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2019 • APS March Meeting Abstracts

Faceted liquid droplets: when colloids are attracted by topological defects

Shir Liber, Alexander Butenko, Eli Sloutskin

Particles at disordered droplet interfaces were extensively investigated, aiming both at their fundamental physics and at their applications in particle-stabilized pharmaceuticals and aerosols. Yet, particles residing at the ubiquitous ordered interfaces have never been studied. We study the dynamics of tracer colloids, incorporated into a curved 2nm-thick crystal, forming at T= T s 26 o C at the interface of liquid oil-in-water emulsion droplets. We demonstrate the particles to be spontaneously dragged to particular surface locations, identified with topological defects within the crystalline structure. At T= T d< T s, the droplets undergo an unprecedented sphere-to-icosahedron shape transformation, with their bulk remaining liquid. At T d, the attractors self-position onto the vertices of the icosahedra and fix there the colloids' positions. At an even lower temperature, the particles are spontaneously expelled from the droplets …

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2019 • bioRxiv, 547570, 2019

Applications of community detection algorithms to large biological datasets

Itamar Kanter, Gur Yaari, Tomer Kalisky

Recent advances in data acquiring technologies in biology have led to major challenges in mining relevant information from large datasets. For example, single-cell RNA sequencing technologies are producing expression and sequence information from tens of thousands of cells in every single experiment. A common task in analyzing biological data is to cluster samples or features (e.g., genes) into groups sharing common characteristics. This is an NP-hard problem for which numerous heuristic algorithms have been developed. However, in many cases, the clusters created by these algorithms do not reflect biological reality. To overcome this, a Networks Based Clustering (NBC) approach was recently proposed, by which the samples or genes in the dataset are first mapped to a network and then community detection (CD) algorithms are used to identify clusters of nodes. Here, we created an open …

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Dec 2018 • Physical Review B

Extracting many-particle entanglement entropy from observables using supervised machine learning

Richard Berkovits

Entanglement, which quantifies nonlocal correlations in quantum mechanics, is the fascinating concept behind much of the aspiration towards quantum technologies. Nevertheless, directly measuring the entanglement of a many-particle system is very challenging. Here, we show that via supervised machine learning using a convolutional neural network, we can infer the entanglement from a measurable observable for a disordered interacting quantum many-particle system. Several structures of neural networks were tested and a convolutional neural network akin to structures used for image and speech recognition performed the best. After training on a set of 500 realizations of disorder, the network was applied to 200 new realizations and its results for the entanglement entropy were compared to a direct computation of the entanglement entropy. Excellent agreement was found, except for several rare regions …

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Dec 2018 • Electrochimica Acta

Fast kinetics in free-standing porous Cu3P anode for Li-ion batteries

Valeria Yarmiayev, Yana Miroshnikov, Gregory Gershinsky, Victor Shokhen, David Zitoun

Anode materials for Li-ion batteries based on a conversion mechanism show very high theoretical specific capacities. In particular, phosphide materials display volumetric and gravimetric capacities far beyond graphite, approaching those of silicon-based materials. However, the slow kinetics and large mechanical strain during the conversion process are challenging issues toward enabling phosphide-based anode materials.Here, we synthesize a copper phosphide free-standing membrane and show the benefits of this approach, which provides lighter electrodes with faster kinetics during lithiation and delithiation. The Cu3P membrane is both binder-free and carbon black-free, and its synthetic process involves a simple chemical vapor deposition of phosphorus on a composite polymer-copper membrane at a moderate temperature of 429 °C. Microscopic and other methods show the purity of the phase and of the …

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Dec 2018 • ACS Applied Energy Materials

Structural Characterization and Room Temperature Low-Frequency Raman Scattering from MAPbI3 Halide Perovskite Films Rigidized by Cesium Incorporation

Vinayaka H Damle, Laxman Gouda, Shay Tirosh, Yaakov R Tischler

The structural instability of organometal halide perovskites (OHP) is one of the major issues concerning commercialization of perovskite solar cells. Probing this intrinsic instability is one of the major milestones and challenging tasks toward enhancing the lifespan of the material. Here we have incorporated Cs ions into methylammonium lead iodide (MAPbI3) films and studied the thin film structural and optical properties. Incorporation of Cs into MAPbI3 leads to formation of both α-CsPbI3 and ∂-CsPbI3 phases, black and yellow, respectively, as indicated by the evolution of the optical band edge and X-ray diffraction (XRD) spectrum. At a concentration of 20% Cs ions, we observe the existence of a stable α-CsPbI3 phase. Incorporating 59% or more Cs ions yields the yellow phase of CsPbI3, due to alloying of Cs with the MAPbI3 matrix. The structural transformations observed in absorption spectra and XRD are …

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Dec 2018 • Applied Materials Today

Vapour transport deposition of fluorographene oxide films and electro-optical device applications

Rahul Sharma, Ravi K Biroju, Ofer Sinai, Hagai Cohen, Krishna Rani Sahoo, Vlada Artel, Hadas Alon, Adi Levi, A Subrahmanyam, Wolfgang Theis, Doron Naveh, Tharangattu N Narayanan

Fluorographene is one of the most interesting 2D materials owing to its span of electronic properties, from a conductor to wide-gap insulator, controlled by the compositional carbon to fluorine ratio. Unlike the chemically inert graphene, fluorographene is recognized for its rich chemistry, particularly at ambient, allowing tailoring its physical properties. Here, we report on single step, catalyst free, wafer-scale synthesis of fluorographene oxide (FGO) ultra-thin films (∼4 nm thickness) by physical vapour deposition. The FGO, possessing 7% fluorine content, comprises few-nanometer domains of sp2-sp3 carbon with high thermal stability, as confirmed by several analytical methods. We show that FGO can be utilized as an active hetero-layer on a few-layer MoS2 field effect transistor (FET), significantly improving the performance of MoS2 optoelectronic devices with an extended spectral response towards the near infrared …

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Dec 2018 • ACS nano 12 (12), 11725-11730, 2018

Decoding the information contained in fluorophore radiation patterns

Maia Brunstein, Adi Salomon, Martin Oheim

Dipole radiation patterns change when a fluorescent molecule comes close to the boundary between media of different refractive indices. Near-interface molecules emit mostly into the higher-index medium, predominantly around the critical angle. The radiation pattern encodes information about the emitter distance, orientation, and the refractive index of the embedding medium. Analyses of the supercritical angle fluorescence on pupil plane images can retrieve this information and have been applied both for refractometry with subcellular resolution and for the detection of metabolically active cancerous cells. In this issue of ACS Nano, Ferdman et al. employ this strategy in a label-free assay for detecting single bacteria, based on measuring the refractive-index change produced by bacterial growth in a fluorophore-coated microfluidic channel.

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Dec 2018 • Nature physics

Imaging quantum fluctuations near criticality

A Kremen, H Khan, YL Loh, TI Baturina, N Trivedi, A Frydman, B Kalisky

A quantum phase transition (QPT) occurs between two competing phases of matter at zero temperature, driven by quantum fluctuations. Although the presence of these fluctuations is well established, they have not been locally imaged in space, and their local dynamics has not been studied so far. We use a scanning superconducting quantum interference device to image quantum fluctuations near the QPT from a superconductor to an insulator. We find fluctuations of the diamagnetic response in both space and time that survive well below the transition temperature, demonstrating their quantum nature. The fluctuations appear as telegraph-like noise with a range of characteristic times and a non-monotonic temperature dependence, revealing unexpected quantum granularity. The lateral dimension of these fluctuations grows towards criticality, offering a new measurable length scale. Our results provide physical …

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Dec 2018 • ACS Applied Energy Materials

Scalable silver oxo-sulfide catalyst for electrochemical water splitting

Victor Shokhen, Yulia Kostikov, Ignacio Borge-Durán, Yelena Gershinsky, Ilya Grinberg, Gilbert D Nessim, David Zitoun

One of the bottlenecks toward the successful implementation of alternative energies is the lack of methods for sustainable generation of hydrogen fuel as an energy carrier. Given that water will be at the very least an important component of the hydrogen production feedstock, sustainable catalysts are needed for the electrochemical generation of hydrogen from water. Herein, we report on the electrochemical activation of a silver-based catalyst for the efficient hydrogen evolution reaction (HER) in acidic conditions at high current densities. After activation, the catalyst is chemically and electrochemically stable over days. The starting material, silver sulfide, is synthesized by a simple and scalable chemical vapor deposition process. Upon electrochemical activation, the pristine material is converted to mesoporous silver coated with a silver oxo-sulfide layer which is highly active toward HER. Detailed microscopy and …

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Dec 2018 • ACS Energy Letters

Anion Effects on Cathode Electrochemical Activity in Rechargeable Magnesium Batteries: A Case Study of V2O5

Ran Attias, Michael Salama, Baruch Hirsch, Reeta Pant, Yosef Gofer, Doron Aurbach

One of the holy grails in research and development focused on rechargeable magnesium batteries is development of “conventional” electrolyte solutions that are compatible with both anode and cathode and support highly reversible magnesium electrochemical activity. In the last couple of years, MgTFSI2, a “simple” salt, attracted considerable attention owing to its high solubility in a range of relevant solvents and apparent compatibility with magnesium anode and cathode materials. Nonetheless, questions were raised regarding the validity of the chemical and electrochemical inertness attributed to the TFSI anion, in particular when electrochemistry of magnesium is in the spotlight. Here, we demonstrate the impact of the TFSI anion on the intercalation kinetics of Mg ions into V2O5. The importance of this work is the fact that V2O5 is considered to be the most attractive high-voltage/high-capacity cathode for …

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Nov 2018 • Inorganic chemistry

Bond Order Conservation Principle and Peculiarities of the Metal–Metal Bonding

Elena Levi, Doron Aurbach, Carlo Gatti

Pauling’s principles developed later in the bond valence model (BVM) are fundamental in description of bonding in ionic solids and surface phenomena on metals, but applicability of these principles to the metal–metal bonds in the bulk compounds was demonstrated only recently, with a spotlight on the bond valence–bond length correlations. This work is focused on the bond order conservation in cluster compounds and determination of empiric bond valence parameters for the metal–metal bonds, which ensure very simple and reasonably accurate bonding analysis, with zero cost, in any complex cluster compound. Such peculiarities of cluster compounds as matrix effect and nonuniform distribution of the ionic charges (bond valence sums) on the ligands around metal clusters, as well as other important examples of the BVM application to compounds with metal–metal bonds, are discussed.

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Nov 2018 • ACS chemical neuroscience 10 (1), 36-38, 2018

Phospho-Tau impairs nuclear-cytoplasmic transport

Timir Tripathi, Jay Prakash, Yaron Shav-Tal

Aggregation of hyperphosphorylated tau is the hallmark of several tauopathies, including Alzheimer’s disease (AD). Although the mechanism underlying tau-associated neuronal damage remains unclear, it is believed that tau hyperphosphorylation is one of the key features in disease progression. A recent study demonstrates that hyperphosphorylated tau (P-tau) interacts with components of the nuclear pore complex (NPC) to impair nuclear-cytoplasmic transport and contribute to tau-induced neurotoxicity. The NPC thus represents a point of convergence between pathological tau and neuronal dysfunction in AD.

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Nov 2018 • Nano letters

Current-Induced Crossover of Flux Periodicity from h/2e to h/e in a Superconducting Nb Nano-Ring

Omri Sharon, Avner Avraham Shaulov, Jorge Berger, Amos Sharoni, Richard Berkovits, Yosef Yeshurun

Magnetoresistance measurements in a granular Nb nanoring reveal current-induced crossover between two distinct quantum coherence effects. At low bias currents, Cooper-pair coherence is manifested by Little–Parks oscillations with flux periodicity of h/2e. At high bias currents, magnetoresistance oscillations with flux periods of h/e are observed and interpreted as Aharonov–Bohm oscillations, reflecting the phase coherence of individual quasi-particles. The model explaining these data views the ring as a chain of superconducting grains weakly coupled by tunnel junctions. Low bias currents allow coherent tunneling of Cooper pairs between the grains. Increasing the current above the critical current of all the junctions creates a quasi-particles conduction channel along the ring, allowing for quantum interference of quasi-particles.

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Nov 2018 • ChemElectroChem

Solvent Effects on the Reversible Intercalation of Magnesium‐Ions into V2O5 Electrodes

Ran Attias, Michael Salama, Baruch Hirsch, Yosef Gofer, Doron Aurbach

The choice for solvents in electrolyte solutions for non‐aqueous magnesium batteries is currently limited to ethers. However, the scientific community regularly uses acetonitrile (ACN) based electrolyte solutions as model systems in order to characterize new cathode materials for rechargeable Magnesium batteries. In this study, we demonstrated the effect of dimethoxyethane (DME), an important solvent for rechargeable magnesium systems, on the reversible intercalation of Mg2+ cations into thin, monolithic V2O5 films. The effect of DME on the intercalation kinetic have been examined via chronopotentiometry, galvanostatic and galvanostatic intermittent titration (GITT) measurements. In addition, we explored basic scientific questions related to the structure of ACN:DME based electrolyte solutions via Raman spectroscopy and surface chemistry of V2O5/Mg(ClO4)2/ACN:DME systems via X‐ray photoelectron …

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Nov 2018 • Entropy 20 (11), 854, 2018

The Weak Reality That Makes Quantum Phenomena More Natural: Novel Insights and Experiments

Yakir Aharonov, Eliahu Cohen, Mordecai Waegell, Avshalom Elitzur

While quantum reality can be probed through measurements, the Two-State Vector Formalism (TSVF) reveals a subtler reality prevailing between measurements. Under special pre-and post-selections, odd physical values emerge. This unusual picture calls for a deeper study. Instead of the common, wave-based picture of quantum mechanics, we suggest a new, particle-based perspective: Each particle possesses a definite location throughout its evolution, while some of its physical variables (characterized by deterministic operators, some of which obey nonlocal equations of motion) are carried by “mirage particles” accounting for its unique behavior. Within the time interval between pre-and post-selection, the particle gives rise to a horde of such mirage particles, of which some can be negative. What appears to be “no-particle”, known to give rise to interaction-free measurement, is in fact a self-canceling pair of positive and negative mirage particles, which can be momentarily split and cancel out again. Feasible experiments can give empirical evidence for these fleeting phenomena. In this respect, the Heisenberg ontology is shown to be conceptually advantageous compared to the Schrödinger picture. We review several recent advances, discuss their foundational significance and point out possible directions for future research. View Full-Text

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Nov 2018 • ChemPhysChem

Chiral Purity of Crystals Using Low‐Frequency Raman Spectroscopy

Irena Nemtsov, Yitzhak Mastai, Yaakov R Tischler, Hagit Aviv

The pharmaceutical industry is in need of new techniques to identify the chirality of solids due to regulatory and safety concerns regarding the biological activity of enantiomers. In this study, we present for the first time the application of low‐frequency Raman spectroscopy as a new and sensitive method for analyzing the chiral purity of crystals. Using this method, we were able to identify small amounts, as low as 1 % w/w, of an enantiomer in racemic crystals. To demonstrate the capabilities of the method, we used a model system based on chiral crystals of enantiopure, racemic crystals and their mixtures in various ratios. We found that the low‐frequency Raman spectra of racemic and enantiopure crystals are significantly different, reflecting the different hydrogen bond networks. Moreover, a comparison of the sensitivity of enantiomeric excess in chiral crystals to that of circular dichroism and X‐ray diffraction …

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Nov 2018 • APL Photonics

Invited article: distributed analysis of nonlinear wave mixing in fiber due to forward Brillouin scattering and Kerr effects

Yosef London, Hilel Hagai Diamandi, Gil Bashan, Avi Zadok

Forward stimulated Brillouin scattering (F-SBS) is a third-order nonlinear-optical mechanism that couples between two co-propagating optical fields and a guided acoustic mode in a common medium. F-SBS gives rise to nonlinear wave mixing along optical fibers, which adds up with four-wave mixing induced by the Kerr effect. In this work, we report the distributed mapping of nonlinear wave mixing processes involving both mechanisms along standard single-mode fiber, in analysis, simulation, and experiment. Measurements are based on a multi-tone, optical time-domain reflectometry setup, which is highly frequency-selective. The results show that F-SBS leads to nonlinear wave mixing processes that are more complex than those that are driven by the Kerr effect alone. The dynamics are strongly dependent on the exact frequency detuning between optical field components. When the detuning is chosen near an F …

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Nov 2018 • Scientific reports

Growth mechanisms and electronic properties of vertically aligned MoS2

Chen Stern, Shmuel Grinvald, Moshe Kirshner, Ofer Sinai, Mark Oksman, Hadas Alon, Oren E Meiron, Maya Bar-Sadan, Lothar Houben, Doron Naveh

Thin films of layered semiconductors emerge as highly promising materials for energy harvesting and storage, optoelectronics and catalysis. Their natural propensity to grow as oriented crystals and films is one of their distinct properties under recent focal interest. Specifically, the reaction of transition metal films with chalcogen vapor can result in films of vertically aligned (VA) layers, while metal-oxides react with chalcogens in vapor phase to produce horizontally aligned crystals and films. The growth mechanisms of vertically oriented films are not yet fully understood, as well as their dependence on the initial metal film thickness and growth conditions. Moreover, the resulting electronic properties and the role of defects and disorder had not yet been studied, despite their critical influence on catalytic and device performance. In this work, we study the details of oriented growth of MoS 2 with complementary theoretical …

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Oct 2018 • Advanced Materials

Metallic Networks: Nanoporous Metallic Networks: Fabrication, Optical Properties, and Applications (Adv. Mater. 41/2018)

Racheli Ron, Emir Haleva, Adi Salomon

In article number 1706755, Adi Salomon and co-workers discuss nanoporous metals made of a 3D solid skeleton with a sub-optical-wavelength size of both particles and voids. Their disordered nanostructure endows them with interesting optical properties. Large-scale metallic networks enable connection between the nanoworld and the macroscopic world, and may pave the way to original materials with exclusive optoelectronic properties.

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Oct 2018 • Proceedings of the National Academy of Sciences

Completely top–down hierarchical structure in quantum mechanics

Yakir Aharonov, Eliahu Cohen, Jeff Tollaksen

Can a large system be fully characterized using its subsystems via inductive reasoning? Is it possible to completely reduce the behavior of a complex system to the behavior of its simplest “atoms”? In this paper we answer these questions in the negative for a specific class of systems and measurements. After a general introduction of the topic, we present the main idea with a simple two-particle example, where strong correlations arise between two apparently empty boxes. This leads to surprising effects within atomic and electromagnetic systems. A general construction based on pre- and postselected ensembles is then suggested, wherein the N-body correlation can be genuinely perceived as a global property, as long as one is limited to performing measurements which we term “strictly local.” We conclude that under certain boundary conditions, higher-order correlations within quantum mechanical systems can …

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Oct 2018 • Life science alliance

S-phase transcriptional buffering quantified on two different promoters

Sharon Yunger, Pinhas Kafri, Liat Rosenfeld, Eliraz Greenberg, Noa Kinor, Yuval Garini, Yaron Shav-Tal

Imaging of transcription by quantitative fluorescence-based techniques allows the examination of gene expression kinetics in single cells. Using a cell system for the in vivo visualization of mammalian mRNA transcriptional kinetics at single-gene resolution during the cell cycle, we previously demonstrated a reduction in transcription levels after replication. This phenomenon has been described as a homeostasis mechanism that buffers mRNA transcription levels with respect to the cell cycle stage and the number of transcribing alleles. Here, we examined how transcriptional buffering enforced during S phase affects two different promoters, the cytomegalovirus promoter versus the cyclin D1 promoter, that drive the same gene body. We found that global modulation of histone modifications could completely revert the transcription down-regulation imposed during replication. Furthermore, measuring these levels of …

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