bluuebunny/crossref_metadata_2025 huggingface dataset:
Levels of interleukin‐17 in gingival crevicular fluid and in supernatants of cellular cultures of gingival tissue from patients with chronic periodontitis
Authors: Vernal Rolando , Dutzan Nicolás , Chaparro Alejandra , Puente Javier , Antonieta Valenzuela María , Gamonal Jorge
Published: March 2005

Background and Aims: Interleukin‐17 (IL‐17) is a T‐cell‐derived cytokine that may play an important role in the initiation or maintenance of the pro‐inflammatory response and has recently been found to stimulate osteoclastic resorption. The purpose of the present study was to determine the presence of IL‐17 in gingival crevicular fluid (GCF) samples and in the culture supernatants of gingival cells from patients with chronic periodontitis.

Method: GCF samples were collected during 30 s from two sites in 16 patients from periodontally affected sites (probing depth 5 mm, attachment loss 3 mm). The comparison with healthy controls was carried out by collecting GCF samples from eight healthy volunteers. GCF was collected using a paper strip and ELISA was performed to determine the total amount of IL‐17. Supernatant cellular cultures of gingival cells were obtained from periodontal biopsies taken from 12 periodontitis patients and from eight healthy control subjects during the surgical removal of wisdom teeth. Spontaneous and phytohaemagglutinin (PHA)‐stimulated levels of IL‐17 were determined by ELISA.

Results: The total amount of cytokine IL‐17 was significantly higher in the periodontitis group than the control group (45.9 versus 35.6 pg, p=0.005). Significantly higher GCF volume and amount of total proteins were obtained from periodontitis patients as compared with control subjects (0.98 versus 0.36 μl, p=0.0005; 0.12 versus 0.05 μg, p=0.0005, respectively). A higher concentration of IL‐17 was detected in culture supernatants from periodontitis patients compared with healthy subjects, either without stimulation (36.28±8.39 versus 28.81±1.50 μg/ml, p=0.011) or with PHA stimulation (52.12±14.56 versus 39.00±4.90 μg/ml, p=0.012). Treatment with PHA induced a significant increase in the production of IL‐17 in healthy subjects and periodontitis patients (p=0.001 and 0.003).

Conclusions: The total amount of cytokine IL‐17 in GCF samples and in the culture supernatants of gingival cells are significantly increased in periodontal disease.
Periodontal dressing (Vocopac®) influences outcomes in a two‐step treatment procedure
Authors: Sigusch B. W. , Pfitzner A. , Nietzsch T. , Glockmann E.
Published: March 2005

Objectives: It is not clear if periodontal dressing influences the long‐term results in a non‐surgical treatment procedure.

Material and Methods: The periodontal parameters (pre‐baseline) of 36 patients with aggressive periodontitis were obtained before the patients were treated initially (1st step) by a dental hygienist, who completely removed the supra‐ and subgingival concrements. Baseline parameters were raised 3 weeks after the 1st step, before the 2nd therapy step was conducted. It consisted of a non‐surgical procedure, which comprised a closed full‐mouth manual root curettage (root planing), immediate systemic application of metronidazole, and the placement of a periodontal dressing (Vocopac®, Voco). The patients were randomized to two test groups having their periodontal packs removed after 3–4 days (group 1, n=12) and 7–8 days (group 2, n=12), respectively and a control group (n=12) without periodontal dressing. Clinical parameters were raised again after 6 and 24 months.

Results: Six and 24 months later, changes in probing pocket depth (PPD) and probing attachment level (PAL) were observed in all three groups compared with baseline, but the difference was significant in group 2 only. In addition, group 2 showed a greater reduction in mean PPD and also a significantly greater gain of attachment in comparison with the controls.

Conclusion: Wound dressing has a positive effect on clinical long‐term results using a two‐step non‐surgical procedure. Moreover, removing the dressing after 7–8 days leads to clearly better results than removing it earlier.
Areca nut extracts modulated expression of alkaline phosphatase and receptor activator of nuclear factor κB ligand in osteoblasts
Authors: Ling Li‐Jane , Ho Feng‐Chuang , Chen Yen‐Ting , Holborow Douglas W. , Liu Tsung‐Yun , Hung Shan‐Ling
Published: March 2005

Objectives: Areca chewers have a higher prevalence of periodontal diseases than non‐chewers. This study was to determine the possible effects of ripe areca nut extracts (rANE) on viability and gene expression of alkaline phosphatase (ALP), receptor activator of nuclear factor‐κB ligand (RANKL) and osteoprotegerin (OPG) in human osteoblasts.

Methods: The effects of rANE on cell viability of osteoblast‐like MG63 cells were determined using 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5 diphenyltetrazolium bromide (MTT) that measures metabolic activity. Gene expression of ALP, RANKL and OPG was examined using reverse transcription‐polymerase chain reaction. ALP activity and RANKL protein were further examined using substrate assay and confocal laser scanning microscopy, respectively.

Results: Relative viability was reduced to approximately 50% when 25 μg/ml of rANE was used. The expression of OPG mRNA in MG63 cells was not altered by rANE. However, decreased levels of mRNA and enzyme activity of ALP were observed. Moreover, the expressions of mRNA and protein of RANKL were stimulated by rANE in a dose‐dependent manner.

Conclusions: The rANE affected morphology and viability of osteoblasts. We also present novel evidence demonstrating that areca nut may compromise the periodontal health of areca chewers by suppression of ALP gene expression and elevation of RANKL gene expression in osteoblasts.
Periodontal infection as a possible severity factor for rheumatoid arthritis
Authors: Ribeiro Juliana , Leão Anna , Novaes Arthur B.
Published: March 2005

Objective: Clinical effects of periodontal treatment on biochemical and clinical markers of disease severity in rheumatoid arthritis (RA) patients with periodontal disease were evaluated.

Methods: Forty‐two patients were assigned to two groups, G1 (n=16) and G2 (n=26). G1 patients were submitted to oral hygiene instruction and professional tooth cleaning and G2 patients additionally had full‐mouth scaling and root planing (SRP). Clinical periodontal measurements were obtained at baseline and 3 months after periodontal treatment. A Health Assessment Questionnaire (HAQ) was used to evaluate their performance on daily living. Rheumatoid factor (RF), erythrocyte sedimentation rate (ESR) and drug therapy were assessed.

Results: Both groups presented a full‐mouth improvement in all periodontal clinical parameters (p<0.05), with the exception of clinical attachment level (CAL) and probing pocket depth (PPD) >6 mm for G1. G2 showed greater mean reductions on PPD >4 mm than G1 (p<0.001). HAQ analyses showed a reduction on the degree of disability of G2, but not statistically significant. ESR was significantly reduced for G2 after SRP although RF did not show statistical reductions.

Conclusion: The data suggest that periodontal treatment with SRP might have an effect on the ESR reduction.
Plasminogen activator system in smokers and non‐smokers with and without periodontal disease
Authors: Buduneli Nurcan , Buduneli Eralp , Kardeşler Levent , Lappin David , Kinane Denis F.
Published: March 2005

Background: The present study assessed levels of plasminogen activator (PA) system proteins in gingival crevicular fluid (GCF) and serum of chronic gingivitis, chronic periodontitis patients and periodontally healthy subjects and evaluated how smoking influenced these levels.

Methods: Twenty chronic gingivitis; 20 chronic periodontitis patients and 20 periodontally healthy volunteers were consecutively recruited according to the inclusion criteria so that exactly half of the subjects in each category were smokers. GCF samples from four sites together with serum samples were obtained from each subject. GCF levels of tissue type PA (t‐PA), urokinase type PA (u‐PA), PA inhibitor‐1 (PAI‐1) and PA inhibitor‐2 (PAI‐2) and serum concentrations of cotinine, u‐PA and PAI‐1 were analysed by enzyme‐linked immunosorbent assay.

Results: The only statistically significant difference between smokers and non‐smokers was a lower GCF PAI‐2 concentrations in healthy smokers compared with healthy non‐smokers (p<0.01). Gingivitis and periodontitis patients had higher GCF concentrations of PAI‐2 than healthy subjects (p<0.002 and p<0.02 respectively). The ratio of u‐PA:PAI‐1 and t‐PA:PAI‐1 were significantly higher in GCF of smokers with periodontitis compared with “healthy” smokers, whereas the ratio of t‐PA:PAI‐2 was significantly lower in smokers with periodontal disease (p<0.05).

Conclusions: GCF levels of the PA system proteins are increased in chronic gingivitis and periodontitis compared with healthy gingiva. Smoking had only subtle effects on the GCF PA system proteins with the exception of PAI‐2, and the balance of activators and inhibitors. These findings suggest one mechanism whereby smoking may exert detrimental effects on the periodontal tissues.
Scaling and root planing, systemic metronidazole and professional plaque removal in the treatment of chronic periodontitis in a Brazilian population II – microbiological results
Authors: Carvalho L. H. , D'Avila G. B. , Leão A. , Gonçalves C. , Haffajee A. D. , Socransky S. S. , Feres M.
Published: March 2005

Objective: The current investigation evaluated changes in levels and proportions of 39 bacterial species in subgingival plaque samples after scaling and root planing (SRP) alone or in combination with systemic metronidazole and/or professional cleaning in subjects with chronic periodontitis.

Methods: Forty‐four adult subjects (mean age 45±6 years) with periodontitis were randomly assigned in four treatment groups, a control (C, n=10) that received SRP and placebo and three test groups treated as follows: T1 (n=12): SRP and metronidazole (M, 400 mg tid) for 10 days; T2 (n=12): SRP, weekly professional supragingival plaque removal for 3 months (PC) and placebo; and T3 (n=10): SRP, M and PC. Subgingival plaque samples were taken from seven sites per subject at baseline and 90 days post‐therapy. Counts of 39 subgingival species were determined using checkerboard DNA–DNA hybridization. Significance of differences over time was determined using the Wilcoxon signed ranks test and among groups using ancova.

Results: The mean counts of the majority of the species were reduced post‐therapy in the 4 treatment groups. Counts (× 105±SEM) of Porphyromonas gingivalis, Tannerella forsythensis and Treponema denticola were significantly reduced in groups T2 and T3. Levels of beneficial species, such as some Actinomyces species, Veillonella parvula, Streptococcus sanguis, Streptococcus oralis and Streptococcus gordonii were minimally affected in levels when the combined therapy was applied (T3). Mean proportions of red complex species decreased from 18.4% at baseline to 3% at 90 days post‐therapy in group T3 (p<0.01), from 25.8% to 2.3% in group T2 (p<0.01), from 17.7% to 5.6% in group T1 (p<0.05) and from 19.4% to 8.8% in group C (NS). Proportions of the suspected periodontal pathogens from the orange complex were also markedly reduced in groups T2 and T3.

Conclusions: All treatments reduced counts and proportions of red complex species. Adjunctive therapy appeared to have a greater effect and also affected members of the orange complex.
Stress, burnout and health in the clinical period of dental education
Authors: Pöhlmann K. , Jonas I. , Ruf S. , Harzer W.
Published: March 2005

The study examined the extent of stress, burnout and health problems experienced by fourth and fifth year dental students from the three universities of Dresden, Freiburg and Bern. The objectives of the study were to: (i) identify frequent sources of stress and to report the prevalence rates of burnout and health problems in dental students, (ii) determine the rate of students suffering from severe burnout symptoms and (iii) identify stress factors related to the burnout symptoms of emotional exhaustion and depersonalisation. A total of 161 dental students from Dresden, Freiburg and Bern participated in the study. They completed the Psychosocial Stress Inventory, the Maslach Burnout Inventory and the Health Survey Questionnaire. Frequent sources of stress were limitation of leisure time, examination anxiety and the transition stress that was related to the adaptation to the demands of the clinical phase of dental education. Few differences existed between the students of the fourth and the fifth study year. Study‐related stress was lowest in Bern and considerably higher in Dresden. Differences of mean levels of burnout symptoms were found only for the burnout dimension of emotional exhaustion. Students from Dresden and Freiburg were more emotionally exhausted than students from Bern, students from Dresden also reported more health problems than students from Bern or Freiburg. Ten per cent of the dental students suffered from severe emotional exhaustion, 17% complained about a severe lack of accomplishment and 28% reported severe depersonalisation symptoms. Forty‐four per cent of the variance of emotional exhaustion was explained by study‐related factors such as lack of leisure time, examination anxiety and transition stress. The only predictor of depersonalisation was a lack of social integration, accounting for 3% of the variance. A lack of social integration may be an indicator of low social competence which may cause difficulties in dealing with patients adequately and therefore result in depersonalisation. The results indicate a need to identify the group of students who may have insufficient social skills for dealing adequately with the patients, and to train them accordingly.
Computer‐mediated instructional video: a randomised controlled trial comparing a sequential and a segmented instructional video in surgical hand wash
Authors: Schittek Janda M. , Tani Botticelli A. , Mattheos N. , Nebel D. , Wagner A. , Nattestad A. , Attström R.
Published: March 2005

Background:  Video‐based instructions for clinical procedures have been used frequently during the preceding decades.

Aim:  To investigate in a randomised controlled trial the learning effectiveness of fragmented videos vs. the complete sequential video and to analyse the attitudes of the user towards video as a learning aid.

Materials and methods:  An instructional video on surgical hand wash was produced. The video was available in two different forms in two separate web pages: one as a sequential video and one fragmented into eight short clips. Twenty‐eight dental students in the second semester were randomised into an experimental (n = 15) and a control group (n = 13). The experimental group used the fragmented form of the video and the control group watched the complete one. The use of the videos was logged and the students were video taped whilst undertaking a test hand wash. The videos were analysed systematically and blindly by two independent clinicians. The students also performed a written test concerning learning outcome from the videos as well as they answered an attitude questionnaire.

Results:  The students in the experimental group watched the video significantly longer than the control group. There were no significant differences between the groups with regard to the ratings and scores when performing the hand wash. The experimental group had significantly better results in the written test compared with those of the control group. There was no significant difference between the groups with regard to attitudes towards the use of video for learning, as measured by the Visual Analogue Scales. Most students in both groups expressed satisfaction with the use of video for learning.

Conclusion:  The students demonstrated positive attitudes and acceptable learning outcome from viewing CAL videos as a part of their pre‐clinical training. Videos that are part of computer‐based learning settings would ideally be presented to the students both as a segmented and as a whole video to give the students the option to choose the form of video which suits the individual student's learning style.
Patients treated by dental students in outreach: the first year of a pilot project
Authors: Elkind A. , Potter C. , Watts C. , Blinkhorn F. , Duxbury J. , Hull P. , Blinkhorn A. S.
Published: March 2005

Abstract  This paper describes the patients treated by 4th year undergraduate students during the first year of a pilot outreach course to teach Restorative Dentistry in community clinics in 2001—02. Data were collected from 908 summaries of patient treatment completed by the students, and from 139 patient questionnaires. Some 75% of patients were aged between 16 and 64, 58% were female, and 16% had dental phobia or anxiety. Most lived locally to the clinic and 41% made their initial contact as an emergency or drop‐in. Some 37% made only a single visit (including children treated as emergencies) but 22% made six or more visits. Did not attend (DNA) was a problem and 18% of patients DNA to complete their treatment. Students undertook the full range of restorative procedures, with the emphasis on direct restorations, preventive treatment and advice, scaling, extractions and emergency treatment. Patients’ main reasons for attending the clinic were lay recommendation, the need for treatment, convenience, free treatment, or the lack of access to a dentist. Some 30% said they did not have or did not know of an alternative source of dental care, and half had not seen a dentist for at least 2 years. The study demonstrates that despite difficulties related to attendance, a suitable patient base can be established offering students the opportunity to provide comprehensive care for adults in a primary care setting.
Continuing professional development – global perspectives: synopsis of a workshop held during the International Association of Dental Research meeting in Gothenburg, Sweden, 2003. Part 2: regulatory and accreditation systems and evidence for improving the performance of the dental team
Authors: Best H. A. , Eaton K. A. , Plasschaert A. , Toh C. G. , Grayden S. K. , Senakola E. , Rohlin M.
Published: March 2005

This paper is the second in a series of two that report on continuing professional development (CPD). Details of the informants and the methodologies used were reported in the first paper. This paper reports the data and information presented on the topics of regulatory and accreditation systems for CPD and evidence that CPD improves the performance of the oral health team. By June 2003, participation in CPD was mandatory in most of the states of the USA, all Canadian Provinces, the UK and Latvia and was likely to become mandatory in a number of other countries in the near future. A variety of accreditation systems were reported including collecting CPD points, which in some countries were weighted depending on the type of CPD activity, and re‐certification examinations. Very few studies for the effectiveness of dental CPD were identified. However, in general it was concluded that there is little evidence for the effectiveness of CPD for the oral health team. The main recommendation from this study is that a systematic review of the effectiveness of CPD in improving the performance of the oral health team and patient based outcomes be undertaken. A range of other research questions was also identified including: how can CPD be best matched to clinicians’ needs rather than demands?
Clinical significance of total and lipid bound sialic acid levels in oral pre‐cancerous conditions and oral cancer
Authors: B. Rajpura Kinnari , S. Patel Prabhudas , G. Chawda Jyoti , M. Shah Raksha
Published: March 2005

Background:  Altered glycosylation of glycoconjugates is among the important molecular changes that accompany malignant transformation. The purpose of our study was to investigate clinical usefulness of circulatory levels of total and lipid bound sialic acid for early diagnosis and management of oral cavity cancer patients.

Methods:  Blood samples were collected from 41 untreated oral cancer patients, 20 patients with oral pre‐cancerous conditions (OPC) and 20 healthy subjects. Serum sialic acid (total and lipid bound) levels were measured spectrophotometrically.

Results:  Serum levels of total and lipid bound sialic acid were significantly elevated (P < 0.001) in untreated oral cancer patients as compared to healthy individuals as well as patients with OPC. Multivariate analysis documented that the progressive rise in total and lipid bound sialic acid was significantly associated (P = 0.0001 and 0.039, respectively) with stage of malignant disease.

Conclusion:  The data revealed significant elevations in sialic acid levels in oral cancer patients and suggested potential utility of these parameters in diagnosis as well as determining clinical stage of the malignant disease.
HCV clearance patterns in saliva and serum of patients with chronic HCV infection under interferon plus ribavirin therapy
Authors: Diz Dios P. , Castro A. , Rodríguez I. , Reforma N. G. , Castro M. , Eirea M. , Hermida M.
Published: March 2005

Statements of the problem:  Hepatitis C virus (HCV)‐RNA is often present in saliva of HCV‐infected patients, with plasma viral load being the only known predictable factor. Interferon plus ribavirin therapy yields a sustained reduction in HCV viremia. This study aimed to assess the presence of HCV in saliva and serum specimens from patients undergoing this combination therapy (CT).

Method of study:  Paired serum and saliva specimens were collected from 44 chronic HCV‐infected patients at basal time, 4 and 12 weeks after CT onset, at the end of treatment and 6 months latter. Serum HCV‐RNA levels were determined by the polymerase chain reaction (PCR) Amplicor system. Presence of HCV‐RNA in saliva was tested by a highly sensitive non‐commercialized nested‐PCR.

Results:  The HCV‐RNA was detected in 26 saliva specimens at basal time (59.1%). In 34.1% of cases, a concordance viral clearance pattern in serum and saliva was observed in both responders (pattern 1a) and non‐responders (pattern 1b). In pattern 2 (13.6% of cases), HCV was detected longer during CT in serum than in saliva (pattern 2a) or in saliva than in serum (pattern 2b). In 11.3% of patients, viral clearance was corroborated either in their serum (pattern 3a) or in their saliva (pattern 3b), but not in both fluids. Of the eight primary responders with 1a clearance pattern, seven were sustained responders. None of the patients with 2a clearance pattern was a sustained responder. Of the two primary responders showing the 3b salivary pattern, one had already relapsed in the first 6 months of follow up.

Conclusions:  The present results suggest that the monitoring of salivary levels of HCV would be a helpful means of determining sustained antiviral effects of interferon and ribavirin in the treatment of HCV disease.
Expression of apoptotic and cell proliferation regulatory proteins in actinic cheilitis
Authors: Martínez A. , Brethauer U. , Rojas I. G. , Spencer M. , Mucientes F. , Borlando J. , Rudolph M. I.
Published: March 2005

Background:  Actinic cheilitis (AC) is a pre‐malignant lesion caused by ultraviolet (UV) radiation. The apoptotic proteins p53, bax, bcl‐2, and the proliferation marker Ki‐67, are known to play an important role in UV‐exposed skin and carcinomas, therefore, these markers were assessed in AC and compared with normal lip and oral mucosa.

Methods:  AC (n = 13), normal lip (n = 7) and oral mucosa (n = 6) biopsies were stained immunohistochemically for p53, bax, bcl‐2 and Ki‐67, to determine their expression and distribution.

Results:  p53 was over‐expressed in AC as compared with normal lip and oral mucosa (P < 0.003). Although bcl‐2 expression was higher in AC than in oral mucosa (P < 0.002), it was significantly reduced as compared with normal lip (P < 0.04). Bax expression remained unchanged, and Ki‐67 was significantly increased in AC and normal lip as compared with oral mucosa (P < 0.05).

Conclusion:  The results suggest that DNA‐damaged cells by UV radiation in AC are eliminated by apoptosis.
Expression of IgSF in salivary adenoid cystic carcinoma and its relationship with invasion and metastasis
Authors: Xue Fan , Zhang Yincheng , Liu Feng , Jing Jie , Ma Min
Published: March 2005

Background:  The aim of the present work was to study the potential effect of intercellular adhesion molecule‐1 (ICAM‐1), vascular cell adhesion molecule‐1 (VCAM‐1) and neural cell adhesion molecule (NCAM) of immunoglobulin superfamily on the invasion and metastasis of salivary adenoid cystic carcinoma (SACC).

Method:  The expressions of ICAM‐1, VCAM‐1 and NCAM of forty cases with SACC were examined by immunohistochemical methods using respective kits.

Results:  A significant relation showed between the expression level and histological differentiation, expression of ICAM‐1 and VCAM‐1 in solid SACC was greatly increased compared with NCAM; SACC with metastatic lymph node or local recurrence displayed significant relationship to the up‐regulation of ICAM‐1 and VCAM‐1, and to the down‐regulation of NCAM.

Conclusions:  It is proposed that ICAM‐1 and VCAM‐1 may play a role in the invasion and metastasis of SACC. NCAM may be an invasion‐resistant adhesion molecule.
BIOLOGICAL VALIDATION OF TOMATO PULP CONTINUOUS HEAT PROCESS
Authors: PACHECO CRISTIANA DE PAULA , DE MASSAGUER PILAR RODRIGUEZ
Published: March 2005

This research validated the commercial process applied to tomato pulp (pH 4.3 and 8 Brix) packed in Tetra Brik packages. Spores of Bacillus coagulans and Neosartorya fischeri were selected as targets. The heat resistance of both microorganisms, tested independently, was compared. The redesigned thermal processes were carried out in a aseptic processing and tested by indirect inoculation and retrieval with spores immobilized in alginate/tomato balls. The results showed that processes for 30 s at 115C or greater did not allow the survival of heat‐resistant molds. For bacterial spores, processes for 30 s at 109C or greater showed no survivors. Although, 30 s at 115C will control both types of spoilage spores, concern for possible C. botulinum growth attributed to metabiosis in product with varying initial populations of molds and residual oxygen content dictated, a process recommendation of 60 s at 126C for safety reasons.
THE USE OF RHEOLOGY TO CHARACTERIZE FLOW BEHAVIOR OF LIQUORICE SOLUTIONS
Authors: GABRIELE DOMENICO , CURCIO STEFANO , MIGLIORI MASSIMO , DE CINDIO BRUNO
Published: March 2005

The rheological behavior of liquorice solutions at different concentrations (ranging between 30 and 60 Brix) and temperatures (in the range between 25 and 80C) has been investigated performing both dynamic tests in the linear viscoelastic region and steady shear tests, in 0.1–100 s−1 shear rate range, by using a stress controlled rheometer (DSR 200, Rheometric Scientific, USA) and parallel plate geometry (φ = 40 mm). Small amplitude oscillations has shown the presence of both moduli also at the lowest tested concentration, with G′ greater than G″, except for the 30 Brix sample. It has been found that experimental viscosity data show a good agreement with a power law model, thus allowing the estimation of both the friction factor and the pressure drops in a typical pipeline used for liquorice solution conveying. It has been observed that the assumption of Newtonian behavior can lead to the erroneous design of the apparatuses that have to process liquorice extracts.
Thermoeconomic Diagnosis: Zooming Strategy Applied to Highly Complex Energy Systems. Part 1: Detection and Localization of Anomalies*
Authors: Verda Vittorio , Serra Luis , Valero Antonio
Published: March 2005

This paper presents a summary of our most recent advances in Thermoeconomic Diagnosis, developed during the last three years, and how they can be integrated in a zooming strategy oriented toward the operational diagnosis of complex systems. In fact, this paper can be considered a continuation of the work presented at the International Conference ECOS’99 in which the concepts of malfunction (intrinsic and induced) and dysfunction were analyzed in detail. These concepts greatly facilitate and simplify the analysis, the understanding, and the quantification of how the presence of an anomaly, or malfunction, affects the behavior of the other plant devices and of the whole system. However, what remains unresolved is the so-called inverse problem of diagnosing, i.e., given two states of the plant (actual and reference operating conditions), find the causes of deviation of the actual conditions with respect to the reference conditions. The present paper tackles this problem and describes significant advances in addressing how to locate the actual causes of malfunctions, based on the application of procedures for filtering induced effects that hide the real causes of degradation. In this paper a progressive zooming thermoeconomic diagnosis procedure, which allows one to concentrate the analysis in an ever more specific zone is described and applied to a combined cycle. In an accompanying paper the accuracy of the diagnosis results is discussed, depending on choice of the thermoeconomic model.
Numerical Modeling of PEM Fuel Cells Under Partially Hydrated Membrane Conditions
Authors: Cao Jun , Djilali Ned
Published: March 2005

In proton-exchange membrane fuel cells it is particularly important to maintain appropriate water content and temperature in the electrolyte membrane. The water balance depends on the coupling between diffusion of water, pressure variation, and the electro-osmotic drag in the membrane. In this paper we apply conservation laws for water and current, in conjunction with an empirical relationship between electro-osmotic drag and water content, to obtain a transport equation for water molar concentration and to derive a new equation for the electric potential that strictly accounts for variable water content and is more accurate than the conventionally used Laplace’s equation. The model is coupled with a computational fluid dynamics model that includes the porous gas diffusion electrodes and the reactant flow channels. The resulting coupled model accounts for multi-species diffusion (Stefan-Maxwell equation); first-order reaction kinetics (Butler-Volmer equation); proton transport (Nernst-Planck equation); and water transport in the membrane (Schlo¨gl equation). Numerical simulations for a two-dimensional cell are performed over nominal current densities ranging from i=0.4 to i=1.2 A/cm2. The relationship between humidification and the membrane potential loss is investigated, and the impact and importance of two-dimensionality, temperature, and pressure nonuniformities are analyzed and discussed.
Discrete Green’s Function Measurements in a Single Passage Turbine Model
Authors: Mukerji Debjit , Eaton John K.
Published: March 2005

The superposition-based Discrete Green’s Function (DGF) technique provides a general representation of convective heat transfer that can capture the numerous flow and thermal complexities of the gas turbine environment and provide benchmark data for the validation of computational codes. The main advantages of the DGF technique are that the measurement apparatus is easier to fabricate than a uniform heat flux or uniform temperature surface, and that the results are applicable to any choice of discretized thermal boundary condition. Once determined for a specific flow condition, the DGF results can be used, for example, with measured surface temperature data to estimate the surface heat flux. In this study, the experimental DGF approach was extended to the suction side blade surface of a single passage model of a turbine cascade. Full-field thermal data were acquired using a steady state, liquid crystal-based imaging technique. The objective was to compute a 10×10 one-dimensional DGF matrix in a realistic turbomachinery geometry. The inverse 1-D DGF matrix, G−1, was calculated and its uncertainties estimated. The DGF-based predictions for the temperature rise and Stanton number distributions on a uniform heat flux surface were found to be in good agreement with experimental data. The G matrix obtained by a direct inversion of G−1 provided reasonable heat transfer predictions for standard thermal boundary conditions.
Energy Economy With a Variable Speed Drive in an Oxygen Trim Controlled Boiler House
Authors: Kilicaslan Ibrahim , Ozdemir Engin
Published: March 2005

This paper investigates the potentional for energy saving in a boiler house that can be achieved through installing a variable speed drive (VSD) for the fan motor by including an oxygen trim control cycle. This investigation is carried out through surveys; energy saving calculations are based on experimental data. In particular, some unique energy saving measures and energy efficiency improvements in the boiler associated with the VSD system are analytically and experimentally studied. In this study, the relation between excess air ratio and boiler efficiency was investigated in a water tube boiler that has the capacity of producing 55 tons of steam per unit time at 245°C and 20 bar pressure. The boiler combustion air is supplied from a fan driven by a 30 kW 1450 rpm induction motor. Since the fan motor running at nominal speed has supplied the same airflow rate, excess air amount and exhaust gas temperature were very high at low loads. The boiler efficiency was low due to thermal energy losses and also consequently led to electrical energy losses. After implementation of the VSD, stack temperature was reduced from 200°C to 142°C, so the boiler efficiency was increased about 2.5% and 8000 kWh of electrical energy were saved in a month. The energy losses associated with excess air rate and its cost to manufacturers are evaluated and quantified. An overview and analysis of such conservation measures, along with the potential energy and cost savings, the implementation cost, and simple payback period are also given.
A Review of Shaped Hole Turbine Film-Cooling Technology
Authors: Bunker Ronald S.
Published: March 2005

Film cooling represents one of the few game-changing technologies that has allowed the achievement of today’s high firing temperature, high-efficiency gas turbine engines. Over the last 30 years, only one major advancement has been realized in this technology, that being the incorporation of exit shaping to the film holes to result in lower momentum coolant injection jets with greater surface coverage. This review examines the origins of shaped film cooling and summarizes the extant literature knowledge concerning the performance of such film holes. A catalog of the current literature data is presented, showing the basic shaping geometries, parameter ranges, and types of data obtained. Specific discussions are provided for the flow field and aerodynamic losses of shaped film hole coolant injection. The major fundamental effects due to coolant-to-gas blowing ratio, compound angle injection, cooling hole entry flow character, and mainstream turbulence intensity are each reviewed with respect to the resulting adiabatic film effectiveness and heat transfer coefficients for shaped holes. A specific example of shaped film effectiveness is provided for a production turbine inlet vane with comparison to other data. Several recent unconventional forms of film hole shaping are also presented as a look to future potential improvements.
Influence of Entrance Geometry on Heat Transfer in Rotating Rectangular Cooling Channels (AR=4:1) With Angled Ribs
Authors: Wright Lesley M. , Fu Wen-Lung , Han Je-Chin
Published: March 2005

The effect of entrance geometry on the heat transfer in rotating, narrow rectangular cooling channels is investigated in this study. Both smooth channels and channels with angled ribs are considered with three different entrance conditions: fully developed, sudden contraction, and partial sudden contraction. The rectangular channel has as aspect ratio of 4:1, and it is oriented at 135° with respect to the plane of rotation. In the test section with angled ribs, the ribs are angled at 45° to the mainstream flow. The rib height-to-hydraulic diameter ratio e/Dh is 0.078, and the rib pitch-to-height ratio P/e is 10. The range of flow parameters includes Reynolds number (Re=5000–40,000), rotation number (Ro=0.0–0.302), and inlet coolant-to-wall density ratio (Δρ/ρ=0.12). The heat transfer at the entrance of the heated portion of the smooth channel is significantly enhanced with the sudden contraction and partial sudden contraction entrances. In the smooth rotating channels, the effect of the entrance geometry is also present; however, as the rotation number increases, the effect of the entrance geometry decreases. It was also found in this study that the sudden and partial sudden contraction entrances provide higher heat transfer enhancement than the fully developed entrance through the first three to four hydraulic diameters of the channels with angled ribs. Again, the effect of the entrance geometry is greater in the stationary channels with angled ribs than the rotating channels with ribs. In both stationary and rotating channels, the influence of the entrance geometry on the heat transfer is more apparent in the smooth channels than in the ribbed channels.
Performance Characteristics of Regenerative Flow Compressors for Natural Gas Compression Application
Authors: Raheel Mukarrum , Engeda Abraham
Published: March 2005

In this paper we discuss the application of regenerative flow compressors (RFC) for low-pressure natural gas compression required by microturbine systems. A brief overview of fundamentals and the hypothesis of the operation of RFC is presented. A mathematical model to describe the complex three-dimensional corkscrew flow pattern in RFC is discussed. Governing equations for the blade and channel region are developed. A one-dimensional (1-D) performance prediction code for RFC based on governing equations and loss models is developed and performance results are compared with experimental data on a multistage RFC. Excellent agreement between theoretical and experimental results is observed, thus validating the proposed mathematical model.
Effect of Input Variability on the Performance of Turbine Blade Thermal Design Using Monte Carlo Simulation: An Exploratory Study
Authors: Muwanga Roland S. , Sreekanth Sri , Grigore Daniel , Trindade Ricardo , Lucas Terry
Published: March 2005

A probabilistic approach to the thermal design and analysis of cooled turbine blades is presented. Various factors that affect the probabilistic performance of the blade thermal design are grouped into categories and a select number of factors known to be significant, for which the variability could be assessed are modeled as random variables. The variability data for these random variables were generated from separate Monte Carlo simulations (MCS) of the combustor and the upstream stator and secondary air system. The oxidation life of the blade is used as a measure to evaluate the thermal design as well as to evaluate validity of the methods. Two approaches have been explored to simulate blade row life variability and compare it with the field data. Field data from several engine removals are used for investigating the approach. Additionally a response surface approximation technique has been explored to expedite the simulation process. The results indicate that the conventional approach of a worst-case analysis is overly conservative and analysis based on nominal values could be very optimistic. The potential of a probabilistic approach in predicting the actual variability of the blade row life is clearly evident in the results. However, the results show that, in order to predict the blade row life variability adequately, it is important to model the operating condition variability. The probabilistic techniques such as MCS could become very practical when approximation techniques such as response surface modeling are used to represent the analytical model.
Computational Analysis of Heat Transfer Enhancement in Square Ducts With V-Shaped Ribs: Turbine Blade Cooling
Authors: Jia R. , Sunde´n B. , Faghri M.
Published: March 2005

Experimental studies have revealed that both downstream and upstream pointing V-shaped ribs result in more heat transfer enhancement than transverse straight ribs in ducts. However, based on the available experimental results, contradiction exists whether the upstream or the downstream pointing V-shaped ribs orientation is superior for better enhancement in heat transfer. Further investigations are thus needed concerning the heat transfer and fluid flow phenomena in ducts with V-shaped ribs to clarify this. In the present investigation a numerical approach is taken and the heat and fluid flow is numerically simulated by a multi-block parallel 3D solver. For turbulence modeling, the v2¯ f-kε model is employed but results from previous EASM calculations are also considered in analyzing and attempting to understand the various experimental data. Large eddy simulations (LES) are also carried to evaluate the accuracy and reliability of the results of Reynolds-averaged Navier-Stokes (RANS) methods and to understand the underlying physical phenomena. It is suggested that the discrepancy between the various experiments most probably is due to the measurement methods, or the number of sampling points. With the TC (thermocouples) technique, a few sampling points are not sufficient to represent the heat transfer behavior in V-shaped ribs, due to the uneven distribution of the heat transfer coefficients.
Film Effectiveness Downstream of a Row of Compound Angle Film Holes
Authors: Taslim and M. E. , Khanicheh A.
Published: March 2005

Effects that two different compound-angle film-hole configurations have on film cooling effectiveness are investigated. Effectiveness measurements have been made downstream of a single row of compound-angle cylindrical holes with a diameter of 7.5 mm, and a single row of compound-angle, diffuser-shaped holes with an inlet diameter of 7.5 mm. Both geometries were inclined with respect to the coverage surface at an angle α of 25 deg. The cylindrical holes, however, were oriented perpendicular to the high-temperature airflow direction while the diffuser-shaped holes had a compound angle of 45 deg with respect to the high temperature air flow direction. Both geometries were tested over a blowing ratio range of 0.7 to 4.0 Surface temperatures were measured along four longitudinal rows of thermocouples covering the downstream area between two adjacent holes. The results showed that the best overall protection over the widest range of blowing ratios was provided by the diffuser-shaped film cooling holes, particularly at high blowing ratios. The increased cross-sectional area at the shaped hole exit lead to a reduction of the momentum flux of the jet exiting the hole. Therefore, the penetration of the jet into the main flow was reduced, resulting in an increased cooling effectiveness. CFD analyses were also performed to study the film cooling effectiveness downstream of the row of holes. Comparisons between the test and numerical results showed a reasonable agreement between the two, thus CFD can be considered a viable tool to predict the cooling performance of different film cooling configurations in a parametric study.
2‐Step IMAT and 2‐Step IMRT: A geometrical approach
Authors: Bratengeier Klaus
Published: March 2005

The purpose of this paper is to develop a method that reduces the number of segments for intensity modulated arc therapy (IMAT) and intensity modulated radiotherapy (IMRT) for concave target volumes (TV). The aim was to utilize no more than two intensity levels per organ at risk (OAR) and to derive both optimal segment widths and weights from geometric considerations. Brahme's model of an annular target surrounding a circular OAR was used as test model. Brahme's solution was substituted by a single segment added to a simple field blocking the OAR. Width and weight of the segment were the free parameters to optimize. The objective function to minimize was the root mean square (rms) error of the dose in the target volume. One boundary condition was—neglecting scatter—“zero‐dose” to the OAR. The resulting rules for width and weight of the additive segment are referred to as “optimized 2‐Step IMAT” and “2‐Step IMRT.” The recommendations were applied to some simplified plans representing clinical cases using a commercial planning system. Optimized 2‐Step IMAT improved the rms by a factor of 4 with respect to techniques simply blocking the OAR. The additional segment reduced the rms below 3% for cases with gaps between OAR and TV larger than 8% of the TV diameter. The results for 2‐Step IMAT are applicable to IMRT and aperture modulated arc therapy (AMAT). 2‐Step IMAT can be utilized for noncylindrical cases and for more than one OAR. A geometrical and topological approach to IMAT and IMRT can be useful to understand fluence profiles. The results could be applied to ameliorate other topology‐based procedures used in some planning systems. Basic mechanisms of 2‐Step IMAT can assist with the creation of rules for adaptive IMRT to compensate for patient motion.
Dosimetric effect of collimating jaws for small multileaf collimated fields
Authors: Chow James C. L. , Seguin Melanie , Alexander Andrew
Published: March 2005

The dosimetric effects from the jaw positioned close to the small field (, , and ) side‐edge generated by a single‐focused multileaf collimator (MLC) were measured and studied. The measurement is important in intensity modulated radiotherapy (IMRT) because generally the jaw cannot perfectly cover all the leaf‐ends in a segment of irregular field. This leads to additional dose contributed by (1) the end surface of the jaw, (2) the leaf‐end, and (3) the inter‐ and intraleaf leakage/transmissions during the dosimetric measurement. Moreover, most of the conventional treatment planning systems ignore these effects in the dose calculation. In this study, measurements were made using a Varian 21 EX linear accelerator with 6 MV photon beam through a MLC containing 120 leaves. Percentage depth dose, beam profile, and output for small fields were measured by varying the jaw at different positions away from the leaf‐ends in the field side‐edge. Moving the jaw away from the leaf‐ends increases the output and penumbra width for the small fields. Such increase is particularly significant when the field size is small and the degree of increase changes quickly when the jaw‐end is at about 1–2 cm from the leaf‐end. It is suggested that measurements should be carried out in the IMRT commissioning to provide information to physicists in reviewing the treatment planning system's accuracy regarding leaf leakage/transmission and jaw effects.