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Dipolar field

Muyi He, You Jiang, Dan Guo, Xingchuang Xiong, Xiang Fang, Wei Xu
A dual-polarity linear ion trap (LIT) mass spectrometer was developed in this study, and the method for simultaneously controlling and detecting cations and anions was proposed and realized in the LIT. With the application of an additional dipolar DC field on the ejection electrodes of an LIT, dual-polarity mass spectra could be obtained, which include both the mass-to-charge (m/z) ratio and charge polarity information of an ion. Compared with conventional method, the ion ejection and detection efficiency could also be improved by about one-fold...
May 25, 2017: Journal of the American Society for Mass Spectrometry
Z M Dai, W Liu, X T Zhao, T T Wang, S K Li, Yongsheng Yu, X G Zhao, Z D Zhang
We report on a field induced domain evolutionary procedure in the anisotropic Nd-Dy-Fe-Co-B/MgO/Fe multilayers by using first-order-reversal-curves and magnetic force microscopy. Different reversal behaviors and domain sizes are found in well coupled and decoupled multilayers by changing the thickness of the spacer layer. The competition between dipolar magnetostatic energy and Zeeman energy is evaluated by in-field observation throughout nucleation and annihilation processes. In addition, lithography-patterned arrays of soft Fe disks onto a continuous Nd-Dy-Fe-Co-B hard-magnetic layer are designed...
May 25, 2017: Nanoscale
Petra Rovó, Rasmus Linser
This paper deals with the theoretical foundation of proton magic-angle-spinning rotating-frame relaxation (R1ρ) and establishes the range of validity and accuracy of the presented approach to describe low-amplitude microsecond timescale motion in the solid state. Beside heteronuclear dipolar and chemical shift anisotropy interactions, a major source of relaxation for protons is the homonuclear dipolar interaction. For this latter relaxation process no general analytical equation has been published until now which would describe the R1ρ relaxation at any spinning-speed, spin-lock field, or tilt-angle...
May 23, 2017: Journal of Physical Chemistry. B
Andrew J Pell, Kevin J Sanders, Sebastian Wegner, Guido Pintacuda, Clare P Grey
We propose two broadband pulse schemes for (14)N solid-state magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) that achieves (i) complete population inversion and (ii) efficient excitation of the double-quantum spectrum using low-power single-sideband-selective pulses. We give a comprehensive theoretical description of both schemes using a common framework that is based on the jolting-frame formalism of Caravatti et al. [J. Magn. Reson. 55, 88 (1983)]. This formalism is used to determine for the first time that we can obtain complete population inversion of (14)N under low-power conditions, which we do here using single-sideband-selective adiabatic pulses...
May 21, 2017: Journal of Chemical Physics
Euna Jo, Sejun Park, Jooseop Lee, Soonchil Lee, Jeong Hyun Shim, Takehito Suzuki, Takuro Katsufuji
The simultaneous occurrence of the structural and magnetic phase transitions observed in MnV2O4 is one clear example of strong interplay among the spin, orbital and lattice degrees of freedom. The structure of MnV2O4 is switched by the magnetic field and the linear magnetostriction is very high. The orbital order mediates the interaction between the spin and the lattice generating these phenomena. In this work, we present experimental evidence of an orbital order in MnV2O4 and its reorientation under a rotating magnetic field as obtained by nuclear magnetic resonance(NMR)...
May 19, 2017: Scientific Reports
Muath Nairat, Morgan Webb, Michael P Esch, Vadim V Lozovoy, Benjamin G Levine, Marcos Dantus
The optically populated excited state wave packet propagates along multidimensional intramolecular coordinates soon after photoexcitation. This action occurs alongside an intermolecular response from the surrounding solvent. Disentangling the multidimensional convoluted signal enables the possibility to separate and understand the initial intramolecular relaxation pathways over the excited state potential energy surface. Here we track the initial excited state dynamics by measuring the fluorescence yield from the first excited state as a function of time delay between two color femtosecond pulses for several cyanine dyes having different substituents...
May 18, 2017: Physical Chemistry Chemical Physics: PCCP
Dirk Romeis, Philipp Metsch, Markus Kästner, Marina Saphiannikova
In the literature, different theoretical models have been proposed to describe the properties of systems which consist of magnetizable particles that are embedded into an elastomer matrix. It is well known that such magneto-sensitive elastomers display a strong magneto-mechanical coupling when subjected to an external magnetic field. Nevertheless, the predictions of available models often vary significantly since they are based on different assumptions and approximations. Up to now the actual accuracy and the limits of applicability are widely unknown...
April 2017: Physical Review. E
Yann Chalopin, Jean-Claude Bacri, Florence Gazeau, Martin Devaud
Clusters of magnetic nanoparticles have received considerable interest in various research fields. Their capacity to generate heat under an alternating magnetic field has recently opened the way to applications such as cancer therapy by hyperthermia. This work is an attempt to investigate the collective effects of interacting dipoles embedded in magnetic nano-particles (MNP) to predict their thermal dissipation with a liquid. We first present a general approach, based on the tracking of the microscopic dipole fluctuations, to access to the dissipation spectra of any spatial distribution of MNPs...
May 10, 2017: Scientific Reports
Harsha Bajaj, Silvia Acosta Gutierrez, Igor Bodrenko, Giuliano Malloci, Mariano Andrea Scorciapino, Mathias Winterhalter, Matteo Ceccarelli
Transport of molecules through biological membranes is a fundamental process in biology, facilitated by selective channels and general pores. The architecture of some outer membrane pores in Gram-negative bacteria, common to other eukaryotic pores, suggests them as prototypes of electrostatically regulated nanosieve devices. In this study, we sensed the internal electrostatics of the two most abundant outer membrane channels of Escherichia coli, using norfloxacin as a dipolar probe in single molecule electrophysiology...
May 12, 2017: ACS Nano
Jie Li, Ming-Jie Zhu, Ying-Hua Wang, Ren-Chao Jin, Jia-Qi Li, Zheng-Gao Dong
The far-field radiation of a single dipolar emitter can be controlled by coupling to toroidal dipole resonance attached to metallic double flat rings, realizing a conversion from non- to super-radiating. The underlying physical mechanism is the hybridization interference of toroidal and electric dipoles under an asymmetric configuration by introducing a radial displacement of the dipolar emitter. By embedding gain medium in the gap spacer between double flat rings, the directional far-field super-radiating power can achieve a tremendous enhancement with a moderate requirement on the gain coefficient, promoting light-matter interaction manipulation...
May 9, 2017: Scientific Reports
Maria Makrinich, Rupal Gupta, Tatyana Polenova, Amir Goldbourt
The ability of various pulse types, which are commonly applied for distance measurements, to saturate or invert quadrupolar spin polarization has been compared by observing their effect on magnetization recovery curves under magic-angle spinning. A selective central transition inversion pulse yields a bi-exponential recovery for a diamagnetic sample with a spin-3/2, consistent with the existence of two processes: the fluctuations of the electric field gradients with identical single (W1) and double (W2) quantum quadrupolar-driven relaxation rates, and spin exchange between the central transition of one spin and satellite transitions of a dipolar-coupled similar spin...
April 21, 2017: Solid State Nuclear Magnetic Resonance
Joe G Donaldson, Per Linse, Sofia S Kantorovich
Systems whose magnetic response can be finely tuned using control parameters, such as temperature and external magnetic field strength, are extremely desirable, functional materials. Magnetic nanoparticles, in particular suspensions thereof, offer opportunities for this controllability to be realised. Cube-like particles are particularly mono-disperse examples that, together with their favourable packing behaviour, make them of significant interest for study. Using a combination of analytical calculations and molecular dynamics we have studied the self-assembly of permanently magnetised dipolar superballs...
May 18, 2017: Nanoscale
Katharina Märker, Subhradip Paul, Carlos Fernández-de-Alba, Daniel Lee, Jean-Marie Mouesca, Sabine Hediger, Gaël De Paëpe
The self-assembly of small organic molecules is an intriguing phenomenon, which provides nanoscale structures for applications in numerous fields from medicine to molecular electronics. Detailed knowledge of their structure, in particular on the supramolecular level, is a prerequisite for the rational design of improved self-assembled systems. In this work, we prove the feasibility of a novel concept of NMR-based 3D structure determination of such assemblies in the solid state. The key point of this concept is the deliberate use of samples that contain (13)C at its natural isotopic abundance (NA, 1...
February 1, 2017: Chemical Science
Katie L M Harriman, Jennifer J Le Roy, Liviu Ungur, Rebecca J Holmberg, Ilia Korobkov, Muralee Murugesu
The preparation of η-cyclopentadienyl (η(5)-C5R5), η-arene (η(6)-C6R6), and η-cyclooctatetraenyl (η(8)-C8R8) bridging motifs are common in organometallic chemistry; however, the synthetic preparation of η-cycloheptatrienyl (η(7)-C7R7) bridging motifs has remained a synthetic challenge in 4f chemistry. To this end, we have developed a synthetic route towards a series of rare dinuclear organolanthanide inverse sandwich complexes containing the elusive η(7)-C7H7 bridge. Herein, we present the structures and magnetic properties of the lanthanide inverse sandwich complexes [KLn2(C7H7)(N(SiMe3)2)4] (Ln = Gd(III) (1), Dy(III) (2), Er(III) (3)) and [K(THF)2Er2(C7H7)(N(SiMe3)2)4] (4)...
January 1, 2017: Chemical Science
Seojun Lee, Hyungchae Kim, Jongcheon Lee, Changsoon Kim
We investigate scattering of surface plasmon polaritons (SPPs) at a planar metal-dielectric interface by a dielectric nanocube embedded in the metal layer using finite element method-based simulations. The scattering characteristics of the embedded nanocube, such as the scattering and absorption cross sections, far-field scattering patterns, reflectance, and transmittance, are calculated as functions of the wavelength of the incident SPP waves in the visible range. The main features of the characteristics are explained in connection with the excitation of plasmonic eigenmodes of the embedded nanocube...
April 17, 2017: Optics Express
Marine Schott, Anne Bernand-Mantel, Laurent Ranno, Stefania Pizzini, Jan Vogel, Hélène Béa, Claire Baraduc, Stéphane Auffret, Gilles Gaudin, Dominique Givord
Nanoscale magnetic skyrmions are considered as potential information carriers for future spintronics memory and logic devices. Such applications will require the control of their local creation and annihilation, which involves so far solutions that are either energy consuming or difficult to integrate. Here we demonstrate the control of skyrmion bubbles nucleation and annihilation using electric field gating, an easily integrable and potentially energetically efficient solution. We present a detailed stability diagram of the skyrmion bubbles in a Pt/Co/oxide trilayer and show that their stability can be controlled via an applied electric field...
April 27, 2017: Nano Letters
Camilla Terenzi, Sabine Bouguet-Bonnet, Daniel Canet
At ambient temperature, conversion from 100% enriched para-hydrogen (p-H2; singlet state) to ortho-hydrogen (o-H2; triplet state) leads necessarily to the thermodynamic equilibrium proportions: 75% of o-H2 and 25% of p-H2. When p-H2 is dissolved in a diamagnetic organic solvent, conversion is very slow and can be considered as arising from nuclear spin relaxation phenomena. A first relaxation mechanism, specific to the singlet state and involving a combination of auto-correlation and cross correlation spectral densities, can be retained: randomly fluctuating magnetic fields due to inter-molecular dipolar interactions...
April 21, 2017: Journal of Chemical Physics
Fabio Novelli, Saeideh Ostovar Pour, Jonathan Tollerud, Ashkan Roozbeh, Dominique R T Appadoo, Ewan W Blanch, Jeffrey A Davis
Here we reveal details of the interaction between human lysozyme proteins, both native and fibrils, and their water environment by intense terahertz time domain spectroscopy. With the aid of a rigorous dielectric model, we determine the amplitude and phase of the oscillating dipole induced by the THz field in the volume containing the protein and its hydration water. At low concentrations, the amplitude of this induced dipolar response decreases with increasing concentration. Beyond a certain threshold, marking the onset of the interactions between the extended hydration shells, the amplitude remains fixed but the phase of the induced dipolar response, which is initially in phase with the applied THz field, begins to change...
May 11, 2017: Journal of Physical Chemistry. B
Andrey A Kuznetsov, Alexander F Pshenichnikov
Langevin dynamics simulation is used to study the suspension of interacting magnetic nanoparticles (dipolar spheres) in a zero applied magnetic field and in the presence of a gravitational (centrifugal) field. A particular emphasis is placed on the equilibrium vertical distribution of particles in the infinite horizontal slab. An increase in the dipolar coupling constant λ (the ratio of dipole-dipole interaction energy to thermal energy) from zero to seven units causes an increase in the particle segregation coefficient by several orders of magnitude...
March 2017: Physical Review. E
Seok-Yeong Chä, Uwe R Fischer
We consider an analogue de Sitter cosmos in an expanding quasi-two-dimensional Bose-Einstein condensate with dominant dipole-dipole interactions between the atoms or molecules in the ultracold gas. It is demonstrated that a hallmark signature of inflationary cosmology, the scale invariance of the power spectrum of inflaton field correlations, experiences strong modifications when, at the initial stage of expansion, the excitation spectrum displays a roton minimum. Dipolar quantum gases thus furnish a viable laboratory tool to experimentally investigate, with well-defined and controllable initial conditions, whether primordial oscillation spectra deviating from Lorentz invariance at trans-Planckian momenta violate standard predictions of inflationary cosmology...
March 31, 2017: Physical Review Letters
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