bluuebunny/crossref_metadata_2025 huggingface dataset:
p-Nitrobenzoic Acid α2u Nephropathy in 13-week Studies is not Associated with Renal Carcinogenesis in 2-year Feed Studies
Authors: Williams Kyha D. , Dunnick June , Horton John , Greenwell Arnold , Eldridge Sandra R. , Elwell Michael , Sills Robert C.
Published: January 2003

The objective of this study was to characterize the renal toxicity and carcinogenicity of p-nitrobenzoi c acid in F344 rats. Dose levels in 13-week and 2-year studies ranged from 630—10,000 ppm and 1,250—5,000 ppm, respectively. At 13 weeks, renal lesions included minimal to mild hyaline droplet accumulation in male rats and karyomegaly in male and female rats. At 2 years, renal lesions included proximal tubule epithelial cell hyperplasia in male rats and oncocytic hyperplasia in high-dose male and female rats, and a decreased severity of nephropathy in males and females. The hyaline droplets in renal tubular epithelial cells of male rats at 13 weeks were morphologically similar to those described in α2u-globulin nephropathy. Using immunohistochemica l methods, α2u-globulin accumulation was associated with the hyaline droplets. In addition, at 13 weeks, cell proliferation as detected by PCNA immunohistochemistry was signifi cantly increased in males exposed to 5,000 and 10,000 ppm when compared to controls. Cytotoxicity associated with α2u-globulin nephropathy such as single-cell necrosis of the P2 segment epithelium or accumulation of granular casts in the outer medulla did not occur in the 13-week study. In addition, chronic treatment related nephrotoxic lesions attributed to accumulation of α 2u-globulin such as linear foci of mineralization within the renal papilla, hyperplasia of the renal pelvis urothelium and kidney tumors were not observed. Although there was histologic evidence of α2u-globulin accumulation in male rats at 13 weeks, the minimal severity of nephropathy suggests that the degree of cytotoxicity was below the threshold, which would contribute to the development of renal tumors at 2 years.
Collagen Matrix in Development and Progression of Experimentally Induced Respiratory Neoplasms in the Hamster
Authors: Laitakari Jaakko , Stenbäck Frej
Published: January 2003

Intratracheal instillations of 7H-dibenzo(c, g)carbazole (DBC), a tobacco smoke component, into Syrian golden hamsters, resulted in preneoplastic lesions and benign and malignant respiratory neoplasms. Neoplastic progression was associated with specifi cchanges in the extracellular matrix (ECM), dependent on the stage of tumor development. DBC-induced tracheobronchial squamous metaplasia was associated with an increase in collagen type I and type III deposition in the subepithelial ECM, as observed by computer-assisted image analysis of immunohistochemical staining for the aminoterminal propeptides of collagen type I (PINP) and collagen type III (PIIINP). Increased collagen matrix synthesis was detected in dysplasia by in situ hybridization of α1(I) mRNA for collagen I and α1(III) mRNA for collagen type III after continued exposure to DBC. In well-differentiated squamous cell carcinomas with an expansive growth pattern, collagen deposition increased, as did fi ber size. In moderately differentiated neoplasms, basement membrane (BM) destruction and invasion was associated with a destructive growth pattern and decreases in collagen synthesis and the deposition of new collagen. Preserved deposition of mature collagen was detected by staining for the telopeptide of collagen type I propeptide. In less differentiated tumors, ECM development was minimal, with few and small fi bers, possibly explaining the rapid development of these neoplasms. Transforming growth factor β (TGF β 1) immunoreactivity was increased in hyperplastic epithelium and well differentiated neoplasms and decreased in dysplasia and less differentiated squamous cell carcinomas, while TGF β 2 and TGF β3 expression was also distinct in neoplastic cells. Collagen synthesis and epithelial differentiation were associated with an increased number of myofibroblasts in the ECM and with increased TGF β3 immunoreactivity in differentiated cells and in the matrix. The nature of the composition of the ECM was related to neoplastic growth and progression when analyzed by computer-associated image analysis, revealing alterations in collagen structure, size, and shape.
Induction of DNA Synthesis in Mouse Liver Following Increases of DNA Adduct Levels Elicited by Very Low Cumulative Doses of the Genotoxic Hepatocarcinogen 7H-dibenzo[c,g]carbazole
Authors: Dorchies Olivier , Perin-Roussel Odette , Gillardeaux Olivier , Vericat Joan-Albert , Roome Nigel Oliver , Prenez Annick , Perin François
Published: January 2003

The purpose of this work was to investigate the administration of very low but repeated doses of a genotoxic carcinogen and an eventual correlation with cellular DNA synthesis. The compound 7H-dibenzo[c,g]carbazole is a genotoxic carcinogen in the mouse liver and was administered topically at the dose of 13.35 μg per animal every 2 days to give a total of 13 applications. Animals were sacrificed 48 hours after every 2 applications until the 10th treatment, then 48 hours after every treatment. Postulated genotoxic effects such as DNA adduct formation were detected by the 32P-post labeling assay. Liver sections were examined for microscopic changes and DNA synthesis. Results showed an increase of the total DNA adduct level in the liver throughout the study with a slowing down in the level after the sixth application of the compound. This change could correspond to the onset of DNA synthesis and to the moderate hepatocellular apoptosis which was observed. The DNA synthesis, which was considered to be secondary to the cytotoxicity induced by the high level of DNA adducts altering normal cellular activity, could also be the opportunity to fix the DNA adducts into heritable mutations. These results raise the question regarding the risk assessment in humans exposed regularly to very low doses of chemicals in the environment: for non-proliferating tissue, the regular accumulation of DNA adducts could remain silent until a “threshold level” is reached from which stimulation of the DNA synthesis may fix the DNA adducts into heritable mutations, eventually leading to tumors.
Expression of Transforming Growth Factor (TGF)-β1 and TGF-β Type II Receptor in Preneoplastic Lesions During Chemical Hepatocarcinogenesis of Rats
Authors: Do Youn Park  , Soon Yeol Hwang  , Kang Suek Suh
Published: January 2003

Transforming growth factor (TGF)- β1 is an important apoptotic growth inhibitor of hepatocyte proliferation, and the expression of TGF- β1, which regulates cell proliferation, is closely associated with the expression level of TGF- β type II receptor (TGR2). Moreover, TGF- β1 expression has been regarded to be an important change in hepatocarcinogenesis . We undertook this study to investigate the gene expression and protein localization of TGF- β1 and TGR2 and their relationship with apoptosis in the chemically induced hepatocarcinogenesi s of the rat, as produced using Solt and Farber's method, during the promotion stage (up to 56 days after partial hepatectomy). Northern blot analysis showed a slight, but not a significant, increase in TGF- β1 transcripts, and a significant decrease in the TGR2 transcripts during the later stage of our experiments (42 days after partial hepatectomy). Immunohistochemical study showed that TGF- β 1-positive preneoplastic hepatocytes increased with time, and this correlated with an increase of TGR2 negative or reduced TGR2 expressed preneoplastic lesions. The TUNEL method revealed that apoptotic cells increased with time and were more numerous in the adjacent liver parenchyme than preneoplastic lesions. Our data suggest that the expressions of TGF- β1 and TGR2 are significantly altered during the promotion stage of hepatocarcinogenesi s of rat and that these changes might contribute to the development and progression of preneoplastic lesions.
Methylmercury Poisoning in Common Marmosets—A Study of Selective Vulnerability Within the Cerebral Cortex
Authors: Eto Komyo , Yasutake Akira , Kuwana Takashi , Korogi Yukunori , Akima Michio , Shimozeki Toshie , Tokunaga Hidehiro , Kaneko Yosuke
Published: January 2003

Neuropathological lesions found in chronic human Minamata disease tend to be localized in the calcarine cortex of occipital lobes, the pre- and postcentral lobuli, and the temporal gyri. The mechanism for the selective vulnerability is still not clear, though several hypotheses have been proposed. One hypothesi s is vascular and postulates that the lesions are the result of ischemia secondary to compression of sulcal arteries from methylmercury-induced cerebral edema. To test this hypothesis, we studied common marmosets because the cerebrum of marmosets has 2 distinct deep sulci, the calcarine and Sylvian fi ssures. MRI analysis, mercury assays of tissue specimens, histologic and histochemical studies of the brain are reported and discussed. Brains sacrifi ced early after exposure to methylmercury showed high contents of methylmercury and edema of the cerebral white matter. These results may explain the selective cortical degeneration along the deep cerebral fi ssures or sulci.
The Roles of Estrogen and Progestin in Producing Deciduosarcoma and Other Lesions in the Rabbit
Authors: Jänne Olli A. , Zook Bernard C. , Didolkar Ashok K. , Sundaram Kalyan , Nash Harold A.
Published: January 2003

The interactions of estrogens and progestins in producing decidualization, deciduosarcoma, and other lesions in the rabbit were explored. Steroids were delivered by silicone elastomer implants placed subdermally except for oral dosing in 1 experiment. Varying doses of levonorgestre l (LNG) were given with and without estradiol (E 2) and varying doses of E2 with and without LNG. LNG alone delivered at an estimated mean dose of 233 μg/day did not result in endometrial decidualization or deciduosarcoma. Both conditions occurred when E2 was added to the regimen and increased as the dose of E2 was increased. Sixty μg of E2 per day produced endometrial decidualization in all test animals in a 2-month exposure, but deciduosarcom a occurred only when LNG was also supplied and increased as the LNG dose was increased. Progesterone given with E2 resulted in deciduosarcoma in most rabbits. Ethynylestradiol alone at 30 μ g/day delivered by implants produced splenic and ovarian deciduosarcoma s in 1 of 5 test animals. Adding LNG resulted in more numerous and widespread deciduosarcomas. These experiments indicate that exogenous estrogen is necessary for decidualization of the endometrium and to production of deciduosarcoma in the nonpregnant rabbit. Exogenous progestin promotes the process. Necrosis of the uterine wall tended to increase with increasing dose of estrogens.
Background and Framework for ILSI's Collaborative Evaluation Program on Alternative Models for Carcinogenicity Assessment
Authors: Robinson Denise E. , Macdonald James S.
Published: January 2003

The willingness of the agencies involved in the regulation of pharmaceuticals to accept data from newly proposed models for carcinogenicity testing (eg, transgenic animals, neonatal rodent models, initiation-promotionmodels) has stimulated international interest in gaining experience and a greater understanding of the strengths and limitations of the specifi c models. Over a 4-year period, the International Life Sciences Institute (ILSI) Health and Environmental Science Institute (HESI) has coordinated a large-scale collaborative research program to help to better characterize the responsiveness of several models proposedfor use in carcinogenicity assessment. The overall objective of this partnership among industry, government, and academic scientists was to evaluate the ability of these new models to provide useful information for human cancer risk assessment. This research program reflected a commitment of nearly US$35 million by over 50 industrial, government, and academic laboratories from the United States, Europe, and Japan. Evaluation of the models required the development of standardized protocols to allow reproducibility and comparability of data obtained across multiple laboratories. Test compounds were selected on the basis of mechanistically meaningful carcinogenic activity or noncarcinogenicity in the rodent bioassay as well as humans. Criteria were established for dose selection, pathology review, quality control, and for evaluation of study outcome. The database from these studies represents an important contribution to the future application of new models for human cancer risk assessment. Beyond the data, the collaborative process by which the models were evaluated may also represent a prototype for assessing new methods in the future.
Tg.AC Genetically Altered Mouse: Assay Working Group Overview of Available Data
Authors: Eastin William C. , Mennear John H. , Tennant Ray W. , Stoll Ray E. , Branstetter Dan G. , Bucher John R. , Mccullough Bruce , Binder Robert L. , Spalding Judson W. , Mahler Joel F.
Published: January 2003

In a Government/Industry/Academic partnership to evaluate alternative approaches to carcinogenicity testing, 21 pharmaceutical agents representing a variety of chemical and pharmacological classes and possessing known human and or rodent carcinogenic potential were selected for study in several rodent models. The studies from this partnership project, coordinated by the International Life Sciences Institute, provide additional data to better understand the models' limitations and sensitivity in identifying carcinogens. The results of these alternative model studies were reviewed by members of Assay Working Groups (AWG) composed of scientists fromgovernmentand industry with expertise in toxicology, genetics, statistics, and pathology. The Tg.AC genetically manipulated mouse was one of the models selected for this project based on previous studies indicating that Tg.AC mice seem to respond to topical application of either mutagenic or nonmutagenic carcinogens with papilloma formation at the site of application. This communication describes the results and AWG interpretations of studies conducted on 14 chemicals administered by the topical and oral (gavage and/or diet) routes to Tg.AC genetically manipulated mice. Cyclosporin A, an immunosuppresant human carcinogen, ethinyl estradiol and diethylstilbestrol (human hormone carcinogens) and clofi brate, an hepatocarcinogenicperoxisome proliferator in rodents, were considered clearly positive in the topical studies. In the oral studies, ethinyl estradiol and diethylstilbestrol were negative, cyclosporin was considered equivocal, and results were not available for the clofibrate study. Of the 3 genotoxic human carcinogens (phenacetin, melphalan, and cyclophosphamide), phenacetin was negative by both the topical and oral routes. Melphalan and cyclophosphamide are, respectively, direct and indirect DNA alkylating agents and topical administration of both caused equivocal responses. With the exception of clofi brate, Tg.AC mice did not exhibit tumor responses to the rodent carcinogens that were putative human noncarcinogens, (di(2-ethylhexyl )phthalate, methapyraline HCl, phenobarbital Na, reserpine, sulfamethoxazole or WY-14643, or the nongenotoxic, noncarcinogen, sulfisoxazole) regardless of route of administration. Based on the observed responses in these studies, it was concluded by the AWG that the Tg.AC model was not overly sensitive and possesses utility as an adjunct to the battery of toxicity studies used to establish human carcinogenic risk.
CB6F1-rasH2 Mouse: Overview of Available Data
Authors: Usui Toshimi , Mutai Mamoru , Hisada Shigeru , Takoaka Masaya , Soper Keith A. , Mccullough Bruce , Alden Carl
Published: January 2003

This article presents data from short-term carcinogenicity studies of compounds tested in the CB6F1-rasH2 transgenic mouse as part of the International Life Sciences Institutes' (ILSI) Health and Environmental Sciences' (HESI) Alternative to Carcinogenicity Testing (ACT) project. Additionally, data from other studies that were not conducted as part of the ILSI program, but used comparable or slightly modifi ed protocols, are included here. A signifi cant number (3 of 4) of the genotoxic carcinogens tested were positive in the rasH2 mouse; the other compound was equivocally positive. The positive control, N-Methyl-N-nitrosurea (MNU), gave reproducible responses across all participating laboratories with tumors noted at multiple sites in the animal. The immunosuppressive human carcinogen, Cyclosporin A, was equivocal. Two hormones that are human tumorigens, Diethylstilbestrol and 17β-Estradiol, gave positive and negative results, respectively. Of the twelve additional compounds tested that are classifi ed as non-genotoxic rodent carcinogens and putative human non-carcinogens, only the two peroxisome proliferators (clofi brate and diethylhexylphthalate(DEHP)) produced a positive response (liver effects). The three non-genotoxic non-carcinogens that were tested also gave negative responses in the rasH2 model. This result provides confi dence that the model is likely to have a low false-positive rate.
Alternative Models for Carcinogenicity Testing: Weight of Evidence Evaluations Across Models
Authors: Cohen Samuel M.
Published: January 2003

Twenty-one chemicals were evaluated by standardized protocols in 6 mouse models that have been sugggested as alternatives to the 2-year mouse bioassay. Included were genotoxic and nongenotoxic chemicals, carcinogens and noncarcinogens, immunosuppressive and estrogenic agents, peroxisome proliferators, and chemicals producing cancer in rodents by other mechanisms. Mice were sacrificed at the end of 6 to 12 months, depending on the model. Standardized histopathology, biostatistical analyses, and criteria for overall evaluation of the results were employed. The TgAC transgenic (dermal and oral administration), the Tg-rasH2 transgenic, the heterozygous p53 gene knockout, the homozygous XPA and homozygous XPA—heterozygous p53 gene knockout, and the neonatal mouse models were evaluated. The chemicals were also evaluated in the in vitro SHE assay. Comparison of the results between the various in vivo models suggest that they might have usefulness as screening bioassays for hazard identification for potential human carcinogens. They have the benefits of being quicker, less expensive, and involve fewer animals than the traditional 2-year mouse bioassay. They do not appear to be overly sensitive. However, they do not definitively distinguish between genotoxic and nongenotoxic carcinogens, and they do not have 100% specifi city for identifying human carcinogens. Like the 2-year bioassay, the results from these models need to be evaluated in conjunction with other information on a chemical in an overall weight-of-evidence, integrated analytical approach to assess risk for human exposures.
The Society of Toxicologic Pathology's Position on Statistical Methods for Rodent Carcinogenicity Studies
Authors: Morton Daniel
Published: January 2003

Diplomate ACVP Diplomate ABT President, Society of Toxicologic Pathology
New strategies to overcome antimicrobial resistance in Streptococcus pneumoniae with β-lactam antibiotics
Authors: Aguilar L. , Giménez M. J. , Garcia-Rey C. , Martín J. E.
Published: January 2003

The worldwide epidemic of antibiotic resistance in Streptococcus pneumoniae appears to advance inexorably and the measures taken to date to contain its progression have not been successful. Consideration should be given to the complex relationship between antibiotic consumption and resistance to the drug administered and also to other agents in the same and other antibiotic groups. We propose an integrated triple strategy that maximizes the use of the current antibiotic arsenal and is designed to curb the spread of resistance in S. pneumoniae. There are three main parts to this strategy: (i) reduction of prescribing, with particular emphasis on those drugs whose consumption has been shown to correlate strongly with resistance; (ii) development of new formulations or dosing schedules of those drugs whose pharmacodynamic parameters are better suited to cope with highly resistant strains; and (iii) encouragement of the use of antibiotics with the maximal capability of bacterial eradication. We believe such a strategy would reduce the spread of resistance both in the current ecological situation and in the post-pneumococcal vaccination era to come. Of all current antibiotics amoxicillin meets the above requirements, and seems to be the least ecologically disturbing oral antibiotic with regard to resistance in S. pneumoniae .
β-Lactam activity against resistant pneumococcal strains is enhanced by the immune system
Authors: Casal J. , Giménez M. J. , Aguilar L. , Yuste J. , Jado I. , Tarragó D. , Fenoll A.
Published: January 2003

Pandemic resistance in Streptococcus pneumoniae is compromising antibiotic activity. Antibiotics that act on the cell wall, such as β-lactams, may have a combined effect with the immune system against S. pneumoniae , since both act on the bacterial envelope. This combined effect can be studied in vitro or in vivo with respect to bacterial killing, since lysis is the end-point of both β-lactams and the immune system. We review here the in vitro increase in the bactericidal activity of aminopenicillins by non-specific immunity (complement and polymorphonuclear leucocytes). Few data are available on the collaboration of specific immunity and β-lactams. We also review the effect of the presence of specific antibodies on the in vivo T > MIC needed for the therapeutic efficacy of amoxicillin, and on blood bacterial clearance in animal models. The effect that immunity has on pharmacodynamic parameters, such as T > MIC, in non-human studies may be used as a tool to predict the effect of these pharmacodynamic variations in overcoming resistance and its selection, in the context of increasing the use of pneumococcal conjugated vaccines.
Pharmacodynamic and kinetic basis for the selection of pneumococcal resistance in the upper respiratory tract
Authors: Soriano F. , Rodriguez-Cerrato V.
Published: January 2003

The oropharynx is both the reservoir where antibiotic-resistant Streptococcus pneumoniae strains are selected and the focus for further spread of these organisms. In order to select antibiotic-resistant organisms, the antibiotic must be able to eradicate the susceptible population. How an antibiotic acts on oropharyngeal flora is not fully understood, although data on salivary antibiotic concentrations could be useful for establishing some correlation. Many β-lactam antibiotics are very active against S. pneumoniae , and although their saliva concentrations are very low, there may be enough to eradicate the majority of β-lactam-sensitive strains. Other antibiotics achieve salivary concentrations in the range 10–30% of serum concentrations (erythromycin, clindamycin, doxycycline and rifampicin), and are also able to eradicate the antibiotic-susceptible population. Antibiotics achieving higher salivary concentrations (≥40% of the serum levels) are not very active against S. pneumoniae (ciprofloxacin) or are able to eradicate antibiotic-sensitive and -intermediate strains (clarithromycin, azithromycin and telithromycin). Only antibiotics for which there are no highly resistant pneumococcal strains, for instance some β-lactams administered at very high dose and for a short course, are associated with a lower risk of antibiotic resistance selection. To diminish the risk, the antibiotics should be dosed in order to obtain inhibitory quotients (maximal serum concentration/MIC ratios) ≥ 4, which depends not only on the antibiotic concentration achieved but also on the lack of highly resistant organisms.
Implications of antimicrobial resistance in the empirical treatment of community-acquired respiratory tract infections: the case of macrolides
Authors: Lonks J. R. , Garau J. , Medeiros A. A.
Published: January 2003

Macrolide resistance among pneumococci is increasing worldwide and is associated with increasing macrolide use. Recent studies show that use of macrolides and azalides increases nasopharyngeal carriage of both macrolide-resistant and penicillin-resistant pneumococci. Carriage of a resistant pneumococcus may foster dissemination. The clinical relevance of in vitro resistance has been debated. However, recent data from a matched case–control study showed that 18 (24%) of 76 patients had breakthrough bacteraemia with an erythromycin-resistant pneumococcus while taking a macrolide, whereas none of the 136 matched controls with an erythromycin-susceptible pneumococcal bacteraemia was taking a macrolide ( P = 0.0000001). Moreover, five (24%) of 21 patients bacteraemic with the low-level resistant M phenotype and none of the 40 matched controls were taking a macrolide ( P = 0.00157). These data indicate that macrolide resistance due to both the efflux and the methylase mechanisms is clinically relevant. Furthermore, they favour guidelines for the empirical treatment of outpatients with community-acquired pneumonia that recommend high-dose oral amoxicillin and reserve coverage of atypical pathogens for selected high-risk populations.
Knowledge, values and ideas: rethinking the notion of a social science
Authors: Armour Leslie
Published: January 2003

The fragmentation of knowledge poses serious threats to a survival when scientific and technological know‐how constantly outrun understanding of societies and individuals. A significant problem associated with this state of affairs is the unquestioned separation of facts and values. This paper has two immediate aims. The first is to argue that there is knowledge of values. The second is to look at some issues in the social sciences and to show this conclusion bears on the possibilities for the reunification of knowledge. Issues in economics, sociology, and anthropology are examined kin terms of detailed examples.
Sustainable economic development and the environment
Authors: Salih Thamir M.
Published: January 2003

To maximize society's welfare, economists should be concerned with the efficient use of the stock of natural resources. The stock of natural resources is a gift of nature. The usefulness of this stock comes from its alternative uses, e.g. existence, exploitation and bequest. Therefore, the maintenance of this stock should be part and parcel of economic policymaking, particularly in less developed countries. Otherwise, the latter countries will face scarcity of wealth induced by decline of their environment.
Visualizing complexity in corporate identity on the Internet: an empirical investigation
Authors: Teck Foo Check
Published: January 2003

Everyday a plethora of fresh, new corporate logos floods the Internet. Yet how people perceive such visuals is but very little understood. Here, the visual impacts of design complexity as embedded in corporate e‐logos are investigated empirically. Contrary to widely held beliefs, people are attracted to complexity in the design of an e‐logo. More instructively, a complex e‐logo may enhance the perceptions of a firm as being creative and professional. This methodology may be adapted for testing whether a corporate e‐logo is communicating to diverse Internet audiences.
Bridging the gaps between environmental engineering and environmental natural science education
Authors: Dominik J. , Loizeau J.‐L. , Thomas R.L.
Published: January 2003

Environmental education at technical schools and at universities has distinctive features, the profiles of which are tailored according to the teaching models of engineers and academics respectively. In this paper we suggest that the exchange of teachers and teaching methods between polytechnics and universities can be profitable for both parties. For engineers it should bring a broader perspective and more global understanding of environmental systems, while for university graduates it should help them to understand better the practical problems and limits of technical solutions. The forms of exchange and their potential benefits are still not explored sufficiently. Examples of some relatively modest forms of collaboration in environmental education between the Polytechnic of Lausanne and the University of Geneva are given to show that more vigorous exchange would facilitate mutual understanding of graduates in their future environmental careers. Better mutual understanding between engineers and natural scientists clearly will increase the societal relevance of environmental education and increase the efficiency of interdisciplinary teams.
Sustainable engineering design: an interactive multimedia case study
Authors: Perdan Slobodan , Azapagic Adisa
Published: January 2003

This paper presents an interactive multimedia case study in waste water management developed at the University of Surrey, UK. The case study considers waste water treatment methods used in a typical sewage treatment works (STW). The works uses a biological treatment process which depends on the provision of dissolved oxygen to the incoming waste water stream. There are several alternative ways of providing oxygen and this case study explores the technical, environmental, economic and social aspects of the various alternatives. The aim of the case study is to suggest which criteria chemical engineers should consider in order to identify more sustainable process alternatives. The case study is developed as an IT‐based interactive learning package (CD‐ROM).
Feedback Stabilization of Quasi-Integrable Hamiltonian Systems
Authors: Zhu W. Q. , Huang Z. L.
Published: January 2003

A procedure for designing a feedback control to asymptotically stabilize with probability one quasi-integrable Hamiltonian system is proposed. First, a set of averaged Ito^ stochastic differential equations for controlled first integrals is derived from given equations of motion of the system by using the stochastic averaging method for quasi-integrable Hamiltonian systems. Second, a dynamical programming equation for infinite horizon performance index with unknown cost function is established based on the stochastic dynamical programming principle. Third, the asymptotic stability with probability one of the optimally controlled system is analyzed by evaluating the largest Lyapunov exponent of the fully averaged Ito^ equations for the first integrals. Finally, the cost function and feedback control law are determined by the requirement of stabilization of the system. An example is worked out in detail to illustrate the application of the proposed procedure and the effect of optimal control on the stability of the system.
Time-Resolved Vane-Rotor Interaction in a High-Pressure Turbine Stage
Authors: Miller R. J. , Moss R. W. , Ainsworth R. W. , Horwood C. K.
Published: January 2003

This paper describes the time-varying aerodynamic interaction mechanisms that have been observed within a transonic high-pressure turbine stage; these are inferred from the time-resolved behavior of the rotor exit flow field. It contains results both from an experimental program in a turbine test facility and from numerical predictions. Experimental data was acquired using a fast-response aerodynamic probe capable of measuring Mach number, whirl angle, pitch angle, total pressure, and static pressure. A 3-D time-unsteady viscous Navier-Stokes solver was used for the numerical predictions. The unsteady rotor exit flowfield is formed from a combination of four flow phenomena: the rotor wake, the rotor trailing edge recompression shock, the tip-leakage flow, and the hub secondary flow. This paper describes the time-resolved behavior of each phenomenon and discusses the interaction mechanisms from which each originates. Two significant vane periodic changes (equivalent to a time-varying flow in the frame of reference of the rotor) in the rotor exit flowfield are identified. The first is a severe vane periodic fluctuation in flow conditions close to the hub wall and the second is a smaller vane periodic fluctuation occurring at equal strength over the entire blade span. These two regions of periodically varying flow are shown to be caused by two groups of interaction mechanisms. The first is thought to be caused by the interaction between the wake and secondary flow of the vane with the downstream rotor; and the second is thought to be caused by a combination of the interaction of the vane trailing edge recompression shock with the rotor, and the interaction between the vane and rotor potential fields.
Wake, Shock, and Potential Field Interactions in a 1.5 Stage Turbine—Part II: Vane-Vane Interaction and Discussion of Results
Authors: Miller R. J. , Moss R. W. , Ainsworth R. W. , Harvey N. W.
Published: January 2003

The composition of the time-resolved surface pressure field around a high-pressure rotor blade caused by the presence of neighboring blade rows is investigated with the individual effects of wake, shock and potential field interaction being determined. Two test geometries are considered: first, a high-pressure turbine stage coupled with a swan-necked diffuser exit duct; secondly, the same high pressure stage but with a vane located in the downstream duct. Both tests were conducted at engine-representative Mach and Reynolds numbers and experimental data was acquired using fast-response pressure transducers mounted on the mid-height streamline of the HP rotor blades. The results are compared to time-resolved computational predictions of the flow field in order to aid interpretation of experimental results and to determine the accuracy with which the computation predicts blade interaction. In the first half of this paper it is shown that, in addition to the two main interaction mechanisms (upstream vane-rotor and rotor-downstream vane interactions, presented in Part I of this paper) a third interaction occurs. This new interaction mechanism is shown to be caused by the interaction between the downstream vane’s potential field and the upstream vane’s trailing edge potential field and shock. The unsteady rotor surface static pressure fluctuations caused by this interaction are shown to occur on the late rotor suction surface at a frequency corresponding to the difference in the numbers of upstream and downstream vanes. The second part to the paper discusses the mechanisms that cause vane-rotor-vane interaction. The rotor’s operating point is periodically altered as it passes the downstream vane. It is shown that for a large downstream vane, the flow conditions in the rotor passage, at any instant in time, are close to being steady state.
Heat and Mass Transfer Characteristics of a Temperature and Concentration Combined Convection Due to a Vertical Ice Plate Melting
Authors: Sugawara M. , Irvine Thomas F. , Tago M.
Published: January 2003

The melting of a vertical ice plate into a calcium chloride aqueous solution (CaCl2-H2O mixture) in a rectangular cavity is considered numerically and experimentally. The ice plate melts spontaneously with decreasing temperature at the melting front even when there exists no initial temperature difference between ice and liquid. Visual observations in the liquid reveal a complicated natural convection affected by the concentration/temperature gradients which appear near the melting front. Melt water gradually contaminates an upper region in the initially homogeneous liquid, that causes the melting rate to decrease. Aspect ratio H/W of the liquid region does not affect the melting rate within an early melting stage, however large aspect ratio causes the melting rate to decrease during the melting process. A two-dimensional numerical model reflecting actual ice melting conditions predicts, approximately, the transient melting mass, and the transient temperature/concentration decrease in the melting system. It is seen that the Sherwood number at the melting front is larger when compared with previous results concerning double diffusive convection. The Nusselt number at the melting front is quantitatively considered experimentally and analytically.
A New Tailpipe Design for GE Frame-Type Gas Turbines to Substantially Lower Pressure Losses
Authors: Golomb Richard , Sahai Vivek , Cheng Dah Yu
Published: January 2003

Many GE frame gas turbines have a unique 90-deg tailpipe exhaust system that contains struts, diffusers, and turning vanes. As confirmed in a recent report by GE and other authors, it is known in the industry that this tailpipe design has large pressure losses. In this recent report a pressure loss as high as 60 in. of water (0.15 kgs/sqcm) was cited. Due to the flow separations they create, the report indicates that the struts can cause very high-pressure losses in the turbine. The report also states that these pressure losses can vary with different turbine load conditions. Cheng Fluid Systems and Cheng Power Systems have conducted a study aimed at substantially reducing these pressure losses. Flow control technology introduced to the refinery industry, i.e., the Cheng Rotation Vane (CRV) and the Large Angle Diffuser (LAD) can be used to mitigate the flow separation and turbulence that occurs in turns, bends, and large sudden expansions. Specifically the CRV addresses the flow separations in pipe turns, and the LAD addresses the flow problems that occur with large sudden expansion areas. The paper will introduce the past experience of the CRV and LAD, and will then use computer simulations to show the flow characteristics around a new design. First, the study meticulously goes through the entire GE exhaust system, starting with the redesign of the airfoil shape surrounding the struts. This new design has a larger angle of attack and minimizes the flow separations over a much wider operating range. Second, the pros and cons of the concentric turning vanes are studied and it is shown that they are more flow restrictive, rather than flow enhancing. Third, it is shown that the highly turbulent rectangular box-type exhaust ducting design, substantially contributes to high noise levels and pressure losses. In this paper a completed design will be shown that incorporates a new airfoil shape for the struts, and by using CRV flow technology in combination with the LAD flow technology, the pressure recovery can be enhanced. If the pressure losses could be reduced by 40 inches of water (0.10 kgs/sqcm), the turbine efficiency could be increased by 5%, and the power output could be increased by 6%.
Free-Stream Turbulence Effects on Film Cooling With Shaped Holes
Authors: Saumweber Christian , Schulz Achmed , Wittig Sigmar
Published: January 2003

A comprehensive set of generic experiments has been conducted to investigate the effect of elevated free-stream turbulence on film cooling performance of shaped holes. A row of three cylindrical holes as a reference case, and two rows of holes with expanded exits, a fanshaped (expanded in lateral direction), and a laidback fanshaped hole (expanded in lateral and streamwise direction) have been employed. With an external (hot gas) Mach number of Mam=0.3 operating conditions are varied in terms of free-stream turbulence intensity (up to 11%), integral length scale at constant turbulence intensity (up to 3.5 hole inlet diameters), and blowing ratio. The temperature ratio is fixed at 0.59 leading to an enginelike density ratio of 1.7. The results indicate that shaped and cylindrical holes exhibit very different reactions to elevated free-stream turbulence levels. For cylindrical holes film cooling effectiveness is reduced with increased turbulence level at low blowing ratios whereas a small gain in effectiveness can be observed at high blowing ratios. For shaped holes, increased turbulence intensity is detrimental even for the largest blowing ratio M=2.5. In comparison to the impact of turbulence intensity the effect of varying the integral length scale is found to be of minor importance. Finally, the effect of elevated free-stream turbulence in terms of heat transfer coefficients was found to be much more pronounced for the shaped holes.
Turbine Tip and Shroud Heat Transfer and Loading—Part A: Parameter Effects Including Reynolds Number, Pressure Ratio, and Gas-to-Metal Temperature Ratio
Authors: Polanka Marc D. , Hoying Donald A. , Meininger Matthew , MacArthur Charles D.
Published: January 2003

Turbine tip and shroud flow and heat transfer are some of the most complex, yet important, issues in turbine design. Most of the work performed to date has been performed in linear cascades and has investigated such items as the effect of tip geometries and turbulence on tip and shroud pressure and heat transfer. There have been very few full annulus or rotating measurements in the literature. Experimental measurements have been made on a single stage high pressure turbine at the US Air Force Turbine Research Facility (TRF) to aid in the understanding of this phenomena. The TRF is a full scale, rotating rig that operates at matched flow conditions to the true turbine environment. Heat flux measurements were acquired with both Pyrex insert strip and button gages, while the pressure measurements were taken with surface-mounted Kulite® pressure transducers. This paper presents one of the first full rotating, simultaneous pressure and heat transfer measurements to be taken in the turbine tip shroud region. These measurements provide some of the details needed for accurately quantifying the true flow condition in this complex flow regime. Comparisons between the present data and the existing 2-D cascade data were made. This investigation quantified the effects of Reynolds number, inlet temperature, turbine pressure ratio and inlet flow temperature profiles. This provides a benchmark data set for validation of numerical codes.
The Investigation of Turbine and Exhaust Interactions in Asymmetric Flows— Blade-Row Models Applied
Authors: Liu J. J. , Hynes T. P.
Published: January 2003

This paper describes the blade-row models applied to the asymmetric flow-field coupling between turbine and exhaust system. Numerical actuator disk is applied to represent a turbine blade row around the whole annulus and flow properties across the disk can jump to achieve required flow turning and entropy rise. The derivation of disk boundary conditions and the implementation in CFD solvers are described in detail. Validation of the actuator disk model and sample application of the present numerical approach are presented.
Evolution of Upstream Propagating Shock Waves From a Transonic Compressor Rotor
Authors: Prasad Anil
Published: January 2003

The evolution of upstream propagating shock waves from the isolated transonic compressor designated NASA Rotor-35 is examined numerically. Results from the numerical simulations are compared with those from a semi-analytical two-dimensional model based on the nonlinear acoustic interaction of shock waves in the axial-tangential plane upstream of the rotor. The evolution determined from a two-dimensional viscous computational solution is found to agree well with the semi-analytical prediction and confirms that shock wave evolution is a primarily inviscid phenomenon. Radial variations are found to increase the rate of decay of the shock wave amplitude in comparison to the prediction from the semi-analytical two-dimensional model. The velocity field from the three-dimensional viscous solution compares well with experimental measurements, indicating that the initial shock strength and shock wave evolution immediately upstream of the rotor blade leading edge are accurately captured. The upstream-propagating shock system is found responsible for nearly 20% of the total loss attributable to the rotor, and is consistent with earlier transonic airfoil cascade studies. The axial decay rate of the upstream induced circumferential static pressure distortion is found to be an order of magnitude slower at spanwise locations with supersonic relative inlet Mach numbers than those at which it is subsonic. As a consequence of this slower decay rate, it is found that the axial gap to the upstream stator would need to be about twice that used for subsonic blade sections.
A Study on Impeller-Diffuser Interaction—Part I: Influence on the Performance
Authors: Ziegler Kai U. , Gallus Heinz E. , Niehuis Reinhard
Published: January 2003

The interaction between impeller and diffuser is considered to have strong influence on the flow in centrifugal compressors. However, the knowledge about this influence is still not satisfying. This two-part paper presents an experimental investigation of the effect of impeller-diffuser interaction on the unsteady and the time averaged flow field configuration in impeller and diffuser and the performance of these components. The flat wedge vaned diffuser of the investigated compressor allows an independent adjustment of diffuser vane angle and radial gap between impeller exit and diffuser vane inlet. Attention is mainly directed to the radial gap, as it determines the intensity of the impeller-diffuser interaction. Part I deals with the integral flow losses and the diffusion in impeller, diffuser and the entire compressor. An extensive test series with steady probe measurements at impeller exit and diffuser exit was performed at 10 different diffuser geometries and different operating points. The results show that in most cases smaller radial gaps are leading to a more homogeneous flow field at diffuser vane exit and to a higher diffuser pressure recovery resulting in a higher compressor efficiency. On the other hand, impeller efficiency is hardly affected by the radial gap. In Part II, measurements with a laser-2-focus velocimeter are presented illuminating the reasons for the effects found. The experimental results are published as an open CFD test case under the name “Radiver.”
A Study on Impeller-Diffuser Interaction—Part II: Detailed Flow Analysis
Authors: Ziegler Kai U. , Gallus Heinz E. , Niehuis Reinhard
Published: January 2003

The interaction between impeller and diffuser is considered to have strong influence on the flow in centrifugal compressors. However, the knowledge about this influence is still not satisfying. This two-part paper presents an experimental investigation of the effect of impeller-diffuser interaction on the unsteady and the time-averaged flow field in impeller and diffuser and the performance of these components. The flat wedge vaned diffuser of the investigated compressor allows an independent adjustment of diffuser vane angle and radial gap between impeller exit and diffuser vane inlet. Attention is mainly directed to the radial gap, as it determines the intensity of the impeller-diffuser interaction. In Part I it was shown that smaller radial gaps improve diffuser pressure recovery, whereas impeller efficiency is hardly affected. Part II focuses on the reasons for these effects. Measurements with a laser-2-focus velocimeter in the highly unsteady flow field between the impeller exit region and diffuser throat were performed at three different diffuser geometries allowing a detailed flow analysis. Especially the unsteady results show that for a smaller radial gap more impeller wake fluid is conveyed towards the highly loaded diffuser vane pressure side reducing its loading and leading to a better diffusion in the diffuser channel. Concerning the impeller flow, it was found that a smaller radial gap is leading to a noticeable reduction of the wake region at impeller exit. The experimental results are intended to be published as an open CFD test case under the name “Radiver.”