WorldWideScience

Sample records for arterial wall dynamics

  1. Identification of arterial wall dynamics in conscious dogs.

    Science.gov (United States)

    Gamero, L G; Armentano, R L; Barra, J G; Simon, A; Levenson, J

    2001-07-01

    Viscoelastic properties determine the dynamic behaviour of the arterial wall under pulsatile pressure and flow, suggesting time- or frequency-dependent responses to changes in wall stress and strain. The objectives of the present study were: (i) to develop a simplified model to derive simultaneously the elastic, viscous and inertial wall moduli; (ii) to assess Young's modulus as a function of frequency, in conscious, chronically instrumented dogs. Parametric discrete time models were used to characterise the dynamics of the arterial system based on thoracic aortic pressure (microtransducer) and diameter (sonomicrometry) measurements in control steady state and during activation of smooth muscle with the alpha-adrenoceptor agonist phenylephrine (5 microg kg(-1) min(-1), I.V.), in eight conscious dogs. The linear autoregressive model and a physically motivated non-linear model were fitted to the input-output (stress-strain) relationship. The aortic buffering function (complex Young's modulus) was obtained in vivo from the identified linear model. Elastic, viscous and inertial moduli were significantly increased from control state ((44.5 +/- 7.7) x 10(4) Pa; (12.3 +/- 4.7) x 10(4) Pa s; (0.048 +/- 0.028) x 10(4) Pa s(2) ) to active state ((85.3 +/- 29.5) x 10(4) Pa, P model, did not present significant differences compared with those derived using the non-linear model. In control conditions, the magnitude of the normalised complex Young's modulus was found to be similar to that reported in previous animal studies ranging from 1 to 10 Hz. During vascular smooth muscle activation, this modulus was found to be increased with regard to control conditions (P parametric modelling approach allows us to verify that vascular smooth muscle activation increases the elastic, viscous and inertial moduli with the advantage of being able to track their time evolution. Furthermore, under activation, the aortic wall remains stiff in the physiological frequency range, suggesting the

  2. Effects of wall condition on flow distributions in arterial modeling: comparison of rigid, dynamic, and compliant walls

    Energy Technology Data Exchange (ETDEWEB)

    He, Fan [Beijing University of Civil Engineering and Architecture, Beijing (China); Hua, Lu; Gao, Li jian [Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (China)

    2016-03-15

    Blood flow distributions were evaluated using various computational strategies. Three commonly used wall conditions in arterial modeling were employed, namely rigid, dynamic and compliant walls. The results show that the velocity distributions are similar under rigid and dynamic walls, developing into the Poiseuille flow, but they are blunt under compliant walls. The peak pressure under rigid walls is highest, but the model of dynamic walls has a good approximation of pressure against the model of compliant walls. The results indicate that a model of compliant walls appears to be a computationally and reasonably accurate approximation of blood velocity distributions compared with the analysis under rigid or dynamic walls. Introducing fluid-structure interaction into arterial modeling is necessary to ensure reliable results and information. However, a model of dynamic walls seems to be a computationally inexpensive yet reasonably accurate approximation for pressure.

  3. Development of novel short-term heating angioplasty: thermal denaturation dynamics of collagen in artery wall

    Science.gov (United States)

    Shimazaki, N.; Tokunaga, H.; Katou, Y.; Hayashi, T.; Arai, T.

    2009-02-01

    We have studied to develop the new thermal angioplasty methodology, photo-thermo dynamic balloon angioplasty (PTDBA), which provides artery dilatation with short-term (<15s) and uniform heating through the balloon by the combination of the efficient laser driven heat generation and fluid perfusion. Thermal denaturation degree of the collagen in artery media may be the important factor to attain sufficient artery dilatation for the PTDBA. In order to predict the optimum heating condition i.e. the balloon temperature and heating duration, we investigated the thermal denaturation dynamics of artery collagen in ex vivo. The extracted fresh porcine carotid artery was used. The temperature-dependent light scattering property and mechanical property of the artery specimen were simultaneously measured during artery temperature rising by specially made setup to assess the denaturation of arterial collagen. The change rate of the backscattered light intensity from the artery specimen; I(T)/I0 with 633nm was measured to evaluate the artery scattering property change with the thermal denaturation. The artery specimen was heated from 25°C to 80°C with constant temperature rising rate of 3°C/min. The measured I(T)/I0 was suddenly increased over 48°C. This boundary temperature might be the initiation temperature of the arterial collagen denaturation. We defined the variation of the I(T)/I0 as the collagen denaturation ratio, and calculated the reactive enthalpy by the chemical equilibrium theory. Since the calculated enthalpy was similar to the enthalpy in literature report, the variety of I(T)/I0 during the temperature rising might be attributed to the collagen conformational change due to the denaturation. In terms of the artery internal force measurement, the artery force was decreased with increasing of the artery temperature up to 65°C (i.e. softening), and increased over 65°C (i.e. shrinkage). We confirmed that the changes of the backscattered light (at 633nm in

  4. Wall shear stress in intracranial aneurysms and adjacent arteries

    Institute of Scientific and Technical Information of China (English)

    Fuyu Wang; Bainan Xu; Zhenghui Sun; Chen Wu; Xiaojun Zhang

    2013-01-01

    Hemodynamic parameters play an important role in aneurysm formation and growth. However, it is difficult to directly observe a rapidly growing de novo aneurysm in a patient. To investigate possible associations between hemodynamic parameters and the formation and growth of intracranial aneurysms, the present study constructed a computational model of a case with an internal carotid artery aneurysm and an anterior communicating artery aneurysm, based on the CT angiography findings of a patient. To simulate the formation of the anterior communicating artery aneurysm and the growth of the internal carotid artery aneurysm, we then constructed a model that virtually removed the anterior communicating artery aneurysm, and a further two models that also progressively decreased the size of the internal carotid artery aneurysm. Computational simulations of the fluid dynamics of the four models were performed under pulsatile flow conditions, and wall shear stress was compared among the different models. In the three aneurysm growth models, increasing size of the aneurysm was associated with an increased area of low wall shear stress, a significant decrease in wall shear stress at the dome of the aneurysm, and a significant change in the wall shear stress of the parent artery. The wall shear stress of the anterior communicating artery remained low, and was significantly lower than the wall shear stress at the bifurcation of the internal carotid artery or the bifurcation of the middle cerebral artery. After formation of the anterior communicating artery aneurysm, the wall shear stress at the dome of the internal carotid artery aneurysm increased significantly, and the wall shear stress in the upstream arteries also changed significantly. These findings indicate that low wall shear stress may be associated with the initiation and growth of aneurysms, and that aneurysm formation and growth may influence hemodynamic parameters in the local and adjacent arteries.

  5. Determination of arterial wall shear stress

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The arteries can remodel their structure and function to adapt themselves to the mechanical environment. In various factors that lead to vascular remodeling, the shear stress on the arterial wall induced by the blood flow is of great importance. However, there are many technique difficulties in measuring the wall shear stress directly at present. In this paper, through analyzing the pulsatile blood flow in arteries, a method has been proposed that can determine the wall shear stress quantitatively by measuring the velocity on the arterial axis, and that provides a necessary means to discuss the influence of arterial wall shear stress on vascular remodeling.

  6. The influence of artery wall curvature on the anatomical assessment of stenosis severity derived from fractional flow reserve: a computational fluid dynamics study.

    Science.gov (United States)

    Govindaraju, Kalimuthu; Viswanathan, Girish N; Badruddin, Irfan Anjum; Kamangar, Sarfaraz; Salman Ahmed, N J; Al-Rashed, Abdullah A A A

    2016-11-01

    This study aims to investigate the influence of artery wall curvature on the anatomical assessment of stenosis severity and to identify a region of misinterpretation in the assessment of per cent area stenosis (AS) for functionally significant stenosis using fractional flow reserve (FFR) as standard. Five artery models of different per cent AS severity (70, 75, 80, 85 and 90%) were considered. For each per cent AS severity, the angle of curvature of the arterial wall varied from straight to an increasingly curved model (0°, 30°, 60°, 90° and 120°). Computational fluid dynamics was performed under transient physiologic hyperemic flow conditions to investigate the influence of artery wall curvature on the pressure drop and the FFR. The findings in this study may be useful in in vitro anatomical assessment of functionally significant stenosis. The FFR decreased with increasing stenosis severity for a given curvature of the artery wall. Moreover, a significant decrease in FFR was found between straight and curved models discussed for a given severity condition. These findings indicate that the curvature effect was included in the FFR assessment in contrast to minimum lumen area (MLA) or per cent AS assessment. The MLA or per cent AS assessment may lead to underestimation of stenosis severity. From this numerical study, an uncertainty region could be evaluated using the clinical FFR cutoff value of 0.8. This value was observed at 81.98 and 79.10% AS for arteries with curvature angles of 0° and 120° respectively. In conclusion, the curvature of the artery should not be neglected in in vitro anatomical assessment. PMID:27052093

  7. ON WALL SHEAR STRESS OF ARTERY

    Institute of Scientific and Technical Information of China (English)

    Liu Zhao-rong; Liu Bao-yu; Qin Kai-rong

    2003-01-01

    In this paper, a method was proposed that the wall shear stress of artery could be determined by measuring the centerline axial velocity and radial motion of arterial wall simultaneously.The method is simple in application and can get higher precision when it is used to determine the shear stress of arterial wall in vivo.As an example, the shear stress distribution in periodic oscillatory flow of human carotid was calculated and discussed.The computed results show that the shear stress distribution at any given instant is almost uniform and will be zero at the centerline and tends to maximum at the vessel wall.

  8. Simulated lipoprotein transport in the wall of branched arteries.

    Science.gov (United States)

    Darbeau, M Z; Lutz, R J; Collins, W E

    2000-01-01

    Study of arterial blood flow dynamics improves our understanding of the development of cardiovascular diseases such as atherosclerosis. The transport and accumulation of macromolecules in the arterial wall can be influenced by local fluid mechanics. We used numeric simulations to investigate such transport in a T-junction model. Presumably an in vitro experiment would consist of gel segments inserted in the walls of a mechanical flow T-junction model near branch points where separation and recirculation zones are expected. The transport of low density lipoprotein (LDL) was investigated theoretically at these sites in a two dimensional numeric T-branch model. In the numeric model, the hydraulic conductivity of the porous gel wall segments was varied for a fixed species diffusivity to provide simulations with wall transmural Peclet numbers ranging from 0.3 to 30. Steady state flow patterns in the lumen of the two dimensional T-branch were simulated at Reynolds numbers of 250 and 500, using the software package FIDAP 7.61 to implement the finite element method. The simulations demonstrated that wall Peclet numbers greater than 1.0 were needed to achieve species concentration gradients within the wall that varied in the axial direction, thereby reflecting the influence of disturbed flow and pressure patterns in the lumen. As expected, the transmural concentration gradients were steeper when convection predominated. Blood flow in the lumen can influence the distribution of macromolecules in the arterial wall and needs to be investigated for the relevance to atherosclerosis.

  9. Is arterial wall-strain stiffening an additional process responsible for atherosclerosis in coronary bifurcations?: an in vivo study based on dynamic CT and MRI.

    Science.gov (United States)

    Ohayon, Jacques; Gharib, Ahmed M; Garcia, Alberto; Heroux, Julie; Yazdani, Saami K; Malvè, Mauro; Tracqui, Philippe; Martinez, Miguel-Angel; Doblare, Manuel; Finet, Gérard; Pettigrew, Roderic I

    2011-09-01

    Coronary bifurcations represent specific regions of the arterial tree that are susceptible to atherosclerotic lesions. While the effects of vessel compliance, curvature, pulsatile blood flow, and cardiac motion on coronary endothelial shear stress have been widely explored, the effects of myocardial contraction on arterial wall stress/strain (WS/S) and vessel stiffness distributions remain unclear. Local increase of vessel stiffness resulting from wall-strain stiffening phenomenon (a local process due to the nonlinear mechanical properties of the arterial wall) may be critical in the development of atherosclerotic lesions. Therefore, the aim of this study was to quantify WS/S and stiffness in coronary bifurcations and to investigate correlations with plaque sites. Anatomic coronary geometry and cardiac motion were generated based on both computed tomography and MRI examinations of eight patients with minimal coronary disease. Computational structural analyses using the finite element method were subsequently performed, and spatial luminal arterial wall stretch (LW(Stretch)) and stiffness (LW(Stiff)) distributions in the left main coronary bifurcations were calculated. Our results show that all plaque sites were concomitantly subject to high LW(Stretch) and high LW(Stiff), with mean amplitudes of 34.7 ± 1.6% and 442.4 ± 113.0 kPa, respectively. The mean LW(Stiff) amplitude was found slightly greater at the plaque sites on the left main coronary artery (mean value: 482.2 ± 88.1 kPa) compared with those computed on the left anterior descending and left circumflex coronary arteries (416.3 ± 61.5 and 428.7 ± 181.8 kPa, respectively). These findings suggest that local wall stiffness plays a role in the initiation of atherosclerotic lesions.

  10. Determination of arterial wall shear stress

    Institute of Scientific and Technical Information of China (English)

    LIU; Zhaorong

    2001-01-01

    [1]Langille, B. L., 7Donnell, F., Reductions in arterial diameter produced by chronic decreases in blood flow are endothelium-dependent, Science, 1986, 231: 405—407.[2]Langer, R., Vacanti, J. P., Tissue engineering, Science, 1993, 260: 920—926.[3]Kamiya, A., Togawa, T., Adaptive regulation of wall shear stress to flow change in the canine carotid artery, Am. J. Physiol. (Heart Circ. Physiol.), 1980, 239: H14—H21.[4]Fung, Y. C., Biomechanics: Motion, Flow, Stress, and Growth, New York: Springer-Verlag, 1990.[5]Liu, S. Q., Biomechanical basis of vascular tissue engineering, Critical Reviews in Biomedical Engineering, 1999, 27: 75—148.[6]Ando, J., Kamiya, A., Blood flow and vascular endothelium cell function, Frontiers Med. Biological Eng., 1993, 5: 245—264.[7]Ku, D. N., Giddens, D. P., Zarins, D. K. et al., Pulsatile flow and atherosclerosis in the human carotid bifurcation-positive correlation between plaque location and low and oscillating shear stress, Atherosclerosis, 1985, 5: 293—302.[8]Liu Zhaorong, Li Xixi, Theory and Method on Hemodynamics (in Chinese), Shanghai: Fudan University Press, 1997.

  11. Diabetes Mellitus, ArterialWall, and Cardiovascular Risk Assessment

    OpenAIRE

    Michaela Kozakova; Carlo Palombo

    2016-01-01

    Diabetes mellitus is an independent risk factor for atherothrombotic cardiovascular disease. Adults with diabetes are two to four times more likely to develop heart disease or stroke than adults without diabetes. The two major features of diabetes, i.e., hyperglycemia and insulin-resistance, trigger arterial stiffening and increase the susceptibility of the arterial wall to atherosclerosis at any given age. These pathological changes in the arterial wall may provide a functional and structura...

  12. Arterial Wall Properties and Womersley Flow in Fabry Disease

    Directory of Open Access Journals (Sweden)

    Dimitriadis Emilios

    2002-01-01

    Full Text Available Abstract Background Fabry disease is an X-linked recessive lysosomal storage disease resulting in the cellular accumulation of globotriaosylceramide particularly globotriaosylceramide. The disease is characterized by a dilated vasculopathy with arterial ectasia in muscular arteries and arterioles. Previous venous plethysomographic studies suggest enhanced endothelium-dependent vasodilation in Fabry disease indicating a functional abnormality of resistance vessels. Methods We examined the mechanical properties of the radial artery in Fabry disease, a typical fibro-muscular artery. Eight control subjects and seven patients with Fabry disease had a right brachial arterial line placed allowing real time recording of intra-arterial blood pressure. Real time B-mode ultrasound recordings of the right radial artery were obtained simultaneously allowing calculation of the vessel wall internal and external diameter, the incremental Young's modulus and arterial wall thickness. By simultaneously measurement of the distal index finger-pulse oximetry the pulse wave speed was calculated. From the wave speed and the internal radial artery diameter the volume flow was calculated by Womersley analysis following truncation of the late diastolic phase. Results No significant difference was found between Fabry patients and controls for internal or external arterial diameters, the incremental Young's modulus, the arterial wall thickness, the pulse wave speed and the basal radial artery blood flow. Further, no significant difference was found for the radial artery blood flow in response to intra-arterial acetylcholine or sodium nitroprusside. Both drugs however, elevated the mean arterial flow. Conclusions The current study suggests that no structural or mechanical abnormality exists in the vessel wall of fibro-muscular arteries in Fabry disease. This may indicate that a functional abnormality downstream to the conductance vessels is the dominant feature in

  13. Dynamic diffuse optical tomography imaging of peripheral arterial disease

    OpenAIRE

    Khalil, Michael A.; Kim, Hyun K.; Kim, In-Kyong; Flexman, Molly; Dayal, Rajeev; Shrikhande, Gautam; Hielscher, Andreas H.

    2012-01-01

    Peripheral arterial disease (PAD) is the narrowing of arteries due to plaque accumulation in the vascular walls. This leads to insufficient blood supply to the extremities and can ultimately cause cell death. Currently available methods are ineffective in diagnosing PAD in patients with calcified arteries, such as those with diabetes. In this paper we investigate the potential of dynamic diffuse optical tomography (DDOT) as an alternative way to assess PAD in the lower extremities. DDOT is a ...

  14. Asymptotic Dynamics of Monopole Walls

    CERN Document Server

    Cross, R

    2015-01-01

    We determine the asymptotic dynamics of the U(N) doubly periodic BPS monopole in Yang-Mills-Higgs theory, called a monopole wall, by exploring its Higgs curve using the Newton polytope and amoeba. In particular, we show that the monopole wall splits into subwalls when any of its moduli become large. The long-distance gauge and Higgs field interactions of these subwalls are abelian, allowing us to derive an asymptotic metric for the monopole wall moduli space.

  15. Dynamical domain wall and localization

    Directory of Open Access Journals (Sweden)

    Yuta Toyozato

    2016-03-01

    Full Text Available Based on the previous works (Toyozato et al., 2013 [24]; Higuchi and Nojiri, 2014 [25], we investigate the localization of the fields on the dynamical domain wall, where the four-dimensional FRW universe is realized on the domain wall in the five-dimensional space–time. Especially we show that the chiral spinor can localize on the domain wall, which has not been succeeded in the past works as the seminal work in George et al. (2009 [23].

  16. Artery Wall Imaging and Effects of Postmenopausal Estrogen Therapy

    OpenAIRE

    Rodriguez-Macias Wallberg, Kenny A.

    2005-01-01

    Postmenopausal estrogen therapy, initiated early in the menopause, seems to protect against development of atherosclerosis and cardiovascular diseases. This thesis concerns studies of artery wall thickness and arterial stiffness estimated by noninvasive ultrasound techniques in long-term estrogen treated postmenopausal women who initiated therapy at the time of the menopause. A noninvasive 25 MHz high-frequency ultrasound technique was validated in the imaging of superficial arteries by using...

  17. Ultrasound settings significantly alter arterial lumen and wall thickness measurements

    Directory of Open Access Journals (Sweden)

    Green Daniel J

    2008-01-01

    Full Text Available Abstract Background Flow-mediated dilation (FMD and carotid intima-medial thickness (CIMT, measured by ultrasound, are widely used to test the efficacy of cardioprotective interventions. Although assessment methods vary, automated edge-detecting image analysis software is routinely used to measure changes in FMD and CIMT. We aimed to quantify the effect that commonly adjusted ultrasound settings have on arterial lumen and wall thickness measurements made with CIMT measurement software. Methods We constructed phantom arteries from a tissue-mimicking agar compound and scanned them in a water bath with a 10 MHz multi-frequency linear-array probe attached to a high-resolution ultrasound machine. B-mode images of the phantoms were recorded with dynamic range (DR and gain set at five decibel (dB increments from 40 dB to 60 dB and -10 dB to +10 dB respectively. Lumen diameter and wall-thickness were measured off-line using CIMT measurement software. Results Lumen measurements: there was a strong linear relationship between DR and gain and measured lumen diameter. For a given gain level, a 5 dB increase in DR reduced the measured lumen diameter by 0.02 ± 0.004 mm (p CIMT measurements: For a fixed gain level, a 5 dB increase in DR increased measured wall thickness by 0.003 ± 0.002 mm (p Conclusion DR, gain and probe distance significantly alter lumen diameter and CIMT measurements made using image analysis software. When CIMT and FMD are used to test the efficacy of cardioprotective interventions, the DR, gain and probe position used to record baseline scans should be documented and replicated in post-treatment scans in individual trial subjects. If more than one sonographer or imaging centre is used to collect data, the study protocol should document specific DR and gain settings to be used in all subjects.

  18. Diabetes Mellitus, Arterial Wall, and Cardiovascular Risk Assessment

    Science.gov (United States)

    Kozakova, Michaela; Palombo, Carlo

    2016-01-01

    Diabetes mellitus is an independent risk factor for atherothrombotic cardiovascular disease. Adults with diabetes are two to four times more likely to develop heart disease or stroke than adults without diabetes. The two major features of diabetes, i.e., hyperglycemia and insulin-resistance, trigger arterial stiffening and increase the susceptibility of the arterial wall to atherosclerosis at any given age. These pathological changes in the arterial wall may provide a functional and structural background for cardiovascular events. The present paper provides a critical overview of the clinical evidence linking diabetes-related metabolic abnormalities to cardiovascular risk, debates the pathophysiologic mechanisms through which insulin resistance and hyperglycemia may affect the arterial wall, and discusses the associations between vascular biomarkers, metabolic abnormalities and cardiovascular events. PMID:26861377

  19. Dynamics of monopole walls

    OpenAIRE

    Maldonado, R; R. S. Ward

    2014-01-01

    The moduli space of centred Bogomolny–Prasad–Sommerfield 2-monopole fields is a 4-dimensional manifold M with a natural metric, and the geodesics on M correspond to slow-motion monopole dynamics. The best-known case is that of monopoles on R3 , where M is the Atiyah–Hitchin space. More recently, the case of monopoles periodic in one direction (monopole chains) was studied a few years ago. Our aim in this note is to investigate M for doubly-periodic fields, which may be visualized as monopole ...

  20. Sonographic assessment of splanchnic arteries and the bowel wall

    Energy Technology Data Exchange (ETDEWEB)

    Dietrich, C.F. [Medical Department II, Caritas-Krankenhaus, Uhlandstr. 7, D-97980 Bad Mergentheim (Germany)], E-mail: Christoph.dietrich@ckbm.de; Jedrzejczyk, M.; Ignee, A. [Medical Department II, Caritas-Krankenhaus, Uhlandstr. 7, D-97980 Bad Mergentheim (Germany)

    2007-11-15

    The intestinal wall can be visualized using high resolution transabdominal ultrasound. The normal intestinal wall thickness in the terminal ileum, cecum, and right and left colon is <2 mm when examined with graded compression. It is important to appreciate that a contracted intestinal segment can be misinterpreted as a thickened wall. Vascularisation can be mainly displayed in the second hyperechoic layer (submucosal layer) as well as vessels penetrating the muscularis propria. Imaging of the gastrointestinal wall is dependent on the experience of the examiner as well dependent on the equipment used. Acute or chronic inflammation of the intestinal wall is accompanied by increased perfusion of the mesentery, which can be displayed non-quantitatively with colour duplex. In contrast, ischemia is characterised by hypoperfusion of the mesenteric arteries and the bowel wall. The most promising sonographic approach in assessing splanchnic arteries and the bowel wall is combining the analysis of superior and inferior mesenteric inflow by pulsed Doppler scanning (systolic and diastolic velocities, resistance index) with the end-organ vascularity by colour Doppler imaging diminishing the influence of examination technique only displaying bowel wall vascularity. Colour Doppler imaging has been described as helpful in a variety of gastrointestinal disorders, particularly in patients with Crohn's disease, celiac disease, mesenteric artery stenosis and other ischemic gastrointestinal diseases, graft versus host disease and hemorrhagic segmental colitis.

  1. Sonographic assessment of splanchnic arteries and the bowel wall

    International Nuclear Information System (INIS)

    The intestinal wall can be visualized using high resolution transabdominal ultrasound. The normal intestinal wall thickness in the terminal ileum, cecum, and right and left colon is <2 mm when examined with graded compression. It is important to appreciate that a contracted intestinal segment can be misinterpreted as a thickened wall. Vascularisation can be mainly displayed in the second hyperechoic layer (submucosal layer) as well as vessels penetrating the muscularis propria. Imaging of the gastrointestinal wall is dependent on the experience of the examiner as well dependent on the equipment used. Acute or chronic inflammation of the intestinal wall is accompanied by increased perfusion of the mesentery, which can be displayed non-quantitatively with colour duplex. In contrast, ischemia is characterised by hypoperfusion of the mesenteric arteries and the bowel wall. The most promising sonographic approach in assessing splanchnic arteries and the bowel wall is combining the analysis of superior and inferior mesenteric inflow by pulsed Doppler scanning (systolic and diastolic velocities, resistance index) with the end-organ vascularity by colour Doppler imaging diminishing the influence of examination technique only displaying bowel wall vascularity. Colour Doppler imaging has been described as helpful in a variety of gastrointestinal disorders, particularly in patients with Crohn's disease, celiac disease, mesenteric artery stenosis and other ischemic gastrointestinal diseases, graft versus host disease and hemorrhagic segmental colitis

  2. Solutions of the Maxwell viscoelastic equations for displacement and stress distributions within the arterial wall.

    Science.gov (United States)

    Hodis, S; Zamir, M

    2008-08-01

    Mechanical events within the thickness of the vessel wall caused by pulsatile blood flow are considered, with focus on axial dynamics of the wall, driven by the oscillatory drag force exerted by the fluid on the endothelial layer of the wall. It is shown that the focus on the axial direction makes it possible to derive simplified equations of motion which, combined with a viscoelastic model of the wall material, makes it possible in turn to obtain solutions in closed form for the displacement and stress of material elements within the wall. The viscoelastic model allows a study of the dynamics of the wall with different ratios of viscosity to elasticity of the wall material, to mimic changes in the properties of the arterial wall caused by disease or aging. It is found that when the wall is highly viscous the displacements and stresses caused by the flow are confined to a thin layer close to the inner boundary of the wall, while as the wall material becomes less viscous and more rigid the displacements and stresses spread deeper into the thickness of the wall to affect most of its elements.

  3. A discrete mesoscopic particle model of the mechanics of a multi-constituent arterial wall.

    Science.gov (United States)

    Witthoft, Alexandra; Yazdani, Alireza; Peng, Zhangli; Bellini, Chiara; Humphrey, Jay D; Karniadakis, George Em

    2016-01-01

    Blood vessels have unique properties that allow them to function together within a complex, self-regulating network. The contractile capacity of the wall combined with complex mechanical properties of the extracellular matrix enables vessels to adapt to changes in haemodynamic loading. Homogenized phenomenological and multi-constituent, structurally motivated continuum models have successfully captured these mechanical properties, but truly describing intricate microstructural details of the arterial wall may require a discrete framework. Such an approach would facilitate modelling interactions between or the separation of layers of the wall and would offer the advantage of seamless integration with discrete models of complex blood flow. We present a discrete particle model of a multi-constituent, nonlinearly elastic, anisotropic arterial wall, which we develop using the dissipative particle dynamics method. Mimicking basic features of the microstructure of the arterial wall, the model comprises an elastin matrix having isotropic nonlinear elastic properties plus anisotropic fibre reinforcement that represents the stiffer collagen fibres of the wall. These collagen fibres are distributed evenly and are oriented in four directions, symmetric to the vessel axis. Experimental results from biaxial mechanical tests of an artery are used for model validation, and a delamination test is simulated to demonstrate the new capabilities of the model. PMID:26790998

  4. Wall Shear Stress Distribution in Patient Specific Coronary Artery Bifurcation

    Directory of Open Access Journals (Sweden)

    Vahab Dehlaghi

    2010-01-01

    Full Text Available Problem statement: Atherogenesis is affected by hemodynamic parameters, such as wall shear stress and wall shear stress spatial gradient. These parameters are largely dependent on the geometry of arterial tree. Arterial bifurcations contain significant flow disturbances. Approach: The effects of branch angle and vessel diameter ratio at the bifurcations on the wall shear stress distribution in the coronary arterial tree based on CT images were studied. CT images were digitally processed to extract geometrical contours representing the coronary vessel walls. The lumen of the coronary arteries of the patients was segmented using the open source software package (VMTK. The resulting lumens of coronary arteries were fed into a commercial mesh generator (GAMBIT, Fluent Inc. to generate a volume that was filled with tetrahedral elements. The FIDAP software (Fluent Corp. was used to carry out the simulation by solving Navier-Stokes equations. The FIELDVIEW software (Version 10.0, Intelligent Light, Lyndhurst, NJ was used for the visualization of flow patterns and the quantification of wall shear stress. Post processing was done with VMTK and MATLAB. A parabolic velocity profile was prescribed at the inlets and outlets, except for 1. Stress free outlet was assigned to the remaining outlet. Results: The results show that for angle lower than 90°, low shear stress regions are observed at the non-flow divider and the apex. For angle larger than 90°, low shear stress regions only at the non-flow divider. By increasing of diameter of side branch ratio, low shear stress regions in the side branch appear at the non-flow divider. Conclusion: It is concluded that not only angle and diameter are important, but also the overall 3D shape of the artery. More research is required to further quantify the effects angle and diameter on shear stress patterns in coronaries.

  5. Impact of exercise training on arterial wall thickness in humans.

    NARCIS (Netherlands)

    Thijssen, D.H.J.; Cable, N.T.; Green, D.J.

    2012-01-01

    Thickening of the carotid artery wall has been adopted as a surrogate marker of pre-clinical atherosclerosis, which is strongly related to increased cardiovascular risk. The cardioprotective effects of exercise training, including direct effects on vascular function and lumen dimension, have been co

  6. A new high-resolution spectral approach to noninvasively evaluate wall deformations in arteries.

    Science.gov (United States)

    Bazan, Ivonne; Negreira, Carlos; Ramos, Antonio; Brum, Javier; Ramirez, Alfredo

    2014-01-01

    By locally measuring changes on arterial wall thickness as a function of pressure, the related Young modulus can be evaluated. This physical magnitude has shown to be an important predictive factor for cardiovascular diseases. For evaluating those changes, imaging segmentation or time correlations of ultrasonic echoes, coming from wall interfaces, are usually employed. In this paper, an alternative low-cost technique is proposed to locally evaluate variations on arterial walls, which are dynamically measured with an improved high-resolution calculation of power spectral densities in echo-traces of the wall interfaces, by using a parametric autoregressive processing. Certain wall deformations are finely detected by evaluating the echoes overtones peaks with power spectral estimations that implement Burg and Yule Walker algorithms. Results of this spectral approach are compared with a classical cross-correlation operator, in a tube phantom and "in vitro" carotid tissue. A circulating loop, mimicking heart periods and blood pressure changes, is employed to dynamically inspect each sample with a broadband ultrasonic probe, acquiring multiple A-Scans which are windowed to isolate echo-traces packets coming from distinct walls. Then the new technique and cross-correlation operator are applied to evaluate changing parietal deformations from the detection of displacements registered on the wall faces under periodic regime. PMID:24688596

  7. A New High-Resolution Spectral Approach to Noninvasively Evaluate Wall Deformations in Arteries

    Directory of Open Access Journals (Sweden)

    Ivonne Bazan

    2014-01-01

    Full Text Available By locally measuring changes on arterial wall thickness as a function of pressure, the related Young modulus can be evaluated. This physical magnitude has shown to be an important predictive factor for cardiovascular diseases. For evaluating those changes, imaging segmentation or time correlations of ultrasonic echoes, coming from wall interfaces, are usually employed. In this paper, an alternative low-cost technique is proposed to locally evaluate variations on arterial walls, which are dynamically measured with an improved high-resolution calculation of power spectral densities in echo-traces of the wall interfaces, by using a parametric autoregressive processing. Certain wall deformations are finely detected by evaluating the echoes overtones peaks with power spectral estimations that implement Burg and Yule Walker algorithms. Results of this spectral approach are compared with a classical cross-correlation operator, in a tube phantom and “in vitro” carotid tissue. A circulating loop, mimicking heart periods and blood pressure changes, is employed to dynamically inspect each sample with a broadband ultrasonic probe, acquiring multiple A-Scans which are windowed to isolate echo-traces packets coming from distinct walls. Then the new technique and cross-correlation operator are applied to evaluate changing parietal deformations from the detection of displacements registered on the wall faces under periodic regime.

  8. Constitutive modelling of an arterial wall supported by microscopic measurements

    Directory of Open Access Journals (Sweden)

    Vychytil J.

    2012-06-01

    Full Text Available An idealized model of an arterial wall is proposed as a two-layer system. Distinct mechanical response of each layer is taken into account considering two types of strain energy functions in the hyperelasticity framework. The outer layer, considered as a fibre-reinforced composite, is modelled using the structural model of Holzapfel. The inner layer, on the other hand, is represented by a two-scale model mimicing smooth muscle tissue. For this model, material parameters such as shape, volume fraction and orientation of smooth muscle cells are determined using the microscopic measurements. The resulting model of an arterial ring is stretched axially and loaded with inner pressure to simulate the mechanical response of a porcine arterial segment during inflation and axial stretching. Good agreement of the model prediction with experimental data is promising for further progress.

  9. Ultrasound settings significantly alter arterial lumen and wall thickness measurements

    OpenAIRE

    Green Daniel J; Reed Christopher J; Potter Kathleen; Hankey Graeme J; Arnolda Leonard F

    2008-01-01

    Abstract Background Flow-mediated dilation (FMD) and carotid intima-medial thickness (CIMT), measured by ultrasound, are widely used to test the efficacy of cardioprotective interventions. Although assessment methods vary, automated edge-detecting image analysis software is routinely used to measure changes in FMD and CIMT. We aimed to quantify the effect that commonly adjusted ultrasound settings have on arterial lumen and wall thickness measurements made with CIMT measurement software. Meth...

  10. Gelsolin amyloid angiopathy causes severe disruption of the arterial wall.

    Science.gov (United States)

    Koskelainen, Susanna; Pihlamaa, Tiia; Suominen, Sinikka; Zhao, Fang; Salo, Tuula; Risteli, Juha; Baumann, Marc; Kalimo, Hannu; Kiuru-Enari, Sari

    2016-08-01

    Hereditary gelsolin amyloidosis (HGA) is a dominantly inherited systemic disease reported worldwide. HGA is characterized by ophthalmological, neurological, and dermatological manifestations. AGel amyloid accumulates at basal lamina of epithelial and muscle cells, thus amyloid angiopathy is encountered in nearly every organ. HGA patients have cardiovascular, hemorrhagic, and potentially vascularly induced neurological problems. To clarify pathomechanisms of AGel angiopathy, we performed histological, immunohistochemical, and electron microscopic analyses on facial temporal artery branches from 8 HGA patients and 13 control subjects. We demonstrate major pathological changes in arteries: disruption of the tunica media, disorganization of vascular smooth muscle cells, and accumulation of AGel fibrils in arterial walls, where they associate with the lamina elastica interna, which becomes fragmented and diminished. We also provide evidence of abnormal accumulation and localization of collagen types I and III and an increase of collagen type I degradation product in the tunica media. Vascular smooth muscle cells appear to be morphologically and semi-quantitatively normal, only their basal lamina is often thickened. In conclusion, angiopathy in HGA results in severe disruption of arterial walls, characterized by prominent AGel deposition, collagen derangement and severe elastolysis, and it may be responsible for several, particularly hemorrhagic, disease manifestations in HGA. PMID:27198069

  11. Wall morphology, blood flow and wall shear stress: MR findings in patients with peripheral artery disease

    Energy Technology Data Exchange (ETDEWEB)

    Galizia, Mauricio S.; Barker, Alex; Collins, Jeremy; Carr, James [Northwestern University, Department of Radiology, Feinberg School of Medicine, Chicago, IL (United States); Liao, Yihua [Northwestern University' s Feinberg School of Medicine, Department of Preventive Medicine, Chicago, IL (United States); McDermott, Mary M. [Northwestern University' s Feinberg School of Medicine, Department of Preventive Medicine, Chicago, IL (United States); Northwestern University' s Feinberg School of Medicine, Department of Medicine, Chicago, IL (United States); Markl, Michael [Northwestern University, Department of Radiology, Feinberg School of Medicine, Chicago, IL (United States); Northwestern University, Department Biomedical Engineering, McCormick School of Engineering, Chicago, IL (United States)

    2014-04-15

    To investigate the influence of atherosclerotic plaques on femoral haemodynamics assessed by two-dimensional (2D) phase-contrast (PC) magnetic resonance imaging (MRI) with three-directional velocity encoding. During 1 year, patients with peripheral artery disease and an ankle brachial index <1.00 were enrolled. After institutional review board approval and written informed consent, 44 patients (age, 70 ± 12 years) underwent common femoral artery MRI. Patients with contra-indications for MRI were excluded. Sequences included 2D time-of-flight, proton-density, T1-weighted and T2-weighted MRI. Electrocardiogram (ECG)-gated 2D PC-MRI with 3D velocity encoding was acquired. A radiologist classified images in five categories. Blood flow, velocity and wall shear stress (WSS) along the vessel circumference were quantified from the PC-MRI data. The acquired images were of good quality for interpretation. There were no image quality problems related to poor ECG-gating or slice positioning. Velocities, oscillatory shear stress and total flow were similar between patients with normal arteries and wall thickening/plaque. Patients with plaques demonstrated regionally increased peak systolic WSS and enhanced WSS eccentricity. Combined multi-contrast morphological imaging of the peripheral arterial wall with PC-MRI with three-directional velocity encoding is a feasible technique. Further study is needed to determine whether flow is an appropriate marker for altered endothelial cell function, vascular remodelling and plaque progression. (orig.)

  12. Shape dynamics of growing cell walls

    CERN Document Server

    Banerjee, Shiladitya; Dinner, Aaron R

    2015-01-01

    We introduce a general theoretical framework to study the shape dynamics of actively growing and remodeling surfaces. Using this framework we develop a physical model for growing bacterial cell walls and study the interplay of cell shape with the dynamics of growth and constriction. The model allows us to derive constraints on cell wall mechanical energy based on the observed dynamics of cell shape. We predict that exponential growth in cell size requires a constant amount of cell wall energy to be dissipated per unit volume. We use the model to understand and contrast growth in bacteria with different shapes such as spherical, ellipsoidal, cylindrical and toroidal morphologies. Coupling growth to cell wall constriction, we predict a discontinuous shape transformation, from partial constriction to cell division, as a function of the chemical potential driving cell-wall synthesis. Our model for cell wall energy and shape dynamics relates growth kinetics with cell geometry, and provides a unified framework to d...

  13. Passive cigarette smoking induces inflammatory injury in human arterial walls

    Institute of Scientific and Technical Information of China (English)

    ZOU Ni; HONG Jiang; DAI Qiu-yan

    2009-01-01

    Background Epidemiological studies have shown that both active and passive cigarette smoking increase the risk of atherosclerosis. But very little is known about the biological processes induced by passive cigarette smoking that contribute to atheresclerosis. We observe the expression of a few of biological and inflammatory markers in human arterial walls in vitro which were treated with the second-hand smoke solution (sidestream whole, SSW), and discuss the possible mechanism of inflammatory injury induced by second-hand smoke.Methods The biological markers (platelet endothelial cell adhesion molecule-1, PECAM-1; α-smooth muscle actin, α-SMA; collagen Ⅳ, Col Ⅳ) and inflammatory markers (vascular cell adhesion molecule-1, VCAM-1; monocyte chemoattractant protein-1, MCP-1; interleukin-8, IL-8) of human aortal wall were tested by immunofluorescence staining. The levels of MCP-1 and IL-8 mRNA expression were detected by reverse transcription-polymerase chain reaction (RT-PCR).Results No distinct difference was observed between SSW and the control group on the expression of biological markers as assessed by the light microscope. But the inflammatory markers VCAM-1, MCP-1 and IL-8 on the subendothelial layer and smooth muscle cell layers, which are near the endothelium of arterial wall, were strongly stained in the SSW group compared with the control group. Their fluorescence intensities in the 1:40 SSW group (VCAM-1: 0.35±0.04, MCP-1: 0.34±0.05, IL-8: 0.37±0.05) and the 1:20 SSW group (VCAM-1: 0.40±0.04, MCP-1: 0.52±0.09, IL-8: 0.51±0.07) were significantly stronger than the control group (VCAM-1: 0.12±0.04, MCP-1: 0.06±0.02, IL-8: 0.24±0.03) by semi-quantitative analysis of immunofluorescence (P <0.001 vs control). MCP-1 mRNA expression in the 1:40 SSW (0.15±0.04) and the 1:20 SSW (0.19±0.06) group was significantly higher than in the control group (0.09±0.03) (P <0.05, P <0.01 vs control); IL-8 mRNA expression in the 1:40 SSW (0.64±0.12) and 1

  14. Relationship of sonographic wall components of the brachial artery to hypertension and coronary atherosclerosis

    OpenAIRE

    Frick, Matthias; Alber, Hannes F; Rinner, Alexander; Suessenbacher, Alois; Ulmer, Hanno; Schwarzacher, Severin P; Pachinger, Otmar; Weidinger, Franz

    2005-01-01

    Abstract The aim of this study was to determine whether sonographically assessed intimal (echodense, ED) or medial (echolucent, EL) thickening of the brachial artery is associated with coronary artery disease (CAD) and/or arterial hypertension (HT). In 201 patients the ED and EL wall components, as well as the total wall thickness of the brachial artery, were measured with high-resolution ultrasound (13 MHz). According to the presence or absence of CAD and HT, the patients were div...

  15. Linear and nonlinear viscoelastic arterial wall models: application on animals

    CERN Document Server

    Ghigo, Arthur; Armentano, Ricardo; Lagrée, Pierre-Yves; Fullana, Jose-Maria

    2016-01-01

    This work deals with the viscoelasticity of the arterial wall and its influence on the pulse waves. We describe the viscoelasticity by a non-linear Kelvin-Voigt model in which the coefficients are fitted using experimental time series of pressure and radius measured on a sheep's arterial network. We obtained a good agreement between the results of the nonlinear Kelvin-Voigt model and the experimental measurements. We found that the viscoelastic relaxation time-defined by the ratio between the viscoelastic coefficient and the Young's modulus-is nearly constant throughout the network. Therefore, as it is well known that smaller arteries are stiffer, the viscoelastic coefficient rises when approaching the peripheral sites to compensate the rise of the Young's modulus, resulting in a higher damping effect. We incorporated the fitted viscoelastic coefficients in a nonlinear 1D fluid model to compute the pulse waves in the network. The damping effect of viscoelasticity on the high frequency waves is clear especiall...

  16. Calculation of arterial wall temperature in atherosclerotic arteries: effect of pulsatile flow, arterial geometry, and plaque structure

    Directory of Open Access Journals (Sweden)

    Kim Taehong

    2007-03-01

    Full Text Available Abstract Background This paper presents calculations of the temperature distribution in an atherosclerotic plaque experiencing an inflammatory process; it analyzes the presence of hot spots in the plaque region and their relationship to blood flow, arterial geometry, and inflammatory cell distribution. Determination of the plaque temperature has become an important topic because plaques showing a temperature inhomogeneity have a higher likelihood of rupture. As a result, monitoring plaque temperature and knowing the factors affecting it can help in the prevention of sudden rupture. Methods The transient temperature profile in inflamed atherosclerotic plaques is calculated by solving an energy equation and the Navier-Stokes equations in 2D idealized arterial models of a bending artery and an arterial bifurcation. For obtaining the numerical solution, the commercial package COMSOL 3.2 was used. The calculations correspond to a parametric study where arterial type and size, as well as plaque geometry and composition, are varied. These calculations are used to analyze the contribution of different factors affecting arterial wall temperature measurements. The main factors considered are the metabolic heat production of inflammatory cells, atherosclerotic plaque length lp, inflammatory cell layer length lmp, and inflammatory cell layer thickness dmp. Results The calculations indicate that the best location to perform the temperature measurement is at the back region of the plaque (0.5 ≤ l/lp ≤ 0.7. The location of the maximum temperature, or hot spot, at the plaque surface can move during the cardiac cycle depending on the arterial geometry and is a direct result of the blood flow pattern. For the bending artery, the hot spot moves 0.6 millimeters along the longitudinal direction; for the arterial bifurcation, the hot spot is concentrated at a single location due to the flow recirculation observed at both ends of the plaque. Focusing on the

  17. A New High-Resolution Spectral Approach to Noninvasively Evaluate Wall Deformations in Arteries

    OpenAIRE

    Ivonne Bazan; Carlos Negreira; Antonio Ramos; Javier Brum; Alfredo Ramirez

    2014-01-01

    By locally measuring changes on arterial wall thickness as a function of pressure, the related Young modulus can be evaluated. This physical magnitude has shown to be an important predictive factor for cardiovascular diseases. For evaluating those changes, imaging segmentation or time correlations of ultrasonic echoes, coming from wall interfaces, are usually employed. In this paper, an alternative low-cost technique is proposed to locally evaluate variations on arterial walls, which are dyna...

  18. Adaptive optics assisted visualization of thickened retinal arterial wall in a patient with controlled malignant hypertension

    Directory of Open Access Journals (Sweden)

    Arichika S

    2014-10-01

    Full Text Available Shigeta Arichika, Akihito Uji, Nagahisa Yoshimura Department of Ophthalmology and Visual Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan Purpose: We aimed to visualize the retinal arterial wall thickness, assisted by noninvasive adaptive optics scanning laser ophthalmoscopy (AO-SLO.Methods: The arterial wall thickness was measured and compared between one normal subject and one patient suffering from malignant hypertensive retinopathy.Results: Increased arterial wall thickness was revealed with a newly developed AO-SLO system, in a retinal artery of 1-papilla diameter temporal inferior to the optic disc. The average wall thickness, with hypertension, was 18.7 µm, and the wall-to-lumen ratio was 0.44, both bigger than normal.Conclusion: AO-SLO enabled us to evaluate the retinal wall thickness in the hypertensive patient. The arterial walls were thickened compared with normal. AO-SLO may facilitate future noninvasive study of arterial walls in human medicine. Keywords: wall thickness, AO-SLO, hypertensive retinopathy

  19. Optimization of Condition of Ultrasonic Beam for Measurement of Small Change in Thickness of Arterial Wall

    Science.gov (United States)

    Watanabe, Masaru; Hasegawa, Hideyuki; Kanai, Hiroshi

    2002-05-01

    We previously developed a method for measuring small changes in thickness of the arterial wall during one cardiac cycle. Knowledge of this change in thickness is useful for in vivo assessment of the regional elasticity of the arterial wall. In this study, from computer simulations, it is found that measurement error depends on the distance of the ultrasonic beam from the center of the artery and it can be reduced by optimally setting the focal position. In basic experiments using a silicone rubber tube and in in vivo experiments with a human carotid artery, it is found that by optimizing the focal position, measurement of the change in thickness becomes more robust against mispositioning of the ultrasonic beam. From these results, it is demonstrated that optimum focal positioning provides more robustness in measurement, even if there is arterial wall motion causing the position of the ultrasonic beam to deviate from the center of the artery.

  20. Dynamic response of flexible retaining walls

    Energy Technology Data Exchange (ETDEWEB)

    Younan, A.H.; Veletsos, A.S.; Bandyopadhyay, K.

    1997-01-01

    Making use of an extension of a recently proposed, relatively simple, approximate method of analysis, a critical evaluation is made of the response to horizontal ground shaking of flexible walls retaining a uniform, linear, viscoelastic stratum of constant thickness and semiinfinite extent in the horizontal direction. Both cantilever and top-supported walls are examined. Following a detailed description of the method and of its rate of convergence, comprehensive numerical solutions are presented that elucidate the action of the system and the effects of the various parameters involved. The parameters varied include the flexibility of the wall, the condition of top support, and the characteristics of the ground motion. The effects of both harmonic base motions and an actual earthquake record are examined. Special attention is paid to the effects of long-period, effectively static excitations. A maximum dynamic response is then expressed as the product of the corresponding static response and an appropriate amplification or deamplification factor. The response quantities examined include the displacements of the wall relative to the moving base, the dynamic wall pressures, and the total wall force, base shear and base moment.

  1. Ultrasonic Estimation of Mechanical Properties of Pulmonary Arterial Wall Under Normoxic and Hypoxic Conditions

    Science.gov (United States)

    Waters, Kendall R.; Mukdadi, Osama M.

    2005-04-01

    Secondary pediatric pulmonary hypertension is a disease that could benefit from improved ultrasonic diagnostic techniques. We perform high-frequency in vitro ultrasound measurements (25 MHz to 100 MHz) on fresh and fixed pulmonary arterial walls excised from normoxic and hypoxic Long-Evans rat models. Estimates of the elastic stiffness coefficients are determined from measurements of the speed of sound. Preliminary results indicate that hypoxia leads to up to increase of 20 % in stiffening of the pulmonary arterial wall.

  2. Assessment of normal and atherosclerotic arterial wall thickness with an intravascular ultrasound imaging catheter.

    OpenAIRE

    Mallery, JA; Tobis, JM; Griffith, J.; Gessert, J; McRae, M; Moussabeck, O; Bessen, M; Moriuchi, M; Henry, WL

    1990-01-01

    A prototype intravascular ultrasound imaging catheter with a 20 MHz transducer was used to obtain 59 cross-sectional images in 14 segments of human atherosclerotic arteries. Three distinct components of the arterial wall were visualized on the ultrasound images: a highly reflective intima, an echolucent media, and a moderately reflective adventitia. Images were obtained at 1 mm increments in vitro and were compared with histologic sections at the same levels. Measurements of the arterial laye...

  3. Triptans induce vasoconstriction of human arteries and veins from the thoracic wall

    DEFF Research Database (Denmark)

    Wackenfors, Angelica; Jarvius, Malin; Ingemansson, Richard;

    2005-01-01

    A common side effect of migraine treatment with triptans is chest symptoms. The origin of these symptoms is not known. The aim of the present study was to examine the vasocontractile effect of triptans in human arteries and veins from the thoracic wall and in coronary artery bypass grafts. In vitro...... detected by real-time PCR in all blood vessels studied. In conclusion, triptans induce vasoconstriction in arteries and veins from the thoracic wall, most likely by activation of 5-HT1B receptors. This response could be observed in only 38% to 57% of the patients, which may provide an explanation for why...

  4. 3D quantitative visualization of altered LV wall thickening dynamics caused by coronary microembolization

    Science.gov (United States)

    Eusemann, Christian D.; Mohlenkamp, Stefan; Ritman, Erik L.; Robb, Richard A.

    2001-05-01

    Regional heart wall dynamics has been shown to be a sensitive indicator of LV wall ischemia. Rates of local LV wall thickening during a cardiac cycle can be measured and illustrated using functional parametric mappings. This display conveys the spatial distribution of dynamic strain in the myocardium and thereby provides a rapid qualitative appreciation of the severity and extent of the ischemic region. 3D reconstructions were obtained in an anesthetized pig from 8 adjacent, shortaxis, slices of the left ventricle imaged with an Electron Beam Computer Tomograph at 11 time points through one complete cardiac cycle. The 3D reconstructions were obtained before and after injection of 100 micrometer microspheres into the Left Anterior Descending (LAD) coronary artery. This injection causes microembolization of LAD artery branches within the heart wall. The image processing involved radially dividing the tomographic images of the myocardium into small subdivisions with color encoding of the local magnitude of regional thickness or regional velocities of LV wall thickening throughout the cardiac cycle. We compared the effectiveness of animation of wall thickness encoded in color versus a static image of computed rate of wall thickness change in color. The location, extent and severity of regional wall akinesis or dyskinesis, as determined from these displays, can then be compared to the region of embolization as indicated by the distribution of altered LV wall perfusion.

  5. Quantification of pulmonary arterial wall distensibility using parameters extracted from volumetric micro-CT images

    Science.gov (United States)

    Johnson, Roger H.; Karau, Kelly L.; Molthen, Robert C.; Dawson, Christopher A.

    1999-09-01

    Stiffening, or loss of distensibility, of arterial vessel walls is among the manifestations of a number of vascular diseases including pulmonary arterial hypertension. We are attempting to quantify the mechanical properties of vessel walls of the pulmonary arterial tree using parameters derived from high-resolution volumetric x-ray CT images of rat lungs. The pulmonary arterial trees of the excised lungs are filled with a contrast agent. The lungs are imaged with arterial pressures spanning the physiological range. Vessel segment diameters are measured from the inlet to the periphery, and distensibilities calculated from diameters as a function of pressure. The method shows promise as an adjunct to other morphometric techniques such as histology and corrosion casting. It possesses the advantages of being nondestructive, characterizing the vascular structures while the lungs are imaged rapidly and in a near-physiological state, and providing the ability to associate mechanical properties with vessel location in the intact tree hierarchy.

  6. MR imaging of the arterial wall in normal volunteers and arteriosclerotic patients

    International Nuclear Information System (INIS)

    MR angiography is based on the signal characteristics of flowing blood, whereas the arterial wall is not delineated. Its visualization requires maximal spatial resolution and reliable compensation for moving spins. Presaturation and rephasing gradients were applied to spin-echo and fast low-angle shot (FLASH) sequences combined with a reduction of the field of view to approximately 10 cm. Three-dimensional FLASH sequences demonstrated spin saturation within the imaging volume without additional radio-frequency pulses and was sensitive to alterations in the arterial wall. CHESS techniques (fat sensitive) suppressed signal from the normal arterial wall. Small fatty or sclerotic deposits in the femoral, popliteal, and carotid walls were detected prior to marked stenosis

  7. Cell-wall dynamics in growing bacteria

    Science.gov (United States)

    Furchtgott, Leon; Wingreen, Ned; Huang, Kerwyn Casey

    2010-03-01

    Bacterial cells come in a large variety of shapes, and cell shape plays an important role in the regulation of many biological functions. Cell shape in bacterial cells is dictated by a cell wall composed of peptidoglycan, a polymer made up of long, stiff glycan strands and flexible peptide crosslinks. Although much is understood about the structural properties of peptidoglycan, little is known about the dynamics of cell wall organization in bacterial cells. In particular, during cell growth, how does the bacterial cell wall continuously expand and reorganize while maintaining cell shape? In order to investigate this question quantitatively, we model the cell wall of the Gram-negative bacterium Escherichia coli using a simple elastic model, in which glycan and peptide subunits are treated as springs with different spring constants and relaxed lengths. We consider the peptidoglycan network as a single-layered network of these springs under tension due to an internal osmotic pressure. Within this model, we simulate possible hypotheses for cell growth as different combinations of addition of new springs and breakage of old springs.

  8. A finite element study of balloon expandable stent for plaque and arterial wall vulnerability assessment

    Science.gov (United States)

    Karimi, Alireza; Navidbakhsh, Mahdi; Razaghi, Reza

    2014-07-01

    The stresses induced within plaque tissues and arterial layers during stent expansion inside an atherosclerotic artery can be exceeded from the yield stresses of those tissues and, consequently, lead to plaque or arterial layer rupture. The distribution and magnitude of the stresses in each component involved in stenting might be clearly different for different plaque types and different arterial layers. In this study, a nonlinear finite element simulation was employed to investigate the effect of plaque composition (calcified, cellular, and hypocellular) on the stresses induced in the arterial layers (intima, media, and adventitia) during implantation of a balloon expandable coronary stent into a stenosed artery. The atherosclerotic artery was assumed to consist of a plaque and normal/healthy arterial tissues on its outer side. The results indicated a significant influence of plaque types on the maximum stresses induced within the plaque wall and arterial layers during stenting but not when computing maximum stress on the stent. The stress on the stiffest calcified plaque wall was in the fracture level (2.38 MPa), whereas cellular and hypocellular plaques remain stable owing to less stress on their walls. Regardless of plaque types, the highest von Mises stresses were observed on the stiffest intima layer, whereas the lowest stresses were seen to be located in less stiff media layer. The computed stresses on the intima layer were found to be high enough to initiate a rupture in this stiff layer. These findings suggest a higher risk of arterial vascular injury for the intima layer, while a lower risk of arterial injury for the media and adventitia layers.

  9. Lateral abdominal wall hematoma as a rare complication after carotid artery stenting: a case report

    Directory of Open Access Journals (Sweden)

    Satomi Jyunichiro

    2009-11-01

    Full Text Available Abstract Abdominal wall hematoma is a rare and life-threatening complication after carotid artery stenting (CAS, but it can occur when activated clotting time is prolonged. We report a right lateral abdominal wall hematoma caused by rupture of the superficial circumflex iliac artery after CAS in a 72-year-old man with severe stenosis of the origin of the right internal carotid artery. We performed CAS for the targeted lesion while activated clotting time exceeded 300 seconds. After 2 hours, he complained of right lateral abdominal pain. Abdominal computed tomography revealed an extensive hematoma in the right lateral abdominal wall. Activated clotting time was 180 seconds at this point. Seven hours later, he developed hypotension and hemoglobin level dropped to 11.3 g/dl. Subsequent computed tomography showed enlargement of the hematoma. Emergent selective angiography of the external iliac artery revealed active bleeding from the right superficial circumflex iliac artery. Transcatheter arterial embolization with Gelfoam and microcoils was performed successfully. With more CAS procedures being performed, it is important for endovascular surgeons and radiologists to consider the possibility of abdominal wall hematoma in this situation.

  10. Basic fibroblast growth factor gene transfection in repair of internal carotid artery aneurysm wall

    Institute of Scientific and Technical Information of China (English)

    Lei Jiao; Ming Jiang; Jinghai Fang; Yinsheng Deng; Zejun Chen; Min Wu

    2012-01-01

    Surgery or interventional therapy has some risks in the treatment of cerebral aneurysm. We established an internal carotid artery aneurysm model by dripping elastase in the crotch of the right internal and external carotid arteries of New Zealand rabbits. Following model induction, lentivirus carrying basic fibroblast growth factor was injected through the ear vein. We found that the longer the action time of the lentivirus, the smaller the aneurysm volume. Moreover, platelet-derived growth factor expression in the aneurysm increased, but smooth muscle 22 alpha and hypertension-related gene 1 mRNA expression decreased. At 1, 2, 3, and 4 weeks following model establishment, following 1 week of injection of lentivirus carrying basic fibroblast growth factor, the later the intervention time, the more severe the blood vessel damage, and the bigger the aneurysm volume, the lower the smooth muscle 22 alpha and hypertension-related gene 1 mRNA expression. Simultaneously, platelet-derived growth factor expression decreased. These data suggest that recombinant lentivirus carrying basic fibroblast growth factor can repair damaged cells in the aneurysmal wall and inhibit aneurysm dynamic growth, and that the effect is dependent on therapeutic duration.

  11. Dynamic damping of domain walls in weak ferromagnets

    International Nuclear Information System (INIS)

    A microscopic theory is developed for the energy dissipation of a moving domain wall of a weak ferromagnetic by interaction between the wall and thermal magnons. Different dynamic regimes are considered - translational wall motion and propagation of flexure waves along the wall. The special roles of small system-energy terms that disturb the soliton character of the domain wall, and of the fact that the wall does not reflect the magnons with which it interacts, are pointed out. A phenomenological equation that describes consistently the domain-wall dynamics and relaxation is proposed on the basis of the microscopic calculations

  12. Artery buckling analysis using a two-layered wall model with collagen dispersion.

    Science.gov (United States)

    Mottahedi, Mohammad; Han, Hai-Chao

    2016-07-01

    Artery buckling has been proposed as a possible cause for artery tortuosity associated with various vascular diseases. Since microstructure of arterial wall changes with aging and diseases, it is essential to establish the relationship between microscopic wall structure and artery buckling behavior. The objective of this study was to developed arterial buckling equations to incorporate the two-layered wall structure with dispersed collagen fiber distribution. Seven porcine carotid arteries were tested for buckling to determine their critical buckling pressures at different axial stretch ratios. The mechanical properties of these intact arteries and their intima-media layer were determined via pressurized inflation test. Collagen alignment was measured from histological sections and modeled by a modified von-Mises distribution. Buckling equations were developed accordingly using microstructure-motivated strain energy function. Our results demonstrated that collagen fibers disperse around two mean orientations symmetrically to the circumferential direction (39.02°±3.04°) in the adventitia layer; while aligning closely in the circumferential direction (2.06°±3.88°) in the media layer. The microstructure based two-layered model with collagen fiber dispersion described the buckling behavior of arteries well with the model predicted critical pressures match well with the experimental measurement. Parametric studies showed that with increasing fiber dispersion parameter, the predicted critical buckling pressure increases. These results validate the microstructure-based model equations for artery buckling and set a base for further studies to predict the stability of arteries due to microstructural changes associated with vascular diseases and aging. PMID:27031686

  13. Dynamic exercise enhances regional cerebral artery mean flow velocity

    DEFF Research Database (Denmark)

    Linkis, P; Jørgensen, L G; Olesen, H L;

    1995-01-01

    Dynamic exercise enhances regional cerebral artery mean flow velocity. J. Appl. Physiol. 78(1): 12-16, 1995.--Anterior (ACA) and middle (MCA) cerebral artery mean flow velocities (Vmean) and pulsatility indexes were determined using transcranial Doppler in 14 subjects during dynamic exercise afte...

  14. Lipogenesis in arterial wall and vascular smooth muscular cells: regulation and abnormalities in insulin-resistance

    Directory of Open Access Journals (Sweden)

    Feugier Patrick

    2009-12-01

    Full Text Available Abstract Background Vascular smooth muscular cells (VSMC express lipogenic genes. Therefore in situ lipogenesis could provide fatty acids for triglycerides synthesis and cholesterol esterification and contribute to lipid accumulation in arterial wall with aging and during atheroma. Methods We investigated expression of lipogenic genes in human and rat arterial walls, its regulation in cultured VSMC and determined if it is modified during insulin-resistance and diabetes, situations with increased risk for atheroma. Results Zucker obese (ZO and diabetic (ZDF rats accumulated more triglycerides in their aortas than their respective control rats, and this triglycerides content increased with age in ZDF and control rats. However the expression in aortas of lipogenic genes, or of genes involved in fatty acids uptake, was not higher in ZDF and ZO rats and did not increase with age. Expression of lipogenesis-related genes was not increased in human arterial wall (carotid endarterectomy of diabetic compared to non-diabetic patients. In vitro, glucose and adipogenic medium (ADM stimulated moderately the expression and activity of lipogenesis in VSMC from control rats. LXR agonists, but not PXR agonist, stimulated also lipogenesis in VSMC but not in arterial wall in vivo. Lipogenic genes expression was lower in VSMC from ZO rats and not stimulated by glucose or ADM. Conclusion Lipogenic genes are expressed in arterial wall and VSMC; this expression is stimulated (VSMC by glucose, ADM and LXR agonists. During insulin-resistance and diabetes, this expression is not increased and resists to the actions of glucose and ADM. It is unlikely that this metabolic pathway contribute to lipid accumulation of arterial wall during insulin-resistance and diabetes and thus to the increased risk of atheroma observed in these situations.

  15. Fluorescent tags to explore cell wall structure and dynamics.

    OpenAIRE

    Martine eGonneau; Herman eHöfte; Samantha eVernhettes

    2012-01-01

    Plant cell walls are highly dynamic and heterogeneic structures, which vary between celltypes, growth stages but also between microdomains within a single cell wall. In this review, we summarize the imaging techniques using fluorescent tags that are currently being used and which should in the coming years revolutionize our understanding of the dynamics of cell wall architecture and the cellular processes involved in synthesis of cell wall components.

  16. Fluorescent tags to explore cell wall structure and dynamics

    OpenAIRE

    Gonneau, Martine; Höfte, Herman; Vernhettes, Samantha

    2012-01-01

    Plant cell walls are highly dynamic and heterogeneous structures, which vary between cell types, growth stages but also between microdomains within a single cell wall. In this review, we summarize the imaging techniques using fluorescent tags that are currently being used and which should in the coming years revolutionize our understanding of the dynamics of cell wall architecture and the cellular processes involved in the synthesis of cell wall components.

  17. Changes in CT angiographic opacification of porcine coronary artery wall with patchy altered flow in vasa vasorum.

    Science.gov (United States)

    Moritz, Regina; Anderson, Jill L; Vercnocke, Andrew J; Wentz, Robert J; Ritman, Erik L

    2013-08-01

    To evaluate the potential of whole-body CT to detect localized areas of decreased or increased vascularity in coronary arterial walls. We used both microsphere embolization of coronary artery vasa vasorum to generate small areas of hypoperfusion and surrounding hyperperfusion of the arterial wall and diet-induced hypercholesterolemia. As a stimulus for localized angiogenesis, such as occurs in early plaque formation in the coronary arterial wall, microspheres were injected selectively into the LAD coronary artery lumens of anesthetized pigs. Fourteen pigs (acute) then had a segment of their LAD harvested during injection of contrast medium and snap-frozen for subsequent cryo-static micro-CT. An additional thirteen pigs (chronic) were allowed to recover, fed a high cholesterol diet and 3 months later were again anesthetized and a segment of the LAD artery harvested and scanned. The spatial distribution of the contrast agent within the arterial wall was measured in contiguous micro-CT images at right angles to the lumen axis with the area of wall in each cross-sectional image being approximately (0.1 mm)(3) in size. In the acute animals there were no localized areas of increased contrast around the hypoperfused embolized perfusion territories in the arterial wall, but in the chronic animals the hypoperfused areas were surrounded by increased contrast. These results suggest that CT might be able to detect localized regions of increased vascularity in the arterial wall as an indicator of early atherosclerotic stimulation of vasa vasorum proliferation. PMID:23443339

  18. PREFACE: Domain wall dynamics in nanostructures Domain wall dynamics in nanostructures

    Science.gov (United States)

    Marrows, C. H.; Meier, G.

    2012-01-01

    Domain structures in magnetic materials are ubiquitous and have been studied for decades. The walls that separate them are topological defects in the magnetic order parameter and have a wide variety of complex forms. In general, their investigation is difficult in bulk materials since only the domain structure on the surface of a specimen is visible. Cutting the sample to reveal the interior causes a rearrangement of the domains into a new form. As with many other areas of magnetism, the study of domain wall physics has been revitalised by the advent of nanotechnology. The ability to fabricate nanoscale structures has permitted the formation of simplified and controlled domain patterns; the development of advanced microscopy methods has permitted them to be imaged and then modelled; subjecting them to ultrashort field and current pulses has permitted their dynamics to be explored. The latest results from all of these advances are described in this special issue. Not only has this led to results of great scientific beauty, but also to concepts of great applicability to future information technologies. In this issue the reader will find the latest results for these domain wall dynamics and the high-speed processes of topological structures such as domain walls and magnetic vortices. These dynamics can be driven by the application of magnetic fields, or by flowing currents through spintronic devices using the novel physics of spin-transfer torque. This complexity has been studied using a wide variety of experimental techniques at the edge of the spatial and temporal resolution currently available, and can be described using sophisticated analytical theory and computational modelling. As a result, the dynamics can be engineered to give rise to finely controlled memory and logic devices with new functionality. Moreover, the field is moving to study not only the conventional transition metal ferromagnets, but also complex heterostructures, novel magnets and even other

  19. An experimental study on the effect of fluorouracil of two preparations on target arterial wall

    International Nuclear Information System (INIS)

    Objective: To probe into the influence of 5-Fu polyphase liposome and 5-Fu solution injection on a target artery. Methods: Fourteen rabbits were divided into the group A of 5-Fu polyphase liposome and group B of 5-Fu injection. Of 7 cases per group, 5 cases had a femoral artery approach and 2 cases via an ear artery. Angiography and pathological examinations under light microscope of the femoral artery were made 7 days after administration via femoral artery and pathological examination under electron microscope of the ear artery 24 hours after administration via ear artery. Results: In group B, the local narrowing was clearly shown in 4 of 5 cases of femoral arteriography. Denudation and fragmentation of hyperplastic endothelial cells, rupture and discontinuity of internal elastic membrane were seen under light microscope in the stenotic vessels. Fragmentation of endothelial cell membrane, vacuolization of cytoplasm and hazy mitochondrial structures were seen under electron microscope. In group A, femoral arteriography was normal, and only mild degree of exfoliation and hyperplasia of endothelium were seen under light microscope. Integrity of endothelial cell membrane, vacuoles in cytoplasm, swollen mitochondria with visible ridge and irregular nucleus were seen under electron microscope. Conclusions: The stimulation and injury to target arterial wall by 5-Fu polyphase liposome was obviously milder than that of 5-Fu solution injection

  20. A NEW UNSTEADY THREE DIMENSIONAL MODEL FOR MACROMOLECULAR TRANSPORT AND WATER FILTRATION ACROSS THE ARTERIAL WALL

    Institute of Scientific and Technical Information of China (English)

    黄浩; 温功碧

    2001-01-01

    A new unsteady three-dimensional convective-diffusive mathematical model for the transportation of macromolecules and water across the arterial wall was proposed . After the formation of leaky junctions due to the mitosis of endothelial cell of the arterial wall, the macromolecular transport happens surrounding the leaky cells. The arterial wall was divided into four layers: the endothelial layer, the subendothelial intima, the internal elastic lamina and the media for the convenience of research. The time-dependent concentration growth,the effect of the shape of endothelial cell and the effect of physiological parameters were analyzed. The analytical solution of velocity field and pressure field of water flow across the arterial wall were obtained; and concentration distribution of three macromolecules ; LDL,HRP and Albumin, were calculated with numerical simulation method. The new theory predicts, the maximum and distribution areas of time dependent concentration with round shape endothelial cell are both larger than that with ellipse-shape endothelial cell. The model also predicts the concentration growth is much alike that of a two-dimensional model and it shows that the concentration reaches its peak at the leaky junction where atherosclerotic formation frequently occurs and falls down rapidly in a limited area beginning from its earlier time growth to the state when macromolecular transfer approaches steadily. These predictions of the new model are in agreement with the experimental observation for the growth and concentration distribution of LDL and Albumin.

  1. Transduction of a Foreign Histocompatibility Gene into the Arterial Wall Induces Vasculitis

    Science.gov (United States)

    Nabel, Elizabeth G.; Plautz, Gregory; Nabel, Gary J.

    1992-06-01

    Autoimmune vasculitis represents a disease characterized by focal inflammation within arteries at multiple sites in the vasculature. Therapeutic interventions in this disease are empirical and often unsuccessful, and the mechanisms of immune injury are not well-defined. The direct transfer of recombinant genes and their expression in the arterial wall provides an opportunity to explore the pathogenesis and treatment of vascular disease. In this report, an animal model for vasculitis has been developed. Inflammation has been elicited by direct gene transfer of a foreign class I major histocompatibility complex gene, HLA-B7, to specific sites in porcine arteries. Transfer and expression of this recombinant gene was confirmed by a polymerase chain reaction and immunohistochemistry, and cytolytic T cells specific for HLA-B7 were detected. These findings demonstrate that expression of a recombinant gene in the vessel wall can induce a focal immune response and suggest that vessel damage induced by cell-mediated immune injury can initiate vasculitis.

  2. Accurate evaluation of viscoelasticity of radial artery wall during flow-mediated dilation in ultrasound measurement

    Science.gov (United States)

    Sakai, Yasumasa; Taki, Hirofumi; Kanai, Hiroshi

    2016-07-01

    In our previous study, the viscoelasticity of the radial artery wall was estimated to diagnose endothelial dysfunction using a high-frequency (22 MHz) ultrasound device. In the present study, we employed a commercial ultrasound device (7.5 MHz) and estimated the viscoelasticity using arterial pressure and diameter, both of which were measured at the same position. In a phantom experiment, the proposed method successfully estimated the elasticity and viscosity of the phantom with errors of 1.8 and 30.3%, respectively. In an in vivo measurement, the transient change in the viscoelasticity was measured for three healthy subjects during flow-mediated dilation (FMD). The proposed method revealed the softening of the arterial wall originating from the FMD reaction within 100 s after avascularization. These results indicate the high performance of the proposed method in evaluating vascular endothelial function just after avascularization, where the function is difficult to be estimated by a conventional FMD measurement.

  3. Regional calcium distribution and ultrasound images of the vessel wall in human carotid arteries

    Science.gov (United States)

    Szikszai, Z.; Kertész, Zs.; Uzonyi, I.; Szíki, G. Á.; Magyar, M. T.; Molnár, S.; Ida, Y.; Csiba, L.

    2005-04-01

    Arterial calcification can take place at two sites in the vessel wall: the intima and the media. Intimal calcification occurs exclusively within atherosclerotic plaques, while medial calcification may develop independently. Extensive calcified plaques in the carotid arteries can be easily detected by B-mode ultrasonic imaging. The calcium content might correlate with the ultrasound reflectance of the vessel wall, and could be a surrogate marker for arteriosclerosis. In this study, segments of human carotid arteries collected at autopsy were examined by ultrasonography in vitro and calcium distributional maps of sections from the same segments were determined by particle induced X-ray emission. Our aim was to make a first step towards investigating the relationship between the calcium distributional maps and the respective ultrasound images.

  4. Optimization of Focal Position of Ultrasonic Beam in Measurement of Small Change in Arterial Wall Thickness

    Science.gov (United States)

    Watanabe, Masaru; Kanai, Hiroshi

    2001-05-01

    We have previously developed a method for measurement of a small change in thickness of the arterial wall during a single cardiac cycle [H. Kanai, M. Sato, Y. Koiwa and N. Chubachi: IEEE Trans. UFFC 43 (1996) 791]. The resultant change in thickness is shown to be useful for the in vivo assessment of the regional elasticity of the arterial wall. Although the accuracy of the measurement of the change in thickness is found to be within 1 μm, it is affected by the interference of ultrasonic pulses. In this study, we simulate the propagation of ultrasonic pulses transmitted and received by a linear probe. In the simulation experiments, the ultrasonic pulses generated by a computer are reflected by a tube, which has a small change in wall thickness of 10 μm. The optimum focal position of the ultrasonic beam is determined by evaluating the root-mean-square (rms) error in the measured change in thickness.

  5. Quantifying [F-18]fluorodeoxyglucose uptake in the arterial wall

    DEFF Research Database (Denmark)

    Blomberg, Björn Alexander; Bashyam, A.; Ramachandran, A.;

    2015-01-01

    -18-FDG was determined in the aortic wall by calculating the blood pool-corrected maximum standardized uptake value (cSUV(MAX)) and cSUV(MEAN). The PVE-corrected SUVMEAN (pvcSUV(MEAN)) was also calculated using F-18-FDG PET/CT and CECT images. Finally, corresponding target-to-background ratios (TBR......) were calculated. Results At 60 min, pvcSUV(MEAN) was on average 3.1 times greater than cSUV(MAX) (P SUV(MEAN) (P SUV(MEAN) was on average 2.6 times greater than cSUV(MAX) (P SUV(MEAN) (P

  6. Plaque components affect wall stress in stented human carotid artery: A numerical study

    Science.gov (United States)

    Fan, Zhen-Min; Liu, Xiao; Du, Cheng-Fei; Sun, An-Qiang; Zhang, Nan; Fan, Zhan-Ming; Fan, Yu-Bo; Deng, Xiao-Yan

    2016-09-01

    Carotid artery stenting presents challenges of in-stent restenosis and late thrombosis, which are caused primarily by alterations in the mechanical environment of the artery after stent implantation. The present study constructed patient-specific carotid arterial bifurcation models with lipid pools and calcified components based on magnetic resonance imaging. We numerically analyzed the effects of multicomponent plaques on the distributions of von Mises stresses (VMSs) in the patient-specific models after stenting. The results showed that when a stent was deployed, the large soft lipid pool in atherosclerotic plaques cushioned the host artery and reduced the stress within the arterial wall; however, this resulted in a sharp increase of VMS in the fibrous cap. When compared with the lipid pool, the presence of the calcified components led to slightly increased stresses on the luminal surface. However, when a calcification was located close to the luminal surface of the host artery and the stenosis, the local VMS was elevated. Overall, compared with calcified components, large lipid pools severely damaged the host artery after stenting. Furthermore, damage due to the calcified component may depend on location.

  7. Fast domain wall dynamics in amorphous and nanocrystalline magnetic microwires

    Energy Technology Data Exchange (ETDEWEB)

    Varga, R., E-mail: rvarga@upjs.sk [Institute of Physics, Faculty of Science, UPJS, Park Angelinum 9, 041 54, Kosice (Slovakia); Klein, P.; Richter, K. [Institute of Physics, Faculty of Science, UPJS, Park Angelinum 9, 041 54, Kosice (Slovakia); Zhukov, A. [Dept. Fisica de Materiales, Fac. Quimica, UPV/EHU, San Sebastian (Spain); Vazquez, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Ines de la Cruz 3, 28049 Cantoblanco, Madrid (Spain)

    2012-10-15

    We have studied the effect of thermal treatment on the domain wall dynamics of FeSiB and FeCoMoB microwires. It was shown that annealing in transversal magnetic field increases the domain wall mobility as well as the domain wall velocity. Annealing under the tensile stress hinders the appearance of the monodomain structure but application of tensile stress leads to the magnetic bistability having the domain wall mobility twice higher that in as-cast state. Further increase of the tensile stress reduces the domain wall mobility but the domain wall velocity increases as a result of the decrease of critical propagation field. Annealing of the FeCoMoB microwire by Joule heating leads to introduction of the circular anisotropy that favors the vortex domain wall. Such treatment increases the domain wall mobility as well as the maximum domain wall velocity.

  8. Serum carotenoids reduce progression of early atherosclerosis in the carotid artery wall among Eastern Finnish men.

    Directory of Open Access Journals (Sweden)

    Jouni Karppi

    Full Text Available BACKGROUND: Several previous epidemiologic studies have shown that high blood levels of carotenoids may be protective against early atherosclerosis, but results have been inconsistent. We assessed the association between atherosclerotic progression, measured by intima-media thickness of the common carotid artery wall, and serum levels of carotenoids. METHODS: We studied the effect of carotenoids on progression of early atherosclerosis in a population-based study. The association between concentrations of serum carotenoids, and intima-media thickness of the common carotid artery wall was explored in 840 middle-aged men (aged 46-65 years from Eastern Finland. Ultrasonography of the common carotid arteries were performed at baseline and 7-year follow-up. Serum levels of carotenoids were analyzed at baseline. Changes in mean and maximum intima media thickness of carotid artery wall were related to baseline serum carotenoid levels in covariance analyses adjusted for covariates. RESULTS: In a covariance analysis with adjustment for age, ultrasound sonographer, maximum intima media thickness, examination year, body mass index, systolic blood pressure, smoking, physical activity, serum LDL cholesterol, family history of coronary heart disease, antihypertensive medication and serum high sensitivity C-reactive protein, 7-year change in maximum intima media thickness was inversely associated with lycopene (p = 0.005, α-carotene (p = 0.002 and β-carotene (p = 0.019, respectively. CONCLUSIONS: The present study shows that high serum concentrations of carotenoids may be protective against early atherosclerosis.

  9. Magnetic domain-wall dynamics in wide permalloy strips

    Science.gov (United States)

    Estévez, Virginia; Laurson, Lasse

    2016-02-01

    Domain walls in soft permalloy strips may exhibit various equilibrium micromagnetic structures depending on the width and thickness of the strip, ranging from the well-known transverse and vortex walls in narrow and thin strips to double and triple vortex walls recently reported in wider strips [V. Estévez and L. Laurson, Phys. Rev. B 91, 054407 (2015), 10.1103/PhysRevB.91.054407]. Here, we analyze the field driven dynamics of such domain walls in permalloy strips of widths from 240 nm up to 6 μ m , using the known equilibrium domain wall structures as initial configurations. Our micromagnetic simulations show that the domain wall dynamics in wide strips is very complex, and depends strongly on the geometry of the system, as well as on the magnitude of the driving field. We discuss in detail the rich variety of the dynamical behaviors found, including dynamic transitions between different domain wall structures, periodic dynamics of a vortex core close to the strip edge, transitions towards simpler domain wall structures of the multi-vortex domain walls controlled by vortex polarity, and the fact that for some combinations of the strip geometry and the driving field the system cannot support a compact domain wall.

  10. Dynamic contrast-enhanced ultrasound and transient arterial occlusion for quantification of arterial perfusion reserve in peripheral arterial disease

    International Nuclear Information System (INIS)

    Objective: To quantify muscular micro-perfusion and arterial perfusion reserve in peripheral arterial disease (PAD) with dynamic contrast-enhanced ultrasound (CEUS) and transient arterial occlusion. Materials and methods: This study had local institutional review board approval and written informed consent was obtained from all subjects. We examined the dominant lower leg of 40 PAD Fontaine stage IIb patients (mean age, 65 years) and 40 healthy volunteers (mean age, 54 years) with CEUS (7 MHz; MI, 0.28) during continuous intravenous infusion of 4.8 mL microbubbles. Transient arterial occlusion at mid-thigh level simulated physical exercise. With time–CEUS–intensity curves obtained from regions of interest within calf muscles, we derived the maximum CEUS signal after occlusion (max) and its time (tmax), slope to maximum (m), vascular response after occlusion (AUCpost), and analysed accuracy, receiver operating characteristic (ROC) curves, and correlations with ankle-brachial index (ABI) and walking distance. Results: All parameters differed in PAD and volunteers (p max was delayed (31.2 ± 13.6 vs. 16.7 ± 8.5 s, p post as optimal parameter combination for diagnosing PAD and therefore impaired arterial perfusion reserve. Conclusions: Dynamic CEUS with transient arterial occlusion quantifies muscular micro-perfusion and arterial perfusion reserve. The technique is accurate to diagnose PAD.

  11. Multiscale, structure-based modeling for the elastic mechanical behavior of arterial walls.

    Science.gov (United States)

    Stylianopoulos, Triantafyllos; Barocas, Victor H

    2007-08-01

    Passive elastic behavior of arterial wall remains difficult to model. Although phenomenological and structural models exist, the question of how the three-dimensional network structure of the collagen in the artery determines its mechanical properties is still open. A model is presented that incorporates a collagen network as well as the noncollagenous material that comprise the artery. The collagen architecture is represented as a network of interconnected fibers, and a neo-Hookean constitutive equation is used to describe the contribution of the noncollagenous matrix. The model is multiscale in that volume-averaging theory is applied to the collagen network, and it is structural in that parameters of the microstructure of the collagen network were considered instead of a macroscopic constitutive law. The computational results provided a good fit to published experimental data for decellularized porcine carotid arteries. The model predicted increased circumferential compliance for increased axial stretch, consistent with previously published reports, and a relatively small sensitivity to open angle. Even at large extensions, the model predicted that the noncollagenous matrix would be in compression, preventing collapse of the collagen network. The incorporation of fiber-fiber interactions led to an accurate model of artery wall behavior with relatively few parameters. The counterintuitive result that the noncollagenous component is in compression during extension and inflation of the tissue suggests that the collagen is important even at small strains, with the noncollagenous components supporting the network, but not resisting the load directly. More accurate representation of the microstructure of the artery wall is needed to explore this issue further. PMID:17655483

  12. Wall-to-lumen ratio of intracranial arteries measured by indocyanine green angiography

    Science.gov (United States)

    Nakagawa, Daichi; Shojima, Masaaki; Yoshino, Masanori; Kin, Taichi; Imai, Hideaki; Nomura, Seiji; Saito, Toki; Nakatomi, Hirofumi; Oyama, Hiroshi; Saito, Nobuhito

    2016-01-01

    Background: The wall-to-lumen ratio (WLR) is an important parameter in vascular medicine because it indicates the character of vascular wall as well as the degree of stenosis. Despite the advances in medical imaging technologies, it is still difficult to measure the thin-walled normal intracranial arteries, and the reports on the WLR of normal intracranial artery are limited. It might be possible to calculate the WLR using the indocyanine green (ICG) angiography, which is used to observe intracranial vessels during microsurgery. Purpose: To evaluate the WLR of normal intracranial arteries using ICG angiography. Materials and Methods: From the three cases in which ICG angiography was recorded with a ruler during microsurgery, 20 measurement points were chosen for the analysis. The ICG was injected intravenously with a dose of 0.2 mg/kg, and the vessels were inspected at high magnification using an operating microscope equipped with near-infrared illumination system. The vessel outer diameter and the luminal diameter were measured using the images before and after the ICG arrival based on the pixel ratio method using a ruler as reference, respectively. The WLR was calculated as 0.5 × (vessel outer diameter − vessel luminal diameter). Results: The WLR (mean ± standard deviation) of normal intracranial arteries was 0.086 ± 0.022. The WLR tended to be high in small arteries. Conclusion: The WLR of normal intracranial arteries calculated using ICG angiography was consistent with the WLR reported in the previous reports based on human autopsy.

  13. The dynamics of pulsatile flow in distensible model arteries.

    Science.gov (United States)

    Liepsch, D W; Zimmer, R

    1995-12-01

    Deposits and blockages are often found in the carotid, coronary, renal and femoral arteries. This paper deals with laser-Doppler velocity measurements in models of bifurcations of the human femoral arteries. Several models were prepared for the studies: a simplified 35 degrees glass model, two elastic-silicone-rubber models with a wall thickness of 1 mm and 2 mm, and true-to-scale rigid and elastic models. These measurements give a clearer picture of how hemodynamics influences the formation of atherosclerotic plaques where there is a hardening of the arterial walls and a loss of elasticity. In addition to the effects of elasticity, the influence of the flow's pulsatility were studied. The measurements were done in steady and pulsatile flow. From the velocity measurements the shear stresses were calculated.

  14. Coronary Artery Calcium, Carotid Artery Wall Thickness and Cardiovascular Disease Outcomes in Adults 70 to 99 Years Old

    OpenAIRE

    Newman, Anne B; Naydeck, Barbara L.; Ives, Diane G.; Boudreau, Robert M.; Sutton-Tyrrell, Kim; O Leary, Daniel H.; Kuller, Lewis H.

    2008-01-01

    Few population studies have evaluated the associations of both coronary artery calcium (CAC) and carotid ultrasound with cardiovascular events, especially in adults > 70 years of age. At the Pittsburgh Field Center of the Cardiovascular Health Study, 559 men and women, mean age 80.2 (SD 4.1) years had CAC score assessed by electron beam computerized tomography scan and common and internal carotid intimal-medial wall thickness (CCA-IMT and ICA-IMT) by carotid ultrasound between 1998−2000 and w...

  15. High-resolution Magnetic Resonance Vessel Wall Imaging for Intracranial Arterial Stenosis

    Institute of Scientific and Technical Information of China (English)

    Xian-Jin Zhu; Wu Wang; Zun-Jing Liu

    2016-01-01

    Objective:To discuss the feasibility and clinical value of high-resolution magnetic resonance vessel wall imaging (HRMR VWI) for intracranial arterial stenosis.Date Sources:We retrieved information from PubMed database up to December 2015,using various search terms including vessel wall imaging (VWI),high-resolution magnetic resonance imaging,intracranial arterial stenosis,black blood,and intracranial atherosclerosis.Study Selection:We reviewed peer-reviewed articles printed in English on imaging technique of VWI and characteristic findings of various intracranial vasculopathies on VWI.We organized this data to explain the value of VWI in clinical application.Results:VWI with black blood technique could provide high-quality images with submillimeter voxel size,and display both the vessel wall and lumen of intracranial artery simultaneously.Various intracranial vasculopathies (atherosclerotic or nonatherosclerotic) had differentiating features including pattern of wall thickening,enhancement,and vessel remodeling on VWI.This technique could be used for determining causes of stenosis,identification of stroke mechanism,risk-stratifying patients,and directing therapeutic management in clinical practice.In addition,a new morphological classification based on VWI could be established for predicting the efficacy of endovascular therapy.Conclusions:This review highlights the value of HRMR VWI for discrimination of different intracranial vasculopathies and directing therapeutic management.

  16. Automated image segmentation and registration of vessel wall MRI for quantitative assessment of carotid artery vessel wall dimensions and plaque composition

    NARCIS (Netherlands)

    Klooster, Ronald van 't

    2014-01-01

    The main goal of this thesis was to develop methods for automated segmentation, registration and classification of the carotid artery vessel wall and plaque components using multi-sequence MR vessel wall images to assess atherosclerosis. First, a general introduction into atherosclerosis and differe

  17. Altered Metabolism of LDL in the Arterial Wall Precedes Atherosclerosis Regression

    DEFF Research Database (Denmark)

    Bartels, Emil D.; Christoffersen, Christina; Lindholm, Marie W.;

    2015-01-01

    Rationale: Plasma cholesterol lowering is beneficial in patients with atherosclerosis. However, it is unknown how it affects entry and degradation of low-density lipoprotein (LDL) particles in the lesioned arterial wall. Objective: We studied the effect of lipid-lowering therapy on LDL permeability...... and degradation of LDL particles in atherosclerotic aortas of mice by measuring the accumulation of iodinated LDL particles in the arterial wall. Methods and Results: Cholesterol-fed, LDL receptor–deficient mice were treated with either an anti-Apob antisense oligonucleotide or a mismatch control antisense...... oligonucleotide once a week for 1 or 4 weeks before injection with preparations of iodinated LDL particles. The anti-Apob antisense oligonucleotide reduced plasma cholesterol by ≈90%. The aortic LDL permeability and degradation rates of newly entered LDL particles were reduced by ≈50% and ≈85% already after 1...

  18. Plant cell wall dynamics and wall-related susceptibility in plant–pathogen interactions

    OpenAIRE

    Bellincampi, Daniela; Cervone, Felice; Lionetti, Vincenzo

    2014-01-01

    The cell wall is a dynamic structure that often determines the outcome of the interactions between plants and pathogens. It is a barrier that pathogens need to breach to colonize the plant tissue. While fungal necrotrophs extensively destroy the integrity of the cell wall through the combined action of degrading enzymes, biotrophic fungi require a more localized and controlled degradation of the cell wall in order to keep the host cells alive and utilize their feeding structures. Also bacteri...

  19. Plant cell wall dynamics and wall-related susceptibility in plant-pathogen interactions

    OpenAIRE

    Daniela eBellincampi; Felice eCervone; Vincenzo eLionetti

    2014-01-01

    The cell wall is a dynamic structure that often determines the outcome of the interactions between plants and pathogens. It is a barrier that pathogens need to breach to colonize the plant tissue. While fungal necrotrophs extensively destroy the integrity of the cell wall through the combined action of degrading enzymes, biotrophic fungi require a more localized and controlled degradation of the cell wall in order to keep the host cells alive and utilize their feeding structures. Also bacteri...

  20. A Crucial Role of Glycoprotein VI for Platelet Recruitment to the Injured Arterial Wall In Vivo

    OpenAIRE

    Massberg, Steffen; Gawaz, Meinrad; Grüner, Sabine; Schulte, Valerie; Konrad, Ildiko; Zohlnhöfer, Dietlind; Heinzmann, Ulrich; Nieswandt, Bernhard

    2003-01-01

    Platelet adhesion and aggregation at sites of vascular injury is crucial for hemostasis but may lead to arterial occlusion in the setting of atherosclerosis and precipitate diseases such as myocardial infarction. A current hypothesis suggests that platelet glycoprotein (GP) Ib interaction with von Willebrand factor recruits flowing platelets to the injured vessel wall, where subendothelial fibrillar collagens support their firm adhesion and activation. However, so far this hypothesis has not ...

  1. Arterial wall stiffness in patients with essential hypertension at young age

    Directory of Open Access Journals (Sweden)

    Kolesnik E.L.

    2014-11-01

    Full Text Available Research objective was investigating arterial wall stiffness in patients with hypertension at young age and assessing the relationship between subclinical target organs damage and ambulatory blood pressure monitoring (ABPM parameters. 30 male patients aged 18-35 years with essential hypertension stage I and II, hypertension 1 and 2nd grade were surveyed. The examination included general clinical methods, echocardiography, ABPM and suprasystolic sfigmography. It was found that the pulse wave velocity (PWVao (r = 0,557 p <0,01, central aortic blood pressure (SBPao (r = 0,492 p <0,01 and augmentation index (AIxao (r = 0,489 p <0.01 significantly increased with the pa¬tients’ age. Abdominal obesity (r = 0,566 p <0,01 and BMI (r = 0,599 p <0,01 impacted on the PWVao acceleration. Increasing of the left ventricular mass index (LVMI is highly associated with SBPao (r = 0,506 p <0,05 and PWVao (r = 0,434 p <0,05. According to ABPM the most significant correlation with arterial wall stiffness parameters demon¬strated diastolic blood pressure (DBP daytime level (AIxao (r = 0,418 p <0,01, with PWVao (r = 0,699 p <0.01 and SBPao (r = 0,695 p <0,01. Thus, age, excessive body weight and obesity should be considered as unfavorable factors that worsen arterial wall stiffness in patients with hypertension at the age before 35 years. Increase of DBP levels especially during the day causes maximum negative impact on the arterial wall stiffness parameters according to ABPM. Increased SBPao and PWVao in patients with hypertension at a young age are associated with increased left ventricular mass index.

  2. Serum Carotenoids Reduce Progression of Early Atherosclerosis in the Carotid Artery Wall among Eastern Finnish Men

    OpenAIRE

    Jouni Karppi; Sudhir Kurl; Kimmo Ronkainen; Jussi Kauhanen; Laukkanen, Jari A.

    2013-01-01

    BACKGROUND: Several previous epidemiologic studies have shown that high blood levels of carotenoids may be protective against early atherosclerosis, but results have been inconsistent. We assessed the association between atherosclerotic progression, measured by intima-media thickness of the common carotid artery wall, and serum levels of carotenoids. METHODS: We studied the effect of carotenoids on progression of early atherosclerosis in a population-based study. The association between conce...

  3. Computerized flow and vessel wall analyses of coronary arteries for detection of non-calcified plaques in coronary CT angiography

    Science.gov (United States)

    Wei, Jun; Zhou, Chuan; Chan, Heang-Ping; Chughtai, Aamer; Agarwal, Prachi; Hadjiiski, Lubomir; Kazerooni, Ella

    2016-03-01

    The buildup of non-calcified plaques (NCP) that are vulnerable to rupture in coronary arteries is a risk for myocardial infarction. We are developing a computer-aided detection (CADe) system to assist radiologists in detecting NCPs in cCTA. A major challenge of NCP detection is the large number of false positives (FPs) caused by the small sized coronary arteries, image noise and artifacts. In this study, our purpose is to design new image features to reduce FPs. A data set of 98 cCTA scans was retrospectively collected from patient files. We first used vessel wall analysis, in which topological features were extracted from vessel wall and fused with a support-vector machine, to identify the NCP candidates from the segmented coronary tree. Computerized flow dynamic (CFD) features that characterize the change in blood flow due to the presence of plaques and a vascular cross-sectional (VCS) feature that quantifies the presence of low attenuation region at the vessel wall were designed for FP reduction. Using a leave-one-out resampling method, a support vector machine classifier was trained to merge the features into a NCP likelihood score using the vessel wall features alone or in combination with the new CDF and VCS features. The performance of the new features in classification of true NCPs and FPs was evaluated by the area under the receiver operating characteristic (ROC) curve (AUC). Without the new CFD and VCS features, the test AUC was 0.84+/-0.01. The AUC was improved to 0.88+/-0.01 with the addition of the new features. The improvement was statistically significant (p differentiation of NCPs from FPs in cCTA.

  4. Age dependent dynamics of intima-media complex thickness in elderly patients with arterial hypertension

    Directory of Open Access Journals (Sweden)

    Sadjaya L.A.

    2011-09-01

    Full Text Available Aim: To estimate the dynamics of intima-media complex in elderly patients with arterial hypertension. Materials: 179 elderly patients with arterial hypertension were involved in the study. Mean intima-media wall thickness (IMT of common carotid arteries in plaque-free sites and prevalence of plaques were evaluated by B-mode ultrasound investigation (Philips Envisor HD, USA. Results: IMT changing was of nonlinear character, remained stable up to 74 years. Mean rate of the following IMT augmentation was 0.157 mm per year. Frequency of atherosclerotic plaque revealing was significantly increased since the 7th decade. Significant correlation between IMT and systolic, diastolic, mean blood pressure levels or medication spectrum was not revealed. Conclusion: Received data proved significant influence of aging upon IMT enlargement

  5. Finite element formulation and analysis for an arterial wall with residual and active stresses.

    Science.gov (United States)

    Kida, Naoki; Adachi, Taiji

    2015-08-01

    In this study, for predicting arterial function and pathogenesis from a mechanical viewpoint, we develop a continuum mechanical model of an arterial wall that embodies residual and active stresses following a traditional anisotropic passive constitutive law. The residual and active stresses are incorporated into finite element methods based on a two-field variational principle described in the Lagrangian form. The linearisation of nonlinear weak-form equations derived from this variational principle is then described for developing an original finite element algorithm. Numerical simulations reveal the following: (i) residual stresses lead to a reduction in stress gradient regardless of the magnitude of external load; (ii) active stresses help homogenise stress distribution under physiological external load, but this homogeneity collapses under pathological external load; (iii) when residual and active stresses act together, the effect of the residual stresses is relatively obscured by that of the active stresses. We conclude that residual stresses have minor but persistent mechanical effects on the arterial wall under both physiological and pathological external loads; active stresses play an important role in the physiological functions and pathogenesis of arteries, and the mechanical effect of residual stresses is dependent on the presence/absence of active stresses.

  6. Changes in pulmonary arterial wall mechanical properties and lumenal architecture with induced vascular remodeling

    Science.gov (United States)

    Molthen, Robert C.; Heinrich, Amy E.; Haworth, Steven T.; Dawson, Christopher A.

    2004-04-01

    To explore and quantify pulmonary arterial remodeling we used various methods including micro-CT, high-resolution 3-dimensional x-ray imaging, to examine the structure and function of intact pulmonary vessels in isolated rat lungs. The rat is commonly used as an animal model for studies of pulmonary hypertension (PH) and the accompanying vascular remodeling, where vascular remodeling has been defined primarily by changes in the vessel wall composition in response to hypertension inducing stimuli such as chronic hypoxic exposure (CHE) or monocrotaline (MCT) injection. Little information has been provided as to how such changes affect the vessel wall mechanical properties or the lumenal architecture of the pulmonary arterial system that actually account for the hemodynamic consequences of the remodeling. In addition, although the link between primary forms of pulmonary hypertension and inherited genetics is well established, the role that genetic coding plays in hemodynamics and vascular remodeling is not. Therefore, we are utilizing Fawn-Hooded (FH), Sprague-Dawley (SD) and Brown Norway (BN)rat strains along with unique imaging methods to parameterize both vessel distensibility and lumenal morphometry using a principal pulmonary arterial pathway analysis based on self-consistency. We have found for the hypoxia model, in addition to decreased body weight, increased hematocrit, increased right ventricular hypertrophy, the distensibility of the pulmonary arteries is shown to decrease significantly in the presence of remodeling.

  7. Relaxed incremental variational approach for the modeling of damage-induced stress hysteresis in arterial walls.

    Science.gov (United States)

    Schmidt, Thomas; Balzani, Daniel

    2016-05-01

    In this paper, a three-dimensional relaxed incremental variational damage model is proposed, which enables the description of complex softening hysteresis as observed in supra-physiologically loaded arterial tissues, and which thereby avoids a loss of convexity of the underlying formulation. The proposed model extends the relaxed formulation of Balzani and Ortiz [2012. Relaxed incremental variational formulation for damage at large strains with application to fiber-reinforced materials and materials with truss-like microstructures. Int. J. Numer. Methods Eng. 92, 551-570], such that the typical stress-hysteresis observed in arterial tissues under cyclic loading can be described. This is mainly achieved by constructing a modified one-dimensional model accounting for cyclic loading in the individual fiber direction and numerically homogenizing the response taking into account a fiber orientation distribution function. A new solution strategy for the identification of the convexified stress potential is proposed based on an evolutionary algorithm which leads to an improved robustness compared to solely Newton-based optimization schemes. In order to enable an efficient adjustment of the new model to experimentally observed softening hysteresis, an adjustment scheme using a surrogate model is proposed. Therewith, the relaxed formulation is adjusted to experimental data in the supra-physiological domain of the media and adventitia of a human carotid artery. The performance of the model is then demonstrated in a finite element example of an overstretched artery. Although here three-dimensional thick-walled atherosclerotic arteries are considered, it is emphasized that the formulation can also directly be applied to thin-walled simulations of arteries using shell elements or other fiber-reinforced biomembranes.

  8. Relaxed incremental variational approach for the modeling of damage-induced stress hysteresis in arterial walls.

    Science.gov (United States)

    Schmidt, Thomas; Balzani, Daniel

    2016-05-01

    In this paper, a three-dimensional relaxed incremental variational damage model is proposed, which enables the description of complex softening hysteresis as observed in supra-physiologically loaded arterial tissues, and which thereby avoids a loss of convexity of the underlying formulation. The proposed model extends the relaxed formulation of Balzani and Ortiz [2012. Relaxed incremental variational formulation for damage at large strains with application to fiber-reinforced materials and materials with truss-like microstructures. Int. J. Numer. Methods Eng. 92, 551-570], such that the typical stress-hysteresis observed in arterial tissues under cyclic loading can be described. This is mainly achieved by constructing a modified one-dimensional model accounting for cyclic loading in the individual fiber direction and numerically homogenizing the response taking into account a fiber orientation distribution function. A new solution strategy for the identification of the convexified stress potential is proposed based on an evolutionary algorithm which leads to an improved robustness compared to solely Newton-based optimization schemes. In order to enable an efficient adjustment of the new model to experimentally observed softening hysteresis, an adjustment scheme using a surrogate model is proposed. Therewith, the relaxed formulation is adjusted to experimental data in the supra-physiological domain of the media and adventitia of a human carotid artery. The performance of the model is then demonstrated in a finite element example of an overstretched artery. Although here three-dimensional thick-walled atherosclerotic arteries are considered, it is emphasized that the formulation can also directly be applied to thin-walled simulations of arteries using shell elements or other fiber-reinforced biomembranes. PMID:26341795

  9. Dynamic stiffness for thin-walled structures by power series

    Institute of Scientific and Technical Information of China (English)

    ZHU Bin; LEUNG A.Y.T.

    2006-01-01

    The dynamic stiffness method is introduced to analyze thin-walled structures including thin-walled straight beams and spatial twisted helix beam. A dynamic stiffness matrix is formed by using frequency dependent shape functions which are exact solutions of the governing differential equations. With the obtained thin-walled beam dynamic stiffness matrices, the thin-walled frame dynamic stiffness matrix can also be formulated by satisfying the required displacements compatibility and forces equilibrium, a method which is similar to the finite element method (FEM). Then the thin-walled structure natural frequencies can be found by equating the determinant of the system dynamic stiffness matrix to zero. By this way, just one element and several elements can exactly predict many modes of a thin-walled beam and a spatial thin-walled frame, respectively. Several cases are studied and the results are compared with the existing solutions of other methods. The natural frequencies and buckling loads of these thin-walled structures are computed.

  10. Pulmonary arterial wall distensibility assessed by intravascular ultrasound in children with congenital heart disease : an indicator for pulmonary vascular disease?

    NARCIS (Netherlands)

    Berger, Rolf M F; Cromme-Dijkhuis, Adri H; Hop, Wim C J; Kruit, Marco N; Hess, John; Berger, Rudolphus

    2002-01-01

    BACKGROUND: Both pulmonary hypertension and pulmonary overflow are associated with functional and structural changes of the pulmonary arterial wall. Current techniques to evaluate the pulmonary vasculature neglect the pulsatile nature of pulmonary flow. STUDY OBJECTIVES: To determine whether the dyn

  11. Nonextensive statistical dynamics applied to wall turbulence

    CERN Document Server

    Ellingsen, Simen Å

    2014-01-01

    We apply a formalism of nonextensive statistical mechanics to experimental wall turbulence data, for the first time to our knowledge. Wind tunnel data for velocity differences a streamwise distance $r$ apart are compared to the prediction from theory as developed by Beck. The simplest theory, in which all free parameters are removed, is found to reproduce statistics for the wall-normal velocity component remarkably well, even for $r$ well beyond the corresponding integral scale, while the corresponding description of the streamwise velocity fluctuations is reasonable at separations below the integral scale. A least-squares 2-parameter fit is performed, and the dependence of the optimum parameter values on wall separation and $r$ is analysed. Both parameters are found to be approximately independent of wall-separation in the logarithmic sub-layer.

  12. Non-Newtonian effects of blood on LDL transport inside the arterial lumen and across multi-layered arterial wall with and without stenosis

    Science.gov (United States)

    Deyranlou, Amin; Niazmand, Hamid; Sadeghi, Mahmood-Reza; Mesri, Yaser

    2016-06-01

    Blood non-Newtonian behavior on low-density lipoproteins (LDL) accumulation is analyzed numerically, while fluid-multilayered arteries are adopted for nonstenotic and 30%-60% symmetrical stenosed models. Present model considers non-Newtonian effects inside the lumen and within arterial layers simultaneously, which has not been examined in previous studies. Navier-Stokes equations are solved along with the mass transport convection-diffusion equations and Darcy’s model for species transport inside the luminal flow and across wall layers, respectively. Carreau model for the luminal flow and the modified Darcy equation for the power-law fluid within arterial layers are employed to model blood rheological characteristics, appropriately. Results indicate that in large arteries with relatively high Reynolds number Newtonian model estimates LDL concentration patterns well enough, however, this model seriously incompetent for regions with low WSS. Moreover, Newtonian model for plasma underestimates LDL concentration especially on luminal surface and across arterial wall. Therefore, applying non-Newtonian model seems essential for reaching to a more accurate estimation of LDL distribution in the artery. Finally, blood flow inside constricted arteries demonstrates that LDL concentration patterns along the stenoses inside the luminal flow and across arterial layers are strongly influenced as compared to the nonstenotic arteries. Additionally, among four stenosis severity grades, 40% stenosis is prone to more LDL accumulation along the post-stenotic regions.

  13. Dynamic load test of Arquin-designed CMU wall.

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, Richard Pearson

    2010-02-01

    The Arquin Corporation has developed a new method of constructing CMU (concrete masonry unit) walls. This new method uses polymer spacers connected to steel wires that serve as reinforcing as well as a means of accurately placing the spacers so that the concrete block can be dry stacked. The hollows of the concrete block are then filled with grout. As part of a New Mexico Small Business Assistance Program (NMSBA), Sandia National Laboratories conducted a series of tests that dynamically loaded wall segments to compare the performance of walls constructed using the Arquin method to a more traditional method of constructing CMU walls. A total of four walls were built, two with traditional methods and two with the Arquin method. Two of the walls, one traditional and one Arquin, had every third cell filled with grout. The remaining two walls, one traditional and one Arquin, had every cell filled with grout. The walls were dynamically loaded with explosive forces. No significant difference was noted between the performance of the walls constructed by the Arquin method when compared to the walls constructed by the traditional method.

  14. Posterior Wall Capture and Femoral Artery Stenosis Following Use of StarClose Closing Device: Diagnosis and Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Stefanczyk, Ludomir [Medical University of Lodz, First Department of Radiology and Diagnostic Imaging (Poland); Elgalal, Marcin T., E-mail: telgalal@yahoo.co.uk [Medical University of Lodz, Second Department of Radiology and Diagnostic Imaging (Poland); Szubert, Wojciech; Grzelak, Piotr [Medical University of Lodz, First Department of Radiology and Diagnostic Imaging (Poland); Szopinski, Piotr [Institute of Haematology and Transfusion Medicine, Department of Vascular Surgery (Poland); Majos, Agata [Medical University of Lodz, Second Department of Radiology and Diagnostic Imaging (Poland)

    2013-10-15

    A case of femoral artery obstruction following application of a StarClose type arterial puncture closing device (APCD) is presented. Ultrasonographic and angiographic imaging of this complication was obtained. The posterior wall of the vessel was accidentally caught in the anchoring element of the nitinol clip. This complication was successfully resolved by endovascular treatment and the implantation of a stent.

  15. Plasma levels of the arterial wall protein fibulin-1 are associated with carotid-femoral pulse wave velocity

    DEFF Research Database (Denmark)

    Laugesen, Esben; Høyem, Pernille; Christiansen, Jens Sandahl;

    2013-01-01

    -associated extracellular matrix protein, fibulin-1, was recently found in higher concentrations in the arterial wall and in plasma in patients with long duration type 2 diabetes. Furthermore, plasma fibulin-1 independently predicted total mortality and was associated with pulse pressure, an indirect measure of arterial...

  16. Time course of arterial remodelling in diameter and wall thickness above and below the lesion after a spinal cord injury

    OpenAIRE

    Dick H J Thijssen; de Groot, Patricia C. E.; van den Bogerd, Arne; Veltmeijer, Matthijs; Cable, N. Timothy; Green, Daniel J.; Hopman, Maria T. E.

    2012-01-01

    Physical inactivity in response to a spinal cord injury (SCI) represents a potent stimulus for conduit artery remodelling. Changes in conduit artery characteristics may be induced by the local effects of denervation (and consequent extreme inactivity below the level of the lesion), and also by systemic adaptations due to whole body inactivity. Therefore, we assessed the time course of carotid (i.e. above lesion) and common femoral artery (i.e. below lesion) lumen diameter and wall thickness a...

  17. Dynamic contrast-enhanced ultrasound and transient arterial occlusion for quantification of arterial perfusion reserve in peripheral arterial disease

    Energy Technology Data Exchange (ETDEWEB)

    Amarteifio, E., E-mail: erick.amarteifio@med.uni-heidelberg.de [University Hospital of Heidelberg, Department of Diagnostic and Interventional Radiology, Heidelberg (Germany); Department of Radiology, German Cancer Research Center, Heidelberg (Germany); Wormsbecher, S. [University Hospital of Heidelberg, Department of Diagnostic and Interventional Radiology, Heidelberg (Germany); Department of Radiology, German Cancer Research Center, Heidelberg (Germany); Krix, M. [University Hospital of Heidelberg, Department of Diagnostic and Interventional Radiology, Heidelberg (Germany); Department of Radiology, German Cancer Research Center, Heidelberg (Germany); Bracco Imaging Germany, Konstanz (Germany); Demirel, S. [University Hospital of Heidelberg, Department of Vascular Surgery, Heidelberg (Germany); Braun, S. [Department of Biostatistics, German Cancer Research Center, Heidelberg (Germany); Delorme, S. [Department of Radiology, German Cancer Research Center, Heidelberg (Germany); Boeckler, D. [University Hospital of Heidelberg, Department of Vascular Surgery, Heidelberg (Germany); Kauczor, H.-U. [University Hospital of Heidelberg, Department of Diagnostic and Interventional Radiology, Heidelberg (Germany); Weber, M.-A. [University Hospital of Heidelberg, Department of Diagnostic and Interventional Radiology, Heidelberg (Germany); Department of Radiology, German Cancer Research Center, Heidelberg (Germany)

    2012-11-15

    Objective: To quantify muscular micro-perfusion and arterial perfusion reserve in peripheral arterial disease (PAD) with dynamic contrast-enhanced ultrasound (CEUS) and transient arterial occlusion. Materials and methods: This study had local institutional review board approval and written informed consent was obtained from all subjects. We examined the dominant lower leg of 40 PAD Fontaine stage IIb patients (mean age, 65 years) and 40 healthy volunteers (mean age, 54 years) with CEUS (7 MHz; MI, 0.28) during continuous intravenous infusion of 4.8 mL microbubbles. Transient arterial occlusion at mid-thigh level simulated physical exercise. With time-CEUS-intensity curves obtained from regions of interest within calf muscles, we derived the maximum CEUS signal after occlusion (max) and its time (t{sub max}), slope to maximum (m), vascular response after occlusion (AUC{sub post}), and analysed accuracy, receiver operating characteristic (ROC) curves, and correlations with ankle-brachial index (ABI) and walking distance. Results: All parameters differed in PAD and volunteers (p < 0.014). In PAD, t{sub max} was delayed (31.2 {+-} 13.6 vs. 16.7 {+-} 8.5 s, p < 0.0001) and negatively correlated with ankle-brachial-index (r = -0.65). m was decreased in PAD (4.3 {+-} 4.6 mL/s vs. 13.1 {+-} 8.4 mL/s, p < 0.0001) and had highest diagnostic accuracy (sensitivity/specificity, 75%/93%) for detection of diminished muscular micro-perfusion in PAD (cut-off value, m < 5{approx}mL/s). Discriminant analysis and ROC curves revealed m, and AUC{sub post} as optimal parameter combination for diagnosing PAD and therefore impaired arterial perfusion reserve. Conclusions: Dynamic CEUS with transient arterial occlusion quantifies muscular micro-perfusion and arterial perfusion reserve. The technique is accurate to diagnose PAD.

  18. Computational fluid dynamics evaluation of incomplete stent apposition in a tapered artery

    Science.gov (United States)

    Poon, Eric; Thondapu, Vikas; Ooi, Andrew; Hayat, Umair; Barlis, Peter; Moore, Stephen

    2015-11-01

    Coronary stents are deployed to prop open blocked arteries and restore normal blood flow, however in-stent restenosis (ISR) and stent thrombosis (ST) remain possibly catastrophic complications. Computational fluid dynamics (CFD) analyses can elucidate the pathological impact of alterations in coronary hemodynamics and correlate wall shear stress (WSS) with atherosclerotic processes. The natural tapering of a coronary artery often leads to proximal incomplete stent apposition (ISA) where stent struts are not in contact with the vessel wall. By employing state-of-the-art computer-aided design (CAD) software, generic open-cell and closed-cell coronary stent designs were virtually deployed in an idealised tapered coronary artery. Pulsatile blood flow (80 mL/min at 75 beats/min) was carried out numerically on these CAD models using a finite volume solver. CFD results reveal significant fluctuations in proximal WSS and large recirculation regions in the setting of proximal ISA, resulting in regions of high wall shear stress gradient (WSSG) that have been previously linked to poor endothelial cell coverage and vascular injury. The clinical significance of these proximal high WSSG regions will be correlated with findings from high-resolution in-vivo imaging. Supported by the Australian Research Council (LP120100233) and Victorian Life Sciences Computation Initiative (VR0210).

  19. A mathematical model for estimating the axial stress of the common carotid artery wall from ultrasound images.

    Science.gov (United States)

    Soleimani, Effat; Mokhtari-Dizaji, Manijhe; Saberi, Hajir; Sharif-Kashani, Shervin

    2016-08-01

    Clarifying the complex interaction between mechanical and biological processes in healthy and diseased conditions requires constitutive models for arterial walls. In this study, a mathematical model for the displacement of the carotid artery wall in the longitudinal direction is defined providing a satisfactory representation of the axial stress applied to the arterial wall. The proposed model was applied to the carotid artery wall motion estimated from ultrasound image sequences of 10 healthy adults, and the axial stress waveform exerted on the artery wall was extracted. Consecutive ultrasonic images (30 frames per second) of the common carotid artery of 10 healthy subjects (age 44 ± 4 year) were recorded and transferred to a personal computer. Longitudinal displacement and acceleration were extracted from ultrasonic image processing using a block-matching algorithm. Furthermore, images were examined using a maximum gradient algorithm and time rate changes of the internal diameter and intima-media thickness were extracted. Finally, axial stress was estimated using an appropriate constitutive equation for thin-walled tubes. Performance of the proposed model was evaluated using goodness of fit between approximated and measured longitudinal displacement statistics. Values of goodness-of-fit statistics indicated high quality of fit for all investigated subjects with the mean adjusted R-square (0.86 ± 0.08) and root mean squared error (0.08 ± 0.04 mm). According to the results of the present study, maximum and minimum axial stresses exerted on the arterial wall are 1.7 ± 0.6 and -1.5 ± 0.5 kPa, respectively. These results reveal the potential of this technique to provide a new method to assess arterial stress from ultrasound images, overcoming the limitations of the finite element and other simulation techniques. PMID:26563198

  20. Magnetic field effects for copper suspended nanofluid venture through a composite stenosed arteries with permeable wall

    Energy Technology Data Exchange (ETDEWEB)

    Akbar, Noreen Sher; Butt, Adil Wahid, E-mail: adil.maths86@gmail.com

    2015-05-01

    In the present paper magnetic field effects for copper nanoparticles for blood flow through composite stenosis in arteries with permeable wall are discussed. The copper nanoparticles for the blood flow with water as base fluid is not explored yet. The equations for the Cu–water nanofluid are developed first time in the literature and simplified using long wavelength and low Reynolds number assumptions. Exact solutions have been evaluated for velocity, pressure gradient, the solid volume fraction of the nanoparticles and temperature profile. The effect of various flow parameters on the flow and heat transfer characteristics is utilized. - Highlights: • It is observed that the velocity profile is symmetric for all the parameters and when we increase slip parameter α then there will be more resistance between blood and arteries, hence the blood flow slows down and velocity profile decreases. • It is seen that the velocity field rises due to high electromagnetic forces and buoyancy forces as compared to viscous forces. • It is also noticed that velocity is high for all the parameters in case of pure water as compare to Cu-water because copper makes arteries more flexible that makes the blood flow speed slow. • When we rise heat absorption parameter β then definitely temperature increases rapidly. • The wall shear stress increases for different values of the slip parameter α and the Darcy number D{sub α} with rapid change in copper as compared to pure water.

  1. Contrast-enhanced magnetic resonance angiography of carotid arterial wall in pigs.

    Science.gov (United States)

    Lin, W; Abendschein, D R; Haacke, E M

    1997-01-01

    This study was designed to investigate the effects of contrast agents on MR images of balloon-injured carotid arteries containing atherosclerotic-like lesions. We have evaluated an intravascular contrast agent, MS-325 (METASYN INC., Cambridge, MA) and an extravascular contrast agent, Optimark, (Mallinckrodt Medical Inc., St. Louis, MO) on MR angiograms obtained 4 weeks after balloon hyperinflation-induced injury of the left common carotid artery in 12 hypercholesterolemic minipigs. High in-plane resolution (.8 x .4 mm2), thin slice (1 mm) time-of-flight gradient echo sequences were used to acquire the MR angiographic images. Vascular lumen definition was compared before and after a single bolus intravenous injection of a contrast agent. Digital subtraction angiograms were obtained from all pigs after MR imaging. High grade stenosis developed in 1 of the 12 pigs and five pigs had complete occlusion of the injured vessel. The remaining pigs exhibited essentially no visible stenoses as assessed either by MR angiography or digital subtraction angiography. The vessel walls of the stenosed and occluded vessels were visible after the injection of either intravascular or extravascular contrast agent. Histologic analyses showed well developed neovascularization in the neointima or occlusive thrombosis. We conclude that the observed contrast-enhanced vessel wall is caused by an increased vascular supply associated with thrombosis and neointimal thickening that leads to an accumulation of contrast agent in the abnormal vessel walls after the injection of the T1-shortening paramagnetic contrast agent. PMID:9039613

  2. Effect of hypertension on low-density lipoprotein transport within a multi-layered arterial wall: modelling consistent with experiments

    CERN Document Server

    Jesionek, Katarzyna; Kostur, Marcin

    2016-01-01

    The influence of hypertension on low-density lipoproteins intake into the arterial wall is an important factor for understanding mechanisms of atherosclerosis. It has been experimentally observed that the increased pressure leads to the higher level of the LDL inside the wall. In this paper we attempt to construct a model of the LDL transport which reproduces quantitatively experimental outcomes. We supplement the well known four-layer arterial wall model to include two pressure induced effects: the compression of the intima tissue and the increase of the fraction of leaky junctions. We demonstrate that such model can reach the very good agreement with experimental data.

  3. Dynamics of a membrane interacting with an active wall.

    Science.gov (United States)

    Yasuda, Kento; Komura, Shigeyuki; Okamoto, Ryuichi

    2016-05-01

    Active motions of a biological membrane can be induced by nonthermal fluctuations that occur in the outer environment of the membrane. We discuss the dynamics of a membrane interacting hydrodynamically with an active wall that exerts random velocities on the ambient fluid. Solving the hydrodynamic equations of a bound membrane, we first derive a dynamic equation for the membrane fluctuation amplitude in the presence of different types of walls. Membrane two-point correlation functions are calculated for three different cases: (i) a static wall, (ii) an active wall, and (iii) an active wall with an intrinsic time scale. We focus on the mean squared displacement (MSD) of a tagged membrane describing the Brownian motion of a membrane segment. For the static wall case, there are two asymptotic regimes of MSD (∼t^{2/3} and ∼t^{1/3}) when the hydrodynamic decay rate changes monotonically. In the case of an active wall, the MSD grows linearly in time (∼t) in the early stage, which is unusual for a membrane segment. This linear-growth region of the MSD is further extended when the active wall has a finite intrinsic time scale. PMID:27300924

  4. CARDIAC TRANSPLANT REJECTION AND NON-INVASIVE COMON CAROTID ARTERY WALL FUNCTIONAL INDICES

    Directory of Open Access Journals (Sweden)

    A. O. Shevchenko

    2015-01-01

    Full Text Available Allograft rejection would entail an increase in certain blood biomarkers and active substances derived from activated inflammatory cells which could influence entire vascular endothelial function and deteriorate arterial wall stiffness. We propose that carotid wall functional indices measured with non-invasive ultrasound could we valuable markers of the subclinical cardiac allograft rejection. Aim. Our goal was to analyze the clinical utility of functional common carotid wall (CCW variables measured with high-resolution Doppler ultrasound as a non-invasive screening tool for allograft rejection in cardiac transplant patients (pts. Methods. One hundred and seventy one pts included 93 cardiac recipients, 30 dilated cardiomyopathy waiting list pts, and 48 stable coronary artery disease (SCAD pts without decompensated heart failure were included. Along with resistive index (Ri, pulsative index (Pi, and CCW intima-media thickness (IMT, CCW rigidity index (iRIG was estimated using empirical equation. Non-invasive evaluation was performed in cardiac transplant recipients prior the endomyo- cardial biopsy. Results. Neither of Ri, Pi, or CCW IMT were different in studied subgroups. iRIG was signifi- cantly lower in SCAD pts when compared to the dilated cardiomyopathy subgroup. The later had similar values with cardiac transplant recipients without rejection. Antibody-mediated and cellular rejection were found in 22 (23.7% and 17 (18.3% cardiac recipients, respectively. Mean iRIG in pts without rejection was significantly lower in comparison to antibody-mediated rejection and cell-mediated (5514.7 ± 2404.0 vs 11856.1 ± 6643.5 and 16071.9 ± 10029.1 cm/sec2, respectively, p = 0.001. Area under ROC for iRIG was 0.90 ± 0.03 units2. Analysis showed that iRIG values above estimated treshold 7172 cm/sec2 suggested relative risk of any type of rejection 17.7 (95%CI = 6.3–49.9 sensitivity 80.5%, specificity – 81.1%, negative predictive value – 84

  5. Joint segmentation of lumen and outer wall from femoral artery MR images: Towards 3D imaging measurements of peripheral arterial disease.

    Science.gov (United States)

    Ukwatta, Eranga; Yuan, Jing; Qiu, Wu; Rajchl, Martin; Chiu, Bernard; Fenster, Aaron

    2015-12-01

    Three-dimensional (3D) measurements of peripheral arterial disease (PAD) plaque burden extracted from fast black-blood magnetic resonance (MR) images have shown to be more predictive of clinical outcomes than PAD stenosis measurements. To this end, accurate segmentation of the femoral artery lumen and outer wall is required for generating volumetric measurements of PAD plaque burden. Here, we propose a semi-automated algorithm to jointly segment the femoral artery lumen and outer wall surfaces from 3D black-blood MR images, which are reoriented and reconstructed along the medial axis of the femoral artery to obtain improved spatial coherence between slices of the long, thin femoral artery and to reduce computation time. The developed segmentation algorithm enforces two priors in a global optimization manner: the spatial consistency between the adjacent 2D slices and the anatomical region order between the femoral artery lumen and outer wall surfaces. The formulated combinatorial optimization problem for segmentation is solved globally and exactly by means of convex relaxation using a coupled continuous max-flow (CCMF) model, which is a dual formulation to the convex relaxed optimization problem. In addition, the CCMF model directly derives an efficient duality-based algorithm based on the modern multiplier augmented optimization scheme, which has been implemented on a GPU for fast computation. The computed segmentations from the developed algorithm were compared to manual delineations from experts using 20 black-blood MR images. The developed algorithm yielded both high accuracy (Dice similarity coefficients ≥ 87% for both the lumen and outer wall surfaces) and high reproducibility (intra-class correlation coefficient of 0.95 for generating vessel wall area), while outperforming the state-of-the-art method in terms of computational time by a factor of ≈ 20. PMID:26387053

  6. Impairment of left ventricular regional wall motion in diabetes mellitus without coronary artery disease

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, Ken`ya; Shimonagata, Tuyoshi; Nanto, Shinsuke; Kuroda, Akio; Morozumi, Takakazu; Kamado, Kenji; Nagata, Seiki [Kansai Rosai Hospital, Amagasaki, Hyogo (Japan); Yamasaki, Yoshimitsu

    1996-09-01

    To elucidate the mechanisms of diabetic cardiomyopathy, dual SPECT imaging with thallium-201 (Tl-201) and I-123 beta-methyl-p-iodophenyl pentadecanoic acid (BMIPP), a branched analogue of free fatty acid (FFA), and dipyridamole-infusion Tl-201 scintigraphy were performed in 28 NIDDM patients without coronary artery disease. Twenty eight patients were divided into two groups based on the presence of wall motion abnormalities on cineangiographic left ventriculography (LVG). Nineteen patients with normal wall motion documented on LVG (group A) out of 28 evaluated patients demonstrated normal Tl-201 and I-123 BMIPP uptake in dual SPECT imaging, whereas 9 patients with reduced wall motion (group B) demonstrated reduced I-123 BMIPP uptake when compared with Tl-201 uptake. On dipyridamole-infusion Tl-201 scintigraphy, transient perfusion defects were demonstrated in 4 patients of group B and two patients of group A (p<0.05). These results suggest that small vessel disease and the impairment of myocardial free fatty acid metabolism are etiologic or contributory factors for regional wall motion abnormality in diabetic cardiomyopathy. (author)

  7. Coronary artery wall imaging in mice using osmium tetroxide and micro-computed tomography (micro-CT)

    Energy Technology Data Exchange (ETDEWEB)

    Pai, Vinay M.; Kozlowski, Megan; Donahue, Danielle; Miller, Elishiah; Xiao, Xianghui; Chen, Marcus Y.; Yu, Zu-Xi; Connelly, Patricia; Jeffries, Kenneth; Wen, Han (NIH)

    2012-05-10

    The high spatial resolution of micro-computed tomography (micro-CT) is ideal for 3D imaging of coronary arteries in intact mouse heart specimens. Previously, micro-CT of mouse heart specimens utilized intravascular contrast agents that hardened within the vessel lumen and allowed a vascular cast to be made. However, for mouse coronary artery disease models, it is highly desirable to image coronary artery walls and highlight plaques. For this purpose, we describe an ex vivo contrast-enhanced micro-CT imaging technique based on tissue staining with osmium tetroxide (OsO{sub 4}) solution. As a tissue-staining contrast agent, OsO{sub 4} is retained in the vessel wall and surrounding tissue during the fixation process and cleared from the vessel lumens. Its high X-ray attenuation makes the artery wall visible in CT. Additionally, since OsO{sub 4} preferentially binds to lipids, it highlights lipid deposition in the artery wall. We performed micro-CT of heart specimens of 5- to 25-week-old C57BL/6 wild-type mice and 5- to 13-week-old apolipoprotein E knockout (apoE{sup -/-}) mice at 10 {mu}m resolution. The results show that walls of coronary arteries as small as 45 {mu}m in diameter are visible using a table-top micro-CT scanner. Similar image clarity was achieved with 1/2000th the scan time using a synchrotron CT scanner. In 13-week-old apoE mice, lipid-rich plaques are visible in the aorta. Our study shows that the combination of OsO{sub 4} and micro-CT permits the visualization of the coronary artery wall in intact mouse hearts.

  8. New phenotypic aspects of the decidual spiral artery wall during early post-implantation mouse pregnancy

    Energy Technology Data Exchange (ETDEWEB)

    Elia, Artemis; Charalambous, Fotini [Department of Biological Sciences, University of Cyprus, University Campus, P.O. Box 20537, 1678 Nicosia (Cyprus); Georgiades, Pantelis, E-mail: pgeor@ucy.ac.cy [Department of Biological Sciences, University of Cyprus, University Campus, P.O. Box 20537, 1678 Nicosia (Cyprus)

    2011-12-09

    Highlights: Black-Right-Pointing-Pointer Spiral artery (SA) wall remodeling (SAR) is ill-defined and clinically important. Black-Right-Pointing-Pointer SA muscular phenotype prior to and during SAR in mice is underexplored. Black-Right-Pointing-Pointer SA muscular wall consists of contractile and non-contractile components. Black-Right-Pointing-Pointer SA wall non-contractile component may be synthetic smooth muscle. Black-Right-Pointing-Pointer Timing and extent of SA wall contractile component loss is revealed. -- Abstract: During pregnancy the walls of decidual spiral arteries (SAs) undergo clinically important structural modifications crucial for embryo survival/growth and maternal health. However, the mechanisms of SA remodeling (SAR) are poorly understood. Although an important prerequisite to this understanding is knowledge about the phenotype of SA muscular wall prior to and during the beginning of mouse SAR, this remains largely unexplored and was the main aim of this work. Using histological and immunohistochemical techniques, this study shows for the first time that during early mouse gestation, from embryonic day 7.5 (E7.5) to E10.5, the decidual SA muscular coat is not a homogeneous structure, but consists of two concentric layers. The first is a largely one cell-thick sub-endothelial layer of contractile mural cells (positive for {alpha}-smooth muscle actin, calponin and SM22{alpha}) with pericyte characteristics (NG2 positive). The second layer is thicker, and evidence is presented that it may be of the synthetic/proliferative smooth muscle phenotype, based on absence ({alpha}-smooth muscle actin and calponin) or weak (SM22{alpha}) expression of contractile mural cell markers, and presence of synthetic smooth muscle characteristics (expression of non-muscle Myosin heavy chain-IIA and of the cell proliferation marker PCNA). Importantly, immunohistochemistry and morphometrics showed that the contractile mural cell layer although prominent at E7.5-E8

  9. Theoretical analysis of metallic nanoparticles on blood flow through stenosed artery with permeable walls

    Energy Technology Data Exchange (ETDEWEB)

    Nadeem, S.; Ijaz, S., E-mail: shaguftaijaz11@yahoo.com

    2015-03-06

    The present analysis deals with the study of physical characteristics of blood flow in the presence of stenosis and nanoparticles through a curved channel with permeable walls. Taking mild stenosis case, the governing equations for anticipated model are solved using the corresponding boundary conditions and close-form solutions have been obtained for temperature, velocity and slip velocity by using Cauchy Euler's method. The expressions for the resistance impedance and pressure gradient in the stenotic region have also been obtained and the existence of various pertinent flow parameters, mainly Darcy number, slip parameter and nanoparticles volume fraction, has been discussed through graphs. - Highlights: • Nanoparticles analysis is discussed for diverging converging and non-tapered arteries. • Resistance impedance decreases with an increase in the nanoparticles volume fraction. • Combination of curvature and stenosis shows stenosis dominant the curvature of artery. • Pressure possesses an inverse variation to the resistance with respect to tapering. • Trapping shows that the symmetry destroys due to increase in curvature of curved artery.

  10. Quantitative Evaluation of Left Ventricular Wall Motion in Patient with Coronary Artery Bypass Grafting Using Magnetic Resonance Tagging Technique

    Science.gov (United States)

    Inaba, Tadashi; Nakano, Takahiro; Tsutsumi, Masakazu; Kawasaki, Shingo; Kinosada, Yasutomi; Tokuda, Masataka

    Left ventricular wall motions during systole were investigated from a mechanical perspective by using a magnetic resonance tagging technique. Subjects were 7 patients with coronary artery bypass grafting (CABG). First, by analyzing strain in the left ventricular wall, cardiac contractility was evaluated in the patients with CABG. Next, by calculating displacement in the myocardial wall, paradoxical movements following CABG were quantitatively evaluated. Strain analysis showed local decreases in circumferential strain in 4 of 7 subjects. The results of displacement analysis clarified that following CABG, the degree of radial displacement was small in the septal wall and large in the lateral wall, and circumferential displacement towards the septal wall occurred in the anterior and posterior walls. Since this behavior was seen in both reduced and normal cardiac contractility groups, paradoxical movements in the present patients were not caused by reduced cardiac contractility, but rather by rigid-body motion of the entire heart.

  11. Portal venous arterialization resulting in increased portal inflow and portal vein wall thickness in rats

    Institute of Scientific and Technical Information of China (English)

    Wen-Gang Li; Yong-Liang Chen; Jing-Xi Chen; Lei Qu; Bin-Dang Xue; Zhi-Hai Peng; Zhi-Qiang Huang

    2008-01-01

    AIM:To explore the influence of portal vein hemodynamic changes after portal venous arterialization(PVA) on peribiliary vascular plexus (PVP)morphological structure and hepatic pathology,and to establish a theoretical basis for the clinical application of PVA.METHODS:Sprague-Dawley rats were randomly divided into control and PVA groups.After PVA,hemodynamic changes of the portal vein and morphological structure of hepatohilar PVP were observed using Doppler ultrasound,liver function tests,ink perfusion transparency management and three-dimensional reconstruction of computer microvisualization,and pathological examination was performed on tissue from the bile duct wall and the liver.RESULTS:After PVA,the cross-sectional area and blood flow of the portal vein were increased,and the increase became more significant over time,in a certain range.If the measure to limit the flow in PVA was not adopted,the high blood flow would lead to dilatation of intrahepatic portal vein and its branches,increase in collagen and fiber degeneration in tunica intima.Except glutamic pyruvic transaminase (GPT),other liver function tests were normal.CONCLUSION:Blood with a certain flow and oxygen content is important for filling the PVP and meeting the oxygen requirement of the bile duct wall.After PVA,It is the anatomic basis to maintain normal morphology of hepatohilar bile duct wall that the blood with high oxygen content and high flow in arterialized portal vein may fill PVP by collateral vessel reflux.A adequate measure to limit blood flow is necessary in PVA.

  12. Reconstruction after Anterior Chest Wall Keloid Resection Using Internal Mammary Artery Perforator Propeller Flaps

    Science.gov (United States)

    Ogawa, Rei; Ono, Shimpei; Akaishi, Satoshi; Dohi, Teruyuki; Iimura, Takeshi; Nakao, Junichi

    2016-01-01

    Background: It is difficult to completely resect huge anterior chest wall keloids and then close the wound directly. We report here our retrospective analysis of our case series of patients with such keloids who underwent reconstruction with internal mammary artery perforator (IMAP) pedicled propeller flaps and then received postoperative high-dose-rate superficial brachytherapy. Methods: All consecutive patients with large/severe keloids on the anterior chest wall who underwent keloid resection followed by reconstruction with IMAP-pedicled propeller flaps and then high-dose-rate superficial brachytherapy in our academic hospital were identified. All cases were followed for >18 months. Donor site position, perforator pedicle, flap size, angle of flap rotation, complications, and recurrence were documented. Results: There were nine men and one woman. The average age was 37.9 years. The average follow-up duration was 28.7 months. The largest flap was 16 × 4 cm. The dominant perforators of the internal mammary artery were located in the sixth (n = 2), seventh (n = 5), eighth (n = 1), and ninth (n = 2) intercostal spaces. Twelve months after surgery, patients reported marked relief from keloid-associated pain and itching, except in two patients who underwent partial keloid resection; their remaining keloids were still troublesome but after conservative therapies, including steroid ointments/plasters, the keloids gradually ameliorated. Eighteen months after surgery, there was no keloid recurrence or new development of keloids on the donor site. Conclusions: IMAP-pedicled propeller flaps transfer skin tension from the anterior chest wall to the abdomen. Our series suggests that this approach combined with radiation therapy can control keloid recurrence.

  13. Fluid-structure interaction analysis on the effect of vessel wall hypertrophy and stiffness on the blood flow in carotid artery bifurcation

    Science.gov (United States)

    Lee, Sang Hoon; Choi, Hyoung Gwon; Yoo, Jung Yul

    2012-11-01

    The effect of artery wall hypertrophy and stiffness on the flow field is investigated using three-dimensional finite element method for simulating the blood flow. To avoid the complexity due to the necessity of additional mechanical constraints, we use the combined formulation which includes both the fluid and structural equations of motion into single coupled variational equation. A P2P1 Galerkin finite element method is used to solve the Navier-Stokes equations for fluid flow and arbitrary Lagrangian-Eulerian formulation is used to achieve mesh movement. The Newmark method is employed for solving the dynamic equilibrium equations for linear elastic solid mechanics. The pulsatile, incompressible flows of Newtonian fluids constrained in the flexible wall are analyzed with Womersley velocity profile at the inlet and constant pressure at the outlet. The study shows that the stiffness of carotid artery wall affects significantly the flow phenomena during the pulse cycle. Similarly, it is found that the flow field is also strongly influenced by wall hypertrophy. This work was supported by Mid-career Researcher Program and Priority Research Centers Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2009-0079936 & 2011-0029613).

  14. Cross-Sectional Elasticity Imaging of Carotid Arterial Wall in Short-Axis Plane by Transcutaneous Ultrasound

    Science.gov (United States)

    Nakagawa, Nozomi; Hasegawa, Hideyuki; Kanai, Hiroshi

    2004-05-01

    We have developed the phased tracking method [H. Kanai, M. Sato, Y. Koiwa and N. Chubachi: IEEE Trans. UFFC 43 (1996) 791.] for measuring the minute change in thickness during one heartbeat and the elasticity of the arterial wall with transcutaneous ultrasound. When this method is applied to a plane perpendicular to the axis of the artery (short-axis plane) using a linear-type probe, only an ultrasonic beam which passes through the center of the artery coincides with the direction of the change in thickness. At other beam positions, the wall motion cannot be accurately tracked because the direction of wall expansion slips off the beam. To obtain the cross-sectional image of elasticity in the short-axis plane using transcutaneous ultrasound, in this paper, the directions of ultrasonic beams are designed so that each beam always passes through the center of the artery; thus, they always coincide with the direction of the wall expansion. In basic experiments, the accuracy in elasticity measurement was evaluated using a silicone rubber tube. In in vivo experiments, the minute change in wall thickness was measured along each ultrasonic beam, and the cross-sectional image of elasticity was obtained in the short-axis plane with transcutaneous ultrasound.

  15. DYNAMIC CRUSHING TESTS OF THIN-WALLED MEMBERS UNDER COMPRESSION

    OpenAIRE

    Maria Kotełko; Sebastian Lipa; Radosław J. Mania

    2009-01-01

    The paper deals with the experimental investigation into crushing collapse behaviour of two types of thin-walled structural members: tubular multi-member element subject to lateral crushing load and top hat-section column under axial compression. Especially designed experimental stand, in which a dynamical crushing load is realized by means of hydraulic system, is presented. Experimental, dynamical load-deformation curves are compared with those obtained from FE simulations and obtained from ...

  16. Prevalence and prognosis of myocardial scar in patients with known or suspected coronary artery disease and normal wall motion

    OpenAIRE

    Boonyasirinant Thananya; Saiviroonporn Pairash; Krittayaphong Rungroj; Udompunturak Suthipol

    2011-01-01

    Abstract Background Some patients may have normal wall motion after myocardial infarction. The aim of this study was to determine the prevalence and prognosis of patients with myocardial scar in the absence of abnormal wall motion. We studied patients with suspected or known coronary artery disease (CAD) who were referred for cardiovascular magnetic resonance (CMR) for the assessment of global and regional cardiac function and late gadolinium enhancement (LGE) and had normal left ventricular ...

  17. Bioresorbable microporous stents deliver recombinant adenovirus gene transfer vectors to the arterial wall.

    Science.gov (United States)

    Ye, Y W; Landau, C; Willard, J E; Rajasubramanian, G; Moskowitz, A; Aziz, S; Meidell, R S; Eberhart, R C

    1998-01-01

    The use of intravascular stents as an adjunct for percutaneous transluminal revascularization is limited by two principal factors, acute thrombosis and neointimal proliferation, resulting in restenosis. To overcome these limitations, we have investigated the potential of microporous bioresorbable polymer stents formed from poly(L-lactic acid) (PLLA)/poly(epsilon-caprolactone) (PCL) blends to function both to provide mechanical support and as reservoirs for local delivery of therapeutic molecules and particles to the vessel wall. Tubular PLLA/PCL stents were fabricated by the flotation-precipitation method, and helical stents were produced by a casting/winding technique. Hybrid structures in which a tubular sheath is deposited on a helical skeleton were also generated. Using a two-stage solvent swelling technique, polyethylene oxide has been incorporated into these stents to improve hydrophilicity and water uptake, and to facilitate the ability of these devices to function as drug carriers. Stents modified in this manner retain axial and radial mechanical strength sufficient to stabilize the vessel wall against elastic recoil caused by vasoconstrictive and mechanical forces. Because of the potential of direct gene transfer into the vessel wall to ameliorate thrombosis and neointimal proliferation, we have investigated the capacity of these polymer stents to function in the delivery of recombinant adenovirus vectors to the vessel wall. In vitro, virus stock was observed to readily absorb into, and elute from these devices in an infectious form, with suitable kinetics. Successful gene transfer and expression has been demonstrated following implantation of polymer stents impregnated with a recombinant adenovirus carrying a nuclear-localizing betaGal reporter gene into rabbit carotid arteries. These studies suggest that surface-modified polymer stents may ultimately be useful adjunctive devices for both mechanical support and gene transfer during percutaneous

  18. NONINVASIVE EVALUATION OF VASCULAR WALL STIFFNESSIN HEALTHY ADOLESCENTS, THE RISK FACTORS FOR ARTERIAL HYPERTENSION

    Directory of Open Access Journals (Sweden)

    G. P. Filippov

    2015-01-01

    Full Text Available Objective. To evaluate the main indicators characterizing the rigidity of the vascular wall in healthy ado-lescents with such risk factors (RF for arterial hypertension (AH as a family history on hypertension and smoking. Identify changes in the initial elastic-elastic properties of the arteries at the preclinical stage of development of hypertension.Material and methods. It was formed two groups of comparison. Age studied from 13 to 17 years (mean age (15.00 ± 0.31 years. The first group consisted of 30 healthy adolescents whose parents suffer from hypertension from a young age. The second group consisted of 30 healthy smokers teenager from healthy parents. The control group consisted of 30 healthy adolescents from healthy parents. Determines the basic stiffness of the vascular wall: PWV, CAVI, SAI.Results. A significant in crease in the indicators characterizing the rigidity of the vascular wall in the two comparison groups relative to the control. PWV: 6,89 ± 0,56 (first group, 7.13 ± 0.55 (second group and 5.5 ± 0.41 (control, p < 0.05.L-CAVI: 5,46 ± 0,39 (first group, 5.84 ± 0.61 (second group and 4.32 ± 0.41 (control, p < 0.05.R-CAVI: 5,63 ± 0,39 (first group, 5.89 ± 0.56 (second group and 4.49 ± 0.41(control, p < 0.05. R-AI: 0,89 ± 0,09 (first group, 0.95 ± 0.12 (second group and 0.62 ± 0.1 (control, p < 0.05.Smoking teenagers and adolescents with family history of hypertension, there are changes in the initial stiffness of the vessel wall, which requires the allocation of at-riskfor the development of hypertension and prevention activities at the preclinical stage of development ofthe disease.

  19. Cross-Sectional Elasticity Imaging of Arterial Wall by Comparing Measured Change in Thickness with Model Waveform

    Science.gov (United States)

    Tang, Jiang; Hasegawa, Hideyuki; Kanai, Hiroshi

    2005-06-01

    For the assessment of the elasticity of the arterial wall, we have developed the phased tracking method [H. Kanai et al.: IEEE Trans. Ultrason. Ferroelectr. Freq. Control 43 (1996) 791] for measuring the minute change in thickness due to heartbeats and the elasticity of the arterial wall with transcutaneous ultrasound. For various reasons, for example, an extremely small deformation of the wall, the minute change in wall thickness during one heartbeat is largely influenced by noise in these cases and the reliability of the elasticity distribution obtained from the maximum change in thickness deteriorates because the maximum value estimation is largely influenced by noise. To obtain a more reliable cross-sectional image of the elasticity of the arterial wall, in this paper, a matching method is proposed to evaluate the waveform of the measured change in wall thickness by comparing the measured waveform with a template waveform. The maximum deformation, which is used in the calculation of elasticity, was determined from the amplitude of the matched model waveform to reduce the influence of noise. The matched model waveform was obtained by minimizing the difference between the measured and template waveforms. Furthermore, a random error, which was obtained from the reproducibility among the heartbeats of the measured waveform, was considered useful for the evaluation of the reliability of the measured waveform.

  20. Domain wall dynamics in expanding spaces.

    Science.gov (United States)

    Cao, Francisco J; Zamora-Sillero, Elías; Quintero, Niurka R

    2006-05-01

    We study the effects on the dynamics of kinks due to expansions and contractions of the space. We show that the propagation velocity of the kink can be adiabatically tuned through slow expansions and/or contractions, while its width is given as a function of the velocity. We also analyze the case of fast expansions and/or contractions, where we are no longer on the adiabatic regime. In this case the kink moves more slowly after an expansion-contraction cycle as a consequence of the loss of energy through radiation. All these effects are numerically studied in the nonlinear Klein-Gordon equations (both for the sine-Gordon and for the potential), and they are also studied within the framework of the collective coordinate evolution equations for the width and the center of mass of the kink. These collective coordinate evolution equations are obtained with a procedure that allows us to consider even the case of large expansions and/or contractions.

  1. Model of bound interface dynamics for coupled magnetic domain walls

    Science.gov (United States)

    Politi, P.; Metaxas, P. J.; Jamet, J.-P.; Stamps, R. L.; Ferré, J.

    2011-08-01

    A domain wall in a ferromagnetic system will move under the action of an external magnetic field. Ultrathin Co layers sandwiched between Pt have been shown to be a suitable experimental realization of a weakly disordered 2D medium in which to study the dynamics of 1D interfaces (magnetic domain walls). The behavior of these systems is encapsulated in the velocity-field response v(H) of the domain walls. In a recent paper [P. J. Metaxas , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.237206 104, 237206 (2010)] we studied the effect of ferromagnetic coupling between two such ultrathin layers, each exhibiting different v(H) characteristics. The main result was the existence of bound states over finite-width field ranges, wherein walls in the two layers moved together at the same speed. Here we discuss in detail the theory of domain wall dynamics in coupled systems. In particular, we show that a bound creep state is expected for vanishing H and we give the analytical, parameter free expression for its velocity which agrees well with experimental results.

  2. An algorithmic scheme for the automated calculation of fiber orientations in arterial walls

    Science.gov (United States)

    Fausten, Simon; Balzani, Daniel; Schröder, Jörg

    2016-08-01

    We propose an algorithmic scheme for the numerical calculation of fiber orientations in arterial walls. The basic assumption behind the procedure is that the fiber orientations are mainly governed by the principal tensile stress directions resulting in an improved load transfer within the artery as a consequence of the redistribution of stresses. This reflects the biological motivation that soft tissues continuously adapt to their mechanical environment in order to optimize their load-bearing capacities. The algorithmic scheme proposed here enhances efficiency of the general procedure given in Hariton et al. (Biomech Model Mechanobiol 6(3):163-175, 2007), which consists of repeatedly identifying a favored fiber orientation based on the principal tensile stresses under a certain loading scenario, and then re-calculating the stresses for that loading scenario with the modified favored fiber orientation. Since the method still depends on a highly accurate stress approximation of the finite element formulation, which is not straightforward to obtain in particular for incompressible and highly anisotropic materials, furthermore, a modified model is introduced. This model defines the favored fiber orientation not only in terms of the local principal stresses, but in terms of the volume averages of the principal stresses computed over individual finite elements. Thereby, the influence of imperfect stress approximations can be weakened leading to a stabilized convergence of the reorientation procedure and a more reasonable fiber orientation with less numerical noise. The performance of the proposed fiber reorientation scheme is investigated with respect to different finite element formulations and different favored fiber orientation models, Hariton et al. (Biomech Model Mechanobiol 6(3):163-175, 2007) and Cyron and Humphrey (Math Mech Solids 1-17, 2014). In addition, it is applied to calculate the fiber orientation in a patient-specific arterial geometry.

  3. Data density curves of B-mode ultrasound arterial wall thickness measurements in unaffected control and at-risk populations

    NARCIS (Netherlands)

    de Groot, E; Hovingh, GK; Zwinderman, AH; Wiegman, A; Smit, AJ; Kastelein, JJP

    2005-01-01

    Aim. Atherosclerosis is a slow disease process of arterial walls with onset decades prior to its clinical manifestations. Lifelong follow-up data may help to identify and understand the pathophysiology of this process. These longitudinal data are scarce. Using a standardized imaging and image analys

  4. A Computational Model to Assess Poststenting Wall Stresses Dependence on Plaque Structure and Stenosis Severity in Coronary Artery

    Directory of Open Access Journals (Sweden)

    Zuned Hajiali

    2014-01-01

    Full Text Available The current study presents computational models to investigate the poststenting hemodynamic stresses and internal stresses over/within the diseased walls of coronary arteries which are in different states of atherosclerotic plaque. The finite element method is applied to build the axisymmetric models which include the plaque, arterial wall, and stent struts. The study takes into account the mechanical effects of the opening pressure and its association with the plaque severity and the morphology. The wall shear stresses and the von Mises stresses within the stented coronary arteries show their strong dependence on the plaque structure, particularly the fibrous cap thickness. Higher stresses occur in severely stenosed coronaries with a thinner fibrous cap. Large stress concentrations around the stent struts cause injury or damage to the vessel wall which is linked to the mechanism of restenosis. The in-stent restenosis rate is also highly dependent on the opening pressure, to the extent that stenosed artery is expanded, and geometry of the stent struts. The present study demonstrates, for the first time, that the restenosis is to be viewed as a consequence of biomechanical design of a stent repeating unit, the opening pressure, and the severity and morphology of the plaque.

  5. A possible formation mechanism of double-walled and multi-walled carbon nanotube: a molecular dynamics study

    Science.gov (United States)

    Han, Dianrong; Luo, Chenglin; Dai, Yafei; Zhu, Xingfeng

    2016-09-01

    Molecular dynamics simulations based on an empirical potential were performed to study the interaction of graphene nanoribbons and the single-walled carbon nanotubes. The results indicated that a piece of graphene nanoribbon can form a tube structure inside or outside single-walled carbon nanotubes spontaneously under certain condition. Based on this kind of spontaneous phenomenon, we proposed a new possible formation mechanism of double walled carbon nanotube and multi-walled carbon nanotube, and suggested the possibility of controlling the structure of double-walled carbon nanotube and/or multi-walled carbon nanotube.

  6. Numerical study of wall shear stress-based descriptors in the human left coronary artery.

    Science.gov (United States)

    Pinto, S I S; Campos, J B L M

    2016-10-01

    The present work is about the application of wall shear stress descriptors - time averaged wall shear stress (TAWSS), oscillating shear index (OSI) and relative residence time (RRT) - to the study of blood flow in the left coronary artery (LCA). These descriptors aid the prediction of disturbed flow conditions in the vessels and play a significant role in the detection of potential zones of atherosclerosis development. Hemodynamic descriptors data were obtained, numerically, through ANSYS® software, for the LCA of a patient-specific geometry and for a 3D idealized model. Comparing both cases, the results are coherent, in terms of location and magnitude. Low TAWSS, high OSI and high RRT values are observed in the bifurcation - potential zone of atherosclerosis appearance. The dissimilarities observed in the TAWSS values, considering blood as a Newtonian or non-Newtonian fluid, releases the importance of the correct blood rheologic caracterization. Moreover, for a higher Reynolds number, the TAWSS values decrease in the bifurcation and along the LAD branch, increasing the probability of plaques deposition. Furthermore, for a stenotic LCA model, very low TAWSS and high RRT values in front and behind the stenosis are observed, indicating the probable extension, in the flow direction, of the lesion. PMID:26883291

  7. A statistical state dynamics approach to wall-turbulence

    CERN Document Server

    Farrell, Brian F; Ioannou, Petros J

    2016-01-01

    This paper reviews results demonstrating the benefits of studying wall-bounded shear flows using dynamics for the evolution of the statistical state of the turbulent system. The statistical state dynamics (SSD) approach used in this work employs a second order closure which isolates the interaction between the streamwise mean and the equivalent of the perturbation covariance. This closure restricts nonlinearity in the SSD to that explicitly retained in the streamwise constant mean together with nonlinear interactions between the mean and the perturbation covariance. This dynamical restriction, in which explicit perturbation-perturbation nonlinearity is removed from the perturbation equation, results in a simplified dynamics referred to as the restricted nonlinear (RNL) dynamics. RNL systems in which an ensemble of a finite number of realizations of the perturbation equation share the same mean flow provide tractable approximations to the equivalently infinite ensemble RNL system. The infinite ensemble system,...

  8. Measurement of Elastic Moduli of the Arterial Wall at Multiple Frequencies by Remote Actuation for Assessment of Viscoelasticity

    Science.gov (United States)

    Hasegawa, Hideyuki; Kanai, Hiroshi

    2004-05-01

    To characterize tissues in atherosclerotic plaques, we have developed a method, the phased tracking method, for measuring the strain (change in wall thickness) and elasticity of the arterial wall. However, some types of tissue, such as lipids and blood clots, cannot be discriminated from each other based only on elasticity due to the small difference in their elasticity. For more precise tissue characterization, we have measured the regional viscoelasticity. To obtain the viscoelasticity, in this study, elastic moduli at multiple frequencies were measured with ultrasound by generating the change in internal pressure due to remote cyclic actuation. Furthermore, the viscoelasticity of the arterial wall was estimated from the measured elastic moduli at multiple actuation frequencies.

  9. Mathematical modeling of coupled drug and drug-encapsulated nanoparticle transport in patient-specific coronary artery walls

    KAUST Repository

    Hossain, Shaolie S.

    2011-08-20

    The majority of heart attacks occur when there is a sudden rupture of atherosclerotic plaque, exposing prothrombotic emboli to coronary blood flow, forming clots that can cause blockages of the arterial lumen. Diseased arteries can be treated with drugs delivered locally to vulnerable plaques. The objective of this work was to develop a computational tool-set to support the design and analysis of a catheter-based nanoparticulate drug delivery system to treat vulnerable plaques and diffuse atherosclerosis. A threedimensional mathematical model of coupled mass transport of drug and drug-encapsulated nanoparticles was developed and solved numerically utilizing isogeometric finite element analysis. Simulations were run on a patient-specific multilayered coronary artery wall segment with a vulnerable plaque and the effect of artery and plaque inhomogeneity was analyzed. The method captured trends observed in local drug delivery and demonstrated potential for optimizing drug design parameters, including delivery location, nanoparticle surface properties, and drug release rate. © Springer-Verlag 2011.

  10. Mathematical modeling of coupled drug and drug-encapsulated nanoparticle transport in patient-specific coronary artery walls

    Science.gov (United States)

    Hossain, Shaolie S.; Hossainy, Syed F. A.; Bazilevs, Yuri; Calo, Victor M.; Hughes, Thomas J. R.

    2012-02-01

    The majority of heart attacks occur when there is a sudden rupture of atherosclerotic plaque, exposing prothrombotic emboli to coronary blood flow, forming clots that can cause blockages of the arterial lumen. Diseased arteries can be treated with drugs delivered locally to vulnerable plaques. The objective of this work was to develop a computational tool-set to support the design and analysis of a catheter-based nanoparticulate drug delivery system to treat vulnerable plaques and diffuse atherosclerosis. A three-dimensional mathematical model of coupled mass transport of drug and drug-encapsulated nanoparticles was developed and solved numerically utilizing isogeometric finite element analysis. Simulations were run on a patient-specific multilayered coronary artery wall segment with a vulnerable plaque and the effect of artery and plaque inhomogeneity was analyzed. The method captured trends observed in local drug delivery and demonstrated potential for optimizing drug design parameters, including delivery location, nanoparticle surface properties, and drug release rate.

  11. Framed BPS States, Moduli Dynamics, and Wall-Crossing

    CERN Document Server

    Lee, Sungjay

    2011-01-01

    We formulate supersymmetric low energy dynamics for BPS dyons in strongly-coupled N=2 Seiberg-Witten theories, and derive wall-crossing formulae thereof. For BPS states made up of a heavy core state and n probe (halo) dyons around it, we derive a reliable supersymmetric moduli dynamics with 3n bosonic coordinates and 4n fermionic superpartners. Attractive interactions are captured via a set of supersymmetric potential terms, whose detail depends only on the charges and the special Kaehler data of the underlying N=2 theories. The small parameters that control the approximation are not electric couplings but the mass ratio between the core and the probe, as well as the distance to the marginal stability wall where the central charges of the probe and of the core align. Quantizing the dynamics, we construct BPS bound states and derive the primitive and the semi-primitive wall-crossing formulae from the first principle. We speculate on applications to line operators and Darboux coordinates, and also about extensi...

  12. Framed BPS states, moduli dynamics, and wall-crossing

    Science.gov (United States)

    Lee, Sungjay; Yi, Piljin

    2011-04-01

    We formulate supersymmetric low energy dynamics for BPS dyons in strongly-coupled N = 2 Seiberg-Witten theories, and derive wall-crossing formulae thereof. For BPS states made up of a heavy core state and n probe (halo) dyons around it, we derive a reliable supersymmetric moduli dynamics with 3 n bosonic coordinates and 4 n fermionic superpartners. Attractive interactions are captured via a set of supersymmetric potential terms, whose detail depends only on the charges and the special Kähler data of the underlying N = 2 theories. The small parameters that control the approximation are not electric couplings but the mass ratio between the core and the probe, as well as the distance to the marginal stability wall where the central charges of the probe and of the core align. Quantizing the dynamics, we construct BPS bound states and derive the primitive and the semi-primitive wall-crossing formulae from the first principle. We speculate on applications to line operators and Darboux coordinates, and also about extension to supergravity setting.

  13. Automated registration of multispectral MR vessel wall images of the carotid artery

    Energy Technology Data Exchange (ETDEWEB)

    Klooster, R. van ' t; Staring, M.; Reiber, J. H. C.; Lelieveldt, B. P. F.; Geest, R. J. van der, E-mail: rvdgeest@lumc.nl [Department of Radiology, Division of Image Processing, Leiden University Medical Center, 2300 RC Leiden (Netherlands); Klein, S. [Department of Radiology and Department of Medical Informatics, Biomedical Imaging Group Rotterdam, Erasmus MC, Rotterdam 3015 GE (Netherlands); Kwee, R. M.; Kooi, M. E. [Department of Radiology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Center, Maastricht 6202 AZ (Netherlands)

    2013-12-15

    Purpose: Atherosclerosis is the primary cause of heart disease and stroke. The detailed assessment of atherosclerosis of the carotid artery requires high resolution imaging of the vessel wall using multiple MR sequences with different contrast weightings. These images allow manual or automated classification of plaque components inside the vessel wall. Automated classification requires all sequences to be in alignment, which is hampered by patient motion. In clinical practice, correction of this motion is performed manually. Previous studies applied automated image registration to correct for motion using only nondeformable transformation models and did not perform a detailed quantitative validation. The purpose of this study is to develop an automated accurate 3D registration method, and to extensively validate this method on a large set of patient data. In addition, the authors quantified patient motion during scanning to investigate the need for correction. Methods: MR imaging studies (1.5T, dedicated carotid surface coil, Philips) from 55 TIA/stroke patients with ipsilateral <70% carotid artery stenosis were randomly selected from a larger cohort. Five MR pulse sequences were acquired around the carotid bifurcation, each containing nine transverse slices: T1-weighted turbo field echo, time of flight, T2-weighted turbo spin-echo, and pre- and postcontrast T1-weighted turbo spin-echo images (T1W TSE). The images were manually segmented by delineating the lumen contour in each vessel wall sequence and were manually aligned by applying throughplane and inplane translations to the images. To find the optimal automatic image registration method, different masks, choice of the fixed image, different types of the mutual information image similarity metric, and transformation models including 3D deformable transformation models, were evaluated. Evaluation of the automatic registration results was performed by comparing the lumen segmentations of the fixed image and

  14. Structural alterations of the coronary arterial wall are associated with myocardial flow heterogeneity in type 2 diabetes mellitus

    Energy Technology Data Exchange (ETDEWEB)

    Schindler, Thomas H. [California Univ., Los Angeles, CA (United States). Dept. of Moelecular and Medical Pharmacology, Radiological Science]|[University Hospital of Geneva, Department of Internal Medicine, Cardiovascular Center, Nuclear Cardiology, Geneva (Switzerland); Facta, Alvaro D.; Prior, John O.; Cadenas, Jerson; Zhang, Xiao-Li; Sayre, James; Goldin, Jonathan; Schelbert, Heinrich R. [California Univ., Los Angeles, CA (United States). Dept. of Moelecular and Medical Pharmacology, Radiological Science; Li, Yanjie [University of Southern California, Atherosclerosis Research Unit, Keck School of Medicine, Los Angeles, CA (United States)

    2009-02-15

    To determine the relationship between carotid intima-media thickness (IMT), coronary artery calcification (CAC), and myocardial blood flow (MBF) at rest and during vasomotor stress in type 2 diabetes mellitus (DM). In 68 individuals, carotid IMT was measured using high-resolution vascular ultrasound, while the presence of CAC was determined with electron beam tomography (EBT). Global and regional MBF was determined in milliliters per gram per minute with {sup 13}N-ammonia and positron emission tomography (PET) at rest, during cold pressor testing (CPT), and during adenosine (ADO) stimulation. There was neither a relationship between carotid IMT and CAC (r = 0.10, p = 0.32) nor between carotid IMT and coronary circulatory function in response to CPT and during ADO (r = -0.18, p = 0.25 and r = 0.10, p = 0.54, respectively). In 33 individuals, EBT detected CAC with a mean Agatston-derived calcium score of 44 {+-} 18. There was a significant difference in regional MBFs between territories with and without CAC at rest and during ADO-stimulated hyperemia (0.69 {+-} 0.24 vs. 0.74 {+-} 0.23 and 1.82 {+-} 0.50 vs. 1.95 {+-} 0.51 ml/g/min; p {<=} 0.05, respectively) and also during CPT in DM but less pronounced (0.81 {+-} 0.24 vs. 0.83 {+-} 0.23 ml/g/min; p = ns). The increase in CAC was paralleled with a progressive regional decrease in resting as well as in CPT- and ADO-related MBFs (r = -0.36, p {<=} 0.014; r = -0.46, p {<=} 0.007; and r = -0.33, p {<=} 0.041, respectively). The absence of any correlation between carotid IMT and coronary circulatory function in type 2 DM suggests different features and stages of early atherosclerosis in the peripheral and coronary circulation. PET-measured MBF heterogeneity at rest and during vasomotor stress may reflect downstream fluid dynamic effects of coronary artery disease (CAD)-related early structural alterations of the arterial wall. (orig.)

  15. Measurement of Change in Wall Thickness of Cylindrical Shell Due to Cyclic Remote Actuation for Assessment of Viscoelasticity of Arterial Wall

    Science.gov (United States)

    Hasegawa, Hideyuki; Kanai, Hiroshi; Koiwa, Yoshiro; Butler, James P.

    2003-05-01

    To characterize tissues in atherosclerotic plaques, we have developed a method, the phased tracking method, for measuring the strain (change in wall thickness) and elasticity of the arterial wall. However, some types of tissue, such as lipids and blood clots, cannot be discriminated from each other based only on elasticity because of the small difference in their elasticity. For more precise tissue characterization, we are attempting to measure the regional viscoelasticity. To determine viscoelastic properties, elastic moduli at multiple frequencies were obtained by generating the change in internal pressure due to remote cyclic actuation. From basic experiments using a silicone rubber tube, it was found that the change in internal pressure at the ultrasonic beam position (for measurement of the elastic modulus) can be generated by remotely applied actuation. Furthermore, from the resultant minute changes in wall thickness of less than 10 μm measured by the phased tracking method, elastic moduli were obtained at multiple actuation frequencies.

  16. Carotid artery wall thickness: comparison between sonography and multi-detector row CT angiography

    Energy Technology Data Exchange (ETDEWEB)

    Saba, Luca [University of Cagliari, Department of Radiology, Policlinico Universitario, Cagliari (Italy); Sanfilippo, Roberto; Montisci, Roberto [Policlinico Universitario, Department of Vascular Surgery, Cagliari (Italy); Mallarini, Giorgio [University of Cagliari, Department of Radiology, Policlinico Universitario, Cagliari (Italy); Ospedale San Giovanni di Dio, Institute of Radiology, Cagliari (Italy)

    2010-02-15

    Prospective studies have shown that an increased thickness of the carotid wall is a significant predictor of coronary and cerebrovascular complications. Our purpose was to assess the agreement between multi-detector row computed tomography (CT) angiography (MDCTA) and colour Doppler ultrasound (CD-US) in measuring carotid artery wall thickness (CAWT) and the intima-media thickness (IMT). Altogether, 97 subjects (age range 64-84 years) were prospectively analysed using a four-detector row CT and a sonographic scanner. In total, 46 subjects had shown cerebral ischaemic symptoms. CAWT and IMT were measured in each patient using MDCTA and CD-US (by applying a digital calliper), respectively. Continuous data were described as the mean value {+-} standard deviation and were compared using the Mann-Whitney U test. A p value <0.05 was considered significant. Bland-Altman statistics was employed to measure the agreement between MDCTA and CD-US. CAWT ranged from 0.5 to 1.53 mm, with a mean value of 0.9072 mm. IMT ranged from 0.46 to 1.5 mm, with a mean value of 0.8839 mm. By analysing the Bland-Altman plot, we observed an excellent agreement between CD-US and MDCTA with a bias between methods of 0.023 {+-} 0.0424 mm. A limit of agreement from -0.06 to 0.106 was recorded. Correlation coefficient r was 0.9855 (95% confidence interval 0.9808-0.989). Mann-Whitney U test indicated a p value of 0.377. Obtained results indicated a significant agreement between MDCTA and CD-US in the measurement of CAWT and IMT. (orig.)

  17. Carotid artery wall thickness: comparison between sonography and multi-detector row CT angiography

    International Nuclear Information System (INIS)

    Prospective studies have shown that an increased thickness of the carotid wall is a significant predictor of coronary and cerebrovascular complications. Our purpose was to assess the agreement between multi-detector row computed tomography (CT) angiography (MDCTA) and colour Doppler ultrasound (CD-US) in measuring carotid artery wall thickness (CAWT) and the intima-media thickness (IMT). Altogether, 97 subjects (age range 64-84 years) were prospectively analysed using a four-detector row CT and a sonographic scanner. In total, 46 subjects had shown cerebral ischaemic symptoms. CAWT and IMT were measured in each patient using MDCTA and CD-US (by applying a digital calliper), respectively. Continuous data were described as the mean value ± standard deviation and were compared using the Mann-Whitney U test. A p value <0.05 was considered significant. Bland-Altman statistics was employed to measure the agreement between MDCTA and CD-US. CAWT ranged from 0.5 to 1.53 mm, with a mean value of 0.9072 mm. IMT ranged from 0.46 to 1.5 mm, with a mean value of 0.8839 mm. By analysing the Bland-Altman plot, we observed an excellent agreement between CD-US and MDCTA with a bias between methods of 0.023 ± 0.0424 mm. A limit of agreement from -0.06 to 0.106 was recorded. Correlation coefficient r was 0.9855 (95% confidence interval 0.9808-0.989). Mann-Whitney U test indicated a p value of 0.377. Obtained results indicated a significant agreement between MDCTA and CD-US in the measurement of CAWT and IMT. (orig.)

  18. Nanochannel flow past permeable walls via molecular dynamics

    Science.gov (United States)

    Xie, Jian-Fei; Cao, Bing-Yang

    2016-07-01

    The nanochannel flow past permeable walls with nanopores is investigated by molecular dynamics (MD) simulations, including the density distribution, velocity field, molecular penetration mechanism and surface friction coefficient. A low density distribution has been found at the gas-wall interface demonstrating the low pressure region. In addition, there exists a jump of the gas density on the permeable surface, which indicates the discontinuity of the density distribution across the permeable surface. On the other hand, the nanoscale vortices are observed in nanopores of the permeable wall, and the reduced mass flux of the flow in nanopores results in a shifted hydrodynamic boundary above the permeable surface. Particularly the slip length of the gas flow on the permeable surface is pronounced a non-linear function of the molecular mean free path, which produces a large value of the tangential momentum accommodation coefficient (TMAC) and a big portion of the diffusive refection. Moreover, the gas-gas interaction and multi-collision among gas molecules may take place in nanopores, which contribute to large values of TMAC. Consequently the boundary friction coefficient on the permeable surface is increased because of the energy dissipation consumed by the nanoscale vortices in nanopores. The molecular boundary condition provides us with a new picture of the nanochannel flow past the permeable wall with nanopores.

  19. Comparative measurement of silicon and major elements (P,S,Cl,K,Ca) in arterial walls using macro and microbeam analysis

    International Nuclear Information System (INIS)

    There are few techniques available for the measurement of silicon at trace levels in biological materials. PIXE and prompt nuclear reaction analysis were used to locate and measure silicon and major elements in arterial walls. Macrobeam analysis, carried out by the Van de Graaff accelerator at CENBG, enabled measurement of mean tissue levels. Microbeam analysis, using the nuclear microprobe at Karlsruhe, yielded the distribution of these elements through the thickness of the arterial wall. The microanalyses were performed on arterial walls from healthy rabbits and the macrobeam study was carried out on the same samples and also on human aorta specimens

  20. Diagnostic accuracy of myocardial deformation indices for detecting high risk coronary artery disease in patients without regional wall motion abnormality

    OpenAIRE

    Rostamzadeh, Alireza; Shojaeifard, Maryam; Rezaei, Yousef; Dehghan, Kasra

    2015-01-01

    Background: The prediction of coronary artery disease (CAD) by conventional echocardiographic measurements is principally based on the estimation of ejection fraction and regional wall motion abnormality (RWMA). This study aimed to determine whether strain echocardiography of left ventricle measured by velocity vector imaging (VVI) method could detect patients with a high-risk CAD. Methods: In a prospective study, a total of 119 consecutive patients who were assessed for eligibility were cate...

  1. Characterizaton of the Vessel Geometry, Flow Mechanics and Wall Shear Stress in the Great Arteries of Wildtype Prenatal Mouse

    OpenAIRE

    Choon Hwai Yap; Xiaoqin Liu; Kerem Pekkan

    2014-01-01

    Characterizaton of the Vessel Geometry, Flow Mechanics and Wall Shear Stress in the Great Arteries of Wildtype Prenatal Mouse Choon Hwai Yap1, Xiaoqin Liu2, Kerem Pekkan3* 1 Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore, 2 Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America, 3 Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh...

  2. Characterization of the vessel geometry, flow mechanics and wall shear stress in the great arteries of wildtype prenetal mouse

    OpenAIRE

    Pekkan, Kerem; Yap, C.H.; Liu, X.

    2014-01-01

    Characterizaton of the Vessel Geometry, Flow Mechanics and Wall Shear Stress in the Great Arteries of Wildtype Prenatal Mouse Choon Hwai Yap1, Xiaoqin Liu2, Kerem Pekkan3* 1 Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore, 2 Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America, 3 Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh...

  3. Composition of connective tissues and morphometry of vascular smooth muscle in arterial wall of DOCA-salt hypertensive rats - In relation with arterial remodeling.

    Science.gov (United States)

    Hayashi, Kozaburo; Shimizu, Emiko

    2016-05-01

    Hypertension (HT) was induced in Wistar rats aged 16 and 48 weeks by a deoxycortico-sterone acetate (DOCA)-salt procedure. Common carotid arteries were resected 16 weeks after, and their histological specimens were selectively stained for observations of collagen, elastin, and vascular smooth muscle (VSM) cells. Then, the fractions of collagen and elastin and their radial distributions, and the size and number of VSM cells were determined with an image analyzer. These results were compared with the results from age-matched, non-treated, normotensive (NT) animals and also with those from our previous biomechanical studies. In both age groups, there were no significant differences in the fractions of collagen and elastin, and the ratio of collagen to elastin content between HT and NT arteries. These results correspond well with our previous biomechanical results, which showed no significant difference in wall elasticity between HT and NT vessels. Moreover, in the innermost layer out of 4 layers bordered with thick elastic lamellae, the fraction of collagen was significantly greater in HT arteries than in NT ones, which is attributable to HT-related stress concentration in the layer. VSM cells were significantly hypertrophied and their content was increased by HT, although their total number in the media remained unchanged. The increased size and content of cells correspond to the enhancement of vascular tone and contractility in HT arteries.

  4. Composition of connective tissues and morphometry of vascular smooth muscle in arterial wall of DOCA-salt hypertensive rats - In relation with arterial remodeling.

    Science.gov (United States)

    Hayashi, Kozaburo; Shimizu, Emiko

    2016-05-01

    Hypertension (HT) was induced in Wistar rats aged 16 and 48 weeks by a deoxycortico-sterone acetate (DOCA)-salt procedure. Common carotid arteries were resected 16 weeks after, and their histological specimens were selectively stained for observations of collagen, elastin, and vascular smooth muscle (VSM) cells. Then, the fractions of collagen and elastin and their radial distributions, and the size and number of VSM cells were determined with an image analyzer. These results were compared with the results from age-matched, non-treated, normotensive (NT) animals and also with those from our previous biomechanical studies. In both age groups, there were no significant differences in the fractions of collagen and elastin, and the ratio of collagen to elastin content between HT and NT arteries. These results correspond well with our previous biomechanical results, which showed no significant difference in wall elasticity between HT and NT vessels. Moreover, in the innermost layer out of 4 layers bordered with thick elastic lamellae, the fraction of collagen was significantly greater in HT arteries than in NT ones, which is attributable to HT-related stress concentration in the layer. VSM cells were significantly hypertrophied and their content was increased by HT, although their total number in the media remained unchanged. The increased size and content of cells correspond to the enhancement of vascular tone and contractility in HT arteries. PMID:26987272

  5. Ultrasonic Measurement of Change in Elasticity due to Endothelium Dependent Relaxation Response by Accurate Detection of Artery-Wall Boundary

    Science.gov (United States)

    Kaneko, Takuya; Hasegawa, Hideyuki; Kanai, Hiroshi

    2007-07-01

    Ross hypothesized that an endothelial dysfunction is considered to be an initial step in atherosclerosis. Endothelial cells, which release nitric oxide (NO) in response to shear stress from blood flow, have a function of relaxing smooth muscle in the media of the arterial wall. For the assessment of the endothelial function, there is a conventional method in which the change in the diameter of the brachial artery caused by flow-mediated dilation (FMD) is measured with ultrasound. However, despite the fact that the collagen-rich hard adventitia does not respond to NO, the conventional method measures the change in diameter depending on the mechanical property of the entire wall including the adventitia. Therefore, we developed a method of measuring the change in the thickness and the elasticity of the brachial artery during a cardiac cycle using the phased tracking method for the evaluation of the mechanical property of only the intima-media region. In this study, the initial positions of echoes from the lumen-intima and media-adventitia boundaries are determined using complex template matching to accurately estimate the minute change in the thickness and the elasticity of the brachial and radial arteries. The ambiguity in the determination of such boundaries was eliminated using complex template matching, and the change in elasticity measured by the proposed method was larger than the change in inner diameter obtained by the conventional method.

  6. Carotid artery longitudinal wall motion is associated with local blood velocity and left ventricular rotational, but not longitudinal, mechanics.

    Science.gov (United States)

    Au, Jason S; Ditor, David S; MacDonald, Maureen J; Stöhr, Eric J

    2016-07-01

    Recent studies have identified a predictable movement pattern of the common carotid artery wall in the longitudinal direction. While there is evidence that the magnitude of this carotid artery longitudinal wall motion (CALM) is sensitive to cardiovascular health status, little is known about the determinants of CALM The purpose of this integrative study was to evaluate the contribution of left ventricular (LV) cardiac motion and local blood velocity to CALM Simultaneous ultrasound measurements of CALM, common carotid artery mean blood velocity (MBV), and left ventricular motion were performed in ten young, healthy individuals (6 males; 22 ± 1 years). Peak anterograde CALM occurred at a similar time as peak MBV (18.57 ± 3.98% vs. 18.53 ± 2.81% cardiac cycle; t-test: P = 0.94; ICC: 0.79, P longitudinal displacement was not associated with peak CALM (r = 0.11, P = 0.77). These results suggest that the rotational mechanical movement of the LV base may be closely associated with longitudinal mechanics in the carotid artery. This finding may have important implications for interpreting the complex relationship between ventricular and vascular function.

  7. Domain-wall spin dynamics in kagome antiferromagnets.

    Science.gov (United States)

    Lhotel, E; Simonet, V; Ortloff, J; Canals, B; Paulsen, C; Suard, E; Hansen, T; Price, D J; Wood, P T; Powell, A K; Ballou, R

    2011-12-16

    We report magnetization and neutron scattering measurements down to 60 mK on a new family of Fe based kagome antiferromagnets, in which a strong local spin anisotropy combined with a low exchange path network connectivity lead to domain walls intersecting the kagome planes through strings of free spins. These produce unfamiliar slow spin dynamics in the ordered phase, evolving from exchange-released spin flips towards a cooperative behavior on decreasing the temperature, probably due to the onset of long-range dipolar interaction. A domain structure of independent magnetic grains is obtained that could be generic to other frustrated magnets.

  8. Genetic susceptibility of the arterial wall is an important determinant of atherosclerosis in C57BL/6 and FVB/N mouse strains

    DEFF Research Database (Denmark)

    Shim, Jeong; Handberg, Aase; Östergren, Eva-Britt Caroline;

    2011-01-01

    How genetic variations among inbred mouse strains translate into differences in atherosclerosis susceptibility is of significant interest for the development of new therapeutic strategies. The objective of the present study was to examine whether genetically controlled arterial wall properties in...

  9. Domain wall dynamics in ultra thin manganite film

    Energy Technology Data Exchange (ETDEWEB)

    Uspenskaya, Ludmila [Institute of Solid State Physics RAS, Chernogolovka, 142432 (Russian Federation); Nurgaliev, Timur; Miteva, S, E-mail: uspenska@issp.ac.r [Institute of Electronics, Bulgarian Academy of Sciences (BAS), 72 Tsarigradsko Chaussee, 1784 Sofia (Bulgaria)

    2010-01-01

    Kinetics of magnetization reversal and dynamics of domain walls in thin La{sub 0:7}Sr{sub 0:3}MnO{sub 3} manganite films are studied by magnetooptic visualization technique. Two types of magnetic domain structure are revealed in 20 nm thin film, namely, the small-scale patched domains with perpendicular magnetization, which are formed after zero field cooling, and wide macro-domains with an in-plane magnetization, which appear as a remnant state after saturation by the field of any orientation. The following magnetization reversal is found to occur via the nucleation and thermoactivated motion of the 180{sup 0} domain walls. Strong temperature dependence of dynamic parameters is established near the room temperature. A heating of 10 K above 294 K results in 1.5 reduction of coercivity, in alteration of magnetic permeability, magnetic viscosity and activation volume by order of magnitude. The obtained results could be explained taking into account magnetic after-effects specific for materials with the magnetic ions of transient valence.

  10. Carotid artery wall thickness and ischemic symptoms: evaluation using multi-detector-row CT angiography

    Energy Technology Data Exchange (ETDEWEB)

    Saba, Luca; Caddeo, Giancarlo; Mallarini, Giorgio [Azienda Ospedaliero Universitaria Polo di Monserrato, Department of Radiology, Cagliari (Italy); Sanfilippo, Roberto; Montisci, Roberto [Azienda Ospedaliero Universitaria Polo di Monserrato, Department of Vascular Surgery, Cagliari (Italy); Pascalis, Luigi [Azienda Ospedaliero Universitaria Polo di Cagliari, Division of II Internal Medicine, Cagliari (Italy)

    2008-09-15

    The purpose of this study was to determine if carotid artery wall thickness (CAWT) studied by using multi-detector-row CT angiography (MDCTA) can be considered an effective parameter predictive of increased risk of stroke. A total of 217 patients were retrospectively studied by using MDCTA. In all patients CAWT was measured with an internal digital caliper. Continuous data were described as the mean value {+-} standard deviation (SD), and they were compared with Student's t-test. Scatter plots to determine interobserver agreement were performed, and correlation coefficient was calculated with Pearson statistics. A P value <0.05 was considered to mean statistical significance. Measurements of the distal common CAWT ranged from 0.5 to 1.6 mm. In the patient group without stroke, average CAWT was 0.82 mm (0.22 SD), whereas in patient group with stroke it was 1.096 mm (0.21 SD). CAWT in patients without stroke showed statistical difference (P<0.0001) when compared to patients with stroke. By using a threshold of 1 mm, an important statistical association between thick CAWT and stroke was found (P<0.0001). In fact, patients with {>=}1 mm CAWT had stroke with an odds ratio of 8.16 when compared with patients with <1 mm CAWT. Resulting data suggested that an increased CAWT is an indicator for risk of stroke. This parameter should be considered in addition to other well-known risk factors such as diabetes, hypertension, smoking, and dyslipidemia. (orig.)

  11. The Dynamic Similitude Design Method of Thin Walled Structures and Experimental Validation

    Directory of Open Access Journals (Sweden)

    Zhong Luo

    2016-01-01

    Full Text Available For the applicability of dynamic similitude models of thin walled structures, such as engine blades, turbine discs, and cylindrical shells, the dynamic similitude design of typical thin walled structures is investigated. The governing equation of typical thin walled structures is firstly unified, which guides to establishing dynamic scaling laws of typical thin walled structures. Based on the governing equation, geometrically complete scaling law of the typical thin walled structure is derived. In order to determine accurate distorted scaling laws of typical thin walled structures, three principles are proposed and theoretically proved by combining the sensitivity analysis and governing equation. Taking the thin walled annular plate as an example, geometrically complete and distorted scaling laws can be obtained based on the principles of determining dynamic scaling laws. Furthermore, the previous five orders’ accurate distorted scaling laws of thin walled annular plates are presented and numerically validated. Finally, the effectiveness of the similitude design method is validated by experimental annular plates.

  12. Hemodynamic analysis in an idealized artery tree: differences in wall shear stress between Newtonian and non-Newtonian blood models.

    Directory of Open Access Journals (Sweden)

    Jared C Weddell

    Full Text Available Development of many conditions and disorders, such as atherosclerosis and stroke, are dependent upon hemodynamic forces. To accurately predict and prevent these conditions and disorders hemodynamic forces must be properly mapped. Here we compare a shear-rate dependent fluid (SDF constitutive model, based on the works by Yasuda et al in 1981, against a Newtonian model of blood. We verify our stabilized finite element numerical method with the benchmark lid-driven cavity flow problem. Numerical simulations show that the Newtonian model gives similar velocity profiles in the 2-dimensional cavity given different height and width dimensions, given the same Reynolds number. Conversely, the SDF model gave dissimilar velocity profiles, differing from the Newtonian velocity profiles by up to 25% in velocity magnitudes. This difference can affect estimation in platelet distribution within blood vessels or magnetic nanoparticle delivery. Wall shear stress (WSS is an important quantity involved in vascular remodeling through integrin and adhesion molecule mechanotransduction. The SDF model gave a 7.3-fold greater WSS than the Newtonian model at the top of the 3-dimensional cavity. The SDF model gave a 37.7-fold greater WSS than the Newtonian model at artery walls located immediately after bifurcations in the idealized femoral artery tree. The pressure drop across arteries reveals arterial sections highly resistive to flow which correlates with stenosis formation. Numerical simulations give the pressure drop across the idealized femoral artery tree with the SDF model which is approximately 2.3-fold higher than with the Newtonian model. In atherosclerotic lesion models, the SDF model gives over 1 Pa higher WSS than the Newtonian model, a difference correlated with over twice as many adherent monocytes to endothelial cells from the Newtonian model compared to the SDF model.

  13. Hemodynamic analysis in an idealized artery tree: differences in wall shear stress between Newtonian and non-Newtonian blood models.

    Science.gov (United States)

    Weddell, Jared C; Kwack, JaeHyuk; Imoukhuede, P I; Masud, Arif

    2015-01-01

    Development of many conditions and disorders, such as atherosclerosis and stroke, are dependent upon hemodynamic forces. To accurately predict and prevent these conditions and disorders hemodynamic forces must be properly mapped. Here we compare a shear-rate dependent fluid (SDF) constitutive model, based on the works by Yasuda et al in 1981, against a Newtonian model of blood. We verify our stabilized finite element numerical method with the benchmark lid-driven cavity flow problem. Numerical simulations show that the Newtonian model gives similar velocity profiles in the 2-dimensional cavity given different height and width dimensions, given the same Reynolds number. Conversely, the SDF model gave dissimilar velocity profiles, differing from the Newtonian velocity profiles by up to 25% in velocity magnitudes. This difference can affect estimation in platelet distribution within blood vessels or magnetic nanoparticle delivery. Wall shear stress (WSS) is an important quantity involved in vascular remodeling through integrin and adhesion molecule mechanotransduction. The SDF model gave a 7.3-fold greater WSS than the Newtonian model at the top of the 3-dimensional cavity. The SDF model gave a 37.7-fold greater WSS than the Newtonian model at artery walls located immediately after bifurcations in the idealized femoral artery tree. The pressure drop across arteries reveals arterial sections highly resistive to flow which correlates with stenosis formation. Numerical simulations give the pressure drop across the idealized femoral artery tree with the SDF model which is approximately 2.3-fold higher than with the Newtonian model. In atherosclerotic lesion models, the SDF model gives over 1 Pa higher WSS than the Newtonian model, a difference correlated with over twice as many adherent monocytes to endothelial cells from the Newtonian model compared to the SDF model. PMID:25897758

  14. Impaired Arterial Elasticity Identified by Pulse Waveform Analysis as a Marker for Vascular Wall Damage in Humans With Aging and Hypertension

    Institute of Scientific and Technical Information of China (English)

    Wang Yan; Tao Jun; Tu Chang; Yang Zhen; Xu Mingguo; Wang Jiemei; Jin Yafei; Ma Hong

    2005-01-01

    Objectives Cardiovascular risk factors lead to pathogenesis of atherosclerosis and its clinical events by impairing vascular wall. Endothelial dysfunction is the earliest marker for vascular wall injuries. Development of new method to detect early vascular wall damage has an important clinical implication for the prevention and treatment of cardiovascular diseases. Therefore, the present study was performed to evaluate effect of aging and hypertension, two independent risk factors for cardiovascular diseases, on arterial elasticity by using pulse waveform analysis and investigate whether the changes in arterial elasticity can be used as a risk marker for vascular structural and functional abnormalities. Methods Using modified Windkessel model of the circulation and pulse waveform analysis,C 1 large artery and C2 small artery elasticity indices of 204 Chinese normal healthy subjects ( age 15-80years) and 46 Chinese essential hypertensive patients (age 35-70 years) were measured. Age- and hypertension-related arterial elasticity changes were examined. Results C1 large artery and C2 small artery elasticity indices were reduced with advancing age in healthy subjects. C1 large artery and C2 small artery elasticity indices were negatively correlated with age (r=-0.628, P<0.001; r=-0.595, P<0.001). C1 large artery and C2 small artery elasticity indices in patients with essential hypertension compared with the agematched healthy subjects were (9.31±3.85 ml/mm Hg x 10 versus 15.13±4.14 ml/mmHg x 10, P<0.001) and (3.57± 1.62 ml/mm Hg x 100 versus 7.89±2.91 ml/mmHg ×100 P <0.001), respectively, and were significantly lower than the corresponding healthy subjects. There were negative association between C1large artery and C2 small artery elasticity indices and systolic blood pressure (r=-0.37, P<0.05; r=-0.39,P<0.05) and pulse pressure (r=-0.39, P<0.05; r=0.43,P<0.05) in patients with essential hypertension.Conclusions Advancing age and essential

  15. A theory for water and macromolecular transport in the pulmonary artery wall with a detailed comparison to the aorta.

    Science.gov (United States)

    Zeng, Zhongqing; Jan, Kung-Ming; Rumschitzki, David S

    2012-04-15

    The pulmonary artery (PA) wall, which has much higher hydraulic conductivity and albumin void space and approximately one-sixth the normal transmural pressure of systemic arteries (e.g, aorta, carotid arteries), is rarely atherosclerotic, except under pulmonary hypertension. This study constructs a detailed, two-dimensional, wall-structure-based filtration and macromolecular transport model for the PA to investigate differences in prelesion transport processes between the disease-susceptible aorta and the relatively resistant PA. The PA and aorta models are similar in wall structure, but very different in parameter values, many of which have been measured (and therefore modified) since the original aorta model of Huang et al. (23). Both PA and aortic model simulations fit experimental data on transwall LDL concentration profiles and on the growth of isolated endothelial (horseradish peroxidase) tracer spots with circulation time very well. They reveal that lipid entering the aorta attains a much higher intima than media concentration but distributes better between these regions in the PA than aorta and that tracer in both regions contributes to observed tracer spots. Solutions show why both the overall transmural water flow and spot growth rates are similar in these vessels despite very different material transport parameters. Since early lipid accumulation occurs in the subendothelial intima and since (matrix binding) reaction kinetics depend on reactant concentrations, the lower intima lipid concentrations in the PA vs. aorta likely lead to slower accumulation of bound lipid in the PA. These findings may be relevant to understanding the different atherosusceptibilities of these vessels. PMID:22198178

  16. Large Artery Remodeling and Dynamics following Simulated Microgravity by Prolonged Head-Down Tilt Bed Rest in Humans

    Directory of Open Access Journals (Sweden)

    Carlo Palombo

    2015-01-01

    Full Text Available The effects of simulated microgravity on the static and dynamic properties of large arteries are still mostly unknown. The present study evaluated, using an integrated vascular approach, changes in structure and function of the common carotid and femoral arteries (CCA and CFA after prolonged head-down tilt bed rest (HDTBR. Ten healthy men were enrolled in a 5-week HDTBR study endorsed by the Italian Space Agency (ASI. Arterial geometry, flow, stiffness, and shear rate were evaluated by ultrasound. Local carotid pulse pressure and wave reflection were studied by applanation tonometry. After five weeks of HDTBR, CFA showed a decrease in lumen diameter without significant changes in wall thickness (IMT, resulting in an inward remodeling. Local carotid pulse pressure decreased and carotid-to-brachial pressure amplification increased. The ratio of systolic-to-diastolic volumetric flow in CFA decreased, whereas in CCA it tended to increase. Indices of arterial stiffness and shear rate did not change during HDTBR, either in CCA or CFA. In summary, prolonged HDTBR has a different impact on CCA and CFA structure and flow, probably depending on the characteristics of the vascular bed perfused.

  17. Examination of nanoparticles as a drug carrier on blood flow through catheterized composite stenosed artery with permeable walls.

    Science.gov (United States)

    Ijaz, S; Nadeem, S

    2016-09-01

    In this paper, we have discussed the influence of copper nanoparticles on a blood flow through composite stenosed artery with permeable walls. The nature of blood is discussed mathematically by considering it as viscous nanofluid. The study is carried out for a blood vessel under mild stenosis approximations and expressions of the temperature, velocity, resistance impedance to flow, wall shear stress and the pressure gradient is obtained by using corresponding boundary conditions. Results for the effects of permeability on blood flow through composite stenosis have been discussed graphically. The considered analysis also summarizes that the drug copper nanoparticles are efficient to reduce hemodynamics of stenosis and could be helpful to predict important uses for biomedical applications. Results indicate that nanoparticles are helpful as drug carriers to minimize the effects of resistance impedance to blood flow or coagulation factors due to stenosis. PMID:27393802

  18. Extremal states of energy of a double-layered thick-walled tube - application to residually stressed arteries.

    Science.gov (United States)

    Waffenschmidt, Tobias; Menzel, Andreas

    2014-01-01

    Various biological tissues are designed to optimally support external loads for complex geometries and mechanobiological structures. This results in complex microstructures of such materials. The design of, for instance, (healthy) arteries, which are in the focus of this work, is characterised by a residually stressed fibre-reinforced multi-layered composite with highly non-linear elastic response. The complex interaction of material properties with the geometry and residual stress effects enables the optimal support under different blood pressures, respectively blood flow, within the vessel. The fibres reinforcing the arterial wall, as well as residual stresses present in the vessel, strongly influence its overall behaviour and performance. Turn-over and remodelling processes of the collagenous fibres occurring in the respective layers - either resulting from natural growth phenomena or from artificially induced changes in loading condition such as stent deployment - support the optimisation of the multi-layered composite structure of arteries for the particular loading conditions present in the artery. Within this contribution, the overall energetic properties of an artery are discussed by means of the inflation, bending and extension of a double-layered cylindrical tube. Different states of residual stresses and different fibre orientations are considered so that, for instance, representative fibre angles that result in extremal states of the total potential energy can be identified. In view of turn-over and remodelling processes, these orientations are considered to constitute preferred directions of fibre alignment. In summary, the main goal of this work is to calculate optimal material, structural and loading parameters by concepts of energy-minimisation. Several numerical studies show that the obtained values - such as the fibre orientations, the residual axial stretch and the opening angle - are in good agreement with respective physiological parameters

  19. A control systems approach to quantify wall shear stress normalization by flow-mediated dilation in the brachial artery.

    Directory of Open Access Journals (Sweden)

    Frank C G van Bussel

    Full Text Available Flow-mediated dilation is aimed at normalization of local wall shear stress under varying blood flow conditions. Blood flow velocity and vessel diameter are continuous and opposing influences that modulate wall shear stress. We derived an index FMDv to quantify wall shear stress normalization performance by flow-mediated dilation in the brachial artery. In 22 fasting presumed healthy men, we first assessed intra- and inter-session reproducibilities of two indices pFMDv and mFMDv, which consider the relative peak and relative mean hyperemic change in flow velocity, respectively. Second, utilizing oral glucose loading, we evaluated the tracking performance of both FMDv indices, in comparison with existing indices [i.e., the relative peak diameter increase (%FMD, the peak to baseline diameter ratio (Dpeak/Dbase, and the relative peak diameter increase normalized to the full area under the curve of blood flow velocity with hyperemia (FMD/shearAUC or with area integrated to peak hyperemia (FMD/shearAUC_peak]. Inter-session and intra-session reproducibilities for pFMDv, mFMDv and %FMD were comparable (intra-class correlation coefficients within 0.521-0.677 range. Both pFMDv and mFMDv showed more clearly a reduction after glucose loading (reduction of ~45%, p≤0.001 than the other indices (% given are relative reductions: %FMD (~11%, p≥0.074; Dpeak/Dbase (~11%, p≥0.074; FMD/shearAUC_peak (~20%, p≥0.016 and FMD/shearAUC (~38%, p≤0.038. Further analysis indicated that wall shear stress normalization under normal (fasting conditions is already far from ideal (FMDv << 1, which (therefore does not materially change with glucose loading. Our approach might be useful in intervention studies to detect intrinsic changes in shear stress normalization performance in conduit arteries.

  20. Roles of membrane trafficking in plant cell wall dynamics

    OpenAIRE

    Ebine, Kazuo; Ueda, Takashi

    2015-01-01

    The cell wall is one of the characteristic components of plant cells. The cell wall composition differs among cell types and is modified in response to various environmental conditions. To properly generate and modify the cell wall, many proteins are transported to the plasma membrane or extracellular space through membrane trafficking, which is one of the key protein transport mechanisms in eukaryotic cells. Given the diverse composition and functions of the cell wall in plants, the transpor...

  1. Penium margaritaceum: A Unicellular Model Organism for Studying Plant Cell Wall Architecture and Dynamics

    OpenAIRE

    Domozych, David S

    2014-01-01

    Penium margaritaceum is a new and valuable unicellular model organism for studying plant cell wall structure and developmental dynamics. This charophyte has a cell wall composition remarkably similar to the primary cell wall of many higher plants and clearly-defined inclusive zones containing specific polymers. Penium has a simple cylindrical phenotype with a distinct region of focused wall synthesis. Specific polymers, particularly pectins, can be identified using monoclonal antibodies rais...

  2. Deposition of amyloid β in the walls of human leptomeningeal arteries in relation to perivascular drainage pathways in cerebral amyloid angiopathy.

    Science.gov (United States)

    Keable, Abby; Fenna, Kate; Yuen, Ho Ming; Johnston, David A; Smyth, Neil R; Smith, Colin; Al-Shahi Salman, Rustam; Samarasekera, Neshika; Nicoll, James A R; Attems, Johannes; Kalaria, Rajesh N; Weller, Roy O; Carare, Roxana O

    2016-05-01

    Deposition of amyloid β (Aβ) in the walls of cerebral arteries as cerebral amyloid angiopathy (CAA) suggests an age-related failure of perivascular drainage of soluble Aβ from the brain. As CAA is associated with Alzheimer's disease and with intracerebral haemorrhage, the present study determines the unique sequence of changes that occur as Aβ accumulates in artery walls. Paraffin sections of post-mortem human occipital cortex were immunostained for collagen IV, fibronectin, nidogen 2, Aβ and smooth muscle actin and the immunostaining was analysed using Image J and confocal microscopy. Results showed that nidogen 2 (entactin) increases with age and decreases in CAA. Confocal microscopy revealed stages in the progression of CAA: Aβ initially deposits in basement membranes in the tunica media, replaces first the smooth muscle cells and then the connective tissue elements to leave artery walls completely or focally replaced by Aβ. The pattern of development of CAA in the human brain suggests expansion of Aβ from the basement membranes to progressively replace all tissue elements in the artery wall. Establishing this full picture of the development of CAA is pivotal in understanding the clinical presentation of CAA and for developing therapies to prevent accumulation of Aβ in artery walls. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock. PMID:26327684

  3. Smooth Muscle Specific Overexpression of p22phox Potentiates Carotid Artery Wall Thickening in Response to Injury

    Directory of Open Access Journals (Sweden)

    Michael R. Manogue

    2015-01-01

    Full Text Available We hypothesized that transgenic mice overexpressing the p22phox subunit of the NADPH oxidase selectively in smooth muscle (Tgp22smc would exhibit an exacerbated response to transluminal carotid injury compared to wild-type mice. To examine the role of reactive oxygen species (ROS as a mediator of vascular injury, the injury response was quantified by measuring wall thickness (WT and cross-sectional wall area (CSWA of the injured and noninjured arteries in both Tgp22smc and wild-type animals at days 3, 7, and 14 after injury. Akt, p38 MAPK, and Src activation were evaluated at the same time points using Western blotting. WT and CSWA following injury were significantly greater in Tgp22smc mice at both 7 and 14 days after injury while noninjured contralateral carotids were similar between groups. Apocynin treatment attenuated the injury response in both groups and rendered the response similar between Tgp22smc mice and wild-type mice. Following injury, carotid arteries from Tgp22smc mice demonstrated elevated activation of Akt at day 3, while p38 MAPK and Src activation was elevated at day 7 compared to wild-type mice. Both increased activation and temporal regulation of these signaling pathways may contribute to enhanced vascular growth in response to injury in this transgenic model of elevated vascular ROS.

  4. Shaking table tests and dynamic analyses of masonry wall buildings with flame-shear walls at lower stories

    Institute of Scientific and Technical Information of China (English)

    Xiong Lihong; David Xiong; Wu Ruifeng; Xia Jingqian

    2008-01-01

    This paper describes shaking table tests of three eight-story building models: all are masonry structures in the upper stories, with or without frame-shear walls of one- or two- stories at the bottom. The test results of damage characteristics and seismic responses are provided and compared. Then, nonlinear response analyses are conducted to examine the reliability of the dynamic analysis. Finally, many nonlinear response analyses are performed and it is concluded that for relatively hard sites under a certain lateral stiffness ratio (I.e., the ratio of the stiffness of the lowest upper masonry story to that of the frame-shear wall story), the masonry structure with one-story frame-shear wall at the bottom performs better than a structure built entirely of masonry, and a masonry structure with frame-shear wall of two stories performs better than with one-story frame-shear wall. In relatively soft soil conditions, all three structures have similar performane. In addition, some suggestions that could be helpful for design ofmasomy structures with ground story of frame-shear wall structure in seismic intensity region VII, such as the appropriate lateral stiffness ratio, shear force increase factor of the frame-shear wall story, and permissible maximum height of the building, are proposed.

  5. [Trapped popliteal artery. Early diagnosis by dynamic tests during arteriography (author's transl)].

    Science.gov (United States)

    Metges, P J; Cosnard, G; Pailler, J L; Chantome, M; Flageat, J

    1981-05-01

    An extrinsic functional stenosis was detected in the contralateral popliteal artery during follow-up arteriography in a patient operated upon for a thrombosed trapped popliteal artery. The value of dynamic tests of plantar flexion against resistance with the knee extended, in a conscious patient, is stressed. A recently available contrast medium enables arteriography of the lower limbs to be conducted without a general anaesthetic. Since writing this report, the authors have explored a type II bilateral form of trapped popliteal artery in a 35-year-old man, in whom the diagnosis was determined mainly from dynamic films. PMID:7288729

  6. Automatic detection of the carotid artery boundary on cross-sectional MR image sequences using a circle model guided dynamic programming

    Directory of Open Access Journals (Sweden)

    Brambs Hans

    2011-04-01

    Full Text Available Abstract Background Systematic aerobe training has positive effects on the compliance of dedicated arterial walls. The adaptations of the arterial structure and function are associated with the blood flow-induced changes of the wall shear stress which induced vascular remodelling via nitric oxide delivered from the endothelial cell. In order to assess functional changes of the common carotid artery over time in these processes, a precise measurement technique is necessary. Before this study, a reliable, precise, and quick method to perform this work is not present. Methods We propose a fully automated algorithm to analyze the cross-sectional area of the carotid artery in MR image sequences. It contains two phases: (1 position detection of the carotid artery, (2 accurate boundary identification of the carotid artery. In the first phase, we use intensity, area size and shape as features to discriminate the carotid artery from other tissues and vessels. In the second phase, the directional gradient, Hough transform, and circle model guided dynamic programming are used to identify the boundary accurately. Results We test the system stability using contrast degraded images (contrast resolutions range from 50% to 90%. The unsigned error ranges from 2.86% ± 2.24% to 3.03% ± 2.40%. The test of noise degraded images (SNRs range from 16 to 20 dB shows the unsigned error ranging from 2.63% ± 2.06% to 3.12% ± 2.11%. The test of raw images has an unsigned error 2.56% ± 2.10% compared to the manual tracings. Conclusions We have proposed an automated system which is able to detect carotid artery cross sectional boundary in MRI sequences during heart cycles. The accuracy reaches 2.56% ± 2.10% compared to the manual tracings. The system is stable, reliable and results are reproducible.

  7. Flow and wall shear stress in end-to-side and side-to-side anastomosis of venous coronary artery bypass grafts

    Directory of Open Access Journals (Sweden)

    Poulikakos Dimos

    2007-09-01

    Full Text Available Abstract Purpose Coronary artery bypass graft (CABG surgery represents the standard treatment of advanced coronary artery disease. Two major types of anastomosis exist to connect the graft to the coronary artery, i.e., by using an end-to-side or a side-to-side anastomosis. There is still controversy because of the differences in the patency rates of the two types of anastomosis. The purpose of this paper is to non-invasively quantify hemodynamic parameters, such as mass flow and wall shear stress (WSS, in end-to-side and side-to-side anastomoses of patients with CABG using computational fluid dynamics (CFD. Methods One patient with saphenous CABG and end-to-side anastomosis and one patient with saphenous CABG and side-to-side anastomosis underwent 16-detector row computed tomography (CT. Geometric models of coronary arteries and bypasses were reconstructed for CFD analysis. Blood flow was considered pulsatile, laminar, incompressible and Newtonian. Peri-anastomotic mass flow and WSS were quantified and flow patterns visualized. Results CFD analysis based on in-vivo CT coronary angiography data was feasible in both patients. For both types of CABG, flow patterns were characterized by a retrograde flow into the native coronary artery. WSS variations were found in both anastomoses types, with highest WSS values at the heel and lowest WSS values at the floor of the end-to-side anastomosis. In contrast, the highest WSS values of the side-to-side anastomosis configuration were found in stenotic vessel segments and not in the close vicinity of the anastomosis. Flow stagnation zones were found in end-to-side but not in side-to-side anastomosis, the latter also demonstrating a smoother stream division throughout the cardiac cycle. Conclusion CFD analysis of venous CABG based on in-vivo CT datasets in patients was feasible producing qualitative and quantitative information on mass flow and WSS. Differences were found between the two types of anastomosis

  8. Wall shear stress and initiation of aneurysm around anterior communicating artery in pulsating flow; Myakudoryuchu no nozen kotsu domyaku mawari no kabe sendan oryoku to domyakuryu hasse

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, R.; Kudo, S.; Nakashima, M. [Shibaura Institute of University, Tokyo (Japan); Yamanobe, H. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan); Ujiie, H. [Tokyo Women' s Medical College, Tokyo (Japan); Suhihara, R.

    2000-12-25

    In the present paper, the velocity profile, the wall shear stress and its gradient at the apex of the anterior communicating artery are described in pulsating flow. The anterior communicating artery composing the circle of Willis is one of the predilection sites where the cerebral aneurysm occurs frequently. The flow field around the anterior communicating artery is simulated by two confluent tubes joining at the angle of 60 degrees, two parallel bifurcating tubes, and the junctional tube, bypass, connecting four tubes. The velocity profile is clarified around the apex where the cerebral aneurysm is apt to initiate. In particular, the gradient of wall shear stress around the apex at one confluent tube with much flow rate is estimated, and the relation between the gradient of wall shear stress and the initiation of aneurysm is discussed physiologically. (author)

  9. Smooth muscle cell function and organization of the resistance artery wall

    NARCIS (Netherlands)

    B. Güvenç Tuna

    2014-01-01

    Remodeling of the vascular wall occurs in several cardiovascular pathologies. A structural change in diameter necessarily involves reorganization in both cellular and extracellular matrix components. The significance of matrix remodeling in vascular pathologies is well appreciated, while plasticity

  10. Breast arterial calcification and risk of carotid atherosclerosis: Focusing on the preferentially affected layer of the vessel wall

    Energy Technology Data Exchange (ETDEWEB)

    Sedighi, Nahid, E-mail: nsedighi@sina.tums.ac.ir [Department of Radiology, Shariati Hospital, Tehran University of Medical Sciences. North Kargar Ave., Tehran 14114 (Iran, Islamic Republic of); Radmard, Amir Reza, E-mail: radmard@ams.ac.ir [Department of Radiology, Shariati Hospital, Tehran University of Medical Sciences. North Kargar Ave., Tehran 14114 (Iran, Islamic Republic of); Radmehr, Ali, E-mail: radmehr@sina.tums.ac.ir [Department of Radiology, Shariati Hospital, Tehran University of Medical Sciences. North Kargar Ave., Tehran 14114 (Iran, Islamic Republic of); Hashemi, Pari, E-mail: phtums@yahoo.com [Department of Radiology, Shariati Hospital, Tehran University of Medical Sciences. North Kargar Ave., Tehran 14114 (Iran, Islamic Republic of); Hajizadeh, Abdolmahmoud, E-mail: mroomezi@yahoo.com [Department of Radiology, Shariati Hospital, Tehran University of Medical Sciences. North Kargar Ave., Tehran 14114 (Iran, Islamic Republic of); Taheri, Amir Pejman Hashemi, E-mail: hashemip@sina.tums.ac.ir [Department of Radiology, Shariati Hospital, Tehran University of Medical Sciences. North Kargar Ave., Tehran 14114 (Iran, Islamic Republic of)

    2011-08-15

    Objective: To assess the relationship between breast arterial calcification (BAC) detected on screening mammography and atherosclerosis of carotid arteries considering the most likely involved layer of the arterial wall. Materials and methods: A total of 537 consecutive women who underwent screening mammography were enrolled in this study. Seventy-nine subjects having BAC, aged 46-75 years, and 125 age-matched controls from those without BAC were selected for ultrasound examination of carotid arteries assessing intima-media thickness (IMT) and plaque presence. Participants were divided into three groups of risk including, low-risk: IMT < 0.6 mm without plaque, medium-risk: 0.6 mm {<=} IMT {<=} 0.8 mm without plaque and high-risk: IMT > 0.8 mm and/or plaque. Risk factors for atherosclerosis were obtained from medical records for independent effects. Results: BAC was present in 14.7% of mammograms. According to multivariable logistic regression analyses, significant association was identified between the carotid atherosclerosis risk and presence of BAC. Compared to women with IMT < 0.6 mm, those with 0.6 mm {<=} IMT{<=} 0.8 mm and IMT > 0.8 mm had OR (95% CI) of 4.88 (1.47-16.16) and 23.36 (4.54-120.14), respectively. The OR (95% CI) for carotid plaque was 3.13 (1.3-7.57). There was no interaction between IMT category and plaque. Significant associations were also detected with postmenopausal duration (P = 0.02) and hypertension (P = 0.004). Conclusion: The risk of carotid atherosclerosis increases with the presence of BAC. Women with BAC are more likely to have thicker IMT than plaque, which could be attributed to the preferentially similar affected layer of media causing thick IMT rather than plaque.

  11. Mechanical properties of the aortic arterial wall during 24 hours: a preliminary study in conscious sheep

    International Nuclear Information System (INIS)

    Previous experiences in animals showed a different behavior between the variability of pressure, arterial diameter and elasticity when they were registered for a couple of hours. To better understand arterial mechanics variability, we propose to measure simultaneously aortic pressure and diameter during 24 hours in a sheep. For that purpose, we developed a portable prototype device. It allows continuously recording physiological signals throughout the day and storing them in a solid state memory for later analysis. Pulse wave velocity and Peterson modulus were assessed beat-to-beat as arterial stiffness indexes. We identified 53,762 heart beats during 24 hours that were separated into 2 groups: below or above median mean pressure (71 mmHg). Mean diameter, pulse wave velocity and Peterson modulus increased for higher pressure values (p<0.05) whereas heart rate slowed down (p<0.05). Pressure-diameter loops were successfully recreated all along the experience. This new methodology sets the basis for further experiences involving the estimation of 24 hours arterial mechanics variability.

  12. Measurement of arterial wall thickness as a surrogate marker for atherosclerosis

    NARCIS (Netherlands)

    de Groot, E; Hovingh, GK; Wiegman, A; Duriez, P; Smit, AJ; Fruchart, JC; Kastelein, JJP

    2004-01-01

    Large observational studies and atherosclerosis regression trials of lipid-modifying pharmacotherapy have established that intima-media thickness of the carotid and femoral arteries, as measured noninvasively by B-mode ultrasound, is a valid surrogate marker for the progression of atherosclerotic di

  13. [Inflammatory-destructive biomarkers of atherosclerotic plaques instability. Study of arterial wall and blood].

    Science.gov (United States)

    Ragino, Iu I; Cherniavskiĭ, A M; Polonskaia, Ia V; Volkov, A M; Kashtanova, E V; Tsymbal, S Iu; Polovnikova, E M

    2012-01-01

    Concentrations of tumor necrosis factor, interleukin 1- and its receptor antagonist, IL-6, IL-8, IL-18, IL-2, ligand of CD40 receptor (CD40L), high sensitive C-reactive protein (hsCRP), monocyte chemotactic protein -1, endothelial monocyte activating protein II, adhesive molecules (sICAM-1 and sVCAM-1), matrix metalloproteinase (MMP-3, MMP-7, MMP-9), tissue inhibitor of metalloproteinase (TIMP-1) and endothelin-1 were studied in blood and in coronary artery intima/media of men with coronary atherosclerosis without acute coronary syndrome. Blood levels of hsCRP, IL-8, IL-6 and CD40L were higher, while blood levels of sVCAM and TIMP-1 were lower in men with prevalence of unstable atherosclerotic plaques compared to men with prevalence of stable atherosclerotic plaques in coronary arteries. Blood levels of hsCRP, IL-6 and IL-8 correlated with characteristics of coronary artery atherosclerotic plaques instability. Correlation between hsCRP blood level and hsCRP concentration in coronary artery intima/media material was also revealed. PMID:22839584

  14. CORRELATIONS OF DIFFERENT STRUCTURAL AND FUNCTIONAL CHARACTERISTICS OF ARTERIAL WALL WITH TRADITIONAL CARDIOVASCULAR RISK FACTORS IN HEALTHY PEOPLE OF DIFFERENT AGE. PART 1

    Directory of Open Access Journals (Sweden)

    I. D. Strazhesko

    2016-05-01

    Full Text Available Arterial wall status is determined by several characteristics, the main of them are as follows: pulse wave velocity (PWV, carotid arteries intima-media thickness (IMT, the presence of atherosclerotic plaques, endothelium-dependent vasodilation (EDVD. When these parameters change, the risk for cardiovascular disease (CVD grows. The nature of relationship between these indices in people without CVD clinical signs is understudied, especially in those of older age.Aim. To estimate correlations between different parameters of arterial wall in patients of different age without CVD.Material and methods. A total of 303 people aged 25-91 years without any manifestations of CVD or other chronic diseases and without regular medical treatment were examined. PWV estimation, carotid ultrasound with IMT measurement and atherosclerotic plaques amount calculation and EDVD estimation using reactive hyperemia test were performed. Results. Patients without CVD clinical signs rather often reveal arterial wall lesions already in the younger age group (mean age 40.9±8.7: reduced EDVD – in 26% of the cases, the presence of atherosclerotic plaques – in 22%, increased PWV – in 15%, increased IMT – in 8%. The prevalence of arterial wall alterations in the older age group (mean age 61.19±8.5 increase many-fold. All arterial wall parameters correlate with age. The stronger correlation was revealed between IMT and the amount of atherosclerotic plaques: r=0.46 (р<0.001 in the younger group and r=0.47 (р<0.001 in the older one. We didn’t find any relationship between PWV and EDVD in the younger group and between PWV and the amount of atherosclerotic plaques in the older one. Thickened carotid intima-media increases the risk of arterial stiffness by 2.3 times.Conclusion. Estimation of the state of arterial wall in people of young age without CVD allows detecting individuals who require active CVD prevention. Increased stiffness of arterial wall and the development

  15. Non-invasive Ultrasonic Measurements of Small Mechanical Alterations in Sub-millimeter Walls of Arteries and Phantoms

    Science.gov (United States)

    Brum, J.; Ramos, A.; Bazan, I.; Negreira, C.; Ramirez, A.; Diez, L.

    The detection of changes in the properties of the walls in blood vessels (e.g. modifications in thickness or elasticity) is a promising way for the early diagnosis of cardiovascular diseases (e.g. atherosclerosis), and some attempts have been made using classic ultrasonic images. However, to obtain a reliable non-invasive estimation of these changes still presents many challenges that must be overcome, in particular, to achieve an accurate estimation of the vessel wall thickness, which usually is associated to strain and elasticity alterations happening before the cardiovascular disease presents clinical symptom; to solve efficiently these aspects is a very difficult task. In this work, the application to vessels of a recent ultrasonic method developed by the authors for estimating wall thicknesses is described. This method (based on high-resolution power spectral density - PSD) and its algorithmic responses were tested on an arterial phantom under physiological conditions of flow and pressure, and some results are compared to those obtained using a direct-time thickness estimation and with the resolutions related to our alternative cross-correlation option shown in previous papers. A higher spatial resolution is obtained, for experimental multi-pulse ultrasonic echoes, with this PSD method in comparison to those based on conventional echography, cross correlation operators or other spectral options.

  16. Thermal effects on transverse domain wall dynamics in magnetic nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Leliaert, J., E-mail: jonathan.leliaert@ugent.be [Department of Electrical Energy, Systems and Automation, Ghent University, 9000 Gent (Belgium); Department of Solid State Sciences, Ghent University, 9000 Gent (Belgium); Van de Wiele, B.; Vandermeulen, J.; Coene, A.; Dupré, L. [Department of Electrical Energy, Systems and Automation, Ghent University, 9000 Gent (Belgium); Vansteenkiste, A.; Waeyenberge, B. Van [Department of Solid State Sciences, Ghent University, 9000 Gent (Belgium); Laurson, L. [COMP Centre of Excellence and Helsinki Institute of Physics, Department of Applied Physics, Aalto University School of Science, P.O. Box 11100, FI-00076 Aalto (Finland); Durin, G. [Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino (Italy); ISI Foundation, Via Alassio 11/c, 10126 Torino (Italy)

    2015-05-18

    Magnetic domain walls are proposed as data carriers in future spintronic devices, whose reliability depends on a complete understanding of the domain wall motion. Applications based on an accurate positioning of domain walls are inevitably influenced by thermal fluctuations. In this letter, we present a micromagnetic study of the thermal effects on this motion. As spin-polarized currents are the most used driving mechanism for domain walls, we have included this in our analysis. Our results show that at finite temperatures, the domain wall velocity has a drift and diffusion component, which are in excellent agreement with the theoretical values obtained from a generalized 1D model. The drift and diffusion component are independent of each other in perfect nanowires, and the mean square displacement scales linearly with time and temperature.

  17. Comparison between Carotid Artery Wall Thickness Measured by Multidetector Row Computed Tomography Angiography and Intimae-Media Thickness Measured by Sonography

    OpenAIRE

    Živorad N. Savić; Ivan I. Soldatović; Milan D. Brajović; Aleksandra M. Pavlović; Dušan R. Mladenović; Vesna D. Škodrić-Trifunović

    2011-01-01

    The increased thickness of the carotid wall >1 mm is a significant predictor of coronary and cerebrovascular diseases. The purpose of our study was to assess the agreement between multidetector row computed tomography angiography (MDCTA) in measuring carotid artery wall thickness (CAWT) and color Doppler ultrasound (CD-US) in measuring intimae-media thickness (IMT). Eighty-nine patients (aged 35–81) were prospectively analyzed using a 64-detector MDCTA and a CD-US scanner. Continuous data wer...

  18. Quantifying [{sup 18}F]fluorodeoxyglucose uptake in the arterial wall: the effects of dual time-point imaging and partial volume effect correction

    Energy Technology Data Exchange (ETDEWEB)

    Blomberg, Bjoern A. [University Medical Center Utrecht, Department of Radiology, Utrecht (Netherlands); Odense University Hospital, Department of Nuclear Medicine, Odense (Denmark); Bashyam, Arjun; Ramachandran, Abhinay; Gholami, Saeid; Houshmand, Sina; Salavati, Ali; Werner, Tom; Alavi, Abass [Hospital of the University of Pennsylvania, Department of Radiology, Philadelphia, PA (United States); Zaidi, Habib [Geneva University Hospital, Division of Nuclear Medicine and Molecular Imaging, Geneva (Switzerland); University of Groningen, Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, Groningen (Netherlands)

    2015-08-15

    The human arterial wall is smaller than the spatial resolution of current positron emission tomographs. Therefore, partial volume effects should be considered when quantifying arterial wall {sup 18}F-FDG uptake. We evaluated the impact of a novel method for partial volume effect (PVE) correction with contrast-enhanced CT (CECT) assistance on quantification of arterial wall {sup 18}F-FDG uptake at different imaging time-points. Ten subjects were assessed by CECT imaging and dual time-point PET/CT imaging at approximately 60 and 180 min after {sup 18}F-FDG administration. For both time-points, uptake of {sup 18}F-FDG was determined in the aortic wall by calculating the blood pool-corrected maximum standardized uptake value (cSUV{sub MAX}) and cSUV{sub MEAN}. The PVE-corrected SUV{sub MEAN} (pvcSUV{sub MEAN}) was also calculated using {sup 18}F-FDG PET/CT and CECT images. Finally, corresponding target-to-background ratios (TBR) were calculated. At 60 min, pvcSUV{sub MEAN} was on average 3.1 times greater than cSUV{sub MAX} (P <.0001) and 8.5 times greater than cSUV{sub MEAN} (P <.0001). At 180 min, pvcSUV{sub MEAN} was on average 2.6 times greater than cSUV{sub MAX} (P <.0001) and 6.6 times greater than cSUV{sub MEAN} (P <.0001). This study demonstrated that CECT-assisted PVE correction significantly influences quantification of arterial wall {sup 18}F-FDG uptake. Therefore, partial volume effects should be considered when quantifying arterial wall {sup 18}F-FDG uptake with PET. (orig.)

  19. Reconstruction of three-dimensional coronary arterial dynamics from multi-view angiogram sequences

    Institute of Scientific and Technical Information of China (English)

    SUN Zheng; YU Dao-yin

    2006-01-01

    A method for reconstructing 3-D motion of coronary arteries from single-plane X-ray angiogram sequences on two approximately orthogonal views is proposed.2-D motion is firstly estimated separately along vascular centerlines extracted from angiographic projection pairs.The 3-D displacement vector of each arterial skeleton point at one instant is then reconstructed by calculating the spatial coordinates of its two ends from corresponding projections.3-D configuration and dynamics of arteries are finally characterized.The effectiveness of the algorithm has been demonstrated on vascular phantom images and clinical angiograms and results are encouraging.

  20. Arterialization and anomalous vein wall remodeling in varicose veins is associated with upregulated FoxC2-Dll4 pathway.

    Science.gov (United States)

    Surendran, Sumi; S Ramegowda, Kalpana; Suresh, Aarcha; Binil Raj, S S; Lakkappa, Ravi Kumar B; Kamalapurkar, Giridhar; Radhakrishnan, N; C Kartha, Chandrasekharan

    2016-04-01

    Varicose veins of lower extremities are a heritable common disorder. Mechanisms underlying its pathogenesis are still vague. Structural failures such as valve weakness and wall dilatation in saphenous vein result in venous retrograde flow in lower extremities of body. Reflux of blood leads to distal high venous pressure resulting in distended veins. In an earlier study, we observed a positive association between c.-512C>T FoxC2 gene polymorphism and upregulated FoxC2 expression in varicose vein specimens. FoxC2 overexpression in vitro in venous endothelial cells resulted in the elevated mRNA expression of arterial endothelial markers such as Delta-like ligand 4 (Dll4) and Hairy/enhancer-of-split related with YRPW motif protein 2 (Hey2). We hypothesized that an altered FoxC2-Dll4 signaling underlies saphenous vein wall remodeling in patients with varicose veins. Saphenous veins specimens were collected from 22 patients with varicose veins and 20 control subjects who underwent coronary artery bypass grafting. Tissues were processed for paraffin embedding and sections were immunostained for Dll4, Hey2, EphrinB2, α-SMA, Vimentin, and CD31 antigens and examined under microscope. These observations were confirmed by quantitative real-time PCR and western blot analysis. An examination of varicose vein tissue specimens by immunohistochemistry indicated an elevated expression of Notch pathway components, such as Dll4, Hey2, and EphrinB2, and smooth muscle markers, which was further confirmed by gene and protein expression analyses. We conclude that the molecular alterations in Dll4-Hey2 signaling are associated with smooth muscle cell hypertrophy and hyperplasia in varicose veins. Our observations substantiate a significant role for altered FoxC2-Dll4 signaling in structural alterations of saphenous veins in patients with varicose veins.

  1. Bilateral severe carotid artery stenosis or occlusion : cerebral autoregulation dynamics and collateral flow patterns

    OpenAIRE

    Reinhard, Matthias; Müller, Thomas; Roth, Markus; Guschlbauer, Brigitte; Timmer, Jens; Hetzel, Andreas

    2003-01-01

    BackgroundBilateral severe obstruction of the internal carotid artery is a hemodynamically critical state. We aimed to (1) analyze dynamic cerebral autoregulation (DCA) in affected patients, and (2) to correlate DCA data with different collateral flow patterns.MethodsDCA was assessed noninvasively by transfer function analysis (phase shift) of respiratory-induced oscillations at 0.1 Hz of arterial blood pressure (Finapres method) and cerebral blood flow velocity (transcranial Doppler) in 30 p...

  2. Prevalence and Risk Factors of Carotid Vessel Wall Inflammation in Coronary Artery Disease Patients FDG-PET and CT Imaging Study

    NARCIS (Netherlands)

    J. Bucerius; R. Duivenvoorden; V. Mani; C. Moncrieff; J.H.F. Rudd; C. Calcagno; J. Machac; V. Fuster; M.E. Farkouh; Z.A. Fayad

    2011-01-01

    OBJECTIVES We investigated the prevalence and clinical risk factors of carotid vessel wall inflammation by means of (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) in a population consisting of coronary artery disease (CAD) patients. BACKGROUND The atherosclerotic disease process is

  3. Automatic Generation of Individual Finite-Element Models for Computational Fluid Dynamics and Computational Structure Mechanics Simulations in the Arteries

    Science.gov (United States)

    Hazer, D.; Schmidt, E.; Unterhinninghofen, R.; Richter, G. M.; Dillmann, R.

    2009-08-01

    Abnormal hemodynamics and biomechanics of blood flow and vessel wall conditions in the arteries may result in severe cardiovascular diseases. Cardiovascular diseases result from complex flow pattern and fatigue of the vessel wall and are prevalent causes leading to high mortality each year. Computational Fluid Dynamics (CFD), Computational Structure Mechanics (CSM) and Fluid Structure Interaction (FSI) have become efficient tools in modeling the individual hemodynamics and biomechanics as well as their interaction in the human arteries. The computations allow non-invasively simulating patient-specific physical parameters of the blood flow and the vessel wall needed for an efficient minimally invasive treatment. The numerical simulations are based on the Finite Element Method (FEM) and require exact and individual mesh models to be provided. In the present study, we developed a numerical tool to automatically generate complex patient-specific Finite Element (FE) mesh models from image-based geometries of healthy and diseased vessels. The mesh generation is optimized based on the integration of mesh control functions for curvature, boundary layers and mesh distribution inside the computational domain. The needed mesh parameters are acquired from a computational grid analysis which ensures mesh-independent and stable simulations. Further, the generated models include appropriate FE sets necessary for the definition of individual boundary conditions, required to solve the system of nonlinear partial differential equations governed by the fluid and solid domains. Based on the results, we have performed computational blood flow and vessel wall simulations in patient-specific aortic models providing a physical insight into the pathological vessel parameters. Automatic mesh generation with individual awareness in terms of geometry and conditions is a prerequisite for performing fast, accurate and realistic FEM-based computations of hemodynamics and biomechanics in the

  4. Assessment of influence of traditional cardiovascular risk factors and inflammation on arterial wall structural characteristics in psoriatic arthritis

    Directory of Open Access Journals (Sweden)

    T V Korotaeva

    2009-01-01

    Full Text Available Assessment of influence of traditional cardiovascular risk factors and inflammation on arterial wall structural characteristics in psoriatic arthritis. Objective. To assess possibility of traditional cardiovascular risk (CVR factors application as markers of subclinical atherosclerosis in pts with psoriatic arthritis (PA. Material and methods. 130 pts with PA (51 male and 79 female without clinical signs of coronary heart disease (CHD and stroke. were included. Mean age was 43 years (39-48 years, mean PA duration – 7 years (2 months-42 years, mean psoriasis duration – 15 years (5,5 – 26 years. PA activity was assessed with DAS4. Age, total cholesterol (TC, high density lipoprotein (HDLP, low density lipoprotein (LDLP, C-reactive protein (CRP, fibrinogen, systolic blood pressure, body mass index (BMI, atherogenity coefficient (AC, relative risk of CHD development, presence of diabetes and smoking were evaluated. Mean and maximal intima-media complex thickness (IMCT of common carotid arteries was examined with duplex scanning. Results. TC, LDLP and AC elevation was revealed in all and BMI elevation – in one third of pts. In 55% of pts CVR was mean and higher, in 23,5% CVR was absent and in 21,5% CVR was below mean. CVR significantly correlated with mean and maximal carotid arteries IMCT (R=0,48, p<0,00001 and R=0,41, p<0,00001 and fibrinogen (R=0,22, p<0,011. In women CVR correlated with fibrinogen (R=0,27, p<0,16, BMI (R=0,35, p<0,16, mean and maximal carotid arteries IMCT (R=0,50, p<0,00001 and R=0,38, p<0,0005 respectively and psoriasis duration (R=0,30, p<0,006. In men CVR did not correlated with fibrinogen. CVR did not correlated with DAS4 and CRP. Conclusion. CVR in PA is not connected with traditional markers of inflammation andindex of clinical disease activity.

  5. Microemulsions as model fluids for enhanced oil recovery: dynamics adjacent to planar hydrophilic walls

    Science.gov (United States)

    Frielinghaus, H.; Holderer, O.; Lipfert, F.; Kerscher, M.; Mattauch, S.; Richter, D.

    2012-10-01

    After the dynamics of microemulsions adjacent to a planar hydrophilic wall have been characterized using grazing incidence neutron spin echo spectroscopy, the model of Seifert was employed to explain the discovered acceleration for the surface near lamellar ordered membranes. Reflections of hydrodynamic waves by the wall - or the volume conservation between the membrane and the wall - explain faster relaxations and, therefore, a lubrication effect that is important for flow fields in narrow pores. The whole scenery is now spectated by using different scenarios of a bicontinuous microemulsion exposed to clay particles and of a lamellar microemulsion adjacent to a planar wall. The Seifert concept could successfully be transferred to the new problems.

  6. Magnetic domain wall gratings for magnetization reversal tuning and confined dynamic mode localization

    Science.gov (United States)

    Trützschler, Julia; Sentosun, Kadir; Mozooni, Babak; Mattheis, Roland; McCord, Jeffrey

    2016-08-01

    High density magnetic domain wall gratings are imprinted in ferromagnetic-antiferromagnetic thin films by local ion irradiation by which alternating head-to-tail-to-head-to-tail and head-to-head-to-tail-to-tail spatially overlapping domain wall networks are formed. Unique magnetic domain processes result from the interaction of anchored domain walls. Non-linear magnetization response is introduced by the laterally distributed magnetic anisotropy phases. The locally varying magnetic charge distribution gives rise to localized and guided magnetization spin-wave modes directly constrained by the narrow domain wall cores. The exchange coupled multiphase material structure leads to unprecedented static and locally modified dynamic magnetic material properties.

  7. Carotid thin fluttering bands: A new element of arterial wall remodelling? An ultrasound study.

    Science.gov (United States)

    Costanzo, Luca; Sole, Andrea; Tamburino, Corrado; Di Pino, Luigi

    2015-10-01

    Carotid artery ultrasound is a non-invasive and reproducible technique used for early atherosclerotic assessment. Intimal flap has been described in the presence of dissection or mobile plaque rupture, however presence of carotid thin fluttering bands (TFBs) have not been described yet. To investigate frequency, characteristics and impact of TFBs in carotid lumen of patients who underwent carotid ultrasound scan (CUS). 3341 patients were admitted from January 2009 to January 2014. Patients with history of cerebral ischemia (CI) were excluded. In the cases in which TFBs were observed, a 3-months clinical and CUS follow-up (FU) was performed. TFBs were found in 71 patients (2.1%). The mean age was 63.41 ± 11.20 years (range 42-89). All patients showed a mean increase in intima-media thickness. We identified two subgroups: in 22 patients the TFB was related to a carotid plaque while in 49 no carotid plaque was found. TFB mostly originated in the carotid bulb (88.7%) and was similarly located in carotid arteries (49.3% left-side and 50.7% right-side). CUS and clinical FU were available for all patients (mean duration 25.34 months, median 19). CI occurred in none of the patients. TFB disappeared in 13 patients (18.3%) with no sign or symptoms of CI. In 3 of 49 patients without carotid plaque (6.1%), progressive thickening beneath TFB was observed. TFB is a rare finding. Longer FU is needed to evaluate its prognosis. To date, the pathophysiology is unknown, however it could be related to vascular remodeling. PMID:26179862

  8. Potential for tissue characterization of plaque and arterial wall using intravascular ultrasound

    Science.gov (United States)

    Sudhir, Krishnakutty; Fitzgerald, Peter J.; Yock, Paul G.

    1993-09-01

    Current intravascular ultrasound imaging technology is able to determine the extent and distribution of pathologic processes within the vessel wall, but is not highly sensitive in discriminating between different types of pathologic tissue. `Tissue characterization' refers to a set of computer-based techniques that utilize features of the ultrasound signal beyond basic amplitude to help define the structure of the tissue of interest. Although preliminary results with this approach are encouraging, additional work is needed to define its clinical application in vascular disease.

  9. A model of smooth muscle cell synchronization in the arterial wall

    DEFF Research Database (Denmark)

    Jacobsen, Jens Christian Brings; Aalkjær, Christian; Nilsson, Holger;

    2007-01-01

    . The simulated results point to a permissive role of cGMP in establishing intercellular synchronization. In sufficient concentration, cGMP may activate a cGMP-sensitive calcium-dependent chloride channel, causing a tight spatiotemporal coupling between release of sarcoplasmic reticulum calcium, membrane...... depolarization, and influx of extracellular calcium. Low [cGMP] is associated only with unsynchronized waves. At intermediate concentrations, cells display either waves or whole cell oscillations, but these remain unsynchronized between cells. Whole cell oscillations are associated with rhythmic variation...... in membrane potential and flow of current through gap junctions. The amplitude of these oscillations in potential grows with increasing [cGMP], and, past a certain threshold, they become strong enough to entrain all cells in the vascular wall, thereby initiating sustained vasomotion. In this state...

  10. Stiffness Indices and Fractal Dimension relationship in Arterial Pressure and Diameter Time Series in-Vitro

    Science.gov (United States)

    Cymberknop, L.; Legnani, W.; Pessana, F.; Bia, D.; Zócalo, Y.; Armentano, R. L.

    2011-12-01

    The advent of vascular diseases, such as hypertension and atherosclerosis, is associated to significant alterations in the physical properties of arterial vessels. Evaluation of arterial biomechanical behaviour is related to the assessment of three representative indices: arterial compliance, arterial distensibility and arterial stiffness index. Elasticity is the most important mechanical property of the arterial wall, whose natures is strictly non-linear. Intervention of elastin and collagen fibres, passive constituent elements of the arterial wall, is related to the applied wall stress level. Concerning this, appropriate tools are required to analyse the temporal dynamics of the signals involved, in order to characterize the whole phenomenon. Fractal geometry can be mentioned as one of those techniques. The aim of this study consisted on arterial pressure and diameter signals processing, by means of nonlinear techniques based on fractal geometry. Time series morphology was related to different arterial stiffness states, generated by means of blood flow variations, during experiences performed in vitro.

  11. The subpetrous carotid wall hematoma. A sign of spontaneous dissection of the internal carotid artery on non-enhanced computed tomography. A retrospective study

    Energy Technology Data Exchange (ETDEWEB)

    Jensen-Kondering, U. [Univ. Hospital Schleswig-Holstein, Kiel (Germany). Dept. of Radiology and Neuroradiology; Univ. Hospital Schleswig-Holstein, Kiel (Germany). Dept. of Neurology; Huhndorf, M.; Madjidyar, J.; Jansen, O. [Univ. Hospital Schleswig-Holstein, Kiel (Germany). Dept. of Radiology and Neuroradiology

    2015-03-15

    Spontaneous dissection of the internal carotid artery (CAD) is an increasingly recognized cause for stroke especially in young and middle-aged patients. We hypothesized that non-enhanced cranial computed tomography (NECCT) can visualize the subpetrous carotid wall hematoma and thus enable identification of patients with CAD. We retrospectively reviewed patients with confirmed CAD (n=21) and a control group with ischemic symptoms but without CAD (n=42) who received NECCT at admission. Two independent neuroradiologists rated the presence and shape of SPH, density and diameter of the subpetrous internal carotid artery. Additionally, we correlated the shape of the subpetrous carotid wall hematoma with the grade of stenosis on subsequent angiographic imaging. The subpetrous carotid wall hematoma was present in 14 of 21 patients (Cohen's k = 0.67). Mean diameter was 6.95 ± 1.05 mm in dissected vessels and 5.71 ± 1.52 mm in the contralateral vessel (p<0.05). Mean difference in vessel density was 15.05 ± 8.01 HU (p<0.01). Median grade of stenosis was significantly higher in patients with a full moon- shaped (n=11) than crescent-shaped (n=3) subpetrous carotid wall hematoma (21% vs. 80%, p<0.05). Two-thirds of patients with CAD were correctly identified on NECCT. The extracranial carotid artery should be evaluated in patients with symptoms of cerebral ischemia.

  12. Randomised comparison of the effects of nicardipine and esmolol on coronary artery wall stress: implications for the risk of plaque rupture

    OpenAIRE

    Williams, M.; Low, C.; Wilkins, G; Stewart, R

    2000-01-01

    OBJECTIVE—To determine whether the β blocker esmolol reduces coronary artery wall stress more than the short acting dihydropyridine calcium antagonist nicardipine.
DESIGN—Randomised double blind placebo controlled trial.
SETTING—Tertiary cardiology centre.
PATIENTS—Patients with coronary artery disease.
INTERVENTIONS—20 patients were randomised double blind to an infusion of nicardipine (n = 10) or esmolol (n = 10) titrated to reduce systolic blood pressure by 20 mm Hg.
MAIN OUTCOME MEASURES—...

  13. wall

    Directory of Open Access Journals (Sweden)

    Irshad Kashif

    2016-01-01

    Full Text Available Maintaining indoor climatic conditions of buildings compatible with the occupant comfort by consuming minimum energy, especially in a tropical climate becomes a challenging problem for researchers. This paper aims to investigate this problem by evaluating the effect of different kind of Photovoltaic Trombe wall system (PV-TW on thermal comfort, energy consumption and CO2 emission. A detailed simulation model of a single room building integrated with PV-TW was modelled using TRNSYS software. Results show that 14-35% PMV index and 26-38% PPD index reduces as system shifted from SPV-TW to DGPV-TW as compared to normal buildings. Thermal comfort indexes (PMV and PPD lie in the recommended range of ASHARE for both DPV-TW and DGPV-TW except for the few months when RH%, solar radiation intensity and ambient temperature were high. Moreover PVTW system significantly reduces energy consumption and CO2 emission of the building and also 2-4.8 °C of temperature differences between indoor and outdoor climate of building was examined.

  14. The Effect of Hypertension on the Transport of LDL Across the Deformable Arterial Wall

    Science.gov (United States)

    Dabagh, Mahsa; Jalali, Payman

    2010-05-01

    The influences of increased endothelial cell turnover and deformation of the intima on the transport of low-density lipoprotein (LDL) under hypertension are investigated by applying a multilayered model of aortic wall. The thickness and properties of the endothelium, intima, internal elastic lamina (IEL), and media are affected by the transmural pressure. Navier-Stokes and Brinkman equations are applied for the transport of the transmural flow and the convective-diffusion equation is solved for LDL transport. LDL macromolecules enter the intima through leaky junctions, and then pass through the media layer where they permeate over the surface of smooth muscle cells (SMC). Uptake of LDL by cells is modeled through a uniform reaction evenly distributed in the macroscopically homogeneous media layer. The results show that transmural pressure significantly affects the LDL fluxes across the leaky junction, the intima, fenestral pores in the IEL, and the media layer. Many realistic predictions including the proper magnitudes for the permeability of endothelium and intimal layers, and the hydraulic conductivity of all layers as well as their trends with pressure are predicted by the present model.

  15. Influence of Dzialoshinskii–Moriya interaction on static and dynamic properties of a transverse domain wall

    Energy Technology Data Exchange (ETDEWEB)

    Kravchuk, Volodymyr P., E-mail: vkravchuk@bitp.kiev.ua

    2014-10-01

    It is shown that the Dzialoshinskii–Moriya interaction leads to asymmetrical deformation of the transverse domain wall profile in one-dimensional biaxial magnet. Amplitude of the deformation is linear with respect to the Dzialoshinskii constant D. Corrections caused by the Dzialoshinskii–Moriya interaction are obtained for the number of the domain wall parameters: energy density, Döring mass, and Walker field. The modified q–Φ model with an additional pair of conjugated collective variables is proposed for studying the dynamical properties of the wall with taking into account the internal degrees of freedom. - Highlights: • Dzialoshinskii–Moriya interaction deforms the domain wall profile asymmetrically. • Extended model with 2 pairs of collective variables is proposed for a domain wall. • The Walker field is slightly changed due to the Dzialoshinskii–Moriya interaction.

  16. 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.

  17. EFFECTS OF PARENT ARTERY SEGMENTATION AND ANEURISMALWALL ELASTICITY ON PATIENT-SPECIFIC HEMODYNAMIC SIMULATIONS

    Institute of Scientific and Technical Information of China (English)

    CHEN Jia-liang; DING Guang-hong; YANG Xin-jian; LI Hai-yun

    2011-01-01

    It is well known that hemodynamics and wall tension play an important role in the formation,growth and rupture of aneurysms.In the present study,the authors investigated the influence of parent artery segmentation and aneurismal-wall elasticity on patient-specific hemodynamic simulations with two patient-specific eases of cerebral aneurysms.Realistic models of the aneurysms were constructed from 3-D angiography images and blood flow dynamics was studied under physiologically representative waveform of inflow.For each aneurysm three computational models were constructed:Model 1 with more extensive upstream parent artery with the rigid arterial and aneurismal wall,Model 2 with the partial upstream parent artery with the elastic arterial and aneurismal wall,Model 3 with more extensive upstream parent artery with the rigid wall for arterial wall far from the aneurysm and the elastic wall for arterial wall near the aneurysm.The results show that Model 1 could predict complex intra-aneurismal flow patterns and wall shear stress distribution in the aneurysm,but is unable to give aneurismal wall deformation and tension,Model 2 demonstrates aneurismal wall deformation and tension,but fails to properly model inflow pattern contributed by the upstream parent artery,resulting in local misunderstanding Wall Shear Stress (WSS) distribution,Model 3 can overcome limitations of the former two models,and give an overall and accurate analysis on intra-aneurismal flow patterns,wall shear stress distribution,aneurismal-wall deformation and tension.Therefore we suggest that the proper length of extensive upstream parent artery and aneuri-smal-wall elasticity should be considered carefully in establishing computational model to predict the intra-aneurismal hemodynamic and wall tension.

  18. Dynamic Insulation Systems: Experimental Analysis on a Parietodynamic Wall

    OpenAIRE

    Serra, Valentina; Fantucci, Stefano; Perino, Marco

    2015-01-01

    This paper shows the results of an extensive experimental campaign on a ventilated opaque double skin façade based on hollow clay bricks. The winter thermal performances of the dynamic insulated systems were investigated on two different full scale façade configurations through an experimental campaign in double climatic chamber and guarded heat flow meter apparatus. The laboratory tests on dynamic insulated façade (DIF) in both exhaust and supply configurations show respectively an effective...

  19. Charge, junctions and the scaling dynamics of domain wall networks

    CERN Document Server

    Battye, Richard A

    2010-01-01

    It has been shown that superconducting domain walls in a model with U(1) x Z2 symmetry can form long-lived loops called kinky vortons from random initial conditions in the broken field and a uniform charged background in (2+1) dimensions. In this paper we investigate a similar model with a hyper-cubic symmetry coupled to an unbroken U(1) in which the domain walls can form junctions and hence a lattice. We call this model the charge-coupled cubic-anisotropy (CCCA) model. First, we present a detailed parametric study of the U(1) x Z2 model; features which we vary include the nature of the initial conditions and the coupling constants. This allows us to identify interesting parameters to vary in the more complicated, and hence more computationally intensive, CCCA models. In particular we find that the coefficient of the interaction term can be used to engineer three separate regimes: phase mixing, condensation and phase separation with the condensation regime corresponding to a single value of the coupling const...

  20. Effects of dynamic compression on lentiviral transduction in an in vitro airway wall model

    OpenAIRE

    Tomei, A. A.; Choe, M. M.; Swartz, M. A.

    2008-01-01

    Asthmatic patients are more susceptible to viral infection, and we asked whether dynamic strain on the airway wall (such as that associated with bronchoconstriction) would influence the rate of viral infection of the epithelial and subepithelial cells. To address this, we characterized the barrier function of a three-dimensional culture model of the bronchial airway wall mucosa, modified the culture conditions for optimization of ciliogenesis, and compared epithelial and subepithelial green f...

  1. Nonlinear Dynamic Analysis of Railway Wagon End Wall under the Action of Granular Media

    OpenAIRE

    Jing Wang; Qichang Zhang; Yuebin Yu; Jianxin Han; Dong Li

    2015-01-01

    In wagon end wall system under the action of granular media, the model of the wall is the result of multiple factors. To figure out how the key factors act, the large amplitude vibration together with the contribution from the action of granular media to build the nonlinear dynamics equation of the wagon end wall has been taken into account. In this paper, the effects of varying damping, added mass, and force due to the action of granular media on the patterns of movement and response perform...

  2. A dynamic slip boundary condition for wall-modeled large-eddy simulation

    Science.gov (United States)

    Bose, S. T.; Moin, P.

    2014-01-01

    Wall models for large-eddy simulation (LES) are a necessity to remove the prohibitive resolution requirements of near-wall turbulence in high Reynolds turbulent flows. Traditional wall models often rely on assumptions about the local state of the boundary layer (e.g., logarithmic velocity profiles) and require a priori prescription of tunable model coefficients. In the present study, a slip velocity boundary condition for the filtered velocity field is obtained from the derivation of the LES equations using a differential filter. A dynamic procedure for the local slip length is additionally formulated making the slip velocity wall model free of any a priori specified coefficients. The accuracy of the dynamic slip velocity wall model is tested in a series of turbulent channel flows at varying Reynolds numbers and in the LES of a National Advisory Committee for Aeronautics (NACA) 4412 airfoil at near-stall conditions. The wall-modeled simulations are able to accurately predict mean flow characteristics, including the formation of a trailing-edge separation bubble in NACA 4412 configuration. The validation cases demonstrate the effectiveness of this wall-modeling approach in both attached and separated flow regimes.

  3. Nonlinear Dynamic Analysis of Railway Wagon End Wall under the Action of Granular Media

    Directory of Open Access Journals (Sweden)

    Jing Wang

    2015-01-01

    Full Text Available In wagon end wall system under the action of granular media, the model of the wall is the result of multiple factors. To figure out how the key factors act, the large amplitude vibration together with the contribution from the action of granular media to build the nonlinear dynamics equation of the wagon end wall has been taken into account. In this paper, the effects of varying damping, added mass, and force due to the action of granular media on the patterns of movement and response performance were discussed in detail. Furthermore, the finite element model of end wall-granular media was established. It proves that the theoretical result is correct compared with the FEM results. It indicates that the resonance frequency of the wall declines with the increase of the height of granular media, while the frequency increases with the increase of the particle size of granular media. The nonlinear dynamics of the wall is less affected by the height ratio and particle size of granular media, while it is greatly affected by the height and the thickness of wall, which should be seriously considered in structural design of the wagon.

  4. Feasibility Study of Ex Ovo Chick Chorioallantoic Artery Model for Investigating Pulsatile Variation of Arterial Geometry.

    Directory of Open Access Journals (Sweden)

    Kweon-Ho Nam

    Full Text Available Despite considerable research efforts on the relationship between arterial geometry and cardiovascular pathology, information is lacking on the pulsatile geometrical variation caused by arterial distensibility and cardiomotility because of the lack of suitable in vivo experimental models and the methodological difficulties in examining the arterial dynamics. We aimed to investigate the feasibility of using a chick embryo system as an experimental model for basic research on the pulsatile variation of arterial geometry. Optical microscope video images of various arterial shapes in chick chorioallantoic circulation were recorded from different locations and different embryo samples. The high optical transparency of the chorioallantoic membrane (CAM allowed clear observation of tiny vessels and their movements. Systolic and diastolic changes in arterial geometry were visualized by detecting the wall boundaries from binary images. Several to hundreds of microns of wall displacement variations were recognized during a pulsatile cycle. The spatial maps of the wall motion harmonics and magnitude ratio of harmonic components were obtained by analyzing the temporal brightness variation at each pixel in sequential grayscale images using spectral analysis techniques. The local variations in the spectral characteristics of the arterial wall motion were reflected well in the analysis results. In addition, mapping the phase angle of the fundamental frequency identified the regional variations in the wall motion directivity and phase shift. Regional variations in wall motion phase angle and fundamental-to-second harmonic ratio were remarkable near the bifurcation area. In summary, wall motion in various arterial geometry including straight, curved and bifurcated shapes was well observed in the CAM artery model, and their local and cyclic variations could be characterized by Fourier and wavelet transforms of the acquired video images. The CAM artery model with

  5. Heterogeneity and weak coupling may explain the synchronization characteristics of cells in the arterial wall

    DEFF Research Database (Denmark)

    Jacobsen, Jens Christian Brings; Aalkjær, Christian; Matchkov, Vladimir;

    2008-01-01

    are enrolled into synchronized oscillation.Simulations of coupled SMCs show that the experimentally observed cellular recruitment, the presence of quiescent cells and the variation in oscillation frequency may arise if the cell population is phenotypically heterogeneous. In this case, quiescent cells can...... be entrained at the onset of vasomotion by the collective driving force from the synchronized oscillations in the membrane potential of the surrounding cells. Partial synchronization arises with an increase in the concentration of cyclic guanosine monophosphate, but in a heterogeneous cell population complete......Vascular smooth muscle cells (SMCs) exhibit different types of calcium dynamics. Static vascular tone is associated with unsynchronized calcium waves and the developed force depends on the number of recruited cells. Global calcium transients synchronized among a large number of cells cause rhythmic...

  6. Computational study of the effect of dynamic wall confinement on ventricular filling

    Science.gov (United States)

    Zheng, Xudong; Xue, Qian

    2013-11-01

    Ventricular filling is a major cardiac phase in which the freshly oxygenated blood in the left atrium (LA) enters the left ventricle (LV). There is an increasing consensus that dynamics of transmitral blood flow during filling plays a critical role in dictating overall cardiac health and predicting early changes in cardiac function. The ventricular flow during filling is determined by the interplay of incoming mitral jet and myocardial wall confinement and manifested by a complex morphing pattern of an asymmetric vortex ring. In the current study, we employ computational simulations to explore the effects of dynamic wall confinement on ventricular flow in an idealized left ventricle model. The effects of radial and longitudinal confinement as well as wall motion will be investigated, with special interests on vortex dynamics, such as vortex ring tilting, pinch off and breakdown, intraventricular pressure drop, filling velocity, energy dissipation and blood mixing.

  7. DBIO Best Thesis Award: Mechanics, Dynamics, and Organization of the Bacterial Cytoskeleton and Cell Wall

    Science.gov (United States)

    Wang, Siyuan

    2012-02-01

    Bacteria come in a variety of shapes. While the peptidoglycan (PG) cell wall serves as an exoskeleton that defines the static cell shape, the internal bacterial cytoskeleton mediates cell shape by recruiting PG synthesis machinery and thus defining the pattern of cell-wall synthesis. While much is known about the chemistry and biology of the cytoskeleton and cell wall, much of their biophysics, including essential aspects of the functionality, dynamics, and organization, remain unknown. This dissertation aims to elucidate the detailed biophysical mechanisms of cytoskeleton guided wall synthesis. First, I find that the bacterial cytoskeleton MreB contributes nearly as much to the rigidity of an Escherichia coli cell as the cell wall. This conclusion implies that the cytoskeletal polymer MreB applies meaningful force to the cell wall, an idea favored by theoretical modeling of wall growth, and suggests an evolutionary origin of cytoskeleton-governed cell rigidity. Second, I observe that MreB rotates around the long axis of E. coli, and the motion depends on wall synthesis. This is the first discovery of a cell-wall assembly driven molecular motor in bacteria. Third, I prove that both cell-wall synthesis and the PG network have chiral ordering, which is established by the spatial pattern of MreB. This work links the molecular structure of the cytoskeleton and of the cell wall with organismal-scale behavior. Finally, I develop a mathematical model of cytoskeleton-cell membrane interactions, which explains the preferential orientation of different cytoskeleton components in bacteria.

  8. Middle cerebral artery blood velocity and cerebral blood flow and O2 uptake during dynamic exercise

    DEFF Research Database (Denmark)

    Madsen, P L; Sperling, B K; Warming, T;

    1993-01-01

    Results obtained by the 133Xe clearance method with external detectors and by transcranial Doppler sonography (TCD) suggest that dynamic exercise causes an increase of global average cerebral blood flow (CBF). These data are contradicted by earlier data obtained during less-well-defined conditions....... To investigate this controversy, we applied the Kety-Schmidt technique to measure the global average levels of CBF and cerebral metabolic rate of oxygen (CMRO2) during rest and dynamic exercise. Simultaneously with the determination of CBF and CMRO2, we used TCD to determine mean maximal flow velocity...... in the middle cerebral artery (MCA Vmean). For values of CBF and MCA Vmean a correction for an observed small drop in arterial PCO2 was carried out. Baseline values for global CBF and CMRO2 were 50.7 and 3.63 ml.100 g-1.min-1, respectively. The same values were found during dynamic exercise, whereas a 22% (P

  9. Imaging of vascular dynamics within the foot using dynamic diffuse optical tomography to diagnose peripheral arterial disease

    Science.gov (United States)

    Khalil, M. A.; Kim, H. K.; Hoi, J. W.; Kim, I.; Dayal, R.; Shrikande, G.; Hielscher, A. H.

    2013-03-01

    Peripheral Arterial Disease (PAD) is the narrowing of the functional area of the artery generally due to atherosclerosis. It affects between 8-12 million people in the United States and if untreated this can lead to ulceration, gangrene and ultimately amputation. The current diagnostic method for PAD is the ankle-brachial index (ABI). The ABI is a ratio of the patient's systolic blood pressure in the foot to that of the brachial artery in the arm, a ratio below 0.9 is indicative of affected vasculature. However, this method is ineffective in patients with calcified arteries (diabetic and end-stage renal failure patients), which falsely elevates the ABI recording resulting in a false negative reading. In this paper we present our results in a pilot study to deduce optical tomography's ability to detect poor blood perfusion in the foot. We performed an IRB approved 30 patient study, where we imaged the feet of the enrolled patients during a five stage dynamic imaging sequence. The patients were split up into three groups: 10 healthy subjects, 10 PAD patients and 10 PAD patients with diabetes and they were imaged while applying a pressure cuff to their thigh. Differences in the magnitude of blood pooling in the foot and rate at which the blood pools in the foot are all indicative of arterial disease.

  10. Threshold Setting for Likelihood Function for Elasticity-Based Tissue Classification of Arterial Walls by Evaluating Variance in Measurement of Radial Strain

    Science.gov (United States)

    Tsuzuki, Kentaro; Hasegawa, Hideyuki; Kanai, Hiroshi; Ichiki, Masataka; Tezuka, Fumiaki

    2008-05-01

    Pathologic changes in arterial walls significantly influence their mechanical properties. We have developed a correlation-based method, the phased tracking method [H. Kanai et al.: IEEE Trans. Ultrason. Ferroelectr. Freq. Control 43 (1996) 791], for measurement of the regional elasticity of the arterial wall. Using this method, elasticity distributions of lipids, blood clots, fibrous tissue, and calcified tissue were measured in vitro by experiments on excised arteries (mean±SD: lipids 89±47 kPa, blood clots 131 ±56 kPa, fibrous tissue 1022±1040 kPa, calcified tissue 2267 ±1228 kPa) [H. Kanai et al.: Circulation 107 (2003) 3018; J. Inagaki et al.: Jpn. J. Appl. Phys. 44 (2005) 4593]. It was found that arterial tissues can be classified into soft tissues (lipids and blood clots) and hard tissues (fibrous tissue and calcified tissue) on the basis of their elasticity. However, there are large overlaps between elasticity distributions of lipids and blood clots and those of fibrous tissue and calcified tissue. Thus, it was difficult to differentiate lipids from blood clots and fibrous tissue from calcified tissue by simply thresholding elasticity value. Therefore, we previously proposed a method by classifying the elasticity distribution in each region of interest (ROI) (not a single pixel) in an elasticity image into lipids, blood clots, fibrous tissue, or calcified tissue based on a likelihood function for each tissue [J. Inagaki et al.: Jpn. J. Appl. Phys. 44 (2006) 4732]. In our previous study, the optimum size of an ROI was determined to be 1,500 µm in the arterial radial direction and 1,500 µm in the arterial longitudinal direction [K. Tsuzuki et al.: Ultrasound Med. Biol. 34 (2008) 573]. In this study, the threshold for the likelihood function used in the tissue classification was set by evaluating the variance in the ultrasonic measurement of radial strain. The recognition rate was improved from 50 to 54% by the proposed thresholding.

  11. Dynamical corrections to the anomalous holographic soft-wall model: the pomeron and the odderon

    Energy Technology Data Exchange (ETDEWEB)

    Capossoli, Eduardo Folco [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ (Brazil); Colegio Pedro II, Departamento de Fisica, Rio de Janeiro, RJ (Brazil); Li, Danning [Institute of Theoretical Physics, Chinese Academy of Science (ITP, CAS), Beijing (China); Boschi-Filho, Henrique [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ (Brazil)

    2016-06-15

    In this work we use the holographic soft-wall AdS/QCD model with anomalous dimension contributions coming from two different QCD beta functions to calculate the masses of higher spin glueball states for both even and odd spins and their Regge trajectories, related to the pomeron and the odderon, respectively. We further investigate this model taking into account dynamical corrections due to a dilaton potential consistent with the Einstein equations in five dimensions. The results found in this work for the Regge trajectories within the anomalous soft-wall model with dynamical corrections are consistent with those present in the literature. (orig.)

  12. Dynamic characteristics of multi-walled carbon nanotubes under a transverse magnetic field

    Indian Academy of Sciences (India)

    S Li; H J Xie; X Wang

    2011-02-01

    This paper reports the results of an investigation into the effect of transverse magnetic fields on dynamic characteristics of multi-walled carbon nanotubes (MWNTs). Couple dynamic equations of MWNTs subjected to a transverse magnetic field are derived and solved by considering the Lorentz magnetic forces induced by a transverse magnetic field exerted on MWCNTs. Results show that the transverse magnetic field exerted on MWNTs makes the lowest frequency of the MWNTs nonlinearly decrease and the highest frequency, changeless. When the strength of applied transverse magnetic fields is larger than a given value the two walls of MWNTs appear in the radial and axial coaxial vibration phenomena.

  13. PUVB-mediated prevention of luminal narrowing after arterial wall injury: modulation of mechanical arterial properties as a putative mechanism of action

    Science.gov (United States)

    Perree, Jop; Kerindongo, Raphaela P.; van Leeuwen, Ton G. J. M.

    2001-10-01

    In a previous study we have found that the photodynamic modality PUVB (8-methoxy-Psoralen + UVB) reduces luminal narrowing after arterial endovascular injury. We hypothesized that PUVB may modulate the arterial mechanical properties and tested this hypothesis by measuring the stress as a function of the strain in segments of carotid artery. Furthermore, we have investigated the potential for PUVB-induced cross-linking of extracellular matrix proteins by gel electrophoresis. It was found that both techniques were suitable for testing our hypotheses as evidenced by a statistically significant difference for the positive control. However, no differences between A) control, B) sensitizer only, C) light only and D) PUVB-treated samples could be found with respect to macro- and micro-mechanical properties. Therefore, the hypothesis that PUVB mediates its luminal narrowing reduction effect by directly changing the arterial mechanical properties should be rejected.

  14. Diagnostic accuracy of myocardial deformation indices for detecting high risk coronary artery disease in patients without regional wall motion abnormality

    Science.gov (United States)

    Rostamzadeh, Alireza; Shojaeifard, Maryam; Rezaei, Yousef; Dehghan, Kasra

    2015-01-01

    Background: The prediction of coronary artery disease (CAD) by conventional echocardiographic measurements is principally based on the estimation of ejection fraction and regional wall motion abnormality (RWMA). This study aimed to determine whether strain echocardiography of left ventricle measured by velocity vector imaging (VVI) method could detect patients with a high-risk CAD. Methods: In a prospective study, a total of 119 consecutive patients who were assessed for eligibility were categorized into three groups: (1) without CAD as normal (n=59), (2) 1- or 2-vessel disease as low-risk (n=29), and (3) left main and/or 3-vessel disease as high-risk (n=31). The peaks of systolic strain and strain rate from 18 curves of apical views were averaged as global longitudinal strain and strain rate (GLS and GLSR), respectively; the 6 systolic peaks of strain and strain rate at base- and mid-ventricular of short axis views were averaged as mean radial strain rate (MRSR). Results: GLS, GLSR, and basal MRSR of left ventricle were significantly lower in the high-risk group (P=0.047, P=0.004 and P=0.030, respectively). Receiver operating characteristics curve showed that the optimal values of GLS, GLSR, and basal MRSR for detecting the severe CAD were -17%, -1 s-1, and 1.45 s-1 with the sensitivities of 77%, 71%, and 71% and the specificities of 63%, 67%, and 62%, respectively. Conclusion: Decrements in the GLS, GLSR, and basal MRSR of the left ventricle can detect the high-risk CAD cases among patients without RWMA at rest. PMID:26309603

  15. Microemulsions as model fluids for enhanced oil recovery: dynamics adjacent to planar hydrophilic walls

    Directory of Open Access Journals (Sweden)

    Mattauch S.

    2012-10-01

    Full Text Available After the dynamics of microemulsions adjacent to a planar hydrophilic wall have been characterized using grazing incidence neutron spin echo spectroscopy, the model of Seifert was employed to explain the discovered acceleration for the surface near lamellar ordered membranes. Reflections of hydrodynamic waves by the wall – or the volume conservation between the membrane and the wall – explain faster relaxations and, therefore, a lubrication effect that is important for flow fields in narrow pores. The whole scenery is now spectated by using different scenarios of a bicontinuous microemulsion exposed to clay particles and of a lamellar microemulsion adjacent to a planar wall. The Seifert concept could successfully be transferred to the new problems.

  16. Magnetic domain wall gratings for magnetization reversal tuning and confined dynamic mode localization.

    Science.gov (United States)

    Trützschler, Julia; Sentosun, Kadir; Mozooni, Babak; Mattheis, Roland; McCord, Jeffrey

    2016-01-01

    High density magnetic domain wall gratings are imprinted in ferromagnetic-antiferromagnetic thin films by local ion irradiation by which alternating head-to-tail-to-head-to-tail and head-to-head-to-tail-to-tail spatially overlapping domain wall networks are formed. Unique magnetic domain processes result from the interaction of anchored domain walls. Non-linear magnetization response is introduced by the laterally distributed magnetic anisotropy phases. The locally varying magnetic charge distribution gives rise to localized and guided magnetization spin-wave modes directly constrained by the narrow domain wall cores. The exchange coupled multiphase material structure leads to unprecedented static and locally modified dynamic magnetic material properties. PMID:27487941

  17. Investigation of wall-bounded turbulent flow using Dynamic mode decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Mizuno, Yoshinori; Duke, Daniel; Atkinson, Callum; Soria, Julio, E-mail: yoshinori.mizuno@monash.edu [Laboratory for Turbulence Research in Aerospace and Combustion, Department of Mechanical and Aerospace Engineering, Monash University (Australia)

    2011-12-22

    Dynamics mode decomposition (DMD) which is a method to construct a linear mapping describing the dynamics of a given time-series of any quantities is applied to the analysis of a turbulent channel flow. The flow fields are generated by direct numerical simulations for the friction Reynolds number Re{sub {tau}} = 190. The time-series of the flow fields in a short time-interval in the order of the wall-unit time-scale and in a small spatial domain that encloses a single near-wall structure are used as the inputs to DMD. In some datasets, linearly growing modes that seem to contribute to the well-known self-sustained cycle of the flow structures near the wall are detected.

  18. Dynamics of premixed flames in a narrow channel with a step-wise wall temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kurdyumov, Vadim N. [Department of Energy, CIEMAT, Avda. Complutense 22, 28040 Madrid (Spain); Pizza, Gianmarco [Aerothermochemistry and Combustion Systems Laboratory, Swiss Federal Institute of Technology, Zurich CH-8092 (Switzerland); Combustion Research, Paul Scherrer Institute, Villigen CH-5232 (Switzerland); Frouzakis, Christos E. [Aerothermochemistry and Combustion Systems Laboratory, Swiss Federal Institute of Technology, Zurich CH-8092 (Switzerland); Mantzaras, John [Combustion Research, Paul Scherrer Institute, Villigen CH-5232 (Switzerland)

    2009-11-15

    The effect of channel height, inflow velocity and wall temperature on the dynamics and stability of unity Lewis number premixed flames in channels with specified wall temperature is investigated with steady and transient numerical simulations using a two-dimensional thermo-diffusive model. The simplified model is capable of capturing many of the transitions and the combustion modes observed experimentally and in direct numerical simulations in micro- and meso-scale channels, and indicates that the thermal flame/wall interaction is the mechanism leading to the observed flame instabilities. Finally, an ad-hoc one-dimensional model based on the flame-sheet approximation is tested in its capacity to reproduce some of the flame dynamics of the two-dimensional thermo-diffusive model. (author)

  19. The Effect of Varied Support Models of BJUT-IIVAD on Coronary Arterial blood flow and wall shear stress: A Primary CFD Study.

    Science.gov (United States)

    Zhang, Qi; Gao, Bin; Gu, Kaiyun; Chang, Yu; Xu, Jinchao; Deuflhard, Peter

    2014-09-17

    BJUT-II VAD is a novel left ventricular assist devices. Because of the special connection between the pump and native heart, the hemodynamic effects of BJTU-II VAD on coronary artery are still unclear. Hence, numerical simulations have conducted to clarify changes in hemodynamic effects of different support modes. A patient specific left coronary arterial geometric model is reconstructed based on the CT data. And 3 support modes, "constant speed mode", "co-pulse modes" and "counter pulse mode" are used in this study. The wall shear stress (WSS), wall shear stress gradient (WSSG), cycle averaged wall shear stress (avWSS), oscillatory shear index (OSI) and the flow pattern are calculated to evaluate the hemodynamic states of coronary artery. The computational results demonstrate that the hemodynamic states of coronary artery are directly affected by the support modes. The co-pulse modes could achieve the highest blood perfusion (constant speed: 153ml/min vs. co-pulse: 775ml/min vs. counter pulse: 140ml/min) and the highest avWSS (constant speed: 18.1Pa vs. co-pulse: 42.6Pa vs. counter pulse: 22.6Pa). In addition, the WSS and WSSG at the time of peak blood velocity under the constant speed mode are both lower than those under other two support modes. In contrast, the counter pulse mode generates the highest OSI value (constant speed: 0.365 vs. co-pulse: 0.379 vs. counter pulse: 0.426). In brief, BJUT-II VAD under co-pulse mode may have benefits for improving coronary perfusion and preventing the development of atherosclerosis, however, the constant speed mode may have benefit for preventing the development of plaque vulnerability. PMID:25232766

  20. Dynamic analysis of blast load of coupled shear walls on flexible foundations

    Science.gov (United States)

    Rodgers, Richard Rudolph

    An approximation technique is developed to compute the natural frequencies and mode shapes of coupled shear walls, which are on fixed or flexible foundations. This technique is extended to compute the deflection dynamics of coupled shear wall systems that are laterally loaded by an impulse load. The impulse load is the Mach stem of a blast wave generated by an above ground explosion. The Mach stem height is equal to the height of the coupled shear walls. The developed equations of motion and boundary conditions are derived using Hamilton's principle. The Ritz-Galerkin technique is used to develop matrix eigenvalue equations for computing the mode shapes and natural frequencies. A modal analysis, of infinite order, is chosen to solve the dynamic deflection equations. In order to uncouple the equations of motion, which describe the dynamics of the coupled shear wall system, it was necessary to derive two new orthogonality relations. The uncoupled equations are analytically solved using Duhamel's integral. Using the shape functions computed in the free vibration case, a truncated modal solution for the lateral and longitudinal deflections is derived. Using MATLAB, a program was written, which provides all computations and plots of both the shape functions and dynamic solutions. An example was presented to verify the model and to show the application of this technique.

  1. Age-specific characteristics and coupling of cerebral arterial inflow and cerebrospinal fluid dynamics.

    Directory of Open Access Journals (Sweden)

    Marianne Schmid Daners

    Full Text Available The objective of this work is to quantify age-related differences in the characteristics and coupling of cerebral arterial inflow and cerebrospinal fluid (CSF dynamics. To this end, 3T phase-contrast magnetic resonance imaging blood and CSF flow data of eleven young (24 ± 3 years and eleven elderly subjects (70 ± 5 years with a comparable sex-ratio were acquired. Flow waveforms and their frequency composition, transfer functions from blood to CSF flows and cross-correlations were analyzed. The magnitudes of the frequency components of CSF flow in the aqueduct differ significantly between the two age groups, as do the frequency components of the cervical spinal CSF and the arterial flows. The males' aqueductal CSF stroke volumes and average flow rates are significantly higher than those of the females. Transfer functions and cross-correlations between arterial blood and CSF flow reveal significant age-dependence of phase-shift between these, as do the waveforms of arterial blood, as well as cervical-spinal and aqueductal CSF flows. These findings accentuate the need for age- and sex-matched control groups for the evaluation of cerebral pathologies such as hydrocephalus.

  2. Universal magnetic domain wall dynamics in the presence of weak disorder

    Science.gov (United States)

    Ferré, Jacques; Metaxas, Peter J.; Mougin, Alexandra; Jamet, Jean-Pierre; Gorchon, Jon; Jeudy, Vincent

    2013-10-01

    The motion of elastic interfaces in disordered media is a broad topic relevant to many branches of physics. Field-driven magnetic domain wall motion in ultrathin ferromagnetic Pt/Co/Pt films can be well interpreted within the framework of theories developed to describe elastic interface dynamics in the presence of weak disorder. Indeed, the three theoretically predicted dynamic regimes of creep, depinning, and flow have all been directly evidenced in this model experimental system. We discuss these dynamic regimes and demonstrate how field-driven creep can be controlled not only by temperature and pinning, but also via interactions with magnetic entities located inside or outside the magnetic layer. Consequences of confinement effects in nano-devices are briefly reviewed, as some recent results on domain wall motion driven by an electric current or assisted by an electric field. Finally new theoretical developments and perspectives are discussed.

  3. Time course of arterial remodelling in diameter and wall thickness above and below the lesion after a spinal cord injury

    NARCIS (Netherlands)

    Thijssen, D.H.J.; Groot, P.C. de; Bogerd, A. van den; Veltmeijer, M.; Cable, N.T.; Green, D.J.; Hopman, M.T.E.

    2012-01-01

    Physical inactivity in response to a spinal cord injury (SCI) represents a potent stimulus for conduit artery remodelling. Changes in conduit artery characteristics may be induced by the local effects of denervation (and consequent extreme inactivity below the level of the lesion), and also by syste

  4. The impact of exercise training on conduit artery wall thickness and remodeling in chronic heart failure patients

    NARCIS (Netherlands)

    Maiorana, A.J.; Naylor, L.H.; Exterkate, A.; Swart, A.; Thijssen, D.H.J.; Lam, K.; O'Driscoll, G.; Green, D.J.

    2011-01-01

    Exercise training is an important adjunct to medical therapy in chronic heart failure, but the extent to which exercise impacts on conduit artery remodeling is unknown. The aim of this study was to evaluate the impact of aerobic and resistance exercise training modalities on arterial remodeling in p

  5. Femtosecond Dynamics in Single Wall Carbon Nanotube/Poly(3-Hexylthiophene Composites

    Directory of Open Access Journals (Sweden)

    Alexandrou Ioannis

    2008-01-01

    Full Text Available AbstractFemtosecond transient absorption measurements on single wall carbon nanotube/poly(3-hexylthiophene composites are used to investigate the relaxation dynamics of this blended material. The influence of the addition of nanotubes in polymer matrix on the ultrashort relaxation dynamics is examined in detail. The introduction of nanotube/polymer heterojunctions enhances the exciton dissociation and quenches the radiative recombination of composites. The relaxation dynamics of these composites are compared with the fullerene derivative-polymer composites with the same matrix. These results provide explanation to the observed photovoltaic performance of two types of composites.

  6. Single-Wall Carbon Nanotube Growth from Graphite Layers-a Tight Binding Molecular Dynamics Simulation

    Institute of Scientific and Technical Information of China (English)

    Yuntuan FANG; Min ZHU; Yongshun WANG

    2003-01-01

    The growth of single-wall carbon nanotube from graphite layers is studied by tight binding molecular dynamics simulation. Given temperature of 2500 K or 3500 K and an interval of 0.25 nm for the two layers of graphite, a single-wall carbon nanotube with a zigzag shell will be produced. On the other conditions the carbon nanotube cannot grow or grows with too many defects. All carbon nanotube ends have pentagons which play an important role during the tube ends closing.

  7. Corrections of arterial input function for dynamic H215O PET to assess perfusion of pelvic tumours: arterial blood sampling versus image extraction

    Science.gov (United States)

    Lüdemann, L.; Sreenivasa, G.; Michel, R.; Rosner, C.; Plotkin, M.; Felix, R.; Wust, P.; Amthauer, H.

    2006-06-01

    Assessment of perfusion with 15O-labelled water (H215O) requires measurement of the arterial input function (AIF). The arterial time activity curve (TAC) measured using the peripheral sampling scheme requires corrections for delay and dispersion. In this study, parametrizations with and without arterial spillover correction for fitting of the tissue curve are evaluated. Additionally, a completely noninvasive method for generation of the AIF from a dynamic positron emission tomography (PET) acquisition is applied to assess perfusion of pelvic tumours. This method uses a volume of interest (VOI) to extract the TAC from the femoral artery. The VOI TAC is corrected for spillover using a separate tissue TAC and for recovery by determining the recovery coefficient on a coregistered CT data set. The techniques were applied in five patients with pelvic tumours who underwent a total of 11 examinations. Delay and dispersion correction of the blood TAC without arterial spillover correction yielded in seven examinations solutions inconsistent with physiology. Correction of arterial spillover increased the fitting accuracy and yielded consistent results in all patients. Generation of an AIF from PET image data was investigated as an alternative to arterial blood sampling and was shown to have an intrinsic potential to determine the AIF noninvasively and reproducibly. The AIF extracted from a VOI in a dynamic PET scan was similar in shape to the blood AIF but yielded significantly higher tissue perfusion values (mean of 104.0 ± 52.0%) and lower partition coefficients (-31.6 ± 24.2%). The perfusion values and partition coefficients determined with the VOI technique have to be corrected in order to compare the results with those of studies using a blood AIF.

  8. [Ruptured aneurysm at the anterior wall of the internal carotid artery in a patient with systemic lupus erythematosus and secondary antiphospholipid syndrome].

    Science.gov (United States)

    Chonan, Masashi; Fujimura, Miki; Inoue, Takashi; Tominaga, Teiji

    2011-07-01

    A 60 year-old woman, who had a 45-year history of systemic lupus erythematosus (SLE) and secondary antiphospholipid syndrome, presented with subarachnoid hemorrhage due to a ruptured aneurysm at the anterior wall of the non-branching site of the right internal carotid artery. She underwent radical surgery on the day of onset. In light of the possibility of arterial dissection, we performed extracranial-intracranial bypass prior to careful exploration of the aneurysm. Based on the finding of saccular aneurysm, she ultimately underwent neck clipping of the aneurysm without complication. Postoperative course was uneventful, and she did not suffer from cerebral vasospasm. We recommend early surgical intervention in patients with aneurysmal SAH associated with SLE, while intrinsic pathologies of SLE such as fragile vascular structure and the risk for ischemic complication should be considered.

  9. Evolución de los modelos constitutivos de respuesta pasiva para paredes arteriales//Evolution of constitutive models for passive response of the arterial walls

    Directory of Open Access Journals (Sweden)

    Guillermo Fernández‐Collazo

    2014-08-01

    Full Text Available La respuesta mecánica de las paredes arteriales se modifica como consecuencia del envejecimiento y el desarrollo de enfermedades. Estos cambios se ven reflejados en modificaciones en su estructura, composición, resistencia y forma. La predicción de su comportamiento en dependencia de su estado fisiológico usando modelos biomecánicos se muestra como una potente herramienta en el tratamiento y diagnóstico de aneurismas, ateroesclerosis, hipertensión arterial entre otras. Realizando un profundo análisis de la literatura consultada se presenta un estudio bibliográfico de los modelos constitutivos de paredes arteriales en su respuesta pasiva, clasificándolos y destacando sus principales ventajas, desventajas y la evolución de estos desde los puramente fenomenológicos hasta los más complejos.Palabras claves: modelos, arterias, respuesta pasiva, biomecánica._______________________________________________________________________________AbstractThe mechanical response of arterial walls is modified as a result of aging and disease development. These changes are reflected in changes in its composition, strength, shape and structure. The prediction of their behavior, depending on their physiological state used biomechanical models is shown as a powerful tool in the treatment and diagnosis of aneurysms, atherosclerosis, hypertensionand others. It´s presented in its passive response, a profound analysis of the literature and the bibliographic review of the constitutive models of arterial walls, classifying and highlighting their main advantages, disadvantages and the  volution from purely phenomenological to the most complex response.Key words: models, artery, passive response, biomechanics.

  10. Molecular Dynamics Simulation of Formaldehyde Adsorption and Diffusion in Single-Wall Carbon Nanotube

    Institute of Scientific and Technical Information of China (English)

    Pin Lv; Zhenan Tang; Jun Yu; Yanbing Xue

    2006-01-01

    For gas sensor application, adsorption and diffusion of formaldehyde gas in single-wall carbon nanotube were investigated by using molecular dynamics simulation. The conformations of formaldehyde molecule adsorbed in carbon nanotube were optimized according to principle of minimum energy. The axis of conformatiot is parallel to the axis of carbon nanotube and about 0.3 nm~0.4 nm away from carbon nanotube wall. The conformation, which is different from that of the formaldehyde molecule in the gas-phase, rotates around carbon nanotube axis. The adsorption energy and diffusivity of formaldehyde molecule in single-wall carbon nanotube is of-56.2 kJ/mol and of 0.2× 10-4 cm2/s, respectively.

  11. Neuropsychological dynamics in patients with type 2 diabetes mellitus undergone coronary artery bypass grafting

    Directory of Open Access Journals (Sweden)

    Ol'ga Aleksandrovna Trubnikova

    2012-12-01

    Full Text Available Aim. The study was aimed at evaluation of hospital neuropsychological dynamics in ischemic heart disease patients with comorbid type 2 diabetes mellitus (T2DM undergone on-pump coronary artery bypass grafting.Materials and methods. 14 from a total of 37 examined patients had T2DM. Diabetic patients were found to have lower attention parameters prior to the intervention in comparison to non-diabetic controls. At days 7-10 after the surgery all patients demonstrated deterioration of cognitive functions.Results. We observed deeper deterioration in diabetic patients, regarding attention, memory, sensorimotor speed and quantity of erroneous test responses, as measured against individuals with normal glucose tolerance.Conclusion. Diabetic patients undergone coronary artery bypass surgery show lower cognitive characteristics when compared to controls without T2DM, suggesting this cohort to be a high-risk group for further cognitive decline.

  12. Detecting lower extremity vascular dynamics in patients with peripheral artery disease using diffuse optical tomography

    Science.gov (United States)

    Khalil, Michael A.; Kim, Hyun-Keol K.; Kim, In-Kyong; Dayal, Rajeev; Hielscher, Andreas H.

    2011-02-01

    Peripheral Artery Disease (PAD) affects over 10 million Americans and is associated with significant morbidity and mortality. While in many cases the ankle-brachial index (ABI) can be used for diagnosing the disease, this parameter is not dependable in the diabetic and elderly population. These populations tend to have calcified arteries, which leads to elevated ABI values. Dynamic optical tomography (DDOT) promises to overcome the limitations of the current diagnostic techniques and has the potential to initiate a paradigm shift in the diagnosis of vascular disease. We have performed initial pilot studies involving 5 PAD patients and 3 healthy volunteers. The time traces and tomographic reconstruction obtained from measurements on the feet show significant differences between healthy and affected vasculatures. In addition, we found that DOT is capable of identifying PAD in diabetic patients, who are misdiagnosed by the traditional ABI screening.

  13. High precision Compton backscatter maps of myocardial wall dynamics. Theory and applications.

    Science.gov (United States)

    McInerney, J J; Copenhaver, G L; Herr, M D; Morris, D L; Zelis, R

    1989-09-01

    Compton backscatter imaging (CBI) is a technique that uses x-rays scattered from the closed-chest surface of the heart to obtain high frequency (5 msec) and high precision (+/- 0.1 mm SD) measurements of regional surface displacements and velocities. These measurements are acquired in a three-dimensional format that allows the reconstruction of the epicardial surface and the creation of color coded displacement and velocity maps at many time points during the cardiac cycle. Applications of the technique are shown to characterize detailed regional normal wall displacement and velocity patterns, and the significant alteration of those patterns after coronary embolization. The technique is also applied to the characterization of early diastolic wall dynamics. CBI measurements show that a brief and somewhat paradoxical inward displacement of the anterior ventricular wall occurs during early diastole in normal canines. The wall dynamics associated with this inward displacement suggest a brief collapse of the ventricle subsequent to aortic valve closure. Diastolic collapse velocities and displacements are significantly altered subsequent to coronary occlusion with mean and maximum collapse velocities decreasing by 50% and concomitant inward displacements decreasing by 40%. Data acquisition with CBI is non-invasive, does not require contrast agents or radioisotopes, and uses low irradiation levels (125 kVp, 3-5 ma). The average radiation dose to the heart for a typical study is 250 mrem, significantly lower than that of other radiation based imaging techniques. PMID:2807818

  14. Dynamic response of a pair of walls retaining a viscoelastic solid

    Energy Technology Data Exchange (ETDEWEB)

    Veletsos, A.S.; Parikh, V.H.; Younan, A.H.; Bandyopadhyay, K.

    1995-01-01

    Making use of a previously reported, simple, approximate method of analysis, a critical evaluation is made of the dynamic pressures and forces induced by horizontal ground shaking on a pair of infinitely long, parallel walls retaining a uniform viscoelastic solid. The walls are presumed to be rigid but elastically constrained against rotation at their base. The effects of both harmonic and earthquake-induced excitations are examined. The accuracy of the method is assessed by comparing its predictions for the special case of fixed-based walls with those obtained by an exact method, and comprehensive numerical data are presented which elucidate the underlying response mechanisms, and the effects and relative importance of the parameters involved. The parameters examined include the characteristics of the ground motion, the ratio of the distance between walls to the height of the contained material, and the flexibility of the rotational wall constraints. In addition to valuable insights into the responses of the systems investigated, the results presented provide a convenient framework for the analysis of more complex systems as well.

  15. An improved dynamic non-equilibrium wall-model for large eddy simulation

    Science.gov (United States)

    Park, George Ilhwan; Moin, Parviz

    2014-01-01

    A non-equilibrium wall-model based on unsteady 3D Reynolds-averaged Navier-Stokes (RANS) equations has been implemented in an unstructured mesh environment. The method is similar to that of the wall-model for structured mesh described by Wang and Moin [Phys. Fluids 14, 2043-2051 (2002)], but is supplemented by a new dynamic eddy viscosity/conductivity model that corrects the effect of the resolved Reynolds stress (resolved turbulent heat flux) on the skin friction (wall heat flux). This correction is crucial in predicting the correct level of the skin friction. Unlike earlier models, this eddy viscosity/conductivity model does not have a stress-matching procedure or a tunable free parameter, and it shows consistent performance over a wide range of Reynolds numbers. The wall-model is validated against canonical (attached) transitional and fully turbulent flows at moderate to very high Reynolds numbers: a turbulent channel flow at Reτ = 2000, an H-type transitional boundary layer up to Reθ = 3300, and a high Reynolds number boundary layer at Reθ = 31 000. Application to a separated flow over a NACA4412 airfoil operating close to maximum lift is also considered to test the performance of the wall-model in complex non-equilibrium flows.

  16. Dynamic cone beam CT angiography of carotid and cerebral arteries using canine model

    International Nuclear Information System (INIS)

    Purpose: This research is designed to develop and evaluate a flat-panel detector-based dynamic cone beam CT system for dynamic angiography imaging, which is able to provide both dynamic functional information and dynamic anatomic information from one multirevolution cone beam CT scan. Methods: A dynamic cone beam CT scan acquired projections over four revolutions within a time window of 40 s after contrast agent injection through a femoral vein to cover the entire wash-in and wash-out phases. A dynamic cone beam CT reconstruction algorithm was utilized and a novel recovery method was developed to correct the time-enhancement curve of contrast flow. From the same data set, both projection-based subtraction and reconstruction-based subtraction approaches were utilized and compared to remove the background tissues and visualize the 3D vascular structure to provide the dynamic anatomic information. Results: Through computer simulations, the new recovery algorithm for dynamic time-enhancement curves was optimized and showed excellent accuracy to recover the actual contrast flow. Canine model experiments also indicated that the recovered time-enhancement curves from dynamic cone beam CT imaging agreed well with that of an IV-digital subtraction angiography (DSA) study. The dynamic vascular structures reconstructed using both projection-based subtraction and reconstruction-based subtraction were almost identical as the differences between them were comparable to the background noise level. At the enhancement peak, all the major carotid and cerebral arteries and the Circle of Willis could be clearly observed. Conclusions: The proposed dynamic cone beam CT approach can accurately recover the actual contrast flow, and dynamic anatomic imaging can be obtained with high isotropic 3D resolution. This approach is promising for diagnosis and treatment planning of vascular diseases and strokes.

  17. [Morphological signs of mitochondrial cytopathy in skeletal muscles and micro-vessel walls in a patient with cerebral artery dissection associated with MELAS syndrome].

    Science.gov (United States)

    Sakharova, A V; Kalashnikova, L A; Chaĭkovskaia, R P; Mir-Kasimov, M F; Nazarova, M A; Pykhtina, T N; Dobrynina, L A; Patrusheva, N L; Patrushev, L I; Protskiĭ, S V

    2012-01-01

    Skin and muscles biopsy specimens of a patient harboring A3243G mutation in mitochondrial DNA, with dissection of internal carotid and vertebral arteries, associated with MELAS were studied using histochemical and electron-microscopy techniques. Ragged red fibers, regional variability of SDH histochemical reaction, two types of morphologically atypical mitochondria and their aggregation were found in muscle. There was correlation between SDH histochemical staining and number of mitochondria revealed by electron microscopy in muscle tissue. Similar mitochondrial abnormality, their distribution and cell lesions followed by extra-cellular matrix mineralization were found in the blood vessel walls. In line with generalization of cytopathy process caused by gene mutation it can be supposed that changes found in skin and muscle microvessels also exist in large cerebral vessels causing the vessel wall "weakness", predisposing them to dissection.

  18. Axial stent strut angle influences wall shear stress after stent implantation: analysis using 3D computational fluid dynamics models of stent foreshortening

    Directory of Open Access Journals (Sweden)

    Warltier David C

    2005-10-01

    Full Text Available Abstract Introduction The success of vascular stents in the restoration of blood flow is limited by restenosis. Recent data generated from computational fluid dynamics (CFD models suggest that the vascular geometry created by an implanted stent causes local alterations in wall shear stress (WSS that are associated with neointimal hyperplasia (NH. Foreshortening is a potential limitation of stent design that may affect stent performance and the rate of restenosis. The angle created between axially aligned stent struts and the principal direction of blood flow varies with the degree to which the stent foreshortens after implantation. Methods In the current investigation, we tested the hypothesis that stent foreshortening adversely influences the distribution of WSS and WSS gradients using time-dependent 3D CFD simulations of normal arteries based on canine coronary artery measurements of diameter and blood flow. WSS and WSS gradients were calculated using conventional techniques in ideal (16 mm and progressively foreshortened (14 and 12 mm stented computational vessels. Results Stent foreshortening increased the intrastrut area of the luminal surface exposed to low WSS and elevated spatial WSS gradients. Progressive degrees of stent foreshortening were also associated with strut misalignment relative to the direction of blood flow as indicated by analysis of near-wall velocity vectors. Conclusion The current results suggest that foreshortening may predispose the stented vessel to a higher risk of neointimal hyperplasia.

  19. Carotid artery wall stiffness is increased in patients with small vessel disease: A case-control study

    OpenAIRE

    Salihović-Hajdarević Denisa; Pavlović Aleksandra M.; Smajlović Dževdet; Podgorac Ana; Jovanović Zagorka; Švabić-Međedović Tamara; Čovičković-Šternić Nadežda

    2016-01-01

    Introduction. Cerebral ischemic small-vessel disease (SVD), causing lacunar infarcts and white matter hyperintensities on brain magnetic resonance imaging (MRI), is a progressive disease associated with an increased risk of stroke, dementia and death. Increased arterial stiffness has been associated with ischemic stroke and cerebral SVD independently of common vascular risk factors. Objective. The aim of the study was to analyze arterial stiffness in our pa...

  20. NONLINEAR DYNAMIC INSTABILITY OF DOUBLE-WALLED CARBON NANOTUBES UNDER PERIODIC EXCITATION

    Institute of Scientific and Technical Information of China (English)

    Yiming Fu; Rengui Bi; Pu Zhang

    2009-01-01

    A multiple-elastic beam model based on Euler-Bernoulli-beam theory is presented to investigate the nonlinear dynamic instability of double-walled nanotubes. Taking the geometric nonlinearity of structure deformation, the effects of van der Waais forces as well as the non-coaxial curvature of each nested tube into account, the nonlinear parametric vibration governing equations are derived. Numerical results indicate that the double-walled nanotube (DWNT) can be considered as a single column when the van der Waals forces are sufficiently strong. The stiffness of medium could substantially reduce the area of the nonlinear dynamic instability region, in particular, the geometric nonlinearity can be out of account when the stiffness is large enough. The area of the principal nonlinear instability region and its shifting distance aroused by the nonlinearity both decrease with the increment of the aspect ratio of the nanotubes.

  1. Evaluation of the impact of carotid artery bifurcation angle on hemodynamics by use of computational fluid dynamics: a simulation and volunteer study.

    Science.gov (United States)

    Saho, Tatsunori; Onishi, Hideo

    2016-07-01

    In this study, we evaluated the hemodynamics of carotid artery bifurcation with various geometries using simulated and volunteer models based on magnetic resonance imaging (MRI). Computational fluid dynamics (CFD) was analyzed by use of OpenFOAM. The velocity distribution, streamline, and wall shear stress (WSS) were evaluated in a simulated model with known bifurcation angles (30°, 40°, 50°, 60°, derived from patients' data) and in three-dimensional (3D) healthy volunteer models. Separated flow was observed at the outer side of the bifurcation, and large bifurcation models represented upstream transfer of the point. Local WSS values at the outer bifurcation [both simulated (100 Pa). The bifurcation angle had a significant negative correlation with the WSS value (p<0.05). The results of this study show that the carotid artery bifurcation angle is related to the WSS value. This suggests that hemodynamic stress can be estimated based on the carotid artery geometry. The construction of a clinical database for estimation of developing atherosclerosis is warranted. PMID:27255300

  2. Numerical Investigation on Dynamic Crushing Behavior of Auxetic Honeycombs with Various Cell-Wall Angles

    Directory of Open Access Journals (Sweden)

    Xin-chun Zhang

    2015-02-01

    Full Text Available Auxetic honeycombs have proven to be an attractive advantage in actual engineering applications owing to their unique mechanical characteristic and better energy absorption ability. The in-plane dynamic crushing behaviors of the honeycombs with various cell-wall angles are studied by means of explicit dynamic finite element simulation. The influences of the cell-wall angle, the impact velocity, and the edge thickness on the macro/microdeformation behaviors, the plateau stresses, and the specific energy absorption of auxetic honeycombs are discussed in detail. Numerical results show, that except for the impact velocity and the edge thickness, the in-plane dynamic performances of auxetic honeycombs also rely on the cell-wall angle. The “> <”-mode local deformation bands form under low- or moderate-velocity impacting, which results in lateral compression shrinkage and shows negative Poisson's ratio during the crushing. For the given impact velocity, the plateau stress at the proximal end and the energy-absorbed ability can be improved by increasing the negative cell angle, the relative density, the impact velocity, and the matrix material strength. When the microcell parameters are the constant, the plateau stresses are proportional to the square of impact velocity.

  3. Diameter-dependent bending dynamics of single-walled carbon nanotubes in liquids

    Science.gov (United States)

    Fakhri, Nikta; Tsyboulski, Dmitri A.; Cognet, Laurent; Weisman, R. Bruce; Pasquali, Matteo

    2009-01-01

    By relating nanotechnology to soft condensed matter, understanding the mechanics and dynamics of single-walled carbon nanotubes (SWCNTs) in fluids is crucial for both fundamental and applied science. Here, we study the Brownian bending dynamics of individual chirality-assigned SWCNTs in water by fluorescence microscopy. The bending stiffness scales as the cube of the nanotube diameter and the shape relaxation times agree with the semiflexible chain model. This suggests that SWCNTs may be the archetypal semiflexible filaments, highly suited to act as nanoprobes in complex fluids or biological systems. PMID:19706503

  4. Average arterial input function for quantitative dynamic contrast enhanced magnetic resonance imaging of neck nodal metastases

    OpenAIRE

    Shukla-Dave, Amita; Lee, Nancy; Stambuk, Hilda; Wang, YA; Huang, Wei; Howard T Thaler; Patel, Snehal G.; Shah, Jatin P.; Koutcher, Jason A

    2009-01-01

    Background The present study determines the feasibility of generating an average arterial input function (Avg-AIF) from a limited population of patients with neck nodal metastases to be used for pharmacokinetic modeling of dynamic contrast-enhanced MRI (DCE-MRI) data in clinical trials of larger populations. Methods Twenty patients (mean age 50 years [range 27–77 years]) with neck nodal metastases underwent pretreatment DCE-MRI studies with a temporal resolution of 3.75 to 7.5 sec on a 1.5T c...

  5. Effect of cholesterol lowering on stiffness of aortic and femoral arterial walls in rabbits on a high fat diet

    Institute of Scientific and Technical Information of China (English)

    XUE Li; XU Wan-hai; XU Jin-zhi; ZHANG Tong; BI Hong-yuan; SHEN Bao-zhong

    2009-01-01

    Background Researches in arterial elasticity have increased over the past few years. We investigated the effects of simvastatin on vascular stiffness in fat fed rabbits by ultrasonography.Methods Thirty rabbits were assigned randomly to 3 groups: normal control group (A), the cholesterol group (B), simvastatin group (C: high fat diet for 4 weeks and high fat diet + simvastatin for further 4 weeks). Stiffness coefficient, pressure strain elastic modulus and velocity of pulse waves in abdominal aorta and femoral artery were measured by ultrasonographic echo tracking at the end of the 4th and the 8th weeks.Results At the end of the 4th week, stiffness coefficient, pressure strain elastic modulus and pulse wave velocity of femoral artery were significantly increased in group B compared with those in group A. Similarly, at the end of the 8th week, the same parameters of abdominal aorta were significantly increased in group B compared with those in group A. In contrast, stiffness coefficient, pressure strain elastic modulus and pulse wave velocity of femoral artery were significantly decreased in group C compared with those in group B, however, there was no significant difference in parameters of abdominal aorta between groups B and C.Conclusion Short term administration of simvastatin can improve the elasticity of femoral artery but not abdominal aorta.

  6. Experimental study of the pathogenesis of moyamoya disease: histological changes in the arterial wall caused by immunological reactions in monkeys.

    Directory of Open Access Journals (Sweden)

    Terai Y

    2003-10-01

    Full Text Available Moyamoya disease is a progressive vascular disorder of unknown etiology. Theories of inflammatory and immunologic mechanisms have been proposed as the pathogeneses. We have designed a new method of administering N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP for experimental induction of moyamoya disease using an intravascular interventional technique combined with rod-shaped embolic materials made from lactic acid-glycolic acid copolymer. The embolic materials containing MDP were repeatedly injected into the right internal carotid artery of monkeys in the embolic group. Intravenous injections of MDP solution alone were performed in the intravenous group. Histological examination of the arteries demonstrated reduplication and lamination of the internal elastic laminae, which corresponded with findings of moyamoya disease in both groups. These histological changes occurred not only in the intracranial arteries on the embolization side, but also in the contralateral intracranial and even extracranial arteries. The changes were more prominent in the intravenous group than in the embolic group. We conclude that the systemic humoral factors induced by MDP in this study may be important in the pathogeneses of moyamoya disease. Our observations suggest that moyamoya disease is a systemic vascular disease and has an etiologic factor affecting both intracranial and extracranial arteries

  7. Continuous estimates of dynamic cerebral autoregulation: influence of non-invasive arterial blood pressure measurements

    International Nuclear Information System (INIS)

    Temporal variability of parameters which describe dynamic cerebral autoregulation (CA), usually quantified by the short-term relationship between arterial blood pressure (BP) and cerebral blood flow velocity (CBFV), could result from continuous adjustments in physiological regulatory mechanisms or could be the result of artefacts in methods of measurement, such as the use of non-invasive measurements of BP in the finger. In 27 subjects (61 ± 11 years old) undergoing coronary artery angioplasty, BP was continuously recorded at rest with the Finapres device and in the ascending aorta (Millar catheter, BPAO), together with bilateral transcranial Doppler ultrasound in the middle cerebral artery, surface ECG and transcutaneous CO2. Dynamic CA was expressed by the autoregulation index (ARI), ranging from 0 (absence of CA) to 9 (best CA). Time-varying, continuous estimates of ARI (ARI(t)) were obtained with an autoregressive moving-average (ARMA) model applied to a 60 s sliding data window. No significant differences were observed in the accuracy and precision of ARI(t) between estimates derived from the Finapres and BPAO. Highly significant correlations were obtained between ARI(t) estimates from the right and left middle cerebral artery (MCA) (Finapres r = 0.60 ± 0.20; BPAO r = 0.56 ± 0.22) and also between the ARI(t) estimates from the Finapres and BPAO (right MCA r = 0.70 ± 0.22; left MCA r = 0.74 ± 0.22). Surrogate data showed that ARI(t) was highly sensitive to the presence of noise in the CBFV signal, with both the bias and dispersion of estimates increasing for lower values of ARI(t). This effect could explain the sudden drops of ARI(t) to zero as reported previously. Simulated sudden changes in ARI(t) can be detected by the Finapres, but the bias and variability of estimates also increase for lower values of ARI. In summary, the Finapres does not distort time-varying estimates of dynamic CA obtained with a sliding window combined with an ARMA model, but

  8. Dissipative Particle Dynamics Simulation of Polymer- and Cell-Wall Depletion in Micro-Channels

    Science.gov (United States)

    Fedosov, Dmitry A.; Caswell, Bruce; Em Karniadakis, George

    2008-07-01

    A rising interest in physics of biological systems stimulates a great number of experiments and numerical simulations involving a variety of biological entities. These include bio-polymers and bio-molecules, real organism vesicles and capsules, artificial vesicles used in drug delivery and cells. Macromolecules, vesicles and cells are subject to wall depletion layers observed near solid-fluid interfaces. In the case of red blood cells depletion is often called the cell-free layer and is observed near blood vessel walls. We employ Dissipative Particle Dynamics (DPD) to model depletion layers in biological systems. In case of bio-polymers the simulated depletion layers compare well with the asymptotic lattice theory solution of depletion near a repulsive wall. Vesicles and cells are modeled as coarse-grained cell membranes described by in-plane viscoelastic energy, bending energy, area and volume constraints. We investigate cell-wall depletion for cells having vesicle-like shape and red blood cells, and we correlate our results with membrane coarse-graining and with material properties such as membrane stretching and bending stiffness.

  9. Flow Velocities After Carotid Artery Stenting: Impact of Stent Design. A Fluid Dynamics Study in a Carotid Artery Model with Laser Doppler Anemometry

    International Nuclear Information System (INIS)

    Purpose. To study the influence of a newly developed membrane stent design on flow patterns in a physiologic carotid artery model. Methods. Three different stents were positioned in silicone models of the carotid artery: a stainless steel stent (Wall-stent), a nitinol stent (SelfX), and a nitinol stent with a semipermeable membrane (MembraX). To increase the contact area of the membrane with the vessel wall, another MembranX model was modified at the outflow tract. The membrane consists of a biocompatible silicone-polyurethane copolymer (Elast-Eon) with a pore size of 100 μm. All stents were deployed across the bifurcation and the external carotid artery origin. Flow velocity measurements were performed with laser Doppler anemometry (LDA), using pulsatile flow conditions (Re = 220; flow 0.39 l/min; flow rate ratio ICA:ECA = 70:30) in hemodynamically relevant cross-sections. The hemodynamic changes were analyzed by comparing velocity fluctuations of corresponding flow profiles. Results. The flow rate ratio ICA:ECA shifted significantly from 70/30 to 73.9/26.1 in the MembraX and remained nearly unchanged in the SelfX and Wallstent. There were no changes in the flow patterns at the inflow proximal to the stents. In the stent no relevant changes were found in the SelfX. In the Wallstent the separation zone shifted from the orifice of the ICA to the distal end of the stent. Four millimeters distal to the SelfX and the Wallstent the flow profile returned to normal. In the MembraX an increase in the central slipstreams was found with creation of a flow separation distal to the stent. With a modification of the membrane this flow separation vanished. In the ECA flow disturbances were seen at the inner wall distal to the stent struts in the SelfX and the Wallstent. With the MembraX a calming of flow could be observed in the ECA with a slight loss of flow volume. Conclusions. Stent placement across the carotid artery bifurcation induces alterations of the physiologic flow

  10. Effect of the hydroaffinity and topology of pore walls on the structure and dynamics of confined water

    Energy Technology Data Exchange (ETDEWEB)

    Harrach, Michael F., E-mail: harrach@fkp.tu-darmstadt.de; Klameth, Felix; Drossel, Barbara; Vogel, Michael, E-mail: michael.vogel@physik.tu-darmstadt.de [Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt (Germany)

    2015-01-21

    We perform molecular dynamics simulations to observe the structure and dynamics of SPC/E water in amorphous silica pores and amorphous ice pores with radii slightly larger than 10 Å. In addition to atomically rough pores, we construct completely smooth pores such that the potential felt at a given distance from the pore wall is an averaged atomic potential. As compared to rough walls, smooth walls induce stronger distortions of water structure for both silica and ice confinements. On the other hand, unlike the smooth pores, the rough pores strongly slow down water dynamics at the pore wall. The slowdown vanishes when reducing the atomic charges in the wall, i.e., when varying the hydroaffinity, while keeping the surface topology, indicating that it is not a geometric effect. Rather, it is due to the fact that the wall atoms provide a static energy landscape along the surface, e.g., fixed anchor-points for hydrogen bonds, to which the water molecules need to adapt, blocking channels for structural rearrangement. In the smooth pores, water dynamics can be faster than in the bulk liquid not only at the pore wall but also in the pore center. Changes in the tetrahedral order rather than in the local density are identified as the main cause for this change of the dynamical behavior in the center of smooth pores.

  11. "Sausage-string" appearance of arteries and arterioles can be caused by an instability of the blood vessel wall

    DEFF Research Database (Denmark)

    Jacobsen, Jens Christian Brings; Beierholm, Ulrik; Mikkelsen, Rene;

    2002-01-01

    Vascular damage induced by acute hypertension is preceded by a peculiar pattern where blood vessels show alternating regions of constrictions and dilations ("sausages on a string"). The pattern occurs in the smaller blood vessels, and it plays a central role in causing the vascular damage...... in vascular wall tension. Despite much research, the mechanisms underlying the sausage pattern have remained unknown. Here we present an anisotropic model of the vessel wall and show that the sausage pattern can arise because of an instability of the vessel wall. The model reproduces many of the key features...... observed experimentally. Most importantly, it suggests that the "sausaging" phenomenon is neither caused by a mechanical failure of the vessel wall due to a high blood pressure nor is it due to standing pressure waves caused by the beating of the heart. Rather, it is the expression of a general instability...

  12. Micro-CT image-derived metrics quantify arterial wall distensibility reduction in a rat model of pulmonary hypertension

    Science.gov (United States)

    Johnson, Roger H.; Karau, Kelly L.; Molthen, Robert C.; Haworth, Steven T.; Dawson, Christopher A.

    2000-04-01

    We developed methods to quantify arterial structural and mechanical properties in excised rat lungs and applied them to investigate the distensibility decrease accompanying chronic hypoxia-induced pulmonary hypertension. Lungs of control and hypertensive (three weeks 11% O2) animals were excised and a contrast agent introduced before micro-CT imaging with a special purpose scanner. For each lung, four 3D image data sets were obtained, each at a different intra-arterial contrast agent pressure. Vessel segment diameters and lengths were measured at all levels in the arterial tree hierarchy, and these data used to generate features sensitive to distensibility changes. Results indicate that measurements obtained from 3D micro-CT images can be used to quantify vessel biomechanical properties in this rat model of pulmonary hypertension and that distensibility is reduced by exposure to chronic hypoxia. Mechanical properties can be assessed in a localized fashion and quantified in a spatially-resolved way or as a single parameter describing the tree as a whole. Micro-CT is a nondestructive way to rapidly assess structural and mechanical properties of arteries in small animal organs maintained in a physiological state. Quantitative features measured by this method may provide valuable insights into the mechanisms causing the elevated pressures in pulmonary hypertension of differing etiologies and should become increasingly valuable tools in the study of complex phenotypes in small-animal models of important diseases such as hypertension.

  13. How Can a Radiologist Reveal More Practical Information Using Dynamic Study of Cavernosal Artery After Injection of Vasoactive Agents?

    OpenAIRE

    Bagheri, Seyyed Morteza; Gharib, Mohammad Hadi

    2015-01-01

    Background: Erection is a dynamic multi-stage neurovascular phenomenon consisting of 4 phases. Conventional protocol of color Doppler study can easily overlook these ongoing dynamic events. Objectives: Here, we tried to designate patterns for these dynamic spectral waveform changes of cavernosal arteries in patients with erectile dysfunction and subsequently better describe the extent of their underlying problem. Patients and Methods: We evaluated 59 men who were referred for post-intracavern...

  14. Dynamic torsional buckling of multi-walled carbon nanotubes embedded in an elastic medium

    Institute of Scientific and Technical Information of China (English)

    Chengqi Sun; Kaixin Liu; Guoxing Lu

    2008-01-01

    In this paper the dynamic torsional buckling of multi-walled carbon nanotubes (MWNTs) embedded in an elastic medium is studied by using a continuum mechan-ics model. By introducing initial imperfections for MWNTs and applying the preferred mode analytical method, a buck-ling condition is derived for the buckling load and associ-ated buckling mode. In particular, explicit expressions are obtained for embedded double-walled carbon nanotubes (DWNTs). Numerical results show that, for both the DWNTs and embedded DWNTs, the buckling form shifts from the lower buckling mode to the higher buckling mode with increasing the buckling load, but the buckling mode is invari-able for a certain domain of the buckling load. It is also indicated that, the surrounding elastic medium generally has effect on the lower buckling mode of DWNTs only when compared with the corresponding one for individual DWNTs.

  15. Structural modeling of dahlia-type single-walled carbon nanohorn aggregates by molecular dynamics.

    Science.gov (United States)

    Hawelek, L; Brodka, A; Dore, John C; Hannon, Alex C; Iijima, S; Yudasaka, M; Ohba, T; Kaneko, K; Burian, A

    2013-09-19

    The structure of dahlia-type single-walled carbon nanohorn aggregates has been modeled by classical molecular dynamics simulations, and the validity of the model has been verified by neutron diffraction. Computer-generated models consisted of an outer part formed from single-walled carbon nanohorns with diameters of 20-50 Å and a length of 400 Å and an inner turbostratic graphite-like core with a diameter of 130 Å. The diffracted intensity and the pair correlation function computed for such a constructed model are in good agreement with the neutron diffraction experimental data. The proposed turbostratic inner core explains the occurrence of the additional (002) and (004) graphitic peaks in the diffraction pattern of the studied sample and provides information about the interior structure of the dahlia-type aggregates. PMID:23978218

  16. COMPUTATIONAL FLUID DYNAMICS (CFD) SIMULATIONS OF DRAG REDUCTION WITH PERIODIC MICRO-STRUCTURED WALL

    Institute of Scientific and Technical Information of China (English)

    LI Gang; ZHOU Ming; WU Bo; YE Xia; CAI Lan

    2008-01-01

    Computational fluid dynamics(CFD) simulations are adopted to investigate rectangular microchannel flows with various periodic micro-structured wall by introducing velocity slip boundary condition at low Reynolds number. The purpose of the current study is to numerically find out the effects of periodic micro-structured wall on the flow resistance in rectangular microchannel with the different spacings between microridges ranging from 15 to 60 μm. The simulative results indicate that pressure drop with different spacing between microridges increases linearly with flow velocity and decreases monotonically with slip velocity; Pressure drop reduction also increases with the spacing between microridges at the same condition of slip velocity and flow velocity. The results of numerical simulation are compared with theoretical predictions and experimental results in the literatures. It is found that there is qualitative agreement between them.

  17. Low field domain wall dynamics in artificial spin-ice basis structure

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, J. [School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore); School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Goolaup, S.; Lim, G. J.; Kerk, I. S.; Lew, W. S., E-mail: wensiang@ntu.edu.sg [School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore); Chang, C. H., E-mail: echchang@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Roy, K. [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2015-10-28

    Artificial magnetic spin-ice nanostructures provide an ideal platform for the observation of magnetic monopoles. The formation of a magnetic monopole is governed by the motion of a magnetic charge carrier via the propagation of domain walls (DWs) in a lattice. To date, most experiments have been on the static visualization of DW propagation in the lattice. In this paper, we report on the low field dynamics of DW in a unit spin-ice structure measured by magnetoresistance changes. Our results show that reversible DW propagation can be initiated within the spin-ice basis. The initial magnetization configuration of the unit structure strongly influences the direction of DW motion in the branches. Single or multiple domain wall nucleation can be induced in the respective branches of the unit spin ice by the direction of the applied field.

  18. Ultimate seismic loading test on RC shear wall by applying multi-axes dynamic loads

    International Nuclear Information System (INIS)

    In the current seismic design of nuclear power plant (NPP) buildings in Japan, seismic design loads in the two orthogonal, horizontal directions are obtained independently by seismic response analyses, whereas actual seismic forces jolt the buildings in three directions simultaneously. Therefore, it is important to grasp the seismic response characteristics of an NPP building for three-dimensional earthquake excitation up to the ultimate state of the building to evaluate the seismic margin properly. Nuclear Power Engineering Corporation (NUPEC) has therefore been conducting a project entitled 'Model Tests of Multi-Axis Loading on RC Shear Walls' since 1994 to clarify the effects of multi-directional forces on the ultimate strength of reinforced concrete (RC) seismic shear walls under multi-directional seismic loading conditions. The paper introduces outlines of the whole project and currently on-going dynamic loading test. (author)

  19. Spatio-temporal patterns in ultra-slow domain wall creep dynamics

    CERN Document Server

    Ferrero, Ezequiel E; Giamarchi, Thierry; Kolton, Alejandro B; Rosso, Alberto

    2016-01-01

    In presence of impurities, ferromagnetic and ferroelectric domain walls slide only above a finite external field. Close to this depinning threshold, the wall proceeds by large and abrupt jumps, called avalanches, while, at much smaller field, it creeps by thermal activation. In this work we develop a novel numerical technique that captures the ultra-slow creep regime over huge time scales. We point out the existence of activated events that involve collective reorganizations similar to avalanches, but, at variance with them, display correlated spatio-temporal patterns that resemble the complex sequence of aftershocks observed after a large earthquake. Remarkably, we show that events assembly in independent clusters owning the same scale-free statistics as critical depinning avalanches. This correlated dynamics should be experimentally accessible by magneto-optical imaging of ferro- magnetic films.

  20. Intimal and medial contributions to the hydraulic resistance of the arterial wall at different pressures: a combined computational and experimental study.

    Science.gov (United States)

    Chooi, K Y; Comerford, A; Sherwin, S J; Weinberg, P D

    2016-06-01

    The hydraulic resistances of the intima and media determine water flux and the advection of macromolecules into and across the arterial wall. Despite several experimental and computational studies, these transport processes and their dependence on transmural pressure remain incompletely understood. Here, we use a combination of experimental and computational methods to ascertain how the hydraulic permeability of the rat abdominal aorta depends on these two layers and how it is affected by structural rearrangement of the media under pressure. Ex vivo experiments determined the conductance of the whole wall, the thickness of the media and the geometry of medial smooth muscle cells (SMCs) and extracellular matrix (ECM). Numerical methods were used to compute water flux through the media. Intimal values were obtained by subtraction. A mechanism was identified that modulates pressure-induced changes in medial transport properties: compaction of the ECM leading to spatial reorganization of SMCs. This is summarized in an empirical constitutive law for permeability and volumetric strain. It led to the physiologically interesting observation that, as a consequence of the changes in medial microstructure, the relative contributions of the intima and media to the hydraulic resistance of the wall depend on the applied pressure; medial resistance dominated at pressures above approximately 93 mmHg in this vessel.

  1. Study of the role and distribution of wall shear stress in rabbit atherosclerotic carotid artery%家兔颈动脉粥样硬化壁面剪应力分布及作用的探讨

    Institute of Scientific and Technical Information of China (English)

    黄志芳; 陈明; 张宇辉; 夏良华; 曲俊朴; 王超; 涂志兰; 黄东雅

    2014-01-01

    目的 探讨家兔颈总动脉粥样硬化(AS)发病过程中动脉血管壁上壁面剪应力(WSS)的分布及其对AS进程的影响.方法 24只新西兰大白兔随机分为对照组(正常饲料喂养,12只)和实验组(采用空气干燥加高脂饮食制造AS模型,12只).空气干燥术后2、4、8、12周采用彩色多普勒超声及血流剪应力定量分析软件测定血流动力学参数,分别于术后第4、8、12周处死实验组兔4只,处死前检测血脂,并做病理切片观察颈动脉病变的形态特征,对照组兔在第4周全部处死,获得相应的数据,进行对照分析.结果 实验组的各项血脂指标呈不同程度的升高,与对照组比较差异具有统计学意义(P<0.01).实验组从实施手术开始至术后4周,颈总动脉低WSS数目的分布增加,实验组左侧颈总动脉内约45%的WSS集中在0.2~0.4 N/m2,右侧约36%,左侧颈总动脉WSS降低的速度比右侧进展快.至术后8~12周,实验组颈总动脉低WSS分布反而减少,而高WSS血流点数目增加,实施干燥术后12周,实验组颈总动脉管壁逐渐僵硬、增厚,脂质沉积增加,平滑肌移行增殖,胶原增生,弹性降低,实验组左侧颈总动脉AS程度重于右侧.各项实验结果均证实实验组出现较典型的AS改变.结论 随着AS进程的延长,实验兔颈总动脉局部WSS逐步降低,低WSS进一步刺激血管内皮细胞增生,出现颈总动脉内中膜增厚及血管重构,提示颈总动脉WSS减低与动脉AS的形成有关.%Objective To dynamically observe the distribution of wall shear stress (WSS) in the carotid artery of rabbit and its impact on atherosclerosis(AS) by using AS model.Methods Twenty-four New Zealand white rabbits were randomly divided into control group (normal diet,n =12) and experimental group (air-drying plus high fat diet,n =12).In the 2nd,4th,8th,12th week after operation,hemodynamic parameters were measured by using color Doppler flow imaging and shear stress

  2. 3D assessment of the carotid artery vessel wall volume: an imaging biomarker for diagnosis of the atherosclerotic disease

    Science.gov (United States)

    Afshin, Mariam; Maraj, Tishan; Binesh Marvasti, Tina; Singh, Navneet; Moody, Alan

    2016-03-01

    This study investigates a novel method of 3D evaluation of the carotid vessel wall using two different Magnetic Resonance (MR) sequences. The method focuses on energy minimization by level-set curve boundary evolution. The level-set framework allows for the introduction of prior knowledge that is learnt from some images on the solution. The lumen is detected using a 3D TOF sequence. The lumen MRA segmentation (contours) was then transferred and registered to the corresponding images on the Magnetic Resonance Imaging plaque hemorrhage (MRIPH) sequence. The 3D registration algorithm was applied to align the sequences. The same technique used for lumen detection was then applied to extract the outer wall boundary. Our preliminary results show that the segmentations are well correlated with those obtained from a 2D reference sequence (2D-T1W). The estimated Vessel Wall Volume (VWV) can be used as an imaging biomarker to help radiologists diagnose and monitor atherosclerotic disease. Furthermore, the 3D map of the Vessel Wall Thickness (WVT) and Vessel Wall Signal Intensity may be used as complementary information to monitor disease severity.

  3. The prevalence of Chlamydia pneumoniae in the aortic wall and in peripheral blood of patients scheduled for coronary artery bypass grafting.

    Science.gov (United States)

    Kuczaj, A; Stryjewski, P J; Fudal, M; Domal-Kwiatkowska, D; Ryfiński, B; Sliupkas-Dyrda, E; Smolik, S; Węglarz, L; Mazurek, U; Nowalany-Kozielska, E

    2016-01-01

    Some reports confirm a potential role of Chlamydia pneumoniae (ChP) in atherogenesis. In order to explore possible association between ChP and atherosclerosis, investigations were carried out in which the frequency of ChP in the arterial wall and peripheral blood was assessed in a group of patients with chronic coronary artery disease (CAD). Fifty-seven patients were enrolled in the study, 13 women and 44 men aged 61.8±6.5 (47-74), with previously diagnosed CAD, scheduled for planned coronary artery bypass grafting due to clinical indications. Vessel specimens retrieved from the ascending aorta (as a part of routine proximal venous graft development procedure) and peripheral blood mononuclear cells (PBMCs) from venous blood were evaluated for the presence of ChP DNA. Genomic DNA was extracted from PBMCs and vessel specimens. Quantitative real-time polymerase chain reaction (qPCR) was performed to detect ChP DNA. A statistically more frequent occurrence of ChP was observed in aortic tissues compared to blood samples (70.2% vs 56.1%, respectively). Similarly, the number of ChP DNA genomic copies [n/1μg genomic DNA] was significantly higher in tissue specimens compared to blood samples (89±91 vs 41±77, respectively; p=0.0046). In patients without ChP in blood specimens, we observed significantly higher amounts of ChP in tissue specimens compared to patients with ChP in blood specimens (156±71 vs 107±88, respectively; p=0.0453). No correlation was found between the number of ChP DNA copies [n/1μg genomic DNA] in blood and in aortic specimens. The infection of ChP in the aortic wall was connected with hypercholesterolemia (p=0.029) and diabetes (p=0.03). We conclude that Chlamydia pneumoniae is a pathogen frequently occurring in the aortic wall of patients with CAD. The occurrence of ChP DNA in the aortic tissue is related to classic CAD risk factors such as diabetes and dyslipidemia. PMID:27358129

  4. Anisotropic diffusion of concentrated hard-sphere colloids near a hard wall studied by evanescent wave dynamic light scattering

    OpenAIRE

    Michailidou, V. N.; Swan, J. W.; Brady, J. F.; Petekidis, G.

    2013-01-01

    Evanescent wave dynamic light scattering and Stokesian dynamics simulations were employed to study the dynamics of hard-sphere colloidal particles near a hard wall in concentrated suspensions. The evanescent wave averaged short-time diffusion coefficients were determined from experimental correlation functions over a range of scattering wave vectors and penetration depths. Stokesian dynamics simulations performed for similar conditions allow a direct comparison of both the short-time self- an...

  5. Visualizing the growth dynamics of individual single-wall carbon nanotubes

    DEFF Research Database (Denmark)

    Wagner, Jakob Birkedal; Zhang, Lili; He, Maoshuai;

    In order to meet the increasing demand of faster and more flexible electronics and optical devices and at the same time decrease the use of the critical metals, carbon based devices are in fast development. Single walled carbon nanotube (SWCNT) based electronics is a way of addressing...... around the studied sample at elevated temperature gives a unique way of monitoring gas-solid interactions such as CNT growth. Here we show the direct experimental evidence on the growth dynamics of SW-CNTs from Co/MgO catalysts using CO as carbon source inside the environmental TEM. The evolution...

  6. A New Boundary Model for Simulating Complex and Flexible Wall Bounded Domain in Dissipative Particle Dynamics

    Directory of Open Access Journals (Sweden)

    Saeid Mokhtarian

    2014-01-01

    Full Text Available Despite extensive area of applications, simulation of complex wall bounded problems or any deformable boundary is still a challenge in a Dissipative Particle Dynamics simulation. This limitation is rooted in the soft force nature of DPD and the fact that we need to use an antipenetration model for escaped particles. In the present paper, we propose a new model of antipenetration which preserves the conservation of linear momentum on the boundaries and enables us to simulate complex and flexible boundaries. Finally by performing numerical simulations, we demonstrate the validity of our new model.

  7. Study of the influence of simultaneous variation of magnetic material microstructural features on domain wall dynamics

    International Nuclear Information System (INIS)

    The magnetic Barkhausen noise (MBN) is a phenomenon sensitive to several kinds of magnetic material microstructure changes, as well as to variations in material plastic deformation and stress. This fact stimulates the development of MBN-based non-destructive testing (NDT) techniques for analyzing magnetic materials, being the proposition of such a method, the main objective of the present study. The behavior of the MBN signal envelope, under simultaneous variations of carbon content and plastic deformation, is explained by the domain wall dynamics. Additionally, a non-destructive parameter for the characterization of each of these factors is proposed and validated through the experimental results.

  8. IFE thick liquid wall chamber dynamics: Governing mechanisms andmodeling and experimental capabilities

    Energy Technology Data Exchange (ETDEWEB)

    Raffray, A.R.; Meier, W.; Abdel-Khalik, S.; Bonazza, R.; Calderoni, P.; Debonnel, C.S.; Dragojlovic, Z.; El-Guebaly, L.; Haynes,D.; Latkowski, J.; Olson, C.; Peterson, P.F.; Reyes, S.; Sharpe, P.; Tillack, M.S.; Zaghloul, M.

    2005-01-24

    For thick liquid wall concepts, it is important to understand the different mechanisms affecting the chamber dynamics and the state of the chamber prior to each shot a compared with requirements from the driver and target. These include ablation mechanisms, vapor transport and control, possible aerosol formation, as well as protective jet behavior. This paper was motivated by a town meeting on this subject which helped identify the major issues, assess the latest results, review the capabilities of existing modeling and experimental facilities with respect to addressing remaining issues, and helping guide future analysis and R&D efforts; the paper covers these exact points.

  9. Estimation of Carotid Artery Pulse Wave Velocity by Doppler Ultrasonography

    OpenAIRE

    Mehdi Maerefat; Manijhe Mokhtari Dizaji; Saeed Rahgozar

    2009-01-01

    Background: Pulse wave velocity (PWV) is widely used for estimating the stiffness of an artery. Various invasive and non-invasive methods have been developed to determine PWV over the years. In the present research, the non-invasive estimation of the PWV of large arteries was used as an index for arterial stiffness. Methods: A dynamic model based on the Navier-Stokes equations coupled to elasticity equations was introduced for the PWV in arteries with elastic walls. This system of equations w...

  10. Plaque development, vessel curvature, and wall shear stress in coronary arteries assessed by X-ray angiography and intravascular ultrasound

    OpenAIRE

    Wahle, Andreas; Lopez, John J.; Olszewski, Mark E.; Vigmostad, Sarah C.; Chandran, Krishnan B.; Rossen, James D.; Sonka, Milan

    2006-01-01

    The relationships among vascular geometry, hemodynamics, and plaque development in the coronary arteries are complex and not yet well understood. This paper reports a methodology for the quantitative analysis of in vivo coronary morphology and hemodynamics, with particular emphasis placed on the critical issues of image segmentation and the automated classification of disease severity. We were motivated by the observation that plaque more often developed at the inner curvature of a vessel, pr...

  11. The Plant Cell Wall: A Complex and Dynamic Structure As Revealed by the Responses of Genes under Stress Conditions.

    Science.gov (United States)

    Houston, Kelly; Tucker, Matthew R; Chowdhury, Jamil; Shirley, Neil; Little, Alan

    2016-01-01

    The plant cell wall has a diversity of functions. It provides a structural framework to support plant growth and acts as the first line of defense when the plant encounters pathogens. The cell wall must also retain some flexibility, such that when subjected to developmental, biotic, or abiotic stimuli it can be rapidly remodeled in response. Genes encoding enzymes capable of synthesizing or hydrolyzing components of the plant cell wall show differential expression when subjected to different stresses, suggesting they may facilitate stress tolerance through changes in cell wall composition. In this review we summarize recent genetic and transcriptomic data from the literature supporting a role for specific cell wall-related genes in stress responses, in both dicot and monocot systems. These studies highlight that the molecular signatures of cell wall modification are often complex and dynamic, with multiple genes appearing to respond to a given stimulus. Despite this, comparisons between publically available datasets indicate that in many instances cell wall-related genes respond similarly to different pathogens and abiotic stresses, even across the monocot-dicot boundary. We propose that the emerging picture of cell wall remodeling during stress is one that utilizes a common toolkit of cell wall-related genes, multiple modifications to cell wall structure, and a defined set of stress-responsive transcription factors that regulate them. PMID:27559336

  12. The Plant Cell Wall: A Complex and Dynamic Structure As Revealed by the Responses of Genes under Stress Conditions

    Science.gov (United States)

    Houston, Kelly; Tucker, Matthew R.; Chowdhury, Jamil; Shirley, Neil; Little, Alan

    2016-01-01

    The plant cell wall has a diversity of functions. It provides a structural framework to support plant growth and acts as the first line of defense when the plant encounters pathogens. The cell wall must also retain some flexibility, such that when subjected to developmental, biotic, or abiotic stimuli it can be rapidly remodeled in response. Genes encoding enzymes capable of synthesizing or hydrolyzing components of the plant cell wall show differential expression when subjected to different stresses, suggesting they may facilitate stress tolerance through changes in cell wall composition. In this review we summarize recent genetic and transcriptomic data from the literature supporting a role for specific cell wall-related genes in stress responses, in both dicot and monocot systems. These studies highlight that the molecular signatures of cell wall modification are often complex and dynamic, with multiple genes appearing to respond to a given stimulus. Despite this, comparisons between publically available datasets indicate that in many instances cell wall-related genes respond similarly to different pathogens and abiotic stresses, even across the monocot-dicot boundary. We propose that the emerging picture of cell wall remodeling during stress is one that utilizes a common toolkit of cell wall-related genes, multiple modifications to cell wall structure, and a defined set of stress-responsive transcription factors that regulate them. PMID:27559336

  13. Dynamic Mechanism of Single-Stranded DNA Encapsulated into Single-Wall Carbon Nanotubes: A Molecular Dynamics Simulation Study

    Science.gov (United States)

    Xing, Yan-Fei; Yang, Chuan-Lu; Mo, Yong-Fang; Wang, Mei-Shan; Ma, Xiao-Guang

    2014-02-01

    Hybrids of single-walled carbon nanotubes (SWCNTs) and biological molecules have been utilized for numerous applications in sensing, imaging, and drug delivery. By molecular dynamics simulation, we investigate the encapsulation of single-strand DNA (ssDNA) containing eight adenine bases with (17,17)-(12,12) SWCNTs. The effects of the diameter and length of SWCNTs on the encapsulation process are explored with the calculated curves of the center-of-mass distance, the van der Waals interaction between the ssDNA and SWCNT, the root-mean-square deviation of the ssDNA, and the radius of gyration of the ssDNA. The free energy of the encapsulated ssDNA for each SWCNT is also obtained via steered molecular dynamics simulation. The most suitable SWCNT for encapsulating the ssDNA is also suggested.

  14. A dynamic wall model for Large-Eddy simulations of wind turbine dedicated airfoils

    Science.gov (United States)

    J, Calafell; O, Lehmkuhl; A, Carmona; D, Pérez-Segarra C.; A, Oliva

    2014-06-01

    This work aims at modelling the flow behavior past a wind turbine dedicated airfoil at high Reynolds number and large angle of attack (AoA). The DU-93-W-210 airfoil has been selected. To do this, Large Eddy Simulations (LES) have been performed. Momentum equations have been solved with a parallel unstructured symmetry preserving formulation while the wall-adapting local-eddy viscosity model within a variational multi-scale framework (VMS- WALE) is used as the subgrid-scales model. Since LES calculations are still very expensive at high Reynolds Number, specially at the near-wall region, a dynamic wall model has been implemented in order to overcome this limitation. The model has been validated with a very unresolved Channel Flow case at Reτ = 2000. Afterwards, the model is also tested with the Ahmed Car case, that from the flow physics point of view is more similar to an stalled airfoil than the Channel Flow is, including flow features as boundary layer detachment and recirculations. This case has been selected because experimental results of mean velocity profiles are available. Finally, a flow around a DU-93-W-210 airfoil is computed at Re = 3 x 106 and with an AoA of 15°. Numerical results are presented in comparison with Direct Numerical Simulation (DNS) or experimental data for all cases.

  15. A dynamic signal coordination control method for urban arterial roads and its application

    Institute of Scientific and Technical Information of China (English)

    Guo-jiang SHEN; Yong-yao YANG

    2016-01-01

    We propose a novel dynamic traffic signal coordination method that takes account of the special traffic flow char-acteristics of urban arterial roads. The core of this method includes a control area division module and a signal coordination control module. Firstly, we analyze and model the influences of segment distance, traffic flow density, and signal cycle time on the cor-relation degree between two neighboring intersections. Then, we propose a fuzzy computing method to estimate the correlation degree based on a hierarchical structure and a method to divide the control area of urban arterial roads into subareas based on correlation degrees. Subarea coordination control arithmetic is used to calculate the public cycle time of the control subarea, up-run offset and down-run offset of the section, and the split of each intersection. An application of the method in Shaoxing City, Zhejiang Province, China shows that the method can reduce the average travel time and the average stop rate effectively.

  16. System identification of dynamic closed-loop control of total peripheral resistance by arterial and cardiopulmonary baroreceptors

    Science.gov (United States)

    Aljuri, A. N.; Bursac, N.; Marini, R.; Cohen, R. J.

    2001-01-01

    Prolonged exposure to microgravity in space flight missions (days) impairs the mechanisms responsible for defense of arterial blood pressure (ABP) and cardiac output (CO) against orthostatic stress in the post-flight period. The mechanisms responsible for the observed orthostatic intolerance are not yet completely understood. Additionally, effective counter measures to attenuate this pathophysiological response are not available. The aim of this study was to investigate the ability of our proposed system identification method to predict closed-loop dynamic changes in TPR induced by changes in mean arterial pressure (MAP) and right atrial pressure (RAP). For this purpose we designed and employed a novel experimental animal model for the examination of arterial and cardiopulmonary baroreceptors in the dynamic closed-loop control of total peripheral resistance (TPR), and applied system identification to the analysis of beat-to-beat fluctuations in the measured signals. Grant numbers: NAG5-4989. c 2001. Elsevier Science Ltd. All rights reserved.

  17. Dynamic Behavior of Nanocomposites Reinforced with Multi-Walled Carbon Nanotubes (MWCNTs

    Directory of Open Access Journals (Sweden)

    Chun-Yu Lai

    2013-06-01

    Full Text Available The influence of multi-walled carbon nanotubes (MWCNT on the structural dynamic behavior of MWCNT/epoxy nanocomposites was investigated. Two different types of MWCNTs, pristine MWCNT and functionalized MWCNT, were used in this study. Carboxylic acid-functionalized MWCNTs (MWCNT-COOH were obtained by oxidation pristine MWCNTs via sonication in sulfuric-nitric acid and characterized by Fourier transform infrared spectroscopy (FTIR. Dynamic behaviors of the MWCNT reinforced nanocomposite including the natural frequency and damping ratio were determined using free vibration test. Experimental results showed that the damping ratio of the nanocomposite decreases with the increase of the MWCNT addition, while the natural frequency is increasing with the increase of the MWCNT addition. Functionalized MWCNTs improved the interfacial bonding between the nanotubes and epoxy resin resulting in the reduction of the interfacial energy dissipation ability and enhancement of the stiffness.

  18. DEVELOPMENT OF CALCULATING MODEL APPLICABLE FOR CYLINDER WALL DYNAMIC HEAT TRANSFER

    Institute of Scientific and Technical Information of China (English)

    ZHONG Minjun; SHI Tielin

    2007-01-01

    In the calculation of submarine air conditioning load of the early stage, the obtained heat is regarded as cooling load. The confusion of the two words causing the cooling load figured out is abnormally high, and the change of air conditioning cooling load can not be indicated. In accordance with submarine structure and heat transfer characteristics of its inner components, Laplace transformation to heat conduction differential equation of cylinder wall is carried out. The dynamic calculation of submarine conditioning load based on this model is also conducted, and the results of calculation are compared with those of static cooling load calculation. It is concluded that the dynamic cooling load calculation methods can illustrate the change of submarine air conditioning cooling load more accurate than the static one.

  19. Comparison between Carotid Artery Wall Thickness Measured by Multidetector Row Computed Tomography Angiography and Intimae-Media Thickness Measured by Sonography

    Directory of Open Access Journals (Sweden)

    Živorad N. Savić

    2011-01-01

    Full Text Available The increased thickness of the carotid wall >1 mm is a significant predictor of coronary and cerebrovascular diseases. The purpose of our study was to assess the agreement between multidetector row computed tomography angiography (MDCTA in measuring carotid artery wall thickness (CAWT and color Doppler ultrasound (CD-US in measuring intimae-media thickness (IMT. Eighty-nine patients (aged 35–81 were prospectively analyzed using a 64-detector MDCTA and a CD-US scanner. Continuous data were described as the mean value ± standard deviation, and were compared using the Mann–Whitney U test. A p value <0.05 was considered significant. Bland–Altman statistics were employed to measure the agreement between MDCTA and CD-US. CAWT ranged from 0.62 to 1.60 mm, with a mean value of 1.09 mm. IMT ranged from 0.60 to 1.55 mm, with a mean value of 1.06 mm. We observed an excellent agreement between CD-US and MDCTA in the evaluation of the common carotid artery thickness, with a bias between methods of 0.029 mm (which is a highly statistically important difference of absolute values [t = 43.289; p < 0.01] obtained by paired T test, and limits of agreement from 0.04 to 0.104. Pearson correlation coefficient was 0.9997 (95% CI 0.9996–0.9998; p < 0.01. We conclude that there is an excellent correlation between CAWT and IMT measurements obtained with the MDCTA and CD-US.

  20. Renal blood flow regulation and arterial pressure fluctuations: a case study in nonlinear dynamics

    DEFF Research Database (Denmark)

    Holstein-Rathlou, N H; Marsh, D J

    1994-01-01

    The arterial blood pressure, a physiological variable on which all renal excretory processes depend, fluctuates over a wide range of amplitudes and frequencies. Much of this variation originates in nonrenal vascular beds to support nonrenal tasks, and the fluctuations provide a noisy environment...... a relatively noise-free environment in which to work. Because of the time-varying nature of the blood pressure, we have concentrated in this review on the now substantial body of work on the dynamics of renal blood flow regulation and the underlying mechanisms. Renal vascular control mechanisms are not simply...... of experimental hypertension provide tubular pressure records that pass statistical tests for ordered structure and sensitive dependence on initial conditions in the reconstructed state space, two of the hallmarks of deterministic chaos. These records also pass recent more stringent tests for chaos...

  1. Endotoxemia reduces cerebral perfusion but enhances dynamic cerebrovascular autoregulation at reduced arterial carbon dioxide tension*

    DEFF Research Database (Denmark)

    Brassard, Patrice; Kim, Yu-Sok; van Lieshout, Johannes;

    2012-01-01

    . INTERVENTIONS:: Systemic hemodynamics, middle cerebral artery mean flow velocity, and dynamic cerebral autoregulation evaluated by transfer function analysis in the very low (0.15 Hz) frequency ranges were monitored in these volunteers before and after an endotoxin bolus (2 ng/kg; Escherichia coli...... flow velocity (37 ± 9 cm·sec vs. 47 ± 10 cm·sec; p velocity variability (1.0 ± 1.0 [cm·sec] Hz vs. 2.8 ± 1.5 [cm·sec] Hz; p ...·sec.mm Hg vs. 0.74 ± 0.17 cm·sec.mm Hg; p velocity phase difference (p

  2. Age determination of vessel wall hematoma in spontaneous cervical artery dissection: A multi-sequence 3T Cardiovascular Magnetic resonance study

    Directory of Open Access Journals (Sweden)

    Habs Maximilian

    2011-11-01

    Full Text Available Abstract Background Previously proposed classifications for carotid plaque and cerebral parenchymal hemorrhages are used to estimate the age of hematoma according to its signal intensities on T1w and T2w MR images. Using these classifications, we systematically investigated the value of cardiovascular magnetic resonance (CMR in determining the age of vessel wall hematoma (VWH in patients with spontaneous cervical artery dissection (sCAD. Methods 35 consecutive patients (mean age 43.6 ± 9.8 years with sCAD received a cervical multi-sequence 3T CMR with fat-saturated black-blood T1w-, T2w- and TOF images. Age of sCAD was defined as time between onset of symptoms (stroke, TIA or Horner's syndrome and the CMR scan. VWH were categorized into hyperacute, acute, early subacute, late subacute and chronic based on their signal intensities on T1w- and T2w images. Results The mean age of sCAD was 2.0, 5.8, 15.7 and 58.7 days in patients with acute, early subacute, late subacute and chronic VWH as classified by CMR (p Conclusions Signal intensities of VWH in sCAD vary over time and multi-sequence CMR can help to determine the age of an arterial dissection. Furthermore, findings of this study suggest that the time course of carotid hematomas differs from that of cerebral hematomas.

  3. Dynamic Response of High Rise Structures Under The Influence of Shear Walls

    Directory of Open Access Journals (Sweden)

    Syed Khasim Mutwalli

    2014-09-01

    Full Text Available This study presents the procedure for seismic performance estimation of high-rise buildings based on a concept of the capacity spectrum method. In 3D analytical model of thirty storied buildings have been generated for symmetric buildings Models and analyzed using structural analysis tool ETABS. The analytical model of the building includes all important components that influence the mass, strength, stiffness and deformability of the structure. To study the effect of concrete core wall & shear wall at different positions during earthquake, seismic analysis using both linear static, linear dynamic and non-linear static procedure has been performed. The deflections at each storey level has been compared by performing Equivalent static, response spectrum method as well as pushover method has also been performed to determine capacity, demand and performance level of the considered building models. From the below studies it has been observed that non-linear pushover analysis provide good estimate of global as well as local inelastic deformation demands and also reveals design weakness that may remain hidden in an elastic analysis and also the performance level of the structure. Storey drifts are found within the limit as specified by code (IS: 1893-2002 in Equivalent static, linear dynamic & non-linear static analysis.

  4. Dynamic stiffness matrix of thin-walled composite I-beam with symmetric and arbitrary laminations

    Science.gov (United States)

    Kim, Nam-Il; Shin, Dong Ku; Park, Young-Suk

    2008-11-01

    For the spatially coupled free vibration analysis of thin-walled composite I-beam with symmetric and arbitrary laminations, the exact dynamic stiffness matrix based on the solution of the simultaneous ordinary differential equations is presented. For this, a general theory for the vibration analysis of composite beam with arbitrary lamination including the restrained warping torsion is developed by introducing Vlasov's assumption. Next, the equations of motion and force-displacement relationships are derived from the energy principle and the first order of transformed simultaneous differential equations are constructed by using the displacement state vector consisting of 14 displacement parameters. Then explicit expressions for displacement parameters are derived and the exact dynamic stiffness matrix is determined using force-displacement relationships. In addition, the finite-element (FE) procedure based on Hermitian interpolation polynomials is developed. To verify the validity and the accuracy of this study, the numerical solutions are presented and compared with analytical solutions, the results from available references and the FE analysis using the thin-walled Hermitian beam elements. Particular emphasis is given in showing the phenomenon of vibrational mode change, the effects of increase of the modulus and the bending-twisting coupling stiffness for beams with various boundary conditions.

  5. Absolute Versus Relative Myocardial Blood Flow by Dynamic CT Myocardial Perfusion Imaging in Patients With Anatomic Coronary Artery Disease

    NARCIS (Netherlands)

    Wichmann, Julian L.; Meinel, Felix G.; Schoepf, U. Joseph; Lo, Gladys G.; Choe, Yeon Hyeon; Wang, Yining; Vliegenthart, Rozemarijn; Varga-Szemes, Akos; Muscogiuri, Giuseppe; Cannao, Paola M.; De Cecco, Carlo N.

    2015-01-01

    OBJECTIVE. The purpose of this study was to evaluate differences in the diagnostic accuracy of absolute and relative territorial myocardial blood flow (MBF) derived from stress dynamic CT myocardial perfusion imaging (MPI) for the detection of significant coronary artery stenosis. MATERIALS AND METH

  6. Monitoring of gadolinium-BOPTA uptake into the vessel wall during magnetic resonance (MR)-guided angioplasty of the peripheral arteries with a paclitaxel/gadolinium-BOPTA-coated balloon. An experimental study at 3 Tesla

    Energy Technology Data Exchange (ETDEWEB)

    Neizel, M.; Kelm, M. [University Hospital Duesseldorf (Germany). Dept. of Cardiology, Pneumology and Angiology; Ruebben, A.; Weiss, N. [Aachen Resonance, Aachen (Germany); Guenther, R.W. [University Hospital Aachen (Germany). Dept. of Radiology; Krombach, G.A. [University Hospital Giessen (Germany). Dept. of Radiology

    2014-04-15

    Purpose: The success of paclitaxel distribution within the vessel wall during paclitaxel-coated balloon angioplasty to prevent restenosis cannot be monitored under X-ray guidance. The aim of this pilot study was to demonstrate the feasibility of monitoring Gadolinium-BOPTA delivery within the vessel wall during magnetic resonance (MR)-guided paclitaxel/Gadolinium-BOPTA-coated balloon angioplasty of the peripheral arteries. Materials and methods: 6 pigs (47 ± 2 kg) were investigated. All experiments were performed using a 3 Tesla MR scanner. MR-guided bilaterial angioplasty of the iliac arteries was performed using a paclitaxel/MR contrast agent-coated balloon catheter. The feasibility of monitoring the delivery of Gadolinium-BOPTA to the vessel was assessed in 4 animals. In two additional animals, bilateral stenosis was surgically induced in the iliac arteries. Delivery of paclitaxel to the vessel wall was monitored using a 3 D T1-weighted gradient echo (GE) sequence for delineation of the vessel wall. Normalized signal intensity (SI) of the vessel wall was measured before and repeatedly after the intervention for 45 min. in all animals. Results: Paclitaxel/gadolinium-BOPTA-coated balloon angioplasty was successfully accomplished in all iliac arteries (n = 12). In animals with stenosis MR-angiography demonstrated successful dilatation (n = 4). The normalized SI of the vessel wall on T1-weighted GE images significantly increased after the intervention in all animals with and without stenosis for more than 45 min. (p < 0.001). Conclusion: Monitoring of Gadolinium-BOPTA into the vessel wall during MR-guided coated balloon angioplasty is feasible. This is a first step towards providing a tool for the online control of homogenous drug delivery after paclitaxel-coated balloon angioplasty. (orig.)

  7. Probing nuclear dynamics and architecture using single-walled carbon nanotubes

    Science.gov (United States)

    Jung, Yoon; Li, Junang; Fakhri, Nikta

    Chromatin is a multiscale dynamic architecture that acts as a template for many biochemical processes such as transcription and DNA replication. Recent developments such as Hi-C technology enable an identification of chromatin interactions across an entire genome. However, a single cell dynamic view of chromatin organization is far from understood. We discuss a new live cell imaging technique to probe the dynamics of the nucleus at a single cell level using single-walled carbon nanotubes (SWNTs). SWNTs are non-perturbing rigid rods (diameter of 1 nm and length of roughly 100 nm) that fluoresce in the near infrared region. Due to their high aspect ratio, they can diffuse in tight spaces and report on the architecture and dynamics of the nucleoplasm. We develop 3D imaging and tracking of SWNTs in the volume of the nucleus using double helix point spread function microscopy (DH-PSF) and discuss the capabilities of the DH-PSF for inferring the 3D orientation of nanotubes based on vectorial diffraction theory.

  8. Modelos constitutivos para paredes arteriales, descripción del movimiento y estado de deformación//Constitutive models for arterial walls, description of movement and state of deformation

    Directory of Open Access Journals (Sweden)

    Diana Otero‐Martínez

    2014-08-01

    Full Text Available Las paredes arteriales son uno de los tejidos blandos encontrados en los seres vivos. Tienen como características ser no lineales, incompresibles y anisotrópicos. En los últimos años se han desarrollado un conjunto de modelos constitutivos que consideran un material hiperelástico. Algunos de estos modelos consideran isotropía del material pero han demostrado no ser adecuados paramodelar el comportamiento de arterias sanas. Los modelos más difundidos en este sentido consideran el material anisotrópico debido a la organización de las fibras de colágeno y a pesar de haber sido formulados para describir la conducta arterial pueden ser utilizados para representar el comportamiento de otros tejidos blandos como la vena cava infra-renal, la pared intestinal, las propiedades mecánicas del esófago, entre otros. Algunos autores incluso los han utilizado para modelar también el daño en las arterias.Palabras claves: modelo constitutivo, tejido arterial, elasticidad, pared aortica, análisis de tensiones, respuesta pasiva._________________________________________________________________________________AbstractArterial walls are one of the soft tissues found in living organism. They are non lineal, incompressible and anisotropic. A set of constitutive models have been developed considering a hyperelastic material. Some of these models consider material isotropy but they have proved to be inadequate for modeling healthy arterial behavior. Mostly used models consider the anisotropic material due to the collagens fibers and nevertheless they have been created to describe arterial behavior can be also used for modeling different soft tissue behavior as infrarenal vena cava, intestine wall, mechanical properties of the esophagus, among others. General author have used them for modeling arterial damage.Key words: constitutive modelling, arterial tissue, elasticity, aortic wall, stress análisis, passive response.

  9. Diagnosis of Intracranial Artery Dissection

    Science.gov (United States)

    KANOTO, Masafumi; HOSOYA, Takaaki

    2016-01-01

    Cerebral arterial dissection is defined as a hematoma in the wall of a cervical or an intracranial artery. Cerebral arterial dissection causes arterial stenosis, occlusion, and aneurysm, resulting in acute infarction and hemorrhage. Image analysis by such methods as conventional angiography, computed tomography, magnetic resonance imaging, and so on plays an important role in diagnosing cerebral arterial dissection. In this study, we explore the methods and findings involved in the diagnosis of cerebral arterial dissection. PMID:27180630

  10. Anisotropic diffusion of concentrated hard-sphere colloids near a hard wall studied by evanescent wave dynamic light scattering

    Science.gov (United States)

    Michailidou, V. N.; Swan, J. W.; Brady, J. F.; Petekidis, G.

    2013-10-01

    Evanescent wave dynamic light scattering and Stokesian dynamics simulations were employed to study the dynamics of hard-sphere colloidal particles near a hard wall in concentrated suspensions. The evanescent wave averaged short-time diffusion coefficients were determined from experimental correlation functions over a range of scattering wave vectors and penetration depths. Stokesian dynamics simulations performed for similar conditions allow a direct comparison of both the short-time self- and collective diffusivity. As seen earlier [V. N. Michailidou, G. Petekidis, J. W. Swan, and J. F. Brady, Phys. Rev. Lett. 102, 068302 (2009)] while the near wall dynamics in the dilute regime slow down compared to the free bulk diffusion, the reduction is negligible at higher volume fractions due to an interplay between the particle-wall and particle-particle hydrodynamic interactions. Here, we provide a comprehensive comparison between experiments and simulations and discuss the interplay of particle-wall and particle-particle hydrodynamics in the self- and cooperative dynamics determined at different scattering wave vectors and penetration depths.

  11. Assesment of perfusion in glial tumors with arterial spin labeling; comparison with dynamic susceptibility contrast method

    Energy Technology Data Exchange (ETDEWEB)

    Cebeci, H, E-mail: hcebeci16@gmail.com [Department of Radiology, Uludag University Medical School, Bursa (Turkey); Aydin, O [Department of Radiology, Uludag University Medical School, Bursa (Turkey); Ozturk-Isik, E; Gumus, C [Department of Biomedical Engineering, Yeditepe University, Istanbul (Turkey); Inecikli, F [Department of Radiology, Kanuni Sultan Suleyman Educational and Research Hospital, Istanbul (Turkey); Bekar, A; Kocaeli, H [Department of Neurosurgery, Uludag University Medical School, Bursa (Turkey); Hakyemez, B [Department of Radiology, Uludag University Medical School, Bursa (Turkey)

    2014-10-15

    Highlights: • We compared the perfusion parameters obtained with both DSC and ASL perfusion imaging methods. • In ASL perfusion imaging, we also created quantitative CBF maps. • All patients included in the study had histopathological diagnose. • All MR examinations are done with 3T MR imaging system. - Abstract: Purpose: Arterial spin labeling perfusion imaging (ASL-PI) is a non-invasive perfusion imaging method that can be used for evaluation and quantification of cerebral blood flow (CBF). Aim of our study was to evaluating the efficiency of ASL in histopathological grade estimation of glial tumors and comparing findings with dynamic susceptibility contrast perfusion imaging (DSC-PI) method. Methods: This study involved 33 patients (20 high-grade and 13 low-grade gliomas). Multiphase multislice pulsed ASL MRI sequence and a first-passage gadopentetate dimeglumine T2*-weighted gradient-echo single-shot echo-planar sequence were acquired for all the patients. For each patient, perfusion relative signal intensity (rSI), CBF and relative CBF (rCBF) on ASL-PI and relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) values on DSC-PI were determined. The relative signal intensity of each tumor was determined as the maximal SI within the tumor divided by SI within symetric region in the contralateral hemisphere on ASL-PI. rCBV and rCBF were calculated by deconvolution of an arterial input function. Relative values of the lesions were obtained by dividing the values to the normal appearing symmetric region on the contralateral hemisphere. For statistical analysis, Mann–Whitney ranksum test was carried out. Receiver operating characteristic curve (ROC) analysis was performed to assess the relationship between the rCBF-ASL, rSI-ASL, rCBV and rCBF ratios and grade of gliomas. Their cut-off values permitting best discrimination was calculated. The correlation between rCBV, rCBF, rSI-ASL and rCBF-ASL and glioma grade was assessed using

  12. Impact of flame-wall interaction on premixed flame dynamics and transfer function characteristics

    KAUST Repository

    Kedia, K.S.

    2011-01-01

    In this paper, we numerically investigate the response of a perforated-plate stabilized laminar methane-air premixed flame to imposed inlet velocity perturbations. A flame model using detailed chemical kinetics mechanism is applied and heat exchange between the burner plate and the gas mixture is incorporated. Linear transfer functions, for low mean inlet velocity oscillations, are analyzed for different equivalence ratio, mean inlet velocity, plate thermal conductivity and distance between adjacent holes. The oscillations of the heat exchange rate at the top of the burner surface plays a critical role in driving the growth of the perturbations over a wide range of conditions, including resonance. The flame response to the perturbations at its base takes the form of consumption speed oscillations in this region. Flame stand-off distance increases/decreases when the flame-wall interaction strengthens/weakens, impacting the overall dynamics of the heat release. The convective lag between the perturbations and the flame base response govern the phase of heat release rate oscillations. There is an additional convective lag between the perturbations at the flame base and the flame tip which has a weaker impact on the heat release rate oscillations. At higher frequencies, the flame-wall interaction is weaker and the heat release oscillations are driven by the flame area oscillations. The response of the flame to higher amplitude oscillations are used to gain further insight into the mechanisms. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

  13. Dynamic Analysis of Horizontally Curved Thin-Walled Box-Girder Bridge due to Moving Vehicle

    Directory of Open Access Journals (Sweden)

    K. Nallasivam

    2007-01-01

    Full Text Available The impact on curved box-girder bridges due to vehicle moving across rough bridge deck have been analyzed using bridge-vehicle coupled dynamics. The bridge deck unevenness has been assumed to be a homogeneous random process in space specified by a PSD function. The analysis incorporates the effect of centrifugal forces due to vehicle moving on curved bridge. The curved box-girder bridge has been numerically modeled using computationally efficient thin-walled box-beam finite elements which take into account the torsional warping, distortion and distortional warping, that are important features of thin-walled box girders. Rigid vehicle with longitudinal and transverse input to the wheels giving rise to heave-pitch-roll degrees of freedom has been considered. The theoretical bridge model used in simulation study has been validated by a free vibration experiment using impact excitation. The impact factors for several response parameters such as bending moment, shear force, torsional moment, torsional bi-moment, distortional moment, distortional bi-moment and vertical deflections have been obtained for various bridge-vehicle parameters. Both constant velocity and forward acceleration of the vehicle have been considered to examine impact factor. The results highlighted that the impact factors of a curved box girder bridge corresponding to torsion, distortion and their corresponding bimoments have been observed to be generally very high, while those of the other responses are also relatively higher than that of corresponding straight box girder bridge.

  14. Growth of single-walled gold nanotubes confined in carbon nanotubes, studied by molecular dynamics simulations

    Science.gov (United States)

    Han, Yang; Hu, Ting; Dong, Jinming

    2013-01-01

    Growth of the single-walled gold nanotube (SWGNT), confined in the single-walled carbon nanotube (SWCNT) has been studied by using the classical molecular dynamics (MD) simulations, in which two different empirical potentials (the glue and EAM potentials) are used for the interaction between gold atoms. It is found that under the glue potential, three new SWGNTs, (3, 2), (4, 2) and (6, 3) gold tubes can be formed, in addition to the previously found (3, 3), (4, 3) and (5, 3) ones, among which two achiral ones, (4, 2) and (6, 3) gold tubes are particularly interesting because they were thought to be not the tube-like structures, or to have large enough diameter, permitting an extra gold atom chain in it. However, when the EAM potential is used, only four SWGNTs, i.e., (3, 2), (4, 2), (4, 3) and (5, 3) gold tubes could be formed in our MD simulations. After comparing all the MD simulation results with those of the first principles calculations, it is found that the EAM potential is better to describe the interaction between gold atoms than the glue potential for the MD simulation on the growth of gold tubular structure in confined CNT.

  15. Reptation dynamics of single-walled carbon nanotubes in a permanent network

    Science.gov (United States)

    Fakhri, Nikta; Mackintosh, Fred; Cognet, Laurent; Lounis, Brahim; Pasquali, Matteo

    2010-03-01

    Single-walled carbon nanotubes (SWCNTs) are an ideal system of semiflexible filaments with tunable bending stiffness. By exploiting their near-infrared fluorescence, we image directly the motion of SWCNTs in a network (agarose gel). We determine the SWCNT diameter (and bending stiffness) spectroscopically, and we control the network pore size by changing the agarose concentration. Image analysis shows clearly that SWCNTs move by reptation through the pore network. We quantify the dependence of SWCNTs mobility on SWCNT bending stiffness, length and pore sizes. Our results show conclusively that, even when the SWCNT length is much smaller than the persistence length, the flexibility of filaments enhances rotational diffusion. These results confirm earlier predictions of Odijk (1983), and show that the Doi-Edwards scaling fails to capture the filaments' motion. This study provides a fundamental understanding of reptation dynamics of semiflexible filaments.

  16. Dynamics of capillary infiltration of liquids into a highly aligned multi-walled carbon nanotube film.

    Science.gov (United States)

    Boncel, Sławomir; Walczak, Krzysztof Z; Koziol, Krzysztof K K

    2011-01-01

    The physical compatibility of a highly aligned carbon nanotube (HACNT) film with liquids was established using a fast and convenient experimental protocol. Two parameters were found to be decisive for the infiltration process. For a given density of nanotube packing, the thermodynamics of the infiltration process (wettability) were described by the contact angle between the nanotube wall and a liquid meniscus (θ). Once the wettability criterion (θ capillarity for a steady process (Lucas-Washburn law), where the nanoscale capillary force, here supported by gravity, is compensated by viscous drag. This most general theory of capillarity can be applied in a prediction of both wettability of HACNT films and the dynamics of capillary rise in the intertube space in various technological applications.

  17. Compressive characteristics of single walled carbon nanotube with water interactions investigated by using molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Wong, C.H., E-mail: chwong@ntu.edu.sg; Vijayaraghavan, V.

    2014-01-24

    The elastic properties of single walled carbon nanotube (SWCNT) with surrounding water interactions are studied using molecular dynamics simulation technique. The compressive loading characteristic of carbon nanotubes (CNTs) in a fluidic medium such as water is critical for its role in determining the lifetime and stability of CNT based nano-fluidic devices. In this paper, we conducted a comprehensive analysis on the effect of geometry, chirality and density of encapsulated water on the elastic properties of SWCNT. Our studies show that defect density and distribution can strongly impact the compressive resistance of SWCNTs in water. Further studies were conducted on capped SWCNTs with varying densities of encapsulated water, which is necessary to understand the strength of CNT as a potential drug carrier. The results obtained from this paper will help determining the potential applications of CNTs in the field of nano-electromechanical systems (NEMS) such as nano-biological and nano-fluidic devices.

  18. Films, layers and droplets: The effect of near-wall fluid structure on spreading dynamics

    CERN Document Server

    Yin, Hanyu; Thiele, Uwe; Archer, Andrew J

    2016-01-01

    We present a study of the spreading of liquid droplets on a solid substrate at very small scales. We focus on the regime where effective wetting energy (binding potential) and surface tension effects significantly influence steady and spreading droplets. In particular, we focus on strong packing and layering effects in the liquid near the substrate due to underlying density oscillations in the fluid caused by attractive substrate-liquid interactions. We show that such phenomena can be described by a thin-film (or long-wave or lubrication) model including an oscillatory Derjaguin (or disjoining/conjoining) pressure, and explore the effects it has on steady droplet shapes and the spreading dynamics of droplets on both, an adsorption (or precursor) layer and completely dry substrates. At the molecular scale, commonly used two-term binding potentials with a single preferred minimum controlling the adsorption layer height are inadequate to capture the rich behaviour caused by the near-wall layered molecular packin...

  19. Dynamics of three-dimensional helical domain wall in cylindrical NiFe nanowires

    Science.gov (United States)

    Wong, D. W.; Chandra Sekhar, M.; Gan, W. L.; Purnama, I.; Lew, W. S.

    2015-05-01

    We report on a micromagnetic study on the dynamics of current-driven helical domain wall (DW) in cylindrical NiFe nanowires. The helical DW is a three-dimensional transition region between magnetizations with clockwise and anticlockwise vortex orientations. A minimum current density is needed to overcome an intrinsic pinning to drive the helical DW, and the propagation along the nanowire is accompanied by a rotational motion. As the driving current strength is increased, the rotation ceases while the DW propagates at an increased velocity. However, a velocity barrier is experienced which results in the decrease of the DW mobility. Throughout its motion, the propagated helical DW maintains a stable profile without showing any sign of structural breakdown even at relatively high driving current.

  20. Bifurcation of resistive wall mode dynamics predicted by magnetohydrodynamic-kinetic hybrid theory

    Energy Technology Data Exchange (ETDEWEB)

    Yang, S. X.; Wang, Z. X., E-mail: zxwang@dlut.edu.cn [Key Laboratory of Materials Modification by Beams of the Ministry of Education, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Wang, S.; Hao, G. Z., E-mail: haogz@swip.ac.cn; Song, X. M.; Wang, A. K. [Southwestern Institute of Physics, P.O.Box 432, Chengdu 610041 (China); Liu, Y. Q. [Culham Centre for Fusion Energy, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Southwestern Institute of Physics, P.O.Box 432, Chengdu 610041 (China)

    2015-09-15

    The magnetohydrodynamic-kinetic hybrid theory has been extensively and successfully applied for interpreting experimental observations of macroscopic, low frequency instabilities, such as the resistive wall mode, in fusion plasmas. In this work, it is discovered that an analytic version of the hybrid formulation predicts a bifurcation of the mode dynamics while varying certain physical parameters of the plasma, such as the thermal particle collisionality or the ratio of the thermal ion to electron temperatures. This bifurcation can robustly occur under reasonably large parameter spaces as well as with different assumptions, for instance, on the particle collision model. Qualitatively similar bifurcation features are also observed in full toroidal computations presented in this work, based on a non-perturbative hybrid formulation.

  1. Molecular Dynamics for Elastic and Plastic Deformation of a Single-Walled Carbon Nanotube Under Nanoindentation

    Institute of Scientific and Technical Information of China (English)

    FANG Te-Hua; JIAN Sheng-Rui; CHUU Der-San

    2004-01-01

    @@ Mechanical characteristics of a suspended (10, 10) single-walled carbon nanotube (SWCNT) during atomic force microscopy (AFM) nanoindentation are investigated at different temperatures by molecular dynamics simulations.The results indicate that the Young modulus of the (10, 10) SWCNT under temperatures of 300-600K is 1.2-1.3 TPa. As the temperature increases, the Young modulus of the SWCNT increases, but the axial strain of the SWCNT decreases. The strain-induced spontaneous formation of the Stone-Wales defects and the rippled behaviour under inhomogeneous stress are studied. The rippled behaviour of the SWCNT is enhanced with the increasing axial strain. The adhesive phenomenon between the probe and the nanotube and the elastic recovery of the nanotube during the retraction are also investigated.

  2. Molecular Dynamics Study of Double-Walled Carbon Nanotubes for Nano-Mechanical Manipulation

    Science.gov (United States)

    Kimoto, Yoshihisa; Mori, Hideki; Mikami, Tomohito; Akita, Seiji; Nakayama, Yoshikazu; Higashi, Kenji; Hirai, Yoshihiko

    2005-04-01

    Double-walled carbon nanotubes (DWNTs) are expected to be useful as elements in nano-mechanical systems such as nanobearings and nanosliders. A molecular dynamics simulation is carried out to estimate the relative motion between the inner and outer tubes. The force required to pull the inner tube out of the outer tube is evaluated quantitatively by pulling the inner tube under a constant velocity for DWNTs with various inter-tube spacings and chiralities. When the inner tube is pulled under smaller constant force, the inner tube vibrates inside the outer tube without being pulled out, and an energetics is applied to explain the critical force and vibrational amplitude. The constant force induces not only vibration along the tube axis but also rotation around the tube axis, which indicates the possibility of creating a slider crank mechanism using a DWNT.

  3. Molecular dynamics simulation of the test of single-walled carbon nanotubes under tensile loading

    Institute of Scientific and Technical Information of China (English)

    FU ChenXin; CHEN YunFei; JIAO JiWei

    2007-01-01

    Molecular dynamics (MD) simulations were performed to do the test of single-walled carbon nanotubes (SWCNT) under tensile loading with the use of Brenner potential to describe the interactions of atoms in SWCNTs. The Young's modulus and tensile strength for SWCNTs were calculated and the values found are 4.2 TPa and 1.40―1.77 TPa, respectively. During the simulation, it was found that if the SWCNTs are unloaded prior to the maximum stress, the stress-strain curve for unloading process overlaps with the loading one, showing that the SWCNT's deformation up to its fracture point is completely elastic. The MD simulation also demonstrates the fracture process for several types of SWCNT and the breaking mechanisms for SWCNTs were analyzed based on the energy and structure behavior.

  4. Molecular dynamics simulation of the test of single-walled carbon nanotubes under tensile loading

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Molecular dynamics (MD) simulations were performed to do the test of sin-gle-walled carbon nanotubes (SWCNT) under tensile loading with the use of Bren-ner potential to describe the interactions of atoms in SWCNTs. The Young’s modulus and tensile strength for SWCNTs were calculated and the values found are 4.2 TPa and 1.40―1.77 TPa, respectively. During the simulation, it was found that if the SWCNTs are unloaded prior to the maximum stress, the stress-strain curve for unloading process overlaps with the loading one, showing that the SWCNT’s de-formation up to its fracture point is completely elastic. The MD simulation also demonstrates the fracture process for several types of SWCNT and the breaking mechanisms for SWCNTs were analyzed based on the energy and structure be-havior.

  5. Design and validation of a system to simulate coronary flexure dynamics on arterial segments perfused ex vivo.

    Science.gov (United States)

    VanEpps, J Scott; Londono, Ricardo; Nieponice, Alejandro; Vorp, David A

    2009-02-01

    Cyclic flexure of the coronary arteries can lead to spatially varying fluid and solid stress patterns. These patterns may explain the heterogenous distribution of atherosclerotic lesions. Here we describe the design and validation of an experimental system to simulate coronary-like flexure dynamics on intact arterial segments ex vivo. Our previously described ex vivo perfusion system was modified with a polymer flexure membrane controlled by a custom data acquisition/motion control system. The system was validated by perfusing arterial segments with pulsatile hemodynamics with or without cyclic flexure. Digital images were obtained to quantify dynamic vessel curvature and arc length. Tissue integrity was assessed by histology. The device generated physiologic curvatures (0-1.8 cm(-1)) at 1 Hz with a physiologic phase relationship with the pressure waveform. Additionally, the in vivo longitudinal extension ratio (40%) was maintained within 2.3% during the flexure cycle. Twelve hours of cyclic contact with the membrane did not compromise arterial segment integrity. This device provides a novel method to examine how the local biomechanical milieu could impact atherosclerotic lesion localization. PMID:18297319

  6. Long-term effects of biodegradable versus durable polymer-coated sirolimus-eluting stents on coronary arterial wall morphology assessed by virtual histology intravascular ultrasound

    Institute of Scientific and Technical Information of China (English)

    LIU Hui-liang; ZHANG Jiao; JIN Zhi-geng; LUO Jian-ping; MA Dong-xing; YANG Sheng-li; LIU Ying; HAN Wei; JING Li-min; MENG Rong-ying

    2011-01-01

    Background The durable presence of polymer coating on drug-eluting stent (DES) surface may be one of the principal reasons for stent thrombosis. The long-term coronary arterial response to biodegradable polymer-coated sirolimus-eluting stent (BSES) in vivo remained unclear.Methods Forty-one patients were enrolled in this study and virtual histology intravascular ultrasound (VH-IVUS) was performed to assess the native artery vascular responses to BSES compared with durable polymer-coated SES (DSES) during long-term follow-up (median: 8 months). The incidence of necrotic core abutting to the lumen was evaluated at follow-up.Results With similar in-stent late luminal loss (0.15 mm (0.06-0.30 mm) vs. 0.19 mm (0.03-0.30 mm), P=0.772), the overall incidence of necrotic core abutting to the lumen was significantly less in BSES group than in DSES group (44% vs.63%, P <0.05) (proximal 18%, stented site 14% and distal 12% in BSES group, proximal 19%, stented site 28% and distal 16% in DSES group). The DSES-treated segments had a significant higher incidence of necrotic core abutting to the lumen through the stent struts (73% vs. 36%, P <0.01). In addition, more multiple necrotic core abutting to the lumen was observed in DSES group (overall: 63% vs. 36%, P <0.05). Furthermore, when the stented segments with necrotic core abutting to the lumen had been taken into account only, DSES-treated lesions tended to contain more multiple necrotic core abutting to the lumen through the stent struts than BSES-treated lesions (74% vs. 33%), although there was no statistically significant difference between them (P=0.06).Conclusions By VH-IVUS analysis at follow-up, a greater frequency of stable lesion morphometry was shown in lesions treated with BSESs compared with lesions treated with DSESs. The major reason was BSES produced less toxicity to the arterial wall and facilitated neointimal healing as a result of polymer coating on DES surface biodegraded as time went by.

  7. A new picture of cell wall protein dynamics in elongating cells of Arabidopsis thaliana: Confirmed actors and newcomers

    Directory of Open Access Journals (Sweden)

    Jamet Elisabeth

    2008-09-01

    Full Text Available Abstract Background Cell elongation in plants requires addition and re-arrangements of cell wall components. Even if some protein families have been shown to play roles in these events, a global picture of proteins present in cell walls of elongating cells is still missing. A proteomic study was performed on etiolated hypocotyls of Arabidopsis used as model of cells undergoing elongation followed by growth arrest within a short time. Results Two developmental stages (active growth and after growth arrest were compared. A new strategy consisting of high performance cation exchange chromatography and mono-dimensional electrophoresis was established for separation of cell wall proteins. This work allowed identification of 137 predicted secreted proteins, among which 51 had not been identified previously. Apart from expected proteins known to be involved in cell wall extension such as xyloglucan endotransglucosylase-hydrolases, expansins, polygalacturonases, pectin methylesterases and peroxidases, new proteins were identified such as proteases, proteins related to lipid metabolism and proteins of unknown function. Conclusion This work highlights the CWP dynamics that takes place between the two developmental stages. The presence of proteins known to be related to cell wall extension after growth arrest showed that these proteins may play other roles in cell walls. Finally, putative regulatory mechanisms of protein biological activity are discussed from this global view of cell wall proteins.

  8. Real-time ultrasound-tagging to track the 2D motion of the common carotid artery wall in vivo

    Energy Technology Data Exchange (ETDEWEB)

    Zahnd, Guillaume, E-mail: g.zahnd@erasmusmc.nl [Biomedical Imaging Group Rotterdam, Departments of Radiology and Medical Informatics, Erasmus MC, Rotterdam 3000 CA (Netherlands); Salles, Sébastien; Liebgott, Hervé; Vray, Didier [Université de Lyon, CREATIS, CNRS UMR 5220, INSERM U1044, INSA-Lyon, Université Lyon 1, Lyon 69100 (France); Sérusclat, André [Department of Radiology, Louis Pradel Hospital, Lyon 69500 (France); Moulin, Philippe [Department of Endocrinology, Louis Pradel Hospital, Hospices Civils de Lyon, Université Lyon 1, Lyon 69100, France and INSERM UMR 1060, Lyon 69500 (France)

    2015-02-15

    Purpose: Tracking the motion of biological tissues represents an important issue in the field of medical ultrasound imaging. However, the longitudinal component of the motion (i.e., perpendicular to the beam axis) remains more challenging to extract due to the rather coarse resolution cell of ultrasound scanners along this direction. The aim of this study is to introduce a real-time beamforming strategy dedicated to acquire tagged images featuring a distinct pattern in the objective to ease the tracking. Methods: Under the conditions of the Fraunhofer approximation, a specific apodization function was applied to the received raw channel data, in real-time during image acquisition, in order to introduce a periodic oscillations pattern along the longitudinal direction of the radio frequency signal. Analytic signals were then extracted from the tagged images, and subpixel motion tracking of the intima–media complex was subsequently performed offline, by means of a previously introduced bidimensional analytic phase-based estimator. Results: The authors’ framework was applied in vivo on the common carotid artery from 20 young healthy volunteers and 6 elderly patients with high atherosclerosis risk. Cine-loops of tagged images were acquired during three cardiac cycles. Evaluated against reference trajectories manually generated by three experienced analysts, the mean absolute tracking error was 98 ± 84 μm and 55 ± 44 μm in the longitudinal and axial directions, respectively. These errors corresponded to 28% ± 23% and 13% ± 9% of the longitudinal and axial amplitude of the assessed motion, respectively. Conclusions: The proposed framework enables tagged ultrasound images of in vivo tissues to be acquired in real-time. Such unconventional beamforming strategy contributes to improve tracking accuracy and could potentially benefit to the interpretation and diagnosis of biomedical images.

  9. Dynamics of capillary infiltration of liquids into a highly aligned multi-walled carbon nanotube film

    Directory of Open Access Journals (Sweden)

    Sławomir Boncel

    2011-06-01

    Full Text Available The physical compatibility of a highly aligned carbon nanotube (HACNT film with liquids was established using a fast and convenient experimental protocol. Two parameters were found to be decisive for the infiltration process. For a given density of nanotube packing, the thermodynamics of the infiltration process (wettability were described by the contact angle between the nanotube wall and a liquid meniscus (θ. Once the wettability criterion (θ < 90° was met, the HACNT film (of free volume equal to 91% was penetrated gradually by the liquid in a rate that can be linearly correlated to dynamic viscosity of the liquid (η. The experimental results follow the classical theory of capillarity for a steady process (Lucas–Washburn law, where the nanoscale capillary force, here supported by gravity, is compensated by viscous drag. This most general theory of capillarity can be applied in a prediction of both wettability of HACNT films and the dynamics of capillary rise in the intertube space in various technological applications.

  10. Dynamic mechanical analysis of single walled carbon nanotubes/polymethyl methacrylate nanocomposite films

    Institute of Scientific and Technical Information of China (English)

    Ali Badawi; N. Al-Hosiny

    2015-01-01

    Dynamic mechanical properties of nanocomposite films with different ratios of single walled carbon nan-otubes/polymethyl methacrylate (SWCNTs/PMMA) are studied. Nanocomposite films of different ratios (0, 0.5, 1.0, and 2.0 weight percent (wt%)) of SWCNTs/PMMA are fabricated by using a casting technique. The morphological and struc-tural properties of both SWCNT powder and SWCNTs/PMMA nanocomposite films are investigated by using a high resolution transmission electron microscope and x-ray diffractometer respectively. The mechanical properties including the storage modulus, loss modulus, loss factor (tanδ) and stiffness of the nanocomposite film as a function of tempera-ture are recorded by using a dynamic mechanical analyzer at a frequency of 1 Hz. Compared with pure PMMA film, the nanocomposite films with different ratios of SWCNTs/PMMA are observed to have enhanced storage moduli, loss moduli and high stiffness, each of which is a function of temperature. The intensity of the tanδ peak for pure PMMA film is larger than those of the nanocomposite films. The glass transition temperature (Tg) of SWCNTs/PMMA nanocomposite film shifts towards the higher temperature side with respect to pure PMMA film from 91.2 ◦C to 99.5 ◦C as the ratio of SWCNTs/PMMA increases from 0 to 2.0 wt%.

  11. Calculation of the neutron electric dipole moment with two dynamical flavors of domain wall fermions

    CERN Document Server

    Berruto, F; Orginos, K; Soni, A

    2005-01-01

    We present a study of the neutron electric dipole moment ($\\vec d_N$) within the framework of lattice QCD with two flavors of dynamical lig ht quarks. The dipole moment is sensitive to the topological structure of the gaug e fields, and accuracy can only be achieved by using dynamical, or sea quark, calc ulations. However, the topological charge evolves slowly in these calculations, le ading to a relatively large uncertainty in $\\vec d_N$. It is shown, using quenched configurations, that a better sampling of the charge d istribution reduces this problem, but because the CP even part of the fermion determinant is absent, both the topological charge dis tribution and $\\vec d_N$ are pathological in the chiral limit. We discuss the statistical and systematic uncertainties arising from the topological charge distr ibution and unphysical size of the quark mass in our calculations and prospects fo r eliminating them. Our calculations employ the RBC collaboration two flavor domain wall fermion and DBW2 gauge action l...

  12. Estimation of Carotid Artery Pulse Wave Velocity by Doppler Ultrasonography

    Directory of Open Access Journals (Sweden)

    Mehdi Maerefat

    2009-06-01

    Full Text Available Background: Pulse wave velocity (PWV is widely used for estimating the stiffness of an artery. Various invasive and non-invasive methods have been developed to determine PWV over the years. In the present research, the non-invasive estimation of the PWV of large arteries was used as an index for arterial stiffness. Methods: A dynamic model based on the Navier-Stokes equations coupled to elasticity equations was introduced for the PWV in arteries with elastic walls. This system of equations was completed by clinical information obtained from the Doppler ultrasound images of the carotid artery of 40 healthy male volunteers. For this purpose, the Doppler ultrasound images were recorded and saved in a computer; and subsequently center-line blood velocity, arterial wall thickness, and arterial radius were measured by offline processing. Results: The results from the analytic solution of the completed equations showed that the mean value of PWV for the group of healthy volunteers was 2.35 m/s when the mean arterial radius was used as the neutral radius and 5.00 m/s when the end-diastole radius was used as the neutral radius. It is noteworthy that the latter value closely complies with that reported by other researchers. Conclusion: By applying this method, a non-invasive clinical and local evaluation of the common carotid artery stiffness via a Doppler ultrasound measurement will be possible.

  13. Determination of arterial input function in dynamic susceptibility contrast MRI using group independent component analysis technique

    Science.gov (United States)

    Chen, Sharon; Liu, Ho-Ling; Yang, Yihong; Hsu, Yuan-Yu; Chuang, Keh-Shih

    2006-12-01

    Quantification of cerebral blood flow (CBF) with dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI) requires the determination of the arterial input function (AIF). The segmentation of surrounding tissue by manual selection is error-prone due to the partial volume artifacts. Independent component analysis (ICA) has the advantage in automatically decomposing the signals into interpretable components. Recently group ICA technique has been applied to fMRI study and showed reduced variance caused by motion artifact and noise. In this work, we investigated the feasibility and efficacy of the use of group ICA technique to extract the AIF. Both simulated and in vivo data were analyzed in this study. The simulation data of eight phantoms were generated using randomized lesion locations and time activity curves. The clinical data were obtained from spin-echo EPI MR scans performed in seven normal subjects. Group ICA technique was applied to analyze data through concatenating across seven subjects. The AIFs were calculated from the weighted average of the signals in the region selected by ICA. Preliminary results of this study showed that group ICA technique could not extract accurate AIF information from regions around the vessel. The mismatched location of vessels within the group reduced the benefits of group study.

  14. Dynamic Contrast-Enhanced MRI Assessment of Hyperemic Fractional Microvascular Blood Plasma Volume in Peripheral Arterial Disease: Initial Findings

    OpenAIRE

    Bas Versluis; Marjolein H G Dremmen; Nelemans, Patty J; Wildberger, Joachim E.; Geert-Willem Schurink; Tim Leiner; Walter H Backes

    2012-01-01

    OBJECTIVES: The aim of the current study was to describe a method that assesses the hyperemic microvascular blood plasma volume of the calf musculature. The reversibly albumin binding contrast agent gadofosveset was used in dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) to assess the microvascular status in patients with peripheral arterial disease (PAD) and healthy controls. In addition, the reproducibility of this method in healthy controls was determined. MATERIALS AND METH...

  15. Coupled Static and Dynamic Buckling Modelling of Thin-Walled Structures in Elastic Range Review of Selected Problems

    Directory of Open Access Journals (Sweden)

    Kołakowski Zbigniew

    2016-06-01

    Full Text Available A review of papers that investigate the static and dynamic coupled buckling and post-buckling behaviour of thin-walled structures is carried out. The problem of static coupled buckling is sufficiently well-recognized. The analysis of dynamic interactive buckling is limited in practice to columns, single plates and shells. The applications of finite element method (FEM or/and analytical-numerical method (ANM to solve interaction buckling problems are on-going. In Poland, the team of scientists from the Department of Strength of Materials, Lodz University of Technology and co-workers developed the analytical-numerical method. This method allows to determine static buckling stresses, natural frequencies, coefficients of the equation describing the post-buckling equilibrium path and dynamic response of the plate structure subjected to compression load and/or bending moment. Using the dynamic buckling criteria, it is possible to determine the dynamic critical load. They presented a lot of interesting results for problems of the static and dynamic coupled buckling of thin-walled plate structures with complex shapes of cross-sections, including an interaction of component plates. The most important advantage of presented analytical-numerical method is that it enables to describe all buckling modes and the post-buckling behaviours of thin-walled columns made of different materials. Thin isotropic, orthotropic or laminate structures were considered.

  16. DYNAMIC RESPONSE OF HIGH RISE STRUCTURES UNDER THE INFLUENCE OF DISCRETE STAGGERED SHEAR WALLS

    Directory of Open Access Journals (Sweden)

    Dr. B. KAMESHWARI

    2011-10-01

    Full Text Available It is well-established fact that shear walls are quite effective in lateral load resistance of low-rise to medium-rise reinforced concrete buildings. Restriction in the architectural design by the presence of the shear walls may contribute to discourage the engineers from adopting the shear walls. Due to this a new concept ofproviding storey deep and bay wide discrete staggered shear wall panels have been introduced. In this study, the effect of various configurations of shear walls on high-rise structure is analysed. The drift and inter-storey drift of the structure in the following configurations of shear wall panels is studied and is compared with that of bare frame: (1 Conventional shear walls. (2 Alternate arrangement of shear walls. (3 Diagonal arrangement of shear walls. (4 Zigzag arrangement of shear walls. (5 Influence of lift core walls. Of the configurations studied, the zigzag shear wall configuration is found to be better than the other systems studied in controlling the response to earthquake loading. The diagonal configuration is found to be having significant role in controlling the response of structures to earthquake.

  17. Endovascular aneurysm repair alters renal artery movement : A preliminary evaluation using dynamic CTA

    NARCIS (Netherlands)

    Muhs, Bart E.; Teutelink, Arno; Prokop, Matthias; Vincken, Koen L.; Moll, Frans L.; Verhagen, Hence J. M.

    2006-01-01

    Purpose: To observe the natural renal artery motion during cardiac cycles in patients with abdominal aortic aneurysm (AAA) and how the implantation of stent-grafts may distort this movement. Methods: Data on 29 renal arteries from 15 male patients (mean age 72.6 years, range 66-83) treated with Tale

  18. Link between deviations from Murray's Law and occurrence of low wall shear stress regions in the left coronary artery.

    Science.gov (United States)

    Doutel, E; Pinto, S I S; Campos, J B L M; Miranda, J M

    2016-08-01

    Murray developed two laws for the geometry of bifurcations in the circulatory system. Based on the principle of energy minimization, Murray found restrictions for the relation between the diameters and also between the angles of the branches. It is known that bifurcations are prone to the development of atherosclerosis, in regions associated to low wall shear stresses (WSS) and high oscillatory shear index (OSI). These indicators (size of low WSS regions, size of high OSI regions and size of high helicity regions) were evaluated in this work. All of them were normalized by the size of the outflow branches. The relation between Murray's laws and the size of low WSS regions was analysed in detail. It was found that the main factor leading to large regions of low WSS is the so called expansion ratio, a relation between the cross section areas of the outflow branches and the cross section area of the main branch. Large regions of low WSS appear for high expansion ratios. Furthermore, the size of low WSS regions is independent of the ratio between the diameters of the outflow branches. Since the expansion ratio in bifurcations following Murray's law is kept in a small range (1 and 1.25), all of them have regions of low WSS with similar size. However, the expansion ratio is not small enough to completely prevent regions with low WSS values and, therefore, Murray's law does not lead to atherosclerosis minimization. A study on the effect of the angulation of the bifurcation suggests that the Murray's law for the angles does not minimize the size of low WSS regions. PMID:27157126

  19. Diagnostic value of transmural perfusion ratio derived from dynamic CT-based myocardial perfusion imaging for the detection of haemodynamically relevant coronary artery stenosis

    NARCIS (Netherlands)

    A. Coenen (Adriaan); M. Lubbers (Marisa); A. Kurata (Akira); A.K. Kono (Atsushi K.); A. Dedic (Admir); R.G. Chelu (Raluca Gabriela); M.L. Dijkshoorn (Marcel); Rossi, A. (Alexia); van Geuns, R.-J.M. (Robert-Jan M.); K. Nieman (Koen)

    2016-01-01

    textabstractObjectives: To investigate the additional value of transmural perfusion ratio (TPR) in dynamic CT myocardial perfusion imaging for detection of haemodynamically significant coronary artery disease compared with fractional flow reserve (FFR). Methods: Subjects with suspected or known coro

  20. Static Properties and Current-Driven Dynamics of Domain Walls in Perpendicular Magnetocrystalline Anisotropy Nanostrips with Rectangular Cross-Section

    Directory of Open Access Journals (Sweden)

    Eduardo Martinez

    2012-01-01

    Full Text Available The current-induced domain wall motion along thin ferromagnetic strips with high perpendicular magnetocrystalline anisotropy is studied by means of full micromagnetic simulations and the extended one-dimensional model, taking into account thermal effects and edge roughness. A slow creep regime, where the motion is controlled by wall pinning and thermal activation, and a flow regime with linear variation of the DW velocity, are observed. In asymmetric stacks, where the Rashba spin-orbit field stabilizes the domain wall against turbulent transformations, the steady linear regime is extended to higher currents, leading to higher velocities than in single-layer or symmetric stacks. The pinning and depinning at and from a local constriction were also studied. The results indicate that engineering pinning sites in these strips provide an efficient pathway to achieve both high stability against thermal fluctuations and low-current depinning avoiding Joule heating. Finally, the current-driven dynamics of a pinned domain wall is examined, and both the direct and the alternating contributions to the induced voltage signal induced are characterized. It was confirmed that the direct contribution to the voltage signal can be linearly enhanced with the number of pinned walls, an observation which could be useful to develop domain-wall-based nano-oscillators.

  1. NUMERICAL SIMULATION FOR DYNAMIC INITIAL SHOCK PARAMETERS OF COUPLING CHARGE ON BOREHOLE WALL UNDER THE ACTION OF HIGH EXPLOSIVES

    Institute of Scientific and Technical Information of China (English)

    倪芝芳; 李玉民

    1996-01-01

    According to detonation theory and hydrodynamic principle, a physical model has been set up in this paper. Based on the model a methodology for calculating dynamic initial shock parameters such as shock pressure p,,, shock wave velosity Dm etc. of coupling charge on borehole wall has ben developed. The shock parameters have been calculated when high explosives works on granite, limestone and marble respectively. The magnitude of every parameter on borehole wall has been obtained from ignited dot to the end of borehole along axial direction. Some important conclusions are also gained.

  2. Correlated Switching Dynamics in the Nanoscale Proximity of 90∘ Ferroelectric Domain Walls

    Science.gov (United States)

    Lei, Shiming; Wang, Xueyun; Cheong, S. W.; Chen, L. Q.; Kalinin, Sergei; Gopalan, Venkatraman

    2015-03-01

    Ferroelectrics are materials which have a built in polarization in their crystal structure even in the absence of an electric field. Domain walls themselves can possess dramatically different properties than the bulk ferroelectrics themselves. Previously we discovered that the universally present 180° walls have an order of magnitude lower domain switching threshold field than the bulk. This effect extends up to many microns around a wall, though the wall itself is unit cell thick. Here we present new results on 90° walls in PbTiO3 single crystals that show similar proximity effect and correlated switching. Our SSPFM imaging across the a / c / a domain walls suggests a strong correlated switching behavior in the proximity of the inclined 90° domain walls, even at a small AC driving voltage of 1V without DC bias on the tip. Consistent with phase-field modeling results, the inclined extended domain walls is found to act as nucleation sites in ferroelectric materials, and give rise to the domain wall asymmetrical broadening across the domain wall.

  3. Topology density correlator on dynamical domain-wall ensembles with nearly frozen topological charge

    CERN Document Server

    Fukaya, H; Cossu, G; Hashimoto, S; Kaneko, T; Noaki, J

    2014-01-01

    Global topological charge decorrelates very slowly or even freezes in fine lattice simulations. On the other hand, its local fluctuations are expected to survive and lead to the correct physical results as long as the volume is large enough. We investigate this issue on recently generated configurations including dynamical domain-wall fermions at lattice spacings a = 0.08 fm and finer. We utilize the Yang-Mills gradient flow to define the topological charge density operator and calculate its long-distance correlation, through which we propose a new method for extracting the topological susceptibility in a sub-volume. This method takes care of the finite volume correction, which reduces the bias caused by the global topological charge. Our lattice data clearly show a shorter auto-correlation time than that of the naive definition using the whole lattice, and are less sensitive to the global topological history. Numerical results show a clear sea-quark mass dependence, which agrees well with the prediction of c...

  4. Dynamics of functionalized single wall carbon nanotubes in solution studied by incoherent neutron scattering experiments

    International Nuclear Information System (INIS)

    We have studied, by incoherent neutron scattering experiments, the dynamics of a colloidal suspension of functionalized single wall carbon nanotubes (SWNTs). The nanotubes have been functionalized with pentyl ester groups attached at the ends and suspended in deuterated toluene with a concentration of 2.6 mg SWNT/1 ml of deuterated toluene. The experimental techniques were incoherent elastic neutron scattering (IENS) and incoherent quasielastic neutron scattering (IQNS). In the temperature range between 4 K and 300 K, three phases were observed by IENS measurements: a solid phase for Tg, an undercooled liquid phase for Tgm and a liquid phase for T>Tm. Furthermore, in the high temperature range of the undercooled liquid phase, hysteresis loops in the heating and cooling scans were observed. The lower limit of the hysteresis loop defines the critical crossover temperature Tc. IQNS measurements in the liquid phase and a cooling scan of the undercooled liquid phase were performed. Three different quasielastic peaks were identified, two in the liquid phase and another one in the undercooled liquid phase. The widths of the quasielastic peaks are discussed as a generalized diffusion function which can be factorized as a temperature dependent diffusion function and a Q dependent structure function. From the comparison of the diffusion function with the viscosity of toluene, we conclude that two components are in the long-time range Brownian motion and the other one in the short-time range Brownian motion

  5. Molecular dynamics simulation on adsorption of pyrene-polyethylene onto ultrathin single-walled carbon nanotube

    Science.gov (United States)

    Cai, Lu; Lv, Wenzhen; Zhu, Hong; Xu, Qun

    2016-07-01

    The mechanism of the adsorption of pyrene-polyethylene (Py-PE) onto ultrathin single-walled carbon nanotube (SWNT) was studied by using all-atom molecular dynamics (MD) simulations. We found that solvent polarity and pyrene group are two critical factors in the Py-PE decoration on ultrathin SWNT. Combined MD simulations with free energy calculations, our results indicate that larger solvent polarity can decrease the contribution of conformation entropy, but contributes little to the interaction energy, moreover, larger SWNT diameter can decrease the contribution of conformation entropy but lead to the increasing of the interaction energy. In polar organic solvent (N, N-Dimethylacetamide), the pyrene group plays a key role in the adsorption of Py-PE onto ultrathin SWNT, not only facilitates the spontaneous adsorption of Py-PE onto ultrathin SWNT, but also helps to form compact structure between themselves in the final adsorption states. While in aqueous solution, pyrene group no longer works as an anchor, but still affects a lot to the final adsorption conformation. Our present work provides detailed theoretical clue to understand the noncovalent interaction between aromatic segment appended polymer and ultrathin SWNT, and helps to explore the potential application of ultrathin SWNT in the fields of hybrid material, biomedical and electronic materials.

  6. Nonlinear dynamics of bi-layered graphene sheet, double-walled carbon nanotube and nanotube bundle

    Science.gov (United States)

    Gajbhiye, Sachin O.; Singh, S. P.

    2016-05-01

    Due to strong van der Waals (vdW) interactions, the graphene sheets and nanotubes stick to each other and form clusters of these corresponding nanostructures, viz. bi-layered graphene sheet (BLGS), double-walled carbon nanotube (DWCNT) and nanotube bundle (NB) or ropes. This research work is concerned with the study of nonlinear dynamics of BLGS, DWCNT and NB due to nonlinear interlayer vdW forces using multiscale atomistic finite element method. The energy between two adjacent carbon atoms is represented by the multibody interatomic Tersoff-Brenner potential, whereas the nonlinear interlayer vdW forces are represented by Lennard-Jones 6-12 potential function. The equivalent nonlinear material model of carbon-carbon bond is used to model it based on its force-deflection relation. Newmark's algorithm is used to solve the nonlinear matrix equation governing the motion of the BLGS, DWCNT and NB. An impulse and harmonic excitations are used to excite these nanostructures under cantilevered, bridged and clamped boundary conditions. The frequency responses of these nanostructures are computed, and the dominant resonant frequencies are identified. Along with the forced vibration of these structures, the eigenvalue extraction problem of armchair and zigzag NB is also considered. The natural frequencies and corresponding mode shapes are extracted for the different length and boundary conditions of the nanotube bundle.

  7. Structural ensemble dynamics based closure model for wall-bounded turbulent flow

    Institute of Scientific and Technical Information of China (English)

    Zhen-Su She; Ning Hu; You Wu

    2009-01-01

    Wall-bounded turbulent flow involves the development of multi-scale turbulent eddies, as well as a sharply varying boundary layer. Its theoretical descriptions are yet phenomenological. We present here a new framework called structural ensemble dynamics (SED), which aims at using systematically all relevant statistical properties of turbulent structures for a quantitative description of ensemble means. A new set of closure equations based on the SED approach for a turbulent channel flow is presented. SED order functions are defined, and numerically determined from data of direct numerical simulations (DNS). Computational results show that the new closure model reproduces accurately the solution of the original Navier-Stokes simulation, including the mean velocity profile, the kinetic energy of the stream-wise velocity component, and every term in the energy budget equation. It is suggested that the SED-based studies of turbulent structure builds a bridge between the studies of physical mechanisms of turbulence and the development of accurate model equations for engineering predictions.

  8. Spin wave dynamics in Heisenberg ferromagnetic/antiferromagnetic single-walled nanotubes

    Science.gov (United States)

    Mi, Bin-Zhou

    2016-09-01

    The spin wave dynamics, including the magnetization, spin wave dispersion relation, and energy level splitting, of Heisenberg ferromagnetic/antiferromagnetic single-walled nanotubes are systematically calculated by use of the double-time Green's function method within the random phase approximation. The role of temperature, diameter of the tube, and wave vector on spin wave energy spectrum and energy level splitting are carefully analyzed. There are two categories of spin wave modes, which are quantized and degenerate, and the total number of independent magnon branches is dependent on diameter of the tube, caused by the physical symmetry of nanotubes. Moreover, the number of flat spin wave modes increases with diameter of the tube rising. The spin wave energy and the energy level splitting decrease with temperature rising, and become zero as temperature reaches the critical point. At any temperature, the energy level splitting varies with wave vector, and for a larger wave vector it is smaller. When pb=π, the boundary of first Brillouin zone, spin wave energies are degenerate, and the energy level splittings are zero.

  9. Nanoscale soldering of axially positioned single-walled carbon nanotubes: a molecular dynamics simulation study.

    Science.gov (United States)

    Cui, Jianlei; Yang, Lijun; Zhou, Liang; Wang, Yang

    2014-02-12

    The miniaturization of electronics devices into the nanometer scale is indispensable for next-generation semi-conductor technology. Carbon nanotubes (CNTs) are considered to be the promising candidates for future interconnection wires. To study the carbon nanotubes interconnection during nanosoldering, the melting process of nanosolder and nanosoldering process between single-walled carbon nanotubes are simulated with molecular dynamics method. As the simulation results, the melting point of 2 nm silver solder is about 605 K because of high surface energy, which is below the melting temperature of Ag bulk material. In the nanosoldering process simulations, Ag atoms may be dragged into the nanotubes to form different connection configuration, which has no apparent relationship with chirality of SWNTs. The length of core filling nanowires structure has the relationship with the diameter, and it does not become longer with the increasing diameter of SWNT. Subsequently, the dominant mechanism of was analyzed. In addition, as the heating temperature and time, respectively, increases, more Ag atoms can enter the SWNTs with longer length of Ag nanowires. And because of the strong metal bonds, less Ag atoms can remain with the tight atomic structures in the gap between SWNT and SWNT. The preferred interconnection configurations can be achieved between SWNT and SWNT in this paper.

  10. Assessment of vessel permeability by combining dynamic contrast-enhanced and arterial spin labeling MRI.

    Science.gov (United States)

    Liu, Ho-Ling; Chang, Ting-Ting; Yan, Feng-Xian; Li, Cheng-He; Lin, Yu-Shi; Wong, Alex M

    2015-06-01

    The forward volumetric transfer constant (K(trans)), a physiological parameter extracted from dynamic contrast-enhanced (DCE) MRI, is weighted by vessel permeability and tissue blood flow. The permeability × surface area product per unit mass of tissue (PS) in brain tumors was estimated in this study by combining the blood flow obtained through pseudo-continuous arterial spin labeling (PCASL) and K(trans) obtained through DCE MRI. An analytical analysis and a numerical simulation were conducted to understand how errors in the flow and K(trans) estimates would propagate to the resulting PS. Fourteen pediatric patients with brain tumors were scanned on a clinical 3-T MRI scanner. PCASL perfusion imaging was performed using a three-dimensional (3D) fast-spin-echo readout module to determine blood flow. DCE imaging was performed using a 3D spoiled gradient-echo sequence, and the K(trans) map was obtained with the extended Tofts model. The numerical analysis demonstrated that the uncertainty of PS was predominantly dependent on that of K(trans) and was relatively insensitive to the flow. The average PS values of the whole tumors ranged from 0.006 to 0.217 min(-1), with a mean of 0.050 min(-1) among the patients. The mean K(trans) value was 18% lower than the PS value, with a maximum discrepancy of 25%. When the parametric maps were compared on a voxel-by-voxel basis, the discrepancies between PS and K(trans) appeared to be heterogeneous within the tumors. The PS values could be more than two-fold higher than the K(trans) values for voxels with high K(trans) levels. This study proposes a method that is easy to implement in clinical practice and has the potential to improve the quantification of the microvascular properties of brain tumors.

  11. Comparison of arterial spin labeling and dynamic susceptibility contrast perfusion MRI in patients with acute stroke.

    Directory of Open Access Journals (Sweden)

    Yen-Chu Huang

    Full Text Available BACKGROUND: The aim of this study was to evaluate whether arterial spin labeling (ASL perfusion magnetic resonance imaging (MRI can reliably quantify perfusion deficit as compared to dynamic susceptibility contrast (DSC perfusion MRI. METHODS: Thirty-nine patients with acute ischemic stroke in the anterior circulation territory were recruited. All underwent ASL and DSC MRI perfusion scans within 30 hours after stroke onset and 31 patients underwent follow-up MRI scans. ASL cerebral blood flow (CBF and DSC time to maximum (T(max maps were used to calculate the perfusion defects. The ASL CBF lesion volume was compared to the DSC Tmax lesion volume by Pearson's correlation coefficient and likewise the ASL CBF and DSC T(max lesion volumes were compared to the final infarct sizes respectively. A repeated measures analysis of variance and least significant difference post hoc test was used to compare the mean lesion volumes among ASL CBF, DSC T(max >4-6 s and final infarct. RESULTS: Mean patient age was 72.6 years. The average time from stroke onset to MRI was 13.9 hours. The ASL lesion volume showed significant correlation with the DSC lesion volume for T(max >4, 5 and 6 s (r = 0.81, 0.82 and 0.80; p5 s (29.2 ml, p6 s (21.8 ml, p5 or 6 s were close to mean final infarct size. CONCLUSION: Quantitative measurement of ASL perfusion is well correlated with DSC perfusion. However, ASL perfusion may overestimate the perfusion defects and therefore further refinement of the true penumbra threshold and improved ASL technique are necessary before applying ASL in therapeutic trials.

  12. Common carotid artery wall thickness and external diameter as predictors of prevalent and incident cardiac events in a large population study

    Directory of Open Access Journals (Sweden)

    Bursac Zoran

    2007-03-01

    Full Text Available Abstract Background Arterial diameters enlarge in response to wall thickening, plaques, and many atherosclerotic risk factors. We hypothesized that right common carotid artery (RCCA diameter would be independently associated with cardiac disease and improve risk discrimination. Methods In a middle-aged, biracial population (baseline n = 11225, we examined associations between 1 standard deviation increments of baseline RCCA diameter with prevalent myocardial infarction (MI and incident cardiac events (MI or cardiac death using logistic regression and Cox proportional hazards models, respectively. Areas under the receiver operator characteristic curve (AUC were used to estimate model discrimination. Results MI was present in 451 (4% participants at baseline (1987–89, and incident cardiac events occurred among 646 (6% others through 1999. Adjusting for IMT, RCCA diameter was associated with prevalent MI (female OR = 2.0, 95%CI = 1.61–2.49; male OR = 1.16, 95% CI = 1.04–1.30 and incident cardiac events (female HR = 1.75, 95% CI = 1.51–2.02; male HR = 1.27, 95% CI = 1.15–1.40. Associations were attenuated but persisted after adjustment for risk factors (not including IMT (prevalent MI: female OR = 1.73, 95% CI = 1.40–2.14; male OR = 1.14, 95% CI = 1.02–1.28, and incident cardiac events: female HR = 1.26, 95% CI = 1.08–1.48; male HR = 1.19, 95% CI = 1.08–1.32. After additional adjustment for IMT, diameter was associated with incident cardiac events in women (HR = 1.18, 95% CI = 1.00–1.40 and men (HR = 1.17, 95% CI = 1.06–1.29, and with prevalent MI only in women (OR = 1.73; 95% CI = 1.37–2.17. In women, when adjustment was limited, diameter models had larger AUC than other models. Conclusion RCCA diameter is an important correlate of cardiac events, independent of IMT, but adds little to overall risk discrimination after risk factor adjustment.

  13. Domain wall dynamics in Fe-rich glass covered amorphous microwires

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Jesus Daniel [Departamento de Fisica, Facultad de Ciencias, Universidad de Oviedo (Spain); Institute of Physics, Faculty of Science, UPJS, Kosice (Slovakia); Ruiz, Alvaro; Cobos, Raul F.; Ribot, Ivan; Vega, Victor; Alvarez, Pablo; Sanchez, Maria Luisa; Sanchez Ll., Jose Luis; Prida, Victor M. de la; Hernando, Blanca [Departamento de Fisica, Facultad de Ciencias, Universidad de Oviedo (Spain)

    2009-04-15

    The influence of glass covering on domain wall propagation in Fe{sub 65}B{sub 15}Si{sub 15}C{sub 5} amorphous microwires is studied, before and after glass removal. High values of domain wall velocity and mobility have been obtained. The domain wall velocity depends linearly on the driving magnetic field. However, the mobility of the domain wall is very different in both situations studied. The results are explained due to the modification of internal stress distribution after glass removing, that change the domain structure of the sample. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Single-Walled Carbon Nanotube Dynamics in Simple and Complex Media

    Science.gov (United States)

    Fakhri, Nikta

    Understanding the dynamics of single-walled carbon nanotubes (SWNTs) in simple and complex environments is crucial for establishing potential application of nanotube architectures for materials and biosciences. In this thesis we employ the visualization and analysis tools to image and quantify and the Brownian bending and diffusion of SWNTs in different media in order to understand and eventually to tailor nanotube mobility in confined environments. We image Brownian bending dynamics of SWNTs in water using Near-infrared (NIR) fluorescence microscopy. The bending stiffness of each chirality-assigned SWNT is extracted from the variance of the curvature fluctuations. Relaxation times of the bending fluctuations are measured from the autocorrelation of SWNT shapes. We find that the bending stiffness scales as the cube of the nanotube diameter, in agreement with an elastic continuum model. The measured shape relaxation times are in excellent agreement with the semiflexible chain model, showing that SWNTs may truly be considered as the ideal model semiflexible filaments. The motion of stiff objects in crowded environments has been investigated for more than three decades in polymer science and biophysics; yet, theory and experiments have not established whether a minute amount of flexibility affects the mobility of stiff slender filaments. We image the Brownian motion of SWNTs in a network by NIR fluorescence microscopy. We show direct evidence of SWNTs reptating in the network, and confirm that their small flexibility enhances significantly their rotational diffusion. Our results establish the reptation dynamics of stiff filaments and provide a framework to tailor SWNTs mobility in confined media. By varying SWNT surface modifications, we can selectively tune the sensitivity of the carbon nanotubes to the different physical properties of the porous media for sensing applications, We introduce a simple procedure for dispersion of SWNTs in aqueous solutions using

  15. Computer modeling of tasks in dynamics of viscoelastic thin-walled elements in structures of variable thickness

    Directory of Open Access Journals (Sweden)

    R.A. Abdikarimov

    2014-08-01

    Full Text Available The paper presents a numerical method and algorithm for solving tasks in dynamics of viscoelastic thin-walled elements in structures of variable thickness. The equations of motion concerning deflections are described by partial integro-differential equations (PIDE. Using Bubnov-Galerkin’s method, based on the polynomial approximation of deflections, the task is limited to the study of the system of ordinary IDEs, where the independent variable is time. The solution to the system of IDEs is obtained by the offered numerical method, which results into the algorithm of the numerical solution and the program in the Delphi algorithmic language. The study of nonlinear vibrations of thin-walled elements in structures, allowing for variable thickness in the geometrical nonlinear statement, has enabled revealing a number of mechanical effects. Depending on physico-mechanical and geometrical parameters of the considered viscoelastic thin-walled elements in structures, the authors reccommend how to use the rigidity of the system.

  16. Starling resistor versus compliance. Which explains the zero-flow pressure of a dynamic arterial pressure-flow relation?

    Science.gov (United States)

    Magder, S

    1990-07-01

    Arterial pressure at zero flow (Pz = 0) that is higher than venous pressure (Pv) in dynamic pressure-flow relations has been explained by the presence of an arteriolar Starling resistor (SR) mechanism (i.e., vascular waterfall) or the discharge of vascular capacitance. To determine which was predominant, I studied in vivo hind limbs of 18 anesthetized dogs in which femoral arteries were cannulated with in-line electromagnetic flow probes to measure inflow (Qin), Pv was controlled, and collateral flow was eliminated with a tourniquet. Pz = 0 was obtained by turning flow to zero. Three tests were applied: 1) Pv was raised in steps with either constant Qin or constant arterial pressure (Pa) to determine the pressure at which upstream vascular characteristics were affected by a change in Pv, 2) the time to reach Pz = 0 was varied to determine compliance effects, and 3) an equation was developed to determine if experimentally derived parameters could explain Pz = 0 without invoking an SR. With constant Qin and a Pz = 0 of 56.9 +/- 11.7 mm Hg (time to Pz = 0, 3 seconds), Pv could be raised by 9.6 +/- 6.2 to 16.3 +/- 6.0 mm Hg before Pa increased, and with constant Pa, Pv could be raised by 6.8 +/- 7.3 to 14.0 +/- 8.0 mm Hg before Qin decreased. With increasing times to reach Pz = 0, Pz = 0 initially dropped precipitously, but then decreased by only a small amount over the next 5-10 seconds even though arterial pressure was much above Pv. This could be explained by an SR mechanism with a critical pressure of 42.3 +/- 11.4 mm Hg and an arterial compliance of 0.0104 +/- 0.0023 ml.mm Hg-1 (n = 6). There was no value for the compliance that described the results when the arterial outflow pressure was Pv. Thus, this study supports the hypothesis that an SR mechanism is present in the vascular system. It is most likely precapillary, and in the resting limb, it has a value of 40-50 mm Hg. However, Pz = 0 in dynamic pressure-flow studies of less than 4 seconds is also greatly

  17. Solid-State NMR on bacterial cells: selective cell wall signal enhancement and resolution improvement using dynamic nuclear polarization

    International Nuclear Information System (INIS)

    Dynamic nuclear polarization (DNP) enhanced solid-state nuclear magnetic resonance (NMR) has recently emerged as a powerful technique for the study of material surfaces. In this study, we demonstrate its potential to investigate cell surface in intact cells. Using Bacillus subtilis bacterial cells as an example, it is shown that the polarizing agent 1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol (TOTAPOL) has a strong binding affinity to cell wall polymers (peptidoglycan). This particular interaction is thoroughly investigated with a systematic study on extracted cell wall materials, disrupted cells, and entire cells, which proved that TOTAPOL is mainly accumulating in the cell wall. This property is used on one hand to selectively enhance or suppress cell wall signals by controlling radical concentrations and on the other hand to improve spectral resolution by means of a difference spectrum. Comparing DNP-enhanced and conventional solid-state NMR, an absolute sensitivity ratio of 24 was obtained on the entire cell sample. This important increase in sensitivity together with the possibility of enhancing specifically cell wall signals and improving resolution really opens new avenues for the use of DNP-enhanced solid-state NMR as an on-cell investigation tool. (authors)

  18. Pure Optical Dephasing Dynamics in Semiconducting Single-Walled Carbon Nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Graham, Matt [University of California, Berkeley; Fleming, Graham [University of California, Berkeley; Ma, Yingzhong [ORNL; Green, Alexander A. [Northwestern University, Evanston; Hersam, Mark C. [Northwestern University, Evanston

    2011-01-01

    We report a detailed study of ultrafast exciton dephasing processes in semiconducting single-walled carbon nanotubes (SWNTs) employing a sample highly enriched in a single tube species, the (6,5) tube. Systematic measurements of femtosecond pump-probe, two-pulse photon echo and three-pulse photon echo peak shift over a broad range of excitation intensities and lattice temperature (from 4.4 to 292 K) enable us to quantify the timescales of pure optical dephasing (T 2 ), along with exciton-exciton and exciton-phonon scattering, environmental effects as well as spectral diffusion. While the exciton dephasing time (T2 ) increases from 205 fs at room temperature to 320 fs at 70 K, we found that further decrease of the lattice temperature leads to a shortening of the T2 times. This complex temperature dependence was found to arise from an enhanced relaxation of exciton population at lattice temperatures below 80 K. By quantitatively accounting the contribution from the population relaxation, the corresponding pure optical dephasing times increase monotonically from 225 fs at room temperature to 508 fs at 4.4 K. We further found that below 180 K, the inverse of the pure dephasing time (1/T 2 ) scales linearly with temperature with a slope of 6.7 0.6 eV/K, which suggests dephasing arising from one-phonon scattering (i.e. acoustic phonons). In view ofthe large dynamic disorder of the surrounding environment, the origin of the long room temperature pure dephasing time is proposed to result from reduced strength of exciton-phonon coupling by motional narrowing over nuclear fluctuations. This consideration further suggests the occurrence of remarkable initial exciton delocalization, and makes nanotubes ideal to study many-body effects in spatially confined systems.

  19. Dynamics of functionalized single wall carbon nanotubes in solution studied by incoherent neutron scattering experiments

    Energy Technology Data Exchange (ETDEWEB)

    Urbina, A; Miguel, C [Departamento Electronica, Universidad Politecnica de Cartagena, Plaza Hospital 1, 30202 Cartagena (Spain); Delgado, J L; Langa, F [Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, 45071, Toledo (Spain); DIaz-Paniagua, C [Centro Espanol de MetrologIa, 28760 Madrid (Spain); Jimenez, M [Institut Laue-Langevin, 39042 Grenoble Cedex (France); Batallan, F [Instituto de Ciencia de Materiales de Madrid, CSIC, 28049 Madrid (Spain)], E-mail: antonio.urbina@upct.es

    2008-03-12

    We have studied, by incoherent neutron scattering experiments, the dynamics of a colloidal suspension of functionalized single wall carbon nanotubes (SWNTs). The nanotubes have been functionalized with pentyl ester groups attached at the ends and suspended in deuterated toluene with a concentration of 2.6 mg SWNT/1 ml of deuterated toluene. The experimental techniques were incoherent elastic neutron scattering (IENS) and incoherent quasielastic neutron scattering (IQNS). In the temperature range between 4 K and 300 K, three phases were observed by IENS measurements: a solid phase for TT{sub m}. Furthermore, in the high temperature range of the undercooled liquid phase, hysteresis loops in the heating and cooling scans were observed. The lower limit of the hysteresis loop defines the critical crossover temperature T{sub c}. IQNS measurements in the liquid phase and a cooling scan of the undercooled liquid phase were performed. Three different quasielastic peaks were identified, two in the liquid phase and another one in the undercooled liquid phase. The widths of the quasielastic peaks are discussed as a generalized diffusion function which can be factorized as a temperature dependent diffusion function and a Q dependent structure function. From the comparison of the diffusion function with the viscosity of toluene, we conclude that two components are in the long-time range Brownian motion and the other one in the short-time range Brownian motion.

  20. Extracellular Matrix Remodeling by Dynamic Strain in a Three-Dimensional Tissue-Engineered Human Airway Wall Model

    OpenAIRE

    Choe, Melanie M.; Sporn, Peter H. S.; Swartz, Melody A.

    2006-01-01

    Airway wall remodeling is a hallmark of asthma, characterized by subepithelial thickening and extracellular matrix (ECM) remodeling. Mechanical stress due to hyperresponsive smooth muscle cells may contribute to this remodeling, but its relevance in a three-dimensional environment (where the ECM plays an important role in modulating stresses felt by cells) is unclear. To characterize the effects of dynamic compression in ECM remodeling in a physiologically relevant three-dimensional environme...

  1. Correlations of coronary plaque wall thickness with wall pressure and wall pressure gradient: a representative case study

    OpenAIRE

    Liu Biyue; Zheng Jie; Bach Richard; Tang Dalin

    2012-01-01

    Abstract Background There are two major hemodynamic stresses imposed at the blood arterial wall interface by flowing blood: the wall shear stress (WSS) acting tangentially to the wall, and the wall pressure (WP) acting normally to the wall. The role of flow wall shear stress in atherosclerosis progression has been under intensive investigation, while the impact of blood pressure on plaque progression has been under-studied. Method The correlations of wall thickness (WT) with wall pressure (WP...

  2. Powell dynamic identification of displacement parameters of indeterminate thin-walled curve box based on FCSE theory

    Institute of Scientific and Technical Information of China (English)

    Jian Zhang; Chu-Wei Zhou; Jia-Shou Zhuo

    2011-01-01

    The FCSE controlling equation of pinned thinwalled curve box was derived and the indeterminate problem of continuous thin-walled curve box with diaphragm was solved based on flexibility theory. With Bayesian statistical theory, dynamic Bayesian error function of displacement parameters of indeterminate curve box was founded. The corresponding formulas of dynamic Bayesian expectation and variance were deduced. Combined with one-dimensional Fibonacci automatic search scheme of optimal step size,the Powell optimization theory was utilized to research the stochastic identification of displacement parameters of indeterminate thin-walled curve box. Then the identification steps were presented in detail and the corresponding calculation procedure was compiled. Through some classic examples, it is obtained that stochastic performances of systematic parameters and systematic responses are simultaneously deliberated in dynamic Bayesian error function. The one-dimensional optimization problem of the optimal step size is solved by adopting Fibonacci search method. And the Powell identification of displacement parameters of indeterminate thin-walled curve box has satisfied numerical stability and convergence, which demonstrates that the presented method and the compiled procedure are correct and reliable.The project was supported by the National Natural Science Foundation of China ( 10472045.10772078 and 11072108 and the Science Foundation of NUAA(S0851-013).During parameters' iterative processes, the Powell theory is irrelevant with the calculation of finite curve strip element (FCSE) partial differentiation, which proves high computation efficiency of the studied method.

  3. Dynamic modeling of the vascular system in the state-space.

    Science.gov (United States)

    Monzon, Jorge E; Pisarello, Maria I; Alvarez Picaza, Carlos; Veglia, Julian I

    2010-01-01

    Modern control theory allows the representation of cardiac dynamics in the state-space, describing the operation of the vascular systems in terms of the cushioning effect of the arterial wall facing compliance changes. In this paper we use state equations to modeling the effect of the compliance variations on the arterial wall. The characteristics of the dynamics and of the calculated parameters of the model allow the distinction of hypertensive and normotensive subjects, in accordance to real clinical data. PMID:21096181

  4. 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).

  5. Fungal Cell Wall Dynamics and Infection Site Microenvironments: Signal Integration and Infection Outcome

    OpenAIRE

    Shepardson, Kelly M.; Cramer, Robert A.

    2013-01-01

    Upon entrance into the host, fungi encounter a myriad of host effector products and microenvironments that they sense and adapt to for survival. Alterations of the structure and composition of the cell wall is a major fungal adaptation mechanism to evade these environments. Here we discuss recent findings of host-microenvironmental induced fungal cell wall changes, including structure, composition, and protein content, and their effects on host immune responses. A take home message from these...

  6. Arterial blood flow and microcirculatory changes in a rat groin flap after thrombosis induced by electrical stimulation of the artery.

    Science.gov (United States)

    Qi, Y; Gazelius, B; Linderoth, B; Lundeberg, T

    2002-03-01

    An experimental model of acute arterial thrombosis was developed in a rat groin flap model. Electrical stimulation was delivered to the flap artery while measuring blood flow in the artery and in the flap microcirculation using a laser Doppler system. Electrical stimulation produced an occlusive thrombosis in 10 rats within 68.1 +/- 19.26 (mean +/- SE) min. Thrombosis formation produced a rapid decrease of the LDF readings in the artery (90%) and in the flap (70%), the decrease being fairly parallel. Following the spontaneous thrombolysis, the artery perfusion recovered to baseline level but the flap blood flow only recovered by 10-20%. During electrical stimulation there was no change of the systemic blood pressure. The dynamic course of thrombus formation was documented on a videotape recorder through a microscope-mounted video camera and monitored on a television screen. Segments of the artery were obtained during and at the end of the experiments. The histological examination revealed arterial thrombosis composed of red blood cells, fibrin, and white blood cells, without any significant architectural and endothelial changes in the vessel walls. The study suggests that this model using electric vessel stimulation is effective for inducing arterial thrombosis and provides a simple method for recording the dynamic course of thrombus formation. PMID:11866541

  7. Dynamic Response and Signal to Noise Ratio Investigation of NIR-FBG Dynamic Sensing System for Monitoring Thin- walled Composite Plate

    Science.gov (United States)

    Hafizi, Z. M.; Epaarachchi, J.

    2015-12-01

    Optical fiber systems for dynamic response measurement become an attractive study nowadays especially in the field of Structural Health Monitoring (SHM). This work presents the investigation of an optical fiber sensor system utilizing Near Infra-Red Fiber Bragg Grating (NIR-FBG) sensor for SHM of a thin-walled composite structure. In this study, a comparison between the experimental result and simulation study using finite element analysis has been presented. By comparing both results, the FBG dynamic sensing system was shown to have an excellent capability in acquiring dynamic response due to flexural wave propagations. In the meantime, a signal to noise ratio (SNR) study was also performed to several FBG dynamic sensor systems; particularly to see the comparison between NIR-FBG sensor and 1550 nm FBG sensor. Furthermore, with a proper configuration, an NIR-FBG system was proved to have better performance than the 1550 nm based FBG sensor.

  8. 超高场强小动物磁共振成像活体观察小鼠颈动脉内膜损伤后的动态变化%Dynamically observing carotid artery intimal injury in mice using 7T micro-MR imaging

    Institute of Scientific and Technical Information of China (English)

    陈骏; 贾振宇; 马占龙; 张秀明; 汪有锦; 王圆圆; 滕皋军

    2010-01-01

    Objective To dynamically observe stenosis and wall thickness of carotid artery with endothelium injury in mouse using 7T micro-MR imaging in vivo. Methods A mouse model of carotid artery intimal injury was established by removing endothelium with a flexible wire. The lumen diameter, lumen area, wall thickness and wall area of the injured arteries were observed, and serial MR scanning was performed in different time points after operation. Results The injured arteries and perivascular parenchyma were clearly observed by MR imaging. Before and 1, 5, 10 and 15 days after artery injury, the lumen diameter were (0.57±0.07)mm,(0.41±0.19)mm, (0.44±0.10)mm, (0.43±0.10)mm and (0.47±0.11)mm respectively, and the lumen area were (0.30±0.06)mm2, (0.18±0.11)mm2, (0.18±0.06)mm2, (0.18±0.06)mm2 and (0.22±0.07)mm2. The thickness of artery wall was(0.23±0.12)mm, and the area of artery wall was (0.35±0.24)mm2 15days after artery injury. Conclusions Stenosis and wall thickening of carotid artery after the artery intimal injury of mouse can be dynamically observed on MR imaging in vivo.%目的 磁共振成像(MRI)活体观察内膜损伤后小鼠颈动脉管腔狭窄和管壁增厚的动态过程.方法 金属丝损伤法建立小鼠颈动脉内膜损伤模型,术后不同的时间点行MRI扫描,动态观察损伤血管的表现,包括管腔内径和面积、管壁的厚度和面积.结果 MRI能够清晰地观察小鼠颈动脉内膜损伤后的变化以及血管周围软组织的表现.小鼠颈动脉内膜损伤前、损伤后1、5、10d和15d管腔内径分别为(0.57±0.07)、(0.41±0.19)、(0.44±0.10)、(0.43±0.10)mm和(0.47±0.11)mm.管腔面积分别为:(0.30±0.06)、(0.18±0.11)、(0.18±0.06)、(0.18±0.06)mm2和(0.22±0.07)mm2.术后第15天患侧血管壁厚度为(0.23±0.12)mm,管壁面积为(0.35±0.24)mm2.结论 MRI可以在活体观察小鼠颈动脉内膜损伤后管腔狭窄和管壁增厚的动态变化过程.

  9. Measurement of arterial compliance in vivo.

    Science.gov (United States)

    Wiinberg, N

    2000-01-01

    Measurement of arterial compliance is of interest in evaluating patients with atherosclerosis and other diseases which affect the vessels. Arterial compliance is the relation between changes in transmural pressure and volume of an arterial segment, where a high compliance signifies large changes in volume per change in transmural pressure. The relation between changes in transmural pressure and volume is far from linear as compliance increases progressively with decreases in blood pressure. A change in compliance could indicate static changes in arterial wall composition, i.e. the relation between elastic and collagen fibres and accumulation of disease related deposits or dynamic changes caused by alterations in muscular tone. The most used method reflecting arterial compliance is the measurement of pulse wave velocity. However, the pulse wave velocity method measures compliance at ambient transmural pressures and is affected both by the actual blood pressure and the rate of pressure change. Another commonly used method employs the echo-tracking technique to measure the arterial diameter simultaneously with continuous blood pressure monitoring. By this method it is possible to calculate arterial compliance for continuous pressure values between the diastole and the systole. The volume-oscillometry method is based on the fact that the artery can be made to collapse at the end of the diastole by an occlusive cuff while it remains open in a pressure dependent manner during the rest of the cardiac cycle. Changes in the arterial volume is transmitted to the cuff, where it induces a measurable change in pressure, and hence the volume of the artery can be calculated at different values of transmural pressures. Using this method on normal subjects has shown that the arterial compliance decreases with increasing age and that females have lower compliance than males primarily due to a smaller diameter of their arteries. It has also been shown that patients with essential

  10. Correlation between arterial wall stiffness, N-terminal prohormone of brain natriuretic peptide, functional and structural myocardial abnormalities in patients with type 2 diabetes mellitus and cardiac autonomic neuropathy

    Directory of Open Access Journals (Sweden)

    Viktoriya Aleksandrovna Serhiyenko

    2013-12-01

    Full Text Available Aim. To assess arterial wall stiffness, plasma levels of of N-terminal prohormone of brain natriuretic peptide (NT-proBNP, as well as functional state and structure of the myocardium in patients with type 2 diabetes mellitus (T2DM and cardiac autonomic neuropathy (CAN.Materials and Methods. The study involved a total of 65 patients with T2DM. 12 had no evidence of cardiovascular disease (CVD or CAN, 14 were diagnosed with subclinical stage of CAN, 18 – with functional stage, and 21 – with organic stage. We measured aortic pulse wave velocity (PWV, aortic augmentation index (AIx, brachial artery AIx, ambulatory arterial stiffness index (AASI and plasma levels of NT-proBNP. Clinical examination included ECG, Holter monitoring, ambulatory BP measurement and echocardiography.Results. Patients with isolated T2DM showed a trend for increased vascular wall stiffness. PWV was increased in patients with subclinical stage of CAN. Aortic and brachial AIx, PWV and AASI were elevated in patients with functional stage of CAN, PWV being significantly higher vs. subclinical CAN subgroup. Organic stage was characterized by pathologically increased values of all primary parameters; PWV and AASI were significantly higher compared with other groups. Development and progression of CAN was accompanied by an increase in NT-proBNP plasma levels. Concentration of NT-proBNP was in direct correlation with left ventricular mass (LVM and PWV. PWV and LVM values also directly correlated between themselves.Conclusion. Development and progression of CAN in patients with T2DM is accompanied by an increase in vascular wall stiffness. The elevation of plasma NT-proBNP in patients with T2DM correlates with the development of CAN and is significantly and independently associated with an increase in LVM and PWV. Our data suggests the pathophysiological interconnection between metabolic, functional and structural myocardial abnormalities in patients with T2DM and CAN.

  11. Dynamic behavior of radiant cooling system based on capillary tubes in walls made of high performance concrete

    DEFF Research Database (Denmark)

    Mikeska, Tomás; Svendsen, Svend

    2015-01-01

    the small amount of fresh air required by standards to provide a healthy indoor environment.This paper reports on experimental analyses evaluating the dynamic behavior of a test room equipped with a radiant cooling system composed of plastic capillary tubes integrated into the inner layer of sandwich wall...... elements made of high performance concrete. The influence of the radiant cooling system on the indoor climate of the test room in terms of the air, surface and operative temperatures and velocities was investigated.The results show that the temperature of the room air can be kept in a comfortable range...... using cooling water for the radiant cooling system with a temperature only about 4K lower than the temperature of the room air. The relatively high speed reaction of the designed system is a result of the slim construction of the sandwich wall elements made of high performance concrete. (C) 2015...

  12. Shape effects on dynamics of inertia-free spheroids in wall turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Challabotla, Niranjan Reddy; Zhao, Lihao; Andersson, Helge I. [Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim (Norway)

    2015-06-15

    The rotational motion of inertia-free spheroids has been studied in a numerically simulated turbulent channel flow. Although inertia-free spheroids were translated as tracers with the flow, neither the disk-like nor the rod-like particles adapted to the fluid rotation. The flattest disks preferentially aligned their symmetry axes normal to the wall, whereas the longest rods were parallel with the wall. The shape-dependence of the particle orientations carried over to the particle rotation such that the mean spin was reduced with increasing departure from sphericity. The streamwise spin fluctuations were enhanced due to asphericity, but substantially more for prolate than for oblate spheroids.

  13. Nonadiabatic Spin Torque Investigated Using Thermally Activated Magnetic Domain Wall Dynamics

    DEFF Research Database (Denmark)

    Eltschka, M.; Woetzel, Mathias; Rhensius, J.;

    2010-01-01

    Using transmission electron microscopy, we investigate the thermally activated motion of domain walls (DWs) between two positions in Permalloy (Ni80Fe20) nanowires at room temperature. We show that this purely thermal motion is well described by an Arrhenius law, allowing for a description...... magnetization gradients present....

  14. Some factors affecting the dynamics of a plasma-wall interaction simulator

    International Nuclear Information System (INIS)

    Isotope mixing and thermal desorption from samples exposed in a glow discharge apparatus were used to study the factors affecting hydrogen recycle and wall inventory. Conditions were chosen to be similar to those expected at the walls in today's experimental fusion devices. The size and nature of the hydrogen reservoir in the wall after plasma pulses was investigated by thermal desorption techniques. Large amounts of deuterium, i.e., 5 x 1015 D cm-2 remain in the sample 4 min after a single 200 ms plasma pulse. While this result may be explained by a model using bulk diffusion and traps, it is suggested that either a spectrum of desorption energies, or a concentration dependent recombination coefficient, may also be useful in describing the thermal desorption processes. Experiments with various pumping conditions show that readsorption of molecular hydrogen isotopes on the wall should be considered in modeling hydrogen recycle and isotope changeover processes. HD formation without plasmas confirms the role readsorption plays. (orig.)

  15. Synthetic reconstruction of dynamic blood flow in cortical arteries using optical coherence tomography for the evaluation of vessel compliance

    Science.gov (United States)

    Baraghis, Edward; Bolduc, Virginie; Gillis, Marc-Antoine; Srinivasan, Vivek J.; Thorin, Éric; Boudoux, Caroline; Lesage, Frédéric

    2011-03-01

    Optical Coherence Tomography (OCT) has recently been used to produce 3D angiography of microvasculature in the rodent brain in-vivo and blood flow maps of large vessels. Key enabling developments were novel algorithms for detecting Doppler shifts produced by moving scatterers and new scanning protocols tailored to increase sensitivity to small flow speeds. These progresses were pushed by the need for a non invasive imaging modality to monitor quantitative blood flow at a higher resolution and a greater depth than could be achieved by other means. The rationale for this work originates from new hypotheses regarding the role of blood regulation in neurodegenerative diseases and from current investigations of animal models of vascular degeneration. In this work we demonstrate the synthetic reconstruction of dynamic blood flow in mice over the course of a single cardiac cycle in an 800μm wide by ~ 3mm deep B-Frame slice with a lateral resolution of 10μm and a depth resolution of 7μm. Images were taken using a cranial window over the exposed parietal bone of mice skull. Electrocardiography (ECG) recordings were co registered with the OCT A lines at high temporal resolution. QRS peak detection was then used to locate the time value of each A-line in the cardiac cycle and to reconstruct a synthetic temporal frame over one cardiac cycle. Doppler speed in this cardiac cycle was used to measure temporal variations of flow inside arteries and of their area. Three dimensional volume scans yielded measurements of quantitative blood flow on the same arteries. Using these informations a measure of compliance could be established. Comparing measures between atherosclerotic (ATX) and wild type (WT) mice revealed higher blood flow in WT mice, suggested lower systemic compliance in the ATX group but higher compliance of cerebral vasculature on these mice. These results are consistent with expectations showing that OCT is a potential tool for in-vivo arterial compliance evaluation.

  16. Noninvasive Monitoring of Arterial Viscoelastic Indices Using a Foil-type Pressure Sensor

    Science.gov (United States)

    Maruyama, Hiromi; Hirano, Harutoyo; Kutluk, Abdugheni; Tsuji, Toshio; Fukuda, Osamu; Ueno, Naohiro; Ukawa, Teiji; Nakamura, Ryuji; Saeki, Noboru; Kawamoto, Masashi; Yoshizumi, Masao

    This paper proposes a noninvasive method for estimating the dynamic characteristics of arterial walls using pulse waves measured in various parts of the body by a foil-type pressure sensor. The sensor not only has high sensitivity and flexibility but also features the ability to continuously measure the alternating-current component of pulse waves. These capabilities make it suitable for estimating the dynamic characteristics of arterial walls. In this paper, a foil-type pressure sensor was employed to measure pulse waves based on the tonometry approach, and a method of estimating changes in arterial viscoelastic indices was proposed based on the measured pulse waves and photoplethysmograms. In order to accurately measure blood pressure, first, we examined suitable mechanical forces to the sensor, and found that values of 5-25[N] yielded the best performance. We then estimated the arterial viscoelastic indices of a radial artery and a dorsal pedis artery when mechanical pain stimuli were applied to the subjects. The results suggested that the estimated indices can be used to quantitatively assess vascular response caused by sympathicotonia. We thus concluded that the proposed method enabled noninvasive measurement of pulse waves in the dorsal pedis artery and estimation of arterial viscoelastic indices.

  17. Interstitial and arterial-venous [K+] in human calf muscle during dynamic exercise

    DEFF Research Database (Denmark)

    Green, S; Langberg, Henning; Skovgaard, D;

    2000-01-01

    little information on the response of [K+]I to exercise in human skeletal muscle. Five young healthy subjects performed plantar flexion exercise for four 5 min periods at increasing power outputs ( approximately 1-6 W) with 10 min intervening recovery periods, as well as for two 5 min periods...... with ischaemia at approximately 1 and approximately 3 W. Microdialysis probes were inserted into the gastrocnemius medialis muscle of the right leg to measure [K+]I, and K+ release from the plantar flexors during and after incremental exercise was calculated from plasma flow and arterial-venous differences for K...

  18. Detection of the posterior superior alveolar artery in the lateral sinus wall using computed tomography/cone beam computed tomography: a prevalence meta-analysis study and systematic review.

    Science.gov (United States)

    Varela-Centelles, P; Loira-Gago, M; Seoane-Romero, J M; Takkouche, B; Monteiro, L; Seoane, J

    2015-11-01

    A systematic search of MEDLINE, Embase, and Proceedings Web of Science was undertaken to assess the prevalence of the posterior superior alveolar artery (PSAA) in the lateral sinus wall in sinus lift patients, as identified using computed tomography (CT)/cone beam computed tomography (CBCT). For inclusion, the article had to report PSAA detection in the bony wall using CT and/or CBCT in patients with subsinus edentulism. Studies on post-mortem findings, mixed samples (living and cadaveric), those presenting pooled results only, or studies performed for a sinus pathology were excluded. Heterogeneity was checked using an adapted version of the DerSimonian and Laird Q test, and quantified by calculating the proportion of the total variance due to between-study variance (Ri statistic). Eight hundred and eleven single papers were reviewed and filtered according to the inclusion/exclusion criteria. Ten studies were selected (1647 patients and 2740 maxillary sinuses (study unit)). The pooled prevalence of PSAA was 62.02 (95% confidence interval (CI) 46.33-77.71). CBCT studies detected PSAA more frequently (78.12, 95% CI 61.25-94.98) than CT studies (51.19, 95% CI 42.33-60.05). Conventional CT revealed thicker arteries than CBCT. It is concluded that PSAA detection is more frequent when CBCT explorations are used. Additional comparative studies controlling for potential confounding factors are needed to ascertain the actual diagnostic value of radiographic explorations for assessing the PSAA prior to sinus floor elevation procedures. PMID:26215383

  19. Low frequency arterial wall movements for indirect blood pressure measurement in man. Validation of a method for non-invasive assessment of blood pressure under the influence of isoprenaline and angiotensin.

    Science.gov (United States)

    Dietz, U; Belz, G G

    1991-05-01

    In order to measure blood pressure noninvasively, the second derivative of the low frequency wall movements of the brachial artery were registered with a piezo-electric pressure probe during deflation of a Riva-Rocci cuff along with the actual cuff pressure. Two characteristic phenomena of this signal have been suggested to reflect systolic and diastolic blood pressure. Appearance of a positive spike phenomenon (S) was suggested to indicate systolic blood pressure and disappearance of a negative preanacrotic notch (D) to indicate diastolic blood pressure. To prove the validity of these suggestions, these phenomena were assessed in 10 young healthy males during isoprenaline and angiotensin induced changes of blood pressure. Intraarterial (A. radialis) and auscultatory (A. brachialis) blood pressures were recorded simultaneously. Determination of systolic blood pressure with the S phenomenon agreed well with invasive and auscultatory results. Invasive diastolic values agreed well with the cuff pressure at the last signal before disappearance of the preanacrotic notch (D1). Data from auscultation agreed less well with the D1 phenomenon. With increasing doses of isoprenaline, the diastolic measurements (D1) tended to be lower than the invasive ones. However, this discrepancy was far discreeter than that seen with ordinary auscultatory blood pressure measurement. We therefore conclude that registrations of low frequency arterial wall movements yield distinct characteristic spike phenomena useful for measurement of blood pressure in good agreement with the invasive method. In addition, the method provides clearly documented records and should be useful in situations which rely on a valid indirect method. PMID:1898428

  20. Growth dynamics of inner tubes inside cobaltocene-filled single-walled carbon nanotubes

    Science.gov (United States)

    Kharlamova, M. V.; Kramberger, Christian; Saito, Takeshi; Shiozawa, Hidetsugu; Pichler, Thomas

    2016-08-01

    We have synthesized cobaltocene-filled 1.7-nm-mean diameter single-walled carbon nanotubes (SWCNTs) and transformed them into double-walled carbon nanotubes by annealing at temperatures between 500 and 1000 °C for 2 h in vacuum. We analyze the temperature-dependent inner tube growth inside the filled SWCNTs by Raman spectroscopy. The changes in intensity of the Raman peaks of inner tubes with the diameters ranging from 0.832 to 1.321 nm with increasing annealing temperature are traced. It is revealed that the growth temperatures of larger diameter inner tubes are higher than the ones of smaller diameter tubes. A decrease in the diameter of the inner tubes by ~0.4 nm leads to a decrease in the growth temperature by ~200 °C.

  1. Diffusion of H2 and D2 Confined in Single-Walled Carbon Nanotubes: Quantum Dynamics and Confinement Effects.

    Science.gov (United States)

    Mondelo-Martell, Manel; Huarte-Larrañaga, Fermín

    2016-08-25

    We present quantum dynamics calculations of the diffusion constant of H2 and D2 along a single-walled carbon nanotube at temperatures between 50 and 150 K. We calculate the respective diffusion rates in the low-pressure limit by adapting well-known approaches and methods from the chemical dynamics field using two different potential energy surfaces to model the C-H interaction. Our results predict a usual kinetic isotope effect, with H2 diffusing faster than D2 in the higher temperature range but a reverse trend at temperatures below 50-70 K. These findings are consistent with experimental observation in similar systems and can be explained by the different effective size of both isotopes resulting from their different zero-point energy. PMID:27459476

  2. Statics and field-driven dynamics of transverse domain walls in biaxial nanowires under uniform transverse magnetic fields

    Science.gov (United States)

    Lu, Jie

    2016-06-01

    In this work, we report analytical results on transverse domain wall (TDW) statics and field-driven dynamics in quasi-one-dimensional biaxial nanowires under arbitrary uniform transverse magnetic fields (TMFs) based on the Landau-Lifshitz-Gilbert equation. Without axial driving fields, the static TDW should be symmetric about its center while twisted in its azimuthal angle distribution. By decoupling polar and azimuthal degrees of freedom, an approximate solution is provided which reproduces these features to a great extent. When an axial driving field is applied, the dynamical behavior of a TDW is viewed as the response of its static profile to external excitations. By means of the asymptotic expansion method, the TDW velocity in the traveling-wave mode is obtained, which provides the extent and boundary of the "velocity-enhancement" effect of TMFs on TDWs in biaxial nanowires. Finally, numerical simulations are performed and strongly support our analytics.

  3. Dynamic Response of High Rise Structures Under The Influence of Shear Walls

    OpenAIRE

    Syed Khasim Mutwalli; Dr. Shaik Kamal Mohammed Azam

    2014-01-01

    This study presents the procedure for seismic performance estimation of high-rise buildings based on a concept of the capacity spectrum method. In 3D analytical model of thirty storied buildings have been generated for symmetric buildings Models and analyzed using structural analysis tool ETABS. The analytical model of the building includes all important components that influence the mass, strength, stiffness and deformability of the structure. To study the effect of concrete core wall & shea...

  4. The dynamics of a capsule in a wall-bounded oscillating shear flow

    CERN Document Server

    Zhu, LaiLai; Brandt, Luca

    2015-01-01

    The motion of an initially spherical capsule in a wall-bounded oscillating shear flow is investigated via an accelerated boundary integral implementation. The neo-Hookean model is used as the constitutive law of the capsule membrane. The maximum wall-normal migration is observed when the oscillation period of the imposed shear is of the order of the relaxation time of the elastic membrane; hence, the optimal capillary number scales with the inverse of the oscillation frequency and the ratio agrees well with the theoretical prediction in the limit of high-frequency oscillation. The migration velocity decreases monotonically with the frequency of the applied shear and the capsule-wall distance. We report a significant correlation between the capsule lateral migration and the normal stress difference induced in the flow. The periodic variation of the capsule deformation is roughly in phase with that of the migration velocity and normal stress difference, with twice the frequency of the imposed shear. The maximum...

  5. Dynamic Interplay of Coherent Rotations and Domain Wall Motion in Faraday Rotators based on Ferromagnetic Crystals

    Science.gov (United States)

    Garzarella, Anthony; Wu, Dong; Shinn, Mannix

    Under small, externally-applied magnetic fields, the Faraday rotation in magneto-optic material containing ferromagnetic domains is driven primarily by two principal mechanisms: domain wall motion and coherent domain rotations. Domain wall motion yields a larger Faraday responsivity but is limited by magnetically induced optical incoherence and by damping effects. Coherent domain rotation yields smaller Faraday rotations, but exhibits a flatter and broader frequency response. The two mechanisms occur along orthogonal principal axes and may be probed independently. However, when probed along an oblique angle to the principal axes, the relationship between the Faraday rotation and the external field changes from linear to tensorial. Although this may lead to more complicated phenomena (e.g. a sensitivity axis that depends on RF frequency), the interplay of domain rotation and domain wall motion can be exploited to improve responsivity or bandwidth. The detailed experimental data can be understood in terms of a quantitative model for the magnitude and direction of the responsivity vector. Applications to magnetic field sensors based on arrayed bismuth doped iron garnet films will be emphasized in this presentation.

  6. The dynamics of field and current-driven magnetic domain wall depinning

    Science.gov (United States)

    Beach, Geoffrey; Knutson, Carl; Tsoi, Maxim; Erskine, James

    2008-03-01

    The depinning of a magnetic domain wall from a well-defined potential well was studied experimentally on timescales ranging from minutes down to tens of nanoseconds. At longer timescales, the behavior follows the classical Neel-Brown model of thermal activation, one of the few observations of this process for the ideal case of a single energy barrier. Below one microsecond, however, the depinning rate becomes independent of the activation volume and assumes a more universal behavior. This transition is due to a vanishing of the energy barrier at a critical field, beyond which the rate of depinning depends primarily on the torque supplied by the field and spin current. A dc spin-polarized current flowing across the domain wall has the effect of lowering the energy barrier by an amount that is predominantly quadratic in current, independent of its direction. This is seen to arise from a shift of the wall in the energy potential due to the adiabatic component of spin-transfer torque.

  7. The Dynamics and Thermodynamics of Soft-Wall AdS/QCD

    CERN Document Server

    Kelley, Thomas M

    2011-01-01

    Gauge/Gravity dualities open the non-perturbative realms of strongly-coupled gauge theories to analytic treatment. Anti-de Sitter Space/Conformal Field The- ory, one way of connecting gravity dual models to gauge theories, is a correspon- dence between a ten-dimensional Type IIB superstring theory in AdS5 \\times S 5 and a N = 4 super Yang Mills theory. To describe systems that are experimentally ac- cessible, however, the formal correspondence is modified into a phenomenological duality between a five-dimensional gravity model and a strongly coupled QCD-like gauge theory. This duality is referred to as AdS/QCD. This work explores aspects of the soft-wall AdS/QCD model. The phrase 'soft wall' refers to the means of breaking the conformal symmetry and introducing a mass scale to the gauge side of the duality. We add higher-order terms to the soft-wall Lagrangian and calculate the effect on physical observables. Meson mass spectra gain a more complex structure, exhibiting a better match with the experimental val...

  8. Dynamics of chest wall volume regulation during constant work rate exercise in patients with chronic obstructive pulmonary disease

    Energy Technology Data Exchange (ETDEWEB)

    Takara, L.S.; Cunha, T.M.; Barbosa, P.; Rodrigues, M.K.; Oliveira, M.F.; Nery, L.E. [Setor de Função Pulmonar e Fisiologia Clínica do Exercício, Disciplina de Pneumologia, Departamento de Medicina, Universidade Federal de São Paulo, São Paulo, SP (Brazil); Neder, J.A. [Setor de Função Pulmonar e Fisiologia Clínica do Exercício, Disciplina de Pneumologia, Departamento de Medicina, Universidade Federal de São Paulo, São Paulo, SP (Brazil); Division of Respiratory and Critical Care Medicine, Department of Medicine, Queen' s University, Kingston, ON (Canada)

    2012-10-15

    This study evaluated the dynamic behavior of total and compartmental chest wall volumes [(V{sub CW}) = rib cage (V{sub RC}) + abdomen (V{sub AB})] as measured breath-by-breath by optoelectronic plethysmography during constant-load exercise in patients with stable chronic obstructive pulmonary disease. Thirty males (GOLD stages II-III) underwent a cardiopulmonary exercise test to the limit of tolerance (Tlim) at 75% of peak work rate on an electronically braked cycle ergometer. Exercise-induced dynamic hyperinflation was considered to be present when end-expiratory (EE) V{sub CW} increased in relation to resting values. There was a noticeable heterogeneity in the patterns of V{sub CW} regulation as EEV{sub CW} increased non-linearly in 17/30 “hyperinflators” and decreased in 13/30 “non-hyperinflators” (P < 0.05). EEV{sub AB} decreased slightly in 8 of the “hyperinflators”, thereby reducing and slowing the rate of increase in end-inspiratory (EI) V{sub CW} (P < 0.05). In contrast, decreases in EEV{sub CW} in the “non-hyperinflators” were due to the combination of stable EEV{sub RC} with marked reductions in EEV{sub AB}. These patients showed lower EIV{sub CW} and end-exercise dyspnea scores but longer Tlim than their counterparts (P < 0.05). Dyspnea increased and Tlim decreased non-linearly with a faster rate of increase in EIV{sub CW} regardless of the presence or absence of dynamic hyperinflation (P < 0.001). However, no significant between-group differences were observed in metabolic, pulmonary gas exchange and cardiovascular responses to exercise. Chest wall volumes are continuously regulated during exercise in order to postpone (or even avoid) their migration to higher operating volumes in patients with COPD, a dynamic process that is strongly dependent on the behavior of the abdominal compartment.

  9. Dynamics of chest wall volume regulation during constant work rate exercise in patients with chronic obstructive pulmonary disease

    Directory of Open Access Journals (Sweden)

    L.S. Takara

    2012-12-01

    Full Text Available This study evaluated the dynamic behavior of total and compartmental chest wall volumes [(V CW = rib cage (V RC + abdomen (V AB] as measured breath-by-breath by optoelectronic plethysmography during constant-load exercise in patients with stable chronic obstructive pulmonary disease. Thirty males (GOLD stages II-III underwent a cardiopulmonary exercise test to the limit of tolerance (Tlim at 75% of peak work rate on an electronically braked cycle ergometer. Exercise-induced dynamic hyperinflation was considered to be present when end-expiratory (EE V CW increased in relation to resting values. There was a noticeable heterogeneity in the patterns of V CW regulation as EEV CW increased non-linearly in 17/30 "hyperinflators" and decreased in 13/30 "non-hyperinflators" (P < 0.05. EEV AB decreased slightly in 8 of the "hyperinflators", thereby reducing and slowing the rate of increase in end-inspiratory (EI V CW (P < 0.05. In contrast, decreases in EEV CW in the "non-hyperinflators" were due to the combination of stable EEV RC with marked reductions in EEV AB. These patients showed lower EIV CW and end-exercise dyspnea scores but longer Tlim than their counterparts (P < 0.05. Dyspnea increased and Tlim decreased non-linearly with a faster rate of increase in EIV CW regardless of the presence or absence of dynamic hyperinflation (P < 0.001. However, no significant between-group differences were observed in metabolic, pulmonary gas exchange and cardiovascular responses to exercise. Chest wall volumes are continuously regulated during exercise in order to postpone (or even avoid their migration to higher operating volumes in patients with COPD, a dynamic process that is strongly dependent on the behavior of the abdominal compartment.

  10. Dynamics of chest wall volume regulation during constant work rate exercise in patients with chronic obstructive pulmonary disease

    International Nuclear Information System (INIS)

    This study evaluated the dynamic behavior of total and compartmental chest wall volumes [(VCW) = rib cage (VRC) + abdomen (VAB)] as measured breath-by-breath by optoelectronic plethysmography during constant-load exercise in patients with stable chronic obstructive pulmonary disease. Thirty males (GOLD stages II-III) underwent a cardiopulmonary exercise test to the limit of tolerance (Tlim) at 75% of peak work rate on an electronically braked cycle ergometer. Exercise-induced dynamic hyperinflation was considered to be present when end-expiratory (EE) VCW increased in relation to resting values. There was a noticeable heterogeneity in the patterns of VCW regulation as EEVCW increased non-linearly in 17/30 “hyperinflators” and decreased in 13/30 “non-hyperinflators” (P < 0.05). EEVAB decreased slightly in 8 of the “hyperinflators”, thereby reducing and slowing the rate of increase in end-inspiratory (EI) VCW (P < 0.05). In contrast, decreases in EEVCW in the “non-hyperinflators” were due to the combination of stable EEVRC with marked reductions in EEVAB. These patients showed lower EIVCW and end-exercise dyspnea scores but longer Tlim than their counterparts (P < 0.05). Dyspnea increased and Tlim decreased non-linearly with a faster rate of increase in EIVCW regardless of the presence or absence of dynamic hyperinflation (P < 0.001). However, no significant between-group differences were observed in metabolic, pulmonary gas exchange and cardiovascular responses to exercise. Chest wall volumes are continuously regulated during exercise in order to postpone (or even avoid) their migration to higher operating volumes in patients with COPD, a dynamic process that is strongly dependent on the behavior of the abdominal compartment

  11. Vortex dynamics and wall shear stress behaviour associated with an elliptic jet impinging upon a flat plate

    Science.gov (United States)

    Long, J.; New, T. H.

    2016-07-01

    Vortical structures and dynamics of a Re h = 2100 elliptic jet impinging upon a flat plate were studied at H/ d h = 1, 2 and 4 jet-to-plate separation distances. Flow investigations were conducted along both its major and minor planes using laser-induced fluorescence and digital particle image velocimetry techniques. Results show that the impingement process along the major plane largely consists of primary jet ring-vortex and wall-separated secondary vortex formations, where they subsequently separate from the flat plate at smaller H/ d h = 1 and 2 separation distances. Key vortex formation locations occur closer to the impingement point as the separation distance increases. Interestingly, braid vortices and rib structures begin to take part in the impingement process at H/ d h = 4 and wave instabilities dominate the flow field. In contrast, significantly more coherent primary and secondary vortices with physically larger vortex core sizes and higher vortex strengths are observed along the minor plane, with no signs of braid vortices and rib structures. Lastly, influences of these different flow dynamics on the major and minor plane instantaneous and mean skin friction coefficient levels are investigated to shed light on the effects of separation distance on the wall shear stress distributions.

  12. The dynamics of plant cell-wall polysaccharide decomposition in leaf-cutting ant fungus gardens

    DEFF Research Database (Denmark)

    Moller, Isabel Eva; de Fine Licht, Henrik Hjarvard; Harholt, Jesper;

    2011-01-01

    The degradation of live plant biomass in fungus gardens of leaf-cutting ants is poorly characterised but fundamental for understanding the mutual advantages and efficiency of this obligate nutritional symbiosis. Controversies about the extent to which the garden-symbiont Leucocoprinus gongylophorus......, to map the occurrence of cell wall polymers in consecutive sections of the fungus garden of the leaf-cutting ant Acromyrmex echinatior. We show that pectin, xyloglucan and some xylan epitopes are degraded, whereas more highly substituted xylan and cellulose epitopes remain as residuals in the waste...

  13. Time-resolved magnetization dynamics of cross-tie domain walls in permalloy microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Miguel, J; Kurde, J; Piantek, M; Kuch, W [Institut fuer Experimentalphysik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin (Germany); Sanchez-Barriga, J; Heitkamp, B; Kronast, F; Duerr, H A [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Strasse 15, D-12489 Berlin (Germany); Bayer, D; Aeschlimann, M, E-mail: jorge.miguel@fu-berlin.d [Fachbereich Physik, Universitaet Kaiserslautern, Erwin-Schroedinger Strasse 46, D-67663 Kaiserslautern (Germany)

    2009-12-02

    We report on a picosecond time-resolved x-ray magnetic circular dichroic-photoelectron emission microscopy study of the evolution of the magnetization components of a microstructured permalloy platelet comprising three cross-tie domain walls. A laser-excited photoswitch has been used to apply a triangular 80 Oe, 160 ps magnetic pulse. Micromagnetic calculations agree well with the experimental results, both in time and frequency, illustrating the large angle precession in the magnetic domains with magnetization perpendicular to the applied pulse, and showing how the magnetic vortices revert their core magnetization while the antivortices remain unaffected.

  14. Domain-wall dynamics at micropatterned constrictions in ferromagnetic (Ga,Mn)As epilayers

    OpenAIRE

    Honolka, J.; Masmanidis, S.; Tang, H. X.; Roukes, M.L.; Awschalom, D. D.

    2005-01-01

    The influence of sub-µm geometric constrictions on 90° magnetic domain-wall nucleation and propagation in stripes of ferromagnetic (Ga0.95,Mn0.05)As was explored. Measurements of the magnetic switching behavior were performed during ramping of an external magnetic field at constant rate and at constant field in the time domain. Demagnetizing fields are found to play a crucial role in the switching behavior around the region of the constriction. Depending on the sample's initial magnetization ...

  15. Ultrafast carrier dynamics in purified and as-grown single-walled carbon nanotube films

    Institute of Scientific and Technical Information of China (English)

    Long Yong-Bing; Song Li; Zhang Chun-Yu; Wang Li; Fu Pan-Ming; Zhang Zhi-Guo; Xie Si-Shen; Wang Guo-Ping

    2005-01-01

    Ultrafast time-resolved optical transmissions in purified and as-grown single-walled carbon nanotube films are measured at a temperature of 200K. The signal of the purified sample shows a crossover from photobleaching to photoabsorption. The former and the latter are interpreted as the state filling and the red shift of the π-plasmon,respectively. The signal of the as-grown sample can be perfectly fitted by a single-exponential with a time constant of 232fs. The disappearance of the negative component in the as-grown sample is attributed to the charge transfer between the semiconducting nanotubes and the impurities.

  16. Test of the diffusing-diffusivity mechanism using near-wall colloidal dynamics

    CERN Document Server

    Matse, Mpumelelo

    2016-01-01

    The diffusing-diffusivity mechanism proposed by Chubynsky and Slater [PRL 113, 098302, 2014] predicts that, in environments where the diffusivity changes gradually, the displacement distribution becomes non-Gaussian, even though the mean-squared displacement (MSD) grows linearly with time. Here, we report single-particle tracking measurements of the diffusion of colloidal spheres near a planar wall. Because the local effective diffusivity is known, we have been able to carry out the first direct test of this mechanism for diffusion in inhomogeneous media.

  17. Seismic shear wall ISP NUPEC's seismic ultimate dynamic response test. Comparison report

    International Nuclear Information System (INIS)

    In the seismic design of a nuclear power plant, evaluation of the ultimate strength of the nuclear reactor building is an important subject for assessment of seismic reliability of the plant. In order to carry out the evaluation, the response characteristics of reinforced concrete seismic shear walls up to their ultimate state have to be understood. For this purpose, there is a need to develop reliable non-linear response analysis methods which enables the reliable ultimate strength evaluation of nuclear reactor buildings. Along with this need, many computer codes have been developed. These computer codes are compared. (K.A.)

  18. Effects of Pulsatile Pressure on Stress Distributionin Artery Wall at in Vivo Longitudinal Limit Constraint%脉动血压对在体轴向极限强约束血管壁应力分布的影响

    Institute of Scientific and Technical Information of China (English)

    陈泳; 覃开蓉; 滕忠照; 柳兆荣

    2000-01-01

    本文详细分析正弦脉动压力载荷对动脉管壁应力分布的影响。结果表明,对某确定时刻,包含在运动方程中的惯性项对血管壁应力的影响很小,可忽略不计;在体轴向极限强约束下,血管壁周向应力随时间的变化曲线与压力曲线同相位和同周期,而且振幅不随频率的快慢而改变。一个心动周期内,血管内、外壁处周向应力随时间变化的平均值只与脉动压力载荷的平均值有关,而振幅主要与脉压有关,在内壁处随平均压的改变有一定变化,但在外壁处受平均压的影响很小。%In this paper, the effects of the sinusoidal pulsatile pressure on the stress distribution in the artery wall will be studied. Results show that the acceleration term in the equation of motion has little influence on the stress in the artery wall, and can be ignored. At in vivo longitudinal limit constraint, the variation of the circumferential stress with time have the same phase and period with the curves of the pulsatile pressure, and the amplitudes have no change with the frequency. During a cardiac cycle, the mean circumferential stress in the inner and outer wall only relates to the mean pressure, and the pulsatile stress value is mainly connected with the pulsatile pressure. The change of mean pressure has some influence to the pulsatile value in the inner wall, and little influence in the outer wall.

  19. Dynamics of fragmentation and multiple vacancy generation in irradiated single-walled carbon nanotubes

    International Nuclear Information System (INIS)

    The results from mass spectrometry of clusters sputtered from Cs+ irradiated single-walled carbon nanotubes (SWCNTs) as a function of energy and dose identify the nature of the resulting damage in the form of multiple vacancy generation. For pristine SWCNTs at all Cs+ energies, C2 is the most dominant species, followed by C3, C4 and C1. The experiments were performed in three stages: in the first stage, Cs+ energy E(Cs+) was varied. During the second stage, the nanotubes were irradiated continuously at E(Cs+) = 5 keV for 1,800 s. Afterwards, the entire sequence of irradiation energies was repeated to differentiate between the fragmentation patterns of the pristine and of heavily irradiated SWCNTs. The sputtering and normalized yields identify the quantitative and relative extent of the ion-induced damage by creating double, triple and quadruple vacancies; the single vacancies are least favored. Sputtering from the heavily irradiated SWCNTs occurs not only from the damaged and fragmented nanotubes, but also from the inter-nanotube structures that are grown due to the accumulation of the sputtered clusters. Similar irradiation experiments were performed with the multi-walled carbon nanotubes; the results confirmed the dominant C2 followed by C3, C4 and C1

  20. Heart wall motion analysis by dynamic 3D strain rate imaging from tissue Doppler echocardiography

    Science.gov (United States)

    Hastenteufel, Mark; Wolf, Ivo; de Simone, Raffaele; Mottl-Link, Sibylle; Meinzer, Hans-Peter

    2002-04-01

    The knowledge about the complex three-dimensional (3D) heart wall motion pattern, particular in the left ventricle, provides valuable information about potential malfunctions, e.g., myocardial ischemia. Nowadays, echocardiography (cardiac ultrasound) is the predominant technique for evaluation of cardiac function. Beside morphology, tissue velocities can be obtained by Doppler techniques (tissue Doppler imaging, TDI). Strain rate imaging (SRI) is a new technique to diagnose heart vitality. It provides information about the contraction ability of the myocardium. Two-dimensional color Doppler echocardiography is still the most important clinical method for estimation of morphology and function. Two-dimensional methods leads to a lack of information due to the three-dimensional overall nature of the heart movement. Due to this complex three-dimensional motion pattern of the heart, the knowledge about velocity and strain rate distribution over the whole ventricle can provide more valuable diagnostic information about motion disorders. For the assessment of intracardiac blood flow three-dimensional color Doppler has already shown its clinical utility. We have developed methods to produce strain rate images by means of 3D tissue Doppler echocardiography. The tissue Doppler and strain rate images can be visualized and quantified by different methods. The methods are integrated into an interactively usable software environment, making them available in clinical everyday life. Our software provides the physician with a valuable tool for diagnosis of heart wall motion.

  1. Hemodynamics in Idealized Stented Coronary Arteries: Important Stent Design Considerations

    OpenAIRE

    Beier, Susann; Ormiston, John; Webster, Mark; Cater, John; Norris, Stuart; Medrano-Gracia, Pau; Young, Alistair; Cowan, Brett

    2015-01-01

    Stent induced hemodynamic changes in the coronary arteries are associated with higher risk of adverse clinical outcome. The purpose of this study was to evaluate the impact of stent design on wall shear stress (WSS), time average WSS, and WSS gradient (WSSG), in idealized stent geometries using computational fluid dynamics. Strut spacing, thickness, luminal protrusion, and malapposition were systematically investigated and a comparison made between two commercially available stents (Omega and...

  2. Pharmacological modulation of arterial stiffness.

    LENUS (Irish Health Repository)

    Boutouyrie, Pierre

    2011-09-10

    Arterial stiffness has emerged as an important marker of cardiovascular risk in various populations and reflects the cumulative effect of cardiovascular risk factors on large arteries, which in turn is modulated by genetic background. Arterial stiffness is determined by the composition of the arterial wall and the arrangement of these components, and can be studied in humans non-invasively. Age and distending pressure are two major factors influencing large artery stiffness. Change in arterial stiffness with drugs is an important endpoint in clinical trials, although evidence for arterial stiffness as a therapeutic target still needs to be confirmed. Drugs that independently affect arterial stiffness include antihypertensive drugs, mostly blockers of the renin-angiotensin-aldosterone system, hormone replacement therapy and some antidiabetic drugs such as glitazones. While the quest continues for \\'de-stiffening drugs\\

  3. The Effect of Shear Wall Distribution on the Dynamics of Reinforced Concrete Structures

    International Nuclear Information System (INIS)

    The inclusion of a soft storey in multistory concrete buildings is a feature gaining popularity in urban areas where land is of exorbitant cost. In earthquake prone zones, this feature has been observed in post earthquake investigations. Although engineers are prepared to accept the notion that a soft storey poses a weak link in Seismic Design, yet the idea demands better understanding. The following study illustrates the importance of the judicious distribution of shear walls. The selected building is analyzed through nine numerical models which address the behavior of framed structures. The parameters discussed include, inter alias, the fundamental period of vibration, lateral displacements, axial and shear forces. It is noticed that an abrupt change in stiffness between the soft storey and the level above is responsible for increasing the strength demand on first storey columns. Extending the elevator shafts throughout the soft storey is strongly recommended

  4. Time-domain solution for transient dynamic response of a large-diameter thin-walled pipe pile

    Science.gov (United States)

    Ding, Xuanming; Liu, Hanlong; Chu, Jian; Cheng, Ke

    2015-06-01

    The propagation of stress waves in a large-diameter pipe pile for low strain dynamic testing cannot be explained properly by traditional 1D wave theories. A new computational model is established to obtain a wave equation that can describe the dynamic response of a large-diameter thin-walled pipe pile to a transient point load during a low strain integrity test. An analytical solution in the time domain is deduced using the separation of variables and variation of constant methods. The validity of this new solution is verified by an existing analytical solution under free boundary conditions. The results of this time domain solution are also compared with the results of a frequency domain solution and field test data. The comparisons indicate that the new solution agrees well with the results of previous solutions. Parametric studies using the new solution with reference to a case study are also carried out. The results show that the mode number affects the accuracy of the dynamic response. A mode number greater than 10 is required to enable the calculated dynamic responses to be independent of the mode number. The dynamic response is also greatly affected by soil properties. The larger the side resistance, the smaller the displacement response and the smaller the reflected velocity wave crest. The displacement increases as the stress waves propagate along the pile when the pile shaft is free. The incident waves of displacement and velocity responses of the pile are not the same among different points in the circumferential direction on the pile top. However, the arrival time and peak value of the pile tip reflected waves are almost the same among different points on the pile top.

  5. FE-analysis of dynamic creep-damage in thin-walled structures

    OpenAIRE

    Morachkovsky, Oleg; Breslavsky, Dmitry; Burlayenko, Vyacheslav

    2002-01-01

    The models for description of creep-damage behaviour in materials and thin shallow shells and plates deforming in conditions of joint action of static and fast cyclic load are given. The properties of the proposed material model were established by comparison of experimental and numerical data. The method for numerical simulation by in-house code of a dynamic creep and long-term strength of shallow shells and plates is created on the basis of the FEM. New laws of dynamic creep influence on st...

  6. Random perturbations of arterial blood pressure for the assessment of dynamic cerebral autoregulation

    International Nuclear Information System (INIS)

    The assessment of cerebral autoregulation (CA) relies mostly on methods that modulate arterial blood pressure (ABP). Despite advances, the gold standard of assessment remains elusive and clinical practicality is limited. We investigate a novel approach of assessing CA, consisting of the intermittent application of thigh cuffs using square wave sequences. Our aim was to increase ABP variability whilst minimizing volunteer discomfort, thus improving assessment acceptability. Two random square wave sequences and two maximum pressure settings (80 and 150 mmHg) were used, corresponding to four manoeuvres that were conducted in random order after a baseline recording. The intermittent application of thigh cuffs resulted in an amplitude dependent increase in ABP (p = 0.001) and cerebral blood flow velocity (CBFV) variability (p = 0.026) compared to baseline. No statistically significant differences in mean heart rate or heart rate variability were observed (p = 0.108 and p = 0.350, respectively), suggesting that no significant sympathetic response was elicited. No significant differences in the CBFV step response were observed, suggesting no distortion of autoregulatory parameters resulted from the use of thigh cuffs. We conclude that pseudorandom binary sequences are an effective and safe alternative for increasing ABP variability. This new approach shows great promise as a tool for the robust assessment of CA. (paper)

  7. Dynamics of 2+1 dimensional SOS surfaces above a wall: slow mixing induced by entropic repulsion

    CERN Document Server

    Caputo, Pietro; Martinelli, Fabio; Sly, Allan; Toninelli, Fabio Lucio

    2012-01-01

    We study the Glauber dynamics for the (2+1)D Solid-On-Solid model above a hard wall and below a far away ceiling, on an $L \\times L$ box of $Z^2$ with zero boundary conditions, at large inverse-temperature $\\beta$. It was shown by Bricmont, El-Mellouki and Fr\\"ohlich (1986) that the floor constraint induces an entropic repulsion effect which lifts the surface to an average height $H \\asymp (1/\\beta)\\log L$. As an essential step in understanding the effect of entropic repulsion on the Glauber dynamics we determine the equilibrium height $H$ to within an additive constant: $H=(1/4\\beta)\\log L+O(1)$. We then show that starting from zero initial conditions the surface rises to its final height $H$ through a sequence of metastable transitions between consecutive levels. The time for a transition from height $h=aH $, $a\\in (0,1)$, to height $h+1$ is roughly $\\exp(c L^a)$ for some constant $c>0$. In particular, the mixing time of the dynamics is exponentially large in $L$, i.e., $T_{mix} \\geq e^{c L}$. We also provi...

  8. Dual anterior descending coronary artery associated with coronary artery disease

    Directory of Open Access Journals (Sweden)

    Siqueira Luciane da L. V.

    2003-01-01

    Full Text Available The patient is a male with risk factors for coronary artery disease, who was referred for cardiac catheterization after acute myocardial infarction in the inferior wall. The patient underwent transluminal coronary angioplasty in the right coronary artery with successful stent implantation.

  9. Exact dynamic stiffness matrix of non-symmetric thin-walled curved beams subjected to initial axial force

    Science.gov (United States)

    Nam-Il, Kim; Moon-Young, Kim

    2005-06-01

    An improved numerical method to exactly evaluate the dynamic element stiffness matrix is proposed for the spatially coupled free vibration analysis of non-symmetric thin-walled curved beams subjected to uniform axial force. For this purpose, firstly equations of motion, boundary conditions and force-deformation relations are rigorously derived from the total potential energy for a curved beam element. Next systems of linear algebraic equations with non-symmetric matrices are constructed by introducing 14 displacement parameters and transforming the fourth-order simultaneous differential equations into the first-order simultaneous equations. And then explicit expressions for displacement parameters are numerically evaluated via eigensolutions and the exact 14×14 element stiffness matrix is determined using force-deformation relations. In order to demonstrate the validity and the accuracy of this study, the spatially coupled natural frequencies of non-symmetric thin-walled curved beams subjected to uniform compressive and tensile forces are evaluated and compared with analytical and finite element solutions using Hermitian curved beam elements or ABAQUS's shell element. In addition, some results by the parametric study are reported.

  10. Resistive wall instabilities and tearing mode dynamics in the EXTRAP T2R thin shell reversed-field pinch

    Science.gov (United States)

    Malmberg, J.-A.; Brunsell, P. R.

    2002-01-01

    Observations of resistive wall instabilities and tearing mode dynamics in the EXTRAP T2R thin shell (τw=6 ms) reversed field pinch are described. A nonresonant mode (m=1,n=-10) with the same handedness as the internal field grows nearly exponentially with an average growth time of about 2.6 ms (less than 1/2 of the shell time) consistent with linear stability theory. The externally nonresonant unstable modes (m=1,n>0), predicted by linear stability theory, are observed to have only low amplitudes (in the normal low-Θ operation mode of the device). The radial field of the dominant internally resonant tearing modes (m=1,n=-15 to n=-12) remain low due to spontaneous fast mode rotation, corresponding to angular phase velocities up to 280 krad/s. Phase aligned mode structures are observed to rotate toroidally with an average angular velocity of 40 krad/s, in the opposite direction of the plasma current. Toward the end of the discharge, the radial field of the internally resonant modes grows as the modes slow down and become wall-locked, in agreement with nonlinear computations. Fast rotation of the internally resonant modes has been observed only recently and is attributed to a change of the front-end system (vacuum vessel, shell, and TF coil) of the device.

  11. Dynamic analysis of moisture transport through walls and associated cooling loads in the hot/humid climate of Florianopolis, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, N.; Winkelmann, F.C. [Lawrence Berkeley Lab., CA (United States). Energy and Environment Div.; Lamberts, R.; Philippi, P.C.; Da Cunha Neto, J.A.B. [Federal Univ. of Santa Catarina, Florianopolis, Santa Catarina (Brazil). Mechanical Engineering Dept.

    1996-04-01

    The authors describe the use of a dynamic model of combined heat and mass transfer to analyze the effects on cooling loads of transient moisture storage and transport through walls with porous building materials, under varying boundary conditions. The materials studied were brick, lime mortar and autoclaved cellular concrete. The physical properties of these materials, such as mass transport coefficients, thermal conductivity and specific heat, were taken to be functions of moisture content. The simulation results were compared to those obtained by pure conduction heat transfer without moisture effects. Also analyzed were the influence on cooling loads of high moisture content due to rain soaking of materials, and the influence of solar radiation on sunny and cloudy days. The weather used was a hot/humid summer period in Florianopolis (South Brazil). It is shown that neglecting moisture migration or assuming that the physical properties of wall materials do not depend on moisture content can result in large errors in sensible and latent heat transfer.

  12. Molecular dynamics simulation of melting and crystallization processes of polyethylene clusters confined in armchair single-walled carbon nanotubes.

    Science.gov (United States)

    Zhou, Zhou; Wang, Jinjian; Zhu, Xiaolei; Lu, Xiaohua; Guan, Wenwen; Yang, Yuchen

    2015-01-01

    The confined interaction is important to understand the melting and crystallization of polymers within single-wall carbon tube (SWNT). However, it is difficult for us to observe this interaction. In the current work, the structures and behaviors of melting and crystallization for polyethylene (PE) clusters confined in armchair single-walled carbon nanotubes ((n,n)-SWNTs) are investigated and examined based on molecular dynamics (MD) simulations. The nonbonded energies, structures, Lindemman indices, radial density distributions, and diffusion coefficients are used to demonstrate the features of melting phase transition for PE clusters confined in (n,n)-SWNTs. The chain end-to-end distance (R(n)) and chain end-to-end distribution are used to examine the flexibility of the PE chain confined in SWNT. The global orientational order parameter (P2) is employed to reveal the order degree of whole PE polymer. The effect of polymerization degree on melting temperature and the influence of SWNT chirality on structure of PE cluster are examined and discussed. Results demonstrate that within the confined environment of SWNT, PE clusters adopt novel co-axial crystalline layer structure, in which parallel chains of each layer are approximately vertical to tube axis. The disordered-ordered transformation of PE chains in each layer is an important structural feature for crystallization of confined PE clusters. SWNTs have a considerable effect on the structures and stabilities of the confined PE clusters.

  13. Detection of a coronary artery vessel wall: performance of 0.3 mm fine-cell detector computed tomography-a phantom study

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Minoru [Multi-dimension Biomedical Imaging and Information Laboratory in Research Park, Keio University School of Medicine, Tokyo (Japan); Jinzaki, Masahiro; Tanami, Yutaka; Matsumoto, Kazuhiro; Ueno, Akihisa; Kuribayashi, Sachio [Department of Diagnostic Radiology, Keio University School of Medicine, Tokyo (Japan); Nukui, Masatake; Imai, Yasuhiro; Ishihara, Yotaro; Nishide, Akihiko; Sasaki, Kosuke, E-mail: jinzaki@rad.med.keio.ac.jp [CT Engineering, GE Healthcare Japan, Tokyo (Japan)

    2011-08-21

    The purpose of this study was to evaluate whether experimental fine-cell detector computed tomography with a 0.3125 mm cell (0.3 mm cell CT) can improve the detection of coronary vessel walls compared with conventional 64-slice computed tomography with a 0.625 mm cell (0.6 mm cell CT). A coronary vessel wall phantom was scanned using 0.6 mm cell CT and 0.3 mm cell CT. The data for 0.3 mm cell CT were obtained using four protocols: a radiation dose equal, double, triple or quadruple that were used in the 0.6 mm cell CT protocol. The detectable size of the vessel wall was assessed based on the first and second derivative functions, and the minimum measurable values were compared using a paired t-test. As a result, the minimum detectable wall thickness of 0.6 mm cell CT (1.5 mm) was significantly larger than that of 0.3 mm cell CT performed using the triple- and quadruple-dose protocols (0.9 mm) and the double-dose protocol (1.1 mm). The difference in the minimum detectable vessel wall thickness measured using 0.6 mm cell CT (1.5 {+-} 0.1 mm) and 0.3 mm cell CT (0.9 {+-} 0.1 mm, 1.1 {+-} 0.2 mm) was significant (p < 0.01). We concluded that 0.3 mm cell CT improved the detection of coronary vessel walls when a more than double-dose protocol was used compared with 0.6 mm cell CT.

  14. Carotid Artery Wall Layer Dimensions during and after Pre-eclampsia : An investigation using non-invasive high-frequency ultrasound

    OpenAIRE

    Akhter, Tansim

    2013-01-01

    Pre-eclampsia is associated with increased risk of cardiovascular disease (CVD) later in life. The ‘gold standard’ for estimating cardiovascular risk - ultrasound assessment of the common carotid artery intima-media thickness (CCA-IMT) - does not convincingly demonstrate this increased risk. The aim of this thesis was to examine whether high-frequency (22 MHz) ultrasound assessment of the individual CCA intima and media layers and calculation of the intima/media (I/M) ratio - can indicate the...

  15. STUDY OF STATIC AND DYNAMIC STABILITY OF THIN-WALLED BARS EXCITED BY PERIODICAL AXIAL EXTERNAL FORCES.

    Directory of Open Access Journals (Sweden)

    Minodora Maria PASĂRE

    2010-10-01

    Full Text Available In these paper, starting from the relations for the displacements and spinning the transversal section of a bar with thin walls of sections opened expressed by the corresponding influence functions and introducing the components of the exterior forces distributed and the moments of the exterior forces distributed due to the inertia forces, the exciting axial forces together with the following effect of these and of the reaction forces of the elastic environment for leaning it may reach to the system of the equations of parametric vibrations under the form of three integral equation These equations may serve for the study of vibrations of the bars, to study the static stability and to study the dynamic stability

  16. Measurement of particle trajectories, dynamics, surface adhesion and detachment in near-wall shear flows using 3D velocimetry

    Science.gov (United States)

    Guasto, Jeffrey; Schmidt, Brian; Lawrence, Michael; Breuer, Kenneth

    2007-11-01

    Three-dimensional total internal reflection velocimetry (3D-TIRV) is used to measure the trajectories of fluorescent tracer particles within 200 nm of a wall. Diffusion and shear-induced motion can result in mean velocity measurement errors, and by taking measurements using different particle sizes and sampling times, we quantify these effects and compare with theory. We also use 3D-TIRV to observe and characterize the adhesion, surface rolling and release dynamics of particles that can adhere to the surface through the action of biological binding proteins. Particles coated with P-Selectin are allowed to adhere to and detach from a PSGL-1-coated microchannel surface, modeling the interaction between leukocytes (white blood cells) and blood vessels, respectively. Binding affinities, bond strengths and hydrodynamic interactions are inferred from the trajectory data.

  17. Systematics analyses on nucleon isovector observables in 2+1-flavor dynamical domain-wall lattice QCD near physical mass

    CERN Document Server

    Ohta, Shigemi

    2014-01-01

    Analyses on possible systematics in some isovector nucleon observables in the RBC+UKQCD 2+1-flavor dynamical domain-wall fermion (DWF) lattice-QCD are presented. The vector charge, axial charge, quark momentum and helicity fractions, and transversity are discussed using mainly the Iwasaki\\(\\times\\)DSDR ensemble at pion mass of 170 MeV. No autocorrelation issue is observed in the vector charge and quark momentum and helicity fractions. Blocked Jack-knife analyses expose significant growth of estimated error for the axial charge with increasing block sizes that are similar to or larger than the known autocorrelation time of the gauge-field topological charge. Similar growth is seen in the transversity. These two observables, however, do not seem correlated with the topological charge.

  18. Gas dynamic and time resolved imaging studies of single-wall carbon nanotubes growth in the laser ablation process

    Science.gov (United States)

    Sen, Rahul; Suzuki, S.; Kataura, H.; Achiba, Y.

    2001-10-01

    Single-wall carbon nanotubes (SWNTs) were synthesized by laser ablation of Ni-Co-graphite composite targets at 1200 °C under flowing argon. The effects of the temperature gradient near the target and the gas flow rate on the diameter distribution of SWNTs were studied in order to understand their growth dynamics. The diameter distribution of the SWNTs, analyzed by Raman spectroscopy, was dependent on the gas flow rate when there was a temperature gradient around the target. Time resolved scattering images from the ablated species at different flow rates indicated that velocities of backward moving species increased with increasing flow rate. These findings are used to estimate the time required for nucleation and the growth of SWNTs.

  19. Dynamic pulmonary perfusion imaging in patients with idiopathic pulmonary arterial hypertension

    International Nuclear Information System (INIS)

    Objective: To investigate the value of dynamic PPI in patients with IPAH. Methods: Twenty consecutive patients with IPAH underwent dynamic PPI and right ventricular catheterization. Ten healthy volunteers were also recruited in this study as control. Total lung ROI was drawn to calculate time-activity curves from dynamic PPI. Lung equilibrium time (LET), the duration from 99Tcm-MAA entering the lungs to equilibrium, was measured. Comparisons between two groups were carried out using t-test. Correlations between LET and hemodynamic parameters were determined by Pearson correlation analysis. Results: LET was significantly prolonged in IPAH patients over the control group ((33.9 ± 15.5) s vs (14.4 ± 3.7) s, t=5.340, P<0.001). Significant correlations were found between LET and mPAP (r=0.566, P<0.01) and between LET and total pulmonary resistance (TPR) measured by right heart catheterization (r=0.688, P<0.05). LET had a negative linear relationship with CI (r=-0.480, P<0.05). Conclusion: Dynamic PPI is a practical and noninvasive method for evaluating the haemodynamic function of right heart in patients with IPAH. (authors)

  20. Dynamic contrast-enhanced MRI assessment of hyperemic fractional microvascular blood plasma volume in peripheral arterial disease: initial findings.

    Directory of Open Access Journals (Sweden)

    Bas Versluis

    Full Text Available OBJECTIVES: The aim of the current study was to describe a method that assesses the hyperemic microvascular blood plasma volume of the calf musculature. The reversibly albumin binding contrast agent gadofosveset was used in dynamic contrast-enhanced magnetic resonance imaging (DCE MRI to assess the microvascular status in patients with peripheral arterial disease (PAD and healthy controls. In addition, the reproducibility of this method in healthy controls was determined. MATERIALS AND METHODS: Ten PAD patients with intermittent claudication and 10 healthy control subjects were included. Patients underwent contrast-enhanced MR angiography of the peripheral arteries, followed by one DCE MRI examination of the musculature of the calf. Healthy control subjects were examined twice on different days to determine normative values and the interreader and interscan reproducibility of the technique. The MRI protocol comprised dynamic imaging of contrast agent wash-in under reactive hyperemia conditions of the calf musculature. Using pharmacokinetic modeling the hyperemic fractional microvascular blood plasma volume (V(p, unit: % of the anterior tibial, gastrocnemius and soleus muscles was calculated. RESULTS: V(p was significantly lower for all muscle groups in PAD patients (4.3±1.6%, 5.0±3.3% and 6.1±3.6% for anterior tibial, gastrocnemius and soleus muscles, respectively compared to healthy control subjects (9.1±2.0%, 8.9±1.9% and 9.3±2.1%. Differences in V(p between muscle groups were not significant. The coefficient of variation of V(p varied from 10-14% and 11-16% at interscan and interreader level, respectively. CONCLUSIONS: Using DCE MRI after contrast-enhanced MR angiography with gadofosveset enables reproducible assessment of hyperemic fractional microvascular blood plasma volume of the calf musculature. V(p was lower in PAD patients than in healthy controls, which reflects a promising functional (hemodynamic biomarker for the

  1. Effects of an impermeable wall in dissipative dynamics of saturated porous media

    CERN Document Server

    Harris, Pietro Artale

    2016-01-01

    A phase transition model for porous media in consolidation is studied. The model is able to describe the phenomenon of fluid-segregation during the consolidation process, i.e., the coexistence of two phases di?ering from fluid content inside the porous medium under static load. Considering pure Darcy dissipation, the dynamics is described by a Cahn-Hilliard-like system of partial differential equations (PDE). The goal, here, is to study the dynamics of the formation of stationary fluid-rich bubbles. The evolution of the strain and fluid density pro?files of the porous medium is analyzed in two physical situation: fluid free to flow through the boundaries of the medium and fluid flow prevented at one of the two boundaries. Morover, an analytic result on the position of the interface between the two phases is provided.

  2. Dynamic interactions between poly(3-hexylthiophene) and single-walled carbon nanotubes in marginal solvent.

    Science.gov (United States)

    Luo, Yanqi; Santos, Franceska A; Wagner, Taylor W; Tsoi, Eric; Zhang, Shanju

    2014-06-01

    Interfacial interactions between conjugated polymers and carbon nanotubes are pivotal in determining the device performance of nanotube-based polymer electronic devices. Here, we report on interfacial structures and crystallization kinetics of poly(3-hexylthiophene) (P3HT) in the presence of single-walled carbon nanotubes (SWNTs) in anisole by means of transmission electron microscope (TEM) and ultraviolet-visible (UV-vis) absorption spectroscopy. Confined on SWNT surfaces, the P3HT forms nanofibril crystals perpendicular to the long axis of SWNTs. The equilibrium dissolution temperature of the P3HT crystals in anisole is determined to be 381 ± 10 K according to the Hoffman-Weeks extrapolation approach. Upon cooling, the polymer solution spontaneously undergoes a time-dependent chromism. Various kinetics factors such as crystallization temperature, concentration, and SWNT loading have been investigated. It is found that the growth rate (G) of the crystals scales with concentration (C) as G ∝ C(1.70±0.16). The Avrami model is utilized to analyze the nucleation mechanism and the Avrami exponents vary between 1.0 and 1.3. The Lauritzen-Hoffman theory is applied to study the chain-folding process. The fold surface free energy is calculated to be (5.28-11.9) × 10(-2) J m(-2). It is evident that the addition of 0.30 wt % SWNTs reduces the fold surface free energy by 55.6%. PMID:24856901

  3. The dynamics of plant cell-wall polysaccharide decomposition in leaf-cutting ant fungus gardens.

    Directory of Open Access Journals (Sweden)

    Isabel E Moller

    Full Text Available The degradation of live plant biomass in fungus gardens of leaf-cutting ants is poorly characterised but fundamental for understanding the mutual advantages and efficiency of this obligate nutritional symbiosis. Controversies about the extent to which the garden-symbiont Leucocoprinus gongylophorus degrades cellulose have hampered our understanding of the selection forces that induced large scale herbivory and of the ensuing ecological footprint of these ants. Here we use a recently established technique, based on polysaccharide microarrays probed with antibodies and carbohydrate binding modules, to map the occurrence of cell wall polymers in consecutive sections of the fungus garden of the leaf-cutting ant Acromyrmex echinatior. We show that pectin, xyloglucan and some xylan epitopes are degraded, whereas more highly substituted xylan and cellulose epitopes remain as residuals in the waste material that the ants remove from their fungus garden. These results demonstrate that biomass entering leaf-cutting ant fungus gardens is only partially utilized and explain why disproportionally large amounts of plant material are needed to sustain colony growth. They also explain why substantial communities of microbial and invertebrate symbionts have evolved associations with the dump material from leaf-cutting ant nests, to exploit decomposition niches that the ant garden-fungus does not utilize. Our approach thus provides detailed insight into the nutritional benefits and shortcomings associated with fungus-farming in ants.

  4. Dynamics of fragmentation and multiple vacancy generation in irradiated single-walled carbon nanotubes

    CERN Document Server

    Javeed, Sumera; Ahmad, Shoaib

    2016-01-01

    The results from mass spectrometry of clusters sputtered from Cs+ irradiated single-walled carbon nano-tubes (SWCNTs) as a function of energy and dose identify the nature of the resulting damage in the form of multiple vacancy generation. For pristine SWCNTs at all Cs+ energies, C2 is the most dominant species, followed by C3, C4 and C1. The experiments were performed in three stages: in the first stage, Cs+ energy E(Cs+) was varied. During the second stage, the nanotubes were irradiated continuously at E(Cs+) = 5 keV for 1,800 s. Afterwards, the entire sequence of irradiation energies was repeated to differentiate between the fragmentation patterns of the pristine and of heavily irradiated SWCNTs. The sputtering and normalized yields identify the quantitative and relative extent of the ion-induced damage by creating double, triple and quadruple vacancies; the single vacancies are least favored. Sputtering from the heavily irradiated SWCNTs occurs not only from the damaged and fragmented nanotubes, but also f...

  5. Statical and dynamical soil-structure interaction between diaphragm wall and its surrounding soil in the embankment dam with diaphragm wall under soil core. Renzoku chichuheki wo yusuru firu dam no chichuheki to jiban tono seiteki doteki sogo sayo

    Energy Technology Data Exchange (ETDEWEB)

    Kanazawa, K.; Nishigori, T. (Electric Power Development Co. Ltd., Tokyo (Japan)); Watanabe, H. (Saitama University, Saitama (Japan). Faculty of Engineering); Takada, M. (Chiba Prefectural Government, Chiba (Japan))

    1992-12-15

    In case of applying the diaphragm cutoff wall to the foundation treatment of embankment dam to be constructed on the alluvial deposit, it is indispensable to take the seismic influence into consideration for the design. In the present paper, study was made of statical and dynamical soil-structure interaction between the diaphragm wall and its surrounding soil. Study through numerical analysis was also made of dam stability for the dams typified by Tadami's which was taken as an example. The influence of rigidity was particularly studied of diaphragm wall through comparison between the ordinary concrete (A) and bentonite concrete (B), and the dynamical characteristics were confirmed through in-situ vibration test. For example, the following was elucidated as a result of test: As for the state of stress at the time of embankment completion, the diaphragm wall which uses high rigidity A gives a strong stress concentration on its top and tends to simultaneously generate a weak point in stress distribution due to the arch action on the lateral surface near its top. However in case of using low rigidity B, it is considerably improved. 16 refs., 22 figs., 2 tabs.

  6. MR imaging of hepatocellular carcinoma: usefulness of four-phase dynamic imaging including early arterial phase

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong Guk; Yu, Jeong Sik; Kim, Ki Whang; Kim, Tae Hoon; Jo, Byung June; Kim, Jai Keun; Oh, Sei Jung; Ahn, Chang Soo; Kim, Ji Hyung [Yonsei Univ. College of Medicine, Seoul (Korea, Republic of)

    1999-01-01

    To evaluate the usefulness of four-phase dynamic MR imaging technique by analyzing the imaging features of hepatocellular carcinoma(HCC). We reviewed four-phase dynamic MR images of 63 lesions in 38 patients. MR imaging of the whole liver on gradient T1-weighted sequence was obtained at 10 seconds(phase 1), 35 seconds(phase 2), 60 seconds(phase 3), and 5 minutes(phase 4) after the start of Gd-DTPA(0.1 mmol/kg) hand injection(3-4cc/sec) through the vein. We evaluated the degree of lesional contrast enhancement during each phase by comparing surrounding liver parenchyma, and analyzed signal intensity in lesions over and less than 2cm, respectively. The number of lesions showing high signal intensity compared with surrounding liver parenchyma was 52(83%) during phase 1, 30(48%) during phase 2, 12(19%) during phase 3, and 4(6%) during phase 4. During each phase, the number of lesions with signal intensity lower than that of surrounding liver parenchyma was 7(11%), 2(3%), 7(11%) and 21(33%), respectively. Thirty-four lesions were enhanced only during phase 1 and eleven during only phase 2. In tumors less than 2cm(n=40), more enhanced lesions were during phase 1(n=33) than more during phase 2(n=16)(p=0.0020). During each phase, four-phase dynamic MR imaging is useful for the effective detection of HCC showing varying degrees of contrast enhancement.

  7. Computational fluid dynamics simulation of ethanol steam reforming in catalytic wall microchannels

    OpenAIRE

    Uriz, I.; Arzamendi, G.; López, E.; Llorca Piqué, Jordi; Gandía, L.M.

    2011-01-01

    A three-dimensional computational fluid dynamics (CFD) simulation study of the ethanol steam reforming (ESR) in microreactors with square channels has been carried out. A phenomenological kinetic model describing the ESR on a Co3O4–ZnO catalyst has been established and implemented in the CFD codes. This model includes the ethanol dehydrogenation to acetaldehyde, ethanol decomposition to CO and CH4, acetaldehyde steam reforming to H2 and CO2 and water–gas shift as the reactions des...

  8. Characteristic dynamic modes and domain-wall motion in magnetic nanotubes excited by resonant rotating magnetic fields

    Science.gov (United States)

    Yang, Jaehak; Kim, Junhoe; Kim, Bosung; Cho, Young-Jun; Lee, Jae-Hyeok; Kim, Sang-Koog

    2016-07-01

    We performed micromagnetic numerical calculations to explore a cylindrical nanotube's magnetization dynamics and domain-wall (DW) motions driven by eigen-circular-rotating magnetic fields of different frequencies. We discovered the presence of two different localized DW oscillations as well as asymmetric ferromagnetic resonance precession and azimuthal spin-wave modes at the corresponding resonant frequencies of the circular-rotating fields. Associated with these intrinsic modes, there exist very contrasting DW motions of different speed and propagation direction for a given DW chirality. The direction and speed of the DW propagation were found to be controllable according to the rotation sense and frequency of noncontact circular-rotating fields. Furthermore, spin-wave emissions from the moving DW were observed at a specific field frequency along with their Doppler effect. This work furthers the fundamental understanding of soft magnetic nanotubes' intrinsic dynamic modes and spin-wave emissions and offers an efficient means of manipulating the speed and direction of their DW propagations.

  9. ANALYSIS OF PULSATILE BLOOD FLOW IN AXIALLY MOVING ARTERIES

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In order to study motional properties of pulsatile blood flow in axially moving arteries, the authors derived some expressions of the pulsatile blood flow from the basic equations of motion for blood and vascular walls, including an axial blood velocity equation, a flow rate equation and a wall shear stress equation, which described not only the overall axial movement of the arteries but also the elastic properties of the vascular walls, discussed the effects of the arterial wall elasticity on the wall shear stress in coronary arteries in terms of these expressions, and analyzed changes of motional properties of pulsatile blood flow between an elastic arterial tube model and a rigid tube model. The results proved the inference by J.E. Moore Jr. et al. (1994) that the axial movement of arteries be as important in determining coronary artery hemodynamics as the elastic property of the vascular wall.

  10. Bilateral accessory thoracodorsal artery.

    Science.gov (United States)

    Natsis, Konstantinos; Totlis, Trifon; Tsikaras, Prokopios; Skandalakis, Panagiotis

    2006-09-01

    The subscapular artery arises from the third part of the axillary artery and gives off the circumflex scapular and the thoracodorsal arteries. Although anatomical variations of the axillary artery are very common, the existence of a unilateral accessory thoracodorsal artery has been described in the literature only once. There are no reports of bilateral accessory thoracodorsal artery, in the literature. In the present study, a bilateral accessory thoracodorsal artery, originating on either side of the third part of the axillary artery, is described in a 68-year-old female cadaver. All the other branches of the axillary artery had a typical origin, course, distribution and termination. This extremely rare anatomical variation apart from the anatomical importance also has clinical significance for surgeons in this area. Especially, during the dissection or mobilization of the latissimus dorsi that is partly used for coverage problems in many regions of the body and also in dynamic cardiomyoplasty, any iatrogenic injury of this accessory artery may result in ischemia and functional loss of the graft.

  11. Dynamic analysis with a fractional-order chaotic system for estimation of peripheral arterial disease in diabetic foot

    International Nuclear Information System (INIS)

    Lower-extremity peripheral arterial disease (PAD) is caused by narrowing or occlusion of vessels in patients like type 2 diabetes mellitus, the elderly and smokers. Patients with PAD are mostly asymptomatic; typical early symptoms of this limb-threatening disorder are intermittent claudication and leg pain, suggesting the necessity for accurate diagnosis by invasive angiography and ankle-brachial pressure index. This index acts as a gold standard reference for PAD diagnosis and categorizes its severity into normal, low-grade and high-grade, with respective cut-off points of ≥0.9, 0.9–0.5 and <0.5. PAD can be assessed using photoplethysmography as a diagnostic screening tool, displaying changes in pulse transit time and shape, and dissimilarities of these changes between lower limbs. The present report proposed photoplethysmogram with fractional-order chaotic system to assess PAD in 14 diabetics and 11 healthy adults, with analysis of dynamic errors based on various butterfly motion patterns, and color relational analysis as classifier for pattern recognition. The results show that the classification of PAD severity among these testees was achieved with high accuracy and efficiency. This noninvasive methodology potentially provides timing and accessible feedback to patients with asymptomatic PAD and their physicians for further invasive diagnosis or strict management of risk factors to intervene in the disease progression. (paper)

  12. Dynamic analysis with a fractional-order chaotic system for estimation of peripheral arterial disease in diabetic foot

    Science.gov (United States)

    Li, Chien-Ming; Du, Yi-Chun; Wu, Jian-Xing; Lin, Chia-Hung; Ho, Yueh-Ren; Chen, Tainsong

    2013-08-01

    Lower-extremity peripheral arterial disease (PAD) is caused by narrowing or occlusion of vessels in patients like type 2 diabetes mellitus, the elderly and smokers. Patients with PAD are mostly asymptomatic; typical early symptoms of this limb-threatening disorder are intermittent claudication and leg pain, suggesting the necessity for accurate diagnosis by invasive angiography and ankle-brachial pressure index. This index acts as a gold standard reference for PAD diagnosis and categorizes its severity into normal, low-grade and high-grade, with respective cut-off points of ≥0.9, 0.9-0.5 and diabetics and 11 healthy adults, with analysis of dynamic errors based on various butterfly motion patterns, and color relational analysis as classifier for pattern recognition. The results show that the classification of PAD severity among these testees was achieved with high accuracy and efficiency. This noninvasive methodology potentially provides timing and accessible feedback to patients with asymptomatic PAD and their physicians for further invasive diagnosis or strict management of risk factors to intervene in the disease progression.

  13. The effect of the conductivity of drift chamber walls on the dynamics of a relativistic electron beam with a virtual cathode

    Science.gov (United States)

    Badarin, A. A.; Kurkin, S. A.; Koronovskii, A. A.; Hramov, A. E.

    2015-12-01

    The effect of conductivity of walls of a drift chamber of the axial vircator on the behavior of a relativistic electron beam with a supercritical current was investigated. The dynamics of a relativistic electron beam is shown to be characterized by the formation of a virtual cathode of complex structure with two or three potential minima in the azimuthal direction, which rotate around the drift space axis. It is established that variation in the conductivity of drift chamber walls leads to stepwise switching of the generation frequency and a sharp change in the output power. Dependences of the output radiation power of the investigated vircator system on the conductivity of drift chamber walls for two characteristic regimes of the dynamics of a relativistic electron beam were obtained.

  14. Investigation of dynamic SPECT measurements of the arterial input function in human subjects using simulation, phantom and human studies

    Science.gov (United States)

    Winant, Celeste D.; Aparici, Carina Mari; Zelnik, Yuval R.; Reutter, Bryan W.; Sitek, Arkadiusz; Bacharach, Stephen L.; Gullberg, Grant T.

    2012-01-01

    Computer simulations, a phantom study and a human study were performed to determine whether a slowly rotating single-photon computed emission tomography (SPECT) system could provide accurate arterial input functions for quantification of myocardial perfusion imaging using kinetic models. The errors induced by data inconsistency associated with imaging with slow camera rotation during tracer injection were evaluated with an approach called SPECT/P (dynamic SPECT from positron emission tomography (PET)) and SPECT/D (dynamic SPECT from database of SPECT phantom projections). SPECT/P simulated SPECT-like dynamic projections using reprojections of reconstructed dynamic 94Tc-methoxyisobutylisonitrile (94Tc-MIBI) PET images acquired in three human subjects (1 min infusion). This approach was used to evaluate the accuracy of estimating myocardial wash-in rate parameters K1 for rotation speeds providing 180° of projection data every 27 or 54 s. Blood input and myocardium tissue time-activity curves (TACs) were estimated using spatiotemporal splines. These were fit to a one-compartment perfusion model to obtain wash-in rate parameters K1. For the second method (SPECT/D), an anthropomorphic cardiac torso phantom was used to create real SPECT dynamic projection data of a tracer distribution derived from 94Tc-MIBI PET scans in the blood pool, myocardium, liver and background. This method introduced attenuation, collimation and scatter into the modeling of dynamic SPECT projections. Both approaches were used to evaluate the accuracy of estimating myocardial wash-in parameters for rotation speeds providing 180° of projection data every 27 and 54 s. Dynamic cardiac SPECT was also performed in a human subject at rest using a hybrid SPECT/CT scanner. Dynamic measurements of 99mTc-tetrofosmin in the myocardium were obtained using an infusion time of 2 min. Blood input, myocardium tissue and liver TACs were estimated using the same spatiotemporal splines. The spatiotemporal maximum

  15. Nitinol Stent Oversizing in Patients Undergoing Popliteal Artery Revascularization: A Finite Element Study.

    Science.gov (United States)

    Gökgöl, Can; Diehm, Nicolas; Nezami, Farhad Rikhtegar; Büchler, Philippe

    2015-12-01

    Nitinol stent oversizing is frequently performed in peripheral arteries to ensure a desirable lumen gain. However, the clinical effect of mis-sizing remains controversial. The goal of this study was to provide a better understanding of the structural and hemodynamic effects of Nitinol stent oversizing. Five patient-specific numerical models of non-calcified popliteal arteries were developed to simulate the deployment of Nitinol stents with oversizing ratios ranging from 1.1 to 1.8. In addition to arterial biomechanics, computational fluid dynamics methods were adopted to simulate the physiological blood flow inside the stented arteries. Results showed that stent oversizing led to a limited increase in the acute lumen gain, albeit at the cost of a significant increase in arterial wall stresses. Furthermore, localized areas affected by low Wall Shear Stress increased with higher oversizing ratios. Stents were also negatively impacted by the procedure as their fatigue safety factors gradually decreased with oversizing. These adverse effects to both the artery walls and stents may create circumstances for restenosis. Although the ideal oversizing ratio is stent-specific, this study showed that Nitinol stent oversizing has a very small impact on the immediate lumen gain, which contradicts the clinical motivations of the procedure.

  16. Sex differences in intracranial arterial bifurcations

    DEFF Research Database (Denmark)

    Lindekleiv, Haakon M; Valen-Sendstad, Kristian; Morgan, Michael K;

    2010-01-01

    Subarachnoid hemorrhage (SAH) is a serious condition, occurring more frequently in females than in males. SAH is mainly caused by rupture of an intracranial aneurysm, which is formed by localized dilation of the intracranial arterial vessel wall, usually at the apex of the arterial bifurcation. T....... The female preponderance is usually explained by systemic factors (hormonal influences and intrinsic wall weakness); however, the uneven sex distribution of intracranial aneurysms suggests a possible physiologic factor-a local sex difference in the intracranial arteries....

  17. Modelling the performance of the tapered artery heat pipe design for use in the radiator of the solar dynamic power system of the NASA Space Station

    Science.gov (United States)

    Evans, Austin Lewis

    1988-01-01

    The paper presents a computer program developed to model the steady-state performance of the tapered artery heat pipe for use in the radiator of the solar dynamic power system of the NASA Space Station. The program solves six governing equations to ascertain which one is limiting the maximum heat transfer rate of the heat pipe. The present model appeared to be slightly better than the LTV model in matching the 1-g data for the standard 15-ft test heat pipe.

  18. Feasibility of Using Limited-Population-Based Arterial Input Function for Pharmacokinetic Modeling of Osteosarcoma Dynamic Contrast-Enhanced MRI Data

    OpenAIRE

    Wang, YA; Huang, Wei; Panicek, David M.; Schwartz, Lawrence H.; Koutcher, Jason A

    2008-01-01

    For clinical dynamic contrast-enhanced (DCE) MRI studies, it is often not possible to obtain reliable arterial input function (AIF) in each measurement. Thus, it is important to find a representative AIF for pharmacokinetic modeling of DCE-MRI data when individual AIF (Ind-AIF) measurements are not available. A total of 16 patients with osteosarcomas in the lower extremity (knee region) underwent multislice DCE-MRI. Reliable Ind-AIFs were obtained in five patients with a contrast injection ra...

  19. Binding of single walled carbon nanotube to WT and mutant HIV-1 proteases: analysis of flap dynamics and binding mechanism.

    Science.gov (United States)

    Meher, Biswa Ranjan; Wang, Yixuan

    2012-09-01

    Most of the currently treated HIV-1 protease (HIV-PR) inhibitors have been prone to suffer from the mutations associated drug resistance. Therefore, it is necessary to search for potent alternatives against the drug resistance. In the current study we have tested the single-walled carbon nanotube (SWCNT) as an inhibitor in wild type (WT) as well as in three primary mutants (I50V(PR), V82A(PR) and I84V(PR)) of the HIV-1-PR through docking the SWCNT in the active site region, and then performed all-atom MD simulations for the complexes. The conformational dynamics of HIV-PR with a 20 ns trajectory reveals that the SWCNT can effectively bind to the HIV-1-PR active site and regulate the flap dynamics such as maintaining the flap-flap closed. To gain an insight into the binding affinity, we also performed the MM-PBSA based binding free energy calculations for the four HIV-PR/SWCNT complexes. It was observed that, although the binding between the SWCNT and the HIV-PR decreases due to the mutations, the SWCNTs bind to the HIV-PRs 3-5 folds stronger than the most potent HIV-1-PR inhibitor, TMC114. Remarkably, the significant interactions with binding energy higher than 1kcal/mol focus on the flap and active regions, which favors closing flap-flap and deactivating the active residues of the HIV-PR. The flap dynamics and binding strength information for HIV-PR and SWCNTs can help design SWCNT-based HIV-1-PR inhibitors. PMID:23142620

  20. Computational fluid dynamics study of liquid droplet impingement erosion in the inner wall of a bent pipe

    International Nuclear Information System (INIS)

    The bent pipe wall thinning phenomenon has been often found at the elbow of pipelines in the power engineering industry. Liquid droplet impingement (LDI) erosion could be regarded to be one of the major causes of unexpected troubles occasionally occurred in the inner bent pipe surface. In this paper, three-dimensional numerical simulations are conducted for a bent pipe. Typically the pipe diameter is 170mm and the bending angle is 90 degree, the mass flow rate of droplet is 4.5 x 10-3 kg/s with the velocity of 280m/s at the entry. The calculations employ a two-phase flow model. A computational fluid dynamic tool has been adopted by using one-way and two-way fluid-droplet coupled system in high Reynolds number regions. This computational fluid model is built up by incompressible Reynolds averaged Navier-Stokes equations using different turbulent flow computational models and the SIMPLE algorithm, and the numerical droplet model adopts the Lagrangian approach. The momentum transfers between droplet and carrier fluid are calculated by using two different fluid-droplet coupled methods. The interactional force between carrier and droplet are taken into account by momentum transfer in Eulerian-Lagrangian approaches. Based on the carrier streamlines and droplet trajectories, the two-way calculation using the interactional momentum transfer calculations could be a more appropriate model to simulate the bent pipe wall thinning phenomena, the effects of droplet size are also demonstrated numerically. Finally, it is shown that turbulence models are not sensitive to the involved droplets. (author)

  1. Assessing strength and dynamics of the Oligocene Antarctic Circumpolar Current using organic-walled dinoflagellate cysts

    Science.gov (United States)

    Bijl, P.; Houben, A. J.; Sangiorgi, F.; Brinkhuis, H.

    2013-12-01

    The Oligocene Epoch (33.9-23 Ma) is the time interval in the Cenozoic that saw the establishment of a continental-scale Antarctic ice-sheet. Numerical modelling studies suggest that alongside continental ice, first sea-ice conditions may have started along the East Antarctic Margin, but this conclusion lacks support from field evidence. Other numerical models predict that hysteresis effects within the ice sheet will make a continental-size Antarctic ice sheet rather insensitive to warming. In contrast, deep-water benthic foraminiferal oxygen isotope records across the Oligocene suggest dramatic waxing and waning of Antarctic ice sheets. The role of opening of Southern Ocean Gateways on the process of building and sustaining Antarctic continental ice has been questioned in the past. Particularly uncertain is the timing of the installation of a strong Antarctic Circumpolar Current (ACC), and the dynamics of its strength in the earlier phases of Gateway throughflow. Integrated Ocean Drilling Expedition 318 drilled the Antarctic Margin in 2010, and recovered sediments from the early phase of Antarctic glaciation. With this record, we can now evaluate the robustness of the results of the numerical models and the oceanographic changes with field data. Sediments recovered from Site U1356 yields a thick and relatively complete (albeit compromised by core gaps) Oligocene succession both of which are chrono-stratigraphically well-calibrated with use of nannoplankton- dinocyst- and magnetostratigraphy. Notably, this record yields well-preserved dinoflagellate cysts (dinocysts). Dinocysts are the fossilizable remains of dinoflagellates, some of which are today specifically linked to the high (seasonal) productivity of the ecosystems associated with sea-ice and oceanic fronts. In the earliest Oligocene, just after the onset of Antarctic glaciation, we document the installation of dinoflagellate cyst assemblages that bear remarkable similarity with those of the present

  2. Dynamic study of lower limb arteries using the ECTRICKS MRI technique; La perspective d'une etude dynamique des arteres des membres inferieures en IRM grace a la sequence ECTRICKS

    Energy Technology Data Exchange (ETDEWEB)

    Nicolas, M.; Laurent, V.; Tissier, S.; Cannard, L.; Leclerc, J.C.; Beot, S.; Regent, D. [Centre Hospitalier Universitaire Nancy-Brabois, Service de Radiologie Adultes, 54 - Vandoeuvre-les-Nancy (France)

    2005-01-15

    Purpose. This article presents a new MR angiography technique, Elliptic Centric Time Resolved Imaging on Contrast KineticS (ECTRICKS), which allows dynamic evaluation of the lower limb arteries opacification when venous return prevents adequate diagnostic evaluation of calf arteries. Patient and methods. Comparative examination of the calf arteries in 59 patients using a standard MRA technique and the ECTRICKS technique. Results. A total of 33 examinations could be compared. Additional arteries could be evaluated in 10% of our patient population using the ECTRICKS technique, and in 20% for our diabetic population. Arterial evaluation was better with the ECTRICKS technique in patients with diabetes and venous insufficiency. Conclusion. ECTRICKS is a good complementary sequence for evaluating the calf arteries in patients with diabetes or early venous return. (author)

  3. Molecular dynamics study of radiation damage and microstructure evolution of zigzag single-walled carbon nanotubes under carbon ion incidence

    Science.gov (United States)

    Li, Huan; Tang, Xiaobin; Chen, Feida; Huang, Hai; Liu, Jian; Chen, Da

    2016-07-01

    The radiation damage and microstructure evolution of different zigzag single-walled carbon nanotubes (SWCNTs) were investigated under incident carbon ion by molecular dynamics (MD) simulations. The radiation damage of SWCNTs under incident carbon ion with energy ranging from 25 eV to 1 keV at 300 K showed many differences at different incident sites, and the defect production increased to the maximum value with the increase in incident ion energy, and slightly decreased but stayed fairly stable within the majority of the energy range. The maximum damage of SWCNTs appeared when the incident ion energy reached 200 eV and the level of damage was directly proportional to incident ion fluence. The radiation damage was also studied at 100 K and 700 K and the defect production decreased distinctly with rising temperature because radiation-induced defects would anneal and recombine by saturating dangling bonds and reconstructing carbon network at the higher temperature. Furthermore, the stability of a large-diameter tube surpassed that of a thin one under the same radiation environments.

  4. The fluid dynamic and shear environment in the NASA/JSC rotating-wall perfused-vessel bioreactor

    Science.gov (United States)

    Begley, C. M.; Kleis, S. J.

    2000-01-01

    The rotating-wall perfused-vessel (RWPV) bioreactor, used for both microgravity and Earth-based cell science experiments, is characterized in terms of the fluid dynamic and fluid shear stress environment. A numerical model of the flow field is developed and verified with laser Doppler velocimeter measurements. The effects of changes in operating conditions, including rotation rates and fluid perfusion rates, are investigated with the numerical model. The operating conditions typically used for ground-based experiments (equal rotation of the inner and outer cylinders) leads to flow patterns with relatively poor mass distribution characteristics. Approximately 50% of the inlet-perfused fluid bypasses the bulk of the fluid volume and flows to the perfusion exit. For operating conditions typical in microgravity, small differential rotation rates between the inner and outer cylinders lead to greatly improved flow distribution patterns and very low fluid shear stress levels over a large percentage of the fluid volume. Differences in flow patterns for the different operating conditions are explored. Large differences in the hydrodynamic environments for operating conditions typical of true microgravity and ground-based "microgravity simulations" are demonstrated.

  5. Tailoring Pull-out Properties of Single-Walled Carbon Nanotube Bundles by Varying Binding Structures through Molecular Dynamics Simulation.

    Science.gov (United States)

    Zhang, Liuyang; Wang, Xianqiao

    2014-08-12

    Single-walled carbon nanotubes (SWCNTs) have demonstrated a remarkable capacity for self-assembly into nanobundles through intermolecular van der Waals interactions, bestowing these agglomerates extraordinary mechanical, thermal, and electrical properties. However, how to improve the binding ability of SWCNT bundles to mitigate the delamination and sliding effects between individual nanotubes remains to be further investigated. By utilizing molecular dynamics simulation, here we present the construction of SWCNT bundles with discrete cylindrical and continuous helical binders by noncovalent coating of the bundle surface with sp(2)-hybridized carbon networks. Meanwhile, by modifying the binding potentials between the binder and SWCNT bundles to mimic the different binding types actually used, the bound SWCNT bundle presents a variety of distinct mechanical properties unmatched by unbound bundles. The pull-out tests with discrete binders portray an intriguing force-displacement curve which can help determine the number of discrete binders used in the system. SWCNT bundles with binders depict unique mechanical properties which can differentiate them from unbound SWCNT bundles. These findings provide compelling evidence that bound SWCNT bundles will open up novel avenues for a variety of applications, especially in nanocomposites.

  6. Arterial spin labelling MRI for assessment of cerebral perfusion in children with moyamoya disease: comparison with dynamic susceptibility contrast MRI

    Energy Technology Data Exchange (ETDEWEB)

    Goetti, Robert [University Children' s Hospital Zurich, Department of Diagnostic Imaging, Zurich (Switzerland); University Hospital Zurich, Department of Diagnostic and Interventional Radiology, Zurich (Switzerland); O' Gorman, Ruth [University Children' s Hospital Zurich, Center for MR Research, Zurich (Switzerland); Khan, Nadia [University Children' s Hospital Zurich, Moyamoya Center, Division of Neurosurgery, Department of Surgery, Zurich (Switzerland); Kellenberger, Christian J.; Scheer, Ianina [University Children' s Hospital Zurich, Department of Diagnostic Imaging, Zurich (Switzerland)

    2013-05-15

    This study seeks to evaluate the diagnostic accuracy of cerebral perfusion imaging with arterial spin labelling (ASL) MR imaging in children with moyamoya disease compared to dynamic susceptibility contrast (DSC) imaging. Ten children (7 females; age, 9.2 {+-} 5.4 years) with moyamoya disease underwent cerebral perfusion imaging with ASL and DSC on a 3-T MRI scanner in the same session. Cerebral perfusion images were acquired with ASL (pulsed continuous 3D ASL sequence, 32 axial slices, TR = 5.5 s, TE = 25 ms, FOV = 24 cm, matrix = 128 x 128) and DSC (gradient echo EPI sequence, 35 volumes of 28 axial slices, TR = 2,000 ms, TE = 36 ms, FOV = 24 cm, matrix = 96 x 96, 0.2 ml/kg Gd-DOTA). Cerebral blood flow maps were generated. ASL and DSC images were qualitatively assessed regarding perfusion of left and right ACA, MCA, and PCA territories by two independent readers using a 3-point-Likert scale and quantitative relative cerebral blood flow (rCBF) was calculated. Correlation between ASL and DSC for qualitative and quantitative assessment and the accuracy of ASL for the detection of reduced perfusion per territory with DSC serving as the standard of reference were calculated. With a good interreader agreement ({kappa} = 0.62) qualitative perfusion assessment with ASL and DSC showed a strong and significant correlation ({rho} = 0.77; p < 0.001), as did quantitative rCBF (r = 0.79; p < 0.001). ASL showed a sensitivity, specificity and accuracy of 94 %, 93 %, and 93 % for the detection of reduced perfusion per territory. In children with moyamoya disease, unenhanced ASL enables the detection of reduced perfusion per vascular territory with a good accuracy compared to contrast-enhanced DSC. (orig.)

  7. Flow Instability Detected by High-Resolution Computational Fluid Dynamics in Fifty-Six Middle Cerebral Artery Aneurysms.

    Science.gov (United States)

    Varble, Nicole; Xiang, Jianping; Lin, Ning; Levy, Elad; Meng, Hui

    2016-06-01

    Recent high-resolution computational fluid dynamics (CFD) studies have detected persistent flow instability in intracranial aneurysms (IAs) that was not observed in previous in silico studies. These flow fluctuations have shown incidental association with rupture in a small aneurysm dataset. The aims of this study are to explore the capabilities and limitations of a commercial cfd solver in capturing such velocity fluctuations, whether fluctuation kinetic energy (fKE) as a marker to quantify such instability could be a potential parameter to predict aneurysm rupture, and what geometric parameters might be associated with such fluctuations. First, we confirmed that the second-order discretization schemes and high spatial and temporal resolutions are required to capture these aneurysmal flow fluctuations. Next, we analyzed 56 patient-specific middle cerebral artery (MCA) aneurysms (12 ruptured) by transient, high-resolution CFD simulations with a cycle-averaged, constant inflow boundary condition. Finally, to explore the mechanism by which such flow instabilities might arise, we investigated correlations between fKE and several aneurysm geometrical parameters. Our results show that flow instabilities were present in 8 of 56 MCA aneurysms, all of which were unruptured bifurcation aneurysms. Statistical analysis revealed that fKE could not differentiate ruptured from unruptured aneurysms. Thus, our study does not lend support to these flow instabilities (based on a cycle-averaged constant inflow as opposed to peak velocity) being a marker for rupture. We found a positive correlation between fKE and aneurysm size as well as size ratio. This suggests that the intrinsic flow instability may be associated with the breakdown of an inflow jet penetrating the aneurysm space. PMID:27109451

  8. Dynamics of propagating turbulent pipe flow structures. Part I: Effect of drag reduction by spanwise wall oscillation

    CERN Document Server

    Duggleby, A; Paul, M R

    2006-01-01

    The results of a comparative analysis between turbulent pipe flow and drag reduced turbulent pipe flow by spanwise wall oscillation based upon a Karhunen-Loeve expansion are presented. The turbulent flow is generated by a direct numerical simulation at a Reynolds number Re_\\tau = 150. The spanwise wall oscillation is imposed as a velocity boundary condition with an amplitude of A^+ = 20 and a period of T^+ = 50. The flow is driven by a constant pressure gradient, resulting in a 27% mean velocity increase with wall oscillation. The peaks of the Reynolds stress and root-mean-squared velocities shift away from the wall and the Karhunen-Loeve dimension of the turbulent attractor is reduced from 2453 to 102. The coherent vorticity structures are pushed away from the wall into higher speed flow, causing an increase of their advection speed of 34% as determined by a normal speed locus. The mechanism of drag reduction by spanwise wall oscillation is discussed.

  9. Localized domain wall nucleation dynamics in asymmetric ferromagnetic rings revealed by direct time-resolved magnetic imaging

    Science.gov (United States)

    Richter, Kornel; Krone, Andrea; Mawass, Mohamad-Assaad; Krüger, Benjamin; Weigand, Markus; Stoll, Hermann; Schütz, Gisela; Kläui, Mathias

    2016-07-01

    We report time-resolved observations of field-induced domain wall nucleation in asymmetric ferromagnetic rings using single direction field pulses and rotating fields. We show that the asymmetric geometry of a ring allows for controlling the position of nucleation events, when a domain wall is nucleated by a rotating magnetic field. Direct observation by scanning transmission x-ray microscopy (STXM) reveals that the nucleation of domain walls occurs through the creation of transient ripplelike structures. This magnetization state is found to exhibit a surprisingly high reproducibility even at room temperature and we determine the combinations of field strengths and field directions that allow for reliable nucleation of domain walls and directly quantify the stability of the magnetic states. Our analysis of the processes occurring during field induced domain wall nucleation shows how the effective fields determine the nucleation location reproducibly, which is a key prerequisite toward using domain walls for spintronic devices.

  10. Fluid-structure interaction in abdominal aortic aneurysms: effects of asymmetry and wall thickness

    Directory of Open Access Journals (Sweden)

    Muluk Satish C

    2005-11-01

    Full Text Available Abstract Background Abdominal aortic aneurysm (AAA is a prevalent disease which is of significant concern because of the morbidity associated with the continuing expansion of the abdominal aorta and its ultimate rupture. The transient interaction between blood flow and the wall contributes to wall stress which, if it exceeds the failure strength of the dilated arterial wall, will lead to aneurysm rupture. Utilizing a computational approach, the biomechanical environment of virtual AAAs can be evaluated to study the affects of asymmetry and wall thickness on this stress, two parameters that contribute to increased risk of aneurysm rupture. Methods Ten virtual aneurysm models were created with five different asymmetry parameters ranging from β = 0.2 to 1.0 and either a uniform or variable wall thickness to study the flow and wall dynamics by means of fully coupled fluid-structure interaction (FSI analyses. The AAA wall was designed to have a (i uniform 1.5 mm thickness or (ii variable thickness ranging from 0.5 – 1.5 mm extruded normally from the boundary surface of the lumen. These models were meshed with linear hexahedral elements, imported into a commercial finite element code and analyzed under transient flow conditions. The method proposed was then compared with traditional computational solid stress techniques on the basis of peak wall stress predictions and cost of computational effort. Results The results provide quantitative predictions of flow patterns and wall mechanics as well as the effects of aneurysm asymmetry and wall thickness heterogeneity on the estimation of peak wall stress. These parameters affect the magnitude and distribution of Von Mises stresses; varying wall thickness increases the maximum Von Mises stress by 4 times its uniform thickness counterpart. A pre-peak systole retrograde flow was observed in the AAA sac for all models, which is due to the elastic energy stored in the compliant arterial wall and the expansion

  11. Pulsatile flow characterization in a vessel phantom with elastic wall using ultrasonic particle image velocimetry technique: the impact of vessel stiffness on flow dynamics.

    Science.gov (United States)

    Qian, Ming; Niu, Lili; Wong, Kelvin Kian Loong; Abbott, Derek; Zhou, Qifa; Zheng, Hairong

    2014-09-01

    This study aims to experimentally investigate the impact of vessel stiffness on the flow dynamics of pulsatile vascular flow. Vessel phantoms with elastic walls were fabricated using polyvinyl alcohol cryogel to result in stiffness ranging from 60.9 to 310.3 kPa and tested with pulsatile flows using a flow circulation set-up. Two-dimensional instantaneous and time-dependent flow velocity and shear rate vector fields were measured using ultrasonic particle image velocimetry (EchoPIV). The waveforms of peak velocities measured by EchoPIV were compared with the ultrasonic pulse Doppler spectrum, and the measuring accuracy was validated. The cyclic vessel wall motion and flow pressure were obtained as well. The results showed that vessel stiffening influenced the waveforms resulting from vessel wall distension and flow pressure, and the fields of flow velocity and shear rate. The stiffer vessel had smaller inner diameter variation, larger pulse pressure and median pressure. The velocity and shear rate maximized at peak systole for all vessels. The results showed a decrease in wall shear stress for a stiffer vessel, which can initiate the atherosclerotic process. Our study elucidates the impact of vessel stiffness on several flow dynamic parameters, and also demonstrates the EchoPIV technique to be a useful and powerful tool in cardiovascular research.

  12. Quantum chemical molecular dynamics simulation of single-walled carbon nanotube cap nucleation on an iron particle.

    Science.gov (United States)

    Ohta, Yasuhito; Okamoto, Yoshiko; Page, Alister J; Irle, Stephan; Morokuma, Keiji

    2009-11-24

    The atomic scale details of single-walled carbon nanotube (SWNT) nucleation on metal catalyst particles are elusive to experimental observations. Computer simulation of metal-catalyzed SWNT nucleation is a challenging topic but potentially of great importance to understand the factors affecting SWNT diameters, chirality, and growth efficiency. In this work, we use nonequilibrium density functional tight-binding molecular dynamics simulations and report nucleation of sp(2)-carbon cap structures on an iron particle consisting of 38 atoms. One C(2) molecule was placed every 1.0 ps around an Fe(38) cluster for 30 ps, after which a further 410 ps of annealing simulation without carbon supply was performed. We find that sp(2)-carbon network nucleation and annealing processes occur in three sequential and repetitive stages: (A) polyyne chains on the metal surface react with each other to evolve into a Y-shaped polyyne junction, which preferentially form a five-membered ring as a nucleus; (B) polyyne chains on the first five-membered ring form an additional fused five- or six-membered ring; and (C) pentagon-to-hexagon self-healing rearrangement takes place with the help of short-lived polyyne chains, stabilized by the mobile metal atoms. The observed nucleation process resembles the formation of a fullerene cage. However, the metal particle plays a key role in differentiating the nucleation process from fullerene cage formation, most importantly by keeping the growing cap structure from closing into a fullerene cage and by keeping the carbon edge "alive" for the addition of new carbon material.

  13. The dynamic of aterosclerosis affection on brachio-cefalic arterys of the high risk patients under the hypolipidemic treatment

    Directory of Open Access Journals (Sweden)

    V.V. Simerzin

    2010-06-01

    Full Text Available Purpose. To study the statin influence on lipid exchange and the degree of the brachiocefalic arterys alteration. Methods. The research included 33 high risk patients. The patients inverstigation included lipid spectrum, blood coagulation indexes, by the means of triplex scanning of the brachiochefalic arterys the thickness of the intima - media complex and the expression of stenosis of carotid, vertebral and subclavian arterys were measured. Results. All the patients were divided into the groups according to the total cholesterol and low density lipoprotein cholesterol levels. Patients were divided into subgroups according to the expression of stenosis. The 1 group of patients received rosuvastating 10 mg, the 2 group - atorvastain 20 mg, 3the 3 group - simvastatin 40 mg. This inverstigation shows that the high risk patients with high levels of total cholesterol and low density lipoproteins have the highest expressiveness of brachiocefalic arterys atherosclerosis affection. Conclusion. The assignment of the statins to these patients is accompanied by the lowering of the levels of total cholesterol and low density lipoproteins and the quantity of arteries affected by the atherosclerosis and also by decreasing of the stenosis expression

  14. In-vitro validation of a novel model-based approach to the measurement of arterial blood flow waveforms from dynamic digital x-ray images

    Science.gov (United States)

    Rhode, Kawal; Lambrou, Tryphon; Seifalian, Alexander M.; Hawkes, David J.

    2002-04-01

    We have developed a waveform shape model-based algorithm for the extraction of blood flow from dynamic arterial x-ray angiographic images. We have carried out in-vitro validation of this technique. A pulsatile physiological blood flow circuit was constructed using an anthropomorphic cerebral vascular phantom to simulate the cerebral arterial circulation with whole blood as the fluid. Instantaneous recording of flow from an electromagnetic flow meter (EMF) provided the gold standard measurement. Biplane dynamic digital x-ray images of the vascular phantom with injection of contrast medium were acquired at 25 fps using a PC frame capture card with calibration using a Perspex cube. Principal component analysis was used to construct a shape model by collecting 434 flow waveforms from the EMF under varying flow conditions. Blood flow waveforms were calculated from the angiographic data by using our previous concentration-distance curve matching (ORG) algorithm and by using the new model-based (MB) algorithm. Both instantaneous and mean flow values calculated using the MB algorithm showed greater correlation, less bias, and lower variability than those calculated using the ORG algorithm when compared to the EMF values. We have successfully demonstrated that use of a priori waveform shape information can improve flow measurements from dynamic x-ray angiograms.

  15. Structure and Dynamics of Brachypodium Primary Cell Wall Polysaccharides from Two-Dimensional 13C Solid-State Nuclear Magnetic Resonance Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tuo [Ames Lab., Ames, IA (United States); Salazar, Andre [Iowa State Univ., Ames, IA (United States); Zabotina, Olga A. [Iowa State Univ., Ames, IA (United States); Hong, Mei [Ames Lab., Ames, IA (United States)

    2014-04-10

    The polysaccharide structure and dynamics in the primary cell wall of the model grass Brachypodium distachyon are investigated for the first time using solid-state nuclear magnetic resonance (NMR). While both grass and non-grass cell walls contain cellulose as the main structural scaffold, the former contains xylan with arabinose and glucuronic acid substitutions as the main hemicellulose, with a small amount of xyloglucan (XyG) and pectins, while the latter contains XyG as the main hemicellulose and significant amounts of pectins. We labeled the Brachypodium cell wall with 13C to allow two-dimensional (2D) 13C correlation NMR experiments under magic-angle spinning. Well-resolved 2D spectra are obtained in which the 13C signals of cellulose, glucuronoarabinoxylan (GAX), and other matrix polysaccharides can be assigned. The assigned 13C chemical shifts indicate that there are a large number of arabinose and xylose linkages in the wall, and GAX is significantly branched at the developmental stage of 2 weeks. 2D 13C–13C correlation spectra measured with long spin diffusion mixing times indicate that the branched GAX approaches cellulose microfibrils on the nanometer scale, contrary to the conventional model in which only unbranched GAX can bind cellulose. The GAX chains are highly dynamic, with average order parameters of 0.4. Biexponential 13C T1 and 1H T relaxation indicates that there are two dynamically distinct domains in GAX: the more rigid domain may be responsible for cross-linking cellulose microfibrils, while the more mobile domain may fill the interfibrillar space. This dynamic heterogeneity is more pronounced than that of the non-grass hemicellulose, XyG, suggesting that GAX adopts the mixed characteristics of XyG and pectins. Moderate differences in cellulose rigidity are observed between the Brachypodium and Arabidopsis cell walls

  16. Arterial Ageing

    OpenAIRE

    Lee, Seung-Jun; Park, Sung-Ha

    2013-01-01

    Arterial ageing is characterized by age associated degeneration and sclerosis of the media layer of the large arteries. However, besides ageing, clinical conditions, which enhance oxidative stress and inflammation act to accelerate the degree of arterial ageing. In this review, we summarized the pathophysiology and contributing factors that accelerate arterial ageing. Among them, we focused on hypertension, the renin-angiotensin-aldosterone system and vascular inflammation which are modifiabl...

  17. Temperature gradient-induced fluid pumping inside a single-wall carbon nanotube: A non-equilibrium molecular dynamics study

    Science.gov (United States)

    Faraji, Fahim; Rajabpour, Ali

    2016-09-01

    In this paper we investigate the fluid transport inside a single-wall carbon nanotube induced by a temperature gradient along the tube length, focusing on the effect of fluid-wall interaction strength. It is found that the fluid moves from the hot side of the nanotube towards the cold side. By increasing the fluid-wall interaction strength, the fluid volumetric flux assumes a maximum, increases, and then decreases. Fluid transport is pressure-driven in weak interactions; in contrast, in strong interactions, the fluid is broken into two parts in the radial direction. Fluid transport in the central regions of the tube is pressure-driven, while it is surface-driven in the areas close to the wall.

  18. Arterial-Ventricular Uncoupling with Age and Disease

    Directory of Open Access Journals (Sweden)

    Paul David Chantler

    2012-05-01

    Full Text Available Age is the dominant risk factor for cardiovascular diseases. Understanding the coupling between the left ventricle (LV and arterial system, termed arterial-ventricular coupling (EA/ELV, provides important mechanistic insights into the complex cardiovascular system and its changes with aging in the absence and presence of disease. EA/ELV can be indexed by the ratio of effective arterial elastance (EA; a measure of the net arterial load exerted on the left ventricle to left ventricular end-systolic elastance (ELV; a load-independent measure of left ventricular chamber performance. At rest, in healthy individuals, EA/ELV is maintained within a narrow range, which allows the cardiovascular system to optimize energetic efficiency at the expense of mechanical efficacy. The age-associated alterations to arterial structure and function, including diameter, wall thickness, wall stiffness, and endothelial dysfunction, contribute to a gradual increase in resting EA with age. Remarkably there is a corresponding increase in resting ELV with age due to alterations to LV remodeling (loss in myocyte number, increased collagen and function. During dynamic exercise there is an acute mismatch between the arterial and ventricular systems due to a disproportionate increase in ELV (approximately 200% compared to EA (approximately 40%, to ensure that sufficient cardiac performance is achieved to meet the increased energetic requirements of the body. As a result EA/ELV decreases from an average of 0.58 to 0.34, and 0.52 to 0.27 in men and women, respectively. However, with advancing age the reduction in EA/ELV to acute maximal exercise is blunted, due to a blunted ELV. In this review, we provide an overview of the concept of EA/ELV, and examine the effects of age in the absence and presence of disease on EA/ELV and its functional consequences, and potential therapeutic interventions.

  19. A new picture of cell wall protein dynamics in elongating cells of Arabidopsis thaliana: Confirmed actors and newcomers

    OpenAIRE

    Jamet Elisabeth; Pont-Lezica Rafael; Borderies Gisèle; Canut Hervé; Irshad Muhammad

    2008-01-01

    Abstract Background Cell elongation in plants requires addition and re-arrangements of cell wall components. Even if some protein families have been shown to play roles in these events, a global picture of proteins present in cell walls of elongating cells is still missing. A proteomic study was performed on etiolated hypocotyls of Arabidopsis used as model of cells undergoing elongation followed by growth arrest within a short time. Results Two developmental stages (active growth and after g...

  20. Dynamic evaluation of absorbed dose to the bladder wall with a balloon-bladder phantom during a study using [(18)F]fluorodeoxyglucose positron emission imaging.

    Science.gov (United States)

    Wu, T H; Liu, R S; Dong, S L; Chung, Y W; Chou, K L; Lee, J S

    2002-08-01

    An accurate evaluation of the absorbed dose to the bladder wall from 2-[(18)F]fluoro-2-deoxy-d-glucose (FDG) is clinically important because the bladder is considered as a critical organ in most positron emission tomography (PET) studies that cumulate about 20% of the total activity injection during image procedures. In the MIRD calculation, no allowance is made for the inclusion of all the dynamic parameters that affect the actual dose to the bladder wall to be taken in the dose assessment. The goal of the study is to propose a dose evaluation model by using a dynamic bladder phantom and time-activity curves from the bladder PET imaging. The proposed model takes all dynamic parameters into account and provides a much more accurate dose estimation to the bladder. In this study, the lowest dose to the bladder wall was obtained at the conditions of having a larger initial volume for the bladder contents and a higher production rate for urine. It is then advised patients to drink a bulk amount of water before the FDG injection or after urine voiding to facilitate urine production and to enlarge the bladder surface area, which are the most crucial steps in reducing the dose to the bladder wall. In our study, the voiding schedule in dose calculation plays certain roles although it is much more critical in the conventional MIRD calculation. The model estimated that the lowest dose to the bladder would occur at an initial void about 40 min after the FDG injection and the urine voiding was as complete as possible. PMID:12124480

  1. Dynamics of clinical semiotics in children with pathological tortuosity of internal carotid arteries in remote period after surgical management.

    Science.gov (United States)

    Shoĭkhet, Ya N; Khorev, N G; Kulikova, N I; Beller, A V; Kulikov, V P; Miller, V E

    2010-01-01

    The present study enrolling a total of eighty-eight 4-to-16-year-old children and adolescents was aimed at detailed elaboration and formalization of clinical signs of the internal carotid artery pathological kinking syndrome. To achieve these objectives, the authors carried out a comparative analysis of clinical manifestations of the disease in the surgically treated subjects (constituting the Surgery Group comprising 43 children and adolescents) and non-operated patients (making up the Comparison Group consisting of 45 age- and gender-matched subjects). There were no baseline differences in the incidence rate of clinical syndromes and symptoms between the groups of the would-be operated and conservatively treated patients. Also studied were the remote outcomes (1-to-12-year follow up) of surgical correction for pathological tortuosity of the internal carotid artery. The incidence rate of regression of neurological symptomatology along different clinical signs after surgery was shown to vary within a wide range from 11.6% to 96.3%. Resection of the proximal portion of the internal carotid artery with re-implantation into the old ostium turned out to be clinically effective in 90.0% of cases, with the haemodynamic efficacy amounting to 83.3%. Arteriolysis of the internal carotid artery rendered a clinical effect in 75% of cases, with a haemodynamical effect thereof equalling 25.0%. The decision as to the type of a surgical intervention to perform was primarily made based on the findings of angiography of the internal carotid artery. The operation of arteriolysis did not lead to deterioration of the child's condition.

  2. Cell Geometry Guides the Dynamic Targeting of Apoplastic GPI-Linked Lipid Transfer Protein to Cell Wall Elements and Cell Borders in Arabidopsis thaliana

    Science.gov (United States)

    Wasteneys, Geoffrey

    2013-01-01

    During cellular morphogenesis, changes in cell shape and cell junction topology are fundamental to normal tissue and organ development. Here we show that apoplastic Glycophosphatidylinositol (GPI)-anchored Lipid Transfer Protein (LTPG) is excluded from cell junctions and flat wall regions, and passively accumulates around their borders in the epidermal cells of Arabidopsis thaliana. Beginning with intense accumulation beneath highly curved cell junction borders, this enrichment is gradually lost as cells become more bulbous during their differentiation. In fully mature epidermal cells, YFP-LTPG often shows a fibrous cellulose microfibril-like pattern within the bulging outer faces. Physical contact between a flat glass surface and bulbous cell surface induces rapid and reversible evacuation from contact sites and accumulation to the curved wall regions surrounding the contact borders. Thus, LTPG distribution is dynamic, responding to changes in cell shape and wall curvature during cell growth and differentiation. We hypothesize that this geometry-based mechanism guides wax-carrying LTPG to functional sites, where it may act to “seal” the vulnerable border surrounding cell-cell junctions and assist in cell wall fortification and cuticular wax deposition. PMID:24260561

  3. Blood serum atherogenicity and coronary artery calcification.

    Science.gov (United States)

    Sobenin, Igor A; Myasoedova, Veronica A; Anisimova, Elena V; Pavlova, Xenia N; Möhlenkamp, Stefan; Schmermund, Axel; Seibel, Rainer; Berenbein, Sina; Lehmann, Nils; Moebus, Susanne; Jöckel, KarlHeinz; Orekhov, Alexander N; Erbel, Raimund

    2014-01-01

    The phenomenon of blood serum atherogenicity was described as the ability of human serum to induce lipid accumulation in cultured cells. The results of recent two-year prospective study in asymptomatic men provided the evidence for association between the changes in serum atherogenicity and dynamics of carotid intima-media thickness progression. The present study was undertaken to test the hypothesis that blood serum atherogenicity and its changes in dynamics may be associated with accumulation of coronary calcium in subclinical atherosclerosis. It was performed in 782 CHD-free participants of The Heinz Nixdorf RECALL (Risk Factors, Evaluation of Coronary Calcium and Lifestyle) Study, in whom blood samples have been taken at the baseline and at the end of 5-year follow-up. Opposite to the previous findings, the changes in serum atherogenicity did not correlate neither with the extent of coronary artery calcification, nor with the changes in Agatston CAC score. There was a moderate but significant rise in serum atherogenicity after 5-year followup period, and the same dynamics was observed for Agatston CAC score, but not for convenient lipid-related risk factors. The absence of association of the changes in serum atherogenicity with the changes in Agatston CAC score, along with previous findings, provides a point of view that serum-induced intracellular cholesterol accumulation is not related to the processes of calcium deposition in arterial wall, since the last one reflects the progression of already existing subclinical atherosclerotic lesions. PMID:24533940

  4. Multidimensional solid-state NMR studies of the structure and dynamics of pectic polysaccharides in uniformly 13C-labeled Arabidopsis primary cell walls

    Energy Technology Data Exchange (ETDEWEB)

    Dick-Perez, Marilu; Wang, Tuo; Salazar, Andre; Zabotina, Olga A.; Hong, Mei

    2012-07-08

    Plant cell wall (CW) polysaccharides are responsible for the mechanical strength and growth of plant cells; however, the high-resolution structure and dynamics of the CW polysaccharides are still poorly understood because of the insoluble nature of these molecules. Here, we use 2D and 3D magic-angle-spinning (MAS) solid-state NMR (SSNMR) to investigate the structural role of pectins in the plant CW. Intact and partially depectinated primary CWs of Arabidopsis thaliana were uniformly labeled with 13C and their NMR spectra were compared. Recent 13C resonance assignment of the major polysaccharides in Arabidopsis thaliana CWs allowed us to determine the effects of depectination on the intermolecular packing and dynamics of the remaining wall polysaccharides. 2D and 3D correlation spectra show the suppression of pectin signals, confirming partial pectin removal by chelating agents and sodium carbonate. Importantly, higher cross peaks are observed in 2D and 3D 13C spectra of the depectinated CW, suggesting higher rigidity and denser packing of the remaining wall polysaccharides compared with the intact CW. 13C spin–lattice relaxation times and 1H rotating-frame spin–lattice relaxation times indicate that the polysaccharides are more rigid on both the nanosecond and microsecond timescales in the depectinated CW. Taken together, these results indicate that pectic polysaccharides are highly dynamic and endow the polysaccharide network of the primary CW with mobility and flexibility, which may be important for pectin functions. This study demonstrates the capability of multidimensional SSNMR to determine the intermolecular interactions and dynamic structures of complex plant materials under near-native conditions. Copyright © 2012 John Wiley & Sons, Ltd.

  5. Computational Fluid Dynamics Modeling of Steam Condensation on Nuclear Containment Wall Surfaces Based on Semiempirical Generalized Correlations

    Directory of Open Access Journals (Sweden)

    Pavan K. Sharma

    2012-01-01

    Full Text Available In water-cooled nuclear power reactors, significant quantities of steam and hydrogen could be produced within the primary containment following the postulated design basis accidents (DBA or beyond design basis accidents (BDBA. For accurate calculation of the temperature/pressure rise and hydrogen transport calculation in nuclear reactor containment due to such scenarios, wall condensation heat transfer coefficient (HTC is used. In the present work, the adaptation of a commercial CFD code with the implementation of models for steam condensation on wall surfaces in presence of noncondensable gases is explained. Steam condensation has been modeled using the empirical average HTC, which was originally developed to be used for “lumped-parameter” (volume-averaged modeling of steam condensation in the presence of noncondensable gases. The present paper suggests a generalized HTC based on curve fitting of most of the reported semiempirical condensation models, which are valid for specific wall conditions. The present methodology has been validated against limited reported experimental data from the COPAIN experimental facility. This is the first step towards the CFD-based generalized analysis procedure for condensation modeling applicable for containment wall surfaces that is being evolved further for specific wall surfaces within the multicompartment containment atmosphere.

  6. Cell Wall

    OpenAIRE

    Jamet, Elisabeth; Canut, Hervé; Boudart, Georges; Albenne, Cécile; Pont-Lezica, Rafael F

    2008-01-01

    This chapter covers our present knowledge of cell wall proteomics highlighting the distinctive features of cell walls and cell wall proteins in relation to problems encountered for protein extraction, separation and identification. It provides clues to design strategies for efficient cell wall proteomic studies. It gives an overview of the kinds of proteins that have yet been identified: the expected proteins vs the identified proteins. Finally, the new vision of the cell wall proteome, and t...

  7. Automatic detection of local arterial input functions through Independent Component Analysis on Dynamic Contrast enhanced Magnetic Resonance Imaging.

    Science.gov (United States)

    Narvaez, Mario; Ruiz-Espana, Silvia; Arana, Estanislao; Moratal, David

    2015-08-01

    Arterial Input Function (AIF) is obtained from perfusion studies as a basic parameter for the calculus of hemodynamic variables used as surrogate markers of the vascular status of tissues. However, at present, its identification is made manually leading to high subjectivity, low repeatability and considerable time consumption. We propose an alternative method to automatically identify local AIF in perfusion images using Independent Component Analysis. PMID:26737244

  8. A novel platelet-rich arterial thrombosis model in rabbits. Simple, reproducible, and dynamic real-time measurement by using double-opposing inverted-sutures model.

    Science.gov (United States)

    Shieh, S J; Chiu, H Y; Shi, G Y; Wu, C M; Wang, J C; Chen, C H; Wu, H L

    2001-09-01

    Though numerous animal thrombosis models have been introduced, an easy, reliable, and reproducible arterial thrombosis model remains a continuing challenge prior to a thrombolytic study. In an effort to evaluate the efficiency of various recombinant thrombolytic agents with specific affinity to activated platelets in vivo, we developed a novel double-opposing inverted-sutures model to create a platelet-rich thrombus in the femoral artery of rabbits. The arteriotomy was done semicircumferentially, and variously sized microsurgical sutures were introduced intraluminally in a double-opposing inverted manner. The animals were divided into three groups according to the double-opposing inverted-sutures used: Group 1 with 10-0 nylon (n=6), Group 2 with 9-0 nylon (n=6), and Group 3 with 8-0 nylon (n=22). The superficial epigastric branch was cannulated with a thin polyethylene (PE) tube for intraarterial administration of the studied thrombolytic agent. The blood flow was continuously measured with a real-time ultrasonic flow meter. Within 2 h of installation of the sutures, there was no thrombus formation in either Group 1 or 2. In Group 3, the thrombosis rate was 91% (20 of 22) under a steady baseline flow (with an average of 12.23+/-2.40 ml/min). It was highly statistically significant with a P-value of .0000743 using Fisher's Exact Test. The averaged time to thrombosis was 21.8+/-9.8 min. The ultrasonic flow meter to record the dynamic real-time measurement of blood flow was a guideline for thrombus formation or dissolution, which was correlated with the morphological findings of stenotic status of the vessel detected by the Doppler sonography. The components of the thrombus were proven to be platelet-rich predominant by histological examination via hematoxylin and eosin (H&E) stain and transmission electron microscopy (TEM). To confirm that the double-opposing inverted-sutures model would be useful for a study of thrombolytic agents, we evaluated the effects of

  9. Sex differences in intracranial arterial bifurcations

    DEFF Research Database (Denmark)

    Lindekleiv, Haakon M; Valen-Sendstad, Kristian; Morgan, Michael K;

    2010-01-01

    Subarachnoid hemorrhage (SAH) is a serious condition, occurring more frequently in females than in males. SAH is mainly caused by rupture of an intracranial aneurysm, which is formed by localized dilation of the intracranial arterial vessel wall, usually at the apex of the arterial bifurcation...

  10. The design of a reflectionless arterial prosthesis

    OpenAIRE

    Kol, Guy Richard; Woafo, Paul

    2010-01-01

    We propose a new technique to characterize a reflectionless arterial prosthesis. The corresponding transmission and reflection coefficients are determined from the geometric and the elastic properties of the arterial wall, and the interaction between the latter and the prosthesis are studied accordingly.

  11. Numerical Simulation of Coronary Artery Bypass Graft with an Assistant Graft

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; WANG Feng

    2014-01-01

    The conventional bypass design is to implant a graft on the stenosed host artery allowing blood to flow bypass the stenotic artery. However, restenosis is a challenging problem which finally results in reoperation. The purpose of this paper is to propose a new bypass graft design of coronary artery with an assistant graft for the treatment of coronary artery stenosis. An additional assistant graft was employed in the new design compared with the conventional ETS anastomosis. Numerical simulations were performed by means of finite volume method using computational fluid dynamics (CFD) solver. Results demonstrated that the new anastomoses model provided a more smooth flow at the distal ETS anastomosis without any stagnation point on anastomotic bed and vortex formation in the heel region. Oscillatory shear index (OSI) and time-averaged wall shear stress gradient (TAWSSG) at the artery bed of the distal ETS anastomosis were reduced. The coronary artery bypass graft with an assistant graft is feasible to improve the local hemodynamics and diminish the probability of restenosis in the treatment of coronary artery stenosis.

  12. The normal distribution of thoracoabdominal aorta small branch artery ostia

    International Nuclear Information System (INIS)

    The purpose of this study was to determine the normal distribution of aortic branch artery ostia. CT scans of 100 subjects were retrospectively reviewed. The angular distributions of the aorta with respect to the center of the T3 to L4 vertebral bodies, and of branch artery origins with respect to the center of the aorta were measured. At each vertebral body level the distribution of intercostal/lumbar arteries and other branch arteries were calculated. The proximal descending aorta is posteriorly placed becoming a midline structure, at the thoracolumbar junction, and remains anterior to the vertebral bodies within the abdomen. The intercostal and lumbar artery ostia have a distinct distribution. At each vertebral level from T3 caudally, one intercostal artery originates from the posterior wall of the aorta throughout the thoracic aorta, while the other intercostal artery originates from the medial wall of the descending thoracic aorta high in the chest, posteromedially from the mid-thoracic aorta, and from the posterior wall of the aorta low in the chest. Mediastinal branches of the thoracic aorta originate from the medial and anterior wall. Lumbar branches originate only from the posterior wall of the abdominal aorta. Aortic branch artery origins arise with a bimodal distribution and have a characteristic location. Mediastinal branches of the thoracic aorta originate from the medial and anterior wall. Knowing the location of aortic branch artery ostia may help distinguish branch artery pseudoaneurysms from penetrating ulcers.

  13. CONSTRUCTION TECHNOLOGY OF TIMBER-FRAME HOUSES RESISTANT TO DYNAMIC LOADS – STUDY ON MODELS OF EXTERIOR WALLS

    Directory of Open Access Journals (Sweden)

    Marcin Szczepanski

    2015-11-01

    Full Text Available The aim of this paper is to show the numeric representation of experimental studies concerning the behaviour of exterior wall models of a timber-frame house under harmonic loading. A single wall model according to traditional technology of timber-frame house walls (filling with mineral wool was tested. The analysis was conducted for the following frequencies: 0.5 Hz, 1.0 Hz, 2.0 Hz and 5.0 Hz for various values of the specified displacement. A number of hysteresis loops were obtained for each of the tests. Based on them, the damping ratio as well as stiffness were calculated. The skeleton model filled with mineral wool (traditional technology experienced serious damage under larger displacements. The results of the study have been used to propose a numerical model of wall filled with mineral wool. The proposed numerical model is consistent with the results for the values ​​obtained during the experimental study, which proves the correctness of the adopted solution.

  14. Influence of tissue preservation methods on arterial geometry and echogenicity

    DEFF Research Database (Denmark)

    Sillesen, H.; Wilhjelm, J; Vogt, Katja;

    1997-01-01

    original, ultrasound, ultrasonic measurement, vessel diameter, wall thickness, measurement of echogenicity, freezing of specimen, formalin fixation, pressurized formalin fixation, porcine artery......original, ultrasound, ultrasonic measurement, vessel diameter, wall thickness, measurement of echogenicity, freezing of specimen, formalin fixation, pressurized formalin fixation, porcine artery...

  15. Evaluation of wall thinning of PWR feed water piping with the coupled model of static electrochemical analysis and dynamic double oxide layer analysis

    International Nuclear Information System (INIS)

    In order to confirm applicability and accuracy of FAC evaluation methods based on the coupled FAC model of static electrochemical analysis and dynamic oxide layer growth analysis, wall thinning rates calculated with the proposed methods were compared with those measured for the secondary piping of a PWR plant. Distributions of flow velocity and temperature along the whole system were calculated with 1D and 2D CFD codes and corrosive conditions were calculated with a N2H4-O2 reaction analysis code. Precise flow turbulence at major parts of the system was analyzed with the 3D CFD codes to obtain mass transfer coefficients at structure surfaces. Then, wall thinning rates were calculated with the coupled FAC model by applying the mass transfer coefficients. Flow distribution calculated with the 3D CFD codes for a large scale piping system could be extrapolated to those at the very surface of the piping to obtain a precise distribution of mass transfer coefficients at the region of interest. Wall thinning rates calculated by applying the obtained mass transfer coefficients agreed with the measured rates within a factor of 2. From demonstration of the FAC evaluation model, the effects of water chemistry improvement on FAC mitigation on feed water piping and its adverse effects on steam generator have been calculated, and then, sufficient mitigation effects of suitable oxygen injection into the feed water line on FAC without any serious adverse effect on SG have been confirmed. (author)

  16. Arterial input function calculation in dynamic contrast-enhanced MRI: an in vivo validation study using co-registered contrast-enhanced ultrasound imaging

    International Nuclear Information System (INIS)

    Developing a method of separating intravascular contrast agent concentration to measure the arterial input function (AIF) in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) of tumours, and validating its performance in phantom and in vivo experiments. A tissue-mimicking phantom was constructed to model leaky tumour vasculature and DCE-MR images of this phantom were acquired. An in vivo study was performed using tumour-bearing rabbits. Co-registered DCE-MRI and contrast-enhanced ultrasound (CEUS) images were acquired. An independent component analysis (ICA)-based method was developed to separate the intravascular component from DCE-MRI. Results were validated by comparing the time-intensity curves with the actual phantom and in vivo curves. Phantom study: the AIF extracted using ICA correlated well with the true intravascular curve. In vivo study: the AIFs extracted from DCE-MRI using ICA were very close to the true AIF. Intravascular component images were very similar to the CEUS images. The contrast onset times and initial wash-in slope of the ICA-derived AIF showed good agreement with the CEUS curves. ICA has the potential to separate the intravascular component from DCE-MRI. This could eliminate the requirement for contrast medium uptake measurements in a major artery and potentially result in more accurate pharmacokinetic parameters. (orig.)

  17. End tidal-to-arterial CO2 and O2 gas gradients at low- and high-altitude during dynamic end-tidal forcing.

    Science.gov (United States)

    Tymko, Michael M; Ainslie, Philip N; MacLeod, David B; Willie, Chris K; Foster, Glen E

    2015-06-01

    We sought to characterize and quantify the performance of a portable dynamic end-tidal forcing (DEF) system in controlling the partial pressure of arterial CO2 (Pa(CO2)) and O2 (Pa(O2)) at low (LA; 344 m) and high altitude (HA; 5,050 m) during an isooxic CO2 test and an isocapnic O2 test, which is commonly used to measure ventilatory and vascular reactivity in humans (n = 9). The isooxic CO2 tests involved step changes in the partial pressure of end-tidal CO2 (PET(CO2)) of -10, -5, 0, +5, and +10 mmHg from baseline. The isocapnic O2 test consisted of a 10-min hypoxic step (PET(O2) = 47 mmHg) from baseline at LA and a 5-min euoxic step (PET(O2) = 100 mmHg) from baseline at HA. At both altitudes, PET(O2) and PET(CO2) were controlled within narrow limits (DEF. Future research is needed to validate these prediction algorithms and determine the implications of end-tidal-to-arterial gradients in the assessment of ventilatory and/or vascular reactivity. PMID:25810386

  18. Correlations of coronary plaque wall thickness with wall pressure and wall pressure gradient: a representative case study

    Directory of Open Access Journals (Sweden)

    Liu Biyue

    2012-07-01

    Full Text Available Abstract Background There are two major hemodynamic stresses imposed at the blood arterial wall interface by flowing blood: the wall shear stress (WSS acting tangentially to the wall, and the wall pressure (WP acting normally to the wall. The role of flow wall shear stress in atherosclerosis progression has been under intensive investigation, while the impact of blood pressure on plaque progression has been under-studied. Method The correlations of wall thickness (WT with wall pressure (WP, blood pressure on the lumen wall and spatial wall pressure gradient (WPG in a human atherosclerotic right coronary artery were studied. The pulsatile blood flow was simulated using a three dimensional mathematical model. The blood was treated as an incompressible viscous non-Newtonian fluid. The geometry of the artery was re-constructed using an in vivo intravascular ultrasound (IVUS 44-slice dataset obtained from a patient with consent obtained. The WT, the WP and the WPG were averaged on each slice, respectively, and Pearson correlation analysis was performed on slice averaged base. Each slice was then divided into 8 segments and averaged vessel WT, WP and WPG were collected from all 352 segments for correlation analysis. Each slice was also divided into 2 segments (inner semi-wall of bend and outer semi-wall of bend and the correlation analysis was performed on the 88 segments. Results Under mean pressure, the Pearson coefficient for correlation between WT and WP was r = − 0.52 (p  Conclusions Results from this representative case report indicated that plaque wall thickness correlated negatively with wall pressure (r = −0.81 by slice and positively with wall pressure gradient (r = 0.45. The slice averaged WT has a strong linear relationship with the slice averaged WP. Large-scale patient studies are needed to further confirm our findings.

  19. Dynamic 3D printed titanium copy prosthesis: a novel design for large chest wall resection and reconstruction.

    Science.gov (United States)

    Aragón, Javier; Pérez Méndez, Itzell

    2016-06-01

    Due to high rates of complications, chest wall resection and reconstruction is a high risk procedure when large size of resection is required. Many different prosthetic materials have been used with similar results. Recently, thanks to the new advances in technology, personalized reconstruction have been possible with specific custom-made prosthesis. Nevertheless, they all generate certain amount of stiffness in thoracic motion because of his rigidity. In this report, we present a forward step in prosthesis design based on tridimensional titanium-printed technology. An exact copy of the resected chest wall was made, even endowing simulated sternochondral articulations, to achieve the most exact adaptation and best functional results, with a view to minimize postoperative complications. This novel design, may constitute an important step towards the improvement of the functional postoperative outcomes compared to the other prosthesis, on the hope, to reduce postoperative complications. PMID:27293863

  20. Dynamical scaling, domain-growth kinetics, and domain-wall shapes of quenched two-dimensional anisotropic XY models

    DEFF Research Database (Denmark)

    Mouritsen, Ole G.; Praestgaard, Eigil

    1988-01-01

    size varies with time, R(t)∼tn, is for both models at zero temperature determined to be n≃0.25, independent of P. At finite temperatures, the growth kinetics is found to cross over to the Lifshitz-Allen-Cahn law characterized by n≃0.50. The results support the idea of two separate zero...... infinite to zero temperature as well as to nonzero temperatures below the ordering transition. The continuous nature of the spin variables causes the domain walls to be ‘‘soft’’ and characterized by a finite thickness. The steady-state thickness of the walls can be varied by a model parameter, P. At zero...

  1. Arterial endothelial function measurement method and apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Maltz, Jonathan S; Budinger, Thomas F

    2014-03-04

    A "relaxoscope" (100) detects the degree of arterial endothelial function. Impairment of arterial endothelial function is an early event in atherosclerosis and correlates with the major risk factors for cardiovascular disease. An artery (115), such as the brachial artery (BA) is measured for diameter before and after several minutes of either vasoconstriction or vasorelaxation. The change in arterial diameter is a measure of flow-mediated vasomodification (FMVM). The relaxoscope induces an artificial pulse (128) at a superficial radial artery (115) via a linear actuator (120). An ultrasonic Doppler stethoscope (130) detects this pulse 10-20 cm proximal to the point of pulse induction (125). The delay between pulse application and detection provides the pulse transit time (PTT). By measuring PTT before (160) and after arterial diameter change (170), FMVM may be measured based on the changes in PTT caused by changes in vessel caliber, smooth muscle tone and wall thickness.

  2. Computational Fluid Dynamics Modeling of Steam Condensation on Nuclear Containment Wall Surfaces Based on Semiempirical Generalized Correlations

    OpenAIRE

    Pavan K Sharma; Gera, B.; R. K. Singh; K. K. Vaze

    2012-01-01

    In water-cooled nuclear power reactors, significant quantities of steam and hydrogen could be produced within the primary containment following the postulated design basis accidents (DBA) or beyond design basis accidents (BDBA). For accurate calculation of the temperature/pressure rise and hydrogen transport calculation in nuclear reactor containment due to such scenarios, wall condensation heat transfer coefficient (HTC) is used. In the present work, the adaptation of a commercial CFD code w...

  3. Low prevalence of significant carotid artery disease in Iranian patients undergoing elective coronary artery bypass

    Directory of Open Access Journals (Sweden)

    Karimi Fatemeh

    2007-01-01

    Full Text Available Abstract Background Coronary artery bypass grafting ranks as one of the most frequent operations worldwide. The presence of carotid artery stenosis may increase the stroke rate in the perioperative period. Routine preoperative noninvasive assessment of the carotid arteries are recommended in many institutions to reduce the stroke rate. Methods 271 consecutive patients undergoing coronary artery bypass grafting at Shaheed Madani hospital of Tabriz, Iran (age, 58.5 Y; 73.1% male underwent preoperative ultrasonography for assessment of carotid artery wall thickness. Results Plaque in right common, left common, right internal and left internal carotid arteries was detected in 4.8%, 7.4%, 43.2% and 42.1% of patients respectively. 5 patients (1.8% had significant ( Conclusion Consecutive Iranian patients undergoing elective coronary artery bypass surgery show a very low prevalence of significant carotid artery disease.

  4. Consistence study of carotid artery wall thickness by MDCTA and high-frequency ultrasound%MDCTA与高频超声检测颈动脉壁厚度的一致性研究

    Institute of Scientific and Technical Information of China (English)

    洪玮; 赵刚; 王弘; 邱晓明; 王珍

    2012-01-01

    Objective To explore the relevance and consistence between multi-detector row computed tomography angi-ography (MDCTA) and high-frequency ultrasound in measuring carotid artery wall thickness (CAWT) and the intima-media thickness (IMT). Methods Altogether, 64 subjects were prospectively analysed using a 64-detector row CT and high-frequency ultrasound. And they were classified as non-plaque group and plaque group. CAWT and IMT were measured in each patient using MDCTA and ultrasound, respectively. CAWT and IMT were compared and dependency analysed. Bland-Altman statistics was employed to measure the consistency between MDCTA and ultrasound. Results There was not significant difference between CAWT and IMT in the same group ( P > 0. 05). There was a high degree of correlation between all the common carotid artery CAWT and IMT, correlation coefficient was 0. 912 ( P <0. 01). By analysing the Bland-Altman plot, we observed a good consistence between CAWT and IMT with a bias between methods of 0. 029 mm and limit of consistence from 0. 187 mm to 0. 244 mm. Conclusion There was a good consistency between MDCTA and high-frequency ultrasound in the measurement of CAWT and IMT. CAWT can be used as an evaluating indicator of carotid atherosclerosis by MDCTA.%目的 探讨多层螺旋CT血管造影(MDCTA)检测颈总动脉壁厚度(CAWT)与高频超声检测颈总动脉内-中膜层厚度(IMT)的相关性和一致性.方法 应用MDCTA和高频超声对64例患者颈总动脉CAWT和IMT分别进行扫描,分为无斑块组和有斑块组,统计学比较CAWT与IMT的差异性和相关性,用Bland-Altman分析比较两者的一致性.结果 两组患者颈总动脉CAWT与IMT比较无统计学差异(P>0.05),相关性分析呈高度正相关,相关系数为0.912(P<0.O1),Bland-Altman分析存在较好一致性,偏倚为0.029mm,一致性界限为0.187~0.244mm.结论 MDCTA测量颈总动脉CAWT与高频超声测量颈总动脉IMT之间存在高度相关性和较好一致

  5. Oxygen transfer in human carotid artery bifurcation

    Institute of Scientific and Technical Information of China (English)

    Z.G.Zhang; Y.B.Fan; X.Y.Deng

    2007-01-01

    Arterial bifurcations are places where blood flow may be disturbed and slow recirculation flow may occur.To reveal the correlation between local oxygen transfer and atherogenesis, a finite element method was employed to simulate the blood flow and the oxygen transfer in the human carotid artery bifurcation. Under steady-state flow conditions, the numerical simulation demonstrated a variation in local oxygen transfer at the bifurcation, showing that the convective condition in the disturbed flow region may produce uneven local oxygen transfer at the blood/wall interface.The disturbed blood flow with formation of slow eddies in the carotid sinus resulted in a depression in oxygen supply to the arterial wall at the entry of the sinus, which in turn may lead to an atherogenic response of the arterial wall, and contribute to the development of atherosclerotic stenosis there.

  6. Numerical simulation of pulsatile flow with newtonian and non-newtonian behavior in arterial stenosis

    Directory of Open Access Journals (Sweden)

    MM Movahedi

    2008-03-01

    Full Text Available Background: There is considerable evidence that vascular fluid dynamics plays an important role in the developmentand prevalence of atherosclerosis which is one of the most widespread disease in humans .The onset and prevalence of atherosclerosis hemodynamic parameter are largely affected by geometric parameters. If any obstacle interferes with the blood flow, the above parameters change dramatically. Most of the arterial diseases, such as atherosclerosis, occur in the arteries with complex patterns of fluid flow where the blood dynamics plays an important role. Arterial stenosis mostly occurs in an area with a complex pattern of fluid flow, such as coronary artery, aorta bifurcation, carotid and vessels of lower limbs. During the past three decades, many experimental studies have been performed on the hemodynamic role of the blood in forming sediment in the inner wall of the vessels. It has been shown that forming sediment in the inner wall of vessels depends on the velocity of fluid and also on the amount of wall shear stress.Methods: We have examined the effect on the blood flow of local stenosis in carotid artery in numerical form using the incompressible Navier-Stockes equations. The profile of the velocity in different parts and times in the pulsatile cycle, separation and reattachment points on the wall, the distance stability of flow and also alteration caused by the wall shear stress in entire vessel were shown and compared with two behaviors flow (Newtonian and Non-Newtonian.Finally we describe the influence of the severity of the stenosis on the separation and reattachmentpoints for a Non-Newtonian fuid. Results: In the present study, we have pointed very low and high oscillating WSS (Wall Shear Stress values play a significant role in the development of forming sediment in the inner wall of vessels. Also, we obtain this probability is higher for Newtonian than Non-Newtonian fluid behavior.Conclusion: Based on our results, the

  7. Impact of scaffold micro and macro architecture on Schwann cell proliferation under dynamic conditions in a rotating wall vessel bioreactor

    International Nuclear Information System (INIS)

    Over the last decade tissue engineering has emerged as a powerful alternative to regenerate lost tissues owing to trauma or tumor. Evidence shows that Schwann cell containing scaffolds have improved performance in vivo as compared to scaffolds that depend on cellularization post implantation. However, owing to limited supply of cells from the patients themselves, several approaches have been taken to enhance cell proliferation rates to produce complete and uniform cellularization of scaffolds. The most common approach is the application of a bioreactor to enhance cell proliferation rate and therefore reduce the time needed to obtain sufficiently significant number of glial cells, prior to implantation. In this study, we show the application of a rotating wall bioreactor system for studying Schwann cell proliferation on nanofibrous spiral shaped scaffolds, prepared by solvent casting and salt leaching techniques. The scaffolds were fabricated from polycaprolactone (PCL), which has ideal mechanical properties and upon degradation does not produce acidic byproducts. The spiral scaffolds were coated with aligned or random nanofibers, produced by electrospinning, to provide a substrate that mimics the native extracellular matrix and the essential contact guidance cues. At the 4 day time point, an enhanced rate of cell proliferation was observed on the open structured nanofibrous spiral scaffolds in a rotating wall bioreactor, as compared to static culture conditions. However, the cell proliferation rate on the other contemporary scaffolds architectures such as the tubular and cylindrical scaffolds show reduced cell proliferation in the bioreactor as compared to static conditions, at the same time point. Moreover, the rotating wall bioreactor does not alter the orientation or the phenotype of the Schwann cells on the aligned nanofiber containing scaffolds, wherein, the cells remain aligned along the length of the scaffolds. Therefore, these open structured spiral

  8. Impact of scaffold micro and macro architecture on Schwann cell proliferation under dynamic conditions in a rotating wall vessel bioreactor

    Energy Technology Data Exchange (ETDEWEB)

    Valmikinathan, Chandra M.; Hoffman, John [Department of Chemistry, Chemical Biology and Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030 (United States); Yu, Xiaojun, E-mail: xyu@stevens.edu [Department of Chemistry, Chemical Biology and Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030 (United States)

    2011-01-01

    Over the last decade tissue engineering has emerged as a powerful alternative to regenerate lost tissues owing to trauma or tumor. Evidence shows that Schwann cell containing scaffolds have improved performance in vivo as compared to scaffolds that depend on cellularization post implantation. However, owing to limited supply of cells from the patients themselves, several approaches have been taken to enhance cell proliferation rates to produce complete and uniform cellularization of scaffolds. The most common approach is the application of a bioreactor to enhance cell proliferation rate and therefore reduce the time needed to obtain sufficiently significant number of glial cells, prior to implantation. In this study, we show the application of a rotating wall bioreactor system for studying Schwann cell proliferation on nanofibrous spiral shaped scaffolds, prepared by solvent casting and salt leaching techniques. The scaffolds were fabricated from polycaprolactone (PCL), which has ideal mechanical properties and upon degradation does not produce acidic byproducts. The spiral scaffolds were coated with aligned or random nanofibers, produced by electrospinning, to provide a substrate that mimics the native extracellular matrix and the essential contact guidance cues. At the 4 day time point, an enhanced rate of cell proliferation was observed on the open structured nanofibrous spiral scaffolds in a rotating wall bioreactor, as compared to static culture conditions. However, the cell proliferation rate on the other contemporary scaffolds architectures such as the tubular and cylindrical scaffolds show reduced cell proliferation in the bioreactor as compared to static conditions, at the same time point. Moreover, the rotating wall bioreactor does not alter the orientation or the phenotype of the Schwann cells on the aligned nanofiber containing scaffolds, wherein, the cells remain aligned along the length of the scaffolds. Therefore, these open structured spiral

  9. Binding of Single Walled Carbon Nanotube to WT and Mutant HIV-1 Proteases: Analysis of Flap Dynamics and Binding Mechanism

    OpenAIRE

    Meher, Biswa Ranjan; Wang, Yixuan

    2012-01-01

    Most of the currently treated HIV-1 protease (HIV-PR) inhibitors have been prone to suffer from the mutations associated drug resistance. Therefore, it is necessary to search for potent alternatives against the drug resistance. In the current study we have tested the single-walled carbon nanotube (SWCNT) as an inhibitor in wild type (WT) as well as in three primary mutants (I50VPR, V82APR and I84VPR) of the HIV-1-PR through docking the SWCNT in the active site region, and then performed all-a...

  10. Microfluidic strategy to investigate dynamics of small blood vessel function

    Science.gov (United States)

    Yasotharan, Sanjesh; Bolz, Steffen-Sebastian; Guenther, Axel

    2010-11-01

    Resistance arteries (RAs, 30-300 microns in diameter) that are located within the terminal part of the vascular tree regulate the laminar perfusion of tissue with blood, via the peripheral vascular resistance, and hence controls the systemic blood pressure. The structure of RAs is adapted to actively controlling flow resistance by dynamically changing their diameter, which is non-linearly dependent on the temporal variation of the transmural pressure, perfusion flow rate and spatiotemporal changes in the chemical environment. Increases in systemic blood pressure (hypertension) resulting from pathologic changes in the RA response represent the primary risk factor for cardiovascular diseases. We use a microfluidic strategy to investigate small blood vessels by quantifying structural variations within the arterial wall, RA outer contour and diameter over time. First, we document the artery response to vasomotor drugs that were homogeneously applied at step-wise increasing concentration. Second, we investigate the response in the presence of well-defined axial and circumferential heterogeneities. Artery per- and superfusion is discussed based on microscale PIV measurements of the fluid velocity on both sides of the arterial wall. Structural changes in the arterial wall are quantified using cross-correlation and proper orthogonal decomposition analyses of bright-field micrographs.

  11. A study of the hemodynamics of anterior communicating artery aneurysms

    Science.gov (United States)

    Cebral, Juan R.; Castro, Marcelo A.; Putman, Christopher M.

    2006-03-01

    In this study, the effects of unequal physiologic flow conditions in the internal carotid arteries on the intra-aneurysmal hemodynamics of anterior communicating artery aneurysms were investigated. Patient-specific vascular computational fluid dynamics models of five cerebral aneurysms were constructed from bilateral 3D rotational angiography images. The aneurysmal hemodynamics was analyzed under a range of physiologic flow conditions including the effects of unequal mean flows and phase shifts between the flow waveforms of the left and right internal carotid arteries. A total of five simulations were performed for each patient, and unsteady wall shear stress (WSS) maps were created for each flow condition. Time dependent curves of average WSS magnitude over selected regions on the aneurysms were constructed and used to analyze the influence of the inflow conditions. It was found that mean flow imbalances in the feeding vessels tend to shift the regions of elevated WSS (flow impingement region) towards the dominating inflow jet and to change the magnitude of the WSS peaks. However, the overall qualitative appearance of the WSS distribution and velocity simulations is not substantially affected. In contrast, phase differences tend to increase the temporal complexity of the hemodynamic patterns and to destabilize the intra-aneurysmal flow pattern. However, these effects are less important when the A1 confluence is less symmetric, i.e. dominated by one of the A1 segments. Conditions affecting the flow characteristics in the parent arteries of cerebral aneurysms with more than one avenue of inflow should be incorporated into flow models.

  12. Bending and twisting of an in vivo coronary artery at a bifurcation.

    Science.gov (United States)

    Pao, Y C; Lu, J T; Ritman, E L

    1992-03-01

    Dynamic changes in the geometric shape and dimensions of a left coronary artery tree were extracted from the computer-tomographically reconstructed three-dimensional images of an in situ beating heart of an anesthetized dog. Wireframe models of the left coronary artery tree at 16 different instants of a cardiac cycle were constructed for the study of its flexing motion. For quantifying the local bending and twisting of the left coronary artery tree, the anatomic landmarks of the bifurcation points are selected as focussed locations. At these points, the space curves of the tree at different cardiac instants were first derived in parametric forms. Curvature and torsion expressions are next obtained in terms of the derivatives with respect to the parameter. This analysis revealed that during the initial contraction of the heart wall, a 2% reduction per millisecond in the radius of curvature occurred near the bifurcation point where the left circumflex coronary artery descends toward the apex of the heart. When the left ventricular chamber reached a maximum value, the radius of curvature was found to decrease at a rate of 2.3% ms-1. At the end of diastole, an increase in the radius of curvature at a rate of 5.7% ms-1 was observed. The twisting rates per unit length of artery near the bifurcation point of the selected artery were found to range from -0.62 to 0.63 degrees ms-1.

  13. Heterogeneous mechanics of the mouse pulmonary arterial network.

    Science.gov (United States)

    Lee, Pilhwa; Carlson, Brian E; Chesler, Naomi; Olufsen, Mette S; Qureshi, M Umar; Smith, Nicolas P; Sochi, Taha; Beard, Daniel A

    2016-10-01

    Individualized modeling and simulation of blood flow mechanics find applications in both animal research and patient care. Individual animal or patient models for blood vessel mechanics are based on combining measured vascular geometry with a fluid structure model coupling formulations describing dynamics of the fluid and mechanics of the wall. For example, one-dimensional fluid flow modeling requires a constitutive law relating vessel cross-sectional deformation to pressure in the lumen. To investigate means of identifying appropriate constitutive relationships, an automated segmentation algorithm was applied to micro-computerized tomography images from a mouse lung obtained at four different static pressures to identify the static pressure-radius relationship for four generations of vessels in the pulmonary arterial network. A shape-fitting function was parameterized for each vessel in the network to characterize the nonlinear and heterogeneous nature of vessel distensibility in the pulmonary arteries. These data on morphometric and mechanical properties were used to simulate pressure and flow velocity propagation in the network using one-dimensional representations of fluid and vessel wall mechanics. Moreover, wave intensity analysis was used to study effects of wall mechanics on generation and propagation of pressure wave reflections. Simulations were conducted to investigate the role of linear versus nonlinear formulations of wall elasticity and homogeneous versus heterogeneous treatments of vessel wall properties. Accounting for heterogeneity, by parameterizing the pressure/distention equation of state individually for each vessel segment, was found to have little effect on the predicted pressure profiles and wave propagation compared to a homogeneous parameterization based on average behavior. However, substantially different results were obtained using a linear elastic thin-shell model than were obtained using a nonlinear model that has a more

  14. Heterogeneous mechanics of the mouse pulmonary arterial network.

    Science.gov (United States)

    Lee, Pilhwa; Carlson, Brian E; Chesler, Naomi; Olufsen, Mette S; Qureshi, M Umar; Smith, Nicolas P; Sochi, Taha; Beard, Daniel A

    2016-10-01

    Individualized modeling and simulation of blood flow mechanics find applications in both animal research and patient care. Individual animal or patient models for blood vessel mechanics are based on combining measured vascular geometry with a fluid structure model coupling formulations describing dynamics of the fluid and mechanics of the wall. For example, one-dimensional fluid flow modeling requires a constitutive law relating vessel cross-sectional deformation to pressure in the lumen. To investigate means of identifying appropriate constitutive relationships, an automated segmentation algorithm was applied to micro-computerized tomography images from a mouse lung obtained at four different static pressures to identify the static pressure-radius relationship for four generations of vessels in the pulmonary arterial network. A shape-fitting function was parameterized for each vessel in the network to characterize the nonlinear and heterogeneous nature of vessel distensibility in the pulmonary arteries. These data on morphometric and mechanical properties were used to simulate pressure and flow velocity propagation in the network using one-dimensional representations of fluid and vessel wall mechanics. Moreover, wave intensity analysis was used to study effects of wall mechanics on generation and propagation of pressure wave reflections. Simulations were conducted to investigate the role of linear versus nonlinear formulations of wall elasticity and homogeneous versus heterogeneous treatments of vessel wall properties. Accounting for heterogeneity, by parameterizing the pressure/distention equation of state individually for each vessel segment, was found to have little effect on the predicted pressure profiles and wave propagation compared to a homogeneous parameterization based on average behavior. However, substantially different results were obtained using a linear elastic thin-shell model than were obtained using a nonlinear model that has a more

  15. Comprehensive Population-Averaged Arterial Input Function for Dynamic Contrast–Enhanced vMagnetic Resonance Imaging of Head and Neck Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Onxley, Jennifer D.; Yoo, David S. [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States); Muradyan, Naira [iCAD Inc., Nashua, New Hampshire (United States); MacFall, James R. [Department of Radiology, Duke University Medical Center, Durham, North Carolina (United States); Brizel, David M. [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States); Department of Surgery, Duke University Medical Center, Durham, North Carolina (United States); Craciunescu, Oana I., E-mail: Oana.Craciunescu@duke.edu [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States)

    2014-07-01

    Purpose: To generate a population-averaged arterial input function (PA-AIF) for quantitative analysis of dynamic contrast-enhanced MRI data in head and neck cancer patients. Methods and Materials: Twenty patients underwent dynamic contrast-enhanced MRI during concurrent chemoradiation therapy. Imaging consisted of 2 baseline scans 1 week apart (B1/B2) and 1 scan after 1 week of chemoradiation therapy (Wk1). Regions of interest (ROIs) in the right and left carotid arteries were drawn on coronal images. Plasma concentration curves of all ROIs were averaged and fit to a biexponential decay function to obtain the final PA-AIF (AvgAll). Right-sided and left-sided ROI plasma concentration curves were averaged separately to obtain side-specific AIFs (AvgRight/AvgLeft). Regions of interest were divided by time point to obtain time-point-specific AIFs (AvgB1/AvgB2/AvgWk1). The vascular transfer constant (K{sub trans}) and the fractional extravascular, extracellular space volume (V{sub e}) for primaries and nodes were calculated using the AvgAll AIF, the appropriate side-specific AIF, and the appropriate time-point-specific AIF. Median K{sub trans} and V{sub e} values derived from AvgAll were compared with those obtained from the side-specific and time-point-specific AIFs. The effect of using individual AIFs was also investigated. Results: The plasma parameters for AvgAll were a{sub 1,2} = 27.11/17.65 kg/L, m{sub 1,2} = 11.75/0.21 min{sup −1}. The coefficients of repeatability (CRs) for AvgAll versus AvgLeft were 0.04 min{sup −1} for K{sub trans} and 0.02 for V{sub e}. For AvgAll versus AvgRight, the CRs were 0.08 min{sup −1} for K{sub trans} and 0.02 for V{sub e}. When AvgAll was compared with AvgB1/AvgB2/AvgWk1, the CRs were slightly higher: 0.32/0.19/0.78 min{sup −1}, respectively, for K{sub trans}; and 0.07/0.08/0.09 for V{sub e}. Use of a PA-AIF was not significantly different from use of individual AIFs. Conclusion: A PA-AIF for head and neck cancer

  16. Regional and voxel-wise comparisons of blood flow measurements between dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) and arterial spin labeling (ASL) in brain tumors.

    Science.gov (United States)

    White, Carissa M; Pope, Whitney B; Zaw, Taryar; Qiao, Joe; Naeini, Kourosh M; Lai, Albert; Nghiemphu, Phioanh L; Wang, J J; Cloughesy, Timothy F; Ellingson, Benjamin M

    2014-01-01

    The objective of the current study was to evaluate the regional and voxel-wise correlation between dynamic susceptibility contrast (DSC) and arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) measurement of cerebral blood flow (CBF) in patients with brain tumors. Thirty patients with histologically verified brain tumors were evaluated in the current study. DSC-MRI was performed by first using a preload dose of gadolinium contrast, then collecting a dynamic image acquisition during a bolus of contrast, followed by posthoc contrast agent leakage correction. Pseudocontinuous ASL was collected using 30 pairs of tag and control acquisition using a 3-dimensional gradient-echo spin-echo (GRASE) acquisition. All images were registered to a high-resolution anatomical atlas. Average CBF measurements within regions of contrast-enhancement and T2 hyperintensity were evaluated between the two modalities. Additionally, voxel-wise correlation between CBF measurements obtained with DSC and ASL were assessed. Results demonstrated a positive linear correlation between DSC and ASL measurements of CBF when regional average values were compared; however, a statistically significant voxel-wise correlation was only observed in around 30-40% of patients. These results suggest DSC and ASL may provide regionally similar, but spatially different measurements of CBF.

  17. Effect of Vaginal or Systemic Estrogen on Dynamics of Collagen Assembly in the Rat Vaginal Wall1

    Science.gov (United States)

    Montoya, T. Ignacio; Maldonado, P. Antonio; Acevedo, Jesus F.; Word, R. Ann

    2014-01-01

    ABSTRACT The objective of this study was to compare the effects of systemic and local estrogen treatment on collagen assembly and biomechanical properties of the vaginal wall. Ovariectomized nulliparous rats were treated with estradiol or conjugated equine estrogens (CEEs) either systemically, vaginal CEE, or vaginal placebo cream for 4 wk. Low-dose local CEE treatment resulted in increased vaginal epithelial thickness and significant vaginal growth without uterine hyperplasia. Furthermore, vaginal wall distensibility increased without compromise of maximal force at failure. Systemic estradiol resulted in modest increases in collagen type I with no change in collagen type III mRNA. Low-dose vaginal treatment, however, resulted in dramatic increases in both collagen subtypes whereas moderate and high dose local therapies were less effective. Consistent with the mRNA results, low-dose vaginal estrogen resulted in increased total and cross-linked collagen content. The inverse relationship between vaginal dose and collagen expression may be explained in part by progressive downregulation of estrogen receptor-alpha mRNA with increasing estrogen dose. We conclude that, in this menopausal rat model, local estrogen treatment increased total and cross-linked collagen content and markedly stimulated collagen mRNA expression in an inverse dose-effect relationship. High-dose vaginal estrogen resulted in downregulation of estrogen receptor-alpha and loss of estrogen-induced increases in vaginal collagen. These results may have important clinical implications regarding the use of local vaginal estrogen therapy and its role as an adjunctive treatment in women with loss of vaginal support. PMID:25537371

  18. Parametric response mapping of dynamic CT for predicting intrahepatic recurrence of hepatocellular carcinoma after conventional transcatheter arterial chemoembolization

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Seung Joon; Kim, Hyung Sik [Gachon University Gil Hospital, Department of Radiology, Incheon (Korea, Republic of); Kim, Jonghoon [Sungkyunkwan University, Department of Electronic Electrical and Computer Engineering, Suwon (Korea, Republic of); Seo, Jongbum [Yonsei University, Department of Biomedical Engineering, Wonju (Korea, Republic of); Lee, Jong-min [Hanyang University, Department of Biomedical Engineering, Seoul (Korea, Republic of); Park, Hyunjin [Sungkyunwkan University, School of Electronic and Electrical Engineering, Suwon (Korea, Republic of)

    2016-01-15

    The aim of our study was to determine the diagnostic value of a novel image analysis method called parametric response mapping (PRM) for prediction of intrahepatic recurrence of hepatocellular carcinoma (HCC) treated with conventional transcatheter arterial chemoembolization (TACE). This retrospective study was approved by the IRB. We recruited 55 HCC patients who achieved complete remission (CR) after TACE and received longitudinal multiphasic liver computed tomography (CT). The patients fell into two groups: the recurrent tumour group (n = 29) and the non-recurrent tumour group (n = 26). We applied the PRM analysis to see if this technique could distinguish between the two groups. The results of the PRM analysis were incorporated into a prediction algorithm. We retrospectively removed data from the last time point and attempted to predict the response to therapy of the removed data. The PRM analysis was able to distinguish between the non-recurrent and recurrent groups successfully. The prediction algorithm detected response to therapy with an area under the curve (AUC) of 0.76, while the manual approach had AUC 0.64. Adopting PRM analysis can potentially distinguish between recurrent and non-recurrent HCCs and allow for prediction of response to therapy after TACE. (orig.)

  19. [Determinants of vascular wall stiffness in patients with chronic renal disease undergoing hemodialysis].

    Science.gov (United States)

    Kharlamova, U V; Il'icheva, O E

    2012-01-01

    Examination of 109 patients with chronic renal disease undergoing hemodialysis revealed significant impairment of arterial wall distensibility (accordingly, decreased Peterson's and Young's elastic moduli, distensibility coefficient). The relative thickness of the common carotid artery and pulse wave velocity were significantly greater than in practically healthy subjects. Independent factors influencing arterial wall rigidity included age, arterial pressure, total cholesterol and homocystein, stable metabolites of nitric oxide, creatinine, calcium, phosphorus levels, calcium x phosphorus product, duration of hemodialysis, interdialytic weight gain. PMID:23516853

  20. Cell Wall Growth and Modulation Dynamics in a Model Unicellular Green Alga—Penium margaritaceum: Live Cell Labeling with Monoclonal Antibodies

    OpenAIRE

    Domozych, David S; Hannah Brechka; Alicia Britton; Marc Toso

    2011-01-01

    Penium margaritaceum is a unicellular charophycean green alga that possesses cell wall polymers similar to those of land plants. Several wall macromolecules of this alga are recognized by monoclonal antibodies specific for wall polymer epitopes of land plants. Immunofluorescence protocols using these antibodies may be employed to label specific cell wall constituents of live cells. Fluorescent labeling persists for several days, and this attribute allows for tracing of wall epitopes in both l...

  1. Effect of Coronary Artery Stenosis on the Transmural Extent of the Rest Myocardial Perfusion of Different Segments of Left Ventricular Wall Using 640 Slices CT%静息态下冠状动脉狭窄对左室壁透壁心肌灌注影响的640层CT研究

    Institute of Scientific and Technical Information of China (English)

    陈为军; 李丹; 孙永青; 卢明明; 全冠民; 车东东; 袁涛; 刘亚飞; 门肾力; 杨卓

    2012-01-01

    目的 确定静息态下透壁心肌灌注指数(TPR)的正常值,并探讨静息态下不同分支的冠状动脉狭窄与各冠状动脉分支的不同狭窄程度对左室壁不同节段TPR的影响.方法 274例患者行Toshiba 640层CT检查,包括冠状动脉CTA及左心室室壁CT灌注(CTP)检查.根据冠状动脉狭窄程度及17节段进行分组.计算正常组及不同冠状动脉狭窄程度组之间相应节段内TPR是否存在差异,以及冠状动脉狭窄程度与相应节段TPR的相关性.结果 前降支及左旋支病变对于左室壁心肌灌注影响较为明显,前降支狭窄主要影响中间段前壁(r=-0.288)、心尖段前壁(r=-0.263)及中间段间隔壁(r=-0.196),左旋支主要影响基底部前侧壁(r=-0.241)、基底部后侧壁(r=-0.279)及心尖段侧壁(r=-0.201),而右冠状动脉病变影响较小,主要影响中间段后壁(r=-0.195);冠状动脉中、重度狭窄组对于左室壁心肌灌注影响程度较大(P<0.05),轻度狭窄影响较小;左室前壁心肌灌注最易受到冠状动脉狭窄影响;在静息状态下前降支供血区域组、左旋支供血区域组及右冠状动脉供血区域组正常心肌和重度狭窄心肌平均TPR值分别为1.14±0.09和1.07±0.13、1.13±0.11和1.06±0.14、1.15±0.14和1.10±0.12.结论 不同冠状动脉分支狭窄分别可以影响不同节段的心肌透壁灌注;不同冠状动脉狭窄程度可以不同程度地影响心肌的TPR,二者具有相关性;静息状态下TPR正常值大于负荷状态下TPR.本研究提供了TPR静息态下的正常值.%Objective To evaluate the influence of different branches and degree of the coronary artery stenosis on the myocardial transmural perfusion ratio of different segments of left ventricular wall, and to discuss the normal myocardial transmural perfusion ratio(TPR) of each territory of left ventricular wall in the rest state. Methods CT images of 274 patients who received Toshiba 640 slices CT for CTA and CTP

  2. Simulation of stent deployment in a realistic human coronary artery

    Directory of Open Access Journals (Sweden)

    van der Steen Anton FW

    2008-08-01

    Full Text Available Abstract Background The process of restenosis after a stenting procedure is related to local biomechanical environment. Arterial wall stresses caused by the interaction of the stent with the vascular wall and possibly stress induced stent strut fracture are two important parameters. The knowledge of these parameters after stent deployment in a patient derived 3D reconstruction of a diseased coronary artery might give insights in the understanding of the process of restenosis. Methods 3D reconstruction of a mildly stenosed coronary artery was carried out based on a combination of biplane angiography and intravascular ultrasound. Finite element method computations were performed to simulate the deployment of a stent inside the reconstructed coronary artery model at inflation pressure of 1.0 MPa. Strut thickness of the stent was varied to investigate stresses in the stent and the vessel wall. Results Deformed configurations, pressure-lumen area relationship and stress distribution in the arterial wall and stent struts were studied. The simulations show how the stent pushes the arterial wall towards the outside allowing the expansion of the occluded artery. Higher stresses in the arterial wall are present behind the stent struts and in regions where the arterial wall was thin. Values of 200 MPa for the peak stresses in the stent strut were detected near the connecting parts between the stent struts, and they were only just below the fatigue stress. Decreasing strut thickness might reduce arterial damage without increasing stresses in the struts significantly. Conclusion The method presented in this paper can be used to predict stresses in the stent struts and the vessel wall, and thus evaluate whether a specific stent design is optimal for a specific patient.

  3. Cigarette smoking in military pilots and intima-media thickness of the carotid arteries

    OpenAIRE

    Jovelić Stojan; Hajduković Zoran; Jovelić Aleksandra; Rađen Slavica

    2005-01-01

    Background. It is well known that smoking is associated with an increase in arterial wall thickness. However, most studies of this problem have been undertaken in age and sex heterogeneous groups, as well as in patients with already present other conventional risk factors. The aim of this study was to assess the effect of cigarette smoking on arterial wall thickness of the common carotid artery in asymptomatic pilots. Methods. The imaging of intima−media thickness of the posterior wall of the...

  4. Complex Dynamics and Chaos Control in Coronary Artery System%冠状动脉系统的复杂动态与混沌控制

    Institute of Scientific and Technical Information of China (English)

    石艳香; 刘桂荣; 白定勇

    2011-01-01

    研究两类冠状动脉系统:N型与S型.利用Melnikov方法,得到两类系统在参数条件下产生Smale马蹄意义上的混沌的阀值.通过数值模拟,不仅可以证明理论分析的正确性,同时显示出理想的分支图形和更多新的复杂动力学行为.数值模拟包括相图、势能图、同宿分支曲线和分支图,通过这些较直观地反映出系统随周期激励外力强弱变化的动态特性、复杂性和非线性特征,揭示了系统的分支形式以及通向混沌运动的道路.最后对系统的混沌运动状态进行了有效的控制.%N-type and S-type, two types of coronary artery system are investigated. Applying Melnikov method,the threshold conditions for the occurrence of Smale horse chaos of the two types are obtained respectively. By numerical simulation,not only the correctness of theoretical analysis is proven but also the ideal graphics and more new bifurcation of the complex dynamic behavior are shown. Numerical simulations.including phase diagram, potential diagrams, homoclinic bifurcation curve diagrams and bifurcation diagrams,are used to investigate the dynamic characteristics,the complexity and the nonlinear dynamics characteristic of the two systems,and to reveal bifurcation forms and the road leading to chaotic motion. Finally the chaotic states of motion are effectively controlled.

  5. Wonderful Walls

    Science.gov (United States)

    Greenman, Jim

    2006-01-01

    In this article, the author emphasizes the importance of "working" walls in children's programs. Children's programs need "working" walls (and ceilings and floors) which can be put to use for communication, display, storage, and activity space. The furnishings also work, or don't work, for the program in another sense: in aggregate, they serve as…

  6. Ambiguous walls

    DEFF Research Database (Denmark)

    Mody, Astrid

    2012-01-01

    of “ambiguous walls” as a more “critical” approach to design [1]. The concept of ambiguous walls refers to the diffuse status a lumious and possibly responsive wall will have. Instead of confining it can open up. Instead of having a static appearance, it becomes a context over time. Instead of being hard...

  7. Carotid artery surgery

    Science.gov (United States)

    Carotid endarterectomy; CAS surgery; Carotid artery stenosis - surgery; Endarterectomy - carotid artery ... through the catheter around the blocked area during surgery. Your carotid artery is opened. The surgeon removes ...

  8. Comparison between multi-detector row CT angiography and Doppler ultrasound on detecting carotid artery wall thickness%多层螺旋CT与Doppler超声对颈动脉壁层厚度的对比性研究

    Institute of Scientific and Technical Information of China (English)

    赵刚; 查云飞; 王弘; 洪玮; 邱晓明; 王珍; 肖友梅

    2013-01-01

    Objective To explore the relationship and consistency between multi-detector row computed tomography angiography (MDCTA) and color Doppler ultrasound (CD-US) in measuring carotid artery wall thickness (CAWT) and intima-media thickness (IMT). Methods CAWT and IMT of 38 subjects were measured using MDCTA and CD-US, respectively. Linear correlation analysis was performed to analyze the correlation between the results from CAWT and IMT,and Bland-Altman statistics was employed to analyze the consistency between them. Results The IMT value measured by CD-US was (0.85+0.16) mm, and the CAWT value measured by MDCTA was (0.87.± 0.18) mm (P > 0.05), and there was a high degree of correlation between them (correlation coefficient was 0.958,P< 0.01). An excellent consistency between CAWT and IMT was found by Bland-Altman plot, with a bias of 0.026 mm and the limit of consistency from -0.023 to 0.075. Conclusions There were significant correlation and consistency between MDCTA and CD-US in detecting CAWT and IMT. As a more objective and comprehensive new method, MDCTA can replace CD-US in the evaluation of early carotid atherosclerosis.%目的:探讨多层螺旋CT血管造影(MDCTA)和彩色多普勒超声(CD-US)在检测颈总动脉壁厚度(CAWT)和颈总动脉内膜-中层厚度(IMT)中的相关性和一致性.方法:应用MDCTA和CD-US分别对38例受试者颈总动脉的CAWT和IMT进行检测,用Pearson直线相关分析比较CAWT和IMT的相关性,用Bland-Altman分析比较两者的一致性.结果:MDCTA测量的颈总动脉CAWT为(0.87±0.18)mm,CD-US测量的颈总动脉IMT为(0.85±0.16)mm,两者比较无统计学差异,有高度相关性,相关系数为0.958,P<0.01,Bland-Altman分析两者间存在良好一致性,偏倚为0.026 mm,一致性界限为-0.023 ~ 0.075.结论:MDCTA和CD-US在检测颈总动脉CAWT和IMT时存在良好的相关性和一致性,MDCTA可以替代CD-US,作为一种评价颈动脉早期粥样硬化的更加客观全面的新方法.

  9. Dynamic electrocardiogram of coronary artery disease.%动态心电图对冠心病的诊断价值

    Institute of Scientific and Technical Information of China (English)

    吴洁芝; 施剑萍; 陈玉芳; 郭跃萍

    2012-01-01

      Objective: To study the dynamic electrocardiogram of coronary heart disease in clinical diagnostic value. METHODS: March 2010 to April 2012, 45 cases in our hospital in patients with coronary heart disease for the study, al patients underwent 12-lead Holter checks and coronary angiography, analysis of 12-lead Holter diagnostic accuracy rate. Contrast the different lesions in patients with coronary heart disease, 12-lead ECG diagnostic value.Results: Coronary artery stenosis more than 50% in 35 patients, including the use of 12-lead Holter detection of ischemic ST-segment changes of 30 cases. Multivessel disease patients diagnostic accuracy rate in single-vessel disease (p <0.05). Conclusion: The use of dynamic ECG for diagnosing coronary artery disease, in particular, a more accurate diagnosis of multivessel disease.%  目的研究探讨动态心电图对冠心病的临床诊断价值.方法选择2010年3月-2012年4月我办收治的冠心病患者45例为研究对象,所有患者均进行12导联动态心电图检查和冠状动脉造影检查,分析12导联动态心电图的诊断准确率.对比不同病变冠心病患者的12导联心电图诊断价值.结果冠状动脉狭窄在50%以上患者35例,其中使用12导联动态心电图检查,检出缺血性 ST 段改变30例.其中多支病变组患者诊断准确率高于单支病变组,p <0.05.结论使用动态心电图检查对冠心病的诊断价值较高,尤其是对多支病变组诊断更准确.

  10. Semiconducting single-walled carbon nanotubes sorting with a removable solubilizer based on dynamic supramolecular coordination chemistry

    Science.gov (United States)

    Toshimitsu, Fumiyuki; Nakashima, Naotoshi

    2014-10-01

    Highly pure semiconducting single-walled carbon nanotubes (SWNTs) are essential for the next generation of electronic devices, such as field-effect transistors and photovoltaic applications; however, contamination by metallic SWNTs reduces the efficiency of their associated devices. Here we report a simple and efficient method for the separation of semiconducting- and metallic SWNTs based on supramolecular complex chemistry. We here describe the synthesis of metal-coordination polymers (CP-Ms) composed of a fluorene-bridged bis-phenanthroline ligand and metal ions. On the basis of a difference in the ‘solubility product’ of CP-M-solubilized semiconducting SWNTs and metallic SWNTs, we readily separated semiconducting SWNTs. Furthermore, the CP-M polymers on the SWNTs were simply removed by adding a protic acid and inducing depolymerization to the monomer components. We also describe molecular mechanics calculations to reveal the difference of binding and wrapping mode between CP-M/semiconducting SWNTs and CP-M/metallic SWNTs. This study opens a new stage for the use of such highly pure semiconducting SWNTs in many possible applications.

  11. Hereditary and environmental influences on arterial function.

    Science.gov (United States)

    Hayward, C S; Benetos, A

    2007-07-01

    1. With the ageing population and increasing heart failure, arterial function has been shown to contribute to cardiovascular risk because of its adverse effects on ventriculovascular coupling. Population studies have confirmed independent prognostic information of arterial stiffening on cardiovascular survival. 2. The term 'arterial function' encompasses a range of phenotypes, including measures of arterial structure/remodelling, measures of arterial wall mechanics, surrogate measures of stiffness and of wave reflection. There exists significant interaction between these measures and none is truly independent of the others. Added to this complexity is the recognition that, although arterial function has a strong genetic component, quantification requires a range of techniques from twin to family and population studies. 3. The contribution of heritability is often derived from statistical models with input from genomic scanning and candidate gene studies. Studies to date confirm a significant heritable component for the majority of phenotypes examined. However, it has also been recognized that the factors involved in blood pressure maintenance are likely to be separate to those in arterial structural degeneration with ageing. Candidate genes for arterial function go beyond those of the sympathetic and renin-angiotensin systems and include genes involved in signalling pathways and extracellular matrix modulation. 4. The present review examines the evidence for heritability of the major arterial function phenotypes with environmental and ageing modulation. A brief overview of the impact of atherosclerotic risk factors on arterial function is included.

  12. Effect of Sodium Dodecyl Sulfate Adsorption on the Behavior of Water inside Single Walled Carbon Nanotubes with Dissipative Particle Dynamics Simulation.

    Science.gov (United States)

    Vo, Minh D; Papavassiliou, Dimitrios V

    2016-01-01

    Dissipative particle dynamics (DPD) simulations were utilized to investigate the ability of sodium dodecyl sulfate (SDS) to adsorb inside a single-walled, arm-chair carbon nanotube (SWCNT), as well as the effect of surfactant on the properties of water inside the SWCNT. The diameter of the SWCNT varied from 1 to 5 nm. The radial and axial density profiles of water inside the SWCNTs were computed and compared with published molecular dynamics results. The average residence time and diffusivity were also calculated to show the size effect on mobility of water inside the SWCNT. It was found that nanotubes with diameter smaller than 3 nm do not allow SDS molecules to enter the SWCNT space. For larger SWCNT diameter, SDS adsorbed inside and outside the nanotube. When SDS was adsorbed in the hollow part of the SWCNT, the behavior of water inside the nanotube was found to be significantly changed. Both radial and axial density profiles of water inside the SWCNT fluctuated strongly and were different from those in bulk phase. In addition, SDS molecules increased the retention of water beads inside SWCNT (d ≥ 3nm) while water diffusivity was decreased. PMID:27092476

  13. Effect of Sodium Dodecyl Sulfate Adsorption on the Behavior of Water inside Single Walled Carbon Nanotubes with Dissipative Particle Dynamics Simulation

    Directory of Open Access Journals (Sweden)

    Minh D. Vo

    2016-04-01

    Full Text Available Dissipative particle dynamics (DPD simulations were utilized to investigate the ability of sodium dodecyl sulfate (SDS to adsorb inside a single-walled, arm-chair carbon nanotube (SWCNT, as well as the effect of surfactant on the properties of water inside the SWCNT. The diameter of the SWCNT varied from 1 to 5 nm. The radial and axial density profiles of water inside the SWCNTs were computed and compared with published molecular dynamics results. The average residence time and diffusivity were also calculated to show the size effect on mobility of water inside the SWCNT. It was found that nanotubes with diameter smaller than 3 nm do not allow SDS molecules to enter the SWCNT space. For larger SWCNT diameter, SDS adsorbed inside and outside the nanotube. When SDS was adsorbed in the hollow part of the SWCNT, the behavior of water inside the nanotube was found to be significantly changed. Both radial and axial density profiles of water inside the SWCNT fluctuated strongly and were different from those in bulk phase. In addition, SDS molecules increased the retention of water beads inside SWCNT (d ≥ 3nm while water diffusivity was decreased.

  14. Carotid Artery Screening

    Science.gov (United States)

    ... Resources Professions Site Index A-Z Carotid Artery Screening What is carotid artery screening? Who should consider ... about carotid artery screening? What is carotid artery screening? Screening examinations are tests performed to find disease ...

  15. Soft-spring wall based non-periodic boundary conditions for non-equilibrium molecular dynamics of dense fluids

    Energy Technology Data Exchange (ETDEWEB)

    Ghatage, Dhairyashil; Tomar, Gaurav, E-mail: gtom@mecheng.iisc.ernet.in; Shukla, Ratnesh K., E-mail: ratnesh@mecheng.iisc.ernet.in [Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012 (India)

    2015-03-28

    Non-equilibrium molecular dynamics (MD) simulations require imposition of non-periodic boundary conditions (NPBCs) that seamlessly account for the effect of the truncated bulk region on the simulated MD region. Standard implementation of specular boundary conditions in such simulations results in spurious density and force fluctuations near the domain boundary and is therefore inappropriate for coupled atomistic-continuum calculations. In this work, we present a novel NPBC model that relies on boundary atoms attached to a simple cubic lattice with soft springs to account for interactions from particles which would have been present in an untruncated full domain treatment. We show that the proposed model suppresses the unphysical fluctuations in the density to less than 1% of the mean while simultaneously eliminating spurious oscillations in both mean and boundary forces. The model allows for an effective coupling of atomistic and continuum solvers as demonstrated through multiscale simulation of boundary driven singular flow in a cavity. The geometric flexibility of the model enables straightforward extension to nonplanar complex domains without any adverse effects on dynamic properties such as the diffusion coefficient.

  16. Soft-spring wall based non-periodic boundary conditions for non-equilibrium molecular dynamics of dense fluids

    Science.gov (United States)

    Ghatage, Dhairyashil; Tomar, Gaurav; Shukla, Ratnesh K.

    2015-03-01

    Non-equilibrium molecular dynamics (MD) simulations require imposition of non-periodic boundary conditions (NPBCs) that seamlessly account for the effect of the truncated bulk region on the simulated MD region. Standard implementation of specular boundary conditions in such simulations results in spurious density and force fluctuations near the domain boundary and is therefore inappropriate for coupled atomistic-continuum calculations. In this work, we present a novel NPBC model that relies on boundary atoms attached to a simple cubic lattice with soft springs to account for interactions from particles which would have been present in an untruncated full domain treatment. We show that the proposed model suppresses the unphysical fluctuations in the density to less than 1% of the mean while simultaneously eliminating spurious oscillations in both mean and boundary forces. The model allows for an effective coupling of atomistic and continuum solvers as demonstrated through multiscale simulation of boundary driven singular flow in a cavity. The geometric flexibility of the model enables straightforward extension to nonplanar complex domains without any adverse effects on dynamic properties such as the diffusion coefficient.

  17. Role of cyclic nucleotide-dependent actin cytoskeletal dynamics:Ca(2+](i and force suppression in forskolin-pretreated porcine coronary arteries.

    Directory of Open Access Journals (Sweden)

    Kyle M Hocking

    Full Text Available Initiation of force generation during vascular smooth muscle contraction involves a rise in intracellular calcium ([Ca(2+]i and phosphorylation of myosin light chains (MLC. However, reversal of these two processes alone does not account for the force inhibition that occurs during relaxation or inhibition of contraction, implicating that other mechanisms, such as actin cytoskeletal rearrangement, play a role in the suppression of force. In this study, we hypothesize that forskolin-induced force suppression is dependent upon changes in actin cytoskeletal dynamics. To focus on the actin cytoskeletal changes, a physiological model was developed in which forskolin treatment of intact porcine coronary arteries (PCA prior to treatment with a contractile agonist resulted in complete suppression of force. Pretreatment of PCA with forskolin suppressed histamine-induced force generation but did not abolish [Ca(2+]i rise or MLC phosphorylation. Additionally, forskolin pretreatment reduced filamentous actin in histamine-treated tissues, and prevented histamine-induced changes in the phosphorylation of the actin-regulatory proteins HSP20, VASP, cofilin, and paxillin. Taken together, these results suggest that forskolin-induced complete force suppression is dependent upon the actin cytoskeletal regulation initiated by the phosphorylation changes of the actin regulatory proteins and not on the MLC dephosphorylation. This model of complete force suppression can be employed to further elucidate the mechanisms responsible for smooth muscle tone, and may offer cues to pathological situations, such as hypertension and vasospasm.

  18. Validation of an optical flow algorithm to measure blood flow waveforms in arteries using dynamic digital x-ray images

    Science.gov (United States)

    Rhode, Kawal; Lambrou, Tryphon; Hawkes, David J.; Hamilton, George; Seifalian, Alexander M.

    2000-06-01

    We have developed a weighted optical flow algorithm for the extraction of instantaneous blood velocity from dynamic digital x-ray images of blood vessels. We have carried out in- vitro validation of this technique. A pulsatile physiological blood flow circuit was constructed using sections of silicone tubing to simulate blood vessels with whole blood as the fluid. Instantaneous recording of flow from an electromagnetic flow meter (EMF) provided the gold standard measurement. Biplanar dynamic digital x-ray images of the blood vessel with injection of contrast medium were acquired at 25 fps using a PC frame capture card. Imaging of a Perspex calibration cube allowed 3D reconstruction of the vessel and determination of true dimensions. Blood flow waveforms were calculated off-line on a Sun workstation using the new algorithm. The correlation coefficient between instantaneous blood flow values obtained from the EMF and the x-ray method was r equals 0.871, n equals 1184, p less than 0.0001. The correlation coefficient for average blood flow was r equals 0.898, n equals 16, p less than 0.001. We have successfully demonstrated that our new algorithm can measure pulsatile blood flow in a vessel phantom. We aim to use this algorithm to measure blood flow clinically in patients undergoing vascular interventional procedures.

  19. Concentration polarization of atherogenic lipids in the arterial system

    Institute of Scientific and Technical Information of China (English)

    DENG; Xiaoyan; (邓小燕); WANG; Guixue; (王贵学)

    2003-01-01

    The transport of atherogenic lipids (LDL) in a straight segment of an artery with a semi-permeable wall was simulated numerically. The numerical analysis predicted that a mass transport phenomenon called 'concentration polarization' of LDL might occur in the arterial system. Under normal physiological flow conditions, the luminal surface LDL concentration was 5%-14% greater than the bulk concentration in a straight segment of an artery. The luminal surface LDL concentration at the arterial wall was flow-dependent, varying linearly with the filtration rate across the arterial wall and inversely with wall shear rate. At low wall shear rate, the luminal surface LDL concentration was very sensitive to changes in flow conditions, decreasing sharply as wall shear rate increased. In order to verify the numerical analysis, the luminal surface concentration of bovine serum albumin (as a tracer macromolecule) in the canine carotid artery was measured in vitro by directly taking liquid samples from the luminal surface of the artery. The experimental result was in very good agreement with the numerical analysis. The authors believe that the mass transport phenomenon of 'concentration polarization' may indeed exist in the human circulation and play an important role in the localization of atherosclerosis.

  20. Arterial structure and function in vascular ageing: are you as old as your arteries?

    Science.gov (United States)

    Thijssen, Dick H J; Carter, Sophie E; Green, Daniel J

    2016-04-15

    Advancing age may be the most potent independent predictor of future cardiovascular events, a relationship that is not fully explained by time-related changes in traditional cardiovascular risk factors. Since some arteries exhibit differential susceptibility to atherosclerosis, generalisations regarding the impact of ageing in humans may be overly simplistic, whereas in vivo assessment of arterial function and health provide direct insight. Coronary and peripheral (conduit, resistance and skin) arteries demonstrate a gradual, age-related impairment in vascular function that is likely to be related to a reduction in endothelium-derived nitric oxide bioavailability and/or increased production of vasoconstrictors (e.g. endothelin-1). Increased exposure and impaired ability for defence mechanisms to resist oxidative stress and inflammation, but also cellular senescence processes, may contribute to age-related changes in vascular function and health. Arteries also undergo structural changes as they age. Gradual thickening of the arterial wall, changes in wall content (i.e. less elastin, advanced glycation end-products) and increase in conduit artery diameter are observed with older age and occur similarly in central and peripheral arteries. These changes in structure have important interactive effects on artery function, with increases in small and large arterial stiffness representing a characteristic change with older age. Importantly, direct measures of arterial function and structure predict future cardiovascular events, independent of age or other cardiovascular risk factors. Taken together, and given the differential susceptibility of arteries to atherosclerosis in humans, direct measurement of arterial function and health may help to distinguish between biological and chronological age-related change in arterial health in humans.