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The characterization of thin liquid films is relevant to many engineering applications, ranging from oil and chemical industry to refrigeration systems, to cooling of light water nuclear reactors. The total internal reflection method (TIRM) is an optical method known for decades for being able to non-intrusively measure film thickness of a wide range of fluids flowing over a transparent wall, but systematic studies on the accuracy of the method are still missing. In this work, TIRM is presented and all the main potential error sources related to the application of such measurement are thoroughly characterized. The analysis includes the potential impact of variation of the refractive index on the measured thickness, the extension of the experimental calibration range to a broader set of measurable thicknesses and the effect of the inhomogeneity of the film free surface on the measured thickness. This latter aspect was never investigated in detail before because of the inherent complexity of the involved physical phenomena, but an in-house developed ray-tracing simulation allows new insights into the problem. Overall, the present paper redefines the utilization limitations and the accuracy of TIRM. [ABSTRACT FROM AUTHOR]

We generalize Atsuyama's result on the geometry of symmetric spaces of type EVI to the case of fields of characteristic zero. We relate the possible mutual positions of two points with the classification of balanced symplectic ternary algebras (also known as Freudenthal triple systems). [ABSTRACT FROM AUTHOR]

Measuring the flow rate in High-Temperature Gas-cooled Reactors is a challenge for traditional flowmeters due to the high flow rate (10 to 15 m/s at nominal operating conditions), high operating temperatures (>700°C), and high neutron flux and gamma fields in the reactor core. This paper discusses developing a novel flowmeter that can work under these extreme conditions. Oak Ridge National Laboratory first proposed using acoustics to measure the flow in the reactor, more specifically, using a Kelvin-Helmholtz resonator to correlate the gas flow rate with vibration frequency. With the primary goal of developing an acoustic measurement technique, we propose an acoustic corrugated pipe as a candidate for the development of a novel gas flowmeter. Experimental investigations on corrugated pipes have confirmed the dependence of the whistling frequency on the gas flow rate. Also, a tube-in-tube configuration is proposed for the flowmeter prototype, which can help mitigate resonance between the system and the flowmeter. Experimental investigation using the prototype has shown good independence from the piping system. Furthermore, Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations have been performed and validated with a satisfactory agreement, providing confidence that URANS models can adequately predict the characteristic curve (flow rate versus frequency) of the corrugated pipe and can therefore be used to optimize the flowmeter designs cost-effectively. [ABSTRACT FROM AUTHOR]

Thin nanocrystalline transparent Al-doped ZnO (1–10 at.% Al) films were synthesized by solid-phase pyrolysis at 700 °C. Synthesized Al-doped ZnO films were investigated by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM). All obtained materials were crystallized into the wurtzite structure, which was confirmed by XRD. The material crystallinity decreases with the introduction of aluminum. SEM and TEM showed that the films are continuous and have a uniform distribution of nanoparticles with an average size of 15–20 nm. TEM confirmed the production of Al-doped ZnO films. The transmittance of Al-doped ZnO films in the range of 400–1000 nm is more than 94%. The introduction of 1% Al into ZnO leads to a narrowing of the band gap compared to ZnO to a minimum value of 3.26 eV and a sharp decrease in the response time to the radiation exposure with a wavelength of 400 nm. An increase in aluminum concentration leads to a slight increase in the band gap, which is associated with the Burstein–Moss effect. The minimum response time (8 s) was shown for film containing 10% Al, which is explained by the shortest average lifetime of charge carriers (4 s). [ABSTRACT FROM AUTHOR]

Thin nanocomposite films based on zinc oxide (ZnO) added with cobalt oxide (Co3O4) were synthesized by solid-phase pyrolysis. According to XRD, the films consist of a ZnO wurtzite phase and a cubic structure of Co3O4 spinel. The crystallite sizes in the films increased from 18 nm to 24 nm with growing annealing temperature and Co3O4 concentration. Optical and X-ray photoelectron spectroscopy data revealed that enhancing the Co3O4 concentration leads to a change in the optical absorption spectrum and the appearance of allowed transitions in the material. Electrophysical measurements showed that Co3O4-ZnO films have a resistivity up to 3 × 104 Ohm∙cm and a semiconductor conductivity close to intrinsic. With advancing the Co3O4 concentration, the mobility of the charge carriers was found to increase by almost four times. The photosensors based on the 10Co-90Zn film exhibited a maximum normalized photoresponse when exposed to radiation with wavelengths of 400 nm and 660 nm. It was found that the same film has a minimum response time of ca. 26.2 ms upon exposure to radiation of 660 nm wavelength. The photosensors based on the 3Co-97Zn film have a minimum response time of ca. 58.3 ms versus the radiation of 400 nm wavelength. Thus, the Co3O4 content was found to be an effective impurity to tune the photosensitivity of radiation sensors based on Co3O4-ZnO films in the wavelength range of 400–660 nm. [ABSTRACT FROM AUTHOR]

Abstract Turbulent mixing of coolant streams can result in an oscillatory mixing phenomenon called thermal striping. These fluctuations have the potential to lead to anticipated thermal fatigue failures in advanced nuclear reactors. To predict thermal striping, robust and computationally affordable modeling tools that are capable of accurately representing complex turbulence are needed. Hybrid turbulence approaches, such as detached-eddy simulation and scale-adaptive simulation, have shown some success in resolving complex unsteady turbulence for massively separated flows, however the applicability of these models to internal flows is limited.A STRUCTure-based (STRUCT) second-generation Unsteady Reynolds-Averaged Navier–Stokes turbulence model was recently proposed at the Massachusetts Institute of Technology to robustly extend the applicability of hybrid closures. In this work, the STRUCT model is evaluated using experimental data taken at the Reactor Cavity Cooling System separate-effects test facility at the University of Michigan. The experiments observed the interaction of parallel symmetric rectangular jets, and include measurements for mean profiles of velocity and Reynolds stresses. In the present work, the simulation results are assessed against mean profiles of velocity and Reynolds stresses, demonstrating the ability to reproduce the unsteadiness of the jets in close agreement with the measurements at considerably reduced computational cost. [ABSTRACT FROM AUTHOR]

Gas sensors based on the multi-sensor platform MSP 632, with thin nanocomposite films based on tin dioxide with a low content of zinc oxide (0.5–5 mol.%), were synthesized using a solid-phase low-temperature pyrolysis technique. The resulting gas-sensitive ZnO-SnO2 films were comprehensively studied by atomic force microscopy, Kelvin probe force microscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. The obtained films are up to 200 nm thick and consist of ZnO-SnO2 nanocomposites, with ZnO and SnO2 crystallite sizes of 4–30 nm. Measurements of ZnO-SnO2 films containing 0.5 mol.% ZnO showed the existence of large values of surface potential, up to 1800 mV, leading to the formation of a strong surface electric field with a strength of up to 2 × 107 V/cm. The presence of a strong surface electric field leads to the best gas-sensitive properties: the sensor's responsivity is between two and nine times higher than that of sensors based on ZnO-SnO2 films of other compositions. A study of characteristics sensitive to NO2 (0.1–50 ppm) showed that gas sensors based on the ZnO-SnO2 film demonstrated a high sensitivity to NO2 with a concentration of 0.1 ppm at an operating temperature of 200 °C. [ABSTRACT FROM AUTHOR]

Let $G$ be a split semisimple algebraic group over a field and let $A^*$ be an oriented cohomology theory in the Levine–Morel sense. We provide a uniform approach to the $A^*$ -motives of geometrically cellular smooth projective $G$ -varieties based on the Hopf algebra structure of $A^*(G)$. Using this approach, we provide various applications to the structure of motives of twisted flag varieties. [ABSTRACT FROM AUTHOR]

Stable density stratification in a large enclosure could significantly hamper the effectiveness of natural convection cooling in pool-type liquid metal or gas-cooled advanced reactors. In addition, accurate prediction of stratified front behavior remains to be a challenging task for turbulence modeling. With the rapid growth of high-performance-computing capabilities in recent years, conducting high-fidelity simulations for a large-timescale transient has become more affordable and hence a valuable data source to support turbulence modeling as well as to gain further physical insights. In this work, direct numerical simulation is performed at experiment-consistent conditions to simulate the density stratification transient High-Resolution Jet (HiRJET) facility. Specifically, we focus on the case where an injected aqueous sugar solution has 1.5% density higher than that in the enclosure. In the early stage of the transient, the impingement of the denser jet to the bottom surface of the enclosure promoted turbulent mixing locally. This rendered the establishment of the mixture layer, formation and swift upward propagation of the stratified front, and elevation with (locally) the highest vertical concentration gradient. As the front rose, the diminishing turbulent mass flux slowed down the propagation, and a larger vertical concentration gradient was established. In this stage, both the velocity and the concentration scalar showed large-timescale fluctuation behavior around the stratified front. For the concentration time signal, the characteristic frequency in the power spectral density was found to agree well with the Brunt-Väisällä frequency. The preliminary validation endeavor showed that the stratified front location and the corresponding concentration gradient magnitude in the simulation agreed well with the experiment data. Further validation will mainly revolve around benchmarking against high-resolution density measurement and high-order flow statistics. [ABSTRACT FROM AUTHOR]

AbstractAccurate models of turbulent buoyant flows are essential for the design of the cooling circuit of nuclear reactors and passive safety systems. However, available models fail to fully capture the physics of turbulent mixing when buoyancy becomes predominant with respect to momentum. Therefore, high-fidelity experiments of well-controlled fundamental flows are needed to develop and validate more accurate models. We analyze experiments of positive and negative turbulent buoyant jets, both in uniform and stratified environments, with the aim of understanding the thermal hydraulics of turbulent mixing with variable density and providing high-fidelity data for the development and validation of turbulence models. Non-intrusive, simultaneous particle image velocimetry and laser-induced fluorescence measurements were carried out to acquire instantaneous velocity and concentration fields on a vertical section parallel to the axis of a jet in the self-similar region. The refractive index matching method was applied to measure high-resolution buoyant jets with up to 8.6% density difference. These data are free of the typical errors that characterize optical measurements of buoyancy-driven flows (e.g. natural and mixed convection) where the refractive index of the fluid is inhomogeneous throughout the measurement domain. Turbulent statistics and entrainment of buoyant jets in uniform and stratified environments are presented. These data are compared with non-buoyant jets in a uniform environment, as a reference to investigate the effects of buoyancy and stratification on turbulent mixing. The results will be used for the assessment of current turbulence models and as a basis for the development of a new model that captures turbulent mixing. [ABSTRACT FROM AUTHOR]

Results reported in the literature have shown that the turbulence models currently implemented in computational fluid dynamics (CFD) commercial codes (e.g., ANSYS-CFX, STAR-CCM+, and FLUENT) have a tendency to overestimate thermal stratification and underestimate turbulent mixing when buoyancy effects become dominant with respect to momentum effects. Also, standard large eddy simulation models cannot fully capture the behavior of jets interacting with stratified environments because the assumption of turbulence isotropy of the smaller scales breaks down. Because of light diffraction and image distortion, it is challenging to apply nonintrusive optical flow measurements, like particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF), to get experimental data for CFD validations when there are density variances involved in the flow. However, a refractive index matching (RIM) technique that has been recently developed in our Experimental and Computational Multiphase Flow Laboratory allows us to perform high-resolution measurements of velocity fields and scalar fields for turbulent buoyant jet flow in the presence of density differences as high as 8.6%. To form a fully turbulent round free jet, an experimental facility was designed with a jet nozzle diameter of 2 mm, located at the bottom of a cubic tank with 30-cm side length. The jet flow is established by a servo-engine-driven piston to eliminate possible fluctuations introduced by the motor. A high-fidelity synchronized PIV/PLIF system was utilized in conjunction with RIM to measure the velocity and concentration fields in the self-similar regions of a jet flow with a density difference of 3.16% for aqueous solutions. With Reynolds numbers of 4000 and 10 000, the jet impinging with a two-layer stably stratified environment is compared to the positively buoyant jet with lighter fluid injected into denser surroundings. Detailed quantifications of the measurement uncertainties are also carried out. The experimental results are presented in terms of turbulent statistics and the analysis of jet penetration depths. [ABSTRACT FROM AUTHOR]

New LHCb Collaboration results on pentaquarks with hidden charm1 are discussed. These results fit nicely in the hadrocharmonium pentaquark scenario. 2 , 3 , In the new data the old LHCb pentaquark P c (4 4 5 0) splits into two states P c (4 4 4 0) and P c (4 4 5 7). We interpret these two almost degenerated hadrocharmonium states with J P = 1 / 2 − and J P = 3 / 2 − , as a result of hyperfine splitting between hadrocharmonium states predicted in Ref. 2. It arises due to QCD multipole interaction between color-singlet hadrocharmonium constituents. We improve the theoretical estimate of hyperfine splitting 2 , 3 that is compatible with the experimental data. The new P c (4 3 1 2) state finds a natural explanation as a bound state of χ c 0 and a nucleon, with I = 1 / 2 , J P = 1 / 2 + and binding energy 42 MeV. As a bound state of a spin- 0 meson and a nucleon, hadrocharmonium pentaquark P c (4 3 1 2) does not experience hyperfine splitting. We find a series of hadrocharmonium states in the vicinity of the wide P c (4 3 8 0) pentaquark that can explain its apparently large decay width. We compare the hadrocharmonium and molecular pentaquark scenarios and discuss their relative advantages and drawbacks. [ABSTRACT FROM AUTHOR]

This article examines Bulgaria's electronic trade with India between 1967 and 1990. The developing world became a formative learning experience for the computer industry, as it came up against both a highly protectionist state trying to foster its own industry, and competition from Western companies playing to different rules than COMECON rivals. In order to gain a place in this lucrative market, Bulgarian computer enterprises developed their technical services, advertising and negotiating capacities, learning how to be capitalists in a socialist world. This 'learning through competition and copying' was a feedback channel that changed the way that the company operated in other parts of the world, diversifying its marketing and user services within the socialist world too, standing out from the other socialist industries. As such, this global operation was a formative experience for many executives and technicians, making them a group that was plugged into international expertise networks. Thus the computer became a channel for being part of the emerging information economy, and the Global South became a place to meet the First World without restriction. The article thus shows India's importance to Bulgaria as a space to learn from and profit in, rather than an object of socialist development. [ABSTRACT FROM AUTHOR]

Abstract Let G be a split semisimple linear algebraic group over a field k 0. Let E be a G -torsor over a field extension k of k 0. Let h be an algebraic oriented cohomology theory in the sense of Levine–Morel. Consider a twisted form E / B of the variety of Borel subgroups G / B over k. Following the Kostant–Kumar results on equivariant cohomology of flag varieties we establish an isomorphism between the Grothendieck groups of the h-motivic subcategory generated by E / B and the category of finitely generated projective modules of certain Hecke-type algebra H which depends on the root datum of G , on the torsor E and on the formal group law of the theory h. In particular, taking h to be the Chow groups with finite coefficients F p and E to be a generic G -torsor we prove that all finitely generated projective indecomposable submodules of an affine nil-Hecke algebra H of G with coefficients in F p are isomorphic to each other and correspond to the (non-graded) generalized Rost–Voevodsky motive for (G , p). [ABSTRACT FROM AUTHOR]

Introduction. Diabetes mellitus (DM) is one of the most widespread diseases of the endocrine system in the world. The global incidence of DM is increasing every year. Data presented by IDF Atlas 2016 show that 1 in 7 births is affected by gestational diabetes. In the Republic of Moldova, the registration of DM cases is not unified, this is why we decided to study which group is at risk for the development of gestational diabetes, along with some features of management and its impact on the birth of children with a large mass. Methodology. The prospective case-control study was performed within the Scientific Laboratory of Obstetrics of IMSP, Mother and Child Institute (IMC), in the period 2021-2022. The research included 253 births in IMC: 48 births in patients with a diagnosis of DM and 205 births without diagnosed non-transmissible diseases. Twin pregnancy cases were excluded from the study. Results. In the group of patients with DM, there was a higher proportion of patients aged above 35 years old – 33.3% (n=15) versus 13.1% (n=41). Such age increases the risk of DM (OR=3.3; 95% CI; 1.58-7.00; p<0.001). Of the patients with DM, 62.5% came from rural areas. The urban environment can be a protective factor against DM (OR=0.52; 95% CI; 0.27-0.988). Among patients with DM, children weighing more than 4000 g were in 48.39% versus 15.63% (p<0.05). The probability of a pregnant woman to give birth to a macrosomic fetus, being diagnosed with DM, is six times higher compared to pregnant women without DM (OR=6.17; 95% CI; 2.89-13.2). Conclusions. It is necessary to prevent the DM in the rural population. Multigestational and multiparous women require counseling regarding the possible development of diabetes mellitus. The need of the insulin therapy is underestimated in patients with diabetes mellitus. [ABSTRACT FROM AUTHOR]

Plasma-induced fluid convection is a poorly understood phenomenon originating at the plasma–liquid interface. Diffusive transport, both natural and driven, as well as convection effects determines the rate at which reactive species are produced at the interface and those diffusing from gas phase, ultimately mix within the solution. Efficient mass transfer rates are important to a number of applications ranging from water purification to plasma medicine. In order to understand the mechanisms of plasma-generated active species’ transport through the plasma–liquid interface, a new 2-D Hele–Shaw-like cell was constructed to allow shadowgraph and particle image velocimetry (PIV) measurements of the interface. The plasma-induced flow field in the liquid water as observed using PIV revealed the formation of vortices as well as significant velocity shear, particularly near the bubble interface in the bulk liquid. These flows appear to be related to streamer strikes at the interface. The stability analysis was carried out to investigate the presence of the Kelvin–Helmholtz instability and to determine if the observed perturbations to the flow field were stable. The circulation flows were found to be consistent with Marangoni convection. Additionally, shadowgraph images showed that the streamers impact at the interface locally compress the fluid, thereby driving diffusive flow, density gradients, and interfacial capillary waves. [ABSTRACT FROM AUTHOR]

In this article a scientific prove for a new technology to maximize the accelerating gradient in superconducting cavities by processing on higher order mode frequencies is presented. As dominant energy source the heating of field emitters by an induced rf current (rf-heating) is considered. The field emitter structure is assumed to be a chain of conductive particles, which are formed by attractive forces. [ABSTRACT FROM AUTHOR]

Radiation transmission measurement methods have become widely implemented in the study of two-phase flow due to leaping advancements in detector efficiency, spatial resolution, and high-speed measurement capabilities. However, radiation-based measurements of boiling experiments bear several challenges due to the mismatch of calibration to experimental conditions, beam hardening, thermal expansion, and material and working fluid density changes with temperature. The present research focuses on developing methods to analyze the high-resolution X-ray radiography measurements of the post-critical heat flux (Post-CHF) heat transfer facility built at the University of Michigan that is intended to perform high-pressure and high-temperature measurements; the experimental test section is made of Incoloy-800H and is characterized as a cylindrical geometry expanding 1.0 m in length. The broad goal of the experiment is to build a high-resolution database to develop models for inverted annular film boiling and inverted slug film boiling through dispersed flow film boiling. The methods developed in this research model the thermal effects of the postulated challenges in order to properly scale the X-ray calibration measurements to the experimental conditions. Additionally, a cross-section-weighted method is developed to estimate the axial void fraction; this method is validated by modeling the test section with synthetic void fraction data. Last, preliminary high-speed X-ray measurements performed at subcooled boiling conditions are presented and analyzed with the developed methods, which include bubbly, slug, and churn flows. [ABSTRACT FROM AUTHOR]

Air ingress measurements using the 1/20th-scaled Helium Air Ingress gas Reactor Experiment (HAIRE) facility show key geometric variables of interest and their effect on air ingress in small- and medium-sized breaks in High Temperature Gas cooled Reactors. These variables include but are not limited to break diameter, break angle, and break wall thickness. Differing wall thicknesses for the same break diameter can have order-of-magnitude changes to the air ingress rate, which is a key figure of merit in the air ingress accident scenario. Additionally, different break sizes can change the importance of the angle in the break scenario. With smaller breaks, the flow will not transition from intermittent flow, to countercurrent flow, to diffusive flow as the break rotates from vertically upward toward vertically downward. This would lead to less variability with smaller breaks, which in turn would make the accident scenario more predictable for smaller-sized breaks. [ABSTRACT FROM AUTHOR]

We give an explicit construction of Lie algebras of type E 7 out of a Lie algebra of type D 6 with some restrictions. Up to odd degree extensions, every Lie algebra of type E 7 arises this way. For Lie algebras that admit a 56-dimensional representation we provide a more symmetric construction based on an observation of Manivel; the input is seven quaternion algebras subject to some relations. [ABSTRACT FROM AUTHOR]

In this article we investigate ordinary and equivariant Rost motives. We provide an equivariant motivic decomposition of the variety of full flags of a split semisimple algebraic group [ABSTRACT FROM AUTHOR]

In this paper we present a novel experimental technique aimed at the simultaneous measurement of velocity and scalar fluctuations with high spatial and time resolution. Measurements have been performed using wire-mesh sensors in combination with Stereo Particle Image Velocimetry (SPIV) to achieve synchronized measurements of both velocity and scalar fluctuations, and therefore of the turbulent fluxes u j ′ φ ′ ‾ . The proof-of-concept of this measurement technique was obtained on a jet flow experimental facility HiRJet (High Resolution Jet) developed and built in the Experimental and Computational Multiphase Flow (ECMF) laboratory at the University of Michigan. Acquired experimental data indicates a high temporal resolution of proposed technique and capabilities of achieving a high level of synchronization which is confirmed by cross-correlation between wire-mesh and SPIV signals. [ABSTRACT FROM AUTHOR]

In the present paper we report about the first attempt to demonstrate and assess the ability of state-of-the-art high-fidelity computational tools to reproduce the complex patterns of CRUD deposits found on the surface of operating Pressurized Water Reactors (PWRs) fuel rods. A fuel assembly of the Seabrook Unit 1 PWR was selected as the test problem. During Seabrook Cycle 5, CRUD induced power shift (CIPS) and CRUD induced localized corrosion (CILC) failures were observed. Measurements of the clad oxide thickness on both failed and non-failed rods are available, together with visual observations and the results from CRUD scrapes of peripheral rods. Blind simulations were performed using the Computational Fluid Dynamics (CFD) code STAR-CCM+ coupled to an advanced chemistry code, MAMBA, developed at Los Alamos National Laboratory. The blind simulations were then compared to plant data, which were released after completion of the simulations. [ABSTRACT FROM AUTHOR]

We present a description of low-lying baryon states (below 2 GeV) based on the general soliton model, which follows from QCD in the limit of large number of colors. Relation to the quark model is discussed. The model describes the spectrum of baryons below 2 GeV with no extra nor missing states. Main properties of baryons (mass splitting and widths) are calculated and relations independent of the specific soliton model are derived. These relations agree rather well with the data. [ABSTRACT FROM AUTHOR]

Abstract: Schubert calculus has been in the intersection of several fast developing areas of mathematics for a long time. Originally invented as the description of the cohomology of homogeneous spaces, it has to be redesigned when applied to other generalized cohomology theories such as the equivariant, the quantum cohomology, K-theory, and cobordism. All this cohomology theories are different deformations of the ordinary cohomology. In this note, we show that there is, in some sense, the universal deformation of Schubert calculus which produces the above mentioned by specialization of the appropriate parameters. We build on the work of Lerche Vafa and Warner. The main conjecture these authors made was that the classical cohomology of a Hermitian symmetric homogeneous manifold is a Jacobi ring of an appropriate potential. We extend this conjecture and provide a simple proof. Namely, we show that the cohomology of the Hermitian symmetric space is a Jacobi ring of a certain potential and the equivariant and the quantum cohomology and the K-theory is a Jacobi ring of a particular deformation of this potential. This suggests to study the most general deformations of the Frobenius algebra of cohomology of these manifolds by considering the versal deformation of the appropriate potential. The structure of the Jacobi ring of such potential is a subject of well developed singularity theory. This gives a potentially new way to look at the classical, the equivariant, the quantum and other flavors of Schubert calculus. [Copyright &y& Elsevier]

In order to assess the accuracy and validity of subchannel, system, and computational fluid dynamics codes, the Paul Scherrer Institut has participated in the OECD/NRC PSBT benchmark with the thermal-hydraulic system code TRACE5.0 developed by US NRC, the subchannel code FLICA4 developed by CEA, and the computational fluid dynamic code STAR-CD developed by CD-adapco. The PSBT benchmark consists of a series of void distribution exercises and departure from nucleate boiling exercises. The results reveal that the prediction by the subchannel code FLICA4 agrees with the experimental data reasonably well in both steady-state and transient conditions. The analyses of single-subchannel experiments by means of the computational fluid dynamic code STAR-CD with the CD-adapco boiling model indicate that the prediction of the void fraction has no significant discrepancy from the experiments. The analyses with TRACE point out the necessity to performadditional assessment of the subcooled boiling model and bulk condensation model of TRACE. [ABSTRACT FROM AUTHOR]

Abstract: A computational fluid dynamic (CFD) model for the pressure vessel of the evolutionary pressurized reactor (EPR™) was developed and validated. The aim of this model is the simulation of transients where three-dimensional effects play a strong role, such as boron dilution and main steam line break (MSLB) scenarios. First, a full solid (CAD) model has been built, that includes all details of the reactor pressure vessel (RPV) and the internals which are important for fluid dynamic analyses. The solid model has then been used as basis for the generation of the computational mesh necessary to carry out CFD simulations. Both a hexahedral and a polyhedral mesh have been created. The CFD model has been validated against experimental results of the JULIETTE facility, a 1:5 scaled mock-up of the EPR™ reactor RPV built by AREVA and equipped with advanced instrumentation. The performances of the hexahedral and the polyhedral meshes are investigated in relation to the agreement with experimental data, convergence and CPU requirements. In addition, the effect of the cold-leg swirls on the velocity field inside the RPV is investigated. These swirls mimic the effects of the main coolant recirculation pumps on the flow field at the entrance of the RPV. It is shown that the CFD model is able to capture the shift of the maximum velocity in the downcomer annulus observed in the experimental results. Good qualitative as well as quantitative agreement with the experimental data is achieved. [Copyright &y& Elsevier]

Abstract: TGF-β1 induces differentiation and total inhibition of cardiac MyoFb cell division and DNA synthesis. These effects of TGF-β1 are irreversible. Inhibition of MyoFb proliferation is accompanied with the expression of Smad1, Mad1, p15Ink4B and total inhibition of telomerase activity. Surprisingly, TGF-β1-activated MyoFbs are growth-arrested not only at G1-phase but also at S-phase of the cell cycle. Staining with TUNEL indicates that these cells carry DNA damages. However, the absolute majority of MyoFbs are non-apoptotic cells as established with two apoptosis-specific methods, flow cytometry and caspase-dependent cleavage of cytokeratin 18. Expression in MyoFbs of proliferative cell nuclear antigen even in the absence of serum confirms that these MyoFbs perform repair of DNA damages. These results suggest that TGF-β1-activated MyoFbs can be growth-arrested by two checkpoints, the G1/S checkpoint, which prevents cells from entering S-phase and the intra-S checkpoint, which is activated by encountering DNA damage during the S phase or by unrepaired damage that escapes the G1/S checkpoint. Despite carrying of the DNA damages TGF-β1-activated MyoFbs are highly functional cells producing lysyl oxidase and contracting the collagen matrix. [Copyright &y& Elsevier]

We compute the algebraic Morava K-theory ring of split special orthogonal and spin groups. In particular, we establish certain stabilization results for the Morava K-theory of special orthogonal and spin groups. Besides, we apply these results to study Morava motivic decompositions of orthogonal Grassmannians. For instance, we determine all indecomposable summands of the Morava motives of a generic quadric. [ABSTRACT FROM AUTHOR]

The bubbling of particle-contaminated gases through a liquid pool, called aerosol scrubbing, is a reliable, robust, and efficient collection technique to retain harmful aerosols from industrial processes or hazardous incidents. In this multiphase mass transfer phenomenon, the two-phase flow mechanics strongly influences the particle transport from the gas in the bubble to the surrounding liquid. The numerical and experimental studies have primarily focused on ideal flows and separate test effects. Here we developed a new experimental approach to assess the aerosol mass transfer and two-phase flow hydrodynamics simultaneously via tomographic conductivity measurements using a Wire-mesh sensor and an electrolytic aerosol scrubbed in a prototypical water column. The bubble phenomenology and size distribution can be effectively captured, and the aerosol deposition coefficient can be determined by measuring the electrolytic concentration increase in the liquid phase. Our integral results of the total retained mass in the column are compared with the aerosol mass concentration determined with filter measurements showing good agreement. We study the influence of the position and presence of the wire-mesh sensor on the results. The location has minor effects due to the high mixing level of the liquid phase. It is observed that the wire-mesh sensor could increase the mass transfer by not more than 5–10 %. We finally compare our mass transfer results with algebraic model predictions and suggest improvements to detect and study the mass transfer at the local bubble scale. • Two-phase flow and aerosol transfer simultaneous measurements with Wire-mesh sensor. • Bubble and aerosol size distribution characterization of a pool scrubbing process. • Calculation of an experimental aerosol deposition coefficient using void fraction and mass flux. • Assessment of the Wire-mesh sensor accuracy and intrusiveness on aerosol retention. [ABSTRACT FROM AUTHOR]

In the present work, two large eddy simulations (LESs) of single isothermal jets discharging into large enclosure facilities are proposed. The geometries and tested flow conditions correspond to scaled experiments of the upper plenum of high-temperature gas-cooled reactors. More specifically, two reference experiments were conducted at Texas A&M University and Michigan University. The objective of the present work is to validate these simulations with their corresponding reference experiments. The proposed LES models are performed with NekRS, a spectral element code with graphics processing unit capabilities developed at Argonne National Laboratory. These simulations were performed on the Summit supercomputer at Oak Ridge National Laboratory. For validation purposes, first- and second-order statistics from the computational fluid dynamics (CFD) calculation are compared with measurements obtained from the experiments. The models proved to be accurate, as these results are in good agreement. Additionally, flow visualization is provided showing that these models are able to retrieve similar effects to what are described in the literature for this type of flow configuration. Finally, the proposed models are part of a broader effort under the current Integrated Research Project of Nuclear Energy Advanced Modeling and Simulation 1.1, whose main objective is to deliver fast-running models to accurately predict complex physical phenomena, including for instance, turbulent mixing and thermal stratification. In this regard, the CFD models proposed here will be used to generate a high-fidelity data set to be applied in conjunction with data-driven methods to improve turbulence modeling closures. [ABSTRACT FROM AUTHOR]

AbstractThe system thermal-hydraulic (STH) code SAM has been coupled to the computational fluid dynamics (CFD) code Simcenter STARCCM+ utilizing a hybrid domain overlapping coupling method in space and an explicit coupling in time. The coupling aims to extend the STH code’s applicability to scenarios where local momentum and energy transfers are important yet difficult for STH standalone models to capture, such as three-dimensional (3D) mixing and thermal stratification. The coupling method’s numerical stability was previously verified against multiple test cases including two closed-loop configurations, and it was validated against a double T-junction experiment with 3D scalar mixing.In the present work, the method is validated against the TALL-3D STH/CFD coupling benchmark facility. TALL-3D is a liquid-metal facility with a large, pool-type enclosure (test section) that exhibits 3D flow effects to be modeled by a CFD code. The rest of the system exhibits approximately one-dimensional behavior that is well predicted by a STH code. First, a STAR-CCM+ CFD model of the 3D test section is validated against experimental temperature data. Then a SAM-STARCCM+ coupled model is validated against six different TALL-3D steady states and includes SAM standalone results for comparison. Last, the coupled model is validated against two TALL-3D transients: one exhibiting flow reversal in the test section and one exhibiting nonlinear, limit cycle oscillations (LCOs).For the first transient, the SAM-STARCCM+ coupled model properly predicts an increase in the test section’s inlet temperature during flow reversal, and this increase is not predicted by the SAM standalone model. The coupled model also better predicts initial flow recovery and subsequent oscillations as the system approaches a final natural circulation state. For the second transient, no true final steady state is observed due to LCOs. Neither the SAM-STARCCM+ coupled model nor the SAM standalone model can perfectly capture the experiment’s changing oscillation frequency during the transient. Nevertheless, the coupled model does reproduce the general oscillatory feedback observed.This is a significant achievement because the present coupling only uses an explicit coupling in time, as opposed to a tighter, semi-implicit coupling. In comparison, STH/CFD coupling efforts previously performed by other authors required a semi-implicit coupling to obtain similar results to this work. The strengths of the novel coupling scheme validated in the present paper lie in the superior convergence characteristics and the much simpler, nonintrusive implementation. [ABSTRACT FROM AUTHOR]

Investigates guanylate cyclase activity in human erythrocytes by evaluating the intracellular guanosine 3',5'-cyclic monophosphate (cGMP) content in the presence of agents that exert specific effects on soluble or particulate guanylate cyclase. Increase in intraerythrocyte cGMP content; Atrial natriuretic peptide; Activation of the erythrocyte Na+/H+ exchange.

Investigates guanylate cyclase activity in human erythrocytes by evaluating the intracellular guanosine 3'-5'-cyclic monophosphate content in the presence of various agents that exert specific effects on soluble or particulate guanylate cyclase. Erythrocyte preparation; ATP depletion of erythrocytes; Oxidation of intraerythrocyte hemoglobin by NaNO2.

Human atrial natriuretic peptide (ANP) fragments ANP-(127-150) or ANP-III and ANP-(127-149) or ANP-II activate Na+/H+ exchange in human erythrocytes at concentrations as low as 1 pM. Both ANP-(127-147) or ANP-I and ANP-(129-150) or des-Ser5, Ser6-ANP-III have no effect on erythrocyte Na+/H+ exchange. ANP-III also produces a time-dependent increase of intraerythrocyte guanosine 3′,5′-phosphate (cGMP) concentration. M&B 22,948, a specific inhibitor of cGMP phosphodiesterase, increases Na+/H+ exchange and the intracellular concentration of cGMP. Both 8-bromoguanosine 3',5'-phosphate (8-Br-cGMP) and dibutyryl-cGMP mimic the effect of ANP-III on erythrocyte Na+/H+ exchange. Our data suggest that human erythrocytes possess guanylate-cyclase activity stimulated by ANP-III and that activation of Na+/H+ exchange by this peptide is mediated by cGMP. Human erythrocytes display a high degree of sensitivity to ANP-III or ANP-II and a specificity for ANP-fragment structures just as cells with established ANP-specific receptors. [ABSTRACT FROM AUTHOR]

High-resolution two-phase flow data in the rod bundle are important in the development and validation of high-fidelity models for computational fluid dynamics and subchannel codes, in particular, those pertaining to light water reactor cooling systems. The Michigan Adiabatic Rod Bundle Flow Experiment (MARBLE) has been constructed as a modular assembly of an 8 × 8 lattice rod bundle to simulate scaled pressurized water reactor and boiling water reactor subchannel assemblies. To establish a high-spatial resolution database of the void fraction in the reactor fuel assembly geometries, tomographic measurements were performed with the High-Resolution Gamma-ray Tomography System, which was designed and built in house; the detector system has a spatial resolution of less than 1.0 mm using 240 LYSO (Lu1.8Y0.2SiO5) scintillators with a fan-beam array. In the present study, the local void fraction was measured with the MARBLE facility under various air-water flow conditions (jg = 0.04 to 0.85 m/s and jl = 0.12 to 0.77 m/s) covering from bubbly to cap-turbulent flows. The local void fraction was also successfully measured under nonuniform and asymmetric air bubble distribution conditions with an investigation of the effect of spacer grids and mixing vanes on void drift across subchannels. [ABSTRACT FROM AUTHOR]

Nonintrusive optical methods of flow visualization, like particle image velocity (PIV) and planar laser-induced fluorescence (PLIF), have been widely applied to obtain instantaneous velocity and concentration fields with high spatial and temporal resolutions. When there are density variances involved in the flow, however, the optical measurements become challenging. To prevent the laser sheet which is used to illuminate the flow from getting deflected due to the changes of densities, it is essential to match the refractive indices for the solutions used in the experiments. A methodology based on the mixing behavior of a ternary-component system is applied in this work and an index-matched density ratio of 3.16% has been obtained. To form a nonconfined round free jet, an experimental facility was designed with a jet nozzle diameter of 2 mm located at the bottom of a cubic tank with 30-cm side length. The jet flow is established by a servo-engine-driven piston to eliminate possible fluctuations introduced by the motor. A high-fidelity synchronized PIV/PLIF system was utilized to measure the velocity and concentration fields in the self-similar regions for the jet flow with density differences as well as for the reference cases in uniform environments. Results are analyzed and compared in terms of turbulent statistics. Important for validations of computational fluid dynamics simulations, turbulent eddy viscosity as well as turbulent diffusivity are computed according to the Boussinesq hypothesis and the standard gradient-diffusion hypothesis. Scalar transport has been characterized for the jet self-similar region compared with previous literature using pipe-shaped jet nozzle in terms of the decay constants, jet spreading rates, and virtual origins. [ABSTRACT FROM AUTHOR]

Heat pipe microreactors are reactor designs that primarily use liquid-metal heat pipes to cool the core. The main interest in heat pipes is the fact that they can remove heat passively. This, along with the use of liquid metal, allows the reactor to operate at higher temperatures. Although the use of heat pipes in nuclear reactors is new, liquid-metal heat pipe technology is mature. Nevertheless, experimental data on heat pipes are scarce, and very little is known about their behavior during abnormal operations and close to their thermal limits. Therefore, new experiments and accurate heat pipe simulations are needed to develop reliable closure models. This work describes a joint experimental and numerical investigation into heat pipes that attempts an initial closure of this gap. The numerical and experimental efforts are currently proceeding in parallel, aimed at different aspects of heat pipes. The numerical part is focused on gaps in local closures, and the experiments capture the overall heat pipe behavior. [ABSTRACT FROM AUTHOR]

Abstract Hybrid Reynolds-Averaged Navier-Stokes–Large Eddy Simulation was used to reveal detailed flow information and timescales in an isothermal reactor cavity cooling system plenum four-jet configuration. Plenum asymmetry and nonuniformity work together to cause premature jet merging. Bulk stirring in the plenum causes lateral jet vortex shedding, strong jet-jet interactions, swirl, and premature confluence. Two dominant transient modes exist: a jet flow timescale and then a plenum circulation timescale that is nearly three orders of magnitude larger. A primary consequence is that frequencies far less than the presumed 10 Hz threshold for thermal striping are pervasive. A second result is that scale-resolved computational fluid dynamics (CFD) models (as well as experimental rigs) need hundreds of seconds of statistically stationary flow time (tens of thousands of jet timescales) to produce stationary time averages. Fluid typically arrives at positions on the laser sheet in less time than it spends at those positions fluctuating in the streamwise and lateral directions. Also, a previously undocumented, but experimentally confirmed, vortex trap was identified via CFD. Finally, two-point velocity correlation analyses demonstrated a few dozen strong correlations across positions on the laser sheet. Expected close-proximity correlations emerged, but others across larger spaces also were connected. Most of these correlated at timescales close to that of the jet. [ABSTRACT FROM AUTHOR]

In detailed previous work by the authors, an innovative decay heat removal (DHR) system has been proposed and designed for the Integral Inherently Safe Light Water Reactor (I2S-LWR). The current paper studies the inadvertent actuation of one DHR system train during I2S-LWR normal operation due to a false signal or operator action. The RELAP5 code is used to perform a one-dimensional study, and important thermal-hydraulic characteristics, including primary loop coolant flow rate, pressure, temperature, DHR primary-side flow rate, and coolant temperature, are achieved during this transient. Then, a detailed computational fluid dynamics simulation utilizing STARCCM+ is carried out to investigate the coolant mixing characteristics in the downcomer and lower plenum and obtain the local thermal-hydraulic conditions at the reactor core inlet. It is found that as a consequence of inadvertent DHR actuation, the maximum overcooling at the reactor core inlet is about 3 K, which would not result in significant reactivity insertion. Furthermore, a more severe transient of inadvertent DHR operation with intermediate loop break is studied, and the results show that this would not lead to more significant overcooling to the I2S-LWR core compared with inadvertent DHR operation without intermediate loop break. This work is an indispensable supplement for DHR system comprehensive assessment in the I2S-LWR project. [ABSTRACT FROM AUTHOR]