bluuebunny/crossref_metadata_2025 huggingface dataset:
Tapered image charge detector for measuring velocity distributions of submicrometer particle scattering
Authors: Miller Morgan E. C. , Mezher Michelle , Continetti Robert E.
Published: June 2020

A novel detector for measuring the post-impact velocities (trajectory and speed) of charged submicrometer particles is presented. A stack of tapered cylindrically symmetric electrodes connected to a set of image charge detection circuits is used in conjunction with an image-charge-sensitive target to measure the incident velocity and scattered trajectories of charged particles following impact with the target. This particle detector is used in conjunction with a mass, charge, and energy-selected source of collimated charged particles. Polystyrene latex spheres were used to characterize the performance of the detector, and examples of scattering trajectories are analyzed to demonstrate detector functionality. Measurements of the coefficient of restitution for 500 nm diameter tin particles are also reported and compared with previous measurements performed with a simpler image-charge detector. Finally, the angular distribution for 500 nm tin particles scattering from highly polished molybdenum at an incident velocity of 150 m/s is reported.
Molecule hopping images reveal adsorption behavior of organic semiconductor on silicon surface
Authors: Patrick Chris
Published: June 2020

Scanning tunneling microscopy shows how the organic semiconductor cobalt phthalocyanine adsorbs on dangling bond defects in a silicon-boron system.
Kinetic theory of low-voltage beam discharge instability in rare gases
Authors: Sukhomlinov V. , Matveev R. , Mustafaev A. , Timofeev N.
Published: June 2020

The kinetic theory of a low-voltage beam discharge instability in He is developed in the conditions, when the distance between electrodes is of the order of electron–atom collision length and the density of electrons in a primary beam is up to ten percent of the plasma density. The dispersion equation and its numerical and analytical solutions are obtained. The stability loss of this discharge is described in the framework of the problem with initial and boundary conditions. A significant dispersion is found in the propagation of harmonic disturbances in this system. On the basis of the developed theory, the areas of applicability of the hydrodynamic approach to the consideration of the system “cold electron beam - cold plasma” are elucidated. The theory significantly expands the range of parameters of the electron beam–plasma system, where a quantitative description of the spatial and temporal dynamics of wave propagation in such a system is possible. In the well-known special cases, such as a “weak electron beam - cold plasma,” the results obtained coincide with the data of other authors.
The regime of multi-stage trapping in free-electron lasers operating in the super-radiant and SASE regimes
Authors: Savilov A. V.
Published: June 2020

The use of electron–wave interaction systems consisting of several tapered sections is considered as a method of efficiency enhancement of free-electron lasers (FELs) operating in different regimes of emission of a short wave pulse from a short electron bunch. These regimes are the principally multi-frequency self-amplified spontaneous emission regime traditionally used in short-wavelength FELs and the regime of electron–wave group synchronism, in which super-radiation of a quasi-monochromatic wave packet propagating together with the electron bunch occurs. In both the cases, the use of multi-stage trapping of electrons in the bunch by the radiated wave provides a significant (at least by an order of magnitude) increase in efficiency as compared to the saturated-stage efficiency in regular systems.
Large-area microwire MoSi single-photon detectors at 1550 nm wavelength
Authors: Charaev I. , Morimoto Y. , Dane A. , Agarwal A. , Colangelo M. , Berggren K. K.
Published: June 2020

We demonstrate saturated internal detection efficiency at 1550 nm wavelengths for meander-shaped superconducting nanowire single-photon detectors made of 3 nm thick MoSi films with widths of 1 and 3 μm and active areas up to 400 × 400 μm2. Despite hairpin turns and a large number of squares (up to 104) in the device, the dark count rate was measured to be ∼103 cps at 99% of the switching current. This value is about two orders of magnitude lower than the results reported recently for short MoSi devices with shunt resistors. We also found that 5 nm thick MoSi detectors with the same geometry were insensitive to single near-infrared photons, which may be associated with different levels of suppression of the superconducting order parameter. However, our results obtained on 3 nm thick MoSi devices are in good agreement with predictions in the frame of a kinetic-equation approach.
Investigation of magnetic anisotropy and heat dissipation in thin films of compensated antiferromagnet CuMnAs by pump–probe experiment
Authors: Surýnek M. , Saidl V. , Kašpar Z. , Novák V. , Campion R. P. , Wadley P. , Němec P.
Published: June 2020

We recently reported on a method to determine the easy axis position in a 10 nm thick film of the fully compensated antiferromagnet CuMnAs. The film had a uniaxial magnetic anisotropy and the technique utilized a magneto-optical pump and probe experiment [Saidl et al. Nat. Photonics 11, 91 (2017)]. In this contribution, we discuss the applicability of this method for the investigation of a broader set of epitaxial CuMnAs films having different thicknesses. This work reveals that the equilibrium magnetic anisotropy can be studied only in samples, where this anisotropy is rather strong. However, in the majority of CuMnAs films, the impact of a strong pump pulse induces nano-fragmentation of the magnetic domains and, therefore, the magnetic anisotropy measured by the pump–probe technique differs substantially from that in the equilibrium conditions. We also demonstrate that the optical pump–probe experiment can be used very efficiently to study the local heating and heat dissipation in CuMnAs epitaxial layers. In particular, we determined the electron–phonon relaxation time in CuMnAs. We also observed that, for a local film heating by a focused laser, the thinner films are heated more, but the heat is dissipated considerably faster than in the case of thicker films. This illustrates that the optical pump–probe experiment is a valuable characterization tool for the heat management optimization in the CuMnAs memory devices and can be applied in a similar way to those used during the heat-assisted magnetic recording technology development for the latest generation of hard drive disks.
Superconducting microwire detectors based on WSi with single-photon sensitivity in the near-infrared
Authors: Chiles J. , Buckley S. M. , Lita A. , Verma V. B. , Allmaras J. , Korzh B. , Shaw M. D. , Shainline J. M. , Mirin R. P. , Nam S. W.
Published: June 2020

We report on the fabrication and characterization of single-photon-sensitive WSi superconducting detectors with wire widths from 1 μm to 3 μm. The devices achieve the saturated internal detection efficiency at a wavelength of 1.55 μm and exhibit maximum count rates in excess of 105 s−1. We also investigate the material properties of the silicon-rich WSi films used for these devices. We find that many devices with active lengths of several hundred micrometers exhibit critical currents in excess of 50% of the depairing current. A meandered detector with a 2.0 μm wire width is demonstrated over a surface area of 362 × 362 μm2, showcasing the material and device quality achieved.
Effect of electron kinetics on plasma density in inductively coupled plasmas using a passive resonant antenna
Authors: Kim Ju-Ho , Chung Chin-Wook
Published: June 2020

We investigated the profiles of electron and ion densities dependence on the gas pressure in the inductively coupled plasma with a passive resonant antenna. The inner powered antenna and the passive resonant antenna are independently installed on the top of the chamber, and a power of 13.56 MHz is applied to the powered antenna. A significant change in the plasma density profile is observed when the capacitance of the passive resonant antenna is adjusted from non-resonance to resonance. At a high pressure of 50 mTorr, the point of maximum electron density and temperature shift from near the powered antenna to near the passive resonant antenna. However, at a low pressure of 1 mTorr, the profile of the electron density and temperature hardly change, and the maximum electron density at resonance increases about 1.4 times (at 150 W) to 4 times (at 50 W) higher than at non-resonance. The controllability of the electron density profile, which depends on the gas pressure, can be understood by the electron kinetics effect, and the increase in the electron density can be explained by the increase in power transfer efficiency calculated from the circuit model. The electron density profile at bulk is compared to the ion density distribution at the wafer-level, and the results are discussed with the relevant physical mechanisms.
All-fiber focused beam generator integrated on an optical fiber tip
Authors: Yu Jian , Wang Yi-Ping , Yang Wu , Bai Zhi-Yong , Xie Zhenwei , Liu Zhao , Liao Chang-Rui
Published: June 2020

We report a compact all-fiber focused vortex beam generator, where a spiral zone plate (SZP) is integrated on the tip of a composite optical fiber microstructure with the femtosecond laser two-photon polymerization. The experimental characteristics of the beam produced from the focused vortex beam generators, such as the focal length, focal spot diameter, and vortex topological charge, are in excellent agreement with the results from finite-difference time-domain simulations. Adjusting the design parameters of the SZP integrated on the fiber tip, we can realize the precise manipulation of the generator’s output light field. Since the intrinsic high divergence of a vortex beam during propagation is effectively overcome, the generators may have potential applications for optical fiber optical wrench, all-fiber stimulated emission depletion microscopy, or orbital angular momentum fiber communication. Moreover, the compact generators also have a good anti-interference ability and long-term stability.
A realistic non-local heat engine based on Coulomb-coupled systems
Authors: Singha Aniket
Published: June 2020

Optimal non-local heat engines based on Coulomb-coupled systems demand a sharp step-like change in the energy-resolved system-to-reservoir coupling around the ground state of quantum dots. Such a sharp step-like transition in the system-to-reservoir coupling cannot be achieved in a realistic scenario. Here, I propose a realistic design for a non-local heat engine based on the Coulomb-coupled system, which circumvents the need for any change in the system-to-reservoir coupling, demanded by the optimal setups discussed in the literature. I demonstrate that an intentionally introduced asymmetry (or energy difference) in the ground state configuration between adjacent tunnel-coupled quantum dots, in conjugation with Coulomb coupling, is sufficient to convert the stochastic fluctuations from a non-local heat source into a directed flow of thermoelectric current. The performance, along with the regime of operation, of the proposed heat engine is then theoretically investigated using the quantum master-equation approach. It is demonstrated that the theoretical maximum power output for the proposed setup is limited to about 50% of the optimal design. Despite a lower performance compared to the optimal setup, the novelty of the proposed design lies in the conjunction of fabrication simplicity along with a reasonable power output. At the end, the sequential transport processes leading to a performance deterioration of the proposed setup are analyzed and a method to alleviate such transport processes is discussed. The setup proposed in this paper can be used to design and fabricate high-performance non-local cryogenic heat engines.
Superconducting levitation of a mg-scale cavity mirror
Authors: Jiang Xiaodong , Rudge Josiah , Hosseini Mahdi
Published: June 2020

We demonstrate an optomechanical platform based on a levitated small high reflective (HR)-coated mirror above a superconductor disk. We use this levitated mirror at ambient condition to detect the magnetic field with a sensitivity of 370 pT /Hz. Moreover, the levitated mirror is used as the end mirror of a Fabry–Pérot cavity to create an optical resonance that could be used to study coherent radiation pressure forces. The platform provides a sensitive tool to measure the various forces exerted on the mirror and it offers the possibility of the coherent optical trapping of macroscopic objects.
Comment on “The asymptotic iteration method revisited” [J. Math. Phys. 61, 033501 (2020)]
Authors: Fernández Francisco M.
Published: June 2020

In this comment, we show that the eigenvalues of a quartic anharmonic oscillator obtained recently by means of the asymptotic iteration method may not be as accurate as the authors claim them to be.
Influence of toroidal rotation from electron cyclotron resonance heating in KSTAR
Authors: Lee S. G.
Published: June 2020

Toroidal rotation behaviors from electron cyclotron resonance heating (ECH) injected Ohmic and high confinement mode (H-mode) plasmas are investigated in KSTAR. The on-axis ECH injection induces core toroidal rotation reversal by neoclassical toroidal viscosity (NTV) damping torque coincided with trapped electron mode (TEM)-driven co-current rotation torque in the countercurrent rotating Ohmic plasmas. In the ECH triggered H-mode plasmas with enhanced heating power, the toroidal rotation in the central region turns to the countercurrent direction and co-current direction in the outer region of the plasma.
Surface plasmon coupling for selectively enhanced random lasing in periodically patterned silver columnar thin film metamaterials
Authors: Kumar Rajesh , Tiwari Anjani Kumar , Anantha Ramakrishna S.
Published: June 2020

Periodically patterned sculptured plasmonic thin films, consisting of forests of nanocolumns of metals like silver on a periodic grating, offer a very rich landscape for light–matter interactions. Multiple light scattering, plasmonic resonances, anisotropy, hyperbolic dispersions, and Bragg scattering: a plethora of effects come together in these systems to offer various possibilities. We realize an efficient random laser by infiltrating a laser dye into such a grating of silver nanocolumns and optically pumping the system. The densely packed plasmonic nanocolumns provide feedback through efficient scattering, while the optically pumped dye solution in the voids provides for amplification. The periodicity and anisotropy provide for an angle and polarization selective enhanced coupling of the pump laser via the propagating surface plasmon resonances in the system.
Design and fabrication of field-plated normally off
β
-Ga2O3 MOSFET with laminated-ferroelectric charge storage gate for high power application
Authors: Feng Zhaoqing , Cai Yuncong , Li Zhe , Hu Zhuangzhuang , Zhang Yanni , Lu Xing , Kang Xuanwu , Ning Jing , Zhang Chunfu , Feng Qian , Zhang Jincheng , Zhou Hong , Hao Yue
Published: June 2020

In this work, an enhancement-mode (E-mode) β-Ga2O3 metal-oxide-semiconductor field-effect transistor (MOSFET) has been achieved by incorporating a laminated-ferroelectric charge storage gate (L-FeG) structure [Al2O3/HfO2/Al2O3/Hf0.5Zr0.5O2 (HZO) of 10/5/2/16 nm]. The band diagram between L-FeG dielectrics (Al2O3, HfO2, and HZO) and β-Ga2O3 was determined by x-ray photoelectron spectroscopy. After applying a gate pulse with an intensity of +18 V and width of 1 ms, the saturation current of the E-mode device was measured to be 23.2 mA/mm, which shows a negligible current reduction compared to that of 22.1 mA/mm in a depletion- (D-) mode device. In addition, the threshold voltage (VTH) is only shifted by 2.76% and 2.18%, respectively, after applying the gate stress and gate-drain stress of 15 V for 104 s. Meanwhile, a high breakdown voltage of 2142 V and specific on-resistance (RON,sp) of 23.84 mΩ·cm2 were also achieved, which correspond to a state-of-art high power figure of merit of 192.5 MW/cm2, showing the great potential of combing the ferroelectric gate stack and lateral Ga2O3 MOSFET as next generation power devices.
Magnetic field dependence of the effective magnetic moment of multi-core nanoparticles
Authors: Kahmann Tamara , Ludwig Frank
Published: June 2020

The magnetic moment of magnetic nanoparticles (MNPs) is one of the key parameters for various applications. We have experimentally studied the effective magnetic moment of multi-core MNPs and especially their dependence on the applied magnetic field. In contrast to single-core MNPs, the situation is considerably more complex since the effective magnetic moment depends on the size of individual crystallites, their packing density, core configuration, and, thus, the interaction between them. Different approaches to determine the effective magnetic moment are applied for two multi-core MNP systems (FeraSpin XL and BNF Starch). The effective magnetic moment at low magnetic fields is obtained from the ac susceptibility spectra measured at ac field amplitudes up to 9 mT. The obtained values are compared with the high-field values measured at 7 T. In the small-field range (up to 9 mT), a linear field dependence of the effective magnetic moment is found for FeraSpin XL while the value of BNF Starch was found to be nearly constant. The low-field values of both MNP systems are smaller than the values at larger fields, proving the magnetic field dependence of the effective magnetic moment of multi-core MNPs. The estimated values are discussed within a simple model. A consistent picture was found for BNF Starch while the model fails for FeraSpin XL. The different behaviors of both studied multi-core MNP systems are related to the magnetic interactions between the individual crystallites inside a multi-core structure, which are strong for FeraSpin XL due to the high packing density of the crystallites.
Non-adiabatic transitions in the reaction of fluorine with methane
Authors: Zhao Bin , Manthe Uwe
Published: June 2020

Reactions of methane with different atoms are benchmark examples of elementary reaction processes intensively studied by theory and experiment. Due to the presence of conical intersections and spin–orbit coupling, non-adiabatic transitions can occur in reactions with F, Cl, or O atoms. Extending detailed quantum theory beyond the Born–Oppenheimer approximation for polyatomic reaction processes, non-adiabatic wave packet dynamics calculations studying the F(2P3/2)/F*(2P1/2) + CHD3 → HF + CD3 reaction on accurate vibronically and spin–orbit coupled diabatic potential energy surfaces are presented. Non-adiabatic transitions are found to increase the reactivity compared to Born–Oppenheimer theory and are more prominent than in triatomic reactions previously studied. Furthermore, the lifetimes of reactive resonances are reduced. The reactivity of F(2P3/2) is found to exceed the one of F*(2P1/2) even at low collision energies.
A common rule governing differentiation kinetics of mouse cortical progenitors
Authors: Sahara Setsuko , Kodama Takashi , Stevens Charles F.
Published: June 2020

The balance between proliferation and differentiation of stem cells and progenitors determines the size of an adult brain region. While the molecular mechanisms regulating proliferation and differentiation of cortical progenitors have been intensively studied, an analysis of the kinetics of progenitor choice between self-renewal and differentiation in vivo is, due to the technical difficulties, still unknown. Here we established a descriptive mathematical model to estimate the probability of self-renewal or differentiation of cortical progenitor behaviors in vivo, a variable we have termed the expansion coefficient. We have applied the model, one which depends only on experimentally measured parameters, to the developing mouse cortex where the expansive neuroepithelial cells and neurogenic radial glial progenitors are coexisting. Surprisingly, we found that the expansion coefficients of both neuroepithelium cells and radial glial progenitors follow the same developmental trajectory during cortical development, suggesting a common rule governing self-renewal/differentiation behaviors in mouse cortical progenitor differentiation.
On-demand modulation of 3D-printed elastomers using programmable droplet inclusions
Authors: Mea Hing Jii , Delgadillo Luis , Wan Jiandi
Published: June 2020

One of the key thrusts in three-dimensional (3D) printing and direct writing is to seamlessly vary composition and functional properties in printed constructs. Most inks used for extrusion-based printing, however, are compositionally static and available approaches for dynamic tuning of ink composition remain few. Here, we present an approach to modulate extruded inks at the point of print, using droplet inclusions. Using a glass capillary microfluidic device as the printhead, we dispersed droplets in a polydimethylsiloxane (PDMS) continuous phase and subsequently 3D printed the resulting emulsion into a variety of structures. The mechanical characteristics of the 3D-printed constructs can be tuned in situ by varying the spatial distribution of droplets, including aqueous and liquid metal droplets. In particular, we report the use of poly(ethylene glycol) diacrylate (PEGDA) aqueous droplets for local PDMS chemistry alteration resulting in significant softening (85% reduced elastic modulus) of the 3D-printed constructs. Furthermore, we imparted magnetic functionality in PDMS by dispersing ferrofluid droplets and rationally designed and printed a rudimentary magnetically responsive soft robotic actuator as a functional demonstration of our droplet-based strategy. Our approach represents a continuing trend of adapting microfluidic technology and principles for developing the next generation of additive manufacturing technology.
Vaccination as a social contract
Authors: Korn Lars , Böhm Robert , Meier Nicolas W. , Betsch Cornelia
Published: June 2020

Most vaccines protect both the vaccinated individual and the society by reducing the transmission of infectious diseases. In order to eliminate infectious diseases, individuals need to consider social welfare beyond mere self-interest—regardless of ethnic, religious, or national group borders. It has therefore been proposed that vaccination poses a social contract in which individuals are morally obliged to get vaccinated. However, little is known about whether individuals indeed act upon this social contract. If so, vaccinated individuals should reciprocate by being more generous to a vaccinated other. On the contrary, if the other doesn’t vaccinate and violates the social contract, generosity should decline. Three preregistered experiments investigated how a person’s own vaccination behavior, others’ vaccination behavior, and others’ group membership influenced a person’s generosity toward respective others. The experiments consistently showed that especially compliant (i.e., vaccinated) individuals showed less generosity toward nonvaccinated individuals. This effect was independent of the others’ group membership, suggesting an unconditional moral principle. An internal metaanalysis (n= 1,032) confirmed the overall social contract effect. In a fourth experiment (n= 1,212), this pattern was especially pronounced among vaccinated individuals who perceived vaccination as a moral obligation. It is concluded that vaccination is a social contract in which cooperation is the morally right choice. Individuals act upon the social contract, and more so the stronger they perceive it as a moral obligation. Emphasizing the social contract could be a promising intervention to increase vaccine uptake, prevent free riding, and, eventually, support the elimination of infectious diseases.
Direct discrimination of structured light by humans
Authors: Sarenac Dusan , Kapahi Connor , Silva Andrew E. , Cory David G. , Taminiau Ivar , Thompson Benjamin , Pushin Dmitry A.
Published: June 2020

Significance

Recent technological advances have enabled the creation of custom light fields with remarkable properties. Here we report an experiment that merges human visual perception with structured wavefronts and optical states that are nonseparable in polarization and spatial modes of light. We demonstrate that humans are able to discriminate between two polarization-coupled orbital angular momentum states with a high probability when directly viewing a structured light beam. The work brings the techniques of structured light to visual science applications and paves the way for methods of characterizing the structure of the macula and conducting experiments with human detectors and optical states with nonseparable modes.
A seawater throttle on H
2
production in Precambrian serpentinizing systems
Authors: Tutolo Benjamin M. , Seyfried William E. , Tosca Nicholas J.
Published: June 2020

Significance

Our current understanding of the redox state of Earth’s ancient atmosphere is heavily dependent on the assumption that ancient low-temperature serpentinizing systems produced abundant H
2
, as they do today. Here, we examine this assumption using data that constrain Fe partitioning in serpentine minerals. We find that H
2
production is linked to a Si deficiency in the serpentine structure, which itself is caused by low SiO
2
(aq) concentrations in fluids derived from modern seawater. Calculations accounting for this dependence of H
2
production on seawater SiO
2
(aq) imply that Precambrian serpentinizing systems would have produced up to about two orders of magnitude less H
2
than today, prompting a reexamination of atmospheric redox state and H
2
-dependent origins of life scenarios on early Earth.
The Whi2p-Psr1p/Psr2p complex regulates interference competition and expansion of cells with competitive advantage in yeast colonies
Authors: Maršíková Jana , Pavlíčková Martina , Wilkinson Derek , Váchová Libuše , Hlaváček Otakar , Hatáková Ladislava , Palková Zdena
Published: June 2020

Yeast form complex highly organized colonies in which cells undergo spatiotemporal phenotypic differentiation in response to local gradients of nutrients, metabolites, and specific signaling molecules. Colony fitness depends on cell interactions, cooperation, and the division of labor between differentiated cell subpopulations. Here, we describe the regulation and dynamics of the expansion of papillae that arise during colony aging, which consist of cells that overcome colony regulatory rules and disrupt the synchronized colony structure. We show that papillae specifically expand within the U cell subpopulation in differentiated colonies. Papillae emerge more frequently in some strains than in others. Genomic analyses further revealed that the Whi2p-Psr1p/Psr2p complex (WPPC) plays a key role in papillae expansion. We show that cells lacking a functional WPPC have a sizable interaction-specific fitness advantage attributable to production of and resistance to a diffusible compound that inhibits growth of other cells. Competitive superiority and high relative fitness of
whi2
and
psr1psr2
strains are particularly pronounced in dense spatially structured colonies and are independent of TORC1 and Msn2p/Msn4p regulators previously associated with the WPPC function. The WPPC function, described here, might be a regulatory mechanism that balances cell competition and cooperation in dense yeast populations and, thus, contributes to cell synchronization, pattern formation, and the expansion of cells with a competitive fitness advantage.
Probing and manipulating embryogenesis via nanoscale thermometry and temperature control
Authors: Choi Joonhee , Zhou Hengyun , Landig Renate , Wu Hai-Yin , Yu Xiaofei , Von Stetina Stephen E. , Kucsko Georg , Mango Susan E. , Needleman Daniel J. , Samuel Aravinthan D. T. , Maurer Peter C. , Park Hongkun , Lukin Mikhail D.
Published: June 2020

Understanding the coordination of cell-division timing is one of the outstanding questions in the field of developmental biology. One active control parameter of the cell-cycle duration is temperature, as it can accelerate or decelerate the rate of biochemical reactions. However, controlled experiments at the cellular scale are challenging, due to the limited availability of biocompatible temperature sensors, as well as the lack of practical methods to systematically control local temperatures and cellular dynamics. Here, we demonstrate a method to probe and control the cell-division timing in
Caenorhabditis elegans
embryos using a combination of local laser heating and nanoscale thermometry. Local infrared laser illumination produces a temperature gradient across the embryo, which is precisely measured by in vivo nanoscale thermometry using quantum defects in nanodiamonds. These techniques enable selective, controlled acceleration of the cell divisions, even enabling an inversion of division order at the two-cell stage. Our data suggest that the cell-cycle timing asynchrony of the early embryonic development in
C. elegans
is determined independently by individual cells rather than via cell-to-cell communication. Our method can be used to control the development of multicellular organisms and to provide insights into the regulation of cell-division timings as a consequence of local perturbations.
Intrinsically stretchable electrode array enabled in vivo electrophysiological mapping of atrial fibrillation at cellular resolution
Authors: Liu Jia , Zhang Xinyuan , Liu Yuxin , Rodrigo Miguel , Loftus Patrick D. , Aparicio-Valenzuela Joy , Zheng Jukuan , Pong Terrence , Cyr Kevin J. , Babakhanian Meghedi , Hasi Jasmine , Li Jinxing , Jiang Yuanwen , Kenney Christopher J. , Wang Paul J. , Lee Anson M. , Bao Zhenan
Published: June 2020

Significance

Electrophysiological mapping of chronic atrial fibrillation (AF) at high throughput and high resolution is critical for understanding its underlying mechanism and guiding definitive treatment such as cardiac ablation, but current electrophysiological tools are limited by either low spatial resolution or electromechanical uncoupling of the beating heart. We herein introduce a microfabricated high-density, fully elastic electrode (termed elastrode) array for complex electrophysiological signal recording in vivo. We demonstrated the capability to identify clinically relevant electrophysiological heterogeneity in the pathologic state of pacing-induced chronic AF that was captured and correlated with state-of-the-art clinical techniques, which show the potential to apply this elastrode array toward elucidating the mechanism of AF at a cellular level and developing targeted AF therapy.
Impact of α-synuclein pathology on transplanted hESC-derived dopaminergic neurons in a humanized α-synuclein rat model of PD
Authors: Hoban Deirdre B. , Shrigley Shelby , Mattsson Bengt , Breger Ludivine S. , Jarl Ulla , Cardoso Tiago , Nelander Wahlestedt Jenny , Luk Kelvin C. , Björklund Anders , Parmar Malin
Published: June 2020

Significance

Stem cell-based dopamine (DA) neuron replacement holds great potential for the treatment of Parkinson’s disease (PD). Preclinical assessments have largely been limited to transplantation in the standard 6-hydroxydopamine toxin model of PD which does not reflect the pathological features of the disease. Here, we have developed and characterized an accelerated and humanized α-synuclein model of PD which better recapitulates the behavioral and pathological features of PD. We transplanted hESC-derived DA neurons in this model, finding they could survive, innervate, and integrate into host circuitry but that some grafted cells acquired the α-synuclein pathology at later time points. This has previously been observed in some patients who received fetally derived DA grafts but has thus far been difficult to model preclinically.
Protein complex stoichiometry and expression dynamics of transcription factors modulate stem cell division
Authors: Clark Natalie M. , Fisher Adam P. , Berckmans Barbara , Van den Broeck Lisa , Nelson Emily C. , Nguyen Thomas T. , Bustillo-Avendaño Estefano , Zebell Sophia G. , Moreno-Risueno Miguel A. , Simon Rüdiger , Gallagher Kimberly L. , Sozzani Rosangela
Published: June 2020

Stem cells divide and differentiate to form all of the specialized cell types in a multicellular organism. In the
Arabidopsis
root, stem cells are maintained in an undifferentiated state by a less mitotically active population of cells called the quiescent center (QC). Determining how the QC regulates the surrounding stem cell initials, or what makes the QC fundamentally different from the actively dividing initials, is important for understanding how stem cell divisions are maintained. Here we gained insight into the differences between the QC and the cortex endodermis initials (CEI) by studying the mobile transcription factor SHORTROOT (SHR) and its binding partner SCARECROW (SCR). We constructed an ordinary differential equation model of SHR and SCR in the QC and CEI which incorporated the stoichiometry of the SHR-SCR complex as well as upstream transcriptional regulation of SHR and SCR. Our model prediction, coupled with experimental validation, showed that high levels of the SHR-SCR complex are associated with more CEI division but less QC division. Furthermore, our model prediction allowed us to propose the putative upstream SHR regulators SEUSS and WUSCHEL-RELATED HOMEOBOX 5 and to experimentally validate their roles in QC and CEI division. In addition, our model established the timing of QC and CEI division and suggests that SHR repression of QC division depends on formation of the SHR homodimer. Thus, our results support that SHR-SCR protein complex stoichiometry and regulation of SHR transcription modulate the division timing of two different specialized cell types in the root stem cell niche.
RNA-dependent sterol aspartylation in fungi
Authors: Yakobov Nathaniel , Fischer Frédéric , Mahmoudi Nassira , Saga Yusuke , Grube Christopher D. , Roy Hervé , Senger Bruno , Grob Guillaume , Tatematsu Shunsuke , Yokokawa Daisuke , Mouyna Isabelle , Latgé Jean-Paul , Nakajima Harushi , Kushiro Tetsuo , Becker Hubert D.
Published: June 2020

Significance

Bacteria are known to add amino acids (aa) to membrane lipids to resist antimicrobials and escape immune responses. This surface lipid aminoacylation process requires diverting aminoacyl-tRNAs from protein synthesis. While widespread in bacteria, no analogous lipid remodeling system had thus far been evidenced in eukaryotes. We uncovered that most fungi tRNA-dependently add aspartate onto ergosterol (ergosteryl-3β-
O
-
l
-aspartate [Erg-Asp]), the major sterol found in fungal membranes. Asp addition is catalyzed by an ergosteryl-3β-
O
-
l
-aspartate synthase (ErdS) and its removal by a dedicated hydrolase (ErdH). This pathway is conserved across “higher” fungi, including pathogens. Given the central roles of sterols and derivatives in fungi, we propose that the Erg-Asp homeostasis system might impact membrane remodeling, trafficking, antimicrobial resistance, or pathogenicity.
Wounding-induced changes in cellular pressure and localized auxin signalling spatially coordinate restorative divisions in roots
Authors: Hoermayer Lukas , Montesinos Juan Carlos , Marhava Petra , Benková Eva , Yoshida Saiko , Friml Jiří
Published: June 2020

Wound healing in plant tissues, consisting of rigid cell wall-encapsulated cells, represents a considerable challenge and occurs through largely unknown mechanisms distinct from those in animals. Owing to their inability to migrate, plant cells rely on targeted cell division and expansion to regenerate wounds. Strict coordination of these wound-induced responses is essential to ensure efficient, spatially restricted wound healing. Single-cell tracking by live imaging allowed us to gain mechanistic insight into the wound perception and coordination of wound responses after laser-based wounding in
Arabidopsis
root. We revealed a crucial contribution of the collapse of damaged cells in wound perception and detected an auxin increase specific to cells immediately adjacent to the wound. This localized auxin increase balances wound-induced cell expansion and restorative division rates in a dose-dependent manner, leading to tumorous overproliferation when the canonical TIR1 auxin signaling is disrupted. Auxin and wound-induced turgor pressure changes together also spatially define the activation of key components of regeneration, such as the transcription regulator ERF115. Our observations suggest that the wound signaling involves the sensing of collapse of damaged cells and a local auxin signaling activation to coordinate the downstream transcriptional responses in the immediate wound vicinity.
Clonally expanding smooth muscle cells promote atherosclerosis by escaping efferocytosis and activating the complement cascade
Authors: Wang Ying , Nanda Vivek , Direnzo Daniel , Ye Jianqin , Xiao Sophia , Kojima Yoko , Howe Kathryn L. , Jarr Kai-Uwe , Flores Alyssa M. , Tsantilas Pavlos , Tsao Noah , Rao Abhiram , Newman Alexandra A. C. , Eberhard Anne V. , Priest James R. , Ruusalepp Arno , Pasterkamp Gerard , Maegdefessel Lars , Miller Clint L. , Lind Lars , Koplev Simon , Björkegren Johan L. M. , Owens Gary K. , Ingelsson Erik , Weissman Irving L. , Leeper Nicholas J.
Published: June 2020

Significance

Cardiovascular disease remains the world’s leading killer, despite the widespread use of cholesterol-lowering medicines. Recent studies suggest a portion of this residual risk may result from the clonal expansion of cells within the atherosclerotic plaques of diseased blood vessels. How these cells promote inflammation and whether they can be therapeutically targeted remain unclear. The current study suggests that clonally expanding cells may cause disease by triggering the complement cascade while evading immune surveillance. However, these cells also appear to be susceptible to therapies that reactivate phagocytic clearance pathways, suggesting a potential treatment approach for heart disease similar to current oncology efforts directed against the cancer stem cell.
The 3′ processing of antisense RNAs physically links to chromatin-based transcriptional control
Authors: Fang Xiaofeng , Wu Zhe , Raitskin Oleg , Webb Kimberly , Voigt Philipp , Lu Tiancong , Howard Martin , Dean Caroline
Published: June 2020

Significance

RNA-mediated chromatin regulation is central to gene expression in many organisms. However, the mechanisms by which RNA influences the local chromatin environment are still poorly understood. Here, we show how RNA 3′ processing factors, which promote proximal polyadenylation of an
Arabidopsis
antisense transcript, physically associate with the chromatin modifiers FLD/LD/SDG26. The chromatin modifiers exist in a protein complex that inhibits H3K4me1 and H3K36me3 accumulation. By antagonizing transcription, the FLD/LD/SDG26-containing complex promotes H3K27me3 accumulation, reducing transcriptional initiation and elongation rates. This cotranscriptionally mediated chromatin silencing mechanism may be widely relevant for gene regulation in many organisms.
Propensity rules and interference effects in laser-assisted photoionization of helium and neon
Authors: Bertolino Mattias , Busto David , Zapata Felipe , Dahlström Jan Marcus
Published: June 2020

We investigate the angle-resolved photoelectron spectra from laser-assisted photoionization for helium and neon atoms using an ab initio method based on time-dependent surface flux and configuration interaction singles. We find that the shape of the distributions can be interpreted using a propensity rule, an intrinsic difference in the absorption and the emission processes, as well as interference effects between multiple paths to the final angular momentum state. The difference between absorption and emission is hidden in the first sideband in neon due to the multiple competing m channels, while in the second sideband a qualitative difference between absorption and emission is observed. In the m-resolved case, a clear difference is observed already in the first sideband, as exemplified in helium and m-resolved neon.
Dosimetric comparison between single and double isocenters VMAT for SRT with multiple targets
Authors: Lwin Lwin Kyaw Wai , Suriyapee Sivalee , Jumpangern Chotika , Sanghangthum Taweap
Published: June 2020

The focal irradiation approach for brain metastasis (BMs) Stereotactic Radiosurgery (SRS) or Stereotactic Radiotherapy (SRT) has emerged as an important modality for multiple BMs. This study aimed to evaluate the dosimetric effects between single isocentre (SI) and double isocentres (DI) VMAT SRT of multiple brain metastases. Eighteen VMAT SRT plans with varying lesions size, number and distance were simulated on patient CT image using Eclipse treatment planning system version 15. The plan consists of 3 techniques in: 2 coplanar arcs SI, 1 coplanar combine with 2 non-coplanar arcs SI and 2 non-coplanar and 1 coplanar arc DI. The VMAT plans were generated with 21Gy prescription dose to all lesions in 3 fractions. The plans were evaluated in terms of Gradient index (Paddick GI), Conformity index (Paddick CI), and Homogeneity index (ICRU HI) for PTV and V12Gy and V6Gy for normal brain. The same dose constraints were used to optimize for all cases. On the average result from 3 techniques, 3 arcs SI plans and DI were better in GI (14.79±5.83, 13.70±4.72) and CI (0.63±0.08, 0.62±0.09) than 2 arcs SI (17.56±6.15, 0.62±0.11), while HI values was comparable for all techniques. For normal brain, V12Gy for 2 arcs and 3 arcs SI plans were comparable with DI and the volumes of normal brain receiving 6 Gy in 3 arcs SI and DI (77.40 ± 34.30 cm3, 68.94 ± 30.50 cm3) were better than 2 arcs SI (108.10 ± 57.20 cm3). Moreover, the number of arcs, monitoring units and treatment time were also increased and inconvenience in practice in DI. In conclusion, 3 arcs non-coplanar SI VMAT technique presents the suitable in dosimetric evaluation in 2-5 lesions metastases SRT.
Computer-Aided Diagnosis (CAD) to Detect Brain Abnormality from PET Image using Artificial Neural Network (ANN)
Authors: Kusumawardani Y. , Ratianto  , Prajitno P. , Soejoko D. S.
Published: June 2020

PET imaging is powerful to diagnose the presence of abnormalities, staging cancer, and evaluating radiotherapy treatment results. Sometimes, small uptake is not easily visual recognized, hence an additional supporting method for its detection is needed. In this study, Computer-Aided Diagnosis (CAD) of brain abnormalities from PET images using segmentation and classification methods based on a feature in the form of Gray Level CoOccurrence Matrix (GLCM) was developed Artificial Neural Network (ANN) is used to deal with the classification problems arising in this application. We develop CAD in this study using MATLAB. A total number of samples were 360 images with 180 abnormal (14 patient) and 180 normal (20 patient) images were used as training and testing data. The result based on Receiver Operating Characteristic (ROC) illustrated that the training error was 4.22 ± 2.37 % and the test error was 12.30 ± 3.47%. These results mean that this developed CAD system can recognize normal and abnormal brain images.
Current-Voltage Response of Cold White LED Strip to Radiotherapeutic Electron and Photon Beams: A Preliminary Study
Authors: Damulira E , Yusoff MNS , Omar AF , Taib NHM , Kamal SAM , Dani SM , Abdullah R
Published: June 2020

Photonic devices such as photodiodes, phototransistors, solar cells, and charge-coupled devices (CCDs) have been associated with clinical radiation detection in recent studies. Light Emitting Diodes (LEDs) are of low-cost in comparison to photodiodes and available in various flexible designs, including surface mount devices (SMDs). LEDs are purposely designed to emit light, but they can also be implemented for detecting light in a photovoltaic mode. Despite the LED-related merits, a few studies, compared to other photonic devices, especially photodiodes, have adopted them as medical radiation detectors. This research hence exploits the LED’s dual applicability by investigating a cold/cool white LED strip current-voltage (C-V) signal response to photon and electron beams. Radiation parameters such as beam energy, angle of incidence, field size, surface source distance (SSD), and monitor units (prescribed dose) were varied. According to the obtained results, the electron beams induced a 10% higher C-V signal compared to photon beams. An angular dependence was also observed, i.e., the C-V signal fluctuated due to a variation in the irradiation angles; -45°, -25°, 0°, 25°, 45°, and radiation type – photon and electron beams. The C-V signal response to SSD alterations additionally produced bimodal signal graphs, skewed towards shorter SSDs, for all the beams used in this study. Finally, the C-V signal was generally linear to the prescribed dose for both the photon and electron beams. Overall, the response of LEDs to photon and electron beams separately exhibited a similar signal trend for the beam energy, field size, angular dependence, and SSD parameter variations. On the other hand, dose linearity produced contrasting signal trends across the photon and electron beams.
Stopping power ratio databases for proton therapy dose calculation
Authors: Pischom N , Asavaphatiboon S , Tangboonduangjit P , Liamsuwan T
Published: June 2020

In modern radiation therapy, ion beams are increasingly used for cancer treatment. Protons are light ions that have Bragg peak characteristic in the depth dose distribution that is optimal for minimizing dose to surrounding normal tissues. In proton therapy treatment planning, the stopping power ratio (SPR) of a given medium to that of water is used for calculating the water-equivalent pathlength (WEPL) of tissues in the patient. Since SPR is related to the computed tomography (CT) number, the conversion from CT numbers to SPRs can be used to find WEPLs of tissue voxels, which are sequentially applied in selecting the initial proton energy. In this work, we investigated the effect of using different CT number to SPR conversion models on proton pencil beam dose calculation. In the SPR calculation, either elemental mean excitation energy (I-value) from the ICRU report or elemental mass stopping power from SRIM software were used. For each approach, four energy dependent scenarios were investigated. The ICRU model and the SRIM model showed a monotonic correlation of SPRs for most tissue types. The 2D dose distribution was calculated by a MATLAB-based proton therapy treatment planning system, PSPLAN. The results suggest that elemental I-values and elemental mass stopping power can be used interchangeably for SPR calculation. Moreover, CT number to SPR conversion models obtained for specific proton energy and average proton energy did not cause difference in pencil beam dose calculation unless the proton energy was relatively low.