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Pulse transit time

Xiaoyu Shi, Qing Chang, Junhua Tong, Yunjie Feng, Zhaona Wang, Dahe Liu
The working threshold is an important parameter to assess the performance of cavity-free random lasers. Here, the temporal profile measurement is proposed as an alternative method to determine the thresholds of the surface plasmon based random lasers pumped by ns pulses based on analyzing the delay time (t Delay) and rising time (t R) of the emission signal. The obvious and slight inflection points of the curves of t Delay and t R varying with the pump power density are observed as indicators for the thresholds of random lasing and for the transition of lasing mode, respectively...
July 13, 2017: Scientific Reports
Juan Bolea, Jesús Lázaro, Eduardo Gil, Eva Rovira, José M Remartínez, Pablo Laguna, Esther Pueyo, Augusto Navarro, Raquel Bailón
Prophylactic treatment has been proved to reduce hypotension incidence after spinal anesthesia during cesarean labor. However, the use of pharmacological prophylaxis could carry out undesirable side-effects on mother and fetus. Thus, the prediction of hypotension becomes an important challenge. Hypotension events are hypothesized to be related to a malfunctioning of autonomic nervous system (ANS) regulation of blood pressure. In this work, ANS responses to positional changes of 51 pregnant women programmed for a cesarean labor were explored for hypotension prediction...
July 11, 2017: Annals of Biomedical Engineering
Alejandro Molina-Sánchez, Davide Sangalli, Ludger Wirtz, Andrea Marini
In single-layer WSe2, a paradigmatic semiconducting transition metal dichalcogenide, a circularly polarized laser field can selectively excite electronic transitions in one of the inequivalent K(±) valleys. Such a selective valley population corresponds to a pseudospin that can be used as a degree of freedom in valleytronics provided that the time scale for valley depolarization is sufficiently large. Yet, the mechanism behind the valley depolarization still remains heavily debated. Recent time-dependent Kerr experiments have provided an accurate way to visualize the valley dynamics by measuring the rotation of a linearly polarized probe pulse applied after a circularly polarized pump pulse...
July 10, 2017: Nano Letters
K Grygoryeva, J Rakovský, O Votava, M Fárník
We demonstrate a visualization of quantum mechanical phenomena with the velocity map imaging (VMI) technique, combining vibrationally mediated photodissociation (VMP) of a simple diatomic HCl with the VMI of its H-photofragments. Free HCl molecules were excited by a pump infrared (IR) laser pulse to particular rotational J levels of the v = 2 vibrational state, and subsequently a probe ultraviolet laser photodissociated the molecule at a fixed wavelength of 243.07 nm where also the H-fragments were ionized...
July 7, 2017: Journal of Chemical Physics
Bowen Li, Shu-Wei Huang, Yongnan Li, Chee Wei Wong, Kenneth K Y Wong
Single-shot real-time characterization of optical waveforms with sub-picosecond resolution is essential for investigating various ultrafast optical dynamics. However, the finite temporal recording length of current techniques hinders comprehensive understanding of many intriguing ultrafast optical phenomena that evolve over a timescale much longer than their fine temporal details. Inspired by the space-time duality and by stitching of multiple microscopic images to achieve a larger field of view in the spatial domain, here a panoramic-reconstruction temporal imaging (PARTI) system is devised to scale up the temporal recording length without sacrificing the resolution...
July 5, 2017: Nature Communications
Guangfei Zhang, Caifeng Shan, Ihor Kirenko, Xi Long, Ronald M Aarts
Blood pressure (BP) is critical in diagnosing certain cardiovascular diseases such as hypertension. Some previous studies have proved that BP can be estimated by pulse transit time (PTT) calculated by a pair of photoplethysmography (PPG) signals at two body sites. Currently, contact PPG (cPPG) and imaging PPG (iPPG) are two feasible ways to obtain PPG signals. In this study, we proposed a hybrid system (called the ICPPG system) employing both methods that can be implemented on a wearable device, facilitating the measurement of BP in an inconspicuous way...
July 1, 2017: Sensors
Feng Guo, Na Zhang, Wei Jin, Jun Chang
We theoretically study the dynamic time evolution following laser pulse pumping in an antiferromagnetic insulator Cr2O3. From the photoexcited high-spin quartet states to the long-lived low-spin doublet states, the ultrafast demagnetization processes are investigated by solving the dissipative Schrödinger equation. We find that the demagnetization times are of the order of hundreds of femtoseconds, in good agreement with recent experiments. The switching times could be strongly reduced by properly tuning the energy gaps between the multiplet energy levels of Cr(3+)...
June 28, 2017: Journal of Chemical Physics
David P Franke, Moritz P D Pflüger, Kohei M Itoh, Martin S Brandt
We study single- and multiquantum transitions of the nuclear spins of an ensemble of ionized arsenic donors in silicon and find quadrupolar effects on the coherence times, which we link to fluctuating electrical field gradients present after the application of light and bias voltage pulses. To determine the coherence times of superpositions of all orders in the 4-dimensional Hilbert space, we use a phase-cycling technique and find that, when electrical effects were allowed to decay, these times scale as expected for a fieldlike decoherence mechanism such as the interaction with surrounding ^{29}Si nuclear spins...
June 16, 2017: Physical Review Letters
Valérie Potin, Arnaud Cacucci, Nicolas Martin
We analyze structure and composition of titanium-based metal/oxide periodic multilayers prepared by reactive sputtering. The reactive gas pulsing process is involved to periodically inject the oxygen gas during the multilayers deposition. This approach allows the growth of regular and tunable nanometric TiO2/Ti periods with thicknesses ranging from 14 to 50nm. The interfacial layer between oxide and metallic layers is mainly the fcc-TiO phase as clearly pointed out by transmission electron microscopy and associated electron spectroscopies...
June 21, 2017: Micron: the International Research and Review Journal for Microscopy
Enis Tuncer
High temperature polymeric materials for electrical insulation and energy storage are needed for transformational power applications such as pulsed-power and hybrid electrical vehicles. One of the candidate materials has been polyetherimide, an amorphous thermoplastic with a glass transition over 200 (°)C. Here, the dielectric studies on the material are reported by taking into account the polarization and conduction processes in the polyetherimide. The dielectric data were analyzed with the distribution of relaxation times approach with Debye expression as the kernel in the inversion algorithm, the results then created the relaxation map for polyetherimide...
June 2017: European Physical Journal. E, Soft Matter
Tolga Han Efe, Mehmet Doğan, Cem Özişler, Tolga Çimen, Mehmet Ali Felekoğlu, Ahmet Göktuğ Ertem, Engin Algül, Sadık Açıkel
OBJECTIVE: Systemic lupus erythematosus (SLE) is a chronic, inflammatory, and autoimmune connective tissue disease. One of the leading causes of mortality among SLE patients is pulmonary hypertension. The aim of this study was to evaluate the association between echocardiographic findings, including the pulmonary pulse transit time and pulmonary hypertension parameters, in SLE patients. METHODS: Thirty SLE patients (aged 39.9±11 years, 28 females) as the study group and 34 age- and sex-matched healthy volunteers (aged 37...
June 22, 2017: Anatolian Journal of Cardiology
Lu Chen, Suman Mallick, Ying Ning Tan, Miao Meng, Chun Y Liu
Three quadruply bonded dimolybdenum complexes equipped with a triarylamine pendant, [(DAniF)3Mo2(μ-O2CC6H4N(C6H4CH3)2] (DAniF = N,N'-di(p-anisyl)formamidinate; [OO-ph-N]), [(DAniF)3Mo2(μ-OSCC6H4N(C6H4CH3)2] ([OS-ph-N]), and [(DAniF)3Mo2(μ-S2CC6H4N(C6H4CH3)2] ([SS-ph-N]), have been synthesized and characterized by single crystal X-ray diffraction. In electrochemical measurements, the redox couple for the organic amine group becomes irreversible, reflecting the substantially strong electronic interaction between the dimetal center and organic redox site...
June 21, 2017: Inorganic Chemistry
Yuan Zheng, Michael Marx, G Wilson Miller, Kim Butts Pauly
PURPOSE: MR acoustic radiation force imaging (MR-ARFI) provides a method to visualize the focal spot of a focused ultrasound (FUS) beam without introducing a significant temperature rise. With conventional spoiled MR-ARFI pulse sequences, the ARFI phase always equals the motion-encoded phase. In this work, MR-ARFI using transition band balanced steady-state free precession (bSSFP) is presented, which improves the sensitivity of MR-ARFI with high acquisition speed. THEORY AND METHODS: Motion-encoding gradients (MEG) are inserted into bSSFP sequences for MR-ARFI...
June 20, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Bruno Albertazzi, Norimasa Ozaki, Vasily Zhakhovsky, Anatoly Faenov, Hideaki Habara, Marion Harmand, Nicholas Hartley, Denis Ilnitsky, Nail Inogamov, Yuichi Inubushi, Tetsuya Ishikawa, Tetsuo Katayama, Takahisa Koyama, Michel Koenig, Andrew Krygier, Takeshi Matsuoka, Satoshi Matsuyama, Emma McBride, Kirill Petrovich Migdal, Guillaume Morard, Haruhiko Ohashi, Takuo Okuchi, Tatiana Pikuz, Narangoo Purevjav, Osami Sakata, Yasuhisa Sano, Tomoko Sato, Toshimori Sekine, Yusuke Seto, Kenjiro Takahashi, Kazuo Tanaka, Yoshinori Tange, Tadashi Togashi, Kensuke Tono, Yuhei Umeda, Tommaso Vinci, Makina Yabashi, Toshinori Yabuuchi, Kazuto Yamauchi, Hirokatsu Yumoto, Ryosuke Kodama
The understanding of fracture phenomena of a material at extremely high strain rates is a key issue for a wide variety of scientific research ranging from applied science and technological developments to fundamental science such as laser-matter interaction and geology. Despite its interest, its study relies on a fine multiscale description, in between the atomic scale and macroscopic processes, so far only achievable by large-scale atomic simulations. Direct ultrafast real-time monitoring of dynamic fracture (spallation) at the atomic lattice scale with picosecond time resolution was beyond the reach of experimental techniques...
June 2017: Science Advances
Cong Chen, Zhensheng Tao, Adra Carr, Piotr Matyba, Tibor Szilvási, Sebastian Emmerich, Martin Piecuch, Mark Keller, Dmitriy Zusin, Steffen Eich, Markus Rollinger, Wenjing You, Stefan Mathias, Uwe Thumm, Manos Mavrikakis, Martin Aeschlimann, Peter M Oppeneer, Henry Kapteyn, Margaret Murnane
Electron-electron interactions are the fastest processes in materials, occurring on femtosecond to attosecond timescales, depending on the electronic band structure of the material and the excitation energy. Such interactions can play a dominant role in light-induced processes such as nano-enhanced plasmonics and catalysis, light harvesting, or phase transitions. However, to date it has not been possible to experimentally distinguish fundamental electron interactions such as scattering and screening. Here, we use sequences of attosecond pulses to directly measure electron-electron interactions in different bands of different materials with both simple and complex Fermi surfaces...
June 19, 2017: Proceedings of the National Academy of Sciences of the United States of America
Fang Wang, S S Jyothirmayee Aravind, Hao Wu, Joseph Forys, Venkat Venkataraman, Kandalam Ramanujachary, Xiao Hu
Green graphene materials prepared by photoreduction of graphite oxide were first time blended with aqueous-based silk fibroin proteins to improve the mechanical and thermal properties of silk biomaterials, and their nanocomposite interaction mechanism was illustrated. Powder X-ray diffraction (XRD) analysis confirmed the complete exfoliation of graphite oxide to graphene in presence of focused pulses of solar radiation. By varying the concentration of graphene (0.1wt% to 10wt%), a series of free standing graphene-silk films were prepared and were systematically characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and nanoindentation measurements...
October 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Aurora Magliocca, Emanuele Rezoagli, Thomas Anthony Anderson, Sara Maria Burns, Fumito Ichinose, Hovig Vatche Chitilian
BACKGROUND: Orthotopic liver transplantation (OLT) is characterized by significant intraoperative hemodynamic variability. Accurate and real-time cardiac output (CO) monitoring aids clinical decision making during OLT. The purpose of this study is to compare accuracy, precision, and trending ability of CO estimation obtained noninvasively using pulse wave transit time (estimated continuous cardiac output [esCCO; Nihon Kohden, Tokyo, Japan]) or thoracic bioimpedance (ICON; Osypka Medical GmbH, Berlin, Germany) to thermodilution cardiac output (TDCO) measured with a pulmonary artery catheter...
June 8, 2017: Anesthesia and Analgesia
K R Nandipati, Z Lan, H Singh, S Mahapatra
A first principles quantum dynamics study of N-H photodissociation of pyrrole on the S0-(1)πσ(*)(A21) coupled electronic states is carried out with the aid of an optimally designed UV-laser pulse. A new photodissociation path, as compared to the conventional barrier crossing on the πσ*1 state, opens up upon electronic transitions under the influence of pump-dump laser pulses, which efficiently populate both the dissociation channels. The interplay of electronic transitions due both to vibronic coupling and the laser pulse is observed in the control mechanism and discussed in detail...
June 7, 2017: Journal of Chemical Physics
A Sitnikov, E Kalabukhova, V Oliynyk, M Kolisnichenko
We present the design and development of a single stage pulse power amplifier working in the frequency range 32-38 GHz based on a monolithic microwave integrated circuit (MMIC). We have designed the MMIC power amplifier by using the commercially available packaged GaAs pseudomorphic high electron mobility transistor. The circuit fabrication and assembly process includes the elaboration of the matching networks for the MMIC power amplifier and their assembling as well as the topology outline and fabrication of the printed circuit board of the waveguide-microstrip line transitions...
May 2017: Review of Scientific Instruments
W B Doriese, P Abbamonte, B K Alpert, D A Bennett, E V Denison, Y Fang, D A Fischer, C P Fitzgerald, J W Fowler, J D Gard, J P Hays-Wehle, G C Hilton, C Jaye, J L McChesney, L Miaja-Avila, K M Morgan, Y I Joe, G C O'Neil, C D Reintsema, F Rodolakis, D R Schmidt, H Tatsuno, J Uhlig, L R Vale, J N Ullom, D S Swetz
We describe a series of microcalorimeter X-ray spectrometers designed for a broad suite of measurement applications. The chief advantage of this type of spectrometer is that it can be orders of magnitude more efficient at collecting X-rays than more traditional high-resolution spectrometers that rely on wavelength-dispersive techniques. This advantage is most useful in applications that are traditionally photon-starved and/or involve radiation-sensitive samples. Each energy-dispersive spectrometer is built around an array of several hundred transition-edge sensors (TESs)...
May 2017: Review of Scientific Instruments
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