bluuebunny/crossref_metadata_2025 huggingface dataset:
Electronic Pancreatoscopy for The Diagnosis of Pancreatic Diseases
Authors: Kodama Tadashi , Koshitani Tatsuya , Sato Hideki , Imamura Yoichi , Kato Keimei , Abe Mitsumasa , Wakabayashi Naoki , Tatsumi Yoshihide , Horii Yoshiyuki , Yamane Yukio , Yamagishi Hisakazu
Published: March 2004

ABSTRACT

OBJECTIVES:

Diagnostic pancreatoscopy was performed in 56 patients using the newly developed peroral electronic pancreatoscope (PEPS). The diagnostic value of the PEPS for pancreatic diseases was evaluated.

METHODS:

The PEPS (external diameter = 2.1 mm, bidirectional tip deflection) was developed with a minute 50,000-pixel interline charge-coupled device. Pancreatoscopy was performed by means of an endoscopic retrograde approach without sphincterotomy. The cases examined were normal (three), chronic pancreatitis (32), pancreatic cancer (eight), and intraductal papillary mucinous tumors (13).

RESULTS:

Of the 56 cases, 42 (75%) were adequately seen. In normal cases, fine capillary vessels were clearly visualized on the smooth whitish-pink mucosa. Findings in chronic pancreatitis included protein plugs, calcified stones, rough whitish mucosa, scar formation, edema, erythema, and indistinct capillary appearance. All the stenoses of chronic pancreatitis could be differentiated from those of pancreatic cancer with the PEPS. In the pancreatic cancer cases, all patients had stenoses or duct cutoffs; most cases had friable mucosa with erythema and erosive changes, and a single patient had a compressed pancreatic duct wall covered with normal epithelium. In the cases of intraductal papillary mucinous tumors, papillary tumors were visualized with extreme clarity. In the case of adenocarcinoma, the PEPS revealed oval-shaped tumors with spotty redness or villous tumors with dilation of capillary vessels. Moderate acute pancreatitis was recognized after pancreatoscopy in one of the 56 cases (1.8%).

CONCLUSIONS:

Electronic pancreatoscopy with the PEPS is feasible in most patients and technically safe, and improves diagnostic yield over conventional pancreatoscopy.
Combined Ligation and Sclerotherapy Versus Ligation Alone for Secondary Prophylaxis of Esophageal Variceal Bleeding: A Meta-Analysis
Authors: Singh Pankaj , Pooran Nakechand , Indaram Anant , Bank Simmy
Published: March 2004

ABSTRACT

OBJECTIVES:

Variceal ligation has been shown to be superior to sclerotherapy in prevention of rebleeding and improving survival in patients with cirrhosis. However, 25% of patients will rebleed before completion of treatment. A number of trials have compared the combination of ligation and sclerotherapy to ligation alone in achieving rapid and complete eradication of esophageal varices, with conflicting results.

METHODS:

Two reviewers independently identified seven randomized, controlled trials that compared endoscopic variceal ligation with the combination of sclerotherapy and ligation for the treatment of esophageal varices. Studies were identified by searching MEDLINE, reviewing references from retrieved articles, and scanning abstracts from conference proceedings. For each outcome, odds ratios (ORs) were calculated using fixed-effects and random-effects models. The Mantel-Haenszel test for statistical heterogeneity was used to assess the validity of combining results from individual studies.

RESULTS:

No significant difference was seen in cessation of actively bleeding varices (OR = 1.01, 95% CI = 0.43–2.36), variceal rebleeding (OR = 1.12, CI = 0.69–1.81), and mortality (OR = 1.1, CI = 0.70–1.74) in patients with variceal ligation versus patients receiving the combination treatment of ligation and sclerotherapy. Treatment sessions required to achieve complete variceal eradication were similar in the two treatment arms. A significantly higher incidence of esophageal stricture was seen in combination therapy (p < 0.001).

CONCLUSIONS:

The combination of ligation and sclerotherapy offers no advantage over ligation alone in prevention of rebleeding and in reduction of mortality. It is also associated with a higher complication rate of esophageal stricture.
Prospective Validation of The Rockall Risk Scoring System for Upper Gi Hemorrhage in Subgroups of Patients With Varices and Peptic Ulcers
Authors: Sanders D S , Carter M J , Goodchap R J , Cross S S , Gleeson D C , Lobo A J
Published: March 2004

ABSTRACT

OBJECTIVES:

The Rockall risk assessment score was devised to allow prediction of the risk of rebleeding and death in patients with upper GI hemorrhage. The score was derived by multivariate analysis in a cohort of patients with upper GI hemorrhage and subsequently validated in a second cohort. Only 4.4% of patients included in the initial study had esophageal varices, and analysis was not performed according to the etiology of the bleeding. Our aim was to assess the validity of the Rockall risk scoring system in predicting rebleeding and mortality in patients with esophageal varices or peptic ulcers.

METHODS:

Admissions (n = 358) over 32 months to a single specialist GI bleeding unit were scored prospectively. The distribution of episodes of rebleeding and mortality by Rockall score were statistically analyzed using Fisher's exact test with 99% CIs calculated using a Monte Carlo method. The Child-Pugh score was determined in patients with esophageal varices.

RESULTS:

The Rockall score was predictive of both rebleeding and mortality in patients with variceal hemorrhage (both ps < 0.0005), as was the Child-Pugh score (p = 0.001 and p < 0.0005, respectively). The initial Rockall score was predictive of mortality in patients with peptic ulcers (p = 0.01), although the complete score was not (p > 0.05). The complete score did, however, predict rebleeding in these patients (p = 0.001).

CONCLUSION:

This is the first study to validate the Rockall score in specific subgroups of patients with esophageal varices or peptic ulcers and suggests that it is particularly applicable to variceal hemorrhage.
Generational Differences in The Age at Diagnosis With Ibd: Genetic Anticipation, Bias, Or Temporal Effects
Authors: Faybush E M , Blanchard J F , Rawsthorne P , Bernstein C N
Published: March 2004

ABSTRACT

OBJECTIVE:

Previous cross-sectional research has demonstrated generational differences in age at diagnosis (AAD) in inflammatory bowel disease (IBD). This observation has at times been ascribed to genetic anticipation, but could also be due to biases related to case ascertainment or follow-up or to temporal changes in IBD epidemiology. We aimed to explore this issue using a population-based database.

METHODS:

In 1995 we used the comprehensive administrative databases in the province of Manitoba, Canada to establish a population-based IBD Research Registry that includes clinical and demographic information for persons. We contacted those subjects within our Research Registry who reported having any family members with IBD and their family members for verification of diagnosis and AAD. Differences in AAD between familial pairs were calculated. In addition, to assess whether duration of follow-up accounted for generational differences in AAD, we computed the mean AAD for subjects with and without family histories of IBD based on age at the time of interview (i.e., <45 and ≥45 yr of age).

RESULTS:

Of the 2445 persons with IBD in the Research Registry, 548 reported positive family histories, and 315 of these (58%) were reached by telephone. There were 169 Crohn's disease and 146 ulcerative colitis subjects with positive family histories. The mean AADs for the parents, aunts/uncles, and grandparents were significantly greater than the mean AADs for the children, nieces/nephews, and grandchildren, respectively. There was a doubling of the mean AAD when comparing the grandparent/grandchild cases with the parent/child or aunt/uncle–niece/nephew cases. No statistically significant difference in anticipation was observed, whether or not the older generation was male or female or had Crohn's disease or ulcerative colitis. The AAD was substantially greater for those interviewed at ≥45 yr of age for subjects with and without family histories. However, there was no substantial difference in mean AAD between familial and nonfamilial subjects.

CONCLUSION:

The present study has demonstrated that there is a tendency for children to be younger than their parents at the time of diagnosis of familial IBD, and that this difference in mean AAD is almost doubled for grandparent/grandchild pairs. However, we conclude that these differences are most likely due to a bias based on length of follow-up or recent multigenerational temporal changes in the risk of IBD, or both.
Outcomes of Infants Born To Mothers With Inflammatory Bowel Disease: A Population-Based Cohort Study
Authors: Dominitz Jason A , Young Josephine C C , Boyko Edward J
Published: March 2004

ABSTRACT

OBJECTIVE:

Limited population-based data on inflammatory bowel disease (IBD) and pregnancy outcomes exist. The purpose of this study is to determine the association between maternal IBD status and adverse pregnancy outcomes.

METHODS:

Using computerized birth records of infants born to mothers with Crohn's disease (CD) or ulcerative colitis (UC) and mothers without diagnoses of IBD (no-IBD) in Washington State, we performed a cross-sectional retrospective study to determine gestational age, birth weight, and congenital malformations.

RESULTS:

Preterm delivery was seen in 15.2% of CD births, 10.4% of UC births, and 7.2% of no-IBD births. Low birth weight was found in 16.8% of CD births, 7.6% of UC births, and 5.3% of no-IBD births. Smallness for gestational age was present in 15.2% of CD births, 10.5% of UC births, and 6.9% of no-IBD births. Only CD births were at significantly increased risk of preterm delivery (p < 0.0025), low birth weight (p < 0.001), and smallness for gestational age (p < 0.001). Congenital malformations were more commonly recorded in UC births than in controls (7.9% vs 1.7%, p < 0.001), whereas 3.4% of CD births had malformations recorded. Using multivariable logistic regression, CD births were more likely to be preterm (odds ratio [OR] = 2.3, 95% CI = 1.4–3.8) and have low birth weights (OR = 3.6, CI = 2.2–5.9) and smallness for gestational age (OR = 2.3, CI = 1.3–3.9). UC births were more likely to have congenital malformations reported (OR = 3.8, CI = 1.5–9.8).

CONCLUSIONS:

Maternal IBD is associated with increased odds of preterm delivery, low birth weight, smallness for gestational age (CD), and reporting of congenital malformations (UC).
Lymphonodular Hyperplasia of The Terminal Ileum Associated With Colitis Shows An Increased γδ+ T-Cell Density in Children
Authors: Kokkonen Jorma , Ruuska Tarja , Karttunen Tuomo J , Mäki Markku
Published: March 2004

ABSTRACT

OBJECTIVE:

Recently we reported a close association between lymphonodular hyperplasia (LNH) of the bulb of the duodenum and increased densities of intraepithelial γδ+ T-cells in subjects with untreated food allergies. In this study we sought to determine whether children with LNH of the terminal ileum (TI) show a similar correlation.

METHODS:

The mucosal specimens taken by colonoscopy from the TIs of 22 children with LNH of the TI without colitis, 13 with right-sided colitis or pancolitis, nine with left-sided colitis, eight with Crohn's disease, and three endoscopically healthy subjects were studied for T-cell subsets with monoclonal antibodies using a three-layer peroxidase staining method.

RESULTS:

LNH of the TI was found in 32 of the 55 subjects (58%). In 22 it was the only endoscopic finding, but in nine of 13 subjects (69%) it was related to right-sided colitis or pancolitis. In patients with left-sided colitis or Crohn's disease it was diagnosed only rarely. In the whole study population, LNH of the TI showed a significant association with the increment in the density of γδ+ T-cells. The subjects with LNH of the TI and colitis starting from the cecum showed the highest values, discriminating them statistically from any other study group. Accordingly their γδ+/CD3+ ratio was high. Even in the subjects with LNH of the TI without colitis, the increment in γδ+ T-cells was significant as compared with the subjects with left-sided colitis. Upregulations of D-related expression on the mucosa of the TI were similar regardless of the presence of LNH or colitis or an increment in γδ+ T-cells.

CONCLUSION:

Our preliminary observations showed increased densities of intraepithelial γδ+ T-cells and elevated γδ+/CD3+ ratios in subjects with LNH on the mucosa of the TI, especially if related to colitis starting at the cecum, but not in subjects with typical left-sided colitis or granulomatous Crohn's disease. The study also provides further evidence suggesting the significance of food-borne antigens in the pathogenetic mechanism of right-sided colitis or pancolitis. The finding also indicates the significance of classifying colitis into γδ-positive and -negative diseases, and has implications for the treatment of these entities.
Synergistic Inhibitory Effect of Cyclosporin A and Vitamin D Derivatives on T-Lymphocyte Proliferation in Active Ulcerative Colitis
Authors: Stio Maria , Treves Cristina , Celli Alessandra , Tarantino Ottaviano , d'Albasio Giuseppe , Bonanomi Andrea Giovanni
Published: March 2004

ABSTRACT

OBJECTIVE:

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the hormonal active form of vitamin D3, could represent a potentially therapeutic agent in autoimmune diseases. Cyclosporin A (CsA) shows immunoregulatory properties, which, in many respects, seem to be similar to those of 1,25(OH)2D3. Our aim was to investigate the possible synergistic effect exerted by CsA in combination with 1,25(OH)2D3 or its nonhypercalcemic analogues, EB 1089 and KH 1060, on the proliferative response of T lymphocytes obtained from active ulcerative colitis patients.

METHODS:

The T lymphocyte-enriched population was treated with phytohemagglutinin and CsA (doses from 1 ng to 1000 ng/ml) alone or in association with 1,25(OH)2D3 or EB 1089 or KH 1060 (0.1, 1, 10 nM final concentration). Cell proliferation was determined by [3H]thymidine incorporation and analyzed on day 5 of culture.

RESULTS:

After incubation with CsA, T lymphocyte proliferation was significantly inhibited in comparison with the vehicle-treated cultures. However, T lymphocytes from ulcerative colitis patients were significantly more sensitive to CsA than those from healthy controls. The inhibition in T lymphocyte proliferation, after treatment of the cultures with CsA associated with either 1,25(OH)2D3 or EB 1089 or KH 1060, was synergistic at well-defined concentrations.

CONCLUSIONS:

Taking into account the lowest CsA dose (1 ng/ml), the highest synergistic inhibition in the proliferation of T lymphocytes prepared from ulcerative colitis patients was found combining CsA and 10 nM of 1,25(OH)2D3 or 10 nM of EB 1089 or KH 1060 at the three concentrations. The results obtained, associating the lowest CsA dose and the lowest KH 1060 concentration, may suggest an alternative therapeutic approach in these patients, reducing the dose, and consequently the toxicity, of CsA.
Prevalence of Autonomic Dysfunction in Cirrhotic and Noncirrhotic Portal Hypertension
Authors: Rangari Manisha , Sinha S , Kapoor Dharmesh , Mohan Jagdish C , Sarin Shiv K
Published: March 2004

ABSTRACT

OBJECTIVE:

Autonomic dysfunction is common in patients with cirrhosis of the liver, but more so in patients with decompensated state, and is associated with increased mortality. We evaluated the presence and extent of autonomic dysfunction in patients with extrahepatic portal venous obstruction (EHPVO) and noncirrhotic portal fibrosis (NCPF), diseases with relatively preserved liver functions.

METHODS:

Heart rate variability in response to standing, deep breathing, and Valsalva maneuver and blood pressure response to sustained handgrip and standing were studied in 18 patients with EHPVO (13 mol/L, 5 F, mean age 15.2 ± 6 yr), 12 patients with NCPF (5 mol/L, 7 F, mean age 26.4 ± 8 yr), 15 patients with cirrhosis (7 mol/L, 8 F, mean age 12.6 ± 6 yr), and 17 healthy controls (11 mol/L, 6 F, mean age 18.6 ± 3 yr). Time-domain parameters of heart rate variability on 24-h ambulatory monitoring were assessed in all the patients.

RESULTS:

Autonomic dysfunction was observed in 67% of EHPVO, 25% of NCPF, and 80% of cirrhotic subjects but none of the healthy controls (p < 0.05). Four of five time-domain heart rate variability indices showed significant abnormalities in patients with EHPVO (p < 0.05) and cirrhosis (p < 0.05), when compared with patients with NCPF and healthy controls.

CONCLUSIONS:

Autonomic dysfunction is frequently encountered in patients with EHPVO and cirrhosis, and the presence of autonomic dysfunction in patients with noncirrhotic portal hypertension suggests a primary role of portal hypertension per se in the dysfunction.
Tumor Necrosis Factor Genetic Polymorphisms and Response To Antiviral Therapy in Patients With Chronic Hepatitis C
Authors: Rosen Hugo R , McHutchison John G , Conrad Andrew J , Lentz Jennifer J , Marousek Gail , Rose Steven L , Zaman Atif , Taylor Kent , Chou Sunwen
Published: March 2004

ABSTRACT

OBJECTIVE:

Hepatitis C virus (HCV) is the major causal agent of non-A, non-B hepatitis and the leading indication for liver transplantation worldwide. The emerging field of immunogenetics has confirmed the significant role of heritability in host immune responses to infectious pathogens. Both the major and non-major histocompatibility complex genes are increasingly identified as candidate genes hypothesized to influence the susceptibility to, or the course of, a particular disease. We hypothesized that polymorphisms within the major histocompatibility complex class III region that encode for tumor necrosis factors (TNF)-α and TNF-β might be predictive of response to antiviral therapy in patients with chronic hepatitis C.

METHODS:

A total of 155 subjects, including 110 HCV-seropositive individuals undergoing antiviral therapy and 45 ethnically similar HCV-negative controls, were studied. The HCV-positive patients had undergone antiviral treatment with either interferon monotherapy (n = 73) or in combination with ribavirin (n = 37) and were categorized as either nonresponders, sustained responders, or relapsers. Sixty (55%) patients had genotype 1 (1a or 1b). Genomic DNA was extracted, followed by polymerase chain reaction amplification and sequencing for two promoter TNF-α variants (at positions –238 and –308), as well as restriction fragment length analysis for four polymorphic loci within the TNF-β gene (NcoI, TNFc, aa13, aa26).

RESULTS:

Although there was a trend toward higher frequency of the A allele in the TNF 238 promoter among HCV-infected patients (12% vs 4%), there were no significant differences in the distribution of the genotypic polymorphisms between patients and controls. Patients with the TNF 238 A allele had higher pretreatment viral loads as compared with patients homozygous for the wild type allele (7.2 × 106 ± 4.2 × 106 copies/ml vs 3.8 × 106 ± 0.34 × 106 copies/ml, p = 0.03). However, there was no association between TNF genetic markers, including multiple haplotypic combinations, and response to therapy. In addition, there was no correlation with these polymorphic loci and histological severity of liver disease.

CONCLUSIONS:

Although previous work has suggested potential roles for TNF in the pathogenesis of HCV infection, we were unable to identify any link between TNF genetic polymorphisms and histological severity or response to antiviral therapy.
The Cost-Effectiveness of Hepatitis A Vaccination in Patients With Chronic Hepatitis C Viral Infection in The United States
Authors: Arguedas Miguel R , Heudebert Gustavo R , Fallon Michael B , Stinnett Aaron A
Published: March 2004

ABSTRACT

OBJECTIVE:

Hepatitis A vaccination is recommended for patients with chronic hepatitis C. Our aim was to analyze the cost-effectiveness of hepatitis A vaccination in these patients. The specific strategies evaluated were: no vaccination, targeted vaccination, and universal vaccination.

METHODS:

Clinical estimates were based on published data. Costs estimates were based on published data and institutional Medicare reimbursement rates. Health-related quality-of-life weights were derived from published data and expert estimates. The target population consisted of patients 45 yr of age with chronic hepatitis C followed every 6 months until death. We adopted a societal perspective.

RESULTS:

Compared with no vaccination, targeted vaccination was associated with an incremental cost-effectiveness ratio of $51,000 per quality-adjusted life-year. The incremental cost-effectiveness ratio of universal vaccination compared with targeted vaccination was $3,900,000 per quality-adjusted life-year. The results were particularly sensitive to the incidence of hepatitis A, probability of fulminant hepatic failure, and costs of hepatitis A antibody screening and vaccination.

CONCLUSIONS:

Targeted vaccination for hepatitis A in patients with chronic hepatitis C may be a cost-effective strategy to decrease the morbidity and mortality associated with hepatitis A superinfection. Universal vaccination is not a cost-effective alternative to targeted vaccination in this target population.
Hepatitis C Infection in African Americans: Its Natural History and Histological Progression
Authors: Wiley Thelma E , Brown Jennifer , Chan Juliana
Published: March 2004

ABSTRACT

OBJECTIVE:

The aim of this retrospective analysis was to determine the natural history of hepatitis C virus infection in African Americans versus non-African Americans by evaluating the clinical, virological, and histological findings.

METHODS:

We examined in a retrospective manner the demographics, mode of infection, virological features, and histological progression of HCV infection in African Americans versus non-African Americans. There were 355 patients who met criteria based on adequate liver biopsy specimens and exclusion of other hepatic diseases.

RESULTS:

African Americans (n = 112) were significantly more likely to be infected with genotype 1 virus (88%) than were non-African Americans (n = 243; 67%; p ≤ 0.001). Baseline HCV RNA levels were similar, although baseline ALT values were significantly lower in African Americans (80.0 μl ± 5.5 vs 112.1 μl ± 6.2; p ≤ 0.001). African Americans were significantly older at the time of presentation and were significantly more likely to be women (p ≤ 0.02). In African Americans, there was a trend toward less cirrhosis (22% vs 30%; p ≤ 0.1) and significantly less piecemeal necrosis on liver biopsy. Non-African Americans had significantly higher fibrosis scores, ALT values, and piecemeal necrosis ratings, and tended to progress more rapidly to cirrhosis. This difference in histological progression between the two groups was not explained by differences in alcohol consumption.

CONCLUSION:

The lower ALT, piecemeal necrosis scores, and slower progression of fibrosis in African Americans may reflect less immunological recognition of HCV-infected liver cells.
Extraction, Isolation, and Sds-Page Analysis of Purified Gastric Mucin in A Patient With Menetrier's Disease
Authors: Mall Anwar S , Dent David M , McLeod Heather , Kahn Delawir , Taylor Kathryn , Hickman Rosemary
Published: March 2004

ABSTRACT

Menetrier's disease is a rare condition characterized by marked proliferation of gastric mucosa with variable mucus secretion and achlorhydria. Although crude mucus secretion and gastric aspirates have been evaluated in this disease for output of dry matter, hexosamine, fucose, protein content, and transforming growth factor α activity, we report for the first time the isolation, purification, and gel electrophoresis of mucin from crude mucus scrapings. The fragmentation pattern of mucin in Menetrier's disease demonstrated less large polymeric mucin than the control. There was also a band of ∼55–65 kd M
r on polyacrylamide gel electrophoresis similar to that found in gastric carcinoma or peptic ulcer, but absent in the control specimens.
Reevaluation of Colon Cancer Staging—Stricture Presence Reflects Advanced Disease?
Authors: Koch Timothy R
Published: March 2004

ABSTRACT

No appropriate macroscopic classification of advanced colorectal cancers (A-CRCs) is available for assessing their tumor behavior. In the present study, A-CRCs were classified macroscopically as either stricture or nonstricture type, and the differences in clinicopathological features, mode of recurrence, and prognosis between the two types were investigated. The subjects were 166 patients with A-CRCs invading beyond the muscular layer who had undergone curative surgical resections. Fresh resected specimens from these patients were used for the study. The A-CRCs were classified as stricture or nonstricture type according to whether or not they showed marked fold convergence and/or stricture of the intestinal tract (more than 30% wall shrinkage) that had the appearance of a bow tie. Of the 166 A-CRCs, 47 (28%) were classified as stricture type. This type was significantly more frequent in the colon (37% [37/101]) than in the rectum (15% [10/65]) (p = 0.003). The stricture type was more frequently associated with an abundance of fibrosis than the nonstricture type (76% [28/37] vs 39% [25/64] in the colon, p < 0.001; 100% [10/10] vs 42% [23/55] in the rectum, p < 0.001). The recurrence rate was also higher with the stricture type than with the nonstricture type in both the colon (51% [19/37] vs 17% [11/64], p = 0.003) and rectum (80% [8/10] vs 38% [21/55], p = 0.01). The time to recurrence was significantly shorter for the stricture type in both the colon (p < 0.001) and rectum (p = 0.02). These results indicate that the macroscopic type of A-CRCs according to the presence or absence of wall stricture sign may reflect their tumor behavior, although this behavior appears to be complex and related to tumor progression. This classification could be important clinically to assess tumor behavior simply.
Management of Primary Sclerosing Cholangitis
Authors: Lee Young-Mee , Kaplan Marshall M
Published: March 2004

ABSTRACT

PREAMBLE Guidelines for clinical practice are intended to indicate preferred approaches to medical problems as established by scientifically valid research. Double blind, placebo-controlled studies are preferable, but reports and expert review articles are also utilized in a thorough review of the literature conducted through the National Library of Medicine's MEDLINE. When only data that will not withstand objective scrutiny are available, a recommendation is identified as a consensus of experts. Guidelines are applicable to all physicians who address the subject, without regard to specialty training or interests, and are intended to indicate the preferable but not necessarily the only acceptable approach to a specific problem. Guidelines are intended to be flexible and must be distinguished from standards of care that are inflexible and rarely violated. Given the wide range of specifics in any health care problem, the physician must always choose the course best suited to the individual patient and the variables in existence at the moment of decision. Guidelines are developed under the auspices of the American College of Gastroenterology and its Practice Parameters Committee and approved by the Board of Trustees. Each has been intensely reviewed and revised by the Committee, other experts in the field, physicians who will use them, and specialists in the science of decision of analysis. The recommendations of each guideline are therefore considered valid at the time of their production based on the data available. New developments in medical research and practice pertinent to each guideline will be reviewed at an established time and indicated at publication to assure continued validity.
Flow Field Computations of Combustor-Turbine Interactions Relevant to a Gas Turbine Engine
Authors: Stitzel Sarah , Thole Karen A.
Published: March 2004

The current demands for high-performance gas turbine engines can be reached by raising combustion temperatures to increase power output. High combustion temperatures create a harsh environment that leads to the consideration of the durability of the combustor and turbine sections. This paper presents a computational study of a flow field that is representative of what occurs in a combustor and how that flow field convects through the first downstream stator vane. The results of this study indicate that the development of the secondary flow field in the turbine is highly dependent on the incoming total pressure profile. The endwall heat transfer is also found to depend strongly on the secondary flow field.
Heat-Transfer Measurements and Predictions for the Vane and Blade of a Rotating High-Pressure Turbine Stage
Authors: Haldeman Charles W. , Dunn Michael G.
Published: March 2004

This paper describes heat-transfer measurements and predictions obtained for the vane and blade of a rotating high-pressure turbine stage. The measurements were obtained with the stage operating at design corrected conditions. A previous paper described the aerodynamics and the blade midspan location heat-transfer data and compared these experimental results with predictions. The intent of the current paper is to concentrate on the measurements and predictions for the 20%, 50%, and 80% span locations on the vane, the vane inner and outer endwall, the 20% and 96% span location on the blade, the blade tip (flat tip), and the stationary blade shroud. Heat-transfer data obtained at midspan for three different thermal-barrier-coated vanes (fine, medium, and coarse) are also presented. Boundary-layer heat-transfer predictions at the off-midspan locations are compared with the measurements for both the vane and the blade. The results of a STAR-CD (a commercial code) three-dimensional prediction are compared with the 20% and 96% span results for the blade surface. Predictions are not available for comparison with the tip and shroud experimental results.
The Effects of Wake-Passing Unsteadiness Over a Highly Loaded Compressor-Like Flat Plate
Authors: Ottavy Xavier , Vilmin Stephane , Hodson Howard , Gallimore Simon
Published: March 2004

The present study is concerned with wake-induced unsteady effects in axial-compressor blade rows. The goal is to exploit these effects in order to design high-lift blades without increasing the profile loss, as has been achieved for low-pressure turbine blades. In the first part of this paper, the experimental means and the computational fluid dynamics tools are described. The rig features a flat plate that can be subjected to different velocity distributions representative of the suction side of a real compressor blade. Cylindrical bars mounted on a moving system simulate the incoming wakes from the upstream blade row in the compressor. Results are presented for steady flow and for unsteady compressor-like conditions. In all cases, the separation bubble of the steady flow is suppressed by the turbulence that is induced in the boundary layer by the wakes at approximately 10% of the suction side. Its reappearance is then delayed by a region of stable laminar-like flow and low loss due to the so-called calming effect that follows the wake-induced patch. The paper describes these phenomena in detail for one particular pressure distribution. It is then shown that it should be possible to increase the lift by 35% while keeping the same level of loss as the initial conventional pressure distribution of the study.
The Effects of High Mainstream Turbulence and Turbine Vane Film Cooling on the Dispersion of a Simulated Hot Streak
Authors: Jenkins Sean , Varadarajan Krishnakumar , Bogard David G.
Published: March 2004

This paper presents the combined effects of high turbulence and film cooling on the dispersion of a simulated hot streak as it passes over a scaled-up nozzle guide vane. Experimental data demonstrates a considerable decay in the strength of a hot streak due to turbulence effects alone. Film cooling further reduces the peak temperature values resulting in a reduction of the peak temperature in the hot streak on the order of 75% relative to the upstream peak temperature in the hot streak. Comparisons are made between high turbulence Tu=20% and moderate turbulence Tu=3.5% as well as between different blowing conditions for the suction side, showerhead, and pressure side film cooling holes on a simulated nozzle guide vane.
Mistuning Identification of Bladed Disks Using a Fundamental Mistuning Model—Part I: Theory
Authors: Feiner D. M. , Griffin J. H.
Published: March 2004

This paper is the first in a two-part study of identifying mistuning in bladed disks. It develops a new method of mistuning identification based on measurements of the vibratory response of the system as a whole. As a system-based method, this approach is particularly suited to integrally bladed rotors, whose blades cannot be removed for individual measurements. The method is based on a recently developed reduced order model of mistuning called the fundamental mistuning model (FMM) and is applicable to isolated families of modes. Two versions of FMM system identification are presented: a basic version that requires some prior knowledge of the system’s properties, and a somewhat more complex version that determines the mistuning completely from experimental data.
Mistuning Identification of Bladed Disks Using a Fundamental Mistuning Model—Part II: Application
Authors: Feiner D. M. , Griffin J. H.
Published: March 2004

This paper is the second in a two-part study of identifying mistuning in bladed disks. It presents experimental validation of a new method of mistuning identification based on measurements of the vibratory response of the system as a whole. As a system-based method, this approach is particularly suited to integrally bladed rotors, whose blades cannot be removed for individual measurements. The method is based on a recently developed reduced-order model of mistuning called the fundamental mistuning model (FMM) and is applicable to isolated families of modes. Two versions of FMM system identification are applied to the experimental data: a basic version that requires some prior knowledge of the system’s properties, and a somewhat more complex version that determines the mistuning completely from experimental data.
Tailored Structural Design and Aeromechanical Control of Axial Compressor Stall—Part I: Development of Models and Metrics
Authors: McGee O. G. , Graf M. B. , Fre´chette L. G.
Published: March 2004

This two-part paper presents general methodologies for the evaluation of passive compressor stabilization strategies using tailored structural design and aeromechanical feedback control (Part I), and quantitatively compares the performance of several aeromechanical stabilization approaches which could potentially be implemented in gas turbine compression systems (Part II). Together, these papers offer a systematic study of the influence of ten aeromechanical feedback controllers to increase the range of stable compressor operation, using static pressure sensing and local structural actuation to postpone modal stall inception. In this part, the stability of aeromechanically compensated compressors was determined from the linearized structural-hydrodynamic equations of stall inception. New metrics were derived, which measure the level of aeromechanical damping, or control authority of aeromechanical feedback stabilization. They indicate that the phase between the pressure disturbances and the actuation is central to assess the impact of aeromechanical interactions on compressors stability.
Tailored Structural Design and Aeromechanical Control of Axial Compressor Stall—Part II: Evaluation of Approaches
Authors: Fre´chette L. G. , McGee O. G. , Graf M. B.
Published: March 2004

A theoretical evaluation was conducted delineating how aeromechanical feedback control can be utilized to stabilize the inception of rotating stall in axial compressors. Ten aeromechanical control methodologies were quantitatively examined based on the analytical formulations presented in the first part of this paper. The maximum operating range for each scheme is determined for optimized structural parameters, and the various schemes are compared. The present study shows that the most promising aeromechanical designs and controls for a class of low-speed axial compressors were the use of dynamic fluid injection. Aeromechanically incorporating variable duct geometries and dynamically re-staggered IGV and rotor blades were predicted to yield less controllability. The aeromechanical interaction of a flexible casing wall was predicted to be destabilizing, and thus should be avoided by designing sufficiently rigid structures to prevent casing ovalization or other structurally induced variations in tip clearance. Control authority, a metric developed in the first part of this paper, provided a useful interpretation of the aeromechanical damping of the coupled system. The model predictions also show that higher spatial modes can become limiting with aeromechanical feedback, both in control of rotating stall as well as in considering the effects of lighter, less rigid structural aeroengine designs on compressor stability.
Generic Friction Models for Time-Domain Vibration Analysis of Bladed Disks
Authors: Petrov E. P. , Ewins D. J.
Published: March 2004

New efficient models have been developed to describe dynamic friction effects in order to facilitate analysis of the vibration of bladed disks in the time domain. These friction models describe friction forces occurring at contact interfaces under time-varying normal load variations, including cases of separation. The friction models developed allow one to take into account time-varying friction contact parameters, such as friction coefficient and contact stiffness coefficients. Anisotropy and variation of the friction characteristics over the contact surfaces are included in the proposed models. The capabilities of the new friction models are demonstrated. Analysis of the friction forces is performed for different motion trajectories and different time variations of the normal load, and the effects of anisotropy, variation in time of the friction characteristics and normal load variation are discussed. A numerical analysis of transient vibrations of shrouded blades using the new models is presented.
A Method for Use of Cyclic Symmetry Properties in Analysis of Nonlinear Multiharmonic Vibrations of Bladed Disks
Authors: Petrov E. P.
Published: March 2004

An effective method for analysis of periodic forced response of nonlinear cyclically symmetric structures has been developed. The method allows multiharmonic forced response to be calculated for a whole bladed disk using a periodic sector model without any loss of accuracy in calculations and modeling. A rigorous proof of the validity of the reduction of the whole nonlinear structure to a sector is provided. Types of bladed disk forcing for which the method may be applied are formulated. A multiharmonic formulation and a solution technique for equations of motion have been derived for two cases of description for a linear part of the bladed disk model: (i) using sector finite element matrices and (ii) using sector mode shapes and frequencies. Calculations validating the developed method and a numerical investigation of a realistic high-pressure turbine bladed disk with shrouds have demonstrated the high efficiency of the method.
Measurement and Prediction of Heat Transfer Distributions on an Aft-Loaded Vane Subjected to the Influence of Catalytic and Dry Low NOx Combustor Turbulence
Authors: Ames F. E. , Argenziano M. , Wang C.
Published: March 2004

Aft-loaded vane designs can have an impact on surface heat transfer distributions by accelerating boundary layers for a greater portion of the suction surface. New combustion systems developed for low emissions have produced substantial changes to the characteristics of inlet turbulence entering nozzle guide vanes. This paper documents heat transfer rates on an aft-loaded vane subject to turbulence generated by mock combustion configurations representative of recently developed catalytic and dry low NOx (DLN) combustors. Four different inlet turbulence conditions with levels ranging up to 21% are documented in this study and vane heat transfer rates are acquired at vane exit chord Reynolds numbers ranging from 500,000 to 2,000,000. Heat transfer distributions show the influence of the turbulence conditions on heat transfer augmentation and transition. Cascade aerodynamics are well documented and match pressure distributions predicted by a commercial computational fluid dynamics (CFD) code for this large-scale low-speed facility. The aft-loaded vane pressure distribution exhibits a minimum value at about 50% arc on the suction surface. This comprehensive vane heat transfer data set is expected to represent an excellent test case for vane heat transfer predictive methods. Predictive comparisons are shown based on a two-dimensional boundary layer code using an algebraic turbulence model for augmentation as well as a transition model.
Numerical Optimization of Turbomachinery Bladings
Authors: Burguburu Ste´phane , Toussaint Clement , Bonhomme Christophe , Leroy Gilles
Published: March 2004

An optimization process is used to design bladings in turbomachinery. A gradient-based method is coupled to Navier-Stokes solvers and is applied to three different bladings. A new rotor blade of a transonic compressor is designed by using a quasi three-dimensional approach, with a significant efficiency improvement at the design point. The off-design behavior of this new compressor is also checked afterwards. The same quasi three-dimensional approach is used on a stator blade of a turbine, but the whole stage is computed in this case. The losses are locally reduced, proving the good sensitivity of the solver. Finally, a new three-dimensional rotor blade of a compressor is designed by applying deformation functions on the initial shape. The efficiency is improved over a wide range of mass flow. The whole results indicate that the optimization process can find improved design and can be integrated in a design procedure.
Aerodynamic Blade Row Interactions in an Axial Compressor—Part I: Unsteady Boundary Layer Development
Authors: Mailach Ronald , Vogeler Konrad
Published: March 2004

This two-part paper presents experimental investigations of unsteady aerodynamic blade row interactions in the first stage of the four-stage low-speed research compressor of Dresden. Both the unsteady boundary layer development and the unsteady pressure distribution of the stator blades are investigated for several operating points. The measurements were carried out on pressure side and suction side at midspan. In Part I of the paper the investigations of the unsteady boundary layer behavior are presented. The experiments were carried out using surface-mounted hot-film sensors. Additional information on the time-resolved flow between the blade rows were obtained with a hot-wire probe. The unsteady boundary layer development is strongly influenced by the incoming wakes. Within the predominantly laminar boundary layer in the front part of the blade a clear response of the boundary layer to the velocity and turbulence structure of the incoming wakes can be observed. The time-resolved structure of the boundary layer for several operating points of the compressor is analyzed in detail. The topic “calmed regions,” which can be coupled to the wake passing, is discussed. As a result an improved description of the complex boundary layer structure is given.
Pressure and Flow Characteristics in a Rotating Two-Pass Square Duct With 45-Deg Angled Ribs
Authors: Liou Tong-Miin , Dai Guang-Yuan
Published: March 2004

Measurements are presented of the local velocity and wall static-pressure distributions by using laser-Doppler velocimeter and pressure transducers, respectively, in a rotating two-pass square duct with ribs placed on the leading and trailing walls at an angle of 45 deg to the main stream. The ribs were square in cross section and in a parallel mode of arrangement. The rib-height/duct-height ratio and the pitch/rib-height ratio were 0.136 and 10, respectively. The duct Reynolds number was 1×104 and rotation number Ro ranged from 0 to 0.2. Results are addressed in terms of the evolutions of both main flow and cross-stream secondary flow, the distributions of the pressure coefficient, and the variation of friction factor with Ro. In addition, the relationships between the regional averaged Nusselt number, transverse and convective mean velocity component, and turbulent kinetic energy are documented. Simple expressions are obtained to correlate friction factor with Ro, which are lacking in the published literature for ducts ribbed with 45- deg ribs. The 45-deg ribs are found to reduce the friction loss to 60% of the 90-deg ribs for rotating duct under the same operating conditions. For CFD reference, the fully developed flow condition is absent for the rotating ribbed duct investigated. The measured evolution of complex secondary flow vortices is believed to be a challenge to numerical simulations.
Direct Activation of the ATM Protein Kinase by the Mre11/Rad50/Nbs1 Complex
Authors: Lee Ji-Hoon , Paull Tanya T.
Published: April 2004

The complex containing the Mre11, Rad50, and Nbs1 proteins (MRN) is essential for the cellular response to DNA double-strand breaks, integrating DNA repair with the activation of checkpoint signaling through the protein kinase ATM (ataxia telangiectasia mutated). We demonstrate that MRN stimulates the kinase activity of ATM in vitro toward its substrates p53, Chk2, and histone H2AX. MRN makes multiple contacts with ATM and appears to stimulate ATM activity by facilitating the stable binding of substrates. Phosphorylation of Nbs1 is critical for MRN stimulation of ATM activity toward Chk2, but not p53. Kinase-deficient ATM inhibits wild-type ATM phosphorylation of Chk2, consistent with the dominant-negative effect of kinase-deficient ATM in vivo.
Is the use of trees with superior growth a threat to soil nutrient availability? A case study with Norway spruce
Authors: Bélanger Nicolas , Paré David , Bouchard Mireille , Daoust Gaëtan
Published: April 2004

The renewed interest in the use of fast-growing tree species is accompanied by concerns about the adverse effects that these trees may have on soil. Four Norway spruce (Picea abies (L.) Karst.) provenance trials in Quebec were used to test the hypothesis that a more vigorous growth would not occur at the expense of marginalizing available nutrient pools. On these sites, the provenance showing the greatest overall productivity (high treatment) and the one showing the lowest productivity (low treatment) were studied. The divergence in total aboveground nutrient contents between the high and low treatments was high in all sites (i.e., 161%209%). Increased nutrient immobilization in trees did not cause any significant soil depletion of available base cations or total N at any site. Moreover, exchangeable Ca concentrations, cation-exchange capacity, and exchangeable Ca pools in the forest floor were significantly higher in the high treatment. It is concluded that in the short term, increased nutrient immobilization in trees does not create an apparent depletion of available base cations, perhaps because of a stimulation of soil mineral weathering and (or) a better retention of nutrients by the trees. Also, an effort to simulate mineral weathering using PROFILE showed the need for model improvement for applications at the plot level.