bluuebunny/crossref_metadata_2025 huggingface dataset:
Widely distributed red algae often represent hidden introductions, complexes of cryptic species or species with strong phylogeographic structure
Authors: Díaz‐Tapia Pilar , Maggs Christine A. , Macaya Erasmo C. , Verbruggen Heroen
Published: August 2018

Despite studies suggesting that most seaweeds are poor dispersers, many red algal species are reported to have circumglobal distributions. Such distributions have mostly been based on morphological identifications, but molecular data have revealed a range of issues with morphologically defined species boundaries. Consequently, the real distribution of such reportedly circumglobal species must be questioned. In this study, we analyzed molecular data sets (rbcL gene) of nine species in the Rhodomelaceae for which samples were available from widely spaced geographical locations. Three overall patterns were identified: (i) species showing strong phylogeographic structure (i.e., phylogenetic similarity correlates with geographical provenance), often to the point that populations from different locations could be considered as different species (Lophosiphonia obscura, Ophidocladus simpliciusculus, Polysiphonia villum, and Xiphosiphonia pinnulata); (ii) species with a broad distribution that is explained, in part, by putative human‐mediated transport (Symphyocladia dendroidea and Polysiphonia devoniensis); and (iii) non‐monophyletic complexes of cryptic species, most with a more restricted distribution than previously thought (Herposiphonia tenella, Symphyocladia dendroidea, and the Xiphosiphonia pennata complex that includes the species Xiphosiphonia pinnulata and Symphyocladia spinifera). This study shows that widely distributed species are the exception in marine red algae, unless they have been spread by humans.
A randomized controlled and long‐term linaclotide study of irritable bowel syndrome with constipation patients in Japan
Authors: Fukudo Shin , Miwa Hiroto , Nakajima Atsushi , Haruma Ken , Kosako Masanori , Nakagawa Ayako , Akiho Hiraku , Yamaguchi Yusuke , Johnston Jeffrey M. , Currie Mark , Kinoshita Yoshikazu
Published: August 2018

Background

Clinical testing was required to verify the effect of linaclotide 0.5 mg/d in patients with irritable bowel syndrome with constipation (IBS‐C) in Japan.

Methods

This was a randomized, double‐blind, placebo‐controlled (Part 1) and long‐term, open‐label extension (Part 2) study of linaclotide at 60 hospitals and clinics in Japan. Patients with IBS‐C diagnosed using Rome III criteria (n = 500) were randomly assigned to linaclotide 0.5 mg (n = 249) or placebo (n = 251) for a 12‐week treatment period followed by open‐label treatment with linaclotide (n = 324) for an additional 40 weeks. The primary endpoints were the responder rate of global improvement of IBS symptoms and complete spontaneous bowel movement (CSBM) during 12 weeks. The secondary endpoints included responder rates of SBM and abdominal pain/discomfort relief.

Key Results

Part 1: The responder rates for global improvement and for CSBM frequency were significantly higher for linaclotide compared to placebo (P < 0.001). Secondary endpoints including responder rates for SBM and abdominal pain/discomfort relief in the linaclotide group were also significantly greater than those in the placebo group. Part 2: Patients switched from placebo to linaclotide showed similar responder rates for global improvement and CSBM frequency to those in patients who continued to receive linaclotide, supporting sustained efficacy. Diarrhea was seen in 14.5% of patients; all cases were mild or moderate.

Conclusions and Inferences

This study suggests that a linaclotide dose of 0.5 mg is effective and safe for IBS‐C patients in Japan.
Canonical and noncanonical ethylene signaling pathways that regulate Arabidopsis susceptibility to the cyst nematode Heterodera schachtii
Authors: Piya Sarbottam , Binder Brad M. , Hewezi Tarek
Published: August 2018

Plant‐parasitic cyst nematodes successfully exploit various phytohormone signaling pathways to establish a new hormonal equilibrium that facilitates nematode parasitism. Although it is largely accepted that ethylene regulates plant responses to nematode infection, a mechanistic understanding of how ethylene shapes plant–nematode interactions remains largely unknown.

In this study, we examined the involvement of various components regulating ethylene perception and signaling in establishing Arabidopsis susceptibility to the cyst nematode Heterodera schachtii using a large set of well‐characterized single and higher order mutants.

Our analyses revealed the existence of two pathways that separately engage ethylene with salicylic acid (SA) and cytokinin signaling during plant response to nematode infection. One pathway involves the canonical ethylene signaling pathway in which activation of ethylene signaling results in suppression of SA‐based immunity. The second pathway involves the ethylene receptor ETR1, which signals independently of SA acid to affect immunity, instead altering cytokinin‐mediated regulation of downstream components.

Our results reveal important mechanisms through which cyst nematodes exploit components of ethylene perception and signaling to affect the balance of hormonal signaling through ethylene interaction with SA and cytokinin networks. This hormonal interaction overcomes plant defense and provokes a susceptible response.
Early esophageal cancer: the significance of surgery, endoscopy, and chemoradiation
Authors: Mönig Stefan , Chevallay Mickael , Niclauss Nadja , Zilli Thomas , Fang Wentao , Bansal Ajay , Hoeppner Jens
Published: August 2018

Early carcinomas of the esophagus are histologically classified as adenocarcinoma or squamous cell carcinoma and microscopically subdivided into mucosal and submucosal carcinomas depending on infiltration depth. The prevalence of lymph node metastasis in mucosal carcinoma remains low. However, lymph node metastases arise frequently from tumors with submucosal infiltration, with increasing prevalence in the deeper submucosal sublayers. According to current German guidelines, endoscopic resection is the recommended treatment in mucosal adenocarcinoma without histologic risk factors (lymphatic invasion 1, vascular invasion 1, >grade 2, R1‐margin). In superficial submucosal infiltration without histologic risk factors, endoscopic resection can be considered. In squamous cell carcinoma, endoscopic resection is indicated up to middle layer mucosal carcinoma. Beyond these criteria, surgical resection should be considered. The gold standard is a subtotal transthoracic esophagectomy with two‐field lymphadenectomy. Total esophagectomy is performed in cervical esophageal carcinoma and transhiatal extended gastrectomy in carcinoma of the cardia. Minimally invasive procedures show good oncologic results and reduce the morbidity of radical esophagectomy. Reduced morbidity might be an argument for surgical resection in borderline cases between endoscopic and surgical resection. In early squamous cell cancer, the combination of endoscopic resection and adjuvant chemoradiotherapy is a therapeutic option with promising results.
When less is more: On politicians’ attitudes to remuneration
Authors: Pedersen Lene Holm , Pedersen Rasmus T. , Bhatti Yosef
Published: August 2018

While politicians’ remuneration is a key issue in the relationship between citizens and politicians, there is still limited knowledge about the politicians’ own views on this issue. This article investigates how politicians’ attitudes regarding pay are affected by their motivation, political ideology and party position as well as institutional position. Using data from a survey among municipal politicians in Denmark (n= 838), our analyses suggest that politicians with different levels of extrinsic motivation sort into parties with different political ideologies. Left‐wing politicians express a strong distaste for high pay, probably for strategic as well as ideological reasons. In addition, institutional position matters. Chairmen prefer higher rewards for chairmen, but the backbenchers also prefer higher rewards for the chairmen—if they come from the same party. The results help us understand why politicians do not necessarily act in line with the fundamental assumption that individuals prefer more pay to less.
Solving the Interface Problem Without Translation: The Same Format Thesis
Authors: Ferretti Gabriele , Caiani Silvano Zipoli
Published: August 2018

In this article, we propose a new account concerning the interlock between intentions and motor representations (henceforth: MRs), showing that the interface problem is not as deep as previously proposed. Before discussing our view, in the first section we report the ideas developed in the literature by those who have tried to solve this puzzle before us. The article proceeds as follows. In Sections 2 and 3, we address the views by Butterfill and Sinigaglia, and Mylopoulos and Pacherie, respectively, and argue that both solutions entail a translation between representational formats, which both accounts aim to avoid. In Section 4, we present our brand‐new claim, according to which intentions and MRs partially share the same motor format, inasmuch as executable action concepts are naturally represented in the agent's motor system together with the action's outcomes. Indeed, since intentions are constituted by executable action concepts and since there is evidence that action concepts are represented (and, thus, built) in the same motor format as action outcomes, the interlock between intentions and MRs no longer constitutes a problem. Then, in Section 5, we report empirical evidence in support of our claim, and before concluding, in Section 6 we briefly clarify our relations with two very recent accounts that criticized the proposals by Mylopoulos and Pacherie and Butterfill and Sinigaglia: Shepherd's and Burnston's. Finally, in Section 7, we offer some remarks about the philosophical idea defended here. The basic insight is that interface without translation is possible because action concepts are such stuff as MRs are made on.
Effects of emphysema on physiological and prognostic characteristics of lung function in idiopathic pulmonary fibrosis
Authors: Yoon Hee‐Young , Kim Tae Hoon , Seo Joon Beom , Lee Sang Min , Lim Soyeoun , Lee Han Na , Kim Namkug , Han Minkyu , Kim Dong Soon , Song Jin Woo
Published: August 2018

Background and objective

Combined pulmonary fibrosis and emphysema (CPFE) is characterized by preserved lung volume and slower lung function decline. However, it is unclear at what extent emphysema begins to impact respiratory physiology and prognostic characteristics in idiopathic pulmonary fibrosis (IPF). We estimated the extent of emphysema that could be used to define CPFE in IPF.

Methods

The extent of emphysema was observed on high‐resolution computed tomography scans and measured by a texture‐based automated quantification system in 209 IPF patients. We analysed the impact of differences in the extent of emphysema on the annual decline rate and prognostic significance of lung function parameters.

Results

The extent of emphysema was ≥5% in 53 patients (25%), ≥10% in 23 patients (11%) and ≥15% in 12 patients (6%). Patients with emphysema to an extent of ≥5% were more frequently men and ever‐smokers; they had more preserved lung volume and lower forced vital capacity (FVC) decline rates than those with no or trivial emphysema. The FVC decline rate was a significant predictor of mortality in patients with no or trivial emphysema (hazard ratio (HR): 0.933, P < 0.001) and in patients with an extent of emphysema ≥5% (HR: 0.906, P < 0.001). However, diffusing capacity of the lung for carbon monoxide (DLCO) was the most significant prognostic factor in those patients with an extent of emphysema ≥10% (HR: 0.972, P = 0.040) and ≥15% (HR: 0.942, P = 0.023). A 10% cut‐off value for the extent of emphysema created the most significant difference in the annual FVC decline rate in IPF patients.

Conclusion

In IPF, emphysema to an extent of ≥10% affects both the annual decline rate and the prognostic significance of FVC. This extent could be used to define CPFE.
The effect of language, spatial factors, masker type and memory span on speech‐in‐noise thresholds in sequential bilingual children
Authors: MacCutcheon Douglas , Pausch Florian , Fels Janina , Ljung Robert
Published: August 2018

This study considers whether bilingual children listening in a second language are among those on which higher processing and cognitive demands are placed when noise is present. Forty‐four Swedish sequential bilingual 15 year‐olds were given memory span and vocabulary assessments in their first and second language (Swedish and English). First and second language speech reception thresholds (SRTs) at 50% intelligibility for numbers and colors presented in noise were obtained using an adaptive procedure. The target sentences were presented in simulated, virtual classroom acoustics, masked by either 16‐talker multi‐talker babble noise (MTBN) or speech shaped noise (SSN), positioned either directly in front of the listener (collocated with the target speech), or spatially separated from the target speech by 90° to either side. Main effects in the Spatial and Noise factors indicated that intelligibility was 3.8 dB lower in collocated conditions and 2.9 dB lower in MTBN conditions. SRTs were unexpectedly higher by 0.9 dB in second language conditions. Memory span significantly predicted 17% of the variance in the second language SRTs, and 9% of the variance in first language SRTs, indicating the possibility that the SRT task places higher cognitive demands when listening to second language speech than when the target is in the listener's first language.
Evaluation of retinal morphology of canine sudden acquired retinal degeneration syndrome using optical coherence tomography and fluorescein angiography
Authors: Osinchuk Stephanie C. , Leis Marina L. , Salpeter Elyse M. , Sandmeyer Lynne S. , Grahn Bruce H.
Published: August 2018

Purpose

To describe the optical coherence tomography (OCT) and fluorescein angiography changes in dogs with sudden acquired retinal degeneration syndrome (SARDS).

Methods

Retinal OCT was performed on 10 SARDS dogs and eight control dogs. Tomograms were collected in four quadrants around the optic nerve. Measurements were collected from the photoreceptor layer, the outer nuclear layer, the outer retina, the inner retina and the whole retina thickness in all quadrants. Sodium fluorescein was injected intravenously and serial fundic photographs were collected for a 5 minute period post‐injection.

Results

In all quadrants, the outer nuclear layer (dorsal temporalP = 0.0000, dorsal nasalP = 0.0001, ventral temporalP = 0.0002, ventral nasalP = 0.000) and outer retina (dorsal temporalP = 0.0001, dorsal nasalP = 0.0002, ventral temporalP = 0.0054, ventral nasalP = 0.0084) measurements were significantly decreased in SARDS dogs. The whole retina thickness was significantly decreased in the dorsal temporal (P = 0.0082) and ventral temporal (P = 0.0428) retina. There were no significant differences in the photoreceptor layer thickness or inner retinal thickness between SARDS and control dogs. All SARDS dogs had a loss of definition of all of the photoreceptor bands on OCT. Two SARDS dogs had multifocal small retinal detachments and one of these dogs exhibited fluorescein leaking at the detachment sites.

Conclusions

The significant reduction in the outer nuclear layer and the loss of band signals in the photoreceptor layers in dogs with SARDS identified on OCT support the previous histopathology findings. Small detachments may occasionally be detected on OCT and they may leak fluorescein.
High field magnetic resonance imaging is comparable with gross anatomy for description of the normal appearance of soft tissues in the equine stifle
Authors: Daglish Jodie , Frisbie David D. , Selberg Kurt T. , Barrett Myra F.
Published: August 2018

High field magnetic resonance imaging (MRI) is increasingly used for horses with suspected stifle disease, however there is limited available information on normal imaging anatomy and potential incidental findings. The aim of this prospective, anatomic study was to develop an optimized high field MRI protocol for evaluation of the equine stifle and provide detailed descriptions of the normal MRI appearance of the stifle soft tissues, using ultrasound and gross pathological examination as comparison tests. Nine cadaver limbs were acquired from clinically normal horses. Stifles were evaluated ultrasonographically and then by an extensive 1.5 T MRI protocol. Subsequently, all stifles were evaluated for gross pathologic change. Findings were compared between gross evaluation and MRI imaging and described. No soft tissue structure abnormalities were identified on any evaluation. Specific descriptive findings of the meniscotibial, meniscofemoral, collateral, patellar and cruciate ligaments, and the menisci were reported. The high field MRI protocol described in this study provided high spatial and contrast resolution of the soft tissue structures, and this in turn allowed visualization of detailed structural characteristics, such as striations and variations in signal intensity. Findings supported the use of high field MRI as a modality for the evaluation of the soft tissues of the equine stifle. As clinical availability of this modality increases in the future, authors anticipate that new stifle diseases will be detected that have not previously been identified with other imaging modalities.
Themes of Reflective Thinking as a Predictor of Physical Education and Sport Pre-Service Teachers’ the Entrepreneurial Characteristics
Authors: Adatepe Sadık , Kul Murat
Published: August 2018

Today, entrepreneurship has gained great importance, especially with the transition from industrial society to information society. Therefore, in order to ensure economic and social development of societies, entrepreneurship must comprehensively be supported, encouraged and entrepreneurship education has to be provided. Many similar qualities and skills among individuals having reflective thinking abilities and entrepreneurial individuals arise when reflective thinking, one of the higher-level thinking skills, is defined as the cognitive inquiry that will lead the individual to produce new knowledge and develop alternative ways. The purpose of this research is to identify whether physical education and sports teachers' reflective thinking themes predict entrepreneurial characteristics. Research is designed in accordance with the relational screening model. Semerci (2007), “Reflective Thinking Tendency Scale” and Yilmaz and Sunbul (2009), “Entrepreneurship Scale for University Students” were used as data collection tool. Multilevel regression analysis was benefitted in the analyze of the data.  As a result of this research, it is determined that effective and interrogated teaching sub-dimension was the most independent variable contributing to the entrepreneurial characteristics of physical education and sports pre-service teachers and this was followed by continuous and intentional thinking, responsibility of teaching and science and looking professional sub-dimensions. It has also been determined that sub-dimensions such as open-mindedness, foresighted and sincere and researcher do not make a meaningful contribution to the prediction of entrepreneurial characteristics. Based on these results, it can be said that a pre-service teacher with high entrepreneurial characteristics will have higher reflective thinking tendencies. Besides, it is also possible to analyze how thinking skills such as critical thinking, creative thinking, problem solving and supra-cognitive thinking predict entrepreneurial characteristics.
Thermal Performance Optimization in Electric Vehicle Power Trains by Locally Orthotropic Surface Layer Design
Authors: Petrovic Mario , Nomura Tsuyoshi , Yamada Takayuki , Izui Kazuhiro , Nishiwaki Shinji
Published: August 2018

In this paper, the application of orthotropic material orientation optimization for controlling heat flow in electric car power trains is presented. The design process is applied to a case model, which conducts heat while storing heat-sensitive electronic components. The core of the case is designed using a low thermal conductivity material on order to focus the heat flow into the surface layer, which is designed using a high thermal conductivity material. Material orthotropy is achieved in the surface layer of the case by removing the material at points determined by the optimization analysis. For this purpose, an orthotropic material orientation optimization method was extended to calculate optimal material distribution. This is achieved by transforming the initially obtained optimal orientation vector field into a scalar field through the use of coupled time-dependent nonisotropic Helmholtz equations. Multiple parameters allow the control of the scalar field and therefore the control over material distribution in accordance to the optimal orientation. This allows the material distribution pattern to be scaled depending on the desired manufacturing method. The analysis method is applied to divert heat flow from a specific section of the model while focusing the heat flow to another section. The results are shown for a model with a 0.1 mm thick surface layer of copper and are compared to those results from several other materials and layer thicknesses. Finally, the manufactured design is presented.
Bulk Flow and Near Wall Hemodynamics of the Rabbit Aortic Arch and Descending Thoracic Aorta: A 4D PC-MRI Derived Computational Fluid Dynamics Study
Authors: Molony D. S. , Park J. , Zhou L. , Fleischer C. C. , Sun H. Y. , Hu X. P. , Oshinski J. N. , Samady H. , Giddens D. P. , Rezvan A.
Published: August 2018

Animal models offer a flexible experimental environment for studying atherosclerosis. The mouse is the most commonly used animal, however, the underlying hemodynamics in larger animals such as the rabbit are far closer to that of humans. The aortic arch is a vessel with complex helical flow and highly heterogeneous shear stress patterns which may influence where atherosclerotic lesions form. A better understanding of intraspecies flow variation and the impact of geometry on flow may improve our understanding of where disease forms. In this work, we use magnetic resonance angiography (MRA) and 4D phase contrast magnetic resonance imaging (PC-MRI) to image and measure blood velocity in the rabbit aortic arch. Measured flow rates from the PC-MRI were used as boundary conditions in computational fluid dynamics (CFD) models of the arches. Helical flow, cross flow index (CFI), and time-averaged wall shear stress (TAWSS) were determined from the simulated flow field. Both traditional geometric metrics and shape modes derived from statistical shape analysis were analyzed with respect to flow helicity. High CFI and low TAWSS were found to colocalize in the ascending aorta and to a lesser extent on the inner curvature of the aortic arch. The Reynolds number was linearly associated with an increase in helical flow intensity (R = 0.85, p < 0.05). Both traditional and statistical shape analyses correlated with increased helical flow symmetry. However, a stronger correlation was obtained from the statistical shape analysis demonstrating its potential for discerning the role of shape in hemodynamic studies.
Siting Wind Turbines Near Cliffs: The Effect of Ruggedness
Authors: Rowcroft Jerome , Burton David , Blackburn Hugh. M. , Sheridan John
Published: August 2018

Wind farms have often been located in close proximity to coastal cliffs to take advantage of the consistent wind regimes associated with many coastal regions, as well as to extract any available increase in flow speed that might be generated by such cliffs. However, coastal cliffs are often rugged as a result of erosion and the natural shape of the landform. This research explores the impact of the three-dimensional cliff topography on the wind flow. Specifically, wind tunnel testing is conducted, modeling the naturally occurring ruggedness as sawtooth lateral variations of various amplitudes applied to a forward facing step (FFS). Surface shear stress visualization techniques have been employed to derive the flow topology associated with different topographies, while pressure probe measurements are used to measure the development of wind speed and turbulence intensity (TI). Pressure probe measurements and surface pressure taps also assist to determine the lateral and vertical extents of the vortex structures identified. In particular, flow fields characterized by the probe measurements were consistent with vortex bursting that is described by various researchers in the flow over delta wings. Such bursting is observed as a stagnation and corresponding expansion of the vortex. Based on these observations, recommendations are provided for the siting of wind turbines near analogous cliffs.
Discrepancy Prediction in Dynamical System Models Under Untested Input Histories
Authors: Neal Kyle , Hu Zhen , Mahadevan Sankaran , Zumberge Jon
Published: August 2018

This paper presents a probabilistic framework for discrepancy prediction in dynamical system models under untested input time histories, based on information gained from validation experiments. Two surrogate modeling-based methods, namely observation surrogate and bias surrogate, are developed to predict the bias of a dynamical system simulation model under untested input time history. In the first method, a surrogate model is built for the observed experimental output, and the model bias for the untested input is obtained by comparing the output of the observation surrogate with the output of the physics-based model. The second method constructs a surrogate model for the bias in terms of the inputs in the conducted experiments. The bias surrogate model is then used to correct the simulation model prediction at each time-step under a predictor–corrector scheme to predict the model bias under untested conditions. A neural network-based surrogate modeling technique is employed to implement the proposed methodology. The bias prediction result is reported in a probabilistic manner, in order to account for the uncertainty of the surrogate model prediction. An air cycle machine case study is used to demonstrate the effectiveness of the proposed bias prediction framework.
Enhanced Specific Heat of Sodium Acetate Trihydrate by In-Situ Nanostructure Synthesis
Authors: Mostafavi Amirhossein , Suzuki Shunkei , Changla Sumeet , Pinto Aditya , Ipposhi Shigetoshi , Shin Donghyun
Published: August 2018

Recent studies have shown that doping nanoparticles (NPs) into a molten salt eutectic can induce salt molecules to form a stelliform nanostructure that can enhance the effective heat capacity of the mixture. This phenomenon can result from a unique characteristic of a eutectic molten salt system, which can self-form a nanostructure on a nanoscale solid surface. Hence, such an enhancement was only observed in a molten salt eutectic. Similarly, a stelliform nanostructure can be artificially synthesized and dispersed in other liquids. Mixing polar-ended molecules with a NP in a medium can induce the polar-ended molecules ionically bonded to a NP to form a stelliform nanostructure. Hence, this may enhance the effective heat capacity of the mixture. In this study, we disperse various NPs and polar-ended materials into a sodium acetate trihydrate (SAT) at different ratios to explore the effect of NP type and concentration as well as polar-ended materials and their concentrations on the resultant heat capacity of SAT. The result shows that the specific heat capacity was the highest with silica NP at 1% concentration of weight and polar-ended material at 4% concentration.
Assessment of External Heat Transfer Modeling of a Laboratory-Scale Combustor: Effects of Pressure-Housing Environment and Semi-Transparent Viewing Windows
Authors: Rodrigues P. , Gicquel O. , Darabiha N. , Geigle K. P. , Vicquelin R.
Published: August 2018

Many laboratory-scale combustors are equipped with viewing windows to allow for characterization of the reactive flow. Additionally, pressure housing is used in this configuration to study confined pressurized flames. Since the flame characteristics are influenced by heat losses, the prediction of wall temperature fields becomes increasingly necessary to account for conjugate heat transfer (CHT) in simulations of reactive flows. For configurations similar to this one, the pressure housing makes the use of such computations difficult in the whole system. It is, therefore, more appropriate to model the external heat transfer beyond the first set of quartz windows. The present study deals with the derivation of such a model, which accounts for convective heat transfer from quartz windows external face cooling system, free convection on the quartz windows 2, quartz windows radiative properties, radiative transfer inside the pressure housing, and heat conduction through the quartz window. The presence of semi-transparent viewing windows demands additional care in describing its effects in combustor heat transfers. Because this presence is not an issue in industrial-scale combustors with opaque enclosures, it remains hitherto unaddressed in laboratory-scale combustors. After validating the model for the selected setup, the sensitivity of several modeling choices is computed. This enables a simpler expression of the external heat transfer model that can be easily implemented in coupled simulations.
Flyer Thickness Effect in the Impact Welding of Aluminum to Steel
Authors: Lee Taeseon , Zhang Shunyi , Vivek Anupam , Kinsey Brad , Daehn Glenn
Published: August 2018

Impact welding is a material processing technology that enables metallurgical bonding in the solid state using a high-speed oblique collision. In this study, the effects of thickness of the flier and collision angle on weld interface morphology were investigated through the vaporizing foil actuator welding (VFAW) of AA1100-O to AISI 1018 Steel. The weld interfaces at various controlled conditions show wavelength increasing with the flier thickness and collision angle. The AA1100-O flier sheets ranged in thickness from 0.127 to 1.016 mm. The velocity of the fliers was directly measured by in situ photon Doppler velocimetry (PDV) and kept nearly constant at 670 m/s. The collision angles were controlled by a customized steel target with a set of various collision angles ranging from 8 deg to 28 deg. A numerical solid mechanics model was optimized for mesh sizes and provided to confirm the wavelength variation. Temperature estimates from the model were also performed to predict local melting and its complex spatial distribution near the weld interface and to compare that prediction to experiments.
Gas Turbine Fouling: A Comparison Among 100 Heavy-Duty Frames
Authors: Aldi Nicola , Casari Nicola , Morini Mirko , Pinelli Michele , Spina Pier Ruggero , Suman Alessio
Published: August 2018

Over recent decades, the variability and high costs of the traditional gas turbine fuels (e.g., natural gas) have pushed operators to consider low-grade fuels for running heavy-duty frames. Synfuels, obtained from coal, petroleum, or biomass gasification, could represent valid alternatives in this sense. Although these alternatives match the reduction of costs and, in the case of biomass sources, would potentially provide a CO2 emission benefit (reduction of the CO2 capture and sequestration costs), these low-grade fuels have a higher content of contaminants. Synfuels are filtered before the combustor stage, but the contaminants are not removed completely. This fact leads to a considerable amount of deposition on the nozzle vanes due to the high temperature value. In addition to this, the continuous demand for increasing gas turbine efficiency determines a higher combustor outlet temperature. Current advanced gas turbine engines operate at a turbine inlet temperature (TIT) of (1400–1500) °C, which is high enough to melt a high proportion of the contaminants introduced by low-grade fuels. Particle deposition can increase surface roughness, modify the airfoil shape, and clog the coolant passages. At the same time, land-based power units experience compressor fouling, due to the air contaminants able to pass through the filtration barriers. Hot sections and compressor fouling work together to determine performance degradation. This paper proposes an analysis of the contaminant deposition on hot gas turbine sections based on machine nameplate data. Hot section and compressor fouling are estimated using a fouling susceptibility criterion. The combination of gas turbine net power, efficiency, and TIT with different types of synfuel contaminants highlights how each gas turbine is subjected to particle deposition. The simulation of particle deposition on 100 gas turbines ranging from 1.2 MW to 420 MW was conducted following the fouling susceptibility criterion. Using a simplified particle deposition calculation based on TIT and contaminant viscosity estimation, the analysis shows how the correlation between type of contaminant and gas turbine performance plays a key role. The results allow the choice of the best heavy-duty frame as a function of the fuel. Low-efficiency frames (characterized by lower values of TIT) show the best compromise in order to reduce the effects of particle deposition in the presence of high-temperature melting contaminants. A high-efficiency frame is suitable when the contaminants are characterized by a low-melting point thanks to their lower fuel consumption.
Modeling of Solar Power Plant for Electricity Generation and Water Desalination
Authors: Ahmed Mohamed H. , Amin Amr M. A. , Fath Hassan El Banna
Published: August 2018

This paper presents the simulation and modeling of the concentrated solar power (CSP) plant for multipurpose applications at Borg El Arab in Egypt. The plant produces 1 MWe and 250 m3 of distilled water using steam turbine and electric generator. The purpose of using different applications is to improve the overall efficiency and the coefficient of performance of the plant. The trnsys simulation platform was used for simulating the thermal performance of the solar power and desalination plant covering the parabolic trough concentrator (PTC), storage tank with an integrated steam generator, a backup unit, steam turbine, electric generator, and two effects desalination unit. The temperature and energy profiles of the plant were investigated for the PTC, steam generator and the electric generator. The results prove that the simulation could be used to support the operation of the CSP plant and for improving the performance of the cogeneration plant at Borg El Arab.
Flow Through Microchannels With Textured Walls: A Theory for Moderately Slow Variations
Authors: Dewangan Mainendra Kumar , Datta Subhra
Published: August 2018

A microchannel with topographical texture on one or more of its walls is often employed to achieve objectives such as mixing, pumping and bio-molecular detection in microfluidics. Flow through a microchannel with sinusoidal ridges on one of its walls, when the ridges are oriented in the direction of flow, is studied. The classical infinitely-slow-variation or lubrication analysis is extended through a systematic scaling and perturbation procedure for applicability to moderately slow variations. Finite element simulations are used to assess the relative strengths and weaknesses of moderately and infinitely slow-variation theories as well as a small-amplitude theory from the literature based on the domain perturbation technique. Depending on the wavelength of patterning, the hydraulic permeability can either decrease or increase with pattern amplitude with a transitional behavior from an initial decrease to subsequent increase is observed at certain wavelengths.
Wetting of Water Drops on a PMMA Substrate in Viscous Medium
Authors: Trinavee Kumari , Kumar Gunda Naga Siva , Mitra Sushanta K.
Published: August 2018

There is a significant surge in the development of water repellant (superhydrophobic), oil repellent (superoleophobic) surfaces. Though these surfaces are well studied for air medium (inviscid), still there is a lack of fundamental understanding of wetting behavior in presence of surrounding viscous medium. In the present work, we investigate the wetting behaviour of water drops on a PMMA substrate surrounded by viscous oil medium for a wide range of viscosity ratio. The sessile drop is generated at the needle tip (J-needle for denser oil) close to the PMMA substrate to initiate the spreading of a water drop on the substrate. Experimentally measured contact angle at static equilibrium can well interpret the wetting behaviour of water drop on PMMA substrate placed in oil (surrounding medium). It is also observed that the theoretical values of water (drop)-oil and oil (drop)-water system satisfy the Young’s equation of two liquid system, but certain percentage errors are observed when compared to experimental results. These differences are interpreted in terms of interfacial energies of the two-liquid systems. In addition, ‘complementary hysteresis’ model recently put forward by Ozkan et al. [Surf. Topogr.: Metrol. Prop.2017,5,024002] is modified to study the wetting characteristics. Finally, based on the comparison of experimental and theoretical values, a short perspective is provided on the potential of a stable thin lubricant film under the droplet that changes the wetting characteristics of the substrate.
Dynamics of Artificial Helical Microswimmers Under Confinement
Authors: Caldag Hakan Osman , Yesilyurt Serhat
Published: August 2018

Understanding trajectories of natural and artificial helical swimmers under confinement is important in biology and for controlled swimming in potential medical applications. Swimmers follow helical or straight trajectories depending on whether the helical tail is pushing or pulling the swimmer. To investigate swimming dynamics of helical swimmers further, we present a Computational Fluid Dynamics (CFD) model for simulation of an artificial microswimmer in cylindrical channels. The microswimmer has a cylindrical head and a left-handed helical tail. The kinematic model solves for the position and rotation of the swimmer based on the linear and angular velocities of the force-free swimmer from a CFD model. Third-order Adams-Bashforth solver is used to obtain the orientation and the position of the swimmer. Viscous, gravitational, magnetic and contact forces and torques are considered in the model. The model is validated with experimental results. 3D trajectories, propulsion and tangential velocities are reported.
Milliliter Scale Acoustophoresis Based Bioparticle Processing Platform
Authors: Faridi Muhammad Asim , Shahzad Adnan Faqui , Russom Aman , Wiklund Martin
Published: August 2018

Bioparticles such as mammalian cells and bacteria can be manipulated directly or indirectly for multiple applications such as sample preparation for diagnostic applications mainly up-concentration, enrichment & separation as well as immunoassay development. There are various active and passive microfluidic particle manipulation techniques where Acoustophoresis is a powerful technique showing high cell viability. The use of disposable glass capillaries for acoustophoresis, instead of cleanroom fabricated glass-silicon chip can potentially bring down the cost factor substantially, aiding the realization of this technique for real-world diagnostic devices. Unlike available chips and capillary-based microfluidic devices, we report milliliter-scale platform able to accommodate 1ml of a sample for acoustophoresis based processing on a market available glass capillary. Although it is presented as a generic platform but as a demonstration we have shown that polystyrene suspending medium sample can be processed with trapping efficiency of 87% and the up-concentration factor of 10 times in a flow through manner i.e., at 35μl/min. For stationary volume accommodation, this platform practically offers 50 times more sample handling capacity than most of the microfluidic setups. Furthermore, we have also shown that with diluted blood (0.6%) in a flow-through manner, 82% of the white blood cells (WBCs) per ml could be kept trapped. This milliliter platform could potentially be utilized for assisting in sample preparation, plasma separation as well as a flow-through immunoassay assay development for clinical diagnostic applications.
Effect of Microstructures on Superhydrophobic and Slippery Lubricant-Infused Porous Surfaces During Condensation Phase-Change
Authors: Orejon Daniel , Maeda Yota , Lv Fengyong , Zhang Peng , Takata Yasuyuki
Published: August 2018

Superhydrophobic surfaces (SHSs) and slippery lubricant-infused porous surfaces (SLIPSs) are receiving increasing attention for their excellent anti-icing, anti-fogging, self-cleaning and condensation heat transfer properties. The ability of such surfaces to passively shed and repel water is mainly due to the low-adhesion between the liquid and the solid surface, i.e., low contact angle hysteresis, when compared to hydrophilic or to hydrophobic surfaces. In this work we investigated the effect of surface structure on the condensation performance on SHSs and SLIPSs. Three different SHSs with structures varying from the micro- to the nano-scale were fabricated following easy and scalable etching and oxidation growth procedures. The condensation performance on such surfaces was evaluated by optical microscopy in a temperature and humidity controlled environmental chamber. On SHSs important differences on the size and on the number of the coalescing droplets required for the jump to ensue were found when varying the surface structure underneath the condensing droplets. A surface energy analysis is proposed to account for the suppression of the droplet-jumping performance in the presence of microstructures. On other hand, by impregnating the same SHSs with a low surface tension oil, i.e., SLIPSs, the adhesion between the condensate and the SLIPSs can be further reduced. On SLIPSs slight differences on the droplet density over time and shedding performance upon the inclusion of microstructures were observed. Droplets were found to shed faster and with smaller diameters on SLIPSs in the presence of microstructures when compared to solely nanostructured SLIPSs.

We conclude that on SHSs the droplet-jumping performance of micrometer droplets is deteriorated in the presence of microstructures with the consequent decrease in the heat transfer performance, whereas on SLIPSs the droplet self-removal is actually improved in the presence of microstructures.
Effect of the Pressure Drop Oscillation on the Local Heat Transfer Coefficient in a Heated Horizontal Pipe
Authors: Park Il Woong , Fernandino Maria , Dorao Carlos Alberto
Published: August 2018

Two-phase flow instabilities have been studied during the past decades. Pressure drop oscillation (PDO) shows a relatively larger amplitude oscillation compared with other instabilities. This oscillation typically occurs when the system has compressible volume and operates in a negative slope region of the pressure drop versus flow rate curve. The characteristics of the PDO has been studied experimentally and theoretically. Even though research has been performed for identifying the characteristics of the PDO, how the PDO affects the heat transfer coefficient (HTC) remain unclear. In this study, the heat transfer coefficient is experimentally studied during pressure drop oscillation. The experiment is conducted with a heated horizontal tube with 5 mm inner diameter and 2.0 meters in length, and the R-134a is used a working fluid. For the cases studied, no significant effect of the PDO on the average heat transfer coefficient was observed.
Influence of the Groove-Patterned Cooling Tube on the Film Cooling Performance of Gas Turbine
Authors: Kim Hyun-Oh , Kim Hak-Sun , Kim Youn-Jea
Published: August 2018

The gas turbine performance significantly depends on the temperature of working fluid. In order to improve the efficiency of gas turbine, it is required to increase turbine inlet temperature. However, the working fluid in high temperature conditions causes thermal stress which could damage turbine blades. One of the methods to require turbine blades by controlling the temperature of working fluid is a film-cooling method. In this study, cooling tubes with various aspect ratios of groove length (L/Lt) with groove diameter of d = 1.2 mm were considered to enhance the film cooling efficiency. In addition, effects of blowing ratios (M) and diffuser angles (δ) of the cooling tube were considered. Numerical investigations were conducted using ANSYS ver. 17.1, and film cooling efficiencies of each case were obtained. Especially, the case with groove length aspect ratio of L/Lt = 0.4 at blowing ratio M = 1.4 and diffuser angle δ = 3.5° showed the highest cooling efficiency of 18% among all model cases.
Modeling of Flow Distribution in Proton Exchange Membrane Fuel Cell
Authors: Babaie Rizvandi Omid , Yesilyurt Serhat
Published: August 2018

Analysis and design of flow fields for proton exchange membrane fuel cell (PEMFC) require coupled solution of the flow fields, gas transport and electrochemical reaction kinetics in the anode and the cathode. Computational cost prohibits the widespread use of three-dimensional models of the anode and cathode flow fields, gas diffusion layers (GDL), catalyst layers (CL) and the membrane for fluid flow and mass transport. On the other-hand, detailed cross-sectional two-dimensional models cannot resolve the effects of the anode and cathode flow field designs. Here, a two-dimensional in-plane model is developed for the resolution of the effects of anode and cathode flow channels and GDLs, catalyst layers are treated as thin-layers of reaction interfaces and the membrane is considered as a thin-layer that resist the transfer of species and the ionic current. Brinkman equations are used to model the in-plane flow distribution in the channels and the GDLs to account for the momentum transport in the channels and the porous GDLs. Fick’s law equations are used to model transport of gas species in the channels and GDLs by advection and diffusion mechanisms, and electrochemical reactions in the CL interfaces are modeled by Butler-Volmer equations. Complete features of the flow in the channels and inlet and outlet manifolds are included in the model using resistance relationships in the through-plane direction. The model is applied to a small cell having an active area of 1.3 cm2 and consisting of 8 parallel channels in the anode and a double serpentine in the cathode. Effects of the anode and cathode stoichiometric ratios on the cell performance and hydrogen utilization are investigated. Results demonstrate that for a sufficiently high cathode stoichiometric ratio enough, anode stoichiometric ratio can be lowered to unity to obtain very high hydrogen utilization and output power.
Miniaturized Tubular Cooling Crystallizer With Solid-Liquid Flow for Process Development
Authors: Schmalenberg Mira , Hohmann Lukas , Kockmann Norbert
Published: August 2018

Production of fine chemicals and pharmaceuticals often includes solid-liquid suspension flow. For continuous cooling a tubular crystallizer was designed based on the coiled flow inverter (CFI) concept, providing a narrow residence time distribution (RTD) of the liquid phase. Counter-current cooling allows for a smooth adjustment of the axial temperature profile. Successful operation of up to 50 g min−1 in a prototype with 4 mm inner diameter was scaled down to a tube-in-tube CFI crystallizer (CFIC) with an inner diameter of 1.6 mm and varying length from 7.8 to 54.6 m. This leads to a significantly lower consumption of chemicals in process development with lower total mass flow rates of 15–20 g min−1. Due to modular design, mean residence time (3.8 to 6.9 min) and mean cooling rate (0.6 to 1.4 K·min−1) were varied at constant mass flow rate. Crystallization growth rate and yield are analyzed with the L-alanine/water test system and seed crystals of 125–180 μm.