bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensory discrimination of the viscosity of thickened liquids for dysphagia management
Authors: Zhong Lei , Hadde Enrico K. , Zhou Zeguang , Xia Yao , Chen Jianshe
Published: August 2018

Thickened water and thickened milk are frequently used in dysphagia management. However, there is still lack of information regarding the correlation between their measured viscosity and sensory viscosity. In this work, the relationship was investigated by rheological measurements and a series of tactile sensory tests. Both magnitude estimation (ME) and triangle protocols were used for the evaluation. The rheological data indicated that both thickened water and thickened milk were shear thinning, but the shear viscosity of thickened milk was obviously higher than that of thickened water for the same amount of thickeners. For the participants considered, the perception of thickened water and thickened milk both obeyed the Stevens' power law according to the results of ME. It was found in the triangle assessments that within the proposed nectar‐ and honey‐thick viscosity ranges, participants were able to correctly discriminate a 0.83‐fold and a 1.05‐fold increase in shear viscosity for thickened water and thickened milk, respectively. Results of both ME and triangle tests suggested that human abilities in detecting the viscosity changes of thickened water and thickened milk by finger tactile sensory were similar within nectar‐ and honey‐thick viscosity range in spite of their different compositions and rheological properties.

Practical applications

Thickened water and thickened milk are commonly used in the management of individuals with dysphagia to improve their quality of life. However, it is difficult to determine the optimal thickening degree in clinical practice because there is a lack of information of the perception of their rheological properties. To investigate the human sensory ability in detecting viscosity differences of thickened water and thickened milk is essential to improve our understanding of the perception of thickened liquids. Moreover, it provides significant information for manufacturing high quality thickened liquids products and for setting guidelines for effectively preparing and serving thickened liquids to individuals with dysphagia.
The burden of suboptimal breastfeeding in Mexico: Maternal health outcomes and costs
Authors: Unar‐Munguía Mishel , Stern Dalia , Colchero Monica Arantxa , González de Cosío Teresita
Published: August 2018

Longer duration of breastfeeding is associated with a lower risk of type 2 diabetes, breast and ovarian cancer, myocardial infarction, and hypertension diseases in women. Mexico has one of the lowest breastfeeding rates worldwide; therefore, estimating the disease and economic burden of such rates is needed to influence public policy. We considered suboptimal breastfeeding when fewer than 95% of parous women breastfeed for less than 24 months per child, according to the World Health Organization recommendations. We quantified the lifetime excess cases of maternal health outcomes, premature death, disability‐adjusted life years, direct costs, and indirect costs attributable to suboptimal breastfeeding practices from Mexico in 2012. We used a static microsimulation model for a hypothetical cohort of 100,000 Mexican women to estimate the lifetime economic cost and disease burden of type 2 diabetes, breast and ovarian cancer, myocardial infarction, and hypertension in mothers, due to suboptimal breastfeeding, compared with an optimal scenario of 95% of parous women breastfeeding for 24 months. We expressed cost in 2016 USD. We used a 3% discount rate and tested in sensitivity analysis 0% and 5% discount rates. We found that the 2012 suboptimal scenario was associated with 5,344 more cases of all analysed diseases, 1,681 additional premature deaths, 66,873 disability‐adjusted life years, and 561.94 million USD for direct and indirect costs over the lifetime of a cohort of 1,116 million Mexican women. Findings suggest that investments in strategies to enable more women to optimally breastfeed could result in important health and cost savings.
Gene expression profiling reveals deep‐sea coral response to the Deepwater Horizon oil spill
Authors: DeLeo Danielle M. , Herrera Santiago , Lengyel Stephen D. , Quattrini Andrea M. , Kulathinal Rob J. , Cordes Erik E.
Published: August 2018

Deep‐sea coral communities are key components of the Gulf of Mexico ecosystem and were adversely affected by the Deepwater Horizon (DWH) oil spill. Coral colonies exposed to oil and dispersant exhibited mortality, damage and physiological signatures of stress. Understanding how corals respond to oil and dispersant exposure at the molecular level is important to elucidate the sublethal effects of the DWH disaster and reveal broader patterns of coral stress responses. Gene expression profiles from RNAseq data were compared between corals at an impacted site and from a reference site. A total of 1,439 differentially expressed genes (≥twofold) were shared among impacted Paramuricea biscaya colonies. Genes involved in oxidative stress, immunity, wound repair, tissue regeneration and metabolism of xenobiotics were significantly differentially expressed in impacted corals. Enrichment among the overexpressed genes indicates the corals were enduring high metabolic demands associated with cellular stress responses and repair mechanisms. Underexpression of genes vital to toxin processing also suggests a diminished capacity to cope with environmental stressors. Our results provide evidence that deep‐sea corals exhibited genome‐wide cellular stress responses to oil and dispersant exposure and demonstrate the utility of next‐generation sequencing for monitoring anthropogenic impacts in deep waters. These analyses will facilitate the development of diagnostic markers for oil and dispersant exposure in deep‐sea invertebrates and inform future oil spill response efforts.
Sporisorium reilianum possesses a pool of effector proteins that modulate virulence on maize
Authors: Ghareeb Hassan , Zhao Yulei , Schirawski Jan
Published: August 2018

The biotrophic maize head smut fungus Sporisorium reilianum is a close relative of the tumour‐inducing maize smut fungus Ustilago maydis with a distinct disease aetiology. Maize infection with S. reilianum occurs at the seedling stage, but spores first form in inflorescences after a long endophytic growth phase. To identify S. reilianum‐specific virulence effectors, we defined two gene sets by genome comparison with U. maydis and with the barley smut fungus Ustilago hordei. We tested virulence function by individual and cluster deletion analysis of 66 genes and by using a sensitive assay for virulence evaluation that considers both disease incidence (number of plants with a particular symptom) and disease severity (number and strength of symptoms displayed on any individual plant). Multiple deletion strains of S. reilianum lacking genes of either of the two sets (sr10057, sr10059, sr10079, sr10703, sr11815, sr14797 and clusters uni5‐1, uni6‐1, A1A2, A1, A2) were affected in virulence on the maize cultivar ‘Gaspe Flint’, but each of the individual gene deletions had only a modest impact on virulence. This indicates that the virulence of S. reilianum is determined by a complex repertoire of different effectors which each contribute incrementally to the aggressiveness of the pathogen.
A comparison of various intragastric balloons for the assessment of gastric motility
Authors: Janssen Pieter , Goelen Nick , Tack Jan
Published: August 2018

Background

There is a clear need for a novel method to readily assess gastric motility in daily clinical practice.

Methods

In a crossover design, 10 noncompliant balloons of different shape and volume (25‐350 mL), attached to a classic feeding tube, were introduced in the stomach of eight healthy volunteers. In the same experiment, a High‐Resolution Manometry (HRM) catheter was positioned throughout the stomach. Gastric motility was recorded during fasting (2 hours) and liquid nutrient administration (30 minutes). Motility was quantified using a peak detection algorithm. Symptoms were recorded throughout the experiment using visual analog scales (100 mm). Results are presented as mean ± SD.

Key Results

The % time during which motility‐induced pressure increments could be detected with HRM but not by the balloon varied from 42 ± 24% in the smallest (25 mL) balloon to 1 ± 1% in the 330 mL balloon. On the other hand, bloating, discomfort and nausea scores were 0 ± 0, 0 ± 0 and 2 ± 5 mm, respectively, for the smallest balloon (25 mL) while these scores were 28 ± 38, 13 ± 30, and 38 ± 30 mm, respectively, for the largest balloon (350 mL). A phase III contraction pattern was consistently evoked in balloons with a volume >200 mL.

Conclusion

Gastric motility could be assessed more accurately with larger volume balloons, while epigastric symptoms were evoked with increasing balloon volume. The optimal balloon to measure gastric motility has a 5 cm diameter and is 11 cm long (210 mL). A nasogastric balloon catheter can now be developed that enables relatively easy monitoring of gastric motility in patients with epigastric symptoms.
Signaling of free fatty acid receptors 2 and 3 differs in colonic mucosa following selective agonism or coagonism by luminal propionate
Authors: Tough Iain R. , Forbes Sarah , Cox Helen M.
Published: August 2018

Background

Propionate exhibits affinity for free fatty acid receptor 2 (FFA2, formerly GPR43) and FFA3 (GPR41). These two G protein‐coupled receptors (GPCRs) are expressed by enteroendocrine L cells that contain anorectic peptide YY (PYY) and glucagon‐like peptide 1 (GLP‐1), while FFA3 is also expressed by enteric neurons. Few studies have investigated the individual roles of FFA2 and FFA3 in propionate's gastrointestinal (GI) effects. Here, we compared FFA2, FFA3, and propionate mucosal responses utilizing selective ligands including an FFA3 antagonist, in mouse and human colonic mucosa.

Methods

Vectorial ion transport was measured in native colonic preparations from normal mouse and human colon with intact submucosal innervation. Endogenous fecal pellet propulsion was monitored in colons isolated from wild‐type (WT) and PYY−/− mice.

Key Results

FFA2 and FFA3 signaling differed significantly. FFA2 agonism involved endogenous L cell‐derived PYY and was glucose dependent, while FFA3 agonism was independent of PYY and glucose, but required submucosal enteric neurons for activity. Tonic FFA3 activity was observed in mouse and human colon mucosa. Apical propionate responses were a combination of FFA2‐PYY mediation and FFA3 neuronal GLP‐1‐ and CGRP‐dependent signaling in mouse ascending colon mucosa. Propionate also slowed WT and PYY−/− colonic transit, and this effect was blocked by a GLP‐1 receptor antagonist.

Conclusions & Inferences

We conclude that luminal propionate costimulates FFA2 and FFA3 pathways, reducing anion secretion and slowing colonic motility; FFA2 via PYY mediation and FFA3 signaling by activation of enteric sensory neurons.
Cancer of the gastroesophageal junction: a diagnosis, classification, and management review
Authors: Chevallay Mickael , Bollschweiler Elfriede , Chandramohan Servarayan M. , Schmidt Thomas , Koch Oliver , Demanzoni Giovanni , Mönig Stefan , Allum William
Published: August 2018

Management of gastroesophageal junction (GEJ) adenocarcinoma is a controversial topic. The rising incidence of this cancer requires a clear consensus to ensure proper management. Application of oncological principles for tumors of the esophagus or stomach is not possible because of comparative differences in the biology of GEJ adenocarcinoma, leading to different therapeutic options. Staging work‐up with endoscopy, endosonography, and PET is essential to inform the choice of neoadjuvant treatment and surgical approach to GEJ adenocarcinoma. Surgery remains the only curative treatment and should be undertaken in specialized centers.
Selective permeability of boundaries in a knowledge brokering team
Authors: Kislov Roman
Published: August 2018

Knowledge brokering teams are increasingly deployed in the public sector to promote coordination and integration across previously separated practices. Permeability of external boundaries surrounding such teams is, however, often taken for granted and has so far received relatively little attention. To address this gap, this article presents the findings of an in‐depth qualitative longitudinal case study of a knowledge brokering team operating in the fragmented healthcare context. It argues that boundary spanning, which increases the permeability of the team boundary, can coexist with the strategies of disengagement, such as boundary buffering and boundary reinforcement, which reduce permeability. The tension between these seemingly opposing strategies can be resolved through selective permeability, whereby the strength of the external team boundary varies depending on the out‐group with which the team interacts, the out‐group's mode of participation, the individual boundary spanner(s) deployed and the stage of the boundary spanning project.
Frost fatigue response to simulated frost drought using a centrifuge in Acer mono Maxim
Authors: Zhang Wen , Jiang Zaimin , Zhao Han , Feng Feng , Cai Jing
Published: August 2018

In the coldest part of winter, water uptake is blocked by the frozen soil and frozen stems known as ‘frost drought’ causing severe embolisms in woody plants. Frost drought in stems was simulated in a centrifuge by a synergy between freeze–thaw cycles and the different tensions induced by changing the rotation speed. Frost fatigue was defined as a reduction of embolism resistance after a freeze–thaw cycle and determined from ‘vulnerability curves’, which showed percent losses of conductivity vs tension (positive value) or xylem pressure (negative value). Different tensions combined with a controlled freeze–thaw cycle were induced to investigate the effects on frost resistance over the course of year. During the growing season, Acer mono Maxim. developed significant frost fatigue, and a significant positive correlation was found between frost fatigue response and exogenous tension. During the dormant season, A. mono showed very high embolism resistance to frost drought, even under a tension of 2 MPa. When the exogenous tension was increased to 3 MPa while the stem was frozen, significant frost fatigue occurred. Longer freezing times had more serious effects on frost fatigue in A. mono. A hypothesis was raised that at the same low temperature, the severer the drought (higher tension) when stems were frozen, the higher frost fatigue response would be induced.
The complex interactions of Ostreid herpesvirus 1, Vibrio bacteria, environment and host factors in mass mortality outbreaks of Crassostrea gigas
Authors: Alfaro Andrea C. , Nguyen Thao V. , Merien Fabrice
Published: August 2018

From the first detection in the Eastern oysters (Crassostrea virginica) in 1972, herpes‐like viruses/herpesviruses have been identified in at least 20 bivalve species and have caused massive mortalities in six cultured species of bivalves. Among them, the Pacific oyster (Crassostrea gigas) is most threatened by massive mortalities associated with detection of Ostreid herpesvirus 1 (OsHV‐1) and its variants. These mortality events have been reported in more than 12 countries, and OsHV‐1 itself has been reported in 15 countries worldwide. Traditionally, the genotype OsHV‐1 (or OsHV‐1 Var) is the main contributor to bivalve mortalities, but the emergence of variants (e.g. OsHV‐1 μVar and related ones, acute viral necrosis virus—AVNV, OsHV‐1‐SB) is now responsible for new mortality outbreaks in Pacific oysters and other bivalve species. In addition to OsHV‐1, Vibrio bacteria and other abiotic and host factors also significantly contribute to mortality outbreaks. To this end, the current contribution aims to synthesize the body of literature on our current knowledge of these mass mortality events to provide insights into the role of each risk factor and complex interactions in the disease process. Specifically, this review encompasses our current knowledge and critical gaps. Important suggestions for future investigation are also presented.
Oxytetracycline in intensive aquaculture: water quality during and after its administration, environmental fate, toxicity and bacterial resistance
Authors: Leal Joana F. , Santos Eduarda B.H. , Esteves Valdemar I.
Published: August 2018

Oxytetracycline (OTC) is one of the most used antibiotics in aquaculture. This raises concerns due to its effects in human and animal health, the environmental contamination and the consequences arising therefrom. This review focuses on the OTC application in intensive aquaculture. It compiles and complements the dispersed information, presenting a comprehensive study about the OTC effects, from its administration to farmed fish, until its release into the surrounding aquatic systems. Several topics about OTC are presented and discussed: physical–chemical properties, interaction with ions, application to farmed fish, effects in water quality and possible treatments, biological activity and toxicity of OTC by‐products, environmental fate. Based on the information gathered, one concludes that OTC establishes strong complexes with Ca2+ and Mg2+, which may have implications on its biological activity. OTC acts as inhibitor of protein synthesis and is poorly metabolized or unmetabolized by fish. Its common recommended daily dose is about 75 mg kg−1 but depends on the administration conditions and on target fish species. Regarding OTC removal from water within a semiclosed aquaculture's water circuit, ozonation and photodegradation are not completely efficient methods as none of them promotes total mineralization. However, photodegradation can be applied as a complementary method prior to ozonation, allowing to reduce costs. OTC by‐products do not appear to retain its biological activity, but toxicity studies mimicking environmental conditions were not found. In open circuits (cages), water column where OTC is administered not suffer a specific treatment and the antibiotic is easily spread by the surrounding environments, affecting their inhabitants. OTC is released in the aquatic system in freely dissolved form and/or associated with organic or inorganic compounds, being subjected to natural photolysis, hydrolysis and/or biodegradation.
Statin combined with exercise training is more effective to improve functional status in dyslipidemic older adults
Authors: Baptista Liliana C. , Veríssimo Manuel Teixeira , Martins Raul A.
Published: August 2018

Background

Exercise training (EX) and statins are first‐line therapies to manage dyslipidemia.

Purpose

This study aims to analyze the effect of EX and statins on functional status and cardiovascular risk (CVR) in dyslipidemic older adults with comorbidities.

Methods

Participants (n = 981) underwent one of 3 conditions: (a) multicomponent exercise training (EX; n = 298; 74% females); (b) statins (ST; n = 178; 65% females); (c) combined therapy—exercise plus ST therapy (ST+EX; n = 505; 79% females). Functional fitness, anthropometry, hemodynamic and lipid profiles, and were assessed at baseline and after 2‐years.

Results

EX and ST+EX participants improved all the functional status variables, whereas ST participants aggravated all the outcomes. Triglycerides and HDL‐cholesterol maintained unchanged and total cholesterol decreased in the three groups, whereas LDL‐cholesterol (LDL‐C) decreased in EX and ST+EX groups but not in ST group. EX and ST+EX groups decreased body mass index (BMI), systolic and diastolic blood pressure; contrarily, ST group increased these variables.

Conclusion

Statins combined with exercise training or exercise alone are more effective to improve functional status, to manage cholesterol levels and overall cardiovascular risk factors in dyslipidemic older adults with comorbidities than ST alone. Furthermore, current results suggest that isolated statin therapy decreases functional status and other cardiovascular risk factors.
Comparative oncology: The paradigmatic example of canine and human mast cell neoplasms
Authors: Willmann Michael , Hadzijusufovic Emir , Hermine Olivier , Dacasto Mauro , Marconato Laura , Bauer Karin , Peter Barbara , Gamperl Susanne , Eisenwort Gregor , Jensen‐Jarolim Erika , Müller Mathias , Arock Michel , Vail David M. , Valent Peter
Published: August 2018

In humans, advanced mast cell (MC) neoplasms are rare malignancies with a poor prognosis. Only a few preclinical models are available, and current treatment options are limited. In dogs, MC neoplasms are the most frequent malignant skin tumours. Unlike low‐grade MC neoplasms, high‐grade MC disorders usually have a poor prognosis with short survival. In both species, neoplastic MCs display activating KIT mutations, which are considered to contribute to disease evolution. Therefore, tyrosine kinase inhibitors against KIT have been developed. Unfortunately, clinical responses are unpredictable and often transient, which remains a clinical challenge in both species. Therefore, current efforts focus on the development of new improved treatment strategies. The field of comparative oncology may assist in these efforts and accelerate human and canine research regarding diagnosis, prognostication, and novel therapies. In this article, we review the current status of comparative oncology approaches and perspectives in the field of MC neoplasms.
A complication probability study for a definitive‐intent, moderately hypofractionated image‐guided intensity‐modulated radiotherapy protocol for anal sac adenocarcinoma in dogs
Authors: Meier Valeria , Besserer Jürgen , Roos Malgorzata , Rohrer Bley Carla
Published: August 2018

Previous trials showed the importance of administering radiation therapy (RT) with small doses per fraction in canine pelvic tumours to maintain acceptable toxicity levels. With increased accuracy/precision of RT, namely intensity‐modulated RT (IMRT), this approach might be challenged. Theoretical toxicity calculations for a new definitive‐intent moderately hypofractionated RT protocol for canine anal sac adenocarcinomas (ASAC) were performed, focussing on the risk of toxicity in pelvic organs at risk (OAR). Computed tomography datasets of 18 dogs with stage 3b ASAC were included. Re‐planning with margins for daily image‐guidance/IMRT was performed and a new protocol isoeffective to previously described definitive‐intent protocols was computed. Dose‐volume information were derived from individual plans and used for normal tissue complication probability (NTCP) computations. A 12 × 3.8 Gy protocol was computed for risk estimation. Tumour volumes ranged from 27.9 to 820.4 cm3 (mean 221.3 cm3 ± 188.9). For late rectal toxicity/bleeding ≥grade 2, median risk probability was 2.3% inter quartile range (IQR: 5.9; 95% confidence interval (CI): 1.2, 8.4) (rho = 0.436) and 3.4% (IQR: 0.96; 95%CI: 3.1, 4.0) (rho = 0.565), respectively. Median late toxicities in urinary bladder, kidneys and small bowel were <1%, except in one kidney. Myelopathy/myelonecrosis had a median risk probability of 4.1% (IQR: 23.5; 95%CI: 2.1, 25.2) (rho = 0.366) and 5.6% (IQR: 13.5; 95%CI: 3.1, 14.1) (rho = 0.363), respectively. However, graded risk showed a probability estimate for late spinal cord toxicity of ≥5% in 8/18 patients. The daily‐imaging IMRT 12 × 3.8 Gy protocol for canine ASAC seems tolerable for most cases, even in advanced disease. Theoretical dose computations serve as estimate, but are safe measures before implementing new protocols into clinical use.
Assessment of coagulation‐ultrafiltration performance for the treatment of primary wastewater using alum sludge
Authors: Mazari Lilia , Abdessemed Djamal , Szymczyk Anthony , Trari Mohamed
Published: August 2018

The main purpose of this research was to develop an effective and inexpensive pretreatment for ultrafiltration (UF) membrane process in order to treat a primary effluent for its reuse in several applications by avoiding biological treatment. For that the impacts of reuse alum sludge liquid recovered by the drinking water treatment plant of Boudouaou (Algiers area) has been examined on the water quality in coagulation–sedimentation processes. The tests were carried out on a primary effluent of wastewater treatment plant. The elemental analysis by x‐ray fluorescence showed that the tested sludge is composed mainly of Al2O3 (41%) and SiO2 (44%). The efficiency of alum sludge as primary coagulant was compared with a conventional metal‐ion coagulant (fresh alum) using a jar test apparatus for simultaneous removals of turbidity, UV254 and chemical oxygen demand (COD). For dose of 30 mg Al/L, the sludge was effective as primary coagulant for removing the turbidity, COD and UV254.
Removal of Sudan dyes from environmental waters and food samples with amine functionalized magnetic silica nanoparticles as solid‐phase extraction adsorbent
Authors: Ghasemi Amin , Es'haghi Zarrin , Jamali Mohammad Reza
Published: August 2018

In this research, the amine functionalized magnetic silica‐based nanocomposite as a solid‐phase extraction adsorbent coupled with high‐performance liquid chromatography was applied for the preconcentration and determination of Sudan dyes in environmental waters and a food sample. The synthesized core‐shell Fe3O4@silica nanoparticles were functionalized with amino groups and characterized by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and Fourier transform infrared spectroscopy techniques. The experimental parameters optimized and under the best conditions, the sorbent was successfully used to extract the target analytes. The result showed that a good linearity with a r‐value of greater 0.990, and the limits of detection were from 0.082 to 0.12 µg L−1. The relative recoveries obtained by analysing the spiked water samples were in the range of 90–102% and the relative standard deviations were between 0.590 and 7.94%.
Influential factors for metal ions removal using extracellular polymeric substances produced by Cloacibacterium normanense
Authors: Wang Xiaoju , Hua Zulin , Mao Haitao
Published: August 2018

This study was conducted to investigate the interactions between metal ions and extracellular polymeric substances (EPS) with pH, contact time, compositions of EPS and concentration of EPS. The proteins were the dominated components in EPS of compositions. In particular, the optimal pH for the flocculation of EPS was approximately pH 5.0, except for Hg(II) which is stable in alkaline environments. The heavy removal efficiency of Ni and Al increased from 33 to 81% and 59 to 64%, respectively, when the contact time increased from 0.5 to 1.3 h. Furthermore, the EPS adsorption satisfactorily correlated Freundlich isotherm with the data of Al, Fe, Ni and Zn, with R2 ranging from 0.93 to 0.99, but poorly for Cu, with R2 ranging from 0.81 to 0.88. The results revealed that the flocculating capacity and metal removal ability of the EPS produced by Cloacibacterium normanense represent a good alternative as a bioflocculant and low‐cost adsorbent.
East Asian English learners crossing Outer and Inner Circle boundaries
Authors: Kobayashi Yoko
Published: August 2018

Drawing upon world Englishes theory and research, in particular, studies that re‐examine Kachru's Three Circles model, the present study addresses Japanese English learners’ sojourn experiences in the ASEAN Outer Circle and/or the Western Inner Circle nations. It numerically and qualitatively cross‐examines two groups in terms of sojourn motives, gender differences, and interest in the other type of sojourn. The study suggests that without veering from ‘native English’ norms, Japanese youth informed about the ASEAN nations’ international visibility embrace opportunities to study in these nations and broaden their notion of English(es). Also discussed are pedagogical implications for, for example, the implementation of study‐in‐ASEAN programs for many Expanding Circle female students majoring in West‐oriented degree programs.
A New Type of Planar Two Degree-of-Freedom Remote Center-of-Motion Mechanism Inspired by the Peaucellier–Lipkin Straight-Line Linkage
Authors: Chen Genliang , Wang Jiepeng , Wang Hao
Published: August 2018

Benefiting from small incisions, reduced risk of infection, less pain, and fast recovery, minimally invasive surgery has shown tremendous advantages for patients. In these kinds of procedures, remote center-of-motion (RCM) mechanisms play an important role in performing operations through small incisions. Inspired by the Peaucellier–Lipkin straight-line cell, this paper presents the design and verification of a new type of planar two degree-of-freedom (DOF) RCM mechanism. A synthesized planar RCM mechanism is realized by a symmetric linkage actuated by two circular motion generators. The main merit of the proposed 2DOF RCM mechanism is its straightforward kinematics, which results in a simple control scheme. One of the candidate mechanisms, which is simple in structure and easy to fabricate, is intensively investigated. A prototype was built, on which preliminary experiments have been conducted, to verify the feasibility of the proposed new mechanism. The experimental results show that the fabricated 2DOF prototype has a nearly stationary remote center of motion. Therefore, the prototype has potential applicability in robot-assisted minimally invasive surgeries.
Influencing Mechanism of Rubber Wheel on Contact Pressure and Metal Removal in Corrugated Rail Grinding by Abrasive Belt
Authors: Fan Wengang , Liu Yueming , Song Xiaoyang , Cheng Jifa , Li Jianyong
Published: August 2018

Rail grinding has been widely recognized as an essential measure in routine maintenance of railway network in the world. Compared with other technologies, the emerging abrasive belt grinding process for direct rail maintenance rather than limited polishing finish has shown the convincing potential to improve metal removal rate and surface quality. However, the influencing mechanism of the rubber wheel on contact pressure and metal removal for the corrugated rails is yet unknown. This paper develops a contact pressure model to obtain the boundary curve and the stress distribution of the contact zone between the rubber wheel with concave peripheral surface and the rail surface with corrugation. Based on this, the metal removal model is subsequently established through the abrasive processing theory. Finite element (FE) simulations and grinding tests are finally implemented. Results confirm the above-mentioned theoretical models of contact pressure and metal removal and show the significant influences of the rubber wheel's feature on contact pressure and metal removal.
Patterns of Regenerative Milling Chatter Under Joint Influences of Cutting Parameters, Tool Geometries, and Runout
Authors: Niu Jinbo , Ding Ye , Geng Zunmin , Zhu LiMin , Ding Han
Published: August 2018

The regenerative milling chatter is usually regarded as some kind of bifurcation or chaos behaviors of the machining system. Although several chatter patterns such as the secondary Hopf, the period doubling, and the cyclic fold bifurcations were once reported, their relationships with cutting conditions remain undiscovered. This paper aims to uncover the dynamic mechanism of distinct chatter behaviors in general milling scenarios. First, two complementary methods, i.e., the generalized Runge–Kutta method and the time-domain simulation technique, are presented to jointly study the distribution rule of chatter patterns in stability lobe diagrams for milling processes with general flute-spacing tools considering runout. The theoretical predictions are validated by one published example and two cutting experiments under three different cutting conditions. Furthermore, the cutting signal characteristics and cutting surface topography of distinct chatter patterns are analyzed and compared in detail. On this basis, this paper studies the joint influences of cutting parameters, tool geometries, and runout on regenerative chatter behaviors with the proposed methods.
Design Exploration of Reliably Manufacturable Materials and Structures With Applications to Negative Stiffness Metamaterials and Microstereolithography1
Authors: Morris Clinton , Bekker Logan , Haberman Michael R. , Seepersad Carolyn C.
Published: August 2018

One of the challenges in designing metamaterials for additive manufacturing (AM) is accounting for the differences between as-designed and as-built geometries and material properties. From a designer's perspective, these differences can lead to degradation of part and metamaterial performance, which is especially difficult to accommodate in small-lot or one-of-a-kind production. In this context, each part is unique, and therefore, extensive iteration is costly. Designers need a means of exploring the design space while simultaneously considering the reliability of additively manufacturing particular candidate designs. In this work, a design exploration approach, based on Bayesian network classifiers (BNC), is extended to incorporate manufacturing variation into the design exploration process and identify designs that reliably meet performance requirements when this variation is taken into account. The example application is the design of negative stiffness (NS) metamaterials, in which small volume fractions of NS inclusions are embedded within a host material. The resulting metamaterial or composite exhibits macroscopic mechanical stiffness and loss properties that exceed those of the base matrix material. The inclusions are fabricated with microstereolithography with features on the scale of tens of microns, but variability is observed in material properties and dimensions from specimen to specimen. This variability is measured and modeled via design, fabrication, and characterization of metrology parts. The quantified manufacturing variability is incorporated into the BNC approach as a manufacturability classifier to identify candidate designs that achieve performance targets reliably, even when manufacturing variability is taken into account.
Effect of Aluminized Coating on Combined Low and High Cycle Fatigue Life of Turbine Blade at Elevated Temperature
Authors: Chen Cao , Yan Xiaojun , Zhang Xiaoyong , Zhang Yingsong , Gui Min , Tao Min
Published: August 2018

Some cracks were detected on the fir-tree root of turbine blade in an in-service aero-engine, and the aluminized coating was considered to be the main cause of these cracks. To study the effect of aluminized coating on fatigue life of turbine blade, the combined low and high cycle fatigue (CCF) tests are carried out at elevated temperature on both aluminized and untreated turbine blades. Probability analysis of test data is conducted and the result indicates that the median life is decreased by 62.2% due to the effect of the aluminized coating. Further study on the mechanism of crack initiation and propagation has been conducted based on fractography and cross section morphology analysis by using scanning electron microscope (SEM), and the results indicate: (1) The aluminized coating consists of two layers, of which the inner layer is considered to contain the σ phase and it reduces the resistance to fatigue of blade. (2) Many cavities are found in the inner layer of aluminized coating, which lead to the initiation of cracks and result in the reduction of crack initiation life. (3) The marker band widths of aluminized and untreated blade are very close, which indicated the aluminized coating may have no effect on the crack propagation life of the blade.
Effect of Fine TiC Particle Reinforcement on the Dry Sliding Wear Behavior of In Situ Synthesized ZA27 Alloy
Authors: David Roshita , Dasgupta Rupa , Prasad B. K.
Published: August 2018

The in situ method of making zinc-aluminum composites wherein TiC has been introduced has been investigated in the present paper for its microstructural, physical, and dry sliding wear behavior and compared with the base alloy. In the present study, ZA-27 alloy reinforced with 5 and 10 vol % TiC was taken into consideration. The results indicate that the wear rate and coefficient of friction of composites were lower than that of base alloy. The material loss in terms of both wear volume loss and wear rate increases with increase in load and sliding distance, respectively, while coefficient of friction follows a reverse trend with increase in load. Better performance was obtained for 5% TiC reinforcement than with 10% probably due to agglomeration of particles resulting in nonuniform dispersion. Worn surfaces were analyzed by scanning electron microscopy (SEM) analysis.
Effects of Size and Sodium Dodecyl Sulfate on Mass Transfer for Liquid-Liquid Two-Phase Flow in Non-Circular Glass Microchannels
Authors: Svensson Astrid , Wu Zan , Sunden Bengt
Published: August 2018

This study concerns effects of two main variables on hydrodynamics and mass transfer in the liquid-liquid two-phase slug flow regime. The influence of size of square and rectangular microchannels and presence of sodium dodecyl sulfate (SDS) are investigated. Three microchannels with dimensions 600×600 (MC600), 400×400 (MC400) and 600×300 (MC300) μm were used with hydraulic diameters of 600, 400 and 400 μm respectively. The results revealed that decreasing the hydraulic diameter improved the interfacial area due to slug length enlargement in both phases. Furthermore, mass transfer resistance was reduced because of enhanced internal circulations, leading to considerable enhancement of the overall mass transfer coefficient KL. It was also found that the enhancement of KL was greater in the square MC400 microchannel than in the rectangular MC300, as compared to the MC600. The enhancing benefit from internal circulations in organic slugs in rectangular microchannels decreased at higher aqueous flow rates due to enlarged stagnant liquid film flow between the organic slug and the microchannel wall.

The presence of SDS slightly increased the interfacial area by reducing the slug length in both phases. However, there was a significant decrement in KL, due to a greater mass transfer resistance.
Evaporation From a Simulated Soil Pore: Effects of Relative Humidity
Authors: Chakraborty Partha P. , Derby Melanie M.
Published: August 2018

Reduction of irrigation is a pressing issue in the food-water-energy nexus. Around two-third of global water withdrawals are used for irrigation in the areas with insufficient rainfall. In the U.S. Central High Plains, the Ogallala Aquifer is responsible for providing water for the production of corn, wheat, soybeans, and cattle; reducing the evaporation of water from soil provides an excellent opportunity to decrease the need for irrigation. In this paper, evaporation of sessile 4-μl water droplets from a single simulated soil pore was observed. Soil pores were created using three 2.35-mm hydrophilic glass or hydrophobic Teflon beads of the same size. The experiments were conducted at the same temperature (20° C) and two relative humidity levels, 45% and 60% RH. Evaporation times were recorded and the transport phenomena were captured using a high-speed camera. Relative humidity directly affected evaporation; evaporation times were lower at the lower RH. The glass surface had higher wettability and therefore the droplets were more stretched on the glass beads, more droplet-air areas were created and evaporation times were approximately 30 minutes at 60% RH. The Teflon surface was hydrophobic, for which air-water contact areas were lower, and evaporation times were longer — approximately 40 minutes at 60% RH. As evaporation progressed, a liquid island formed between two beads at both 45% and 60% RH in for glass and Teflon pores. The rate of decrease of the radius of the liquid island was shorter in Teflon than glass beads, which corresponded to lower evaporation rates from Teflon.
Effect of Periodic Flow Structure on Heat Transfer in Milliscale Confined Impinging Newtonian and Non-Newtonian Flow
Authors: Chatterjee Ajay , Fabris Drazen
Published: August 2018

Impinging flows are widely used to enhance convective heat transfer by promoting separation, recirculation and higher rates of local convection. We consider unsteady flow and heat transfer effects in a prototypical T-shaped geometry as an impinging jet. Depending on the relative length scales, the steady laminar flow in this geometry may lose stability and transition to time periodic flow even at a low Reynolds number. A key feature of the periodic structure is the presence of ‘twin’ circulation regions adjacent to the jet column, and separation vortices anchored at the impinging surface in place of the wall jet in steady flow. The separation vortices are located above shear layers lying along the confining plane of the geometry which is flush with the jet exit. Consequently, convective heat transfer is enhanced across this plane. We present calculations to show the effect of the structure of the periodic flow on heat transfer rates across the two parallel surfaces. For a shear thinning fluid the local Nusselt number at the confining surface averaged over a long length scale (∼ 50 times the nozzle width) is more than twice as large compared to that in steady flow, while for the Newtonian fluid the mean Nusselt number increases about 60%. A mild increase in the transport rate across the impinging surface is also observed. Thus flow periodicity due to instability of the steady flow field provides a mechanism to increase the total heat transfer rate across the two surfaces.
Active Sensors for Gas-Liquid Mass Transfer Studies in Capillaries
Authors: Krieger Waldemar , Dinter Robin , Wiese Georg , zur Horst-Meyer Santer , Kockmann Norbert
Published: August 2018

Gas-liquid and gas-liquid-solid reactions in microstructured devices are an active field in scientific research with many industrial applications. High surface-to-volume ratio as well as enhanced heat and mass transfer are advantageous making microstructured devices a promising technology to overcome mass transfer limitations. The implementation of traditional sensors and analytical methods is a drawback when investigating mass transfer phenomena within microstructured devices, since they disturb the flow and reactor characteristics. Offline measurement techniques provide limited insight into flow structure, while noninvasive online measurement techniques either cannot provide local results or require a sophisticated setup. In this work, a noninvasive ultrasonic sensor (SONOTEC, Germany) is used to measure particle concentration and bubble length in Taylor flow. Particle concentration and bubble detection is derived from the ultrasonic signal. Further, an Arduino based slider setup is developed, which is equipped with a computed-vision system to track bubbles in Taylor flow. This setup can be combined with optical analytical methods allowing for investigating the entire life time of a single bubble or liquid slug.
Controlling Interfacial Flow Instability via Micro Engineered Surfaces Towards Multiscale Channel Fabrication
Authors: Islam Tanveer ul , Gandhi Prasanna S.
Published: August 2018

Hierarchical branched structures exist in nature in diverse forms, functions and scales stretching from micro to very large sizes. Typically effective as heat and mass transfer networks, ordered hierarchal/ multiscale branched/ tree-like networks could be fabricated by controlling a fluid reshaping process in a device called ‘Multiport Hele-Shaw cell’. Control over the instability by employing micro-modified cell plates, containing ‘source-holes’ as ports, rearranges the fluid into ordered tree-like networks. Reshaping is an outcome of ‘Saffman-Taylor interface instability’ induced by the displacement of a high-viscous fluid by a relatively low-viscous one in the cell. A new configuration of ‘source-holes’, is proposed here to control the instability towards shaping of high-viscous fluid into ordered multiscale treelike layouts. The process is lithography-less method of shaping the fluid spontaneously into 3D layouts in a very short interval of time. Fabricated structures are UV-cured and cast into channel-networks in an elastomer PDMS.
Transient Thermal Characteristics for a Liquid Drop Impacting a Hot PCM Substrate
Authors: Khan Abdul Ahad , Choudhary Dilip , Basavanna Abhishek , Najmee Salman , Crisantes Jessica , Dhillon Navdeep S.
Published: August 2018

The physics of the transient behavior of liquid drops impacting hot or cold surfaces are of significance in many different applications such as spray cooling, aircraft icing, etc. Further, the transient heating and cooling of vapor spots and liquid patches is of significance in determining the heat transfer performance parameters in phase change processes such as boiling and condensation. The thermal transients in all these processes are primarily dictated by the passive thermal properties of the solid substrate (e.g. thermal conductivity, specific heat) and by the flow conditions. An active control (or manipulation) of these thermal transients could provide a means to enhance the performance parameters in various phase change-based heat transfer processes. In this study, we experimentally explore the effect of a solid-liquid phase change material (PCM) coating on the thermal characteristics of a liquid drop impacting a hot surface. High-speed optical and infrared imaging techniques are employed for visualizing the flow and measuring the temperatures, respectively. The PCM, depending on its melting temperature and due to its latent heat of fusion, disrupts the normal process of the heating of the drop and cooling of the substrate. The insights obtained from these findings can have a significant impact on several technologies in the areas of phase change-based heat transfer and thermal management.
Modeling the Influence of Marangoni Flows on the Leidenfrost State on Solid and Liquid Substrates
Authors: Shahriari Arjang , Acharya Palash V. , Bahadur Vaibhav
Published: August 2018

Boiling heat transfer affects various processes related to energy, water and manufacturing. In the film boiling regime, heat transfer is substantially lower than in the nucleate boiling regime, due to the formation of a vapor layer at the solid-liquid interface (Leidenfrost effect). In this work, we present analytical modeling of the Leidenfrost state of droplets on solid and liquid substrates. A key aspect of this study is the focus on surface tension gradients on the surface of a liquid (Leidenfrost droplet or liquid substrate), which actuate thermo-capillary driven Marangoni flows. It is noted that this work develops a first-order simplified model, which assumes a uniform vapor layer thickness. The presence of Marangoni flows has non-trivial implications on the resulting thickness of the Leidenfrost vapor layer. Our analysis shows that the pumping effect generated in the vapor layer due to Marangoni flows can significantly reduce the Leidenfrost vapor layer thickness.
Measurements for Condensation of Steam-Ethanol Mixtures in Microchannels
Authors: Chai Lei , Hua Nan , Xu Rong Ji , Liu Jiong Hui , Yu Guang Xu , Rose John W. , Wang Hua Sheng
Published: August 2018

The paper reports heat-transfer measurements for condensation of pure steam and steam-ethanol mixtures in parallel horizontal microchannels in an aluminum test section cooled from above and below by water in counter-current flow. The local heat flux and channel surface temperature were determined from temperatures measured by 100 thermocouples accurately located in small holes above and below the microchannels and spaced at 10 locations in the flow direction. Tests were conducted for a range of vapor mass fluxes and cooling intensities. The streamwise distributions of channel heat flux, channel surface temperature and vapor quality were obtained by curve-fitting the test block temperatures. Heat-transfer coefficients were obtained for the cases where complete condensation did not occur in the channels by assuming linear pressure distribution between accurately measured pressures at inlet and exit and assuming saturation conditions in the two-phase flow region of the channels.