bluuebunny/crossref_metadata_2025 huggingface dataset:
Exogenous hormones
Authors: WINTHER J. F. , DREYER L. , TRYGGVADOTTIR L.
Published: October 2011

The well‐described influence of several aspects of reproductive life on the risk for cancer in the reproductive organs has raised concern regarding the safety of exogenous hormones, particularly since sex hormones have become one of the most widely used drugs among women in the western world. The major areas of application include oral contraception and hormone replacement therapy in women with menopausal symptoms. Since the introduction of oral contraceptives onto the Nordic market in the late 1960s, the number of users has grown steadily, to reach proportions of long‐term users among women aged 15–45 years in 1985 ranging between 6% (Norway) and 19% (Sweden) and proportions of current users in 1994 ranging between 20% (Norway) and 28% (Sweden). Such data on the current and long‐term use of oral contraceptives by the female populations, linked with relative estimates of adverse (cancers of the breast and uterine cervix) and beneficial effects (protection against cancers of the ovary and endometrium), indicate that 95 cases of breast cancer and 40 of cervical cancer will be caused by oral contraceptives annually around 2000 in the Nordic countries, which corresponds to 0.6% of all breast cancers and approximately 3% of all cervical cancers. The beneficial effects include an annual prevention around the year 2000 of approximately 350 cases of ovarian cancer and a similar number of endometrial cancer, for a total about 700 cancer cases annually. The prevalence of long‐term users (≥5 years) of hormone replacement therapy among Nordic women aged 40–69 in 1995 was estimated to be 10–11%, which on the basis of an associated relative risk for breast cancer ranging from 1.2–1.5 suggests than an annual total of 260 cases of breast cancer could be avoided in the Nordic countries around the year 2000 if hormone replacement therapy were eliminated. This corresponds to 1.8% of all notified cases of breast cancer among women in these countries.
CRABP‐II‐ and FABP5‐independent all‐trans retinoic acid resistance in COLO 16 human cutaneous squamous cancer cells
Authors: Chen Nan‐Nan , Li Yan , Wu Mo‐Li , Liu Zhi‐Li , Fu Yuan‐Shan , Kong Qing‐You , Chen Xiao‐Yan , Li Hong , Liu Jia
Published: October 2011

Abstract:  The effect of all‐trans retinoic acid (ATRA) on cutaneous squamous cell carcinomas (c‐SCC) has been poorly described. Because the imbalance of CRABP‐II‐mediated anticancer signalling and FABP5‐mediated growth‐promoting signalling was supposed to be related with ATRA sensitivities of cancer cells, COLO16 human c‐SCC cell line was selected to check underlying mechanism leading to ATRA resistance by multiple experimental approaches. The results revealed that COLO 16 cells were resistant to 15 μm ATRA treatment. FABP5 as well as the elements related with CRABP‐II signalling (CYP26A1, CYP26B1, CRABP‐I, RARα/β/γ and RXRα/β/γ) and with FABP5 signalling (PPARβ/δ) were expressed, but CRABP‐II was undetectable in COLO 16 cells. 5‐Aza treatment enhanced CRABP‐II expression but further bisulfite sequencing PCR‐DNA sequencing revealed no methylation in CRABP‐II promoter region. Transfection of CRABP‐II‐expressing plasmids or FABP5 siRNA or both successfully manipulated the level(s) of target gene expression but failed to overcome ATRA resistance in the transfectants. In conclusion, CRABP‐II and FABP5 expression were imbalanced in ATRA‐resistant COLO 16 cells. 5‐Aza‐enhanced CRABP‐II expression and unmethylation in CRABP‐II promoter region suggest the methylation of certain CRABP‐II regulatory gene(s) in COLO 16 cells. As neither restoration of CRABP‐II expression nor the increased CRABP‐II versus FABP5 ratio can overcome ATRA resistance of COLO 16 cells, additional ATRA‐resistant mechanism(s) may present in human c‐SCCs and COLO 16 cells would be of value in addressing this issue.
Interleukin‐6 in oral diseases: a review
Authors: Nibali L , Fedele S , D’Aiuto F , Donos N
Published: October 2011

Oral Diseases (2012) 18, 236–243

Interleukin‐6 (IL‐6) is a pleomorphic cytokine involved in a number of physiologic and pathologic processes including response to trauma and infection and development and progression of inflammation and malignancy. IL‐6 is emerging as an important mediator and novel therapeutic target for chronic inflammatory diseases and cancer. The present study reviews the available evidence regarding the association between IL‐6 and a range of oral diseases including infections (periodontal disease and endodontic infections), immunologically mediated disorders (oral lichen planus and Sjögren’s syndrome) and malignancy (oral cancer and precancer). The role of common genetic variants of IL‐6 in determining individual susceptibility to certain oral diseases, as well as novel therapeutic strategies based on IL‐6 inhibition are also discussed.
Nightguard Vital Bleaching: Side Effects and Patient Satisfaction 10 to 17 Years Post‐Treatment
Authors: BOUSHELL LEE W. , RITTER ANDRÉ V. , GARLAND GLENN E. , TIWANA KAREN K. , SMITH LYNN R. , BROOME ANGELA , LEONARD RALPH H.
Published: October 2011

Statement of the Problem:  The long‐term patient satisfaction and safety of nightguard vital bleaching (NGVB) requires further evaluation.

Purpose of the Study:  The purpose of this study was to evaluate patients' satisfaction and identify side effects of NGVB up to 17 years post‐treatment.

Materials and Methods:  Thirty‐one participants who had completed previous NGVB studies using 10% carbamide peroxide were contacted at least 10 years post‐treatment (range 10–17 years, average 12.3 years). Participants reported shade satisfaction (very satisfied [VS], partially satisfied [PS], or not satisfied [NS]) as well as potential complications. Participants had teeth # 6 to 11 examined for tooth vitality, gingival inflammation (Löe's Gingival Index [GI]), and radiographically for external cervical resorption (ECR).

Results:  All of the participants had successful lightening of their teeth. Sixty‐one percent (19) had not retreated their teeth. Of those who had not retreated their teeth and who responded to the question of whitening satisfaction, 31% (4/13) were VS, 54% (7/13) were PS, and 15% (2/13) were NS with their current shade. Of those who had retreated their teeth, all were VS or PS. Ninety‐one percent of the examined teeth had GI = 0 (normal), 7% had GI = 1 (mild inflammation), and 2% had GI = 2 (moderate inflammation). Sixty‐nine percent of teeth tested responded to a cold stimulus. Radiographs did not detect ECR or apical lesions. No participant reported having a gingival biopsy post‐treatment, and 87% would whiten again.

Conclusions:  Patient satisfaction with NGVB may last as long as 12.3 years in average (range 10–17 years) post‐treatment. GI and ECR findings were considered within the normal expectations for the sample studied, suggesting minimal clinical post‐NGVB side effects up to 17 years.

CLINICAL SIGNIFICANCE

Nightguard vital bleaching provides patient satisfaction with minimal side effects up to 17 years post‐treatment.

(J Esthet Restor Dent ••:••–••, 2011)
What is the self?
Authors: Hanna Robert
Published: October 2011

In this paper I briefly sketch a theory that answers the question “what is the self?,” where this question is understood in a scientific sense that includes both natural science and systematic fundamental metaphysics. As selves, we are essentially rational human minded animals or real persons in a fully natural and desperately non‐ideal world—animals with meaningful lives, for better or worse.
A self‐fulfilling prophecy: linking belief to behavior
Authors: Sternberg Esther , Critchley Simon , Gallagher Shaun , Raman V.V.
Published: October 2011

Moderated by Esther Sternberg (author of Healing Spaces: The Science of Place and Well‐being), philosopher Simon Critchley (the New School for Social Research), cognitive scientist Shaun Gallagher (University of Central Florida), and physicist V.V. Raman (Rochester Institute of Technology) survey how the self is shaped by interactions with the environment; how free will, responsibility, and other traits emerge; and how character and virtue become targets for constructing the self. The following is an edited transcript of the discussion that occurred April 28, 2011, 7:00–8:15 PM, at the New York Academy of Sciences in New York City.
Who am I? Beyond “I think, therefore I am”
Authors: Voorhoeve Alex , During Elie , Jopling David , Wilson Timothy , Kamm Frances
Published: October 2011

Can we ever truly answer the question, “Who am I?” Moderated by Alex Voorhoeve (London School of Economics), neuro‐philosopher Elie During (University of Paris, Ouest Nanterre), cognitive scientist David Jopling (York University, Canada), social psychologist Timothy Wilson (University of Virginia), and ethicist Frances Kamm (Harvard University) examine the difficulty of achieving genuine self‐knowledge and how the pursuit of self‐knowledge plays a role in shaping the self.
The Proteome of the Locus Ceruleus in Parkinson's Disease: Relevance to Pathogenesis
Authors: van Dijk Karin D. , Berendse Henk W. , Drukarch Benjamin , Fratantoni Silvina A. , Pham Thang V. , Piersma Sander R. , Huisman Evelien , Brevé John J.P. , Groenewegen Henk J. , Jimenez Connie R. , van de Berg Wilma D.J.
Published: October 2011

The locus ceruleus is among the earliest affected brain regions in Parkinson's disease (PD) showing Lewy body pathology and neuronal loss. To improve our understanding of the pathogenesis of PD, we performed the first proteomic analysis ever of post‐mortem locus ceruleus tissue of six pathologically confirmed PD patients, and six age‐ and gender‐matched non‐neurological controls. In total 2495 proteins were identified, of which 87 proteins were differentially expressed in the locus ceruleus of PD patients compared with controls. The majority of these differentially expressed proteins are known to be involved in processes that have been implicated in the pathogenesis of PD previously, including mitochondrial dysfunction, oxidative stress, protein misfolding, cytoskeleton dysregulation and inflammation. Several individual proteins were identified that have hitherto not been associated with PD, such as regucalcin, which plays a role in maintaining intracellular calcium homeostasis, and isoform 1 of kinectin, which is involved in transport of cellular components along microtubules. In addition, pathway analysis suggests a pathogenetic role for aminoacyl‐tRNA‐biosynthesis. These findings indicate that the proteome of the locus ceruleus of PD patients and non‐neurological controls provides data that are relevant to the pathogenesis of PD, reflecting both known and potentially novel pathogenetic pathways.
Afterglow Thermoluminescence Measured in Isolated Chloroplasts
Authors: Belatik Ahmed , Essemine Jemaa , Hotchandani Surat , Carpentier Robert
Published: October 2011

The thermoluminescence afterglow (AG) measured in plant leaves originates from the S2/S3QB− charge pair recombination in photosystem II (PSII) initiated by reverse electron flow from stromal reductants to PQ and then to the QB site in PSII centers that are in the S2/S3QB state. In this study, we show that this luminescence, absent in isolated thylakoid membranes, can be measured in intact chloroplasts that retain their stromal content including the electron acceptor pool (oxidized ferredoxin/NADP+) of photosystem I. The properties of the chloroplasts AG emission is similar to the AG in leaves in terms of temperature maximum, period‐four modulation, far‐red light stimulation, and antimycin A inhibition.
High mobility reduces beta‐diversity among orthopteran communities – implications for conservation
Authors: MARINI LORENZO , ÖCKINGER ERIK , BATTISTI ANDREA , BOMMARCO RICCARDO
Published: October 2011

Abstract. 1. The analysis ofβ‐diversity, i.e. species turnover, across space is central to a wide array of ecological and evolutionary topics, also providing critical information to conservation planning. Although dispersal limitation has been demonstrated to play an important role in determining insect community structure, very little research has been done to test whether mobility might affect the diversity distribution of species across multiple spatial scales.

2. We considered orthopterans (EnsiferaandCaelifera) inhabiting hay meadows to test whether species mobility modifiesβ‐diversity patterns across three nested spatial scales (1‐m2plots within meadow, 1000‐m2meadows within landscape, and 19.6‐km2landscapes within a region) and along a gradient of management intensity.

3. Orthopteran community composition varied most significantly over broader spatial scales. Larger proportion of regionalγ‐diversity was mainly composed ofβ‐diversity at the landscape scale, whereas this proportion was smaller at the plot and meadow scale.

4. Mobility, but not management, strongly modifiedβ‐diversity patterns. Sedentary species contributed to a greater proportion ofβ‐diversity across all the investigated scales compared with mobile species.

5. Measures currently included in most agri‐environment schemes have only focused on the extensive management at the field scale. Our results imply that orthopteran diversity would benefit from maintaining extensively managed meadows scattered throughout the whole region, as the loss of species‐rich isolated grassland patches due to abandonment or eutrophication might cause severe reductions of the regional species pool. Increasing connectivity might be also considered as a complementary measure to increase species occupancy and population persistence, particularly for sedentary species.
Collaborative research to support transition towards integrating flood risk management in urban development
Authors: van Herk S. , Zevenbergen C. , Rijke J. , Ashley R.
Published: October 2011

Urban development and regeneration present windows of opportunity to help reduce flood vulnerability. Much recent research stresses the need for better integration of flood risk into planning processes. However, there is limited experience in incorporating flood risk management in urban planning. Demonstration projects can help in overcoming this lack of experience and facilitate a transition towards integrated flood risk management and spatial planning; taking longer term flexible and adaptive approaches. This paper demonstrates that the process of research, if collaborative, can contribute to the better integration of flood risk in urban planning. Collaborative research can support demonstration projects and their wider uptake, as well as policy development and subsequently a transition to integrated flood risk management. It also provides greater freedom to use different approaches, consider a broader range of problems and solutions, bring stakeholders together and facilitate capacity building. This paper calls for collaborative research that facilitates social learning and is impact focussed, preferably supporting innovative demonstration projects.
Movement Choremes: Bridging Cognitive Understanding and Formal Characterizations of Movement Patterns1
Authors: Klippel Alexander
Published: October 2011

This article discusses an approach to characterizing movement patterns (paths/trajectories) of individual agents that allows for relating aspects of cognitive conceptualization of movement patterns with formal spatial characterizations. To this end, we adopt a perspective of characterizing movement patterns on the basis of perceptual and conceptual invariants that we termmovement choremes(MCs). MCs are formally grounded by behaviorally validating qualitative spatio‐temporal calculi. Relating perceptual and cognitive aspects of space and formal theories of spatial information has shown promise to foster understanding of the semantics of movement patterns. Specifically, we discuss our approach in relation to existing qualitative formalisms such as the region connection calculus and the Egenhofer’s intersection formalisms. We show that the MC approach is compatible with these approaches but offers additional opportunities to improve the cognitive adequacy of these formalisms. We summarize this paper using a movement taxonomy that also provides guidance for future research.
Aqueous alteration of kamacite in CM chondrites
Authors: PALMER Eric E. , LAURETTA Dante S.
Published: October 2011

Abstract– The study of aqueous alteration of kamacite in CM chondrites provides insight on the conditions, products, and relative timing of aqueous alteration. We studied unaltered, partially altered, and fully altered kamacite grains from Murray, Murchison, Cold Bokkeveld, and Nogoya using optical microscopy, electron microprobe analysis, scanning electron microscopy, and Raman spectroscopy. From textual evidence and chemical analysis, we established three separate microchemical environments. 1) In a microchemical environment with a high S activity, kamacite alters to form tochilinite, P‐bearing sulfides, eskolaite, and schreibersite. Mass balance calculations show that 81% of the Fe in kamacite is removed from the alteration region, making it available for the formation of other minerals or Fe‐rich aureoles. The release of Fe can alter the mesostasis of type‐I chondrules forming cronstedtite. 2) In a microchemical environment with a high Si activity and a low S activity, kamacite alters to form cronstedtite with small accessory sulfide inclusions. 3) A microchemical environment with limited S and Si activity results in kamacite alteration forming magnetite. The resulting magnetite retains associated Ni that can distinguish it from precipitated magnetite. In addition, the accessory phases of pentlandite and apatite can be formed if S or Ca are present. Finally, we note that small tochilinite grains in the matrix lack typical Ni, P, and Co levels, suggesting that they did not form from kamacite but possibly by sulfidization of magnetite.
Instability in an Elastic-Plastic Cylindrical Shell Under Axial Compression
Authors: Ariaratnam S. T. , Dubey R. N.
Published: October 2011

The condition for bifurcation of equilibrium for an elastic-plastic cylindrical shell under axial compression is established. The shape of the yield surface has been left arbitrary; hence the result is applicable to a wide class of inelastic solids. It is shown that the value of the critical stress is quite sensitive to the variation in the unit normal to the local yield surface.
Analysis of Pulsating Flows in Infinite and Finite Conical Nozzles
Authors: Chiang T. , Hsing F. C. , Pan C. H. T. , Elrod H. G.
Published: October 2011

The pulsating flows in both infinite and finite conical nozzles were analyzed theoretically. Sinusoidal pressure disturbances were impressed at the nozzle exit for the infinite nozzle and at either the inlet or at the exit for the case of a finite nozzle. The results have been calculated in terms of mass-flux response. The parameters involved are the Mach number and the modified Strouhal number; the inlet and exit radii ratio enters as an additional parameter for a finite nozzle. The results for an infinite conical nozzle indicate that, when the frequency is low, the quasistatic relationship between the pressure and mass-flux fluctuations holds; the same was reported in reference [1]. But, as the frequency increases, the dynamic characteristics of the pulsating flow become important. And, at high frequencies, the mass-flux response is less than the quasistatic value by an amount depending on the Mach number. For a finite conical nozzle the quasistatic condition is still valid if the frequency is low. However, at higher frequencies, the dynamic behavior becomes critically dependent on the frequency expressed in terms of w, for a given nozzle geometry and exit Mach number.
On the Initial Slope of Elastic-Plastic Boundaries in Combined Longitudinal and Torsional Wave Propagation
Authors: Ting T. C. T.
Published: October 2011

The elastic-plastic boundaries which start at the end of a tube in wave propagation of combined longitudinal and torsional stresses are studied. The longitudinal and torsional stresses applied at the end of the tube are assumed to be continuous and the initial slope of the boundaries are determined analytically for all possible combinations of the time derivatives of stresses before and after the elastic-plastic boundaries occur. It is seen that a continuous loading into a higher yield surface at the end of the tube does not necessarily produce a continuous plastic region near the end of the tube. Also, more than one elastic and plastic region can be generated near the end of the tube even though the stresses at the end of the tube are continuously increasing to a higher yield surface. These and other unexpected results are presented in this paper.
A Bounding Principle in the Theory of Work-Hardening Plasticity
Authors: Soechting J. F. , Lance R. H.
Published: October 2011

A displacement bounding principle for continua loaded into the plastic range is presented. Use is made of Drucker’s inequality and the existence of a maximum complimentary work path between any two stress states. The bounding principle is applied to several examples.
The Elastic Deformation of a Circular Rod of Finite Length for an Axially Symmetric End Face Loading
Authors: Blair J. M. , Veeder J. I.
Published: October 2011

The problem of determining the deformation of an elastic rod of finite dimensions under a symmetrical axial loading is reduced to the solution of an infinite system of simultaneous linear equations. An approximate numerical solution is obtained for the case when the load acts uniformly over an outer annular region of the end face, and it is shown that the maximum radial displacement increases as the width of the annulus decreases. The application of the results to the problem of circumferential ridging of nuclear reactor fuel elements is discussed. It is concluded that the compression between adjacent rods probably contributes to ridge formation, but that the magnitude of the contribution cannot be determined without a knowledge of the compressive plastic stress-strain characteristics of the material.
Elastic-Plastic, Work-Hardening Arches
Authors: Chern Jenn-Ming , Nemat-Nasser S.
Published: October 2011

A set of integral equations is developed for the stress rates that correspond to a given rate of loading from a given elastoplastic state in an elastic-plastic, work-hardening sandwich arch. Methods of solving these integral equations are considered. It is found that the integral-equation approach permits solutions which are as accurate as desired even when the loading program involves extensive partial unloadings. Thus the results of this paper may prove useful for checking various existing numerical techniques.
The Dynamic Response of Cylindrical and Conical Panels
Authors: Rossettos J. N. , Parisse R. F.
Published: October 2011

The dynamic response of cylindrical and conical panels subjected to arbitrary time-varying load distributions is studied and appropriate equations are presented. Convenient trigonometric series are used, in conjunction with finite-difference methods, to reduce the governing equations to sets of matrix equations. The numerical solution procedure involves time integration, using an unconditionally stable implicit (Houbolt) scheme, together with a Gaussian elimination technique particularly suited to the banded matrices involved. Calculated results treat the effects of conicity and various support conditions on the structural response. Individual cases show quantitatively how cylindrical panel response is more sensitive than that of conical panels to changes in edge restraint.
Nonlinear Response of a Cylindrical Shell to an Impulsive Pressure
Authors: Lovell E. G. , McIvor I. K.
Published: October 2011

When a circular cylindrical shell (plane strain) is subjected to a uniform radial impulse, the resulting circular mode may be unstable. In such a case flexural motion is excited, resulting in rather large displacements and stress. A previous nonlinear analysis [1]1 used a linear inextensionality constraint and displacement representation for the flexural response. A formulation employing a nonlinear inextensionality constraint is presented in this paper, and a comparison is made with the earlier work. The most significant result is a fundamental difference between the equations of motion; in this analysis the nonlinear modal coupling is primarily inertial. The condition for stability of the circular mode is unaffected, but substantial differences may occur in the long-term (nonlinear) response.
The Side-Force Problem for Shallow Helicoidal Shells
Authors: Wan F. Y. M.
Published: October 2011

The side-force problem for a shallow helicoidal shell is shown to be the complete static-geometric analog of the pure bending problem for the same shell. The solution of the former in terms of elementary functions is obtained, without another set of independent calculations, simply by applying the rules of the static-geometric duality to that of the latter. The analogy also enables us to use the same computer program developed for the pure bending problem (without any modification) to generate numerical results for the side-force problem.
Stresses in Largely Deflected Cantilever Beams Subjected to Gravity
Authors: Lee Han-Chow , Durelli A. J. , Parks V. J.
Published: October 2011

Stresses and displacements in largely deflected cantilever beams subjected to gravity were analyzed by means of photoelasticity. The results obtained for stresses and moments are normalized and presented parametrically for increasing amounts of deflection. For comparison purposes the results obtained using elementary beam theory (small deflection) and large deflection theory are also included.
Snap-Through Buckling of a Viscoelastic von Mises Truss in a Random Temperature Field
Authors: Ziegler Franz
Published: October 2011

The reduction of the expected lifetime of a temperature-sensitive viscoelastic von Mises truss caused by small random temperature fluctuations is calculated, assuming the probability density of the temperature process to be a known (symmetric) function. Results are derived for a normal and a rectangular probability distribution of the temperature fluctuations.
The Moire´ Method for Measuring Large Plane Deformations: General Theory and Application to Homogeneous Deformation
Authors: Martin L. P. , Ju F. D.
Published: October 2011

Moire´ fringe equations are developed for directly determining the components of Green’s and Conchy’s deformation tensors from fringe pitch and angle measurements. The equations are derived using the method of indicial representation of the specimen and master grid geometries. The master grid may be arbitrarily changed during the course of an experiment to obtain more easily measurable patterns. The results are specifically verified for the measurement of a large simple shear deformation.
Longitudinal Impact on a Hollow Cone
Authors: Kenner V. H. , Goldsmith W. , Sackman J. L.
Published: October 2011

Longitudinal elastic waves were produced in a truncated hollow aluminum cone with a wall thickness of 1/4 in. and an apex angle of 20 deg by the central impact of steel spheres ranging in diameter from 1/2 in to 1/16 in. This arrangement yielded transients whose dominant wavelengths varied by about a decade in the domain where geometrical dispersion was found to be critical. The input pulse at the truncated end was measured by means of piezoelectric crystals, while transmitted strains were observed by means of semiconductor gages on both the interior and exterior surfaces of the hollow cone. The results were compared with a corresponding one-dimensional analysis.
Nonlinear Vibrations of Shallow Spherical Shells
Authors: Grossman P. L. , Koplik B. , Yu Yi-Yuan
Published: October 2011

Based on a system of nonlinear dynamic equations and the associated variational equation of motion derived for elastic spherical shells (deep or shallow), an investigation of the axisymmetric vibrations of spherical caps with various edge conditions is made by carrying out a consistent sequence of approximations with respect to space and time. Numerical results are obtained for both free and forced oscillations involving finite deflection. The effect of curvature is examined, with particular emphasis on the transition from a flat plate to a curved shell. In fact, in such a transition, the nonlinearity of the hardening type gradually reverses into one of softening.
Excitation of an Elastic Cylindrical Shell by a Transient Acoustic Wave
Authors: Geers T. L.
Published: October 2011

An infinite, elastic, circular cylindrical shell submerged in an infinite fluid medium is engulfed by a transverse, transient acoustic wave. The governing equations for modal shell response are reduced through the application of a new method of solution to two simultaneous equations in time; these equations are particularly amenable to solution by machine computation. Numerical results are presented for the first six modes of a uniform sandwich shell submerged in water and excited by a plane step-wave. These results are then used to evaluate the accuracy of a number of approximations which have been employed previously to treat this and similar problems. The results are also used to compute displacement, velocity, and flexural strain responses at certain points in the sandwich shell.
Transverse Vibration of a Viscoelastic Column With Initial Curvature Under Periodic Axial Load
Authors: Stevens K. K.
Published: October 2011

The lateral response of a slightly curved viscoelastic column subjected to a periodic axial load P0 + P1 cos ωt is investigated. The analysis makes use of the complex modulus representation for linear viscoelastic materials. It is shown that the lateral vibrations stemming from imperfections can be of significant amplitude. Experimentally determined amplitude-frequency curves for a polymethyl methacrylate (Plexiglas) column are presented, and are found to be in excellent agreement with the theory. It is shown that there is an analogy between the dynamic instability and the static buckling of imperfect columns.
Free Vibrations of Reinforced Elastic Shells
Authors: Garnet Hyman , Levy Alvin
Published: October 2011

A technique is presented for the analysis of a wide class of reinforced, elastic structures undergoing free vibrations while subject to constraints imposed by the reinforcing elements. The technique consists of replacing the constrained structure by an equivalent model, a structure without reinforcing elements, undergoing free vibrations while subject to a loading system which consists of the structure-reinforcing element interaction forces. These forces are introduced as displacement-dependent loads, whose magnitudes reflect the elastic and inertial properties of the reinforcing elements. The displacements of the constrained body are expanded in terms of the normal modes of the unconstrained body. This approach leads to a set of manageable governing equations describing the behavior of the reinforced body exactly. A solution to these equations may then be obtained to any desired degree of accuracy. The technique is illustrated by computations performed for the case of a ring reinforced, circular cylindrical shell.
Large Deflections of an Inflated Cylindrical Tent
Authors: Ross E. W.
Published: October 2011

This report analyzes the large deformations of a cylindrical, inflated, single-wall tent due to wind pressure and is based on the membrane theory for large deflections but small strains. The tent cross section is a sector of a circle in the undeformed position, and the wind is blowing on it in the broadside direction. The tent motion is taken as plane, and it is assumed that the wind pressure distribution is known in the deformed state. The problem is solved by numerical analysis and results are presented for the stress, deformed shape, aerodynamic resultants, and anchor forces. The problem is of theoretical interest because the linear membrane theory does not have a unique solution for it, and also because it illustrates that the method of small deformations superposed on large is of little help when the large deformation is of inextensional type.
On the Contact Problem of Cylinders Containing a Shallow Longitudinal Surface Depression
Authors: Chiu Y. P.
Published: October 2011

Numerical results are presented in this paper for the determination of contact extent and maximum contact pressure for the contact of an elastic cylinder and a rigid cylinder containing a shallow longitudinal surface depression at the center of the contact. The profile of the depression is smoothly connected to the cylindrical surface by means of two arcs of equal radius. Comparison was made between the results of this solution and the well-known Hertzian solution without the depression. An approximate solution is given for the case that the contact under the arcs of small radius is narrow compared with that under the cylindrical surface. As the corner radius approaches zero, the magnitude of the pressure peak occurring at the shoulders of the depression varies inversely with 1/3 power of the corner radius.
High-Frequency Response of an Elastic Spherical Shell
Authors: Feit David , Junger M. C.
Published: October 2011

The classical solution of the point-excited spherical shell, in the form of a normal-mode series, converges poorly for large frequencies. By applying the Watson-Sommerfeld transformation to this series, the response is expressed as a sum of only two terms. These terms can be interpreted, respectively, as the near-field response and propagating flexural wave field of an infinite flat plate, the latter term being multiplied by a factor whose maxima coincide with the natural frequencies of the shell.
Stresses in Fiber-Reinforced Composites With Imperfect Bonding
Authors: Erdogan F. , Ozbek T.
Published: October 2011

The axially symmetric problem of an infinite elastic fiber embedded into an infinite matrix of different thermomechanical properties is considered. It is assumed that the composite contains imperfections in the form of interface cracks or a broken fiber. The integral equations for the singular part of the problem are obtained by considering concentrated dislocations on the fiber-matrix interface and using the results as Green’s functions. The resulting system of singular integral equations is solved, the expressions for stress intensity factors at the points of singularity and the strain-energy release rate are obtained, and a numerical example is given.
Pulse Propagation in a Poroelastic Solid
Authors: Jones John Paul
Published: October 2011

The problem of a stress pulse applied to a semi-infinite region of a poroelastic medium is examined to determine the effect of a stress pulse on equipment located underground. If dissipation is neglected, an applied step pulse splits into two pulses that propagate unchanged in shape, each moving at one of the dilatational speeds of the medium. If dissipation is included, the step pulse splits into a “smeared-out” component and a component that retains the sharp front. The latter component travels at a speed that would occur if the fluid and solid were locked together. It is concluded that linear poroelastic dissipative mechanisms are insufficient in themselves to yield a substantial reduction in accelerations for equipment buried in a saturated soil.
On the Stability of Hill’s Equation With Four Independent Parameters
Authors: Rand Richard H.
Published: October 2011

The stability of Hill’s equation with four independent parameters is studied by using Floquet theory and perturbations. Examples are given which demonstrate how the resulting analysis may be applied to a wide variety of stability problems.
Transient Motion of a Rigid Cylinder Produced by Elastic and Acoustic Waves
Authors: Forrestal M. J. , Alzheimer W. E.
Published: October 2011

A rigid, circular cylinder embedded in an elastic medium is subjected to a plane stress wave whose front is parallel to the axis of the cylinder. Expressions for the displacement, velocity, and acceleration of the cylinder are derived, and numerical results are presented for an incident stress wave with a step distribution in time. Formulas for the response of the cylinder produced by an acoustic wave are also presented, and it is shown that the responses from the elastic and acoustic waves are identical when the cylinder density is equal to the medium density. These results can be used as influence functions to determine the response of the cylinder produced by a plane wave with arbitrary time dependence.
Parametric Torsional Stability of a Bar Under Axial Excitation
Authors: Tso W. K.
Published: October 2011

A study is made on the parametric torsional stability of an elastic cantilever of rectangular cross section under dynamic axial loading. The coupling between the longitudinal and torsional motions exists due to the “shortening effect.” The problem is so formulated that the stability of torsional vibrations is represented by a Mathieu equation, the stability of which is well known. The effect of longitudinal vibrations on the torsional stability is investigated. The steady-state torsional-vibrational response curves are given analytically, and the effect of longitudinal damping on the boundary of stability and the steady-state response curves is also determined.
Stability of Shallow Arches Against Snap-Through Under Timewise Step Loads
Authors: Hsu C. S.
Published: October 2011

The dynamic stability of simply supported, shallow arches subjected to timewise step loads is studied in this paper. Presented is a general method which allows us to treat arches of arbitrary shape and load of arbitrary spatial distribution. Specific problems investigated are sinusoidal arches under sinusoidal loads, the effects of the second harmonics in the arch shape and in the load distribution, and sinusoidal arches subjected to uniform loads or concentrated and eccentric loads. The results are expressed in the form of sufficiency conditions for stability and sufficiency conditions for instability. The criteria given in this paper are reliable because the analysis does not involve truncating the solutions to a small number of modes.
Convergence of the Finite Element Method in the Theory of Elasticity
Authors: Johnson M. W. , McLay R. W.
Published: October 2011

The foundations of the theory of the finite element method as it applies to linear elasticity are investigated. A particular boundary-value problem in plane stress is considered and the variational principle for the finite element method is shown to be equivalent to it. Mean and uniform convergence of the finite element solution to that of the boundary-value problem is demonstrated with careful consideration given to the stress singularities. A counterexample is presented in which a set of functions, admissible to the variational principle, is shown not to converge.
Dynamic Snap-Through of Imperfect Viscoelastic Shallow Arches
Authors: Huang N. C. , Nachbar W.
Published: October 2011

Dynamic snap-through or dynamic buckling of imperfect viscoelastic shallow arches with hinged ends is considered under step loads of infinite duration. Attention is principally devoted to the influence both of small imperfections and of small amounts of damping, acting together, on the critical loads. For the problem considered, the Voigt model is used for viscoelasticity, the deflection is represented by the first two harmonic modes, and imperfections have the shape of the second (antisymmetric) mode. Results obtained by numerical integration of the differential equations show that the critical load exhibits a jump discontinuity in the limit for vanishing imperfection. Critical loads for slightly imperfect and elastic (inviscid) arches are slightly higher than those from the saddle-point formula of Hoff and Bruce [1, p. 276], confirming that the formula gives a lower bound on the critical load. However, critical loads for arches with slight imperfection and slight viscosity are considerably higher than for the slightly imperfect elastic arches. Another closed-form expression is shown to be in good agreement with these results. For finite amounts of viscosity, the critical loads tend rapidly to the values obtained for infinite viscosity, which are the same as the critical loads for quasi-static buckling. Apart from the jump discontinuity at zero, the critical load for any viscosity decreases continuously and monotonically with imperfection.
Limit Analysis and Yield-Line Theory
Authors: Sawczuk Antoni , Hodge P. G.
Published: October 2011

The relationship between limit analysis and yield-line analysis is investigated. Attention is restricted to simply supported, isotropic slabs subjected to single-point loadings. It is found that conventional yield-line analyses quite often give substantial overestimates of the carrying capacity. A general method is formulated for finding the yield-point load, and various examples are considered.
Peristaltic Transport
Authors: Fung Y. C. , Yih C. S.
Published: October 2011

Peristaltic pumping (viscous fluid flow induced by a sinusoidal traveling wave motion of the walls of a tube) at moderate amplitudes of motion is analyzed in the two-dimensional case. The nonlinear convective acceleration is considered and the nonslip condition is applied on the wavy wall (rather than on the mean position) in order to account for the mean flow induced by the wall motion. In the case in which there is no other cause of flow, the mean flow induced by the peristaltic motion of the wall is proportional to the square of the amplitude ratio (wave amplitude/half width of channel). The velocity profile depends on the mean pressure gradient. In this paper only those cases in which the pressure gradient will produce a flow of the same order of magnitude as that induced by the peristaltic motion are considered. If the pressure gradient is positive and equal to a certain critical value, then the velocity is zero on the center line. Pumping against a positive pressure gradient greater than the critical value would induce a backward flow (reflux) in the core region of the stream. There will be no reflux if the pressure gradient is smaller than the critical value. The velocity profile and the value of the critical pressure gradient are presented in this paper.
Whirl Dynamics of a Rotor Partially Filled With Liquid
Authors: Wolf J. A.
Published: October 2011

A spinning rotor, mounted on an elastic shaft and containing a symmetrically located cylindrical chamber partially filled with liquid, is assumed to undergo a small whirling motion. In the analysis, rotor unbalance, gravity, and gyroscopic terms are considered negligible, and the liquid motion is taken as being axially uniform. The added liquid produces a lowering of the usual synchronous critical speed. In addition, waves in the liquid layer couple with rotor whirl motion to produce a range of self-excited asynchronous whirl speeds above the critical, similar to those observed for nonsymmetrical solid rotors. Experiments completely corroborate the analytical results.
Elastic-Plastic Boundaries in Combined Longitudinal and Torsional Plastic Wave Propagation
Authors: Clifton R. J.
Published: October 2011

Assuming a one-dimensional rate independent theory of combined longitudinal and torsional plastic wave propagation in a thin-walled tube, restrictions are obtained on the possible speeds of elastic-plastic boundaries. These restrictions are shown to depend on the type of discontinuity at the boundary and on whether loading or unloading is occurring. The range of unloading (loading) wave speeds for the case when the nth time derivative of the solution is the first derivative that is discontinuous across the boundary is the complement of the range of unloading (loading) wave speeds for the case when the first discontinuity is in the (n + 1)th time derivative. Thus all speeds are possible for elastic-plastic boundaries corresponding to either loading or unloading. The general features of the discontinuities associated with loading and unloading boundaries are established, and examples are presented of unloading boundaries overtaking simple waves.
The Elastic Contact of Rough Spheres
Authors: Greenwood J. A. , Tripp J. H.
Published: October 2011

The Hertzian theory of elastic contact between spheres is extended by considering one of the spheres to be rough, so that contact occurs, as in practice, at a number of discrete microcontacts. It is found that the Hertzian results are valid at sufficiently high loads, but at lower loads the effective pressure distribution is much lower and extends much further than for smooth surfaces. The relevance to the physical-contact theory of friction and electric contact is considered.
A General Theory of Optimal Plastic Design
Authors: Prager William , Shield R. T.
Published: October 2011

The method of optimal plastic design used by Marc¸al and Prager [1] is reviewed and generalized to arbitrary one and two-dimensional plastic structures, and the uniqueness of optimal designs is discussed.
Free and Forced Oscillations of a Liquid in an Axisymmetric Tank at Low-Gravity Environments
Authors: Yeh Gordon C. K.
Published: October 2011

This paper presents a procedure to analyze the free and forced liquid sloshing motions in an axisymmetric tank of arbitrary shape at low-gravity environments. The free-vibration problem is solved by extending the analysis of Satterlee and Reynolds for a circular cylindrical tank with a flat bottom. The forced-motion problem is solved by first expanding the velocity potential, the interface wave height, and the forcing functions in terms of the normal mode shapes obtained in the free-vibration analysis. The solutions hold for any arbitrary horizontal translational motion of the tank.
Plastic Analysis of Rib-Reinforced Cylindrical Shells
Authors: Biron Andre , Sawczuk Antoni
Published: October 2011

Using the strain-mapping method for the Tresca yield condition, the yield surface is derived for a cylindrical shell with a wall reinforced by longitudinal ribs on one side. Results are given for the case where the axial load is zero. As a sample problem utilizing this surface and as an appropriate method for solving nonlinear equations, the solution of a cantilever shell under constant pressure is obtained.
Approximate Analytical Solutions of the Finite-Deflection Equations for a Shallow Spherical Shell
Authors: Holston A.
Published: October 2011

Approximate solutions are obtained, by Newton’s method, for shells subjected to uniform and/or point loads in the prebuckled or postbuckled configurations. Comparison of results with numerical solutions shows maximum deviations of 5 percent for clamped shells subjected to uniform loads in the prebuckled configuration. Similar comparisons for other cases show larger deviations. A characteristic load is developed which compares favorably with numerical buckling loads.
Axisymmetric Torsional Stresses in a Solid Containing Two Partially Bonded Rigid Spherical Inclusions
Authors: Goree J. G. , Wilson H. B.
Published: October 2011

An analysis of the three-dimensional mixed boundary-value problem of an infinite elastic body containing two identical partially bonded rigid spherical inclusions and subjected to an axisymmetric torsional stress field is presented. The order of the singularity in the stresses at the points of separation between the matrix and the inclusions is determined and the form of this singular stress field is utilized in determining a solution to the dual Legendre series generated from the boundary conditions. Numerical results are presented.
Microslips Between Contacting Paraboloids
Authors: Mow V. G. , Chow P. L. , Ling F. F.
Published: October 2011

A generalization of a Hertz problem and that of a Mindlin problem were found for fourth-order paraboloids in contact. In particular, microslips and annulus of slip were sought. To this end an inverse method was devised. Moreover, an optimization procedure is described for finding the geometry for a given loading condition and set of material properties, within the family of paraboloids, which gives minimum slip. It has been shown in an example that the annulus of slip may be reduced by 60 percent while the maximum slip may be reduced by 90 percent.