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Sample records for aortic wall structure

  1. Aortic Wall Injury Related to Endovascular Therapy for Aortic Coarctation.

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    Tretter, Justin T; Jones, Thomas K; McElhinney, Doff B

    2015-09-01

    Aortic wall complications can occur in unrepaired aortic coarctation (CoA) and after surgical repair or endovascular treatment. This review summarizes the available literature and current understanding of aortic wall injury (AWI) surrounding the management of CoA, focusing specifically on acute and follow-up AWI after endovascular treatment. There have been 23 reported cases of aortic rupture after endovascular treatment for CoA, including angioplasty alone, bare metal stenting, and primary covered stent therapy. Even if these published cases represent only a minority of ruptures that have actually occurred, the incidence is substantially <1%. The incidence of acute aneurysm formation was 0% to 13% after angioplasty, 0% to 5% after bare metal stent placement, and <1% after covered stent placement. The reported incidence and natural history of both acute and new AWI during follow-up after endovascular therapy for CoA varies considerably, likely secondary to ascertainment and reporting biases and inconsistent definitions. Although important AWI after endovascular treatment of CoA seems to be declining in frequency with increasing experience and improving technology, it remains one of the most important potential adverse outcomes. Long-term surveillance for new AWI and monitoring of existing AWI is mandatory, with institution of appropriate treatment when necessary. A central research focus in this population should be determination of the appropriate treatment for both native and recurrent CoA across various ages with regard to limiting recurrent CoA and preventing associated aortic wall complications, in addition to determining the appropriate treatment of various AWI. Consistent definitions and reporting are necessary to truly understand the incidence of, risk factors for, and measures protective against AWI after angioplasty or stent implantation for CoA.

  2. Finite Element Implementation of a Structurally-Motivated Constitutive Relation for the Human Abdominal Aortic Wall with and without Aneurysms

    DEFF Research Database (Denmark)

    Enevoldsen, Marie Sand; Henneberg, Kaj-Åge; Lönn, L

    2011-01-01

    The structural integrity of the abdominal aorta is maintained by elastin, collagen, and vascular smooth muscle cells. Changes with age in the structure can lead to develop-ment of aneurysms. This paper presents initial work to capture these changes in a finite element model (FEM) of a structural......-ly-motivated anisotropic constitutive relation for the “four fiber family” arterial model. First a 2D implementation is used for benchmarking the FEM implementation to fitted biaxial stress-strain data obtained experimentally from four different groups of persons; 19-29 years, 30-60 years, 61-79 years and abdominal aortic...

  3. Effects of the flexibility of the arterial wall on the wall shear stresses and wall tension in Abdominal Aortic Aneurysms.

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    Salsac, Anne-Virginie; Fernandez, Miguel; Chomaz, Jean-Marc

    2005-11-01

    As an abdominal aortic aneurysm develops, large changes occur in the composition and structure of the arterial wall, which result in its stiffening. So far, most studies, whether experimental or numerical, have been conducted assuming the walls to be rigid. A numerical simulation of the fluid structure interactions is performed in different models of aneurysms in order to analyze the effects that the wall compliance might have on the flow topology. Both symmetric and non-symmetric models of aneurysms are considered, all idealistic in shape. The wall mechanical properties are varied in order to simulate the progressive stiffening of the walls. The spatial and temporal distributions of wall tension are calculated for the different values of the wall elasticity and compared to the results for the rigid walls. In the case of rigid walls, the calculation of the wall shear stresses and pressure compare very well with experimental results.

  4. Decreased expression of fibulin-4 in aortic wall of aortic dissection.

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    Huawei, P; Qian, C; Chuan, T; Lei, L; Laing, W; Wenlong, X; Wenzhi, L

    2014-02-01

    In this research, we will examine the expression of Fibulin-4 in aortic wall to find out its role in aortic dissection development. The samples of aortic wall were obtained from 10 patients operated for acute ascending aortic dissection and five patients for chronic ascending aortic dissection. Another 15 pieces of samples from patients who had coronary artery bypass were as controls. The aortic samples were stained with aldehyde magenta dyeing to evaluate the arrangement of elastic fibers. The Fibulin-4 protein and mRNA expression were both determined by Western blot and realtime quantitative polymerase chain reaction. Compared with the control group, both in acute and chronic ascending aortic dissection, elastic fiber fragments increased and the expression of fibulin-4 protein significantly decreased (P= 0.045 < 0.05). The level of fibulin-4 mRNA decreased in acute ascending aortic dissection (P= 0.034 < 0.05), while it increased in chronic ascending aortic dissection (P=0.004 < 0.05). The increased amounts of elastic fiber fragments were negatively correlated with the expression of fibulin-4 mRNA in acute ascending aortic dissection. In conclusion, in aortic wall of ascending aortic dissection, the expression of fibulin-4 protein decreased and the expression of fibulin-4 mRNA was abnormal. Fibulin-4 may play an important role in the pathogenesis of aortic dissection.

  5. Ascending aortic wall cohesion: comparison of bicuspid and tricuspid valves.

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    Benedik, Jaroslav; Pilarczyk, Kevin; Wendt, Daniel; Indruch, Jiri; Flek, Radek; Tsagakis, Konstantinos; Alaeddine, Savvas; Jakob, Heinz

    2012-01-01

    Objectives. Bicuspid aortic valve (AV) represents the most common form of congenital AV malformation, which is frequently associated with pathologies of the ascending aorta. We compared the mechanical properties of the aortic wall between patients with bicuspid and tricuspid AV using a new custom-made device mimicking transversal aortic wall shear stress. Methods. Between 03/2010 and 07/2011, 190 consecutive patients undergoing open aortic valve replacement at our institution were prospectively enrolled, presenting either with a bicuspid (group 1, n = 44) or a tricuspid (group 2, n = 146) AV. Aortic wall specimen were examined with the "dissectometer" resulting in nine specific aortic-wall parameters derived from tensile strength curves (TSC). Results. Patients with a bicuspid AV showed significantly more calcified valves (43.2% versus 15.8%, P group (P = 0.003, P = 0.02, P = 0.01). We found no difference in the aortic wall cohesion between both groups as revealed by shear stress testing (P = 0.72, P = 0.40, P = 0.41). Conclusion. We observed no differences of TSC in patients presenting with tricuspid or bicuspid AVs. These results may allow us to assume that the morphology of the AV and the pathology of the ascending aorta are independent.

  6. Bicuspid aortic valve hemodynamics does not promote remodeling in porcine aortic wall concavity

    Institute of Scientific and Technical Information of China (English)

    Samantha K Atkins; Alison N Moore; Philippe Sucosky

    2016-01-01

    AIM: To investigate the role of type-I left-right bicuspid aortic valve(LR-BAV) hemodynamic stresses in the remodeling of the thoracic ascending aorta(AA) concavity, in the absence of underlying genetic or structural defects.METHODS: Transient wall shear stress(WSS) profiles in the concavity of tricuspid aortic valve(TAV) and LR-BAV AAs were obtained computationally. Tissue specimens excised from the concavity of normal(nondilated) porcine AAs were subjected for 48 h to those stress environments using a shear stress bioreactor. Tissue remodeling was characterized in terms of matrix metalloproteinase(MMP) expression and activity via immunostaining and gelatin zymography.RESULTS: Immunostaining semi-quantification results indicated no significant difference in MMP-2 and MMP-9 expression between the tissue groups exposed to TAV and LR-BAV AA WSS(P = 0.80 and P = 0.19, respectively). Zymography densitometry revealed no difference in MMP-2 activity(total activity, active form and latent form) between the groups subjected to TAV AA and LR-BAV AA WSS(P = 0.08, P = 0.15 and P = 0.59, respectively).CONCLUSION: The hemodynamic stress environment present in the concavity of type-I LR-BAV AA does not cause any significant change in proteolytic enzyme expression and activity as compared to that present in the TAV AA.

  7. Improving the efficiency of abdominal aortic aneurysm wall stress computations.

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    Zelaya, Jaime E; Goenezen, Sevan; Dargon, Phong T; Azarbal, Amir-Farzin; Rugonyi, Sandra

    2014-01-01

    An abdominal aortic aneurysm is a pathological dilation of the abdominal aorta, which carries a high mortality rate if ruptured. The most commonly used surrogate marker of rupture risk is the maximal transverse diameter of the aneurysm. More recent studies suggest that wall stress from models of patient-specific aneurysm geometries extracted, for instance, from computed tomography images may be a more accurate predictor of rupture risk and an important factor in AAA size progression. However, quantification of wall stress is typically computationally intensive and time-consuming, mainly due to the nonlinear mechanical behavior of the abdominal aortic aneurysm walls. These difficulties have limited the potential of computational models in clinical practice. To facilitate computation of wall stresses, we propose to use a linear approach that ensures equilibrium of wall stresses in the aneurysms. This proposed linear model approach is easy to implement and eliminates the burden of nonlinear computations. To assess the accuracy of our proposed approach to compute wall stresses, results from idealized and patient-specific model simulations were compared to those obtained using conventional approaches and to those of a hypothetical, reference abdominal aortic aneurysm model. For the reference model, wall mechanical properties and the initial unloaded and unstressed configuration were assumed to be known, and the resulting wall stresses were used as reference for comparison. Our proposed linear approach accurately approximates wall stresses for varying model geometries and wall material properties. Our findings suggest that the proposed linear approach could be used as an effective, efficient, easy-to-use clinical tool to estimate patient-specific wall stresses.

  8. Wall shear stress indicators in abnormal aortic geometries

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    Prahl Wittberg, Lisa; van Wyk, Stevin; Fuchs, Laszlo; Gutmark, Ephraim; Gutmark-Little, Iris

    2015-11-01

    Cardiovascular disease, such as atherosclerosis, occurs at specific locations in the arterial tree. Characterizing flow and forces at these locations is crucial to understanding the genesis of disease. Measures such as time average wall shear stress, oscillatory shear index, relative residence time and temporal wall shear stress gradients have been shown to identify plaque prone regions. The present paper examines these indices in three aortic geometries obtained from patients whose aortas are deformed due to a genetic pathology and compared to one normal geometry. This patient group is known to be prone to aortic dissection and our study aims to identify early indicators that will enable timely intervention. Data obtained from cardiac magnetic resonance imaging is used to reconstruct the aortic arch. The local unsteady flow characteristics are calculated, fully resolving the flow field throughout the entire cardiac cycle. The Quemada model is applied to account for the non-Newtonian properties of blood, an empirical model valid for different red blood cell loading. The impact of the deformed aortic geometries is analyzed to identify flow patterns that could lead to arterial disease at certain locations.

  9. Simulations of blood flow in patient-specific aortic dissections with a deformable wall model

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    Baeumler, Kathrin; Vedula, Vijay; Sailer Karmann, Anna; Marsden, Alison; Fleischmann, Dominik

    2016-11-01

    Aortic dissection is a life-threatening condition in which blood penetrates into the vessel wall, creating a second flow channel, often requiring emergency surgical repair. Up to 50% of patients who survive the acute event face late complications like aortic dilatation and eventual rupture. Prediction of late complications, however, remains challenging. We therefore aim to perform accurate and reliable patient-specific simulations of blood flow in aortic dissections, validated by 4D-Flow MRI. Among other factors, this is a computational challenge due to the compliance of the vessel walls and the large degree of membrane deformation between the two flow channels. We construct an anatomic patient-specific model from CT data including both flow channels and the membrane between them. We then run fluid structure interaction simulations using an arbitrary Lagrangian-Eulerian (ALE) formulation within a multiscale variational framework, employing stabilized finite element methods. We compare hemodynamics between a rigid and a deformable wall model and examine membrane dynamics and pressure differences between the two flow channels. The study focuses on the computational and modeling challenges emphasizing the importance of employing a deformable wall model for aortic dissections.

  10. Using The Descending Aortic Wall Thickness Measured In Transesophageal Echocardiography As A Risk Marker For Aortic Dissection

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    Zaher Fanari

    2015-04-01

    Full Text Available Objective: The aim of this study is to estimate whether aortic wall thickness is increased in patients with Aortic dissection (AD compared to low risk control group and can be used in addition to aortic diameter as a risk marker of AD. Background: AD occurs due to pathologies that may increase thickness of the aortic wall. Transesophageal echocardiography (TEE has the ability to visualise both the thoracic aortic wall and lumen. Aortic diameter has been used to predict aortic dissection and timing of surgery, but it is not always predictive of that risk. Methods: In 48 patients with AD who underwent TEE were examined retrospectively and compared to 48 control patients with patent foramen ovale (PFO. We measured aortic diameter at different levels, intimal/medial thickness (IMT and complete wall thickness (CMT. Demographic data and cardiovascular risk factors were reviewed. The data was analysed using ANOVA and student t test. Results: (AD patients were older [mean age 66 AD vs. 51 PFO], had more hypertension, diabetes, hyperlipidemia and Coronary artery disease. Both IMT and CMT in the descending aorta were increased in AD group [(1.85 vs. 1.43 mm; P=0.03 and 2.93 vs. 2.46 mm; p=0.01. As expected the diameter of ascending aorta was also greater in AD (4.61 vs. 2.92 cm; P=0.004. Conclusions: CMT and IMT in the descending aorta detected by TEE is greater in patients with AD when compared to control and may add prognostic data to that of aortic diameter

  11. Partially uncovered Cheatham platinum-covered stent to treat complex aortic coarctation associated with aortic wall aneurysm.

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    Butera, Gianfranco; Piazza, Luciane

    2015-04-01

    Percutaneous treatment of aortic coarctation is a widely used option. Covered stents have increased the profile of efficacy and safety of this procedure. Here we report on a 32-year-old woman with significant aortic recoarctation associated with aortic wall aneurysm and close proximity of both lesions to the origin of both the subclavian arteries. It was decided to manually and partially uncover the proximal part of the stent to have a hybrid stent that could act as a bare stent at the level of the origin of the subclavian arteries and as a covered stent at the level of the aneurysm.

  12. Impact of poroelasticity of intraluminal thrombus on wall stress of abdominal aortic aneurysms

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    Polzer Stanislav

    2012-08-01

    Full Text Available Abstract Background The predictions of stress fields in Abdominal Aortic Aneurysm (AAA depend on constitutive descriptions of the aneurysm wall and the Intra-luminal Thrombus (ILT. ILT is a porous diluted structure (biphasic solid–fluid material and its impact on AAA biomechanics is controversially discussed in the literature. Specifically, pressure measurements showed that the ILT cannot protect the wall from the arterial pressure, while other (numerical and experimental studies showed that at the same time it reduces the stress in the wall. Method To explore this phenomenon further a poroelastic description of the ILT was integrated in Finite Element (FE Models of the AAA. The AAA model was loaded by a pressure step and a cyclic pressure wave and their transition into wall tension was investigated. To this end ILT’s permeability was varied within a microstructurally motivated range. Results The two-phase model verified that the ILT transmits the entire mean arterial pressure to the wall while, at the same time, it significantly reduces the stress in the wall. The predicted mean stress in the AAA wall was insensitive to the permeability of the ILT and coincided with the results of AAA models using a single-phase ILT description. Conclusion At steady state, the biphasic ILT behaves like a single-phase material in an AAA model. Consequently, computational efficient FE single-phase models, as they have been exclusively used in the past, accurately predict the wall stress in AAA models.

  13. Bicuspid aortic valve hemodynamics: a fluid-structure interaction study

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    Chandra, Santanu; Seaman, Clara; Sucosky, Philippe

    2011-11-01

    The bicuspid aortic valve (BAV) is a congenital defect in which the aortic valve forms with two leaflets instead of three. While calcific aortic valve disease (CAVD) also develops in the normal tricuspid aortic valve (TAV), its progression in the BAV is more rapid. Although studies have suggested a mechano-potential root for the disease, the native BAV hemodynamics remains largely unknown. This study aimed at characterizing BAV hemodynamics and quantifying the degree of wall-shear stress (WSS) abnormality on BAV leaflets. Fluid-structure interaction models validated with particle-image velocimetry were designed to predict the flow and leaflet dynamics in idealized TAV and BAV anatomies. Valvular function was quantified in terms of the effective orifice area. The regional leaflet WSS was characterized in terms of oscillatory shear index, temporal shear magnitude and temporal shear gradient. The predictions indicate the intrinsic degree of stenosis of the BAV anatomy, reveal drastic differences in shear stress magnitude and pulsatility on BAV and TAV leaflets and confirm the side- and site-specificity of the leaflet WSS. Given the ability of abnormal fluid shear stress to trigger valvular inflammation, these results support the existence of a mechano-etiology of CAVD in the BAV.

  14. Aortic aneurysm after patch aortoplasty for coarctation: analysis of patch size and wall growth.

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    Al-Hroob, A; Husayni, T S; Freter, A; Chiemmongkoltip, P; Ilbawi, M N; Arcilla, R A

    2003-01-01

    Aortic aneurysm may develop after surgery for coarctation of aorta especially patch aortoplasty. The size of patch and of adjacent native aortic wall was analyzed to determine whether aortic dilatation represents a true aneurysm. Electron beam tomography (EBT) was done on 19 patients, three months to 17.5 years after patch aortoplasty. Tomograms of aorta were obtained in 6-mm slices, and maximal cross-sectional area was digitized to obtain: total circumference (Ct), patch component (Cp), and aortic wall component (Cw). Ct, Cp, and Cw were normalized to the circumference of distal aorta (Cda) as: isthmus/distal aorta (Ct/Cda), patch segment/distal aorta (Cp/Cda), wall segment/distal aorta (Cw/Cda). Ct/Cda ranged from 109% to 260%. In 12 patients (group A), it varied from 168% to 260%; and in seven (group B), 109% to 133%. There was strong correlation (r = 0.92) between Ct/Cda and Cp/Cda. Ct/Cda, Cp/Cda, and Cp/Cw were higher in group A than B (p <0.001) but Cw/Cda did not differ. Cw/Cda was greater than the coarctation/distal aorta diameter ratios of preoperative angiograms, consistent with accelerated aortic wall growth postsurgery. No definite aneurysm was seen. Localized dilatation of aorta following patch aortoplasty in children is primarily due to a large synthetic patch and, partly, to increased aortic wall growth. Serial EBT or magnetic resonance imaging is indicated to monitor aortic wall growth and occurrence of aneurysm.

  15. Effect of Selenium Supplementation on Redox Status of the Aortic Wall in Young Spontaneously Hypertensive Rats.

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    Ruseva, Boryana; Atanasova, Milena; Tsvetkova, Reni; Betova, Tatyana; Mollova, Margarita; Alexandrova, Margarita; Laleva, Pavlina; Dimitrova, Aneliya

    2015-01-01

    Selenium (Se) is an exogenous antioxidant that performs its function via the expression of selenoproteins. The aim of this study was to explore the effect of varying Se intake on the redox status of the aortic wall in young spontaneously hypertensive rats (SHR). Sixteen male Wistar Kyoto (WKY) rats and nineteen male SHR, 16-week-old, were tested after being given diets with different Se content for eight weeks. They were divided into 4 groups: control groups of WKY NSe and SHR NSe on an adequate Se diet and groups of WKY HSe and SHR HSe that received Se supplementation. The Se nutritional status was assessed by measuring whole blood glutathione peroxidase-1 (GPx-1) activity. Serum concentration of lipid hydroperoxides and serum level of antibodies against advanced glycation end products (anti-AGEs abs) were determined. Expression of GPx-1 and endothelial nitric oxide synthase (eNOS) were examined in aortic wall. Se supplementation significantly increased GPx-1 activity of whole blood and in the aortas of WKY and SHR. Decreased lipid peroxidation level, eNOS-3 expression in the aortic wall, and serum level of anti-AGEs abs were found in SHR HSe compared with SHR NSe. In conclusion, Se supplementation improved the redox status of the aortic wall in young SHR.

  16. Effect of Selenium Supplementation on Redox Status of the Aortic Wall in Young Spontaneously Hypertensive Rats

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    Boryana Ruseva

    2015-01-01

    Full Text Available Selenium (Se is an exogenous antioxidant that performs its function via the expression of selenoproteins. The aim of this study was to explore the effect of varying Se intake on the redox status of the aortic wall in young spontaneously hypertensive rats (SHR. Sixteen male Wistar Kyoto (WKY rats and nineteen male SHR, 16-week-old, were tested after being given diets with different Se content for eight weeks. They were divided into 4 groups: control groups of WKY NSe and SHR NSe on an adequate Se diet and groups of WKY HSe and SHR HSe that received Se supplementation. The Se nutritional status was assessed by measuring whole blood glutathione peroxidase-1 (GPx-1 activity. Serum concentration of lipid hydroperoxides and serum level of antibodies against advanced glycation end products (anti-AGEs abs were determined. Expression of GPx-1 and endothelial nitric oxide synthase (eNOS were examined in aortic wall. Se supplementation significantly increased GPx-1 activity of whole blood and in the aortas of WKY and SHR. Decreased lipid peroxidation level, eNOS-3 expression in the aortic wall, and serum level of anti-AGEs abs were found in SHR HSe compared with SHR NSe. In conclusion, Se supplementation improved the redox status of the aortic wall in young SHR.

  17. Quantification of progression and regression of descending thoracic aortic wall thickness by enhanced computed tomography

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    Yokoyama, Kenichi; Takasu, Junichiro; Yamamoto, Rie; Taguchi, Rie; Itani, Yasutaka; Ito, Yuichi; Watanabe, Shigeru; Masuda, Yoshiaki [Chiba Univ. (Japan). School of Medicine

    2001-04-01

    The purpose of this study is to verify the usefulness of the quantification of aortic wall involvement by enhanced computed tomography (CT). One-hundred thirteen Japanese patients underwent two enhanced CT of the descending thoracic aorta at intervals. We sliced the descending thoracic aorta continuously from the level of the tracheal bifurcation with 1 cm intervals, and we defined aortic wall volume (AWV) (cm{sup 3}) as the sum of a 7-slice area of aortic wall involving calcification. The average of AWV increased from 7.95{+-}2.92 cm{sup 3} to 8.70{+-}2.98 cm{sup 3}. The developmental rate of AWV ({delta}AWV) was 0.270{+-}0.281 cm{sup 3}/year. {delta}AWV did not have a significant correlation with any risk factor at the baseline. {delta}AWV had significant correlation with total cholesterol, (LDL-C) low-density lipoprotein cholesterol and LDL-C/(HDL-C) high-density lipoprotein cholesterol ratio at the follow-up, and by multivariate analysis with only the LDL-C/HDL-C ratio. {delta}AWV was not correlated with the intake status of hypoglycemic, antihypertensive or lipid-lowering drugs. The cut-off level of total cholesterol with the most significant odds ratio for progression of aortic wall was 190 mg/dl, and that of LDL-C was 130 mg/dl. This method proved to be useful for the non-invasive assessment of aortic wall thickness. (author)

  18. Correlation of echocardiographic wall stress and left ventricular pressure and function in aortic stenosis.

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    DePace, N L; Ren, J F; Iskandrian, A S; Kotler, M N; Hakki, A H; Segal, B L

    1983-04-01

    Previous studies have suggested that left ventricular pressure (P) can be predicted in patients with aortic stenosis by the equation P = 235 h/r, where 235 is a constant peak wall stress (sigma), h is end-systolic wall thickness, and r is end-systolic dimension/2; h and r are measured by M-mode echocardiography. In 73 patients with aortic stenosis (valve area less than 0.7 cm2), measured and predicted left ventricular pressure correlated poorly (r = 0.17). The measured wall stress in our patients varied from 120 to 250 mm Hg in patients with normal left ventricular function and from 250 to 550 mm Hg in patients with abnormal function. The correlation between sigma and h was only fair (r = 0.53), because many patients had inappropriate left ventricular hypertrophy. There was a statistically significant correlation between ejection fraction and sigma (r = 0.62) and between ejection fraction and end-systolic dimension (r = -0.70), but there was considerable scatter of ejection fractions for any given end-systolic dimension. We conclude that sigma is not constant in aortic stenosis, and the use of a constant sigma to predict left ventricular pressure is unreliable; inappropriate left ventricular hypertrophy may explain why sigma is not constant. M-mode echocardiography is not reliable in assessing the severity of aortic stenosis in adults; such assessment requires precise measurements of pressure gradients and flow by cardiac catheterization.

  19. Cellular regulation of the structure and function of aortic valves

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    Ismail El-Hamamsy

    2010-01-01

    Full Text Available The aortic valve was long considered a passive structure that opens and closes in response to changes in transvalvular pressure. Recent evidence suggests that the aortic valve performs highly sophisticated functions as a result of its unique microscopic structure. These functions allow it to adapt to its hemodynamic and mechanical environment. Understanding the cellular and molecular mechanisms involved in normal valve physiology is essential to elucidate the mechanisms behind valve disease. We here review the structure and developmental biology of aortic valves; we examine the role of its cellular parts in regulating its function and describe potential pathophysiological and clinical implications.

  20. Pressure dependency of aortic pulse wave velocity in vivo is not affected by vasoactive substances that alter aortic wall tension ex vivo.

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    Butlin, Mark; Lindesay, George; Viegas, Kayla D; Avolio, Alberto P

    2015-05-15

    Aortic stiffness, a predictive parameter in cardiovascular medicine, is blood pressure dependent and experimentally requires isobaric measurement for meaningful comparison. Vasoactive drug administration to change peripheral resistance and blood pressure allows such isobaric comparison but may alter large conduit artery wall tension, directly changing aortic stiffness. This study quantifies effects of sodium nitroprusside (SNP, vasodilator) and phenylephrine (PE, vasoconstrictor) on aortic stiffness measured by aortic pulse wave velocity (aPWV) assessed by invasive pressure catheterization in anaesthetized Sprague-Dawley rats (n = 7). This was compared with nondrug-dependent alteration of blood pressure through reduced venous return induced by partial vena cava occlusion. In vivo drug concentration was estimated by modeling clearance rates. Ex vivo responses of excised thoracic and abdominal aortic rings to drugs was measured using myography. SNP administration did not alter aPWV compared with venous occlusion (P = 0.21-0.87). There was a 5% difference in aPWV with PE administration compared with venous occlusion (P arteries in vivo. However, similar drug concentrations affect aortic ring wall tension ex vivo. Future studies investigating in vivo and ex vivo kinetics will need to elucidate mechanisms for this marked difference.

  1. Structure of axionic domain walls

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    Huang, M. C.; Sikivie, P.

    1985-09-01

    The structure of axionic domain walls is investigated using the low-energy effective theory of axions and pions. We derive the spatial dependence of the phases of the Peccei-Quinn scalar field and the QCD quark-antiquark condensates inside an axionic domain wall. Thence an accurate estimate of the wall surface energy density is obtained. The equations of motion for axions, photons, leptons, and baryons in the neighborhood of axionic domain walls are written down and estimates are given for the wall reflection and transmission coefficients of these particles. Finally, we discuss the energy dissipation by axionic domain walls oscillating in the early universe due to the reflection of particles in the primordial soup.

  2. Structure of axionic domain walls

    Energy Technology Data Exchange (ETDEWEB)

    Huang, M.C.; Sikivie, P.

    1985-09-15

    The structure of axionic domain walls is investigated using the low-energy effective theory of axions and pions. We derive the spatial dependence of the phases of the Peccei-Quinn scalar field and the QCD quark-antiquark condensates inside an axionic domain wall. Thence an accurate estimate of the wall surface energy density is obtained. The equations of motion for axions, photons, leptons, and baryons in the neighborhood of axionic domain walls are written down and estimates are given for the wall reflection and transmission coefficients of these particles. Finally, we discuss the energy dissipation by axionic domain walls oscillating in the early universe due to the reflection of particles in the primordial soup.

  3. MRI-based Determination of Reference Values of Thoracic Aortic Wall Thickness in a General Population

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    Mensel, Birger; Quadrat, Alexander; Schneider, Tobias; Kuehn, Jens-Peter; Hegenscheid, Katrin [University Medicine Greifswald, Institute of Diagnostic Radiology and Neuroradiology, Greifswald (Germany); Doerr, Marcus [University Medicine Greifswald, Department of Internal Medicine, Greifswald (Germany); DZHK (German Center for Cardiovascular Research), Greifswald (Germany); Voelzke, Henry [University Medicine Greifswald, Institute for Community Medicine, Greifswald (Germany); DZHK (German Center for Cardiovascular Research), Greifswald (Germany); Lieb, Wolfgang [Christian Albrechts University, Institute of Epidemiology, Kiel (Germany); Lorbeer, Roberto [University Medicine Greifswald, Institute for Community Medicine, Greifswald (Germany)

    2014-09-15

    To provide age- and sex-specific reference values for MRI-derived wall thickness of the ascending and descending aorta in the general population. Data of 753 subjects (311 females) aged 21-81 years were analysed. MRI was used to determine the aortic wall thickness (AWT). Equations for reference value calculation according to age were established for females and males. Median wall thickness of the ascending aorta was 1.46 mm (5th-95th range: 1.15-1.88 mm) for females and 1.56 mm (1.22-1.99 mm) for males. Median wall thickness of the descending aorta was 1.26 mm (0.97-1.58 mm) in females and 1.36 mm (1.04-1.75 mm) in males. While median and 5th and 95th percentiles for the ascending and descending aorta increased with age in both sexes, the association between age and median AWT was stronger in males than in females for both the ascending and descending aorta. Reference values for the ascending and descending AWT are provided. In a healthy sample from the general population, the wall of the ascending aorta is thicker than the wall of the descending aorta, and both walls are thicker in males than females. The increase in wall thickness with age is greater in males. (orig.)

  4. Multimodal optical measurement in vitro of surface deformations and wall thickness of the pressurized aortic arch.

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    Genovese, Katia; Humphrey, Jay D

    2015-04-01

    Computational modeling of arterial mechanics continues to progress, even to the point of allowing the study of complex regions such as the aortic arch. Nevertheless, most prior studies assign homogeneous and isotropic material properties and constant wall thickness even when implementing patient-specific luminal geometries obtained from medical imaging. These assumptions are not due to computational limitations, but rather to the lack of spatially dense sets of experimental data that describe regional variations in mechanical properties and wall thickness in such complex arterial regions. In this work, we addressed technical challenges associated with in vitro measurement of overall geometry, full-field surface deformations, and regional wall thickness of the porcine aortic arch in its native anatomical configuration. Specifically, we combined two digital image correlation-based approaches, standard and panoramic, to track surface geometry and finite deformations during pressurization, with a 360-deg fringe projection system to contour the outer and inner geometry. The latter provided, for the first time, information on heterogeneous distributions of wall thickness of the arch and associated branches in the unloaded state. Results showed that mechanical responses vary significantly with orientation and location (e.g., less extensible in the circumferential direction and with increasing distance from the heart) and that the arch exhibits a nearly linear increase in pressure-induced strain up to 40%, consistent with other findings on proximal porcine aortas. Thickness measurements revealed strong regional differences, thus emphasizing the need to include nonuniform thicknesses in theoretical and computational studies of complex arterial geometries.

  5. Effect of Selenium Supplementation on Redox Status of the Aortic Wall in Young Spontaneously Hypertensive Rats

    OpenAIRE

    2015-01-01

    Selenium (Se) is an exogenous antioxidant that performs its function via the expression of selenoproteins. The aim of this study was to explore the effect of varying Se intake on the redox status of the aortic wall in young spontaneously hypertensive rats (SHR). Sixteen male Wistar Kyoto (WKY) rats and nineteen male SHR, 16-week-old, were tested after being given diets with different Se content for eight weeks. They were divided into 4 groups: control groups of WKY NSe and SHR NSe on an adequ...

  6. A comparison of modelling techniques for computing wall stress in abdominal aortic aneurysms

    Directory of Open Access Journals (Sweden)

    McGloughlin Timothy M

    2007-10-01

    Full Text Available Abstract Background Aneurysms, in particular abdominal aortic aneurysms (AAA, form a significant portion of cardiovascular related deaths. There is much debate as to the most suitable tool for rupture prediction and interventional surgery of AAAs, and currently maximum diameter is used clinically as the determining factor for surgical intervention. Stress analysis techniques, such as finite element analysis (FEA to compute the wall stress in patient-specific AAAs, have been regarded by some authors to be more clinically important than the use of a "one-size-fits-all" maximum diameter criterion, since some small AAAs have been shown to have higher wall stress than larger AAAs and have been known to rupture. Methods A patient-specific AAA was selected from our AAA database and 3D reconstruction was performed. The AAA was then modelled in this study using three different approaches, namely, AAA(SIMP, AAA(MOD and AAA(COMP, with each model examined using linear and non-linear material properties. All models were analysed using the finite element method for wall stress distributions. Results Wall stress results show marked differences in peak wall stress results between the three methods. Peak wall stress was shown to reduce when more realistic parameters were utilised. It was also noted that wall stress was shown to reduce by 59% when modelled using the most accurate non-linear complex approach, compared to the same model without intraluminal thrombus. Conclusion The results here show that using more realistic parameters affect resulting wall stress. The use of simplified computational modelling methods can lead to inaccurate stress distributions. Care should be taken when examining stress results found using simplified techniques, in particular, if the wall stress results are to have clinical importance.

  7. Quantitative Assessment of Wall Shear Stress in an Aortic Coarctation - Impact of Virtual Interventions

    Science.gov (United States)

    Karlsson, Matts; Andersson, Magnus; Lantz, Jonas

    2014-11-01

    Turbulent and wall impinging blood flow causes abnormal shear forces onto the lumen and may play an important role in the pathogenesis of numerous cardiovascular diseases. In the present study, wall shear stress (WSS) and related flow parameters were studied in a pre-treated aortic coarctation (CoA) as well as after several virtual interventions using computational fluid dynamics (CFD). Patient-specific geometry and flow conditions were derived from magnetic resonance imaging (MRI) data. Finite element analysis was performed to acquire six different dilated CoAs. The unsteady pulsatile flow was resolved by large eddy simulation (LES) including non-Newtonian blood rheology. Pre-intervention, the presence of jet flow wall impingement caused an elevated WSS zone, with a distal region of low and oscillatory WSS. After intervention, cases with a more favorable centralized jet showed reduced high WSS values at the opposed wall. Despite significant turbulence reduction post-treatment, enhanced regions of low and oscillatory WSS were observed for all cases. This numerical method has demonstrated the morphological impact on WSS distribution in an CoA. With the predictability and validation capabilities of a combined CFD/MRI approach, a step towards patient-specific intervention planning is taken.

  8. Histochemical and immunohistochemical analysis of ruptured atherosclerotic abdominal aortic aneurysm wall

    Directory of Open Access Journals (Sweden)

    Tanasković Irena

    2010-01-01

    Full Text Available Background/Aim. The main complication of the atherosclerotic abdominal aortic aneurism (AAA is her rupture that begins with lesion in intima and rupture. The purpose of this work was to determine immunocytochemical and morphofunctional characteristics of the cells in aortic wall in ruptured atherosclerotic abdominal aortic aneurysm. Method. During the course of this study, 20 samples of atherosclerotic AAA were analyzed, all of them obtained during authopsy. The samples were fixed in 4% formalin and embedded in paraffin. Sections of 5 μm thickness were stained histochemically (of Heidenhain azan stain and Periodic acid Schiff - PAS stain and immunocytochemically using a DAKO LSAB+/HRP technique to identify α-smooth muscle actin (α-SMA, vimentin, myosin heavy chains (MHC, desmin, S-100 protein, CD45 and CD68 (DAKO specification. Results. The results of our study showed that ruptured atherosclerotic AAA is characterized by a complete absence of endothelial cells, the disruption of basal membrane and internal elastic lamina, as well as a presence of the remains of hypocellular complicated atherosclerotic lesion in intima. On the plaque margins, as well as in the media, smooth muscle cells (SMCs are present, which express a α-SMA and vimentin (but without MHC or desmin expression, as well as leukocyte infiltration, and a large number of foam cells. Some of the foam cells show a CD68-immunoreactivity, while the others show vimentin- and S-100 protein-immunoreactivity. Media is thinned out with a disorganized elastic lamellas, while adventitia is characterized by inflammatory inflitrate (infection. Conclusion. Rupture of aneurysm occurs from the primary intimal disruption, which spreads into thinned out media and adventitia. Rupture is caused by unstable atherom, hypocellularity, loss of contractile characteristics of smooth muscle cells in intima and media, neovascularization of the media, as well as by the activity of the macrophages in the

  9. 3-D segmentation and quantitative analysis of inner and outer walls of thrombotic abdominal aortic aneurysms

    Science.gov (United States)

    Lee, Kyungmoo; Yin, Yin; Wahle, Andreas; Olszewski, Mark E.; Sonka, Milan

    2008-03-01

    An abdominal aortic aneurysm (AAA) is an area of a localized widening of the abdominal aorta, with a frequent presence of thrombus. A ruptured aneurysm can cause death due to severe internal bleeding. AAA thrombus segmentation and quantitative analysis are of paramount importance for diagnosis, risk assessment, and determination of treatment options. Until now, only a small number of methods for thrombus segmentation and analysis have been presented in the literature, either requiring substantial user interaction or exhibiting insufficient performance. We report a novel method offering minimal user interaction and high accuracy. Our thrombus segmentation method is composed of an initial automated luminal surface segmentation, followed by a cost function-based optimal segmentation of the inner and outer surfaces of the aortic wall. The approach utilizes the power and flexibility of the optimal triangle mesh-based 3-D graph search method, in which cost functions for thrombus inner and outer surfaces are based on gradient magnitudes. Sometimes local failures caused by image ambiguity occur, in which case several control points are used to guide the computer segmentation without the need to trace borders manually. Our method was tested in 9 MDCT image datasets (951 image slices). With the exception of a case in which the thrombus was highly eccentric, visually acceptable aortic lumen and thrombus segmentation results were achieved. No user interaction was used in 3 out of 8 datasets, and 7.80 +/- 2.71 mouse clicks per case / 0.083 +/- 0.035 mouse clicks per image slice were required in the remaining 5 datasets.

  10. Proteins associated with the size and expansion rate of the abdominal aortic aneurysm wall as identified by proteomic analysis

    DEFF Research Database (Denmark)

    Urbonavicius, Sigitas; Lindholt, Jes S.; Delbosc, Sandrine

    2010-01-01

    Identification of biomarkers for the natural history of abdominal aortic aneurysms (AAA) holds the key to non-surgical intervention and improved selection for AAA repair. We aimed to associate the basic proteomic composition of AAA wall tissue with the expansion rate and size in patients with AAA....

  11. Fluid-Structure Interaction in Abdominal Aortic Aneurysm: Effect of Modeling Techniques

    Directory of Open Access Journals (Sweden)

    Shengmao Lin

    2017-01-01

    Full Text Available In this work, the impact of modeling techniques on predicting the mechanical behaviors of abdominal aortic aneurysm (AAA is systematically investigated. The fluid-structure interaction (FSI model for simultaneously capturing the transient interaction between blood flow dynamics and wall mechanics was compared with its simplified techniques, that is, computational fluid dynamics (CFD or computational solid stress (CSS model. Results demonstrated that CFD exhibited relatively smaller vortexes and tends to overestimate the fluid wall shear stress, compared to FSI. On the contrary, the minimal differences in wall stresses and deformation were observed between FSI and CSS models. Furthermore, it was found that the accuracy of CSS prediction depends on the applied pressure profile for the aneurysm sac. A large pressure drop across AAA usually led to the underestimation of wall stresses and thus the AAA rupture. Moreover, the assumed isotropic AAA wall properties, compared to the anisotropic one, will aggravate the difference between the simplified models with the FSI approach. The present work demonstrated the importance of modeling techniques on predicting the blood flow dynamics and wall mechanics of the AAA, which could guide the selection of appropriate modeling technique for significant clinical implications.

  12. Fluid-Structure Interaction in Abdominal Aortic Aneurysm: Effect of Modeling Techniques.

    Science.gov (United States)

    Lin, Shengmao; Han, Xinwei; Bi, Yonghua; Ju, Siyeong; Gu, Linxia

    2017-01-01

    In this work, the impact of modeling techniques on predicting the mechanical behaviors of abdominal aortic aneurysm (AAA) is systematically investigated. The fluid-structure interaction (FSI) model for simultaneously capturing the transient interaction between blood flow dynamics and wall mechanics was compared with its simplified techniques, that is, computational fluid dynamics (CFD) or computational solid stress (CSS) model. Results demonstrated that CFD exhibited relatively smaller vortexes and tends to overestimate the fluid wall shear stress, compared to FSI. On the contrary, the minimal differences in wall stresses and deformation were observed between FSI and CSS models. Furthermore, it was found that the accuracy of CSS prediction depends on the applied pressure profile for the aneurysm sac. A large pressure drop across AAA usually led to the underestimation of wall stresses and thus the AAA rupture. Moreover, the assumed isotropic AAA wall properties, compared to the anisotropic one, will aggravate the difference between the simplified models with the FSI approach. The present work demonstrated the importance of modeling techniques on predicting the blood flow dynamics and wall mechanics of the AAA, which could guide the selection of appropriate modeling technique for significant clinical implications.

  13. Fluid-Structure Interaction in Abdominal Aortic Aneurysm: Effect of Modeling Techniques

    Science.gov (United States)

    Lin, Shengmao; Han, Xinwei; Bi, Yonghua; Ju, Siyeong

    2017-01-01

    In this work, the impact of modeling techniques on predicting the mechanical behaviors of abdominal aortic aneurysm (AAA) is systematically investigated. The fluid-structure interaction (FSI) model for simultaneously capturing the transient interaction between blood flow dynamics and wall mechanics was compared with its simplified techniques, that is, computational fluid dynamics (CFD) or computational solid stress (CSS) model. Results demonstrated that CFD exhibited relatively smaller vortexes and tends to overestimate the fluid wall shear stress, compared to FSI. On the contrary, the minimal differences in wall stresses and deformation were observed between FSI and CSS models. Furthermore, it was found that the accuracy of CSS prediction depends on the applied pressure profile for the aneurysm sac. A large pressure drop across AAA usually led to the underestimation of wall stresses and thus the AAA rupture. Moreover, the assumed isotropic AAA wall properties, compared to the anisotropic one, will aggravate the difference between the simplified models with the FSI approach. The present work demonstrated the importance of modeling techniques on predicting the blood flow dynamics and wall mechanics of the AAA, which could guide the selection of appropriate modeling technique for significant clinical implications. PMID:28321413

  14. Self-gated CINE MRI for combined contrast-enhanced imaging and wall-stiffness measurements of murine aortic atherosclerotic lesions.

    Directory of Open Access Journals (Sweden)

    Brigit den Adel

    Full Text Available BACKGROUND: High-resolution contrast-enhanced imaging of the murine atherosclerotic vessel wall is difficult due to unpredictable flow artifacts, motion of the thin artery wall and problems with flow suppression in the presence of a circulating contrast agent. METHODS AND RESULTS: We applied a 2D-FLASH retrospective-gated CINE MRI method at 9.4T to characterize atherosclerotic plaques and vessel wall distensibility in the aortic arch of aged ApoE(-/- mice after injection of a contrast agent. The method enabled detection of contrast enhancement in atherosclerotic plaques in the aortic arch after I.V. injection of micelles and iron oxides resulting in reproducible plaque enhancement. Both contrast agents were taken up in the plaque, which was confirmed by histology. Additionally, the retrospective-gated CINE method provided images of the aortic wall throughout the cardiac cycle, from which the vessel wall distensibility could be calculated. Reduction in plaque size by statin treatment resulted in lower contrast enhancement and reduced wall stiffness. CONCLUSIONS: The retrospective-gated CINE MRI provides a robust and simple way to detect and quantify contrast enhancement in atherosclerotic plaques in the aortic wall of ApoE(-/- mice. From the same scan, plaque-related changes in stiffness of the aortic wall can be determined. In this mouse model, a correlation between vessel wall stiffness and atherosclerotic lesions was found.

  15. Single-walled carbon nanotubes (SWCNTs) induce vasodilation in isolated rat aortic rings.

    Science.gov (United States)

    Gutiérrez-Hernández, J M; Ramirez-Lee, M A; Rosas-Hernandez, H; Salazar-García, S; Maldonado-Ortega, D A; González, F J; Gonzalez, C

    2015-06-01

    Single-walled carbon nanotubes (SWCNTs) are used in biological systems with impact in biomedicine in order to improve diagnostics and treatment of diseases. However, their effects upon the vascular system, are not fully understood. Endothelium and smooth muscle cells (SMC) communicate through release of vasoactive factors as nitric oxide (NO) to maintain vascular tone. The aim of this study was to evaluate the effect of SWCNTs on vascular tone using isolated rat aortic rings, which were exposed to SWCNTs (0.1, 1 and 10 μg/mL) in presence and absence of endothelium. SWCNTs induced vasodilation in both conditions, indicating that this effect was independent on endothelium; moreover that vasodilation was NO-independent, since its blockage with L-NAME did not modify the observed effect. Together, these results indicate that SWCNTs induce vasodilation in the macrovasculature, may be through a direct interaction with SMC rather than endothelium independent of NO production. Further investigation is required to fully understand the mechanisms of action and mediators involved in the signaling pathway induced by SWCNTs on the vascular system.

  16. Three-dimensional macro-scale assessment of regional and temporal wall shear stress characteristics on aortic valve leaflets.

    Science.gov (United States)

    Cao, K; Bukač, M; Sucosky, P

    2016-01-01

    The aortic valve (AV) achieves unidirectional blood flow between the left ventricle and the aorta. Although hemodynamic stresses have been shown to regulate valvular biology, the native wall shear stress (WSS) experienced by AV leaflets remains largely unknown. The objective of this study was to quantify computationally the macro-scale leaflet WSS environment using fluid-structure interaction modeling. An arbitrary Lagrangian-Eulerian approach was implemented to predict valvular flow and leaflet dynamics in a three-dimensional AV geometry subjected to physiologic transvalvular pressure. Local WSS characteristics were quantified in terms of temporal shear magnitude (TSM), oscillatory shear index (OSI) and temporal shear gradient (TSG). The dominant radial WSS predicted on the leaflets exhibited high amplitude and unidirectionality on the ventricularis (TSM>7.50 dyn/cm(2), OSI 325.54 dyn/cm(2) s) but low amplitude and bidirectionality on the fibrosa (TSM 0.38, TSG 0.25). This study provides new insights into the role played by leaflet-blood flow interactions in valvular function and critical hemodynamic stress data for the assessment of the hemodynamic theory of AV disease.

  17. Genetic and Epigenetic Regulation of Aortic Aneurysms

    Science.gov (United States)

    Kim, Ha Won

    2017-01-01

    Aneurysms are characterized by structural deterioration of the vascular wall leading to progressive dilatation and, potentially, rupture of the aorta. While aortic aneurysms often remain clinically silent, the morbidity and mortality associated with aneurysm expansion and rupture are considerable. Over 13,000 deaths annually in the United States are attributable to aortic aneurysm rupture with less than 1 in 3 persons with aortic aneurysm rupture surviving to surgical intervention. Environmental and epidemiologic risk factors including smoking, male gender, hypertension, older age, dyslipidemia, atherosclerosis, and family history are highly associated with abdominal aortic aneurysms, while heritable genetic mutations are commonly associated with aneurysms of the thoracic aorta. Similar to other forms of cardiovascular disease, family history, genetic variation, and heritable mutations modify the risk of aortic aneurysm formation and provide mechanistic insight into the pathogenesis of human aortic aneurysms. This review will examine the relationship between heritable genetic and epigenetic influences on thoracic and abdominal aortic aneurysm formation and rupture. PMID:28116311

  18. Transport and coherent structures in wall turbulence

    CERN Document Server

    Tardu, Sedat

    2014-01-01

    Wall bounded turbulent flows are of major importance in industrial and environmental fluid mechanics. The structure of the wall turbulence is intrinsically related to the coherent structures that play a fundamental role in the transport process. The comprehension of their regeneration mechanism is indispensable for the development of efficient strategies in terms of drag control and near wall turbulence management. This book provides an up-to-date overview on the progress made in this specific area in recent years.

  19. Structure of the Elastin-Contractile Units in the Thoracic Aorta and How Genes That Cause Thoracic Aortic Aneurysms and Dissections Disrupt This Structure.

    Science.gov (United States)

    Karimi, Ashkan; Milewicz, Dianna M

    2016-01-01

    The medial layer of the aorta confers elasticity and strength to the aortic wall and is composed of alternating layers of smooth muscle cells (SMCs) and elastic fibres. The SMC elastin-contractile unit is a structural unit that links the elastin fibres to the SMCs and is characterized by the following: (1) layers of elastin fibres that are surrounded by microfibrils; (2) microfibrils that bind to the integrin receptors in focal adhesions on the cell surface of the SMCs; and (3) SMC contractile filaments that are linked to the focal adhesions on the inner side of the membrane. The genes that are altered to cause thoracic aortic aneurysms and aortic dissections encode proteins involved in the structure or function of the SMC elastin-contractile unit. Included in this gene list are the genes encoding protein that are structural components of elastin fibres and microfibrils, FBN1, MFAP5, ELN, and FBLN4. Also included are genes that encode structural proteins in the SMC contractile unit, including ACTA2, which encodes SMC-specific α-actin and MYH11, which encodes SMC-specific myosin heavy chain, along with MYLK and PRKG1, which encode kinases that control SMC contraction. Finally, mutations in the gene encoding the protein linking integrin receptors to the contractile filaments, FLNA, also predispose to thoracic aortic disease. Thus, these data suggest that functional SMC elastin-contractile units are important for maintaining the structural integrity of the aorta.

  20. Heterogeneous distribution of a diffusional tracer in the aortic wall of normal and atherosclerotic rabbits

    Energy Technology Data Exchange (ETDEWEB)

    Tsutsui, H.; Tomoike, H.; Nakamura, M. (Kyushu Univ., Fukuoka (Japan))

    1990-08-01

    Tracer distribution as an index of nutritional support across the thoracic and abdominal aortas in rabbits in the presence or absence of atherosclerotic lesions was evaluated using ({sup 14}C)antipyrine, a metabolically inert, diffusible indicator. Intimal plaques were produced by endothelial balloon denudation of the thoracic aorta and a 1% cholesterol diet. After a steady intravenous infusion of 200 microCi of ({sup 14}C)antipyrine for 60 seconds, thoracic and abdominal aortas and the heart were excised, and autoradiograms of 20-microns-thick sections were quantified, using microcomputer-aided densitometry. Regional radioactivity and regional diffusional support, as an index of nutritional flow estimated from the timed collections of arterial blood, was 367 and 421 nCi.g-1 (82 and 106 ml.min-1.100 g-1) in thoracic aortic media of the normal and atherosclerotic rabbits, respectively. Radioactivity at the thickened intima was 179 nCi.g-1 (p less than 0.01 versus media). The gruel was noted at a deeper site within the thickened intima, and diffusional support here was 110 nCi.g-1 (p less than 0.01 versus an average radioactivity at the thickened intima). After ligating the intercostal arteries, regional tracer distribution in the media beneath the fibrofatty lesion, but not the plaque-free intima, was reduced to 46%. Thus, in the presence of advanced intimal thickening, the heterogeneous distribution of diffusional flow is prominent across the vessel wall, and abluminal routes are crucial to meet the increased demands of nutritional requirements.

  1. Aortic and Cardiac Structure and Function Using High-Resolution Echocardiography and Optical Coherence Tomography in a Mouse Model of Marfan Syndrome

    Science.gov (United States)

    Lee, Ling; Cui, Jason Z.; Cua, Michelle; Esfandiarei, Mitra; Sheng, Xiaoye; Chui, Winsey Audrey; Xu, Michael Haoying; Sarunic, Marinko V.; Beg, Mirza Faisal; van Breemen, Cornelius; Sandor, George G. S.

    2016-01-01

    Marfan syndrome (MFS) is an autosomal-dominant disorder of connective tissue caused by mutations in the fibrillin-1 (FBN1) gene. Mortality is often due to aortic dissection and rupture. We investigated the structural and functional properties of the heart and aorta in a [Fbn1C1039G/+] MFS mouse using high-resolution ultrasound (echo) and optical coherence tomography (OCT). Echo was performed on 6- and 12-month old wild type (WT) and MFS mice (n = 8). In vivo pulse wave velocity (PWV), aortic root diameter, ejection fraction, stroke volume, left ventricular (LV) wall thickness, LV mass and mitral valve early and atrial velocities (E/A) ratio were measured by high resolution echocardiography. OCT was performed on 12-month old WT and MFS fixed mouse hearts to measure ventricular volume and mass. The PWV was significantly increased in 6-mo MFS vs. WT (366.6 ± 19.9 vs. 205.2 ± 18.1 cm/s; p = 0.003) and 12-mo MFS vs. WT (459.5 ± 42.3 vs. 205.3 ± 30.3 cm/s; pMarfan patients including significant aortic dilation, central aortic stiffness, LV systolic and diastolic dysfunction. This is the first demonstration of the direct measurement in vivo of pulse wave velocity non-invasively in the aortic arch of MFS mice, a robust measure of aortic stiffness and a critical clinical parameter for the assessment of pathology in the Marfan syndrome. PMID:27824871

  2. [Inflammatory abdominal aortic aneurysm].

    Science.gov (United States)

    Ziaja, K; Sedlak, L; Urbanek, T; Kostyra, J; Ludyga, T

    2000-01-01

    The reported incidence of inflammatory abdominal aortic aneurysm (IAAA) is from 2% to 14% of patients with abdominal aortic aneurysm and the etiology of this disease is still discussed--according to the literature several pathogenic theories have been proposed. From 1992 to 1997 32 patients with IAAA were operated on. The patients were mostly symptomatic--abdominal pain was present in 68.75% cases, back pain in 31.25%, fever in 12.5% and weight loss in 6.25% of the operated patients. In all the patients ultrasound examination was performed, in 4 patients CT and in 3 cases urography. All the patients were operated on and characteristic signs of inflammatory abdominal aortic aneurysm like: thickened aortic wall, perianeurysmal infiltration or retroperitoneal fibrosis with involvement of retroperitoneal structures were found. In all cases surgery was performed using transperitoneal approach; in three cases intraoperatively contiguous abdominal organs were injured, which was connected with their involvement into periaortic inflammation. In 4 cases clamping of the aorta was done at the level of the diaphragmatic hiatus. 3 patients (9.37%) died (one patient with ruptured abdominal aortic aneurysm). Authors present diagnostic procedures and the differences in the surgical tactic, emphasizing the necessity of the surgical therapy in patients with inflammatory abdominal aortic aneurysm.

  3. Flow cytometric assessment of circulating platelet and erythrocytes microparticles in young thalassemia major patients: relation to pulmonary hypertension and aortic wall stiffness.

    Science.gov (United States)

    Tantawy, Azza A G; Adly, Amira A M; Ismail, Eman A R; Habeeb, Nevin M

    2013-06-01

    Heart disease is the leading cause of mortality and morbidity in β-thalassemia major (β-TM). Aggregability of abnormal red cells and membrane-derived microparticles (MPs) stemming from activated platelets and erythrocytes are responsible for thrombotic risk. We measured platelet and erythrocyte MPs (PMPs and ErMPs) in 60 young β-TM patients compared with 40 age- and sex-matched healthy controls and assessed their relation to clinicopathological characteristics and aortic elastic properties. Patients were studied stressing on transfusion history, splenectomy, thrombotic events, chelation therapy, hematological and coagulation profiles, flow cytometric measurement of PMPs (CD41b(+) ) and ErMPs (glycophorin A(+) ) as well as echocardiographic assessment of aortic elastic properties. Aortic stiffness index and pulmonary artery pressure were significantly higher, whereas aortic strain and distensibility were lower in TM patients than controls (P 2500 μg/L (P < 0.001). Compliant patients on chelation therapy had lower MPs levels than non-compliant patients (P < 0.001). PMPs and ErMPs were positively correlated to markers of hemolysis, serum ferritin, D-dimer, vWF Ag, and aortic stiffness, whereas negatively correlated to hemoglobin level and aortic distensibility (P < 0.05). We suggest that increased MPs may be implicated in vascular dysfunction, pulmonary hypertension risk, and aortic wall stiffness observed in thalassemia patients. Their quantification could provide utility for early detection of cardiovascular abnormalities and monitoring the biological efficacy of chelation therapy.

  4. Relation of aortic calcification, wall thickness, and distensibility with severity of coronary artery disease: evaluation with coronary CT angiography

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Seonah; Yong, Hwan Seok; Doo, Kyung Won; Kang, Eun-Young; Woo, Ok Hee; Choi, Eun Jung [Dept. of Radiology, Korea Univ. Guro Hospital, Korea Univ. College of Medicine, Seoul (Korea, Republic of)], e-mail: yhwanseok@naver.com

    2012-10-15

    Background Three known risk factors for aortic atherosclerosis predict the severity of coronary artery disease (CAD): aortic calcification (AC), aortic wall thickness (AWT), and aortic distensibility (AD). Purpose To determine the relationship of AC, AWT, and AD with the severity of CAD. Material and Methods A total of 104 patients who underwent both coronary CT angiography (CCTA) and invasive coronary angiography were enrolled. The severity of CAD was assessed by three methods: the segment involvement score (SIS), the segment stenosis score (SSS), and the modified Gensini score (mG). We quantified AC using the Agatston method on low-dose ungated chest CT (LDCT). We measured AWT at the thickest portion of the descending thoracic aorta on CCTA. AD was calculated as the difference between the maximum and minimum areas of the ascending aorta and the pulse pressure. The relationships between the severity of CAD and the three aortic factors were assessed. Results The AC and AWT of the thoracic aorta were significantly higher in the occlusive CAD (OCAD) group (1984.21 {+-} 2986.10 vs. 733.00 {+-} 1648.71, P = 0.01; 4.13 {+-} 1.48 vs. 3.40 {+-} 1.01, P = 0.22). Patients with OCAD had more than one epicardial coronary artery with >50% luminal stenosis. The AC (r = 0.453 with SIS; r = 0.454 with SSS; r = 0.427 with mG) and the AWT (r = 0.279 with SIS; r = 0.324 with SSS; r = 0.304 with mG) were significantly correlated with all three methods, and the AD was negatively correlated with the SIS (r = - 0.221, P < 0.05, respectively) in the unadjusted model. After adjustment for cardiovascular risk factors, only the correlations between AC and all three methods assessing CAD remained significant. Conclusion There are significant relationships between AC, AWT and AD and severity of CAD. In particular, AC measured on LDCT is the most consistent predictor of severity of CAD.

  5. Structure of the Elastin-Contractile Units in the Thoracic Aorta and How Genes that Cause Thoracic Aortic Aneurysms and Dissections Disrupt this Structure

    OpenAIRE

    Karimi, Ashkan; Milewicz, Dianna M.

    2015-01-01

    The medial layer of the aorta confers elasticity and strength to the aortic wall and is composed of alternating layers of smooth muscle cells (SMCs) and elastic fibers. The SMC elastin-contractile unit is a structural unit that links the elastin fibers to the SMCs and is characterized by the following: 1. Layers of elastin fibers that are surrounded by microfibrils. 2. Microfibrils that bind to the integrin receptors in focal adhesions on the cell surface of the SMCs. 3. SMC contractile filam...

  6. 3D analysis of vortical structures in an abdominal aortic aneurysm by stereoscopic PIV

    Science.gov (United States)

    Deplano, Valérie; Guivier-Curien, Carine; Bertrand, Eric

    2016-11-01

    The present work presents an experimental in vitro three-dimensional analysis of the flow dynamics in an abdominal aortic aneurysm (AAA) through stereoscopic particle image velocimetry (SPIV) measurements. The experimental set-up mimics the pathophysiological context involving a shear thinning blood analogue fluid, compliant AAA and aorto-iliac bifurcation walls and controlled inlet and outlet flow rate and pressure waveforms as well as working fluid temperature. SPIV was carefully calibrated and conducted to assess the three velocity components in the AAA volume. For the first time in the literature, the 3D vortex ring genesis, propagation, and vanishing in the AAA bulge are experimentally described and quantified. In comparison with classical 2-component PIV measurements (2C PIV), the third component of the velocity vector was shown to be of importance in such a geometry, especially, during the deceleration phase of the flow rate. The 3D velocity magnitude reached up more than 20 % of the 2D one showing that 2C PIV are definitively not accurate enough to provide a complete description of flow behaviour in an AAA. In addition to potential clinical implications of a full 3D vortex ring description in AAA evolution, the 3D in vitro experimental quantification of the flow dynamics carried out in the present study offers an interesting tool for the validation of fluid-structure interaction numerical studies dealing with AAA.

  7. Hydrogen uptake in vanadium first wall structures

    Energy Technology Data Exchange (ETDEWEB)

    Simonen, E.P.; Jones, R.H. [Pacific Northwest National Laboratory, Richland, WA (United States)

    1996-04-01

    Evaluation of hydrogen sources and transport are needed to assess the mechanical integrity of V structures. Two sources include implantation and transmutation. The proposed coatings for the DEMO and ITER first wall strongly influence retention of hydrogen isotopes. Upper limit calculations of hydrogen inventory were based on recycling to the plasma and an impermeable coolant-side coating. Hydrogen isotope concentrations in V approaching 1,000 appm may be activated.

  8. Fluid structure interaction simulation in three-layered aortic aneurysm model under pulsatile flow: comparison of wrapping and stenting.

    Science.gov (United States)

    Gao, Feng; Ueda, Hiroshi; Gang, Li; Okada, Hiroshi

    2013-04-26

    One treatment method for aortic aneurysm is the invasive insertion of a stent into the aneurysm. Another method is wrapping the aneurysm using newly developed expanded polytetrafluoroethylene (PTFE) material. A virtual stented aneurysm model and a wrapped aneurysm model were created to study the flow and wall dynamics by means of fluid-structure interaction analyses. The flow velocity and pressure distribution as well as the deformation and wall stress were investigated. Stenting significantly changed the blood flow pattern and the vortexes in the aneurysm. Wrapping increased the thickness of the aneurysm wall and increased the strength of the vessel wall. The maximum von Mises stress in the stented model was found to be 220,494 Pa and 228,218 Pa at the time of peak flow and peak pressure, respectively. This was reduced by 37.8% and 36.7% to 137,200 and 144,354 Pa, respectively, in the wrapped model. Our results provide information that may improve the understanding of the biomechanics of stenting and wrapping.

  9. On coherent structure in wall turbulence

    CERN Document Server

    Sharma, A S

    2013-01-01

    A new theory of coherent structure in wall turbulence is presented. The theory is the first to predict packets of hairpin vortices and other structure in turbulence, and their dynamics, based on an analysis of the Navier-Stokes equations, under an assumption of a turbulent mean profile. The assumption of the turbulent mean acts as a restriction on the class of possible structures. It is shown that the coherent structure is a manifestation of essentially low-dimensional flow dynamics, arising from a critical layer mechanism. Using the decomposition presented in McKeon & Sharma (J. Fluid Mech, 658, 2010), complex coherent structure is recreated from minimal superpositions of response modes predicted by the analysis, which take the form of radially-varying travelling waves. By way of example, simple combinations of these modes are offered that predicts hairpins and modulated hairpin packets. The phase interaction also predicts important skewness and correlation results known in the literature. It is also sho...

  10. [Structure and function of fungal cell wall].

    Science.gov (United States)

    Ohno, Naohito

    2008-12-01

    Cell wall glycans of fungi/yeasts are reviewed. Fungi/yeasts produce various kinds of polysaccharides. As part of the cell wall they are interlinked with other components forming a huge network. The insolubility and complex with multiple components makes the research very tough. Studies on beta-glucan have been performed from various views, such as chemistry, conformation, solubility, tissue distribution and metabolism, biological activity, clinical application, receptor, biosynthesis, and antibody. Studies on mannan focus on immunotoxicity, such as anaphylactoid reaction and coronary arteritis induction. alpha-glucan, chitin, and capsular polysaccharide were also mentioned in relation to structure and genes. Compared with human and animal polysaccharides, fungi/yeasts polysaccharides have very characteristic properties.

  11. Wall grid structure for interior scene synthesis

    KAUST Repository

    Xu, Wenzhuo

    2015-02-01

    We present a system for automatically synthesizing a diverse set of semantically valid, and well-arranged 3D interior scenes for a given empty room shape. Unlike existing work on layout synthesis, that typically knows potentially needed 3D models and optimizes their location through cost functions, our technique performs the retrieval and placement of 3D models by discovering the relationships between the room space and the models\\' categories. This is enabled by a new analytical structure, called Wall Grid Structure, which jointly considers the categories and locations of 3D models. Our technique greatly reduces the amount of user intervention and provides users with suggestions and inspirations. We demonstrate the applicability of our approach on three types of scenarios: conference rooms, living rooms and bedrooms.

  12. Fluid-structure interaction of a patient-specific abdominal aortic aneurysm treated with an endovascular stent-graft.

    LENUS (Irish Health Repository)

    Molony, David S

    2009-01-01

    BACKGROUND: Abdominal aortic aneurysms (AAA) are local dilatations of the infrarenal aorta. If left untreated they may rupture and lead to death. One form of treatment is the minimally invasive insertion of a stent-graft into the aneurysm. Despite this effective treatment aneurysms may occasionally continue to expand and this may eventually result in post-operative rupture of the aneurysm. Fluid-structure interaction (FSI) is a particularly useful tool for investigating aneurysm biomechanics as both the wall stresses and fluid forces can be examined. METHODS: Pre-op, Post-op and Follow-up models were reconstructed from CT scans of a single patient and FSI simulations were performed on each model. The FSI approach involved coupling Abaqus and Fluent via a third-party software - MpCCI. Aneurysm wall stress and compliance were investigated as well as the drag force acting on the stent-graft. RESULTS: Aneurysm wall stress was reduced from 0.38 MPa before surgery to a value of 0.03 MPa after insertion of the stent-graft. Higher stresses were seen in the aneurysm neck and iliac legs post-operatively. The compliance of the aneurysm was also reduced post-operatively. The peak Post-op axial drag force was found to be 4.85 N. This increased to 6.37 N in the Follow-up model. CONCLUSION: In a patient-specific case peak aneurysm wall stress was reduced by 92%. Such a reduction in aneurysm wall stress may lead to shrinkage of the aneurysm over time. Hence, post-operative stress patterns may help in determining the likelihood of aneurysm shrinkage post EVAR. Post-operative remodelling of the aneurysm may lead to increased drag forces.

  13. Fluid-structure interaction of a patient-specific abdominal aortic aneurysm treated with an endovascular stent-graft

    Directory of Open Access Journals (Sweden)

    McGloughlin Tim M

    2009-10-01

    Full Text Available Abstract Background Abdominal aortic aneurysms (AAA are local dilatations of the infrarenal aorta. If left untreated they may rupture and lead to death. One form of treatment is the minimally invasive insertion of a stent-graft into the aneurysm. Despite this effective treatment aneurysms may occasionally continue to expand and this may eventually result in post-operative rupture of the aneurysm. Fluid-structure interaction (FSI is a particularly useful tool for investigating aneurysm biomechanics as both the wall stresses and fluid forces can be examined. Methods Pre-op, Post-op and Follow-up models were reconstructed from CT scans of a single patient and FSI simulations were performed on each model. The FSI approach involved coupling Abaqus and Fluent via a third-party software - MpCCI. Aneurysm wall stress and compliance were investigated as well as the drag force acting on the stent-graft. Results Aneurysm wall stress was reduced from 0.38 MPa before surgery to a value of 0.03 MPa after insertion of the stent-graft. Higher stresses were seen in the aneurysm neck and iliac legs post-operatively. The compliance of the aneurysm was also reduced post-operatively. The peak Post-op axial drag force was found to be 4.85 N. This increased to 6.37 N in the Follow-up model. Conclusion In a patient-specific case peak aneurysm wall stress was reduced by 92%. Such a reduction in aneurysm wall stress may lead to shrinkage of the aneurysm over time. Hence, post-operative stress patterns may help in determining the likelihood of aneurysm shrinkage post EVAR. Post-operative remodelling of the aneurysm may lead to increased drag forces.

  14. Free-breathing black-blood CINE fast-spin echo imaging for measuring abdominal aortic wall distensibility: A feasibility study.

    Science.gov (United States)

    Lin, Jyh-Miin; Patterson, Andrew; Chao, Tzu-Cheng; Zhu, Chengcheng; Chang, Hing-Chiu; Mendes, Jason; Chung, Hsiao-Wen; Gillard, Jonathan; Graves, Martin

    2017-03-22

    The paper reports a free-breathing black-blood CINE fast-spin echo (FSE) technique for measuring abdominal aortic wall motion. The free-breathing CINE FSE includes the following MR techniques: 1) variable-density sampling with fast iterative reconstruction; 2) inner-volume imaging; and 3) a blood-suppression preparation pulse. The proposed technique was evaluated in eight healthy subjects. The inner-volume imaging significantly reduced the intraluminal artifacts of respiratory motion (p = 0.015). The quantitative measurements were a diameter of 16.3 ± 2.8 mm and wall distensibility of 2.0 ± 0.4 mm (12.5 ± 3.4%) and 0.7 ± 0.3 mm (4.1 ± 1.0%) for the anterior and posterior walls, respectively. The cyclic cross-sectional distensibility was 35 ± 15% greater in the systolic phase than in the diastolic phase. In conclusion, we developed a feasible CINE FSE method to measure the motion of the abdominal aortic wall, which will enable clinical scientists to study the elasticity of the abdominal aorta.

  15. Immersed smoothed finite element method for fluid-structure interaction simulation of aortic valves

    Science.gov (United States)

    Yao, Jianyao; Liu, G. R.; Narmoneva, Daria A.; Hinton, Robert B.; Zhang, Zhi-Qian

    2012-12-01

    This paper presents a novel numerical method for simulating the fluid-structure interaction (FSI) problems when blood flows over aortic valves. The method uses the immersed boundary/element method and the smoothed finite element method and hence it is termed as IS-FEM. The IS-FEM is a partitioned approach and does not need a body-fitted mesh for FSI simulations. It consists of three main modules: the fluid solver, the solid solver and the FSI force solver. In this work, the blood is modeled as incompressible viscous flow and solved using the characteristic-based-split scheme with FEM for spacial discretization. The leaflets of the aortic valve are modeled as Mooney-Rivlin hyperelastic materials and solved using smoothed finite element method (or S-FEM). The FSI force is calculated on the Lagrangian fictitious fluid mesh that is identical to the moving solid mesh. The octree search and neighbor-to-neighbor schemes are used to detect efficiently the FSI pairs of fluid and solid cells. As an example, a 3D idealized model of aortic valve is modeled, and the opening process of the valve is simulated using the proposed IS-FEM. Numerical results indicate that the IS-FEM can serve as an efficient tool in the study of aortic valve dynamics to reveal the details of stresses in the aortic valves, the flow velocities in the blood, and the shear forces on the interfaces. This tool can also be applied to animal models studying disease processes and may ultimately translate to a new adaptive methods working with magnetic resonance images, leading to improvements on diagnostic and prognostic paradigms, as well as surgical planning, in the care of patients.

  16. Carbon nanocones: wall structure and morphology

    Directory of Open Access Journals (Sweden)

    Stine Nalum Naess, Arnljot Elgsaeter, Geir Helgesen and Kenneth D Knudsen

    2009-01-01

    Full Text Available Large-scale production of conical carbon nanostructures is possible through pyrolysis of hydrocarbons in a plasma torch process. The resulting carbon cones occur in five distinctly different forms, and disc-shaped particles are produced as well. The structure and properties of these carbon cones and discs have been relatively little explored until now. Here we characterize the structure of these particles using transmission electron microscopy, synchrotron x-ray and electron diffraction. The carbon nanocones are found to exhibit several interesting structural features; instead of having a uniform cross-section, the walls consist of a relatively thin inner graphite-like layer with a non-crystalline envelope, where the amount of the latter can be modified significantly by annealing. The cones appear with a well-defined faceting along the cone edge, demonstrating strict long-range atomic ordering; they also present occasional examples of symmetry breaking, such as two apexes appearing in the same carbon nanocone.

  17. Aortic insufficiency

    Science.gov (United States)

    ... page, please enable JavaScript. Aortic insufficiency is a heart valve disease in which the aortic valve does not close ... aortic insufficiency Images Aortic insufficiency References Carabello BA. Valvular heart disease. In: Goldman L, Schafer AI, eds. Goldman's Cecil ...

  18. Fluid-structure interaction analysis of the flow through a stenotic aortic valve

    Science.gov (United States)

    Maleki, Hoda; Labrosse, Michel R.; Durand, Louis-Gilles; Kadem, Lyes

    2009-11-01

    In Europe and North America, aortic stenosis (AS) is the most frequent valvular heart disease and cardiovascular disease after systemic hypertension and coronary artery disease. Understanding blood flow through an aortic stenosis and developing new accurate non-invasive diagnostic parameters is, therefore, of primarily importance. However, simulating such flows is highly challenging. In this study, we considered the interaction between blood flow and the valve leaflets and compared the results obtained in healthy valves with stenotic ones. One effective method to model the interaction between the fluid and the structure is to use Arbitrary Lagrangian-Eulerian (ALE) approach. Our two-dimensional model includes appropriate nonlinear and anisotropic materials. It is loaded during the systolic phase by applying pressure curves to the fluid domain at the inflow. For modeling the calcified stenotic valve, calcium will be added on the aortic side of valve leaflets. Such simulations allow us to determine the effective orifice area of the valve, one of the main parameters used clinically to evaluate the severity of an AS, and to correlate it with changes in the structure of the leaflets.

  19. M型超声检测腹主动脉前后壁运动的初步研究%Primary studies of anteroposterior abdominal aortic wall motion with M-mode ultrasound

    Institute of Scientific and Technical Information of China (English)

    辛群; 蔡珠虹; 包俊敏; 梅志军; 景在平

    2011-01-01

    Objective To find out the characteristics of anteroposterior abdominal aortic wall motion and to consider the potential implications of such variations. Methods M-mode ultrasound was used to measure abdominal aortic wall motion in human (n=20) and 2 animal species [dogs (n=8), and pigs (n=5)]. Anterior wall displacement (da),posterior wall displacement (dp), and diastolic diameter (Da) were measured. The ratio of displacement to the diameter was calculated (da/Dd. and dp/Dd). Results Aortic diameter varied from to (6.34±0.84) mm (dog) to (13.76±1.11) mm (human).Anterior wall displacement was about 3 times greater than the posterior among the species studied. The ratio of wall displacement to diastolic diameter were similar for the anterior and posterior walls. Wall displacement increased linearly with the diameter. Conclusions Abdominal aortic wall dynamics are similar in humans and animals regardless of the aortic size, with more anterior than posterior wall motion. These data suggest increased .dynamic strain of the anterior wall,which may help explain why human abdominal aortic aneurysms initially develop anteriorly. Haemodynamies plays an important role in the abdominal aortic aneurysm pathogenesis.%目的:应用M型超声观测正常腹主动脉前后壁运动的特征.方法:采集健康人组、健康犬组、健康猪组腹主动脉的M型超声图像,测量动脉前壁和后壁振幅(da和dP)、舒张期动脉直径(Dd),取其平均值;并分别计算各组数值:前壁振幅/舒张期动脉直径(da/Dd),后壁振幅/舒张期动脉直径(dp/Dd).结果:三组结果显示腹主动脉前壁振幅高于后壁振幅,差异有统计学意义(P<0.01).各组中管壁振幅与管径呈正相关.da/Dd和dp/Dd组间比较,差异无统计学意义.结论:正常腹主动脉前、后壁的运动差异与腹主动脉瘤的形成有一定关系,提示血液动力学因素在腹主动脉瘤发病机制中起着重要作用.

  20. combined spatially and temporally structured walls

    Directory of Open Access Journals (Sweden)

    D. N. Riahi

    1999-01-01

    Full Text Available Benney's theory of evolution of disturbances in shear flows over smooth and flat boundary is extended to study for shear flows over combined spatially and temporally corrugated walls. Perturbation and multiple-scales analyses are employed for the case where both amplitude of the corrugations and the amplitude of wave motion are small. Analyses for instability of modulated mean shear flows with respect to spanwise-periodic disturbance rolls and for the subsequent vortex formation and vortex stability are presented, and the effects of the corrugated walls on the resulting flow and vortices are determined. It is found that particular corrugated walls can originate and control the longitudinal vortices, while some other types of corrugated walls can enhance instability of such vortices.

  1. Computational analysis of an aortic valve jet with Lagrangian coherent structures

    Science.gov (United States)

    Shadden, Shawn C.; Astorino, Matteo; Gerbeau, Jean-Frédéric

    2010-03-01

    Important progress has been achieved in recent years in simulating the fluid-structure interaction around cardiac valves. An important step in making these computational tools useful to clinical practice is the development of postprocessing techniques to extract clinically relevant information from these simulations. This work focuses on flow through the aortic valve and illustrates how the computation of Lagrangian coherent structures can be used to improve insight into the transport mechanics of the flow downstream of the valve, toward the goal of aiding clinical decision making and the understanding of pathophysiology.

  2. 18F-FDG PET-CT uptake is a feature of both normal diameter and aneurysmal aortic wall and is not related to aneurysm size

    Energy Technology Data Exchange (ETDEWEB)

    Barwick, Tara D. [Imperial College Healthcare NHS Trust, Charing Cross Hospital, Department of Radiology/Nuclear Medicine, London (United Kingdom); Hammersmith Hospital, Department of Surgery and Cancer, Imperial College London, London (United Kingdom); Lyons, O.T.A.; Waltham, M. [King' s College London, BHF Centre of Research Excellence and NIHR Biomedical Research Centre at King' s Health Partners, Academic Department of Surgery, London (United Kingdom); Mikhaeel, N.G. [Guy' s and St Thomas' Foundation NHS Trust, Department of Oncology, London (United Kingdom); O' Doherty, M.J. [King' s Health Partners, Clinical PET Centre, St Thomas' Hospital, London (United Kingdom)

    2014-12-15

    Aortic metabolic activity is suggested to correlate with presence and progression of aneurysmal disease, but has been inadequately studied. This study investigates the 2-[{sup 18}F] fluoro-2-deoxy-D-glucose ({sup 18}F-FDG) uptake in a population of infra-renal abdominal aortic aneurysms (AAA), compared to a matched non-aneurysmal control group. The Positron Emission Tomography - Computed Tomography (PET/CT) database was searched for infra-renal AAA. Exclusion criteria were prior repair, vasculitis, and saccular/mycotic thoracic or thoraco-abdominal aneurysms. Matching of 159 non-aneurysmal (<3 cm diameter) controls from the same population was assessed. Infra-renal aortic wall FDG uptake was assessed using visual analysis; maximum standardized uptake value (SUV{sub max}) and target to background mediastinal blood pool ratio (TBR) were documented. Predictors of FDG uptake (age, sex, aortic diameter, hypertension, statin use, and diabetes) were assessed using univariate analysis. Follow-up questionnaires were sent to referring clinicians. Aneurysms (n = 151) and controls (n = 159) were matched (p > 0.05) for age, sex, diabetes, hypertension, smoking status, statin use, and indication for PET/CT. Median aneurysm diameter was 5.0 cm (range 3.2-10.4). On visual analysis there was no significant difference in the overall numbers with increased visual uptake 24 % (36/151) in the aneurysm group vs. 19 % (30/159) in the controls, p = ns. SUV{sub max} was slightly lower in the aneurysm group vs. controls (mean (2 SD) 1.75(0.79) vs. 1.84(0.58), p = 0.02). However there was no difference in TBR between the AAA group and controls (mean (2 SD) 1.03 (0.46) vs. 1.05(0.31), p = 0.36). During a median 18 (interquartile range 8-35) months' follow-up 20 were repaired and four were confirmed ruptured. The level of metabolic activity as assessed by {sup 18}F-FDG PET/CT in infra-renal AAA does not correlate with aortic size and does not differ between aneurysms and matched controls

  3. Structural Studies of Complex Carbohydrates of Plant Cell Walls

    Energy Technology Data Exchange (ETDEWEB)

    Darvill, Alan [Univ. of Georgia, Athens, GA (United States); Hahn, Michael G. [Univ. of Georgia, Athens, GA (United States); O' Neill, Malcolm A. [Univ. of Georgia, Athens, GA (United States); York, William S. [Univ. of Georgia, Athens, GA (United States)

    2015-02-17

    Most of the solar energy captured by land plants is converted into the polysaccharides (cellulose, hemicellulose, and pectin) that are the predominant components of the cell wall. These walls, which account for the bulk of plant biomass, have numerous roles in the growth and development of plants. Moreover, these walls have a major impact on human life as they are a renewable source of biomass, a source of diverse commercially useful polymers, a major component of wood, and a source of nutrition for humans and livestock. Thus, understanding the molecular mechanisms that lead to wall assembly and how cell walls and their component polysaccharides contribute to plant growth and development is essential to improve and extend the productivity and value of plant materials. The proposed research will develop and apply advanced analytical and immunological techniques to study specific changes in the structures and interactions of the hemicellulosic and pectic polysaccharides that occur during differentiation and in response to genetic modification and chemical treatments that affect wall biosynthesis. These new techniques will make it possible to accurately characterize minute amounts of cell wall polysaccharides so that subtle changes in structure that occur in individual cell types can be identified and correlated to the physiological or developmental state of the plant. Successful implementation of this research will reveal fundamental relationships between polysaccharide structure, cell wall architecture, and cell wall functions.

  4. 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.

  5. Aortic dissection

    Science.gov (United States)

    ... linked to aortic dissection include: Bicuspid aortic valve Coarctation (narrowing) of the aorta Connective tissue disorders (such ... failure Aneurysm Aortic insufficiency Blood clots Cardiac tamponade Coarctation of the aorta Hardening of the arteries High ...

  6. Spontaneous retrograde dissection of the ascending aorta in a patient with a bicuspid aortic valve.

    Science.gov (United States)

    Akgullu, Cagdas; Hekim, Tolga; Eryilmaz, Ufuk; Kurtoğlu, Tünay; Gürcün, Uğur

    2013-06-23

    Bicuspid aortic valve (BAV) is a congenital anomaly associated with structural weakness of the aortic wall. Sudden onset of symptoms in patients with BAV, such as sudden severe back pain, and pulse inequality between the extremities or tension disparity should alert clinicians to acute aortic syndromes, as they require prompt diagnosis and management. Retrograde aortic dissection, which is a rare form of acute aortic syndrome, is an uncommon life-threatening entity and may produce atypical computed tomography (CT) or magnetic resonance imaging findings, leading to difficulty in diagnosis. We report on a 51-year-old male patient with BAV and spontaneous retrograde ascending aortic dissection. CT findings were confusing and the diagnosis was made via transoesophageal echocardiography. After the diagnosis, the patient was treated with a modified Bentall procedure. He did not have any complications and was stable four months after the operation.

  7. Modeling Effects on Forces in Shear Wall-Frame Structures

    Directory of Open Access Journals (Sweden)

    Adang Surahman

    2015-05-01

    Full Text Available Shear walls are added to a structural system to reduce lateral deformations in moment resisting frames and are designed to carry a major portion of lateral load induced by an earthquake. A small percentage error in the shear wall calculation will have a significant effect on the frame forces. The results show that even a slight difference in structural assumption, or modeling, results in significant differences. Some of these differences are beyond the values that are covered by safety factors for errors in modeling. The differences are more obvious in the upper stories. It is not recommended to overestimate shear wall stiffness, nor underestimate frame stiffness.

  8. Medially constrained deformable modeling for segmentation of branching medial structures: Application to aortic valve segmentation and morphometry.

    Science.gov (United States)

    Pouch, Alison M; Tian, Sijie; Takebe, Manabu; Yuan, Jiefu; Gorman, Robert; Cheung, Albert T; Wang, Hongzhi; Jackson, Benjamin M; Gorman, Joseph H; Gorman, Robert C; Yushkevich, Paul A

    2015-12-01

    Deformable modeling with medial axis representation is a useful means of segmenting and parametrically describing the shape of anatomical structures in medical images. Continuous medial representation (cm-rep) is a "skeleton-first" approach to deformable medial modeling that explicitly parameterizes an object's medial axis and derives the object's boundary algorithmically. Although cm-rep has effectively been used to segment and model a number of anatomical structures with non-branching medial topologies, the framework is challenging to apply to objects with branching medial geometries since branch curves in the medial axis are difficult to parameterize. In this work, we demonstrate the first clinical application of a new "boundary-first" deformable medial modeling paradigm, wherein an object's boundary is explicitly described and constraints are imposed on boundary geometry to preserve the branching configuration of the medial axis during model deformation. This "boundary-first" framework is leveraged to segment and morphologically analyze the aortic valve apparatus in 3D echocardiographic images. Relative to manual tracing, segmentation with deformable medial modeling achieves a mean boundary error of 0.41 ± 0.10 mm (approximately one voxel) in 22 3DE images of normal aortic valves at systole. Deformable medial modeling is additionally demonstrated on pathological cases, including aortic stenosis, Marfan syndrome, and bicuspid aortic valve disease. This study demonstrates a promising approach for quantitative 3DE analysis of aortic valve morphology.

  9. Domain walls, domain wall transformations and structural changes in permalloy nanowires when subjected to current pulses

    Energy Technology Data Exchange (ETDEWEB)

    Hempe, E.M. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Department of Physics, Universitaet Regensburg, Universitaetsstrasse 31, 93040 Regensburg (Germany); Klaeui, M.; Krzyk, S.; Ruediger, U. [Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Kasama, T. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Backes, D. [Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Junginger, F. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Heyderman, L.J. [Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Dunin-Borkowski, R. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Center for Electron Nanoscopy, DTU (Denmark)

    2007-12-15

    We report the direct transmission electron microscopy observation of spin structure transformations in nanoscale Permalloy zigzag wires due to Joule heating during the injection of current pulses. This heating is sufficient to overcome the energy barriers separating the different metastable domain wall spin structures. Due to the large energy barriers these are stable and observable at room temperature by off-axis electron holography and Fresnel imaging. The interaction between different domain walls is probed and the main pinning mechanism is determined to be the edge roughness. In addition to transformations, we also report on thermally assisted domain wall hopping between two pinning sites and structural changes that occur when the samples are subjected to even higher current pulses. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Structural and Histochemical Alterations in the Aortic Valves of Elderly Patients: A Comparative Study of Aortic Stenosis, Aortic Regurgitation, and Normal Valves

    Science.gov (United States)

    Katoh, Hideki

    2016-01-01

    The aim of this study was to reveal the pathogenesis of aortic stenosis (AS) and regurgitation (AR) by comparing differences in mechanical and biochemical alterations. We applied scanning acoustic microscopy (SAM) to measure the speed of sound (SOS) through valves to estimate the elasticity and monitor sensitivity to protease treatment, as the SOS is correlated with the stiffness of materials, which is reduced after digestion by proteases. The fibrosa of both the AS and AR groups were stiffer than the fibrosa of the normal group. The AR group displayed significantly stiffer fibrosa than the AS group, with the exception of calcified areas. The AS group showed significantly decreased SOS values following protease digestion, whereas the AR showed little reduction. The AS group presented type III collagen in the fibrosa and the ventricularis. In the AR group, both type I collagen and type III collagen coexisted in the fibrosa and the ventricularis. Upon immunostaining for advanced glycation end-products, the AS group showed sparse, weak staining, whereas the AR group presented a strong, band-like positive reaction in the fibrosa. In conclusion, tissue remodelling associated with damage and repair is associated with AS pathogenesis, whereas static chemical alterations with slow collagen turnover induce AR. PMID:27747234

  11. Impact of modeling fluid-structure interaction in the computational analysis of aortic root biomechanics.

    Science.gov (United States)

    Sturla, Francesco; Votta, Emiliano; Stevanella, Marco; Conti, Carlo A; Redaelli, Alberto

    2013-12-01

    Numerical modeling can provide detailed and quantitative information on aortic root (AR) biomechanics, improving the understanding of AR complex pathophysiology and supporting the development of more effective clinical treatments. From this standpoint, fluid-structure interaction (FSI) models are currently the most exhaustive and potentially realistic computational tools. However, AR FSI modeling is extremely challenging and computationally expensive, due to the explicit simulation of coupled AR fluid dynamics and structural response, while accounting for complex morphological and mechanical features. We developed a novel FSI model of the physiological AR simulating its function throughout the entire cardiac cycle. The model includes an asymmetric MRI-based geometry, the description of aortic valve (AV) non-linear and anisotropic mechanical properties, and time-dependent blood pressures. By comparison to an equivalent finite element structural model, we quantified the balance between the extra information and the extra computational cost associated with the FSI approach. Tissue strains and stresses computed through the two approaches did not differ significantly. The FSI approach better captured the fast AV opening and closure, and its interplay with blood fluid dynamics within the Valsalva sinuses. It also reproduced the main features of in vivo AR fluid dynamics. However, the FSI simulation was ten times more computationally demanding than its structural counterpart. Hence, the FSI approach may be worth the extra computational cost when the tackled scenarios are strongly dependent on AV transient dynamics, Valsalva sinuses fluid dynamics in relation to coronary perfusion (e.g. sparing techniques), or AR fluid dynamic alterations (e.g. bicuspid AV).

  12. Static and dynamic buckling of thin-walled plate structures

    CERN Document Server

    Kubiak, Tomasz

    2013-01-01

    This monograph deals with buckling and postbuckling behavior of thin plates and thin-walled structures with flat wall subjected to static and dynamic load. The investigations are carried out in elastic range. The basic assumption here is the  thin plate theory. This method is used to determination the buckling load and postbuckling analysis of thin-walled structures subjected to static and dynamic load. The book introduces two methods for static and dynamic buckling investigation which allow for a wider understanding of the phenomenon. Two different methods also can allow uncoupling of the phenomena occurring at the same time and attempt to estimate their impact on the final result. A general mathematical model, adopted in proposed analytical-numerical method, enables the consideration of all types of stability loss i.e.local, global and interactive forms of buckling. The applied numerical-numerical method includes adjacent of walls, shear-lag phenomenon and a deplanation of cross-sections.

  13. Post-stenotic aortic dilatation

    Directory of Open Access Journals (Sweden)

    Jahangiri Marjan

    2006-03-01

    Full Text Available Abstract Aortic stenosis is the most common valvular heart disease affecting up to 4% of the elderly population. It can be associated with dilatation of the ascending aorta and subsequent dissection. Post-stenotic dilatation is seen in patients with AS and/or aortic regurgitation, patients with a haemodynamically normal bicuspid aortic valve and following aortic valve replacement. Controversy exists as to whether to replace the aortic root and ascending aorta at the time of aortic valve replacement, an operation that potentially carries a higher morbidity and mortality. The aetiology of post-stenotic aortic dilatation remains controversial. It may be due to haemodynamic factors caused by a stenotic valve, involving high velocity and turbulent flow downstream of the stenosis, or due to intrinsic pathology of the aortic wall. This may involve an abnormality in the process of extracellular matrix remodelling in the aortic wall including inadequate synthesis, degradation and transport of extracellular matrix proteins. This article reviews the aetiology, pathology and management of patients with post-stenotic aortic dilatation.

  14. Thick-walled carbon composite multifunctional structures

    Science.gov (United States)

    Haake, John M.; Jacobs, Jack H.; McIlroy, Bruce E.

    1997-06-01

    Satellite programs are moving in the direction of smaller and lighter structures. Technological advances have permitted more sophisticated equipment to be consolidated into compact spaces. Micro-satellites, between 10 and 100 kg, will incorporate micro-electric devices into the lay-up of the satellite structure. These structures will be designed to carry load, provide thermal control, enhance damping, and include integrated passive electronics. These multifunctional structures offer lighter weight, reduced volume, and a 'smarter' overall package for incorporation of sensors, electronics, fiber optics, powered appendages or active components. McDonnell Douglas Corporation (MDC) has applied technology from the synthesis and processing of intelligent cost effective structures (SPICES) and independent research and development (IRAD) programs to the modular instrument support system (MISS) for multifunctional space structures and micro-satellites. The SPICES program was funded by the Defense Advanced Research Projects Agency (DARPA) to develop affordable manufacturing processes for smart materials to be used in vibration control, and the MISS program was funded by NASA-Langley. The MISS program was conceived to develop concepts and techniques to make connections between different multifunctional structures. MDA fabricated a trapezoidal carbon composite structure out of IM7/977-3 tape prepreg. Flex circuits, thermal and optical conduits were embedded to realize a utility modular connector. These provide electrical, thermal, optical and mechanical connections between micro- satellite components. A quick disconnect mount was also developed to accommodate a variety of devices such as solar arrays, power sources, thermal transfer and vibration control modules.

  15. Ultrasound Evaluation of an Abdominal Aortic Fluid-Structure Interaction Model

    DEFF Research Database (Denmark)

    Traberg, Marie Sand; Jensen, Jørgen Arendt

    2014-01-01

    Ultrasound measurements are used for evaluating biomechanics of the abdominal aorta (AA) predicted by a fluid- structure interaction (FSI) simulation model. FSI simulation models describe the complete arterial physiology by quantify- ing the mechanical response in the vessel wall caused by the pe......Ultrasound measurements are used for evaluating biomechanics of the abdominal aorta (AA) predicted by a fluid- structure interaction (FSI) simulation model. FSI simulation models describe the complete arterial physiology by quantify- ing the mechanical response in the vessel wall caused...... by the percolating pulsating blood. But the predictability of FSI models needs validation for these to be usable for diagnostic purposes. Ultrasound measurements are suitable for such an evaluation as the wall displacement can be measured in vivo and compared to the wall displacement simulated in the FSI model....... Spectral Doppler velocity data from 3 healthy male volunteers were used to construct inlet profiles for the FSI model. Simultaneously, wall movement was tracked and used for comparison to FSI model results. Ultrasound data were acquired using a scanner equipped with a research interface. The wall...

  16. Shear-layer structures in near-wall turbulence

    Science.gov (United States)

    Johansson, A. V.; Alfredsson, P. H.; Kim, J.

    1987-01-01

    The structure of internal shear layer observed in the near-wall region of turbulent flows is investigated by analyzing flow fields obtained from numerical simulations of channel and boundary-layer flows. It is found that the shear layer is an important contributor to the turbulence production. The conditionally averaged production at the center of the structure was almost twice as large as the long-time mean value. The shear-layer structure is also found to retain its coherence over streamwise distances on the order of a thousand viscous length units, and propagates with a constant velocity of about 10.6 u sub rho throughout the near wall region.

  17. Domain and wall structures in films with helical magnetization profile

    Energy Technology Data Exchange (ETDEWEB)

    Dubuget, Vincent [Laboratoire d' Electrodynamique des Materiaux Avances, Universite Francois Rabelais, CNRS UMR 6157, Parc de Grandmont, F-37200 Tours (France); CEA, DAM, Le Ripault, F-37260 Monts (France); Thiaville, Andre [Laboratoire de Physique des Solides, Universite Paris-Sud, CNRS UMR 8502, Bat. 510, F-91405 Orsay (France); Adenot-Engelvin, Anne-Lise, E-mail: anne-lise.adenot-engelvin@cea.f [CEA, DAM, Le Ripault, F-37260 Monts (France); Duverger, Francois; Dubourg, Sebastien [CEA, DAM, Le Ripault, F-37260 Monts (France)

    2011-06-15

    We study soft magnetic bilayers having orthogonal, in-plane easy axes. The layers are thicker than the Bloch wall width linked to the anisotropy, so that a helical magnetization with a large angle exists across the sample thickness. The magnetic domains structure has been investigated at both sample surfaces, using magneto-optical microscopy. The domain structure is found to be similar to that of double films with biquadratic coupling. Two kinds of domain walls are identified, namely with a 90{sup o} and 180{sup o} rotation of the average magnetization. The detailed structure and energy of these walls are studied by micromagnetic calculations. - Research highlights: This paper is devoted to the peculiar domain structure resulting from an anisotropy distribution in the thickness of the sample, realized through specific elaboration conditions. The helical magnetization profile obtained leads to a complex dynamic behaviour described and modelled in Phys.Rev. B 80, 134412 (published in October 2009) which has been already cited three times. This paper sheds light on of the demagnetized state of such samples: a variety of domains structure has been observed by Kerr microscopy, under various saturation fields. The most striking conclusion is driven by the analysis of the magnetization process which implies the co-existence of two types of domain walls in the sample, with four possible directions for the mean magnetization. The magnetization profile of the two walls has been confirmed by numerical simulation.

  18. Seismic strengthening of RC structures with exterior shear walls

    Indian Academy of Sciences (India)

    Hasan Kaplan; Salih Yilmaz; Nihat Cetinkaya; Ergin Atimtay

    2011-02-01

    Vulnerable buildings and their rehabilitation are important problems for earthquake regions. In recent decades the goal of building rehabilitation and strengthening has gained research attention and numerous techniques have been developed to achieve this. However, most of these strengthening techniques disturb the occupants, who must vacate the building during renovation. In this study, a new strengthening alternative for RC structures, namely exterior shear walls, has been experimentally investigated under reversed cyclic loading. Using the proposed technique, it is possible to strengthen structures without disturbing their users or vacating the building during renovation. In this technique, shear walls are installed in parallel to the building’s exterior sides. It has been observed that the usage of exterior shear walls considerably improve the capacity and sway stiffness of RC structures. The experimental results have also been compared and found to be in agreement with the numerical solutions. Post attached exterior shear walls behaved as a monolithic member of the structure. Design considerations for the exterior shear wall-strengthened buildings have also been discussed in the paper.

  19. Structure of ductile iron in thin walled castings

    Directory of Open Access Journals (Sweden)

    M. Górny

    2007-12-01

    Full Text Available It this work it has been shown that it is possible to produce thin wall ductile iron (TWDI castings with considerably length using Archimedes spiral with wall thickness of 1, 2 and 3 mm. Inmould technique was used to produce TWDI. It has been estimated castability and metallographic investigations were made using different moulding materials. From castability measurements result that it is possible to obtain thin wall ductile iron castings with wall thickness down to 1 mm with castability of 200 mm. Using mould with small ability to absorb heat castability increases twice. At wall thickness equal 3 mm castability reaches 1000 mm and using LDASC sand its value increases to over 1500 mm. Structure parameters for different wall thickness and moulding materials (graphite nodule count, ferrite and cementite fraction are plotted versus distance from the beginning of spiral. It is shown strong influence of LDASC sand (material with small ability to absorb heat on structure parameters (NF, Vf i VC revealing gradient character of TWDI.

  20. Method and apparatus for constructing an underground barrier wall structure

    Science.gov (United States)

    Dwyer, Brian P.; Stewart, Willis E.; Dwyer, Stephen F.

    2002-01-01

    A method and apparatus for constructing a underground barrier wall structure using a jet grout injector subassembly comprising a pair of primary nozzles and a plurality of secondary nozzles, the secondary nozzles having a smaller diameter than the primary nozzles, for injecting grout in directions other than the primary direction, which creates a barrier wall panel having a substantially uniform wall thickess. This invention addresses the problem of the weak "bow-tie" shape that is formed during conventional jet injection when using only a pair of primary nozzles. The improvement is accomplished by using at least four secondary nozzles, of smaller diameter, located on both sides of the primary nozzles. These additional secondary nozzles spray grout or permeable reactive materials in other directions optimized to fill in the thin regions of the bow-tie shape. The result is a panel with increased strength and substantially uniform wall thickness.

  1. CT of thoracic aortic aneurysms.

    Science.gov (United States)

    Posniak, H V; Olson, M C; Demos, T C; Benjoya, R A; Marsan, R E

    1990-09-01

    Aneurysms of the thoracic aorta are most often the result of arteriosclerotic disease. Other causes include degeneration of the medial layer of the aortic wall, either idiopathically or due to genetic disorders such as Marfan syndrome; aortic dissection; trauma; syphilis and other bacterial infection; noninfective aortitis; and congenital anomaly. We review normal anatomy of the aorta and discuss our technique and interpretation of computed tomography (CT) in the evaluation of the thoracic aorta. We illustrate the CT appearance of different types of aortic aneurysms as well as discuss the use of CT for assessing complications of aneurysms, for postoperative follow-up, and in the differentiation of aortic aneurysm from a paraaortic mass.

  2. Primary Cell Wall Structure in the Evolution of Land Plants

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Investigation of the primary cell walls of lower plants improves our understanding of the cell biology of these organisms but also has the potential to improve our understanding of cell wall structure and function in angiosperms that evolved from lower plants. Cell walls were prepared from eight species, ranging from a moss to advanced gymnosperms, and subjected to sequential chemical extraction to separate the main polysaccharide fractions. The glycosyl compositions of these fractions were then determined by gas chromatography. The results were compared among the eight plants and among data from related studies reported in the existing published reports to identify structural features that have been either highly conserved or clearly modified during evolution. Among the highly conserved features are the presence of a cellulose framework, the presence of certain hemicelluloses such as xyloglucan, and the presence of rhamnogalacturonan Ⅱ, a domain in pectic polysaccharides. Among the modified features are the abundance of mannosyl-containing hemicelluloses and the presence of methylated sugars.

  3. Cell wall structure and function in lactic acid bacteria.

    Science.gov (United States)

    Chapot-Chartier, Marie-Pierre; Kulakauskas, Saulius

    2014-08-29

    The cell wall of Gram-positive bacteria is a complex assemblage of glycopolymers and proteins. It consists of a thick peptidoglycan sacculus that surrounds the cytoplasmic membrane and that is decorated with teichoic acids, polysaccharides, and proteins. It plays a major role in bacterial physiology since it maintains cell shape and integrity during growth and division; in addition, it acts as the interface between the bacterium and its environment. Lactic acid bacteria (LAB) are traditionally and widely used to ferment food, and they are also the subject of more and more research because of their potential health-related benefits. It is now recognized that understanding the composition, structure, and properties of LAB cell walls is a crucial part of developing technological and health applications using these bacteria. In this review, we examine the different components of the Gram-positive cell wall: peptidoglycan, teichoic acids, polysaccharides, and proteins. We present recent findings regarding the structure and function of these complex compounds, results that have emerged thanks to the tandem development of structural analysis and whole genome sequencing. Although general structures and biosynthesis pathways are conserved among Gram-positive bacteria, studies have revealed that LAB cell walls demonstrate unique properties; these studies have yielded some notable, fundamental, and novel findings. Given the potential of this research to contribute to future applied strategies, in our discussion of the role played by cell wall components in LAB physiology, we pay special attention to the mechanisms controlling bacterial autolysis, bacterial sensitivity to bacteriophages and the mechanisms underlying interactions between probiotic bacteria and their hosts.

  4. Effect of age on aortic atherosclerosis

    Institute of Scientific and Technical Information of China (English)

    Michael A. Chen; Miwa Kawakubo; Patrick M. Colletti; Dongxiang Xu; Laurie LaBree Dustin; Robert Detrano; Stanley P Azen; Nathan D. Wong; Xue-Qiao Zhao

    2013-01-01

    Objective To examine the association of atherosclerosis burden in the survivors of an asymptomatic elderly cohort study and its relationship to other coronary risk factors (specifically, age) by evaluating aortic atherosclerotic wall burden by magnetic resonance imaging (MRI). Methods A total of 312 participants in an ongoing observational cohort study underwent cardiac and descending thoracic aorta imaging by MRI. Maximum wall thickness was measured and the mean wall thickness calculated. Wall/outer wall ratio was used as a normalized wall index (NWI) adjusted for artery size difference among participants. Percent wall volume (PWV) was calculated as NWI × 100. Results In this asymptomatic cohort (mean age: 76 years), the mean (SD) aortic wall area and wall thickness were 222 ± 45 mm2 and 2.7 ± 0.4 mm, respectively. Maximum wall thickness was 3.4 ± 0.6 mm, and PWV was 32% ± 4%. Women appeared to have smaller wall area, but after correcting for their smaller artery size, had significantly higher PWV than men (P = 0.03). Older age was associated with larger wall area (P = 0.04 for trend) with similar PWVs. However, there were no statistically significant associations between standard risk factors, Framingham global risk, or metabolic syndrome status, therapy for cholesterol or hypertension, coronary or aortic calcium score, and the aortic wall burden. Aortic calcification was associated with coronary calcification. Conclusions Asymptomatic elderly in this cohort had a greater descending thoracic aortic wall volume that correlated with age, and women had a significantly increased PWV compared to men. In these survivors, the atherosclerotic aortic wall burden was not significantly associated with traditional risk factors or with coronary or aortic calcium scores or coronary calcium progression. Results suggest that age, or as yet unidentified risk factor(s), may be responsible for the increase in atherosclerosis.

  5. SSI response of a typical shear wall structure. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, J.J.; Schewe, E.C.; Maslenikov, O.R.

    1984-04-01

    The Simplified Methods project of the US NRC-funded Seismic Safety Margins Research Program (SSMRP) has as its goal the development of a methodology to perform routine seismic probabilistic risk assessments of commercial nuclear power plants. The study reported here develops calibration factors to relate best estimate response to design values accounting for approximations and simplifications in SSI analysis procedures. Nineteen cases were analyzed and in-structure response compared. The structure of interest was a typical shear wall structure. 6 references, 44 figures, 22 tables.

  6. Effect of transverse aortic constriction on cardiac structure, function and gene expression in pregnant rats.

    Directory of Open Access Journals (Sweden)

    Nils Thomas Songstad

    Full Text Available BACKGROUND: There is an increased risk of heart failure and pulmonary edema in pregnancies complicated by hypertensive disorders. However, in a previous study we found that pregnancy protects against fibrosis and preserves angiogenesis in a rat model of angiotensin II induced cardiac hypertrophy. In this study we test the hypothesis that pregnancy protects against negative effects of increased afterload. METHODS: Pregnant (gestational day 5.5-8.5 and non-pregnant Wistar rats were randomized to transverse aortic constriction (TAC or sham surgery. After 14.2 ± 0.14 days echocardiography was performed. Aortic blood pressure and left ventricular (LV pressure-volume loops were obtained using a conductance catheter. LV collagen content and cardiomyocyte circumference were measured. Myocardial gene expression was assessed by real-time polymerase chain reaction. RESULTS: Heart weight was increased by TAC (p<0.001 but not by pregnancy. Cardiac myocyte circumference was larger in pregnant compared to non-pregnant rats independent of TAC (p = 0.01, however TAC per se did not affect this parameter. Collagen content in LV myocardium was not affected by pregnancy or TAC. TAC increased stroke work more in pregnant rats (34.1 ± 2.4 vs 17.5 ± 2.4 mmHg/mL, p<0.001 than in non-pregnant (28.2 ± 1.7 vs 20.9 ± 1.5 mmHg/mL, p = 0.06. However, it did not lead to overt heart failure in any group. In pregnant rats, α-MHC gene expression was reduced by TAC. Increased in the expression of β-MHC gene was higher in pregnant (5-fold compared to non-pregnant rats (2-fold after TAC (p = 0.001. Nine out of the 19 genes related to cardiac remodeling were affected by pregnancy independent of TAC. CONCLUSIONS: This study did not support the hypothesis that pregnancy is cardioprotective against the negative effects of increased afterload. Some differences in cardiac structure, function and gene expression between pregnant and non-pregnant rats following TAC indicated that

  7. Biomechanical implications of excessive endograft protrusion into the aortic arch after thoracic endovascular repair.

    Science.gov (United States)

    Rinaudo, Antonino; Raffa, Giuseppe Maria; Scardulla, Francesco; Pilato, Michele; Scardulla, Cesare; Pasta, Salvatore

    2015-11-01

    Endografts placed in the aorta for thoracic endovascular aortic repair (TEVAR) may determine malappositioning to the lesser curvature of the aortic wall, thus resulting in a devastating complication known as endograft collapse. This premature device failure commonly occurs in young individuals after TEVAR for traumatic aortic injuries as a result of applications outside the physical conditions for which the endograft was designed. In this study, an experimentally-calibrated fluid-structure interaction (FSI) model was developed to assess the hemodynamic and stress/strain distributions acting on the excessive protrusion extension (PE) of endografts deployed in four young patients underwent TEVAR. Endograft infolding was experimentally measured for different hemodynamic scenarios by perfusion testing and then used to numerically calibrate the mechanical behavior of endograft PE. Results evinced that the extent of endograft can severely alter the hemodynamic and structural loads exerted on the endograft PE. Specifically, PE determined a physiological aortic coarctation into the aortic arch characterized by a helical flow in the distal descending aorta. High device displacement and transmural pressure across the stent-graft wall were found for a PE longer than 21 mm. Finally, marked intramural stress and principal strain distributions on the protruded segment of the endograft wall may suggest failure due to material fatigue. These critical parameters may contribute to the endograft collapse observed clinically and can be used to design new devices more suitable for young individuals to be treated with an endoprosthesis for TEVAR of blunt traumatic aortic injuries.

  8. Stent graft implantation in an aortic pseudoaneurysm associated with a fractured Cheatham-Platinum stent in aortic coarctation.

    Science.gov (United States)

    Kuhelj, Dimitrij; Berden, Pavel; Podnar, Tomaž

    2016-03-01

    We report a case of aortic pseudoaneurysm associated with a fractured bare Cheatham-Platinum stent following stenting for aortic coarctation. These complications were recognised 6 years after the implantation procedure and were successfully managed by percutaneous stent graft implantation. Staged approach for stent dilatation might prevent development of aortic pseudoaneurysms. In addition, careful follow-up is warranted after stenting for aortic coarctation, particularly in patients with recognised aortic wall injury.

  9. EXPRESSION OF MATRIX METALLOPROTEINASE-9 IN HUMANABDOMINAL AORTIC ANEURYSMAL TISSUES

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Abdominal aortic aneuryzms(AAAs)are char-acterized by the degradation of structural proteins,including both collagen and elastin and remodelingof the extracellular matrix(ECM).The matrixmetalloproteinases(MMPs)are responsible for col-lagen and elastin degradation withinthe aortic wall.Up to date,14MMPs have beenidentified.Amongthem,in particular,MMP-9(92-kDtypeⅣcolla-genase)shows strong elastinolytic activity[1].Recentstudies showedthat elevated plasmalevel of MMP-9wasassociated with AAAs,i mplicating its p...

  10. Clinical trial of doxycycline for matrix metalloproteinase-9 inhibition in patients with an abdominal aneurysm doxycycline selectively depletes aortic wall neutrophils and cytotoxic t cells

    NARCIS (Netherlands)

    Lindeman, J.H.N.; Abdul-Hussien, H.; Bockel, J.H. van; Wolterbeek, R.; Kleemann, R.

    2009-01-01

    Background-Doxycycline has been shown to effectively inhibit aneurysm formation in animal models of abdominal aortic aneurysm. Although this effect is ascribed to matrix metalloproteinase-9 inhibition, such an effect is unclear in human studies. We reevaluated the effect of doxycycline on aortic wal

  11. Airway wall stiffening increases peak wall shear stress: a fluid-structure interaction study in rigid and compliant airways.

    Science.gov (United States)

    Xia, Guohua; Tawhai, Merryn H; Hoffman, Eric A; Lin, Ching-Long

    2010-05-01

    The airflow characteristics in a computed tomography (CT) based human airway bifurcation model with rigid and compliant walls are investigated numerically. An in-house three-dimensional (3D) fluid-structure interaction (FSI) method is applied to simulate the flow at different Reynolds numbers and airway wall stiffness. As the Reynolds number increases, the airway wall deformation increases and the secondary flow becomes more prominent. It is found that the peak wall shear stress on the rigid airway wall can be five times stronger than that on the compliant airway wall. When adding tethering forces to the model, we find that these forces, which produce larger airway deformation than without tethering, lead to more skewed velocity profiles in the lower branches and further reduced wall shear stresses via a larger airway lumen. This implies that pathologic changes in the lung such as fibrosis or remodeling of the airway wall-both of which can serve to restrain airway wall motion-have the potential to increase wall shear stress and thus can form a positive feed-back loop for the development of altered flow profiles and airway remodeling. These observations are particularly interesting as we try to understand flow and structural changes seen in, for instance, asthma, emphysema, cystic fibrosis, and interstitial lung disease.

  12. Aortic Wave Dynamics and Its Influence on Left Ventricular Workload

    Science.gov (United States)

    Pahlevan, Niema; Gharib, Morteza

    2010-11-01

    Clinical and epidemiologic studies have shown that hypertension plays a key role in development of left ventricular (LV) hypertrophy and ultimately heart failure mostly due to increased LV workload. Therefore, it is crucial to diagnose and treat abnormal high LV workload at early stages. The pumping mechanism of the heart is pulsatile, thus it sends pressure and flow wave into the compliant aorta. The wave dynamics in the aorta is dominated by interplay of heart rate (HR), aortic rigidity, and location of reflection sites. We hypothesized that for a fixed cardiac output (CO) and peripheral resistance (PR), interplay of HR and aortic compliance can create conditions that minimize LV power requirement. We used a computational approach to test our hypothesis. Finite element method with direct coupling method of fluid-structure interaction (FSI) was used. Blood was assumed to be incompressible Newtonian fluid and aortic wall was considered elastic isotropic. Simulations were performed for various heart rates and aortic rigidities while inflow wave, CO, and PR were kept constant. For any aortic compliance, LV power requirement becomes minimal at a specific heart rate. The minimum shifts to higher heart rates as aortic rigidity increases.

  13. Electromagnetic simulation study of dielectric wall accelerator structures

    Institute of Scientific and Technical Information of China (English)

    ZHAO Quan-Tang; ZHANG Zi-Min; YUAN Ping; CAO Shu-Chun; SHEN Xiao-Kang; JING Yi; LIU Ming; ZHAO Hong-Wei

    2012-01-01

    Two types of dielectric wall accelerator (DWA) structures,a bi-polar Blumlein line and zero integral pulse line (ZIP) structures were investigated.The high gradient insulator simulated by the particle in cell code confirms that it has little influence on the axial electric field.The results of simulations using CST microwave studio indicate how the axial electric field is formed,and the electric field waveforms agree with the theoretical one very well.The influence of layer-to-layer coupling in a ZIP structure is much smaller and the electric field waveform is much better.The axial of the Blumlein structure's electric field has better axial stability.From both of the above,it found that for a shorter pulse width,the axial electric field is much higher and the pulse stability and fidelity are much better.The CST simulation is very helpful for designing DWA structures.

  14. Fluid-Structure Interaction Study of Transcatheter Aortic Valve Dynamics Using Smoothed Particle Hydrodynamics.

    Science.gov (United States)

    Mao, Wenbin; Li, Kewei; Sun, Wei

    2016-12-01

    Computational modeling of heart valve dynamics incorporating both fluid dynamics and valve structural responses has been challenging. In this study, we developed a novel fully-coupled fluid-structure interaction (FSI) model using smoothed particle hydrodynamics (SPH). A previously developed nonlinear finite element (FE) model of transcatheter aortic valves (TAV) was utilized to couple with SPH to simulate valve leaflet dynamics throughout the entire cardiac cycle. Comparative simulations were performed to investigate the impact of using FE-only models vs. FSI models, as well as an isotropic vs. an anisotropic leaflet material model in TAV simulations. From the results, substantial differences in leaflet kinematics between FE-only and FSI models were observed, and the FSI model could capture the realistic leaflet dynamic deformation due to its more accurate spatial and temporal loading conditions imposed on the leaflets. The stress and the strain distributions were similar between the FE and FSI simulations. However, the peak stresses were different due to the water hammer effect induced by the fluid inertia in the FSI model during the closing phase, which led to 13-28% lower peak stresses in the FE-only model compared to that of the FSI model. The simulation results also indicated that tissue anisotropy had a minor impact on hemodynamics of the valve. However, a lower tissue stiffness in the radial direction of the leaflets could reduce the leaflet peak stress caused by the water hammer effect. It is hoped that the developed FSI models can serve as an effective tool to better assess valve dynamics and optimize next generation TAV designs.

  15. 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.

  16. Stress analysis for wall structure in mobile hot cell design

    Energy Technology Data Exchange (ETDEWEB)

    Bahrin, Muhammad Hannan, E-mail: hannan@nuclearmalaysia.gov.my; Rahman, Anwar Abdul, E-mail: anwar@nuclearmalaysia.gov.my; Hamzah, Mohd Arif, E-mail: arif@nuclearmalaysia.gov.my; Mamat, Mohd Rizal; Azman, Azraf; Hasan, Hasni [Prototype and Plant Development Centre, Technical Services Division, Malaysian Nuclear Agency (Malaysia)

    2016-01-22

    Malaysian Nuclear Agency is developing a Mobile Hot Cell (MHC) in order to handle and manage Spent High Activity Radioactive Sources (SHARS) such as teletherapy heads and irradiators. At present, there are only two units of MHC in the world, in South Africa and China. Malaysian Mobile Hot cell is developed by Malaysian Nuclear Agency with the assistance of IAEA expert, based on the design of South Africa and China, but with improved features. Stress analysis has been performed on the design in order to fulfil the safety requirement in operation of MHC. This paper discusses the loading analysis effect from the sand to the MHC wall structure.

  17. Electronic structure of multi-walled carbon fullerenes

    Science.gov (United States)

    Doore, Keith; Cook, Matthew; Clausen, Eric; Lukashev, Pavel V.; Kidd, Tim E.; Stollenwerk, Andrew J.

    2017-02-01

    Despite an enormous amount of research on carbon based nanostructures, relatively little is known about the electronic structure of multi-walled carbon fullerenes, also known as carbon onions. In part, this is due to the very high computational expense involved in estimating electronic structure of large molecules. At the same time, experimentally, the exact crystal structure of the carbon onion is usually unknown, and therefore one relies on qualitative arguments only. In this work we present the results of a computational study on a series of multi-walled fullerenes and compare their electronic structures to experimental data. Experimentally, the carbon onions were fabricated using ultrasonic agitation of isopropanol alcohol and deposited onto the surface of highly ordered pyrolytic graphite using a drop cast method. Scanning tunneling microscopy images indicate that the carbon onions produced using this technique are ellipsoidal with dimensions on the order of 10 nm. The majority of differential tunneling spectra acquired on individual carbon onions are similar to that of graphite with the addition of molecular-like peaks, indicating that these particles span the transition between molecules and bulk crystals. A smaller, yet sizable number exhibited a semiconducting gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels. These results are compared with the electronic structure of different carbon onion configurations calculated using first-principles. Similar to the experimental results, the majority of these configurations are metallic with a minority behaving as semiconductors. Analysis of the configurations investigated here reveals that each carbon onion exhibiting an energy band gap consisted only of non-metallic fullerene layers, indicating that the interlayer interaction is not significant enough to affect the total density of states in these structures.

  18. Developmental programming of aortic and renal structure in offspring of rats fed fat-rich diets in pregnancy

    DEFF Research Database (Denmark)

    Armitage, James A.; Lakasing, Lorin; Taylor, Paul D.

    2005-01-01

    programmes the development of increased blood pressure, insulin resistance, dyslipidaemia, obesity and mesenteric artery endothelial dysfunction in adult offspring. To further characterize the mechanism of hypertension in this model we have examined vascular and renal structure in adult offspring of Sprague......-Dawley rats fed a control diet (OC) or lard-rich diet (OHF) during pregnancy and suckling followed by a control diet post-weaning. To gain further insight, we assessed aortic reactivity and elasticity in an organ bath preparation and renal renin and Na+,K+-ATPase activity. Plasma aldosterone concentration...

  19. Heterotic domain wall solutions and SU(3) structure manifolds

    CERN Document Server

    Gray, James; Lust, Dieter

    2012-01-01

    We examine compactifications of heterotic string theory on manifolds with SU(3) structure. In particular, we study N = 1/2 domain wall solutions which correspond to the perturbative vacua of the 4D, N =1 supersymmetric theories associated to these compactifications. We extend work which has appeared previously in the literature in two important regards. Firstly, we include two additional fluxes which have been, heretofore, omitted in the general analysis of this situation. This allows for solutions with more general torsion classes than have previously been found. Secondly, we provide explicit solutions for the fluxes as a function of the torsion classes. These solutions are particularly useful in deciding whether equations such as the Bianchi identities can be solved, in addition to the Killing spinor equations themselves. Our work can be used to straightforwardly decide whether any given SU(3) structure on a six-dimensional manifold is associated with a solution to heterotic string theory. To illustrate how...

  20. Aortic biomechanics in hypertrophic cardiomyopathy

    Science.gov (United States)

    Badran, Hala Mahfouz; Soltan, Ghada; Faheem, Nagla; Elnoamany, Mohamed Fahmy; Tawfik, Mohamed; Yacoub, Magdi

    2015-01-01

    Background: Ventricular-vascular coupling is an important phenomenon in many cardiovascular diseases. The association between aortic mechanical dysfunction and left ventricular (LV) dysfunction is well characterized in many disease entities, but no data are available on how these changes are related in hypertrophic cardiomyopathy (HCM). Aim of the work: This study examined whether HCM alone is associated with an impaired aortic mechanical function in patients without cardiovascular risk factors and the relation of these changes, if any, to LV deformation and cardiac phenotype. Methods: 141 patients with HCM were recruited and compared to 66 age- and sex-matched healthy subjects as control group. Pulse pressure, aortic strain, stiffness and distensibility were calculated from the aortic diameters measured by M-mode echocardiography and blood pressure obtained by sphygmomanometer. Aortic wall systolic and diastolic velocities were measured using pulsed wave Doppler tissue imaging (DTI). Cardiac assessment included geometric parameters and myocardial deformation (strain and strain rate) and mechanical dyssynchrony. Results: The pulsatile change in the aortic diameter, distensibility and aortic wall systolic velocity (AWS') were significantly decreased and aortic stiffness index was increased in HCM compared to control (P < .001) In HCM AWS' was inversely correlated to age(r = − .32, P < .0001), MWT (r = − .22, P < .008), LVMI (r = − .20, P < .02), E/Ea (r = − .16, P < .03) LVOT gradient (r = − 19, P < .02) and severity of mitral regurg (r = − .18, P < .03) but not to the concealed LV deformation abnormalities or mechanical dyssynchrony. On multivariate analysis, the key determinant of aortic stiffness was LV mass index and LVOT obstruction while the role LV dysfunction in aortic stiffness is not evident in this population. Conclusion: HCM is associated with abnormal aortic mechanical properties. The severity of cardiac

  1. Single-Walled Carbon-Nanotubes-Based Organic Memory Structures

    Directory of Open Access Journals (Sweden)

    Sundes Fakher

    2016-09-01

    Full Text Available The electrical behaviour of organic memory structures, based on single-walled carbon-nanotubes (SWCNTs, metal–insulator–semiconductor (MIS and thin film transistor (TFT structures, using poly(methyl methacrylate (PMMA as the gate dielectric, are reported. The drain and source electrodes were fabricated by evaporating 50 nm gold, and the gate electrode was made from 50 nm-evaporated aluminium on a clean glass substrate. Thin films of SWCNTs, embedded within the insulating layer, were used as the floating gate. SWCNTs-based memory devices exhibited clear hysteresis in their electrical characteristics (capacitance–voltage (C–V for MIS structures, as well as output and transfer characteristics for transistors. Both structures were shown to produce reliable and large memory windows by virtue of high capacity and reduced charge leakage. The hysteresis in the output and transfer characteristics, the shifts in the threshold voltage of the transfer characteristics, and the flat-band voltage shift in the MIS structures were attributed to the charging and discharging of the SWCNTs floating gate. Under an appropriate gate bias (1 s pulses, the floating gate is charged and discharged, resulting in significant threshold voltage shifts. Pulses as low as 1 V resulted in clear write and erase states.

  2. The Structure of Plant Cell Walls: II. The Hemicellulose of the Walls of Suspension-cultured Sycamore Cells.

    Science.gov (United States)

    Bauer, W D; Talmadge, K W; Keegstra, K; Albersheim, P

    1973-01-01

    The molecular structure, chemical properties, and biological function of the xyloglucan polysaccharide isolated from cell walls of suspension-cultured sycamore (Acer pseudoplatanus) cells are described. The sycamore wall xyloglucan is compared to the extracellular xyloglucan secreted by suspension-cultured sycamore cells into their culture medium and is also compared to the seed "amyloid" xyloglucans.Xyloglucan-or fragments of xyloglucan-and acidic fragments of the pectic polysaccharides are released from endopolygalacturonase-pretreated sycamore walls by treatment of these walls with 8 m urea, endoglucanase, or 0.5 n NaOH. Some of the xyloglucan thus released is found to cochromatograph with the acidic pectic fragments on diethylaminoethyl Sephadex. The chemical or enzymic treatments required for the release of xyloglucan from the walls and the cochromatography of xyloglucan with the acidic pectic fragments indicate that xyloglucan is covalently linked to the pectic polysaccharides and is noncovalently bound to the cellulose fibrils of the sycamore cell wall.The molecular structure of sycamore xyloglucan was characterized by methylation analysis of the oligosaccharides obtained by endoglucanase treatment of the polymer. The structure of the polymer is based on a repeating heptasaccharide unit which consists of 4 residues of beta-1-4-linked glucose and 3 residues of terminal xylose. A single xylose residue is glycosidically linked to carbon 6 of 3 of the glucosyl residues.

  3. Active stabilization of thin-wall structures under compressive loading

    Science.gov (United States)

    Welham, Jared; Calius, Emilio P.; Chase, J. Geoffrey

    2003-08-01

    The active suppression of elastic buckling instability has the potential to significantly increase the effective strength of thin-wall structures. Despite all the interest in smart structures, the active suppression of buckling has received comparatively little attention. This paper addresses the effects of embedded actuation on the compression buckling strength of laminated composite plates through analysis and simulation. Numerical models are formulated that include the influence of essential features such as sensor uncertainty and noise, actuator saturation and control architecture on the buckling process. Silicon-based strain sensors and diffuse laser distance sensors are both considered for use in the detection of incipient buckling behavior due to their increased sensitivity. Actuation is provided by paired distributions of piezo-electric material incorporated into both sides of the laminate. Optimal controllers are designed to command the structure to deform in ways that interfere with the development of buckling mode shapes. Commercial software packages are used to solve the resulting non-linear equations, and some of the tradeoffs are enumerated. Overall, the results show that active buckling control can considerably enhance resistance to instability under compressive loads. These buckling load predictions demonstrate the viability of optimal control and piezo-electric actuation for implementing active buckling control. Due to the importance of early detection, the relative effectiveness of active buckling control is shown to be strongly dependent on the performance of the sensing scheme, as well as on the characteristics of the structure.

  4. Experimental Study and Numerical Simulation of Hypervelocity Projectile Impact on Double-Wall Structure

    Institute of Scientific and Technical Information of China (English)

    陈沿海; 张庆明; 黄风雷

    2004-01-01

    Tests of hypervelocity projectile impact on double-wall structure were performed with the front wall ranging from 0.5 mm to 2.0 mm thick and different impact velocities. Smooth particle hydrodynamics (SPH) code in LS-DYNA was employed for the simulation of hypervelocity impact on the double-wall structure. By using elementary shock wave theory, the experimental results above are analyzed. The analysis can provide an explanation for the penetration mechanism of hypervelocity projectile impact on double-wall structure about the effect of front wall thickness and impact velocity.

  5. Design criteria for structural design of silage silo walls

    OpenAIRE

    von Wachenfelt, Hans; Nilsson, Christer; Östergaard, Göran; Olofsson, Anders; Karlsson, Marie

    2014-01-01

    Existing Swedish design guidelines (JBR) cover silo wall heights up to about 3 m. These guidelines presumably overestimate the forces and pressures exerted by silage juice when silo walls are more than 3 m high, which could result in over-sizing, material waste and increased capital costs. This study determined silage physical properties in terms of horizontal wall pressure and evaluated silage juice levels in silos with a wall height of 3 m or more.Wall pressure was measured by transducers m...

  6. Aortic stenosis

    Science.gov (United States)

    ... Images Aortic stenosis Heart valves References Carabello BA. Valvular heart disease. In: Goldman L, Schafer AI, eds. Goldman's Cecil ... ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/ ...

  7. Abdominal Aortic Aneurysm (AAA)

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Abdominal Aortic Aneurysm (AAA) Abdominal aortic aneurysm (AAA) occurs when atherosclerosis ... an abdominal aortic aneurysm treated? What is an abdominal aortic aneurysm? The aorta, the largest artery in the body, ...

  8. Role of Microvascular Tone and Extracellular Matrix Contraction in the Regulation of Interstitial Fluid: Implications for Aortic Dissection.

    Science.gov (United States)

    Mallat, Ziad; Tedgui, Alain; Henrion, Daniel

    2016-09-01

    The pathophysiology of aortic dissection is poorly understood, and its risk is resistant to medical treatment. Most studies have focused on a proposed pathogenic role of transforming growth factor-β in Marfan disease and related thoracic aortic aneurysms and aortic dissections. However, clinical testing of this concept using angiotensin II type 1 receptor antagonists to block transforming growth factor-β signaling fell short of promise. Genetic mutations that predispose to thoracic aortic aneurysms and aortic dissections affect components of the extracellular matrix and proteins involved in cellular force generation. Thus, a role for dysfunctional mechanosensing in abnormal aortic wall remodeling is emerging. However, how abnormal mechanosensing leads to aortic dissection remains a mystery. Here, we review current knowledge about the regulation of interstitial fluid dynamics and myogenic tone and propose that alteration in contractile force reduces vascular tone in the microcirculation (here, aortic vasa vasorum) and leads to elevations of blood flow, transmural pressure, and fluid flux into the surrounding aortic media. Furthermore, reduced contractile force in medial smooth muscle cells coupled with alteration of structural components of the extracellular matrix limits extracellular matrix contraction, further promoting the formation of intramural edema, a critical step in the initiation of aortic dissection. The concept is supported by several pathophysiological and clinical observations. A direct implication of this concept is that drugs that lower blood pressure and limit interstitial fluid accumulation while preserving or increasing microvascular tone would limit the risk of dissection. In contrast, drugs that substantially lower microvascular tone would be ineffective or may accelerate the disease and precipitate aortic dissection.

  9. Structural basis of cell wall cleavage by a staphylococcal autolysin.

    Directory of Open Access Journals (Sweden)

    Sebastian Zoll

    2010-03-01

    Full Text Available The major autolysins (Atl of Staphylococcus epidermidis and S. aureus play an important role in cell separation, and their mutants are also attenuated in virulence. Therefore, autolysins represent a promising target for the development of new types of antibiotics. Here, we report the high-resolution structure of the catalytically active amidase domain AmiE (amidase S. epidermidis from the major autolysin of S. epidermidis. This is the first protein structure with an amidase-like fold from a bacterium with a gram-positive cell wall architecture. AmiE adopts a globular fold, with several alpha-helices surrounding a central beta-sheet. Sequence comparison reveals a cluster of conserved amino acids that define a putative binding site with a buried zinc ion. Mutations of key residues in the putative active site result in loss of activity, enabling us to propose a catalytic mechanism. We also identified and synthesized muramyltripeptide, the minimal peptidoglycan fragment that can be used as a substrate by the enzyme. Molecular docking and digestion assays with muramyltripeptide derivatives allow us to identify key determinants of ligand binding. This results in a plausible model of interaction of this ligand not only for AmiE, but also for other PGN-hydrolases that share the same fold. As AmiE active-site mutations also show a severe growth defect, our findings provide an excellent platform for the design of specific inhibitors that target staphylococcal cell separation and can thereby prevent growth of this pathogen.

  10. The fine structure of the Acanthamoeba polyphaga cyst wall.

    Science.gov (United States)

    Lemgruber, Leandro; Lupetti, Pietro; De Souza, Wanderley; Vommaro, Rossiane C; da Rocha-Azevedo, Bruno

    2010-04-01

    Members of the genus Acanthamoeba are present in diverse environments, from freshwater to soil, and also in humans, causing serious brain and corneal infections. Their life cycle presents two stages: the dividing trophozoite and the quiescent cyst. The structures of these life stages have been studied for many years, and structural data have been used for taxonomy. The ultrastructural work on Acanthamoeba cysts was carried out previously by routine transmission electron microscopy (TEM), a process that requires the use of chemical fixation, a procedure that can cause serious artifacts in the ultrastructure of the studied material. In order to prevent fixation artifacts, we processed Acanthamoeba polyphaga cysts by ultrarapid freezing, followed by freeze-fracturing and deep-etching, in order to obtain a 3D visualization of the arrangements of the cyst wall. The exocyst presented an irregular surface, with vesicles located within or near this layer. The endocyst, instead, showed a biphasic arrangement with a more compact district in its innermost part, and a more loosened outer layer. For this reason, it was difficult to distinguish the filaments present in the intercyst space from those forming the endocyst. Surprisingly, the intercyst space was thinner when compared with samples processed by conventional TEM, evidencing the possible damage consequent to the use of chemical fixation.

  11. 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.

  12. The dorsal shell wall structure of Mesozoic ammonoids

    Directory of Open Access Journals (Sweden)

    Gregor Radtke

    2017-03-01

    Full Text Available The study of pristine preserved shells of Mesozoic Ammonoidea shows different types of construction and formation of the dorsal shell wall. We observe three major types: (i The vast majority of Ammonoidea, usually planispirally coiled, has a prismatic reduced dorsal shell wall which consists of an outer organic component (e.g., wrinkle layer, which is the first layer to be formed, and the subsequently formed dorsal inner prismatic layer. The dorsal mantle tissue suppresses the formation of the outer prismatic layer and nacreous layer. With the exception of the outer organic component, secretion of a shell wall is omitted at the aperture. A prismatic reduced dorsal shell wall is always secreted immediately after the hatching during early teleoconch formation. Due to its broad distribution in (planispiral Ammonoidea, the prismatic reduced dorsal shell wall is probably the general state. (ii Some planispirally coiled Ammonoidea have a nacreous reduced dorsal shell wall which consists of three mineralized layers: two prismatic layers (primary and secondary dorsal inner prismatic layer and an enclosed nacreous layer (secondary dorsal nacreous layer. The dorsal shell wall is omitted at the aperture and was secreted in the rear living chamber. Its layers are a continuation of an umbilical shell doubling (reinforcement by additional shell layers that extends towards the ventral crest of the preceding whorl. The nacreous reduced dorsal shell wall is formed in the process of ontogeny following a prismatic reduced dorsal shell wall. (iii Heteromorph and some planispirally coiled taxa secrete a complete dorsal shell wall which forms a continuation of the ventral and lateral shell layers. It is formed during ontogeny following a prismatic reduced dorsal shell wall or a priori. The construction is identical with the ventral and lateral shell wall, including a dorsal nacreous layer. The wide distribution of the ability to form dorsal nacre indicates that it is

  13. [Paradigm shifts in aortic pathology: clinical and therapeutic implications. Clinical imaging in chronic and acute aortic syndromes. The aorta as a cause of cardiac disease].

    Science.gov (United States)

    Nistri, Stefano; Roghi, Alberto; Mele, Donato; Biagini, Elena; Chiodi, Elisabetta; Colombo, Ettore; d'Amati, Giulia; Leone, Ornella; Angelini, Annalisa; Basso, Cristina; Pepe, Guglielmina; Rapezzi, Claudio; Thiene, Gaetano

    2014-06-01

    Multimodal imaging plays a pivotal role in the assessment of the thoracic aorta, both in chronic and acute settings. Moving from improved knowledge on the structure and function of the aortic wall, as well as on its pathophysiology and histopathology, appropriate utilization of each imaging modality results into a better definition of the patient's need and proper treatment strategy. This review is aimed at highlighting the most critical aspects in this field, providing cardiologists with some novel clues for the imaging approach to patients with thoracic aortic disease.

  14. Valve morphology effect in aortic coarctation flow using realistic silicon models and magnetic resonance imaging

    Science.gov (United States)

    Marrufo, Oscar; Solis-Najera, Sergio; Pibarot, Philippe; Kadem, Lyes; Kesharvarz-Motamed, Zahra; Rodriguez, Alfredo O.; Garcia, Julio

    2014-11-01

    Aortic valve morphology and phenotype may alter the aortic wall structure and its normal flow hemodynamics. However, the relationship between altered flow patterns and progression of wall pathology is often not fully understood in patients with aortic coartation and needs larger experimental work. In this study, we introduced a compatible experimental setup with magnetic resonance imaging (MRI) using a realistic aortic coarctation (AoCo) silicon model which can replicate physiological flow conditions (pressure, flow-wave, and systemic load). We evaluated the aortic valve hemodynamics of a normal tricuspid valve and a stenotic bicuspid valve using valve effective orifice area (EOA), peak and mean transvalvular pressure gradient (TPG). AoCo severity was assessed by the AoCo pressure gradient. For the tricuspid valve we obtained an EOA = 1.89 cm2, a peak TPG = 10 mmHg, and a mean TPG = 5 mmHg. For the bicuspid valve we obtained an EOA = 1.03 cm2, a peak TPG = 37 mmHg and a mean TPG = 13 mmHg. Furthermore, AoCo with tricuspid valve led to a peak AoCo pressure gradient (PG) = 11 mmHg and a mean PG = 5 mmHg. AoCo with bicuspid valve led to a peak PG = 6 mmHg and a mean PG = 3 mmHg. Aortic flow reattachment was more evident in presence of bicuspid valve and helical flow was present in all cases. This study showed that silicon prototyping in combination with MRI velocity measurements could successfully be used to assess hemodynamic effects of aortic valve morphology in aortic coarctation flow.

  15. Spectrum of Aortic Valve Abnormalities Associated with Aortic Dilation Across Age Groups in Turner Syndrome

    Science.gov (United States)

    Olivieri, Laura J.; Baba, Ridhwan Y.; Arai, Andrew E.; Bandettini, W. Patricia; Rosing, Douglas R.; Bakalov, Vladimir; Sachdev, Vandana; Bondy, Carolyn A.

    2014-01-01

    Background Congenital aortic valve fusion is associated with aortic dilation, aneurysm and rupture in girls and women with Turner syndrome (TS). Our objective was to characterize aortic valve structure in subjects with TS, and determine the prevalence of aortic dilation and valve dysfunction associated with different types of aortic valves. Methods and Results The aortic valve and thoracic aorta were characterized by cardiovascular magnetic resonance imaging in 208 subjects with TS in an IRB-approved natural history study. Echocardiography was used to measure peak velocities across the aortic valve, and the degree of aortic regurgitation. Four distinct valve morphologies were identified: tricuspid aortic valve (TAV) 64%(n=133), partially fused aortic valve (PF) 12%(n=25), bicuspid aortic valve (BAV) 23%(n=47), and unicuspid aortic valve (UAV) 1%(n=3). Age and body surface area (BSA) were similar in the 4 valve morphology groups. There was a significant trend, independent of age, towards larger BSA-indexed ascending aortic diameters (AADi) with increasing valve fusion. AADi were (mean +/− SD) 16.9 +/− 3.3 mm/m2, 18.3 +/− 3.3 mm/m2, and 19.8 +/− 3.9 mm/m2 (p<0.0001) for TAV, PF and BAV+UAV respectively. PF, BAV, and UAV were significantly associated with mild aortic regurgitation and elevated peak velocities across the aortic valve. Conclusions Aortic valve abnormalities in TS occur with a spectrum of severity, and are associated with aortic root dilation across age groups. Partial fusion of the aortic valve, traditionally regarded as an acquired valve problem, had an equal age distribution and was associated with an increased AADi. PMID:24084490

  16. Study Effective of Wind Load on Behavior of ShearWall in Frame Structure

    Directory of Open Access Journals (Sweden)

    Mahdi Hosseini

    2014-11-01

    Full Text Available Wind load is really the result of wind pressures acting on the building surfaces during a wind event. This wind pressure is primarily a function of the wind speed because the pressure or load increases with the square of the wind velocity.Structural walls, or shear walls, are elements used to resist lateral loads, such as those generated by wind and earthquakes. Structural walls are considerably deeper than typical beams or columns. This attribute gives structural walls considerable in-plane stiffness which makes structural walls a natural choice for resisting lateral loads. In addition to considerable strength, structural walls can dissipate a great deal of energy if detailed properly. Walls are an invaluable structural element when protecting buildings from seismic events. Buildings often rely on structural walls as the main lateral force resisting system. Shear walls are required to perform in multiple ways. Shear walls can then be designed to limit building damage to the specified degree. The loaddeformation response of the structural walls must be accurately predicted and related to structural damage in order to achieve these performance goals under loading events of various magnitudes. The applied load is generally transferred to the wall by a diaphragm or collector or drag member. The performance of the framed buildings depends on the structural system adopted for the structure The term structural system or structural frame in structural engineering refers to load-resisting sub-system of a structure. The structural system transfers loads through interconnected structural components or members. These structural systems need to be chosen based on its height and loads and need to be carried out, etc. The selection of appropriate structural systems for building must satisfy both strength and stiffness requirements. The structural system must be adequate to resist lateral and gravity loads that cause horizontal shear deformation and

  17. Study the Effectiveof Seismic load on Behavior of Shear Wall in Frame Structure

    Directory of Open Access Journals (Sweden)

    Dr.Hadi Hosseini

    2014-11-01

    Full Text Available Structural walls, or shear walls, are elements used to resist lateral loads, such as those generated by wind and earthquakes. Structural walls are considerably deeper than typical beams or columns. This attribute gives structural walls considerable in-plane stiffness which makes structural walls a natural choice for resisting lateral loads. In addition to considerable strength, structural walls can dissipate a great deal of energy if detailed properly. Walls are an invaluable structural element when protecting buildings from seismic events. Buildings often rely on structural walls as the main lateral force resisting system. Shear walls are required to perform in multiple ways. Shear walls can then be designed to limit building damage to the specified degree. The load-deformation response of the structural walls must be accurately predicted and related to structural damage in order to achieve these performance goals under loading events of various magnitudes. The applied load is generally transferred to the wall by a diaphragm or collector or drag member. The performance of the framed buildings depends on the structural system adopted for the structure The term structural system or structural frame in structural engineering refers to load-resisting sub-system of a structure. The structural system transfers loads through interconnected structural components or members. These structural systems need to be chosen based on its height and loads and need to be carried out, etc. The selection of appropriate structural systems for building must satisfy both strength and stiffness requirements. The structural system must be adequate to resist lateral and gravity loads that cause horizontal shear deformation and overturning deformation. The efficiency of a structural system is measured in terms of their ability to resist lateral load, which increases with the height of the frame. A building can be considered as tall when the effect of lateral loads is

  18. Domain wall structure transition during magnetization reversal process in magnetic nanowires

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The analytical micromagnetics and numerical simulations were used to investigate the domain wall structure during the magnetization reversal in nanowires. Micromagnetic analysis shows that the domain wall structure is mainly determined by the competition between the demagnetization energy and exchange energy. The wall with vortex magnetization structure in cross-section is energetically more favorable for wires with large diameter. With the reduction of diameter the exchange energy increases. At a critical diameter the vortex structure can not be sustained and the transition from vortex wall to transverse wall occurs. The critical diameters for this transition are about 40 nm for Ni wire and 20 nm for Fe wire, respectively. A series of micromagnetic simulations on the cone-shaped wire confirm the analytical results. The simulations also show that during the reversal process the vortex domain wall moves much faster than the transverse one.

  19. Structural finite element analysis of ITER In-wall shield

    Energy Technology Data Exchange (ETDEWEB)

    Shaikh, Moinuddin S., E-mail: moins@iter-india.org [ITER-India, Institute for Plasma Research, A-29, GIDC Electronic Estate, Sector 25, Gandhinagar 382016 (India); Pathak, H.A. [ITER-India, Institute for Plasma Research, A-29, GIDC Electronic Estate, Sector 25, Gandhinagar 382016 (India); Oliver, Tailhardat [Assystem EOS, Zac Saint Martin, 23 Rue Benjamin Franklin, 84120 Pertuis (France); Wang, Xiaoyu [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France)

    2013-10-15

    The In-wall shielding (IWS) located between two shells of the vacuum vessel is part of the vacuum vessel of ITER. The function of the IWS is to provide neutron shielding and to reduce toroidal field ripple. The IWS plates are fastened using M30 bolts to hold them securely and the IWS blocks are mounted to the support ribs using the brackets and M20 bolts. The paper presents a structural finite element analysis of one sample IWS block carried out using ANSYS* to establish the benchmark analysis procedure of the IWS blocks. Boundary conditions are set taking into account the assembly procedure of the IWS blocks. The analysis is carried out in three load steps (1). Pretension on M30 (2). Pretension on M30 and M20 and (3) pretension on M30 and M20 plus Electromagnetic forces, dynamic forces, Seismic forces, etc. The stresses and displacements of individual IWS components are evaluated against their allowable stress limits as per an ASME guideline. The ITER-India’s results of analysis are compared with the ITER-IO’s results for the worst category 3-load step 3 and they are found comparable. This establishes the analysis procedure to be used for all of the IWS blocks.

  20. Adventitial vasa vasorum arteriosclerosis in abdominal aortic aneurysm.

    Directory of Open Access Journals (Sweden)

    Hiroki Tanaka

    Full Text Available Abdominal aortic aneurysm (AAA is a common disease among elderly individuals. However, the precise pathophysiology of AAA remains unknown. In AAA, an intraluminal thrombus prevents luminal perfusion of oxygen, allowing only the adventitial vaso vasorum (VV to deliver oxygen and nutrients to the aortic wall. In this study, we examined changes in the adventitial VV wall in AAA to clarify the histopathological mechanisms underlying AAA. We found marked intimal hyperplasia of the adventitial VV in the AAA sac; further, immunohistological studies revealed proliferation of smooth muscle cells, which caused luminal stenosis of the VV. We also found decreased HemeB signals in the aortic wall of the sac as compared with those in the aortic wall of the neck region in AAA. The stenosis of adventitial VV in the AAA sac and the malperfusion of the aortic wall observed in the present study are new aspects of AAA pathology that are expected to enhance our understanding of this disease.

  1. Fluid-structure interaction model of aortic valve with porcine-specific collagen fiber alignment in the cusps.

    Science.gov (United States)

    Marom, Gil; Peleg, Mor; Halevi, Rotem; Rosenfeld, Moshe; Raanani, Ehud; Hamdan, Ashraf; Haj-Ali, Rami

    2013-10-01

    Native aortic valve cusps are composed of collagen fibers embedded in their layers. Each valve cusp has its own distinctive fiber alignment with varying orientations and sizes of its fiber bundles. However, prior mechanical behavior models have not been able to account for the valve-specific collagen fiber networks (CFN) or for their differences between the cusps. This study investigates the influence of this asymmetry on the hemodynamics by employing two fully coupled fluid-structure interaction (FSI) models, one with asymmetric-mapped CFN from measurements of porcine valve and the other with simplified-symmetric CFN. The FSI models are based on coupled structural and fluid dynamic solvers. The partitioned solver has nonconformal meshes and the flow is modeled by employing the Eulerian approach. The collagen in the CFNs, the surrounding elastin matrix, and the aortic sinus tissues have hyperelastic mechanical behavior. The coaptation is modeled with a master-slave contact algorithm. A full cardiac cycle is simulated by imposing the same physiological blood pressure at the upstream and downstream boundaries for both models. The mapped case showed highly asymmetric valve kinematics and hemodynamics even though there were only small differences between the opening areas and cardiac outputs of the two cases. The regions with a less dense fiber network are more prone to damage since they are subjected to higher principal stress in the tissues and a higher level of flow shear stress. This asymmetric flow leeward of the valve might damage not only the valve itself but also the ascending aorta.

  2. Ang II enhances noradrenaline release from sympathetic nerve endings thus contributing to the up-regulation of metalloprotease-2 in aortic dissection patients' aorta wall.

    Directory of Open Access Journals (Sweden)

    Zhipeng Hu

    Full Text Available OBJECT: To test the hypothesis that angiotensin II (Ang II could enhance noradrenaline (NA release from sympathetic nerve endings of the aorta thus contributing to the up-regulation of matrix metalloproteinase 2 (MMP-2 during the formation of aortic dissection (AD. METHODS: Ang II, NA, MMP-2, MMP-9 of the aorta sample obtained during operation from aortic dissection patients were detected by High Performance Liquid Chromatography and ELISA and compared with controls. Isotope labelling method was used to test the impact of exogenous Ang II and noradrenaline on the NA release and MMP-2, MMP-9 expression on Sprague Dawley (SD rat aorta rings in vitro. Two kidneys, one clip, models were replicated for further check of that impact in SD rats in vivo. RESULTS: The concentration of Ang II, MMP-2, 9 was increased and NA concentration was decreased in aorta samples from AD patients. Exogenous Ang II enhanced while exogenous NA restrained NA release from aortic sympathetic endings. The Ang II stimulated NA release and the following MMP-2 up-regulation could be weakened by Losartan and chemical sympathectomy. Beta blocker did not influence NA release but down-regulated MMP-2. Long term in vivo experiments confirmed that Ang II could enhance NA release and up-regulate MMP-2. CONCLUSIONS: AD is initiated by MMP-2 overexpression as a result of increased NA release from sympathetic nervous endings in response to Ang II. This indicates an interaction of RAS and SAS during the formation of AD.

  3. MicroRNAs, fibrotic remodeling, and aortic aneurysms

    Science.gov (United States)

    Milewicz, Dianna M.

    2012-01-01

    Aortic aneurysms are a common clinical condition that can cause death due to aortic dissection or rupture. The association between aortic aneurysm pathogenesis and altered TGF-β signaling has been the subject of numerous investigations. Recently, a TGF-β–responsive microRNA (miR), miR-29, has been identified to play a role in cellular phenotypic modulation during aortic development and aging. In this issue of JCI, Maegdefessel and colleagues demonstrate that decreasing the levels of miR-29b in the aortic wall can attenuate aortic aneurysm progression in two different mouse models of abdominal aortic aneurysms. This study highlights the relevance of miR-29b in aortic disease but also raises questions about its specific role. PMID:22269322

  4. Evaluation of inflammatory cells in abdominal aortic aneurysmal wall by tomography emission positron; Anevrisme de l aorte abdominale et inflammation vasculaire: place de la tomographie par emission de positons

    Energy Technology Data Exchange (ETDEWEB)

    Sakalihasan, N. [Service de chirurgie cardiovasculaire et thoracique, CHU de liege, domaine universitaire du Sart Tilman, batimant B-35, 4000 liege 1, (Belgium); Hustinx, R. [Service de medecine nucleaire, CHU de Liege, (Belgium); Gomez, P.; Defraigne, J.O. [Departement de medecine nucleaire, CHU de Liege, (Belgium)

    2009-05-15

    The objective was to identify the methods of functional imaging and the molecular markers that could help to predict the imminence of a rupture in abdominal aortic aneurysm. The potential of the PET was studied to detect a hyper-metabolic state in the aneurysm wall and this information was connected with the evolution of the disease. An uptake of F.D.G. in the aneurysm wall reflects the presence of a great density of inflammatory cells (macrophages, lymphocytes, polymorphonuclear cells). It has been observed an accumulation of polymorphonuclear cells accompanying a dense infiltration of macrophages and lymphocytes only in the site of break. Our preliminary study and our most recent observations (not yet published) suggest a possible relationship between the F.G.D. captation by the aneurysm wall and the start of the activity of the matrix metallo-proteinases leading to the break. The PET scan could be useful for high risk patients because a positive PET imaging stigmatizes a greater risk of break. consequently, the positive PET imaging represents a diagnosis argument to proceed to a surgical operation, despite the age of the patient, the size of the abdominal aorta aneurysm and the higher operative risk. however, more data to better define the criteria of using the PET/T.D.M. in the evaluation of abdominal aorta aneurysm and to determine its exact contribution in the treatment determination. (N.C.)

  5. Structure of ristocetin A in complex with a bacterial cell-wall mimetic

    OpenAIRE

    Nahoum, Virginie; Spector, Sherri; Loll, Patrick J.

    2009-01-01

    The crystal structure of the complex between ristocetin A and the cell-wall peptide mimetic N-acetyl-lysine-d-alanine-d-alanine has been solved. Structural details explaining the anticooperativity of the antibiotic have been identified.

  6. A technique of aortic annulus enlargement with a Freestyle stentless bioprosthesis.

    Science.gov (United States)

    Bical, Olivier M; Nutu, Ovidiu; Deleuze, Philippe

    2012-02-01

    We describe our surgical technique to manage a small aortic annulus during aortic valve replacement. Starting with the posterior annular enlargement incision described by Manouguian, a stentless porcine aortic root, with excision of the left and right porcine coronary segments and conservation of the mural wall (Freestyle MS design, Medtronic, Minneapolis, MN ), was used. The Freestyle bioprosthesis enlarges the aortic annulus using a direct suture of the valve on the enlarged annulus, and the aorta is closed by a direct suture of the mural wall of the bioprosthesis. Therefore, the aortic annulus enlargement is made only using the aortic bioprosthesis, without other material.

  7. Infected abdominal aortic aneurysm due to Morganella morganii: CT findings.

    Science.gov (United States)

    Kwon, Oh Young; Lee, Jong Seok; Choi, Han Sung; Hong, Hoon Pyo; Ko, Young Gwan

    2011-02-01

    An infected aortic aneurysm, or mycotic aneurysm, is a rare arterial dilatation due to destruction of the infected vessel wall. Common pathogens resulting in an infected aortic aneurysm are Salmonella and Clostridium species, as well as Staphylococcus aureus; Morganella morganii, on the other hand, is very rare. An infected abdominal aortic aneurysm has tendencies to grow rapidly and to rupture. The mortality rate is high in patients undergoing emergent surgical intervention. We report the case of a 65-year-old man who presented with an infected abdominal aortic aneurysm caused by M. morganii. A high index of suspicion and imaging tests are necessary in order to diagnose an infected aortic aneurysm.

  8. Treatment of infrarenal abdominal aortic dissection concomitant with an aneurysm

    Institute of Scientific and Technical Information of China (English)

    WANG Li-xin; ZHU Ting; FU Wei-guo; WANG Yu-qi; XI Xun; GUO Da-qiao; CHEN Bin; JIANG Jun-hao; YANG Ju; SHI Zhen-yu

    2007-01-01

    @@ Aortic dissection occurs when layers of the aortic walls are separated by the blood flow through an intimal tear. Dissection of the aorta most frequently originates in the ascending aorta (70%), followed by the descending aorta (22%), the aortic arch (7%) and the abdominal aorta (1/%).1 The dissection limited to the abdominal aorta is rare.2 An isolated abdominal aortic dissection (IAAD) concomitant with an abdominal aortic aneurysm (AAA) is uncommon. We present here one patient with IAAD and AAA treated by endovascular therapy.

  9. Experimental and theoretical studies on concrete structures with special-shaped shear walls

    Directory of Open Access Journals (Sweden)

    LIU Jianxin

    2014-06-01

    Full Text Available On the basis of concept design and staggered shear panels structure,this paper puts forward a new reinforced concrete high rise biuding structure with special-shaped shear walls and presents an experimental study of the seismic performance of the new special-shaped shear walls structure under low reversed cyclic loading using MTS electro hydraulic servo system.Compared with experimental results,a finite element analysis on this special-shaped shear wall structure,which considers the nonlinearity of concrete structure,is found suitable.It shows that the experimental results fairly confirms to the calculated values,which indicates that this new structure has advantages as good architecture function,big effective space,high overall lateral stiffness,fine ductility,advanced seismic behavior,etc..That is,the close r agreement between the theoretical and experimental results indicates the proposed shear wall structure has wide applications.

  10. Evaluation of Biaxial Mechanical Properties of Aortic Media Based on the Lamellar Microstructure

    Directory of Open Access Journals (Sweden)

    Hadi Taghizadeh

    2015-01-01

    Full Text Available Evaluation of the mechanical properties of arterial wall components is necessary for establishing a precise mechanical model applicable in various physiological and pathological conditions, such as remodeling. In this contribution, a new approach for the evaluation of the mechanical properties of aortic media accounting for the lamellar structure is proposed. We assumed aortic media to be composed of two sets of concentric layers, namely sheets of elastin (Layer I and interstitial layers composed of mostly collagen bundles, fine elastic fibers and smooth muscle cells (Layer II. Biaxial mechanical tests were carried out on human thoracic aortic samples, and histological staining was performed to distinguish wall lamellae for determining the dimensions of the layers. A neo-Hookean strain energy function (SEF for Layer I and a four-parameter exponential SEF for Layer II were allocated. Nonlinear regression was used to find the material parameters of the proposed microstructural model based on experimental data. The non-linear behavior of media layers confirmed the higher contribution of elastic tissue in lower strains and the gradual engagement of collagen fibers. The resulting model determines the nonlinear anisotropic behavior of aortic media through the lamellar microstructure and can be assistive in the study of wall remodeling due to alterations in lamellar structure during pathological conditions and aging.

  11. Evaluation of regional aortic distensibility using color kinesis.

    Science.gov (United States)

    Kato, Yoshimasa; Kotoh, Keiju; Yamashita, Akio; Furuta, Hidetoshi; Shimazu, Chikasi; Misaki, Takurou

    2003-01-01

    Regional aortic stiffness cannot be evaluated by conventional methods. Regional aortic wall velocity during systole in the descending aorta was evaluated by using transesophageal echocardiography with color kinesis. The authors defined regional aortic distensibility (RAD) by considering pulse pressure, with RAD (microm/s/mm Hg) = (regional aortic wall velocity)/(pulse pressure). RAD was evaluated in 38 patients who had coronary artery disease (CAD) and 10 who did not. RAD decreased depending on aging (partial regression coefficient was -5.39 x 10(-1), pkinesis provides information on characteristic difference between calcified and noncalcified plaque.

  12. Aortic root size and prevalence of aortic regurgitation in elite strength trained athletes.

    Science.gov (United States)

    Babaee Bigi, Mohammad Ali; Aslani, Amir

    2007-08-01

    Athletes involved in mainly static or isometric exercise (e.g., weight lifting, power lifting, and bodybuilding) develop pressure overloads due to the high systemic arterial pressure found in this type of exercise. It is hypothesized that chronically elevated aortic wall tension in strength-trained athletes is associated with aortic dilatation and regurgitation. The aim of this study was to evaluate aortic root size and the prevalence of aortic regurgitation in elite strength-trained athletes. The cohort included 100 male athletes (mean age 22.1 +/- 3.6 years; all were finalists or medalists in the country) and 128 healthy age- and height-matched subjects (the control group). Aortic root diameters at end-diastole were measured at 4 locations: (1) the aortic annulus, (2) the sinuses of Valsalva, (3) the sinotubular junction, and (4) the maximal diameter of the proximal ascending aorta. Aortic root diameters at all levels were significantly greater in the strength-trained athletes (p 18 and 36 and 54 months), progressive enlargement was found at all aortic diameters. In conclusion, aortic root diameters in all segments of the aortic root were significantly greater in elite strength-trained athletes compared with an age- and height-matched population.

  13. [Aortic valve replacement as an independent predictive factor for later development of aortic dissection].

    Science.gov (United States)

    von Kodolitsch, Y; Simic, O; Bregenzer, T; Dresler, C; Haverich, A; Nienaber, C A

    1998-08-01

    Dissection of the ascending aorta (type A) following later after aortic valve replacement has been described with increasing frequency. This study analyzes the role of aortic valve replacement for the evolution of late dissection. In a series of 80 consecutive patients with type A dissection, a previous aortic valve replacement had been performed in 12 cases (15%). In addition to arterial hypertension (p syndrome (p factor for type A dissection. Dissection occurred 3 +/- 4 years after aortic valve replacement with a clinical and anatomical profile similar to classic dissection as proven by comparison to a group of 62 patients with classic dissection associated with arterial hypertension or Marfan syndrome. With 75% and 66%, respectively, 30 day and 1 year survival of patients with dissection following later after aortic valve replacement was similar to patients with classic type A dissection. Extensive thinning and/or fragility (p associated with a high risk for late dissection; this finding was substantiated by comparison to a control group of 10 consecutive patients with a similarly dilated aortic root but no dissection. Type and diameter of valve prostheses, cross-clamp time, NYHA functional class, and left ventricular ejection fraction were unrelated to late dissection. Previous aortic valve replacement is an independent predisposing factor for a dissection of the ascending aorta later. At the time of aortic valve replacement, prophylactic replacement or wrapping of the ascending aorta should be considered in patients with a thinned/fragile aortic wall even without a markedly dilated aortic root.

  14. Degree of coupling in high-rise mixed shear walls structures

    Indian Academy of Sciences (India)

    J C D Hoenderkamp

    2012-08-01

    A simple method of analysis is presented to determine the influence of single shear walls (SSW) on the degree of coupling DoC and on the peak shear demand PSD for beams of coupled shear walls (CSW) in mixed shear wall structures (MSW). Non-coupled lateral load resisting structures such as singular planar walls and cores will reduce primary bending moments in the coupled shear wall bents of MSW structures thereby increasing the degree of coupling. They will also change the location and magnitude of the maximum shear in and rotation of the coupling beams. These changes in the coupled wall bents may increase the demand on their performance beyond capacity. It is, therefore, important to have an indication of the change in the coupling beam design parameters at an early stage of the design. The proposed graphical method is based on the continuous medium theory and allows a rapid assessment of the structural behaviour of coupled shear wall bents in mixed shear wall structures that are subject to horizontal loading.

  15. Study on Seismic Behavior of Recycled Concrete Energy-efficient Homes Structure Wall

    Directory of Open Access Journals (Sweden)

    Dong Lan

    2016-01-01

    Full Text Available The main point is to study the seismic behavior of the lattice type recycled concrete energy saving wall under low-cyclic loading,to provide the basis for the seismic performance of application of recycled concrete lattice wall in energy-saving residential structure. Design two walls with the same structure measures, include Lattice type recycled concrete wall and natural concrete wall, they are tested under low-cycle repetitive loading, compared failure mode and seismic performance in different reinforcement conditions of side column. The bearing capacity and ductility of recycled aggregate concrete are better than natural aggregate concrete, The stiffness degradation curves and the skeleton curves of the walls are basically the same, both of them have better seismic energy dissipation capacity. Lattice type concrete wall is good at seismic performance, recycled aggregate concrete is good at plastic deformation ability, it is advantageous to seismic energy dissipation of wall, it can be applied in energy efficient residential structure wall.

  16. Local Impact Simulation of SC Wall Structures using Aircraft Engine Projectile

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Chulhun; Lee, Jungwhee; Lee, Hanjoo [Dankook Univ., Yongin (Korea, Republic of); Jung, Raeyoung; Hyun, Changhun [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2013-05-15

    SC wall structure developed for nuclear power plant buildings consists of plain concrete and two steel plates on both surface of the concrete, while RC structure consists of re bar and concrete. SC structure has higher scabbing resistance than RC structure due to the action of steel plate on the rear side of impact. Therefore SC structure is known as more effective structure from the viewpoint of aircraft crash than RC structure. However, most of the recent researches and experiments about local impact damage deal with RC structures, and the effect of re bar and steel plate is not considered reasonably. Although Walter et al. and Make-work et al. suggested a formula for evaluating perforation depth of steel plate covered RC walls, most of the previous researches about SC structure are focused on perforation and scabbing due to the impact of hard projectile, rather than soft projectile such as an aircraft. In this research a soft projectile, i. e. aircraft engine, is utilized for impact simulation of RC and SC walls. To evaluate local damage of SC wall structures, parametric study with the variables of wall thickness and steel ratio of the cover plate is performed, and the results are compared with those of RC structures. Since scabbing was prevented by the steel plates, penetration mode of damage was observed in SC walls while scabbing damage was occurred in RC walls. It is confirmed that the rear steel plate not only contains concrete debris, but also reduces the internal damage of the concrete walls. Penetration depth of SC walls did not largely vary due to the increasing steel ratio, and similar results to RC walls were observed when the wall thickness is larger than a certain value since the impact resistance of SC wall is mainly governed by the thickness of concrete part. Therefore, it is expected that similar level of impact resistance to RC structure can be produced with the minimum thickness of steel plates of SC structure. According to these results, SC

  17. Micro-aerial vehicle type wall-climbing robot mechanism for structural health monitoring

    Science.gov (United States)

    Shin, Jae-Uk; Kim, Donghoon; Kim, Jong-Heon; Myung, Hyun

    2013-04-01

    Currently, the maintenance or inspection of large structures is labor-intensive, so it has a problem of the large cost due to the staffing professionals and the risk for hard to reach areas. To solve the problem, the needs of wall-climbing robot are emerged. Infra-based wall-climbing robots to maintain an outer wall of building have high payload and safety. However, the infrastructure for the robot must be equipped on the target structure and the infrastructure isn't preferred by the architects since it can injure the exterior of the structure. These are the reasons of why the infra-based wall-climbing robot is avoided. In case of the non-infra-based wall-climbing robot, it is researched to overcome the aforementioned problems. However, most of the technologies are in the laboratory level since the payload, safety and maneuverability are not satisfactory. For this reason, aerial vehicle type wall-climbing robot is researched. It is a flying possible wallclimbing robot based on a quadrotor. It is a famous aerial vehicle robot using four rotors to make a thrust for flying. This wall-climbing robot can stick to a vertical wall using the thrust. After sticking to the wall, it can move with four wheels installed on the robot. As a result, it has high maneuverability and safety since it can restore the position to the wall even if it is detached from the wall by unexpected disturbance while climbing the wall. The feasibility of the main concept was verified through simulations and experiments using a prototype.

  18. Bicuspid Aortic Valve

    Science.gov (United States)

    2006-08-01

    aortic valvular disease, endocarditis, ascending aortic aneurysm and aortic dissection.1-4 There is also an association of BAV with coarctation of...for aortic aneurysm , patients with BAV appear to have additional risks for aortic disease. Nistri et al.12 reported significant aortic root...Congenital heart disease in patients with Turner’s syndrome. Italian study group for Turner syndrome (ISGTS). J Pediatr 1998; 133:688-692. 7. Schmid

  19. An abdominal aortic calcification as a RISK FACTOR FOR cardio -cerebral events in patients with peripheral arterial

    Directory of Open Access Journals (Sweden)

    V. A. Zelinskiy

    2012-01-01

    Full Text Available Background. The patients with abdominal aortic calcification have a high risk of cardiocerebral events, but the pathways of them have not been reported so far. The goal of our study was to assess the structure and function of myocardium and to determine the morphological features of carotid artery atherosclerosis in patients with abdominal aortic calcification.Materials and methods. A total of 167 executive patients with peripheral arterial disease were enrolled in study. The study group included 85 patients with abdominal aortic calcification (men – 95.3 %; age median was – 66.6 ± 12. Control group included 82 patients without objective signs of abdominal aortic calcification. Abdominal aortic calcification was detected by CT imaging. All patients have undergone echocardiography and duplex scanning of carotid arteries.Results. Prevalence and severity of ischemic heart disease and cerebrovascular disease were statistically significant higher in patients with abdominal aortic calcification (91.7, 65.8 % vs. 67, 37.3 % (р < 0.01. We have found statistically significant differences between groupsin heart structure and function. A high left ventricular wall thickness (р < 0.01, left atrium dilation (р < 0.01 and enhanced of left ventricular mass (р < 0.05, ejection fraction reduction (р < 0.05 and more common diastolic dysfunction (р < 0.05 were determined inpatients with abdominal aortic calcification. An intima-media thickness of the common carotid artery was significantly higher in study group patients (1.38 ± 0.07 mm vs. 1.14 ± 0.06 mm (р < 0.001.Conclusion. Our findings suggested that abdominal aortic calcification is main reason of hypertrophy and dilation in the left heart due to enhanced peripheral resistance. Hypertrophy and dilation in the left heart is provided a high risk of cardiovascular events in patients withabdominal aortic calcification.

  20. Fluid-Structure Simulations of a Ruptured Intracranial Aneurysm: Constant versus Patient-Specific Wall Thickness.

    Science.gov (United States)

    Voß, S; Glaßer, S; Hoffmann, T; Beuing, O; Weigand, S; Jachau, K; Preim, B; Thévenin, D; Janiga, G; Berg, P

    2016-01-01

    Computational Fluid Dynamics is intensively used to deepen the understanding of aneurysm growth and rupture in order to support physicians during therapy planning. However, numerous studies considering only the hemodynamics within the vessel lumen found no satisfactory criteria for rupture risk assessment. To improve available simulation models, the rigid vessel wall assumption has been discarded in this work and patient-specific wall thickness is considered within the simulation. For this purpose, a ruptured intracranial aneurysm was prepared ex vivo, followed by the acquisition of local wall thickness using μCT. The segmented inner and outer vessel surfaces served as solid domain for the fluid-structure interaction (FSI) simulation. To compare wall stress distributions within the aneurysm wall and at the rupture site, FSI computations are repeated in a virtual model using a constant wall thickness approach. Although the wall stresses obtained by the two approaches-when averaged over the complete aneurysm sac-are in very good agreement, strong differences occur in their distribution. Accounting for the real wall thickness distribution, the rupture site exhibits much higher stress values compared to the configuration with constant wall thickness. The study reveals the importance of geometry reconstruction and accurate description of wall thickness in FSI simulations.

  1. Aortic Stenosis.

    Science.gov (United States)

    Bakaeen, Faisal G; Rosengart, Todd K; Carabello, Blase A

    2017-01-03

    This issue provides a clinical overview of aortic stenosis, focusing on screening, diagnosis, treatment, and practice improvement. The content of In the Clinic is drawn from the clinical information and education resources of the American College of Physicians (ACP), including MKSAP (Medical Knowledge and Self-Assessment Program). Annals of Internal Medicine editors develop In the Clinic in collaboration with the ACP's Medical Education and Publishing divisions and with the assistance of additional science writers and physician writers.

  2. Structure reconstruction of TiO2-based multi-wall nanotubes: first-principles calculations.

    Science.gov (United States)

    Bandura, A V; Evarestov, R A; Lukyanov, S I

    2014-07-28

    A new method of theoretical modelling of polyhedral single-walled nanotubes based on the consolidation of walls in the rolled-up multi-walled nanotubes is proposed. Molecular mechanics and ab initio quantum mechanics methods are applied to investigate the merging of walls in nanotubes constructed from the different phases of titania. The combination of two methods allows us to simulate the structures which are difficult to find only by ab initio calculations. For nanotube folding we have used (1) the 3-plane fluorite TiO2 layer; (2) the anatase (101) 6-plane layer; (3) the rutile (110) 6-plane layer; and (4) the 6-plane layer with lepidocrocite morphology. The symmetry of the resulting single-walled nanotubes is significantly lower than the symmetry of initial coaxial cylindrical double- or triple-walled nanotubes. These merged nanotubes acquire higher stability in comparison with the initial multi-walled nanotubes. The wall thickness of the merged nanotubes exceeds 1 nm and approaches the corresponding parameter of the experimental patterns. The present investigation demonstrates that the merged nanotubes can integrate the two different crystalline phases in one and the same wall structure.

  3. 基质金属蛋白酶及其抑制剂在腹主动脉瘤发病中的作用%Effect of matrix metalloproteinase and its inhibitor in the formation of abdominal aortic aneurysms

    Institute of Scientific and Technical Information of China (English)

    吴建秋; 景在平

    2001-01-01

    Extracellular matrix plays an important role in maintaining organic structure and function, cellular proliferation and differentiation of normal aorta. Extracellular matrix proteolysis and remodeling of aortic wall resulting from degradation of matrix proteins characterize abdominal aortic aneurysm (AAA). Matrix metalloproteinase and its inhibitor have been implicated as potentially important in this disease, and MMP/TIMP ratios may be the key of AAA formation and development.

  4. 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.

  5. Mitigation of blast loadings on structures by an anti-blast plastic water wall

    Institute of Scientific and Technical Information of China (English)

    张力; 陈力; 方秦; 张亚栋

    2016-01-01

    Seven in-situ tests were carried out in far field to study the blast mitigation effect of a kind of water filled plastic wall. Test results show that the mitigation effect of water filled plastic wall is remarkable. The maximum reduction of peak reflected overpressure reaches up to 94.53%, as well as 36.3% of the minimum peak reflected overpressure reduction in the scaled distance ranging from 1.71 m/kg1/3 to 3.42 m/kg1/3. Parametric studies were also carried out. The effects of the scaled gauge height, water/charge scaled distance (the distance between the explosive charge and the water wall), water wall scaled height and water/structure scaled distance (the distance between the water wall and the structure) were systematically investigated and compared with the usual rigid anti-blast wall. It is concluded that these parameters affect the mitigation effects of plastic water wall on blast loadings significantly, which is basically consistent to the trend of usual rigid anti-blast wall. Some formulae are also derived based on the numerical and test results, providing a simple but reliable prediction model to evaluate the peak overpressure of mitigated blast loadings on the structures.

  6. The Small-Scale Structure of Acceleration in Wall Turbulence

    Science.gov (United States)

    Christensen, Kenneth T.; Adrian, Ronald J.

    2001-11-01

    Temporal and convective derivatives of velocity are measured in the streamwise--wall-normal plane of turbulent channel flow at Re_τ=547, 1133, and 1734 using a new technique called particle-image accelerometry. Pairs of temporally-resolved instantaneous velocity fields are acquired in rapid succession using a two-CCD-camera arrangement, and the associated instantaneous temporal and convective derivatives of velocity are computed numerically from this data. Advection of the small-scale vortices embedded within the flow dominates the small-scale behavior of the velocity time-derivative as noted in both the instantaneous rate-of-change fields as well as in the statistics of the temporal derivative. However, in a reference frame traveling with the vortices, a marked deceleration is present and represents the evolution of the flow. This large-scale deceleration is conjectured to be the dynamic influence of larger-scale vortices present further away from the wall on the smaller scale vortices present closer to the wall.

  7. Effects of calcination temperature on the pore size and wall crystalline structure of mesoporous alumina.

    Science.gov (United States)

    Sun, Zhong-Xi; Zheng, Ting-Ting; Bo, Qi-Bing; Du, Miao; Forsling, Willis

    2008-03-01

    In this paper, mesoporous alumina with different pore sizes and wall crystalline structures was synthesized at calcination temperatures over 550 degrees C. The characterization of the samples calcined at 550, 800, 1100, and 1300 degrees C, respectively, was performed using TEM, XRD, FTIR, TG/DTA, and N2 adsorption/desorption techniques. The correlation between pore size and wall crystalline structure on calcination temperature was systematically investigated.

  8. Effects of Openings in Shear Wall on Seismic Response of Structure

    Directory of Open Access Journals (Sweden)

    Vishal A. Itware

    2015-07-01

    Full Text Available The paper investigates the effects of openings in shear wall on seismic response of structures. For parametric study 6 and 12 storied 7x3 bays apartment buildings with typical floor plan of 35mx15m and floor height of 3m with different openings size and location in shear walls were modeled in STAAD pro. An equivalent static analysis for three dimensional models of the buildings was performed as per IS 1893 (part 1: 2002. Seismic responses of the analyzed structures were compared. The results reveal that for opening area 20%, the stiffness of the system is significantly affected by openings configuration in shear walls.

  9. Modeling of individual coherent structures in wall region of a turbulent boundary layer

    Institute of Scientific and Technical Information of China (English)

    周恒; 陆昌根; 罗纪生

    1999-01-01

    Models for individual coherent structures in the wall region of a turbulent boundary layer are proposed. Method of numerical simulations is used to follow the evolution of the structures. It is found that the proposed model does bear many features of coherent structures found in experiments.

  10. Soya beans and Maize : The effect of chemical and physical structure of cell wall polysaccharides on fermentation kinetics

    OpenAIRE

    Laar, van de, P.

    2000-01-01

    The analysis of the relationship between cell wall composition and fermentation of endosperm cell walls of soya beans and maize was approached from three different angles. Firstly, the fermentation (rate and extent of fermentation, the sugar degradation pattern, and volatile fatty acid production) of soya bean and maize cell walls was analysed, both in situ and in vitro. This analysis revealed that the physical structure of the cell wall (particle size and cell wall thickness) influences cell...

  11. Aortic valve bypass

    DEFF Research Database (Denmark)

    Lund, Jens T; Jensen, Maiken Brit; Arendrup, Henrik;

    2013-01-01

    In aortic valve bypass (AVB) a valve-containing conduit is connecting the apex of the left ventricle to the descending aorta. Candidates are patients with symptomatic aortic valve stenosis rejected for conventional aortic valve replacement (AVR) or transcatheter aortic valve implantation (TAVI...

  12. Solidified structure of thin-walled titanium parts by vertical centrifugal casting

    Directory of Open Access Journals (Sweden)

    Wu Shiping

    2011-05-01

    Full Text Available The solidified structure of the thin-walled and complicated Ti-6Al-4V castings produced by the vertical centrifugal casting process was studied in the present work. The results show that the wall thickness of the section is featured with homogeneously distributed fine equiaxial grains, compared with the microstructure of the thick-walled section. The grain size of the castings has a tendency to decrease gradually with the increasing of the centrifugal radius. The inter-lamellar space in thick-walled casting parts is bigger than that of the thin-walled parts, and the profile of inter-lamellar space is not susceptible to the centrifugal radius.

  13. Domain wall spin structures in mesoscopic Fe rings probed by high resolution SEMPA

    Science.gov (United States)

    Krautscheid, Pascal; Reeve, Robert M.; Lauf, Maike; Krüger, Benjamin; Kläui, Mathias

    2016-10-01

    We present a combined theoretical and experimental study of the energetic stability and accessibility of different domain wall spin configurations in mesoscopic magnetic iron rings. The evolution is investigated as a function of the width and thickness in a regime of relevance to devices, while Fe is chosen as a material due to its simple growth in combination with attractive magnetic properties including high saturation magnetization and low intrinsic anisotropy. Micromagnetic simulations are performed to predict the lowest energy states of the domain walls, which can be either the transverse or vortex wall spin structure, in good agreement with analytical models, with further simulations revealing the expected low temperature configurations observable on relaxation of the magnetic structure from saturation in an external field. In the latter case, following the domain wall nucleation process, transverse domain walls are found at larger widths and thicknesses than would be expected by just comparing the competing energy terms demonstrating the importance of metastability of the states. The simulations are compared to high spatial resolution experimental images of the magnetization using scanning electron microscopy with polarization analysis to provide a phase diagram of the various spin configurations. In addition to the vortex and simple symmetric transverse domain wall, a significant range of geometries are found to exhibit highly asymmetric transverse domain walls with properties distinct from the symmetric transverse wall. Simulations of the asymmetric walls reveal an evolution of the domain wall tilting angle with ring thickness which can be understood from the thickness dependencies of the contributing energy terms. Analysis of all the data reveals that in addition to the geometry, the influence of materials properties, defects and thermal activation all need to be taken into account in order to understand and reliably control the experimentally accessible

  14. Free torsion of thin-walled structural members of open- and closed-sections

    Institute of Scientific and Technical Information of China (English)

    Long-yuan LI; D. EASTERBROOK

    2014-01-01

    Free torsion of thin-walled structures of open- and closed-sections is a classical elastic mechanics problem, which, in literature, is often solved by the method of membrane analogy. The method of membrane analogy, however, can be only applied to structures of a single material. If the structure consists of both open-and closed-sections, the method of membrane analogy is difficult to be applied. In this paper, a new method is presented for solving the free torsion of thin-walled structures of open- and/or closed-sections with multiple materials. By utilizing a simple statically indeterminate concept, torsional equations are derived based on the equilibrium and compatibility conditions. The method presented here not only is very simple and easy to understand but also can be applied to thin-walled structures of combined open-and closed-sections with multiple materials.

  15. Vacuum Domain Walls in D-dimensions Local and Global Space-Time Structure

    CERN Document Server

    Cvetic, M; Cvetic, Mirjam; Wang, Jing

    2000-01-01

    We study local and global gravitational effects of (D-2)-brane configurations (domain-walls) in the vacuum of D-dimensional space-time. We focus on infinitely thin vacuum domain walls with arbitrary cosmological constants on either side of the wall. In the comoving frame of the wall we derive a general metric Ansatz, consistent with the homogeneity and isotropy of the space-time intrinsic to the wall, and employ Israel's matching conditions at the wall. The space-time, intrinsic to the wall, is that of (D-1)-dimensional Freedman-Lemaitre-Robertson-Walker universe (with k=-1,0,1) which has a (local) description as either anti-deSitter, Minkowski or deSitter space-time. For each of these geometries, we provide a systematic classification of the local and global space-time structure transverse to the walls, for those with both positive and negative tension; they fall into different classes according to the values of their energy density relative to that of the extreme (superysmmetric) configurations. We find tha...

  16. Structure and stability of SnS2-based single- and multi-wall nanotubes

    Science.gov (United States)

    Bandura, Andrei V.; Evarestov, Robert A.

    2015-11-01

    Hybrid density functional method PBE0 which mixes the 75% Perdew-Burke-Ernzerhof and 25% Hartree-Fock exchange functional has been applied for investigation of the electronic and atomic structures of nanotubes obtained by rolling up of hexagonal layers of tin disulfide. Calculations have been performed on the basis of the localized atomic functions by means of the CRYSTAL09 computer code. The calculated strain energy of SnS2 single-wall nanotubes approximately obeys the R- 2 law (R is nanotube radius) of the classical elasticity theory. The SnS2 nanotube electronic band structures yield a semiconducting behavior. Band gap of single-wall nanotubes decreases linearly with R- 1. The dispersion force correction is found to be important for prediction of the multi-wall nanotube stability. The distance and interaction energy between the single-wall components of the double-wall nanotubes are proved to be close to the distance and interaction energy between layers in the bulk crystal. Analysis of the relaxed nanotube shape using the offered method demonstrates a small but noticeable deviation from completely cylindrical cross-section of the external walls in the armchair-like double- and triple-walled nanotubes.

  17. Reynolds number invariance of the structure inclination angle in wall turbulence.

    Science.gov (United States)

    Marusic, Ivan; Heuer, Weston D C

    2007-09-14

    Cross correlations of the fluctuating wall-shear stress and the streamwise velocity in the logarithmic region of turbulent boundary layers are reported over 3 orders of magnitude change in Reynolds number. These results are obtained using hot-film and hot-wire anemometry in a wind tunnel facility, and sonic anemometers and a purpose-built wall-shear stress sensor in the near-neutral atmospheric surface layer on the salt flats of Utah's western desert. The direct measurement of fluctuating wall-shear stress in the atmospheric surface layer has not been available before. Structure inclination angles are inferred from the cross correlation results and are found to be invariant over the large range of Reynolds number. The findings justify the prior use of low Reynolds number experiments for obtaining structure angles for near-wall models in the large-eddy simulation of atmospheric surface layer flows.

  18. Wall effect on fluid-structure interactions of a tethered bluff body

    Science.gov (United States)

    Sharma, Sumant; Raghav, Vrishank; Komerath, Narayanan; Smith, Marilyn

    2013-11-01

    Wind tunnel experiments have shown an unexplained amplification of the free motion of a tethered bluff body in a small wind tunnel relative to that in a large wind tunnel. The influence of wall proximity on fluid-structure interaction is explored using a compound pendulum motion in the plane orthogonal to a steady freestream with a doublet model for aerodynamic forces. Wall proximity amplifies a purely symmetric single degree of freedom oscillation with the addition of an out-of-phase force. The success of this simple level of simulation enables progress to develop metrics for unsteady wall interference in dynamic testing of tethered bluff bodies.

  19. Time Variation of the Fine Structure Constant in the Spacetime of a Cosmic Domain Wall

    Science.gov (United States)

    Campanelli, L.; Cea, P.; Tedesco, L.

    The gravitational field produced by a domain wall acts as a medium with spacetime-dependent permittivity ɛ. Therefore, the fine structure constant α=e2/4πɛ will be a time-dependent function at fixed position. The most stringent constraint on the time-variation of α comes from the natural reactor Oklo and gives |˙ α /α | < few × 10-17 yr-1. This limit constrains the tension of a cosmic domain wall to be less than σ ≲ 10-2 MeV3, and then represents the most severe limit on the energy density of a cosmic wall stretching our Universe.

  20. Time Variation of the Fine Structure Constant in the Spacetime of a Domain Wall

    CERN Document Server

    Campanelli, L; Tedesco, L

    2005-01-01

    The gravitational field produced by a domain wall acts as a medium with spacetime-dependent permittivity \\epsilon. Therefore, the fine structure constant \\alpha = e^2/4 \\pi \\epsilon will be a time-dependent function at fixed position. The most stringent constraint on the time-variation of \\alpha comes from the natural reactor Oklo and gives |\\dot{\\alpha}/\\alpha| < few 10^{-17} yr^{-1}. This limit constrains the tension of a cosmic domain wall to be less than \\sigma \\lesssim 10^{-2} MeV^3, and then represents the most severe limit on the energy density of a cosmic wall stretching our Universe.

  1. Numerical Comparison of Active Acoustic and Structural Noise Control in a Stiffened Double Wall Cylinder

    Science.gov (United States)

    Grosveld, Ferdinand W.

    1996-01-01

    The active acoustic and structural noise control characteristics of a double wall cylinder with and without ring stiffeners were numerically evaluated. An exterior monopole was assumed to acoustically excite the outside of the double wall cylinder at an acoustic cavity resonance frequency. Structural modal vibration properties of the inner and outer shells were analyzed by post-processing the results from a finite element analysis. A boundary element approach was used to calculate the acoustic cavity response and the coupled structural-acoustic interaction. In the frequency region of interest, below 500 Hz, all structural resonant modes were found to be acoustically slow and the nonresonant modal response to be dominant. Active sound transmission control was achieved by control forces applied to the inner or outer shell, or acoustic control monopoles placed just outside the inner or outer shell. A least mean square technique was used to minimize the interior sound pressures at the nodes of a data recovery mesh. Results showed that single acoustic control monopoles placed just outside the inner or outer shells resulted in better sound transmission control than six distributed point forces applied to either one of the shells. Adding stiffeners to the double wall structure constrained the modal vibrations of the shells, making the double wall stiffer with associated higher modal frequencies. Active noise control obtained for the stiffened double wall configurations was less than for the unstiffened cylinder. In all cases, the acoustic control monopoles controlled the sound transmission into the interior better than the structural control forces.

  2. Load-carrying capacity of lightly reinforced, prefabricated walls of lightweight aggregate concrete with open structure

    DEFF Research Database (Denmark)

    Goltermann, Per

    2009-01-01

    The paper presents and evaluates the results of a coordinated testing of prefabricated, lightly reinforced walls of lightweight aggregate concrete with open structure. The coordinated testing covers all wall productions in Denmark and will therefore provide a representative assessment of the qual...... of the quality actually produced. Existing and new formulas for the capacity are evaluated by comparison to the test results and a new model with a good correlation with the test results is presented....

  3. High-R Walls for New Construction Structural Performance: Wind Pressure Testing

    Energy Technology Data Exchange (ETDEWEB)

    DeRenzis, A.; Kochkin, V.

    2013-01-01

    This technical report is focused primarily on laboratory testing that evaluates wind pressure performance characteristics for wall systems constructed with exterior insulating sheathing. This research and test activity will help to facilitate the ongoing use of non-structural sheathing options and provide a more in-depth understanding of how wall system layers perform in response to high wind perturbations normal to the surface.

  4. High-R Walls for New Construction Structural Performance. Wind Pressure Testing

    Energy Technology Data Exchange (ETDEWEB)

    DeRenzis, A. [NAHB Research Center Industry Partnership, Upper Marlboro, MD (United States); Kochkin, V. [NAHB Research Center Industry Partnership, Upper Marlboro, MD (United States)

    2013-01-01

    This technical report is focused primarily on laboratory testing that evaluates wind pressure performance characteristics for wall systems constructed with exterior insulating sheathing. This research and test activity will help to facilitate the ongoing use of non-structural sheathing options and provide a more in-depth understanding of how wall system layers perform in response to high wind perturbations normal to the surface.

  5. Intercellular relations and wall structures in mature embryo sacs of four species of angiosperms

    Directory of Open Access Journals (Sweden)

    Monique Fougére-Rifot

    2014-01-01

    Full Text Available During the maturation process of an ovule, the internal walls of the embryo sac becomes gradually thinner from the poles to the central cell. The thinning process results in an association of two plasma membranes with no polysaccharide structure betwen them. The presence of one disymmetrical ER cistern along the walls during the thinning process permits to anticipate a turn-over of carbohydrates.

  6. THE STRUCTURAL ANALYSIS OF STEEL SILOS WITH CYLINDRICAL-WALL BEARING AND PROFILE-STEEL BEARING

    OpenAIRE

    Zhengjun Tang; Daibiao Zhou; Chenwei Peng; Wenping Wu

    2015-01-01

    The silos are widely used in bulk material in many fields such as agriculture, mining, chemical, electric power storage, etc. Thin metal cylindrical silo shells are vulnerable to buckling failure caused by the compressive wall friction force. In this paper, the structural analysis of two types of steel silo with cylindrical-wall bearing and profile-steel bearing is implemented by Abaqus finite element analysis. The results indicate that under the same loading conditions, steel silos with prof...

  7. Progressive collapse resisting capacity of reinforced concrete load bearing wall structures

    Institute of Scientific and Technical Information of China (English)

    Alireza Rahai; Alireza Shahin; Farzad Hatami

    2015-01-01

    Reinforced concrete (RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the “load factor” parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.

  8. Abdominal aortic aneurysms

    DEFF Research Database (Denmark)

    Lindholt, Jes Sanddal

    2010-01-01

    Although the number of elective operations for abdominal aortic aneurysms (AAA) is increasing, the sex- and age-standardised mortality rate of AAAs continues to rise, especially among men aged 65 years or more. The lethality of ruptured AAA continues to be 80-95%, compared with 5-7% by elective....... The acceptance rate was 77%, and 95% accept control scans. Furthermore, persons at the highest risk of having an AAA attend screening more frequently. We found that 97% of the interval cases developed from aortas that initially measured 2.5-2.9 cm - i.e. approx. only 5% attenders need re-screening at 5-year...... methods for measuring the degree of wall calcification must be developed and validated....

  9. Numerical Analysis of Composite Steel Concrete Structural Shear Walls with Steel Encased Profiles

    Directory of Open Access Journals (Sweden)

    Daniel Dan

    2009-01-01

    Full Text Available The use of common reinforced concrete shear walls in high rise buildings is sometimes limited because of the large amount of reinforcement localized at the end of the element. A good alternative in avoiding this disadvantage is to use composite steel concrete structural shear walls with steel encased profiles. This solution used for high rise buildings, offers to designers lateral stiffness, shear capacity and high bending resisting moment of structural walls. The encasement of the steel shapes in concrete is applied also for the following purposes: flexural stiffening and strengthening of compression elements; fire protection; potentially easier repairs after moderate damage; economy with respect both to material and construction. Until now in the national and international literature poor information about nonlinear behaviour of composite steel concrete structural shear walls with steel encased profiles is available. A theoretical and experimental program related to the behaviour of steel concrete structural shear walls with steel encased profiles is developed at “Politehnica” University of Timişoara. The program refers to six different elements, which differ by the shape of the steel encased profile and also by the arrangement of steel shapes on the cross section of the element. In order to calibrate the elements for experimental study some numerical analysis were made. The paper presents the results of numerical analysis with details of stress distribution, crack distribution, structural stiffness at various loads, and load bearing capacity of the elements.

  10. Abdominal aortic aneurysm and histological, clinical, radiological correlation.

    Science.gov (United States)

    Rodella, Luigi Fabrizio; Rezzani, Rita; Bonomini, Francesca; Peroni, Michele; Cocchi, Marco Angelo; Hirtler, Lena; Bonardelli, Stefano

    2016-04-01

    To date, the pathogenesis of abdominal aortic aneurism (AAA) still remains unclear. As such, the aim of this study was to evaluate changes of the aortic structure during AAA. We analysed the microscopic frame of vessels sections, starting from the primum movens leading to abnormal dilatation. AAA samples were collected and processed through various staining methods (Verhoeff-Van Gieson, Masson Goldner, Sirius Red). Subsequently, the vessel morphology and collagenic web of the tunica media and adventitia were determined and the amount of type I and type III collagen was measured. We also applied immune-histochemistry markers for CD34 and PGP 9.5 in order to identify vascular and nerve structures in the aorta. Immune-positivity quantification was used to calculate the percentage of the stained area. We found increasing deposition of type I collagen and reduced type III collagen in both tunica media and adventitia of AAA. The total amount of vasa vasorum, marked with CD34, and nerva vasorum, marked with PGP 9.5, was also higher in AAA samples. Cardiovascular risk factors (blood pressure, dyslipidemia, cigarette smoking) and radiological data (maximum aneurism diameter, intra-luminal thrombus, aortic wall calcification) increased these changes. These results suggest that the tunica adventitia may have a central role in the pathogenesis of AAA as clearly there are major changes characterized by rooted inflammatory infiltration. The presence of immune components could explain these modifications within the framework of the aorta.

  11. COUPLED VIBRATION OF STRUCTURAL THIN-WALLED CORES

    Institute of Scientific and Technical Information of China (English)

    Shiu Cho; J.S. Kuang

    2000-01-01

    This paper presents an analysis of the coupled vibration of asymmetric core structures in tall buildings. The governing equation of free vibration and its corresponding eigenvalue problem, which is a set of equations for laterally flexural vibrations in two different directions coupled by a warping-St. Venant torsional vibration, are derived. Based on the Calerkin method, a generalized approximate method is developed for the analysis of coupled vibration and thus proposed for determining the natural fiequeneies and mode shapes of the structure in triply-coupled vibration. The results of the proposed method for the example structure show good agreement with those of the FEM analysis. The proposed method has been shown to provide a sim ple and rapid, yet accurate, means for coupled vibration analysis of core structures.

  12. Bicuspid Aortic Valve Disease and Ascending Aortic Aneurysms: Gaps in Knowledge

    Directory of Open Access Journals (Sweden)

    Katie L. Losenno

    2012-01-01

    Full Text Available The bicuspid aortic valve is the most common congenital cardiac anomaly in developed nations. The abnormal bicuspid morphology of the aortic valve results in valvular dysfunction and subsequent hemodynamic derangements. However, the clinical presentation of bicuspid aortic valve disease remains quite heterogeneous with patients presenting from infancy to late adulthood with variable degrees of valvular stenosis and insufficiency and associated abnormalities including aortic coarctation, hypoplastic left heart structures, and ascending aortic dilatation. Emerging evidence suggests that the heterogeneous presentation of bicuspid aortic valve phenotypes may be a more complex matter related to congenital, genetic, and/or connective tissue abnormalities. Optimal management of patients with BAV disease and associated ascending aortic aneurysms often requires a thoughtful approach, carefully assessing various risk factors of the aortic valve and the aorta and discerning individual indications for ongoing surveillance, medical management, and operative intervention. We review current concepts of anatomic classification, pathophysiology, natural history, and clinical management of bicuspid aortic valve disease with associated ascending aortic aneurysms.

  13. Role of mechanotransduction in vascular biology: focus on thoracic aortic aneurysms and dissections.

    Science.gov (United States)

    Humphrey, Jay D; Schwartz, Martin A; Tellides, George; Milewicz, Dianna M

    2015-04-10

    Thoracic aortic diseases that involve progressive enlargement, acute dissection, or rupture are influenced by the hemodynamic loads and mechanical properties of the wall. We have only limited understanding, however, of the mechanobiological processes that lead to these potentially lethal conditions. Homeostasis requires that intramural cells sense their local chemomechanical environment and establish, maintain, remodel, or repair the extracellular matrix to provide suitable compliance and yet sufficient strength. Proper sensing, in turn, necessitates both receptors that connect the extracellular matrix to intracellular actomyosin filaments and signaling molecules that transmit the related information to the nucleus. Thoracic aortic aneurysms and dissections are associated with poorly controlled hypertension and mutations in genes for extracellular matrix constituents, membrane receptors, contractile proteins, and associated signaling molecules. This grouping of factors suggests that these thoracic diseases result, in part, from dysfunctional mechanosensing and mechanoregulation of the extracellular matrix by the intramural cells, which leads to a compromised structural integrity of the wall. Thus, improved understanding of the mechanobiology of aortic cells could lead to new therapeutic strategies for thoracic aortic aneurysms and dissections.

  14. Structure and Phase State of Bone Apatite of Calcified Aortic Fragments with Osteoporosis

    Directory of Open Access Journals (Sweden)

    Ya.V. Khyzhnya

    2013-10-01

    Full Text Available The paper represents the results of the study on the structure and phase composition of bone apatite and fragments of calcified aorta of the same experimental animal with model osteoporosis. Examination by the X-ray and electron diffraction, electron microscopy and infrared spectroscopy reveals that pathological calcification of rabbit aorta with model osteoporosis in crystal-chemical terms is the imperfect calcium apatite Ca10(PO46(OH2. Temperature growth of ectopic apatite crystals during annealing at 900C is similar to bioapatite of bone.

  15. Seismic Analysis of Shear-Wall Structures with Vertically Installed Dampers

    Institute of Scientific and Technical Information of China (English)

    Yang Jun; Li Li; Fan Aiwu

    2005-01-01

    Shear-wall structures are quite common in seismic areas because of their successful seismic behavior during severe earthquakes. But shear walls are prone to brittle failure. This study proposes a new method of vertically installed dampers (VID) to reduce the vibration in shear-wall structures. The motion characteristic of a vertical damping system is that every mass has horizontal and rotational displacements simultaneously. The establishment of dynamic equations should take into account the equilibrium conditions of both horizontal and rotational vibrations. Dynamic equilibrium equations of VID systems are derived from a model of a structure with VID. An example shear-wall structure, with and without VID, is studied. There are some changes in the characteristics of the maximum horizontal displacement response. Without dampers, the relative displacements between different floors in the shear wall increase with height. With dampers, the relative displacements are more uniformly distributed, and lateral displacements at the top and at the bottom are closer. When the damping coefficient is 1 000 kN·s/m, the numerical results reveal that the maximum horizontal displacement and the maximum rotational displacement of the top floor have reduced by 59.3 % and 54.8 % respectively.

  16. Organised structures in wall turbulence as deduced from stability theory-based methods

    Indian Academy of Sciences (India)

    P K Sen; S V Veeravalli; P W Carpenter; G Joshi; P S Josan

    2007-02-01

    In earlier work, we have explored the relevance of hydrodynamic stability theory to fully developed turbulent wall flows. Using an extended Orr-Summerfeld Equation, based on an anisotropic eddy-viscosity model, it was shown that there exists a wide range of unstable wave numbers (wall modes), which mimic some of the key features of turbulent wall flows. Here we present experimental confirmation for the same. There is good qualitative and quantitative agreement between theory and experiment. Once the dominant coherent structure is obtained from stability theory, control of turbulence would be the next logical step. As shown, the use of a compliant wall shows considerable promise. We also present some theoretical work for bypass transition (Klebanoff/K-modes), wherein the receptivity of a laminar boundary layer to a vortex sheet in the freestream has been studied. Further, it is shown that triadic interaction between K-modes, 2D TS waves and 3D TS waves can lead to rapid algebraic growth. A similar mechanism seems to carry over to inner wall structures in wall turbulence and perhaps this is the “root cause” for sustenance of turbulence.

  17. Study on near-wall turbulence structures with local Reynolds stress

    Institute of Scientific and Technical Information of China (English)

    LiLI; ChunxiaoXU; GuixiangCUI; ZhaoshunZHANG

    2000-01-01

    The direct-numerical-simulated channel turbulence is analyzed with twodimensional wavelet transform. Considering the relation between turbulence coherent structure and Reynolds stress in near wall region, the local Reynolds stress (LRS) is defined.A new method for extracting coherent signals from turbulence based on the LRS is developed. Velocity fluctuations are decomposed to coherent signals and background signals. It is found that the scaling exponents of coherent signals have a considerable deviation from the Kolmogorov scaling law q/3 (K41 theory), while that, of background signals is very close to q/3. It is confirmed that coherent signals are mainly responsible for the anomalous scalings.Locally characterized by the positive peaks of LRS, the typical structures in near wall regionare obtained by conditional statistical averaging. It is shown that the local character of near-wall turbulence structures can be effectively described with LRS.

  18. THE STRUCTURAL ANALYSIS OF STEEL SILOS WITH CYLINDRICAL-WALL BEARING AND PROFILE-STEEL BEARING

    Directory of Open Access Journals (Sweden)

    Zhengjun Tang

    2015-04-01

    Full Text Available The silos are widely used in bulk material in many fields such as agriculture, mining, chemical, electric power storage, etc. Thin metal cylindrical silo shells are vulnerable to buckling failure caused by the compressive wall friction force. In this paper, the structural analysis of two types of steel silo with cylindrical-wall bearing and profile-steel bearing is implemented by Abaqus finite element analysis. The results indicate that under the same loading conditions, steel silos with profile-steel bearing and cylindrical-Wall bearing have similar values in Mises stress, but the steel silo with profile-steel bearing has a smaller radial displacement and a better capability of buckling resistance. Meanwhile, the total steel volumes reduced 8.0% comparing to the steel silo with cylindrical-wall bearing. Therefore, steel soil with profile-steel bearing not only has a less steel volumes but also a good stability.

  19. Isogeometric analysis for thin-walled composite structures

    NARCIS (Netherlands)

    Guo, Y.

    2016-01-01

    The conceptual ideas behind isogeometric analysis (IGA) are aimed at unifying computer aided design (CAD) and finite element analysis (FEA). Isogeometric analysis employs the non-uniform rational B-spline functions (NURBS) used for the geometric description of a structure to approximate its physical

  20. Graft Copolymerization of Acrylic Acid onto Fungal Cell Wall Structural Polysaccharide

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Acrylic acid was graft-copolymerized onto Rhi. oryzae's cell wall structural polysacchaxide directly and efficiently in aqueous solution with ceric ammonium nitrate as initiator. The maximal grafting percentage of 135.5% was obtained under the condition of [Ce4+]=5mmol.L-1, [AA]=1mol.L-1, T=60°C and t=3h. Graft copolymerization was suggested to proceed through free radical reaction mechanism. Grafting occurred primarily on chitosan. Acrylic acid was also attempted to be grafted onto Asp. niger cell wall structural polysaccharide, and only 44.2% of grafting percentage was resulted.

  1. Controlling methods of a newly developed extra aortic counter-pulsation device using shape memory alloy fibers.

    Science.gov (United States)

    Hashem, Mohamed O; Yamada, A; Tsuboko, Y; Muira, H; Homma, D; Shiraishi, Y; Yambe, T

    2013-01-01

    Diastolic counter-pulsation has been used to provide circulatory augmentation for short term cardiac support. The success of intra-aortic balloon pump (IABP) therapy has generated interest in long term counter-pulsation strategies to treat heart failure patients. The authors have been developing a totally implantable extra aortic pulsation device for the circulatory support of heart failure patients, using 150 µm Ni-Ti anisotropic shape memory alloy (SMA) fibers. These fibers contract by Joule heating with an electric current supply. The special features of our design are as follow: non blood contacting, extra aortic pulsation function synchronizing with the native heart, a wrapping mechanical structure for the aorta in order to achieve its assistance as the aortomyoplsty and the extra aortic balloon pump. The device consisted of rubber silicone wall plates, serially connected for radial contraction. We examined the contractile function of the device, as well as it controlling methods; the phase delay parameter and the pulse width modulation, in a systemic mock circulatory system, with a pneumatically driven silicone left ventricle model, arterial rubber tubing, a peripheral resistance unit, and a venous reservoir. The device was secured around the aortic tubing with a counter-pulsation mode of 1:4 against the heartbeat. Pressure and flow waveforms were measured at the aortic outflow, as well as its driving condition of the contraction phase width and the phase delay. The device achieved its variable phase control for co-pulsation or counter-pulsation modes by changing the phase delay of the SMA fibers. Peak diastolic pressure significantly augmented, mean flow increased (p<0.05) according to the pulse width modulation. Therefore the newly developed extra aortic counter-pulsation device using SMA fibers, through it controlling methods indicated its promising alternative extra aortic approach for non-blood contacting cardiovascular circulatory support.

  2. Autologous adventitial overlay method reinforces anastomoses in aortic surgery.

    Science.gov (United States)

    Minato, Naoki; Okada, Takayuki; Sumida, Tomohiko; Watanabe, Kenichi; Maruyama, Takahiro; Kusunose, Takashi

    2014-05-01

    In this study, we present an inexpensive and effective method for providing a secure and hemostatic anastomosis using autologous adventitia obtained from a dissected or aneurysmal wall. The resected aortic wall is separated between the adventitia and media, and a soft, 2 × 10-cm adventitial strip is overlaid to cover the anastomotic margin. A graft is sutured to the aortic stump. This autologous adventitial overlay method can inexpensively and strongly reinforce the anastomosis during aortic surgery for dissection or aneurysm and will contribute to anastomotic hemostasis and long-term stability.

  3. Aortic Annular Enlargement during Aortic Valve Replacement

    Directory of Open Access Journals (Sweden)

    Selman Dumani

    2016-09-01

    Full Text Available In the surgery of aortic valve replacement is always attempted, as much as possible, to implant the larger prosthesis with the mains goals to enhance the potential benefits, to minimise transvalvular gradient, decrease left ventricular size and avoid the phenomenon of patient-prosthesis mismatch. Implantation of an ideal prosthesis often it is not possible, due to a small aortic annulus. A variety of aortic annulus enlargement techniques is reported to avoid patient-prosthesis mismatch. We present the case that has submitted four three times open heart surgery. We used Manouguian technique to enlarge aortic anulus with excellent results during the fourth time of surgery.

  4. Analytical and Numerical Evaluation of Limit States of MSE Wall Structure

    Science.gov (United States)

    Drusa, Marián; Vlček, Jozef; Holičková, Martina; Kais, Ladislav

    2016-12-01

    Simplification of the design of Mechanically Stabilized Earth wall structures (MSE wall or MSEW) is now an important factor that helps us not only to save a time and costs, but also to achieve the desired results more reliably. It is quite common way in practice, that the designer of a section of motorway or railway line gives order for design to a supplier of geosynthetics materials. However, supplier company has experience and skills, but a general designer does not review the safety level of design and its efficiency, and is simply incorporating into the overall design of the construction project. Actually, large number of analytical computational methods for analysis and design of MSE walls or similar structures are known. The problem of these analytical methods is the verification of deformations and global stability of structure. The article aims to clarify two methods of calculating the internal stability of MSE wall and their comparison with FEM numerical model. Comparison of design approaches allows us to draft an effective retaining wall and tells us about the appropriateness of using a reinforcing element.

  5. Structure of Plant Cell Walls: XI. GLUCURONOARABINOXYLAN, A SECOND HEMICELLULOSE IN THE PRIMARY CELL WALLS OF SUSPENSION-CULTURED SYCAMORE CELLS.

    Science.gov (United States)

    Darvill, J E; McNeil, M; Darvill, A G; Albersheim, P

    1980-12-01

    The isolation, purification, and partial characterization of a glucuronoarabinoxylan, a previously unobserved component of the primary cell walls of dicotyledonous plants, are described. The glucuronoarabinoxylan constitutes approximately 5% of the primary walls of suspension-cultured sycamore cells. This glucuronoarabinoxylan possesses many of the structural characteristics of analogous polysaccharides that have been isolated from the primary and secondary cell walls of monocots as well as from the secondary cell walls of dicots. The glucuronoarabinoxylan of primary dicot cell walls has a linear beta-1,4-linked d-xylopyranosyl backbone with both neutral and acidic sidechains attached at intervals along its length. The acidic sidechains are terminated with glucuronosyl or 4-O-methyl glucuronosyl residues, whereas the neutral sidechains are composed of arabinosyl and/or xylosyl residues.

  6. Finite-Temperature Atomic Structure of 180^o Ferroelectric Domain Walls in PbTiO3

    OpenAIRE

    Angoshtari, Arzhang; Yavari, Arash

    2010-01-01

    In this letter we obtain the finite-temperature structure of 180^o domain walls in PbTiO3 using a quasi-harmonic lattice dynamics approach. We obtain the temperature dependence of the atomic structure of domain walls from 0K up to room temperature. We also show that both Pb-centered and Ti-centered 180^o domain walls are thicker at room temperature; domain wall thickness at T=300K is about three times larger than that of T=0K. Our calculations show that Ti-centered domain walls have a lower f...

  7. Aortic aneurysm repair - endovascular

    Science.gov (United States)

    EVAR; Endovascular aneurysm repair - aorta; AAA repair - endovascular; Repair - aortic aneurysm - endovascular ... Endovascular aortic repair is done because your aneurysm is very large, growing quickly, or is leaking or bleeding. You may have ...

  8. Abdominal aortic aneurysm

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/000162.htm Abdominal aortic aneurysm To use the sharing features on this page, ... blood to the abdomen, pelvis, and legs. An abdominal aortic aneurysm occurs when an area of the aorta becomes ...

  9. Omega-3 Polyunsaturated Fatty Acids: Structural and Functional Effects on the Vascular Wall.

    Science.gov (United States)

    Zanetti, Michela; Grillo, Andrea; Losurdo, Pasquale; Panizon, Emiliano; Mearelli, Filippo; Cattin, Luigi; Barazzoni, Rocco; Carretta, Renzo

    2015-01-01

    Omega-3 polyunsaturated fatty acids (n-3 PUFA) consumption is associated with reduced cardiovascular disease risk. Increasing evidence demonstrating a beneficial effect of n-3 PUFA on arterial wall properties is progressively emerging. We reviewed the recent available evidence for the cardiovascular effects of n-3 PUFA focusing on structural and functional properties of the vascular wall. In experimental studies and clinical trials n-3 PUFA have shown the ability to improve arterial hemodynamics by reducing arterial stiffness, thus explaining some of its cardioprotective properties. Recent studies suggest beneficial effects of n-3 PUFA on endothelial activation, which are likely to improve vascular function. Several molecular, cellular, and physiological pathways influenced by n-3 PUFA can affect arterial wall properties and therefore interfere with the atherosclerotic process. Although the relative weight of different physiological and molecular mechanisms and the dose-response on arterial wall properties have yet to be determined, n-3 PUFA have the potential to beneficially impact arterial wall remodeling and cardiovascular outcomes by targeting arterial wall stiffening and endothelial dysfunction.

  10. Omega-3 Polyunsaturated Fatty Acids: Structural and Functional Effects on the Vascular Wall

    Directory of Open Access Journals (Sweden)

    Michela Zanetti

    2015-01-01

    Full Text Available Omega-3 polyunsaturated fatty acids (n-3 PUFA consumption is associated with reduced cardiovascular disease risk. Increasing evidence demonstrating a beneficial effect of n-3 PUFA on arterial wall properties is progressively emerging. We reviewed the recent available evidence for the cardiovascular effects of n-3 PUFA focusing on structural and functional properties of the vascular wall. In experimental studies and clinical trials n-3 PUFA have shown the ability to improve arterial hemodynamics by reducing arterial stiffness, thus explaining some of its cardioprotective properties. Recent studies suggest beneficial effects of n-3 PUFA on endothelial activation, which are likely to improve vascular function. Several molecular, cellular, and physiological pathways influenced by n-3 PUFA can affect arterial wall properties and therefore interfere with the atherosclerotic process. Although the relative weight of different physiological and molecular mechanisms and the dose-response on arterial wall properties have yet to be determined, n-3 PUFA have the potential to beneficially impact arterial wall remodeling and cardiovascular outcomes by targeting arterial wall stiffening and endothelial dysfunction.

  11. Experimental study on aortic remodeling in sinoaortic denervated rats

    Institute of Scientific and Technical Information of China (English)

    MIAO Chao-yu; TAO Xia; GUAN Yun-feng; YANG You-cai; CHU Zheng-xu; SU Ding-feng

    2001-01-01

    Objective: To study the aortic remodeling produced by chronic sinoaortic denervation (SAD) and its time course, and to study the role of humoral factor in the SAD-induced aortic remodeling. Methods: In rats with chronic SAD or sham operation, the aortic structure was measured by computer-assisted image analysis, the aortic function by isolated artery preparation, and angiotensin Ⅱ concentration by radioimmunoassay. Results and Conclusion: The aortic structural remodeling developed progressively at 4, 8, 16 and 32 weeks after SAD. Aortic structural remodeling after SAD expressed mainly as aortic hypertrophy due to SMC growth and collagen accumulation. The aortic contraction elicited by norepinephrine (NE) was progressively increased 8, 16 and 32 weeks after SAD. The aortic relaxation elicited by acetylcholine (ACh) was depressed 8, 16 and 32 weeks after SAD. In addition, in 32-week SAD rats the NE-induced contraction was not increased by endothelial denudation. These indicated that the increased contraction and depressed relaxation after SAD were related to the change of endothelium and/or the change of interaction between endothelium and SMC. In 10-week SAD rats, plasma angiotensin Ⅱ concentration remained unchanged, whereas aortic angiotensin Ⅱ concentration was significantly increased, suggesting that activation of tissue renin-angiotensin system may be involved in SAD-induced aortic remodeling.

  12. Aortic growth rates in chronic aortic dissection

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, A.M. [Department of Radiology, Division of Thoracic Radiology, University of Michigan Medical Center (United States)]. E-mail: ainekell@med.umich.edu; Quint, L.E. [Department of Radiology, Division of Thoracic Radiology, University of Michigan Medical Center (United States); Nan, B. [School of Public Health, University of Michigan, Ann Arbor, Michigan (United States); Zheng, J. [School of Public Health, University of Michigan, Ann Arbor, Michigan (United States); Cronin, P. [Department of Radiology, Division of Thoracic Radiology, University of Michigan Medical Center (United States); Deeb, G.M. [Division of Cardiac Surgery, University of Michigan Medical Center (United States); Williams, D.M. [Division of Vascular Interventional Imaging, University of Michigan Medical Center (United States)

    2007-09-15

    Aim: To determine and compare rates of descending aortic enlargement and complications in chronic aortic dissection with and without a proximal aortic graft. Methods and materials: Fifty-two patients with dissection involving the descending aorta and who had undergone at least two computed tomography (CT) examinations at our institution between November, 1993 and February, 2004 were identified, including 24 non-operated patients (four type A, 20 type B) and 28 operated patients (type A). CT examinations per patient ranged from two to 10, and follow-up ranged from 1-123 months (mean 49 months, median 38.5 months). On each CT image, the aortic short axis (SA), false lumen (FL), and true lumen (TL) diameters were measured at the longitudinal midpoint of the dissection and at the point of maximum aortic diameter. Complications were tabulated, including aortic rupture and aortic enlargement requiring surgery. Results: For non-operated patients, the midpoint and maximum point SA, TL, and FL diameters increased significantly over time. For operated patients, the midpoint and maximum point SA and FL diameters increased significantly over time. In both groups, aortic enlargement was predominantly due to FL expansion. Diameter increases in non-operated patients were significantly larger than those in operated patients. The rate of change in aortic diameter was constant, regardless of aortic size. Four non-operated and six operated patients developed aortic complications. Conclusions: In patients with a dissection involving the descending thoracic aorta, the FL increased in diameter over time, at a constant rate, and to a greater degree in non-operated patients (mostly type B) compared with operated patients (all type A)

  13. STRUCTURAL EVALUATION OF PSSDB WALL PANEL WITH SQUARE OPENING AND VARIED SCREW SPACING

    Directory of Open Access Journals (Sweden)

    SITI HAWA HAMZAH

    2009-03-01

    Full Text Available Profiled steel sheet dry boards or PSSDB system is an alternative composite construction system comprising of profiled steel sheet compositely connected to dry boards by self-tapping self-driving screws. PSSDB system was used widely as flooring system in the lightweight construction of buildings and office space in factories. Due to its superiority in the installation techniques, PSSDB system was expanded in the application as load bearing wall panel system in buildings. The PSSDB system is as an alternative construction technique on load bearing wall panel that offers cost savings synonymously with the rapid progress of science and technology which leads to the shift from traditional utilization of construction materials to newer construction techniques. A finite element analysis was carried out to determine the effect of screw spacing on the PSSDB wall panel. The spacing selected was between 100 mm to 500 mm, at an increment of 100 mm in each different model. The wall panel measured 3000 mm by 3000 mm with a 1200 mm square window opening, 78 mm thick and butt joints vertically positioned in the dry boards. This paper looks into the system as load bearing wall panels, analyzing it under axial compressive load using established Finite Element technique. The deformation profile of the PSSDB wall panel system showed a single curvature deformation profile, maximum lateral displacement at two-thirds wall panel height and critical sections at the upper corners of the square opening. The finite element analysis had provided good prediction of the structural behavior of the PSSDB wall panel system and it is concluded that the PW200 model possesses the optimum arrangement of the fixing screws used.

  14. Review of Ballistic Limit Equations for Composite Structure Walls of Satellites

    Science.gov (United States)

    Schaefer, Frank K.*; Schneider, E.; Lambert, M.

    2004-08-01

    In this paper a review of existing ballistic limit equations for CFRP (Carbon Fibre Reinforced Plastics) structure walls of satellites is given, and two new ballistic limit equations are presented. The predictive capabilities of the equations are compared to a set of experimental hypervelocity impact test data of CFRP plates and CFRP honeycomb sandwich panels (satellite structure wall) from ENVISAT, AXAF, and a generic technology program. In the literature, three ballistic limit equations for sandwich panels (SP) made from CFRP face-sheets and Al- honeycomb (H/C) core were found and analyzed (Frost's approach, Approach using Christiansen's Whipple shield Ballistic Limit Equation (BLE), and Taylor's approach). Furthermore, in this paper, a new ballistic limit equation was proposed for CFRP H/C SP (Modified ESA Triple Wall Equation) and for composite panels (plates) with and without MLI attached to the surface. The amount of impact data on CFRP structure walls of satellites found in the literature was rather scarce. The new BLE for CFRP plates makes good predictions to the available set of test data. For the BLE for CFRP H/C SP, it was found that Frost's approach and application of Christiansen's BLE to CFRP H/C SP lead to an overprediction of the ballistic limit diameters for ENVISAT structure walls and the samples of the generic technology program. Taylor's approach and the newly designed MET ballistic limit equation have both yielded good predictions for all samples except for the AXAF samples that had rather thin-walled face-sheets and a thin Al H/C core: for these samples the predictions were conservative. Thus, for use in risk analysis tools for satellites (e. g. ESA's ESABASE/DEBRIS tool or NASA's BUMPER code), it is recommended to use either the MET or Taylor equation.

  15. Seismic retroftting of RC columns with RC jackets and wing walls with different structural details

    Science.gov (United States)

    Chang, Shuenn-Yih; Chen, Ting-Wei; Tran, Ngoc-Cuong; Liao, Wen-I.

    2014-06-01

    An original reinforced concrete (RC) column and four strengthened specimens, two with RC jackets and two with wing walls, were tested in this study. The original column specimen was designed to comply with older (pre-1999) design standards so that the usual detailing deficiencies in existing school buildings in Taiwan could be simulated. Two different structural details were chosen to fabricate the full-scale specimens for each retrofitting technique. The study confirmed that either RC jacketing or the installation of wing walls with two different structural details can effectively improve the stiffness and strength of an existing column. RC jacketing shows a better improvement in energy dissipation and ductility when compared to the columns with wing walls installed. This is because the two RC jacketed columns experienced a flexural failure, while a shear failure was found in the two columns with the wing walls installed, and thus led to a drastic decrease of the maximum lateral strengths and ductility. Since many factors may affect the installation of a post-installed anchor, it is better to use standard hooks to replace post-installed anchors in some specific points when using RC jacketing or installing wing walls.

  16. Advancements in identifying biomechanical determinants for abdominal aortic aneurysm rupture.

    Science.gov (United States)

    Kontopodis, Nikolaos; Metaxa, Eleni; Papaharilaou, Yannis; Tavlas, Emmanouil; Tsetis, Dimitrios; Ioannou, Christos

    2015-02-01

    Abdominal aortic aneurysms are a common health problem and currently the need for surgical intervention is determined based on maximum diameter and growth rate criteria. Since these universal variables often fail to predict accurately every abdominal aortic aneurysms evolution, there is a considerable effort in the literature for other markers to be identified towards individualized rupture risk estimations and growth rate predictions. To this effort, biomechanical tools have been extensively used since abdominal aortic aneurysm rupture is in fact a material failure of the diseased arterial wall to compensate the stress acting on it. The peak wall stress, the role of the unique geometry of every individual abdominal aortic aneurysm as well as the mechanical properties and the local strength of the degenerated aneurysmal wall, all confer to rupture risk. In this review article, the assessment of these variables through mechanical testing, advanced imaging and computational modeling is reviewed and the clinical perspective is discussed.

  17. Spiral plume structures in turbulent natural convection between two vertical walls

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    By means of direct numerical simulation, coherent structures are investigated in turbulent natural convection between two vertical differentially heated walls. It is observed that large-scale spanwise vortices and spiral plume structures exist together in the flow. Spiral plume structures appear at the positions with relatively large helicity, large normal vorticity and high fluctuating temperature. In this note, the shape, the characteristics and formation of the spiral structures are studied and compared with those in Rayleigh-Bénard convection. The conditional sampling analysis indicates the main properties of the spiral structures.

  18. Large structural, thin-wall castings made of metals subject to hot tearing, and their fabrication

    Science.gov (United States)

    Smashey, Russell W. (Inventor)

    2001-01-01

    An article, such as a gas turbine engine mixer, is made by providing a mold structure defining a thin-walled, hollow article, and a base metal that is subject to hot tear cracking when cast in a generally equiaxed polycrystalline form, such as Rene' 108 and Mar-M247. The article is fabricated by introducing the molten base metal into the mold structure, and directionally solidifying the base metal in the mold structure to form a directionally oriented structure. The directionally oriented structure may be formed of a single grain or oriented multiple grains.

  19. Quantum Oscillations of the Nanoscale Structural Inhomogeneities of the Domain Wall in Magnetic Bubble.

    Science.gov (United States)

    Shevchenko, A B; Barabash, M Yu

    2015-12-01

    It is shown that at low temperatures, quantum oscillations of nanoscale structural inhomogeneities (the vertical Bloch line and the Bloch point) occur in the domain walls of cylindrical magnetic domains formed in a uniaxial magnetic film with strong magnetic anisotropy. The conditions for the excitation of these oscillations are determined.

  20. Hemodynamics of the Aortic Jet and Implications for Detection of Aortic Stenosis Murmurs

    Science.gov (United States)

    Zhu, Chi; Seo, Junghee; Bakhshaee, Hani; Mittal, Rajat

    2016-11-01

    Cardiac auscultation with a stethoscope has served as the primary method for qualitative screening of cardiovascular conditions for over a hundred years. However, a lack of quantitative understanding of the flow mechanism(s) responsible for the generation of the murmurs, as well as the effect of intervening tissue on the propagation of these murmurs has been a significant limiting factor in the advancement of automated cardiac auscultation. In this study, a multiphysics computational modeling approach is used to investigate these issues. Direct numerical simulation (DNS) is used to explore the fluid dynamics of the jets formed at the aortic valve and the pressure fluctuations generated by the interaction of this jet with the aortic wall. Subsequently, structural wave propagation in the tissue is resolved by a high-order, linear viscoelastic wave solver in order to explore the propagation of the murmurs through a tissue-like material. The implications of these results for cardiac auscultation are discussed. The authors would like to acknowledge the financial support from NSF Grants IIS-1344772, CBET-1511200, and computational resource by XSEDE NSF Grant TG-CTS100002.

  1. Embedded Acoustic Black Holes for semi-passive broadband vibration attenuation in thin-walled structures

    Science.gov (United States)

    Zhao, Liuxian; Semperlotti, Fabio

    2017-02-01

    We explore the use of structure-embedded Acoustic Black Holes (ABH) to design thin-walled structural components exhibiting broadband vibration attenuation characteristics. The ABH is a geometric taper with a power-law profile fully integrated into the structural component and able to induce a smooth and progressive decrease of both the velocity and the wavelength of flexural waves. Previous studies have shown these characteristics to be critical to enable highly efficient vibration attenuation systems. The performance of ABH thin-walled structures is numerically and experimentally evaluated under both transient and steady state excitation conditions. Both numerical and experimental results suggest that the proposed approach enables highly efficient and broadband vibration attenuation performance.

  2. Experimental determination of excitonic band structures of single-walled carbon nanotubes using circular dichroism spectra

    Science.gov (United States)

    Wei, Xiaojun; Tanaka, Takeshi; Yomogida, Yohei; Sato, Naomichi; Saito, Riichiro; Kataura, Hiromichi

    2016-10-01

    Experimental band structure analyses of single-walled carbon nanotubes have not yet been reported, to the best of our knowledge, except for a limited number of reports using scanning tunnelling spectroscopy. Here we demonstrate the experimental determination of the excitonic band structures of single-chirality single-walled carbon nanotubes using their circular dichroism spectra. In this analysis, we use gel column chromatography combining overloading selective adsorption with stepwise elution to separate 12 different single-chirality enantiomers. Our samples show higher circular dichroism intensities than the highest values reported in previous works, indicating their high enantiomeric purity. Excitonic band structure analysis is performed by assigning all observed Eii and Eij optical transitions in the circular dichroism spectra. The results reproduce the asymmetric structures of the valence and conduction bands predicted by density functional theory. Finally, we demonstrate that an extended empirical formula can estimate Eij optical transition energies for any (n,m) species.

  3. Structural evaluation of W-211 flexible receiver platforms and tank pit walls

    Energy Technology Data Exchange (ETDEWEB)

    Shrivastava, H.P.

    1997-11-03

    This document is a structural analysis of the Flexible Receiver Platforms and the tank-pit wall during removal of equipment and during a accidental drop of that equipment. The platform and the pit walls must withstand a accidental drop of a mixer and transfer pumps in specific pits in tanks 102-AP and 104-AP. A mixer pump will be removed from riser 11 in pit 2A on tank 241-AP-102. A transfer pump will be removed from riser 13 in pit 2D on tank 241-AP-102 and another transfer pump will be removed from riser 3A in pit 4A on tank 241-AP-104.

  4. Right ventricular wall abscess in structurally normal heart after leg osteomyelitis: First case.

    Science.gov (United States)

    Ahmad, Tanveer; Pasarad, Ashwini Kumar; Kishore, Kolkebaile Sadanand; Maheshwarappa, Nandakumar Neralakere

    2016-09-01

    A 3-year-old girl presented with fever and acute dyspnea for 4 days. She had suffered an injury to the left lower leg 3 weeks earlier, with abscess formation. Magnetic resonance imaging showed osteomyelitis of the lower tibia. Echocardiography showed a mass in the right ventricular wall. She underwent concomitant heart surgery for removal of the right ventricular mass and limb arthrotomy. We believe this is a first reported case in which a ventricular wall abscess developed in a structurally normal heart following leg osteomyelitis.

  5. The Influence of Infill Wall Topology and Seismic Characteristics on the Response and Damage Distribution in Frame Structures

    Directory of Open Access Journals (Sweden)

    Nikos Nanos

    2013-01-01

    Full Text Available This paper identifies the effects of infill wall existence and arrangement in the seismic response of frame structures utilising the global structural damage index after Park/Ang (GDIPA and the maximum interstorey drift ratio (MISDR to express structural seismic response. Five different infill wall topologies of a 10-storey frame structure have been selected and analysed presenting an improved damage distribution model for infill wall bearing frames, hence promoting the use of nonstructural elements as a means of improving frame structural seismic behaviour and highlighting important aspects of structural response, demonstrating the suitability of such element implementation beyond their intended architectural scope.

  6. Control of Dynamic Response of Thin-Walled Composite Beams using Structural Tailoring and Piezoelectric Actuation

    OpenAIRE

    Na, Sungsoo

    1997-01-01

    A dual approach integrating structural tailoring and adaptive materials technology and designed to control the dynamic response of cantilever beams subjected to external excitations is addressed. The cantilevered structure is modeled as a thin-walled beam of arbitrary cross-section and incorporates a number of non-classical effects such as transverse shear, warping restraint, anisotropy of constituent materials and heterogeneity of the construction. Whereas structura...

  7. Structures of xyloglucans in primary cell walls of gymnosperms, monilophytes (ferns sensu lato) and lycophytes.

    Science.gov (United States)

    Hsieh, Yves S Y; Harris, Philip J

    2012-07-01

    Little is known about the structures of the xyloglucans in the primary cell walls of vascular plants (tracheophytes) other than angiosperms. Xyloglucan structures were examined in 13 species of gymnosperms, 13 species of monilophytes (ferns sensu lato), and two species of lycophytes. Wall preparations were obtained, extracted with 6 M sodium hydroxide, and the extracts treated with a xyloglucan-specific endo-(1→4)-β-glucanase preparation. The oligosaccharides released were analysed by matrix-assisted laser-desorption ionisation time-of-flight mass spectrometry and by high-performance anion-exchange chromatography. The xyloglucan oligosaccharide profiles from the gymnosperm walls were similar to those from the walls of most eudicotyledons and non-commelinid monocotyledons, indicating that the xyloglucans were fucogalactoxyloglucans, containing the fucosylated units XXFG and XLFG. The xyloglucan oligosaccharide profiles for six of the monilophyte species were similar to those of the gymnosperms, indicating they were also fucogalactoxyloglucans. Phylogenetically, these monilophyte species were from both basal and more derived orders. However, the profiles for the other monilophyte species showed various significant differences, including additional oligosaccharides. In three of the species, these additional oligosaccharides contained arabinosyl residues which were most abundant in the profile of Equisetum hyemale. The two species of lycophytes examined, Selaginella kraussiana and Lycopodium cernuum, had quite different xyloglucan oligosaccharide profiles, but neither were fucogalactoxyloglucans. The S. kraussiana profile had abundant oligosaccharides containing arabinosyl residues. The L. cernuum profile indicated the xyloglucan had a very complex structure.

  8. Regulation of genes involved in cell wall synthesis and structure during Ustilago maydis dimorphism.

    Science.gov (United States)

    Robledo-Briones, Mariana; Ruiz-Herrera, José

    2013-02-01

    The cell wall is the structure that provides the shape to fungal cells and protects them from the difference in osmotic pressure existing between the cytosol and the external medium. Accordingly, changes in structure and composition of the fungal wall must occur during cell differentiation, including the dimorphic transition of fungi. We analyzed, by use of microarrays, the transcriptional regulation of the 639 genes identified to be involved in cell wall synthesis and structure plus the secretome of the Basidiomycota species Ustilago maydis during its dimorphic transition induced by a change in pH. Of these, 189 were differentially expressed during the process, and using as control two monomorphic mutants, one yeast like and the other mycelium constitutive, 66 genes specific of dimorphism were identified. Most of these genes were up-regulated in the mycelial phase. These included CHS genes, genes involved in β-1,6-glucan synthesis, N-glycosylation, and proteins containing a residue of glycosylphosphatidylinositol, and a number of genes from the secretome. The possible significance of these data on cell wall plasticity is discussed.

  9. 8th Annual Glycoscience Symposium: Integrating Models of Plant Cell Wall Structure, Biosynthesis and Assembly

    Energy Technology Data Exchange (ETDEWEB)

    Azadi, Paratoo [Univ. of Georgia, Athens, GA (United States)

    2015-09-24

    The Complex Carbohydrate Research Center (CCRC) of the University of Georgia holds a symposium yearly that highlights a broad range of carbohydrate research topics. The 8th Annual Georgia Glycoscience Symposium entitled “Integrating Models of Plant Cell Wall Structure, Biosynthesis and Assembly” was held on April 7, 2014 at the CCRC. The focus of symposium was on the role of glycans in plant cell wall structure and synthesis. The goal was to have world leaders in conjunction with graduate students, postdoctoral fellows and research scientists to propose the newest plant cell wall models. The symposium program closely followed the DOE’s mission and was specifically designed to highlight chemical and biochemical structures and processes important for the formation and modification of renewable plant cell walls which serve as the basis for biomaterial and biofuels. The symposium was attended by both senior investigators in the field as well as students including a total attendance of 103, which included 80 faculty/research scientists, 11 graduate students and 12 Postdoctoral students.

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

    Science.gov (United States)

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

    2016-10-01

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

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

    Science.gov (United States)

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

    2010-01-01

    We present a structured light system to dynamically measure human chest wall motion for respiratory volume estimation. Based on a projection of an encoded color pattern and a few active markers attached to the trunk, respiratory volumes are obtained by evaluating the 3-D topographic changes of the chest wall in an anatomically consistent measuring region during respiration. Three measuring setups are established: a single-sided illuminating-recording setup for standing posture, an inclined single-sided setup for supine posture, and a double-sided setup for standing posture. Results are compared with the pneumotachography and show good agreement in volume estimations [correlation coefficient: R>0.99 (Pevaluation with high accuracy, but also regional pulmonary function assessment in different chest wall behaviors, with the advantage of whole-field measurement.

  12. A XANES characterization of structural defects in single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Zhong Jun [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Song Li [Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); Yan Dongwei [Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China); Wu Ziyu [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China) and National Center for NanoScience and Technology, Beijing 100080 (China)]. E-mail: wuzy@mail.ihep.ac.cn; Wang Chunru [Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China); Xie Sishen [Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); Qian Haijie [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2006-11-15

    Structural defects play an important role in the physics of carbon nanototube. However, very few investigations of the structural changes induced by purifying process and other treatments have been performed by means of X-ray absorption near-edge structure (XANES) spectroscopy. We used XANES spectroscopy to detect the presence of defects induced in single-walled carbon nanotubes (SWNTs) by nitric acid treated processes and by an Ar{sup +} ion bombardment. The relationship between the features in XANES spectrum and the structural defects has been discussed systematically. Data also addresses evidence of oxygen effect induced by aging on nanotubes.

  13. Colloidal membranes of hard rods: unified theory of free edge structure and twist walls.

    Science.gov (United States)

    Kaplan, C Nadir; Meyer, Robert B

    2014-07-14

    Monodisperse suspensions of rod like chiral fd viruses are condensed into a rod-length thick colloidal monolayers of aligned rods by depletion forces. Twist deformations of the molecules are expelled to the monolayer edge as in a chiral smectic A liquid crystal, and a cholesteric band forms at the edge. Coalescence of two such isolated membranes results in a twist wall sandwiched between two regions of aligned rods, dubbed π-walls. By modeling the membrane as a binary fluid of coexisting cholesteric and chiral smectic A liquid-crystalline regions, we develop a unified theory of the π-walls and the monolayer edge. The mean-field analysis of our model yields the molecular tilt profiles, the local thickness change, and the crossover from smectic to cholesteric behavior at the monolayer edge and across the π-wall. Furthermore, we calculate the line tension associated with the formation of these interfaces. Our model offers insights regarding the stability and the detailed structure of the π-wall and the monolayer edge.

  14. Structural studies of complex carbohydrates of plant cell walls. Progress report, June 15, 1992--June 14, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Darvill, A.G.

    1994-10-01

    This report contains the abstracts of fourteen papers published, in press, or in preparation reporting on research activities to investigate the structure, as well as the function of cell walls in plants. This document also contains research on methods to determine the structure of complex carbohydrates of the cell walls.

  15. Idiopathic thoracic aortic aneurysm at pediatric age.

    Science.gov (United States)

    Marín-Manzano, E; González-de-Olano, D; Haurie-Girelli, J; Herráiz-Sarachaga, J I; Bermúdez-Cañete, R; Tamariz-Martel, A; Cuesta-Gimeno, C; Pérez-de-León, J

    2009-03-01

    A 6-year-old-boy presented with epigastric pain and vomiting over 1 year. Chest X-ray and esophagogastric transit showed a mediastinal mass. A chest computerized tomography angiogram demonstrated a descending thoracic aortic aneurysm. Analytical determinations carried out were all negative. The aneurysm was surgically repaired using a Dacron patch. The anatomopathological study described atherosclerotic lesions with calcifications, compatible with an atherosclerotic aneurysm wall. Aneurysms are uncommon in the pediatric population. Usually, no pathogenesis can be determined, and thus, such cases are grouped as idiopathic. Direct repair with or without patch is a therapeutic alternative in pediatric aneurysms and can allow the growth of the aortic circumference.

  16. Diffusion of Alexa Fluor 488-conjugated dendrimers in rat aortic tissue.

    Science.gov (United States)

    Cho, Brenda S; Roelofs, Karen J; Majoros, Istvan J; Baker, James R; Stanley, James C; Henke, Peter K; Upchurch, Gilbert R

    2006-11-01

    In this study, the distribution of labeled dendrimers in native and aneurysmal rat aortic tissue was examined. Adult male rats underwent infrarenal aorta perfusion with generation 5 (G5) acetylated Alexa Fluor 488-conjugated dendrimers for varying lengths of time. In a second set of experiments, rats underwent aortic elastase perfusion followed by aortic dendrimer perfusion 7 days later. Aortic diameters were measured prior to and postelastase perfusion, and again on the day of harvest. Aortas were harvested 0, 12, or 24 h postperfusion, fixed, and mounted. Native aortas were harvested and viewed as negative controls. Aortic cross-sections were viewed and imaged using confocal microscopy. Dendrimers were quantified (counts/high-powered field). Results were evaluated by repeated measures ANOVA and Student's t-test. We found that in native aortas, dendrimers penetrated the aortic wall in all groups. For all perfusion times, fewer dendrimers were present as time between dendrimer perfusion and aortic harvest increased. Longer perfusion times resulted in increased diffusion of dendrimers throughout the aortic wall. By 24 h, the majority of the dendrimers were through the wall. Dendrimers in aneurysmal aortas, on day 0 postdendrimer perfusion, diffused farther into the aortic wall than controls. In conclusion, this study documents labeled dendrimers delivered intra-arterially to native rat aortas in vivo, and the temporal diffusion of these molecules within the aortic wall. Increasing perfusion time and length of time prior to harvest resulted in continued dendrimer diffusion into the aortic wall. These preliminary data provide a novel mechanism whereby local inhibitory therapy may be delivered locally to aortic tissue.

  17. Evolution and dynamics of shear-layer structures in near-wall turbulence

    Science.gov (United States)

    Johansson, Arne V.; Alfredsson, P. H.; Kim, John

    1991-01-01

    Near-wall flow structures in turbulent shear flows are analyzed, with particular emphasis on the study of their space-time evolution and connection to turbulence production. The results are obtained from investigation of a database generated from direct numerical simulation of turbulent channel flow at a Reynolds number of 180 based on half-channel width and friction velocity. New light is shed on problems associated with conditional sampling techniques, together with methods to improve these techniques, for use both in physical and numerical experiments. The results clearly indicate that earlier conceptual models of the processes associated with near-wall turbulence production, based on flow visualization and probe measurements need to be modified. For instance, the development of asymmetry in the spanwise direction seems to be an important element in the evolution of near-wall structures in general, and for shear layers in particular. The inhibition of spanwise motion of the near-wall streaky pattern may be the primary reason for the ability of small longitudinal riblets to reduce turbulent skin friction below the value for a flat surface.

  18. Vibro-acoustic modelling of aircraft double-walls with structural links using Statistical Energy Analysis

    Science.gov (United States)

    Campolina, Bruno L.

    The prediction of aircraft interior noise involves the vibroacoustic modelling of the fuselage with noise control treatments. This structure is composed of a stiffened metallic or composite panel, lined with a thermal and acoustic insulation layer (glass wool), and structurally connected via vibration isolators to a commercial lining panel (trim). The goal of this work aims at tailoring the noise control treatments taking design constraints such as weight and space optimization into account. For this purpose, a representative aircraft double-wall is modelled using the Statistical Energy Analysis (SEA) method. Laboratory excitations such as diffuse acoustic field and point force are addressed and trends are derived for applications under in-flight conditions, considering turbulent boundary layer excitation. The effect of the porous layer compression is firstly addressed. In aeronautical applications, compression can result from the installation of equipment and cables. It is studied analytically and experimentally, using a single panel and a fibrous uniformly compressed over 100% of its surface. When compression increases, a degradation of the transmission loss up to 5 dB for a 50% compression of the porous thickness is observed mainly in the mid-frequency range (around 800 Hz). However, for realistic cases, the effect should be reduced since the compression rate is lower and compression occurs locally. Then the transmission through structural connections between panels is addressed using a four-pole approach that links the force-velocity pair at each side of the connection. The modelling integrates experimental dynamic stiffness of isolators, derived using an adapted test rig. The structural transmission is then experimentally validated and included in the double-wall SEA model as an equivalent coupling loss factor (CLF) between panels. The tested structures being flat, only axial transmission is addressed. Finally, the dominant sound transmission paths are

  19. BiFeO3 domain wall energies and structures: a combined experimental and density functional theory+U study.

    Science.gov (United States)

    Wang, Yi; Nelson, Chris; Melville, Alexander; Winchester, Benjamin; Shang, Shunli; Liu, Zi-Kui; Schlom, Darrell G; Pan, Xiaoqing; Chen, Long-Qing

    2013-06-28

    We determined the atomic structures and energies of 109°, 180°, and 71° domain walls in BiFeO3, combining density functional theory+U calculations and aberration-corrected transmission electron microscopy images. We find a substantial Bi sublattice shift and a rather uniform Fe sublattice across the walls. The calculated wall energies (γ) follow the sequence γ109<γ180<γ71 for the 109°, 180°, and 71° walls. We attribute the high 71° wall energy to an opposite tilting rotation of the oxygen octahedra and the low 109° wall energy to the opposite twisting rotation of the oxygen octahedra across the domain walls.

  20. Pebble bed structures in the vicinity of concave and convex walls

    Energy Technology Data Exchange (ETDEWEB)

    Reimann, Joerg, E-mail: reimann-langhans@web.de [Karlsruhe Institute of Technology, Karlsruhe (Germany); Brun, Emmanuel [European Synchrotron Radiation Facility, Grenoble (France); Ludwig-Maximilians-University, Garching (Germany); Ferrero, Claudio [European Synchrotron Radiation Facility, Grenoble (France); Vicente, Jérôme [Polytech Marseille, Marseille (France)

    2015-10-15

    Highlights: • Detailed tomography experiments were performed to study the packing structure close to concave and convex walls. • A model for arbitrary container geometries is proposed to predict the inner packing factor based on the known total packing factor. • The results are important for the design of ceramic breeder blankets. • The results are relevant for models describing the thermo-mechanical interaction of pebble beds with the blanket structure. - Abstract: Computed tomography experiments were performed with mostly spherical particles in containers with concave, plane and convex walls. Regular pebble packings exist also close to convex cylindrical walls even if the cylinder-to-pebble diameter ratio is about 1, characteristic of thermocouples within the pebble bed. A model for arbitrary container shapes is proposed which predicts the inner packing factor based on the known total packing factor. With increasing vibration efficiency the total packing factor rises because the zones with structured packing increase. Depending on container dimensions, a structured packing can occur in the total pebble bed. Large packing factors are desirable, however, these pebble beds can probably no longer be considered as isotropic with respect to thermo-mechanic properties.

  1. Micromagnetic structure of the domain wall with Bloch lines in an electric field

    Science.gov (United States)

    Borich, M. A.; Tankeev, A. P.; Smagin, V. V.

    2016-07-01

    The micromagnetic structure of the domain wall (DW) with periodically distributed horizontal Bloch lines in a ferromagnetic film in an external electric field has been studied. The effect of the electric field on the internal DW micromagnetic structure is caused by inhomogeneous magnetoelectric coupling. Possible scenarios of the DW internal structure transformations implemented with varying the electric fields strength have been analyzed in detail. For each scenario, static characteristics of the system, such as the energy, DW profile, DW effective thickness, and electric polarization have been calculated.

  2. Structural proteins of the primary cell wall: extraction, purification, and analysis.

    Science.gov (United States)

    Lamport, Derek T A; Tan, Li; Kieliszewski, Marcia J

    2011-01-01

    Structural proteins of the primary cell wall present unusual but interesting problems for structural biologists in particular and plant biologists in general. As structure is the key to function; then the biochemical isolation of these glycoproteins for further study is paramount. Here, we detail the "classical" method for isolating soluble extensin monomers by elution of monomeric precursors to network extensin from tissue cultures. We also outline an additional approach involving genetic engineering that can potentially yield the complete genomic range of extensins and other hydroxyproline-rich glycoprotein (HRGPs) currently underutilized for biotechnology.

  3. Structural insight into the transglycosylation step of bacterial cell-wall biosynthesis.

    Science.gov (United States)

    Lovering, Andrew L; de Castro, Liza H; Lim, Daniel; Strynadka, Natalie C J

    2007-03-09

    Peptidoglycan glycosyltransferases (GTs) catalyze the polymerization step of cell-wall biosynthesis, are membrane-bound, and are highly conserved across all bacteria. Long considered the "holy grail" of antibiotic research, they represent an essential and easily accessible drug target for antibiotic-resistant bacteria, including methicillin-resistant Staphylococcus aureus. We have determined the 2.8 angstrom structure of a bifunctional cell-wall cross-linking enzyme, including its transpeptidase and GT domains, both unliganded and complexed with the substrate analog moenomycin. The peptidoglycan GTs adopt a fold distinct from those of other GT classes. The structures give insight into critical features of the catalytic mechanism and key interactions required for enzyme inhibition.

  4. 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.

  5. Structure of Plant Cell Walls : XXVI. The Walls of Suspension-Cultured Sycamore Cells Contain a Family of Rhamnogalacturonan-I-Like Pectic Polysaccharides.

    Science.gov (United States)

    Ishii, T; Thomas, J; Darvill, A; Albersheim, P

    1989-02-01

    Considerable information has been obtained about the primary structures of suspension-cultured sycamore (Acer pseudoplatanus) cell-wall pectic polysaccharides, i.e. rhamnogalacturonan I, rhamnogalacturonan II, and homogalacturonan. However, these polysaccharides, which are solubilized from the walls by endo-alpha-1,4-polygalacturonase, account for only about half of the pectic polysaccharides known to be present in sycamore cell walls. We now report that, after exhaustive treatment with endo-alpha-1,4-polygalacturonase, additional pectic polysaccharides were extracted from sycamore cell walls by treatment with Na(2)CO(3) at 1 and 22 degrees C. These previously uncharacterized polysaccharides accounted for approximately 4% of the cell wall. Based on the glycosyl and glycosyl-linkage compositions and the nature of the products obtained by treating the quantitatively predominant NaCO(3)-extracted polysaccharides with lithium metal dissolved in ethylenediamine, the polysaccharides were found to strongly resemble rhamnogalacturonan I. However, unlike rhamnogalacturonan I that characteristically had equal amounts of 2- and 2,4-linked rhamnosyl residues in its backbone, the polysaccharides extracted in Na(2)CO(3) at 1 degrees C had markedly disparate ratios of 2- to 2,4-linked rhamnosyl residues. We concluded that polysaccharides similar to rhamnogalacturonan I but with different degrees of branching are present in the walls of suspension-cultured sycamore cells.

  6. Supravalvular aortic stenosis in adult with anomalies of aortic arch vessels and aortic regurgitation

    Science.gov (United States)

    Valente, Acrisio Sales; Alencar, Polyanna; Santos, Alana Neiva; Lobo, Roberto Augusto de Mesquita; de Mesquita, Fernando Antônio; Guimarães, Aloyra Guedis

    2013-01-01

    The supravalvular aortic stenosis is a rare congenital heart defect being very uncommon in adults. We present a case of supravalvular aortic stenosis in adult associated with anomalies of the aortic arch vessels and aortic regurgitation, which was submitted to aortic valve replacement and arterioplasty of the ascending aorta with a good postoperative course. PMID:24598962

  7. Direct measurement of chiral structure and transport in single- and multi-walled carbon nanotubes

    Science.gov (United States)

    Cui, Taoran; Lin, Letian; Qin, Lu-Chang; Washburn, Sean

    2016-11-01

    Electrical devices based on suspended multi-wall carbon nanotubes were constructed and studied. The chiral structure of each shell in a particular nanotube was determined using nanobeam electron diffraction in a transmission electron microscope. The transport properties of the carbon nanotube were also measured. The nanotube device length was short enough that the transport was nearly ballistic, and multiple subbands contributed to the conductance. Thermal excitation of carriers significantly affected nanotube resistance at room temperature.

  8. The Structure of Plant Cell Walls: I. The Macromolecular Components of the Walls of Suspension-cultured Sycamore Cells with a Detailed Analysis of the Pectic Polysaccharides.

    Science.gov (United States)

    Talmadge, K W; Keegstra, K; Bauer, W D; Albersheim, P

    1973-01-01

    This is the first in a series of papers dealing with the structure of cell walls isolated from suspension-cultured sycamore cells (Acer pseudoplatanus). These studies have been made possible by the availability of purified hydrolytic enzymes and by recent improvements in the techniques of methylation analysis. These techniques have permitted us to identify and quantitate the macromolecular components of sycamore cell walls. These walls are composed of 10% arabinan, 2% 3,6-linked arabinogalactan, 23% cellulose, 9% oligo-arabinosides (attached to hydroxyproline), 8% 4-linked galactan, 10% hydroxyproline-rich protein, 16% rhamnogalacturonan, and 21% xyloglucan.The structures of the pectic polymers (the neutral arabinan, the neutral galactan, and the acidic rhamnogalacturonan) were obtained, in part, by methylation analysis of fragments of these polymers which were released from the sycamore walls by the action of a highly purified endopolygalacturonase. The data suggest a branched arabinan and a linear 4-linked galactan occurring as side chains on the rhamnogalacturonan. Small amounts or pieces of a xyloglucan, the wall hemicellulose, appear to be covalently linked to some of the galactan chains. Thus, the galactan appears to serve as a bridge between the xyloglucan and rhamnogalacturonan components of the wall.The rhamnogalacturonan consists of an alpha-(1 --> 4)-linked galacturonan chain which is interspersed with 2-linked rhamnosyl residues. The rhamnosyl residues are not randomly distributed in the chain but probably occur in units of rhamnosyl- (1 --> 4)-galacturonosyl- (1 --> 2)-rhamnosyl. This sequence appears to alternate with a homogalacturonan sequence containing approximately 8 residues of 4-linked galacturonic acid. About half of the rhamnosyl residues are branched, having a substituent attached to carbon 4. This is likely to be the site of attachment of the 4-linked galactan.The hydroxyprolyl oligo-arabinosides of the hydroxyproline-rich glycoprotein

  9. Unexpected death caused by rupture of a dilated aorta in an adult male with aortic coarctation.

    Science.gov (United States)

    Leth, Peter Mygind; Knudsen, Peter Thiis

    2015-09-01

    Aortic coarctation (AC) is a congenital aortic narrowing. We describe for the first time the findings obtained by unenhanced post mortem computed tomography (PMCT) in a case where the death was caused by cardiac tamponade from a ruptured aneurysmal dilatation of the ascending aorta and the aortic arch without dissection combined with aortic coarctation. The patient, a 46-year-old man, was found dead at home. PMCT showed haemopericardium and dilatation of the ascending aorta and the aortic arch. This appearance led to the mistaken interpretation that the images represented a dissecting aneurysm. The autopsy showed instead a thin-walled and floppy dilatation of the ascending aorta and aortic arch with a coarctation just proximal to the ligamentum arteriosum. A longitudinal tear was found in the posterior aortic wall just above the valves. Blood in the surrounding soft tissue intersected with a large haematoma (1000ml) in the pericardial sac. Cardiac hypertrophy (556g) was observed in the patient, though no other cardiovascular abnormalities were found. Histological analysis showed cystic medial necrosis of the ascending aortic wall. A ruptured aneurysmal dilatation of the ascending aorta and the aortic arch without aortic dissection associated with AC is an uncommon cause of haemopericardium that has only been described a few times before. The case is discussed in relation to other reported cases and in the context of the present understanding of this condition.

  10. INTERACTIVE STUDY BETWEEN IDENTICAL COHERENT STRUCTURES IN THE WALL REGION OF A TURBULENT BOUNDARY LAYER

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A theoretical model for identical coherent structures in the wall region of a turbulent boundary layer was proposed, using the idea of general resonant triad of the hydrodynamic stability. The evolution of the structures in the wall region of a turbulent boundary layer was studied by combining the compact finite differences of high numerical accuracy and the Fourier spectral hybrid method for solving the three dimensional Navier-Stokes equations. In this method, the third order mixed explicit-implicit scheme was applied for the time integration. The fifth-order upwind compact finite difference schemes for the nonlinear convection terms in the physical space, and the sixth-order center compact schemes for the derivatives in spectral space were introduced, respectively. The fourth-order compact schemes satisfied by the velocities and pressure in spectral space was derived. As an application, the method was implemented to the wall region of a turbulent boundary to study the evolution of identical coherent structures. It is found that the numerical results are satisfactory.

  11. Automatic analysis of image of surface structure of cell wall-deficient EVC.

    Science.gov (United States)

    Li, S; Hu, K; Cai, N; Su, W; Xiong, H; Lou, Z; Lin, T; Hu, Y

    2001-01-01

    Some computer applications for cell characterization in medicine and biology, such as analysis of surface structure of cell wall-deficient EVC (El Tor Vibrio of Cholera), operate with cell samples taken from very small areas of interest. In order to perform texture characterization in such an application, only a few texture operators can be employed: the operators should be insensitive to noise and image distortion and be reliable in order to estimate texture quality from images. Therefore, we introduce wavelet theory and mathematical morphology to analyse the cellular surface micro-area image obtained by SEM (Scanning Electron Microscope). In order to describe the quality of surface structure of cell wall-deficient EVC, we propose a fully automatic computerized method. The image analysis process is carried out in two steps. In the first, we decompose the given image by dyadic wavelet transform and form an image approximation with higher resolution, by doing so, we perform edge detection of given images efficiently. In the second, we introduce many operations of mathematical morphology to obtain morphological quantitative parameters of surface structure of cell wall-deficient EVC. The obtained results prove that the method can eliminate noise, detect the edge and extract the feature parameters validly. In this work, we have built automatic analytic software named "EVC.CELL".

  12. Fluid-structure-interaction analysis for welded pipes with flow-accelerated corrosion wall thinning

    Energy Technology Data Exchange (ETDEWEB)

    Sun, L.; Ding, Y., E-mail: lan.sun@cnl.ca [Canadian Nuclear Laboratories, Chalk River, Ontario (Canada)

    2016-06-15

    The flow-accelerated corrosion (FAC) entrance effect results in enhanced wall thinning immediately downstream of a weld if the weld connects an upstream FAC-resistant material with a downstream less resistant material. The weld regions, especially those with local repairs, are susceptible to cracking due to the high residual stresses induced by fabrication. The combined effects of the FAC entrance effect and high stresses at a weld might compromise the structural integrity of the piping and lead to a failure. Weld degradation by FAC entrance effect has been observed at nuclear and fossil power plants. This paper describes an application using fluid-structure-interaction (FSI) modelling to study the combined effects of FAC wall thinning, weld residual stresses, and in-service loads on welded structures. Simplified cases analyzed were based on CANDU outlet feeder conditions. The analysis includes the flow and mass transfer modelling of the FAC entrance effect using computational fluid dynamics (CFD) and nonlinear structural analyses of the welded structures with wall thinning and an assumed weld residual stress and strain distribution. The FSI analyses were performed using ANSYS Workbench, an integrated platform that enables the coupling of CFD and structural analysis solutions. The obtained results show that the combination of FAC, weld residual stresses, in-service loads (including the internal pressure) and (or) extreme loads could cause high stresses and affect the integrity of the welded pipes. The present work demonstrated that the FSI modelling can be used as an effective approach to assess the integrity of welded structures. (author)

  13. Direct numerical simulation of Taylor-Couette flow with grooved walls: torque scaling and flow structure

    CERN Document Server

    Zhu, Xiaojue; Verzicco, Roberto; Lohse, Detlef

    2015-01-01

    We present direct numerical simulations of Taylor-Couette flow with grooved walls at a fixed radius ratio $\\eta=r_i/r_o=0.714$ with inner cylinder Reynolds number up to $Re_i=3.76\\times10^4$, corresponding to Taylor number up to $Ta=2.15\\times10^9$. The grooves are axisymmetric V-shaped obstacles attached to the wall with a tip angle of $90^\\circ$. Results are compared with the smooth wall case in order to investigate the effects of grooves on Taylor-Couette flow. We focus on the effective scaling laws for the torque, flow structures, and boundary layers. It is found that, when the groove height is smaller than the boundary layer thickness, the torque is the same as that of the smooth wall cases. With increasing $Ta$, the boundary layer thickness becomes smaller than the groove height. Plumes are ejected from tips of the grooves and a secondary circulation between the latter is formed. This is associated to a sharp increase of the torque and thus the effective scaling law for the torque vs. $Ta$ becomes much ...

  14. Valvular Aortic Stenosis: A Proteomic Insight

    Directory of Open Access Journals (Sweden)

    Fernando Vivanco

    2010-02-01

    Full Text Available Calcified aortic valve disease is a slowly progressive disorder that ranges from mild valve thickening with no obstruction of blood flow, known as aortic sclerosis, to severe calcification with impaired leaflet motion or aortic stenosis. In the present work we describe a rapid, reproducible and effective method to carry out proteomic analysis of stenotic human valves by conventional 2-DE and 2D-DIGE, minimizing the interference due to high calcium concentrations. Furthermore, the protocol permits the aortic stenosis proteome to be analysed, advancing our knowledge in this area. Summary: Until recently, aortic stenosis (AS was considered a passive process secondary to calcium deposition in the aortic valves. However, it has recently been highlighted that the risk factors associated with the development of calcified AS in the elderly are similar to those of coronary artery disease. Furthermore, degenerative AS shares histological characteristics with atherosclerotic plaques, leading to the suggestion that calcified aortic valve disease is a chronic inflammatory process similar to atherosclerosis. Nevertheless, certain data does not fit with this theory making it necessary to further study this pathology. The aim of this study is to develop an effective protein extraction protocol for aortic stenosis valves such that proteomic analyses can be performed on these structures. In the present work we have defined a rapid, reproducible and effective method to extract proteins and that is compatible with 2-DE, 2D-DIGE and MS techniques. Defining the protein profile of this tissue is an important and challenging task that will help to understand the mechanisms of physiological/pathological processes in aortic stenosis valves.

  15. Estudo comparativo da eficácia do etanol e do ácido L-glutâmico na prevenção da calcificação das cúspides e parede aórtica porcina: estudo experimental em ratos Comparative study on the efficacy of ethanol and of l-glutamic acid for preventing calcification of pig cusps and aortic wall: experimental study in rats

    Directory of Open Access Journals (Sweden)

    George Ronald Soncini da ROSA

    2002-06-01

    pouches for each rat. We called each group as follows: GDA (control group, E80% (the group whose structures were previously prepared with ethanol 80% and GA 0.8% (group previously prepared with L-glutamic acid 0.8%; in those groups we measured calcium and performed a microscopic analysis seeking for any calcification, its location and intensity; inflammatory infiltrate, location and type, during a 15, 30, and 60-day period after the implant. RESULTS: Calcium was found in the aortic cusp in the E80% group (1.30±0.21 mg calcium/mg tissue at day 15, (1.05±0.22 mg calcium/mg tissue at day 30, and (0.53±0.42 mg calcium/mg tissue at day 60; in the GA 0.8% group (12.17±0.66 mg calcium/mg tissue at day 15, (15.31±2.82 mg calcium/mg tissue at day 30, and (34.24±16.28 mg calcium/mg tissue at day 60; and in the control group, GDA at day 15 (12.44±2.26 mg calcium/mg tissue, at day 30 (13.44±3.34 mg calcium/mg tissue, and at day 60 (50.85±8.71 µg calcium/mg tissue. As for the calcium measured in the aortic wall, in the E80% group we found (4.62±0.68 µg calcium/mg tissue at day 15, (9.47±2.59 µg calcium/mg tissue at day 30, and (23.56±7.75 µg calcium/mg tissue at day 60; in the GA 0.8% group at day 15 (4.31±0.85 µg calcium/mg tissue, at day 30 (7.69±1.48 µg calcium/mg tissue, and at day 60 (20.50±1.22 µg calcium/mg tissue; and in the control group (GDA at day 15 (7.34±1.32 µg calcium/mg tissue, at day 30 (9.28±0.76 µg calcium/mg tissue, at day 60 (27.60±1.08 µg calcium/mg tissue. Microscopic evaluation of the aortic cusp, showed a progressive calcification in those fixed with GDA. Such process was found partially in the GA 0.8% group, and totally absent in the E80% group. As for the assessment of the aortic wall segments, we also observed progressive calcification, which was not inhibited by the treatment with either GA 0.8% or E80%. CONCLUSIONS: We concluded that a pre-treatment with ethanol at 80% inhibited calcification in pig aortic cusps, however it was

  16. On the vibration of double-walled carbon nanotubes using molecular structural and cylindrical shell models

    Science.gov (United States)

    Ansari, R.; Rouhi, S.; Aryayi, M.

    2016-01-01

    The vibrational behavior of double-walled carbon nanotubes is studied by the use of the molecular structural and cylindrical shell models. The spring elements are employed to model the van der Waals interaction. The effects of different parameters such as geometry, chirality, atomic structure and end constraint on the vibration of nanotubes are investigated. Besides, the results of two aforementioned approaches are compared. It is indicated that by increasing the nanotube side length and radius, the computationally efficient cylindrical shell model gives rational results.

  17. Reinforcement of thin-walled root canal structures for placement of esthetic dowels: a clinical report.

    Science.gov (United States)

    Ayad, Mohamed F; Bahannan, Salma A; Rosenstiel, Stephen F

    2011-01-01

    Thin-walled root canals always present a challenge to dentists to select a restorative treatment that does not further weaken the thin tooth structure. The prognosis of dowel and core restorations can be unpredictable. This clinical report describes the treatment of a patient with extensive caries extending into the root canal of an endodontically treated maxillary central incisor. The use of a flowable composite resin in combination with a quartz fiber reinforced post is described, resulting in the rehabilitation of a structurally compromised root canal with satisfactory esthetic and functional outcomes.

  18. Structural performance of new thin-walled concrete sandwich panel system reinforced with bfrp shear connectors

    DEFF Research Database (Denmark)

    Hodicky, Kamil; Hulin, Thomas; Schmidt, Jacob Wittrup

    2013-01-01

    This paper presents a new thin-walled concrete sandwich panel system reinforced with basalt fiber-reinforced plastic (BFRP) with optimum structural performances and a high thermal resistance developed by Connovate and Technical University of Denmark. The shear connecting system made of a BFRP grid...... is described and provides information on the structural design with its advantages. Experimental and numerical investigations of the BFRP connecting systems were performed. The experimental program included testing of small scale specimens by applying shear (push-off) loading and semi-full scale specimens...

  19. Lunar Return Reentry Thermal Analysis of a Generic Crew Exploration Vehicle Wall Structures

    Science.gov (United States)

    Ko, William L.; Tran, Van T.; Bowles, Jeff

    2007-01-01

    Thermostructural analysis was performed on generic crew exploration vehicle (GCEV) heat shielded wall structures subjected to reentry heating rates based on five potential lunar return reentry trajectories. The GCEV windward outer wall is fabricated with a graphite/epoxy composite honeycomb sandwich panel and the inner wall with an aluminum honeycomb sandwich panel. The outer wall is protected with an ablative Avcoat-5026-39H/CG thermal protection system (TPS). A virtual ablation method (a graphical approximation) developed earlier was further extended, and was used to estimate the ablation periods, ablation heat loads, and the TPS recession layer depths. It was found that up to 83 95 percent of the total reentry heat load was dissipated in the TPS ablation process, leaving a small amount (3-15 percent) of the remaining total reentry heat load to heat the virgin TPS and maintain the TPS surface at the ablation temperature, 1,200 F. The GCEV stagnation point TPS recession layer depths were estimated to be in the range of 0.280-0.910 in, and the allowable minimum stagnation point TPS thicknesses that could maintain the substructural composite sandwich wall at the limit temperature of 300 F were found to be in the range of 0.767-1.538 in. Based on results from the present analyses, the lunar return abort ballistic reentry was found to be quite attractive because it required less TPS weight than the lunar return direct, the lunar return skipping, or the low Earth orbit guided reentry, and only 11.6 percent more TPS weight than the low Earth orbit ballistic reentry that will encounter a considerable weight penalty to obtain the Earth orbit. The analysis also showed that the TPS weight required for the lunar return skipping reentry was much more than the TPS weight necessary for any of the other reentry trajectories considered.

  20. To Problem Pertaining to Calculation of Resistance to Heat Transfer in Modern Structures of Building External Walls

    Directory of Open Access Journals (Sweden)

    L. V. Nesterov

    2007-01-01

    Full Text Available The paper presents a new methodology for determination of resistance to heat transfer of building external walls with the introduction of heat engineering uniformity factors obtained on the basis of calculating two- and three-dimensional temperature pattern. The methodology makes it possible to take into account influence of joints, connections with adjoining structures and jambs of external walls.

  1. Intramural aortic hematomas; Intramurale Haematome der Aorta

    Energy Technology Data Exchange (ETDEWEB)

    Raab, B.W.; Vosshenrich, R.; Fischer, U.; Funke, M.; Grabbe, E. [Goettingen Univ. (Germany). Abt. fuer Roentgendiagnostik

    2001-08-01

    Intramural hematomas (IMH) are regarded as a hemorrhage into the aortic wall. In general a traumatic form can be differentiated from a spontaneous non-traumatic. There is a predisposition of IMH with arterial hypertension and mesoectodermal dysplastic syndromes. The diagnosis is established with the clinical presentation in combination with the findings of different imaging modalities. Acute and subacute discomfort associated with a tendency of collaps are considered as typical presenting complaints. A semicircular or concentric thickening of the aortic wall with the absence of blood flow or a dissection membran are typical findings in transesophageal echocardiography, computed tomography and magnetic resonance tomography. From a differential diagnostic point of view a distinction from atherosclerotic wall changes, intraluminal thrombi and inflammatory aortic diseases is essential. The IMH is considered as an early presentation of aortic dissection, put into and treated according to the Stanford classification. In the course of natural history an IMH can disappear, rupture or progress into a classic aortic dissection. (orig.) [German] Das intramurale Haematom (IMH) ist eine Einblutung in die Aortenwand. Grundsaetzlich kann zwischen traumatischer Genese und einer atraumatischen spontanen Form unterschieden werden. Praedisponierend sind arterielle Hypertension und mesoektodermale Dysplasiesyndrome. Die Diagnose ergibt sich aus der Klinik und den Befunden in den bildgebenden Verfahren. Zu den klinischen Symptomen zaehlen akut oder subakut auftretende Schmerzen, assoziiert mit einer Kollapsneigung. Typische Befunde in der transoesophagealen Echokardiographie, der Computer- oder der Magnetresonanztomographie sind eine halbmondfoermige oder konzentrische Wandverdickung der Aorta ohne Nachweis von Blutfluss oder einer Dissektionsmembran mit Dichtewerten bzw. Signalintensitaeten in Abhaengigkeit vom Alter der Einblutung. Differenzialdiagnostisch ist eine Abgrenzung

  2. Acute aortic and mitral valve regurgitation following blunt chest trauma.

    Science.gov (United States)

    Bernabeu, Eduardo; Mestres, Carlos A; Loma-Osorio, Pablo; Josa, Miguel

    2004-03-01

    Traumatic rupture of intracardiac structures is an uncommon phenomenon although there are a number of reports with regards to rupture of the tricuspid, mitral and aortic valves. We report the case of a 25-year-old patient who presented with acute aortic and mitral valve regurgitation of traumatic origin. Both lesions were seen separated by 2 weeks. Pathophysiology is reviewed. The combination of both aortic and mitral lesions following blunt chest trauma is almost exceptional.

  3. 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.

  4. Simulations of super-structure domain walls in two dimensional assemblies of magnetic nanoparticles

    DEFF Research Database (Denmark)

    Jordanovic, Jelena; Beleggia, Marco; Schiøtz, Jakob

    2015-01-01

    We simulate the formation of domain walls in two-dimensional assemblies of magnetic nanoparticles. Particle parameters are chosen to match recent electron holography and Lorentz microscopy studies of almost monodisperse cobalt nanoparticles assembled into regular, elongated lattices....... As the particles are small enough to consist of a single magnetic domain each, their magnetic interactions can be described by a spin model in which each particle is assigned a macroscopic "superspin." Thus, the magnetic behaviour of these lattices may be compared to magnetic crystals with nanoparticle superspins...... oriented along the long dimension of nanoparticle assemblies rather than along the short dimension. This is unlike what is typically observed in continuous magnetic materials, where the exchange interaction introduces an energetic cost proportional to the area of the domain walls. Structural disorder...

  5. Structures, nanomechanics, and disintegration of single-walled GaN nanotubes: atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Jeong Won; Hwang, Ho Jung; Song, Ki Oh; Choi, Won Young; Byun, Ki Ryang [Chung-Ang University, Seoul (Korea, Republic of); Kwon, Oh Keun [Semyung University, Jecheon (Korea, Republic of); Lee, Jun Ha [Sangmyung University, Chonan (Korea, Republic of); Kim, Won Woo [Juseong College, Cheongwon (Korea, Republic of)

    2003-09-15

    We have investigated the structural, mechanical, and thermal properties of single-walled GaN nanotubes by using atomistic simulations and a Tersoff-type potential. The Tersoff potential for GaN effectively describes the properties of GaN nanotubes. The nanomechanics of GaN nanotubes under tensile and compressive loadings have also been investigated, and Young's modulus has been calculated. The caloric curves of single-walled GaN nanotubes can be divided into three regions corresponding to nanotubes, the disintegrating range, and vapor. Since the stability or the stiffness of a tube decreases with increasing curving sheet-to-tube strain energy, the disintegration temperatures of GaN nanotubes are closely related to the curving sheet-to-tube strain energy.

  6. Physical, functional and structural characterization of the cell wall fractions from baker's yeast Saccharomyces cerevisiae.

    Science.gov (United States)

    Borchani, Chema; Fonteyn, Fabienne; Jamin, Guilhem; Paquot, Michel; Thonart, Philippe; Blecker, Christophe

    2016-03-01

    The yeast cell wall of Saccharomyces cerevisiae is an important source of β-d-glucan, a glucose homopolymer with many functional, nutritional and human health benefits. In the present study, the yeast cell wall fractionation process involving enzymatic treatments (savinase and lipolase enzymes) affected most of the physical and functional characteristics of extracted fractions. Thus, the fractionation process showed that β-d-glucan fraction F4 had significantly higher swelling power and fat binding capacity compared to other fractions (F1, F2 and F3). It also exhibited a viscosity of 652.12mPas and a high degree of brightness of extracted β-d-glucan fraction. Moreover, the fractionation process seemed to have an effect on structural and thermal properties of extracted fractions. Overall, results showed that yeast β-d-glucan had good potential for use as a prebiotic ingredient in food, as well as medicinal and pharmaceutical products.

  7. High-R Walls for New Construction Structural Performance: Integrated Rim Header Testing

    Energy Technology Data Exchange (ETDEWEB)

    DeRenzis, A. [NAHB Research Center, Upper Marlboro, MD (United States); Kochkin, V. [NAHB Research Center, Upper Marlboro, MD (United States); Wiehagen, J. [NAHB Research Center, Upper Marlboro, MD (United States)

    2013-01-01

    Two prominent approaches within the Building America Program to construct higher R-value walls have included use of larger dimension framing and exterior rigid foam insulation. These approaches have been met with some success; however for many production builders, where the cost of changing framing systems is expensive, the changes have been slow to be realized. In addition, recent building code changes have raised some performance issues for exterior sheathing and raised heel trusses, for example, that indicates a need for continued performance testing for wall systems. The testing methods presented in this report evaluate structural rim header designs over openings up to 6 ft wide and applicable to one- and two-story homes.

  8. FBN1 Mutations in Patients With Descending Thoracic Aortic Dissections

    Science.gov (United States)

    Brautbar, Ariel; LeMaire, Scott A.; Franco, Luis M.; Coselli, Joseph S.; Milewicz, Dianna M.; Belmont, John W.

    2013-01-01

    Aortic aneurysm and dissection cause significant morbidity and mortality. There are several known single gene disorders that predispose to isolated aortic disease and eventually aneurysm and dissection. FBN1 mutations are associated with multiple clinical phenotypes, including Marfan syndrome (MFS), MASS phenotype, and familial ectopia lentis, but rarely with isolated aortic aneurysm and dissection. In this report, we describe three patients who presented with primary descending thoracic aortic dissection and who were found to have an FBN1 mutation. None of the patients fulfilled clinical criteria for the diagnosis of MFS, and all had few or none of the skeletal features typical of the condition. Two patients had a history of long-term hypertension, and such a history was suspected in the third patient. These observations suggest that some individuals with FBN1 mutations have significant aortic disease involvement of other systems that is typical of FBN1 mutation-related syndromes. Superimposed risk factors, such as hypertension, may weaken the aortic wall and eventually lead to aortic dissection. Given that the cost continues to decrease, we suggest that diagnostic DNA sequencing for FBN1 mutations in patients with thoracic aortic aneurysms and dissection may be a practical clinical step in evaluating such patients and at-risk family members. PMID:20082464

  9. Aortic Remodeling Following Transverse Aortic Constriction in Mice is Attenuated with AT1 Receptor Blockade

    Science.gov (United States)

    Kuang, Shao-Qing; Geng, Liang; Prakash, Siddharth K.; Cao, Jiu-Mei; Guo, Steven; Villamizar, Carlos; Kwartler, Callie S.; Ju, Xiaoxi; Brasier, Allan R.; Milewicz, Dianna M.

    2016-01-01

    Objective Although hypertension is the most common risk factor for thoracic aortic diseases, it is not understood how increased pressures on the ascending aorta lead to aortic aneurysms. We investigated the role of Ang II type 1 (AT1) receptor activation in ascending aortic remodeling in response to increased biomechanical forces using a transverse aortic constriction (TAC) mouse model. Approach and Results Two weeks after TAC, the increased biomechanical pressures led to ascending aortic dilatation, aortic wall thickening and medial hypertrophy. Significant adventitial hyperplasia and inflammatory responses in TAC ascending aortas were accompanied by increased adventitial collagen, elevated inflammatory and proliferative markers, and increased cell density due to accumulation of myofibroblasts and macrophages. Treatment with losartan significantly blocked TAC induced vascular inflammation and macrophage accumulation. However, losartan only partially prevented TAC induced adventitial hyperplasia, collagen accumulation and ascending aortic dilatation. Increased Tgfb2 expression and phosphorylated-Smad2 staining in the medial layer of TAC ascending aortas was effectively blocked with losartan. In contrast, the increased Tgfb1 expression and adventitial phospho-Smad2 staining were only partially attenuated by losartan. In addition, losartan significantly blocked Erk activation and ROS production in the TAC ascending aorta. Conclusions Inhibition of the AT1 receptor using losartan significantly attenuated the vascular remodeling associated with TAC but did not completely block the increased TGF- β1 expression, adventitial Smad2 signaling and collagen accumulation. These results help to delineate the aortic TGF-β signaling that is dependent and independent of the AT1 receptor after TAC. PMID:23868934

  10. A Literature Review of the Numerical Analysis of Abdominal Aortic Aneurysms Treated with Endovascular Stent Grafts

    Directory of Open Access Journals (Sweden)

    David Roy

    2012-01-01

    Full Text Available The purpose of this paper is to present the basic principles and relevant advances in the computational modeling of abdominal aortic aneurysms and endovascular aneurysm repair, providing the community with up-to-date state of the art in terms of numerical analysis and biomechanics. Frameworks describing the mechanical behavior of the aortic wall already exist. However, intraluminal thrombus nonhomogeneous structure and porosity still need to be well characterized. Also, although the morphology and mechanical properties of calcifications have been investigated, their effects on wall stresses remain controversial. Computational fluid dynamics usually assumes a rigid artery wall, whereas fluid-structure interaction accounts for artery compliance but is still challenging since arteries and blood have similar densities. We discuss alternatives to fluid-structure interaction based on dynamic medical images that address patient-specific hemodynamics and geometries. We describe initial stresses, elastic boundary conditions, and statistical strength for rupture risk assessment. Special emphasis is accorded to workflow development, from the conversion of medical images into finite element models, to the simulation of catheter-aorta interactions and stent-graft deployment. Our purpose is also to elaborate the key ingredients leading to virtual stenting and endovascular repair planning that could improve the procedure and stent-grafts.

  11. Water structures inside and outside single-walled carbon nanotubes under perpendicular electric field

    Institute of Scientific and Technical Information of China (English)

    Zhen XU; Guo-hui HU; Zhi-liang WANG; Zhe-wei ZHOU

    2014-01-01

    The structures of water inside and outside (6,6), (8,8), and (10,10) single-walled carbon nanotubes (SWCNTs) under an electric field perpendicular to the tube axis are investigated by molecular dynamics simulations. The results show that dipole reorientation induced by electric field plays a significant role on the structures of confined water inside and outside SWCNTs. Inside SWCNTs, the average water occupancy and the average number of hydrogen bonds (H-bonds) per water molecule decrease as the electric intensity increases. Because the field intensity is sufficiently strong, the initial water structures inside the SWCNTs are destroyed, and the isolated water clusters are found. Outside SWCNTs, the azimuthal distributions of the density and the average number of H-bonds per water molecule around the solid walls become more and more asymmetric as the electric intensity increases. The percentages of water molecules involved in 0-5 H-bonds for all the three types of SWCNTs under different field intensities are displayed. The results show that those water molecules involved with most H-bonds are the most important to hold the original structures. When the electric field direction is parallel with the original preferred orientation, the density and the H-bond connections in water will be increased; when the electric field direction is perpendicular to the original preferred orientation, the density and the H-bond connections in water will be decreased.

  12. The Importance of Hydraulic Structures for Society: Quay Walls and Dikes in the Netherlands

    Directory of Open Access Journals (Sweden)

    de Gijt J.G.

    2015-12-01

    Full Text Available Since mankind exists, men have undertaken engineering activities to make their life more pleasant and secure. However this has not been an easy task, especially in the past. The knowledge of mathematics and physics to describe engineering problems became available only since 1400-1500. Nevertheless, great achievements have been made by man before that time, e.g. the pyramids in Egypt, the first sluice in China, the Borobudur temple in Indonesia, and the design and building activities of the Inca’s in South America. To illustrate this development, also the world economy, world ecology will be shortly mentioned. The structures that are briefly discussed in this paper are: soil and concrete dams for generating electricity, reservoirs for irrigation and drinking water, dikes, sluices, inland and sea, tunnels, and quay walls. This paper presents an overview of hydraulic structures in general with the emphasis on quay walls and dikes in the Netherlands. Examples of these structures will be discussed illustrating present state of the art and also with a view to the future. Conclusions and recommendations are given to enhance the knowledge of hydraulic structures.

  13. Unusual presenting of acute aortic dissection due to penetrating atheromatous ulcer.

    Science.gov (United States)

    Atas, Halil; Durmus, Erdal; Sunbul, Murat; Birkan, Yasar; Ozben, Beste

    2014-07-01

    Penetrating atheromatous ulcer (PAU) is an atherosclerotic ulcer penetrating the internal elastic lamina of the aortic wall causing a hematoma within the media layer of aorta. They are commonly located in the descending aorta of the elderly and hypertensive patients. They may rarely be complicated by aortic dissection. We report a relative young normotensive patient presenting with acute aortic dissection due to PAU located in the ascending aorta.

  14. [Genetic aspects of the pathogenesis of aortic abdominal aneurysms].

    Science.gov (United States)

    Waliszewski, Krzysztof; Słomski, Ryszard; Oszkinis, Grzegorz; Majewski, Wacław

    2005-01-01

    In industrialized countries the number of abdominal aortic aneurysms (AAA) is continuously rising. In recent years the mortality rate tripled and it is the number 13 cause of death in United States. Despite many identified risk factors and understanding of their pathomechanisms, the pathogenesis of AAA remains unclear. Thanks to the epidemiological researches and improvement of molecular techniques it was noted that AAA may have a genetic bases. The diversity between the possible genomic defects that could lead to the development of aneurytic changes was also suggested. This has a direct relationship with the complexity of the aortic wall structure and therefore with the number of potential injury locations. Current genetic research confirms the changes in expression and the many polymorphic variants of genes coding structural and enzymatic proteins. Thus, AAA seems to be a disease with multifactor pathogenesis and numerous possible genome anomaly variants. Hence, it seems that the complete understanding of the genetic bases of AAA continuous to be distant. However, efforts in this matter remain valuable, giving hope for an improved diagnosis, prophylaxis and treatment of this disease. This article is a review of the available knowledge regarding the genetic origin of AAA.

  15. Synthesis of siliceous hollow spheres with large mesopore wall structure by supercritical CO2-in-water interface templating.

    Science.gov (United States)

    Wang, Jiawei; Xia, Yongde; Wang, Wenxin; Mokaya, Robert; Poliakoff, Martyn

    2005-01-14

    Hollow silica spheres with large mesopore wall structures have been synthesized via CO(2)-in-water emulsion templating in the presence of PEO-PPO-PEO block copolymers under supercritical fluid conditions.

  16. Fluid dynamics of aortic root dilation in Marfan syndrome

    CERN Document Server

    Querzoli, Giorgio; Espa, Stefania; Costantini, Martina; Sorgini, Francesca

    2014-01-01

    Aortic root dilation and propensity to dissection are typical manifestations of the Marfan Syndrome (MS), a genetic defect leading to the degeneration of the elastic fibres. Dilation affects the structure of the flow and, in turn, altered flow may play a role in vessel dilation, generation of aneurysms, and dissection. The aim of the present work is the investigation in-vitro of the fluid dynamic modifications occurring as a consequence of the morphological changes typically induced in the aortic root by MS. A mock-loop reproducing the left ventricle outflow tract and the aortic root was used to measure time resolved velocity maps on a longitudinal symmetry plane of the aortic root. Two dilated model aortas, designed to resemble morphological characteristics typically observed in MS patients, have been compared to a reference, healthy geometry. The aortic model was designed to quantitatively reproduce the change of aortic distensibility caused by MS. Results demonstrate that vorticity released from the valve ...

  17. Elastic fiber regeneration in vitro and in vivo for treatment of experimental abdominal aortic aneurysm

    Institute of Scientific and Technical Information of China (English)

    XIONG Jiang; GUO Wei; WEI Ren; ZUO Shang-wei; LIU Xiao-ping; ZHANG Tao

    2013-01-01

    Background The pathological characteristics of abdominal aortic aneurysm (AAA) involved the regression of extracellular matrix (ECM) in aortic walls,especially elastic structure in medial layer.As the major structural protein of aorta,elastin contributes to the extensibility and elastic recoil of the vessels.We hypothesized that overexpression of elastin in vessel walls might regenerate the elastic structure of ECM,restore the elastic structure of the aneurysmal wall,and eventually lead to a reduction of aortic diameters (ADs) in an experimental model of AAA.Methods Tropoelastin (TE) of Sprague Dawley (SD) rat was synthesized by reverse transcription polymerase chain reaction and used to construct adneviral vectors containing elastin precursor protein (AdTE-GFP).Cultured vascular smooth muscle cells (VSMCs) from aortas of male SD rats were transfected with AdTE-GFP,AdGFP,adenoviral vector (AdNull),and phosphate buffered saline (PBS).Immunofluorescence staining was performed to determine the expression of elastin in transfected cells.The expression of elastic fibers in ECM of VSMCs transfected with AdTE-GFP were detected by fluorescence microscopy and transmission electron microscopy (TEM) at 1,3,and 5 days following gene transfer.The AAA vessel walls were infused with AdTE-GFP or an empty AdNull,or PBS directly into the aneurysmal lumen.ADs of the aneurysms were compared in infused aortas.Formation of new elastic fibers in vivo was assessed by hematoxylin and eosin,and elastic von-Giesson staining.Recombinant elastin-GFP in vivo was identified by immunohistochemical staining.Results Elastic fibers were increased both in ECM of VSMC and in vessel walls after gene transfer.Histological studies revealed that the AdTE-GFP-transduced aortas had elastic fiber regeneration in the aneurysmal walls.The AdTE-GFP-transduced aortas showed a decreased AD (23.04%±14.49%,P <0.01) in AAA vessel walls.Conclusions Elastic fibers have been successfully overexpressed both in

  18. Therapeutics Targeting Drivers of Thoracic Aortic Aneurysms and Acute Aortic Dissections: Insights from Predisposing Genes and Mouse Models.

    Science.gov (United States)

    Milewicz, Dianna M; Prakash, Siddharth K; Ramirez, Francesco

    2017-01-14

    Thoracic aortic diseases, including aneurysms and dissections of the thoracic aorta, are a major cause of morbidity and mortality. Risk factors for thoracic aortic disease include increased hemodynamic forces on the ascending aorta, typically due to poorly controlled hypertension, and heritable genetic variants. The altered genes predisposing to thoracic aortic disease either disrupt smooth muscle cell (SMC) contraction or adherence to an impaired extracellular matrix, or decrease canonical transforming growth factor beta (TGF-β) signaling. Paradoxically, TGF-β hyperactivity has been postulated to be the primary driver for the disease. More recently, it has been proposed that the response of aortic SMCs to the hemodynamic load on a structurally defective aorta is the primary driver of thoracic aortic disease, and that TGF-β overactivity in diseased aortas is a secondary, unproductive response to restore tissue function. The engineering of mouse models of inherited aortopathies has identified potential therapeutic agents to prevent thoracic aortic disease.

  19. Relationships among the structural topology, bond strength, and mechanical properties of single-walled aluminosilicate nanotubes.

    Science.gov (United States)

    Liou, Kai-Hsin; Tsou, Nien-Ti; Kang, Dun-Yen

    2015-10-21

    Carbon nanotubes (CNTs) are regarded as small but strong due to their nanoscale microstructure and high mechanical strength (Young's modulus exceeds 1000 GPa). A longstanding question has been whether there exist other nanotube materials with mechanical properties as good as those of CNTs. In this study, we investigated the mechanical properties of single-walled aluminosilicate nanotubes (AlSiNTs) using a multiscale computational method and then conducted a comparison with single-walled carbon nanotubes (SWCNTs). By comparing the potential energy estimated from molecular and macroscopic material mechanics, we were able to model the chemical bonds as beam elements for the nanoscale continuum modeling. This method allowed for simulated mechanical tests (tensile, bending, and torsion) with minimum computational resources for deducing their Young's modulus and shear modulus. The proposed approach also enabled the creation of hypothetical nanotubes to elucidate the relative contributions of bond strength and nanotube structural topology to overall nanotube mechanical strength. Our results indicated that it is the structural topology rather than bond strength that dominates the mechanical properties of the nanotubes. Finally, we investigated the relationship between the structural topology and the mechanical properties by analyzing the von Mises stress distribution in the nanotubes. The proposed methodology proved effective in rationalizing differences in the mechanical properties of AlSiNTs and SWCNTs. Furthermore, this approach could be applied to the exploration of new high-strength nanotube materials.

  20. 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.

  1. Structure of Ristocetin A in Complex with a Bacterial Cell-wall Mimetic

    Energy Technology Data Exchange (ETDEWEB)

    Nahoum, V.; Spector, S; Loll, P

    2009-01-01

    Antimicrobial drug resistance is a serious public health problem and the development of new antibiotics has become an important priority. Ristocetin A is a class III glycopeptide antibiotic that is used in the diagnosis of von Willebrand disease and which has served as a lead compound for the development of new antimicrobial therapeutics. The 1.0 A resolution crystal structure of the complex between ristocetin A and a bacterial cell-wall peptide has been determined. As is observed for most other glycopeptide antibiotics, it is shown that ristocetin A forms a back-to-back dimer containing concave binding pockets that recognize the cell-wall peptide. A comparison of the structure of ristocetin A with those of class I glycopeptide antibiotics such as vancomycin and balhimycin identifies differences in the details of dimerization and ligand binding. The structure of the ligand-binding site reveals a likely explanation for ristocetin A's unique anticooperativity between dimerization and ligand binding.

  2. Structural and electronic properties of boron-doped double-walled silicon carbide nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Behzad, Somayeh, E-mail: somayeh.behzad@gmail.co [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Moradian, Rostam [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Nano Science and Technology Research Center, Razi University, Kermanshah (Iran, Islamic Republic of); Computational Physical Science Research Laboratory, Department of Nano Science, Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Chegel, Raad [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of)

    2010-12-01

    The effects of boron doping on the structural and electronic properties of (6,0)-(14,0) double-walled silicon carbide nanotube (DWSiCNT) are investigated by using spin-polarized density functional theory. It is found that boron atom could be more easily doped in the inner tube. Our calculations indicate that a Si site is favorable for B under C-rich condition and a C site is favorable under Si-rich condition. Additionally, B-substitution at either single carbon or silicon atom site in DWSiCNT could induce spontaneous magnetization.

  3. Three-dimensional polymeric structures of single-wall carbon nanotubes

    Science.gov (United States)

    Lian, Chao-Sheng; Wang, Jian-Tao

    2014-05-01

    We explore by ab initio calculations the possible crystalline phases of polymerized single-wall carbon nanotubes (P-SWNTs) and determine their structural, elastic, and electronic properties. Based on direct cross-linking and intertube sliding-assisted cross-linking mechanisms, we have identified a series of stable three-dimensional polymeric structures for the zigzag nanotubes up to (10,0). Among proposed P-SWNT phases, the structures with favorable diamond-like sp3 intertube bonding configuration and small tube cross-section distortion are found to be the most energetically stable ones. These polymeric crystalline phases exhibit high bulk and shear moduli superior to SWNT bundles, and show metallic or semiconducting properties depending on the diameter of constituent tubes. We also propose by hydrostatic pressure simulations that the intertube sliding between van der Waals bonded nanotubes may be an effective route to promote the polymerization of SWNTs under pressure.

  4. Three-dimensional polymeric structures of single-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Lian, Chao-Sheng; Wang, Jian-Tao, E-mail: wjt@aphy.iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-05-28

    We explore by ab initio calculations the possible crystalline phases of polymerized single-wall carbon nanotubes (P-SWNTs) and determine their structural, elastic, and electronic properties. Based on direct cross-linking and intertube sliding-assisted cross-linking mechanisms, we have identified a series of stable three-dimensional polymeric structures for the zigzag nanotubes up to (10,0). Among proposed P-SWNT phases, the structures with favorable diamond-like sp{sup 3} intertube bonding configuration and small tube cross-section distortion are found to be the most energetically stable ones. These polymeric crystalline phases exhibit high bulk and shear moduli superior to SWNT bundles, and show metallic or semiconducting properties depending on the diameter of constituent tubes. We also propose by hydrostatic pressure simulations that the intertube sliding between van der Waals bonded nanotubes may be an effective route to promote the polymerization of SWNTs under pressure.

  5. Impact of structural design criteria on first wall surface heat flux limit

    Energy Technology Data Exchange (ETDEWEB)

    Majumdar, S. [Argonne National Lab., IL (United States)

    1998-09-01

    The irradiation environment experienced by the in-vessel components of fusion reactors presents structural design challenges not envisioned in the development of existing structural design criteria such as the ASME Code or RCC-MR. From the standpoint of design criteria, the most significant issues stem from the irradiation-induced changes in material properties, specifically the reduction of ductility, strain hardening capability, and fracture toughness with neutron irradiation. Recently, Draft 7 of the ITER structural design criteria (ISDC), which provide new rules for guarding against such problems, was released for trial use by the ITER designers. The new rules, which were derived from a simple model based on the concept of elastic follow up factor, provide primary and secondary stress limits as functions of uniform elongation and ductility. The implication of these rules on the allowable surface heat flux on typical first walls made of type 316 stainless steel and vanadium alloys are discussed.

  6. Nanocatalyst structure as a template to define chirality of nascent single-walled carbon nanotubes.

    Science.gov (United States)

    Gómez-Gualdrón, Diego A; Zhao, Jin; Balbuena, Perla B

    2011-01-01

    Chirality is a crucial factor in a single-walled carbon nanotube (SWCNT) because it determines its optical and electronic properties. A chiral angle spanning from 0° to 30° results from twisting of the graphene sheet conforming the nanotube wall and is equivalently expressed by chiral indexes (n,m). However, lack of chirality control during SWCNT synthesis is an obstacle for a widespread use of these materials. Here we use first-principles density functional theory (DFT) and classical molecular dynamics (MD) simulations to propose and illustrate basic concepts supporting that the nanocatalyst structure may act as a template to control the chirality during nanotube synthesis. DFT optimizations of metal cluster (Co and Cu)∕cap systems for caps of various chiralities are used to show that an inverse template effect from the nascent carbon nanostructure over the catalyst may exist in floating catalysts; such effect determines a negligible chirality control. Classical MD simulations are used to investigate the influence of a strongly interacting substrate on the structure of a metal nanocatalyst and illustrate how such interaction may help preserve catalyst crystallinity. Finally, DFT optimizations of carbon structures on stepped (211) and (321) cobalt surfaces are used to demonstrate the template effect imparted by the nanocatalyst surface on the growing carbon structure at early stages of nucleation. It is found that depending on the step structure and type of building block (short chains, single atoms, or hexagonal rings), thermodynamics favor armchair or zigzag termination, which provides guidelines for a chirality controlled process based on tuning the catalyst structure and the type of precursor gas.

  7. The Structure of Plant Cell Walls: IV. A Structural Comparison of the Wall Hemicellulose of Cell Suspension Cultures of Sycamore (Acer PseudoPlatAnus) and of Red Kidney Bean (Phaseolus Vulgaris).

    Science.gov (United States)

    Wilder, B M; Albersheim, P

    1973-05-01

    The molecular structure and chemical properties of the hemicellulose present in the isolated cell walls of suspension cultures of sycamore (Acer pseudoplatanus) cells has recently been described by Bauer et al. (Plant Physiol. 51: 174-187). The hemicellulose of the sycamore primary cell wall is a xyloglucan. This polymer functions as an important cross-link in the structure of the cell wall; the xyloglucan is hydrogen-bonded to cellulose and covalently attached to the pectic polymers.The present paper describes the structure of a xyloglucan present in the walls and in the extracellular medium of suspension-cultured Red Kidney bean (Phaseolus vulgaris) cells and compares the structure of the bean xyloglucan with the structure of the sycamore xyloglucan. Although some minor differences were found, the basic structure of the xyloglucans in the cell walls of these distantly related species is the same. The structure is based on a repeating heptasaccharide unit which consists of four residues of beta-1, 4-linked glucose and three residues of terminal xylose linked to the 6 position of three of the glucosyl residues.

  8. Evaluation of Distensibility and Stiffness of Ascending Aortic Aneurysm using Magnetic Resonance Imaging

    Directory of Open Access Journals (Sweden)

    Kaushal Kishore Tiwari

    2016-12-01

    Conclusions: MRI measurement of aortic diameters, distensibility, and flow wave velocity is an easy, reliable and reproducible technique. Distensibility and pulse wave velocity define the elasticity of the aorta. We have observed that elasticity of aortic wall is decreased in ascending aorta aneurysm patients. Keywords: ascending aorta aneurysm; distensibility; pulse wave velocity; MRI. | PubMed

  9. 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.

  10. Subcoronary versus supracoronary aortic stenosis. an experimental evaluation

    Directory of Open Access Journals (Sweden)

    Hasenkam J Michael

    2011-08-01

    Full Text Available Abstract Background Valvular aortic stenosis is the most common cause of left ventricular hypertrophy due to gradually increasing pressure work. As the stenosis develop the left ventricular hypertrophy may lead to congestive heart failure, increased risk of perioperative complications and also increased risk of sudden death. A functional porcine model imitating the pathophysiological nature of valvular aortic stenosis is very much sought after in order to study the geometrical and pathophysiological changes of the left ventricle, timing of surgery and also pharmacological therapy in this patient group. Earlier we developed a porcine model for aortic stenosis based on supracoronary aortic banding, this model may not completely imitate the pathophysiological changes that occurs when valvular aortic stenosis is present including the coronary blood flow. It would therefore be desirable to optimize this model according to the localization of the stenosis. Methods In 20 kg pigs subcoronary (n = 8, supracoronary aortic banding (n = 8 or sham operation (n = 4 was preformed via a left lateral thoracotomy. The primary endpoint was left ventricular wall thickness; secondary endpoints were heart/body weight ratio and the systolic/diastolic blood flow ratio in the left anterior descending coronary. Statistical evaluation by oneway anova and unpaired t-test. Results Sub- and supracoronary banding induce an equal degree of left ventricular hypertrophy compared with the control group. The coronary blood flow ratio was slightly but not significantly higher in the supracoronary group (ratio = 0.45 compared with the two other groups (subcoronary ratio = 0.36, control ratio = 0.34. Conclusions A human pathophysiologically compatible porcine model for valvular aortic stenosis was developed by performing subcoronary aortic banding. Sub- and supracoronary aortic banding induce an equal degree of left ventricular hypertrophy. This model may be valid for experimental

  11. USAGE OF MICRO-MODULAR HEAT-INSULATION LAYER IN STRUCTURES OF WALL PANELS

    Directory of Open Access Journals (Sweden)

    V. D. Sizov

    2014-01-01

    Full Text Available The paper presents an analysis of requirements to existing heat-insulation layers in enclosure structures of wall panels has been carried out, a general principles on development of thermal insulation systems, substantiation on the necessity to develop a new wall panel design with improved thermal characteristics. The proposed design of the wall panel differs from the existing one in the fact that its external layer is made of protective sheets being perforated in their top and bottom parts with perforated aluminum foil layer placed on them. Air layer performs function of one of thermal insulation layers, and the second layer is made up in the form of several micro-modular sub-layers which are divided by perforated aluminum foil and a grid. An inner concrete layer is also separated from micro-modular layers by aluminum foil. Protective sheets and the grid can be made of aluminum or polyethylene.The arrangement of hollow micro-modular cells in the zone of negative temperatures prevents condensate accumulation. The arrangement of the perforated aluminum foil layers between micro- modular layers leads to increase in thermal resistance of the panel due to decrease of a radiant component in presence of several screens and does not interfere with a vapor permeability of thermal insulation layers from micro-modules. At the same time placement of a non-perforated foil layer on an inside panel layer interferes with penetration of water vapor from rooms in micro-modular thermal insulation layers.Technological principles lie in the arrangement of perforation slots in the top and bottom zones of protective sheets that allows to delete excess moisture from thermal insulation layers and air layer and also leads to improvement of thermo-technical characteristics, durability and reliability in construction operation as a whole. The executed calculations of heat and humidity fields in external enclosure structures confirm advantages of the presented technical

  12. Nanostructured carbon electrocatalyst supports for intermediate-temperature fuel cells: Single-walled versus multi-walled structures

    Science.gov (United States)

    Papandrew, Alexander B.; Elgammal, Ramez A.; Tian, Mengkun; Tennyson, Wesley D.; Rouleau, Christopher M.; Puretzky, Alexander A.; Veith, Gabriel M.; Geohegan, David B.; Zawodzinski, Thomas A.

    2017-01-01

    It is unknown if nanostructured carbons possess the requisite electrochemical stability to be used as catalyst supports in the cathode of intermediate-temperature solid acid fuel cells (SAFCs) based on the CsH2PO4 electrolyte. To investigate this application, single-walled carbon nanohorns (SWNHs) and multi-walled carbon nanotubes (MWNTs) were used as supports for Pt catalysts in SAFCs operating at 250 °C. SWNH-based cathodes display greater maximum activity than their MWNT-based counterparts at a cell voltage of 0.8 V, but are unstable in the SAFC cathode as a consequence of electrochemical carbon corrosion. MWNT-based cells are resistant to this effect and capable of operation for at least 160 h at 0.6 V and 250 °C. Cells fabricated with nanostructured carbon supports are more active (52 mA cm-1vs. 28 mA cm-1 at 0.8 V) than state-of-the-art carbon-free formulations while simultaneously displaying enhanced Pt utilization (40 mA mgPt-1vs. 16 mA mgPt-1 at 0.8 V). These results suggest that MWNTs are a viable support material for developing stable, high-performance, low-cost air electrodes for solid-state electrochemical devices operating above 230 °C.

  13. Lamb-Wave Embedded NDE with Piezoelectric Wafer Active Sensors for Structural Health Monitoring of Thin-Wall Structures

    Science.gov (United States)

    Giurgiutiu, Victor

    2004-02-01

    Piezoelectric wafer active sensors (PWAS) are inexpensive, non-intrusive, unobtrusive devices that can be surface-mounted on existing structures or inserted between the layers of new composite structures. The PWAS can be used in both active and passive modes. PWAS generate and detect Lamb waves and enable the development of embedded NDE concepts. This paper will present two embedded NDE concepts based on the PWAS technology and Lamb waves approach. The first concept utilizes traveling Lamb waves and could be described as embedded ultrasonics. It is shown that embedded PWAS are able to reproduce most of the conventional ultrasonic techniques, such as pitch-catch, pulse-echo, and phased array. Several experiments using Lamb waves traveling in thin-wall structures are presented.

  14. Structure Functions in Wall-bounded Flows at High Reynolds Number

    Science.gov (United States)

    Yang, Xiang; Marusic, Ivan; Johnson, Perry; Meneveau, Charles

    2016-11-01

    The scaling of the structure function Dij = (where i = 1,2,3 and r is the two-point displacement, ui is the velocity fluctuation in the xi direction), is studied in wall-bounded flows at high Reynolds number within the framework of the Townsend attached eddy model. While the scaling of Dij has been the subject of several studies, previous work focused on the scaling of D11 for r = (Δx ,0,0) (for streamwise velocity component and displacements only in the streamwise direction). Using the Hierarchical-Random-Additive formalism, a recently developed attached-eddy formalism, we propose closed-form formulae for the structure functionDij with two-point displacements in arbitrary directions, focusing on the log region . The work highlights new scalings that have received little attention, e.g. the scaling of Dij for r =(0, Δy, Δz) and for i ≠ j . As the knowledge on Dij leads directly to that of the Reynolds stress, statistics of the filtered flow field, etc., an analytical formula of Dij for arbitrary r can be quite useful for developing physics-based models for wall-bounded flows and validating existing LES and reduced order models.

  15. Ignition, Flame Structure and Near-Wall Burning in Transverse Hydrogen Jets in Supersonic Crossflow

    Science.gov (United States)

    Gamba, Mirko; Godfrey Mungal, M.; Hanson, Ronald K.

    2010-11-01

    The work aims at investigating near-wall ignition and flame structure in transverse underexpanded hydrogen jets in high-enthalpy supersonic crossflows generated in an expansion tube. Crossflow conditions are held fixed at M=2.4, p=40 kPa and T 1400 K, while jet-to-crossflow momentum flux ratios J in the range 0.3-5.0 are considered. Schlieren and OH^* chemiluminescence imaging are used to characterize flow structure, ignition and flame penetration, while the instantaneous reaction zone is identified with planar laser-induced fluorescence imaging of OH on side- and plan-view planes. The upstream separation length is found to scale as J^0.44D (D jet diameter). Similarly, the ignition point xig strongly depends on J: xig tends to a limiting value of ˜22D as J->0, and the flame is anchored in the upstream recirculation region and lee-side of the jet for J>3. Flame penetration is well described by the traditional form k(x/DJ)^m where both k and m are found to depend on J but these parameters reach a limiting value of k 1 and m 0.3 for J>2. The roles of the unsteady bow shock, the separation and recirculation regions on the near-wall ignition, stabilization and mixing at large J are discussed.

  16. A study of the turbulence structures of wall-bounded shear flows

    Science.gov (United States)

    Chong, M. S.; Soria, J.; Perry, A. E.; Chacin, J.; Na, Y.; Cantwell, B. J.

    1996-01-01

    This project extends the study of the structure of wall-bounded flows using the topological properties of eddying motions as developed by Chong et al. (1990), Soria et al. (1992, 1994), and as recently extended by Blackburn et al. (1996) and Chacin et al. (1996). In these works, regions of flow which are focal in nature are identified by being enclosed by an isosurface of a positive small value of the discriminant of the velocity gradient tensor. These regions resemble the attached vortex loops suggested first by Theodorsen (1955). Such loops are incorporated in the attached eddy model versions of Perry & Chong (1982), Perry et al. (1986), and Perry & Marusic (1995), which are extensions of a model first formulated by Townsend (1976). The DNS data of wall bounded flows studied here are from the zero pressure gradient flow of Spalart (1988) and the boundary layer with separation and reattachment of Na & Moin (1996). The flow structures are examined from the viewpoint of the attached eddy hypothesis.

  17. Optical signature of structural defects in single walled and multiwalled carbon nanotubes.

    Science.gov (United States)

    Singh, Dilip K; Iyer, P K; Giri, P K

    2009-09-01

    Though defects are invariably present in as-grown and purified carbon nanotubes (NTs), spectroscopic properties of defects in NTs have not been established yet. In this work, single walled (SW) and multiwalled (MW) carbon nanotubes (NTs) grown by chemical vapor deposition have been studied by high resolution transmission electron microscopy (HRTEM), Raman scattering and photoluminescence (PL), electron spin resonance (ESR) and thermo gravometric (TGA) analysis. Raman spectra of both SWNT and MWNT show additional features in the frequency range intermediate between 600-1300 cm(-1) and 1700-2600 cm(-1), in addition to well-known radial breathing modes, D- and G-bands. Room temperature PL studies show two broad but distinct peaks centered at approximately 2.05 eV and approximately 2.33 eV, for both SWNT and MWNT samples. TGA analysis shows very low impurity content in MWNT sample as compared to the SWNT sample. HRTEM analysis reveals various kinds of structural defects in nanotube wall. With the help of HRTEM and ESR studies, we argue that the intermediate frequency Raman modes and the visible PL from the pristine NTs are definite signatures of structural defects in the nanotubes.

  18. FOXE3 mutations predispose to thoracic aortic aneurysms and dissections.

    Science.gov (United States)

    Kuang, Shao-Qing; Medina-Martinez, Olga; Guo, Dong-Chuan; Gong, Limin; Regalado, Ellen S; Reynolds, Corey L; Boileau, Catherine; Jondeau, Guillaume; Prakash, Siddharth K; Kwartler, Callie S; Zhu, Lawrence Yang; Peters, Andrew M; Duan, Xue-Yan; Bamshad, Michael J; Shendure, Jay; Nickerson, Debbie A; Santos-Cortez, Regie L; Dong, Xiurong; Leal, Suzanne M; Majesky, Mark W; Swindell, Eric C; Jamrich, Milan; Milewicz, Dianna M

    2016-03-01

    The ascending thoracic aorta is designed to withstand biomechanical forces from pulsatile blood. Thoracic aortic aneurysms and acute aortic dissections (TAADs) occur as a result of genetically triggered defects in aortic structure and a dysfunctional response to these forces. Here, we describe mutations in the forkhead transcription factor FOXE3 that predispose mutation-bearing individuals to TAAD. We performed exome sequencing of a large family with multiple members with TAADs and identified a rare variant in FOXE3 with an altered amino acid in the DNA-binding domain (p.Asp153His) that segregated with disease in this family. Additional pathogenic FOXE3 variants were identified in unrelated TAAD families. In mice, Foxe3 deficiency reduced smooth muscle cell (SMC) density and impaired SMC differentiation in the ascending aorta. Foxe3 expression was induced in aortic SMCs after transverse aortic constriction, and Foxe3 deficiency increased SMC apoptosis and ascending aortic rupture with increased aortic pressure. These phenotypes were rescued by inhibiting p53 activity, either by administration of a p53 inhibitor (pifithrin-α), or by crossing Foxe3-/- mice with p53-/- mice. Our data demonstrate that FOXE3 mutations lead to a reduced number of aortic SMCs during development and increased SMC apoptosis in the ascending aorta in response to increased biomechanical forces, thus defining an additional molecular pathway that leads to familial thoracic aortic disease.

  19. Effects of phosphorus-doping upon the electronic structures of single wall carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    CHEN AQing; SHAO QingYi; LIN ZhiCheng

    2009-01-01

    The phosphorus-doped single wall carbon nanotube (PSWCNT) is studied by using First-Principle methods based on Density Function Theory (DFT). The formation energy, total energy, band structure, geometry structure and density of states are calculated. It is found that the formation energy of the P-doped single carbon nanotubes increases with diameters; the total energy of carbon nanotubes with the same diameter decreases as the doping rate increases. The effects of impurity position on the im-purity level are discussed. It illustrates that the position of the impurity level may depend on the C-P-C bond angle. According to the above results, it is feasible to substitute a carbon atom with a phosphorus atom in SWCNT. It is also found that P-doped carbon nanotubes are N type semiconductor.

  20. Effects of phosphorus-doping upon the electronic structures of single wall carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The phosphorus-doped single wall carbon nanotube(PSWCNT) is studied by using First-Principle methods based on Density Function Theory(DFT).The formation energy,total energy,band structure,geometry structure and density of states are calculated.It is found that the formation energy of the P-doped single carbon nanotubes increases with diameters;the total energy of carbon nanotubes with the same diameter decreases as the doping rate increases.The effects of impurity position on the impurity level are discussed.It illustrates that the position of the impurity level may depend on the C-P-C bond angle.According to the above results,it is feasible to substitute a carbon atom with a phosphorus atom in SWCNT.It is also found that P-doped carbon nanotubes are N type semiconductor.

  1. Large rotation FE transient analysis of piezolaminated thin-walled smart structures

    Science.gov (United States)

    Zhang, S. Q.; Schmidt, R.

    2013-10-01

    A geometrically nonlinear large rotation shell theory is proposed for dynamic finite element (FE) analysis of piezoelectric integrated thin-walled smart structures. The large rotation theory, which has six independent kinematic parameters but expressed by five nodal degrees of freedom (DOFs), is based on first-order shear deformation (FOSD) hypothesis. The two-dimensional (2D) FE model is constructed using eight-node quadrilateral shell elements with five mechanical DOFs per node and one electrical DOF per piezoelectric material layer with linear constitutive equations. The linear and nonlinear dynamic responses are determined by the central difference algorithm (CDA) and the Newmark method. The results are compared with those obtained by simplified nonlinear theories, as well as those reported in the literature. It is shown that the present large rotation theory yields considerable improvement if the structures undergo large displacements and rotations.

  2. Evolutionary divergence of β-expansin structure and function in grasses parallels emergence of distinctive primary cell wall traits.

    Science.gov (United States)

    Sampedro, Javier; Guttman, Mara; Li, Lian-Chao; Cosgrove, Daniel J

    2015-01-01

    Expansins are wall-loosening proteins that promote the extension of primary cell walls without the hydrolysis of major structural components. Previously, proteins from the EXPA (α-expansin) family were found to loosen eudicot cell walls but to be less effective on grass cell walls, whereas the reverse pattern was found for EXPB (β-expansin) proteins obtained from grass pollen. To understand the evolutionary and structural bases for the selectivity of EXPB action, we assessed the extension (creep) response of cell walls from diverse monocot families to EXPA and EXPB treatments. Cell walls from Cyperaceae and Juncaceae (families closely related to grasses) displayed a typical grass response ('β-response'). Walls from more distant monocots, including some species that share with grasses high levels of arabinoxylan, responded preferentially to α-expansins ('α-response'), behaving in this regard like eudicots. An expansin with selective activity for grass cell walls was detected in Cyperaceae pollen, coinciding with the expression of genes from the divergent EXPB-I branch that includes grass pollen β-expansins. The evolutionary origin of this branch was located within Poales on the basis of phylogenetic analyses and its association with the 'sigma' whole-genome duplication. Accelerated evolution in this branch has remodeled the protein surface in contact with the substrate, potentially for binding highly substituted arabinoxylan. We propose that the evolution of the divergent EXPB-I group made a fundamental change in the target and mechanism of wall loosening in the grass lineage possible, involving a new structural role for xylans and the expansins that target them.

  3. Understanding effect of wall structure on the hydrothermal stability of mesostructured silica SBA-15.

    Science.gov (United States)

    Zhang, Fuqiang; Yan, Yan; Yang, Haifeng; Meng, Yan; Yu, Chengzhong; Tu, Bo; Zhao, Dongyuan

    2005-05-12

    Mesostructured silica SBA-15 materials with different structural parameters, such as pore size, pore volume, and wall thickness, etc., were prepared by varying the postsynthesis hydrothermal treatment temperature and adding inorganic salts. The hydrothermal stabilities of these materials in steam (100% water vapor) were systematically investigated using a variety of techniques including powder X-ray diffraction, transmission electron microscopy, nitrogen sorption, and (29)Si solid-state NMR. The effect of the pore size, microporosity or mesoporosity, and wall thickness on the stability was discussed. The results show that all of the SBA-15 materials have a good hydrothermal stability under steam of 600 degrees C for at least 24 h. N(2) sorption measurements show that the Brumauer-Emmett-Teller surface area of SBA-15 materials is decreased by about 62% after treatment under steam at 600 degrees C for 24 h. The materials with thicker walls and more micropores show relatively better hydrothermal stability in steam of 600 degrees C. Interestingly, we found that the microporosity of the mesostructured silica SBA-15 is a very important factor for the hydrothermal stability. To the materials with more micropores, the recombination of Si-O-Si bonds during the high-temperature steam treatment may not cause direct destruction to the wall structure. As a result, SBA-15 materials with more micropores show better stability in pure steam of 600 degrees C. Nevertheless, these materials are easily destroyed in steam of 800 degrees C for 6 h. Two methods to effectively improve the hydrothermal stability are introduced here: one is a high-temperature treatment, and another is a carbon-propping thermal treatment. Thermal treatment at 900 degrees C can enhance the polymerization degree of Si-O-Si bonds and effectively improve the hydrothermal stability of these SBA-15 materials in 800 degrees C steam for 12 h. But, this approach will cause very serious shrinkage of the mesopores

  4. Wall Turbulence.

    Science.gov (United States)

    Hanratty, Thomas J.

    1980-01-01

    This paper gives an account of research on the structure of turbulence close to a solid boundary. Included is a method to study the flow close to the wall of a pipe without interferring with it. (Author/JN)

  5. Catalase overexpression in aortic smooth muscle prevents pathological mechanical changes underlying abdominal aortic aneurysm formation.

    Science.gov (United States)

    Maiellaro-Rafferty, Kathryn; Weiss, Daiana; Joseph, Giji; Wan, William; Gleason, Rudolph L; Taylor, W Robert

    2011-08-01

    The causality of the associations between cellular and mechanical mechanisms of abdominal aortic aneurysm (AAA) formation has not been completely defined. Because reactive oxygen species are established mediators of AAA growth and remodeling, our objective was to investigate oxidative stress-induced alterations in aortic biomechanics and microstructure during subclinical AAA development. We investigated the mechanisms of AAA in an angiotensin II (ANG II) infusion model of AAA in apolipoprotein E-deficient (apoE(-/-)) mice that overexpress catalase in vascular smooth muscle cells (apoE(-/-)xTg(SMC-Cat)). At baseline, aortas from apoE(-/-)xTg(SMC-Cat) exhibited increased stiffness and the microstructure was characterized by 50% more collagen content and less elastin fragmentation. ANG II treatment for 7 days in apoE(-/-) mice altered the transmural distribution of suprarenal aortic circumferential strain (quantified by opening angle, which increased from 130 ± 1° at baseline to 198 ± 8° after 7 days of ANG II treatment) without obvious changes in the aortic microstructure. No differences in aortic mechanical behavior or suprarenal opening angle were observed in apoE(-/-)xTg(SMC-Cat) after 7 days of ANG II treatment. These data suggest that at the earliest stages of AAA development H(2)O(2) is functionally important and is involved in the control of local variations in remodeling across the vessel wall. They further suggest that reduced elastin integrity at baseline may predispose the abdominal aorta to aneurysmal mechanical remodeling.

  6. Reproducibility of ECG-gated Ultrasound Diameter Assessment of Small Abdominal Aortic Aneurysms

    DEFF Research Database (Denmark)

    Bredahl, K; Eldrup, N; Meyer, C

    2013-01-01

    No standardised ultrasound procedure to obtain reliable growth estimates for abdominal aortic aneurysms (AAA) is currently available. We investigated the feasibility and reproducibility of a novel approach controlling for a combination of vessel wall delineation and cardiac cycle variation....

  7. Flow in an Aortic Coarctation

    Science.gov (United States)

    Loma, Luis; Miller, Paul; Hertzberg, Jean

    2009-11-01

    Coarctation of the aorta is a congenital cardiovascular defect that causes a constriction in the descending thoracic aorta. To gain a better understanding of the cause of post-surgical problems, a rigid glass and a compliant in vitro model of the aortic arch and descending aorta with a coarctation were constructed. Near-physiologic compliance was obtained using a silicone elastomer. Stereoscopic PIV was used to obtain 3D velocity maps. Results show a high speed turbulent jet formed at the exit of the coarctation. Flow in the rigid model was significantly different from in the compliant model. In the rigid model, the jet was symmetric, creating a toroidal recirculation area. In the compliant model, the jet was directed towards the medial wall, inducing flow reversal only at the lateral wall. Peak velocities and turbulence intensities were higher in the rigid model, however shear rate values in the compliant model were significantly above both the rigid model and normal in vivo values at the medial wall. In both models the reattachment region fluctuated, creating oscillatory shear.

  8. Structural-and-functional alterations in the arterial wall and clinical manifestations of nonspecific aortoarteritis.

    Science.gov (United States)

    Pokrovskiĭ, A V; Kuntsevich, G I; Zotikov, E A; Burtseva, E A; Kulbak, V A

    2009-01-01

    The authors studied structural-and-functional properties of the arterial wall, also assessing elastic properties of the common femoral artery and the brachial artery flow-dependent dilatation (FDD) index in a total of thirty-six patients presenting with nonspecific aortoarteritis (NAA). The overwhelming majority of the patients, i. e., twenty-four (89%), showed a statistically significant decrease in the FDD as compared with the control-group patients (P<0.05). We revealed a statistically reliable (P=0.0005) inverse correlation between the level of systolic arterial pressure and an increase in the rigidity index of the common femoral artery wall. Also determined was a correlation of the femoral artery wall rigidity (systolic AP equalling 140 mm Hg and higher) and the brachial artery flow-dependent dilatation index (r=-0.61). All the patients suffering from non-specific aortoarteritis were diagnosed as having a decrease in the elasticity values, accompanied by an increase in systolic arterial pressure (r=0.36; P=0.07). Comparing the level of systolic arterial pressure with the values of the distensibility coefficient and compliance coefficient revealed a weak inverse correlation (r=-0.28 and 0.21, respectively). Evaluating the impact of duration of the disease on the distensibility coefficient, compliance coefficient and the rigidity index made it possible to detect a statistically significant (P=0.0039) direct correlation between the rigidity index and the duration of non-specific aortoarteritis. To a leaser degree, the duration of the inflammatory process influenced the distensibility coefficient and compliance coefficient (r=-0.28; r=-0.30, respectively; P=0.06).

  9. Asymptomatic papillary fibroelastoma of the Aortic valve in a young woman - a case report

    Directory of Open Access Journals (Sweden)

    Pitsis Antonis

    2009-09-01

    Full Text Available Abstract Echocardiography represents an invaluable diagnostic tool for the detection of intracardiac masses while simultaneously provides information about their size, location, mobility and attachment site as well as the presence and extent of any consequent hemodynamic derangement. A 29-year-old asymptomatic young woman with incidental transthoracic echocardiographic (TTE discovery of an aortic valve mass is presented. The 2-dimensional TTE showed a mobile, pedunculated mass, attached by a thin stalk to the aortic surface of the right coronary aortic cusp at the junction of its base with the anterior aortic wall. The importance of valve sparing tumour resection even in asymptomatic patients is emphasised.

  10. Aortic Valve Disease

    Science.gov (United States)

    ... that is safest for you based on your individual symptoms and circumstances. Recovery Recovery Most aortic valve ... is safe to do so. You should anticipate spending several days, but likely not more than a ...

  11. Bicuspid aortic valve

    Science.gov (United States)

    ... aortic disease. In: Otto CM, Bonow RO, eds. Valvular Heart Disease: A Companion to Braunwald's Heart Disease . 4th ed. ... PA: Elsevier Saunders; 2014:chap 13. Carabello BA. Valvular heart disease. In: Goldman L, Schafer AI, eds. Goldman's Cecil ...

  12. Aortic Valve Regurgitation

    Science.gov (United States)

    ... inside your heart that involves heart valves. Rheumatic fever. Rheumatic fever — a complication of strep throat and once a ... the United States — can damage the aortic valve. Rheumatic fever is still prevalent in developing countries but rare ...

  13. Aortic Valve Stenosis

    Science.gov (United States)

    ... evaluation of aortic stenosis in adults. http://www.uptodate.com/home. Accessed April 29, 2014. Mohty D, ... Valvular heart disease in elderly adults. http://www.uptodate.com/home. Accessed May 2, 2014. Bonow RO, ...

  14. Infolding of covered stents used for aortic coarctation: report of two cases.

    Science.gov (United States)

    Wan, Andrea W; Lee, Kyong-Jin; Benson, Lee N

    2014-01-01

    Covered stents have been used for the treatment of aortic coarctation to protect the arterial wall during dilation. Early results have shown them to be safe and effective. We report two cases of infolding of the proximal edge of a covered aortic coarctation stent. Management required implantation of a second stent. Poor stent apposition to the vessel wall and/or recoil may allow conditions for these events to occur.

  15. Cell-wall structural changes in wheat straw pretreated for bioethanol production

    Directory of Open Access Journals (Sweden)

    Jørgensen Henning

    2008-04-01

    Full Text Available Abstract Background Pretreatment is an essential step in the enzymatic hydrolysis of biomass and subsequent production of bioethanol. Recent results indicate that only a mild pretreatment is necessary in an industrial, economically feasible system. The Integrated Biomass Utilisation System hydrothermal pretreatment process has previously been shown to be effective in preparing wheat straw for these processes without the application of additional chemicals. In the current work, the effect of the pretreatment on the straw cell-wall matrix and its components are characterised microscopically (atomic force microscopy and scanning electron microscopy and spectroscopically (attenuated total reflectance Fourier transform infrared spectroscopy in order to understand this increase in digestibility. Results The hydrothermal pretreatment does not degrade the fibrillar structure of cellulose but causes profound lignin re-localisation. Results from the current work indicate that wax has been removed and hemicellulose has been partially removed. Similar changes were found in wheat straw pretreated by steam explosion. Conclusion Results indicate that hydrothermal pretreatment increases the digestibility by increasing the accessibility of the cellulose through a re-localisation of lignin and a partial removal of hemicellulose, rather than by disruption of the cell wall.

  16. Intactness of cell wall structure controls the in vitro digestion of starch in legumes.

    Science.gov (United States)

    Dhital, Sushil; Bhattarai, Rewati R; Gorham, John; Gidley, Michael J

    2016-03-01

    Increasing the level of starch that is not digested by the end of the small intestine and therefore enters the colon ('resistant starch') is a major opportunity for improving the nutritional profile of foods. One mechanism that has been shown to be successful is entrapment of starch within an intact plant tissue structure. However, the level of tissue intactness required for resistance to amylase digestion has not been defined. In this study, intact cells were isolated from a range of legumes after thermal treatment at 60 °C (starch not gelatinised) or 95 °C (starch gelatinised) followed by hydrolysis using pancreatic alpha amylase. It was found that intact cells, isolated at either temperature, were impervious to amylase. However, application of mechanical force damaged the cell wall and made starch accessible to digestive enzymes. This shows that the access of enzymes to the entrapped swollen starch is the rate limiting step controlling hydrolysis of starch in cooked legumes. The results suggest that a single cell wall could be sufficient to provide an effective delivery of starch to the large intestine with consequent nutritional benefits, provided that mechanical damage during digestion is avoided.

  17. The mechanism of domain-wall structure formation in Ar-Kr submonolayer films on graphite

    Directory of Open Access Journals (Sweden)

    A. Patrykiejew

    2014-12-01

    Full Text Available Using Monte Carlo simulation method in the canonical ensemble, we have studied the commensurate-incommensurate transition in two-dimensional finite mixed clusters of Ar and Kr adsorbed on graphite basal plane at low temperatures. It has been demonstrated that the transition occurs when the argon concentration exceeds the value needed to cover the peripheries of the cluster. The incommensurate phase exhibits a similar domain-wall structure as observed in pure krypton films at the densities exceeding the density of a perfect (√3x√3R30º commensurate phase, but the size of commensurate domains does not change much with the cluster size. When the argon concentration increases, the composition of domain walls changes while the commensurate domains are made of pure krypton. We have constructed a simple one-dimensional Frenkel-Kontorova-like model that yields the results being in a good qualitative agreement with the Monte Carlo results obtained for two-dimensional systems.

  18. Assessment of vascular contrast and wall motion of the aortic root and ascending aorta on MDCT angiography: dual-source high-pitch vs non-gated single-source acquisition schemes

    Energy Technology Data Exchange (ETDEWEB)

    Christensen, Jared D.; Seaman, Danielle M.; Lungren, Matthew P.; Hurwitz, Lynne M.; Boll, Daniel T. [Duke University Medical Center, Department of Radiology, Durham, NC (United States)

    2014-05-15

    This retrospective study assessed whether dual-source high-pitch computed tomographic angiography (CTA) offered advantages over single-source standard-pitch techniques in the evaluation of the ascending aorta. Twenty patients who received both thoracic dual-source high-pitch and single-source standard-pitch CTAs within 1 year were assessed. Dual-source CTAs were performed; standard-pitch imaging used dose-modulated 120 kVp/150 mAs and 0.8 pitch compared with high-pitch protocols employing dose-modulated 120 kVp/250 mAs and 2.4 target pitch. Radiation dose was documented. Contrast-to-noise ratios (CNRs) at sinuses of the Valsalva (CNR{sub Valsalva}) and ascending aorta (CNR{sub Aorta}) were calculated. Dose/CNR for each technique was compared with paired t-tests. Motion at aortic valve, aortic root and ascending aorta were assessed with four-point scales and Mann-Whitney U tests; longitudinal extension of motion was compared with paired t-tests. Significantly lower motion scores for high-pitch, compared with standard-pitch acquisitions for aortic annulus, 0 vs. 2, aortic root, 0 vs. 3, and ascending aorta, 0 vs. 2, were achieved. Significantly reduced longitudinal extension of motion at aortic root, 4.9 mm vs 15.7 mm, and ascending aorta, 4.9 mm vs 21.6 mm, was observed. Contrast was not impacted: CNR{sub Valsalva}, 45.6 vs 46.3, and CNR{sub Aorta}, 45.3 vs 47.1. CTDI{sub vol} was significantly decreased for high-pitch acquisitions, 13.9 mGy vs 15.8 mGy. Dual-source high-pitch CTAs significantly decreased motion artefact without negatively impacting vascular contrast and radiation dose. circle Dual-source high-pitch CTA significantly decreased motion artefact of the ascending aorta. circle Dual-source high-pitch CTA did not negatively impact on vascular contrast. circle Dual-source high-pitch CTA significantly decreased radiation dose compared with single-source standard-pitch acquisitions. (orig.)

  19. Structural basis for selective recognition of pneumococcal cell wall by modular endolysin from phage Cp-1.

    Science.gov (United States)

    Hermoso, Juan A; Monterroso, Begoña; Albert, Armando; Galán, Beatriz; Ahrazem, Oussama; García, Pedro; Martínez-Ripoll, Martín; García, José Luis; Menéndez, Margarita

    2003-10-01

    Pneumococcal bacteriophage-encoded lysins are modular choline binding proteins that have been shown to act as enzymatic antimicrobial agents (enzybiotics) against streptococcal infections. Here we present the crystal structures of the free and choline bound states of the Cpl-1 lysin, encoded by the pneumococcal phage Cp-1. While the catalytic module displays an irregular (beta/alpha)(5)beta(3) barrel, the cell wall-anchoring module is formed by six similar choline binding repeats (ChBrs), arranged into two different structural regions: a left-handed superhelical domain configuring two choline binding sites, and a beta sheet domain that contributes in bringing together the whole structure. Crystallographic and site-directed mutagenesis studies allow us to propose a general catalytic mechanism for the whole glycoside hydrolase family 25. Our work provides the first complete structure of a member of the large family of choline binding proteins and reveals that ChBrs are versatile elements able to tune the evolution and specificity of the pneumococcal surface proteins.

  20. Immersed boundary peridynamics (IB/PD) method to simulate aortic dissection

    Science.gov (United States)

    Bhalla, Amneet Pal Singh; Griffith, Boyce

    2016-11-01

    Aortic dissection occurs when an intimal tear in the aortic wall propagates into the media to form a false lumen within the vessel wall. Rupture of the false lumen and collapse of the true lumen both carry a high risk of morbidity and mortality. Surgical treatment consists of either replacement of a portion of the aorta, or stent implantation to cover the affected segment. Both approaches carry significant risks: open surgical intervention is highly invasive, whereas stents can be challenging to implant and offer unclear long-term patient outcomes. It is also difficult to time optimally the intervention to ensure that the benefits of treatment outweigh its risks. In this work we develop innovative fluid-structure interaction (FSI) model combining elements from immersed boundary (IB) and peridynamics (PD) methods to simulate tears in membranes. The new approach is termed as IB/PD method. We use non-ordinary state based PD to represent material hyperelasticity. Several test problems are taken to validate peridynamics approach to model structural dynamics, with and without accounting for failure in the structures. FSI simulations using IB/PD method are compared with immersed finite element method (IB/FE) to validate the new hybrid approach. NIH Award R01HL117163 NSF Award ACI 1450327.

  1. Remote sensing of voids in large concrete structures: runways, taxiways, bridges, and building walls and roofs

    Science.gov (United States)

    Weil, Gary J.

    1998-10-01

    Maintenance of our world's infrastructure presents many unique challenges. Engineering and maintenance personnel must maintain around the clock service to millions of people each year while maintaining millions of cubic meters of concrete distributed throughout facilities. This infrastructure includes runways, taxiways, roadways, walkways, bridges, building walls and roofs. Presently only a limited number of accurate and economical techniques exist to test this myriad of concrete structures for integrity and safety as well as insure that they meet original design specifications. Remote sensing, non-destructive testing techniques, such as Infrared Thermography, Ground Penetrating Radar, Magnetometer and Pachometer, measure physical properties affected by the various materials and conditions found within, and under, concrete infrastructure. These techniques have established reputations for accurate investigations of concrete anomalies. This paper will review the applications of different non- destructive testing techniques on many concrete infrastructure components.

  2. Nondestructive testing of airport concrete structures: runways, taxiways, roads, bridges, building walls, and roofs

    Science.gov (United States)

    Weil, Gary J.

    1998-03-01

    Maintenance of airport infrastructure presents many unique challenges. Airport engineering and maintenance personnel must maintain around the clock service to millions of people each year while maintaining millions of cubic meters of concrete distributed throughout the facilities. This infrastructure includes runways, taxiways, roadways, walkways, bridges, building walls and roofs. Presently only a limited number of accurate and economical techniques exist to test this myriad of concrete structures for integrity and safety as well as insure that they meet original design specifications. Remote sensing, non-destructive testing techniques, such as IR thermography, ground penetrating radar, magnetometer and pachometer, measure physical properties affected by the various materials and conditions found within, and under, concrete infrastructure. These techniques have established reputations for accurate investigations of concrete anomalies.

  3. Fracture toughness of irradiated candidate materials for ITER first wall/blanket structures: Summary report

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, D.J.; Pawel, J.E.; Grossbeck, M.L.; Rowcliffe, A.F. [Oak Ridge National Lab., TN (United States)] [and others

    1996-04-01

    Disk compact specimens of candidate materials for first wall/blanket structures in ITER have been irradiated to damage levels of about 3 dpa at nominal irradiation temperatures of either 90 250{degrees}C. These specimens have been tested over a temperature range from 20 to 250{degrees}C to determine J-integral values and tearing moduli. The results show that irradiation at these temperatures reduces the fracture toughness of austenic stainless steels, but the toughness remains quite high. The toughness decreases as the temperature increases. Irradiation at 250{degrees}C is more damaging that at 90{degrees}C, causing larger decreases in the fracture toughness. The ferritic-martensitic steels HT-9 and F82H show significantly greater reductions in fracture toughness that the austenitic stainless steels.

  4. Superconductivity on the density-wave background with soliton-wall structure

    Science.gov (United States)

    Grigoriev, P. D.

    2009-03-01

    Superconductivity (SC) may microscopically coexist with density wave (DW) when the nesting of the Fermi surface (FS) is not perfect. There are, at least, two possible microscopic structures of a DW state with quasi-particle states remaining on the Fermi level and leading to the Cooper instability: (i) the soliton-wall phase and (ii) the small ungapped FS pockets. The dispersion of such quasi-particle states strongly differs from that without DW, and so do the properties of SC on the DW background. The upper critical field H in such an SC state strongly increases as the system approaches the critical pressure, where SC first appears. H may considerably exceed its typical value without DW and has unusual upward curvature as function of temperature. The results obtained explain the experimental observations in layered organic superconductors (TMTSF)2PF6 and α-(BEDT-TTF)2KHg(SCN)4.

  5. Structure and Properties of poly (para phynelyne benzobisoxazole) (PBO) /single wall carbon nano tube composite fibers

    Science.gov (United States)

    Kumar, Satish; Zhang, Xiefei; Bhattacharyya, Arup R.; Min, Byung G.; Dang, T. D.; Arnold, F. E.; Vaia, Richard A.; Ramesh, S.; Willis, P. A.; Hauge, R. H.; Smalley, R. E.

    2002-03-01

    The liquid crystalline compositions are prepared by the in-situ polycondensation of diamines and diacid monomers in the presence of single wall carbon nano tubes (SWNT). Processing of the new compositions into fibers provide hybrid materials with improved mechanical properties. The in-situ polymerizations were carried out in polyphosphoric acid (PPA). Carbon nano tubes as high as 10 wt.polymer weight have been utilized. Fiber spinning has been carried out using dry jet wet spinning using a piston driven spinning system and the fiber coagulated in water and subsequently vacuum dried and heat treated in nitrogen at 400oC. Structure and properties of these fibers have been studied. Tensile strength of the composite fibers increased by about 50morphology of these fibers have been studied using X- ray diffraction and scanning electron microscopy.

  6. Nonlinear mechanics of thin-walled structures asymptotics, direct approach and numerical analysis

    CERN Document Server

    Vetyukov, Yury

    2014-01-01

    This book presents a hybrid approach to the mechanics of thin bodies. Classical theories of rods, plates and shells with constrained shear are based on asymptotic splitting of the equations and boundary conditions of three-dimensional elasticity. The asymptotic solutions become accurate as the thickness decreases, and the three-dimensional fields of stresses and displacements can be determined. The analysis includes practically important effects of electromechanical coupling and material inhomogeneity. The extension to the geometrically nonlinear range uses the direct approach based on the principle of virtual work. Vibrations and buckling of pre-stressed structures are studied with the help of linearized incremental formulations, and direct tensor calculus rounds out the list of analytical techniques used throughout the book. A novel theory of thin-walled rods of open profile is subsequently developed from the models of rods and shells, and traditionally applied equations are proven to be asymptotically exa...

  7. Tuning Electronic Structures of BN and C Double-Wall Hetero-Nanotubes

    Directory of Open Access Journals (Sweden)

    Xueran Liu

    2015-01-01

    Full Text Available First principle calculations based on density functional theory with the generalized gradient approximation were carried out to investigate the energetic and electronic properties of carbon and boron nitride double-wall hetero-nanotubes (C/BN-DWHNTs with different chirality and size, including an armchair (n, n carbon nanotube (CNT enclosed in (m, m boron nitride nanotube (BNNT and a zigzag (n, 0 CNT enclosed in (m, 0 BNNT. The electronic structure of these DWHNTs under a transverse electric field was also investigated. The ability to tune the band gap with changing the intertube distance (di and imposing an external electric field (F of zigzag DWHNTs provides the possibility for future electronic and electrooptic nanodevice applications.

  8. Computation of macro-fiber composite integrated thin-walled smart structures

    Science.gov (United States)

    Zhang, S. Q.; Zhang, S. Y.; Chen, M.; Bai, J.; Li, J.

    2016-07-01

    Due to high flexibility, reliability, and strong actuation forces, piezo fiber based composite smart material, macro-fiber composite (MFC), is increasingly applied in various fields for vibration suppression, shape control, and health monitoring. The complexity arrangement of MFC materials makes them difficult in numerical simulations. This paper develops a linear electro-mechanically coupled finite element (FE) model for composite laminated thin-walled smart structures bonded with MFC patches considering arbitrary piezo fiber orientation. Two types of MFCs are considered, namely, MFC-d31 in which the d 31 effect dominates the actuation forces, and MFC-d33 which mainly uses the d 33 effect. The proposed FE model is validated by static analysis of an MFC bonded smart plate.

  9. Phase transitions, interfacial fluctuations and hidden symmetries for fluids near structured walls

    Indian Academy of Sciences (India)

    A O Parry; J M Romero-Enrique

    2005-05-01

    Fluids adsorbed at micro-patterned and geometrically structured substrates can exhibit novel phase transitions and interfacial fluctuation effects distinct from those characteristic of wetting at planar, homogeneous walls. We review recent theoretical progress in this area paying particular attention to filling transitions pertinent to fluid adsorption near wedges, which have highlighted a deep connection between geometrical and contact angles. We show that filling transitions are not only characterized by large scale interfacial fluctuations leading to universal critical singularities but also reveal hidden symmetries with short-ranged critical wetting transitions and properties of dimensional reduction. We propose a non-local interfacial model which fulfills all these properties and throws light on long-standing problems regarding the order of the 3D short-range critical wetting transition.

  10. Chlorophenol sorption on multi-walled carbon nanotubes: DFT modeling and structure-property relationship analysis.

    Science.gov (United States)

    Watkins, Marquita; Sizochenko, Natalia; Moore, Quentarius; Golebiowski, Marek; Leszczynska, Danuta; Leszczynski, Jerzy

    2017-02-01

    The presence of chlorophenols in drinking water can be hazardous to human health. Understanding the mechanisms of adsorption under specific experimental conditions would be beneficial when developing methods to remove toxic substances from drinking water during water treatment in order to limit human exposure to these contaminants. In this study, we investigated the sorption of chlorophenols on multi-walled carbon nanotubes using a density functional theory (DFT) approach. This was applied to study selected interactions between six solvents, five types of nanotubes, and six chlorophenols. Experimental data were used to construct structure-adsorption relationship (SAR) models that describe the recovery process. Specific interactions between solvents and chlorophenols were taken into account in the calculations by using novel specific mixture descriptors.

  11. Serviceability limit state related to excessive lateral deformations to account for infill walls in the structural model

    Directory of Open Access Journals (Sweden)

    G. M. S. ALVA

    Full Text Available Brazilian Codes NBR 6118 and NBR 15575 provide practical values for interstory drift limits applied to conventional modeling in order to prevent negative effects in masonry infill walls caused by excessive lateral deformability, however these codes do not account for infill walls in the structural model. The inclusion of infill walls in the proposed model allows for a quantitative evaluation of structural stresses in these walls and an assessment of cracking in these elements (sliding shear diagonal tension and diagonal compression cracking. This paper presents the results of simulations of single-story one-bay infilled R/C frames. The main objective is to show how to check the serviceability limit states under lateral loads when the infill walls are included in the modeling. The results of numerical simulations allowed for an evaluation of stresses and the probable cracking pattern in infill walls. The results also allowed an identification of some advantages and limitations of the NBR 6118 practical procedure based on interstory drift limits.

  12. Near-edge X-ray absorption fine structure spectroscopy-assisted purification of single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Yan Dongwei [Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China); Zhong Jun [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Wang Chunru [Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China)], E-mail: crwang@iccas.ac.cn; Wu Ziyu [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)], E-mail: wuzy@ihep.ac.cn

    2007-07-15

    Single-walled carbon nanotubes were produced by the conventional arc discharge method, and purified with a two-step treatment. First, the raw soot containing single-walled carbon nanotubes was burned up at ca. 350 deg. C in air to remove amorphous carbon, and then it was treated by strong acidic solvents to remove metal catalysts. Near-edge X-ray absorption fine structure spectroscopy was applied to analyze the defects on single-walled carbon nanotubes in whole purification process, so the experimental conditions can be optimized, and finally high-purity single-walled carbon nanotubes were obtained as revealed by various spectroscopic characterizations such as scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and Raman spectroscopy.

  13. Transcatheter aortic valve implantation: status and challenges.

    Science.gov (United States)

    Fishbein, Gregory A; Schoen, Frederick J; Fishbein, Michael C

    2014-01-01

    Calcific aortic valve disease of the elderly is the most prevalent hemodynamically-significant valvular disease, and the most common lesion requiring valve replacement in industrialized countries. Transcatheter aortic valve implantation is a less invasive alternative to classical aortic valve replacement that can provide a therapeutic option for high-risk or inoperable patients with aortic stenosis. These devices must be biocompatible, have excellent hemodynamic performance, be easy to insert, be securely anchored without sutures, and be durable, without increased risk of thrombosis or infection. To date, complications are related to the site of entry for insertion, the site of implantation (aorta, coronary ostia, base of left ventricle), and to the structure and design of the inserted device. However, as with any novel technology unanticipated complications will develop. Goals for future development will be to make the devices more effective, more durable, safer, and easier to implant, so as to further improve outcome for patients with severe aortic stenosis. The pathologist participating in research and development, and examination of excised devices will have a critical role in improving outcome for these patients.

  14. Energy efficiency of the Rural Wall multi-layer structure in low-rise building design

    Directory of Open Access Journals (Sweden)

    T.A. Golova

    2014-12-01

    Full Text Available This paper presents the study on energy efficiency of various wall design solutions and a new multi-layer wall design for low-rise construction as well as the results of television studies on multi-layer and single-layer envelopes. Indoor climate parameters for various wall design solutions are determined. The study reveals the optimal wall design solutions and specifies the theoretical assessment of their energy efficiency in compliance with Russia's national building code 23-02-2003. The paper presents calculations of building heat loss through the exterior building envelope, reduced resistance to heat transfer of walls and total heat loss of the building with the selected outer wall design during the heating season. Recommendations on the application of the new multi-layer wall design using local wall materials in the construction of energy-efficient low-rise buildings are developed. The recommendations include requirements for wall materials, thermal calculations, production guidelines, properties of layers in a multi-layer walls and physical and mechanical properties of wall layers.

  15. 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.

  16. Experimental and Theoretical Studies of the Structures and Interactions of Vancomycin Antibiotics with Cell Wall Analogues

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Zhibo; Vorpagel, Erich R.; Laskin, Julia

    2008-10-01

    Surface-induced dissociation (SID) of the singly protonated complex of vancomycin antibiotic with cell wall peptide analogue (Nα,Nε-diacetyl-L-Lys-D-Ala-D-Ala) was studied using a 6 T Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FT-ICR MS) specially configured for SID experiments. The binding energy between the vancomycin and the peptide was obtained from the RRKM modeling of the time- and energy resolved fragmentation efficiency curves (TFECs) of the precursor ion and its fragments. Electronic structure calculations of the geometries, proton affinities and binding energies were performed for several model systems including vancomycin (V), vancomycin aglycon (VA), Nα,Nε-diacetyl-L-Lys-D-Ala-D-Ala, and non-covalent complexes of VA with N-acetyl-D-Ala-D-Ala and Nα,Nε-diacetyl-L-Lys-D-Ala-D-Ala at the B3LYP/6-31G(d) level of theory. Comparison between the experimental and computational results suggests that the most probable structure of the complex observed in our experiments corresponds to the neutral peptide bound to the vancomycin protonated at the secondary amino group of the N-methyl-leucine residue. The experimental binding energy of 30.9 ± 1.8 kcal/mol is in good agreement with the binding energy of 29.3 ± 2.5 kcal/mol calculated for the model system representing the preferred structure of the complex.

  17. Abdominal aortic aneurysms : clinical insights and outcome after endovascular repair

    NARCIS (Netherlands)

    Zandvoort, H.J.A.

    2013-01-01

    Abdominal aortic aneurysm (AAA) is a focal dilatation of the abdominal aorta. The pathophysiology of AAA is a complex multifactorial process and much is still unknown. Histologic and biochemical analysis of AAA wall characteristics can contribute to a better insight in AAA pathophysiology. To make t

  18. Turbulent structures in wall-bounded shear flows observed via three-dimensional numerical simulators. [using the Illiac 4 computer

    Science.gov (United States)

    Leonard, A.

    1980-01-01

    Three recent simulations of tubulent shear flow bounded by a wall using the Illiac computer are reported. These are: (1) vibrating-ribbon experiments; (2) study of the evolution of a spot-like disturbance in a laminar boundary layer; and (3) investigation of turbulent channel flow. A number of persistent flow structures were observed, including streamwise and vertical vorticity distributions near the wall, low-speed and high-speed streaks, and local regions of intense vertical velocity. The role of these structures in, for example, the growth or maintenance of turbulence is discussed. The problem of representing the large range of turbulent scales in a computer simulation is also discussed.

  19. Structural insights into the pH-controlled targeting of plant cell-wall invertase by a specific inhibitor protein

    OpenAIRE

    Hothorn, Michael; Van den Ende, Wim; Lammens, Willem; Rybin, Vladimir; Scheffzek, Klaus

    2010-01-01

    Invertases are highly regulated enzymes with essential functions in carbohydrate partitioning, sugar signaling, and plant development. Here we present the 2.6 Å crystal structure of Arabidopsis cell-wall invertase 1 (INV1) in complex with a protein inhibitor (CIF, or cell-wall inhibitor of β-fructosidase) from tobacco. The structure identifies a small amino acid motif in CIF that directly targets the invertase active site. The activity of INV1 and its interaction with CIF are strictly pH-depe...

  20. Screening for Abdominal Aortic Aneurysm

    Science.gov (United States)

    Understanding Task Force Recommendations Screening for Abdominal Aortic Aneurysm The U.S. Preventive Services Task Force (Task Force) has issued a final recommendation statement on Screening for Abdominal Aortic Aneurysm. This final ...

  1. Abdominal aortic aneurysm repair - open

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/007392.htm Abdominal aortic aneurysm repair - open To use the sharing features on this page, please enable JavaScript. Open abdominal aortic aneurysm repair is surgery to fix a widened part ...

  2. Extraordinary improvement of the graphitic structure of continuous carbon nanofibers templated with double wall carbon nanotubes.

    Science.gov (United States)

    Papkov, Dimitry; Beese, Allison M; Goponenko, Alexander; Zou, Yan; Naraghi, Mohammad; Espinosa, Horacio D; Saha, Biswajit; Schatz, George C; Moravsky, Alexander; Loutfy, Raouf; Nguyen, Sonbinh T; Dzenis, Yuris

    2013-01-22

    Carbon nanotubes are being widely studied as a reinforcing element in high-performance composites and fibers at high volume fractions. However, problems with nanotube processing, alignment, and non-optimal stress transfer between the nanotubes and surrounding matrix have so far prevented full utilization of their superb mechanical properties in composites. Here, we present an alternative use of carbon nanotubes, at a very small concentration, as a templating agent for the formation of graphitic structure in fibers. Continuous carbon nanofibers (CNF) were manufactured by electrospinning from polyacrylonitrile (PAN) with 1.2% of double wall nanotubes (DWNT). Nanofibers were oxidized and carbonized at temperatures from 600 °C to 1850 °C. Structural analyses revealed significant improvements in graphitic structure and crystal orientation in the templated CNFs, with the largest improvements observed at lower carbonization temperatures. In situ pull-out experiments showed good interfacial bonding between the DWNT bundles and the surrounding templated carbon matrix. Molecular Dynamics (MD) simulations of templated carbonization confirmed oriented graphitic growth and provided insight into mechanisms of carbonization initiation. The obtained results indicate that global templating of the graphitic structure in fine CNFs can be achieved at very small concentrations of well-dispersed DWNTs. The outcomes reveal a simple and inexpensive route to manufacture continuous CNFs with improved structure and properties for a variety of mechanical and functional applications. The demonstrated improvement of graphitic order at low carbonization temperatures in the absence of stretch shows potential as a promising new manufacturing technology for next generation carbon fibers.

  3. Monocyte transmigration induced by modification of low density lipoprotein in cocultures of human aortic wall cells is due to induction of monocyte chemotactic protein 1 synthesis and is abolished by high density lipoprotein.

    OpenAIRE

    Navab, M; Imes, S S; Hama, S Y; Hough, G P; Ross, L.A.; Bork, R W; Valente, A. J.; Berliner, J A; Drinkwater, D C; Laks, H

    1991-01-01

    Incubation of cocultures of human aortic endothelial (HAEC) and smooth muscle cells (HASMC) with LDL in the presence of 5-10% human serum resulted in a 7.2-fold induction of mRNA for monocyte chemotactic protein 1 (MCP-1), a 2.5-fold increase in the levels of MCP-1 protein in the coculture supernatants, and a 7.1-fold increase in the transmigration of monocytes into the subendothelial space of the cocultures. Monocyte migration was inhibited by 91% by antibody to MCP-1. Media collected from t...

  4. Effects of hanging wall and forward directivity in the 1999 Chi-Chi earthquake on inelastic displacement response of structures

    Institute of Scientific and Technical Information of China (English)

    Li Shuang; Xie Lili

    2007-01-01

    The characteristics of the inelastic response of structures affected by hanging wall and forward directivity in the 1999 Chi-Chi earthquake are investigated. Inelastic displacement ratios (IDRs) for ground motions impacted by these nearfield effects are evaluated and comprehensively compared to far-field ground motions. In addition, the inelastic displacement responses to hanging wall and footwall ground motions are compared. It is concluded that the inelastic displacement response is significantly affected in the short period range by hanging wall and in the long period range by footwall. Although high peak ground acceleration was observed at hanging wall stations, the IDRs for structures on hanging wall sites are only larger than footwall sites in the very long period range. Forward directivity effects result in larger IDRs for periods longer than about 0.5s. Adopting statistical relationships for IDRs established using far-field ground motions may lead to either overestimation or underestimation in the seismic evaluation of existing structures located in near-field regions, depending on their fundamental vibration periods.

  5. Structural characteristics of oligomeric DNA strands adsorbed onto single-walled carbon nanotubes.

    Science.gov (United States)

    Roxbury, Daniel; Jagota, Anand; Mittal, Jeetain

    2013-01-10

    The single-stranded DNA to single-walled carbon nanotube (SWCNT) hybrid continues to attract significant interest as an exemplary biological molecule-nanomaterial conjugate. In addition to their many biomedical uses, such as in vivo sensing and delivery of molecular cargo, DNA-SWCNT hybrids enable the sorting of SWCNTs according to their chirality. Current experimental methods have fallen short of identifying the actual structural ensemble of DNA adsorbed onto SWCNTs that enables and controls several of these phenomena. Molecular dynamics (MD) simulation has been a useful tool for studying the structure of these hybrid molecules. In recent studies, using replica exchange MD (REMD) simulation we have shown that novel secondary structures emerge and that these structures are DNA-sequence and SWCNT-type dependent. Here, we use REMD to investigate in detail the structural characteristics of two DNA-SWCNT recognition pairs: (TAT)(4)-(6,5)-SWCNT, i.e., DNA sequence TATTATTATTAT bound to the (6,5) chirality SWCNT, and (CCG)(2)CC-(8,7)-SWCNT as well as off-recognition pairs (TAT)(4)-(8,7)-SWCNT and (CCG)(2)CC-(6,5)-SWCNT. From a structural clustering analysis, dominant equilibrium structures are identified and show a right-handed self-stitched motif for (TAT)(4)-(6,5) in contrast to a left-handed β-barrel for (CCG)(2)CC-(8,7). Additionally, characteristics such as DNA end-to-end distance, solvent accessible SWCNT surface area, DNA hydrogen bonding between bases, and DNA dihedral distributions have been probed in detail as a function of the number of DNA strands adsorbed onto the nanotube. We find that the DNA structures adsorbed onto a nanotube are also stabilized by significant numbers of non-Watson-Crick hydrogen bonds (intrastrand and interstrand) in addition to π-π stacking between DNA bases and nanotube surface and Watson-Crick pairs. Finally, we provide a summary of DNA structures observed for various DNA-SWCNT hybrids as a preliminary set of motifs that may be

  6. Correlation of Processing, Inner Structure, and Part Properties of Injection Moulded Thin-Wall Parts on Example of Polyamide 66

    Directory of Open Access Journals (Sweden)

    Dietmar Drummer

    2014-01-01

    Full Text Available In micro- and thin-wall injection moulding the process conditions affect the developed internal structures and thus the resulting part properties. This paper investigates exemplarily on polyamide 66 the interactions of different cooling conditions on the morphological and crystalline structures. The investigations reveal that a slow cooling rate of the melt results in a homogeneous morphology and a higher degree of crystallinity and also a favoured crystalline structure. Consequently, the dielectric behaviour and light transmitting part properties are affected.

  7. Hemodynamic predictors of aortic dilatation in bicuspid aortic valve by velocity-encoded cardiovascular magnetic resonance

    Directory of Open Access Journals (Sweden)

    Ramamurthy Senthil

    2010-01-01

    Full Text Available Abstract Background Congenital Bicuspid Aortic Valve (BAV is a significant risk factor for serious complications including valve dysfunction, aortic dilatation, dissection, and sudden death. Clinical tools for identification and monitoring of BAV patients at high risk for development of aortic dilatation, an early complication, are not available. Methods This paper reports an investigation in 18 pediatric BAV patients and 10 normal controls of links between abnormal blood flow patterns in the ascending aorta and aortic dilatation using velocity-encoded cardiovascular magnetic resonance. Blood flow patterns were quantitatively expressed in the angle between systolic left ventricular outflow and the aortic root channel axis, and also correlated with known biochemical markers of vessel wall disease. Results The data confirm larger ascending aortas in BAV patients than in controls, and show more angled LV outflow in BAV (17.54 ± 0.87 degrees than controls (10.01 ± 1.29 (p = 0.01. Significant correlation of systolic LV outflow jet angles with dilatation was found at different levels of the aorta in BAV patients STJ: r = 0.386 (N = 18, p = 0.048, AAO: r = 0.536 (N = 18, p = 0.022, and stronger correlation was found with patients and controls combined into one population: SOV: r = 0.405 (N = 28, p = 0.033, STJ: r = 0.562 (N = 28, p = 0.002, and AAO r = 0.645 (N = 28, p Conclusions The results of this study provide new insights into the pathophysiological processes underlying aortic dilatation in BAV patients. These results show a possible path towards the development of clinical risk stratification protocols in order to reduce morbidity and mortality for this common congenital heart defect.

  8. [Congenital aortic stenosis].

    Science.gov (United States)

    Yamaguchi, M

    2001-08-01

    Recent advances in and controversies concerning the management of children with congenital valvular aortic stenosis are discussed. In neonates with critical aortic stenosis, improved survival has recently been reported after surgical open valvotomy and balloon valvuloplasty, although it is difficult at this point to compare the results of the two procedures and determine their differential indications. Good results have also been achieved after extended aortic valvuloplasty for recurrent aortic stenosis and/or insufficiency, but the length of follow-up in these patients is still short. The technique first reported in 1991 for bilateral enlargement fo a small annulus permits the insertion of an aortic valve 3-4 sizes larger than the native annulus. It entails no risk of distorting the mitral valve, damaging the conduction system or important branches of the coronary arteries, or resulting in left ventricular dysfunction. The Ross procedure is now widely applied in the West, with reports of early mortality rates of less than 5% and event-free survival rates of 80-90% during follow-up of 4-8 years. Longer follow-up and continued careful evaluation are required to resolve the issue of possible dilatation and subsequent neoaortic valve dysfunction and pulmonary stenosis due to allograft degeneration after pulmonary autograft root replacement in children.

  9. Structure of the complex between teicoplanin and a bacterial cell-wall peptide: use of a carrier-protein approach

    Energy Technology Data Exchange (ETDEWEB)

    Economou, Nicoleta J.; Zentner, Isaac J. [Drexel University College of Medicine, 245 North 15th Street, Philadelphia, PA 19102 (United States); Lazo, Edwin; Jakoncic, Jean; Stojanoff, Vivian [Brookhaven National Laboratory, Upton, NY 11973 (United States); Weeks, Stephen D.; Grasty, Kimberly C.; Cocklin, Simon; Loll, Patrick J. [Drexel University College of Medicine, 245 North 15th Street, Philadelphia, PA 19102 (United States)

    2013-04-01

    Using a carrier-protein strategy, the structure of teicoplanin bound to its bacterial cell-wall target has been determined. The structure reveals the molecular determinants of target recognition, flexibility in the antibiotic backbone and intrinsic radiation sensitivity of teicoplanin. Multidrug-resistant bacterial infections are commonly treated with glycopeptide antibiotics such as teicoplanin. This drug inhibits bacterial cell-wall biosynthesis by binding and sequestering a cell-wall precursor: a d-alanine-containing peptide. A carrier-protein strategy was used to crystallize the complex of teicoplanin and its target peptide by fusing the cell-wall peptide to either MBP or ubiquitin via native chemical ligation and subsequently crystallizing the protein–peptide–antibiotic complex. The 2.05 Å resolution MBP–peptide–teicoplanin structure shows that teicoplanin recognizes its ligand through a combination of five hydrogen bonds and multiple van der Waals interactions. Comparison of this teicoplanin structure with that of unliganded teicoplanin reveals a flexibility in the antibiotic peptide backbone that has significant implications for ligand recognition. Diffraction experiments revealed an X-ray-induced dechlorination of the sixth amino acid of the antibiotic; it is shown that teicoplanin is significantly more radiation-sensitive than other similar antibiotics and that ligand binding increases radiosensitivity. Insights derived from this new teicoplanin structure may contribute to the development of next-generation antibacterials designed to overcome bacterial resistance.

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

    Directory of Open Access Journals (Sweden)

    Paula eGuzmán

    2014-09-01

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

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

    Science.gov (United States)

    Guzmán, Paula; Fernández, Victoria; Graça, José; Cabral, Vanessa; Kayali, Nour; Khayet, Mohamed; Gil, Luis

    2014-01-01

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

  12. Changes in plant cell-wall structure of corn stover due to hot compressed water pretreatment and enhanced enzymatic hydrolysis.

    Science.gov (United States)

    Zhou, Wei; Yang, Maohua; Wang, Caixia; Liu, Jianfei; Xing, Jianmin

    2014-08-01

    Corn stover is a potential feedstock for biofuel production. This work investigated physical and chemical changes in plant cell-wall structure of corn stover due to hot compressed water (HCW) pretreatment at 170-190 °C in a tube reactor. Chemical composition analysis showed the soluble hemicellulose content increased with pretreatment temperature, whereas the hemicellulose content decreased from 29 to 7 % in pretreated solids. Scanning electron microscopy revealed the parenchyma-type second cell-wall structure of the plant was almost completely removed at 185 °C, and the sclerenchyma-type second cell wall was greatly damaged upon addition of 5 mmol/L ammonium sulfate during HCW pretreatment. These changes favored accessibility for enzymatic action. Enzyme saccharification of solids by optimized pretreatment with HCW at 185 °C resulted in an enzymatic hydrolysis yield of 87 %, an enhancement of 77 % compared to the yield from untreated corn stover.

  13. Structural model for the first wall W-based material in ITER project

    Institute of Scientific and Technical Information of China (English)

    Dehua Xu; Xinkui He; Shuiquan Deng; Yong Zhao

    2014-01-01

    The preparation, characterization, and test of the first wall materials designed to be used in the fusion reactor have remained challenging problems in the material science. This work uses the first-principles method as implemented in the CASTEP package to study the influ-ences of the doped titanium carbide on the structural sta-bility of the W–TiC material. The calculated total energy and enthalpy have been used as criteria to judge the structural models built with consideration of symmetry. Our simulation indicates that the doped TiC tends to form its own domain up to the investigated nano-scale, which implies a possible phase separation. This result reveals the intrinsic reason for the composite nature of the W–TiC material and provides an explanation for the experimen-tally observed phase separation at the nano-scale. Our approach also sheds a light on explaining the enhancing effects of doped components on the durability, reliability, corrosion resistance, etc., in many special steels.

  14. Turbulent boundary layer control through spanwise wall oscillation using Kagome lattice structures

    Science.gov (United States)

    Bird, James; Santer, Matthew; Morrison, Jonathan

    2015-11-01

    It is well established that a reduction in skin-friction and turbulence intensity can be achieved by applying in-plane spanwise forcing to a surface beneath a turbulent boundary layer. It has also been shown in DNS (M. Quadrio, P. Ricco, & C. Viotti; J. Fluid Mech; 627, 161, 2009), that this phenomenon is significantly enhanced when the forcing takes the form of a streamwise travelling wave of spanwise perturbation. In the present work, this type of forcing is generated by an active surface comprising a compliant structure, based on a Kagome lattice geometry, supporting a membrane skin. The structural design ensures negligible wall normal displacement while facilitating large in-plane velocities. The surface is driven pneumatically, achieving displacements of 3 mm approximately, at frequencies in excess of 70 Hz for a turbulent boundary layer at Reτ ~ 1000 . As the influence of this forcing on boundary layer is highly dependent on the wavenumber and frequency of the travelling wave, a flat surface was designed and optimised to allow these forcing parameters to be varied, without reconfiguration of the experiment. Simultaneous measurements of the fluid and surface motion are presented, and notable skin-friction drag reduction is demonstrated. Airbus support agreement IW202838 is gratefully acknowledged.

  15. Wall-crossing structures in Donaldson-Thomas invariants, integrable systems and Mirror Symmetry

    CERN Document Server

    Kontsevich, Maxim

    2013-01-01

    We introduce the notion of Wall-Crossing Structure and discuss it in several examples including complex integrable systems, Donaldson-Thomas invariants and Mirror Symmetry. For a big class of non-compact Calabi-Yau 3-folds we construct complex integrable systems of Hitchin type with the base given by the moduli space of deformations of those 3-folds. Then Donaldson-Thomas invariants of the Fukaya category of such a Calabi-Yau 3-fold can be (conjecturally) described in two more ways: in terms of the attractor flow on the base of the corresponding complex integrable system and in terms of the skeleton of the mirror dual to the total space of the integrable system. The paper also contains a discussion of some material related to the main subject, e.g. Betti model of Hitchin systems with irregular singularities, WKB asymptotics of connections depending on a small parameter, attractor points in the moduli space of complex structures of a compact Calabi-Yau 3-fold, relation to cluster varieties, etc.

  16. Aortic valve replacement

    DEFF Research Database (Denmark)

    Kapetanakis, Emmanouil I; Athanasiou, Thanos; Mestres, Carlos A;

    2008-01-01

    mortality were collected. Group analysis by patient geographic distribution and by annular diameter of the prosthesis utilized was conducted. Patients with a manufacturer's labeled prosthesis size > or = 21 mm were assigned to the 'large' aortic size subset, while those with a prosthesis size ... assigned to the 'small' aortic size subset. Effective orifice area indices were calculated for all patients to assess the geographic distribution of patient-prosthesis mismatch. Univariable and multivariable logistic regression analyses adjusting for possible confounding variables were performed. RESULTS...... differences in the distribution of either gender or BSA. In the multivariable model, south European patients were seven times more likely to receive a smaller-sized aortic valve (OR = 6.5, 95% CI = 4.82-8.83, p

  17. Robotic aortic surgery.

    Science.gov (United States)

    Duran, Cassidy; Kashef, Elika; El-Sayed, Hosam F; Bismuth, Jean

    2011-01-01

    Surgical robotics was first utilized to facilitate neurosurgical biopsies in 1985, and it has since found application in orthopedics, urology, gynecology, and cardiothoracic, general, and vascular surgery. Surgical assistance systems provide intelligent, versatile tools that augment the physician's ability to treat patients by eliminating hand tremor and enabling dexterous operation inside the patient's body. Surgical robotics systems have enabled surgeons to treat otherwise untreatable conditions while also reducing morbidity and error rates, shortening operative times, reducing radiation exposure, and improving overall workflow. These capabilities have begun to be realized in two important realms of aortic vascular surgery, namely, flexible robotics for exclusion of complex aortic aneurysms using branched endografts, and robot-assisted laparoscopic aortic surgery for occlusive and aneurysmal disease.

  18. Influence of large-eddy breakup device on near-wall turbulent structures in turbulent boundary layer

    Science.gov (United States)

    Kim, Joon-Seok; Hwang, Jinyul; Yoon, Min; Ahn, Junsun; Sung, Hyung Jin; Flow Control Lab Team

    2016-11-01

    Direct numerical simulation of a large-eddy breakup (LEBU) device in a spatially developing turbulent boundary layer was performed to investigate the influence of outer structures on the near-wall turbulence. The thin and rectangular shaped LEBU device was placed on y / δ = 0 . 8 and the device reduced the skin-friction coefficient (Cf) up to 17%. Decomposition of Cf showed that the contribution of the Reynolds shear stress decreased along the wall-normal direction. The reduction of the Reynolds shear stress was associated with the decrease of the ejection and sweep events, and in particular the latter was significantly reduced compared to the former in the near-wall region. The spanwise length scale of high-speed structures was more shortened than that of low-speed very near the wall (y+ = 20). As a result, the dispersive motions induced by the outer sweeps were weakened leading to the reduction of Cf even the LEBU device located far from the wall. This work was supported by the Creative Research Initiatives (No. 2016-004749) program of the National Research Foundation of Korea (MSIP).

  19. Influence of Zn ion implantation on structures and field emission properties of multi-walled carbon nanotube arrays

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The structures and field emission properties of multi-walled carbon nanotube arrays implanted with Zn+ by MEVVA ion implanter have been investigated.The results revealed that Zn+implantation induced structural damage and that the top of carbon nanotubes with multi-layered graphite structure were transformed into carbon nanowires with amorphous structure.Meanwhile,C:Zn solid solution was synthesized after Zn+ implantation.The turn-on field and threshold field were 0.80 and 1.31 V/μm,respectively for original multi-walled carbon nanotube arrays and were reduced to 0.66 and 1.04 V/μm due to the synthesis of C and Zn composite,in which the work function was reduced after low doses of Zn+implantation.It is indicated that low doses of Zn+implantation can improve field emission performance of multi-walled carbon nanotube arrays.Otherwise,high doses of Zn+implantation can reduce field emission properties of multi-walled carbon nanotube arrays,because radiation damage reduces the electric field enhancement factor.

  20. Pulsatile blood flow in Abdominal Aortic Aneurysms

    Science.gov (United States)

    Salsac, Anne-Virginie; Lasheras, Juan C.; Singel, Soeren; Varga, Chris

    2001-11-01

    We discuss the results of combined in-vitro laboratory measurements and clinical observations aimed at determining the effect that the unsteady wall shear stresses and the pressure may have on the growth and eventual rupturing of an Abdominal Aortic Aneurysm (AAA), a permanent bulging-like dilatation occurring near the aortic bifurcation. In recent years, new non-invasive techniques, such as stenting, have been used to treat these AAAs. However, the development of these implants, aimed at stopping the growth of the aneurysm, has been hampered by the lack of understanding of the effect that the hemodynamic forces have on the growth mechanism. Since current in-vivo measuring techniques lack the precision and the necessary resolution, we have performed measurements of the pressure and shear stresses in laboratory models. The models of the AAA were obtained from high resolution three-dimensional CAT/SCANS performed in patients at early stages of the disease. Preliminary DPIV measurements show that the pulsatile blood flow discharging into the cavity of the aneurysm leads to large spikes of pressure and wall shear stresses near and around its distal end, indicating a possible correlation between the regions of high wall shear stresses and the observed location of the growth of the aneurysm.

  1. Electron irradiation-induced change of structure and damage mechanisms in multi-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    杨剑群; 李兴冀; 刘超铭; 马国亮; 高峰

    2015-01-01

    Owing to their unique structure and excellent electrical property, carbon nanotubes (CNTs) as an ideal candidate for making future electronic components have great application potentiality. In order to meet the requirements for space appli-cation in electronic components, it is necessary to study structural changes and damage mechanisms of multi-walled carbon nanotubes (MWCNTs), caused by the irradiations of 70 and 110 keV electrons. In the paper, the changes of structure and damage mechanisms in the irradiated MWCNTs, induced by the irradiations of 70 and 110 keV electrons, are investigated. The changes in surface morphology and structure of the irradiated MWCNT film are characterized using scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, x-ray diffraction analysis (XRD), and electron paramagnetic resonance (EPR) spectroscopy. It is found that the MWCNTs show different behaviors in structural changes after 70 and 110 keV electron irradiation due to different damage mechanisms. SEM results reveal that the irra-diation of 70 keV electrons does not change surface morphology of the MWCNT film, while the irradiation of 110 keV electrons with a high fluence of 5 × 1015 cm−2 leads to evident morphological changes, such as the formation of a rough surface, the entanglement of nanotubes and the shrinkage of nanotubes. Based on Raman spectroscopy, XPS, and XRD analyses, it is confirmed that the irradiation of 70 keV electrons increases the interlayer spacing of the MWCNTs and disorders their structure through electronic excitations and ionization effects, while the irradiation of 110 keV electrons obviously reduces the interlayer spacing of the MWCNTs and improves their graphitic order through knock-on atom dis-placements. The improvement of the irradiated MWCNTs by 110 keV electrons is attributed to the restructuring of defect sites induced by knock-on atom displacements. EPR spectroscopic analyses reveal that the MWCNTs

  2. Control of cracking in R.C. Structures: Numerical simulation of a squat shear wall

    NARCIS (Netherlands)

    Damoni, C.; Belletti, B.; Lilliu, G.

    2013-01-01

    In this paper the behavior of a squat shear wall subjected to monotonic shear loading is investigated. The study fits into the experimental program driven by CEOS.fr on modeling of the behavior of the tested mocks-ups (monotonic and cycling loading-under prevented or free shrinkage). The shear wall

  3. First-principles calculations on the structure and electronic properties of boron doping zigzag single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    WEN QingBo; YU ShanSheng; ZHENG WeiTao

    2009-01-01

    Calculations have been made for single-walled zigzag (n, 0) carbon nanotubes containing substitutional boron impurity atoms using ab initio density functional theory. It is found that the formation energies of these nanotubes depend on the tube diameter, as do the electronic properties, and show periodic fea-ture that results from their different π bonding structures compared to those of perfect zigzag carbon nanotubes. When more boron atoms are incorporated into a single-walled zigzag carbon nanotube, the substitutional boron atoms tend to come together to form structure of BC3 nanodomains, and B-doped tubes have striking acceptor states above the top of the valence bands. For the structure of BC3, there are two kinds of configurations with different electronic structures.

  4. First-principles calculations on the structure and electronic properties of boron doping zigzag single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Calculations have been made for single-walled zigzag(n,0) carbon nanotubes containing substitutional boron impurity atoms using ab initio density functional theory.It is found that the formation energies of these nanotubes depend on the tube diameter,as do the electronic properties,and show periodic fea-ture that results from their different π bonding structures compared to those of perfect zigzag carbon nanotubes.When more boron atoms are incorporated into a single-walled zigzag carbon nanotube,the substitutional boron atoms tend to come together to form structure of BC3 nanodomains,and B-doped tubes have striking acceptor states above the top of the valence bands.For the structure of BC3,there are two kinds of configurations with different electronic structures.

  5. Randomized clinical trial of mast cell inhibition in patients with a medium-sized abdominal aortic aneurysm

    DEFF Research Database (Denmark)

    Sillesen, H; Eldrup, N; Hultgren, R

    2015-01-01

    BACKGROUND: Abdominal aortic aneurysm (AAA) is thought to develop as a result of inflammatory processes in the aortic wall. In particular, mast cells are believed to play a central role. The AORTA trial was undertaken to investigate whether the mast cell inhibitor, pemirolast, could retard...

  6. Blood flow characteristics in the ascending aorta after TAVI compared to surgical aortic valve replacement.

    Science.gov (United States)

    Trauzeddel, Ralf Felix; Löbe, Ulrike; Barker, Alex J; Gelsinger, Carmen; Butter, Christian; Markl, Michael; Schulz-Menger, Jeanette; von Knobelsdorff-Brenkenhoff, Florian

    2016-03-01

    Ascending aortic blood flow characteristics are altered after aortic valve surgery, but the effect of transcatheter aortic valve implantation (TAVI) is unknown. Abnormal flow may be associated with aortic and cardiac remodeling. We analyzed blood flow characteristics in the ascending aorta after TAVI in comparison to conventional stented aortic bioprostheses (AVR) and healthy subjects using time-resolved three-dimensional flow-sensitive cardiovascular magnetic resonance imaging (4D-flow MRI). Seventeen patients with TAVI (Edwards Sapien XT), 12 with AVR and 9 healthy controls underwent 4D-flow MRI of the ascending aorta. Target parameters were: severity of vortical and helical flow pattern (semiquantitative grading from 0 = none to 3 = severe) and the local distribution of systolic wall shear stress (WSSsystole). AVR revealed significantly more extensive vortical and helical flow pattern than TAVI (p = 0.042 and p = 0.002) and controls (p flow than controls (p blood flow eccentricity (64.7 and 66.7%, respectively), whereas controls showed central blood flow (88.9%). TAVI and AVR exhibited an asymmetric distribution of WSSsystole in the mid-ascending aorta with local maxima at the right anterior aortic wall and local minima at the left posterior wall. In contrast, controls showed a symmetric distribution of WSSsystole along the aortic circumference. Blood flow was significantly altered in the ascending aorta after TAVI and AVR. Changes were similar regarding WSSsystole distribution, while TAVI resulted in less helical and vortical blood flow.

  7. Superconductivity on the density-wave background with soliton-wall structure

    Energy Technology Data Exchange (ETDEWEB)

    Grigoriev, P.D. [L. D. Landau Institute for Theoretical Physics, Chernogolovka 142432 (Russian Federation)], E-mail: grigorev@itp.ac.ru

    2009-03-01

    Superconductivity (SC) may microscopically coexist with density wave (DW) when the nesting of the Fermi surface (FS) is not perfect. There are, at least, two possible microscopic structures of a DW state with quasi-particle states remaining on the Fermi level and leading to the Cooper instability: (i) the soliton-wall phase and (ii) the small ungapped FS pockets. The dispersion of such quasi-particle states strongly differs from that without DW, and so do the properties of SC on the DW background. The upper critical field H{sub c2} in such an SC state strongly increases as the system approaches the critical pressure, where SC first appears. H{sub c2} may considerably exceed its typical value without DW and has unusual upward curvature as function of temperature. The results obtained explain the experimental observations in layered organic superconductors (TMTSF){sub 2}PF{sub 6} and {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4}.

  8. Structure, stability, and motion of dislocations in double-wall carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    Zhang Kai-Wang; Li Zhong-Qiu; Wu Jian; Peng Xiang-Yang; Tan Xin-Jun; Sun Li-Zhong; Zhong Jian-Xin

    2012-01-01

    In this paper,a novel double-wall carbon nanotube (DWCNT) with both edge and screw dislocations is studied by using the molecular dynamics (MD) method. The differences between two adjacent tubule indexes of armchair and zigzag nanotubes are determined to be 5 and 9,respectively,by taking into account the symmetry,integrality,and thermal stability of the composite structures. It is found that melting first occurs near the dislocations,and the melting temperatures of the dislocated armchair and zigzag DWCNTs are around 2600 K-2700 K.At the premelting temperatures,the shrink of the dislocation loop,which is comprised of edge and screw dislocations,implies that the composite dislocation in DWCNTs has self-healing ability.The dislocated DWCNTs first fracture at the edge dislocations,which induces the entire break in axial tensile test. The dislocated DWCNTs have a smaller fracture strength compared to the perfect DWCNTs.Our results not only match with the dislocation glide of carbon nanotubes (CNTs) in experiments,but also can free from the electron beam radiation under experimental conditions observed by the high resolution transmission electron microscope (HRTEM),which is deemed to cause the motion of dislocation loop.

  9. Structure, stability, and motion of dislocations in double-wall carbon nanotubes

    Science.gov (United States)

    Zhang, Kai-Wang; Li, Zhong-Qiu; Wu, Jian; Peng, Xiang-Yang; Tan, Xin-Jun; Sun, Li-Zhong; Zhong, Jian-Xin

    2012-10-01

    In this paper, a novel double-wall carbon nanotube (DWCNT) with both edge and screw dislocations is studied by using the molecular dynamics (MD) method. The differences between two adjacent tubule indexes of armchair and zigzag nanotubes are determined to be 5 and 9, respectively, by taking into account the symmetry, integrality, and thermal stability of the composite structures. It is found that melting first occurs near the dislocations, and the melting temperatures of the dislocated armchair and zigzag DWCNTs are around 2600 K—2700 K. At the pre-melting temperatures, the shrink of the dislocation loop, which is comprised of edge and screw dislocations, implies that the composite dislocation in DWCNTs has self-healing ability. The dislocated DWCNTs first fracture at the edge dislocations, which induces the entire break in axial tensile test. The dislocated DWCNTs have a smaller fracture strength compared to the perfect DWCNTs. Our results not only match with the dislocation glide of carbon nanotubes (CNTs) in experiments, but also can free from the electron beam radiation under experimental conditions observed by the high resolution transmission electron microscope (HRTEM), which is deemed to cause the motion of dislocation loop.

  10. Templated Synthesis of Single-Walled Carbon Nanotubes with Specific Structure.

    Science.gov (United States)

    Yang, Feng; Wang, Xiao; Li, Meihui; Liu, Xiyan; Zhao, Xiulan; Zhang, Daqi; Zhang, Yan; Yang, Juan; Li, Yan

    2016-04-19

    Single-walled carbon nanotubes (SWNTs) have shown great potential in various applications attributed to their unique structure-dependent properties. Therefore, the controlled preparation of chemically and structurally pristine SWNTs is a crucial issue for their advanced applications (e.g., nanoelectronics) and has been a great challenge for two decades. Epitaxial growth from well-defined seeds has been shown to be a promising strategy to control the structure of SWNTs. Segments of carbon nanotubes, including short pipes from cutting of preformed nanotubes and caps from opening of fullerenes or cyclodehydrogenation of polycyclic hydrocarbon precursors, have been used as the seeds to grow SWNTs. Single-chirality SWNTs were obtained with both presorted chirality-pure SWNT segments and end caps obtained from polycyclic hydrocarbon molecules with designed structure. The main challenges of nanocarbon-segment-seeded processes are the stability of the seeds, yield, and efficiency. Catalyst-mediated SWNT growth is believed to be more efficient. The composition and morphology of the catalyst nanoparticles have been widely reported to affect the chirality distribution of SWNTs. However, chirality-specific SWNT growth is hard to achieve by alternating catalysts. The specificity of enzyme-catalyzed reactions brings us an awareness of the essentiality of a unique catalyst structure for the chirality-selective growth of SWNTs. Only catalysts with the desired atomic arrangements in their crystal planes can act as structural templates for chirality-specific growth of SWNTs. We have developed a new family of catalysts, tungsten-based intermetallic compounds, which have high melting points and very special crystal structures, to facilitate the growth of SWNTs with designed chirality. By the use of W6Co7 catalysts, (12,6) SWNTs were directly grown with purity higher than 92%. Both high-resolution transmission electron microscopy measurements and density functional theory simulations

  11. Impact of different aortic valve calcification patterns on the outcome of transcatheter aortic valve implantation: A finite element study.

    Science.gov (United States)

    Sturla, Francesco; Ronzoni, Mattia; Vitali, Mattia; Dimasi, Annalisa; Vismara, Riccardo; Preston-Maher, Georgia; Burriesci, Gaetano; Votta, Emiliano; Redaelli, Alberto

    2016-08-16

    Transcatheter aortic valve implantation (TAVI) can treat symptomatic patients with calcific aortic stenosis. However, the severity and distribution of the calcification of valve leaflets can impair the TAVI efficacy. Here we tackle this issue from a biomechanical standpoint, by finite element simulation of a widely adopted balloon-expandable TAVI in three models representing the aortic root with different scenarios of calcific aortic stenosis. We developed a modeling approach realistically accounting for aortic root pressurization and complex anatomy, detailed calcification patterns, and for the actual stent deployment through balloon-expansion. Numerical results highlighted the dependency on the specific calcification pattern of the "dog-boning" of the stent. Also, local stent distortions were associated with leaflet calcifications, and led to localized gaps between the TAVI stent and the aortic tissues, with potential implications in terms of paravalvular leakage. High stresses were found on calcium deposits, which may be a risk factor for stroke; their magnitude and the extent of the affected regions substantially increased for the case of an "arc-shaped" calcification, running from commissure to commissure. Moreover, high stresses due to the interaction between the aortic wall and the leaflet calcifications were computed in the annular region, suggesting an increased risk for annular damage. Our analyses suggest a relation between the alteration of the stresses in the native anatomical components and prosthetic implant with the presence and distribution of relevant calcifications. This alteration is dependent on the patient-specific features of the calcific aortic stenosis and may be a relevant indicator of suboptimal TAVI results.

  12. Unoperated aortic aneurysm

    DEFF Research Database (Denmark)

    Perko, M J; Nørgaard, M; Herzog, T M;

    1995-01-01

    From 1984 to 1993, 1,053 patients were admitted with aortic aneurysm (AA) and 170 (15%) were not operated on. The most frequent reason for nonoperative management was presumed technical inoperability. Survivals for patients with thoracic, thoracoabdominal, and abdominal AA were comparable...... hypertension were predictive of mortality, whereas...

  13. NUCLEON STRUCTURE IN LATTICE QCD WITH DYNAMICAL DOMAIN--WALL FERMIONS QUARKS.

    Energy Technology Data Exchange (ETDEWEB)

    LIN H.-W.; OHTA, S.

    2006-10-02

    We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with 220 gauge configurations each. The lattice cutoff is a{sup -1} {approx} 1.7GeV and the spatial volume is about (1.9fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments {sub u-d}/{sub {Delta}u-{Delta}d} are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is a{sup -1} {approx} 1.6GeV and the spatial volume is about (3.0fm){sup 3}. Even with preliminary statistics of 25-30 gauge configurations, the ratios g{sub A}/g{sub V} and {sub u-d}/{sub {Delta}u-{Delta}d} are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d{sub 1}, though yet to be renormalized, appears small in both sets.

  14. Enhancing 4D PC-MRI in an aortic phantom considering numerical simulations

    Science.gov (United States)

    Kratzke, Jonas; Schoch, Nicolai; Weis, Christian; Müller-Eschner, Matthias; Speidel, Stefanie; Farag, Mina; Beller, Carsten J.; Heuveline, Vincent

    2015-03-01

    To date, cardiovascular surgery enables the treatment of a wide range of aortic pathologies. One of the current challenges in this field is given by the detection of high-risk patients for adverse aortic events, who should be treated electively. Reliable diagnostic parameters, which indicate the urge of treatment, have to be determined. Functional imaging by means of 4D phase contrast-magnetic resonance imaging (PC-MRI) enables the time-resolved measurement of blood flow velocity in 3D. Applied to aortic phantoms, three dimensional blood flow properties and their relation to adverse dynamics can be investigated in vitro. Emerging "in silico" methods of numerical simulation can supplement these measurements in computing additional information on crucial parameters. We propose a framework that complements 4D PC-MRI imaging by means of numerical simulation based on the Finite Element Method (FEM). The framework is developed on the basis of a prototypic aortic phantom and validated by 4D PC-MRI measurements of the phantom. Based on physical principles of biomechanics, the derived simulation depicts aortic blood flow properties and characteristics. The framework might help identifying factors that induce aortic pathologies such as aortic dilatation or aortic dissection. Alarming thresholds of parameters such as wall shear stress distribution can be evaluated. The combined techniques of 4D PC-MRI and numerical simulation can be used as complementary tools for risk-stratification of aortic pathology.

  15. The mechanism for the generation of coherent structures in the wall region of a turbulent boundary layer

    Institute of Scientific and Technical Information of China (English)

    周恒; 熊忠民

    1995-01-01

    By using the idea of resonant triad of the theory of hydrodynamic stability, a theoretical model was proposed for the generation of the coherent structures in the wall region of a turbulent boundary layer. The obtained structural configuration, the spanwise length scale and the convective speed of the coherent structures are in agreement with those obtained by numerical simulations. To further characterize these structures, the probability density distribution of the non-dimensional circulation difference of the largely unsymmetric streamwise vortex pairs has been calculated. Its comparison with those obtained by the numerical simulations is in general satisfactory.

  16. Study of coherent structures of turbulence with large wall-normal gradients in thermophysical properties using direct numerical simulation

    Science.gov (United States)

    Reinink, Shawn K.; Yaras, Metin I.

    2015-06-01

    Forced-convection heat transfer in a heated working fluid at a thermodynamic state near its pseudocritical point is poorly predicted by correlations calibrated with data at subcritical temperatures and pressures. This is suggested to be primarily due to the influence of large wall-normal thermophysical property gradients that develop in proximity of the pseudocritical point on the concentration of coherent turbulence structures near the wall. The physical mechanisms dominating this influence remain poorly understood. In the present study, direct numerical simulation is used to study the development of coherent vortical structures within a turbulent spot under the influence of large wall-normal property gradients. A turbulent spot rather than a fully turbulent boundary layer is used for the study, for the coherent structures of turbulence in a spot tend to be in a more organized state which may allow for more effective identification of cause-and-effect relationships. Large wall-normal gradients in thermophysical properties are created by heating the working fluid which is near the pseudocritical thermodynamic state. It is found that during improved heat transfer, wall-normal gradients in density accelerate the growth of the Kelvin-Helmholtz instability mechanism in the shear layer enveloping low-speed streaks, causing it to roll up into hairpin vortices at a faster rate. It is suggested that this occurs by the baroclinic vorticity generation mechanism which accelerates the streamwise grouping of vorticity during shear layer roll-up. The increased roll-up frequency leads to reduced streamwise spacing between hairpin vortices in wave packets. The density gradients also promote the sinuous instability mode in low-speed streaks. The resulting oscillations in the streaks in the streamwise-spanwise plane lead to locally reduced spanwise spacing between hairpin vortices forming over adjacent low-speed streaks. The reduction in streamwise and spanwise spacing between

  17. Thoracic aortic aneurysm: reading the enemy's playbook.

    Science.gov (United States)

    Elefteriades, John A

    2008-05-01

    The vast database of the Yale Center for Thoracic Aortic Disease--which includes information on 3000 patients with thoracic aortic aneurysm or dissection, with 9000 catalogued images and 9000 patient-years of follow-up--has, over the last decade, permitted multiple glimpses into the "playbook" of this virulent disease. Understanding the precise behavioral features of thoracic aortic aneurysm and dissection permits us more effectively to combat this disease. In this monograph, we will first review certain fundamentals--in terms of anatomy, nomenclature, imaging, diagnosis, medical, surgical, and stent treatment. After reviewing these fundamentals, we will proceed with a detailed exploration of lessons learned by peering into the operational playbook of thoracic aortic aneurysm and dissection. Among the glimpses afforded in the behavioral playbook of this disease are the following: 1 Thoracic aortic aneurysm, while lethal, is indolent. Mortality usually does not occur until after years of growth. 2 The aneurysmal ascending thoracic aorta grows slowly: about 0.1 cm per year (the descending aorta grows somewhat faster). 3 Over a patient's lifetime, "hinge points" at which the likelihood of rupture or dissection skyrockets are seen at 5.5 cm for the ascending and 6.5 cm for the descending aorta. Intervening at 5 cm diameter for the ascending and 6 cm for the descending prevents most adverse events. 4 Symptomatic aneurysms require resection regardless of size. 5 The yearly rate of rupture, dissection, or death is 14.1% for a patient with a thoracic aorta of 6 cm diameter. 6 The mechanical properties of the aorta deteriorate markedly at 6 cm diameter (distensibility falls, and wall stress rises)--a finding that "dovetails" perfectly with observations of the clinical behavior of the thoracic aorta. 7 Thoracic aortic aneurysm and dissection are largely inherited diseases, with a predominantly autosomal-dominant pattern. The specific genetics are being elucidated at the

  18. Histopathological study of congenital aortic valve malformations in 32 children

    Institute of Scientific and Technical Information of China (English)

    HUANG Ping; WANG Hongwei; LI Yanping; CHENG Peixuan; LIU Qingjun; ZHANG Zhenlu; LIU Jianying

    2007-01-01

    The histopathological characteristics of congenital aortic valve malformations in children were investigated.All the native surgically excised aortic valves from 32 pediatric patients suffering from symptomatic aortic valve dysfunction due to congenital aortic valve malformations between January 2003 and December 2005 were studied macroscopically and microscopically.The patients' medical records were reviewed and the clinical information was extracted.The diagnosis was made by the clinical presentation,preoperative echocardiography,intraoperative examination,and postoperative histopathological study,excluding rheumatic ot degenerative aortic valve diseases,infective endocarditis and primary connective tissue disorders,e.g.Marfan syndrome.Among 32 children with congenital aortic valve malformations,the age was ranged from six to 18 years,with a mean of 14.9 years,and there were 27 boys and five girls (male:female = 5.4:1).There were five cases of aortic stenosis (AS,15.62%),25 cases of aortic insufficiency (AI,78.13 %)and two cases of AS-AI (6.25%),without other valve diseases.Twenty cases still had other congenital heart diseases:ventricular septal defect (19 cases),patent ductus arteriosus (two cases),double-chambered right ventricle (one case),aneurysm of the right anterior aortic sinus of valsalva (three cases).Histopathological examination indicated that the cusps became thickening with unequal size,irregular shape (coiling and prolapse edge),enhanced hardness,and partly calcification.Microscopic investigation revealed the unsharp structure of valve tissue,fibrosis,myxomatous,reduced collagen fiber,rupture of elastic fibers,different degrees of infiltration of inflammatory cells,secondary calcareous and lipid deposit,and secondary fibrosis.Congenital aortic valve malformations in children involve males more than females,mostly associated with other congenital heart diseases.Aortic insufficiency is more common in children with congenital aortic valve

  19. Transverse and vortex domain wall structure in magnetic nanowires with uniaxial in-plane anisotropy.

    Science.gov (United States)

    Bryan, M T; Bance, S; Dean, J; Schrefl, T; Allwood, D A

    2012-01-18

    Micromagnetic and analytical models are used to investigate how in-plane uniaxial anisotropy affects transverse and vortex domain walls in nanowires where shape anisotropy dominates. The effect of the uniaxial anisotropy can be interpreted as a modification of the effective wire dimensions. When the anisotropy axis is aligned with the wire axis (θ(a) = 0), the wall width is narrower than when no anisotropy is present. Conversely, the wall width increases when the anisotropy axis is perpendicular to the wire axis (θ(a) = π/2). The anisotropy also affects the nanowire dimensions at which transverse walls become unstable. This phase boundary shifts to larger widths or thicknesses when θ(a) = 0, but smaller widths or thicknesses when θ(a) = π/2.

  20. [The thickness/radius ratio of the left ventricle in aortic stenosis. Prognostic and therapeutic implications].

    Science.gov (United States)

    Guadalajara, J F; Martínez, C; Huerta, D

    1990-01-01

    Using two-D echocardiography and cardiac catheterization we studied the performance of left ventricle in severe aortic stenosis with normal ventricular function (10 patients), and with heart failure (11 patients). With appropriate hypertrophy increased ventricular function, is found resulting in systolic wall stress normalization. When hypertrophic mechanism is unable to normalize the systolic wall stress; afterload increases with ensuing heart failure (inadequate hypertrophy). Surgical treatment in those cases reduces the afterload and increases de ventricular function. Normalization of systolic wall stress in patients with severe aortic stenosis and heart failure means irreversible myocardial damage.

  1. External wall structure of green rural houses in Daqing, China, based on life cycle and ecological footprint theories

    Directory of Open Access Journals (Sweden)

    Hong Jin

    2015-09-01

    Full Text Available Daqing is situated in one of the severely cold regions of China. The living environment in this region is extremely poor because of the harsh climate and the backward economy. The external wall is an important component of the external envelope of buildings, and it greatly contributes to the indoor thermal environment. By taking the external wall as the research object, this study summarizes the characteristics of the external wall structure and analyzes the common materials used in existing rural residences. Specifically, we combine life cycle theory and ecological footprint (EF theory and introduce the green external wall structure, as well as its application in practice, in accordance with the local ecosystem. Results show that anecological residence offers a better environment and greater economic benefits than a traditional residence. The annual energy consumption, CO2 consumption, and EF of the ecological residence in this study are lower than those of the traditional residence by 69.61%, 17.5 t, and 99.47%, respectively.

  2. Three-dimensional structures and turbulence closure of the wake developing in a wall shear layer

    Science.gov (United States)

    Hah, C.

    1981-01-01

    The turbulent wake interacting with the rotating wall shear layer is investigated analytically and numerically. The turbulent wakes of the rotating blades in a compressor which are interacting with the rotating hub-wall boundary layer are analyzed. A modified version of the closure model of the pressure-strain correlation term in the Reynolds stress transport equation is developed to predict the effect of rotation, which is appreciable for the present flow because the thick hub-wall boundary layer is interacting with the rotor wake. It is noted that the Poisson type equation for the pressure-strain correlation has an extra rotation term when the entire flow field is rotating. This extra rotation term is modeled to accommodate the effect of rotation. In addition, the standard correction for the wall effect is incorporated for the utilized Reynolds stress closure model. The rotation-modified Reynolds stress closure model is used to predict the present flow, and the predictions are compared with the experimental data. The experimental data reveal that the characteristics of the three-dimensional turbulent wake interacting with the wall shear layer are considerably altered by the effects of the wall and the rotation. These features are predicted with good accuracy by the turbulence closure model developed.

  3. Extended aortic valvuloplasty: a new approach for the management of congenital valvar aortic stenosis.

    Science.gov (United States)

    Ilbawi, M N; DeLeon, S Y; Wilson, W R; Roberson, D A; Husayni, T S; Quinones, J A; Arcilla, R A

    1991-09-01

    A new technique for the treatment of congenital valvar aortic stenosis is described. It consists of augmenting the aortic cusp by extending the commissurotomy incision into the aortic wall around the leaflet insertion, mobilizing the valve cusp attachment at the commissures, and freeing the aortic insertion of the rudimentary commissure. The results of standard valvotomy performed on 48 patients (group 1) were compared with those of the new extended valvuloplasty carried out on 16 patients (group 2). The two groups were comparable in age at operation (2.7 +/- 2.1 years for group 1 versus 2.1 +/- 1.7 years for group 2; p = not significant) and in preoperative pressure gradient (58 +/- 25 mm Hg for group 1 versus 61 +/- 36 mm Hg for group 2; p = not significant). There was no operative mortality in either group. Follow-up is available on all patients, with a mean of 4.3 +/- 2.6 years for group 1 versus 1.7 +/- 0.5 years for group 2 (p = 0.05). There was one late death in group 1. Postoperative gradient was 47 +/- 13 mm Hg in group 1 versus 19 +/- 13 mm Hg in group 2 (p = 0.05). Moderate or severe regurgitation was present in 18 patients (38%) in group 1 and 2 patients (13%) in group 2 (p = not significant). Reoperation was needed in 8 patients (17%) in group 1 versus 2 patients (13%) in group 2 (p = not significant). The described valvuloplasty procedure addresses the unique pathological features of valvar aortic stenosis and provides better relief of the obstruction than the presently available techniques. Longer follow-up is needed to determine the late results of this approach.

  4. Influence of the structural properties on the pseudocritical magnetic behavior of single-wall ferromagnetic nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Salazar-Enriquez, C.D. [PCM Computational Applications, Universidad Nacional de Colombia - Sede Manizales, A.A. 127 Manizales (Colombia); Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [PCM Computational Applications, Universidad Nacional de Colombia - Sede Manizales, A.A. 127 Manizales (Colombia); Restrepo, J. [Grupo de Magnetismo y Simulacion Gplus, Instituto de Fisica, Universidad de Antioquia, A.A. 1226 Medellin (Colombia)

    2012-04-15

    In this work we address the influence of the crystalline structure, concretely when the system under study is formed by square or hexagonal unit cells, upon the magnetic properties and pseudocritical behavior of single-wall ferromagnetic nanotubes. We focus not only on the effect of the geometrical shape of the unit cell but also on their dimensions. The model employed is based on the Monte Carlo method, the Metropolis dynamics and a nearest neighbors classical Heisenberg Hamiltonian. Magnetization per magnetic site, magnetic susceptibility, specific heat and magnetic energy were computed. These properties were computed varying the system size, unit cell dimension and temperature. The dependence of the nearest neighbor exchange integral on the nanotubes geometrical characteristics is also discussed. Results revealed a strong influence of the system topology on the magnetic properties caused by the difference in the coordination number between square and hexagonal unit cell. Moreover, the nanotubes diameter influence on magnetic properties is only observed at very low values, when the distance between atoms is less than it, presented by the 2D sheet. On the other hand, it was concluded that the surface-related finite-size effects do not influence the magnetic nanotubes properties, contrary to the case of other nano-systems as thin films and nanoparticles among others. - Highlights: Black-Right-Pointing-Pointer Unit cell geometry has strong influence on the magnetic properties in ferromagnetic nanotubes. Black-Right-Pointing-Pointer The nanotube diameter increase produces a decrease of interaction between nearest neighbor. Black-Right-Pointing-Pointer Surface-related finite-size effects do not influence the magnetic nanotubes properties.

  5. [Stanford type a acute aortic dissection with pectus excavatum].

    Science.gov (United States)

    Kuwata, Toshiyuki; Fukuda, Hirotsugu; Yoshitatsu, Masao; Yamada, Yasuyuki; Shibasaki, Ikuko; Inoue, Yuho; Hori, Takayuki; Ogawa, Hironaga; Tsuchiya, Go; Shimizu, Riha; Takei, Yusuke

    2012-11-01

    Pectus excavatum is generally an isolated abnormality of the chest wall. However, some patients have a concomitant pectus deformity and cardiac & aortic disease. Decisions must be made regarding the operative approach and whether the pectus excavatum should be corrected during the same session. We report 2 patients with acute Stanford type A aortic dissection and pectus excavatum who underwent emergency operation. In case 1, median sternotomy is an unsuitable approach for open heart surgery, since the heart and great vessels are displace into the left hemithorax. But combined sternotomy and left anterior thoracotomy provided excellent surgical exposure. In case 2, we proceeded with a leftsided costotomy of four ribs and place a normal chest retractor providing as excellent exposure as combined sternotomy and left anterior thoracotomy. A left-sided costotomy of four ribs can be performed safely, eliminating the risks of median sternotomy in acute stanford type A aortic dissection with pectus excavatum.

  6. Simulation of bifurcated stent grafts to treat abdominal aortic aneurysms (AAA)

    CERN Document Server

    Egger, Jan; Freisleben, Bernd

    2016-01-01

    In this paper a method is introduced, to visualize bifurcated stent grafts in CT-Data. The aim is to improve therapy planning for minimal invasive treatment of abdominal aortic aneurysms (AAA). Due to precise measurement of the abdominal aortic aneurysm and exact simulation of the bifurcated stent graft, physicians are supported in choosing a suitable stent prior to an intervention. The presented method can be used to measure the dimensions of the abdominal aortic aneurysm as well as simulate a bifurcated stent graft. Both of these procedures are based on a preceding segmentation and skeletonization of the aortic, right and left iliac. Using these centerlines (aortic, right and left iliac) a bifurcated initial stent is constructed. Through the implementation of an ACM method the initial stent is fit iteratively to the vessel walls - due to the influence of external forces (distance- as well as balloonforce). Following the fitting process, the crucial values for choosing a bifurcated stent graft are measured, ...

  7. 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.

  8. Transcatheter aortic valve-in-valve implantation of a CoreValve in a degenerated aortic bioprosthesis.

    Science.gov (United States)

    Bruschi, Giuseppe; DeMarco, Federico; Oreglia, Jacopo; Colombo, Paola; Fratto, Pasquale; Lullo, Francesca; Paino, Roberto; Martinelli, Luigi; Klugmann, Silvio

    2010-03-01

    In recent years percutaneous aortic valve implantation has emerged as an alternative therapy to treat patients with symptomatic aortic stenosis considered to be high-risk surgical candidates. We report our experience of a percutaneous retrograde CoreValve implantation in a 77-year-old female with aortic bioprosthesis structural degeneration. The patient underwent aortic valve replacement for aortic stenosis in 1999 with the implantation of a 23 mm Carpentier-Edwards; her last echocardiography showed a severe bioprosthesis stenosis. After evaluation by cardiac surgeons and cardiologist, considering the high risk re-do surgical procedure (Logistic Euroscore 30%) and severe comorbidities (severe pulmonary hypertension, hepatocellular carcinoma and severe osteoporosis), a percutaneous aortic valve-in-valve replacement was preferred. A successful percutaneous 26 mm CoreValve prosthesis implantation was performed with the patient awake with local anesthesia and mild sedation. The patient was discharged after 10 days of hospitalization and she is in NYHA functional class I at follow-up. Our experience, characterized by a multidisciplinary approach, necessary to offer the safest conditions and care for patients, demonstrates the feasibility of a new, promising indication for the use of a transcatheter valve implantation: percutaneous treatment of a degenerated aortic bioprosthesis.

  9. Tobacco smoking and aortic aneurysm

    DEFF Research Database (Denmark)

    Sode, Birgitte F; Nordestgaard, Børge G; Grønbæk, Morten

    2012-01-01

    General Population Study, respectively. According to the magnitude of the hazard ratios, tobacco consumption was the most important risk factor for hospitalization and death from aortic aneurysm, followed by male sex and hypertension in both cohorts. The population attributable risk of aortic aneurysm...... outcomes due to tobacco consumption was 64% and 47% in the Copenhagen City Heart Study and Copenhagen General Population Study, respectively, and ranked highest among population attributable risks of aortic aneurysm in both cohorts. The absolute 10-year risk for hospitalization or death from aortic......BACKGROUND: We determined the predictive power of tobacco smoking on aortic aneurysm as opposed to other risk factors in the general population. METHODS: We recorded tobacco smoking and other risk factors at baseline, and assessed hospitalization and death from aortic aneurysm in 15,072 individuals...

  10. Tissue Responses to Stent Grafts with Endo-Exo-Skeleton for Saccular Abdominal Aortic Aneurysms in a Canine Model

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Il Young; Chung, Jin Wook; Kim, Hyo Cheol [Dept. of Radiology and Institute of Radiation Medicine, Seoul National University College of Medicine, Clinical Research Institute, Seoul (Korea, Republic of); Choi, Young Ho; So Young Ho [Dept. of Radiology, Seoul National University Boramae Hospital, Seoul (Korea, Republic of); Kim, Hyun Beom [Dept. of Radiology, National Cancer Center, Goyang (Korea, Republic of); Min, Seung Kee [Dept. of Surgery, Seoul National University College of Medicine, Seoul (Korea, Republic of); Park, Jae Hyung [Dept. of Radiology, Gachon University Gil Medical Center, Incheon (Korea, Republic of)

    2014-10-15

    We evaluated the effect of close contact between the stent and the graft on the induction of endothelial covering on the stent graft placed over an aneurysm. Saccular abdominal aortic aneurysms were made with Dacron patch in eight dogs. The stent graft consisted of an inner stent, a expanded polytetrafluoroethylene graft, and an outer stent. After sacrificing the animals, the aortas with an embedded stent graft were excised. The aortas were inspected grossly and evaluated microscopically. The animals were sacrificed at two (n = 3), six (n = 3), and eight months (n = 2) after endovascular repair. In two dogs, the aortic lumen was occluded at two months after the placement. On gross inspection of specimens from the other six dogs with a patent aortic lumen, stent grafts placed over the normal aortic wall were covered by glossy white neointima, whereas, stent grafts placed over the aneurysmal aortic wall were covered by brownish neointima. On microscopic inspection, stent grafts placed over the normal aortic wall were covered by thin neointima (0.27 ± 0.05 mm, mean ± standard deviation) with an endothelial layer, and stent grafts placed over the aneurysmal aortic wall were covered by thick neointima (0.62 ± 0.17 mm) without any endothelial lining. Transgraft cell migration at the normal aortic wall was more active than that at the aneurysmal aortic wall. Close contact between the stent and the graft, which was achieved with stent grafts with endo-exo-skeleton, could not enhance endothelial covering on the stent graft placed over the aneurysms.

  11. Discrimination of the wall effect in a thin counter with micro-gap structure for neutron position sensing

    Energy Technology Data Exchange (ETDEWEB)

    Sakae, Takeji; Manabe, Tohru; Kitamura, Yasunori; Nohtomi, Akihiro [Kyushu Univ., Fukuoka (Japan); Sakamoto, Sigeyasu

    1996-07-01

    Simulation by the Monte Carlo method is applied to estimate the wall effect in a thermal neutron counter having a new function for discriminating the effect. The counter is designed to have paralleled electrodes with micro-gap structure. A resistive anode is used for position sensing on the center of a set of the three electrode. The structure can be made by simple arrangement of anode and cathode wires on an insulator plane. The calculation shows discrimination of the wall effect can be achieved by coincident counting of two or three elements included in the counter. By using the coincident counting, the thickness of the neutron counter can be made into 1 mm with the information of the total energy created in the neutron detection. (author)

  12. Spin distributions and dynamics in domain walls guided by soft magnetic nanowire structures

    Science.gov (United States)

    Yang, Jusang; Erskine, James L.

    2017-01-01

    Numerical simulations are used to investigate static and dynamic properties of spin distributions within domain walls confined by rectangular cross section Permalloy nanowire conduits having widths up to 1000 nm and thickness up to 50 nm. Phase boundaries and critical regions associated with domain-wall spin distributions of various topologies [transverse (or asymmetric transverse), vortex, double-vortex, triple-vortex and cross-tie] are accurately determined using high-performance computing resources. Mobility curves are calculated that characterize domain-wall propagation for an interesting region of the spin texture phase diagram: 20 nm thick nanowires with widths of 60-700 nm at axial drive fields extending to 150 Oe. The simulations (and corresponding experiments, which are discussed), reveal new propagating fixed configuration domain-wall topologies with enhanced velocity. Effects of temperature on the spin distributions and dynamics are explored, by conducting simulations that include separately varying temperature-dependent parameters (saturation magnetization and exchange constant) and simulating effects of temperature-dependent fluctuations using the Langevin dynamics feature of the simulation code. Related temperature-dependent experiments are discussed. The simulation studies demonstrate a close connection between static and (field-driven) dynamic spin configurations in nanowire-confined domain walls and demonstrate the importance of exploring model-system parameter space at high numerical precision.

  13. Nonlinear Modeling of Autoclaved Aerated Concrete Masonry Wall Strengthened using Ferrocement Sandwich Structure

    KAUST Repository

    M., Abdel-Mooty

    2011-01-01

    Autoclaved Aerated Concrete (AAC) block are used mainly as non-load-bearing walls that provide heat insulation. This results in considerable saving in cooling energy particularly in hot desert environment with large variation of daily and seasonal temperatures. However, due to the relatively low strength there use load bearing walls is limited to single storey and low-rise construction. A system to enhance the strength of the AAC masonry wall in resisting both inplane vertical and combined vertical and lateral loads using ferrocement technology is proposed in this research. The proposed system significantly enhances the load carrying capacity and stiffness of the AAC wall without affecting its insulation characteristics. Ferrocement is made of cement mortar reinforced with closely spaced wire mesh. Full scale wall specimens with height of 2100mm and width of 1820mm were tested with different configuration of ferrocement. A finite elementmodel is developed and verified against the experimentalwork. The results of the finite element model correlates well with the experimental results.

  14. Complete Soil-Structure Interaction (SSI) Analyses of I-walls Embedded in Level Ground During Flood Loading

    Science.gov (United States)

    2012-09-01

    8217 El=-2.5’ Sheet pile tip ERDC/ITL TR-12-4 10 (CWALSHT) ( Dawkins 1991) and procedures outlined in HQUSACE (1994). The initial design depth of...mechanics. 6th ed. New York: Chapman and Hall. Dawkins , W. P. 1991. User’s guide: Computer program for design and analysis of sheet- pile walls by... Dawkins , R. Mosher, and I. Hallal. 1997. Soil-structure interaction effects in floodwalls. Electronic Journal of Geotechnical Engineering. http

  15. Nucleon structure from mixed action calculations using 2+1 flavors of asqtad sea and domain wall valence fermions

    Energy Technology Data Exchange (ETDEWEB)

    Bratt, Jonathan; Engelhardt, Michael; Haegler, Philipp; Huey-Wen, Lin; Lin, Meifeng; Meyer, Harvey; Musch, Bernhard; Negele, John; Orginos, Konstantinos; Pochinsky, Andrew; Procura, Massimiliano; Richards, David; Schroers, Wolfram; Syritsyn, Sergey

    2010-11-01

    We present high statistics results for the structure of the nucleon from a mixed-action calculation using 2+1 flavors of asqtad sea and domain wall valence fermions. We perform extrapolations of our data based on different chiral effective field theory schemes and compare our results with available information from phenomenology. We discuss vector and axial form factors of the nucleon, moments of generalized parton distributions, including moments of forward parton distributions, and implications for the decomposition of the nucleon spin.

  16. Mesothelial/monocytic incidental cardiac excrescences (cardiac MICE) associated with acute aortic dissection: a study of two cases

    Science.gov (United States)

    Strecker, Thomas; Bertz, Simone; Wachter, David Lukas; Weyand, Michael; Agaimy, Abbas

    2015-01-01

    Acute aortic dissection is a life-threatening condition mainly caused by hypertension, atherosclerotic disease and other degenerative diseases of the connective tissue of the aortic wall. Mesothelial/monocytic incidental cardiac excrescences (cardiac MICE) is a rare benign reactive tumor-like lesion composed of admixture of histiocytes, mesothelial cells, and inflammatory cells set within a fibrinous meshwork without a vascular network or supporting stroma. Cardiac MICE occurring in association with aortic dissection is exceptionally rare (only one such case reported to date). We herein report on the surgical repair of two Stanford type A aortic dissections caused by idiopathic giant cell aortitis in a 66-year-old-woman and by atherosclerotic disease in a 58-year-old-man, respectively. In both cases, the dissections could be visualized via computed tomography. Histopathology showed cardiac incidental MICE within the external aortic wall near the pericardial surface which was confirmed by immunohistochemistry. PMID:26097568

  17. Ruptured abdominal aortic aneurysm.

    Science.gov (United States)

    Sachs, T; Schermerhorn, M

    2010-06-01

    Ruptured abdominal aortic aneurysm (AAA) continues to be one of the most lethal vascular pathologies we encounter. Its management demands prompt and efficient evaluation and repair. Open repair has traditionally been the mainstay of treatment. However, the introduction of endovascular techniques has altered the treatment algorithm for ruptured AAA in most major medical centers. We present recent literature and techniques for ruptured AAA and its surgical management.

  18. Infrarenal Aortic Occlusion

    Science.gov (United States)

    Traverso, L. W.; Baker, J. D.; Dainko, E. A.; Machleder, H. I.

    1978-01-01

    Twenty-eight patients with total occlusion of the infrarenal aorta have been seen at the UCLA Hospitals in the past 11 years. Claudication was the presenting complaint in all but one patient, with one-third having ischemic rest pain. The average age of these patients was 54 years, and their histories revealed a surprising absence of myocardial infarction, stroke, or diabetes, although 40% had essential hypertension. Heavy tobacco use, however, was characteristic of the entire group. Arteriography proved valuable in identifying and characterizing the vascular abnormalities, but posed problems in technique and interpretation. Significant distal arterial disease was detected radiographically in only 21% of these patients. Operative correction of the aortic occlusion was performed on 26 patients, 18 by aortic bypass grafts and eight by aorto-iliac endarterectomy, with one early postoperative death. Although the thrombus extended to the renal artery origins in 77% of the cases, a well-designed technical approach did not require renal artery occlusion. Using serial creatinine determinations, one case of renal insufficiency was detected which was associated with prolonged postoperative hypotension. Although the extent of distal disease was more severe in those who underwent bypass, symptoms of claudication returned earlier and were more prominent in the endarterectomy group. This recurrence of systems was not favorably altered by sympathectomy performed concomitantly with the initial procedure. Even though this condition seems to pose difficult technical obstacles and has a poor prognosis, infrarenal aortic occlusion can be successfully treated by aortic bypass, with favorable long-term results, if particular attention is paid to elements of the preoperative evaluation and the intraoperative technical requirements peculiar to this relatively uncommon disease entity. ImagesFig. 1.Fig. 2.Fig. 3. PMID:646479

  19. Fourier transform mid infrared spectroscopy applications for monitoring the structural plasticity of plant cell walls

    Science.gov (United States)

    Largo-Gosens, Asier; Hernández-Altamirano, Mabel; García-Calvo, Laura; Alonso-Simón, Ana; Álvarez, Jesús; Acebes, José L.

    2014-01-01

    Fourier transform mid-infrared (FT-MIR) spectroscopy has been extensively used as a potent, fast and non-destructive procedure for analyzing cell wall architectures, with the capacity to provide abundant information about their polymers, functional groups, and in muro entanglement. In conjunction with multivariate analyses, this method has proved to be a valuable tool for tracking alterations in cell walls. The present review examines recent progress in the use of FT-MIR spectroscopy to monitor cell wall changes occurring in muro as a result of various factors, such as growth and development processes, genetic modifications, exposition or habituation to cellulose biosynthesis inhibitors and responses to other abiotic or biotic stresses, as well as its biotechnological applications. PMID:25071791

  20. Reorganization of Coherent Structures Downstream a Circular Cylinder Located between Two Parallel Walls

    Directory of Open Access Journals (Sweden)

    F. Rehimi

    2011-01-01

    Full Text Available Experiments were performed at low Reynolds numbers in the range 75 Re 275 in the wake of a circular cylinder of dc diameter placed symmetrically between two parallel walls of H height. 2D2C particle image velocimetry (PIV was used to investigate the flow downstream the cylinder. In the unsteady flow regime downstream the cylinder, the detached primary vortices (Pi interact with walls generating secondary ones (Pi’ and modify the cylinder wake dynamic. The kinematical properties (advection velocity, circulation, rotation kinetic energy, etc. of the generated secondary vortices are studied and compared with the primary ones in order to show how the walls influence the von Kármán vortex street. The authors propose here a relation between the circulations and kinetic energies of primary and secondary vortices.

  1. Fenestrated Stent Graft Repair of Abdominal Aortic Aneurysm: Hemodynamic Analysis of the Effect of Fenestrated Stents on the Renal Arteries

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Zhonghua; Chaichana, Thanapong [Curtin University of Technology, Perth (Australia)

    2010-02-15

    We wanted to investigate the hemodynamic effect of fenestrated stents on the renal arteries with using a fluid structure interaction method. Two representative patients who each had abdominal aortic aneurysm that was treated with fenestrated stent grafts were selected for the study. 3D realistic aorta models for the main artery branches and aneurysm were generated based on the multislice CT scans from two patients with different aortic geometries. The simulated fenestrated stents were designed and modelled based on the 3D intraluminal appearance, and these were placed inside the renal artery with an intra-aortic protrusion of 5.0-7.0 mm to reflect the actual patients' treatment. The stent wire thickness was simulated with a diameter of 0.4 mm and hemodynamic analysis was performed at different cardiac cycles. Our results showed that the effect of the fenestrated stent wires on the renal blood flow was minimal because the flow velocity was not significantly affected when compared to that calculated at pre-stent graft implantation, and this was despite the presence of recirculation patterns at the proximal part of the renal arteries. The wall pressure was found to be significantly decreased after fenestration, yet no significant change of the wall shear stress was noticed at post-fenestration, although the wall shear stress was shown to decrease slightly at the proximal aneurysm necks. Our analysis demonstrates that the hemodynamic effect of fenestrated renal stents on the renal arteries is insignificant. Further studies are needed to investigate the effect of different lengths of stent protrusion with variable stent thicknesses on the renal blood flow, and this is valuable for understanding the long-term outcomes of fenestrated repair.

  2. Manipulation of multiple 360o domain wall structures and its current-driven motion in a magnetic nanostripe

    Directory of Open Access Journals (Sweden)

    Wenjun Dong

    2015-11-01

    Full Text Available Dynamics of multiple transverse walls (TWs in a magnetic nanostripe is studied by micromagnetic simulations. It shows that, when TWs are arranged in a stripe with same orientation, they will attract each other and finally annihilate. However, when adjacent TWs are arranged with opposite orientation, a metastable complex wall can be formed, e.g., two TWs lead to 360o wall. For three or more TWs, the formed complex wall includes a number of 360o substructures, which is called multiple 360o structure (M360S here. The M360S itself may be used to store multiple logical data since each 360o substructure can act as logical ”0” or ”1”. On the other hand, the M360S may behave like single TW under an applied current, namely, the M360S can be driven steadily by current like that of single TW. A parity effect of the number of 360o substructures on the critical current for the annihilation is found. Namely, when the number is odd or even, the critical current increase or decrease with the increasing of the number, respectively. The parity effect is relevant to the out-of-plane magnetic moment of the M360S.

  3. 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.

  4. Micromanaging Abdominal Aortic Aneurysms

    Directory of Open Access Journals (Sweden)

    Lars Maegdefessel

    2013-07-01

    Full Text Available The contribution of abdominal aortic aneurysm (AAA disease to human morbidity and mortality has increased in the aging, industrialized world. In response, extraordinary efforts have been launched to determine the molecular and pathophysiological characteristics of the diseased aorta. This work aims to develop novel diagnostic and therapeutic strategies to limit AAA expansion and, ultimately, rupture. Contributions from multiple research groups have uncovered a complex transcriptional and post-transcriptional regulatory milieu, which is believed to be essential for maintaining aortic vascular homeostasis. Recently, novel small noncoding RNAs, called microRNAs, have been identified as important transcriptional and post-transcriptional inhibitors of gene expression. MicroRNAs are thought to “fine tune” the translational output of their target messenger RNAs (mRNAs by promoting mRNA degradation or inhibiting translation. With the discovery that microRNAs act as powerful regulators in the context of a wide variety of diseases, it is only logical that microRNAs be thoroughly explored as potential therapeutic entities. This current review summarizes interesting findings regarding the intriguing roles and benefits of microRNA expression modulation during AAA initiation and propagation. These studies utilize disease-relevant murine models, as well as human tissue from patients undergoing surgical aortic aneurysm repair. Furthermore, we critically examine future therapeutic strategies with regard to their clinical and translational feasibility.

  5. Particle Image Velocimetry studies of bicuspid aortic valve hemodynamics

    Science.gov (United States)

    Saikrishnan, Neelakantan; Yap, Choon-Hwai; Yoganathan, Ajit P.

    2010-11-01

    Bicuspid aortic valves (BAVs) are a congenital anomaly of the aortic valve with two fused leaflets, affecting about 1-2% of the population. BAV patients have much higher incidence of valve calcification & aortic dilatation, which may be related to altered mechanical forces from BAV hemodynamics. This study aims to characterize BAV hemodynamics using Particle Image Velocimetry(PIV). BAV models are constructed from normal explanted porcine aortic valves by suturing two leaflets together. The valves are mounted in an acrylic chamber with two sinuses & tested in a pulsatile flow loop at physiological conditions. 2D PIV is performed to obtain flow fields in three planes downstream of the valve. The stenosed BAV causes an eccentric jet, resulting in a very strong vortex in the normal sinus. The bicuspid sinus vortex appears much weaker, but more unstable. Unsteady oscillatory shear stresses are also observed, which have been associated with adverse biological response; characterization of the hemodynamics of BAVs will provide the first step to understanding these processes better. Results from multiple BAV models of varying levels of stenosis will be presented & higher stenosis corresponded to stronger jets & increased aortic wall shear stresses.

  6. Invasive aspergillosis in the aortic arch with infectious Aspergillus lesions in pulmonary bullae

    Directory of Open Access Journals (Sweden)

    Isao Watanabe

    2015-03-01

    Full Text Available A patient with pulmonary bullae died of massive hemoptysis. At autopsy a hole was observed in the aortic wall. A microscopic examination indicated small Aspergillus lesions in pulmonary bullae and extensive necrotic lesions with Aspergillus hyphae in the media of the thoracic aorta. These findings led to a diagnosis of invasive aspergillosis in the aortic arch. This is a rare case in which Aspergillus invaded the aorta in a patient without hematologic neoplasms or neutropenia.

  7. Aortic Dissection of Unknown Origin in a Young Patient: A Case Report

    OpenAIRE

    Majid Hajimaghsoudi; Faeze Zeinali; Mehdi Bagherabadi; Morteza Saeedi

    2016-01-01

    Aortic dissection occurs when a tear develops in the wall of the aorta, which is rare in the young population. This fatal disorder is hard to diagnose, especially in young patients. We present the case of aortic dissection in a 15-year-old boy referred to the Emergency Department of Yazd University of Medical Sciences in November 2015. The patient presented to our department with sudden acute chest pain. Emergent computed tomography (CT) scanning of the brain, chest, and abdomen reflected bil...

  8. Stanford-A acute aortic dissection, inflammation, and metalloproteinases: a review.

    Science.gov (United States)

    Cifani, Noemi; Proietta, Maria; Tritapepe, Luigi; Di Gioia, Cira; Ferri, Livia; Taurino, Maurizio; Del Porto, Flavia

    2015-01-01

    Acute aortic dissection (AAD) is a life-threatening disease with an incidence of about 2.6-3.6 cases per 100,000/year. Depending on the site of rupture, AAD is classified as Stanford-A when the ascending aortic thoracic tract and/or the arch are involved, and Stanford-B when the descending thoracic aorta and/or aortic abdominal tract are targeted. It was recently shown that inflammatory pathways underlie aortic rupture in both type A and type B Stanford AAD. An immune infiltrate has been found within the middle and outer tunics of dissected aortic specimens. It has also been observed that the recall and activation of macrophages inside the middle tunic are key events in the early phases of AAD. Macrophages are able to release metalloproteinases (MMPs) and pro-inflammatory cytokines which, in turn, give rise to matrix degradation and neoangiogenesis. An imbalance between the production of MMPs and MMP tissue inhibitors is pivotal in the extracellular matrix degradation underlying aortic wall remodelling in dissections occurring both in inherited conditions and in atherosclerosis. Among MMPs, MMP-12 is considered a specific marker of aortic wall disease, whatever the genetic predisposition may be. The aim of this review is, therefore, to take a close look at the immune-inflammatory mechanisms underlying Stanford-A AAD.

  9. Svensson Class IV Ascending Aortic Dissection, Often Confused With Penetrating Ulcer

    Directory of Open Access Journals (Sweden)

    Mitsomoy Michel Francklyn

    2015-03-01

    Full Text Available We present the case of a 64 years old male patient who had recently suffered an infective aortic valve endocarditis (Streptococcus agalactiae complicated by embolic arthritis of the right hip. Initial echocardiography revealed moderate aortic insufficiency developed on a tricuspidaortic valve with a small vegetation (5 mm × 4 mm on the left coronary cusp. Furthermore, ananeurysmal dilatation of the ascending aorta (maximal diameter, 54 mm was noted. Other heartvalves and left ventricular function were considered normal. The patient completed a 4 weekscourse of antibiotherapy, and the right hip arthritis was treated by drainage and synovectomy.The patient was subsequently referred to surgery on an outpatient basis for the aneurysm of theascending aorta. Preoperative computed tomography showed localized aortic dissection of thetubular ascending aorta characterized by an intimal tear without medial hematoma but excentricbulging of the aortic wall. This lesion was initially considered a penetrating ulcer of the aortic wallThe operative specimen allowed to make differential diagnosis with a penetrating aortic ulcer byshowing that the lesion did not develop within an atherosclerotic plaque. However, downstreamextension of the dissection was probably limited by the presence of transmural calcifications on itsdistal side. The patient underwent successful complete aortic root replacement using a stentlessFreestyle bioprosthesis with Dacron graft extension as reported previously

  10. Mesenchymal stem cells for treatment of aortic aneurysms

    Institute of Scientific and Technical Information of China (English)

    Aika; Yamawaki-Ogata; Ryotaro; Hashizume; Xian-Ming; Fu; Akihiko; Usui; Yuji; Narita

    2014-01-01

    An aortic aneurysm(AA) is a silent but life-threatening disease that involves rupture. It occurs mainly in aging and severe atherosclerotic damage of the aortic wall. Even though surgical intervention is effective to prevent rupture, surgery for the thoracic and thoraco-abdom-inal aorta is an invasive procedure with high mortality and morbidity. Therefore, an alternative strategy for treatment of AA is required. Recently, the molecular pathology of AA has been clarified. AA is caused by an imbalance between the synthesis and degradation of extracellular matrices in the aortic wall. Chronic inflam-mation enhances the degradation of matrices directly and indirectly, making control of the chronic inflamma-tion crucial for aneurysmal development. Meanwhile, mesenchymal stem cells(MSCs) are known to be ob-tained from an adult population and to differentiate into various types of cells. In addition, MSCs have not only the potential anti-inflammatory and immunosuppres-sive properties but also can be recruited into damagedtissue. MSCs have been widely used as a source for celltherapy to treat various diseases involving graft-versus-host disease, stroke, myocardial infarction, and chronicinflammatory disease such as Crohn’s disease clinically.Therefore, administration of MSCs might be availableto treat AA using anti-inflammatory and immnosup-pressive properties. This review provides a summary ofseveral studies on "Cell Therapy for Aortic Aneurysm"including our recent data, and we also discuss the pos-sibility of this kind of treatment.

  11. In vivo hypertensive arterial wall uptake of radiolabeled liposomes

    Energy Technology Data Exchange (ETDEWEB)

    Hodis, H.N.; Amartey, J.K.; Crawford, D.W.; Wickham, E.; Blankenhorn, D.H. (Univ. of Southern California School of Medicine, Los Angeles (USA))

    1990-06-01

    Using five sham-operated and seven aortic coarctation-induced hypertensive New Zealand White rabbits intravenously injected with neutral small unilamellar vesicles loaded with (111In)nitrilotriacetic acid, we demonstrated in vivo that the normal aortic arterial wall participates in liposome uptake and that this uptake is increased in the hypertensive aortic wall by approximately threefold (p less than or equal to 0.0001). Among the three regions examined, aortic arch, thoracic aorta, and lower abdominal aorta, the difference in uptake between the normotensive and hypertensive arterial walls was significantly different, p less than or equal to 0.05, p less than or equal to 0.0001, and p less than 0.05, respectively. The uptake by the different regions of the hypertensive arterial wall is consistent with the pathological changes present in these areas. Furthermore, the extent of liposome uptake by the aortic wall is strongly correlated with the height of the blood pressure (r = 0.85, p = 0.001, n = 11). We conclude that neutral small unilamellar liposomes can be used to carry agents into the arterial wall in vivo in the study of hypertensive vascular disease and could be especially useful for the delivery of pharmacologically or biologically active agents that would otherwise be inactivated within the circulation or are impermeable to the arterial wall.

  12. Structure and function of the first full-length murein peptide ligase (Mpl cell wall recycling protein.

    Directory of Open Access Journals (Sweden)

    Debanu Das

    Full Text Available Bacterial cell walls contain peptidoglycan, an essential polymer made by enzymes in the Mur pathway. These proteins are specific to bacteria, which make them targets for drug discovery. MurC, MurD, MurE and MurF catalyze the synthesis of the peptidoglycan precursor UDP-N-acetylmuramoyl-L-alanyl-γ-D-glutamyl-meso-diaminopimelyl-D-alanyl-D-alanine by the sequential addition of amino acids onto UDP-N-acetylmuramic acid (UDP-MurNAc. MurC-F enzymes have been extensively studied by biochemistry and X-ray crystallography. In gram-negative bacteria, ∼30-60% of the bacterial cell wall is recycled during each generation. Part of this recycling process involves the murein peptide ligase (Mpl, which attaches the breakdown product, the tripeptide L-alanyl-γ-D-glutamyl-meso-diaminopimelate, to UDP-MurNAc. We present the crystal structure at 1.65 Å resolution of a full-length Mpl from the permafrost bacterium Psychrobacter arcticus 273-4 (PaMpl. Although the Mpl structure has similarities to Mur enzymes, it has unique sequence and structure features that are likely related to its role in cell wall recycling, a function that differentiates it from the MurC-F enzymes. We have analyzed the sequence-structure relationships that are unique to Mpl proteins and compared them to MurC-F ligases. We have also characterized the biochemical properties of this enzyme (optimal temperature, pH and magnesium binding profiles and kinetic parameters. Although the structure does not contain any bound substrates, we have identified ∼30 residues that are likely to be important for recognition of the tripeptide and UDP-MurNAc substrates, as well as features that are unique to Psychrobacter Mpl proteins. These results provide the basis for future mutational studies for more extensive function characterization of the Mpl sequence-structure relationships.

  13. Transcatheter Aortic Valve Replacement in Bicuspid Aortic Valve Disease

    DEFF Research Database (Denmark)

    Mylotte, Darren; Lefevre, Thierry; Søndergaard, Lars

    2014-01-01

    BACKGROUND: Limited information exists describing the results of transcatheter aortic valve (TAV) replacement in patients with bicuspid aortic valve (BAV) disease (TAV-in-BAV). OBJECTIVES: This study sought to evaluate clinical outcomes of a large cohort of patients undergoing TAV-in-BAV. METHODS...

  14. The effect of fibronectin on structural and biological properties of single walled carbon nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Mottaghitalab, Fatemeh [Department of Nanobiotechnology, Faculty of Biological Sciences, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Farokhi, Mehdi [National cell bank of Iran, Pasteur Institute, Tehran (Iran, Islamic Republic of); Atyabi, Fatemeh [Department of Pharmaceutical Nanoechnology, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Omidvar, Ramin [Department of Biomedical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran (Iran, Islamic Republic of); Shokrgozar, Mohammad Ali, E-mail: mashokrgozar@pasteur.ac.ir [National cell bank of Iran, Pasteur Institute, Tehran (Iran, Islamic Republic of); Sadeghizadeh, Majid, E-mail: sadeghma@modares.ac.ir [Department Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran (Iran, Islamic Republic of)

    2015-06-01

    Highlights: • Increasing the cytocompatibility of single walled carbon nanotube by loading fibronectin. • Enhancing the hydrophilicity and nanosurface roughness of single walled carbon nanotube after loading fibronectin. • Fibronectin makes the surface properties of single walled carbon nanotube more suitable for cell proliferation and growth. - Abstract: Despite the attractive properties of carbon nanotubes (CNTs), cytoxicity and hydrophobicity are two main considerable features which limit their application in biomedical fields. It was well established that treating CNTs with extracellular matrix components could reduce these unfavourable characteristics. In an attempt to address these issues, fibronectin (FN) with different concentrations was loaded on single walled carbon nanotubes (SWCNTs) substrate. Scanning electron microscope, atomic force microscopy (AFM), contact angles and X-ray photoelectron spectroscopy (XPS) were preformed in order to characterize FN loaded SWCNTs substrates. According to XPS and AFM results, FN could interact with SWCNTs and for this, the hydrophilicity of SWCNTs was improved. Additionally, SWCNT modified with FN showed less cytotoxicity compared with neat SWCNT. Finally, FN was shown to act as an interesting extracellular component for enhancing the biological properties of SWCNT.

  15. Structural and chemical evolution of single-wall carbon nanotubes under atomic and molecular deuterium interaction

    NARCIS (Netherlands)

    Lisowski, W.; Keim, E.G.; Berg, van den A.H.J.; Smithers, M.A.

    2005-01-01

    The interaction of atomic (D) and molecular (D2) deuterium, as present in a (D + D2) gas mixture, with single-wall carbon nanotubes (SWNTs) has been studied by means of a combination of scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The SWNT samp

  16. Spectral and spatial structure of extreme ultraviolet radiation in laser plasma-wall interactions

    NARCIS (Netherlands)

    Kuznetsov, A. S.; Stuik, R.; F. Bijkerk,; Shevelko, A. P.

    2012-01-01

    Intense extreme ultraviolet (XUV) radiation was observed during the interaction of low-temperature laser plasmas and wall materials. Laser plasmas with electron temperature T-e similar to 40 eV were created on massive solid targets (CF2 and Al) by an excimer KrF laser (248 nm/0.5 J/13 ns/1 Hz). The

  17. Effects of tebuconazole on morphology, structure, cell wall components and trichothecene production of Fusarium culmorum in vitro.

    Science.gov (United States)

    Kang, Z; Huang, L; Krieg, U; Mauler-Machnik, A; Buchenauer, H

    2001-06-01

    The effects of tebuconazole, a systemic fungicide, on the morphology, structure, cell wall components and toxin production of Fusarium culmorum were investigated in vitro. Treatment was by application of four filter paper strips (0.75 cm x 5.0 cm) soaked in 20 micrograms ml-1 fungicide placed around a point inoculum in Petri dishes. Mycelial growth was strongly inhibited by fungicide treatment. Scanning electron microscopic observations showed that the fungicide caused irregular swelling and excessive branching of hyphae. The morphological changes induced by the fungicide at the ultrastructural level included considerable thickening of the hyphal cell walls, excessive septation, the formation of the incomplete septa, extensive vacuolisation, accumulation of lipid bodies and progressing necrosis or degeneration of the hyphal cytoplasm. Non-membrane inclusion bodies were often detected in the hyphal cytoplasm. Furthermore, the formation of new hyphae (daughter hyphae) inside collapsed hyphal cells was common following treatment. The daughter hyphae also displayed severe alterations such as irregular thickening of the cell walls and necrosis of the cytoplasm. Using cytochemical techniques, the labelling densities of chitin and beta-1,3-glucan in the cell walls of the fungicide-treated hyphae were more pronounced than in those of the control hyphae. Moreover, immunogold labelling with antiserum against deoxynivalenol (DON) revealed that Fusarium toxin DON was localized in the cell walls, cytoplasm, mitochondria and vacuoles of the hyphae from the control and the fungicide treatment, but the labelling density in the fungicide-treated hyphae decreased dramatically compared with the control hyphae, indicating that tebuconazole reduced Fusarium toxin production of the fungus.

  18. Water structuring and hydroxide ion binding at the interface between water and hydrophobic Walls of varying rigidity and van der Waals interactions

    NARCIS (Netherlands)

    Vacha, Robert; Zangi, Ronen; Engberts, Jan B. F. N.; Jungwirth, Pavel

    2008-01-01

    The interfacial behavior of hydroxide ions has been investigated by means of molecular dynamics simulations of aqueous KOH solutions between hydrophobic carbon-like walls. In agreement with previous calculations, we show that a rigid, attractive wall strongly structures water molecules in neighborin

  19. Flow-sensitive in-vivo 4D MR imaging at 3T for the analysis of aortic hemodynamics and derived vessel wall parameters; Die Analyse aortaler Haemodynamik und Gefaesswandparameter mittels fluss-sensitiver in-vivo 4D-MRT bei 3 Tesla

    Energy Technology Data Exchange (ETDEWEB)

    Frydrychowicz, A.; Markl, M.; Stalder, A.F.; Bock, J.; Bley, T.A.; Berger, A.; Russe, M.F.; Hennig, J.; Langer, M. [Freiburg Univ. (Germany). Abt. Roentgendiagnostik; Harloff, A. [Freiburg Univ. (Germany). Abt. Klinische Neurologie und Neurophysiologie; Schlensak, C. [Freiburg Univ. (Germany). Abt. Herz- und Gefaesschirurgie

    2007-05-15

    Modern phase contrast MR imaging at 3 Tesla allows the depiction of 3D morphology as well as the acquisition of time-resolved blood flow velocities in 3 directions. In combination with state-of-the-art visualization and data processing software, the qualitative and quantitative analysis of hemodynamic changes associated with vascular pathologies is possible. The 4D nature of the acquired data permits free orientation within the vascular system of interest and offers the opportunity to quantify blood flow and derived vessel wall parameters at any desired location within the data volume without being dependent on predefined 2D slices. The technique has the potential of overcoming the limitations of current diagnostic strategies and of implementing new diagnostic parameters. In light of the recent discussions regarding the influence of the wall shear stress and the oscillatory shear index on the genesis of arteriosclerosis and dilatative vascular processes, flow-sensitive 4D MRI may provide the missing diagnostic link. Instead of relying on experience-based parameters such as aneurysm size, new hemodynamic considerations can deepen our understanding of vascular pathologies. This overview reviews the underlying methodology at 3T, the literature on time-resolved 3D MR velocity mapping, and presents case examples. By presenting the pre- and postoperative assessment of hemodynamics in a thoracic aortic aneurysm and the detailed analysis of blood flow in a patient with coarctation we underline the potential of time-resolved 3D phase contrast MR at 3T for hemodynamic assessment of vascular pathologies, especially in the thoracic aorta. (orig.)

  20. Aortic root geometry in aortic stenosis patients (a SEAS substudy)

    DEFF Research Database (Denmark)

    Bahlmann, Edda; Nienaber, Christoph A; Cramariuc, Dana

    2011-01-01

    AIMS: To report aortic root geometry by echocardiography in a large population of healthy, asymptomatic aortic stenosis (AS) patients in relation to current vendor-specified requirements for transcatheter aortic valve implantation (TAVI). METHODS AND RESULTS: Baseline data in 1481 patients...... with asymptomatic AS (mean age 67 years, 39% women) in the Simvastatin Ezetimibe in AS study were used. The inner aortic diameter was measured at four levels: annulus, sinus of Valsalva, sinotubular junction and supracoronary, and sinus height as the annulo-junctional distance. Analyses were based on vendor......-specified requirements for the aortic root geometry for current available prostheses, CoreValve and Edwards-Sapien. The ratio of sinus of Valsalva height to sinus width was 1:2. In multivariate linear regression analysis, larger sinus of Valsalva height was associated with older age, larger sinus of Valsalva diameter...

  1. Analysis of Multi-Loop Control Structures of Dividing-Wall Distillation Columns Using a Fundamental Model

    Directory of Open Access Journals (Sweden)

    Salvador Tututi-Avila

    2014-02-01

    Full Text Available Dividing-wall columns (DWCs have significant potential as energy-efficient processes for the separation of multicomponent mixtures. However, in addition to an efficient steady state design, dynamics and control also play a major part for the success of a technology. This is especially so for complex distillation systems. This paper investigates the dynamics of a dividing wall column used for the separation of ternary mixtures. A detailed dynamic first principles-based model of the column I s developed in gPROMS. The model is used to generate data used for control loop pairing via the Relative Gain Array (RGA, and controller parameters are found by using Internal Model Control (IMC tuning. The best control structures for DWC systems, involving four different ternary mixtures, and two different feed compositions for each mixture, are investigated.

  2. Nonoperative management of pediatric aortic injury with seat belt syndrome.

    Science.gov (United States)

    Parrish, Dan W; Barnhorst, Amanda; Trebska-McGowan, Katarzyna; Amendola, Michael; Haynes, Jeffrey H

    2015-08-01

    "Seat belt syndrome" was first described by Garret and Braunstein in 1962. The syndrome involves skin and abdominal wall ecchymosis (seat belt sign) intra-abdominal solid organ and visceral injuries, as well as Chance fractures (compression and/or wedging deformity of the anterior portion of the vertebral body with disruption or fracture of the posterior elements, generally at L1-L3). We present a case of a 12-year-old male involved in a high-speed motor vehicle collision wearing only a lap belt resulting in seat belt syndrome, with disruption of the abdominal wall, mesenteric avulsion with multiple intestinal perforations, abdominal aortic dissection, and an L2 Chance fracture with cord transection. Intraoperative decision making is outlined with this scenario of complex injuries, and the literature of seat belt syndrome associated with blunt aortic injuries and its management is reviewed.

  3. Perspectives on stem cell-based elastic matrix regenerative therapies for abdominal aortic aneurysms.

    Science.gov (United States)

    Bashur, Chris A; Rao, Raj R; Ramamurthi, Anand

    2013-06-01

    Abdominal aortic aneurysms (AAAs) are potentially fatal conditions that are characterized by decreased flexibility of the aortic wall due to proteolytic loss of the structural matrix. This leads to their gradual weakening and ultimate rupture. Drug-based inhibition of proteolytic enzymes may provide a nonsurgical treatment alternative for growing AAAs, although it might at best be sufficient to slow their growth. Regenerative repair of disrupted elastic matrix is required if regression of AAAs to a healthy state is to be achieved. Terminally differentiated adult and diseased vascular cells are poorly capable of affecting such regenerative repair. In this context, stem cells and their smooth muscle cell-like derivatives may represent alternate cell sources for regenerative AAA cell therapies. This article examines the pros and cons of using different autologous stem cell sources for AAA therapy, the requirements they must fulfill to provide therapeutic benefit, and the current progress toward characterizing the cells' ability to synthesize elastin, assemble elastic matrix structures, and influence the regenerative potential of diseased vascular cell types. The article also provides a detailed perspective on the limitations, uncertainties, and challenges that will need to be overcome or circumvented to translate current strategies for stem cell use into clinically viable AAA therapies. These therapies will provide a much needed nonsurgical treatment option for the rapidly growing, high-risk, and vulnerable elderly demographic.

  4. 腹主动脉瘤动脉壁血管平滑肌细胞增殖及凋亡的研究%Vascular smooth muscle cell proliferation and apoptosis of the aortic wall during the development of abdominal aortic aneurysm

    Institute of Scientific and Technical Information of China (English)

    李大勇; 车艳; 杨镛; 张强; 吕延伟

    2004-01-01

    目的研究腹主动脉瘤(abdominal aortic aneurysm,AAA)在发病不同时期动脉壁平滑肌细胞(smooth muscle cells,SMC)增殖与凋亡的改变. 方法建立大鼠AAA模型,分别于术后3 d、1、2、3、4周切取腹主动脉,应用原位DNA片段末端标记(TUNEL)和免疫组织化学方法检测腹主动脉壁中SMC凋亡和相关基因bcl-2、bax蛋白以及增殖细胞核抗原(PCNA)、α-血管平滑肌肌动蛋白(α-actin)的表达. 结果 TUNEL及PCNA表达高峰时段分别为术后2~3周和1周;术后3 d至1周凋亡细胞少于PCNA阳性SMC,2~4周多于PCNA阳性SMC且SMC数量明显减少;bcl-2与bax蛋白表达分别于术后1、3周达到峰值(P<0.01). 结论动脉壁SMC增殖和凋亡的失衡与AAA发病密切相关;bcl-2与bax基因参与了对AAA动脉壁中SMC凋亡的调控.

  5. The Lamportian cell wall

    Energy Technology Data Exchange (ETDEWEB)

    Keiliszewski, M.; Lamport, D. (Michigan State Univ. Plant Research Lab., East Lansing (United States))

    1991-05-01

    The Lamportian Warp-Weft hypothesis suggests a cellulose-extensin interpenetrating network where extensin mechanically couples the load-bearing cellulose microfibrils in a wall matrix that is best described as a microcomposite. This model is based on data gathered from the extensin-rich walls of tomato and sycamore cell suspension culture, wherein extensin precursors are insolubilized into the wall by undefined crosslinks. The authors recent work with cell walls isolated from intact tissue as well as walls from suspension cultured cells of the graminaceous monocots maize and rice, the non-graminaceous monocot asparagus, the primitive herbaceous dicot sugar beet, and the gymnosperm Douglas Fir indicate that although extensins are ubiquitous to all plant species examined, they are not the major structural protein component of most walls examined. Amino acid analyses of intact and HF-treated walls shows a major component neither an HRGP, nor directly comparable to the glycine-rich wall proteins such as those associated with seed coat walls or the 67 mole% glycine-rich proteins cloned from petunia and soybean. Clearly, structural wall protein alternatives to extensin exist and any cell wall model must take that into account. If we assume that extracellular matrices are a priori network structures, then new Hypless' structural proteins in the maize cell wall raise questions about the sort of network these proteins create: the kinds of crosslinks involved; how they are formed; and the roles played by the small amounts of HRGPs.

  6. Association of Ficolin-3 with abdominal aortic aneurysm presence and progression

    DEFF Research Database (Denmark)

    Fernandez-García, Carlos-Ernesto; Burillo, Elena; Lindholt, Jes S

    2017-01-01

    BACKGROUND: Abdominal aortic aneurysm (AAA) patients are usually asymptomatic and AAA evolution is unpredictable. Ficolin-3, mainly synthesized by the liver, is a molecule of the lectin complement-activation pathway involved in AAA pathophysiology. OBJECTIVES: To define extrahepatic sources...... from healthy tissue. Moreover, ficolin-3 mRNA levels in AAA wall were greatly increased compared with healthy aortic walls. Immunohistochemistry of AAA tissue demonstrated increased ficolin-3, while little staining was present in healthy walls. Finally, increased ficolin-3 levels were observed in AAA...... patients' plasma (n=478) compared with control plasma (n=176), which persisted after adjustment for risk factors [Adj. OR=5.29 (95% CI.:3.27;8.57)]. Moreover, a positive association of ficolin-3 with aortic diameter (Rho=0.25) and need for surgical repair was observed, also after adjustment for potential...

  7. Strain-controlled magnetic domain wall propagation in hybrid piezoelectric/ferromagnetic structures

    Science.gov (United States)

    Lei, Na; Devolder, Thibaut; Agnus, Guillaume; Aubert, Pascal; Daniel, Laurent; Kim, Joo-Von; Zhao, Weisheng; Trypiniotis, Theodossis; Cowburn, Russell P.; Chappert, Claude; Ravelosona, Dafiné; Lecoeur, Philippe

    2013-01-01

    The control of magnetic order in nanoscale devices underpins many proposals for integrating spintronics concepts into conventional electronics. A key challenge lies in finding an energy-efficient means of control, as power dissipation remains an important factor limiting future miniaturization of integrated circuits. One promising approach involves magnetoelectric coupling in magnetostrictive/piezoelectric systems, where induced strains can bear directly on the magnetic anisotropy. While such processes have been demonstrated in several multiferroic heterostructures, the incorporation of such complex materials into practical geometries has been lacking. Here we demonstrate the possibility of generating sizeable anisotropy changes, through induced strains driven by applied electric fields, in hybrid piezoelectric/spin-valve nanowires. By combining magneto-optical Kerr effect and magnetoresistance measurements, we show that domain wall propagation fields can be doubled under locally applied strains. These results highlight the prospect of constructing low-power domain wall gates for magnetic logic devices.

  8. Microwave detection of surface and volume moisture in building walls and related structures

    Science.gov (United States)

    Bastida, E. M.; Ricca, A. M.

    Microwave technique for non-contacting volume and surface moisture measurements in concrete and building walls is described. The reflection and attenuation coefficients of an electromagnetic wave, in the microwave spectrum region, impinging upon a humid wall are studied. Reflection and attenuation are related to the water content. The attenuation coefficient is related to the space-average humidity, while reflection measurements depend also on the humidity profile. By means of a computer simulation surface humidity and surface humidity gradient are both measured by reflectometric techniques. Combining reflection and attenuation measurements, information about the humidity profile is obtained in a non-contacting way. Experimental results on reflection and attenuation measurements are also presented.

  9. Fruit wall anatomical structure of the genus Betula section Lenta (Betulaceae

    Directory of Open Access Journals (Sweden)

    Olga V. Yatsenko

    2014-04-01

    Full Text Available The fruits of the Lentae are referred to lower syncarpous nuts. Unlike most birches, the three-lobed scales in section Lentae stay attached to the axis for a long time. The fruit wall is differentiated into epicarp (derivative of outer tissues of inferior ovary, the tissues of receptacular origin and the pericarp itself (mesocarp and the endocarp derivating from the ovary wall. The epicarp consists of two zones: epidermis and subepidermal zone. Two-four layers of larger sclerenchymatous cells represent the mesocarp. Several layers of parenchymatous cells, which are squeezed and partly obliterated by fruit maturity, compose endocarp. The morphogenetic type of fruit of the genus Betula section Lentae is the pyrenarium of the Olea-type.

  10. Wavelet spectrum analysis on energy transfer of multi-scale structures in wall turbulence

    Institute of Scientific and Technical Information of China (English)

    Zhen-yan XIA; Yan TIAN; Nan JIANG

    2009-01-01

    The streamwise velocity components at different vertical heights in wall turbulence were measured. Wavelet transform was used to study the turbulent energy spectra, indicating that the global spectrum results from the weighted average of Fourier spectrum based on wavelet scales. Wavelet transform with more vanishing moments can express the declining of turbulent spectrum. The local wavelet spectrum shows that the physical phenomena such as deformation or breakup of eddies are related to the vertical position in the boundary layer, and the energy-containing eddies exist in a multi-scale form. Moreover, the size of these eddies increases with the measured points moving out of the wall. In the buffer region, the small scale energy-containing eddies with higher frequency are excited. In the outer region, the maximal energy is concentrated in the low-frequency large-scale eddies, and the frequency domain of energy-containing eddies becomes narrower.

  11. Direct numerical simulation of Taylor–Couette flow with grooved walls: torque scaling and flow structure

    NARCIS (Netherlands)

    Zhu, X.; Ostilla-Monico, Rodolfo; Verzicco, R.; Lohse, D.

    2016-01-01

    We present direct numerical simulations of Taylor–Couette flow with grooved walls at a fixed radius ratio ${\\it\\eta}=r_{i}/r_{o}=0.714$η=ri/ro=0.714 with inner cylinder Reynolds number up to $Re_{i}=3.76\\times 10^{4}$Rei=3.76×104, corresponding to Taylor number up to $Ta=2.15\\times 10^{9}$Ta=2.15×10

  12. Effects of stem structure and cell wall components on bending strength in wheat

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Morphological traits, anatomical features, chemical components and bending stress in the stems of three genotypes of wheat (Triticum aestivum L.), namely Xiaoyan54, 8602 and Xiaoyan81, were examined by means of light microscopy coupled with Fourier transform infrared spectroscopy (FTIR). Noticeable changes in morphological and anatomical traits were observed, including outer radius of stem, the ratio of stem outer radius to stem wall thickness, various tissue proportions and variations among different types of vascular bundles. The results of chemical analysis revealed that Xiaoyan81 had the highest cellulose content in comparison with Xiaoyan54 and 8602, whereas lignin level in Xiaoyan81 was lower than that in 8602 but higher that that in Xiaoyan54. Bending stress analysis demonstrated that Xiaoyan81 may be the main target for identification, for it had the highest bending stress among the stems of three genotypes. Associated with bending stress, all the results presented here suggested that the ratio of stem wall thickness to its outer radius, schlerenchyma tissue proportion, the average number of big VB per unit and the cellulose content are four important factors affecting the mechanical strength of Xiaoyan81 wheat stems, which can be considered as the key parameters for selecting varieties with bending stress. Therefore, it was suggested that in the selection of lodging resistant cultivars one should consider those characterized with large ratio of outer radius of stem to stem wall thickness, greaterschlerenchyma tissue proportion, high average number of big VB per unit with high cellulose content in their stems.

  13. PIV Measurement of Wall Shear Stress and Flow Structures within an Intracranial Aneurysm Model

    Science.gov (United States)

    Chow, Ricky; Sparrow, Eph; Campbell, Gary; Divani, Afshin; Sheng, Jian

    2012-11-01

    The formation and rupture of an intracranial aneurysm (IA) is a debilitating and often lethal event. Geometric features of the aneurysm bulb and upstream artery, such as bulb size, bulb shape, and curvature of the artery, are two groups of factors that define the flow and stresses within an IA. Abnormal flow stresses are related to rupture. This presentation discusses the development of a quasi-3D PIV technique and its application in various glass models at Re = 275 and 550 to experimentally assess at a preliminary level the impact of geometry and flow rate. Some conclusions are to be drawn linking geometry of the flow domain to rupture risk. The extracted results also serve as the baseline case and as a precursor to a companion presentation by the authors discussing the impact of flow diverters, a new class of medical devices. The PIV experiments were performed in a fully index-matched flow facility, allowing for unobstructed observations over complex geometry. A reconstruction and analysis method was devised to obtain 3D mean wall stress distributions and flow fields. The quasi 3D measurements were reconstructed from orthogonal planes encompassing the entire glass model, spaced 0.4mm apart. Wall shear stresses were evaluated from the near-wall flow viscous stresses.

  14. Structural insights into the pH-controlled targeting of plant cell-wall invertase by a specific inhibitor protein

    Science.gov (United States)

    Hothorn, Michael; Van den Ende, Wim; Lammens, Willem; Rybin, Vladimir; Scheffzek, Klaus

    2010-01-01

    Invertases are highly regulated enzymes with essential functions in carbohydrate partitioning, sugar signaling, and plant development. Here we present the 2.6 Å crystal structure of Arabidopsis cell-wall invertase 1 (INV1) in complex with a protein inhibitor (CIF, or cell-wall inhibitor of β-fructosidase) from tobacco. The structure identifies a small amino acid motif in CIF that directly targets the invertase active site. The activity of INV1 and its interaction with CIF are strictly pH-dependent with a maximum at about pH 4.5. At this pH, isothermal titration calorimetry reveals that CIF tightly binds its target with nanomolar affinity. CIF competes with sucrose (Suc) for the same binding site, suggesting that both the extracellular Suc concentration and the pH changes regulate association of the complex. A conserved glutamate residue in the complex interface was previously identified as an important quantitative trait locus affecting fruit quality, which implicates the invertase–inhibitor complex as a main regulator of carbon partitioning in plants. Comparison of the CIF/INV1 structure with the complex between the structurally CIF-related pectin methylesterase inhibitor (PMEI) and pectin methylesterase indicates a common targeting mechanism in PMEI and CIF. However, CIF and PMEI use distinct surface areas to selectively inhibit very different enzymatic scaffolds. PMID:20858733

  15. Structural insights into the pH-controlled targeting of plant cell-wall invertase by a specific inhibitor protein.

    Science.gov (United States)

    Hothorn, Michael; Van den Ende, Wim; Lammens, Willem; Rybin, Vladimir; Scheffzek, Klaus

    2010-10-05

    Invertases are highly regulated enzymes with essential functions in carbohydrate partitioning, sugar signaling, and plant development. Here we present the 2.6 Å crystal structure of Arabidopsis cell-wall invertase 1 (INV1) in complex with a protein inhibitor (CIF, or cell-wall inhibitor of β-fructosidase) from tobacco. The structure identifies a small amino acid motif in CIF that directly targets the invertase active site. The activity of INV1 and its interaction with CIF are strictly pH-dependent with a maximum at about pH 4.5. At this pH, isothermal titration calorimetry reveals that CIF tightly binds its target with nanomolar affinity. CIF competes with sucrose (Suc) for the same binding site, suggesting that both the extracellular Suc concentration and the pH changes regulate association of the complex. A conserved glutamate residue in the complex interface was previously identified as an important quantitative trait locus affecting fruit quality, which implicates the invertase-inhibitor complex as a main regulator of carbon partitioning in plants. Comparison of the CIF/INV1 structure with the complex between the structurally CIF-related pectin methylesterase inhibitor (PMEI) and pectin methylesterase indicates a common targeting mechanism in PMEI and CIF. However, CIF and PMEI use distinct surface areas to selectively inhibit very different enzymatic scaffolds.

  16. MAT2A mutations predispose individuals to thoracic aortic aneurysms.

    Science.gov (United States)

    Guo, Dong-chuan; Gong, Limin; Regalado, Ellen S; Santos-Cortez, Regie L; Zhao, Ren; Cai, Bo; Veeraraghavan, Sudha; Prakash, Siddharth K; Johnson, Ralph J; Muilenburg, Ann; Willing, Marcia; Jondeau, Guillaume; Boileau, Catherine; Pannu, Hariyadarshi; Moran, Rocio; Debacker, Julie; Bamshad, Michael J; Shendure, Jay; Nickerson, Deborah A; Leal, Suzanne M; Raman, C S; Swindell, Eric C; Milewicz, Dianna M

    2015-01-08

    Up to 20% of individuals who have thoracic aortic aneurysms or acute aortic dissections but who do not have syndromic features have a family history of thoracic aortic disease. Significant genetic heterogeneity is established for this familial condition. Whole-genome linkage analysis and exome sequencing of distant relatives from a large family with autosomal-dominant inheritance of thoracic aortic aneurysms variably associated with the bicuspid aortic valve was used for identification of additional genes predisposing individuals to this condition. A rare variant, c.1031A>C (p.Glu344Ala), was identified in MAT2A, which encodes methionine adenosyltransferase II alpha (MAT IIα). This variant segregated with disease in the family, and Sanger sequencing of DNA from affected probands from unrelated families with thoracic aortic disease identified another MAT2A rare variant, c.1067G>A (p.Arg356His). Evidence that these variants predispose individuals to thoracic aortic aneurysms and dissections includes the following: there is a paucity of rare variants in MAT2A in the population; amino acids Glu344 and Arg356 are conserved from humans to zebrafish; and substitutions of these amino acids in MAT Iα are found in individuals with hypermethioninemia. Structural analysis suggested that p.Glu344Ala and p.Arg356His disrupt MAT IIα enzyme function. Knockdown of mat2aa in zebrafish via morpholino oligomers disrupted cardiovascular development. Co-transfected wild-type human MAT2A mRNA rescued defects of zebrafish cardiovascular development at significantly higher levels than mRNA edited to express either the Glu344 or Arg356 mutants, providing further evidence that the p.Glu344Ala and p.Arg356His substitutions impair MAT IIα function. The data presented here support the conclusion that rare genetic variants in MAT2A predispose individuals to thoracic aortic disease.

  17. Abdominal aortic aneurysm surgery

    DEFF Research Database (Denmark)

    Gefke, K; Schroeder, T V; Thisted, B

    1994-01-01

    The goal of this study was to identify patients who need longer care in the ICU (more than 48 hours) following abdominal aortic aneurysm (AAA) surgery and to evaluate the influence of perioperative complications on short- and long-term survival and quality of life. AAA surgery was performed in 553......, 78% stated that their quality of life had improved or was unchanged after surgery and had resumed working. These data justify a therapeutically aggressive approach, including ICU therapy following AAA surgery, despite failure of one or more organ systems....

  18. Prediction of the evolution of the aortic diameter according to the thrombus signal from MR images on small abdominal aortic aneurysms

    Directory of Open Access Journals (Sweden)

    A. Mutiara

    2011-03-01

    Full Text Available We have studied T1 and T2 weighted MR images of thrombus from examination of patients with small abdominal aortic aneurysms in order to know whether the thrombus signal can be linked with the aortic diameter enlargement, and then could predict rupture risk of the aorta wall. Data were obtained from 16 patients with Small Abdominal Aortic Aneurysms (SAAA who had been examined since July 2006 to January 2010 with MR Images.Several parameters were used to study the thrombus signal, such as mean, median, standard deviation, skewness and kurtosis. Each parameter was calculated for the thrombus area, and the signal in the muscle was used to normalize the mean, median and standard deviation of signal in thrombus. After then, those parameters were compared with evolution of the aortic diameter.13 of the 16 patient with SAAA had a thrombus. Unfortunately there were no correlations between thrombus signals with the evolution of the aortic diameter (R often less then 0.3. But some parameter show links between thrombus signal and maximum diameter (mean (R=0.318, median (R=0.318, skewness (R=0.304 or with D maximum diameter (mean (R=0.512.We cannot use thrombus signal alone as the parameter to predict the evolution of the aortic diameter. This study is the first step of our overall study. In the next step, we will use blood flow velocity with 3D/4D modelisation on the aortic aneurysm as a comparison parameter for predicting the rupture risk of the aortic wall. Moreover, relationship between flow data and thrombus will be studied.

  19. Glucose Suppresses Biological Ferroelectricity in Aortic Elastin

    Science.gov (United States)

    Liu, Yuanming; Wang, Yunjie; Chow, Ming-Jay; Chen, Nataly Q.; Ma, Feiyue; Zhang, Yanhang; Li, Jiangyu

    2013-04-01

    Elastin is an intriguing extracellular matrix protein present in all connective tissues of vertebrates, rendering essential elasticity to connective tissues subjected to repeated physiological stresses. Using piezoresponse force microscopy, we show that the polarity of aortic elastin is switchable by an electrical field, which may be associated with the recently discovered biological ferroelectricity in the aorta. More interestingly, it is discovered that the switching in aortic elastin is largely suppressed by glucose treatment, which appears to freeze the internal asymmetric polar structures of elastin, making it much harder to switch, or suppressing the switching completely. Such loss of ferroelectricity could have important physiological and pathological implications from aging to arteriosclerosis that are closely related to glycation of elastin.

  20. Glucose Suppresses Biological Ferroelectricity in Aortic Elastin

    Science.gov (United States)

    Liu, Yuanming; Wang, Yunjie; Chow, Ming-Jay; Chen, Nataly Q.; Ma, Feiyue; Zhang, Yanhang; Li, Jiangyu

    2013-01-01

    Elastin is an intriguing extracellular matrix protein present in all connective tissues of vertebrates, rendering essential elasticity to connective tissues subjected to repeated physiological stresses. Using piezoresponse force microscopy, we show that the polarity of aortic elastin is switchable by an electrical field, which may be associated with the recently discovered biological ferroelectricity in the aorta. More interestingly, it is discovered that the switching in aortic elastin is largely suppressed by glucose treatment, which appears to freeze the internal asymmetric polar structures of elastin, making it much harder to switch, or suppressing the switching completely. Such loss of ferroelectricity could have important physiological and pathological implications from aging to arteriosclerosis that are closely related to glycation of elastin. PMID:23679639

  1. Reference Values for Cardiac and Aortic Magnetic Resonance Imaging in Healthy, Young Caucasian Adults

    Science.gov (United States)

    Eikendal, Anouk L. M.; Bots, Michiel L.; Haaring, Cees; Saam, Tobias; van der Geest, Rob J.; Westenberg, Jos J. M.; den Ruijter, Hester M.; Hoefer, Imo E.; Leiner, Tim

    2016-01-01

    Background Reference values for morphological and functional parameters of the cardiovascular system in early life are relevant since they may help to identify young adults who fall outside the physiological range of arterial and cardiac ageing. This study provides age and sex specific reference values for aortic wall characteristics, cardiac function parameters and aortic pulse wave velocity (PWV) in a population-based sample of healthy, young adults using magnetic resonance (MR) imaging. Materials and Methods In 131 randomly selected healthy, young adults aged between 25 and 35 years (mean age 31.8 years, 63 men) of the general-population based Atherosclerosis-Monitoring-and-Biomarker-measurements-In-The-YOuNg (AMBITYON) study, descending thoracic aortic dimensions and wall thickness, thoracic aortic PWV and cardiac function parameters were measured using a 3.0T MR-system. Age and sex specific reference values were generated using dedicated software. Differences in reference values between two age groups (25–30 and 30–35 years) and both sexes were tested. Results Aortic diameters and areas were higher in the older age group (all p<0.007). Moreover, aortic dimensions, left ventricular mass, left and right ventricular volumes and cardiac output were lower in women than in men (all p<0.001). For mean and maximum aortic wall thickness, left and right ejection fraction and aortic PWV we did not observe a significant age or sex effect. Conclusion This study provides age and sex specific reference values for cardiovascular MR parameters in healthy, young Caucasian adults. These may aid in MR guided pre-clinical identification of young adults who fall outside the physiological range of arterial and cardiac ageing. PMID:27732640

  2. Transcatheter aortic valve implantation vs. surgical aortic valve replacement for treatment of severe aortic stenosis

    DEFF Research Database (Denmark)

    Siontis, George C M; Praz, Fabien; Pilgrim, Thomas

    2016-01-01

    AIMS: In view of the currently available evidence from randomized trials, we aimed to compare the collective safety and efficacy of transcatheter aortic valve implantation (TAVI) vs. surgical aortic valve replacement (SAVR) across the spectrum of risk and in important subgroups. METHODS AND RESULTS...

  3. [Aortic valve replacement for the small aortic annulus].

    Science.gov (United States)

    Oshima, H; Usui, A; Akita, T; Ueda, Y

    2006-04-01

    Aortic valve surgery for the small aortic annulus is still challenging for surgeons. Recently, the new types of high performance prosthesis have been developed and the chance of an aortic root enlargement (ARE) is decreasing. In this study, we propose the ideal strategy of the aortic surgery for the small aortic annulus. We analyzed the clinical records of 158 patients who underwent aortic valve replacement from August 1999 to October 2005 in our institution. The small aortic annulus was observed in 38 patients (24%). Fourteen patients of this group underwent ARE. Patient-prosthesis mismatch (PPM) was less frequently observed in patients with ARE compared to those without ARE. The additional time required for ARE was not considerable, and neither ischemic time nor cardiopulmonary bypass time was significantly prolonged by ARE. In conclusion, we have to select a prosthesis with sufficient orifice area to avoid PPM, otherwise we should choose an option of ARE. For this consideration, we definitely need the chart that demonstrates the relationship between the nominal size of various types of prostheses and the size of a patient's annulus that those prostheses actually fit.

  4. Valve-sparing aortic root replacement and aortic valve repair in a patient with acromegaly and aortic root dilatation

    Directory of Open Access Journals (Sweden)

    Karel Van Praet

    2015-07-01

    Full Text Available Aortic regurgitation and dilatation of the aortic root and ascending aorta are severe complications of acromegaly. The current trend for management of an aortic root aneurysm is valve-sparing root replacement as well as restoring the diameter of the aortic sinotubular junction (STJ and annulus. Our case report supports the recommendation that in patients with acromegaly, severe aortic root involvement may indicate the need for surgery.

  5. [Numerical Simulation of Propagation of Electric Excitation in the Heart Wall Taking into Account Its Fibrous-Laminar Structure].

    Science.gov (United States)

    Vasserman, I N; Matveenko, V P; Shardakov, I N; Shestakov, A P

    2015-01-01

    The propagation of excitation wave in the inhomogeneous anisotropic finite element model of cardiac muscle is investigated. In this model, the inhomogeneity stands for the rotation of anisotropy axes through the wall thickness and results from a fibrous-laminar structure of the cardiac muscle tissue. Conductivity of the cardiac muscle is described using a monodomain model and the Aliev-Panfilov equations are used as the relationships between the transmembrane current and transmembrane potential. Numerical simulation is performed by applying the splitting algorithm, in which the partial differential solution to the nonlinear boundary value problem is reduced to a sequence of simple ordinary differential equations and linear partial differential equations. The simulation is carried out for a rectangular block of the cardiac tissue, the minimal size of which is considered to be the thickness of the heart wall. Two types of distribution of the fiber orientation angle are discussed. The first case corresponds 'to the left ventricle of a dog. The endocardium and epicardium fibers are generally oriented in the meridional direction. The angle of fiber orientation varies smoothly through the wall thickness making a half-turn. A circular layer, in which the fibers are oriented in the circumferential direction locates deep in the cardiac wall. The results of calculations show that for this case the wave form strongly depends on a place of initial excitation. For the endocardial and epicardial initial excitation one can see the earlier wave front propagation in the endocardium and epicardium, respectively. At the intramural initial excitation the simultaneous wave front propagation in the endocardium and epicardium occurs, but there is a wave front lag in the middle of the wall. The second case refers to the right ventricle of a swine, in which the endocardium and epicardium fibers are typically oriented in the circumferential direction, whereas the subepicardium fibers

  6. In vitro flow assessment: from PC-MRI to computational fluid dynamics including fluid-structure interaction

    Science.gov (United States)

    Kratzke, Jonas; Rengier, Fabian; Weis, Christian; Beller, Carsten J.; Heuveline, Vincent

    2016-04-01

    Initiation and development of cardiovascular diseases can be highly correlated to specific biomechanical parameters. To examine and assess biomechanical parameters, numerical simulation of cardiovascular dynamics has the potential to complement and enhance medical measurement and imaging techniques. As such, computational fluid dynamics (CFD) have shown to be suitable to evaluate blood velocity and pressure in scenarios, where vessel wall deformation plays a minor role. However, there is a need for further validation studies and the inclusion of vessel wall elasticity for morphologies being subject to large displacement. In this work, we consider a fluid-structure interaction (FSI) model including the full elasticity equation to take the deformability of aortic wall soft tissue into account. We present a numerical framework, in which either a CFD study can be performed for less deformable aortic segments or an FSI simulation for regions of large displacement such as the aortic root and arch. Both of the methods are validated by means of an aortic phantom experiment. The computational results are in good agreement with 2D phase-contrast magnetic resonance imaging (PC-MRI) velocity measurements as well as catheter-based pressure measurements. The FSI simulation shows a characteristic vessel compliance effect on the flow field induced by the elasticity of the vessel wall, which the CFD model is not capable of. The in vitro validated FSI simulation framework can enable the computation of complementary biomechanical parameters such as the stress distribution within the vessel wall.

  7. Structural characterization of the acid-degraded secondary cell wall polymer of Geobacillus stearothermophilus PV72/p2.

    Science.gov (United States)

    Petersen, Bent O; Sára, Margit; Mader, Christoph; Mayer, Harald F; Sleytr, Uwe B; Pabst, Martin; Puchberger, Michael; Krause, Eberhard; Hofinger, Andreas; Duus, Jens Ø; Kosma, Paul

    2008-06-09

    The secondary cell wall polymer (SCWP) from Geobacillus stearothermophilus PV72/p2, which is involved in the anchoring of the surface-layer protein to the bacterial cell wall layer, is composed of 2-amino-2-deoxy- and 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-mannose, and 2-acetamido-2-deoxy-D-mannuronic acid. The primary structure of the acid-degraded polysaccharide--liberated by HF-treatment from the cell wall--was determined by high-field NMR spectroscopy and mass spectrometry using N-acetylated and hydrolyzed polysaccharide derivatives as well as Smith-degradation. The polysaccharide was shown to consist of a tetrasaccharide repeating unit containing a pyruvic acid acetal at a side-chain 2-acetamido-2-deoxy-alpha-D-mannopyranosyl residue. Substoichiometric substitutions of the repeating unit were observed concerning the degree of N-acetylation of glucosamine residues and the presence of side-chain linked 2-acetamido-2-deoxy-beta-D-glucopyranosyl units: [Formula: see text].

  8. Characteristics of hemodynamics in abdominal aortic aneurysm and its treatment%腹主动脉瘤血流动力学特点和对策

    Institute of Scientific and Technical Information of China (English)

    舒畅; 王暾

    2012-01-01

    The research of hemodynamic characteristics in abdominal aortic aneurysm focuses on blood pressure, blood flow, aortic wall stress, shear stress, as well as the physiopathologic changes caused by the specific hemodynamic situations. The hemodynamic characteristics lead to aortic aneurysm progressing, asymmetry and mural thrombosis. Meanwhile, the spatial structure of abdominal aortic aneurysm results in the particular hemodynamic characteristics. Researching of the hemodynamic status is an important method of analyzing the development and rupture risk of abdominal aortic aneurysm, and make prevention and treatment strategies.%腹主动脉瘤内的血流动力学主要研究瘤体内的动脉压、血流的状况,以及血流作用于主动脉壁的张力和剪切力的分布情况,同时研究主动脉壁随血流动力学改变发生的相应的结构和功能改变.血流动力学因素导致腹主动脉瘤发生并逐渐增大,呈不规则形态生长,瘤体内形成附壁血栓;而瘤体的形态改变同时也改变其内血流动力学特点.明确腹主动脉瘤内的血流动力学特点,有助于分析疾病进程,评估腹主动脉瘤破裂的风险,指导临床治疗工作,同时为早期预防腹主动脉瘤的发生和发展提供理论依据.

  9. Reinforced aortic root reconstruction for acute type A aortic dissection involving the aortic root

    Directory of Open Access Journals (Sweden)

    Han Qing-qi

    2013-06-01

    Full Text Available OBJECTIVE: There are debates regarding the optimal approach for AAAD involving the aortic root. We described a modified reinforced aortic root reconstruction approach for treating AAAD involving the aortic root. METHODS: A total of 161 patients with AAAD involving the aortic root were treated by our modified reinforced aortic root reconstruction approach from January 1998 to December 2008. Key features of our modified approach were placement of an autologous pericardial patch in the false lumen, lining of the sinotubular junction lumen with a polyester vascular ring, and wrapping of the vessel with Teflon strips. Outcome measures included post-operative mortality, survival, complications, and level of aortic regurgitation. RESULTS: A total of 161 patients were included in the study (mean age: 43.3 1 15.5 years. The mean duration of follow-up was 5.1 1 2.96 years (2-12 years. A total of 10 (6.2% and 11 (6.8% patients died during hospitalization and during follow-up, respectively. Thirty-one (19.3% patients experienced postoperative complications. The 1-, 3-, 5-, and 10-year survival rates were 99.3%, 98%, 93.8%, and 75.5%, respectively. There were no instances of recurrent aortic dissection, aortic aneurysm, or pseudoaneurysm during the entire study period. The severity of aortic regurgitation dramatically decreased immediately after surgery (from 28.6% to 0% grade 3-4 and thereafter slightly increased (from 0% to 7.2% at 5 years and 9.1% at 10 years. CONCLUSION: This modified reinforced aortic root reconstruction was feasible, safe and durable/effective, as indicated by its low mortality, low postoperative complications and high survival rate.

  10. Developing LBM Process Parameters for Ti-6Al-4V Thin Wall Structures and Determining the Corresponding Mechanical Characteristics

    Science.gov (United States)

    Ahuja, Bhrigu; Schaub, Adam; Karg, Michael; Lechner, Michael; Merklein, Marion; Schmidt, Michael

    The Laser Beam Melting (LBM) process technology within the family of Additive Manufacturing technology is characterized by its ability to fabricate fully dense 3D structures directly from micro-sized metal powder. With the current state of the art, Ti-6Al-4V has been processed using LBM machine systems constituting a laser with a beam diameter of about 100 μm. In order to fabricate structures with smaller wall thicknesses, processing of Ti-6Al-4V is attempted on the LBM machine system, Realizer SLM 50 consisting of a laser with a beam diameter 10 μm. The proposed paper presents the development of process parameters for fabricating fully dense Ti-6Al-4V 3D structures using the LBM machine system, Realizer SLM 50. Further experiments are carried out to determine the wall thickness and mechanical properties achievable using the selected process parameters. Analysis and scientific arguments are presented to explain the influence of building direction and heat treatment on mechanical properties.

  11. Out-of-plane (SH) soil-structure interaction: a shear wall with rigid and flexible ring foundation

    Science.gov (United States)

    Le, Thang; Lee, Vincent W.; Luo, Hao

    2016-02-01

    Soil-structure interaction (SSI) of a building and shear wall above a foundation in an elastic half-space has long been an important research subject for earthquake engineers and strong-motion seismologists. Numerous papers have been published since the early 1970s; however, very few of these papers have analytic closed-form solutions available. The soil-structure interaction problem is one of the most classic problems connecting the two disciplines of earthquake engineering and civil engineering. The interaction effect represents the mechanism of energy transfer and dissipation among the elements of the dynamic system, namely the soil subgrade, foundation, and superstructure. This interaction effect is important across many structure, foundation, and subgrade types but is most pronounced when a rigid superstructure is founded on a relatively soft lower foundation and subgrade. This effect may only be ignored when the subgrade is much harder than a flexible superstructure: for instance a flexible moment frame superstructure founded on a thin compacted soil layer on top of very stiff bedrock below. This paper will study the interaction effect of the subgrade and the superstructure. The analytical solution of the interaction of a shear wall, flexible-rigid foundation, and an elastic half-space is derived for incident SH waves with various angles of incidence. It found that the flexible ring (soft layer) cannot be used as an isolation mechanism to decouple a superstructure from its substructure resting on a shaking half-space.

  12. Plant Cell Wall Proteomics: Mass Spectrometry Data, a Trove for Research on Protein Structure/Function Relationships

    Institute of Scientific and Technical Information of China (English)

    Cécile Albenne; Hervé Canut; Georges Boudart; Yu Zhang; Héléne San Clemente; Rafael Pont-Lezica; Elisabeth Jamet

    2009-01-01

    Proteomics allows the large-scale study of protein expression either in whole organisms or in purified organ-elles. In particular, mass spectrometry (MS) analysis of gel-separated proteins produces data not only for protein identi-fication, but for protein structure, location, and processing as well. An in-depth analysis was performed on MS data from etiolated hypocotyl cell wall proteomics of Arabidopsis thaliana. These analyses show that highly homologous members of multigene families can be differentiated. Two lectins presenting 93% amino acid identity were identified using peptide mass fingerprinting. Although the identification of structural proteins such as extensins or hydroxyproline/proline-rich proteins (H/PRPs) is arduous, different types of MS spectra were exploited to identify and characterize an H/PRR Matu-ration events in a couple of cell wall proteins (CWPs) were analyzed using site mapping. N-glycosylation of CWPs as well as the hydroxylation or oxidation of amino acids were also explored, adding information to improve our understanding of CWP structure/function relationships. A bioinformatic tool was developed to locate by means of MS the N-terminus of mature secreted proteins and N-glycosylation.

  13. Plant cell wall proteomics: mass spectrometry data, a trove for research on protein structure/function relationships.

    Science.gov (United States)

    Albenne, Cécile; Canut, Hervé; Boudart, Georges; Zhang, Yu; San Clemente, Hélène; Pont-Lezica, Rafael; Jamet, Elisabeth

    2009-09-01

    Proteomics allows the large-scale study of protein expression either in whole organisms or in purified organelles. In particular, mass spectrometry (MS) analysis of gel-separated proteins produces data not only for protein identification, but for protein structure, location, and processing as well. An in-depth analysis was performed on MS data from etiolated hypocotyl cell wall proteomics of Arabidopsis thaliana. These analyses show that highly homologous members of multigene families can be differentiated. Two lectins presenting 93% amino acid identity were identified using peptide mass fingerprinting. Although the identification of structural proteins such as extensins or hydroxyproline/proline-rich proteins (H/PRPs) is arduous, different types of MS spectra were exploited to identify and characterize an H/PRP. Maturation events in a couple of cell wall proteins (CWPs) were analyzed using site mapping. N-glycosylation of CWPs as well as the hydroxylation or oxidation of amino acids were also explored, adding information to improve our understanding of CWP structure/function relationships. A bioinformatic tool was developed to locate by means of MS the N-terminus of mature secreted proteins and N-glycosylation.

  14. Mechanically durable and highly conductive elastomeric composites from long single-walled carbon nanotubes mimicking the chain structure of polymers.

    Science.gov (United States)

    Ata, Seisuke; Kobashi, Kazufumi; Yumura, Motoo; Hata, Kenji

    2012-06-13

    By using long single-walled carbon nanotubes (SWNTs) as a filler possessing the highest aspect ratio and small diameter, we mimicked the chain structure of polymers in the matrix and realized a highly conductive elastomeric composite (30 S/cm) with an excellent mechanical durability (4500 strain cycles until failure), far superior to any other reported conductive elastomers. This exceptional mechanical durability was explained by the ability of long and traversing SWNTs to deform in concert with the elastomer with minimum stress concentration at their interfaces. The conductivity was sufficient to operate many active electronics components, and thus this material would be useful for practical stretchable electronic devices.

  15. The investigation of coherent structures in the wall region of a supersonic turbulent boundary layer based on DNS database

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Through temporal mode direct numerical simulation, flow field database of a fully developed turbulent boundary layer on a flat plate with Mach number 4.5 and Reynolds number Reθ =1094 has been obtained. Commonly used detection meth- ods in experiments are applied to detecting coherent structures in the flow field, and it is found that coherent structures do exist in the wall region of a supersonic turbulent boundary layer. The detected results show that a low-speed streak is de- tected by using the Mu-level method, the rising parts of this streak are detected by using the second quadrant method, and the crossing regions from a low-speed streak to the high-speed one are detected by using the VITA method respectively. Notwithstanding that different regions are detected by different methods, they are all accompanied by quasi-stream-wise vortex structures.

  16. The investigation of coherent structures in the wall region of a supersonic turbulent boundary layer based on DNS database

    Institute of Scientific and Technical Information of China (English)

    HUANG ZhangFeng; ZHOU Heng; LUO JiSheng

    2007-01-01

    Through temporal mode direct numerical simulation, flow field database of a fully developed turbulent boundary layer on a flat plate with Mach number 4.5 and Reynolds number Reθ=1094 has been obtained. Commonly used detection methods in experiments are applied to detecting coherent structures in the flow field,and it is found that coherent structures do exist in the wall region of a supersonic turbulent boundary layer. The detected results show that a low-speed streak is detected by using the Mu-level method, the rising parts of this streak are detected by using the second quadrant method, and the crossing regions from a low-speed streak to the high-speed one are detected by using the VITA method respectively.Notwithstanding that different regions are detected by different methods, they are all accompanied by quasi-stream-wise vortex structures.

  17. Plasma levels of cathepsins L, K, and V and risks of abdominal aortic aneurysms

    DEFF Research Database (Denmark)

    Lv, Bing-Jie; Lindholt, Jes S; Wang, Jing;

    2013-01-01

    Cathepsin L (CatL), cathepsin K (CatK), and cathepsin V (CatV) are potent elastases implicated in human arterial wall remodeling. Whether plasma levels of these cathepsins are altered in patients with abdominal aortic aneurysms (AAAs) remains unknown.......Cathepsin L (CatL), cathepsin K (CatK), and cathepsin V (CatV) are potent elastases implicated in human arterial wall remodeling. Whether plasma levels of these cathepsins are altered in patients with abdominal aortic aneurysms (AAAs) remains unknown....

  18. Structural profiling and biological performance of phospholipid-hyaluronan functionalized single-walled carbon nanotubes

    DEFF Research Database (Denmark)

    Dvash, Ram; Khatchatouriants, Artium; Solmesky, Leonardo J

    2013-01-01

    In spite of significant insolubility and toxicity, carbon nanotubes (CNTs) erupt into the biomedical research, and create an increasing interest in the field of nanomedicine. Single-walled CNTs (SWCNTs) are highly hydrophobic and have been shown to be toxic while systemically administrated. Thus......, SWCNTs have to be functionalized to render water solubility and biocompatibility. Herein, we introduce a method for functionalizing SWCNT using phospholipids (PL) conjugated to hyaluronan (HA), a hydrophilic glycosaminoglycan, with known receptors on many types of cancer and immune cells...

  19. Structure of single-wall carbon nanotubes purified and cut using polymer

    Science.gov (United States)

    Zhang, M.; Yudasaka, M.; Koshio, A.; Jabs, C.; Ichihashi, T.; Iijima, S.

    2002-01-01

    Following on from our previous report that a monochlorobenzene solution of polymethylmethacrylate is useful for purifying and cutting single-wall carbon nanotubes (SWNTs) and thinning SWNT bundles, we show in this report that polymer and residual amorphous carbon can be removed by burning in oxygen gas. The SWNTs thus obtained had many holes (giving them a worm-eaten look) and were thermally unstable. Such severe damage caused by oxidation is unusual for SWNTs; we think that they were chemically damaged during ultrasonication in the monochlorobenzene solution of polymethylmethacrylate.

  20. Helical structure of longitudinal vortices embedded in turbulent wall-bounded flow

    DEFF Research Database (Denmark)

    Velte, Clara Marika; Hansen, Martin Otto Laver; Okulov, Valery

    2009-01-01

    Embedded vortices in turbulent wall-bounded flow over a flat plate, generated by a passive rectangular vane-type vortex generator with variable angle \\beta to the incoming flow in a low-Reynolds number flow (Re = 2600 based on the inlet grid mesh size L = 0:039 m and free stream velocity U......_{\\infty} = 1.0 ms^{-1}) have been studied with respect to helical symmetry. The studies were carried out in a low-speed closed-circuit wind tunnel utilizing Stereoscopic Particle Image Velocimetry (SPIV). The vortices have been shown to possess helical symmetry, allowing the flow to be described in a simple...

  1. Three-band decomposition analysis in multiscale FSI models of abdominal aortic aneurysms

    Science.gov (United States)

    Nestola, Maria G. C.; Gizzi, Alessio; Cherubini, Christian; Filippi, Simonetta

    2016-07-01

    Computational modeling plays an important role in biology and medicine to assess the effects of hemodynamic alterations in the onset and development of vascular pathologies. Synthetic analytic indices are of primary importance for a reliable and effective a priori identification of the risk. In this scenario, we propose a multiscale fluid-structure interaction (FSI) modeling approach of hemodynamic flows, extending the recently introduced three-band decomposition (TBD) analysis for moving domains. A quantitative comparison is performed with respect to the most common hemodynamic risk indicators in a systematic manner. We demonstrate the reliability of the TBD methodology also for deformable domains by assuming a hyperelastic formulation of the arterial wall and a Newtonian approximation of the blood flow. Numerical simulations are performed for physiologic and pathologic axially symmetric geometry models with particular attention to abdominal aortic aneurysms (AAAs). Risk assessment, limitations and perspectives are finally discussed.

  2. Simulation of blood flow within the abdominal aorta. Computational fluid dynamics in abdominal aortic aneurysms before and after interventions; Simulation des Blutflusses in der abdominellen Aorta. Die numerische Simulation des Blutflusses in abdominellen Aortenaneurysmen vor und nach Intervention

    Energy Technology Data Exchange (ETDEWEB)

    Frauenfelder, T.; Alkadhi, H.; Marincek, B.; Schertler, T. [Universitaetsspital Zuerich, Institut fuer Diagnostische Radiologie, Zuerich (Switzerland); Boutsianis, E. [ETH Zuerich, Labor fuer Computerwissenschaften und Engineering, Zuerich (Switzerland)

    2007-11-15

    The goal of numeric analysis of aortic blood flow is to evaluate the mechanisms leading to an aortic aneurysm with regard to the risk of a rupture and to describe the effect of interventional therapy. Numeric analysis is based on virtual models of vascular structures and the physical characteristics of the vessel wall, of blood as fluidum, and the blood flow. Using this information, numeric analysis solves the appropriate equations. The results can be displayed quantitatively and qualitatively. The results of numeric flow simulation show that in abdominal aortic aneurysms the wall pressure, which is of vital importance for the risk of rupture, depends on several factors, one being the location of the intraluminal thrombus. In models of aneurysms after stent grafting, numeric analysis can be used to evaluate factors leading to stent migration. Although numeric analysis of aortic blood flow still has several limitations, recent studies have shown that this method has the potential for improved estimation of the rupture risk of aortic aneurysms in the near future. (orig.) [German] Das Ziel der numerischen Simulation des Blutflusses in der Aorta ist, die Mechanik der Entstehung von Aortenaneurysmen im Hinblick auf das Rupturrisiko zu untersuchen und die Wirkungen interventioneller Massnahmen zu beschreiben. Die Grundlage der numerischen Simulation sind virtuelle Modelle von Gefaessen und die physikalischen Eigenschaften der Gefaessbestandteile, des Blutes und der Stroemung. Basierend auf diesen Angaben werden mit Hilfe numerischer Methoden die stroemungsmechanischen Probleme des Blutflusses naeherungsweise geloest. Die Ergebnisse koennen dann quantitativ und qualitativ dargestellt werden. Die Ergebnisse der numerischen Flusssimulation zeigen, dass in abdominellen Aortenaneurysmen die Hoehe des Wanddrucks, der von entscheidender Bedeutung fuer das Rupturrisiko ist, von verschiedenen Faktoren, wie z. B. der Lage des Wandthrombus, abhaengt. In Modellen mit Stentgrafts

  3. Structural stability of transparent conducting films assembled from length purified single-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    J. M. Harris; G. R. S. Iyer; D. O. Simien; J. A. Fagan; J. Y. Huh; J. Y. Chung; S. D. Hudson; J. Obrzut; J. F. Douglas; C. M. Stafford; E. K. Hobbie

    2011-01-01

    Single-wall carbon nanotube (SWCNT) films show significant promise for transparent electronics applications that demand mechanical flexibility, but durability remains an outstanding issue. In this work, thin membranes of length purified single-wall carbon nanotubes (SWCNTs) are uniaxially and isotropically compressed by depositing them on prestrained polymer substrates. Upon release of the strain, the topography, microstructure, and conductivity of the films are characterized using a combination of optical/fluorescence microscopy, light scattering, force microscopy, electron microscopy, and impedance spectroscopy. Above a critical surface mass density, films assembled from nanotubes of well-defined length exhibit a strongly nonlinear mechanical response. The measured strain dependence reveals a dramatic softening that occurs through an alignment of the SWCNTs normal to the direction of prestrain, which at small strains is also apparent as an anisotropic increase in sheet resistance along the same direction. At higher strains, the membrane conductivities increase due to a compression-induced restoration of conductive pathways. Our measurements reveal the fundamental mode of elasto-plastic deformation in these films and suggest how it might be suppressed.

  4. Artificial chemical and magnetic structure at the domain walls of an epitaxial oxide

    Science.gov (United States)

    Noheda, Beatriz

    Progress in nanotechnology requires new paradigms for materials synthesis that allow controlling their functionality down to the smallest scales. Here we report a novel two-dimensional ferromagnetic phase that is synthesized at the domain walls (DWs) of the antiferromagnetic insulator TbMnO3 when grown in thin layers under epitaxial strain. This Mn oxide phase presents an atomic arrangement that does not exist in bulk and cannot be synthesized by standard chemical routes. The number of 2D ferromagnetic sheets can be controlled by tuning the thickness of the thin films, giving rise to volume fractions that go up to 25% of the total film volume. Such novel phases are driven by a unique environment induced by the symmetry breaking and large stresses present at domain walls, which function as nanoreactors. This new class of nanoscale materials may find innovative applications in nanoelectronics and spintronics. The work is published as S. Farokhipoor, C. Magén, S. Venkatesan, J. Íñiguez, C. J. M. Daumont, D. Rubi, E. Snoeck, M. Mostovoy, C. de Graaf, A. Müller, M. Döblinger, C. Scheu, B. Noheda, Nature 515, 379 (2014)

  5. Monte Carlo calculations on the magnetization profile and domain wall structure in bulk systems and nanoconstricitons

    Energy Technology Data Exchange (ETDEWEB)

    Serena, P. A. [Instituto de Ciencias de Materiales de Madrid, Madrid (Spain); Costa-Kraemer, J. L. [Instituto de Microelectronica de Madrid, Madrid (Spain)

    2001-03-01

    A Monte Carlo algorithm suitable to study systems described by an anisotropic Heisenberg Hamiltonian is presented. This technique has been tested successfully with 3D and 2D systems, illustrating how magnetic properties depend on the dimensionality and the coordination number. We have found that magnetic properties of constrictions differ from those appearing in bulk. In particular, spin fluctuations are considerable larger than those calculated for bulk materials. In addition, domain walls are strongly modified when a constriction is present, with a decrease of the domain-wall width. This decrease is explained in terms of previous theoretical works. [Spanish] Se presenta un algoritmo de Monte Carlo para estudiar sistemas discritos por un hamiltoniano anisotropico de Heisenburg. Esta tecnica ha sido probada exitosamente con sistemas de dos y tres dimensiones, ilustrado con las propiedades magneticas dependen de la dimensionalidad y el numero de coordinacion. Hemos encontrado que las propiedades magneticas de constricciones difieren de aquellas del bulto. En particular, las fluctuaciones de espin son considerablemente mayores. Ademas, las paredes de dominio son fuertemente modificadas cuando una construccion esta presente, originando un decrecimiento del ancho de la pared de dominio. Damos cuenta de este decrecimiento en terminos de un trabajo teorico previo.

  6. Structural alteration of cell wall pectins accompanies pea development in response to cold.

    Science.gov (United States)

    Baldwin, Laëtitia; Domon, Jean-Marc; Klimek, John F; Fournet, Françoise; Sellier, Hélène; Gillet, Françoise; Pelloux, Jérôme; Lejeune-Hénaut, Isabelle; Carpita, Nicholas C; Rayon, Catherine

    2014-08-01

    Pea (Pisum sativum) cell wall metabolism in response to chilling was investigated in a frost-sensitive genotype 'Terese' and a frost-tolerant genotype 'Champagne'. Cell walls isolated from stipules of cold acclimated and non-acclimated plants showed that cold temperatures induce changes in polymers containing xylose, arabinose, galactose and galacturonic acid residues. In the tolerant cultivar Champagne, acclimation is accompanied by increases in homogalacturonan, xylogalacturonan and highly branched Rhamnogalacturonan I with branched and unbranched (1→5)-α-arabinans and (1→4)-β-galactans. In contrast, the sensitive cultivar Terese accumulates substantial amounts of (1→4)-β-xylans and glucuronoxylan, but not the pectins. Greater JIM7 labeling was observed in Champagne compared to Terese, indicating that cold acclimation also induces an increase in the degree of methylesterification of pectins. Significant decrease in polygalacturonase activities in both genotypes were observed at the end of cold acclimation. These data indicate a role for esterified pectins in cold tolerance. The possible functions for pectins and their associated arabinans and galactans in cold acclimation are discussed.

  7. Modelling of single walled carbon nanotube cylindrical structures with finite element method simulations

    Science.gov (United States)

    Günay, E.

    2016-04-01

    In this study, the modulus of elasticity and shear modulus values of single-walled carbon nanotubes SWCNTs were modelled by using both finite element method and the Matlab code. Initially, cylindrical armchair and zigzag single walled 3D space frames were demonstrated as carbon nanostructures. Thereafter, macro programs were written by the Matlab code producing the space truss for zigzag and armchair models. 3D space frames were introduced to the ANSYS software and then tension, compression and additionally torsion tests were performed on zigzag and armchair carbon nanotubes with BEAM4 element in obtaining the exact values of elastic and shear modulus values. In this study, two different boundary conditions were tested and especially used in torsion loading. The equivalent shear modulus data was found by averaging the corresponding values obtained from ten different nodal points on the nanotube path. Finally, in this study it was determined that the elastic constant values showed proportional changes by increasing the carbon nanotube diameters up to a certain level but beyond this level these values remained stable.

  8. A mathematical model of aortic aneurysm formation

    Science.gov (United States)

    Hao, Wenrui; Gong, Shihua; Wu, Shuonan; Xu, Jinchao; Go, Michael R.; Friedman, Avner; Zhu, Dai

    2017-01-01

    Abdominal aortic aneurysm (AAA) is a localized enlargement of the abdominal aorta, such that the diameter exceeds 3 cm. The natural history of AAA is progressive growth leading to rupture, an event that carries up to 90% risk of mortality. Hence there is a need to predict the growth of the diameter of the aorta based on the diameter of a patient’s aneurysm at initial screening and aided by non-invasive biomarkers. IL-6 is overexpressed in AAA and was suggested as a prognostic marker for the risk in AAA. The present paper develops a mathematical model which relates the growth of the abdominal aorta to the serum concentration of IL-6. Given the initial diameter of the aorta and the serum concentration of IL-6, the model predicts the growth of the diameter at subsequent times. Such a prediction can provide guidance to how closely the patient’s abdominal aorta should be monitored. The mathematical model is represented by a system of partial differential equations taking place in the aortic wall, where the media is assumed to have the constituency of an hyperelastic material. PMID:28212412

  9. Blood flow characteristics in the aortic arch

    Science.gov (United States)

    Prahl Wittberg, Lisa; van Wyk, Stevin; Mihaiescu, Mihai; Fuchs, Laszlo; Gutmark, Ephraim; Backeljauw, Philippe; Gutmark-Little, Iris

    2012-11-01

    The purpose with this study is to investigate the flow characteristics of blood in the aortic arch. Cardiovascular diseases are associated with specific locations in the arterial tree. Considering atherogenesis, it is claimed that the Wall Shear Stress (WSS) along with its temporal and spatial gradients play an important role in the development of the disease. The WSS is determined by the local flow characteristics, that in turn depends on the geometry as well as the rheological properties of blood. In this numerical work, the time dependent fluid flow during the entire cardiac cycle is fully resolved. The Quemada model is applied to account for the non-Newtonian properties of blood, an empirical model valid for different Red Blood Cell loading. Data obtained through Cardiac Magnetic Resonance Imaging have been used in order to reconstruct geometries of the the aortic arch. Here, three different geometries are studied out of which two display malformations that can be found in patients having the genetic disorder Turner's syndrome. The simulations show a highly complex flow with regions of secondary flow that is enhanced for the diseased aortas. The financial support from the Swedish Research Council (VR) and the Sweden-America Foundation is gratefully acknowledged.

  10. [Role of computational fluid dynamics in thoracic aortic diseases research: technical superiority and application prospect].

    Science.gov (United States)

    Li, Weihao; Shen, Chenyang; Zhang, Xiaoming; Zhang, Tao

    2015-08-01

    Computational fluid dynamics (CFD) technology has the potential to simulate normal or pathologic aortic blood flow changes of mechanical properties and flow field, thereby helping researchers understand and reveal the occurrence, development and prognosis of aortic disease. In aortic diseases research, the initial conditions of CFD numerical simulation has experienced a developed process from idealization (forward engineering), rigid vessel wall, uniform cross-sections, laminar flow and stable blood flow towards personalization (reverse engineering), elastic vessel wall (fluid-solid coupling technique), cone-shaped diminishing cross-sections, turbulent flow, pulsatile blood flow. In this review, the research status, the technical superiority and application prospect of CFD technology were discussed with examples in following three major application areas: (1) dynamics characteristic and mechanical properties in normal thoracic aorta; (2) occurrence, advance and disruptive risk predicting in thoracic aortic aneurysm; (3) therapeutic effect and aneurysmal dilatation simulation in thoracic aortic dissection. For the future, the CFD technology may profoundly put an influence on the awareness to aortic diseases and treatment strategies.

  11. Aortic Regurgitation Generates a Kinematic Obstruction Which Hinders Left Ventricular Filling.

    Science.gov (United States)

    Okafor, Ikechukwu; Raghav, Vrishank; Condado, Jose F; Midha, Prem A; Kumar, Gautam; Yoganathan, Ajit P

    2017-01-13

    An incompetent aortic valve (AV) results in aortic regurgitation (AR), where retrograde flow of blood into the left ventricle (LV) is observed. In this work, we parametrically characterized the detailed changes in intra-ventricular flow during diastole as a result of AR in a physiological in vitro left-heart simulator (LHS). The loss of energy within the LV as the level of AR increased was also assessed. The validated LHS consisted of an optically-clear, flexible wall LV and a modular AV holder. Two-component, planar, digital particle image velocimetry was used to visualize and quantify intra-ventricular flow. A large coherent vortical structure which engulfed the whole LV was observed under control conditions. In the cases with AR, the regurgitant jet was observed to generate a "kinematic obstruction" between the mitral valve and the LV apex, preventing the trans-mitral jet from generating a coherent vortical structure. The regurgitant jet was also observed to impinge on the inferolateral wall of the LV. Energy dissipation rate (EDR) for no, trace, mild, and moderate AR were found to be 1.15, 2.26, 3.56, and 5.99 W/m(3), respectively. This study has, for the first time, performed an in vitro characterization of intra-ventricular flow in the presence of AR. Mechanistically, the formation of a "kinematic obstruction" appears to be the cause of the increased EDR (a metric quantifiable in vivo) during AR. EDR increases non-linearly with AR fraction and could potentially be used as a metric to grade severity of AR and develop clinical interventional timing strategies for patients.

  12. Haemodynamic predictors of a penetrating atherosclerotic ulcer rupture using fluid-structure interaction analysis.

    Science.gov (United States)

    D'Ancona, Giuseppe; Amaducci, Andrea; Rinaudo, Antonino; Pasta, Salvatore; Follis, Fabrizio; Pilato, Michele; Baglini, Roberto

    2013-09-01

    We present preliminary data on the flow-induced haemodynamic and structural loads exerted on a penetrating atherosclerotic aortic ulcer (PAU). Specifically, one-way fluid-structure interaction analysis was performed on the aortic model reconstructed from a 66-year-old male patient with a PAU that evolved into an intramural haematoma and rupture of the thoracic aorta. The results show that elevated blood pressure (117 mmHg) and low flow velocity at the aortic wall (0.15 m/s(2)) occurred in the region of the PAU. We also found a low value of time-averaged wall shear stress (1.24 N/m(2)) and a high value of the temporal oscillation in the wall shear stress (oscillatory shear index = 0.13) in the region of the PAU. After endovascular treatment, these haemodynamic parameters were distributed uniformly on the luminal surface of the stent graft. These findings suggest that wall shear stress could be considered one of the major haemodynamic factors indicating the structural fragility of the PAU wall, which ultimately lead to PAU growth and rupture.

  13. Cell Wall Proteome

    OpenAIRE

    Boudart, Georges; Minic, Zoran; Albenne, Cécile; Canut, Hervé; Jamet, Elisabeth; Pont-Lezica, Rafael F

    2007-01-01

    In this chapter, we will focus on the contribution of proteomics to the identification and determination of the structure and function of CWPs as well as discussing new perspectives in this area. The great variety of proteins found in the plant cell wall is described. Some families, such as glycoside hydrolases, proteases, lectins, and inhibitors of cell wall modifying enzymes, are discussed in detail. Examples of the use of proteomic techniques to elucidate the structure of various cell wall...

  14. Seatbelt triad: severe abdominal wall disruption, hollow viscus injury, and major vascular injury.

    Science.gov (United States)

    Kulvatunyou, Narong; Albrecht, Roxie M; Bender, Jeffrey S; Friese, Randy S; Joseph, Bellal; Latifi, Rifat; O'Keefe, Terrance; Wynn, Julie L; Rhee, Peter M

    2011-05-01

    The triad of seatbelt-related severe abdominal wall disruption, hollow viscus injury, and distal abdominal aortic injury after a motor vehicle collision is uncommon. We present a small case series involving those three clinical features with the goal of preventing a future missed diagnosis of the distal abdominal aortic injury in particular.

  15. Histology of a Marfan aorta 4.5 years after personalized external aortic root support.

    Science.gov (United States)

    Pepper, John; Goddard, Martin; Mohiaddin, Raad; Treasure, Tom

    2015-09-01

    In 2008, a 26-year old man had personalized external aortic root support (PEARS) with a macroporous mesh. He was the 16th of 46 patients to have this operation. He had a typical Marfan habitus. His mother died of this disease as did his brother, with an aortic dissection. The patient himself died suddenly 4.5 years after his PEARS operation. At autopsy, there was no blood in the pericardium. The coronary orifices and proximal arteries were normal. His bicuspid aortic valve was minimally regurgitant as it was prior to operation and remained throughout follow-up. Macroscopically the implanted mesh was embedded in the adventitia and not separable from the aortic wall. Microscopically it was fully incorporated with collagen fibres as has been seen in our animal studies. The unsupported aortic arch showed some focal fragmentation of elastic fibres and a mild increase in mucopolysaccharides consistent with Marfan syndrome. These appearances were not present in the supported aortic root, which had the histological appearance of a normal aorta. He was the first patient to die with an implant. The histological appearances suggest the possibility that the incorporated support of the aortic root allowed recovery of the microstructure of the media.

  16. Evaluation of aortic cannula jet lesions in a porcine cardiopulmonary bypass (CPB) model.

    Science.gov (United States)

    Schnürer, C; Hager, M; Györi, G; Velik-Salchner, C; Moser, P L; Laufer, G; Lorenz, I H; Kolbitsch, C

    2011-02-01

    In cardiosurgery patients atherosclerotic debris displaced from the cannulation site but also from the opposite aortic wall by the "sandblast-like" effect of the high-pressure jet emanating from the cannula is a potential source of intraoperative arterial embolization and consequently postoperative neurologic dysfunction. The present study examined the extent to which shear stress exerted on the intact aortic intima by an aortic cannula jet stream can cause endothelial lesions that promote thrombogenesis and consequently thrombembolism. A single-stream, straight-tip aortic cannula was used in a porcine cardiopulmonary bypass (CPB) model. Following a 120-minute CPB pump run, a 60-minute stabilization period was allowed before sacrificing the pigs (N.=40) for histological evaluation of the ascending aorta and the brain. Opposite the cannulation site endothelial lesions (diameter: 3.81±1.3 mm; depth: 0.017±0.003 mm) were present in 22.5% (9/40) of aortic specimens. Cerebral thrombembolic lesions were not found. The present study showed that single-stream, straight-tip aortic cannulas caused jet lesions of the formerly intact aortic endothelium opposite the cannulation site in 22.5% of cases in a porcine CPB model.

  17. NUMERICAL ANALYSIS OF THE CRITICAL STATE OF THIN-WALLED STRUCTURE WITH Z-PROFILE CROSS SECTION

    Directory of Open Access Journals (Sweden)

    Patryk Różyło

    2017-03-01

    Full Text Available The object of the study was the thin-walled profile with Z-shaped cross section made of the carbon-epoxy composite. Material model was prepared based on the implemented orthotropic properties. The purpose of study was to determine the value of the critical load at which buckling occurs, the form of buckling and operating characteristics in critical condition. In order to achieve this numerical analysis were carried out. Additionally, the effects of the modification in arrangement of layers of the laminate to the stability and strength of thin-walled composite structures was presented. Numerical studies were carried out using commercial simulation software - ABAQUS®. Within the FEM research, both forms of buckling and the associated critical load, dependent on the configuration the layers of the composite were achieved. Analysis of the obtained results, allowed the evaluation of the structure's work in relation to the level of energy consumption or rigidity estimation. In the paper only numerical simulations of the critical state were conducted.

  18. Argyres-Douglas Loci, Singularity Structures and Wall-Crossings in Pure N=2 Gauge Theories with Classical Gauge Groups

    CERN Document Server

    Seo, Jihye

    2012-01-01

    N=2 Seiberg-Witten theories allow an interesting interplay between the Argyres-Douglas loci, singularity structures and wall-crossing formulae. In this paper we investigate this connection by first studying the singularity structures of hyper-elliptic Seiberg-Witten curves for pure N=2 gauge theories with SU(r+1) and Sp(2r) gauge groups, and propose new methods to locate the Argyres-Douglas loci in the moduli space, where multiple mutually non-local BPS states become massless. In a region of the moduli space, we compute dyon charges for all 2r+2 and 2r+1 massless dyons for SU(r+1) and Sp(2r) gauge groups respectively for rank r>1. From here we elucidate the connection to the wall-crossing phenomena for pure Sp(4) Seiberg-Witten theory near the Argyres-Douglas loci, despite our emphasis being only at the massless sector of the BPS spectra. We also present 2r-1 candidates for the maximal Argyres-Douglas points for pure SO(2r+1) Seiberg-Witten theory.

  19. Energetics and structure of organic molecules embedded in single-wall carbon nanotubes from first principles: The example of benzene

    Science.gov (United States)

    Milko, Matus; Ambrosch-Draxl, Claudia

    2011-08-01

    Stability and structural properties of nanopeapods are investigated by means of density-functional theory (DFT) including van der Waals interactions. As a prototypical system of organic π-conjugated molecules embedded into single-wall carbon nanotubes, we study benzene inside zig-zag nanotubes (n,0), with n ranging from 10 to 18. We explore the position and orientation of the molecule inside the cavity and find the optimal tube diameter for encapsulation to be around 1 nm. We compute that, overall, the molecule tends to align its molecular plane parallel to the tube axis. The internal orientation and molecule-wall distance depend, however, quite strongly on the tube diameter. The overall energy minimum is found for a situation in which the benzene ring takes a tilted position inside the (13,0) nanotube. Chirality turns out not to play a role in terms of the energetics. When benzene arrays are confined in nanotubes, the intermolecular distances can differ from those in the gas phase. Intermolecular interactions are important and further stabilize the peapods. As these as well as the molecule-tube interactions are governed by dispersive forces, we critically assess the performance of different DFT-based methods in this respect. Comparing four different computational schemes including both ab initio and semi-empirical treatment of van der Waals interactions, we conclude that vdW-DF is most reliable in terms of energetics and structural properties of these hybrids.

  20. 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...

  1. FUNCTIONAL AORTIC STIFFNESS:ROLE OF CD4+ T LYMPHOCYTES

    Directory of Open Access Journals (Sweden)

    Beenish A. Majeed

    2015-08-01

    Full Text Available The immune system is suggested to be essential in vascular remodeling and stiffening. To study the dependence upon lymphocytes in vascular stiffening, we compared an angiotensin II-model of vascular stiffening in normal C57BL/6J mice with lymphocyte-deficient RAG 1-/- mice and additionally characterized the component of vascular stiffness due to vasoconstriction versus vascular remodeling. Chronic angiotensin II increased aortic pulse wave velocity, effective wall stiffness, and effective Young’s modulus in C57BL/6J mice by 3-fold but caused no change in the RAG 1-/- mice. These functional measurements were supported by aortic morphometric analysis. Adoptive transfer of CD4+ T helper lymphocytes restored the angiotensin II-mediated aortic stiffening in the RAG 1-/- mice. In order to account for the hydraulic versus material effects of angiotensin II on pulse wave velocity, subcutaneous osmotic pumps were removed after 21 days of angiotensin II-infusion in the WT mice to achieve normotensive values. The pulse wave velocity decreased from 3- to 2-fold above baseline values up to 7 days following pump removal. This study supports the pivotal role of the CD4+ T-lymphocytes in angiotensin II-mediated vascular stiffening and that angiotensin II-mediated aortic stiffening is due to the additive effect of active vascular smooth muscle vasoconstriction and vascular remodeling.

  2. Mycotic Saccular Abdominal Aortic Aneurysm in an Infant after Cardiac Catheterization: A Case Report.

    Science.gov (United States)

    Benrashid, Ehsan; McCoy, Christopher C; Rice, Henry E; Shortell, Cynthia K; Cox, Mitchell W

    2015-10-01

    Abdominal aortic aneurysms (AAAs) are a rare entity in the pediatric population. Children with mycotic (infectious) AAA in particular are at risk of life-threatening rupture due to their rapid expansion coupled with aortic wall thinning and deterioration. Here, we present the case of a 10-month-old infant with prior 2-staged repair for hypoplastic left heart syndrome that was incidentally discovered to have a mycotic AAA on abdominal ultrasound (US) for evaluation of renovascular hypertension. Before the time of evaluation with US, the infant had developed methicillin-resistant Staphylococcus aureus bacteremia 3 days after cardiac catheterization with percutaneous thoracic aortic balloon angioplasty. She had normal aortic contours on contrasted computed tomography scan of the abdomen approximately 2 weeks before the aforementioned US evaluation. This infant subsequently underwent open aneurysmorrhaphy with cryopreserved vein patch angioplasty with resolution of her aneurysmal segment.

  3. A tale of two neglected systems - structure and function of the thin- and thick-walled sieve tubes in monocotyledonous leaves.

    Directory of Open Access Journals (Sweden)

    Ted eBotha

    2013-08-01

    Full Text Available There is a large body of information relating to the ontogeny, development and the vasculature of eudicotyledonous leaves. However there is less information available concerning the vascular anatomy of monocotyledonous leaves. This is surprising, given that there are two uniquely different phloem systems present in large groups such as grasses and sedges. Monocotyledonous leaves contain marginal, large, intermediate and small longitudinal veins that are interconnected by numerous transverse veins. The longitudinal veins contain two metaphloem sieve tube types, which, based upon their ontogeny and position within the phloem, are termed early (thin-walled and late (thick-walled sieve tubes. Early metaphloem comprises sieve tubes, companion cells and vascular parenchyma cells, whilst the late metaphloem, contains thick-walled sieve tubes that lack companion cells. Thick-walled sieve tubes are generally adjacent to, or no more than one cell removed from the metaxylem. Unlike thin-walled sieve tube-companion cell complexes, thick-walled sieve tubes are connected to parenchyma by pore-plasmodesma units and are generally symplasmically isolated from the thin walled sieve tubes. This paper addresses key structural and functional differences between thin- and thick-walled sieve tubes and explores the unique advantages of alternate transport strategies that this 5 to 7 million year old dual system may offer. It would seem that these two systems may enhance, add to, or play a significant role in increasing the efficiency of solute retrieval as well as of assimilate transfer.

  4. Phase-averaged waveforms of Reynolds stress in wall turbulence during the burst events of coherent structures

    Institute of Scientific and Technical Information of China (English)

    JIANG Nan; LIU Wei; LIU JianHua; TIAN Yan

    2008-01-01

    The time sequence signals of instantaneous longitudinal and normal velocity components at different vertical locations in the turbulent boundary layer over a smooth flat plate have been finely measured by constant temperature anemometry of model IFA-300 and X-shaped hot-wire sensor probe in a wind tunnel. The longitudinal and normal velocity components have been decomposed into multi-scales by wavelet transform. The upward eject and downward sweep motions in a burst process of coherent structure have been detected by the maximum energy criterion of identifying burst event in wall turbulence through wavelet analysis. The relationships of phase-averaged waveforms among longitudinal velocity component, normal velocity component and Reynolds stress component have been studied through a correlation function method. The dynamics course of coherent structures and their effects on statistical characteristics of turbulent flows are analyzed.

  5. A variable limit for the instability parameter of wall-frame or core-frame bracing structures

    Directory of Open Access Journals (Sweden)

    R. J. Ellwanger

    Full Text Available This work aims to investigate the viability and convenience of adopting a variable limit α1 for the instability parameter of buildings with reinforced concrete wall-frame or core-frame structures. Initially, the evolution of tall buildings global stability theory is summarized, giving emphasis to define when a second order analysis is needed. The treatment given to this subject by the present Brazilian code for concrete structures design (NBR 6118:2007 is also showed. It follows a detailed analytical study that led to the derivation of an equation for the variable limit α1; a series of examples is presented to check its accuracy. Results are analyzed, showing the validity bounds of the equation and research directions are suggested, in order to improve it.

  6. Liquid Wall Chambers

    Energy Technology Data Exchange (ETDEWEB)

    Meier, W R

    2011-02-24

    The key feature of liquid wall chambers is the use of a renewable liquid layer to protect chamber structures from target emissions. Two primary options have been proposed and studied: wetted wall chambers and thick liquid wall (TLW) chambers. With wetted wall designs, a thin layer of liquid shields the structural first wall from short ranged target emissions (x-rays, ions and debris) but not neutrons. Various schemes have been proposed to establish and renew the liquid layer between shots including flow-guiding porous fabrics (e.g., Osiris, HIBALL), porous rigid structures (Prometheus) and thin film flows (KOYO). The thin liquid layer can be the tritium breeding material (e.g., flibe, PbLi, or Li) or another liquid metal such as Pb. TLWs use liquid jets injected by stationary or oscillating nozzles to form a neutronically thick layer (typically with an effective thickness of {approx}50 cm) of liquid between the target and first structural wall. In addition to absorbing short ranged emissions, the thick liquid layer degrades the neutron flux and energy reaching the first wall, typically by {approx}10 x x, so that steel walls can survive for the life of the plant ({approx}30-60 yrs). The thick liquid serves as the primary coolant and tritium breeding material (most recent designs use flibe, but the earliest concepts used Li). In essence, the TLW places the fusion blanket inside the first wall instead of behind the first wall.

  7. CONGENITAL QUADRICUSPID AORTIC-VALVE

    NARCIS (Netherlands)

    BROUWER, MHJ; DEGRAAF, JJ; EBELS, T

    1993-01-01

    Two patients with a quadricuspid aortic valve are described, one of them with concomitant juxtaposed coronary orifices facing the right hand facing sinus. The etiology and incidence of this congenital anomaly will be discussed.

  8. Transcatheter Aortic Heart Valve Thrombosis

    DEFF Research Database (Denmark)

    Hansson, Nicolaj C; Grove, Erik L; Andersen, Henning R;

    2016-01-01

    BACKGROUND: There is increasing focus on transcatheter heart valve (THV) thrombosis. However, there are limited data on incidence, clinical implications and predisposing factors of THV thrombosis following transcatheter aortic valve replacement (TAVR). OBJECTIVES: We assessed the incidence...

  9. Adult thoracic and abdominal aortic

    Directory of Open Access Journals (Sweden)

    Randa O. Kaddah

    2016-06-01

    Conclusion: Aortic COA could be found in any segment of the aorta. Proper identification of the anatomical details and pressure gradient studies are important factors affecting the plan of management.

  10. Minimally invasive aortic valve replacement

    DEFF Research Database (Denmark)

    Foghsgaard, Signe; Schmidt, Thomas Andersen; Kjaergard, Henrik K

    2009-01-01

    In this descriptive prospective study, we evaluate the outcomes of surgery in 98 patients who were scheduled to undergo minimally invasive aortic valve replacement. These patients were compared with a group of 50 patients who underwent scheduled aortic valve replacement through a full sternotomy....... The 30-day mortality rate for the 98 patients was zero, although 14 of the 98 mini-sternotomies had to be converted to complete sternotomies intraoperatively due to technical problems. Such conversion doubled the operative time over that of the planned full sternotomies. In the group of patients whose...... is an excellent operation in selected patients, but its true advantages over conventional aortic valve replacement (other than a smaller scar) await evaluation by means of randomized clinical trial. The "extended mini-aortic valve replacement" operation, on the other hand, is a risky procedure that should...

  11. Loss of function mutation in LOX causes thoracic aortic aneurysm and dissection in humans.

    Science.gov (United States)

    Lee, Vivian S; Halabi, Carmen M; Hoffman, Erin P; Carmichael, Nikkola; Leshchiner, Ignaty; Lian, Christine G; Bierhals, Andrew J; Vuzman, Dana; Mecham, Robert P; Frank, Natasha Y; Stitziel, Nathan O

    2016-08-01

    Thoracic aortic aneurysms and dissections (TAAD) represent a substantial cause of morbidity and mortality worldwide. Many individuals presenting with an inherited form of TAAD do not have causal mutations in the set of genes known to underlie disease. Using whole-genome sequencing in two first cousins with TAAD, we identified a missense mutation in the lysyl oxidase (LOX) gene (c.893T > G encoding p.Met298Arg) that cosegregated with disease in the family. Using clustered regularly interspaced short palindromic repeats (CRISPR)/clustered regularly interspaced short palindromic repeats-associated protein-9 nuclease (Cas9) genome engineering tools, we introduced the human mutation into the homologous position in the mouse genome, creating mice that were heterozygous and homozygous for the human allele. Mutant mice that were heterozygous for the human allele displayed disorganized ultrastructural properties of the aortic wall characterized by fragmented elastic lamellae, whereas mice homozygous for the human allele died shortly after parturition from ascending aortic aneurysm and spontaneous hemorrhage. These data suggest that a missense mutation in LOX is associated with aortic disease in humans, likely through insufficient cross-linking of elastin and collagen in the aortic wall. Mutation carriers may be predisposed to vascular diseases because of weakened vessel walls under stress conditions. LOX sequencing for clinical TAAD may identify additional mutation carriers in the future. Additional studies using our mouse model of LOX-associated TAAD have the potential to clarify the mechanism of disease and identify novel therapeutics specific to this genetic cause.

  12. A general formalism for the determination of the effective mass of the nanoscale structural inhomogeneities of the domain wall in uniaxial ferromagnets.

    Science.gov (United States)

    Shevchenko, Andriy; Barabash, Maksym

    2015-01-01

    On the basis of the method of gyrotropic Thiele forces, we build a formalism that allows the determination of the effective mass of the nanoscales structural elements of the domain wall (DW): vertical Bloch line and Bloch point in uniaxial ferromagnets. As shown, the effective mass of these magnetic inhomogeneities depends on the value of the gyrotropic domain wall bend that is created by their movement.

  13. Left ventricular remodeling and hypertrophy in patients with aortic stenosis: insights from cardiovascular magnetic resonance

    Directory of Open Access Journals (Sweden)

    Dweck Marc R

    2012-07-01

    Full Text Available Abstract Background Cardiovascular magnetic resonance (CMR is the gold standard non-invasive method for determining left ventricular (LV mass and volume but has not been used previously to characterise the LV remodeling response in aortic stenosis. We sought to investigate the degree and patterns of hypertrophy in aortic stenosis using CMR. Methods Patients with moderate or severe aortic stenosis, normal coronary arteries and no other significant valve lesions or cardiomyopathy were scanned by CMR with valve severity assessed by planimetry and velocity mapping. The extent and patterns of hypertrophy were investigated using measurements of the LV mass index, indexed LV volumes and the LV mass/volume ratio. Asymmetric forms of remodeling and hypertrophy were defined by a regional wall thickening ≥13 mm and >1.5-fold the thickness of the opposing myocardial segment. Results Ninety-one patients (61±21 years; 57 male with aortic stenosis (aortic valve area 0.93±0.32cm2 were recruited. The severity of aortic stenosis was unrelated to the degree (r2=0.012, P=0.43 and pattern (P=0.22 of hypertrophy. By univariate analysis, only male sex demonstrated an association with LV mass index (P=0.02. Six patterns of LV adaption were observed: normal ventricular geometry (n=11, concentric remodeling (n=11, asymmetric remodeling (n=11, concentric hypertrophy (n=34, asymmetric hypertrophy (n=14 and LV decompensation (n=10. Asymmetric patterns displayed considerable overlap in appearances (wall thickness 17±2mm with hypertrophic cardiomyopathy. Conclusions We have demonstrated that in patients with moderate and severe aortic stenosis, the pattern of LV adaption and degree of hypertrophy do not closely correlate with the severity of valve narrowing and that asymmetric patterns of wall thickening are common. Trial registration ClinicalTrials.gov Reference Number: NCT00930735

  14. [New aspects in aortic valve disease].

    Science.gov (United States)

    Tornos, P

    2001-01-01

    Renewed interest for aortic valve disease has evolved in recent years. Aortic valve replacement has become the second most frequent cause of cardiac surgery, following coronary bypass surgery. In addition, the etiologic and physiopathologic knowledge of this disorder has improved. In the present paper we analyze three aspects of the disease which are, at present, the subject of study and controversy: first, we discuss the possible relationship between degenerative aortic stenosis and atherosclerosis; second, the involvement of the aortic root in cases of bicuspid aortic valve; and third, the surgical indications in asymptomatic patients with either aortic stenosis or regurgitation.

  15. Structural characterization of a mixed-linkage glucan deficient mutant reveals alteration in cellulose microfibril orientation in rice coleoptile mesophyll cell walls

    Directory of Open Access Journals (Sweden)

    Andreia Michelle Smith-Moritz

    2015-08-01

    Full Text Available The CELLULOSE SYNTHASE-LIKE F6 (CslF6 gene was previously shown to mediate the biosynthesis of mixed-linkage glucan (MLG, a cell wall polysaccharide that is hypothesized to be a tightly associated with cellulose and also have a role in cell expansion in the primary cell wall of young seedlings in grass species. We have recently shown that loss-of-function cslf6 rice mutants do not accumulate MLG in most vegetative tissues. Despite the absence of a structurally important polymer, MLG, these mutants are unexpectedly viable and only show a moderate growth compromise compared to wild type. Therefore these mutants are ideal biological systems to test the current grass cell wall model. In order to gain a better understanding of the role of MLG in the primary wall, we performed in-depth compositional and structural analyses of the cell walls of three day-old rice seedlings using various biochemical and novel microspectroscopic approaches. We found that cellulose content as well as matrix polysaccharide composition was not significantly altered in the MLG deficient mutant. However, we observed a significant change in cellulose microfibril bundle organization in mesophyll cell walls of the cslf6 mutant. Using synchrotron source Fourier Transform Mid-Infrared Spectromicroscopy for high-resolution imaging, we determined that the bonds associated with cellulose and arabinoxylan, another major component of the primary cell was of grasses, were in a lower energy configuration compared to wild type, suggesting a slightly weaker primary wall in MLG deficient mesophyll cells. Taken together, these results suggest that MLG may influence cellulose deposition in mesophyll cell walls without significantly affecting anisotropic growth thus challenging MLG importance in cell wall expansion.

  16. Electrospun single-walled carbon nanotube/polyvinyl alcohol composite nanofibers: structure property relationships

    Science.gov (United States)

    Naebe, Minoo; Lin, Tong; Staiger, Mark P.; Dai, Liming; Wang, Xungai

    2008-07-01

    Polyvinyl alcohol (PVA) nanofibers and single-walled carbon nanotube (SWNT)/PVA composite nanofibers have been produced by electrospinning. An apparent increase in the PVA crystallinity with a concomitant change in its main crystalline phase and a reduction in the crystalline domain size were observed in the SWNT/PVA composite nanofibers, indicating the occurrence of a SWNT-induced nucleation crystallization of the PVA phase. Both the pure PVA and SWNT/PVA composite nanofibers were subjected to the following post-electrospinning treatments: (i) soaking in methanol to increase the PVA crystallinity, and (ii) cross-linking with glutaric dialdehyde to control the PVA morphology. Effects of the PVA morphology on the tensile properties of the resultant electrospun nanofibers were examined. Dynamic mechanical thermal analyses of both pure PVA and SWNT/PVA composite electrospun nanofibers indicated that SWNT-polymer interaction facilitated the formation of crystalline domains, which can be further enhanced by soaking the nanofiber in methanol and/or cross-linking the polymer with glutaric dialdehyde.

  17. Electrospun single-walled carbon nanotube/polyvinyl alcohol composite nanofibers: structure-property relationships

    Energy Technology Data Exchange (ETDEWEB)

    Naebe, Minoo; Lin Tong; Wang Xungai [Centre for Material and Fibre Innovation, Deakin University, Geelong, VIC 3217 (Australia); Staiger, Mark P [Department of Mechanical Engineering, University of Canterbury, Christchurch (New Zealand); Dai Liming [Department of Chemical and Materials Engineering, University of Dayton, Dayton, OH 45469 (United States)], E-mail: tong.lin@deakin.edu.au

    2008-07-30

    Polyvinyl alcohol (PVA) nanofibers and single-walled carbon nanotube (SWNT)/PVA composite nanofibers have been produced by electrospinning. An apparent increase in the PVA crystallinity with a concomitant change in its main crystalline phase and a reduction in the crystalline domain size were observed in the SWNT/PVA composite nanofibers, indicating the occurrence of a SWNT-induced nucleation crystallization of the PVA phase. Both the pure PVA and SWNT/PVA composite nanofibers were subjected to the following post-electrospinning treatments: (i) soaking in methanol to increase the PVA crystallinity, and (ii) cross-linking with glutaric dialdehyde to control the PVA morphology. Effects of the PVA morphology on the tensile properties of the resultant electrospun nanofibers were examined. Dynamic mechanical thermal analyses of both pure PVA and SWNT/PVA composite electrospun nanofibers indicated that SWNT-polymer interaction facilitated the formation of crystalline domains, which can be further enhanced by soaking the nanofiber in methanol and/or cross-linking the polymer with glutaric dialdehyde.

  18. Turbulent flow structure response to a varying wall-roughness arrangement: a modelling study

    Science.gov (United States)

    Jakirlic, Suad; Krumbein, Benjamin; Fooroghi, Pourya; Magagnato, Franco; Frohnapfel, Bettina; Darmstadt Collaboration; Karlsruhe Collaboration

    2016-11-01

    Presently adopted approach to the modelling of rough surfaces relies on introducing an additional drag term in the appropriately 'filtered' Navier-Stokes equations, accounting for the form drag and blockage effects, the roughness elements exert on the flow. A non-dimensional drag function D(y) accounting for the shape of roughness elements is introduced. It is evaluated by applying a reference DNS of an open channel flow over a wall characterized by varying arrangement (aligned/staggered) of differently-shaped/sized roughness elements at a bulk Reynolds number Re =6500 by Fooroghi et al.. The prime objective of the present work is to assess the roughness model capability to predict mean velocities and turbulent intensities in conjunction with a recently formulated hybrid LES/RANS (Reynolds-Averaged Navier-Stokes) model, based on the Very Large Eddy Simulation (VLES) concept of Speziale. A seamless transition from RANS to LES is enabled depending on the ratio of the turbulent viscosities associated with the unresolved scales corresponding to the LES cut-off and those related to the turbulent properties of the VLES residual motion.

  19. Structure and Properties of Self-assembled Narural Rubber/Multi-walled Carbon Nanotube Composites

    Institute of Scientific and Technical Information of China (English)

    PENG Zheng; FENG Chunfang; LUO Yongyue; YI Zhifeng; KONG Lingxue

    2011-01-01

    Natural rubber (NR)/multi-walled carbon nanotube (MWCNTs) composites were prepared by combining self-assembly and latex compounding techniques.The acid-treated MWCNTs (H2SO4∶HNO3=3∶1,volume ratio) were self-assembled with poly (diallyldimethylammonium chloride) (PDDA) through electrostatic adhesion.In the second assembling,NR/MWCNTs composites were developed by mixing MWCNTs/PDDA solution with NR latex.The results show that MWCNTs are homogenously distributed throughout the NR matrix as single tube and present a great interfacial adhesion with NR phase when MWCNTs contents are less than 3 wt%.Moreover,the addition of the MWCNTs brings about the remarkable enhancement in tensile strength and crosslink density compared with the NR host,and the data peak at 2 wt% MWCNTs loadings.When more MWCNTs are loaded,aggregations of MWCNTs are gradually generated,and the tensile strength and crosslink both decrease to a certain extent.

  20. Joining and fabrication techniques for high temperature structures including the first wall in fusion reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ho Jin; Lee, B. S.; Kim, K. B

    2003-09-01

    The materials for PFC's (Plasma Facing Components) in a fusion reactor are severely irradiated with fusion products in facing the high temperature plasma during the operation. The refractory materials can be maintained their excellent properties in severe operating condition by lowering surface temperature by bonding them to the high thermal conducting materials of heat sink. Hence, the joining and bonding techniques between dissimilar materials is considered to be important in case of the fusion reactor or nuclear reactor which is operated at high temperature. The first wall in the fusion reactor is heated to approximately 1000 .deg. C and irradiated severely by the plasma. In ITER, beryllium is expected as the primary armour candidate for the PFC's; other candidates including W, Mo, SiC, B4C, C/C and Si{sub 3}N{sub 4}. Since the heat affected zones in the PFC's processed by conventional welding are reported to have embrittlement and degradation in the sever operation condition, both brazing and diffusion bonding are being considered as prime candidates for the joining technique. In this report, both the materials including ceramics and the fabrication techniques including joining technique between dissimilar materials for PFC's are described. The described joining technique between the refractory materials and the dissimilar materials may be applicable for the fusion reactor and Generation-4 future nuclear reactor which are operated at high temperature and high irradiation.

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

    Science.gov (United States)

    Yin, Hanyu; Sibley, David N.; Thiele, Uwe; Archer, Andrew J.

    2017-02-01

    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 or 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 behavior caused by the near-wall layered molecular packing. The adsorption layer is often submonolayer in thickness, i.e., the dynamics along the layer consists of single-particle hopping, leading to a diffusive dynamics, rather than the collective hydrodynamic motion implicit in standard thin-film models. We therefore modify the model in such a way that for thicker films the standard hydrodynamic theory is realized, but for very thin layers a diffusion equation is recovered.

  2. Polysaccharides from the green seaweed Codium decorticatum. Structure and cell wall distribution.

    Science.gov (United States)

    Fernández, Paula Virginia; Raffo, María Paula; Alberghina, Josefina; Ciancia, Marina

    2015-03-06

    The cell wall polysaccharides from Codium decorticatum and their assembly were studied and these results were compared with those obtained previously for this genus. The water soluble polysaccharides are: (i) Pyruvylated and sulfated 3- and 6-linked β-D-galactans with sulfate mainly on C-4 and also on C-6. Pyruvate ketals are linked to O-3 and O-4 of terminal β-D-galactose or O-4 and O-6 of 3-linked β-D-galactose. (ii) Sulfated 3-linked β-L-arabinans substituted on C-2 or C-2 and C-4 predominantly with sulfate, but also with single stubs of arabinose, and (iii) 4-linked β-D-mannans with a low degree of sulfation on C-2. The whole polysaccharide system comprises 6.9% of sulfated polysaccharides and 32.9% of fibrillar polysaccharides, mostly insoluble mannans. By in situ localization it was possible to detect two similar fibrillar layers separated by a zone rich in charged polymers. Besides, arabinogalactan proteins co-localized with the fibrillar components.

  3. Domain wall dynamics under electric field in CoFeB-MgO structures with perpendicular magnetic anisotropy (Conference Presentation)

    Science.gov (United States)

    Ravelosona, Dafine

    2016-10-01

    One crucial breakthrough in spin electronics has recently been achieved regarding the possibility to move magnetic domain walls (DWs) in magnetic tracks using the sole action of an electrical current instead of a conventional magnetic field. Here, we will present our recent results of DW dynamics obtained in Ta-CoFeB-MgO nanodevices with perpendicular magnetic anisotropy (PMA), which are widely used in STT-RAM applications, and discuss the critical problems to be addressed for implementation into a memory device. Using NV center microscopy to map DW pinning along a magnetic wire, we will first show1 that Ta/CoFeB(1nm)/MgO structures exhibit a very low density of pinning defects with respect to others materials with PMA. Then, we will focus on the possibility to use Electric Field Effect to control domain wall motion with low power dissipation. We will demonstrate gate voltage modulation of DW dynamics using different approaches based on dielectrics, piezoelectrics and ionic liquid layers.

  4. EXPRESSION OF MATRIX METALLOPROTEINASE-9 IN HUMAN ABDOMINAL AORTIC ANEURYSMAL TISSUES

    Institute of Scientific and Technical Information of China (English)

    Ma Zhong; Wang Ling; Qi Guangyu; Joerg. Heckenkamp

    2006-01-01

    Objective To study the effects of MMP-9 (Matrix Metalloproteinase-9, MMP-9) in the pathogenesis of abdominal aortic aneurysms (AAAs) by localizing the expression of MMP-9 in the aneurysmal tissues. Methods By means of immunohistochemistry, the frozen sections (5 μm) with aneurysmal tissues (n = 10) were incubated with MMP-9 antibody-added agents, then the sections were stained and observed under the microscope to localize the expression of MMP-9, which displayed a brown precipitate within the arterial walls. The normal arterial wall tissues(n= 10)and the diseased arterial wall tissues from the arterial occlusive diseases (AODs) (n= 15) were also immunized exactly the same way as control. Results A quantity of positive granules which appeared within the aortic media showed the strong expression of MMP-9 in the AAAs, with the positive rate reaching 95%(19/20), while no expression of MMP-9 was observed in the normal artery. However, the scattered distributed positive granules were scen within the arterial wall of some cases of the AODs, implying the weak positive expression of MMP-9 in this disease with the positive rate of 26.7%(4/15). There was a significant difference of the expression of MMP-9 within the arterial wall between the AAAs and AODs(P<0. 01). Conclusion High expression of MMP-9 within the aortic media faciliatates the degradation of collagen and elastin fibres and subsequent dilation of the aortic artery , thus playing an important role in the pathogenesis of AAAs. To refrain MMP-9 from enhanced expressing within the aortic wall is of clinical significance in the prevention and treatment of AAAs.

  5. Simulation of polyethylene oxide : improved structure using better models for hydrogen and flexible walls.

    Energy Technology Data Exchange (ETDEWEB)

    Halley, J. W.; Duan, Y.; Nielsen, B.; Redfern, P. C.; Curtiss, L. A.; Univ. of Minnesota

    2001-08-22

    We describe calculations of the structure of amorphous polyethylene oxide using a previously reported model, but with better treatment of hydrogen positions and in a code which allows relaxation of stresses in the polymerized sample by Rahman-Parrinello techniques. We also report the effects of two different intermolecular force field potentials and find that our earlier, empirical force field produces better agreement with experimental neutron scattering results than a force field derived from ab initio electronic structure calculations.

  6. Synthesis of palladium nanoparticle modified reduced graphene oxide and multi-walled carbon nanotube hybrid structures for electrochemical applications

    Science.gov (United States)

    Hu, Jie; Zhao, Zhenting; Zhang, Jun; Li, Gang; Li, Pengwei; Zhang, Wendong; Lian, Kun

    2017-02-01

    In this work, palladium (Pd) nanoparticles functionalized reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) hybrid structures (Pd/rGO-MWCNTs) were successfully prepared by a combination of electrochemical reduction with electrodeposition method. The morphology, structure, and composition of the Pd/rGO-MWCNTs hybrid were characterized by scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy. The as-synthesized hybrid structures were modified on the glassy carbon electrode (GCE) and further utilized for hydrazine sensing. Electrochemical impedance spectroscopic, cyclic voltammetry and single-potential amperometry experiments were carried out on Pd/rGO-MWCNTs hybrid structures to investigate the interface properties and sensing performance. The measured results demonstrate that the fabricated Pd/rGO-MWCNTs/GCE sensor show a high sensitivity of 7.09 μA μM-1 cm-2 in a large concentration range of 1.0 to 1100 μM and a low detection limit of 0.15 μM. Moreover, the as-prepared sensor exhibits good selectivity and stability for the determination of hydrazine under interference conditions.

  7. Fractal structures of single-walled carbon nanotubes in biologically relevant conditions: role of chirality vs. media conditions.

    Science.gov (United States)

    Khan, Iftheker A; Aich, Nirupam; Afrooz, A R M Nabiul; Flora, Joseph R V; Schierz, P Ariette; Ferguson, P Lee; Sabo-Attwood, Tara; Saleh, Navid B

    2013-11-01

    Aggregate structure of covalently functionalized chiral specific semiconducting single-walled carbon nanotubes (SWNTs) was systematically studied employing static light scattering (SLS). Fractal dimensions (Df) of two specific chirality SWNTs-SG65 and SG76 with (6, 5) and (7, 6) chiral enrichments-were measured under four biological exposure media conditions, namely: Dulbecco's Modified Eagle Medium (DMEM), Minimum Essential Medium (MEM), Roswell Park Memorial Institute (RPMI) 1640 medium, and 0.9% saline solution. The SWNTs exhibited chiral dependence on Df with SG65 showing more fractal or loosely bound aggregate structures, i.e., lower Df values (range of 2.24±0.03 to 2.64±0.05), compared to the SG76 sample (range of 2.58±0.13 to 2.90±0.08). All the Df values reported are highly reproducible, measured from multiple SLS runs and estimated with 'random block-effects' statistical analysis that yielded all p values to be fractal aggregates. Moreover, presence of fetal bovine serum (FBS) and bovine serum albumin (BSA), used to mimic the in vitro cell culture condition, reduced the Df values, i.e., created more fractal structures. Steric hindrance to aggregation was identified as the key mechanism for creating the fractal structures. Also, increase in FBS concentration from 1% to 10% resulted in increasingly lower Df values.

  8. Chronic contained rupture of an abdominal aortic aneurysm presenting as a Grynfeltt lumbar hernia. A case report.

    Science.gov (United States)

    Dobbeleir, J; Fourneau, I; Maleux, G; Daenens, K; Vandekerkhof, J; Nevelsteen, A

    2007-06-01

    We report a unique case of chronic contained thoraco-abdominal aneurysm rupture presenting as a Grynfeltt lumbar hernia. A 79-year-old man presented with backpain and a bluish swelling in the left lumbar region in the presence of a non tender aortic aneurysm. CT scan confirmed contained rupture of a type IV thoraco-abdominal aortic aneurysm. The peri-aortic haematoma protruded through the lumbar wall causing a Grynfeltt lumbar hernia. The aneurysm was replaced through a thoraco-phreno-lumbotomy. The patient survived and is doing well six months postoperatively.

  9. Isogeometric Analysis of Deformation, Inelasticity and Fracture In Thin-Walled Structures

    Science.gov (United States)

    de Borst, René

    2016-08-01

    The basic idea of isogeometric analysis (IGA) is to use splines, which are the functions commonly used in computer-aided design (CAD) to describe the geometry, as the basis function for the analysis as well. A main advantage is that a sometimes elaborate meshing process is by-passed. Another benefit is that spline basis-functions possess a higher-order degree of continuity, which enables a more accurate representation of the stress. Further, the order of continuity of the basis-functions can be reduced locally by knot insertion. This feature can be used to model interfaces and cracks as discontinuities in the displacement field. In order to study failure-mechanisms in thin-walled composite materials, an accurate representation of the full three-dimensional stress field is mandatory. A continuum shell formulation is an obvious choice. Continuum shell elements can be developed based on the isogeometric concept. They exploit NURBS basis functions to construct the mid-surface of the shell. In combination with a higher-order B-spline basis function in the thickness direction a complete three-dimensional representation of the shell is obtained. This isogeometric shell formulation can be implemented in a standard finite element code using Bézier extraction. Weak and strong discontinuities can be introduced in the B-spline function using knot-insertion to model material interfaces and delaminations rigorously as discontinuities in the displacement field. The exact representation of material interfaces vastly improves the accuracy of the through-the- thickness stress field. The ability to provide a double knot insertion enables a straightforward analysis of delamination growth in layered composite shells. Illustrative examples will be given.

  10. Low-density lipoprotein accumulation within a carotid artery with multilayer elastic porous wall: fluid-structure interaction and non-Newtonian considerations.

    Science.gov (United States)

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

    2015-09-18

    Low-density lipoprotein (LDL), which is recognized as bad cholesterol, typically has been regarded as a main cause of atherosclerosis. LDL infiltration across arterial wall and subsequent formation of Ox-LDL could lead to atherogenesis. In the present study, combined effects of non-Newtonian fluid behavior and fluid-structure interaction (FSI) on LDL mass transfer inside an artery and through its multilayer arterial wall are examined numerically. Navier-Stokes equations for the blood flow inside the lumen and modified Darcy's model for the power-law fluid through the porous arterial wall are coupled with the equations of mass transfer to describe LDL distributions in various segments of the artery. In addition, the arterial wall is considered as a heterogeneous permeable elastic medium. Thus, elastodynamics equation is invoked to examine effects of different wall elasticity on LDL distribution in the artery. Findings suggest that non-Newtonian behavior of filtrated plasma within the wall enhances LDL accumulation meaningfully. Moreover, results demonstrate that at high blood pressure and due to the wall elasticity, endothelium pores expand, which cause significant variations on endothelium physiological properties in a way that lead to higher LDL accumulation. Additionally, results describe that under hypertension, by increasing angular strain, endothelial junctions especially at leaky sites expand more dramatic for the high elastic model, which in turn causes higher LDL accumulation across the intima layer and elevates atherogenesis risk.

  11. Simulation for transthoracic echocardiography of aortic valve

    Science.gov (United States)

    Nanda, Navin C.; Kapur, K. K.; Kapoor, Poonam Malhotra

    2016-01-01

    Simulation allows interactive transthoracic echocardiography (TTE) learning using a virtual three-dimensional model of the heart and may aid in the acquisition of the cognitive and technical skills needed to perform TTE. The ability to link probe manipulation, cardiac anatomy, and echocardiographic images using a simulator has been shown to be an effective model for training anesthesiology residents in transesophageal echocardiography. A proposed alternative to real-time reality patient-based learning is simulation-based training that allows anesthesiologists to learn complex concepts and procedures, especially for specific structures such as aortic valve. PMID:27397455

  12. The Nano-Memory Devices of a Single Wall and Peapod Structural Carbon Nanotube Field Effect Transistor

    Science.gov (United States)

    Lee, C. H.; Kang, K. T.; Park, K. S.; Kim, M. S.; Kim, H. S.; Kim, H. G.; Fischer, J. E.; Johnson, A. T.

    2003-08-01

    The rediscovery and the memory application of single walled carbon nanotubes (SWNTs) give a new method in nanoelectronics applications. At first we will report the memory effects of a SWNT, and attempt to use this property in a memory device. To use a SWNT field effect transistor (FET) as a charge-storage memory device, the device operates by injecting electrons from the nanotube channel of a TubeFET into charge traps on the surface of the SiO2 gate dielectric, thus shifting the threshold voltage. This memory can be written and erased many times, and has a hold time of hundreds of seconds at room temperature. At second we have attempted to make a Peapod tubeFET. It is the structure that a C60 was contained within the tube and separated from it by a graphitic Van der Waals gap. I-V property of the Peapod shows semiconducting property.

  13. The growth model and electronic properties of single- and double-walled zigzag silicon nanotubes: Depending on the structures

    Science.gov (United States)

    Lin, Xiang; Lu, Junzhe; Liu, Jing; Tang, Yuchao; Zhu, Hengjiang

    2017-02-01

    The growth model and electronic properties of the capped zigzag single- and double-walled silicon nanotubes (SWSiNTs and DWSiNTs) are studied with the Density Functional Theory (DFT) method. Particularly, the morphologies of the silicon nanotubes (SiNTs) and the layer-by-layer growth process are explored. Capping of SiNTs is explained well in terms of pentagons. It seems that pentagons or heptagons play apivotal role during the SiNTs growth. Moreover, the structures of the finite SWSiNTs and DWSiNTs are studied. Finally, the infinite SWSiNTs and DWSiNTs can be set up with the repeat unit cells based on the periodic trait of the corresponding finite SiNTs. All of the zigzag SWSiNTs and DWSiNTs have a narrow band gap.

  14. DFT Study on Structural and Mechanical Properties of Single-walled Carbon and Boron Nitride Nanotubes Functionalized with Carbenes

    Directory of Open Access Journals (Sweden)

    I.K. Petrushenko

    2016-10-01

    Full Text Available This paper presents quantum chemistry study on structural and mechanical properties of a series of single-walled carbon nanotubes (SWCNTs and boron nitride nanotubes (BNNTs functionalized with carbenes. At the PBE/SVP level, the obtained data on pristine nanotubes are in good accordance with the results of previous experimental and theoretical studies. The calculations show that carbenes functionalization, in general, distorts both SWNCTs and BNNTs frameworks, but there exists the difference between ‘axial’ and ‘circumferential’ functionalization. It turns out that in both cases elastic properties diminish with increasing concentration of adsorbents, however, the functionalized SWCNTs and BNNTs remain strong enough to be suitable for reinforcement of composites.

  15. Successful Anticoagulation Therapy for Antiphospholipid Syndrome with Mobile Aortic Thrombi

    Science.gov (United States)

    Park, Hyun Oh; Moon, Seong Ho; Kim, Jong Woo; Byun, Joung Hun; Kim, Sung Hwan; Yang, Jun Ho; Lee, Chung-Eun; Kim, Jong-Duk

    2016-01-01

    Hypercoagulable states have been associated with aortic thrombosis. Antiphospholipid syndrome (APS) is one of the commonest types of acquired thrombophilia. We report the case of successful anticoagulation management in an APS patient with mobile thrombi within the aorta. A 58-year-old male patient presented to the emergency department (ED) with right-sided hemiparesis. His first symptoms were noted approximately 12–16 hours before presentation to the ED. Magnetic resonance imaging of the brain showed acute embolic infarction of the left frontal and parietotemporal lobes. Transesophageal echocardiography (TEE) and computed tomography angiography (CTA) demonstrated mobile thrombi attached to the wall of the ascending aorta and aortic arch. The patient was diagnosed with APS based on positivity of anti-beta-2 glycoprotein 1 antibodies, and was initiated on anticoagulation therapy. Repeated TEE and CTA revealed complete resolution of the thrombi after 12 days of treatment; the patient was discharged well. PMID:28042559

  16. Percutaneous aortic valve replacement using a W-model valved stent: a preliminary feasibility study in sheep

    Institute of Scientific and Technical Information of China (English)

    BAI Yuan; ZONG Gang-jun; WANG Yan-yan; JIANG Hai-bin; LI Wei-ping; WU Hong; ZHAO Xian-xian; QIN Yong-wen

    2009-01-01

    Background Percutaneous aortic valve replacement is a promising strategy in the treatment of patients with aortic valve stenosis. And many kinds of valved stents have been implanted in selected patients worldwide. However, the clinical experience is still limited. We developed a W-model valved stent and evaluated the feasibility and safety of percutaneous implantation of the device in the native aortic valve position.Methods A self expanding nitinol stent with W-model, containing porcine pericardium valves in its proximal part, was implanted in six sheep by means of a 14 French catheter through the right common lilac artery under guidance of fluoroscopy. During stent deployment the original aortic valve was pushed against the aortic wall by the self expanding force of the stent while the new valve was expanded. These sheep were followed up shortly after procedure with supra-aortic angiogram and left ventriculography. Additionally, one sheep was sacrificed after the procedure for anatomic evaluation.Results It was possible to replace the aortic valve in the beating heart in four sheep. The procedure failed in two sheep due to coronary orifice occlusion in one case and severe aortic valve regurgitation in the other case. One sheep was killed one hour after percutaneous aortic valve replacement for anatomic evaluation. There were no signs of damage of the aortic intima, or of obstruction of the coronary orifice.Conclusions Percutaneous aortic valve replacement with a W-model valved stent in the beating heart is possible. Further studies are mandatory to assess safety and efficacy of this kind of valved stent in larger sample size and by longer follow-up period.

  17. Intraventricular filling in physical models of the left ventricle: influence of aortic pressure

    Science.gov (United States)

    Nelsen, Nicholas; Samaee, Milad; Santhanakrishnan, Arvind

    2016-11-01

    Clinical studies using medical imaging have provided evidence on the formation of an intraventricular vortex in the left ventricle (LV) during diastolic phase of the cardiac cycle. However, the question of how the vortex characteristics are altered with aortic pressure remains unclear. This is of relevance to hypertensive heart disease and heart failure with normal ejection fraction. Using an experimental left heart simulator, we have previously shown that increasing LV wall stiffness results in reduction of the filling vortex circulation. In this study, we investigate the effects of varying aortic pressure in addition to wall stiffness. A series of flexible-walled LV models with varying wall stiffness were tested in a pulsatile flow loop. 2D particle image velocimetry was used to visualize intraventricular flow and calculate filling vortex circulation. The flow circuit was first setup with the least stiffness LV physical model, and tuned to physiological aortic pressure, cardiac output and ejection fraction. We then iteratively tested LV models with increasing stiffness without changing circuit variables. Comparisons of the filling vortex circulation with changing aortic pressure relative to the baseline and increased LV stiffness models will be presented.

  18. Therapeutic Prospect of Adipose-Derived Stromal Cells for the Treatment of Abdominal Aortic Aneurysm

    NARCIS (Netherlands)

    Parvizi, Mojtaba; Harmsen, Martin C.

    2015-01-01

    Aneurysm refers to the dilation of the vessel wall for more than 50%. Abdominal aortic aneurysm (AAA) refers to the dilation and weakening of all three layers of the abdominal aorta, which mostly occur infrarenally. The population aged above 50 years is at risk of AAA development, while a familiar h

  19. Imaging of aortic valve dynamics in 4D OCT

    Directory of Open Access Journals (Sweden)

    Schnabel Christian

    2015-09-01

    Full Text Available The mechanical components of the heart, especially the valves and leaflets, are enormous stressed during lifetime. Therefore, those structures undergo different pathophysiological tissue transformations which affect cardiac output and in consequence living comfort of affected patients. These changes may lead to calcific aortic valve stenosis (AVS, the major heart valve disease in humans. The knowledge about changes of the dynamic behaviour during the course of this disease and the possibility of early stage diagnosis is of particular interest and could lead to the development of new treatment strategies and drug based options of prevention or therapy. 4D optical coherence tomography (OCT in combination with high-speed video microscopy were applied to characterize dynamic behaviour of the murine aortic valve and to characterize dynamic properties during artificial stimulation. We present a promising tool to investigate the aortic valve dynamics in an ex vivo disease model with a high spatial and temporal resolution using a multimodal imaging setup.

  20. Abdominal aortic aneurysm repair - open - discharge

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000240.htm Abdominal aortic aneurysm repair - open - discharge To use the sharing features ... References Orandi BJ, Black JH. Open repair of abdominal aortic aneurysms. In: Cameron JL, Cameron AM, eds. Current Surgical ...