bluuebunny/crossref_metadata_2025 huggingface dataset:
Total Knee Arthroplasty following Knee Arthroscopy in Patients over 50
Authors: Buck J. Stewart , Odum Susan M. , Salava Jonathan K. , Macknet David M. , Fehring Thomas K. , Springer Bryan D.
Published: December 2021

The purpose of this study was to evaluate the conversion rate of knee arthroscopy to ipsilateral total knee arthroplasty (TKA) within 2 years in patients aged 50 or older at the time of arthroscopy. The administrative database from a large, physician-owned orthopaedic practice (>100 surgeons) was queried to identify patients over the age of 50 who had undergone arthroscopic knee surgery between January 1, 2006 and January 2, 2015. The subset of patients who converted to TKA within 2 years after knee arthroscopy was identified and matched by age and sex to a control population that did not convert to TKA. Rates of conversion to TKA were calculated. Prearthroscopic digital radiographs were reviewed and Kellgren–Lawrence (KL) grades were compared among case and control populations. Univariable analyses and multivariable regression analysis were performed. Eight hundred seven of 16,061 (5.02%) patients aged 50 or older were converted to TKA within 2 years following ipsilateral knee arthroscopy. In univariable analysis, the rate of conversion to TKA in patients aged between 50 and 54 was 2.94%, compared with 4.44% in patients aged between 55 and 64, and 8.32% in patients 65 or older (p < 0.0001). Female sex was associated with a higher rate of conversion to TKA in univariable analysis (5.93 vs. 4.02% in males, p < 0.0001). KL grades were higher among patients who converted to TKA compared with those who did not (p < 0.0001). In a multivariable regression model controlling for age, sex, and KL grade, only increased KL grade was associated with increased odds of conversion to TKA. In the appropriately selected older patient, the risk of conversion to TKA within 2 years of knee arthroscopy is low (∼5%). Patients with KL grade 2 or higher at the time of arthroscopy should be counseled on the increased odds of early conversion to TKA.
A Single-Center Retrospective Evaluation of Unplanned Pediatric Critical Care Upgrades
Authors: Yoder Lisa R. , Dillon Bridget , DeMartini Theodore K. M. , Zhou Shouhao , Thomas Neal J. , Krawiec Conrad
Published: December 2021

Background Inappropriate triage of critically ill pediatric patients can lead to poor outcomes and suboptimal resource utilization. This study aimed to determine and describe the demographic characteristics, diagnostic categories, and timing of unplanned upgrades to the pediatric intensive care unit (PICU) that required short (< 24 hours of care) and extended (≥ 24 hours of care) stays. In this article, we hypothesized that we will identify demographic characteristics, diagnostic categories, and frequent upgrade timing periods in both of these groups that may justify more optimal triage strategies.

Methods This was a single-institution retrospective study of unplanned PICU upgrades between 2012 and 2018. The cohort was divided into two groups (short and extended PICU stay). We reviewed the electronic health record and evaluated for: demographics, mortality scores, upgrade timing (7a-3p, 3p-11p, 11p-7a), lead-in time (time spent on clinical service before upgrade), patient origin, and diagnostic category.

Results Four hundred and ninety-eight patients' unplanned PICU upgrades were included. One hundred and nine patients (21.9%) required a short and 389 (78.1%) required an extended PICU stay. Lead-in time (mean, standard deviation) was significantly lower in the short group (0.65 ± 0.66 vs. 0.91 ± 0.82) (p = 0.0006). A higher proportion of short group patients (59, 46.1%) were upgraded during the 3p-11p shift (p = 0.0077).

Conclusion We found that approximately one-fifth of PICU upgrades required less than 24 hours of critical care services, were more likely to be transferred between 3p-11p, and had lower lead-in times. In institutions where ill pediatric patients can be admitted to either a PICU or a monitored step-down unit, this study highlights quality improvement opportunities, particularly in recognizing which pediatric patients truly need critical care.
Flash-over propagation simulation upon spacecrafts solar panels
Authors: Monnin L. , Hess S. L. G. , Roussel J.-F. , Sarrailh P. , Payan D.
Published: December 2021

A plasma expansion model is developed. It is used to compute flash-over propagation upon spacecraft solar panels. In order to take into consideration the plasma extinction, a cathode spot model is developed and coupled to a plasma expansion model. A minimum on the sheath potential has been found, and it explains the end of plasma emission by the cathode and, therefore, the end of the plasma expansion. Numerical results are compared with experimental measurements and are in good agreement with them. The model can be later used to prevent arcing on spacecrafts solar panels.
SARS-CoV-2 emerging complexity and global dynamics
Authors: Bertacchini Francesca , Pantano Pietro S. , Bilotta Eleonora
Published: December 2021

The novel SARS-CoV-2 virus, prone to variation when interacting with spatially extended ecosystems and within hosts, can be considered a complex dynamic system. Therefore, it behaves creating several space–time manifestations of its dynamics. However, these physical manifestations in nature have not yet been fully disclosed or understood. Here we show 4D and 2D space–time patterns of the rate of infected individuals on a global scale, giving quantitative measures of transitions between different dynamical behaviors. By slicing the spatiotemporal patterns, we found manifestations of the virus behavior, such as cluster formation and bifurcation. Furthermore, by analyzing morphogenesis processes by entropy, we have been able to detect the virus phase transitions, typical of adaptive biological systems. Our results for the first time describe the virus patterning behavior processes all over the world, giving them quantitative measures. We know that the outcomes of this work are still partial and more advanced analyses of the virus behavior in nature are necessary. However, we think that the set of methods implemented can provide significant advantages to better analyze the viral behavior in the approach of system biology, thus expanding knowledge and improving pandemic problem solving.
Probing lattice dynamics in ST 12 phase germanium nanowires by Raman spectroscopy
Authors: Raha Sreyan , Srivastava Divya , Biswas Subhajit , Garcia-Gil Adrià , Karttunen Antti J. , Holmes Justin D. , Singha Achintya
Published: December 2021

Germanium (Ge) plays a crucial role in setting up important functionalities for silicon-compatible photonics. Diamond cubic germanium is an extensively studied semiconductor, although its other exotic forms, like BC8, ST8, ST12 phases, may possess distinct electronic properties. We have fabricated stable ST12-Ge nanowires via a self-seeded bottom-up three phase growth in a confined supercritical toluene environment. Here, we report on the direct evidence of the presence of the ST12 phase by a combination of Raman spectroscopy and first-principles calculations using density functional theory (DFT). It is important to remark that the DFT calculation predicts all the Raman active optical phonon modes of the P 4321 structure, and it is in very good agreement with the experimental results. The phonon dynamics as a function of temperature is investigated through Raman measurements at temperatures varying from 80 to 300 K. First-order temperature coefficients for all the observed Raman modes are estimated from the linear temperature dependence of the phonon shifts. A complete set of isobaric Grüneisen parameters is reported for all Raman modes of ST12-Ge nanowire, and the values are lower compared to the same for Si, dc-Ge bulk, and Ge nanowire. These results have important implications for understanding thermal properties of ST12-Ge nanowire.
Pressure induced structural phase transitions of technologically significant mercurous chloride at room temperature: An account from first-principle DFT and Born–Oppenheimer molecular dynamics studies
Authors: Ghosh Swarup , Chowdhury Joydeep
Published: December 2021

This paper reports for the first time an in-depth study based on first-principle calculations to unveil the underlying physics that governs the pressure induced structural phase transitions of Hg2Cl2 compound at room temperature. The phonon dispersion relations and phonon density of states have been critically explored for the tetragonal and orthorhombic phases of the compound to unveil the phonon modes associated with the phase transitions. The nature of the phase transition whether it is “displacive” or of “order–disorder” type has also been explored. We believe that the present study based on density functional theory and Born–Oppenheimer molecular dynamics calculations will help understand the underlying physics behind the above referred phase transitions and the anisotropic behavior of the compound, which in turn bears technologically significant relevance for its applications in optoelectronic devices, acousto-optic tunable filters, and in fiber-optic communication systems.
Aerothermodynamic characteristics of hypersonic curved compression ramp flows with bistable states
Authors: Tang Ming-Zhi , Wang Gang , Xie Zhu-Xuan , Zhou Wen-Feng , Hu Yan-Chao , Yang Yan-Guang
Published: December 2021

The aerothermodynamic characteristics (including wall friction Cf, pressure pw, and heat flux St) in curved compression ramp (CCR) flows with bistable states are studied numerically and theoretically. Direct numerical simulations of bistable states of separation/attachment induced by variation of the turning angle ϕ, as well as the influence of inflow Mach number and wall temperature on dual-solution interval, are carried out. Distributions of wall friction, pressure and heat flux are analyzed. Further, the emergence of the first and second minima of Cf in the separation bubble is interpreted, which are dominated by the adverse pressure gradient induced by separation and reattachment shock, respectively. The present results and analysis indicate that the reversed-flow singularity of F. T. Smith (Proc. R. Soc. London. A: Math. Phys. Sci. 420, 21–52 (1988)] is less likely to occur in CCR flows. The prediction of pressure peak ppk of separation states confirms the model based on the minimum viscous dissipation theorem [Hu et al., Phys. Fluids 32(10), 101702 (2020)]. While the pressure overshoot pos can be analyzed by shock-polars with pressure match of compression and expansion process. The correlation between heat flux peak and pressure peak of both separation and attachment states is also discussed in terms of the classical power relation.
Laser ignited combustion of mesoporous nitrocellulose/graphene oxide composite aerogel with strong photo-thermal sensitivity and high flame propagation rate
Authors: Shi X. R. , Yang L. F. , Tian L. , Shen J. P. , Li Z. Q. , Pei C. H.
Published: December 2021

In this paper, mesoporous nitrocellulose (NC)/graphene oxide (GO) composite aerogel is manufactured by a sol-gel method followed by supercritical carbon dioxide drying. The effects of GO on the microstructure, decomposition, and thermal conductivity are studied. The laser absorption, laser ignition property, and combustion performance of NC aerogel and NC/aerogel are also investigated. The results indicate that NC/GO aerogel is established by the combination of NC nano-fibers and GO sheets, and the aerogels are mesoporous with average pore size at 40 nm. Moreover, the thermal stability of aerogels is decreased by the nano-structure of NC, and the laser absorption is significantly increased by the nano-porous structure and the adoption of GO. In addition, the laser ignition and combustion efficiency are also greatly improved by the nano-porous aerogel structure and the incorporation of evenly uniformly dispersed GO sheets with high photothermal conversion efficiency and thermal conductivity. Laser ignition times reduced by 73.7% and 99.6% are obtained, and flame propagation rates up to 4.7 and 12.3 times are observed for NC aerogel and NC/5 wt. % GO aerogel, respectively.
The role of noise in PIC and Vlasov simulations of the Buneman instability
Authors: Tavassoli Arash , Chapurin Oleksandr , Jimenez Marilyn , Papahn Zadeh Mina , Zintel Trevor , Sengupta Meghraj , Couëdel Lénaïc , Spiteri Raymond J. , Shoucri Magdi , Smolyakov Andrei
Published: December 2021

The effects of noise in particle-in-cell (PIC) and Vlasov simulations of the Buneman instability in unmagnetized plasmas are studied. It is found that, in the regime of low drift velocity, the linear stage of the instability in PIC simulations differs significantly from the theoretical predictions, whereas in the Vlasov simulations it does not. A series of highly resolved PIC simulations with increasingly large numbers of macroparticles per cell is performed using a number of different PIC codes. All the simulations predict highly similar growth rates that are several times larger than those calculated from the linear theory. As a result, we find that the true convergence of the PIC simulations in the linear regime is elusive to achieve in practice and can easily be misidentified. The discrepancy between the theoretical and the observed growth rates is attributed to the initial noise inherently present in PIC simulations, but not in Vlasov simulations, that causes particle trapping even though the fraction of trapped particles is low. We show analytically that even weak distortions of the electron velocity distribution function (such as flattening due to particle trapping) result in significant modifications of the growth rates. It is also found that the common quiet-start method for PIC simulations leads to more accurate growth rates but only if the maximum growth rate mode is perturbed initially. We demonstrate that the quiet-start method does not completely remedy the noise problem because the simulations generally exhibit inconsistencies with the linear theory.
Direct orbital selection within the domain-based local pair natural orbital coupled-cluster method
Authors: Bensberg Moritz , Neugebauer Johannes
Published: December 2021

Domain-based local pair natural orbital coupled cluster (DLPNO-CC) has become increasingly popular to calculate relative energies (e.g., reaction energies and reaction barriers). It can be applied within a multi-level DLPNO-CC-in-DLPNO-CC ansatz to reduce the computational cost and focus the available computational resources on a specific subset of the occupied orbitals. We demonstrate how this multi-level DLPNO-CC ansatz can be combined with our direct orbital selection (DOS) approach [M. Bensberg and J. Neugebauer, J. Chem. Phys. 150, 214106 (2019)] to automatically select orbital sets for any multi-level calculation. We find that the parameters for the DOS procedure can be chosen conservatively such that they are transferable between reactions. The resulting automatic multi-level DLPNO-CC method requires no user input and is extremely robust and accurate. The computational cost is easily reduced by a factor of 3 without sacrificing accuracy. We demonstrate the accuracy of the method for a total of 61 reactions containing up to 174 atoms and use it to predict the relative stability of conformers of a Ru-based catalyst.
Machine learning prediction of 2D perovskite photovoltaics and interaction with energetic ion implantation
Authors: Feng Hong-Jian , Ma Ping
Published: December 2021

Atomic-level prediction combined with machine learning (ML) and density functional theory (DFT) is carried out to accelerate the fast discovery of potential photovoltaics from the 2D perovskites. Based on the ML prediction, stability test, optical absorption, and the theoretical power conversion efficiency (PCE) evaluation, two promising photovoltaics, i.e., Sr2VON3 and Ba2VON3, are discovered with PCE as high as 30.35% and 26.03%, respectively. Cu, Ag, C, N, H, and He ion implantation are adopted to improve the photovoltaic performance of the high-efficiency and best stable perovskite Sr2VON3. The time-dependent DFT electronic stopping calculations for energetic ion implanted Sr2VON3 indicate that the excited electrons from the valence band contribute to the electron–phonon coupling, the evolution and formation of the defects, and the photovoltaic performance. This work opens the way to the high-accuracy fast discovery of the high-efficiency and environmentally stable 2D perovskites solar cells and the further engineering improvement in photovoltaic performance by ion implantation.
An efficient three-dimensional non-hydrostatic model for undular bores in open channels
Authors: Ai Congfang , Ma Yuxiang , Ding Weiye , Xie Zhihua , Dong Guohai
Published: December 2021

A three-dimensional (3D) non-hydrostatic model is presented to simulate open-channel free-surface flows involving undular bores. The 3D unsteady mass conservation and momentum equations are solved using an explicit projection method in a nonstandard staggered grid. The grid system is built from a two-dimensional horizontal structured grid by adding horizontal layers. The model is validated using four typical benchmark problems, including undular bore development, an undular bore generated by a sudden discharge, and two test cases involving undular hydraulic jumps. The proposed model results are compared with experimental data and results from other models. Overall, the agreement between the proposed model results and experimental data is generally good, demonstrating the capability of the model to resolve undular bores. In addition, the non-hydrostatic pressure field under the undular free surface is revealed, and the efficiency of the proposed model is presented. It is shown that the proposed model behaves better than a volume of fluid model in terms of efficiency, because the proposed model can use fewer computational grid cells to resolve undular bores in open channels.
Density dependent local structures in InTe phase-change materials
Authors: Sun Suyang , Zhang Bo , Wang Xudong , Zhang Wei
Published: December 2021

Chalcogenide phase-change materials based random access memory (PCRAM) is one of the leading candidates for the development of non-volatile memory and neuro-inspired computing technologies. Recent work shows indium to be an important alloying element for PCRAM, while a thorough understanding of the parent compound InTe, in particular, its amorphous phase, is still lacking. In this work, we carry out ab initio simulations and chemical bonding analyses on amorphous and various crystalline polymorphs of InTe. We reveal that the local geometries are highly density dependent in amorphous structures, forming In-centered tetrahedral motifs under ambient conditions but defective octahedral motifs under pressure, which stems from the bonding characters of its crystalline polymorphs. In addition, our ab initio molecular dynamics simulations predict rapid crystallization capability of InTe under pressure. Finally, we make a suggestion for better use of indium and propose an “active” device design to utilize both thermal and mechanical effects for phase-change applications.
Band-edge emission enhancement in sputtered ZnO thin films with ultraviolet surface lattice resonances
Authors: Simon Thomas , Kostcheev Sergei , Rumyantseva Anna , Béal Jérémie , Gérard Davy , Martin Jérôme
Published: December 2021

Metallic nanostructures acting as optical nanoantennas can significantly enhance the photoluminescence (PL) of nearby emitters. Albeit luminescence enhancement factors of several orders of magnitude have been reported for quantum dots or molecules, in the case of bulk emitters, the magnitude of the plasmonic enhancement is strongly hindered by the weak spatial overlap between the active medium and the electromagnetic modes of the nanoantenna. Here, we propose a solid-state ultraviolet emitter based on a thin film of zinc oxide (ZnO) coupled with an array of aluminum (Al) nanoparticles. The Al nanorod array is designed to sustain surface lattice resonances (SLRs) in the near ultraviolet, which are hybrid modes exhibiting a Fano-like lineshape with narrowed linewidth relatively to the non-hybridized plasmonic modes. By changing both the period of the array and the dimensions of the nanorods, the generated SLR is tuned either to the near band-edge (NBE) emission of ZnO or to the excitation wavelength. We experimentally demonstrate that NBE emission can be increased up to a factor of 3 compared to bare ZnO. The underlying PL enhancement mechanisms are experimentally investigated and compared with numerical simulations. We also demonstrate that SLRs are more efficient for the ZnO luminescence enhancement compared to localized surface plasmon resonances.
Comparison and validation of various turbulence models for U-bend flow with a magnetic resonance velocimetry experiment
Authors: Han Yong , Zhou Ling , Bai Ling , Shi Weidong , Agarwal Ramesh
Published: December 2021

Turbulence modeling plays an important role in the accurate prediction of turbulent fluid motion in computational fluid dynamics simulations using the Reynolds-averaged Navier–Stokes equations. A new one-equation Wray–Agarwal (WA) turbulence model has recently been developed by the present authors to improve the prediction of nonequilibrium turbulent flows with large separation and curvature. In this paper, the WA turbulence model is employed to simulate the internal turbulent flow characteristics in a U-bend, and the computed results are compared with experimental data. The results obtained from four other commonly used turbulence models, viz., the one-equation Spalart–Allmaras, two-equation standard k-ε, renormalization group k-ε, and shear stress transport k-ω models, are also compared. Detailed experimental data are obtained using magnetic resonance velocimetry. The results computed with the five different turbulence models show that the WA turbulence model gives the highest accuracy in predicting the complex three-dimensional turbulent characteristics of flow with large curvature in a U-bend.
On the effect of a penetrating recirculation region on the bifurcations of the flow past a permeable sphere
Authors: Ciuti M. , Zampogna G. A. , Gallaire F. , Camarri S. , Ledda P. G.
Published: December 2021

We study the flow past a permeable sphere modeled using homogenization theory. The flow through the porous medium is described by the Darcy law, in which the permeability quantifies the resistance for the fluid to pass through the microstructure. A slip condition on the tangential velocity at the interface between the fluid and porous region is employed to account for the viscous effects in the proximity of the interface. The steady and axisymmetric flow is first characterized under the assumption of a homogenous and isotropic porous medium. In a certain range of permeability, the recirculation region penetrates inside the sphere, resulting in a strong modification of the linear stability properties of the flow and in a decrease in the critical Reynolds numbers for the flow instability. However, for very large permeabilities, a critical permeability value is identified, beyond which the steady and axisymmetric flow remains always linearly stable. The hypothesis of a homogenous porous medium is then relaxed, and the effect of polynomial distributions of permeability inside the body is studied. Interestingly, some macroscopic flow properties do not significantly vary with the permeability distributions, provided that their average is maintained constant. The analysis is concluded by outlining a simplified procedure to retrieve the full-scale structure corresponding to a considered distribution of permeability.
Targeted polyelectrolyte complex micelles treat vascular complications in vivo
Authors: Zhou Zhengjie , Yeh Chih-Fan , Mellas Michael , Oh Myung-Jin , Zhu Jiayu , Li Jin , Huang Ru-Ting , Harrison Devin L. , Shentu Tzu-Pin , Wu David , Lueckheide Michael , Carver Lauryn , Chung Eun Ji , Leon Lorraine , Yang Kai-Chien , Tirrell Matthew V. , Fang Yun
Published: December 2021

Significance

Vascular disease is a leading cause of human morbidity and mortality and current therapies mainly target systemic risk factors but not the diseased vasculature per se. We have devised a targeted nanomedicine approach engineering self-assembled polyelectrolyte complex micelles that target inflamed vascular endothelium and simultaneously encapsulate therapeutic nucleic acids. We showed that this targeted nanomedicine strategy effectively delivers therapeutic nucleotides to inflamed endothelium in vivo. The causal role of increased endothelial miR-92a in driving atherosclerosis is established by a new transgenic mouse line. We demonstrated that targeted polyelectrolyte complex micelles significantly enhance the anti–miR-92a therapy treating vascular complications in vivo.
Hobit confers tissue-dependent programs to type 1 innate lymphoid cells
Authors: Yomogida Kentaro , Bigley Tarin M. , Trsan Tihana , Gilfillan Susan , Cella Marina , Yokoyama Wayne M. , Egawa Takeshi , Colonna Marco
Published: December 2021

Significance

Innate responses against viral infection and other intracellular pathogens rely on immune cells that are capable of lysing infected cells and producing interferon-gamma (IFNγ). These cells encompass two major cell lineages: natural killer (NK) cells and type 1 innate lymphoid cells (ILC1s). While NK cells have been extensively characterized, identification of ILC1s and their distinction from NK cells are less clear. The transcription factor Hobit encoded byZfp683has been put forth as a prototypic feature of ILC1s. By analyzingZfp683reporter, fate-map, and -deficient mice, we demonstrate that the impact of Hobit on ILC1 identity and transcriptional and functional programs is tissue- and context-dependent. Thus, ILC1s adapt to local stimuli and tailor their responses to the tissue niche.
Distributed least squares prediction for functional linear regression*
Authors: Tong Hongzhi
Published: December 2021

To cope with the challenges of memory bottleneck and algorithmic scalability when massive data sets are involved, we propose a distributed least squares procedure in the framework of functional linear model and reproducing kernel Hilbert space. This approach divides the big data set into multiple subsets, applies regularized least squares regression on each of them, and then averages the individual outputs as a final prediction. We establish the non-asymptotic prediction error bounds for the proposed learning strategy under some regularity conditions. When the target function only has weak regularity, we also introduce some unlabelled data to construct a semi-supervised approach to enlarge the number of the partitioned subsets. Results in present paper provide a theoretical guarantee that the distributed algorithm can achieve the optimal rate of convergence while allowing the whole data set to be partitioned into a large number of subsets for parallel processing.
Study on the high birefringence and low confinement loss terahertz fiber based on the combination of double negative curvature and nested claddings
Authors: Yuan Ziwei , Wang Yi , Yan Dexian , Cao Mingxuan , Meng Miao , Li Xiangjun , Sun Shuai
Published: December 2021

A novel double negative curvature nested fiber structure is designed by adding extra circular cladding tubes to enhance the birefringence and reduce the confinement loss. The fiber structure is composed of eight circular cladding tubes and two semi-elliptical nested tubes. The transmission performances of terahertz fiber, including birefringence, confinement loss, dispersion and effective mode field area, are studied by changing the parameters of cladding tubes. In the frequency range of 1.75–2.6 THz, the broad bandwidth of 850 GHz with high birefringence (above 10−4) can be achieved. The confinement loss of y-polarization mode with the frequency of 2.575 THz can be as low as 0.00231 dB cm−1. The waveguide dispersion coefficient is between ±0.188 ps (THz cm)−1 in the frequency range of 2.0–2.475 THz. The maximum effective mode field area of x-polarization mode is 2.618 × 10−6 m2 at 2.6 THz.
Solution-processed whispering-gallery-mode microsphere lasers based on colloidal CsPbBr3 perovskite nanocrystals
Authors: Xie Minghong , Gong Wenxiao , Kong Lei , Liu Yang , Mi Yang , Guo Heng , Luo Sheng-Nian
Published: December 2021

Perovskite nanocrystals (NCs) have emerged as attractive gain materials for solution-processed microlasers. Despite the recent surge of reports in this field, it is still challenging to develop low-cost perovskite NC-based microlasers with high performance. Herein, we demonstrate low-threshold, spectrally tunable lasing from ensembles of CsPbBr3 NCs deposited on silica microspheres. Multiple whispering-gallery-mode lasing is achieved from individual NC/microspheres with a low threshold of ∼3.1 μJ cm−2 and cavity quality factor of ∼1193. Through time-resolved photoluminescence measurements, electron–hole plasma recombination is elucidated as the lasing mechanism. By tuning the microsphere diameter, the desirable single-mode lasing is successfully achieved. Remarkably, the CsPbBr3 NCs display durable room-temperature lasing under ∼107 shots of pulsed laser excitation, substantially exceeding the stability of conventional colloidal NCs. These CsPbBr3 NC-based microlasers can be potentially useful in photonic applications.
Projection-to-image transform frame: a lightweight block reconstruction network for computed tomography
Authors: Ma Genwei , Zhao Xing , Zhu Yining , Zhang Huitao
Published: December 2021

Several reconstruction networks have been invented to solve the problem of learning-based computed tomography (CT) reconstruction. However, the application of neural networks to tomographic reconstruction remains challenging due to unacceptable memory space requirements. In this study, we present a novel lightweight block reconstruction network (LBRN), which transforms the reconstruction operator into a deep neural network by unrolling the filter back-projection (FBP) method. Specifically, the proposed network contains two main modules, which respectively correspond to the filter and back-projection of the FBP method. The first module of the LBRN decouples the relationship of the Radon transform between the reconstructed image and the projection data. Therefore, the following module, block back-projection, can use the block reconstruction strategy. Because each image block is only connected with part-filtered projection data, the network structure is greatly simplified and the parameters of the whole network are dramatically reduced. Moreover, this approach is trained end-to-end, working directly from raw projection data, and does not depend on any initial images. Five reconstruction experiments are conducted to evaluate the performance of the proposed LBRN: full angle, low-dose CT, region of interest, metal artifact reduction and a real data experiment. The results of the experiments show that the LBRN can be effectively introduced into the reconstruction process and has outstanding advantages in terms of different reconstruction problems.
Linking topological features of the Hofstadter model to optical diffraction figures
Authors: Di Colandrea Francesco , D’Errico Alessio , Maffei Maria , Price Hannah M , Lewenstein Maciej , Marrucci Lorenzo , Cardano Filippo , Dauphin Alexandre , Massignan Pietro
Published: December 2021

In two, three and even four spatial dimensions, the transverse responses experienced by a charged particle on a lattice in a uniform magnetic field are fully controlled by topological invariants called Chern numbers, which characterize the energy bands of the underlying Hofstadter Hamiltonian. These remarkable features, solely arising from the magnetic translational symmetry, are captured by Diophantine equations which relate the fraction of occupied states, the magnetic flux and the Chern numbers of the system bands. Here we investigate the close analogy between the topological properties of Hofstadter Hamiltonians and the diffraction figures resulting from optical gratings. In particular, we show that there is a one-to-one relation between the above mentioned Diophantine equation and the Bragg condition determining the far-field positions of the optical diffraction peaks. As an interesting consequence of this mapping, we discuss how the robustness of diffraction figures to structural disorder in the grating is a direct analogue of the robustness of transverse conductance in the quantum Hall effect.
Quantum properties near the instability boundary in optomechanical system
Authors: Fang Han-Hao , Deng Zhi-Jiao , Zhu Zhigang , Zhou Yan-Li
Published: December 2021

The properties of the system near the instability boundary are very sensitive to external disturbances, which is important for amplifying some physical effects or improving the sensing accuracy. In this paper, the quantum properties near the instability boundary in a simple optomechanical system have been studied by numerical simulation. Calculations show that the transitional region connecting the Gaussian states and the ring states when crossing the boundary is sometimes different from the region centered on the boundary line, but it is more essential. The change of the mechanical Wigner function in the transitional region directly reflects its bifurcation behavior in classical dynamics. Besides, quantum properties, such as mechanical second-order coherence function and optomechanical entanglement, can be used to judge the corresponding bifurcation types and estimate the parameter width and position of the transitional region. The non-Gaussian transitional states exhibit strong entanglement robustness, and the transitional region as a boundary ribbon can be expected to replace the original classical instability boundary line in future applications.
A radiation–temperature coupling model of the optical fiber attenuation spectrum in the Ge/P co-doped fiber
Authors: Li Yong , Zhang Haoshi , Wang Xiaowei , Jin Jing
Published: December 2021

A radiation–temperature coupling model of optical fiber attenuation spectrum has been developed. The spectrum in Ge/P co-doped fiber ranging from 800 nm–1600 nm at different temperatures and doses was measured and decomposed according to the configurational coordinate model based on which the power-law model was employed to predict the intensity of the color center absorption band at different doses. And the fiber loss in space was predicted by the model. This work will benefit the application of fibers in a complicated radiation environment.
Optimized quantum singular value thresholding algorithm based on a hybrid quantum computer
Authors: Ge Yangyang , Wang Zhimin , Zheng Wen , Zhang Yu , Yu Xiangmin , Kang Renjie , Xin Wei , Lan Dong , Zhao Jie , Tan Xinsheng , Li Shaoxiong , Yu Yang
Published: December 2021

Quantum singular value thresholding (QSVT) algorithm, as a core module of many mathematical models, seeks the singular values of a sparse and low rank matrix exceeding a threshold and their associated singular vectors. The existing all-qubit QSVT algorithm demands lots of ancillary qubits, remaining a huge challenge for realization on near-term intermediate-scale quantum computers. In this paper, we propose a hybrid QSVT (HQSVT) algorithm utilizing both discrete variables (DVs) and continuous variables (CVs). In our algorithm, raw data vectors are encoded into a qubit system and the following data processing is fulfilled by hybrid quantum operations. Our algorithm requires O[log(MN)] qubits with O(1) qumodes and totally performs O(1) operations, which significantly reduces the space and runtime consumption.
Phase-matching quantum key distribution with light source monitoring
Authors: Li Wen-Ting , Wang Le , Li Wei , Zhao Sheng-Mei
Published: December 2021

The transmission loss of photons during quantum key distribution (QKD) process leads to the linear key rate bound for practical QKD systems without quantum repeaters. Phase matching quantum key distribution (PM-QKD) protocol, an novel QKD protocol, can overcome the constraint with a measurement-device-independent structure, while it still requires the light source to be ideal. This assumption is not guaranteed in practice, leading to practical secure issues. In this paper, we propose a modified PM-QKD protocol with a light source monitoring, named PM-QKD-LSM protocol, which can guarantee the security of the system under the non-ideal source condition. The results show that our proposed protocol performs almost the same as the ideal PM-QKD protocol even considering the imperfect factors in practical systems. PM-QKD-LSM protocol has a better performance with source fluctuation, and it is robust in symmetric or asymmetric cases.
Practical security analysis of continuous-variable quantum key distribution with an unbalanced heterodyne detector
Authors: Kong Lingzhi , Liu Weiqi , Jing Fan , He Chen
Published: December 2021

When developing a practical continuous-variable quantum key distribution (CVQKD), the detector is necessary at the receiver’s side. We investigate the practical security of the CVQKD system with an unbalanced heterodyne detector. The results show that unbalanced heterodyne detector introduces extra excess noise into the system and decreases the lower bound of the secret key rate without awareness of the legitimate communicators, which leaves loopholes for Eve to attack the system. In addition, we find that the secret key rate decreases more severely with the increase in the degree of imbalance and the excess noise induced by the imbalance is proportional to the intensity of the local oscillator (LO) under the same degree of imbalance. Finally, a countermeasure is proposed to resist these kinds of effects.
Inward diffusion driven by low frequency fluctuations in self-organizing magnetospheric plasma
Authors: Kenmochi N. , Yokota Y. , Nishiura M. , Saitoh H. , Sato N. , Nakamura K. , Mori T. , Ueda K. , Yoshida Z.
Published: December 2021

The new findings for dynamic process of inward diffusion in the magnetospheric plasma are reported on the Ring Trap 1 (RT-1) experiment: (i) the evolution of local density profile in the self-organized process has been analyzed by the newly developed tomographic reconstruction applying a deep learning method; (ii) the impact of neutral-gas injection excites low-frequency fluctuations, which continues until the peaked density profile recovers. The fluctuations have magnetic components (suggesting the high-beta effect) which have two different frequencies and propagation directions. The phase velocities are of the order of magnetization drifts, and both the velocities and the intensities increase in proportion to the electron density. The self-regulating mechanism of density profile works most apparently in the naturally made confinement system, magnetosphere, which teaches the basic physics of long-lived structures underlying every stationary confinement scheme.
Study of Heterogeneous Plasma Created by Magneto-Plasma Compressor and Erosive Capillary Discharge
Authors: Klimov A I , Belov N K , Brovkin V G , Pashchina A S
Published: December 2021

Magneto-plasma compressor with a pulsed capillary erosive plasma generator (MPC-EP) has been designed, manufactured and tested at the first time. This MPC-EP was used to study the physical properties of a high-energy long-lived heterogeneous plasma (ELHP) created by pulsed capillary erosive plasma generator (EP) at the wide range of pressure and temperature. The results of measurements of the parameters of the shock wave created by the MPC-EP, as well as optical spectroscopy and soft X-ray spectroscopy are presented.
Oblique shock wave reflection at plasma array presence
Authors: Elliott S , Firsov A A , Leonov S B
Published: December 2021

This work discusses the effect of a filamentary plasma array on shock wave (SW) reflection pattern and on a shock-induced separation zone geometry. It includes experimental and computational components both. The experimentation was performed in the supersonic blowdown test rig SBR-50 at the University of Notre Dame at flow Mach number M=2, stagnation pressure P0=1.7-2.7 bar and stagnation temperature T0=300 K. Oblique shock wave generator composed of a symmetric solid wedge was installed on the top wall of test section while the filamentary plasma generator was arranged on the opposite wall. Thus, the main SW originating from the wedge impinged the plasma area. As a result of the SW-plasma interaction, the flowfield was significantly modified, including a shift of the main SW upstream and redistribution of wall pressure over the test section. The computational analysis allowed a 3D reconstruction of the SW interaction with the plasma array. The physics of SW-plasma array interaction are also discussed.
Influence of mechanical action on the development of electrodynamic phenomena in ionized gas
Authors: Basargin I V , Baryshnikov A S , Saharov V A , Popov P A , Gerasimenko A B
Published: December 2021

A special feature of this work is the study of the effect of mechanical mode disturbances on the discharge and plasma flow. It is found that the mechanical impact of a shock wave in a dense gas in an electric field of high intensity almost to the ignition voltage causes an electrical “breakdown” as current peaks. The ultrasonic effect on the flow of the reacting plasma of the air as shown by the analytical study of the thin layer of the plasma flow changes the type of flow.
Flow separation control on a smooth ledge using an arc discharge in a magnetic field
Authors: Kazanskii P N , Moralev I A , Kotvitskii A Ya
Published: December 2021

This paper presents results of experimental study for surface MHD arc actuator as vortex generator in boundary layer of smooth ledge. The study was held at flow velocities 20 to 50 m/s. The pulsed arc discharge was organized in external magnetic field. The amplitude of current was 80 A, while pulse duration was 80 μs. The flow velocity was measured by PIV method. It was founded that the location of the arc breakdown is critically impotent. The arc must be struck just above the separation point. The operation of the actuator in a pulse-periodic mode leads to a shift in the middle position of the flow separation point at frequencies up to 700 Hz and higher. A three-dimensional analysis of the separation region structure behind the MHD actuator shows that the main effect on the flow occurs in the interelectrode gap.
Influence of the Condition of the Exposed Electrode Edge in the SDBD on the Discharge Operation Mode in Argon
Authors: Selivonin I , Moralev I
Published: December 2021

The paper is devoted to the phenomenological study of the operating modes of a surface barrier discharge in argon in the case of treated by the discharge and new aluminum and copper electrodes. It is shown that without preliminary treating of the edges of the electrodes in the case of copper and aluminum electrodes, the discharge has a different spatial structure determined by the self-organization of the DBD. After erosion cleaning of the electrode edges, the identical operating modes are established. Such effects confirm the former assumption that the key factor determining the mode of the discharge operation for various electrode materials is the surface charge built on the oxides deposited on the edge. The different dynamics of oxides in the case of copper and aluminum electrodes is determined by the resistance of the oxides of these metals to sputtering, which is indirectly confirmed by the estimation of the binding energy for these materials.
Ionization wave propagation in a long capillary tube in the presence of a low-current glow discharge in low-pressure helium
Authors: Akishev Yu S , Karalnik V B , Petryakov A V
Published: December 2021

The experimental results on the study of the positive ionization wave propagating along a long capillary tube are presented. The ionization wave was initiated by eigther high-voltage pulse of positive polarity applied over a long capillary tube with helium or high-voltage pulse applied over the same tube but in presence of low-current glow discharge. The spreading of this wave is accompanied by the surface charge deposition. The usage of the fine-sectioned outer electrode allows one to find out the features of the positive ionization wave in both cases (with or without low-current discharge).
Mismatch of frequencies of ac voltage and streamers propagation in cold atmospheric plasma jet for typical regimes of cancer cell treatment
Authors: Schweigert I , Alexandrov A , Zakrevsky D , Milakhina E , Patrakova E , Troitskaya O , Birykov M , Koval O
Published: December 2021

Cold atmospheric plasma (CAP) jet generated by the plasma source at 2-6 kV ac voltages with frequencies of 10-50 kHz demonstrate the different modes of operation. Depending on the voltage frequency and amplitude, some streamers in the plasma jet are short and decay before they approach the treated surface. In this case, the effect on the viability of cancer cells when exposed to CAP jet strongly depends on the mode of operation of the discharge or, in other words, on how many times the streamers hit the bio-target during the treatment. The effect on different modes on cancer cells A549 viability is reported.
Numerical Modeling of Pulse-Periodic Nanosecond Discharges
Authors: Bityurin V A , Bocharov A N , Dobrovolskaya A S , Kuznetsova T N , Popov N A , Filimonova E A
Published: December 2021

The first results of the numerical simulation of the Pulse-Periodic Nanosecond discharge in pin-to-pin configuration in 2Dt approximation of the full self-consist system of Navier-Stocks equation for real thermo-chemically non-equilibrium gases, drift-diffusion approximation of the low temperature plasma evolution in external electric and magnetic field and, alternative – arc (spark) discharge model of high-density energy input discharge. The intuitive criteria of the alternative discharge models re-switch are proposed and tested. The pin-to-pin the pulse-periodic nanosecond 5-MHz discharge has been considered for 1 microsecond interval. It was found that rather strong longitudinal non-uniformities of main physical parameters are created at the first corona stage of the interelectrode conducting channel. These nonuniformities reveal long-lived features that have define strong effect on the discharge performance
Thermal efficiency of metal foams on pool boiling
Authors: Manetti L L , Moita A S , Cardoso E M
Published: December 2021

This paper presents an experimental work on pool boiling using HFE-7100 at saturated conditions, under atmospheric pressure, and copper and nickel foams as the heating surface with four different thicknesses varying between 0.5 mm and 3 mm, followed by an analysis of the effect of foam fin-efficiency based on Ghosh model. All foams showed a better heat transfer coefficient (HTC) than the plain surface; however, as the heat flux increased, the HTC from the thicker nickel foams decreased due to the bubble vapor flow inside the foam. On the other hand, the thinner nickel foam showed better HTC at high heat fluxes with a maximum enhancement of 120%. The foam efficiency presented a similar tendency with the HTC, i.e., as the thickness decreases the efficiency increases; however, as compared with copper foams with a similar area but different porous diameter, the copper foams are 40% more efficient than the nickel ones due to the foam material, which has a thermal conductivity 4.5 times higher.
Interfacial waviness during condensation heat transfer
Authors: Berto A , Lavieille P , Azzolin M , Bortolin S , Miscevic M , Del Col D
Published: December 2021

Heat transfer coefficients and liquid film thickness have been measured during convective condensation inside a 3.4 mm internal diameter channel. Condensation tests have been run with refrigerant R245fa during vertical downflow at mass velocity equal to 50 kg m-2 s-1 and 100 kg m-2 s-1. The test section is composed of two heat exchangers for the measurement of the heat transfer coefficient connected by means of a glass tube designed for the visualization of the two-phase flow patterns and for the measurement of the liquid film thickness. The liquid film thickness is determined by coupling a shadowgraph technique and chromatic confocal measurements. The measured values of heat transfer coefficient and liquid film thickness are reported and analysed together to investigate the effect of waves on the condensation heat transfer mechanisms.