bluuebunny/crossref_metadata_2025 huggingface dataset:
Homocysteine inhibits endothelial cell growth via DNA hypomethylation of the cyclin Agene
Authors: Jamaluddin Md S. , Chen Irene , Yang Fan , Jiang Xiaohua , Jan Michael , Liu Xiaoming , Schafer Andrew I. , Durante William , Yang Xiaofeng , Wang Hong
Published: August 2007

We reported previously that homocysteine (Hcy) inhibits endothelial cell (EC) growth by transcriptional inhibition of the cyclin A gene via a hypomethylation-related mechanism. In this study, we examined the effect of Hcy on epigenetic modification of the cyclin A gene and its biologic role in human ECs. Cyclin A mRNA levels were significantly suppressed by Hcy and a DNA methyltransferase inhibitor. The cyclin A promoter contains a CpG island spanning a 477-bp region (−277/200). Bisulfite sequencing followed by polymerase chain reaction (PCR) amplification of the cyclin A promoter (−267/37) showed that Hcy eliminated methylation at 2 CpG sites in the cyclin A promoter, one of which is located on the cycle-dependent element (CDE). Mutation of CG sequence on the CDE leads to a 6-fold increase in promoter activity. Hcy inhibited DNA methyltransferase 1 (DNMT1) activity by 30%, and reduced the binding of methyl CpG binding protein 2 (MeCP2) and increased the bindings of acetylated histone H3 and H4 in the cyclin A promoter. Finally, adenovirus-transduced DNMT1 gene expression reversed the inhibitory effect of Hcy on cyclin A expression and EC growth inhibition. In conclusion, Hcy inhibits cyclin A transcription and cell growth by inhibiting DNA methylation through suppression of DNMT1 in ECs.
Nuclear and mitochondrial data reveal different evolutionary processes in the Lake Tanganyika cichlid genus Tropheus
Authors: Egger Bernd , Koblmüller Stephan , Sturmbauer Christian , Sefc Kristina M
Published: August 2007

Background

Cichlid fishes are notorious for their wealth of intra- and interspecific colour pattern diversity. In Lake Tanganyika, the endemic genus Tropheus represents the most impressive example for geographic variation in the pattern and hue of integument colouration, but the taxonomy of the over 100 mostly allopatric colour morphs remains to a large degree unresolved. Previous studies of mitochondrial DNA sequence data revealed polyphyly of the six nominally described species and complex phylogeographic patterns influenced by lake level fluctuations and population admixture, and suggested the parallel evolution of similar colour patterns in divergent evolutionary lineages. A gene tree of a rapidly radiating group may be subject to incomplete and stochastic lineage sorting, and to overcome this problem we used multi-locus, nuclear AFLP data in comparison with mtDNA sequences to study diversification, migration and introgression in Tropheus colour morphs in Lake Tanganyika.

Results

Significant incongruence between phylogenetic reconstructions from mitochondrial and AFLP data suggested incomplete sorting of mitochondrial haplotypes as well as frequent introgression between differentiated lineages. In contrast to the mitochondrial phylogeny, the AFLP phenogram was largely congruent with species classifications, colour pattern similarities, and in many cases also with the current geographic distribution of populations, and did not produce evidence of convergent colour pattern evolution. Homoplasy in the AFLP data was used to identify populations that were strongly affected by introgression.

Conclusion

Different evolutionary processes were distinguished by the combination of mitochondrial and AFLP data. Mitochondrial phylogeographic patterns retained signals of large-scale migration events triggered by historical, major lake level fluctuations, whereas AFLP data indicated genetic cohesion among local groups of populations resulting from secondary contact of adjacent populations in the course of the more frequently occurring, minor lake level fluctuations. There was no support for the parallel evolution of similar colour patterns in the AFLP data. Genetic signatures of introgression and hybridisation detected in several populations suggest that lake level fluctuations drove the stunning diversification of Tropheus morphs not only through population fragmentation, but also by promoting hybridisation between differentiated morphs in secondary contact.
Subclinical sympathetic neuropathy appears early in the course of Crohn's disease
Authors: Ohlsson Bodil , Sundkvist Göran , Lindgren Stefan
Published: August 2007

Background

We have previously demonstrated that patients with Crohn's disease (CD) of long duration have signs of autonomic neuropathy. The aim of this study was to examine whether autonomic neuropathy is an early manifestation of CD, or a sign appearing late in the course.

Methods

Twenty patients, median age 40 years, with a short duration of CD were included. Examination of autonomic reflexes included heart rate reaction to tilt (acceleration index – AI, brake index – BI) and heart rate variation to deep-breathing (expiration/inspiration index-E/I). Seven years later the same examinations were repeated, and in addition we examined the vasoconstriction response to indirect cooling by laser Doppler (vasoconstriction-index – VAC-index). The results were compared with healthy individuals.

Results

There was no difference in the blood pressure between controls and the patients with CD at rest, but eight minutes after tilt, the systolic blood pressure was lowered in patients compared to controls, both at the first assessment (p = 0.016) and after seven years (p = 0.042). The change in systolic blood pressure between rest and eight minutes after tilt was not significant at the first assessment, while a significant change compared to controls was observed seven years later (p = 0.028). This indicates a progressive dysfunction. There were no differences in E/I, AI, BI or VAC indexes between patients and controls.

Conclusion

Patients with CD suffer from autonomic neuropathy early in their disease, suggesting involvement of many different organ systems in this entity.
Susceptibility to type 1 diabetes conferred by the PTPN22C1858T polymorphism in the Spanish population
Authors: Santiago Jose Luis , Martínez Alfonso , de la Calle Hermenegildo , Fernández-Arquero Miguel , Figueredo M Ángeles , de la Concha Emilio G , Urcelay Elena
Published: August 2007

Background

The protein tyrosine phosphatase N22 gene (PTPN22) encodes a lymphoid-specific phosphatase (LYP) which is an important downregulator of T cell activation. A PTPN22 polymorphism, C1858T, was found associated with type 1 diabetes (T1D) in different Caucasian populations. In this study, we aimed at confirming the role of this variant in T1D predisposition in the Spanish population.

Methods

A case-control was performed with 316 Spanish white T1D patients consecutively recruited and 554 healthy controls, all of them from the Madrid area. The PTPN22 C1858T SNP was genotyped in both patients and controls using a TaqMan Assay in a 7900 HT Fast Real-Time PCR System.

Results

We replicated for the first time in a Spanish population the association of the 1858T allele with an increased risk for developing T1D [carriers of allele T vs. CC: OR (95%) = 1.73 (1.17–2.54); p = 0.004]. Furthermore, this allele showed a significant association in female patients with diabetes onset before age 16 years [carriers of allele T vs. CC: OR (95%) = 2.95 (1.45–6.01), female patients vs female controls p = 0.0009]. No other association in specific subgroups stratified for gender, HLA susceptibility or age at onset were observed.

Conclusion

Our results provide evidence that the PTPN22 1858T allele is a T1D susceptibility factor also in the Spanish population and it might play a different role in susceptibility to T1D according to gender in early-onset T1D patients.
Health care utilization and costs in Saskatchewan's registered Indian population with diabetes
Authors: Pohar Sheri L , Johnson Jeffrey A
Published: August 2007

Background

The prevalence of diabetes in North American is recognized to be higher in Aboriginal populations. The relative magnitude of health care utilization and expenditures between Aboriginal and non-Aboriginal populations is uncertain, however. Our objective was to compare health care utilization and per capita expenditures according to Registered Indian and diabetes status in the province of Saskatchewan.

Methods

Administrative databases from Saskatchewan Health were used to identify registered Indians and the general population diabetes cases and two controls for each diabetes case. Health care resource utilization (physician visits, hospitalizations, day surgeries and dialysis) and costs for these individuals in the 2001 calendar year were determined. The odds of having used each resource category, adjusted for age and location of residence, was assessed according to Registered Indian and diabetes status. The average number of encounters for each resource category and per capita healthcare expenditures were also determined.

Results

Registered Indian diabetes cases were younger than general population cases (45.7 ± 14.5 versus 58.4 ± 16.4 years, p < 0.001) and fewer were male (42.3% versus 53.2%, p < 0.001). Registered Indians were more likely to visit a physician, be hospitalized or receive dialysis than the general population, regardless of diabetes status. Diabetes increased the probability of having used all resource categories for both Registered Indians and the general population. Per capita health care expenditures for the diabetes subgroups were more than twice that of their respective controls and were 40% to 60% higher for registered Indians than the general population, regardless of diabetes status.

Conclusion

Relative to individuals without the disease, both registered Indians and the general population with diabetes had substantially higher health care utilization and costs. Excess hospitalization and dialysis suggested that registered Indians with and without diabetes experienced greater morbidity than the general population.
Redox stress proteins are involved in adaptation response of the hyperthermoacidophilic archaeon Sulfolobus solfataricus to nickel challenge
Authors: Salzano Anna M , Febbraio Ferdinando , Farias Tiziana , Cetrangolo Giovanni P , Nucci Roberto , Scaloni Andrea , Manco Giuseppe
Published: August 2007

Background

Exposure to nickel (Ni) and its chemical derivatives has been associated with severe health effects in human. On the contrary, poor knowledge has been acquired on target physiological processes or molecular mechanisms of this metal in model organisms, including Bacteria and Archaea. In this study, we describe an analysis focused at identifying proteins involved in the recovery of the archaeon Sulfolobus solfataricus strain MT4 from Ni-induced stress.

Results

To this purpose, Sulfolobus solfataricus was grown in the presence of the highest nickel sulphate concentration still allowing cells to survive; crude extracts from treated and untreated cells were compared at the proteome level by using a bi-dimensional chromatography approach. We identified several proteins specifically repressed or induced as result of Ni treatment. Observed up-regulated proteins were largely endowed with the ability to trigger recovery from oxidative and osmotic stress in other biological systems. It is noteworthy that most of the proteins induced following Ni treatment perform similar functions and a few have eukaryal homologue counterparts.

Conclusion

These findings suggest a series of preferential gene expression pathways activated in adaptation response to metal challenge.
Adrenal involvement in the biostimulatory effect of bulls
Authors: Tauck Shaun A , Olsen Jesse R , Berardinelli James G
Published: August 2007

Background

The objective was to evaluate if cortisol concentrations are associated with the resumption of luteal activity in postpartum, primiparous cows exposed to bulls. The hypotheses were that 1) interval from start of exposure to resumption of luteal activity; 2) proportions of cows that resumed luteal function during the exposure period; and 3) cortisol concentrations do not differ among cows exposed or not exposed to bulls (Exp. 1), and cows continuously exposed to bull or steer urine (Exp. 2).

Methods

In Exp. 1, 28 anovular cows were exposed (BE; n = 13) or not exposed (NE; n = 15) to bulls for 30 d at 58 d after calving. In Exp. 2, 38 anovular cows were fitted with a controlled urine delivery device at 45 d after calving and exposed continuously (24 h/d) to bull (BUE; n = 19) or steer (SUE; n = 19) urine. Length of exposure was ~64 d. Blood samples were collected from each cow on D 0 and every 3 d throughout exposure periods in both experiments and assayed for progesterone. Cortisol was assayed in samples collected on D 0, 8, 16, and 24 in Exp. 1; and, D 0, 19, 38, and 57 in Exp. 2.

Results

In Exp. 1, interval from the start of exposure to resumption of luteal activity was shorter (P < 0.05) for BE cows than NE cows, similarly, more (P < 0.05) BE cows than NE cows resumed luteal function during the exposure period. In Exp. 2, there was no difference in intervals from the start of exposure to resumption of luteal activity and proportions of cows that resumed luteal function during the exposure period between BUE and SUE cows. In Exp. 1, there was no difference in cortisol concentrations between BE and NE cows at the start of the experiment (D 0), however, cortisol concentrations were greater (P < 0.05) in BE cows than NE cows on D 9, 18, and 27. In Exp. 2, cortisol concentrations were higher for BUE than SUE cows on D 0 (P < 0.05), thereafter cortisol decreased (P < 0.05) but did not differ between BUE and SUE cows.

Conclusion

We conclude that the physical presence of bulls stimulates resumption of luteal activity and is coincident with increased cortisol concentrations, and hypothesize a possible association between adrenal activation and the biostimulatory effect of bulls.
Perigraft air is not always pathological: a case report
Authors: Ball Elizabeth , Morris-Stiff Gareth , Coxon Mari , Lewis Michael H
Published: August 2007

Background

The presence of perigraft air is a common finding in the immediate post-operative phase following abdominal aortic aneurysm repair whilst the later appearance of air, in association with elevated inflammatory markers, is regarded as being indicative of the serious complication of graft infection. What is not known is at what timepoint following surgery does the perigraft air become a significant finding.

Case Presentation

We report the case of a 71 year old man who underwent a computed tomography scan 15 days following repair of an abdominal aortic aneurysm because of the presence of unexplained pyrexia. The scan showed the presence of perigraft air and a small haematoma. The patient was managed conservatively and after 6 weeks the air and haematoma had resolved completely.

Conclusion

The presence of perigraft air in the early postoperative phase is probably a normal finding, is not associated with graft infection and can be managed non-operatively.
No relationship between circulating levels of sex steroids and mammographic breast density: the Prospect-EPIC cohort
Authors: Verheus Martijn , Peeters Petra HM , van Noord Paulus AH , van der Schouw Yvonne T , Grobbee Diederick E , van Gils Carla H
Published: August 2007

Background

High breast density is associated with increased breast cancer risk. Epidemiologic studies have shown an increase in breast cancer risk in postmenopausal women with high levels of sex steroids. Hence, sex steroids may increase postmenopausal breast cancer risk via an increase of breast density. The objective of the present study was to study the relation between circulating oestrogens and androgens as well as sex hormone binding globulin (SHBG) in relation to breast density.

Methods

We conducted a cross-sectional study among 775 postmenopausal women, using baseline data of a random sample of the Prospect-EPIC study. Prospect-EPIC is one of two Dutch cohorts participating in the European Prospective Investigation into Cancer and Nutrition, and women were recruited via a breast cancer screening programme. At enrolment a nonfasting blood sample was taken and a mammogram was made. Oestrone, oestradiol, dehydroepiandrosterone sulfate, androstenedione, testosterone and SHBG levels were measured, using double-antibody radioimmunoassays. Concentrations of free oestradiol and free testosterone were calculated from the measured oestradiol, testosterone and SHBG levels Mammographic dense and nondense areas were measured using a semiquantitative computerized method and the percentage breast density was calculated. Mean breast measures for quintiles of hormone or SHBG levels were estimated using linear regression analyses.

Results

Both oestrogens and testosterone were inversely related with percent breast density, but these relationships disappeared after adjustment for BMI. None of the sex steroids or SHBG was associated with the absolute measure of breast density, the dense area.

Conclusion

The results of our study do not support the hypothesis that sex steroids increase postmenopausal breast cancer risk via an increase in breast density.
Influence of dextran-70 on systemic inflammatory response and myocardial ischaemia-reperfusion following cardiac operations
Authors: Gombocz Károly , Beledi Ágnes , Alotti Nasri , Kecskés Gábor , Gábor Valéria , Bogár Lajos , Kőszegi Tamás , Garai János
Published: August 2007

Introduction

Experimental studies have demonstrated that dextran-70 reduces the leukocyte–endothelium interaction, but clinical evidence is still lacking. Our objective was to justify the anti-inflammatory effect of dextran-70 following cardiac operations.

Methods

Forty patients undergoing coronary bypass surgery (n = 32) or aortic valve replacement (n = 8) were enrolled in this prospective, randomized, double-blind study. Two groups were formed. In group A (n = 20), dextran-70 infusion was administered at a dose of 7.5 ml/kg before the initiation of cardiopulmonary bypass and at a dose of 12.5 ml/kg after the cessation of cardiopulmonary bypass. Group B served as a control with identical amounts of gelatin infusion (n = 20). The plasma concentration of procalcitonin, C-reactive protein, IL 6, IL 6r, IL 8, IL 10, soluble endothelial leukocyte adhesion molecule-1, soluble intercellular adhesion molecule-1, cardiac troponin-I and various haemodynamic parameters were measured in the perioperative period. Multivariate methods were used for statistical analysis.

Results

In group A, lower peak (median) plasma levels of procalcitonin (0.2 versus 1.4, p < 0.001), IL 8 (5.6 versus 94.8, p < 0.001), IL 10 (47.2 versus 209.7, p = 0.001), endothelial leukocyte adhesion molecule-1 (88.5 versus 130.6, p = 0.033), intercellular adhesion molecule-1 (806.7 versus 1,375.7, P = 0.001) and troponin-I (0.22 versus 0.66, p = 0.018) were found. There was no significant difference in IL 6, IL-6r and C-reactive protein values between groups. Higher figures of the cardiac index (p = 0.010) along with reduced systemic vascular resistance (p = 0.005) were noted in group A.

Conclusion

Our investigation demonstrated that the use of dextran-70 reduces the systemic inflammatory response and cardiac troponin-I release following cardiac operation.

Trial registration number

ISRCTN38289094.
Inclusion of CA-125 Does Not Improve Mathematical Models Developed to Distinguish Between Benign and Malignant Adnexal Tumors
Authors: Timmerman Dirk , Van Calster Ben , Jurkovic Davor , Valentin Lil , Testa Antonia C. , Bernard Jean-Pierre , Van Holsbeke Caroline , Van Huffel Sabine , Vergote Ignace , Bourne Tom
Published: August 2007

Purpose

To test the value of serum CA-125 measurements alone or as part of a multimodal strategy to distinguish between malignant and benign ovarian tumors before surgery based on a large prospective multicenter study (International Ovarian Tumor Analysis).

Patients and Methods

Patients with at least one persistent ovarian mass preoperatively underwent transvaginal ultrasonography using gray scale imaging to assess tumor morphology and color Doppler imaging to obtain indices of blood flow.

Results

Data from 809 patients recruited from nine centers were included in the analysis; 567 patients (70%) had benign tumors and 242 (30%) had malignant tumors—of these 152 were primary invasive (62.8%), 52 were borderline malignant (21.5%), and 38 were metastatic (15.7%). A logistic regression model including CA-125 (M2) resulted in an area under the receiver operating characteristic curve (AUC) of 0.934 and did not outperform a published (M1) without serum CA-125 information (AUC, 0.936). Specifically designed new models including CA-125 for premenopausal women (M3) and for postmenopausal women (M4) did not perform significantly better than the model without CA-125 (M1; AUC, 0.891 v AUC, 0.911 and AUC, 0.975 v AUC, 0.949, respectively). In postmenopausal patients, serum CA-125 alone (AUC, 0.920) and the risk of malignancy index (AUC, 0.924) performed very well. Results were very similar when the models were prospectively tested on a group of 345 new patients with adnexal masses of whom 126 had malignant tumors (37%).

Conclusion

Adding information on CA-125 to clinical information and ultrasound information does not improve discrimination of mathematical models between benign and malignant adnexal masses.
Phase III Trial of High-Dose Sequential Chemotherapy With Peripheral Blood Stem Cell Support Compared With Standard Dose Chemotherapy for First-Line Treatment of Advanced Ovarian Cancer: Intergroup Trial of the AGO-Ovar/AIO and EBMT
Authors: Möbus Volker , Wandt Hannes , Frickhofen Norbert , Bengala Carmelo , Champion Kim , Kimmig Rainer , Ostermann Helmut , Hinke Axel , Ledermann Jonathan A.
Published: August 2007

Purpose

Although ovarian cancer is one of the most chemotherapy-sensitive solid tumors, cure after radical surgery and chemotherapy is uncommon. A randomized trial comparing high-dose sequential chemotherapy with peripheral blood stem cell (PBSC) support with platinum-based combination chemotherapy was conducted to investigate whether dose-intensification improves outcome.

Patients and Methods

One hundred forty-nine patients with untreated ovarian cancer were randomly assigned after debulking surgery to receive standard combination chemotherapy or sequential high-dose (HD) treatment with two cycles of cyclophosphamide and paclitaxel followed by three cycles of HD carboplatin and paclitaxel with PBSC support. HD melphalan was added to the final cycle. The median age was 50 years (range, 20 to 65 years) and International Federation of Gynecology and Obstetrics stage was IIb/IIc in 4%, III in 78%, and IV in 17%.

Results

Seventy-six percent of patients received all five cycles in the HD arm and the main toxicities were neuro-/ototoxicity, gastrointestinal toxicity, and infection and one death from hemorrhagic shock. After a median follow-up of 38 months, the progression-free survival was 20.5 months in the standard arm and 29.6 months in the HD arm (hazard ratio [HR], 0.84; 95% CI, 0.56 to 1.26; P, .40). Median overall survival (OS) was 62.8 months in the standard arm and 54.4 months in the HD arm (HR, 1.17; 95% CI, 0.71 to 1.94; P, .54).

Conclusion

This is the first randomized trial comparing sequential HD versus standard dose chemotherapy in first-line treatment of patients with advanced ovarian cancer. We observed no statistically significant difference in progression-free survival or OS and conclude that HD chemotherapy does not appear to be superior to conventional dose chemotherapy.
Speech without Words
Authors: Yuhai Han
Published: August 2007

Translated by Matthew A. Hale
Asymptotic analysis of the corner-behaviour of a rigid punch bonded to an elastic substrate
Authors: Bohórquez L , Hills D. A
Published: August 2007

The contact between a flat-faced rigid block and an elastic half-plane has been studied, showing that an asymptotic solution correctly captures the stress field adjacent to the contact corners for all values of Poisson's ratio. It is shown that, in practical cases, the plastic zone, which is inevitably present at the contact corners, envelopes the oscillatory behaviour implied locally but is surrounded by an elastic hinterland correctly represented by the asymptote.
Optimizing the sensitivity of the small-disc creep test to damage and test conditions
Authors: Evans M , Wang D
Published: August 2007

The small-creep disc test is seen as a promising solution to the problem of sampling from in-service components for remanent life estimation. However, experimental studies have revealed substantial scatter in failure times resulting from variations in test and apparatus geometries. These studies therefore suggest that there exists a set of conditions that both minimizes the scatter and also maximizes the sensitivity of the disc test to the determination of remanent life, so enabling reliable estimates of the remaining life to be made. The objective of this paper is to identify such an optimum.

The large scatter present in small-disc test data would make the identification of this optimum problematic and inconclusive using an experimental approach. Instead this paper uses a numerical model of the disc test to predict failure times over a wide range of test conditions. The resulting response surface is then approximated using a polynomial and from this model the optimum set of test conditions is identified. Full verification of the model (and the optimum) can then be more successfully accomplished by carrying out experiments close to the optimum conditions where scatter is the smallest.

The model was shown to be capable of predicting actual experimental creep test results. Using this approach, failure times were found to be most sensitive to disc thickness and hole diameter but least sensitive to disc diameter. Under clamping, the optimum test geometry was insensitive to the applied load but sensitive to the level of damage. Without clamping, the optimum geometry was insensitive to both of these. The paper gives optimum conditions for various levels of damage under both conditions.
An inverse method for the determination of full field stresses from experimentally measured normal strains
Authors: Yu T-J , Sankar B. V , Arakere N K , Vaidyanathan R
Published: August 2007

Certain diffraction-based techniques that measure strains in bulk samples are limited to determination of normal strains. A numerical inverse method is developed to determine full field stresses from the experimentally determined normal strains in isotropic solids under plane stress conditions. The method is based on satisfying the equations of equilibrium and the constitutive relations. The finite difference method is employed to solve the equations and to determine the complete stress field. Furthermore, a least-squares procedure is used to determine the unknown functions of integration in conjunction with known values of shear stress along a reference line. The method is verified by using the normal strain fields in various specimens obtained using both finite element analysis and exact elasticity solutions. It is found that the proposed method predicts the shear stresses accurately in the examples considered.
Analysis of creep-induced strains and stresses in notches subjected to a cyclic load
Authors: Nuñez J E , Glinka G
Published: August 2007

A method for the estimation of time-dependent strains and stresses in notches subjected to a cyclic load is discussed in the paper. The proposed solution is an extension of the methodology proposed previously for notches under a steady external load. A new algorithm is proposed to predict the creep response near notches in plane stress components subjected to cyclic loads. Predictions were compared with finite element data, and good agreement was obtained for various geometrical and material configurations.
Elastic stress concentration at radial crossholes in pressurized thick cylinders
Authors: Comlekci T , Mackenzie D , Hamilton R , Wood J
Published: August 2007

Results of a parametric finite element analysis investigation of stress concentration at radial crossholes in pressurized cylinders are presented in numerical and graphical form. The analysis shows that the location of maximum stress does not generally occur at the junction between the bores, as is commonly supposed, but at some small distance up the crosshole from the junction. Maximum stress concentration factors (SCFs) are defined on the basis of the maximum principal stress, von Mises equivalent stress, and stress intensity. Three-dimensional plots of the SCF against the cylinder radius ratio b/a and the crosshole-to-main-bore-radius ratio c/a are presented. The SCFs were found to vary across the range of geometries considered with local minima identified within the parameter range in most cases. The results therefore allow designers to select optimum b/a and c/a ratios to minimize stress concentration in real problems.
On the stress analysis of a wound coil with application to electromagnet manufacture
Authors: Huber J E , Nowell D , Hills D. A
Published: August 2007

This paper presents an axisymmetric stress analysis of electromagnet manufacture. The processes covered are coil winding, mandrel removal, and heating or cooling. The effects of variable winding tension, mandrel elasticity, and coil-mandrel anisotropy are analysed. Distributions of radial and tangential stress are presented for a wide range of example geometries and conditions, and the use of the techniques to optimize residual stress fields at the conceptual design stage is discussed. The analysis has clear application to other winding processes such as coiling of sheet and manufacture of composite tubes. Comparisons are made between the current analysis and previous analyses of these other processes which have appeared in the literature.
Fracture mechanics approach to design analysis of notches, steps, and internal cut-outs in planar components
Authors: Gray T. G F , Wood J
Published: August 2007

A new approach to the assessment and optimization of geometric stress-concentrating features is proposed on the basis of the correspondence between sharp crack or corner stressfield intensity factors and conventional elastic stress concentration factors (SCFs) for radiused transitions. This approach complements the application of finite element analysis (FEA) and the use of standard SCF data from the literature. The method makes it possible to develop closed-form solutions for SCFs in cases where corresponding solutions for the sharp crack geometries exist. This is helpful in the context of design optimization. The analytical basis of the correspondence is shown, together with the limits on applicability where stress-free boundaries near the stress concentrating feature are present or adjacent features interact. Examples are given which compare parametric results derived from FEA with closed-form solutions based on the proposed method. New information is given on the stress state at a 90° corner or width step, where the magnitude of the stress field intensity is related to that of the corresponding crack geometry. This correspondence enables the user to extend further the application of crack-tip stress-field intensity information to square-cornered steps, external U-grooves, and internal cut-outs.
Coupled torsional-lateral vibration of the unbalanced rotor system with external excitations
Authors: Shen X. Y , Jia J H , Zhao M , Jing J. P
Published: August 2007

The coupled torsional-lateral model of the rotor system is set up and governing equations are derived using the Lagrange approach with six degrees of freedom. The gyroscopic effect and gravity are included. Two kinds of unbalance, namely static unbalance and dynamic unbalance, are considered in the rotor system. Torsional and lateral motions are subjected to external excitations. Through numerical simulation, the developed model is used and the coupled torsional-lateral vibrations of the unbalanced rotor system under external excitations are investigated. Some new phenomena are found and discussed.
Mobility investigation of a designed and developed segmented rubber track vehicle on Sepang peat terrain in Malaysia
Authors: Rahman A , Yahya A , Mohiuddin A K M
Published: August 2007

The traction mechanics of a vehicle was developed based on the track-terrain interaction mechanism. The vehicle was tested on three different terrains: terrain I, terrain II, and terrain III. The tractive effort of the vehicle increased 14 per cent when the moisture content of the terrain increased from 59.85 per cent to 81.06 per cent. A traction coefficient of 48 per cent of the vehicle's gross weight justified the vehicle's optimum design for the Sepang peat terrain. Less variability of the vehicle's tractive effort for straight motion in the range of 7.5 per cent to 13.2 per cent and for turning motion in the range of 9 per cent to 11.5 per cent between the predicted and measured tractive effort on the peat terrain III for different loading and operating speeds substantiate the validity of the developed mathematical model.
A dynamic precedence queue mechanism to assign efficient bandwidth in controller area networks
Authors: Yun J-M , Choi H-S , Lee J-M
Published: August 2007

This paper presents a dynamic precedence queue mechanism to resolve unexpected transmission delay of a lower priority transaction in a controller area network (CAN)-based system that keeps a fixed priority in data transactions. The mechanism is implemented in the upper sublayer of the data link layer (DLL), which is fully compatible with the original medium access control layer protocol of the CAN. Thus, the mechanism can be implemented dynamically while the data transactions are continuing without any hardware modification. The CAN protocol was originally developed to be used in the automotive industry and was recently applied for a broader class of automated factories. Even though the CAN is able to satisfy most real-time requirements found in automated environments, it is not able to enforce either a fair subdivision of the network bandwidth among the stations or a satisfactory distribution of the access delays in message transmissions. The proposed solution provides a superset of the CAN logical link layer control, which can coexist with older CAN applications. Through real experiments, effectiveness of the proposed mechanism has been verified.
Data-driven algorithms for engine friction estimation
Authors: Stotsky A A
Published: August 2007

Errors in the estimation of friction torque in modern spark ignition automotive engines necessitate the development of real-time algorithms for adaptation of the friction torque. Friction torque in the engine control unit is presented as a look-up table with two input variables (the engine speed and indicated engine torque). The algorithms proposed in this paper estimate the engine friction torque via the crankshaft speed fluctuations at the fuel cut-off state and at idle. A computationally efficient filtering algorithm for reconstruction of the first harmonic of a periodic signal is used to recover an amplitude which corresponds to engine events from the noise-contaminated engine speed measurements at the fuel cut-off state. The values of the friction torque at the nodes of the look-up table are updated, when new measured data of the friction torque are available. New data-driven algorithms which are based on a stepwise regression method are developed for adaptation of look-up tables. The algorithms are verified by using a spark ignition six-cylinder prototype engine.
Brake squeal noise due to disc run-out
Authors: Park J-P , Choi Y-S
Published: August 2007

To understand brake squeal noise, the sound and vibration of an automobile brake system were measured using a brake dynamometer. The experimental results show that an important factor in squeal generation is the run-out due to disc misalignment. A three-degrees-of-freedom model is developed for the brake system, where the run-out effect and non-linear friction characteristic are included. A stability analysis of the model was also performed to predict the generation of squeal with the modification of the brake system. The results show that squeal generation is dependent on the run-out rather than the friction characteristic between the pad and disc.
Using the swirl phenomenon in automotive engine mufflers
Authors: Mohammed Ali A A K , Ali Y D , Jassim R K
Published: August 2007

This paper presents a new and cost-effective design for automotive engine mufflers using the swirl phenomenon. The new design results have been compared with the commercial mufflers with and without a catalytic converter and have shown that the noise level is competitive at high rotational speeds, that there is a reduction in back pressure up to 60 per cent which ultimately reduces HC and CO, and that there is an improvement in combustion efficiency of up to 2.11 per cent.
Enhancement of the combustion process in dual-fuel engines at part loads using exhaust gas recirculation
Authors: Pirouzpanah V , Saray R Khoshbakhti
Published: August 2007

Dual-fuel engines at part loads inevitably suffer from lower thermal efficiency and higher carbon monoxide and unburned fuel emission. The present work was carried out to investigate the combustion characteristics of a dual-fuel (diesel-gas) engine at part loads, using a single-zone combustion model with detailed chemical kinetics for combustion of natural gas fuel. The authors have developed software in which the pilot fuel is considered as a subsidiary zone and a heat source derived from two superimposedWiebe combustion functions to account for its contribution to ignition of the gaseous fuel and the rest of the total released energy. The chemical kinetics mechanism consists of 112 reactions with 34 species. This quasi-two-zone combustion model is able to establish the development of the combustion process with time and the associated important operating parameters, such as pressure, temperature, heat release rate (HRR), and species concentration. Therefore, this paper describes an attempt to investigate the combustion phenomenon at part loads and using hot exhaust gas recirculation (EGR) to improve the above-mentioned drawbacks and problems. By employing this technique, it is found that lower percentages of EGR and allowance for its thermal and radical effects have a positive influence on performance and emission parameters of dual-fuel engines at part loads. Predicted values show good agreement with corresponding experimental values under special engine operating conditions (quarter-load, 1400 r/min). Implications are discussed in detail.
Optimal design of engine mount rubber considering stiffness and fatigue strength
Authors: Lee J S , Kim S C
Published: August 2007

Engine mount rubber (EMR) is an important vehicle component to isolate the vehicle structure from engine vibration. The paper deals with optimal design of EMR considering the material stiffness and fatigue strength of a rubber. The objective is to minimize both the weight and the maximum stress of EMR, and to maximize the fatigue life cycle subjected to constraints on the static stiffness of the rubber. A hyperelastic rubber model with a high strain range is used to accommodate the non-linear behaviour of EMR in the stress and fatigue analysis. In the context of approximate optimization, a back-propagation neural network is used to construct global response surfaces between input design variables and output responses of objective functions and constraints. A microgenetic algorithm (MGA) is adopted as a global optimizer in order to consider the inherent non-linearity of analysis model as well. A multi-objective optimization result shows improved design performances regarding the reduction in the maximum stress and the increase in the life cycle with acceptable material stiffness.
Control of a spark ignition homogeneous charge compression ignition mode transition on a gasoline direct injection engine
Authors: Tian G , Wang Z , Ge Q , Wang J , Shuai S
Published: August 2007

The hybrid combustion mode is an ideal operation strategy for a gasoline homogeneous charge compression ignition (HCCI) engine. A stable and smooth spark ignition (SI)/HCCI switch has been an issue in the research on multimode combustion. In this paper, the switch process has two key issues; the cam profile and throttle opening. With the developed two-stage cam system, the valve phase strategy can be switched within one engine cycle, from the normal cam profile for the SI mode to a negative valve overlap (NVO) profile for the HCCI mode, or vice versa. For a smoother and more stable switch, the throttle change was separated from the cam profile switch, which was called the stepped switch. The effect of throttle opening on HCCI combustion was studied, and the results showed that the concept of the stepped switch was reliable. With gasoline direct injection (GDI) the combustion mode switches from both SI and HCCI sides were smooth, rapid, and robust, without any abnormal combustion such as knocking and misfiring.
Experimental study on vapour pressure of dimethyl ether blended in diesel oil
Authors: Li Genbao , Zhou Longbao , Liu Shenghua , Pan Keyu
Published: August 2007

Experiments have been conducted to determine the vapour pressure of dimethyl ether (DME) blended in diesel oil in a thermophysical property measurement system with high accuracy. Based on previous research on the viscosity of DME blends, three blends at 10, 20, and 30 wt% DME in diesel oil were chosen for this study. Experimental results indicate that DME can be soluble in diesel oil at room temperature. The vapour pressure of blends is lower than that of pure DME at a certain temperature and decreases with increase in diesel oil in DME, which helps to eliminate vapour lock in the fuel supply system of the engines. In addition, the cloud point of blends decreases as the fraction of DME in the diesel oil increases, which is beneficial to the operation of the engines at a lower ambient temperature.
Collapse study of thin-walled polygonal section columns subjected to oblique loads
Authors: Hosseini-Tehrani P , Pirmohammad S
Published: August 2007

The present paper deals with the collapse simulation of aluminium alloy extruded polygonal section columns subjected to oblique loads. Oblique load conditions in numerical simulations are applied by means of impacting a declined rigid wall on the tubes with no friction in this task. The explicit finite element code LS-DYNA is used to simulate the crash behaviour of polygonal section columns that are undergoing both axial and bending collapse situations. In order to validate LS-DYNA results the collapse procedure of square columns is successfully simulated and the obtained numerical results are compared with actual available experimental data. Mean crush loads and permanent displacements corresponding to load angles have been investigated, considering columns with square, hexagonal, octagonal, decagonal, and circular cross-sections. It is shown that the octagonal cross-section has better characteristics from the point of view of vehicle crashworthiness under oblique load conditions.
Fuzzy logic consequent perturbation analysis for electric vehicles
Authors: Economou J T , Tsourdos A , White B A
Published: August 2007

This paper presents a methodology for the estimation of upper and lower bounds due to sensor errors for the class of fuzzy Sugeno systems with linear consequent polynomials. The proposed method was also applied to the electrical permanent magnet actuator of an electric vehicle in order to demonstrate its effectiveness. Fuzzy logic Sugeno modelling approaches mainly concentrate on inserting uncertainty in the fuzzy antecedent. In this paper the focus is on perturbations in the consequent polynomial parameters for every possible rule.
In-situ engineering of cartilage repair: a pre-clinical in-vivo exploration of a novel system
Authors: Seedhom B B , Luo Z-J , Goldsmith A J , Toyoda T , Lorrison J C , Guardamagna L
Published: August 2007

This investigation explores a new cartilage repair technique that uses a novel method to secure a non-woven multifilamentous scaffold in the defect site after microfracture. The hypothesis is that a scaffold provides a larger surface area for attachment and proliferation of the mesenchymal stem cells that migrate from the bone marrow. Two in-vivo studies were undertaken in an ovine model. The first study, which lasted for 8 weeks, aimed to compare the new technique with microfracture. Chondral defects, 7 mm in diameter, were created in both femoral medial condyles of five ewes. One defect was treated with the new technique while the contralateral knee was treated with microfracture alone. The results revealed that the quantity of repair tissue was significantly greater in the defects treated with the new system. The second study had two time points, 3 and 6 months, and used 13 ewes. In this study, both defects were treated with the new technique but one received additional subchondral drilling in order to stimulate extra tissue growth. The majority of the implants had good tissue induction, filling 50-100 per cent of the defect volume, while the compressive modulus of the repairs was in the range of 40-70 per cent of that for the surrounding cartilage. In addition, hyaline-like cartilage was seen in all the repairs which had the additional drilling of the subchondral bone.
The fate of implanted autologous chondrocytes in regenerated articular cartilage
Authors: Min B-H , Woo J-I , Kim W H , Kweon O-K , Triffitt J T , Choi B H , Park S R
Published: August 2007

Autologous chondrocyte implantation (ACI) is used to treat some articular cartilage defects. However, the fate of the cultured chondrocytes after in-vivo transplantation and their role in cartilage regeneration remains unclear. To monitor the survival and fate of such cells in vivo, the chondrocytes were labelled with a lipophilic dye and the resultant regenerated tissue in dogs examined. It was found that, 4 weeks after implantation, the osteochondral defects were filled with regenerative tissue that resembled hyaline cartilage. Fluorescence microscopy of frozen sections of the regenerated tissue revealed that the majority of cells were derived from the DiI-labelled implanted chondrocytes. From these results, it was concluded that a large population of implanted autologous chondrocytes can survive at least 4 weeks after implantation and play a direct role in cartilage regeneration. However, it remains unknown whether other cells, such as periosteal cells or bone marrow stromal stem cells, are involved in the regeneration of cartilage after ACI.
Nanomechanical properties of alginate-recovered chondrocyte matrices for cartilage regeneration
Authors: Tomkoria S , Masuda K , Mao J
Published: August 2007

Tissue-engineered cartilage constructs designed for in-vivo applications intuitively should mimic the mechanical properties of native cartilage. The objective of the present work was to characterize the nanomechanical properties of alginate-recovered chondrocyte matrices as a function of ex-vivo incubation time. Chondrocytes isolated from the articular cartilage of the mature bovine metacarpophalangeal joints were cultured with alginate hydrogel to allow for the formation of extracellular matrices. The recovered chondral constructs after 2, 4, 8, and 12 weeks of ex-vivo incubation were analysed using nanoindentation with atomic force microscopy to determine their mechanical properties. Chondral constructs had average Young's moduli of 123±22 kPa, 174±31 kPa, 373±40 kPa, and 564±79 kPa after incubation for 2, 4, 8, and 12 weeks respectively, indicating the gradual attainment of mechanical stiffness. This escalating trend of micromechanical properties as a function of increasing ex-vivo incubation time suggests that chondral constructs via a tissue-engineering approach are capable of elaborating extracellular matrices and increase mechanical stiffness. The relationship between Young's modulus and incubation time of the chondral constructs is useful in the design and fabrication of tissue-engineered cartilage constructs.