bluuebunny/crossref_metadata_2025 huggingface dataset:
Periodontal repair in dogs: effect of recombinant human transfornning growth factor‐β1 on guided tissue regeneration
Authors: Wikesjö Ulf M. E. , Razi Saghi S. , Sigurdsson Thorarinn J. , Tatakis Dimitris N. , Lee Michael B. , Ongpipattanakul Boonsri , Nguyen Tue , Hardwick Ross
Published: December 2005

Abstract. This study evaluated alveolar bone and cementum regeneration following surgical implantation of recombinant human transforming growth factor‐β1 (rhTGF‐β1) in conjunction with guided tissue regeneration (GTR). Supraalvcolar, critical size, periodontal defects were surgically created around the 3rd and 4th mandibular premolar teeth in right and left jaw quadrants in 5 beagle dogs. Alternate jaw quadrants in consecutive animals received rhTGF‐β1 in a CaCO3/ hydroxyethyl starch carrier with GTR, or carrier with GTR alone (control), 20μg of rhTGF‐/A in buffer solution was incorporated into approximately 0.8 ml of carrier for each defect scheduled to receive rhTGF‐β1. Animals were sacrificed at week 4 postsurgery and tissue blocks were harvested and processed for histo‐metric analysis. Clinical healing was generally uneventful. Minor membrane exposures were observed. Defects with membrane exposure displayed an inflammatory infiltrate underneath the membrane. Bone regeneration of trabecular nature, apparent in all animals, was generally limited to the very apical aspect of the defects. Cementum regeneration was limited without obvious differences between experimental conditions. Comparing rhTGF‐β to control defects, statistically significant differences were found for area (1.8±0.4 and 1.3±0.6 mm2, respectively: p<0.05) and density (0.3±0.1 and 0.2±0.03. respectively: p<0.05) of alveolar bone regeneration. Observed differences are small and represent a clinically insignificant potential for enhanced regeneration in this preclinieal model. Within the limitations of study, it may be concluded that rhTGF‐β1 has a restricted potential to enhance alveolar bone regeneration in conjunction with GTR.
Evaluation of osteocalcin and pyridinium crosslinks of bone collagen as markers of bone turnover in gingival crevicular fluid during different stages of orthodontic treatment
Authors: Griffiths G. S. , Moulson A. M. , Petrie A. , James I. T.
Published: December 2005

Abstract. Osteocalcin (Oc) and the collagen cross‐links pyridinoline (Pyr) and deoxypyridinoline (dPyr) arc used as markers of bone turnover in metabolic bone diseases. The aims of this study were: 1) to establish if Oc, Pyr and dPyr can be detected in GCF and 2) using the orthodontic tooth movement model of alveolar bone resorption to evaluate GCF levels of osteocalcin and these collagen cross‐links as markers of bone breakdown. Plaque, colour and bleeding indices, probing measurements and GCF samples were collected at two sites in each of 20 adolescents, during 4 stages of fixed appliance therapy: (1) prior to appliance lit. (2) post appliance fit, (3) during active retraction of the maxillary canines. (4) during retention. GCF was collected onto filter paper strips and the volume determined by weighing. An ELISA kit was used for the detection of osteocalcin, whereas Pyr and dPyr were assayed using high performance liquid chromotography (HPLC). Wilcoxon signed ranks test and Bonferroni correction revealed statistically significant increases in plaque (p= 0.012), GCF volume (p= 0.024) and osteocalcin concentration (p= 0.012). between stages 1 and 2. There were no statistically significant differences between the other variables at this stage or between any of the variables at stages 2 and 3, or between stages 3 and 4, All but 3 of the GCF samples yielded detectable osteocalcin, with large site and subject variation. The median values of osteocalcin and osteocalcin concentration of all the samples were 87.,5 pg and 66 pg/μl, with a range of 0–1,248 pg. 0–1,572 pg/μl. The detection of osteocalein in GCF during every stage, the wide variation between subjects, and the lack of a consistent pattern related to stages of orthodontic treatment, suggests that osteocalcin may merely be a constituent of GCF associated with the developing dentition, which would reduce its potential as a marker of bone turnover in this group. None of the 16 GCF samples analysed for Pyr and dPyr gave a positive result. This study confirms that fitting an orthodontic appliance results in plaque accumulation and increased gingival inflammation, and that GCF volume is the most sensitive indicator of that inflammation. Osteocalcin was detected in GCF collected from adolescents, whereas Pyr and dPyr could not be detected. Further work is required lo establish whether GCF osteocalcin levels can be used as a marker of bone turnover, and whether improvements in the sensitivity of detecting Pyr & dPyr make further study of these promising bone markers worthwhile.
GTR treatment of degree III furcation defects following application of enamel matrix proteins
Authors: Araújo M. G. , Lindhe J.
Published: December 2005

Abstract. The aim of the present study was to evaluate the effect of enamel matrix proteins (EMD) on periodontal wound healing in degree III furcation defects in dogs. The experiment was performed in 5 foxhound dogs, 2 months prior to the start of the experiment, the 2nd and 4th lower premolars were extracted. Degree Iii furcation defects were created in the 3rd mandibular premolars (2P3). The furcation defects were subsequently exposed to reconstructive surgery, Buccal and lingual full thickness flaps were elevated in the lower premolar regions. The exposed root surfaces of the experimental teeth were planed. A notch was placed in the roots at the base of the defect. In one side of the mabdible (Test group), phosphoric acid gel was applied over the root surfaces for 15 s. The acid was removed by flushing the root surfaces with sterile saline. Subsequently, a gel of EMD was applied to cover all instrumented root surfaces. Following gel application, a resorbable barrier membrane was adjusted to cover the buccal and lingual entrances of the furcation defect. The flaps were repositioned to cover the barrier and sutured. The contralateral premolar (Control group) received the same treatment, but acid etching was not performed and EMD was not applied prior to barrier installation, 4 months after reconstructive surgery, the animals were sacrificed and biopsies from the 3P3 regions harvested. The biopsies were placed in a fixative, demineralized in EDTA, dehydrated and embedded in paraffin, 3 mesiodistal sections, representing the central portion of the furcation site, were selected for histological analysis of the defect. The furcation defects of both the Test and Control groups were clinically closed and were found to harbor bone and periodontal ligament tissue which appeared to be in structural continuity with a newly formed root cementum. The relative amounts of mineralized bone, bone marrow and periodontal ligament tissue that had formed were similar in the Test and the Control group. In the Test group, however, the cementum that had formed in the apical portion of the furcation detect was different from the corresponding tissue in the coronal portion, and also different from the cementum observed in the Control group. In the apical portion of the test defect a thin (12 μm) acellular cementum had been laid down, while in the coronal portion a thick (32 μm) cellular cementum, similar to the cementum found in the Control group. could be observed. The current observation, hence, seems to confirm that EMD when applied onto an instrumented and acid etched dentine surface may create an environment conducive for the formation of acellular cementum.
Assessment of alveolar bone levels from intraoral radiographs in subjects between ages 15 and 94 years seeking dental care
Authors: Persson Rigmor E. , Hollender Lars G. , Persson G. Rutger
Published: December 2005

Abstract. Studies have shown that <20% of the US population has periodontal disease. Studies of radiographs have shown that alveolar bone loss increases with age. Bone loss assessed from intraoral radiographs describing 10,282 teeth from 416 subjects seeking dental care during a 3 month period at the University of Washington were studied. The mean age of the subjects was 47.2 years (SD±15.2). The youngest subjects (15–24) had on average 29.6 teeth (SD±2.2) and the oldest subjects (75–94) 19.3 teeth (SD±6.6). This difference was statistically significant (F=16.57. p<0.00l). No association was found between alveolar bone loss (CEJ‐ABC). and TMD symptoms. Smoking was significantly associated with both general bone loss (CEJ‐ABC) (x2=114.9. p<0.0001), and vertical bone defects (angular) (x2= 101.8. p<0.0001). In this study population (15–94 years), alveolar bone loss progressed as defined by the slope (β=0.29) between age 15–34, but was almost flat from age 50 years (β=0.04). The data suggested an overall rate of alveolar bone loss of 0.02 mm per year. Stepwise multiple regression analysis showed that smoking was the primary factor in bone loss (t=7.7, p<0.0001), followed by age (t=7.0. p<0.001) and gender (t=3.0. p<0.01). TMD symptoms could not explain the presence and severity of horizontal or vertical defects. If the CEJ‐ABC distance above the mean plus 2× the SD was used as the cutoff value to define abnormal bone levels. 10.9% of the younger (15–45 years), and 10.7%) of the older subjects (50–94) had significant alveolar bone loss. 73.9% of the younger and 100% of the older subjects with such extent of alveolar bone loss were smokers.
Phylloquinone in gingival crevicular fluid in adult periodontitis
Authors: Rawlinson Andrew , Walsh Trevor F. , Lee Allison , Hodges Stephen J.
Published: December 2005

Abstract. Phylloquinone is a lipid soluble vitamin which is an absolute growth requirement for black‐pigmented anaerobes, many of which are implicated in the aetiology of periodontal diseases. This cross‐sectional study aimed to detect the levels of phylloquinone in GCF from healthy and diseased sites in subjects with adult periodontitis, in order to investigate further its potential role in the disease process. The sample consisted of eighteen patients with adult periodontitis. Periodontal probing depths, attachment levels and gingival indices were recorded from one healthy and one diseased site in each subject. GCF was sampled and the amount of phylloquinone in each sample was determined using reverse‐phase high performance liquid chromatography coupled to electrochemical detection. The mean amount of phylloquinone in accumulated GCF from diseased sites was 406 pg/site and 80 pg/site from healthy sites (p=0.013). When the amounts of phylloquinone in GCF were expressed as concentrations the values were 228 ng/ml and 3350 ng/ml for diseased and healthy sites respectively (p=0.084). These findings suggest the levels of phylloquinone in GCF differs in periodontal health and disease in subjects with adult periodontitis. The total phylloquinone at diseased sites may provide the nutritional requirements favouring the growth of black‐pigmented anaerobes.
A split‐mouth placebo‐controlled study to determine the effect of amorphous calcium phosphate in the treatment of dentine hypersensitivity
Authors: Yates R. , Owens J. , Jackson R. , Newcombe R. G. , Addy M.
Published: December 2005

Abstract. Many treatments for dentine hypersensitivity are formulated to directly or indirectly occlude the open dentinal tubules associated with the condition. Combining solutions of calcium chloride and potassium phosphate can result in the precipitation of amorphous calcium phosphate. Such a system applied to exposed dentine could occlude dentinal tubules and reduce sensitivity. The aims of this study using a placebo control were to assess the therapeutic value of amorphous calcium phosphate in dentine hypersensitivity and provide further information on the apparently natural improvement in the condition frequently observed in clinical trials. 38 subjects with dentine hypersensitivity affecting 1 tooth in each left and right sides of the jaws were recruited into this split mouth, randomised, double‐blind study. At baseline, sensitivity was scored by the subjects on a 0–10 visual apologue scale after tactile, cool and cold water and evaporative stimulation of the test teeth. Active and control, water, solutions were then applied by a 2nd clinician. After 24 h, subjects returned for rescoring. On days 7 and 14, subjects were again rescored and the treatments reapplied. Further follow‐up appointments for rescoring were on days 21, 28, 56 and 84. Plaque scores also were recorded from test teeth at each visit. Overall sensitivity decreased considerably and to a similar degree in test and control teeth with no consistent significant treatment difference. Plaque scores also decreased through the study period. It is concluded that either the amorphous calcium phosphate was without therapeutic effect or the activity was masked by the placebo response in the control teeth.
Evaluation of the incidence of gingival abrasion as a result of toothbrushing
Authors: Danser M. M. , Timmerman M. F. , IJzerman Y. , Bulthuis H. , van der Velden U. , van der Weijden G. A.
Published: December 2005

Abstract. The aims of the present study were: (1) to establish the incidence of gingival abrasion as a result of toothbrushing. using a manual and electric toothbrush: (2) to establish the influence of filament end‐rounding on the incidence of gingival abrasion and the efficacy of toothbrushing: (3) to assess whether the speed of the electric brush has a feedback‐effect on the brushing force used and to correlate the incidence of gingival abrasion with force. 2 experiments were earned out. In the first experiment, 50 subjects brushed for 3 weeks every other day with either a manual (Butler 411) or an electric toothbrush (Braun/Oral‐B Ultra Plaque Remover‐D9). All received brief instructions and were asked to abstain from oral hygiene 24 hrs before their appointment. After disclosing the teeth and gums with Mira‐2‐Tone solution, plaque and gingival abrasion were assessed. Next, the panellists brushed in a random split‐mouth order. After brushing and a second disclosing, plaque and abrasion were re‐assessed. The results showed that the incidence of gingival abrasion was comparable for the manual and the D9. Using a similar design as in experiment no. 1, in experiment no. 2 a new group of 47 subjects brushed for 3 weeks alternating between the Braun/Oral‐B Plaque Reniover‐D7 and D9. At the appointment, the subjects first brushed in a split‐mouth order with the D9 with 2 different types of endrounding. Plaque and abrasion were assessed. Immediately following this brushing exercise, the subjects re‐brushed with the D7 (2800 rot/min) and the D9 (3600 rot/min) during which brushing force was measured. The results of this experiment showed that end‐rounding has no effect on plaque removal but does effect the incidence of gingival abrasion. Brushing force is not influenced by the speed of the brushhead and no correlation with the incidence of gingival abrasion was observed. In conclusion, the results of this study show that gingival abrasion is not influenced by brushing force, but is affected by filament endrounding.
The mucosal attachment at different abutments
Authors: Abrahamsson I. , Berglundh T. , Glantz P.‐O. , Lindhe J.
Published: December 2005

Abstract. The present experiment was performed to examine if the material used in the abutment part of an implant system influenced the quality of the mucosal barrier that formed following implant installation. 5 beagle dogs were included in the study. The mandibular premolars and the 1st. 2nd and 3rd maxillary premolars were extracted. Three fixtures of the Brånemark System® were installed in each mandibular quadrant (a total of 6 fixtures per animal). Abutment connection was performed after 3 months of healing. In each dog the following types of abutments were used: 2 “control abutments” (c.p. titanium). 2 “ceramic abutments” (highly sintered Al2O3), 1 “gold abutment”, and 1 “short titanium abutment”. This “short titanium abutment” was provided with an outer structure made of dental porcelain fused to gold. Following abutment connection a plaque control program was initiated and maintained for 6 months. The animals were sacrificed and perfused with a fixative. The mandibles were removed and each implant region was dissected, demineralized in EDTA and embedded in EPON®. Semithin sections representing the mesial, distal, buccal and lingual aspects of the peri‐implant tissues were produced and subjected to histological examination. The findings from the analysis demonstrated that the material used in the abutment portion of the implant influenced the location and the quality of the attachment that occurred between the periimplant mucosa and the implant. Abutments made of c.p. titanium or ceramic allowed the formation of a mucosal attachment which included one epithelial and one connective tissue portion that were about 2 mm and 1–1.5 mm high, respectively. At sites where abutments made of gold alloy or dental porcelain were used, no proper attachment formed at the abutment level, but the soft tissue margin receded and bone resorption occurred. The abutment fixture junction was hereby occasionally exposed and the mucosal barrier became established to the fixture portion of the implant. It was suggested that the observed differences were the result of varying adhesive properties of the materials studied or by variations in their resistance to corrosion.
High levels of soluble intercellular adhesion molecule‐1 (ICAM‐1) in crevicular fluid of periodontitis patients with plaque
Authors: Molé Nathalie , March Anne Kennel‐de , Martin Gérard , Miller Neal , Béné Marie C. , Faure Gilbert C.
Published: December 2005

Abstract. The intercellular adhesion tnolecule‐1 (ICAM‐1) is a membrane‐bound molecule involved in cell‐cell adhesive interactions which is upregulated on inflammatory epithelial cells. The levels of soluble ICAM‐1 (sICAM‐1) shed into the gingival crevicular fluid (GCF) were studied in healthy patients and patients with gingivitis, adult periodontitis or rapidly progressive periodontitis, using an ELISA technique. Clinical parameters including plaque index, gingival index, probing depth, and bleeding on probing were recorded following careful sampling of GCF with standardised filter strips. In GCF, sICAM‐1 levels were higher for patients with plaque (p=0.04) and for patients with inflammation (p=0.02), but did not correlate with disease classifications. These results suggest that elevated GCF sICAM‐1 levels may represent increased shedding of this molecule in the interstitial fluid as a result of membrane‐bound ICAM‐1 upregulation on ICAM‐1 gingival‐bearing cells in relation with plaque accumulation and inflammation.
Effect of expertise and visual contribution on postural control in soccer
Authors: Paillard Th. , Noé F.
Published: December 2005

This work analyzes the postural performance and the use of visual information in soccer players according to their level of competition. Two groups of healthy soccer players were investigated at the mid‐competition season: an amateur (AM) (n=15) group composed of regional‐level players and a professional group at a national level (PRO) (n=15). Posture was assessed by measuring the center of foot pressure (COP) with a force platform during a test (51.2 s) of bipedal quiet standing posture. The test was completed with eyes open (the subjects looked at a fixed‐level target at a distance of 2 m) and closed (they kept their gaze in a straight‐ahead direction). The statistical analysis showed that PRO soccer players were more stable than AM soccer players. Moreover, the contribution of vision in postural maintenance was less important in the PRO players than in the AM players. The present study suggests that intense training allows PRO soccer players to become less dependent on vision to control their posture such that vision can be dedicated to treating the information, that emanates from the game.
An examination of the factorial structure of the Norwegian version of the sport anxiety scale
Authors: Abrahamsen F. E. , Roberts G. C. , Pensgaard A. M.
Published: December 2005

The purpose of the present research was to develop and validate a Norwegian version of the sport anxiety scale (SAS‐N), a multidimensional sport performance trait anxiety inventory. The SAS consists of three unique dimensions measuring somatic anxiety, worry and concentration disruption, respectively. The translation–back translation method was used in development of the SAS‐N, and athletes from different sports in Norway (N=282) participated in the study. The findings are similar to those of the English original, and lend support for the use of this instrument with Norwegian athlete subjects.
Fibrodysplasia ossificans progressiva. An unusual cause of restricted mandibular movement
Authors: van der Meij EH , Becking AG , van der Waal I
Published: December 2005

A 9‐year‐old girl is presented who was initially misdiagnosed and finally diagnosed with fibrodysplasia ossificans progressiva only after presentation with progressive limitation of her mouth opening. The clinical, histopathological, and molecular biological aspects of this uncommon disorder will be discussed. Furthermore, dental and surgical guidelines will be described.
Repeats of LacdiNAc and fucosylated LacdiNAc on N‐glycans of the human parasite Schistosoma mansoni
Authors: Wuhrer Manfred , Koeleman Carolien A. M. , Deelder André M. , Hokke Cornelis H.
Published: December 2005

N‐Glycans from glycoproteins of the worm stage of the human parasite Schistosoma mansoni were enzymatically released, fluorescently labelled and analysed using various mass spectrometric and chromatographic methods. A family of 28 mainly core‐α1–6‐fucosylated, diantennary N‐glycans of composition Hex3−4HexNAc6−12Fuc1−6 was found to carry dimers of N,N′‐diacetyllactosediamine [LacdiNAc or LDN; GalNAc(β1–4)GlcNAc(β1‐] with or without fucose α1–3‐linked to the N‐acetylglucosamine residues in the antennae {GalNAc(β1–4)[±Fuc(α1–3)]GlcNAc(β1–3)GalNAc(β1–4)[±Fuc(α1–3)]GlcNAc(β1‐}. To date, oligomeric LDN and oligomeric fucosylated LDN (LDNF) have been found only on N‐glycans from mammalian cells engineered to express Caenorhabditis elegansβ4‐GalNAc transferase and human α3‐fucosyltransferase IX [Z. S. Kawar et al. (2005) J Biol Chem280, 12810–12819]. It now appears that LDN(F) repeats can also occur in a natural system such as the schistosome parasite. Like monomeric LDN and LDNF, the dimeric LDN(F) moieties found here are expected to be targets of humoral and cellular immune responses during schistosome infection.
Structural diversity of angiotensin‐converting enzyme
Authors: Bingham Richard J. , Dive Vincent , Phillips Simon E. V. , Shirras Alan D. , Isaac R. Elwyn
Published: December 2005

The crystal structure of a Drosophila angiotensin‐converting enzyme (ANCE) has recently been solved, revealing features important for the binding of ACE inhibitors and allowing molecular comparisons with the structure of human testicular angiotensin‐converting enzyme (tACE). ACER is a second Drosophila ACE that displays both common and distinctive properties. Here we report further functional differences between ANCE and ACER and have constructed a homology model of ACER to help explain these. The model predicts a lack of the Cl–‐binding sites, and therefore the strong activation of ACER activity towards enkephalinamide peptides by NaCl suggests alternative sites for Cl– binding. There is a marked difference in the electrostatic charge of the substrate channel between ANCE and ACER, which may explain why the electropositive peptide, MKRSRGPSPRR, is cleaved efficiently by ANCE with a low Km, but does not bind to ACER. Bradykinin (BK) peptides are excellent ANCE substrates. Models of BK docked in the substrate channel suggest that the peptide adopts an N‐terminal β‐turn, permitting a tight fit of the peptide in the substrate channel. This, together with ionic interactions between the guanidino group of Arg9 of BK and the side chains of Asp360 and Glu150 in the S2′ pocket, are possible reasons for the high‐affinity binding of BK. The replacement of Asp360 with a histidine in ACER would explain the higher Km recorded for the hydrolysis of BK peptides by this enzyme. Other differences in the S2′ site of ANCE and ACER also explain the selectivity of RXPA380, a selective inhibitor of human C‐domain ACE, which also preferentially inhibits ACER. These structural and enzymatic studies provide insight into the molecular basis for the distinctive enzymatic features of ANCE and ACER.
Structural Interaction Fingerprints: A New Approach to Organizing, Mining, Analyzing, and Designing Protein–Small Molecule Complexes
Authors: Singh Juswinder , Deng Zhan , Narale Gaurav , Chuaqui Claudio
Published: December 2005

The combination of advances in structure‐based drug design efforts in the pharmaceutical industry in parallel with structural genomics initiatives in the public domain has led to an explosion in the number of structures of protein–small molecule complexes structures. This information has critical importance to both the understanding of the structural basis for molecular recognition in biological systems and the design of better drugs. A significant challenge exists in managing this vast amount of data and fully leveraging it. Here, we review our work to develop a simple, fast way to store, organize, mine, and analyze large numbers of protein–small molecule complexes. We illustrate the utility of the approach to the management of inhibitor complexes from the protein kinase family. Finally, we describe our recent efforts in applying this method to the design of target‐focused chemical libraries.
An Element-Free Galerkin-Finite Element Coupling Method for Elasto-Plastic Contact Problems
Authors: Liu Tianxiang , Liu Geng , Wang Q. Jane
Published: December 2005

The element-free Galerkin-finite element (EFG-FE) coupling method, combined with the linear mathematical programming technique, is utilized to solve two-dimensional elasto-plastic contact problems. Two discretized models for an elastic cylinder contacting with a rigid plane are used to investigate the boundary effects in a contact problem when using the EFG-FE coupling method under symmetric conditions. The influences of the number of Gauss integration points and the size supporting the weight function in the meshless region on the contact pressure and stress distributions are studied and discussed by comparing the numerical results with the theoretical ones. Furthermore, the elasto-plastic contact problems of a smooth cylinder with a plane and a rough surface with a plane are analyzed by means of the EFG-FE method and different elasto-plasticity models.
TEHD Analysis of Thrust Bearings With PTFE-Faced Pads
Authors: Glavatskih S. B. , Fillon Michel
Published: December 2005

Results of a combined theoretical and experimental investigation into the operation of thrust bearings with polytetrafluoroethylene (PTFE)-faced pads are reported. Bearing performance is analyzed in terms of temperature, power loss, oil film thickness and pressure. These parameters are first calculated using a THD model. The effect of PTFE facing on bearing thermal performance is then presented and discussed. A TEHD model is subsequently employed. Obtained TEHD results show that oil film thickness and temperature are strongly affected by the PTFE layer. Theoretical results are compared with measured temperature, oil film thickness, and pressure.
A Novel Approach in the Direct Kinematics of Stewart Platform Mechanisms with Planar Platforms
Authors: Akçali İ. D. , Mutlu H.
Published: December 2005

In handling the kinematic analysis of two rigid bodies connected to each other by six legs through the use of six double spherical joints, methods have been implemented both in the formulation and solution phases of the problem. A three-dimensional problem has been viewed, in fact, as a multitude of two-dimensional works on several planes, the intersections of which yield relationships allowing transition between adjacent planes. Thus formulation is purely based on the geometric structure consisting of eight planes of interest, ending in the three fundamental equations involving three angles between the base and side triangular planes. In solving the resulting three equations, an efficient strategy has been established to come up with 16 solution sets effectively. Extensions of the theory have been shown to include the analyses of other Stewart platform models. Efficiency and effectiveness of the approach has been verified on numerical examples.
Tribological Properties and Acoustic Emissions of Some Thermoplastics Sliding Against SAE52100
Authors: Benabdallah Habib S.
Published: December 2005

Measurements were made of the dynamic friction; wear volume and acoustic signal (AE) of several thermoplastics rubbing against smooth SAE-52100 steel. Polyoxymethylene, polyamide, poly(amide-imide), polypropylene, Poly(vinyl chloride), polytetrafluoroethylene, and polyethylene, were investigated using pin-on-disk configuration. Sliding speeds ranged from 0.05 to 0.45 m∕s, and normal loads from 40 to 160 N (2–8 MPa) for sliding distances varying from 4 to 20 km. Orthogonal experimental design and analysis method was used to develop wear equations expressing wear volume as function of the operating parameters. Consistent relations were also found between the integrated AE signal over time and the wear volume as well as the friction work.
Effect of Intermolecular Forces on the Static and Dynamic Performance of Air Bearing Sliders: Part II—Dependence of the Stability on Hamaker Constant, Suspension Preload and Pitch Angle
Authors: Gupta Vineet , Bogy David B.
Published: December 2005

Intermolecular and surface forces contribute significantly to the total forces acting on air bearing sliders for flying heights below 5 nm. Their contributions to the total force increase sharply with the reduction in flying height, and hence their existence can no longer be ignored in air bearing simulation for hard disk drives. Various experimentally observed dynamic instabilities can be explained by the inclusion of these forces in the model for low flying sliders. In this paper parametric studies are presented using a 3-DOF model to better understand the effect of the Hamaker constants, suspension pre load and pitch angle on the dynamic stability/instability of the sliders. A stiffness matrix is used to characterize the stability in the vertical, pitch, and roll directions. The fly height diagrams are used to examine the multiple equilibriums that exist for low flying heights. It has been found that the system instability increases as the magnitude of the van der Waals force increases. It has also been found that higher suspension pre load and higher pitch angles tend to stabilize the system.
Navier–Stokes Analysis of a Regular Two-Dimensional Roughness Pattern Under Turbulent Flow Regime
Authors: Billy Frédéric , Arghir Mihai , Pineau Gérard
Published: December 2005

The present work deals with the flow characteristics induced by a two-dimensional textured surface. The texture consists of identical and equally spaced rectangles with characteristic lengths at least one order of magnitude larger than the clearance of the thin film. Periodic boundary conditions enable the analysis of a single groove and the complete Navier–Stokes analysis is carried on for turbulent flow Reynolds numbers. The analysis is performed for shear driven flows (Couette), pressure driven flows (Poiseuille), and combined Couette–Poiseuille flows. First, the presence of inertial forces generated by the groove is emphasized by the momentum balance performed for the computational cell. The peculiar effect of the groove is also shown by the rotor and the stator shear stresses variations. Finally, it is shown that despite the presence of fluid inertia forces, cell-averaged rotor, and stator shear stresses obtained for pure Couette or Poiseuille flows can be added or subtracted to obtain with good accuracy the characteristics of combined shear and pressure driven flows.
Fan-Shaped Hole Effects on the Aero-Thermal Performance of a Film-Cooled Endwall
Authors: Barigozzi Giovanna , Benzoni Giuseppe , Franchini Giuseppe , Perdichizzi Antonio
Published: December 2005

The present paper investigates the effects of a fan-shaped hole endwall cooling geometry on the aero-thermal performance of a nozzle vane cascade. Two endwall cooling geometries with four rows of holes were tested, for different mass flow rate ratios: the first configuration is made of cylindrical holes, whereas the second one features conical expanded exits and a reduced number of holes. The experimental analysis is mainly focused on the variations of secondary flow phenomena related to different injection rates, as they have a strong relationship with the film cooling effectiveness. Secondary flow assessment was performed through downstream 3D aerodynamic measurements, by means of a miniaturized 5-hole probe. The results show that at high injection rates, the passage vortex and the 3D effects tend to become weaker, leading to a strong reduction of the endwall cross flow and to a more uniform flow in spanwise direction. This is of course obtained at the expense of a significant increase of losses. The thermal behavior was then investigated through the analysis of adiabatic effectiveness distributions on the two endwall configurations. The wide-banded thermochromic liquid crystals (TLC) technique was used to determine the adiabatic wall temperature. Using the measured distributions of film-cooling adiabatic effectiveness, the interaction between the secondary flow vortices and the cooling jets can be followed in good detail all over the endwall surface. Fan-shaped holes have been shown to perform better than cylindrical ones: at low injection rates, the cooling performance is increased only in the front part of the vane passage. A larger improvement of cooling coverage all over the endwall is attained with a larger mass flow rate, about 1.5% of core flow, without a substantial increase of the aerodynamic losses.
Heat Transfer and Film-Cooling Measurements on a Stator Vane With Fan-Shaped Cooling Holes
Authors: Colban W. , Gratton A. , Thole K. A. , Haendler M.
Published: December 2005

In a typical gas turbine engine, the gas exiting the combustor is significantly hotter than the melting temperature of the turbine components. The highest temperatures in an engine are typically seen by the turbine inlet guide vanes. One method used to cool the inlet guide vanes is film cooling, which involves bleeding comparatively low-temperature, high-pressure air from the compressor and injecting it through an array of discrete holes on the vane surface. To predict the vane surface temperatures in the engine, it is necessary to measure the heat transfer coefficient and adiabatic film-cooling effectiveness on the vane surface. This study presents heat transfer coefficients and adiabatic effectiveness levels measured in a scaled-up, two-passage cascade with a contoured endwall. Heat transfer measurements indicated that the behavior of the boundary layer transition along the suction side of the vane showed sensitivity to the location of film-cooling injection, which was simulated through the use of a trip wire placed on the vane surface. Single-row adiabatic effectiveness measurements without any upstream blowing showed jet lift-off was prevalent along the suction side of the airfoil. Single-row adiabatic effectiveness measurements on the pressure side, also without upstream showerhead blowing, indicated jet lifted-off and then reattached to the surface in the concave region of the vane. In the presence of upstream showerhead blowing, the jet lift-off for the first pressure side row was reduced, increasing adiabatic effectiveness levels.
Effect of Midpassage Gap, Endwall Misalignment, and Roughness on Endwall Film-Cooling
Authors: Cardwell N. D. , Sundaram N. , Thole K. A.
Published: December 2005

To maintain acceptable turbine airfoil temperatures, film cooling is typically used whereby coolant, extracted from the compressor, is injected through component surfaces. In manufacturing a turbine, the first stage vanes are cast in either single airfoils or double airfoils. As the engine is assembled, these singlets or doublets are placed in a turbine disk in which there are inherent gaps between the airfoils. The turbine is designed to allow outflow of high-pressure coolant rather than hot gas ingestion. Moreover, it is quite possible that the singlets or doublets become misaligned during engine operation. It has also become of interest to the turbine community as to the effect of corrosion and deposition of particles on component heat transfer. This study uses a large-scale turbine vane in which the following two effects are investigated: the effect of a midpassage gap on endwall film cooling and the effect of roughness on endwall film cooling. The results indicate that the midpassage gap was found to have a significant effect on the coolant exiting from the combustor-turbine interface slot. When the gap is misaligned, the results indicate a severe reduction in the film-cooling effectiveness in the case where the pressure side endwall is below the endwall associated with the suction side of the adjacent vane.
Turbulent Transport in Pin Fin Arrays: Experimental Data and Predictions
Authors: Ames F. E. , Dvorak L. A.
Published: December 2005

The objective of this research has been to experimentally investigate the fluid dynamics of pin fin arrays in order to clarify the physics of heat transfer enhancement and uncover problems in conventional turbulence models. The fluid dynamics of a staggered pin fin array has been studied using hot wire anemometry with both single- and x-wire probes at array Reynolds numbers of 3000, 10,000, and 30,000. Velocity distributions off the endwall and pin surface have been acquired and analyzed to investigate turbulent transport in pin fin arrays. Well resolved 3D calculations have been performed using a commercial code with conventional two-equation turbulence models. Predictive comparisons have been made with fluid dynamic data. In early rows where turbulence is low, the strength of shedding increases dramatically with increasing Reynolds numbers. The laminar velocity profiles off the surface of pins show evidence of unsteady separation in early rows. In row three and beyond, laminar boundary layers off pins are quite similar. Velocity profiles off endwalls are strongly affected by the proximity of pins and turbulent transport. At the low Reynolds numbers, the turbulent transport and acceleration keep boundary layers thin. Endwall boundary layers at higher Reynolds numbers exhibit very high levels of skin friction enhancement. Well-resolved 3D steady calculations were made with several two-equation turbulence models and compared with experimental fluid mechanic and heat transfer data. The quality of the predictive comparison was substantially affected by the turbulence model and near-wall methodology.
The Influence of Turbulence on Wake Dispersion and Blade Row Interaction in an Axial Compressor
Authors: Henderson Alan D. , Walker Gregory J. , Hughes Jeremy D.
Published: December 2005

The influence of free-stream turbulence on wake dispersion and boundary layer transition processes has been studied in a 1.5-stage axial compressor. An inlet grid was used to produce turbulence characteristics typical of an embedded stage in a multistage machine. The grid turbulence strongly enhanced the dispersion of inlet guide vane (IGV) wakes. This modified the interaction of IGV and rotor wakes, leading to a significant decrease in periodic unsteadiness experienced by the downstream stator. These observations have important implications for the prediction of clocking effects in multistage machines. Boundary layer transition characteristics on the outlet stator were studied with a surface hot-film array. Observations with grid turbulence were compared with those for the natural low turbulence inflow to the machine. The transition behavior under low turbulence inflow conditions with the stator blade element immersed in the dispersed IGV wakes closely resembled the behavior with elevated grid turbulence. It is concluded that with appropriate alignment, the blade element behavior in a 1.5-stage axial machine can reliably indicate the blade element behavior of an embedded row in a multistage machine.
Design and Testing of a Transonic Linear Cascade Tunnel With Optimized Slotted Walls
Authors: Rona Aldo , Paciorri Renato , Geron Marco
Published: December 2005

In linear cascade wind tunnel tests, a high level of pitchwise periodicity is desirable to reproduce the azimuthal periodicity in the stage of an axial compressor or turbine. Transonic tests in a cascade wind tunnel with open jet boundaries have been shown to suffer from spurious waves, reflected at the jet boundary, that compromise the flow periodicity in pitch. This problem can be tackled by placing at this boundary a slotted tailboard with a specific wall void ratio s and pitch angle α. The optimal value of the s-α pair depends on the test section geometry and on the tunnel running conditions. An inviscid two-dimensional numerical method has been developed to predict transonic linear cascade flows, with and without a tailboard, and quantify the nonperiodicity in the discharge. This method includes a new computational boundary condition to model the effects of the tailboard slots on the cascade interior flow. This method has been applied to a six-blade turbine nozzle cascade, transonically tested at the University of Leicester. The numerical results identified a specific slotted tailboard geometry, able to minimize the spurious reflected waves and regain some pitchwise flow periodicity. The wind tunnel open jet test section was redesigned accordingly. Pressure measurements at the cascade outlet and synchronous spark schlieren visualization of the test section, with and without the optimized slotted tailboard, have confirmed the gain in pitchwise periodicity predicted by the numerical model.
Effects of Reynolds Number and Freestream Turbulence on Turbine Tip Clearance Flow
Authors: Matsunuma Takayuki
Published: December 2005

Tip clearance losses represent a major efficiency penalty of turbine blades. This paper describes the effect of tip clearance on the aerodynamic characteristics of an unshrouded axial-flow turbine cascade under very low Reynolds number conditions. The Reynolds number based on the true chord length and exit velocity of the turbine cascade was varied from 4.4×104 to 26.6×104 by changing the velocity of fluid flow. The freestream turbulence intensity was varied between 0.5% and 4.1% by modifying turbulence generation sheet settings. Three-dimensional flow fields at the exit of the turbine cascade were measured both with and without tip clearance using a five-hole pressure probe. Tip leakage flow generated a large high total pressure loss region. Variations in the Reynolds number and freestream turbulence intensity changed the distributions of three-dimensional flow, but had no effect on the mass-averaged tip clearance loss of the turbine cascade.
Investigation of Vortex Shedding and Wake-Wake Interaction in a Transonic Turbine Stage Using Laser-Doppler-Velocimetry and Particle-Image-Velocimetry
Authors: Göttlich E. , Woisetschläger J. , Pieringer P. , Hampel B. , Heitmeir F.
Published: December 2005

The current paper presents a time-resolved experimental flow investigation in a highly loaded transonic gas turbine stage operating continuously under engine representative conditions. The measurement was performed with a two-component laser-doppler-velocimeter (LDV) and a three-component stereoscopic particle-image-velocimeter (3C-PIV). Unsteady velocity data were obtained in axis perpendicular planes (LDV) and tangential planes (3C-PIV) between stator and rotor as well as downstream of the rotor. The results of the time-resolved investigation at several radii show the vortex shedding process from the trailing edges of nozzle guide vanes and rotor blades. This vortex shedding was found to be phase locked to higher harmonics of the blade passing frequency. Pressure waves evoked by reflection of the trailing edge shocks of the vanes on the passing rotor blades interact with the boundary layers on the rear suction side of the vanes and on the rotor blade surfaces while running upstream and downstream the flow. They are responsible for this phase-locking phenomenon of the shedding vortices. At midspan, the vortices shedding from stator and rotor blades were also observed by PIV. The in-plane vorticity distribution was used to discuss the wake-wake interaction indicating that wake segments from the nozzle guide vanes were chopped by the rotor blades. These chopped segments are still visible in the distributions as a pair of counter rotating vortices. The nozzle wake segments are transported through the rotor passages by the flow, influencing the vortex street of the rotor blades as they pass by with the higher velocity of the main flow. A comparison with a numerical simulation is also given.
Film Cooling Effectiveness and Heat Transfer on the Trailing Edge Cutback of Gas Turbine Airfoils With Various Internal Cooling Designs
Authors: Martini P. , Schulz A. , Bauer H.-J.
Published: December 2005

The present study deals with trailing edge film cooling on the pressure side cutback of gas turbine airfoils. Before being ejected tangentially onto the inclined cut-back surface the coolant air passes a partly converging passage that is equipped with turbulators such as pin fins and ribs. The experiments are conducted in a generic setup and cover a broad variety of internal cooling designs. A subsonic atmospheric open-loop wind tunnel is utilized for the tests. The test conditions are characterized by a constant Reynolds number of Rehg=250000, a turbulence intensity of Tuhg=7%, and a hot gas temperature of Thg=500K. Due to the ambient temperature of the coolant, engine realistic density ratios between coolant and hot gas can be realized. Blowing ratios cover a range of 0.20<M<1.25. The experimental data to be presented include discharge coefficients, adiabatic film cooling effectiveness, and heat transfer coefficients in the near slot region (x∕H<15). The results clearly demonstrate the strong influence of the internal cooling design and the relatively thick pressure side lip (t∕H=1) on film cooling performance downstream of the ejection slot.
Error Analysis on Finite Element Modeling of Involute Spur Gears
Authors: Wang Jian D. , Howard Ian M.
Published: December 2005

Finite element analysis can incorporate two-dimensional (2D) modeling if the geometry, load, and boundary conditions meet the requirements. For many applications, a wide range of problems are solved in 2D, due to the efficiency and costs of computation. However, care has to be taken to avoid modeling errors from significantly influencing the result. When the application area is nonlinear, such as when modeling contact problems or fracture analysis, etc, the 2D assumption must be used cautiously. In this paper, a large number of 2D and three-dimensional (3D) gear models were investigated using finite element analysis. The models included contact analysis between teeth in mesh, a gear body (disk), and teeth with and without a crack at the tooth root. The model results were compared using parameters such as the torsional (mesh) stiffness, tooth stresses and the stress intensity factors that are obtained under assumptions of plane stress, plane strain, and 3D analysis. The models considered variations of face width of the gear from 5 mm to 300 mm. This research shows that caution must be used especially where 2D assumptions are used in the modeling of solid gears.