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Dipolar field

J Cividini, D Mukamel, H A Posch
Steady-state properties of a driven tracer moving in a narrow two-dimensional (2D) channel of quiescent medium are studied. The tracer drives the system out of equilibrium, perturbs the density and pressure fields, and gives the bath particles a nonzero average velocity, creating a current in the channel. Three models in which the confining effect of the channel is probed are analyzed and compared in this study: the first is the simple symmetric exclusion process (SSEP), for which the stationary density profile and the pressure on the walls in the frame of the tracer are computed...
January 2017: Physical Review. E
L Carletti, D Rocco, A Locatelli, C De Angelis, V F Gili, M Ravaro, I Favero, G Leo, M Finazzi, L Ghirardini, M Celebrano, G Marino, A V Zayats
We review recent achievements in the field of nanoscale nonlinear AlGaAs photonics based on all-dielectric optical antennas. After discussing the motivation and main technological challenges for the development of an AlGaAs monolithic platform for χ ((2)) nonlinear nanophotonics, we present numerical and experimental investigations of the second-order nonlinear response and physical reasons for high efficiency of second-order nonlinear interactions in the AlGaAs nano-antennas. In particular, we emphasize the role of the dipolar resonances at the fundamental frequency and the multipolar resonances at the second harmonic wavelength...
February 16, 2017: Nanotechnology
Mohammadhasan Dinpajooh, Marshall D Newton, Dmitry V Matyushov
The separation of slow nuclear and fast electronic polarization in problems related to electron mobility in polarizable media was considered by Pekar 70 years ago. Within dielectric continuum models, this separation leads to the Pekar factor in the free energy of solvation by the nuclear degrees of freedom. The main qualitative prediction of Pekar's perspective is a significant, by about a factor of two, drop of the nuclear solvation free energy compared to the total (electronic plus nuclear) free energy of solvation...
February 14, 2017: Journal of Chemical Physics
V H Prevost, O M Girard, S Mchinda, G Varma, D C Alsop, G Duhamel
A pulsed inhomogeneous magnetization transfer (ihMT)-prepared fast imaging sequence was implemented at 11.75 T for preclinical studies on mouse central nervous system. A strategy based on filtering the ihMT signal originating from short dipolar relaxation time (T1D ) components is proposed. It involves increasing the repetition time of consecutive radiofrequency (RF) pulses of the dual saturation and allows improved signal specificity for long T1D myelinated structures. Furthermore, frequency offset, power and timing saturation parameters were adjusted to optimize the ihMT sensitivity...
February 14, 2017: NMR in Biomedicine
N A Sergeev, M Paczwa, M Olszewski, A M Panich
Temperature dependencies of (27)Al and (23)Na nuclear magnetic resonance spectra and spin-lattice relaxations in mordenite have been studied in static and magic angle spinning regimes. Our data show that the spin-lattice relaxations of the (23)Na and (27)Al nuclei are mainly governed by interaction of nuclear quadrupole moments with electric field gradients of the crystal, modulated by translational motion of water molecules in the mordenite channels. At temperatures below 200 K, the dipolar interaction of nuclear spins with paramagnetic impurities becomes an important relaxation mechanism of the (23)Na and (27)Al nuclei...
2017: Applied Magnetic Resonance
Anna Naumova, Carsten Tschierske, Kay Saalwächter
In recent years, the analysis of proton double-quantum NMR build-up curves has become an important tool to quantify anisotropic mobility in different kinds of soft materials such as polymer networks or liquid crystals. In the former case, such data provides a measure of orientation-dependent residual (time-averaged) dipolar couplings arising from anisotropic segmental motions, informing about the length and the state of local stretching of the network chains. Previous studies of macroscopically ordered, i.e...
January 26, 2017: Solid State Nuclear Magnetic Resonance
Hui Dong, Seong-Min Hwang, Michael Wendland, Lixing You, John Clarke, Ben Inglis
PURPOSE: To investigate tissue-specific differences, a quantitative comparison was made between relaxation dispersion in postmortem pig brain measured at ultralow fields (ULF) and spin locking at 7 tesla (T). The goal was to determine whether ULF-MRI has potential advantages for in vivo human brain imaging. METHODS: Separate specimens of gray matter and white matter were investigated using an ULF-MRI system with superconducting quantum interference device (SQUID) signal detection to measure T1ULF at fields from 58...
February 5, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Wenyang Wu, Mingjie Wan, Ping Gu, Zhuo Chen, Zhenling Wang
We theoretically investigate the coupling between molecular excitons and dipolar Fano-like cavity plasmon resonance in two-layered core-shell resonators consisting of a dielectric core with high refractive index and a thin metal outer shell gapped by a low refractive index thin dielectric layer containing molecules. We demonstrate that associated with the excitation of the dipolar Fano-like cavity plasmon, the electric fields can be highly localized within the dielectric gap shell, leading to very small mode volumes...
January 23, 2017: Optics Express
A Blank
ESR spectroscopy can be efficiently used to acquire the distance between two spin labels placed on a macromolecule by measuring their mutual dipolar interaction frequency, as long as the distance is not greater than ∼10 nm. Any hope to significantly increase this figure is hampered by the fact that all available spin labels have a phase memory time (Tm), restricted to the microseconds range, which provides a limited window during which the dipolar interaction frequency can be measured. Thus, due to the inverse cubic dependence of the dipolar frequency over the labels' separation distance, evaluating much larger distances, e...
February 2, 2017: Physical Chemistry Chemical Physics: PCCP
A M Martin, N G Marchant, D H J O'Dell, N G Parker
The experimental realization of quantum-degenerate Bose gases made of atoms with sizeable magnetic dipole moments has created a new type of fluid, known as a quantum ferrofluid, which combines the extraordinary properties of superfluidity and ferrofluidity. A hallmark of superfluids is that they are constrained to rotate through vortices with quantized circulation. In quantum ferrofluids the long-range dipolar interactions add new ingredients by inducing magnetostriction and instabilities, and also affect the structural properties of vortices and vortex lattices...
March 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Pär Håkansson
Molecular dynamics and quantum chemistry methods are implemented to quantify nuclear spin-1/2 pair singlet-state relaxation rates for three molecular systems at low magnetic field and room temperature. Computational methodology is developed for weak interactions, particularly important for singlet states at low field. These include spin-rotation and spin-internal-motion effects, which describe the coupling of the spin-carrying nuclei to fluctuating local magnetic fields induced by the overall and internal molecular fluctuations, respectively...
January 25, 2017: Physical Chemistry Chemical Physics: PCCP
Qi-Jie Zhang, Jin-Jing Li, Xiang Lin, Ying-Qian Lu, Xin-Xin Guo, En-Lin Dong, Miao Zhao, Jin He, Ning Wang, Wan-Jin Chen
Spinal muscular atrophy (SMA) is a lethal autosomal recessive neurological disease characterized by selective degeneration of motor neurons in the spinal cord. In recent years, the development of cellular reprogramming technology has provided an alternative and effective method for obtaining patient-specific neurons in vitro. In the present study, we applied this technology to the field of SMA to acquire patient-specific induced motor neurons that were directly converted from fibroblasts via the forced expression of 8 defined transcription factors...
January 13, 2017: Oncotarget
P Gast, D Mance, E Zurlo, K L Ivanov, M Baldus, M Huber
To understand the dynamic nuclear polarization (DNP) enhancements of biradical polarizing agents, the magnetic resonance parameters need to be known. We describe a tailored EPR approach to accurately determine electron spin-spin coupling parameters using a combination of standard (9 GHz), high (95 GHz) and ultra-high (275 GHz) frequency EPR. Comparing liquid- and frozen-solution continuous-wave EPR spectra provides accurate anisotropic dipolar interaction D and isotropic exchange interaction J parameters of the DNP biradical AMUPol...
February 1, 2017: Physical Chemistry Chemical Physics: PCCP
Frédéric Mentink-Vigier, Shimon Vega, Gaël De Paëpe
A deeper understanding of parameters affecting Magic Angle Spinning Dynamic Nuclear Polarization (MAS-DNP), an emerging nuclear magnetic resonance hyperpolarization method, is crucial for the development of new polarizing agents and the successful implementation of the technique at higher magnetic fields (>10 T). Such progress is currently impeded by computational limitation which prevents the simulation of large spin ensembles (electron as well as nuclear spins) and to accurately describe the interplay between all the multiple key parameters at play...
February 1, 2017: Physical Chemistry Chemical Physics: PCCP
Nghia Tuan Duong, Yusuke Nishiyama
Recent study has demonstrated the application of the proton-detected heteronuclear multi-quantum coherence (HMQC) at ultrafast Magic Angle Spinning (MAS) to probe quadrupolar nuclei including (14)N and (35)Cl. In addition, for half-integer quadrupolar nucleus like (35)Cl, the quadrupolar product can be calculated based on the shift difference between the center band of satellite transition (ST) and the central transition (CT) peaks. The applicability of this technique is further investigated on spin I=5/2, namely (27)Al nucleus, and kaolin is chosen as the testing sample...
January 4, 2017: Solid State Nuclear Magnetic Resonance
Olivier Saurel, Iordan Iordanov, Guillaume Nars, Pascal Demange, Tanguy Le Marchand, Loren B Andreas, Guido Pintacuda, Alain Milon
The role of membrane proteins in cellular mechanism strongly depends on their dynamics, and solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) is a unique method to exhaustively characterize motions of proteins in a lipid environment. Herein, we make use of advances in (1)H-detected MAS NMR to describe the dynamics of the membrane domain of the Outer membrane protein A of Klebsiella pneumoniae (KpOmpA). By measuring (1)H-(15)N dipolar-coupling as well as (15)N R1 and R1ρ relaxation rates at fast (60 kHz) MAS and high magnetic field (1 GHz), we were able to describe the motions of the residues of the β-barrel as a collective rocking of low amplitude and of hundreds of nanoseconds time scale...
February 1, 2017: Journal of the American Chemical Society
Filippo Nisic, Elena Cariati, Alessia Colombo, Claudia Dragonetti, Simona Fantacci, Eleonora Garoni, Elena Lucenti, Stefania Righetto, Dominique Roberto, J A Gareth Williams
The synthesis and characterization of three 5-π-delocalized-donor-1,3-di(2-pyridyl)benzenes is reported along with that of their related cyclometallated platinum(ii) complexes and N,N-dimethylated iodide salts. The second-order nonlinear optical (NLO) properties of all the compounds have been determined by the Electric Field Induced Second Harmonic generation technique, showing how the μβEFISH absolute value of 1,3-di(2-pyridyl)benzenes can be tuned by the nature of the substituent on position 5 of the central benzene ring, and greatly increased by cyclometallation to Pt or by N-methylation...
January 5, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
C Trupthi Devaiah, B Hemavathi, T N Ahipa
Versatile conjugated small molecules bearing cyanopyridone core (CP1-5), composed of various donor/acceptor moieties at position -4 and -6 have been designed, developed and characterized. Their solvatochromic studies were conducted and analyzed using Lippert-Mataga, Kamlet-Taft and Catalan solvent scales and interesting results were obtained. The polarizability/dipolarity of the solvent greatly influenced the spectra. The electrochemical studies were carried out using cyclic voltammetry to calculate the HOMO-LUMO energy levels...
March 15, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Zichun Wang, Yijiao Jiang, Olivier Lafon, Julien Trébosc, Kyung Duk Kim, Catherine Stampfl, Alfons Baiker, Jean-Paul Amoureux, Jun Huang
Zeolites and amorphous silica-alumina (ASA), which both provide Brønsted acid sites (BASs), are the most extensively used solid acid catalysts in the chemical industry. It is widely believed that BASs consist only of tetra-coordinated aluminum sites (Al(IV)) with bridging OH groups in zeolites or nearby silanols on ASA surfaces. Here we report the direct observation in ASA of a new type of BAS based on penta-coordinated aluminum species (Al(V)) by (27)Al-{(1)H} dipolar-mediated correlation two-dimensional NMR experiments at high magnetic field under magic-angle spinning...
December 15, 2016: Nature Communications
Sai Chaitanya Chiliveri, Mandar V Deshmukh
The advent of Transverse Relaxation Optimized SpectroscopY (TROSY) and perdeuteration allowed biomolecular NMR spectroscopists to overcome the size limitation barrier (approx. 20 kDa) in de novo structure determination of proteins. The utility of these techniques was immediately demonstrated on large proteins and protein complexes (e.g. GroELGroES, ClpP protease, Hsp90-p53, 20S proteasome, etc.). Further, recent methodological developments such as Residual Dipolar Couplings and Paramagnetic Relaxation Enhancement allowed accurate measurement of long-range structural restraints...
December 2016: Journal of Biosciences
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