bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclic tangential flow filtration system for isolation of extracellular vesicles
Authors: Kim Kimin , Park Jungjae , Jung Jik-Han , Lee Ruri , Park Ji-Ho , Yuk Jong Min , Hwang Hyundoo , Yeon Ju Hun
Published: February 2021

Size-based filtration techniques have been developed for high-throughput isolation of extracellular vesicles (EVs). Conventional direct filtration systems have limitations in that large particles generally not only block the pores of the membrane but also damage the particles because of the high fluid pressure. Here, we propose a cyclic tangential flow filtration (TFF) system that includes two membranes with pore sizes of 200 and 30 nm, connected to a peristaltic pump that feeds the stream flowing to the membrane for continuous circulation. The cyclic TFF system is better able to isolate the specific 30–200 nm size range in one step through dual cyclic filtration compared with direct filtration (DF) and single cyclic TFF (scTFF). We further introduced a buffer-exchange process to the dcTFF system after filtration to remove contaminants for more efficient purification. As a result of comparative evaluation of dcTFF and ExoQuick, EVs isolated by dcTFF had more abundant exosome markers and active EVs. The cyclic TFF system not only has great potential to separate EVs with high selectivity and separation efficiency in small volumes of samples but can also be used in clinical applications, including medical diagnostic procedures.
Optimal design and validation of atom trapping and atomic storage time for active hydrogen maser
Authors: Liu Shanmin , Wang Likun , Wu Xiaoguang , Guo Ming , Chen Xin , Zhu Hongbin , Wang Pengcheng , Wang Bin , Wang Wei
Published: February 2021

From microwave atomic clocks to light clocks, atomic or ionic clocks often rely on atom or ion trapping or manipulation technology. Trapping hydrogen (H) atoms in atomic storage bulbs (ASBs) is one of the key technologies of H atomic clocks. H atoms remain in an ASB for some time during which they undergo several relaxation processes (including spin-exchange collision relaxation, atom–wall collision relaxation, and magnetic-field inhomogeneity relaxation) and interact with the electromagnetic field within the resonant cavity in the TE011 mode, giving rise to continuous atomic transitions and self-oscillations. In this study, an optimal atomic storage time Tb for a H maser was determined by optimizing various collisional relaxation times of the atomic ensemble and reducing the width of the atomic resonance line through the continuously adjustable length and radius of the opening of an ASB at various atomic beam intensities ξ (which is the number of atoms in the atomic beam), namely, 3 × 1012 atoms/s, 4 × 1012 atoms/s, and 5 × 1012 atoms/s, while keeping the structural properties and physical conditions of the H maser unchanged. For ξ = 5 × 1012 atoms/s and Tb ≈ 0.8 s, a frequency stability of 0.95 × 10−15 could be achieved at 1000 s.
A K–L model with improved realizability for turbulent mixing
Authors: Xiao Mengjuan , Zhang Yousheng , Tian Baolin
Published: February 2021

Turbulent mixing, induced by Rayleigh–Taylor (RT), Richtmyer–Meshkov (RM), and Kelvin–Helmholtz (KH) instabilities, broadly occurs in both practical astrophysics and inertial confined fusion problems. The Reynolds-averaged Navier–Stokes models remain the most viable approach for the solution of these practical flows. The commonly used mixing models based on the standard eddy viscosity formulation are shown to be capable of accurately predicting the global mixing zone width. However, we find that this approach will become non-realizable for local flow characteristics in the case of a large mean strain rate, including yielding the negative normal stress and the unphysically large turbulence kinetic energy (TKE) in the presence of shocks. This can affect the numerical robustness in calculating turbulent statistics and give rise to highly inaccurate predictions for complex mixings. To overcome this problem, a realizable K–L mixing model is developed, extended from the standard K–L model given by our recent works. A new eddy viscosity formulation is used and modified from the work by Shih et al. to reproduce the growth rate of the KH mixing. This new model yields similar results as the standard model for canonical RT, RM, and KH mixings. However, for complex mixing problems, the present model gives a significant improvement in physically capturing the turbulence characteristics, e.g., predicting the non-negative normal stress for RT mixing with the initial tilted interface and the appropriate TKE when shock interacts with the mixing zone for spherical implosion.
Oscillatory Couette flow of rarefied binary gas mixtures
Authors: Zhang Yue , Wang Peng , Guo Zhaoli
Published: February 2021

The oscillatory Couette flow of binary gas mixtures is numerically investigated on the basis of the McCormack model. The dependence of the velocity and shear stress amplitudes and the penetration depth on the gas rarefaction and the oscillation parameters is studied numerically. Two typical mixtures of noble gases, i.e., a neon–argon (Ne–Ar) mixture with a molecular mass ratio less than 2 and a helium–xeon (He–Xe) mixture with a molecular mass ratio of about 32, are considered to explore the influences of the molecular mass ratio and molar concentration. It is found that the Ne–Ar mixture exhibits similar behavior with a single gas, while significant deviations can be observed between a single gas and the He–Xe mixture. Particularly when the gases are in the transitional and near-continuum regimes and the oscillation frequency is high, the amplitudes of velocity and shear stress for the He–Xe mixture vary non-monotonically between the plates as the molar concentration of the light species He exceeds 50% due to the oscillation superposition of the two species. These findings are helpful to design the structure of micro-electromechanical devices.
W layer thickness dependence of the spin–orbit effective fields in NiFe/W bilayers
Authors: Li Shufa , Zhu Tao , Chen Chunlei , Wang Hui
Published: February 2021

Spin–orbit torques (SOTs) generated by in-plane current injection in a ferromagnetic metal (FM)/heavy metal (HM) bilayer offers a new route to electrically manipulate magnetization. Here, we report on two sizable spin–orbit field contributions from the spin Hall effect and Rashba effect in NiFe/W bilayers by using the planar Hall effect. Both spin–orbit fields decrease with increasing W layer thickness. Importantly, the spin–orbit field contributing from the spin Hall effect decreases faster than the one from the Rashba effect as the thickness of W layer increases, leading to the sign change of the field-like torque at thicker W. Our results illustrate the co-contributions of the Rashba effect and the spin Hall effect to the field-like SOT in NiFe/W bilayer giving more insight into the effect of the field-like SOT in a FM/HM bilayer.
Electronic charge transfer during metal/SiO2 contact: Insight from density functional theory
Authors: Antony Andrew C. , Thelen Dean , Zhelev Nikolay , Adib Kaveh , Manley Robert G.
Published: February 2021

Contact charging of hydroxylated SiO2/metal interfaces is studied using density functional theory calculations. Atomic scale models are generated for hydroxylated α-cristobalite interfaced with three different fcc metals: Al, Pt, and Au. Regions of electron accumulation and depletion are highest in magnitude near the SiO2/Pt and SiO2/Au interfaces and lower at the SiO2/Al interface. One key finding of this work is that the presence of a metal surface near the hydroxylated SiO2 induces electronic states at the SiO2 surface within the apparent insulating bandgap. The magnitude of these states is highest for Pt and Au contacts and lowest for Al, indicating that the amount of charge transfer at the interface trends with the density of electronic defect states. Such electronic defect states reside near the fermi level of the system and it is proposed that these states from surface oxygen atoms are at least partly responsible for the electronic charge transfer mechanism between a metal and an insulator.
Electronic circular dichroism spectra using the algebraic diagrammatic construction schemes of the polarization propagator up to third order
Authors: Scott Mikael , Rehn Dirk R. , Coriani Sonia , Norman Patrick , Dreuw Andreas
Published: February 2021

Expressions for the calculation of rotatory strengths using the algebraic diagrammatic construction (ADC) scheme of the polarization propagator in both length and velocity gauges have been implemented. This enables the simulation of electronic circular dichroism (ECD) spectra at the ADC level up to third order of perturbation theory. The ADC(n) methods produce rotatory strengths of comparable accuracy to those obtained with coupled cluster methods of corresponding approximation levels, as evaluated for methyloxirane, methylthiirane, dimethyloxirane, dimethylthiirane, hydrogen peroxide, and dihydrogen disulfide. ECD spectra of (1R)-camphor, (1R)-norcamphor, and (1R)-fenchone computed at the third order ADC(3) level of theory are shown to agree very favorably with experimental gas phase spectra, demonstrating the usefulness of ADC for the calculation of chiro-optical properties of organic molecules. ADC(2) in combination with the polarizable continuum model is shown to successfully reproduce the ECD spectrum of the L-epinephrine enantiomer in water, further demonstrating the applicability of this approach.
Long-time stable colloidal Zn–Ag–In–S quantum dots with tunable midgap-involved emission
Authors: Sabzevari Zahra , Sahraei Reza , Jawhar Nawzad Nadhim , Yazici Ahmet Faruk , Mutlugun Evren , Soheyli Ehsan
Published: February 2021

Quaternary Zn–Ag–In–S (ZAIS) quantum dots (QDs) with efficient, tunable, and stable photoluminescence (PL) emission were prepared via a simple, effective, and low-cost reflux method. The structural analysis revealed the dominance of the quantum confinement effect. The calculated PL emission quantum yield was enhanced from 8.2% to 28.7% with experimental parameters indicating their marked influence on the PL emission properties of the final product. Particularly, it was found that by varying the precursors' feeding ratio, tunable emission from green to red was achieved. A set of direct and indirect pieces of evidence such as the broad-band emission spectrum (FWHM > 100 nm), large Stokes shift more than 120 nm, and predominantly a biexponentially long-lived decay profile with an average lifetime of about 366 ns were observed, showing the contribution of midgap localized energy levels in the recombination process. These data were obtained independently on the experimental condition used, which confirmed that this is mostly an intrinsic electronic property of quaternary In-based QDs. Finally, to ensure the stability of QDs in terms of colloidal and optical emission, their emission ability was evaluated after 26 months of storage. Colloidal QDs were still luminescent with strong yellowish-orange color with emission efficiency of ∼20.3% after 26 months. The combination of synthesis simplicity, compositional non-toxicity, PL emission superiority (strong, tunable, stable, and long lifetime emission), and colloidal stabilities confirms that the present ZAIS QDs are promising candidates for a wide range of applications in biomedicine, anticounterfeiting, and optoelectronics.
Solute induced jittery motion of self-propelled droplets
Authors: Dwivedi Prateek , Si Bishwa Ranjan , Pillai Dipin , Mangal Rahul
Published: February 2021

The intriguing role of the presence of solutes in the activity of a self-propelling droplet is investigated. A system of self-propelling micrometer-sized 4-Cyano-4′-pentylbiphenyl (5CB) droplets in an aqueous solution of tetradecyltrimethylammonium bromide (TTAB) as the surfactant is considered. It is shown that the addition of glycerol causes the active 5CB droplet to exhibit a transition from smooth to jittery motion. The motion is found to be independent of the droplet size and the nematic state of 5CB. Analogous experiments with Polyacrylamide (PAAm), Polyvinylpyrrolidone (PVP), and Polyvinyl Alcohol (PVA), as solutes, confirm that such a transition cannot merely be explained solely based on the viscosity or Peclet number of the system. We propose that the specific nature of physicochemical interactions between the solute and the droplet interface is at the root of this transition. The experiments show that the timescales associated with the influx and redistribution of surfactants at the interface are altered in the presence of solutes. Glycerol and PVP significantly enhance the rate of solubilization of the 5CB droplets resulting in a quicker re-distribution of the adsorbed TTAB molecules on the interface, causing the droplet to momentarily stop and then restart in an independent direction. On the other hand, low solubilization rates in the presence of PAAm and PVA lead to smooth trajectories. Our hypothesis is supported by the time evolution of droplet size and interfacial velocity measurements in the presence and absence of solute. Overall, our results provide fundamental insights into the complex interactions emerging due to the presence of solutes.
Magnetic excitation and dissipation of multilayer two-dimensional resonators
Authors: Ben-Shimon Yahav , Ya'akobovitz Assaf
Published: February 2021

Two-dimensional (2D) resonators are attractive for a wide range of applications, such as filters, sensors, and energy harvesters. In most cases, these resonators are excited electrostatically, which dictates adjacent electrode geometry that limits the design flexibility. In the present work, we demonstrate the magnetic excitation of 2D resonators. Contrary to electrostatic excitation, the magnetic field can be applied from a distance, and as a result, this approach offers greater flexibility in the design of these devices. We characterized the magnetic excitation of devices of varying thicknesses (from 17 nm to 170 nm) and found that their resonance frequencies are in the mega-hertz range. In addition, we thoroughly studied dissipation mechanisms in our devices and found that magnetic excitation enhances energy loss due to resistive heating and magnetic losses. In addition, we found that the interactions between the resonators and air molecules are a dominant mechanism of dissipation, although it also promotes the cooling of the resonators through the transfer of heat to the air. Therefore, this work sets the groundwork for the development of magnetic 2D resonators, which will be integrated into flexible actuators, resonant sensors, etc.
Exchange interactions in topological/antiferromagnetic heterostructures
Authors: Chen RongRong , Dou Shuang , Stepanyuk V. S. , Xue DeSheng , Jia ChengLong , Tao Kun
Published: February 2021

Performing ab initio calculations, we investigate exchange interactions between the topological insulator and the antiferromagnetic films in detail. In this work, choosing the Bi2Te3/CrSb heterostructure as a typical model system, we prove that the magnitude of the magnetic anisotropy and the spin direction of heterostructures can be manipulated by tuning the interfacial exchange coupling with the stacking modes between the Bi2Te3 and the CrSb films. The exchange gap in various heterostructures ranges from 21.1 meV in the type-C stacking to 36.2 meV in the type-B stacking. We demonstrate that the magnetic anisotropy energy of the system originates from the hybridization between different atomic orbitals at the interface. Moreover, large induced magnetic moments were found at the interface.
Surface buckling with deterministic peaks/valleys regulated by bio-inspired micro-structures periodically distributed on elastic bilayers
Authors: Xie Juhua , Li Ao , Wang Xian , Zhu Minhao , Huang Yin , Feng Xue
Published: February 2021

Surface buckling for film/substrate systems has an extensive application in flexible electronics, microfluidics, and adhesives. The location of the peaks and valleys, however, is still unpredictable due to its strong dependency upon external perturbations and the inevitable edge effects. Inspired by the sharp spines on ribbed stems of an echinopsis cactus, periodic surface micro-structures, including pyramidal intaglios and pyramidal reliefs, are adopted to tune the buckling experimentally and numerically. Although the instability patterns in our research are similar to those regulated by the stiff film pattern geometry, the wavelengths are nearly uniform in the whole area without obvious edge effects in the position of the surface micro-structures. The number of the wrinkle-like patterns between two micro-structures is equal to n when the width of the normalized center to center distance d¯ is in a range of about n−0.4 to n+0.6. More importantly, the pyramidal intaglios and pyramidal reliefs have well-regulated but opposite locations in different instability patterns, which means that the peaks and valleys are predictable upon the surface buckling. The deterministic peaks/valleys of the surface instability regulated by micro-structures provides a worthy guidance on the topography design, such as the distribution of the functional components in stretchable electronics based on structural designs.
High-performance single crystal CH3NH3PbI3 perovskite x-ray detector
Authors: Geng Xiangshun , Zhang Hainan , Ren Jun , He Peiyi , Zhang Peigen , Feng Qixin , Pan Kai , Dun Guanhua , Wang Fangwei , Zheng Xinran , Tian He , Xie Dan , Yang Yi , Ren Tian-Ling
Published: February 2021

Organic–inorganic hybrid perovskites have exhibited unprecedented advantages for x-ray photon detection due to their exotic properties. Their high-crystalline quality has a great impact for high-detection sensitivity under a low electric field, especially related to the synthesis method. In this work, we analyze the capability of CH3NH3PbI3 (MAPbI3) perovskites as an x-ray detection material and propose to control the temperature gradient (TG) during the synthesis of MAPbI3 single crystal perovskites for device fabrication. Our results show that the decreasing TG can effectively reduce the trap density and improve the crystal quality, which could lead to a boosted sensitivity of 1471.7 μC/Gyair/cm2 under a low electric field of 3.3 V/mm. In addition, a higher detection sensitivity can be achieved by increasing the electric field. Our work presents a strategy to construct high-performance direct x-ray detectors.
Infrared spectroscopy of RG–Co+(H2O) complexes (RG = Ar, Ne, He): The role of rare gas “tag” atoms
Authors: Marks Joshua H. , Miliordos Evangelos , Duncan Michael A.
Published: February 2021

RGn–Co+(H2O) cation complexes (RG = Ar, Ne, He) are generated in a supersonic expansion by pulsed laser vaporization. Complexes are mass-selected using a time-of-flight spectrometer and studied with infrared laser photodissociation spectroscopy, measuring the respective mass channels corresponding to the elimination of the rare gas “tag” atom. Spectral patterns and theory indicate that the structures of the ions with a single rare gas atom have this bound to the cobalt cation opposite the water moiety in a near-C2v arrangement. The O–H stretch vibrations of the complex are shifted compared to those of water because of the metal cation charge-transfer interaction; these frequencies also vary systematically with the rare gas atom attached. The efficiencies of photodissociation also vary with the rare gas atoms because of their widely different binding energies to the cobalt cation. The spectrum of the argon complex could only be measured when at least three argon atoms were attached. In the case of the helium complex, the low binding energy allows the spectra to be measured for the low-frequency H–O–H scissors bending mode and for the O–D stretches of the deuterated analog. The partially resolved rotational structure for the antisymmetric O–H and O–D stretches reveals the temperature of these complexes (6 K) and establishes the electronic ground state. The helium complex has the same 3B1 ground state as the tag-free complex studied previously by Metz and co-workers [“Dissociation energy and electronic and vibrational spectroscopy of Co+(H2O) and its isotopomers,” J. Phys. Chem. A 117, 1254 (2013)], but the A rotational constant is contaminated by vibrational averaging from the bending motion of the helium.
Study of canonical spin glass behavior in Co doped LaMnO3
Authors: Bhat Farooq H. , Khan Ghazala A. , Kataria Gitansh , Kumar Ravi , Sahdev Deshdeep , Malik Manzoor A.
Published: February 2021

Temperature-dependent magnetic and a.c. susceptibility measurements were done on single phase polycrystalline LaMn1-yCoyO3 (y = 0.1, 0.4) samples. The field cooled and zero field cooled magnetic measurements performed indicate the presence of spin glass state which is established using a.c. susceptibility measurements. The a.c. susceptibility data analyzed using Arrhenius and Vogel–Fulcher (VF) law reveal the presence of canonical spin glass.
Molecular reprogramming and phenotype switching in
Staphylococcus aureus
lead to high antibiotic persistence and affect therapy success
Authors: Huemer Markus , Mairpady Shambat Srikanth , Bergada-Pijuan Judith , Söderholm Sandra , Boumasmoud Mathilde , Vulin Clément , Gómez-Mejia Alejandro , Antelo Varela Minia , Tripathi Vishwachi , Götschi Sandra , Marques Maggio Ewerton , Hasse Barbara , Brugger Silvio D. , Bumann Dirk , Schuepbach Reto A. , Zinkernagel Annelies S.
Published: February 2021

Significance

Persisters represent a bacterial subpopulation that survive high antibiotic concentrations without being resistant. Their role in clinics in persistent infections and their molecular and functional landscape is not fully established.
Staphylococcus aureus
is a pathobiont that causes severe invasive infections often difficult to treat. Here, we assessed
S. aureus
recovered directly from persistent infections and show that host-mediated stress and antibiotic exposure promoted persister formation. Using a multiomics approach and enrichment of persisters, we were able to draw a molecular atlas of persisters, to correlate accumulation of insoluble proteins and ATP depletion with dormancy and persistence. Our results give insights into the molecular profile of bacterial persisters and provide a guide for therapy optimization for persistent
S. aureus
infections.
SOX2 is required independently in both stem and differentiated cells for pituitary tumorigenesis in
p27
-null mice
Authors: Moncho-Amor Veronica , Chakravarty Probir , Galichet Christophe , Matheu Ander , Lovell-Badge Robin , Rizzoti Karine
Published: February 2021

Significance

Tumor development can depend on cell intrinsic dysfunction, but, in some cases, extrinsic factors are important drivers. Here, we established a genetically tractable model, demonstrating that the same gene is relevant both cell autonomously and noncell autonomously for tumorigenesis. Deletion of
p27
, down-regulated in many tumors, predominantly leads to development of murine pituitary tumors. SOX2, transcriptionally derepressed in absence of P27, is important for tumorigenesis in this and other models, but little is known about its interaction. Using loss-of-function and lineage tracing approaches, we establish its regulatory interaction in vivo and show that SOX2 is required independently, both in endocrine and stem cells, to orchestrate tumorigenesis in absence of P27, establishing a powerful model to investigate mechanisms of tumor development.
Chemokine-biased robust self-organizing polarization of migrating cells in vivo
Authors: Olguin-Olguin Adan , Aalto Anne , Maugis Benoît , Boquet-Pujadas Aleix , Hoffmann Dennis , Ermlich Laura , Betz Timo , Gov Nir S. , Reichman-Fried Michal , Raz Erez
Published: February 2021

Significance

Bleb-driven cell migration plays important roles in diverse biological processes. Here, we present the mechanism for polarity establishment and maintenance in blebbing cells in vivo. We show that actin polymerization defines the leading edge, the position where blebs form. We show that the cell front can direct the formation of the rear by facilitating retrograde flow of proteins that limit the generation of blebs at the opposite aspect of the cell. Conversely, localization of bleb-inhibiting proteins at one aspect of the cell results in the establishment of the cell front at the opposite side. These antagonistic interactions result in robust polarity that can be initiated in a random direction, or oriented by a chemokine gradient.
The effects of school closures on SARS-CoV-2 among parents and teachers
Authors: Vlachos Jonas , Hertegård Edvin , B. Svaleryd Helena
Published: February 2021

Significance

Many countries closed schools during the pandemic to contain the spread of SARS-CoV-2. Sweden closed upper-secondary schools, while lower-secondary schools remained open, allowing for an evaluation of school closures. This study analyzes the impact of school closures on the spread of SARS-CoV-2 by comparing groups exposed and not exposed to open schools. We find that exposure to open schools resulted in a small increase in infections among parents. Among teachers, the infection rate doubled, and infections spilled over to their partners. This suggests that keeping lower-secondary schools open had a minor impact on the overall spread of SARS-CoV-2 in society. However, teachers are affected, and measures to protect them could be considered.
Zc3h10 regulates adipogenesis by controlling translation and F-actin/mitochondria interaction
Authors: Audano Matteo , Pedretti Silvia , Ligorio Simona , Gualdrini Francesco , Polletti Sara , Russo Marta , Ghisletti Serena , Bean Camilla , Crestani Maurizio , Caruso Donatella , De Fabiani Emma , Mitro Nico
Published: February 2021

The commitment of mesenchymal stem cells to preadipocytes is stimulated by hormonal induction. Preadipocytes induced to differentiate repress protein synthesis, remodel their cytoskeleton, and increase mitochondrial function to support anabolic pathways. These changes enable differentiation into mature adipocytes. Our understanding of the factors that coordinately regulate the early events of adipocyte differentiation remains incomplete. Here, by using multipronged approaches, we have identified zinc finger CCCH-type containing 10 (Zc3h10) as a critical regulator of the early stages of adipogenesis. Zc3h10 depletion in preadipocytes resulted in increased protein translation and impaired filamentous (F)-actin remodeling, with the latter detrimental effect leading to mitochondrial and metabolic dysfunction. These defects negatively affected differentiation to mature adipocytes. In contrast, Zc3h10 overexpression yielded mature adipocytes with remarkably increased lipid droplet size. Overall, our study establishes Zc3h10 as a fundamental proadipogenic transcription factor that represses protein synthesis and promotes F-actin/mitochondria dynamics to ensure proper energy metabolism and favor lipid accumulation.
Yolk sac, but not hematopoietic stem cell–derived progenitors, sustain erythropoiesis throughout murine embryonic life
Authors: Soares-da-Silva Francisca , Freyer Laina , Elsaid Ramy , Burlen-Defranoux Odile , Iturri Lorea , Sismeiro Odile , Pinto-do-Ó Perpétua , Gomez-Perdiguero Elisa , Cumano Ana
Published: February 2021

In the embryo, the first hematopoietic cells derive from the yolk sac and are thought to be rapidly replaced by the progeny of hematopoietic stem cells. We used three lineage-tracing mouse models to show that, contrary to what was previously assumed, hematopoietic stem cells do not contribute significantly to erythrocyte production up until birth. Lineage tracing of yolk sac erythromyeloid progenitors, which generate tissue resident macrophages, identified highly proliferative erythroid progenitors that rapidly differentiate after intra-embryonic injection, persisting as the major contributors to the embryonic erythroid compartment. We show that erythrocyte progenitors of yolk sac origin require 10-fold lower concentrations of erythropoietin than their hematopoietic stem cell–derived counterparts for efficient erythrocyte production. We propose that, in a low erythropoietin environment in the fetal liver, yolk sac–derived erythrocyte progenitors efficiently outcompete hematopoietic stem cell progeny, which fails to generate megakaryocyte and erythrocyte progenitors.
Analysis of classical neutrophils and polymorphonuclear myeloid-derived suppressor cells in cancer patients and tumor-bearing mice
Authors: Veglia Filippo , Hashimoto Ayumi , Dweep Harsh , Sanseviero Emilio , De Leo Alessandra , Tcyganov Evgenii , Kossenkov Andrew , Mulligan Charles , Nam Brian , Masters Gregory , Patel Jaymala , Bhargava Vipul , Wilkinson Patrick , Smirnov Denis , Sepulveda Manuel A. , Singhal Sunil , Eruslanov Evgeniy B. , Cristescu Razvan , Loboda Andrey , Nefedova Yulia , Gabrilovich Dmitry I.
Published: February 2021

In this study, using single-cell RNA-seq, cell mass spectrometry, flow cytometry, and functional analysis, we characterized the heterogeneity of polymorphonuclear neutrophils (PMNs) in cancer. We describe three populations of PMNs in tumor-bearing mice: classical PMNs, polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), and activated PMN-MDSCs with potent immune suppressive activity. In spleens of mice, PMN-MDSCs gradually replaced PMNs during tumor progression. Activated PMN-MDSCs were found only in tumors, where they were present at the very early stages of the disease. These populations of PMNs in mice could be separated based on the expression of CD14. In peripheral blood of cancer patients, we identified two distinct populations of PMNs with characteristics of classical PMNs and PMN-MDSCs. The gene signature of tumor PMN-MDSCs was similar to that in mouse activated PMN-MDSCs and was closely associated with negative clinical outcome in cancer patients. Thus, we provide evidence that PMN-MDSCs are a distinct population of PMNs with unique features and potential for selective targeting opportunities.
Tissue texture extraction in indocyanine green fluorescence imaging for breast-conserving surgery
Authors: Leiloglou Maria , Chalau Vadzim , Kedrzycki Martha S , Thiruchelvam Paul , Darzi Ara , Leff Daniel R , Elson Daniel S
Published: February 2021

A two-camera fluorescence system for indocyanine green (ICG) signal detection has been developed and tested in a clinical feasibility trial of ten patients, with a resolution in the submillimetre scale. Immediately after systemic ICG injection, the two-camera system can detect ICG signals in vivo (∼2.5 mg

l

−
1

or 3.2 ×

10

−
6

M). Qualitative assessment has shown that the fluorescence signal does not always correlate with the cancer location in the surgical scene. Conversely, fluorescence image texture metrics when used with the logistic regression model yields good accuracy scores in detecting cancer. We have demonstrated that intraoperative fluorescence imaging for resection guidance is a feasible solution to tackle the current challenge of positive resection margins in breast conserving surgery.
From thermal catalysis to plasma catalysis: a review of surface processes and their characterizations
Authors: Zhang S , Oehrlein G S
Published: February 2021

The use of atmospheric pressure plasma to enhance catalytic chemical reactions involves complex surface processes induced by the interactions of plasma-generated fluxes with catalyst surfaces. Industrial implementation of plasma catalysis necessitates optimizing the design and realization of plasma catalytic reactors that enable chemical reactions that are superior to conventional thermal catalysis approaches. This requires the fundamental understanding of essential plasma-surface interaction mechanisms of plasma catalysis from the aspect of experimental investigation and theoretical analysis or computational modeling. In addition, experimental results are essential to validate the relative theoretical models and hypotheses of plasma catalysis that was rarely understood so far, compared to conventional thermal catalysis. This overview focuses on two important application areas, nitrogen fixation and methane reforming, and presents a comparison of important aspects of the state of knowledge of these applications when performed using either plasma-catalysis or conventional thermal catalysis. We discuss the potential advantage of plasma catalysis over thermal catalysis from the aspects of plasma induced synergistic effect andin situcatalyst regeneration.In-situ/operandosurface characterization of catalysts in plasma catalytic reactors is a significant challenge since the high pressure of realistic plasma catalysis systems preclude the application of many standard surface characterization techniques that operate in a low-pressure environment. We present a review of the status of experimental approaches to probe gas-surface interaction mechanisms of plasma catalysis, including an appraisal of demonstrated approaches for integrating surface diagnostic tools into plasma catalytic reactors. Surface characterizations of catalysts in plasma catalytic reactors demand thorough instrumentations of choices of plasma sources, catalyst forms, and the relative characterization tools. We conclude this review by presenting open questions on self-organized patterns in plasma catalysis.
Study of cathode-spot crater and droplet formation in a vacuum arc
Authors: Wang Lijun , Zhang Xiao , Li Jiagang , Luo Ming , Jia Shenli
Published: February 2021

A 3D transient model of a cathode-spot crater and droplet formation in a vacuum arc is developed. The model includes mass, momentum, heat transfer (energy), current continuity and potential equations. Using the energy flux density, current density and pressure as external parameters, the shape of the cathode-spot crater and the temperature, velocity, potential and current density distributions at each time step are determined via numerical simulation. Under symmetrical conditions, the 3D simulation results are highly consistent with those from the previous 2D model. The new cathode spot tends to appear in the direction in which the protrusion is largest because the liquid-metal velocity is lower and the liquid-metal ridge radius is larger in this direction. The effect of the external transverse magnetic field is considered by using a symmetric space function to represent the pressure and energy flux density of the plasma cloud. Simulation results show that even small changes in the plasma cloud distribution have a significant impact on the cathode-spot crater process and droplet formation. Since the pressure is asymmetric, the crater becomes asymmetric and the new cathode spot tends to appear opposite to the direction of the Ampere force. Based on this phenomenon, a possible explanation for the retrograde motion phenomenon of cathode spots is proposed.
Raw GNSS observations from Android smartphones: characteristics and short-baseline RTK positioning performance
Authors: Gao Rui , Xu Li , Zhang Baocheng , Liu Teng
Published: February 2021

The release of raw global navigation satellite system (GNSS) observations by Google Android makes high-precision positioning possible with low-cost smart devices. This study contributes to this research trend by constructing a stochastic model based on raw GNSS observation characteristics from Android smartphones and verifying the feasibility of smartphone-based ambiguity fixing in the short-baseline real-time kinematic (RTK) case. This study uses the raw observation standard deviations (ROSTDs) delivered by the Android application programming interface (API) as a stochastic model and takes advantage of the multipath index from the API to rule out unusable observations. As well as these, the ambiguity integer property is investigated by analyzing the residuals of double-differenced carrier-phase observations associated with one smartphone and one geodetic-grade receiver. Furthermore, we note that the carrier-phase observations collected by tested smartphones do not have the integer property but for the Huawei P30 and Xiaomi 8 devices, such an integer property can be successfully recovered by means of detrending. With the use of ROSTD-dependent weighting, we first perform single-point positioning (SPP) and real-time differentition (RTD) using pseudorange observations delivered by the Huawei P30 and Xiaomi 8 devices. The results show that the stochastic model is applicable to the Xiaomi 8. Moreover, the three-dimensional root-mean-square (3D-RMS) errors of the two smartphones for SPP are 1.28 m and 1.96 m, and the 3D-RMS errors for RTD are 0.79 m and 1.64 m, respectively. We next test the RTK positioning performance based on a short-baseline of 882 m using carrier-phase observations with recovered integer ambiguities. For the Huawei P30, the positioning errors achieved were 7.8, 2.4, 1.1 mm for the east, north, and up (ENU) components at the time of first fix while for the Xiaomi 8, the positioning errors achieved were 4.3, 4.2, 4.2 mm for the ENU components at the time of first fix.
Hollow porous BiOCl microspheres assembled with single layer of nanocrystals: spray solution combustion synthesis and the enhanced photocatalytic properties
Authors: Yang Zhongxiang , Shang Zhichao , Liu Fang , Chen Yirui , Wang Xiaohong , Zhang Bangsheng , Liu Guiqing
Published: February 2021

The hollow porous microspheres assembled with BiOCl nanocrystals were successfully synthesized via a facile spray solution combustion synthesis method. The microstructure, morphology, absorbance, optical properties of the samples were investigated in detail. The results show that hollow porous BiOCl microspheres have narrow band gaps (2.66–2.71 eV), and the degradation rate of rhodamine B (RhB) can reach 98% under visible light irradiation for 60 min. Furthermore, the mechanism of the photocatalytic degradation of RhB was proposed through the experiment of trapping active species. This excellent photocatalytic property can be ascribed to the larger specific surface area and the special microstructure.
Interventional respiratory motion compensation by simultaneous fluoroscopic and nuclear imaging: a phantom study
Authors: Dietze Martijn M A , Kunnen Britt , Lam Marnix G E H , de Jong Hugo W A M
Published: February 2021

Purpose. A compact and mobile hybrid c-arm scanner, capable of simultaneously acquiring nuclear and fluoroscopic projections and SPECT/CBCT, was developed to aid fluoroscopy-guided interventional procedures involving the administration of radionuclides (e.g. hepatic radioembolization). However, as in conventional SPECT/CT, the acquired nuclear images may be deteriorated by patient respiratory motion. We propose to perform compensation for respiratory motion by extracting the motion signal from fluoroscopic projections so that the nuclear counts can be gated into motion bins. The purpose of this study is to quantify the performance of this motion compensation technique with phantom experiments. Methods. Anthropomorphic phantom configurations that are representative of distributions obtained during the pre-treatment procedure of hepatic radioembolization were placed on a stage that translated with three different motion patterns. Fluoroscopic projections and nuclear counts were simultaneously acquired under planar and SPECT/CBCT imaging. The planar projections were visually assessed. The SPECT reconstructions were visually assessed and quantitatively assessed by calculating the activity recovery of the spherical inserts in the phantom. Results. The planar nuclear projections of the translating anthropomorphic phantom were blurry when no motion compensation was applied. With motion compensation, the nuclear projections became representative of the stationary phantom nuclear projection. Similar behavior was observed for the visual quality of SPECT reconstructions. The mean error of the activity recovery in the uncompensated SPECT reconstructions was 15.8% ± 0.9% for stable motion, 11.9% ± 0.9% for small variations, and 11.0% ± 0.9% for large variations. When applying motion compensation, the mean error decreased to 1.8% ± 1.6% for stable motion, 2.2% ± 1.5% for small variations, and 5.2% ± 2.5% for large variations. Conclusion. A compact and mobile hybrid c-arm scanner, capable of simultaneously acquiring nuclear and fluoroscopic projections, can perform compensation for respiratory motion. Such motion compensation results in sharper planar nuclear projections and increases the quantitative accuracy of the SPECT reconstructions.
H2RSPET: a 0.5 mm resolution high-sensitivity small-animal PET scanner, a simulation study
Authors: Lai Youfang , Wang Qian , Zhou Shiwei , Xie Zhaoheng , Qi Jinyi , Cherry Simon R , Jin Mingwu , Chi Yujie , Du Junwei
Published: February 2021

With the goal of developing a total-body small-animal PET system with a high spatial resolution of ∼0.5 mm and a high sensitivity >10% for mouse/rat studies, we simulated four scanners using the graphical processing unit-based Monte Carlo simulation package (gPET) and compared their performance in terms of spatial resolution and sensitivity. We also investigated the effect of depth-of-interaction (DOI) resolution on the spatial resolution. All the scanners are built upon 128 DOI encoding dual-ended readout detectors with lutetium yttrium oxyorthosilicate (LYSO) arrays arranged in 8 detector rings. The solid angle coverages of the four scanners are all ∼0.85 steradians. Each LYSO element has a cross-section of 0.44 × 0.44 mm2 and the pitch size of the LYSO arrays are all 0.5 mm. The four scanners can be divided into two groups: (1) H2RS110-C10 and H2RS110-C20 with 40 × 40 LYSO arrays, a ring diameter of 110 mm and axial length of 167 mm, and (2) H2RS160-C10 and H2RS160-C20 with 60 × 60 LYSO arrays, a diameter of 160 mm and axial length of 254 mm. C10 and C20 denote the crystal thickness of 10 and 20 mm, respectively. The simulation results show that all scanners have a spatial resolution better than 0.5 mm at the center of the field-of-view (FOV). The radial resolution strongly depends on the DOI resolution and radial offset, but not the axial resolution and tangential resolution. Comparing the C10 and C20 designs, the former provides better resolution, especially at positions away from the center of the FOV, whereas the latter has 2× higher sensitivity (∼10% versus ∼20%). This simulation study provides evidence that the 110 mm systems are a good choice for total-body mouse studies at a lower cost, whereas the 160 mm systems are suited for both total-body mouse and rat studies.
Conversion factor for size specific dose estimation of head CT scans based on age, for individuals from 0 up to 18 years old
Authors: Honorio da Silva Edilaine , Baffa Oswaldo , Elias Jorge , Buls Nico
Published: February 2021

Assessing the radiation doses received by patients in computed tomography is still challenging. To overcome this, the American Association of Physicists in Medicine has introduced the concept of the size specific dose estimate (SSDE). However, the calculation of SSDE for head CT scans requires the knowledge of attenuation characteristics of the volume scanned, making its implementation in the daily clinical workflow cumbersome. In this study, we defined conversion coefficients from CTDIvol,16cm to SSDE for head CT scans based solely on the age of the patient. Using the head circumference-for-age from the child growth standards of the World Health Organization (WHO), the effective diameter-for-age was calculated for male and female individuals from 0 to 60 months-old. The effective diameter was converted into a water equivalent diameter-for-age, using a correlation established from the measurements of both quantities in 295 exams of male and female patients, from 0 to 18 years-old. WHO-estimated water equivalent diameter-for-age was validated against the measured water equivalent diameter-for-age. The head circumference-for-age from WHO was extrapolated for male and females individuals up to 18 years-old and their respective water equivalent diameter were estimated. Finally, the SSDE was calculated for all the CT head scans performed in a 9-years period in patients aged from 0 to 18 years old. Typical values of CTDIvol,16cm and DLP were also defined. SSDE varied from 0.80 up to 1.16 of the CTDIvol,16cm, depending on sex and age of the patient. WHO-estimated water equivalent diameter-for-age differed less than 20% from the measured water equivalent diameter-for-age. Typical values of SSDE varied from 28.5 up to 38.9 mGy, while typical values ranged from 30.9 up to 47.6 mGy for the CTDIvol,16cm and from 417.6 up to 861.1 mGy*cm for the DLP. SSDE can be directly calculated for head CT scans once the age of the patient is known.
A Novel Fault Diagnosis Strategy of MMC Battery Energy Storage System Based on SPVD
Authors: Yibin Tao , Shi Yin , Xin Zhan , Guanjun Li , Zhong Liu
Published: February 2021

With the vigorous development of renewable energy, high-power energy storage systems have become a key technology for energy transformation. Electrochemical energy storage systems based on modular multilevel converters have become a hot and difficult research topic due to their modular design, fast dynamic response, and excellent output quality. The MMC-BESS system contains a large number of sub-modules, each of which is a potential fault point. How to quickly diagnose and locate faults is the main research content of this article. First, the mathematical model of MMC-BESS is established, and the observer is constructed to judge whether the system is in a fault state. Second, the changing trend of the fault status of the sub-module is analyzed, and a fault location strategy based on port voltage discrimination is proposed. Finally, the experimental verification of the proposed diagnostic strategy proves the effectiveness and feasibility of the diagnostic strategy.
Compensation of Subdivision Error of Capacitance Encoder Based on Lissajous Graphic Analysis
Authors: Wang Aijia , Ding Hongchang , Hou Han , Li Kun , Zhao Changfu
Published: February 2021

With the development of measurement technology in the direction of precision, high speed, automation, integration, intelligence, economy, non-contact and multifunction, it has simple structure, small size, low energy consumption and strong adaptability. And other advantages have been widely used. However, the sensor of the capacitive encoder works in the state of low voltage and low current, and is extremely susceptible to the influence of the external electric field and magnetic field, causing problems such as input signal distortion and system failure. With the increasing requirements of the manufacturing industry for stability and accuracy, it is of great significance to analyze the capacitive coding error and improve the accuracy. This article analyzes the error generated by the capacitive encoder, enumerates the influence of DC deviation, amplitude deviation, phase deviation, and high-order harmonics on the interpolation error, and compensates the error signal for the aspects that cause larger errors. The sine and cosine signals are close to the ideal state.
An Improved Research on Frequency-Fixed Cascaded SOGI Single-Phase PLL
Authors: Gu Yukun , Jin Ke , Yang Chen
Published: February 2021

The second-order generalized integrator (SOGI) with band-pass filtering characteristics is widely used in the design of advanced single-phase phase-locked loops (PLLs). But this type of PLL has insufficient ability to restrain dc biases, which limits their applications under certain conditions. Recently, a PLL adopting two cascade SOGI structures is called the cascaded generalized integrator PLL (CGI-PLL), which has perfect dc offsets blocking capability. However, the two output signals of the quadrature signal generator (QSG) formed by frequency-fixed CGI have different amplitudes, which makes the second harmonic oscillations appear in the estimated parameters of the PLL while the frequency deviates from the nominal frequency. Similarly, the in-phase output signal of CGI-based QSG is not synchronized with the fundamental frequency component of the grid voltage under frequency drifts, which is the reason for the phase offset error in the PLL outputs in the steady state. Some compensation strategies are added to correct the error that exists in the frequency-fixed CGI-PLL when the frequency deviates from the nominal value.