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Tomislav Suhina, Saeed Amirjalayer, Sander Woutersen, Daniel Bonn, Albert M Brouwer
Molecular rotors based on meso-substituted boron-dipyrromethane (BODIPY) are widely recognized fluorescent viscosity sensors. The viscosity dependence of their fluorescence arises from an efficient excited-state deactivation process that can only occur when molecular-scale motion is not hindered. Here, we use visible and IR pump-probe spectroscopies combined with TD-DFT calculations to show that this fluorescence deactivation takes place through a fast and irreversible process which does not involve intermediate electronic states...
July 19, 2017: Physical Chemistry Chemical Physics: PCCP
Stefan Boës, Gregor Ochsner, Raffael Amacher, Anastasios Petrou, Mirko Meboldt, Marianne Schmid Daners
A mock circulation allows the in vitro investigation, development, and testing of ventricular assist devices. An aqueous-glycerol solution is commonly used to mimic the viscosity of blood. Due to evaporation and temperature changes, the viscosity of the solution drifts from its initial value and therefore, deviates substantially from the targeted viscosity of blood. Additionally, the solution needs to be exchanged to account for changing viscosities when mimicking different hematocrits. This article presents a method to control the viscosity in a mock circulation...
July 17, 2017: Artificial Organs
Aurimas Vyšniauskas, Ismael López-Duarte, Nicolas Duchemin, Thanh-Truc Vu, Yilei Wu, Ekaterina M Budynina, Yulia A Volkova, Eduardo Peña Cabrera, Diana E Ramírez-Ornelas, Marina K Kuimova
Microviscosity is a key parameter controlling the rate of diffusion and reactions on the microscale. One of the most convenient tools for measuring microviscosity is by fluorescent viscosity sensors termed 'molecular rotors'. BODIPY-based molecular rotors in particular proved extremely useful in combination with fluorescence lifetime imaging microscopy, for providing quantitative viscosity maps of living cells as well as measuring dynamic changes in viscosity over time. In this work, we investigate several new BODIPY-based molecular rotors with the aim of improving on the current viscosity sensing capabilities and understanding how the structure of the fluorophore is related to its function...
July 18, 2017: Physical Chemistry Chemical Physics: PCCP
Ravi Chawla, Katie M Ford, Pushkar P Lele
The stator-complex in the bacterial flagellar motor is responsible for surface-sensing. It remodels in response to perturbations in viscous loads, recruiting additional stator-units as the load increases. Here, we tested a hypothesis that the amount of torque generated by each stator-unit modulates its association with the rotor. To do this, we measured stator-binding to the rotor in mutants in which motors reportedly develop lower torque compared to wildtype motors. First, we employed a strain lacking fliL...
July 17, 2017: Scientific Reports
Pascale Gauthier, Jean-Michel Cardot, Erick Beyssac, Jean-Marc Aiache
Different previous works have shown that various kinds of spheres can be manufactured by rotor granulation in a 'single pot process' using a lipid base: Hydrogenated Castor Oil. This single pot technology is based on wet granulation where all components are placed in powder form in the rotor bowl; then, they are continuously suspended in a fluidized air, with a tangentially sprayed liquid solution. This process allows the granulation and sphere manufacture during the same time. Previous experiments have studied the influence of the formulation and the manufacturing process parameters on spheres in term of feasibility and dissolution properties...
July 17, 2017: Pharmaceutical Development and Technology
Fethi Farhani, Chiheb Ben Regaya, Abderrahmen Zaafouri, Abdelkader Chaari
This paper describes a robust and efficient speed control of a three phase induction machine (IM) subjected to load disturbances. First, a Multiple-Input Multiple-Output (MIMO) PI-Backstepping controller is proposed for a robust and highly accurate tracking of the mechanical speed and rotor flux. Asymptotic stability of the control scheme is proven by Lyapunov Stability Theory. Second, an active online optimization algorithm is used to optimize the efficiency of the drive system. The efficiency improvement approach consists of adjusting the rotor flux with respect to the load torque in order to minimize total losses in the IM...
July 13, 2017: ISA Transactions
Alexandre Roulet, Stefan Nimmrichter, Juan Miguel Arrazola, Stella Seah, Valerio Scarani
The triumph of heat engines is their ability to convert the disordered energy of thermal sources into useful mechanical motion. In recent years, much effort has been devoted to generalizing thermodynamic notions to the quantum regime, partly motivated by the promise of surpassing classical heat engines. Here, we instead adopt a bottom-up approach: we propose a realistic autonomous heat engine that can serve as a test bed for quantum effects in the context of thermodynamics. Our model draws inspiration from actual piston engines and is built from closed-system Hamiltonians and weak bath coupling terms...
June 2017: Physical Review. E
Hiroki Tutu, Katsuya Ouchi, Takehiko Horita
With a model for two-dimensional (2D) Brownian rotary ratchets being capable of producing a net torque under athermal random forces, its optimization for mean angular momentum (L), mean angular velocity (ω), and efficiency (η) is considered. In the model, supposing that such a small ratchet system is placed in a thermal bath, the motion of the rotor in the stator is described by the Langevin dynamics of a particle in a 2D ratchet potential, which consists of a static and a time-dependent interaction between rotor and stator; for the latter, we examine a force [randomly directed dc field (RDDF)] for which only the direction is instantaneously updated in a sequence of events in a Poisson process...
June 2017: Physical Review. E
Jean-Nicolas Dumez, Basile Vuichoud, Daniele Mammoli, Aurélien Bornet, Arthur C Pinon, Gabriele Stevanato, Benno Meier, Geoffrey Bodenhausen, Sami Jannin, Malcolm H Levitt
We have induced hyperpolarized long-lived states in compounds containing 13C-bearing methyl groups by dynamic nuclear polarization (DNP) at cryogenic temperatures, followed by dissolution with a warm solvent. The hyperpolarized methyl long-lived states give rise to enhanced antiphase 13C NMR signals in solution, which often persist for times much longer than the 13C and 1H spin-lattice relaxation times under the same conditions. The DNP-induced effects are similar to quantum-rotor-induced-polarization (QRIP), but are observed in a wider range of compounds, since they do not depend critically on the height of the rotational barrier...
July 14, 2017: Journal of Physical Chemistry Letters
Zachary Laksman, Marianne Wauchop, Eric Lin, Stephanie Protze, Jeehoon Lee, Wallace Yang, Farzad Izaddoustdar, Sanam Shafaattalab, Lior Gepstein, Glen F Tibbits, Gordon Keller, Peter H Backx
Since current experimental models of Atrial Fibrillation (AF) have significant limitations, we used human embryonic stem cells (hESCs) to generate an atrial-specific tissue model of AF for pharmacologic testing. We generated atrial-like cardiomyocytes (CMs) from hESCs which preferentially expressed atrial-specific genes, and had shorter action potential (AP) durations compared to ventricular-like CMs. We then generated confluent atrial-like CM sheets and interrogated them using optical mapping techniques. Atrial-like CM sheets (~1 cm in diameter) showed uniform AP propagation, and rapid re-entrant rotor patterns, as seen in AF could be induced...
July 13, 2017: Scientific Reports
Aafrin M Pettiwala, Prabhat K Singh
The inevitable importance of basic amino acids, arginine and lysine, in human health and metabolism demands construction of efficient sensor systems for them. However, there are only limited reports on the 'ratiometric' detection of basic amino acids which is further restricted by the use of chemically complex sensor molecules, which impedes their prospect for practical applications. Herein, we report a ratiometric sensor system build on simple mechanism of disassociation of novel emissive Thioflavin-T H-aggregates from heparin surface, when subjected to interaction with basic amino acids...
June 29, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Jeremy Glynn, Howard Song, Bryan Hull, Stanley Withers, Jill Gelow, James Mudd, Albert Starr, Richard Wampler
Widespread use of heart transplantation is limited by the scarcity of donor organs. Total artificial heart (TAH) development has been pursued to address this shortage, especially to treat patients who require biventricular support. We have developed a novel TAH that utilizes a continuously spinning rotor that shuttles between two positions to provide pulsatile, alternating blood flow to the systemic and pulmonary circulations without artificial valves. Flow rates and pressures generated by the TAH are controlled by adjusting rotor speed, cycle frequency, and the proportion of each cycle spent pumping to either circulation...
July 13, 2017: Artificial Organs
Merve S Özer, Anup Rana, Pronay K Biswas, Michael Schmittel
An off-axis supramolecular rotor was composed of four components: a zinc-porphyrin based stator with four phenanthroline stations and a zinc-salphen based rotator were self-assembled with DABCO and four copper(i) ions to furnish the rotor ROT-2 in quantitative yield. The DABCO serves as a connecting axle between the rotator and the stator, while the rotator is additionally connected to two copper(i)-loaded phenanthroline stations of the stator via its two pyridine terminals (Npy → [Cu(phen)](+)). For the thermally activated rotation both Npy → [Cu(phen)](+) interactions have to be cleaved...
July 12, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Manish Kalla, Prashanthan Sanders, Jonathan M Kalman, Geoffrey Lee
Catheter ablation is now at the forefront of the management of symptomatic atrial fibrillation (AF). Its role in paroxysmal AF is well defined with considerable data supporting its role. Catheter ablation in persistent AF has been less effective and the subject of considerable debate. Mechanistic studies have demonstrated the critical role of pulmonary vein physiology in paroxysmal AF, whereas the mechanisms that sustain persistent AF are not well understood. Additional substrate ablation in persistent AF has not improved long-term outcomes and the use of novel mapping technologies to assess rotor activity remains controversial...
June 13, 2017: Heart, Lung & Circulation
T M Ngapo, L Vachon
Particle size analysis has been proposed as a measure of myofibrillar fragmentation resulting from post-mortem proteolysis in meat. The aim of this study was to examine the effect of homogenisation speed, dispersing aggregate size and centrifugation on particle size characteristics of pork loin. Particle size characteristics were significantly (P≤0.023) greater for samples aged 2 than 8d for all but the 80 and 90% quantiles. Differentiation with ageing was only achieved when homogenised at 11,000rpm using the smaller dispersing aggregate (9 vs 13mm rotor diameters)...
July 3, 2017: Meat Science
Anna K Huff, Rebecca B Mackenzie, C J Smith, Kenneth R Leopold
Acetic sulfuric anhydride, CH3COOSO2OH, was produced by the reaction of SO3 and CH3COOH in a supersonic jet. Four isotopologues were observed by microwave spectroscopy. Spectra of both A and E internal rotor states were observed and analyzed, yielding a value of 241.093(30) cm(-1) for the methyl group internal rotation barrier of the parent species. Similar values were obtained for the other isotopologues studied. M06-2X/6-311++G(3df,3pd) calculations indicate that the formation of the anhydride proceeds via a π2 + π2 + σ2 cycloaddition reaction within the CH3COOH-SO3 complex...
July 19, 2017: Journal of Physical Chemistry. A
Susumu Tao, Samuel F Way, Joshua Garland, Jonathan Chrispin, Luisa A Ciuffo, Muhammad A Balouch, Saman Nazarian, David D Spragg, Joseph E Marine, Ronald D Berger, Hugh Calkins, Hiroshi Ashikaga
Persistent atrial fibrillation (AF) can be viewed as disintegrated patterns of information transmission by action potential across the communication network consisting of nodes linked by functional connectivity. To test the hypothesis that ablation of persistent AF is associated with improvement in both local and global connectivity within the communication networks, we analyzed multi-electrode basket catheter electrograms of 22 consecutive patients (63.5 ± 9.7 years, 78% male) during persistent AF before and after the focal impulse and rotor modulation-guided ablation...
2017: PloS One
Ying-Jin Wang, Jin-Chang Guo, Hua-Jin Zhai
Planar boron clusters form dynamic rotors, either as molecular Wankel motors or subnanoscale tank treads, the latter being exemplified by an elongated B11(-) cluster. For an in-depth mechanistic understanding of the rotors, we investigate herein a doped boron cluster, B10C, in which a C atom isovalently substitutes B(-) in the B11(-) tank tread. Two critical structures are achieved: the Cs ((1)A') global minimum (GM) with C positioned in the peripheral ring and the C2v ((1)A1) local minimum (LM) with C in the diatomic core...
July 13, 2017: Nanoscale
Takahiro Iijima, Tadashi Shimizu
We examined a simple two-dimensional (2)H nuclear magnetic resonance spectroscopy for paramagnetic solids utilizing off-magic-angle spinning (OMAS). By adding a rotor-synchronized 180° pulse to rotational echo (RE) measurement, the effect of the shift interaction was removed from the indirect dimension. The obtained pure-quadrupole spectrum could be simulated by calculating a quasi-one-dimensional NMR signal without considering the shift interaction. The sensitivity of the proposed method was compared with that of previous static NMR methods...
June 29, 2017: Solid State Nuclear Magnetic Resonance
Angiolina Comotti, Silvia Bracco, Fabio Castiglioni, Simona Galli, Mattia Negroni, Angelo Maspero, Piero Sozzani
A metal organic framework (MOF) engineered to contain in its scaffold rod-like struts featuring ultra-fast molecular rotors showed extremely rapid 180° flip reorientation with rotational rates of 1011 Hz at 150 K. Crystal-pore accessibility of the MOF allowed the CO2 molecules to enter the cavities and control the rotor spinning speed down to 105 Hz at 150K. Rotor dynamics, as modulated by CO2 loading/unloading in the porous crystals, was described by 1H T1 and 2H NMR spectroscopy. This strategy enabled the regulation of rotary motion by the diffusion of the gas within the channels and the determination of the energetics of rotary dynamics in the presence of CO2...
July 4, 2017: Chemistry: a European Journal
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