The value of regional wall motion abnormalities on 99Tcm-MIBI gated cardiac SPECT in predicting angiographic stenoses of coronary artery

International Nuclear Information System (INIS)

Li Dianfu; Huang Jun; Zhu Tiebing; Wang Liansheng; Yang Zhijian; Feng Jianlin; Li Jianhua; Chen Jianwei; Chang Guojun

2004-01-01

Objective: To determine the magnitude of angiographic stenoses of coronary artery in reversible regional wall motion abnormalities (RWMA) present in exercise stress 99 Tc m -methoxyisobutylisonitrile (MIBI) gated SPECT myocardial perfusion imaging (MPI). Methods: One hundred and sixteen patients undergoing coronary angiography two weeks before and after the exercise stress 99 Tc m -MIBI gated SPECT MPI. Images were acquired 15 to 20 min after stress. A five grades and twenty segments marking system was introduced to assess the RWMA and thickening of left ventricles. Results: The sensitivity of reversible RWMA for detecting ≥75% angiographic stenoses was 65%, with a specificity of 97%. Reversible RWMA has a high positive predictive value (98%) for stratification between severe angiographic stenoses of 75% and non-severe stenoses (less than 75%). Multivariate analysis showed that the post-stress wall motion (SSSWM), exercise wall motion differentiation value (SDSWM) and summed stress score (SSS) were the independent risk factor of coronary artery jeopardy score. Conclusions: Reversible RWMA, as shown by exercise stress 99 Tc m -MIBI gated SPECT MPI, is a significant predictor of angiographic disease with very high specificity and positive predictive values. Exercise reversible RWMA can rise the assessment value of angiographic severity in MPI

Intraventricular flow alterations due to dyssynchronous wall motion

Science.gov (United States)

Pope, Audrey M.; Lai, Hong Kuan; Samaee, Milad; Santhanakrishnan, Arvind

2015-11-01

Roughly 30% of patients with systolic heart failure suffer from left ventricular dyssynchrony (LVD), in which mechanical discoordination of the ventricle walls leads to poor hemodynamics and suboptimal cardiac function. There is currently no clear mechanistic understanding of how abnormalities in septal-lateral (SL) wall motion affects left ventricle (LV) function, which is needed to improve the treatment of LVD using cardiac resynchronization therapy. We use an experimental flow phantom with an LV physical model to study mechanistic effects of SL wall motion delay on LV function. To simulate mechanical LVD, two rigid shafts were coupled to two segments (apical and mid sections) along the septal wall of the LV model. Flow through the LV model was driven using a piston pump, and stepper motors coupled to the above shafts were used to locally perturb the septal wall segments relative to the pump motion. 2D PIV was used to examine the intraventricular flow through the LV physical model. Alterations to SL delay results in a reduction in the kinetic energy (KE) of the flow field compared to synchronous SL motion. The effect of varying SL motion delay from 0% (synchronous) to 100% (out-of-phase) on KE and viscous dissipation will be presented. This research was supported by the Oklahoma Center for Advancement of Science and Technology (HR14-022).

Noninvasive assessment of right ventricular wall motion by radionuclide cardioangiography

International Nuclear Information System (INIS)

Nishimura, Tsunehiko; Uehara, Toshiisa; Naito, Hiroaki; Hayashida, Kohei; Kozuka, Takahiro

1981-01-01

Radionuclide cardioangiography is a useful method to evaluate the left ventricular wall motion in various heart diseases. It has been also attempted to assess the right ventricular wall motion simultaneously by radionuclide method. In this study, using the combination of first-pass (RAO 30 0 ) and multi-gate (LAO 40 0 ) method, the site of right vetricle was classified in five. (1 inflow, 2 sinus, 3 outflow, 4 septal, 5 lateral) and the degree of wall motion was classified in four stages (dyskinesis, akinesis, hypokinesis, normal) according to the AHA committee report. These methods were applied clinically to forty-eight patients with various heart diseases. In the cases with right ventricular pressure or volume overload such as COLD, pulmonary infarction, the right ventricle was dilated and the wall motion was reduced in all portions. Especially, in the cases with right ventricular infarction, the right ventricular wall motion was reduced in the infarcted area. The findings of radionuclide method were in good agreement with those of contrast right ventriculography or echocardiography. In conclusion, radionuclide cardioangiography is a useful and noninvasive method to assess not only the left but also the right ventricular wall motion. (author)

Reversible Stress Cardiomyopathy Presenting as Acute Coronary Syndrome with Elevated Troponin in the Absence of Regional Wall Motion Abnormalities: A Forme Fruste of Stress Cardiomyopathy?

Directory of Open Access Journals (Sweden)

Mahesh Anantha Narayanan

2014-01-01

Full Text Available We present a case of reversible stress cardiomyopathy in a surgical patient, described here as a forme fruste due to its atypical features. It is important to recognize such unusual presentation of stress cardiomyopathy that mimics acute coronary syndrome. Stress cardiomyopathy commonly presents as acute coronary syndrome and is characterized by typical or atypical variants of regional wall motion abnormalities. We report a 60-year-old Caucasian male with reversible stress cardiomyopathy following a sternal fracture fixation. Although the patient had several typical features of stress cardiomyopathy including physical stress, ST-segment elevation, elevated cardiac biomarkers and normal epicardial coronaries, there were few features that were atypical, including unusual age, gender, absence of regional wall motion abnormalities, high lateral ST elevation, and high troponin-ejection fraction product. In conclusion, this could represent a forme fruste of stress cardiomyopathy.

Tissue Doppler imaging of carotid plaque wall motion: a pilot study

Directory of Open Access Journals (Sweden)

Naylor A Ross

2003-12-01

Full Text Available Abstract Background Studies suggest the physical and mechanical properties of vessel walls and plaque may be of clinical value in the diagnosis and treatment of cardiovascular atherosclerotic disease. The purpose of this pilot study was to investigate the potential clinical application of ultrasound Tissue Doppler Imaging (TDI of Arterial Wall Motion (AWM and to quantify simple wall motion indices in normal and diseased carotid arteries. Methods 224 normal and diseased carotid arteries (0–100% stenoses were imaged in 126 patients (age 25–88 years, mean 68 ± 11. Longitudinal sections of the carotid bifurcation were imaged using a Philips HDI5000 scanner and L12-5 probe under optimized TDI settings. Temporal and spatial AWMs were analyzed to evaluate the vessel wall displacements and spatial gradients at peak systole averaged over 5 cardiac cycles. Results AWM data were successfully extracted in 91% of cases. Within the carotid bifurcation/plaque region, the maximum wall dilation at peak systole ranged from -100 to 750 microns, mean 335 ± 138 microns. Maximum wall dilation spatial gradients ranged 0–0.49, mean 0.14 ± 0.08. The AWM parameters showed a wide variation and had poor correlation with stenoses severity. Case studies illustrated a variety of pertinent qualitative and quantitative wall motion features related to the biophysics of arterial disease. Conclusion Our clinical experience, using a challenging but realistic imaging protocol, suggests the use of simple quantitative AWM measures may have limitations due to high variability. Despite this, pertinent features of AWM in normal and diseased arteries demonstrate the potential clinical benefit of the biomechanical information provided by TDI.

Magnetization reversal in ferromagnetic spirals via domain wall motion

Science.gov (United States)

Schumm, Ryan D.; Kunz, Andrew

2016-11-01

Domain wall dynamics have been investigated in a variety of ferromagnetic nanostructures for potential applications in logic, sensing, and recording. We present a combination of analytic and simulated results describing the reliable field driven motion of a domain wall through the arms of a ferromagnetic spiral nanowire. The spiral geometry is capable of taking advantage of the benefits of both straight and circular wires. Measurements of the in-plane components of the spirals' magnetization can be used to determine the angular location of the domain wall, impacting the magnetoresistive applications dependent on the domain wall location. The spirals' magnetization components are found to depend on the spiral parameters: the initial radius and spacing between spiral arms, along with the domain wall location. The magnetization is independent of the parameters of the rotating field used to move the domain wall, and therefore the model is valid for current induced domain wall motion as well. The speed of the domain wall is found to depend on the frequency of the rotating driving field, and the domain wall speeds can be reliably varied over several orders of magnitude. We further demonstrate a technique capable of injecting multiple domain walls and show the reliable and unidirectional motion of domain walls through the arms of the spiral.

Changes in sitting posture induce multiplanar changes in chest wall shape and motion with breathing.

Science.gov (United States)

Lee, Linda-Joy; Chang, Angela T; Coppieters, Michel W; Hodges, Paul W

2010-03-31

This study examined the effect of sitting posture on regional chest wall shape in three dimensions, chest wall motion (measured with electromagnetic motion analysis system), and relative contributions of the ribcage and abdomen to tidal volume (%RC/V(t)) (measured with inductance plethysmography) in 7 healthy volunteers. In seven seated postures, increased dead space breathing automatically increased V(t) (to 1.5 V(t)) to match volume between conditions and study the effects of posture independent of volume changes. %RC/V(t) (pplane changes in sitting posture alter three-dimensional ribcage configuration and chest wall kinematics during breathing, while maintaining constant respiratory function. Copyright 2010 Elsevier B.V. All rights reserved.

Segmental wall-motion analysis in the right anterior oblique projection: comparison of exercise equilibrium radionuclide ventriculography and exercise contrast ventriculography

International Nuclear Information System (INIS)

Brady, T.J.; Thrall, J.H.; Keyes, J.W. Jr.; Brymer, J.F.; Walton, J.A.; Pitt, B.

1980-01-01

Thirty-nine patients with known or suspected coronary artery disease were studied at rest and during supine bicycle exercise with radionuclide and contrast left ventriculography. Analysis of regional wall motion was made by visual evaluation of the five standard 30 0 right anterior oblique (RAO) wall segments in the contrast images and the corresponding 10 0 RAO radionuclide segments. The radionuclide studies were evaluated independently by three observers using a five-point grading system. The interobserver wall-motion grading agreed completely in more than 80% of segments at rest and exercise, and agreed within one wall-motion grade in more than 95% of segments. The comparison of wall-motion grades between radionuclide and contrast ventriculograms showed complete agreement in 86% of segments at rest and in 78% during exercise, and agreement within one wall-motion grade in 97% of rest and 96% of exercise segments. Visual evaluation of 10 0 RAO rest and exercise radionuclide ventriculograms compares favorably with rest and exercise 30 0 RAO contrast ventriculograms and demonstrates satisfactory interobserver agreement

Myocardial imaging with 99mTc-Tetrofosmin: Influence of post-stress acquisition time, regional radiotracer uptake, and wall motion abnormalities on the clinical result.

Science.gov (United States)

Giorgetti, Assuero; Kusch, Annette; Casagranda, Mirta; Tagliavia, Irene D'Aragona; Marzullo, Paolo

2010-04-01

We previously demonstrated that early (15', T1) post-stress myocardial imaging with Tetrofosmin could be more accurate than standard acquisitions (45', T2) in identifying coronary artery disease. To clarify this phenomenon, 120 subjects (age 61 +/- 10 years) with both T1 and T2 scans were divided into Group 1 (53/120 pts) with more ischemia at T1 vs T2 imaging (T1-T2SDS > or = 3); Group 2 (67/120 pts) with similar results (T1-T2SDS statistic and semiquantitative wall motion/thickening values were obtained. Analysis of T1 and T2 post-stress myocardial counts demonstrated a significant Tetrofosmin wash-out rate that was higher in Group 1 control nonischemic regions (15 +/- 8% vs 13.6 +/- 9.6%, P stress wall thickening (T1-T2) was lower in Group 1 ischemic regions (-4.5 +/- 9.15% vs -1.90 +/- 7.0%, P stress acquisition time because of ischemic-induced regional wall thickening abnormalities and the existence of a differential radiotracer myocardial wash-out.

Induced motion of domain walls in multiferroics with quadratic interaction

Energy Technology Data Exchange (ETDEWEB)

Gerasimchuk, Victor S., E-mail: viktor.gera@gmail.com [National Technical University of Ukraine “Kyiv Polytechnic Institute”, Peremohy Avenue 37, 03056 Kiev (Ukraine); Shitov, Anatoliy A., E-mail: shitov@mail.ru [Donbass National Academy of Civil Engineering, Derzhavina Street 2, 86123 Makeevka, Donetsk Region (Ukraine)

2013-10-15

We theoretically study the dynamics of 180-degree domain wall of the ab-type in magnetic materials with quadratic magnetoelectric interaction in external alternating magnetic and electric fields. The features of the oscillatory and translational motions of the domain walls and stripe structures depending on the parameters of external fields and characteristics of the multiferroics are discussed. The possibility of the domain walls drift in a purely electric field is established. - Highlights: • We study DW and stripe DS in multiferroics with quadratic magnetoelectric interaction. • We build up the theory of oscillatory and translational (drift) DW and DS motion. • DW motion can be caused by crossed alternating electric and magnetic fields. • DW motion can be caused by alternating “pure” electric field. • DW drift velocity is formed by the AFM and Dzyaloshinskii interaction terms.

Geometric Relations for CYLEX Test Tube-Wall Motion

Science.gov (United States)

Hill, Larry

2015-06-01

The CYLinder EXpansion (CYLEX) test is a (precision, instrumented, high-purity annealed copper) pipe bomb. Its essential measured quantities are detonation speed and tube-wall motion. Its main purpose is to calibrate detonation product equations of state (EOS) by measuring how product fluid pushes metal. In its full complexity, CYLEX is an integral test, for which EOS calibration requires the entire system to be computationally modeled and compared to salient data. Stripped to its essence, CYLEX is a non-integral test for which one may perform the inverse problem, to infer the EOS directly from data. CYLEX analysis can be simplified by the fact that the test constituents achieve a steady traveling wave structure; this allows derivation of several useful geometric relationships regarding tube wall motion. The first such treatment was by G.I. Taylor. Although his analysis was limited to small wall deflection angles, he asserted that the results remain valid for arbitrary ones. I confirm this attribute and present additional useful relationships. In the past decade, CYLEX wall-motion instrumentation has migrated almost entirely from streak camera to PDV, yet discrepancies remain between the two methods. I further present geometric relationships that shed light on this issue. Work supported by the U.S. DOE.

Rashba spin–orbit coupling effects on a current-induced domain wall motion

International Nuclear Information System (INIS)

Ryu, Jisu; Seo, Soo-Man; Lee, Kyung-Jin; Lee, Hyun-Woo

2012-01-01

A current-induced domain wall motion in magnetic nanowires with a strong structural inversion asymmetry [I.M. Miron, T. Moore, H. Szambolics, L.D. Buda-Prejbeanu, S. Auffret, B. Rodmacq, S. Pizzini, J. Vogel, M. Bonfim, A. Schuhl, G. Gaudin, Nat. Mat. 10 (2011) 419] seems to have novel features such as the domain wall motion along the current direction or the delay of the onset of the Walker breakdown. In such a highly asymmetric system, the Rashba spin–orbit coupling (RSOC) may affect a domain wall motion. We studied theoretically the RSOC effects on a domain wall motion and found that the RSOC, indeed, can induce the domain wall motion along the current direction in certain situations. It also delays the Walker breakdown and for a strong RSOC, the Walker breakdown does not occur at all. The RSOC effects are sensitive to the magnetic anisotropy of nanowires and also to the ratio between the Gilbert damping parameter α and the non-adiabaticity parameter β. - Highlights: ► Effects of Rashba spin–orbit coupling on a domain wall motion is calculated. ► The effects depend highly on the anisotropy of a magnetic system. ► It modifies the wall velocity for the system with a perpendicular magnetic anisotropy. ► The modified velocity can be along the current direction in certain situations. ► Rashba spin–orbit coupling also hinders the onset of the Walker breakdown.

Reasons for the lack of benefit of immediate angioplasty during recombinant tissue plasminogen activator therapy for acute myocardial infarction: a regional wall motion analysis. European Cooperative Study Group

NARCIS (Netherlands)

Arnold, A. E.; Serruys, P. W.; Rutsch, W.; Simoons, M. L.; de Bono, D. P.; Tijssen, J. G.; Lubsen, J.; Verstraete, M.

1991-01-01

Regional ventricular wall motion analysis utilizing three different methods was performed on predischarge left ventriculograms from 291 of 367 patients enrolled in a randomized trial of single chain recombinant tissue-type plasminogen activator (rt-PA), aspirin and heparin with and without immediate

Assessment of cardiac performance with quantitative radionuclide angiocardiography: sequential left ventricular ejection fraction, normalized left ventricular ejection rate, and regional wall motion

International Nuclear Information System (INIS)

Marshall, R.C.; Berger, H.J.; Costin, J.C.; Freedman, G.S.; Wolberg, J.; Cohen, L.S.; Gotischalk, A.; Zaret, B.L.

1977-01-01

Sequential quantitative first pass radionuclide angiocardiograms (RA) were used to measure left ventricular ejection fraction (LVEF) and left ventricular ejection rate (LVER), and to assess regional wall motion (RWM) in the anterior (ANT) and left anterior oblique (LAO) positions. Studies were obtained with a computerized multicrystal scintillation camera suitable for acquiring high count-rate data. Background was determined in a new fashion by selecting frames temporally from the left ventricular region of interest time-activity curve. A ''representative'' cardiac cycle was formed by summing together counts over three to six cardiac cycles. From this background corrected, high count-rate ''representative''cardiac cycle, LVEF, LVER, and RWM were determined. In 22 patients with normal sinus rhythm in the absence of significant valvular regurgitation, RA LVEF correlated well with that measured by contrast angiography (r = 0.95). LVER correlated well with LVEF measured at contrast angiography (r = 0.90) and allowed complete separation of those with normal (LVER = 3.4 +- 0.17 sec -1 ) and abnormal (LVER = 1.22 +- 0.11 sec -1 ) (P < 0.001) left ventricular performance. This separation was independent of background. Isoproterenol infusion in five normal subjects caused LVER to increase by 81 +- 17% while LVEF increased by 10 +- 2.0%. RWM was correctly defined in 21/22 patients and 89% of left ventricular segments with abnormal wall motion

Imaging of left ventricular wall motion via venous DSA

International Nuclear Information System (INIS)

Witte, G.; Roediger, W.; Buecheler, E.; Hamburg Univ.

1986-01-01

Until now, angiographical and nuclear medicine examination techniques for imaging left ventricular wall motion have been presenting with difficulties endemic to the methods themselves. For the first time in cardiological diagnostics, digital subtraction angiography (DSA) makes it possible to perform a fairly non-invasive examination with good spatial and temporal resolution. Functional analytic evaluation, however, still demands time-consuming, complicated post-processing. In this article we introduce a method that uses an additive window technique for the immediate generation of wall motion images. (orig.) [de

Micromagnetic analysis of current-induced domain wall motion in a bilayer nanowire with synthetic antiferromagnetic coupling

Energy Technology Data Exchange (ETDEWEB)

Komine, Takashi, E-mail: komine@mx.ibaraki.ac.jp; Aono, Tomosuke [Faculty of Engineering, Ibaraki University 4-12-1, Nakanarusawa, Hitachi, Ibaraki, 316-8511 (Japan)

2016-05-15

We demonstrate current-induced domain wall motion in bilayer nanowire with synthetic antiferromagnetic (SAF) coupling by modeling two body problems for motion equations of domain wall. The influence of interlayer exchange coupling and magnetostatic interactions on current-induced domain wall motion in SAF nanowires was also investigated. By assuming the rigid wall model for translational motion, the interlayer exchange coupling and the magnetostatic interaction between walls and domains in SAF nanowires enhances domain wall speed without any spin-orbit-torque. The enhancement of domain wall speed was discussed by energy distribution as a function of wall angle configuration in bilayer nanowires.

Linear motion feed through with thin wall rubber sealing element

Science.gov (United States)

Mikhailov, V. P.; Deulin, E. A.

2017-07-01

The patented linear motion feedthrough is based on elastic thin rubber walls usage being reinforced with analeptic string fixed in the middle part of the walls. The pneumatic or hydro actuators create linear movement of stock. The length of this movement is two times more the rubber wall length. This flexible wall is a sealing element of feedthrough. The main advantage of device is negligible resistance force that is less then mentioned one in sealing bellows that leads to positioning error decreasing. Nevertheless, the thin wall rubber sealing element (TRE) of the feedthrough is the main unreliable element that was the reason of this element longevity research. The theory and experimental results help to create equation for TRE longevity calculation under vacuum or extra high pressure difference action. The equation was used for TRE longevity determination for hydraulic or vacuum equipment realization also as it helps for gas flow being leaking through the cracks in thin walls of rubber sealing element of linear motion feedthrough calculation.

Evaluation of segmental left ventricular wall motion by equilibrium gated radionuclide ventriculography.

Science.gov (United States)

Van Nostrand, D; Janowitz, W R; Holmes, D R; Cohen, H A

1979-01-01

The ability of equilibrium gated radionuclide ventriculography to detect segmental left ventricular (LV) wall motion abnormalities was determined in 26 patients undergoing cardiac catheterization. Multiple gated studies obtained in 30 degrees right anterior oblique and 45 degrees left anterior oblique projections, played back in a movie format, were compared to the corresponding LV ventriculograms. The LV wall in the two projections was divided into eight segments. Each segment was graded as normal, hypokinetic, akinetic, dyskinetic, or indeterminate. Thirteen percent of the segments in the gated images were indeterminate; 24 out of 27 of these were proximal or distal inferior wall segments. There was exact agreement in 86% of the remaining segments. The sensitivity of the radionuclide technique for detecting normal versus any abnormal wall motion was 71%, with a specificity of 99%. Equilibrium gated ventriculography is an excellent noninvasive technique for evaluating segmental LV wall motion. It is least reliable in assessing the proximal inferior wall and interventricular septum.

Domain wall motion in ferromagnetic systems with perpendicular magnetization

International Nuclear Information System (INIS)

Szambolics, H.; Toussaint, J.-Ch.; Marty, A.; Miron, I.M.; Buda-Prejbeanu, L.D.

2009-01-01

Although we lack clear experimental evidence, apparently out-of-plane magnetized systems are better suited for spintronic applications than the in-plane magnetized ones, mainly due to the smaller current densities required for achieving domain wall motion. [Co/Pt] multilayers belong to the first category of materials, the out-of-plane magnetization orientation arising from the strong perpendicular magnetocrystalline anisotropy. If the magnetization arranges itself out-of-plane narrow Bloch walls occur. In the present paper, both field and current-driven domain wall motion have been investigated for this system, using micromagnetic simulations. Three types of geometries have been taken into account: bulk, thin film and wire, and for all of them a full comparison is done between the effect of the applied field and injected current. The reduction of the system's dimension induces the decrease of the critical field and the critical current, but it does not influence the domain wall displacement mechanism.

Avaliação quantitativa da movimentação parietal regional do ventrículo esquerdo na endomiocardiofibrose Quantitative assessment of left ventricular regional wall motion in endomyocardial fibrosis

Directory of Open Access Journals (Sweden)

Charles Mady

2005-03-01

motion in patients with endomyocardial fibrosis (EMF. METHODS: The study comprised 88 patients, 59 of the female sex, with a mean age of 39±13 years (range, 9 to 65 and with echocardiographic and angiographic evidence of left ventricular EMF. The intensity of fibrous tissue buildup on contrast cineventriculography was classified as mild, moderate, or severe. The overall left ventricular ejection fraction (LVEF was determined by using the area-length method on ventriculography. The motion was measured in 100 equidistant chords perpendicular to the centerline drawn in the middle of the final diastolic and systolic contours and normalized to cardiac size. Five left ventricular segments were analyzed: A - apical; AL - anterolateral; AB - anterobasal; IA - inferoapical; IB - inferobasal. Abnormality was expressed in units of standard deviation of the mean motion in a normal population of reference, comprised of 103 patients with normal LV according to clinical and electrocardiographic data, and angiographic standards. RESULTS: Mean LVEF was 0.47±0.12. Fibrous tissue buildup in the left ventricle was mild in 12 patients, moderate in 40, and severe in 36. The regions with the poorest ventricular wall motion were A (-1.4±1.6 standard deviation/chords and IA (-1.6±1.8 standard deviation/chords compared with that in AB (-0.3±1.9 standard deviation/chords, AL (-0.5±1.8 standard deviation/chords and IB (-0.9±1.3 standard deviation/chords. No relation was observed between the intensity of fibrous tissue buildup and regional ventricular wall motion. CONCLUSION: A change in LV regional wall motion exists in EMF, and it is independent of the intensity of fibrous tissue buildup qualitatively assessed. Nonuniform involvement of the LV should be considered when planning surgery for this disease.

Myocardial metabolism, perfusion, wall motion and electrical activity in Duchenne muscular dystrophy

International Nuclear Information System (INIS)

Perloff, J.K.; Henze, E.; Schelbert, H.R.

1982-01-01

The cardiomyopathy of Duchenne's muscular dystrophy originates in the posterobasal left ventricle and extends chiefly to the contiguous lateral wall. Ultrastructural abnormalities in these regions precede connective tissue replacement. We postulated that a metabolic fault coincided with or antedated the subcellular abnormality. Accordingly, regional left ventricular metabolism, perfusion and wall motion were studied using positron computed tomography and metabolic isotopes supplemented by thallium perfusion scans, equilibrium radionuclide angiography and M-mode and two-dimensional echocardiography. To complete the assessment, electrocardiograms, vectorcardiograms, 24 hour taped electrocardiograms and chest x-rays were analyzed. Positron computed tomography utilizing F-18 2-fluoro 2-deoxyglucose (FDG) provided the first conclusive evidence supporting the hypothesis of a premorphologic regional metabolic fault. Thus, cardiac involvement in duchenne dystrophy emerges as a unique form of heart disease, genetically targeting specific regions of ventricular myocardium for initial metabolic and subcellular changes. Reported ultrastructural abnormalities of the impulse and conduction systems provide, at least in part, a basis for the clinically observed sinus node, intraatrial, internodal, AV nodal and infranodal disorders

Segmentation of arterial vessel wall motion to sub-pixel resolution using M-mode ultrasound.

Science.gov (United States)

Fancourt, Craig; Azer, Karim; Ramcharan, Sharmilee L; Bunzel, Michelle; Cambell, Barry R; Sachs, Jeffrey R; Walker, Matthew

2008-01-01

We describe a method for segmenting arterial vessel wall motion to sub-pixel resolution, using the returns from M-mode ultrasound. The technique involves measuring the spatial offset between all pairs of scans from their cross-correlation, converting the spatial offsets to relative wall motion through a global optimization, and finally translating from relative to absolute wall motion by interpolation over the M-mode image. The resulting detailed wall distension waveform has the potential to enhance existing vascular biomarkers, such as strain and compliance, as well as enable new ones.

Current-induced domain wall motion in magnetic nanowires with spatial variation

International Nuclear Information System (INIS)

Ieda, Jun'ichi; Sugishita, Hiroki; Maekawa, Sadamichi

2010-01-01

We model current-induced domain wall motion in magnetic nanowires with the variable width. Employing the collective coordinate method we trace the wall dynamics. The effect of the width modulation is implemented by spatial dependence of an effective magnetic field. The wall destination in the potential energy landscape due to the magnetic anisotropy and the spatial nonuniformity is obtained as a function of the current density. For a nanowire of a periodically modulated width, we identify three (pinned, nonlinear, and linear) current density regimes for current-induced wall motion. The threshold current densities depend on the pulse duration as well as the magnitude of wire modulation. In the nonlinear regime, application of ns order current pulses results in wall displacement which opposes or exceeds the prediction of the spin transfer mechanism. The finding explains stochastic nature of the domain wall displacement observed in recent experiments.

Assessment of left ventricular wall motion and function by cross-sectional echocardiography

International Nuclear Information System (INIS)

Ono, Akifumi; Hirata, Shunkichi; Ishikawa, Kyozo

1982-01-01

The clinical efficacy of cross-sectional echocardiography (CSE) was evaluated with M-mode echocardiography and radionuclide cardioangiography (RCG) in 50 cases including 30 patients with myocardial infarction. Segmental wall motion by CSE was highly correlated with segmental wall motion and left ventricular ejection fraction by RCG (r = 0.89 in the former, r = -0.84 in the latter). On the other hand, the left ventricular ejection fraction by M-mode echocardiography revealed a fairly well correlation with that by RCG ( r = 0.68). These results suggest that, as compared with RCG, CSE is quite useful in an evaluation of left ventricular function and in a detection of segmental wall motion abnormalities. (author)

Unidirectional Magnon-Driven Domain Wall Motion due to Interfacial Dzyaloshinskii-Moriya Interaction

KAUST Repository

Lee, Seo-Won

2018-03-28

We theoretically study magnon-driven motion of a tranverse domain wall in the presence of interfacial Dzyaloshinskii-Moriya interaction (DMI). Contrary to previous studies, the domain wall moves along the same direction regardless of the magnon-flow direction. Our symmetry analysis reveals that the odd order DMI contributions to the domain wall velocity are independent of the magnon-flow direction. Corresponding DMI-induced asymmetric transitions from a spin-wave state to another give rise to a large momentum transfer to the domain wall without nonreciprocity and much reflection. This counterintuitive unidirectional motion occurs not only for a spin wave with a single wavevector but also for thermal magnons with distributed wavevectors.

Unidirectional Magnon-Driven Domain Wall Motion due to Interfacial Dzyaloshinskii-Moriya Interaction

KAUST Repository

Lee, Seo-Won; Kim, Kyoung-Whan; Moon, Jung-Hwan; Go, Gyungchoon; Manchon, Aurelien; Lee, Hyun-Woo; Everschor-Sitte, Karin; Lee, Kyung-Jin

2018-01-01

We theoretically study magnon-driven motion of a tranverse domain wall in the presence of interfacial Dzyaloshinskii-Moriya interaction (DMI). Contrary to previous studies, the domain wall moves along the same direction regardless of the magnon-flow direction. Our symmetry analysis reveals that the odd order DMI contributions to the domain wall velocity are independent of the magnon-flow direction. Corresponding DMI-induced asymmetric transitions from a spin-wave state to another give rise to a large momentum transfer to the domain wall without nonreciprocity and much reflection. This counterintuitive unidirectional motion occurs not only for a spin wave with a single wavevector but also for thermal magnons with distributed wavevectors.

Color structured light system of chest wall motion measurement for respiratory volume evaluation

Science.gov (United States)

Chen, Huijun; Cheng, Yuan; Liu, Dongdong; Zhang, Xiaodong; Zhang, Jue; Que, Chengli; Wang, Guangfa; Fang, Jing

2010-03-01

We present a structured light system to dynamically measure human chest wall motion for respiratory volume estimation. Based on a projection of an encoded color pattern and a few active markers attached to the trunk, respiratory volumes are obtained by evaluating the 3-D topographic changes of the chest wall in an anatomically consistent measuring region during respiration. Three measuring setups are established: a single-sided illuminating-recording setup for standing posture, an inclined single-sided setup for supine posture, and a double-sided setup for standing posture. Results are compared with the pneumotachography and show good agreement in volume estimations [correlation coefficient: R>0.99 (Pvolume during the isovolume maneuver (standard deviationpulmonary functional differences between the diseased and the contralateral sides of the thorax, and subsequent improvement of this imbalance after drainage. These results demonstrate the proposed optical method is capable of not only whole respiratory volume evaluation with high accuracy, but also regional pulmonary function assessment in different chest wall behaviors, with the advantage of whole-field measurement.

Domain-walls motion in glass-coated CoFeSiB amorphous microwires

Energy Technology Data Exchange (ETDEWEB)

Antonov, A.S. E-mail: as.antonov@mtu-net.ru; Buznikov, N.A.; Granovsky, A.B.; Joura, A.V.; Rakhmanov, A.L.; Yakunin, A.M

2002-08-01

A method for observation of domain-walls motion in amorphous microwires with circular magnetic anisotropy is proposed. Using the method, the magnetization reversal of glass-coated Co-based microwires induced by current pulses of high amplitude is studied. The magnetization reversal is shown to occur due to the nucleation of the domain walls at the sample ends and their subsequent motion along the microwire. The dependencies of the domain-wall velocity on the current pulse amplitude and a longitudinal DC magnetic field are measured. A model describing main features of experimental data is presented.

Domain-walls motion in glass-coated CoFeSiB amorphous microwires

International Nuclear Information System (INIS)

Antonov, A.S.; Buznikov, N.A.; Granovsky, A.B.; Joura, A.V.; Rakhmanov, A.L.; Yakunin, A.M.

2002-01-01

A method for observation of domain-walls motion in amorphous microwires with circular magnetic anisotropy is proposed. Using the method, the magnetization reversal of glass-coated Co-based microwires induced by current pulses of high amplitude is studied. The magnetization reversal is shown to occur due to the nucleation of the domain walls at the sample ends and their subsequent motion along the microwire. The dependencies of the domain-wall velocity on the current pulse amplitude and a longitudinal DC magnetic field are measured. A model describing main features of experimental data is presented

Strain-encoded cardiac MRI as an adjunct for dobutamine stress testing: incremental value to conventional wall motion analysis.

Science.gov (United States)

Korosoglou, Grigorios; Lossnitzer, Dirk; Schellberg, Dieter; Lewien, Antje; Wochele, Angela; Schaeufele, Tim; Neizel, Mirja; Steen, Henning; Giannitsis, Evangelos; Katus, Hugo A; Osman, Nael F

2009-03-01

High-dose dobutamine stress MRI is safe and feasible for the diagnosis of coronary artery disease (CAD) in humans. However, the assessment of cine scans relies on the visual interpretation of regional wall motion, which is subjective. Recently, strain-encoded MRI (SENC) has been proposed for the direct color-coded visualization of myocardial strain. The purpose of our study was to compare the diagnostic value of SENC with that provided by conventional wall motion analysis for the detection of inducible ischemia during dobutamine stress MRI. Stress-induced ischemia was assessed by wall motion analysis and by SENC in 101 patients with suspected or known CAD and in 17 healthy volunteers who underwent dobutamine stress MRI in a clinical 1.5-T scanner. Quantitative coronary angiography deemed as the standard reference for the presence or absence of significant CAD (> or =50% diameter stenosis). On a coronary vessel level, SENC detected inducible ischemia in 86 of 101 versus 71 of 101 diseased coronary vessels (P or =50% stenosis (area under the curve, 0.96; SE, 0.01; 95% CI, 0.94 to 0.98; P<0.001). The direct color-coded visualization of strain on MR images is a useful adjunct for dobutamine stress MRI, which provides incremental value for the detection of CAD compared with conventional wall motion readings on cine images.

Reliable 5-min real-time MR technique for left-ventricular-wall motion analysis

International Nuclear Information System (INIS)

Katoh, Marcus; Spuentrup, Elmar; Guenther, Rolf W.; Buecker, Arno; Kuehl, Harald P.; Lipke, Claudia S.A.

2007-01-01

The aim of this study was to investigate the value of a real-time magnetic resonance imaging (MRI) approach for the assessment of left-ventricular-wall motion in patients with insufficient transthoracic echocardiography in terms of accuracy and temporal expenditure. Twenty-five consecutive patients were examined on a 1.5-Tesla whole-body MR system (ACS-NT, Philips Medical Systems, Best, NL) using a real-time and ECG-gated (the current gold standard) steady-state free-precession (SSFP) sequence. Wall motion was analyzed by three observers by consensus interpretation. In addition, the preparation, scanning, and overall examination times were measured. The assessment of the wall motion demonstrated a close agreement between the two modalities resulting in a mean κ coefficient of 0.8. At the same time, each stage of the examination was significantly shortened using the real-time MR approach. Real-time imaging allows for accurate assessment of left-ventricular-wall motion with the added benefit of decreased examination time. Therefore, it may serve as a cost-efficient alternative in patients with insufficient echocardiography. (orig.)

Internal friction due to domain-wall motion in martensitically transformed A15 compounds

International Nuclear Information System (INIS)

Snead, C.L. Jr.; Welch, D.O.

1985-01-01

A lattice instability in A15 materials in some cases leads to a cubic-to-tetragonal martensitic transformation at low temperatures. The transformed material orients in lamellae with c axes alternately aligned along the directions producing domain walls between the lamellae. An internal-friction (delta) feature below T/sub m/ is attributed to stress-induced domain-wall motion. The magnitude of the friction increases as temperature is lowered below T/sub m/ as (1-c/a) increases, and behaves as (1-c/a) 2 from T/sub m/ down to the superconducting critical temperature where the increasing tetragonality is inhibited. The effect of strain in the lattice is to decrease the domain-wall internal friction, but not affect T/sub m/. Neutron-induced disorder and the addition of some third-elements in alloying decrease both delta and T/sub m/, with some elements reducing only the former. Less than 1 at. % H is seen to completely suppress both delta and T/sub m. Martensitically transformed V 2 Zr demonstrates low-temperature internal-friction and modulus behavior consists with easy β/m wall motion relative to the easy m/m motion of the A15's. For the V 2 Zr, a peak in delta is observed, qualitatively in agreement with expected β/m wall motion

Clinical significance of exercise-induced left ventricular wall motion abnormality occurring at a low heart rate

International Nuclear Information System (INIS)

Kimchi, A.; Rozanski, A.; Fletcher, C.; Maddahi, J.; Swan, H.J.; Berman, D.S.

1987-01-01

We studied the relationship between the heart rate at the time of onset of exercise-induced wall motion abnormality and the severity of coronary artery disease in 89 patients who underwent exercise equilibrium radionuclide ventriculography as part of their evaluation for coronary artery disease. Segmental wall motion was scored with a five-point system (3 = normal; -1 = dyskinesis); a decrease of one score defined the onset of wall motion abnormality. The onset of wall motion abnormality at less than or equal to 70% of maximal predicted heart rate had 100% predictive accuracy for coronary artery disease and higher sensitivity than the onset of ischemic ST segment depression at similar heart rate during exercise: 36% (25 of 69 patients with coronary disease) vs 19% (13 of 69 patients), p = 0.01. Wall motion abnormality occurring at less than or equal to 70% of maximal predicted heart rate was present in 49% of patients (23 of 47) with critical stenosis (greater than or equal to 90% luminal diameter narrowing), and in only 5% of patients (2 of 42) without such severe stenosis, p less than 0.001. The sensitivity of exercise-induced wall motion abnormality occurring at a low heart rate for the presence of severe coronary artery disease was similar to that of a deterioration in wall motion by more than two scores during exercise (49% vs 53%) or an absolute decrease of greater than or equal to 5% in exercise left ventricular ejection fraction (49% vs 45%)

Fractional Brownian motion with a reflecting wall

Science.gov (United States)

Wada, Alexander H. O.; Vojta, Thomas

2018-02-01

Fractional Brownian motion, a stochastic process with long-time correlations between its increments, is a prototypical model for anomalous diffusion. We analyze fractional Brownian motion in the presence of a reflecting wall by means of Monte Carlo simulations. Whereas the mean-square displacement of the particle shows the expected anomalous diffusion behavior ˜tα , the interplay between the geometric confinement and the long-time memory leads to a highly non-Gaussian probability density function with a power-law singularity at the barrier. In the superdiffusive case α >1 , the particles accumulate at the barrier leading to a divergence of the probability density. For subdiffusion α implications of these findings, in particular, for applications that are dominated by rare events.

Echocardiographic Wall Motion Abnormality in Posterior Myocardial Infarction: The Diagnostic Value of Posterior Leads

Directory of Open Access Journals (Sweden)

A Darehzereshki

2008-06-01

Full Text Available Background: For the purpose of ascertaining myocardial infarction (MI and ischemia, the sensitivity of the initial 12-lead ECG is inadequate. It is risky to diagnose posterior MI using only precordial reciprocal changes, since the other leads may be more optimally positioned for the identification of electrocardiographic changes. In this study, we evaluated the relationship between electrocardiography changes and wall motion abnormalities in patients with posterior MI for earlier and better diagnosis of posterior MI.Methods: In this prospective cross-sectional study, we enrolled patients with posterior MI who had come to the Emergency Department of Shariati Hospital with their first episode of chest pain. A 12-lead surface electrocardiogram using posterior leads (V7-V9 was performed for all participants. Patients with ST elevation >0.05 mV or pathologic Q wave in the posterior leads, as well as those with specific changes indicating posterior MI in V1-V2, were evaluated by echocardiography in terms of wall motion abnormalities. All data were analyzed using SPSS and p<0.05 were considered statistically significant.Results: Of a total 79 patients enrolled, 48 (60.8% were men, and the mean age was 57.35±8.22 years. Smoking (54.4% and diabetes (48% were the most prevalent risk factors. In the echocardiographic evaluation, all patients had wall motion abnormalities in the left ventricle and 19 patients (24.1% had wall motion abnormalities in the right ventricle. The most frequent segment with motion abnormality among the all patients was the mid-posterior. The posterior leads showed better positive predictive value than the anterior leads for posterior wall motion abnormality.Conclusion: Electrocardiography of the posterior leads in patients with acute chest pain can help in earlier diagnosis and in time treatment of posterior MI.

Domain wall motions in perpendicularly magnetized CoFe/Pd multilayer nanowire

DEFF Research Database (Denmark)

Meng, Zhaoliang; Kumar, Manoj; Qiu, Jinjun

2014-01-01

Current-induced domain wall (DW) motion is investigated in a 600nm wide nanowire using multilayer film with a structure of Ta(5nm)/Pd(5nm)/[CoFe(0.4nm)/Pd(1.2nm)]15/Ta(5nm) in terms of anomalous Hall effect measurements. It is found that motion of DWs can be driven by a current density as low as 1...

Minimization of Ohmic losses for domain wall motion in ferromagnetic nanowires

Science.gov (United States)

Abanov, Artem; Tretiakov, Oleg; Liu, Yang

2011-03-01

We study current-induced domain-wall motion in a narrow ferromagnetic wire. We propose a way to move domain walls with a resonant time-dependent current which dramatically decreases the Ohmic losses in the wire and allows driving of the domain wall with higher speed without burning the wire. For any domain wall velocity we find the time-dependence of the current needed to minimize the Ohmic losses. Below a critical domain-wall velocity specified by the parameters of the wire the minimal Ohmic losses are achieved by dc current. Furthermore, we identify the wire parameters for which the losses reduction from its dc value is the most dramatic. This work was supported by the NSF Grant No. 0757992 and Welch Foundation (A-1678).

Patient motion effects on the quantification of regional myocardial blood flow with dynamic PET imaging

Energy Technology Data Exchange (ETDEWEB)

Hunter, Chad R. R. N.; Kemp, Robert A. de, E-mail: RAdeKemp@ottawaheart.ca [Physics Department, Room 3302 Herzberg Laboratories, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada and Cardiac Imaging, University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, Ontario K1Y 4W7 (Canada); Klein, Ran [Department of Nuclear Medicine, Ottawa Hospital, Civic Campus, 1053 Carling Avenue, Ottawa, Ontario K1Y 4E9 (Canada); Beanlands, Rob S. [Cardiac Imaging, University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, Ontario K1Y 4W7 (Canada)

2016-04-15

Purpose: Patient motion is a common problem during dynamic positron emission tomography (PET) scans for quantification of myocardial blood flow (MBF). The purpose of this study was to quantify the prevalence of body motion in a clinical setting and evaluate with realistic phantoms the effects of motion on blood flow quantification, including CT attenuation correction (CTAC) artifacts that result from PET–CT misalignment. Methods: A cohort of 236 sequential patients was analyzed for patient motion under resting and peak stress conditions by two independent observers. The presence of motion, affected time-frames, and direction of motion was recorded; discrepancy between observers was resolved by consensus review. Based on these results, patient body motion effects on MBF quantification were characterized using the digital NURBS-based cardiac-torso phantom, with characteristic time activity curves (TACs) assigned to the heart wall (myocardium) and blood regions. Simulated projection data were corrected for attenuation and reconstructed using filtered back-projection. All simulations were performed without noise added, and a single CT image was used for attenuation correction and aligned to the early- or late-frame PET images. Results: In the patient cohort, mild motion of 0.5 ± 0.1 cm occurred in 24% and moderate motion of 1.0 ± 0.3 cm occurred in 38% of patients. Motion in the superior/inferior direction accounted for 45% of all detected motion, with 30% in the superior direction. Anterior/posterior motion was predominant (29%) in the posterior direction. Left/right motion occurred in 24% of cases, with similar proportions in the left and right directions. Computer simulation studies indicated that errors in MBF can approach 500% for scans with severe patient motion (up to 2 cm). The largest errors occurred when the heart wall was shifted left toward the adjacent lung region, resulting in a severe undercorrection for attenuation of the heart wall. Simulations

Patient motion effects on the quantification of regional myocardial blood flow with dynamic PET imaging

International Nuclear Information System (INIS)

Hunter, Chad R. R. N.; Kemp, Robert A. de; Klein, Ran; Beanlands, Rob S.

2016-01-01

Purpose: Patient motion is a common problem during dynamic positron emission tomography (PET) scans for quantification of myocardial blood flow (MBF). The purpose of this study was to quantify the prevalence of body motion in a clinical setting and evaluate with realistic phantoms the effects of motion on blood flow quantification, including CT attenuation correction (CTAC) artifacts that result from PET–CT misalignment. Methods: A cohort of 236 sequential patients was analyzed for patient motion under resting and peak stress conditions by two independent observers. The presence of motion, affected time-frames, and direction of motion was recorded; discrepancy between observers was resolved by consensus review. Based on these results, patient body motion effects on MBF quantification were characterized using the digital NURBS-based cardiac-torso phantom, with characteristic time activity curves (TACs) assigned to the heart wall (myocardium) and blood regions. Simulated projection data were corrected for attenuation and reconstructed using filtered back-projection. All simulations were performed without noise added, and a single CT image was used for attenuation correction and aligned to the early- or late-frame PET images. Results: In the patient cohort, mild motion of 0.5 ± 0.1 cm occurred in 24% and moderate motion of 1.0 ± 0.3 cm occurred in 38% of patients. Motion in the superior/inferior direction accounted for 45% of all detected motion, with 30% in the superior direction. Anterior/posterior motion was predominant (29%) in the posterior direction. Left/right motion occurred in 24% of cases, with similar proportions in the left and right directions. Computer simulation studies indicated that errors in MBF can approach 500% for scans with severe patient motion (up to 2 cm). The largest errors occurred when the heart wall was shifted left toward the adjacent lung region, resulting in a severe undercorrection for attenuation of the heart wall. Simulations

Patient motion effects on the quantification of regional myocardial blood flow with dynamic PET imaging.

Science.gov (United States)

Hunter, Chad R R N; Klein, Ran; Beanlands, Rob S; deKemp, Robert A

2016-04-01

Patient motion is a common problem during dynamic positron emission tomography (PET) scans for quantification of myocardial blood flow (MBF). The purpose of this study was to quantify the prevalence of body motion in a clinical setting and evaluate with realistic phantoms the effects of motion on blood flow quantification, including CT attenuation correction (CTAC) artifacts that result from PET-CT misalignment. A cohort of 236 sequential patients was analyzed for patient motion under resting and peak stress conditions by two independent observers. The presence of motion, affected time-frames, and direction of motion was recorded; discrepancy between observers was resolved by consensus review. Based on these results, patient body motion effects on MBF quantification were characterized using the digital NURBS-based cardiac-torso phantom, with characteristic time activity curves (TACs) assigned to the heart wall (myocardium) and blood regions. Simulated projection data were corrected for attenuation and reconstructed using filtered back-projection. All simulations were performed without noise added, and a single CT image was used for attenuation correction and aligned to the early- or late-frame PET images. In the patient cohort, mild motion of 0.5 ± 0.1 cm occurred in 24% and moderate motion of 1.0 ± 0.3 cm occurred in 38% of patients. Motion in the superior/inferior direction accounted for 45% of all detected motion, with 30% in the superior direction. Anterior/posterior motion was predominant (29%) in the posterior direction. Left/right motion occurred in 24% of cases, with similar proportions in the left and right directions. Computer simulation studies indicated that errors in MBF can approach 500% for scans with severe patient motion (up to 2 cm). The largest errors occurred when the heart wall was shifted left toward the adjacent lung region, resulting in a severe undercorrection for attenuation of the heart wall. Simulations also indicated that the

Minimization of Ohmic Losses for Domain Wall Motion in a Ferromagnetic Nanowire

Science.gov (United States)

Tretiakov, O. A.; Liu, Y.; Abanov, Ar.

2010-11-01

We study current-induced domain-wall motion in a narrow ferromagnetic wire. We propose a way to move domain walls with a resonant time-dependent current which dramatically decreases the Ohmic losses in the wire and allows driving of the domain wall with higher speed without burning the wire. For any domain-wall velocity we find the time dependence of the current needed to minimize the Ohmic losses. Below a critical domain-wall velocity specified by the parameters of the wire the minimal Ohmic losses are achieved by dc current. Furthermore, we identify the wire parameters for which the losses reduction from its dc value is the most dramatic.

Clinical impact of ' in-treatment' wall motion abnormalities in hypertensive patients with left ventricular hypertrophy: the LIFE study

DEFF Research Database (Denmark)

Cicala, S.; Simone, G. de; Wachtell, K.

2008-01-01

Objectives Left ventricular systolic wall motion abnormalities have prognostic value. Whether wall motion detected by serial echocardiographic examinations predicts prognosis in hypertensive patients with left ventricular hypertrophy ( LVH) without clinically recognized atherosclerotic disease ha...

Damping of the domain walls motion in Co-based amorphous ribbons with helical magnetic anisotropy: Part III

International Nuclear Information System (INIS)

Zhmetko, D.N.; Zhmetko, S.D.

2009-01-01

The damping of the motion of domain walls of a sandwich domain structure by the eddy currents magnetic fields, the stray fields and the hysteresis friction fields is investigated. The blocking of the motion of domain walls by the eddy currents magnetic fields is discovered.

Motion control in double-walled carbon nanotube systems using a Stone-Thrower-Wales defect cluster

International Nuclear Information System (INIS)

Liu Ping; Zhang Yongwei

2010-01-01

The ability to control the motion of a single molecule will have an important impact in nano-mechanical systems. Multi-walled carbon nanotube systems, which have extremely low intertube friction and strong motion confinement, can form the basis for mechanically based motion control. We devise two molecular motion control units based on double-walled carbon nanotubes embedded with a Stone-Thrower-Wales defect cluster, and perform molecular dynamics simulations to determine the characteristics of these two control units. We show that one of the molecular control units is able to perform a logic operation on one logic input and produce three logic outputs, while the other is able to produce two logic outputs. Potential applications of the motion control units include molecular switches, shuttles and mechanically based logic devices.

Left ventricular wall motion abnormalities evaluated by factor analysis as compared with Fourier analysis

International Nuclear Information System (INIS)

Hirota, Kazuyoshi; Ikuno, Yoshiyasu; Nishikimi, Toshio

1986-01-01

Factor analysis was applied to multigated cardiac pool scintigraphy to evaluate its ability to detect left ventricular wall motion abnormalities in 35 patients with old myocardial infarction (MI), and in 12 control cases with normal left ventriculography. All cases were also evaluated by conventional Fourier analysis. In most cases with normal left ventriculography, the ventricular and atrial factors were extracted by factor analysis. In cases with MI, the third factor was obtained in the left ventricle corresponding to wall motion abnormality. Each case was scored according to the coincidence of findings of ventriculography and those of factor analysis or Fourier analysis. Scores were recorded for three items; the existence, location, and degree of asynergy. In cases of MI, the detection rate of asynergy was 94 % by factor analysis, 83 % by Fourier analysis, and the agreement in respect to location was 71 % and 66 %, respectively. Factor analysis had higher scores than Fourier analysis, but this was not significant. The interobserver error of factor analysis was less than that of Fourier analysis. Factor analysis can display locations and dynamic motion curves of asynergy, and it is regarded as a useful method for detecting and evaluating left ventricular wall motion abnormalities. (author)

ECG-gated blood pool tomography in the determination of left ventricular volume, ejection fraction, and wall motion

International Nuclear Information System (INIS)

Underwood, S.R.; Ell, P.J.; Jarritt, P.H.; Emanuel, R.W.; Swanton, R.H.

1984-01-01

ECG-gated blood pool tomography promises to provide a ''gold standard'' for noninvasive measurement of left ventricular volume, ejection fraction, and wall motion. This study compares these measurements with those from planar radionuclide imaging and contrast ventriculography. End diastolic and end systolic blood pool images were acquired tomographically using an IGE400A rotating gamma camera and Star computer, and slices were reconstructed orthogonal to the long axis of the heart. Left ventricular volume was determined by summing the areas of the slices, and wall motion was determined by comparison of end diastolic and end systolic contours. In phantom experiments this provided an accurate measurement of volume (r=0.98). In 32 subjects who were either normal or who had coronary artery disease left ventricular volume (r=0.83) and ejection fraction (r=0.89) correlated well with those using a counts based planar technique. In 16 of 18 subjects who underwent right anterior oblique X-ray contrast ventriculography, tomographic wall motion agreed for anterior, apical, and inferior walls, but abnormal septal motion which was not apparent by contrast ventriculography, was seen in 12 subjects tomographically. All 12 had disease of the left anterior descending coronary artery and might have been expected to have abnormal septal motion. ECG-gated blood pool tomography can thus determine left ventricular volume and ejection fraction accurately, and provides a global description of wall motion in a way that is not possible from any single planar image

Domain Wall Motion in Magnetic Nanostrips under the Influence of Rashba Field

Directory of Open Access Journals (Sweden)

Vito Puliafito

2012-01-01

Full Text Available Spin-orbit Rashba effect applies a torque on the magnetization of a ferromagnetic nanostrip in the case of structural inversion asymmetry, also affecting the steady domain wall motion induced by a spin-polarized current. This influence is here analytically studied in the framework of the extended Landau-Lifshitz-Gilbert equation, including the Rashba effect as an additive term of the effective field. Results of previous micromagnetic simulations and experiments have shown that this field yields an increased value of the Walker breakdown current together with an enlargement of the domain wall width. In order to analytically describe these results, the standard travelling wave ansatz for the steady domain wall motion is here adopted. Results of our investigations reveal the impossibility to reproduce, at the same time, the previous features and suggest the need of a more sophisticated model whose development requires, in turn, additional information to be extracted from ad hoc micromagnetic simulations.

Enhancement of spin Hall effect induced torques for current-driven magnetic domain wall motion: Inner interface effect

KAUST Repository

Bang, Do; Yu, Jiawei; Qiu, Xuepeng; Wang, Yi; Awano, Hiroyuki; Manchon, Aurelien; Yang, Hyunsoo

2016-01-01

We investigate the current-induced domain wall motion in perpendicular magnetized Tb/Co wires with structure inversion asymmetry and different layered structures. We find that the critical current density to drive domain wall motion strongly depends on the layered structure. The lowest critical current density ∼15MA/cm2 and the highest slope of domain wall velocity curve are obtained for the wire having thin Co sublayers and more inner Tb/Co interfaces, while the largest critical current density ∼26MA/cm2 required to drive domain walls is observed in the Tb-Co alloy magnetic wire. It is found that the Co/Tb interface contributes negligibly to Dzyaloshinskii-Moriya interaction, while the effective spin-orbit torque strongly depends on the number of Tb/Co inner interfaces (n). An enhancement of the antidamping torques by extrinsic spin Hall effect due to Tb rare-earth impurity-induced skew scattering is suggested to explain the high efficiency of current-induced domain wall motion.

Enhancement of spin Hall effect induced torques for current-driven magnetic domain wall motion: Inner interface effect

KAUST Repository

Bang, Do

2016-05-23

We investigate the current-induced domain wall motion in perpendicular magnetized Tb/Co wires with structure inversion asymmetry and different layered structures. We find that the critical current density to drive domain wall motion strongly depends on the layered structure. The lowest critical current density ∼15MA/cm2 and the highest slope of domain wall velocity curve are obtained for the wire having thin Co sublayers and more inner Tb/Co interfaces, while the largest critical current density ∼26MA/cm2 required to drive domain walls is observed in the Tb-Co alloy magnetic wire. It is found that the Co/Tb interface contributes negligibly to Dzyaloshinskii-Moriya interaction, while the effective spin-orbit torque strongly depends on the number of Tb/Co inner interfaces (n). An enhancement of the antidamping torques by extrinsic spin Hall effect due to Tb rare-earth impurity-induced skew scattering is suggested to explain the high efficiency of current-induced domain wall motion.

Quantitative assessment of regional left ventricular motion using endocardial landmarks

NARCIS (Netherlands)

C.J. Slager (Cornelis); T.E.H. Hooghoudt (Ton); P.W.J.C. Serruys (Patrick); J.C.H. Schuurbiers (Johan); J.H.C. Reiber (Johan); G.T. Meester (Geert); P.D. Verdouw (Pieter); P.G. Hugenholtz (Paul)

1986-01-01

textabstractIn this study the hypothesis is tested that the motion pattern of small anatomic landmarks, recognizable at the left ventricular endocardial border in the contrast angiocardiogram, reflects the motion of the endocardial wall. To verify this, minute metal markers were inserted in the

Limited diagnostic accuracy of gated myocardial perfusion SPECT for wall motion analysis in patients with asymmetric septal hypertrophy

International Nuclear Information System (INIS)

Seo, J.H.; Ahn, B.C.; Bae, J.H.; Jeong, S.Y.; Lee, J.; Lee, K.B.

2004-01-01

Objective: Although gated SPECT(G-SPECT) using Tc-99m MIBI is well-known diagnostic modality in the evaluation of myocardial perfusion and wall motion analysis, there were limited reports for subjects with asymmetric septal hypertrophy (ASH). This study was performed to evaluate the clinical usefulness of G-SPECT for assessments of myocardial perfusion and wall motion analysis in patients with ASH on 2D-echocardiography(Echo). Methods: Thirty patients (male 18, 59 12 years) with ASH on Echo (septal wall thickness 13 mm and 1.3 times as thick as that of posterior wall) underwent Tc-99m MIBI G-SPECT. Two studies were performed within one month. No patient had experienced any significant cardiac event, nor had changed medical and surgical therapy during the studies. Functional parameters of the left ventricle were acquired with QGS software(AutoQUANTTM). Three experts performed visual interpretation for the presence of septal thickening and perfusion abnormalities on G-SPECT and two experienced cardiologists measured dimension, thickness and wall motion of the left ventricle on Echo. Results: Mean septum thickness measured by Echo was 1.90 0.50 cm, and the septum/posterior wall thickness ratio was 1.85 0.51. On visual SPECT analysis, 14 patients (46.7%) were interpreted as with thickened septum and 17 patients (57%) as with abnormal perfusion. All 3 patients who underwent coronary angiography showed significant luminal stenosis and also had perfusion abnormalities on SPECT. On Echo, only one patient showed septal hypokinesia, who showed anteroseptal infarction on SPECT, and the others showed normal septal wall motion. But 13 patients (54%) among 24 patients showed septal hypokinesia on G-SPECT. Patients with thickened septum on SPECT had thicker septum (2.3 vs 1.6 cm) and higher septum/posterior wall thickness ratio (2.2 vs 1.6) on Echo, compared with patients without septal thickening on SPECT. Conclusions: Although G-SPECT could proffer diagnostic accuracy for

Interventional heart wall motion analysis with cardiac C-arm CT systems

International Nuclear Information System (INIS)

Müller, Kerstin; Maier, Andreas K; Schwemmer, Chris; Hornegger, Joachim; Zheng, Yefeng; Wang, Yang; Lauritsch, Günter; Rohkohl, Christopher; Fahrig, Rebecca

2014-01-01

Today, quantitative analysis of three-dimensional (3D) dynamics of the left ventricle (LV) cannot be performed directly in the catheter lab using a current angiographic C-arm system, which is the workhorse imaging modality for cardiac interventions. Therefore, myocardial wall analysis is completely based on the 2D angiographic images or pre-interventional 3D/4D imaging. In this paper, we present a complete framework to study the ventricular wall motion in 4D (3D+t) directly in the catheter lab. From the acquired 2D projection images, a dynamic 3D surface model of the LV is generated, which is then used to detect ventricular dyssynchrony. Different quantitative features to evaluate LV dynamics known from other modalities (ultrasound, magnetic resonance imaging) are transferred to the C-arm CT data. We use the ejection fraction, the systolic dyssynchrony index a 3D fractional shortening and the phase to maximal contraction (ϕ i, max ) to determine an indicator of LV dyssynchrony and to discriminate regionally pathological from normal myocardium. The proposed analysis tool was evaluated on simulated phantom LV data with and without pathological wall dysfunctions. The LV data used is publicly available online at https://conrad.stanford.edu/data/heart. In addition, the presented framework was tested on eight clinical patient data sets. The first clinical results demonstrate promising performance of the proposed analysis tool and encourage the application of the presented framework to a larger study in clinical practice. (paper)

Serial thallium-201 myocardial imaging after dipyridamole infusion: diagnostic utility in detecting coronary stenoses and relationship to regional wall motion

International Nuclear Information System (INIS)

Leppo, J.; Boucher, C.A.; Okada, R.D.; Newell, J.B.; Strauss, H.W.; Pohost, G.M.

1982-01-01

After a 4-minute i.v. dipyridamole infusion, 0.14 mg/kg/min, serial thallium-201 scans were obtained in 60 patients undergoing cardia catheterization. Forty patients had significant (greater than or equal to50% stenosis) coronary artery disease (CAD), and 20 patients had normal coronary arteries or trivial lesions. The images were graded qualitatively for thallium activity by three observers. Sensitivity was 93% (37 of 40) and specificity was 80% (16 of 20). The sensitivity and specificity of the thallium-201 study were not affected by the extent of CAD, the presence of Q waves, or propranolol therapy. Twenty-seven of 37 patients who had initial defects (73%) had complete thallium redistribution of one or more defects. Patient-by-patient anlaysis using a regression model of all patients showed that the fate of a segmental thallium defect predicted abnormal wall motion by angiography better than ECG Q waves. The presence of propranolol therapy or collaterals did not significantly affect the thallium redistribution results. It is concluded that qualitative interpretation by multiple observers of thallium images after dipyridamole infusion is a highly sensitive and specific test for CAD. After dipyridamole, as with exercise stress, the extent of thallium redistribution is related to the degree of myocardial wall motion abnormality

Current-driven vortex domain wall motion in wire-tube nanostructures

Energy Technology Data Exchange (ETDEWEB)

Espejo, A. P. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); Institute of Nanostructure and Solid State Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg (Germany); Vidal-Silva, N. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); López-López, J. A. [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso (Chile); Goerlitz, D.; Nielsch, K. [Institute of Nanostructure and Solid State Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg (Germany); Escrig, J. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Av. Ecuador 3493, 9170124 Santiago (Chile)

2015-03-30

We have investigated the current-driven domain wall motion in nanostructures comprised of a pair of nanotube and nanowire segments. Under certain values of external magnetic fields, it is possible to pin a vortex domain wall in the transition zone between the wire and tube segments. We explored the behavior of this domain wall under the action of an electron flow applied in the opposite direction to the magnetic field. Thus, for a fixed magnetic field, it is possible to release a domain wall pinned simply by increasing the intensity of the current density, or conversely, for a fixed current density, it is possible to release the domain wall simply decreasing the magnetic external field. When the domain wall remains pinned due to the competition between the current density and the magnetic external field, it exhibits a oscillation frequency close to 8 GHz. The amplitude of the oscillations increases with the current density and decreases over time. On the other hand, when the domain wall is released and propagated through the tube segment, this shows the standard separation between a steady and a precessional regime. The ability to pin and release a domain wall by varying the geometric parameters, the current density, or the magnetic field transforms these wire-tube nanostructures in an interesting alternative as an on/off switch nano-transistor.

Analysis of Human's Motions Based on Local Mean Decomposition in Through-wall Radar Detection

Science.gov (United States)

Lu, Qi; Liu, Cai; Zeng, Zhaofa; Li, Jing; Zhang, Xuebing

2016-04-01

Observation of human motions through a wall is an important issue in security applications and search-and rescue. Radar has advantages in looking through walls where other sensors give low performance or cannot be used at all. Ultrawideband (UWB) radar has high spatial resolution as a result of employment of ultranarrow pulses. It has abilities to distinguish the closely positioned targets and provide time-lapse information of targets. Moreover, the UWB radar shows good performance in wall penetration when the inherently short pulses spread their energy over a broad frequency range. Human's motions show periodic features including respiration, swing arms and legs, fluctuations of the torso. Detection of human targets is based on the fact that there is always periodic motion due to breathing or other body movements like walking. The radar can gain the reflections from each human body parts and add the reflections at each time sample. The periodic movements will cause micro-Doppler modulation in the reflected radar signals. Time-frequency analysis methods are consider as the effective tools to analysis and extract micro-Doppler effects caused by the periodic movements in the reflected radar signal, such as short-time Fourier transform (STFT), wavelet transform (WT), and Hilbert-Huang transform (HHT).The local mean decomposition (LMD), initially developed by Smith (2005), is to decomposed amplitude and frequency modulated signals into a small set of product functions (PFs), each of which is the product of an envelope signal and a frequency modulated signal from which a time-vary instantaneous phase and instantaneous frequency can be derived. As bypassing the Hilbert transform, the LMD has no demodulation error coming from window effect and involves no negative frequency without physical sense. Also, the instantaneous attributes obtained by LMD are more stable and precise than those obtained by the empirical mode decomposition (EMD) because LMD uses smoothed local

Identification and Assessment of Paradoxical Ventricular Wall Motion Using ECG Gated Blood Pool Scan - Comparison of cine Loop , Phase Analysis and Paradox Image -

International Nuclear Information System (INIS)

Lee, Jae Tae; Kim, Gwang Weon; Lee, Kyu Bo; Chung, Byung Chun; Whang, Kee Suk; Chae, Sung Chul; Paek, Wee Hyun; Cheon, Jae Eun; Lee, Hyong Woo; Chung, Jin Hong

1990-01-01

Sixty-four patients with paradoxical ventricular wall motion noticed both in angiocardiography or 2-dimensional echocardiography were assessed by ECG gated blood pool scan (GBPS). Endless cine loop image, phase and amplitude images and paradox image obtained by visual inspection of each cardiac beat or Fourier transformation of acquired raw data were investigated to determine the incremental value of GBPS with these processing methods for identification of paradoxical ventricular wall motion. The results were as follows:1) Paradoxical wall motions were observed on interventricular septum in 34 cases, left ventricular free wall in 26 and right ventricular wall in 24. Underlying heart diseases were is chemic (23 cases) valvular(9), congenital heart disease (12), cardiomyopathy (5), pericardial effusion(5), post cardiac surgery(3), corpulmonale (2), endocarditis (l) and right ventricular tumor(l). 2) Left ventricular ejection fractions of patients with paradoxical left ventricular wall motion were significantly lower than those with paradoxical septal motion (p <0.005). 3) The sensitivity of each processing methods for detecting paradoxical wall motion was 76.9% by phase analysis, 74.6% by endless cine loop mapping and 68.4% by paradox image manipulation respectively. Paradoxial motions visualized only in phase, paradox or both images were appeared as hypokinesia or akinesia in cine loop image. 4) All events could be identified by at least one of above three processing methods, however only 34 cases (48.4%) showed the paradoxical motions in all of the three images. By these findings, we concluded that simultaneous inspection of all above three processing methods-endless cine loop, phase analysis and paradox image is necessary for accurate identification and assessment of paradoxical ventricular wall motion when performing GBPS.

Identification and Assessment of Paradoxical Ventricular Wall Motion Using ECG Gated Blood Pool Scan - Comparison of cine Loop , Phase Analysis and Paradox Image -

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Lee, Jae Tae; Kim, Gwang Weon; Lee, Kyu Bo; Chung, Byung Chun; Whang, Kee Suk; Chae, Sung Chul; Paek, Wee Hyun; Cheon, Jae Eun [Kyungpook National University School of Medicine, Daegu (Korea, Republic of); Lee, Hyong Woo; Chung, Jin Hong [Yeongnam National University College of Medicine, Daegu (Korea, Republic of)

1990-07-15

Sixty-four patients with paradoxical ventricular wall motion noticed both in angiocardiography or 2-dimensional echocardiography were assessed by ECG gated blood pool scan (GBPS). Endless cine loop image, phase and amplitude images and paradox image obtained by visual inspection of each cardiac beat or Fourier transformation of acquired raw data were investigated to determine the incremental value of GBPS with these processing methods for identification of paradoxical ventricular wall motion. The results were as follows:1) Paradoxical wall motions were observed on interventricular septum in 34 cases, left ventricular free wall in 26 and right ventricular wall in 24. Underlying heart diseases were is chemic (23 cases) valvular(9), congenital heart disease (12), cardiomyopathy (5), pericardial effusion(5), post cardiac surgery(3), corpulmonale (2), endocarditis (l) and right ventricular tumor(l). 2) Left ventricular ejection fractions of patients with paradoxical left ventricular wall motion were significantly lower than those with paradoxical septal motion (p <0.005). 3) The sensitivity of each processing methods for detecting paradoxical wall motion was 76.9% by phase analysis, 74.6% by endless cine loop mapping and 68.4% by paradox image manipulation respectively. Paradoxial motions visualized only in phase, paradox or both images were appeared as hypokinesia or akinesia in cine loop image. 4) All events could be identified by at least one of above three processing methods, however only 34 cases (48.4%) showed the paradoxical motions in all of the three images. By these findings, we concluded that simultaneous inspection of all above three processing methods-endless cine loop, phase analysis and paradox image is necessary for accurate identification and assessment of paradoxical ventricular wall motion when performing GBPS.

Prediction of wall motion improvement after coronary revascularization in patients with postmyocardial infarction. Diagnostic value of dobutamine stress echocardiography and myocardial contrast echocardiography

International Nuclear Information System (INIS)

Waku, Sachiko; Ohkubo, Tomoyuki; Takada, Kiyoshi; Ishihara, Tadashi; Ohsawa, Nakaaki; Adachi, Itaru; Narabayashi, Isamu

1997-01-01

The diagnostic value of dobutamine stress echocardiography, myocardial contrast echocardiography and dipyridamole stress thallium-201 single photon emission computed tomography (SPECT) for predicting recovery of wall motion abnormality after revascularization was evaluated in 13 patients with postmyocardial infarction. Seventeen segments showed severe wall motion abnormalities before revascularization. Nine segments which had relatively good Tl uptake on delayed SPECT images despite severely abnormal wall motion were opacified during myocardial contrast echocardiography, and showed improved wall motion after revascularization. In contrast, three segments which had poor Tl uptake and severely abnormal wall motion were not opacified during myocardial contrast echocardiography, and showed no improvement in wall motion during dobutamine stress echocardiography and after revascularization. The following three findings were assumed to be signs of myocardial viability: good Tl uptake on delayed SPECT images, improved wall motion by dobutamine stress echocardiography, and positive opacification of the myocardium by myocardiai contrast echocardiography. Myocardial contrast echocardiography had the highest sensitivity (100%) and negative predictive value (100%). Delayed SPECT images had the highest specificity (100%) and positive predictive value (100%). Dobutamine stress echocardiography had a sensitivity of 83.0%, specificity of 80.0%, positive predictive value of 90.9%, and negative predictive value of 66.7%, respectively. Myocardial contrast echocardiography showed the lowest specificity (60.0%). The techniques of dobutamine stress echocardiography and SPECT, though noninvasive, may underestimate wall motion improvement after revascularization. Further examination by myocardial contrast echocardiography is recommended to assess myocardial viability for determining the indications for coronary revascularization in spite of its invasiveness. (author)

Large-scale influences in near-wall turbulence.

Science.gov (United States)

Hutchins, Nicholas; Marusic, Ivan

2007-03-15

Hot-wire data acquired in a high Reynolds number facility are used to illustrate the need for adequate scale separation when considering the coherent structure in wall-bounded turbulence. It is found that a large-scale motion in the log region becomes increasingly comparable in energy to the near-wall cycle as the Reynolds number increases. Through decomposition of fluctuating velocity signals, it is shown that this large-scale motion has a distinct modulating influence on the small-scale energy (akin to amplitude modulation). Reassessment of DNS data, in light of these results, shows similar trends, with the rate and intensity of production due to the near-wall cycle subject to a modulating influence from the largest-scale motions.

Influence of temperature on current-induced domain wall motion and its Walker breakdown

International Nuclear Information System (INIS)

Fan, Lvchao; Hu, Jingguo; Su, Yuanchang; Zhu, Jinrong

2016-01-01

The current-driven domain wall propagation along a thin ferromagnetic strip with thermal field is studied by means of micromagnetic simulations. The results show that the velocity of domain wall is almost independent of temperature until Walker breakdown happened. However the thermal field can suppress Walker breakdown and makes domain wall move faster. Further analysis indicates that the thermal field tends to keep the out-of-plane magnetic moment of the domain wall stay in high value, which can promote domain wall motion and suppress the Walker breakdown by breaking the period of domain wall transformation. - Highlights: • Influences of temperature on the displacement and the velocity of DW are shown. • The suppression of Walker breakdown by temperature is given. • The reason for suppressing Walker breakdown is analyzed. • The breaking transformation period of Walker breakdown by temperature is given.

Incremental value of regional wall motion analysis immediately after exercise for the detection of single-vessel coronary artery disease. Study by separate acquisition, dual-isotope ECG-gated single-photon emission computed tomography

International Nuclear Information System (INIS)

Yoda, Shunichi; Sato, Yuichi; Matsumoto, Naoya; Tani, Shigemasa; Takayama, Tadateru; Uchiyama, Takahisa; Saito, Satoshi

2005-01-01

Although the detection of wall motion abnormalities gives incremental value to myocardial perfusion single-photon emission computed tomography (SPECT) in the diagnosis of extensive coronary artery disease (CAD) and high-grade single-vessel CAD, whether or not it is useful in the diagnosis of mild, single-vessel CAD has not been studied previously. Separate acquisition, dual isotope electrocardiogram (ECG)-gated SPECT was performed in 97 patients with a low likelihood of CAD (Group 1) and 46 patients with single-vessel CAD (Group 2). Mild CAD was defined by stenosis of 50-75% (Group 2a, n=22) and moderate to severe CAD was defined by stenosis ≥76% (Group 2b, n=24). Myocardial perfusion and wall motion were graded by a 5 point-scale, 20-segment model. The sensitivity of myocardial perfusion alone was 50% for Group 2a, 83% for Group 2b and 67% for Group 2 as a whole. The overall specificity was 90%. When the wall motion analysis was combined, the sensitivity was increased to 82% in Group 2a and 92% in Group 2b. The ability to detect a wall motion abnormality immediately after exercise gives incremental diagnostic value to myocardial perfusion SPECT in the identification of mild, single-vessel CAD. (author)

Current-induced domain wall motion in nanoscale ferromagnetic elements

Energy Technology Data Exchange (ETDEWEB)

Malinowski, G [Laboratoire de Physique des Solides, CNRS, Universite Paris-sud 11, 91405 Orsay Cedex (France); Boulle, O [SPINTEC, CEA/CNRS/UJF/GINP, INAC, 38054 Grenoble Cedex 9 (France); Klaeui, M, E-mail: Klaeui@uni-mainz.de [SwissFEL, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Laboratory of Nanomagnetism and Spin Dynamics, Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne (Switzerland)

2011-09-28

We review the details of domain wall (DW) propagation due to spin-polarized currents that could potentially be used in magnetic data storage devices based on domains and DWs. We discuss briefly the basics of the underlying spin torque effect and show how the two torques arising from the interaction between the spin-polarized charge carriers and the magnetization lead to complex dynamics of a spin texture such as a DW. By direct imaging we show how confined DWs in nanowires can be displaced using currents in in-plane soft-magnetic materials, and that when using short pulses, fast velocities can be attained. For high-anisotropy out-of-plane magnetized wires with narrow DWs we present approaches to deducing the torque terms and show that in these materials potentially more efficient domain wall motion could be achieved.

In-vivo quantification of wall motion in cerebral aneurysms from 2D cine phase contrast magnetic resonance images

Energy Technology Data Exchange (ETDEWEB)

Karmonik, C. [The Methodist Hospital Research Inst., Houston (United States); Diaz, O.; Klucznik, R. [The Methodist Hospital, Houston (United States); Grossman, R. [The Methodist Hospital, Houston (United States). Neurosurgery

2010-02-15

Purpose: The quantification of wall motion in cerebral aneurysms is of interest for the assessment of aneurysmal rupture risk, for providing boundary conditions for computational simulations and as a validation tool for theoretical models. Materials and Methods: 2D cine phase contrast magnetic resonance imaging (2D pcMRI) in combination with quantitative magnetic resonance angiography (QMRA) was evaluated for measuring wall motion in 7 intracranial aneurysms. In each aneurysm, 2 (in one case 3) cross sections, oriented approximately perpendicular to each other, were measured. Results: The maximum aneurysmal wall distention ranged from 0.16 mm to 1.6 mm (mean 0.67 mm), the maximum aneurysmal wall contraction was -1.91 mm to -0.34 mm (mean 0.94 mm), and the average wall displacement ranged from 0.04 mm to 0.31 mm (mean 0.15 mm). Statistically significant correlations between average wall displacement and the shape of inflow curves (p-value < 0.05) were found in 7 of 15 cross sections; statistically significant correlations between the displacement of the luminal boundary center point and the shape of inflow curves (p-value < 0.05) were found in 6 of 15 cross sections. Conclusion: 2D pcMRI in combination with QMRA is capable of visualizing and quantifying wall motion in cerebral aneurysms. However, application of this technique is currently restricted by its limited spatial resolution. (orig.)

Relation of external surface to internal tumor motion studied with cine CT

International Nuclear Information System (INIS)

Chi, P.-C.M.; Balter, Peter; Luo Dershan; Mohan, Radhe; Pan Tinsu

2006-01-01

The accuracy of delivering gated-radiation therapy to lung tumors using an external respiratory surrogate relies on not only interfractional and intrafractional reproducibility, but also a strong correlation between external motion and internal tumor motion. The purpose of this work was to use the cine images acquired by four-dimensional computed tomography acquisition protocol to study the relation between external surface motion and internal tumor motion. The respiratory phase information of tumor motion and chest wall motion was measured on the cine images using a proposed region-of-interest (ROI) method and compared to measurement of an external respiratory monitoring device. On eight lung patient data sets, the phase shifts were measured between (1) the signal of a real-time positioning-management (RPM) respiratory monitoring device placed in the abdominal region and four surface locations on the chest wall (2) the RPM signal in the abdominal region and tumor motions, and (3) chest wall surface motions and tumor motions. Respiratory waveforms measured at different surface locations during the same respiratory cycle often varied and had significant phase shifts. Seven of the 8 patients showed the abdominal motion leading chest wall motion. The best correlation (smallest phase shift) was found between the abdominal motion and the superior-inferior (S-I) tumor motion. A wide range of phase shifts was observed between external surface motion and tumor anterior-posterior (A-P)/lateral motion. The result supported the placement of the RPM block in the abdominal region and suggested that during a gated therapy utilizing the RPM system, it is necessary to place the RPM block at the same location as it is during treatment simulation in order to reduce potential errors introduced by the position of the RPM block. Correlations between external motions and lateral/A-P tumor motions were inconclusive due to a combination of patient selection and the limitation of the ROI

Strain-Encoded Cardiac Magnetic Resonance Imaging as an Adjunct for Dobutamine Stress Testing. Incremental Value to Conventional Wall Motion Analysis

Science.gov (United States)

Korosoglou, Grigorios; Lossnitzer, Dirk; Schellberg, Dieter; Lewien, Antje; Wochele, Angela; Schaeufele, Tim; Neizel, Mirja; Steen, Henning; Giannitsis, Evangelos; Katus, Hugo A.; Osman, Nael F.

2009-01-01

Background High-dose dobutamine stress magnetic resonance imaging (DS-MRI) is safe and feasible for the diagnosis of coronary artery disease (CAD) in humans. However, the assessment of cine scans relies on the visual interpretation of regional wall motion, which is subjective. Recently, Strain-Encoded MRI (SENC) has been proposed for the direct color-coded visualization of myocardial strain. The purpose of our study was to compare the diagnostic value of SENC to that provided by conventional wall motion analysis for the detection of inducible ischemia during DS-MRI. Methods and Results Stress induced ischemia was assessed by wall motion analysis and by SENC in 101 patients with suspected or known CAD and in 17 healthy volunteers who underwent DS-MRI in a clinical 1.5T scanner. Quantitative coronary angiography deemed as the standard reference for the presence or absence of significant CAD (≥50% diameter stenosis). On a coronary vessel level, SENC detected inducible ischemia in 86/101 versus 71/101 diseased coronary vessels (p<0.01 versus cine), and showed normal strain response in 189/202 versus 194/202 vessels with <50% stenosis (p=NS versus cine). On a patient level, SENC detected inducible ischemia in 63/64 versus 55/64 patients with CAD (p<0.05 versus cine), and showed normal strain response in 32/37 versus 34/37 patients without CAD (p=NS versus cine).Quantification analysis demonstrated a significant correlation between strain rate reserve (SRreserve) and coronary artery stenosis severity (r²=0.56, p<0.001), and a cut-off value of SRreserve=1.64 deemed as a highly accurate marker for the detection of stenosis≥50% (AUC=0.96, SE=0.01, 95% CI = 0.94–0.98, p<0.001). Conclusions The direct color-coded visualization of strain on MR-images is a useful adjunct for DS-MRI, which provides incremental value for the detection of CAD compared to conventional wall motion readings on cine images. PMID:19808579

Comparison of the effects of streptokinase and tissue plasminogen activator on regional wall motion after first myocardial infarction: analysis by the centerline method with correction for area at risk.

Science.gov (United States)

Cross, D B; Ashton, N G; Norris, R M; White, H D

1991-04-01

In a trial of streptokinase versus recombinant tissue-type plasminogen activator (rt-PA) for a first myocardial infarction, 270 patients were randomized. Regional left ventricular function was assessed in 214 patients at 3 weeks. The infarct-related artery was the left anterior descending artery in 78 patients, the right coronary artery in 122 and a dominant left circumflex artery in 14. Analysis was by the centerline method with a novel correction for the area of myocardium at risk, whereby the search region was determined by the anatomic distribution of the infarct-related artery. Infarct-artery patency at 3 weeks was 73% in the streptokinase group and 71% in the rt-PA group. Global left ventricular function did not differ between the two groups. Mean chord motion (+/- SD) in the most hypokinetic half of the defined search region was similar in the streptokinase and rt-PA groups (-2.4 +/- 1.5 versus -2.3 +/- 1.3, p = 0.63). There were no differences in hyperkinesia of the noninfarct zone. Compared with conventional centerline analysis, regional wall motion in the defined area at risk was significantly more abnormal. The two methods correlated strongly, however (r = 0.99, p less than 0.0001), and both methods produced similar overall results. Patients with a patent infarct-related artery and those with an occluded artery at the time of catheterization had similar levels of global function (ejection fraction 58 +/- 12% versus 57 +/- 12%, p = 0.58).(ABSTRACT TRUNCATED AT 250 WORDS)

Processive motions of MreB micro-filaments coordinate cell wall growth

Science.gov (United States)

Garner, Ethan

2012-02-01

Rod-shaped bacteria elongate by the action of cell-wall synthesis complexes linked to underlying dynamic MreB filaments, but how these proteins function to allow continued elongation as a rod remains unknown. To understand how the movement of these filaments relates to cell wall synthesis, we characterized the dynamics of MreB and the cell wall elongation machinery using high-resolution particle tracking in Bacillus subtilis. We found that both MreB and the elongation machinery move in linear paths across the cell, moving at similar rates (˜20nm / second) and angles to the cell body, suggesting they function as single complexes. These proteins move circumferentially around the cell, principally perpendicular to its length. We find that the motions of these complexes are independent, as they can pause and reverse,and also as nearby complexes move independently in both directions across one surface of the cell. Inhibition of cell wall synthesis with antibiotics or depletions in the cell wall synthesis machinery blocked MreB movement, suggesting that the cell wall synthetic machinery is the motor in this system. We propose that bacteria elongate by the uncoordinated, circumferential movements of synthetic complexes that span the plasma membrane and insert radial hoops of new peptidoglycan during their transit.

Geometric Control Over the Motion of Magnetic Domain Walls

International Nuclear Information System (INIS)

N.A. Sinitsyn; V.V. Dobrovitski; S. urazhdin; Avadh Saxena

2008-01-01

We propose a method that enables a precise control of magnetic patterns and relies only on the fundamental properties of the wire as well as on the choice of the path in the controlled parameter space but not on the rate of motion along this path. Possible experimental realizations of this mechanism are discussed. In particular, we show that the domain walls in magnetic nanowires can be translated by rotation of the magnetic easy axis or by applying pulses of magnetic field directed transverse to the magnetic easy axis

Spatio-temporal characteristics of large scale motions in a turbulent boundary layer from direct wall shear stress measurement

Science.gov (United States)

Pabon, Rommel; Barnard, Casey; Ukeiley, Lawrence; Sheplak, Mark

2016-11-01

Particle image velocimetry (PIV) and fluctuating wall shear stress experiments were performed on a flat plate turbulent boundary layer (TBL) under zero pressure gradient conditions. The fluctuating wall shear stress was measured using a microelectromechanical 1mm × 1mm floating element capacitive shear stress sensor (CSSS) developed at the University of Florida. The experiments elucidated the imprint of the organized motions in a TBL on the wall shear stress through its direct measurement. Spatial autocorrelation of the streamwise velocity from the PIV snapshots revealed large scale motions that scale on the order of boundary layer thickness. However, the captured inclination angle was lower than that determined using the classic method by means of wall shear stress and hot-wire anemometry (HWA) temporal cross-correlations and a frozen field hypothesis using a convection velocity. The current study suggests the large size of these motions begins to degrade the applicability of the frozen field hypothesis for the time resolved HWA experiments. The simultaneous PIV and CSSS measurements are also used for spatial reconstruction of the velocity field during conditionally sampled intense wall shear stress events. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1315138.

Controlled motion of domain walls in submicron amorphous wires

Energy Technology Data Exchange (ETDEWEB)

Ţibu, Mihai; Lostun, Mihaela; Rotărescu, Cristian; Atiţoaie, Alexandru; Lupu, Nicoleta; Óvári, Tibor-Adrian, E-mail: taovari@phys-iasi.ro; Chiriac, Horia [Department of Magnetic Materials and Devices, National Institute of Research and Development for Technical Physics, Iaşi, 700050 (Romania); Allwood, Dan A. [Department of Materials Science and Engineering, University of Sheffield, Sheffield, S1 3JD (United Kingdom)

2016-05-15

Results on the control of the domain wall displacement in cylindrical Fe{sub 77.5}Si{sub 7.5}B{sub 15} amorphous glass-coated submicron wires prepared by rapid quenching from the melt are reported. The control methods have relied on conical notches with various depths, up to a few tens of nm, made in the glass coating and in the metallic nucleus using a focused ion beam (FIB) system, and on the use of small nucleation coils at one of the sample ends in order to apply magnetic field pulses aimed to enhance the nucleation of reverse domains. The notch-based method is used for the first time in the case of cylindrical ultrathin wires. The results show that the most efficient technique of controlling the domain wall motion in this type of samples is the simultaneous use of notches and nucleation coils. Their effect depends on wire diameter, notch depth, its position on the wire length, and characteristics of the applied pulse.

Radial motion of the carotid artery wall: A block matching algorithm approach

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Effat Soleimani

2012-06-01

Full Text Available Introduction: During recent years, evaluating the relation between mechanical properties of the arterialwall and cardiovascular diseases has been of great importance. On the other hand, motion estimation of thearterial wall using a sequence of noninvasive ultrasonic images and convenient processing methods mightprovide useful information related to biomechanical indexes and elastic properties of the arteries and assistdoctors to discriminate between healthy and diseased arteries. In the present study, a block matching basedalgorithm was introduced to extract radial motion of the carotid artery wall during cardiac cycles.Materials and Methods: The program was implemented to the consecutive ultrasonic images of thecommon carotid artery of 10 healthy men and maximum and mean radial movement of the posterior wall ofthe artery was extracted. Manual measurements were carried out to validate the automatic method andresults of two methods were compared.Results: Paired t-test analysis showed no significant differences between the automatic and manualmethods (P>0.05. There was significant correlation between the changes in the instantaneous radialmovement of the common carotid artery measured with the manual and automatic methods (withcorrelation coefficient 0.935 and P<0.05.Conclusion: Results of the present study showed that by using a semi automated computer analysismethod, with minimizing the user interfere and no attention to the user experience or skill, arterial wallmotion in the radial direction can be extracted from consecutive ultrasonic frames

Modulated Magnetic Nanowires for Controlling Domain Wall Motion: Toward 3D Magnetic Memories

KAUST Repository

Ivanov, Yurii P.; Chuvilin, Andrey; Lopatin, Sergei; Kosel, Jü rgen

2016-01-01

Cylindrical magnetic nanowires are attractive materials for next generation data storage devices owing to the theoretically achievable high domain wall velocity and their efficient fabrication in highly dense arrays. In order to obtain control over domain wall motion, reliable and well-defined pinning sites are required. Here, we show that modulated nanowires consisting of alternating nickel and cobalt sections facilitate efficient domain wall pinning at the interfaces of those sections. By combining electron holography with micromagnetic simulations, the pinning effect can be explained by the interaction of the stray fields generated at the interface and the domain wall. Utilizing a modified differential phase contrast imaging, we visualized the pinned domain wall with a high resolution, revealing its three-dimensional vortex structure with the previously predicted Bloch point at its center. These findings suggest the potential of modulated nanowires for the development of high-density, three-dimensional data storage devices. © 2016 American Chemical Society.

Modulated Magnetic Nanowires for Controlling Domain Wall Motion: Toward 3D Magnetic Memories

KAUST Repository

Ivanov, Yurii P.

2016-05-03

Cylindrical magnetic nanowires are attractive materials for next generation data storage devices owing to the theoretically achievable high domain wall velocity and their efficient fabrication in highly dense arrays. In order to obtain control over domain wall motion, reliable and well-defined pinning sites are required. Here, we show that modulated nanowires consisting of alternating nickel and cobalt sections facilitate efficient domain wall pinning at the interfaces of those sections. By combining electron holography with micromagnetic simulations, the pinning effect can be explained by the interaction of the stray fields generated at the interface and the domain wall. Utilizing a modified differential phase contrast imaging, we visualized the pinned domain wall with a high resolution, revealing its three-dimensional vortex structure with the previously predicted Bloch point at its center. These findings suggest the potential of modulated nanowires for the development of high-density, three-dimensional data storage devices. © 2016 American Chemical Society.

Trajectory of coronary motion and its significance in robotic motion cancellation.

Science.gov (United States)

Cattin, Philippe; Dave, Hitendu; Grünenfelder, Jürg; Szekely, Gabor; Turina, Marko; Zünd, Gregor

2004-05-01

To characterize remaining coronary artery motion of beating pig hearts after stabilization with an 'Octopus' using an optical remote analysis technique. Three pigs (40, 60 and 65 kg) underwent full sternotomy after receiving general anesthesia. An 8-bit high speed black and white video camera (50 frames/s) coupled with a laser sensor (60 microm resolution) were used to capture heart wall motion in all three dimensions. Dopamine infusion was used to deliberately modulate cardiac contractility. Synchronized ECG, blood pressure, airway pressure and video data of the region around the first branching point of the left anterior descending (LAD) coronary artery after Octopus stabilization were captured for stretches of 8 s each. Several sequences of the same region were captured over a period of several minutes. Computerized off-line analysis allowed us to perform minute characterization of the heart wall motion. The movement of the points of interest on the LAD ranged from 0.22 to 0.81 mm in the lateral plane (x/y-axis) and 0.5-2.6 mm out of the plane (z-axis). Fast excursions (>50 microm/s in the lateral plane) occurred corresponding to the QRS complex and the T wave; while slow excursion phases (movement of the coronary artery after stabilization appears to be still significant. Minute characterization of the trajectory of motion could provide the substrate for achieving motion cancellation for existing robotic systems. Velocity plots could also help improve gated cardiac imaging.

Reversible wall motion abnormality on adenosine stress/rest thallium-201 gated myocardial SPECT is an independent predictor of coronary artery disease

International Nuclear Information System (INIS)

Park, Eun Kyung; Lee, Won Woo; So, Young; Eo, Jae Seon; Lee, Dong Soo; Chung, June Key; Lee, Myung Chul; Kim, Sang Eun; Kim, Cheol Ho; Lee, Sang Woo

2004-01-01

As early as 10 minutes after adenosine stress, immediate post-stress wall motion (ipsWM) can be evaluated on adenosine stress/rest TI-201 gated SPECT (gSPECT). To widen application of TI-201 in gated SPECT, we investigated image quality, LV parameters (EF, EDV, and ESV) reproducibility, and diagnostic competency of gSPECT regarding ipsWM evaluation Myocardial perfusion and wall motion were evaluated by 5-point scoring system in 20-segment model. Image quality was assessed using weighted Kappa (Kw) for inter-and intra-observer agreements of wall motion scores (n=49). Reproducibility was examined through repeated acquisition (n=31). Diagnostic competency was evaluated versus coronary angiography (CAG) and multivariate logistic regression analysis was performed to identify significant predictors of coronary artery disease (CAD) among stress abnormal perfusion (SSSp), stress abnormal wall motion (SSSwm), and reversible abnormal wall motion (SDSwm) (n=60). Kw for ipsWM was significantly better than that for rest regarding inter- (0.717 vs 0.489) and intra-observer agreements (0.792 vs 0.688) (p<0.05). 2SD for ipsWM was smaller than that for rest at EF (8.6% vs 10.7%) and ESV (6.0ml vs 8.4ml). Sensitivities of SSSp, SSSwm, and SDSwm were 63.3% (19/30), 63.3% (19/30), and 43.3% (13/30) and specificities 83.3% (25/30), 83.3% (25/30), and 86.7% (26/30), respectively. By multivariate analysis, SSSp (p=0.013) and SDSwm (p=0.039) remained significant predictors. Additionally, SSSwm or SDSwm could find undetected CAD in 54.5% (6/11) of patients with normal perfusion. TI-201 can be successfully applied to gated SPECT for ipsWM evaluation. Moreover, reversible wall motion abnormality on gSPECT is an independent predictor of significant CAD

The value of regional wall motion abnormalities on gated mycardiac perfusion imaging in perfusion imaging in predicting angiographic stenoses of coronary artery

International Nuclear Information System (INIS)

Yao Lixin; Liu Binbin

2007-01-01

Objective: To determine the possible level of angiographic stenoses of coronary artery at which reversible regional wall motion abnormalities (RWMA) are present on 99m Tc-sestamibi ( 99m Tc-MIBI)-gated myocardial perfusion imaging (MPI). Methods: ninty patients undergoing coronary angiography MPI within two weeks were recruited. A five grades and nine segments marking system was introduced to assess the RWMA and thickening of left ventricles. Results: The sensitivity of reversible RWMA for detecting ≥75% angiographic stenoses was 64%,with a specificity of 95% and positive predictive value of 97%. The presence of reversible RWMA was able to stratify patients with severe angiographic stenoses of 75% or more from those less than 75% with high positive predictive value. A good correlation was noted between the presence of reversible RWMA and the coronary artery jeopardy score. Multivariate analysis showed that the post-stress RWMA and reversible RWMA scores and positive dipyridamole-stress exercise electrocardiogram(ECG) were significant predictors of angiographic severity. Conclusions: Reversible RWMA, as shown by dipyridamole stress 99m Tc-MIBI MPI, is a significant predictor of angiographic disease with very high specificity and adds incremental value to MPI for the assessment of angiographic severity. (authors)

Quantification of the relative contribution of the different right ventricular wall motion components to right ventricular ejection fraction: the ReVISION method.

Science.gov (United States)

Lakatos, Bálint; Tősér, Zoltán; Tokodi, Márton; Doronina, Alexandra; Kosztin, Annamária; Muraru, Denisa; Badano, Luigi P; Kovács, Attila; Merkely, Béla

2017-03-27

Three major mechanisms contribute to right ventricular (RV) pump function: (i) shortening of the longitudinal axis with traction of the tricuspid annulus towards the apex; (ii) inward movement of the RV free wall; (iii) bulging of the interventricular septum into the RV and stretching the free wall over the septum. The relative contribution of the aforementioned mechanisms to RV pump function may change in different pathological conditions.Our aim was to develop a custom method to separately assess the extent of longitudinal, radial and anteroposterior displacement of the RV walls and to quantify their relative contribution to global RV ejection fraction using 3D data sets obtained by echocardiography.Accordingly, we decomposed the movement of the exported RV beutel wall in a vertex based manner. The volumes of the beutels accounting for the RV wall motion in only one direction (either longitudinal, radial, or anteroposterior) were calculated at each time frame using the signed tetrahedron method. Then, the relative contribution of the RV wall motion along the three different directions to global RV ejection fraction was calculated either as the ratio of the given direction's ejection fraction to global ejection fraction and as the frame-by-frame RV volume change (∆V/∆t) along the three motion directions.The ReVISION (Right VentrIcular Separate wall motIon quantificatiON) method may contribute to a better understanding of the pathophysiology of RV mechanical adaptations to different loading conditions and diseases.

Influence of exchange coupling on current-driven domain wall motion in a nanowire

International Nuclear Information System (INIS)

Komine, Takashi; Takahashi, Kota; Murakami, Hiroshi; Sugita, Ryuji

2010-01-01

In this study, the effect of exchange stiffness constant on current-driven domain wall motion in nanowires with in-plane magnetic anisotropy (IMA) and perpendicular magnetic anisotropy (PMA) has been investigated using micromagnetic simulation. The critical current density in a nanowire with IMA decreases as the exchange stiffness constant decreases because the domain wall width at the upper edge of the nanowire narrows according to the decrease of the exchange stiffness constant. On the other hand, the critical current density in a nanowire with PMA slightly decreases contrary to that of IMA although the domain wall width reasonably decreases as the exchange stiffness constant decreases. The slight reduction rate of the critical current density is due to the increase of the effective hard-axis anisotropy of PMA nanowire.

Observation of hohlraum-wall motion with spectrally selective x-ray imaging at the National Ignition Facility

Energy Technology Data Exchange (ETDEWEB)

Izumi, N., E-mail: izumi2@llnl.gov; Meezan, N. B.; Divol, L.; Hall, G. N.; Barrios, M. A.; Jones, O.; Landen, O. L.; Kroll, J. J.; Vonhof, S. A.; Nikroo, A.; Bailey, C. G.; Hardy, C. M.; Ehrlich, R. B.; Town, R. P. J.; Bradley, D. K.; Hinkel, D. E.; Moody, J. D. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Jaquez, J. [General Atomics, San Diego, California 9212 (United States)

2016-11-15

The high fuel capsule compression required for indirect drive inertial confinement fusion requires careful control of the X-ray drive symmetry throughout the laser pulse. When the outer cone beams strike the hohlraum wall, the plasma ablated off the hohlraum wall expands into the hohlraum and can alter both the outer and inner cone beam propagations and hence the X-ray drive symmetry especially at the final stage of the drive pulse. To quantitatively understand the wall motion, we developed a new experimental technique which visualizes the expansion and stagnation of the hohlraum wall plasma. Details of the experiment and the technique of spectrally selective x-ray imaging are discussed.

Motion of a Janus particle very near a wall

Science.gov (United States)

Rashidi, Aidin; Wirth, Christopher L.

2017-12-01

This article describes the simulated Brownian motion of a sphere comprising hemispheres of unequal zeta potential (i.e., "Janus" particle) very near a wall. The simulation tool was developed and used to assist in the methodology development for applying Total Internal Reflection Microscopy (TIRM) to anisotropic particles. Simulations of the trajectory of a Janus sphere with cap density matching that of the base particle very near a boundary were used to construct 3D potential energy landscapes that were subsequently used to infer particle and solution properties, as would be done in a TIRM measurement. Results showed that the potential energy landscape of a Janus sphere has a transition region at the location of the boundary between the two Janus halves, which depended on the relative zeta potential magnitude. The potential energy landscape was fit to accurately obtain the zeta potential of each hemisphere, particle size, minimum potential energy position and electrolyte concentration, or Debye length. We also determined the appropriate orientation bin size and regimes over which the potential energy landscape should be fit to obtain system properties. Our simulations showed that an experiment may require more than 106 observations to obtain a suitable potential energy landscape as a consequence of the multivariable nature of observations for an anisotropic particle. These results illustrate important considerations for conducting TIRM for anisotropic particles.

3-D simulation of hanging wall effect at dam site

Science.gov (United States)

Zhang, L.; Xu, Y.

2017-12-01

Hanging wall effect is one of the near fault effects. This paper focuses on the difference of the ground motions on the hanging wall side between the footwall side of the fault at dam site considering the key factors, such as actual topography, the rupture process. For this purpose, 3-D ground motions are numerically simulated by the spectrum element method (SEM), which takes into account the physical mechanism of generation and propagation of seismic waves. With the SEM model of 548 million DOFs, excitation and propagation of seismic waves are simulated to compare the difference between the ground motion on the hanging wall side and that on the footwall side. Take Dagangshan region located in China as an example, several seismogenic finite faults with different dip angle are simulated to investigate the hanging wall effect. Furthermore, by comparing the ground motions of the receiving points, the influence of several factors on hanging wall effect is investigated, such as the dip of the fault and the fault type (strike slip fault or dip-slip fault). The peak acceleration on the hanging wall side is obviously larger than those on the footwall side, which numerically evidences the hanging wall effect. Besides, the simulation shows that only when the dip is less than 70° does the hanging wall effect deserve attention.

Predictive values of early rest/24 hour delay Tl-201 perfusion SPECT for wall motion improvement in patients with acute myocardial infarction after reperfusion

International Nuclear Information System (INIS)

Hyun, In Young; Kwan, June

1998-01-01

We studied early rest/24 hour delay Tl-201 perfusion SPECT for prediction of wall motion improvement after reperfusion in patients with acute myocardial infarction. Among 17 patients (male/female=11/6, age: 59±13) with acute myocardial infarction, 15 patients were treated with percutaneous transcoronary angioplasty (direct:2, delay:11) and intravenous urokinase (2). Spontaneous resolution occurred in infarct related arteries of 2 patients. We confirmed TIMI 3 flow of infarct-related artery after reperfusion in all patients with coronary angiography. We performed rest Tl-201 perfusion SPECT less then 6 hours after reperfusion and delay Tl-201 perfusion SPECT next day. Tl-201 uptake was visually graded as 4 point score from normal (0) to severe defect (3). Rest Tl-201 uptake ≤2 or combination of rest Tl-201 uptake ≤2 or late reversibility were considered to be viable. Myocardial wall motion was graded as 5 point score from normal (1) to dyskinesia (5). Myocardial wall motion was considered to be improved when a segment showed an improvement ≥1 grade in follow up echo compared with the baseline values. Among 98 segments with wall motion abnormality, the severity of myocardial wall motion decrease was as follow: mild hypokinesia: 18/98 (18%), severe hypokinesia: 28/98 (29%), akinesia: 51/98 (52%), dyskinesia: 1/98 (1%). The wall motion improved in 85%. Redistribution (13%), and reverse redistribution (4%) were observed in 24 hour delay SPECT. Positive predictive value (PPV) and negative predictive value (NPV) of combination of late reversibility and rest Tl-201uptake were 99%, and 54%.PPV and NPV of rest Tl-201 uptake were 100% and 52% respectively. Predictive values of comibination of rest Tl-201 uptake and late reversibility were not significantly different compared with predictive values of rest Tl-201 uptake only. We conclude that early Tl-201 perfusion SPECT predict myocardial wall motion improvement with excellent positive but relatively low negative

Comparison of various quantization methods of segmental ventricular wall motion in ischemic heart disease

International Nuclear Information System (INIS)

Probst, P.; Moore, R.; Kim, S.W.; Zollikofer, C.; Amplatz, K.

1981-01-01

Numerous methods of measuring regional myocardial wall motion are in use. A critical comparison is needed to assess the strengths, weaknesses, accuracy, and precision of these methods. This paper reports the evaluation of five methods using computer-assisted interactive graphics. Fifty cines were selected: 16 from normal subjects, and 34 from patients with proven cardiovascular diseases. Tracings were made of the opacified left ventricle in end systole and dastole and digitized. All fifty cines were analyzed by five methods using computer-implemented graphic techniques. The reults included a display of the silhouettes, which were translated and rotated according to various methods. In addition, the percent contraction for eleven myocardial regions was tabulated and displayed. The sixteen cines from normal subjects were used to derive 1 range of 'house' normal values for region contraction patterns with which the measurements from the 34 abnormal patients were compared. The five methods were evaluated by comparing results from the computer-aided analysis with the visual assessment of two experienced radiologists. One method was found, the results from which agreed with the radiologists' visual impression for every case. This computer-aided method was quantitative and reproducible. Consequently, it can give information which supplements the visual impression. (orig.) [de

First-person and third-person verbs in visual motion-perception regions.

Science.gov (United States)

Papeo, Liuba; Lingnau, Angelika

2015-02-01

Verb-related activity is consistently found in the left posterior lateral cortex (PLTC), encompassing also regions that respond to visual-motion perception. Besides motion, those regions appear sensitive to distinctions among the entities beyond motion, including that between first- vs. third-person ("third-person bias"). In two experiments, using functional magnetic resonance imaging (fMRI), we studied whether the implied subject (first/third-person) and/or the semantic content (motor/non-motor) of verbs modulate the neural activity in the left PLTC-regions responsive during basic- and biological-motion perception. In those sites, we found higher activity for verbs than for nouns. This activity was modulated by the person (but not the semantic content) of the verbs, with stronger response to third- than first-person verbs. The third-person bias elicited by verbs supports a role of motion-processing regions in encoding information about the entity beyond (and independently from) motion, and sets in a new light the role of these regions in verb processing. Copyright © 2014 Elsevier Inc. All rights reserved.

Self-similarity in the inertial region of wall turbulence.

Science.gov (United States)

Klewicki, J; Philip, J; Marusic, I; Chauhan, K; Morrill-Winter, C

2014-12-01

The inverse of the von Kármán constant κ is the leading coefficient in the equation describing the logarithmic mean velocity profile in wall bounded turbulent flows. Klewicki [J. Fluid Mech. 718, 596 (2013)] connects the asymptotic value of κ with an emerging condition of dynamic self-similarity on an interior inertial domain that contains a geometrically self-similar hierarchy of scaling layers. A number of properties associated with the asymptotic value of κ are revealed. This is accomplished using a framework that retains connection to invariance properties admitted by the mean statement of dynamics. The development leads toward, but terminates short of, analytically determining a value for κ. It is shown that if adjacent layers on the hierarchy (or their adjacent positions) adhere to the same self-similarity that is analytically shown to exist between any given layer and its position, then κ≡Φ(-2)=0.381966..., where Φ=(1+√5)/2 is the golden ratio. A number of measures, derived specifically from an analysis of the mean momentum equation, are subsequently used to empirically explore the veracity and implications of κ=Φ(-2). Consistent with the differential transformations underlying an invariant form admitted by the governing mean equation, it is demonstrated that the value of κ arises from two geometric features associated with the inertial turbulent motions responsible for momentum transport. One nominally pertains to the shape of the relevant motions as quantified by their area coverage in any given wall-parallel plane, and the other pertains to the changing size of these motions in the wall-normal direction. In accord with self-similar mean dynamics, these two features remain invariant across the inertial domain. Data from direct numerical simulations and higher Reynolds number experiments are presented and discussed relative to the self-similar geometric structure indicated by the analysis, and in particular the special form of self

Validation of a novel modified wall motion score for estimation of left ventricular ejection fraction in ischemic and non-ischemic cardiomyopathy

Energy Technology Data Exchange (ETDEWEB)

Scholl, David, E-mail: David.Scholl@utoronto.ca [Imaging Research Laboratories, Robarts Research Institute, London, Ontario (Canada); Kim, Han W., E-mail: hanwkim@gmail.com [Duke Cardiovascular Magnetic Resonance Center, Division of Cardiology, Duke University, NC (United States); Shah, Dipan, E-mail: djshah@tmhs.org [The Methodist DeBakey Heart Center, Houston, TX (United States); Fine, Nowell M., E-mail: nowellfine@gmail.com [Division of Cardiology, Department of Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario (Canada); Tandon, Shruti, E-mail: standon4@uwo.ca [Division of Cardiology, Department of Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario (Canada); Thompson, Terry, E-mail: thompson@lawsonimaging.ca [Lawson Health Research Institute, London, Ontario (Canada); Department of Medical Biophysics, University of Western Ontario, London, Ontario (Canada); Drangova, Maria, E-mail: mdrangov@imaging.robarts.ca [Imaging Research Laboratories, Robarts Research Institute, London, Ontario (Canada); Department of Medical Biophysics, University of Western Ontario, London, Ontario (Canada); White, James A., E-mail: jwhite@imaging.robarts.ca [Division of Cardiology, Department of Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario (Canada); Lawson Health Research Institute, London, Ontario (Canada); Imaging Research Laboratories, Robarts Research Institute, London, Ontario (Canada)

2012-08-15

Background: Visual determination of left ventricular ejection fraction (LVEF) by segmental scoring may be a practical alternative to volumetric analysis of cine magnetic resonance imaging (MRI). The accuracy and reproducibility of this approach for has not been described. The purpose of this study was to validate a novel segmental visual scoring method for LVEF estimation using cine MRI. Methods: 362 patients with known or suspected cardiomyopathy were studied. A modified wall motion score (mWMS) was used to blindly score the wall motion of all cardiac segments from cine MRI imaging. The same datasets were subjected to blinded volumetric analysis using endocardial contour tracing. The population was then separated into a model cohort (N = 181) and validation cohort (N = 181), with the former used to derive a regression equation of mWMS versus true volumetric LVEF. The validation cohort was then used to test the accuracy of this regression model to estimate the true LVEF from a visually determined mWMS. Reproducibility testing of mWMS scoring was performed upon a randomly selected sample of 20 cases. Results: The regression equation relating mWMS to true LVEF in the model cohort was: LVEF = 54.23 - 0.5761 Multiplication-Sign mWMS. In the validation cohort this equation produced a strong correlation between mWMS-derived LVEF and true volumetric LVEF (r = 0.89). Bland and Altman analysis showed no systematic bias in the LVEF estimated using the mWMS (-0.3231%, 95% limits of agreement -12.22% to 11.58%). Inter-observer and intra-observer reproducibility was excellent (r = 0.93 and 0.97, respectively). Conclusion: The mWMS is a practical tool for reporting regional wall motion and provides reproducible estimates of LVEF from cine MRI.

Direct observation of current-induced motion of a 3D vortex domain wall in cylindrical nanowires

KAUST Repository

Ivanov, Yurii P.

2017-05-08

The current-induced dynamics of 3D magnetic vortex domain walls in cylindrical Co/Ni nanowires are revealed experimentally using Lorentz microscopy and theoretically using micromagnetic simulations. We demonstrate that a spin-polarized electric current can control the reversible motion of 3D vortex domain walls, which travel with a velocity of a few hundred meters per second. This finding is a key step in establishing fast, high-density memory devices based on vertical arrays of cylindrical magnetic nanowires.

Direct observation of current-induced motion of a 3D vortex domain wall in cylindrical nanowires

KAUST Repository

Ivanov, Yurii P.; Chuvilin, Andrey; Lopatin, Sergei; Mohammed, Hanan; Kosel, Jü rgen

2017-01-01

The current-induced dynamics of 3D magnetic vortex domain walls in cylindrical Co/Ni nanowires are revealed experimentally using Lorentz microscopy and theoretically using micromagnetic simulations. We demonstrate that a spin-polarized electric current can control the reversible motion of 3D vortex domain walls, which travel with a velocity of a few hundred meters per second. This finding is a key step in establishing fast, high-density memory devices based on vertical arrays of cylindrical magnetic nanowires.

Steady motion of skyrmions and domains walls under diffusive spin torques

KAUST Repository

Elías, Ricardo Gabriel

2017-03-09

We explore the role of the spin diffusion of conducting electrons in two-dimensional magnetic textures (domain walls and skyrmions) with spatial variation of the order of the spin precession length λex. The effect of diffusion reflects in four additional torques that are third order in spatial derivatives of magnetization and bilinear in λex and in the nonadiabatic parameter β′. In order to study the dynamics of the solitons when these diffusive torques are present, we derive the Thiele equation in the limit of steady motion and we compare the results with the nondiffusive limit. When considering a homogenous current these torques increase the longitudinal velocity of transverse domain walls of width Δ by a factor (λex/Δ)2(α/3), α being the magnetic damping constant. In the case of single skyrmions with core radius r0 these new contributions tend to increase the Magnus effect in an amount proportional to (λex/r0)2(1+2αβ′).

Steady motion of skyrmions and domains walls under diffusive spin torques

KAUST Repository

Elí as, Ricardo Gabriel; Vidal-Silva, Nicolas; Manchon, Aurelien

2017-01-01

We explore the role of the spin diffusion of conducting electrons in two-dimensional magnetic textures (domain walls and skyrmions) with spatial variation of the order of the spin precession length λex. The effect of diffusion reflects in four additional torques that are third order in spatial derivatives of magnetization and bilinear in λex and in the nonadiabatic parameter β′. In order to study the dynamics of the solitons when these diffusive torques are present, we derive the Thiele equation in the limit of steady motion and we compare the results with the nondiffusive limit. When considering a homogenous current these torques increase the longitudinal velocity of transverse domain walls of width Δ by a factor (λex/Δ)2(α/3), α being the magnetic damping constant. In the case of single skyrmions with core radius r0 these new contributions tend to increase the Magnus effect in an amount proportional to (λex/r0)2(1+2αβ′).

Rapid estimation of left ventricular ejection fraction in acute myocardial infarction by echocardiographic wall motion analysis

DEFF Research Database (Denmark)

Berning, J; Rokkedal Nielsen, J; Launbjerg, J

1992-01-01

Echocardiographic estimates of left ventricular ejection fraction (ECHO-LVEF) in acute myocardial infarction (AMI) were obtained by a new approach, using visual analysis of left ventricular wall motion in a nine-segment model. The method was validated in 41 patients using radionuclide...

Dual breath-hold magnetic resonance cine evaluation of global and regional cardiac function

International Nuclear Information System (INIS)

Wintersperger, Bernd J.; Dietrich, Olaf; Huber, Armin; Reiser, Maximilian F.; Schoenberg, Stefan O.; Sincleair, Spencer; Runge, Val M.

2007-01-01

The purpose of our study was to evaluate the accuracy of a multislice cine magnetic resonance imaging (MRI) technique with parallel imaging in regard to global and regional left ventricular function. Forty-two individuals underwent cine MRI on a 1.5-tesla scanner. Cine MRI used a steady-state free precession technique and was performed as a single-slice technique (nonTSENSE cine) and an accelerated multislice technique (TSENSE cine) with five slices per breath-hold. End diastolic volume (EDV), end systolic volume (ESV), and ejection fraction (EF) were evaluated for all data sets and in regard to regional wall motion and regional wall motion analysis, and quantitative regional wall thickness and systolic thickening were also assessed. EDV, ESV, and EF based on TSENSE cine showed excellent correlation to the nonTSENSE cine approach (all r 2 =0.99, P<0.001). While EDV evaluations showed a small underestimation for TSENSE cine, ESV and EF showed accurate results compared with nonTSENSE cine. Both readers showed good agreement (κ=0.72) in regional wall motion assessment comparing both techniques. Data acquisition for the multislice approach was significantly shorter (∝75%) that in single-slice cine. We conclude that accurate evaluation of regional wall motion and left ventricular EF is possible using accelerated multislice cine MR with high spatial and temporal resolution. (orig.)

Carotid artery wall motion analysis from B-mode ultrasound using adaptive block matching: in silico evaluation and in vivo application

International Nuclear Information System (INIS)

Gastounioti, A; Stoitsis, J S; Nikita, K S; Golemati, S

2013-01-01

Valid risk stratification for carotid atherosclerotic plaques represents a crucial public health issue toward preventing fatal cerebrovascular events. Although motion analysis (MA) provides useful information about arterial wall dynamics, the identification of motion-based risk markers remains a significant challenge. Considering that the ability of a motion estimator (ME) to handle changes in the appearance of motion targets has a major effect on accuracy in MA, we investigated the potential of adaptive block matching (ABM) MEs, which consider changes in image intensities over time. To assure the validity in MA, we optimized and evaluated the ABM MEs in the context of a specially designed in silico framework. ABM FIRF2 , which takes advantage of the periodicity characterizing the arterial wall motion, was the most effective ABM algorithm, yielding a 47% accuracy increase with respect to the conventional block matching. The in vivo application of ABM FIRF2 revealed five potential risk markers: low movement amplitude of the normal part of the wall adjacent to the plaques in the radial (RMA PWL ) and longitudinal (LMA PWL ) directions, high radial motion amplitude of the plaque top surface (RMA PTS ), and high relative movement, expressed in terms of radial strain (RSI PL ) and longitudinal shear strain (LSSI PL ), between plaque top and bottom surfaces. The in vivo results were reproduced by OF LK(WLS) and ABM KF-K2 , MEs previously proposed by the authors and with remarkable in silico performances, thereby reinforcing the clinical values of the markers and the potential of those MEs. Future in vivo studies will elucidate with confidence the full potential of the markers. (paper)

Fluids in micropores. V. Effects of thermal motion in the walls of a slit-micropore

International Nuclear Information System (INIS)

Diestler, D.J.; Schoen, M.

1996-01-01

Previous articles in this series have concerned the prototypal slit-pore with rigid walls, in which a Lennard-Jones (12,6) monatomic film is constrained between two plane-parallel walls comprising like atoms fixed in the face-centered-cubic (fcc) (100) configuration. The behavior of molecularly thin films in the rigid-wall prototype is governed by the template effect, whereby solid films can form epitaxially when the walls are properly aligned in the lateral directions. In this article the influence of thermal motion of the wall atoms on the template effect is investigated. The walls are treated as Einstein solids, the atoms moving independently in harmonic potentials centered on rigidly fixed equilibrium positions in the fcc (100) configuration. The force constant f c is a measure of the stiffness of the walls, the rigid-wall limit being f c =∞. Formal thermodynamic and statistical mechanical analyses of the system are carried out. The results of grand canonical ensemble Monte Carlo simulations indicate that for values of f c characteristic of a soft (e.g., noble-gas) crystal dynamic coupling between wall and film has a substantial influence on such equilibrium properties as normal stress (load) and interfacial tensions. In general, the softer the walls (i.e., the smaller the value of f c ), the weaker the template effect and hence the softer and more disordered the confined film. copyright 1996 American Institute of Physics

Both semiquantitative degree of rest Tl-201 uptake and reversibility at 24 hour-delay were needed to predict wall motion improvement after bypass surgery

International Nuclear Information System (INIS)

Lee, D. S.; Yoon, S. N.; Kim, K. B.; Jeong, Z. K.; Lee, M. C.; Ko, C. S.

1997-01-01

Controversy still exists about how to use the uptake at rest and 24 hour delay in rest redistribution Tl-201 SPECT to predict improvement of wall motion abnormality after bypass surgery. To find the best way to combine diagnostic efficacy of Tl-201 SPECT to predict myocardial viability, we studied the predictive values (positive: PPV, negative: NPV) of rest and 24 hour-delay Tl-201 SPECT in 21 patients. Wall motion was assessed comparing preoperative post-stress gated Tc-99m-MIBI SPECT with that of 3 months after surgery. Four point scoring system was used for 17 myocardial segments to asses uptakes ( 0 to 3 for normal to defect) at rest and 24 hour-delay and wall motion ( 0 to 3 for normal to dyskinesia). Ejection fraction improved after surgery (5011% vs 4313%). Intra-observer and inter-observer reproducibility of EF was 7 and 9% respectively when we used 3D Perfusion-Motion Map. Sixty seven segments showed wall motion abnormality before surgery. Predictive values of rest Tl-201 uptake decrease were as follows: 0: 15/15(100%), 1: 30/34(88%), 2: 6/11 (55%), 3: 3/7(43%). So PPV of mild decrease was 88%, and NPV of severe decrease was 50%. Delayed reversibility was evaluated in 37 segments (15 patients). Twenty seven segment had persistence or aggravation, but the other 10 segments improved at 24 hour delay. PPV of reversible 10 segments was 80%, and NPV of reversibility was only 46%. PPV of combination of rest Tl-201 uptake of mild degree and 24 hour reversibility was 86% (38/44) and NPV of neither one was 88%. We concluded that both semi-quantitative degree of Tl-201 uptake at rest and reversibility at 24 hour delay was the best to warrant or abandon postoperative improvement of abnormal wall motion found at preoperative post-stress gated myocardial SPECT

Role of spin diffusion in current-induced domain wall motion for disordered ferromagnets

KAUST Repository

Akosa, Collins Ashu; Kim, Won-Seok; Bisig, André ; Klä ui, Mathias; Lee, Kyung-Jin; Manchon, Aurelien

2015-01-01

Current-induced spin transfer torque and magnetization dynamics in the presence of spin diffusion in disordered magnetic textures is studied theoretically. We demonstrate using tight-binding calculations that weak, spin-conserving impurity scattering dramatically enhances the nonadiabaticity. To further explore this mechanism, a phenomenological drift-diffusion model for incoherent spin transport is investigated. We show that incoherent spin diffusion indeed produces an additional spatially dependent torque of the form ∼∇2[m×(u⋅∇)m]+ξ∇2[(u⋅∇)m], where m is the local magnetization direction, u is the direction of injected current, and ξ is a parameter characterizing the spin dynamics (precession, dephasing, and spin-flip). This torque, which scales as the inverse square of the domain wall width, only weakly enhances the longitudinal velocity of a transverse domain wall but significantly enhances the transverse velocity of vortex walls. The spatial-dependent spin transfer torque uncovered in this study is expected to have significant impact on the current-driven motion of abrupt two-dimensional textures such as vortices, skyrmions, and merons.

Role of spin diffusion in current-induced domain wall motion for disordered ferromagnets

KAUST Repository

Akosa, Collins Ashu

2015-03-12

Current-induced spin transfer torque and magnetization dynamics in the presence of spin diffusion in disordered magnetic textures is studied theoretically. We demonstrate using tight-binding calculations that weak, spin-conserving impurity scattering dramatically enhances the nonadiabaticity. To further explore this mechanism, a phenomenological drift-diffusion model for incoherent spin transport is investigated. We show that incoherent spin diffusion indeed produces an additional spatially dependent torque of the form ∼∇2[m×(u⋅∇)m]+ξ∇2[(u⋅∇)m], where m is the local magnetization direction, u is the direction of injected current, and ξ is a parameter characterizing the spin dynamics (precession, dephasing, and spin-flip). This torque, which scales as the inverse square of the domain wall width, only weakly enhances the longitudinal velocity of a transverse domain wall but significantly enhances the transverse velocity of vortex walls. The spatial-dependent spin transfer torque uncovered in this study is expected to have significant impact on the current-driven motion of abrupt two-dimensional textures such as vortices, skyrmions, and merons.

Effects of temperature gradient induced nanoparticle motion on conduction and convection of fluid

International Nuclear Information System (INIS)

Zhou Leping; Peterson, George P.; Yoda, Minani; Wang Buxuan

2012-01-01

The role of temperature gradient induced nanoparticle motion on conduction and convection was investigated. Possible mechanisms for variations resulting from variations in the thermophysical properties are theoretically and experimentally discussed. The effect of the nanoparticle motion on conduction is demonstrated through thermal conductivity measurement of deionized water with suspended CuO nanoparticles (50 nm in diameter) and correlated with the contributions of Brownian diffusion, thermophoresis, etc. The tendencies observed is that the magnitude of and the variation in the thermal conductivity increases with increasing volume fraction for a given temperature, which is due primarily to the Brownian diffusion of the nanoparticles. Using dimensional analysis, the thermal conductivity is correlated and both the interfacial thermal resistance and near-field radiation are found to be essentially negligible. A modification term that incorporates the contributions of Brownian motion and thermophoresis is proposed. The effect of nanoscale convection is illustrated through an experimental investigation that utilized fluorescent polystyrene nanoparticle tracers (200 nm in diameter) and multilayer nanoparticle image velocimetry. The results indicate that both the magnitude and the deviation of the fluid motion increased with increasing heat flux in the near-wall region. Meanwhile, the fluid motion tended to decrease with the off-wall distance for a given heating power. A corresponding numerical study of convection of pure deionized water shows that the velocity along the off-wall direction is several orders of magnitude lower than that of deionized water, which indicates that Brownian motion in the near-wall region is crucial for fluid with suspended nanoparticles in convection.

Magnet fall inside a conductive pipe: motion and the role of the pipe wall thickness

Energy Technology Data Exchange (ETDEWEB)

Donoso, G; Ladera, C L; Martin, P [Departamento de Fisica, Universidad Simon BolIvar, Apdo. 89000, Caracas 1080 (Venezuela, Bolivarian Republic of)], E-mail: clladera@usb.ve, E-mail: pmartin@usb.ve

2009-07-15

Theoretical models and experimental results are presented for the retarded fall of a strong magnet inside a vertical conductive non-magnetic tube. Predictions and experimental results are in good agreement modelling the magnet as a simple magnetic dipole. The effect of varying the pipe wall thickness on the retarding magnetic drag is studied for pipes of different materials. Conductive pipes of thinner walls produce less dragging force and the retarded fall of the magnet is seen to consist of an initial transient accelerated regime followed by a stage of uniform motion. Alternative models of the magnet field are also presented that improve the agreement between theory and experiments.

Roughness Effects on Organized Motions in a Wall Shear Layer Flow

Science.gov (United States)

Haigermoser, Christian; Vesely, Lukas; Lapolla, Massimillano; Onorato, Michele

2006-11-01

Turbulent boundary layer measurements on a zero-pressure gradient flat plate with two different roughness, a 2D and a 3D roughness, were carried out. The main object of the study was to investigate the impact of the wall roughness on the turbulent flow structures. The momentum thickness Reynolds number for the smooth wall was Reθ˜ 1900. PIV measurements were taken in the streamwise wall-normal plane. The PIV images covered the whole logarithmic region and the major part of the outer layer. The instant flow images for the two roughness show features similar to the one expected in a smooth wall turbulent boundary layer, as described by Adrian et al. (JFM 2000). Statistical analysis was performed to enlighten quantitative differences between the different flow fields. For instance, two point streamwise velocity correlations show that the major effect of the roughness is to tilt the inclination of the hairpin vortex packets towards the wall normal direction; being the 3D roughness more effective in producing this displacement. Full results will be shown and discussed during the presentation.

Prognostic value of high-dose dobutamine stress magnetic resonance imaging in 1,493 consecutive patients: assessment of myocardial wall motion and perfusion.

Science.gov (United States)

Korosoglou, Grigorios; Elhmidi, Yacine; Steen, Henning; Schellberg, Dieter; Riedle, Nina; Ahrens, Johannes; Lehrke, Stephanie; Merten, Constanze; Lossnitzer, Dirk; Radeleff, Jannis; Zugck, Christian; Giannitsis, Evangelos; Katus, Hugo A

2010-10-05

This study sought to determine the prognostic value of wall motion and perfusion assessment during high-dose dobutamine stress (DS) cardiac magnetic resonance imaging (MRI) in a large patient cohort. DS-MRI offers the possibility to integrate myocardial perfusion and wall motion analysis in a single examination for the detection of coronary artery disease (CAD). A total of 1,493 consecutive patients with suspected or known CAD underwent DS-MRI, using a standard protocol in a 1.5-T magnetic resonance scanner. Wall motion and perfusion were assessed at baseline and during stress, and outcome data including cardiac death, nonfatal myocardial infarction ("hard events"), and "late" revascularization performed >90 days after the MR scans were collected during a 2 ± 1 year follow-up period. Fifty-three hard events, including 14 cardiac deaths and 39 nonfatal infarctions, occurred during the follow-up period, whereas 85 patients underwent "late" revascularization. Using multivariable regression analysis, an abnormal result for wall motion or perfusion during stress yielded the strongest independent prognostic value for both hard events and late revascularization, clearly surpassing that of clinical and baseline magnetic resonance parameters (for wall motion: adjusted hazard ratio [HR] of 5.9 [95% confidence interval (CI): 2.5 to 13.6] for hard events and of 3.1 [95% CI: 1.7 to 5.6] for late revascularization, and for perfusion: adjusted HR of 5.4 [95% CI: 2.3 to 12.9] for hard events and of 6.2 [95% CI: 3.3 to 11.3] for late revascularization, p < 0.001 for all). DS-MRI can accurately identify patients who are at increased risk for cardiac death and myocardial infarction, separating them from those with normal findings, who have very low risk for future cardiac events. (Prognostic Value of High Dose Dobutamine Stress Magnetic Resonance Imaging; NCT00837005). Copyright © 2010 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Controlling magnetic domain wall motion in the creep regime in He+-irradiated CoFeB/MgO films with perpendicular anisotropy

International Nuclear Information System (INIS)

Herrera Diez, L.; García-Sánchez, F.; Adam, J.-P.; Devolder, T.; Eimer, S.; El Hadri, M. S.; Ravelosona, D.; Lamperti, A.; Mantovan, R.; Ocker, B.

2015-01-01

This study presents the effective tuning of perpendicular magnetic anisotropy in CoFeB/MgO thin films by He + ion irradiation and its effect on domain wall motion in a low field regime. Magnetic anisotropy and saturation magnetisation are found to decrease as a function of the irradiation dose which can be related to the observed irradiation-induced changes in stoichiometry at the CoFeB/MgO interface. These changes in the magnetic intrinsic properties of the film are reflected in the domain wall dynamics at low magnetic fields (H) where irradiation is found to induce a significant decrease in domain wall velocity (v). For all irradiation doses, domain wall velocities at low fields are well described by a creep law, where Ln(v) vs. H −1∕4 behaves linearly, up to a maximum field H*, which has been considered as an approximation to the value of the depinning field H dep . In turn, H* ≈ H dep is seen to increase as a function of the irradiation dose, indicating an irradiation-induced extension of the creep regime of domain wall motion

Motional Effect on Wall Shear Stresses

DEFF Research Database (Denmark)

Kock, Samuel Alberg; Torben Fründ, Ernst; Yong Kim, Won

Atherosclerosis is the leading cause of death and severe disability. Wall Shear Stress (WSS), the stress exerted on vessel walls by the flowing blood is a key factor in the development of atherosclerosis. Computational Fluid Dynamics (CFD) is widely used for WSS estimations. Most CFD simulations...... are based on static models to ease computational burden leading to inaccurate estimations. The aim of this work was to estimate the effect of vessel wall deformations (expansion and bending) on WSS levels....

Improved stage of infarction wall motion in AMI. Association between the presence or absence of mismatch in myocardial scintigrams of Tl and BMIPP and CK release pattern

International Nuclear Information System (INIS)

Kurihara, Masato; Abe, Masahiro; Abe, Toshihiro; Nagai, Yoshikazu; Ibukiyama, Chiharu

1998-01-01

Binuclear myocardial scintigraphy with BMIPP and 201 TlCl was conducted on 40 patients with myocardial infarction. In all of 40 patients, reperfusion therapy in the acute stage succeeded. The relationship between serum CK release pattern and timing of improvement of wall motion at infarct-related area in the chronic stage was investigated. The patients were divided into 3 groups according to the early or late appearance of peak CK, and the presence or absence of B type mismatch in dual myocardial scintigraphy with BMIPP and 201 TlCl obtained one month after acute onset of myocardial infarction. Infarct size obtained from 201 TlCl scintigraphy and wall motion related to infarction were also investigated immediately after reperfusion and one month thereafter, respectively. No differences were recognized between Group I, in which the infarct area had B type mismatch with early appearance of CK peak, and Group II, in which the infarct area also had B type mismatch with the late appearance of CK peak. Although the wall motion did not change at all in Group I, it improved in Group II one month after reperfusion. Group III did not demonstrate B type mismatch with late appearance of CK peak and smaller infarct size compared to those in Group I and Group II. The wall motion in Group III had a tendency to improve immediately after reperfusion and maintain that level one month later. The timing of improvement of wall motion after successful reperfusion in the area with B type mismatch was not uniform. This suggests that the nonuniformity of the timing of improvement of wall motion in the area with B type mismatch is partly attributable to some kinds of injury to myocardium caused by reperfusion. (author)

Unidirectional effect in domain wall propagation observed in bistable glass-coated microwire

Energy Technology Data Exchange (ETDEWEB)

Onufer, J., E-mail: jozef.onufer@tuke.sk; Ziman, J., E-mail: jan.ziman@tuke.sk; Kladivová, M., E-mail: maria.kladivova@tuke.sk

2015-12-15

Systematic study of domain wall velocity versus applied magnetic field dependences in glass-coated amorphous Fe{sub 77.5}Si{sub 7.5}B{sub 15} wire was carried out, revealing the existence of a very interesting phenomenon. Domain wall mobility can be significantly different in cases when magnetization reversal caused by domain wall motion results in different orientation of magnetization. The magnitude and sign of this so-called unidirectional effect can change along the wire. There are also samples with weak unidirectional effect in which it is possible, in regions of higher values of applied magnetic field, to observe the highest wall velocities. It is very probable that damping of domain wall motion is responsible for this effect. As a hypothesis a mechanism based on eddy current damping of domain wall motion was proposed for interpretation of this effect. In the framework of this mechanism asymmetric and non-linear volt-ampere characteristics of the metal–glass interface might be responsible for the unidirectional effect. - Highlights: • Unidirectional effect in domain wall propagation was observed. • The magnitude and sign of the unidirectional effect can change along the wire. • A hypothesis for interpretation of the unidirectional effect is proposed.

Energy-imbalance mechanism of domain wall motion induced by propagation spin waves in finite magnetic nanostripe

International Nuclear Information System (INIS)

Zhu, Jinrong; Han, Zhaoyan; Su, Yuanchang; Hu, Jingguo

2014-01-01

The mechanism of the domain wall (DW) motions induced by spin wave in finite magnetic nanostripe is studied by micromagnetic simulations. We find that the spin-wave induced DM motions are always accompanied by an energy imbalance between two sides of the DW. The DW motion can be attributed to the expansion of the low-energy-density area and the contraction of the high-energy-density area. The energy imbalance strongly depends on whether the spin wave passes through the DW or is reflected by the DW. In the area of the spin wave propagation, the energy density increases with the time. However, in the superposition area of the incident spin wave and the reflected spin wave, the energy density decreases with the increasing of the time. It shows that this energy imbalance can be controlled by tuning the frequency of the spin wave. Finally, the effect of the damping parameter value is discussed. - Highlights: • The mechanism of the spin-wave induced DW motions is studied. • The spin-wave induced DW motions and the energy imbalance mechanism are given. • The DW motion with the same direction to that of SW is explained. • The DW motion with the opposite direction to that of SW is explained

Simultaneous effects of slip and wall properties on MHD peristaltic motion of nanofluid with Joule heating

International Nuclear Information System (INIS)

Hayat, T.; Nisar, Z.; Ahmad, B.; Yasmin, H.

2015-01-01

This paper is devoted to the magnetohydrodynamic (MHD) peristaltic transport of nanofluid in a channel with wall properties. Flow analysis is addressed in the presence of viscous dissipation, partial slip and Joule heating effects. Mathematical modelling also includes the salient features of Brownian motion and thermophoresis. Both analytic and numerical solutions are provided. Comparison between the solutions is shown in a very good agreement. Attention is focused to the Brownian motion parameter, thermophoresis parameter, Hartman number, Eckert number and Prandtl number. Influences of various parameters on skin friction coefficient, Nusselt and Sherwood numbers are also investigated. It is found that both the temperature and nanoparticles concentration are increasing functions of Brownian motion and thermophoresis parameters. - Highlights: • Temperature rises when Brownian motion and thermophoresis effects intensify. • Temperature profile increases when thermal slip parameter increases. • Concentration field is a decreasing function of concentration slip parameter. • Temperature decreases whereas concentration increases for Hartman number

Simultaneous effects of slip and wall properties on MHD peristaltic motion of nanofluid with Joule heating

Energy Technology Data Exchange (ETDEWEB)

Hayat, T. [Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000 (Pakistan); Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Department of Mathematics, King Abdulaziz University, P.O. Box 80257, Jeddah 21589 (Saudi Arabia); Nisar, Z. [Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000 (Pakistan); Ahmad, B. [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Department of Mathematics, King Abdulaziz University, P.O. Box 80257, Jeddah 21589 (Saudi Arabia); Yasmin, H., E-mail: qau2011@gmail.com [Department of Mathematics, COMSATS Institute of Information Technology, G.T. Road, Wah Cantt 47040 (Pakistan)

2015-12-01

This paper is devoted to the magnetohydrodynamic (MHD) peristaltic transport of nanofluid in a channel with wall properties. Flow analysis is addressed in the presence of viscous dissipation, partial slip and Joule heating effects. Mathematical modelling also includes the salient features of Brownian motion and thermophoresis. Both analytic and numerical solutions are provided. Comparison between the solutions is shown in a very good agreement. Attention is focused to the Brownian motion parameter, thermophoresis parameter, Hartman number, Eckert number and Prandtl number. Influences of various parameters on skin friction coefficient, Nusselt and Sherwood numbers are also investigated. It is found that both the temperature and nanoparticles concentration are increasing functions of Brownian motion and thermophoresis parameters. - Highlights: • Temperature rises when Brownian motion and thermophoresis effects intensify. • Temperature profile increases when thermal slip parameter increases. • Concentration field is a decreasing function of concentration slip parameter. • Temperature decreases whereas concentration increases for Hartman number.

Changes in dynamic embryonic heart wall motion in response to outflow tract banding measured using video densitometry

Science.gov (United States)

Stovall, Stephanie; Midgett, Madeline; Thornburg, Kent; Rugonyi, Sandra

2016-11-01

Abnormal blood flow during early cardiovascular development has been identified as a key factor in the pathogenesis of congenital heart disease; however, the mechanisms by which altered hemodynamics induce cardiac malformations are poorly understood. This study used outflow tract (OFT) banding to model increased afterload, pressure, and blood flow velocities at tubular stages of heart development and characterized the immediate changes in cardiac wall motion due to banding in chicken embryo models with light microscopy-based video densitometry. Optical videos were used to acquire two-dimensional heart image sequences over the cardiac cycle, from which intensity data were extracted along the heart centerline at several locations in the heart ventricle and OFT. While no changes were observed in the synchronous contraction of the ventricle with banding, the peristaltic-like wall motion in the OFT was significantly affected. Our data provide valuable insight into early cardiac biomechanics and its characterization using a simple light microscopy-based imaging modality.

Detecting multiple moving objects in crowded environments with coherent motion regions

Science.gov (United States)

Cheriyadat, Anil M.; Radke, Richard J.

2013-06-11

Coherent motion regions extend in time as well as space, enforcing consistency in detected objects over long time periods and making the algorithm robust to noisy or short point tracks. As a result of enforcing the constraint that selected coherent motion regions contain disjoint sets of tracks defined in a three-dimensional space including a time dimension. An algorithm operates directly on raw, unconditioned low-level feature point tracks, and minimizes a global measure of the coherent motion regions. At least one discrete moving object is identified in a time series of video images based on the trajectory similarity factors, which is a measure of a maximum distance between a pair of feature point tracks.

Controlling magnetic domain wall motion in the creep regime in He{sup +}-irradiated CoFeB/MgO films with perpendicular anisotropy

Energy Technology Data Exchange (ETDEWEB)

Herrera Diez, L., E-mail: liza.herrera-diez@ief.u-psud.fr; García-Sánchez, F.; Adam, J.-P.; Devolder, T.; Eimer, S.; El Hadri, M. S.; Ravelosona, D. [Institut d' Electronique Fondamentale, Université Paris-Sud, UMR CNRS 8622, 91405 Orsay (France); Lamperti, A.; Mantovan, R. [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20864 Agrate (MB) (Italy); Ocker, B. [Singulus Technology AG, Hanauer Landstrasse 103, 63796 Kahl am Main (Germany)

2015-07-20

This study presents the effective tuning of perpendicular magnetic anisotropy in CoFeB/MgO thin films by He{sup +} ion irradiation and its effect on domain wall motion in a low field regime. Magnetic anisotropy and saturation magnetisation are found to decrease as a function of the irradiation dose which can be related to the observed irradiation-induced changes in stoichiometry at the CoFeB/MgO interface. These changes in the magnetic intrinsic properties of the film are reflected in the domain wall dynamics at low magnetic fields (H) where irradiation is found to induce a significant decrease in domain wall velocity (v). For all irradiation doses, domain wall velocities at low fields are well described by a creep law, where Ln(v) vs. H{sup −1∕4} behaves linearly, up to a maximum field H*, which has been considered as an approximation to the value of the depinning field H{sub dep}. In turn, H* ≈ H{sub dep} is seen to increase as a function of the irradiation dose, indicating an irradiation-induced extension of the creep regime of domain wall motion.

[Segmental wall movement of the left ventricle in healthy persons and myocardial infarct patients studied by a catheter-less nuclear medical method (camera-cinematography of the heart)].

Science.gov (United States)

Geffers, H; Sigel, H; Bitter, F; Kampmann, H; Stauch, M; Adam, W E

1976-08-01

Camera-Kinematography is a nearly noninvasive method to investigate regional motion of the myocard, and allows evaluation of the function of the heart. About 20 min after injection of 15-20 mCi of 99mTC-Human-Serum-Albumin, when the tracer is distributed homogenously within the bloodpool, data acquisition starts. Myocardial wall motion is represented in an appropriate quasi three-dimensional form. In this representation scars can be revealed as "silent" (akinetic) regions, aneurysms by asynchronic motion. Time activity curves for arbitrarily chosen regions can be calculated and give an equivalent for regional volume changes. 16 patients with an old infarction have been investigated. In fourteen cases the location and extent of regions with abnormal motion could be evaluated. Only two cases of a small posterior wall infarction did not show deviations from normal contraction pattern.

Effects of non-invasive ventilation and posture on chest wall volumes and motion in patients with amyotrophic lateral sclerosis: a case series.

Science.gov (United States)

Magalhães, Cristiana M; Fregonezi, Guilherme A; Vidigal-Lopes, Mauro; Vieira, Bruna S P P; Vieira, Danielle S R; Parreira, Verônica F

2016-01-01

The effects of non-invasive ventilation (NIV) on the breathing pattern and thoracoabdominal motion of patients with amyotrophic lateral sclerosis (ALS) are unknown. 1) To analyze the influence of NIV on chest wall volumes and motion assessed by optoelectronic plethysmography in ALS patients and 2) to compare these parameters in the supine and sitting positions to those of healthy individuals (without NIV). Nine ALS patients were evaluated in the supine position using NIV. In addition, the ALS patients and nine healthy individuals were evaluated in both sitting and supine positions. Statistical analysis was performed using the paired Student t-test or Wilcoxon test and the Student t-test for independent samples or Mann-Whitney U test. Chest wall volume increased significantly with NIV, mean volume=0.43 (SD=0.16)L versus 0.57 (SD=0.19)L (p=0.04). No significant changes were observed for the pulmonary rib cage, abdominal rib cage, or abdominal contribution. The index of the shortening velocity of the diaphragmatic muscle, mean=0.15 (SD=0.05)L/s versus 0.21 (SD=0.05)L/s (pNIV. Comparisons between the supine and sitting positions showed similar changes in chest wall motion in both groups. However, the ALS patients presented a significantly lower contribution of the abdomen in the supine position compared with the controls, mean=56 (SD=13) versus 69 (SD=10) (p=0.02). NIV improved chest wall volumes without changing the contribution of the chest wall compartment in ALS patients. In the supine position, ALS patients had a lower contribution of the abdomen, which may indicate early diaphragmatic dysfunction.

Measurement of the near-wall velocity profile for a nanofluid flow inside a microchannel

Science.gov (United States)

Kanjirakat, Anoop; Sadr, Reza

2015-11-01

Hydrodynamics and anomalous heat transfer enhancements have been reported in the past for colloidal suspensions of nano-sized particles dispersed in a fluid (nanofluids). However, such augmentations may manifest itself by study of fluid flow characteristics near in the wall region. Present experimental study reports near-wall velocity profile for nanofluids (silicon dioxide nanoparticles in water) measured inside a microchannel. An objective-based nano-Particle Image Velocimetry (nPIV) technique is used to measure fluid velocity within three visible depths, O(100nm), from the wall. The near-wall fluid velocity profile is estimated after implementing the required corrections for optical properties and effects caused by hindered Brownian motion, wall-particle interactions, and non-uniform exponential illumination on the measurement technique. The fluid velocities of nanofluids at each of the three visible depths are observed to be higher than that of the base fluid resulting in a higher shear rate in this region. The relative increase in shear rates for nanofluids is believed to be the result of the near-wall shear-induced particle migration along with the Brownian motion of the nanoparticles. This research is funded by NPRP grant # 08-574-2-239 from the Qatar National Research Fund (a member of Qatar Foundation).

Aging near the wall in colloidal glasses

Science.gov (United States)

Cao, Cong; Huang, Xinru; Weeks, Eric

In a colloidal glass system, particles move slower as sample ages. In addition, their motions may be affected by their local structure, and this structure will be different near a wall. We examine how the aging process near a wall differs from that in the bulk of the sample. In particular, we use a confocal microscope to observe 3D motion in a bidisperse colloidal glass sample. We find that flat walls induce the particles to organize into layers. The aging process behaves differently near the boundary, especially within the first three layers. Particle motion near the wall is noticeably slower but also changes less dramatically with age. We compare and contrast aging seen in samples with flat and rough walls.

Effects of non-invasive ventilation and posture on chest wall volumes and motion in patients with amyotrophic lateral sclerosis: a case series

Directory of Open Access Journals (Sweden)

Cristiana M. Magalhães

2016-01-01

Full Text Available ABSTRACT Background The effects of non-invasive ventilation (NIV on the breathing pattern and thoracoabdominal motion of patients with amyotrophic lateral sclerosis (ALS are unknown. Objectives 1 To analyze the influence of NIV on chest wall volumes and motion assessed by optoelectronic plethysmography in ALS patients and 2 to compare these parameters in the supine and sitting positions to those of healthy individuals (without NIV. Method Nine ALS patients were evaluated in the supine position using NIV. In addition, the ALS patients and nine healthy individuals were evaluated in both sitting and supine positions. Statistical analysis was performed using the paired Student t-test or Wilcoxon test and the Student t-test for independent samples or Mann-Whitney U test. Results Chest wall volume increased significantly with NIV, mean volume=0.43 (SD=0.16L versus 0.57 (SD=0.19L (p=0.04. No significant changes were observed for the pulmonary rib cage, abdominal rib cage, or abdominal contribution. The index of the shortening velocity of the diaphragmatic muscle, mean=0.15 (SD=0.05L/s versus 0.21 (SD=0.05L/s (p<0.01, and abdominal muscles, mean=0.09 (SD=0.02L/s versus 0.14 (SD=0.06L/s (p<0.01, increased during NIV. Comparisons between the supine and sitting positions showed similar changes in chest wall motion in both groups. However, the ALS patients presented a significantly lower contribution of the abdomen in the supine position compared with the controls, mean=56 (SD=13 versus 69 (SD=10 (p=0.02. Conclusions NIV improved chest wall volumes without changing the contribution of the chest wall compartment in ALS patients. In the supine position, ALS patients had a lower contribution of the abdomen, which may indicate early diaphragmatic dysfunction.

Kinematic model of some types of motion of matter in active regions

International Nuclear Information System (INIS)

Platov, Yu.V.

1983-01-01

The kinematics of matter motion in variable magnetic fields of active regions on the Sun in the MHD approximation of a strong field and cold plasma is investigated. It is shown that the variation of sunspot magnetic moments lead to the development of different active phenomena in the solar atmosphere. The development of such phenomena at first can occur at the phase of active region growth, when new sunspots together with developed sunspots emerge in an active region or relative motions take place in a sunspot group

Sci-Fri PM: Radiation Therapy, Planning, Imaging, and Special Techniques - 11: Quantification of chest wall motion during deep inspiration breast hold treatments using cine EPID images and a physics based algorithm

Energy Technology Data Exchange (ETDEWEB)

Alpuche Aviles, Jorge E.; VanBeek, Timothy [CancerCare Manitoba, Winnipeg (Canada); Sasaki, David; Rivest, Ryan; Akra, Mohamed [CancerCare Manitoba, Winnipeg (Canada); University of Manitoba, Winnipeg (Canada)

2016-08-15

Purpose: This work presents an algorithm used to quantify intra-fraction motion for patients treated using deep inspiration breath hold (DIBH). The algorithm quantifies the position of the chest wall in breast tangent fields using electronic portal images. Methods: The algorithm assumes that image profiles, taken along a direction perpendicular to the medial border of the field, follow a monotonically and smooth decreasing function. This assumption is invalid in the presence of lung and can be used to calculate chest wall position. The algorithm was validated by determining the position of the chest wall for varying field edge positions in portal images of a thoracic phantom. The algorithm was used to quantify intra-fraction motion in cine images for 7 patients treated with DIBH. Results: Phantom results show that changes in the distance between chest wall and field edge were accurate within 0.1 mm on average. For a fixed field edge, the algorithm calculates the position of the chest wall with a 0.2 mm standard deviation. Intra-fraction motion for DIBH patients was within 1 mm 91.4% of the time and within 1.5 mm 97.9% of the time. The maximum intra-fraction motion was 3.0 mm. Conclusions: A physics based algorithm was developed and can be used to quantify the position of chest wall irradiated in tangent portal images with an accuracy of 0.1 mm and precision of 0.6 mm. Intra-fraction motion for patients treated with DIBH at our clinic is less than 3 mm.

Evaluation of global and regional left ventricular function obtained by quantitative gated SPECT using {sup 99m}Tc-tetrofosmin for left ventricular dysfunction

Energy Technology Data Exchange (ETDEWEB)

Ban, Kazunobu; Nakajima, Tohru; Iseki, Harukazu; Abe, Sumihisa; Handa, Shunnosuke; Suzuki, Yutaka [Tokai Univ., Isehara, Kanagawa (Japan). School of Medicine

2000-08-01

The quantitative gated SPECT (QGS) software is able to calculate LV volumes and visualize LV wall motion and perfusion throughout the cardiac cycle using an automatic edge detection algorithm of the left ventricle. We evaluated the reliability of global and regional LV function assessment derived from QGS by comparing it with the results from left ventriculo-cineangiography (LVG). In 20 patients with left ventricular dysfunction who underwent ECG gated {sup 99m}Tc-tetrofosmin SPECT, the end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (LVEF) were calculated. The QGS-assessed regional wall motion was determined using the cinematic display. QGS-derived EDV, ESV and LVEF correlated well with those by LVG (p<0.001 for each). There was a good correlation between wall motion score (WMS) derived from the QGS and the LVG (r=0.40, p<0.05). In some patients with extensive myocardial infarction, there was a discrepancy in the regional wall motion results between QGS and LVG. The ECG-gated SPECT using QGS is useful to evaluate global and regional LV functions in left ventricular dysfunction. (author)

Spanwise vorticity and wall normal velocity structure in the inertial region of turbulent boundary layers

Science.gov (United States)

Cuevas Bautista, Juan Carlos; Morrill-Winter, Caleb; White, Christopher; Chini, Gregory; Klewicki, Joseph

2017-11-01

The Reynolds shear stress gradient is a leading order mechanism on the inertial domain of turbulent wall-flows. This quantity can be described relative to the sum of two velocity-vorticity correlations, vωz and wωy . Recent studies suggest that the first of these correlates with the step-like structure of the instantaneous streamwise velocity profile on the inertial layer. This structure is comprised of large zones of uniform momentum segregated by slender regions of concentrated vorticity. In this talk we study the contributions of the v and ωz motions to the vorticity transport (vωz) mechanism through the use of experimental data at large friction Reynolds numbers, δ+. The primary contributions to v and ωz were estimated by identifying the peak wavelengths of their streamwise spectra. The magnitudes of these peaks are of the same order, and are shown to exhibit a weak δ+ dependence. The peak wavelengths of v, however, exhibit a strong wall-distance (y) dependence, while the peak wavelengths of ωz show only a weak y dependence, and remain almost O (√{δ+}) in size throughout the inertial domain. This research was partially supported by the National Science Foundation and partially supported by the Australian Research Council.

Rectal Balloon for the Immobilization of the Prostate Internal Motion

International Nuclear Information System (INIS)

Lee, Sang Kyu; Beak, Jong Geal; Kim, Joo Ho; Jeon, Byong Chul; Cho, Jeong Hee; Kim, Dong Wook; Song, Tae Soo; Cho, Jae Ho; Na, Soo Kyong

2005-01-01

The using of endo-rectal balloon has proposed as optimal method that minimized the motion of prostate and the dose of rectum wall volume for treated prostate cancer patients, so we make the customized rectal balloon device. In this study, we analyzed the efficiency of the Self-customized rectal balloon in the aspects of its reproducibility. In 5 patients, for treatment planning, each patient was acquired CT slice images in state of with and without rectal balloon. Also they had CT scanning same repeated third times in during radiation treatment (IMRT). In each case, we analyzed the deviation of rectal balloon position and verified the isodose distribution of rectum wall at closed prostate. Using the rectal balloon, we minimized the planning target volume (PTV) by decreased the internal motion of prostate and overcome the dose limit of radiation therapy in prostate cancer by increased the gap between the rectum wall and high dose region. The using of rectal balloon, although, was reluctant to treat by patients. View a point of immobilization of prostate internal motion and dose escalation of GTV (gross tumor volume), its using consider large efficient for treated prostate cancer patients.

New Ground Motion Prediction Models for Caucasus Region

Science.gov (United States)

Jorjiashvili, N.

2012-12-01

The Caucasus is a region of numerous natural hazards and ensuing disasters. Analysis of the losses due to past disasters indicates the those most catastrophic in the region have historically been due to strong earthquakes. Estimation of expected ground motion is a fundamental earthquake hazard assessment. The most commonly used parameter for attenuation relation is peak ground acceleration because this parameter gives useful information for Seismic Hazard Assessment. Because of this, many peak ground acceleration attenuation relations have been developed by different authors. Besides, a few attenuation relations were developed for Caucasus region: Ambraseys et al. (1996,2005) which were based on entire European region and they were not focused locally on Caucasus Region; Smit et.al. (2000) that was based on a small amount of acceleration data that really is not enough. Since 2003 construction of Georgian Digital Seismic Network has started with the help of number of International organizations, Projects and Private companies. The works conducted involved scientific as well as organizational activities: Resolving technical problems concerning communication and data transmission. Thus, today we have a possibility to get real time data and make scientific research based on digital seismic data. Generally, ground motion and damage are influenced by the magnitude of the earthquake, the distance from the seismic source to site, the local ground conditions and the characteristics of buildings. Estimation of expected ground motion is a fundamental earthquake hazard assessment. This is the reason why this topic is emphasized in this study. In this study new GMP models are obtained based on new data from Georgian seismic network and also from neighboring countries. Estimation of models are obtained by classical, statistical way, regression analysis. Also site ground conditions are considered because the same earthquake recorded at the same distance may cause different damage

Smoke regions extraction based on two steps segmentation and motion detection in early fire

Science.gov (United States)

Jian, Wenlin; Wu, Kaizhi; Yu, Zirong; Chen, Lijuan

2018-03-01

Aiming at the early problems of video-based smoke detection in fire video, this paper proposes a method to extract smoke suspected regions by combining two steps segmentation and motion characteristics. Early smoldering smoke can be seen as gray or gray-white regions. In the first stage, regions of interests (ROIs) with smoke are obtained by using two step segmentation methods. Then, suspected smoke regions are detected by combining the two step segmentation and motion detection. Finally, morphological processing is used for smoke regions extracting. The Otsu algorithm is used as segmentation method and the ViBe algorithm is used to detect the motion of smoke. The proposed method was tested on 6 test videos with smoke. The experimental results show the effectiveness of our proposed method over visual observation.

Cartan frames for heart wall fiber motion

NARCIS (Netherlands)

Samari, Babak; Aumentado-Armstrong, Tristan; Strijkers, Gustav J.; Froeling, Martijn; Siddiqi, Kaleem

2017-01-01

Current understanding of heart wall fiber geometry is based on ex vivo static data obtained through diffusion imaging or histology. Thus, little is known about the manner in which fibers rotate as the heart beats. Yet, the geometric organization of moving fibers in the heart wall is key to its

Comparison of Quantitative Wall Motion Analysis and Strain For Detection Of Coronary Stenosis With Three-Dimensional Dobutamine Stress Echocardiography

Science.gov (United States)

Parker, Katherine M.; Clark, Alexander P.; Goodman, Norman C.; Glover, David K.; Holmes, Jeffrey W.

2015-01-01

Background Quantitative analysis of wall motion from three-dimensional (3D) dobutamine stress echocardiography (DSE) could provide additional diagnostic information not available from qualitative analysis. In this study we compare the effectiveness of 3D fractional shortening (3DFS), a measure of wall motion computed from 3D echocardiography (3DE), to strain and strain rate measured with sonomicrometry for detecting critical stenoses during DSE. Methods Eleven open-chest dogs underwent DSE both with and without a critical stenosis. 3DFS was measured from 3DE images acquired at peak stress. 3DFS was normalized by subtracting average 3DFS during control peak stress (Δ3DFS). Strains in the perfusion defect (PD) were measured from sonomicrometry, and PD size and location were measured with microspheres. Results A Δ3DFS abnormality indicated the presence of a critical stenosis with high sensitivity and specificity (88% and 100%, respectively), and Δ3DFS abnormality size correlated with PD size (R2=0.54). The sensitivity and specificity for Δ3DFS was similar to that for area strain (88%, 100%) and circumferential strain and strain rate (88%, 92% and 88%, 86%, respectively), while longitudinal strain and strain rate were less specific. Δ3DFS correlated significantly with both coronary flow reserve (R2=0.71) and PD size (R2=0.97), while area strain correlated with PD size only (R2=0.67), and other measures were not significantly correlated with flow reserve or PD size. Conclusion Quantitative wall motion analysis using Δ3DFS is effective for detecting critical stenoses during DSE, performing similarly to 3D strain, and provides potentially useful information on the size and location of a perfusion defect. PMID:24815588

Effects of non-invasive ventilation and posture on chest wall volumes and motion in patients with amyotrophic lateral sclerosis: a case series

OpenAIRE

Magalh?es, Cristiana M.; Fregonezi, Guilherme A.; Vidigal-Lopes, Mauro; Vieira, Bruna S. P. P.; Vieira, Danielle S. R.; Parreira, Ver?nica F.

2016-01-01

ABSTRACT Background The effects of non-invasive ventilation (NIV) on the breathing pattern and thoracoabdominal motion of patients with amyotrophic lateral sclerosis (ALS) are unknown. Objectives 1) To analyze the influence of NIV on chest wall volumes and motion assessed by optoelectronic plethysmography in ALS patients and 2) to compare these parameters in the supine and sitting positions to those of healthy individuals (without NIV). Method Nine ALS patients were evaluated in the supine...

Investigation of domain wall motion in RE-TM magnetic wire towards a current driven memory and logic

Energy Technology Data Exchange (ETDEWEB)

Awano, Hiroyuki

2015-06-01

Current driven magnetic domain wall (DW) motions of ferri-magnetic TbFeCo wires have been investigated. In the case of a Si substrate, the critical current density (Jc) of DW motion was successfully reduced to 3×10{sup 6} A/cm{sup 2}. Moreover, by using a polycarbonate (PC) substrate with a molding groove of 600 nm width, the Jc was decreased to 6×10{sup 5} A/cm{sup 2}. In order to fabricate a logic in memory, a current driven spin logics (AND, OR, NOT) have been proposed and successfully demonstrated under the condition of low Jc. These results indicate that TbFeCo nanowire is an excellent candidate for next generation power saving memory and logic.

Quantification of wall motion and phase of contraction in tomographic gated blood pool studies using length-based Fourier analysis

Energy Technology Data Exchange (ETDEWEB)

Nakajima, Kenichi; Bunko, Hisashi; Taki, Junichi; Nambu, Ichiro; Shiire, Yasushi; Tonami, Norihisa; Hisada, Kinichi; Tada, Akira; Kojima, Kazuhkio

1985-03-01

Length-based Fourier analysis, a new method for quantification of wall motion and timing of contraction, was applied to tomographic gated blood pool study. Two parameters, percent-length shortening (%LS) and length-based phase were calculated based on the time-length curves from a center to ventricular edges, and compared with the count-based method. In mathematical models for tomographic gated blood pool images, the severity of asynergy was easily determined by length-based method, and the accuracy of the parameters was good. As to the setting of the center, fixed center provided more reliable parameters than the method using movable center, i.e., when a center of gravity was determined in each frame. By length-based Fourier analysis, quantification of wall motion was easily performed, and the initial inward movement caused by the accessory conduction pathway was assessed in patients with Wolff-Parkinson-White syndrome. Length-based approach was considered to be reasonable and effective because the movements of the ventricular edges are essential in tomographic gated blood pool images.

Quantification of wall motion and phase of contraction in tomographic gated blood pool studies using length-based Fourier analysis

International Nuclear Information System (INIS)

Nakajima, Kenichi; Bunko, Hisashi; Taki, Junichi; Nambu, Ichiro; Shiire, Yasushi; Tonami, Norihisa; Hisada, Kinichi; Tada, Akira; Kojima, Kazuhiko.

1985-01-01

Length-based Fourier analysis, a new method for quantification of wall motion and timing of contraction, was applied to tomographic gated blood pool study. Two parameters, percent-length shortening (%LS) and length-based phase were calculated based on the time-length curves from a center to ventricular edges, and compared with the count-based method. In mathematical models for tomographic gated blood pool images, the severity of asynergy was easily determined by length-based method, and the accuracy of the parameters was good. As to the setting of the center, fixed center provided more reliable parameters than the method using movable center, i.e., when a center of gravity was determined in each frame. By length-based Fourier analysis, quantification of wall motion was easily performed, and the initial inward movement caused by the accessory conduction pathway was assessed in patients with Wolff-Parkinson-White syndrome. Length-based approach was considered to be reasonable and effective because the movements of the ventricular edges are essential in tomographic gated blood pool images. (author)

High-Frequency Ground-Motion Parameters from Weak-Motion Data in the Sicily Channel and Surrounding Regions

Science.gov (United States)

D'Amico, Sebastiano; Akinci, Aybige; Pischiutta, Marta

2018-03-01

In this paper we characterize the high frequency (1.0 - 10 Hz) seismic wave crustal attenuation and the source excitation in the Sicily Channel and surrounding regions using background seismicity from weak-motion database. The data set includes 15995 waveforms related to earthquakes having local magnitude ranging from 2.0 to 4.5 recorded between 2006 and 2012. The observed and predicted ground motions form the weak-motion data are evaluated in several narrow frequency bands from 0.25 to 20.0 Hz. The filtered observed peaks are regressed to specify a proper functional form for the regional attenuation, excitation and site specific term separately. The results are then used to calibrate effective theoretical attenuation and source excitation models using the Random Vibration Theory (RVT). In the log-log domain, the regional seismic wave attenuation and the geometrical spreading coefficient are modeled together. The geometrical spreading coefficient, g (r), modeled with a bilinear piecewise functional form and given as g (r) ∝ r-1.0 for the short distances (r selected reference distance with a magnitude independent roll-off spectral parameter, κ 0.04 s and with a Brune stress drop parameter increasing with moment magnitude, from Δσ = 2 MPa for Mw = 2.0 to Δσ = 13 MPa for Mw = 4.5. For events M≤4.5 (being Mwmax = 4.5 available in the dataset) the stress parameters are obtained by correlating the empirical/excitation source spectra with the Brune spectral model as function of magnitude. For the larger magnitudes (Mw>4.5) outside the range available in the calibration dataset where we do not have recorded data, we extrapolate our results through the calibration of the stress parameters of the Brune source spectrum over the Bindi et al. (2011) ground motion prediction equation (GMPE) selected as a reference model (hereafter also ITA10).

Nonsingular walls in plane cholesteric layers

International Nuclear Information System (INIS)

Belyakov, V A; Osipov, M A; Stewart, I W

2006-01-01

The structure of a straight interface (wall) between regions with differing values of the pitch in planar cholesteric layers with finite strength of the surface anchoring is investigated theoretically. It is found that the shape and strength of the anchoring potential influences essentially the structure of the wall and a motionless wall between thermodynamically stable regions without a singularity in the director distribution in the layer can exist for sufficiently weak anchoring only. More specifically, for the existence of such a wall the dimensionless parameter S d = K 22 /Wd (where W is the depth of the anchoring potential, K 22 is the elastic twist modulus and d is the layer thickness) should exceed its critical value, which is dependent on the shape of the anchoring potential. General equations describing the director distribution in the wall are presented. Detailed analysis of these equations is carried out for the case of infinitely strong anchoring at one surface and finite anchoring strength at the second layer surface. It is shown that the wall width L is directly dependent upon the shape and strength of the anchoring potential and that its estimate ranges from d to (dL p ) 1/2 (where L p = K 22 /W is the penetration length), corresponding to different anchoring strengths and shape potentials. The dependence of the director distribution in the wall upon all three Frank elastic moduli is analytically found for some specific limiting cases of the model anchoring potentials. Motion of the wall is briefly investigated and the corresponding calculations performed under the assumption that the shape of a moving wall is the same as a motionless one. It is noted that experimental investigation of the walls in planar cholesteric layers can be used for the determination of the actual shape of surface anchoring potentials

Gated blood pool tomography for the evaluation of global and regional left ventricular function in comparison to planar techniques and echocardiography.

Science.gov (United States)

Canclini, S; Terzi, A; Rossini, P; Vignati, A; La Canna, G; Magri, G C; Pizzocaro, C; Giubbini, R

2001-01-01

Multigated radionuclide ventriculography (MUGA) is a simple and reliable tool for the assessment of global systolic and diastolic function and in several studies it is still considered a standard for the assessment of left ventricular ejection fraction. However the evaluation of regional wall motion by MUGA is critical due to two-dimensional imaging and its clinical use is progressively declining in favor of echocardiography. Tomographic MUGA (T-MUGA) is not widely adopted in clinical practice. The aim of this study was to compare T-MUGA to planar MUGA (P-MUGA) for the assessment of global ejection fraction and to transthoracic echocardiography for the evaluation of regional wall motion. A 16-segment model was adopted for the comparison with echo regional wall motion. For each one of the 16 segments the normal range of T-MUGA ejection fraction was quantified and a normal data file was defined; the average value -2.5 SD was used as the lower threshold to identify abnormal segments. In addition, amplitude images from Fourier analysis were quantified and considered abnormal according to three different thresholds (25, 50 and 75% of the maximum). In a study group of 33 consecutive patients the ejection fraction values of T-MUGA highly correlated with those of P-MUGA (r = 0.93). The regional ejection fraction (according to the normal database) and the amplitude analysis (50% threshold) allowed for the correct identification of 203/226 and 167/226 asynergic segments by echocardiography, and of 269/302 and 244/302 normal segments, respectively. Therefore sensitivity, specificity and overall accuracy to detect regional wall motion abnormalities were 90, 89, 89% and 74, 81, 79% for regional ejection fraction and amplitude analysis, respectively. T-MUGA is a reliable tool for regional wall motion evaluation, well correlated with echocardiography, less subjective and able to provide quantitative data.

Current induced domain wall motion and tilting in Pt/Co/Ta structures with perpendicular magnetic anisotropy in the presence of the Dyzaloshinskii–Moriya interaction

Science.gov (United States)

Yun, Jijun; Li, Dong; Cui, Baoshan; Guo, Xiaobin; Wu, Kai; Zhang, Xu; Wang, Yupei; Mao, Jian; Zuo, Yalu; Xi, Li

2018-04-01

Current induced domain wall motion (CIDWM) was studied in Pt/Co/Ta structures with perpendicular magnetic anisotropy and the Dyzaloshinskii–Moriya interaction (DMI) by the spin-orbit torque (SOT). We measured the strength of DMI and SOT efficiency in Pt/Co/Ta with the variation of the thickness of Ta using a current induced hysteresis loop shift method. The results indicate that the DMI stabilizes a chiral Néel-type domain wall (DW), and the DW motion can be driven by the enhanced large SOT generated from Pt and Ta with opposite signs of spin Hall angle in Pt/Co/Ta stacks. The CIDWM velocity, which is 104 times larger than the field driven DW velocity, obeys a creep law, and reaches around tens of meters per second with current density of ~106 A cm‑2. We also found that the Joule heating accompanied with current also accelerates the DW motion. Meanwhile, a domain wall tilting was observed, which increases with current density increasing. These results can be explained by the spin Hall effect generated from both heavy metals Pt and Ta, inherent DMI, and the current accompanying Joule heating effect. Our results could provide some new designing prospects to move multiple DWs by SOT for achieving racetrack memories.

Domain wall and interphase boundary motion in (1−x)Bi(Mg{sub 0.5}Ti{sub 0.5})O{sub 3}–xPbTiO{sub 3} near the morphotropic phase boundary

Energy Technology Data Exchange (ETDEWEB)

Tutuncu, Goknur [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Chen, Jun; Fan, Longlong [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Fancher, Chris M.; Zhao, Jianwei [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Forrester, Jennifer S.; Jones, Jacob L., E-mail: JacobJones@ncsu.edu [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

2016-07-28

Electric field-induced changes in the domain wall motion of (1−x)Bi(Mg{sub 0.5}Ti{sub 0.5})O{sub 3}–xPbTiO{sub 3} (BMT-xPT) near the morphotropic phase boundary (MPB) where x = 0.37 (BMT-37PT) and x = 0.38 (BMT-38PT), are studied by means of synchrotron x-ray diffraction. Through Rietveld analysis and profile fitting, a mixture of coexisting monoclinic (Cm) and tetragonal (P4mm) phases is identified at room temperature. Extrinsic contributions to the property coefficients are evident from electric-field-induced domain wall motion in both the tetragonal and monoclinic phases, as well as through the interphase boundary motion between the two phases. Domain wall motion in the tetragonal and monoclinic phases for BMT-37PT is larger than that of BMT-38PT, possibly due to this composition's closer proximity to the MPB. Increased interphase boundary motion was also observed in BMT-37PT. Lattice strain, which is a function of both intrinsic piezoelectric strain and elastic interactions of the grains (the latter originating from domain wall and interphase boundary motion), is similar for the respective tetragonal and monoclinic phases.

Assessment of ventricular wall motion with focused echocardiography during cardiac arrest to predict survival

Directory of Open Access Journals (Sweden)

Can Ozen

2016-03-01

Full Text Available Objectives: Our primary goal is to investigate the hypothesis that in patients with a detectable ventricular wall motion (VWM in cardiac ultrasonography (US during cardiopulmonary resuscitation (CPR, survival rate is significantly more than in patients without VWM in US. Material and methods: In our prospective, single center study, 129 adult cardiac arrest (CA patients were enrolled. Cardiac US according to Focus Assessed Transthoracic Echo (FATE protocol was performed before CPR. Presence of VWM was recorded on forms along with demographic data, initial rhythm, CA location, presence of return of spontaneous circulation (ROSC and time until ROSC was obtained. Results: 129 patients were included. ROSC was obtained in 56/77 (72.7% patients with VWM and 3/52 (5.8% patients without VWM which is statistically significant (p > 0.001. Presence of VWM is 95% (95% CI: 0.95–0.99 sensitive and 70% (95% CI: 0.58–0.80 specific for ROSC. 43/77 (55.8% patients with VWM and 1 (1.9% of 52 patients without VWM survived to hospital admission which was statistically significant (p < 0.001. Presence of VWM was 100% (95% CI: 0.87–1.00 sensitive and 54% (95% CI: 0.43–0.64 specific for survival to hospital admission. Conclusion: No patient without VWM in US survived to hospital discharge. Only 3 had ROSC in emergency department and only 1 survived to hospital admission. This data suggests no patient without VWM before the onset of CPR survived to hospital discharge and this may be an indication to end resuscitative efforts early in these patients. Keywords: Cardiopulmonary resuscitation, Ultrasonography, Echocardiography, Ventricular wall motion

Prediction of improvement of myocardial wall motion after coronary artery bypass surgery using rest Tl-201/dipyridamole stress gated Tc-99m-MIBI/24 hour delay Tl-201 SPECT

International Nuclear Information System (INIS)

Lee, Dong Soo; Lee, Won Woo; Yeo, Jeong Yeo; Kim, Seok Ki; Kim, Ki Bong; Chung, June Key; Lee, Myung Chul

1998-01-01

Using rest Tl-201/ dipyridamole stress gated Tc-99m-MIBI/24 hour delay Tl-201 SPECT, we investigated the predictive values of the markers of the stress-rest reversibility (Rev), Tl-201 rest perfusion (Rest), Tl-201 24 hour redistribution (Del) and Tc-99m-MIBI gated systolic thickening (Thk) for wall motion improvement after coronary artery bypass surgery. In 39 patients (M:F=34:5, age 58±8), preoperative and postoperative (3 months) SPECT were compared. 24 hour delayed SPECT was done in 16 patients having perfusion defects at rest. Perfusion or wall motion was scored from 0 to 3 (0: normal to 3: defect or dyskinesia). Wall motion was abnormal in 142 segments among 585 segments of 99 artery territories which were surgically revascularized. After bypass surgery, ejection fraction increased from 37.8±9.0% to 45.5±12.3% in 22 patients who had decreased ejectin fraction preoperatively. Wall motion improved in 103 (72.5%) segments among 142 dysfunctional segments. Positive predictive values (PPV) of Rev, Rest, Del, and Thk were 83%, 76%, 43%, and 69% respectively. Negative predictive values (NPV) of Rev, Rest, Del, and Thk were 48%, 44%, 58%, and 21%, respectively. Rest/gated stress/delay SPECT had PPV of 74% and NPV of 46%. Through univariate logistic regression analysis revealed Rev( p=0.0008) and Rest (p=0.024) as significant predictors, stepwise multivariate test found Rev as the only good predictor (p=0.0008). Among independent predictors obtained by rest Tl-201/stress gated Tc-99m-MIBI/delayed Tl-201 myocardial SPECT for wall motion improvement after bypass surgery, stress-rest reversibility was the single most useful predictor

Analysis of particle-wall interaction

International Nuclear Information System (INIS)

Raszillier, H.; Durst, F.

1988-01-01

The vertical motion of a rigid sphere in a quiescent viscous fluid towards a horizontal plane wall is analized by a simplified equation of motion, which takes into account as the only wall correction that to the Stokes drag force. The phase space analysis for this equation is sketched; it has been motivated by measurements performed at the LSTM-Erlangen. A more detailed exposition is given in the Erlangen report LSTM 222/T/87. (orig.)

Cardiac functional mapping for thallium-201 myocardial perfusion, washout, wall motion and phase using single-photon emission computed tomography (SPECT)

International Nuclear Information System (INIS)

Nakajima, Kenichi; Bunko, Hisashi; Taniguchi, Mitsuru; Taki, Junichi; Tonami, Norihisa; Hisada, Kinichi; Hirano, Takako; Wani, Hidenobu.

1986-01-01

A method for three-dimensional functional mapping of Tl-201 myocardial uptake, washout, wall motion and phase was developed using SPECT. Each parameter was mapped using polar display in the same format. Normal values were determined in Tl-201 exercise study in 16 patients. Myocardial counts were lower in the septum and inferior wall and the difference of counts between anterior and inferior walls were greater in man compared with the perfusion pattern in woman. Washout was slower at septum and inferior wall in man, and slightly slower at inferior wall in woman. In gated blood-pool tomography, length-based and count-based Fourier analyses were applied to calculate the parameters of contraction and phase. The results of both Fourier analyses generally agreed; however, the area of abnormality was slightly different. Phase maps were useful for the assessment of asynergy as well as in patients with conduction disorders. These cardiac functional maps using SPECT were considered to be effective for the understanding of three-dimensional informations of cardiac function. (author)

Hydrodynamics of ultra-relativistic bubble walls

Energy Technology Data Exchange (ETDEWEB)

Leitao, Leonardo, E-mail: lleitao@mdp.edu.ar; Mégevand, Ariel, E-mail: megevand@mdp.edu.ar

2016-04-15

In cosmological first-order phase transitions, gravitational waves are generated by the collisions of bubble walls and by the bulk motions caused in the fluid. A sizeable signal may result from fast-moving walls. In this work we study the hydrodynamics associated to the fastest propagation modes, namely, ultra-relativistic detonations and runaway solutions. We compute the energy injected by the phase transition into the fluid and the energy which accumulates in the bubble walls. We provide analytic approximations and fits as functions of the net force acting on the wall, which can be readily evaluated for specific models. We also study the back-reaction of hydrodynamics on the wall motion, and we discuss the extrapolation of the friction force away from the ultra-relativistic limit. We use these results to estimate the gravitational wave signal from detonations and runaway walls.

Five-dimensional motion compensation for respiratory and cardiac motion with cone-beam CT of the thorax region

Science.gov (United States)

Sauppe, Sebastian; Hahn, Andreas; Brehm, Marcus; Paysan, Pascal; Seghers, Dieter; Kachelrieß, Marc

2016-03-01

We propose an adapted method of our previously published five-dimensional (5D) motion compensation (MoCo) algorithm1, developed for micro-CT imaging of small animals, to provide for the first time motion artifact-free 5D cone-beam CT (CBCT) images from a conventional flat detector-based CBCT scan of clinical patients. Image quality of retrospectively respiratory- and cardiac-gated volumes from flat detector CBCT scans is deteriorated by severe sparse projection artifacts. These artifacts further complicate motion estimation, as it is required for MoCo image reconstruction. For high quality 5D CBCT images at the same x-ray dose and the same number of projections as todays 3D CBCT we developed a double MoCo approach based on motion vector fields (MVFs) for respiratory and cardiac motion. In a first step our already published four-dimensional (4D) artifact-specific cyclic motion-compensation (acMoCo) approach is applied to compensate for the respiratory patient motion. With this information a cyclic phase-gated deformable heart registration algorithm is applied to the respiratory motion-compensated 4D CBCT data, thus resulting in cardiac MVFs. We apply these MVFs on double-gated images and thereby respiratory and cardiac motion-compensated 5D CBCT images are obtained. Our 5D MoCo approach processing patient data acquired with the TrueBeam 4D CBCT system (Varian Medical Systems). Our double MoCo approach turned out to be very efficient and removed nearly all streak artifacts due to making use of 100% of the projection data for each reconstructed frame. The 5D MoCo patient data show fine details and no motion blurring, even in regions close to the heart where motion is fastest.

Regional wall movement of the left ventricle in coronary heat diseases

International Nuclear Information System (INIS)

Schad, N.

1979-01-01

The regional wall movement of the left ventriculus is a substantial criterion for the treatment of coronary heart diseases. The non-invasive and riskless intravenous injections of a bolus of Technetium 99m-Pertechnetat and the recording of the first passage through the heart allow to present the regional wall movement of the left ventriculus and, in addition, to make a statement on the haemodynamic feed back effects on lungs and the right heart. The congruency with the wall movement determined invasively, in the contrast substance angiocardiogram, is high both for the normokinesis and for hypo-, A - and dyskinesis (90-92%). The examination proved good in following groups of patients and makes the decision on the further proceding easier: 1) After myocardial infarction. 2) In ishaemia-ECG or persistent ST-elevation. 3) In unstable progressive angina pectoris. 4) In unclear breast aches and negative ECG on exertion. 5) For course control after conservative and surgial therapy. The myocardial reserve can be shown using a after nitroglycerin administration. An investigation on exertion can find out affected vessel territories in the circulation. (orig.) [de

Numerical Simulation of Flow Features and Energy Exchange Physics in Near-Wall Region with Fluid-Structure Interaction

Science.gov (United States)

Zhang, Lixiang; Wang, Wenquan; Guo, Yakun

Large eddy simulation is used to explore flow features and energy exchange physics between turbulent flow and structure vibration in the near-wall region with fluid-structure interaction (FSI). The statistical turbulence characteristics in the near-wall region of a vibrating wall, such as the skin frictional coefficient, velocity, pressure, vortices, and the coherent structures have been studied for an aerofoil blade passage of a true three-dimensional hydroturbine. The results show that (i) FSI greatly strengthens the turbulence in the inner region of y+ < 25; and (ii) the energy exchange mechanism between the flow and the vibration depends strongly on the vibration-induced vorticity in the inner region. The structural vibration provokes a frequent action between the low- and high-speed streaks to balance the energy deficit caused by the vibration. The velocity profile in the inner layer near the vibrating wall has a significant distinctness, and the viscosity effect of the fluid in the inner region decreases due to the vibration. The flow features in the inner layer are altered by a suitable wall vibration.

Hydrodynamics of ultra-relativistic bubble walls

Directory of Open Access Journals (Sweden)

Leonardo Leitao

2016-04-01

Full Text Available In cosmological first-order phase transitions, gravitational waves are generated by the collisions of bubble walls and by the bulk motions caused in the fluid. A sizeable signal may result from fast-moving walls. In this work we study the hydrodynamics associated to the fastest propagation modes, namely, ultra-relativistic detonations and runaway solutions. We compute the energy injected by the phase transition into the fluid and the energy which accumulates in the bubble walls. We provide analytic approximations and fits as functions of the net force acting on the wall, which can be readily evaluated for specific models. We also study the back-reaction of hydrodynamics on the wall motion, and we discuss the extrapolation of the friction force away from the ultra-relativistic limit. We use these results to estimate the gravitational wave signal from detonations and runaway walls.

Comparison of different methods for assessment of left ventricular regional motility using the gated blood pool method

International Nuclear Information System (INIS)

Neumann, P.; Schicha, H.; Karsch, K.R.; Kreuzer, H.; Emrich, D.

1983-01-01

The following methods of evaluation were compared: qualitative analysis of cine mode; qualitative analysis of parametric scans obtained by Fourier analysis including the phase histogram; quantitative analysis of regional ejection fraction (EF). Regional wall motion abnormalities of high degree (akinesia, dyskinesia) were recognized by all three methods with a high sensitivity of 89.7-96.6% without statistically significant differences. The sensitivity for detecting hypokinetic segments was significantly lower (50.0-68.2%) without statistically significant differences between the three methods. Sensitivity for all kinds of wall motion abnormalities could be increased by combining the quantitative method of regional EF with the qualitative evaluation after Fourier analysis

Influence of strong perturbations on wall-bounded flows

Science.gov (United States)

Buxton, O. R. H.; Ewenz Rocher, M.; Rodríguez-López, E.

2018-01-01

Single-point hot-wire measurements are made downstream of a series of spanwise repeating obstacles that are used to generate an artificially thick turbulent boundary layer. The measurements are made in the near field, in which the turbulent boundary layer is beginning to develop from the wall-bounded wakes of the obstacles. The recent paper of Rodríguez-López et al. [E. Rodríguez-López et al., Phys. Rev. Fluids 1, 074401 (2016), 10.1103/PhysRevFluids.1.074401] broadly categorized the mechanisms by which canonical turbulent boundary layers eventually develop from wall-bounded wakes into two distinct mechanisms, the wall-driven and wake-driven mechanisms. In the present work we attempt to identify the geometric parameters of tripping arrays that trigger these two mechanisms by examining the spectra of the streamwise velocity fluctuations and the intermittent outer region of the flow. Using a definition reliant upon the magnitude of the velocity fluctuations, an intermittency function is devised that can discriminate between turbulent and nonturbulent flow. These results are presented along with the spectra in order to try to ascertain which aspects of a trip's geometry are more likely to favor the wall-driven or wake-driven mechanism. The geometrical aspects of the trips tested are the aspect ratio, the total blockage, and the blockage at the wall. The results indicate that the presence, or not, of perforations is the most significant factor in affecting the flow downstream. The bleed of fluid through the perforations reenergizes the mean recirculation and leads to a narrower intermittent region with a more regular turbulent-nonturbulent interface. The near-wall turbulent motions are found to recover quickly downstream of all of the trips with a wall blockage of 50%, but a clear influence of the outer fluctuations, generated by the tip vortices of the trips, is observed in the near-wall region for the high total blockage trips. The trip with 100% wall blockage is

A programmable motion phantom for quality assurance of motion management in radiotherapy

International Nuclear Information System (INIS)

Dunn, L.; Franich, R.D.; Kron, T.; Taylor, M.L.; Johnston, P.N.; McDermott, L.N.; Callahan, J.

2012-01-01

A commercially available motion phantom (QUASAR, Modus Medical) was modified for programmable motion control with the aim of reproducing patient respiratory motion in one dimension in both the anterior–posterior and superior–inferior directions, as well as, providing controllable breath-hold and sinusoidal patterns for the testing of radiotherapy gating systems. In order to simulate realistic patient motion, the DC motor was replaced by a stepper motor. A separate 'chest-wall' motion platform was also designed to accommodate a variety of surrogate marker systems. The platform employs a second stepper motor that allows for the decoupling of the chest-wall and insert motion. The platform's accuracy was tested by replicating patient traces recorded with the Varian real-time position management (RPM) system and comparing the motion platform's recorded motion trace with the original patient data. Six lung cancer patient traces recorded with the RPM system were uploaded to the motion platform's in-house control software and subsequently replicated through the phantom motion platform. The phantom's motion profile was recorded with the RPM system and compared to the original patient data. Sinusoidal and breath-hold patterns were simulated with the motion platform and recorded with the RPM system to verify the systems potential for routine quality assurance of commercial radiotherapy gating systems. There was good correlation between replicated and actual patient data (P 0.003). Mean differences between the location of maxima in replicated and patient data-sets for six patients amounted to 0.034 cm with the corresponding minima mean equal to 0.010 cm. The upgraded motion phantom was found to replicate patient motion accurately as well as provide useful test patterns to aid in the quality assurance of motion management methods and technologies.

An automated four-point scale scoring of segmental wall motion in echocardiography using quantified parametric images

International Nuclear Information System (INIS)

Kachenoura, N; Delouche, A; Ruiz Dominguez, C; Frouin, F; Diebold, B; Nardi, O

2010-01-01

The aim of this paper is to develop an automated method which operates on echocardiographic dynamic loops for classifying the left ventricular regional wall motion (RWM) in a four-point scale. A non-selected group of 37 patients (2 and 4 chamber views) was studied. Each view was segmented according to the standardized segmentation using three manually positioned anatomical landmarks (the apex and the angles of the mitral annulus). The segmented data were analyzed by two independent experienced echocardiographists and the consensual RWM scores were used as a reference for comparisons. A fast and automatic parametric imaging method was used to compute and display as static color-coded parametric images both temporal and motion information contained in left ventricular dynamic echocardiograms. The amplitude and time parametric images were provided to a cardiologist for visual analysis of RWM and used for RWM quantification. A cross-validation method was applied to the segmental quantitative indices for classifying RWM in a four-point scale. A total of 518 segments were analyzed. Comparison between visual interpretation of parametric images and the reference reading resulted in an absolute agreement (Aa) of 66% and a relative agreement (Ra) of 96% and kappa (κ) coefficient of 0.61. Comparison of the automated RWM scoring against the same reference provided Aa = 64%, Ra = 96% and κ = 0.64 on the validation subset. Finally, linear regression analysis between the global quantitative index and global reference scores as well as ejection fraction resulted in correlations of 0.85 and 0.79. A new automated four-point scale scoring of RWM was developed and tested in a non-selected database. Its comparison against a consensual visual reading of dynamic echocardiograms showed its ability to classify RWM abnormalities.

Magneto-optical study of domain wall dynamics and giant Barkhausen jump in magnetic microwires

International Nuclear Information System (INIS)

Chizhik, A.; Zhukov, A.; Blanco, J.M.; Gonzalez, J.

2012-01-01

Investigation of surface domain walls motion in Co-rich magnetic microwires has been performed in circular and axial magnetic fields. The dc axial magnetic field acceleration of the domain wall motion related to the influence of the axial field on the structure of the moving domain wall has been discovered. Pulsed axial magnetic field induced unidirectional motion of surface domain wall also has been found.

Thinner regions of intracranial aneurysm wall correlate with regions of higher wall shear stress: a 7.0 tesla MRI

Science.gov (United States)

Blankena, Roos; Kleinloog, Rachel; Verweij, Bon H.; van Ooij, Pim; ten Haken, Bennie; Luijten, Peter R.; Rinkel, Gabriel J.E.; Zwanenburg, Jaco J.M.

2016-01-01

Purpose To develop a method for semi-quantitative wall thickness assessment on in vivo 7.0 tesla (7T) MRI images of intracranial aneurysms for studying the relation between apparent aneurysm wall thickness and wall shear stress. Materials and Methods Wall thickness was analyzed in 11 unruptured aneurysms in 9 patients, who underwent 7T MRI with a TSE based vessel wall sequence (0.8 mm isotropic resolution). A custom analysis program determined the in vivo aneurysm wall intensities, which were normalized to signal of nearby brain tissue and were used as measure for apparent wall thickness (AWT). Spatial wall thickness variation was determined as the interquartile range in AWT (the middle 50% of the AWT range). Wall shear stress was determined using phase contrast MRI (0.5 mm isotropic resolution). We performed visual and statistical comparisons (Pearson’s correlation) to study the relation between wall thickness and wall shear stress. Results 3D colored AWT maps of the aneurysms showed spatial AWT variation, which ranged from 0.07 to 0.53, with a mean variation of 0.22 (a variation of 1.0 roughly means a wall thickness variation of one voxel (0.8mm)). In all aneurysms, AWT was inversely related to WSS (mean correlation coefficient −0.35, P<0.05). Conclusions A method was developed to measure the wall thickness semi-quantitatively, using 7T MRI. An inverse correlation between wall shear stress and AWT was determined. In future studies, this non-invasive method can be used to assess spatial wall thickness variation in relation to pathophysiologic processes such as aneurysm growth and –rupture. PMID:26892986

Impact of a drop onto a wetted wall: description of crown formation and propagation

Science.gov (United States)

Roisman, I. V.; Tropea, C.

2002-12-01

The impact of a drop onto a liquid film with a relatively high impact velocity, leading to the formation of a crown-like ejection, is studied theoretically. The motion of a kinematic discontinuity in the liquid film on the wall due to the drop impact, the formation of the upward jet at this kinematic discontinuity and its elevation are analysed. Four main regions of the drop and film are considered: the perturbed liquid film on the wall inside the crown, the unperturbed liquid film on the wall outside the crown, the upward jet forming a crown, and the free rim bounding this jet. The theory of Yarin & Weiss (1995) for the propagation of the kinematic discontinuity is generalized here for the case of arbitrary velocity vectors in the inner and outer liquid films on the wall. Next, the mass, momentum balance and Bernoulli equations at the base of the crown are considered in order to obtain the velocity and the thickness of the jet on the wall. Furthermore, the dynamic equations of motion of the crown are developed in the Lagrangian form. An analytical solution for the crown shape is obtained in the asymptotic case of such high impact velocities that the surface tension and the viscosity effects can be neglected in comparison to inertial effects. The edge of the crown is described by the motion of a rim, formed due to the surface tension.

Noninvasive detection of coronary artery wall thickening with age in healthy subjects using high resolution MRI with beat-to-beat respiratory motion correction.

Science.gov (United States)

Scott, Andrew D; Keegan, Jennifer; Mohiaddin, Raad H; Firmin, David N

2011-10-01

To demonstrate coronary artery wall thickening with age in a small healthy cohort using a highly efficient, reliable, and reproducible high-resolution MR technique. A 3D cross-sectional MR vessel wall images (0.7 × 0.7 × 3 mm resolution) with retrospective beat-to-beat respiratory motion correction (B2B-RMC) were obtained in the proximal right coronary artery of 21 healthy subjects (age, 22-62 years) with no known cardiovascular disease. Lumen and outer wall (lumen + vessel wall) areas were measured in one central slice from each subject and average wall thickness and wall area/outer wall area ratio (W/OW) calculated. Imaging was successful in 18 (86%) subjects with average respiratory efficiency 99.3 ± 1.7%. Coronary vessel wall thickness and W/OW significantly correlate with subject age, increasing by 0.088 mm and 0.031 per decade respectively (R = 0.53, P = 0.024 and R = 0.48, P = 0.046). No relationship was found between lumen area and vessel wall thickness (P = NS), but outer wall area increased significantly with vessel wall thickness at 19 mm(2) per mm (P = 0.046). This is consistent with outward vessel wall remodeling. Despite the small size of our healthy cohort, using high-resolution MR imaging and B2B-RMC, we have demonstrated increasing coronary vessel wall thickness and W/OW with age. The results obtained are consistent with outward vessel wall remodeling. Copyright © 2011 Wiley-Liss, Inc.

Swimming trajectories of a three-sphere microswimmer near a wall

Science.gov (United States)

Daddi-Moussa-Ider, Abdallah; Lisicki, Maciej; Hoell, Christian; Löwen, Hartmut

2018-04-01

The hydrodynamic flow field generated by self-propelled active particles and swimming microorganisms is strongly altered by the presence of nearby boundaries in a viscous flow. Using a simple model three-linked sphere swimmer, we show that the swimming trajectories near a no-slip wall reveal various scenarios of motion depending on the initial orientation and the distance separating the swimmer from the wall. We find that the swimmer can either be trapped by the wall, completely escape, or perform an oscillatory gliding motion at a constant mean height above the wall. Using a far-field approximation, we find that, at leading order, the wall-induced correction has a source-dipolar or quadrupolar flow structure where the translational and angular velocities of the swimmer decay as inverse third and fourth powers with distance from the wall, respectively. The resulting equations of motion for the trajectories and the relevant order parameters fully characterize the transition between the states and allow for an accurate description of the swimming behavior near a wall. We demonstrate that the transition between the trapping and oscillatory gliding states is first order discontinuous, whereas the transition between the trapping and escaping states is continuous, characterized by non-trivial scaling exponents of the order parameters. In order to model the circular motion of flagellated bacteria near solid interfaces, we further assume that the spheres can undergo rotational motion around the swimming axis. We show that the general three-dimensional motion can be mapped onto a quasi-two-dimensional representational model by an appropriate redefinition of the order parameters governing the transition between the swimming states.

Atlas-based analysis of cardiac shape and function: correction of regional shape bias due to imaging protocol for population studies.

Science.gov (United States)

Medrano-Gracia, Pau; Cowan, Brett R; Bluemke, David A; Finn, J Paul; Kadish, Alan H; Lee, Daniel C; Lima, Joao A C; Suinesiaputra, Avan; Young, Alistair A

2013-09-13

Cardiovascular imaging studies generate a wealth of data which is typically used only for individual study endpoints. By pooling data from multiple sources, quantitative comparisons can be made of regional wall motion abnormalities between different cohorts, enabling reuse of valuable data. Atlas-based analysis provides precise quantification of shape and motion differences between disease groups and normal subjects. However, subtle shape differences may arise due to differences in imaging protocol between studies. A mathematical model describing regional wall motion and shape was used to establish a coordinate system registered to the cardiac anatomy. The atlas was applied to data contributed to the Cardiac Atlas Project from two independent studies which used different imaging protocols: steady state free precession (SSFP) and gradient recalled echo (GRE) cardiovascular magnetic resonance (CMR). Shape bias due to imaging protocol was corrected using an atlas-based transformation which was generated from a set of 46 volunteers who were imaged with both protocols. Shape bias between GRE and SSFP was regionally variable, and was effectively removed using the atlas-based transformation. Global mass and volume bias was also corrected by this method. Regional shape differences between cohorts were more statistically significant after removing regional artifacts due to imaging protocol bias. Bias arising from imaging protocol can be both global and regional in nature, and is effectively corrected using an atlas-based transformation, enabling direct comparison of regional wall motion abnormalities between cohorts acquired in separate studies.

Mitigation of sliding motion of a cask-canister by fluid-structure interaction in an annular region - 59208

International Nuclear Information System (INIS)

Ito, Tomohiro; Fujiwara, Yoshihiro; Shintani, Atsuhiko; Nakagaw, Chihiro; Furuta, Kazuhisa

2012-01-01

The cask-canister system is a coaxial circular cylindrical structure in which several spent fuels are installed. This system is a free-standing structure thus, it is very important to reduce sliding motion for very large seismic excitations. In this study, we propose a mitigation method for sliding motion. Water is installed in an annular region between a cask and a canister. The equations of motion are derived taking fluid-structure interaction into consideration for nonlinear sliding motion analyses. Based on these equations, mitigation effects of sliding motions are studied analytically. Furthermore, a fundamental test model of a cask-canister system is fabricated and shaking table tests are conducted. From the analytical and test results, sliding motion mitigation effects are investigated. In this paper, the sliding motion of the cask-canister system subjected to a horizontal base excitation is studied and the effectiveness of water filled in the annular region between the cask and the canister is evaluated. This water brings inertia force coupling effect which is proportional to acceleration of the cask and the canister. Therefore, due to this fluid coupling, the cask and canister system couples through 3 types of forces, i.e., spring force, damping force and inertia force of the liquid. Equations of motion for the sliding motion are derived based on the fluid-structure coupling effects formulated by Fritz. Based on these equations of motion, nonlinear sliding motion of the cask-canister system is analyzed and the sliding suppression effects are investigated numerically. Furthermore, a fundamental test model of a cask-canister system is fabricated and the shaking table tests are conducted. From these analytical and test results, the sliding motion suppression effects due to fluid-structure coupling effects are investigated. As a result, it is confirmed that the inertia coupling effects due to water filled in the annular region are relatively large, and the

Collective coordinate models of domain wall motion in perpendicularly magnetized systems under the spin hall effect and longitudinal fields

Energy Technology Data Exchange (ETDEWEB)

Nasseri, S. Ali, E-mail: ali.nasseri@isi.it [ISI Foundation - Via Alassio 11/c –10126 Torino (Italy); Politecnico di Torino - Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Moretti, Simone; Martinez, Eduardo [University of Salamanca - Cardenal Plá y Deniel, 22, 37008 Salamanca (Spain); Serpico, Claudio [ISI Foundation - Via Alassio 11/c –10126 Torino (Italy); University of Naples Federico II - Via Claudio 21, 80125 Napoli (Italy); Durin, Gianfranco [ISI Foundation - Via Alassio 11/c –10126 Torino (Italy); Istituto Nazionale di Ricerca Metrologica (INRIM) - Strada delle Cacce 91, 10135 Torino (Italy)

2017-03-15

Recent studies on heterostructures of ultrathin ferromagnets sandwiched between a heavy metal layer and an oxide have highlighted the importance of spin-orbit coupling (SOC) and broken inversion symmetry in domain wall (DW) motion. Specifically, chiral DWs are stabilized in these systems due to the Dzyaloshinskii-Moriya interaction (DMI). SOC can also lead to enhanced current induced DW motion, with the Spin Hall effect (SHE) suggested as the dominant mechanism for this observation. The efficiency of SHE driven DW motion depends on the internal magnetic structure of the DW, which could be controlled using externally applied longitudinal in-plane fields. In this work, micromagnetic simulations and collective coordinate models are used to study current-driven DW motion under longitudinal in-plane fields in perpendicularly magnetized samples with strong DMI. Several extended collective coordinate models are developed to reproduce the micromagnetic results. While these extended models show improvements over traditional models of this kind, there are still discrepancies between them and micromagnetic simulations which require further work. - Highlights: • Moving DWs in PMA material maintain their structure under longitudinal in-plane fields. • As a result of longitudinal fields, magnetization in the domains becomes canted. • A critical longitudinal field was identified and correlated with the DMI strength. • A canted collective coordinate model was developed for DW motion under in-plane fields.

Fundamental and clinical evaluation of Fourier analysis for the detection of regional wall contraction abnormalities in the patients with myocardial infarction

International Nuclear Information System (INIS)

Murata, H.; Toyama, H.; Tabuchi, H.; Muraki, T.; Ohtake, E.; Chiba, K.; Yamada, H.

1982-01-01

The purpose of the present study are to evaluate fundamentally the method of Fourier analysis and to detect regional wall motion abnormality of the infarcted lesions by Fourier analysis. Fourier analyses were performed using the data obtained by first pass method in right anterior oblique projection (RAO) and by equilibrium method in left anterior oblique projection (LAO), and amplitude and phase were calculated. Amplitude and phase values needed to be corrected by R-R interval. On the detection of myocardial infarction, Fourier analyses in RAO and in LAO had same value for anterior infarctions. The analysis in RAO was more sensitive to detect infero-posterior lesions. On the other hand, the analysis in LAO was more sensitive for septal and lateral lesions

Segmental front line dynamics of randomly pinned ferroelastic domain walls

Science.gov (United States)

Puchberger, S.; Soprunyuk, V.; Schranz, W.; Carpenter, M. A.

2018-01-01

Dynamic mechanical analysis (DMA) measurements as a function of temperature, frequency, and dynamic force amplitude are used to perform a detailed study of the domain wall motion in LaAlO3. In previous DMA measurements Harrison et al. [Phys. Rev. B 69, 144101 (2004), 10.1103/PhysRevB.69.144101] found evidence for dynamic phase transitions of ferroelastic domain walls in LaAlO3. In the present work we focus on the creep-to-relaxation region of domain wall motion using two complementary methods. We determine, in addition to dynamic susceptibility data, waiting time distributions of strain jerks during slowly increasing stress. These strain jerks, which result from self-similar avalanches close to the depinning threshold, follow a power-law behavior with an energy exponent ɛ =1.7 ±0.1 . Also, the distribution of waiting times between events follows a power law N (tw) ∝tw-(n +1 ) with an exponent n =0.9 , which transforms to a power law of susceptibility S (ω ) ∝ω-n . The present dynamic susceptibility data can be well fitted with a power law, with the same exponent (n =0.9 ) up to a characteristic frequency ω ≈ω* , where a crossover from stochastic DW motion to the pinned regime is well described using the scaling function of Fedorenko et al. [Phys. Rev. B 70, 224104 (2004), 10.1103/PhysRevB.70.224104].

Current-induced domain wall motion in Ni{sub 80}Fe{sub 20} nanowires with low depinning fields

Energy Technology Data Exchange (ETDEWEB)

Malinowski, Gregory; Loerincz, Andreas; Krzyk, Stephen; Moehrke, Philipp; Bedau, Daniel; Boulle, Olivier; Rhensius, Jan; Klaeui, Mathias [Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, D-78457 (Germany); Heyderman, Laura J [Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Cho, Young Jin; Seo, Sunae, E-mail: gregory.malinowski@uni-konstanz.d [Samsung Electronics, San 14-1 Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do (Korea, Republic of)

2010-02-03

In this paper, we report on domain wall (DW) motion induced by current pulses at variable temperature in 900 nm wide and 25 nm thick Ni{sub 80}Fe{sub 20} wires with low pinning fields. By using Ar ion milling to pattern our wires rather than the conventional lift-off technique, a depinning field as low as {approx}2-3 Oe at room temperature is obtained. Comparison with previous results acquired on similar wires with much higher pinning shows that the critical current density scales with the depinning field, leading to a critical current density of {approx}2.5 x 10{sup 11} A m{sup -2} at 250 K. Moreover, when a current pulse with a current density larger than the critical current density is injected, the DW is not necessarily depinned but it can undergo a modification of its spin structure which hinders current-induced DW motion. Hence, reliable propagation of the DW requires an accurate adjustment of the pulsed current density.

Regionalization of ground motion attenuation in the conterminous United States

International Nuclear Information System (INIS)

Chung, D.H.; Bernreuter, D.L.

1979-01-01

Attenuation results from geometric spreading and from absorption. The former is almost independent of crustal geology or physiographic region. The latter depends strongly on crustal geology and the state of the earth's upper mantle. Except for very high-frequency waves, absorption does not affect ground motion at distances less than 25 to 50 km. Thus, in the near-field zone, the attenuation in the eastern United States will be similar to that in the western United States. Most of the differences in ground motion can be accounted for by differences in attenuation caused by differences in absorption. The other important factor is that for some Western earthquakes the fault breaks the earth's surface, resulting in larger ground motion. No Eastern earthquakes are known to have broken the earth's surface by faulting. The stress drop of Eastern earthquakes may be higher than for Western earthquakes of the same seismic moment, which would affect the high-frequency spectral content. This factor is believed to be of much less significance than differences in absorption in explaining the differences in ground motion between the East and the West. 6 figures

Wall-based identification of coherent structures in wall-bounded turbulence

Science.gov (United States)

Sanmiguel Vila, C.; Flores, O.

2018-04-01

During the last decades, a number of reduced order models based on coherent structures have been proposed to describe wall-bounded turbulence. Many of these models emphasize the importance of coherent wall-normal velocity eddies (ν-eddies), which drive the generation of the very long streamwise velocity structures observed in the logarithmic and outer region. In order to use these models to improve our ability to control wall-bounded turbulence in realistic applications, these ν-eddies need to be identified from the wall in a non-intrusive way. In this paper, the possibility of using the pressure signal at the wall to identify these ν-eddies is explored, analyzing the cross-correlation between the wall-normal velocity component and the pressure fluctuations at the wall in a DNS of a turbulent channel flow at Reτ = 939. The results show that the cross-correlation has a region of negative correlation upstream, and a region of positive correlation backwards. In the spanwise direction the correlation decays monotonously, except very close to the wall where a change of sign of the correlation coefficient is observed. Moreover, filtering the pressure fluctuations at the wall in space results in an increase of the region where the cross-correlation is strong, both for the positively and the negatively correlated regions. The use of a time filter for the pressure fluctuations at the wall yields different results, displacing the regions of strong correlation without changing much their sizes. The results suggest that space-filtering the pressure at the wall is a feasible way to identify ν-eddies of different sizes, which could be used to trigger turbulent control strategies.

Dominance of free wall radial motion in global right ventricular function of heart transplant recipients.

Science.gov (United States)

Lakatos, Bálint Károly; Tokodi, Márton; Assabiny, Alexandra; Tősér, Zoltán; Kosztin, Annamária; Doronina, Alexandra; Rácz, Kristóf; Koritsánszky, Kinga Bianka; Berzsenyi, Viktor; Németh, Endre; Sax, Balázs; Kovács, Attila; Merkely, Béla

2018-03-01

Assessment of right ventricular (RV) function using conventional echocardiography might be inadequate as the radial motion of the RV free wall is often neglected. Our aim was to quantify the longitudinal and the radial components of RV function using three-dimensional (3D) echocardiography in heart transplant (HTX) recipients. Fifty-one HTX patients in stable cardiovascular condition without history of relevant rejection episode or chronic allograft vasculopathy and 30 healthy volunteers were enrolled. RV end-diastolic (EDV) volume and total ejection fraction (TEF) were measured by 3D echocardiography. Furthermore, we quantified longitudinal (LEF) and radial ejection fraction (REF) by decomposing the motion of the RV using the ReVISION method. RV EDV did not differ between groups (HTX vs control; 96 ± 27 vs 97 ± 2 mL). In HTX patients, TEF was lower, however, tricuspid annular plane systolic excursion (TAPSE) decreased to a greater extent (TEF: 47 ± 7 vs 54 ± 4% [-13%], TAPSE: 11 ± 5 vs 21 ± 4 mm [-48%], P < .0001). In HTX patients, REF/TEF ratio was significantly higher compared to LEF/TEF (REF/TEF vs LEF/TEF: 0.58 ± 0.10 vs 0.27 ± 0.08, P < .0001), while in controls the REF/TEF and LEF/TEF ratio was similar (0.45 ± 0.07 vs 0.47 ± 0.07). Current results confirm the superiority of radial motion in determining RV function in HTX patients. Parameters incorporating the radial motion are recommended to assess RV function in HTX recipients. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Multi-region approach to free-boundary three-dimensional tokamak equilibria and resistive wall instabilities

Science.gov (United States)

Ferraro, N. M.; Jardin, S. C.; Lao, L. L.; Shephard, M. S.; Zhang, F.

2016-05-01

Free-boundary 3D tokamak equilibria and resistive wall instabilities are calculated using a new resistive wall model in the two-fluid M3D-C1 code. In this model, the resistive wall and surrounding vacuum region are included within the computational domain. This implementation contrasts with the method typically used in fluid codes in which the resistive wall is treated as a boundary condition on the computational domain boundary and has the advantage of maintaining purely local coupling of mesh elements. This new capability is used to simulate perturbed, free-boundary non-axisymmetric equilibria; the linear evolution of resistive wall modes; and the linear and nonlinear evolution of axisymmetric vertical displacement events (VDEs). Calculated growth rates for a resistive wall mode with arbitrary wall thickness are shown to agree well with the analytic theory. Equilibrium and VDE calculations are performed in diverted tokamak geometry, at physically realistic values of dissipation, and with resistive walls of finite width. Simulations of a VDE disruption extend into the current-quench phase, in which the plasma becomes limited by the first wall, and strong currents are observed to flow in the wall, in the SOL, and from the plasma to the wall.

Multi-region approach to free-boundary three-dimensional tokamak equilibria and resistive wall instabilities

Energy Technology Data Exchange (ETDEWEB)

Ferraro, N. M., E-mail: nferraro@pppl.gov; Lao, L. L. [General Atomics, La Jolla, California 92186 (United States); Jardin, S. C. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Shephard, M. S.; Zhang, F. [Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2016-05-15

Free-boundary 3D tokamak equilibria and resistive wall instabilities are calculated using a new resistive wall model in the two-fluid M3D-C1 code. In this model, the resistive wall and surrounding vacuum region are included within the computational domain. This implementation contrasts with the method typically used in fluid codes in which the resistive wall is treated as a boundary condition on the computational domain boundary and has the advantage of maintaining purely local coupling of mesh elements. This new capability is used to simulate perturbed, free-boundary non-axisymmetric equilibria; the linear evolution of resistive wall modes; and the linear and nonlinear evolution of axisymmetric vertical displacement events (VDEs). Calculated growth rates for a resistive wall mode with arbitrary wall thickness are shown to agree well with the analytic theory. Equilibrium and VDE calculations are performed in diverted tokamak geometry, at physically realistic values of dissipation, and with resistive walls of finite width. Simulations of a VDE disruption extend into the current-quench phase, in which the plasma becomes limited by the first wall, and strong currents are observed to flow in the wall, in the SOL, and from the plasma to the wall.

Dynamics of domain wall driven by spin-transfer torque

International Nuclear Information System (INIS)

Chureemart, P.; Evans, R. F. L.; Chantrell, R. W.

2011-01-01

Spin-torque switching of magnetic devices offers new technological possibilities for data storage and integrated circuits. We have investigated domain-wall motion in a ferromagnetic thin film driven by a spin-polarized current using an atomistic spin model with a modified Landau-Lifshitz-Gilbert equation including the effect of the spin-transfer torque. The presence of the spin-transfer torque is shown to create an out-of-plane domain wall, in contrast to the external-field-driven case where an in-plane wall is found. We have investigated the effect of the spin torque on domain-wall displacement, domain-wall velocity, and domain-wall width, as well as the equilibration time in the presence of the spin-transfer torque. We have shown that the minimum spin-current density, regarded as the critical value for domain-wall motion, decreases with increasing temperature.

OSCILLATING LIGHT WALL ABOVE A SUNSPOT LIGHT BRIDGE

Energy Technology Data Exchange (ETDEWEB)

Yang, Shuhong; Zhang, Jun; Jiang, Fayu [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Xiang, Yongyuan, E-mail: shuhongyang@nao.cas.cn [Fuxian Solar Observatory, Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China)

2015-05-10

With the high tempo-spatial Interface Region Imaging Spectrograph 1330 Å images, we find that many bright structures are rooted in the light bridge of NOAA 12192, forming a light wall. The light wall is brighter than the surrounding areas, and the wall top is much brighter than the wall body. The New Vacuum Solar Telescope Hα and the Solar Dynamics Observatory 171 and 131 Å images are also used to study the light-wall properties. In 1330, 171, and 131 Å, the top of the wall has a higher emission, while in the Hα line, the wall-top emission is very low. The wall body corresponds to bright areas in 1330 Å and dark areas in the other lines. The top of the light wall moves upward and downward successively, performing oscillations in height. The deprojected mean height, amplitude, oscillation velocity, and the dominant period are determined to be 3.6 Mm, 0.9 Mm, 15.4 km s{sup −1}, and 3.9 minutes, respectively. We interpret the oscillations of the light wall as the leakage of p-modes from below the photosphere. The constant brightness enhancement of the wall top implies the existence of some kind of atmospheric heating, e.g., via the persistent small-scale reconnection or the magneto-acoustic waves. In another series of 1330 Å images, we find that the wall top in the upward motion phase is significantly brighter than in the downward phase. This kind of oscillation may be powered by the energy released due to intermittent impulsive magnetic reconnection.

Optical wall dynamics induced by coexistence of monostable and bistable spatial regions.

Science.gov (United States)

Odent, V; Louvergneaux, E; Clerc, M G; Andrade-Silva, I

2016-11-01

When nonequilibrium extended homogeneous systems exhibit multistability, it leads to the presence of domain walls between the existing equilibria. Depending on the stability of the steady states, the dynamics differs. Here, we consider the interface dynamics in the case of a spatially inhomogeneous system, namely, an optical system where the control parameter is spatially Gaussian. Then interfaces connect the monostable and the bistable nonuniform states that are associated with two distinct spatial regions. The coexistence of these two regions of different stability induces relaxation dynamics and the propagation of a wall with a time-dependent speed. We emphasize analytically these two dynamical behaviors using a generic bistable model. Experimentally, an inhomogeneous Gaussian light beam traveling through either a dye-doped liquid crystal cell or a Kerr cavity depicts these behaviors, in agreement with the theoretical predictions.

Wall Street: money never sleeps : Motion picture (2010)

OpenAIRE

Lauri Lucente, Gloria; Buhagiar, Celaine

2011-01-01

The Social Network : Harvard student Mark Zuckerberg creates the social networking site that would become known as Facebook, but is later sued by two brothers who claimed he stole their idea, and the cofounder who was later squeezed out of the business. Wall Street: money never sleeps : Now out of prison but still disgraced by his peers, Gordon Gekko works his future son-in-law, an idealistic stock broker, when he sees an opportunity to take down a Wall Street enemy and rebuild his empire.

Electronic motion in the pre-oscillation phase of a smooth bore magnetron

International Nuclear Information System (INIS)

Garelis, E.; Hickman, R.B.

1979-01-01

The calculation of the electronic motion in the pre-oscillation phase of a smooth bore magnetron is the problem of calculating the electronic motion in the region between two concentric cylinders with an applied radial electric field and a constant axial B/sub z/ magnetic field. The inner cylinder represents the electron emitting cathode and the outer cylinder represents the anode. The emission is assumed to be space charge limited. This results in an electronic cloud surrounding the cathode. The radial velocity of the electrons is limited by the space charge and in addition the axial magnetic field tends to curve the path of the electrons so that they return to the cathode. Consequently, the electronic orbit extends to some distance r 0 from the cathode and for values of the radius r > r 0 exists a charge free region. The model assumes relativistic electronic motion with self-consistent magnetic fields. The magnetic flux is assumed to be conserved; i.e., conducting cylindrical walls

Refinement of motion correction strategies for lower-cost CT for under-resourced regions of the world

Science.gov (United States)

Wells, Jered R.; Segars, W. Paul; Kigongo, Christopher J. N.; Dobbins, James T., III

2011-03-01

This paper describes a recently developed post-acquisition motion correction strategy for application to lower-cost computed tomography (LCCT) for under-resourced regions of the world. Increased awareness regarding global health and its challenges has encouraged the development of more affordable healthcare options for underserved people worldwide. In regions such as sub-Saharan Africa, intermediate level medical facilities may serve millions with inadequate or antiquated equipment due to financial limitations. In response, the authors have proposed a LCCT design which utilizes a standard chest x-ray examination room with a digital flat panel detector (FPD). The patient rotates on a motorized stage between the fixed cone-beam source and FPD, and images are reconstructed using a Feldkamp algorithm for cone-beam scanning. One of the most important proofs-of-concept in determining the feasibility of this system is the successful correction of undesirable motion. A 3D motion correction algorithm was developed in order to correct for potential patient motion, stage instabilities and detector misalignments which can all lead to motion artifacts in reconstructed images. Motion will be monitored by the radiographic position of fiducial markers to correct for rigid body motion in three dimensions. Based on simulation studies, projection images corrupted by motion were re-registered with average errors of 0.080 mm, 0.32 mm and 0.050 mm in the horizontal, vertical and depth dimensions, respectively. The overall absence of motion artifacts in motion-corrected reconstructions indicates that reasonable amounts of motion may be corrected using this novel technique without significant loss of image quality.

Measurement of global and regional left ventricular performance with isotope technique in coronary heart disease

International Nuclear Information System (INIS)

Bostroem, P.-A.; Svensson, M.; Lilja, B.

1988-01-01

To evaluate left ventricular function in coronary artery disease, radionuclide measurements of global and regional ejection fraction (EF), regional wall motion and phase analyses of left ventricular contraction were performed by equilibrium technique, using sup(99m)Tc. One group of patients with angina pectoris and one group with myocardial infarction were compared with a control group. All above-mentioned parameters significantly separated the infarction group from the reference group both at rest and during work, while the group of patients with angina pectoris showed disturbances mainly during work, such as impaired ability to increase global and regional ejection fraction and regional wall motion. Adding regional analysis and phase analysis to the global EF determination increases the possibility of studying the left ventricular function. However, this addition has a limited value in detecting impaired left ventricular function compared to the determination of just global EF in patients with angina pectoris and in patients with myocardial infarction. (author)

Determination of GMPE functional form for an active region with limited strong motion data: application to the Himalayan region

Science.gov (United States)

Bajaj, Ketan; Anbazhagan, P.

2018-01-01

Advancement in the seismic networks results in formulation of different functional forms for developing any new ground motion prediction equation (GMPE) for a region. Till date, various guidelines and tools are available for selecting a suitable GMPE for any seismic study area. However, these methods are efficient in quantifying the GMPE but not for determining a proper functional form and capturing the epistemic uncertainty associated with selection of GMPE. In this study, the compatibility of the recent available functional forms for the active region is tested for distance and magnitude scaling. Analysis is carried out by determining the residuals using the recorded and the predicted spectral acceleration values at different periods. Mixed effect regressions are performed on the calculated residuals for determining the intra- and interevent residuals. Additionally, spatial correlation is used in mixed effect regression by changing its likelihood function. Distance scaling and magnitude scaling are respectively examined by studying the trends of intraevent residuals with distance and the trend of the event term with magnitude. Further, these trends are statistically studied for a respective functional form of a ground motion. Additionally, genetic algorithm and Monte Carlo method are used respectively for calculating the hinge point and standard error for magnitude and distance scaling for a newly determined functional form. The whole procedure is applied and tested for the available strong motion data for the Himalayan region. The functional form used for testing are five Himalayan GMPEs, five GMPEs developed under NGA-West 2 project, two from Pan-European, and one from Japan region. It is observed that bilinear functional form with magnitude and distance hinged at 6.5 M w and 300 km respectively is suitable for the Himalayan region. Finally, a new regression coefficient for peak ground acceleration for a suitable functional form that governs the attenuation

Dynamics of plane-symmetric thin walls in general relativity

International Nuclear Information System (INIS)

Wang, A.

1992-01-01

Plane walls (including plane domain walls) without reflection symmetry are studied in the framework of Einstein's general relativity. Using the distribution theory, all the Einstein field equations and Bianchi identities are split into two groups: one holding in the regions outside of the wall and the other holding at the wall. The Einstein field equations at the wall are found to take a very simple form, and given explicitly in terms of the discontinuities of the metric coefficients and their derivatives. The Bianchi identities at the wall are also given explicitly. Using the latter, the interaction of a plane wall with gravitational waves and some specific matter fields is studied. In particular, it is found that, when a gravitational plane wave passes through a wall, if the wall has no reflection symmetry, the phenomena, such as reflection, stimulation, or absorption, in general, occur. It is also found that, unlike for gravitational waves, a massless scalar wave or an electromagnetic wave continuously passes through a wall without any reflection. The repulsion and attraction of a plane wall are also studied. It is found that the acceleration of an observer who is at rest relative to the wall usually consists of three parts: one is due to the force produced by the wall, the second is due to the force produced by the space-time curvature, which is zero if the wall has reflection symmetry, and the last is due to the accelerated motion of the wall. As a result, a repulsive (attractive) plane wall may not be repulsive (attractive) at all. Finally, the collision and interaction among the walls are studied

Rotational Response of Toe-Restrained Retaining Walls to Earthquake Ground Motions

National Research Council Canada - National Science Library

Ebeling, Robert M; White, Barry C

2006-01-01

.... The PC software CorpsWallRotate (sometimes referred to as CWRotate) was developed to perform an analysis of permanent wall rotation for each proposed retaining wall section to a user-specified earthquake acceleration time-history...

The stochastic nature of the domain wall motion along high perpendicular anisotropy strips with surface roughness

International Nuclear Information System (INIS)

Martinez, Eduardo

2012-01-01

The domain wall dynamics along thin ferromagnetic strips with high perpendicular magnetocrystalline anisotropy driven by either magnetic fields or spin-polarized currents is theoretically analyzed by means of full micromagnetic simulations and a one-dimensional model, including both surface roughness and thermal effects. At finite temperature, the results show a field dependence of the domain wall velocity in good qualitative agreement with available experimental measurements, indicating a low field, low velocity creep regime, and a high field, linear regime separated by a smeared depinning region. Similar behaviors were also observed under applied currents. In the low current creep regime the velocity-current characteristic does not depend significantly on the non-adiabaticity. At high currents, where the domain wall velocity becomes insensitive to surface pinning, the domain wall shows a precessional behavior even when the non-adiabatic parameter is equal to the Gilbert damping. These analyses confirm the relevance of both thermal fluctuations and surface roughness for the domain wall dynamics, and that complete micromagnetic modeling and one-dimensional studies taking into account these effects are required to interpret the experimental measurements in order to get a better understanding of the origin, the role and the magnitude of the non-adiabaticity. (paper)

Post mastectomy linac IMRT irradiation of chest wall and regional nodes: dosimetry data and acute toxicities

International Nuclear Information System (INIS)

Ma, Jinli; Li, Jiongyan; Xie, Jiang; Chen, Jian; Zhu, Chuanying; Cai, Gang; Zhang, Zhen; Guo, Xiaomao; Chen, Jiayi

2013-01-01

Conventional post-mastectomy radiation therapy is delivered with tangential fields for chest wall and separate fields for regional nodes. Although chest wall and regional nodes delineation has been discussed with RTOG contouring atlas, CT-based planning to treat chest wall and regional nodes as a whole target has not been widely accepted. We herein discuss the dosimetric characteristics of a linac IMRT technique for treating chest wall and regional nodes as a whole PTV after modified radical mastectomy, and observe acute toxicities following irradiation. Patients indicated for PMRT were eligible. Chest wall and supra/infraclavicular region +/−internal mammary nodes were contoured as a whole PTV on planning CT. A simplified linac IMRT plan was designed using either integrated full beams or two segments of half beams split at caudal edge of clavicle head. DVHs were used to evaluate plans. The acute toxicities were followed up regularly. Totally, 85 patients were enrolled. Of these, 45 had left-sided lesions, and 35 received IMN irradiation. Planning designs yielded 55 integrated and 30 segmented plans, with median number of beams of 8 (6–12). The integrated and segmented plans had similar conformity (1.41±0.14 vs. 1.47±0.15, p=0.053) and homogeneity indexes (0.13±0.01 vs. 0.14±0.02, p=0.069). The percent volume of PTV receiving >110% prescription dose was <5%. As compared to segmented plans, integrated plans typically increased V 5 of ipsilateral lung (p=0.005), and heart (p=0.001) in patients with left-sided lesions. Similarly, integrated plans had higher spinal cord D max (p=0.009), ipsilateral humeral head (p<0.001), and contralateral lung D mean (p=0.019). During follow-up, 36 (42%) were identified to have ≥ grade 2 radiation dermatitis (RD). Of these, 35 developed moist desquamation. The median time to onset of moist desquamation was 6 (4–7) weeks from start of RT. The sites of moist desquamation were most frequently occurred in anterior axillary

Gravitational field of spherical domain wall in higher dimension

Indian Academy of Sciences (India)

An exact solution of Einstein's equations is found describing the gravitational field of a spherical domain wall with nonvanishing stress component in the direction perpendicular to the plane of the wall. Also we have studied the motion of test particle around the domain wall.

Numerical approximation of flow in a symmetric channel with vibrating walls

Directory of Open Access Journals (Sweden)

Sváček P.

2010-12-01

Full Text Available In this paper the numerical solution of two dimensional fluid-structure interaction problem is addressed. The fluid motion is modelled by the incompressible unsteady Navier-Stokes equations. The spatial discretization by stabilized finite element method is used. The motion of the computational domain is treated with the aid of Arbitrary Lagrangian Eulerian (ALE method. The time-space problem is solved with the aid of multigrid method. The method is applied onto a problem of interaction of channel flow with moving walls, which models the air flow in the glottal region of the human vocal tract. The pressure boundary conditions and the effects of the isotropic and anisotropic mesh refinement are discussed. The numerical results are presented.

Near-Wall Turbulence Modelling of Rotating and Curved Shear Flows

Energy Technology Data Exchange (ETDEWEB)

Pettersson, Bjoern Anders

1997-12-31

This thesis deals with verification and refinement of turbulence models within the framework of the Reynolds-averaged approach. It pays special attention to modelling the near-wall region, where the turbulence is strongly non-homogeneous and anisotropic. It also studies in detail the effects associated with an imposed rotation of the reference frame or streamline curvature. The objective with near-wall turbulence closure modelling is to formulate a set of equations governing single point turbulence statistics, which can be solved in the region of the flow which extends to the wall. This is in contrast to the commonly adopted wall-function approach in which the wall-boundary conditions are replaced by matching conditions in the logarithmic region. The near-wall models allow more flexibility by not requiring any such universal behaviour. Assessment of the novel elliptic relaxation approach to model the proximity of a solid boundary reveals an encouraging potential used in conjunction with second-moment and eddy-viscosity closures. The most natural level of closure modelling to predict flows affected by streamline curvatures or an imposed rotation of the reference frame is at the second-moment closure (SMC) level. Although SMCs naturally accounts for the effects of system rotation, the usual application of a scalar dissipation rate equation is shown to require ad hoc corrections in some cases in order to give good results. The elliptic relaxation approach is also used in conjunction with non-linear pressure-strain models and very encouraging results are obtained for rotating flows. Rotational induced secondary motions are vital to predicting the effects of system rotation. Some severe weaknesses of non-linear pressure-strain models are also indicated. Finally, a modelling methodology for anisotropic dissipation in nearly homogeneous turbulence are proposed. 84 refs., 56 figs., 16 tabs.

The plasma-wall interaction region: a key low temperature plasma for controlled fusion

International Nuclear Information System (INIS)

Counsell, G F

2002-01-01

The plasma-wall interaction region of a fusion device provides the interface between the hot core plasma and the material surfaces. To obtain acceptably low levels of erosion from these surfaces requires most of the power leaving the core to be radiated. This is accomplished in existing devices by encouraging plasma detachment, in which the hot plasma arriving in the region is cooled by volume recombination and ion-neutral momentum transfer with a dense population of neutrals recycled from the surface. The result is a low temperature (1 eV e e >10 19 m -3 ) but weakly ionized (n 0 >10 20 m -3 , n e /n 0 <0.1) plasma found nowhere else in the fusion environment. This plasma provides many of the conditions found in industrial plasmas exploiting plasma chemistry and the presence of carbon in the region (in the form of carbon-fibre composite used in the plasma facing materials) can result in the formation of deposited hydrocarbon films. The plasma-wall interaction region is therefore among the most difficult in fusion to model, requiring an understanding of atomic, molecular and surface physics issues

Assessment of global and regional LV function obtained by quantitative gated SPECT using {sup 99m}Tc-tetrofosmin. Comparison with left ventricular cineangiography and echocardiography

Energy Technology Data Exchange (ETDEWEB)

Ban, Kazunobu; Nakajima, Toru; Aoki, Naoto; Abe, Sumihisa; Handa, Shunnosuke; Suzuki, Yutaka [Tokai Univ., Isehara, Kanagawa (Japan). School of Medicine

1998-11-01

The quantitative gated SPECT (QGS) software that has automatic edge detection algorithm of the left ventricle, is able to calculate LV volumes and visualize LV wall motion with perfusion throughout the cardiac cycle. We evaluated the reliability of global and regional LV function derived from QGS using {sup 99m}Tc-tetrofosmin by comparing with left ventricular cineangiography (LVG) and echocardiography (ECHO). In 22 cardiac patients, end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (LVEF) were calculated. Using cinematic display, regional LV wall motion were scored on a 3-point scale (1=normal, 2=hypokinesis, 3=akinesis; WMS). EDV, ESV and LVEF correlated well with those by LVG (p<0.001 for each). Correlation between WMS derived from QGS and ECHO was high (r=0.85, p<0.001). There was an inverse correlation between WMS and LVEF (r=0.77, p<0.001). In conclusion, QGS is useful to evaluate global LV function. Regional wall motion evaluated by QGS is good enough for clinical application. (author)

Examination of near-wall hindered Brownian diffusion of nanoparticles: Experimental comparison to theories by Brenner (1961) and Goldman et al. (1967)

International Nuclear Information System (INIS)

Choi, C. K.; Margraves, C. H.; Kihm, K. D.

2007-01-01

Multilayered distributions of hindered mean square displacement (MSD) for nanoparticles are measured in the near-wall region within 500 nm from the solid surface using total internal reflection fluorescence microscopy, an evanescent wave microscopic imaging technique. Examined particles are yellow-green (505/515) polystyrene fluorescent nanospheres of 100, 250, and 500 nm radii with a specific gravity of 1.055. To ensure the measurement accuracy, special care is taken to minimize photobleaching of fluorescent particles by adding neutral density filters to optimally reduce the excitation power. The experimental results for parallel MSDs to the solid surface validate the theory of hindered diffusion [A. J. Goldman, R. G. Cox, and H. Brenner, 'Slow viscous motion of a sphere parallel to a plane - I: Motion through a quiescent fluid', Chem. Eng. Sci. 22, 637 (1967)] of spheres based on viscous slow-down in the near-wall region. It is also reported that the effect of adding sodium chloride up to 10 mM to the solution has little effect on the parallel diffusive motion of the tested nanoparticles. Experimental evidence shows that normal MSDs, for submicroscopic charged nanoparticles, are substantially different from Einstein's 2DΔt due to the deterministic motion arising from electrostatic forces

PREFACE: Domain wall dynamics in nanostructures Domain wall dynamics in nanostructures

Science.gov (United States)

Marrows, C. H.; Meier, G.

2012-01-01

forms of ordered phases such as antiferromagnetism and ferroelectricity. We would like to thank the scientists from all over the world who happily agreed to contribute their latest results to this special issue, and the Journal of Physics: Condensed Matter staff for their help, patience and professionalism. In such a fast-moving field it is not possible to give a definitive account, and this special issue can be no more than a snapshot of the current state of knowledge regarding this topic. Nevertheless, we hope that this collection of papers is a useful resource for experienced workers in the field, forms a useful introduction to researchers early in their careers and inspires others in related areas of nanotechnology to enter into the study of domain dynamics in nanostructures. Domain wall dynamics in nanostructures contents Temperature estimation in a ferromagnetic Fe-Ni nanowire involving a current-driven domain wall motionA Yamaguchi, A Hirohata, T Ono and H Miyajima Magnetization reversal in magnetic nanostripes via Bloch wall formation M Zeisberger and R Mattheis Magnetic soft x-ray microscopy of the domain wall depinning process in permalloy magnetic nanowiresMi-Young Im, Lars Bocklage, Guido Meier and Peter Fischer Domain wall propagation in meso- and nanoscale ferroelectrics R G P McQuaid, M McMillen, L-W Chang, A Gruverman and J M Gregg Transverse and vortex domain wall structure in magnetic nanowires with uniaxial in-plane anisotropyM T Bryan, S Bance, J Dean, T Schrefl and D A Allwood The stochastic nature of the domain wall motion along high perpendicular anisotropy strips with surface roughness Eduardo Martinez Temperature-dependent dynamics of stochastic domain-wall depinning in nanowiresClemens Wuth, Peter Lendecke and Guido Meier Controlled pinning and depinning of domain walls in nanowires with perpendicular magnetic anisotropyTheo Gerhardt, André Drews and Guido Meier The interaction of transverse domain wallsBenjamin Krüger The increase of the

Boundary layer theory approach to the concentration layer adjacent to the ceiling wall of a hydrogen leakage: Axisymmetric impinging and far regions

Energy Technology Data Exchange (ETDEWEB)

El-Amin, M.F.; Kanayama, H. [Department of Mechanical Engineering, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)

2009-02-15

As hydrogen leaks into a partially open space with a ceiling wall, a boundary layer of hydrogen can be constructed under that wall due to the impingement on the wall and the buoyancy force. The resulting boundary layer can be divided into two regions, namely the stagnation-point region and the far region. When the geometry of the source of the hydrogen leak is circular, such as a pinhole or an o-ring, the behavior of leakage flow will be axisymmetric due to the resulting radial jet. In contrast, when the geometry of the source of the hydrogen leak is planar, such as a crack, the behavior of leakage flow will be planar due to the resulting planar jet. Previously, we studied the planar case in the context of both the stagnation-point flow region [El-Amin MF, Kanayama H. Boundary layer theory approach to the concentration layer adjacent to a ceiling wall at impinging region of a hydrogen leakage. Int J Hydrogen Energy 2008; 33(21): 6393-00] and the far region [El-Amin MF, Inoue M, Kanayama H. Boundary layer theory approach to the concentration layer adjacent to a ceiling wall of a hydrogen leakage: far region. Int J Hydrogen Energy 2008; 33(24):7642-7]. This paper is concerned with both the stagnation-point flow region and the far region of the axisymmetric concentration boundary layer adjacent to a ceiling wall. Flow in the stagnation-point region is treated as Hiemenz flow, while it is treated as Blasius flow in the far region. The current results are compared with the planar cases [El-Amin MF, Kanayama H. Boundary layer theory approach to the concentration layer adjacent to a ceiling wall at impinging region of a hydrogen leakage. Int J Hydrogen Energy 2008; 33(21): 6393-00; El-Amin MF, Inoue M, Kanayama H. Boundary layer theory approach to the concentration layer adjacent to a ceiling wall of a hydrogen leakage: far region. Int J Hydrogen Energy 2008; 33(24):7642-7] for both stagnation-point flow and far regions. Both momentum and concentration boundary layer

Determination of optimum insulation thicknesses of the external walls and roof (ceiling) for Turkey's different degree-day regions

International Nuclear Information System (INIS)

Sisman, Nuri; Kahya, Emin; Aras, Nil; Aras, Haydar

2007-01-01

The external walls and roof of a building are the interface between its interior and the outdoor environment. Insulation of the external walls and roof is the most cost-effective way of controlling the outside elements to make homes more comfortable. Although insulation is generally accepted as a factor increasing the building costs, with the calculations we have shown that this is not the case. Fuel consumption and operational costs are reduced by increasing the thickness of the external walls and roof (ceiling), despite an increase in the investment costs. According to Turkish Standard Number 825 (TS 825), there are four different degree-day (DD) regions, and the required heat loads for the buildings in these regions exhibit large differences. Therefore, a method based on costs is needed for the determination of optimum insulation thicknesses of different DD regions. In this study, optimum insulation thicknesses for different DD regions of Turkey, namely, Izmir (DD: 1450), Bursa (DD: 2203), Eskisehir (DD: 3215) and Erzurum (DD: 4856), have been determined for a lifetime of N years, maximizing the present worth value of annual energy savings for insulated external walls

The Importance of Spatiotemporal Information in Biological Motion Perception: White Noise Presented with a Step-like Motion Activates the Biological Motion Area.

Science.gov (United States)

Callan, Akiko; Callan, Daniel; Ando, Hiroshi

2017-02-01

Humans can easily recognize the motion of living creatures using only a handful of point-lights that describe the motion of the main joints (biological motion perception). This special ability to perceive the motion of animate objects signifies the importance of the spatiotemporal information in perceiving biological motion. The posterior STS (pSTS) and posterior middle temporal gyrus (pMTG) region have been established by many functional neuroimaging studies as a locus for biological motion perception. Because listening to a walking human also activates the pSTS/pMTG region, the region has been proposed to be supramodal in nature. In this study, we investigated whether the spatiotemporal information from simple auditory stimuli is sufficient to activate this biological motion area. We compared spatially moving white noise, having a running-like tempo that was consistent with biological motion, with stationary white noise. The moving-minus-stationary contrast showed significant differences in activation of the pSTS/pMTG region. Our results suggest that the spatiotemporal information of the auditory stimuli is sufficient to activate the biological motion area.

Level crossings, excess times, and transient plasma–wall interactions in fusion plasmas

Energy Technology Data Exchange (ETDEWEB)

Theodorsen, A., E-mail: audun.theodorsen@uit.no; Garcia, O. E., E-mail: odd.erik.garcia@uit.no [Department of Physics and Technology, UiT The Arctic University of Norway, N-9037 Tromsø (Norway)

2016-04-15

Based on a stochastic model for intermittent fluctuations in the boundary region of magnetically confined plasmas, an expression for the level crossing rate is derived from the joint distribution of the process and its derivative. From this the average time spent by the process above a certain threshold level is obtained. This provides novel predictions of plasma–wall interactions due to transient transport events associated with a radial motion of blob-like structures in the scrape-off layer.

Empirical ground-motion relations for subduction-zone earthquakes and their application to Cascadia and other regions

Science.gov (United States)

Atkinson, G.M.; Boore, D.M.

2003-01-01

Ground-motion relations for earthquakes that occur in subduction zones are an important input to seismic-hazard analyses in many parts of the world. In the Cascadia region (Washington, Oregon, northern California, and British Columbia), for example, there is a significant hazard from megathrust earthquakes along the subduction interface and from large events within the subducting slab. These hazards are in addition to the hazard from shallow earthquakes in the overlying crust. We have compiled a response spectra database from thousands of strong-motion recordings from events of moment magnitude (M) 5-8.3 occurring in subduction zones around the world, including both interface and in-slab events. The 2001 M 6.8 Nisqually and 1999 M 5.9 Satsop earthquakes are included in the database, as are many records from subduction zones in Japan (Kyoshin-Net data), Mexico (Guerrero data), and Central America. The size of the database is four times larger than that available for previous empirical regressions to determine ground-motion relations for subduction-zone earthquakes. The large dataset enables improved determination of attenuation parameters and magnitude scaling, for both interface and in-slab events. Soil response parameters are also better determined by the data. We use the database to develop global ground-motion relations for interface and in-slab earthquakes, using a maximum likelihood regression method. We analyze regional variability of ground-motion amplitudes across the global database and find that there are significant regional differences. In particular, amplitudes in Cascadia differ by more than a factor of 2 from those in Japan for the same magnitude, distance, event type, and National Earthquake Hazards Reduction Program (NEHRP) soil class. This is believed to be due to regional differences in the depth of the soil profile, which are not captured by the NEHRP site classification scheme. Regional correction factors to account for these differences are

Uniformly Processed Strong Motion Database for Himalaya and Northeast Region of India

Science.gov (United States)

Gupta, I. D.

2018-03-01

This paper presents the first uniformly processed comprehensive database on strong motion acceleration records for the extensive regions of western Himalaya, northeast India, and the alluvial plains juxtaposing the Himalaya. This includes 146 three components of old analog records corrected for the instrument response and baseline distortions and 471 three components of recent digital records corrected for baseline errors. The paper first provides a background of the evolution of strong motion data in India and the seismotectonics of the areas of recording, then describes the details of the recording stations and the contributing earthquakes, which is finally followed by the methodology used to obtain baseline corrected data in a uniform and consistent manner. Two different schemes in common use for baseline correction are based on the application of the Ormsby filter without zero pads (Trifunac 1971) and that on the Butterworth filter with zero pads at the start as well as at the end (Converse and Brady 1992). To integrate the advantages of both the schemes, Ormsby filter with zero pads at the start only is used in the present study. A large number of typical example results are presented to illustrate that the methodology adopted is able to provide realistic velocity and displacement records with much smaller number of zero pads. The present strong motion database of corrected acceleration records will be useful for analyzing the ground motion characteristics of engineering importance, developing prediction equations for various strong motion parameters, and calibrating the seismological source model approach for ground motion simulation for seismically active and risk prone areas of India.

THE PROPER MOTIONS OF THE DOUBLE RADIO SOURCE n IN THE ORION BN/KL REGION

International Nuclear Information System (INIS)

Rodríguez, Luis F.; Loinard, Laurent; Zapata, Luis; Lizano, Susana; Dzib, Sergio A.; Menten, Karl M.; Gómez, Laura

2017-01-01

We have extended the time baseline for observations of the proper motions of radio sources in the Orion BN/KL region from 14.7 to 22.5 years. We present improved determinations for the sources BN and I. In addition, we address the proper motions of the double radio source n, that have been questioned in the literature. We confirm that all three sources are moving away at transverse velocities of tens of kilometers per second from a region in-between them, where they were located about 500 years ago. Source n exhibits a new component that we interpret as due to a one-sided ejection of free–free emitting plasma that took place after 2006.36. We used the highly accurate relative proper motions between sources BN and I to determine that their closest separation took place in the year 1475 ± 6, when they were within ∼100 au or less from each other in the plane of the sky.

THE PROPER MOTIONS OF THE DOUBLE RADIO SOURCE n IN THE ORION BN/KL REGION

Energy Technology Data Exchange (ETDEWEB)

Rodríguez, Luis F.; Loinard, Laurent; Zapata, Luis; Lizano, Susana [Instituto de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán, México (Mexico); Dzib, Sergio A.; Menten, Karl M. [Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Gómez, Laura, E-mail: l.rodriguez@crya.unam.mx [Joint ALMA Observatory, Alonso de Córdoba 3107, Vitacura, Santiago (Chile)

2017-01-10

We have extended the time baseline for observations of the proper motions of radio sources in the Orion BN/KL region from 14.7 to 22.5 years. We present improved determinations for the sources BN and I. In addition, we address the proper motions of the double radio source n, that have been questioned in the literature. We confirm that all three sources are moving away at transverse velocities of tens of kilometers per second from a region in-between them, where they were located about 500 years ago. Source n exhibits a new component that we interpret as due to a one-sided ejection of free–free emitting plasma that took place after 2006.36. We used the highly accurate relative proper motions between sources BN and I to determine that their closest separation took place in the year 1475 ± 6, when they were within ∼100 au or less from each other in the plane of the sky.

Role of wall-attached structures in the interface of the quiescent core region in turbulent pipe flow

Science.gov (United States)

Yang, Jongmin; Hwang, Jinyul; Sung, Hyung Jin

2017-11-01

The effects of low- and high-speed structures on the interface of the quiescent core region are explored using direct numerical simulation data of turbulent pipe flow. The quiescent core region is a uniform momentum zone located at the center of the pipe flow, which contains the highest streamwise momentum with a low level of turbulence. The interface of the quiescent core region can be identified from the probability density function of the streamwise modal velocity. In the vicinity of the interface of the quiescent core region, the streamwise velocity changes abruptly. The abrupt jump in velocity causes an increase of the velocity gradient. The interface of the quiescent core region is similar to the laminar superlayer in turbulent/non-turbulent interface. The interface of the quiescent core region contains the low- and high-speed structures. They can be classified into wall-attached and detached structures depending on the distance between the structures and the wall. The influence of the detached structures accounted for most of the number of detected structures is negligible due to its small volume. Conversely, the wall-attached structures adjacent to the interface have a huge influence on the statistical amount of the interface, such as entrainment characteristics. This work was supported by the Creative Research Initiatives (No. 2017-013369) program of the National Research Foundation of Korea (MSIP).

Regional ejection fraction: a quantitative radionuclide index of regional left ventricular performance

International Nuclear Information System (INIS)

Maddox, D.E.; Wynne, J.; Uren, R.; Parker, J.A.; Idoine, J.; Siegel, L.C.; Neill, J.M.; Cohn, P.F.; Holman, B.L.

1979-01-01

Left ventricular regional ejection fractions were derived from background-corrected, time-activity curves in 43 patients assessed by both gated equilibrium radionuclide angiocardiography and left ventricular contrast angiography. From a single, modified left anterior oblique projection, the regional change in background corrected counts was determined in each of three anatomic regions. The normal range for regional radionuclide ejection fraction was determined in 10 patients with normal contrast ventriculograms and without obstructive coronary artery disease at coronary arteriography. Regional ejection fraction was compared with percent segmental axis shortening and extent of akinetic segments in corresponding regions of the contrast ventriculogram. Radionuclide and roentgenographic methods were in agreement as to the presence or absence of abnormal wall motion in 83 of 99 left ventricular regions (84%) in 33 patients evaluated prospectively. Comparison of regional ejection fraction demonstrated significant differences between regions with roentgenographically determined normokinesis hypokinesis, and akinesis. We conclude that the left ventricular regional ejection fraction provides a reliable quantitative assessment of regional left ventricular performance

Development of a rocking R/C shear wall system implementing repairable structural fuses

Science.gov (United States)

Parsafar, Saeed; Moghadam, Abdolreza S.

2017-09-01

In the last decades, the concept of earthquake resilient structural systems is becoming popular in which the rocking structure is considered as a viable option for buildings in regions of high seismicity. To this end, a novel wall-base connection based on the " repairable structure" approach is proposed and evaluated. The proposed system is made of several steel plates and high strength bolts act as a friction connection. To achieve the desired rocking motion in the proposed system, short-slotted holes are used in vertical directions for connecting the steel plates to the shear wall (SW). The experimental and numerical studies were performed using a series of displacement control quasi-static cyclic tests on a reference model and four different configurations of the proposed connection installed at the wall corners. The seismic response of the proposed system is compared to the conventional SW in terms of energy dissipation and damage accumulation. In terms of energy dissipation, the proposed system depicted better performance with 95% more energy dissipation capability compared to conventional SW. In terms of damage accumulation, the proposed SW system is nearly undamaged compared to the conventional wall system, which was severely damaged at the wall-base region. Overall, the introduced concept presents a feasible solution for R/C structures when a low-damage design is targeted, which can improve the seismic performance of the structural system significantly.

Auditory motion in the sighted and blind: Early visual deprivation triggers a large-scale imbalance between auditory and "visual" brain regions.

Science.gov (United States)

Dormal, Giulia; Rezk, Mohamed; Yakobov, Esther; Lepore, Franco; Collignon, Olivier

2016-07-01

How early blindness reorganizes the brain circuitry that supports auditory motion processing remains controversial. We used fMRI to characterize brain responses to in-depth, laterally moving, and static sounds in early blind and sighted individuals. Whole-brain univariate analyses revealed that the right posterior middle temporal gyrus and superior occipital gyrus selectively responded to both in-depth and laterally moving sounds only in the blind. These regions overlapped with regions selective for visual motion (hMT+/V5 and V3A) that were independently localized in the sighted. In the early blind, the right planum temporale showed enhanced functional connectivity with right occipito-temporal regions during auditory motion processing and a concomitant reduced functional connectivity with parietal and frontal regions. Whole-brain searchlight multivariate analyses demonstrated higher auditory motion decoding in the right posterior middle temporal gyrus in the blind compared to the sighted, while decoding accuracy was enhanced in the auditory cortex bilaterally in the sighted compared to the blind. Analyses targeting individually defined visual area hMT+/V5 however indicated that auditory motion information could be reliably decoded within this area even in the sighted group. Taken together, the present findings demonstrate that early visual deprivation triggers a large-scale imbalance between auditory and "visual" brain regions that typically support the processing of motion information. Copyright © 2016 Elsevier Inc. All rights reserved.

Cine MR imaging assessment of regional left ventricular systolic wall thickening in patients with remote myocardial infarction

International Nuclear Information System (INIS)

Pfugfelder, P.; White, R.D.; Sechtem, U.; Gould, R.G.; Higgins, C.B.

1986-01-01

Cine MR imaging, a new rapid imaging technique, was used to acquire transverse images of the heart at a rate of 16-30 frames per cardiac cycle. Left ventricular wall thickness was measured at end diastole and end systole in six regions in the midventricular section of 13 healthy subjects and seven patients with previously documented myocardial infarction. Mean percent systolic wall thickening (%SWT) was 51% +- 26% in healthy subjects. In patients, %SWT was -8% +- 22% in the infarct zone and 42% +- 22% in the normal myocardium. In addition to the qualitative information derived from the cinematic display, determination of regional %SWT by cine-MR imaging may be useful for quantifying regional left ventricular dysfunction

Small scale structure in the wall region of a turbulent boundary layer

International Nuclear Information System (INIS)

Bogar, T.J.

1975-01-01

This paper is a report of the construction and application of an extremely small hot-wire X-probe (typical dimensions of 100 μ) to the measurement of Reynolds stress in the wall region of the turbulent boundary layer of a flat plate at high Reynolds number (Re/sub theta/ = 11,300). In the present flow, the size of the probe corresponds to a dimensionless length based on wall parameters of lu/sub tau//ν = 3. Probe construction methods are described. The Wyngaard-Lumley constant temperature anemometer used to heat the wire is analyzed, and a direct acoustical frequency calibration of the wire is made. This calibration shows the small wire to have uniform frequency response to 15 kHz. A novel calibration technique is employed using a high speed, digital mini-computer to determine the velocity in the stream direction and in a direction normal to the wall by matching the unique voltage pairs produced by the X-wire array in a turbulent flow to the voltage pairs produced when the probe is exposed to a known uniform flow inclined at various angles

Regional Characterization of the Crust in Metropolitan Areas for Prediction of Strong Ground Motion

Science.gov (United States)

Hirata, N.; Sato, H.; Koketsu, K.; Umeda, Y.; Iwata, T.; Kasahara, K.

2003-12-01

Introduction: After the 1995 Kobe earthquake, the Japanese government increased its focus and funding of earthquake hazards evaluation, studies of man-made structures integrity, and emergency response planning in the major urban centers. A new agency, the Ministry of Education, Science, Sports and Culture (MEXT) has started a five-year program titled as Special Project for Earthquake Disaster Mitigation in Urban Areas (abbreviated to Dai-dai-toku in Japanese) since 2002. The project includes four programs: I. Regional characterization of the crust in metropolitan areas for prediction of strong ground motion. II. Significant improvement of seismic performance of structure. III. Advanced disaster management system. IV. Investigation of earthquake disaster mitigation research results. We will present the results from the first program conducted in 2002 and 2003. Regional Characterization of the Crust in Metropolitan Areas for Prediction of Strong Ground Motion: A long-term goal is to produce map of reliable estimations of strong ground motion. This requires accurate determination of ground motion response, which includes a source process, an effect of propagation path, and near surface response. The new five-year project was aimed to characterize the "source" and "propagation path" in the Kanto (Tokyo) region and Kinki (Osaka) region. The 1923 Kanto Earthquake is one of the important targets to be addressed in the project. The proximity of the Pacific and Philippine Sea subducting plates requires study of the relationship between earthquakes and regional tectonics. This project focuses on identification and geometry of: 1) Source faults, 2) Subducting plates and mega-thrust faults, 3) Crustal structure, 4) Seismogenic zone, 5) Sedimentary basins, 6) 3D velocity properties We have conducted a series of seismic reflection and refraction experiment in the Kanto region. In 2002 we have completed to deploy seismic profiling lines in the Boso peninsula (112 km) and the

Evaluation of a Thermoplastic Immobilization System for Breast and Chest Wall Radiation Therapy

International Nuclear Information System (INIS)

Strydhorst, Jared H.; Caudrelier, Jean-Michel; Clark, Brenda G.; Montgomery, Lynn A.; Fox, Greg; MacPherson, Miller S.

2011-01-01

We report on the impact of a thermoplastic immobilization system on intra- and interfraction motion for patients undergoing breast or chest wall radiation therapy. Patients for this study were treated using helical tomotherapy. All patients were immobilized using a thermoplastic shell extending from the shoulders to the ribcage. Intrafraction motion was assessed by measuring maximum displacement of the skin, heart, and chest wall on a pretreatment 4D computed tomography, while inter-fraction motion was inferred from patient shift data arising from daily image guidance procedures on tomotherapy. Using thermoplastic immobilization, the average maximum motion of the external contour was 1.3 ± 1.6 mm, whereas the chest wall was found to be 1.6 ± 1.9 mm. The day-to-day setup variation was found to be large, with random errors of 4.0, 12.0, and 4.5 mm in the left-right, superior-inferior, and anterior-posterior directions, respectively, and the standard deviations of the systematic errors were found to be 2.7, 9.8, and 4.1 mm. These errors would be expected to dominate any respiratory motion but can be mitigated by daily online image guidance. Using thermoplastic immobilization can effectively reduce respiratory motion of the chest wall and external contour, but these gains can only be realized if daily image guidance is used.

Non-invasive evaluation of regional function of the left ventricle

International Nuclear Information System (INIS)

Schad, N.; Nickel, O.

1980-01-01

Assessment of regional left ventricular function with first pass angiocardiography in the RAO view almost entirely depends on high image statistics, accurate border definition and background subtraction, as well as an analysis of so called functional images which regionally measure and illustrate functional change during heart action. During first bolus transit the multicrystal camera gives an average of 300,000 cts/sec allowing precise border definition because of steepness of count changes at the LV-border. A varying background adjacent to each border point and also over the LV is subtracted. Measurements of segmental hemiaxis shortening and of zonal ejection fractions in the three zones supplied by the major coronary arteries have been performed. Clinical applications comprise examinations at rest, peak exercise, after nitroglycerin administration and after bypass graft surgery. Wall motion measured by means of hemiaxis shortening (210 segments) showed good correlation with angiocardiography in 91% of segments with normokinesis, in 90% asynergic and 88% of hypokinetic segments. Functional images corrected false negativ and false positiv wall motion measurements. In patients after myocardial infarction, there was (after NTG-administration) a significant increase in hemiaxis shortening in asynergic segment, but not in dyskinesias. Exercise studies in patients with wall motion disorders showed a significantly higher increase in global ejection fraction in patients with resting EF-values and 58% than above that value. Zonal ejection fractions after bypass surgery showed an average increase of 6.4 points if complete vascularization was performed, but no zonal increase or decrease when vascularization was incomplete or the zone included a previous myocardial infarction. (orig.) [de

Comparison of Kalman-filter-based approaches for block matching in arterial wall motion analysis from B-mode ultrasound

International Nuclear Information System (INIS)

Gastounioti, A; Stoitsis, J; Nikita, K S; Golemati, S

2011-01-01

Block matching (BM) has been previously used to estimate motion of the carotid artery from B-mode ultrasound image sequences. In this paper, Kalman filtering (KF) was incorporated in this conventional method in two distinct scenarios: (a) as an adaptive strategy, by renewing the reference block and (b) by renewing the displacements estimated by BM or adaptive BM. All methods resulting from combinations of BM and KF with the two scenarios were evaluated on synthetic image sequences by computing the warping index, defined as the mean squared error between the real and estimated displacements. Adaptive BM, followed by an update through the second scenario at the end of tracking, ABM K F-K2, minimized the warping index and yielded average displacement error reductions of 24% with respect to BM. The same method decreased estimation bias and jitter over varying center frequencies by 30% and 64%, respectively, with respect to BM. These results demonstrated the increased accuracy and robustness of ABM K F-K2 in motion tracking of the arterial wall from B-mode ultrasound images, which is crucial in the study of mechanical properties of normal and diseased arterial segments

Parkinson-related changes of activation in visuomotor brain regions during perceived forward self-motion.

Directory of Open Access Journals (Sweden)

Anouk van der Hoorn

Full Text Available Radial expanding optic flow is a visual consequence of forward locomotion. Presented on screen, it generates illusionary forward self-motion, pointing at a close vision-gait interrelation. As particularly parkinsonian gait is vulnerable to external stimuli, effects of optic flow on motor-related cerebral circuitry were explored with functional magnetic resonance imaging in healthy controls (HC and patients with Parkinson's disease (PD. Fifteen HC and 22 PD patients, of which 7 experienced freezing of gait (FOG, watched wide-field flow, interruptions by narrowing or deceleration and equivalent control conditions with static dots. Statistical parametric mapping revealed that wide-field flow interruption evoked activation of the (pre-supplementary motor area (SMA in HC, which was decreased in PD. During wide-field flow, dorsal occipito-parietal activations were reduced in PD relative to HC, with stronger functional connectivity between right visual motion area V5, pre-SMA and cerebellum (in PD without FOG. Non-specific 'changes' in stimulus patterns activated dorsolateral fronto-parietal regions and the fusiform gyrus. This attention-associated network was stronger activated in HC than in PD. PD patients thus appeared compromised in recruiting medial frontal regions facilitating internally generated virtual locomotion when visual motion support falls away. Reduced dorsal visual and parietal activations during wide-field optic flow in PD were explained by impaired feedforward visual and visuomotor processing within a magnocellular (visual motion functional chain. Compensation of impaired feedforward processing by distant fronto-cerebellar circuitry in PD is consistent with motor responses to visual motion stimuli being either too strong or too weak. The 'change'-related activations pointed at covert (stimulus-driven attention.

Unwinding motion of a twisted active region filament

Energy Technology Data Exchange (ETDEWEB)

Yan, X. L.; Xue, Z. K.; Kong, D. F. [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Liu, J. H. [Department of Physics, Shijiazhuang University, Shijiazhuang 050035 (China); Xu, C. L. [Yunnan Normal University, Kunming 650092 (China)

2014-12-10

To better understand the structures of active region filaments and the eruption process, we study an active region filament eruption in active region NOAA 11082 in detail on 2010 June 22. Before the filament eruption, the opposite unidirectional material flows appeared in succession along the spine of the filament. The rising of the filament triggered two B-class flares at the upper part of the filament. As the bright material was injected into the filament from the sites of the flares, the filament exhibited a rapid uplift accompanying the counterclockwise rotation of the filament body. From the expansion of the filament, we can see that the filament consisted of twisted magnetic field lines. The total twist of the filament is at least 5π obtained by using a time slice method. According to the morphology change during the filament eruption, it is found that the active region filament was a twisted flux rope and its unwinding motion was like a solar tornado. We also find that there was a continuous magnetic helicity injection before and during the filament eruption. It is confirmed that magnetic helicity can be transferred from the photosphere to the filament. Using the extrapolated potential fields, the average decay index of the background magnetic fields over the filament is 0.91. Consequently, these findings imply that the mechanism of solar filament eruption could be due to the kink instability and magnetic helicity accumulation.

Spin Hall driven domain wall motion in magnetic bilayers coupled by a magnetic oxide interlayer

Science.gov (United States)

Liu, Yang; Furuta, Masaki; Zhu, Jian-Gang Jimmy

2018-05-01

mCell, previously proposed by our group, is a four-terminal magnetoresistive device with isolated write- and read-paths for all-spin logic and memory applications. A mCell requires an electric-insulating magnetic layer to couple the spin Hall driven write-path to the magnetic free layer of the read-path. Both paths are magnetic layers with perpendicular anisotropy and their perpendicularly oriented magnetization needs to be maintained with this insertion layer. We have developed a magnetic oxide (FeOx) insertion layer to serve for these purposes. We show that the FeOx insertion layer provides sufficient magnetic coupling between adjacent perpendicular magnetic layers. Resistance measurement shows that this magnetic oxide layer can act as an electric-insulating layer. In addition, spin Hall driven domain wall motion in magnetic bi-layers coupled by the FeOx insertion layer is significantly enhanced compared to that in magnetic single layer; it also requires low voltage threshold that poses possibility for power-efficient device applications.

Impact of patient motion on myocardial perfusion SPECT

International Nuclear Information System (INIS)

Huang Kemin; Feng Yanlin; He Xiaohong; Wen Guanghua; Yu Fengwen; Liu Shusheng; Liu Dejun; Yuan Jianwei; Yang Ming

2008-01-01

Objective: It is well known that patient motion may cause artifacts in myocardial SPECT images and affect clinical diagnosis. The aim of the study was to evaluate the effects of motion on quality and semi-quantitative results of myocardial perfusion images. Methods: Six healthy volunteers un- derwent myocardial perfusion SPECT. The raw data in each case was manually shifted 1-6 frames and 1 4 pixels, respectively by using the motion correction software. The shifted raw data were then reconstructed. A semi-quantitative software was used to assess the myocardial perfusion of left ventricle. The quality and semi-quantitative results of the tomographic images reconstructed from the raw data with and without motion were compared and analyzed. SPSS 12.0 was used for data analysis. Results: There was no visible artifact and semi-quantitative difference on the data with 1 frame and (or) 1 pixel shift when compared with the original data without shift. The image artifacts became significantly deteriorated when the number of flame and (or) pixel shift was increased. In general, the image artifact of inferior and posterior wall was related to the upward shift, and that of anterior and infero-posterior wall was related to the downward shift, that of septal, anterior, infero-postefior wall and apex was related to right-ward shift, and the septal and infero-posterior wall was related to the left-ward shift. The differences along the x-axis shift were more prominent than that of the y-axis (t=2.848, P<0.01), and the differences in the downward and rightward shift were more severe than the upward and leftward shift (t=2.941, 6.598; all P<0.01), respectively. Conclusions: Image artifacts became significant when there was motion induced by manual shift of more than one flame and (or) one pixel. Different motion directions were closely related to different segments of left ventricle. (authors)

Motion of the esophagus due to cardiac motion.

Directory of Open Access Journals (Sweden)

Jacob Palmer

Full Text Available When imaging studies (e.g. CT are used to quantify morphological changes in an anatomical structure, it is necessary to understand the extent and source of motion which can give imaging artifacts (e.g. blurring or local distortion. The objective of this study was to assess the magnitude of esophageal motion due to cardiac motion. We used retrospective electrocardiogram-gated contrast-enhanced computed tomography angiography images for this study. The anatomic region from the carina to the bottom of the heart was taken at deep-inspiration breath hold with the patients' arms raised above their shoulders, in a position similar to that used for radiation therapy. The esophagus was delineated on the diastolic phase of cardiac motion, and deformable registration was used to sequentially deform the images in nearest-neighbor phases among the 10 cardiac phases, starting from the diastolic phase. Using the 10 deformation fields generated from the deformable registration, the magnitude of the extreme displacements was then calculated for each voxel, and the mean and maximum displacement was calculated for each computed tomography slice for each patient. The average maximum esophageal displacement due to cardiac motion for all patients was 5.8 mm (standard deviation: 1.6 mm, maximum: 10.0 mm in the transverse direction. For 21 of 26 patients, the largest esophageal motion was found in the inferior region of the heart; for the other patients, esophageal motion was approximately independent of superior-inferior position. The esophagus motion was larger at cardiac phases where the electrocardiogram R-wave occurs. In conclusion, the magnitude of esophageal motion near the heart due to cardiac motion is similar to that due to other sources of motion, including respiratory motion and intra-fraction motion. A larger cardiac motion will result into larger esophagus motion in a cardiac cycle.

A kinematic approach for efficient and robust simulation of the cardiac beating motion.

Directory of Open Access Journals (Sweden)

Takashi Ijiri

Full Text Available Computer simulation techniques for cardiac beating motions potentially have many applications and a broad audience. However, most existing methods require enormous computational costs and often show unstable behavior for extreme parameter sets, which interrupts smooth simulation study and make it difficult to apply them to interactive applications. To address this issue, we present an efficient and robust framework for simulating the cardiac beating motion. The global cardiac motion is generated by the accumulation of local myocardial fiber contractions. We compute such local-to-global deformations using a kinematic approach; we divide a heart mesh model into overlapping local regions, contract them independently according to fiber orientation, and compute a global shape that satisfies contracted shapes of all local regions as much as possible. A comparison between our method and a physics-based method showed that our method can generate motion very close to that of a physics-based simulation. Our kinematic method has high controllability; the simulated ventricle-wall-contraction speed can be easily adjusted to that of a real heart by controlling local contraction timing. We demonstrate that our method achieves a highly realistic beating motion of a whole heart in real time on a consumer-level computer. Our method provides an important step to bridge a gap between cardiac simulations and interactive applications.

Dressed Domain Walls and holography

International Nuclear Information System (INIS)

Grisa, Luca; Pujolas, Oriol

2008-01-01

The cutoff version of the AdS/CFT correspondence states that the Randall Sundrum scenario is dual to a Conformal Field Theory (CFT) coupled to gravity in four dimensions. The gravitational field produced by relativistic Domain Walls can be exactly solved in both sides of the correspondence, and thus provides one further check of it. We show in the two sides that for the most symmetric case, the wall motion does not lead to particle production of the CFT fields. Still, there are nontrivial effects. Due to the trace anomaly, the CFT effectively renormalizes the Domain Wall tension. On the five dimensional side, the wall is a codimension 2 brane localized on the Randall-Sundrum brane, which pulls the wall in a uniform acceleration. This is perceived from the brane as a Domain Wall with a tension slightly larger than its bare value. In both cases, the deviation from General Relativity appears at nonlinear level in the source, and the leading corrections match to the numerical factors.

Extending Counter-streaming Motion from an Active Region Filament to a Sunspot Light Bridge

Science.gov (United States)

Wang, Haimin; Liu, Rui; Li, Qin; Liu, Chang; Deng, Na; Xu, Yan; Jing, Ju; Wang, Yuming; Cao, Wenda

2018-01-01

We analyze high-resolution observations from the 1.6 m telescope at Big Bear Solar Observatory that cover an active region filament. Counter-streaming motions are clearly observed in the filament. The northern end of the counter-streaming motions extends to a light bridge, forming a spectacular circulation pattern around a sunspot, with clockwise motion in the blue wing and counterclockwise motion in the red wing, as observed in the Hα off-bands. The apparent speed of the flow is around 10–60 km s‑1 in the filament, decreasing to 5–20 km s‑1 in the light bridge. The most intriguing results are the magnetic structure and the counter-streaming motions in the light bridge. Similar to those in the filament, the magnetic fields show a dominant transverse component in the light bridge. However, the filament is located between opposed magnetic polarities, while the light bridge is between strong fields of the same polarity. We analyze the power of oscillations with the image sequences of constructed Dopplergrams, and find that the filament’s counter-streaming motion is due to physical mass motion along fibrils, while the light bridge’s counter-streaming motion is due to oscillation in the direction along the line-of-sight. The oscillation power peaks around 4 minutes. However, the section of the light bridge next to the filament also contains a component of the extension of the filament in combination with the oscillation, indicating that some strands of the filament are extended to and rooted in that part of the light bridge.

Analysis of the relationship between myocardial viability and regional left ventricular wall motion

International Nuclear Information System (INIS)

Furutani, Yuhji; Ozaki, Masaharu; Yamamoto, Takeshi; Sato, Shinichi; Saiki, Atsushi; Kusukawa, Reizo

1993-01-01

Myocardial viability was determined by using postsystolic shortening (PSS) as an index, as obtained by cardiac blood pool scintigraphy with Tc-99m HSA. The findings were compared with those of thallium-201 myocardial SPECT. The study population was comparised of 41 patients with single blood vessel disease in the left anterior descending artery (34 with old myocardial infarction and 7 with effort angina pectoris). Left ventricular area was divided into 6 segments, and global and regional left ventricular blood volume curves were obtained. Delayed end-systole was the most common in the apex (41%), followed by the upper septum (37%) and lower septum (10%). PSS resulting from delayed end-systole was seen in 36 areas. PSS/end-diastolic volume (EDV) and PSS/systolic volume (SV) were obtained by adjusting end-diastolic and stroke counts, respectively. Thallium-201 myocardial SPECT images were divided into 5 segments to obtain defect score (DS) for visual Tl uptake. Both PSS/EDV and PSS/SV were greater in association with more delayed end-systole, greater DS, and lower reginal ejection fraction. Areas showing greater PSS were associated with less myocardial viability, as observed on Tl myocardial SPECT images. Thus, PSS seemed to reflect the degree of myocardial necrosis within the region of interest. (N.K.)

The dust motion inside the magnetized sheath - The effect of drag forces

International Nuclear Information System (INIS)

Pandey, B. P.; Samarian, A.; Vladimirov, S. V.

2010-01-01

The isolated charged dust inside the magnetized plasma sheath moves under the influence of the electron and ion drag force and the sheath electrostatic field. The charge on the dust is a function of its radius as well as the value of the ambient sheath potential. It is shown that the charge on the dust determines its trajectory and dust performs the spiraling motion inside the sheath. The location of the turning spiral is determined by the number of negative charge on the dust, which in turn is a function of the dust radius. The back and forth spiraling motion finally causes the dust to move in a small, narrow region of the sheath. For a bigger dust particle, the dust moves closer to the sheath presheath boundary suggesting that the bigger grains, owing to the strong repulsion between the wall and dust, will be unable to travel inside the sheath. Only small, micron-sized grains can travel closer to the wall before repulsion pushes it back toward the plasma-sheath boundary. The temporal behavior of the spiraling dust motion appears like a damped harmonic oscillation, suggesting that the plasma drag force causes dissipation of the electrostatic energy. However, after initial damping, the grain keeps oscillating although with much smaller amplitude. The possible application of the present results to the ongoing sheath experiments is discussed.

Chemical and structural analysis of Eucalyptus globulus and E. camaldulensis leaf cuticles: a lipidized cell wall region

Directory of Open Access Journals (Sweden)

Paula eGuzmán

2014-09-01

Full Text Available The plant cuticle has traditionally been conceived as an independent hydrophobic layer that covers the external epidermal cell wall. Due to its complexity, the existing relationship between cuticle chemical composition and ultra-structure remains unclear to date. This study aimed to examine the link between chemical composition and structure of isolated, adaxial leaf cuticles of Eucalyptus camaldulensis and E. globulus by the gradual extraction and identification of lipid constituents (cutin and soluble lipids, coupled to spectroscopic and microscopic analyses. The soluble compounds and cutin monomers identified could not be assigned to a concrete internal cuticle ultra-structure. After cutin depolymerization, a cellulose network resembling the cell wall was observed, with different structural patterns in the regions ascribed to the cuticle proper and cuticular layer, respectively. Our results suggest that the current cuticle model should be revised, stressing the presence and major role of cell wall polysaccharides. It is concluded that the cuticle may be interpreted as a modified cell wall region which contains additional lipids. The major heterogeneity of the plant cuticle makes it difficult to establish a direct link between cuticle chemistry and structure with the existing methodologies.

Domain wall kinetics of lithium niobate single crystals near the hexagonal corner

Energy Technology Data Exchange (ETDEWEB)

Choi, Ju Won [Department of Physics and Photon Science, Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of); Ko, Do-Kyeong [Department of Physics and Photon Science, Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of); Advanced Photonics Research Institute, GIST, 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of); Yu, Nan Ei, E-mail: neyu@gist.ac.kr, E-mail: jhro@pnu.edu [Advanced Photonics Research Institute, GIST, 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of); Kitamura, Kenji [National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Ro, Jung Hoon, E-mail: neyu@gist.ac.kr, E-mail: jhro@pnu.edu [Department of Biomedical Engineering, School of Medicine, Pusan National University, Busan 602-739 (Korea, Republic of)

2015-03-09

A mesospheric approach based on a simple microscopic 2D Ising model in a hexagonal lattice plane is proposed to explain macroscopic “asymmetric in-out domain wall motion” observation in the (0001) plane of MgO-doped stoichiometric lithium niobate. Under application of an electric field that was higher than the conventional coercive field (E{sub c}) to the ferroelectric crystal, a natural hexagonal domain was obtained with walls that were parallel to the Y-axis of the crystal. When a fraction of the coercive field of around 0.1E{sub c} is applied in the reverse direction, this hexagonal domain is shrunk (moved inward) from the corner site into a shape with a corner angle of around 150° and 15° wall slopes to the Y-axis. A flipped electric field of 0.15E{sub c} is then applied to recover the natural hexagonal shape, and the 150° corner shape changes into a flat wall with 30° slope (moved outward). The differences in corner domain shapes between inward and outward domain motion were analyzed theoretically in terms of corner and wall site energies, which are described using the domain corner angle and wall slope with respect to the crystal Y-axis, respectively. In the inward domain wall motion case, the energy levels of the evolving 150° domain corner and 15° slope walls are most competitive, and could co-exist. In the outward case, the energy levels of corners with angles >180° are highly stable when compared with the possible domain walls; only a flat wall with 30° slope to the Y-axis is possible during outward motion.

The predictive value of 201Tl rest-redistribution and 18F-fluorodeoxyglucose SPECT for wall motion recovery after recent reperfused myocardial infarction.

Science.gov (United States)

González, Patricio; Massardo, Teresa; Coll, Claudia; Humeres, Pamela; Sierralta, Paulina; Jofré, M Josefina; Yovanovich, Jorge; Aramburu, Ivonne; Brugère, Solange; Chamorro, Hernán

2004-04-01

201Tl and 18F-FDG are useful for acute myocardial infarction (MI) assessment. The goal of this study was to compare their predictive value for wall motion recovery in the culprit area after a recent reperfused MI using SPECT technique. Forty-one patients (mean age: 56 +/- 12 years) were included, 81% of them male; all were studied within 1-24 days post MI. They underwent angioplasty in 27 cases (12 primary); bypass grafting in 10 cases and successful thrombolysis in 4. SPECT 201Tl injected at rest and redistribution (R-R) and also 18F-FDG, were performed on different days. Processed tomograms were interpreted blinded to clinical or angiographic data. Segmental wall motion assessed with echocardiography at baseline was compared with the 3 month follow up. Sensitivity [Confidence Interval] for 201Tl R-R was 74.6% [60.5-84.5], for FDG it was 82.1% [70.8-90.4]; specificities were 73% [64.3-80.5] and 54.8% [45.6-63.7], respectively. 18F-FDG tended to be more sensitive than 201Tl R-R, but the latter was more specific (p < 0.0004). Both 201Tl RR and 18F-FDG presented high negative predictive value (p: ns). In recent MI, SPECT 201Tl R-R is a valuable and widely available technique for viability detection, with similar sensitivity and significant better specificity than SPECT 18F-FDG.

Wall-motion tracking in fetal echocardiography-Influence of frame rate on longitudinal strain analysis assessed by two-dimensional speckle tracking.

Science.gov (United States)

Enzensberger, Christian; Achterberg, Friederike; Graupner, Oliver; Wolter, Aline; Herrmann, Johannes; Axt-Fliedner, Roland

2017-06-01

Frame rates (FR) used for strain analysis assessed by speckle tracking in fetal echocardiography show a considerable variation. The aim of this study was to investigate the influence of the FR on strain analysis in 2D speckle tracking. Fetal echocardiography was performed prospectively on a Toshiba Aplio 500 system and a Toshiba Artida system, respectively. Based on an apical or basal four-chamber view of the fetal heart, cine loops were stored with a FR of 30 fps (Aplio 500) and 60 fps (Artida/Aplio 500). For both groups (30fps and 60fps), global and segmental longitudinal peak systolic strain (LPSS) values of both, left (LV) and right ventricle (RV), were assessed by 2D wall-motion tracking. A total of 101 fetuses, distributed to three study groups, were included. The mean gestational age was 25.2±5.0 weeks. Mean global LPSS values for RV in the 30 fps group and in the 60 fps group were -16.07% and -16.47%, respectively. Mean global LPSS values for LV in the 30 fps group and in the 60 fps group were -17.54% and -17.06%, respectively. Comparing global and segmental LPSS values of both, the RV and LV, did not show any statistically significant differences within the two groups. Performance of myocardial 2D strain analysis by wall-motion tracking was feasible with 30 and 60 fps. Obtained global and segmental LPSS values of both ventricles were relatively independent from acquisition rate. © 2017, Wiley Periodicals, Inc.

Abnormal Motion of the Interventricular Septum after Coronary Artery Bypass Graft Surgery: Comprehensive Evaluation with MR Imaging

International Nuclear Information System (INIS)

Choi, Seong Hoon; Choi, Sang Il; Chun, Eun Ju; Chang, Huk Jae; Park, Kay Hyun; Lim, Cheong; Kim, Shin Jae; Kang, Joon Won; Lim, Tae Hwan

2010-01-01

To define the mechanism associated with abnormal septal motion (ASM) after coronary artery bypass graft surgery (CABG) using comprehensive MR imaging techniques. Eighteen patients (mean age, 58 ± 12 years; 15 males) were studied with comprehensive MR imaging using rest/stress perfusion, rest cine, and delayed enhancement (DE)-MR techniques before and after CABG. Myocardial tagging was also performed following CABG. Septal wall motion was compared in the ASM and non-ASM groups. Preoperative and postoperative results with regard to septal wall motion in the ASM group were also compared. We then analyzed circumferential strain after CABG in both the septal and lateral walls in the ASM group. All patients had normal septal wall motion and perfusion without evidence of non-viable myocardium prior to surgery. Postoperatively, ASM at rest and/or stress state was documented in 10 patients (56%). However, all of these had normal rest/stress perfusion and DE findings at the septum. Septal wall motion after CABG in the ASM group was significantly lower than that in the non- ASM group (2.1±5.3 mm vs. 14.9±4.7 mm in the non-ASM group; p < 0.001). In the ASM group, the degree of septal wall motion showed a significant decrease after CABG (preoperative vs. postoperative = 15.8±4.5 mm vs. 2.1±5.3 mm; p = 0.007). In the ASM group after CABG, circumferential shortening of the septum was even larger than that of the lateral wall (-20.89±5.41 vs. -15.41±3.7, p < 0.05) Abnormal septal motion might not be caused by ischemic insult. We suggest that ASM might occur due to an increase in anterior cardiac mobility after incision of the pericardium

Walker-type velocity oscillations of magnetic domain walls

International Nuclear Information System (INIS)

Vella-Coleiro, G.P.

1976-01-01

We report stroboscopic observations of the radial motion of a magnetic bubble domain wall in an epitaxial LuGdAl iron garnet film. At high drive fields, initial velocities up to 9500 cm/sec were measured, and the domain wall was observed to move backwards during the field pulse, in agreement with calculations based on the Walker model

Experimental motion behavior of submerged fuel racks

International Nuclear Information System (INIS)

Ellingson, F.J.; Wachter, W.; Moscardini, R.L.

1989-01-01

The design of submerged nuclear storage racks for light water reactor nuclear fuel has undergone a change from fixed position to a free-standing arrangement. Seismic analysis of the motion of the free-standing racks requires three-dimensional computer modeling that uses past studies of hydrodynamic mass and hydraulic coupling for rigid flat plates. This paper describes the results of experiments that show a reduced value for hydrodynamic mass and coupling forces when flexible elements are involved. To support this work, experiments were run with two full-scale welded box sections submerged in a water tank. The preliminary results indicate reduction in hydrodynamic mass due to box wall flexibility, a lack of impacting of box wall to box wall over the entire frequency range, and large hydrodynamic coupling forces under all test conditions. It is hypothesized that the coupling forces are sufficiently strong to prevent rotational motion of one rack when surrounded by adjacent racks

Ground Motion Prediction Models for Caucasus Region

Science.gov (United States)

Jorjiashvili, Nato; Godoladze, Tea; Tvaradze, Nino; Tumanova, Nino

2016-04-01

Ground motion prediction models (GMPMs) relate ground motion intensity measures to variables describing earthquake source, path, and site effects. Estimation of expected ground motion is a fundamental earthquake hazard assessment. The most commonly used parameter for attenuation relation is peak ground acceleration or spectral acceleration because this parameter gives useful information for Seismic Hazard Assessment. Since 2003 development of Georgian Digital Seismic Network has started. In this study new GMP models are obtained based on new data from Georgian seismic network and also from neighboring countries. Estimation of models is obtained by classical, statistical way, regression analysis. In this study site ground conditions are additionally considered because the same earthquake recorded at the same distance may cause different damage according to ground conditions. Empirical ground-motion prediction models (GMPMs) require adjustment to make them appropriate for site-specific scenarios. However, the process of making such adjustments remains a challenge. This work presents a holistic framework for the development of a peak ground acceleration (PGA) or spectral acceleration (SA) GMPE that is easily adjustable to different seismological conditions and does not suffer from the practical problems associated with adjustments in the response spectral domain.

Can large-scale oblique undulations on a solid wall reduce the turbulent drag?

Science.gov (United States)

Ghebali, Sacha; Chernyshenko, Sergei I.; Leschziner, Michael A.

2017-10-01

Direct numerical simulations of fully developed turbulent channel flows with wavy walls are undertaken. The wavy walls, skewed with respect to the mean flow direction, are introduced as a means of emulating a Spatial Stokes Layer (SSL) induced by in-plane wall motion. The transverse shear strain above the wavy wall is shown to be similar to that of a SSL, thereby affecting the turbulent flow and leading to a reduction in the turbulent skin-friction drag. However, some important differences with respect to the SSL case are brought to light too. In particular, the phase variations of the turbulent properties are accentuated and, unlike in the SSL case, there is a region of increased turbulence production over a portion of the wall, above the leeward side of the wave, thus giving rise to a local increase in dissipation. The pressure- and friction-drag levels are carefully quantified for various flow configurations, exhibiting a combined maximum overall-drag reduction of about 0.6%. The friction-drag reduction is shown to behave approximately quadratically for small wave slopes and then linearly for higher slopes, whilst the pressure-drag penalty increases quadratically. The transverse shear-strain layer is shown to be approximately Reynolds-number independent when the wave geometry is scaled in wall units.

Assessment of regional left ventricular function by Dual Source Computed Tomography: Interobserver variability and validation to laevocardiography

Energy Technology Data Exchange (ETDEWEB)

Pflederer, T. [Department of Internal Medicine 2 (Cardiology), University of Erlangen (Germany)], E-mail: tobiaspflederer@web.de; Ho, K.T. [Department of Cardiology, Tan Tock Seng Hospital (Singapore)], E-mail: contact@ttsh.com.sg; Anger, T. [Department of Internal Medicine 2 (Cardiology), University of Erlangen (Germany)], E-mail: thomas.anger@uk-erlangen.de; Kraehner, R. [Department of Internal Medicine 2 (Cardiology), University of Erlangen (Germany)], E-mail: robert.kraehner@uk-erlangen.de; Ropers, D. [Department of Internal Medicine 2 (Cardiology), University of Erlangen (Germany)], E-mail: dieter.ropers@uk-erlangen.de; Muschiol, G. [Department of Internal Medicine 2 (Cardiology), University of Erlangen (Germany)], E-mail: gerd.muschiol@uk-erlangen.de; Renz, A. [Department of Internal Medicine 2 (Cardiology), University of Erlangen (Germany)], E-mail: alexandra.renz@uk-erlangen.de; Daniel, W.G. [Department of Internal Medicine 2 (Cardiology), University of Erlangen (Germany)], E-mail: werner.daniel@uk-erlangen.de; Achenbach, S. [Department of Internal Medicine 2 (Cardiology), University of Erlangen (Germany)], E-mail: stephan.achenbach@uk-erlangen.de

2009-10-15

Objective: Assessment of left ventricular function is possible in contrast-enhanced cardiac CT data sets. However, rapid ventricular motion especially in systole can lead to artifacts. Dual Source Computed Tomography (DSCT) has high temporal resolution which effectively limits motion artifact. We therefore assessed the accuracy of DSCT to detect regional left ventricular wall motion abnormalities in comparison to invasive cine angiocardiography. Methods: We analyzed DSCT data sets of 50 patients (39 male, 11 female, mean age: 61 {+-} 10 years) which were acquired after intravenous injection of 55-70 mL contrast agent (rotation time: 330 ms, collimation: 2 mm x 64 mm x 0.6 mm, 120 kV, 380 mAs, ECG-correlated tube current modulation). 10 data sets consisting of transaxial slices with a slice thickness of 1.5 mm, an increment of 1.0 mm and a matrix of 256 x 256 pixels were reconstructed at 10 time instants during the cardiac cycle (0-90% in 10% increments). The data sets were analyzed visually by two independent readers, using standard left ventricular planes, concerning regional wall motion abnormalities. DSCT was verified in a blinded fashion against cine ventriculography performed during cardiac catheterization (RAO and LAO projection), using a 7-segment model. Analysis was performed on a per-patient (presence of at least one hypo-, a- or dyskinetic segment) and on a per-segment basis. Results: Concerning the presence of a wall motion abnormality, the two observers agreed in 340/350 segments (97%) and 48/50 patients (96%). In invasive cine angiocardiography, 22 of 50 patients displayed at least one segment with abnormal contraction. To detect these patients, DSCT showed a sensitivity of 95% (21/22), specificity of 96% (27/28), positive predictive value of 95% and negative predictive value of 96%. Out of a total of 350 left ventricular segments, 66 segments had abnormal contraction in cine angiocardiography (34 hypokinetic, 26 akinetic, 6 dyskinetic). For detection

CP-violating profile of the electroweak bubble wall

Energy Technology Data Exchange (ETDEWEB)

Funakubo, Koichi [Saga Univ. (Japan). Dept. of Physics; Kakuto, Akira; Otsuki, Shoichiro; Takenaga, Kazunori; Toyoda, Fumihiko

1995-11-01

In any scenario of the electroweak baryogenesis, the profile of the CP violating bubble wall, created at the first-order phase transition, plays an essential role. We attempt to determine it by solving the equations of motion for the scalars in the two-Higgs-doublet model at the transition temperature. According to the parameters in the potential, we found three solutions. Two of them smoothly connect the CP-violating broken phase and the symmetric phase, while the other connects CP-conserving vacua but violates CP in the intermediate region. We also estimate the chiral charge flux, which will be turned into the baryon density in the symmetric phase by the sphaleron process. (author).

Late-Stage Vortical Structures and Eddy Motions in a Transitional Boundary Layer

International Nuclear Information System (INIS)

Xiao-Bing, Liu; Zheng-Qing, Chen; Chao-Qun, Liu

2010-01-01

A high-order direct numerical simulation of flow transition over a flat-plate at a free stream Mach number 0.5 is carried out. Formation and development of three-dimensional vortical structures, typically shown as A-vortices, hairpin vortices and ring-like vortices, are observed. Numerical results show that there is a strong downdraft motion of fluid excited by every ring-like vortex in the late-stage of the transition process. At two sides of the vortical structure centerline, the downdraft motions induced by the ring-like vortex and the rotating legs superimpose. This is responsible for the appearance of a high-speed streak associated with the positive spike observed in a previous investigation and the appearance of a high-shear layer in the near wall region. (fundamental areas of phenomenology(including applications))

Direct flow/motion, coils, and field strength concerns in MRI

International Nuclear Information System (INIS)

Moran, P.R.

1986-01-01

Specific flow/motion bipolar phase-gradient encodings are interlaced into MR sequences for direct NMR imaging of motion quantities, velocity, acceleration, etc. This allows evaluation of the functional properties of tissue, blood flow, heart-wall velocity, vortical-eddies in vascular disease, and perfusion assessment. Attention to fundamentals and basics is important in designing successful flow/motion imaging sequences. 2 refs.; 5 figs

Robust Myocardial Motion Tracking for Echocardiography: Variational Framework Integrating Local-to-Global Deformation

Directory of Open Access Journals (Sweden)

Chi Young Ahn

2013-01-01

Full Text Available This paper proposes a robust real-time myocardial border tracking algorithm for echocardiography. Commonly, after an initial contour of LV border is traced at one or two frames from the entire cardiac cycle, LV contour tracking is performed over the remaining frames. Among a variety of tracking techniques, optical flow method is the most widely used for motion estimation of moving objects. However, when echocardiography data is heavily corrupted in some local regions, the errors bring the tracking point out of the endocardial border, resulting in distorted LV contours. This shape distortion often occurs in practice since the data acquisition is affected by ultrasound artifacts, dropouts, or shadowing phenomena of cardiac walls. The proposed method is designed to deal with this shape distortion problem by integrating local optical flow motion and global deformation into a variational framework. The proposed descent method controls the individual tracking points to follow the local motions of a specific speckle pattern, while their overall motions are confined to the global motion constraint being approximately an affine transform of the initial tracking points. Many real experiments show that the proposed method achieves better overall performance than conventional methods.

PROPER MOTIONS OF YOUNG STELLAR OUTFLOWS IN THE MID-INFRARED WITH SPITZER (IRAC). I. THE NGC 1333 REGION

International Nuclear Information System (INIS)

Raga, A. C.; Noriega-Crespo, A.; Carey, S. J.; Arce, H. G.

2013-01-01

We use two 4.5 μm Spitzer (IRAC) maps of the NGC 1333 region taken over a ∼7 yr interval to determine proper motions of its associated outflows. This is a first successful attempt at obtaining proper motions of stellars' outflow from Spitzer observations. For the outflow formed by the Herbig-Haro objects HH7, 8, and 10, we find proper motions of ∼9-13 km s –1 , which are consistent with previously determined optical proper motions of these objects. We determine proper motions for a total of eight outflows, ranging from ∼10 to 100 km s –1 . The derived proper motions show that out of these eight outflows, three have tangential velocities ≤20 km s –1 . This result shows that a large fraction of the observed outflows have low intrinsic velocities and that the low proper motions are not merely a projection effect.

A human motion model based on maps for navigation systems

Directory of Open Access Journals (Sweden)

Kaiser Susanna

2011-01-01

Full Text Available Abstract Foot-mounted indoor positioning systems work remarkably well when using additionally the knowledge of floor-plans in the localization algorithm. Walls and other structures naturally restrict the motion of pedestrians. No pedestrian can walk through walls or jump from one floor to another when considering a building with different floor-levels. By incorporating known floor-plans in sequential Bayesian estimation processes such as particle filters (PFs, long-term error stability can be achieved as long as the map is sufficiently accurate and the environment sufficiently constraints pedestrians' motion. In this article, a new motion model based on maps and floor-plans is introduced that is capable of weighting the possible headings of the pedestrian as a function of the local environment. The motion model is derived from a diffusion algorithm that makes use of the principle of a source effusing gas and is used in the weighting step of a PF implementation. The diffusion algorithm is capable of including floor-plans as well as maps with areas of different degrees of accessibility. The motion model more effectively represents the probability density function of possible headings that are restricted by maps and floor-plans than a simple binary weighting of particles (i.e., eliminating those that crossed walls and keeping the rest. We will show that the motion model will help for obtaining better performance in critical navigation scenarios where two or more modes may be competing for some of the time (multi-modal scenarios.

Regional amplification of ground motion in central Mexico. Results from coda-length magnitude data and preliminary modeling

Science.gov (United States)

Cárdenas, Martín; Chávez-García, Francisco J.; Gusev, Alexander

Seismic ground motion in central Mexico is amplified relative to ground motion observed at the same epicentral distance along the Pacific Coast in a frequency band that includes destructive ground motion at Mexico City. Although several hypothesis have been advanced, at present there is no generally accepted explanation of such amplification. We have analyzed coda-length magnitude data reported by Servicio Sismológico Nacional (SSN) for events recorded during 1993 to increase our understanding of the spatial distribution of this phenomenon. Our results indicate that regional amplification: (a) is detected by magnitude residual computed at each station, relative to the average of SSN network;and (b) is likely related to the crustal structure under the central portion of the Transmexican Volcanic Belt (TMVB). Finally, preliminary wave propagation modelling (using SH wave, finite difference method) suggests that crustal heterogeneity is a possible cause of regional amplification. However, if this is so, it is required that both geometry and velocity distribution vary between the coast and Mexico City.

Assessment of Bladder Motion for Clinical Radiotherapy Practice Using Cine-Magnetic Resonance Imaging

International Nuclear Information System (INIS)

McBain, Catherine A.; Khoo, Vincent S.; Buckley, David L.; Sykes, Jonathan S.; Green, Melanie M.; Cowan, Richard A.; Hutchinson, Charles E.; Moore, Christopher J.; Price, Patricia M.

2009-01-01

Purpose: Organ motion is recognized as the principal source of inaccuracy in bladder radiotherapy (RT), but there is currently little information on intrafraction bladder motion. Methods and Materials: We used cine-magnetic resonance imaging (cine-MRI) to study bladder motion relevant to intrafraction RT delivery. On two occasions, a 28 minute cine-MRI sequence was acquired from 10 bladder cancer patients and 5 control participants immediately after bladder emptying, after abstinence from drinking for the preceding hour. From the resulting cine sequences, bladder motion was subjectively assessed. To quantify bladder motion, the bladder was contoured in imaging volume sets at 0, 14, and 28 min to measure changes to bladder volumes, wall displacements, and center of gravity (COG) over time. Results: The dominant source of bladder motion during imaging was bladder filling (up to 101% volume increase); rectal and small bowel movements were transient, with minimal impact. Bladder volume changes were similar for all participants. However for bladder cancer patients, wall displacements were larger (up to 58 mm), less symmetrical, and more variable compared with nondiseased control bladders. Conclusions: Significant and individualized intrafraction bladder wall displacements may occur during bladder RT delivery. This important source of inaccuracy should be incorporated into treatment planning and verification.

Large scale structures in a turbulent boundary layer and their imprint on wall shear stress

Science.gov (United States)

Pabon, Rommel; Barnard, Casey; Ukeiley, Lawrence; Sheplak, Mark

2015-11-01

Experiments were performed on a turbulent boundary layer developing on a flat plate model under zero pressure gradient flow. A MEMS differential capacitive shear stress sensor with a 1 mm × 1 mm floating element was used to capture the fluctuating wall shear stress simultaneously with streamwise velocity measurements from a hot-wire anemometer traversed in the wall normal direction. Near the wall, the peak in the cross correlation corresponds to an organized motion inclined 45° from the wall. In the outer region, the peak diminishes in value, but is still significant at a distance greater than half the boundary layer thickness, and corresponds to a structure inclined 14° from the wall. High coherence between the two signals was found for the low-frequency content, reinforcing the belief that large scale structures have a vital impact on wall shear stress. Thus, estimation of the wall shear stress from the low-frequency velocity signal will be performed, and is expected to be statistically significant in the outer boundary layer. Additionally, conditionally averaged mean velocity profiles will be presented to assess the effects of high and low shear stress. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1315138.

Direct measurements of wall shear stress by buried wire gages in a shock-wave boundary-layer interaction region

Science.gov (United States)

Murthy, V. S.; Rose, W. C.

1977-01-01

Detailed measurements of wall shear stress (skin friction) were made with specially developed buried wire gages in the interaction regions of a Mach 2.9 turbulent boundary layer with externally generated shocks. Separation and reattachment points inferred by these measurements support the findings of earlier experiments which used a surface oil flow technique and pitot profile measurements. The measurements further indicate that the boundary layer tends to attain significantly higher skin-friction values downstream of the interaction region as compared to upstream. Comparisons between measured wall shear stress and published results of some theoretical calculation schemes show that the general, but not detailed, behavior is predicted well by such schemes.

Quantification of 3D myocardium motion in gated SPECT

International Nuclear Information System (INIS)

Gutierrez, Marco A.; Furuie, Sergio S.; Melo, Candido P.; Meneghetti, Jose C.; Moura, Lincoln

1996-01-01

A method to quantify 3 D left ventricle motion by the optical flow technique extended to the voxel space is described. The left ventricle wall motion is represented by a series of 3 D velocity vector which is computed automatically by the proposed method for each voxel on the sequence of cardiac volumes

Assessment of seismic design response factors of concrete wall buildings

Science.gov (United States)

Mwafy, Aman

2011-03-01

To verify the seismic design response factors of high-rise buildings, five reference structures, varying in height from 20- to 60-stories, were selected and designed according to modern design codes to represent a wide range of concrete wall structures. Verified fiber-based analytical models for inelastic simulation were developed, considering the geometric nonlinearity and material inelasticity of the structural members. The ground motion uncertainty was accounted for by employing 20 earthquake records representing two seismic scenarios, consistent with the latest understanding of the tectonic setting and seismicity of the selected reference region (UAE). A large number of Inelastic Pushover Analyses (IPAs) and Incremental Dynamic Collapse Analyses (IDCAs) were deployed for the reference structures to estimate the seismic design response factors. It is concluded that the factors adopted by the design code are adequately conservative. The results of this systematic assessment of seismic design response factors apply to a wide variety of contemporary concrete wall buildings with various characteristics.

Reynolds stress analysis of EMHD-controlled wall turbulence. Part I. Streamwise forcing

International Nuclear Information System (INIS)

Crawford, C.H.; Karniadakis, G.E.

1997-01-01

In this work we investigate numerically turbulent flow of low electrical conductivity fluid subject to electro-magnetic (EMHD) forcing. The configuration is similar to the one considered in the experimental work of Henoch and Stace [Phys. Fluids 7, 1371 (1995)] but in a channel geometry. The lower wall of the channel is covered with alternating streamwise electrodes and magnets to create a Lorentz force in the positive streamwise direction. Two cases are considered in detail corresponding to interaction parameter values of 0.4 (case 1) and 0.1 (case 2). The effect of switching off and on the electrodes is also studied for the two cases. At the Reynolds number considered (Re τ ∼200), a drag increase was obtained for all cases, in agreement with the experiments of Henoch and Stace. A Reynolds stress analysis was performed based on a new decomposition of the gradients normal to the wall of the Reynolds stress -u'v'. It was found that the vortex stretching term w'w 2 ' and the spanwise variation of the stress component u'w' are responsible for the drag increase. More specifically, the term ∂(u'w')/∂x 3 is associated with secondary vortical motions in the near-wall and becomes large and positive for large shear stress in regions where fluid is moving toward the wall. In contrast, negative values are associated with regions of lower shear where fluid is being lifted away from the wall. Unlike the unperturbed flow, in the controlled flow high speed near-wall streamwise jets are present (case 1) even in the time-averaged fields. Other changes in turbulence structure are quantified using streak spacing, vortex lines, vorticity quadrant analysis, and plots of the rms value of the vorticity angle. copyright 1997 American Institute of Physics

Cardiac MRI: evaluation of phonocardiogram-gated cine imaging for the assessment of global und regional left ventricular function in clinical routine

International Nuclear Information System (INIS)

Nassenstein, Kai; Schlosser, Thomas; Orzada, Stephan; Haering, Lars; Czylwik, Andreas; Zenge, Michael; Mueller, Edgar; Eberle, Holger; Bruder, Oliver; Ladd, Mark E.; Maderwald, Stefan

2012-01-01

To validate a phonocardiogram (PCG)-gated cine imaging approach for the assessment of left ventricular (LV) function. In this prospective study, cine MR imaging of the LV was performed twice in 79 patients by using retrospectively PCG- and retrospectively ECG-gated cine SSFP sequences at 1.5 T. End-diastolic volumes (EDV), end-systolic volumes (ESV), stroke volumes (SV), ejection fraction (EF), muscle mass (MM), as well as regional wall motion were assessed. Subgroup analyses were performed for patients with valvular defects and for patients with dysrhythmia. PCG-gated imaging was feasible in 75 (95%) patients, ECG-gating in all patients. Excellent correlations were observed for all volumetric parameters (r > 0.98 for all variables analysed). No significant differences were observed for EDV (-0.24 ± 3.14 mL, P = 0.5133), ESV (-0.04 ± 2.36 mL, P = 0.8951), SV (-0.20 ± 3.41 mL, P = 0.6083), EF (-0.16 ± 1.98%, P = 0.4910), or MM (0.31 ± 4.2 g, P = 0.7067) for the entire study cohort, nor for either of the subgroups. PCG- and ECG-gated cine imaging revealed similar results for regional wall motion analyses (115 vs. 119 segments with wall motion abnormalities, P = 0.3652). The present study demonstrates that PCG-gated cine imaging enables accurate assessment of global and regional LV function in the vast majority of patients in clinical routine. (orig.)

Regeneration of near-wall turbulence structures

Science.gov (United States)

Hamilton, James M.; Kim, John J.; Waleffe, Fabian A.

1993-01-01

An examination of the regeneration mechanisms of near-wall turbulence and an attempt to investigate the critical Reynolds number conjecture of Waleffe & Kim is presented. The basis is an extension of the 'minimal channel' approach of Jimenez and Moin which emphasizes the near-wall region and further reduces the complexity of the turbulent flow. Reduction of the flow Reynolds number to the minimum value which will allow turbulence to be sustained has the effect of reducing the ratio of the largest scales to the smallest scales or, equivalently, of causing the near-wall region to fill more of the area between the channel walls. In addition, since each wall may have an active near-wall region, half of the channel is always somewhat redundant. If a plane Couette flow is instead chosen as the base flow, this redundancy is eliminated: the mean shear of a plane Couette flow has a single sign, and at low Reynolds numbers, the two wall regions share a single set of structures. A minimal flow with these modifications possesses, by construction, the strongest constraints which allow sustained turbulence, producing a greatly simplified flow in which the regeneration process can be examined.

Scaling and interaction of self-similar modes in models of high Reynolds number wall turbulence.

Science.gov (United States)

Sharma, A S; Moarref, R; McKeon, B J

2017-03-13

Previous work has established the usefulness of the resolvent operator that maps the terms nonlinear in the turbulent fluctuations to the fluctuations themselves. Further work has described the self-similarity of the resolvent arising from that of the mean velocity profile. The orthogonal modes provided by the resolvent analysis describe the wall-normal coherence of the motions and inherit that self-similarity. In this contribution, we present the implications of this similarity for the nonlinear interaction between modes with different scales and wall-normal locations. By considering the nonlinear interactions between modes, it is shown that much of the turbulence scaling behaviour in the logarithmic region can be determined from a single arbitrarily chosen reference plane. Thus, the geometric scaling of the modes is impressed upon the nonlinear interaction between modes. Implications of these observations on the self-sustaining mechanisms of wall turbulence, modelling and simulation are outlined.This article is part of the themed issue 'Toward the development of high-fidelity models of wall turbulence at large Reynolds number'. © 2017 The Author(s).

Seismic proof test of shielding block walls

International Nuclear Information System (INIS)

Ohte, Yukio; Watanabe, Takahide; Watanabe, Hiroyuki; Maruyama, Kazuhide

1989-01-01

Most of the shielding block walls used for building nuclear facilities are built by dry process. When a nuclear facility is designed, seismic waves specific at each site are set as input seismic motions and they are adopted in the design. Therefore, it is necessary to assure safety of the shielding block walls for earthquake by performing anti-seismic experiments under the conditions at each site. In order to establish the normal form that can be applied to various seismic conditions in various areas, Shimizu Corp. made an actual-size test samples for the shielding block wall and confirmed the safety for earthquake and validity of normalization. (author)

Fast switching and signature of efficient domain wall motion driven by spin-orbit torques in a perpendicular anisotropy magnetic insulator/Pt bilayer

Science.gov (United States)

Avci, Can Onur; Rosenberg, Ethan; Baumgartner, Manuel; Beran, Lukáš; Quindeau, Andy; Gambardella, Pietro; Ross, Caroline A.; Beach, Geoffrey S. D.

2017-08-01

We report fast and efficient current-induced switching of a perpendicular anisotropy magnetic insulator thulium iron garnet by using spin-orbit torques (SOT) from the Pt overlayer. We first show that, with quasi-DC (10 ms) current pulses, SOT-induced switching can be achieved with an external field as low as 2 Oe, making TmIG an outstanding candidate to realize efficient switching in heterostructures that produce moderate stray fields without requiring an external field. We then demonstrate deterministic switching with fast current pulses (≤20 ns) with an amplitude of ˜1012 A/m2, similar to all-metallic structures. We reveal that, in the presence of an initially nucleated domain, the critical switching current is reduced by up to a factor of five with respect to the fully saturated initial state, implying efficient current-driven domain wall motion in this system. Based on measurements with 2 ns-long pulses, we estimate the domain wall velocity of the order of ˜400 m/s per j = 1012 A/m2.

Large-eddy simulation of heavy particle dispersion in wall-bounded turbulent flows

Energy Technology Data Exchange (ETDEWEB)

Salvetti, M.V. [DICI, University of Pisa, I-56122 Pisa (Italy)

2015-03-10

Capabilities and accuracy issues in Lagrangian tracking of heavy particles in velocity fields obtained from large-eddy simulations (LES) of wall-bounded turbulent flows are reviewed. In particular, it is shown that, if no subgrid scale (SGS) model is added to the particle motion equations, particle preferential concentration and near-wall accumulation are significantly underestimated. Results obtained with SGS modeling for the particle motion equations based on approximate deconvolution are briefly recalled. Then, the error purely due to filtering in particle tracking in LES flow fields is singled out and analyzed. The statistical properties of filtering errors are characterized in turbulent channel flow both from an Eulerian and a Lagrangian viewpoint. Implications for stochastic SGS modeling in particle motion equations are briefly outlined.

The effect of regional variation of seismic wave attenuation on the strong ground motion from earthquakes

Energy Technology Data Exchange (ETDEWEB)

Chung, D H; Bernreuter, D L

1981-10-01

Attenuation is caused by geometric spreading and absorption. Geometric spreading is almost independent of crustal geology and physiographic region, but absorption depends strongly on crustal geology and the state of the earth's upper mantle. Except for very high frequency waves, absorption does not affect ground motion at distances less than about 25 to 50 km. Thus, in the near-field zone, the attenuation in the eastern United States is similar to that in the western United States. Beyond the near field, differences in ground motion can best be accounted for by differences in attenuation caused by differences in absorption. The stress drop of eastern earthquakes may be higher than for western earthquakes of the same seismic moment, which would affect the high-frequency spectral content. But we believe this factor is of much less significance than differences in absorption in explaining the differences in ground motion between the East and the West. The characteristics of strong ground motion in the conterminous United States are discussed in light of these considerations, and estimates are made of the epicentral ground motions in the central and eastern United States. (author)

Interpretation of scrape-off layer profile evolution and first-wall ion flux statistics on JET using a stochastic framework based on fillamentary motion

Science.gov (United States)

Walkden, N. R.; Wynn, A.; Militello, F.; Lipschultz, B.; Matthews, G.; Guillemaut, C.; Harrison, J.; Moulton, D.; Contributors, JET

2017-08-01

This paper presents the use of a novel modelling technique based around intermittent transport due to filament motion, to interpret experimental profile and fluctuation data in the scrape-off layer (SOL) of JET during the onset and evolution of a density profile shoulder. A baseline case is established, prior to shoulder formation, and the stochastic model is shown to be capable of simultaneously matching the time averaged profile measurement as well as the PDF shape and autocorrelation function from the ion-saturation current time series at the outer wall. Aspects of the stochastic model are then varied with the aim of producing a profile shoulder with statistical measurements consistent with experiment. This is achieved through a strong localised reduction in the density sink acting on the filaments within the model. The required reduction of the density sink occurs over a highly localised region with the timescale of the density sink increased by a factor of 25. This alone is found to be insufficient to model the expansion and flattening of the shoulder region as the density increases, which requires additional changes within the stochastic model. An example is found which includes both a reduction in the density sink and filament acceleration and provides a consistent match to the experimental data as the shoulder expands, though the uniqueness of this solution can not be guaranteed. Within the context of the stochastic model, this implies that the localised reduction in the density sink can trigger shoulder formation, but additional physics is required to explain the subsequent evolution of the profile.

Dominant region: a basic feature for group motion analysis and its application to teamwork evaluation in soccer games

Science.gov (United States)

Taki, Tsuyoshi; Hasegawa, Jun-ichi

1998-12-01

This paper proposes a basic feature for quantitative measurement and evaluation of group behavior of persons. This feature called 'dominant region' is a kind of sphere of influence for each person in the group. The dominant region is defined as a region in where the person can arrive earlier than any other persons and can be formulated as Voronoi region modified by replacing the distance function with a time function. This time function is calculated based on a computational model of moving ability of the person. As an application of the dominant region, we present a motion analysis system of soccer games. The purpose of this system is to evaluate the teamwork quantitatively based on movement of all the players in the game. From experiments using motion pictures of actual games, it is suggested that the proposed feature is useful for measurement and evaluation of group behavior in team sports. This basic feature may be applied to other team ball games, such as American football, basketball, handball and water polo.

Characterization of Slow Orbit Motion in the SPEAR3

International Nuclear Information System (INIS)

Sunilkumar, Nikita

2012-01-01

SPEAR3 is a third-generation synchrotron light source storage ring. The beam stability requirements are ∼10% of the beam size, which is about 1 micron in the vertical plane. Hydrostatic level system (HLS) measurements show that the height of the SPEAR3 tunnel floor varies by tens of microns daily. We present analysis of the HLS data, including accounting for common-mode tidal motion. We discuss the results of experiments done to determine the primary driving source of ground motion. We painted the accelerator tunnel walls white; we temporarily installed Mylar over the asphalt in the center of the accelerator; and we put Mylar over a section of the tunnel walls.

Tracking using motion estimation with physically motivated inter-region constraints

KAUST Repository

Arif, Omar

2014-09-01

We propose a method for tracking structures (e.g., ventricles and myocardium) in cardiac images (e.g., magnetic resonance) by propagating forward in time a previous estimate of the structures using a new physically motivated motion estimation scheme. Our method estimates motion by regularizing only within structures so that differing motions among different structures are not mixed. It simultaneously satisfies the physical constraints at the interface between a fluid and a medium that the normal component of the fluid\\'s motion must match the normal component of the medium\\'s motion and the No-Slip condition, which states that the tangential velocity approaches zero near the interface. We show that these conditions lead to partial differential equations with Robin boundary conditions at the interface, which couple the motion between structures. We show that propagating a segmentation across frames using our motion estimation scheme leads to more accurate segmentation than traditional motion estimation that does not use physical constraints. Our method is suited to interactive segmentation, prominently used in commercial applications for cardiac analysis, where segmentation propagation is used to predict a segmentation in the next frame. We show that our method leads to more accurate predictions than a popular and recent interactive method used in cardiac segmentation. © 2014 IEEE.

Hazard-to-Risk: High-Performance Computing Simulations of Large Earthquake Ground Motions and Building Damage in the Near-Fault Region

Science.gov (United States)

Miah, M.; Rodgers, A. J.; McCallen, D.; Petersson, N. A.; Pitarka, A.

2017-12-01

We are running high-performance computing (HPC) simulations of ground motions for large (magnitude, M=6.5-7.0) earthquakes in the near-fault region (steel moment frame buildings throughout the near-fault domain. For ground motions, we are using SW4, a fourth order summation-by-parts finite difference time-domain code running on 10,000-100,000's of cores. Earthquake ruptures are generated using the Graves and Pitarka (2017) method. We validated ground motion intensity measurements against Ground Motion Prediction Equations. We considered two events (M=6.5 and 7.0) for vertical strike-slip ruptures with three-dimensional (3D) basin structures, including stochastic heterogeneity. We have also considered M7.0 scenarios for a Hayward Fault rupture scenario which effects the San Francisco Bay Area and northern California using both 1D and 3D earth structure. Dynamic, inelastic response of canonical buildings is computed with the NEVADA, a nonlinear, finite-deformation finite element code. Canonical buildings include 3-, 9-, 20- and 40-story steel moment frame buildings. Damage potential is tracked by the peak inter-story drift (PID) ratio, which measures the maximum displacement between adjacent floors of the building and is strongly correlated with damage. PID ratios greater 1.0 generally indicate non-linear response and permanent deformation of the structure. We also track roof displacement to identify permanent deformation. PID (damage) for a given earthquake scenario (M, slip distribution, hypocenter) is spatially mapped throughout the SW4 domain with 1-2 km resolution. Results show that in the near fault region building damage is correlated with peak ground velocity (PGV), while farther away (> 20 km) it is better correlated with peak ground acceleration (PGA). We also show how simulated ground motions have peaks in the response spectra that shift to longer periods for larger magnitude events and for locations of forward directivity, as has been reported by

Existence of k⁻¹ power-law scaling in the equilibrium regions of wall-bounded turbulence explained by Heisenberg's eddy viscosity.

Science.gov (United States)

Katul, Gabriel G; Porporato, Amilcare; Nikora, Vladimir

2012-12-01

The existence of a "-1" power-law scaling at low wavenumbers in the longitudinal velocity spectrum of wall-bounded turbulence was explained by multiple mechanisms; however, experimental support has not been uniform across laboratory studies. This letter shows that Heisenberg's eddy viscosity approach can provide a theoretical framework that bridges these multiple mechanisms and explains the elusiveness of the "-1" power law in some experiments. Novel theoretical outcomes are conjectured about the role of intermittency and very-large scale motions in modifying the k⁻¹ scaling.

Setup error and motion during deep inspiration breath-hold breast radiotherapy measured with continuous portal imaging

DEFF Research Database (Denmark)

Lutz, Christina Maria; Poulsen, Per Rugaard; Fledelius, Walther

2016-01-01

BACKGROUND: The position and residual motion of the chest wall of breast cancer patients during treatment in deep inspiration breath-hold (DIBH) were investigated. MATERIAL AND METHODS: The study included 58 left-sided breast cancer patients treated with DIBH three-dimensional (3D) conformal......). At every third treatment fraction, continuous portal images were acquired. The time-resolved chest wall position during treatment was compared with the planned position to determine the inter-fraction setup errors and the intra-fraction motion of the chest wall. RESULTS: The DIBH compliance was 95% during...

Brownian motion of tethered nanowires.

Science.gov (United States)

Ota, Sadao; Li, Tongcang; Li, Yimin; Ye, Ziliang; Labno, Anna; Yin, Xiaobo; Alam, Mohammad-Reza; Zhang, Xiang

2014-05-01

Brownian motion of slender particles near a boundary is ubiquitous in biological systems and in nanomaterial assembly, but the complex hydrodynamic interaction in those systems is still poorly understood. Here, we report experimental and computational studies of the Brownian motion of silicon nanowires tethered on a substrate. An optical interference method enabled direct observation of microscopic rotations of the slender bodies in three dimensions with high angular and temporal resolutions. This quantitative observation revealed anisotropic and angle-dependent hydrodynamic wall effects: rotational diffusivity in inclined and azimuth directions follows different power laws as a function of the length, ∼ L(-2.5) and ∼ L(-3), respectively, and is more hindered for smaller inclined angles. In parallel, we developed an implicit simulation technique that takes the complex wire-wall hydrodynamic interactions into account efficiently, the result of which agreed well with the experimentally observed angle-dependent diffusion. The demonstrated techniques provide a platform for studying the microrheology of soft condensed matters, such as colloidal and biological systems near interfaces, and exploring the optimal self-assembly conditions of nanostructures.

Algebraic motion of vertically displacing plasmas

Science.gov (United States)

Pfefferlé, D.; Bhattacharjee, A.

2018-02-01

The vertical motion of a tokamak plasma is analytically modelled during its non-linear phase by a free-moving current-carrying rod inductively coupled to a set of fixed conducting wires or a cylindrical conducting shell. The solutions capture the leading term in a Taylor expansion of the Green's function for the interaction between the plasma column and the surrounding vacuum vessel. The plasma shape and profiles are assumed not to vary during the vertical drifting phase such that the plasma column behaves as a rigid body. In the limit of perfectly conducting structures, the plasma is prevented to come in contact with the wall due to steep effective potential barriers created by the induced Eddy currents. Resistivity in the wall allows the equilibrium point to drift towards the vessel on the slow timescale of flux penetration. The initial exponential motion of the plasma, understood as a resistive vertical instability, is succeeded by a non-linear "sinking" behaviour shown to be algebraic and decelerating. The acceleration of the plasma column often observed in experiments is thus concluded to originate from an early sharing of toroidal current between the core, the halo plasma, and the wall or from the thermal quench dynamics precipitating loss of plasma current.

Domain wall motion in magnetically frustrated nanorings

Science.gov (United States)

Lubarda, M. V.; Escobar, M. A.; Li, S.; Chang, R.; Fullerton, E. E.; Lomakin, V.

2012-06-01

We describe a magnetically frustrated nanoring (MFNR) configuration which is formed by introducing antiferromagnetic coupling across an interface orthogonal to the ring's circumferential direction. Such structures have the unique characteristic that only one itinerant domain wall (DW) can exist in the ring, which does not need to be nucleated or injected into the structure and can never escape making it analogous to a magnetic Möbius strip. Numerical simulations show that the DW in a MFNR can be driven consecutively around the ring with a prescribed cyclicity, and that the frequency of revolutions can be controlled by the applied field. The energy landscapes can be controlled to be flat allowing for low fields of operation or to have a barrier for thermal stability. Potential logic and memory applications of MFNRs are considered and discussed.

Smooth- and rough-wall boundary layer structure from high spatial range particle image velocimetry

Science.gov (United States)

Squire, D. T.; Morrill-Winter, C.; Hutchins, N.; Marusic, I.; Schultz, M. P.; Klewicki, J. C.

2016-10-01

Two particle image velocimetry arrangements are used to make true spatial comparisons between smooth- and rough-wall boundary layers at high Reynolds numbers across a very wide range of streamwise scales. Together, the arrangements resolve scales ranging from motions on the order of the Kolmogorov microscale to those longer than twice the boundary layer thickness. The rough-wall experiments were obtained above a continuous sandpaper sheet, identical to that used by Squire et al. [J. Fluid Mech. 795, 210 (2016), 10.1017/jfm.2016.196], and cover a range of friction and equivalent sand-grain roughness Reynolds numbers (12 000 ≲δ+≲ 18000, 62 ≲ks+≲104 ). The smooth-wall experiments comprise new and previously published data spanning 6500 ≲δ+≲17 000 . Flow statistics from all experiments show similar Reynolds number trends and behaviors to recent, well-resolved hot-wire anemometry measurements above the same rough surface. Comparisons, at matched δ+, between smooth- and rough-wall two-point correlation maps and two-point magnitude-squared coherence maps demonstrate that spatially the outer region of the boundary layer is the same between the two flows. This is apparently true even at wall-normal locations where the total (inner-normalized) energy differs between the smooth and rough wall. Generally, the present results provide strong support for Townsend's [The Structure of Turbulent Shear Flow (Cambridge University Press, Cambridge, 1956), Vol. 1] wall-similarity hypothesis in high Reynolds number fully rough boundary layer flows.

Multi-level nonlinear modeling verification scheme of RC high-rise wall buildings

OpenAIRE

Alwaeli, W.; Mwafy, A.; Pilakoutas, K.; Guadagnini, M.

2017-01-01

Earthquake-resistant reinforced concrete (RC) high-rise wall buildings are designed and detailed to respond well beyond the elastic range under the expected earthquake ground motions. However, despite their considerable section depth, in terms of analysis, RC walls are still often treated as linear elements, ignoring the effect of deformation compatibility. Due to the limited number of available comprehensive experimental studies on RC structural wall systems subjected to cycling loading, few...

Evaluation of cardiac motion and function by cine magnetic resonance imaging

International Nuclear Information System (INIS)

Kondo, Takeshi; Kurokawa, Hiroshi; Anno, Hirofumi

1992-01-01

Cardiac cine magnetic resonance imaging (MRI) was studied to evaluate the cardiac motion and function, and a water-stream phantom study was performed to clarify whether it was possible to quantitatively assess the valvular regurgitation flow by the size of the flow void. In normal subjects, the left ventricular (LV) epicardial apex swung up to the base only a few millimeters, and the mitral annulus ring moved about 14 mm as mean value toward the apex during systole. Those motions of mitral annulus ring may contribute to the left atrial filling. The LV longitudinal shortening and torsions were shown by the tagging method. This tagging method was the best method for estimating cardiac motions. Cardiac cine MRI using software including a modified Simpson's method program and a wall motion analysis program was useful for routine LV volumetry and wall motion analysis because it was a simple and reliable method. Our water-stream phantom studies demonstrated that it might be difficult to perform quantitative evaluation of valvular regurgitation flow by using only the size of the flow void without acquiring information relating to the orifice area. (author)

Ratchet Effects and Domain Wall Energy Landscapes in Amorphous Magnetic Films with 2D Arrays of Asymmetric Holes

Science.gov (United States)

Martin, J. I.; Alija, A.; Sobrado, I.; Perez-Junquera, A.; Rodriguez-Rodriguez, G.; Velez, M.; Alameda, J. M.; Marconi, V. I.; Kolton, A. B.; Parrondo, J. M. R.

2009-03-01

The driven motion of domain walls in extended magnetic films patterned with 2D arrays of asymmetric holes has been found to be subject to two different crossed ratchet effects [1] which results in an inversion of the sign of domain wall motion rectification as a function of the applied magnetic field. This effect can be understood in terms of the competition between drive, elasticity and asymmetric pinning as revealed by a simple 4̂-model. In order to optimize the asymmetric hole design, the relevant energy landscapes for domain wall motion across the array of asymmetric holes have been calculated by micromagnetic simulations as a function of array geometrical characteristics. The effects of a transverse magnetic field on these two crossed ratchet effects will also be discussed in terms of the decrease in domain wall energy per unit area and of the modifications in the magnetostatic barriers for domain wall pinning at the asymmetric inclusions. Work supported by Spanish MICINN.[1] A. Perez-Junquera et al, Phys. Rev. Lett. 100 (2008) 037203

Comparison of theoretical and test results on shear wall seismic response

International Nuclear Information System (INIS)

Gantenbein, F.; Wang, F.; Dalbera, J.

1991-01-01

As reinforced concrete shear walls are important resisting components of buildings in nuclear power facilities, it is important to study their ultimate behavior under dynamic loading. An experimental and analytical work has been undertaken on shear walls with and without openings, in order to develop and validate their model. This paper is related to the walls without openings. While pretest calculations have already been reported (Wang and al. 1989) and the test results are given in Gantenbein and al. 1991, this paper is mainly related to the comparison of test and calculation results on the wall initial stiffness and the time history of the wall motion

Wall shear stress characterization of a 3D bluff-body separated flow

Science.gov (United States)

Fourrié, Grégoire; Keirsbulck, Laurent; Labraga, Larbi

2013-10-01

Efficient flow control strategies aimed at reducing the aerodynamic drag of road vehicles require a detailed knowledge of the reference flow. In this work, the flow around the rear slanted window of a generic car model was experimentally studied through wall shear stress measurements using an electrochemical method. The mean and fluctuating wall shear stress within the wall impact regions of the recirculation bubble and the main longitudinal vortex structures which develop above the rear window are presented. Correlations allow a more detailed characterization of the recirculation phenomenon within the separation bubble. In the model symmetry plane the recirculation structure compares well with simpler 2D configurations; specific lengths, flapping motion and shedding of large-scale vortices are observed, these similarities diminish when leaving the middle plane due to the strong three-dimensionality of the flow. A specific attention is paid to the convection processes occurring within the recirculation: a downstream convection velocity is observed, in accordance with 2D recirculations from the literature, and an upstream convection is highlighted along the entire bubble length which has not been underlined in some previous canonical configurations.

Reinforcement mechanism of multi-anchor wall with double wall facing

Science.gov (United States)

Suzuki, Kouta; Kobayashi, Makoto; Miura, Kinya; Konami, Takeharu; Hayashi, Taketo

2017-10-01

The reinforced soil wall has high seismic performance as generally known. However, the seismic behavior has not been clarified accurately yet, especially on multi-anchor wall with double wall facing. Indefinite behavior of reinforced soil wall during earthquake make us complicated in case with adopting to the abutment, because of arrangement of anchor plate as reinforcement often different according to the width of roads. In this study, a series of centrifuge model tests were carried out to investigate the reinforcement mechanism of multi anchor wall with double wall facing from the perspective of the vertical earth pressure. Several types of reinforce arrangement and rigid wall were applied in order to verify the arch function in the reinforced regions. The test results show unique behavior of vertical earth pressure, which was affected by arch action. All the vertical earth pressure placed behind facing panel, are larger than that of middle part between facing panel despite of friction between backfill and facing panel. Similar results were obtained in case using rigid wall. On the other hands, the vertical earth pressure, which were measured at the 3cm high from bottom of model container, shows larger than that of bottom. This results show the existence of arch action between double walls. In addition, it implies that the wall facing of such soil structure confined the backfill as pseudo wall, which is very reason that the multi anchor wall with double wall facing has high seismic performance.

Successive Homologous Coronal Mass Ejections Driven by Shearing and Converging Motions in Solar Active Region NOAA 12371

International Nuclear Information System (INIS)

Vemareddy, P.

2017-01-01

We study the magnetic field evolution in AR 12371, related to its successive eruptive nature. During the disk transit of seven days, the active region (AR) launched four sequential fast coronal mass ejections (CMEs), which are associated with long duration M-class flares. Morphological study delineates a pre-eruptive coronal sigmoid structure above the polarity inversion line (PIL) similar to Moore et al.’s study. The velocity field derived from tracked magnetograms indicates persistent shear and converging motions of polarity regions about the PIL. While these shear motions continue, the crossed arms of two sigmoid elbows are being brought to interaction by converging motions at the middle of the PIL, initiating the tether-cutting reconnection of field lines and the onset of the CME explosion. The successive CMEs are explained by a cyclic process of magnetic energy storage and release referred to as “sigmoid-to-arcade-to-sigmoid” transformation driven by photospheric flux motions. Furthermore, the continued shear motions inject helicity flux with a dominant negative sign, which contributes to core field twist and its energy by building a twisted flux rope (FR). After a limiting value, the excess coronal helicity is expelled by bodily ejection of the FR, which is initiated by some instability as realized by intermittent CMEs. This AR is in contrast with the confined AR 12192 with a predominant negative sign and larger helicity flux, but much weaker (−0.02 turns) normalized coronal helicity content. While predominant signed helicity flux is a requirement for CME eruption, our study suggests that the magnetic flux normalized helicity flux is a necessary condition accommodating the role of background flux and appeals to a further study of a large sample of ARs.

Successive Homologous Coronal Mass Ejections Driven by Shearing and Converging Motions in Solar Active Region NOAA 12371

Energy Technology Data Exchange (ETDEWEB)

Vemareddy, P., E-mail: vemareddy@iiap.res.in [Indian Institute of Astrophysics, II Block, Koramangala, Bengalure-560034 (India)

2017-08-10

We study the magnetic field evolution in AR 12371, related to its successive eruptive nature. During the disk transit of seven days, the active region (AR) launched four sequential fast coronal mass ejections (CMEs), which are associated with long duration M-class flares. Morphological study delineates a pre-eruptive coronal sigmoid structure above the polarity inversion line (PIL) similar to Moore et al.’s study. The velocity field derived from tracked magnetograms indicates persistent shear and converging motions of polarity regions about the PIL. While these shear motions continue, the crossed arms of two sigmoid elbows are being brought to interaction by converging motions at the middle of the PIL, initiating the tether-cutting reconnection of field lines and the onset of the CME explosion. The successive CMEs are explained by a cyclic process of magnetic energy storage and release referred to as “sigmoid-to-arcade-to-sigmoid” transformation driven by photospheric flux motions. Furthermore, the continued shear motions inject helicity flux with a dominant negative sign, which contributes to core field twist and its energy by building a twisted flux rope (FR). After a limiting value, the excess coronal helicity is expelled by bodily ejection of the FR, which is initiated by some instability as realized by intermittent CMEs. This AR is in contrast with the confined AR 12192 with a predominant negative sign and larger helicity flux, but much weaker (−0.02 turns) normalized coronal helicity content. While predominant signed helicity flux is a requirement for CME eruption, our study suggests that the magnetic flux normalized helicity flux is a necessary condition accommodating the role of background flux and appeals to a further study of a large sample of ARs.

A Study on the Nonmetallic Inclusion Motions in a Swirling Flow Submerged Entry Nozzle in a New Cylindrical Tundish Design

Science.gov (United States)

Ni, Peiyuan; Ersson, Mikael; Jonsson, Lage Tord Ingemar; Jönsson, Pär Göran

2018-04-01

Different sizes and shapes of nonmetallic inclusions in a swirling flow submerged entry nozzle (SEN) placed in a new tundish design were investigated by using a Lagrangian particle tracking scheme. The results show that inclusions in the current cylindrical tundish have difficulties remaining in the top tundish region, since a strong rotational steel flow exists in this region. This high rotational flow of 0.7 m/s provides the required momentum for the formation of a strong swirling flow inside the SEN. The results show that inclusions larger than 40 µm were found to deposit to a smaller extent on the SEN wall compared to smaller inclusions. The reason is that these large inclusions have Separation number values larger than 1. Thus, the swirling flow causes these large size inclusions to move toward the SEN center. For the nonspherical inclusions, large size inclusions were found to be deposited on the SEN wall to a larger extent, compared to spherical inclusions. More specifically, the difference of the deposited inclusion number is around 27 pct. Overall, it was found that the swirling flow contains three regions, namely, the isotropic core region, the anisotropic turbulence region and the near-wall region. Therefore, anisotropic turbulent fluctuations should be taken into account when the inclusion motion was tracked in this complex flow. In addition, many inclusions were found to deposit at the SEN inlet region. The plotted velocity distribution shows that the inlet flow is very chaotic. A high turbulent kinetic energy value of around 0.08 m2/s2 exists in this region, and a recirculating flow was also found here. These flow characteristics are harmful since they increase the inclusion transport toward the wall. Therefore, a new design of the SEN inlet should be developed in the future, with the aim to modify the inlet flow so that the inclusion deposition is reduced.

Quantitative analysis of regional myocardial performance in coronary artery disease

Science.gov (United States)

Stewart, D. K.; Dodge, H. T.; Frimer, M.

1975-01-01

Findings from a group of subjects with significant coronary artery stenosis are given. A group of controls determined by use of a quantitative method for the study of regional myocardial performance based on the frame-by-frame analysis of biplane left ventricular angiograms are presented. Particular emphasis was placed upon the analysis of wall motion in terms of normalized segment dimensions, timing and velocity of contraction. The results were compared with the method of subjective assessment used clinically.

Speculation about near-wall turbulence scales

International Nuclear Information System (INIS)

Yurchenko, N F

2008-01-01

A strategy to control near-wall turbulence modifying scales of fluid motion is developed. The boundary-layer flow is shown to respond selectively to the scale of streamwise vortices initiated, e.g. with the spanwise regular temperature distribution over a model surface. It is used to generate sustainable streamwise vortices and thus to optimize integral flow characteristics.

Domain walls collision in Fe-rich and Co-rich glass covered microwires

Directory of Open Access Journals (Sweden)

Gonzalez J.

2013-01-01

Full Text Available We report the results of the investigation of domain walls propagation in Fe-rich and Co-rich microwires performed using Sixtus-Tonks and magneto-optical Kerr effect techniques. It was found that under certain experimental conditions we are able to create the regime of the motion of two domain walls moving to opposite directions which terminates by the collision of the domain walls. Also the domain walls collision was visualized using magneto-optical Kerr effect microscope when the surface giant Barkhausen jump induced by circular magnetic field has been observed.

Model and experimental vizualisation of a bubble interacting with an inclined wall

Science.gov (United States)

Podvin, Berengere; Khoja, Suleman; Attinger, Daniel; Moraga, Francisco

2006-11-01

We describe the motion of an air bubble rising through water as it interacts with a wall of variable inclination. The bubble diameter varies about O(1) mm. We use lubrication theory to determine the modification of the bubble interface and compute the hydrodynamic force exerted by the wall. The present work is an extension of Moraga et al's model [Computers and Fluids 2006], which was devised for a horizontal wall. The predictions of the model are checked against experimental visualizations. The influence of the Weber number, Reynolds number and wall inclination is examined

Plasma-wall interactions

International Nuclear Information System (INIS)

Behrisch, Rainer

1978-01-01

The plasma wall interactions for two extreme cases, the 'vacuum model' and the 'cold gas blanket' are outlined. As a first step for understanding the plasma wall interactions the elementary interaction processes at the first wall are identified. These are energetic ion and neutral particle trapping and release, ion and neutral backscattering, ion sputtering, desorption by ions, photons and electrons and evaporation. These processes have only recently been started to be investigated in the parameter range of interest for fusion research. The few measured data and their extrapolation into regions not yet investigated are reviewed

Analysis of secondary motions in square duct flow

Science.gov (United States)

Modesti, Davide; Pirozzoli, Sergio; Orlandi, Paolo; Grasso, Francesco

2018-04-01

We carry out direct numerical simulations (DNS) of square duct flow spanning the friction Reynolds number range {Re}τ * =150-1055, to study the nature and the role of secondary motions. We preliminarily find that secondary motions are not the mere result of the time averaging procedure, but rather they are present in the instantaneous flow realizations, corresponding to large eddies persistent in both space and time. Numerical experiments have also been carried out whereby the secondary motions are suppressed, hence allowing to quantifying their effect on the mean flow field. At sufficiently high Reynolds number, secondary motions are found to increase the friction coefficient by about 3%, hence proportionally to their relative strength with respect to the bulk flow. Simulations without secondary motions are found to yield larger deviations on the mean velocity profiles from the standard law-of-the-wall, revealing that secondary motions act as a self-regulating mechanism of turbulence whereby the effect of the corners is mitigated.

F2 phenomenological test on fuel motion (Interim report)

International Nuclear Information System (INIS)

Palm, R.G.; Fink, C.L.; Stewart, R.R.; Gehl, S.M.; Rothman, A.B.

1976-09-01

TREAT F-series tests are being conducted to provide data on fuel motion at accident power levels from one to about ten times design for use in development of fuel motion models. Test F2 was conducted to evaluate motion of high power fuel in a hypothetical LMFBR unprotected TUC (transient undercooling) accident. Fuel and fuel-boundary conditions following coolant boiling and dryout under TUC conditions are achieved in each F-series test with a single fuel element surrounded by a nuclear heated wall in a dry test capsule. Test F2 was conducted with a low burnup but restructured fuel element to investigate the effect of fuel vapor pressure on fuel motion. Results are presented and discussed

Enhanced washout of 99mTc-tetrofosmin in hypertrophic cardiomyopathy: quantitative comparisons with regional 123I-BMIPP uptake and wall thickness determined by MRI

International Nuclear Information System (INIS)

Thet-Thet-Lwin, Tohoru; Takeda, Jin; Wu, Yuko; Fumikura, Keiji; Iida, Satoru; Kawano, Iwao; Yamaguchi, Yuji; Itai

2003-01-01

The diagnostic value of technetium-99m tetrofosmin (TF) washout in hypertrophic cardiomyopathy (HCM) was examined by investigating its relation to the metabolic abnormality depicted by iodine-123 β-methyl-p-iodophenylpentadecanoic acid (BMIPP) uptake and the left ventricular (LV) myocardial wall thickness as measured by magnetic resonance imaging (MRI). TF washout was evaluated in 31 patients with HCM and 23 normal control subjects using 30-min (early) and 3-h (delayed) TF single-photon emission tomography images. The LV myocardial wall was divided into 19 segments and the percentage TF washout, regional BMIPP uptake and LV wall thickness were measured in each segment. Mean TF washout in the patients with HCM was significantly faster than that in normal control subjects (23.7±5.7 vs 13.4±4.1, P<0.0001). In the patients with HCM, TF washout showed an excellent correlation with MRI wall thickness (r=0.82, P<0.0001) and a good inverse correlation with regional BMIPP uptake (r=-0.72, P<0.0001). In addition, a good linear correlation was observed between TF uptake and MRI wall thickness in the 19 regional segments. In conclusion, the degree of TF washout corresponds well with the severity of myocardial wall thickness and the degree of metabolic abnormality in patients with HCM. These results suggest that enhanced TF washout might provide additional clinical information regarding metabolic alterations in HCM. (orig.)

Enhanced washout of 99mTc-tetrofosmin in hypertrophic cardiomyopathy: quantitative comparisons with regional 123I-BMIPP uptake and wall thickness determined by MRI.

Science.gov (United States)

Thet-Thet-Lwin; Takeda, Tohoru; Wu, Jin; Fumikura, Yuko; Iida, Keiji; Kawano, Satoru; Yamaguchi, Iwao; Itai, Yuji

2003-07-01

The diagnostic value of technetium-99m tetrofosmin (TF) washout in hypertrophic cardiomyopathy (HCM) was examined by investigating its relation to the metabolic abnormality depicted by iodine-123 beta-methyl- p-iodophenylpentadecanoic acid (BMIPP) uptake and the left ventricular (LV) myocardial wall thickness as measured by magnetic resonance imaging (MRI). TF washout was evaluated in 31 patients with HCM and 23 normal control subjects using 30-min (early) and 3-h (delayed) TF single-photon emission tomography images. The LV myocardial wall was divided into 19 segments and the percentage TF washout, regional BMIPP uptake and LV wall thickness were measured in each segment. Mean TF washout in the patients with HCM was significantly faster than that in normal control subjects (23.7+/-5.7 vs 13.4+/-4.1, P<0.0001). In the patients with HCM, TF washout showed an excellent correlation with MRI wall thickness ( r=0.82, P<0.0001) and a good inverse correlation with regional BMIPP uptake ( r=-0.72, P<0.0001). In addition, a good linear correlation was observed between TF uptake and MRI wall thickness in the 19 regional segments. In conclusion, the degree of TF washout corresponds well with the severity of myocardial wall thickness and the degree of metabolic abnormality in patients with HCM. These results suggest that enhanced TF washout might provide additional clinical information regarding metabolic alterations in HCM.

Motion and shape change when using an endorectal balloon during prostate radiation therapy

International Nuclear Information System (INIS)

Court, Laurence E.; D'Amico, Anthony V.; Kadam, Dnyanesh; Cormack, Robert

2006-01-01

Purpose: To investigate motion and shape change when using an endorectal balloon (ERB) in patients receiving radiotherapy for prostate cancer. Methods: In nine patients treated for prostate cancer using an ERB, the anterior wall of the ERB was contoured on right lateral images taken immediately before irradiation, and on left lateral images taken immediately after irradiation. Changes in the contours were used to calculate inter-fraction shape change and inter-imaging motion and shape change. Inter-imaging motion describes changes that occur after the right lateral image is taken that are seen in the left lateral image. Results: Eighty-six percent of all inter-imaging shifts of the anterior wall of the ERB were in the posterior direction (mean: 1.8 mm, 1 SD: 1.8 mm, maximum posterior shift: 2.8-7.2 mm). The inter-fraction shape change (1 SD) of the anterior wall was equivalent to a change in the angle of the balloon of 2.5-5.7 deg., with a range of 8-20 deg., depending on the patient. Inter-imaging shape changes were similar in size. Conclusions: The inter-imaging motion and shape changes may be explained by the patient relaxing some time after insertion of the ERB, indicating that it could be reduced by a waiting period after insertion before irradiation. Development of image-guided localization strategies should consider intra-fraction motion and also inter- and intra-fraction shape change

Three-dimensional fluid flow phenomena in the blade end wall corner region

Science.gov (United States)

Hazarika, B. K.; Raj, R.; Boldman, D. R.

1986-01-01

Flow visualization, static and total pressure measurements, and mean velocity profile measurements with a single-sensor inclined hot wire probe, are used in a study of three-dimensional flow at a turbine blade end wall corner region for six critical axial stations along the blade chord. Three vortices are identified: (1) a horseshoe vortex near the leading edge; (2) a corner eddy between the horseshoe vortex and the corner; and (3) a vortex at the rear portion of the corner due to the corner eddy's secondary flow. Attention is given to the relative size and rate-of-spread of the vortices in the streamwise direction.

Volume Modulated Arc Therapy (VMAT for pulmonary Stereotactic Body Radiotherapy (SBRT in patients with lesions in close approximation to the chest wall

Directory of Open Access Journals (Sweden)

Thomas J. FitzGerald

2013-02-01

Full Text Available Chest wall pain and discomfort has been recognized as a significant late effect of radiation therapy in historical and modern treatment models. Stereotactic Body Radiotherapy (SBRT is becoming an important treatment tool in oncology care for patients with intrathoracic lesions. For lesions in close approximation to the chest wall including lesions requiring motion management, SBRT techniques can deliver high dose to the chest wall. As an unintended target of consequence, there is possibility of generating significant chest wall pain and discomfort as a late effect of therapy. The purpose of this paper is to evaluate the potential role of Volume Modulated Arc Therapy (VMAT technologies in decreasing chest wall dose in SBRT treatment of pulmonary lesions in close approximation to the chest wall.Ten patients with pulmonary lesions of various sizes and topography in close approximation to the chest wall were selected for retrospective review. All volumes including target, chest wall, ribs, and lung were contoured with maximal intensity projection maps and four-dimensional computer tomography planning. Radiation therapy planning consisted of static techniques including Intensity Modulated Radiation Therapy compared to VMAT therapy to a dose of 60Gy in 12Gy fractions. Dose volume histogram to rib, chest wall, and lung were compared between plans with statistical analysis.In all patients dose and volume were improved to ribs and chest wall using VMAT technologies compared to static field techniques. On average, volume receiving 30Gy to the chest wall was improved by 72%;the ribs by 60%. In only one patient did the VMAT treatment technique increase pulmonary volume receiving 20Gy (V20.VMAT technology has potential of limiting radiation dose to sensitive chest wall regions in patients with lesions in close approximation to this structure. This would also have potential value to lesions treated with SBRT in other body regions where targets abut critical

Motion of a vortex line near the boundary of a semi-infinite uniform condensate

International Nuclear Information System (INIS)

Mason, Peter; Berloff, Natalia G.; Fetter, Alexander L.

2006-01-01

We consider the motion of a vortex in an asymptotically homogeneous condensate bounded by a solid wall where the wave function of the condensate vanishes. For a vortex parallel to the wall, the motion is essentially equivalent to that generated by an image vortex, but the depleted surface layer induces an effective shift in the position of the image compared to the case of a vortex pair in an otherwise uniform flow. Specifically, the velocity of the vortex can be approximated by U≅((ℎ/2π)/2m)(y 0 -√(2)ξ) -1 , where y 0 is the distance from the center of the vortex to the wall, ξ is the healing length of the condensate, and m is the mass of the boson

Analysis of wall-packed-bed thermal interactions

International Nuclear Information System (INIS)

Gorbis, Z.R.; Tillack, M.S.; Tehranian, F.; Abdou, M.A.

1995-01-01

One of the major issues remaining for ceramic breeder blankets involves uncertainties in heat transfer and thermomechanical interactions within the breeder and multiplier regions. Particle bed forms are considered in many reactor blanket designs for both the breeder and Be multiplier. The effective thermal conductivity of beds and the wall-bed thermal conductance are still not adequately characterized, particularly under the influence of mechanical stresses. The problem is particularly serious for the wall conductance between Be and its cladding, where the uncertainty can be greater than 50%. In this work, we describe a new model for the wall-bed conductance that treats the near-wall region as a finite-width zone. The model includes an estimate of the region porosity based on the number of contact points, and the contact area for smooth surfaces. It solves the heat conduction in a near-wall unit cell. The model is verified with existing data and used to predict the range of wall conductances expected in future simulation experiments and in reactor applications. (orig.)

A Wind Tunnel Investigation of the Influence of Solar-Induced Wall-Heating on the Flow Regime within a Simulated Urban Street Canyon

International Nuclear Information System (INIS)

Kovar-Panskus, A.; Moulinneuf, L.; Savory, E.; Abdelqari, A.; Sini, J.-F.; Rosant, J.-M.; Robins, A.; Toy, N.

2002-01-01

A wind tunnel study has been undertaken to assess the influence of solar-induced wall heating on the airflow pattern within a street canyon under low-speed wind conditions. This flow is normally dominated by large-scale vortical motion, such that the wind moves downwards at the downstream wall. In the present work the aim has been to examine whether the buoyancy forces generated at this wall by solar-induced heating are of sufficient strength to oppose the downward inertial forces and, thereby, change the canyon flow pattern. Such changes will also influence the dispersion of pollutants within the street. In the experiments the windward-facing wall of a canyon has been uniformly heated to simulate the effect of solar radiation.Four different test cases, representing different degrees of buoyancy (defined by a test Froude number, Fr), have been examined using a simple, 2-D, square-section canyon model in a wind tunnel. For reference purposes, the neutral case (no wall heating), has also been studied. The approach flow boundary layer conditions have been well defined, with the wind normal to the main canyon axis, and measurements have been taken of canyon wall and air temperatures and profiles of mean velocities and turbulence intensities.Analysis of the results shows clear differences in the flow patterns. As Fr decreases from the neutral case there are reductions of up to 50% in the magnitudes of the reverseflow velocities near the ground and in the upward motion near the upstream wall. A marked transition occurs at Fr ∼ 1, where the single dominant vortex, existing at higher Fr values, weakens and moves upwards whilst a lower region of relatively stagnant flow appears. This transition had previously been observed in numerical model predictions but at a Fr at least an order of magnitude higher

Precision and accuracy in CT attenuation measurement of vascular wall using region-of-interest supported by differentiation curve

International Nuclear Information System (INIS)

Suzuki, Shigeru; Kidouchi, Takashi; Kuwahara, Sadatoshi; Vembar, Mani; Takei, Ryoji; Yamamoto, Asako

2012-01-01

Objectives: To evaluate the precision and accuracy in CT attenuation measurement of vascular wall using region-of-interest (ROI) supported by differentiation curves. Study design: We used vascular models (actual attenuation value of the wall: 87 HU) with wall thicknesses of 1.5, 1.0, or 0.5 mm, filled with contrast material of 250, 348, or 436 HU. The nine vascular models were scanned with a 64-detector CT. The wall attenuation values were measured using three sizes (diameter: 0.5, 1.0, and 1.5 mm) of ROIs without differentiation curves. Sixteen measurements were repeated for each vascular model by each of two operators. Measurements supported by differentiation curves were also performed. We used analyses of variance with repeated measures for the measured attenuations for each size of the ROI. Results: Without differentiation curves, there were significant differences in the attenuation values of the wall among the three densities of contrast material, and the attenuation values tended to be overestimated more as the contrast material density increased. Operator dependencies were also found in measurements for 0.5- and 1.5-mm thickness models. With differentiation curves, measurements were not possible for 0.5- and 1.0-mm thickness models. Using differentiation curves for 1.5-mm thickness models with a ROI of 1.0- or 1.5-mm diameter, the wall attenuations were not affected by the contrast material densities and were operator independent, measuring between 75 and 103 HU. Conclusions: The use of differentiation curves can improve the precision and accuracy in wall attenuation measurement using a ROI technique, while measurements for walls of ≤1.0 mm thickness are difficult.

Linear modeling of turbulent skin-friction reduction due to spanwise wall motion

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Duque-Daza, Carlos; Baig, Mirza; Lockerby, Duncan; Chernyshenko, Sergei; Davies, Christopher; University of Warwick Team; Imperial College Team; Cardiff University Team

2012-11-01

We present a study on the effect of streamwise-travelling waves of spanwise wall velocity on the growth of near-wall turbulent streaks using a linearized formulation of the Navier-Stokes equations. The changes in streak amplification due to the travelling waves induced by the wall velocity are compared to published results of direct numerical simulation (DNS) predictions of the turbulent skin-friction reduction over a range of parameters; a clear correlation between these two sets of results is observed. Additional linearized simulations but at a much higher Reynolds numbers, more relevant to aerospace applications, produce results that show no marked differences to those obtained at low Reynolds number. It is also observed that a close correlation exists between DNS data of drag reduction and a very simple characteristic of the ``generalized'' Stokes layer generated by the streamwise-travelling waves. Carlos.Duque-Daza@warwick.ac.uk - School of Engineering, University of Warwick, Coventry CV4 7AL, UK caduqued@unal.edu.co - Department of Mechanical and Mechatronics Engineering, Universidad Nacional de Colombia.

Breaking of chiral symmetry in vortex domain wall propagation in ferromagnetic nanotubes

International Nuclear Information System (INIS)

Otálora, J.A.; López-López, J.A.; Landeros, P.; Vargas, P.; Núñez, A.S.

2013-01-01

This paper is focused to the field-induced dynamics of vortex-like domain walls (VDWs) in magnetic nanotubes (MNTs). Based on a dissipative Lagrangian formalism that fully includes damping as well as exchange and dipole–dipole coupling, it is shown that VDW motion is very sensitive to the chirality, giving rise to a chiral asymmetry in the vortex wall propagation. As a consequence, the dynamics of the wall is fundamentally different to that of nanostripes and solid nanowires. Besides the well-known Walker breakdown that stands at the onset of the precessional wall motion, it is found an additional breakdown field (called here the chiral breakdown) that modifies the steady regime of VDWs. We also show outstanding VDWs dynamical properties at low applied fields, as low-field mobilities (∼10km/(sT)) and very short relaxation times (∼1ns), offering a reliable fast control of VDWs velocities (∼1000m/s at applied fields of 0.7 mT). - Highlights: • We model analytically the dynamics of vortex domain walls in magnetic nanotubes. • We fully include damping, exchange and dipole–dipole coupling. • The wall dynamics is fundamentally different to that of nanostripes. • We report and describe an extra dynamical instability, the Chiral Breakdown field. • We report outstanding dynamical properties at weak magnetic fields

Breaking of chiral symmetry in vortex domain wall propagation in ferromagnetic nanotubes

Energy Technology Data Exchange (ETDEWEB)

Otálora, J.A., E-mail: jorge.otalora@usm.cl [Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, Valparaíso (Chile); López-López, J.A.; Landeros, P.; Vargas, P. [Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, Valparaíso (Chile); Núñez, A.S. [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Blanco Encalada 2008, Santiago (Chile)

2013-09-15

This paper is focused to the field-induced dynamics of vortex-like domain walls (VDWs) in magnetic nanotubes (MNTs). Based on a dissipative Lagrangian formalism that fully includes damping as well as exchange and dipole–dipole coupling, it is shown that VDW motion is very sensitive to the chirality, giving rise to a chiral asymmetry in the vortex wall propagation. As a consequence, the dynamics of the wall is fundamentally different to that of nanostripes and solid nanowires. Besides the well-known Walker breakdown that stands at the onset of the precessional wall motion, it is found an additional breakdown field (called here the chiral breakdown) that modifies the steady regime of VDWs. We also show outstanding VDWs dynamical properties at low applied fields, as low-field mobilities (∼10km/(sT)) and very short relaxation times (∼1ns), offering a reliable fast control of VDWs velocities (∼1000m/s at applied fields of 0.7 mT). - Highlights: • We model analytically the dynamics of vortex domain walls in magnetic nanotubes. • We fully include damping, exchange and dipole–dipole coupling. • The wall dynamics is fundamentally different to that of nanostripes. • We report and describe an extra dynamical instability, the Chiral Breakdown field. • We report outstanding dynamical properties at weak magnetic fields.

Some analyses on the plasma motion in the space active region of the axial symmetry

International Nuclear Information System (INIS)

Li Zhongyuan; Hu Wenrui.

1986-04-01

In general, the potential magnetic field may gradually be twisted into the force-free magnetic field with the current produced by plasma rotation. In this paper, it is pointed out that if the magnetic field has no singularity on the symmetric axis, then the potential magnetic field cannot be twisted into the force-free magnetic field. Namely, it is not a perfect approach that the energy storage is only caused by the pure azimuthal motion in the active region. Besides the pure spiral motion, the unsteady coupling process between the magnetic field and both the toroidal and the poloidal velocity components should be analyzed. Finally, in the present note, some features of the kinematical force-free magnetic field of the axial symmetry are presented by the authors. (author)

Audiovisual biofeedback improves motion prediction accuracy.

Science.gov (United States)

Pollock, Sean; Lee, Danny; Keall, Paul; Kim, Taeho

2013-04-01

The accuracy of motion prediction, utilized to overcome the system latency of motion management radiotherapy systems, is hampered by irregularities present in the patients' respiratory pattern. Audiovisual (AV) biofeedback has been shown to reduce respiratory irregularities. The aim of this study was to test the hypothesis that AV biofeedback improves the accuracy of motion prediction. An AV biofeedback system combined with real-time respiratory data acquisition and MR images were implemented in this project. One-dimensional respiratory data from (1) the abdominal wall (30 Hz) and (2) the thoracic diaphragm (5 Hz) were obtained from 15 healthy human subjects across 30 studies. The subjects were required to breathe with and without the guidance of AV biofeedback during each study. The obtained respiratory signals were then implemented in a kernel density estimation prediction algorithm. For each of the 30 studies, five different prediction times ranging from 50 to 1400 ms were tested (150 predictions performed). Prediction error was quantified as the root mean square error (RMSE); the RMSE was calculated from the difference between the real and predicted respiratory data. The statistical significance of the prediction results was determined by the Student's t-test. Prediction accuracy was considerably improved by the implementation of AV biofeedback. Of the 150 respiratory predictions performed, prediction accuracy was improved 69% (103/150) of the time for abdominal wall data, and 78% (117/150) of the time for diaphragm data. The average reduction in RMSE due to AV biofeedback over unguided respiration was 26% (p biofeedback improves prediction accuracy. This would result in increased efficiency of motion management techniques affected by system latencies used in radiotherapy.

Vertical land motion controls regional sea level rise patterns on the United States east coast since 1900

Science.gov (United States)

Piecuch, C. G.; Huybers, P. J.; Hay, C.; Mitrovica, J. X.; Little, C. M.; Ponte, R. M.; Tingley, M.

2017-12-01

Understanding observed spatial variations in centennial relative sea level trends on the United States east coast has important scientific and societal applications. Past studies based on models and proxies variously suggest roles for crustal displacement, ocean dynamics, and melting of the Greenland ice sheet. Here we perform joint Bayesian inference on regional relative sea level, vertical land motion, and absolute sea level fields based on tide gauge records and GPS data. Posterior solutions show that regional vertical land motion explains most (80% median estimate) of the spatial variance in the large-scale relative sea level trend field on the east coast over 1900-2016. The posterior estimate for coastal absolute sea level rise is remarkably spatially uniform compared to previous studies, with a spatial average of 1.4-2.3 mm/yr (95% credible interval). Results corroborate glacial isostatic adjustment models and reveal that meaningful long-period, large-scale vertical velocity signals can be extracted from short GPS records.

Large exchange-dominated domain wall velocities in antiferromagnetically coupled nanowires

Science.gov (United States)

Kuteifan, Majd; Lubarda, M. V.; Fu, S.; Chang, R.; Escobar, M. A.; Mangin, S.; Fullerton, E. E.; Lomakin, V.

2016-04-01

Magnetic nanowires supporting field- and current-driven domain wall motion are envisioned for methods of information storage and processing. A major obstacle for their practical use is the domain-wall velocity, which is traditionally limited for low fields and currents due to the Walker breakdown occurring when the driving component reaches a critical threshold value. We show through numerical and analytical modeling that the Walker breakdown limit can be extended or completely eliminated in antiferromagnetically coupled magnetic nanowires. These coupled nanowires allow for large domain-wall velocities driven by field and/or current as compared to conventional nanowires.

Visual motion imagery neurofeedback based on the hMT+/V5 complex: evidence for a feedback-specific neural circuit involving neocortical and cerebellar regions

Science.gov (United States)

Banca, Paula; Sousa, Teresa; Catarina Duarte, Isabel; Castelo-Branco, Miguel

2015-12-01

Objective. Current approaches in neurofeedback/brain-computer interface research often focus on identifying, on a subject-by-subject basis, the neural regions that are best suited for self-driven modulation. It is known that the hMT+/V5 complex, an early visual cortical region, is recruited during explicit and implicit motion imagery, in addition to real motion perception. This study tests the feasibility of training healthy volunteers to regulate the level of activation in their hMT+/V5 complex using real-time fMRI neurofeedback and visual motion imagery strategies. Approach. We functionally localized the hMT+/V5 complex to further use as a target region for neurofeedback. An uniform strategy based on motion imagery was used to guide subjects to neuromodulate hMT+/V5. Main results. We found that 15/20 participants achieved successful neurofeedback. This modulation led to the recruitment of a specific network as further assessed by psychophysiological interaction analysis. This specific circuit, including hMT+/V5, putative V6 and medial cerebellum was activated for successful neurofeedback runs. The putamen and anterior insula were recruited for both successful and non-successful runs. Significance. Our findings indicate that hMT+/V5 is a region that can be modulated by focused imagery and that a specific cortico-cerebellar circuit is recruited during visual motion imagery leading to successful neurofeedback. These findings contribute to the debate on the relative potential of extrinsic (sensory) versus intrinsic (default-mode) brain regions in the clinical application of neurofeedback paradigms. This novel circuit might be a good target for future neurofeedback approaches that aim, for example, the training of focused attention in disorders such as ADHD.

Electrocardiographic changes of acute lateral wall myocardial infarction: a reappraisal based on scintigraphic localization of the infarct

International Nuclear Information System (INIS)

Movahed, A.; Becker, L.C.

1984-01-01

To determine how often acute lateral myocardial infarcts may be electrocardiographically silent, a new approach was utilized in which subjects were selected by admission thallium scintigraphy. Thirty-one patients with their first infarction were identified with moderate to severe perfusion defects of the lateral and posterolateral walls, persistent over 7 days and associated with severe wall motion abnormalities. Patients with involvement of the anterior, septal or inferior regions were not included. In nine patients, the perfusion defect extended to the anterolateral wall: all developed ST elevation and Q waves in at least one of the lateral leads (I, aVL or V6) but none showed changes in the inferior leads (II, III or aVF). In the other 22 patients, the perfusion defect was limited to the lateral and posterolateral walls: only 12 showed ST elevations (inferior leads only in 7, lateral leads only in 2, both leads in 3) and only 9 developed Q waves (inferior in all). In 8 of these 22 patients, the infarct was silent in the sense that no ST segment elevation or Q waves were seen, although ST depressions or T wave inversions, or both, in all but one patient were compatible with subendocardial infarction. The results indicate that the standard electrocardiogram is insensitive to changes in the lateral and posterolateral regions. Additional diagnostic studies are needed for proper localization and sizing of acute myocardial infarcts

Fractality and the law of the wall

Science.gov (United States)

Xu, Haosen H. A.; Yang, X. I. A.

2018-05-01

Fluid motions in the inertial range of isotropic turbulence are fractal, with their space-filling capacity slightly below regular three-dimensional objects, which is a consequence of the energy cascade. Besides the energy cascade, the other often encountered cascading process is the momentum cascade in wall-bounded flows. Despite the long-existing analogy between the two processes, many of the thoroughly investigated aspects of the energy cascade have so far received little attention in studies of the momentum counterpart, e.g., the possibility of the momentum-transferring scales in the logarithmic region being fractal has not been considered. In this work, this possibility is pursued, and we discuss one of its implications. Following the same dimensional arguments that lead to the D =2.33 fractal dimension of wrinkled surfaces in isotropic turbulence, we show that the large-scale momentum-carrying eddies may also be fractal and non-space-filling, which then leads to the power-law scaling of the mean velocity profile. The logarithmic law of the wall, on the other hand, corresponds to space-filling eddies, as suggested by Townsend [The Structure of Turbulent Shear Flow (Cambridge University Press, Cambridge, 1980)]. Because the space-filling capacity is an integral geometric quantity, the analysis presented in this work provides us with a low-order quantity, with which, one would be able to distinguish between the logarithmic law and the power law.

Modelling the nonlinear behaviour of double walled carbon nanotube based resonator with curvature factors

Science.gov (United States)

Patel, Ajay M.; Joshi, Anand Y.

2016-10-01

This paper deals with the nonlinear vibration analysis of a double walled carbon nanotube based mass sensor with curvature factor or waviness, which is doubly clamped at a source and a drain. Nonlinear vibrational behaviour of a double-walled carbon nanotube excited harmonically near its primary resonance is considered. The double walled carbon nanotube is harmonically excited by the addition of an excitation force. The modelling involves stretching of the mid plane and damping as per phenomenon. The equation of motion involves four nonlinear terms for inner and outer tubes of DWCNT due to the curved geometry and the stretching of the central plane due to the boundary conditions. The vibrational behaviour of the double walled carbon nanotube with different surface deviations along its axis is analyzed in the context of the time response, Poincaré maps and Fast Fourier Transformation diagrams. The appearance of instability and chaos in the dynamic response is observed as the curvature factor on double walled carbon nanotube is changed. The phenomenon of Periodic doubling and intermittency are observed as the pathway to chaos. The regions of periodic, sub-harmonic and chaotic behaviour are clearly seen to be dependent on added mass and the curvature factors in the double walled carbon nanotube. Poincaré maps and frequency spectra are used to explicate and to demonstrate the miscellany of the system behaviour. With the increase in the curvature factor system excitations increases and results in an increase of the vibration amplitude with reduction in excitation frequency.

MHD peristaltic motion of Johnson-Segalman fluid in a channel with compliant walls

International Nuclear Information System (INIS)

Hayat, T.; Javed, Maryiam; Asghar, S.

2008-01-01

A mathematical model for magnetohydrodynamic (MHD) flow of a Johnson-Segalman fluid in a channel with compliant walls is analyzed. The flow is engendered due to sinusoidal waves on the channel walls. A series solution is developed for the case in which the amplitude ratio is small. Our computations show that the mean axial velocity of a Johnson-Segalman fluid is smaller than that of a viscous fluid. The variations of various interesting dimensionless parameters are graphed and discussed

Stochastic ground motion simulation

Science.gov (United States)

Rezaeian, Sanaz; Xiaodan, Sun; Beer, Michael; Kougioumtzoglou, Ioannis A.; Patelli, Edoardo; Siu-Kui Au, Ivan

2014-01-01

Strong earthquake ground motion records are fundamental in engineering applications. Ground motion time series are used in response-history dynamic analysis of structural or geotechnical systems. In such analysis, the validity of predicted responses depends on the validity of the input excitations. Ground motion records are also used to develop ground motion prediction equations(GMPEs) for intensity measures such as spectral accelerations that are used in response-spectrum dynamic analysis. Despite the thousands of available strong ground motion records, there remains a shortage of records for large-magnitude earthquakes at short distances or in specific regions, as well as records that sample specific combinations of source, path, and site characteristics.

From Regional Hazard Assessment to Nuclear-Test-Ban Treaty Support - InSAR Ground Motion Services

Science.gov (United States)

Lege, T.; Kalia, A.; Gruenberg, I.; Frei, M.

2016-12-01

There are numerous scientific applications of InSAR methods in tectonics, earthquake analysis and other geologic and geophysical fields. Ground motion on local and regional scale measured and monitored via the application of the InSAR techniques provide scientists and engineers with plenty of new insights and further understanding of subsurface processes. However, the operational use of InSAR is not yet very widespread. To foster the operational utilization of the Copernicus Sentinel Satellites in the day-to-day business of federal, state and municipal work and planning BGR (Federal Institute for Geosciences and Natural Resources) initiated workshops with potential user groups. Through extensive reconcilement of interests and demands with scientific, technical, economic and governmental stakeholders (e.g. Ministries, Mining Authorities, Geological Surveys, Geodetic Surveys and Environmental Agencies on federal and state level, SMEs, German Aerospace Center) BGR developed the concept of the InSAR based German National Ground Motion Service. One important backbone for the nationwide ground motion service is the so-called Persistent Scatterer Interferometry Wide Area Product (WAP) approach developed with grants of European research funds. The presentation shows the implementation of the ground motion service and examples for product developments for operational supervision of mining, water resources management and spatial planning. Furthermore the contributions of Copernicus Sentinel 1 radar data in the context of CTBT are discussed. The DInSAR processing of Sentinel 1 IW (Interferometric Wide Swath) SAR acquisitions from January 1st and 13th Jan. 2016 allow for the first time a near real time ground motion measurement of the North Korean nuclear test site. The measured ground displacements show a strong spatio-temporal correlation to the calculated epicenter measured by teleseismic stations. We are convinced this way another space technique will soon contribute even

One-dimensional Fermi accelerator model with moving wall described by a nonlinear van der Pol oscillator.

Science.gov (United States)

Botari, Tiago; Leonel, Edson D

2013-01-01

A modification of the one-dimensional Fermi accelerator model is considered in this work. The dynamics of a classical particle of mass m, confined to bounce elastically between two rigid walls where one is described by a nonlinear van der Pol type oscillator while the other one is fixed, working as a reinjection mechanism of the particle for a next collision, is carefully made by the use of a two-dimensional nonlinear mapping. Two cases are considered: (i) the situation where the particle has mass negligible as compared to the mass of the moving wall and does not affect the motion of it; and (ii) the case where collisions of the particle do affect the movement of the moving wall. For case (i) the phase space is of mixed type leading us to observe a scaling of the average velocity as a function of the parameter (χ) controlling the nonlinearity of the moving wall. For large χ, a diffusion on the velocity is observed leading to the conclusion that Fermi acceleration is taking place. On the other hand, for case (ii), the motion of the moving wall is affected by collisions with the particle. However, due to the properties of the van der Pol oscillator, the moving wall relaxes again to a limit cycle. Such kind of motion absorbs part of the energy of the particle leading to a suppression of the unlimited energy gain as observed in case (i). The phase space shows a set of attractors of different periods whose basin of attraction has a complicated organization.

Peculiarities of low-frequency dielectric spectra and domain wall motion in gadolinium molybdate

International Nuclear Information System (INIS)

Galiyarova, N.M.; Gorin, S.V.; Dontsova, L.I.; Shil'nikov, A.V.; Shuvalov, L.A.

1994-01-01

Low-frequency Debye dispersion of dielectric permeability in GMO with the low values of high-frequency limit ε ∞ was investigated in a wide temperature range as well as in fields of variable amplitude. The features of domain boundaries motion were studied at the partial repolarization in monopolar P-pulsed fields. The model of cooperationrelaxation motion brifing in parallel with positive to negative contribution to polarization that explained the low values of ε ∞ was suggested

Domain wall energy landscapes in amorphous magnetic films with asymmetric arrays of holes

International Nuclear Information System (INIS)

Alija, A; Perez-Junquera, A; RodrIguez-RodrIguez, G; Velez, M; Alameda, J M; MartIn, J I; Marconi, V I; Kolton, A B; Parrondo, J M R; Anguita, J V

2009-01-01

Arrays of asymmetric holes have been defined in amorphous Co-Si films by e-beam lithography in order to study domain wall motion across the array subject to the asymmetric pinning potential created by the holes. Experimental results on Kerr effect magnetooptical measurements and hysteresis loops are compared with micromagnetic simulations in films with arrays of triangular holes. These show that the potential asymmetry favours forward wall propagation for flat walls but, if the wall contains a kink, net backward wall propagation is preferred at low fields, in agreement with minor loop experiments. The difference between the fields needed for forward and backward flat wall propagation increases as the size of the triangular holes is reduced, becoming maximum for 1 μm triangles, which is the characteristic length scale set by domain wall width.

Domain wall energy landscapes in amorphous magnetic films with asymmetric arrays of holes

Science.gov (United States)

Alija, A.; Pérez-Junquera, A.; Rodríguez-Rodríguez, G.; Vélez, M.; Marconi, V. I.; Kolton, A. B.; Anguita, J. V.; Alameda, J. M.; Parrondo, J. M. R.; Martín, J. I.

2009-02-01

Arrays of asymmetric holes have been defined in amorphous Co-Si films by e-beam lithography in order to study domain wall motion across the array subject to the asymmetric pinning potential created by the holes. Experimental results on Kerr effect magnetooptical measurements and hysteresis loops are compared with micromagnetic simulations in films with arrays of triangular holes. These show that the potential asymmetry favours forward wall propagation for flat walls but, if the wall contains a kink, net backward wall propagation is preferred at low fields, in agreement with minor loop experiments. The difference between the fields needed for forward and backward flat wall propagation increases as the size of the triangular holes is reduced, becoming maximum for 1 µm triangles, which is the characteristic length scale set by domain wall width.

Characterization of Pancreatic Tumor Motion Using Cine MRI: Surrogates for Tumor Position Should Be Used With Caution

International Nuclear Information System (INIS)

Feng, Mary; Balter, James M.; Normolle, Daniel; Adusumilli, Saroja; Cao Yue; Chenevert, Thomas L.; Ben-Josef, Edgar

2009-01-01

Purpose: Our current understanding of intrafraction pancreatic tumor motion due to respiration is limited. In this study, we characterized pancreatic tumor motion and evaluated the application of several radiotherapy motion management strategies. Methods and Materials: Seventeen patients with unresectable pancreatic cancer were enrolled in a prospective internal review board-approved study and imaged during shallow free-breathing using cine MRI on a 3T scanner. Tumor borders were agreed on by a radiation oncologist and an abdominal MRI radiologist. Tumor motion and correlation with the potential surrogates of the diaphragm and abdominal wall were assessed. These data were also used to evaluate planning target volume margin construction, respiratory gating, and four-dimensional treatment planning for pancreatic tumors. Results: Tumor borders moved much more than expected. To provide 99% geometric coverage, margins of 20 mm inferiorly, 10 mm anteriorly, 7 mm superiorly, and 4 mm posteriorly are required. Tumor position correlated poorly with diaphragm and abdominal wall position, with patient-level Pearson correlation coefficients of -0.18-0.43. Sensitivity and specificity of gating with these surrogates was also poor, at 53%-68%, with overall error of 35%-38%, suggesting that the tumor may be underdosed and normal tissues overdosed. Conclusions: Motion of pancreatic tumor borders is highly variable between patients and larger than expected. There is substantial deformation with breathing, and tumor border position does not correlate well with abdominal wall or diaphragmatic position. Current motion management strategies may not account fully for tumor motion and should be used with caution.

Enhanced washout of {sup 99m}Tc-tetrofosmin in hypertrophic cardiomyopathy: quantitative comparisons with regional {sup 123}I-BMIPP uptake and wall thickness determined by MRI

Energy Technology Data Exchange (ETDEWEB)

Thet-Thet-Lwin, Tohoru; Takeda, Jin; Wu, Yuko; Fumikura, Keiji; Iida, Satoru; Kawano, Iwao; Yamaguchi, Yuji; Itai [Institute of Clinical Medicine, University of Tsukuba, Tennodai 1-1-1, 305-8575, Tsukuba-shi, Ibaraki-ken (Japan)

2003-07-01

The diagnostic value of technetium-99m tetrofosmin (TF) washout in hypertrophic cardiomyopathy (HCM) was examined by investigating its relation to the metabolic abnormality depicted by iodine-123 {beta}-methyl-p-iodophenylpentadecanoic acid (BMIPP) uptake and the left ventricular (LV) myocardial wall thickness as measured by magnetic resonance imaging (MRI). TF washout was evaluated in 31 patients with HCM and 23 normal control subjects using 30-min (early) and 3-h (delayed) TF single-photon emission tomography images. The LV myocardial wall was divided into 19 segments and the percentage TF washout, regional BMIPP uptake and LV wall thickness were measured in each segment. Mean TF washout in the patients with HCM was significantly faster than that in normal control subjects (23.7{+-}5.7 vs 13.4{+-}4.1, P<0.0001). In the patients with HCM, TF washout showed an excellent correlation with MRI wall thickness (r=0.82, P<0.0001) and a good inverse correlation with regional BMIPP uptake (r=-0.72, P<0.0001). In addition, a good linear correlation was observed between TF uptake and MRI wall thickness in the 19 regional segments. In conclusion, the degree of TF washout corresponds well with the severity of myocardial wall thickness and the degree of metabolic abnormality in patients with HCM. These results suggest that enhanced TF washout might provide additional clinical information regarding metabolic alterations in HCM. (orig.)

Criteria for definition of regional functional improvement on quantitative post-stress gated myocardial SPET after bypass surgery in patients with ischaemic cardiomyopathy

International Nuclear Information System (INIS)

Lee, Dong Soo; Cheon, Gi Jeong; Paeng, Jin Chul; Chung, June-Key; Lee, Myung Chul; Kim, Ki Bong

2002-01-01

Myocardial viability can be defined as functional improvement of dysfunctional myocardium after revascularization. The purpose of this study was to define the optimal criteria for definition of regional functional improvement after coronary artery bypass graft (CABG) surgery on quantitative gated single-photon emission tomography (SPET). Thirty-two patients (26 men, 6 women; age 56±13 years) with coronary artery disease (three-vessel disease, 17; two-vessel disease, 15; previous history of myocardial infarction, 9) and severe left ventricular dysfunction (LVEF≤35%) underwent CABG. Rest thallium-201/dipyridamole stress technetium-99m methoxyisobutylisonitrile gated myocardial SPET was performed before and 3 months after CABG. Global LV functional improvement was defined as either an improvement in LVEF of 10% (n=15) or an improvement in LVEF of 5% combined with a decrease in end-systolic volume of 10 ml (n=2) after CABG on quantitative gated SPET. Postoperative regional wall thickening improvement (ΔRWT), regional wall motion improvement (ΔRWM) and regional resting (ΔRP) and stress perfusion improvement (ΔRstrP) were used to determine global functional improvement by ROC curve analysis, and the optimal criteria for definition of viable regional dysfunctional myocardium were defined on the ROC curves. Correlations were verified by determining the number of improved myocardial regions and LVEF improvement. LVEF was improved from 25%±6% to 34%±11% after CABG. A total of 229 segments were dysfunctional (wall motion ≤2 mm, thickening ≤20%) before CABG. On ROC curve analysis using global functional improvement as an indicator of viability, the areas under the ROC curves (AUCs) of ΔRWT and ΔRWM were 0.717 and 0.620, respectively. The AUC of ΔRWT was significantly larger than that of ΔRWM (P=0.009) and the optimal cut-off value of ΔRWT was 15%. The AUCs of ΔRP and ΔRstrP were not significant. The correlation coefficients between summed ΔRWT and �

Vaporized wall material/plasma interaction during plasma disruption

International Nuclear Information System (INIS)

Merrill, B.J.; Carroll, M.C.; Jardin, S.C.

1983-01-01

The purpose of this paper is to discuss a new plasma disruption model that has been developed for analyzing the consequences to the limiter/first wall structures. This model accounts for: nonequilibrium surface vaporization for the ablating structure, nonequilibrium ionization of and radiation emitted from the ablated material in the plasma, plasma particle and energy transport, and plasma electromagnetic field evolution during the disruption event. Calculations were performed for a 5 ms disruption on a stainless steel flat limiter as part of a D-shaped first wall. These results indicated that the effectiveness of the ablated wall material to shield the exposed structure is greater than predicted by earlier models, and that the rate of redeposition of the ablated wall material ions is very dramatic. Impurity transport along magnetic field lines, global plasma motion, and radiation transport in an optically thick plasma are important factors that require additional modeling. Experimental measurements are needed to verify these models

3D cardiac wall thickening assessment for acute myocardial infarction

Science.gov (United States)

Khalid, A.; Chan, B. T.; Lim, E.; Liew, Y. M.

2017-06-01

Acute myocardial infarction (AMI) is the most severe form of coronary artery disease leading to localized myocardial injury and therefore irregularities in the cardiac wall contractility. Studies have found very limited differences in global indices (such as ejection fraction, myocardial mass and volume) between healthy subjects and AMI patients, and therefore suggested regional assessment. Regional index, specifically cardiac wall thickness (WT) and thickening is closely related to cardiac function and could reveal regional abnormality due to AMI. In this study, we developed a 3D wall thickening assessment method to identify regional wall contractility dysfunction due to localized myocardial injury from infarction. Wall thickness and thickening were assessed from 3D personalized cardiac models reconstructed from cine MRI images by fitting inscribed sphere between endocardial and epicardial wall. The thickening analysis was performed in 5 patients and 3 healthy subjects and the results were compared against the gold standard 2D late-gadolinium-enhanced (LGE) images for infarct localization. The notable finding of this study is the highly accurate estimation and visual representation of the infarct size and location in 3D. This study provides clinicians with an intuitive way to visually and qualitatively assess regional cardiac wall dysfunction due to infarction in AMI patients.

Building a Lego wall: Sequential action selection.

Science.gov (United States)

Arnold, Amy; Wing, Alan M; Rotshtein, Pia

2017-05-01

The present study draws together two distinct lines of enquiry into the selection and control of sequential action: motor sequence production and action selection in everyday tasks. Participants were asked to build 2 different Lego walls. The walls were designed to have hierarchical structures with shared and dissociated colors and spatial components. Participants built 1 wall at a time, under low and high load cognitive states. Selection times for correctly completed trials were measured using 3-dimensional motion tracking. The paradigm enabled precise measurement of the timing of actions, while using real objects to create an end product. The experiment demonstrated that action selection was slowed at decision boundary points, relative to boundaries where no between-wall decision was required. Decision points also affected selection time prior to the actual selection window. Dual-task conditions increased selection errors. Errors mostly occurred at boundaries between chunks and especially when these required decisions. The data support hierarchical control of sequenced behavior. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Attenuation Tomography Based on Strong Motion Data: Case Study of Central Honshu Region, Japan

Science.gov (United States)

Kumar, Parveen; Joshi, A.; Verma, O. P.

2013-12-01

Three-dimensional frequency dependent S-wave quality factor (Qβ(f)) value for the central Honshu region of Japan has been determined in this paper using an algorithm based on inversion of strong motion data. The method of inversion for determination of three-dimensional attenuation coefficients is proposed by H ashida and S himazaki (J Phys Earth. 32, 299-316, 1984) and has been used and modified by J oshi (Curr Sci. 90, 581-585, 2006; Nat Hazards. 43, 129-146, 2007) and J oshi et al. (J. Seismol. 14, 247-272, 2010). Twenty-one earthquakes digitally recorded on strong motion stations of Kik-net network have been used in this work. The magnitude of these earthquake ranges from 3.1 to 4.2 and depth ranging from 5 to 20 km, respectively. The borehole data having high signal to noise ratio and minimum site effect is used in the present work. The attenuation structure is determined by dividing the entire area into twenty-five three-dimensional blocks of uniform thickness having different frequency-dependent shear wave quality factor. Shear wave quality factor values have been determined at frequencies of 2.5, 7.0 and 10 Hz from record in a rectangular grid defined by 35.4°N to 36.4°N and 137.2°E to 138.2°E. The obtained attenuation structure is compared with the available geological features in the region and comparison shows that the obtained structure is capable of resolving important tectonic features present in the area. The proposed attenuation structure is compared with the probabilistic seismic hazard map of the region and shows that it bears some remarkable similarity in the patterns seen in seismic hazard map.

Domain wall motion and electromechanical strain in lead-free piezoelectrics: Insight from the model system (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} using in situ high-energy X-ray diffraction during application of electric fields

Energy Technology Data Exchange (ETDEWEB)

Tutuncu, Goknur [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Li, Binzhi [Department of Chemical Engineering and Materials Science, University of California, Davis, Davis, California 95616 (United States); Bowman, Keith [Illinois Institute of Technology, Armour College of Engineering, Chicago, Illinois 60616 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Jones, Jacob L., E-mail: JacobJones@ncsu.edu [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

2014-04-14

The piezoelectric compositions (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} (BZT-xBCT) span a model lead-free morphotropic phase boundary (MPB) between room temperature rhombohedral and tetragonal phases at approximately x = 0.5. In the present work, in situ X-ray diffraction measurements during electric field application are used to elucidate the origin of electromechanical strain in several compositions spanning the tetragonal compositional range 0.6 ≤ x ≤ 0.9. As BCT concentration decreases towards the MPB, the tetragonal distortion (given by c/a-1) decreases concomitantly with an increase in 90° domain wall motion. The increase in observed macroscopic strain is predominantly attributed to the increased contribution from 90° domain wall motion. The results demonstrate that domain wall motion is a significant factor in achieving high strain and piezoelectric coefficients in lead-free polycrystalline piezoelectrics.

Computer-aided detection of bladder wall thickening in CT urography (CTU)

Science.gov (United States)

Cha, Kenny H.; Hadjiiski, Lubomir M.; Chan, Heang-Ping; Caoili, Elaine M.; Cohan, Richard H.; Weizer, Alon Z.; Gordon, Marshall N.; Samala, Ravi K.

2018-02-01

We are developing a computer-aided detection system for bladder cancer in CT urography (CTU). Bladder wall thickening is a manifestation of bladder cancer and its detection is more challenging than the detection of bladder masses. We first segmented the inner and outer bladder walls using our method that combined deep-learning convolutional neural network with level sets. The non-contrast-enhanced region was separated from the contrast-enhanced region with a maximum-intensity-projection-based method. The non-contrast region was smoothed and gray level threshold was applied to the contrast and non-contrast regions separately to extract the bladder wall and potential lesions. The bladder wall was transformed into a straightened thickness profile, which was analyzed to identify regions of wall thickening candidates. Volume-based features of the wall thickening candidates were analyzed with linear discriminant analysis (LDA) to differentiate bladder wall thickenings from false positives. A data set of 112 patients, 87 with wall thickening and 25 with normal bladders, was collected retrospectively with IRB approval, and split into independent training and test sets. Of the 57 training cases, 44 had bladder wall thickening and 13 were normal. Of the 55 test cases, 43 had wall thickening and 12 were normal. The LDA classifier was trained with the training set and evaluated with the test set. FROC analysis showed that the system achieved sensitivities of 93.2% and 88.4% for the training and test sets, respectively, at 0.5 FPs/case.

Myocardial gated single photon emission tomography (GSPECT) in men and women with low probability of coronary artery disease - qualitative assessment of beating slices and polar plots

International Nuclear Information System (INIS)

Dziuk, M.; Canizales, A.; Britton, K.E.

2001-01-01

Assessment of the variability of regional wall motion and thickening in men and women with normal left ventricular contraction and low probability of CAD by GSPECT. The rest 99mTcMyoview GSPECT protocol (700 Mbq) was performed in 28 women and 14 men. Qualitative beating slices - QLGS and polar plots - QGS were analyzed independently by scoring the colour scale (1 - severe impairment, 4 - normal). Then the regional wall motion and thickening in the anterior, lateral, inferior walls, the septum and apex were estimated. In all patients the motion in the inferior wall and septum assessed on polar maps were significantly different than one in QLGS but better in the apex. Regional wall thickening was underestimated in QGS polar plots in the anterior wall, septum, inferior and lateral wall. End diastolic and end systolic volumes were significantly greater in men (90±29, 69±25, p<0.02 and 40±20, 22±12, p<0.002 for EDV and ESV respectively). In the later group all walls except the inferior showed higher QGS thickening score in comparison to men. The motion score in the anterior wall was also significantly bigger (p<0.05). The visual regional motion and thickening assessment on beating slices in gated SPECT seems to be more reliable than polar plots in patients with normal left ventricular contraction and low probability of coronary artery disease. Gated SPECT polar maps show better myocardial thickening in women probably due to the smaller left ventricle size and subsequent partial volume effect. (author)

Direct numerical simulation of MHD flow with electrically conducting wall

International Nuclear Information System (INIS)

Satake, S.; Kunugi, T.; Naito, N.; Sagara, A.

2006-01-01

The 2D vortex problem and 3D turbulent channel flow are treated numerically to assess the effect of electrically conducting walls on turbulent MHD flow. As a first approximation, the twin vortex pair is considered as a model of a turbulent eddy near the wall. As the eddy approaches and collides with the wall, a high value electrical potential is induced inside the wall. The Lorentz force, associated with the potential distribution, reduces the velocity gradient in the near-wall region. When considering a fully developed turbulent channel flow, a high electrical conductivity wall was chosen to emphasize the effect of electromagnetic coupling between the wall and the flow. The analysis was performed using DNS. The results are compared with a non-MHD flow and MHD flow in the insulated channel. The mean velocity within the logarithmic region in the case of the electrically conducting wall is slightly higher than that in the non-conducting wall case. Thus, the drag is smaller compared to that in the non-conducting wall case due to a reduction of the Reynolds stress in the near wall region through the Lorentz force. This mechanism is explained via reduction of the production term in the Reynolds shear stress budget

Coupling between Current and Dynamic Magnetization : from Domain Walls to Spin Waves

Science.gov (United States)

Lucassen, M. E.

2012-05-01

So far, we have derived some general expressions for domain-wall motion and the spin motive force. We have seen that the β parameter plays a large role in both subjects. In all chapters of this thesis, there is an emphasis on the determination of this parameter. We also know how to incorporate thermal fluctuations for rigid domain walls, as shown above. In Chapter 2, we study a different kind of fluctuations: shot noise. This noise is caused by the fact that an electric current consists of electrons, and therefore has fluctuations. In the process, we also compute transmission and reflection coefficients for a rigid domain wall, and from them the linear momentum transfer. More work on fluctuations is done in Chapter 3. Here, we consider a (extrinsically pinned) rigid domain wall under the influence of thermal fluctuations that induces a current via spin motive force. We compute how the resulting noise in the current is related to the β parameter. In Chapter 4 we look into in more detail into the spin motive forces from field driven domain walls. Using micro magnetic simulations, we compute the spin motive force due to vortex domain walls explicitly. As mentioned before, this gives qualitatively different results than for a rigid domain wall. The final subject in Chapter 5 is the application of the general expression for spin motive forces to magnons. Although this might seem to be unrelated to domain-wall motion, this calculation allows us to relate the β parameter to macroscopic transport coefficients. This work was supported by Stichting voor Fundamenteel Onderzoek der Materie (FOM), the Netherlands Organization for Scientific Research (NWO), and by the European Research Council (ERC) under the Seventh Framework Program (FP7).

Discontinuity Preserving Image Registration through Motion Segmentation: A Primal-Dual Approach

Directory of Open Access Journals (Sweden)

Silja Kiriyanthan

2016-01-01

Full Text Available Image registration is a powerful tool in medical image analysis and facilitates the clinical routine in several aspects. There are many well established elastic registration methods, but none of them can so far preserve discontinuities in the displacement field. These discontinuities appear in particular at organ boundaries during the breathing induced organ motion. In this paper, we exploit the fact that motion segmentation could play a guiding role during discontinuity preserving registration. The motion segmentation is embedded in a continuous cut framework guaranteeing convexity for motion segmentation. Furthermore we show that a primal-dual method can be used to estimate a solution to this challenging variational problem. Experimental results are presented for MR images with apparent breathing induced sliding motion of the liver along the abdominal wall.

Plasma behavior and plasma-wall interaction in magnetic fusion divices

International Nuclear Information System (INIS)

Ohtsuka, Hideo

1984-10-01

To study the fundamental behavior of plasma in magnetic field is the main subject in the early stage of the magnetic fusion research. At the next stage, it is necessary to overcome some actual problems in order to attain reactor grade plasmas. One of them is to control impurities in the plasma. In these points of view, we carried out several experiments or theoretical analyses. Firstly, anomalous loss mechanisms in magnetic field were investigated in a toroidal multipole device JFT-1 and the role of motions of charged particles in the magnetic field was exhibited. Various measurements of plasma in the scrape-off layer were made in a divertor tokamak JFT-2a and in an ordinary tokamak JFT-2. The former study demonstrated the first successful divertor operation of the tokamak device and the latter one clarified the mechanism of arcing on the tokamak first wall. As to arcing, a new theory which describes the retrograde motion, the well known strange motion of arcs in a magnetic field, was proposed. Good agreement with the experimental results was shown. Finally, by considering a zero-dimensional sputtering model a self-consistent relation between light and metal impurities in tokamak plasmas was obtained. It was shown that the relation well describes some fundamental aspects of the plasma-wall interaction. As a conclusion, the importance of simple behavior of charged particles in magnetic fields was pointed out not only for the plasma confinement but also for the plasma-wall interaction. (author)

Inhomogeneous nucleation and domain wall motion with Barkhausen avalanches in epitaxial PbZr0.4Ti0.6O3 thin films

International Nuclear Information System (INIS)

Yang, Sang Mo; Kim, Hun Ho; Kim, Tae Heon; Kim, Ik Joo; Yoon, Jong Gul

2012-01-01

We investigated the ferroelectric (FE) domain nucleation and domain wall motion in epitaxial PbZr 0.4 Ti 0.6 O 3 capacitors by using modified piezoresponse force microscopy with the domain-tracing method. From time-dependent FE domain evolution images, we observed that defect-mediated inhomogeneous nucleation occurred with a stochastic nature. In addition, we found that the number of nuclei N(t) was linearly proportional to log t, where t is the accumulated time of the applied pulse fields. The time-dependence of N(t) suggests a distribution of energy barriers for nucleation, which may determine the stochastic nature of domain nucleation. We also observed that the domain grew with consecutive Barkhausen avalanches and that the growth direction became anisotropic when the domain radius was larger than a critical radius of about 100 nm.

Fast Numerical Simulation of Focused Ultrasound Treatments During Respiratory Motion With Discontinuous Motion Boundaries.

Science.gov (United States)

Schwenke, Michael; Georgii, Joachim; Preusser, Tobias

2017-07-01

Focused ultrasound (FUS) is rapidly gaining clinical acceptance for several target tissues in the human body. Yet, treating liver targets is not clinically applied due to a high complexity of the procedure (noninvasiveness, target motion, complex anatomy, blood cooling effects, shielding by ribs, and limited image-based monitoring). To reduce the complexity, numerical FUS simulations can be utilized for both treatment planning and execution. These use-cases demand highly accurate and computationally efficient simulations. We propose a numerical method for the simulation of abdominal FUS treatments during respiratory motion of the organs and target. Especially, a novel approach is proposed to simulate the heating during motion by solving Pennes' bioheat equation in a computational reference space, i.e., the equation is mathematically transformed to the reference. The approach allows for motion discontinuities, e.g., the sliding of the liver along the abdominal wall. Implementing the solver completely on the graphics processing unit and combining it with an atlas-based ultrasound simulation approach yields a simulation performance faster than real time (less than 50-s computing time for 100 s of treatment time) on a modern off-the-shelf laptop. The simulation method is incorporated into a treatment planning demonstration application that allows to simulate real patient cases including respiratory motion. The high performance of the presented simulation method opens the door to clinical applications. The methods bear the potential to enable the application of FUS for moving organs.

High-speed schlieren videography of vortex-ring impact on a wall

Science.gov (United States)

Kissner, Benjamin; Hargather, Michael; Settles, Gary

2011-11-01

Ring vortices of approximately 20 cm diameter are generated through the use of an Airzooka toy. To make the vortex visible, it is seeded with difluoroethane gas, producing a refractive-index difference with the air. A 1-meter-diameter, single-mirror, double-pass schlieren system is used to visualize the ring-vortex motion, and also to provide the wall with which the vortex collides. High-speed imaging is provided by a Photron SA-1 digital video camera. The Airzooka is fired toward the mirror almost along the optical axis of the schlieren system, so that the view of the vortex-mirror collision is normal to the path of vortex motion. Vortex-wall interactions similar to those first observed by Walker et al. (JFM 181, 1987) are recorded at high speed. The presentation will consist of a screening and discussion of these video results.

Motion-induced dose artifacts in helical tomotherapy

Energy Technology Data Exchange (ETDEWEB)

Kim, Bryan; Chen, Jeff; Battista, Jerry [London Regional Cancer Program, London Health Sciences Centre, London, ON (Canada); Kron, Tomas [Peter MacCallum Cancer Center, Melbourne (Australia)], E-mail: bryan.kim@lhsc.on.ca

2009-10-07

Tumor motion is a particular concern for a complex treatment modality such as helical tomotherapy, where couch position, gantry rotation and MLC leaf opening all change with time. In the present study, we have investigated the impact of tumor motion for helical tomotherapy, which could result in three distinct motion-induced dose artifacts, namely (1) dose rounding, (2) dose rippling and (3) IMRT leaf opening asynchronization effect. Dose rounding and dose rippling effects have been previously described, while the IMRT leaf opening asynchronization effect is a newly discovered motion-induced dose artifact. Dose rounding is the penumbral widening of a delivered dose distribution near the edges of a target volume along the direction of tumor motion. Dose rippling is a series of periodic dose peaks and valleys observed within the target region along the direction of couch motion, due to an asynchronous interplay between the couch motion and the longitudinal component of tumor motion. The IMRT leaf opening asynchronization effect is caused by an asynchronous interplay between the temporal patterns of leaf openings and tumor motion. The characteristics of each dose artifact were investigated individually as functions of target motion amplitude and period for both non-IMRT and IMRT helical tomotherapy cases, through computer simulation modeling and experimental verification. The longitudinal dose profiles generated by the simulation program agreed with the experimental data within {+-}0.5% and {+-}1.5% inside the PTV region for the non-IMRT and IMRT cases, respectively. The dose rounding effect produced a penumbral increase up to 20.5 mm for peak-to-peak target motion amplitudes ranging from 1.0 cm to 5.0 cm. Maximum dose rippling magnitude of 25% was calculated, when the target motion period approached an unusually high value of 10 s. The IMRT leaf opening asynchronization effect produced dose differences ranging from -29% to 7% inside the PTV region. This information

Deriving the equations of motion of porous isotropic media

International Nuclear Information System (INIS)

Pride, S.R.; Gangi, A.F.; Morgan, F.D.

1992-01-01

The equations of motion and stress/strain relations for the linear dynamics of a two-phase, fluid/solid, isotropic, porous material have been derived by a direct volume averaging of the equations of motion and stress-strain relations known to apply in each phase. The equations thus obtained are shown to be consistent with Biot's equations of motion and stress/strain relations; however, the effective fluid density in the equation of relative flow has an unambiguous definition in terms of the tractions acting on the pore walls. The stress/strain relations of the theory correspond to 'quasistatic' stressing (i.e., inertial effects are ignored). It is demonstrated that using such quasistatic stress/strain relations in the equations of motion is justified whenever the wavelengths are greater than a length characteristic of the averaging volume size. 37 refs., 2 figs

Langevin equation of a fluid particle in wall-induced turbulence

NARCIS (Netherlands)

Brouwers, J.J.H.

2010-01-01

We derive the Langevin equation describing the stochastic process of fluid particle motion in wall-inducedturbulence (turbulent flow in pipes, channels, and boundary layers including the atmospheric surface layer).The analysis is based on the asymptotic behavior at a large Reynolds number. We use

Motion contrast using optical coherence tomography

Science.gov (United States)

Fingler, Jeffrey Paul

Diagnosis of ophthalmic diseases like age-related macular degeneration is very important for treatment of the disease as well as the development of future treatments. Optical coherence tomography (OCT) is an optical interference technique which can measure the three-dimensional structural information of the reflecting layers within a sample. In retinal imaging, OCT is used as the primary diagnostic tool for structural abnormalities such as retinal holes and detachments. The contrast within the images of this technique is based upon reflectivity changes from different regions of the retina. This thesis demonstrates the developments of methods used to produce additional contrast to the structural OCT images based on the tiny fluctuations of motion experienced by the mobile scatterers within a sample. Motion contrast was observed for motions smaller than 50 nm in images of a variety of samples. Initial contrast method demonstrations used Brownian motion differences to separate regions of a mobile Intralipid solution from a static agarose gel, chosen in concentration to minimize reflectivity contrast. Zebrafish embryos in the range of 3-4 days post fertilization were imaged using several motion contrast methods to determine the capabilities of identifying regions of vascular flow. Vasculature identification was demonstrated in zebrafish for blood vessels of all orientations as small as 10 microns in diameter. Mouse retinal imaging utilized the same motion contrast methods to determine the contrast capabilities for motions associated with vasculature within the retina. Improved contrast imaging techniques demonstrated comparable images to fluorescein angiography, the gold standard of retinal vascular imaging. Future studies can improve the demonstrated contrast analysis techniques and apply them towards human retinal motion contrast imaging for ophthalmic diagnostic purposes.

Small-scale deflagration cylinder test with velocimetry wall-motion diagnostics

Energy Technology Data Exchange (ETDEWEB)

Hooks, Daniel E [Los Alamos National Laboratory; Hill, Larry G [Los Alamos National Laboratory; Pierce, Timothy H [Los Alamos National Laboratory

2010-01-01

Predicting the likelihood and effects of outcomes resultant from thermal initiation of explosives remains a significant challenge. For certain explosive formulations, the general outcome can be broadly predicted given knowledge of certain conditions. However, there remain unexplained violent events, and increased statistical understanding of outcomes as a function of many variables, or 'violence categorization,' is needed. Additionally, the development of an equation of state equivalent for deflagration would be very useful in predicting possible detailed event consequences using traditional hydrodynamic detonation moders. For violence categorization, it is desirable that testing be efficient, such that it is possible to statistically define outcomes reliant on the processes of initiation of deflagration, steady state deflagration, and deflagration to detonation transitions. If the test simultaneously acquires information to inform models of violent deflagration events, overall predictive capabilities for event likelihood and consequence might improve remarkably. In this paper we describe an economical scaled deflagration cylinder test. The cyclotetramethylene tetranitramine (HMX) based explosive formu1lation PBX 9501 was tested using different temperature profiles in a thick-walled copper cylindrical confiner. This test is a scaled version of a recently demonstrated deflagration cylinder test, and is similar to several other thermal explosion tests. The primary difference is the passive velocimetry diagnostic, which enables measurement of confinement vessel wall velocities at failure, regardless of the timing and location of ignition.

Normal left ventricular wall motion measured with two-dimensional myocardial tagging

DEFF Research Database (Denmark)

Qi, P; Thomsen, C; Ståhlberg, F

1993-01-01

contraction towards the center of the left ventricle, a motion of the base of the heart towards the apex, and a rotation of the left ventricle around its long axis. The direction of left ventricular rotation changed from early systole to late systole. The base and middle levels of the left ventricle rotated...

Quantifying the predictability of diaphragm motion during respiration with a noninvasive external marker

International Nuclear Information System (INIS)

Vedam, S.S.; Kini, V.R.; Keall, P.J.; Ramakrishnan, V.; Mostafavi, H.; Mohan, R.

2003-01-01

The aim of this work was to quantify the ability to predict intrafraction diaphragm motion from an external respiration signal during a course of radiotherapy. The data obtained included diaphragm motion traces from 63 fluoroscopic lung procedures for 5 patients, acquired simultaneously with respiratory motion signals (an infrared camera-based system was used to track abdominal wall motion). During these sessions, the patients were asked to breathe either (i) without instruction, (ii) with audio prompting, or (iii) using visual feedback. A statistical general linear model was formulated to describe the relationship between the respiration signal and diaphragm motion over all sessions and for all breathing training types. The model parameters derived from the first session for each patient were then used to predict the diaphragm motion for subsequent sessions based on the respiration signal. Quantification of the difference between the predicted and actual motion during each session determined our ability to predict diaphragm motion during a course of radiotherapy. This measure of diaphragm motion was also used to estimate clinical target volume (CTV) to planning target volume (PTV) margins for conventional, gated, and proposed four-dimensional (4D) radiotherapy. Results from statistical analysis indicated a strong linear relationship between the respiration signal and diaphragm motion (p<0.001) over all sessions, irrespective of session number (p=0.98) and breathing training type (p=0.19). Using model parameters obtained from the first session, diaphragm motion was predicted in subsequent sessions to within 0.1 cm (1 σ) for gated and 4D radiotherapy. Assuming a 0.4 cm setup error, superior-inferior CTV-PTV margins of 1.1 cm for conventional radiotherapy could be reduced to 0.8 cm for gated and 4D radiotherapy. The diaphragm motion is strongly correlated with the respiration signal obtained from the abdominal wall. This correlation can be used to predict diaphragm

Respiratory lung motion analysis using a nonlinear motion correction technique for respiratory-gated lung perfusion SPECT images

International Nuclear Information System (INIS)

Ue, Hidenori; Haneishi, Hideaki; Iwanaga, Hideyuki; Suga, Kazuyoshi

2007-01-01

This study evaluated the respiratory motion of lungs using a nonlinear motion correction technique for respiratory-gated single photon emission computed tomography (SPECT) images. The motion correction technique corrects the respiratory motion of the lungs nonlinearly between two-phase images obtained by respiratory-gated SPECT. The displacement vectors resulting from respiration can be computed at every location of the lungs. Respiratory lung motion analysis is carried out by calculating the mean value of the body axis component of the displacement vector in each of the 12 small regions into which the lungs were divided. In order to enable inter-patient comparison, the 12 mean values were normalized by the length of the lung region along the direction of the body axis. This method was applied to 25 Technetium (Tc)-99m-macroaggregated albumin (MAA) perfusion SPECT images, and motion analysis results were compared with the diagnostic results. It was confirmed that the respiratory lung motion reflects the ventilation function. A statistically significant difference in the amount of the respiratory lung motion was observed between the obstructive pulmonary diseases and other conditions, based on an unpaired Student's t test (P<0.0001). A difference in the motion between normal lungs and lungs with a ventilation obstruction was detected by the proposed method. This method is effective for evaluating obstructive pulmonary diseases such as pulmonary emphysema and diffuse panbronchiolitis. (author)

Effect of metallic walls on dynamos generated by laminar boundary-driven flow in a spherical domain.

Science.gov (United States)

Guervilly, Céline; Wood, Toby S; Brummell, Nicholas H

2013-11-01

We present a numerical study of dynamo action in a conducting fluid encased in a metallic spherical shell. Motions in the fluid are driven by differential rotation of the outer metallic shell, which we refer to as "the wall." The two hemispheres of the wall are held in counter-rotation, producing a steady, axisymmetric interior flow consisting of differential rotation and a two-cell meridional circulation with radial inflow in the equatorial plane. From previous studies, this type of flow is known to maintain a stationary equatorial dipole by dynamo action if the magnetic Reynolds number is larger than about 300 and if the outer boundary is electrically insulating. We vary independently the thickness, electrical conductivity, and magnetic permeability of the wall to determine their effect on the dynamo action. The main results are the following: (a) Increasing the conductivity of the wall hinders the dynamo by allowing eddy currents within the wall, which are induced by the relative motion of the equatorial dipole field and the wall. This processes can be viewed as a skin effect or, equivalently, as the tearing apart of the dipole by the differential rotation of the wall, to which the field lines are anchored by high conductivity. (b) Increasing the magnetic permeability of the wall favors dynamo action by constraining the magnetic field lines in the fluid to be normal to the wall, thereby decoupling the fluid from any induction in the wall. (c) Decreasing the wall thickness limits the amplitude of the eddy currents, and is therefore favorable for dynamo action, provided that the wall is thinner than the skin depth. We explicitly demonstrate these effects of the wall properties on the dynamo field by deriving an effective boundary condition in the limit of vanishing wall thickness.

Recorded motions of the 6 April 2009 Mw 6.3 L'Aquila, Italy, earthquake and implications for building structural damage: Overview

Science.gov (United States)

Celebi, M.; Bazzurro, P.; Chiaraluce, L.; Clemente, P.; Decanini, L.; Desortis, A.; Ellsworth, W.; Gorini, A.; Kalkan, E.; Marcucci, S.; Milana, G.; Mollaioli, F.; Olivieri, M.; Paolucci, R.; Rinaldis, D.; Rovelli, A.; Sabetta, F.; Stephens, C.

2010-01-01

The normal-faulting earthquake of 6 April 2009 in the Abruzzo Region of central Italy caused heavy losses of life and substantial damage to centuriesold buildings of significant cultural importance and to modern reinforcedconcrete- framed buildings with hollow masonry infill walls. Although structural deficiencies were significant and widespread, the study of the characteristics of strong motion data from the heavily affected area indicated that the short duration of strong shaking may have spared many more damaged buildings from collapsing. It is recognized that, with this caveat of shortduration shaking, the infill walls may have played a very important role in preventing further deterioration or collapse of many buildings. It is concluded that better new or retrofit construction practices that include reinforcedconcrete shear walls may prove helpful in reducing risks in such seismic areas of Italy, other Mediterranean countries, and even in United States, where there are large inventories of deficient structures. ?? 2010, Earthquake Engineering Research Institute.

Turbine airfoil with outer wall thickness indicators

Science.gov (United States)

Marra, John J; James, Allister W; Merrill, Gary B

2013-08-06

A turbine airfoil usable in a turbine engine and including a depth indicator for determining outer wall blade thickness. The airfoil may include an outer wall having a plurality of grooves in the outer surface of the outer wall. The grooves may have a depth that represents a desired outer surface and wall thickness of the outer wall. The material forming an outer surface of the outer wall may be removed to be flush with an innermost point in each groove, thereby reducing the wall thickness and increasing efficiency. The plurality of grooves may be positioned in a radially outer region of the airfoil proximate to the tip.

Changing trend in congenital abdominal wall defects in Eastern region of Ireland.

LENUS (Irish Health Repository)

McDonnell, R

2002-09-01

In the past six years, there have been reports from abroad of an unexplained rise in the birth prevalence rate of the congenital abdominal wall defect gastroschisis, while rates for the macroscopically similar anomaly omphalocoele have remained stable. The Dublin EUROCAT Registry of congenital anomalies monitors trends in the birth prevalence of birth defects in the eastern region of Ireland. We analysed births of children with omphalocoele and gastroschisis born in the period 1981-2000, with comparisons of a number of demographic and obstetric variables. During the 20 year period the birth prevalence rate for omphalocoele remained stable at 2.5\\/10,000 births, whereas the rate for gastroschisis increased significantly during the 1990s from 1.0\\/10,000 in 1991 to 4.9\\/10,000 in 2000. Most of the increase occurred among mothers under 25 years of age. Omphalocoele was associated with a relatively high proportion of other major congenital anomalies. This study showed that there has been an unexpected rise in the birth prevalence of gastroschisis in the region, similar to that experienced in other countries in the same time period and likely to have common aetiological features.

Phenomenology of wall-bounded Newtonian turbulence.

Science.gov (United States)

L'vov, Victor S; Pomyalov, Anna; Procaccia, Itamar; Zilitinkevich, Sergej S

2006-01-01

We construct a simple analytic model for wall-bounded turbulence, containing only four adjustable parameters. Two of these parameters are responsible for the viscous dissipation of the components of the Reynolds stress tensor. The other two parameters control the nonlinear relaxation of these objects. The model offers an analytic description of the profiles of the mean velocity and the correlation functions of velocity fluctuations in the entire boundary region, from the viscous sublayer, through the buffer layer, and further into the log-law turbulent region. In particular, the model predicts a very simple distribution of the turbulent kinetic energy in the log-law region between the velocity components: the streamwise component contains a half of the total energy whereas the wall-normal and cross-stream components contain a quarter each. In addition, the model predicts a very simple relation between the von Kármán slope k and the turbulent velocity in the log-law region v+ (in wall units): v+=6k. These predictions are in excellent agreement with direct numerical simulation data and with recent laboratory experiments.

The effect of partial poloidal wall sections on the wall stabilization of external kink modes

International Nuclear Information System (INIS)

Ward, D.J.

1996-02-01

An analysis of the effect on the wall stabilization of external kink modes due to toroidally continuous gaps in the resistive wall is performed. The effects with and without toroidal rotation are studied. For a high-β equilibrium, the mode structure is localized on the outboard side. Therefore, outboard gaps greatly increase the growth rate when there is no rotation. For resistive wall stabilization by toroidal rotation, the presence of gaps has the same effect as moving the wall farther away, i.e. destabilizing for the ideal plasma mode, and stabilizing for the resistive wall mode. The region of stability, in terms of wall position, is reduced in size and moved closer to the plasma. However, complete stabilization becomes possible at considerably reduced rotation frequencies. For a high-β, reverse-shear equilibrium both the resistive wall mode and the ideal plasma mode can be stabilized by close fitting discrete passive plates on the outboard side. The necessary toroidal rotation frequency to stabilize the resistive wall mode using these plates is reduced by a factor of three compared to that for a poloidally continuous and complete wall at the same plasma-wall separation. (author) 15 figs., 24 refs

MHD stabilization of high β mirror plasma partially enclosed by conducting wall

International Nuclear Information System (INIS)

Li, X.Z.; Kesner, J.; Lane, B.

1985-04-01

An MHD formulation is used to study a wall stabilized high β mirror plasma with isotropic pressure. The stabilizing wall extends axially only a part of the distance between the mirror midplane and throat. We model this arrangement using a wall that approaches the plasma surface in the bad curvature region and is distant from the plasma in the good curvature region. A variational method is used to solve the equation in the distant wall region and an iterative method is used to solve the equation when the wall is close to the plasma. A jump condition is used to connect the regions of close and distant plasma-wall proximity. A simple trial function is used to perform the variational calculation (the choice of trial function is substantiated by an exact numerical solution). The results show that for a low mirror ratio case more conducting wall surface is needed for stability than in the high mirror ratio case. This agrees with the physical mechanism of the wall stabilization

Soil-structure Interaction in the Seismic Response of Coupled Wall-frame Structures on Pile Foundations

International Nuclear Information System (INIS)

Carbonari, S.; Dezi, F.; Leoni, G.

2008-01-01

This paper presents a study on the seismic response of coupled wall-frame structures founded on piles. A complete soil-structure interaction analysis is carried out with reference to a case study. Three different soils and seven real accelerograms are considered. Local site response analyses are performed in order to evaluate the incoming free-field motion at different depths and the ground motion amplifications. A numerical model, accounting for the pile-soil-pile interaction and for material and radiation damping, is used to evaluate the impedance matrix and the foundation input motion. The domain decomposition technique is adopted to perform time-domain seismic analyses introducing Lumped Parameter Models to take into account the impedance of the soil-structure system. Applications show that the rocking phenomena affect the behaviour of the structure by changing the base shear distribution within the wall and the frame and by increasing the structural displacements

Sound Transmission in a Duct with Sudden Area Expansion, Extended Inlet, and Lined Walls in Overlapping Region

Directory of Open Access Journals (Sweden)

Ahmet Demir

2016-01-01

Full Text Available The transmission of sound in a duct with sudden area expansion and extended inlet is investigated in the case where the walls of the duct lie in the finite overlapping region lined with acoustically absorbent materials. By using the series expansion in the overlap region and using the Fourier transform technique elsewhere we obtain a Wiener-Hopf equation whose solution involves a set of infinitely many unknown expansion coefficients satisfying a system of linear algebraic equations. Numerical solution of this system is obtained for various values of the problem parameters, whereby the effects of these parameters on the sound transmission are studied.

Cervical spine motion: radiographic study

International Nuclear Information System (INIS)

Morgan, J.P.; Miyabayashi, T.; Choy, S.

1986-01-01

Knowledge of the acceptable range of motion of the cervical spine of the dog is used in the radiographic diagnosis of both developmental and degenerative diseases. A series of radiographs of mature Beagle dogs was used to identify motion within sagittal and transverse planes. Positioning of the dog's head and neck was standardized, using a restraining board, and mimicked those thought to be of value in diagnostic radiology. The range of motion was greatest between C2 and C5. Reports of severe disk degeneration in the cervical spine of the Beagle describe the most severely involved disks to be C4 through C7. Thus, a high range of motion between vertebral segments does not seem to be the cause for the severe degenerative disk disease. Dorsoventral slippage between vertebral segments was seen, but was not accurately measured. Wedging of disks was clearly identified. At the atlantoaxio-occipital region, there was a high degree of motion within the sagittal plane at the atlantoaxial and atlanto-occipital joints; the measurement can be a guideline in the radiographic diagnosis of instability due to developmental anomalies in this region. Lateral motion within the transverse plane was detected at the 2 joints; however, motion was minimal, and the measurements seemed to be less accurate because of rotation of the cervical spine. Height of the vertebral canal was consistently noted to be greater at the caudal orifice, giving some warning to the possibility of overdiagnosis in suspected instances of cervical spondylopathy

Atomic motions in the αβ-region of glass-forming polymers: molecular versus mode coupling theory approach

International Nuclear Information System (INIS)

Colmenero, Juan; Narros, Arturo; Alvarez, Fernando; Arbe, Arantxa; Moreno, Angel J

2007-01-01

We present fully atomistic molecular dynamics simulation results on a main-chain polymer, 1,4-polybutadiene, in the merging region of the α- and β-relaxations. A real-space analysis reveals the occurrence of localized motions ('β-like') in addition to the diffusive structural relaxation. A molecular approach provides a direct connection between the local conformational changes reflected in the atomic motions and the secondary relaxations in this polymer. Such local processes occur just in the time window where the β-process of the mode coupling theory is expected. We show that the application of this theory is still possible and yields an unusually large value of the exponent parameter. This result might originate from the competition between two mechanisms for dynamic arrest: intermolecular packing and intramolecular barriers for local conformational changes ('β-like')

Free-breathing black-blood CINE fast-spin echo imaging for measuring abdominal aortic wall distensibility: a feasibility study

Science.gov (United States)

Lin, Jyh-Miin; Patterson, Andrew J.; Chao, Tzu-Cheng; Zhu, Chengcheng; Chang, Hing-Chiu; Mendes, Jason; Chung, Hsiao-Wen; Gillard, Jonathan H.; Graves, Martin J.

2017-05-01

The paper reports a free-breathing black-blood CINE fast-spin echo (FSE) technique for measuring abdominal aortic wall motion. The free-breathing CINE FSE includes the following MR techniques: (1) variable-density sampling with fast iterative reconstruction; (2) inner-volume imaging; and (3) a blood-suppression preparation pulse. The proposed technique was evaluated in eight healthy subjects. The inner-volume imaging significantly reduced the intraluminal artifacts of respiratory motion (p  =  0.015). The quantitative measurements were a diameter of 16.3  ±  2.8 mm and wall distensibility of 2.0  ±  0.4 mm (12.5  ±  3.4%) and 0.7  ±  0.3 mm (4.1  ±  1.0%) for the anterior and posterior walls, respectively. The cyclic cross-sectional distensibility was 35  ±  15% greater in the systolic phase than in the diastolic phase. In conclusion, we developed a feasible CINE FSE method to measure the motion of the abdominal aortic wall, which will enable clinical scientists to study the elasticity of the abdominal aorta.

Elevated uptake of plasma macromolecules by regions of arterial wall predisposed to plaque instability in a mouse model.

Directory of Open Access Journals (Sweden)

Zahra Mohri

Full Text Available Atherosclerosis may be triggered by an elevated net transport of lipid-carrying macromolecules from plasma into the arterial wall. We hypothesised that whether lesions are of the thin-cap fibroatheroma (TCFA type or are less fatty and more fibrous depends on the degree of elevation of transport, with greater uptake leading to the former. We further hypothesised that the degree of elevation can depend on haemodynamic wall shear stress characteristics and nitric oxide synthesis. Placing a tapered cuff around the carotid artery of apolipoprotein E -/- mice modifies patterns of shear stress and eNOS expression, and triggers lesion development at the upstream and downstream cuff margins; upstream but not downstream lesions resemble the TCFA. We measured wall uptake of a macromolecular tracer in the carotid artery of C57bl/6 mice after cuff placement. Uptake was elevated in the regions that develop lesions in hyperlipidaemic mice and was significantly more elevated where plaques of the TCFA type develop. Computational simulations and effects of reversing the cuff orientation indicated a role for solid as well as fluid mechanical stresses. Inhibiting NO synthesis abolished the difference in uptake between the upstream and downstream sites. The data support the hypothesis that excessively elevated wall uptake of plasma macromolecules initiates the development of the TCFA, suggest that such uptake can result from solid and fluid mechanical stresses, and are consistent with a role for NO synthesis. Modification of wall transport properties might form the basis of novel methods for reducing plaque rupture.

Multibunch resistive wall instability damping with feedback

International Nuclear Information System (INIS)

Zhabitskij, V.M.; Korenev, I.L.; Yudin, L.A.

1992-01-01

The theory of multibunch transverse resistive wall instability damping with feedback is development. The system of coupling equations is obtained for description of bunched beam motion. The general solution and eigen frequencies are found. But for two bunches or multi bunches the tune splitting is found. The band of the tune splitting is calculated. The influence of the tune splitting on the damper system stability is discussed. 14 refs

Auditory motion-specific mechanisms in the primate brain.

Directory of Open Access Journals (Sweden)

Colline Poirier

2017-05-01

Full Text Available This work examined the mechanisms underlying auditory motion processing in the auditory cortex of awake monkeys using functional magnetic resonance imaging (fMRI. We tested to what extent auditory motion analysis can be explained by the linear combination of static spatial mechanisms, spectrotemporal processes, and their interaction. We found that the posterior auditory cortex, including A1 and the surrounding caudal belt and parabelt, is involved in auditory motion analysis. Static spatial and spectrotemporal processes were able to fully explain motion-induced activation in most parts of the auditory cortex, including A1, but not in circumscribed regions of the posterior belt and parabelt cortex. We show that in these regions motion-specific processes contribute to the activation, providing the first demonstration that auditory motion is not simply deduced from changes in static spatial location. These results demonstrate that parallel mechanisms for motion and static spatial analysis coexist within the auditory dorsal stream.

Control of self-motion in dynamic fluids: fish do it differently from bees.

Science.gov (United States)

Scholtyssek, Christine; Dacke, Marie; Kröger, Ronald; Baird, Emily

2014-05-01

To detect and avoid collisions, animals need to perceive and control the distance and the speed with which they are moving relative to obstacles. This is especially challenging for swimming and flying animals that must control movement in a dynamic fluid without reference from physical contact to the ground. Flying animals primarily rely on optic flow to control flight speed and distance to obstacles. Here, we investigate whether swimming animals use similar strategies for self-motion control to flying animals by directly comparing the trajectories of zebrafish (Danio rerio) and bumblebees (Bombus terrestris) moving through the same experimental tunnel. While moving through the tunnel, black and white patterns produced (i) strong horizontal optic flow cues on both walls, (ii) weak horizontal optic flow cues on both walls and (iii) strong optic flow cues on one wall and weak optic flow cues on the other. We find that the mean speed of zebrafish does not depend on the amount of optic flow perceived from the walls. We further show that zebrafish, unlike bumblebees, move closer to the wall that provides the strongest visual feedback. This unexpected preference for strong optic flow cues may reflect an adaptation for self-motion control in water or in environments where visibility is limited. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Magnetic hysteresis and domain wall dynamics in single chain magnets with antiferromagnetic interchain coupling

Energy Technology Data Exchange (ETDEWEB)

Bukharov, A A; Ovchinnikov, A S; Baranov, N V [Department of Physics, Ural State University, Ekaterinburg, 620083 (Russian Federation); Inoue, K [Institute for Advanced Materials Research, Hiroshima University, Hiroshima (Japan)

2010-11-03

Using Monte Carlo simulations we investigate magnetic hysteresis in two- and three-dimensional systems of weakly antiferromagnetically coupled spin chains based on a scenario of domain wall (kink) motion within the chains. By adapting the model of walkers to simulate the domain wall dynamics and using the Ising-like dipole-dipole model, we study the effects of interchain coupling, temperature and anisotropy axis direction on hysteresis curves.

Intermittency and scaling laws for wall bounded turbulence

NARCIS (Netherlands)

Benzi, R.; Amati, G.; Casciola, C.M.; Toschi, F.; Piva, R.

1999-01-01

Well defined scaling laws clearly appear in wall bounded turbulence, very close to the wall, where a distinct violation of the refined Kolmogorov similarity hypothesis (RKSH) occurs together with the simultaneous persistence of scaling laws. A new form of RKSH for the wall region is here proposed in

Intermittency and scaling laws for wall bounded turbulence

OpenAIRE

Benzi, R.; Amati, G.; Casciola, C. M.; Toschi, F.; Piva, R.

1998-01-01

Well defined scaling laws clearly appear in wall bounded turbulence, even very close to the wall, where a distinct violation of the refined Kolmogorov similarity hypothesis (RKSH) occurs together with the simultaneous persistence of scaling laws. A new form of RKSH for the wall region is here proposed in terms of the structure functions of order two which, in physical terms, confirms the prevailing role of the momentum transfer towards the wall in the near wall dynamics.

Elastohydrodynamics of a sliding, spinning and sedimenting cylinder near a soft wall

OpenAIRE

Salez, Thomas; Mahadevan, L.

2014-01-01

We consider the motion of a fluid-immersed negatively buoyant particle in the vicinity of a thin compressible elastic wall, a situation that arises in a variety of technological and natural settings. We use scaling arguments to establish different regimes of sliding, and complement these estimates using thin-film lubrication dynamics to determine an asymptotic theory for the sedimentation, sliding, and spinning motions of a cylinder. The resulting theory takes the form of three coupled nonlin...

From Boltzmann equations to steady wall velocities

International Nuclear Information System (INIS)

Konstandin, Thomas; Rues, Ingo; Nardini, Germano; California Univ., Santa Barbara, CA

2014-07-01

By means of a relativistic microscopic approach we calculate the expansion velocity of bubbles generated during a first-order electroweak phase transition. In particular, we use the gradient expansion of the Kadanoff-Baym equations to set up the fluid system. This turns out to be equivalent to the one found in the semi-classical approach in the non-relativistic limit. Finally, by including hydrodynamic deflagration effects and solving the Higgs equations of motion in the fluid, we determine velocity and thickness of the bubble walls. Our findings are compared with phenomenological models of wall velocities. As illustrative examples, we apply these results to three theories providing first-order phase transitions with a particle content in the thermal plasma that resembles the Standard Model.

Drift motions of small-scale irregularities in the high-latitude F region: An experimental comparison with plasma drift motions

International Nuclear Information System (INIS)

Ruohoniemi, J.M.; Greenwald, R.A.; Baker, K.B.; Villain, J.P.; McCready, M.A.

1987-01-01

On the evening of January 6, 1986, coordinated observations were carried out with the Johns Hopkins University Applied Physics Laboratory HF coherent scatter radar at Goose Bay, Labrador, and the SRI International incoherent scatter radar at Sondre Stromfjord, Greenland. The common field of view comprised a section of high-latitude F region ionosphere centered on the great circle plane between the radar sites. Over a 40-min period, the HF radar observed strong backscatter from small-scale (13.9 m) field-aligned irregularities. The bulk line-of-sight drift velocity of the irregularities is deduced from the backscatter data. The returns collected simultaneously with the incoherent scatter radar are processed for estimates of the mean line-of-sight ion velocity. Approximately 100 distinct comparisons are possible between the two sets of velocity estimates. Reversals exceeding 1,000 m/s are present in both. In this paper, the authors demonstrate a correspondence between the measured irregularity and ion drifts that is consistent with the supposition that the motion of the irregularities is dominated by convective drift of the ambient plasma. This indicates that the small-scale irregularities detected by HF radars in the high-latitude F region can serve as tracers of ionospheric convective drift

Novel instrumentation to detect sliding and erratic bed load motion

CSIR Research Space (South Africa)

Ilgner, HJ

2014-09-01

Full Text Available stationary beds on thick-walled pipes within a minute, only the 2 mm-thin spool pieces were able to detect erratic bed motions due to the sensors’ fast response capability. This required additional features to focus the sensing area directly onto the pipe...

Hyperattenuating aortic wall on postmortem computed tomography (PMCT)

Energy Technology Data Exchange (ETDEWEB)

Shiotani, Seiji; Kohno, Mototsugu; Ohashi, Noriyoshi; Yamazaki, Kentaroh; Nakayama, Hidetsugu; Ito, Yoshiyuki; Kaga, Kazunori; Ebashi, Toshio [Tsukuba Medical Center Hospital, Ibaraki (Japan); Itai, Yuji [Tsukuba Univ., Ibaraki (Japan). Inst. of Clinical Medicine

2002-08-01

The purpose of this study was to quantitatively evaluate the finding of hyperattenuating aortic wall on postmortem computed tomography (PMCT) and investigate its causes. Our subjects were 50 PMCT of non-traumatic deaths and 50 CT of living persons (live CT). The ascending aorta at the level of the carina was visually assessed regarding the presence or absence of hyperattenuating aortic wall and hematocrit effect on PMCT and live CT. The diameter, thickness of the aortic wall, and CT number (HU) of the aortic wall and the lumen were also measured. Hyperattenuating aortic wall was detected in 100% of PMCT and 2% of live CT. The diameter of the aortic wall was 2.9{+-}0.5 cm on PMCT and 3.5{+-}0.5 cm on live CT, showing a significant difference. The thickness of the aortic wall was 2 mm on PMCT. Hematocrit effect was observed in 46% of PMCT and in none of live CT. With PMCT, there was a significant difference between the CT numbers of the upper and lower half portions of the lumen (19.6{+-}11.7/30.9{+-}12.9), whereas, with live CT, there was no such significant difference (37.4{+-}7.6/38.9{+-}6.7), with the overall value of 38.2{+-}6.7. The CT number of the aortic wall was 49.9{+-}10.9 on PMCT. The causes of hyperattenuating aortic wall on PMCT are considered to be increased attenuation due to contraction of the aortic wall, a lack of motion artifact, and decreased attenuation of the lumen due to dilution of blood after massive infusion at the time of cardiopulmonary resuscitation. (author)

Structural domain walls in polar hexagonal manganites

Science.gov (United States)

Kumagai, Yu

2014-03-01

The domain structure in the multiferroic hexagonal manganites is currently intensely investigated, motivated by the observation of intriguing sixfold topological defects at their meeting points [Choi, T. et al,. Nature Mater. 9, 253 (2010).] and nanoscale electrical conductivity at the domain walls [Wu, W. et al., Phys. Rev. Lett. 108, 077203 (2012).; Meier, D. et al., Nature Mater. 11, 284 (2012).], as well as reports of coupling between ferroelectricity, magnetism and structural antiphase domains [Geng, Y. et al., Nano Lett. 12, 6055 (2012).]. The detailed structure of the domain walls, as well as the origin of such couplings, however, was previously not fully understood. In the present study, we have used first-principles density functional theory to calculate the structure and properties of the low-energy structural domain walls in the hexagonal manganites [Kumagai, Y. and Spaldin, N. A., Nature Commun. 4, 1540 (2013).]. We find that the lowest energy domain walls are atomically sharp, with {210}orientation, explaining the orientation of recently observed stripe domains and suggesting their topological protection [Chae, S. C. et al., Phys. Rev. Lett. 108, 167603 (2012).]. We also explain why ferroelectric domain walls are always simultaneously antiphase walls, propose a mechanism for ferroelectric switching through domain-wall motion, and suggest an atomistic structure for the cores of the sixfold topological defects. This work was supported by ETH Zurich, the European Research Council FP7 Advanced Grants program me (grant number 291151), the JSPS Postdoctoral Fellowships for Research Abroad, and the MEXT Elements Strategy Initiative to Form Core Research Center TIES.

Near-inertial motions in the DeSoto Canyon during Hurricane Georges

Science.gov (United States)

Jordi, Antoni; Wang, Dong-Ping; Hamilton, Peter

2016-09-01

Hurricane Georges passed directly over an array of 13 moorings deployed in the DeSoto Canyon in the northern Gulf of Mexico on 27-28 September 1998. Current velocity data from the mooring array were analyzed together with a primitive-equation model simulation with realistic hurricane forcing, to characterize the generation and propagation of the hurricane-generated near-inertial waves. The model successfully reproduces the observed mean (sub-inertial) and near-inertial motions. The upper ocean response is strongly impacted by the canyon 'wall': a strong jet is formed along the slope, and the near-inertial motions on the shelf are rapidly suppressed. The model results moreover suggest that strong near-inertial waves in the mixed layer are mostly trapped in an energy flux recirculating gyre around the canyon. This gyre retains the near-inertial energy in the canyon region and enhances the transfer of near-inertial energy below the mixed layer. Additional simulations with idealized topographies show that the presence of a steep slope rather than the canyon is fundamental for the generation of this recirculating gyre. The near-inertial wave energy budget shows that during the study period the wind generated an input of 6.79 × 10-2 Wm-2 of which about 1/3, or 2.43 × 10-2 Wm-2, was transferred below the mixed layer. The horizontal energy flux into and out of the canyon region, in contrast, was relatively weak.

Self-gated CINE MRI for combined contrast-enhanced imaging and wall-stiffness measurements of murine aortic atherosclerotic lesions

NARCIS (Netherlands)

den Adel, Brigit; van der Graaf, Linda M.; Strijkers, Gustav J.; Lamb, Hildo J.; Poelmann, Robert E.; van der Weerd, Louise

2013-01-01

High-resolution contrast-enhanced imaging of the murine atherosclerotic vessel wall is difficult due to unpredictable flow artifacts, motion of the thin artery wall and problems with flow suppression in the presence of a circulating contrast agent. We applied a 2D-FLASH retrospective-gated CINE MRI

Sunspot Light Walls Suppressed by Nearby Brightenings

Energy Technology Data Exchange (ETDEWEB)

Yang, Shuhong; Zhang, Jun; Hou, Yijun; Li, Xiaohong [CAS Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Erdélyi, Robertus [Solar Physics and Space Plasma Research Centre, School of Mathematics and Statistics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Yan, Limei, E-mail: shuhongyang@nao.cas.cn [Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029 (China)

2017-07-01

Light walls, as ensembles of oscillating bright structures rooted in sunspot light bridges, have not been well studied, although they are important for understanding sunspot properties. Using the Interface Region Imaging Spectrograph and Solar Dynamics Observatory observations, here we study the evolution of two oscillating light walls each within its own active region (AR). The emission of each light wall decays greatly after the appearance of adjacent brightenings. For the first light wall, rooted within AR 12565, the average height, amplitude, and oscillation period significantly decrease from 3.5 Mm, 1.7 Mm, and 8.5 minutes to 1.6 Mm, 0.4 Mm, and 3.0 minutes, respectively. For the second light wall, rooted within AR 12597, the mean height, amplitude, and oscillation period of the light wall decrease from 2.1 Mm, 0.5 Mm, and 3.0 minutes to 1.5 Mm, 0.2 Mm, and 2.1 minutes, respectively. Particularly, a part of the second light wall even becomes invisible after the influence of a nearby brightening. These results reveal that the light walls are suppressed by nearby brightenings. Considering the complex magnetic topology in light bridges, we conjecture that the fading of light walls may be caused by a drop in the magnetic pressure, where the flux is canceled by magnetic reconnection at the site of the nearby brightening. Another hypothesis is that the wall fading is due to the suppression of driver source ( p -mode oscillation), resulting from the nearby avalanche of downward particles along reconnected brightening loops.

Effects of premedication with oral hydroxyzine on patient motion during inhalation of 32% xenon for regional cerebral blood flow mapping

International Nuclear Information System (INIS)

Sesay, M.; Dousset, V.; Caille, J.M.; Maurette, P.; Tanaka, Akira

2000-01-01

Because of its anesthetic properties, inhalation of 30-35% Xenon is associated with uncontrolled patient motion in 3-15% of the cases. This constitutes a major setback to regional cerebral blood flow studies with Xenon-enhanced computed tomography (Xe-CT CBF). The present study attempted to determine the effects of oral premedication with hydroxyzine (H) in the control of motion. Patients scheduled for Xe-CT CBF, aged 20-55 years, were randomly allocated to 3 groups: H 50 mg (n=41), H 100 mg (n=36) or Placebo (n=43). The drugs were administered orally 90 minutes before Xenon inhalation. This consisted a gas mixture of 32% Xe and 25% oxygen. Motion was classified as controlled or uncontrolled depending on whether CBF data acquisition was possible or not. Anxiolysis and sedation were evaluated by a visual analogue scale. Motion was significantly reduced in the H 50 mg (0.8% vs 2.5% in the H 100 mg and 6.7% in the Placebo group). An anxiolytic effect of hydroxyzine was suggested. (author)

Optical spin-transfer-torque-driven domain-wall motion in a ferromagnetic semiconductor

Czech Academy of Sciences Publication Activity Database

Ramsay, A.J.; Roy, P.E.; Haigh, J.A.; Otxoa, R.M.; Irvine, A.C.; Janda, T.; Campion, R. P.; Gallagher, B. L.; Wunderlich, Joerg

2015-01-01

Roč. 114, č. 6 (2015), "067202-1"-"067202-5" ISSN 0031-9007 R&D Projects: GA ČR GB14-37427G Institutional support: RVO:68378271 Keywords : magnetic domain walls * magneto-optics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.645, year: 2015

Insights into Ground-Motion Processes from Intensity Data (Invited)

Science.gov (United States)

Atkinson, G. M.

2009-12-01

Analysis of intensity data gathered from the on-line “Did You Feel It?” (DYFI) questionnaire program (Wald et al., 1999, Seism. Res. L.) provides new insights into both contemporary and historical ground-motion processes; this is particularly important for sparsely-instrumented regions. The value of the DYFI data lies in their vast quantities and large spatial coverage. With thousands to tens of thousands of respondents providing information on the felt and damage characteristics of widely-felt earthquakes, DYFI intensity data provide surprisingly high resolution of ground-motion features. The large data quantities allow techniques such as binning to be used to bring out these features in a statistically-stable way (Atkinson and Wald, 2007, Seism. Res. L.), while correlations of the statistics of DYFI intensities with instrumental ground motions provide the link between intensity and engineering ground-motion parameters (Wald et al., 1999, Earthquake Spectra). This link is largely independent of region if its dependence on earthquake magnitude and distance is taken into account (Kaka and Atkinson, 2007, BSSA). Thus DYFI data provide a valuable tool with which ground motions can be estimated, if their felt and damage effects have been reported. This is useful both for understanding contemporary events in sparsely-instrumented regions, and for re-evaluating historical events, for which only intensity data are available. By using calibrated intensity observations, a number of ground-motion processes can be investigated based on DYFI and/or historical intensity data. For example, intensity data shed light on source scaling issues, and whether source parameters vary regionally. They can also be used to document regional attenuation features, such as the attenuation rate and its variation with distance (Atkinson and Wald, 2007). A key uncertainty in these investigations concerns the effect of spectral shape on intensity; the spectral shape is influenced by site

Effects of ship motions on laminar flow in tubes

Energy Technology Data Exchange (ETDEWEB)

Yan, B.H., E-mail: yanbh1986@163.co [Department of Nuclear Science and Engineering, Naval University of Engineering, 717 Jiefang Street, Wuhan 430033 (China); Yu, L. [Department of Nuclear Science and Engineering, Naval University of Engineering, 717 Jiefang Street, Wuhan 430033 (China); Yang, Y.H. [School of Nuclear Science and Engineering, Shanghai Jiao Tong University, 800 Dong Chuan Road, Shanghai 200240 (China)

2010-01-15

The thermal-hydraulics of barge-mounted floating nuclear desalination plants is the incentive for this study. Laminar flow in tubes in heaving motion is modeled. The friction factor and heat transfer coefficient are obtained. All the equations of laminar flow in steady state are applicable for heeling motion. The effect of ship motions on the laminar developing region is also analyzed. The ship motions can weaken the boundary layer in the laminar developing region and strengthen the laminar frictional resistance. The effect of ship motions on the instability of laminar flow is also investigated. The ship motions do not affect the instability point, but they can shorten the distance between the instability point and the transition point, and cause the transition from laminar flow to turbulent flow to occur earlier.

The plasma-wall transition layers in the presence of collisions with a magnetic field parallel to the wall

Science.gov (United States)

Moritz, J.; Faudot, E.; Devaux, S.; Heuraux, S.

2018-01-01

The plasma-wall transition is studied by means of a particle-in-cell (PIC) simulation in the configuration of a parallel to the wall magnetic field (B), with collisions between charged particles vs. neutral atoms taken into account. The investigated system consists of a plasma bounded by two absorbing walls separated by 200 electron Debye lengths (λd). The strength of the magnetic field is chosen such as the ratio λ d / r l , with rl being the electron Larmor radius, is smaller or larger than unity. Collisions are modelled with a simple operator that reorients randomly ion or electron velocity, keeping constant the total kinetic energy of both the neutral atom (target) and the incident charged particle. The PIC simulations show that the plasma-wall transition consists in a quasi-neutral region (pre-sheath), from the center of the plasma towards the walls, where the electric potential or electric field profiles are well described by an ambipolar diffusion model, and in a second region at the vicinity of the walls, called the sheath, where the quasi-neutrality breaks down. In this peculiar geometry of B and for a certain range of the mean-free-path, the sheath is found to be composed of two charged layers: the positive one, close to the walls, and the negative one, towards the plasma and before the neutral pre-sheath. Depending on the amplitude of B, the spatial variation of the electric potential can be non-monotonic and presents a maximum within the sheath region. More generally, the sheath extent as well as the potential drop within the sheath and the pre-sheath is studied with respect to B, the mean-free-path, and the ion and electron temperatures.

Dynamical correlations for vicious random walk with a wall

International Nuclear Information System (INIS)

Nagao, Taro

2003-01-01

A one-dimensional system of nonintersecting Brownian particles is constructed as the diffusion scaling limit of Fisher's vicious random walk model. N Brownian particles start from the origin at time t=0 and undergo mutually avoiding motion until a finite time t=T. Dynamical correlation functions among the walkers are exactly evaluated in the case with a wall at the origin. Taking an asymptotic limit N→∞, we observe discontinuous transitions in the dynamical correlations. It is further shown that the vicious walk model with a wall is equivalent to a parametric random matrix model describing the crossover between the Bogoliubov-deGennes universality classes

Gravity-induced dynamics of a squirmer microswimmer in wall proximity

Science.gov (United States)

Rühle, Felix; Blaschke, Johannes; Kuhr, Jan-Timm; Stark, Holger

2018-02-01

We perform hydrodynamic simulations using the method of multi-particle collision dynamics and a theoretical analysis to study a single squirmer microswimmer at high Péclet number, which moves in a low Reynolds number fluid and under gravity. The relevant parameters are the ratio α of swimming to bulk sedimentation velocity and the squirmer type β. The combination of self-propulsion, gravitational force, hydrodynamic interactions with the wall, and thermal noise leads to a surprisingly diverse behavior. At α > 1 we observe cruising states, while for α < 1 the squirmer resides close to the bottom wall with the motional state determined by stable fixed points in height and orientation. They strongly depend on the squirmer type β. While neutral squirmers permanently float above the wall with upright orientation, pullers float for α larger than a threshold value {α }th} and are pinned to the wall below {α }th}. In contrast, pushers slide along the wall at lower heights, from which thermal orientational fluctuations drive them into a recurrent floating state with upright orientation, where they remain on the timescale of orientational persistence.

Granular packings with moving side walls

International Nuclear Information System (INIS)

Landry, James W.; Grest, Gary Stephen

2004-01-01

The effects of movement of the side walls of a confined granular packing are studied by discrete element, molecular dynamics simulations. The dynamical evolution of the stress is studied as a function of wall movement both in the direction of gravity as well as opposite to it. For all wall velocities explored, the stress in the final state of the system after wall movement is fundamentally different from the original state obtained by pouring particles into the container and letting them settle under the influence of gravity. The original packing possesses a hydrostaticlike region at the top of the container which crosses over to a depth-independent stress. As the walls are moved in the direction opposite to gravity, the saturation stress first reaches a minimum value independent of the wall velocity, then increases to a steady-state value dependent on the wall velocity. After wall movement ceases and the packing reaches equilibrium, the stress profile fits the classic Janssen form for high wall velocities, while some deviations remain for low wall velocities. The wall movement greatly increases the number of particle-wall and particle-particle forces at the Coulomb criterion. Varying the wall velocity has only small effects on the particle structure of the final packing so long as the walls travel a similar distance.

Complex regional pain syndrome with associated chest wall dystonia: a case report

Directory of Open Access Journals (Sweden)

Schwartzman Robert J

2011-09-01

Full Text Available Abstract Patients with complex regional pain syndrome (CRPS often suffer from an array of associated movement disorders, including dystonia of an affected limb. We present a case of a patient with long standing CRPS after a brachial plexus injury, who after displaying several features of the movement disorder previously, developed painful dystonia of chest wall musculature. Detailed neurologic examination found palpable sustained contractions of the pectoral and intercostal muscles in addition to surface allodynia. Needle electromyography of the intercostal and paraspinal muscles supported the diagnosis of dystonia. In addition, pulmonary function testing showed both restrictive and obstructive features in the absence of a clear cardiopulmonary etiology. Treatment was initiated with intrathecal baclofen and the patient had symptomatic relief and improvement of dystonia. This case illustrates a novel form of the movement disorder associated with CRPS with response to intrathecal baclofen treatment.

Automated segmentation of the atrial region and fossa ovalis towards computer-aided planning of inter-atrial wall interventions.

Science.gov (United States)

Morais, Pedro; Vilaça, João L; Queirós, Sandro; Marchi, Alberto; Bourier, Felix; Deisenhofer, Isabel; D'hooge, Jan; Tavares, João Manuel R S

2018-07-01

Image-fusion strategies have been applied to improve inter-atrial septal (IAS) wall minimally-invasive interventions. Hereto, several landmarks are initially identified on richly-detailed datasets throughout the planning stage and then combined with intra-operative images, enhancing the relevant structures and easing the procedure. Nevertheless, such planning is still performed manually, which is time-consuming and not necessarily reproducible, hampering its regular application. In this article, we present a novel automatic strategy to segment the atrial region (left/right atrium and aortic tract) and the fossa ovalis (FO). The method starts by initializing multiple 3D contours based on an atlas-based approach with global transforms only and refining them to the desired anatomy using a competitive segmentation strategy. The obtained contours are then applied to estimate the FO by evaluating both IAS wall thickness and the expected FO spatial location. The proposed method was evaluated in 41 computed tomography datasets, by comparing the atrial region segmentation and FO estimation results against manually delineated contours. The automatic segmentation method presented a performance similar to the state-of-the-art techniques and a high feasibility, failing only in the segmentation of one aortic tract and of one right atrium. The FO estimation method presented an acceptable result in all the patients with a performance comparable to the inter-observer variability. Moreover, it was faster and fully user-interaction free. Hence, the proposed method proved to be feasible to automatically segment the anatomical models for the planning of IAS wall interventions, making it exceptionally attractive for use in the clinical practice. Copyright © 2018 Elsevier B.V. All rights reserved.

Wind effect on the motion of medium-scale travelling ionospheric disturbances in the E region of the ionosphere

International Nuclear Information System (INIS)

Kikvilashvili, G.B.; Sharadze, Z.S.; Mosashvili, N.V.

1988-01-01

Madium-scale travelling ionospheric disturbances (MSTID) in the ionosphere E region in Tbilisi area are investigated by means of spectral analysis of f 0 E s and f b E s variations, synchronously recorded in the three scattered points. The winds at the E s layers formation heights were measured simultaneously by D1 method in one of these points. It is established, that the MSTID motion direction in summer-time E region is controlled by the background thermospheric winds: disturbances mostly more across and against the wind. Tidal winds make the main contribution into the MSTID rate day variations

Coupled Dzyaloshinskii walls and their current-induced dynamics by the spin Hall effect

Energy Technology Data Exchange (ETDEWEB)

Martínez, Eduardo, E-mail: edumartinez@usal.es [Dpto. de Fisica Aplicada, Universidad de Salamanca, Plaza de los Caídos s/n, E-37008 Salamanca (Spain); Alejos, Óscar [Dpto. de Electricidad y Electrónica, Universidad de Valladolid, Paseo de Belén, 7, E-47011 Valladolid (Spain)

2014-07-14

The nucleation of domain walls in ultrathin ferromagnetic/heavy-metal bilayers is studied by means of micromagnetic simulations. In the presence of interfacial Dzyaloshinskii-Moriya interaction, the nucleated walls naturally adopt a homochiral configuration with internal magnetization pointing antiparallely. The interaction between these walls was analyzed and described in terms of a classical dipolar force between the magnetic moments of the walls, which couples their dynamics. Additionally, the current-induced motion of two homochiral walls in the presence of longitudinal fields was also studied by means of a simple one-dimensional model and micromagnetic modeling, considering both one free-defect strip and another one with random edge roughness. It is evidenced that in the presence of pinning due to edge roughness, the in-plane longitudinal field introduces an asymmetry in the current-induced depinning, in agreement with recent experimental results.

Coupled Dzyaloshinskii walls and their current-induced dynamics by the spin Hall effect

International Nuclear Information System (INIS)

Martínez, Eduardo; Alejos, Óscar

2014-01-01

The nucleation of domain walls in ultrathin ferromagnetic/heavy-metal bilayers is studied by means of micromagnetic simulations. In the presence of interfacial Dzyaloshinskii-Moriya interaction, the nucleated walls naturally adopt a homochiral configuration with internal magnetization pointing antiparallely. The interaction between these walls was analyzed and described in terms of a classical dipolar force between the magnetic moments of the walls, which couples their dynamics. Additionally, the current-induced motion of two homochiral walls in the presence of longitudinal fields was also studied by means of a simple one-dimensional model and micromagnetic modeling, considering both one free-defect strip and another one with random edge roughness. It is evidenced that in the presence of pinning due to edge roughness, the in-plane longitudinal field introduces an asymmetry in the current-induced depinning, in agreement with recent experimental results.

Interaction of flexible surface hairs with near-wall turbulence.

Science.gov (United States)

Brücker, Ch

2011-05-11

The interaction of near-wall turbulence with hairy surfaces is investigated in a turbulent boundary layer flow along a flat plate in an oil channel at Re = 1.2 × 10⁶. The plate is covered locally with a dense carpet of elastomeric micro-hairs (length L = 1 mm, length in viscous units L( + ) = 30) which are arranged in a regular grid (60 × 30 hairs with a streamwise spacing Δx( + )≈15 and a spanwise spacing Δy( + )≈30). Instead of the micro-structures used in previous studies for sensory applications, the surface hairs are considerably larger and much more densely distributed with a spacing of S/D wall-normal directions. Near-wall high-frequency disturbances excited by the passage of turbulent sweeps are dampened over their course along the carpet. The cooperative action of the hairs leads to an energy transfer from small-scale motion to larger scales, thus increasing the coherence of the motion pattern in streamwise and spanwise directions. As a consequence of the specific arrangement of the micro-hairs in streamwise columns a reduced spanwise meandering and stabilization of the streamwise velocity streaks is achieved by promoting varicose waves and inhibiting sinusoidal waves. Streak stabilization is known to be a major contributor to turbulent drag reduction. Thus it is concluded that hairy surfaces may be of benefit for turbulent drag reduction as hypothesized by Bartenwerfer and Bechert (1991 Z. Flugwiss. Weltraumforsch. 15 19-26).

Domain wall engineering through exchange bias

International Nuclear Information System (INIS)

Albisetti, E.; Petti, D.

2016-01-01

The control of the structure and position of magnetic domain walls is at the basis of the development of different magnetic devices and architectures. Several nanofabrication techniques have been proposed to geometrically confine and shape domain wall structures; however, a fine tuning of the position and micromagnetic configuration is hardly achieved, especially in continuous films. This work shows that, by controlling the unidirectional anisotropy of a continuous ferromagnetic film through exchange bias, domain walls whose spin arrangement is generally not favored by dipolar and exchange interactions can be created. Micromagnetic simulations reveal that the domain wall width, position and profile can be tuned by establishing an abrupt change in the direction and magnitude of the exchange bias field set in the system. - Highlights: • Micromagnetic simulations study domain walls in exchange biased thin films. • Novel domain wall configurations can be stabilized via exchange bias. • Domain walls nucleate at the boundary of regions with different exchange bias. • Domain wall width and spin profile are controlled by tuning the exchange bias.

The local domain wall position in ferromagnetic thin wires: simultaneous measurement of resistive and transverse voltages at multiple points

International Nuclear Information System (INIS)

Hanada, R.; Sugawara, H.; Aoki, Y.; Sato, H.; Shigeto, K.; Shinjo, T.; Ono, T.; Miyajima, H.

2002-01-01

We have simultaneously measured the field dependences of voltages at multiple pairs of resistance and transverse voltage probes in ferromagnetic wires (with either magnetic or non-magnetic voltage probes). Both the resistive (through the giant magnetoresistance and anisotropic magnetoresistance) and transverse voltages (through the planar Hall effect) exhibit abrupt jumps, reflecting discrete motion of domain walls or rotations of magnetization. Voltage probes, even if non-magnetic, are found to affect the jump fields depending on the sample conditions. We demonstrate that the specific information on the domain (wall) motion along a thin ferromagnetic wire could be obtained from the jump fields. (author)

Comparison of two-dimensional echocardiography with gated radionuclide ventriculography in the evaluation of global and regional left ventricular function in acute myocardial infarction

International Nuclear Information System (INIS)

Van Reet, R.E.; Quinones, M.A.; Poliner, L.R.; Nelson, J.G.; Waggoner, A.D.; Kanon, D.; Lubetkin, S.J.; Pratt, C.M.; Winters, W.L. Jr.

1984-01-01

Two-dimensional echocardiography and gated radionuclide ventriculography were performed in 93 patients (66 men, 27 women; mean age 61 years) with 95 episodes of acute myocardial infarction within 48 hours and at 10 days after infarction. Abnormal motion of an inferior or posterior wall segment was seen in 91% of inferoposterior infarctions by echocardiography versus 61% seen by radionuclide ventriculography. Ejection fractions determined by echocardiography and radionuclide ventriculography correlated well (r . 0.82) and did not change from the first 48 hours to 10 days after infarction (0.48 +/- 0.14). Similarly, wall motion score showed minimal change from the first 48 hours to 10 days. In-hospital mortality was 37 and 42% in patients with an ejection fraction of 0.35 or less by echocardiography and radionuclide ventriculography, respectively. No mortality was seen in patients with an ejection fraction above 0.40 by either test. The echocardiographic wall motion score was also predictive of mortality (40 versus 2%; score less than or equal to 0.50 versus greater than 0.50). The 1 year mortality rate in the 81 short-term survivors was 17%. Mortality was lowest in patients with an ejection fraction above 0.49 or wall motion score above (0.79 (2 to 5%) and worse in those with an ejection fraction below 0.36 or wall motion score below 0.51 (36 to 63%) by either technique. Thus in acute myocardial infarction, echocardiography and radionuclide ventriculography provide a comparable assessment of left ventricular function and wall motion in anterior infarction. Echocardiography appears more sensitive in detecting inferoposterior wall motion abnormalities. Both techniques are capable of identifying subgroups of patients with a high risk of death during the acute event and with an equally high mortality rate over a 1 year follow-up period

Effect of historical earthquakes on pre-stressed anchor tie back diaphragm wall and on near-by building

Directory of Open Access Journals (Sweden)

Kamal Mohamed Hafez Ismail Ibrahim

2013-04-01

Full Text Available Pre-stressed tie back anchored diaphragm walls are considered one of the safest lateral supports which help in overall stability when there is a significant difference in land level between back and front of these walls. Permanent lateral supports to these walls are frequently represented by supporting it laterally with foundation and floor slabs of the building. In this paper a special study of one raw anchor diaphragm wall subjected to different earthquake dynamic loads will be presented. The wall retains an excavation of 9.5 m and supports laterally a near-by 5 floor building. Five historical strong motions with different fundamental frequencies are subjected on the wall. The wall displacement, straining actions, anchor extreme force and the influence of variation of anchor stiffness are calculated using a dynamic Plaxis finite element program. The soil is considered as elasto-plastic material and represented using Mohr–Coulomb criteria, the wall and the anchor are considered to behave elastically. Prescribed displacement at the lower bottom boundary represents the earthquake motion. Far left and right absorbent boundaries are assumed to prevent dynamic wave reflection. Four static phases representing construction procedure and one dynamic loading phase are considered. It is found that the straining actions of different historical earthquakes match in shape with each other, the only change is in the amplitude which is affected by earthquake fundamental frequency and its intensity. The maximum dynamic lateral displacement of the wall is at its free top. The near-by building shows a differential settlement towards the wall which causes a change in the sign and amplitude of the straining actions. Increasing the stiffness of anchor was also studied and it was found that it reduces too much the maximum dynamic top wall lateral displacement.

Topological domain walls in helimagnets

Science.gov (United States)

Schoenherr, P.; Müller, J.; Köhler, L.; Rosch, A.; Kanazawa, N.; Tokura, Y.; Garst, M.; Meier, D.

2018-05-01

Domain walls naturally arise whenever a symmetry is spontaneously broken. They interconnect regions with different realizations of the broken symmetry, promoting structure formation from cosmological length scales to the atomic level1,2. In ferroelectric and ferromagnetic materials, domain walls with unique functionalities emerge, holding great promise for nanoelectronics and spintronics applications3-5. These walls are usually of Ising, Bloch or Néel type and separate homogeneously ordered domains. Here we demonstrate that a wide variety of new domain walls occurs in the presence of spatially modulated domain states. Using magnetic force microscopy and micromagnetic simulations, we show three fundamental classes of domain walls to arise in the near-room-temperature helimagnet iron germanium. In contrast to conventional ferroics, the domain walls exhibit a well-defined inner structure, which—analogous to cholesteric liquid crystals—consists of topological disclination and dislocation defects. Similar to the magnetic skyrmions that form in the same material6,7, the domain walls can carry a finite topological charge, permitting an efficient coupling to spin currents and contributions to a topological Hall effect. Our study establishes a new family of magnetic nano-objects with non-trivial topology, opening the door to innovative device concepts based on helimagnetic domain walls.

Active Brownian particles near straight or curved walls: Pressure and boundary layers

Science.gov (United States)

Duzgun, Ayhan; Selinger, Jonathan V.

2018-03-01

Unlike equilibrium systems, active matter is not governed by the conventional laws of thermodynamics. Through a series of analytic calculations and Langevin dynamics simulations, we explore how systems cross over from equilibrium to active behavior as the activity is increased. In particular, we calculate the profiles of density and orientational order near straight or circular walls and show the characteristic width of the boundary layers. We find a simple relationship between the enhancements of density and pressure near a wall. Based on these results, we determine how the pressure depends on wall curvature and hence make approximate analytic predictions for the motion of curved tracers, as well as the rectification of active particles around small openings in confined geometries.

The dynamics of the asymmetric motion of domain walls of sandwich domain structure in a Fe-based amorphous ribbon

Energy Technology Data Exchange (ETDEWEB)

Zhmetko, D.N., E-mail: sergey.zhmetko@gmail.com [Department of Physics, Zaporizhzhya National University, 66 Zhukovsky Street, 69063 Zaporizhzhya (Ukraine); Zhmetko, S.D. [Department of Physics, Zaporizhzhya National University, 66 Zhukovsky Street, 69063 Zaporizhzhya (Ukraine); Troschenkov, Y.N. [Institute for Magnetism, 36-b Vernadsky Boulevard, 03142 Kyiv (Ukraine); Matsura, A.V. [Department of Physics, Zaporizhzhya National University, 66 Zhukovsky Street, 69063 Zaporizhzhya (Ukraine)

2013-08-15

The frequency dependence of asymmetry of the domain walls velocity relative to the middle plane of amorphous ribbon is investigated. An additional pressure of the same direction acting on each domain wall caused by dependence of eddy current damping on the coordinate of the domain wall is revealed. The microscopic mechanisms of this additional pressure are considered. - Highlights: ► Additional pressure on the domain wall, caused by inhomogeneity of its damping. ► Asymmetry of the coordinate of the nucleation of domain walls and their damping. ► Connection between the components of additional pressure and its direction. ► Interaction of domain walls with the surface defects of the amorphous ribbon.

The dynamics of the asymmetric motion of domain walls of sandwich domain structure in a Fe-based amorphous ribbon

International Nuclear Information System (INIS)

Zhmetko, D.N.; Zhmetko, S.D.; Troschenkov, Y.N.; Matsura, A.V.

2013-01-01

The frequency dependence of asymmetry of the domain walls velocity relative to the middle plane of amorphous ribbon is investigated. An additional pressure of the same direction acting on each domain wall caused by dependence of eddy current damping on the coordinate of the domain wall is revealed. The microscopic mechanisms of this additional pressure are considered. - Highlights: ► Additional pressure on the domain wall, caused by inhomogeneity of its damping. ► Asymmetry of the coordinate of the nucleation of domain walls and their damping. ► Connection between the components of additional pressure and its direction. ► Interaction of domain walls with the surface defects of the amorphous ribbon

Assessment of the Global and Regional Land Hydrosphere and Its Impact on the Balance of the Geophysical Excitation Function of Polar Motion

Science.gov (United States)

Wińska, Małgorzata; Nastula, Jolanta; Kołaczek, Barbara

2016-02-01

The impact of continental hydrological loading from land water, snow and ice on polar motion excitation, calculated as hydrological angular momentum (HAM), is difficult to estimate, and not as much is known about it as about atmospheric angular momentum (AAM) and oceanic angular momentum (OAM). In this paper, regional hydrological excitations to polar motion are investigated using monthly terrestrial water storage data derived from the Gravity Recovery and Climate Experiment (GRACE) mission and from the five models of land hydrology. The results show that the areas where the variance shows large variability are similar for the different models of land hydrology and for the GRACE data. Areas which have a small amplitude on the maps make an important contribution to the global hydrological excitation function of polar motion. The comparison of geodetic residuals and global hydrological excitation functions of polar motion shows that none of the hydrological excitation has enough energy to significantly improve the agreement between the observed geodetic excitation and geophysical ones.

Colon wall motility: comparison of novel quantitative semi-automatic measurements using cine MRI.

Science.gov (United States)

Hoad, C L; Menys, A; Garsed, K; Marciani, L; Hamy, V; Murray, K; Costigan, C; Atkinson, D; Major, G; Spiller, R C; Taylor, S A; Gowland, P A

2016-03-01

Recently, cine magnetic resonance imaging (MRI) has shown promise for visualizing movement of the colonic wall, although assessment of data has been subjective and observer dependent. This study aimed to develop an objective and semi-automatic imaging metric of ascending colonic wall movement, using image registration techniques. Cine balanced turbo field echo MRI images of ascending colonic motility were acquired over 2 min from 23 healthy volunteers (HVs) at baseline and following two different macrogol stimulus drinks (11 HVs drank 1 L and 12 HVs drank 2 L). Motility metrics derived from large scale geometric and small scale pixel movement parameters following image registration were developed using the post ingestion data and compared to observer grading of wall motion. Inter and intra-observer variability in the highest correlating metric was assessed using Bland-Altman analysis calculated from two separate observations on a subset of data. All the metrics tested showed significant correlation with the observer rating scores. Line analysis (LA) produced the highest correlation coefficient of 0.74 (95% CI: 0.55-0.86), p cine MRI registered data provides a quick, accurate and non-invasive method to detect wall motion within the ascending colon following a colonic stimulus in the form of a macrogol drink. © 2015 John Wiley & Sons Ltd.

Thermophoretic Motion of Water Nanodroplets confined inside Carbon Nanotubes

DEFF Research Database (Denmark)

Zambrano, Harvey A; Walther, Jens Honore; Koumoutsakos, Petros

2009-01-01

We study the thermophoretic motion of water nanodroplets confined inside carbon nanotubes using molecular dynamics simulations. We find that the nanodroplets move in the direction opposite the imposed thermal gradient with a terminal velocity that is linearly proportional to the gradient....... The translational motion is associated with a solid body rotation of the water nanodroplet coinciding with the helical symmetry of the carbon nanotube. The thermal diffusion displays a weak dependence on the wetting of the water-carbon nanotube interface. We introduce the use of the Moment Scaling Spectrum (MSS......) in order to determine the characteristics of the motion of the nanoparticles inside the carbon nanotube. The MSS indicates that affinity of the nanodroplet with the walls of the carbon nanotubes is important for the isothermal diffusion, and hence for the Soret coefficient of the system....

Simulation of a DC electric arc furnace for steelmaking: study in the arc and bath regions