bluuebunny/crossref_metadata_2025 huggingface dataset:
The strip patch test – indication in occupational dermatology demonstrated with a case history
Authors: Dickel Heinrich , Scola Nina , Altmeyer Peter
Published: July 2009

In occupational dermatology, repeat patch testing is a frequent occurrence when an expert opinion is required. As a result, discrepancies in test results may affect the legal position in respect of insurance and a reduction in the level of disability. The strip patch test (SPT) supports the diagnosis of allergic contact dermatitis when a weak sensitization is present or when a weak sensitizer with poor epidermal penetration is involved leading to a false‐negative patch test result. We report on a 30‐year‐old man working as an industrial mechanic from 1995 to 2006. After approval of an occupational disease no. 5101 of the German ordinance on industrial disease in 2007, he went to court claiming compensation. The sensitization with clinical and occupational relevance to potassium dichromate that was decisive for the evaluation for insurance purposes was first confirmed in a patch test in 2005. Succeeding tests in 2006 in the context of an expert opinion and in 2008 in the context of our decisive expert opinion remained negative. We could reconfirm the potassium dichromate sensitization only by the SPT performed in the proposed standardized manner. The potassium dichromate allergy was the determining factor in the assessment for insurance purposes. This resulted in an adjustment in the severity of disability and a pension entitlement. From this case it is obvious that the detection of a SPT‐positive and patch test‐negative sensitization may have a significant impact on the situation with respect to the legal and insurance position.
The Lady Has a Price: Charity and Gratitude in Alencar's Diva
Authors: De Almeida Cardoso André Cabral
Published: July 2009

In his novel Diva, nineteenth‐century Brazilian romanticist José de Alencar re‐articulates the sentimental notions of charity and gratitude, investing them with new ideological contours, different from the ones they assumed in European sentimental fiction. In Alencar's text, charity and gratitude cease to be an expression of bourgeois ideology in order to function as instruments to support patriarchal power. While in European sentimental discourse they paved the way for the establishment of the contract as an ideological construct that was seen as the basis for modern social relations, in Alencar's nineteenth‐century Brazil they appear as elements that resist the idea of contractual social relations.
Limits on the location of planetesimal formation in self-gravitating protostellar discs
Authors: Clarke C. J. , Lodato G.
Published: July 2009

In this Letter, we show that if planetesimals form in spiral features in self-gravitating discs, as previously suggested by the idealized simulations of Rice et al., then in realistic protostellar discs, this process will be restricted to the outer regions of the disc (i.e. at radii in excess of several tens of au). This restriction relates to the requirement that dust has to be concentrated in spiral features on a time-scale that is less than the (roughly dynamical) lifetime of such features, and that such rapid accumulation requires spiral features whose fractional amplitude is not much less than unity. This in turn requires that the cooling time-scale of the gas is relatively short, which restricts the process to the outer disc. We point out that the efficient conversion of a large fraction of the primordial dust in the disc into planetesimals could rescue this material from the well-known problem of rapid inward migration at an approximate metre-size scale and that in principle the collisional evolution of these objects could help to resupply small dust to the protostellar disc. We also point out the possible implications of this scenario for the location of planetesimal belts inferred in debris discs around main sequence stars, but stress that further dynamical studies are required in order to establish whether the disc retains a memory of the initial site of planetesimal creation.
Boundary shear acceleration in the jet of MKN501
Authors: Sahayanathan S.
Published: July 2009

The high-resolution image of the jet of the BL Lac object MKN501 in radio shows a limb-brightened feature. An explanation of this feature as an outcome of the differential Doppler boosting of jet spine and jet boundary due to transverse velocity structure of the jet requires large viewing angle. However, this inference contradicts with the constraints derived from the high-energy γ-ray studies unless the jets bend over a large angle immediately after the γ-ray zone (close to the central engine). In this Letter, we propose an alternate explanation to the limb-brightened feature of MKN501 by considering the diffusion of electrons accelerated at the boundary shear layer into the jet medium, and this consideration does not require large viewing angle. Also, the observed difference in the spectral index at the jet boundary and jet spine can be understood within the framework of shear acceleration.
THERMOPHYSICAL PROPERTIES OF JACKFRUIT PULP AFFECTED BY CHANGES IN MOISTURE CONTENT AND TEMPERATURE
Authors: SOUZA MICHELLE A. , BONOMO RENATA C.F. , FONTAN RAFAEL C.I. , MINIM LUIS ANTONIO , COIMBRA JANE SÉLIA DOS REIS
Published: July 2009

Thermophysical properties of jackfruit (Artocarpus heterophyllus L.) pulp affected by temperature and moisture content were analyzed. Density (ρ), heat capacity (cp) and thermal diffusivity (α) were experimentally determined at moisture content between 65% m/m and 95% m/m, and temperatures between 5 and 85C. Then, thermal conductivity was calculated from experimental results of thermal diffusivity, specific heat and density. The empirical models for each property as a function of moisture content and temperature were obtained (R2 ≥ 0.90). Estimated equations were fitted to the experimental data for density and specific heat, and the accuracy of those equations was checked.

PRACTICAL APPLICATIONS

The design of juice concentrate plants needs thermophysical parameters. Information about tropical and exotic fruits, such as jackfruit, is insufficient, and much specific information is still unknown. The knowledge of how temperature and moisture content affect properties such as density, specific heat, thermal diffusivity and thermal conductivity will enable the development, adaptation and optimization of more efficient specific equipment for processing jackfruit.
EFFECT OF HYDROGEN PEROXIDE PRETREATMENT ON THE ENZYMATIC HYDROLYSIS OF CELLULOSE
Authors: SHEN GUANGLIN , TAO HONG , ZHAO MOUMING , YANG BAO , WEN DONGQI , YUAN QINGZHAO , RAO GUOHUA
Published: July 2009

In this work, the effect of oxidation pretreatment on the enzymatic hydrolysis of cellulose in tobacco stems was evaluated. A comparison was made between the effect of H2O2 pretreatment and conventional alkali pretreatment on the weight loss of cellulose, lignins and hemicelluloses of tobacco stems. The effects of H2O2 concentration, pretreatment time and temperature on the enzymatic hydrolysis of tobacco stems were investigated. This pretreatment could give a higher recovery of cellulose and better removal of lignin and hemicellulose than alkali‐only pretreatment. Compared with the untreated stems, the yield of reducing sugar pretreated by H2O2 pretreatment (pH 11.5, 0.6% H2O2) for 9 h at 60C increased 347.2%. The results of scanning electron microscope and X‐ray diffraction analysis also showed that the structural and crystalline properties of the tobacco stems were changed by pretreatment, and they were in favor of the following enzymatic hydrolysis. The optimal pretreatment conditions were 60C of temperature, 0.6% of H2O2 concentration and 9 h of time, which were calculated by orthogonal experiments.

PRACTICAL APPLICATIONS

Pretreatment on lignocellulosic materials to disrupt the recalcitrant structure is helpful for their bioconversion into low‐molecular weight substances. The tobacco stems were pretreated by H2O2 oxidation before subjecting to enzymatic hydrolysis by cellulase in this work. This pretreatment was confirmed effectively to improve the recovery of celllulose, and helpful to remove lignin and hemicellulose. Moreover, the yield of reducing sugar produced by cellulase hydrolysis was apparently improved. These results were helpful for the extensive development of tobacco stems.
Surveillance of Trend and Distribution of Stroke Mortality by Subtype, Age, Gender, and Geographic Areas in Tianjin, China, 1999–2006
Authors: Wang X. , Jiang G. , Choi B. C. K. , Wang D. , Wu T. , Pan Y. , Boulton M.
Published: July 2009

Background

The purpose of this study was to analyze the epidemiological trend and distribution of stroke mortality in the city of Tianjin, China, in order to provide evidence for the prevention and control of stroke.

Methods

The study was based on 102 718 cases of stroke mortality in Tianjin between 1999 and 2006. The cause of death was coded according to the International Classification of Diseases into stroke subtypes. Standardized mortality rates were calculated for stroke and its subtypes, adjusted for age and gender using the year 2000 world standard population. The age, gender, and geographic distribution of stroke and subtype mortality were analyzed. χ2-tests were used to determine the statistical significance of differences in mortality trends.

Results

The stroke mortality rate in Tianjin declined from 133·52/100000/year in 1999 to 102·52/100000/year in 2006. The stroke mortality rate for males was higher than that for females. Stroke mortality rates increased with increasing age. The subtypes of stroke have changed considerably in Tianjin. Hemorrhagic was major in 1999–2001, while cerebral infarction attained the first rank and accounted for more than 50% of stroke mortality in 2002–2006. The most pronounced finding was that the proportion of ischemic stroke was 66·65% in the urban population and over 20% higher than that in the rural area. Stroke in the suburban area was mainly hemorrhagic stroke, up to 62·67%.

Conclusions

There are significant differences in the distribution of stroke mortality by subtype, age, gender, and geographic areas in Tianjin, China. Various subtypes of stroke are associated with different risk factors and therefore require different public health prevention and control measures. This study provides pertinent information for formulation of measures for the prevention and control of stroke.
CADISP-Genetics: An International Project Searching for Genetic Risk Factors of Cervical Artery Dissections
Authors: Debette S. , Metso T. M. , Pezzini A. , Engelter S. T. , Leys D. , Lyrer P. , Metso A. J. , Brandt T. , Kloss M. , Lichy C. , Hausser I. , Touze E. , Markus H. S. , Abboud S. , Caso V. , Bersano A. , Grau A. , Altintas A. , Amouyel P. , Tatlisumak T. , Dallongeville J. , Grond-Ginsbach C. ,   on behalf of the CADISP-groupw†
Published: July 2009

Background

Cervical artery dissection (CAD) is a frequent cause of ischemic stroke, and occasionally death, in young adults. Several lines of evidence suggest a genetic predisposition to CAD. However, previous genetic studies have been inconclusive mainly due to insufficient numbers of patients. Our hypothesis is that CAD is a multifactorial disease caused by yet largely unidentified genetic variants and environmental factors, which may interact. Our aim is to identify genetic variants associated with an increased risk of CAD and possibly gene-environment interactions.

Methods

We organized a multinational European network, Cervical Artery Dissection and Ischemic Stroke Patients (CADISP), which aims at increasing our knowledge of the pathophysiological mechanisms of this disease in a large group of patients. Within this network, we are aiming to perform a de novo genetic association analysis using both a genome-wide and a candidate gene approach. For this purpose, DNA from approximately 1100 patients with CAD, and 2000 healthy controls is being collected. In addition, detailed clinical, laboratory, diagnostic, therapeutic, and outcome data are being collected from all participants applying predefined criteria and definitions in a standardized way. We are expecting to reach the above numbers of subjects by early 2009. Conclusions We present the strategy of a collaborative project searching for the genetic risk factors of CAD. The CADISP network will provide detailed and novel data on environmental risk factors and genetic susceptibility to CAD.
Bacterial Inactivation by Solar Ultraviolet Radiation Compared with Sensitivity to 254 nm Radiation
Authors: Coohill Thomas P. , Sagripanti Jose‐Luis
Published: July 2009

Our goal was to derive a quantitative factor that would allow us to predict the solar sensitivity of vegetative bacterial cells to natural solar radiation from the wealth of data collected for cells exposed to UVC (254 nm) radiation. We constructed a solar effectiveness spectrum for inactivation of vegetative bacterial cells by combining the available action spectra for vegetative cell killing in the solar range with the natural sunlight spectrum that reaches the ground. We then analyzed previous studies reporting the effects of solar radiation on vegetative bacterial cells and on bacterial spores. Although UVC‐sensitive cells were also more sensitive to solar radiation, we found no absolute numerical correlation between the relative solar sensitivity of vegetative cells and their sensitivity to 254 nm radiation. The sensitivity of bacterial spores to solar exposure during both summer and winter correlated closely to their UVC sensitivity. The estimates presented here should make it possible to reasonably predict the time it would take for natural solar UV to kill bacterial spores or with a lesser degree of accuracy, vegetative bacterial cells after dispersion from an infected host or after an accidental or intentional release.
Cationic Hypericin Derivatives as Novel Agents with Photobactericidal Activity: Synthesis and Photodynamic Inactivation of Propionibacterium acnes
Authors: Hager Beate , Strauss Wolfgang S. L. , Falk Heinz
Published: July 2009

The present communication describes for the first time the synthesis and preliminary testing of two cationic hypericin derivatives. Uncharged hypericin derivatives with ω,ω’‐attached C2‐linkers leading to a pyridyl or a 4‐dimethylaminophenyl residue were prepared and subsequently quaternized by means of iodomethane. Photobactericidal activity was assessed using Propionibacterium acnes. The quaternary N,N,N‐trimethyl‐anilinium derivative displayed a pronounced photodynamic inactivation of the bacteria at low incubation concentrations (<100 nm) and a short incubation time (1 h) after illumination with yellow light (590 nm, 20 J cm−2), whereas the photobactericidal efficacy of the N‐methyl‐pyridinium derivative was negligible under identical experimental conditions.
A Role for Hydrogen Peroxide in the Pro‐apoptotic Effects of Photodynamic Therapy
Authors: Price Michael , Terlecky Stanley R. , Kessel David
Published: July 2009

Although the first reactive oxygen species (ROS) formed during irradiation of photosensitized cells is almost invariably singlet molecular oxygen (1O2), other ROS have been implicated in the phototoxic effects of photodynamic therapy (PDT). Among these are superoxide anion radical (•O2−), hydrogen peroxide (H2O2) and hydroxyl radical (•OH). In this study, we investigated the role of H2O2 in the pro‐apoptotic response to PDT in murine leukemia P388 cells. A primary route for detoxification of cellular H2O2 involves the peroxisomal enzyme catalase. Inhibition of catalase activity by 3‐amino‐1,2,4‐triazole led to an increased apoptotic response. PDT‐induced apoptosis was impaired by addition of an exogenous recombinant catalase analog (CAT‐skl) that was specifically designed to enter cells and more efficiently localize in peroxisomes. A similar effect was observed upon addition of 2,2′‐bipyridine, a reagent that can chelate Fe+2, a co‐factor in the Fenton reaction that results in the conversion of H2O2 to •OH. These results provide evidence that formation of H2O2 during irradiation of photosensitized cells contributes to PDT efficacy.
Modeling environmentally associated morphological and genetic variation in a rainforest bird, and its application to conservation prioritization
Authors: Thomassen Henri A. , Buermann Wolfgang , Milá Borja , Graham Catherine H. , Cameron Susan E. , Schneider Christopher J. , Pollinger John P. , Saatchi Sassan , Wayne Robert K. , Smith Thomas B.
Published: July 2009

To better understand how environment shapes phenotypic and genetic variation, we explore the relationship between environmental variables across Ecuador and genetic and morphological variation in the wedge‐billed woodcreeper (Glyphorynchus spirurus), a common Neotropical rainforest bird species. Generalized dissimilarity models show that variation in amplified fragment length polymorphism markers was strongly associated with environmental variables on both sides of the Andes, but could also partially be explained by geographic distance on the western side of the Andes. Tarsus, wing, tail, and bill lengths and bill depth were well explained by environmental variables on the western side of the Andes, whereas only tarsus length was well explained on the eastern side. Regions that comprise the highest rates of genetic and phenotypic change occur along steep elevation gradients in the Andes. Such environmental gradients are likely to be particularly important for maximizing adaptive diversity to minimize the impacts of climate change. Using a framework for conservation prioritization based on preserving ecological and evolutionary processes, we found little overlap between currently protected areas in Ecuador and regions we predicted to be important in maximizing adaptive variation.
Current challenges in understanding melanogenesis: bridging chemistry, biological control, morphology, and function
Authors: Simon John D , Peles Dana , Wakamatsu Kazumasa , Ito Shosuke
Published: July 2009

Melanin is a natural pigment produced within organelles, melanosomes, located in melanocytes. Biological functions of melanosomes are often attributed to the unique chemical properties of the melanins they contain; however, the molecular structure of melanins, the mechanism by which the pigment is produced, and how the pigment is organized within the melanosome remains to be fully understood. In this review, we examine the current understanding of the initial chemical steps in the melanogenesis. Most natural melanins are mixtures of eumelanin and pheomelanin, and so after presenting the current understanding of the individual pigments, we focus on the mixed melanin systems, with a critical eye towards understanding how studies on individual melanin do and do not provide insight in the molecular aspects of their structures. We conclude the review with a discussion of important issues that must be addressed in future research efforts to more fully understand the relationship between molecular and functional properties of this important class of natural pigments.
The taming of the shrew? The immunology of corneal transplantation
Authors: Pleyer Uwe , Schlickeiser Stephan
Published: July 2009

Corneal transplantation, first reported a century ago, is the oldest and most frequent form of solid tissue transplantation. Although keratoplasty is also considered as the most successful transplant procedure, several studies indicate that the long term survival of corneal grafts is even lower than that of transplanted parenchymatous organs. Despite the immune privilege enjoyed by the cornea and anterior segment of the eye, immunologic graft rejection is a major limitation to corneal transplantation. This review gives an update on corneal immunobiology and the mechanisms of corneal graft rejection, focusing on antigen presentation, as well as on the molecular and cellular mediators of this particular immune response.
Obstacles to action in arthritis: a community case‐control study
Authors: HUTTON Ingrid , GAMBLE Greg , MCLEAN Grant , BUTCHER Hugh , GOW Peter , DALBETH Nicola
Published: July 2009

Objective: Despite the benefits of physical activity, people with arthritis are less active than the general population. The aim of this study was to determine the motivators and obstacles to physical activity for adults with arthritis.

Methods: Participants were identified from the Obstacles to Action Study, a community based study of 8163 adults, which explored barriers and motivators to physical activity. A 1 : 1 case‐control study was designed; cases were identified as those participants who reported arthritis (n = 1106). Each case was matched with an age, sex and ethnicity‐matched non‐arthritis control (n = 1106).

Results: Cases were less likely to achieve recommended physical activity targets (58.8%vs. 68.1%P = 0.00001). Furthermore, fewer people with arthritis believed that physical activity would help them lead healthy lives (86.7%vs. 91.3%P = 0.006) or viewed physical activity as a priority (53.8%vs. 59.8%P = 0.005). Cases were less confident in their abilities to try a new activity (37.1%vs. 43.7%P = 0.002) or maintain a healthy weight (65.0%vs. 74.3%P = 0.00001). Cases also reported greater negative impact scores for barriers to activity, particularly arthritis, accessibility, cost and discomfort while exercising. Motivators and environmental barriers to activity were similar for cases and controls. These findings persisted after adjusting for educational level, body mass index and comorbidities.

Conclusion: People with arthritis are less active and demonstrate different attitudes toward physical activity. Although people with arthritis identify similar environmental barriers, they have different psychosocial barriers. In order to design effective physical activity programs for people with arthritis, these barriers must be specifically addressed.
Bilateral atypical femoral diaphyseal fractures in a patient treated with alendronate sodium
Authors: LEE Joon Kiong
Published: July 2009

Antiresorptive agents have been used as primary or first‐line therapy in managing patients with osteoporosis. Bisphosphonates in particular are used widely to reduce bone resorption, increase bone mineral density, improve bone quality and therefore reduce fracture risk. However, prolonged use of bisphosphonates may cause over‐suppression of bone resorption, leading on to accumulation of micro‐damage in bone. This in turn might lead on to atypical femoral fractures. A patient treated with alendronate sodium for 8 years, and presenting with bilateral atypical femoral diaphyseal fractures is reported. X‐rays of both femurs showed typical horizontal fracture line involving the thick lateral cortex with short oblique fracture pattern over the medial cortex. This fracture pattern was further confirmed with intra‐operative examination of the fracture ends. Histopathological examination of the endocortical fragment removed from the proximal fracture end showed absence of osteoclasts and osteoblasts. Bone mineral density with dual energy X‐ray absorptiometry (DXA) scan showed osteopenia over the femoral neck. Blood investigations did not show significant abnormalities. Bone turnover marker levels were not reliable, as presence of fracture might have altered the marker levels. Both femoral fractures united well. The patient reported here had complete pictures on X‐ray examination, intra‐operative findings, histopathological examination, DXA, as well as blood test results. Complete data should be collected from patients treated with alendronate sodium presenting with atypical femoral fractures to show any link between the use of alendronate sodium with atypical fracture of femur.
The Pho regulon influences biofilm formation and type three secretion in Pseudomonas aeruginosa
Authors: Haddad Ahmed , Jensen Vanessa , Becker Tanja , Häussler Susanne
Published: July 2009

Research into the molecular mechanisms of the switch from highly motile to biofilm forming Pseudomonas fluorescens bacteria recently uncovered a role of inorganic phosphate as an important environmental regulatory factor to control c‐di‐GMP levels in the cell. In this study we present evidence that in the opportunistic pathogen P. aeruginosa the Pho regulon inhibits biofilm formation and is required for the repression of the type three secretion system. We furthermore identified an EAL domain protein as a downstream effector of the Pho regulon, which at least partially mediated the observed inhibition. Interestingly, inhibition of the P. aeruginosa virulence phenotype was Pho regulon‐dependent in both a PA14 and a PAO1 strain background; however, in PA14 this inhibition was independent on the availability of inorganic phosphate, whereas in PAO1 phosphate enhanced biofilm formation independently of the inhibitory activity of the Pho regulon. These results clearly show that the Pho regulon contributes to the expression of the virulence phenotype in P. aeruginosa and add even more complexity to the strain‐specific regulation of bacterial behaviour by environmental cues.
Perfect powers from products of consecutive terms in arithmetic progression
Authors: Győry K. , Hajdu L. , Pintér Á.
Published: July 2009

We prove that for any positive integersx,dandkwith gcd (x,d)=1 and 3<k<35, the productx(x+d)⋯(x+(k−1)d) cannot be a perfect power. This yields a considerable extension of previous results of Győryet al.and Bennettet al., which covered the cases wherek≤11. We also establish more general theorems for the case wherexcan also be a negative integer and where the product yields an almost perfect power. As in the proofs of the earlier theorems, for fixedkwe reduce the problem to systems of ternary equations. However, our results do not follow as a mere computational sharpening of the approach utilized previously; instead, they require the introduction of fundamentally new ideas. Fork>11, a large number of new ternary equations arise, which we solve by combining the Frey curve and Galois representation approach with local and cyclotomic considerations. Furthermore, the number of systems of equations grows so rapidly withkthat, in contrast with the previous proofs, it is practically impossible to handle the various cases in the usual manner. The main novelty of this paper lies in the development of an algorithm for our proofs, which enables us to use a computer. We apply an efficient, iterated combination of our procedure for solving the new ternary equations that arise with several sieves based on the ternary equations already solved. In this way, we are able to exclude the solvability of the enormous number of systems of equations under consideration. Our general algorithm seems to work for larger values ofkas well, although there is, of course, a computational time constraint.
Chromium Activity Measurements in Nickel Based Alloys for Very High Temperature Reactors: Inconel 617, Haynes 230, and Model Alloys
Authors: Gossé Stéphane , Alpettaz Thierry , Chatain Sylvie , Guéneau Christine
Published: July 2009

The alloys Haynes 230 and Inconel 617 are potential candidates for the intermediate heat exchangers (IHXs) of (very) high temperature reactors ((V)-HTRs). The behavior under corrosion of these alloys by the (V)-HTR coolant (impure helium) is an important selection criterion because it defines the service life of these components. At high temperature, the Haynes 230 is likely to develop a chromium oxide on the surface. This layer protects from the exchanges with the surrounding medium and thus confers certain passivity on metal. At very high temperature, the initial microstructure made up of austenitic grains and coarse intra- and intergranular M6C carbide grains rich in W will evolve. The M6C carbides remain and some M23C6 richer in Cr appear. Then, carbon can reduce the protective oxide layer. The alloy loses its protective coating and can corrode quickly. Experimental investigations were performed on these nickel based alloys under an impure helium flow (Rouillard, F., 2007, “Mécanismes de formation et de destruction de la couche d’oxyde sur un alliage chrominoformeur en milieu HTR,” Ph.D. thesis, Ecole des Mines de Saint-Etienne, France). To predict the surface reactivity of chromium under impure helium, it is necessary to determine its chemical activity in a temperature range close to the operating conditions of the heat exchangers (T≈1273 K). For that, high temperature mass spectrometry measurements coupled to multiple effusion Knudsen cells are carried out on several samples: Haynes 230, Inconel 617, and model alloys 1178, 1181, and 1201. This coupling makes it possible for the thermodynamic equilibrium to be obtained between the vapor phase and the condensed phase of the sample. The measurement of the chromium ionic intensity (I) of the molecular beam resulting from a cell containing an alloy provides the values of partial pressure according to the temperature. This value is compared with that of the pure substance (Cr) at the same temperature. These calculations provide thermodynamic data characteristic of the chromium behavior in these alloys. These activity results call into question those previously measured by Hilpert and Ali-Khan (1978, “Mass Spectrometric Studies of Alloys Proposed for High-Temperature Reactor Systems: I. Alloy IN-643,” J. Nucl. Mater., 78, pp. 265–271; 1979, “Mass Spectrometric Studies of Alloys Proposed for High-Temperature Reactor Systems: II. Inconel Alloy 617 and Nimomic Alloy PE 13,” J. Nucl. Mater., 80, pp. 126–131), largely used in the literature.
Measurement of Biodiesel Blend and Conventional Diesel Spray Structure Using X-Ray Radiography
Authors: Kastengren A. L. , Powell C. F. , Im K.-S. , Wang Y.-J. , Wang J.
Published: July 2009

The near-nozzle structure of several nonevaporating biodiesel-blend sprays has been studied using X-ray radiography. Radiography allows quantitative measurements of the fuel distribution in sprays to be made with high temporal and spatial resolution. Measurements have been made at different values of injection pressure, ambient density, and with two different nozzle geometries to understand the influences of these parameters on the spray structure of the biodiesel blend. These measurements have been compared with corresponding measurements of Viscor, a diesel calibration fluid, to demonstrate the fuel effects on the spray structure. Generally, the biodiesel-blend spray has a similar structure to the spray of Viscor. For the nonhydroground nozzle used in this study, the biodiesel-blend spray has a slightly slower penetration into the ambient gas than the Viscor spray. The cone angle of the biodiesel-blend spray is generally smaller than that of the Viscor spray, indicating that the biodiesel-blend spray is denser than the Viscor spray. For the hydroground nozzle, both fuels produce sprays with initially wide cone angles that transition to narrow sprays during the steady-state portion of the injection event. These variations in cone angle with time occur later for the biodiesel-blend spray than for the Viscor spray, indicating that the dynamics of the injector needle as it opens are somewhat different for the two fuels.
Deformation Bounds for Cyclically Loaded Shell Structures Operating Under Creep Conditions
Authors: Cocks Alan C. F. , Leckie F. A.
Published: July 2009

Constitutive relations, based on the Bailey-Orowan’s creep theory, are used to develop a maximum work condition which includes the influence of an internal state. A bounding theorem on displacement is obtained for structures subjected to cyclic loading. An application of the bound is illustrated.
Possible Experimental X-Ray Diffractometry Evidence of Couple-Stresses
Authors: Gola M. M. , Coppa P.
Published: July 2009

The technique of measuring residual strain using X-ray diffractometry is examined with respect to prior attempts to experimentally validate couple-stress or micropolar theories. When subjected to grinding, polycrystalline materials (such as steel or others of technical interest) exhibit residual strains with very peculiar features whose explanation is still controversial. This paper suggests how a formally correct explanation can be formulated in terms of the theories based on couple-stresses. This new hypothesis is critically compared with competing theories found in the recent literature. It is proposed that, for the case of thin layers subjected to extremely high stress gradients, X-ray diffractometry is the most appropriate technique for investigating couple-stress or micropolar phenomena.
Stiffness of an Elastic Circular Cylinder of Finite Length
Authors: Robert Michel , Keer L. M.
Published: July 2009

An analytical solution is proposed to determine the stiffness of an elastic circular cylinder clamped at one end, while the other end undergoes any rigid-body displacement; the lateral surface is stress-free. The validity of Saint-Venant’s principle has been assessed by computing the solution of this problem for cylinders having different aspect ratios. On the other hand, the solution agrees with the thin layer theory when the aspect ratio becomes infinitely small. Therefore, the solution proposed here fills up the gap between beam theory and thin layer theory.
The Interface Crack Under Combined Loading
Authors: Gautesen A. K. , Dundurs John
Published: July 2009

The interface crack subjected to a combined tension-compression and shear loading is considered in the Comninou formulation, which by properly incorporating contact zones at the crack tips avoids contradictions, such as overlapping of material. It is shown that the resulting integral equation can be solved exactly. Moreover, simple asymptotic — yet very accurate — formulae are derived for the quantities of major physical interest and a comparison made with the previous results given by Comninou.
Longitudinal Shearing of a Weakly Bonded Fiber Composite
Authors: Steif Paul S. , Dollar Anna
Published: July 2009

The longitudinal shearing of a unidirectional fiber composite which sustains slippage at the fiber-matrix interface is studied theoretically. An expression for the effective shear modulus of the composite, assuming a dilute concentration of fibers, is derived. The necessary quantities are found from the solution to the problem of a single slipping fiber in an infinite matrix. A singular integral equation governing this problem is derived and solved numerically. Results for the progression of slip and for the effective shear modulus are presented.
Post-Buckling Analysis of Stiffened Laminated Panel
Authors: Sheinman Izhak , Frostig Yeoshua
Published: July 2009

An analytical-numerical procedure is applied to investigate the post-buckling behavior of a composite laminated stiffened panel. The panel is modeled by plate elements for which the nonlinear equations are derived (via a variational principle) in terms of the lateral displacement and Airy stress function, and treated by resolving the variables into eigenfunctions in conjunction with a finite-difference scheme.
Response of a Compliant Slab to Viscous Incompressible Fluid Flow
Authors: Evrensel C. A. , Kalnins A.
Published: July 2009

The interaction of a compliant slab and the flow of a viscous fluid is explored theoretically. Both laminar and turbulent boundary-layer flow cases are considered. The slab is treated as an infinite, elastic or viscoelastic solid of finite thickness, bonded to a rigid half-space. The two media are coupled through stresses and velocities, in both tangential and normal directions, on the deformed surface of the slab. The proposed mathematical model is used to predict the appearance of unstable surface waves of the coating. According to the model, instabilities of a highly viscoelastic slab originate in the form of waves with phase speeds at about 2.3 percent of the flow velocity while the wave speed for a slab with zero to moderate viscosity is in the range of 50–60 percent of the flow velocity, which confirms previous experimental results. The predicted onset velocities of slow propagating waves for turbulent flow over plastisol gel are within 10 percent of those observed experimentally.
Equivalent Linearization for Hysteretic Systems Under Random Excitation
Authors: Wen Y. K.
Published: July 2009

A method of equivalent linearization for smooth hysteretic systems under random excitation is proposed. The hysteretic restoring force is modeled by a nonlinear differential equation and the equation of motion is linearized directly in closed form without recourse to Krylov-Bogoliubov technique. Compared with previously proposed similar methods, the formulation of the present method is versatile and considerably simpler. The accuracy of this method is verified against Monte-Carlo simulation for all response levels. It has a great potential in the analysis of multidegree-of-freedom and degrading systems.
The Stabilization of a North-Seeking Platform Using a Dynamically Tuned Hooke’s Joint Gyroscope
Authors: Burdess J. S. , Fox C. H. J.
Published: July 2009

The paper shows that the ideally tuned Hooke’s joint gyroscope is capable of operating as a gyrocompass. The dynamic response of the compass is examined in detail and its accuracy as a north-seeking device is assessed. It it shown that small amounts of mistuning will result in gross errors. The need for precision tuning is eliminated by supporting the gyroscope on a single-degree-of-freedom platform. It is shown that if the platform is driven via feedback of the gyrorotor displacement in azimuth then the response of the combined system is essentially that of the ideal gyroscope. The overall system is insensitive to misturning errors and will automatically align the gyrospin axis with true north irrespective of any initial offset. The effects of damping, mass unbalance, and platform misalignment are assessed.
An Explosive Loading Technique for the Uniform Expansion of 304 Stainless Steel Cylinders at High Strain Rates
Authors: Forrestal M. J. , Duggin B. W. , Butler R. I.
Published: July 2009

A new explosive loading technique is applied to study the uniform plastic expansion and fracture initiation of 304 stainless steel cylinders. An annular layer of dry PETN high explosive is placed in contact with the inner diameter of the cylinder and surface-initiated with an array of etched copper bridgewires. This technique produces a simultaneous detonation of the explosive and a nearly uniform expansion of the stainless steel cylinders.
Optimal Cool-Down in Linear Viscoelasticity
Authors: Weitsman Y.
Published: July 2009

An optimal temperature path is derived for a thin viscoelastic plate which is cooled from a stress-free state against geometric constraints. The optimal path, which minimizes the final residual stress due to cool down, is shown to possess discontinuities at the initial and final times and to be smooth and continuous during all intermediate times. An iterative convergent scheme is provided for a wide class of linear viscoelastic responses and typical paths are determined for two specific cases. In addition, a time-temperature path which maintains constant stress values during cool-down is derived. The problem is motivated by the cooling process of composite materials.
Fabrics: Orthotropic Materials With a Stress-Free Shear Mode
Authors: Christoffersen J.
Published: July 2009

A material model of elastic fabrics is proposed. In this, orthotropy and a vanishing shear rigidity is assumed. Full nonlinear equations are derived and simplifications valid for small material rotations are proposed. Even the simplified model is nonlinear, but it is demonstrated that, in certain instances, a linearization, leading to harmonic equations, is admissible. This is exemplified by the case of a crack in an infinite sheet.
On the Singular Eigenfunctions for Plane Harmonic Problems in Composite Regions
Authors: Sinclair G. B.
Published: July 2009

This paper is concerned with the singular behavior of harmonic functions at the vertex of a plane, composite, wedge region. Separable harmonic functions which include logarithmic terms are investigated for their possible existence in the vicinity of the vertex. The eigenequations governing existence are examined and explicit determination of the singular eigenvalues made for several combinations of boundary and interface conditions. The results enable an appreciation of the possible singular nature in such problems which aids any complete (numerical) analysis.
Transient and Residual Thermoviscoelastic Stresses in Glass
Authors: Crochet M. J. , Denayer A.
Published: July 2009

After discussing the constitutive relations of inorganic glasses and their strong dependence upon temperature history, we construct a numerical algorithm in order to calculate transient and residual stresses during manufacture. The method is applied to calculating stresses generated during the annealing process of bottles.
A Generalized von Mises Criterion for Yield and Fracture
Authors: Yang W. H.
Published: July 2009

Yield and fracture criteria for real materials are to a varying degree affected by a state of hydrostatic stress. Some materials, after certain deformation history, exhibit different yield point when the direction of the stress is reversed, a behavior known as the Bauschinger effect. These physical phenomena are not represented by the von Mises criterion. Based on a convexity theorem of matrices, a generalization of the von Mises criterion is presented. The new criterion satisfies the convexity requirement of plasticity theory and, with two scalar functions of deformation history α and β, produces a class of hardening behavior. The current values of α and β account for the effect of hydrostatic stress and an aspect of the Bauschinger effect on yield and fracture. The generalized criterion reduces to the form of the von Mises criterion as a special case.
Dynamic Stability of Annular Plates Under Pulsating Torsion
Authors: Tani J. , Nakamura T.
Published: July 2009

The dynamic stability of annular plates under periodic torsion is analyzed by means of the Galerkin method in conjunction with Hsu’s procedure. The instability regions associated with both principal and combination parametric resonances are clarified for relatively low frequency ranges. It is found that under the purely periodic torsion only the combination instability region exists, while under the simultaneous action of the static torsion the principal instability region exists also. The circumferential phase difference of two vibration modes excited simultaneously at the resonance is also found to change remarkably the relative width of the instability region.
Dynamic Response of a Plate With Arbitrary Shape
Authors: Nagaya K.
Published: July 2009

This paper is concerned with a method for solving dynamic response problems of a thin plate with arbitrary shape based on the classical plate theory. The result for an arbitrarily shaped plate subjected to general transient loads is obtained by utilizing the Fourier expansion collocation method. As an example, the dynamic response of a truncated elliptical plate subjected to a uniformly distributed exponentially decaying impact load is investigated. To verify the present method, numerical calculations are also carried out for a circular plate, and the results obtained are compared with the exact ones.
Homogenization and Smoothing: A Unified View of Two Derivations of Effective Property Theories and Extensions
Authors: Fishman L. , McCoy J. J.
Published: July 2009

The response of a continuum characterized by two widely differing length scales, parameterized by the dimensionless ratio ε, is considered in the context of the composite materials problem. The development of a bulk property theory appropriate in the ε → 0 limit is examined, both from the perspective of the deterministic homogenization literature and the smoothing method associated with statistical continuum theory, and a unified framework is established. The extension of bulk property theories through the development of ordered expansions in powers of ε is discussed and specifically related to analogous treatments in linear-gas relaxation theory.
On the Computation of the Confluent Hypergeometric Function at Densely Spaced Points
Authors: Spanos P-T. D.
Published: July 2009

An algorithm is described for computing the values of the confluent hypergeometric function at several points spaced densely along an interval of real numbers. Numerical data obtained by using this algorithm and pertaining to a commonly made approximation for the first-passage problem of the response amplitude of a lightly damped and randomly excited linear oscillator are presented.
On the Uniqueness and Stability of Endochronic Theory
Authors: Hsieh B. J.
Published: July 2009

Several numerical and analytical analyses are described which evaluate the uniqueness and stability of solutions of mechanical models whose material behaviors are governed by the endochronic theory of plasticity. It has been found that the simplest form of this theory does show some “material instability” in the sense it does not satisfy Drucker’s postulate when subjected to certain conditions. In other words, an endochronic material creeps under the action of applied force for dynamic problems. However, this “instability” or “lack of a hysteresis loop” can be circumvented by using more general forms of the endochronic theory when necessary. It is also shown that the endochronic solution is at least as unique as that of the elastoplastic theory. No numerical difficulties particular to this theory are observed even when the simplest form is used.
A Nonlinear Theory of Viscoelasticity for Application to Elastomers
Authors: Christensen R. M.
Published: July 2009

A simple nonlinear theory of viscoelasticity has been developed for application to elastomers. The theory is the viscoelastic generalization of the kinetic theory of rubber elasticity, and it is used to model time and rate-dependent effects. The method of derivation reveals that the theory is applicable to stress-imposed rather than strain-imposed conditions. Thus the creep test provides the logical means for deducing the material properties of the theory, while the relaxation-test technique is not applicable. When the long time asymptotic state is at the same level of deformation for both tests, the sources and degree of nonlinearity in relaxation tests are shown to be more severe than those involved in creep tests. A simple means is deduced for obtaining the creep function from the nonlinear creep response of the elastomer.
Plastic Deformation of a Laminated Plate With a Hole
Authors: Bahei-El-Din Y. A. , Dvorak G. J.
Published: July 2009

The elastic-plastic behavior of a (0/90) symmetric FP-Al plate containing a circular hole is investigated using the finite-element method. Of principal concern are plastic yielding at the circular hole and fracture of the plate caused by failure of the fiber at the hole. The results illustrate the significance of plasticity in deformation of metal-matrix composites. The behavior of the laminated plate is compared with that of a geometrically similar plate made of an unreinforced matrix material, for uniaxial loading/unloading/reloading sequences. The comparison reveals significant differences in the role of plastic deformation in these two materials. Specifically, plastic yielding in the matrix of the laminated plate at the circular hole leads to a substantial increase in the local stress concentration in the elastic fibers adjacent to the hole boundary. Also, it is found that the fiber reinforcement causes a large increase in the stiffness and strength of the composite, but only a minor elevation of its yield strength. Therefore, to take advantage of the mechanical properties of the metal matrix composite material, it is necessary to admit working loads which exceed its elastic limit.
On the Unbonded Contact Between Plates and Layered Cylinders
Authors: Soong T.-C. , Li C.
Published: July 2009

An approximate solution is presented for the deflection of a thin plate and for the stresses and deformation of a layered circular cylinder in which the plate is pressed against the layered soft cylinder by a hard cylinder. The contact is considered as frictionless, and the plate has an initial curvature. Since the load on the plate is radial and the initial curvature is arbitrary, nonlinear beam theory is used. The state of the layered circular cylinder is described by a general stress function. The collocation method is used to relate loading and displacements between the contact surface of the plate and the soft substrate of the cylinder.