bluuebunny/crossref_metadata_2025 huggingface dataset:
Irsogladine maleate abolishes the increase in interleukin‐8 levels caused by outer membrane protein 29 from Aggregatibacter (Actinobacillus) actinomycetemcomitans through the ERK pathway in human gingival epithelial cells
Authors: Kishimoto A. , Fujita T. , Shiba H. , Komatsuzawa H. , Takeda K. , Kajiya M. , Hayashida K. , Kawaguchi H. , Kurihara H.
Published: June 2008

Background and Objective:  Irsogladine maleate (IM) suppresses the increase in interleukin (IL)‐8 production induced by outer membrane protein (OMP) 29 from Aggregatibacter (Actinobacillus) actinomycetemcomitans in cultures of human gingival epithelial cells (HGEC). However, how IM suppresses the OMP29‐induced increase in IL‐8 expression remains unknown. In this study, we focused on intracellular signaling pathways to elucidate the mechanism behind the suppression.

Material and Methods:  HGEC, which had been pretreated with inhibitors of intracellular signaling molecules, were exposed to OMP29 (1 μg/mL) with or without IM (1 μm). IL‐8 expression at the mRNA and protein levels was examined by real‐time polymerase chain reaction and enzyme‐linked immunosorbent assay, respectively. Extracellular signal‐regulated kinase (ERK) activity was measured with a p44/42 mitogen‐activated protein kinase assay kit.

Results:  An ERK inhibitor, PD98059, as well as IM, obviated the OMP29‐induced increase in IL‐8 levels in HGEC. A Jun kinase inhibitor, SP600125, and a nuclear factor κB inhibitor, PDTC, did not influence the OMP29‐induced increase in IL‐8 mRNA expression. The OMP29 stimulated phosphorylation of ERK in HGEC. Irsogladine maleate inhibited the phosphorylation.

Conclusion:  The suppression of the phosphorylation of ERK by IM in HGEC culminates in inhibition of the OMP29‐induced increase in IL‐8.
Differential gender effects of a reduced‐calorie diet on systemic inflammatory and immune parameters in nonhuman primates
Authors: Ebersole J. L. , Steffen M. J. , Reynolds M. A. , Branch‐Mays G. L. , Dawson D. R. , Novak K. F. , Gunsolley J. C. , Mattison J. A. , Ingram D. K. , Novak M. J.
Published: June 2008

Background and Objective:  Dietary manipulation, including caloric restriction, has been shown to impact host response capabilities significantly, particularly in association with aging. This investigation compared systemic inflammatory and immune‐response molecules in rhesus monkeys (Macaca mulatta).

Material and Methods:  Monkeys on continuous long‐term calorie‐restricted diets and a matched group of animals on a control ad libitum diet, were examined for systemic response profiles including the effects of both gender and aging.

Results:  The results demonstrated that haptoglobin and α1‐antiglycoprotein levels were elevated in the serum of male monkeys. Serum IgG responses to Campylobacter rectus, Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis were significantly elevated in female monkeys. While only the antibody to Fusobacterium nucleatum was significantly affected by the calorie‐restricted diet in female monkeys, antibody levels to Prevotella intermedia, C. rectus and Treponema denticola demonstrated a similar trend.

Conclusion:  In this investigation, only certain serum antibody levels were influenced by the age of male animals, which was seemingly related to increasing clinical disease in this gender. More generally, analytes were modulated by gender and/or diet in this oral model system of mucosal microbial challenge.
Distribution of 10 periodontal bacterial species in children and adolescents over a 7‐year period
Authors: Nakano K , Miyamoto E , Tamura K , Nemoto H , Fujita K , Nomura R , Ooshima T
Published: June 2008

Objective:  There is scant information available regarding the distribution of periodontal bacterial species in children and adolescents over an extended period. The purpose of this study was to compare bacterial profiles in the same individuals over a period of 7 years.

Subject and methods:  Twenty‐six children and adolescents from whom dental plaque and saliva specimens were obtained during both the first (1999–2000) and second (2006–2007) periods, were analyzed. Bacterial DNA was extracted from each specimen and the presence of 10 periodontal bacterial species was determined using a PCR method, with a focus on the red complex species of Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia.

Results:  Subjects with red complex species in saliva specimens obtained during the second collection possessed a significantly higher number of total bacterial species than those without. The detection rate of the red complex species in the second collection period samples was significantly greater in subjects who had two or more species detected in samples taken during the first collection compared with the other subjects.

Conclusion:  Subjects possessing red complex species may be at possible risk for infection with a high number of periodontal bacterial species during adolescent and younger adult years.
An internal ribosome entry site mediates the initiation of soluble guanylyl cyclase β2 mRNA translation
Authors: Vazquez‐Padron Roberto I. , Pham Si M. , Mateu Dania , Khan Sheik , Aitouche Abdelouahab
Published: June 2008

The soluble guanylyl cyclases (sGC), the receptor for nitric oxide, are heterodimers consisting of an α‐ and β‐subunit. This study aimed to investigate the translational mechanism of the sGC β2‐subunit. Two mRNA species for sGC β2 were isolated from human kidney. These transcripts had dissimilar 5′‐untranslated regions (5′‐UTRs). The most abundant sGC β2 mRNA showed numerous upstream open reading frames (ORFs) and stable secondary structures that inhibitedin vivoandin vitrotranslation.To evaluate whether these 5′‐UTRs harbored an internal ribosome entry site (IRES) that allows translation by an alternative mechanism, we inserted these regions between the two luciferase genes of a bicistronic vector. Transfection of those genetic constructs into HeLa cells demonstrated that both sGC β2 leaders had IRES activity in a cell‐type dependent manner. Finally, the secondary structural model of the sGC β2 5′‐UTR predicts a Y‐type pseudoknot that characterizes the IRES of cellular mRNAs. In conclusion, our findings suggest that sGC β2 5′‐UTRs have IRES activity that may permit sGC β2 expression under conditions that are not optimal for scanning‐dependent translation.
Ribosome assembly in Escherichia coli strains lacking the RNA helicase DeaD/CsdA or DbpA
Authors: Peil Lauri , Virumäe Kai , Remme Jaanus
Published: June 2008

Ribosome subunit assembly in bacteria is a fast and efficient process. Among the nonribosomal proteins involved in ribosome biogenesis are RNA helicases. We describe ribosome biogenesis in Escherichia coli strains lacking RNA helicase DeaD (CsdA) or DbpA. Ribosome large subunit assembly intermediate particles (40S) accumulate at 25 °C and at 37 °C in the absence of DeaD but not without DbpA. 23S rRNA is incompletely processed in the 40S and 50S particles of the DeaD− strain. Pulse labeling showed that the 40S particles are converted nearly completely into functional ribosomes. The rate of large ribosomal subunit assembly was reduced about four times in DeaD‐deficient cells. Functional activity tests of the ribosomal particles demonstrated that the final step of 50S assembly, the activation step, was affected when DeaD was not present. The results are compatible with the model that predicts multiple DeaD‐catalyzed structural transitions of the ribosome large subunit assembly.
Expression of resistance to Leptosphaeria maculans in Brassica napus double haploid lines in France and Australia is influenced by location
Authors: Delourme R. , Brun H. , Ermel M. , Lucas M.O. , Vallee P. , Domin C. , Walton G. , Li Hua , Sivasithamparam K. , Barbetti M.J.
Published: June 2008

Blackleg, caused by Leptosphaeria maculans, is a major disease of oilseed rape (Brassica napus), worldwide, including Australia and France. The aims of these studies were first, to determine if higher levels of resistance to L. maculans could be generated in double haploid (DH) lines derived from spring‐type B. napus cv. Grouse, which has a good level of field resistance to blackleg; and second, to determine whether the resistance to blackleg disease of individual DH lines responds differentially to different L. maculans field populations within and between the two countries. DH lines were extracted from cv. Grouse and tested in field experiments carried out in both France and Australia against natural L. maculans populations. Extracting and screening DH lines were an effective means to select individual lines with greatly improved expression of resistance to blackleg crown canker disease in comparison with the original parental population. However, relative disease resistance rankings for DH lines were not always consistent between sites. The higher level of resistance in France was shown to be because of a high expression level of quantitative resistance in the French growing conditions. Big differences were observed for some DH lines between the 2004 and the 2005 field sites in Australia where the L. maculans populations differed by their virulence on single dominant gene‐based resistant lines derived from Brassica rapa ssp. sylvestris. This differential behaviour could not be clearly explained by the specific resistance genes until now identified in these DH lines. This investigation highlights the potential to derive DH lines with superior levels of resistance to L. maculans compared with parental populations. However, in locations with particularly high pathogen diversity, such as in southern Australia, multiyear and multisite evaluations should be performed to screen for the most efficient material in different situations.
Sexually Transmitted Infection Among Adolescents Receiving Special Education Services
Authors: Mandell David S. , Eleey Catharine C. , Cederbaum Julie A. , Noll Elizabeth , Katherine Hutchinson M. , Jemmott Loretta S. , Blank Michael B.
Published: June 2008

Background:  To estimate the relative risk of sexually transmitted infections (STIs) among children identified as having learning disabilities through the special education system.

Methods:  This cross‐sectional study used special education data and Medicaid data from Philadelphia, Pennsylvania, for calendar year 2002. The sample comprised 51,234 Medicaid‐eligible children, aged 12‐17 years, 8015 of whom were receiving special education services. Claims associated with diagnoses of STIs were abstracted, and logistic regression was used to estimate the odds of STI among children in different special education categories.

Results:  There were 3% of males and 5% of females who were treated for an STI through the Medicaid system in 2002. Among females, those in the mental retardation (MR) category were at greatest risk (6.9%) and those in the emotionally disturbed or “no special education” category at lowest risk (4.9% each). Among males, STIs were most prevalent among those classified as mentally gifted (6.7%) and lowest among those in the MR category (3.0%). In adjusted analyses, males with specific learning disabilities and females with MR or who were academically gifted were at excess risk for STIs.

Conclusions:  The finding that children with learning disabilities are at similar or greater risk for contracting STIs as other youth suggests the need to further understand their risk behaviors and the potential need to develop prevention programs specific to their learning needs.
Is Immigrant Status Relevant in School Violence Research? An Analysis With Latino Students
Authors: Peguero Anthony A.
Published: June 2008

Background:  The role of race and ethnicity is consistently found to be linked to the likelihood of students experiencing school violence–related outcomes; however, the findings are not always consistent. The variation of likelihood, as well as the type, of student‐related school violence outcome among the Latino student population may be attributed to immigrant status.

Methods:  Drawing from the Education Longitudinal Study of 2002, this research investigates if the role of immigrant status and English proficiency are pertinent for 1457 nationally representative public school Latino students’ experiences with school violence–related outcomes.

Results:  Third‐generation immigrant students were more likely than first‐ and second‐generation students to be victimized while at school, as well as receive a formal disciplinary school sanction. On the other hand, first‐generation immigrant children were less likely to be a victim of crime while at school and receive a formal disciplinary sanction in comparison to second‐ and third‐generation immigrants. However, first‐generation immigrant students were the most likely to feel unsafe at school. Additionally, nonnative English‐speaking students were more likely to report being a victim of school violence in comparison to native English speakers.

Conclusions:  This study indicates that immigrant status–related variables should be included in school violence research. Furthering the investigation of school and local community characteristics of immigration and assimilation and their impact upon children’s lives and their exposure to violence is essential for a growing immigrant population.
Regional differences in length at sexual maturity for female blue whales based on recovered Soviet whaling data
Authors: Branch T. A. , Mikhalev Y. A.
Published: June 2008

Abstract

New blue whale ovarian corpora data from illegal Soviet catches in the Southern Hemisphere and northern Indian Ocean were recovered from the original logbooks. Catches north of 52°S were assumed to be pygmy blue whales (Balaenoptera musculus brevicauda, n= 1,272); those south of 56°S were assumed to be Antarctic (true) blue whales (B. m. intermedia, n= 153). Three probable Antarctic blue whales north of 52°S were excluded. Lengths at which 50% and 95% of females become sexually mature (L50 and L95) were estimated from a Bayesian logistic model. These estimates are more precise than previous Japanese estimates because Soviet catches below the legal minimum of 70 ft (21.3 m) were 32 times greater. For pygmy blue whales L50 was 19.2 m (95% interval 19.1–19.3 m) and L95 was 20.5 m (95% interval 20.4–20.7 m). Antarctic L50 (23.4 m, 95% interval 22.9–23.9 m) was much longer than L50 for pygmy blue whale regions (18.4–19.9 m). The median L50 for the northern Indian Ocean was 0.5–0.6 m shorter than for pygmy blue whales from other regions; although statistically significant, these small length differences provide little support for northern Indian Ocean blue whales being a separate subspecies, B. m. indica.
Deuterobiosphere the Chemosynthetic Second Biosphere of the Globe. A First Review
Authors: POR Francis D.
Published: June 2008

With the discovery of Ophel, a chemosynthesis‐based continental subterranean environment (Por 2007), it became evident that such environments, previously known only from the sea, are spanning the world as a parallel biosphere, the deuterobiosphere. In this preliminary contribution the different known biomes of the deuterobiosphere are reviewed and some general and comparative features are listed.
Alien species of mammals and their impact on natural ecosystems in the biosphere reserves of Russia
Authors: NERONOV Valery M. , KHLYAP Ludmila A. , BOBROV Vladimir V. , WARSHAVSKY Andrey A.
Published: June 2008

The paper analyses the results of a survey of 37 Russian biosphere reserves using questionnaires concerning the presence of alien species of mammals, their pathways of penetration, and their impacts on protected ecosystems. The penetration of alien mammals into terrestrial ecosystems of Russia is extensive, both in places with maximum human environmental impact (inhabited areas and agricultural lands) and in biosphere reserves with minimal human impact. There are 62 mammal species registered as alien in Russian ecosystems and they account for 22% of the terrestrial mammal fauna of Russia. The percentage of alien species in biosphere reserves is 32.6% at most. In most regions, Castor fiber, Ondatra zibethicus, Nyctereutes procyonoides, Canis familiaris, Neovison vison and Sus scrofa are very dangerous, and both Castor fiber and Sus scrofa can have environment‐forming impacts.
Risk factors of ophthalmic disorders in children with developmental delay
Authors: Sandfeld Nielsen Lisbeth , Jensen Hanne , Skov Liselotte
Published: June 2008

Purpose:  To identify diagnoses that increase the risk of ophthalmic disorders in developmentally delayed children.

Methods:  A cross‐sectional study of 1126 Danish children with developmental delay (IQ ≤ 80), aged 4–15 years [mean age 10 years 1 month; standard deviation (SD) 3 years 2 months; 702 boys, 424 girls]. Ophthalmological and paediatric data were obtained from 719 children. The relative risks (RRs) of ophthalmic disorders were calculated for low IQ, low birth weight, low gestational age, asphyxia, cerebral palsy (CP), epilepsy, neuroradiologically verified cerebral abnormalities, Down’s syndrome and other genetic syndromes.

Results:  Adjusted RR showed that visual impairment was correlated to CP [RR 2.3, 95% confidence interval (CI) 1.3–4.2], epilepsy (RR 2.5, 95% CI 1.5–4.2), verified cerebral changes (RR 1.9, 95% CI 1.1–3.3) and Down’s syndrome (RR 2.7, 95% CI 1.2–6.3). Adjusted RR showed that refractive errors were correlated to CP (RR 1.5, 95% CI 1.1–2.1) and Down’s syndrome (RR 2.2, 95% CI 1.5–3.2). Adjusted RR showed that strabismus was correlated to cerebral changes (RR 1.8, 95% CI 1.2–2.5).

Conclusion:  The RR of ophthalmic disorders in developmentally delayed children is increased if the child has CP, epilepsy, verified cerebral abnormalities or a genetic syndrome; referral for ophthalmological evaluation should be performed on suspicion of these conditions.
Acute myeloid leukemia with multilineage dysplasia in an alpaca
Authors: Steinberg Jennifer D. , Olver Christine S. , Davis William C. , Arzt Jonathan , Johnson Jennifer , Callan Robert
Published: June 2008

Abstract: An 18‐year‐old female alpaca was presented to the Colorado State University Veterinary Teaching Hospital for chronic ill thrift over a 1‐year period. Six weeks previously, an infected left mandibular cheek tooth was removed by oral extraction. On physical examination the patient was cachectic, lethargic, and weak. Abnormalities on the CBC included neutropenia, thrombocytosis, and severe nonregenerative, macrocytic, hypochromic anemia. Dysplastic nucleated erythrocytes and micromegakaryocytes were observed on the peripheral blood smear. Neutrophils, bands, and metamyelocytes appeared markedly toxic. Numerous blasts containing variable numbers of fine azurophilic granules were also observed. Based on their morphology, the cells were interpreted to be progranulocytes and myeloblasts, and a presumptive diagnosis of acute myeloid leukemia (AML) was made. The blast cells accounted for 60% of the nucleated cell population on bone marrow aspirates, further supporting a diagnosis of AML with multilineage dysplasia. Post mortem examination showed infiltration of the neoplastic cells into spleen, liver, kidney, and lymph nodes. Based on histologic findings, the morphologic diagnoses were disseminated myeloid neoplasia, chronic regionally extensive tooth root abscess, and membranous glomerulonephritis. The neoplastic cells were CD172a‐positive on flow cytometry, chloroacetate esterase‐positive by cytochemistry, and myeloperoxidase‐positive by immunohistochemistry, confirming myeloid origin. To our knowledge, this is the first case of AML with multilineage dysplasia in an alpaca, with only one other case of myelodysplasia described previously in this species.
Analysis of a Three-Dimensional Tank-Liquid-Soil Interaction Problem
Authors: Seeber R. , Fischer F. D. , Rammerstorfer F. G.
Published: June 2008

A three-dimensional analysis of the dynamic behavior of liquid-filled elastic cylindrical tanks based on flexible grounds, undergoing horizontal and vertical earthquake excitation is presented. The interaction of the ideal fluid with the elastic shell and with the flexible ground yields a problem of linear potential theory which must be solved together with the equations of motion of the shell and of the ground. With the unknown modal shapes of vibration developed in Fourier and in Fourier-Bessel series, the partial differential equations are transformed into coupled generalized equations of vibration by a weighted residual approach. The results show the strong influence of the flexible ground characterized by a remarkable shifting of natural frequencies, by the existence of additional natural frequencies, and by high damping ratios.
Rectangular Pressure Vessels of Finite Length
Authors: Blach A. E. , Hoa V. S. , Kwok C. K. , Ahmed A. K. W.
Published: June 2008

Design Rules in the ASME Code, Section VIII, Division 1, cover the design of unreinforced and reinforced rectangular pressure vessels. These rules are based on “infinitely long” vessels of non-circular cross section and stresses calculated are based on a linearized “small deflection” theory of plate bending. In actual practice, many pressure vessels can be found which are of finite length, often operating successfully under pressures two to three times as high as those permitted under the Code rules cited. This paper investigates the effects of finite length on the design formulae given by the ASME Code, and also a design method based on “large deflection” theory coefficients for short rectangular pressure vessels. Results based on analysis are compared with values obtained from finite element computations, and with experimental data from strain gage measurements on a test pressure vessel.
A Simplified Axisymmetric Analysis of Steel Containment Under General Dynamic Pressure
Authors: Fanous F. , Greimann L.
Published: June 2008

Loadings to cause severe accidents on containment buildings can include combinations of uniform internal pressure, dynamic pressure, and seismic. Most studies that have been conducted to predict containment building capacity have focused on the effect of over pressurization on containment performance. A simple methodology that permits rapid and reasonably accurate analysis for assessing the capacity of steel containment buildings; due to global or local uniform or spatially varying dynamic loading was developed. An axisymmetric model was used and the circumferential variation of the pressure, displacements, and stress resultants were represented by Fourier series. Shell vibration and buckling analysis were performed using modified versions of BOSOR4 and BOSOR5 finite difference codes. The modified version of BOSOR5 allows the input of pressures that vary along the meridional direction. These pressures were increased until failure of the containment occurred. Failure was defined to occur when membrane strains reached twice the yield strain or the bifurcation point was introduced. The axisymmetric analysis demonstrated a powerful tool to access the capacity of steel containment buildings.
Thermal Ratcheting Criteria and Behavior of Piping Elbows
Authors: Ueda M. , Kano T. , Yoshitoshi A.
Published: June 2008

A thermal ratcheting test was performed using an elbow model test specimen subjected to sustained primary load and cyclic thermal transient strains. Under severe loading conditions incremental longitudinal strains are observed in the region where a circumferential angle is around ± π/9 from the side of the elbow, while the elbow cross section was ovalized cycle by cycle causing large circumferential bending strain at around φ = π/2. It was shown by the test and analyses that the maximum primary membrane stress in an elbow is an essential parameter for thermal ratcheting behavior of elbows. Direct application of thermal ratcheting criteria in the ASME Code Case N-47 showed considerable conservative estimation and an improved thermal ratcheting criterion for elbows is recommended.
Three-Dimensional Finite Element Analysis of Temperatures and Stresses in a Single-Pass Butt-Welded Pipe
Authors: Karlsson R. I. , Josefson B. L.
Published: June 2008

Temperatures, stresses, and deformations in a single-pass butt-welded pipe are studied with a full three-dimensional finite element model. The model covers the whole circumference and the complete welding sequence; i.e., no assumption of axi-symmetry is made. The pipe studied has an outer diameter of 114.3 mm and a wall thickness of 8.8 mm. The material is carbon-manganese steel. The MIG-welding simulated results in a very high cooling rate. Low-temperature solid-state phase transformations, therefore, become significant and of importance to the residual stress field. The material model in the FE-code used (ADINA) is extended for that purpose. Notable calculated results are the residual compressive hoop stresses in the weld and the residual circumferential stress variations, especially in the beginning and end regions of the weld.
A Phenomenological Description on Thermomechanical Behavior of Shape
Memory Alloys
Authors: Tanaka K.
Published: June 2008

A constitutive theory, which consists of the constitutive equation and the transformation kinetics, is proposed to describe the thermomechanical behaviors of the shape memory alloys. Simulation in Ti-Ni alloy proves a good applicability of the theory when the overall characteristics of the stress-strain-temperature relation and the recovery stress induced in the heating process are studied in the uniaxial state.
Flexibility of Trunnion Piping Elbows
Authors: Lewis G. D. , Chao Y. J.
Published: June 2008

Trunnion piping elbows are commonly used in piping systems in power and chemical plants. The flexibility of the trunnion piping elbows is normally less than that of the plain piping elbows. In this paper, the finite element method is used to derive the in-plane and out-of-plane flexibility factors of trunnion piping elbows. The results can be easily adopted into the piping flexibility analysis.
Static and Dynamic Analysis of Flaw Stability in Piping
Systems
Authors: Quiñones D. F. , Nickell R. E. , Norris D. M.
Published: June 2008

Static and dynamic pretest simulations of a degraded nuclear piping test are performed to investigate crack stability and piping integrity. The purpose of this study is to provide system design guidance for a large-diameter piping test and to gain insight on modeling dynamic crack behavior in austenitic and carbon steel base metal and weldments. Combined operating temperature and pressure plus an idealized seismic loading are applied until substantial crack growth, leakage, or pipe guillotining is predicted. The importance of modeling elbow deformation and plasticity is demonstrated.
Analysis of Type 316 Stainless Steel Behavior Under Fatigue, Creep
and Combined Fatigue-Creep Loading
Authors: Gomuc R. , Bui-Quoc T. , Biron A. , Bernard M.
Published: June 2008

A phenomenological approach, already used for other materials, is applied for the prediction of the behavior of 316 stainless steel under fatigue, creep or combined fatigue-creep loadings. The approach is based on the reduction of either the fatigue limit or the creep strength due to damage accumulation. For multilevel loading, an interaction parameter is introduced to account for the interaction effect between two different loading levels. Some particular aspects concerning the application of the procedure are discussed and the life predictions are compared with those obtained by some other techniques. The essential characteristic of the proposed approach is to provide a reasonably good prediction of life for the material subjected to the prescribed loadings using material constants which are determined through minimal experimental data.
Minimization of Stresses and Pressure Surges
Authors: Elansary A. S. , Contractor D. N.
Published: June 2008

The control of stresses and liquid pressure surges in pipes is an important problem in the design of hydraulic pipe networks. The method of characteristics has been used to solve the transient stresses and pressures in liquid-filled piping systems. The friction force is included in the equation of motion for the fluid and the pipe wall. The maximum pressure and maximum stress at any point along the length of the pipe are evaluated for the entire simulation time. The Von Mises criterion is used for the stress calculation. A nonlinear search technique has been developed using the simplex method. The optimal valve closure is sought, that will minimize the maximum pressure and/or stresses. A continuous optimal valve closure policy is specified using spline functions. Numerical examples are presented showing the reduction of the dynamic stress and the dynamic pressure from linear valve closure to optimal valve closure.
Creep-Fatigue Assessment Methods Using Elastic Analysis Results and Adjustments
Authors: Severud L. K.
Published: June 2008

The design of mechanical components that operate in elevated temperature environment where creep effects are significant usually requires creep-fatigue assessments. The ASME Code Case N-47 contains rules for these assessments based on both inelastic and elastic stress analysis. Although an inelastic stress analysis generally more accurately predicts effects from creep and plasticity, an elastic analysis is often preferred since it is much simpler and less costly. New creep-fatigue rules for use with elastic analysis results have recently been proposed to enhance the rules’ accuracy and usefulness. This paper describes such new methods and rules for creep-fatigue assessments. Ingredients of the new methods include elastic follow-up, ratcheting, multiaxiality, plasticity, creep, and relaxation considerations and associated adjustment factors. The basis for the adjustments and a comparison of results to those obtained using inelastic analysis are provided. The new methods will provide a wider range of practical application of elastic creep-fatigue rules than permitted by previous code methods in design of components for elevated temperature service.
Stress and Strength Analysis of Equal-Diameter Tees
Authors: Zhixiang J. , Qingjiang Z. , Siding Z.
Published: June 2008

The elastic stress distribution of four models (β=Do/Di=1.07, 1.20, unreinforced and weld-reinforced) under five typical external loadings and the strength of six models (in addition to β=1.50) under internal pressure are investigated experimentally. The maximum stress factors are obtained. The influences of weld-reinforced structure on stress distribution and strength characteristics of tees are discussed. The finite-element predictions of unreinforced tees with β=1.07, 1.11, 1.15, 1.20 are carried out. The predicted stress distributions agree well with measured results. The relation between β and stress concentration factors under various loadings are obtained.
Displacements in Oil Storage Tanks Caused by Localized Differential Settlement
Authors: Kamyab H. , Palmer S. C.
Published: June 2008

This paper presents design charts for predicting the maximum radial distortion of open-topped storage tanks caused by localized differential settlement of the tank foundations. It is well known that differential settlement can produce radial deflection of the tank shell sufficient to cause jamming of the floating roof. Predictions of shell deflections have often assumed the shell to be inextensional, an assumption which may not always be valid, particularly where the settlement is localized. Consequently, the authors have recently completed a more refined analysis of the deflections and stresses in the shell and the primary wind girder [1] in which the shell is considered to act as a membrane. They concluded that this membrane analysis is valid for all practical applications and proposed a procedure for predicting shell displacements caused by any general differential settlement profile using Fourier analysis. This paper firstly reviews the new membrane analysis and then illustrates its application to two specific localized settlement profiles commonly found in practice to produce easy-to-use design charts. Finally, the paper refers to experimental testing of a model tank, carried out to verify the validity of these design charts [2].
Mechanical Design of Small-Bore Electromagnetic Launchers
Authors: Thakore A. K. , Fahrenthold E. P.
Published: June 2008

The development of special-purpose pressure vessels for small-bore, high-velocity electromagnetic launchers has characteristically employed low modulus composites and bolted steel frames. Such designs exhibit low structural stiffness, particularly at high operating currents. Although these designs can be modified to improve mechanical performance, numerical modeling results indicate that basic changes are needed to allow operation at the high bore pressures characteristic of newly developed pulsed power supplies. The indicated design changes introduce a requirement for fast fracture and fatigue reliability analysis of low tensile strength ceramic parts.
Creep-Fatigue Evaluation Based on the Overstress
Authors: Asada Y. , Okamoto Y. , Hashimoto T.
Published: June 2008

There is summarized a series of creep-fatigue data on a normalized and tempered 2 1/4Cr-1Mo steel obtained at 550°C in a very high vacuum environment under a wide variety of a strain-time program. A special feature of a stress-strain response of the steel is described to give the overstress and the internal back stress. A damage equation is developed to predict a creep-fatigue behavior which is free from the environmental effect.
Experimental Studies of Ratcheting of Pressurized Pipe
Authors: Scavuzzo R. J. , Lam P. C. , Gau J. S.
Published: June 2008

In these studies, both dynamic and static tests were conducted on pressurized pipe. Dynamic tests were run on 1 in. Schedule 40 and Schedule 10 seamless 304 stainless steel pipe. Welded 1 in. Schedule 40 304 stainless steel pipe and seamless carbon steel (ASTM A106) pipe were tested statically. Internal pressures varied from 1000 psi to 3000 psi. In these tests, axial bending stresses from either inertial loads or static loads were superposed on to the initial pressure stresses. Strain gages were used to measure the cyclic strains on the outer walls of the pipe. Measurements indicated that ratcheting occurred primarily in the hoop direction and varied from a maximum at the top and bottom of the pipe that had the highest bending stresses to zero at the neutral axis. Though ratcheting occurred primarily in the hoop direction, some ratcheting in the axial direction was observed in 304 stainless steel pipe in both static and dynamic tests. Axial ratcheting was insignificant in the carbon steel pipe. Data obtained from these tests are presented. Measured ratcheting strains are compared to approximations of Beaney, Edmunds and Beer and to finite element computations.
Flow-Induced Vibrations in Two-Phase Flow
Authors: Chen S. S.
Published: June 2008

Two-phase flow exists in many shell-and-tube heat exchangers and power generation components. The flowing fluid is a source of energy that can induce small-amplitude subcritical oscillations and large-amplitude dynamic instabilities. In fact, many practical system components have experienced excessive flow-induced vibrations. This paper reviews the current understanding of vibration of circular cylinders in quiescent fluid, cross-flow, and axial flow, with emphasis on excitation mechanisms, mathematical models, and available experimental data. A unified theory is presented for cylinders oscillating under different flow conditions.
Flow-Induced Vibration Analysis of Tube Bundles—A Proposed Section III Appendix N Nonmandatory Code
Authors: Au-Yang M. K. , Blevins R. D. , Mulcahy T. M.
Published: June 2008

This paper presents guidelines for flow-induced vibration analysis of tubes and tube bundles such as those commonly encountered in steam generators, heat exchangers, condensers and nuclear fuel bundles. It was proposed as a nonmandatory code to be included in Section III Appendix N (N-1300 series) of the American Society of Mechanical Engineers (ASME) Boiler Code. In preparing this code, the authors tried to limit themselves to the better-defined flow excitation mechanisms—vortex-induced vibration, fluid-elastic instability and turbulence-induced vibration—and include only the more-established methods. References are, however, given for other methods whenever justified. This guideline covers only design analysis. A companion guideline on the testing and data analysis of heat exchanger tube banks was proposed as part of the ASME Code on Operations and Maintenance of Nuclear Plants. The latter is not included in this paper.
Beam Theory and Its Suitability for the Analysis of Pipes
Authors: Fan H. , Widera G. E. O. , Afshari P.
Published: June 2008

The use of the asymptotic expansion technique when applied to the three-dimensional elasticity equations is outlined and used to demonstrate the development of an asymptotic beam theory and associated boundary conditions. The formulation thus obtained holds for arbitrary cross section shapes and is applied here to pipes. It can be used to provide benchmark solutions to test the suitability of engineering beam and shell theories.
An Integral Equation Solution for Limit Loads Applied to Lugs on Cylindrical Shells
Authors: Brooks G. N.
Published: June 2008

A lower-bound limit analysis of loaded integral lugs on cylindrical shells is presented. Normal force and circumferential and longitudinal moment loadings on the lug are considered. The equilibrium solution, necessary for a lower bound, is obtained as a convolution integral of the concentrated load solutions of linear shallow shell theory. The load distribution is chosen to satisfy the yield condition everywhere, while maximizing the load. A simplified yield condition in terms of the shell stress resultants is used. Failure is assumed to occur in the shell, not the lug. Encouraging comparisons with available experimental results for moment-loaded rectangular lugs on pipes are presented. The use of shallow shell theory enables the problem geometry to be described by one less parameter than complete shell theory.
An Investigation of Thermal Stress Ranges Under Stratification Loadings
Authors: Liu T. H. , Cranford E. L.
Published: June 2008

This paper deals with a unique and severe stratification phenomena in the pressurizer surge line piping system. The methodology used in the calculation of total stress state includes pressure stresses from internal pressure, global thermal stresses from the constraining of the system by supports, local thermal stresses from hot/cold stratified condition, and transient thermal stresses in the pipe and at structural discontinuities. Special discussion on the interpolation to obtain moment loadings from one state of thermal condition to the next with nonlinear gapped support system is presented. Finally, the thermal cycling associated with operating transients in the surge line system is also addressed.
Dynamic Response of Pipelines Buried in Back-Filled Trenches
Authors: Liu S. W. , Datta S. K. , Khair K. R. , Shah A. H.
Published: June 2008

Dynamic response of pipelines buried in a back-filled rectangular trench in a semi-infinite medium has been investigated. The pipelines are modeled as long cylindrical shells of small thickness. By using the boundary integral representation and finite element method, we have studied the three-dimensional response to account for either plane P or SV wave incident at an arbitrary angle to the pipe-axis. Numerical results are presented for the normal displacements, displacements along pipe-axis, and the hoop stresses in the pipe wall. It is shown that the response depends critically on the back-filled material as well as on the directions of propagation of the incident waves.
A More Accurate Method for Predicting the Prestresses in a Multilayer Wrapped Cylindrical Vessel
Authors: Boudjelida K. , Ghosn A. H. , Sabbaghian M.
Published: June 2008

The prestresses in the walls of multilayered weld-wrapped cylindrical pressure vessels are mainly created by the transverse shrinkage of the welded layers. Current design practices consider only the shrinkage of longitudinal weld seams, resulting from constant temperature gradients. Such practices ignore the contribution to shrinkage from the remaining part of the welded plate and would, therefore, yield approximate values for the corresponding prestresses. In the present work the shrinkage of the full layer is determined, and hence a more accurate method for predicting the weld wrapping stresses is offered. The heat transfer problem during welding is addressed and modeled. A three-dimensional heat conduction problem with a heat source traveling at constant speed is formulated and solved. Using Green’s function, the transient temperature distribution is determined. A two-dimensional model is also employed, and the corresponding temperature solution is obtained. A numerical example for the two-dimensional model is worked out for a single welded layer. Comparison between the value of the layer shrinkage calculated by the method described in this paper (variable layer temperature) and that obtained by the current industry method (constant temperature gradient) shows that the latter yields a higher (more conservative) value, and hence will underpredict the prestresses in the layer and the vessel.
A Stress Analysis of Pipe Flange Connections
Authors: Sawa T. , Higurashi N. , Akagawa H.
Published: June 2008

The use of pipe flange connections is standardized in the codes of JIS, ASME, DIN and so on. However, these codes are almost entirely dependent on experience, and subsequently some problems concerning pipe flange connections have been encountered. In the present paper, the distribution of contact stresses which governs the sealing performance is analyzed as a three-body contact problem, using an axisymmetrical three-dimensional theory of elasticity. The effects of the stiffness and the thickness of raised face metallic gaskets on the contact stresses and the effective gasket seating width are shown by numerical calculation. Moreover, stresses produced on the hub, the load factor (the relationship between an increment of bolt axial force and an internal pressure), and the maximum stress caused in bolts are analyzed. For verification, experiments are carried out. The analytical results are satisfactorily consistent with the experimental results.
Experiments on Tube/Support Interaction With Feedback-Controlled Instability
Authors: Antunes J. , Axisa F. , Vento M. A.
Published: June 2008

Due to tube-support gaps in heat-exchangers, low-frequency modes may develop and become unstable at comparatively low flow velocities. This kind of linear fluidelastic instability results in a negative modal damping value, which is a function of the flow velocity. The response amplitude of the unstable tubes increases steadily until tube-support impact becomes unavoidable. These extremely nonlinear vibratory motions have a high-risk potential, as tube velocities and impact forces can be of very considerable magnitude. This paper reports results on a series of laboratory experiments, intended to validate nonlinear calculations on vibro-impact dynamics of heat exchanger tube bundles under fluidelastic instability. The test model was designed for unidirectional motion and the results obtained should be fairly representative of the actual behavior of the U-bend portion of the heat exchanger tube bundles. The system instability is generated by a velocity feedback loop. This method presents significant advantages due to simplicity of the setup and the controllability of the system parameters, in particular concerning the negative damping ratio of the unstable model. A comparison of experimental and computed system dynamics is presented for several values of the instability growth rate and for various initial conditions of the motion. Influence of other parameters, such as tube-support gap magnitude and gap symmetry, is asserted for realistically ranged values. Results show that several steady motion regimes may arises, depending on the system parameters and initial conditions of the motion, which is a fact of engineering significance. Furthermore, a satisfactory qualitative and quantitative agreement was obtained between theoretical predictions and test data.
Interaction in Primary-Secondary Systems
Authors: Igusa T. , Der Kiureghian A.
Published: June 2008

Primary-secondary systems, consisting of a primary subsystem supporting a relatively light secondary subsystem, are characterized by special dynamic characteristics. One important characteristic is interaction, which is mathematically manifested by coupling between the equations of motion of the two subsystems and results in a reduction in the secondary response. The dynamic analysis of P-S systems is often performed using a decoupled system of equations which is simpler to analyze, but may give overly conservative results leading to unnecessarily costly designs. In this paper, interaction in P-S systems is examined in detail, criteria for assessing the importance of interaction are developed, and the concepts are illustrated with examples of interacting systems.
A Method for Suppression of Pressure Pulse in Fluid-Filled Piping—Part II: Experimental Verification
Authors: Shin Y. W. , Bielick E. F. , Wiedermann A. H. , Ockert C. E.
Published: June 2008

A simple, nondestructive method to suppress pressure pulses in fluid-filled piping was proposed and theoretically analyzed in the previous companion paper. In this paper, the proposed method is verified experimentally. The results of experiments performed for the range of parameters of practical importance indicated that the attenuation of pressure pulses was sufficiently large for practical applications and in accordance with the theoretical predictions. This paper describes the experimental setup and the test models of the proposed pulse suppression devices and discusses the experimental results. In particular, the measured attenuation factors (transmitted pressure/incident pressure) are presented and compared with the theoretical predictions.
Residual Stresses in Transition Zones of Heat Exchanger Tubes
Authors: Updike D. P. , Kalnins A. , Caldwell S. M.
Published: June 2008

A theoretical model of an expanded tube-to-tubesheet joint is developed and examined with the objective to determine the residual stresses in the transition zone, which lies between the expanded and unexpanded regions of the tube. Owing to their effect on the development of stress corrosion cracks, the residual tensile stresses on the surfaces of the tube are of particular interest. A mathematical model that can predict these residual stresses is developed. Results of the model show that the maximum tensile residual stresses are axial and occur on the inside diameter of the expanded tube. It is shown in a parameter study that, for expansions that ensure a leak-tight joint, the maximum residual tensile axial stress on the inside surface of the tube reaches 80–95 percent of the yield stress of the tube, regardless of the geometrical and material parameters of the tube and tubesheet.
Implications of Stress Dependency of the Thermal Expansion Coefficient on Thermal Buckling
Authors: Bert C. W. , Fu C.
Published: June 2008

A thermosolid mechanics analysis based on sound thermodynamic and mechanical principles is derived for a thermoelastic solid in which the elastic coefficient is temperature-dependent, and thus the TEC (thermal expansion coefficient) must be stress-dependent. The theory is applied to the case of slender elastic members with full axial restraint and subjected to a uniform increase in temperature. Numerical results are presented for a wide range of materials and slenderness ratios.