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Pulse transit time

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https://www.readbyqxmd.com/read/28102355/determining-arterial-wave-transit-time-from-a-single-aortic-pressure-pulse-in-rats-vascular-impulse-response-analysis
#1
Ru-Wen Chang, Chun-Yi Chang, Liang-Chuan Lai, Ming-Shiou Wu, Tai-Horng Young, Yih-Sharng Chen, Chih-Hsien Wang, Kuo-Chu Chang
Arterial wave transit time (τw) in the lower body circulation is an effective biomarker of cardiovascular risk that substantially affects systolic workload imposed on the heart. This study evaluated a method for determining τw from the vascular impulse response on the basis of the measured aortic pressure and an assumed triangular flow (Q(tri)). The base of the unknown Q(tri) was constructed with a duration set equal to ejection time. The timing of the peak triangle was derived using a fourth-order derivative of the pressure waveform...
January 19, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28090301/pulmonary-pulse-wave-transit-time-is-associated-with-right-ventricular-pulmonary-artery-coupling-in-pulmonary-arterial-hypertension
#2
Kurt W Prins, E Kenneth Weir, Stephen L Archer, Jeremy Markowitz, Lauren Rose, Marc Pritzker, Richard Madlon-Kay, Thenappan Thenappan
Pulmonary pulse wave transit time (pPTT), defined as the time for the systolic pressure pulse wave to travel from the pulmonary valve to the pulmonary veins, has been reported to be reduced in pulmonary arterial hypertension (PAH); however, the underlying mechanism of reduced pPTT is unknown. Here, we investigate the hypothesis that abbreviated pPTT in PAH results from impaired right ventricular-pulmonary artery (RV-PA) coupling. We quantified pPTT using pulsed-wave Doppler ultrasound from 10 healthy age- and sex-matched controls and 36 patients with PAH...
December 2016: Pulmonary Circulation
https://www.readbyqxmd.com/read/28089491/satellite-and-central-transitions-selective-1-h-27-al-d-hmqc-experiments-at-very-fast-mas-for-quadrupolar-couplings-determination
#3
Nghia Tuan Duong, Yusuke Nishiyama
Recent study has demonstrated the application of the proton-detected heteronuclear multi-quantum coherence (HMQC) at ultrafast Magic Angle Spinning (MAS) to probe quadrupolar nuclei including (14)N and (35)Cl. In addition, for half-integer quadrupolar nucleus like (35)Cl, the quadrupolar product can be calculated based on the shift difference between the center band of satellite transition (ST) and the central transition (CT) peaks. The applicability of this technique is further investigated on spin I=5/2, namely (27)Al nucleus, and kaolin is chosen as the testing sample...
January 4, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28071764/aligned-copper-nanorod-arrays-for-highly-efficient-generation-of-intense-ultra-broadband-thz-pulses
#4
S Mondal, Q Wei, W J Ding, H A Hafez, M A Fareed, A Laramée, X Ropagnol, G Zhang, S Sun, Z M Sheng, J Zhang, T Ozaki
We demonstrate an intense broadband terahertz (THz) source based on the interaction of relativistic-intensity femtosecond lasers with aligned copper nanorod array targets. For copper nanorod targets with a length of 5 μm, a maximum 13.8 times enhancement in the THz pulse energy (in ≤20 THz spectral range) is measured as compared to that with a thick plane copper target under the same laser conditions. A further increase in the nanorod length leads to a decrease in the THz pulse energy at medium frequencies (≤20 THz) and increase of the electromagnetic pulse energy in the high-frequency range (from 20-200 THz)...
January 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28065997/rapid-evaporation-at-the-superheat-limit-of-methanol-ethanol-butanol-and-n-heptane-on-platinum-films-supported-by-low-stress-sin-membranes
#5
Eric J Ching, C Thomas Avedisian, Richard C Cavicchi, Do Hyun Chung, Jeff Rah, Michael J Carrier
The bubble nucleation temperatures of several organic liquids (methanol, ethanol, butanol, n-heptane) on stress-minimized platinum (Pt) films supported by SiN membranes is examined by pulse-heating the membranes for times ranging from 1 µs to 10 µs. The results show that the nucleation temperatures increase as the heating rates of the Pt films increase. Measured nucleation temperatures approach predicted superheat limits for the smallest pulse times which correspond to heating rates over 10(8) K/s, while nucleation temperatures are significantly lower for the longest pulse times...
October 2016: International Journal of Heat and Mass Transfer
https://www.readbyqxmd.com/read/28063656/effect-of-cyclic-redox-oscillations-on-water-quality-in-freshwater-acid-sulfate-soil-wetlands
#6
Niloofar Karimian, Scott G Johnston, Edward D Burton
Restoration of acid sulfate soil (ASS) wetlands by freshwater re-flooding can lead to the reformation of various Fe(II) and reduced inorganic sulfur (RIS) species in surface soil layers. However, in many locations, wetland water levels undergo large seasonal fluctuations that drive extreme redox oscillations. Newly formed RIS species [e.g. greigite, mackinawite, nano-pyrite and S(0)] and Fe(II) are vulnerable to rapid oxidation during dry periods and may generate substantial acidity. Rainfall following a dry period may then mobilise acidity and metal cations in surface waters prior to eventual recovery in pH by re-establishment of reducing conditions...
January 4, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28060961/pilot-study-estimation-of-stroke-volume-and-cardiac-output-from-pulse-wave-velocity
#7
Yurie Obata, Maki Mizogami, Daniel Nyhan, Dan E Berkowitz, Jochen Steppan, Viachaslau Barodka
BACKGROUND: Transesophageal echocardiography (TEE) is increasingly replacing thermodilution pulmonary artery catheters to assess hemodynamics in patients at high risk for cardiovascular morbidity. However, one of the drawbacks of TEE compared to pulmonary artery catheters is the inability to measure real time stroke volume (SV) and cardiac output (CO) continuously. The aim of the present proof of concept study was to validate a novel method of SV estimation, based on pulse wave velocity (PWV) in patients undergoing cardiac surgery...
2017: PloS One
https://www.readbyqxmd.com/read/28059179/rabi-oscillations-produced-by-adiabatic-pulse-due-to-initial-atomic-coherence
#8
Anatoly A Svidzinsky, Hichem Eleuch, Marlan O Scully
If an electromagnetic pulse is detuned from atomic transition frequency by amount Δ>1/τ, where τ is the turn-on time of the pulse, then atomic population adiabatically follows the pulse intensity without causing Rabi oscillations. Here we show that, if initially, the atom has nonzero coherence, then the adiabatic pulse yields Rabi oscillations of atomic population ρ<sub>aa</sub>(t), and we obtain analytical solutions for ρ<sub>aa</sub>(t). Our findings can be useful for achieving generation of coherent light in the backward direction in the QASER scheme in which modulation of the coupling between light and atoms is produced by Rabi oscillations...
January 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/28046980/we-fg-206-05-new-arterial-spin-labeling-method-for-simultaneous-estimation-of-arterial-cerebral-blood-volume-cerebral-blood-flow-and-arterial-transit-time
#9
M Johnston, H Liu, C Whitlow, Y Jung
PURPOSE: To demonstrate the feasibility of a novel Arterial Spin Labeling (ASL) method for simultaneously measuring cerebral blood flow (CBF), arterial transit time (ATT), and arterial cerebral blood volume (aCBV) without the use of a contrast agent. METHODS: A series of multi-TI ASL images were acquired from one healthy subject on a 3T Siemens Skyra, with the following parameters: PCASL labeling with variable TI [300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000] ms, labeling bolus 1400 ms when TI allows, otherwise 100 ms less than TI, TR was minimized for each TI, two sinc shaped pre-saturation pulses were applied in the imaging plane immediately before 2D EPI acquisition...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28018731/accurate-measurement-of-the-pulse-wave-delay-with-imaging-photoplethysmography
#10
Alexei A Kamshilin, Igor S Sidorov, Laura Babayan, Maxim A Volynsky, Rashid Giniatullin, Oleg V Mamontov
Assessment of the cardiovascular parameters using noncontact video-based or imaging photoplethysmography (IPPG) is usually considered as inaccurate because of strong influence of motion artefacts. To optimize this technique we performed a simultaneous recording of electrocardiogram and video frames of the face for 36 healthy volunteers. We found that signal disturbances originate mainly from the stochastically enhanced dichroic notch caused by endogenous cardiovascular mechanisms, with smaller contribution of the motion artefacts...
December 1, 2016: Biomedical Optics Express
https://www.readbyqxmd.com/read/27997159/the-formation-time-of-ti-o-%C3%A2-and-ti-o-%C3%A2-ti-radicals-at-the-n-srtio3-aqueous-interface-during-photocatalytic-water-oxidation
#11
Xihan Chen, Stephanie N Choing, Daniel J Aschaffenburg, C D Pemmaraju, David Prendergast, Tanja Cuk
The initial step of photocatalytic water oxidation reaction at the metal oxide/aqueous interface involves intermediates formed by trapping photogenerated, valence band holes on different reactive sites of the oxide surface. In SrTiO3, these one-electron intermediates are radicals located in Ti-O(•) (oxyl) and Ti-O(•)-Ti (bridge) groups arranged perpendicular and parallel to the surface respectively, and form electronic states in the band gap of SrTiO3. Using an ultrafast sub band gap probe of 400 nm and white light, we excited transitions between these radical states and the conduction band...
December 20, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27993286/pulse-transit-time-changes-in-subjects-exhibiting-sleep-disordered-breathing
#12
Biswajit Chakrabarti, Stephen Emegbo, Sonya Craig, Nick Duffy, John O'Reilly
INTRODUCTION: Pulse Transit Time (PTT) represents a non-invasive marker of sleep fragmentation in OSAS. Little is known regarding PTT in sleepy subjects exhibiting nocturnal Inspiratory Flow Limitation (IFL) in the absence of apneas or desaturation. MATERIALS AND METHODS: The IFL cohort was gender and age matched to subjects with OSAS and a cohort where Sleep Disordered Breathing (SBD)/IFL was absent ("Non Flow Limited" or NFL cohort); PTT Arousal index (PTT Ar) defined by number of PTT arousals per hour...
January 2017: Respiratory Medicine
https://www.readbyqxmd.com/read/27976852/four-dimensional-ultrafast-electron-microscopy-insights-into-an-emerging-technique
#13
Aniruddha Adhikari, Jeffrey K Eliason, Jingya Sun, Riya Bose, David J Flannigan, Omar F Mohammed
Four-dimensional ultrafast electron microscopy (4D-UEM) is a novel analytical technique that aims to fulfill the long-held dream of researchers to investigate materials at extremely short spatial and temporal resolutions by integrating the excellent spatial resolution of electron microscopes with the temporal resolution of ultrafast femtosecond laser-based spectroscopy. The ingenious use of pulsed photoelectrons to probe surfaces and volumes of materials enables time-resolved snapshots of the dynamics to be captured in a way hitherto impossible by other conventional techniques...
January 3, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/27976741/weighing-scale-based-pulse-transit-time-is-a-superior-marker-of-blood-pressure-than-conventional-pulse-arrival-time
#14
Stephanie L-O Martin, Andrew M Carek, Chang-Sei Kim, Hazar Ashouri, Omer T Inan, Jin-Oh Hahn, Ramakrishna Mukkamala
Pulse transit time (PTT) is being widely pursued for cuff-less blood pressure (BP) monitoring. Most efforts have employed the time delay between ECG and finger photoplethysmography (PPG) waveforms as a convenient surrogate of PTT. However, these conventional pulse arrival time (PAT) measurements include the pre-ejection period (PEP) and the time delay through small, muscular arteries and may thus be an unreliable marker of BP. We assessed a bathroom weighing scale-like system for convenient measurement of ballistocardiography and foot PPG waveforms - and thus PTT through larger, more elastic arteries - in terms of its ability to improve tracking of BP in individual subjects...
December 15, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27960498/monitoring-electron-photon-dressing-in-wse2
#15
Umberto De Giovannini, Hannes Hübener, Angel Rubio
Optical pumping of solids creates a nonequilibrium electronic structure where electrons and photons combine to form quasiparticles of dressed electronic states. The resulting shift of electronic levels is known as the optical Stark effect, visible as a red shift in the optical spectrum. Here we show that in a pump-probe setup we can uniquely define a nonequilibrium quasiparticle bandstructure that can be directly measurable with photoelectron spectroscopy. The dynamical photon-dressing (and undressing) of the many-body electronic states can be monitored by pump-probe time and angular-resolved photoelectron spectroscopy (tr-ARPES) as the photon-dressed bandstructure evolves in time depending on the pump-probe pulse overlap...
December 14, 2016: Nano Letters
https://www.readbyqxmd.com/read/27958571/comparison-of-attosecond-streaking-and-rabbitt
#16
L Cattaneo, J Vos, M Lucchini, L Gallmann, C Cirelli, U Keller
Recent progress in the generation of ultra-short laser pulses has enabled the measurement of photoionization time delays with attosecond precision. For single photoemission time delays the most common techniques are based on attosecond streaking and the reconstruction of attosecond beating by interference of two-photon transitions (RABBITT). These are pump-probe techniques employing an extreme-ultraviolet (XUV) single attosecond pump pulse for streaking or an attosecond pump pulse train for RABBITT, and a phase-locked infrared (IR) probe pulse...
December 12, 2016: Optics Express
https://www.readbyqxmd.com/read/27936763/nanocavity-integrated-van-der-waals-heterostructure-light-emitting-tunneling-diode
#17
Chang-Hua Liu, Genevieve Clark, Taylor Fryett, Sanfeng Wu, Jiajiu Zheng, Fariba Hatami, Xiaodong Xu, Arka Majumdar
Developing a nanoscale, integrable, and electrically pumped single mode light source is an essential step toward on-chip optical information technologies and sensors. Here, we demonstrate nanocavity enhanced electroluminescence in van der Waals heterostructures (vdWhs) at room temperature. The vertically assembled light-emitting device uses graphene/boron nitride as top and bottom tunneling contacts and monolayer WSe2 as an active light emitter. By integrating a photonic crystal cavity on top of the vdWh, we observe the electroluminescence is locally enhanced (>4 times) by the nanocavity...
December 12, 2016: Nano Letters
https://www.readbyqxmd.com/read/27934203/transition-from-samo-to-rydberg-state-ionization-in-c60-in-femtosecond-laser-fields
#18
H Li, B Mignolet, Z Wang, K J Betsch, K D Carnes, I Ben-Itzhak, C L Cocke, F Remacle, M F Kling
The transition between two distinct ionization mechanisms in femtosecond laser fields at 785 nm is observed for C60 molecules. The transition occurs in the investigated intensity range from 3 to 20 TW/cm(2) and is visualized in electron kinetic energy spectra below the one-photon energy (1.5 eV) obtained via velocity map imaging. Assignment of several observed broad spectral peaks to ionization from superatom molecular orbitals (SAMOs) and Rydberg states is based on time-dependent density functional theory simulations...
November 17, 2016: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/27934073/growth-of-highly-strained-ceo2-ultrathin-films
#19
Yezhou Shi, Sang Chul Lee, Matteo Monti, Colvin Wang, Zhuoluo A Feng, William D Nix, Michael F Toney, Robert Sinclair, William C Chueh
Large biaxial strain is a promising route to tune the functionalities of oxide thin films. However, large strain is often not fully realized due to the formation of misfit dislocations at the film/substrate interface. In this work, we examine the growth of strained ceria (CeO2) thin films on (001)-oriented single crystal yttria-stabilized zirconia (YSZ) via pulsed-laser deposition. By varying the film thickness systematically between 1 and 430 nm, we demonstrate that ultrathin ceria films are coherently strained to the YSZ substrate for thicknesses up to 2...
November 22, 2016: ACS Nano
https://www.readbyqxmd.com/read/27933918/dissociation-dynamics-and-electronic-structures-of-highly-excited-ferrocenium-ions-studied-by-femtosecond-xuv-absorption-spectroscopy
#20
Adam S Chatterley, Florian Lackner, C D Pemmaraju, Daniel M Neumark, Stephen R Leone, Oliver Gessner
The dissociation dynamics of ferrocene are explored following strong field ionization using femtosecond time-resolved extreme ultraviolet (XUV) transient absorption spectroscopy. Employing transitions in the vicinity of the iron 3p (M2,3) edge, the dissociation is monitored from the point of view of the iron atom. With low strong field pump intensities (≈2 × 10(13) W cm(-2)), only ferrocenium cations are produced, and their iron 3p absorption spectrum is reported. It very closely resembles the 3p spectrum of atomic Fe(+) ions but is red-shifted by 0...
December 8, 2016: Journal of Physical Chemistry. A
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