bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of Myc family proteins eradicates KRas-driven lung cancer in mice
Authors: Soucek Laura , Whitfield Jonathan R. , Sodir Nicole M. , Massó-Vallés Daniel , Serrano Erika , Karnezis Anthony N. , Swigart Lamorna Brown , Evan Gerard I.
Published: March 2013

The principal reason for failure of targeted cancer therapies is the emergence of resistant clones that regenerate the tumor. Therapeutic efficacy therefore depends on not only how effectively a drug inhibits its target, but also the innate or adaptive functional redundancy of that target and its attendant pathway. In this regard, the Myc transcription factors are intriguing therapeutic targets because they serve the unique and irreplaceable role of coordinating expression of the many diverse genes that, together, are required for somatic cell proliferation. Furthermore, Myc expression is deregulated in most—perhaps all—cancers, underscoring its irreplaceable role in proliferation. We previously showed in a preclinical mouse model of non-small-cell lung cancer that systemic Myc inhibition using the dominant-negative Myc mutant Omomyc exerts a dramatic therapeutic impact, triggering rapid regression of tumors with only mild and fully reversible side effects. Using protracted episodic expression of Omomyc, we now demonstrate that metronomic Myc inhibition not only contains Ras-driven lung tumors indefinitely, but also leads to their progressive eradication. Hence, Myc does indeed serve a unique and nondegenerate role in lung tumor maintenance that cannot be complemented by any adaptive mechanism, even in the most aggressive p53-deficient tumors. These data endorse Myc as a compelling cancer drug target.
Adiponectin and endothelial markers in postmenopausal women taking oral or transdermal hormone therapy
Authors: Ruszkowska Barbara , Sokup Alina , Kulwas Arleta , Kwapisz Justyna , Góralczyk Krzysztof , Socha Maciej W. , Rhone Piotr , Rość Danuta
Published: March 2013

Objective

To assess the concentration of adiponectin, soluble E‐selectin, soluble thrombomodulin and tissue activator plasminogen antigen in postmenopausal women who received oral or transdermal hormone therapy.

Design

Case–control study.

Setting

Polish university hospitals.

Population

Seventy‐six healthy postmenopausal women.

Method

Forty‐six women who received oral (n = 26) or transdermal (n = 20) hormone therapy and a control group without such medication (n = 30), all aged 44–58 years.

Main outcome measures

Plasma concentrations of adiponectin, soluble E‐selectin, soluble thrombomodulin and tissue activator plasminogen antigen by enzyme‐linked immunosorbent assay.

Results

We found a significantly higher concentration of adiponectin in women on oral and transdermal therapy in comparison to the control group and a significantly lower concentration of soluble E‐selectin in women who received oral hormone therapy vs. the control group. A significantly higher concentration of tissue activator plasminogen antigen was obtained in the group of women using transdermal menopausal hormone therapy compared with those receiving oral therapy and with the control group.

Conclusions

Reduced levels of soluble E‐selectin in women using menopausal hormone therapy could lead to reduction in the intensity of expression of the adhesion factors on the surface of the vascular endothelium. Menopausal hormone therapy might have advantageous effects on vascular endothelial function through adiponectin. Transdermal therapy may have adverse effects associated with elevated tissue activator plasminogen antigen levels and thereby the higher risk of ischemic heart disease.
Patient education has a positive effect in patients with a stoma: a systematic review
Authors: Danielsen A. K. , Burcharth J. , Rosenberg J.
Published: March 2013

Aim

A systematic review was performed to assess whether education of patients having stoma formation improves quality of life and whether it is cost effective.

Method

A literature search was performed to identify studies on the structured education of ostomates and outcome using the following databases: MEDLINE, Cinahl, Embase, Cochrane and PsycInfo. Inclusion criteria were: clinical studies reporting effects of educational interventions in relation to patients with a stoma. Commentaries or studies not testing an intervention were excluded.

Results

Seven articles met the inclusion criteria of having rigorously evaluated an educational programme related to living with a stoma. The programmes were organized in different ways and had explored various interventions. The results showed an increase in health‐related quality of life, as measured using a stoma quality of life instrument (P = 0.00001) and with the Short Form 36 (SF‐36) (P = 0.000–0.006), an increase in proficiency in management of the stoma (P = 0.0005), two studies pointed to a reduction in postoperative hospital stay (8 days vs 10 days, P = 0.029; and 8 days vs 14 days, P = 0.17), a significant reduction in cost in the intervention group ($US 8570.54) compared with the control group ($US 7396.90) as well as higher effectiveness scores in the intervention group (166.89) compared with the control group (110.98), a significant rise in stoma‐related knowledge (P = 0.0000) and an increase in psychosocial adjustment (P = 0.000).

Conclusion

Structured patient education aimed at patients' psychosocial needs seems to have a positive effect on quality of life as well as on cost. The interventions may be performed before, during or after hospital stay. However, the available data come from few studies with differences in interventions and in study design, and further studies are therefore needed before a final conclusion can be drawn.
Prevalence of Asperger syndrome among patients of an Early Intervention in Psychosis team
Authors: Davidson Conor , Greenwood Nick , Stansfield Alison , Wright Stephen
Published: March 2013

Background

There is a lack of systematic studies into comorbidity of Asperger syndrome and psychosis.

Aim

To determine the prevalence of Asperger syndrome among patients of an early intervention in psychosis service.

Methods

This study was a cross‐sectional survey consisting of three phases: screening, case note review and diagnostic interviews. All patients on caseload (n = 197) were screened using the Autism Spectrum Disorder in Adults Screening Questionnaire. The case notes of patients screened positive were then reviewed for information relevant to Asperger syndrome. Those suspected of having Asperger syndrome were invited for a diagnostic interview.

Results

Thirty patients were screened positive. Three of them already had a diagnosis of Asperger syndrome made by child and adolescent mental health services. After case note review, 13 patients were invited to interview. Four did not take part, so nine were interviewed. At interview, four were diagnosed with Asperger syndrome. In total, seven patients had Asperger syndrome. Thus, the prevalence rate in this population is at least 3.6%.

Conclusions

The results suggest that the prevalence of Asperger syndrome in first‐episode psychosis is considerably higher than that in the general population. Clinicians working in early intervention teams need to be alert to the possibility of Asperger syndrome when assessing patients.
Intrinsic vs. extrinsic influences on life history expression: metabolism and parentally induced temperature influences on embryo development rate
Authors: Martin Thomas E. , Ton Riccardo , Niklison Alina
Published: March 2013

Intrinsic processes are assumed to underlie life history expression and trade‐offs, but extrinsic inputs are theorised to shift trait expression and mask trade‐offs within species. Here, we explore application of this theory across species. We do this based on parentally induced embryo temperature as an extrinsic input, and mass‐specific embryo metabolism as an intrinsic process, underlying embryonic development rate. We found that embryonic metabolism followed intrinsic allometry rules among 49 songbird species from temperate and tropical sites. Extrinsic inputs via parentally induced temperatures explained the majority of variation in development rates and masked a relationship with metabolism; metabolism explained a minor proportion of the variation in development rates among species, and only after accounting for temperature effects. We discuss evidence that temperature further obscures the expected interspecific trade‐off between development rate and offspring quality. These results demonstrate the importance of considering extrinsic inputs to trait expression and trade‐offs across species.
Dysphagia in Duchenne muscular dystrophy assessed by validated questionnaire
Authors: Archer Sally K. , Garrod Rachel , Hart Nicholas , Miller Simon
Published: March 2013

Background

Duchenne muscular dystrophy (DMD) leads to progressive muscular weakness and death, most typically from respiratory complications. Dysphagia is common in DMD; however, the most appropriate swallowing assessments have not been universally agreed and the symptoms of dysphagia remain under‐reported.

Aims

To investigate symptoms of dysphagia in DMD and to determine the potential of the validated Sydney Swallow Questionnaire (SSQ) to diagnose dysphagia in this patient group.

Methods & Procedures

Three participant groups completed the SSQ and the results were compared: nine DMD participants with dysphagia, six DMD participants without dysphagia and 12 healthy controls.

Outcomes & Results

The questionnaire scores for dysphagic DMD participants were significantly higher than for non‐dysphagic DMD participants (p = 0.039) and for healthy controls (p ≤ 0.001). The diagnostic ability of the questionnaire was good for detecting dysphagia in participants with DMD (receiver operating characteristic (ROC) area under the curve = 0.89, p = 0.013), with a cut‐off score of 224.5 (13.2%) giving a sensitivity of 0.78 and a specificity of 0.83 for determining dysphagia. Dysphagic participants rated time to eat a meal, swallowing hard food, swallowing thick liquids and needing to cough up or spit during meals with the highest severity of all questionnaire items. Results of the questionnaire by item are presented to inform the clinician of the symptoms of dysphagia in DMD.

Conclusions & Implications

DMD leads to pervasive symptoms of dysphagia. The simple SSQ is a clinically informative assessment tool for patients with DMD.
Stress Management, Depression, and Immune Status in Lower‐Income Racial/Ethnic Minority Women Co‐infected with HIV and HPV
Authors: Lopez Corina R. , Antoni Michael H. , Seay Julia , Potter Jonelle , O'Sullivan MaryJo , Fletcher Mary Ann , Pereira Deirdre , Whitehead Nicole
Published: March 2013

The stress of co‐infection with human immunodeficiency virus (HIV) and human papillomavirus (HPV), in race/ethnic minority women, may increase depression and immune decrements. Compromised immunity in HIV+ HPV+ women may increase the odds of cervical dysplasia. Thus, we tested the efficacy of a 10‐week cognitive behavioral stress management (CBSM) group intervention and hypothesized that CBSM would decrease depression and improve immune status (CD4+ T‐cells, natural killer [NK] cells). HIV+ HPV+ women (n = 71) completed the Beck Depression Inventory and provided blood samples, were randomized to CBSM or a control condition, and were re‐assessed post‐intervention. Women in CBSM revealed less depression, greater NK cells, and marginally greater CD4+ T‐cells post‐intervention vs. controls. Stress management may improve mood and immunity in HIV+ HPV+ lower‐income minority women.
Policy Convergence with or without theEuropeanUnion: The Interaction of Policy Success,EUMembership and Policy Convergence
Authors: Fink Simon
Published: March 2013

TheEuropeanUnion (EU) is often seen as an institutional environment that facilitates the exchange of information about the effects of policies, and thus promotes convergence towards successful policies. However, current qualitative studies analyze onlyEUmembers and cannot dismiss the hypothesis that the relation between policy success and policy convergence is universal and not affected byEUmembership. The article analyzes a dyadic data set on privatization policies in the electricity sector to test the interaction hypothesis that jointEUmembership not only causes policy convergence, but also increases the effect of policy success on policy convergence. The result is that economic success of privatizations in role‐model countries and jointEUmembership both increase the probability of policy convergence. However, there is no interaction between policy success and jointEUmembership. Thus, contrary to widely held assumptions, jointEUmembership does not amplify learning from each other's policy success.
Effects of motivational interviewing to promote weight loss in obese children
Authors: Wong Emmy MY , Cheng May MH
Published: March 2013

Aims and objectives

To assess the effects of motivational interviewing for obese children and telephone consultation for parents to promote weight loss in obese children.

Background

Childhood obesity is a worldwide health problem that leads to serious metabolic and physiological consequences. An effective intervention to manage obesity is essential. Motivational interviewing is designed to resolve ambivalence, enhance intrinsic motivation and promote confidence in a person's ability to make behaviour changes. It has shown promise in the adult obesity literature as effecting positive health behaviour changes. Motivational interviewing has also been proposed as an effective method for improving the weight loss of obese children.

Design

A pre–post quasi‐experimental design with repeated measures was used.

Methods

The study was conducted in four primary schools over an 11‐month period in 2010–2011. Obese children (n = 185) were screened from 791 school children studying the equivalent toUKgrades 5 and 6 and were divided into three groups: motivational interviewing, motivational interviewing+ and a control group. The motivational interviewing group (n = 70) children were provided with motivational interviewing counselling; the motivational interviewing+ group (n = 66) children were provided with motivational interviewing counselling while telephone consultation was provided for their parents; and the control group did not receive any intervention (n = 49).

Results

Children in both the motivational interviewing and motivational interviewing+ groups showed significant improvement in their weight‐related behaviour and obesity‐related anthropometric measures from the baseline to the end of the 14‐week intervention, while the control group had significant deterioration in their anthropometric measures.

Conclusion

Motivational interviewing appears to be a promising intervention for promoting weight loss in obese children. Motivational interviewing counselling may be extended to obese children of different age groups.

Relevance to clinical practice

This study indicates that motivational interviewing is a useful method for improving behaviour changes in eating, physical activity and weight loss for obese children, suggesting the benefits of such intervention.
Pharmacokinetics and perioperative efficacy of intravenous ketorolac in dogs
Authors: Cagnardi P. , Zonca A. , Gallo M. , Villa R. , Carli S. , Beccaglia M. , Fonda D. , Ravasio G.
Published: March 2013

Ketorolac (KET) is a nonsteroidal anti‐inflammatory drug approved for the use in humans that possesses a potent analgesic activity, comparable to morphine, and could represent a useful tool to control acute pain also in animals. The clinical efficacy and pharmacokinetic profile of intravenous (IV) ketorolac tromethamine (0.5 mg/kg) were studied in 15 dogs undergoing gonadectomy. Intra‐operative cardiorespiratory variables were monitored, and post‐operative pain was assessed using a subjective pain score (0–24) in all dogs, whereas the pharmacokinetic profile of the drug was determined in 10 animals. During surgery, mean minimal alveolar concentration of isoflurane was 1.69 ± 0.11%, and normocapnia and spontaneous ventilation were maintained in all animals. During pain assessment, no significant differences between males and females were found, and in no case rescue analgesia was necessary. No adverse effects were reported. Serum samples were purified by solid‐phase extraction and analysed by HPLC with UV‐Vis detection. A large variability was observed in serum concentrations. The kinetics of ketorolac was described by a noncompartmental analysis. The elimination half‐life (t½λz) and ClB were 10.95 ± 7.06 h and 92.66 ± 84.49 mL/h/kg, respectively, and Vdss and Vz were 1030.09 ± 620.50 mL/kg and 1512.25 ± 799.13 mL/kg, respectively. AUC(0→last) and MRT(0→last) were 6.08 ± 3.28 h × μg/mL and 5.59 ± 2.12 h, respectively. The results indicate that ketorolac possess good post‐operative analgesic effects until about 6 h after administration in dogs undergoing moderately painful surgery.
Sturgeon conservation genomics: SNP discovery and validation using RAD sequencing
Authors: Ogden R. , Gharbi K. , Mugue N. , Martinsohn J. , Senn H. , Davey J. W. , Pourkazemi M. , McEwing R. , Eland C. , Vidotto M. , Sergeev A. , Congiu L.
Published: March 2013

Caviar‐producing sturgeons belonging to the genus Acipenser are considered to be one of the most endangered species groups in the world. Continued overfishing in spite of increasing legislation, zero catch quotas and extensive aquaculture production have led to the collapse of wild stocks across Europe and Asia. The evolutionary relationships among Adriatic, Russian, Persian and Siberian sturgeons are complex because of past introgression events and remain poorly understood. Conservation management, traceability and enforcement suffer a lack of appropriate DNA markers for the genetic identification of sturgeon at the species, population and individual level. This study employed RAD sequencing to discover and characterize single nucleotide polymorphism (SNP) DNA markers for use in sturgeon conservation in these four tetraploid species over three biological levels, using a single sequencing lane. Four population meta‐samples and eight individual samples from one family were barcoded separately before sequencing. Analysis of 14.4 Gb of paired‐end RAD data focused on the identification of SNPs in the paired‐end contig, with subsequent in silico and empirical validation of candidate markers. Thousands of putatively informative markers were identified including, for the first time, SNPs that show population‐wide differentiation between Russian and Persian sturgeons, representing an important advance in our ability to manage these cryptic species. The results highlight the challenges of genotyping‐by‐sequencing in polyploid taxa, while establishing the potential genetic resources for developing a new range of caviar traceability and enforcement tools.
Cross‐border rubber cultivation between China and Laos: Regionalization by Akha and Tai rubber farmers
Authors: Sturgeon Janet C.
Published: March 2013

This paper is a multi‐sited ethnography of cross‐border rubber cultivation between China and Laos. Smallholder minority rubber farmers from Xishuangbanna (China) have forged successful informal share‐cropping arrangements to grow rubber trees on the land of relatives and friends in neighbouring Laos. By becoming rich and entrepreneurial rural citizens, Akha and Tai farmers have also, in their own eyes, raised their own ‘quality’ (suzhi) and see themselves as ‘modern’. By examining various meanings of ‘modern’ in China, and contrasting the rubber farmers' experience with Jacob Eyferth's notion of rural ‘deskilling’, this paper shows how through learning to plant, cultivate and tap rubber, these farmers have taken on the discipline and technical knowledge of ‘modern’ workers and become ‘skilled’. By rising in ‘quality’, minority farmers on China's periphery challenge the entrenched binaries of urban/rural, modern/backward, prosperous/poor and Han/minority nationality. Xishuangbanna minority farmers acknowledge that they are also ‘backward’ in the Chinese social hierarchy, but their extension of rubber cultivation to kin and others in Laos has confirmed their modernity as dispensers of development, technical know‐how and ‘superior’ Chinese culture to Lao farmers who are ‘backward and poor’. In contrast to large state rubber farms that have failed to establish rubber plantations in northern Laos, minority farmers have created regionalization.
Agricultural liberalization, cotton markets and buyers’ relations in Zimbabwe, 2001–2008
Authors: Masuka Godwin
Published: March 2013

The paper examines the relations between seed cotton buyers in Zimbabwe's deregulated cotton sector. It draws upon interviews with officials from cotton companies to expose the disagreements and lack of cooperation among them over side marketing of contracted seed cotton and in maintaining common industry standards. In this context, the paper discusses cotton sector reforms spearheaded by some industry stakeholders aimed to address problems in the cotton sector. Despite the companies’ official agreement to the draft reforms of 2004, there were simmering tensions and disputes that strained relations among them. The government's unwillingness to intervene and provide coordination exacerbated problems in the cotton sector. Further, the paper highlights the contradictions in neo‐liberal reforms that seek to promote competitive agricultural markets, and argue against state intervention and strong regulation of markets. It argues that there is a need to reconceptualize the role of the state in some predatory and developing countries that liberalized agricultural markets because of the multiple and uneven effects of the lack of regulation and absence of institutions in the private sector.
Design and Development of an Advanced Two-Stage Centrifugal Compressor
Authors: Palmer D. L. , Waterman W. F.
Published: March 2013

This paper describes the aeromechanical design and development of a 3.3 kg/s (7.3 lb/sec), 14:1 pressure ratio two-stage centrifugal compressor, which is used in the T800-LHT-800 helicopter engine. The design employs highly nonradial, splitter bladed impellers with swept leading edges and compact vaned diffusers to achieve high performance in a small and robust configuration. The development effort quantified the effects of impeller diffusion and passive inducer shroud bleed on surge margin as well as the effects of impeller loading on tip clearance sensitivity and the impact of sand erosion and shroud roughness on performance. The developed compressor exceeded its performance objectives with a minimum of 23 percent surge margin without variable geometry. The compressor provides a high-performance, rugged, low-cost configuration ideally suited for helicopter applications.
Surface Heating Effect on Local Heat Transfer in a Rotating Two-Pass Square Channel With 60 deg Angled Rib Turbulators
Authors: Zhang Y. M. , Han J. C. , Parsons J. A. , Lee C. P.
Published: March 2013

The influence of uneven wall temperature on the local heat transfer coefficient in a rotating, two-pass, square channel with 60 deg ribs on the leading and trailing walls was investigated for Reynolds numbers from 2500 to 25,000 and rotation numbers from 0 to 0.352. Each pass, composed of six isolated copper sections, had a length-to-hydraulic diameter ratio of 12. The mean rotating radius-to-hydraulic diameter ratio was 30. Three thermal boundary condition cases were studied: (A) all four walls at the same temperature, (B) all four walls at the same heat flux, and (C) trailing wall hotter than leading with side walls unheated and insulated. Results indicate that rotating ribbed wall heat transfer coefficients increase by a factor of 2 to 3 over the rotating smooth wall data and at reduced coefficient variation from inlet to exit. As rotation number (or buoyancy parameter) increases, the first pass (outflow) trailing heat transfer coefficients increase and the first pass leading heat transfer coefficients decrease, whereas the reverse is true for the second pass (inflow). The direction of the Coriolis force reverses from the outflow trailing wall to the inflow leading wall. Differences between the first pass leading and trailing heat transfer coefficients increase with rotation number. A similar behavior is seen for the second pass leading and trailing heat transfer coefficients, but the differences are reduced due to buoyancy changing from aiding to opposing the inertia force. The results suggest that uneven wall temperature has a significant impact on the local heat transfer coefficients. The heat transfer coefficients on the first pass leading wall for cases B and C are up to 70–100 percent higher than that for case A, while the heat transfer coefficients on the second pass trailing wall for cases B and C are up to 20–50 percent higher.
Experimental Study of the Effects of Bleed Holes on Heat Transfer and Pressure Drop in Trapezoidal Passages With Tapered Turbulators
Authors: Taslim M. E. , Li T. , Spring S. D.
Published: March 2013

Trailing edge cooling cavities in modern gas turbine blades often have trapezoidal cross-sectional areas of relatively low aspect ratio. To enhance cooling effectiveness in these passages, they are roughened with tapered turbulators. Furthermore, to provide additional cooling for the trailing edge, the cooling air may be ejected through trailing edge slots as it moves radially along the cooling passage. The tapered turbulators, in conjunction with the presence of these slots along the smaller base of the trapezoidal cavity, create both spanwise and longitudinal variations in heat transfer coefficient on the turbulated walls. Moreover, the continuous variation of cooling air velocity along these passages causes a continuous change in static pressure, which also requires investigation. Liquid crystals are used in this experimental investigation to study the effects of tapered turbulators on heat transfer coefficients in trailing edge passages with and without bleed holes. The tapered turbulators are configured on two opposite walls of the trapezoidal test section in a staggered arrangement with an angle of attack to the mainstream flow, α, of 90 deg. Nine different test geometries consisting of two passage aspect ratios, AR, were tested over a range of turbulator aspect ratios, ARt, blockage ratios, emax/Dh, pitch-to-height ratios, S/emax, and Reynolds numbers. Channel pressure losses were also measured and both heat transfer and friction factor results for several geometries are compared. It is concluded that (a) there exists a large spanwise variation in heat transfer coefficient in test sections with no bleed holes, (b) adding bleed holes to the smaller base of the trapezoidal cavity gives a spanwise velocity component to the mainstream flow and reduces this variation, and (c) Nusselt numbers measured in the test sections with bleed holes correlate well with local Reynolds number.
Detailed Heat Transfer Coefficient Measurements and Thermal Analysis at Engine Conditions of a Pedestal With Fillet Radii
Authors: Wang Z. , Ireland P. T. , Jones T. V.
Published: March 2013

The heat transfer coefficient over the surface of a pedestal with fillet radii has been measured using thermochromic liquid crystals and the transient heat transfer method. The tests were performed at engine representative Reynolds numbers for a geometry typical of those used in turbine blade cooling systems. The heat conduction process that occurs in the engine was subsequently modeled numerically with a finite element discretization of the solid pedestal. The measured heat transfer coefficients were used to derive the exact boundary conditions applicable to the engine. The temperature field within the pedestal, calculated using the correct heat transfer coefficient distribution, is compared to that calculated using an area-averaged heat transfer coefficient. Metal temperature differences of 90 K are predicted across the blade wall.
Flow Between Contrarotating Disks
Authors: Gan X. , Kilic M. , Owen J. M.
Published: March 2013

The paper describes a combined experimental and computational study of laminar and turbulent flow between contrarotating disks. Laminar computations produce Batchelor-type flow: Radial outflow occurs in boundary layers on the disks and inflow is confined to a thin shear layer in the midplane; between the boundary layers and the shear layer, two contrarotating cores of fluid are formed. Turbulent computations (using a low-Reynolds-number k–ε turbulence model) and LDA measurements provide no evidence for Batchelor-type flow, even for rotational Reynolds numbers as low as 2.2 × 104. While separate boundary layers are formed on the disks, radial inflow occurs in a single interior core that extends between the two boundary layers; in the core, rotational effects are weak. Although the flow in the core was always found to be turbulent, the flow in the boundary layers could remain laminar for rotational Reynolds numbers up to 1.2 × 105. For the case of a superposed outflow, there is a source region in which the radial component of velocity is everywhere positive; radially outward of this region, the flow is similar to that described above. Although the turbulence model exhibited premature transition from laminar to turbulent flow in the boundary layers, agreement between the computed and measured radial and tangential components of velocity was mainly good over a wide range of nondimensional flow rates and rotational Reynolds numbers.
Darryl E. Metzger Memorial Session Paper: The Streamwise Development of Go¨rtler Vortices in a Favorable Pressure Gradient
Authors: Finnis M. V. , Brown A.
Published: March 2013

Measurements are presented of the streamwise velocity variation within a laminar boundary layer on a concave surface of 4 m radius of curvature for which the free-stream velocity gradient factor (ν/U02)dU0/dx was approximately 1 × 10−6. The stream velocity variation was consistent with the presence of counterrotating vortices resulting from the Go¨rtler instability. The vortices exhibited exponential growth over the streamwise extent of the measurements to a disturbance amplitude of approximately 13 percent of the local free-stream velocity. The vortex growth rates were found to be less than those for a zero velocity gradient factor, indicating that a favorable pressure gradient stabilizes the flow with respect to the Go¨rtler instability. Boundary layer profiles at local upwash and downwash positions are compared with the linear theory for which the mean flow was modeled using the Pohlhausen approximation to the solution of the boundary layer equations. The agreement between the measured and predicted profiles indicates that the linear stability theory can provide a fair approximation to the small amplitude growth of the Go¨rtler instability.
Computation and Simulation of Wake-Generated Unsteady Pressure and Boundary Layers in Cascades: Part 1—Description of the Approach and Validation
Authors: Fan S. , Lakshminarayana B.
Published: March 2013

The unsteady pressure and boundary layers on a turbomachinery blade row arising from periodic wakes due to upstream blade rows are investigated in this paper. A time-accurate Euler solver has been developed using an explicit four-stage Runge–Kutta scheme. Two-dimensional unsteady nonreflecting boundary conditions are used at the inlet and the outlet of the computational domain. The unsteady Euler solver captures the wake propagation and the resulting unsteady pressure field, which is then used as the input for a two-dimensional unsteady boundary layer procedure to predict the unsteady response of blade boundary layers. The boundary layer code includes an advanced k–ε model developed for unsteady turbulent boundary layers. The present computational procedure has been validated against analytic solutions and experimental measurements. The validation cases include unsteady inviscid flows in a flat-plate cascade and a compressor exit guide vane (EGV) cascade, unsteady turbulent boundary layer on a flat plate subject to a traveling wave, unsteady transitional boundary layer due to wake passing, and unsteady flow at the midspan section of an axial compressor stator. The present numerical procedure is both efficient and accurate in predicting the unsteady flow physics resulting from wake/blade-row interaction, including wake-induced unsteady transition of blade boundary layers.
Rotordynamic Forces Due to Turbine Tip Leakage: Part II—Radius Scale Effects and Experimental Verification
Authors: Song S. J. , Martinez-Sanchez M.
Published: March 2013

This paper presents a radius scale actuator disk model, which describes the flow response to a whirling/spinning rotor in an unshrouded turbine. At each azimuth, the upstream-downstream flow variables are matched by the results from a steady blade scale analysis presented in a companion paper, with allowance for mass storage in the stator-rotor region. The new model can accurately predict the magnitude of both direct and cross excitation forces as well as their breakdown into work extraction and pressure effects. The trends versus the mean flow coefficient and interblade distance are predicted. While underpredicted, a trend versus mean rotor tip clearance height is also indicated. Thus, the new model captures the dominant physical effects caused by a whirling/spinning rotor in an unshrouded turbine.
Aerodynamic Aspects of Endwall Film-Cooling
Authors: Friedrichs S. , Hodson H. P. , Dawes W. N.
Published: March 2013

This paper describes an investigation of the aerodynamic aspects of endwall film-cooling, in which the flow field downstream of a large-scale low-speed linear turbine cascade has been measured. The integrated losses and locations of secondary flow features with and without endwall film-cooling have been determined for variations of both the coolant supply pressure and injection location. Together with previous measurements of adiabatic film-cooling effectiveness and surface-flow visualization, these results reveal the nature of the interactions between the ejected coolant and the flow in the blade passage. Measured hole massflows and a constant static pressure mixing analysis, together with the measured losses, allow the decomposition of the losses into three distinct entropy generation mechanisms: loss generation within the hole, loss generation due to the mixing of the coolant with the mainstream, and change in secondary loss generation in the blade passage. Results show that the loss generation within the coolant holes is substantial and that ejection into regions of low static pressure increases the loss per unit coolant massflow. Ejection upstream of the three-dimensional separation lines on the endwall changes secondary flow and reduces its associated losses. The results show that it is necessary to take the three-dimensional nature of the endwall flow into account in the design of endwall film-cooling configurations.
Numerical Simulation of Turbine Blade Boundary Layer and Heat Transfer and Assessment of Turbulence Models
Authors: Luo J. , Lakshminarayana B.
Published: March 2013

The boundary layer development and convective heat transfer on transonic turbine nozzle vanes are investigated using a compressible Navier–Stokes code with three low-Reynolds-number k–ε models. The mean-flow and turbulence transport equations are integrated by a four-stage Runge–Kutta scheme. Numerical predictions are compared with the experimental data acquired at Allison Engine Company. An assessment of the performance of various turbulence models is carried out. The two modes of transition, bypass transition and separation-induced transition, are studied comparatively. Effects of blade surface pressure gradients, free-stream turbulence level, and Reynolds number on the blade boundary layer development, particularly transition onset, are examined. Predictions from a parabolic boundary layer code are included for comparison with those from the elliptic Navier–Stokes code. The present study indicates that the turbine external heat transfer, under real engine conditions, can be predicted well by the Navier–Stokes procedure with the low-Reynolds-number k–ε models employed.
Investigation of the Calmed Region Behind a Turbulent Spot
Authors: Gostelow J. P. , Walker G. J. , Solomon W. J. , Hong G. , Melwani N.
Published: March 2013

Measurements are presented of the calmed region behind triggered wave packets and turbulent spots under a controlled diffusion adverse pressure gradient in a wind tunnel. Similar measurements are also presented from the stator blades of an axial flow compressor, where turbulent spots are induced by the passing of rotor wakes. The purpose is to gain an appreciation of turbulent spot behavior under a strong adverse pressure gradient as a foundation for the more accurate modeling of spots and their environment in predictions of transitional boundary layer flows. Under an adverse pressure gradient the calmed region behind the spot is extensive; its interaction with the surrounding boundary layer is complex and is dependent on whether the surrounding natural boundary layer is laminar or turbulent. Some insights are gleaned concerning the behavior of the calmed region, which will subsequently be used in attempts to model the calmed region. Although these fundamental investigations of the calmed region have been extensive, much remains to be understood.
Analysis of Tempering and Rehardening for Grinding of Hardened Steels
Authors: Fedoseev O. B. , Malkin S.
Published: March 2013

An analysis is presented to predict the hardness distribution in the subsurface of hardened steel due to tempering and rehardening associated with high temperatures generated in grinding. The grinding temperatures are modeled with a triangular heat source at the grinding zone and temperature-dependent thermal properties. The temperature history, including the effect of multiple grinding passes, is coupled with thermally activated reaction equations for tempering and for reaustenitization which is the rate controlling step in rehardening. Experimental results from the literature are found to be in good agreement with the analytical predictions.
Thermal Aspects of Grinding: The Effect of the Wheel Bond on Heat Transfer to an Abrasive Grain
Authors: Harris M. W. , Lavine A. S.
Published: March 2013

Heat generated during grinding can cause thermal damage to the workpiece and wheel. It is therefore important to understand the thermal aspects of grinding. This paper addresses heat conduction into the wheel, by considering a single abrasive grain in contact with the workpiece. In particular, the effect of the bond material on conduction into the grain is investigated. The results for the grain surface temperature are given in terms of parameters describing the geometry and thermal properties of the grain and bond. The beneficial effect of a high thermal conductivity for both the grain and the bond is clearly demonstrated.
Factors Influencing the Particle Size Distribution in an Abrasive Waterjet
Authors: Labus T. J. , Neusen K. F. , Alberts D. G. , Gores T. J.
Published: March 2013

A basic investigation of the factors which influence the abrasive jet mixing process was conducted. Particle size analysis was performed on abrasive samples for the “as-received” condition, at the exit of the mixing tube, and after cutting a target material. Grit size distributions were obtained through sieve analysis for both water and air collectors. Two different mixing chamber geometries were evaluated, as well as the effects of pressure, abrasive feed rate, cutting speed, and target material properties on particle size distributions. An analysis of the particle size distribution shows that the main particle breakdown is from 180 microns directly to 63 microns or less, for a nominal 80 grit garnet. This selective breakdown occurs during the cutting process, but not during the mixing process.
Effect of Fretting on Thermal Deformation of a Machine Structure
Authors: Attia M. H. , Kops L.
Published: March 2013

Thermal deformation of machine tools is a prime concern due to its significant effect on machining error. Accurate prediction of the thermal deformation of the structure is critically dependent on the understanding and modelling of the heat transfer process at the joint. An integrated system approach to the tribological and thermoelastic behavior of the joint led to the development of an algorithm to calculate the thermal and deformation response of the structure, with the behavior of the joint taken into account. To implement this algorithm using the conventional finite element method, the dynamic contact element is introduced to model the static, dynamic, and thermal properties of the joint. Based on the experimental findings for the rheological properties of a joint undergoing a micro-slip, a multi-Voigt model is used. The dynamic contact element accounts also for the effect of fretting and the oscillatory mode of motion on the thermal contact resistance.
Finite Element Analysis of Metal Forming Processes on Personal Computers
Authors: Yan Li-lai , Xu Song-qing , Li Guo-ji
Published: March 2013

The main difficulty in running a rigid-plastic finite element program for metal forming analysis on a personal computer lies in the lengthy computation, typical of non-linear problems. To make the PC more acceptable for forming analyses in industrial applications, some measures have been proposed, such as using a higher order IVP solver and modifying the generation of the initial velocity field to account for the existence of rigid zones, if any. As a result, 2-D metal forming problems with moderate shape complexity can be solved on PCs within a reasonable length of time.
Experimental Investigation of Galling Resistance in OCTG Connections
Authors: Ertas A. , Carper H. J. , Cuvalci O. , Ekwaro-Osire S. , Blackstone W. R.
Published: March 2013

The results of galling experiments are strongly dependent on the method used and vary from test machine to test machine. However, by a well-developed test method and testing machine, one can obtain reliable and repeatable results. The primary objective of this research is to develop a new test method and machine for evaluating galling resistance in OCTG (oil country tubular goods) connections. Through the application of basic principles of statistical design of experiments, the galling resistance in OCTG threaded connections has been investigated. For estimating the nominal failure stress, two statistical methods, namely, up-and-down and frequency distribution, have been applied and compared. Galling resistance, one of the most important design factors of OCTG connections, has been studied and discussed.
Robotic Instrumented Complaint Wrist
Authors: Xu Yangsheng , Paul R. P.
Published: March 2013

A robotic complaint wrist which combines a passive compliance device and a displacement sensor has been developed and tested. The device provides the necessary flexibility to accommodate transitions between the position control and force control modes, and avoid large impact forces as a robot makes contact with parts, as well as correct positioning errors and allow the relaxation of tolerances in assembly and manufacturing operations. The device installed between a robot arm and end-effector is composed of two parts: a passive compliance device and a sensing mechanism. The passive compliance is provided by a rubber structure; its configuration can be arranged to yield the desired stiffness ratio along and about each axis. The sensing mechanism consists of a six-joint serial linkage with a transducer at each point. The measured deflection is used to actively control the contact forces and compensate for the positioning error during motion and contact. In this paper, the design features of two prototypes of the device are described. A systematic hybrid position/force control scheme incorporating the device is presented.
Computer-Aided Process Planning for Turned Parts Using Fundamental and Heuristic Principles
Authors: Korde U. P. , Bora B. C. , Stelson K. A. , Riley D. R.
Published: March 2013

Research on generative computer-aided process planning (CAPP) for turned parts using combined fundamental and heuristic principles is presented. The rationale for the process planning approach is that many preconditions of machining processes can be expressed as a small number of domain principles. The domain is defined by processes and the part description as features for simple turned parts. The motivation is to detect faulty designs early on in the design process. Preliminary designs defined by features are first evaluated using manufacturability rules in a rule-based expert system, developed in LISP. Manufacturability rules are based on feature properties such as accessibility, stability, and critical material thickness. The rules were acquired from design and manufacturing personnel from industry through interviews. Parts that satisfy the manufacturability checks are used to generate all feasible process plans. A search algorithm selects the “best” process plan from the feasible set. Process plans are generated and subsequently optimized using two distinct sets of feasibility and optimality criteria which may be either fundamental or heuristic in nature. The presently incorporated criteria successfully restrict the set of plans to a small number without missing any apparently feasible process plans. Manufacturability evaluation, feasible process plans, and optimal process plans for actual industrial parts have been obtained and compared.
Thermal Energy Distributions in the Workpiece During Cutting With an Abrasive Waterjet
Authors: Ohadi M. M. , Ansari A. I. , Hashish M.
Published: March 2013

Distribution of thermal energy in the workpiece during cutting with an abrasive waterjet (AWJ) was studied experimentally. Detailed time-temperature measurements in the workpiece as a function of jet pressure, traverse rate, workpiece material, and workpiece orientation were performed. It is shown that maximum temperatures occur at the immediate vicinity of the cutting interface and sharply decay thereafter with increasing distance from the interface. A higher jet pressure and/or a lower traverse speed results in higher temperatures in the workpiece. A material with higher thermal conductivity experiences higher temperatures during the cut. Within the workpiece, higher temperatures occur at inner zones where the jet-induced cooling effects are minimum.
Tool Temperatures in Interrupted Metal Cutting
Authors: Stephenson D. A. , Ali A.
Published: March 2013

This paper summarizes the results of theoretical and experimental studies of tool temperatures in interrupted cutting. In the theoretical study, the temperature in a semi-infinite rectangular corner heated by a time-varying heat flux with various spatial distributions is used to investigate the general nature of the tool temperature distribution. The results of this analysis are compared with infrared and tool-chip thermocouple cutting temperature measurements from interrupted end turning tests on 2024 aluminum and gray cast iron at speeds up to 18 m/s. The results show that temperatures are generally lower in interrupted cutting than in continuous cutting under the same conditions. Temperatures depend primarily on the length of cutting cycles and secondarily on the length of cooling intervals between cycles. For short cutting cycles the peak and average surface temperatures are relatively low, but they increase rapidly as the cutting cycle is lengthened and approach steady-state values for long cycles. Temperatures increase for very short cooling intervals, since in this case heat does not disperse between heating cycles, but for moderate and large values varying the cooling interval has little effect on temperatures. The theoretical analysis reproduces the qualitative trends but underestimates temperatures for short cutting cycles. The accuracy of the analysis could be improved by using a transient model to calculate the amount of heat entering the tool from the tool-chip contact.