bluuebunny/crossref_metadata_2025 huggingface dataset:
Post‐and‐Core Assemblies Made With an Accelerated Pattern Elimination Technique
Authors: Bailey John H. , Sherrard David J.
Published: March 2005

Purpose

Accelerated pattern elimination has the potential for increasing productivity. This study evaluated the accelerated pattern elimination technique using three commonly used phosphate‐bonded investments.

Materials and Methods

Part one of this study determined the mean time interval from start of mixing to the maximum exothermic setting reaction temperature for each investment. A chromel/alumel thermocouple was placed at the heat center of a methylcellulose lined casting ring, using wet or dry ring liner. Investments were vacuum mixed at the recommended ratio for the accelerated technique. Colloidal silica solution and ddH2O were combined at a 50:50 ratio to meet the manufacturer's recommended liquid volume. Part two determined the dimensional reproduction of a standardized pattern and its casting using both casting techniques. Mixing ratios were the same as in part one for the accelerated technique and 75% colloidal silica to 25% double‐distilled water (ddH2O) for the conventional technique. The accelerated technique used the mean setting time established in part one followed by a 15‐minute furnace holding time at 725°C (1350°F). The conventional technique used a 1‐hour bench setting time, followed by placing the mold into a cold furnace. A controlled rate of climb to a maximum temperature of 725°C (1350°F) was used with a 1‐hour soak time. Each pattern and its casting were measured at four sites: (1) Length of the post‐and‐core assembly, (2) maximum core diameter, (3) post diameter at the core base, and (4) post diameter at its apex.

Results

A significant difference was found between the time interval to maximum exothermic setting reaction temperature for all the investments (P < .01). The accelerated technique produced castings with a relative dimensional increase of 0.11% to 4.80%. The conventional technique ranged from a 0.04% decrease in size to an increase of 3.65%. Castings made with the accelerated technique were significantly different than those made with the conventional technique (P < .01).

Conclusions

Differences in the time interval to maximum exothermic setting reaction temperature indicate that each phosphate investment should have a recommended setting time before introduction into the furnace. The carbon‐containing investment showed the least relative change of the three investments evaluated for both casting techniques.
The Use of Light‐Cured Composite Resin on Altered Diagnostic Casts
Authors: Davis Michael W.
Published: March 2005

Light‐cured composite resin as an alternative to wax for altered diagnostic casts is demonstrated. The value of altered diagnostic casts as a diagnostic tool is addressed. The benefits in the use of composite resin versus the traditional use of wax are emphasized.
Restoring a Failed Prefabricated Post and Core With a Sleeve Casting: A Clinical Report
Authors: Harrison Lewis , Goldfogel Marvin
Published: March 2005

A clinical case is described, and a technique is explained for making a custom sleeve cast post and core to salvage a fractured crown previously treated with an unretrievable prefabricated post. The restorative problem was to design and fabricate some sort of cast post and core that could be cemented to the remaining post. The amalgam and cement in the pulp chamber and coronal portion of the root canal were carefully removed so that a direct pattern could be made to form a tube which would surround the coronal part of the existing post like a sleeve. This sleeve casting was designed to provide attachment for a core to support a new restoration. This direct pattern technique results in a retained core that joins the already cemented post and provides a sound core for the retention of a new crown.
A Systematic Approach to Definitive Planning for Osseointegrated Implant Prostheses
Authors: Wicks Russell A.
Published: March 2005

Thoughtful design selection is crucial for the perpetual success of any dental implant restoration. This article reviews treatment considerations specific to the postsurgical presentation of the implant patient. Deviations from the originally planned design may be necessary at this time. Indications for the selection of specific prosthetic modalities are offered in a sequence of paradigms to support the cognitive skills of the inexperienced clinician.
A Comprehensive Approach to Die Trimming
Authors: Mansueto Michael A. , Phoenix Rodney D.
Published: March 2005

Proper trimming of stone dies is an essential step in fixed prosthodontics. Die trimming requires meticulous technique and a thorough understanding of required elements in die design. By dividing the die into three zones, die contour requirements can be better understood, discussed, and demonstrated. A two‐step technique provides optimal results, incorporating a logical plan with the use of proper magnification and illumination.
A Direct Provisional Restoration for Decreased Occlusal Wear and Improved Marginal Integrity: A Hybrid Technique
Authors: Fehling A. W. , Neitzke Craig
Published: March 2005

A direct technique for the fabrication of provisional restorations is described. Occluding surfaces of the provisional restoration are veneered with a light‐cure composite resin for increased wear resistance and improved occlusal stability. Also described is a method for reestablishing the provisional restoration's margins to achieve optimal tissue health.
Anatomic Site Evaluation of Edentulous Maxillae for Dental Implant Placement
Authors: Razavi Ramin , Zena Robert B. , Khan Zafrulla , Gould Alan R.
Published: March 2005

Purpose This study evaluated 17 edentulous cadavers for bone quantity and quality of the alveolar process of the maxilla for the purpose of dental implant placement.

Materials and Methods The maxillary arch was divided into four anatomically defined regions for measurements of bone quantity. Bone quality was assessed histologically and described by trabecular bone patterns and tissue composition.

Results Average bone height with a minimum thickness of 4 mm was as follows: region 1, 12.1 ± 4.9 mm; region 2, 14.1 ± 7.2 mm; region 3, 6.1 ± 2.8 mm; and region 4, 8.5 ± 2.2 mm. Histological evaluation showed increased trabeculation and thicker cortex in the maxillary anterior area, regions 1 and 2. Region 3, the floor of the maxillary sinus area, had the least amount of bone; however, the quality of bone was superior to that of region 4, the maxillary tuberosity area. Trabecular distance or marrow spaces ranged from 40 μm to 2 mm with larger spaces associated with the posterior maxilla.

Conclusions Maxillary tuberosity is the least desirable site for the placement of implants in the maxilla. The area corresponding to the first and second molars had the least bone thickness. All measures of bone preservation need to be considered, especially in this area.
Color Stability of Hybrid Ionomers After Accelerated Aging
Authors: Davis Bianca A. , Friedl Karl‐Heinz , Powers John M.
Published: March 2005

Purpose The color stability and surface roughness of three commercial hybrid ionomers were determined in vitro after accelerated aging. Three shades of each hybrid ionomer prepared in light‐cured and dark‐cured conditions were tested.

Materials and Methods Samples were aged in an artificial aging chamber by subjecting them to total ultraviolet light irradiation of 150 kJ/m2 over a period of 77 hours. Color (CIE LAB system) was measured before and after aging on a reflection spectrophotometer. Surface roughness was measured with a profilometer.

Results After accelerated aging, all samples became lighter. Photac‐Fil Aplicap (ESPE‐Premier, Norristown, PA) and Fuji II LC (GC America, Chicago, IL) also became less chromatic (less red and less yellow). Among the light‐cured samples, Fuji II LC had the greatest change in color followed by Photac‐Fil Aplicap and Vitremer (3M Dental Products, St Paul, MN). For the dark‐cured samples, Fuji II LC had the greatest change in color followed by Vitremer and Photac‐Fil Aplicap. There were no differences in delta E* between the two lightest shades, but the darker shades of each product showed the greatest changes in color. All samples became significantly rougher after aging.

Conclusions Hybrid ionomers changed color significantly and perceptibly after in vitro accelerated aging. Surfaces became significantly rougher and showed evidence of cracking and degradation.
Predoctoral Implant Dentistry Programs in US Dental Schools
Authors: Weintraub Annette M. , Seckinger Robert , Berthold Peter , Weintraub Gerald S.
Published: March 2005

Surveys of US dental schools over the last 20 years have reported a continual increase in the number and types of predoctoral and postdoctoral implant dentistry programs being taught. The purpose of the following article is to report on the results of a survey intended to update the status of predoctoral programs with respect to their curricular placement, departmental jurisdictions, and course contents. In June 1993, 54 US dental schools received the implant dentistry curriculum survey, and 50 of the schools (93%) returned responses. Results indicate that the trend toward implementation of more predoctoral implant dentistry programs has been sustained, with 86% of schools reporting the existence of implant curricula. This compares with 33% and 73% of US schools having such programs in 1974 and 1989, respectively. The major reasons that schools gave for not having implant dentistry courses for predoctoral students are a lack of curriculum time and scarce financial resources. The dental disciplines most frequently guiding such programs are oral surgery and periodontics. Schools offer varying degrees of lectures, laboratories, and clinical experiences in predoctoral implant dentistry, with the number of curriculum hours peaking in years three and four. General curricular topics most commonly include a historical overview of implant dentistry, diagnosis and treatment planning, classifications and types of dental implants, and surgical and prosthodontic procedures. Seventeen percent of schools require some form of undergraduate clinical implant dentistry exposure for all of their students.
Recurrence of Mandibular Tori After Surgical Removal: Two Case Reports
Authors: Brunsvold Michael A. , Kaiser David A. , Faner Richard M.
Published: March 2005

Mandibular tori are sometimes removed to enhance periodontal and prosthodontic treatment. The exact cause of these benign bony overgrowths is not well understood, and therefore, their potential to recur after removal is also uncertain. Two case reports are presented in this article that provide evidence that at least some mandibular tori recur after surgical removal. One patient was followed‐up for 11 years, and the other patient was followed‐up for 14 years.
Dimensional Accuracy of Three Different Alginate Impression Materials
Authors: Cohen Brett I. , Pagnillo Mark , Deutsch Allan S. , Lee Musikant Barry
Published: March 2005

Purpose The purpose of this study was to evaluate the dimensional stability of three different alginate impression materials (Jeltrate [Caulk Dentsply, LD Caulk Division, Dentsply International, Milford, DE], Hydrogum [Zhermack, Padoua, Italy], and a new hydrophilic alginate material [Essential Dental Systems, South Hackensack, NJ]) under five different storage conditions.

Materials and Methods The study was divided into four groups with at least eight samples in each group. The five storage conditions were as follows: immediate, 10 minutes with a wet towel, 30 minutes without a wet towel, 1 hour with a wet towel, and 24 hours with a wet towel. A 4 × 5 factorial two‐way analysis of variance (P < .05) was used on each dependent variable. Dunnett's test was used to compare each alginate with Jeltrate.

Results The new hydrophilic alginate (group 4, 2:2) showed smaller measurements in the buccolingual and diagonal dimensions compared with Jeltrate (control).

Conclusions The immediate method (measured buccolingually and diagonally) produced more accurate casts for the alginate materials studied. All other materials studied were similar statistically. The new hydrophilic alginate in group 3 resulted in similar dimensional accuracy compared with Jeltrate and Hydrogum and incorporated 25% less water.
Accuracy of Wax, Autopolymerized, and Light‐Polymerized Resin Pattern Materials
Authors: Iglesias Alan , Powers John M. , Pierpont Hugh P.
Published: March 2005

Purpose

The marginal fit of MOD inlay and full‐crown patterns fabricated from wax, autopolymerized acrylic resin, and two light‐polymerized, diacrylate resin pattern materials was compared on standardized dies.

Materials and Methods

Four pattern materials were studied—two light‐polymerized, diacrylate resin materials (Palavit G LC and Triad VLC Burnout Paste), an inlay wax, and an autopolymerized resin (Duralay). Patterns were fabricated using incremental and bulk techniques on stone dies made from addition silicone impressions of American Dental Association MOD and full‐crown master dies. Gaps were measured with a measuring microscope in four marginal areas on the master dies at 1 and 24 hours after fabrication.

Results

For the MOD inlay patterns, marginal gaps ranged from 7 to 23 μm, and the light‐polymerized, diacrylate resins and autopolymerized acrylic resin material had statistically smaller gaps than the inlay wax. For the full‐crown patterns, marginal gaps ranged from 10 to 23 μm, with the exception of the autopolymerized acrylic resin prepared by the bulk technique (40 to 46 μm). With the incremental technique, the light‐polymerized, diacrylate resins and inlay wax had statistically smaller gaps than the autopolymerized acrylic resin material. Overall, the incremental technique produced equal or smaller marginal gaps than the bulk technique for full‐crown patterns. Generally, the patterns measured at 1 hour had smaller marginal gaps than at 24 hours.

Conclusions

When measured on intra‐ and extracoronal master dies, the light‐polymerized, diacrylate resins had equal or better marginal fit, compared with wax or autopolymerized acrylic resin, and were less affected by placement technique and storage. The marginal gaps of all four pattern materials ranged from 7 to 46 μ and are within the range of clinical acceptability.
The Twin‐Flex Removable Partial Denture: Design, Fabrication, and Clinical Usage
Authors: Mansueto Michael A. , Phoenix Rodney D.
Published: March 2005

A rationale for the use of Twin‐Flex clasps is presented. Twin‐Flex clasps may provide improved esthetics, an increased number of clasping sites, and enhanced patient comfort when compared with conventional clasping systems. Two fabrication methods are described, and departures from conventional clasping techniques are explained.
Zygomatic complex fractures in a suburban Nigerian population
Authors: Ugboko Vincent , Udoye Christopher , Ndukwe Kizito , Amole Adewumi , Aregbesola Stephen
Published: March 2005

Abstract –  A retrospective analysis of 128 zygomatic complex fractures was undertaken. There were 109 males (85.2%) and 19 females (14.8%), aged 3–74 years (mean ± SD, 33 ± 12.6 years). Patients in the third decade of life (38.3%) recorded the highest incidence. Road traffic accidents (74.2%) mainly from automobile (61.7%) and motorcycle (9.4%) involvement were the predominant etiology. While 38.8% of them presented within the first 24 h, males were relatively earlier than their female counterparts, although this was not statistically significant (P > 0.05).

Class 3 fractures were the commonest (50%), followed by classes 2 (zygomatic arch) and 4, respectively. Most class 6 fractures (6.3%) resulted from gunshot injuries. There were 116 unilateral (left 63, right 53) and 12 bilateral fractures with the right side of the face recording more zygomatic arch fractures. In addition, statistical significance was observed between etiology, class and type of fracture (P < 0.05). One hundred and twenty‐four (136 fractures) patients were available for treatment as four declined. Twelve cases did not require treatment while others were managed by either closed or open reduction under general anesthesia. Gillies’ temporal approach was the commonest (57.1%) surgical technique employed. However the unstable nature of the fractures necessitated open reduction and transosseous wiring in 33 cases. The high prevalence of zygomatic complex fractures arising from vehicular accidents reflects the poor status of the road network in rural and suburban Nigerian communities. Hence government should improve on existing infrastructures, decongest the highways and enforce traffic laws amongst road users. In addition, the need to encourage massive investments in safer alternative transport systems is emphasized.
Evaluation of a Drug‐Drug Interaction Alert Structure through the Retrospective Analysis of Statins‐Macrolides Co‐Prescriptions
Authors: Morera Tomas , Gervasini Guillermo , Carrillo Juan Antonio , Benitez Julio
Published: March 2005

Abstract: The aim of this work was the evaluation of the existent drug interaction alert structure in Spain, which is based on yellow cards notifications and circulation of drug alert letters, through the retrospective analysis of CYP3A‐metabolized statins and macrolides co‐prescriptions in the Spanish province of Badajoz between May and September 2001. The period of study was planned to include the release of 2 drug alert letters released by the Spanish Drug Agency in June and July, addressed to all healthcare professionals, which warned against the concomitant prescription of statins and inhibitors of their metabolism, e.g. macrolides antibacterials. 4,600,764 prescriptions were examined, 664 of which corresponded to combinations of statins and macrolides. Although a decrease was detected in the number of these co‐prescriptions throughout the study, 80 of these corresponding to 67 patients were still being prescribed in September, after the warnings by the Spanish Drug Agency had been released. 431 physicians prescribed these drugs simultaneously, with 22.9% of them having more than one patient at potential risk. Doctors working at rural healthcare centres or not directly attached to any healthcare facility were more prone to prescribe unsafe coprescriptions than those working at urban health centre. This study shows that the present drug alert system is not fully efficient when facing a situation like the one retrospectively reviewed in this study, in which a prompt action, in this case termination of potentially hazardous coprescriptions, was required. New systems developed to improve prescribing, including a new method based on personal contact between Drug Surveillance Centres and general practitioners, are discussed.
USE OF CONFIDENCE ELLIPSES IN A PCA APPLIED TO SENSORY ANALYSIS APPLICATION TO THE COMPARISON OF MONOVARIETAL CIDERS
Authors: HUSSON FRANÇOIS , BOCQUET VALÉRY , PAGÈS JÉRÔME
Published: March 2005

In a descriptive sensory analysis, a principal component analysis (PCA) is usually applied to analyze products with attributes. To visualize the variability of a mean point (i.e., the center of gravity of the product), we introduced confidence ellipses. In this particular application, resampling methods are performed. Twenty products composed of five varieties of cider were studied. We would like to know if these five varieties are different. Confidence ellipses reveal differences between varieties foreshadowed in PCA.
Thermal Damage Prediction for Collagenous Tissues Part I: A Clinically Relevant Numerical Simulation Incorporating Heating Rate Dependent Denaturation*
Authors: Aksan Alptekin , McGrath John J. , Nielubowicz, David S.
Published: March 2005

Subablative thermotherapy is frequently used for the treatment of joint instability related diseases. In this therapy, mechanically deformed collagenous tissues are thermally shrunk and the stability of the tissue is re-established. In this research, the thermal damage fields generated by three different clinical heating modalities (monopolar and bipolar radio frequency and Ho:YAG laser) are compared numerically using finite element analysis. The heating rate dependent denaturation characteristics of collagenous tissues are incorporated into the model using experimental data from in vitro experimentation with rabbit patellar tendons. It is shown that there are significant differences among the thermal damage profiles created by these modalities, explaining the main reason for the discrepancies reported in the literature in terms of the efficacy and safety of each modality. In the complementary paper, the accuracy of the model presented here is verified by in vitro experimentation with a model collagenous tissue and by quantifying the denaturation-induced birefringence change using Optical Coherence Tomography and Magnetic Resonance Imaging.
Projector approach to the inertia operator
Authors: Dumais Jean-François
Published: March 2005

The inertia operator of a mass distribution is presented as a weight sum of projectors. Simplifications and insights brought by this geometrical approach are discussed. The paper ends with comments on the physical meaning of the inertia operator.
Letter to the Editor
Authors: Ponting R. Lee
Published: March 2005

The efficiency and cost effectiveness of solar hot water heaters are discussed. (AIP)
Letter to the Editor
Authors: Cohen Bernard L.
Published: March 2005

The economics of solar hot water heaters is considered as applicable to U.S. houses. (AIP)
An audio-tutorial electricity and magnetism laboratory for introductory physics
Authors: Chimino David F. , Hoyer Ruben R.
Published: March 2005

An audio-tutorial laboratory which accompanies an introductory electromagnetism course at Michigan Technological University has been in operation for three years. The application of this laboratory method to electricity and magnetism provided unique problems in the design of experiments and in the selection of instruments. In some cases new apparatus had to be designed and built. A set of eight experiments is in use. Several involve the electrical system of an automobile.
Form of the manifestly covariant Lagrangian
Authors: Johns Oliver Davis
Published: March 2005

The preferred form for the manifestly covariant Lagrangian function of a single, charged particle in a given electromagnetic field is the subject of some disagreement in the textbooks. Some authors use a ‘‘homogeneous’’ Lagrangian and others use a ‘‘modified’’ form in which the covariant Hamiltonian function is made to be nonzero. We argue in favor of the ‘‘homogeneous’’ form. We show that the covariant Lagrangian theories can be understood only if one is careful to distinguish quantities evaluated on the varied (in the sense of the calculus of variations) world lines from quantities evaluated on the unvaried world lines. By making this distinction, we are able to derive the Hamilton–Jacobi and Klein–Gordon equations from the ‘‘homogeneous’’ Lagrangian, even though the covariant Hamiltonian function is identically zero on all world lines. The derivation of the Klein–Gordon equation in particular gives Lagrangian theoretical support to the derivations found in standard quantum texts, and is also shown to be consistent with the Feynman path-integral method. We conclude that the ‘‘homogeneous’’ Lagrangian is a completely adequate basis for covariant Lagrangian theory both in classical and quantum mechanics. The article also explores the analogy with the Fermat theorem of optics, and illustrates a simple invariant notation for the Lagrangian and other four-vector equations.
The Hamilton–Jacobi equation for Coulomb scattering
Authors: Rowe E. G. Peter
Published: March 2005

The Hamilton–Jacobi equation for time-independent, nonrelativistic, classical Coulomb scattering is solvable by very elementary means. Everything of interest about the important system of Coulomb scattering orbits can be found exactly and analytically using only a knowledge of vector analysis.
‘‘Whispering’’ waves in a wineglass
Authors: Apfel Robert E.
Published: March 2005

Surface waves in a wineglass do not whisper. But they do illuminate a special class of wave phenomena and, therefore, are instructive to study. The wine is an added benefit.
Power series expansion solution to a classical problem in electrostatics
Authors: Estevez G. A. , Bhuiyan L. B.
Published: March 2005

Using a power series expansion and differential calculus, the normal derivative of the magnitude of the static electric field near the surface of a curved conductor is obtained. This provides an alternative way of solving a problem which is usually treated by an application of Gauss’s theorem.
On the adequacy of Newtonian particle mechanics for solving the rigid double pendulum problem
Authors: Felszeghy Stephen F.
Published: March 2005

In an earlier article in this journal [W. Stadler, Am. J. Phys. 50, 595 (1982)], an attempt was made to solve for the motion of a three-particle rigid double pendulum using only the axioms of Newtonian particle mechanics. In the process of solution, an incomplete set of equations was used which led to the erroneous conclusion that the Newtonian axioms are insufficient to solve the problem. It is shown in the present article that when the rigid double pendulum problem is formulated with four particles, together with appropriate constraints, the problem can be solved entirely with the Newtonian axioms.
Optical simulation of low-energy electron diffraction patterns
Authors: Burch Kathryn D. , Huang J. L. , Greenler Robert G.
Published: March 2005

An optical analog can be constructed for the diffraction of low-energy electrons from a single-crystal surface covered with a layer of adsorbed molecules. The project is of appropriate difficulty and duration for an undergraduate student project and the results can yield insight into current research problems. The optical simulation of low-energy electron diffraction patterns also makes an effective classroom demonstration for introducing the concept of the wave nature of particles.
Fourier analysis with Lissajous figures
Authors: Ong P. P. , Tang S. H.
Published: March 2005

A practical method for Fourier analysis of a periodic waveform using only low-cost equipment is described. The method is suitable for any periodic voltage signal whose frequency can be continuously varied. By employing multistage tuning it can realize an accuracy that is limited only by that of the waveform of the test signal. The method is didactic and has the aesthetic appeal of the myriad variations of Lissajous figures. It is also suitable for mass duplication as a standard classroom experiment in the undergraduate laboratory. Exemplary results are shown for the square and triangular waves generated with simple circuit designs.
Electrostatic potential due to a Fermi-type charge distribution
Authors: Estévez Gentil , Bhuiyan L. B.
Published: March 2005

Starting from first principles, the potential due to a centrosymmetric charge distribution that vanishes at infinity is obtained. The result is applied to derive an analytical expression for the nuclear electrostatic potential due to the Fermi two-parameter model charge distribution. A numerical evaluation of the electrostatic energy associated with this potential is given, for independent variations of the two parameters of the distribution.
Minimum uncertainty states and their time evolution
Authors: Howard Stephen , Roy Sanat K.
Published: March 2005

The minimum uncertainty states are discussed in detail. A simple method is described for obtaining the time evolution of such states in a parabolic potential.
Piecewise linear anharmonic LRC circuit for demonstrating ‘‘soft’’ and ‘‘hard’’ spring nonlinear resonant behavior
Authors: Flerackers E. L. M. , Janssen H. J. , Beerden L.
Published: March 2005

Piecewise linear LRC circuits are described which allow a clear demonstration of ‘‘soft’’ and ‘‘hard’’ spring nonlinear resonant behavior. Amplitude- and phase-response curves obtained with these circuits are also presented.
Microcomputer spreadsheet programs in the physics laboratory
Authors: Feinberg Richard , Knittel Max
Published: March 2005

We describe the operation of the microcomputer spreadsheet program and examine several of its applications as a calculational aid in the undergraduate physics laboratory. It will be shown to be a useful tool in the areas of data handling, error analysis, and experimental design.
Ideal ballistic trajectories revisited
Authors: Buckmaster H. A.
Published: March 2005

The various relations that can be derived to describe ideal ballistic trajectories are summarized when (i) the inclined plane is of negative, zero, or positive slope; (ii) the launch and target sites differ in elevation; and (iii) the launch site is obscured from the target site. It is shown that a new simple intuitive physical argument can be used to determine the launch angle θm which yields maximum range for (i) and (ii). This approach enables students without a knowledge of calculus to analyze these ballistic trajectory problems. Comments are made on the communality of analysis involved in these related kinematic problems.
Measuring the active gravitational mass of a moving object
Authors: Olson D. W. , Guarino R. C.
Published: March 2005

If a heavy object with rest mass M moves past you with a velocity comparable to the speed of light, you will be attracted gravitationally towards its path as though it had an increased mass. If the relativistic increase in active gravitational mass is measured by the transverse (and longitudinal) velocities which such a moving mass induces in test particles initially at rest near its path, then we find, with this definition, that Mrel=γ(1+β2)M. Therefore, in the ultrarelativistic limit, the active gravitational mass of a moving body, measured in this way, is not γM but is approximately 2γM.
Science as a human endeavor: A freshman seminar
Authors: Silverman M. P.
Published: March 2005

A selection of readings and topics of discussion is described which served as the basis of a seminar to help first-term freshmen, particularly those with little prior exposure to science, develop a more accurate and sympathetic perspective of the nature of science. Emphasis is placed on science as a human activity rather than as a methodological abstraction. Reading material is drawn largely from the personal experiences and expository writings of contemporary scientists who are also gifted interpreters of science.
Theoretical support for the generalized correspondence principle
Authors: Fadner W. L.
Published: March 2005

Although most people associate the correspondence principle with quantum mechanics, it has been used more generally for many years in the development of theories in essentially all branches of physics. Based upon simple assumptions which would seem to be necessary for any exact science, a more precise statement of the generalized correspondence principle is provided, with due regard to the accuracy of theories. Term correspondence is presented as a corollary to the principle. Evidently, the principle has as strong a basis as other scientific theories. Its value in theory development as well as in furthering the understanding of the history of science is discussed.
Maxwellian and cavity electromagnetic fields within continuous sources
Authors: Yaghjian Arthur D.
Published: March 2005

Maxwellian and cavity electromagnetic fields are derived within a continuous source distribution of volume current or electric and magnetic polarization densities by direct, rigorous differentiation of the vector potential. The derivation, which uses only operations of vector calculus, reveals naturally the contributions from interior and exterior source regions. Results are obtained for static and arbitrarily time-varying fields as well as for time-harmonic fields.
The conventionality of synchronization
Authors: Erlichson Herman
Published: March 2005

A proof that absolute synchronization is impossible is sketched. The proof divides synchronization schemes into two broad classes: single-agent schemes and two-agent schemes. The application of the proof to several synchronization schemes (the rigid rod, clock transport, and wave-front synchronization) is discussed. The conclusion is the same as was stated by Einstein in his 1905 relativity paper—synchronization must utilize a convention.
Holographic gratings for the physics laboratory
Authors: George Simon , Truman Mike , Murty M. V. R. K.
Published: March 2005

A holographic transmission grating is made using a 15-mW He–Ne laser (Spectra Physics Model No. 124B). Two front-surface mirrors are used to obtain two coherent beams by the method of division of wavefront. The interference pattern is recorded on a high-resolution photographic plate. The value of ‘‘d’’ the grating constant is calculated using the relationship between the fringe spacing and the angle between the two interfering beams. This value is then compared with the one obtained by using the grating equation, a spectrometer, and a mercury lamp. From the results obtained and in view of the fact that He–Ne lasers are readily available in physics laboratories, this experiment is recommended as suitable for an advanced undergraduate optics and spectroscopy or quantum physics laboratory.
A simple geometric model for visualizing the motion of a Foucault pendulum
Authors: Hart John B. , Miller Raymond E. , Mills Robert L.
Published: March 2005

A geometrical model of the Foucault pendulum is presented, which corrects some common misconceptions concerning the ‘‘fixed’’ plane in which the pendulum oscillates. It is shown visually, and by the use of metric geometry, that the direction of oscillation of the pendulum undergoes a parallel displacement as it moves along the Earth’s spherical surface. However, this direction of oscillation is not fixed relative to the stars.
Microcomputer interfacing: A course for science majors
Authors: Lietz Gerard P.
Published: March 2005

A course in microcomputer interfacing for science majors is described. The emphasis is on attaching devices to the computer rather than interconnecting the components of the computer itself. Lab exercises use an 8-bit microcomputer, the Rockwell AIM 65 (now marketed by Dynatem, Inc., 22600-D Lambert Street, El Toro, CA 92630), but they are not computer specific. Topics covered include handshaking, polling, interrupts, A/D and D/A conversion, and stepping motor control. Assembly language is introduced and used throughout the course.
Trouble on the loop-the-loop
Authors: Tea Peter L.
Published: March 2005

Energy considerations give an incorrect value for the minimum height from which a sphere may be released on the approach track of a loop-the-loop, assuming that the sphere rolls without slipping. Analytical and graphical methods are described for predicting whether the sphere will negotiate the top of the circular loop for arbitrary conditions of release height and coefficients of friction. Finally, a situation in which a sphere commences to slip immediately upon release is discussed.
System physics: A uniform approach to the branches of classical physics
Authors: Burkhardt H.
Published: March 2005

A systematic frame for the theory of classical physics is presented. The purpose of the modification in structure of the science is to economize the teaching, learning, and application of physics, and the communication with other disciplines. Isomorphic procedures applicable to the branches of physics and to other sciences are recommended. A system is defined as an imagined container; its contents of extensive (substancelike) quantities are used to describe the state of the system; balance equations account for the dynamic change in a system’s state through processes. The procedure, essentially a space integral formulation of macroscopic transport equations, is applied to physics by using the extensive quantity of entropy and the conserved extensive quantities of mass, energy, momentum, angular momentum, and electric charge. Examples are given from the areas of mechanics, electricity, and heat.
The antenna formula: An application of single-slit diffraction theory
Authors: Bush R. T.
Published: March 2005

The famous Friis antenna formula relating received power to transmitted power, distance between antennas, wavelength, and antenna areas is derived in the Fraunhofer approximation utilizing the results of single-slit diffraction theory. Since the original exact formula was derived from Fresnel theory this Fraunhofer treatment improves its accessibility for undergraduates.
Measurement of the thermal conductivity of liquids using a transient hot wire technique
Authors: Fox J. N. , Gaggini N. W. , Wangsani R.
Published: March 2005

The thermal conductivity of a liquid is measured using a transient hot wire technique. This technique employs a very thin wire that is used both as a heating element and thermometer. The data are collected before the onset of convection currents in the liquid. Results are presented for several liquids.
Strange attractors of a bouncing ball
Authors: Mello T. M. , Tufillaro N. B.
Published: March 2005

We demonstrate the existence of strange attractors in a simple dissipative mechanical system, a bouncing ball subject to repeated impacts with a vibrating table.
Movable chalkboards in the science lecture hall
Authors: Bartlett Albert A.
Published: March 2005

The functional educational goals of moving chalkboards in the science lecture hall are reviewed and a number of different arrangements of moving chalkboards are described along with a tabulation of their advantages and disadvantages. A set of moving chalkboards has been designed and constructed to meet the educational goals in an optimum way. These boards are described in detail.
Ancient heliocentrists, Ptolemy, and the equant
Authors: Rawlins Dennis
Published: March 2005

Evidence is presented suggesting an ancient heliocentrist origin for geocentrist C. Ptolemy’s planetary orbit elements and the equant. Pliny’s data for Venus are shown to be inconsistent with geocentricity, and a heliocentric period-relation is found to be the basis of Ptolemy’s previously unexplained and astonishingly accurate tables of the mean motion of Mars, the very planet whose orbit produced the equant. The admirable correctness of his adopted Mars elements is patently inconsistent with the ordmag 1° inaccuracy of Ptolemy’s geocentric model and of his alleged empirical production.
The Kepler problem recast: Use of a transverse velocity transformation and the invariant velocities
Authors: Shore Ferdinand J.
Published: March 2005

For conservative central forces the constancy of angular momentum provides a more natural substitution than is normally used to transform the force law into a differential equation. This is a transverse velocity substitution, which emphasizes angular rather than radial dependence for dynamical variables, implying a functional rotation. The method gives the standard results in new forms and they are expressed in more natural units of length, time, velocity, and energy than appears in other approaches. For the inverse square force the transverse velocity explicitly depends on the two invariant velocities, and the total energy is the difference of the kinetic energies for the two velocities. The invariant angular momentum is the sum of two variable angular momenta for the two velocities. The Laplace–Runge–Lenz vector is one of a triplet of orthogonal invariant vectors, the cross product of the invariant momentum and angular momentum. For noncircular trajectories this triplet and the scalar total energy are constants of the motion.
A simple model for water-wave dispersion relations
Authors: Crawford Frank S.
Published: March 2005

The dispersion relation between angular frequency and wave number is derived for both deep and shallow water waves. (AIP)
Teaching wave functions in the laboratory
Authors: Bahr John L. , Blake A. J.
Published: March 2005

The interpretation of the photoelectron spectrum of nitrogen provides an opportunity for students to apply their knowledge of the wave functions for a simple vibrator.
The velocity of sound in a closed tube
Authors: Eddy J. K. , Fox J. N. , Gaggini N. W. , Ramsey D. , Kirkpatrick T.
Published: March 2005

A demonstration experiment is described that permits computer acquisition and real-time display of data on the sound intensity versus length of a closed tube. Subsequent analysis of the distance between resonant sound peaks provides the values for the velocities of sound in various gases.
Response to ‘‘Comment on ‘Bell’s theorem and the foundation of quantum physics’ ’’ [Am. J. Phys. 5
5, 1142 (1987)]
Authors: Stapp Henry P.
Published: March 2005

The principle of EPR locality is discussed. (AIP) e
The nuclear reactor accident at Chernobyl, USSR
Authors: Cohen Bernard L.
Published: March 2005

The sequence of events and the consequences of the nuclear reactor accident at Chernobyl, USSR in April 1986 are reviewed. The background material in nuclear reactor and nuclear explosion physics required for understanding these events is extensively explained, and the differences between U.S. and Chernobyl-type reactors are pointed out.
Cryptic Paraflagellar Rod in Endosymbiont-Containing Kinetoplastid Protozoa
Authors: Gadelha Catarina , Wickstead Bill , de Souza Wanderley , Gull Keith , Cunha-e-Silva Narcisa
Published: March 2005

Cilia and flagella are central to many biological processes in a diverse range of organisms. The kinetoplastid protozoa are very appealing models for the study of flagellar function, particularly in the light of the availability of extensive trypanosomatid genome information. In addition to the highly conserved 9 + 2 axoneme, the kinetoplastid flagellum contains a characteristic paraflagellar rod structure (PFR). The PFR is necessary for full motility and provides support for metabolic regulators that may influence flagellar beating. However, there is an intriguing puzzle: one clade of endosymbiont-containing kinetoplastids apparently lack a PFR yet are as motile as species that possess a PFR and are able to attach to the invertebrate host epithelia. We investigated how these organisms are able to locomote despite the apparent lack of PFR. Here we have identified a
PFR1
gene in the endosymbiont-bearing trypanosome
Crithidia deanei
. This gene is expressed in
C. deanei
and is able to partially complement a
pfr1
null mutation in
Leishmania mexicana
cells, demonstrating that the encoded protein is functional. Careful reexamination of
C. deanei
flagellar ultrastructure revealed a greatly reduced PFR missed by many previous analyses. This affirms the PFR as a canonical organelle of kinetoplastids. Moreover, although PFR proteins have been conserved in evolution, primary sequence differences contribute to particular PFR morphotypes characteristic of different kinetoplastid species.
Genomic Analysis of
PIS1
Gene Expression
Authors: Gardocki Mary E. , Bakewell Margaret , Kamath Deepa , Robinson Kelly , Borovicka Kathy , Lopes John M.
Published: March 2005

The
Saccharomyces cerevisiae PIS1
gene is essential and required for the final step in the de novo synthesis of phosphatidylinositol. Transcription of the
PIS1
gene is uncoupled from the factors that regulate other yeast phospholipid biosynthetic genes. Most of the phospholipid biosynthetic genes are regulated in response to inositol and choline via a regulatory circuit that includes the Ino2p:Ino4p activator complex and the Opi1p repressor.
PIS1
is regulated in response to carbon source and anaerobic growth conditions. Both of these regulatory responses are modest, which is not entirely surprising since
PIS1
is essential. However, even modest regulation of
PIS1
expression has been shown to affect phosphatidylinositol metabolism and to affect cell cycle progression. This prompted the present study, which employed a genomic screen, database mining, and more traditional promoter analysis to identify genes that affect
PIS1
expression. A screen of the viable yeast deletion set identified 120 genes that affect expression of a
PIS1-lacZ
reporter. The gene set included several peroxisomal genes, silencing genes, and transcription factors. Factors suggested by database mining, such as Pho2 and Yfl044c, were also found to affect
PIS1-lacZ
expression. A
PIS1
promoter deletion study identified an upstream regulatory sequence element that was required for carbon source regulation located downstream of three previously defined upstream activation sequence elements. Collectively, these studies demonstrate how a collection of genomic and traditional strategies can be implemented to identify a set of genes that affect the regulation of an essential gene.
Global transcriptome analysis of the C57BL/6J mouse testis by SAGE: evidence for nonrandom gene order
Authors: Divina Petr , Vlček Čestmír , Strnad Petr , Pačes Václav , Forejt Jiří
Published: March 2005

Background

We generated the gene expression profile of the total testis from the adult C57BL/6J male mice using serial analysis of gene expression (SAGE). Two high-quality SAGE libraries containing a total of 76 854 tags were constructed. An extensive bioinformatic analysis and comparison of SAGE transcriptomes of the total testis, testicular somatic cells and other mouse tissues was performed and the theory of male-biased gene accumulation on the X chromosome was tested.

Results

We sorted out 829 genes predominantly expressed from the germinal part and 944 genes from the somatic part of the testis. The genes preferentially and specifically expressed in total testis and testicular somatic cells were identified by comparing the testis SAGE transcriptomes to the available transcriptomes of seven non-testis tissues. We uncovered chromosomal clusters of adjacent genes with preferential expression in total testis and testicular somatic cells by a genome-wide search and found that the clusters encompassed a significantly higher number of genes than expected by chance. We observed a significant 3.2-fold enrichment of the proportion of X-linked genes specific for testicular somatic cells, while the proportions of X-linked genes specific for total testis and for other tissues were comparable. In contrast to the tissue-specific genes, an under-representation of X-linked genes in the total testis transcriptome but not in the transcriptomes of testicular somatic cells and other tissues was detected.

Conclusion

Our results provide new evidence in favor of the theory of male-biased genes accumulation on the X chromosome in testicular somatic cells and indicate the opposite action of the meiotic X-inactivation in testicular germ cells.
Health care reform and job satisfaction of primary health care physicians in Lithuania
Authors: Buciuniene Ilona , Blazeviciene Aurelija , Bliudziute Egle
Published: March 2005

Background

The aim of this research paper is to study job satisfaction of physicians and general practitioners at primary health care institutions during the health care reform in Lithuania.

Methods

Self-administrated anonymous questionnaires were distributed to all physicians and general practitioners (N = 243, response rate – 78.6%), working at Kaunas primary health care level establishments, in October – December 2003.

Results

15 men (7.9%) and 176 women (92.1%) participated in the research, among which 133 (69.6%) were GPs and 58 (30.4%) physicians. Respondents claimed to have chosen to become doctors, as other professions were of no interest to them. Total job satisfaction of the respondents was 4.74 point (on a 7 point scale). Besides 75.5% of the respondents said they would not recommend their children to choose a PHC level doctor's profession. The survey also showed that the respondents were most satisfied with the level of autonomy they get at work – 5.28, relationship with colleagues – 5.06, and management quality – 5.04, while compensation (2.09), social status (3.36), and workload (3.93) turned to be causing the highest dissatisfaction among the respondents. The strongest correlation (Spearmen's ratio) was observed between total job satisfaction and such factors as the level of autonomy – 0.566, workload – 0.452, and GP's social status – 0.458.

Conclusion

Total job satisfaction of doctors working at primary health care establishments in Lithuania is relatively low, and compensation, social status, and workload are among the key factors that condition PHC doctors' dissatisfaction with their job.