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Colin Greatwood, Thomas S Richardson, Jim Freer, Rick M Thomas, A Rob MacKenzie, Rebecca Brownlow, David Lowry, Rebecca E Fisher, Euan G Nisbet
As part of an NERC-funded project investigating the southern methane anomaly, a team drawn from the Universities of Bristol, Birmingham and Royal Holloway flew small unmanned multirotors from Ascension Island for the purposes of atmospheric sampling. The objective of these flights was to collect air samples from below, within and above a persistent atmospheric feature, the Trade Wind Inversion, in order to characterise methane concentrations and their isotopic composition. These parameters allow the methane in the different air masses to be tied to different source locations, which can be further analysed using back trajectory atmospheric computer modelling...
May 23, 2017: Sensors
Marisa Aguiar, Alan Stolzer, Douglas D Boyd
BACKGROUND: Flying over mountainous and/or high elevation terrain is challenging due to rapidly changeable visibility, gusty/rotor winds and downdrafts and the necessity of terrain avoidance. Herein, general aviation accident rates and mishap cause/factors were determined (2001-2014) for a geographical region characterized by such terrain. METHODS: Accidents in single piston engine-powered aircraft for states west of the US continental divide characterized by mountainous terrain and/or high elevation (MEHET) were identified from the NTSB database...
May 19, 2017: Accident; Analysis and Prevention
Anna I Sulatskaya, Andrey V Lavysh, Alexander A Maskevich, Irina M Kuznetsova, Konstantin K Turoverov
Fluorescence of thioflavin T (ThT) is a proven tool for amyloid fibrils study. The correct model of ThT binding to fibrils is crucial to clarify amyloid fibrils structure and mechanism of their formation. Although there are convincing evidences that ThT has molecular rotor nature, implying it's binding to fibrils in monomer form, speculations concerning ThT binding to fibrils in aggregated forms appear in literature so far. The elaborated approach for fluorescence intensity correction on the inner filter effects applied to ThT aqueous solutions with a wide range of concentration allowed characterizing ThT excimers fluorescence and showing its difference from that of ThT bound to fibrils...
May 19, 2017: Scientific Reports
A Metzner, J Riedl, K-H Kuck
Catheter-based ablation is an established treatment option for patients with symptomatic atrial fibrillation (AF). Pulmonary vein isolation is the established cornerstone of all ablation strategies. However, the rate of electrical reconduction of previously isolated pulmonary veins is high and associated with recurrence of AF. Novel and innovative mapping and ablation systems are being developed or are under clinical evaluation aiming for higher durability of pulmonary vein isolation. Additional ablation strategies for patients with recurrence of AF despite persistent isolation of the pulmonary veins are under evaluation...
May 18, 2017: Herz
Pronay Kumar Biswas, Suchismita Saha, Yerramsetti Nanaji, Anup Rana, Michael Schmittel
Four-component nanorotors are prepared by the self-assembly of stator [Cu4(4)](4+) with its four copper(I)-loaded phenanthroline stations and various rotators carrying one, two, or three pyridine terminals. The fourth component, 1,4-diazabicyclo[2.2.2]octane, serves as a connecting axle between rotator and stator. Capitalizing on the heteroleptic pyridyl and phenanthroline metal complexes concept, the rotator's pyridine terminals are connected to the copper(I)-loaded phenanthroline stations (Npy → [Cu(phen)](+)) in the STOP state and disconnected in the transition state of rotation...
May 17, 2017: Inorganic Chemistry
Vinay Kumar Pandey, Indrani Kar, Chitralekha Mahanta
In this paper, an adaptive control method using multiple models with second level adaptation is proposed for a class of nonlinear multi-input multi-output (MIMO) coupled systems. Multiple estimation models are used to tune the unknown parameters at the first level. The second level adaptation provides a single parameter vector for the controller. A feedback linearization technique is used to design a state feedback control. The efficacy of the designed controller is validated by conducting real time experiment on a laboratory setup of twin rotor MIMO system (TRMS)...
May 13, 2017: ISA Transactions
Shunyue Wang, Fengtian Han, Boqian Sun, Haixia Li
Air-film damping, which dominates over other losses, plays a significant role in the dynamic response of many micro-fabricated devices with a movable mass suspended by various bearing mechanisms. Modeling the damping characteristics accurately will be greatly helpful to the bearing design, control, and test in various micromotor devices. This paper presents the simulated and experimental squeeze-film air damping results of an electrostatic bearing for use in a rotary high-speed micromotor. It is shown that the boundary condition to solve the three-dimensional Reynolds equation, which governs the squeeze-film damping in the air gap between the rotor and its surrounding stator sealed in a three-layer evacuated cavity, behaves with strong cross-axis coupling characteristics...
May 13, 2017: Sensors
Andrés Aguilar-Granda, Salvador Pérez-Estrada, Elı Sánchez-González, J Raziel Álvarez, Joelis Rodríguez-Hernández, Mario Rodríguez, Arian E Roa, Simón Hernández-Ortega, Ilich A Ibarra, Braulio Rodríguez-Molina
We report for the first time the high sorption properties of a molecular rotor with no permanent voids or channels in its crystal structure. Such crystalline phase originates from THF, DCM, or the irreversible desolvation of entrapped benzene molecules. From these, the benzene in its solvate form acts as rotation stopper, as supported by dynamic characterization using solid-state (2)H NMR experiments. In the solvent-free form, the diffusion of small quantities of iodine vapors caused a significant change in the intramolecular rotation, increasing the known activation energy to rotation from 8...
May 25, 2017: Journal of the American Chemical Society
C Lemeš, K-H Kuck, S Mathew
Despite the very promising initial results of clinical studies, catheter ablation of persistent atrial fibrillation (AF) remains a challenge in modern electrophysiology. On the basis of the hypothesized pathophysiological mechanisms, a variety of ablation strategies have been developed over the course of time. The current ablation strategies range from pulmonary vein isolation (PVI) alone as first-line therapy, through ablation of multiple linear lesions, ablation of complex fractionated atrial electrograms (CFAE), rotor ablation, isolation of fibrotic and scar tissue up to isolation of the left atrial appendage (LAA); however, it is unclear even to the present day whether these complex and time-consuming strategies actually improve the success rate of ablation therapy...
May 12, 2017: Herz
Caroline H Roney, Chris D Cantwell, Jason D Bayer, Norman A Qureshi, Phang Boon Lim, Jennifer H Tweedy, Prapa Kanagaratnam, Nicholas S Peters, Edward J Vigmond, Fu Siong Ng
BACKGROUND: Recent studies have demonstrated conflicting mechanisms underlying atrial fibrillation (AF), with the spatial resolution of data often cited as a potential reason for the disagreement. The purpose of this study was to investigate whether the variation in spatial resolution of mapping may lead to misinterpretation of the underlying mechanism in persistent AF. METHODS AND RESULTS: Simulations of rotors and focal sources were performed to estimate the minimum number of recording points required to correctly identify the underlying AF mechanism...
May 2017: Circulation. Arrhythmia and Electrophysiology
Sumit Sarkar, Sanku Paul, Chetan Vishwakarma, Sunil Kumar, Gunjan Verma, M Sainath, Umakant D Rapol, M S Santhanam
Quantum systems lose coherence upon interaction with the environment and tend towards classical states. Quantum coherence is known to exponentially decay in time so that macroscopic quantum superpositions are generally unsustainable. In this work, slower than exponential decay of coherences is experimentally realized in an atom-optics kicked rotor system subjected to nonstationary Lévy noise in the applied kick sequence. The slower coherence decay manifests in the form of quantum subdiffusion that can be controlled through the Lévy exponent...
April 28, 2017: Physical Review Letters
Aman Jindal, Sukumaran Vasudevan
Ethylene glycol is a typical rotor molecule with the three dihedral angles that allow for a number of possible conformers. The geometry of the molecule in the liquid state brings into sharp focus the competition between intra- and inter-molecular interactions in deciding conformation. Here, we report a conformational analysis of ethylene glycol in the liquid state from ab initio molecular dynamics simulations. Our results highlight the importance of intermolecular hydrogen bonding over intramolecular interactions in the liquid, with the central OCCO linkage adopting both gauche and trans geometries in contrast to the gas phase, wherein only the gauche has been reported...
May 24, 2017: Journal of Physical Chemistry. B
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
Likui Yang, Kun Cai, Jiao Shi, Qing H Qin
Many factors can have a significant influence on the output power of a thermally driven rotary nanomotor made of carbon nanotubes (CNTs). Making use of a computational molecular dynamics approach, we evaluate for the first time the output power of a nanomotor, considering some of the main factors including temperature, the diameter of the rotor and the number of IRD atoms (N) on the stator. When applying extra-resistant torque to the rotor to let the stable value of the rotational frequency of the rotor fluctuate near zero, the value of the resistant torque can be considered as the output power of the rotor...
May 26, 2017: Nanotechnology
Kai Sun, Min-Long Tao, Yu-Bing Tu, Jun-Zhong Wang
Molecular rotors with an off-center axis and the chiral feature of achiral CuPc molecules on a semi-metallic Bi(111) surface have been investigated by means of a scanning tunneling microscopy (STM) at liquid nitrogen (LN₂) temperature. The rotation axis of each CuPc molecular rotor is located at the end of a phthalocyanine group. As molecular coverage increases, the CuPc molecules are self-assembled into various nanoclusters and finally into two-dimensional (2D) domains, in which each CuPc molecule exhibits an apparent chiral feature...
May 4, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Zsuzsanna Kis, Dominic A Theuns, Rohit Bhagwandien, Sip Wijchers, Sing-Chien Yap, Tamas Szili-Torok
BACKGROUND: There remains controversy about the optimal ablation technique and termination rate of atrial fibrillation (AF) during catheter ablation in patients with persistent AF. The aim of this study was to determine the rate and timing of AF termination during combined pulmonary vein isolation (PVI) and focal impulse and rotor modulation (FIRM)-guided ablation of rotational activity (RoAc). METHODS: This single-center, prospective cohort study enrolled 38 consecutive patients (63% male, mean age 63 ± 11 years) with persistent AF (mean left atrial size: 46 ± 7 mm), who underwent FIRM mapping and ablation of the identified RoAcs followed by PVI...
May 4, 2017: Journal of Cardiovascular Electrophysiology
Wei Wang, Wei Hu, Pei Yang, Xiao Qian Dang, Xiao Hui Li, Kun Zheng Wang
INTRODUCTION: Core decompression is an efficient treatment for early stage ischemic necrosis of the femoral head. In conventional procedures, the pre-operative X-ray only shows one plane of the ischemic area, which often results in inaccurate drilling. This paper introduces a new method that uses computer-assisted technology and rapid prototyping to enhance drilling accuracy during core decompression surgeries and presents a validation study of cadaveric tests. METHODS: Twelve cadaveric human femurs were used to simulate early-stage ischemic necrosis...
2017: PloS One
Josef M Maier, Ping Li, Erik C Vik, Christopher J Yehl, Sharon M S Strickland, Ken D Shimizu
A molecular torsion balance was designed to study and measure OH-π interactions between protic solvents and aromatic surfaces. These specific solvent-solute interactions were measured via their influence on the folded-unfolded equilibrium of an N-arylimide rotor. Protic solvents displayed systematically weaker solvophobic interactions than aprotic solvents with similar solvent cohesion parameters. This was attributed to the formation of OH-π interactions between the protic solvents and the exposed aromatic surfaces in the unfolded conformer that offset the stronger solvophobic effects for protic solvents...
May 9, 2017: Journal of the American Chemical Society
Thomas van Leeuwen, Wojciech Danowski, Edwin Otten, Sander J Wezenberg, Ben L Feringa
The enantiomeric homogeneity of light-driven molecular motors based on overcrowded alkenes is crucial in their application as either unidirectional rotors or as chiral multistate switches. It was challenging to obtain these compounds as single enantiomers via the established synthetic procedures due to loss of optical purity in the key step, i.e., the Barton-Kellogg olefination reaction. Searching for strategies to avoid racemization, a new class of light-driven molecular motors was designed, synthesized, and studied...
May 19, 2017: Journal of Organic Chemistry
Jason M Hudzik, Joseph William Bozzelli
Reaction pathways are influenced by thermochemical properties, species stability, and chemical kinetics. Understanding these factors allows for an understanding of the reaction paths and formation of intermediate species. Enthalpies of formation (ΔHf °298), entropies (S°298), heat capacities (Cp(T)), oxygen-hydrogen (O-H), and oxygen- oxygen (O-O) bond dissociation energies (BDEs) are reported for hydroxyl and hydroperoxide substituted furan, methylfuran, and methoxyfuran species. Standard enthalpies of formation for parent and radical species have been determined using density functional theory B3LYP/6-31G(d,p) , B3LYP/6-311G(2d,2p), and M06-2X/6-31G(d,p) along with higher level CBS-QB3 and CBS-APNO composite methods...
May 1, 2017: Journal of Physical Chemistry. A
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