bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of 6% tetrastarch or lactated Ringer's solution on blood coagulation in hemorrhaged dogs
Authors: Diniz Miriely S. , Teixeira‐Neto Francisco J. , Gonçalves Daniele S. , Celeita‐Rodríguez Nathalia , Girotto Carolina H. , Fonseca Mariana W. , Takahira Regina K.
Published: October 2018

Background

Tetrastarch solution (TS) can impair coagulation but the clinical relevance of this impairment is unclear in veterinary medicine.

Objective

Compare the effects of volume replacement (VR) with lactated Ringer's solution (LRS) or 6% TS on coagulation in hemorrhaged dogs.

Animals

Six healthy English Pointer dogs (19.7‐35.3 kg).

Methods

Prospective crossover study. Dogs were anesthetized without hemorrhage and VR (control). Two weeks later, dogs were hemorrhaged under anesthesia on 2 occasions (8‐week washout intervals) and randomly received VR with LRS or TS at 3:1 or 1:1 of shed blood, respectively, aiming to decrease the hematocrit to 33%. Rotational thromboelastometry and other coagulation variables were determined before 0.5, 2, and 4 hours after VR during anesthesia and 24 hours after VR (conscious dogs).

Results

Buccal mucosal bleeding time did not differ between treatments after VR. Activated partial thromboplastin time increased from controls 4 hours after TS (P = 0.045). Clot formation time (CFT) and alfa‐angle increased from controls from 0.5 to 4 hours after LRS (CFT, P ≤ 0.0001‐0.02; alpha angle, P = 0.0001‐0.02) and from 0.5 to 2 hours after TS (CFT, P = 0.0002‐0.01; alpha angle, P = 0.0005‐0.02). The maximum clot firmness decreased from controls from 0.5 to 4 hours after LRS (P ≤ 0.0001‐0.01) and TS (P ≤ 0.0001‐0.04).

Conclusions and Clinical Relevance

Tetrastarch does not impair primary hemostasis and induces transient dilutional coagulopathy that is similar to LRS because, when compared to a 3 times higher volume of LRS in hemorrhaged dogs, it does not cause greater interference on the viscoelastic properties of the coagulum.
Female preterm indigenous Australian infants have lower renal volumes than males: A predisposing factor for end‐stage renal disease?
Authors: Kandasamy Yogavijayan , Rudd Donna , Lumbers Eugenie R , Smith Roger
Published: October 2018

Aim

Indigenous Australians have an increased risk of developing chronic kidney disease (CKD). Indigenous women have a higher rate of CKD than men. In a cohort of Indigenous and non‐Indigenous preterm neonates, we assessed total renal volume (TRV) (a proxy indicator for nephron number). We hypothesized that there would be no difference in renal volume between these two groups at term corrected (37 weeks gestation).

Methods

Normally grown preterm neonates less than 32 weeks of gestation were recruited and at term corrected dates, the neonates underwent renal ultrasonography (TRV measurements), urine microalbumin‐creatinine ratio and serum analysis for Cystatin C measurement for estimated glomerular filtration rate (eGFR) calculation.

Results

One hundred and five neonates (38 Indigenous; 67 non‐Indigenous) were recruited. Indigenous neonates were significantly more premature and of lower birth weight. At term corrected age, Indigenous neonates had a significantly smaller TRV (18.5 (4.2) vs 21.4 (5.1) cm3; P = 0.027) despite no significant difference in body weight. Despite having a smaller TRV, there was no significant difference in eGFR between Indigenous and Non‐indigenous neonates (47.8 [43.2–50.4] vs 46.2 [42.6–53.3] ml/min per 1.73 m2; P = 0.986). These infants achieve similar eGFR through hyperfiltration, which likely increases their future risk of CKD. There was no difference in microalbumin‐creatinine ratio. Female Indigenous neonates, however, had significantly smaller TRV compared with Indigenous male neonates (15.9 (3.6) vs 20.6 (3.6) cm3; P = 0.006), despite no difference in eGFR, birth weight, gestational age, and weight at term corrected.

Conclusion

The difference in TRV is likely to be an important risk factor for the difference in morbidity and mortality from renal disease reported between male and female Indigenous adults.
Multiple independent origins of intermediate species between Sorbus aucuparia and S. hybrida (Rosaceae) in the Baltic region
Authors: Levin Joel , Fay Michael F. , Pellicer Jaume , Hedrén Mikael
Published: October 2018

Populations intermediate between the diploid and sexual Sorbus aucuparia and the tetraploid and facultative apomictic Sorbus hybrida are scattered in coastal regions of southern Scandinavia. Our aims were to investigate whether these populations were of local and independent origins, whether they were morphologically and molecularly distinct from each other and whether they could give rise to constant offspring by apomixis. Six intermediate populations from the Baltic Sea basin were studied for variation at nuclear and plastid microsatellite loci, for morphological differentiation patterns, and for ploidy level by flow cytometry. Seeds were sown to check for constancy with the mother plants. Three populations from Gotland and possibly the small population from Uppland were in each case fixed for a unique combination of genetic markers, had restricted variation in leaf shape and were morphologically divergent from each other. Flow cytometry analysis showed that the four genetically monomorphic populations were consistently triploid. Cultivation showed that offspring from trees within two of the monomorphic populations had leaf shapes closely similar to the mother individuals. In contrast, a population from Gotland and a population from Åland were variable at molecular marker loci and were variable in leaf shape. The three monomorphic Gotland populations and possibly also the Uppland population propagate asexually by apomixis, and they have independent origins. The two variable populations are apparently composed of hybrids that have been formed repeatedly and independently between individuals of the two parental species growing at the same sites. One of the Gotland apomicts has already been described as Sorbus teodori. Sorbus faohraei Hedrén & J.Levin and Sorbus atrata Hedrén & J.Levin are described as new apomictic species from Gotland.
The Effectiveness of Single‐Sex Schools through Out‐of‐School Activities: Evidence from South Korea
Authors: Hahn Youjin , Wang Liang Choon
Published: October 2018

Students’ out‐of‐school activities and time use can play a crucial role in facilitating the effect of schools on students’ achievement. Using data from Seoul, South Korea, where students are randomly assigned into schools, we show that when single‐sex schools improve students’ test performance, their effect is positive on students’ time spent on study‐related out‐of‐school activities. Our results indicate that out‐of‐school activities explain roughly 21%–30% of the effect of single‐sex schooling on test performance.
Homeostatic and neurocognitive control of energy intake in response to exercise in pediatric obesity: a psychobiological framework
Authors: Thivel D. , Finlayson G. , Blundell J. E.
Published: October 2018

While energy intake and energy expenditure have long been studied independently, the alarming progression of obesity has led to a more integrative approach to energy balance considering their potential interactions. Although the available literature concerned with the effect of chronic and acute exercise on energy intake and appetite control in adults is considerable, these questions remain less explored among children and adolescents. Based on the search of four databases (Medline, Embase, PsycINFO and Cochrane Library; articles published until May 2018), the objective of this review is to summarize and discuss the effect of acute and chronic physical exercise on energy intake and appetite control in children and adolescents with obesity, and to identify the physiological and neurocognitive signals and pathways involved. Evidence suggested that acute intensive exercise has the potential to reduce subsequent energy intake in children and adolescents with obesity but not healthy weight, through both peripheral (mainly gastro‐peptides) and neurocognitive (neural responses to food cues) pathways. The nutritional responses to chronic physical activity remain less clear and require further consideration, especially from an anti‐obesity perspective.
Environmentally‐induced noise dampens and reddens with increasing trophic level in a complex food web
Authors: Kuparinen Anna , Perälä Tommi , Martinez Neo D. , Valdovinos Fernanda S.
Published: October 2018

Stochastic variability of key abiotic factors including temperature, precipitation and the availability of light and nutrients greatly influences species’ ecological function and evolutionary fate. Despite such influence, ecologists have typically ignored the effect of abiotic stochasticity on the structure and dynamics of ecological networks. Here we help to fill that gap by advancing the theory of how abiotic stochasticity, in the form of environmental noise, affects the population dynamics of species within food webs. We do this by analysing an allometric trophic network model of Lake Constance subjected to positive (red), negative (blue), and non‐autocorrelated (white) abiotic temporal variability (noise) introduced into the carrying capacity of basal species. We found that, irrespective of the colour of the introduced noise, the temporal variability of the species biomass within the network both reddens (i.e. its positive autocorrelation increases) and dampens (i.e. the magnitude of variation decreases) as the environmental noise is propagated through the food web by its feeding interactions from the bottom to the top. The reddening reflects a buffering of the noise‐induced population variability by complex food web dynamics such that non‐autocorrelated oscillations of noise‐free deterministic dynamics become positively autocorrelated. Our research helps explain frequently observed red variability of natural populations by suggesting that ecological processing of environmental noise through food webs with a range of species’ body sizes reddens population variability in nature.
Butterfly–host plant synchrony determines patterns of host use across years and regions
Authors: Toftegaard Tenna , Posledovich Diana , Navarro‐Cano José A. , Wiklund Christer , Gotthard Karl , Ehrlén Johan
Published: October 2018

Variation in the degree of synchrony among host plants and herbivores can disrupt or intensify species interactions, alter the strength of natural selection on traits associated with phenological timing, and drive novel host plant associations. We used field observations from three regions during four seasons to examine how timing of the butterfly herbivore Anthocharis cardamines relative to six host plant species (Arabis hirsuta, Cardamine pratensis, Arabis glabra, Arabidopsis thaliana, Thlaspi caerulescens and Capsella bursa‐pastoris) influenced host species use and the choice of host plant individuals within populations. Butterflies laid a larger fraction of their eggs on species that were closer to the butterfly's preferred stage of development than on other host species. Within host plant populations, butterflies showed a stronger preference for individuals with a late phenology when plants within the population were on average more developed at the time of butterfly flight. Our results suggest that changes in synchrony between herbivores and their host plants are associated with changes in both host species use and the choice of host plant individuals differing in phenology within populations. This is likely to be an important mechanism generating variation in interaction intensities and trait selection in the wild, and therefore also relevant for understanding how anthropogenic induced changes, such as global warming, will influence natural communities.
Comparative pharmacokinetics of tacrolimus in de novo pediatric transplant recipients randomized to receive immediate‐ or prolonged‐release tacrolimus
Authors: Vondrak Karel , Dhawan Anil , Parisi Francesco , Grenda Ryszard , Debray Dominique , Marks Stephen D. , Webb Nicholas J. A. , Lachaux Alain , Kazeem Gbenga , Undre Nasrullah
Published: October 2018

Phase 2, parallel‐group, multicenter, open‐label, 4‐week study, comparing PK of PR‐T vs IR‐T in de novo pediatric patients undergoing primary kidney, liver, or heart transplantation. Patients randomized 1:1 to receive once daily, PR‐T‐, or twice‐daily, IR‐T‐based regimens; dose adjustments permitted after Day 1. Twenty‐four‐hour PK profiles collected on Days 1, 7, and 28. Primary endpoint: tacrolimus AUC24. Secondary end points included tacrolimus C24 and Cmax. Endpoints compared between PR‐T and IR‐T on Days 1, 7, and 28. Predefined similarity interval for CIs of LSM ratios: 80%‐125%. PK analysis set comprised 33 patients (PR‐T, n = 15; IR‐T, n = 18). Overall, AUC24 and Cmax were lower on Day 1 vs 7 and 28. Geometric LSM ratios of PR‐T:IR‐T on Days 1, 7, and 28 were 66.3%, 92.5%, 99.9%, respectively, for AUC24; 66.3%, 82.2%, 90.9% for C24; and 77.3%, 120.3%, 92.2% for Cmax. AUC24 90% CI within predefined similarity interval on Day 28; other 90% CIs fell outside. Linear relationship was similar between AUC24 and C24, and between tacrolimus formulations, suggesting that the same therapeutic drug monitoring method can be used with both formulations in de novo pediatric allograft recipients.
Electoral Vulnerability and Presidential Support in the House of Representatives
Authors: Hickey Patrick T.
Published: October 2018

This article investigates whether electoral vulnerability affects how a member of Congress behaves on presidential support votes. It argues that electorally vulnerable members of the House will be more responsive to their constituents’ views about the president. As a result, vulnerable members of Congress can be critical to the success or failure of the president’s legislative efforts. I investigate presidential support scores from 1993 to 2016 and find that electoral vulnerability conditions how members of Congress vote when the president takes a position on a bill. Even in today’s highly polarized and highly partisan Congress, the combination of electoral vulnerability and the president’s standing in members’ constituencies can cause members to cross party lines on presidential support votes.
The effect of free trade agreements revisited: Does residual trade cost bias matter?
Authors: Kharel Paras
Published: October 2018

This paper revisits a prominent gravity model‐based empirical literature on the effects of free trade agreements by accounting for a potential bias caused by unobservable trade costs that operate through general equilibrium constraints. It embeds state‐of‐the‐art panel estimation techniques in a recently proposed two‐step remedy that features a constrained ANOVA‐type estimation. Using a dataset on manufacturing trade flows in eight sectors in 40 countries and a rest‐of‐the‐world aggregate for the period 1990–2002, it finds evidence of significant residual trade cost bias. The direction and magnitude of bias vary across sectors, with the standard one‐step approach used in the literature overestimating or underestimating the partial effect of free trade agreements by up to 110 percent. Overall, coefficients on trade costs variables are jointly significantly different between the standard method and the two‐step method. The biases in partial effect estimates translate into biases in general equilibrium effects.
Preliminary findings in 30 dogs treated with micropulse transscleral cyclophotocoagulation for refractory glaucoma
Authors: Sapienza John S. , Kim Kay , Rodriguez Elena , DiGirolamo Nicola
Published: October 2018

Objective

The purpose of this study was to report the preliminary results of a novel micropulse transscleral diode laser cyclophotocoagulation (MP‐TSCP) as primary therapy for glaucomatous dogs.

Animal Studied

Client owned dogs undergoing MP‐TSCP therapy at a veterinary referral center.

Procedure

Retrospective study of dogs with glaucoma that were treated with MP‐TSCP with a minimum of 1 month (range: 1‐18 months) of follow‐up. Reported outcomes were intraocular pressure (IOP), treatment parameters, reduction in medications, complications, and incidence of repeat therapy.

Results

Thirty dogs (35 eyes) were evaluated. The mean age was 9.0 years. Mean preoperative IOP was 34.5 mm Hg. Mean postoperative IOP at 1 month (35/35 eyes) was 22 mm Hg, 2 months (26/35 eyes) was 20.5 mm Hg, 4 months (20/35 eyes) was 19 mm Hg, 6 months (10/35 eyes) was 19 mm Hg, 12 months (8/35 eyes) was 21 mm Hg. First treatment success rate was 19/35 eyes (54.3%). Repeat laser was performed in 11 eyes with 4/11 eyes responding favorably for a total IOP control of 23/35 eyes (65.7%). Mean energy levels employed were 137.5 seconds and 2351 mW at 31.3% duty cycle. Reduction in medications was from a mean of 3.6 medications preoperatively to 3.1 medications postoperatively. Complications included corneal ulcers 5/35 eyes (14.3%), uncontrolled IOP in 12/35 eyes (34.3%) and repeat treatment in 11/35 eyes (31.4%).

Conclusions

MP‐TSCP was successful in controlling IOP in most patients as well as to reduce postoperative medications with minimal resultant intraocular inflammation and complications. The micropulse procedure also can be repeated. Future investigations to study effective treatment parameters are warranted in a larger series of patients over a longer period of evaluation.
The practice of transfusion and fluid bolus therapy in neonates
Authors: Keir Amy K. , Stanworth Simon J.
Published: October 2018

There is increasing uncertainty over the potential benefits and harms of volume expansion in paediatric and adult critical care settings. In addition, there are increasing numbers of reports of adverse effects and association with RBC transfusions in neonates, including transfusion‐associated necrotizing enterocolitis. Preterm infants <28 weeks’ gestation in particular are likely more vulnerable to volume shifts and changes in blood pressure due to their unique physiology. This review paper will provide an overview of the current evidence base supporting the use of RBC transfusion thresholds and the use of fluid bolus therapy in neonates. We will argue that enhanced data collection and collaborations through neonatal networks, development of international consensus definitions of transfusion adverse effects and associations, as well as haemodynamic compromise in neonates, are needed to further advance research in these areas.
Numerical modeling of fluid–structure interaction between sewage water flow and bar screen to improve the screening process
Authors: Ali Haider , Kim Kyung Won , Bang Sung Gi , Chae Hyun Bae , Shin Seung Wook , Park Cheol Woo
Published: October 2018

A self‐cleaning bar screen is often used in the first filtration level of a wastewater treatment plant to screen out solid debris from sewage water. The screening process of the bar screen was numerically investigated using the arbitrary Lagrangian–Eulerian method to model the fluid–structure interaction between the sewage water and bar screen. The bar screen design is improved by installing a rotating subscreen under the bar screen to prevent solid waste from passing through. The effects of bar screen on the water flow were examined using hydrodynamic properties. The structural properties were estimated to observe the effects of water flow on the parts of the bar screen. Various inlet flow rates and positions of subscreen and rake were used to examine their effects on velocity, pressure coefficient, structural deformation and von Mises stress. The screening process decreased with the increase in sewage flow rates. The water flow significantly affected the bar screen when the subscreen and rake are not in contact.
An investigation of shedding and super‐shedding of Shiga toxigenic Escherichia coli O157 and E. coli O26 in cattle presented for slaughter in the Republic of Ireland
Authors: McCabe Evonne , Burgess Catherine M. , Lawal Dolapo , Whyte Paul , Duffy Geraldine
Published: October 2018

Shiga toxigenic Escherichia coli (STEC) are an important group of pathogens and can be transmitted to humans from direct or indirect contact with cattle faeces. This study investigated the shedding of E. coli O157 and O26 in cattle at the time of slaughter and factors associated with super‐shedding (SS) animals. Rectoanal mucosal swab (RAMS) samples were collected from cattle (n = 1,317) at three large Irish commercial beef abattoirs over an 18 month period, and metadata were collected at the time of sampling regarding farm of origin, animal age, breed and gender. RAMS swabs were examined for the presence and numbers of E. coli O157 and O26 using a previously developed quantitative real‐time PCR protocol. Samples positive by PCR were culturally examined and isolates analysed for the presence of stx subtypes, eae and phylogroup. Any samples with counts >104 CFU/swab of STEC O157 or O26 were deemed to be super‐shedders. Overall, 4.18% (55/1,317) of RAMS samples were positive for STEC O157, and 2.13% (28/1,317) were classified as STEC O157 SS. For STEC O26, 0.76% (10/1,317) of cattle were positive for STEC O26, and 0.23% (3/1,317) were classified as super‐shedders. Fewer STEC shedders and SS were noted among older animals (>37 months). There was a seasonal trend observed for STEC O157, with the highest prevalence of shedding and SS events in the autumn (August to October). The majority of E. coli O157 (50/55) isolates had stx2 and were eae positive, with no significant difference between SS and low shedders (LS). Interestingly, all STEC O26 (n = 10) were eae negative and had varied stx profiles. This study demonstrates that, while the overall shedding rates are relatively low in cattle at slaughter, among positive animals there is a high level of SS, which may pose a higher risk of cross‐contamination during slaughter.
Evaluation of Low Back Pain in Field Hockey Players
Authors: Gümüş Mustafa , Akalin Tevfik Cem , Kudak Hüseyin Hakan , Çekin Resul , Çiplak Mustafa Ertuğrul , Emektar Bilal , Bostan Geylan
Published: October 2018

It is aimed to evaluate the conditions of low back pain in field hockey players. 196 field hockey players and 170 of similar age range university students participated voluntarily. Participants demographic characteristics, low back pain history, and risk factors were questioned, Biering Sorensen Test (BST) was administered to test the strength and endurance of the back extensors. The data were evaluated in the SPSS 20 for Windows package program. Student's T-Test, ANOVA Test, Post-Hoc Bonferroni Test and Pearson Correlation Analysis were used for statistical analysis. Analysis results were evaluated at 95% confidence interval, p<0.05 was accepted as statistically significant difference. The lifelong prevalence was 82% in the athletes group and 66% in the control group; however, there was no statistically significant difference between the two groups (p=0.524). In terms of frequency of back pain (VAS) in the last three months, there was a significant difference between the athletes and the control groups (p<0.05). The BST average duration of national athletes was 95.2±18.5 sec of super league athletes was 101.3±15.4 sec, and of control group was 110.6±16.8 sec. A statistically significant difference was found between the national athletes and the control group according to BST scores (p=0.001). Compared to national athletes, super league athletes, and control groups, it has been found that being a Field Hockey National Players pose much more risk for low back pain. It was found that low back pain was widespread amongst athletes, and it is seen at a higher rate in national field hockey players.
Developmental maturation of activity‐induced K+ and pH transients and the associated extracellular space dynamics in the rat hippocampus
Authors: Larsen Brian Roland , Stoica Anca , MacAulay Nanna
Published: October 2018

Key points

Neuronal activity induces fluctuation in extracellular space volume, [K+]o and pHo, the management of which influences neuronal function

The neighbour astrocytes buffer the K+ and pH and swell during the process, causing shrinkage of the extracellular space

In the present study, we report the developmental rise of the homeostatic control of the extracellular space dynamics, for which regulation becomes tighter with maturation and thus is proposed to ensure efficient synaptic transmission in the mature animals

The extracellular space dynamics of volume, [K+]o and pHo evolve independently with developmental maturation and, although all of them are inextricably tied to neuronal activity, they do not couple directly.

Neuronal activity in the mammalian central nervous system associates with transient extracellular space (ECS) dynamics involving elevated K+ and pH and shrinkage of the ECS. These ECS properties affect membrane potentials, neurotransmitter concentrations and protein function and are thus anticipated to be under tight regulatory control. It remains unresolved to what extent these ECS dynamics are developmentally regulated as synaptic precision arises and whether they are directly or indirectly coupled. To resolve the development of homeostatic control of [K+]o, pH, and ECS and their interaction, we utilized ion‐sensitive microelectrodes in electrically stimulated rat hippocampal slices from rats of different developmental stages (postnatal days 3–28). With the employed stimulation paradigm, the stimulus‐evoked peak [K+]o and pHo transients were stable across age groups, until normalized to neuronal activity (field potential amplitude), in which case the K+ and pH shifted significantly more in the younger animals. By contrast, ECS dynamics increased with age until normalized to the field potential, and thus correlated with neuronal activity. With age, the animals not only managed the peak [K+]o better, but also displayed swifter post‐stimulus removal of [K+]o, in correlation with the increased expression of the α1‐3 isoforms of the Na+/K+‐ATPase, and a swifter return of ECS volume. The different ECS dynamics approached a near‐identical temporal pattern in the more mature animals. In conclusion, although these phenomena are inextricably tied to neuronal activity, our data suggest that they do not couple directly.
La incorporación y el aumento de oferta de alimentos industrializados en las dietas de las unidades domésticas y su relación con el abandono del sistema de subsistencia propio en las comunidades rurales mayas de Yucatán, México
Authors: Otero Prevost David Enrique , Gurri García Francisco Delfín , Mariaca Méndez Ramón , Guízar Vázquez Jr. Francisco
Published: October 2018

El presente trabajo de investigación se dedica al estudio de la relación del abandono de la milpa, el sistema de subsistencia desarrollado alrededor del maíz como cultivo básico en Mesoamérica, con la oferta de alimentos industrializados. Así, se analiza cuál de esos factores es el responsable de la incorporación de alimentos de ese tipo a la dieta de las unidades domésticas rurales mayas de Yucatán, México. Mediante un análisis de varianza de dos vías se comparó la proporción de alimentos industrializados consumidos por unidades doméstica campesinas que hacían milpa con las que ya no la implementaban en comunidades 1 con diferente oferta de alimentos industrializados. Se encontró que, en relación con las unidades domésticas que ya no hacían milpa, las milperas consumían una menor proporción de alimentos industrializados, independientemente de la oferta que ofreciera su comunidad de residencia.
An New Immersed Boundary Method With Level Set Based Geometry Representation and Volume Fraction Based Body Force Calculation
Authors: Yao Guangfa
Published: October 2018

Immersed boundary method has got increasing attention in modeling fluid-solid interaction using computational fluid dynamics due to its robustness and simplicity. It simulates fluid-solid interaction by adding a body force in the momentum equation without a body conforming mesh generation involved. Different immersed boundary methods have been presented and applied to solve fluid flow with immersed solid bodies. The main difference between these immersed boundary methods is how the body force is calculated. In this paper, a new immersed boundary method is proposed. The body force is calculated based on the volume fraction of the solid body immersed in fluid. Compared to the existing and similar methods, the new method develops a mechanism to calculate the body force and thereby more accurately resolve the physics on the solid-fluid interface. The solid body is represented using a level set that facilitates the calculation of the solid volume fraction. The body force derivation is presented and the method is validated against the test cases with existing analytical solutions or well established numerical solutions. A good match was reached.
Hybrid Eulerian Multiphase-Dense Discrete Phase Model Approach for Numerical Simulation of Dense Particle-Laden Turbulent Flows Within Vertical Multi-Stage Cyclone Heat Exchanger
Authors: Cristea Eugen-Dan , Conti Pierangelo
Published: October 2018

This article describes a CFD engineering application developed to investigate numerically the multiphase, non-isothermal, turbulent flow physics within the suspension preheater of a dry-process rotary cement kiln. The multi–stage cyclone preheater is a counter-current heat exchanger.

We used the CFD flow solver ANSYS-Fluent R18.1. to accomplish this task. The hybrid Eulerian multiphase-dense discrete phase model is a coupled Eulerian-Lagrangian technique. The primary carrier-phase is treated as a continuum by solving the Navier-Stokes equations, while the secondary discrete dispersed-phase is solved by tracking the particle parcels through the calculated flow field. The multiphase turbulence of the carrier-phase is modeled using the Reynolds stress transport model. The dispersed-phase interactions are modeled through the specific collisions models provided by the kinetic theory of granular flow and/or discrete element method. The Eulerian multiphase-DDPM method provided a quiet stable solution for a medium/high mass loading (solid to gas mass ratio 0.89:1).

The four-stage cyclone suspension preheater is analyzed for its operating performance i.e. overall pressure drop and global collection efficiency of cyclone stages, calcination degree at bottom cyclone stage, flue gas temperature at 1st. cyclone stage and availability to get more insight of very complex multi-phase flow patterns within this equipment. The set of industrial measurements, collected during a heat and mass balance of a dry process rotary cement kiln, were used to verify and to validate part of the simulation results.
Gas-Liquid Two-Phase Flow Pattern Analysis Inside a Centrifugal Impeller Based on CFD Results
Authors: Si QiaoRui
Published: October 2018

Numerical results obtained by calculations using URANS k-epsilon turbulence model combined with the Euler-Euler inhomogeneous two-phase model are presented including different inlet void fraction values in the inlet section of a centrifugal pump. Local information inside the impeller are extracted from CFD results to get more deep understanding on gas and water flow structures. Results explain the reason why pump performance degradation is more pronounced for low flow rates compared to high flow rates and the importance of inlet void fraction evolution with inlet gas fraction. They also confirm what has been already measured for overall performance modification and more locally visualized in existing open literature in such research field.
Systematic Development and Mesh Sensitivity Analysis of a Mathematical Model for an Anode Baking Furnace
Authors: Nakate Prajakta , Lahaye Domenico , Vuik Cornelis , Talice Marco
Published: October 2018

The anode baking process is developed and improved since the 1980s due to its importance in Aluminium industry. The process is characterized by multiple physical phenomena including turbulent flow, combustion process, conjugate heat transfer, and radiation. In order to obtain an efficient process with regards to quality of anodes, soot-free combustion, reduction of NOx and minimization of energy, a mathematical model can be developed. A mathematical model describes the physical phenomena and provides a deeper understanding of the process.

Turbulent flow is one of the important physical phenomena in an anode baking process. In the present work, isothermal turbulent flow is studied in detail with respect to two turbulence models in COMSOL Multiphysics software. The difference between wall boundary conditions for these models and their sensitivity towards the boundary layer mesh is investigated. A dimen-sionless distance in viscous scale units is used as a parameter for comparison of models with and without a boundary layer mesh. The investigation suggests that the boundary layer mesh for both turbulence models increase the accuracy of flow field near walls. Moreover, it is observed that along with the accuracy, the numerical convergence of Spalart-Allmaras turbulence model in COMSOL Multiphysics is highly sensitive to the boundary layer mesh. Therefore, development of converged Spalart-Allmaras model for the complete geometry is difficult due to the necessity of refined mesh. Whereas, the numerical convergence of k-ε model in COMSOL Multiphysics is less sensitive to the dimen-sionless viscous scale unit distance. A converged solution of the complete geometry k-ε model is feasible to obtain even with less refined mesh at the boundary. However, a comparison of a developed solution of k-ε model with another simulation environment indicates differences which enhance the requirement of having converged Spalart-Allmaras model for complete geometry.
Numerical Study on the Performance of a Centrifugal Impeller With Self-Adaptive Casing Treatment
Authors: Gong M. Q. , Chen H. S. , Xu Y. J. , Deng J. Q.
Published: October 2018

The stall margin and choke margin of centrifugal compressor could be increased by using Self-Adaptive Casing Treatment (SACT). The previous numerical research mainly focuses on making parametric optimization rather than the selection of turbulence model and flow field analysis of the compressor with SACT. In this work, the 3D steady state simulations were carried out to obtain the performance and flow field of the Krain impeller with and without SACT by ANSYS-CFX. Four turbulence models including k-Epsilon turbulence model, RNG k-Epsilon turbulence model, Shear Stress Transport (SST) turbulence model and BSL Reynolds Stress (BSL) turbulence model were used to simulate the Krain impeller with a vaneless constant area diffuser. The numerical data were validated by the experimental data in reference. The results of this study showed that different turbulence models led to differences in performance predictions and flow field characteristics, and the overall performance and flow field features could be predicted more accurately by using SST turbulence model. The bypass flow and reinjected flow were respectively observed in the hole when the Krain impeller with SACT worked at large and small mass flow rate conditions. And the stable working range of the Krain impeller was expanded by using SACT. In addition, the development of the low-velocity fluid at the blade tip region was restrained with the application of SACT.
Fouling Analysis on Energy Dissipation Orifice Plates With Sediment Contained Water Flow
Authors: Qian Jin-yuan , Chen Min-rui , Gao Zhi-xin , Jin Zhi-jiang
Published: October 2018

Hydropower stations play an important role in discharging the flood. Especially in wet seasons, the river water always contains several percentages of sediment, and the velocity of the water flowing through the flood discharging tunnel is very high. Arranging some energy dissipation orifice plates in the flood discharging tunnel, cannot only reduce the pressure and flow velocity, but also deposit sediment and reduce the sediment content. However, fouling on energy dissipation orifice plates can initiate material corrosion of perforated plates, even weaken the energy dissipation performance. In this paper, the fouling performance on energy dissipation orifice plates with sediment contained water flow is investigated. To begin with, the pressure along the path is used to compare with a reported experiment to verify the reliability of the numerical method. Then, effects of the solid particle diameter, the sediment volume concentration and the inlet flow velocity on the particle distribution are observed. The results show that with the increase of the Reynolds number, the sediment volume fraction and the sediment particle diameter, more sediments accumulate at both surfaces of the orifice plate. The Reynolds number and the sediment volume fraction affect the upstream surface more significantly, while the effect of sediment particle diameter is more notable on the downstream surface. Additionally, the energy dissipation coefficient of the orifice plate is mainly dominated by the Reynolds number. This work is of significance for further analysis of fouling problems in energy dissipation orifice plates or similar fluid machinery.
Internal Groove Influenced Thermohydraulic Performance on an Air-Channel
Authors: Mahmood Gazi I. , Samson Aasa
Published: October 2018

Internal fins, protrusions, and porous foams enhance the local convective heat transfer at the channel walls in the heat exchangers, electronic chips for cooling, and solar panels for cooling and heating by promoting the local turbulence in flow. However, the fluid pumping power in the channel suffers due to the blockage and high pressure drop caused by the fins, protrusions, and foams. The present article reports the experimental friction factors and Nusselt numbers in a rectangular channel with an array of internal grooves in one wall. The grooves provide the minimum flow blockage, but still promote the local turbulence to enhance the surface heat transfer. The cylindrical grooves are machined at 45° to the mean air-flow direction in one of the wide walls of the channel of aspect ratio of 40.6:1. The ratio of groove print-diameter to depth is 2.83:1. The objectives are to investigate the effects of groove pitch on the thermal performance in the channel as the flow Reynolds number (Re) varies between 600 and 15000. Two ratios of groove-pitch to print-diameter are employed — 3.2:1 and 4.5:1. The measurements include the distributions of the wall staticpressure and heat transfer coefficient along the channel wall having the grooves. The pressure distributions are obtained at the adiabatic condition. The heat transfer coefficients are obtained with the constant heat flux boundary condition from the grooved surface. The measurements are also obtained in the smooth channel when the grooved wall is replaced by a smooth wall for comparisons with the grooved channel. The results indicate the ratio of Darcy friction factor (f/fo) for the grooved channel (f) to that for the smooth channel (fo) increases with the Re by 27% and 41% at the maximum for the two grooves. The f/fo ratios are slightly higher for the grooves with the smaller pitch. The fully developed Nusselt number ratio (Nu/Nuo) for the grooved channel (Nu) to that for the smooth channel (Nuo) increases with the Re by 37% at the maximum for the two grooves. However, the thermal performance quantified by the ratio (Nu/Nuo)/(f/fo)1/3 is higher for the smaller pitch grooves for most of the Reynolds numbers > 2000. The results thus contribute to the design of heat exchangers and cooling channels for high thermal performance with the ratio (Nu/Nuo)/(f/fo)1/3 > 1.0 based on the smaller surface area, pumping power, and heat duty.
Hybrid LES/RANS Model for Simulation of Particle Dispersion and Deposition
Authors: Sajjadi H. , Salmanzadeh M. , Ahmadi G. , Jafari S.
Published: October 2018

Particle dispersion and deposition in a modeled room was investigated using the Lattice Boltzmann method (LBM) in conjunction with the hybrid RANS/LES turbulence model. For this new model a combination of LES and RANS models was used to reduce the computational cost of using the full LES in the entire domain. Here the near wall region was simulated by the RANS model, while the rest of the domain was analyzed using the LES model within the framework of the LBM. The k-ε turbulence model was applied in the RANS region. For using the k-ε model in the LBM framework, two additional distribution functions for k and ε were defined. For the LES region the sub-grid scale turbulence effects were simulated through a Smagorinsky model. To study the particle dispersion and deposition in the modeled room, particles with different sizes (diameters of 10nm to 10 μm) were investigated. The simulated results for particle dispersion and deposition showed that the predictions of the present hybrid method were quite similar to the earlier LES-LBM. In addition, the predictions of the hybrid model for the particle deposition and dispersion were closer to the LES simulation results compared to those of the k-ε model. It was shown that the Brownian excitation is very important for nanoparticles and the number of deposited particles for 10nm particles is higher than those for the larger 100nm and 1μm particles. The deposition rate for 10 μm particles is also high due to the inertial effects.
Experimental Study on Modeled Caudal Fins Propelling by Elastic Deformation
Authors: Baba N. , Obi S.
Published: October 2018

The present study proposes a new device for the experiment of self-propelling bodies in the water. As opposed to the studies in the past whose experiments were often carried out in a water channel with a given freestream velocity, the new device allows the model to swim under an actual self-propelling condition. The adopted model mimics the caudal fin of various shapes and made of elastic material, and the self-propelling speed is investigated primarily as a function of the forcing frequency. The influence of the amplitude of forced vibration and the materials of different elasticity is also investigated. The flow field around the model fin has been measured by PIV to characterize the flow pattern produced by the fin-motion.
The Role of Meridional Geometry in Aerodynamic Design of Centrifugal Compressor
Authors: Ito Sasuga , Yamada Kazutoyo , Furukawa Masato , Manabe Kaito , Oka Nobuhito , Tomita Isao , Hayashi Yoshihiro
Published: October 2018

Higher aerodynamic performance of turbochargers has been demanded because of vehicle engine down-sizing. Centrifugal compressors for automotive turbochargers require higher efficiency and wider operating range. Meridional geometry of the centrifugal compressors is one of their design specifications and it drastically affects the aerodynamic performance of the compressors. In this study, we designed the meridional geometry by using the aerodynamic design method based on a meridional viscous flow analysis and investigated the relation between the meridional geometry and the aerodynamic performance by analyzing meridional viscous flow calculation results and three-dimensional RANS calculation results. As a result, the relation between the boundary layer development near the shroud and the mass flux at the trailing edge was found out according to the meridional viscous flow calculation results. In addition, the relation and the performance improvement were confirmed according to experimental results.
Internal Flow Analysis in a Two-Channel Pump Used for Salt Transportation
Authors: Wang Jiaqi , Luo Xianwu , Li Wanming , Ji Bin
Published: October 2018

Two-channel pumps usually have very complicated flow field due to the special impeller geometry. The present paper treats the internal flow analysis based on numerical simulation so as to investigate the pumping performance and passage erosion for a two-channel centrifugal pump used for transporting salt particles. The static state flows are calculated by applying RANS method and k-omega SST turbulence model. The numerical results indicate that there are strong circulation flows near the impeller inlet and blade pressure side, and zones with high turbulent kinetic energy near impeller exit when the pump is operated under the designed flow rate i.e. Qd. Pressure decay is also found at the rear part of blade pressure side. At the operation condition of 1.3Qd, the internal flow becomes better. Further, the numerical analysis based on Eulerian-Lagrangian method shows the trajectory of salt particle, salt particle concentration and erosion rate in the pump. It is noted that the salt particles go smoothly in the flow passage due to the large section size of the pump, and there is severe erosion at the blade leading edge and the wall of volute casing due to strong impingement and high particle concentration. Thus, these areas such as blade leading edge and the wall of volute casing are the zones with high erosion risk in the two-channel pump.
Development and Validation of Enthalpy-Porosity Method for Artificial Ground Freezing Under Seepage Conditions
Authors: Alzoubi Mahmoud A. , Sasmito Agus P.
Published: October 2018

Groundwater flow has an undesirable effect on ice growth in artificial ground freezing (AGF) process: high water flow could hinder the hydraulic sealing between two freeze pipes. Therefore, a reliable prediction of the multiphysics ground behavior under seepage flow conditions is compulsory. This paper describes a mathematical model that considers conservation of mass, momentum, and energy. The model has been derived, validated, and implemented to simulate the multiphase heat transfer between freeze pipes and surrounded porous ground structure with and without the presence of groundwater seepage. The paper discusses, also, the influence of the coolant’s temperature, the spacing between two freeze pipes, and the seepage temperature on time needed to create a closed, frozen wall. The results indicate that spacing between two pipes and seepage velocity have the highest impact on the closure time and the frozen body width.
Turbulent Flow Characteristics Over Offset Wall Confined Columns in a Channel at Low Reynolds Numbers
Authors: Toxopeus Kira , Siddiqui Kamran
Published: October 2018

The current study is focused on the flow through offset, wall confined vertical inserts in a channel. The columns are intended to act as the thermal storage media, which continuously exchange heat with the channel fluid to regulate it thermally. These columns could, for example, be filled with a phase change material (PCM) for passive thermal regulation, or have hot or cold fluid pumped through them for active thermal regulation. The current study has two parts: (1) the flow characterization without heat transfer, and (2) flow characterization during thermal exchange with a PCM used for regulation of bulk fluid temperature. The work presented here is focused only on the first part of the study.

The experiments were conducted in a narrow channel, with water as the working fluid. Two geometries of the vertical columns (circular and square) and two offset lengths were considered. For each configuration, experiments were conducted at Reynolds numbers of 20, 50 and 90 (based of the column’s characteristic length). Particle image velocimetry was used to measure the two-dimensional velocity field in a horizontal plane at multiple regions of interest along the length of the channel to characterize the flow passing over columns. The results indicate vortex shedding at the two higher Reynolds numbers. The generation, magnitude and decay rate of turbulent energy is shown to have an offset dependency at Re = 90, but a column shape dependency at Re = 50. The mean flow has a shape dependency due to the difference in separation point over the square and circular columns.