bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective up‐regulation of functional mu‐opioid receptor splice variants by chronic opioids
Authors: Chakrabarti Sumita , Madia Priyanka A. , Gintzler Alan R.
Published: December 2015

We recently reported (Verzillo, et al. J. Neurochem: 130, 790–796, 2014) that chronic systemic morphine selectively up‐regulates mRNA encoding two C‐terminal μ‐opioid receptor (MOR) splice variants, MOR‐1C1 and MOR‐1B2 (MOR‐1B2/‐1C1). Given the known disconnects between changes in levels of mRNA and corresponding protein, it is essential to directly demonstrate that chronic opioid treatment elevates functional MOR‐1B2/‐1C1 protein prior to inferring relevance of these MOR variants to spinal opioid tolerance mechanisms. Accordingly, we investigated the ability of chronic opioid exposure to up‐regulate MOR protein in Chinese hamster ovary cells stably transfected with rat MOR variants MOR‐1B2, MOR‐1C1, or MOR‐1 (considered to be the predominant MOR). Findings revealed that chronic treatment with the clinically relevant opioids morphine, oxycodone and hydrocodone substantially up‐regulated membrane MOR‐1B2/‐1C1 protein. This up‐regulation was abolished by the protein synthesis inhibitor cycloheximide, eliminating contributions from receptor redistribution. The increment in MOR‐1B2/‐1C1 protein was paralleled by a significant increment in opioid agonist‐stimulated GTPγS‐binding (reflective of increased aggregate MOR G protein coupling) indicating that up‐regulated MOR‐1B2/‐1C1 represented functional receptors. Strikingly, these tolerance‐associated adaptations of MOR‐1B2/‐1C1 differed considerably from those of MOR‐1. Antithetical regulation of MOR‐1B2/‐1C1 and MOR‐1 by chronic opioids has significant implications for the design of new therapeutic agents to counteract opioid analgesic tolerance and accompanying addiction. Since chronic opioids induce MOR‐1B2/‐1C1 up‐regulation in spinal cord of males, but not females, elucidating cellular compartments and intracellular pathways mediating MOR‐1B2/‐1C1 up‐regulation and defining their unique signaling attributes would enable a precision medicinal approach to pain management and addiction therapy.

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In the spinal cord of males, but not females, chronic morphine up‐regulates mRNA encoding two mu‐opioid receptor (MOR) variants, MOR‐1B2 and MOR‐1C1 (MOR‐1B2/‐1C1). We now demonstrate that chronic treatment with the clinically relevant opioids morphine, hydrocodone or oxycodone up‐regulates MOR‐1B2/‐1C1 functional protein, which is dependent on de novo protein synthesis. Findings underscore the importance of unique signaling attributes of MOR variants to sexually dimorphic tolerance mechanisms.
Fluoxetine induces vascular endothelial growth factor/Netrin over‐expression via the mediation of hypoxia‐inducible factor 1‐alpha in SH‐SY5Y cells
Authors: Wang Jiayi , Zhou Xiaoyu , Lu Haiyan , Song Mingrui , Zhao Jinglong , Wang Qiaoshu
Published: December 2015

Fluoxetine has become one of the most promising drugs for improving clinical outcome in patients with cerebral infarction. Although the clinical efficacy of fluoxetine has been preliminarily demonstrated, its mechanism remains unclear. Hypoxia‐inducible factor 1‐alpha (HIF‐1α) is upstream to Netrin and vascular endothelial growth factor (VEGF), and under hypoxia conditions it may induce expression of Netrin‐1 and VEGF in vascular endothelial cells. We sought to explore whether it can regulate their expression in hypoxia and mediate the effect of fluoxetine in hypoxia. In this study, the effect of hypoxia on the expression of VEGF and Netrin was observed in vitro by real‐time PCR and western blotting in SH‐SY5Y cells; the binding sites of HIF‐1α in VEGF and Netrin gene promoters were identified by luciferase reporter; the effect of fluoxetine on binding of HIF‐1α with Netrin and VEGF promoters in hypoxia was observed by Chromatin Immunoprecipitation (ChIP) Assay. We prove that HIF‐1α regulates transcription of both VEGF and Netrin, and that in hypoxia fluoxetine up‐regulates VEGF and Netrin expression via mediation of HIF‐1α that binds to hypoxia‐response element sites of VEGF and Netrin promoters. Our study indicates that HIF‐1α may play an important role in the treatment of cerebral infarction through mediating the recovery of neurological function induced by fluoxetine, which provides theoretical basis for the development of gene therapeutic drugs targeting HIF‐1α.

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We show that hypoxia‐inducible factor 1‐alpha (HIF‐1α) regulates transcription of both vascular endothelial growth factor (VEGF) and Netrin. Furthermore, we also show that in hypoxia fluoxetine up‐regulates VEGF and Netrin expression via mediation of HIF‐1α that binds to hypoxia‐response element (HRE) sites of VEGF and Netrin promoters. Our study indicates that HIF‐1α may play an important role in the treatment of cerebral infarction through mediating the recovery of neurological function induced by fluoxetine. These findings provide a theoretical basis for development of gene therapeutic drugs targeting HIF‐1α.
Regulation of Multidrug Resistance P‐Glycoprotein in the Developing Blood–Brain Barrier: Interplay between Glucocorticoids and Cytokines
Authors: Iqbal M. , Baello S. , Javam M. , Audette M. C. , Gibb W. , Matthews S. G.
Published: December 2015

P‐glycoprotein (P‐gp) encoded by Abcb1 provides protection to the developing brain from xenobiotics. P‐gp in brain endothelial cells (BECs) derived from the developing brain microvasculature is up‐regulated by glucocorticoids and inhibited by pro‐inflammatory cytokines in vitro. However, little is known about how prenatal maternal glucocorticoid treatment can affect Abcb1/P‐gp function and subsequent cytokine regulation in foetal BECs. We hypothesised that glucocorticoid exposure increases Abcb1/P‐gp in the foetal brain microvasculature and enhances the sensitivity of Abcb1/P‐gp in BECs to the inhibitory effects of cytokines. BECs isolated from dexamethasone‐ or vehicle‐exposed foetal guinea pigs were cultured and treated with interleukin‐1β, interleukin‐6 or tumour necrosis factor‐α, and Abcb1/P‐gp expression and function were assessed. Prenatal dexamethasone exposure significantly increased Abcb1/P‐gp expression/activity and cytokine receptor levels in BECs of the foetal brain microvasculature. Foetal dexamethasone exposure in vivo also increased the subsequent responsiveness of BECs to pro‐inflammatory cytokines in vitro. In conclusion, maternal treatment with synthetic glucocorticoids appears to prematurely mature P‐gp mediated drug resistance at the foetal BBB in vivo and profoundly impact the subsequent responsiveness of P‐gp to pro‐inflammatory cytokines in the foetal BEC. The significance of these findings to foetal brain protection against xenobiotics and other P‐gp substrates in vivo requires further elaboration. However, the results of the present study may have implications for human pregnancy and foetal brain protection, particularly in cases of preterm birth combined with infection.
Working memory – not processing speed – mediates fluid intelligence deficits associated with attention deficit/hyperactivity disorder symptoms
Authors: Brydges Christopher R. , Ozolnieks Krista L. , Roberts Gareth
Published: December 2015

Attention deficit/hyperactivity disorder (ADHD) is a psychological condition characterized by inattention and hyperactivity. Cognitive deficits are commonly observed in ADHD patients, including impaired working memory, processing speed, and fluid intelligence, the three of which are theorized to be closely associated with one another. In this study, we aimed to determine if decreased fluid intelligence was associated with ADHD, and was mediated by deficits in working memory and processing speed. This study tested 142 young adults from the general population on a range of working memory, processing speed, and fluid intelligence tasks, and an ADHD self‐report symptoms questionnaire. Results showed that total and hyperactive ADHD symptoms correlated significantly and negatively with fluid intelligence, but this association was fully mediated by working memory. However, inattentive symptoms were not associated with fluid intelligence. Additionally, processing speed was not associated with ADHD symptoms at all, and was not uniquely predictive of fluid intelligence. The results provide implications for working memory training programs for ADHD patients, and highlight potential differences between the neuropsychological profiles of ADHD subtypes.
Physiological and biochemical changes of females of Piracanjuba, subjected to induced reproduction
Authors: Zanoni M. A. , Costa F. G. , de Carvalho S. , Seiva F. R. F.
Published: December 2015

The aim of this experiment was to compare the level of fish female stress during induced reproduction with pituitary extract by two different methods, natural and semiextruded. The reproductive efficiency was 62.5% in the seminatural treatment and 100% in the extruded. Obtained egg volume was 5200 ml and 4000 ml, for seminatural and extruded treatments respectively. The mean number of eggs was 46.7 for the seminatural and 52.0 and for the extruded treatment. The percentage of viable eggs was, respectively, 87.2% and 8.17% for the natural treatment and extruded semimethods. Blood samples were collected to quantify cortisol and glucose levels, as well as red cell series and lymphocyte count. Fishes submitted to induction procedures showed elevated cortisol and glucose levels, compared to the control animals. The results for haematocrit, haemoglobin concentration and red blood cell count showed no significant differences among groups. Significant differences found in the number of lymphocytes and monocytes suggest the general adaptation syndrome. Our results suggest the reproductive induction process with extrusion of gametes as a more stressful method than seminatural reproduction process.
Investigation of nutriactive phytochemical – gamma‐oryzanol in experimental animal models
Authors: Szcześniak K. A. , Ostaszewski P. , Ciecierska A. , Sadkowski T.
Published: December 2015

Gamma‐oryzanol (GO) is an abundant dietary antioxidant that is considered to have beneficial effects in cardiovascular disease, cancer and diabetes. Other potential properties of GO include inhibition of gastric acid secretion and decreased post‐exercise muscle fatigue. GO is a unique mixture of triterpene alcohol and sterol ferulates present in rice bran oil, a byproduct of rice processing. GO has been studied by many researchers over the last three decades. In particular, the utility of GO supplementation has been documented in numerous animal models. A large variety of species was examined, and various experimental methodologies and targets were applied. The aim of this study was to summarize the body of research on GO supplementation in animals and to examine possible mechanisms of GO action. Furthermore, while the safety of GO supplementation in animals has been well documented, studies demonstrating pharmacokinetics, pharmacodynamics and efficiency are less clear. The observed differences in these findings are also discussed.
Impact of heat stress, nutritional restriction and combined stresses (heat and nutritional) on growth and reproductive performance of Malpura rams under semi‐arid tropical environment
Authors: Maurya V. P. , Sejian V. , Kumar D. , Naqvi S. M. K.
Published: December 2015

A study was conducted to assess the combined effect of heat stress and nutritional restriction on growth and reproductive performances in Malpura rams. Twenty‐eight adult Malpura rams (average body weight (BW) 66.0 kg) were used in this study. The rams were divided into four groups: CON (n = 7; control), HES (n = 7; heat stress), NUS (n = 7; nutritional stress) and COS (n = 7; combined stress). The study was conducted for a period of 2 months. CON and HES rams had ad libitum access to their feed while NUS and COS rams were under restricted feed (30% intake of CON rams) to induce nutritional stress. The HES and COS rams were kept in climatic chamber at 42 °C and 55% relative humidity for 6 h a day between 10 : 00 h and 16 : 00 h to induce heat stress. Body weight increased significantly (p < 0.05) in CON as compared to NUS and COS. When compared within groups, scrotal width morning, scrotal width afternoon, scrotal circumference morning and scrotal circumference afternoon were significantly (p < 0.05) larger in CON while smaller in COS rams. The higher testicular length was recorded both during morning (p < 0.05) and afternoon (p < 0.01) in COS rams while the lowest in NUS rams. The highest plasma testosterone concentration was recorded in CON and lowest in COS rams. Semen volume and mass motility also differed significantly (p < 0.05) between the groups. The highest semen volume and mass motility was recorded in CON and NUS while lowest in both HES and COS rams. It can be concluded from this study that when two stressors occur simultaneously, they may have severe impact on reproductive performance of rams.
Correlations between physiological parameters related with kidney function and minute‐by‐minute urine output
Authors: Otero Abraham , Cardinal‐Fernández Pablo , Nin Nicolás , Rojas Yeny , Oteiza Lorena , Garcia‐Carmona Rodrigo , Caffarena Gabriel , Lorente José A.
Published: December 2015

Aim

Recently, devices capable of measuring minute‐by‐minute urine output (UOm) have become available. It is not known how UOm correlates with physiological parameters in normal conditions and in disease states characterized by vascular dysfunction. This paper analyzes correlations between UOm and physiological parameters related to kidney perfusion to provide some insight about UOm pathophysiological interpretation and its relationship with renal blood flow.

Methods

We studied 14 male pigs were anesthetized, tracheostomized, and mechanically ventilated. Mean systemic blood pressure (PART), mean pulmonary artery blood pressure (PPA), carotid artery blood flow (QCA), as well as total (QREN), cortical (QCOR) and medullary (QMED) renal blood flows, and the renal resistive index (RRI) were measured or calculated. Animals received an intravenous dose of live E. coli for the induction of sepsis (septic group), or an equivalent amount of normal saline (nonseptic group). Three groups were studied: nonseptic (n = 6) and septic (n = 4), both receiving for resuscitation NaCl 0.9% at 4 mL/kg per h; and septic (n = 4), receiving for resuscitation NaCl 0.9% at 17 mL/kg per h. Animals were monitored for 5 h after the induction of sepsis.

Results

In septic animals, UOm was strongly positively correlated with QREN (Kendall's τ = 0.770, P < 0.05), QCOR (τ = –0.566, P < 0.05) and QMED (τ = 0.632, P < 0.05); and negatively correlated with PPA (τ = –0.524, P < 0.05) and RRI (τ = –0.672, P < 0.05). Control animals exhibited weaker correlations.

Conclusion

UOm is a good physiological surrogate marker of total and regional renal blood flows and vascular resistance, particularly under septic conditions, probably reflecting glomerulo‐tubular dysfunction in sepsis.
Progression and outcomes of non‐dialysis dependent chronic kidney disease patients: A single center longitudinal follow‐up study
Authors: Khan Yusra Habib , Sarriff Azmi , Adnan Azreen Syazril , Khan Amer Hayat , Mallhi Tauqeer Hussain , Jummaat Fauziah
Published: December 2015

Aim

Despite increase global prevalence of End stage renal disease (ESRD) and subsequent need for renal replacement therapy (RRT), relatively little is known about disease progression and prognosis of earlier stages of CKD. Current study was conducted to examine rate of CKD progression, predictors of ESRD and death.

Methods

A total 621 patients with estimated glomerular filtration rate (eGFR) of 15‐59ml/min/1.73m2 (CKD stage 3 & 4) were selected and followed up for 10 years or until ESRD or death, whichever occurred first. Subjects who did not meet inclusion criteria were excluded (n=1474).

Results

Annual cumulative decline in eGFR was 3.01±0.40 ml/min/1.73m2. Overall disease progression was observed in 60% patients while 18% died. Among patients with CKD stage 3, 21% progressed to stage 4, 10% to stage 5ND (non‐dialysis) and 31% to RRT while mortality was observed in 16% patients. On the other hand, 8% patients with CKD stage 4 progressed to stage 5ND, 31% to RRT and mortality was observed in 24% cases. Patients with CVD, higher systolic blood pressure, elevated phosphate levels, heavy proteinuria, microscopic hematuria and use of diuretics were more likely to develop ESRD. Advancing age, low eGFR, low systolic blood pressure, low hemoglobin and baseline diabetes were found to be significant predictors of mortality while being female reduced risk of mortality.

Conclusion

Our data suggest that, in this CKD cohort, patients were more likely to develop ESRD than death. Prime importance should be given to mild forms of CKD to retard and even reverse CKD progression.
Genome‐wide recombination dynamics are associated with phenotypic variation in maize
Authors: Pan Qingchun , Li Lin , Yang Xiaohong , Tong Hao , Xu Shutu , Li Zhigang , Li Weiya , Muehlbauer Gary J. , Li Jiansheng , Yan Jianbing
Published: December 2015

Meiotic recombination is a major driver of genetic diversity, species evolution, and agricultural improvement. Thus, an understanding of the genetic recombination landscape across the maize (Zea mays) genome will provide insight and tools for further study of maize evolution and improvement.

Here, we used c. 50 000 single nucleotide polymorphisms to precisely map recombination events in 12 artificial maize segregating populations. We observed substantial variation in the recombination frequency and distribution along the ten maize chromosomes among the 12 populations and identified 143 recombination hot regions.

Recombination breakpoints were partitioned into intragenic and intergenic events. Interestingly, an increase in the number of genes containing recombination events was accompanied by a decrease in the number of recombination events per gene. This kept the overall number of intragenic recombination events nearly invariable in a given population, suggesting that the recombination variation observed among populations was largely attributed to intergenic recombination. However, significant associations between intragenic recombination events and variation in gene expression and agronomic traits were observed, suggesting potential roles for intragenic recombination in plant phenotypic diversity.

Our results provide a comprehensive view of the maize recombination landscape, and show an association between recombination, gene expression and phenotypic variation, which may enhance crop genetic improvement.
YouTube as a source of information on mouth (oral) cancer
Authors: Hassona Y , Taimeh D , Marahleh A , Scully C
Published: December 2015

Objectives

We examined the content of YouTube™ videos on mouth (oral) cancer and evaluated their usefulness in promoting early detection of oral cancer.

Materials and Methods

A systematic search of YouTube™ for videos containing information on mouth cancer was conducted using the keywords ‘mouth cancer’ and ‘oral cancer’. Demographics of videos, including type, source, length, and viewers’ interaction, were evaluated, and three researchers independently assessed the videos for usefulness in promoting early detection of oral cancer.

Results

A total of 188 YouTube™ videos (152 patient‐oriented educational videos and 36 testimonial videos) were analyzed. The overall usefulness score ranged from 0 to 10 (mean = 3.56 ± 2.44). The most useful videos ranked late on the viewing list, and there was no significant correlation between video usefulness and viewing rate, viewers’ interaction, and video length. Videos uploaded by individual users were less useful compared with videos uploaded by professional organizations or by healthcare professionals.

Conclusion

Healthcare professionals, academic institutions, and professional organizations have a responsibility for improving the content of YouTube™ about mouth cancer by uploading useful videos, and directing patients to reliable information sources.
Confluence and Contours: Reflexive Management of Environmental Risk
Authors: Soane Emma , Schubert Iljana , Pollard Simon , Rocks Sophie , Black Edgar
Published: December 2015

Government institutions have responsibilities to distribute risk management funds meaningfully and to be accountable for their choices. We took a macro‐level sociological approach to understanding the role of government in managing environmental risks, and insights from micro‐level psychology to examine individual‐level risk‐related perceptions and beliefs. Survey data from 2,068 U.K. citizens showed that lay people's funding preferences were associated positively with beliefs about responsibility and trust, yet associations with perception varied depending on risk type. Moreover, there were risk‐specific differences in the funding preferences of the lay sample and 29 policymakers. A laboratory‐based study of 109 participants examined funding allocation in more detail through iterative presentation of expert information. Quantitative and qualitative data revealed a meso‐level framework comprising three types of decisionmakers who varied in their willingness to change funding allocation preferences following expert information: adaptors, responders, and resistors. This research highlights the relevance of integrated theoretical approaches to understanding the policy process, and the benefits of reflexive dialogue to managing environmental risks.
hERG quality control and the long QT syndrome
Authors: Foo Brian , Williamson Brittany , Young Jason C. , Lukacs Gergely , Shrier Alvin
Published: December 2015

Long‐QT syndrome type‐2 (LQT2) is characterized by reduced functional expression of the human ether‐à‐go‐go related (hERG) gene product, resulting in impaired cardiac repolarization and predisposition to fatal arrhythmia. Previous studies have implicated abnormal trafficking of misfolded hERG as the primary mechanism of LQT2, with misfolding being caused by mutations in the hERG gene (inherited) or drug treatment (acquired). More generally, environmental and metabolic stresses present a constant challenge to the folding of proteins, including hERG, and must be countered by robust protein quality control (QC) systems. Disposal of partially unfolded yet functional plasma membrane (PM) proteins by protein QC contributes to the loss‐of‐function phenotype in various conformational diseases including cystic fibrosis (CF) and long‐QT syndrome type‐2 (LQT2). The prevalent view has been that the loss of PM expression of hERG is attributed to biosynthetic block by endoplasmic reticulum (ER) QC pathways. However, there is a growing appreciation for protein QC pathways acting at post‐ER cellular compartments, which may contribute to conformational disease pathogenesis. This article will provide a background on the structure and cellular trafficking of hERG as well as inherited and acquired LQT2. We will review previous work on hERG ER QC and introduce the more novel view that there is a significant peripheral QC at the PM and peripheral cellular compartments. Particular attention is drawn to the unique role of the peripheral QC system in acquired LQT2. Understanding the QC process and players may provide targets for therapeutic intervention in dealing with LQT2.

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Experimental Assessment of Laser Textured Cutting Tools in Dry Cutting of Aluminum Alloys
Authors: Xing Youqiang , Deng Jianxin , Wang Xingsheng , Ehmann Kornel , Cao Jian
Published: December 2015

To improve the friction conditions and reduce adhesion at the tool's rake face in dry cutting of aluminum alloys, three types of laser surface textures were generated on the rake face of cemented carbide tools. Orthogonal dry cutting tests on 6061 aluminum alloy tubes were carried out with the textured and conventional tools (CT). The effect of the texture geometry on the cutting performance was assessed in terms of cutting forces, friction coefficient, chip compression ratio, shear angle, tool adhesions, chip morphology, and machined surface quality. The results show that the textured tools can improve the cutting performance at low cutting speeds, and that the tool with rectangular type of textures is the most effective.
An Approach for the Gear Rolling Contact Fatigue Acceleration
Authors: Li Sheng , Wagner Jeremy J.
Published: December 2015

This study proposes an approach for the acceleration of the experimental gear rolling contact fatigue (RCF) crack formation. By increasing the rotational velocity of a gear pair, the RCF experimental time period is reduced. However, the film thickness is increased to improve the fatigue performance, to counteract which it is proposed to raise the lubricant temperature to reduce the film thickness. A physics-based gear contact fatigue model is used to quantify and offset the effects of the rotational velocity and the lubricant temperature on the crack nucleation.
Parameterized Design Optimization of a Magnetohydrodynamic Liquid Metal Active Cooling Concept
Authors: Hartl Darren J. , Galvan Edgar , Malak Richard J. , Baur Jeffrey W.
Published: December 2015

The success of model-based multifunctional material design efforts relies on the proper development of multiphysical models and advanced optimization algorithms. This paper addresses both in the context of a structure that includes a liquid metal (LM) circuit for integrated cooling. We demonstrate for the first time on a complex engineering problem the use of a parameterized approach to design optimization that solves a family of optimization problems as a function of parameters exogenous to the subsystem of interest. This results in general knowledge about the capabilities of the subsystem rather than a restrictive point solution. We solve this specialized problem using the predictive parameterized Pareto genetic algorithm (P3GA) and show that it efficiently produces results that are accurate and useful for design exploration and reasoning. A “population seeding” approach allows an efficient multifidelity approach that combines a computationally efficient reduced-fidelity algebraic model with a computationally intensive finite-element model. Using data output from P3GA, we explore different design scenarios for the LM thermal management concept and demonstrate how engineers can make a final design selection once the exogenous parameters are resolved.
Monotonic, Low-Cycle Fatigue, and Ultralow-Cycle Fatigue Behaviors of the X52, X60, and X65 Piping Steel Grades
Authors: Pereira J. C. R. , de Jesus A. M. P. , Fernandes A. A. , Varelis G.
Published: December 2015

Seismic actions, soil settlements and landslides, fluctuations in permafrost layers, accidental loads, and reeling are responsible for large plastic deformations and widespread yielding of pipelines, which may lead to damage or failure, either due to monotonic loading or cyclic plastic strain fluctuations of high amplitude and short duration (e.g., Ni < ∼100 cycles). The damage associated to high intensity cyclic plasticity shows a combination of distinct mechanisms typical of both monotonic and low-cycle fatigue (LCF) (∼102 < Ni < ∼104 cycles) damage regimes. This fatigue domain is often called ultralow-cycle fatigue (ULCF) or extreme-low-cycle fatigue, in order to distinguish it from LCF. Despite monotonic ductile fracture and LCF have been subjected to significant research efforts and a satisfactory level of understanding of these phenomena has been already established, ULCF is neither sufficiently investigated nor understood. Consequently, further advances should be done since the data available in literature is scarce for this fatigue regime. In addition, ULCF tests are very challenging and there are no specific standards available in literature providing guidance. In this work, the performances of the X52, X60, and X65 API steel grades under monotonic, LCF, and ULCF loading conditions are investigated by means of an experimental program. Smooth specimens are susceptive to instability under ULCF tests. To overcome or minimize this shortcoming, antibuckling devices may be used in the ULCF tests. The use of notched specimens facilitates the deformation localization and therefore contributes to overcome the instability problems. However, the nonuniform stress/strain states raise difficulties concerning the analysis of the experimental data, requiring the use of multiaxial stress/strain parameters. Optical methods and nonlinear finite-element models were used to assess the strain and stress histories at critical locations, which were used to assess some existing damage models.
Flow-Excited Acoustic Resonance of Trapped Modes of a Ducted Rectangular Cavity
Authors: Bolduc Michael , Ziada Samir , Lafon Philippe
Published: December 2015

Flow over ducted cavities can lead to strong resonances of the trapped acoustic modes due to the presence of the cavity within the duct. Aly and Ziada (2010, “Flow-Excited Resonance of Trapped Modes of Ducted Shallow Cavities,” J. Fluids Struct., 26(1), pp. 92–120; 2011, “Azimuthal Behaviour of Flow-Excited Diametral Modes of Internal Shallow Cavities,” J. Sound Vib., 330(15), pp. 3666–3683; and 2012, “Effect of Mean Flow on the Trapped Modes of Internal Cavities,” J. Fluids Struct., 33, pp. 70–84) investigated the excitation mechanism of acoustic trapped modes in axisymmetric cavities. These trapped modes in axisymmetric cavities tend to spin because they do not have preferred orientation. The present paper investigates rectangular cross-sectional cavities as this cavity geometry introduces an orientation preference to the excited acoustic mode. Three cavities are investigated, one of which is square while the other two are rectangular. In each case, numerical simulations are performed to characterize the acoustic mode shapes and the associated acoustic particle velocity fields. The test results show the existence of stationary modes, being excited either consecutively or simultaneously, and a particular spinning mode for the cavity with square cross section. The computed acoustic pressure and particle velocity fields of the excited modes suggest complex oscillation patterns of the cavity shear layer because it is excited, at the upstream corner, by periodic distributions of the particle velocity along the shear layer circumference.
Effects of a Venturi-Type Flow Restrictor on the Thermal-Hydraulic Response of the Secondary Side of a Pressurized Water Reactor Steam Generator to a Main Steam Line Break
Authors: Chull Jo Jong , Moody Frederick J.
Published: December 2015

A numerical analysis has been performed to simulate the transient thermal-hydraulic response to a main steam line break (MSLB) for the secondary side of a steam generator (SG) model equipped with a venturi-type SG outlet flow restrictor at a pressurized water reactor (PWR) plant. To investigate the effects of the flow restrictor on the thermal-hydraulic response of SG to the MSLB, numerical calculation results for the SG model equipped with the flow restrictor are compared to those obtained for an SG model without the restrictor. Both analysis models contain internal structures. The present computational fluid dynamics (CFD) model has been examined by comparing to a simple analytical model. It is confirmed from the comparison that the CFD model simulates the transient response of the SG secondary to the MSLB physically plausibly and minutely. Based on the CFD analysis results for both cases with or without the restrictor, it is seen that the intensities of the steam velocity and dynamic pressure are considerably attenuated in the SG model equipped with the restrictor comparing to the case in the SG model without the restrictor.
Mapping the Efficiency for a Hydrostatic Transmission
Authors: Manring Noah D.
Published: December 2015

Efficiency maps have long been used by engineers to understand the topographical behavior of their machinery. Most commonly, efficiency maps have been generated for internal combustion engines, where the torque–speed curve for the engine shows the wide-open-throttle line with constant efficiency lines drawn beneath this maximum operating limit. From such maps, engineers have been able to determine the most efficiency operating point for the engine, given a desired output power (torque and speed). There currently exists a great interest in using hydrostatic transmissions for improving the operating efficiency of an internal combustion engine. However, efficiency maps for hydrostatic transmissions, similar to efficiency maps for internal combustion engines, do not exist in the literature and therefore it is difficult to assess the overall efficiency gains that are achieved when using a hydrostatic transmission in these applications. This paper proposes a method for generating efficiency maps for hydrostatic transmissions, and presents a typical set of maps that may be used as a first approximation for assessing transmission efficiency. The results of this paper are nondimensional and are generalized for a transmission of any size. As shown in this research, there are regimes of transmission operation in which the efficiency is nearly independent of either the output torque, or the output speed. Furthermore, it is shown that maximum operating efficiencies typically exist at high output speeds, and mid-to-high output torques.
Cloud Cavitating Flow Over a Submerged Axisymmetric Projectile and Comparison Between Two-Dimensional RANS and Three-Dimensional Large-Eddy Simulation Methods
Authors: Wang Yiwei , Huang Chenguang , Fang Xin , Yu Xianian , Wu Xiaocui , Du Tezhuan
Published: December 2015

For the cloud cavitation around slender axisymmetric projectiles, a two-dimensional (2D) numerical method was based on the mixture approach with Singhal cavitation model and modified renormalization-group (RNG) k–ε turbulence model, and a three-dimensional (3D) method was established with large-eddy simulation (LES) and volume of fraction (VOF) approach. The commercial computational fluid dynamic (CFD) software fluent is used for the 2D simulation, and the open source code OpenFOAM is adopted for the 3D calculation. Experimental and numerical results were presented on a typical case, in which the projectile moves with a quasi-constant axial speed. Simulation results agree well with experimental results. An analysis of the evolution of cavitating flow was performed, and the related physical mechanism was discussed. Results demonstrate that shedding cavity collapse plays an important role in the generation and acceleration of re-entry jet, which is the main reason for the instability of cloud cavitation. The 2D Reynolds-Averaged Navier–Stokes (RANS) method can represent the physical phenomena effectively. The 3D LES method can give an efficient simulation on the shedding vortices, and considerable accurate shapes of shedding cavities are captured.
Heat Transfer During Near-Critical-Pressure Condensation of Refrigerant Blends
Authors: Garimella Srinivas , Andresen Ulf C. , Mitra Biswajit , Jiang Yirong , Fronk Brian M.
Published: December 2015

Heat transfer during condensation of refrigerant blends R404A and R410A flowing through horizontal tubes with 0.76 ≤ D ≤ 9.4 mm at nominal Pr = 0.8–0.9 was investigated. Local heat transfer coefficients were measured for the mass flux range 200 < G < 800 kg m−2 s−1 in small quality increments over the entire vapor–liquid region. Heat transfer coefficients increased with quality and mass flux, while the effect of reduced pressure was not very significant within this range of pressures. The heat transfer coefficients increased with a decrease in diameter. Correlations from the literature were not able to predict the condensation heat transfer coefficient for these fluids at these near-critical pressures over the wide range of tube diameters under consideration. A new flow-regime based model for heat transfer in the wavy, annular, and annular/wavy transition regimes, which predicts 91% of the data within ±25%, is proposed.
Flow Similarity in the Rotor–Stator Interaction Affected Region in Prototype and Model Francis Pump-Turbines in Generating Mode
Authors: Li Zhongjie , Wang Zhengwei , Wei Xianzhu , Qin Daqing
Published: December 2015

Similarities of the flow in the rotor–stator interaction (RSI) affected region (stay vanes, guide vanes, and runner domain) in prototype and model Francis pump-turbines are analyzed using numerical simulations with special attention on the influence of Reynolds number. The ratios of characteristic length and velocity between the prototype and the model are 10.97 and 2.54; thus, the Reynolds numbers differ by about 28 times. Detailed flow analysis argues for higher partial load condition, Q = 0.8Qd, and severe partial load condition, Q = 0.45Qd. The flows in the distributor (spiral casing, stay vanes, and guide vanes domain) are well-behaved for both conditions with no separation, presenting high level of similarity in both space and time domain. The flows in the runners are well-behaved at higher partial load, Q = 0.8Qd, and present good flow similarity and weak Reynolds number effects between the model and the prototype. At severe partial load, Q = 0.45Qd, flow separation develops on the blade pressure sides and partially blocks the runner passages, showing prominent flow discrepancy and stronger Reynolds number effects between the two turbines. For the prototype flow of high Reynolds number, viscous effects have a minor role and less momentum is lost in the boundary layer. Therefore, the flow deceleration is less severe and the emergence of separation is restrained, presenting spatially delayed separation and a less disorganized flow pattern in the prototype. Validated by the model tests and on-site measurements, pressure fluctuations recorded in the vaneless space show that the relative fluctuation amplitudes in the model are slightly higher than those in the prototype. Resorting to dimensionless analytical equations and simulation results, the deviation in pressure fluctuations is found out to be influenced by Reynolds number effects. The research provides an improved understanding of Reynolds number effects on the flow discrepancy and pressure fluctuation difference in the RSI-affected region, which will facilitate better estimations of performance from scale model to prototype.
An Approximate Computational Method for the Fluid Stiction Problem of Two Separating Parallel Plates With Cavitation
Authors: Scheidl Rudolf , Gradl Christoph
Published: December 2015

Stiction forces exerted by a fluid in a thin, quickly widening gap to its boundaries can become a strongly limiting factor of the performance of technical devices, like compressor valves or hydraulic on–off valves. In design optimization, such forces need to be properly and efficiently modeled. Cavitation during parts of a stiction process plays a strong role and needs to be taken into account to achieve a meaningful model. The paper presents an approximate calculation method which uses qualitative solution properties of the non cavitating stiction problem, in particular of its level curves and gradient lines. In this method, the formation of the cavitation boundaries is approximated by an elliptic domain. The pressure distribution along its principle axis is described by a directly integrable differential equation, the evolutions of its boundaries is guided just by pressure boundary conditions when the cavitation zone expands and by a nonlinear differential equation when it shrinks. The results of this approximate model agree quite well with the solutions of a finite volume (FV) model for the fluid stiction problem with cavitation.
Natural Surface Oscillations of Rotating Fluid Along Radial Baffles of Rotor
Authors: Nikiforov A.
Published: December 2015

This paper determines natural and resonant frequencies of radial–circular oscillations (waves) on the nonviscous, incompressible fluid partially and evenly filling similar compartments in a rotor that has the cylindrical chamber, solid radial baffles, and constant angular velocity. It is assumed as follows: influence of the gravity and surface tension is negligibly small as compared to the centrifugal effect; configuration of dynamic equilibrium (unperturbed motion) of fluid is an annular rigid body rotation; and the fluid motion perturbed by small lateral deflections of the rotor does not depend on the axial coordinate (plane motion).
Analytical and Numerical Study of Nearshore Multiple Oscillating Water Columns
Authors: Rezanejad Kourosh , Bhattacharjee Joydip , Guedes Soares Carlos
Published: December 2015

In the present study, the performance of two chamber nearshore oscillating water columns (OWCs) in finite water depth is analyzed based on the linearized water wave theory in the two-dimensional Cartesian coordinate systems. The barriers are assumed to be fixed and the turbine characteristics are assumed linear with respect to the fluctuations of volume flux and pressure inside the chamber. The free surface inside the chambers is modeled as a nonplane wave surface. Two different mathematical models are employed to solve the hydrodynamic problem: the semi-analytic method of matched eigenfunction expansion and the numerical scheme of boundary integral equation method (BIEM). The numerical results are compared with the semi-analytic results and show good agreement. The effects of the distance between the barriers and the length of the barriers on the efficiency of the OWC device are investigated. The results of two chambers OWC are also compared with the results for an equivalent single OWC chamber. Further, the effect of the water depth on the capacity of the wave power absorption is discussed.
Fundamental Combustion Characteristics of Lean and Stoichiometric Hydrogen Laminar Premixed Flames Diluted With Nitrogen or Carbon Dioxide
Authors: Li Hong-Meng , Li Guo-Xiu , Sun Zuo-Yu , Zhou Zi-Hang , Li Yuan , Yuan Ye
Published: December 2015

In this work, the laminar combustion characteristics of H2/N2/air (H2/CO2/air) were systematically investigated under different hydrogen ratios (40–100%) and equivalence ratios (0.4–1.0) in a closed combustion vessel using the spherical expanding flame method associated with Schlieren technology. The unstretched laminar burning velocities were compared with data from previous study, and the result indicates that excellent agreements are obtained. Numerical simulations were also conducted using GRI3.0 and USC II mechanisms to compare with the present experimental results. The Markstein length for H2/inert gas can be decreased by decreasing the equivalence ratio and hydrogen ratio. The results indicate that the H2/inert gas premixed flames tend to be more unstable with the decrease of equivalence ratio and hydrogen ratio. For H2/N2 mixture, the suppression effect on laminar burning velocity is caused by modified specific heat of mixtures and decreased heat release, which result in a decreased flame temperature. For H2/CO2 mixture, the carbon dioxide has stronger dilution effect than nitrogen in reducing laminar burning velocity owing to both thermal effect and chemical effect.
Ramp Tracking in Systems With Nonminimum Phase Zeros: One-and-a-Half Integrator Approach
Authors: Tavazoei Mohammad Saleh
Published: December 2015

In this paper, a simple fractional calculus-based control law is proposed for asymptotic tracking of ramp reference inputs in dynamical systems. Without need to add any zero to the loop transfer function, the proposed technique can guarantee asymptotic ramp tracking in plants having nonminimum phase zeros. The appropriate range for determining the parameters of the proposed control law is also specified. Moreover, the performance of the designed control system in tracking ramp reference inputs is illustrated by different numerical examples.
Elastic Metamaterials With Low-Frequency Passbands Based on Lattice System With On-Site Potential
Authors: Liu Yongquan , Shen Xiaohui , Su Xianyue , Sun C. T.
Published: December 2015

An elastic metamaterial with a low-frequency passband is proposed by imitating a lattice system with linear on-site potential. It is shown that waves can only propagate in the tunable passband. Then, two kinds of elastic metamaterials with double passbands are designed. Great wave attenuation performance can be obtained at frequencies between the two passbands for locally resonant type metamaterials, and at both low and high frequencies for the diatomic type metamaterials. Finally, the strategy to design two-dimensional (2D) metamaterials is demonstrated. The present method can be used to design new types of small-size waveguides, filters, and other devices for elastic waves.
Energy Equation of Gas Flow With Low Velocity in a Microchannel
Authors: Asako Yutaka
Published: December 2015

The energy equation for constant density fluid flow with the viscous dissipation term is often used for the governing equations of gas flow with low velocity in microchannels. If the gas is an ideal gas with low velocity, the average temperatures at the inlet and the outlet of an adiabatic channel are the same based on the first law of the thermodynamics. If the gas is a real gas with low velocity, the average temperature at the outlet is higher or lower than the average temperature at the inlet. However, the outlet temperature which is obtained by solving the energy equation for constant density fluid flow with the viscous dissipation term is higher than the inlet gas temperature, since the viscous dissipation term is always positive. This inconsistency arose from choice of the relationship between the enthalpy and temperature that resulted in neglecting the substantial derivative of pressure term in the energy equation. In this paper, the energy equation which includes the substantial derivative of pressure term is proposed to be used for the governing equation of gas flow with low velocity in microchannels. The proposed energy equation is verified by solving it numerically for flow in a circular microtube. Some physically consistent results are demonstrated.
Heat Transfer Implications of Acoustic Resonances in Turbine Internal Cooling Channels
Authors: Selcan C. , Cukurel B. , Shashank J.
Published: December 2015

In an attempt to investigate the acoustic resonance effect of serpentine passages on internal convection heat transfer, the present work examines a typical high pressure turbine (HPT) blade internal cooling system, based on the geometry of the NASA E3 engine. In order to identify the associated dominant acoustic characteristics, a numerical finite-element method (FEM) simulation (two-step frequency domain analysis) is conducted to solve the Helmholtz equation with and without source terms. Mode shapes of the relevant identified eigenfrequencies (in the 0–20 kHz range) are studied with respect to induced standing sound wave patterns and the local node/antinode distributions. It is observed that despite the complexity of engine geometries, the predominant resonance behavior can be modeled by a same-ended straight duct. Therefore, capturing the physics observed in a generic geometry, the heat transfer ramifications are experimentally investigated in a scaled wind tunnel facility at a representative resonance condition. Focusing on the straight cooling channel's longitudinal eigenmode in the presence of an isolated rib element, the impact of standing sound waves on convective heat transfer and aerodynamic losses are demonstrated by liquid crystal thermometry, local static pressure and sound level measurements. The findings indicate a pronounced heat transfer influence in the rib wake separation region, without a higher pressure drop penalty. This highlights the potential of modulating the aerothermal performance of the system via acoustic resonance mode excitations.