bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting Cardiac Anatomy, Physiology, and Surgical Management Based on Fetal Echocardiography in Heterotaxy Syndrome
Authors: Romanowicz Jennifer , Sinha Pranava , Donofrio Mary T. , Schidlow David N.
Published: July 2021

Objective Heterotaxy syndrome (HS) is often associated with complex congenital heart disease (CHD). While fetal echocardiography (FE) permits accurate prenatal identification of most CHD, the high level of disease complexity in HS may pose challenges in predicting postnatal findings and outcomes. This study aimed to define the accuracy of FE in predicting postnatal anatomy, physiology, and surgical management of CHD in the setting of HS.

Study Design Retrospective single-center cohort study including all patients with a prenatal diagnosis of HS from 2003 to 2018. Anatomic diagnoses from FE reports were compared with postnatal echocardiogram, catheterization, and operative reports. Prenatal predictions were compared with postnatal outcomes with a focus on ductal dependence, time to first intervention (immediate, neonatal period, 1–6 months, or older than 6 months), and surgical approach (single or biventricular).

Results There were 102 pregnancies with fetal HS resulting in 21 terminations, 5 fetal losses, and 76 live births. Of the live births, 55 had significant CHD and available postnatal data for review. Among this group, survival to 1 year was 62% and was no different comparing single versus biventricular surgical approach. FE diagnostic accuracy varied by anatomic feature and was the lowest for diagnosis of venous anatomy. Determination of postnatal care was most accurate for predicting single versus biventricular surgical approach (91%), followed by ductal dependence (75%). Accuracy for predicting time to first intervention was the lowest at 69%. The most common reason for an incorrect prediction was difficulty in assessing the severity of pulmonary stenosis.

Conclusion FE permits accurate predictions regarding surgical approach. Characterizing systemic and pulmonary veins is challenging, as is predicting ductal dependence and time to first intervention. These data suggest that despite the high diagnostic accuracy of CHD in HS, a circumspect approach may be reasonable with regard to predicting some anatomic details and postnatal management decisions.

Key Points
Extracting quantitative biological information from bright-field cell images using deep learning
Authors: Helgadottir Saga , Midtvedt Benjamin , Pineda Jesús , Sabirsh Alan , B. Adiels Caroline , Romeo Stefano , Midtvedt Daniel , Volpe Giovanni
Published: July 2021

Quantitative analysis of cell structures is essential for biomedical and pharmaceutical research. The standard imaging approach relies on fluorescence microscopy, where cell structures of interest are labeled by chemical staining techniques. However, these techniques are often invasive and sometimes even toxic to the cells, in addition to being time consuming, labor intensive, and expensive. Here, we introduce an alternative deep-learning–powered approach based on the analysis of bright-field images by a conditional generative adversarial neural network (cGAN). We show that this is a robust and fast-converging approach to generate virtually stained images from the bright-field images and, in subsequent downstream analyses, to quantify the properties of cell structures. Specifically, we train a cGAN to virtually stain lipid droplets, cytoplasm, and nuclei using bright-field images of human stem-cell–derived fat cells (adipocytes), which are of particular interest for nanomedicine and vaccine development. Subsequently, we use these virtually stained images to extract quantitative measures about these cell structures. Generating virtually stained fluorescence images is less invasive, less expensive, and more reproducible than standard chemical staining; furthermore, it frees up the fluorescence microscopy channels for other analytical probes, thus increasing the amount of information that can be extracted from each cell. To make this deep-learning–powered approach readily available for other users, we provide a Python software package, which can be easily personalized and optimized for specific virtual-staining and cell-profiling applications.
Space radiation electrostatic shielding scaling laws: Beam-like and isotropic angular distributions
Authors: Pal Chowdhury R. , Stegeman L. , Santillana Padilla R. F. , Lund M. L. , Madzunkov S. , Fry D. , Bahadori A. A.
Published: July 2021

Passive radiation shielding alone cannot provide adequate protection for astronauts on long-term, deep-space missions. High atomic number and energy (HZE) ions, and/or their secondaries, can penetrate any realistic mass shielding for long-term deep-space missions and cause damage to cells via direct energy deposition and/or through the production of secondary particles and fragmented nuclei. Active shielding, or the use of electromagnetic fields to deflect or stop incoming ions before reaching the spacecraft, has gained substantial attention over the last decade as a way to augment passive shielding. Recently, a mathematical relationship between a dimensionless scaling parameter characterizing the active shield and the incoming ion and a protected area formed on a downstream detector due to the deflection of HZE ions by the applied field was validated in Earth-based laboratory conditions. In the present work, the mathematical formulation is extended to relate electrostatic shielding efficacy with the ability to deflect positively charged ions with parameters relevant to space applications. Additionally, a modified scaling parameter is formulated to characterize the shielding efficacy of a “family” of electrostatic active shielding configurations for reducing flux density for a space-relevant isotropic source of energetic protons. The results of this study demonstrate a strong correlation among dimensionless scaling parameters and shielding efficacy metrics for space radiation-relevant HZE ions in beam and isotropic angular distributions. Furthermore, it establishes a framework for optimizing design of three-dimensional electrostatic shielding configurations to improve space radiation protection for astronauts on exploration-class missions.
Mind the gap: State-of-the-art technologies and applications for EEG-based brain–computer interfaces
Authors: Portillo-Lara Roberto , Tahirbegi Bogachan , Chapman Christopher A. R. , Goding Josef A. , Green Rylie A.
Published: July 2021

Brain–computer interfaces (BCIs) provide bidirectional communication between the brain and output devices that translate user intent into function. Among the different brain imaging techniques used to operate BCIs, electroencephalography (EEG) constitutes the preferred method of choice, owing to its relative low cost, ease of use, high temporal resolution, and noninvasiveness. In recent years, significant progress in wearable technologies and computational intelligence has greatly enhanced the performance and capabilities of EEG-based BCIs (eBCIs) and propelled their migration out of the laboratory and into real-world environments. This rapid translation constitutes a paradigm shift in human–machine interaction that will deeply transform different industries in the near future, including healthcare and wellbeing, entertainment, security, education, and marketing. In this contribution, the state-of-the-art in wearable biosensing is reviewed, focusing on the development of novel electrode interfaces for long term and noninvasive EEG monitoring. Commercially available EEG platforms are surveyed, and a comparative analysis is presented based on the benefits and limitations they provide for eBCI development. Emerging applications in neuroscientific research and future trends related to the widespread implementation of eBCIs for medical and nonmedical uses are discussed. Finally, a commentary on the ethical, social, and legal concerns associated with this increasingly ubiquitous technology is provided, as well as general recommendations to address key issues related to mainstream consumer adoption.
High resolution x-ray emission spectrometer for multiple hard x-ray emission lines: Demonstration for Cu Kα and Kβ emissions
Authors: Solovyev Mikhail A. , Lockard Jenny V. , Huang XianRong , Heald Steve M. , Sun Cheng-Jun
Published: July 2021

We present a compact 3D printed x-ray emission spectrometer based on the von Hamos geometry that represents a significant upgrade to the existing von Hamos geometry-based miniature x-ray emission spectrometer (miniXES) [Mattern et al., Rev. Sci. Instrum. 83(2), 023901 (2012)]. The upgrades include the incorporation of a higher pixel density 500K detector for improved energy resolution and an enlarged sample area to accommodate a wider range of sample formats. The versatile spectrometer houses removable crystal holders that can be easily exchanged, as well as movable alignment eyelets that give flexibility in Bragg angle selection. Designed for ease of manufacture, all the components, except for the apertures, can be 3D printed and readily assembled. We describe its implementation in measurements of resonant and non-resonant Cu Kα and Kβ x-ray emission and report the theoretical and measured energy resolution and collected solid angle of the emission.
Numerical study on optimization of atmospheric pulse-modulated radio frequency discharges in the very high frequency range
Authors: Wang Xiao-Long , Gao Shu-Han , Zhang Yuan-Tao
Published: July 2021

In this paper, we investigated the optimization of pulse-modulated radio frequency (rf) discharges in the range of very high frequency from 50 to 800 MHz by a fluid model. A very strong Peak Current in the First Period (PCFP) during the power-on phase can be observed only when the excitation frequency is large enough, usually larger than 50 MHz, and the reversal electric field near the anode due to the accumulation of electrons contributes greatly to the formation of this peak current from the simulation data. The highest electron temperature is achieved in the first period, while the largest electron density is usually obtained in the last period during the power-on phase. By increasing the duty cycle, the value of PCFP increases initially, then it reaches the peak value at a duty cycle of approximately 70%, and later it drops to the normal value generated in a continuous rf discharge, and the maximum electron temperature also shows the similar evolution. However, as the duty cycle is increased, the electron density is always enhanced during the power-on phase. According to the simulation results, the duty cycle and modulation frequency can be effectively applied to modulate and optimize the electron density and electron temperature for applications.
Low-energy electron ionization mass spectrometer for efficient detection of low mass species
Authors: Bergin M. , Ward D. J. , Lambrick S. M. , von Jeinsen N. A. , Holst B. , Ellis J. , Jardine A. P. , Allison W.
Published: July 2021

The design of a high-efficiency mass spectrometer is described, aimed at residual gas detection of low mass species using low-energy electron impact, with particular applications in helium atom microscopy and atomic or molecular scattering. The instrument consists of an extended ionization volume, where electrons emitted from a hot filament are confined using a solenoidal magnetic field to give a high ionization probability. Electron space charge is used to confine and extract the gas ions formed, which are then passed through a magnetic sector mass filter before reaching an ion counter. The design and implementation of each of the major components are described in turn, followed by the overall performance of the detector in terms of mass separation, detection efficiency, time response, and background count rates. The linearity of response with emission current and magnetic field is discussed. The detection efficiency for helium is very high, reaching as much as 0.5%, with a time constant of (198 ± 6) ms and a background signal equivalent to an incoming helium flux of (8.7 ± 0.2) × 106 s−1.
Effect of La and Sc co-doping on dielectric and ferroelectric properties of PZT for energy storage capacitors
Authors: Bhattarai Mohan K. , Pavunny Shojan P. , Katiyar Ram S.
Published: July 2021

In this work, we report a systematic study of complex La3+ and Sc3+ doped lead zirconate titanate ceramics with the stoichiometric formula (PbZr0.53Ti0.47)0.90 (LaxSc1−x)0.10O3−δ for x = 0.2, 0.4, 0.6, and 0.8 denoted as PLZTS2, PLZTS4, PLZTS6, and PLZTS8, respectively (abbreviated as PLZTS10x), synthesized using the solid-state reaction method. We carried out dielectric measurements on Ag/PLZTS10x/Ag metal–ferroelectric–metal capacitors as a function of temperature (100–650 K) and frequency (102–106 Hz). Upon increasing La3+ concentration, the dielectric constant was found to be increased up to x = 0.6 and attained the highest value of ∼1800 at room temperature, and consequently, the highest saturation polarization was observed. The relaxor behavior of PLZTS8 can be attributed to the polar nano regions created in the materials. A recoverable energy density of ∼1162 mJ/cm3 with an excellent efficiency of ∼79% was achieved under an applied electric field of 97 kV/cm. The demonstrated high dielectric constant (ɛ′), spontaneous polarization (Ps), and energy density make these bulk materials promising for ferroelectric memory and energy-storage applications.
Influence of elastic anisotropy on measured sound velocities and elastic moduli of polycrystalline cubic solids
Authors: Xu Feng , Djemia Philippe , Belliard Laurent , Huang Haijun , Perrin Bernard , Zerr Andreas
Published: July 2021

Cubic solids such as NaCl, crystalline argon, or H2O-ice VII exhibit significant elastic anisotropy strongly increasing upon compression. As earlier recognized for solid argon and H2O-ice (both exhibiting Zener ratio A > 1), longitudinal sound velocities of their polycrystals, VLav, measured using Brillouin light scattering (BLS) or pulse-echo ultrasonics are much closer to VL⟨111⟩ than to VL⟨100⟩, the VL-extremes in any cubic single crystal. Here, we experimentally confirm, using the technique of time-domain Brillouin scattering, the same tendency for NaCl exhibiting the opposite anisotropy type, A < 1. To understand this tendency, we modelled orientational distribution and the frequency of occurrence of VL values in texture-free polycrystalline samples of NaCl and solid argon. We found a remarkable and predictable asymmetry of VL distributions with maxima at VL⟨110⟩ that is always much closer to VL⟨111⟩. This asymmetry persists in BLS peaks but can be obscured in experiments. In the case of solid argon at 49 GPa, the asymmetry can lead to a moderate deviation of experimental VLav from VLH (obtained from elastic-stiffness constants Cij applying the Hill approximation) by ∼7%. The latter can cause, however, a significant overestimation of the aggregate shear modulus by δG/G ∼ 50% or of the bulk modulus by δB/B ∼ 20% if just one BLS peak of longitudinal modes is detectable. A similar analysis, performed for transverse sound velocities, VT and VTav, has shown that by the use of a BLS spectrum showing peaks of both longitudinal and transverse modes, overestimation of B is similarly high but that of G is much less dramatic.
Manipulating valley-polarized photoluminescence of MoS2 monolayer at off resonance wavelength with a double-resonance strategy
Authors: Huang Lei , Wang Yongkang , Su Huanhuan , Hu Guohua , Deng Chunyu , Sun Yu , Yun Binfeng , Zhang Ruohu , Chen Yunfei , Wang Fengqiu , Cui Yiping
Published: July 2021

The intrinsic spin-valleys in monolayer transition metal dichalcogenides make them promising for exploring new-generation valleytronic and spintronic devices. However, it is very challenging to detect and manipulate a specific valley with off resonance electromagnetic fields at room temperature due to their ultrashort lifetimes and phonon-assisted intervalley scattering. Here, utilizing the sputtering and the focused ion beam milling methods, we fabricate a quasi-three-dimensional chiral microstructure using molybdenum disulfide. Based on chirality and double plasmonic resonances, we realize off resonance wavelength control of valley-polarized photoluminescence at room temperature. Furthermore, we find that the chiral field excitation enhancement (13) and chiral quantum yield amplification (1.35 times) contribute to the huge differences in the photoluminescence of valleys. These results reported here may pave the way for further development of on-chip photonic integration of two-dimensional materials.
Resistivity scaling in epitaxial MAX-phase Ti4SiC3(0001) layers
Authors: Zhang Minghua , Kumar Sushant , Sundararaman Ravishankar , Gall Daniel
Published: July 2021

In situ transport measurements on 5.8–92.1 nm thick epitaxial Ti4SiC3(0001) layers are used to experimentally verify the previously predicted low resistivity scaling. Magnetron co-sputtering from three elemental sources at 1000 °C onto 12-nm-thick TiC(111) nucleation layers on Al2O3(0001) substrates yields epitaxial growth with Ti4SiC3(0001) || Al2O3(0001) and Ti4SiC3(101¯0) || Al2O3(21¯1¯0), a low and thickness-independent surface roughness of 0.6 ± 0.2 nm, and a measured stoichiometric composition. The room-temperature resistivity ρ increases slightly with decreasing thickness, from ρ = 35.2 ± 0.4 to 37.5 ± 1.1 μΩ cm for d = 92.1–5.8 nm, and similarly from 9.5 ± 0.2 to 11.0 ± 0.4 μΩ cm at 77 K, indicating only a minor effect of electron surface scattering on ρ. Data analysis with the classical Fuchs–Sondheimer model yields a room-temperature bulk resistivity ρo = 35.1 ± 0.4 μΩ cm in the basal plane and suggests effective mean free paths λ = 1.1 ± 0.6 at 293 K and λ = 3.0 ± 2.0 nm at 77 K if assuming completely diffuse electron surface scattering. First-principles calculations predict an anisotropic Ti4SiC3 Fermi surface and a product ρoλ = 19.3 × 10−16 Ω m2 in the basal plane. This value is six times larger than that predicted previously and five times larger than the measured temperature-independent effective ρoλ = (3.8 ± 2.1) × 10−16 Ω m2. This deviation can be explained by a high experimental electron scattering specularity of p = 0.8 for Ti4SiC3(0001) surfaces. Air exposure causes a 4% room-temperature resistivity increase for d = 5.8 nm, indicating a decrease in the surface scattering specularity Δp = −0.19. The overall results show that Ti4SiC3 is not directly applicable as an interconnect material due to its relatively large ρo. However, the particularly small resistivity scaling with an effective λ that is more than an order of magnitude smaller than that of Cu confirms the potential of MAX phase materials for high-conductivity narrow interconnects.
The impact of water vapor on the OH reactivity toward CH3CHO at ultra-low temperatures (21.7–135.0 K): Experiments and theory
Authors: Neeman E. M. , González D. , Blázquez S. , Ballesteros B. , Canosa A. , Antiñolo M. , Vereecken L. , Albaladejo J. , Jiménez E.
Published: July 2021

The role of water vapor (H2O) and its hydrogen-bonded complexes in the gas-phase reactivity of organic compounds with hydroxyl (OH) radicals has been the subject of many recent studies. Contradictory effects have been reported at temperatures between 200 and 400 K. For the OH + acetaldehyde reaction, a slight catalytic effect of H2O was previously reported at temperatures between 60 and 118 K. In this work, we used Laval nozzle expansions to reinvestigate the impact of H2O on the OH-reactivity with acetaldehyde between 21.7 and 135.0 K. The results of this comprehensive study demonstrate that water, instead, slows down the reaction by factors of ∼3 (21.7 K) and ∼2 (36.2–89.5 K), and almost no effect of added H2O was observed at 135.0 K.
Mitral valve asymmetry in healthy, pathological, and repaired cases
Authors: Collia Dario
Published: July 2021

The entry of blood into the left ventricle is regulated by the two valve leaflets. Mitral valve prolapse is the primary cause of mitral regurgitation. Mitral valve repair is the gold standard therapeutic procedure for patients with degenerative mitral valve regurgitation and follows two fundamental principles: restoring a good coaptation surface of the flap and correcting annular dilation. This study presents a first step in the direction of addressing the influence of valve geometry on valve fluid dynamics and mitral regurgitation. To this end, it develops a systematic analysis to identify how the level of regurgitation and the efficiency of flow transit in the left ventricle depend on the degree of asymmetry of the leaflets. The analysis is performed starting from a mathematically designed mitral valve and then extended to the actual valves extracted from medical imaging. The specific objective is to evaluate the changes in mitral regurgitation associated with the symmetrical properties of the mitral valve. The broader aim is to begin building physics-based means for evaluating repair options and prosthetic design. Results showed that valve shape does not affect flow; sub-volumes are similar to inflow and vary to outflow due to the presence of false regurgitation under healthy/repaired conditions and regurgitation under pathological conditions affecting the amount of direct flow, delayed and finally the Stroke volume. The best valve asymmetry point was found to be 0.25, while the optimal range was between 0.4 and 0.2, giving an important suggestion to valve surgery.
Negative thermal expansion and itinerant ferromagnetism in Mn1.4Fe3.6Si3
Authors: Singh Vikram , Nath R.
Published: July 2021

We report the thermal expansion, critical behavior, magnetocaloric effect (MCE), and magnetoresistance (MR) on the polycrystalline Mn1.4Fe3.6Si3 compound around the ferromagnetic transition. A large negative volume thermal expansion (αV∼−20×10−6 K−1) is observed across the transition temperature with a strong anisotropic variation of lattice parameters in the ab-plane. The anisotropic magnetoelasticity arises from the competition between magnetic ordering and structural deformation that could be responsible for the large MCE (ΔSm≃−6 J/Kg K) across the magnetic transition in this compound. The large and negative MR (∼−3% in 80 kOe) is also observed at the transition temperature which can be attributed to the suppression of spin disorder. Furthermore, the Rhodes–Wolfarth ratio (RWR >1) and identical field dependence of MR and MCE isotherms indicate the itinerant character of the 3d electrons. The critical exponents determined from the analysis of magnetization and MCE are consistent with the quasi-two-dimensional (2D) Ising model with long range exchange interactions that decays as J(r)∼r−3.41. This unconventional quasi-2D Ising character with long-range interactions can be ascribed to strong ab-plane anisotropy and the delocalized 3d electrons in the studied compound.
Dynamical analysis of early afterdepolarization patterns in a biophysically detailed cardiac model
Authors: Barrio Roberto , Martínez M. Ángeles , Pueyo Esther , Serrano Sergio
Published: July 2021

Arrhythmogenic early afterdepolarizations (EADs) are investigated in a biophysically detailed mathematical model of a rabbit ventricular myocyte, providing their location in the parameter phase space and describing their dynamical mechanisms. Simulations using the Sato model, defined by 27 state variables and 177 parameters, are conducted to generate electrical action potentials (APs) for different values of the pacing cycle length and other parameters related to sodium and calcium concentrations. A detailed study of the different AP patterns with or without EADs is carried out, showing the presence of a high variety of temporal AP configurations with chaotic and quasiperiodic behaviors. Regions of bistability are identified and, importantly, linked to transitions between different behaviors. Using sweeping techniques, one-, two-, and three-parameter phase spaces are provided, allowing ascertainment of the role of the selected parameters as well as location of the transition regions. A Devil’s staircase, with symbolic sequence analysis, is proposed to describe transitions in the ratio between the number of voltage (EAD and AP) peaks and the number of APs. To conclude, the obtained results are linked to recent studies for low-dimensional models and a conjecture is made for the internal dynamical structure of the transition region from non-EAD to EAD behavior using fold and cusp bifurcations and maximal canards.
Comparison and analysis of Al0.7InAsSb avalanche photodiodes with different background doping polarities
Authors: Chen Dekang , McArthur J. Andrew , March Stephen D. , Xue Xingjun , Jones Andrew H. , Dadey Adam A. , Bank Seth R. , Campbell Joe C.
Published: July 2021

Background doping polarity is a key parameter in the design of numerous electrical and optoelectronic devices. It is especially critical for avalanche photodiodes (APDs). Recently, high-performance APDs have been demonstrated based on the AlInAsSb digital alloy materials system. A critical element of this work was the determination of the background doping polarity of the molecular beam epitaxial grown wafers. In this work, we determine the unintentional background doping polarity of Al0.7InAsSb using the double mesa capacitance-voltage technique. We fabricated two p-i-n Al0.7InAsSb structures: one with p-type background polarity and the other with n-type. The measurements indicate that devices with different background doping polarities show different capacitance relations to the mesa diameters; moreover, the relationship reverses at high voltage in a p-type background device. Subsequent simulations reveal that this reversal is caused by electrical field confinement after the depletion reaches the smaller top mesa. These findings are consistent with reports of reduced surface leakage current in double and triple mesa structures.
Energy barriers for Dy and H penetrating graphene on 6H-SiC(0001) and freestanding bilayer graphene from first-principles calculations
Authors: Han Yong , Evans James W. , Tringides Michael C.
Published: July 2021

Currently, intercalation of foreign guest atoms into two-dimensional (2D) layered van der Waals materials is an active research area motivated in part by the development of next-generation energy-storage technologies and optoelectronic devices. One such extensively studied 2D material is the graphene-on-SiC system. To realize and control the desired intercalated structures, it is fundamentally important to understand the kinetic process of intercalation. For the intercalation of a guest atom into graphene layers on SiC substrate, a critical kinetic parameter is the energy barrier of a guest atom penetrating the perfect graphene top layer into the gallery under it. However, accurate theoretical calculations for such penetration barriers are unavailable in literature. From our first-principles density functional theory calculations, we obtain the global energy barriers of 3.47 and 1.80 eV for single Dy and H atoms penetrating the graphene top layer on a graphene buffer layer supported by a Si-terminated 6H-SiC(0001) substrate, respectively. For comparison as well as for examining the lateral strain effects, we also obtain the global barriers of 5.05 and 1.50 eV for single Dy and H atoms penetrating freestanding bilayer graphene with a tensile strain of about 8.8% to match our model for supported graphene, as well as the global barriers of 7.21 and 4.18 eV for penetrating unstrained freestanding bilayer graphene, respectively. From corresponding minimum energy paths with multiple energy minima and saddle points, we can also obtain various local energy barriers and the global backward barrier from the graphene gallery back to the top surface.
Charge carrier mobility of halide perovskite single crystals for ionizing radiation detection
Authors: Zhang Zheng , Saparov Bayram
Published: July 2021

Halide perovskites have recently emerged as promising semiconductor materials for several applications including solar cells, light-emitting diodes, and radiation detectors. The charge carrier transport properties, which could be evaluated by the mobility-lifetime (mu-tau or μ-г) product, serve an important role for the development of halide perovskites for radiation detection applications. In this Perspective, we first explain the charge transport mechanism and the limiting factors that determine the intrinsic charge carrier mobility in halide perovskite single crystals. Then, we overview the techniques and methods that have been employed for evaluating the charge carrier mobility (for both electrons and holes). Finally, we discuss the discrepancy in the experimentally determined carrier mobility from the literature for halide perovskite single crystals, and provide a perspective on future developments for carrier mobility enhancement.
Sufficiently dense Kuramoto networks are globally synchronizing
Authors: Kassabov Martin , Strogatz Steven H. , Townsend Alex
Published: July 2021

Consider any network of n identical Kuramoto oscillators in which each oscillator is coupled bidirectionally with unit strength to at least μ(n−1) other oscillators. There is a critical value of the connectivity, μc, such that whenever μ>μc, the system is guaranteed to converge to the all-in-phase synchronous state for almost all initial conditions, but when μ<μc, there are networks with other stable states. The precise value of the critical connectivity remains unknown, but it has been conjectured to be μc=0.75. In 2020, Lu and Steinerberger proved that μc≤0.7889, and Yoneda, Tatsukawa, and Teramae proved in 2021 that μc>0.6838. This paper proves that μc≤0.75 and explain why this is the best upper bound that one can obtain by a purely linear stability analysis.
A rheological analog for Brownian motion with hydrodynamic memory
Authors: Makris Nicos
Published: July 2021

When the density of the fluid surrounding suspended Brownian particles is appreciable, in addition to the forces appearing in the traditional Ornstein and Uhlenbeck theory of Brownian motion, additional forces emerge as the displaced fluid in the vicinity of the randomly moving Brownian particle acts back on the particle giving rise to long-range force correlations which manifest as a “long-time tail” in the decay of the velocity autocorrelation function known as hydrodynamic memory. In this paper, after recognizing that for Brownian particles immersed in a Newtonian, viscous fluid, the hydrodynamic memory term in the generalized Langevin equation is essentially the 1/2 fractional derivative of the velocity of the Brownian particle, we present a rheological analog for Brownian motion with hydrodynamic memory which consists of a linear dashpot of a fractional Scott Blair element and an inerter. The synthesis of the proposed mechanical network that is suggested from the structure of the generalized Langevin equation simplifies appreciably the calculations of the mean square displacement and its time-derivatives which can also be expressed in terms of the two-parameter Mittag–Leffler function.
Electronic energy transfer in single conjugated polymer molecules revealed by phase-modulated pulse-pair controlled single molecule spectroscopy
Authors: Chen Ruiyun , Li Yao , Guan Wenling , Zhang Guofeng , Qin Chengbing , Hu Jianyong , Xiao Liantuan , Jia Suotang
Published: July 2021

Detailed understanding of the electronic energy transfer dynamics in conjugated polymer molecules and their conformation dependence is central for improving the photophysical properties as well as the performance of devices based on conjugated polymers. In this work, we demonstrate simultaneous measurement of the absorption and emission sites in single conjugated polymer poly[2,7-(9,9-dioctyluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT) molecules based on polarization-resolved confocal fluorescence microscopy with excitation of phase-modulated ultrashort pulse pairs. The evolution of absorbing chromophores can be derived by modulating the relative phase between ultrashort pulse pairs and extracting modulation information in phase-dependent fluorescence. Meanwhile, the emitting chromophore can be measured by polarization-resolved emission. Simultaneous absorption and emission measurements give new insights into the evolution of energy transfer pathways in individual conjugated polymer molecules. The results suggest that the conformation of single conjugated polymer chains can be influenced by solvents. Single PFO-DBT conjugated molecules spin-cast from toluene solution have relatively fixed absorption and emission dipole moments. In contrast, single conjugated polymer molecules prepared with chloroform show multichromophore behavior that is responsible for distribution of absorption and emission in a single chain. The proposed scheme paves the way for further understanding of conformation dependent photophysical properties and the possible role of quantum effects in the energy transfer pathway in both natural and artificial light harvesting systems in the nanoscale.
Dopant-defect interactions in Mg-doped GaN via atom probe tomography
Authors: Licata Olivia G. , Broderick Scott , Rocco Emma , Shahedipour-Sandvik Fatemeh , Mazumder Baishakhi
Published: July 2021

In this work, an in-depth analysis of atomic level dopant-defect interactions in N-polar GaN:Mg was performed using atom probe tomography (APT). The 3D visualization of ion distribution revealed the formation of spherical Mg-rich clusters and the segregation of Mg dopant toward dislocations in MOCVD-grown GaN:Mg. Impurities, such as oxygen and hydrogen, were identified and detected adjacent to Mg-rich dislocations. Crystal stoichiometry around the defect regions was investigated to understand how the defects can influence dopant diffusion. Non-stoichiometric regions of N:Ga were found adjacent to Mg-rich dislocations and overlapping with some Mg-rich clusters, indicating dopant-defect interplay. Variations in N:Ga were not proportional to the Mg content, suggesting that the micro-features (clusters and dislocations) interact differently with local chemistry. Techniques for defining the quality of an APT experiment through invalidation of artifacts are also demonstrated. Mg-rich defects and variations in N:Ga were found to be independent of artifacts related to the evaporation field in APT.
Use of Project ECHO to Promote Evidence Based Care for Justice Involved Adults with Opioid use Disorder
Authors: Adams Zachary W. , Agley Jon , Pederson Casey A. , Bell Lauren A. , Aalsma Matthew C. , Jackson TiAura , Grant Miyah T. , Ott Carol A. , Hulvershorn Leslie A.
Published: July 2021

Background: People with opioid use disorders (OUDs) are at heightened risk for involvement with the criminal justice system. Growing evidence supports the safety and effectiveness of providing empirically supported treatments for OUD, such as medications for OUD (M-OUD), to people with criminal justice involvement including during incarceration or upon reentry into the community. However, several barriers limit availability and accessibility of these treatment options for people with OUDs, including a shortage of healthcare and justice professionals trained in how to implement them. This study evaluated a novel education program, the Indiana Jail OUD Treatment ECHO, designed to disseminate specialty knowledge and improve attitudes about providing M-OUD in justice settings. Methods: Through didactic presentations and case-based learning (10 bimonthly, 90-min sessions), a multidisciplinary panel of specialists interacted with a diverse group of community-based participants from healthcare, criminal justice, law enforcement, and related fields. Participants completed standardized surveys about OUD knowledge and attitudes about delivering M-OUD in correctional settings. Thematic analysis of case presentations was conducted. Results: Among 43 participants with pre- and post-series evaluation data, knowledge about OUD increased and treatment was viewed as more practical after the ECHO series compared to before. Cases presented during the program typically involved complicated medical and psychiatric comorbidities, and recommendations addressed several themes including harm reduction, post-release supports, and integration of M-OUD and non-pharmacological interventions. Conclusions: Evaluation of future iterations of this innovative program should address attendance and provider behavior change as well as patient and community outcomes associated with ECHO participation.
Opioid-Related Incident Severity and Emergency Medical Service Naloxone Administration by Sex in Massachusetts, 2013–2019
Authors: Bettano Amy , Jones Katarina , Fillo Katherine T. , Ficks Ridgely , Bernson Dana
Published: July 2021

Background: A Cross-sectional study of all emergency ambulance runs reported by licensed Emergency Medical Services (EMS) providers between 2013 and 2019 was undertaken to determine if the sex of a patient experiencing opioid-related symptoms had an impact on their odds of receiving naloxone from EMS. Methods: All runs within Massachusetts for individuals 11 years and older with a reported sex between 2013 and 2019 ( n = 5,533,704 runs) were included. Covariates modeled were patient age, year of the incident, and county of the incident. Runs were separated into those that were opioid-related versus not; opioid-related runs were further subdivided into five severity categories including dead on arrival, acute opioid overdose, opioid intoxicated, opioid withdrawal, and other opioid-related incident. Results: Among opioid-related runs, women had 24% lower odds (95% CI 0.68–0.86) of appearing in the dead on arrival category and 20% lower odds (95% CI 0.78–0.82) of appearing in the acute opioid overdose category than men. Among acute opioid overdoses, runs where patient symptoms met Massachusetts EMS guidelines for naloxone administration, women had 18% lower odds (95% CI 0.76–0.89) of receiving naloxone than men. Conclusions: Sex-related differences persist in the odds of naloxone administration by EMS providers when controlling for symptom presentation.
Macrophage-adipocyte communication and cardiac remodeling
Authors: Yepuri Gautham , Hasan Syed Nurul , Schmidt Ann Marie , Ramasamy Ravichandran
Published: July 2021

In obesity complicated by hypertension, multicellular processes integrate to orchestrate cardiac fibrosis; the underlying mechanisms, however, remain elusive. In this issue of JEM, Cheng et al. (2021. J. Exp. Med. https://doi.org/10.1084/jem.20210252) describe adipocyte–macrophage collaboration to foster cardiac fibrosis through the actions of angiotensin II in obesity.
Geodesic scattering on hyperboloids and Knörrer’s map
Authors: Veselov A P , Wu L H
Published: July 2021

We use the results of Moser and Knörrer on relations between geodesics on quadrics and solutions of the classical Neumann system to describe explicitly the geodesic scattering on hyperboloids. We explain the relation of Knörrer’s reparametrisation with projectively equivalent metrics on quadrics introduced by Tabachnikov and independently by Matveev and Topalov, giving a new proof of their result. We show that the projectively equivalent metric is regular on the projective closure of hyperboloids and extend Knörrer’s map to this closure.
Physical and mechanical characterization of sand replaced stone dust concrete
Authors: Humayun Muhammad , Ahad Muhammad Zeeshan , Rehman Ghori Ubaid ur , Naveed Amir , Ahmad Fawad , Arif Muhammad , Afridi Shaista , Sadiq Muhammad , Jan Saeed Ullah , Asif Muhammad
Published: July 2021

In this research work, physical, chemical, morphological, and mechanical behavior as partial replacement of fine aggregate in concrete. Stone dust was acquired from three different sources i.e. Nowshera, Dara, and Besai, while concrete was kept at a ratio of 1:2:4 and water to cement ratio at 0.5 as per ASTM standards for considerable workability. The compressive strength, ultrasonic pulse velocity (UPV), its correlation, density, durability test, x-ray fluorescence (XRF) analysis, and Scanning electron microscopy was carried out. Compressive strength at curing ages of 7, 14, and 28 days with 20%, 30%, and 40% replacement of sand was incorporated in concrete. The results indicated a slight increase in compressive strength at 20% replacement level for the Besai Concrete (BC), Nowshera Concrete (NC), and Dara Concrete (DC). For durability analysis; Rapid Chloride Permeability Test (RCPT) carried out on hardened stone dust-based concrete shows that with the addition of stone dust the voids between fine and coarse aggregates are filled up, less charge will pass, and ultimately durability is increased as per ASTM C 1202. The chemical composition of the stone dust samples, through XRF analysis, indicated that Silica dioxide (SiO2) compounds present in (NC), (DC), and (BC) were 13.34%, 12.339% & 11.593% respectively. The maximum compressive strength development in NC was possibly due to the presence of SiO2 compound in excess quantity in Nowshera stone dust as compared to other samples tested. Hence it can be recommended that locally available stone dust in Peshawar and its surrounding are suitable for a maximum of 40% replacement level.
MDContactCom: a tool to identify differences of protein molecular dynamics from two MD simulation trajectories in terms of interresidue contacts
Authors: Motono Chie , Yanagida Shunsuke , Sato Miwa , Hirokawa Takatsugu
Published: July 2021

Comparing results from multiple MD simulations performed under different conditions is essential during the initial stages of analysis. We propose a tool called MD Contact Comparison (MDContactCom) that compares residue-residue contact fluctuations of two MD trajectories, quantifies the differences, identifies sites that exhibit large differences and visualizes those sites on the protein structure. Using this method, it is possible to identify sites affected by varying simulation conditions and reveal the path of propagation of the effect even when differences between the 3D structure of the molecule and the fluctuation RMSF of each residue is unclear. MDContactCom can monitor differences in complex protein dynamics between two MD trajectories and identify candidate sites to be analyzed in more detail. As such, MDContactCom is a versatile software package for analyzing most MD simulations.

Availability and implementation

MDContactCom is freely available for download on GitLab. The software is implemented in Python3. https://gitlab.com/chiemotono/mdcontactcom.

Supplementary information

Supplementary data are available at Bioinformatics online.
Spicoid morphology of Mapanioideae (Cyperaceae): an evolutionary perspective
Authors: Monteiro Mariana M , Demarco Diego , Larridon Isabel , Prychid Christina J , Prenner Gerhard
Published: July 2021

Cyperaceae subfamily Mapanioideae have reproductive units called spicoids, which are interpreted alternatively as flowers or partial inflorescence, and little is known about morphological variation of spicoids from an evolutionary perspective. Combining morphological and evolutionary analyses, we aimed to assess variation in spicoid morphology and its evolutionary significance. Spicoid morphology of 48 species of Mapanioideae was analysed, and variable characters were selected for downstream analyses. The results showed that the general spicoid morphology is consistent within genera and that character states can vary within genera, supporting molecular phylogenetic relationships. The presence of lateral keeled scales, the number of lateral stamens, inner scales, inner stamens and pistil merosity were shown to be variable. Possible ancestral spicoid morphology was reconstructed as resembling the current morphology of Hypolytrum. Based on the most frequent evolutionary changes observed, the increase in the number of parts (number of inner scales, inner stamens and pistil merosity) seems to be a recurrent process in spicoid evolution, contradicting a previous hypothesis that assumed changes in spicoid morphology towards reduction. Combining molecular and morphological analyses allows us to refine our knowledge of the evolutionary history of Mapanioideae and enhances the understanding of the evolution of Cyperaceae.
Kv2.1 Potassium Channels Regulate Repetitive Burst Firing in Extratelencephalic Neocortical Pyramidal Neurons
Authors: Newkirk Greg S , Guan Dongxu , Dembrow Nikolai , Armstrong William E , Foehring Robert C , Spain William J
Published: July 2021

Coincidence detection and cortical rhythmicity are both greatly influenced by neurons’ propensity to fire bursts of action potentials. In the neocortex, repetitive burst firing can also initiate abnormal neocortical rhythmicity (including epilepsy). Bursts are generated by inward currents that underlie a fast afterdepolarization (fADP) but less is known about outward currents that regulate bursting. We tested whether Kv2 channels regulate the fADP and burst firing in labeled layer 5 PNs from motor cortex of the Thy1-h mouse. Kv2 block with guangxitoxin-1E (GTx) converted single spike responses evoked by dendritic stimulation into multispike bursts riding on an enhanced fADP. Immunohistochemistry revealed that Thy1-h PNs expressed Kv2.1 (not Kv2.2) channels perisomatically (not in the dendrites). In somatic macropatches, GTx-sensitive current was the largest component of outward current with biophysical properties well-suited for regulating bursting. GTx drove ~40% of Thy1 PNs stimulated with noisy somatic current steps to repetitive burst firing and shifted the maximal frequency-dependent gain. A network model showed that reduction of Kv2-like conductance in a small subset of neurons resulted in repetitive bursting and entrainment of the circuit to seizure-like rhythmic activity. Kv2 channels play a dominant role in regulating onset bursts and preventing repetitive bursting in Thy1 PNs.
Optogenetic Activation of Interneuron Subtypes Modulates Visual Contrast Responses of Mouse V1 Neurons
Authors: Shapiro Jared T , Michaud Nicole M , King Jillian L , Crowder Nathan A
Published: July 2021

Interneurons are critical for information processing in the cortex. In vitro optogenetic studies in mouse primary visual cortex (V1) have sketched the connectivity of a local neural circuit comprising excitatory pyramidal neurons and distinct interneuron subtypes that express parvalbumin (Pvalb+), somatostatin (SOM+), or vasoactive intestinal peptide (VIP+). However, in vivo studies focusing on V1 orientation tuning have ascribed discrepant computational roles to specific interneuron subtypes. Here, we sought to clarify the differences between interneuron subtypes by examining the effects of optogenetic activation of Pvalb+, SOM+, or VIP+ interneurons on contrast tuning of V1 neurons while also accounting for cortical depth and photostimulation intensity. We found that illumination of the cortical surface produced a similar spectrum of saturating additive photostimulation effects in all 3 interneuron subtypes, which varied with cortical depth rather than light intensity in Pvalb+ and SOM+ cells. Pyramidal cell modulation was well explained by a conductance-based model that incorporated these interneuron photostimulation effects.