bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic diversity does not explain variation in extra‐pair paternity in multiple populations of a songbird
Authors: Liu I. A. , Johndrow J. E. , Abe J. , Lüpold S. , Yasukawa K. , Westneat D. F. , Nowicki S.
Published: April 2015

Many songbirds are socially monogamous but genetically polyandrous, mating with individuals outside their pair bonds. Extra‐pair paternity (EPP) varies within and across species, but reasons for this variation remain unclear. One possible source of variation is population genetic diversity, which has been shown in interspecific meta‐analyses to correlate with EPP but which has limited support from intraspecific tests. Using eight populations of the genetically polyandrous red‐winged blackbird (Agelaius phoeniceus), including an island population, we investigated whether population‐level differences in genetic diversity led to differences in EPP. We first measured genetic diversity over 10 microsatellite loci and found, as predicted, low genetic diversity in the island population. Additional structure analyses with multilocus genotypes and mtDNA showed the island population to be distinct from the continental populations. However, the island population's EPP rate fell in the middle of the continental populations' distribution, whereas the continental populations themselves showed significant variation in EPP. This result suggests that genetic diversity by itself is not a predictor of EPP rate. We discuss reasons for the departure from previous results, including hypotheses for EPP that do not solely implicate female‐driven behaviour.
Development and cognitive functions in Saudi pre‐school children with feeding problems without underlying medical disorders
Authors: Hegazi Moustafa A , Sehlo Mohammad G , Al‐Jasir Albandari , El‐Deek Basem S
Published: April 2015

Aim

This study was conducted to assess development and cognitive functions in relation to growth in Saudi pre‐school children with feeding problems (FPs) without underlying medical disorders.

Methods

Three hundred fifteen pre‐school children with FPs (221 with normal growth (FP‐N), 62 with failure to thrive (FTT) (FP‐FTT), 32 with overweight (FP‐OW)) and 100 healthy children (Ref group) underwent in‐depth assessment by anthropometric measurements, dietetic history, Behavioral Pediatrics Feeding Assessment Scale, Denver Developmental Screening test (DDST) and Stanford Binet fifth edition intelligence scales (SB‐5).

Results

The main FPs detected in Saudi children were picky eating in 85.5% of FP‐N group, infantile anorexia and poor eating in more than 90% of FP‐FTT group and overeating in 53% of FP‐OW group. FPs were not due to evident psychosocial factors but were mostly related to unhealthy feeding behaviours. FP‐N children were still having normal growth parameters, but they had significantly lower growth parameters than healthy children. Failed screening with DDST was only more significantly recorded in FP‐FTT children than in Ref children (P = 0.04). The overall IQ value by SB‐5 was significantly lower in FP‐FTT group compared with FP‐N group (P = 0.01), in FP‐FTT group compared with Ref group (P < 0.001) as well as in FP‐OW group compared with Ref group (P < 0.001).

Conclusions

Persistent FPs resulted in significant negative impact not only on growth status but also on developmental milestones and cognitive functions of pre‐school children. Healthy feeding habits are mandatory to prevent serious consequences of FPs on growth and development of Saudi pre‐school children.
Transabdominal ultrasound measurement of rectal diameter is dependent on time to defecation in constipated children
Authors: Modin Line , Dalby Kasper , Walsted Anne‐Mette , Jakobsen Marianne
Published: April 2015

Aim

To study whether diurnal variations and time in relation to defecation has to be taken into account when measurements of rectal diameter are used to determine faecal impaction in constipated children.

Methods

Repeated ultrasound measures of rectal diameter were performed in 28 children (14 constipated/14 healthy, aged between 4 and 12 years) every third hour during 24 h. After defecation, three additional scans were performed at 1‐h intervals.

Results

No diurnal variation in rectal diameter was found in the healthy group. In the constipated group, mean rectal diameter was significantly larger at 2 pm (P = 0.038) and 5 pm (P = 0.006). There were significant differences between rectal diameter in the healthy group and the constipated group at 2 pm (P = 0.016) and 5 pm (P = 0.027). When we omitted the rectal diameter of five constipated children who had their first bowel movement after 5 pm, there were no difference between groups (2 pm (P = 0.103)/5 pm (P = 0.644) ). Only in the constipated group, rectal diameter exceeded 3 cm without the patients feeling the urge to defecate.

Conclusion

We found no independent daily variation in either group without relation to defecation. There was a relation between defecation and changes in rectal diameter in both healthy children and constipated children during maintenance treatment.Asking for defecation signals before scanning should be considered a routine question, and a positive answer should cause postponement of the scan.
Feasibility study: Assessing the influence of macronutrient intakes on preterm body composition, using air displacement plethysmography
Authors: McLeod Gemma , Simmer Karen , Sherriff Jill , Nathan Elizabeth , Geddes Donna , Hartmann Peter
Published: April 2015

Aim

Preterm nutrition guidelines target nutrient accretion and growth at intrauterine rates, yet at term equivalent age, the phenotype of the preterm infant differs from that of term infants. Monitoring early changes in preterm body composition (BC) in response to macronutrient intakes may facilitate our understanding of how best to meet preterm nutrition and growth targets.

Method

Macronutrient intakes based on milk analysis were calculated from birth for infants born <33 weeks gestation. BC was measured in the PEA POD when infants were thermodynamically stable, free of intravenous lines and independent of respiratory support. Subsequent BC measurements were taken at least fortnightly until term age. Regression analysis was used to assess macronutrient influences on changes in BC.

Results

Median (range) gestation and birthweight of preterm infants (n = 27) were 29 (25–32) weeks and 1395 (560–2148) g, respectively. The youngest corrected gestational and postnatal ages that infants qualified for a PEA POD measurement were 31.86 and 1.43 weeks, respectively. Fat and total energy intakes were positively associated with increasing fat mass. Protein (with carbohydrate) intake was positively associated with increasing fat‐free mass.

Conclusion

Preterm infants can be measured in the PEA POD as early as 31 weeks corrected gestational age and the method appears sufficiently sensitive to detect influences of macronutrient intake on changes in BC.
Complementary and alternative medicine use among paediatric emergency department patients
Authors: Taylor David McDonald , Dhir Reetika , Craig Simon S , Lammers Thalia , Gardiner Kaya , Hunter Kirrily , Joffe Paul , Krieser David , Babl Franz E
Published: April 2015

Aim

To determine the period prevalence and nature of complementary and alternative medicine (CAM) use among paediatric emergency department (ED) patients and the perceptions of CAM among the CAM administrators.

Methods

A survey was undertaken in four Victorian EDs (January to September 2013). A convenience sample of parents/carers accompanying paediatric patients completed a self‐administered questionnaire. The main outcome measures were CAM use and perceptions of CAM.

Results

The parents/carers of 883 patients participated. Three hundred eighty‐eight (43.9%, 95% confidence interval (CI) 40.6–47.3) and 53 (6.0%, 95% CI 4.6–7.8) patients had taken a CAM within the previous 12 months and on the day of presentation, respectively. There were no gender differences between CAM users and non‐users (P = 0.83). The use of CAM was significantly more common among older patients (P < 0.001), those with European ethnicity (P = 0.046) and among those with chronic disease (P < 0.01). Fish oil, garlic, chamomile and acidophilus were the most commonly used CAM. Only 4.4% of CAM use was reported to the ED doctor. There were reports of potentially dangerous CAM use (St John's wort, ginseng). Parents/carers who had administered CAM were more likely to report that CAMs are safe, drug free and could prevent illness (P < 0.01). In addition, a number of this group reported that CAMs are more effective than prescription medicines and safe when taken with prescription medicines.

Conclusion

CAM use is common among paediatric ED patients although rarely reported to the ED doctor. Parents/carers who administer CAM have differing perceptions of CAM safety from those who do not.
Apportionment of damages for contributory negligence: a fixed or discretionary approach?
Authors: Goudkamp James
Published: April 2015

In most of the common-law world, legislation provides for damages to be apportioned where the claimant is guilty of contributory negligence. This legislation gives judges considerable latitude to determine the extent to which damages should be diminished for contributory negligence. It imposes what will be called a system of ‘discretionary apportionment’. This paper draws attention to the fact that, although most common-law jurisdictions are, by virtue of their apportionment legislation, in the thrall of the paradigm of discretionary apportionment, there are many, varied departures from this paradigm. This paper classifies these departures (which will be called ‘fixed apportionment rules’), emphasises that they conflict with the apportionment legislation and considers how the conflicts ought to be resolved. An important conclusion reached is that it can plausibly be argued that the landmark decision in Froom v Butcher, at least as it has been understood in subsequent cases, was decided per incuriam. Froom sits uncomfortably with the apportionment legislation. Attention is then turned to the arguments for and against a discretionary system of apportionment as opposed to a system that incorporates more fixed apportionment rules. It is contended that much stands to be gained from introducing more fixed apportionment rules.
Shared genetic diversity across the global invasive range of the monk parakeet suggests a common restricted geographic origin and the possibility of convergent selection
Authors: Edelaar Pim , Roques Severine , Hobson Elizabeth A. , Gonçalves da Silva Anders , Avery Michael L. , Russello Michael A. , Senar Juan C. , Wright Timothy F. , Carrete Martina , Tella José L.
Published: April 2015

While genetic diversity is hypothesized to be an important factor explaining invasion success, there is no consensus yet on how variation in source populations or demographic processes affects invasiveness. We used mitochondrial DNA haplotypic and microsatellite genotypic data to investigate levels of genetic variation and reconstruct the history of replicate invasions on three continents in a globally invasive bird, the monk parakeet (Myiopsitta monachus). We evaluated whether genetic diversity at invasive sites could be explained by (i) the native source populations from which they were derived and (ii) demographic bottlenecks during introduction. Genetic data indicated a localized source area for most sampled invasive populations, with limited evidence for admixing of native source populations. This pattern largely coincides with historical data on pet trade exports. However, the invasive populations are genetically more similar than predicted from the export data alone. The extent of bottleneck effects varied among invasive populations. The observed low genetic diversity, evidence of demographic contraction and restricted source area do not support the hypothesis that invasion is favoured by the mixing and recombining of genetic variation from multiple source populations. Instead, they suggest that reduced genetic variation through random processes may not inhibit successful establishment and invasion in this species. However, convergent selection across invasive sites could also explain the observed patterns of reduction and similarity in genetic variation and/or the restricted source area. In general, the alternative explanation of intraspecific variation in invasive potential among genotypes or geographic areas is neglected, but warrants more attention as it could inform comparative studies and management of biological invaders.
MicroRNAs in diabetic nephropathy: functions, biomarkers, and therapeutic targets
Authors: Kato Mitsuo , Natarajan Rama
Published: April 2015

MicroRNAs (miRNAs) are short noncoding RNAs that regulate gene expression by posttranscriptional and epigenetic mechanisms and thereby affect many cellular processes and disease states. Over 2,000 human mature miRNAs have been identified, and at least 60% of all human protein‐coding genes are known to be regulated by miRNAs. MicroRNA biogenesis involves classical transcription regulation and processing by key ribonucleases, as well as other protein factors and epigenetic mechanisms. Diabetic nephropathy (DN), a severe microvascular complication frequently associated with diabetes mellitus, is a major cause of renal failure. Although several mechanisms of regulation of key renal genes implicated in DN pathogenesis have been identified, a greater understanding is needed to develop better treatment modalities. Recent studies show that miRNAs induced in renal cells in vivo and in vitro under diabetic conditions can promote the accumulation of extracellular matrix proteins related to fibrosis and glomerular dysfunction. In this review, we highlight the significance of the expression of miRNAs in various stages of DN and emerging approaches to exploit them as biomarkers for early detection or novel therapeutic targets to prevent progression of DN.
Hiatal hernias are correlated with increased severity of non‐cystic fibrosis bronchiectasis
Authors: McDonnell Melissa Jane , Ahmed Mohammad , Das Jeeban , Ward Chris , Mokoka Matshediso , Breen David P. , O'Regan Anthony , Gilmartin John J. , Bruzzi John , Rutherford Robert M.
Published: April 2015

Background and objective

Hiatal hernias (HH) are associated with gastro‐oesophageal reflux and may contribute to lung disease severity. We aimed to evaluate the prevalence of HH among stable non‐cystic fibrosis bronchiectasis (NCFB) patients and determine associations with disease severity.

Methods

A retrospective cross‐sectional cohort study of 100 consecutive NCFB patients in our institution was performed. Data were collected on baseline variables, microbiology, lung function and radiology, according to the modified Bhalla score. Disease severity was assessed using the Bronchiectasis Severity Index (BSI) and FACED severity scores.

Results

Following expert radiological review, 81 patients were deemed suitable for study inclusion (mean age (SD) 62.6 (12.4), females 55 (67.9%), body mass index (BMI) 26.9 (5.7)); 29 (35.8%) were HH positive (HH+). HH+ patients had a trend towards higher BMI (P = 0.07), and a significantly higher proportion had reflux symptoms (HH+ 62.1% vs HH− 28.8%, P < 0.01). The presence of HH+ was associated with cystic bronchiectasis (HH+ 30.1%, HH− 11.5%; P = 0.03), increased number of lobes involved (HH+ 2.62 (1.54), HH− 2.17 (1.42); P = 0.03), increased extent of bronchiectasis, (HH+ 6.2 (4.7), HH− 4.5 (3.1); P = 0.04), decreased parenchymal attenuation (HH+ 1.0 (1.8), HH− 0.2 (0.5); P = 0.03) and reduced per cent predicted forced expiratory volume in 1 s (HH+ 75.4% (24.5), HH− 90.4% (25.5); P = 0.02). There was no lobar predilection. HH+ was associated with increased disease severity scores: BSI (HH+ 4.93 (1.65), HH− 3.25 (2.13); P < 0.001) and FACED (HH+ 2.21 (1.52), HH− 1.35 (1.43); P < 0.01).

Conclusions

HH+ was associated with worse disease severity in NCFB patients, characterized by decreased lung function, increased extent and severity of radiological disease, and increased composite disease severity scores.
Cognitive and Motivational Biases in Decision and Risk Analysis
Authors: Montibeller Gilberto , von Winterfeldt Detlof
Published: April 2015

Behavioral decision research has demonstrated that judgments and decisions of ordinary people and experts are subject to numerous biases. Decision and risk analysis were designed to improve judgments and decisions and to overcome many of these biases. However, when eliciting model components and parameters from decisionmakers or experts, analysts often face the very biases they are trying to help overcome. When these inputs are biased they can seriously reduce the quality of the model and resulting analysis. Some of these biases are due to faulty cognitive processes; some are due to motivations for preferred analysis outcomes. This article identifies the cognitive and motivational biases that are relevant for decision and risk analysis because they can distort analysis inputs and are difficult to correct. We also review and provide guidance about the existing debiasing techniques to overcome these biases. In addition, we describe some biases that are less relevant because they can be corrected by using logic or decomposing the elicitation task. We conclude the article with an agenda for future research.
The Revenge of History – The Institutional Roots of Post‐Communist Family Policy in the Czech Republic, Hungary and Poland
Authors: Hašková Hana , Saxonberg Steven
Published: April 2015

The authors combine historical and sociological institutional analysis to show that despite the political and socio‐economic transformation in 1990s, the institutional development during and before the communist era provides the best explanation for current childcare policies in Central Europe. While most authors have concentrated on policy changes that have taken place in the region since 1989, this article concentrates on the historical roots of these policies and shows that today's policies are highly influenced by a certain dynamics that had already emerged under communist rule. It shows that a historical institutional approach, which analyses the ‘gendered logic of appropriateness’ and policy legacies at various critical junctures, can explain why family policies in Central Europe had already begun to differ during the communist era, why these main differences continue and why even the changes that have taken place follow logically from historical‐institutional developments.
Service delivery interventions to improve adolescents' linkage, retention and adherence to antiretroviral therapy and HIV care
Authors: MacPherson Peter , Munthali Chigomezgo , Ferguson Jane , Armstrong Alice , Kranzer Katharina , Ferrand Rashida A. , Ross David A.
Published: April 2015

Objectives

Adolescents living with HIV face substantial difficulties in accessing HIV care services and have worse treatment outcomes than other age groups. The objective of this review was to evaluate the effectiveness of service delivery interventions to improve adolescents' linkage from HIV diagnosis to antiretroviral therapy (ART) initiation, retention in HIV care and adherence to ART.

Methods

We systematically searched the Medline, SCOPUS and Web of Sciences databases and conference abstracts from the International AIDS Conference and International Conference on AIDS and STIs in Africa (ICASA). Studies published in English between 1st January 2001 and 9th June 2014 were included. Two authors independently evaluated reports for eligibility, extracted data and assessed methodological quality using the Cochrane risk of bias tool and Newcastle–Ottawa Scale.

Results

Eleven studies from nine countries were eligible for review. Three studies were randomised controlled trials. Interventions assessed included individual and group counselling and education; peer support; directly observed therapy; financial incentives; and interventions to improve the adolescent‐friendliness of clinics. Most studies were of low to moderate methodological quality.

Conclusions

This review identified limited evidence on the effectiveness of service delivery interventions to support adolescents' linkage from HIV diagnosis to ART initiation, retention on ART and adherence to ART. Although recommendations are qualified because of the small numbers of studies and limited methodological quality, offering individual and group education and counselling, financial incentives, increasing clinic accessibility and provision of specific adolescent‐tailored services appear promising interventions and warrant further investigation.
Gestational diabetes mellitus in sub‐Saharan Africa: systematic review and metaregression on prevalence and risk factors
Authors: Mwanri Akwilina W. , Kinabo Joyce , Ramaiya Kaushik , Feskens Edith J. M.
Published: April 2015

Objective

We systematically reviewed publications on prevalence and risk factors for gestational diabetes mellitus (GDM) in the 47 countries of sub‐Saharan Africa.

Methods

We conducted a systematic search in PUBMED and reviewed articles published until June 2014 and searched the references of retrieved articles. We explored sources of heterogeneity among prevalence proportions with metaregression analysis.

Results

Of 1069 articles retrieved 22 studies were included. Half were from West Africa, specifically Nigeria, five from South Africa and six from East and Central Africa. There were differences in screening methods and diagnosis criteria used, even between studies carried out in the same country and same time period. Metaregression analysis indicated high heterogeneity among the studies (I2 = 100, P < 0.001), which could not be sufficiently explained by study setting, population, diagnostic criteria or time trend, although we observed a relatively higher prevalence in studies carried out after 2000 (5.1% vs. 3.2%), when women at risk were selected (6.5% vs. 3.8%) and when more current diagnostic criteria were used (5.1% vs. 4.2%). Associations with risk factors were reported in six studies. Significant risk factors reported in more than one study were overweight and/or obesity, family history for type 2 diabetes, previous stillbirth, previous macrosomic child and age >30 years.

Conclusions

There are few studies on prevalence and risk factors for GDM in Sub‐Saharan Africa and heterogeneity is high. Prevalence was up to about 14% when high‐risk women were studied. Preventive actions should be taken to reduce the short‐ and long‐term complications related to GDM in Sub‐Saharan Africa.
Mesenchymal stem cell–based therapy for nonhealing wounds: today and tomorrow
Authors: Li Meirong , Zhao Yali , Hao Haojie , Han Weidong , Fu Xiaobing
Published: April 2015

Although advancements have been made with traditional therapies, the treatment of chronic nonhealing wounds still remains a tough challenge. In the past two decades, mesenchymal stem cell (MSC)–based therapy has emerged as a promising therapeutic strategy for nonhealing wounds because of their characteristics including self‐renewal and a multidirectional differentiation ability and their easy collection and weak immunogenicity. There is a growing body of basic scientific studies that shed light on the functional mechanism of MSCs in modulating nonhealing wounds. Furthermore, critical advances have been achieved using MSC‐based therapy in preclinical animal models as well as in clinics trials. In this present review, we summarize the mechanisms of MSCs and highlight the important preclinical and clinical trials of MSC therapy for nonhealing wounds. In particular, the combination of MSCs transplantation and tissue‐engineered skin is addressed as a new strategy to optimize the delivery efficiency and therapeutic potential. Additionally, the current drawbacks of MSC therapy and the potential to further optimize the use of MSCs are implied.
Fracture Mechanics Model of Needle Cutting Tissue
Authors: Barnett Andrew C. , Lee Yuan-Shin , Moore Jason Z.
Published: April 2015

This work develops a needle insertion force model based on fracture mechanics, which incorporates the fracture toughness, shear modulus, and friction force of the needle and tissue. Ex vivo tissue experiments were performed to determine these mechanical tissue properties. A double insertion of the needle into the tissue was utilized to determine the fracture toughness. The shear modulus was found by applying an Ogden fit to the stress–strain curve of the tissue achieved through tension experiments. The frictional force was measured by inserting the needle through precut tissue. Results show that the force model predicts within 0.2 N of experimental needle insertion force and the fracture toughness is primarily affected by the needle diameter and needle edge geometry. On average, the tearing force was found to account for 61% of the total insertion force, the spreading force to account for 18%, and the friction force to account for the remaining 21%.
A Novel Technique for Production of Metal Matrix Composites Reinforced With Carbon Nanotubes
Authors: Isaza Cesar , Sierra G. , Meza J. M.
Published: April 2015

The metal matrix composites (MMCs) have been widely used where high specific properties and temperature resistance are required, particularly in aerospace applications. In this work, an ASTM-1100 aluminum alloy in the form of sheets was reinforced with multiwalled carbon nanotubes (MWCNTs) by a novel technique which we have called sandwich technique. Carbon nanotubes (CNTs) are dispersed in a polyvinyl alcohol (PVA) solution; this solution is poured into a container and dried to obtain a reinforced polymer, which is then stretched to obtain a sheet with CNTs aligned in the stretching direction. These composite sheets were stacked with aluminum sheets, and then these stacks were hot compacted in a die using an argon atmosphere to prevent the damage of the CNTs. During this process, most of the polymer evaporates and aluminum diffusion allows obtaining a consolidated matrix with a banded structure of CNTs. The mechanical properties of the composite were measured by tensile and nano-indentation tests, showing increases of up to 100% in the elastic modulus and significant increases in yield and ultimate strength with respect to unreinforced material. Field emission scanning electron microscopy (FESEM) analyses showed a good dispersion of the CNTs within the bands with no evidence of CNTs' damage. No harmful phases were found in the composite after micro X-ray diffraction (XRD) tests. The results showed that the proposed technique is promissory to solve some of the problems in the nano-MMCs manufacturing such as dispersion and alignment of the reinforcing phase.
New Correlations of the Two-Dimensional Turbine Cascade Aerodynamic Performance
Authors: Kuofang Qiang , Naixing Chen
Published: April 2015

Theoretical evaluation and experimental research have been conducted to verify the performance of steam and gas turbines, including exhaust turbines of superchargers. The simplified channel method and hydroelectrical analog method have been used to calculate blade surface velocity distribution. Based on the “fully developed turbulence” assumption, viscous effects are approximately taken into account by using the boundary layer theory. Theoretical optimum profile loss coefficients are given. Effects of velocity profile on losses are analyzed. Turbine cascades have the characteristics of high solidity, high setting angle and high air turning angle, which facilitate the use of the channel concept. On this basis, K.M. Todd’s “passage convergent gradient,” modified O. Zweifel’s “tangential load coefficient” and other effective criteria have been chosen and cascade data correlated. Some relatively accurate semi-empirical formulas for predicting the aerodynamic performance of cascades are formulated.
Design and Development of the Combustor Inlet Diffuser for the NASA/GE Energy Efficient Engine
Authors: Sabla P. E. , Taylor J. R. , Gauntner D. J.
Published: April 2015

Results of an experimental investigation of the aerodynamic performance of a split duct annular combustor inlet diffuser system are presented. Several diffuser configurations were investigated in 3X-scale water table tests and the preferred design was evaluated in full-scale annular airflow model tests. Pressure recovery and flow losses were determined as a function of prediffuser inlet velocity profile, flow extraction at the prediffuser exit, and distribution of flow in the combustor. Inlet velocity profile and turbulence levels were found to have a pronounced effect on system performance. Flow extraction at the prediffuser exit was found to have little influence on system performance. Generally, the annular split duct diffuser system was found to satisfy the performance objectives for the engine.
Turbine Pyrometry: An Equipment Manufacturer’s View
Authors: Beynon T. G. R.
Published: April 2015

Optical pyrometry is potentially a valuable technique for temperature measurement and control in gas turbines. However the problems associated with obtaining a clean signal interpretable as a metal temperature can be formidable. The difficulties are examined here in the light of more than 18 years’ involvement, by the author’s company, with turbine pyrometry. A number of “ground-rules” are formulated which, it is hoped, will be useful to new and prospective users of the method. Experienced users may find the perspective adopted valuable. Some possibilities arising from recent technical developments are highlighted. If certain “ground-rules” can be followed in design of the pyrometer and its installation then this model is trivial. If the rules are contravened the model rapidly becomes intractable. In fast (blade profiling) applications the finite bandwidth of the pyrometer system must be considered. In slow systems the “one-sided” nature of most optical noise cannot be ignored. Finally provision of an adequate optical signal and maintenance of a clean lens are obvious prerequisites.
Using Microprocessors in Fault Monitoring of Aircraft Electronics
Authors: Maybanks A.
Published: April 2015

This paper discusses the Ultra Electronic Controls Fault Identification Moduel (F.I.M.) as used in the Electronic Engine Control Unit (E.C.U.) for the Olympus 593 engines of the Concorde Supersonic Transport Aircraft. This is based on a C.M.O.S. Microprocessor for low power consumption and enables the Module to be applied to existing units without redesign of power supplies. The Module examines the outputs of existing fault monitoring circuits and compares these with software defined reference levels. It then determines from this and other signals taken from the E.C.U. safety consolidation circuits, the Engine Control Sub-System which is at fault. This Module has been in service with British Airways and Air France for close to one year now and the impact on rapid and accurate fault diagnosis, elimination of premature E.C.U. removals and thus reduction of cost ownership of the E.C.U. is discussed.
The Navy PATE Program
Authors: Greco L.
Published: April 2015

From the early days of Navy reciprocating engines through the gas turbine designs of the 1940’s and 50’s, engine test equipment used by the Fleet was relatively simple. As gas turbines developed to higher and higher performance levels, test requirements became more stringent. Engines introduced to the Fleet in the 1970’s required high accuracy test equipment, and therefore, a new trend toward higher precision and digital readout test equipment. Engine test procedures also became increasingly complex due to the complexity of engine designs. During this same time period (early 1970’s) an event was initiated related to gas turbine engine test. NAVAIR began an engine test system standardization effort for Navy IMA’s (Intermediate Maintenance Activities). The NAVAIR standardization effort has resulted in reduced training requirements, reduced maintenance problems, improved logistics support, and sufficient engine test capability to satisfy most complex test requirements. Although the test equipment maintenance and support problems began to dwindle, the operational problems caused by some complex test procedures continued to worsen as qualified Fleet personnel became more scarce. The solution was to develop equipment that could perform the required complex engine test procedure in a fashion that minimized the expertise required by the operator; this solution presented in this paper is PATE (Propulsion Automatic Test Equipment).
Development and Testing of a Ceramic Turbocharger Rotor
Authors: DeBell G. C. , Secord J. R.
Published: April 2015

This paper describes the development of a ceramic turbocharger at Ford Motor Company, Engineering and Research Staff. The potential advantages of reduced turbocharger and vehicle response time and manufacturing cost savings have made the ceramic turbocharger rotor a subject of interest to automotive, ceramic, and turbocharger manufacturers. An Ishikawajima-Harima Heavy Industries Co., Ltd. RH06 turbocharger was modified to incorporate a slip cast reaction bonded silicon nitride rotor to evaluate the effect of reduced rotary inertia on vehicle performance. The results of vacuum spin pit testing, turbocharger test cell testing, 2.3L spark ignition dynamometer tests, and preliminary vehicular tests, are reported.
A Generalized Mathematical Model to Estimate Gas Turbine Starting Characteristics
Authors: Agrawal R. K. , Yunis M.
Published: April 2015

The paper describes a generalized mathematical model to estimate gas turbine performance in the starting regime of the engine. These estimates are then used to calculate the minimum engine starting torque requirements, thereby defining the specifications for the aircraft starting system. Alternatively, the model can also be used to estimate the start up time at any ambient temperature or altitude for a given engine/aircraft starting system combination.
Boundary Layer Development on Turbine Airfoil Suction Surfaces
Authors: Sharma O. P. , Wells R. A. , Schlinker R. H. , Bailey D. A.
Published: April 2015

This paper presents results of a study, supported by NASA Contract NAS3-20646 under the Energy Efficient Engine Program, conducted to investigate the development of boundary layers under the influence of velocity distributions simulating the suction sides of two state-of-the-art turbine airfoils. One velocity distribution represented a forward loaded airfoil (“squared-off” design) while the other represented an aft loaded airfoil (“aft loaded” design). These velocity distributions were simulated in a low-speed high aspect ratio wind tunnel specifically designed for boundary layer investigations. It is intended that the detailed data presented in this paper be used to develop improved turbulence model suitable for application to turbine airfoil design.
Coal-Fired Heaters for CCGT Cogeneration Service
Authors: Campbell J. , Hastings G. A. , Holt C. E.
Published: April 2015

This paper discusses a current research and development program whose object is to advance the technical readiness of large, coal-fired heaters to supply the input to closed-cycle gas turbine cogeneration systems. Such closed-cycle systems become increasingly attractive as energy cost increase. The gas turbine working fluid is completely isolated from the products of coal combustion, thus avoiding corrosion and erosion of the gas turbine system. Additionally, the nature of the thermodynamic cycles is frequently such as to afford substantial savings in coal input requirements as compared to steam turbine based systems producing equivalent process heat and power. This paper describes three fired heater concepts that are under development for CCGT service. The organization of the research and development program, and the development needs of the fired heaters that are to be satisfied by the R&D program, are discussed.
Utilization of Gas Turbines for District Heating Applications
Authors: Oliker I.
Published: April 2015

Technical aspects of utilization of gas turbines for district heating applications are discussed. Economic advantages of gas turbine plants for district heating loads below 700 MWt are presented. Use of gas turbines with steam turbines in different combinations are also discussed.
Some Factors Affecting Altitude Relighting Performance of Turbojet Engine Combustor
Authors: Tian-yu Xiong , Zhao-xiang Huang , Yi-zhen Wang
Published: April 2015

Ignition performance of liquid fuel spray at various fuel/air ratios and the effect of gaseous fuel addition on ignition improvement were investigated on a gas turbine combustor test facility. Distribution of fuel/air ratio with gaseous fuel addition through the spark plug and the fuel nozzle into the flame tube was measured respectively. The universal ignition criterion derived from developed thermal explosion physical model at maximum chemical reaction rate for heterogeneous mixture ignition and the empirical formula of evaporation coefficient in fuel spray are in good agreement with experimental data obtained in dense and dilute fuel spray, and homogeneous mixture.
Rotor-Tip Leakage: Part II — Design Optimization Through Viscous Analysis and Experiment
Authors: Wadia A. R. , Booth T. C.
Published: April 2015

Blade tip losses represent a major efficiency penalty in a turbine rotor. These losses are presently controlled by maintaining close tolerances on tip clearances. This two-part paper outlines a new methodology for predicting and minimizing tip flows, and focuses on the control of tip leakage through minimization of the discharge coefficient to control the normal leakage flow component. Minimization of the discharge coefficient was achieved through viscous analysis and was supported by discharge-rig testing. The analysis for the discharge cross-flow used a stream function-vorticity formulation. Support testing was conducted with a newly developed water table discharge rig in which tip-coolant discharge could also be simulated. Experimental and numerical tip-leakage results are presented on a discharge coefficient parameter for five different tip configurations. In addition, numerical studies were conducted for stationary and rotating blades with and without tip coolant injection.
Cooling Air Flow Characteristics in Gas Turbine Components
Authors: Jen H. F. , Sobanik J. B.
Published: April 2015

An analytical model for the prediction of cooling air flow characteristics (mass flow rate and internal pressure distribution) in gas turbine components is discussed. The model addresses a number of basic flow elements typical to gas turbine components such as orifices, frictional passages, labyrinth seals, etc. Static bench test measurements of the flow characteristics were in good agreement with the analysis. For the turbine blade, the concept of equivalent pressure ratio is introduced and shown to be useful for predicting (1) the cooling air flow rate through the rotor blade at engine conditions from the static rig and (2) cooling air leakage rate at the rotor serration at engine conditions. This method shows excellent agreement with a detailed analytical model at various rotor speeds. A flow calibration procedure preserving flow similarity for blades and rotor assemblies is recommended.
Rotating Blade Vibration Analysis Using Shells
Authors: Leissa A. W. , Lee J. K. , Wang A. J.
Published: April 2015

Shallow shell theory and the Ritz method are employed to determine the frequencies and mode shapes of turbomachinery blades having both camber and twist, rotating with non-zero angles of attack. Frequencies obtained for different degrees of shallowness and thickness are compared with results available in the literature, obtained from finite element analyses of nonrotating blades. Frequencies are also determined for a rotating blade, showing the effects of changing the (1) angular velocity of rotation (2) disk radius and (3) angle of attack, as well as the significance of the most important body force terms.
Evaluation of a Method for Heat Transfer Measurements and Thermal Visualization Using a Composite of a Heater Element and Liquid Crystals
Authors: Hippensteele S. A. , Russell L. M. , Stepka F. S.
Published: April 2015

Commercially available elements of a composite consisting of a plastic sheet coated with liquid crystal, another sheet with a thin layer of a conducting material (gold or carbon), and copper bus bar strips were evaluated and found to provide a simple, convenient, accurate, and low-cost measuring device for use in heat transfer research. The particular feature of the composite is its ability to obtain local heat transfer coefficients and isotherm patterns that provide visual evaluation of the thermal performances of turbine blade cooling configurations. Examples of the use of the composite are presented.
Correction for Streamline Curvature and Coriolis Force in a Boundary Layer Integral Method
Authors: Van Den Braembussche R. A. , Zunino P.
Published: April 2015

The influence of Coriolis forces and streamwise curvature on boundary layers has been introduced into an integral method by adding a correction term to the dissipation factor. This correction term is related to Coriolis forces and streamline curvature in terms of a parameter β which was determined using existing experimental data. Theoretical calculations using this value of show good agreement with experimental results for a wide range of curvature and rotation numbers representing realistic conditions for turbomachinery applications.
The Performance of Centrifugal Compressor Channel Diffusers
Authors: Rodgers C.
Published: April 2015

Test results pertaining to the characteristics of single-stage centrifugal compressors with backswept impellers and channel-type diffusers are presented and analyzed to formulate major performance criteria influencing maximum diffusion capability. For any given stage, it was determined that stage surge (when triggered by diffuser stall), occurred near a constant mean stream velocity diffusion ratio between the impeller tip and diffuser throat. This diffusion ratio attained a maximum value of 1.8 for impeller tip Mach numbers less than unity, but was not unique for all stages, being more intimately coupled with throat blockage accumulation as a function of diffusion rate. This was identified by testing some vaned diffusers beyond the stall limit where rapid blockage accumulation precipitated an immediate decrease in channel diffuser and system static pressure recovery. The results of various experiments in the vaneless space are also described to illustrate the sensitivity of the vaneless space flow upon centrifugal compressor performance.
Design and Investigations of a Three Dimensionally Twisted Diffuser for Centrifugal Compressors
Authors: Jansen M. , Rautenberg M.
Published: April 2015

For a 90-deg centrifugal compressor impeller with an extremely distorted exit flow distribution a vaned diffuser has been designed. The maximum flow angle difference across the diffuser width at the entrance is 29 deg. In order to match the vane inlet angle to this flow angle distribution the diffuser vanes are three dimensionally twisted. The map of the compressor with the twisted diffuser is compared with those using a commonly designed cambered vane diffuser and a straight channel diffuser. On the basis of detailed flow field measurements directly before and behind the diffuser and of the static pressure distribution along the diffuser, the performance of the twisted diffuser is discussed.
Porous Fiber Metal Thermal Barrier Materials
Authors: Tolokan R. P.
Published: April 2015

Fiber metal thermal barriers are used where low thermal conductivity and mechanical integrity are required. Fiber metal materials have good insulating characteristics at low densities; product thermal conductivity is influenced more by numerous air filled pores than by heat flow through the metal fiber skeleton. Fiber metal thermal barriers are produced as randomly oriented fiber sheets in both sintered and unsintered form. Product properties are controlled by choice of alloy, fiber diameter, and porosity (or density). Fiber metal thermal barriers combine insulating properties, mechanical strength and elasticity, oxidation resistance, and temperature capability to 2000°F. Applications include ceramic coating substrates, insulating abradable seals, space shuttle fuel lines and engine components.
A Critical Appraisal of Some Current Incidence Loss Models for the Stator and Rotor of a Mixed Flow Gas Turbine
Authors: Fairbanks F.
Published: April 2015

Incidence losses occur when the gas flow angle does not coincide with the blade angle. Several incidence models which are available to the designer are reviewed and a new method of calculating the incidence losses in the stator and rotor of a mixed flow radial turbine is presented. The results from this model have been compared in the case of a mixed flow radial turbine rotor with the results from the other models and with the experimental results for the stator. All the models assume a change in the tangential component of kinetic energy at stator or rotor inlet. It is concluded that none of these models is satisfactory because they do not take into account the flow pattern in the rotor or stator passages.
The Potential Impact of Future Fuels on Small Gas Turbine Engines
Authors: Saintsbury J. A. , Sampath P.
Published: April 2015

The impact of potential aviation gas turbine fuels available in the near to midterm, is reviewed with particular reference to the small aviation gas turbine engine. The future course of gas turbine combustion R&D, and the probable need for compromise in fuels and engine technology, is also discussed. Operating experience to date on Pratt & Whitney Aircraft of Canada PT6 engines, with fuels not currently considered of aviation quality, is reported.
Time-Marching Analysis of Steady Transonic Flow in Turbomachinery Cascades Using the Hopscotch Method
Authors: Delaney R. A.
Published: April 2015

A rapid, time-marching, numerical scheme based on the hopscotch method is presented for solution of steady, two-dimensional, transonic flow in turbomachinery cascades. The scheme is applied to the strong-conservation form of the unsteady Euler equations written in arbitrary curvilinear coordinates. Cascade solutions are obtained on an orthogonal, body-centered coordinate system. Numerical solution results for two turbine cascades are presented and compared with experimental data to demonstrate the accuracy and computational efficiency of the analysis method.
A Computational Geometry for the Blades and Internal Flow Channels of Centrifugal Compressors
Authors: Casey M. V.
Published: April 2015

A new computational geometry for the blades and internal flow passages of centrifugal compressors is described and examples of its use in the design of industrial compressors are given. The method makes use of Bernstein-Bezier polynomial patches to define the geometrical shape of the flow channels. This has the following main advantages: the surfaces are defined by analytic functions which allow systematic and controlled variation of the shape and give continuous derivatives up to any required order; and the parametric form of the equations allows the blade and channel coordinates to be very simply obtained at any number of points and in any suitable distribution for use in subsequent aerodynamic and stress calculations and for manufacture. The method is particularly suitable for incorporation into a computer aided design procedure.
Dry Friction Damping Mechanisms in Engine Blades
Authors: Srinivasan A. V. , Cutts D. G.
Published: April 2015

In the context of jet engines, significant vibration damping due to dry friction can occur at (a) shroud interfaces of fans and (b) the platform of turbine blades fitted with “platform dampers.” Analytical and experimental studies in regard to this important source of nonaerodynamic damping of blade vibration are presented in this paper. Comparisons between results from analytical models and laboratory test data are made and discussed.