bluuebunny/crossref_metadata_2025 huggingface dataset:
Transgenerational plasticity in Silene vulgaris in response to three types of stress
Authors: Sandner T. M. , van Braak J. L. , Matthies D.
Published: March 2018

The environment experienced by plants can influence the phenotype of their offspring. Such transgenerational plasticity can be adaptive when it results in higher fitness of the offspring under conditions correlated with those experienced by the mother plant. However, it has rarely been tested if such anticipatory parental effects may be induced with different environments.

We grew clonal replicates of Silene vulgaris under control conditions and three types of stress (nutrient deficiency, copper addition and drought), which are known from natural populations of the species. We then subjected offspring from differently treated mother plants to each of the different stress treatments to analyse the influence of maternal and offspring environment on performance and several functional traits.

Current stress treatments strongly influenced biomass and functional traits of the plants, mostly in line with responses predicted by the theory of functional equilibrium. Plant performance was also influenced by maternal stress treatments, and some effects independent of initial size differences remained until harvest. In particular, stressed mothers produced offspring of higher fitness than control plants. However, there was no evidence for treatment‐specific adaptive transgenerational plasticity, as offspring from a mother plant that had grown in a specific environment did not grow better in that environment than other plants.

Our results indicate that the maternal environment may affect offspring traits and performance, but also that this transgenerational plasticity is not necessarily adaptive.
Prenatal triptan exposure and neurodevelopmental outcomes in 5‐year‐old children: Follow‐up from the Norwegian Mother and Child Cohort Study
Authors: Harris Gerd‐Marie Eskerud , Wood Mollie , Ystrom Eivind , Nordeng Hedvig
Published: March 2018

Background

Triptans are commonly used to treat migraine headaches, but data on the long‐term safety of these medications during pregnancy are sparse. Triptans have a biologically plausible mechanism for effects on the fetal brain through binding to 5‐HT1‐receptors, and previous studies show increased risks of externalising behaviour problems in toddlers exposed to triptans during pregnancy.

Methods

We included 3784 children in the Norwegian Mother and Child Cohort Study, whose mothers returned the 5‐year‐questionnaire and reported a history of migraine or triptan use; 353 (9.3%) mothers reported use of triptans during pregnancy, 1509 (39.9%) reported migraine during pregnancy but no triptan use, and 1922 (50.8%) had migraine prior to pregnancy only. We used linear and log‐binomial models with inverse probability weights to examine the association between prenatal triptan exposure and internalising and externalising behaviour, communication, and temperament in 5‐year‐old children.

Results

Triptan‐exposed children scored higher on the sociability trait than unexposed children of mothers with migraine (β 1.66, 95% confidence interval [0.30, 3.02]). We found no other differences in temperament, or increased risk of behaviour or communication problems.

Conclusions

Contrary to results from previous studies in younger children, we found no increased risk of externalising behaviour problems in 5‐year‐old children exposed to triptans in fetal life. Triptan‐exposed children did have slightly more sociable temperaments, but the clinical meaning of this finding is uncertain.
Identifying auditory cortex encoding abnormalities in schizophrenia: The utility of low‐frequency versus 40 Hz steady‐state measures
Authors: Edgar J. C. , Fisk Charles L. , Chen Yu‐Han , Stone‐Howell Breannan , Liu Song , Hunter Michael A. , Huang Mingxiong , Bustillo Juan , Cañive José M. , Miller Gregory A.
Published: March 2018

Magnetoencephalography (MEG) and EEG have identified poststimulus low frequency and 40 Hz steady‐state auditory encoding abnormalities in schizophrenia (SZ). Negative findings have also appeared. To identify factors contributing to these inconsistencies, healthy control (HC) and SZ group differences were examined in MEG and EEG source space and EEG sensor space, with better group differentiation hypothesized for source than sensor measures given greater predictive utility for source measures. Fifty‐five HC and 41 chronic SZ were presented 500 Hz sinusoidal stimuli modulated at 40 Hz during simultaneous whole‐head MEG and EEG. MEG and EEG source models using left and right superior temporal gyrus (STG) dipoles estimated trial‐to‐trial phase similarity and percent change from prestimulus baseline. Group differences in poststimulus low‐frequency activity and 40 Hz steady‐state response were evaluated. Several EEG sensor analysis strategies were also examined. Poststimulus low‐frequency group differences were observed across all methods. Given an age‐related decrease in left STG 40 Hz steady‐state activity in HC (HC > SZ), 40 Hz steady‐state group differences were evident only in younger participants' source measures. Findings thus indicated that optimal data collection and analysis methods depend on the auditory encoding measure of interest. In addition, whereas results indicated that HC and SZ auditory encoding low‐frequency group differences are generally comparable across modality and analysis strategy (and thus not dependent on obtaining construct‐valid measures of left and right auditory cortex activity), 40 Hz steady‐state group‐difference findings are much more dependent on analysis strategy, with 40 Hz steady‐state source‐space findings providing the best group differentiation.
The source is in the sink: Deep‐water deposition by a submarine volcanic arc, Taranaki Basin, New Zealand
Authors: Shumaker Lauren E. , Sharman Glenn R. , King Peter R. , Graham Stephan A.
Published: March 2018

Submarine volcanoes produce sediment that originates and remains in a deep‐water setting, never escaping the water column. This situation puts a twist on the idea of ‘source to sink’ pathways, where both source and sink are in the submarine realm. Submarine volcanoes may play a significant role in basin sedimentation and evolution, but direct observation of sediment production and dispersal from submerged volcanoes is logistically difficult. This study analyzes the Mohakatino Formation, a Miocene deep‐marine unit produced by ancient submarine volcanoes of the Taranaki Basin, New Zealand, to investigate sediment transport and deposition from these volcanoes. Outcrop analysis of the volcanogenic deposits suggests a submarine lobe environment in a north–south elongated sub‐basin, confined by the growing volcanic arc to the north and west and a fault‐controlled topographic high to the east. Composition and sedimentary structures indicate that most deposits in this area are reworked volcanogenic material, rather than primary deposits from individual eruption events, transported to the depocentre by eruption‐initiated and mass wasting‐initiated turbidity currents. This study highlights the need for submarine volcanoes to be considered in source to sink investigations, to ascertain their role as sediment sources to marine basins. Deeply submerged volcanoes are disconnected from some environmental signals, while sedimentation from shallow‐water volcanoes may be especially sensitive to perturbations in sea‐level and climate. In both cases, a short transfer zone between source and sink may increase the likelihood that source area signals are transmitted to the sedimentary record.
Cytomegalovirus resistance in CD34+‐selected hematopoietic cell transplant recipients
Authors: Kim Seong Jin , Huang Yao‐Ting , Foldi Julia , Lee Yeon Joo , Maloy Molly , Giralt Sergio A. , Jakubowski Ann A. , Papanicolaou Genovefa A.
Published: March 2018

Background

Cytomegalovirus (CMV) viremia after CD34+‐selected hematopoietic stem cell transplant (HCT) often requires prolonged antiviral therapy. We report rates and outcomes of resistant CMV in a contemporary cohort of CD34+‐selected HCT recipients managed preemptively.

Methods

We retrospectively reviewed 220 consecutive, CMV‐seropositive recipients (R+), who received CD34+‐selected HCT at Memorial Sloan Kettering Cancer Center between June 2010 and December 2014. Patients were monitored by quantitative CMV PCR and were treated preemptively. CMV resistance was tested by a genotypic assay.

Results

One hundred and sixty‐one (73%) patients developed CMV viremia and 47 (29% of viremic and 21% of total patients) had CMV resistance testing by one‐year from HCT. CMV resistance was confirmed in 19 (12% of viremic and 9% of total) patients and was identified >3 months from HCT in 90% of patients. Twelve patients had mutations in UL97 only; the remaining 7 patients had mutations in UL54 only or UL54 and UL97. By 1 year from HCT, 11 of 19 (58%) patients with mutations had CMV end‐organ disease. CMV‐related mortality in patients with resistance was 42%.

Conclusions

Nine percent of CMV R+, CD34+‐selected HCT recipients had resistant CMV by 1 year from HCT. Of 19 patients with resistant CMV, 58% had CMV end‐organ disease and 42% died of CMV. Effective strategies for CMV prevention and restoration of CMV immunity are needed for CD34+‐selected HCT.
Kinetic of the CMV‐specific T‐cell immune response and CMV infection in CMV‐seropositive kidney transplant recipients receiving rabbit anti‐thymocyte globulin induction therapy: A pilot study
Authors: Martín‐Gandul Cecilia , Pérez‐Romero Pilar , Mena‐Romo Damián , Molina‐Ortega Alejandro , González‐Roncero Francisco M. , Suñer Marta , Bernal Gabriel , Cordero Elisa ,   the Spanish Network for Research in Infectious Diseases (REIPI)
Published: March 2018

Background

Some studies have suggested that rATG treatment may be associated with an increased incidence of CMV infection and delayed CMV immune response. However, the evidences supporting this matter are scarce. This study aims to characterize the kinetic of the CMV‐specific T‐cell immune response before and after rATG induction therapy and the relationship with the development of CMV infection in CMV‐seropositive kidney transplant recipients.

Methods

An observational prospective study of CMV‐seropositive kidney transplant patients that received rATG induction therapy was performed. A pretransplant sample was obtained before the surgery to determine the CMV‐specific immunity. CMV viral load (by PCR) and CMV‐specific T‐cell immune response (by flow cytometry) were determined during the follow‐up at 0.5, 1, 2, 3, 6, and 12 months post transplantation.

Results

A total of 23 patients were included in the study. CMV prophylaxis was administrated for a media of 90 days after transplantation. At the end of follow‐up, 18 (78.3%) patients had CMV‐specific immunity with a median value of 0.31% CD8+CD69+INF‐γ+ T cells at a median of 16 weeks post transplantation. Five patients never acquired CMV‐specific immunity. No statistically significant association between CMV infection and CMV‐specific T‐cell immune response (P = .086) was observed. However, patients with positive pretransplant CMV‐specific immunity developed earlier immunity and achieved higher levels of CD8+CD69+INF‐γ+ T‐cell post‐transplantation than patients with negative pretransplant immunity.

Conclusions

CMV‐specific immune monitoring in addition to CMV‐serology may be useful to stratify patient′s risk of CMV infection before transplantation.
A case report of fatal disseminated Mycobacterium colombiense infection in a renal transplant recipient
Authors: Gosal Jasmine , Lee B. Craig
Published: March 2018

We report the first case of disseminated Mycobacterium colombiense infection in a solid organ transplant recipient. Co‐infection with Cryptococcus neoformans led to fatal multisystem organ failure. We review the pathogen and host factors contributing to these opportunistic infections.
The E3 ubiquitin ligase SP1‐like 1 plays a positive role in peroxisome biogenesis in Arabidopsis
Authors: Pan Ronghui , Satkovich John , Chen Cheng , Hu Jianping
Published: March 2018

Peroxisomes are dynamic organelles crucial for a variety of metabolic processes during the development of eukaryotic organisms, and are functionally linked to other subcellular organelles, such as mitochondria and chloroplasts. Peroxisomal matrix proteins are imported by peroxins (PEX proteins), yet the modulation of peroxin functions is poorly understood. We previously reported that, besides its known function in chloroplast protein import, the Arabidopsis E3 ubiquitin ligase SP1 (suppressor of ppi1 locus1) also targets to peroxisomes and mitochondria, and promotes the destabilization of the peroxisomal receptor–cargo docking complex components PEX13 and PEX14. Here we present evidence that in Arabidopsis, SP1's closest homolog SP1‐like 1 (SPL1) plays an opposite role to SP1 in peroxisomes. In contrast to sp1, loss‐of‐function of SPL1 led to reduced peroxisomal β‐oxidation activity, and enhanced the physiological and growth defects of pex14 and pex13 mutants. Transient co‐expression of SPL1 and SP1 promoted each other's destabilization. SPL1 reduced the ability of SP1 to induce PEX13 turnover, and it is the N‐terminus of SP1 and SPL1 that determines whether the protein is able to promote PEX13 turnover. Finally, SPL1 showed prevalent targeting to mitochondria, but rather weak and partial localization to peroxisomes. Our data suggest that these two members of the same E3 protein family utilize distinct mechanisms to modulate peroxisome biogenesis, where SPL1 reduces the function of SP1. Plants and possibly other higher eukaryotes may employ this small family of E3 enzymes to differentially modulate the dynamics of several organelles essential to energy metabolism via the ubiquitin‐proteasome system.
Direct production of dihydroxylated sesquiterpenoids by a maize terpene synthase
Authors: Liang Jin , Liu Jiang , Brown Reid , Jia Meirong , Zhou Ke , Peters Reuben J. , Wang Qiang
Published: March 2018

The astounding structural and biological diversities of the large class of terpenoid natural products are imparted by both their complex hydrocarbon backbones and further elaboration by the addition of multiple hydroxyl groups, which provide both solubility and specific binding properties. While the role of terpene synthases (TPSs) in generating hydrocarbons with complex backbones is well known, these also are known to generate (singly) hydroxylated products by the addition of water prior to terminating deprotonation. Here a maize sesquiterpene synthase was unexpectedly found to generate dually hydroxylated products directly from (E,E)‐farnesyl diphosphate, primarily eudesmane‐2,11‐diol, along with two closely related structural isomers. The unprecedented formation of these diols was proposed to proceed via initial addition of water to a germacradienyl+ intermediate, followed by protonation of the internal carbon‐6,7‐double‐bond in the resulting hedycarol, with subsequent cyclization and further addition of water to an eudesmolyl+ intermediate. Evidence for the proposed mechanism was provided by labeling studies, as well as site‐directed mutagenesis, based on structural modeling, which identified an active site phenylalanine required for the protonation and further elaboration of hedycaryol. This dihydroxylated sesquiterpenoid synthase was specifically expressed in maize roots and induced by pathogen infection, with its major enzymatic product only detected in root exudates or infected roots, suggesting a role in defense. Regardless of the ultimate metabolic fate or physiological role of these diols, this report not only reveals an unanticipated extension of the catalytic prowess of TPSs, but also provides insight into the underlying enzymatic mechanism.
Lotus japonicus NOOT‐BOP‐COCH‐LIKE1 is essential for nodule, nectary, leaf and flower development
Authors: Magne Kévin , George Jeoffrey , Berbel Tornero Ana , Broquet Blandine , Madueño Francisco , Andersen Stig U. , Ratet Pascal
Published: March 2018

The NOOT‐BOP‐COCH‐LIKE (NBCL) genes are orthologs of Arabidopsis thaliana BLADE‐ON‐PETIOLE1/2. The NBCLs are developmental regulators essential for plant shaping, mainly through the regulation of organ boundaries, the promotion of lateral organ differentiation and the acquisition of organ identity. In addition to their roles in leaf, stipule and flower development, NBCLs are required for maintaining the identity of indeterminate nitrogen‐fixing nodules with persistent meristems in legumes. In legumes forming determinate nodules, without persistent meristem, the roles of NBCL genes are not known. We thus investigated the role of Lotus japonicus NOOT‐BOP‐COCH‐LIKE1 (LjNBCL1) in determinate nodule identity and studied its functions in aerial organ development using LORE1 insertional mutants and RNA interference‐mediated silencing approaches. In Lotus, LjNBCL1 is involved in leaf patterning and participates in the regulation of axillary outgrowth. Wild‐type Lotus leaves are composed of five leaflets and possess a pair of nectaries at the leaf axil. Legumes such as pea and Medicago have a pair of stipules, rather than nectaries, at the base of their leaves. In Ljnbcl1, nectary development is abolished, demonstrating that nectaries and stipules share a common evolutionary origin. In addition, ectopic roots arising from nodule vascular meristems and reorganization of the nodule vascular bundle vessels were observed on Ljnbcl1 nodules. This demonstrates that NBCL functions are conserved in both indeterminate and determinate nodules through the maintenance of nodule vascular bundle identity. In contrast to its role in floral patterning described in other plants, LjNBCL1 appears essential for the development of both secondary inflorescence meristem and floral meristem.
Red blood cell alloimmunization in sickle cell disease: assessment of transfusion protocols during two time periods
Authors: Campbell‐Lee Sally A. , Gvozdjan Kristina , Choi K. Mia , Chen Yi‐Fan , Saraf Santosh L. , Hsu Lewis L. , Gordeuk Victor R. , Strauss Ronald G. , Triulzi Darrell J.
Published: March 2018

BACKGROUND

Prevention of red blood cell (RBC) alloimmunization in patients with sickle cell disease (SCD) focuses on phenotypic RBC matching. We assessed alloimmunization among transfused patients with SCD after implementing leukoreduction and prophylactic antigen matching (PAM).

STUDY DESIGN AND METHODS

Retrospective review of transfusion and medical records for SCD patients 18 months to 81 years of age was performed covering two 5‐year periods: Period 1, no PAM, occasional leukoreduction, and Period 2, consistent leukoreduction and extended PAM (Rh, Kell, S, Fy, Jk) for patients already alloimmunized. Patients transfused in Period 1 were excluded from Period 2.

RESULTS

A total of 293 patients were transfused in Period 1 and 183 in Period 2. Median time between first sample and last type and screen after transfusion was 2.12 years in Period 1 and 1.03 years in Period 2. Initial alloimmunization prevalence was lower in Period 2 (26.2%) versus Period 1 (37.5%) and after subsequent transfusions in Period 2 (23.8%) versus Period 1 (45.7%), although without significant difference after adjusting for number of units transfused, percentage of leukoreduced RBCs, sex, and age. Alloimmunized patients received more nonleukoreduced RBCs in Period 1 than nonalloimmunized. Patients transfused during inflammatory conditions were not significantly more likely to become alloimmunized.

CONCLUSIONS

The prevalence of initial and subsequent RBC alloimmunization in Period 2 was lower than that in Period 1; however, overall prevalence remained high. We recommend leukoreduced, hemoglobin S–negative Rh and Kell PAM RBCs for transfusion of patients with SCD. Component and recipient factors affecting alloimmunization should be studied further.
Spillover effects of Germany's final demand on Southern Europe
Authors: Picek Oliver , Schröder Enno
Published: March 2018

We use data from the World Input‐Output Database to fit a closed multiregional input–output model in order to estimate the size of spillover effects of Germany's final demand on GDP, employment and the trade balance in Southern European countries. We find that spillover effects are rather small. Germany alone will hardly make a significant contribution to the external adjustment process in the European South.
Laryngeal mask airway and transient hypercapnic hyperpnea for video‐endoscopic assessment of unilateral laryngeal paralysis in dogs
Authors: Sakai Daniel M. , Martin‐Flores Manuel , Jones Amanda K. , Hayes Galina M. , McConkey Marina J. , Cheetham Jonathan
Published: March 2018

Objective

To evaluate the ability to assess laryngeal function and to diagnose unilateral laryngeal paralysis (uLP) via airway endoscopy and carbon dioxide (CO2) stimulation.

Study design

Experimental study.

Animals

Six healthy, adult beagles.

Methods

Dogs were anesthetized with sevoflurane and dexmedetomidine. Laryngeal activity was observed via endoscopy placed through a laryngeal mask airway (LMA). The absolute and normalized glottic gap areas (AGGA and NGGA, respectively) and the glottic length (GL) were measured at inspiration and before and after surgically induced uLP. Measurements were obtained at eupnea and during hypercapnic hyperpnea produced by the administration of CO2. Values for each hemilarynx were also measured. Video recordings were observed by 2 surgeons who scored function as normal or uLP.

Results

The AGGA and NGGA increased similarly during CO2 administration in intact dogs and in dogs with uLP; the GL increased in dogs with uLP but not in intact dogs. The AGGA and NGGA of the intact hemilarynx increased more than those of the affected hemilarynx in dogs with uLP. uLP was correctly identified more frequently by observers at hypercapnic hyperpnea than during eupnea.

Conclusion

The increase in AGGA and NGGA at peak inspiration during CO2 administration was not limited by uLP, but asymmetry in hemilarynx AGGA and NGGA was observed in dogs with uLP. CO2 administration facilitated the identification of uLP.

Clinical significance

Laryngeal endoscopy through an LMA coupled with administration of CO2 in anesthetized dogs facilitates the observation of arytenoid function and may improve the diagnosis of naturally occurring mild laryngeal paralysis.
Teamwork, Edison Style
Authors: Miller Caldicott Sarah
Published: March 2018

This article discusses Thomas Edison’s concept of teamwork and collaborations. Edison fundamentally viewed collaboration as a connecting force, a transformational force that facilitated and made possible the development of new knowledge. Edison’s innovations were generated through focused approaches to teamwork and collaboration. He viewed collaboration as the beating heart of his laboratories, a sustaining resource that fueled the knowledge assets of his innovation. Edison designed a process of collaboration that was used across his entire enterprise of more than 200 companies worldwide. Because Edison believed that individuals are vital to collaborative success, he placed emphasis on the contributions of each team member as a critical component of the team’s joint efforts. Because he believed that a diverse group of individuals offered the best chance for collaborative success, Edison consistently created teams that had members from several disciplines. The famous group that drove the breakthrough thinking behind the incandescent electric light consisted of a glassblower, a machinist, a chemist, a mathematician, an instrument maker, and a textile worker, along with Edison himself.
Transformed
Authors: Thornton Jack
Published: March 2018

This article describes the shift in manufacturing of transformers in the United States and its benefits. In the wake of the September 11 attacks, the grid’s heavy reliance on imported equipment was seen as vulnerability. The RecX project focused on transportation and speedy installation of a modularized grid transformer rather than grid standardization. Home-based manufacturing of transformers can have major implications for the security and robustness of the grid. Building big transformers in the United States, closer by thousands of miles to installation sites, can simplify and speed up the development of transformers. Shorter distances can also reduce transport time. Large-scale loss of grid transformers is considered a high-impact, low-frequency event. The distant manufacturing sites and long delivery times that so worried government officials in the past have been seen in a new light. They represent an annual replacement market of several hundred massive machines, sufficient to support a major manufacturing expansion in North America.
Flow Assurance
Authors: Kondapi Phaneendra
Published: March 2018

This article explores various aspects of flow assurance in subsea developments. Flow assurance is an understanding of multiphase flow fluid dynamics and analyses, an ability to identify flow-related problems using state-of-the-art prediction tools, and the knowledge to develop solutions that eliminate, mitigate or remediate flow-related issues encountered in subsea systems. Flow assurance is reliable, safe and cost-efficient management of hydrocarbons from reservoir to export without any flow-related issues over the life cycle of the oil field. Subsea developments continue to escalate in quantity and complexity as the exploration and production companies ramp up exploration of deep-water and ultra-deep-water reservoirs with complex formations in harsh environments with increased challenges. Some of the technologies under thermal solutions are thermal insulation, direct electric heating and electrically-heated pipe-in-pipe. Oil and gas companies generate revenue from the oil produced. If the oil flow stops, their revenue stops. The more it stops the more they lose cash. Hence it can be termed as cash flow assurance. With fluctuating oil prices and unpredictable production issues, engaging flow assurance at every stage starting with the early phase ensures uninterrupted transportation of reservoir fluid from pore to process facilities in a safe manner and insures cash flow.
The Secret Life of the Spine
Authors: Marras William S.
Published: March 2018

This article focuses on research developments by engineers in developing spine models that can prove to be of great use in the medical industry. Using a combination of force monitors and optical sensors to track position, researchers can find links between body position and spinal loading. Detailed spinal models enable researchers to visualize the loads placed on individual spines. Spine models are expected to become important tools for surgeons. Spinal models can provide that type of information. We can individualize them by modifying our general models with information about individuals captured by video analysis and gathered from MRI and CT scans. These models generate animations that show how the spine reacts to force as it moves in space. They highlight where – and why – discs bulge and shifting sections of the vertebrae impinge on nerves. They automatically pinpoint structural overloads.
Summary of the Next Wave of Technology
Authors: Tesar D.
Published: March 2018

This article is a summary of a paper named Next Wave of Technology produced by D. Tesar. The urgent need is to create a balance of all supporting technologies required in electro-mechanical systems, especially those of high economic magnitude. The desired tech base is described in terms of 10 major topics that have been summarized here to indicate its relevance to meeting the needs of mankind, to its potential to reinforce our national security, and to augment our consumer product competitive position. All future machine systems will increasingly be highly nonlinear, reconfigurable to meet changing needs, and architecturally a mixture of serial/parallel control structures. This means that the influence of any one-control input (an actuator) faces an ever changeable physical plant. This complexity can now be addressed by using very low-cost/distributed sensors providing operational data to a criteria-based decision structure with a full evaluation of the system in 5 to 10 milli-sec. A computational revolution for decision-making is now feasible because of accelerating computer technology. This revolution will be based on the geometry of the decision process.
PALS - An Auspicious New Gas Turbine Seal
Authors: Langston Lee S.
Published: March 2018

This article highlights various aspects of a new gas turbine shaft seal called the pressure activated leaf seal (PALS). The paper in detail discusses the architecture and working of a gas turbine seal. PALS is designed to use changing pressure drop forces across the seal to eliminate rub. The seal elements stay clear of the rotor seal surface during start-up and shutdown transients, and subsequently close to a small, non-contacting, steady-state running clearance. During start-up or shutdown, when the axial pressure difference across PALS is small, the leaves are in a relaxed open position, providing a general clearance gap for possible rotor seal surface eccentricities. At operating speeds, the resulting axial pressure difference causes the leaf element to elastically deflect and close, reaching the design clearance when they contact the support member. The test results show that the PALS concept provides for a potentially viable, robust, low leakage seal for gas turbine applications.
A Control-Oriented Model for Trajectory-Based HCCI Combustion Control
Authors: Zhang Chen , Sun Zongxuan
Published: March 2018

Previously, the authors have proposed the concept of piston trajectory-based homogeneous charge compression ignition (HCCI) combustion control enabled by a free piston engine (FPE) and shown its benefits on both engine thermal efficiency and emissions by implementing various piston trajectories. In order to realize the HCCI trajectory-based combustion control in practical applications, a control-oriented model with sufficient chemical kinetics information has to be developed. In this paper, such a model is proposed and its performance, in terms of computational speed and model fidelity, is compared to three existing models: a simplified model using a one-step global reaction, a reduced-order model using Jones–Lindstedt mechanism, and a complex physics-based model including detailed chemical reaction mechanisms. A unique phase separation method is proposed to significantly reduce the computational time and guarantee the prediction accuracy simultaneously. In addition, the paper also shows that the high fidelity of the proposed model is sustained at multiple working conditions, including different air-fuel ratios (AFR), various compression ratios (CR), and distinct piston motion patterns between the two end positions. Finally, an example is presented showing how the control-oriented model enables real-time optimization of the HCCI combustion phasing by varying the trajectories. The simulation results show that the combustion phasing can be adjusted quickly as desired, which further demonstrates the effectiveness of the piston trajectory-based combustion control.
Design of Active Magnetic Bearing Controllers for Rotors Subjected to Gas Seal Forces
Authors: Lauridsen Jonas S. , Santos Ilmar F.
Published: March 2018

Proper design of feedback controllers is crucial for ensuring high performance of active magnetic bearing (AMB) supported rotor dynamic systems. Annular seals in those systems can contribute significant forces, which, in many cases, are hard to model in advance due to complex geometries of the seal and multiphase fluids. Hence, it can be challenging to design AMB controllers that will guarantee robust performance for these kinds of systems. This paper demonstrates the design, simulation, and experimental results of model-based controllers for AMB systems, subjected to dynamic seal forces. The controllers are found using H∞ and μ synthesis and are based on a global rotor dynamic model in which the seal coefficients are identified in situ. The controllers are implemented in a rotor-dynamic test facility with two radial AMBs and one annular seal with an adjustable inlet pressure. The seal is a smooth annular type, with large clearance (worn seal) and with high preswirl, which generates significant cross-coupled forces. The H∞ controller is designed to compensate for the seal forces and the μ controller is furthermore designed to be robust against a range of pressures across the seal. In this study, the rotor is nonrotating. Experimental and simulation results show that significant performance can be achieved using the model-based controllers compared to a reference decentralized proportional-integral-derivative (PID) controller and robustness against large variations of pressure across the seal can be improved by the use of robust synthesized controllers.
Consensus and Flocking With Connectivity Preservation of Uncertain Euler–Lagrange Multi-Agent Systems
Authors: Dong Yi , Huang Jie
Published: March 2018

The consensus problem for multiple Euler–Lagrange systems has been extensively studied under various assumptions on the connectivity of the communication graph. In practice, it is desirable to enable the control law the capability of maintaining the connectivity of the communication graph, thus achieving consensus without assuming the connectivity of the communication graph. We call such a problem as consensus with connectivity preservation. In this paper, we will study this problem for multiple uncertain Euler–Lagrange systems. By combining the adaptive control technique and potential function technique, we will show that such a problem is solvable under a set of standard assumptions. By employing different potential functions, our approach will also lead to the solution of such problems as rendezvous and flocking.
Influence
of the Musculotendon Dynamics on the Muscle Force-Sharing Problem of the Shoulder—A Fully Inverse
Dynamics Approach
Authors: Carlos Quental , Margarida Azevedo , Jorge Ambrósio , S. B. Gonçalves , João Folgado
Published: March 2018

Most dynamic simulations are based on inverse dynamics, being the time-dependent physiological nature of the muscle properties rarely considered due to numerical challenges. Since the influence of muscle physiology on the consistency of inverse dynamics simulations remains unclear, the purpose of the present study is to evaluate the computational efficiency and biological validity of four musculotendon models that differ in the simulation of the muscle activation and contraction dynamics. Inverse dynamic analyses are performed using a spatial musculoskeletal model of the upper limb. The muscle force-sharing problem is solved for five repetitions of unloaded and loaded motions of shoulder abduction and shoulder flexion. The performance of the musculotendon models is evaluated by comparing muscle activation predictions with electromyography (EMG) signals, measured synchronously with motion for 11 muscles, and the glenohumeral joint reaction forces estimated numerically with those measured in vivo. The results show similar muscle activations for all muscle models. Overall, high cross-correlations are computed between muscle activations and the EMG signals measured for all movements analyzed, which provides confidence in the results. The glenohumeral joint reaction forces estimated compare well with those measured in vivo, but the influence of the muscle dynamics is found to be negligible. In conclusion, for slow-speed, standard movements of the upper limb, as those studied here, the activation and musculotendon contraction dynamics can be neglected in inverse dynamic analyses without compromising the prediction of muscle and joint reaction forces.
A Pressure-Base One-Fluid Compressible Formulation for High Speed Two-Phase Flows With Heat and Mass Transfer
Authors: Luo Yan , Zhou Jianqiu , Yang Xia , Jiang Zhanxiang
Published: March 2018

This paper presents a numerical method for high-speed compressible cavitating flows. The method is derived from one-fluid formulation in a sense that the two phases are well mixed and the mixture is considered as a locally homogeneous media. Energy equation is solved to predict the temperature evolution which is then used together with pressure to update the density field. A volume of fluid (VOF) phase-fraction based interface capturing approach is used to capture the phase front between the two immiscible fluids. The derived formulations have been implemented into a pressure-based, segregated algebraic semi-implicit compressible solver in Openfoam, which can be used to solve for high-speed compressible two-phase flows involving phase changing. Numerical examples include the cavitating flows induced by an ultrasonic oscillating horn with and without a counter sample. The numerical results by the proposed method are validated against the published experimental data as well as numerical results and good agreements have been obtained. Our calculation demonstrates that the proposed numerical method is applicable to the study of high-speed two phase flows with phase transition and wave propagation, such as shock waves induced by the collapse of the cavitation bubbles.
Semi-Infinite Solid Solution Adjusted for Radial Systems Using Time-Dependent Participating Volume-to-Surface Ratio and Simplified Solutions for Finite Solids
Authors: Ostrogorsky Aleksandar G. , Mikic Borivoje B.
Published: March 2018

Time-dependent participating volume-to-surface ratio, V(t)/A, is used to adjust the semi-infinite (SI) solid solutions to the radial systems. In cylinders and spheres, the present “radial” SI sold model extends the domain of the planar model from δ ≪ R to δ ≈ R (δ is transient penetration depth and R is radius). The corresponding increase in the time span is from 0 < Fo < 0.01 to 0 < Fo < 0.06). The erfc series solution for finite solids (FS), which converges rapidly at small values of time, is simplified, by truncating the first term of the solution. For cylinders and spheres, the resulting half-term approximations are far more precise than the planar SI solid solutions.
Effect of Severe Plastic Deformation by 120 deg ECAP or Shock Impact on 6061 Aluminum Alloy at High Strain Rates
Authors: Camalet T. , Rusinek A. , Bernier R. , Karon M. , Massion R. , Voyiadjis G. Z. , Adamiak M.
Published: March 2018

The aim of this paper is to analyze the macroscopic behavior of an aluminum alloy after severe plastic deformations (SPD). Samples of 6061 aluminum alloy are processed at room temperature by two techniques of SPD: equal channel angular pressing (ECAP) under quasi-static loading and impact under dynamic loading, using Taylor's test setup. In addition to the mechanical properties, the microstructure evolution of the material is investigated. Half of the samples are aged at 400 °C for 2 h, to remove internal stress in a commercial alloy in order to increase workability of the material. The evolution of the properties and the material behavior after 2, 4, 6, and 8 passes of the 120 deg ECAP process is investigated.
A New Seven Degrees-of-Freedom Parallel Robot With a Foldable Platform
Authors: Haouas Wissem , Dahmouche Redwan , Le Fort-Piat Nadine , Laurent Guillaume J.
Published: March 2018

This paper presents a new parallel robot with an integrated gripper. The grasping capability of the robot is obtained by a foldable platform that can be fully controlled by actuators located on the base of the seven degrees-of-freedom (DoF) parallel structure. This mechanism combines three key specificities in robotics which are compactness, rigidity, and high blocking forces. The paper presents the new structure, its kinematic modeling, and an analysis of its workspace and grasping force capabilities. In addition, a prototype is presented and tested in manipulation and insertion operations, which validates the proposed concept.
Prediction of the Rupture Pressure of Transmission Pipelines With Corrosion Defects
Authors: Abdelghani Mechri , Tewfik Ghomari , Djahida Djouadi , Sid Ahmed Sfiat
Published: March 2018

This paper investigates the rupture of thin-walled ductile cylinders with isolated corrosion defects, subject only to internal pressure. It aims to propose a new solution for predicting the maximum load limit that will rupture a corroded pipeline, regardless of its material, its geometric ratio, or the dimensions of the existing corrosion defect. This solution is the result of several numerical simulations by variation of the length and depth of the defect with the assumption that the width of the defect has a negligible marginal effect. In all our numerical simulation analyses, the rupture was controlled by the Tresca failure criterion which is expressed in terms of material hardening exponent and the ultimate material stress. The proposed solution was then compared with the currently used coded methods, first B31.G, its improved version 0.85dL, and then DNV-RP F101, using an experimental database compiled from the existing literature. As a result, our proposed solution has been validated and has resulted in rupture ratios ranging from approximately 0.7 to 1. Furthermore, it has a tight prediction range compared to the B31.G, 0.85dL, and the DNV-RP F101 methods.
Thermal Stability Experimental Study on Three Types of Organic Binary Phase Change Materials Applied in Thermal Energy Storage System
Authors: Mengjie Song , Liyuan Liao , Fuxin Niu , Ning Mao , Shengchun Liu , Yanxin Hu
Published: March 2018

Phase change materials (PCMs) are widely applied in recent decades due to their good thermal performance in energy systems. Their applications are mainly limited by the phase change temperature and latent heat. Many publications are reported around the characteristic improvement of binary organic PCMs. The thermal stability study on organic binary PCMs used in thermal energy storage applications becomes fundamental and meaningful. In this study, thermal stability of three types of organic binary PCMs was experimentally investigated, which are frequently used in building and industry applications. To qualitatively investigate the stability of composite PCMs, differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FT-IR) spectra testing of samples were also conducted. Experimental results showed that the selected composite PCMs, capric acid (CA), and myristic acid (MA), had the best thermal performances, with its phase change temperature unchanged and heat of fusion decreased only 8.88 J/g, or 4.55%, after 2000 thermal cycles. Furthermore, quality ratio of required PCMs as the variation of operation duration was analyzed to quantitatively prepare the materials. The PCMs can successfully operate about 3125 times when prepared as 1.20 times of its calculated value by starting fusion heat. Conclusions of this research work can also be used for guiding the selection and preparation of other energy storage materials.
Comparison of Piston Concept Design Solutions for Composite Cycle Engines—Part I: Similarity Considerations
Authors: Chatzianagnostou Dimitrios , Staudacher Stephan
Published: March 2018

Composite cycle engines comprising piston engines (PEs) as well as piston compressors (PCs) to achieve hecto pressure ratios represent a target area of current research surpassing gas turbine efficiency. An unclear broad range of design parameters is existing to describe the design space of piston machines for this type of engine architecture. Previously published work focuses on thermodynamic studies only partially considering limitations of the design space. To untie the problem of PE design, a dimensional analysis is carried out reducing the number of parameters and deriving two basic similarity relations. The first one is a function of the mean effective pressure as well as the operating mode and is a direct result from the thermodynamic cycle. The second one is constituted of the stroke-to-bore ratio and the ratio of effective power to piston surface. Similarity relations regarding the PC design are based on Grabow (1993, “Das erweiterte “Cordier”—Diagramm Für Fluidenergiemaschinen und Verbrennungsmotoren,” Forsch. Ingenieurwes., 59, pp. 42–50). A further correlation for PCs is based on the specific compression work and the piston speed. In Part I, data of existing PEs have been subjected to the above similarity parameters unveiling the state-of-the-art design space. This allows a first discussion of current technological constraints. Applying this result to the composite cycle engine gives the design space and a first classification as a low-speed engine. Investigating various design points in terms of number and displacement volume of cylinders confirms the engine speed classification. Part II will expand this investigation using preliminary design studies.
Experimental Performance of a Completely Passive Thermosyphon Cooling System Rejecting Heat by Natural Convection Using the Working Fluids R1234ze, R1234yf, and R134a
Authors: Cataldo Filippo , Thome John Richard
Published: March 2018

The present paper proposes a proof of concept of a completely passive thermosyphon for cooling of power electronics. This thermosyphon is composed of an evaporator to cool down a four-heater pseudo-transistor module and a natural air-cooled condenser to reject the heat into the environment. R1234ze, R1234yf, and R134a are used as the working fluids with charges of 524, 517, and 566 g, respectively, for the low charge tests, and 720, 695, and 715 g for the high charge tests. It has been demonstrated that the refrigerant R1234ze with a low charge is not a good solution for the cooling system proposed here since low evaporator performance and fluid instability have been detected at moderate heat fluxes. In fact, R1234ze needed a larger charge of refrigerant to be safely used, reaching a transistor temperature of 53 °C at a heat load of 65 W. R1234yf and R134a, on the other hand, showed good results for both the low and the high charge cases. The maximum temperatures measured, respectively, were 52 °C and 48 °C at 65 W for the low charge case and 55 °C and 47 °C at 62 W for the high charge case. The corresponding values of overall thermal resistances of the thermosyphon for the working fluids R1234yf and R134a at the maximum heat load are very similar, being in the range of 0.44−0.46 K/W.
Effects of Stall Precursor-Suppressed Casing Treatment on a Low-Speed Compressor With Swirl Distortion
Authors: Dong Xu , Sun Dakun , Li Fanyu , Jin Donghai , Gui Xingmin , Sun Xiaofeng
Published: March 2018

Swirl inlet distortion is usually encountered in modern flight vehicles since their inlet ducts usually consist of one or two bends, such as S-inlet duct. An experimental device is first designed to simulate the swirl inlet distortion and then used to test the effectiveness of a novel casing treatment (CT) on a low-speed compressor under the swirl distortions of various intensities. The influences of co- and counter-rotating swirl inlet distortion on the test compressor and the stabilization ability of this novel CT are well demonstrated by the illustrations of static pressure rise curves and efficiency curves. The dynamic prestall pressure signals are also captured to reflect the perturbation energy in the flow field through which the mechanism of the novel CT will be indicated. The relevant results show that counter-rotating swirl distortion in small intensity could increase the compressive ability of compressor with small efficiency loss, and the co-rotating swirl distortion always brings about detrimental effects on compressor performance. At the same time, the distortion of twin swirls can cause nonuniform total pressure profile which can seriously damage the compressor performance. Besides, the stall precursor-suppressed (SPS) CT shows a good capability of stall margin (SM) enhancement no matter what swirl inlet distortions are encountered in the test compressor.