bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of NSO compounds in the research of hydrocarbon migration direction in the Wangjiagang area of the Dongying sagin the Bohai Bay Basin
Authors: Niu Zicheng , Li Zheng , Wang Xiuhong , Liu Huiping , Wang Juan , Liu Xuan , Wang Ru
Published: March 2021

The determination of hydrocarbon migration direction is an important part in the study of petroleum accumulation in petroliferous basins, and plays an important role in guiding oil and gas exploration activity. Despite their relatively low content in petroleum, the polar nitrogen-, sulphur-and oxygen- containing compounds (collectively referred to as NSO compounds) have great potential in characterizing the hydrocarbon migration process. A series of crude oils along hydrocarbon migration pathway were selected and analysed using GC×GC/TOFMS and GC-MS in the Wangjiagang area of the Dongying sag. Total concentration of NSO compounds and other related parameters are determined to verify the role of different parameters in indicating hydrocarbon migration. Our research result shows that the total amount of NSO compounds, 1-/3-MC ratio, 1,8-/2,7-DMC ratio, 4-/1-MDBF ratio and 2,4-/1,4-DMDBT ratio changes grandully with the increase of migration distances. Thus, these parameters can be applied as effective migration direction indicators in study area. Some other parameters may not be suitable for the identification of hydrocarbon migration direction in the study area.
The Potential Application of Pentacyclic Triterpenoids in the Prevention and Treatment of Retinal Diseases
Authors: Cheng Zhengqi , Li Yue , Zhu Xue , Wang Ke , Ali Youmna , Shu Wenying , Zhang Ting , Zhu Ling , Murray Michael , Zhou Fanfan
Published: March 2021

Retinal diseases are a leading cause of impaired vision and blindness but some lack effective treatments. New therapies are required urgently to better manage retinal diseases. Natural pentacyclic triterpenoids and their derivatives have a wide range of activities, including antioxidative, anti-inflammatory, cytoprotective, neuroprotective, and antiangiogenic properties. Pentacyclic triterpenoids have great potential in preventing and/or treating retinal pathologies. The pharmacological effects of pentacyclic triterpenoids are often mediated through the modulation of signalling pathways, including nuclear factor erythroid-2 related factor 2, high-mobility group box protein 1, 11β-hydroxysteroid dehydrogenase type 1, and Src homology region 2 domain-containing phosphatase-1. This review summarizes recent in vitro and in vivo evidence for the pharmacological potential of pentacyclic triterpenoids in the prevention and treatment of retinal diseases. The
present literature supports the further development of pentacyclic triterpenoids. Future research should now attempt to improve the efficacy and pharmacokinetic behaviour of the agents, possibly by the use of medicinal chemistry and targeted drug delivery strategies.
Comparison of Self-Expanding RDV Perceval S versus TAVI ACURATE neo/TF
Authors: Mauri Victor , Gerfer Stephen , Kuhn Elmar , Adam Matti , Eghbalzadeh Kaveh , Djordjevic Ilija , Ivanov Borko , Gaisendrees Christopher , Frerker Christian , Schmidt Tobias , Mader Navid , Rudolph Tanja , Baldus Stephan , Liakopoulos Oliver , Wahlers Thorsten
Published: March 2021

Background Rapid deployment aortic valve replacement (RDAVR) and transcatheter aortic valve implantation (TAVI) have emerged as increasingly used alternatives to conventional aortic valve replacement to treat patients at higher surgical risk. Therefore, in this single-center study, we retrospectively compared clinical outcomes and hemodynamic performance of two self-expanding biological prostheses, the sutureless and rapid deployment valve (RDV) Perceval-S (PER) and the transcatheter heart valve (THV) ACURATE neo/TF (NEO) in a 1:1 propensity-score-matching (PSM) patient cohort.

Methods A total of 332 consecutive patients with symptomatic aortic valve stenosis underwent either singular RDAVR with PER (119) or TAVI with NEO (213) at our institutions between 2012 and 2017. To compare the unequal patient groups, a 1:1 PSM for preoperative data and comorbidities was conducted. Afterward, 59 patient pairs were compared with regard to relevant hemodynamic parameter, relevant paravalvular leak (PVL), permanent postoperative pacemaker (PPM) implantation rate, and clinical postoperative outcomes.

Results Postoperative clinical short-term outcomes presented with slightly higher rates for 30-day all-cause mortality (PER = 5.1% vs. NEO = 1.7%, p = 0.619) and major adverse cardiocerebral event in PER due to cerebrovascular events (transient ischemic attack [TIA]-PER = 3.4% vs. TIA-NEO = 1.7%, p = 0.496 and Stroke-PER = 1.7% vs. Stroke-NEO = 0.0%, p = 1). Moreover, we show comparable PPM rates (PER = 10.2% vs. NEO = 8.5%, p = 0.752). However, higher numbers of PVL (mild—PER = 0.0% vs. NEO = 55.9%, p = 0.001; moderate or higher—PER = 0.0% vs. NEO = 6.8%, p = 0.119) after TAVI with NEO were observed.

Conclusion Both self-expanding bioprostheses, the RDV-PER and THV-NEO provide a feasible option in elderly and patients with elevated perioperative risk. However, the discussed PER collective showed more postoperative short-term complications with regard to 30-day all-cause mortality and cerebrovascular events, whereas the NEO showed higher rates of PVL.
Researching Interventions to Improve Medication Adherence in Ulcerative Colitis Patients
Authors: Pacheco Mila Palma , Fortes Flora Maria Lorenzo , Santos Raquel Rocha dos , Silva Genoile Oliveira Santana
Published: March 2021

The purpose of this review was to identify interventions that improve adherence to medications in patients with ulcerative colitis (UC). The literature search was carried out between April and June 2020 in the PubMed/MEDLINE database, with the combination of MeSH terms medication adherence; intervention; ulcerative colitis; and inflammatory bowel disease. We restricted our search to articles published in English and Portuguese between March 2010 and March 2020. After the selection, recovery of full-text articles and analysis of the defined criteria, the interventions described in the studies were classified into four domains: educational; behavioral, cognitive behavioral, and multicomponent. In total, six clinical trials met the inclusion criteria and were analyzed. Half of the studies (3; 50%) used multicomponent interventions, 2 (33.3%) focused on behavioral interventions, and 1 (16.7%) applied isolated educational interventions. All studies used indirect methods to measure adherence, with an emphasis on scales and questionnaires. Half of the studies (3; 50%) showed a positive impact on adherence in patients with UC, with evidence that multicomponent interventions, when properly implemented in a clinical trial combining direct and indirect methods to measure medication adherence, appear to increase the chances of better results. We believe that future studies focusing on improving adherence in patients with UC are necessary.
Matrix Metalloproteinase-9 Levels are Associated with Brain Lesion and Persistent Venous Occlusion in Patients with Cerebral Venous Thrombosis
Authors: Aguiar de Sousa Diana , Pereira-Santos Maria Conceição , Serra-Caetano Ana , Neto Lia Lucas , Sousa Ana Luísa , Gabriel Denis , Correia Manuel , Gil-Gouveia Raquel , Oliveira Renato , Penas Sara , Carvalho Dias Mariana , Correia Manuel A. , Carvalho Marta , Sousa Ana E. , Canhão Patrícia , Ferro José M.
Published: March 2021

Background Elucidating mechanisms of brain damage in cerebral venous thrombosis (CVT) would be instrumental to develop targeted therapies and improve prognosis prediction. Matrix metalloproteinase-9 (MMP-9), a gelatinase that degrades major components of the basal lamina, has been associated to blood–brain barrier disruption. We aimed to assess, in patients with CVT, the temporal change in serum concentrations of MMP-9 and its association with key imaging and clinical outcomes.

Methods Pathophysiology of Venous Infarction—PRediction of InfarctiOn and RecanalIzaTion in CVT (PRIORITy-CVT) was a multicenter prospective cohort study of patients with newly diagnosed CVT. Serial collection of peripheral blood samples performed on day 1, 3, and 8, and standardized magnetic resonance imaging on day 1, 8, and 90. MMP-9 was quantified using enzyme-linked immunosorbent assay in 59 patients and 22 healthy controls. Primary outcomes were parenchymal brain lesion, early evolution of brain lesion, early recanalization, and functional outcome on day 90.

Results CVT patients with parenchymal brain lesion had higher baseline concentrations of MMP-9 compared with controls (adjusted p = 0.001). The area under receiver operating characteristic curve value for MMP-9 for predicting brain lesion was 0.71 (95% confidence interval [CI]: 0.57–0.85, p = 0.009). Patients with venous recanalization showed early decline of circulating MMP-9 and significantly lower levels on day 8 (p = 0.021). Higher MMP-9 on day 8 was associated with persistent venous occlusion (odds ratio: 1.20 [per 20 ng/mL], 95% CI: 1.02–1.43, p = 0.030).

Conclusion We report a novel relationship among MMP-9, parenchymal brain damage, and early venous recanalization, suggesting that circulating MMP-9 is a dynamic marker of brain tissue damage in patients with CVT.
Non-asymptotic behavior of the spectrum of the sinc-kernel operator and related applications
Authors: Bonami Aline , Jaming Philippe , Karoui Abderrazek
Published: March 2021

Prolate spheroidal wave functions have recently attracted much attention in applied harmonic analysis, signal processing, and mathematical physics. They are eigenvectors of the sinc-kernel operator Qc: the time- and band-limiting operator. The corresponding eigenvalues play a key role, and the aim of this paper is to obtain precise non-asymptotic estimates with explicit constants related to the spectrum of Qc. This issue is rarely studied in the literature, while the asymptotic behavior of the spectrum of Qc has been well established from the 1960s. However, many recent applications require such non-asymptotic behavior. As applications of our non-asymptotic estimates, we first provide estimates for the constants appearing in the Remez- and Turàn–Nazarov-type concentration inequalities. Then, we give a non-asymptotic upper bound for the gap probability of the sinc determinantal point process. Consequently, one gets a non-asymptotic estimate for the hole probability, associated with bulk scaled asymptotics of a random matrix from the Gaussian unitary ensemble. This last result can be considered as a complement of the various and more involved asymptotic counterparts of this estimate.
Semiclassical WKB problem for the non-self-adjoint Dirac operator with a decaying potential
Authors: Hatzizisis Nicholas , Kamvissis Spyridon
Published: March 2021

In this paper, we examine the semiclassical behavior of the scattering data of a non-self-adjoint Dirac operator with a fairly smooth—but not necessarily analytic—potential decaying at infinity. In particular, using ideas and methods from the work of Langer and Olver [Philos. Trans. R. Soc. London, Ser. A 278(1279), 137–174 (1975)], we provide a rigorous semiclassical analysis of the scattering coefficients, the Bohr–Sommerfeld condition for the location of the eigenvalues, and their corresponding norming constants. Our analysis is motivated by the potential applications to the focusing cubic NLS equation, in view of the well-known fact discovered by Zakharov and Shabat [Sov. Phys. JETP 34(1), 62 (1972)] that the spectral analysis of the Dirac operator is the basis of the solution of the NLS equation via inverse scattering theory. This paper complements and extends a previous work of Fujiié and Kamvissis [J. Math. Phys. 61(1), 011510 (2020)], which considered a more restricted problem for a strictly analytic potential.
Relative breakdown voltage and energy deposition in the liquid and gas phase of multiphase hydrocarbon plasmas
Authors: Wang Kunpeng , Bhuiyan Shariful Islam , Hil Baky Md Abdullah , Kraus Jamie , Campbell Christopher , Jemison Howard , Staack David
Published: March 2021

Pulsed electrical discharges in a gas–liquid mixture deposit energy into both phases. Here, we propose a model to simulate breakdown in multiphase based on experimental data. Furthermore, we estimated breakdown voltage in each phase and then estimated energy deposition in each phase. Discharge in pure liquid showed a highly stochastic nature, having a wide breakdown voltage distribution, while the mean value closely follows a one term power law as a function of gap spacing. When there is external gas injection to the gap, breakdown voltage increased significantly due to charge dissipation on bubble surface. This effect was simulated to predict breakdown voltage in liquid with gas injection at different rates. A multiphase system model was developed to simulate breakdown in the gas–liquid phase. The model is a superposition of power law and Meek criteria physical models for the liquid and gas phases, respectively, with empirically derived coefficients. Energy deposition into each phase was estimated by this model. The gap spacing is the primary factor determining breakdown voltage and energy distribution. In studied conditions, we were able to predict the breakdown voltage and estimate energy deposition into different phases. When the gap and flow rate vary between 2 and 10 mm and flow rate 0–1 LPM, 50%–93% of electrical energy is deposited into the liquid. This model allows for predicting breakdown voltage in a multiphase. Furthermore, it allows for control of the energy distribution among the phases in a multiphase pulsed discharge system.
Homological mirror symmetry of CPn and their products via Morse homotopy
Authors: Futaki Masahiro , Kajiura Hiroshige
Published: March 2021

We propose a way of understanding homological mirror symmetry when a complex manifold is a smooth compact toric manifold. So far, in many examples, the derived category Db(coh(X)) of coherent sheaves on a toric manifold X is compared with the Fukaya–Seidel category of the Milnor fiber of the corresponding Landau–Ginzburg potential. We instead consider the dual torus fibration π: M → B of the complement of the toric divisors in X, where B̄ is the dual polytope of the toric manifold X. A natural formulation of homological mirror symmetry in this setup is to define Fuk(M̄) a variant of the Fukaya category and show the equivalence Db(coh(X))≃Db(Fuk(M̄)). As an intermediate step, we construct the category Mo(P) of weighted Morse homotopy on P≔B̄ as a natural generalization of the weighted Fukaya–Oh category proposed by Kontsevich and Soibelman [Symplectic geometry and mirror symmetry (Seoul, 2000) (World Science Publishing, 2001), p. 203]. We then show that a full subcategory MoE(P) of Mo(P) generates Db(coh(X)) for the cases X is a complex projective space and their products.
The role of clearance mechanisms in the kinetics of pathological protein aggregation involved in neurodegenerative diseases
Authors: Thompson T. B. , Meisl G. , Knowles T. P. J. , Goriely A.
Published: March 2021

The deposition of pathological protein aggregates in the brain plays a central role in cognitive decline and structural damage associated with neurodegenerative diseases. In Alzheimer’s disease, the formation of amyloid-β plaques and neurofibrillary tangles of the tau protein is associated with the appearance of symptoms and pathology. Detailed models for the specific mechanisms of aggregate formation, such as nucleation and elongation, exist for aggregation in vitro where the total protein mass is conserved. However, in vivo, an additional class of mechanisms that clear pathological species is present and is believed to play an essential role in limiting the formation of aggregates and preventing or delaying the emergence of disease. A key unanswered question in the field of neuro-degeneration is how these clearance mechanisms can be modeled and how alterations in the processes of clearance or aggregation affect the stability of the system toward aggregation. Here, we generalize classical models of protein aggregation to take into account both production of monomers and the clearance of protein aggregates. We show that, depending on the specifics of the clearance process, a critical clearance value emerges above which accumulation of aggregates does not take place. Our results show that a sudden switch from a healthy to a disease state can be caused by small variations in the efficiency of the clearance process and provide a mathematical framework to explore the detailed effects of different mechanisms of clearance on the accumulation of aggregates.
Spin-orbit torques: Materials, physics, and devices
Authors: Han Xiufeng , Wang Xiao , Wan Caihua , Yu Guoqiang , Lv Xiaorong
Published: March 2021

Spintronics, that is, the utilization of electron spin to enrich the functionality of microelectronics, has led to the inception of numerous novel devices, particularly magnetic random-access memory (MRAM). Over the last decade, significant effort has been devoted to magnetization manipulation using spin-orbit torque (SOT), which shows great promise for ultrafast and energy-efficient MRAM. In this Perspective, we summarize the latest progress in the study of SOT and highlight some of the technical challenges facing the development of practical SOT devices. After introducing the basic concepts of SOT and its relevance for magnetization switching, we will focus on several methods to realize deterministic SOT switching in the absence of an external field, which is a requirement for practical SOT devices. Additionally, we summarize the materials used in SOT devices. The final section is devoted to the most important recent advances in the application of SOT devices, including SOT-MRAM, spin logic, spin Hall nano-oscillators, and neuromorphic devices.
Computational studies of the electronic structure of copper-doped ZnO quantum dots
Authors: Volnianska O.
Published: March 2021

Copper-doped ZnO quantum dots (QDs) have attracted substantial interest. The electronic structure and optical and magnetic properties of Cu3+(d8)-, Cu2+(d9)-, and Cu+(d10)-doped ZnO QDs with sizes up to 1.5 nm are investigated using the GGA+U approximation, with the +U corrections applied to d (Zn), p(O), and d(Cu) orbitals. Taking +Us parameters, as optimized in previous bulk calculations, we obtain the correct band structure of ZnO QDs. Both the description of electronic structure and thermodynamic charge state transitions of Cu in ZnO QDs agree with the results of bulk calculations due to the strong localization of Cu defect energy levels. Atomic displacements around Cu are induced by strong Jahn–Teller distortion and affect Kohn–Sham energies and thermodynamic transition levels. The average bond length of Cu–O and the defect structure are crucial factors influencing the electronic properties of Cu in ZnO QDs. The analysis of the optical properties of Cu in ZnO QDs is reported. The GGA+U results, compared with the available experimental data, support Dingle’s model [Phys. Rev. Lett. 23, 579 (1969)], in which the structured green luminescence observed in bulk and nanocrystals originates from the [(Cu+, hole) → Cu2+] transition. We also examine the magnetic interaction between the copper pair for two charge states: 0 and +2, and four positions relative to the center of QDs. Ferromagnetic interaction between ions is obtained for every investigated configuration. The magnitude of ferromagnetism increases for positive charge defects due to the strong hybridization of the d(Cu) and p(O) states.
Microscopic modeling of non-normal incidence vertical external cavity surface-emitting laser cavities
Authors: McLaren S. , Kilen I. , Moloney J. V.
Published: March 2021

The optimization of a V-cavity geometry to obtain intense ultrafast pulses for a modelocked vertical external-cavity surface-emitting laser is studied using an expanded form of the transverse Maxwell semiconductor Bloch equations. The influence of the incidence angle and relative cavity arm lengths is considered with respect to both the pump-probe computed instantaneous gain and group delay dispersion and the converged modelocked state. Changes in the angle are seen to lead to modest changes in dispersion but significant deformations of the modelocked pulse. Large changes in relative arm lengths are seen to lead to modest changes in the modelocked pulse with optimal pulses being observed with a 1:1 arm length ratio. The underlying microscopic dynamics are shown to drive these behaviors. This work provides a theoretical means to optimize experimental cavity geometry for desirable modelocking behaviors.
Sinking bubbles in a fluid under vertical vibration
Authors: Li Zhensheng , Zhou Yudian , Xu Liufang
Published: March 2021

The special nonlinear effect of sinking bubbles is observed when the container partially filled with a liquid is excited by vibration. This paper is concerned with this interesting phenomenon in an incompressible viscous fluid under vertical vibration. We construct the theoretical model from the view of vibration mechanics and fluid mechanics. According to theoretical analysis, we derive the accurate model of the bubble moving in the liquid and the added mass caused by it. After that, the control equation of the bubble is given by the force analysis and the differential equation of variable-mass systems. Besides, the critical depth of the sinking bubble is derived based on the method of direct separation of motions. We further explore and analyze the specific reasons why the bubbles sink. At the same time, the conditions where the variable mass has a significant influence on the motion of the object are given. The main factors affecting the sinking of bubbles, density, frequency, and amplitude are numerically simulated and analyzed with different conditions. To prevent or weaken the effect of sinking bubbles in the oscillating fluid, feasible approaches are proposed. Meanwhile, the theory is validated experimentally.
Development of a tunable multi-channel Doppler reflectometer on J-TEXT tokamak
Authors: Ren X. H. , Yang Z. J. , Shi Z. B. , Yang Z. C. , Zha X. Q. , Gao Y. , Zhang Z. C.
Published: March 2021

Doppler reflectometer is a powerful diagnostic tool to study the turbulence for tokamak plasmas. It can provide information on the density fluctuation, the poloidal rotation, the radial electric field, its shear, etc. A tunable multi-channel V-band (50–75 GHz) Doppler reflectometer system has been developed on the J-TEXT tokamak for the measurement under various toroidal magnetic fields. A universal serial bus controlled synthesizer is used as a source that can adjust the probing frequency remotely. This Doppler reflectometer can measure the plasma in 0.3 < ρ < 1 . Its radial resolution is <2 cm, and k⊥ is ∼ 4–12 cm−1. Based on the Doppler reflectometer, the perpendicular turbulence propagation velocity, the profile of the radial electric field, the geodesic acoustic mode, and some other phenomena have been observed on J-TEXT.
Characterizing variability and predictability for air pollutants with stochastic models
Authors: Meyer Philipp G. , Kantz Holger , Zhou Yu
Published: March 2021

We investigate the dynamics of particulate matter, nitrogen oxides, and ozone concentrations in Hong Kong. Using fluctuation functions as a measure for their variability, we develop several simple data models and test their predictive power. We discuss two relevant dynamical properties, namely, the scaling of fluctuations, which is associated with long memory, and the deviations from the Gaussian distribution. While the scaling of fluctuations can be shown to be an artifact of a relatively regular seasonal cycle, the process does not follow a normal distribution even when corrected for correlations and non-stationarity due to random (Poissonian) spikes. We compare predictability and other fitted model parameters between stations and pollutants.
Comparison between slow anisotropic LE4PD fluctuations and the principal component analysis modes of ubiquitin
Authors: Beyerle E. R. , Guenza M. G.
Published: March 2021

The biological function and folding mechanisms of proteins are often guided by large-scale slow motions, which involve crossing high energy barriers. In a simulation trajectory, these slow fluctuations are commonly identified using a principal component analysis (PCA). Despite the popularity of this method, a complete analysis of its predictions based on the physics of protein motion has been so far limited. This study formally connects the PCA to a Langevin model of protein dynamics and analyzes the contributions of energy barriers and hydrodynamic interactions to the slow PCA modes of motion. To do so, we introduce an anisotropic extension of the Langevin equation for protein dynamics, called the LE4PD-XYZ, which formally connects to the PCA “essential dynamics.” The LE4PD-XYZ is an accurate coarse-grained diffusive method to model protein motion, which describes anisotropic fluctuations in the alpha carbons of the protein. The LE4PD accounts for hydrodynamic effects and mode-dependent free-energy barriers. This study compares large-scale anisotropic fluctuations identified by the LE4PD-XYZ to the mode-dependent PCA predictions, starting from a microsecond-long alpha carbon molecular dynamics atomistic trajectory of the protein ubiquitin. We observe that the inclusion of free-energy barriers and hydrodynamic interactions has important effects on the identification and timescales of ubiquitin’s slow modes.
Compressible effects modeling for turbulent cavitating flow in a small venturi channel: An empirical turbulent eddy viscosity correction
Authors: Zhang Xin-Lei , Ge Ming-Ming , Zhang Guang-Jian , Coutier-Delgosha Olivier
Published: March 2021

The Reynolds-averaged Naviers-Stokes (RANS) method coupling with cavitation model is still a practical tool to predict cavitating flows, particularly in industrial applications, due to its computational efficiency. However, the compressibility effects induced by cavitation are not well considered in conventional RANS methods, which often causes the blockage of the reentrant jet and the total steadiness of the simulated cavity. To this end, modeling of compressibility effects becomes critical to predict the characteristics of unsteady cavitating flows. An empirical eddy viscosity correction [Reboudet al., “Two phase flow structure of cavitation: experiment and modeling of unsteady effects,” in 3rd International Symposium on Cavitation CAV1998, Grenoble, France (1998), Vol. 26.] was proposed to consider the compressibility effects induced by cavitation. Although this modification is able to capture unsteady behaviors of cavitating flows in various configurations, it is still not fully analyzed in terms of the turbulent quantities, e.g., Reynolds shear stress. In this work, we investigate the effects of this compressibility correction on the Reynolds shear stress, by comparing with x-ray experimental data in a small Venturi channel. It is shown that the Reboud correction reduces the eddy viscosity in the entire cavity region, which improves the prediction of Reynolds shear stress near the wall significantly. However, the correction depends only on the simulated mixture density, leading to poor predictions near the phase interface where the simulated mixture density has large discrepancies. Based on the results, we propose an empirical eddy viscosity limiter to confine the original correction beneath the cavitating layer and demonstrate the merits of the proposed correction by comparing with experimental measurements.
An implicit discontinuous Galerkin finite element discrete Boltzmann method for high Knudsen number flows
Authors: Ganeshan Karthik , Williams David M.
Published: March 2021

Simulations of the discrete Boltzmann Bhatnagar–Gross–Krook equation are an important tool for understanding fluid dynamics in non-continuum regimes. Here, we introduce a discontinuous Galerkin finite element method for spatial discretization of the discrete Boltzmann equation for isothermal flows with high Knudsen numbers [Kn∼O(1)]. In conjunction with a high-order Runge–Kutta time marching scheme, this method is capable of achieving high-order accuracy in both space and time, while maintaining a compact stencil. We validate the spatial order of accuracy of the scheme on a two-dimensional Couette flow with Kn=1 and the D2Q16 velocity discretization. We then apply the scheme to lid-driven micro-cavity flow at Kn=1,2,and 8, and we compare the ability of Gauss–Hermite (GH) and Newton–Cotes (NC) velocity sets to capture the high non-linearity of the flow-field. While the GH quadrature provides higher integration strength with fewer points, the NC quadrature has more uniformly distributed nodes with weights greater than machine-zero, helping to avoid the so-called ray-effect. Broadly speaking, we anticipate that the insights from this work will help facilitate the efficient implementation and application of high-order numerical methods for complex high Knudsen number flows.
Insights into low Reynolds flow past finite curved cylinders
Authors: Chiatto Matteo , Shang Jessica K. , de Luca Luigi , Grasso Francesco
Published: March 2021

Spectral proper orthogonal decomposition (SPOD) is applied to experimental digital visualizations to scrutinize the properties of the wake flow behind curved cylinders. This technique has been applied to the image data of Shang et al. [“Flow past finite cylinders of constant curvature,” J. Fluid Mech. 837, 896–915 (2018)] to emphasize the main features of the flow and to extract the most energetically and dynamically relevant space-time coherent structures. The study considers different Reynolds numbers and angles of curvature for two cylinder aspect ratios. It is first shown that the SPOD structures reproduce the base flow topology of the digital visualizations, confirming the presence of a single oblique shedding regime for a low aspect ratio and both normal and oblique regimes for a high aspect ratio. The appearance of the instabilities typical of straight cylinders, usually referred to as type-A and -B in literature, is identified as well. As principal results obtained for curved cylinders, increasing the Reynolds number the analysis of SPOD spectra has revealed two reductions in the oscillation frequency of the leading coherent structures, attributed to the occurrence of type-A instability when the wake is still laminar, and to the development of a one-sided vortex dislocation in turbulent regime. The study has also highlighted the gradual transfer of energy between flow structures during the transition from type-A to type-B instabilities, accompanied by high-frequency scales excitement. Some peculiar aspects of SPOD field reconstruction are outlined here, which are suggested by the physical characteristics of the flow.
Numerical investigation of transonic axial compressor rotor flows using an improved transition-sensitized turbulence model
Authors: Cui Bing , Wang Xiaole , Wang Rui , Xiao Zuoli
Published: March 2021

Internal flows of transonic compressor rotors National Aeronautics and Space Administration rotor 67/37 are numerically studied through the Reynolds-averaged Navier–Stokes simulations. In view of the drawbacks of Spalart–Allmaras (S–A) model, it is suggested in this paper that a helicity-modified S–A model is coupled with a transition prediction model to improve the reliability and accuracy of the original S–A model for simulation of the transonic compressor rotor flows. The performance of proposed model is evaluated in comparison with other S–A-type models. The results indicate that the helicity modification can suppress the strong vortex structures which are overpredicted by the original S–A model and the inclusion of a transition prediction model can help capture the transition phenomena on both sides of the rotor blade, which as absent when fully turbulent models are employed. The coupled model proves to provide more accurate simulation results for transonic compressor rotors than other models under consideration. In particular, it is argued that the constants in the helicity modification term should be altered as far as different rotors are concerned. The helicity and transition modified S–A model may have a great prospect for turbomachinery simulation due to its favorable prediction accuracy and low computational cost.
Multicolored absorbing nickel oxide films based on anodic electrochromism and structural coloration
Authors: Qu Hui-Ying , Wang Junxin , Montero José , Li Yao , Österlund Lars , Niklasson Gunnar A.
Published: March 2021

Inorganic electrochromic materials are promising for applications in color-based chromogenic technologies. Limited color control in these materials has, however, hitherto hampered their applications. Here, we show that multicolored nickel oxide (NiO) films can be obtained due to the combined effect of the intrinsic color of NiO and the structural color of the inverse opal structures by tailoring anodic oxide NiO films, exhibiting an absorption tail in the visible region into three-dimensional ordered macroporous inverse opal photonic bandgap structures. Various colors were achieved by the synergistic mechanism of structural and electrochromic coloration, thus realizing a wide spectrum of blue, green, yellow, orange, and brown colors depending on pore size, wall thickness, and viewing angle. Importantly, it is shown that the depth of color can be varied by applying an external potential. The electrochromic coloring of the inverse opal NiO films is found to be very different from the typical optical switching of non-structural NiO films. Thus, our work brings insights into the development of inorganic colored electrochromic materials.
Solitary-wave loads on a three-dimensional submerged horizontal plate: Numerical computations and comparison with experiments
Authors: Geng Tian , Liu Hua , Dias Frederic
Published: March 2021

A parallelized three-dimensional (3D) boundary element method is used to simulate the interaction between an incoming solitary wave and a 3D submerged horizontal plate under the assumption of potential flow. The numerical setup follows closely the setup of laboratory experiments recently performed at Shanghai Jiao Tong University. The numerical results are compared with the experimental results. An overall good agreement is found for the two-dimensional wave elevation, the horizontal force and the vertical force exerted on the plate, and the pitching moment. Even though there are some discrepancies, the comparison shows that a model solving the fully nonlinear potential flow equations with a free surface using a 3D boundary element method can satisfactorily capture the main features of the interaction between nonlinear waves and a submerged horizontal plate.
Using nondirect product Wigner D basis functions and the symmetry-adapted Lanczos algorithm to compute the ro-vibrational spectrum of CH4–H2O
Authors: Wang Xiao-Gang , Carrington Tucker
Published: March 2021

By doing calculations on the methane–water van der Waals complex, we demonstrate that highly converged energy levels and wavefunctions can be obtained using Wigner D basis functions and the Symmetry-Adapted Lanczos (SAL) method. The Wigner D basis is a nondirect product basis and, therefore, efficient when the kinetic energy operator has accessible singularities. The SAL method makes it possible to exploit symmetry to label energy levels and reduce the cost of the calculation, without explicitly using symmetry-adapted basis functions. Line strengths are computed, and new bands are identified. In particular, we find unusually strong transitions between states associated with the isomers of the global minimum and the secondary minimum.
Experimental and numerical modeling of a sloshing problem in a stepped based rectangular tank
Authors: Gándara Tomás , Barrio Ernesto Castillo Del , Cruchaga Marcela , Baiges Joan
Published: March 2021

In this study, the two-dimensional sloshing of water in a stepped based tank partially filled was analyzed using an arbitrary Lagrangian–Eulerian adaptive fixed-mesh method and including the Smagorinsky turbulence model. The numerical model is verified by contrasting the predictions made by the model with experimental results. The tank was subjected to controlled one-directional motion imposed using a shake table. The free surface evolution was followed using ultrasonic sensors, and a high-speed camera was used to record the experiments. The experimental and numerical analyses include a comparison of the wave height at different control points and snapshots of the free surface evolution for two imposed frequencies. Also, a detailed numerical study of the effects of the frequency of the imposed movement, the step height, and the fluid volume on the wave dynamics was performed. Moreover, the effect of fluid viscosity on the dynamics of the free surface was also studied. In brief, the numerical method proved to be accurate, experimental data were reported, and the effects on the numerical results of different physical and numerical aspects were exhaustively analyzed. The proposed results help to understand the sloshing of stepped geometries.
The ultrahigh pressure stability of silver: An experimental and theoretical study
Authors: O’Bannon E. F. , Lipp M. J. , Smith J. S. , Meng Y. , Söderlind P. , Young D. , Jenei Zs.
Published: March 2021

We measured the atomic volume of Ag in a toroidal diamond anvil cell to a maximum pressure of 416 GPa and calculated the atomic volume and elastic constants of Ag up to 750 and 460 GPa, respectively. Our density functional theory calculations at 0 K utilize an all-electron fully relativistic method and agree well with our volume measurements, particularly at pressures above ∼75 GPa. We corrected our experimental results for non-hydrostaticity using a line shift analysis, and the resulting Vinet equation of state (EOS) parameters are reported. We find that the uniaxial stress sustained by Ag increases linearly up to 4.5 GPa at a pressure of 416 GPa. Our experimental results indicate that the fcc structure of Ag remains stable to at least 416 GPa at room temperature. Our theoretical results show that C44 increases as pressure increases and reaches a maximum at ∼100 GPa above which it begins to decrease, a sign that the fcc structure of Ag is becoming unstable, and at V/V0 = 0.30, the bcc structure is lower in energy than fcc.
Mechanical spectral hole burning in glassy polymers—Investigation of polycarbonate, a material with weak β-relaxation
Authors: Chandra Hari Mangalara Satish , Paudel Shreejaya , McKenna Gregory B.
Published: March 2021

Mechanical spectral hole burning (MSHB) has been used to investigate the nonlinear dynamics in polymers, ranging from melts, solutions, block co-polymers, and glasses. MSHB was developed as an analog to the dielectric spectral hole burning method, which is not readily applicable in polymers due to weak dielectric response. While similar holes were observed in both mechanical and dielectric hole burning, the interpretations were different. In the latter case, it has been argued that the holes are related to dynamic heterogeneity as related to an increase in the local temperature of molecular sub-ensembles (spatial heterogeneity), while in the former case, the holes have been related to the type of dynamics (rubbery, Rouse, etc.). Recent work from our laboratories used MSHB to investigate glassy poly(methyl methacrylate) and showed evidence of hole burning and supported the hypothesis that the origin of holes was related to dynamic heterogeneity as evidenced by the holes being developed near the strong β-relaxation in PMMA. In this work, MSHB is used to study polycarbonate, which has a weak β-relaxation, and the results are compared with those observed in PMMA. We observe that the polycarbonate exhibits weak holes and the nature of the holes with a change in pump amplitude and frequency is different than observed in PMMA. These results support the hypothesis that the hole burning observed in amorphous polymers below the glass transition temperature is related to the strength of the β-transition, which, in turn, is related to molecular level heterogeneity in the material dynamics.
Corrigendum to: ACCESS-S1: The new Bureau of Meteorology multi-week to seasonal prediction system
Authors: Hudson Debra , Alves Oscar , Hendon Harry H. , Lim Eun-Pa , Liu Guoqiang , Luo Jing-Jia , MacLachlan Craig , Marshall Andrew G. , Shi Li , Wang Guomin , Wedd Robin , Young Griffith , Zhao Mei , Zhou Xiaobing
Published: March 2021

ACCESS-S1 will be the next version of the Australian Bureau of Meteorology's seasonal prediction system, due to become operational in early 2018. The multiweek and seasonal performance of ACCESS-S1 has been evaluated based on a 23-year hindcast set and compared to the current operational system, POAMA. The system has considerable enhancements compared to POAMA, including higher vertical and horizontal resolution of the component models and state-ofthe-art physics parameterisation schemes. ACCESS-S1 is based on the UK Met Office GloSea5-GC2 seasonal prediction system, but has enhancements to the ensemble generation strategy to make it appropriate for multi-week forecasting, and a larger ensemble size. ACCESS-S1 has markedly reduced biases in the mean state of the climate, both globally and over Australia, compared to POAMA. ACCESS-S1 also better predicts the early stages of the development of the El Niño Southern Oscillation (through the predictability barrier) and the Indian Ocean Dipole, as well as multi-week variations of the Southern Annular Mode and the Madden-Julian Oscillation — all important drivers of Australian climate variability. There is an overall improvement in the skill of the forecasts of rainfall, maximum temperature (Tmax) and minimum temperature (Tmin) over Australia on multi-week timescales compared to POAMA. On seasonal timescales the differences between the two systems are generally less marked. ACCESS-S1 has improved seasonal forecasts over Australia for the austral spring season compared to POAMA, with particularly good forecast reliability for rainfall and Tmax. However, forecasts of seasonal mean Tmax are noticeably less skilful over eastern Australia for forecasts of late autumn and winter compared to POAMA. The study has identified scope for improvement of ACCESS-S in the future, particularly 1) reducing rainfall errors in the Indian Ocean and Maritime Continent regions, and 2) initialising the land surface with realistic soil moisture rather than climatology. The latter impacts negatively on the skill of the temperature forecasts over eastern Australia and is being addressed in the next version of the system, ACCESS-S2.
Artificial intelligence velocimetry and microaneurysm-on-a-chip for three-dimensional analysis of blood flow in physiology and disease
Authors: Cai Shengze , Li He , Zheng Fuyin , Kong Fang , Dao Ming , Karniadakis George Em , Suresh Subra
Published: March 2021

Significance

Microfluidics is an important in vitro platform to gain insights into mechanics of blood flow and mechanisms of pathophysiology of human diseases. Extraction of 3D fields in microfluidics with dense cell suspensions remains a formidable challenge. We present artificial-intelligence velocimetry (AIV) as a general platform to determine 3D flow fields and a microaneurysm-on-a-chip to simulate blood flow in microaneurysms in patients with diabetic retinopathy. AIV is built on physics-informed neural networks that integrate seamlessly 2D images from microfluidic experiments or in vivo observations with physical laws to estimate full 3D velocity and stress fields. AIV could be integrated into imaging technologies to automatically infer key hemodynamic metrics from in vivo and in vitro biomedical images.
Alcohol Trajectories and Subsequent Risk for Opioid Misuse in a Cohort of Urban Adolescents
Authors: Thrul Johannes , Reboussin Beth A. , Rabinowitz Jill A. , Maher Brion S. , Ialongo Nicholas S.
Published: March 2021

Background

The opioid epidemic is a public health emergency in the US. Alcohol is the most widely used addictive substance among all age groups; however, the contribution of different alcohol use trajectories throughout adolescence and young adulthood to the development of opioid misuse in young adulthood among urban minority youth has not been investigated.

Methods

Data are from a study of 580 youth (85% African American, 67% low SES) residing in Baltimore City followed from ages 6–26. Alcohol trajectories were identified between ages 14 and 26 using group-based trajectory modeling. Opioid misuse was defined as using opioid painkillers without a prescription or using heroin between ages 19 and 26. Opioid misuse outcomes were also investigated separately. Logistic regression examined associations of alcohol trajectories with opioid misuse in young adulthood adjusting for socio-demographics, early use of tobacco and cannabis, neighborhood, and peer factors.

Results

Six alcohol use trajectories were identified: Young adult increasing (21.4%), adult increasing (19.1%), abstaining (19.1%), experimenting (15.3%), adolescent increasing (14.8%), and adolescent limited (10.2%). In models fully adjusted for covariates, relative to the abstaining trajectory, the adolescent increasing trajectory was associated with an elevated risk of opioid misuse (aOR = 3.3, 95%CI = 1.4, 7.8) and prescription opioid misuse (aOR = 3.9, 95%CI = 1.4, 10.8) in young adulthood.

Conclusions

Escalating alcohol use in adolescence and young adulthood is associated with an elevated risk of opioid misuse in young adulthood in a cohort of predominantly African American and socio-economically disadvantaged young people. Tailored interventions should target high levels of alcohol use during these developmental periods to reduce risk for opioid misuse among disadvantaged youth.
Plk4 triggers autonomous de novo centriole biogenesis and maturation
Authors: Nabais Catarina , Pessoa Delphine , de-Carvalho Jorge , van Zanten Thomas , Duarte Paulo , Mayor Satyajit , Carneiro Jorge , Telley Ivo A. , Bettencourt-Dias Mónica
Published: March 2021

Centrioles form centrosomes and cilia. In most proliferating cells, centrioles assemble through canonical duplication, which is spatially, temporally, and numerically regulated by the cell cycle and the presence of mature centrioles. However, in certain cell types, centrioles assemble de novo, yet by poorly understood mechanisms. Herein, we established a controlled system to investigate de novo centriole biogenesis, using Drosophila melanogaster egg explants overexpressing Polo-like kinase 4 (Plk4), a trigger for centriole biogenesis. We show that at a high Plk4 concentration, centrioles form de novo, mature, and duplicate, independently of cell cycle progression and of the presence of other centrioles. Plk4 concentration determines the temporal onset of centriole assembly. Moreover, our results suggest that distinct biochemical kinetics regulate de novo and canonical biogenesis. Finally, we investigated which other factors modulate de novo centriole assembly and found that proteins of the pericentriolar material (PCM), and in particular γ-tubulin, promote biogenesis, likely by locally concentrating critical components.
The dark side of the gut: Virome–host interactions in intestinal homeostasis and disease
Authors: Li Yuhao , Handley Scott A. , Baldridge Megan T.
Published: March 2021

The diverse enteric viral communities that infect microbes and the animal host collectively constitute the gut virome. Although recent advances in sequencing and analysis of metaviromes have revealed the complexity of the virome and facilitated discovery of new viruses, our understanding of the enteric virome is still incomplete. Recent studies have uncovered how virome–host interactions can contribute to beneficial or detrimental outcomes for the host. Understanding the complex interactions between enteric viruses and the intestinal immune system is a prerequisite for elucidating their role in intestinal diseases. In this review, we provide an overview of the enteric virome composition and summarize recent findings about how enteric viruses are sensed by and, in turn, modulate host immune responses during homeostasis and disease.