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pulse transmit time

Vyacheslav A Trofimov, Svetlana A Varentsova
We discuss an effective method for detecting and identifying drugs using a high-noise terahertz (THz) signal. We add a noisy THz signal obtained in real conditions to the THz signal transmitted through a sample with the illicit drug methamphetamine. The insufficiency of the standard THz time-domain spectroscopy method is demonstrated, showing that this method detects the spectral features of neutral substances and explosives in a noisy THz signal. The method discussed is based upon time-dependent integral correlation criteria calculated using spectral dynamics of the medium response...
November 20, 2016: Applied Optics
S Chusri, V Chongsuvivatwong, J I Rivera, K Silpapojakul, K Singkhamanan, E McNeil, Y Doi
BACKGROUND: Acinetobacter baumannii is a major hospital-acquired pathogen in Thailand that has a negative effect on patient survival. The nature of its transmission is poorly understood. AIM: To investigate the genotypic and spatiotemporal pattern of A. baumannii infection at a hospital in Thailand. METHODS: The medical records of patients infected with A. baumannii at an 800-bed tertiary care hospital in southern Thailand between January 2010 and December 2011 were reviewed retrospectively...
October 22, 2016: Journal of Hospital Infection
Martin Pekař, Wendy U Dittmer, Nenad Mihajlović, Gijs van Soest, Nico de Jong
The information in an ultrasound image depends on the frequency that is used. In a clinical examination it may therefore be beneficial to generate ultrasound images acquired at multiple frequencies, which is difficult to achieve with conventional transducers. Capacitive micromachined ultrasonic transducers (CMUTs) offer a frequency response that is tunable by the bias voltage. In this study we investigate this frequency tunability for ultrasonic imaging. We characterized a CMUT array operated at bias voltages up to three times higher than the collapse-voltage...
February 2017: Ultrasonics
Desmond H Y Tse, Christopher J Wiggins, Benedikt A Poser
PURPOSE: In order to fully benefit from the improved signal-to-noise and contrast-to-noise ratios at 9.4T, the challenges of B1+ inhomogeneity and the long acquisition time of high-resolution 2D gradient-recalled echo (GRE) imaging were addressed. THEORY AND METHODS: Flip angle homogenized excitations were achieved by parallel transmission (pTx) of 3-spoke pulses, designed by magnitude least-squares optimization in a slice-by-slice fashion; the acquisition time reduction was achieved by simultaneous multislice (SMS) pulses...
October 23, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Jaemyung Lim, Coskun Tekes, F Levent Degertekin, Maysam Ghovanloo
Having intravascular ultrasound (IVUS) imaging capability on guide wires used in cardiovascular interventions may eliminate the need for separate IVUS catheters and expand the use of IVUS in a larger portion of the vasculature. High frequency capacitive micro machined ultrasonic transducer (CMUT) arrays should be integrated with interface electronics and placed on the guide wire for this purpose. Besides small size, this system-on-a-chip (SoC) front-end should connect to the back-end imaging system with a minimum number of wires to preserve the critical mechanical properties of the guide wire...
September 20, 2016: IEEE Transactions on Biomedical Circuits and Systems
H F Martins, K Shi, B C Thomsen, S Martin-Lopez, M Gonzalez-Herraez, S J Savory
A major cause of faults in optical communication links is related to unintentional third party intrusions (normally related to civil/agricultural works) causing fiber breaks or cable damage. These intrusions could be anticipated and avoided by monitoring the dynamic strain recorded along the cable. In this work, a novel technique is proposed to implement real-time distributed strain sensing in parallel with an operating optical communication channel. The technique relies on monitoring the Rayleigh backscattered light from optical communication data transmitted using standard modulation formats...
September 19, 2016: Optics Express
William T Clarke, Matthew D Robson, Stefan Neubauer, Christopher T Rodgers
PURPOSE: We present a new Bloch-Siegert four Angle Saturation Transfer (BOAST) method for measuring the creatine kinase (CK) first-order effective rate constant kf in human myocardium at 7 tesla (T). BOAST combines a variant of the four-angle saturation transfer (FAST) method using amplitude-modulated radiofrequency pulses, phosphorus Bloch-Siegert B1+-mapping to determine the per-voxel flip angles, and nonlinear fitting to Bloch simulations for postprocessing. METHODS: Optimal flip angles and repetition time parameters were determined from Monte Carlo simulations...
August 31, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
David S Hersh, Anthony J Kim, Jeffrey A Winkles, Howard M Eisenberg, Graeme F Woodworth, Victor Frenkel
: : Transcranial focused ultrasound (FUS) can noninvasively transmit acoustic energy with a high degree of accuracy and safety to targets and regions within the brain. Technological advances, including phased-array transducers and real-time temperature monitoring with magnetic resonance thermometry, have created new opportunities for FUS research and clinical translation. Neuro-oncology, in particular, has become a major area of interest because FUS offers a multifaceted approach to the treatment of brain tumors...
November 2016: Neurosurgery
Wen Xiong, Philipp Ambichl, Yaron Bromberg, Brandon Redding, Stefan Rotter, Hui Cao
We experimentally generate and characterize eigenstates of the Wigner-Smith time-delay matrix, called principal modes, in a multimode fiber with strong mode coupling. The unique spectral and temporal properties of principal modes enable global control of temporal dynamics of optical pulses transmitted through the fiber, despite random mode mixing. Our analysis reveals that well-defined delay times of the eigenstates are formed by multipath interference, which can be effectively manipulated by spatial degrees of freedom of input wave fronts...
July 29, 2016: Physical Review Letters
Omar Mansour, Tamie L Poepping, James C Lacefield
Plane-wave imaging is desirable for its ability to achieve high frame rates, allowing the capture of fast dynamic events and continuous Doppler data. In most implementations of plane-wave imaging, multiple low-resolution images from different plane wave tilt angles are compounded to form a single high-resolution image, thereby reducing the frame rate. Compounding improves the lateral beam profile in the high-resolution image, but it also acts as a low-pass filter in slow time that causes attenuation and aliasing of signals with high Doppler shifts...
July 21, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Vitaliy Khlebnikov, Nicolas Geades, Dennis W J Klomp, Hans Hoogduin, Penny Gowland, Olivier Mougin
PURPOSE: To compare two pulsed, volumetric chemical exchange saturation transfer (CEST) acquisition schemes: steady state (SS) and pseudosteady state (PS) for the same brain coverage, spatial/spectral resolution and scan time. METHODS: Both schemes were optimized for maximum sensitivity to amide proton transfer (APT) and nuclear Overhauser enhancement (NOE) effects through Bloch-McConnell simulations, and compared in terms of sensitivity to APT and NOE effects, and to transmit field inhomogeneity...
July 25, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Maja Derlink, Isabelle Abt, Romain Mabon, Charlotte Julian, Meta Virant-Doberlet, Emmanuel Jacquot
The Wheat dwarf virus, the causal agent of the wheat dwarf disease, is transmitted by leafhoppers from the genus Psammotettix and currently the main protection strategy is based on the use of insecticide treatments. Sustainable management strategies for insect vectors should include methods that are targeted to disrupt reproductive behavior and here we investigated the mating behavior of Psammotettix alineus (Dahlbom 1850) in order to determine the role of vibrational signals in intra-specific communication and pair formation...
July 23, 2016: Insect Science
Jialing Lin, Dongxin Lin, Ping Xu, Ting Zhang, Qianting Ou, Chan Bai, Zhenjiang Yao
BACKGROUND: Staphylococcus aureus (S. aureus), including methicillin-resistant Staphylococcus aureus (MRSA), survives in dry conditions and can persist for long periods on surfaces touched by humans. Studies that estimate the proportions and characteristics of S. aureus and MRSA contamination in non-hospital environments are lacking. Therefore, we conducted a proportion meta-analysis and reviewed the features of antibiotic resistance and molecular genetics. METHODS: Articles published between January 2005 and December 2015 that studied proportions of S...
October 2016: Environmental Research
Mickael Mounaix, Daria Andreoli, Hugo Defienne, Giorgio Volpe, Ori Katz, Samuel Grésillon, Sylvain Gigan
We report the broadband characterization of the propagation of light through a multiple scattering medium by means of its multispectral transmission matrix. Using a single spatial light modulator, our approach enables the full control of both the spatial and spectral properties of an ultrashort pulse transmitted through the medium. We demonstrate spatiotemporal focusing of the pulse at any arbitrary position and time with any desired spectral shape. Our approach opens new perspectives for fundamental studies of light-matter interaction in disordered media, and has potential applications in sensing, coherent control, and imaging...
June 24, 2016: Physical Review Letters
Guiji Wang, Xuemiao Chen, Jintao Cai, Xuping Zhang, Tao Chong, Binqiang Luo, Jianheng Zhao, Chengwei Sun, Fuli Tan, Cangli Liu, Gang Wu
A high current pulsed power generator CQ-3-MMAF (Multi-Modules Assembly Facility, MMAF) was developed for material dynamics experiments under ramp wave and shock loadings at the Institute of Fluid Physics (IFP), which can deliver 3 MA peak current to a strip-line load. The rise time of the current is 470 ns (10%-90%). Different from the previous CQ-4 at IFP, the CQ-3-MMAF energy is transmitted by hundreds of co-axial high voltage cables with a low impedance of 18.6 mΩ and low loss, and then hundreds of cables are reduced and converted to tens of cables into a vacuum chamber by a cable connector, and connected with a pair of parallel metallic plates insulated by Kapton films...
June 2016: Review of Scientific Instruments
Joon-Yeon Kim, Bong Joo Kang, Young-Mi Bahk, Yong Seung Kim, Joohyun Park, Won Tae Kim, Jiyeah Rhie, Sanghoon Han, Hyeongtag Jeon, Cheol-Hwan Park, Fabian Rotermund, Dai-Sik Kim
Quantum tunnelling becomes inevitable as gap dimensions in metal structures approach the atomic length scale, and light passing through these gaps can be used to examine the quantum processes at optical frequencies. Here, we report on the measurement of the tunnelling current through a 3-Å-wide metal-graphene-metal gap using terahertz time-domain spectroscopy. By analysing the waveforms of the incident and transmitted terahertz pulses, we obtain the tunnelling resistivity and the time evolution of the induced current and electric fields in the gap and show that the ratio of the applied voltage to the tunnelling current is constant, i...
2016: Scientific Reports
Yu Lung Li, Deepanker Tewari, Courtney C Yealy, David Fardig, Nkuchia M M'ikanatha
Shigellosis is a leading cause of enteric infections in the United States. We compared antimicrobial resistance in Shigella infections related to overseas travel (travel-associated) and in those acquired domestically by analyzing antimicrobial resistance patterns, geographic distributions, and pulsed-field gel electrophoresis (PFGE) patterns. We tested samples (n = 204) from a collection of isolates recovered from patients in Pennsylvania between 2006 and 2014. Isolates were grouped into travel- and non-travel-associated categories...
May 2016: Health Security
Francois Varray, Olivier Bernard, Sonia Assou, Christian Cachard, Didier Vray
There are several simulators for medical ultrasound (US) applications that can fully compute the nonlinear propagation on the transmitted pulse, and the corresponding radiofrequency (RF) images. Creanuis is one recent model used to generate nonlinear RF images; however the time requirements are long compared to linear models using a convolution strategy. In this paper, we describe an approach using convolution coupled with nonlinear information to create a pseudo-acoustic tool that is able to quickly generate realistic US images...
June 10, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Alessandro Ramalli, Enrico Boni, Alessandro Dallai, Francesco Guidi, Stefano Ricci, Piero Tortoli
Transmission of coded pulses and matched receive filtering can improve the ultrasound imaging penetration depth while preserving the axial resolution. This paper shows that the pulse compression technique may be integrated in a low-cost scanner to be profitably used also in spectral Doppler investigations. By operating on beamformed, demodulated, and down-sampled data in the frequency domain, a single digital signal processor is proved sufficient to perform both pulse compression and multigate spectral Doppler algorithms in real time...
November 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Yu S Dadoenkova, N N Dadoenkova, I L Lyubchanskii, D I Sementsov
We present a theoretical study of the reshaping of subpicosecond optical pulses in the vicinity of double-peaked defect-mode frequencies in the spectrum of a one-dimensional photonic crystal with two defect layers and calculate the time delay of the transmitted pulses. We used the transfer matrix method for the evaluation of the transmittivity spectra, and the Fourier transform technique for the calculation of the transmitted pulse envelopes. The most considerable reshaping of the pulses takes place for pulses with a carrier frequency in the defect-mode center and with a spectrum wider than the half-width of the defect mode...
May 10, 2016: Applied Optics
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