bluuebunny/crossref_metadata_2025 huggingface dataset:
A new frontier in laboratory physics: magnetized electron–positron plasmas
Authors: Stoneking M. R. , Pedersen T. Sunn , Helander P. , Chen H. , Hergenhahn U. , Stenson E. V. , Fiksel G. , von der Linden J. , Saitoh H. , Surko C. M. , Danielson J. R. , Hugenschmidt C. , Horn-Stanja J. , Mishchenko A. , Kennedy D. , Deller A. , Card A. , Nißl S. , Singer M. , Singer M. , König S. , Willingale L. , Peebles J. , Edwards M. R. , Chin K.
Published: November 2020

We describe here efforts to create and study magnetized electron–positron pair plasmas, the existence of which in astrophysical environments is well-established. Laboratory incarnations of such systems are becoming ever more possible due to novel approaches and techniques in plasma, beam and laser physics. Traditional magnetized plasmas studied to date, both in nature and in the laboratory, exhibit a host of different wave types, many of which are generically unstable and evolve into turbulence or violent instabilities. This complexity and the instability of these waves stem to a large degree from the difference in mass between the positively and the negatively charged species: the ions and the electrons. The mass symmetry of pair plasmas, on the other hand, results in unique behaviour, a topic that has been intensively studied theoretically and numerically for decades, but experimental studies are still in the early stages of development. A levitated dipole device is now under construction to study magnetized low-energy, short-Debye-length electron–positron plasmas; this experiment, as well as a stellarator device that is in the planning stage, will be fuelled by a reactor-based positron source and make use of state-of-the-art positron cooling and storage techniques. Relativistic pair plasmas with very different parameters will be created using pair production resulting from intense laser–matter interactions and will be confined in a high-field mirror configuration. We highlight the differences between and similarities among these approaches, and discuss the unique physics insights that can be gained by these studies.
Lessons learnt from COVID-19 in adult congenital heart patient in Tehran: a survey-based study of prevention, exposure, susceptibility, and outcomes
Authors: Mohammadzadeh Shabnam , Mehrakizadeh Ali , Safari Saeed , Mirzaaghayan Mohammadreza , Badkoubeh Roya Sattarzade , Tavoosi Anahita , Sardari Akram , Mohammadzadeh Saba , Larti Farnoosh , Veldtman Gruschen R
Published: November 2020

Background:

COVD-19 pandemic has overwhelmed many healthcare systems worldwide. Underlying cardiovascular disease predisposes to greater disease susceptibility and more complications including mortality. Such data is unverified in adults with congenital heart disease (ACHD). The aim of the study is to report the Tehran experience with respect to preventative self-care measures, disease exposure, susceptibility, and outcomes after COVD-19 infection in ACHD patients.

Methods:

A telephone-based survey was conducted in ACHD patients, focusing on new-onset symptoms that might indicate COVID-19 infection, prevention measures, confirmed infection rates, and outcomes.

Results:

Three-hundred and nine ACHD patients, with a mean age of 29.13 years (range from 14 to 72 years, SD = 10.64), and 170 (55%) women were assessed. The majority (86.7%) had moderate or complex ACHD. Two-thirds (67.3%) of the patients practiced high-level preventative self-care measures. After community exposure, 33.3% developed COVID-19, and after household exposure, 43.7% developed COVID-19. There was only one mortality in a post-operative patient. Thirty-seven patients (12%) reported new symptoms including cough (10%), fatigue (8%), fever (7%), and new dyspnoea (6.5%). Amongst 18 (6%) with confirmed COVID-19, there was only 1 mortality in a post-operative patient. Age (adjusted OR = 1.19, 95% CI: 1.07–1.31, p = 0.001), contact with confirmed COVID-19 cases (adjusted OR = 59.34, 95% CI: 3.68–955.10, p = 0.004) were independently associated with COVID-19 infection.

Conclusions:

Mortality risk associated with COVID-19 infection in ACHD patients with moderate or severe disease appears to be relatively low, similar to the general population. Such risk appears to act through conventional risk factors, and in this cohort, we demonstrated age as a significant risk factor in addition to exposure to the development of COVID-19 infection. Preventative self-care measures are a potentially significant and impactful intervention target for intervention and for improving outcomes.
Entertainment Education as a Means to Reduce Anti-Muslim Prejudice – For Whom Does It Work Best?
Authors: Siem Birte , Neymeyer Lisa , Rohmann Anette
Published: November 2020

Abstract. The present research aimed to replicate and extend findings by Murrar and Brauer (2018) , who demonstrated that an entertainment education intervention (a music video) effectively reduced US residents’ anti-Muslim prejudice. Using a German sample ( N = 203), we confirmed that watching the video significantly reduced recipients’ prejudice toward Muslims compared to a control condition and two alternative interventions. Unlike in Murrar and Brauer, however, the intervention’s advantageous effect was driven by recipients’ feelings of intergroup anxiety and perceptions of outgroup malleability rather than their identification with Muslims. Extending Murrar and Brauer’s findings, our results also suggest for whom entertainment education interventions may work best, namely for recipients high in right-wing authoritarianism. The findings’ theoretical and practical implications are discussed.
A fusion of CD63–BCAR4 identified in lung adenocarcinoma promotes tumorigenicity and metastasis
Authors: Bae Kieun , Kim Jin Hee , Jung Hyojik , Kong Sun-Young , Kim Yun-Hee , Kim Sunshin , Lee Geon Kook , Lee Jin Soo , Lee Jake June-Koo , Ju Young Seok , Choi Yang-Kyu , Yoon Kyong-Ah
Published: November 2020

Background

Recently, fusion variants of the breast cancer anti-oestrogen-resistance 4 (BCAR4) gene were recurrently discovered in lung adenocarcinoma from the genome-wide studies. However, the functional characterisation of BCAR4 fusion has not been investigated.

Methods

Based on the analysis of RNA-sequencing data, we identified a fusion transcript of CD63–BCAR4 in a Korean patient with lung adenocarcinoma who did not harbour any known activating mutations in EGFR and KRAS genes. To investigate the oncogenic effect of CD63–BCAR4, in vitro and in vivo animal experiments were performed.

Results

In vitro experiments showed strongly enhanced cell migration and proliferation by the exogenous expression of CD63–BCAR4 protein in bronchial epithelial cells. Cell migration was notably reduced after knockdown of BCAR4 fusion by small-interfering RNA. The tumorigenic and metastatic capability of the CD63–BCAR4 fusion was confirmed by using the mouse xenograft model. Fusion-overexpressed cells result in metastasis to the liver and lung as well as the primary tumours after subcutaneous injection into mice. Cyclin D1, MMP1, Slug and mesenchymal markers were significantly increased after CD63–BCAR4 overexpression in the in vitro and in vivo experiments.

Conclusions

Taken together, our results suggest a newly identified fusion gene, CD63–BCAR4 as a potential novel oncogene in lung adenocarcinoma.
CARF promotes spermatogonial self-renewal and proliferation through Wnt signaling pathway
Authors: Cui Wenhao , He Xiaoli , Zhai Xiaohong , Zhang Huan , Zhang Yuanwei , Jin Fei , Song Xiaomin , Wu Dianqing , Shi Qinghua , Li Lin
Published: November 2020

Collaborator of ARF (CARF) regulates cell proliferative fate through both p53-dependent and -independent mechanisms. Recently, we reported a new function of CARF as a positive regulator of Wnt signaling. Despite these findings, the physiological function of CARF has not been well studied. Here, we generated CARF knockout mice and found that male CARF−/− mice exhibited significantly impaired fertility and Sertoli-cell-only (SCO) syndrome phenotypes. Further studies revealed that loss of CARF in Sertoli cells led to decreased GDNF expression, which hindered spermatogonial stem cells (SSCs) self-renewal. Meanwhile, CARF loss in undifferentiated spermatogonia impaired their proliferation. These two mechanisms together led to SCO syndrome phenotypes, which could be functionally rescued by pharmacological or genetic reactivation of Wnt signaling. Finally, we identified CARFS351F as a potential pathogenic mutation in an SCO patient. Overall, our findings reveal important roles of CARF in spermatogonial self-renewal and proliferation through the Wnt signaling pathway.
Open resource of clinical data from patients with pneumonia for the prediction of COVID-19 outcomes via deep learning
Authors: Ning Wanshan , Lei Shijun , Yang Jingjing , Cao Yukun , Jiang Peiran , Yang Qianqian , Zhang Jiao , Wang Xiaobei , Chen Fenghua , Geng Zhi , Xiong Liang , Zhou Hongmei , Guo Yaping , Zeng Yulan , Shi Heshui , Wang Lin , Xue Yu , Wang Zheng
Published: November 2020

Data from patients with coronavirus disease 2019 (COVID-19) are essential for guiding clinical decision making, for furthering the understanding of this viral disease, and for diagnostic modelling. Here, we describe an open resource containing data from 1,521 patients with pneumonia (including COVID-19 pneumonia) consisting of chest computed tomography (CT) images, 130 clinical features (from a range of biochemical and cellular analyses of blood and urine samples) and laboratory-confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) clinical status. We show the utility of the database for prediction of COVID-19 morbidity and mortality outcomes using a deep learning algorithm trained with data from 1,170 patients and 19,685 manually labelled CT slices. In an independent validation cohort of 351 patients, the algorithm discriminated between negative, mild and severe cases with areas under the receiver operating characteristic curve of 0.944, 0.860 and 0.884, respectively. The open database may have further uses in the diagnosis and management of patients with COVID-19.
Spatial organization in microbial range expansion emerges from trophic dependencies and successful lineages
Authors: Borer Benedict , Ciccarese Davide , Johnson David , Or Dani
Published: November 2020

Evidence suggests that bacterial community spatial organization affects their ecological function, yet details of the mechanisms that promote spatial patterns remain difficult to resolve experimentally. In contrast to bacterial communities in liquid cultures, surface-attached range expansion fosters genetic segregation of the growing population with preferential access to nutrients and reduced mechanical restrictions for cells at the expanding periphery. Here we elucidate how localized conditions in cross-feeding bacterial communities shape community spatial organization. We combine experiments with an individual based mathematical model to resolve how trophic dependencies affect localized growth rates and nucleate successful cell lineages. The model tracks individual cell lineages and attributes these with trophic dependencies that promote counterintuitive reproductive advantages and result in lasting influences on the community structure, and potentially, on its functioning. We examine persistence of lucky lineages in structured habitats where expansion is interrupted by physical obstacles to gain insights into patterns in porous domains.
Tunable iridium catalyst designs with bidentate N-heterocyclic carbene ligands for SABRE hyperpolarization of sterically hindered substrates
Authors: Pham Pierce , Hilty Christian
Published: November 2020

A series of iridium catalysts provides NMR sensitivity enhancement using para-hydrogen. The substrate exchange rate can be tuned for optimal polarization by the choice of an aryl and a nucleophilic moiety in the catalyst.
An atomic scale study of defects in Co2FeAl
Authors: Yadav Ravi Kumar , Govindaraj R.
Published: November 2020

Changes in the local structure and magnetic properties at Fe sites associated with different types of defects were addressed in a detailed manner in Co2FeAl by 57Fe Mössbauer spectroscopy.
Conformational potential energy surfaces and cationic structure of 3,4-dihydro-2H-pyran by VUV-MATI spectroscopy and Franck–Condon fitting
Authors: Kang Do Won , Yoon Do Keun , Kwon Chan Ho
Published: November 2020

Ring conformations of 3,4-dihydro-2H-pyran (34DHP) have attracted considerable interest owing to their structural similarity to cyclohexene, an important molecule in stereochemistry.
Two-dimensional materials in biomedical, biosensing and sensing applications
Authors: Rohaizad Nasuha , Mayorga-Martinez Carmen C. , Fojtů Michaela , Latiff Naziah M. , Pumera Martin
Published: November 2020

2D materials are at the forefront of materials research, advancing in applications for biomedical and bio/sensing. We elucidate properties of 2D materials beyond graphene that are relevant to those applications, as well as their correlation with toxicity.
Transient resonant Auger–Meitner spectra of photoexcited thymine
Authors: Wolf Thomas J. A. , Paul Alexander C. , Folkestad Sarai D. , Myhre Rolf H. , Cryan James P. , Berrah Nora , Bucksbaum Phil H. , Coriani Sonia , Coslovich Giacomo , Feifel Raimund , Martinez Todd J. , Moeller Stefan P. , Mucke Melanie , Obaid Razib , Plekan Oksana , Squibb Richard J. , Koch Henrik , Gühr Markus
Published: November 2020

We present the first investigation of excited state dynamics by resonant Auger–Meitner spectroscopy (also known as resonant Auger spectroscopy) using the nucleobase thymine as an example.
Engineering Yarrowia lipolytica for sustainable production of the chamomile sesquiterpene (−)-α-bisabolol
Authors: Ma Yirong , Li Wenjuan , Mai Jie , Wang Jinpeng , Wei Yongjun , Ledesma-Amaro Rodrigo , Ji Xiao-Jun
Published: November 2020

The oleaginous yeast Yarrowia lipolytica was metabolically engineered to produce the chamomile sesquiterpene (−)-α-bisabolol in a green and sustainable way.
DFT study on the [4+4] domino cycloaddition of ynones with benzylidenepyrazolones to access eight-membered cyclic ethers: effects of DBUvs.Et3N
Authors: Yuan Binfang , Zhou Huimin , Yu Youqing , Guo Xiaogang , Zhao Yu , Zhang Fulan , Zhou Haimei , Huang Huisheng , He Rongxing
Published: November 2020

The difference in the catalytic activity of bases is primarily attributed to their electron-donating ability (t-BuO−> DBU > Et3N).
A review of the research status of CO2 photocatalytic conversion technology based on bibliometrics
Authors: Li Xiaopeng , Wang Li , Su Wei , Xing Yi
Published: November 2020

In order to clarify the research status, hot spots and development trend in the field of conversion of carbon dioxide, a large amount of literature data set in the scientific network database was analyzed by bibliometrics.
A sandwich nanocomposite composed of commercially available SnO and reduced graphene oxide as advanced anode materials for sodium-ion full batteries
Authors: Yang Xu , Liang Hao-Jie , Zhao Xin-Xin , Yu Hai-Yue , Wang Mei-Yi , Nie Xue-Jiao , Wu Xing-Long
Published: November 2020

A sandwich structure with SnO and reduced graphene oxide (SnO/rGO) is designed via freeze drying. It delivers a specific capacity of 109.5 mA h g−1 with a retention of 70.62% after 1200 cycles at 4 A g−1, revealing its stable cycling performance.
Two-dimensional semiconducting Cs(i)/Bi(iii) bimetallic iodide hybrids for light detection
Authors: Lassoued Mohamed Saber , Bi Le-Yu , Wu Zhaoxin , Zhou Guijiang , Zheng Yan-Zhen
Published: November 2020

Two new 2D semiconducting Cs/Bi hybrid compounds are reported here with evident photocurrent responses.
Strength of attraction: pyrene-based hole-transport materials with effective π–π stacking for dopant-free perovskite solar cells
Authors: Tepliakova Marina , Yakushenko Igor K. , Romadina Elena I. , Novikov Artyom V. , Kuznetsov Petr M. , Stevenson Keith J. , Troshin Pavel A.
Published: November 2020

Evaporated pyrene-based hole transport materials deliver 17.9% efficiency in dopant free perovskite solar cells.
Reactivation of natural fractures network by hydraulic fracturing
Authors: Alvarez Leidy Laura , Beserra Leila , Guimarães Leonardo , Manzoli Osvaldo
Published: November 2020

Modelling the process of induced fracture initiation, propagation and interaction with natural fractures is a very challenged task. Significant progress has been made in recent years in the development of complex fracture models to address the needs for more suitable design tools than the conventional planar fracture models. However, some aspects of this complex process are not still fully understood in terms of their impact or importance to the overall fracture geometry, or the complexity of simulating them is beyond the current modelling capabilities or requires computation effort that is not practical for engineering purpose. A technique that has been developed to represent the process of fracture propagation is the Continuous Approximation of Strong Discontinuities, which introduces a special kinematics, capable of representing the process of degradation of the material. One way to implement this approximation is to introduce the effects of a very narrow band of localized deformations within the existing finite elements. In this paper was used a finite element procedure that performs numerical analysis of fluid flow in a deformable porous media in a fully coupled scheme. In this analysis the propagation of the hydraulic fracture occurs specially along the pathway of the natural fractures, due to their lower tensile strength and greater permeability.
Fault reactivation during fluid production, modelled as a multi-physics multi-scale instability
Authors: Lesueur Martin , Poulet Thomas , Veveakis Manolis
Published: November 2020

During fluid production in carbonate reservoir rock under high Pressure and Temperature conditions, the production-enhanced shear-heating of a creeping fault can lead to a thermal run-away. The reactivation of the fault is then accompanied with a large increase of permeability (by orders of magnitude) due to the dissolution of the rock. As a detrimental consequence for the industry, pressure equilibrates between the two compartments of the reservoir delimited by an initially sealing fault. To model such behavior, we present a three-scale framework implementing a THMC fault reactivation model. The framework links the three different scales of the problem: (a) the poro-elastic reservoir (km) scale, where faults are treated as frictional interfaces with the equivalent friction law being determined from the meso-scale; (b) the thermo-poro-chemo-visco-elasto-plastic fault at the meso-scale (m), encompassing all the physics at hand; and (c) its chemo-mechanically altered pore structure at the micro-scale (μm), where meso-scale properties (like permeability) are upscaled. In the present approach, the multiscaling approach allows us to replace the common use of empirical laws to the profit of upscaled physical laws. The framework is used to simulate the fault valve behavior appearing during induced reactivation coming from the production scenario next to a sealing fault.
Chemo-hydro-geomechanics in acidizing assisted hydraulic fracturing
Authors: Hu ManMan , Tang Xiaojie , Hueckel Tomasz
Published: November 2020

Hydraulic fracturing has been widely used for unconventional reservoirs especially after the technique of horizontal drilling was invented. Acidizing treatment is often incorporated as a propagation enhancement of fractures, in particular, for very tight, low-permeability carbonate-rich reservoirs. How an individual crack propagates into a stressed medium subject to fluid pressure acting on the crack surfaces and meanwhile being affected by the chemically aggressive environment is still an open question. This short paper investigates the fundamental coupled chemo-hydro-geomechanics as encountered in typical scenarios of hydraulic fracturing, with a specific focus on the role of acidizing treatment. The constitutive relations consisting of a reactive-chemo-elastic and a reactive-chemo-plastic formulation are presented, followed by the coupling with geochemical processes, namely reactive-diffusion equations. Numerical investigations of two representative cases within the chemo-elastically defined regime are presented, featuring a laboratory injection test and in-situ stress conditions of a deep geothermal reservoir, respectively. The results have demonstrated that the chemical dissolution process plays a critical role in the distribution of circumferential stress around the crack tip as well as the evolution of crack propagation, and that acidizing treatment may accelerate cracking exponentially after sufficient chemical exposure.
Evaluation of rock mechanical properties via scratch testing and its impact on energy production: comprehensive review
Authors: Kolawole Oladoyin , Ispas Ion
Published: November 2020

The scratch test is a non-destructive method made up of pushing a tool across the surface of a weaker rock at a given penetration depth. The uniaxial rock strength (UCS), fracture toughness (KIC), and other geomechanical parameters influences how fracture nucleates, but fracture sizes and geometry adopted in hydraulic fracture design and modeling are most often overestimated. Although several researchers have attempted to evaluate UCS, KICand other geomechanical properties in conventional and unconventional formations through scratch testing method, but there remain differing opinions on the fundamental approach and principles to be adopted in estimating those properties. Therefore, the evaluation of geomechanical parameters and their effect on hydrocarbon exploration, energy storage, and hydrocarbon exploitation remain an important issue for energy industry. In this paper, we present a comprehensive review of the methods of approach, applications, and the mechanics of rock scratching. We show the merits of scratch test over other methods of estimating rock mechanical properties. Our review focuses on over 50 previous experimental studies using scratch tests in the past few decades to investigate UCS, KICand other geomechanical properties, including their impact on rock failure, fracture initiation and propagation. Finally, we highlight the fundamental research questions that are yet to be addressed. We envisage that advancement in our knowledge will improve optimization of hydrocarbon exploitation, energy storage, and field-scale modeling for energy production operations.
Effect of periodic surface temperature on heat transfer in layered saturated soil
Authors: Wang Chu , Fox Patrick J.
Published: November 2020

This paper presents numerical analyses of one-dimensional heat transfer in layered saturated soil with effective porosity and under a periodic temperature boundary condition using the numerical model HT1. The model characterizes the soil layer using separate columns to represent solid matrix and mobile pore fluid components, and a series-parallel approach to model soil thermal conductivity. Numerical simulations are presented to illustrate the effect of fluid velocity, thermal retardation factor, thermal conductivity of solid particles, effective porosity and layer heterogeneity. Numerical results indicate that increasing downward fluid velocity and decreasing retardation factor can increase the distance that temperature oscillations from the surface can propagate into the layer. In addition, decreasing fluid velocity, increasing retardation factor, and increasing thermal conductivity of solid particles can decrease the temperature oscillation amplitude in the soil. Temperature profiles also indicate the significance of soil effective porosity and multiple soil layers on heat transfer behavior.
Comparison of thermo-poroelastic and thermo-poroelastoplastic constitutive models to analyze THM process in clays
Authors: Mir Tamizdoust Mohammadreza , Ghasemi-Fare Omid
Published: November 2020

Thermal pore pressurization in soil media has been investigated for the past few decades. It has been shown that temperature variations may significantly affect thermal pore pressure in clay soils confined deep into the ground. Moreover, thermal loading may lead to stress change and thermal deformation. Thermo-poroelastic and advance thermo-poroelastoplastic constitutive models have been formulated and incorporated numerically to simulate the thermo-hydro-mechanical process. However, the accurate response of soil media during THM process has not been completely understood. Although numerical modelling reasonably predicts the experimental observations, they still could not be used to completely justify the field observations. In this study, the main features of the thermo-poroelastic model are incorporated in a thermo-poroelastoplastic constitutive model (ACMEG-T) to further investigate the effect of different thermal and hydraulic properties on thermo-hydro-mechanical (THM) response of the soil media.
Investigating green infrastructure as potential medium for ground heat exchangers
Authors: Yildiz Anil , Stirling Ross A.
Published: November 2020

Space heating and cooling comprises a significant portion of the overall energy consumption. Ground heat exchangers (GHE), are a sustainable alternative to conventional, non-renewably powered heating and cooling systems. Space is a scarce resource in densely urbanised areas, allocating dedicated locations to build GHE systems can result in high initial capital costs and an inflexibility in retrofitting. An alternative solution is to utilise existing, multi-benefit and resilient Sustainable Drainage Systems (SuDS) in cities. An investigation into the feasibility of utilising SuDS as sites for potential GHEs requires an understanding of their thermal and hydrological behaviour and boundary conditions. This study utilises a heavily-instrumented, vegetated lysimeter setup, exposed to atmospheric conditions, to test a pilot-scale SuDS heat exchanger. Heat rejection into the substrate of a SuDS has been simulated with the application of heat via voltage-controlled heating cables at a depth of 850 mm for 72-hour durations (at three different power inputs) with 96-hours between each power input. These heat dissipation periods are reflected in measured soil temperature profiles. Volumetric water content, matric suction, soil temperature and heat flux are monitored at various locations in the lysimeter. A finite difference modelling scheme has been developed to simulate the variation in soil temperature due to heat rejection.
Investigation of the 3D pore structure of a natural shale - implications for mass transport
Authors: Adler Pierre M. , Davy Catherine A. , Marinova Maya , Mussi Alexandre
Published: November 2020

The multiscale pore structure of a natural shale is obtained by three distinct imaging means. First, micro-tomography image data are extended to provide the spatial arrangement of the minerals and pores observable with a voxel size of 700 nm (denoted here as the macroscopic scale). Second, FIB/SEM provides a 3D representation of the porous clay matrix on the so-called mesoscopic scale (10-20 nm); a connected pore network, devoid of cracks, is obtained for two samples out of five, while the pore network is connected through cracks for two other samples out of five. Third, the nanometric pore network is characterized with tomographic STEM. Using these experimental pore structure data, permeability calculations are performed by the Lattice Boltzmann Method on the nanoscale, on the mesoscale, and on the combination of the two. Upscaling is finally done (by a finite volume approach) on the larger macroscopic scale. Calculations show that, in the absence of cracks, the contribution of the pore structure at the nanoscale, on the overall permeability, is similar to that of the mesoscale. The impact of the most recent tomographic STEM measurements on the overall transport properties is discussed.
Fluid-driven mechanical responses of deformable porous media during two-phase flows: Hele-Shaw experiments and hydro-mechanically coupled pore network modeling
Authors: Jeon Min-Kyung , Hosseini Zadeh Amin , Kim Seunghee , Kwon Tae-Hyuk
Published: November 2020

Injecting fluid into a porous material can cause deformation of the pore structure. This hydro-mechanically coupled (i.e., poromechanical) phenomenon plays an essential role in many geological and biological operations across a wide range of scales, from geologic carbon storage, enhanced oil recovery and hydraulic fracturing to the transport of fluids through living cells and tissues, and to fuel cells. In this study, we conducted an experimental and numerical investigation of the hydro-mechanical coupling during fluid flows in porous media at the fundamental pore-scale. First, experimental demonstrations were undertaken to ascertain the effect of the hydro-mechanical coupling for two-phase fluid flows in either deformable or non-deformable porous media. Next, a hydro-mechanically coupled pore network model (HM-PNM) was employed to test a various range of influential parameters. The HM-PNM results were consistent with the experimental observations, including the advancing patterns of fluids and the development of the poroelastic deformation, when the viscous drop was incorporated. The hydro-mechanical coupling was observed to reduce the inlet pressure required to maintain a constant flow rate, whereas its effect on the pattern of fluid flow was minimal. The interfacial tension alteration also changed the pressure and deformation. The viscosity of invading fluid showed significant effects on both the patterns of fluid displacement and mechanical deformation.
Electrokinetic treatments of soils: potential for geoenergy applications
Authors: Landivar Macias Andony , Rotta Loria Alessandro F.
Published: November 2020

The application of a direct current electric field to porous materials such as soils in the form of an electrokinetic treatment induces a variety of multiphysical phenomena. Critical phenomena involved during an electrokinetic treatment of soils are electrical migration (i.e., movement of ions), electroosmosis (i.e., movement of water), electrolysis (i.e., breakdown of chemical compounds), and electrochemical reactions (i.e., oxidation/reduction and precipitation/mineralization reactions). Such phenomena lead to changes in the structure of soils. As changes in the structure of soils induce variations in their properties and behaviors (e.g., thermo-hydro-mechanical), electrokinetic treatments represent resourceful means to address broad geoengineering challenges. The purpose of this paper is to highlight the potential of electrokinetic treatments as versatile techniques capable of providing solutions for diverse geoengineering applications via a controllable change of the properties and behaviors of soils. From this perspective, this work specifically encompasses electrokinetically induced phenomena in soils and expands on opportunities in the context of geoenergy applications, among others, which can be mediated by electrokinetic treatments.
A numerical study on the coupled hydro-mechanical behaviour of compacted bentonite
Authors: Bosch Jose A. , Ferrari Alessio , Laloui Lyesse
Published: November 2020

Understanding the mechanical behaviour of compacted bentonite upon re-saturation is of outmost importance in most designs of nuclear waste disposal repositories. The behaviour of bentonite is characterized by its stress-path dependency and it is typically interpreted on the basis of its microstructural interactions. Up to now, effective stress-based models have had limited success in reproducing consistently the main responses. Here a recently proposed model for the modelling of volumetric behaviour of compacted bentonites is extended to triaxial stress states. The model is formulated using a conventional effective stress expression and the degree of saturation. Because these two variables are directly related to the water retention, a suitable formulation for bentonites is used. The resulting equations are characterised by a high degree of hydro- mechanical couplings and a low number of material parameters, which can be obtained on the basis of well- established laboratory procedures. In order to demonstrate its capabilities, the model is used to simulate the behaviour of MX-80 bentonite for several stress paths under oedometric conditions. The emphasis is put on the process of parameter determination. The predictive capabilities of the model are also highlighted.
Impacts of hydrate on the lateral stress in sediments
Authors: Kim Jongchan , Zhang Haitao , Seol Yongkoo , Dai Sheng
Published: November 2020

The ratio between the horizontal and the vertical effective stresses is defined as the coefficient of earth pressure at rest Ko. Ko in hydrate-bearing sediments is critical in understanding the stress states in hydrate-bearing sediments, yet has not been previously understood. An oedometer cell equipped with vertical and horizontal stress measurement sensors is used to measure the evolution of Ko in tetrahydrofuran hydrate- bearing sands during hydrate formation and dissociation and vertical stress changes. The results show that the response of Ko in hydrate-bearing specimens reflects the combined effects of hydrate cementation, the viscous nature of hydrate crystals, and the stress levels. These results can enhance the understanding of stress anisotropy and geomechanical behaviors of hydrate reservoirs during gas production.
A study of the thermal properties of an alternative straw-containing building material
Authors: Zlateva Penka , Yordanov Krastin , Petkova-Slipets Rositsa
Published: November 2020

Thermal comfort in buildings is usually achieved through sustainable materials obtained from natural sources, which justifies their use for developing building mixtures. Many natural materials were used as early as in ancient times to build homes that are warm in winter and cool in summer: a mixture of straw, clay and sand is an example of such a material. The objective of this article is to evaluate the effect of a mixture of clay, sand and straw on thermal comfort. For the purposes of this study, several types of sample plates were made from clay and sand mixture by adding different amounts of straw. The experiments were carried out and the thermal conductivity coefficient was determined using the method of infinite flat layer. The results indicate that the combination of different amounts of straw can be considered as good reinforcement of the sand and clay matrix and is characterized by a low thermal conductivity. Furthermore, 3D modelling was performed using Finite Element Analysis (FEA) software and a predictive model of the thermal behaviour of the samples from the different mixtures was developed. The thermal field distribution and the thermal conductivity coefficient thus determined were compared with the experimental data and showed consistency.
Optimization of energy demand during ultrafiltration of cow’s milk with different membranes
Authors: Kodinova Siyka , Dushkova Mariya
Published: November 2020

In this experimental work, the energy demand at different pressures (0,2 MPa and 0,5 MPa), the temperature (20 °C and 50 °C) and the cow’s milk fat (0,1 % and 3,6 %) during ultrafiltration by membranes with different membranes - 10 kDa and 25 kDa, was investigated. The lower values of energy demand were established at lower pressure, fat and higher temperature. The greatest influence had the pressure for two membranes investigated, and the lowest - the fats for membrane 10 kDa and the temperature for membrane 25 kDa, respectively. Membrane 10 kDa had higher energy demand than another membrane.
Thermodynamics of moisture sorption in tobacco (Nicotiana tabacum L.) seeds
Authors: Toshkov Nesho , Lazarov Lazar , Popova Venelina , Ivanova Tanya , Menkov Nikolay
Published: November 2020

In this study, the thermodynamic characteristics of tobacco seeds were investigated, based on experimental data from equilibrium moisture isotherms at desorption. An empirical exponential relationship was found for the decrease of the net isosteric heat and the differential entropy, based on the Clausius-Clapeyron equation, in response to the increase in moisture content; the values of the two parameters varied from 31.09 to 1.46 kJ.mol-1 and from 91.53 to 4.29 J.mol-1.K-1, respectively. The linear relationship between the enthalpy and the entropy in the moisture desoption of tobacco seeds supported the validity of the enthalpy-entropy theory. The value of Gibbs free energy was positive and the harmonic temperature (297.5 K) was lower than the isosteric temperature (339.6 K). The outcomes from the study provide for the deeper insight into the process of moisture desorption of tobacco seeds.
Adaptation of activated sludge with anammox to low temperatures
Authors: Gulshin Igor , Makisha Nikolay
Published: November 2020

The article presents the results of evaluating the ability of activated sludge, saturated with anammox bacteria, to adapt to mesophilic and lower temperature operating conditions. As the main temperature regimes, temperatures of 30, 25, 15, and 13°C were selected. The system has demonstrated stable operation at temperatures about 15°C with the highest degree of purification for ammonium nitrogen - 0.33 mg/L. At the same time, the concentration of nitrites reached 0.07 mg/L taking into account forced nitration. An additional increase in the efficiency of the system requires structural changes in the adopted technological scheme of the bioreactor, however, the introduction of an internal system of recirculation of attached biomass (with load) inside the anammox compartment is considered as an essential element of the system that ensures stability.
Validation study for Large-Eddy Simulation of Forest Flow
Authors: Pitchurov George , Gromke Christof , Denev Jordan A. , Cesar Cunha Galeazzo Flavio
Published: November 2020

The publication presents Large-Eddy Simulation (LES) of flow over a reduced-scale wind tunnel model of a forest canopy. The final aim of the study is to determine factors responsible for damage in forests by strong winds. The wind tunnel forest was represented by an open-porous foam material for the crown layer and wooden dowels for the trunk layer. The forest model was installed in the open test section of a Goettingen-type wind tunnel and Particle Image Velocimetry (PIV) measurements were made for the acquisition of the flow field data. The numerical simulations were performed with OpenFOAM®. The forest was modelled by an additional sink term in the momentum transport equations based on the leaf area density and a characteristic drag coefficient for the underlying tree specimen. Large-eddy simulations with different subgrid-scale (SGS) turbulence models were carried out and compared to wind tunnel data. The Smagorinsky SGS model outperformed the dynamic Lagrangian SGS model in the windward edge region (within a distance of approximately 2 tree heights from the leading edge) whereas the dynamic Lagrangian SGS model showed a better performance for regions farther downstream.
Study of the influence of compressive force on the coefficients of friction for wool-containing fabrics
Authors: Stoyanova Raya , Aleksandrov Sasho , Kapanak Umme
Published: November 2020

Making use of appliance MXD-02, Labthink, China, coefficient of friction at rest with sliding tendency (static coefficient of friction) and coefficient of friction at sliding (dynamic coefficient of friction) for fabrics made of 100% wool as well as woolen fabrics with admixtures of polyamide and polyester were determined. The influence of the magnitude of normal pressure on the coefficients of friction was studied. Experiments taking into consideration the following different directions of relative fabric movement were performed: warp by warp threads, and warp by weft. An analysis of the obtained results was made.
Analysis of coolant flow at the outlet of the physical model of the fuel assembly II. of the nuclear reactor VVER 440 / V213
Authors: Mlynár Peter , Világi František , Závodný Zdenko , Urban František , Ridzoň František
Published: November 2020

To safely and efficiently load the fuel assemblies of the VVER 440 / V 213 nuclear reactor, the relation between the temperature of the coolant at the outlet of the fuel assembly, measured by a thermocouple in the assembly’s axis, and the mean coolant temperature, present in the plane of the thermocouple, must be analysed. Based on the analysis of the coolant flow at the output of the physical model of the fuel assembly I. [1] and published CFD simulations [2,3,4] it was shown, that a special attention has to be paid to the influence of the water flow in the central tube on the temperature and velocity profile of the coolant at the thermocouple’s plane in the fuel assembly. For this reason, an experimental device with a physical model of the fuel assembly II. of the nuclear reactor VVER 440 / V 213 was designed, manufactured, and operated at the Faculty of Mechanical Engineering STU in Bratislava.
Yearly Cost Saving by Using Enthalpy Heat Exchanger During Cooling and Heating
Authors: Križo Kamil , Kapjor Andrej , Vantúch Martin
Published: November 2020

Fresh air has to be constantly supplied to the building by air handling unit, where supplied air is mixed with inside air and optimal temperature, oxygen level is adjusted and level of dust and smoke is reduced. Supply air demand of the building is determined according to number of persons in the room, room area and regulations. Necessity of ventilation rely in supplying room with oxygen, cleaning the air, adjusting temperature and moisture and reduction of odours, gases, dust, bacteria and viruses. Achieving optimal properties of supply air creates huge portion of building energy consumption. To save energy during ventilation, standard air to air sensible heat exchangers are used. They purpose is to recover sensible heat from exhaust air and at the same time avoid contamination of supply air. Drawback of these types of exchangers is limit of recovering moisture, therefore huge portion of energy in form of latent heat is lost. On top of classical plate air to air heat exchanger, enthalpy heat exchanger allows to exchange latent as well as sensible heat [1].
2D Numerical Simulation of a Vacuum Assisted Resin Infusion
Authors: Kazda Adam , Peukert Pavel , Novosád Jan
Published: November 2020

The subject of this work is an application of CFD for simulation of vacuum assisted resin infusion. The microscale behaviour is neglected and fibres in the mould are replaced by the porous zone. Equations for porosity coefficients are altered so the coefficients can be computed from the experiment’s outputs. The experiment is simplified by filling the mould with fibres without additional layers, which are commonly used in industry manufacturing. There are two experiments. The first one is simple and is used like an input for the simulation. Results of second one are compared with the simulation.
Approach to 3D Unsteady CFD Analysis of a Single-Blade Pump
Authors: Matej Kurilla , Branislav Knížat , Róbert Olšiak
Published: November 2020

Single-blade centrifugal pumps are hydraulic machines used in many industrial areas. A unique screw shaped blade enables liquids containing solids and fibrous matters to be pumped. Owing to good pump hydraulic properties on the one hand and unfavourable impeller mechanical properties on the other have single-blade pumps become recently more interesting for researchers regarding the CFD simulations. In this case a conventional CFD approach for multi-blade pumps cannot be applied due to the lack of symmetry of the single-blade impeller. Possible approaches to the CFD simulation of a single-blade impeller in the Ansys Fluent and the Ansys CFX are compared in this paper. A comparison of two CFD meshing tools showed substantial element number decrease of the whole CFD model. This paper presents also the laboratory experiment results of the investigated single-blade pump. The paper describes a new approach to the single-blade CFD simulation through Ansys Fluent which is faster and more user-friendly then the conventional approach.
Maximizing the Safety Production of Energo Gas - Determination of Explosion Characteristics
Authors: Skřínský Jan , Koloničný Jan
Published: November 2020

The article is focused on the determination of explosion characteristics of energo gas produced from an industrial scale, biomass gasifier. The results underline that the composition of energo gas from industrial technology has a significant impact on the gas explosion characteristics. The gas explosion experiments were carried out in the spherical 20-L explosion vessel. The Real gas was sampled into the 50-L Tedlar bags, introduced into the vessel and mixed with air by a partial-pressure method. Absolute explosion pressure for energo gas air mixture was higher than 6 bar for the energo gas optimum concentration close to 30 vol. % of fuel. The maximum rate of pressure rise and the deflagration index have been determined. Obtained explosion characteristics could be used to describe the explosion process and to rate the effects of an explosion.
Increase the efficiency of the fireplace insert with loop heat pipe
Authors: Martvoňová Lucia , Malcho Milan , Jandačka Jozef
Published: November 2020

The article is focused on increasing the efficiency of fireplace inserts by means of a device used to preheat the combustion air with a part of the heat from the flue gases. The proposed device is a heat pipe with a closed loop, where its evaporator takes heat from the flue gas in front of the chimney orifice and transfers it via saturated steam to the condenser. This heats the combustion air and thus increases the thermal efficiency of a small heat source.
Biomineralization of calcium carbonate by marine bacterial strains isolated from calcareous deposits
Authors: Vincent Julia , Sabot René , Lanneluc Isabelle , Refait Philippe , Turcry Philippe , Mahieux Pierre-Yves , Jeannin Marc , Sablé Sophie
Published: November 2020

Biomineralization induced by microbial enzymes, which catalyse CaCO3 precipitation, is a promising field of research for various applications in building eco-materials. Especially, this could provide an eco-friendly process for protection of coastal areas against erosion. In the present investigation, fourteen bacterial strains were isolated and characterized from both natural seawater and calcareous deposits formed on a cathodically protected steel mesh in marine environment. All of them induced calcium carbonate precipitation in various media by producing urease and/or carbonic anhydrase enzymes. The calcium carbonate minerals produced by bacteria were identified by microscopy and µ-Raman spectroscopy. In parallel, an experimental set-up, based on a column reactor, was developed to study biomineralization and microbial capacity of Sporosarcina pasteurii to form sandy agglomerate. These well-known calcifying bacteria degraded the urea present in liquid medium circulating through the column to produce calcium carbonate, which acted as cement between sand particles. The bio-bricks obtained after 3 weeks had a compressive strength of 4.2 MPa. 20% of the inter-granular voids were filled by calcite and corresponded to 13% of the total mass. We successfully showed that bio-column system can be used to evaluate the bacterial ability to agglomerate a sandy matrix with CaCO3.
Situation politique et sociale au Chili : Repères pour une réflexion
Authors: Jofré Daniel , Bilbao Alejandro
Published: November 2020

L’objectif de ce dossier est de développer une approximation de la situation politique et sociale actuelle au Chili : une situation très conflictuelle qui se développe depuis octobre 2019. Il comprend des contributions d’académiques, de chercheurs et de professionnels de diverses disciplines des sciences humaines et sociales. D’une part, il cherche à mettre en évidence les conditions structurelles qui permettent de comprendre le conflit social actuel et, d’autre part, il aborde les expressions de lutte, de résistance et de violence qui sont perçues comme l’expression de tensions inter-générationnelles. En ce sens, il aborde les émotions, les représentations et les désirs exprimés par les citoyens, mais cherche également à identifier les contradictions sociales d’un système politique et économique inégal où la violence dictatoriale est à l’origine.