulb and a source of steady voltage. A naive application of length contraction leads to contradictory results when the encounter is examined from the rail and the shuttle frames, viz., that the bulb should switch off in one frame but should keep glowing in the other. However the interaction between the shuttle and the gap is so arranged that it is possible to analyze the experiment quantitatively in both the Lorentz frames within the framework of elementary relativistic kinematics. It is shown that the results of such a calculation lead to an exact agreement between the observed effects in the two frames. The article includes an Appendix that contains a compact bibliography of several of the paradoxes in the theory of relativity.
The physicist’s toolkit
Authors: Krieger Martin H.
Published: March 2005

A physicist’s ‘‘toolkit’’ might include mathematical, diagrammatic, and modeling tools, including such models as a crystalline solid, a harmonic oscillator, or an inverse square law of interaction. The notion of a toolkit provides a meeting ground for scientists, philosophers, and teachers for appreciating what scientists do. For doing science may be thought of as a craft, skillfully employing a kit of tools.
Teaching of transcendence in physics
Authors: Jaki Stanley L.
Published: March 2005

Efforts aimed at showing that modern physics points to a truly transcendental factor as the explanation of the universe should be welcomed by those who have urged the teaching of physics in a broad cultural context. Those efforts may profit from the following guidelines: avoid the antiontological basis of the Copenhagen interpretation of quantum mechanics; make much of the reality of the universe and its enormous degree of specificity as revealed by general relativity and the cosmic background radiation; exploit Gödel’s incompleteness theorems against any grand unified theory proposed as if it were true a priori and necessarily; and realize that the design argument always presupposes the validity of the cosmological argument.
The strange polarization of the classical atom
Authors: Solem Johndale C.
Published: March 2005

A classical hydrogen atom will polarize in a direction perpendicular to a uniform electric field in its orbital plane. While some features of this unexpected behavior can be reconciled with physical reality, it illustrates representative difficulties of classical mechanics applied to atomic physics. The exceedingly unintuitive results have instructional value for students.
Energy in the center of mass
Authors: Levin Eugene
Published: March 2005

In the collision of a particle (A) with a system of bonded particles (B–C), only the energy in the center of mass reference frame is available for breaking the bond. This is because some of the initial energy must be used in conserving the momentum of the system. This article describes a simple air-track experiment illustrating this well-known fact. Two carts on a horizontal air track are bonded together by small magnets; a sudden impulse is provided to one of the carts by a falling weight. A feature of the experiment is the direct determination of magnetic bond energy by numerical integration of F dx. For cases where the energy in the center of mass is sufficient to break the magnetic bond, the ensuing motion of the system can be described in terms of an effective mass.
A spherical mirror Fabry–Perot interferometer for microwave demonstrations
Authors: Davis Lawrence W. , Patsakos George
Published: March 2005

Although Fabry–Perot interferometers have found widest application in the visible portion of the spectrum, their properties are conveniently observed in the microwave region, where high-quality spherical mirrors are easily fabricated on a lathe, and partially transmitting (high reflectance) flat mesh is commercially available at modest cost. The scaling properties of paraxial beams of such interferometers, as the frequency is varied from optical to microwave for a fixed resonator geometry, are well known. This allows studies that are relevant to contemporary optics research to be carried out in an upper division undergraduate laboratory without the need for sophisticated equipment.
The Rutherford cross section and the perihelion shift of Mercury with the Runge–Lenz vector
Authors: Farina Carlos , Machado Marcos
Published: March 2005

It is shown how the Runge–Lenz vector A can be used to give the orbit equation and the Rutherford cross section without the necessity of solving differential equations. After that, the Greenberg’s method is applied to obtain the perihelion shift of Mercury using the vector A. Some suggestions are given in the conclusions.
Bound states in weak attractive potentials in one-dimensional quantum mechanics
Authors: Bronzan J. B.
Published: March 2005

In one-dimensional quantum mechanics, there is one bound state near zero energy in a weak attractive potential. A series is derived for the bound state energy in powers of the potential. Normally the leading term is O[V2], but when the potential has a long attractive tail, −V0‖a/x‖P, 0<p<1, the leading term is O[(V0)2/(2−p) ].
Electron trajectory in an e/m experiment
Authors: Price Joseph E.
Published: March 2005

A common undergraduate experiment to measure the e/m ratio uses a magnetic field produced by Helmholtz coils to deflect an electron beam. It is usually assumed that the beam is in the symmetrical plane of the coils and that it is in a uniform field identical to the field at the center of the coils. The magnetic induction field at the central position can be calculated from the geometry of the coils. In this paper the magnetic field in the region of the electron beam is calculated and compared to the field at the center of the coils. The height of the beam increases as it traverses the semicircular path and this increase is calculated.
Symbolic proof of the Helmholtz theorem
Authors: Lemos Nivaldo A.
Published: March 2005

Symbolic proof of the Helmholtz theorem on the unique determination of a vector field from its divergence and curl is given which requires only an elementary knowledge of electrostatics and vector analysis. The conditions for uniqueness emerge as natural consequences of the symbolic method employed.
A variational principle in classical thermodynamics
Authors: Buchdahl H. A.
Published: March 2005

Classical thermodynamics as usually formulated is remarkable for the total absence of any variational principles. It is shown here that as far as its implications for quasistatic transitions are concerned the Second Law can be formulated as a variational principle which guarantees the existence of an empirical entropy function.
Solutions to Laplace’s equation using spreadsheets on a personal computer
Authors: Crow T. T.
Published: March 2005

Using a spreadsheet routine on a personal computer, we obtain solutions to Laplace’s equation quickly, even with dielectric interfaces present. This provides an alternative to solving electrostatics problems normally dealt with by relaxation methods in fortran programs or Fourier series solutions.
A two-dimensional flame table
Authors: Daw Harold A.
Published: March 2005

A two-dimensional flame table was constructed for visually demonstrating acoustical modes in a cavity. This flame table is an extension of the one-dimensional flame tube or Rubens flame tube apparatus. Photographs of some of the lower-order modes on rectangular box and cylindrical box flame table cavities are included.
Student understanding in mechanics: A large population survey
Authors: Gunstone Richard F.
Published: March 2005

There has recently been a considerable growth in research probing student understanding in mechanics. Questions based on four such research probes were included in the end-of-high-school physics examination undertaken by some 5500 students. The results obtained give an indication of the extent to which various interpretations of some physical situations are held in a whole population. The possibilities of using research probes as a basis for assessment questions are also illustrated.
The influence of Hermann von Helmholtz on Heinrich Hertz’s contributions to physics
Authors: Mulligan Joseph F.
Published: March 2005

Heinrich Hertz, the discoverer of radio-frequency electromagnetic radiation, also made important contributions to our knowledge of the photoelectric effect, cathode rays, electromagnetic theory, classical mechanics, and meteorology. In 1878 Hertz enrolled at the University of Berlin to study physics under Professor Hermann von Helmholtz. For the rest of his life he maintained a very close personal and scientific relationship with his mentor. The influence of Helmholtz on Hertz’s choice of research topics and on the kind of physicist Hertz became is documented from the writings of these two famous physicists.
Why are resonant frequencies sometimes defined in terms of zero reactance?
Authors: Dudley J. Duane , Strong William J.
Published: March 2005

The resonant frequencies of a sinusoidally driven system are usually defined as those for which some physical response is a relative maximum. There is also a tendency to define them as frequencies for which the reactance of the system vanishes, since zero-reactance frequencies are often approximately equal to maximum-response frequencies and are sometimes easier to calculate. However, there are many systems for which the two types of frequencies are significantly different. There are also systems for which the reactance does not vanish in certain frequency ranges, though maximum responses still occur. It is concluded that vanishing reactance is not valid as a general criterion for resonance, and students should be warned against its use.