bluuebunny/crossref_metadata_2025 huggingface dataset:
Arabidopsis stress associated protein 9 mediates biotic and abiotic stress responsive ABA signaling via the proteasome pathway
Authors: Kang Miyoung , Lee Seonghee , Abdelmageed Haggag , Reichert Angelika , Lee Hee‐Kyung , Fokar Mohamed , Mysore Kirankumar S. , Allen Randy D.
Published: December 2016

Arabidopsis thaliana Stress Associated Protein 9 (AtSAP9) is a member of the A20/AN1 zinc finger protein family known to play important roles in plant stress responses and in the mammalian immune response. Although SAPs of several plant species were shown to be involved in abiotic stress responses, the underlying molecular mechanisms are largely unknown, and little is known about the involvement of SAPs in plant disease responses. Expression of SAP9 in Arabidopsis is up‐regulated in response to dehydration, cold, salinity and abscisic acid (ABA), as well as pathogen infection. Constitutive expression of AtSAP9 in Arabidopsis leads to increased sensitivity to ABA and osmotic stress during germination and post‐germinative development. Plants that overexpress AtSAP9 also showed increased susceptibility to infection by non‐host pathogen Pseudomonas syringae pv. phaseolicola, indicating a potential role of AtSAP9 in disease resistance. AtSAP9 was found to interact with RADIATION SENSITIVE23d (Rad23d), a shuttle factor for the transport of ubiquitinated substrates to the proteasome, and it is co‐localized with Rad23d in the nucleus. Thus, AtSAP9 may promote the protein degradation process by mediating the interaction of ubiquitinated targets with Rad23d. Taken together, these results indicate that AtSAP9 regulates abiotic and biotic stress responses, possibly via the ubiquitination/proteasome pathway.
UVB‐generated Microvesicle Particles: A Novel Pathway by Which a Skin‐specific Stimulus Could Exert Systemic Effects
Authors: Fahy Katherine , Liu Langni , Rapp Christine M. , Borchers Christina , Bihl Ji C. , Chen Yanfang , Simman Richard , Travers Jeffrey B.
Published: December 2016

Ultraviolet B radiation (UVB) exerts profound effects on human skin. Much is known regarding the ability of UVB to generate a plethora of bioactive agents ranging from cytokines and other bioactive proteins, lipid mediators and microRNAs. It is presumed that these agents are in large part responsible for the effects of UVB, which is only absorbed appreciably in the epidermis. However, the exact mechanism by which these bioactive agents can leave the epidermis are as yet unclear. This review addresses the potential role of microvesicle particles (MVP) as UVB signaling agents through transmitting biologic mediators. New data are provided that UVB treatment of human skin explants also generates MVP production. We hypothesize that UVB production of MVPs (UVB‐MVP) could serve this important function of transmitting keratinocyte‐derived bioactive agents. Moreover, we propose that UVB‐MVP formation involves the lipid mediator platelet‐activating factor. This novel pathway has the potential to be exploited pharmacologically to modulate UVB effects.
Selected Least Studied but not Forgotten Bioluminescent Systems
Authors: Oba Yuichi , Stevani Cassius V. , Oliveira Anderson G. , Tsarkova Aleksandra S. , Chepurnykh Tatiana V. , Yampolsky Ilia V.
Published: December 2016

Bioluminescence is a form of chemiluminescence generated by luminous organisms. Luminous taxa have currently been reported from about 800 genera and probably over 10 000 species in the world. On the other hand, their bioluminescent systems, including chemical structures of luciferins/chromophores and the genes encoding luciferases/photoproteins, have been elucidated from only a few taxonomic groups, for example beetles, bacteria, dinoflagellates, ostracods and some cnidarians. Research efforts to understand unknown bioluminescence systems are being conducted around the world, and recently, for example, novel luciferin structures of luminous enchytraeid potworms and fungi were identified by the authors. In this study, we review the current status and perspectives, in the context of postgenomic era, of most likely novel but less‐revealed bioluminescence systems of ten selected organisms: earthworm, parchment tubeworm, fireworm, scaleworm, limpet, millipede, brittle star, acorn worms, tunicate and shark, which indeed are the next focus of our international collaboration.
Interacting protein partners of Arabidopsis RNA‐binding protein AtRBP45b
Authors: Muthuramalingam M. , Wang Y. , Li Y. , Mahalingam R.
Published: December 2016

RNA binding proteins, important players in post‐transcriptional gene regulation, usually exist in ribonuclear complexes. However, even in model systems like Arabidopsis characterisation of RBP associated proteins is limited. In this study, we investigated the interacting proteins of the Arabidopsis AtRBP45b, which is involved in stress signalling.

In vivo localisation of AtRBP45b was conducted using 35S‐GFP. FLAG‐tagged AtRBP45b under control of the 35S promoter in the Atrbp45b‐1 mutant background was used to pull down AtRBP45b interacting proteins. Yeast two‐hybrid analysis, fluorescence energy resonance transfer assays were used to confirm the veracity of the AtRBP45b interacting proteins.

In planta GFP‐tagging indicated AtRBP45b is localised to the nucleus and the cytosol. AtRBP45b protein has a N‐terminal proline‐rich region and a C‐terminal glutamine‐rich domain that are usually involved in protein–protein interactions. Co‐immunoprecipitation followed by mass spectrometry‐based protein sequencing led to identification of 30 proteins that interacted with AtRBP45b. Using information from interactome databases (BIOGRID, INTACT and STRING), pull‐down assays and localisation data, 12 putative interacting proteins were selected for yeast two‐hybrid analysis.

Cap‐binding protein (CBP20, At5g44200) and polyA‐binding protein (PAB8, At1g49760) were shown to interact with AtRBP45b. Based on its interacting partners we speculate that AtRBP45b may play an important role in RNA metabolism, especially in aspects related to mRNA stability and translation initiation during stress conditions in plants.
Seed removal in a tropical North American desert: an evaluation of pre‐ and post‐dispersal seed removal in Stenocereus stellatus
Authors: Álvarez‐Espino R. , Ríos‐Casanova L. , Godínez‐Álvarez H.
Published: December 2016

To determine seed removal influence on seed populations, we need to quantify pre‐ and post‐dispersal seed removal. Several studies have quantified seed removal in temperate American deserts, but few studies have been performed in tropical deserts. These studies have only quantified pre‐ or post‐dispersal seed removal, thus underestimating the influence of seed removal. We evaluated pre‐ and post‐dispersal seed removal in the columnar cactus Stenocereus stellatus in a Mexican tropical desert.

We performed selective exclosure experiments to estimate percentage of seeds removed by ants, birds and rodents during the pre‐ and post‐dispersal phases. We also conducted field samplings to estimate abundance of the most common seed removers.

Birds (10–28%) removed a higher percentage of seeds than ants (2%) and rodents (1–4%) during pre‐dispersal seed removal. Melanerpes hypopolius was probably the main bird removing seeds from fruits. Ants (62–64%) removed a higher percentage of seeds than birds (34–38%) and rodents (16–30%) during post‐dispersal seed removal. Pogonomyrmex barbatus was probably the main ant removing seeds from soil.

Birds and ants are the main pre‐ and post‐dispersal seed removers in S. stellatus, respectively. Further studies in other S. stellatus populations and plants with different life forms and fruit types will contribute to evaluate seed removal in tropical American deserts.
The oxalyl‐CoA synthetase‐regulated oxalate and its distinct effects on resistance to bacterial blight and aluminium toxicity in rice
Authors: Peng C. , Liang X. , Liu E.‐E. , Zhang J.‐J. , Peng X.‐X.
Published: December 2016

Oxalic acid is widely distributed in biological systems and known to play functional roles in plants. The gene AAE3 was recently identified to encode an oxalyl‐CoA synthetase (OCS) in Arabidopsis that catalyses the conversion of oxalate and CoA into oxalyl‐CoA. It will be particularly important to characterise the homologous gene in rice since rice is not only a monocotyledonous model plant, but also a staple food crop.

Various enzymatic and biological methods have been used to characterise the homologous gene.

We first defined that AAE3 in the rice genome (OsAAE3) also encodes an OCS enzyme. Its Km for oxalate is 1.73 ± 0.12 mm, and Vm is 6824.9 ± 410.29 U·min−1·mg protein−1. Chemical modification and site‐directed mutagenesis analyses identified thiols as the active site residues for rice OCS catalysis, suggesting that the enzyme might be regulated by redox state. Subcellular localisation assay showed that the enzyme is located in the cytosol and predominantly distributed in leaf epidermal cells. As expected, oxalate levels increased when OCS was suppressed in RNAi transgenic plants. More interestingly, OCS‐suppressed plants were more susceptible to bacterial blight but more resistant to Al toxicity.

The results demonstrate that the OsAAE3‐encoded protein also acts as an OCS in rice, and may play different roles in coping with stresses. These molecular, enzymatic and functional data provide first‐hand information to further clarify the function and mechanism of OCS in rice plants.
The Missing Element: Examining the Loyalty‐Competence Nexus in Presidential Appointments
Authors: Ouyang Yu , Haglund Evan T. , Waterman Richard W.
Published: December 2016

What distinguishes a loyal appointee from a competent one? Applying novel methodological tools to a unique data set of 3,366 resumes of individuals appointed by Presidents George W. Bush and Barack Obama across 51 different federal institutions, we (1) provide an operational definition of loyalty and competence and (2) demonstrate that there are subdimensions of loyalty and competence. We also provide initial insights into how George W. Bush and Barack Obama employed the various subdimensions of competence and loyalty. Our most important contribution is to provide the missing element in principal–agent models and presidential appointment power, by identifying the background characteristics and subdimensions of loyalty and competence.
The President, the Court, and Policy Implementation
Authors: Thrower Sharece
Published: December 2016

In contrast to research focused on presidential–congressional relations, this article explores the ways in which the president strategically accounts for the courts when deciding how to best influence policy implementation. I argue that as the courts become more ideologically distant from the president and thus more likely to strike down administrative actions, agencies engage in less rulemaking while the president issues more executive orders to supplement agencies' authority to act. An empirical analysis of federal macro‐level data as well as issue‐specific data on labor and environmental policy yields support for the theory's hypotheses.
Effects of implicit theories of ability and stereotype‐inconsistent information on handgrip strength in older adults: A regulatory fit perspective
Authors: Emile Mélanie , Chalabaev Aina , Colson Serge S. , Vaulerin Jerome , Falzon Charlene , D'Arripe‐Longueville Fabienne
Published: December 2016

This study examined whether stereotype‐inconsistent information interacts with implicit theories of ability to affect handgrip strength in older adults. Eighty‐two retired older adults (13 men and 69 women) from 61 to 89 years old (Mage = 75.8 years; SD = 6.9) performed maximum voluntary contractions (MVC) during a handgrip task in a design manipulating implicit theories of ability and stereotype‐inconsistent information related to physical decline with aging. Participants were randomly assigned to one of three groups: incremental condition, entity condition, or control group. The results showed that in the incremental condition the stereotype‐inconsistent information improved the peak MVC, the average MVC, the peak rate of force development (RFD), and RFD in the initial 50 ms of the MVC. This study therefore demonstrated that individuals with an incremental mindset who are exposed to stereotype‐inconsistent information can boost their physical performance. These findings are discussed from the perspective of regulatory fit (i.e., when task framing is congruent with the individual's goal).
The P3 cognitive ERP has at least some sensory modality‐specific generators: Evidence from high‐resolution EEG
Authors: Dreo Jurij , Attia Daniel , Pirtošek Zvezdan , Repovš Grega
Published: December 2016

The P3 can arguably be named the most intensely studied ERP. In spite of more than 40 years of research, fundamental questions regarding the nature of its neural generators remain unresolved. While most studies conclude that the P3 is a true classical “endogenous” potential, and that its surface potential distribution remains constant across sensory modalities, these results are largely based on low‐density EEG recordings, without the use of high‐resolution methods such as the spherical spline Laplacian (SSL). Seventeen healthy participants performed a three‐stimulus oddball task in visual and auditory modality while their EEG was recorded using a 128‐channel system. Comparison of amplitude‐normalized SSL estimated P3 brain‐surface potentials, and analysis of spatial and temporal correlations revealed significant differences between visual and auditory evoked P3 topographies from target and distractor stimuli (but not target minus frequent or distractor minus frequent comparisons). Based on these results, we postulate the likely existence of at least some sensory modality‐specific neuronal generators of the P3.
A right‐ear bias of auditory selective attention is evident in alpha oscillations
Authors: Payne Lisa , Rogers Chad S. , Wingfield Arthur , Sekuler Robert
Published: December 2016

Auditory selective attention makes it possible to pick out one speech stream that is embedded in a multispeaker environment. We adapted a cued dichotic listening task to examine suppression of a speech stream lateralized to the nonattended ear, and to evaluate the effects of attention on the right ear's well‐known advantage in the perception of linguistic stimuli. After being cued to attend to input from either their left or right ear, participants heard two different four‐word streams presented simultaneously to the separate ears. Following each dichotic presentation, participants judged whether a spoken probe word had been in the attended ear's stream. We used EEG signals to track participants' spatial lateralization of auditory attention, which is marked by interhemispheric differences in EEG alpha (8–14 Hz) power. A right‐ear advantage (REA) was evident in faster response times and greater sensitivity in distinguishing attended from unattended words. Consistent with the REA, we found strongest parietal and right frontotemporal alpha modulation during the attend‐right condition. These findings provide evidence for a link between selective attention and the REA during directed dichotic listening.
Are Determinants of Portfolio Flows Always the Same? ‐ South African Results from a Time Varying Parameter Var Model
Authors: Kavli Haakon , Viegi Nicola
Published: January 2017

The literature on determinants of cross‐border capital flows has consistently assumed the determinants of such flows to be constant throughout the sample. This paper investigates this notion by estimating the time varying relationship between portfolio flows to South Africa and two widely accepted determinants of such flows: the sovereign spread and global risk (measured by the CBOE Volatility Index, henceforth VIX). The results show that the time variation is highly significant and a constant parameter model will give biased estimates of the effects of risk on capital flows. The paper also gives important insights to South African policy makers and financial practitioners: Bond flows (non‐resident purchases of South African bonds) have become more sensitive to the VIX after 2010. Share flows were particularly sensitive at the peak of the 2008 global financial crisis, but have at other times not responded in a statistically significant manner to changes in global risk. The relationships are estimated using a time varying parameter vector autoregressive (TVP VAR) model with stochastic volatility.
Coastal uplift rate at Matanzas (Cuba) inferred from MIS5e phreatic overgrowths on speleothems
Authors: De Waele Jo , D'Angeli Ilenia M. , Tisato Nicola , Tuccimei Paola , Soligo Michele , Ginés Joaquín , Ginés Angel , Fornós Joan J. , Villa Igor M. , Grau González Esteban R. , Bernasconi Stefano M. , Bontognali Tomaso R. R.
Published: December 2016

Many morphological elements in Cuba's landscape (e.g. marine terraces, tidal notches) demonstrate that coastal uplift has taken place, but the rate at which this occurs is not known. Carbonate phreatic overgrowths on speleothems have been found in a cave in Central North Cuba, ~1 km from the present coastline at 16 m asl. They form exceptional and unique mushroom‐shaped speleothems and balconies decorating the walls of the rooms. These phreatic overgrowths on speleothems (POS) formed at the oscillating air–water interface in sea‐level controlled anchialine lakes. U/Th dating of these overgrowths suggests ages that are compatible with the Marine Isotope Stage 5e (i.e. 130–115 ka). These POS have fixed this sea‐level highstand and demonstrate that this part of Cuba has been subjected to a much lower uplift rate than previously reported, that is, less than 0.1 mm/year since the last interglacial.
Acute pulmonary involvement by paracoccidiodomycosis disease immediately after kidney transplantation: Case report and literature review
Authors: Radisic Marcelo V. , Linares Laura , Afeltra Javier , Pujato Natalia , Vitale Roxana G. , Bravo Martin , Dotta Ana C. , Casadei Domingo H.
Published: December 2016

Paracoccidioides brasiliensis is the cause of paracoccidioidomycosis, one of the most important systemic mycoses in Latin America. Human disease has been observed in a limited geographic and ecological niche, and it is attributed to exposure to the fungus in soil. Most primary infections are subclinical, as the infection is contained by the host mainly through cell‐mediated immune response. However, as the fungus has the ability to survive in a dormant state for long periods, an impairment of the immune response may lead to reactivation and clinical disease. Surprisingly, paracoccidioidomycosis has rarely been reported in transplanted patients. The aim of this communication is to report a case occurring in a kidney recipient in an acute clinical form immediately after transplantation, and to review the available information on previously reported cases.
Mycobacterium genavense‐induced spindle cell pseudotumor in a pediatric hematopoietic stem cell transplant recipient: Case report and review of the literature
Authors: Coelho Ritika , Hanna Rabi , Flagg Aron , Stempak Lisa M. , Ondrejka Sarah , Procop Gary W. , Harrington Susan , Zembillas Anthony , Kusick Karissa , Gonzalez Blanca E.
Published: December 2016

We describe the first reported pediatric patient to our knowledge with a spindle cell pseudotumor caused by Mycobacterium genavense in a hematopoietic stem cell transplant recipient, and review the literature of such an entity in the transplant population.
An Account of Interference in Associative Memory: Learning the Fan Effect
Authors: Thomson Robert , Harrison Anthony M. , Trafton J. Gregory , Hiatt Laura M.
Published: January 2017

Associative learning is an essential feature of human cognition, accounting for the influence of priming and interference effects on memory recall. Here, we extend our account of associative learning that learns asymmetric item‐to‐item associations over time via experience (Thomson, Pyke, Trafton, & Hiatt, 2015) by including link maturation to balance associations between longer‐term stability while still accounting for short‐term variability. This account, combined with an existing account of activation strengthening and decay, predicts both human response times and error rates for the fan effect (Anderson, 1974; Anderson & Reder, 1999) for both target and foil stimuli.
Initial study of α1,3‐galactosyltransferase gene‐knockout/CD46 pig full‐thickness corneal xenografts in rhesus monkeys
Authors: Dong Xiaojuan , Hara Hidetaka , Wang Ying , Wang Li , Zhang Yingnan , Cooper David K.C. , Dai Yifan , Pan Zhiqiang
Published: January 2017

Background

To investigate graft survival after full‐thickness corneal xenotransplantation from α1,3‐galactosyltransferase gene‐knockout (GTKO) pigs expressing a human complement regulatory protein (GTKO/CD46 pigs) in rhesus monkeys.

Methods

Rhesus monkeys (n=10) were transplanted with full‐thickness corneas from wild‐type (WT; n=4) and GTKO/CD46 (n=4) pigs or from monkeys (n=2). All recipient monkeys received post‐transplant subconjunctival injections of betamethasone. Corneal grafts were evaluated by slit‐lamp. Histopathology, immunohistochemistry of the grafts, and cytokine concentrations in the aqueous humor were tested 6 months after transplantation. Anti‐pig IgM/IgG and anti‐galactose‐α1,3‐galactose (Gal) antibodies were determined by flow cytometry and ELISA, respectively.

Results

The longest graft survival of WT and GTKO/CD46 xenografts was 157 and 171 days, respectively. There was no significant difference in graft survival between WT and GTKO pig corneas. Anterior synechiae occurred in two recipients of WT and all recipients of GTKO/CD46 grafts. All xenograft recipients developed a retrocorneal membrane, inflammatory cells (CD3+ T lymphocytes) infiltrated the corneal stroma, and in the aqueous humor, IL‐6 was increased 6 months after transplantation. Induced antibody responses were documented against Gal and/or non‐Gal pig antigens. In contrast, allografts survived >180 days without any rejection, with no increase in cytokines in the aqueous humor, and no elicited serum anti‐pig antibodies were detected.

Conclusions

α1,3‐galactosyltransferase gene‐knockout/CD46 pig corneas were not associated with prolonged graft survival or a reduced antibody response compared with WT pig corneas. The prevention of the development of anterior synechiae and a retrocorneal membrane after corneal xenotransplantation would appear to be important if prolonged corneal xenograft survival is to be achieved.
A Class Discussion Project for Investment Management and Business Strategy
Authors: Larkin Patrick John , Lee Baeyong
Published: January 2017

This paper presents an instructor’s guide for a class discussion of a notable lecture on stock selection and business strategy by a successful investor and businessman.
Numerical Schemes for Fractional Optimal Control Problems
Authors: Alizadeh Ali , Effati Sohrab , Heydari Aghileh
Published: January 2017

In the present study, variational iteration and Adomian decomposition methods (ADMs) are applied for solving a class of fractional optimal control problems (FOCPs). Also, a comparative study between these two methods is presented. The fractional derivative (FD) in these problems is in the Caputo sense. To solve the problem, first the necessary optimality conditions of FOCP are achieved for a linear tracking fractional optimal control problem, and then, these two methods are used to solve the resulting fractional differential equations (FDEs). It is shown that the modified Adomian decomposition method and variational iteration method (VIM) use the same iterative formula for solving linear and nonlinear FOCPs. The convergence of the modified Adomian decomposition method is analytically studied and to illustrate the validity and applicability of the methods, some examples are provided.
High Throughput Cell-Free Extraction of Plasma by an Integrated Microfluidic Device Combining Inertial Focusing and Membrane
Authors: Zhang Jun , Yan Sheng , Yuan Dan , Alici Gursel , Nguyen Nam-Trung , Li Weihua
Published: December 2016

Plasma is a host of numerous analytes such as proteins, metabolites, circulating nucleic acids (CNAs), and pathogens, and it contains massive information about the functioning of the whole body, which is of great importance for the clinical diagnosis. Plasma needs to be completely cell-free for effective detection of these analytes. The key process of plasma extraction is to eliminate the contamination from blood cells. Centrifugation, a golden standard method for blood separation, is generally lab-intensive, time consuming, and even dangerous to some extent, and needs to be operated by well-trained staffs. Membrane filtration can filter cells very effectively according to its pore size, but it is prone to clogging by dense particle concentration and suffers from limited capacity of filtration. Frequent rinse is lab-intensive and undesirable. In this work, we proposed and fabricated an integrated microfluidic device that combined particle inertial focusing and membrane filter for high efficient blood plasma separation. The integrated microfluidic device was evaluated by the diluted (×1/10, ×1/20) whole blood, and the quality of the extracted blood plasma was measured and compared with that from the standard centrifugation. We found that the quality of the extracted blood plasma from the proposed device can be equivalent to that from the standard centrifugation. This study demonstrates a significant progress toward the practical application of inertial microfluidics with membrane filter for high-throughput and highly efficient blood plasma extraction.
Experimental Investigation of the Air Flow Behavior and Heat Transfer Characteristics in Microchannels With Different Channel Lengths
Authors: Tao Zhi , Zhu Zhibing , Li Haiwang
Published: December 2016

This paper attempts to experimentally investigate the influence of channel length on the flow behavior and heat transfer characteristics in circular microchannels. The diameters of the channels were 0.4 mm and the length of them were 5 mm, 10 mm, 15 mm, and 20 mm, respectively. All experiments were performed with air and completed with Reynolds number in the range of 300–2700. Results of the experiments show that the length of microchannels has remarkable effects on the performance of flow behavior and heat transfer characteristics. Both the friction factor and Poiseuille number drop with the increase of channel length, and the experimental values are higher than the theoretical ones. Moreover, the channel length does not influence the value of critical Reynolds number. Nusselt number decrease as the increase of channel length. Larger Nusselt numbers are obtained in shorter channels. The results also indicate that in all cases, the friction factor decreases and the Poiseuille number increases with the increase of the Reynolds number. It is also observed that the value of critical Reynolds number is between 1500 and 1700 in this paper, which is lower than the value of theoretical critical Reynolds number of 2300.
High-Frequency Thermoacoustic Modulation Mechanisms in Swirl-Stabilized Gas Turbine Combustors—Part I: Experimental Investigation of Local Flame Response
Authors: Berger Frederik M. , Hummel Tobias , Hertweck Michael , Kaufmann Jan , Schuermans Bruno , Sattelmayer Thomas
Published: December 2016

This paper presents the experimental approach for determination and validation of noncompact flame transfer functions of high-frequency, transverse combustion instabilities observed in a generic lean premixed gas turbine combustor. The established noncompact transfer functions describe the interaction of the flame's heat release with the acoustics locally, which is necessary due to the respective length scales being of the same order of magnitude. Spatiotemporal dynamics of the flame are measured by imaging the OH⋆ chemiluminescence signal, phase-locked to the dynamic pressure at the combustor's front plate. Radon transforms provide a local insight into the flame's modulated reaction zone. Applied to different burner configurations, the impact of the unsteady heat release distribution on the thermoacoustic driving potential, as well as distinct flame regions that exhibit high modulation intensity, is revealed. Utilizing these spatially distributed transfer functions within thermoacoustic analysis tools (addressed in this joint publication's Part II) allows then to predict transverse linear stability of gas turbine combustors.
High-Frequency Thermoacoustic Modulation Mechanisms in Swirl-Stabilized Gas Turbine Combustors—Part II: Modeling and Analysis
Authors: Hummel Tobias , Berger Frederik , Hertweck Michael , Schuermans Bruno , Sattelmayer Thomas
Published: December 2016

This paper deals with high-frequency (HF) thermoacoustic instabilities in swirl-stabilized gas turbine combustors. Driving mechanisms associated with periodic flame displacement and flame shape deformations are theoretically discussed, and corresponding flame transfer functions (FTF) are derived from first principles. These linear feedback models are then evaluated by means of a lab-scale swirl-stabilized combustor in combination with part one of this joint publication. For this purpose, the models are used to thermoacoustically characterize a complete set of operation points of this combustor facility. Specifically, growth rates of the first transversal modes are computed, and compared against experimentally obtained pressure amplitudes as an indicator for thermoacoustic stability. The characterization is based on a hybrid analysis approach relying on a frequency domain formulation of acoustic conservation equations, in which nonuniform temperature fields and distributed thermoacoustic source terms/flame transfer functions can be straightforwardly considered. The relative contribution of flame displacement and deformation driving mechanisms–i.e., their significance with respect to the total driving–is identified. Furthermore, promoting/inhibiting conditions for the occurrence of high frequency, transversal acoustic instabilities within swirl-stabilized gas turbine combustors are revealed.
Direct Numerical Simulation of Rotating Cavity Flows Using a Spectral Element-Fourier Method
Authors: Pitz Diogo B. , Chew John W. , Marxen Olaf , Hills Nicholas J.
Published: December 2016

A high-order numerical method is employed to investigate flow in a rotor/stator cavity without heat transfer and buoyant flow in a rotor/rotor cavity. The numerical tool used employs a spectral element discretization in two dimensions and a Fourier expansion in the remaining direction, which is periodic and corresponds to the azimuthal coordinate in cylindrical coordinates. The spectral element approximation uses a Galerkin method to discretize the governing equations, but employs high-order polynomials within each element to obtain spectral accuracy. A second-order, semi-implicit, stiffly stable algorithm is used for the time discretization. Numerical results obtained for the rotor/stator cavity compare favorably with experimental results for Reynolds numbers up to Re1 = 106 in terms of velocities and Reynolds stresses. The buoyancy-driven flow is simulated using the Boussinesq approximation. Predictions are compared with previous computational and experimental results. Analysis of the present results shows close correspondence to natural convection in a gravitational field and consistency with experimentally observed flow structures in a water-filled rotating annulus. Predicted mean heat transfer levels are higher than the available measurements for an air-filled rotating annulus, but in agreement with correlations for natural convection under gravity.
Impulse Mistuning of Blades and Vanes
Authors: Hartung Andreas , Retze Ulrich , Hackenberg Hans-Peter
Published: December 2016

Impulse mistuning is an alternative approach for the reduction of vibration stresses of blades and vanes. In contrast to most other approaches, it is not a direct energy dissipation approach but a mistuning based one. However, the approach is not aimed at making use of the geometrical mistuning of the structure (e.g., a blade or a vane stage). Mistuners, specially designed small bodies are placed at specific locations inside of the component, e.g., of a blade or of a vane. They do not directly dissipate enough energy to cause relevant damping like a friction or friction-impact damper, because of the small mass involved, but rather mistune the eigen frequencies of the structure using impulses (impacts). As a result, the structure absorbs less energy at the original resonance and hence answers with lower vibration amplitude. In fact, impulse mistuning is a special case of absorption—the so-called targeted energy transfer (TET) with “vibro-impact nonlinear energy sinks” (VI-NES)—with very small impact mass involved, and thus, a negligible role of dissipation while experiencing a significant amount of absorption. The energy will be transferred (or “pumped”) to other resonances, sometimes outside of the primary resonance crossing and partially dissipated. We use the names “impulse mistuning” or “mistuners” instead of TET or VI-NES because (in our opinion) it better describes the physics of this special kind of absorption. In the paper, the design and validation of two impulse mistuning systems, for a blade stage and a vane cluster of a lower power turbine, are presented.
Computational Fluid Dynamics and Thermal Analysis of Leaf Seals for Aero-engine Application
Authors: Fico Vincenzo , Pekris Michael J. , Barnes Christopher J. , Jha Rakesh Kumar , Gillespie David
Published: December 2016

Aero-engine gas turbine performance and efficiency can be improved through the application of compliant shaft seal types to certain sealing locations within the secondary air system. Leaf seals offer better performance than traditional labyrinth seals, giving lower leakage flows at design duties. However, for aero-engine applications, seal designs must be able to cope with relatively large off-design seal closures and closure uncertainties. The two-way coupling between temperatures of seal components and seal closures, through the frictional heat generated at the leaf–rotor interface when in contact, represents an important challenge for leaf seal analysis and design. This coupling can lead to leaf wear and loss, rotor overheating, and possibly to unstable sealing system behavior (thermal runaway). In this paper, we use computational fluid dynamics (CFD), finite element (FE) thermal analysis, and experimental data to characterize the thermal behavior of leaf seals. This sets the basis for a study of the coupled thermomechanical behavior. CFD is used to understand the fluid-mechanics of a leaf pack. The leaf seal tested at the Oxford Osney Laboratory is used for the study. Simulations for four seal axial Reynolds number are conducted; for each value of the Reynolds number, leaf tip-rotor contact, and clearance are considered. Distribution of mass flow within the leaf pack, distribution of heat transfer coefficient (HTC) at the leaf surface, and swirl velocity pick-up across the pack predicted using CFD are discussed. The experimental data obtained from the Oxford rig is used to develop a set of thermal boundary conditions for the leaf pack. An FE thermal model of the rig is devised, informed by the aforementioned CFD study. Four experiments are simulated; thermal boundary conditions are calibrated to match the predicted metal temperatures to those measured on the rig. A sensitivity analysis of the rotor temperature predictions to the heat transfer assumptions is carried out. The calibrated set of thermal boundary conditions is shown to accurately predict the measured rotor temperatures.
Measurement of Air Flow Rate Through Perforated Floor Tiles in a Raised Floor Data Center
Authors: Arghode Vaibhav K. , Kang Taegyu , Joshi Yogendra , Phelps Wally , Michaels Murray
Published: December 2016

In a raised floor data center, cold air from a pressurized subfloor plenum reaches the data center room space through perforated floor tiles. Presently, commercial tool “Flow Hood” is used to measure the tile air flow rate. Here, we will discuss the operating principle and the shortcomings of the commercial tool and introduce two other tile air flow rate measurement tools. The first tool has an array of thermal anemometers (named as “Anemometric Tool”), and the second tool uses the principle of temperature rise across a known heat load to measure the tile air flow rate (named as “Calorimetric Tool”). The performance of the tools is discussed for different types of tiles for a wide range of tile air flow rates. It is found that the proposed tools result in lower uncertainty and work better for high porosity tiles, as compared to the commercial tool.
Characterization and Benchmarking of the Low Intertier Thermal Resistance of Three-Dimensional Hybrid Cu/Dielectric Wafer-to-Wafer Bonding
Authors: Oprins Herman , Cherman Vladimir , Webers Tomas , Salahouelhadj Abdellah , Kim Soon-Wook , Peng Lan , Van der Plas Geert , Beyne Eric
Published: December 2016

In this paper, we present the design of a passive test chip with thermal test structures in the Metal 1 layer of the back-end of line (BEOL) for the experimental thermal characterization of the intertier thermal resistance of wafer-pairs fabricated by three-dimensional (3D) hybrid Cu/dielectric wafer-to-wafer (W2W) bonding. The thermal test structures include heater elements and temperature sensors. The steady-state or transient measurement data are combined with a modeling study to extract the thermal resistance of the bonded interface for the fabricated bonded wafer pair. The extracted thermal resistance of the die–die interface created by hybrid wafer-to-wafer bonding is compared to literature data for die-to-die (D2D) or die-to-wafer (D2W) stacking with microbumps. The low thermal resistance of the thin bonded dielectric interface indicates that hybrid Cu/dielectric bonding is a promising technology to create 3D chip stacks with a low thermal die-to-die resistance.
Moisture Ingress, Behavior, and Prediction Inside Semiconductor Packaging: A Review
Authors: Han Bongtae , Kim Dae-Suk
Published: December 2016

Reliability issues associated with moisture have become increasingly important as advanced electronic devices are nowhere more evident than in portable electronic products. The transition to the Pb-free solders, which require higher reflow temperature, makes the problem further exacerbated. Moisture absorbed into semiconductor packages can initiate many failure mechanisms, in particular interfacial delamination, degradation of adhesion strength, etc. The absorbed moisture can also result in catastrophic crack propagation during reflow process, the well-known phenomenon called popcorning. High vapor pressure inside pre-existing voids at material interfaces is known to be a dominant driving force of this phenomenon. This paper reviews various existing mechanisms of water accumulation inside voids. The procedures to obtain the critical hygroscopic properties are described. Advanced numerical modeling schemes to analyze the moisture diffusion phenomenon are followed with selected examples.
Enhanced Robust Design Simulation and Application to Engine Cycle and Technology Design
Authors: Sands Jonathan , Perullo Christopher , Kestner Brian , Mavris Dimitri
Published: December 2016

Increased computing power has enabled designers to efficiently perform robust design analyses of engine systems. Traditional, filtered Monte Carlo methods involve creating surrogate model representations of a physics-based model in order to rapidly generate tens of thousands of model responses as design and technology input parameters are randomly varied within user-defined distributions. The downside to this approach is that the designer is often faced with a large design space, requiring significant postprocessing to arrive at probabilities of meeting design requirements. This research enhances the traditional, filtered Monte Carlo robust design approach by regressing surrogate responses of joint confidence intervals for metric responses of interest. Fitting surrogate responses of probabilistic confidence intervals rather than the raw response data changes the problem the engineer is able to answer. Using the new approach, the question can be better phrased in terms of the probability of meeting certain requirements. A more traditional approach does not have the ability to include confidence in the process without significant postprocessing. The process is demonstrated using a turboshaft engine modeled using the numerical propulsion system simulation (NPSS) program. The new robust design process enables the designer to account for probabilistic impacts of both technology and design variables, resulting in the selection of an engine cycle that is robust to requirements and technology uncertainty.
Investigation of Effective Groove Types for a Film Riding Seal
Authors: Tibos S. M. , Teixeira J. A. , Georgakis C.
Published: December 2016

Over the past two decades, significant efforts have been made to introduce film riding sealing technology on large industrial or aerospace gas turbines. The main challenge comes from the high surface speeds and high temperatures, which lead to large thermal distortions. One approach to tackle the effect of thermally induced distortion is to design a seal to operate at a large film to limit the viscous heat generation. To design a seal pad that maximizes force at relatively high film heights, it is important to select the seal groove type that looks the most promising to deliver this characteristic. Several groove types have been assessed as part of this study. The most promising groove type is the Rayleigh step, which gives the strongest level of combined hydrostatic and hydrodynamic load support while also being easier to tessellate on individual seal segments. The results generated using a uniform grid Reynolds equation method show reasonable agreement with computational fluid dynamics (CFD) calculations. This provides confidence in the validity of the method, approach, and results.
Differential Equation-Based Specification of Turbulence Integral Length Scales for Cavity Flows
Authors: Jefferson-Loveday Richard J.
Published: December 2016

A new modeling approach has been developed that explicitly accounts for expected turbulent eddy length scales in cavity zones. It uses a hybrid approach with Poisson and Hamilton–Jacobi differential equations. These are used to set turbulent length scales to sensible expected values. For complex rim-seal and shroud cavity designs, the method sets an expected length scale based on local cavity width which accurately accounts for the large-scale wakelike flow structures that have been observed in these zones. The method is used to generate length scale fields for three complex rim-seal geometries. Good convergence properties are found, and a smooth transition of length scale between zones is observed. The approach is integrated with the popular Menter shear stress transport (SST) Reynolds-averaged Navier–Stokes (RANS) turbulence model and reduces to the standard Menter model in the mainstream flow. For validation of the model, a transonic deep cavity simulation is performed. Overall, the Poisson–Hamilton–Jacobi model shows significant quantitative and qualitative improvement over the standard Menter and k–ε two-equation turbulence models. In some instances, it is comparable or more accurate than high-fidelity large eddy simulation (LES). In its current development, the approach has been extended through the use of an initial stage of length scale estimation using a Poisson equation. This essentially reduces the need for user objectivity. A key aspect of the approach is that the length scale is automatically set by the model. Notably, the current method is readily implementable in an unstructured, parallel processing computational framework.
Performance Analysis of Printed Circuit Heat Exchanger for Supercritical Carbon Dioxide
Authors: Guo Jiangfeng , Huai Xiulan
Published: December 2016

A printed circuit heat exchanger (PCHE) was selected as the recuperator of supercritical carbon dioxide (S-CO2) Brayton cycle, and the segmental design method was employed to accommodate the rapid variations of properties of S-CO2. The local heat capacity rate ratio has crucial influences on the local thermal performance of PCHE, while having small influences on the frictional entropy generation. The heat transfer entropy generation is far larger than the frictional entropy generation, and the total entropy generation mainly depends on the heat transfer entropy generation. The axial conduction worsens the thermal performance of PCHE, which becomes more and more obvious with the increase of the thickness and thermal conductivity of plate. The evaluation criteria, material, and size of plate have to be selected carefully in the design of PCHE. The present work may provide a practical guidance on the design and optimization of PCHE when S-CO2 is employed as working fluid.
Aerodynamic Performance of Novel Lightweight Turbine Blade
Authors: Okita Yoji , Nita Kozo , Kubo Seiji
Published: December 2016

The primary contribution of this research is to clarify the aerodynamic performance of a novel lightweight turbine blade with internal cooling passage and external film cooling, which is invented aiming at drastic weight reduction of a cooled blade. With a considerably thinner airfoil, a significant separation region is formed along the pressure side, and therefore, aerodynamic performance with such a flow field should be investigated. First, the lightweight-cooled airfoil is designed. In the design process, a conventional thick airfoil is first defined as a baseline. With the baseline airfoil, only the mid and rear parts of pressure side profile are redesigned to thin the airfoil without any change in the suction side geometry. The airfoil geometry is optimized so as not to bring significant aerodynamic loss increase. In this numerical optimization, the airfoil shape is gradually changed and evaluated step-by-step. In every step, an adjoint variable method is used to seek better airfoil shape, and then, the generated new shape is evaluated with full Reynolds-averaged Navier–Stokes (RANS) calculation. This iteration is repeated until any further recognizable weight reduction cannot be obtained without sensitive pressure loss increase and/or the airfoil shape reaches some geometrical constraints. The resultant optimized airfoil is approximately 20% lighter than the baseline hollow airfoil without any noticeable change in aerodynamic loss in the numerical solution. Next, the optimized airfoil is tested in a high-speed linear cascade rig to verify its aerodynamic performance. The baseline airfoil is also tested for comparison. The rig is composed of six airfoil passages. The compressed air is supplied to the cascade and discharges to the atmospheric exhaust chamber. The air is also heated up to about 540 K upstream of the cascade. The cascade exit Mach number at the design point is 1.25, while in the experiment other several off-design conditions are also tested to check if there is any Mach number sensitivity. At the design point, the optimized lightweight airfoil shows less total pressure loss compared to the baseline airfoil. Also, at any other off-design Mach number conditions tested, the magnitude of the pressure loss is less with the lightweight airfoil. These results verify that the proposed airfoil does not only bring a considerable weight advantage but also compares favorably with the conventional airfoil in aerodynamic performance.
Distributed Sliding-Mode Formation Controller Design for Multirobot Dynamic Systems
Authors: Liao Teh-Lu , Yan Jun-Juh , Chan Wei-Shou
Published: January 2017

This paper presents a distributed formation control for multirobot dynamic systems with external disturbances and system uncertainties. First from the Lagrangian analysis, the dynamic model of a wheeled mobile robot can be derived. Then, the robust distributed formation controller is proposed based on sliding-mode control, consensus algorithm, and graph theory. In this study, the robust stability of the closed-loop system is guaranteed by the Lyapunov stability theorem. From the simulation results, the proposed approach provides better formation responses compared to consensus algorithm.