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Jul 2020 • Physical Review Applied

dc SQUID Design with Femtotesla Sensitivity for Quantum-Ready Readouts

I Sochnikov, D Davino, B Kalisky

Among some of the current uses of dc superconducting quantum interference devices (SQUIDs) are qubit readouts and sensors for probing the properties of quantum materials. We present a gradiometric niobium SQUID design with state-of-the-art sensitivity in the femtotesla range, which can be tuned to specific readout requirements. The sensor is a next-generation fractional SQUID with a tightly optimized input coil and a combination of various measures known for restraining parasitic resonances and other detrimental effects. Our design combines the practical usefulness of well-defined pickup loops for well-defined imaging kernel and tunable probing applications with a fractionalization approach to reduce undesired inductances. In addition, our modeling predicts small dimensions for these planar sensors. These features make them of relevance for material studies and for the detection of magnetic fields in small …

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Jul 2020 • Physical Review Letters

Helical Edge States and Quantum Phase Transitions in Tetralayer Graphene

Shi Che, Yanmeng Shi, Jiawei Yang, Haidong Tian, Ruoyu Chen, Takashi Taniguchi, Kenji Watanabe, Dmitry Smirnov, Chun Ning Lau, Efrat Shimshoni, Ganpathy Murthy, Herbert A Fertig

Helical conductors with spin-momentum locking are promising platforms for Majorana fermions. Here we report observation of two topologically distinct phases supporting helical edge states in charge neutral Bernal-stacked tetralayer graphene in Hall bar and Corbino geometries. As the magnetic field B⊥ and out-of-plane displacement field D are varied, we observe a phase diagram consisting of an insulating phase and two metallic phases, with 0, 1, and 2 helical edge states, respectively. These phases are accounted for by a theoretical model that relates their conductance to spin-polarization plateaus. Transitions between them arise from a competition among interlayer hopping, electrostatic and exchange interaction energies. Our work highlights the complex competing symmetries and the rich quantum phases in few-layer graphene.

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Jul 2020 • Rambam Maimonides medical journal 11 (3), 2020

Investigating an Emerging Virus During a Sudden Pandemic Outbreak

Ronit Sarid

At the time of writing, in July 2020, the recently emerging SARS-CoV-2 pandemic has attracted major attention to viral diseases, in particular coronaviruses. In spite of alarming molecular evidence, documentation of interspecies transmission in livestock, and the emergence of two new and relatively virulent human coronaviruses within a 10-year period, many gaps remain in the study and understanding of this family of viruses. This paper provides an overview of our knowledge regarding the coronavirus family, while highlighting their key biological properties in the context of our overall understanding of viral diseases.

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Jun 2020 • Batteries & Supercaps

Cover Feature: Effect of Crystal Structure and Morphology on Na3V2(PO4)2F3 Performances for Na‐Ion Batteries (Batteries & Supercaps 6/2020)

Ayan Mukherjee, Tali Sharabani, Rosy Sharma, Sivan Okashy, Malachi Noked

The Cover Feature illustrates the importance of morphology and crystal structure on the performance of Na 3 V 2 (PO 4) 2 F 3 as a cathode for sodium‐ion batteries. The excellent performance in micro‐hollow spheres is attributed to the orthorhombic crystal structure. More information can be found in the Article by M. Noked and co‐workers.

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Jun 2020 • Scientific reports

Engineering and use of proteinoid polymers and nanocapsules containing agrochemicals

Elisheva Sasson, Ruth Van Oss Pinhasi, Shlomo Margel, Liron Klipcan

To address global challenges such as population growth and climate change, introduction of new technologies and innovations in agriculture are paramount. Polymer-based formulations of agrochemicals have received much attention in recent years, and there is strong motivation to develop agrochemicals that are not harmful to the environment. Proteinoid polymers are produced by thermal step-growth polymerization of natural and unnatural amino acids. Under suitable gentle conditions, the proteinoid polymers may self-assemble to form nano-sized hollow proteinoid nanoparticles (NPs) of a relatively narrow size distribution. Agrochemical molecules may be encapsulated within these hollow proteinoid NPs, integrated in the crude proteinoid shell, or bound covalently/physically to the NP surface. In the present manuscript we prepared and characterized four model proteinoid polymers and NPs: P (KEf), P (KF), P …

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Jun 2020 • arXiv preprint arXiv:2006.14724

Nonlinear resonant X-ray Raman scattering

Johann Haber, Andreas Kaldun, Samuel W Teitelbaum, Alfred QR Baron, Philip H Bucksbaum, Matthias Fuchs, Jerome B Hastings, Ichiro Inoue, Yuichi Inubushi, Dietrich Krebs, Taito Osaka, Robin Santra, Sharon Shwartz, Kenji Tamasaku, David A Reis

We report the observation of a novel nonlinear effect in the hard x-ray range. Upon illuminating Fe and Cu metal foils with intense x-ray pulses tuned near their respective K edges, photons at nearly twice the incoming photon energy are emitted. The signal rises quadratically with the incoming intensity, consistent with two-photon excitation. The spectrum of emitted high-energy photons comprises multiple Raman lines that disperse with the incident photon energy. Upon reaching the double K-shell ionization threshold, the signal strength undergoes a marked rise. Above this threshold, the lines cease dispersing, turning into orescence lines with energies much greater than obtainable by single electron transitions, and additional Raman lines appear. We attribute these processes to electron-correlation mediated multielectron transitions involving double-core hole excitation and various two-electron de-excitation processes to a final state involving one or more L and M core-holes.

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Jun 2020 • Polymers

Antimicrobial properties of polyaniline and polypyrrole decorated with zinc-doped copper oxide microparticles

Moorthy Maruthapandi, Arumugam Saravanan, John HT Luong, Aharon Gedanken

Polyaniline (PANI) and polypyrrole (PPY) were synthesized by carbon dots (CDs) under UV irradiation and then sonicated together with zinc acetate and copper acetate to form the [email protected] and [email protected] composites. The former consisted of agglomerated spherical particles with diameters of 1–5 µm, whereas the latter displayed irregular stick shapes with similar diameters. The bacterial potency of the composites against Escherichia coli and Staphylococcus aureus was enhanced remarkably with Zn doping in the CuO matrix, designated as Zn 0.11 Cu 0.89 O, at 0.144 mg/mL. The cell death was mainly attributed to the release of reactive oxygen species (ROS) that would severely damage DNA, proteins, and lipids. Bacteria could adhere to neutral surfaces of the composites by van der Waals attractive forces. The binding event disrupted the native surface charge of bacterial cells to induce cell lysis and result in eventual cell death. View Full-Text

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Jun 2020 • Advanced Energy Materials

The Sodium Storage Mechanism in Tunnel‐Type Na0.44MnO2 Cathodes and the Way to Ensure Their Durable Operation

Munseok S Chae, Hyojeong J Kim, Hyeri Bu, Jeyne Lyoo, Ran Attias, Ben Dlugatch, Matan Oliel, Yosef Gofer, Seung‐Tae Hong, Doron Aurbach

Tunnel‐type sodium manganese oxide is a promising cathode material for aqueous/nonaqueous sodium‐ion batteries, however its storage mechanism is not fully understood, in part due to the complicated sodium intercalation process. In addition, low cyclability due to manganese dissolution has limited its practical application in rechargeable batteries. Here, the intricate sodium intercalation mechanism of Na0.44MnO2 is revealed by combination of electrochemical characterization, structure determination from powder X‐ray diffraction data, 3D bond valence difference maps, and barrier‐energy calculations of the sodium diffusion. NaI is proposed as an important electrolyte solution additive. It is shown to form a thin, beneficial, and durable cathode surface film that prevents manganese dissolution. The addition of 0.01 m NaI to electrolyte solutions based on alkyl carbonate solvents and NaClO4 greatly improves …

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Jun 2020 • Investigative Ophthalmology & Visual Science

Cortical responses to prosthetic retinal stimulation are affected by the light-adaptive state of the surrounding normal retina

Yossi Mandel, Tamar Arens-Arad, Rivkah Lender, Nairouz Farah, Thomas Flores, Daniel V Palanker

Purpose: Restoration of central vision in age-related macular degeneration is associated with the intriguing situation where central prosthetic vision co-exists with natural peripheral vision. We studied here the effect of the adaptive state of the normal retina on the responses arising from the retinal prosthesis.Methods: We investigated cortical responses to prosthetic retinal stimulation in wild-type (Long Evans) rats implanted with a 1-mm wide photovoltaic subretinal array. Cortical screw electrodes were implanted over the visual cortex. Cortical responses to prosthetic stimulation elicited by near-infrared (NIR, 910nm) pulses (10ms, 2Hz) of various intensities were recorded in anaesthetized rats following overnight dark-adaption and compared to those following retinal exposure to light (535nm) at various intensities and durations.Results: Robust cortical responses have been observed in dark adapted rats, exhibiting a …

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Jun 2020 • Frontiers in Energy Research

Pin-Hole-Free, Homogeneous, Pure CsPbBr3 Films on Flat Substrates by Simple Spin-Coating Modification

Satyajit Gupta, Michael Kulbak, David Cahen

We show a simple modification of spin-coating to obtain pinhole-free, well-covering and uniform films of an all-inorganic Pb-halide perovskite (Pb-HaP), on a flat substrate (i.e., not mesoporous) at standard temperature and pressure. In Pb-HaP-based devices the active film is generally fabricated by spin-coating. This is a challenging task for purely inorganic Pb-HaPs, as, except if nano-crystallites can be used, mostly rough and inhomogeneous thin films with poor optoelectronic quality are obtained. We describe a gas flow-assisted method to fabricate thin conformal films of phase-pure CsPbBr3. First cells made with the resulting CsPbBr3-films, yield solar conversion efficiencies up to 2.5%. Electron beam-induced current measurements of device cross-sections show uniform charge generation profiles, implying  ~ 0.2 m diffusion lengths. Non-encapsulated devices generate stable photocurrent for > 1 hr under continuous illumination at maximum power in ambient.

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Jun 2020 • ACS Catalysis

The Role of Surface Adsorbed Cl– Complexes in Rechargeable Magnesium Batteries

Ran Attias, Munseok S Chae, Ben Dlugatch, Matan Oliel, Yosef Goffer, Doron Aurbach

Most electrolyte solutions supporting highly reversible Mg deposition/dissolution contain chlorides. These come as charged or neutral complex species, frequently as Mg-based complex ions, and Lewis-base anions. The electroactive species are usually comprised also of solvent molecules and chlorides as ligands. Numerous studies had shown the critical role of Cl-based species on the electrochemical reaction kinetics, deposition and dissolution overpotentials, electrocrystallization morphology, and many other imperative aspects of the electrochemical responses. Only very few, quite exotic and not fully studied, Cl-free electrolyte solutions have been reported to maintain reversible Mg deposition. Over the years, several compelling theories have been proposed to explain the decisive role of the Cl-containing species on the electrochemical reaction mechanisms during magnesium deposition and dissolution. The …

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Jun 2020 • Scientific reports

All-optical, an ultra-thin endoscopic photoacoustic sensor using multi-mode fiber

Nadav Shabairou, Benjamin Lengenfelder, Martin Hohmann, Florian Klämpfl, Michael Schmidt, Zeev Zalevsky

Photoacoustic endoscopy (PAE) is a method of in-vivo imaging that uses tissue absorption properties. In PAE, the main tools used to detect the acoustic signal are mechanical ultrasound transducers, which require direct contact and which are difficult to miniaturize. All-optic photoacoustic sensors can challenge this issue as they can provide contact-free sensing. Here, we demonstrate sensing of photo-acoustic signals through a multimode fiber (MMF) which can provide an ultra-thin endoscopic photoacoustic sensor. Furthermore, we show the advantage of using the optical-flow method for speckle sensing and extract the photoacoustic signal despite the mode-mixing along the MMF. Moreover, it is demonstrated for the first time that the speckle reconstruction method can be used without the need for imaging of the speckles as this enables the use of multimode fibers for the speckle method.

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Jun 2020 • Ultrasonics Sonochemistry 64, 105009, 2020

Sonochemical synthesis of carbon dots, mechanism, effect of parameters, and catalytic, energy, biomedical and tissue engineering applications

Raj Kumar, Vijay Bhooshan Kumar, Aharon Gedanken

Carbon-based nanomaterials are gaining more and more interest because of their wide range of applications. Carbon dots (CDs) have shown exclusive interest due to unique and novel physicochemical, optical, electrical, and biological properties. Since their discovery, CDs became a promising material for wide range of research applications from energy to biomedical and tissue engineering applications. At same time several new methods have been developed for the synthesis of CDs. Compared to many of these methods, the sonochemical preparation is a green method with advantages such as facile, mild experimental conditions, green energy sources, and feasibility to formulate CDs and doped CDs with controlled physicochemical properties and lower toxicity. In the last five years, the sonochemically synthesized CDs were extensively studied in a wide range of applications. In this review, we discussed the …

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Jun 2020 • Current Opinion in Colloid & Interface Science 49, 107-117, 2020

Polyhedral liquid droplets: Recent advances in elucidation and application

Orlando Marin, Maria Tkachev, Eli Sloutskin, Moshe Deutsch

The re-discovery of temperature-controlled self-faceting, shaping, and splitting transitions in liquid oil-in-water emulsion droplets, has recently led to a significant progress in the fundamental understanding of these counterintuitive phenomena, sparking scientific controversies, and opening new routes towards their technological applications. These recent developments are reviewed here. The faceting transitions were demonstrated to occur in a wide range of oil: surfactant combinations, for broad temperature ranges, and in droplets of sizes spanning an incredible 13 decades in volume, from nano (11× 10− 9) to yocto (300× 10− 24) liters. Droplets’ polymerization enables forming solid faceted particles, of shapes and sizes otherwise unachievable. Colloids and nanoparticles adsorbed controllably onto the faceted liquid droplets’ interfaces self-position at their vertices and self-expel into the aqueous medium. The self …

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Jun 2020 • Colloids and Surfaces B: Biointerfaces

Cooperative crystallization effect in the formation of sonochemically grafted active materials based on polysaccharides

Yevgenia Shebis, Vijay Bhooshan Kumar, Aharon Gedanken, Elena Poverenov

The current study explores the formation of active eco-friendly materials capable of preventing microbial contamination using in situ ultrasonic grafting of vanillin, curcumin and a curcumin-vanillin mixture on the surfaces of carboxymethylcellulose (CMC) and chitosan films. Spectroscopic, microscopic, physical and mechanical studies revealed that the films grafted with curcumin-vanillin mixture demonstrate improved mechanical properties and higher degree of order. The bioactivity of the prepared films was tested on food model, fresh-cut melons and films with a deposited curcumin-vanillin mixture showed superior antibacterial properties. For instance, this mixture-grafted on CMC films demonstrated a total inhibition of yeast/mold proliferation during 12 days. The HR-SEM studies of the mixture-grafted films revealed the presence of crystalline structures. Cooperative crystallization effect between the curcumin (the …

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Jun 2020 • ACS Energy Letters

Oxidation Stability of Organic Redox Mediators as Mobile Catalysts in Lithium–Oxygen Batteries

Won-Jin Kwak, Jiwon Park, Hun Kim, Jung Min Joo, Doron Aurbach, Hye Ryung Byon, Yang-Kook Sun

Employing organic redox mediators (ORMs) for lithium–oxygen (Li–O2) batteries has emerged as an important strategy to suppress charging overpotentials. Judicious molecular designs of ORMs can also tailor their redox potential and electron-transfer rate to optimize the catalytic efficiency. However, the stability of ORMs in Li–O2 cells was scarcely studied. Here, the catalytic efficiency and stability of several important ORMs are assessed through in situ gas analysis and reactivity tests with singlet oxygen. Some well-known ORMs are detrimentally decomposed during the first cycle in Li–O2 cells, whereas nitroxyl-radical-based ORMs bear the most stable and efficient response. Analogous nitroxyl-radical derivatives further increase round-trip energy efficiency and electron-transfer kinetics. This study underlines chemical stability aspects of ORMs, which are mandatory for the long-term cyclability in Li–O2 cells. We …

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Jun 2020 • Entropy

Large deviations for continuous time random walks

Wanli Wang, Eli Barkai, Stanislav Burov

Recently observation of random walks in complex environments like the cell and other glassy systems revealed that the spreading of particles, at its tails, follows a spatial exponential decay instead of the canonical Gaussian. We use the widely applicable continuous time random walk model and obtain the large deviation description of the propagator. Under mild conditions that the microscopic jump lengths distribution is decaying exponentially or faster ie, Lévy like power law distributed jump lengths are excluded, and that the distribution of the waiting times is analytical for short waiting times, the spreading of particles follows an exponential decay at large distances, with a logarithmic correction. Here we show how anti-bunching of jump events reduces the effect, while bunching and intermittency enhances it. We employ exact solutions of the continuous time random walk model to test the large deviation theory. View Full-Text

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Jun 2020 • Batteries & Supercaps

Effect of Crystal Structure and Morphology on Na3V2(PO4)2F3 Performances for Na‐Ion Batteries

Ayan Mukherjee, Tali Sharabani, Rosy Sharma, Sivan Okashy, Malachi Noked

Na-ion batteries (SIB) are considered promising systems for energy storage devices, however diversity of available cathode materials is lower compared to lithium ion batteries. Recently, Na3V2 (PO4) 2F3 (NVPF) has been demonstrated as promising cathode material for SIB owing to high specific capacity and electrochemical reversibility. However, most of reports demonstrates capacities lower than theoretical value and optimization of electrochemical performances by controlled morphology and crystal structure was not demonstrated yet. Here, we demonstrate a scalable synthesis strategy to tailor the crystal structure and morphology of NVPF and showed that our approach enables to optimize the Na+ ion accommodation, diffusion and stability. A flower morphology (NVPF-F) crystalizes in tetragonal structure, demonstrates discharge capacity of 109.5 mA. hg À 1 and 98.1% columbic efficiency whereas a hollow spherical morphology (NVPF-S) with orthorhombic structure exhibits discharge capacity of 124.8 mA. hg À 1 (very close to theoretical value) and 99.5% columbic efficiency. The observed discharge capacity for NVPF-S is highest reported value which is ascribed due to stable crystal structure and monodispersed morphology. Long term stability with negligible capacity loss is demonstrated over 550 cycles. Our findings shed light on importance of crystal structure and morphology of NVPF on electrochemical response, and realization as cathode material for SIB.

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Jun 2020 • Physical Review Research

Uncertainty and symmetry bounds for the quantum total detection probability

Felix Thiel, Itay Mualem, David A Kessler, Eli Barkai

We investigate a generic discrete quantum system prepared in state| ψ in〉 under repeated detection attempts, aimed to find the particle in state| d〉, for example, a quantum walker on a finite graph searching for a node. For the corresponding classical random walk, the total detection probability P det is unity. Due to destructive interference, one may find initial states| ψ in〉 with P det< 1. We first obtain an uncertainty relation which yields insight on this deviation from classical behavior, showing the relation between P det and energy fluctuations: Δ P Var [H ̂] d≥|〈 d|[H ̂, D ̂]| ψ in〉| 2, where Δ P= P det−|〈 ψ in| d〉| 2 and D ̂=| d〉〈 d| is the measurement projector. Secondly, exploiting symmetry we show that P det≤ 1/ν, where the integer ν is the number of states equivalent to the initial state. These bounds are compared with the exact solution for small systems, obtained from an analysis of the dark and bright …

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Jun 2020 • Nucleic acids research

Polymorphisms in human immunoglobulin heavy chain variable genes and their upstream regions

Ivana Mikocziova, Moriah Gidoni, Ida Lindeman, Ayelet Peres, Omri Snir, Gur Yaari, Ludvig M Sollid

Germline variations in immunoglobulin genes influence the repertoire of B cell receptors and antibodies, and such polymorphisms may impact disease susceptibility. However, the knowledge of the genomic variation of the immunoglobulin loci is scarce. Here, we report 25 potential novel germline IGHV alleles as inferred from rearranged naïve B cell cDNA repertoires of 98 individuals. Thirteen novel alleles were selected for validation, out of which ten were successfully confirmed by targeted amplification and Sanger sequencing of non-B cell DNA. Moreover, we detected a high degree of variability upstream of the V-REGION in the 5′UTR, L-PART1 and L-PART2 sequences, and found that identical V-REGION alleles can differ in upstream sequences. Thus, we have identified a large genetic variation not only in the V-REGION but also in the upstream sequences of IGHV genes. Our findings provide a new …

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Jun 2020 • MRS Bulletin

Defects in halide perovskites: The lattice as a boojum?

Sujit Kumar, Gary Hodes, David Cahen

Although halide perovskites (HaPs) are synthesized in ways that appear antithetical to those required for yielding high-quality semiconductors, the properties of the resulting materials imply, particularly for single crystals, ultralow densities of optoelectronically active defects. This article provides different views of this unusual behavior. We pose the question: Can present models of point defects in solids be used to interpret the experimental data and provide predictive power? The question arises because the measured ultralow densities refer to static defects using our present methods and models, while dynamic defect densities are ultrahigh, a result of the material being relatively soft, with a shallow electrostatic energy landscape, and with anharmonic lattice dynamics. All of these factors make the effects of dynamic defects on the materials’ optoelectronic properties minimal. We hope this article will stimulate …

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