bluuebunny/crossref_metadata_2025 huggingface dataset:
Erwinia uzenensis sp. nov., a novel pathogen that affects European pear trees (Pyrus communis L.)
Authors: Matsuura Takayuki , Mizuno Akifumi , Tsukamoto Takanori , Shimizu Yoshiaki , Saito Norihiko , Sato Shigeyoshi , Kikuchi Shigemi , Uzuki Tsuneyasu , Azegami Koji , Sawada Hiroyuki
Published: October 2011

Bacteria were isolated from black lesions on shoots of European pear trees (Pyrus communis L.) in an orchard in Japan. Previous characterization of this novel pathogen by phenotypic and genotypic methods suggested that it should belong to the genus

Erwinia

but might not correspond to either

Erwinia amylovora

or

Erwinia pyrifoliae

. Here, phylogenetic analyses of the 16S rRNA gene, gyrB, and rpoD gene sequences indicated that it could not be assigned to any recognized species of the genus

Erwinia

. DNA–DNA hybridization confirmed that the bacterial strains represented a novel species. The DNA G+C contents, the fatty acid profile and phenotypic characteristics resembled those previously reported for members of the genus

Erwinia

. On the basis of these and previous results, the pathogen represents a novel species of the genus

Erwinia

, for which the name Erwinia uzenensis sp. nov. (type strain: YPPS 951T = LMG 25843T = NCPPB 4475T) is proposed.
A molecular framework for the inhibition of Arabidopsis root growth in response to boron toxicity
Authors: AQUEA FELIPE , FEDERICI FERNAN , MOSCOSO CRISTIAN , VEGA ANDREA , JULLIAN PASTOR , HASELOFF JIM , ARCE‐JOHNSON PATRICIO
Published: October 2011

Boron is an essential micronutrient for plants and is taken up in the form of boric acid (BA). Despite this, a high BA concentration is toxic for the plants, inhibiting root growth and is thus a significant problem in semi‐arid areas in the world. In this work, we report the molecular basis for the inhibition of root growth caused by boron. We show that application of BA reduces the size of root meristems, correlating with the inhibition of root growth. The decrease in meristem size is caused by a reduction of cell division. Mitotic cell number significantly decreases and the expression level of key core cell cycle regulators is modulated. The modulation of the cell cycle does not appear to act through cytokinin and auxin signalling. A global expression analysis reveals that boron toxicity induces the expression of genes related with abscisic acid (ABA) signalling, ABA response and cell wall modifications, and represses genes that code for water transporters. These results suggest that boron toxicity produces a reduction of water and BA uptake, triggering a hydric stress response that produces root growth inhibition.
PFT1, the MED25 subunit of the plant Mediator complex, promotes flowering through CONSTANS dependent and independent mechanisms in Arabidopsis
Authors: Iñigo Sabrina , Alvarez Mariano J. , Strasser Bárbara , Califano Andrea , Cerdán Pablo D.
Published: October 2011

Two aspects of light are very important for plant development: the length of the light phase or photoperiod and the quality of incoming light. Photoperiod detection allows plants to anticipate the arrival of the next season, whereas light quality, mainly the red to far‐red ratio (R:FR), is an early signal of competition by neighbouring plants. phyB represses flowering by antagonising CO at the transcriptional and post‐translational levels. A low R:FR decreases active phyB and consequently increases active CO, which in turn activates the expression of FT, the plant florigen. Other phytochromes like phyD and phyE seem to have redundant roles with phyB. PFT1, the MED25 subunit of the plant Mediator complex, has been proposed to act in the light‐quality pathway that regulates flowering time downstream of phyB. However, whether PFT1 signals through CO and its specific mechanism are unclear. Here we show that CO‐dependent and ‐independent mechanisms operate downstream of phyB, phyD and phyE to promote flowering, and that PFT1 is equally able to promote flowering by modulating both CO‐dependent and ‐independent pathways. Our data are consistent with the role of PFT1 as an activator of CO transcription, and also of FT transcription, in a CO‐independent manner. Our transcriptome analysis is also consistent with CO and FT genes being the most important flowering targets of PFT1. Furthermore, comparison of the pft1 transcriptome with transcriptomes after fungal and herbivore attack strongly suggests that PFT1 acts as a hub, integrating a variety of interdependent environmental stimuli, including light quality and jasmonic acid‐dependent defences.
Understanding bias in geographic range size estimates
Authors: Sheth Seema N. , Lohmann Lúcia G. , Distler Trisha , Jiménez Iván
Published: October 2011

Aim Estimates of geographic range size derived from natural history museum specimens are probably biased for many species. We aim to determine how bias in these estimates relates to range size.

Location We conducted computer simulations based on herbarium specimen records from localities ranging from the southern United States to northern Argentina.

Methods We used theory on the sampling distribution of the mean and variance to develop working hypotheses about how range size, defined as area of occupancy (AOO), was related to the inter‐specific distribution of: (1) mean collection effort per area across the range of a species (MC); (2) variance in collection effort per area across the range of a species (VC); and (3) proportional bias in AOO estimates (PBias: the difference between the expected value of the estimate of AOO and true AOO, divided by true AOO). We tested predictions from these hypotheses using computer simulations based on a dataset of more than 29,000 herbarium specimen records documenting occurrences of 377 plant species in the tribe Bignonieae (Bignoniaceae).

Results The working hypotheses predicted that the mean of the inter‐specific distribution of MC, VC and PBias were independent of AOO, but that the respective variance and skewness decreased with increasing AOO. Computer simulations supported all but one prediction: the variance of the inter‐specific distribution of VC did not decrease with increasing AOO.

Main conclusions Our results suggest that, despite an invariant mean, the dispersion and symmetry of the inter‐specific distribution of PBias decreases as AOO increases. As AOO increased, range size was less severely underestimated for a large proportion of simulated species. However, as AOO increased, range size estimates having extremely low bias were less common.
STRATEGIC TRADE AND DELEGATED COMPETITION WITH ENDOGENOUS QUALITY CHOICE: IS EXPORT POLICY NEEDED?
Authors: WANG YA‐CHIN , WANG LEONARD F. S.
Published: October 2011

This paper introduces the relative‐performance contract into a vertically differentiated product market and examines how the optimal trade policy and quality choice respond to the incentive mechanism. We find that the high quality firm makes better use of the delegation than the low quality firm in a cross‐border decentralized model. The main difference between the present paper and the strategic trade theory literature is that in this paper the optimal policy is free trade, which does not depend on whether firms compete by prices or quantities, and on whether the goods are substitutes or full complements.
The failure of ‘nationalization by attraction’: Britain's cross‐class alliance against earnings‐related pensions in the 1950s1
Authors: Pemberton Hugh
Published: October 2011

In 1957, the Labour Party published radical proposals for a state earnings‐related pension scheme (‘national superannuation’) whose funds were to be invested in stock markets to generate high returns, and to help modernize and dynamize the British economy. This article explores a sophisticated campaign against the proposal by the insurance industry, and the resistance of the unions. In doing so, it considers the implications of this cross‐class alliance, not least in terms of a possible missed opportunity to build a ‘developmental state’ in the UK, but also in terms of the country's increasingly inadequate and inequitable system of pension provision.
IS IRIS MURDOCH AN UNCONSCIOUS MISOGYNIST? SOME TROUBLE WITH SABINE LOVIBOND, THE MOTHER IN LAW, AND GENDER
Authors: ROBJANT DAVID
Published: October 2011

If in our use of imagery we are all of us the unacknowledged legislators of the world, it would follow that one can ‘serve the cause of sexual equality in education’ by challenging the way our images of the academic are gendered.1 This is the excellent stated purpose of Sabina Lovibond's short new book, Iris Murdoch, Gender and Philosophy.2
Analytical Reflections on Time in Custody
Authors: Hockey David
Published: October 2011

High reoffending rates after release from custody suggest that custodial regimes are not working effectively. An extensive rolling out of rehabilitation programmes across the prison estate has not had a great impact on addressing this problem with respect to repeat or habitual offenders. Drawing from script theory, cognitive deficits and offending patterns, I propose that the general thinking style of such offenders is reinforced by the basic arrangement of custodial regimes and, therefore, time being served, unwittingly reinforces the very cognitive processes that lead to an offending cycle.
‘The Prison is an Outlaw Institution’
Authors: Wacquant Loïc
Published: October 2011

This discussion ofLesPrisons de la misère(Raisons d'agirEditions,Paris, 1999 – expanded and updatedEnglish‐language edition,Prisons ofPoverty,Minneapolis,University ofMinnesotaPress, 2009) responds to queries put forth by the editors ofRde réeland originally published inFrench in that journal inJune 2000 (vol. 3, pp.33–8). It argues that the carceral boom in theUnitedStates results from the penalisation of poverty correlative of the simultaneous revamping of the economic, welfare and justice missions of the state. Pro‐market think tanks have played a driving role in fashioning and diffusingAmerica's ‘punitive common sense’ across theAtlantic, thus accelerating the import of aggressive crime rhetorics and policies inWesternEurope by political elites (including Left governments) seduced by neoliberal ideology. But, while the prison purports to enforce the law and to curtail the disorders generated by economic deregulation, the recent French experience confirms that its very organisation and daily operation make it an outlaw institution. It is promoted as a remedy for criminal insecurity and urban marginality, but it only serves to concentrate and intensify both, even as it makes them temporarily invisible. To get out of the policy and civic impasse into which the penalisation of poverty leads contemporary societies, we must raise anew the quintessentially political question of the purpose(lessness) of incarceration at century's dawn.
Isolation of brain mitochondria from neonatal mice
Authors: Wang Xiaoyang , Leverin Anna‐Lena , Han Wei , Zhu Changlian , Johansson Bengt R. , Jacotot Etienne , Ten Vadim S. , Sims Neil R. , Hagberg Henrik
Published: October 2011

J. Neurochem. (2011) 10.1111/j.1471‐4159.2011.07525.x

Mitochondria are key contributors to many forms of cell death including those resulting from neonatal hypoxic‐ischemic brain injury. Mice have become increasingly popular in studies of brain injury, but there are few reports evaluating mitochondrial isolation procedures for the neonatal mouse brain. Using evaluation of respiratory activity, marker enzymes, western blotting and electron microscopy, we have compared a previously published procedure for isolating mitochondria from neonatal mouse brain (method A) with procedures adapted from those for adult rats (method B) and neonatal rats (method C). All three procedures use Percoll density gradient centrifugation as a key step in the isolation but differ in many aspects of the fractionation procedure and the solutions used during fractionation. Methods A and B both produced highly enriched fractions of well‐coupled mitochondria with high rates of respiratory activity. The fraction from method C exhibited less preservation of respiratory properties and was more contaminated with other subcellular components. Method A offers the advantage of being more rapid and producing larger mitochondrial yields making it useful for routine applications. However, method B produced mitochondria that were less contaminated with synaptosomes and associated cytosolic components that suits studies that have a requirement for higher mitochondrial purification.
Amlodipine besylate and amlodipine camsylate prevent cortical neuronal cell death induced by oxidative stress
Authors: Lee Young Joo , Park Hyun‐Hee , Koh Seong‐Ho , Choi Na‐Young , Lee Kyu‐Yong
Published: October 2011

J. Neurochem. (2011) 10.1111/j.1471‐4159.2011.07529.x

We examined the neuroprotective effects of the long‐acting third‐generation dihydropyridine Ca2+ antagonists, amlodipine besylate (AB) and amlodipine camsylate (AC), on neuronal cell death induced by oxidative stress. Cell viability and levels of free radicals and intracellular signaling proteins were measured after treating primary cultures of cortical neurons with AB, AC, and/or hydrogen peroxide (H2O2) under various conditions. Cell viability was not affected by concentrations of AB or AC up to 5 μM but decreased at higher concentrations. Following H2O2 exposure, the viability of cortical neurons decreased in a concentration‐dependent manner; however, treatment with AB or AC up to 5 μM restored the viability of H2O2‐injured cortical neurons. Treatment with H2O2 increased the level of free radicals in cortical neurons, and pre‐treatment with AB or AC counteracted this in a dose‐dependent manner. Similarly, treatment with AB or AC reduced the declines in p85aPI3K, phosphorylated Akt, phosphorylated GSK‐3β, heat‐shock transcription factor‐1, and Bcl‐2 induced by H2O2, as well as the increases in cyclooxygenase‐2, cytosolic cytochrome c, cleaved caspase 9, and cleaved caspase 3. Our results indicate that AB and AC exert similar neuroprotective effects by reducing oxidative stress, enhancing survival signals, and inhibiting death signals.
Facile Synthesis of Single‐Phase TiO2 Nanocrystals with High Photocatalytic Performance
Authors: Li Guangqin , Zhang Sen , Yu Jianhua
Published: October 2011

A simple method has been developed to synthesize single‐phase TiO2 nanocrystals with uniform morphology and size at room temperature. The morphology and crystal phase of the products can be easily controlled. A possible control mechanism is proposed. The photocatalytic performances of the products were evaluated by the photodegradation of methyl orange in water. The experimental results indicate that the dye degradation efficiencies of the as‐prepared rutile TiO2 nanocrystals are almost twice that of the commercial photocatalyst P25.
Innate immune sensing 2.0 – from linear activation pathways to fine tuned and regulated innate immune networks
Authors: Volz Thomas , Kaesler Susanne , Biedermann Tilo
Published: October 2011

Abstract:  The innate immune system is based on pathogen recognition receptors that bind conserved microbial molecular structures, so called pathogen‐associated molecular patterns (PAMPs). The characterization of the innate immune system was long based on a linear step‐wise concept of recognition, activation pathways and effector defense mechanisms. Only more recently it was recognized that the innate immune system needs regulatory elements, sideways and crosstalks that allows it to fine tune and adapt its response. Thus, it is an emerging field within innate immunity research to try to understand how the immune outcome of innate immune sensing is regulated and why immune responses can be substantially different, even though the same PAMPs may have been ‘sensed’ at the surface organs such as the skin. Only the expansion of the innate immune system from ‘pure’ linear activation pathways to fine tuned and regulated innate immune networks allows us to integrate the generation of gradually accentuated and qualitatively different effector and tolerogenic immune responses. This article provides a review of the basic concepts and players of the innate immune system and will present some of the newer data defining the innate immune networks effectively regulating the immune homoeostasis and immune effector mechanisms with special focus on the skin as one of the organs involved in regulating the immune interface between the environment and the organism.
Treatment with probiotics in experimental oral colonization by Candida albicans in murine model (DBA/2)
Authors: Matsubara VH , Silva EG , Paula CR , Ishikawa KH , Nakamae AEM
Published: October 2011

Oral Diseases (2012) 18, 260–264

The aim of this study is to evaluate the oral colonization by Candida albicans in experimental murine immunosuppressed DBA/2 and treatment with probiotic bacteria. To achieve these objectives, 152 DBA/2‐immunosuppressed mice were orally inoculated with a suspension of C. albicans containing 108 viable yeast cells, the animals were treated with nystatin or with the probiotics (Lactobacillus acidophilus and Lactobacillus rhamnosus). Evaluations were performed by Candida count from oral mucosa swabbing. The oral mucosa colonization by C. albicans started at day 1 after inoculation, remained maximal from day 3 until day 7, and then decreased significantly. Probiotics reduced the C. albicans colonization significantly on the oral mucosa in comparison with the untreated animal group. In the group treated with L. rhamnosus, the reduction in yeast colonization was significantly higher compared with that of the group receiving nystatin. Immunosuppressed animal model DBA/2 is a relevant model for experimental Candida oral colonization, and the treatment with probiotics in this model may be an effective alternative to prevent it.
Axonopathy Is Associated with Complex Axonal Transport Defects in a Model of Multiple Sclerosis
Authors: Kreutzer Mihaela , Seehusen Frauke , Kreutzer Robert , Pringproa Kidsadagorn , Kummerfeld Maren , Claus Peter , Deschl Ulrich , Kalkul Arno , Beineke Andreas , Baumgärtner Wolfgang , Ulrich Reiner
Published: October 2011

Multiple sclerosis (MS) is an inflammatory and neurodegenerative disease characterized by myelin and axonal pathology. In a viral model of MS, we tested whether axonopathy initiation and development are based on an impaired transport of neurofilaments. Spinal cords of Theiler's murine encephalomyelitis virus (TMEV)‐infected and mock‐infected mice and TMEV infected neuroblastoma N1E‐115 cells were analyzed by microarray analysis, light microscopy and electron and laser confocal microscopy. In vivo axonal accumulation of non‐phosphorylated neurofilaments after TMEV infection revealed a temporal development caused by the impairments of the axonal traffic consisting of the downregulation of kinesin family member 5A, dynein cytoplasmic heavy chain 1, tau‐1 and β‐tubulin III expression. In addition, alterations of the protein metabolism were also noticed. In vitro, the TMEV‐infected N1E‐115 cells developed tandem‐repeated swellings similar to in vivo alterations. Furthermore, the hypothesis of an underlying axonal self‐destruction program involving nicotinamide adenine dinucleotide depletion was supported by molecular findings. The obtained data indicate that neurofilament accumulation in TME is mainly the result of dysregulation of their axonal transport machinery and impairment of neurofilament phosphorylation and protein metabolism. The present findings allow a more precise understanding of the complex interactions responsible for initiation and development of axonopathies in inflammatory degenerative diseases.
Revisited: Walch Classification of the Glenoid in Glenohumeral Osteoarthritis
Authors: Kidder Jake F. , Rouleau Dominique M. , Defranco Michael J. , Pons-Villanueva Juan , Dynamidis Savvas
Published: October 2011

Background

Shoulder osteoarthritis is characterized by progressive wear of the joint. To grade the degree of joint deformity, the Walch classification of glenohumeral arthritis has been proposed. This classification is based on five categories (A1, A2, B1, B2, C), although its validity has been questioned.

Methods

The present study proposed a new classification in three categories and compared it in terms of inter- and intra-observer reliability with the complete Walch classification and regroup classification (A, B, C).

Results

One hundred and sixteen computed tomography scans of patients with shoulder arthritis were revised by three independent evaluators and were classified according to the three classifications. The kappa statistics were identical between the new classification and the complete Walch classification (0.87 and 0.874). The regroup Walch classification (A, B, C) demonstrated higher reliability (kappa = 0.92). Most of the disagreement between observers was observed between glenoid B1 and B2.

Discussion

We report the first study on the Walch classification to use a large number of patients and challenge its reliability. According to the results obtained, there is no advantage in changing the classification. Therefore, surgeons must be aware of higher risk of mistake for glenoid type B. The superiority of a classification in terms of the prediction of surgical decisions and outcome has to be determined.
On Transition From Supersonic to Subsonic Flow at Low Reynolds Numbers in a Tube
Authors: Chen R. Y. , Williams J. C.
Published: October 2011

A supersonic low-density gas stream produced in a supersonic nozzle was passed through a circular tube in which the transition from supersonic to subsonic flow took place. Static pressure distributions along the tube (and nozzle) and impact pressure distributions across the tube at several stations were measured to determine the nature of this transition. The impact pressure distributions were used, together with the local static pressure, to infer Mach number and velocity profiles in the tube. When the pressure distributions and center-line Mach number distributions are considered together, one obtains a fairly clear picture of the processes involved in the transition from supersonic to subsonic flow at low Reynolds numbers.
Analytical Investigations of Incompressible Turbulent Swirling Flow in Stationary Ducts
Authors: Rochino A. , Lavan Z.
Published: October 2011

Turbulent swirling flows in stationary cylindrical ducts were investigated analytically using Taylor’s modified vorticity transport theory and von Karman’s similarity hypothesis extended to consider a three-dimensional fluctuating velocity field. The resulting similarity conditions were used to formulate the expression for eddy diffusivity in the entire flow field except in a small region near the pipe wall where a mixing-length expression analogous to that assumed by Prandtl for parallel flow in channels was used. The swirl equation was solved numerically using a constant that was obtained indirectly from an experiment by Taylor, and the analytical results were compared with two different sets of experimental measurements. In both cases, the agreement between experiment and analysis was satisfactory. Some discrepancies appeared when the flow field was predominantly irrotational or in solid-body rotation: This might have been expected since, for these situations, some of the similarity conditions were indeterminate or infinite.
Hertzian Contact-Stress Deformation Coefficients
Authors: Cooper Duane H.
Published: October 2011

Formulations are given for the coefficients λ, μ, ν defined by Hertz in terms of the solution of a transcendental equation involving elliptic integrals and used by him to describe the deformation of bodies subjected to contact stresses. Methods of approximate calculation are explained and errors in the tables prepared by Hertz are noted. For the purpose of providing a more extensive and more accurate tabulation, using an automatic digital computer, these coefficients are reformulated so that a large part of the variation is expressed by means of easily interpreted elementary formulas. The remainder of the variation is tabulated to 6 places for 100 values of the argument. Graphs of the coefficients are also provided.
The Mechanics of Some New Processes of Cup Drawing
Authors: Hillier M. J.
Published: October 2011

An attempt is made to indicate and explain some advantages of processes of cup drawing of metals which use a superposed fluid pressure. The mechanics of tensile necking failure is used to obtain a measure of relative drawability.
Laminar Flow in an Annulus With Arbitrary Time-Varying Pressure Gradient and Arbitrary Initial Velocity
Authors: Prakash Satya
Published: October 2011

In this paper, the problem of incompressible laminar viscous flow in the annular space bounded by two coaxial infinite circular cylinders with an arbitrary time-varying pressure gradient and with an arbitrary initial distribution of velocity has been studied. The present problem generalizes the several earlier works in which the pressure gradient and the initial distribution of velocity have been taken in special forms. The analysis has been made by the use of finite Hankel transform. The case of steady flow when the pressure gradient is constant has been deduced by taking the pressure gradient to be a constant quantity and then letting the time since the start of the motion be infinite. This result has been shown in agreement with the already well-established result.
Dispersive Pulse Propagation Parallel to the Interfaces of a Laminated Composite
Authors: Peck J. C. , Gurtman G. A.
Published: October 2011

This paper presents a theoretical analysis of the geometric dispersion of transient stress waves in a linearly elastic laminated composite. The loading is a uniform pressure of step-function time-dependence, applied to a half space. The laminates are perpendicular to the half-space boundary. The mathematical treatment is borrowed from the theory of wave propagation in rods. Fourier transforms are applied to time and the coordinate in the propagation direction. Inversion of the spatial transform by residues yields a formal solution in the form of an infinite series of integrals. Each of these integrals is the contribution to the transient response from a mode of sinusoidal wave propagation. Application of the saddle-point technique for long-time asymptotic approximation indicates that the low-frequency portion of the integral from the first mode gives the dominant contribution, called the head-of-the-pulse approximation. The form of the expression for the head-of-the-pulse approximation leads to the definition of a characteristic dispersion time τ. Since τ is a single quantity which describes the dispersion of the wave, it simplifies parametric studies. A closed-form algebraic expression for τ is presented, which has a simple dependence on the propagation distance and spacing of the laminates. Numerical examples for boron-epoxy and glass-epoxy laminates are given.
Lateral Vibrations of a Rotating Shaft in a Viscous Fluid
Authors: Wang Chang-Yi
Published: October 2011

A rigid rotating cylindrical shaft is vibrating along a diameter in a viscous fluid. Two different cases are investigated through the method of inner and outer expansions. The case of small amplitude vibrations is characterized by the diffusion of vorticity. The coupling of rotation with vibration introduces a normal force, of both inviscid and viscous origins, perpendicular to the direction of oscillation. As rotation increases, the induced steady streaming becomes more skewed and weaker. The case of fast rotation is characterized by the transport of vorticity. Rotation affects both the drag and normal force. The steady torque is increased due to the induction of a steady secondary rotary flow.
A Theoretical and Experimental Study of Confined Vortex Flow
Authors: Farris G. J. , Kidd G. J. , Lick D. W. , Textor R. E.
Published: October 2011

The interaction of a vortex with a stationary surface was studied both theoretically and experimentally. The flow field examined was that produced by radially inward flow through a pair of concentric rotating porous cylinders that were perpendicular to, and in contact with, a stationary flat plane. The complete Navier-Stokes equations were solved over a range of tangential Reynolds numbers from 0–300 and a range of radial Reynolds numbers from 0 to −13, the minus sign indicating radially inward flow. In order to facilitate the solution, the original equations were recast in terms of a dimensionless stream function, vorticity, and third variable related to the tangential velocity. The general validity of the numerical technique was demonstrated by the agreement between the theoretical and experimental results. Examination of the numerical results over a wide range of parameters showed that the entire flow field is very sensitive to the amount of radial flow, especially at the transition from zero radial flow to some finite value.
Mean Stress Effect on the Shear Fatigue Crack Model—Part 2
Authors: Swenson D. O.
Published: October 2011

An expanded version of Swenson’s shear crack fatigue model is developed to include the effect of the mean stress on cyclic shear crack growth. Five results are concluded for this model. 1 As the mean shear stress is increased for a specified stress range, the cyclic shear crack tip displacement decreases. 2 The shear displacement at the center of the crack appears to be independent of the mean stress and remains constant for a given stress range. 3 An inherent blunting process for crack growth predicts retardation of tip displacement and crack growth for small values of stress range and all mean stress values. 4 The overall plactic zone length for this model does not change during cyclic shear loading although plastic deformation is occurring. 5 The model’s crack tip displacement per cycle is a linear function of the half crack length for prescribed stress range, mean stress, and material properties.
Dynamic Stability of an Impact System Connected With Rock Drilling
Authors: Fu C. C.
Published: October 2011

This paper deals with asymptotic stability of an analytically derived, synchronous as well as nonsynchronous, steady-state solution of an impact system which exhibits piecewise linear characteristics connected with rock drilling. The exact solution, which assumes one impact for a given number of cycles of the external excitation, is derived, its asymptotic stability is examined, and ranges of parameters are determined for which asymptotic stability is assured. The theoretically predicted stability or instability is verified by a digital computer simulation.
Problems of Optimal Structural Design
Authors: Prager W. , Taylor J. E.
Published: October 2011

The paper presents a uniform method of treating a variety of problems of optimal design of sandwich structures. The design procedure consists of two steps: The integration of an optimality condition, which is a differential equation for the optimal displacement field that does not involve any design parameters, and the subsequent determination of the optimal distribution of elastic stiffness or plastic resistance from the usual differential equations of the structure. Optimal elastic design for maximum stiffness, maximum fundamental frequency, or maximum buckling load, and optimal plastic design for maximum safety are treated as examples.
The Roots of Flu¨gge’s Cylindrical Shell Equation
Authors: Rish R. F.
Published: October 2011

A simple method is proposed to obtain the roots of Flu¨gge’s equation when the eigenfunction has a trigonometric expression in the longitudinal direction. The significance of the solution is discussed.
Analysis of the Plastic Flow of Rock Under a Lubricated Punch
Authors: Cheatham J. B. , Paslay P. R. , Fulcher C. W. G.
Published: October 2011

A general three-dimensional plasticity theory is presented for describing the plastic flow of homogeneous, isotropic rock. Normality of the deformation-rate vector to the yield surface is incorporated into the stress-deformation rate law used in the theory. The rock is assumed to be perfectly plastic or nonwork-hardening with a dependence of the yield strength on the hydrostatic component of stress. A particular type of yield surface, which is representative of the behavior of rock, is assumed in an application of the theory. The specific problem considered is the solution for the incipient plane flow under a flat lubricated punch.
Elastic Contact of a Strip Pressed Between Two Cylinders
Authors: Wang C. F.
Published: October 2011

Methods of solving an integral equation that represents the elastic contact of a strip pressed between two identical cylinders are discussed. Fourier cosine transformation is used to derive the integral equation of the contact problem, and approximation kernels are used to obtain the solutions for the cases of thick and thin layers. The solutions for both cases are given as a truncated series of the weighted Tchebyshev polynomials of the first kind, whose coefficients are determined from a system of linear equations. The problem of two circular cylinders pressing on a strip is given as an example. The nature of two approximate solutions are also briefly discussed.
On Numerical Comparisons in Elastic-Plastic Torsion
Authors: Hodge P. G. , Herakovich C. T. , Stout R. B.
Published: October 2011

Three numerical methods are presented for solving the elastic-plastic torsion problem; they are applied to some simple examples. The results are compared to each other and to other known solutions, both for accuracy and for ease of computation.
Edge-Bonded Dissimilar Orthogonal Elastic Wedges Under Normal and
Shear Loading
Authors: Bogy David B.
Published: October 2011

The plane-strain and generalized plane stress problems of two materially dissimilar orthogonal elastic wedges, which are bonded together on one of their faces while arbitrary normal and shearing tractions are prescribed on their remaining faces, are treated within the theory of classical elastostatics. The asymptotic behavior of the solution in the vicinity of the intersection of the bonded and loaded planes is investigated. The stress fields are found to be singular there with singularities of the type r−α, where α depends on the ratio of the two shear moduli and on the two Poisson’s ratios. This dependence is shown graphically for physically relevant values of the elastic constants. The largest value of α for the range of constants considered is 0.311 and occurs when one material is rigid and the other is incompressible.
Continuum Theory for a Laminated Medium
Authors: Sun C.-T. , Achenbach J. D. , Herrmann George
Published: October 2011

A system of displacement equations of motion is presented, pertaining to a continuum theory to describe the dynamic behavior of a laminated composite. In deriving the equations, the displacements of the reinforcing layers and the matrix layers are expressed as two-term expansions about the mid-planes of the layers. Dynamic interaction of the layers is included through continuity relations at the interfaces. By means of a smoothing operation, representative kinetic and strain energy densities for the laminated medium are obtained. Subsequent application of Hamilton’s principle, where the continuity relations are included through the use of Lagrangian multipliers, yields the displacement equations of motion. The distinctive trails of the system of equations are uncovered by considering the propagation of plane harmonic waves. Dispersion curves for harmonic waves propagating parallel to and normal to the layering are presented, and compared with exact curves. The limiting phase velocities at vanishing wave numbers agree with the exact, limits. The lowest antisymmetric mode for waves propagating in the direction of the layering shows the strongest dispersion, which is very well described by the approximate theory over a substantial range of wave numbers.
An Approach to Optimum Shape Determination for a Class of Thin Shells
of Revolution
Authors: Wang Han-Chung , Worley Will J.
Published: October 2011

A method is presented for the determination of an optimum shape of a convex shell of revolution with respect to volume and weight. The technique depends on selecting a multiparameter equation and varying the parameters to achieve a near optimum shape for prescribed failure criteria. As an illustration of the method, the first quadrant of the meridian (x/a)α + (y/b)β = 1 is selected. Here a, b, α, and β are positive constants not necessarily integers, with α and β equal to or greater than unity. Variations in shape are expressed in terms of the parameters b/a, α and β. The procedure is applied to the selection of a thin shell which will fit within the space defined by a circular cylinder of radius b and length 2a. The shell is optimized, in terms of α and β, with respect to volume and weight. The numerical iteration was performed by means of a digital computer.
Dynamic Plastic Buckling of Sandwich Shells
Authors: Vaughan Henry , Lindberg H. E.
Published: October 2011

The formation of small, flexural wrinkles in the walls of a sandwich shell under uniform radial impulse is examined. A buckling criterion based on the magnifications of initial wall imperfections is used to evaluate threshold impulses. Using a given weight of material, this criterion is used to determine the optimum ratios of the inner and outer wall thicknesses for various core thicknesses. It is shown that the optimum shell for a given weight of material and outer diameter is a single-wall shell. The loss in efficiency obtained by using typical sandwich shells is about 30 percent. These results are supported by experimental evidence.
Three-Dimensional Boundary Layers on Cones at Small Angles of Attack
Authors: Pinkus O. , Cousin S. B.
Published: October 2011

Based on an expression given by Cooke, an equation is derived for a three-dimensional “equivalent radius” for cones at a small angle of attack. This function when used in any of the available axisymmetric boundary-layer equations yields corresponding solutions for yawed cones. Expressions for the streamlines along which the above equations are to be integrated are also derived. The method yields a line of possible incipient separation or wake formation in addition to the boundary-layer properties in both the longitudinal and circumferential direction. Numerical solutions including heat transfer effects are presented for a wind tunnel model and compared with experimental results.
Unsteady Motion of a Sphere Along a Circular Path in a Viscous Fluid
Authors: Odar F.
Published: October 2011

Forces on a sphere moving unsteadily along a circular path in a viscous fluid are measured, and it is found that within the experimental range the formula valid for the rectilinear motion has to be modified to account for the curvature of the path.
Coupled Thermoelasticity of Bars
Authors: Dillon O. W.
Published: October 2011

Several boundary-value problems for semi-infinite bars made of a coupled thermoelastic material are solved by means of new functions. These arise in the solutions as “corrections” to classical tabulated functions such as the error function. However, they are not always small compared to their uncoupled equivalents. It turns out that the numerical differences in the solutions of a specific problem are usually small. But interesting phenomena are still found. The stresses produced in the coupled material are larger than those in the uncoupled one. The temperature generated on the face during impact of identical specimens is less than one might expect on simple intuitive grounds. Its time history is also quite interesting. Stress, strain, and thermal precursors exist but they do not propagate at a unique speed, while discontinuities propagate at the isothermal bar velocity. It is found that there is not much difference between the surface temperatures generated in a constant-velocity problem and one in which a constant acceleration is imposed. The temperature gradients are, however, different in these two problems.
The Axisymmetric Thermoelastic Problem in Bispherical Coordinates
Authors: Warren W. E. , Weese J. A.
Published: October 2011

Analytical methods are developed for treating steady-state axisymmetric thermoelastic problems defined in bispherical coordinates. Possible geometrical configurations include the infinite space with two spherical cavities of arbitrary radii and separation distance, the half-space with a spherical cavity, and the thick-walled shell having eccentric spherical boundaries. Thermal conditions must be prescribed at the surface of the body such that the temperature distribution is uniquely determined. The surfaces of the body are traction free. Numerical results for a half-space containing a spherical cavity heated to constant temperature with zero temperature on the plane and at infinity are presented in graphical form for representative geometrical variations.
The Law of the Wall in a Thick Axisymmetric Turbulent Boundary Layer
Authors: Rao G. N. V.
Published: October 2011

An attempt is made to develop a law of the wall for a thick axisymmetric turbulent boundary layer in which the sublayer thickness is comparable to the radius of transverse curvature. Examination of the equations of motion in the viscous sublayer suggests a law similar to that in two-dimensional flow. Available experimental information is consistent with this law, but the structure of turbulence in such thick axisymmetric boundary layers would seem to need further study.
Free Waves in a Plate Supported by a Semi-Infinite Continuum
Authors: Achenbach J. D. , Keshava S. P.
Published: October 2011

Plate equations are used to determine dispersion curves for free waves in a layer and a supporting half space of different elastic properties. The approximate dispersion curves are compared with curves obtained by employing elasticity equations for the layer. For a relatively soft layer, agreement is good at small wave numbers. For a relatively stiff layer, good agreement is obtained over the whole range of wave numbers for which a free wave can exist. A comparison of the displacement distributions in plate and layer shows that the range of wave numbers for which the displacements are well matched is much smaller than the range for which good agreement in phase velocities is obtained. Finally, the dispersion curve for a plate on a Winkler foundation is compared with the corresponding curve for a plate in smooth contact with a semi-infinite continuum.
Universal Velocity Similarity in Fully Turbulent Rotating Flows
Authors: Kinney R. B.
Published: October 2011

An extension of von Ka´rma´n’s similarity hypothesis to a cylindrical geometry has been made in order to establish the conditions under which universal velocity similarity will exist for plane-rotating turbulent flows. A characteristic mixing length is found which is proportional to the radial coordinate. From this result and the other similarity conditions obtained, a family of similar velocity profiles is generated which includes the fully turbulent irrotational profile observed by G. I. Taylor in his rotating cylinder experiments. Universal velocity profile and eddy diffusivity laws are also derived, and the universal constant appearing in the equations is evaluated using Taylor’s velocity and wall shear-stress measurements. The universal profile is shown to be that which corresponds to a constant vorticity for the mean fluid motion.
An Electrooptic Analog for the Solution of the Laplace Equation
Authors: O’Regan R.
Published: October 2011

Laplace’s equation occurs frequently in mathematical physics for problems relating to fluid flow, heat transfer, and so on. For some simple cases, the boundary-value problem can be solved; but more often, the differential equation proves intractable, and numerical analysis or experimental methods are used. The electrooptic analog is an experimental method based upon the fact that an organic dye solution becomes birefringent in an electric field. This effect enables one to determine voltage gradient throughout a two-dimensional field. The boundary conditions most readily applied are prescribed constant values of the electric potential φ on conducting segments of a boundary and ∂φ/∂n = 0 on insulated segments of a boundary. With the known conditions on the boundary and the potential gradient found from experiment, the problem is solved. This analog can be used for all physical problems for which the boundary conditions are applicable, and which satisfy Laplace’s equation.
Solution of One-Dimensional Elastic Wave Problems by the Method of Characteristics
Authors: Chou P. C. , Mortimer R. W.
Published: October 2011

A number of elastic wave problems which involve one space variable are treated, in a unified manner, by a system of second-order hyperbolic partial differential equations, with the generalized displacements as dependent variables. This system of n equations is analyzed by the method of characteristics yielding closed-form equations for the physical characteristics, the characteristic equations, and the propagation of discontinuities. Procedures for numerical integration along the characteristic curves are established. Among the elastic wave problems that may be represented by this unified approach are the Timoshenko beam, plates, bars, and sheets; in all cases, the media may be non-homogeneous. Various approximate shell equations also may be represented. Results of numerical calculations are in agreement with those obtained by other methods.
Waves at a Flexibly Bonded Interface
Authors: Jones J. P. , Whittier J. S.
Published: October 2011

Plane strain-elastic wave propagation is studied for two dissimilar half spaces joined together at a plane interface by an elastic bond. The bond thickness is assumed to be small compared to the wavelength, and an appropriately simplified description of the bond behavior is introduced. Attention is focused on solutions corresponding to the propagation of interface waves along the bond. The existence of interface waves is found to be governed by a parameter involving bond stiffness and wavelength. The limiting case of an infinitely stiff bond corresponds to the interface wave problem first solved by Stoneley, and it is shown that the present analysis yields Stoneley’s frequency equation in this limit. Also, the limiting case of an infinitely soft bond is found as expected to give two Rayleigh surface waves, one in each medium. It is shown analytically that, for intermediate bond stiffnesses, there may occur zero, one, or two interface waves, depending on the properties of the bond and the media. Illustrative numerical examples are presented. It is the conclusion of this study that account must be taken of the stiffness of the bond and the wavelength of the disturbance before it is proper to speak of an interface wave existing or not existing at a bonded interface.
Wave Function Expansions and Perturbation Method for the Diffraction of Elastic Waves by a Parabolic Cylinder
Authors: Thau S. A. , Pao Yih-Hsing
Published: October 2011

The dynamic response, including the stresses at the surface, of a rigid parabolic cylinder in an infinite elastic solid is studied for an incident plane compressional wave. The method of separation of variables in parabolic coordinates is used. With the wave function for one of the scattered waves expanded into a series of those for the other wave, the total scattered fields are then determined numerically by inverting a truncated infinite matrix. The same problem is solved also by a recently developed method of perturbation which describes the two waves in elastic solids in terms of wave functions with a common wave speed. With the latter method, the total scattered waves are determined analytically for the various orders of perturbation, and these results supplement the numerical wave function expansion results in the low-frequency range.
Dynamic Buckling of a Thin Cylindrical Shell Under Axial Impact
Authors: Lindberg H. E. , Herbert R. E.
Published: October 2011

Buckling of thin cylindrical shells from axial impact is studied under the assumption that initial imperfections can be approximated by “white noise.” Linear small-deflection theory is used to calculate the resulting growth of the normal modes, and a statistical analysis gives the expected values for the “preferred” axial and circumferential wave-lengths. Very high-speed photographs (240,000 frames/sec) of shells buckling under axial impact show excellent agreement with the theory and demonstrate that large-deflection buckling follows the pattern established by the early linear motion.