bluuebunny/crossref_metadata_2025 huggingface dataset:
Free‐living and symbiotic lifestyles of a thermotolerant coral endosymbiont display profoundly distinct transcriptomes under both stable and heat stress conditions
Authors: Bellantuono Anthony J. , Dougan Katherine E. , Granados‐Cifuentes Camila , Rodriguez‐Lanetty Mauricio
Published: November 2019

Reef‐building corals depend upon a nutritional endosymbiosis with photosynthetic dinoflagellates of the family Symbiodiniaceae for the majority of their energetic needs. While this mutualistic relationship is impacted by numerous stressors, warming oceans are a predominant threat to coral reefs, placing the future of the world's reefs in peril. Some Symbiodiniaceae species exhibit tolerance to thermal stress, but the in hospite symbiont response to thermal stress is underexplored. To describe the underpinnings of symbiosis and heat stress response, we compared in hospite and free‐living transcriptomes of Durusdinium trenchii, a pan‐tropical heat‐tolerant Symbiodiniaceae species, under stable temperature conditions and acute hyperthermal stress. We discovered that symbiotic state was a larger driver of the transcriptional landscape than heat stress. The majority of differentially expressed transcripts between in hospite and free‐living cells were downregulated, suggesting the in hospite condition is associated with the shutdown of numerous processes uniquely required for a free‐living lifestyle. In the free‐living state, we identified enrichment for numerous cell signalling pathways and other functions related to detecting and responding to a changing environment, as well as transcripts relating to mitosis, meiosis, and motility. In contrast, in hospite cells exhibited enhanced transcriptional activity for photosynthesis and carbohydrate transport as well as chromatin modifications and a disrupted circadian clock. Hyperthermal stress induced drastic alteration of transcriptional activity in hospite, suggesting symbiotic engagement with the host elicited an exacerbated stress response when compared to free‐living D. trenchii. Altogether, the dramatic differences in gene expression between in hospite and free‐living D. trenchii indicate the importance of considering symbiotic state in investigations of symbiosis and hyperthermal stress in Symbiodiniaceae.
A machine learning approach based on multifractal features for crack assessment of reinforced concrete shells
Authors: Athanasiou Apostolos , Ebrahimkhanlou Arvin , Zaborac Jarrod , Hrynyk Trevor , Salamone Salvatore
Published: November 2019

The geometric properties and spatial characteristics of crack patterns are significant indicators of the extent of damage on reinforced concrete structures. However, manual visual assessment is subjective and depends highly on the inspector's skills. The current study proposes an automated approach for the quantification of digitally documented crack patterns on reinforced concrete shell elements subjected to reversed cyclic shear loading. Multifractal analysis is proposed as a feature extractor for images depicting crack patterns and a set of artificial cracks is analyzed, to quantify how the properties of crack patterns vary as a function of cracking inclination. The results of the parametric study motivated the training of a multiclass classification model, which is used to provide damage level estimates for cracked reinforced concrete members. The training of the classifier is performed using experimental data of reinforced concrete shell elements under well‐defined and idealized two‐dimensional pure shear stress loading conditions. A dataset with 119 images from crack patterns of reinforced concrete shells is used for training. The multifractal features successfully translate the shape of the crack patterns into meaningful information about the extent of damage; achieving an overall test accuracy of 89.3%.
Deep convolutional neural networks for uncertainty propagation in random fields
Authors: Luo Xihaier , Kareem Ahsan
Published: November 2019

The development of a reliable and robust surrogate model is often constrained by the dimensionality of the problem. For a system with high‐dimensional inputs/outputs (I/O), conventional approaches usually use a low‐dimensional manifold to describe the high‐dimensional system, where the I/O data are first reduced to more manageable dimensions and then the condensed representation is used for surrogate modeling. In this study, a new solution scheme for this type of problem based on a deep learning approach is presented. The proposed surrogate is based on a particular network architecture, that is, convolutional neural networks. The surrogate architecture is designed in a hierarchical style containing three different levels of model structures, advancing the efficiency and effectiveness of the model in the aspect of training. To assess the model performance, uncertainty quantification is carried out in a continuum mechanics benchmark problem. Numerical results suggest the proposed model is capable of directly inferring a wide variety of I/O mapping relationships. Uncertainty analysis results obtained via the proposed surrogate have successfully characterized the statistical properties of the output fields compared to the Monte Carlo estimates.
Association between allelic variants in the glucagon‐like peptide 1 and cholecystokinin receptor genes with gastric emptying and glucose tolerance
Authors: Anderson Bradley , Carlson Paula , Laurenti Marcello , Vella Adrian , Camilleri Michael , Desai Anshuman , Feuerhak Kelly , Bharucha Adil E.
Published: November 2019

Background

Nutrient‐mediated release of cholecystokinin and glucagon‐like peptide‐1 (GLP‐1) regulates gastric emptying (GE) via duodenogastric feedback mechanisms; GLP‐1 also regulates postprandial insulin secretion. Some patients with functional upper gastrointestinal symptoms have impaired glucose tolerance during enteral dextrose infusion. Our hypothesis was that variants in CCK, GLP‐1, and TCF7L2 (transcription factor 7‐like 2 locus), which is associated with greatest genetic risk for development of type 2 diabetes mellitus, are associated with GE and independently with glucose tolerance. Our aims were to evaluate the associations between these GE, glucose tolerance, and these single nucleotide polymorphisms (SNPs).

Methods

Genetic variants, scintigraphic GE of solids, plasma glucose, insulin, and GLP‐1 during enteral dextrose infusion (75gm over 2 hours) were measured. GE and enteral dextrose infusion were, respectively, evaluated in 44 (27 controls and 17 patients with functional dyspepsia or nausea) and 42 (28 controls, 14 patients) participants; of these, 51 participants consented to assessment of SNPs. Four functional SNPs were studied: rs6923761 and rs1042044 at GLP‐1 receptor, rs7903146 (TCF7L2), and rs1800857 (CCK receptor).

Key Results

Gastric emptying was normal in 38, rapid in 4, and delayed in two participants; 38 had normal, and four had impaired glucose tolerance. The T allele at rs7903146 (TCF7L2) was non‐significantly associated (P = .14) with faster GE. The associations between SNPs and demographic variables, GE thalf, glucose tolerance and plasma GLP1 levels were not significant.

Conclusions & Inferences

There is a trend toward an association between faster GE and the diabetes‐associated allele at rs7903146 in TCF7L2. However, these SNPs were not associated with plasma glucose or GLP1 concentrations during enteral dextrose infusion.
Many ways to drop a fruit: the evolution of abscission zones in the grasses
Authors: Bartlett Madelaine , Patterson Erin
Published: November 2019

This article is a Commentary on Yu et al. (2020), 225: 1799–1815.
Where There Is Connectivity, There Is Surveillance
Authors: SCHMIDT ERIC , COHEN JARED
Published: November 2019

In 2013, NPQ editor Nathan Gardels spoke with Google's executive chairman ERIC SCHMIDT, and the director of the Google Ideas think tank, JARED COHEN, about their new book, The Digital Age: Reshaping the Future of People, Nations and Business.
Bill Gates’ Guru: “I'm Not Impressed With Silicon Valley.” “I Don't Have a Cell Phone.” “I Never Blog.”
Authors: SMIL VACLAV
Published: November 2019

Bill Gates often invokes VACLAV SMIL as his “favorite thinker.” Indeed, Smil is one of the deeper, more original and independent big minds out there today. His book titles range from The Bad Earth and The Cycles of Life to Harvesting the Biosphere.
A quantitative method for inferring locomotory shifts in amniotes during ontogeny, its application to dinosaurs and its bearing on the evolution of posture
Authors: Chapelle Kimberley E. J. , Benson Roger B. J. , Stiegler Josef , Otero Alejandro , Zhao Qi , Choiniere Jonah N.
Published: November 2019

Evolutionary transitions between quadrupedal and bipedal postures are pivotal to the diversification of amniotes on land, including in our own lineage (Hominini). Heterochrony is suggested as a macroevolutionary mechanism for postural transitions but understanding postural evolution in deep time is hindered by a lack of methods for inferring posture in extinct species. Dinosaurs are an excellent natural laboratory for understanding postural transitions because they demonstrate at least four instances of quadrupedality evolving from bipedality, and heterochronic processes have been put forward as an explanatory model for these transitions. We extend a quantitative method for reliably inferring posture in tetrapods to the study of ontogenetic postural transitions using measurements of proportional limb robusticity. We apply this to ontogenetic series of living and extinct amniotes, focusing on dinosaurs. Our method correctly predicts the general pattern of ontogenetic conservation of quadrupedal and bipedal postures in many living amniote species and infers the same pattern in some dinosaurs. Furthermore, it correctly predicts the ontogenetic postural shift from quadrupedal crawling to bipedal walking in humans. We also infer a transition from early ontogenetic quadrupedality to late‐ontogenetic bipedality in the transitional sauropodomorph dinosaur Mussaurus patagonicus and possibly in the early branching ceratopsian Psittacosaurus lujiatunensis but not in the sauropodomorph Massospondylus carinatus. The phylogenetic positions of these ontogenetic shifts suggest that heterochrony may play a role in the macroevolution of posture, at least in dinosaurs. Our method has substantial potential for testing evolutionary transitions between locomotor modes, especially in elucidating the role of evolutionary mechanisms like heterochrony.
Percutaneous Peripheral Nerve Stimulation for Chronic Low Back Pain: Prospective Case Series With 1 Year of Sustained Relief Following Short‐Term Implant
Authors: Gilmore Christopher A. , Kapural Leonardo , McGee Meredith J. , Boggs Joseph W.
Published: November 2019

Introduction

Percutaneous peripheral nerve stimulation (PNS) provides an opportunity to relieve chronic low back pain and reduce opioid analgesic consumption as an alternative to radiofrequency ablation and permanently implanted neurostimulation systems. Traditionally, the use of neurostimulation earlier in the treatment continuum has been limited by its associated risk, invasiveness, and cost.

Methods

Percutaneous PNS leads (SPRINT MicroLead) were placed bilaterally to target the medial branches of the dorsal rami nerves under image guidance. The percutaneous leads were connected to miniature wearable stimulators (SPRINT PNS System) for the 1‐month therapy period, after which the leads were removed. Pain and disability were assessed long‐term up to 12 months after lead removal.

Results

Substantial, clinically significant reductions in average pain intensity (≥50% reduction as measured by the Brief Pain Inventory Short Form) were experienced by a majority of subjects (67%) at end of treatment compared to baseline (average 80% reduction among responders; P < 0.05, analysis of variance; n = 9). Twelve months after the end of PNS treatment, a majority of subjects who completed the long‐term follow‐up visits experienced sustained, clinically significant reductions in pain and/or disability (67%, n = 6; average 63% reduction in pain intensity and 32‐point reduction in disability among responders). No serious or unanticipated adverse events were reported.

Conclusions

This study challenges the long‐held notion that a positive trial of PNS should be followed by a permanent implant in responders. Percutaneous PNS may serve as an effective neurostimulation therapy for patients with chronic low back pain and should be considered earlier in the treatment continuum as a motor‐sparing means of avoiding opioids, denervation, and permanently implanted neurostimulation systems.
The Cognitive Role of Fictionality
Authors: Williams J. Robert G. , Woodward Richard
Published: November 2019

The question of the cognitive role of fictionality is this: what is the correct cognitive attitude to take to p, when it is fictional that p? We began by considering one answer to this question, implicit in the work of Kendall Walton, that the correct response to a fictional proposition is to imagine that proposition. However, this approach is silent in cases of fictional incompleteness, where neither p nor its negation are fictional. We argue that that Waltonians should embrace a pluralistic account of the cognitive role of fictional incompleteness: in some cases of fictional incompleteness, we are permitted to resolve the incompleteness during our engagement with the target fiction, and in other cases, we are obliged not to resolve the incompleteness. But though pluralism is accommodated by Walton’s wider account of fictionality, it puts tension on his motivating idea that fictionality stands to the imagination as truth stands to belief. And so we develop a rival conception of the cognitive role of fictionality that is built around a different analogy: on this evidentialist approach, (known) fictionality stands to the imagination as evidence stands to credence.
Relational Primitivism
Authors: Zylberman Ariel
Published: November 2019

What kind of property is represented by the moral ought? I defend a relational answer: the moral ought represents a primitive relational property of actions required by the original claims of persons. I argue that the relational answer offers a distinctive and compelling account in its own right that also avoids standard difficulties of familiar theories.
Presidential Rhetoric and U.S. Supreme Court Rulings: The Effect of Going Public on Citizen Evaluations of Institutions and Policy
Authors: Montgomery Matthew D. , Rogol Natalie C. , Kingsland Justin T.
Published: November 2019

Little is known about how the public responds to presidential statements on Supreme Court decisions. We argue that the president can serve as a source cue for both supporters and nonsupporters, shaping their opinions about the Supreme Court. This study offers a novel experimental test of presidential impact on individual assessments of the Court and potential sanctions. Our results suggest that individuals who approve of the president are likely to adjust their opinions to reflect the executive's stated position on Supreme Court decisions. However, those who do not support the president will react in a directionally opposed manner. Still, under the right conditions, our study suggests that a strategic president can take advantage of his ability to go public about the judicial branch.
Fate of leaf litter in restored Kandelia obovata (S. L.) mangrove forests with different ages in Jiulong River Estuary, China
Authors: Chen Jiahui , Chen Guangcheng , Gu Yantao , Zhu Heng , Ye Yong
Published: November 2019

Ecological processing of leaf litter plays important roles in carbon dynamics of mangrove forests. Fate of leaf litter, that is, removal by crabs, microbial decomposition, and tidal export was quantified in two restored Kandelia obovata forests with ages of 24 years and 48 years, respectively, from December 2009 to November 2010. Crab abundance was also investigated to test the role of crabs in leaf litter processing. Daily leaf litter production was 1.064 ± 0.108 g C m−2 day−1 at the 24‐year forest and was 0.689 ± 0.040 g C m−2 day−1 at the 48‐year forest. Annual mean removal of leaf litter by crabs was lower at the 24‐year forest than at the 48‐year forest (0.177 ± 0.046 g C m−2 day−1 vs. 0.220 ± 0.050 g C m−2 day−1), due to a higher crab abundance at the older forest. Microbial decomposition and change in standing stock of leaf litter on the forest floor made a negligible contribution to the annual leaf litter production. Tidal exports of leaf litter were estimated as 0.875 ± 0.090 g C m−2 day−1 and 0.458 ± 0.086 g C m−2 day−1 at the 24‐year and 48‐year forests, respectively, accounting for 82.2% and 66.5% of their daily leaf litter production. Turnover rate of leaf litter was higher at the younger forest (1.7 ± 0.4 day−1) than the older forest (1.2 ± 0.3 day−1). Removal of leaf litter by crabs was higher in warm months while tidal export of leaf litter showed a much less apparent seasonal pattern. Spatial variations of crab removal and tidal export of leaf litter with forest zones were observed within each forest, while microbial decomposition of leaf litter was comparable among the different zones. These indicated that the ecosystem functions of restored mangrove forest could not reach a level equivalent to those of a mature forest even 24 years after restoration.
The effectiveness of oral hygiene instructions in sign language among hearing impaired adults in Saudi Arabia
Authors: Fageeh Hytham N. , Mansoor Manawar A.
Published: November 2019

Objective

To improve knowledge of oral health among the hearing impaired in Saudi Arabia using videos with detailed oral hygiene instructions in Arabic sign language.

Methods

Videos of oral hygiene instructions in Arabic sign language were produced under the supervision of a periodontist. Fifty male subjects above 18 years of age were chosen randomly from different deaf schools in Jazan, Saudi Arabia and divided into two groups as follows: Group 1 received printed booklets with oral hygiene instructions, and Group 2 received videos of the same instructions in Arabic sign language. Knowledge regarding oral health and hygiene practice was evaluated with the aid of a questionnaire before and after 4 weeks.

Results

The estimated marginal mean of the knowledge regarding oral hygiene in Group 1 was 3.37, which was slightly increased to 4.40 after 4 weeks of general instructions. The estimated marginal mean in Group 2 was 3.70 before the distribution of the videos, which was significantly increased to 11 after 4 weeks (P < .001).

Conclusion

Videos of oral hygiene instructions in Arabic sign language had immensely improved knowledge regarding oral health and hygiene practices in the deaf/hearing impaired patients in this study.
Characterization of the novel HLA‐DPA1*02:26 allele by sequencing‐based typing
Authors: Cargou Marine , Andreani Marco , Galluccio Tiziana , Guidicelli Gwendaline , Visentin Jonathan
Published: November 2019

HLA‐DPA1*02:26 differs from HLA‐DPA1*02:01:01:02 by one nucleotide substitution in codon 186 in exon 4.
Characterization of the novel HLA‐DRB1*15:178 allele by sequencing‐based typing
Authors: Cargou Marine , Elsermans Vincent , Top Isabelle , Ralazamahaleo Mamy , Visentin Jonathan
Published: November 2019

HLA‐DRB1*15:178 differs from HLA‐DRB1*15:03:01:01 by one nucleotide substitution in codon 213 in exon 4.
Characterization of the novel HLA‐DRB3*02:02:23 allele by sequencing‐based typing
Authors: Cargou Marine , Andreani Marco , Battarra Mariarosa , Blouin Laura , Visentin Jonathan
Published: November 2019

HLA‐DRB3*02:02:23 differs from HLA‐DRB3*02:02:01:02 by one nucleotide substitution in codon 218 in exon 4.
Characterization of the novel HLA‐DRB1*12:82 allele by sequencing‐based typing
Authors: Cargou Marine , Elsermans Vincent , Top Isabelle , Guidicelli Gwendaline , Visentin Jonathan
Published: November 2019

HLA‐DRB1*12:82 differs from HLA‐DRB1*12:01:01:01 by one nucleotide substitution in codon 104 in exon 3.
Decolonizing the Curriculum
Authors: Criser Regine , Knott Suzuko
Published: November 2019

Global German Studies require a reassessment of the global histories, narratives, and injustices that continue to be underrepresented in the classroom as well as a critical reflection of how we define “German.” This article investigates the crucial role of decolonization in the reenvisioning of the discipline. Decolonization is understood as an intentional decentering of dominant voices, an interrogation of whiteness, and a move toward pedagogies incorporating Indigenous epistemologies and social justice practices. The article highlights opportunities for creating a global and decolonized curriculum, which can be implemented across all levels in German language classes, including German Studies courses taught in English. Examples demonstrate how such an approach decenters normative hierarchies that privilege whiteness, the cisgendered, hetero, abled, etc. and simultaneously reframe particular local histories while interrogating global colonizing processes and oppression.
Advocating for Queer of Color Studies in German Graduate Programs
Authors: Layne Priscilla , Malakaj Ervin
Published: November 2019

This article advocates for the inclusion of queer and queer of color discourse into graduate curricula in North American German Studies. It presents a brief overview of major discussions in queer of color studies, proposes sample readings of queer of color texts in Germany that help graduate students develop sophisticated understandings of German cultural history in relation to the formation of globalization and nationalism discourses, and presents a sample syllabus on queer of color discourse and cultural history in Germany.
The Globalized AP German Classroom
Authors: Bauerlein Katrina , Shertzer Rebecca
Published: November 2019

Preparing lifelong, world‐ready German learners means German language instructors must intentionally incorporate globalized themes and tasks into the high school German curriculum. In 2010, the College Board redesigned the AP German Language and Culture Exam to meet these needs. The new exam encompasses six course themes and requires students to complete related authentic tasks. In this conversation, high school German teachers Rebecca Shertzer and Katrina Bauerlein discuss what it can mean to globalize the AP German classroom, how a globalized curriculum aligns with the AP German Language and Culture Exam, and how the AP themes correspond with the World‐Readiness Standards for Learning Languages (2015). In their conversation, they briefly explain the format and expectations of the exam and also share examples from their curricula to demonstrate how they best prepare their students for globalized contexts. Their experiences at different institutions demonstrate that the AP German Language and Culture curriculum (1) gives the instructor the freedom to choose from a diverse array of topics and incorporate related authentic texts and (2) provides a framework for creating authentic tasks related to these texts, while (3) addressing the needs and interests of high school students.
On the Sick Father, the Repentant Sinner, and Other Problems in Medieval Deontic Logic
Authors: Hilpinen Risto
Published: November 2019

Many medieval philosophers and logicians regarded modal logic as a model for epistemic, normative and optative concepts on the basis of their apparent similarities to modal concepts. These interpretations of modal logic led to critical studies of the applicability of modal principles to deontic concepts. Some philosophers presented apparent counterexamples to the deontic interpretation of the Consequence Principle, according to which the consequences of what is obligatory (or permitted) are also obligatory (permitted). These examples are variants of Lennart Åqvist's paradox of the Good Samaritan. In this article it is argued that the examples involve a confusion between the compounded and the divided senses of deontic propositions, and are not genuine counterexamples to the Consequence Principle. If the concept of knowledge is analysed as epistemically satisfactory belief, the paradox of epistemic obligation can be solved in a similar way.
Consumption and exchange rate uncertainty: Evidence from selected Asian countries
Authors: Iyke Bernard Njindan , Ho Sin‐Yu
Published: November 2019

We set out to assess the effects of exchange rate uncertainty on real consumption in selected Asian countries. Consumption influences business cycles, which in turn shape short‐run monetary policy decisions. Hence, understanding factors driving consumption is appealing to policymakers. To date, few studies have analysed the effects of uncertainty on consumption. The available ones generally focus on the long‐run effects, in spite of the fact that the short‐run persistence and adjustments to equilibrium are equally relevant. Our study takes these limitations seriously by distinguishing the short‐ and long‐run effects of exchange rate uncertainty on consumption. Using a flexible dynamic panel data technique that allows long‐run effects to be homogeneous and the short‐run effects to be heterogeneous, we find that uncertainty impedes consumption in the long run. In the short run, however, the effects are immaterial. This evidence remains robust to the measure of uncertainty, asymmetric uncertainty, inflation and the global financial crisis of 2008. By decomposing uncertainty into its temporary and permanent components, we find that the latter have a stronger effect on consumption in the long run than the former. Although both components demand policy attention, the evidence suggests that policymakers should be more concerned with permanent uncertainty.
Fabrication of porous bovine pericardium scaffolds incorporated with bFGF for tissue engineering applications
Authors: Liu Xiaohong , Wu Hao , Lu Fanglin , Li Qin , Xu Zhiyun
Published: November 2019

Background

The design and fabrication of porous scaffolds are important issues for tissue engineering applications. In this study, we attempted to fabricate porous scaffolds using bovine pericardium (BP) and examined whether these scaffolds were beneficial for cell ingrowth and bioactive factors delivery.

Methods

A vacuum‐freeze‐thawing‐Triton X‐100 (VFTT) protocol was used to fabricate porous BP scaffolds. The porous and mechanical properties were assessed using histology, scanning electron microscopy, and mechanical assay. The fabricated scaffolds were seeded with mesenchymal stem cells (MSCs), and cell ingrowth was evaluated. Basic fibroblast growth factor (bFGF) was subsequently incorporated into the fabricated scaffolds. The bioactive factor delivery capacity was evaluated using loading and release studies. The bioactivity of released bFGF was assessed using a rat subcutaneous model.

Results

The BP scaffolds fabricated by the VFTT protocol displayed interconnected porous structures with porosity of 6.82 ± 1.36%.There were no significant differences in thickness, ultimate load, Young's modulus, and ultimate tensile strength between the fabricated porous BP scaffolds and native BPs (all P > .05). However, the water content of BPs was slightly reduced after VFTT treatment (P < .05). Cell ingrowth analysis showed that the seeded MSCs penetrated into the porous BP scaffolds with time of culture, while MSCs were limited to the surface layers of native BPs. Furthermore, bFGF was observed to be effectively loaded onto and released from the porous BP scaffolds. The released bFGF increased the phosphorylation levels of Akt, ERK 1/2, and MEK1/2, promoted host MSC recruitment, and inhibited myofibroblast differentiation in vivo.

Conclusions

The porous BP scaffolds fabricated using a VFTT protocol were promising natural scaffolds for tissue engineering applications, since they had considerable mechanical properties as native BPs, supplied porous channels for cell ingrowth, and possessed bioactive factors delivery capability.
Arterial and venous cerebral blood flow responses to long‐term head‐down bed rest in male volunteers
Authors: Ogoh Shigehiko , Sato Kohei , de Abreu Steven , Denise Pierre , Normand Hervé
Published: November 2019

New Findings

What is the central question of this study?

A heterogeneous cerebral blood flow (CBF) response in the cerebral arteries has been demonstrated in several physiological conditions, and it might be attributable to different physiological properties. However, the whole cerebral haemodynamic response to weightlessness remains unknown.

What is the main finding and its importance?

Long‐term head‐down bed rest caused a heterogeneous CBF response between the anterior and posterior cerebral arteries and between the cerebral arteries and veins. Especially, in contrast to the anterior cerebral circulation, the posterior arterial and venous CBFs were well maintained throughout weightlessness.

In this study, we investigated the whole cerebral haemodynamic response to long‐term head‐down bed rest (HDBR). We hypothesized that long‐term exposure to weightlessness influences cerebral blood flow (CBF) or CBF distribution among cerebral arteries and veins because of the different physiological roles of each cerebral vessel. To test this hypothesis, 10 male volunteers were exposed to −6 deg HDBR for 60 days. Blood flows in the internal carotid artery, external carotid artery and vertebral artery or internal jugular vein and vertebral vein were measured using ultrasonography before and on days 30 and 57 of the HDBR. The internal carotid artery blood flow was reduced on day 30 (P = 0.019) and had returned to the baseline level by day 57. In contrast, the vertebral artery blood flow remained unaltered throughout the HDBR (P = 0.626). The internal jugular vein blood flow was reduced on day 30 (P = 0.009), whereas the vertebral vein blood flow remained unaltered (P = 0.397). These findings suggest that long‐term HDBR causes a heterogeneous CBF response between the anterior and posterior cerebral circulation in the both arteries and veins. The posterior arterial and venous CBFs were well maintained throughout HDBR, and these CBF responses to HDBR were different from the anterior cerebral circulation.
Design and Experimental Validation of Two Cam-Based Force Regulation Mechanisms
Authors: Li Ming , Cheng Wei , Xie Ruili
Published: November 2019

This paper presents the design and experimental validation of two force regulation mechanisms (FRMs) containing a translational cam and a rotational cam, respectively. With the friction-considered profile identification method (FCPIM) to define the cam and through the squeezing between the cam and the spring-supported slider, the FRMs can passively output the desired force over the designed displacement. Under the premise of that the friction coefficient can be accurately obtained, the friction-considered design principle will be significant for the realization of FRMs in actual applications since it is no longer necessary to achieve high accuracy by pursuing the frictionless condition. Hence, the conventional materials and mechanical parts can be directly used to assemble the FRMs without sacrificing the force regulating accuracy. We are highly interested in the actual experimental behavior of the proposed FRMs under the friction-considered condition. Then, prototypes of the two FRMs capable of outputting multiple types of forces including in zero-stiffness, positive and negative stiffness are specially designed, fabricated, and tested quasi-statically. The experimental results verify the correctness of FCPIM since they agree with the design objective well. Meanwhile, the effectiveness of the FCPIM is proved as the errors of the experimental results considering friction is much lower than those ignoring friction. The experiments also show that the noise phenomenon in the testing curves that may affect the judgment of test accuracy can be highly degraded by using more stable and controllable loading tools, which is helpful for future research.
Aero-Thermal Investigation of Convective and Radiative Heat Transfer on Active Clearance Control Manifolds
Authors: Da Soghe Riccardo , Bianchini Cosimo
Published: November 2019

The present paper deals with the characterization of heat transfer on blade tip Active Clearance Control manifolds. Real engine geometries and operating conditions were considered in validated CFD computations to understand the impacts of both manifold surfaces convective and radiative heat transfer on the aero-thermal performance of the system. Different manifold geometries were accounted for also.

The study sorted out that both the radiation and the convective heat transfer on the manifold surfaces are responsible of performance deteriorations as the impingement heat transfer on the casing is considered. The last evidence is motivated by the fresh fluid heat up along the feeding pipe. Radiative heat transfer from the casing to the manifold is found to be relevant, especially in case of high casing temperature or low undercowl flow rates. As a result of the study, is remarked that ACC manifold radiative and convective heat transfer should be considered for a proper system design.
3D Computational Loss Analysis of a Compressor for Heavy Duty Truck Engine Turbochargers
Authors: Abel Matthias , Martinez-Botas Ricardo F. , Wöhr Michael , Müller Markus , Leweux Johannes
Published: November 2019

This paper presents a detailed loss analysis of a centrifugal compressor stage with a vaned diffuser for application in a heavy duty engine turbocharger. The analysis is carried out in order to investigate the loss distribution in the stage. To quantify the impact of different loss types and locations, a detailed validated steady-state 3D CFD solution is employed. The local entropy production rate is calculated for two operating points (full load and part load), which are most relevant to the real world operation of the compressor in a truck application. Two methods are suggested as the procedure for the division of the whole fluid volume into sub-volumes, because this is key for the resulting loss distribution.

The primary loss generating mechanisms are shown at main operating conditions to reveal the regions of improvement. A detailed grid study was conducted to enable the calculation of the entropy ratio. It was possible to capture around 78% (partial load) and 70% (full load) of the entropy production with a mesh with circa 100 million elements. Around half of the losses were due to the boundary layer friction, followed by losses associated with a boundary layer separation resulting from the back-flow at the shroud contour close to the impeller exit and back disk friction accounted for with 6–7% of the stage’s losses.
Determination of Simultaneous Steady-State Movements Using Blade Tip Timing Data
Authors: Mohamed Mohamed , Bonello Philip , Russhard Peter
Published: November 2019

Blade tip timing (BTT) includes a number of uncertainties that discourage its use. One of the main ones is the shift in the equilibrium position of the blade tip due to steady (non-oscillatory) bending and/or twisting of the blade, and axial movement of the bladed disk (blisk)-shaft system. This results in a shift in the effective measurement position of the probe relative to the blade chord, resulting in errors in the tip vibration measurement which can translate to a huge error in the corresponding stress estimate, which relies on calibration against finite element (FE) models. Previous experimentally validated research by the authors introduced a method for quantifying steady movement of a single type (axial, lean, or untwist), using BTT data from not more than two probes. In this paper, a development of the previous method is presented that provides a solution for the case of simultaneous types of blade steady movements. Additional probes are used for determining the direction, but these can be placed at any angular positions. The developed method is validated using a BTT simulator of a blisk, and accurate results obtained. The simultaneous axial and lean movements can be accurately determined when the untwist is negligible, and an uncertainty level can be specified when the untwist is not negligible. The untwist itself can be calculated accurately in all cases of simultaneous movements. Guidelines for the use of the method in different scenarios are provided.
A General Diagnostic Methodology for Sensor Fault Detection, Classification and Overall Health State Assessment
Authors: Manservigi Lucrezia , Venturini Mauro , Ceschini Giuseppe Fabio , Bechini Giovanni , Losi Enzo
Published: November 2019

Sensor fault detection and classification is a key challenge for machine monitoring and diagnostics. To this purpose, a comprehensive approach for Detection, Classification and Integrated Diagnostics of Gas Turbine Sensors (named DCIDS), previously developed by the authors, is improved in this paper to detect and classify different fault classes. For a single sensor or redundant/correlated sensors, the improved diagnostic tool, called I-DCIDS, can identify seven classes of fault, i.e. out of range, stuck signal, dithering, standard deviation, trend coherence, spike and bias. Fault detection is performed by means of basic mathematical laws that require some user-defined input parameters, i.e. acceptability thresholds and windows of observation.

This paper presents in detail the I-DCIDS methodology for sensor fault detection and classification. Moreover, this paper reports some examples of application of the methodology to simulated data to highlight its capability to detect sensor faults which can be commonly encountered in field applications.
Turbocharger Turbine Rotor Design for Low U/C Values
Authors: Chen Hua , Song Yuchao , Gu Aiguo , Zhang Yangfang , Li Hongwei
Published: November 2019

Emission regulations worldwide demand better low-end torque from internal combustion engines. This pushes the operating condition of turbocharger turbine to lower U/C values, where U is the blade tip speed and C is the turbine isentropic spouting velocity which increases with turbine expansion ratio. Traditional radial and some mixed flow turbines, dictated by their rotor design, have their efficiency peaks at U/C value around 0.70, a value considerably larger than desired. In this paper, we deliberate the measures to shift the peak efficiency of turbine rotor toward a lower U/C value than 0.7. The underlying physics of these measures are first explained, CFD and test results where available are then given. Implications to mechanical design, manufacturing and others are also discussed. Finally, an example of a turbine rotor design is given implementing these measures. Test results showed better efficiency was obtained from the design at lower U/C values than from the baseline.
Numerical Research on the Toroidal Shock Wave Focusing Detonation Initiation
Authors: Chen Xiang , Zhao Ningbo , Zheng Hongtao , Jia Xiongbin , Liu Shizheng , Liu Qingbo
Published: November 2019

Pressure gain combustion (PGC) is considered to be a potential technology to increase the cycle efficiency of gas turbine. As one viable candidate for PGC, rotating detonation engine (RDE) draws more attention due to its significant advances in continuous mode of operation. In practical, one of the basic challenges for RDE application is to reliably initiate detonation wave. For this purpose, both detonation initiation mechanism and enhancement approach are urgently needed to be understood. In this work, a toroidal shock wave focusing detonation initiator is presented. On this basis, the two-dimensional numerical simulations are carried out to investigate the detonation initiation characteristics by using the toroidal shock wave focusing. All of the flame acceleration, shock wave focusing, detonation wave forming and propagation are analyzed in detail. The numerical results show that the toroidal shock wave focusing initiator developed in this study can rapidly realize the detonation initiation over a short distance and performs significantly better than the traditional smooth or obstructed tube based imitators under different operating conditions. Under the same operating condition, the novel developed initiator decreases time of 59.2% and distance of 84.7% for the smooth tube based initiator, and time of 52% and distance of 78.9% for the obstructed one. Besides, the multi-fields analysis indicates that both the local explosion induced by shock wave focusing in concave cavity and the entrainment vortex generated by shock wave and jet flame in front of diaphragm are important mechanisms to initiate detonation wave. The present study is expected to enhance the understanding of the physical mechanism of shock wave focusing detonation initiation and contribute to the development of detonation propulsion technology.
Aerodynamic Numerical Investigation of Low-Pressure Steam Turbine Last Stage Under Low Load Conditions With Mode Decomposition Methods
Authors: Hu Ping , Lin Tong , Yang Rui , Zhu Xiaocheng , Du Zhaohui
Published: November 2019

It is common that steam turbine works at different operating points, especially under low load conditions, to cater to complex and varied demands for power generation recently. Considering the long and thin shape of last stage moving blades (LSMBs) in a low-pressure (LP) steam turbine, there are many challenges to design a suitable case which balances global efficiency against sufficient structure strength when suffering excitations at low load operating points. In present work, the aim is to extract specific aerodynamic excitations and recognize their distribution and propagation features. Firstly, steady 3D computational fluid dynamics (CFD) calculations are simulated at 25GV and 17GV (25% and 17% of design mass flow conditions) and corresponding unsteady calculations are performed with enough rotor revolutions to obtain integrated flow periodicities. Unsteady pressure signals near tip region of LSMBs are monitored circumferentially in both static and rotating coordinates. The fast Fourier transformation (FFT) results of unsteady pressure signals show that there are broadband humps with small disturbance amplitudes in low frequency spectrum at 25GV, however, a sharp spike is shown in low frequency spectrum at 17GV. Further, circumferential mode decomposition (CMD) method has been applied to distinguish different fluctuations in frequency and the mode numbers and circumferential propagating pace of which have been obtained. Finally, dynamic mode decomposition (DMD) method has been performed to describe detailed mode shapes of featured flow perturbances both in static and rotating coordinate system. These analyses indicate that at 25GV, a band of unsteady responses with very low amplitude was noted which has some features similar to rotating instability (RI). However, distribution and propagation features of flow unsteadiness at 17GV are in good agreement with rotating stall (RS) in compressor.
Detailed Heat Transfer Coefficient Measurements on a Scaled Realistic Turbine Blade Internal Cooling System
Authors: Shiau Chao-Cheng , Chen Andrew F. , Han Je-Chin , Krewinkel Robert
Published: November 2019

A realistic internal cooling system of a turbine blade includes both ribs and pin-fins inside the passages to enhance the heat transfer. However, the majority studies in the open literature assessing the heat transfer characteristics on a simplified cooling model by examining ribbed-roughen passages and pin-finned passage separately. This work presents the high-resolution heat transfer coefficients of a scaled realistic turbine blade internal cooling design. The cooling system, using a 3D-printed plastic material, consists of an S-shaped inlet, four serpentine passages (three U-bends) of variable aspect ratio, and the trailing edge ejection. Angled ribs are implemented inside the passages and the elongated fins and pins are used near the trailing edge. Two dust holes are realized on the blade tip, the injections are individually controlled to reflect the realistic coolant flow rate variation inside the entire internal cooling system. The tests are conducted at two Reynolds number, 45,000 and 60,000 based on the hydraulic diameter of the inlet passage. Transient heat transfer technique using thermochromic liquid crystal is applied to obtain the detailed heat transfer characteristic inside the cooling channel. The local and averaged Nusselt numbers are also compared with the correlations in the open literature. This paper provides gas turbine designers the difference of local heat transfer distributions between the realistic and simplified internal cooling designs.
A Model for System Instability Analysis in a Multi-Stage Intercooled Industrial Compressor
Authors: Gan Jiaye , Abdelwahab Ahmed , Kilchyk Viktor
Published: November 2019

Compression equipment used for industrial applications are typically comprised of multi-stage intercooled compressor stages. The presence of large volume intercoolers between individual stages adds a layer of complexity currently not present in publicly available surge models both in terms of system behavior and recovery analysis. In this work a compressible, temporal, and spatial model is developed in which the conservation equations are solved numerically for each of the system components, i.e. pipes, plenums and heat exchangers, valves, and individual compressor stages. The model can identify the onset of instability on an individual stage basis as well as the switching that can occur between the controlling stages of the instability onset when the operating conditions change, e.g. changes in inlet conditions, intercooler fouling or cooling tower performance reduction, and speed or guide vane changes. The model is therefore used both as a stage stacking model during the compressor stable operation as well as a model of the transient behavior of the system past the stable operation. An inertial model of the compressor drive train is also incorporated to analyze the effects of power transients, e.g. emergency shut down (ESD), on the system behavior. In this article details of the developed model are provided. Several test cases are presented. The model is then used to demonstrate the proper sizing of a vent valve of a base load compressor to meet the required system response specification in a surge event. The developed model represents an improvement over available transient system models in terms of predicting the post stable behavior of multi-stage intercooled compressors.