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Doppler velocimetry

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https://www.readbyqxmd.com/read/29714277/multiple-light-scattering-in-metallic-ejecta-produced-under-intense-shockwave-compression
#1
J-E Franzkowiak, P Mercier, G Prudhomme, L Berthe
A roughened metallic plate, subjected to intense shock wave compression, gives rise to an expanding ejecta particle cloud. Photonic Doppler velocimetry (PDV), a fiber-based heterodyne velocimeter, is often used to track ejecta velocities in dynamic compression experiments and on nanosecond time scales. Shortly after shock breakout at the metal-vacuum interface, a particular feature observed in many experiments in the velocity spectrograms is what appear to be slow-moving ejecta, below the free-surface velocity...
April 10, 2018: Applied Optics
https://www.readbyqxmd.com/read/29678322/measurement-of-wall-shear-stress-exerted-by-flowing-blood-in-the-human-carotid-artery-ultrasound-doppler-velocimetry-and-echo-particle-image-velocimetry
#2
Phillip E Gates, Arati Gurung, Luciano Mazzaro, Kuni Aizawa, Salim Elyas, William D Strain, Angela C Shore, Robin Shandas
Vascular endothelial cells lining the arteries are sensitive to wall shear stress (WSS) exerted by flowing blood. An important component of the pathophysiology of vascular diseases, WSS is commonly estimated by centerline ultrasound Doppler velocimetry (UDV). However, the accuracy of this method is uncertain. We have previously validated the use of a novel, ultrasound-based, particle image velocimetry technique (echo PIV) to compute 2-D velocity vector fields, which can easily be converted into WSS data. We compared WSS data derived from UDV and echo PIV in the common carotid artery of 27 healthy participants...
April 17, 2018: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/29604750/pdv-based-estimation-of-ejecta-particles-mass-velocity-function-from-shock-loaded-tin-experiment
#3
J-E Franzkowiak, G Prudhomme, P Mercier, S Lauriot, E Dubreuil, L Berthe
A metallic tin plate with a given surface finish of wavelength λ ≃ 60 μm and amplitude h ≃ 8 μm is explosively driven by an electro-detonator with a shock-induced breakout pressure PSB = 28 GPa (unsupported). The resulting dynamic fragmentation process, the so-called "micro-jetting," is the creation of high-speed jets of matter moving faster than the bulk metallic surface. Hydrodynamic instabilities result in the fragmentation of these jets into micron-sized metallic particles constituting a self-expanding cloud of droplets, whose areal mass, velocity, and particle size distributions are unknown...
March 2018: Review of Scientific Instruments
https://www.readbyqxmd.com/read/29587562/correlation-between-umbilical-arterial-ph-values-and-fetal-vertebral-artery-doppler-waveforms-at-the-beginning-of-the-second-stage-of-labor-a-pilot-prospective-study
#4
Danila Morano, Gennaro Scutiero, Piergiorgio Iannone, Giulia Nencini, Elena Mantovani, Antonio Farina, Pantaleo Greco
OBJECTIVE: The aim of this study was to evaluate the association between umbilical arterial pH and fetal vertebral artery Doppler velocimetry waveforms measured at the beginning of the second stage of labor in physiological term pregnancies. METHODS: This was a prospective cohort study of 250 pregnancies. The resistance index, pulsatility index and peak systolic velocity were measured. The relationship between the fetal Doppler and the umbilical arterial pH was evaluated...
March 27, 2018: Journal of Maternal-fetal & Neonatal Medicine
https://www.readbyqxmd.com/read/29577954/assessment-of-flow-dynamics-in-retinal-and-choroidal-microcirculation
#5
REVIEW
Xin Wei, Praveen Kumar Balne, Kenith E Meissner, Veluchamy A Barathi, Leopold Schmetterer, Rupesh Agrawal
Alterations in ocular blood flow have been implicated in mechanisms that lead to vision loss in patients with various ocular disorders such as diabetic retinopathy, glaucoma, and age-related macular degeneration. Assessment of retinal and choroidal blood flow is also a window to evaluate systemic diseases that affect microvasculature. Quantification and qualification of the blood flow in the retina and choroid help us understand pathophysiology, stratify disease risk, and monitor disease progression in these disorders...
March 22, 2018: Survey of Ophthalmology
https://www.readbyqxmd.com/read/29571928/hemodynamic-changes-during-rewarming-phase-of-whole-body-hypothermia-therapy-in-neonates-with-hypoxic-ischemic-encephalopathy
#6
Tai-Wei Wu, Benita Tamrazi, Sadaf Soleymani, Istvan Seri, Shahab Noori
OBJECTIVE: To delineate the systemic and cerebral hemodynamic response to incremental increases in core temperature during the rewarming phase of therapeutic hypothermia in neonatal hypoxic-ischemic encephalopathy (HIE). STUDY DESIGN: Continuous hemodynamic data, including heart rate (HR), mean arterial blood pressure (MBP), cardiac output by electrical velocimetry (COEV ), arterial oxygen saturation, and renal (RrSO2 ) and cerebral (CrSO2 ) regional tissue oxygen saturation, were collected from 4 hours before the start of rewarming to 1 hour after the completion of rewarming...
March 20, 2018: Journal of Pediatrics
https://www.readbyqxmd.com/read/29561210/preparation-and-characterization-of-letrozole-loaded-poly-d-l-lactide-nanoparticles-for-drug-delivery-in-breast-cancer-therapy
#7
Bayan Alemrayat, Abdelbary Elhissi, Husam M Younes
Letrozole (LTZ), an aromatase inhibitor used for the treatment of hormonally-positive breast cancer in postmenopausal women, has poor water solubility, rapid metabolism, and a range of side effects. In this study, polymer-based nanoparticles (NPs) incorporating the drug have been designed and characterized, aimed to control the release, potentially maximize the therapeutic efficiency, and minimize the side effects of the drug. LTZ was incorporated into poly(d,l-lactide) (PDLLA) NPs by employing the emulsion-solvent evaporation technique using a range of drug concentrations...
April 5, 2018: Pharmaceutical Development and Technology
https://www.readbyqxmd.com/read/29532332/experimental-assessment-of-flow-fields-associated-with-heart-valve-prostheses-using-particle-image-velocimetry-piv-recommendations-for-best-practices
#8
REVIEW
Vrishank Raghav, Sudeep Sastry, Neelakantan Saikrishnan
Experimental flow field characterization is a critical component of the assessment of the hemolytic and thrombogenic potential of heart valve substitutes, thus it is important to identify best practices for these experimental techniques. This paper presents a brief review of commonly used flow assessment techniques such as Particle image velocimetry (PIV), Laser doppler velocimetry, and Phase contrast magnetic resonance imaging and a comparison of these methodologies. In particular, recommendations for setting up planar PIV experiments such as recommended imaging instrumentation, acquisition and data processing are discussed in the context of heart valve flows...
March 12, 2018: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/29522755/influence-of-microvascular-sutures-on-shear-strain-rate-in-realistic-pulsatile-flow
#9
R A J Wain, D J Smith, D R Hammond, J P M Whitty
Arterial thrombus formation is directly related to the mechanical shear experienced by platelets within flow. High shear strain rates (SSRs) and large shear gradients cause platelet activation, aggregation and production of thrombus. This study, for the first time, investigates the influence of pulsatile flow on local haemodynamics within sutured microarterial anastomoses. We measured physiological arterial waveform velocities experimentally using Doppler ultrasound velocimetry, and a representative example was applied to a realistic sutured microarterial geometry...
July 2018: Microvascular Research
https://www.readbyqxmd.com/read/29520316/blood-perfusion-in-a-full-thickness-eyelid-flap-investigated-by-laser-doppler-velocimetry-laser-speckle-contrast-imaging-and-thermography
#10
Rafi Sheikh, Khashayar Memarzadeh, Christian Torbrand, Jonas Blohmé, Sandra Lindstedt, Malin Malmsjö
Purpose: The eyelid is commonly dissected and divided in the process of, for example, blepharotomy, entropion repair, or when preparing a full-thickness eyelid flap to reconstruct a tumor defect. No study has yet been conducted to examine how perfusion in an eyelid is affected by dissection, using modern imaging techniques. Methods: The eyelid was divided with a 10-mm vertical incision, 5 mm from the medial canthus, and the incision was extended horizontally by 30 mm to provide a full-thickness eyelid. Blood perfusion was measured along the length of the free dissected eyelid using both laser Doppler velocimetry and laser speckle contrast imaging...
2018: Eplasty
https://www.readbyqxmd.com/read/29505444/pulse-pressure-and-carotid-artery-doppler-velocimetry-as-indicators-of-maternal-volume-status-a-prospective-cohort-study
#11
Justin R Lappen, Stephen A Myers, Norman Bolden, Ziad Shaman, Venkata Angirekula, Edward K Chien
BACKGROUND: Narrow pulse pressure has been demonstrated to indicate low central volume status. In critically ill patients, volume status can be qualitatively evaluated using Doppler velocimetry to assess hemodynamic changes in the carotid artery in response to autotransfusion with passive leg raise (PLR). Neither parameter has been prospectively evaluated in an obstetric population. The objective of this study was to determine if pulse pressure could predict the response to autotransfusion using carotid artery Doppler in healthy intrapartum women...
March 1, 2018: Anesthesia and Analgesia
https://www.readbyqxmd.com/read/29495906/safety-of-a-physical-therapy-protocol-for-women-with-preeclampsia-a-randomized-controlled-feasibility-trial
#12
Tawana Vicente Bertagnolli, Michelle de Souza Rangel Machado, Cristine Jorge Homsi Ferreira, Jackeline de Souza Rangel Machado, Geraldo Duarte, Ricardo Carvalho Cavalli
OBJECTIVE: To assess the feasibility and safety of a physiotherapy protocol applied to pregnant women with preeclampsia. METHODS: Randomized, controlled, single-blind feasibility study, with 24 hospitalized pregnant women with preeclampsia. The intervention group received one session of the physiotherapy. The control group remained under the routine care of the hospital. The primary outcomes were Doppler velocimetry, cardiotocography, and maternal-fetal hemodynamics...
May 2018: Hypertension in Pregnancy
https://www.readbyqxmd.com/read/29492544/a-wearable-transcranial-doppler-ultrasound-phased-array-system
#13
Sabino J Pietrangelo, Hae-Seung Lee, Charles G Sodini
OBJECTIVE:  Practical deficiencies related to conventional transcranial Doppler (TCD) sonography have restricted its use and applicability. This work seeks to mitigate several such constraints through the development of a wearable, electronically steered TCD velocimetry system, which enables noninvasive measurement of cerebral blood flow velocity (CBFV) for monitoring applications with limited operator interaction. MATERIALS AND METHODS: A highly-compact, discrete prototype system was designed and experimentally validated through flow phantom and preliminary human subject testing...
2018: Acta Neurochirurgica. Supplement
https://www.readbyqxmd.com/read/29448409/ultrasonic-measurements-of-the-bulk-flow-field-in-foams
#14
Richard Nauber, Lars Büttner, Kerstin Eckert, Jochen Fröhlich, Jürgen Czarske, Sascha Heitkam
The flow field of moving foams is relevant for basic research and for the optimization of industrial processes such as froth flotation. However, no adequate measurement technique exists for the local velocity distribution inside the foam bulk. We have investigated the ultrasound Doppler velocimetry (UDV), providing the first two-dimensional, non-invasive velocity measurement technique with an adequate spatial (10mm) and temporal resolution (2.5Hz) that is applicable to medium scale foam flows. The measurement object is dry aqueous foam flowing upward in a rectangular channel...
January 2018: Physical Review. E
https://www.readbyqxmd.com/read/29447050/added-value-of-cerebro-placental-ratio-and-uterine-artery-doppler-at-routine-third-trimester-screening-as-a-predictor-of-sga-and-fgr-in-non-selected-pregnancies
#15
M Rial-Crestelo, R J Martinez-Portilla, A Cancemi, J Caradeux, L Fernandez, A Peguero, E Gratacos, Francesc Figueras
OBJECTIVES: The objective of this study is to determine the added value of cerebroplacental ratio (CPR) and uterine Doppler velocimetry at third trimester scan in an unselected obstetric population to predict smallness and growth restriction. METHODS: We constructed a prospective cohort study of women with singleton pregnancies attended for routine third trimester screening (32+0 -34+6 weeks). Fetal biometry and fetal-maternal Doppler ultrasound examinations were performed by certified sonographers...
March 4, 2018: Journal of Maternal-fetal & Neonatal Medicine
https://www.readbyqxmd.com/read/29422212/diagnosis-and-surveillance-of-late-onset-fetal-growth-restriction
#16
REVIEW
Francesc Figueras, Javier Caradeux, Fatima Crispi, Elisenda Eixarch, Anna Peguero, Eduard Gratacos
By consensus, late fetal growth restriction is that diagnosed >32 weeks. This condition is mildly associated with a higher risk of perinatal hypoxic events and suboptimal neurodevelopment. Histologically, it is characterized by the presence of uteroplacental vascular lesions (especially infarcts), although the incidence of such lesions is lower than in preterm fetal growth restriction. Screening procedures for fetal growth restriction need to identify small babies and then differentiate between those who are healthy and those who are pathologically small...
February 2018: American Journal of Obstetrics and Gynecology
https://www.readbyqxmd.com/read/29390757/experimental-investigation-of-the-influence-of-natural-convection-and-end-effects-on-rayleigh-streaming-in-a-thermoacoustic-engine
#17
Islam A Ramadan, Hélène Bailliet, Jean-Christophe Valière
The influence of both the natural convection and end-effects on Rayleigh streaming pattern in a simple standing-wave thermoacoustic engine is investigated experimentally at different acoustic levels. The axial mean velocity inside the engine is measured using both Laser Doppler Velocimetry and Particle Image Velocimetry. The mean flow patterns are categorized in three different regions referred to as "cold streaming" region, "hot streaming" region, and "end-effects" region. In the cold streaming region, the dominant phenomenon is Rayleigh streaming and the mean velocity measurements correspond well with the theoretical expectations of Rayleigh streaming at low acoustic levels...
January 2018: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/29375900/uterine-artery-doppler-velocimetry-in-hypertensive-disorder-of-pregnancy-in-nigeria
#18
Ibukun A Abidoye, Oluwagbemiga O Ayoola, Bukunmi M Idowu, Adeniyi S Aderibigbe, Olabisi M Loto
Aim of the study: To evaluate the value of uterine artery Doppler indices and waveform pattern in predicting fetuses at risk for intrauterine growth restriction in hypertensive disorders of pregnancy. Materials and methods: This was a prospective cross-sectional study including 80 pregnant subjects with hypertensive disorders of pregnancy and two control groups. Uterine artery Doppler sonography was performed in all study participants. Uterine artery Doppler indices across the groups were compared using the analysis of variance (ANOVA) while the presence of prediastolic notch was analyzed with the Chi Square test...
December 2017: Journal of Ultrasonography
https://www.readbyqxmd.com/read/29319201/comparative-study-of-abdominal-versus-transvaginal-ultrasound-for-uterine-artery-doppler-velocimetry-at-11-to-13-weeks
#19
Marie-Elaine Demers, Samuel Dubé, Mélodie Bourdages, Cedric Gasse, Amélie Boutin, Mario Girard, Emmanuel Bujold, Suzanne Demers
OBJECTIVES: To compare the first-trimester uterine artery pulsatility index (PI) measured by abdominal and transvaginal ultrasound (US). METHODS: We performed a prospective study of singleton pregnant women recruited at 11 to 13 weeks' gestation. The mean uterine artery PI was obtained by abdominal followed by transvaginal US. The mean of the left and right uterine artery PIs was used, and differences between approaches were computed. The intraclass correlation coefficient and a Bland-Altman plot were used to compare the two approaches...
January 10, 2018: Journal of Ultrasound in Medicine: Official Journal of the American Institute of Ultrasound in Medicine
https://www.readbyqxmd.com/read/29298455/preterm-preeclampsia-with-severe-features-composite-maternal-and-neonatal-morbidities-associated-with-fetal-growth-restriction
#20
Olaide Ashimi Balogun, Raminder K Khanagura, Heather R Kregel, Farah H Amro, Baha M Sibai, Suneet P Chauhan
OBJECTIVE:  The objective of this study was to compare adverse pregnancy outcomes between fetuses with estimated fetal weight (EFW) < 10 to > 10% in women with preterm preeclampsia (PE) with severe features. MATERIALS AND METHODS:  All women with preterm PE with severe features and nonanomalous singletons with EFW were identified at a tertiary center. Women with oligohydramnios or absent/reversed umbilical Doppler velocimetry were excluded. Using multivariable analysis, we compared the composite maternal and neonatal morbidities (CMM and CNM) between those with appropriate for gestational age (AGA) fetal growth, defined as EFW at 10 to 90th versus those with fetal growth restriction (FGR), defined as EFW < 10th percentile for gestational age (GA)...
January 3, 2018: American Journal of Perinatology
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