bluuebunny/crossref_metadata_2025 huggingface dataset:
Droplet-based valveless microfluidic system for phage-display screening against spheroids
Authors: Sato Tsuyohi , Hamai Akira , Kadonosono Tetsuya , Kizaka-Kondoh Shinae , Omata Toru
Published: April 2022

In this study, we proposed a droplet-based valveless microfluidic system that has the necessary functions to perform the binding, washing, eluting, and collecting processes of phage-display screening against spheroids, which can be expected to present a similar repertoire and number of membrane proteins as in vivo. Although spheroids have much larger sizes than single cells, spheroids are difficult to manipulate through manual operation. The proposed microfluidic system actively controls the position and velocity of droplets using a camera, three air pumps, and three liquid pumps to perform the processes for phage-display screening. The cross section of the microchannel is large in width and height for the passage of spheroids. Valves that can close such a large cross-sectional microchannel are not readily available. Thus, we proposed valveless flow control using liquid pumps. In addition, the proposed microfluidic system involves complex flow channels with airflow subchannels to perform phage-display screening. For washing, nonspecific-binding phages remaining in the flow channels must be minimized. The proposed microfluidic system can perform selective blocking and flush washing. Selective blocking can prevent the airflow channels from becoming hydrophilic with blocking liquid, and flush washing can flush phages remaining in the flow channel. We experimentally verified the functions of the developed microfluidic device based on the proposed system.
The effect of polymer stiffness on magnetization reversal of magnetorheological elastomers
Authors: Clark Andy T. , Marchfield David , Cao Zheng , Dang Tong , Tang Nan , Gilbert Dustin , Corbin Elise A. , Buchanan Kristen S. , Cheng Xuemei M.
Published: April 2022

Ultrasoft magnetorheological elastomers (MREs) offer convenient real-time magnetic field control of mechanical properties that provides a means to mimic mechanical cues and regulators of cells in vitro. Here, we systematically investigate the effect of polymer stiffness on magnetization reversal of MREs using a combination of magnetometry measurements and computational modeling. Poly-dimethylsiloxane-based MREs with Young’s moduli that range over two orders of magnitude were synthesized using commercial polymers Sylgard™ 527, Sylgard 184, and carbonyl iron powder. The magnetic hysteresis loops of the softer MREs exhibit a characteristic pinched loop shape with almost zero remanence and loop widening at intermediate fields that monotonically decreases with increasing polymer stiffness. A simple two-dipole model that incorporates magneto-mechanical coupling not only confirms that micrometer-scale particle motion along the applied magnetic field direction plays a defining role in the magnetic hysteresis of ultrasoft MREs but also reproduces the observed loop shapes and widening trends for MREs with varying polymer stiffnesses.
Experimental and theoretical studies of the fluid elasticity on the motion of macroscopic models of active helical swimmers
Authors: Irilan Yves-Garnard , Cunha Francisco Ricardo
Published: April 2022

This work presents experimental and theoretical studies on the locomotion of helical artificial swimmers at low Reynolds number in both Newtonian and viscoelastic ambient liquids. We examine the effect of fluid elasticity on the propulsive force and torque on the body and speed velocity of the swimmer in terms of two physical parameters: Deborah number (De) and Strouhal number (Sh). For this end, some experiments with prototype microorganisms in creeping flow motion are conducted. In the experiments, a macroscopic swimmer that propels itself by mimicking helical flagella are developed and tested. Three swimming models propelled by a helical tail with different wavelengths are investigated, and their motions examined for both cases: when the ambient solvent is a pure Newtonian viscous fluid and when the base fluid is an elastic polymeric solution. In addition, we also apply the slender body theory and the method of regularized Stokeslet in order to calculate theoretically the force and torque, as function of the Strouhal number (Sh), produced by the helical swimmer moving in a Newtonian fluid. The theoretical results are compared with experimental data, and a very good agreement is observed especially for higher values of Sh within the error bars of the experimental data. In the case of a non-Newtonian base fluid, the flow problem of an Oldroyd-B elastic fluid is solved numerically using a computational code based on a finite element method. The helical swimmer propulsive velocity is calculated in terms of the elastic parameter Deborah number and also compared with the experimental observation when the base fluid is non-Newtonian. It is shown experimentally that the swimming speed increases as the elastic effect in the base fluid increases until a critical Deborah number O(1), when the velocity saturates for a constant value within the experimental error bars. The velocity anisotropy measured experimentally by the ratio of the swimmer speed in two different directions is insensitive to the elastic effect in the base fluids. We complete our discussion on the helical swimmers motion in creeping flow by presenting a comparison between predictions of the speed velocity given by finite elements simulations using an Oldroyd-B model for the base elastic fluid and experimental data. The agreement between the two sets of results is very good within the experimental error bars for the elastic parameter varying from 0 to 2. It may be remarked, however, that while the experimental data tend to saturate at larger De, the simulations results seem to have a continuous increase according to the constitutive model used to describe the base elastic liquid.
Testing the effectiveness of a novel, evidence-based weight management and lifestyle modification programme in primary care: the Healthy Weight Initiative
Authors: Slater Scott , Lambkin David , Schumacher Tracy , Williams Annabelle , Baillie John
Published: April 2022

Introduction Primary care prevention strategies that support and provide tools for general practice have the potential to slow and reverse rates of overweight and obesity. Aim To test the effectiveness of a novel 12-week, online, structured, evidence-based weight management and lifestyle modification programme in general practices. Methods Between August 2018 and March 2020, participants with a body mass index (BMI)  ≥ 25 were recruited from general practices in the Hunter New England and Central Coast Primary Health Network region of Australia. Practices were randomly assigned to deliver a ‘low-intensity’ (LI) or ‘high-intensity’ (HI) variant of the programme. Practitioners were trained in programme delivery. The intervention involved weekly progress and accountability checks and scripted education sessions on evidenced-based nutrition, physical activity and lifestyle modification. The trial included follow-up evaluations at 6 and 12 months. Results In total, 695 participants were recruited from 26 practices. At the end of the 12-week programme, participants in the HI treatment arm lost an average of 3.2 kg (s.d. 3.8) and 29% (50/172) achieved clinically significant weight loss (>5% of initial body weight). Positive results were maintained at evaluations by participants in the HI treatment arm who attended, but only 31% of participants at 6 months and 21% at 12 months were followed up. Discussion Participant engagement and retention and practitioner workload burden are key factors in the design of weight management programmes in primary care. Many lessons can be obtained as a result of this trial, and programme adjustments have been identified to improve its delivery model.
Hypothalamic deep brain stimulation as a strategy to manage anxiety disorders
Authors: Li Han-Tao , Donegan Dane C. , Peleg-Raibstein Daria , Burdakov Denis
Published: April 2022

Significance

Anxiety disorders are among the most prevalent mental illnesses worldwide. Despite significant advances in their treatment, many patients remain treatment resistant. Thus, new treatment modalities and targets are much needed. Therefore, we developed a deep brain stimulation therapy that targets a recently identified anxiety center in the lateral hypothalamus. We show that this therapy rapidly silences anxiety-implicated neurons and immediately relieves diverse anxiety symptoms in a variety of stressful situations. This therapeutic effect occurs without acute or chronic side effects that are typical of many existing treatments, such as physical sedation or memory deficits. These findings identify a clinically applicable new therapeutic strategy for helping patients to manage treatment-resistant anxiety.
Stone AgeYersinia pestisgenomes shed light on the early evolution, diversity, and ecology of plague
Authors: Andrades Valtueña Aida , Neumann Gunnar U. , Spyrou Maria A. , Musralina Lyazzat , Aron Franziska , Beisenov Arman , Belinskiy Andrey B. , Bos Kirsten I. , Buzhilova Alexandra , Conrad Matthias , Djansugurova Leyla B. , Dobeš Miroslav , Ernée Michal , Fernández-Eraso Javier , Frohlich Bruno , Furmanek Mirosław , Hałuszko Agata , Hansen Svend , Harney Éadaoin , Hiss Alina N. , Hübner Alexander , Key Felix M. , Khussainova Elmira , Kitov Egor , Kitova Alexandra O. , Knipper Corina , Kühnert Denise , Lalueza-Fox Carles , Littleton Judith , Massy Ken , Mittnik Alissa , Mujika-Alustiza José Antonio , Olalde Iñigo , Papac Luka , Penske Sandra , Peška Jaroslav , Pinhasi Ron , Reich David , Reinhold Sabine , Stahl Raphaela , Stäuble Harald , Tukhbatova Rezeda I. , Vasilyev Sergey , Veselovskaya Elizaveta , Warinner Christina , Stockhammer Philipp W. , Haak Wolfgang , Krause Johannes , Herbig Alexander
Published: April 2022

Significance

The bacteriumYersinia pestishas caused numerous historically documented outbreaks of plague and research using ancient DNA could demonstrate that it already affected human populations during the Neolithic. However, the pathogen’s genetic diversity, geographic spread, and transmission dynamics during this early period ofY. pestisevolution are largely unexplored. Here, we describe a set of ancient plague genomes up to 5,000 y old from across Eurasia. Our data demonstrate that two genetically distinct forms ofY. pestisevolved in parallel and were both distributed across vast geographic distances, potentially occupying different ecological niches. Interpreted within the archeological context, our results suggest that the spread of plague during this period was linked to increased human mobility and intensification of animal husbandry.
Decline in biological soil crust N-fixing lichens linked to increasing summertime temperatures
Authors: Finger-Higgens Rebecca , Duniway Michael C. , Fick Stephen , Geiger Erika L. , Hoover David L. , Pfennigwerth Alix A. , Van Scoyoc Matthew W. , Belnap Jayne
Published: April 2022

Significance

Across many global drylands, biocrusts form a protective barrier on the soil surface and fill many critical roles in these harsh yet fragile environments. Previous short-term research suggests that climate change and invasive plant introduction can damage and alter biocrust communities, yet few long-term observations exist. Using a globally unique long-term record of continuous biocrust surveys from a rare never-grazed, protected grassland on the US Colorado Plateau, we found lichen species diversity and cover to be negatively correlated with increasing summer air temperatures, while moss species showed more sensitivity to variation in precipitation and invasive grass cover. These results suggest that dryland systems may be at a critical tipping point where ongoing warming could result in biological soil crust degradation.
A plant-specific module for homologous recombination repair
Authors: Wang Xuanpeng , Wang Lili , Huang Yongchi , Deng Zhiping , Li Cunliang , Zhang Jian , Zheng Mingxi , Yan Shunping
Published: April 2022

Significance

DNA damage causes genome instability and numerous diseases including cancers. Homologous recombination repair (HR) is an error-free pathway to repair DNA double-strand breaks, the most serious forms of DNA damage. However, the HR mechanisms in plants are still poorly understood. The transcription factor SOG1 is a master regulator of plant DNA damage responses. In this study, we find that a plant-specific ubiquitin E3 ligase DDRM1 ubiquitinates and stabilizes SOG1 to promote HR. Therefore, DDRM1- SOG1 is a plant-specific module for HR. DDRM1 is an evolutionarily ancient protein, which is identified in mosses, the first land plants, indicating that DNA damage response is an important mechanism for plant evolution from aquatic to land.
Teaching L2 pragmatics to young learners
Authors: Schauer Gila A.
Published: April 2022

This paper reviews research on teaching pragmatics – and more specifically speech acts – to young L2 learners from two perspectives: (1) studies investigating young L2 learners’ pragmatic competence and (2) studies examining the potential of different materials with regard to pragmatics instruction. The review of L2 learners’ speech act competence addresses cross-sectional and longitudinal developmental studies, as well as studies that examined the effects of specific instructional approaches, learning contexts or materials on young L2 learners’ pragmatic competence. The review of studies examining materials addresses both studies focusing on designated L2 teaching materials produced for the explicit purpose of foreign language instruction of young learners, as well as studies examining speech acts included in children’s books. The paper concludes with a discussion of issues relevant to young learners and the teaching and researching of L2 pragmatics.
Verb form error detection in written English of Chinese EFL learners
Authors: Chen Gong , Liang Maocheng
Published: April 2022

In the past few decades, researchers have paid increasing attention to automatic error detection in natural languages, but few have focused on developing an error-checking tool for EFL learners in China. Based on the theory of Pattern Grammar, this study formalizes verb patterns through Link Grammar, a formal grammatical system developed by Sleator and Temperley (1991), and reconstructs an Link Grammar verb dictionary to create an automatic checking tool for verb form errors in Chinese learners’ written English. The test results show that by importing more detailed pattern information of verbs in the Link Grammar dictionary, the Link Grammar parser can identify verb form errors more accurately and effectively than the original and the parsing capability of the Link Grammar parser is improved. The article shows that Pattern Grammar and Link Grammar can work together and be applied to the construction of error-checking tools for EFL learners with promising results.
Journalistic practice in the international press corps
Authors: Comstock Lindy
Published: April 2022

This paper investigates what form journalistic questioning takes within the international press corps when
representatives of different press systems work in close proximity. Within the U.S. context, adversarial questioning is valued as
a key resource to ensure an independent press. Yet independent journalism is not universally upheld in media systems worldwide;
Russian officials have explicitly criticized adversarial reporting by Western journalists in their coverage of Russian affairs.
Questions posed to Russian Presidents Putin and Medvedev in G8/G20 press conferences 2000–2015 were assessed for two indicators:
(a) initiative, and (b) critical content, with the aim to determine whether journalistic practice will converge in an
international context, and whether the rise in adversarialness documented within U.S. presidential press conferences parallels a
more general international phenomenon. Findings show a significant increase in both indicators over time and by presidential term.
Questioning practices exhibited by Russian, non-Western, and Western journalists are discussed.
Source language classification of indirect translations
Authors: Ivaska Ilmari , Ivaska Laura
Published: April 2022

One of the major barriers to the systematic study of indirect translation – that is, translations of translations – is the lack of efficient methods to identify these translations. In this article, we use supervised machine learning to examine whether computers can be harnessed to identify indirect translations. Our data consist of a monolingual comparable corpus that includes (1) nontranslated Finnish texts, (2) direct translations from English, French, German, Greek, and Swedish into Finnish, and (3) indirect translations from Greek (the ultimate source language) via English, French, German, and Swedish (mediating languages) into Finnish. We use n-grams of various types and lengths as feature sets and random forests as the statistical classification technique. To maximize the transferability of the method, the feature sets were implemented in accordance with the Universal Dependencies framework. This study confirms that computers can distinguish between translated and nontranslated Finnish, as well as between Finnish translations made from different source languages. Regarding indirect translations, the ultimate source language has a greater impact on the linguistic composition of indirect Finnish translations than their respective mediating languages. Hence, the indirect translations could not be reliably identified. Therefore, our results suggest that the reliable computational identification of indirect translations and their mediating languages requires a way to control for the effect of the ultimate source language.
Pro-environmental behaviour in China: analysing the impact of attitudinal and contextual factors (Comportamiento proambiental en China: analizando el impacto de los factores actitudinales y contextuales)
Authors: Zhang Keyi , Ruiz Belén , García Juan A. , Amérigo María
Published: April 2022

This research analyses pro-environmental behaviour (considering four categories: transport and mobility, waste management, ecological consumption and activism) according to environmental attitudes and certain contextual factors regarding the neighbourhood of residence. In addition, based on the assumptions of ABC theory, we evaluate the moderating effects of context on the relationship between attitudes and pro-environmental behaviours. The study sample consists of 218 people living in China who completed a questionnaire distributed to an online panel. The data obtained are analysed by means of iterative regressions, t tests for independent samples and regressions using the PROCESS macro for moderating effects. The results show that the four categories of pro-environmental behaviours are explained by different attitudinal dimensions. It is also noted that contextual factors directly impact the four behavioural categories considered and further moderate the relationship between the attitudinal dimensions and two types of behaviours (waste management and ecological consumption). Implications for the design of strategies to promote pro-environmental behaviour among the Chinese population are discussed.
X-ray irradiation triggers immune response in human T-lymphocytes via store-operated Ca2+ entry and NFAT activation
Authors: Tandl Dominique , Sponagel Tim , Alansary Dalia , Fuck Sebastian , Smit Timo , Hehlgans Stephanie , Jakob Burkhard , Fournier Claudia , Niemeyer Barbara A. , Rödel Franz , Roth Bastian , Moroni Anna , Thiel Gerhard
Published: April 2022

Radiation therapy efficiently eliminates cancer cells and reduces tumor growth. To understand collateral agonistic and antagonistic effects of this treatment on the immune system, we examined the impact of x-ray irradiation on human T cells. We find that, in a major population of leukemic Jurkat T cells and peripheral blood mononuclear cells, clinically relevant radiation doses trigger delayed oscillations of the cytosolic Ca2+ concentration. They are generated by store-operated Ca2+ entry (SOCE) following x-ray–induced clustering of Orai1 and STIM1 and formation of a Ca2+ release–activated Ca2+ (CRAC) channel. A consequence of the x-ray–triggered Ca2+ signaling cascade is translocation of the transcription factor nuclear factor of activated T cells (NFAT) from the cytosol into the nucleus, where it elicits the expression of genes required for immune activation. The data imply activation of blood immune cells by ionizing irradiation, with consequences for toxicity and therapeutic effects of radiation therapy.
Experimental study of transition from electron beam to rf-power-controlled plasma in DFCCP in argon with additional ionization by an electron beam
Authors: Zotovich A I , Lopaev D V , Bogdanova M A , Zyryanov S M , Rakhimov A T
Published: April 2022

Radio-frequency (rf) plasma with additional ionization by an electron beam (EB) is considered as a possible method for the independent control of plasma density, mean electron energy and mean ion energy. In this study, spatial transition from EB to rf-power-controlled dual-frequency capacitively coupled plasma (DFCCP) was studied using the following movable diagnostics: Langmuir and hairpin probes, a retarding field energy analyzer and optical emission spectroscopy. The beam (1.1–1.4 keV) is generated by a runaway EB module placed near the plasma chamber wall, while the plasma transition is caused by EB degradation with the distance from the EB module. The study was conducted in Ar at 200 and 400 mTorr gas pressures in 81 and 12 MHz DFCCP. When the EB is on, a significant decrease in the mean electron energy is observed, from 6 eV in the rf plasma down to 0.2–0.8 eV in the EB plasma. The EB also changes the shape of the electron energy probability function, from Druyvesteyn-like in rf plasma to Maxwellian-like. When both EB and rf power are applied, the mean electron energy increase and the electron density decrease, with the distance from the EB module, are observed due to the beam degradation. The ion energy distribution at the bottom electrode in rf plasma peaks at 25–30 eV and shifts down to a few eV in EB plasma. As in conventional DFCCP, the ion energy distribution can be fine-tuned by the application of a low-frequency rf bias. However, the use of an EB allows us to reduce the range of ion energies down to a few eV, which cannot be achieved in conventional rf discharges.
Regulating the bandgap of graphitic carbon nitride via Mn doping for boosting visible-light-driven water reduction
Authors: Wang Shuyan , Wan Chao , Chen Fengqiu , Chong Mingben , Cheng Dang-guo
Published: April 2022

As a low-cost and promising photocatalyst, graphitic carbon nitride (g-C3N4) has aroused major interest for accomplishing visible-light-driven H2 evolution. Nevertheless, rapid recombination of photoexcited electron–holes largely restricts the applications of g-C3N4 in photocatalytic fields. Therefore, metal Mn is introduced into g-C3N4 to tune its bandgap through a simple co-calcination method, effectively improving its photocatalytic performance. Mn doping successfully generates NH–MnⅡ bonds, thus enlarging the surface area and shortening the bandgap of g-C3N4 by moving the valence band upwards, which promotes the migration of photogenerated electrons. Mn-doped materials display extensive photocatalytic performance for water reduction. The hydrogen evolution rate for an optimized CN–Mn-0.20 sample can reach 171 μmol g−1 h−1, which is eight times higher than that for pure g-C3N4. This finding is helpful for the bandgap modification of g-C3N4 by introducing a transition metal to promote the visible-light-driven water reduction and other photocatalytic applications.
Radiation detriment calculation methodology: summary of ICRP Publication 152
Authors: Ban Nobuhiko , Cléro Enora , Vaillant Ludovic , Zhang Wei , Hamada Nobuyuki , Preston Dale , Laurier Dominique
Published: April 2022

Radiation detriment is a concept to quantify the burden of stochastic effects from exposure of the human population to low-dose and/or low-dose-rate ionising radiation. As part of a thorough review of the system of radiological protection, the International Commission on Radiological Protection (ICRP) has compiled a report on radiation detriment calculation methodology as Publication 152. It provides a historical review of the detriment calculation with details of the procedure used in ICRP Publication 103. A selected sensitivity analysis was conducted to identify the parameters and calculation conditions that can be major sources of variation and uncertainty. It has demonstrated that sex, age at exposure, dose and dose-rate effectiveness factor, dose assumption in the lifetime risk calculation, and lethality fraction have a substantial impact on the calculated values of radiation detriment. Discussions are also made on the issues to be addressed and possible ways for improvement toward the revision of general recommendations. These include update of the reference population data and cancer severity parameters, revision of cancer risk models, and better handling of the variation with sex and age. Finally, emphasis is placed on transparency and traceability of the calculation, along with the need to improve the way of expressing and communicating the detriment.
Glided acoustic higher-order topological insulators based on spoof surface acoustic waves
Authors: Yue Zichong , Zhang Zhiwang , Wang Hai-Xiao , Xiong Wei , Cheng Ying , Liu Xiaojun
Published: April 2022

Higher-order topological insulator hosts both gapped edge states and in-gap corner states, which has garnered considerable attentions in the field of condensed matter physics, and most recently is further extended to the classical wave systems. Conventional acoustic metamaterials have intrinsic material and design limitations that prevent them from being used to create such states in subwavelength scale with function reconfigurability. Recently, the acoustic second-order topological insulators (SOTIs) composed of locally resonant metamaterials were reported to solve the problem, where the topological phase transition is induced by shrinking/expanding metamolecules. Here, we propose an acoustic SOTI in subwavelength scale by another protocol, i.e. gliding metamolecules, and the SOTI is pinned in the nontrivial region without the regular topological phase transition. Soda cans metamaterials in free space are utilized to support the spoof surface acoustic waves. With varying the introduced glided angle, the switching from the bulk to edge and corner states can be achieved accordingly. Furthermore, we not only experimentally observe this state switching process, but also illustrate the robustness of the topological corner states against various defects. Our results provide versatile ways to launch acoustic lower-dimensional topological states that might lead to interesting sound concentration applications.
Terahertz bound state in the continuum in dielectric membrane metasurfaces
Authors: Li Zuolong , Yang Quanlong , Shao Tianyu , Xu Yuehong , Wang Luyao , Xu Quan , Zhang Xueqian , Kravchenko Ivan , Gu Jianqiang , Han Jiaguang
Published: April 2022

Mie-resonant metasurfaces composed of subwavelength dielectric resonators enable an efficient route for electromagnetic wave manipulation. Among these manipulations, a localized mode with a high-quality factor coexisting with a continuous spectrum of radiating waves termed bound state in the continuum (BIC) can arouse many exotic applications in photonics. Here, we demonstrate the terahertz BIC in a dielectric membrane metasurface and analyze its resonant nature based on Mie-resonant multipoles and vector spherical harmonics. The intrinsic splitting of the resonances under oblique incidence is also explored, in which the conversion of multipole radiation patterns versus the oblique angle will drive the resonances from BIC to leaky modes or vice versa. Both Γ and off-Γ point BICs could be identified as the superposition cancellation of vector spherical harmonics for both p-wave and s-wave. Our research not only provides a novel perspective for exploring the essence of BIC metasurfaces in the terahertz regime, but also points new opportunities for achieving terahertz BIC metasurfaces with ultra-high quality factors.
On the effects of diabetes mellitus on the mechanical properties of DRG sensory neurons and their possible relation with diabetic neuropathy
Authors: Reyes-Pardo Humberto , Sánchez-Herrera Daniel P , Santillán Moisés
Published: April 2022

Diabetic neuropathy (DN) is one of the principal complications of diabetes mellitus (DM). Dorsal root ganglion (DRG) neurons are the primary sensory neurons that transduce mechanical, chemical, thermal, and pain stimuli. Diabetes-caused sensitivity alterations and presence of pain are due to cellular damage originated by persistent hyperglycemia, microvascular insufficiency, and oxidative and nitrosative stress. However, the underlying mechanisms have not been fully clarified. The present work addresses this problem by hypothesizing that sensitivity changes in DN result from mechanotransduction-system alterations in sensory neurons; especially, plasma membrane affectations. This hypothesis is tackled by means of elastic-deformation experiments performed on DGR neurons from a murine model for type-1 DM, as well a mathematical model of the cell mechanical structure. The obtained results suggest that the plasma-membrane fluidity of DRG sensory neurons is modified by the induction of DM, and that this alteration may correlate with changes in the cell calcium transient that results from mechanical stimuli.
A Numerical Approach to Study Shell-Side Fluid Flow in Shell-and-Tube Heat Exchangers
Authors: Quartararo A. , Di Maio P.A. , Moscato I. , Vallone E. , Guagliardo G.
Published: April 2022

The detailed CFD simulation of the shell-side flow inside shell-and-tube heat exchangers results prohibitive for large-size components, due to the large number of tubes, together with the multi-scale nature of the flow features. To overcome this issue, the porous media approach can be adopted, substituting the tube bundle with a porous domain, where a suitable momentum sink term in the Navier-Stokes equation is provided. In this paper, a novel numerical approach to estimate the crossflow shell-side pressure drop is presented: a complete characterization of the tube bundle was performed by running 2D-CFD steady-state isothermal analyses, collecting pressure gradient magnitudes and directions for different mass flow rates and angles of attack of the incoming flow. The approach was validated against numerical results and compared to the methodologies currently available. Models, assumptions, and boundary conditions are herewith reported and thoroughly discussed, alongside the main results obtained.
Three-dimensional MHD flow in moderate change ratio orifice
Authors: Melchiorri Lorenzo , Tassone Alessandro , Caruso Gianfranco
Published: April 2022

In fusion reactor blanket design, liquid metals are attractive working fluids since it is possible to combine in a single fluid the functions of coolant, tritium carrier and breeder. These electrically conductive fluids flow in the presence of a strong magnetic field, inducing the appearance of Lorentz forces and magnetohydrodynamic MHD effects. Increased pressure loss, particularly in complex geometry elements, is a critical point for blanket design. The MHD flow through an orifice plate made by electroconductive walls (c = 0.01 ÷ 0.1) has been analysed in this paper using ANSYS CFX in the range Re = 108, and Ha = 0 ÷ 300. A wide recirculation region is detected after the flow exits the orifice, with potentially harmful consequences for efficient tritium removal. Large pressure loss occurs in the orifice due to conductive wall and non-negligible axial length. The 3D pressure drop term is characterized through a local resistance coefficient (k) that is found to be k ≈ 0.205 for well conducting walls (c = 0.1) and k ≈ 0.063 for poorly conducting ones (c = 0.01).
Numerical simulation of a low Prandtl number flow over a backward facing step with an anisotropic four-equation turbulence model
Authors: Barbi G. , Chierici A. , Giovacchini V. , Quarta F. , Manservisi S.
Published: April 2022

In recent years the use of liquid metals has become more and more popular for heat transfer applications in many fields ranging from IV generation fast nuclear reactors to solar power plants. Due to their low Prandtl number values, the similarity between dynamical and thermal fields cannot be assumed and sophisticated heat turbulence models are required to take into account the anisotropy of the turbulent heat transfer involving liquid metals. In the present work, we solve an anisotropic four-equation turbulence model coupled with the Reynolds Averaged Navier Stokes system of equations to simulate a turbulent flow of liquid sodium over a vertical backward-facing step. We implement an explicit algebraic model for Reynolds stress tensor and turbulent heat flux that takes into account flow anisotropic behavior. We study forced and mixed convection regimes when a uniform heat flux is applied on the wall behind the step. Linear isotropic approximations for eddy viscosity and eddy thermal diffusivity underestimate the turbulent heat flux components while this anisotropic model shows a better agreement with DNS results.
The influence of Variable Geometry Control on a R290 Ejector Refrigeration System
Authors: Besagni Giorgio , Inzoli Fabio
Published: April 2022

The large-scale deployment of ejector refrigeration systems (i.e., solar-based ejector refrigeration systems), although representing a promising alternative compared with mechanical compressor ones, is hindered due to limitations regarding ejector control modes. Indeed, ejectors are fluid-dynamics controlled devices and, because of their fixed geometry, they operate at their highest efficiency in a narrow range of operating conditions, which is in contrast with the dynamic pressure and temperature levels characterizing real applications. In this context, variable geometry ejectors (VGE) represent a promising solution to increase the flexibility and operation range of this component. The present study aims to extend the present body of knowledge regarding VGE systems, evaluating the impact of a spindle-provided ejector operated with R290 on the performance of the refrigeration system. The analysis has been carried out using an integrated lumped parameter/CFD approach, thus linking the local flow properties and global performances. Different spindle positions have been tested to assess how the different nozzle area ratios affect both the entrainment ratio and the critical pressure. Results showed that increasing primary nozzle area ratio the system can effectively reduce the thermal input, increasing the average COP at the expanse of a lower critical pressure. In conclusion, using a moving spindle control system might ensure an improvement of the ejector performance.
Convective heat transfer CFD analysis of forced flow through a half-stadium serpentine mini-channel at low Reynolds number
Authors: Corti M , Terra C LA , Fanciulli C , Niro A
Published: April 2022

Spiral and serpentine channels are a very interesting solution to enhance heat transfer in small or miniaturized heat exchangers. In order to properly design these devices, of course, it is essential having a good knowledge of heat transfer characteristics of forced flow through this kind of ducts. However, the data base in open literature is rather lacking being investigations concerning flow mainly restricted to Dean number less than 500 and specific geometric parameters. In order to overcome these limits, a CFD analysis of a laminar forced flow through serpentine mini-channels has been started using a commercial code at finite volumes, namely Ansys Fluent. In this paper, after discussing the preliminary CFD analysis carried out on a straight pipe to tune the tool, we present the results on a flow through a half- stadium serpentine mini-channel with Reynolds number ranging between 200 and 2000. As thermal boundary conditions, a uniform wall temperature is assumed on the flat wall of the half-stadium duct, whereas the others are adiabatic. Finally, simultaneously developing flow condition is adopted. Heat transfer performances and pressure drops have been compared with ones in the straight tube, with the same length and hydraulic diameter as the serpentine duct. The results show heat transfer capability increases due to the presence of curvature as well as an earlier transition from laminar to turbulent flow.
Macroscopic model for porous media in oscillating flow for CFD applications
Authors: Di Meglio Armando , Massarotti Nicola , Trombetta Vincenzo
Published: April 2022

In this paper a macroscopic model for porous media in oscillating flow is derived for CFD applications. In non -linear modelling of thermoacoustic devices, their cores, useful for the energy conversion, cannot be, in general, modelled like a traditional porous media through friction factor and Nusselt number correlations, recovered from steady state. In this work the analytical solutions in the frequency domain of the linearized Navier-Stokes equations are spatially averaged for an oscillating flow between parallel plates case to build a macroscopic model of an equivalent porous media through a complex permeability and Nusselt number. The results, obtained by assuming a zero mean temperature gradient, show that there is a good agreement between macroscopic solution of a porous box (representing a parallel plates stack) and the average of the solutions of oscillating flow between parallel plates, both in terms of temperature and velocity fields.
A Eulerian-Lagrangian approach for the CFD analysis of airborne disease transmission in a car cabin
Authors: Grossi G. , Arpino F. , Buonanno G. , Cortellessa G. , Moretti L. , Nagano H. , Stabile L.
Published: April 2022

In indoor environments such as private cars, taxis and public transport, social distance cannot always be applied and virus concentrations can reach high levels. In this paper, a Eulerian-Lagrangian approach is adopted for the transient simulation of aerosol airborne dispersion in a passenger car cabin. The numerical tool, validated by PIV analysis, is applied to study three different scenarios during the respiratory activity. The car ventilation system and the position of the passengers affect the mass of inhaled aerosol and consequently the quality of the passenger compartment air.
Evaluation of the thermal-hydraulic performances of a once-through steam generator in nuclear fusion applications
Authors: Galli Federico , Ciurluini Cristiano , Narcisi Vincenzo , Giannetti Fabio , Caruso Gianfranco
Published: April 2022

After decades of operation in nuclear power plants, Once-Through Steam Generators (OTSGs) were recently proposed for nuclear fusion applications. In particular, they are supposed to be installed in the primary cooling systems of the European Union Demonstration fusion power plant (EU-DEMO). One of the key reactor components is the Breeding blanket (BB). Among the BB concepts that are currently under study, Water-Cooled Lithium-Lead (WCLL) option was considered for this work. The WCLL blanket is divided in two main subsystems, the breeder zone (BZ) and the first wall (FW), each one provided with an independent cooling circuit, named Primary Heat Transfer System (PHTS). Thermal power removed from BB by BZ and FW PHTS is driven to the Power Conversion System (PCS) to be converted into electricity. The thermal coupling is ensured by two OTSGs per system. At the Department of Astronautical, Electrical and Energy Engineering (DIAEE) of Sapienza University of Rome, a simulation activity was carried out to understand the component thermal-hydraulic behavior during DEMO normal operations. For calculation purposes, a full model of the steam generator was prepared by using a modified version of RELAP5/MOD3.3 system code. The computational activity performed allows to preliminary characterize the OTSG thermal-hydraulic performances during both pulse and dwell phases.
Transient analysis of OSU-MASLWR with RELAP5
Authors: Molinari Martina , Narcisi Vincenzo , Ciurluini Cristiano , Giannetti Fabio
Published: April 2022

The present paper deals with the assessment of the original and a modified version of RELAP5/MOD3.3 against the OSU Multi Application Small Light Water Reactor (OSU-MASLWR). The new implemented features regard suitable correlations for the heat transfer coefficient evaluation in helical geometry. Furthermore, two different modelling of the Helical Coil Steam Generator (HCSG) are assessed. In the first approach, HCSG’s primary and secondary sides are collapsed in a single pipe component. In the second model, three equivalent pipes are conceived for the simulation of the three ranks composing the HCSG.

Two different power manoeuvring experiments are reproduced. The simulations highlight a satisfactory agreement in both the transients. Nevertheless, the modified code shows enhanced capabilities in the prediction of the HCSG operation. This is due to the improvements adopted in the modified version of RELAP5/MOD3.3 that allows a better modelling of the dryout phenomena occurring within helical tubes, as well as a better estimation of the primary side heat transfer coefficient. The better agreement of the heat exchange is propagated to the primary system, resulting in a more accurate prediction of the inlet and outlet core temperatures, and primary flow rate.
Effect of non-condensable gas in steam condensation at sub-atmospheric pressure condition
Authors: Giambartolomei G. , Pesetti A. , Raucci M. , Aquaro D.
Published: April 2022

In the International Thermonuclear Experimental Reactor (ITER), a postulated Loss Of Coolant Accident (LOCA) in the Vacuum Vessel (VV) has to be managed with a pressure suppression system working at sub-atmospheric pressure. The operating conditions considerably differ from those experienced in the fission nuclear power plants such as BWR, since the ITER Tokamak works at very low pressure conditions and can withstand a maximum pressure of 0.15 MPa. For this reason, the pressure value must not exceed 10 kPa for a water temperature of 30 °C inside the Vapour Suppression Tanks (VSTs) that are the fundamental components of the Vacuum Vessel Pressure Suppression System (VVPSS). During a LOCA some non-condensable gases (mainly hydrogen and oxygen gases due to the water radiolysis or thermolysis) may be mixed in the steam and this could impair the condensation efficiency. In order to investigate the effects of non-condensable gas on DCC, we conducted a research program funded by ITER Organization at the laboratory of the University of Pisa: we designed and built a small-scale experimental rig to study the steam Direct Contact Condensation (DCC) with the presence of non-condensable gas and simulate the behaviour of a VST. Since DCC can occur with different characteristics, we ran 12 closed mode tests exploring all condensation regimes injecting a certain mass of air with the steam discharged in the subcooled water. The tests started at the saturation pressures corresponding to water temperatures ranging from 40 °C to 80 °C and ended when the free space volume reached the atmospheric pressure. From the analysis of the data acquired during the tests we observed that the condensation efficiency remained higher than 95%. We observed that despite this, the presence of a certain quantity of non-condensable gas has negative aspects on condensation: the condensation regime never reaches stability (the regimes quickly shift towards instability). Furthermore, the presence of air triggers a turbulence of the flow which interferes with the transfer of heat from the steam to the water. Not only the introduction of air into the flow increases linearly the pressure above the water head but its high temperature further contributes to the pressure increase. The air mixed with the flow also forms eddies that can trap the steam and transport it out of the water, preventing it from condensing. Apart from condensation, the most noticeable problem is the rapid increase in pressure inside the condensation tank.
Analysis of an unmitigated 2-inch cold leg LOCA transient with ASTEC and MELCOR codes
Authors: Agnello G , Ederli S , Maccari P , Mascari F
Published: April 2022

The analyses of postulated severe accident sequences play a key role for the international nuclear technical scientific community for the study of the effect of possible actions to prevent significant core degradation and mitigate source term release. To simulate the complexity of phenomena involved in a severe accident, computational tools, known as severe accident codes, have been developed in the last decades. In the framework of NUGENIA TA-2 ASCOM project, the analysis of an unmitigated 2-inch cold leg LOCA transient, occurring in a generic western three-loops PWR-900 MWe, has been carried out with the aim to give some insights on the modelling capabilities of these tools and to characterize the differences in the calculations results. The ASTEC V2.2b code (study carried out with ASTEC V2, IRSN all rights reserved, [2021]), and MELCOR 2.2 code have been used in this code-to-code benchmark exercise. In the postulated transient, the unavailability of all active injection coolant systems has been considered and only the injection of accumulators has been assumed as accident mitigation strategy.
Entropy Generation Analysis on Confined Impinging Slot Jets with Nanofluids in Metal Foam
Authors: Buonomo B , di Pasqua A , Manca O , Nappo S
Published: April 2022

In this paper a numerical entropy generation analysis on confined slot impinging jets made up of a totally filled configuration of metal foam in mixed convection is presented. A two-dimensional domain is assumed and several Peclet numbers (equal to 350, 750, 1500) are considered. Rayleigh numbers is imposed equal to 30000. The employed working fluids are pure water or Al2O3/water based nanofluids. The nanoparticle volume concentrations are in a range from 0% to 4% and the nanoparticle diameter is varied in a range from 20 nm to 80nm. The target surface is characterized by a constant temperature, estimated starting to the value of Rayleigh number. The distance of the target surface is five times greater than the slot jet width. The thermal and fluid dynamic properties of nanofluids are evaluated by a single-phase model method. The model of local thermal non equilibrium (LTNE) is considere in order to simulate the behavior of the metal foam characterized by a number of pores per inch (PPI) equal to 5, 10, 20, 40 and a porosity around 0.90. The data in terms of total global entropy generation related to the thermal and viscous effects are given Results show increasing values of the total entropy generation for increasing values of Peclet number and nanoparticle concentration. This behaviour is more evident at higher Peclet number values. In addition, the total entropy generation increases with the increase of PPI in corresponding to the same porosity value.