bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of feed preference and digestion of three different commercial diets for cats and ferrets
Authors: Fekete S. Gy. , Fodor K. , Proháczik A. , Andrásofszky E.
Published: March 2005

Diet preference and digestibility experiments were conducted using a total of 10 cats and 10 ferrets. The composition of the three different kinds of dry cat feed was as follows (each data are given in dry matter, DM): (i) normal diet (N): 95.3% DM, 33.7% crude protein (CP), 20.4% ether extract (EE), 37.6% nitrogen‐free extract (NFE); (ii) ‘light diet’ (L): 94.2% DM, 31.6% CP, 10.7% EE, 52.2% NFE; (iii) ‘veterinary diet’ (D): 94.57% DM, 38.7% CP, 9.6% EE, 47.2% NFE. During the period of the preference test, the average daily dry matter intake (calculated with the mean of the three diets: 94.7% DM) was 98.0, 15.0 and 16.7 g DM in cats and 25.0, 7.3 and 8.1 g DM in ferrets. The preference rates of the three different diets, expressed in percentage of their total consumption, were as follows: 60.4% N (54.4 g DM), 12.4% L (12.1 g DM) and 27.2% D (26.6 g DM) in cats, and 46.2% N (11.6 g DM), 29.9% L (7.5 g DM) and 23.9% D (6.0 g DM) in ferrets. This indicates that cats and ferrets have a clear preference for diets of higher fat content. In all three diets, the digestibility of CP was significantly (p < 0.05) lower (70.1 ± 5.4 vs. 75.9 ± 5.8) while that of EE was significantly (p < 0.05) higher (95.6 ± 1.5 vs. 89.4 ± 5.3) in ferrets than in cats. The average digestible/metabolizable energy (DE/ME) ratio of feeds turned to be 95.6% for cats and 90.6% for the ferrets. From the data one can conclude that the ferret cannot be used as a model animal for cats either for preference or digestibility studies.
Dioxin residues in the edible tissue of finishing pigs after dioxin feeding
Authors: Spitaler M. , Iben C. , Tausch H.
Published: March 2005

The aim of this study was to determine the contamination of finishing pigs with polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) after feeding either uncontaminated feed or feed contaminated with 0.75, 2 or 4 ng/kg toxic equivalents (TEQ; calculated by multiplying individual congener concentrations by congener‐specific toxicity equivalency factors). The feed was mixed with pure substances of PCDD/Fs to get the intended contamination. Five groups of six piglets each were fed contaminated feed, one group of five piglets served as control. One group was fed contaminated feed (4 ng TEQ/kg) only for the rearing period (6 weeks), and another group for the first 8 weeks of the fattening period (4 ng TEQ/kg feed). The other groups received the contaminated feed during the 12‐weeks fattening period. After slaughtering, the edible parts of the belly, loin and fore‐end were collected and homogenized. The samples of group 2 and 4a were investigated uncooked as well as roasted. Fattening yield and feed conversion (kg feed/kg weight gain) of the animals of all groups were in the normal range (final weight 109.7 kg; feed conversion 2.55–2.69 kg). The PCDD/F‐content in 1 kg fat of the belly, loin and fore‐end in relation to the intake was between 0.016 (4 ng TEQ/kg feed for a 6‐weeks rearing period) and 1.39% (fore‐end; 2 ng TEQ/kg feed for 12‐weeks fattening period). There was a decrease in dioxin residues after a 12‐weeks period but not after a 4‐weeks period of feeding an uncontaminated feed. When feed contaminated with 0.75, 2 and 4 ng TEQ/kg was given for a 12‐weeks fattening period, the residue concentrations of PCDD/F‐TEQ in 1 kg belly was 0.455, 1.07 and 1.55 ng, in 1 kg fore‐end 0.04 ng, 0.32 ng and 0.34 ng and in 1 kg loin 0.015 ng, 0.07 ng and 0.30 ng respectively. Roasting had no influence on the dioxin‐residues. The residues per g belly fat exceed the maximum limits for dioxin in food of 0.6 pg WHO‐PCDD/F‐TEQ/g fat (EC Recommendations 2002/201/EC), when feed containing 0.75 ng PCDD/F‐TEQ/kg is given for 12 weeks. When feed containing 0.4 ng TEQ (maximum content; EC recommendations 2002/201/EC) is given for 12 weeks, approximately 0.55 pg TEQ/g fat can be expected in the food. This value is within the action level of 0.6 pg/g fat of porks. In conclusion, the results of the study allow prediction of dioxin residues in the edible tissue of pork, if the feed contamination is known and the amount of feed intake can be estimated.
Comparison of the nutrient analysis and caloric density of 30 commercial seed mixtures (in toto and dehulled) with 27 commercial diets for parrots
Authors: Werquin G. J. D. L. , De Cock K. J. S. , Ghysels P. G. C.
Published: March 2005

In this paper, an overview is given of the composition of 30 commercially available parrot seed mixtures. As parrots dehull the seeds, the analysis of the total seed mixture tends to differ from that of the ingested feed. Statistical evaluation and comparison of the dehulled seeds vs. the whole seeds indicates that most parrot species are fed a diet rich in fat (31.7 ± 13.1% crude fat) and energy (22.4 ± 2.9 MJ ME/kg). As the analysis of the total seed mixtures underestimates fat and energy content of the ingested feed, it is suggested that researchers, bird nutritionists and bird food producers should calculate diets based on the analysis of the dehulled seeds. Finally, the calculated data were compared with the composition of formulated pelleted/extruded diets on the market. These data indicate that the energy density of most diets (15.6 ± 1.4 MJ ME/kg) is far below the energy density of common seed mixtures.
Studies on digestive physiology and feed digestibilities in captive Indian rhinoceros (Rhinoceros unicornis)
Authors: Clauss M. , Polster C. , Kienzle E. , Wiesner H. , Baumgartner K. , Von Houwald F. , Ortmann S. , Streich W. J. , Dierenfeld E.S.
Published: March 2005

We performed intake, digestibility and ingesta passage studies in 11 Indian rhinoceroses (Rhinoceros unicornis) from four zoological institutions, using total faecal collection for the quantification of faecal output. The regularly fed zoo ration of roughage and concentrates (ration RC) and a roughage‐only ration (ration R) were used; the roughage source differed between the facilities and comprised grass hay, grass silage, straw and lucerne hay. Dry matter intake ranged between 0.8 and 1.3% of body weight on ration RC and 0.5–1.2% on ration R. Digestibility coefficients achieved were similar to those reported for horses on diets of comparable composition. Endogenous losses as determined by linear regression analysis were within the range reported for horses. Measurements of faecal volatile fatty acids, faecal lactate and faecal pH also showed similarity to similar measurements in horses. The mean retention times of fluids (Co‐EDTA) and particles (Cr‐mordanted fibre <2 mm) in the whole gastrointestinal tract averaged 42 and 61 h, respectively, and were the longest ever recorded in a monogastric ungulate with this marker system. The results suggest that the horse is a useful model animal for designing diets for Indian rhinoceroses. Why digestive parameters are similar between these species in spite of enormous differences in body weight and retention times remains to be answered.
Influence of phytase added to a vegetarian diet on bone metabolism in pregnant and lactating sows
Authors: Liesegang A. , Loch L. , Bürgi E. , Risteli J.
Published: March 2005

The purpose of the study was to find out if the supplementation of phytase to a diet of gestating and lactating sows has any effects on performance and bone parameters of the animals. Forty primiparous gilts were assigned into four groups: group A with phytase [4.2 g total phosphorus (P)/kg (gestation) and 4.5 g total P/kg (lactation)], group B without phytase (with phytase supplementation in diet for rearing) and same P content as group A, group C without phytase and higher P contents [5.0 g total P/kg (gestation) and 5.5 g total P/kg (lactation)] and group D with the same diet as group B (no phytase during the rearing). A 6‐phytase was used in this trial (750 FTU/kg diet). The four diets were fed during gestation and lactation. Faeces were collected to determine apparent digestibility of minerals. Blood samples were taken to analyse minerals and bone markers. After weaning the sows were slaughtered and the bones of one hind leg were prepared to measure bone mineral density (BMD) and bone mineral content (BMC) of the tibia. Bone ash and mineral content of the phalanx III were determined. Mean P concentrations in serum decreased during gestation and lactation. But there were no significant differences between the groups. Bone formation marker bone‐specific alkaline phosphatase decreased at the beginning of lactation whereas bone resorption marker serum crosslaps increased. The BMD and BMC of the tibia were slightly higher in the groups fed higher concentrations of P and phytase. The ash and mineral contents of the phalanx were the highest for the group fed the highest concentration of P. The apparent digestibility of P increased during gestation mostly in group A (57%→ 69%). In conclusion, high P content and addition of phytase to the diet induced a slightly higher ash content of the bones. It is of high importance, that sows during gestation absorb enough P, to avoid lamenesses and sudden fractures. As not many studies with phytase have been performed during gestation and lactation in sows yet, we can recommend, that phytase as supplement can be used to keep P in the diet at a lower level without negative consequences for bone health.
Effects of a supranutritional dose of selenate compared with selenite on insulin sensitivity in type II diabetic dbdb mice
Authors: Müller A. S. , Most E. , Pallauf J.
Published: March 2005

The present study was performed to examine the mechanism by which selenate ameliorates the insulin sensitivity in type II diabetic dbdb mice. Therefore, 21‐adult female dbdb mice were randomly assigned to three experimental groups (0Se, SeIV and SeVI) with seven animals per group. Mice of group 0Se were fed with a selenium‐deficient diet (<0.02 mg Se/kg) based on wheat and torula yeast for 8 weeks whereas the mice of groups SeIV (selenite) and SeVI (selenate) were fed with sodium selenite and sodium selenate (up to 35% of the LD50 for mice in eighth week), in addition to the diet by daily tube feeding. Eight weeks of selenate application led to significantly elevated insulin sensitivity in comparison with selenium deficiency and selenite application. The activity of cytosolic protein tyrosine phosphatases (PTPs) as important negative regulators of insulin signalling was reduced from 53.8% to 22.5% in the liver and skeletal muscle of selenate‐treated mice in comparison with the selenium deficient and selenite‐treated controls, suggesting an inhibition of PTPs by intermediary selenate metabolites. In an additional in vitro inhibition study, selenate (oxidation state +VI) did not inhibit PTP activity. Selenium metabolites in the oxidation state +IV were found to be the actual inhibitors of PTP activity. In conclusion, the results of the present study show that one possible mechanism by which supranutritional selenate doses enhance insulin sensitivity in type II diabetic dbdb mice is based on the inhibition of PTPS as negative regulators of insulin signalling. Moreover the cellular metabolism of selenate including its intermediary reduction to the oxidation state +IV seems to play a crucial role during this process.
Characterization of Rhizoctonia solani AG 4HG‐III Causing Stem Canker and Wirestem on Green Amaranth and Chinese Amaranth
Authors: Yang G. H. , Chen H. R. , Naito S. , Ogoshi A.
Published: March 2005

During December 2003, stem canker and wirestem were observed on the stems of green amaranth (Amaranthus viridis) and Chinese amaranth (Amaranthus tricolor) in greenhouses at Ximao district in Yunnnan Province, China. Isolates of Rhizoctonia solani obtained from the two amaranths with stem canker and wirestem, were identical to anastomosis group (AG)‐4. The isolates from diseased plant showed high virulence on young seedlings of two amaranths. Results of sequence analysis of 5.8s rDNA‐ITS of Chinese isolates showed 99–100% sequence similarity with AG‐4HG‐III tester isolates. When compared with other subgroups of AG‐4, Chinese isolates showed similarity levels of 94%. This is the first report of stem canker and wirestem of Green amaranth and Chinese amaranth caused by AG‐4HG‐III and AG‐4HG‐III in China.
The Politics of Violent Opposition in Collapsing States
Authors: Reno William
Published: March 2005

In violent conflicts in places like Congo, Liberia and Sierra Leone, economic interests have crowded out ideologically articulate mass-based social movements for reform or revolutionary change to a degree that was not apparent during earlier anti-colonial struggles. Some scholars offer a ‘looting model’ of rebellion that explains the predations of politicians and warlords but it is not clear why people who receive few benefits from this – or even suffer great harm from them – fail to support ideologues instead, or why self-interested violent entrepreneurs do not offer political programmes to attract more followers. Yet some groups defy this ‘looting model’. Explaining why armed groups vary so greatly in their behaviour provides a means to address important questions: is it possible to construct public authorities out of collapsed states in the twenty-first century, or do local predations and global conditions preclude indigenous state-building in these places? Why do social movements for reform there seem so ineffective? What conditions have to be present for them to succeed? This article considers the nature of rebellion in failing states, focusing on Nigeria to find clues to explain variations in the organization of armed groups.
Cloning and sequencing of Indian water buffalo interleukin‐18 cDNA
Authors: Chaudhury P. , Bera B. C.
Published: March 2005

Full‐length cDNA (582 bp) of the interleukin‐18 (IL‐18) gene of the Indian water buffalo (Bubalus bubalis) was amplified by reverse transcriptase–polymerase chain reaction (RT‐PCR) and sequenced. The deduced amino acid sequence has 99% and 95% similarity with the IL‐18 sequences of cattle and sheep, respectively. There are two amino acid substitutions at positions 132 and 182 in buffalo IL‐18 compared with that of cattle. Phylogenetic analysis showed that the IL‐18 sequence of fish forms a different lineage and is most divergent from that of cattle, buffalo, sheep, pig, dog, horse, human, monkey, mouse, rat and chicken.
Center-of-mass properties of composite systems subject to nonlinear external interactions
Authors: Lock James A.
Published: March 2005

If two bound nonrelativistic quantum particles are each subject to a nonlinear external potential, their Schrödinger equation does not separate in relative and center-of-mass coordinates. For this case, the details of internal state of the composite affect its center-of-mass properties. The extent of this internal state influence is examined for an exactly soluble one-dimensional model system.
APL and the numerical solution of high-order linear differential equations
Authors: Gershenfeld Neil A. , Schadler Edward H. , Bilaniuk O. M.
Published: March 2005

An Nth-order linear ordinary differential equation is rewritten as a first-order equation in an N×N matrix. Taking advantage of the matrix manipulation strength of the APL language this equation is then solved directly, yielding a great simplification over the standard procedure of solving N coupled first-order scalar equations. This eases programming and results in a more intuitive algorithm. Example applications of a program using the technique are given from quantum mechanics and control theory.
Solar escape
Authors: Hendel A. Z.
Published: March 2005

If we try to calculate the minimum velocity a spaceship needs to escape from the solar gravitational field we are likely to get a wrong answer. We illustrate the difficulties with several examples and we give a simple method to solve a certain class of problems.
Instructional laboratory experiment on the sound field of a small ultrasonic transducer
Authors: Kinyuy I. , Stumpf F. B.
Published: March 2005

The directivity pattern and the axial-pressure profile were measured for a small ultrasonic transducer. This is a useful basic experiment for an undergraduate course in sound or musical acoustics.
Lise Meitner and the beta-ray energy controversy: An historical perspective
Authors: Watkins Sallie A.
Published: March 2005

Much has been written about the early history of beta-ray research and the controversy it provoked. Many prominent physicists lent their talents to the solution of this puzzling problem. One of the foremost of these was Lise Meitner, conspicuous in the fray not only because of her creative experimental work, but also because of her attachment to a physical principle—the simplicity of nature. This article reviews the sequence of events as they preceded, coincided with, and followed her work on the subject.
Laboratories and the rise of the physics profession in the nineteenth century
Authors: Phillips Melba
Published: March 2005

There were no established research laboratories before the nineteenth century. Galileo had a small shop, Hooke was a curator of instruments, Boyle worked at home, Newton in his college rooms. Scientists were often amateurs with their own laboratory facilities. Even in universities they could obtain prominence as individuals, but took students only privately, as assistants or apprentices. There was no profession of physics to which one could aspire as a career. The tradition of modern research laboratories and the research school can be traced to Liebig in chemistry, and the extension to physics can be attributed in large part to Gustav Magnus of the University of Berlin, who also invented the physics colloquium. German universities continued to lead the way throughout the second half of the nineteenth century, but by 1900 other industrialized countries (especially Britain, France, and the United States) had developed research schools leading to careers in physics. Research laboratories were also being established by industry and officially by governments.
Spectra of electronic noise signals: A microcomputer experiment
Authors: Jodoin Ronald E. , Irish Wesley
Published: March 2005

We have designed an advanced undergraduate experiment which interfaces a microcomputer to collect samples of noise signals. The data are stored and analyzed for their power spectra. The analysis uses the concepts of autocorrelation and the discrete Fourier transform, and the results are automatically plotted and compared to what is expected. Advantages and limitations of the microcomputer are discussed.
Energy from the evaporation of water
Authors: Bachhuber Carl
Published: March 2005

Some simple idealized engines that consume ambient heat and liquid water and produce work and vapor are described. The consideration of these engines gives (approximate) expressions for the available energy when water evaporates reversibly.
Doppler broadening due to cyclotron motion in a uniform magnetic field
Authors: Vermillion Robert E.
Published: March 2005

The intensity profile of a spectral line originating from an ionic transition within a magnetic field is considered. In a uniform field, the ion cyclotron motion gives rise to Doppler broadening identical to the no-field case. Hence the introduction of a uniform magnetic field does not modify the Doppler profile.
The special theory of relativity and the one-way speed of light
Authors: Townsend Burke
Published: March 2005

Two recent discussions in this journal of the conventionality of the one-way speed of light in the special theory of relativity are corrected and generalized. It is concluded that these discussions reveal no ground for a challenge of the traditional conventionalist thesis.
Mass renormalization in classical electrodynamics
Authors: Griffiths David J. , Owen Russell E.
Published: March 2005

The electromagnetic mass of a charged object can be calculated by three independent methods: (1) mu=u/c2, where u is the field energy of the object at rest, (2) mp=p/v, where p is the field momentum when the particle is moving at speed v, and (3) ms=F/a, where F is the self-force when the object has acceleration a. In the context of a simple dumbbell model we demonstrate that mp=ms, but these in general exceed mu.
The extended Galilean transformation and the path integral
Authors: Holstein Barry R.
Published: March 2005

We demonstrate how the behavior of the Schrödinger equation under the transformation, x′=x+ξ(t),  t′=t, can be easily discerned within the path integral formalism.
A simple mechanical model exhibiting a spontaneous symmetry breaking
Authors: Sivardière Jean
Published: March 2005

We discuss a simple mechanical system and show that it exhibits a spontaneous symmetry breaking quite similar to a Landau second-order phase transition.
Limitation on proper length in special relativity
Authors: Taylor Edwin F. , French A. P.
Published: March 2005

The proper length L* of an accelerating object is limited to the values L*≤c2/a*F where a*F is the proper acceleration of the front end. For the maximum length, the acceleration of the rear end is infinite. The effect rests on the relativity of simultaneity, one of the most difficult relativity concepts for students. We explore some consequences of this result.
Anisotropy, inhomogeneity, and conservation laws
Authors: Olszewski E. A.
Published: March 2005

We consider two versions of Minkowski space, each of which is connected in a nontrivial way. In the first version, which corresponds physically to a static universe with one spatial dimension finite, we introduce a variation of the twin paradox in which neither twin undergoes any acceleration. The resolution of the paradox is shown to derive from the (global) anisotropy of this version of space-time. Furthermore, the (global) anisotropy is shown to imply the existence of a set of preferred inertial frames and the possibility of nonconservation of angular momentum in the absence of any torque. In the second version, which corresponds physically to a universe with one spatial dimension finite but expanding in time, we show that the (global) inhomogeneity of this version of space-time can cause nonconservation of energy and momentum in the absence of any force.
A class of one-dimensional relativistic band models
Authors: Glasser M. L.
Published: March 2005

The solution to the Dirac equation is worked out for a nonlocal separable periodic potential which varies in one direction. The relativistic version of the Kronig–Penney model is obtained as a special case.
Testing laboratory performance
Authors: Theysohn G. , Jodl H.-J.
Published: March 2005

A practical test seems to be a more adequate test type for measuring laboratory achievement than written or oral tests, for it is constructed specifically to examine outcomes in laboratory objectives, which can roughly be described as experimental skills. Several suggestions from various authors are reviewed. Their methods are discussed, and an improved way of testing experimental abilities is proposed. It is shown that under certain conditions performance tests may be highly reliable instruments.
Radioactive half-life measurements in a freshman or sophomore laboratory
Authors: Supon F. W. , Kraushaar J. J.
Published: March 2005

A photomultiplier arrangement is used to determine the half-life of the alpha decay of the 220Rn and 232Th.
Aspects of scientific method in the natural sciences—physics
Authors: Horsfield Edgar
Published: March 2005

In this paper the distinction between ‘‘science’’ and ‘‘nonscience’’ is considered, and the essential ingredients which characterize scientific method such as the construction of models, hypotheses, theories, and paradigms in the physics enterprise are discussed.
The digital pendulum
Authors: Nicklin R. C. , Rafert J. B.
Published: March 2005

A rigid pendulum was attached to an inexpensive rotary potentiometer to which batteries had been connected. As the pendulum swung, a voltage proportional to the angle resulted and was fed to a PET 4016 computer equipped with an analog to digital converter. Position versus time data at rates ranging from 75 to 750 points/cycle were acquired with better than 1% accuracy for multiple cycles of several pendulums released from angles up to 90 degrees. Numerical solutions to the elliptic integrals describing large amplitude motion were compared with experimental data as were small amplitude curve fittings using the method of differential corrections. Agreement was excellent in both cases. Nine suggestions are made for using the digital pendulum for demonstration and laboratory work for students in introductory noncalculus courses through senior experimental work.
Problem-posing physics: A conceptual approach
Authors: Brouwer Wytze
Published: March 2005

Based on an analogy with Paulo Freire’s Pedagogy of the Oppressed a problem-posing model of instruction is presented in order to facilitate the learning of the fundamental concepts of physics.
Simple relationship between energy and adiabatic invariants for systems with a power-law potential
Authors: Cetto A. M. , de la Peña L.
Published: March 2005

A simple relation between the energy E and the adiabatic invariant J is derived for Hamiltonian systems with a potential V=axk by making use of the virial theorem. By further developing a first-order perturbation technique one arrives at a modified expression for the energy in terms of J for V=axk+bxl. The results obtained are valid in classical mechanics, as well as in the semiclassical domain of quantum mechanics.
Solar cells: A laboratory experiment on the temperature dependence of the open-circuit voltage
Authors: Khoury A. , Charles J-P. , Charette J. , Fieux M. , Mialhe P.
Published: March 2005

This paper describes a simple demonstration of the effect of an increase in temperature upon the performance of solar cells under concentrated light. It is shown that the expected increase of the open-circuit voltage is offset by the temperature effect. This experiment should be quite relevant as an introduction to the study of concentration for undergraduate physics laboratories.
One-dimensional quantum scattering in an eigendifferential basis
Authors: Halcomb Lawrence L. , Diestler Dennis J.
Published: March 2005

The one–dimensional problem of a Gaussian wave packet scattering from a square barrier is solved numerically using momentum eigendifferentials, which are normalized superpositions of momentum eigenkets.
Deduction of the general Lorentz transformations from a set of necessary assumptions
Authors: Schwartz H. M.
Published: March 2005

Since Einstein’s first publication on relativity many papers have been published on the logical derivation of the Lorentz transformations, but apparently without any conclusiveness on the subject having been reached. In this paper, by basing the analysis of this problem on purely kinematic postulates that can be shown to be necessary, an attempt is made to achieve a degree of definitiveness in the results that would enhance their usefulness in ongoing studies on the conceptual foundations of relativistic physics.
Measurement of fluid flow using streak photography
Authors: Dickey T. D. , Hartman B. , Hurst E. , Isenogle S.
Published: March 2005

Streak photography has been used primarily for fluid flow visualizations. A method which extends the application of streak photography to velocity measurements is presented. The technique may be applied to a broad range of fluid dynamical experiments and requires only limited technical resources.
Doppler effect in a stratified medium
Authors: Menon V. J. , Agrawal D. C.
Published: March 2005

A derivation of the Doppler effect in a stratified medium based upon the phase function and Galilean transformation is proposed. The results are applied to the case of sound moving in a gas under gravity with a velocity that obeys Rayleigh’s formula.
Electric fields associated with stationary currents
Authors: Varney Robert N. , Fisher Leon H.
Published: March 2005

The solution to a puzzle proposed by Merzbacher in this Journal [Am. J. Phys. 48, 178 (1980)], the determination of the electric field outside a long straight wire carrying a constant current, is discussed.
Conservative model for the damped harmonic oscillator
Authors: Yurke Bernard
Published: March 2005

A conservative model for the damped harmonic oscillator is constructed by attaching a string of infinite extent to the oscillator’s mass. This system may be used to illustrate, in simple terms, a number of important concepts such as radiation damping, the characteristic impedance of a wave propagating medium, Brownian motion, and the Langevin equation.
The spring-mass system revisited
Authors: Cushing James T.
Published: March 2005

A vertically oscillating spring of mass m and spring constant k suspended from its upper end and with a mass M attached to its lower end is a system often used for demonstrations and experiments in introductory physics courses. We discuss the motion of this system for arbitrary values of ε=m/M, 0≤ε<∞ and show explicitly why theory predicts that the amplitude of the lowest normal-mode frequency makes the major contribution to the motion of M (or of the lower end of the spring) for all values of ε. Although a complete understanding of this fact involves detailed mathematical analysis, the results themselves are simply stated and readily verified even by students in an introductory calculus-based physics course. The various predictions of the theory are easily demonstrated with simple equipment and lend themselves nicely to an introductory physics laboratory. These applications are discussed in some detail, and an analog electric circuit is given which exhibits similar behavior.
Interpretations from Helmholtz’ theorem in classical electromagnetism
Authors: Miller Benjamin P.
Published: March 2005

Helmholtz’ theorem is a profound mathematical theorem which provides the definitive relationship between a vector field and mathematically defined source functions. The usual presentations of electromagnetic theory establish the principle sources of the electromagnetic field vectors, but leave the question of completeness unanswered, that is, whether all sources are included. Helmholtz’ theorem provides the basis for investigating the existence of other possible sources, and in at least one case shows a possible source not normally considered. Helmholtz’ theorem also provides a significant result pertaining to the meaning of the inverse square radial field, of which the Newtonian gravitational and Coulombic electrostatic fields are the classical examples. It can be established that the inverse square relation is determined by more elementary properties of the field and of the source function to which it relates.
An experimental model of a classical many-body system
Authors: Pierański Piotr
Published: March 2005

A mechanical model of a classical many-body system is described. Basic ideas and phenomena concerning both the fluid and solid states are illustrated by a series of simple experiments.
Electrodynamics in a dispersive medium: E, B, D, and H
Authors: Smith C. Ray , Inguva Ramarao
Published: March 2005

Various constitutive relations between the sources and electromagnetic fields in a dispersive medium at rest are reviewed. The constitutive relations which are considered lead to the traditional, the Lindhard, and the external-dielectric tensor formulations of electrodynamics; also a formulation which is a generalization of all of these is developed. Finally, the fluid equations are employed in a calculation of the Lindhard dielectric tensor of a magnetized plasma.
Quantization of the Thomson atom
Authors: Sivardière Jean
Published: March 2005

The quantization of the Thomson atom through the Wilson–Sommerfeld rules is presented. It is found that the Thomson model is inconsistent.
Modern architects of the periodic system
Authors: Ruby Lawrence
Published: March 2005

Major discoveries, which have transformed The Periodic System of the Elements from the arrangement suggested by Mendeleev to the current configuration, are reviewed. In particular, the contributions of H. G. J. Moseley and G. T. Seaborg are described.
Spin current density and the hyperfine interaction in hydrogen
Authors: Parker G. W.
Published: March 2005

The hyperfine structure Hamiltonian for hydrogen is derived by evaluating the magnetic field at the nucleus due to the electron’s spin current density. This approach clearly separates the treatment of states with l=0 (Fermi contact term) from those having l≠0.
Characteristics of a Langmuir probe in a magnetic field
Authors: Katz Jonathan , Gabl Edward F. , Tsikis Eugene K. , Lonngren Karl E.
Published: March 2005

An experiment designed to illustrate the characteristics of a Langmuir probe in various magnetic field configurations using a commercially available gas tube and some small permanent magnets is described. The experiment is suitable for an introductory course in plasma physics.
Semiclassical treatment of above-barrier scattering
Authors: Holstein Barry R.
Published: March 2005

We show how the semiclassical approach to barrier penetration based on path integral methods may be generalized to handle the case that the energy of the scattered particle is greater than the height of the potential barrier.
Newton’s P
r
i
n
c
i
p
i
a and the external gravitational field of a spherically symmetric mass distribution
Authors: Weinstock Robert
Published: March 2005

A detailed analysis is offered—with concomitant clarification, correction, and celebration—of the treatment in Newton’s Principia of the external gravitational field produced by a spherically symmetric mass distribution. It is established, in particular, just how close the Principia comes to achieving the most general result (whereby the sphere can be considered as concentrated at its center); it is also shown how the Principia argument could easily have been extended so as to have gone the whole way.
Statics in the momentum current picture
Authors: Herrmann F. , Schmid G. Bruno
Published: March 2005

Newton’s Second Law is equivalent to the continuity equation for momentum in integral form. This insight leads to an alternative picture of forces as momentum currents. The purpose of the present paper is to introduce a new approach to statics problems and their solutions in terms of momentum currents. In particular, the relation between the distribution of momentum currents and the elastic stresses within a medium will be considered and a simple way to pictorially represent those stresses with the help of momentum flow diagrams will be discussed. Handling statics problems in the momentum current picture immediately displays their relationship to analogous problems in electrical network theory. This uncovers a structural relationship between the role of electric charge in the theory of electricity and the role of momentum in mechanics. For example, it will be shown that the familiar method for the solution of statics problems in terms of free-body diagrams is equivalent to the use of a junction rule for momentum currents.
Skin depth and complex magnetic susceptibility: An experimental alternative approach
Authors: Juri Luis O. , Bekeris Victoria I. , Steinmann Ricardo G.
Published: March 2005

A different approach in the discussion of the skin effect in a metal cylinder, is described, where the presence of eddy currents is assumed to be a consequence of an equivalent static magnetization. A low-cost, easy to build mutual inductance bridge is used to measure the equivalent magnetic susceptibility—a function of the skin depth. The use of a lock-in amplifier as a null detector clearly shows the concept of complex magnetic susceptibility. The electrical resistivity of a copper rod is measured as an application thereof. The results are shown and compared to theory achieving excellent agreement.
Locating an orbiting object
Authors: Mottmann J.
Published: March 2005

This article is a brief tutorial on orbit calculations for objects in orbit around the Sun. A method is presented that avoids astronomical terminology as much as possible, avoids spherical trigonometry, and avoids tedious iterative methods for solving a required transcendental equation. Any student with a slight understanding of vectors should be able to calculate the location of an object in its orbit and determine its position as seen by an Earth observer.
Zero angular momentum turns
Authors: Edwards Martin H.
Published: March 2005

Simple explanations are given of three examples of zero angular momentum turns. Humans and cats free of external torques can use internal forces to move parts of their bodies to produce angular momenta L1 and L2 of the parts, whose vector sum may not be zero. Conservation of angular momentum then requires an L3 of the whole body so that L1+L2+L3=0. This can produce a rotation or partial rotation of the body in the absence of any external torque or initial angular momentum.
Relativistic acoustic Doppler effect in the optical limit
Authors: Bachman R. A.
Published: March 2005

It is shown that the relativistic acoustic Doppler effect is a function only of the relative source/observer velocity if, and only if, the acoustic speed equals the speed of light. In this limit, the acoustic formula reduces to the well-known optical Doppler equation. This clearly demonstrates the superfluity of a material medium for light propagation in vacuum and provides yet another illustration of the unique status of the speed of light within the framework of special relativity.
Floating metal ring in an alternating magnetic field
Authors: Mak S. Y. , Young K.
Published: March 2005

The levitation of a metal ring in an alternating magnetic field, often used as a demonstration of induced current in introductory courses, is shown to be due entirely to some rather small phase differences. The fields and phases are directly measured and used to calculate the force, with the result agreeing with the weight of the ring. All theory and measurement are within the reach of students taking a first course in electromagnetism.
The resistance between two contacts in a plane and the capacitance between paraxial cylinders
Authors: Edmonds Dean S. , Corson Michael R.
Published: March 2005

The problem of finding the resistance between two circular contacts on an infinite conducting plane is related to that of the capacity between paraxial cylinders. The general formula for the capacity between two such cylinders is obtained, resulting in a solution for the resistance between any two circular contacts, including the case in which one is inside the circle formed by the other. This approach suggests a new experiment for the undergraduate laboratory using the electrodes and electrolytic tank often found in such laboratories intended for the usual field plotting experiment. The setup for the resistance experiment is described and some results presented.
Transmission of normally incident microwave radiation through parallel plates of material
Authors: Thompson F. , Tsui H.
Published: March 2005

A semiquantitative undergraduate experiment is described which investigates the transmission of microwave radiation through plates of material. Approximate values of n and k are obtained for each material. For low-loss materials, interference fringes are demonstrated.
Generalized relativistic Doppler effect
Authors: Bachman R. A.
Published: March 2005

The formulation of the relativistic Doppler effect is discussed for arbitrary motion of source and observer. Use is made of an intuitive approach done in the reference frame of the medium. The effects of time retardation and dispersion are investigated. It is shown that the general formula presented herein can be readily derived from a less useful standard formula appearing in the literature. The classical Doppler and relativistic optical Doppler effects are deduced as corollaries.
Gravitational fields and the cosmological constant in multidimensional Newtonian universes
Authors: Wilkins D.
Published: March 2005

The distance dependence of gravity is found in Newtonian universes with any number n of space dimensions. Two independent derivations given are based either on (i) requiring that a (hyper) spherical mass gravitate as if all its mass were concentrated at its center, or (ii) using the field equations of general relativity with the cosmological constant Λ. Both approaches lead to identical results. The gravity field at distance r from a point mass has two parts, one going as r1−n, the other as r, i.e., Hooke’s law. The Hookian field obeys a novel form of Gauss’s (flux) law, and is closely related to Λ. The simple mechanical interpretation which emerges gives insight into the meaning of Λ and helps counteract certain prevalent misconceptions.
Experiments on electro-optic effects with a ceramic dielectric
Authors: Ofer H. , Jodl H. J. , Theysohn G.
Published: March 2005

An experimental investigation of the Kerr effect is described which uses the optical ceramic PLZT, instead of the poisonous nitrobenzene, as a birefringent medium. Both the transverse and the longitudinal electro-optic effect can be demonstrated. A wide range of further quantitative measurements may be performed using the optical ceramic. As examples we describe how temperature-dependent properties and hysteresis characteristics of the material can be examined, and demonstrate technical applications such as in welding goggles or for the intensity modulation of a light beam.
A class of exactly soluble many-body Hamiltonians
Authors: Redondo Antonio
Published: March 2005

A class of exactly soluble N-particle Hamiltonians is presented. The matrix representation of these Hamiltonians, which consists of one- and two-body interactions, is block diagonal. The blocks consist of a finite-dimensional matrices which can be easily diagonalized. An example for a system with two particles is discussed.
Classical dynamics and Lie groups
Authors: Louck J. D. , Metropolis N.
Published: March 2005

The phase space time evolution operator for a dynamical system is derived directly from Newton’s equation of motion. This operator is used to show, in an elementary way, how a Lie group enters into the description in phase space of the path of a one-dimensional damped, driven, harmonic oscillator. Concepts from Lie group theory are thus illustrated in a nontrivial but elementary and familiar setting. Generalizations of this method for Hamiltonian systems are outlined in a series of remarks that suggest the broader scope of the subject.
The quest for ultrahigh energies
Authors: Sessler Andrew M.
Published: March 2005

A categorization is given of all the methods for accelerating particles. It is shown that in principle one can employ the large fields of a laser for this purpose as well as the wake fields of intense low-energy particle beams. Discussion is given of four acceleration schemes which offer the possibility of attaining very high-energy particles; namely, the inverse free-electron laser accelerator, the beat-wave accelerator, the wake-field accelerator, and the two-beam accelerator.
Two-density model of the Earth
Authors: Snyder Ralph
Published: March 2005

A model of the Earth is discussed in which a spherical and homogeneous core is surrounded by the mantle, taken to be a spherical shell of constant density. Four pedagogical exercises are worked out using this model: the variation of gravitational acceleration with radius, the moment of inertia of the Earth, the pressure at the center of the Earth, and the tunneling time through the Earth. The results are compared to actual geophysical values and also to the predictions of the single-density model.
To derive the existence of gravity
Authors: Falk Lars
Published: March 2005

The existence of gravitational force is derived from simple arguments based on Newton’s mechanics. The derivation provides physical understanding both of Einstein’s general theory of relativity and its relation to the special theory. In particular, the proportionality between mass and energy is a direct consequence of this derivation.
Velocities, refraction, and particle aspects of water waves
Authors: Breeding J. Ernest
Published: March 2005

Examples are presented which show that water waves behave in some ways like ‘‘fictitious particles.’’ The velocities and refraction equations are developed for a wave packet composed of nonparallel wave components. The relationships between Fermat’s principle, the Euler–Lagrange equation for rays, the ray curvature expression, Snell’s law, and Hamilton’s equations are discussed. The energy transmission rate of a hydron (water wave packet) is used to derive the shoaling and refraction coefficients. The total reflection of water waves is examined. The results for a hydron are compared with those of monochromatic waves.
Optical display of the ambiguity function and the diffraction pattern of a screw—An analogy
Authors: Sethuraman J.
Published: March 2005

The Fraunhofer diffraction pattern of a screw is interpreted as an optical display of essential features of the ambiguity function of a chirp signal. Since no special preparation and optical processing are needed for diffraction, the optical display is very simple to demonstrate and impressive to visualize.
Quantum scattering in two dimensions
Authors: Adhikari Sadhan K.
Published: March 2005

A self-contained discussion of nonrelativistic quantum mechanical potential scattering in two dimensions is presented. The discussion includes, among other topics, partial wave decomposition in coordinate and momentum space, Lippmann–Schwinger integral equations of scattering for the scattering wavefunction and the transition operator, optical theorem, and the unitarity relation for the transition operator. The present definition of the scattering amplitude in terms of the asymptotic wavefunction differs from the usual definition. The present definition has certain advantages, for example, in writing the optical theorem and in studying the analytical properties of the scattering amplitude.
Ladder operators for orbital angular momentum
Authors: de Lange O. L. , Raab R. E.
Published: March 2005

Three pairs of abstract operators are presented which serve as ladder operators for the orbital angular momentum quantum numbers l and m. These operators are used to prove the restriction of l to integral values and also to obtain matrix elements for orbital angular momentum state vectors. The calculations are based entirely on an application of the abstract (Dirac) operator method to orbital angular momentum.
Superposition and energy conservation for small amplitude mechanical waves
Authors: Mathews W. N.
Published: March 2005

The energy that would be carried by a wave produced by the superposition of two small amplitude mechanical waves of the same type would generally differ from the sum of the energies of the component waves in the superposition. Thus energy conservation appears to be violated. In this paper we address the question of the compatibility of the principles of superposition and energy conservation for small amplitude mechanical waves. We show that in the course of producing a pair of waves that interfere constructively, a second pair of waves that interfere destructively is naturally and unavoidably produced. Moreover, we show that the combination of constructive and destructive intereference is just that necessary for energy conservation. Thus we conclude that the principles of superposition and energy conservation are fully compatible.
Time-dependent behavior of strings using Fourier analysis
Authors: Brown Judith C.
Published: March 2005

The time-dependent behavior and spectra of a string with an initial sawtooth or triangular shape are calculated using Fourier series. A comparison is made with the analysis by traveling waves. Results are presented as a series of computer-plotted graphs.
Unitary symmetry and crystal tensors
Authors: Newman D. J. , Chan K. S.
Published: March 2005

It is pointed out that U3 irreducible representation labels may be used to characterize the symmetry properties of Cartesian tensors in relation to their invariance under suffix permutations. A table giving the branching rules for U3 ⊇ R3 provides a simple method for finding the number of independent components in a Cartesian tensor describing the properties of a system (e.g., a crystal) characterized by a point group G. This application allows us to introduce the properties of the Lie group U3 into the undergraduate curriculum in relation to finite group properties.