bluuebunny/crossref_metadata_2025 huggingface dataset:
INCOME AND THE HAMILTONIAN1
Authors: Usher Dan
Published: March 2005

Among the many interpretations of real national income are (i) the return to national wealth and (ii) the Hamiltonian of an appropriately‐chosen dynamic model of the economy. These interpretations are sometimes alleged to be equivalent and to constitute the self‐evidently ideal definition to which statistics of real national income should conform as closely as possible., The allegation is correct on some very restrictive assumptions about technology and taste. Otherwise, these interpretations are inconsistent, inexpedient as definitions of real national income and significantly at variance with the usage in the national accounts. The return to wealth is unmeasurable with the currently‐available data. The Hamiltonian is typically in the wrong units. It is an accurate reflection of neither productive capacity nor welfare in an intertemporal context. It is not well‐defined in a tax‐distorted economy. It is rarely an indicator of the return to wealth.

A personn's income is “the maximum value he can consume during a week and still be as well off at the end of the week as he was at the beginning”

J. R. Hicks2

“…the rigorous search for a meaningful income concept leads to a rejection of all current income concepts and ends up with something closer to a “wealth‐like magnitude,” such as the present discounted value of future consumption. …a standard welfare interpretation of NNP is that it is the largest permanently maintainable value of consumption. …What we have been calling net national product is just the Hamiltonian for a general optimization problem.”

Martin L. weitman3
TRENDS IN HOUSEHOLD WEALTH IN THE UNITED STATES, 1962–83 AND 1983–89
Authors: Wolff Edward N.
Published: March 2005

Using the 1983 and 1989 Surveys of Consumer Finances, I find evidence of sharply increasing house‐hold wealth inequality over this period. Whereas mean wealth increased by 23 percent in real terms, median wealth grew by only 8 percent. The share of the top one‐half percentile rose by five percentage points, while the wealth of the bottom two quintiles showed an absolute decline. The Gini coefficient increased from 0.80 to 0.84. Almost all the growth in real wealth accrued to the top 20 percent of wealthholders. In contrast, the degree of wealth inequality was almost identical in 1983 as in 1962, and real wealth growth was more evenly distributed across the wealth distribution. There is also evidence that the sharp increase in wealth inequality from 1983 to 1989 was due to a correspondingly sharp rise in income inequality, the increase of stock prices relative to housing prices, and relatively slow inflation.
RELATIVE EARNINGS REDUX: YOUTH MOBILITY IN THE 1980s
Authors: Schiller Bradley R.
Published: March 2005

A complete view of inequality should encompass not only measures of distance between hierarchical ranks, but also measures of the extent of individual movement across ranks (mobility). Evidence from the NLSY indicates that relative earnings mobility was pervasive among young workers in the 1980s; possibly even higher than in the 1960s. Gender and race differences are apparent, however.
ELDERLY ASSETS, MEDICAID POLICY, AND SPEND‐DOWN IN NURSING HOMES
Authors: Norton Edward C.
Published: March 2005

Recent economic research has suggested that Medicaid long‐term insurance may reduce the personal savings levels of elderly citizens. This analysis shows that the opposite behavior, due to welfare aversion, actually happens. Barring any behavioral effects, personal wealth and income alone should determine the length of time an individual must stay in a nursing home until spend‐down occurs. Wealth and income data from two different samples of the elderly are used to predict the distribution of time until spend‐down, which is then compared with the actual distribution of the time until spend‐down among residents of nursing homes. Contrary to expectations, it appears that the elderly receive transfers to avoid Medicaid eligibility. This result cannot be explained away by sample selection, demographics, or uncertainty about prices. One implication of this result is that Medicaid could expand eligibility by raising the asset limit without dramatically increasing expenditures or the number of residents who spend‐down.
ALTERNATIVE MEASURES OF THE AVERAGE DURATION OF UNEMPLOYMENT
Authors: Corak Miles , Heisz Andrew
Published: March 2005

Four alternative measures of the average duration of unemployment are examined with the intention of illustrating: (1) the biases inherent in the average incomplete duration of unemployment, a statistic that is often the only one reported by many statistical agencies; and (2) the robustness of the average complete duration of unemployment to a host of assumptions underlying its derivation by non‐parametric methods. Canadian data are employed, but the results offer a guide to the construction of the average complete duration of unemployment that may have broader applications.
ARE SERVICES INCOME‐ELASTIC? SOME NEW EVIDENCE
Authors: Falvey Rodney E. , Gemmell Norman
Published: March 2005

The hypothesis that the demand for services is income‐elastic tended to find support in early empirical work. Recent studies however, adopting improved methodologies and better international data (based on PPP exchange rates), have challenged this conventional wisdom. Using an updated, disaggregated dataset covering 60 countries in 1980 this paper re‐estimates income and price elasticities of demand for services. It rejects the income‐elastic argument overall but confirms a wide range of income elasticity estimates (above and below unity) across different types of services. Estimates are also shown to be sensitive to thea priorimodel of service demand.
INCOME AND WEALTH OVER THE LIFE CYCLE EVIDENCE FROM PANEL DATA
Authors: Alessie Rob , Lusardi Annamaria , Aldershof Trea
Published: March 2005

In this paper we examine household wealth and income in the Netherlands using data from the Socio Economic Panel (SEP) in the period 1987–89. We provide an evaluation of the quality of the data and some simple statistics which describe the behavior of wealth, saving, and income over the life cycle. We find there is substantial heterogeneity in the behavior of households, and wealth holdings vary substantially even among the same age group. By exploiting the panel feature of the SEP, we derive saving from first differencing wealth. We find that a sizeable fraction of households do not dissave when old and we find some evidence in favor of the bequest motive.
THE SENSITIVITY OF INTERNATIONAL POVERTY COMPARISONS
Authors: Blackburn McKinley L.
Published: March 2005

Using data from the Luxembourg Income Study, I study the sensitivity of cross‐national income poverty comparisons to the method in which poverty is measured. Absolute poverty comparisons that keep the purchasing power at the poverty line constant across countries lead to conclusions that differ from relative poverty comparisons in which the real value of the poverty line varies with average income. The absolute poverty ranking of countries also varies as the real value of the poverty line is lowered. Cross‐national differences in household characteristics are largely irrelevant in explaining poverty differences.
THE SENSITIVITY OF INCOME INEQUALITY TO CHOICE OF EQUIVALENCE SCALES
Authors: Aaberge Rolf , Melby Ingrid
Published: March 2005

To account for the fact that a household's needs depend on its size and composition most studies on income inequality adjust the observed household incomes by equivalence scales. However, since the rationale for choosing a specific scale is rather vague the importance of testing the sensitivity of income inequality estimates to choice of equivalence scales has long been acknowledged. The sensitivity studies in the literature are restricted to equivalence scales that do not depend on the income level of the reference household which means that the effect of a rise in the household size on the scale rate does not depend on whether the household is poor or rich. By using Norwegian micro‐data it is shown that the introduction of an income‐dependent scale produces results that are in conflict with the widespread view of robustness of results to choice of equivalence scales.
YOUNG BABY BOOMERS' WEALTH
Authors: Zagorsky Jay L.
Published: March 2005

Researchers know relatively little about the beginnings of wealth accumulation. This paper analyzes the wealth of young baby boomers, individuals born from 1957 to 1964, using a previously ignored wealth data set, the National Longitudinal Survey of Youth 1979 (NLSY79). First, a detailed data quality evaluation is performed. Findings suggest that not cleaning NLSY79 wealth data causes nonsensical results, but there are no other serious problems. Analyzing the cleaned wealth data quantifies many stylized facts. For example, the typical baby boomer's wealth holdings increase by more than $2,000 a year. Married females hold more wealth than either married or unmarried males. Finally, while young boomers start with a majority of their wealth in illiquid holdings such as automobiles and possessions, they rapidly shift their wealth holdings into homes as they grow older.
INCOME MOBILITY IN SPAIN: HOW MUCH IS THERE?
Authors: Cant⊙ Olga
Published: March 2005

Traditional cross‐sectional research is unable to measure the degree of income mobility in an income distribution. Using longitudinal data and various income stability indices, this paper measures the level of permanent inequality (immobility) in Spain for the period 1985–92. Results indicate that the transitory component of inequality is large and the level of income mobility increases over time while income inequality decreases slightly. More stability is found at the top than at the bottom of the income distribution and the range of the registered movements is rather short.
Effects of Labial Margin Design on Stress Distribution of a Porcelain‐Fused‐to‐Metal Crown
Authors: Chai John Y. , Steege John W.
Published: March 2005

Purpose This study compared the stress distribution of three porcelain‐fused‐to‐metal labial margins on a central incisor under simulated occlusal force.

Materials and Methods The margin designs were rounded‐shoulder, rounded‐shoulder with a bevel, and a chamfer.

Results Evaluation of mean equivalent Mises tensile stress did not show any difference at the cement‐dentin and metal‐cement interfaces of the three margins. The mean equivalent Mises tensile stress at the porcelain‐metal interface was found to be significantly higher for rounded‐shoulder when compared with the chamfer. There was no significant difference in the axial stresses along the three interfaces among the three margin designs. Statistically significant differences in radial stresses at some interfaces of the three margin designs were found.

Conclusions The change of cement thickness of the chamfer margin is significantly greater than that of either the rounded‐shoulder or the bevelled‐shoulder margin.
In Vitro Consistency of the Periotest Instrument
Authors: Chai John Y. , Yamada Jason , Pang Iok‐Chao
Published: March 2005

Purpose The consistency of measuring the damping characteristics using the Periotest (Siemens AG, Bensheim, Germany) was studied.

Materials and Methods Periotest values (PTV) of three rods embedded in various depths of impression material were recorded by seven dentists.

Results There is no statistically significant difference among the subjects in measuring PTV of any of the three rods. However, the variation in the occlusal‐gingival position of impact resulted in statistically significant different PTV measurements of each of the three rods. Assessment of mobility of the same objects using a clinical criterion was found to be less consistent as the mobility of the object increased.

Conclusion In vitro PTV measurements are consistent provided that the position of impact is controlled.
Mechanical Properties of Metal Connectors Soldered by Gas Torch Versus an Infrared Technique
Authors: Cheng Ansgar C. , Chai John Y. , Gilbert Jeremy , Jameson Lee M.
Published: March 2005

Purpose The ultimate tensile strength and percentage elongation of solder joints of three alloy systems were tested.

Materials and Methods Solder joints were formed using either an infrared soldering machine or gas‐oxygen torch. Intact solder materials were used as controls.

Results There were no significant differences in percentage elongation among different treatment methods of the solders or among various solder materials. All intact solder materials possessed significantly higher ultimate tensile strength than the joints made with either method. For high‐noble and noble alloy solders, there were no significant differences in ultimate tensile strength of joints made with either method. For base metal alloy solder, the ultimate tensile strength of joints made with the infrared technique was significantly higher than that made with the gas‐oxygen torch technique.

Conclusions The infrared technique can be used as an alternative to the gas‐torch technique for soldering high‐noble and noble alloys. It is superior to the gas‐torch technique for soldering a cobalt‐chromium alloy.
Clasp Retention: The Effects of Five Variables
Authors: LaVere Arthur M.
Published: March 2005

An attempt was made to determine the relative retention of each of the four most commonly used clasp assemblies. They are the rest, proximal plate, 1 bar (RPI); rest, proximal plate, facial circumferential arm (RPA); modified T; and Akers (facial and lingual circumferential arms). A mandibular bilateral distal extension base removable partial denture design was selected because it is most commonly used. A test model was made by removing all mandibular molars from a Columbia Dentoform and replacing the ivorine second bicuspids with natural teeth. These, in turn, were later replaced with gold crowns that were identical in contour to the natural teeth. Eight removable partial dentures were constructed using preformed plastic lingual bars, minor connectors, denture base retention loops, and clasps. Artificial teeth and the denture bases were processed to each framework as for a clinical patient. Each removable partial denture was placed in the Instron testing machine and pulled from the test model. The investigation examined the effectiveness of each of four types of clasps in resisting displacing forces, in both vertical (occlusal) and mesio‐occlusal directions. Each clasp was tested using natural teeth and gold crowns, in dry and wet environments, both with and without indirect retainers. Results indicate that, (1) The RPA clasp was the most retentive of all on natural abutments, against both directions of pull, but only slightly so over the RPI clasp with a vertical pull. (2) The Akers clasp was most retentive against a mesio‐occlusal pull on the gold abutments. (3) Natural tooth structure gives slightly more frictional resistance than a gold surface. (4) The presence of artificial saliva caused little change in forces required for dislodgment. (5) The absence of indirect retainers greatly reduced the retentive properties of the RPD frameworks.
A Three‐Dimensional Finite Element Stress Analysis of Angled Abutments for an Implant Placed in the Anterior Maxilla
Authors: Clelland Nancy L. , Lee June K. , Bimbenet Olivier C. , Brantley William A.
Published: March 2005

Purpose A three‐dimensional mathematical model of the maxilla was developed that was used to analyze the stresses and strains produced by an abutment system capable of three abutment angulations.

Materials and Methods Computed tomography was used to derive the geometry and density values used for the maxillary model. A 3.8 × 10–mm cylindrical implant was embedded in the right central incisor position at a 35° angle to the horizontal plane and parallel to the angulation of the bone site. All geometric and elastic properties for the fixture and the surrounding bone were included in the model. A simulated occlusal load of 178 N was applied along the long axis of 0°, 15°, and 20° abutments. The mathematical models were solved by the Cray Y/MP Ohio Supercomputer (Cray, Eagan, MN) using the ABAQUS software program (Hibbitt, Karlsson, and Sorenson, Providence, RI).

Results Numerical and graphic results were generated for the maximum (tensile) and minimum (compressive) stresses and strains. Principal stresses occurred predominantly in the cortical bone layers, whereas strains occurred mostly in the cancellous bone.

Conclusions In general, there was an increase in the magnitude of stress and strain as the abutment angulation increased. Reported stresses and strains for all three angles were within or slightly above the physiological zone derived from animal studies. A need to investigate the response of human bone to stress and strain was indicated.
The Prosthodontic Management of Endodontically Treated Teeth: A Literature Review. Part III. Tooth Preparation Considerations
Authors: Goodacre Charles J. , Spolnik Kenneth J.
Published: March 2005

The final part of this literature review series presents guidelines for the optimal preparation of teeth to receive posts and cores.
Custom Tinting Denture Bases by Visible Light Cure Lamination
Authors: Berté Joseph J. , Hansen Carl A.
Published: March 2005

A urethane dimethacrylate and tinting powder lamination, chemically bonded to a methyl methacrylate denture base, produces a natural‐appearing distribution of the tints. The characterization is protected by a hard, clear layer of urethane. Procedures are described that achieve this lamination either in the laboratory, before processing the dentures, or after the dentures have been fabricated.
Fabrication of a New Crown and Provisional to an Existing Removable Partial Denture
Authors: Jackson Andrea D. , Butler Craig J.
Published: March 2005

A method of fabricating a new crown to an existing removable partial denture is described. A press‐form plastic shell made from the diagnostic cast provides the outer contours for the abutment tooth, while an acrylic resin coping is fabricated on a die to provide accurate internal adaptation. The acrylic resin coping is seated on the prepared abutment. Autopolymerizing acrylic resin is mixed and placed in the plastic shell that is then placed in the mouth over the coping, forming the acrylic resin crown pattern. The removable partial prosthesis is fitted over the crown pattern intraorally. The pattern is transferred back to the die, the margins are refined, and the casting is completed and finished, avoiding reduction of the established contours. The same plastic shell is used with tooth‐shaded acrylic resin to construct a provisional crown directly in the mouth. This technique allows the patient to wear the removable partial denture while the laboratory procedures are completed.
Color Stability of Heat‐Activated and Chemically Activated Fluid Resin Acrylics
Authors: Wang Xinzhi , Powers John M. , Connelly Mark E.
Published: March 2005

Purpose Heat‐ and chemically activated acrylics processed by compression molding or fluid resin matrix techniques for fabrication of partial dentures were evaluated for color stability by reflection spectrophotometry after accelerated aging.

Materials and Methods Samples of heat‐activated (L 199, PDON, SB) and chemically activated (PR, PVAR, SC) denture base acrylics were polymerized according to manufacturers' instructions. Samples were aged in an artificial aging chamber, and color was measured by CIE L*a*b* on a reflection spectrophotometer at baseline and after each of three aging cycles.

Results At 450 kJ/m2, color changes of two chemically activated acrylics (PR and SC) were perceptible. PR became less red, whereas SC became darker and more yellow. The most color‐stable acrylics were a heat‐activated resin (SB) and one chemically activated acrylic (PVAR).

Conclusions The three heat‐activated acrylics tested were more color‐stable than two of the chemically activated acrylics, but one chemically activated acrylic (PVAR) recommended for a fluid resin matrix technique was color‐stable.
Accelerated Aging Affects Color Stability of Provisional Restorative Materials
Authors: Doray Pamela G. , Wang Xinzhi , Powers John M. , Burgess John O.
Published: March 2005

Purpose The color stability of two shades each of five acrylic resin and seven resin composite provisional restorative materials was evaluated by reflection spectrophotometry following in vitro accelerated aging.

Materials and Methods Specimens of provisional restorative materials were polymerized according to manufacturers' instructions and aged in an artificial aging chamber with exposure to a total ultraviolet irradiation of 60 kj/m2. Color was measured by CIE L*a*b* on a reflection spectrophotometer before and after aging. Color change (ΔE*) was calculated and analyzed statistically.

Results Statistically significant changes in color were observed after accelerated aging. Nine of the 12 provisional materials tested showed perceptible color change of at least one of the shades tested. The most color‐stable materials were the acrylic, Alike, and the resin composites, Luxatemp and Protemp Garant, which had no perceptible color changes under these conditions.

Conclusions Some acrylic resin and composite provisional materials change color significantly and perceptibly when exposed to in vitro accelerated aging conditions.
Physical‐Property Comparison of a Chairside‐ or Laboratory‐Polymerized Permanent Soft‐Liner During 1 Year
Authors: Parr Gregory R. , Rueggeberg Frederick A.
Published: March 2005

Purpose

This investigation examined the influence of polymerization mode and water storage duration on the Shore A hardness, water sorption, resin solubility, and glass transition temperature of Permasoft, a commercial soft denture liner that is polymerized either chairside or in the laboratory.

Materials and Methods

Specimen disks (31‐mm diameter × 10 mm thick) and bars (44 × 8.5 × 1.2 mm) were polymerized following manufacturer's recommendations. The chairside polymerization process was simulated by pouring the mixed components into a mold and processing at 70°C for 15 minutes under 2‐psi pressure. Laboratory‐polymerized specimens of the same dimensions were fabricated by processing under 500‐psi pressure at 100°C for 45 minutes. Specimens were stored in distilled water at 37°C for 1, 7, and 30 days, and 6 and 12 months. Specimens were tested for Shore A hardness, water sorption, resin solubility, and glass transition temperature after the prescribed interval. To determine the effects of polymerization mode and storage time on material properties, a repeated‐measures ANOVA (hardness data) and a two‐way ANOVA (sorption and solubility data) with appropriate post‐hoc tests were used.

Results

Shore A hardness values increased from a low of 9.4 (±0.5) units immediately after fabrication to a maximum of 15.9 (±1.1) units after 1 year. Mode of polymerization did not influence hardness (p= .9851). Water‐sorption values ranged from 4.2 (±0.2%) of dry weight to 14.7 (±2.5%) after 1 year. Resin solubility varied from 10.3 (±0.6%) of preimmersion weight to 15.4 (±1.1%), and immersion duration had no effect on solubility. In addition, after 1 year of storage, no difference in resin solubility or water sorption was found with respect to cure mode. The glass transition temperature for chairside‐polymerized samples approximated −10°C, while that for labpolymerized samples approximated −15°C.

Conclusions

With regard to the material properties evaluated in this study, clinically processed Permasoft liner was equivalent to the laboratory‐processed material.
Flexural Properties and Surface Finishing of Acetal Resin Denture Clasps
Authors: Turner Jonathan W. , Radford David R. , Sherriff Martyn
Published: March 2005

Purpose

This study examined flexural properties of acetal resin to determine the appropriate design for an acetal resin removable partial denture clasp. The effectiveness of various acetal resin polishing procedures was also evaluated using scanning electron microscopy.

Materials and Methods

Loads of up to 1,500 g were applied to cylindrical acetal resin specimen lengths of 5, 10, and 15 mm, and the degree of deflection of the specimen tip was measured. Specimens were 2 mm and 1.5 mm in diameter with a round cross‐section (R2 and R1.5, respectively), as well as 2 mm in diameter and half‐round in cross‐section. Half‐round specimens were loaded with their flat surface vertical and then horizontal (HRV and HRH, respectively). Contour plots showing load and deflection for varying lengths of resin were developed for each cross‐sectional type based on specimen length, and the stiffness was calculated. Additional acetal resin specimens underwent polishing techniques including tungsten carbide burs, aluminium oxide stones, abrasive impregnated rubber points, and “Polish‐D.” Polished specimens were examined with scanning electron microscopy to compare surface roughness.

Results

For the 5‐mm‐length specimens, the median stiffness values decreased in the following order: R2 > HRV > HRH > R1.5. The median stiffness values for the 10‐mm and 15‐mm lengths followed a similar trend. At each length, the R2 specimen was generally at least twice as stiff as other designs. Regarding polishing, the smoothest surface was seen on the specimen that was polished with the rubber point followed by “Polish‐D.”

Conclusions

To have stiffness similar to a cast cobalt‐chromium clasp 15 mm long and 1 mm in diameter, a suitable acetal resin clasp must be shorter (approximately 5 mm) with greater cross‐sectional diameter (approximately 1.4 mm). To obtain a smooth surface, the acetal resin clasp should be polished with a rubber point followed by a material such as “Polish‐D.”
Xenobiotics and the Glucocorticoid Receptor: Additive Antagonistic Effects on Tyrosine Aminotransferase Activity in Rat Hepatoma Cells
Authors: Johansson Maria , Johansson Niklas , Lund Bert‐Ove
Published: March 2005

Abstract: Methylsulfonyl‐PCBs (MeSO2‐PCBs) and some fungicides were studied for their functional effects on the glucocorticoid signal transduction in the Reuber rat hepatoma H‐II‐E‐C3 cell line. 4‐Substituted MeSO2‐PCBs, tolylfluanid and ketoconazole displayed antagonistic effects on dexamethasone‐induced tyrosine aminotransferase specific activity (IC50 ranging from 0.7–5.1 μM), but no agonist activity. These substances also had affinity to the mouse glucocorticoid receptor in competition binding studies, indicating that the inhibition of the middle cerebral artery occlusion‐activity is indeed mediated by receptor binding. Thus, substances with a structural resemblance with a methyl sulfonyl group, such as the fungicide tolylfluanid, may inhibit glucocorticoid receptor‐regulated gene transcription. In co‐exposure experiments with three substances, multivariate modelling showed that the inhibitory effect of 4‐MeSO2‐2,5,6,2′,4′‐pentachlorobiphenyl (4‐MeSO2‐CB91), 4‐MeSO2‐2,3,6,2′,4′,5′‐hexachlorobiphenyl (4‐MeSO2‐CB149) and tolylfluanid on tyrosine aminotransferase activity was close to additive. Thus, co‐exposure to such different chemicals as persistent organic pollutants and pesticides may affect cells additively. Chemical interference with the glucocorticoid hormone system therefore deserves further attention in vivo.
TRAINING EFFECTS ON PERFORMANCE OF DESCRIPTIVE PANELISTS
Authors: CHAMBERS DELORES H. , ALLISON ANN‐MARIE A. , CHAMBERS EDGAR
Published: March 2005

The amount of training necessary to adequately “train” a descriptive panel is a matter of contention. The objectives of this research were to compare the performance of descriptive panelists after short‐term (4 h), moderate (60 h) and extensive training (120 h). Seven screened panelists were chosen to evaluate three commercial tomato pasta sauces after each training period. Panelist performance improved with increased training. Sample differences were observed in all texture attributes and some flavor attributes, even after the shortest training time (4 h). However, more differences were found with at least 60 h of product training. After 120 h of training, product differences for all texture attributes and most of the flavor attributes studied could be ascertained by the trained panelists. These results suggested that only limited training may be necessary to find differences among products for many texture attributes and some flavor attributes. However, extensive training may be required to reduce variation among panelists and increase the discriminant abilities of panelists.
Fracture Mechanics of Thin Plates and Shells Under Combined Membrane, Bending, and Twisting Loads
Authors: Zehnder Alan T. , Viz Mark J.
Published: March 2005

The fracture mechanics of plates and shells under membrane, bending, twisting, and shearing loads are reviewed, starting with the crack tip fields for plane stress, Kirchhoff, and Reissner theories. The energy release rate for each of these theories is calculated and is used to determine the relation between the Kirchhoff and Reissner theories for thin plates. For thicker plates, this relationship is explored using three-dimensional finite element analysis. The validity of the application of two-dimensional (plate theory) solutions to actual three-dimensional objects is analyzed and discussed. Crack tip fields in plates undergoing large deflection are analyzed using von Ka´rma´n theory. Solutions for cracked shells are discussed as well. A number of computational methods for determining stress intensity factors in plates and shells are discussed. Applications of these computational approaches to aircraft structures are examined. The relatively few experimental studies of fracture in plates under bending and twisting loads are also reviewed. There are 101 references cited in this article.
Effect of Microcomputed Tomography Voxel Size on the Finite Element Model Accuracy for Human Cancellous Bone
Authors: Yeni Yener N. , Christopherson Gregory T. , Neil Dong X. , Kim Do-Gyoon , Fyhrie David P.
Published: March 2005

The level of structural detail that can be acquired and incorporated in a finite element (FE) analysis might greatly influence the results of microcomputed tomography (μCT)-based FE simulations, especially when relatively large bones, such as whole vertebrae, are of concern. We evaluated the effect of scanning and reconstruction voxel size on the μCT-based FE analyses of human cancellous tissue samples for fixed- and free-end boundary conditions using different combinations of scan/reconstruction voxel size. We found that the bone volume fraction (BV/TV) did not differ considerably between images scanned at 21 and 50 μm and reconstructed at 21, 50, or 110 μm (−0.5% to 7.8% change from the 21/21 μm case). For the images scanned and reconstructed at 110 μm, however, there was a large increase in BV/TV compared to the 21/21 μm case (58.7%). Fixed-end boundary conditions resulted in 1.8% [coefficient of variation (COV)] to 14.6% (E) difference from the free-end case. Dependence of model output parameters on scanning and reconstruction voxel size was similar between free- and fixed-end simulations. Up to 26%, 30%, 17.8%, and 32.3% difference in modulus (E), and average (VMExp), standard deviation (VMSD) and coefficient of variation (COV) of von Mises stresses, respectively, was observed between the 21/21 μm case and other scan/reconstruction combinations within the same (free or fixed) simulation group. Observed differences were largely attributable to scanning resolution, although reconstruction resolution also contributed significantly at the largest voxel sizes. All 21/21 μm results (taken as the gold standard) could be predicted from the 21/50 radj2=0.91-0.99;p<0.001, 21/110 radj2=0.58-0.99;p<0.02 and 50/50 results radj2=0.61-0.97;p<0.02. While BV/TV, VMSD, and VMExp/σz from the 21/21 could be predicted by those from the 50/110 radj2=0.63-0.93;p<0.02 and 110/110 radj2=0.41-0.77;p<0.05 simulations as well, prediction of E, VMExp, and COV became marginally significant 0.04<p<0.13 at 50/110 and nonsignificant at 110/110 0.21<p<0.70. In conclusion, calculation of cancellous bone modulus, mean trabecular stress, and other parameters are subject to large errors at 110/110 μm voxel size. However, enough microstructural details for studying bone volume fraction, trabecular shear stress scatter, and trabecular shear stress amplification VMExp/σz can be resolved using a 21/110 μm, 50/110 μm, and 110/110 μm voxels for both free- and fixed-end constraints.
Mechanical Properties of Laser Cut Poly(L-Lactide) Micro-Specimens: Implications for Stent Design, Manufacture, and Sterilization
Authors: Grabow Niels , Schlun Martin , Sternberg Katrin , Hakansson Nico , Kramer Sven , Schmitz Klaus-Peter
Published: March 2005

Background: The development of endoluminal stents from polymeric materials requires an understanding of the basic mechanical properties of the polymer and the effects of manufacturing and sterilization on those properties. Methods: Pure poly(L-lactide) (PLLA) and PLLA containing varying amounts of triethylcitrate (TEC) as a plasticizer (5-10-15%) were studied. The specimens were solution-cast and CO2 laser-cut. Specimen dimensions were adapted to the strut size of polymeric vascular stents. The properties of the PLLA micro-specimens were assessed before and after sterilization (EtO cold gas, H2O2-plasma, beta- and gamma-irradiation). Tensile tests, and creep and recovery tests were carried out at 37°C. Additionally the thermal and thermo-mechanical characteristics were investigated using dynamic-mechanical analysis (DMA) and differential scanning calorimetry (DSC). Results: The results showed the dramatic influence of the plasticizer content and sterilization procedure on the mechanical properties of the material. Laser cutting had a lesser effect. Hence the effects of processing and sterilization must not be overlooked in the material selection and design phases of the development process leading to clinical use. Altogether, the results of these studies provide a clearer understanding of the complex interaction between the laser machining process and terminal sterilization on the primary mechanical properties of PLLA and PLLA plasticized with TEC.
Understanding some simple phenomena in thermoacoustics with applications to acoustical heat engines
Authors: Wheatley John , Hofler T. , Swift G. W. , Migliori A.
Published: March 2005

Thermoacoustical phenomena have a long history and are frequently characterized by great complexity. In the present paper, we describe how, by the use of suitable acoustical structures, the phenomena can both be simplified and readily demonstrated. A heuristic discussion is emphasized, which we hope will be useful in teaching the principles. The qualities of certain model apparatus that demonstrate acoustically stimulated entropy flow, a thermally driven acoustic oscillator, and an acoustically driven refrigerator are also presented in semiquantitative detail.
Remarks on brachistochrone–tautochrone problems
Authors: Denman Harry H.
Published: March 2005

A number of recent papers have discussed brachistochrone (minimum-time) and tautochrone (equal-time) curves for a number of gravitational and rotating systems. The symmetry of the physical system is useful in solving brachistochrone problems expressed in variational form. We point out that such symmetries are equally useful in solving the associated Euler–Lagrange equations, or solving tautochrone differential equations. These brachistochrone problems share a common mathematical form, and therefore a common procedure for reducing the problem to quadrature. It is shown that the cusps characteristic of these curves have a simple physical origin. Finally, the question of the most general spherically symmetric gravitation potential for which the brachistochrone and tautochrone curves are identical is answered in implicit form.
Blackwood pendulum experiment and the conservation of linear momentum
Authors: Gupta P. D.
Published: March 2005

By a simple modification of the commercially available ballistic pendulums (e.g., Cenco as well as Beck), we demonstrate that these pendulums are not conceptually and pedagogically suitable for performing the experiment to verify the Law of Conservation of Linear Momentum. With modified equipment, the discrepancy between the true velocity of the projectile ball and the velocity as obtained by performing the collision experiment is shown to be as large as 17% if improper concepts are used for the analysis of the experimental data. The correct analysis, without any assumption about the conservation of linear momentum, is shown to yield experimentally acceptable results to within a few percent.
Compton effect as a double Doppler shift
Authors: Kidd Richard , Ardini James , Anton Anatol
Published: March 2005

The Compton equation is normally developed using the photon model, but it is also capable of derivation based on a classical wave model of light, and there is a considerable history of such derivations, including one by Compton himself. A simple derivation in the laboratory frame based on waves scattered by a statistical aggregate of recoil electrons is developed in this paper, providing a bridge between microscopic events and macroscopic observation, and implications of coexisting wave and particle model derivations of the Compton effect are discussed. The parallel derivations based on contrasting models can also furnish an instructive exercise for students.
Illustration of resonances and the law of exponential decay in a simple quantum-mechanical problem
Authors: Massmann Herbert
Published: March 2005

The exact quantum-mechanical solution of a particle moving in a one-dimensional well formed by a delta barrier in front of an impenetrable well is used to illustrate the relation between scattering resonances and exponential decay from the well.
Effect of wind and altitude on record performance in foot races, pole vault, and long jump
Authors: Frohlich Cliff
Published: March 2005

Using only elementary physics, one can estimate the effect of wind and altitude on performance in several track and field events. Experiments have shown that the power lost to aerodynamic drag forces is about a tenth of the total power expended in running at sprint speeds. From this observation one can calculate the effect of wind or of air density changes on sprinting speed. In pole vaulting, the sprinter converts his kinetic energy into potential energy to clear the bar. In long jumping, he is a projectile, but he is prevented from reaching his optimum distance expected for his initial velocity by the height which he can attain during his jump. For each of these events, performance in moderate winds of 2.0 m/s or at altitudes comparable to Mexico City differ by several percent from performances at sea level or in still air. In longer running races and in bicycle races, aerodynamic forces play an important role in racing strategy. However, since the athletes perform in groups it is difficult to calculate the effect on individual performances.
Coriolis lecture demonstration
Authors: Daw Harold A.
Published: March 2005

This article describes a mechanical system for viewing motion in a rotating reference frame and in particular under a pure Coriolis acceleration. It also discusses how this motion may be made visible to a large audience by using a TV camera in the rotating frame and projecting the motion in the rotating frame on a screen. In addition, the article discusses the theory involved in producing a pure Coriolis acceleration.
Promoting student crossover to the Newtonian world
Authors: Hake R. R.
Published: March 2005

A six-week noncalculus-based introductory course was designed and taught with the intention of promoting students’ conceptual understanding of Newtonian mechanics. Primary emphasis was placed on (1) laboratories structured to induce Socratic dialogue; (2) lectures stressing a qualitative approach to problem solving, and contrasting Newtonian and students’ non-Newtonian concepts of motion; (3) videotapes from The Mechanical Universe series. That the course was effective in promoting student crossover to the Newtonian world was suggested by student performance on pre- and post-course mechanics exams.
The early history of cosmic ray research
Authors: Xu Qiaozhen , Brown Laurie M.
Published: March 2005

We review the prehistory and early history of cosmic ray studies, concentrating on the period 1900–1927. Following the discoveries of the electron and radioactivity just before the turn of the century, the old problem of leakage of charge from a conductor in air was investigated in terms of the new concept of ionization and ionizing radiation, part of which was found to be highly penetrating and to be of extraterrestrial origin. At first supposed to consist only of ultrahigh energy gamma rays, the cosmic ray primaries are now known to be mainly charged particles. The modern period of cosmic ray research began in 1927, when individual particles were studied by cloud-chamber and coincidence counting techniques.
Resource letter IQM-2: Foundations of quantum mechanics since the Bell inequalities
Authors: Ballentine L. E.
Published: March 2005

This Resource Letter provides a guide to the literature on the foundations of quantum mechanics over approximately the past 20 years. Topics covered include Bell’s theorem, interpretation of the quantum state concept, the theory of measurement, and experimental tests of fundamental aspects of the quantum theory of matter and the electromagnetic field. The letter E after an item indicates elementary level of material of general interest to persons becoming informed in the field. The letter I, for intermediate level, indicates material of somewhat more specialized nature; and the letter A indicates rather specialized or advanced material. An asterisk (*) indicates those articles to be included in an accompanying Reprint Book.
Bell’s theorem: Does quantum mechanics contradict relativity?
Authors: Ballentine L. E. , Jarrett Jon P.
Published: March 2005

Special relativity demands a locality principle (no instantaneous action at a distance); locality implies Bell’s theorem; quantum mechanics violates Bell’s inequality, therefore, quantum mechanics contradicts relativity! Or so it would seem. It is shown, however, that the locality principle needed for Bell’s theorem is stronger than the simple locality that is needed to satisfy the demands of relativity and that quantum mechanics satisfies the latter. The stronger locality principle is equivalent to the conjunction of simple locality and predictive completeness, and it is the latter principle that fails. The notion of predictive completeness is weaker than, and is implied by, the completeness criterion of Einstein, Podolsky, and Rosen. But the quantum mechanical state description is not only incomplete but incompletable, for any local complete state description would satisfy Bell’s inequality and disagree with experiment.
Isynchronous motion in classical mechanics
Authors: Osypowski E.T. , Olsson M. G.
Published: March 2005

Those oscillatory motions for which the period is independent of the total energy are investigated. There is only one corresponding symmetric potential, the quadratic potential of the simple harmonic motion but infinite classes of asymmetric potentials must be considered. Geometric and analytic requirements of isochronism are discussed and several specific examples are given.
Time-of-flight measurement of the speed of light using a laser and a low-voltage Pöckels-cell modulator
Authors: Becchetti F. D. , Harvey K. C. , Schwartz B. J. , Shapiro M. L.
Published: March 2005

An advanced undergraduate laboratory experiment is described which uses a laser, low-voltage pulser, and a Pöckels-cell electro-optical modulator to determine the speed of light using time of flight. Accuracy of about 1/2 % is obtained using a calibrated oscilloscope while an uncertainty of less than 0.2% can be obtained using a time-to-analog converter (TAC) and multichannel analyzer (MCA). The experiment is used to illustrate electro-optical modulators and time-of-flight instrumentation.
Light scattering from fibers: An extension of a single-slit diffraction experiment
Authors: Gilliar Wolfgang , Bickel William S. , Videen Gordon , Hoar David
Published: March 2005

The similarities and differences between diffraction from single slits and scattering from single fibers can be dramatically demonstrated by some simple experiments. Geometrical properties such as fiber size, cross section, tilt, and nonuniformity all contribute to the intricate detail of the diffraction pattern. An examination of the role of the complex refractive index, polarized light, and geometrical effects in scattering phenomena will contribute to a deeper understanding of the interaction of light with small apertures and particles.
Rigid-body dynamics of a football
Authors: Brancazio Peter J.
Published: March 2005

The motion of a spinning football provides interesting illustrations of some of the principles of rigid-body motion. The familiar ‘‘wobbly spiral’’ is an example of torque-free precession; it is shown that the ‘‘wobble-to-spin’’ ratio depends only on the principal moments of inertia of the football. The angular momentum of a spinning football is not always conserved in flight. The response of a football to aerodynamic forces can best be understood by comparing its motion to that of a spinning top or gyroscope.
The hydrogen atom in one dimension
Authors: Moss R. E.
Published: March 2005

The Schrödinger, Klein–Gordon, and Dirac equations for the hydrogen atom are solved in D dimensions, where D may be noninteger. For D=1 the nondegenerate ground state with infinite binding energy is obtained as a limit as D tends to 1 for the Schrödinger equation. The corresponding solution of the Klein–Gordon equation is shown to be unacceptable, contradicting previous work. Unexpectedly, no bound state solutions of the Dirac equation with D=1 are found at all. A few comments are made on the D=3 and 2 cases.
Fresnel diffraction effects in misfocused vision
Authors: Lock James A.
Published: March 2005

If a narrow line stimulus on an opposite contrast background is observed with appropriately misfocused vision, the stimulus appears as a number of alternating bright and dark fringes. A numerical calculation of this effect was performed. As a result it was found that the banding phenomenon is a Fresnel diffraction effect depending on the details of both the narrow line stimulus and the eye pupil.
Coherent states of a harmonic oscillator
Authors: Howard Stephen , Roy Sanat K.
Published: March 2005

The coherent states of a harmonic oscillator are introduced following Schrödinger’s definition and the equivalence with other definitions is established. The basic properties of these states are discussed in some detail.
Stellar sky as seen from the vicinity of a black hole
Authors: Schastok Joachim , Soffel Michael , Ruder Hanns , Schneider Manfred
Published: March 2005

The stellar sky—as seen from the vicinity of a black hole—is discussed as a method to visualize the effects of light deflection. For rotating black holes, spatial axes defining the spherical angles of arriving light rays were defined via the direction of the plumb lines. Some light rays circling a strongly rotating black hole (extreme Kerr black hole) are also shown.
Intracellular Glycosylphosphatidylinositols Accumulate on Endosomes: Toxicity of Alpha-Toxin toLeishmania major
Authors: Zheng Zhifeng , Tweten Rodney K. , Mensa-Wilmot Kojo
Published: March 2005

Glycosylphosphatidylinositols (GPIs) are ubiquitous glycolipids in eukaryotes. In the protozoanLeishmania major, GPIs occur “free” or covalently linked to proteins (e.g., gp63) and polysaccharides. While some free GPIs are detected on the plasma membrane, specific sites where GPIs accumulate intracellularly are unknown in most cells, although the glycolipids are synthesized within the secretory system. Herein, we describe a protocol for identifying intracellular sites of GPI accumulation by using alpha-toxin (fromClostridium septicum). Alpha-toxin bound to gp63 and GPIs fromL. major. Intracellular binding sites for alpha-toxin were determined in immunofluorescence assays after removal of GPI-anchored macromolecules (e.g., gp63) from the plasma membrane of fixed cells by using detergent. Endosomes were a major site for GPI accretion inL. major. GPI-less gp63 was detected at the endoplasmic reticulum. In studies with live parasites, alpha-toxin killedL. majorwith a 50% lethal concentration of 0.77 nM.