bluuebunny/crossref_metadata_2025 huggingface dataset:
Early succession of micro‐periphyton communities in kelp bed and barren ground ecological systems
Authors: Uribe Roberto A. , Ortiz Marco , Pacheco Aldo S. , Araya Rubén
Published: December 2014

In shallow sublittoral rocky habitats of the Southeast Pacific, two conspicuous ecological systems exist; kelp beds dominated by large Laminariales algae, and barren grounds dominated by crustose coralline algae and sea urchins. The aim of this study was to examine the successional development of micro‐periphyton communities in both ecological systems using a colonization experiment conducted in Northern Chile. In both ecological systems, we installed replicated ceramic plates at 10 m depth and samples were taken after 1, 2, 4, 6, 8 and 14 days of exposure. Bacteria, diatoms, protozoans and small eukaryotes were identified, quantified and analysed. The succession of micro‐periphyton communities in both ecological systems followed a common pattern consisting of a net accumulation of functional groups and taxa over time; however, the total density of all groups was significantly higher in the kelp beds. In addition, the community structure of the developing micro‐periphytons was different and specific for each ecological system. Although previous studies have suggested that kelp beds and barren grounds are capable of switching from one state to the other without substantial changes in biodiversity, our results show that each of these ecological systems promotes its own successional development, suggesting that they are unique, self‐organized entities. This study is the first step towards an understanding of these ecological systems operating independently at this scale of organization.
The formation and alteration of the Renazzo‐like carbonaceous chondrites III: Toward understanding the genesis of ferromagnesian chondrules
Authors: Schrader Devin L. , Connolly Harold C. , Lauretta Dante S. , Zega Thomas J. , Davidson Jemma , Domanik Kenneth J.
Published: December 2014

To better understand the formation conditions of ferromagnesian chondrules from the Renazzo‐like carbonaceous (CR) chondrites, a systematic study of 210 chondrules from 15 CR chondrites was conducted. The texture and composition of silicate and opaque minerals from each observed FeO‐rich (type II) chondrule, and a representative number of FeO‐poor (type I) chondrules, were studied to build a substantial and self‐consistent data set. The average abundances and standard deviations of Cr2O3 in FeO‐rich olivine phenocrysts are consistent with previous work that the CR chondrites are among the least thermally altered samples from the early solar system. Type II chondrules from the CR chondrites formed under highly variable conditions (e.g., precursor composition, redox conditions, cooling rate), with each chondrule recording a distinct igneous history. The opaque minerals within type II chondrules are consistent with formation during chondrule melting and cooling, starting as S‐ and Ni‐rich liquids at 988–1350 °C, then cooling to form monosulfide solid solution (mss) that crystallized around olivine/pyroxene phenocrysts. During cooling, Fe,Ni‐metal crystallized from the S‐ and Ni‐rich liquid, and upon further cooling mss decomposed into pentlandite and pyrrhotite, with pentlandite exsolving from mss at 400–600 °C. The composition, texture, and inferred formation temperature of pentlandite within chondrules studied here is inconsistent with formation via aqueous alteration. However, some opaque minerals (Fe,Ni‐metal versus magnetite and panethite) present in type II chondrules are a proxy for the degree of whole‐rock aqueous alteration. The texture and composition of sulfide‐bearing opaque minerals in Graves Nunataks 06100 and Grosvenor Mountains 03116 suggest that they are the most thermally altered CR chondrites.
Virulence and in planta movement of Xanthomonas hortorum pv. pelargonii are affected by the diffusible signal factor (DSF)‐dependent quorum sensing system
Authors: Barel Victoria , Chalupowicz Laura , Barash Isaac , Sharabani Galit , Reuven Michal , Dror Orit , Burdman Saul , Manulis‐Sasson Shulamit
Published: December 2014

Xanthomonas hortorum pv. pelargonii (Xhp), the causal agent of bacterial blight in pelargonium, is the most threatening bacterial disease of this ornamental worldwide. To gain an insight into the regulation of virulence in Xhp, we have disrupted the quorum sensing (QS) genes, which mediate the biosynthesis and sensing of the diffusible signal factor (DSF). Mutations in rpfF (encoding the DSF synthase) and rpfC (encoding the histidine sensor kinase of the two‐component system RfpC/RpfG) and overexpression of rpfF showed a significant reduction in incidence and severity of the disease on pelargonium. Confocal laser scanning microscopy images of inoculated plants with a green fluorescent protein (GFP)‐labelled wild‐type strain showed that the pathogen is homogeneously dispersed in the lumen of xylem vessels, reaching the apex and invading the intercellular spaces of the leaf mesophyll tissue within 21 days. In contrast, the rpfF and rpfC knockout mutants, as well as the rpfF‐overexpressing strain, remained confined to the vicinity of the inoculation site. The rpfF and rpfC mutants formed large incoherent aggregates in the xylem vessels that might interfere with upward movement of the bacterium within the plant. Both mutants also formed extended aggregates under in vitro conditions, whereas the wild‐type strain formed microcolonies. Expression levels of putative virulence genes in planta were substantially reduced within 48 h after inoculation with the QS mutants when compared with the wild‐type. The results presented indicate that an optimal DSF concentration is crucial for successful colonization and virulence of Xhp in pelargonium.
Potential role of ATP‐binding cassette transporters against acaricides in the brown dog tick Rhipicephalus sanguineus sensu lato
Authors: CAFARCHIA C. , PORRETTA D. , MASTRANTONIO V. , EPIS S. , SASSERA D. , IATTA R. , IMMEDIATO D. , RAMOS R. A. N. , LIA R. P. , DANTAS‐TORRES F. , KRAMER L. , URBANELLI S. , OTRANTO D.
Published: December 2014

ATP‐binding cassette (ABC) transporters have been shown to be involved in pesticide detoxification in arthropod vectors and are thought to contribute to the development of drug resistance. Little is currently known about the role they play in ticks, which are among the more important vectors of human and animal pathogens. Here, the role of ABC transporters in the transport of fipronil and ivermectin acaricides in the tick Rhipicephalus sanguineus (Ixodida: Ixodidae) was investigated. Larvae were treated with acaricide alone and acaricide in combination with a sub‐lethal dose of the ABC transporter inhibitor cyclosporine A. The LC50 doses and 95% confidence intervals (CIs) estimated by mortality data using probit analysis were 67.930 p.p.m. (95% CI 53.780–90.861) for fipronil and 3741 p.p.m. (95% CI 2857–4647) for ivermectin. The pre‐exposure of larvae to a sub‐lethal dose of cyclosporine A reduced the LC50 dose of fipronil to 4.808 p.p.m. (95% CI 0.715–9.527) and that of ivermectin to 167 p.p.m. (95% CI 15–449), which increased toxicity by about 14‐ and 22‐fold, respectively. The comparison of mortality data for each separate acaricide concentration showed the synergic effect of cyclosporine A to be reduced at higher concentrations of acaricide. These results show for the first time a strong association between ABC transporters and acaricide detoxification in R.sanguineus s.l.
Zonisamide in the early stage of Parkinson's disease
Authors: Maeda Tetsuya , Takano Daiki , Yamazaki Takashi , Satoh Yuichi , Nagata Ken
Published: December 2014

Background

Zonisamide is one of the anti‐parkinsonian agents approved and used in Japan, and it improves motor symptoms and off time in the advanced stage of Parkinson's disease. However, there is no evidence of its efficacy in the early stage of Parkinson's disease.

Aim

To investigate the effect of zonisamide on the early stage of Parkinson's disease.

Methods

We consecutively recruited patients with less than 3 years of disease duration who were treated with levodopa/dopa decarboxylase inhibitor only or additional small amounts of dopamine agonists. We evaluated motor severities with the Unified Parkinson's Disease Rating Scale, non‐motor severities with the Non‐Motor Symptom scale and health‐related quality of daily life with the 39 items of the Parkinson's Disease Questionnaire. Patients also evaluated themselves with the Patient Global Impression of Improvement index. Serum zonisamide levels were monitored throughout the study. After the baseline clinical evaluation, patients received 25 mg of open‐label zonisamide, and were evaluated for 28 weeks.

Results

We recruited 13 patients, and 11 patients completed the study. Adjunctive zonisamide significantly improved the Unified Parkinson's Disease Rating Scale part III score and Patient Global Impression of Improvement after the 12th week. The Non‐Motor Symptom Scale and summary index of the 39‐item Parkinson's Disease Questionnaire showed no significant changes. Mean plasma levels of zonisamide were stable throughout the study. Two patients could not complete because of adverse events.

Conclusions

Zonisamide can be expected to be safe and beneficial to motor symptoms of Parkinson's disease in the early stage as well as the advanced stage.
Testing a mechanistic dispersal model against a dispersal experiment with a wind‐dispersed moss
Authors: Lönnell Niklas , Norros Veera , Sundberg Sebastian , Rannik Üllar , Johansson Victor , Ovaskainen Otso , Hylander Kristoffer
Published: December 2014

Wind is the main dispersal agent for a wide array of species and for these species the environmental conditions under which diaspores are released can potentially modify the dispersal kernel substantially. Little is known about how bryophytes regulate spore release, but conditions affecting peristome movements and vibration of the seta may be important. We modelled airborne spore dispersal of the bryophyte species Discelium nudum (spore diameter 25 μm), in four different release scenarios, using a Lagrangian stochastic dispersion model and meteorological data. We tested the model predictions against experimental data on colonization success at five distances (5, 10, 30, 50 and 100 m) and eight directions from a translocated point source during seven two‐day periods. The model predictions were generally successful in describing the observed colonization patterns, especially beyond 10 m. In the laboratory we established spore release thresholds; horizontal wind speed sd > 0.25 m s−1 induced the seta to vibrate and in relative humidity < 75% the peristome was open. Our dispersal model predicts that the proportion of spores dispersing beyond 100 m is almost twice as large if the spores are released under turbulent conditions than under more stable conditions. However, including release thresholds improved the fit of the model to the colonization data only minimally, with roughly the same amount of variation explained by the most constrained scenario (assuming both vibration of the seta and an open peristome) and the scenario assuming random release. Model predictions under realised experimental conditions suggest that we had a low statistical power to rank the release scenarios due to the lack of measurements of the absolute rate of spore release. Our results hint at the importance of release conditions, but also highlight the challenges in dispersal experiments intended for validating mechanistic dispersal models.
An Innovative Oat‐Based Sterile Emollient Cream in the Maintenance Therapy of Childhood Atopic Dermatitis
Authors: Mengeaud Valerie , Phulpin Chloe , Bacquey Adeline , Boralevi Franck , Schmitt Anne‐Marie , Taieb Alain
Published: December 2014

Although emollients are recommended in the management of atopic dermatitis (AD), regimens for emollient maintenance therapy are awaiting validation. We conducted an international, multicenter, open‐label trial to assess the effects of a 3‐month maintenance treatment regimen with a sterile, preservative‐free emollient cream containing oat plantlets in children (ages 6 mos–6 yrs) with moderate AD. After a 14‐day run‐in stabilization phase using a topical corticosteroid (TCS) treatment of medium potency, 108 children with a SCORing Atopic Dermatitis (SCORAD) index of 20 or less were included in the study. Emollient was applied twice daily for 3 months. Rescue TCS treatment was used only in cases of flare‐ups. The SCORAD index, Patient‐Oriented SCORAD (PO‐SCORAD) index, number of flares, TCS use, and tolerance were assessed at months 1, 2, and 3 (M1, M2, M3). AD severity improved, with a highly significant decrease in the SCORAD and PO‐SCORAD indexes at M2 and M3 (p < 0.001). Changes from baseline to M3 were 48.6 ± 73.6% for SCORAD and 29.6 ± 125.3% for PO‐SCORAD. The number of flares and TCS use significantly decreased by M3 (both p < 0.001). Very good tolerance was recorded in 100% of children at M2 and M3. Notwithstanding the limitations inherent in open‐label trials, twice daily application of the oat‐based sterile emollient cream led to a significant improvement of clinical symptoms, evidenced by parallel changes in the SCORAD and PO‐SCORAD indexes and fewer flare‐ups. Clinical benefit and less TCS use were maintained at M3. Tolerance was very good.
Ovarian Follicular Activity During Late Gestation and Postpartum in Guanaco (Lama guanicoe)
Authors: Riveros JL , Schuler G , Urquieta B , Hoffmann B , Bonacic C
Published: December 2014

Contents

This study evaluated ovarian activity in late gestation and post‐partum in guanacos in captivity. Follicular dynamics was monitored every second day from 40 days before and other 40 after delivery by transrectal sonography and by plasma steroids concentrations. Seven out of eight (87.5%) of gestating females presented ovarian follicular activity under progesterone levels >3 nmol/l with maximum follicular size of 8.42 ± 0.83 mm from days 23 to 1 before delivery. After delivery, all females have follicular wave development from day 0 to 38, with larger follicular size and longer follicular wave phases and interwave interval when compared with pre‐partum data. During post‐partum period, there was a close relationship between follicle size and estradiol‐17β concentration, with r = 0.69 at the beginning of growth phase and r = 0.86 in association with the largest dominant follicle. Plasma estradiol‐17β concentration varied from 11.92 to 198.55 pmol/l. Plasma estrone sulfate, free estrone and progesterone returned to baseline concentrations during peripartal period and remained basal thereafter. The results described follicular activity during late gestation and early post‐partum period. These findings provide relevant information to understand physiological changes occurring during this reproductive key period in seasonal breeders with long gestation duration as New and Old World camelids.
Clarifying the Relationship of Parental Bonding to Suicide Ideation and Attempts
Authors: Saffer Boaz Y. , Glenn Catherine R. , David Klonsky E.
Published: December 2014

Suicide and suicidal behavior are major public health problems, especially among adolescents and young adults. Previous research has established links between parental bonding and suicidality; however, it remains unclear whether parental bonding is associated with suicide ideation, the progression from suicide ideation to suicide attempts, or both. This study examined the relation of parental bonding to suicide ideation and suicide attempts in adolescents from two settings: (1) acute psychiatric care (n = 172) and (2) high school (n = 426). All participants were administered validated measures of parental bonding, suicide ideation, and suicide attempts, as well as emotion dysregulation, loneliness, and self‐worth. In the psychiatric sample, lower parental care significantly differentiated adolescents with a history of suicide attempts from those with suicide ideation only or without histories of suicidality. This pattern remained even after controlling for other known correlates of suicidality (i.e., emotional dysregulation, loneliness, and low self‐worth). Similar effects were found in the community sample, although these findings failed to reach statistical significance. In both samples, parental overprotection was not associated with suicide ideation or suicide attempts. Results suggest that parental care may be an important risk factor for youth suicidal behavior and may help differentiate suicide attempters from suicide ideators.
Cognitive, Cultural, and Linguistic Sources of a Handshape Distinction Expressing Agentivity
Authors: Brentari Diane , Renzo Alessio Di , Keane Jonathan , Volterra Virginia
Published: December 2014

In this paper the cognitive, cultural, and linguistic bases for a pattern of conventionalization of two types of iconic handshapes are described. Work on sign languages has shown that handling handshapes (H‐HSs: those that represent how objects are handled or manipulated) and object handshapes (O‐HSs: those that represent the class, size, or shape of objects) express an agentive/non‐agentive semantic distinction in many sign languages. H‐HSs are used in agentive event descriptions and O‐HSs are used in non‐agentive event descriptions. In this work, American Sign Language (ASL) and Italian Sign Language (LIS) productions are compared (adults and children) as well as the corresponding groups of gesturers in each country using “silent gesture.” While the gesture groups, in general, did not employ an H‐HS/O‐HS distinction, all participants (signers and gesturers) used iconic handshapes (H‐HSs and O‐HSs together) more often in agentive than in no‐agent event descriptions; moreover, none of the subjects produced an opposite pattern than the expected one (i.e., H‐HSs associated with no‐agent descriptions and O‐HSs associated with agentive ones). These effects are argued to be grounded in cognition. In addition, some individual gesturers were observed to produce the H‐HS/O‐HS opposition for agentive and non‐agentive event descriptions—that is, more Italian than American adult gesturers. This effect is argued to be grounded in culture. Finally, the agentive/non‐agentive handshape opposition is confirmed for signers of ASL and LIS, but previously unreported cross‐linguistic differences were also found across both adult and child sign groups. It is, therefore, concluded that cognitive, cultural, and linguistic factors contribute to the conventionalization of this distinction of handshape type.
The family of K2P channels: salient structural and functional properties
Authors: Feliciangeli Sylvain , Chatelain Frank C. , Bichet Delphine , Lesage Florian
Published: December 2014

Potassium channels participate in many biological functions, from ion homeostasis to generation and modulation of the electrical membrane potential. They are involved in a large variety of diseases. In the human genome, 15 genes code for K+ channels with two pore domains (K2P). These channels form dimers of pore‐forming subunits that produce background conductances finely regulated by a range of natural and chemical effectors, including signalling lipids, temperature, pressure, pH, antidepressants and volatile anaesthetics. Since the cloning of TWIK1, the prototypical member of this family, a lot of work has been carried out on their structure and biology. These studies are still in progress, but data gathered so far show that K2P channels are central players in many processes, including ion homeostasis, hormone secretion, cell development and excitability. A growing number of studies underline their implication in physiopathological mechanisms, such as vascular and pulmonary hypertension, cardiac arrhythmias, nociception, neuroprotection and depression. This review gives a synthetic view of the most noticeable features of these channels.
Effect of Rate on Pulsed Laser Deposition of Yttria-Stabilized Zirconia Electrolyte Thin Films for SOFCs
Authors: Mukai T. , Fujita T. , Tsukui S. , Yoshida K. , Adachi M. , Goretta K. C.
Published: December 2014

Yttria-stabilized zirconia (YSZ) thin films were deposited by pulsed laser deposition (PLD) at laser repetition frequencies of 10–50 Hz. Controlling the laser repetition frequency can achieve high deposition rate of YSZ, but high deposition rate at high laser repetition frequency can adversely affect the crystallinity of the resulting film. In the present work, X-ray diffraction (XRD) of YSZ thin films deposited at 10–50 Hz unexpectedly indicated no significant differences. Well-crystallized YSZ thin films were obtained for all laser repetition frequencies. This result may be due to a sufficient substrate temperature of 1000 K during processing. The oxide-ion conductivity of each thin film was comparable to that of bulk YSZ. Only minor differences in Y2O3 content, residual stress, grain size, and grain-boundary width were observed among the films. We concluded that similar quality YSZ thin films were obtained at all deposition frequencies. Oxide-ion conductivity was affected by the temperature at which the substrate was deposited. The YSZ thin films deposited at 900 K and 1000 K showed similar oxide-ion conductivity and films deposited at 800 K showed lower oxide-ion conductivity. This difference could perhaps be due to narrow grain-boundary width. The YSZ thin film with highest oxide-ion conductivity was fabricated at an intermediate substrate temperature of 900 K with a deposition rate of 86 nm·min−1 at 50 Hz, without additional high-temperature annealing greater than 1273 K. The YSZ growth rates were faster than the rates for other gas-phase methods such as midfrequency and DC sputtering.
Simulations Reveal Adverse Hemodynamics in Patients With Multiple Systemic to Pulmonary Shunts
Authors: Esmaily-Moghadam Mahdi , Murtuza Bari , Hsia Tain-Yen , Marsden Alison
Published: December 2014

For newborns diagnosed with pulmonary atresia or severe pulmonary stenosis leading to insufficient pulmonary blood flow, cyanosis can be mitigated with placement of a modified Blalock–Taussig shunt (MBTS) between the innominate and pulmonary arteries. In some clinical scenarios, patients receive two systemic-to-pulmonary connections, either by leaving the patent ductus arteriosus (PDA) open or by adding an additional central shunt (CS) in conjunction with the MBTS. This practice has been motivated by the thinking that an additional source of pulmonary blood flow could beneficially increase pulmonary flow and provide the security of an alternate pathway in case of thrombosis. However, there have been clinical reports of premature shunt occlusion when more than one shunt is employed, leading to speculation that multiple shunts may in fact lead to unfavorable hemodynamics and increased mortality. In this study, we hypothesize that multiple shunts may lead to undesirable flow competition, resulting in increased residence time (RT) and elevated risk of thrombosis, as well as pulmonary overcirculation. Computational fluid dynamics-based multiscale simulations were performed to compare a range of shunt configurations and systematically quantify flow competition, pulmonary circulation, and other clinically relevant parameters. In total, 23 cases were evaluated by systematically changing the PDA/CS diameter, pulmonary vascular resistance (PVR), and MBTS position and compared by quantifying oxygen delivery (OD) to the systemic and coronary beds, wall shear stress (WSS), oscillatory shear index (OSI), WSS gradient (WSSG), and RT in the pulmonary artery (PA), and MBTS. Results showed that smaller PDA/CS diameters can lead to flow conditions consistent with increased thrombus formation due to flow competition in the PA, and larger PDA/CS diameters can lead to insufficient OD due to pulmonary hyperfusion. In the worst case scenario, it was found that multiple shunts can lead to a 160% increase in RT and a 10% decrease in OD. Based on the simulation results presented in this study, clinical outcomes for patients receiving multiple shunts should be critically investigated, as this practice appears to provide no benefit in terms of OD and may actually increase thrombotic risk.
Decreased Elastic Energy Storage, Not Increased Material Stiffness, Characterizes Central Artery Dysfunction in Fibulin-5 Deficiency Independent of Sex
Authors: Ferruzzi J. , Bersi M. R. , Uman S. , Yanagisawa H. , Humphrey J. D.
Published: December 2014

Central artery stiffness has emerged over the past 15 years as a clinically significant indicator of cardiovascular function and initiator of disease. Loss of elastic fiber integrity is one of the primary contributors to increased arterial stiffening in aging, hypertension, and related conditions. Elastic fibers consist of an elastin core and multiple glycoproteins; hence defects in any of these constituents can adversely affect arterial wall mechanics. In this paper, we focus on mechanical consequences of the loss of fibulin-5, an elastin-associated glycoprotein involved in elastogenesis. Specifically, we compared the biaxial mechanical properties of five central arteries—the ascending thoracic aorta, descending thoracic aorta, suprarenal abdominal aorta, infrarenal abdominal aorta, and common carotid artery—from male and female wild-type and fibulin-5 deficient mice. Results revealed that, independent of sex, all five regions in the fibulin-5 deficient mice manifested a marked increase in structural stiffness but also a marked decrease in elastic energy storage and typically an increase in energy dissipation, with all differences being most dramatic in the ascending and abdominal aortas. Given that the primary function of large arteries is to store elastic energy during systole and to use this energy during diastole to work on the blood, fibulin-5 deficiency results in a widespread diminishment of central artery function that can have significant effects on hemodynamics and cardiac function.
An Assessment of Mechanical Properties of A508-3 Steel Used in Chinese Nuclear Reactor Pressure Vessels
Authors: Yu Meifang , Chao Y. J. , Luo Zhen
Published: December 2014

China has very ambitious goals of expanding its commercial nuclear power by 30 GW within the decade and wishes to phase out fossil fuels emissions by 40–45% by 2020 (from 2005 levels). With over 50 new nuclear power plants under construction or planned and a design life of 60 years, any discussions on structural integrity become very timely. Although China adopted its nuclear technology from France or USA at present time, e.g., AP1000 of Westinghouse, the construction materials are primarily “Made in China.” Among all issues, both the accumulation of the knowledge base of the materials and structures used for the power plant and the technical capability of engineering personnel are imminent. This paper attempts to compile and assess the mechanical properties, Charpy V-notch impact energy, and fracture toughness of A508-3 steel used in Chinese nuclear reactor pressure vessels (RPVs). All data are collected from open literature and by no means complete. However, it provides a glimpse into how this domestically produced steel compares with western RPV steels such as USA A533B and Euro 20MnMoNi55.
Printing Three-Dimensional Electrical Traces in Additive Manufactured Parts for Injection of Low Melting Temperature Metals
Authors: Swensen John P. , Odhner Lael U. , Araki Brandon , Dollar Aaron M.
Published: December 2014

While techniques exist for the rapid prototyping of mechanical and electrical components separately, this paper describes a method where commercial additive manufacturing (AM) techniques can be used to concurrently construct the mechanical structure and electronic circuits in a robotic or mechatronic system. The technique involves printing hollow channels within 3D printed parts that are then filled with a low melting point liquid metal alloy that solidifies to form electrical traces. This method is compatible with most conventional fused deposition modeling and stereolithography (SLA) machines and requires no modification to an existing printer, though the technique could easily be incorporated into multimaterial machines. Three primary considerations are explored using a commercial fused deposition manufacturing (FDM) process as a testbed: material and manufacturing process parameters, simplified injection fluid mechanics, and automatic part generation using standard printed circuit board (PCB) software tools. Example parts demonstrate the ability to embed circuits into a 3D printed structure and populate the surface with discrete electronic components.
Sliding-Bar MACCEPA for a Powered Ankle Prosthesis
Authors: Jimenez-Fabian R. , Flynn L. , Geeroms J. , Vitiello N. , Vanderborght B. , Lefeber D.
Published: December 2014

This paper describes a new design that improves several aspects of the mechanically adjustable compliance and controllable equilibrium position actuator (MACCEPA). The proposed design avoids premature wear and attachment issues found in the cable transmission used in previous MACCEPA designs and allows the use of high-performance compact compression springs. The mechanical configuration of the actuator provides an adjustable stiffness with a nonlinear stiffening output torque. The output position of the actuator and its global stiffness are independent from each other. In this work, we provide a mathematical description of the actuation principle along with an experimental verification of its performance in a powered ankle–foot prosthesis. This work is part of the CYBERLEGs project funded by the European Commissions 7th Framework Programme.
Design and Development of a High-Speed and High-Rotation Robot With Four Identical Arms and a Single Platform
Authors: Xie Fugui , Liu Xin-Jun
Published: December 2014

In this paper, a novel parallel kinematic mechanism (PKM) with Schönflies motion has been proposed under the guidance of a graphical type synthesis method. This PKM is composed of four identical arms and a single platform and has high rotational capability. The single-platform structure used in the proposed PKM can reduce structural complexity, increase dynamic response. In addition, the composite parallelogram structure in each arm brings in better limb stiffness. Based on the proposed concept, optimal design is carried out to make the PKM realize its high rotational potential. In this process, an input transmission index (ITI) and an output transmission index (OTI) (the two indices can be used to numerically evaluate motion and force transmission performance of PKMs, respectively) are taken as the performance evaluation criteria. On this basis, some other indices are defined and the corresponding performance atlases are also plotted to investigate the potential workspace. Consequently, dimensional parameters of the discussed PKM are derived on the precondition that the rotational capability should reach at least ±90 deg, and the workspace has also been identified. Based on these foundations, a parallel robot X4 has been developed which can realize high-speed pick-and-place manipulation in industrial lines.
A Predictive Model for Temperature Rise of Spindle–Bearing Integrated System
Authors: Deng Xiaolei , Fu Jianzhong , Zhang Yuwen
Published: December 2014

In order to obtain the thermal characteristics of the spindle–bearing integrated system of the computer numerical control (CNC) machine tools effectively, a mathematical model is established by employing the heat source method (HSM). The thermal characteristics of spindle–bearing system are identified by using the derived mathematical formula, and the presented model is validated by the finite element method (FEM) under four types of conditions corresponding to different heat intensities, heat transfer coefficients, geometrical model sizes, and heat source positions. Compared with the FEM, the presented model has better computational efficiency. The temperature fields of the two spindle systems of a CNC machine tool are predicted by using the present model. The predicted temperature field is compared with the measured data and results show that the maximum relative errors for the two systems are 0.41% and 8.38%, respectively. The proposed model has a potential to be applied in calculating temperature field and thermal deformation or other related engineering area.
Sound Radiation Response of a Rectangular Plate Having a Side Crack of Arbitrary Length, Orientation, and Position
Authors: Bose Tanmoy , Mohanty Amiya R.
Published: December 2014

Here, sound radiation characteristics of a rectangular plate having a side crack of different crack lengths, orientations, and positions are studied considering clamped boundary conditions. First, a free and forced vibration response analysis of a cracked plate is done using the Ritz method. Orthogonal polynomials are used for faster convergence and some corner functions are used to generate the effect of a crack. Radiated sound power and radiation efficiency of the cracked plate are computed by the quadruple integration. A convergence test of radiation efficiency is carried out to fix the number of polynomials and corner functions in the analysis. It is found that the radiation efficiency and radiated sound power computed by the Ritz method are close to the same obtained from the boundary element method (BEM). The natural frequencies computed using the Ritz method are also found to be close to that obtained from the finite element method (FEM). The radiation efficiency curves of different modes are shown for a change in crack length, orientation and position. Finally, the variations of normalized sound power are shown to be due to a change in the crack parameters.
Optimal Design of Gas Turbines Flow Paths Considering Operational Modes
Authors: Boiko Anatoli , Govorushchenko Yuri , Usaty Aleksander , Rudenko Oleksii
Published: December 2014

A new technique for multi-parameter optimization of gas turbines flow paths considering a variable mode for their operation is presented. It allows the estimation of the influence of flow path optimization on performance parameters of gas-turbine units, such as power, efficiency, and fuel consumption. An algorithm for turbine flow path multi-criteria optimization that takes into account the gas-turbine unit operation mode is shown. Approaches to speed up the optimization process are described. Using this technique GT-750-6M low pressure turbine flow path optimization based on real working loads during one year is carried out and the results are analyzed. Due to optimization the unit efficiency was improved at all operating modes. The total fuel economy for considered period makes 50.831 t.
Development of a Cost-Efficient Test Rig for Turbine Loss Education
Authors: aus der Wiesche Stefan , Wulff Steffen , Reinker Felix , Hasselmann Karsten
Published: December 2014

A large number of approaches have been made to predict the total pressure loss coefficients and flow deviation angles to the geometry of turbine cascades and the incoming flow. Students feel typically uncomfortable when faced with turbine loss coefficients during their education, and it is challenging to fully understand turbine losses only by means of theory. The integration of a turbine cascade facility into academic courses might be useful but such test facilities are expensive or not available for a large number of engineering schools. To overcome this issue, a cost-efficient test rig for measurements of the flow through a two-dimensional cascade of turbine blades was designed. This test rig enabled the measurement of the flow through a blade cascade and the formation of wakes. The effect of the inlet flow angle on the cascade performance was investigated easily by students. Based on own measurements, the students were able to apply the most prominent approaches for determining loss coefficients. Furthermore, they compared their results with literature data and predictions of available correlations. By doing that, the importance of blade spacing and Reynolds number level on profile loss coefficients became more transparent and invited to further studies.
Meridian Profile Case Study of the Best Specific Speed and Blade Number
Authors: Tsugawa Takuji
Published: December 2014

In the previous case study of optimum meridian profile of impeller and guidevane, the specific speed was the constant design specification. In this case study, the meridian profiles of optimum specific speed were studied. So, the specific speed is the variable design parameter. The impeller blade number and the guidevane blade number are also the variable design parameters. As the variable design parameters need to change gradually, the blade number is used as real number in the optimum process. In condition of the initial specific speed 1000, initial impeller blade number 2 and initial guidevane blade number 5, the meridian profile of which specific speed has the best efficiency and suction specific speed 1000 was obtained. In condition of the consideration of the only diffusion head loss, the efficiency isn’t affected by impeller outlet normal diameter and rotational speed. In this case study, the loss head of diffusion and the loss head of annular friction are considered. In the process of this optimum study, the 15 variable design parameters were changed constant or variable by two steps. As the result, the best meridian profile of specific speed 785, impeller real blade number 3.4 and guidevane real blade number 14.7 were obtained.
DEM Predictions of NETL Small Scale Challenge Problem
Authors: Elghannay Husam A. , Tafti Danesh K.
Published: December 2014

The Discrete Element Method (DEM) coupled to Computational Fluid Dynamics (CFD) is used to predict dense fluid-particle system in a blind study using the in-house code GenIDLEST (Generalized Incompressible Direct and Large Eddy Simulation of Turbulence). The experimental measurements were performed at the Department of Energy’s (DOE’s) National Energy Technology Laboratory (NETL) at three different superficial velocities in a 0.076m×0.23m×1.22m bubbling fluidized bed with 3.26 mm Nylon beads. Experimental measurements include the mean and rms of pressure drop between specific locations, the first four moments of solid velocity components, and time series of pressure drop at selected locations in the bed. The predictions capture the trends in the change in bed hydrodynamics with an increase in the superficial velocity. While good qualitative agreement is found with experiments, quantitative agreement is fair. Factors that might cause deviations in predictions are discussed.
Optimum Hydraulic Design for a Radial Diffuser Pump Using Orthogonal Experimental Method Based on CFD
Authors: Wang Wenjie , Yuan Shouqi , Pei Ji , Zhang Jinfeng , Yuan Jianping , Mao Jieyun
Published: December 2014

To improve the performance of the centrifugal pump with a vaned diffuser, the influence of impeller geometric parameters on external characteristics of the pump was investigated by Orthogonal Experimental Method (OEM) based on CFD. Blade outlet width b2, blade wrap angle φ, blade outlet angle β2, and blade number Z were selected as the main impeller geometric parameters and the orthogonal experiment of L9 (33*21), which contained 3 levels of the 3 factors and 2 levels of one factor, was done in this study. Three-dimensional steady simulations were conducted by solving the RANS equations in the design procedure with SST k-ω turbulence model, and about 5.3 million structured grids for the whole calculation domains were used. The experimental results were justified by the variance analysis method. The inner flow of the pump was also analyzed in order to obtain the flow behaviors that can affect the pump performance. The results showed that the blade outlet angle β2 had the greatest influence on the efficiency and power. The high efficiency area of the optimal impeller is wider. The final optimized impeller accomplished better pump performance, which meet the design requirements. The velocity distribution in the optimized impeller is more regular and the area of the high turbulence kinetic energy is smaller in the optimal impeller.
Smoke Control of a Car Park by Means of CFD Analyses Using Jet Fans
Authors: Celen Ali , Kundu Balaram , Dalkılıç Ahmet Selim , Kayacı Nurullah , Atayılmaz Sevket Ozgur , Wongwises Somchai
Published: December 2014

Analysis and interpretation of daily emission ventilation with fire ventilation systems in indoor parking lots coupling with jet fans have been done by a CFD program. The ventilation of an eight-story parking lot in Istanbul is carried out and the investigation for a simplified one-story of this system is also considered. The placement of jet fans has been identified on the basis of eliminating dead jones in the passage with the help of air flow analysis. Therefore, the present study may be of great importance as both the fire and smoke can be evacuated effectively by using the optimal position of jet fans in the parking lots to maintain a less polluted atmosphere inside.
Numerical Simulation of Flow Development Downstream Four Perforated Plates for Flow Measurement Accuracy
Authors: Laribi Boualem , Ait Amrane Abdellaziz , Hadj-Abdellah Abdellah
Published: December 2014

Several plates are described in the standard like a flow conditioners. A numerical simulation is done to study the development of the turbulent flow with the presence of four perforated plates. Three of the perforated plates are described in the standard ISO 5167 namely ZANKER, NOVA and NEL plates. The fourth one is a new design and proposed plate. The main goal is a comparative simulation of the four perforated plates to produce the fully developed pipe flow which is a prerequisite for flow measurement accuracy. The flow is analysed in a circular pipe of 100mm diameter.

The disturber used for the simulation is a 90° double bend in two perpendicular planes. The geometry of the perforated plates is different with four types of perforations at different diameters. The flow is insured by air at a Reynolds number of 2.5×105.

The numerical analysis is conducted by the CFD code Fluent which is based on the resolution of the Navier-Stokes equations with k-ε like turbulence model. The parameter discussed in this study is the velocity.

The results show the effectiveness of perforated plates to obtain the fully developed pipe flow at length z/D=20 downstream the disturbers. Downstream this station the contour seems to reach the fully developed pipe flow like at station z/D=100 where the flow is supposed fully developed, and don’t exhibit any instabilities of the velocity contour. Contrary, in the stations upstream we found instability of the flow structure. From some stations we show how much the turbulent mixing downstream the perforated plates is important to reach the fully developed pipe flow. The effectiveness of CFD code Fluent to predict flow development in different installations is done where good predictions are presented.
Heat Transfer Enhancement in Channels With Natural Convection Flow by Kármán Vortex Streets
Authors: Mathis Paul , Herpers Matthias , Müller Dirk
Published: December 2014

In this study, a new method of enhancing heat transfer in heated channels with purely natural convection flow is presented. Blunt bodies which serve as vortex promoters are introduced into the channel, leading to Kármán vortex streets. Vortex shedding behind cylinders and other blunt bodies leads to a convective mixing of the flow, bringing cooler fluid from the center of the channel to the heated walls. Consequently, the temperature gradient is increased and by that the heat transfer.

The purpose of this work is investigating a parameter field in order to identify optimal geometrical parameters for maximizing heat transfer in heated vertical channels. This is done without adding any active mechanical devices for forced convection, but instead by passive means only, meaning cylinders in particular.

A parameter study comprising geometrical degrees of freedom like diameter and position of the vortex promoting bodies and different wall temperatures is performed numerically, indicating a heat transfer enhancement of up to 47.4% compared to the reference case without vortex promoters. The CFD results are compared to heat delivery measurements and visualization data.
Effect of a Joint Experimental-CFD Lab Experience on Perceptions of Data Authority and Student Learning
Authors: Shepard Thomas , Ganesan Krithiga
Published: December 2014

This paper explores modes of instruction for effective student learning and factors that affect student perceptions of information from various sources encountered in undergraduate fluid mechanics. This paper addresses two questions: (i) What source of information do students rely on and have greater confidence in, (ii) What modes of instruction lead to greater understanding of material. These research questions were addressed by considering the conceptual topic of drag on a sphere. In this study, thirty students compared results from experimental lab measurements, CFD (ANSYS-CFX) simulations, and textbook data for drag acting on a sphere. Other concepts covered in the course were done so via lecture and/or lab, but were not examined using CFD. To address the first question, students completed a survey at the end of the experimental portion of lab and a second survey at the end of the CFD portion of lab. To address the second question, student responses to specific final exam questions were analyzed. Our data indicate that students have greater reliance on materials presented via lecture and in the course textbook, than data that originates via hands-on learning methods such as experimental data, and CFD simulations. The results that address the second question indicate that even though there is greater variation in student learning outcome scores, a variety of modes of instruction lead to greater understanding of a topic, even accounting for biases in perceived data authority of various sources of data.
Simulation and Mockup of SNS Jet-Flow Target With Wall Jet for Cavitation Damage Mitigation
Authors: Wendel Mark , Geoghegan Patrick , Felde David
Published: December 2014

Pressure waves created in liquid mercury targets at the pulsed Spallation Neutron Source (SNS) at Oak Ridge National Laboratory induce cavitation damage on the stainless steel target vessel. The cavitation damage is thought to limit the lifetime of the target for power levels at and above 1 MW. Severe through-wall cavitation damage on an internal wall near the beam entrance window has been observed in spent-targets. Surprisingly though, there is very little damage on the walls that bound an annular mercury channel that wraps around the front and outside of the target. The mercury flow through this channel is characterized by smooth, attached streamlines. One theory to explain this lack of damage is that the uni-directional flow biases the direction of the collapsing cavitation bubble, reducing the impact pressure and subsequent damage. The theory has been reinforced by in-beam separate effects data. For this reason, a second-generation SNS mercury target has been designed with an internal wall jet configuration intended to protect the concave wall where damage has been observed. The wall jet mimics the annular flow channel streamlines, but since the jet is bounded on only one side, the momentum is gradually diffused by the bulk flow interactions as it progresses around the cicular path of the target nose. Numerical simulations of the flow through this jet-flow target have been completed, and a water loop has been assembled with a transparent test target in order to visualize and measure the flow field. This paper presents the wall jet simulation results, as well as early experimental data from the test loop.