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Andrew W Wharmby
An empirical formula based on viscoelastic analysis techniques that employs concepts from the fractional calculus that was used to model the dielectric behavior of materials exposed to oscillating electromagnetic fields in the radiofrequency, terahertz, and infrared bands. This work adapts and applies the formula to model viscoelastic behavior of materials that show an apparent increase of phase velocity of vibration with an increase in frequency, otherwise known as anomalous dispersion. A fractional order wave equation is derived through the application of the classic elastic-viscoelastic correspondence principle whose analytical solution is used to describe absorption and dispersion of acoustic waves in the viscoelastic material displaying anomalous dispersion in a specific frequency range...
September 2016: Journal of the Acoustical Society of America
Neil B Stremmel, Christopher J Struck
American National Standards (ANSI Standards) developed by Accredited Standards Committees S1, S2, S3, S3/SC 1, and S12 in the areas of acoustics, mechanical vibration and shock, bioacoustics, animal bioacoustics, and noise, respectively, are published by the Acoustical Society of America (ASA). In addition to these standards, ASA publishes a catalog of Acoustical American National Standards. To receive a copy of the latest Standards catalog, please contact Neil Stremmel.Comments are welcomed on all material in Acoustical Standards News...
September 2016: Journal of the Acoustical Society of America
Damien Lecoq, Charles Pézerat, Fabien Chevillotte, Rémi Bessis
An experimental validation is implemented for the measurement of a weak acoustic component within a turbulent wall pressure by an inverse problem of vibration. The turbulent flow is generated by a forward-facing step in a wind tunnel. In addition to the flow, an acoustic source with a low level excites the plate and plays the role of an additional acoustic component to be identified. The inverse methods called the force analysis technique and the corrected force analysis technique are used to compute the wall pressure fluctuations from the measurement of the plate vibration using an array of 13 accelerometers...
September 2016: Journal of the Acoustical Society of America
Micah R Shepherd, Philip A Feurtado, Stephen C Conlon
Structures with power law tapers exhibit the acoustic black hole (ABH) effect and can be used for vibration reduction. However, the design of ABHs for vibration reduction requires consideration of the underlying theory and its regions of validity. To address the competing nature of the best ABH design for vibration reduction and the underlying theoretical assumptions, a multi-objective approach is used to find the lowest frequency where both criteria are sufficiently met. The Pareto optimality curve is estimated for a range of ABH design parameters...
September 2016: Journal of the Acoustical Society of America
Boris S Aronov, Corey L Bachand
Dependencies of the resonance frequencies and effective coupling coefficients for solid circular cylindrical piezoelements (discs) of finite size are considered as a function of their height-to-diameter aspect ratios, h/2a. At aspect ratios in the range of approximately 0.5 < h/2a < 1.5 the piezoelements are treated analytically, as a two degree-of-freedom coupled system by applying the coupled mode theory approach [Aronov, Bachand, and Brown, J. Acoust. Soc. Am. 126(6), 2983-2990 (2009)]. Results are presented as plots of resonance frequencies and effective coupling coefficients vs aspect ratios...
September 2016: Journal of the Acoustical Society of America
You Chang, Namkeun Kim, Stefan Stenfelt
A whole head finite element model for simulation of bone conducted (BC) sound transmission was developed. The geometry and structures were identified from cryosectional images of a female human head and eight different components were included in the model: cerebrospinal fluid, brain, three layers of bone, soft tissue, eye, and cartilage. The skull bone was modeled as a sandwich structure with an inner and outer layer of cortical bone and soft spongy bone (diploë) in between. The behavior of the finite element model was validated against experimental data of mechanical point impedance, vibration of the cochlear promontories, and transcranial BC sound transmission...
September 2016: Journal of the Acoustical Society of America
Brunella Pinto, Giulia Rusciano, Stefano D'Errico, Nicola Borbone, Antonio Sasso, Vincenzo Piccialli, Luciano Mayol, Giorgia Oliviero, Gennaro Piccialli
BACKGROUND: G-quadruplex DNA is involved in many physiological and pathological processes. Both clinical and experimental studies on DNA G-quadruplexes are slowed down by their enzymatic instability. In this frame, more stable chemically modified analogs are needed. METHODS: The bis-end-linked-(gggt)2 PNA molecule (BEL-PNA) was synthesized using in solution and solid phase synthetic approaches. Quadruplex formation was assessed by circular dichroism (CD) and surface enhanced Raman scattering (SERS)...
November 29, 2016: Biochimica et Biophysica Acta
Vishal Gupta, Pulak M Pandey, Vadim V Silberschmidt
Bone drilling is one of the most common operations used to repair fractured parts of bones. During a bone drilling process, microcracks are generated on the inner surface of the drilled holes that can detrimentally affect osteosynthesis and healing. This study focuses on the investigation of microcracks and pullout strength of cortical-bone screws in drilled holes. It compares conventional surgical bone drilling (CSBD) with rotary ultrasonic bone drilling (RUBD), a novel approach employing ultrasonic vibration with a diamond-coated hollow tool...
November 29, 2016: Medical Engineering & Physics
Anandakumar Amutha, Ranjit Mohan Anjana, Ulagamathesan Venkatesan, Harish Ranjani, Ranjit Unnikrishnan, K M Venkat Narayan, Viswanathan Mohan, Mohammed K Ali
BACKGROUND: There is little data on the incidence of diabetes complications in young onset type 1 diabetes (T1DM) and type 2 diabetes (T2DM) in non European populations. METHODS: From a tertiary diabetes centre, Chennai, India, we recruited 108 T1DM (defined by abrupt onset of symptoms or diabetic ketoacidosis, absent insulin reserve requiring insulin treatment) and 90 T2DM participants (defined by absence of ketosis, good beta-cell reserve, and good response to oral agents) who were diagnosed between the ages of 10 and 25years, and without any evidence of diabetes complications at diagnosis...
November 17, 2016: Diabetes Research and Clinical Practice
Mathias Schubert
A coordinate-invariant generalization of the Lyddane-Sachs-Teller relation is presented for polar vibrations in materials with monoclinic and triclinic crystal systems. The generalization is derived from an eigendielectric displacement vector summation approach, which is equivalent to the microscopic Born-Huang description of polar lattice vibrations in the harmonic approximation. An expression for a general oscillator strength is also described for materials with monoclinic and triclinic crystal systems. A generalized factorized form of the dielectric response characteristic for monoclinic and triclinic materials is proposed...
November 18, 2016: Physical Review Letters
Robinjeet Singh, Garrett D Cole, Jonathan Cripe, Thomas Corbitt
We report a stable double optical spring effect in an optical cavity pumped with a single optical field that arises as a result of birefringence. One end of the cavity is formed by a multilayer Al_{0.92}Ga_{0.08}As/GaAs stack supported by a microfabricated cantilever with a natural mode frequency of 274 Hz. The optical spring shifts the resonance to 21 kHz, corresponding to a suppression of low frequency vibrations by a factor of about 5 000. The stable nature of the optical trap allows the cavity to be operated without any external feedback and with only a single optical field incident...
November 18, 2016: Physical Review Letters
S Jyothi, Tridib Ray, Sourav Dutta, A R Allouche, Romain Vexiau, Olivier Dulieu, S A Rangwala
The direct photodissociation of trapped ^{85}Rb_{2}^{+} (rubidium) molecular ions by the cooling light for the ^{85}Rb magneto-optical trap (MOT) is studied, both experimentally and theoretically. Vibrationally excited Rb_{2}^{+} ions are created by photoionization of Rb_{2} molecules formed photoassociatively in the Rb MOT and are trapped in a modified spherical Paul trap. The decay rate of the trapped Rb_{2}^{+} ion signal in the presence of the MOT cooling light is measured and agreement with our calculated rates for molecular ion photodissociation is observed...
November 18, 2016: Physical Review Letters
Wenzhe Mao, Peng Yuan, Jian Zheng, Weixing Ding, Hong Li, Tao Lan, Adi Liu, Wandong Liu, Jinlin Xie
A compact and lightweight support platform has been used as a holder for the interferometer system on the Keda Torus eXperiment (KTX), which is a reversed field pinch device. The vibration caused by the interaction between the time-varying magnetic field and the induced current driven in the metal optical components has been measured and, following comparison with the mechanical vibration of the KTX device and the refraction effect of the ambient turbulent air flow, has been identified as the primary vibration source in this case...
November 2016: Review of Scientific Instruments
T Akiyama, A Sirinelli, C Watts, P Shigin, G Vayakis, M Walsh
A dispersion interferometer is a reliable density measurement system and is being designed as a complementary density diagnostic on ITER. The dispersion interferometer is inherently insensitive to mechanical vibrations, and a combined polarimeter with the same line of sight can correct fringe jump errors. A proof of the principle of the CO2 laser dispersion interferometer combined with the PEM polarimeter was recently conducted, where the phase shift and the polarization angle were successfully measured simultaneously...
November 2016: Review of Scientific Instruments
E R Scott, R Barchfeld, P Riemenschneider, C W Domier, C M Muscatello, M Sohrabi, R Kaita, Y Ren, N C Luhmann
The Far-infrared Tangential Interferometer/Polarimeter (FIReTIP) system has been refurbished and is being reinstalled on the National Spherical Torus Experiment-Upgrade (NSTX-U) to supply real-time line-integrated core electron density measurements for use in the NSTX-U plasma control system (PCS) to facilitate real-time density feedback control of the NSTX-U plasma. Inclusion of a visible light heterodyne interferometer in the FIReTIP system allows for real-time vibration compensation due to movement of an internally mounted retroreflector and the FIReTIP front-end optics...
November 2016: Review of Scientific Instruments
Zhen Liu, Zhiyuan Yao, Xiang Li, Qianwei Fu
In this contribution, we propose a novel linear piezoelectric motor with a compact stator that is driven by a single mode. The linear piezoelectric motor can realize bidirectional motion by changing the vibration modes of the stator. Finite element analysis is performed to determine the required vibration mode of the stator and obtain the optimal stator structure and dimensions. Furthermore, the trajectories of the driving foot are analyzed with and without consideration of the mechanical contact with the slider...
November 2016: Review of Scientific Instruments
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
M F Brandl, M W van Mourik, L Postler, A Nolf, K Lakhmanskiy, R R Paiva, S Möller, N Daniilidis, H Häffner, V Kaushal, T Ruster, C Warschburger, H Kaufmann, U G Poschinger, F Schmidt-Kaler, P Schindler, T Monz, R Blatt
We report on the design of a cryogenic setup for trapped ion quantum computing containing a segmented surface electrode trap. The heat shield of our cryostat is designed to attenuate alternating magnetic field noise, resulting in 120 dB reduction of 50 Hz noise along the magnetic field axis. We combine this efficient magnetic shielding with high optical access required for single ion addressing as well as for efficient state detection by placing two lenses each with numerical aperture 0.23 inside the inner heat shield...
November 2016: Review of Scientific Instruments
Marco Pagliai, Giordano Mancini, Ivan Carnimeo, Nicola De Mitri, Vincenzo Barone
The electronic absorption spectra of pyridine and nicotine in aqueous solution have been computed using a multistep approach. The computational protocol consists in studying the solute solvation with accurate molecular dynamics simulations, characterizing the hydrogen bond interactions, and calculating electronic transitions for a series of configurations extracted from the molecular dynamics trajectories with a polarizable QM/MM scheme based on the fluctuating charge model. Molecular dynamics simulations and electronic transition calculations have been performed on both pyridine and nicotine...
December 2, 2016: Journal of Computational Chemistry
Myung-Sook Ko, Yon Ju Sim, Do Hyun Kim, Hye-Seon Jeon
Purpose : To observe the effects of whole-body vibration (WBV) training in conjunction with conventional physical therapy (PT) on joint-position sense (JPS), balance, and gait in children with cerebral palsy (CP). Methods: In this randomized controlled study, 24 children with CP were randomly selected either to continue their conventional PT or to receive WBV in conjunction with their conventional PT programme. Exposure to the intervention was intermittent (3 min WBV, 3 min rest) for 20 minutes, twice weekly for 3 weeks...
2016: Physiotherapy Canada. Physiothérapie Canada
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