bluuebunny/crossref_metadata_2025 huggingface dataset:
DEVELOPMENT AND EXPERIMENTAL VALIDATION OF RESPONSE MODELLING FOR TIME-OF-FLIGHT NEUTRON DETECTION AND IMAGING SYSTEMS
Authors: Bradnam Steven C. , Astromskas Vytautas , Ghani Zamir , Gilbert Mark R. , Joyce Malcolm J. , Packer Lee W.
Published: February 2021

The application and feasibility of a time-of-flight neutron detection system is explored for sources with time correlated gamma-ray and neutron emissions, such as the spontaneous fission emitter, Cf-252. For the emission of multiple gamma rays and neutrons from a single spontaneous fission event, a near instantaneous gamma-ray detection followed by a later neutron detection on a multi-detector array allows for an associated time-of-flight to be determined for a neutron arising from that event. Using a suite of purpose developed analysis tools, Monte-Carlo simulation and experimental data are compared for the Cf-252 water tank source facility at Lancaster University. Applying a bespoke time-of-flight imaging algorithm, vector-based optimisation (VBO), the true source location is determined within 21 cm by this approach.
COMPARISON OF WASTE DUE TO IRRADIATED STEELS IN THE ESFR AND DEMO
Authors: Reid Jack , Bailey Greg , Cracknell Edmund , Gilbert Mark , Packer Lee
Published: February 2021

For either nuclear fusion or generation IV fission reactors to be viable as a commercial energy source the decommissioning and waste disposal solutions must be considered during the design. A multi-step simulation process combining Monte Carlo Neutron Transport simulations with inventory simulations have been performed to estimate the activation of steels in key reactor components of the European Sodium-cooled fast Reactor (ESFR). Waste classifications based on UK waste disposal regulations have been applied to the key components to estimate the expected masses of low level and intermediate level waste. The use of reduced activation steels, EUROFER and F82H, in reactor components external to the core results in a factor of 10 reduction in the percentage of waste classified as Intermediate Level Waste (ILW). Waste estimates are compared to existing waste estimates for the European Demonstration fusion reactor (DEMO). The ESFR has a lower percentage of ILW per total reactor mass due to irradiated steels compared to DEMO. However, there is no Higher Activity Waste (HAW) associated with DEMO, compared with arisings from the ESFR spent fission fuel.
RESULTS OF VERA APPLICATION TO THE AP1000® PWR STARTUP
Authors: Franceschini F. , Salazar D. , Godfrey A.
Published: February 2021

This paper describes the application of the Virtual Environment for Reactor Applications, VERA, under development by the Consortium for Advanced Simulation of LWRs (CASL) to the core physics analysis of the AP1000 PWR.

The AP1000 PWR features an advanced first core with radial and axial heterogeneities which provides significant enhancements compared to traditional first cores, allowing best fuel usage and short transition to the equilibrium cycle with subsequent fuel reloads. These core advanced features can pose some challenges to the core physics tools making application of VERA to the AP1000 PWR first core especially relevant to qualify VERA performance.

This paper focuses on the qualification efforts at hot zero power conditions, where Monte-Carlo reference solutions have also been established. In particular, the paper focuses on the comparison of the predictions obtained with VERA for the four AP1000 units that recently started up with the measured values. It is shown that there is excellent agreement between VERA and the key reactor physics parameters measured during the AP1000 startup.
ANALYSIS AND COMPARISON OF APOLLO3® AND TRIPOLI-4® NEUTRON NOISE SOLVERS
Authors: Rouchon Amélie , Le Brun Malkiel Vadée , Zoia Andrea
Published: February 2021

Neutron noise analysis addresses the description of small time-dependent flux fluctuations in reactor cores, induced by small global or local perturbations of the macroscopic cross sections due to density fluctuations of the coolant, to vibrations of fuel elements, control rods, or structural materials. The general noise equations are obtained by assuming small perturbations around a steady-state neutron flux and by subsequently taking the Fourier transform in the frequency domain. Recently, new neutron noise solvers have been implemented in diffusion and transport theory in APOLLO3®, the multi-purpose deterministic transport code developed at CEA, and a new stochastic solver has been implemented for the neutron noise analysis in the frequency domain in the Monte Carlo code TRIPOLI-4®, also developed at CEA. In this paper, we compare the two solvers for the case of fuel pin oscillations in a simplified UOX fuel assembly, in view of proposing the examined configurations as a benchmark for neutron noise calculations.
A FINITE ELEMENT METHOD FOR NEUTRON NOISE ANALYSIS IN HEXAGONAL REACTORS
Authors: Vidal-Ferràndiz A. , Ginestar D. , Carreño A. , Verdú G. , Demazière C.
Published: February 2021

The early detection of anomalies through the analysis of the neutron noise recorded by incore and ex-core instrumentation gives the possibility to take proper actions before such problems lead to safety concerns or impact plant availability. The study of the neutron fluctuations permits to detect and differentiate anomalies depending on their type and possibly to characterize and localize such anomalies. This method is non-intrusive and does not require any external perturbation of the system. To effectively use the neutron noise for reactor diagnostics it is essential to accurately model the effects of the anomalies on the neutron field. This paper deals with the development and validation of a neutron noise simulator for reactors with different geometries. The neutron noise is obtained by solving the frequency-domain two-group neutron diffusion equation in the first order approximation. In order to solve this partial differential equation a code based on a high order finite element method is developed. The novelty of this simulator resides on the possibility of dealing with rectangular meshes in any kind of geometry, thus allowing for complex domains and any location of the perturbation. The finite element method also permits automatic refinements in the cell size (h-adaptability) and in its polynomial degree (p-adaptability) that lead to a fast convergence. In order to show the possibilities of the neutron noise simulator developed a perturbation in a hexagonal two-dimensional reactor is investigated in this paper.
MODELLING AND ANALYSIS OF FUEL ASSEMBLY VIBRATIONAL MODES IN PWRS USING SIMULATE-3K
Authors: Verma V. , Chionis D. , Dokhane A. , Ferroukhi H.
Published: February 2021

Some of the KWU pre-KONVOI PWRs operating across Europe saw a systematic increase in the neutron noise levels over several cycles in the last decade, and subsequently, core internals’ movements, especially vibrations of fuel assemblies with specific designs were identified as one of the plausible causes. Therefore, it is important to develop computational methods that can allow to investigate and predict the reactor noise response to fuel assemblies vibrations. To this aim, the 3D nodal reactor dynamics code SIMULATE-3K is used at PSI with a special module called the ‘assembly vibration model’ that imitates time-dependent motions of fuel assemblies by dynamically modifying the water-gaps surrounding the laterally moving fuel assemblies. The varying water-gaps are represented by the variation in the corresponding two-group macroscopic cross sections generated using the lattice code CASMO-5 in 2D. The studies conducted so far to assess the methodology for full core noise simulations were based on assuming vibrations of a clamped-free cluster of fuel assemblies that are unsupported from both ends. However, as this represents a non-physical movement, further developments were made at PSI to allow simulating more realistic movements of fuel assemblies such as the cantilevered mode vibration. The updated methodology, along with evaluations of the simulated noise response to realistic vibration modes, is presented in this paper. Results show that, as expected, the radial and axial neutron noise behaviour follow the vibration pattern of the imposed time-dependent axial functions corresponding to the natural oscillation modes of the fuel assemblies, thereby providing confidence in the application of the developed methodology for numerical neutron noise analyses of the PWR cores.
EXPERIMENTAL DETERMINATION OF THE ZERO POWER TRANSFER FUNCTION OF THE AKR-2
Authors: Hübner Sebastian , Knospe Alexander , Viebach Marco , Lange Carsten , Hurtado Antonio
Published: February 2021

The transfer function is a basic characteristic of every nuclear reactor. It describes how a perturbation at a given place and time influences the neutron flux. In case of a known perturbation, the determination of characteristic reactor parameters is possible. The present paper shows an experimental method to determine the gain of the zero-power reactor transfer function (ZPTF) of the AKR-2 reactor at TU Dresden and the comparison to the theoretical shape of the ZPTF derived from kinetic parameters simulated with MCNP. For the experiments, a high-precision linear motor axis is used to insert an oscillating perturbation acting at frequencies smaller than the lower bound of the plateau region of the ZPTF. For higher frequencies, a rotating absorber is used. This device emulates an absorber of variable strength. The reactor response is detected with a He-3 counter.

The data evaluation shows good agreement between measured and corresponding theoretical values of the gain of the ZPTF.
Modélisation physique du comportement thermo-mécanique d’un pieu géothermique
Authors: Tang Anh Minh , Yavari Neda , Nguyen Van Tri , Pereira Jean-Michel , Hassen Ghazi
Published: February 2021

Les pieux géothermiques sont les pieux de fondation équipés d’un système échangeur de chaleur entre les locaux qui ont besoin d’être chauffés et/ou rafraîchis et le terrain environnant. Pendant sa durée de vie, un pieu géothermique subit des cycles annuels de température avec une variation de l’ordre d’une vingtaine de degré. Il est donc nécessaire de comprendre l’effet de ces cycles de température sur le comportement mécanique de tels pieux de fondation. Cet article présente une synthèse du programme d’expérimentation mené à l’École des Ponts ParisTech depuis 2010 sur un modèle physique 1 × g. Le pieu modèle considéré dans cette étude est un tube creux en aluminium, de 20 mm de diamètre extérieur et de 600 mm de longueur, équipé d’un système de contrôle de température. Ce dernier est d’abord soumis à une charge axiale constante appliquée en tête puis à des cycles de variation de température. Le comportement du pieu dans un sable sec et dans une argile saturée a été étudié. Ces expérimentations en modèle réduit ont permis d’identifier les principaux effets des cycles de température sur le comportement d’un pieu géothermique à long terme. Les résultats de cette étude sur modèle réduit sont présentés, les avantages et les inconvénients du modèle physique utilisé sont discutés.
Hybridité des formes d’engagement sociétal et financement public. L’exemple du football professionnel français
Authors: Boucher Werner , François Aurélien , Dermit-Richard Nadine
Published: February 2021

Ces dernières années ont témoigné en France d’un phénomène croissant de création d’associations, de fonds de dotation et/ou de fondations par les clubs sportifs professionnels désireux de porter leur engagement sociétal à travers ces structures. Cet article ambitionne ainsi de savoir si ce phénomène traduit une transformation dans la façon dont les clubs s’engagent. Nous avons choisi le football comme terrain d’investigation en retenant l’intégralité des clubs de Ligue 1 disposant d’au moins une de ces structures pour la saison 2018–2019. Au travers d’entretiens menés auprès de responsables opérationnels et de données secondaires, nous montrons le processus d’hybridation de l’engagement à l’œuvre caractérisé par une gouvernance, des ressources ainsi que des actions communes aux clubs et structures dédiées. Si ces nouvelles formes hybrides de l’engagement permettent sa meilleure opérationnalisation, nos résultats montrent, par ailleurs, que son évaluation reste très sommaire. Bien que rendue complexe au regard de l’hybridité observée, l’évaluation de l’engagement sociétal apparaît pourtant essentielle pour justifier son efficacité et ainsi, du point de vue du management public, légitimer les aides publiques directes et/ou indirectes versées conjointement à ces structures et aux clubs les ayant créés.
Krankenhauszukunftsgesetz: Die große Digitalisierungsoffensive
Authors: Riedel Wolfgang , Riedel Hendrik
Published: February 2021

Mit dem Krankenhauszukunftsgesetz stellen Bund und Länder zusätzliche Mittel für die Investition in Notfallkapazitäten und IT-Infrastruktur zur Verfügung. Um an die Fördergelder zu kommen, müssen die Krankenhäuser einiges beachten.
Synthesis of Imidazole and Histidine-Derived Cross-Linkers as Analogues of GOLD and Desmosine
Authors: Bilitewski Ursula , Laschat Sabine , Schädel Nicole , Icik Esra , Martini Maike , Altevogt Luca , Ramming Isabell , Greulich Andreas , Baro Angelika
Published: February 2021

Amino acid derivatives with a central cationic heterocyclic core (e.g., imidazolium) are biologically relevant cross-linkers of proteins and advanced glycation end (AGE) products. Here, imidazolium-containing cross-linkers were synthesized from imidazole or histidine by N-alkylation employing aspartate- and glutamate-derived mesylates as key step. Biological investigations were carried out to probe the biocompatibility of these compounds.
Local and nonlocal spin Seebeck effect in lateral Pt–Cr2O3–Pt devices at low temperatures
Authors: Muduli Prasanta , Schlitz Richard , Kosub Tobias , Hübner René , Erbe Artur , Makarov Denys , Goennenwein Sebastian T. B.
Published: February 2021

We have studied thermally driven magnon spin transport (spin Seebeck effect, SSE) in heterostructures of antiferromagnetic α-Cr2O3 and Pt at low temperatures. Monitoring the amplitude of the local and nonlocal SSE signals as a function of temperature, we found that both decrease with increasing temperature and disappear above 100 K and 20 K, respectively. Additionally, both SSE signals show a tendency to saturate at low temperatures. The nonlocal SSE signal decays exponentially for intermediate injector–detector separation, consistent with magnon spin current transport in the relaxation regime. We estimate the magnon relaxation length of our α-Cr2O3 films to be around 500 nm at 3 K. This short magnon relaxation length along with the strong temperature dependence of the SSE signal indicate that temperature-dependent inelastic magnon scattering processes play an important role in the intermediate range magnon transport. Our observation is relevant to low-dissipation antiferromagnetic magnon memory and logic devices involving thermal magnon generation and transport.
A study of DC electrical breakdown in liquid helium through analysis of the empirical breakdown field distributions
Authors: Phan N. S. , Wei W. , Beaumont B. , Bouman N. , Clayton S. M. , Currie S. A. , Ito T. M. , Ramsey J. C. , Seidel G. M.
Published: February 2021

We report results from a study on electrical breakdown in liquid helium using near-uniform-field stainless steel electrodes with a stressed area of ∼0.7cm2. The distribution of the breakdown field is obtained for temperatures between 1.7 K and 4.0 K, pressures between the saturated vapor pressure and 626 Torr, and with electrodes of different surface polishes. A data-based approach for determining the electrode-surface-area scaling of the breakdown field is presented. The dependence of the breakdown probability on the field strength as extracted from the breakdown field distribution data is used to show that breakdown is a surface phenomenon closely correlated with Fowler–Nordheim field emission from asperities on the cathode. We show that the results from this analysis provide an explanation for the supposed electrode gap-size effect and also allow for a determination of the breakdown-field distribution for arbitrary shaped electrodes. Most importantly, the analysis method presented in this work can be extended to other noble liquids to explore the dependencies for electrical breakdown in those media.
Effective permittivity of co-evaporated metal-organic mixed films
Authors: Mischok Andreas , Hale Nathan , Gather Malte C. , Di Falco Andrea
Published: February 2021

The combination of organics and metals in a composite film holds promise for combining plasmonic interaction with gain and for the realization of epsilon-near-zero (ENZ) metamaterials. In particular, fluorescent organic dyes can be used to compensate the plasmonic losses of a homogenized metal-organic material. Here, we fabricate such films through thermal co-evaporation of silver and an organic host:guest system and investigate experimentally the resulting linear optical properties for varying metal concentrations. We extract the effective permittivity of the resulting films with ellipsometry measurements and demonstrate the formation of silver nanoparticles, resulting in strongly localized surface plasmon resonances until a percolation threshold is reached. Through enhanced light-matter interaction, we observe a maximum of the photoluminescence for a concentration of 15% in volume of metal in the composite material. These results showcase a variety of growth parameters and will be useful for the future design of gain-compensated plasmonics and ENZ metamaterials.
A novel model for incorporation of differential diffusion effects in PDF simulations of non-premixed turbulent flames based on reaction-diffusion manifolds (REDIM)
Authors: Yu Chunkan , Breda Paola , Minuzzi Felipe , Pfitzner Michael , Maas Ulrich
Published: February 2021

In this work, reaction-diffusion manifold (REDIM) reduced chemistry is used in the simulation of turbulent non-premixed flames based on a transported-probability density function model. Differential molecular diffusion is applied in the generation of the manifolds. This is the first work to consider the gradients of the reduced variables as additional parameters in the REDIM model, and one-directional gradients are utilized to generate the REDIM reduced chemistry. Hereby, the influence of turbulence on differential molecular diffusion is automatically considered in terms of reduced variable gradients, and the physical transport properties (e.g., diffusion coefficients) are used in a detailed way, without any additional modeling (e.g., unity-Lewis number assumption). Although the scalar gradients appear as multi-directional in a general turbulent reacting flow, previous direct numerical simulation analysis reveals that REDIMs generated from one-directional gradients can accurately describe the system featuring multi-directional gradients, if this one-directional gradient has a major effect on the chemistry. Here, it is proposed to obtain such gradients under the hypothesis that the flame structure is locally one-dimensional at each spatial position. In order to retrieve the gradients of the reduced variables for the interpolation of the thermo-kinetic states from the REDIM table, the sub-grid gradient is evaluated here from the particle fields. The well-known Sandia series of flames is selected to validate the proposed algorithm. The results show that the new algorithm can reproduce the thermo-kinetic quantities with high accuracy for all investigated flames.
SO(9) characterization of the standard model gauge group
Authors: Krasnov Kirill
Published: February 2021

A recent series of works characterized the Standard Model (SM) gauge group GSM as the subgroup of SO(9) that, in the octonionic model of the latter, preserves the split O=C⊕C3 of the space of octonions into a copy of the complex plane plus the rest. This description, however, proceeded via the exceptional Jordan algebras J3(O),J2(O) and, in this sense, remained indirect. One of the goals of this paper is to provide as explicit a description as possible and also to clarify the underlying geometry. The other goal is to emphasize the role played by different complex structures in the spaces O and O2. We provide a new characterization of GSM: The group GSM is the subgroup of Spin(9) that commutes with a certain complex structure JR in the space O2 of Spin(9) spinors. The complex structure JR is parameterized by a choice of a unit imaginary octonion. This characterization of GSM is essentially octonionic in the sense that JR is restrictive because octonions are non-associative. The quaternionic analog of JR is the complex structure in the space H2 of Spin(5) spinors that commutes with all Spin(5) transformations.
An effective one-dimensional approach to calculating mean first passage time in multi-dimensional potentials
Authors: Gray Thomas H. , Yong Ee Hou
Published: February 2021

Thermally activated escape processes in multi-dimensional potentials are of interest to a variety of fields, so being able to calculate the rate of escape—or the mean first-passage time (MFPT)—is important. Unlike in one dimension, there is no general, exact formula for the MFPT. However, Langer’s formula, a multi-dimensional generalization of Kramers’s one-dimensional formula, provides an approximate result when the barrier to escape is large. Kramers’s and Langer’s formulas are related to one another by the potential of mean force (PMF): when calculated along a particular direction (the unstable mode at the saddle point) and substituted into Kramers’s formula, the result is Langer’s formula. We build on this result by using the PMF in the exact, one-dimensional expression for the MFPT. Our model offers better agreement with Brownian dynamics simulations than Langer’s formula, although discrepancies arise when the potential becomes less confining along the direction of escape. When the energy barrier is small our model offers significant improvements upon Langer’s theory. Finally, the optimal direction along which to evaluate the PMF no longer corresponds to the unstable mode at the saddle point.
Understanding the Polymer Rearrangement of pH-Responsive Nanoparticles
Authors: Deirram Nayeleh , Kermaniyan Sarah S. , Johnston Angus P. R. , Such Georgina K.
Published: February 2021

The use of self-assembled nanoparticles for drug delivery has received significant attention in recent years. However, the dynamic nature of self-assembled polymeric systems means there is a need to develop greater understanding of the inherent stability of these systems. In particular, understanding if these materials remain as discrete nanoparticles, or if there is dynamic exchange of material between particles is critical. Herein, we labelled pH-responsive nanoparticles with fluorescent dyes and then investigated the change in fluorescence when the particles were mixed with unlabelled nanoparticles in order to investigate their potential for polymer rearrangement. Nanoparticles were formed by the nanoprecipitation of pH-responsive poly(ethylene glycol)-block-poly(2-(diethylamino)ethyl methacrylate) (PEG-b-PDEAEMA) as the shell and poly(2-(diethylamino)ethyl methacrylate)-random-poly(2-(diisopropylamino)ethyl methacrylate) (PDEAEMA-r-PDPAEMA) as the core. The core and shell were labelled by incorporating pentafluorophenyl methacrylate (PFPMA) in core or shell respectively and then coupling with either Sulfo-cyanine5 amine or Cyanine3 amine. Exchange of material between nanoparticles was probed by tracking changes in the self-quenching of fluorescently labelled polymers in the core of the nanoparticles. The fluorescence intensity of the labelled nanoparticles was stable when mixed with unlabelled nanoparticles at physiological pH (pH 7.4), suggesting there is limited migration of polymers between particles in this system. This study provides important insights into the use of non-crosslinked nanoparticles under biologically relevant conditions.
Is protein carbonylation a biomarker of seed priming and ageing?
Authors: Boucelha Lilya , Abrous-Belbachir Ouzna , Djebbar Réda
Published: February 2021

For a long time, it has been known that seed priming allows the improvement of plant production and tolerance to abiotic stresses. However, a negative effect on the longevity of the seeds thus primed was observed; these mechanisms are still poorly understood. In addition, it has been shown by several authors that seed ageing is associated with the oxidation and particularly with carbonylation of protein. Our work consisted in studying the AOPP and carbonyl protein at the different parts of the embryo from freshly primed seeds and from those that have been primed for 4 years (after storage). We subjected Vigna unguiculata (L.) Walp. seeds to a single or double hydropriming. Our study showed that hydropriming, and more particularly a double cycle of hydration-dehydration, makes it possible to attenuate the oxidation of the protein while it favours a certain threshold of carbonylation in the freshly dehydrated seeds in order to better trigger the germination process. On the other hand, after a storage period of 4 years, these dehydrated seeds are characterised by a strong accumulation of the products of oxidation and especially carbonylated protein, compared with the untreated seeds, which could explain the decrease of the longevity of these seeds.
Probabilistic pragmatics explains gradience and focality in natural language quantification
Authors: van Tiel Bob , Franke Michael , Sauerland Uli
Published: February 2021

Significance

Theoretical linguistics postulates abstract structures that successfully explain key aspects of language. However, the precise relation between abstract theoretical ideas and empirical data from language use is not always apparent. Here, we propose to empirically test abstract semantic theories through the lens of probabilistic pragmatic modeling. We consider the historically important case of quantity words (e.g., “some,” “all”). Data from a large-scale production study seem to suggest that quantity words are understood via prototypes. But based on statistical and empirical model comparison, we show that a probabilistic pragmatic model that embeds a strict truth-conditional notion of meaning explains the data just as well as a model that encodes prototypes into the meaning of quantity words.
Encoding memory in tube diameter hierarchy of living flow network
Authors: Kramar Mirna , Alim Karen
Published: February 2021

Significance

Simple organisms manage to thrive in complex environments. Having memory about the environment is key in taking informed decisions.
Physarum polycephalum
excels as a giant unicellular eukaryote, being even able to solve optimization problems despite the lack of a nervous system. Here, we follow experimentally the organism’s response to a nutrient source and find that memory about nutrient location is encoded in the morphology of the network-shaped organism. Our theoretical predictions in line with our observations unveil the mechanism behind memory encoding and demonstrate the
P. polycephalum
’s ability to read out previously stored information.
Unfolded and intermediate states of PrP play a key role in the mechanism of action of an antiprion chaperone
Authors: Petrosyan Rafayel , Patra Shubhadeep , Rezajooei Negar , Garen Craig R. , Woodside Michael T.
Published: February 2021

Significance

Many diseases involve the propagation of misfolded proteins as in prion diseases. Compounds that can inhibit conversion into misfolded conformers exist, but their mechanism of action remains poorly understood. By observing the effects of the polymeric antiprion pharmacological chaperone pentosan polysulfate on the folding of single prion protein molecules, we find that interactions with partially and fully unfolded states play an important role. A comparison to previous results for a chaperone with very different chemical properties suggests that antiprion agents help to prevent conversion by interacting with the protein when it unfolds from the native structure during the conversion process. Unfolded states may, therefore, be fruitful targets for developing more effective therapeutic inhibitors of prion and prion-like conversion.
Real-time measurements of aminoglycoside effects on protein synthesis in live cells
Authors: Aguirre Rivera Javier , Larsson Jimmy , Volkov Ivan L. , Seefeldt A. Carolin , Sanyal Suparna , Johansson Magnus
Published: February 2021

Significance

To address the public health challenges caused by the spread of antibiotic resistance, it is critical to enhance our understanding of the mechanisms of action of these compounds. In the present study, we use superresolved single-molecule tracking techniques, to investigate the effect of three aminoglycoside drugs on protein synthesis kinetics directly inside live bacterial cells. Our results imply that these drugs do not completely inhibit bacterial protein synthesis, but only make it slower. Hence, the bactericidal effect of these drugs is likely due to a disturbed, rather than inhibited, protein synthesis process.
Structure of a bacterial OapB protein with its OLE RNA target gives insights into the architecture of the OLE ribonucleoprotein complex
Authors: Yang Yang , Harris Kimberly A. , Widner Danielle L. , Breaker Ronald R.
Published: February 2021

Significance

Bacterial noncoding RNAs (ncRNAs) play key roles in many biological processes including gene regulation, RNA processing and modification, and protein synthesis and translocation. OLE RNAs, found in many Gram-positive species, are one of the largest highly structured ncRNA classes whose biochemical functions remain unknown. In
Bacillus halodurans
, OLE RNAs interact with at least two proteins, OapA and OapB, which are required to assemble a functional OLE ribonucleoprotein (RNP) complex contributing to cellular responses to certain environmental stresses. We established X-ray structural models that reveal the sequence elements and tertiary structural features of OLE RNA that are critical for its specific recognition by OapB, which will aid future exploration of the biological and biochemical functions of the unusual OLE RNP complex.
Acetogenic bacteria utilize light-driven electrons as an energy source for autotrophic growth
Authors: Jin Sangrak , Jeon Yale , Jeon Min Soo , Shin Jongoh , Song Yoseb , Kang Seulgi , Bae Jiyun , Cho Suhyung , Lee Jung-Kul , Kim Dong Rip , Cho Byung-Kwan
Published: February 2021

Significance

To develop an efficient artificial photosynthesis system using acetogen-nanoparticle hybrids, the efficiency of the electron–hole pair generation of nanoparticles must be enhanced to demonstrate extracellular electron utilization by the acetogen. Here we verified that
Clostridium autoethanogenum
, an industrially relevant acetogen, could use electrons generated from size- and structure-controlled chemically synthesized cadmium sulfide nanoparticles displayed on the cell surface under light-exposure conditions. In addition, transcriptomic analysis showed that the electrons generated from nanoparticles were largely transported to the intracellular matrix via the metal ion or flavin-binding proteins. These results illustrate the potential to increase the CO
2
-fixing efficiency of nanoparticle-based artificial photosynthesis by engineering cellular processes related to electron transfer generated from the cathode.
Sea spray aerosol concentration modulated by sea surface temperature
Authors: Liu Shang , Liu Cheng-Cheng , Froyd Karl D. , Schill Gregory P. , Murphy Daniel M. , Bui T. Paul , Dean-Day Jonathan M. , Weinzierl Bernadett , Dollner Maximilian , Diskin Glenn S. , Chen Gao , Gao Ru-Shan
Published: February 2021

Significance

Climate models use pre-industrial atmosphere as the reference to evaluate the impacts of human activities on the Earth’s radiation balance. Sea spray aerosols (SSA) are the key component in the relatively pristine preindustrial conditions that substantially affect model calculations. Currently, the abundance of SSA is poorly constrained. In particular, studies on the influence of sea surface temperature on SSA production have shown disparate results. This uncertainty arises from limited field measurements, especially over remote oceans. Our global aircraft measurements over the remote Pacific and Atlantic Oceans show that higher sea surface temperature enhances the production of SSA. Updating the current parameterization in global models using our observational constraints will improve the estimate of atmospheric SSA budget and human-induced climate change.
Elastic amplification of the Rayleigh–Taylor instability in solidifying melts
Authors: Jambon-Puillet Etienne , Piéchaud Matthieu Royer , Brun P.-T.
Published: February 2021

Significance

Patterns resulting from successive far-from-equilibrium processes are common in nature. Yet, they are challenging to investigate, model, and translate to engineering owing to their complexity coupled to fluctuating developmental conditions. Here we introduce a comparatively simpler system combining a fluidic instability and large solid deformations in solidifying melts to produce soft solids with complex surface geometry. We fully rationalize this different kind of pattern comprising elongated hair-like features using the framework of continuum mechanics. Our work is relevant to the broad range of problems where mechanical deformations and solidification are concomitant and paves the way for the use of multistep moldless approaches for the assembly of complex materials.
Influence of a COVID-19 vaccine’s effectiveness and safety profile on vaccination acceptance
Authors: Kaplan Robert M. , Milstein Arnold
Published: February 2021

Significance

Acceptance of vaccines has been on the decline in recent years. Despite encouraging early results for coronavirus vaccine trials, achieving herd immunity requires substantial uptake. We presented scenarios varying vaccine efficacy, minor side effects, and severe reactions to a sample representative of the US population. Vaccine acceptance improved when the efficacy increased beyond 70%. Respondents were unaffected by the probability of minor side effects, such as a sore arm or fever lasting 24 h. The chances of accepting the vaccine were lower when the probability of serious adverse reactions was 1/100,000 in contrast to 1/million or 1/100 million. A replication showed that the results were largely unchanged following the public announcement that the vaccines were 95% effective.
Active control of plasmon-induced transparency with large tunability and high Q-factor in graphene-black phosphorus hybrid system
Authors: Han Li , Wang Lin , Xing Huaizhong , Chen Xiaoshuang
Published: February 2021

Plasmon-induced transparency phenomena in the mid-infrared caused by the coupling behavior between dipole (bright element) and higher-order modes (dark element) in graphene as well as black phosphorus (BP) nanoribbons are investigated. The transparent windows can be adjusted flexibly by varying the carrier concentration of graphene and BP. It is also shown that the carrier mobility and refractive index of the substrate are the key factors affecting destructive interference. Obvious group delays are obtained near the transparent windows so that the slow light effect can be achieved. Our results allow a better understanding of efficient exploration of surface plasmons with integrated properties of building blocks from a family of two-dimensional materials, with the aim of expanding both photonic bands and functionalities.
Quantitative diagnosis of mechanical faults based on generalized fractal dimensions
Authors: Tang Yaochi , Li Kuohao
Published: February 2021

The bearing is an important part of mechanical equipment. Its condition directly influences the operation of the entire mechanical equipment. Faults in bearings may induce fatal disasters and heavy economic losses, in worst-case scenarios. In fault diagnosis, many studies have only proposed the characteristics of faults; however, without standards for quantifying the faults, automated diagnosis could not be realized. Based on the generalized fractal dimensions (GFDs) and the receiver operating characteristic (ROC) curve, this study proposed a method to characterize initial failure trends and quantize the bearing failure standard. The size of GFDs was calculated using the vibration signal measured during the operation of a bearing. The optimal classification model was determined based on the ROC curve as the criterion of damage. The model trained by the signals of the training group was used in the check analysis of the signals of the validation group. The accuracy of this quantitative analysis was validated by experimental results. Finally, three bearings in different positions were diagnosed by this model under the same test conditions, and the effectiveness of the quantitative diagnosis of damage proposed in this study was validated.
Linearization of the lift-off effect for magnetic flux leakage based on Fourier transform
Authors: Wang Jie , Li Erlong , Wu Jianbo , Xu Xianyou
Published: February 2021

In magnetic flux leakage testing, the lift-off effect shows that testing signal voltages vary with lift-off values. This has many adverse effects on detection and evaluation. This paper proposes a novel method for linearization of the lift-off effect in the spatial domain. The spatial analytical expression is obtained through magnetic dipole theory and the Fourier transform method. An analytical method to linearizethe lift-off effect is proposed. Further, the finite-element method and discrete Fourier transform method are applied to linearize the lift-off effect. Experimental studies are also conducted to verify the analytical results. The linear fitting function of the lift-off effect takes the form of Y = AX + B. When the spatial frequency ω is 35 mm−1, the linear fitting results of the simulation and experiment are Y = −0.23596X−2.0268 and Y = −0.23511X + 4.8152. The goodness of fit R2
is 0.9997 and 0.9975. The results show that the lift-off effect can be linearized in the spatial domain. The coefficient A is slightly affected by the defect size. The coefficient B is strongly related to the defect size. We consider these results to be quite significant.
Graphene-reinforced polymer matrix composites fabricated by in situ shear exfoliation of graphite in polymer solution: processing, rheology, microstructure, and properties
Authors: Hussein Arab H , Dong Zhizhong , Lynch-Branzoi Jennifer , Kear Bernard H , Shan Jerry W , Pelegri Assimina A , Tse Stephen D
Published: February 2021

Effective methods are needed to fabricate the next generation of high-performance graphene-reinforced polymer matrix composites (G-PMCs). In this work, a versatile and fundamental process is demonstrated to produce high-quality graphene-polymethylmethacrylate (G-PMMA) composites via in situ shear exfoliation of well-crystallized graphite particles loaded in highly-viscous liquid PMMA/acetone solutions into graphene nanoflakes using a concentric-cylinder shearing device. Unlike other methods where graphene is added externally to the polymer and mixed, our technique is a single step process where as-exfoliated graphene can bond directly with the polymer with no contamination/handling. The setup also allows for the investigation of the rheology of exfoliation and dispersion, providing process understanding in the attainment of the subsequently heat injection-molded and solidified G-PMC, essential for future manufacturing scalability, optimization, and repeatability. High PMMA/acetone concentration correlates to high mixture viscosity, which at large strain rates results in very-high shear stresses, producing a large number of mechanically-exfoliated flakes, as confirmed by liquid-phase UV–visible spectral analysis. Raman spectroscopy and other imaging evince that single- and bi-layer graphene are readily achieved. Nevertheless, a limit is reached at high mixtures viscosities where the process becomes unstable as non-Newtonian fluid behavior (e.g. viscoelastic) dominates the system. Characterization of microstructure, morphology, and properties of this new class of nanostructured composites reveals interesting trends. Observations by transmission electron microscopy, scanning electron microscopy, and helium ion microscopy of the manufactured G-PMCs show uniform distributions of unadulterated, well-bonded, discontinuous, graphene nanoflakes in a PMMA matrix, which enhances stiffness and strength via a load-transfer mechanism. Elastic modulus of 5.193 GPa and hardness of 0.265 GPa are achieved through processing at 0.7 g ml−1 of acetone/PMMA for 1% wt. starting graphite loading when injected into a sample mold at 200 °C. Mechanical properties exhibit 31% and 28.6% enhancement in elastic modulus and hardness, respectively, as measured by nano-indentation.
The ROS-generating photosensitizer-free NaYF4:Yb,Tm@SiO2 upconverting nanoparticles for photodynamic therapy application
Authors: Kowalik P , Kamińska I , Fronc K , Borodziuk A , Duda M , Wojciechowski T , Sobczak K , Kalinowska D , Klepka M T , Sikora B
Published: February 2021

In this work we adapt rare-earth-ion-doped NaYF4 nanoparticles coated with a silicon oxide shell (NaYF4:20%Yb,0.2%Tm@SiO2) for biological and medical applications (for example, imaging of cancer cells and therapy at the nano level). The wide upconversion emission range under 980 nm excitation allows one to use the nanoparticles for cancer cell (4T1) photodynamic therapy (PDT) without a photosensitizer. The reactive oxygen species (ROS) are generated by Tm/Yb ion upconversion emission (blue and UV light). The in vitro PDT was tested on 4T1 cells incubated with NaYF4:20%Yb,0.2%Tm@SiO2 nanoparticles and irradiated with NIR light. After 24 h, cell viability decreased to below 10%, demonstrating very good treatment efficiency. High modification susceptibility of the SiO2 shell allows for attachment of biological molecules (specific antibodies). In this work we attached the anti-human IgG antibody to silane-PEG-NHS-modified NaYF4:20%Yb,0.2%Tm@SiO2 nanoparticles and a specifically marked membrane model by bio-conjugation. Thus, it was possible to perform a selective search (a high-quality optical method with a very low-level organic background) and eventually damage the targeted cancer cells. The study focuses on therapeutic properties of NaYF4:20%Yb,0.2%Tm@SiO2 nanoparticles and demonstrates, upon biological functionalization, their potential for targeted therapy.
Approaching the radiating X-point in SOLPS-ITER modeling of ASDEX Upgrade H-mode discharges
Authors: Senichenkov I Yu , Kaveeva E G , Rozhansky V A , Voskoboynikov S P , Veselova I Yu , Shtyrkhunov N V , Coster D P , Bonnin X
Published: February 2021

In the present paper the ASDEX Upgrade (AUG) experimental trend of reaching the radiating X-point with nitrogen seeding is reproduced by SOLPS-ITER code modeling. In these experiments the whole divertor region below the X-point is cooled down by the impurity radiation if the seeding rate is large enough, and the maximal radiation is registered from the X-point region, or even from the confinement zone above the X-point. It is demonstrated that for constant seeding rate SOLPS-ITER simulations of the intensively seeded AUG discharges result in that the confined plasma goes into the radiation collapse as a certain threshold in seeding rate is exceeded. This threshold value increases with increasing discharge power. No stable regimes with the electron temperature below 5 eV in the confinement zone even above the X-point are achieved in the modeling if the seeding rate is large enough, in contrast to the experiment. However, such a regime may be achieved if the fueling, seeding and pumping rates are changing in time. Since the SOLPS-ITER code can simulate only steady state, another modeling strategy is chosen. The fueling and seeding rates are artificially reduced by 3 orders of magnitude and the impurity content is set to satisfy the condition that the ratio of electrons contribution originating from fuel atoms to ones coming from impurity atoms is about unity. It is suggested that the radial width of the cooled region in the confinement zone is of the order of the scrape-off layer width λ

q
, since it is driven by the same physics leading the energy flux to go from mostly radial to mostly parallel. Under these conditions, the radiative spot above the X-point behaves as the energy sink similarly to the energy sink near the divertor in the conventional regime. In extreme regimes (with large seeding rate), the width of the cold region inside the separatrix may exceed λ

q
, and up to 90% of discharge power can be radiated from the confined region. An estimate of the poloidal length of the radiative spot is suggested as well. Flow patterns of neutrals, deuterium ions, impurities, electric current and heat flows are analyzed for the regimes with intensive X-point radiation. The formation of an electric potential peak above the X-point is observed in the simulations, and the corresponding E × B drift flux appears to give the largest contribution to the main ion and impurity fluxes. This E × B drift flux together with the large ionization source change the parallel velocity with respect to its neoclassical profile. Consequently, the radial E field deviates from the neoclassical one, which might improve the turbulence suppression.
A magnetorheological fluid based planetary gear transmission for mechanical power-flow control
Authors: Christie M D , Sun S , Quenzer-Hohmuth J , Deng L , Du H , Li W H
Published: February 2021

Power transmission for mechanical systems often involves the use of clutching- or dissipative-elements to protect drive systems and provide steady output power. As standard implementations in motor-driven systems, these devices operate passively or in discrete states, providing limited controllability to the power output. This paper presents a magnetorheological-fluid-based differential (planetary) gear transmission which serves to variably couple motor power through a sun gear input to a load affixed to a planet carrier output. This is achieved both rapidly and continuously through controlled slippage between the ring gear of the device and its casing. Compared to conventional MR clutches, the unique functionality of the differential gearbox enables use of an MR brake with lower inertia than an in-line clutch. Through control of current supplied to the energizing electromagnet of brake component of the transmission, simple and reversible governing of output torque and speed is achieved. This behaviour is modelled and verified through testing, showing a 349% variation in brake torque for constant speed tests from the off state to the maximum capacity of the device, with a 262% variation in brake torque under a harmonic input displacement also observed. The versatility of the device demonstrated through PID speed and torque control.
Study of high-order harmonic generation in xenon based on time-dependent density-functional theory
Authors: Romanov A A , Silaev A A , Sarantseva T S , Frolov M V , Vvedenskii N V
Published: February 2021

The high-order harmonic generation (HHG) in xenon is studied by using the time-dependent density-functional theory. The dynamics of all electrons on the outer 4th and 5th atomic shells is considered with subsequent separation of contributions of different atomic orbitals to the HHG amplitude. It is shown that giant enhancement of HHG yield in a spectral region near 100 eV is caused by perturbation of the electron–electron interaction potential induced by recolliding photoelectron wavepacket originated from the 5p
0 orbital. This perturbation leads to the collective oscillations of all orbitals on the 4th shell closely localized in space and strongly interacting with each other. The resulting HHG yield is enhanced by more than an order of magnitude compared with the response of the single 5p
0 orbital. The high accuracy of the numerical results is confirmed by comparing the calculated HHG spectra and photoionization cross-sections with experimental results and an analytical parameterization of the HHG yield.