bluuebunny/crossref_metadata_2025 huggingface dataset:
History of viral suppression on combination antiretroviral therapy as a predictor of virological failure after a treatment change*
Authors: Reekie J , Mocroft A , Ledergerber B , Beniowski M , Clotet B , Van Lunzen J , Chiesi A , Pradier C , Machala L , Lundgren JD ,   for the EuroSIDA Study Group
Published: February 2010

Objectives

HIV‐infected persons experience different patterns of viral suppression after initiating combination antiretroviral therapy (cART). The relationship between such differences and risk of virological failure after starting a new antiretroviral could help with patient monitoring strategies.

Methods

A total of 1827 patients on cART starting at least one new antiretroviral from 1 January 2000 while maintaining a suppressed viral load were included in the analysis. Poisson regression analysis identified factors predictive of virological failure after baseline in addition to traditional demographic variables. Baseline was defined as the date of starting new antiretrovirals.

Results

Four hundred and fifty‐one patients (24.7%) experienced virological failure, with an incidence rate (IR) of 7.3 per 100 person‐years of follow‐up (PYFU) [95% confidence interval (CI) 6.7–8.0]. After adjustment, patients who had rebounded in the year prior to baseline had a 2.4‐times higher rate of virological failure after baseline (95% CI 1.77–3.26; P<.0001), while there was no increased incidence in patients whose last viral rebound was >3 years prior to baseline [Incidence rate ratio (IRR) 1.06; 95% CI 0.75–1.50; P=0.73] compared with patients who had never virally rebounded. Patients had an 86% (95% CI 1.36–2.55; P<.0001), 53% (95% CI 1.06–2.04; P=0.02) and 5% (95% CI 0.80–1.38; P=0.72) higher virological failure rate after baseline if they were virally suppressed <50%, 50–70% and 70–90% of the time they were on cART prior to baseline, respectively, compared with those virally suppressed >90% of the time.

Discussion

Intensive monitoring after a treatment switch is required in patients who have rebounded recently or have a low percentage of time suppressed while on cART. Consideration should be given to increasing the provision of adherence counselling.
Integrin beta‐3 L33P: a new insight into the pathogenesis of chronic oxaliplatin‐induced peripheral neuropathy?
Authors: Antonacopoulou A. G. , Argyriou A. A. , Scopa C. D. , Kottorou A. , Kominea A. , Peroukides S. , Kalofonos H. P.
Published: February 2010

Aim:  To assess the significance of the ITGB3 polymorphism at residue 33 (ITGB3 L33P) in the development of chronic oxaliplatin‐induced peripheral neuropathy (OXLIPN).

Methods:  Fifty‐five patients with advanced colorectal cancer were genotyped, using allele‐specific primers and sybr green in real‐time PCR. Patients had received adjuvant oxaliplatin‐based chemotherapy. The severity of the OXLIPN was defined by means of the clinical total neuropathy score (TNSc). Following the discontinuation of treatment, 34/55 patients (61.8%) developed OXLIPN. Grade I neurotoxicity was revealed in 13 (38.2%) patients and grade II neurotoxicity in 21 (61.8%) patients.

Results:  Patients without OXLIPN (n = 21) were 19% homozygous for C, 33.3% were heterozygous, and 47.7% were homozygous for T. The corresponding percentages for patients developing any grade of OXLIPN (n = 34) were similar. About half of patients (46.1%) with grade I OXLIPN were heterozygotes (CT), 23.1% were CC, and 30.8% were TT. The majority of patients with grade II OXLIPN were TT (66.7%) with the remaining 33.3% being CT. The TT genotype was associated with increased severity of OXLIPN compared to the genotypes containing the C allele (P = 0.044).

Conclusion:  The ITGB3 L33P seems to be unrelated to the development of OXLIPN, but it appears to be related to its severity.
Spatial variations in the salinity of pore waters in northern deep water Gulf of Mexico sediments: implications for pathways and mechanisms of solute transport
Authors: HANOR J. S. , MERCER J. A.
Published: February 2010

Geofluids (2010) 10, 83–93

Spatial variations in the salinity of pore waters in sedimentary basins can provide important insight into basin‐scale hydrogeologic processes. Although there have been numerous studies of brine seeps in the deep water Gulf of Mexico, much less is known about porewater salinities in the vast areas between seeps. A study has been made of spatial variation in pore water salinities in sediments in an approximately 500 km by 200 km area of the northern deep water (water depth >500 m) Gulf of Mexico sedimentary basin (GOM) to provide insight into pathways and mechanisms of solute transport in this portion of the basin. A second objective was to document salinities in the upper 500 m of the sedimentary section, the approximate depth to which methane hydrates, a potential future energy resource, may be stable. Elevated salinities would reduce the P–T stability range of hydrates. Salinities were calculated from borehole logs using a dual electrical conductivity model. Even though much of the northern GOM is underlain by allochthonous salt most of the undisturbed shallow sedimentary section has not been permeated by hypersaline waters. These waters are limited to areas near brine seeps. Hypersaline waters having salinities in excess of 100 g l−1 become more common at subseafloor depths of 2 km and greater. A field study at Green Canyon 65 and published numerical simulations of fluid flow above tabular salt bodies suggest that brines produced by salt dissolution migrate laterally and pond above salt and/or within minibasins and that the dominant mechanism of vertical solute transport is a combination of compaction‐driven advection and diffusion, not large‐scale thermohaline overturn. Superimposed on this diffuse upward flux of dissolved salt is the more focused and localized expulsion of saline fluids up faults.
Permeability of the continental crust: dynamic variations inferred from seismicity and metamorphism
Authors: INGEBRITSEN S. E. , MANNING C. E.
Published: February 2010

Geofluids (2010) 10, 193–205

The variation of permeability with depth can be probed indirectly by various means, including hydrologic models that use geothermal data as constraints and the progress of metamorphic reactions driven by fluid flow. Geothermal and metamorphic data combine to indicate that mean permeability (k) of tectonically active continental crust decreases with depth (z) according to log k ≈ −14–3.2 log z, where k is in m2 and z in km. Other independently derived, crustal‐scale k–z relations are generally similar to this power‐law curve. Yet there is also substantial evidence for local‐to‐regional‐scale, transient, permeability‐generation events that entail permeabilities much higher than these mean k–z relations would suggest. Compilation of such data yields a fit to these elevated, transient values of log k ≈ −11.5–3.2 log z, suggesting a functional form similar to that of tectonically active crust, but shifted to higher permeability at a given depth. In addition, it seems possible that, in the absence of active prograde metamorphism, permeability in the deeper crust will decay toward values below the mean k–z curves. Several lines of evidence suggest geologically rapid (years to 103 years) decay of high‐permeability transients toward background values. Crustal‐scale k–z curves may reflect a dynamic competition between permeability creation by processes such as fluid sourcing and rock failure, and permeability destruction by processes such as compaction, hydrothermal alteration, and retrograde metamorphism.
Reliability of kinematic measures of functional reaching in children with cerebral palsy
Authors: SCHNEIBERG SHEILA , MCKINLEY PATRICIA , GISEL ERIKA , SVEISTRUP HEIDI , LEVIN MINDY F
Published: February 2010

Aim  The determination of rehabilitation effectiveness in children with cerebral palsy (CP) depends on the metric properties of the outcome measure. We evaluated the reliability of kinematic measures of functional upper limb reaching movements in children with CP.

Method  Thirteen children (ten females, three males) with spastic hemiplegic, diplegic, or quadriplegic CP affecting at least one arm (mean age 9y, SD 1.6y; range 6–11y; Manual Ability Classification System [MACS] levels II–IV) were evaluated three times over 5 weeks. The kinematics of the more affected arm reaching to grasp a 2cm3 block placed at three distances from the body midline were analysed. The reliability (test–retest) of six kinematic variables (endpoint trajectory straightness and smoothness, trunk displacement, elbow extension, shoulder horizontal adduction, and shoulder flexion] was tested and expressed as intraclass correlation coefficients (ICC, model 2,K) and 95% confidence intervals.

Results  Trajectory smoothness, trunk displacement, elbow extension, and shoulder flexion (far target) had the highest ICCs (0.82–0.95). Other kinematic variables had moderate (0.50≤ICC≤0.81) or low (0.17–0.38) reliability. Test–retest reliability was task dependent, as reaches required different degrees of trunk displacement and joint excursion.

Interpretation  Kinematic variables can be used as outcomes in clinical trials to test upper limb intervention effectiveness on motor performance and movement quality. As kinematic variables are task specific, reliability should be interpreted in the context of task requirements.
Social information processing in children and adolescents with neurofibromatosis type 1
Authors: HUIJBREGTS STEPHAN , JAHJA RIANNE , DE SONNEVILLE LEO , DE BREIJ SASCHA , SWAAB‐BARNEVELD HANNA
Published: February 2010

Aim  To examine social information processing in children and adolescents with neurofibromatosis type 1 (NF1).

Method  Thirty‐two children with NF1 (12 males, 20 females; mean age 12y 4mo, SD 4y) and 32 comparison children (12 males, 20 females; mean age 13y 1mo, SD 3y 11mo) completed face recognition, identification of facial emotions (IFE), and matching facial emotions (MFE) tasks. A series of general linear model analyses of variance were used to compare performance between children with NF1 and comparison children.

Results  Children with NF1 performed less accurately than comparison children in the face recognition task when faces were presented ‘in profile’ (p=0.05), when fearful expressions had to be identified in IFE (p=0.017), and across conditions in MFE (p=0.009). When quality of cognitive control (i.e. mean standardized scores on tasks measuring working memory and inhibitory control) was introduced to the analyses, differences in face recognition were no longer significant and differences in MFE were largely reduced (p=0.048). Differences in IFE between the comparison group and children with NF1 remained largely intact (fear: p=0.047).

Interpretation  Children with NF1 have problems in social information processing, which, in part, appear to be caused by cognitive control deficits. Some of the deficits, however, appear to be caused by deficient bottom‐up processing of social signals (e.g. fear recognition).
Selected neonatal outcomes in dizygotic twins after IVF versus non‐IVF pregnancies
Authors: Källén B , Finnström O , Lindam A , Nilsson E , Nygren K‐G , Olausson P Otterblad
Published: February 2010

Please cite this paper as: Källén B, Finnström O, Lindam A, Nilsson E, Nygren K‐G, Otterblad Olausson P. Selected neonatal outcomes in dizygotic twins after IVF versus non‐IVF pregnancies. BJOG 2010;

Objective  To compare neonatal outcome among twins conceived after in vitro fertilisation (IVF) with that of spontaneously conceived twins.

Design  Comparison of different‐sex (dizygotic) twins born after IVF with non‐IVF dizygotic twins.

Setting  National health registers in Sweden.

Population  All births in Sweden during the period 1982–2007.

Methods  We studied gestational duration, lowest birthweight and birthweight difference in the twin pair, presence of one or two twins with a respiratory complication, and with jaundice in one or both twins. Risk estimates were calculated as odds ratios with adjustments for year of birth, maternal age, parity and smoking in pregnancy.

Main outcome measures  Gestational duration, birth weight, respiratory complications, jaundice.

Results  We studied 1545 pairs of dizygotic twins born after IVF, and 8675 pairs of dizygotic twins where IVF was not known to have occurred. The risk for preterm delivery before 32 weeks of gestation was significantly increased among dizygotic twin pairs born after IVF compared with non‐IVF dizygotic twin pairs. No significant difference in low birthweight or birthweight difference within twin pairs was seen. There was an increased occurrence of twin pairs with respiratory problems or jaundice, but only the latter diagnosis occurred in a statistically significant excess.

Conclusions  The study confirms recent findings that IVF is associated with an increased risk for some neonatal complications, not only among singletons but also among twins.
Cesarean Section without Medical Reason, 1997 to 2006: A Swedish Register Study
Authors: Karlström Annika , Rådestad Ingela , Eriksson Carola , Rubertsson Christine , Nystedt Astrid , Hildingsson Ingegerd
Published: February 2010

Abstract:  Background:  Cesarean section performed in the absence of medical indication is of concern in many countries, but studies focusing on its prevalence are inconclusive. The objective of this study was, first, to describe the prevalence of cesarean section without medical reason in terms of the diagnostic code listed in the Swedish Medical Birth Register, and to assess its contribution to the general increase in the number of cesarean sections; and second, to study regional differences and differences in the maternal characteristics of women having a cesarean birth with this diagnostic code.

Methods:  Birth records of 6,796 full‐term cesarean sections in two Swedish regions with the diagnostic code O828 were collected from the Swedish Medical Birth Register. Descriptive data, t test, and logistic regression analysis were used to analyze data.

Results:  The rate of cesarean sections without medical indication increased threefold during the 10‐year period, but this finding represents a minor contribution to the general increase in the number of cesarean sections. The diagnostic code O828 was more common in the capital area (p<0.001). Secondary diagnoses were found, the most frequent of which were previous cesarean section and childbirth‐related fear. Regional differences existed concerning prevalence, classification, maternal sociodemographic, obstetric, and health variables.

Conclusions:  The rate of cesarean sections without medical reasons in terms of the diagnostic code O828 increased during the period. The prevalence and maternal characteristics differed between the regions. Medical code classification is not explicit when it comes to defining cesarean sections without medical reasons and secondary diagnoses are common. (BIRTH 37:1 March 2010)
Cesarean and Vaginal Birth in Canadian Women: A Comparison of Experiences
Authors: Chalmers Beverley , Kaczorowski Janusz , Darling Elizabeth , Heaman Maureen , Fell Deshayne B. , O’Brien Beverley , Lee Lily ,   for the Maternity Experiences Study Group of the Canadian Perinatal Surveillance System
Published: February 2010

Abstract:  Background:  Many publications have examined the reasons behind the rising cesarean delivery rate around the world. Women’s responses to the Maternity Experiences Survey of the Canadian Perinatal Surveillance System were examined to explore correlates of having a cesarean section on other experiences surrounding labor, birth, mother‐infant contact, and breastfeeding.

Methods:  A randomly selected sample of 8,244 estimated eligible women stratified primarily by province and territory was drawn from the May 2006 Canadian Census. Completed responses were obtained from 6,421 women (78%).

Results:  Three‐quarters of the women (73.7%) gave birth vaginally and 26.3 percent by cesarean section, including 13.5 percent with a planned cesarean and 12.8 percent with an unplanned cesarean. In addition to more interventions in labor, women who had a cesarean birth after attempting a vaginal birth had less mother‐infant contact after birth and less optimal breastfeeding practices.

Conclusion:  Findings from the Maternity Experiences Survey indicated that women who have cesarean births experience more interventions during labor and birth and have less optimal birthing and early parenting outcomes. (BIRTH 37:1 March 2010)
Reducing the Risk for Formula‐Fed Infants: Examining the Guidelines
Authors: Hormann Elizabeth
Published: February 2010

ABSTRACT:  Early in this century, outbreaks of Enterobacter sakazakii among infants fed on powdered infant formula in Western Europe and the United States forced a rethinking of the cherished belief that artificial feeding is a very safe choice for infants in the developed world. Alarmed by these reports, the World Health Organization and the Food and Agriculture Organization convened an Expert Meeting in 2004 to determine the causes and again in 2006 to develop guidelines for reducing the risk to infants from intrinsic bacterial contamination in powdered infant formula. Reducing the frequency of contamination at the manufacturing level would eliminate about 80 percent of the problem. Reconstituting the formula with water boiled and cooled to no less than 70° C is critical to destroy remaining bacteria. Arguments from the infant formula industry, some segments of the medical community, and some Western countries against this “lethal step” trivialize the scope and severity of the problem and ignore clear scientific evidence. (BIRTH 37:1 March 2010)
Effects of Ethanol on Extracellular Levels of Adenosine in the Basal Forebrain: An In Vivo Microdialysis Study in Freely Behaving Rats
Authors: Sharma Rishi , Engemann Samuel C. , Sahota Pradeep , Thakkar Mahesh M.
Published: February 2010

Background: Adenosine is implicated to play a pivotal role in mediating many neuronal responses to ethanol. While in vitro studies performed in cell culture have demonstrated that acute ethanol exposure increases extracellular adenosine levels, this effect has not been demonstrated, in vivo,in the brain. We performed an in vivo microdialysis study to examine the effects of local ethanol perfusion on extracellular levels of adenosine in the basal forebrain (BF).

Methods: Under sterile conditions and using a standard surgical protocol, adult male Sprague–Dawley rats were implanted with unilateral microdialysis guide cannula targeted toward the BF. Following postoperative recovery, the microdialysis probe was inserted. After allowing at least 12 to 16 hours for probe insertion recovery, the experiment was begun. Artificial cerebrospinal fluid (aCSF) was perfused (0.7 μl/min) for 80 minutes, and 4 × 20‐minute pre‐ethanol baseline samples were collected. Subsequently, 30, 100, and 300 mM doses of ethanol were perfused. Each ethanol dose was perfused for 80 minutes, and 4 × 20‐minute samples were collected. Finally, aCSF was perfused, and 4 × 20 postethanol samples were collected. Adenosine in the microdialysate was separated and measured with HPLC coupled with an UV detector. On completion, the animals were euthanized, brain removed and processed for histology.

Results: Local ethanol perfusion in the BF produced a significant increase in extracellular adenosine with the highest dose of 300 mM ethanol producing a 4‐fold increase. Cresyl violet (Nissl) staining did not indicate any toxic damage in the area surrounding the probe tip. Choline acetyltransferase immunohistochemistry revealed that all microdialysis probe sites were localized in the BF.

Conclusion: Our study is the first to demonstrate that ethanol acts directly in the brain to increase extracellular adenosine.
Consequences of an Adolescent Onset and Persistent Course of Alcohol Dependence in Men: Adolescent Risk Factors and Adult Outcomes
Authors: Hicks Brian M. , Iacono William G. , McGue Matt
Published: February 2010

Background:  While there is an extensive literature on the correlates of alcohol use disorders (AUD; alcohol abuse and dependence), there are relatively few prospective studies of representative birth cohorts that have examined the unique effects of an adolescent onset and persistent course of AUD on a wide range of psychosocial variables.

Methods:  A longitudinal, community‐based sample of 530 men was used to examine the impact of an adolescent onset (AUD+ at age 17) and persistent course (AUD+ at age 29) of AUD on adolescent and adult functioning including substance use, antisocial behavior, mental health problems, overall psychosocial functioning, environmental risk and protective factors, and social outcomes such as peer and romantic relationships, marriage, educational and occupational attainment, and parenthood.

Results:  An adolescent onset of AUD (n = 57) was associated with severe deficits across multiple domains of psychosocial functioning in adolescence. Measures of behavioral disinhibition in adolescence were strong predictors of a persistent course of AUD (n = 93). Nearly 40% of men with an adolescent onset were able to desist by age 29, and were similar, but not identical to men who never experienced an AUD in terms of adult functioning. Men with an adolescent onset and persistent course of AUD exhibited the most severe deficits in functioning.

Conclusion:  Results emphasize the importance of examining developmental course to understand the etiology of AUD. Our findings are optimistic in that individuals who desist from AUD are able to achieve high levels of psychosocial functioning. Our findings suggest that future research on the persistence of AUD into adulthood should focus on the contributions of behavioral disinhibition and social environment variables including peer and romantic relationships.
The experience of children and families with lymphoedema – a journey within a journey
Authors: Moffatt Christine J , Murray Susie G
Published: February 2010

This paper reports on a study in the UK that explored the experience of children suffering with Lymphoedema and that of their families. Qualitative data was collected from 20 children between the ages of 6 and 18 and their respective parents. Single, semi‐structured interviews were used in which children and their parents were asked to share how lymphoedema impacted on their family life. Children were asked about their school experience, their dreams and their aspirations. Three categories emerged. Firstly, the negotiation of the health care system. Themes included correct diagnosis, finding robust information and reaching a knowledgeable expert. The second category explored the complex role of the parents as advocates. Themes within this category included the dilemmas of parenting and the increasing challenges as children reached adolescence. The final category involved the impact on the family unit. The first theme concerned the integration of lymphoedema into daily activities and the intrusion on family time. The second explored the impact on siblings and the final theme the changing dilemmas as children moved through the stages of childhood and faced adulthood.
Efficacy of Phosphodiesterase Type 5 Inhibitor Treatment in Men with Erectile Dysfunction and Dyslipidemia: A Post Hoc Analysis of the Vardenafil Statin Study
Authors: Miner Martin M. , Barnes Allison , Janning Stephen
Published: February 2010

Introduction

Dyslipidemia occurs often in subjects with erectile dysfunction (ED), but there is little information about how this condition affects ED treatment responses.

Aim

To determine whether low-density lipoprotein cholesterol (LDL-C) levels, total cholesterol (TC)/high-density lipoprotein cholesterol (HDL-C) ratio; or the presence of metabolic syndrome influenced efficacy of vardenafil in men with ED and dyslipidemia.

Methods

Post hoc subgroup analysis of a 12-week study of the influence of lipid levels and presence of metabolic syndrome on the efficacy of vardenafil as measured by International Index of Erectile Function-Erectile Function (IIEF-EF) domain score, responses to Sexual Encounter Profile (SEP) SEP2 and SEP3 questions, duration of erection leading to successful intercourse, and erection duration regardless of the answer to SEP3. Lipid values were obtained at study start, after patients had received at least 3 months of therapy with a statin.

Main Outcome Measures

Outcomes in subjects with LDL-C <100, ≥100 to <130, or ≥130 mg/dL [<2.59, ≥2.59 to <3.36, or ≥3.36 mmol/L]; TC/HDL-C ratio <3.5 vs. ≥3.5, and presence or absence of metabolic syndrome.

Results

Vardenafil improved all endpoints evaluated compared with placebo in all subgroups, however, nominally significant treatment by subgroup interaction terms did not follow a distinct pattern. Increasing LDL-C (P  = 0.033), but not TC/HDL-C ratio or metabolic syndrome, was associated with an increase in treatment response measured by the IIEF-EF domain score. Responses to SEP3 were nominally influenced by LDL-C levels (P  = 0.019), but were not significantly influenced by TC/HDL-C ratio, or the metabolic syndrome. Only higher TC/HDL-C ratios (≥3.5) were associated with larger treatment differences in duration of erection leading to successful intercourse (P = 0.028).

Conclusions

Vardenafil was effective in men with dyslipidemia regardless of LDL-C levels, TC/HDL-C ratio, and/or presence of metabolic syndrome. Despite the known presence of ED and dyslipidemia, other cardiovascular risk factors were apparently not aggressively managed.
THE EFFECT OF DIFFERENT HEAT STERILIZATION REGIMES ON THE QUALITY OF CANNED PROCESSED CHEESE
Authors: LAZÁRKOVÁ ZUZANA , BUŇKA FRANTIŠEK , BUŇKOVÁ LEONA , HOLÁŇ FELIX , KRÁČMAR STANISLAV , HRABĚ JAN
Published: February 2010

The impact of four different regimes of heat sterilization (110C for 100 min, 115C for 32 min, 120C for 10 min and 125C for 3.2 min) on the properties of processed cheeses was evaluated. Also, nonsterilized samples were analyzed. Samples without and with the addition of lactose (0.5–2.0% w/w) were studied because lactose might be present in raw materials at various concentrations and might significantly affect processed cheese quality. All the sterilization regimes ensured inactivation of microflora. When the sterilization temperature was reduced (with simultaneously prolonged exposure time) the samples showed worse sensory properties. Significant hydrolytic changes of proteins and larger amino acid losses were also detected. The smallest changes were noted in products treated at 125C for 3.2 min. The heat treatment at 120C for 10 min caused acceptable modification of cheese properties. Addition of lactose higher than 1.0% w/w was found unsuitable for the production of sterilized processed cheeses.

PRACTICAL APPLICATIONS

Processed cheese is a natural cheese‐based foodstuff manufactured using heat treatment (especially at 80–100C). Sterilized processed cheese is a specific product with prolonged shelf life, which could be used either in everyday life or for military and rescue team boarding during operations (Buňka et al. 2004). This product is manufactured in many countries but only limited scientific information about its quality and properties is available. Powdered skim milk and whey (used mainly for cutting the costs of the ingredients), which contain high amounts of lactose, are widely used in production of processed cheese. Lactose can show a deteriorating effect on the quality of processed cheeses, especially after application of severe heat treatment. Results of this study could be useful for setting sterilization time and temperature in order to manufacture products with high nutritive and sensory value. Moreover, a comparative study exploring acceptable lactose concentration value was carried out.
Development of Trigger Levels to Assess Catchment Disturbance on Stream Suspended Sediment Loads in the Magela Creek Catchment, Northern Territory, Australia
Authors: MOLIERE DENE R. , EVANS KENNETH G.
Published: February 2010

Trigger levels for fine suspended sediment (FSS) load in streams are required to identify rainfall‐runoff events that have significantly elevated FSS loads, compared with expected background loads, as a result of catchment disturbance. Stream FSS load data collected in the mine‐impacted Magela Creek catchment in the wet‐dry tropics were used to derive water quality management trigger levels for two approaches – a Before‐After‐Control‐Impact Paired difference design (BACIP) and a regression relationship between observed FSS load and corresponding event discharge characteristics. The results indicate that both the BACIP and regression relationship approaches behave similarly, with similar FSS load events elevated above trigger levels. Notwithstanding this, it is recommended that in order to reliably assess the location and magnitude of a catchment disturbance on FSS load, a combination of BACIP and regression relationship approaches must be adopted. In this study, an event with a FSS load above trigger levels associated with both BACIP and the regression relationship fitted for the downstream site is considered to be significantly elevated as a result of a disturbance within the mine‐impacted region. While this technique cannot conclusively determine whether the cause of the disturbance is mine‐related or natural (such as fire or bank erosion), it is an efficient statistical method of identifying events that warrant further investigation and management action, if required.
The Meander Paradox—A Topological View
Authors: Gyr Albert
Published: February 2010

Meanders are puzzling phenomena because a meandering river seems to contradict the principle of least action. Different approaches to explain this paradox are outlined by adopting a topological view, which allows for a classification of different types of meanders and to discuss the relevant mechanisms in a rather general manner. It is shown that secondary flows of helical type are the features responsible for the increase in the sediment transport when the slope of rivers decreases due to meandering and that the increase in the discharge is due to a partial Beltramisation of the flow and to a reduction in the friction at the boundary of the helical cells. The review article contains 78 references.
Permeability Measurement Methods in Porous Media of Fiber Reinforced Composites
Authors: Sharma Sanjay , Siginer Dennis A.
Published: February 2010

Accurate measurement of permeability is critical for fluid flow modeling in porous media. Various experimental methods devised to measure permeability as a porous material property in composites are reviewed. Liquid flow and gas flow methods of permeability measurement for in-plane and transverse directions specifically for fiber-reinforced composites are discussed, as well as issues related to these methods and some associated permeability models. Alternative methods of permeability determination based on cross transport phenomenon are reviewed as well.
On the Phenomenon of Pressure Pulses Reflecting Between Blades of Adjacent Blade Rows of Turbo-Machines
Authors: Owczarek Jerzy A.
Published: February 2010

The main emphasis of the paper is on the work done by the writer between the years 1957 and 1992 on the phenomenon of pressure waves in form of pulses which reflect from blades of adjacent blade rows of turbo-machines. The recently revived interest in “acoustic resonances”, whose details are still not well defined or understood, points to a realization that a new look at some previously unrecognized findings is needed to explain problems encountered in operation of compressors and turbines. The purpose of this paper is to call attention of the turbo-machinery community to an important physical phenomenon discovered more than forty years ago about whose existence and consequences there is little awareness today. The turbine test results which led the writer in 1957 to hypothesize the existence of the phenomenon of reflecting pressure pulses are described. Subsequently, his 1966 ASME paper is discussed. In it the writer reported on the photographed observations of pressure pulses reflecting between stationary nozzles and moving blades of a water-table turbine at Lehigh University, on the description of the various types of such waves, and on an explanation of some of the resonant blade excitation frequencies observed by NACA in a turbine of turbojet engine. This is followed by a description of his 1984 ASME paper in which more general formulae were derived for the blade excitation frequencies caused by reflections of pressure pulses between the rotor blades and both upstream and downstream stator vanes. These equations were subsequently used to explain blade excitation frequencies measured in an axial compressor stage. Finally, his 1992 AIAA paper is discussed in which additional formulae relating to the reflecting pressure pulses were derived and the process of formation of a pressure pulse explained. To put this work in perspective, the writer provided, in mostly chronological order, excerpts from reports on operational problems encountered with turbo-machines in service and brief descriptions, from selected publications, of pertinent research work.
Determining the Scatter in Fatigue Crack Growth Rate Based on Variations in Bulk Property Data
Authors: Daily Jeremy S. , Klingbeil Nathan W.
Published: February 2010

A technique to predict the variability of the Paris regime fatigue crack growth rates in ductile materials based on bulk property (yield strength, hardening modulus, and fracture toughness) variation is presented. The prediction, based on the plastic dissipation in the reversed plastic zone ahead of the crack tip, is carried out for Ti-6Al-4V. The empirical distributions of the bulk properties of Ti-6Al-4V are characterized and directly used in the probabilistic assessment of the fatigue crack growth rate. Since computing the plastic dissipation is a computationally intensive procedure, a novel sampling scheme based on confidence interval minimization was used to generate the empirical distribution of fatigue crack growth rate. This technique also predicts correlation between fatigue crack growth rate and fracture toughness, which may be useful in probabilistic design of turbines.
An Experimental and Numerical Study of the Effects of Flow Incidence Angles on the Performance of a Stator Blade Cascade of a High Pressure Steam Turbine
Authors: Chibli Hicham A. , Abdelfattah Sherif A. , Schobeiri M. T. , Kang Chungrog
Published: February 2010

This study aims at quantifying the effects of off-design operation on the aerodynamic performance of a high deflection steam turbine blade linear cascade. The flow incidence on the leading edge of the blades was varied from −15.3° to +21.0° while comprehensive measurements of the resulting flow-fields upstream and downstream of the test section were conducted. This allowed calculating the profile loss coefficient which proved to be insensitive to flow incidence. The experimental results were found to be in good agreement with the output from an in-house numerical investigation using a commercial CFD package.
Non-Axisymmetric End Wall Profiling in Transonic Compressors—Part II: Design Study of a Transonic Compressor Rotor Using Non-Axisymmetric End Walls—Optimization Strategies and Performance
Authors: Reising Steffen , Schiffer Heinz-Peter
Published: February 2010

Secondary flows involving cross flow at high stage loading in modern axial compressors contribute significantly to efficiency limits. This paper summarizes an approach to control end wall flow using non-axisymmetric end walls. The challenge is to find the optimal non-axisymmetric end wall shape that results in the largest gain in performance. An automated multi-objective optimizer connected to a 3-D RANS flow solver was used to design the end wall contour. The process chain was applied to the rotor hub end wall of Configuration I of the Darmstadt Transonic Compressor. Several optimization strategies involving different objective functions to be minimized and the corresponding performances were compared. The parameters considered within the optimization process were isentropic stage efficiency, pressure loss in the rotor, throat area and secondary kinetic energy (SKE). A parameter variation was undertaken, leading to the following observations: Strong penalties on SKE at the rotor outlet and moderate penalties on isentropic efficiency, throat area and pressure ratio led to the best design. Isentropic efficiency could be raised by 0.12%, SKE at the rotor exit was reduced while the total pressure ratio of the stage remained constant. Strong penalties on efficiency and pressure ratio, a moderate one on throat area and a small one on SKE at the rotor outlet all led to a smaller increase in efficiency: 0.06%. On the other hand, a slight raise in the total pressure ratio could be achieved. A third optimization, eliminating the restriction on the throat area, was carried out to see which benefit in performance could be achieved without this geometrical restriction. Since the throat areas of all optimized geometries differ slightly from the datum value, an estimation was derived to see the extent to which the end wall profiling and cross section enlargement contribute to the improvements. Finally, a method to display secondary flows in turbomachinery is introduced. A second CFD simulation is used to calculate the primary flow where the hub end wall is defined as an Euler wall to avoid the end wall boundary layer and so eliminate the cause for some of the secondary flow mechanisms. This method clearly shows how the characteristics of secondary flow can be positively influenced by using non-axisymmetric end walls.
Turbine Stator Well CFD Studies: Effects of Coolant Supply Geometry on Cavity Sealing Performance
Authors: Andreini Antonio , Da Soghe Riccardo , Facchini Bruno
Published: February 2010

The increase of aero engines performance through the improvement of aerodynamic efficiency of main annulus flow is becoming more and more difficult to achieve. However there are still some devices that could be improved to enhance global engine efficiency. Particularly, investigations on the internal air cooling systems, may lead to a reduction of cooling air with a direct benefit to the overall performance. At the same time, further investigations on heat transfer mechanisms within turbine cavities may help to optimize cooling air flows saving engine life duration. This paper presents a CFD study aimed at the characterization of the effects of different geometries for cooling air supply within turbine cavities on wall thermal effectiveness and sealing mass flow rate. Several sealing air supply geometries were considered in order to point out the role of cooling air injection position, swirl number and jet penetration on the cavities sealing performance. The study was set up on a two-stage axial turbine rig developed in a research programme on internal air systems funded by EU (Main Annulus Gas Path Interactions - MAGPI). Steady state calculations were performed using two different computational domains: the first consists in a sector model of the whole turbine including the second stator well, while the second is a cut-down model of the stator well. Thanks to the simplified geometry of the test rig with respect to actual engines, the study has pointed out clear design suggestions regarding the effects of geometry modification of cooling air supply system.
Identification of Speed-Dependent Bearing Coefficients From Unbalance Responses in One Test Run
Authors: Yang Tachung , Lin Kai-Shang
Published: February 2010

It is well known that the bearing coefficients of oil film journal bearings are speed dependent. From the derivation of Tiwari et al., the numbers of unknown coefficients are twice the number of the equations relating to unbalance responses. That means at least two unbalance test runs are necessary to solve the bearing coefficients, no matter how many measurements are made, and the rotating machines have to stop once to adjust the unbalance configurations for the second test run. In this study, second order polynomials are assumed to fit the bearing coefficients in a specific speed range, and unbalance measurements are made at several rotating speeds in that speed range to solve for the polynomial coefficients. The advantages of this approach are that it fulfills the conditions of speed-dependent coefficients, the bearing coefficients can be obtained without stopping the machines, and on-line identification of bearing coefficients can be achieved. Noise reduction and interpolation for the bearing coefficients at other speeds can also be easily attained.
Predicted Rotordynamic Behavior of a Labyrinth Seal as Rotor Surface Speed Approaches Mach 1
Authors: Thorat Manish R. , Childs Dara W.
Published: February 2010

Prior one-control-volume (1CV) models for rotor-fluid interaction in labyrinth seals produce synchronously-reduced (at running-speed), frequency-independent stiffness and damping coefficients. The 1CV model, consisting of a leakage equation, a continuity equation, and a circumferential-momentum equation (for each cavity) was stated to be invalid for rotor surface speeds approaching the speed of sound. However, the present results show that, while the 1CV fluid-mechanic model continues to be valid, the calculated rotordynamic coefficients become strongly frequency dependent. A solution is developed for the reaction-force components for a range of precession frequencies, producing frequency-dependent stiffness and damping coefficients. They can be used to define a Laplace-domain transfer-function model for the reaction-force/rotor-motion components. Calculated rotordynamic results are presented for a simple Jeffcott rotor acted on by a labyrinth seal. The seal radius Rs and running speed ω cause the rotor surface velocity Rsω to equal the speed of sound c0 at ω = 58 krpm. Calculated synchronous-response results due to imbalance coincide for the synchronously-reduced and the frequency-dependent models. For an inlet preswirl ratio of 0.5, both models predict the same log decs out to ω≈14.5 krpm. The synchronously-reduced model predicts an onset speed of instability (OSI) at 15 krpm, but a return to stability at 45 krpm, with subsequent increases in log dec out to 65 krpm. The frequency-dependent model predicts an OSI of 65 krpm. The frequency-dependent models predict small changes in the rotor’s damped natural frequencies. The synchronously-reduced model predicts large changes. The stability-analysis results show that a frequency-dependent labyrinth seal model should be used if the rotor surface speed approaches a significant fraction of the speed of sound. For the present example, observable discrepancies arose when Rsω = 0.26 c0.
The Whole-Engine Model for Clearance Evaluation
Authors: Arkhipov Alexander N. , Karaban Vladimir V. , Putchkov Igor V. , Filkorn Guenter , Kieninger Andreas
Published: February 2010

The evaluation of the blading clearance at the design stage is important for heavy duty gas turbine efficiency. The minimum clearance value at base load is limited by the pinch point clearance during startup and/or shutdown. Therefore, transient analysis is necessary for different operating conditions. 3D transient analysis of a whole engine is labor-intensive; however 2D axisymmetric analysis does not allow consideration of different 3D effects (e.g. twisting, bending, ovality, rotor alignment). In order to overcome these cost and time limitations, the combination of 2D, axisymmetric, whole-engine model results and the scaled deflections caused by different 3D effects is used for the axial and radial clearance engineering assessment during engine operation. The basic rotor and stator closures are taken from the transient analysis using a 2D finite element (FE) model composed of axisymmetric solid and plane stress elements. To take into account 3D effects of airfoil twisting and bending, the 3D FE displacements of the blade are included in the clearance evaluation process. The relative displacements of airfoil tip and reference point at the blade or vane hub are taken from 3D steady-state FE analyses. Then the steady-state displacements of the airfoils are scaled for transient conditions using the proposed technique. Different 3D rotor / stator effects (cold-build clearances and their tolerances, rotor position with respect to stator after assembly, casing bending, deformations of compressor and turbine vane carrier inducing of casing ovalization, exhaust gas housing movements, movements of the rotor in bearings and CVC and TVC support, etc.) are also included as a contributor to the clearances. The results of the calculations are analyzed and compared with good agreements to the clearances measured in engine testing under real operation conditions. The proposed methodology allows assessing the operating clearances between the stator and rotor during the design phase. Optimization of the running clearance is one key measure to upgrade and improve the engine performance during operating experience.
Link-Spring Model of Bump-Type Foil Bearings
Authors: Feng Kai , Kaneko Shigehiko
Published: February 2010

The field experiences of gas foil bearings (GFBs) from the 1960s prove that GFBs offer several advantages over traditional oil bearings and rolling element bearings. They have the potential to be applied in a wide spectrum of turbomachinery. Bump-type foil bearings, which are considered as the best structure for GFBs, can be simply described as a hydrodynamic bearing utilizing the ambient air as the lubricant and a smooth shell supported by a corrugated bump foil as the bearing surface. However, the performance predictions of bump-type foil bearings are difficult due to mechanical complexity of the support elastic structure, especially for the effects of four factors, elasticity of bump foil, interaction forces between bumps, friction forces at contact surfaces, and local deflection of top foil. In this investigation, an analytical model of bump-type foil bearings considering the effects of all above factors is presented. In this model, each bump of the bump strip is simplified to two rigid links and a horizontally spaced spring, whose stiffness is determined from Castigliano’ theorem. Then, interaction forces and friction forces can be coupled with the bump flexibility though the horizontal elementary spring. The local deflection of top foil is described using a Finite Element model and added to the film thickness for the pressure prediction with the Reynolds’ equation. The bump deflections of a strip with ten bumps under different load distributions are calculated with the presented model and the predictions show consistency with published results. Moreover, the predicted bearing load and film thickness of a full bump-type foil bearing using this model are very close to the experimental data. Also, radial clearance and friction force variations in the foil bearing are noted to change the stiffness of bump significantly. And the predictions from the calculation with a proper selection of radial clearance and friction coefficients show extremely good agreement with the experimental data. The assumption of minimum reachable film thickness is based on experimental data to determine the load capacity of bearing. The results demonstrate that the radial clearance of foil bearing has an optimum value for the maximum load capacity.