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Dipolar field

Yves Paul Mbous, Maan Hayyan, Adeeb Hayyan, Won Fen Wong, Mohd Ali Hashim, Chung Yeng Looi
Deep eutectic solvents (DESs) have been touted recently as potential alternatives to ionic liquids (ILs). Although they possess core characteristics that are similar to those of ILs (e.g., low volatility, non-flammability, low melting points, low vapor pressure, dipolar nature, chemical and thermal stability, high solubility, and tuneability), DESs are superior in terms of the availability of raw materials, the ease of storage and synthesis, and the low cost of their starting materials. As such, they have become the subject of intensive research in various sectors, notably the chemical, electrochemical, and biological sectors...
December 3, 2016: Biotechnology Advances
E V Panov, W Baumjohann, R A Wolf, R Nakamura, V Angelopoulos, J M Weygand, M V Kubyshkina
Violent releases of space plasma energy from the Earth's magnetotail during substorms produce strong electric currents and bright aurora. But what modulates these currents and aurora and controls dissipation of the energy released in the ionosphere? Using data from the THEMIS fleet of satellites and ground-based imagers and magnetometers, we show that plasma energy dissipation is controlled by field-aligned currents (FACs) produced and modulated during magnetotail topology change and oscillatory braking of fast plasma jets at 10-14 Earth radii in the nightside magnetosphere...
December 2016: Nature Physics
Ankun Yang, Alexander J Hryn, Marc R Bourgeois, Won-Kyu Lee, Jingtian Hu, George C Schatz, Teri W Odom
Plasmonic nanostructures with enhanced localized optical fields as well as narrow linewidths have driven advances in numerous applications. However, the active engineering of ultranarrow resonances across the visible regime-and within a single system-has not yet been demonstrated. This paper describes how aluminum nanoparticle arrays embedded in an elastomeric slab may exhibit high-quality resonances with linewidths as narrow as 3 nm at wavelengths not accessible by conventional plasmonic materials. We exploited stretching to improve and tune simultaneously the optical response of as-fabricated nanoparticle arrays by shifting the diffraction mode relative to single-particle dipolar or quadrupolar resonances...
November 28, 2016: Proceedings of the National Academy of Sciences of the United States of America
Merlin Pohlit, Paul Eibisch, Maryam Akbari, Fabrizio Porrati, Michael Huth, Jens Müller
Alongside the development of artificially created magnetic nanostructures, micro-Hall magnetometry has proven to be a versatile tool to obtain high-resolution hysteresis loop data and access dynamical properties. Here we explore the application of First Order Reversal Curves (FORC)-a technique well-established in the field of paleomagnetism for studying grain-size and interaction effects in magnetic rocks-to individual and dipolar-coupled arrays of magnetic nanostructures using micro-Hall sensors. A proof-of-principle experiment performed on a macroscopic piece of a floppy disk as a reference sample well known in the literature demonstrates that the FORC diagrams obtained by magnetic stray field measurements using home-built magnetometers are in good agreement with magnetization data obtained by a commercial vibrating sample magnetometer...
November 2016: Review of Scientific Instruments
Prithwish K Nandi, Zdenek Futera, Niall J English
Given the fundamental role of water in governing the biochemistry of enzymes, and in regulating their wider biological activity (e.g., by local water concentration surrounding biomolecules), the influence of extraneous electric and electromagnetic (e/m) fields thereon is of central relevance to biophysics and, more widely, biology. With the increase in levels of local and atmospheric microwave-frequency radiation present in modern life, as well as other electric-field exposure, the impact upon hydration-water layers surrounding proteins, and biomolecules generally, becomes a particularly pertinent issue...
November 28, 2016: Journal of Chemical Physics
Huifang Zhang, Chun Li, Caihong Zhang, Xueqian Zhang, Jianqiang Gu, Biaobing Jin, Jiaguang Han, Weili Zhang
Plasmonic dimers that made from two subwavelength particles have drawn much attention in the recent years, which are quite promising in local field enhancement, sensing, high frequency conductance probing and electron tunneling. In this work, we experimentally investigate the mode transition effect of different plasmonic resonances in double-ring dimers when introducing conductive junction at the dimer gap in the terahertz regime. Without the junction, the dimers support a single dipolar bonding dimer plasmonic (BDP) mode...
November 28, 2016: Optics Express
Moustafa Sherief Moustafa, Saleh Mohammed Al-Mousawi, Hesham R El-Seedi, Mohamed Hilmy Elnagdi
Progress in chemistry synthetic methodologies of cyclic enaminonitriles is reported. Due to this progress, it becomes possible to reactivate these molecules toward electrophiles, nucleophiles and as electron rich dienes in 2+3 dipolar additions and in 4+2 cycloadditions reactions. Synthetizing the polyfunctionalized 4H-pyrans and their fused derivatives is a fascinating field with a multitude of biological implications such as antitumor, cardiotonic, hepatoprotective, antihypertensive, antibronchitis, as well antifungal activity...
November 29, 2016: Mini Reviews in Medicinal Chemistry
Kelley Lynch Heatley, Fuduo Ma, Ning Wu
Colloidal particles are envisioned as analogues of atoms and molecules, however they often lack the complexities present in their counterparts. In this work, we report the assembly of colloidal molecules from a binary mixture of polystyrene spheres (1, 1.6, 2, and 4 μm) under an alternating current electric field. The rich family of assembled oligomers typically consists of a large sphere that is closely surrounded by a number of smaller petal particles, driven by the dipolar attraction between large and small particles...
November 30, 2016: Soft Matter
E Myrovali, N Maniotis, A Makridis, A Terzopoulou, V Ntomprougkidis, K Simeonidis, D Sakellari, O Kalogirou, T Samaras, R Salikhov, M Spasova, M Farle, U Wiedwald, M Angelakeris
In this work, we present the arrangement of Fe3O4 magnetic nanoparticles into 3D linear chains and its effect on magnetic particle hyperthermia efficiency. The alignment has been performed under a 40 mT magnetic field in an agarose gel matrix. Two different sizes of magnetite nanoparticles, 10 and 40 nm, have been examined, exhibiting room temperature superparamagnetic and ferromagnetic behavior, in terms of DC magnetic field, respectively. The chain formation is experimentally visualized by scanning electron microscopy images...
November 29, 2016: Scientific Reports
Cina Foroutan-Nejad, Valery Andrushchenko, Michal Straka
We propose a two-state electric field-driven room-temperature single-molecule switch based on a dipolar molecule enclosed inside ellipsoidal fullerene C70. We show that the two low-energy minima of the molecular dipole inside the C70 cage provide distinguishable molecular states of the system that can be switched by application of an external electric field.
November 28, 2016: Physical Chemistry Chemical Physics: PCCP
Kaustubh R Mote, Vipin Agarwal, P K Madhu
It has been slightly more than fifty years since the first homonuclear spin decoupling scheme, Lee-Goldburg decoupling, was proposed for removing homonuclear dipolar interactions in solid-state nuclear magnetic resonance. A family of such schemes has made observation of high-resolution NMR spectra of abundant spins possible in various applications in solid state. This review outlines the strategies used in this field and the future prospects of homonuclear spin decoupling in solid-state NMR.
November 2016: Progress in Nuclear Magnetic Resonance Spectroscopy
Kakoli Bhattacharya, Veronique Dupuis, Damien Le-Roy, Pritam Deb
Self-organization of magnetic nanoparticles into secondary nanostructures provides an innovative way for designing functional nanomaterials with novel properties, different from the constituent primary nanoparticles as well as their bulk counterparts. Collective magnetic properties of such complex closed packing of magnetic nanoparticles makes them more appealing than the individual magnetic nanoparticles in many technological applications. This work reports the collective magnetic behaviour of magnetic ensembles comprising of single domain Fe3O4 nanoparticles...
February 1, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Le Zhang, Michael Antonacci, Alex Burant, Karl M Koshlap, Rosa Tamara Branca
A remote detection scheme utilizing the distant dipolar field interaction between two different spin species was proposed by Granwehr et al. [J. Magn. Reson. 176(2), 125 (2005)]. In that sequence (1)H spins were detected indirectly via their dipolar field interaction with (129)Xe spins, which served as the sensing spins. Here we propose a modification of the proposed detection scheme that takes advantage of the longer T1 relaxation time of xenon to create a long lasting dipolar field with which the fast relaxing (1)H spins are allowed to interact many times during a single acquisition...
November 21, 2016: Journal of Chemical Physics
S B Mende, H U Frey, V Angelopoulos
Monochromatic all-sky imagers at South Pole and other Antarctic stations of the Automatic Geophysical Observatory chain recorded the aurora in the region where the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites crossed the dayside magnetopause. In several cases the magnetic field lines threading the satellites when mapped to the atmosphere were inside the imagers' field of view. From the THEMIS magnetic field and the plasma density measurements, we were able to locate the position of the magnetopause crossings and map it to the ionosphere using the Tsyganenko-96 field model...
August 2016: Journal of Geophysical Research. Space Physics
S Pursiainen, J Vorwerk, C H Wolters
The goal of this study is to develop focal, accurate and robust finite element method (FEM) based approaches which can predict the electric potential on the surface of the computational domain given its structure and internal primary source current distribution. While conducting an EEG evaluation, the placement of source currents to the geometrically complex grey matter compartment is a challenging but necessary task to avoid forward errors attributable to tissue conductivity jumps. Here, this task is approached via a mathematically rigorous formulation, in which the current field is modeled via divergence conforming H(div) basis functions...
December 21, 2016: Physics in Medicine and Biology
Sophie N Koroloff, Alexander A Nevzorov
Spectroscopic assignment of NMR spectra for oriented uniformly labeled membrane proteins embedded in their native-like bilayer environment is essential for their structure determination. However, sequence-specific assignment in oriented-sample (OS) NMR is often complicated by insufficient resolution and spectral crowding. Therefore, the assignment process is usually done by a laborious and expensive "shotgun" method involving multiple selective labeling of amino acid residues. Presented here is a strategy to overcome poor spectral resolution in crowded regions of 2D spectra by selecting resolved "seed" residues via soft Gaussian pulses inserted into spin-exchange separated local-field experiments...
October 24, 2016: Journal of Magnetic Resonance
Matthias Schmitt, Matthias Wenzel, Fabian Böttcher, Igor Ferrier-Barbut, Tilman Pfau
Self-bound many-body systems are formed through a balance of attractive and repulsive forces and occur in many physical scenarios. Liquid droplets are an example of a self-bound system, formed by a balance of the mutual attractive and repulsive forces that derive from different components of the inter-particle potential. It has been suggested that self-bound ensembles of ultracold atoms should exist for atom number densities that are 10(8) times lower than in a helium droplet, which is formed from a dense quantum liquid...
November 9, 2016: Nature
Chenhui Peng, Taras Turiv, Rui Zhang, Yubing Guo, Sergij V Shiyanovskii, Qi-Huo Wei, Juan de Pablo, Oleg D Lavrentovich
Placing colloidal particles in predesigned sites represents a major challenge of the current state-of-the-art colloidal science. Nematic liquid crystals with spatially varying director patterns represent a promising approach to achieve a well-controlled placement of colloidal particles thanks to the elastic forces between the particles and the surrounding landscape of molecular orientation. Here we demonstrate how the spatially varying director field can be used to control placement of non-spherical particles of boomerang shape...
November 10, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Dirk Romeis, Vladimir Toshchevikov, Marina Saphiannikova
Based on a dipole model for the mutual magnetic interactions among the magnetizable micro-particles in magneto-sensitive elastomers we develop a mean field approach to describe the arrangement of these particles into elongated micro-structures. If these micro-structures are oriented parallel to an external magnetic field the present approach provides an efficient calculation of the behavior of such samples, which is a result of the interplay between micro-structure and shape effects. Accordingly, we are able to draw comprehensive phase diagrams for the resultant deformation and predict for very oblate samples a discontinuous shape change in the presence of a homogeneous external field...
November 4, 2016: Soft Matter
G P Johari
We propose that an electric field's role in changing the structural disorder may be investigated by comparing the field-induced entropy decrease, ΔES, against the pressure-induced and cooling-induced entropy decreases, ΔpS and ΔTS, respectively, for the same increase in the dielectric α-relaxation time, Δτα, or in the viscosity. If these three quantities are found to be the same, the change in the number of microstates, Δln Ω = ΔS/R, would be the same whether there is an electric field-induced dipole vector alignment, or not...
October 28, 2016: Journal of Chemical Physics
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