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Sample records for aortic wall structure

  1. Fluid-structure interaction in abdominal aortic aneurysms: effects of asymmetry and wall thickness

    Directory of Open Access Journals (Sweden)

    Muluk Satish C

    2005-11-01

    Full Text Available Abstract Background Abdominal aortic aneurysm (AAA is a prevalent disease which is of significant concern because of the morbidity associated with the continuing expansion of the abdominal aorta and its ultimate rupture. The transient interaction between blood flow and the wall contributes to wall stress which, if it exceeds the failure strength of the dilated arterial wall, will lead to aneurysm rupture. Utilizing a computational approach, the biomechanical environment of virtual AAAs can be evaluated to study the affects of asymmetry and wall thickness on this stress, two parameters that contribute to increased risk of aneurysm rupture. Methods Ten virtual aneurysm models were created with five different asymmetry parameters ranging from β = 0.2 to 1.0 and either a uniform or variable wall thickness to study the flow and wall dynamics by means of fully coupled fluid-structure interaction (FSI analyses. The AAA wall was designed to have a (i uniform 1.5 mm thickness or (ii variable thickness ranging from 0.5 – 1.5 mm extruded normally from the boundary surface of the lumen. These models were meshed with linear hexahedral elements, imported into a commercial finite element code and analyzed under transient flow conditions. The method proposed was then compared with traditional computational solid stress techniques on the basis of peak wall stress predictions and cost of computational effort. Results The results provide quantitative predictions of flow patterns and wall mechanics as well as the effects of aneurysm asymmetry and wall thickness heterogeneity on the estimation of peak wall stress. These parameters affect the magnitude and distribution of Von Mises stresses; varying wall thickness increases the maximum Von Mises stress by 4 times its uniform thickness counterpart. A pre-peak systole retrograde flow was observed in the AAA sac for all models, which is due to the elastic energy stored in the compliant arterial wall and the expansion

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

    OpenAIRE

    Zaher Fanari; Sumaya Hammami; Muhammad Baraa Hammami; Safa Hammami; Chete Eze-Nliam; Weintraub, William S.

    2015-01-01

    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...

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

    Science.gov (United States)

    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.

  4. Nonlinear spectral imaging microscopy of rabbit aortic wall

    Institute of Scientific and Technical Information of China (English)

    Quangang Liu; Jianxin Chen; Shuangmu Zhuo; Xingshan Jiang; Kecheng Lu

    2009-01-01

    Employing nonlinear spectral imaging technique based on two-photon-excited fluorescence and second-harmonic generation (SHG) of biological tissue, we combine the image-guided spectral analysis method and multi-channel subsequent detection imaging to map and visualize the intrinsic species in a native rabbit aortic wall. A series of recorded nonlinear spectral images excited by a broad range of laser wavelengths (730-910 nm) are used to identify five components in the native rabbit aortic wall, including nicotinamide adenine dinucleotide (NADH), elastic fiber, flavin, porphyrin derivatives, and collagen. Integrating multi-channel subsequent detection imaging technique, the high-resolution, high contrast images of collagen and elastic fiber in the aortic wall are obtained. Our results demonstrate that this method can yield complementary biochemical and morphological information about aortic tissues, which have the potential to determine the tissue pathology associated with mechanical properties of aortic wall and to evaluate the pharmacodynamical studies of vessels.

  5. Changes in wall shear stresses in abdominal aortic aneurysms with increasing wall stiffness

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    Salsac, Anne-Virginie; Fernandez, Miguel

    2006-11-01

    During the growth of abdominal aortic aneurysms, local changes occur in the composition and structure of the diseased wall, resulting in its stiffening. A numerical simulation of the fluid structure interactions is performed in idealized models of aneurysms using a finite element method. A full coupling of the equations governing the pulsatile blood flow and the deformation of the compliant wall is undertaken. The effect of the progressive stiffening of the wall is analyzed at various stages in the growth of the aneurysm. Increasing the wall stiffness alters the distribution of wall shear stresses and leads to an increase in their magnitude. The wall compliance is shown to have a more pronounced effect on non-axisymmetric aneurysms, which sustain large displacements. The overall movement of the aneurysm models increases the three-dimensionality of the flow.

  6. Structural and ultrastructural evaluation of the aortic wall after transplantation of bone marrow-derived cells (BMCs) in a model for atherosclerosis.

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    Felix, Alyne Souza; Monteiro, Nemesis; Rocha, Vinícius Novaes; Oliveira, Genilza; Nascimento, Ana Lucia; de Carvalho, Laís; Thole, Alessandra; Carvalho, Jorge

    2015-08-01

    Stem cells are characterized by their ability to differentiate into multiple cell lineages and display the paracrine effect. The aim of this work was to evaluate the effect of therapy with bone marrow-derived cells (BMCs) on glucose, lipid metabolism, and aortic wall remodeling in mice through the administration of a high-fat diet and subsequent BMCs transplantation. C57BL/6 mice were fed a control diet (CO group) or an atherogenic diet (AT group). After 16 weeks, the AT group was divided into 4 subgroups: an AT 14 days group and AT 21 days group that were given an injection of vehicle and sacrificed after 14 and 21 days, respectively, and an AT-BMC 14 days group and AT-BMC 21 days group that were given an injection of BMCs and sacrificed after 14 and 21 days, respectively. The BMCs transplant had reduced blood glucose, triglycerides, and total cholesterol. There was no significant difference in relation to body mass between the transplanted groups and non-transplanted groups, and all were different than CO. There was no significant difference in the glycemic curve among AT 14 days, AT-BMC 14 days, and AT 21 days, and these were different than the CO and the AT-BMC 21 days groups. The increased thickness of the aortic wall was observed in all atherogenic groups, but was significantly smaller in group AT-BMC 21 days compared to AT 14 days and AT 21 days. Vacuoles in the media tunic, delamination and the thinning of the elastic lamellae were observed in AT 14 days and AT 21 days. The smallest number of these was displayed on the AT-BMC 14 days and AT-BMC 21 days. Marking to CD105, CD133, and CD68 were observed in AT 14 days and AT 21 days. These markings were not observed in AT-BMC 14 days or in AT-BMC 21 days. Electron micrographs show the beneficial remodeling in AT-BMC 14 days and AT-BMC 21 days, and the structural organization was similar to the CO group. Vesicles of pinocytosis, projection of smooth muscle cells, and delamination of the internal elastic lamina

  7. 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 maximum axial and hoop stress in the group of AAA patients was 94.9 kPa (±0.283 kPa) and 94.3 kPa (±0.224 kPa) at maximum stretch ratios of 1.043 and 1.037, respectively. In the 3D simulations, the maximum stress is also found to occur in the AAA patient group, with the highest stress......-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...... in the circumferential direction (275 kPa). Comparison with an already published isotropic model indicates that the latter underestimates the peak stress significantly. Based on these results it is concluded that the four fiber family model has been successfully implemented into a 3D anisotropic finite element model...

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

    OpenAIRE

    Polzer Stanislav; Gasser T; Markert Bernd; Bursa Jiri; Skacel Pavel

    2012-01-01

    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 t...

  9. Proteomic identification of differentially expressed proteins in aortic wall of patients with ruptured and nonruptured abdominal aortic aneurysms

    DEFF Research Database (Denmark)

    Urbonavicius, Sigitas; Lindholt, Jes S.; Vorum, Henrik;

    2009-01-01

    To compare the basic proteomic composition of abdominal aortic aneurysm (AAA) wall tissue in patients with nonruptured and ruptured aneurysms.......To compare the basic proteomic composition of abdominal aortic aneurysm (AAA) wall tissue in patients with nonruptured and ruptured aneurysms....

  10. 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.

  11. Biological Ferroelectricity Uncovered in Aortic Walls by Piezoresponse Force Microscopy

    OpenAIRE

    Liu, Yuanming; Zhang, Yanhang; Chow, Ming-Jay; Chen, Qian Nataly; Li, Jiangyu

    2012-01-01

    Many biological tissues are piezoelectric and pyroelectric with spontaneous polarization. Ferroelectricity, however, has not been reported in soft biological tissues yet. Using piezoresponse force microscopy, we discover that the porcine aortic walls are not only piezoelectric, but also ferroelectric, with the piezoelectric coefficient in the order of 1 pm/V and coercive voltage approximately 10 V. Through detailed switching spectroscopy mapping and relaxation studies, we also find that the p...

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

    Directory of Open Access Journals (Sweden)

    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

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

    Science.gov (United States)

    Fanari, Zaher; Hammami, Sumaya; Hammami, Muhammad Baraa; Hammami, Safa; Eze-Nliam, Chete; Weintraub, William S.

    2015-01-01

    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 visualize 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 analyzed 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. PMID:25984293

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

    Directory of Open Access Journals (Sweden)

    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.

  15. Regulation of aortic wall mechanics and stress : An experimental study in man

    OpenAIRE

    Åstrand, Håkan

    2008-01-01

    The abdominal aorta (AA) in man is a vulnerable artery prone to atherosclerosis as well as aneurysmatic dilation. The underlying aortic composition, mechanical properties as well as the mechanisms responsible for age-related changes and vascular disease are however largely unknown. The aims of this study were 1) to characterize the age- and gender-related changes of the aortic wall components in vivo, using a mechanical model based on ultrasound measurements of pulsatile aortic diameter chang...

  16. Hessian analysis for the delineation of amorphous anomalies in optical coherence tomography images of the aortic wall.

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    Real, Eusebio; Val-Bernal, José Fernando; Revuelta, José M; Pontón, Alejandro; Díez, Marta Calvo; Mayorga, Marta; López-Higuera, José M; Conde, Olga M

    2016-04-01

    The aortic aneurysm is a disease originated mainly in the media layer of the aortic wall due to the occurrence of degraded areas of altered biological composition. These anomalous regions affect the structure and strength of the aorta artery, being their occurrence and extension proportional to the arterial vessel health. Optical Coherence Tomography (OCT) is applied to obtain cross-sectional images of the artery wall. The backscattering mechanisms in tissue make aorta images difficult to analyze due to noise and strong attenuation with penetration. The morphology of anomalies in pathological specimens is also diverse with amorphous shapes and varied dimensions, being these factors strongly related with tissue degradation and the aorta physiological condition. Hessian analysis of OCT images from aortic walls is used to assess the accurate delineation of these anomalous regions. A specific metric of the Hessian determinant is used to delineate degraded regions under blurry conditions and noise. A multiscale approach, based on an anisotropic Gaussian kernel filter, is applied to highlight and aggregate all the heterogeneity present in the aortic wall. An accuracy estimator metric has been implemented to evaluate and optimize the delineation process avoiding subjectivity. Finally, a degradation quantification score has been developed to assess aorta wall condition by OCT with validation against common histology. PMID:27446665

  17. Abdominal aortic aneurysm: Rupture of the anterior wall

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    Drašković Miroljub

    2007-01-01

    Full Text Available Introduction An aneurysm is a focal dilatation of an artery (aorta, involving an increase in diameter of at least 50% as compared to the expected normal diameter (over 3 cm. Abdominal aortic aneurysms (AAA cause thousands of deaths every year, many of which can be prevented with timely diagnosis and treatment. AAA can be asymptomatic for many years, but in one third of patients whose aneurysm ruptured, the mortality rate is 90%. In the past, palpation of the abdomen was the preferred method for identifying AAA. However, diagnostic imaging techniques, such as ultrasonography and computed tomography are more accurate and offer opportunities for early detection of AAA. Case report This paper is a case report of an 83-year old female patient. She was admitted due to severe pain in the abdomen. We already knew about the AAA (from her medical history. After using all available diagnostic procedures, rupture or dissection of the AAA were not confirmed. The patient underwent emergency surgery. During the operation, rupture of the anterior wall of the aneurysm was found. The anterior wall was filled with parietal thrombus, which hermetically closed the perforation. The patient was successfully operated and recovered. Conclusion The aim of this case report was to point out that our diagnostic procedures failed to confirm the rupture of AAA. We decided to apply surgical treatment, based on medical experience, clinical findings, ultrasonography and computed tomography and during operation rupture of AAA was confirmed. Patients with an already diagnosed AAA, or patients with clinical picture of rupture or dissection, are in urgent need for surgery, no matter what diagnostic tools are being used.

  18. 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.

  19. Estimation of wall properties and wall strength of aortic aneurysms using modern imaging techniques. One more step towards a patient-specific assessment of aneurysm rupture risk.

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    Kontopodis, Nikolaos; Georgakarakos, Efstratios; Metaxa, Eleni; Pagonidis, Konstantinos; Papaharilaou, Yannis; Ioannou, Christos V

    2013-08-01

    Abdominal aortic aneurysmal disease is a major health problem with rupture representing its main complication accompanied by great mortality. Elective repair is currently performed with mortality rates 1cm/year enlargement. It is well established that even small AAAs without indication for surgical repair can experience rupture with catastrophic outcomes whereas larger aneurysms often remain intact for a long period. It is recognized, therefore, that the currently used, maximum diameter criterion can not accurately predict AAAs evolution. There is increasing interest in the role of patient-specific biomechanical profiling of AAA development and rupture. Biomechanically, rupture of a vessel occurs when intravascular forces exceed vessel wall structural endurance. Peak Wall Stress (PWS) has been previously shown to better identify AAAs prone to rupture than maximum diameter, but currently stress analysis takes into account several assumptions that influence results to a large extent and limit their use. Moreover stress represents only one of two determinants of rupture risk according to the biomechanical perspective. Wall strength and mechanical properties on the other hand cannot be assessed in vivo but only ex vivo through mechanical studies with mean values of these parameters taken into account for rupture risk estimations. New possibilities in the field of aortic imaging offer promising tools for the validation and advancement of stress analysis and the in vivo evaluation of AAAs' wall properties and wall strength. Documentation of aortic wall motion during cardiac cycle is now feasible through ECG-gated multi-detector CT imaging offering new possibilities towards an individualized method for rupture risk and expansion-rate predictions based on data acquired in vivo. PMID:23714223

  20. 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)

  1. Optical coherence tomography assessment of vessel wall degradation in thoracic aortic aneurysms

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    Real, Eusebio; Eguizabal, Alma; Pontón, Alejandro; Díez, Marta Calvo; Fernando Val-Bernal, José; Mayorga, Marta; Revuelta, José M.; López-Higuera, José M.; Conde, Olga M.

    2013-12-01

    Optical coherence tomography images of human thoracic aorta from aneurysms reveal elastin disorders and smooth muscle cell alterations when visualizing the media layer of the aortic wall. These disorders can be employed as indicators for wall degradation and, therefore, become a hallmark for diagnosis of risk of aneurysm under intraoperative conditions. Two approaches are followed to evaluate this risk: the analysis of the reflectivity decay along the penetration depth and the textural analysis of a two-dimensional spatial distribution of the aortic wall backscattering. Both techniques require preprocessing stages for the identification of the air-sample interface and for the segmentation of the media layer. Results show that the alterations in the media layer of the aortic wall are better highlighted when the textural approach is considered and also agree with a semiquantitative histopathological grading that assesses the degree of wall degradation. The correlation of the co-occurrence matrix attains a sensitivity of 0.906 and specificity of 0.864 when aneurysm automatic diagnosis is evaluated with a receiver operating characteristic curve.

  2. 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.

  3. Effects of aortic root motion on wall stress in the Marfan aorta before and after personalised aortic root support (PEARS) surgery.

    Science.gov (United States)

    Singh, S D; Xu, X Y; Pepper, J R; Izgi, C; Treasure, T; Mohiaddin, R H

    2016-07-01

    Aortic root motion was previously identified as a risk factor for aortic dissection due to increased longitudinal stresses in the ascending aorta. The aim of this study was to investigate the effects of aortic root motion on wall stress and strain in the ascending aorta and evaluate changes before and after implantation of personalised external aortic root support (PEARS). Finite element (FE) models of the aortic root and thoracic aorta were developed using patient-specific geometries reconstructed from pre- and post-PEARS cardiovascular magnetic resonance (CMR) images in three Marfan patients. The wall and PEARS materials were assumed to be isotropic, incompressible and linearly elastic. A static load on the inner wall corresponding to the patients' pulse pressure was applied. Cardiovascular MR cine images were used to quantify aortic root motion, which was imposed at the aortic root boundary of the FE model, with zero-displacement constraints at the distal ends of the aortic branches and descending aorta. Measurements of the systolic downward motion of the aortic root revealed a significant reduction in the axial displacement in all three patients post-PEARS compared with its pre-PEARS counterparts. Higher longitudinal stresses were observed in the ascending aorta when compared with models without the root motion. Implantation of PEARS reduced the longitudinal stresses in the ascending aorta by up to 52%. In contrast, the circumferential stresses at the interface between the supported and unsupported aorta were increase by up to 82%. However, all peak stresses were less than half the known yield stress for the dilated thoracic aorta. PMID:27255604

  4. Spaceflight Affects Postnatal Development of the Aortic Wall in Rats

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    Shin-ichiro Katsuda

    2014-01-01

    Full Text Available We investigated effect of microgravity environment during spaceflight on postnatal development of the rheological properties of the aorta in rats. The neonate rats were randomly divided at 7 days of age into the spaceflight, asynchronous ground control, and vivarium control groups (8 pups for one dam. The spaceflight group rats at 9 days of age were exposed to microgravity environment for 16 days. A longitudinal wall strip of the proximal descending thoracic aorta was subjected to stress-strain and stress-relaxation tests. Wall tensile force was significantly smaller in the spaceflight group than in the two control groups, whereas there were no significant differences in wall stress or incremental elastic modulus at each strain among the three groups. Wall thickness and number of smooth muscle fibers were significantly smaller in the spaceflight group than in the two control groups, but there were no significant differences in amounts of either the elastin or collagen fibers among the three groups. The decreased thickness was mainly caused by the decreased number of smooth muscle cells. Plastic deformation was observed only in the spaceflight group in the stress-strain test. A microgravity environment during spaceflight could affect postnatal development of the morphological and rheological properties of the aorta.

  5. Spaceflight affects postnatal development of the aortic wall in rats.

    Science.gov (United States)

    Katsuda, Shin-ichiro; Yamasaki, Masao; Waki, Hidefumi; Miyake, Masao; O-ishi, Hirotaka; Katahira, Kiyoaki; Nagayama, Tadanori; Miyamoto, Yukako; Hasegawa, Masamitsu; Wago, Haruyuki; Okouchi, Toshiyasu; Shimizu, Tsuyoshi

    2014-01-01

    We investigated effect of microgravity environment during spaceflight on postnatal development of the rheological properties of the aorta in rats. The neonate rats were randomly divided at 7 days of age into the spaceflight, asynchronous ground control, and vivarium control groups (8 pups for one dam). The spaceflight group rats at 9 days of age were exposed to microgravity environment for 16 days. A longitudinal wall strip of the proximal descending thoracic aorta was subjected to stress-strain and stress-relaxation tests. Wall tensile force was significantly smaller in the spaceflight group than in the two control groups, whereas there were no significant differences in wall stress or incremental elastic modulus at each strain among the three groups. Wall thickness and number of smooth muscle fibers were significantly smaller in the spaceflight group than in the two control groups, but there were no significant differences in amounts of either the elastin or collagen fibers among the three groups. The decreased thickness was mainly caused by the decreased number of smooth muscle cells. Plastic deformation was observed only in the spaceflight group in the stress-strain test. A microgravity environment during spaceflight could affect postnatal development of the morphological and rheological properties of the aorta. PMID:25210713

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

    Energy Technology Data Exchange (ETDEWEB)

    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.)

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

    Science.gov (United States)

    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.

  8. Fluid, solid and fluid-structure interaction simulations on patient-based abdominal aortic aneurysm models.

    Science.gov (United States)

    Kelly, Sinead; O'Rourke, Malachy

    2012-04-01

    This article describes the use of fluid, solid and fluid-structure interaction simulations on three patient-based abdominal aortic aneurysm geometries. All simulations were carried out using OpenFOAM, which uses the finite volume method to solve both fluid and solid equations. Initially a fluid-only simulation was carried out on a single patient-based geometry and results from this simulation were compared with experimental results. There was good qualitative and quantitative agreement between the experimental and numerical results, suggesting that OpenFOAM is capable of predicting the main features of unsteady flow through a complex patient-based abdominal aortic aneurysm geometry. The intraluminal thrombus and arterial wall were then included, and solid stress and fluid-structure interaction simulations were performed on this, and two other patient-based abdominal aortic aneurysm geometries. It was found that the solid stress simulations resulted in an under-estimation of the maximum stress by up to 5.9% when compared with the fluid-structure interaction simulations. In the fluid-structure interaction simulations, flow induced pressure within the aneurysm was found to be up to 4.8% higher than the value of peak systolic pressure imposed in the solid stress simulations, which is likely to be the cause of the variation in the stress results. In comparing the results from the initial fluid-only simulation with results from the fluid-structure interaction simulation on the same patient, it was found that wall shear stress values varied by up to 35% between the two simulation methods. It was concluded that solid stress simulations are adequate to predict the maximum stress in an aneurysm wall, while fluid-structure interaction simulations should be performed if accurate prediction of the fluid wall shear stress is necessary. Therefore, the decision to perform fluid-structure interaction simulations should be based on the particular variables of interest in a given

  9. The interactions between bloodstream and vascular structure on aortic dissecting aneurysmal model: A numerical study

    Science.gov (United States)

    Chen, Zeng-Sheng; Fan, Zhan-Ming; Zhang, Xi-Wen

    2013-06-01

    Stent-graft implantation is an important means of clinical treatment for aortic dissecting aneurysm (ADA). However, researches on fluid dynamics effects of stent were rare. Computer simulation was used to investigate the interactions between bloodstream and vascular structure in a stented ADA, which endures the periodic pulse velocity and pressure. We obtained and analyzed the flow velocity distribution, the wall displacement and wall stress in the ADA. By comparing the different results between a non-stented and a stented ADA, we found that the insertion of a vascular graft can make the location of maximum stress and displacement move from the aneurysm lumen wall to the artery wall, accompanied with a greatly decrease in value. These results imply that the placement of a stent-graft of any kind to occlude ADA will result in a decreased chance of rupture.

  10. 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.

  11. 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.

  12. Adipocyte in vascular wall can induce the rupture of abdominal aortic aneurysm

    Science.gov (United States)

    Kugo, Hirona; Zaima, Nobuhiro; Tanaka, Hiroki; Mouri, Youhei; Yanagimoto, Kenichi; Hayamizu, Kohsuke; Hashimoto, Keisuke; Sasaki, Takeshi; Sano, Masaki; Yata, Tatsuro; Urano, Tetsumei; Setou, Mitsutoshi; Unno, Naoki; Moriyama, Tatsuya

    2016-01-01

    Abdominal aortic aneurysm (AAA) is a vascular disease involving the gradual dilation of the abdominal aorta. It has been reported that development of AAA is associated with inflammation of the vascular wall; however, the mechanism of AAA rupture is not fully understood. In this study, we investigated the mechanism underlying AAA rupture using a hypoperfusion-induced animal model. We found that the administration of triolein increased the AAA rupture rate in the animal model and that the number of adipocytes was increased in ruptured vascular walls compared to non-ruptured walls. In the ruptured group, macrophage infiltration and the protein levels of matrix metalloproteinases 2 and 9 were increased in the areas around adipocytes, while collagen-positive areas were decreased in the areas with adipocytes compared to those without adipocytes. The administration of fish oil, which suppresses adipocyte hypertrophy, decreased the number and size of adipocytes, as well as decreased the risk of AAA rupture ratio by 0.23 compared to the triolein administered group. In human AAA samples, the amount of triglyceride in the adventitia was correlated with the diameter of the AAA. These results suggest that AAA rupture is related to the abnormal appearance of adipocytes in the vascular wall. PMID:27499372

  13. Adipocyte in vascular wall can induce the rupture of abdominal aortic aneurysm.

    Science.gov (United States)

    Kugo, Hirona; Zaima, Nobuhiro; Tanaka, Hiroki; Mouri, Youhei; Yanagimoto, Kenichi; Hayamizu, Kohsuke; Hashimoto, Keisuke; Sasaki, Takeshi; Sano, Masaki; Yata, Tatsuro; Urano, Tetsumei; Setou, Mitsutoshi; Unno, Naoki; Moriyama, Tatsuya

    2016-01-01

    Abdominal aortic aneurysm (AAA) is a vascular disease involving the gradual dilation of the abdominal aorta. It has been reported that development of AAA is associated with inflammation of the vascular wall; however, the mechanism of AAA rupture is not fully understood. In this study, we investigated the mechanism underlying AAA rupture using a hypoperfusion-induced animal model. We found that the administration of triolein increased the AAA rupture rate in the animal model and that the number of adipocytes was increased in ruptured vascular walls compared to non-ruptured walls. In the ruptured group, macrophage infiltration and the protein levels of matrix metalloproteinases 2 and 9 were increased in the areas around adipocytes, while collagen-positive areas were decreased in the areas with adipocytes compared to those without adipocytes. The administration of fish oil, which suppresses adipocyte hypertrophy, decreased the number and size of adipocytes, as well as decreased the risk of AAA rupture ratio by 0.23 compared to the triolein administered group. In human AAA samples, the amount of triglyceride in the adventitia was correlated with the diameter of the AAA. These results suggest that AAA rupture is related to the abnormal appearance of adipocytes in the vascular wall. PMID:27499372

  14. 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

  15. 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.

  16. 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....

  17. 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.

  18. 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.

  19. Moss cell walls: structure and biosynthesis

    OpenAIRE

    Alison W. Roberts; Eric M Roberts; Haigler, Candace H.

    2012-01-01

    The genome sequence of the moss Physcomitrella patens has stimulated new research examining the cell wall polysaccharides of mosses and the glycosyl transferases that synthesize them as a means to understand fundamental processes of cell wall biosynthesis and plant cell wall evolution. The cell walls of mosses and vascular plants are composed of the same classes of polysaccharides, but with differences in side chain composition and structure. Similarly, the genomes of P. patens and angiosperm...

  20. 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.

  1. 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.

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

    International Nuclear Information System (INIS)

    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 [14C]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 [14C]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

  3. Ultrastructural characteristics of the vascular wall components of ruptured atherosclerotic abdominal aortic aneurysm

    Directory of Open Access Journals (Sweden)

    Tanasković Irena

    2013-01-01

    Full Text Available The aim of this study was to determine the ultrastructural characteristics of cell populations and extracellular matrix components in the wall of ruptured atherosclerotic abdominal aortic aneurysm (AAA. We analyzed 20 samples of ruptured AAA. For orientation to the light microscopy, we used routine histochemical techniques by standard procedures. For ultrastructural analysis, we applied transmission electron microscopy (TEM. Our results have shown that ruptured AAA is characterized by the remains of an advanced atherosclerotic lesion in the intima followed by a complete absence of endothelial cells, the disruption of basal membrane and disruption of internal elastic lamina. On plaque margins as well as in the inner media we observed smooth muscle cells (SMCs that posses a euchromatic nucleus, a well-developed granulated endoplasmic reticulum around the nucleus and reduced myofilaments. The remains of the ruptured lipid core were acellular in all samples; however, on the lateral sides of ruptured plaque we observed a presence of two types of foam cells (FCs, spindle- and star-shaped. Fusiform FCs possess a well-differentiated basal lamina, caveolae and electron dense bodies, followed by a small number of lipid droplets in the cytoplasm. Star-shaped FCs contain a large number of lipid droplets and do not possess basal lamina. On the inner margins of the plaque, we observed a large number of cells undergoing apoptosis and necrosis, extracellular lipid droplets as well as a large number of lymphocytes. The media was thinned out with disorganized elastic lamellas, while the adventitia exhibited leukocyte infiltration. The presented results suggest that atherosclerotic plaque in ruptured AAA contains vascular SMC synthetic phenotype and two different types of FCs: some were derived from monocyte/macrophage lineage, while others were derived from SMCs of synthetic phenotype. The striking plaque hypocellularity was the result of apoptosis and necrosis

  4. Immersed boundary-finite element model of fluid-structure interaction in the aortic root

    Science.gov (United States)

    Flamini, Vittoria; DeAnda, Abe; Griffith, Boyce E.

    2016-04-01

    It has long been recognized that aortic root elasticity helps to ensure efficient aortic valve closure, but our understanding of the functional importance of the elasticity and geometry of the aortic root continues to evolve as increasingly detailed in vivo imaging data become available. Herein, we describe a fluid-structure interaction model of the aortic root, including the aortic valve leaflets, the sinuses of Valsalva, the aortic annulus, and the sinotubular junction, that employs a version of Peskin's immersed boundary (IB) method with a finite element description of the structural elasticity. As in earlier work, we use a fiber-based model of the valve leaflets, but this study extends earlier IB models of the aortic root by employing an incompressible hyperelastic model of the mechanics of the sinuses and ascending aorta using a constitutive law fit to experimental data from human aortic root tissue. In vivo pressure loading is accounted for by a backward displacement method that determines the unloaded configuration of the root model. Our model yields realistic cardiac output at physiological pressures, with low transvalvular pressure differences during forward flow, minimal regurgitation during valve closure, and realistic pressure loads when the valve is closed during diastole. Further, results from high-resolution computations indicate that although the detailed leaflet and root kinematics show some grid sensitivity, our IB model of the aortic root nonetheless produces essentially grid-converged flow rates and pressures at practical grid spacings for the high Reynolds number flows of the aortic root. These results thereby clarify minimum grid resolutions required by such models when used as stand-alone models of the aortic valve as well as when used to provide models of the outflow valves in models of left-ventricular fluid dynamics.

  5. Intrauterine growth restriction is associated with persistent aortic wall thickening and glomerular proteinuria during infancy

    OpenAIRE

    Zanardo, Vincenzo; Fanelli, Tiziana; Weiner, Gary; Fanos, Vassilios; Zaninotto, Martina; Visentin, Silvia; Cavallin, Francesco; Trevisanuto, Daniele; Cosmi, Erich

    2011-01-01

    Low birth weight, caused either by preterm birth or by intrauterine growth restriction, has recently been associated with increased rates of adult renal and cardiovascular disease. Since aortic intima–media thickening is a noninvasive marker of preclinical vascular disease, we compared abdominal aortic intima–media thickness among intrauterine growth restricted and equivalent gestational age fetuses in utero and at 18 months of age. The relationship between intrauterine growth restriction, fe...

  6. 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

    OpenAIRE

    Lindeman, J. H. N.; Abdul-Hussien, H.; van Bockel, J H; 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 wall protease content in a inical trial and found that doxycycline selectively reduces neutrophil-derived proteases. We thus hypothesized that doxycycline acts through an effect on ascular nflammation...

  7. [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.

  8. Effects of the Transient Blood Flow-Wall Interaction on the Wall Stress Distribution in Abdominal Aortic Aneurysm (AAA)

    Science.gov (United States)

    Tang, Rubing; Geindreau, Christian; Lasheras, Juan

    2006-11-01

    Our static finite element analysis (FEA) of both idealized and real clinical models has shown that the maximum diameter and asymmetry have substantial influence on the AAA wall stress distribution. The thrombus inside the AAA was also found to reduce the magnitude of the wall stresses. To achieve a better understanding of the wall stress distribution in real AAAs, a dynamic FEA was also performed. We considered models, both symmetric and non-symmetric, in which the aorta is assumed isotropic with nonlinear material properties. For the limiting case of rigid walls, the evolution of the flow pattern and the wall shear stresses due to fluid flow at different stages of cardiac cycle predicted by our simulations are compared with experimental results obtained in in-vitro models. A good agreement is found between both results. Finally, we have extended the analysis to the physiologically correct case of deformable walls and characterized the transient effects on the wall stresses.

  9. 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.

  10. Aneurysms: thoracic aortic aneurysms.

    Science.gov (United States)

    Chun, Kevin C; Lee, Eugene S

    2015-04-01

    Thoracic aortic aneurysms (TAAs) have many possible etiologies, including congenital heart defects (eg, bicuspid aortic valves, coarctation of the aorta), inherited connective tissue disorders (eg, Marfan, Ehlers-Danlos, Loeys-Dietz syndromes), and degenerative conditions (eg, medial necrosis, atherosclerosis of the aortic wall). Symptoms of rupture include a severe tearing pain in the chest, back, or neck, sometimes associated with cardiovascular collapse. Before rupture, TAAs may exert pressure on other thoracic structures, leading to a variety of symptoms. However, most TAAs are asymptomatic and are found incidentally during imaging for other conditions. Diagnosis is confirmed with computed tomography scan or echocardiography. Asymptomatic TAAs should be monitored with imaging at specified intervals and patients referred for repair if the TAAs are enlarging rapidly (greater than 0.5 cm in diameter over 6 months for heritable etiologies; greater than 0.5 cm over 1 year for degenerative etiologies) or reach a critical aortic diameter threshold for elective surgery (5.5 cm for TAAs due to degenerative etiologies, 5.0 cm when associated with inherited syndromes). Open surgery is used most often to treat asymptomatic TAAs in the ascending aorta and aortic arch. Asymptomatic TAAs in the descending aorta often are treated medically with aggressive blood pressure control, though recent data suggest that endovascular procedures may result in better long-term survival rates. PMID:25860136

  11. Computational 3D fluid-structure interaction for the aortic valve

    Science.gov (United States)

    Luo, Haoxiang; Chen, Ye; Sun, Wei

    2015-11-01

    Three-dimensional fluid-structure interaction (FSI) involving large deformations of flexible bodies is common in biological systems. A typical example is the heart valves. Accurate and efficient numerical approaches for modeling such systems are still lacking. In this work, we report a successful case of combining an immersed-boundary flow solver with a nonlinear finite-element solid-dynamics solver, both in-house programs, specifically for three-dimensional simulations. Based on the Cartesian grid, the viscous incompressible flow solver can handle boundaries of large displacements with simple mesh generation. The solid-dynamics solver has separate subroutines for analyzing general three-dimensional bodies and thin-walled structures composed of frames, membranes, and plates. Both geometric nonlinearity associated with large displacements and material nonlinearity associated with large strains are incorporated in the solver. The FSI is achieved through a strong coupling and partitioned approach. We have performed several benchmarking cases to validate the FSI solver. Application to the native aortic valve will be demonstrated. Supported by the NSF grant (CBET-1066962).

  12. 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.

  13. 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.

  14. 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...

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

    International Nuclear Information System (INIS)

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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

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

    Science.gov (United States)

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

    2016-01-01

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

  2. Aortic Aneurysm Repair

    Medline Plus

    Full Text Available ... wall will actually thin out. And the big risk here is that if this gets too big ... to the aging baby boomers. Next slide. The risk factors for abdominal aortic aneurysms are males over ...

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

    OpenAIRE

    Martine eGonneau; Herman eHöfte; Samantha eVernhettes

    2012-01-01

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

  4. Fluorescent tags to explore cell wall structure and dynamics

    OpenAIRE

    Gonneau, Martine; Höfte, Herman; Vernhettes, Samantha

    2012-01-01

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

  5. A two-system, single-analysis, fluid-structure interaction technique for modelling abdominal aortic aneurysms.

    Science.gov (United States)

    Kelly, S C; O'Rourke, M J

    2010-01-01

    This work reports on the implementation and validation of a two-system, single-analysis, fluid-structure interaction (FSI) technique that uses the finite volume (FV) method for performing simulations on abdominal aortic aneurysm (AAA) geometries. This FSI technique, which was implemented in OpenFOAM, included fluid and solid mesh motion and incorporated a non-linear material model to represent AAA tissue. Fully implicit coupling was implemented, ensuring that both the fluid and solid domains reached convergence within each time step. The fluid and solid parts of the FSI code were validated independently through comparison with experimental data, before performing a complete FSI simulation on an idealized AAA geometry. Results from the FSI simulation showed that a vortex formed at the proximal end of the aneurysm during systolic acceleration, and moved towards the distal end of the aneurysm during diastole. Wall shear stress (WSS) values were found to peak at both the proximal and distal ends of the aneurysm and remain low along the centre of the aneurysm. The maximum von Mises stress in the aneurysm wall was found to be 408kPa, and this occurred at the proximal end of the aneurysm, while the maximum displacement of 2.31 mm occurred in the centre of the aneurysm. These results were found to be consistent with results from other FSI studies in the literature. PMID:20923114

  6. 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.

  7. 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

  8. 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.

  9. Thin-walled compliant plastic structures for mesoscale fluidic systems

    Science.gov (United States)

    Miles, Robin R.; Schumann, Daniel L.

    1999-06-01

    Thin-walled, compliant plastic structures for meso-scale fluidic systems were fabricated, tested and used to demonstrate valving, pumping, metering and mixing. These structures permit the isolation of actuators and sensors form the working fluid, thereby reducing chemical compatibility issues. The thin-walled, compliant plastic structures can be used in either a permanent, reusable system or as an inexpensive disposable for single-use assay systems. The implementation of valving, pumping, mixing and metering operations involve only an elastic change in the mechanical shape of various portions of the structure. Advantages provided by the thin-walled plastic structures include reduced dead volume and rapid mixing. Five different methods for fabricating the thin-walled plastic structures discussed including laser welding, molding, vacuum forming, thermal heat staking and photolithographic patterning techniques.

  10. ED 02-3 CLINICAL IMPLICATIONS OF CENTRAL HEMODYNAMICS ON AORTIC AND END-ORGAN DISEASES.

    Science.gov (United States)

    Hashimoto, Junichiro

    2016-09-01

    The central aorta constitutes the main trunk of the systemic arterial tree. It dilates passively with cardiac ejection during systole and then constricts with its recoil function during diastole, thereby regulating blood pressure and blood flow. The central pulsatile hemodynamics affects local hemodynamics within as well as downstream of the aorta (e.g., end organs).The aorta progressively stiffens and dilates with advancing age, and such age-dependent change is accelerated by hypertension. According to the law of Laplace, wall stress depends on the diameter and pressure of the blood vessel. This has been confirmed by substantial studies which have associated baseline aortic diameter with subsequent development of aortic dissection and progressive dilatation of aortic lumen. This law can also imply potential importance of local pressure within the aorta (i.e., the central pressure) in predicting the development and progression of aortic aneurysms.Several previous studies have shown that hypertension (together with age and obesity) is related to dilatation of the proximal ascending aorta (rather than of the aortic root). In addition, aortic blood flow abnormality may also be importantly related to aortic dilatation because of strong positive association between the diastole flow reversal and lumen diameter in the proximal thoracic aorta. As for the abdominal (infrarenal) aorta, aneurysmal development and progression have been attributed to aortic segmental stiffening (of the bifurcational versus infrarenal segment) and aortic pressure elevation, respectively.Central pulsatile pressure not only represents aortic wall stress but also determines cardiac afterload and microvascular wall stress in the brain and kidney. Central pulsatile flow (in both directions) could also affect the flow distribution into the upper and lower parts of the body and control end-organ function. Aortic structural change (including segmental stiffening and aneurysmal formation) causes central

  11. Aortic insufficiency

    Science.gov (United States)

    ... Heart valve - aortic regurgitation; Valvular disease - aortic regurgitation; AI - aortic insufficiency ... BA. Valvular heart disease. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine . 25th ed. Philadelphia, PA: ...

  12. 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.

  13. The adventitia: essential regulator of vascular wall structure and function.

    Science.gov (United States)

    Stenmark, Kurt R; Yeager, Michael E; El Kasmi, Karim C; Nozik-Grayck, Eva; Gerasimovskaya, Evgenia V; Li, Min; Riddle, Suzette R; Frid, Maria G

    2013-01-01

    The vascular adventitia acts as a biological processing center for the retrieval, integration, storage, and release of key regulators of vessel wall function. It is the most complex compartment of the vessel wall and is composed of a variety of cells, including fibroblasts, immunomodulatory cells (dendritic cells and macrophages), progenitor cells, vasa vasorum endothelial cells and pericytes, and adrenergic nerves. In response to vascular stress or injury, resident adventitial cells are often the first to be activated and reprogrammed to influence the tone and structure of the vessel wall; to initiate and perpetuate chronic vascular inflammation; and to stimulate expansion of the vasa vasorum, which can act as a conduit for continued inflammatory and progenitor cell delivery to the vessel wall. This review presents the current evidence demonstrating that the adventitia acts as a key regulator of vascular wall function and structure from the outside in. PMID:23216413

  14. Cell wall structure and biogenesis in Aspergillus species.

    Science.gov (United States)

    Yoshimi, Akira; Miyazawa, Ken; Abe, Keietsu

    2016-09-01

    Aspergillus species are among the most important filamentous fungi from the viewpoints of industry, pathogenesis, and mycotoxin production. Fungal cells are exposed to a variety of environmental stimuli, including changes in osmolality, temperature, and pH, which create stresses that primarily act on fungal cell walls. In addition, fungal cell walls are the first interactions with host cells in either human or plants. Thus, understanding cell wall structure and the mechanism of their biogenesis is important for the industrial, medical, and agricultural fields. Here, we provide a systematic review of fungal cell wall structure and recent findings regarding the cell wall integrity signaling pathways in aspergilli. This accumulated knowledge will be useful for understanding and improving the use of industrial aspergilli fermentation processes as well as treatments for some fungal infections. PMID:27140698

  15. 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.

  16. Effects of candesartan cilexetil and amlodipine orotate on receptor for advanced glycation end products expression in the aortic wall of Otsuka Long-Evans Tokushima Fatty (OETFF) type 2 diabetic rats.

    Science.gov (United States)

    Kang, Min-Kyu; Chung, Woo-Baek; Hong, Seul-Ki; Kim, Ok-Ran; Ihm, Sang-Hyun; Chang, Kiyuk; Seung, Ki-Bae

    2016-04-01

    The receptor for advanced glycation end products (RAGE) plays a key role in the development of vascular inflammation and acceleration of atherosclerosis in type 2 diabetes. We investigated the effect of candesartan cilexetil (CDRT) and amlodipine orotate (AMDP) on the expression of RAGE in the aortic walls of Otsuka Long-Evans Tokushima Fatty (OLETF) rats and AGE-treated endothelial cells. Twenty five-week-old OLETF rats were randomized to 8 week treatments consisting of CDRT (n = 8), AMDP (n = 8) or saline (control, n = 8). Immunohistochemical and dihydroethidine staining revealed reduced RAGE and reactive oxygen species (ROS) signals in rats treated with CDRT or AMDP compared with control rats. Both CDRT and AMDP suppressed the expression of p22phox and p47phox NADPH oxidase subunits. However, only CDRT significantly reduced expression of phosphorylated extracellular signal regulated kinase (pERK)1/2 in the aortic wall of OLETF rats. In addition, both drugs reduced RAGE expression and total and mitochondrial ROS production in the AGE-treated endothelial cells. Both ARBs and CCBs reduced RAGE expression in the aortic walls of OLETF rats, which was attributed to decreased ROS production through inhibition of NADPH oxidase. In addition, only CDRT reduced aortic expression of RAGE via suppression of the ERK1/2 pathway unlike AMDP. PMID:26960737

  17. 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

  18. 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.

  19. 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.

  20. Mirror Domain Structures Induced by Interlayer Magnetic Wall Coupling

    Science.gov (United States)

    Lew, W. S.; Li, S. P.; Lopez-Diaz, L.; Hatton, D. C.; Bland, J. A.

    2003-05-01

    We have found that during giant magnetoresistance measurements in ˜10×10 mm2 NiFe/Cu/Co continuous film spin-valve structures, the resistance value suddenly drops to its absolute minimum during the NiFe reversal. The results reveal that the alignment of all magnetic domains in the NiFe film follow exactly that of corresponding domains in the Co film for an appropriate applied field strength. This phenomenon is caused by trapping of the NiFe domain walls through the magnetostatic interaction with the Co domain-wall stray fields. Consequently, the interlayer domain-wall coupling induces a mirror domain structure in the magnetic trilayer.

  1. 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.

  2. Mirror domain structures induced by interlayer magnetic wall coupling.

    Science.gov (United States)

    Lew, W S; Li, S P; Lopez-Diaz, L; Hatton, D C; Bland, J A C

    2003-05-30

    We have found that during giant magnetoresistance measurements in approximately 10 x 10 mm(2) NiFe/Cu/Co continuous film spin-valve structures, the resistance value suddenly drops to its absolute minimum during the NiFe reversal. The results reveal that the alignment of all magnetic domains in the NiFe film follow exactly that of corresponding domains in the Co film for an appropriate applied field strength. This phenomenon is caused by trapping of the NiFe domain walls through the magnetostatic interaction with the Co domain-wall stray fields. Consequently, the interlayer domain-wall coupling induces a mirror domain structure in the magnetic trilayer. PMID:12786582

  3. Material and structural instabilities of single-wall carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    J. Wu; K. C. Hwang; J. Song; Y. Huang

    2008-01-01

    The nonlinear atomistic interactions usually involve softening behavior. Instability resulting directly from this softening are called the material instability, while those unrelated to this softening are called the structural instability. We use the finite-deformation shell theory based on the interatomic potential to show that the tension instability of single-wall carbon nanotubes is the material instability, while the compression and torsion instabilities are structural instability.

  4. Aortic Aneurysm

    Science.gov (United States)

    ... Most aneurysms are in the aorta, the main artery that runs from the heart through the chest and abdomen. There are two types of aortic aneurysm: Thoracic aortic aneurysms (TAA) - these occur in the part of the aorta running through the chest Abdominal aortic aneurysms (AAA) - these occur in the part ...

  5. 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.

  6. Cytokine amplification and macrophage effector functions in aortic inflammation and abdominal aortic aneurysm formation.

    Science.gov (United States)

    Ijaz, Talha; Tilton, Ronald G; Brasier, Allan R

    2016-08-01

    On April 29, 2015, Son and colleagues published an article entitled "Granulocyte macrophage colony-stimulating factor (GM-CSF) is required for aortic dissection/intramural haematoma" in Nature Communications. The authors observed that the heterozygous Kruppel-like transcription factor 6 (KLF6) deficiency or absence of myeloid-specific KLF6 led to upregulation of macrophage GM-CSF expression, promoted the development of aortic hematoma/dissection, and stimulated abdominal aortic aneurysm (AAA) formation when the vessel wall was subjected to an inflammatory stimulus. The additional findings of increased adventitial fibrotic deposition, marked infiltration of macrophages, and increased expression of matrix metalloprotease-9 (MMP-9) and IL-6 were blocked with neutralizing GM-CSF antibodies, or recapitulated in normal mice with excess GM-CSF administration. The authors concluded that GM-CSF is a key regulatory molecule in the development of AAA and further suggested that activation of GM-CSF is independent of the transforming growth factor β (TGFβ)-Smad pathway associated with the Marfan aortic pathology. In this perspective, we expand on this mechanism, drawing from previous studies implicating a similar essential role for IL-6 signaling in macrophage activation, Th17 expansion and aortic dissections. We propose a sequential "two-hit" model of vascular inflammation involving initial vascular injury followed by recruitment of Ly6C(hi) macrophages. Aided by fibroblast interactions inflammatory macrophages produce amplification of IL-6 and GM-CSF expression that converge on a common, pathogenic Janus kinase (JAK)-signal transducers and activations of transcription 3 (STAT3) signaling pathway. This pathway stimulates effector functions of macrophages, promotes differentiation of Th17 lymphocytes and enhances matrix metalloproteinase expression, ultimately resulting in deterioration of vascular wall structural integrity. Further research evaluating the impact of

  7. Structure of single-wall carbon nanotubes: a graphene helix.

    Science.gov (United States)

    Lee, Jae-Kap; Lee, Sohyung; Kim, Jin-Gyu; Min, Bong-Ki; Kim, Yong-Il; Lee, Kyung-Il; An, Kay Hyeok; John, Phillip

    2014-08-27

    Evidence is presented in this paper that certain single-wall carbon nanotubes are not seamless tubes, but rather adopt a graphene helix resulting from the spiral growth of a nano-graphene ribbon. The residual traces of the helices are confirmed by high-resolution transmission electron microscopy and atomic force microscopy. The analysis also shows that the tubular graphene material may exhibit a unique armchair structure and the chirality is not a necessary condition for the growth of carbon nanotubes. The description of the structure of the helical carbon nanomaterials is generalized using the plane indices of hexagonal space groups instead of using chiral vectors. It is also proposed that the growth model, via a graphene helix, results in a ubiquitous structure of single-wall carbon nanotubes. PMID:24838196

  8. Congenital aortic regurgitation in a child with a tricuspid non-stenotic aortic valve.

    OpenAIRE

    Hashimoto, R; Miyamura, H; Eguchi, S

    1984-01-01

    After follow up for seven years a 10 year old boy with congenital aortic regurgitation was found to have a tricuspid non-stenotic aortic valve at operation. The right coronary cusp was dysplastic, thickened, and contracted; the gap between its free margin and aortic wall was bridged with two fibrous bands; and the left coronary and non-coronary cusps were almost normal. The aortic valve was replaced with a prosthesis (St Jude Medical No 23), and the postoperative course was uneventful.

  9. 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.

  10. 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...

  11. 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.

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

    International Nuclear Information System (INIS)

    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

  13. 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

  14. X-ray structure of engineered human Aortic Preferentially Expressed Protein-1 (APEG-1

    Directory of Open Access Journals (Sweden)

    Scheich Christoph

    2005-12-01

    Full Text Available Abstract Background Human Aortic Preferentially Expressed Protein-1 (APEG-1 is a novel specific smooth muscle differentiation marker thought to play a role in the growth and differentiation of arterial smooth muscle cells (SMCs. Results Good quality crystals that were suitable for X-ray crystallographic studies were obtained following the truncation of the 14 N-terminal amino acids of APEG-1, a region predicted to be disordered. The truncated protein (termed ΔAPEG-1 consists of a single immunoglobulin (Ig like domain which includes an Arg-Gly-Asp (RGD adhesion recognition motif. The RGD motif is crucial for the interaction of extracellular proteins and plays a role in cell adhesion. The X-ray structure of ΔAPEG-1 was determined and was refined to sub-atomic resolution (0.96 Å. This is the best resolution for an immunoglobulin domain structure so far. The structure adopts a Greek-key β-sandwich fold and belongs to the I (intermediate set of the immunoglobulin superfamily. The residues lying between the β-sheets form a hydrophobic core. The RGD motif folds into a 310 helix that is involved in the formation of a homodimer in the crystal which is mainly stabilized by salt bridges. Analytical ultracentrifugation studies revealed a moderate dissociation constant of 20 μM at physiological ionic strength, suggesting that APEG-1 dimerisation is only transient in the cell. The binding constant is strongly dependent on ionic strength. Conclusion Our data suggests that the RGD motif might play a role not only in the adhesion of extracellular proteins but also in intracellular protein-protein interactions. However, it remains to be established whether the rather weak dimerisation of APEG-1 involving this motif is physiogically relevant.

  15. Moisture and Structural Analysis for High Performance Hybrid Wall Assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Grin, A. [Building Science Corporation (BSC), Somerville, MA (United States); Lstiburek, J. [Building Science Corporation (BSC), Somerville, MA (United States)

    2012-09-01

    Based on past experience in the Building America program, BSC has found that combinations of materials and approaches—in other words, systems—usually provide optimum performance. Integration is necessary, as described in this research project. The hybrid walls analyzed utilize a combination of exterior insulation, diagonal metal strapping, and spray polyurethane foam and leave room for cavity-fill insulation. These systems can provide effective thermal, air, moisture, and water barrier systems in one assembly and provide structure.

  16. 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.

  17. SSI response of a typical shear wall structure

    International Nuclear Information System (INIS)

    The seismic response of a typical shear structure in a commercial nuclear power plant was investigated for a series of site and foundation conditions using best estimate and design procedures. The structure selected is a part of the Zion AFT complex which is a connected group of reinforced concrete shear wall buildings, typical of nuclear power plant structures. Comparisons between best estimate responses quantified the effects of placing the structure on different sites and founding it in different manners. Calibration factors were developed by comparing simplified SSI design procedure responses to responses calculated by best estimate procedures. Nineteen basic cases were analyzed - each case was analyzed for ten earthquakes targeted to the NRC R.G. 1.60 design response spectra. The structure is a part of the Zion auxiliary-fuel handling turbine building (AFT) complex to the Zion nuclear power plants. (orig./HP)

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

    OpenAIRE

    Dong Lan

    2016-01-01

    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 differ...

  19. Domain wall structure transformations in epitaxial ferrite garnet films

    International Nuclear Information System (INIS)

    Dynamic characteristics of domain walls (DW) in the process of the transformation of their structure occuring under the static field effect in the film plane are investigated. The epitaxiat ferrite-garnet film of the (YSmBa)3(FeGa)5O12 composition with parameters: 4πM=178 Gs (M=saturation magnetization), quality factor approximately equal to 10, thickness = 6.5 μm, band domain structure period = 13.5 μm has been studied. The signal of DW resonance oscillations excited by radio-frequency field with amplitude 0.01:1 Oe, oscillating along the slight magnetization axis perpendicular to the film plane has been observed. The constant magnetic field, H, in the film plane is oriented along the DW and is used not only for the transformation of DW structure but also for changing its resonance frequency by changing it effective mass. The results presented testify to the fact that the resonance methods may be successfully used not only for studying the DW dynamics but also for investigating into the domain wall structure and the process of its transformation

  20. 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.

  1. Distortional Mechanics of Thin-Walled Structural Elements

    DEFF Research Database (Denmark)

    Andreassen, Michael Joachim

    In several industries such as civil, mechanical, and aerospace, thin-walled structures are often used due to the high strength and effective use of the materials. Because of the increased consumption there has been increasing focus on optimizing and more detailed calculations. However, finely...... by discretization of the cross section are now solved analytically and the formulation is valid without special attention and approximation also for closed single or multi-cell cross sections. Furthermore, the found eigenvalues have clear mechanical meaning, since they represent the attenuation of the distortional...

  2. 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.

  3. Aortic wall proteomic analysis in spontaneously hypertensive rats with a blood pressure decrease induced by 6-week load-free swimming

    OpenAIRE

    Feng, Hong; Li, Haiying; ZHANG, DERONG; ZHAO, YUNGANG; Jiang, Ning; Zhao, Xiaoling; Zhang, Yu; TAN, JUNZHEN; Fang, Wen; Zhang, Yong; Liu, Wei

    2015-01-01

    Decreased arterial compliance is one of the earliest detectable manifestations of adverse structural and functional changes within the vessel wall in hypertension. The proteomic approach is a powerful technique to analyze a complex mixture of proteins in various settings. Physical activity level was negatively associated with blood pressure. Sixteen 4-week-old male spontaneously hypertensive rats (SHR) and 16 Wistar-Kyoto (WKY) rats were randomly divided into four groups: i) SHR exercise grou...

  4. 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

  5. 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...

  6. 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...

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

    Science.gov (United States)

    Fakher, Sundes; Nejm, Razan; Ayesh, Ahmad; Al-Ghaferi, Amal; Zeze, Dagou; Mabrook, Mohammed

    2016-01-01

    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. PMID:27598112

  8. 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.

  9. 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.

  10. 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.

  11. Effect of wall structure on pebble stagnation behavior in pebble bed reactor

    International Nuclear Information System (INIS)

    Highlights: • DEM study of wall structure role in preventing near wall crystallization is carried out. • Suggestions on pebble’s kinematic parameters and wall structure design are provided. • Triangle is better than arc and sawtooth shapes for wall structure design. • Wall structure size should be close to the scale of pebble diameter. • Suitable intervals can prevent crystallization without significantly increasing the flow resistance. - Abstract: Crystallization of pebbles in pebble bed is a crucial problem in high temperature gas-cooled pebble-bed reactors. This phenomenon usually happens along the internal surface and leads to a large number of stagnated pebbles, which poses a threat to reactor safety. In real reactor engineering, wall structures have been utilized to avoid this problem. This article verifies the crystallization phenomenon through DEM (discrete element method) simulation, and explains how wall structures work in preventing crystallization. Moreover, several kinematic parameters have been adopted to evaluate wall structures with different shapes, sizes and intervals. Detailed information shows the impact of wall structure on flow field in pebble bed. Lastly, the preferred characteristics of an effective wall structure are suggested for reactor engineering

  12. Aortic stenting.

    Science.gov (United States)

    Droc, Ionel; Calinescu, Francisca Blanca; Droc, Gabriela; Blaj, Catalin; Dammrau, Rolf

    2015-01-01

    The approach to aortic pathology is nowadays more and more endovascular at both thoracic and abdominal levels. Thoracic stenting has gained worldwide acceptance as first intention to treat pathologies of the descending thoracic aorta. Indications have been extended to aortic arch aneurysms and also to diseases of the ascending aorta. The current devices in use for thoracic endovascular repair (TEVAR) are Medtronic Valiant, Gore TAG, Cook Tx2 and Jotec. The choice of the endograft depends on the thoracic aortic pathology and the anatomical suitability. The technological evolution of the abdominal aortic endografts was very rapid, arriving now at the fourth generation. We report the results of 55 elective cases of endovascular abdominal aortic repair (EVAR) performed in two vascular surgical centers in Romania and Germany. The prostheses used were 16 E-vita Abdominal XT, 12 Excluder, eight Talent, seven PowerLink, three Endurant and nine custom-made, fenestrated or branched from Jotec. The mean follow-up was 18 months with CT-scan, duplex ultrasound and contrast-enhanced ultrasound. The mortality was 2%. EVAR tends to become the gold standard for abdominal aortic aneurysm repair. Technological development of the devices with lowest profile introduction systems will permit to extend the anatomical indications to new frontiers. PMID:26200430

  13. Elastoplastic analysis of thin-walled structures in reservoir area

    Institute of Scientific and Technical Information of China (English)

    段绍伟; 罗迎社; 朱育雄

    2008-01-01

    In the structural design of the high pier,in order to analyze the strength and structure stability,the pier was often considered a thin-walled structure.Elastoplastic incremental theory was used to establish the model of elastoplastic stability of high pier.By considering the combined action of pile,soil and pier together,the destabilization bearing capacity was calculated by using 3-D finite element method(3-D FEM) for piers with different pile and section height.Meanwhile,the equivalent stress in different sections of pier was computed and the processor of destabilization was discussed.When the pier is lower,the bearing capacity under mutual effect of pile,soil and pier is less than the situation when mutual effect is not considered;when the pier is higher,their differences are not conspicuous.Along with the increase of the cross-sectional height,the direction of destabilization bearing capacity is varied and the ultimate capacity is buildup.The results of a stability analysis example are almost identical with the practice.

  14. wall

    Directory of Open Access Journals (Sweden)

    Irshad Kashif

    2016-01-01

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

  15. Clinical application of CT virtual endoscopy in the diagnosis of aortic diseases

    International Nuclear Information System (INIS)

    Objective: To evaluate the display ability and the clinical application of CT virtual endoscopy (CTVE) in the diagnosis of aortic disease. Methods: In this group, 147 cases with clinically suspected aortic disease (113 males, 34 females) underwent CTVE and 58 cases had DSA for comparison. 37 cases were confirmed by operation. Results: (1) In the 147 cases, 139 cases showed successful CTVE images. (2) CTVE images could clearly show the inner wall and inner structures of the vessels, the true and false luminal of aortic dissections, and the lesion of false aneurysm. Conclusion: CTVE could provide more information of the vessel by displaying the inner wall and allowing users to map the vessels in a display. It is helpful in correct diagnosis and guiding surgery

  16. 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

  17. Earthquake-induced shear concentration in shear walls above transfer structures

    OpenAIRE

    Su, RKL; Cheng, MH

    2009-01-01

    Due to various architectural constraints and multi-functional requirements for modern buildings, combined structural forms, which typically include shear wall systems in higher zones and moment-resisting frames together with core walls in lower zones, are commonly used for these buildings. Transfer structures are often introduced to transfer the loads from higher to lower zones. Previous experimental and numerical studies have demonstrated that the exterior walls above the transfer structure ...

  18. Xyloglucans from flaxseed kernel cell wall: Structural and conformational characterisation.

    Science.gov (United States)

    Ding, Huihuang H; Cui, Steve W; Goff, H Douglas; Chen, Jie; Guo, Qingbin; Wang, Qi

    2016-10-20

    The structure of ethanol precipitated fraction from 1M KOH extracted flaxseed kernel polysaccharides (KPI-EPF) was studied for better understanding the molecular structures of flaxseed kernel cell wall polysaccharides. Based on methylation/GC-MS, NMR spectroscopy, and MALDI-TOF-MS analysis, the dominate sugar residues of KPI-EPF fraction comprised of (1,4,6)-linked-β-d-glucopyranose (24.1mol%), terminal α-d-xylopyranose (16.2mol%), (1,2)-α-d-linked-xylopyranose (10.7mol%), (1,4)-β-d-linked-glucopyranose (10.7mol%), and terminal β-d-galactopyranose (8.5mol%). KPI-EPF was proposed as xyloglucans: The substitution rate of the backbone is 69.3%; R1 could be T-α-d-Xylp-(1→, or none; R2 could be T-α-d-Xylp-(1→, T-β-d-Galp-(1→2)-α-d-Xylp-(1→, or T-α-l-Araf-(1→2)-α-d-Xylp-(1→; R3 could be T-α-d-Xylp-(1→, T-β-d-Galp-(1→2)-α-d-Xylp-(1→, T-α-l-Fucp-(1→2)-β-d-Galp-(1→2)-α-d-Xylp-(1→, or none. The Mw of KPI-EPF was calculated to be 1506kDa by static light scattering (SLS). The structure-sensitive parameter (ρ) of KPI-EPF was calculated as 1.44, which confirmed the highly branched structure of extracted xyloglucans. This new findings on flaxseed kernel xyloglucans will be helpful for understanding its fermentation properties and potential applications. PMID:27474598

  19. 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.

  20. Balloon aortic valvuloplasty as a bridge to aortic valve surgery for severe aortic stenosis.

    Science.gov (United States)

    Nwaejike, Nnamdi; Mills, Keith; Stables, Rod; Field, Mark

    2015-03-01

    A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was, in patients with severe aortic stenosis, can balloon valvuloplasty be used as a bridge to aortic valve replacement? Altogether 463 papers were found using the reported search, of which 11 papers represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. We conclude that balloon aortic valvuloplasty is recommended as a bridge to aortic valve replacement (AVR) or transcatheter aortic valve implantation (TAVI) in patients with severe symptomatic aortic stenosis. Institutional practices, local and logistic factors can affect patient selection and management approaches to severe aortic stenosis, but having the facility to offer balloon aortic valvuloplasty (especially in the TAVI era) provides another management option for patients who would otherwise have been considered unacceptably high risk for aortic valve surgery. The increased incidence of balloon aortic valvuloplasty mirrors the increase in the use of TAVI with a sharp increase in activity from 2006. Success rates for bridging from balloon aortic valvuloplasty to definite surgical intervention are in the range 26.3-74%, with AVR or TAVI occurring within 8 weeks to 7 months. Complications from balloon aortic valvuloplasty such as aortic regurgitation (AR) can be managed successfully. Up to 40% of patients selected by balloon aortic valvuloplasty to have TAVI or AVR do not have these procedures within 2 years. While most of these patients are excluded for objective clinical reasons such as terminal disease/malignancy or other persistent contraindication, some patients refuse definitive treatment and others die while on the waiting list. Outcomes in patients bridged to AVR/TAVI are better than in patients treated with balloon aortic valvuloplasty

  1. Contemporary Management of Type B Aortic Dissection in the Endovascular Era.

    Science.gov (United States)

    Bannazadeh, Mohsen; Tadros, Rami O; McKinsey, James; Chander, Rajiv; Marin, Michael L; Faries, Peter L

    2016-04-01

    Aortic dissection (AD) is one of the most common catastrophic pathologies affecting the aorta. Anatomic classification is based on the origin of entry tear and its extension. Type A dissections originate in the ascending aorta, whereas the entry tear in Type B dissections starts distal to the left subclavian artery. The patients with aortic dissection who manifest complications such as rupture, malperfusion, aneurysmal degeneration, and intractable pain are classified as complicated AD. Risk factors for developing aortic dissection include age, male gender, and aortic wall structural abnormalities. The most common presenting symptom of acute aortic dissection is pain. Malperfusion occurs as a result of end-organ ischemia due to involvement of aortic branches from the dissecting process. This can happen in various locations causing mesenteric ischemia (mesenteric vessels), stroke (aortic arch vessels), renal failure (renal arteries), spinal ischemia, and limb ischemia (iliac or subclavian arteries). Aneurysmal degeneration is the most common complication of patients with chronic Type B dissection who are managed with medical therapy. Management of Type B aortic dissection (TBAD) remains controversial. Many groups recommend conservative therapy for newly diagnosed TBAD and reserve surgical management for patients who develop complications such as rupture, malperfusion, aneurysmal dilatation, and refractory pain. The mainstay of medical therapy includes antihypertensive medication to reduced ΔP/ ΔT by lowering blood pressure and heart rate. With the continued success of thoracic endovascular aortic repair (TEVAR), this procedure has been extended to treat TBAD in selected patients. The outcomes of TEVAR are promising, with early mortality rates from 10% to 20%. With promising results from these series, some groups recommend early TEVAR in uncomplicated TBAD to prevent future adverse events. The goals of endovascular treatment of TBAD are to cover the entry tear

  2. 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

  3. 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.

  4. 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.

  5. [Esophageal wall structure in people of elderly and senile age].

    Science.gov (United States)

    aminova, G G; Grigorenko, D E; Sapin, M R; Mkhitarov, V A

    2014-01-01

    Using histological methods, the esophageal wall structure and the cytoarchitectonics of mucous membrane were studied in the individuals of elderly (n = 5) and senile (n = 10) age. The control group included the individuals of I (n = 3) and II (n = 3) periods of mature age. It was demonstrated that with advancing age in most cases the destructive processes took place in the epithelium (delamination of the layer, separation of large fragments, formation of microerosions etc.) in most of the studied cases. Lymphocytes, neutrophils and eosinophils were found between the epithelial cells; the numbers of infiltrating cells was increased 2-3 times during aging. Mucosal lamina propria and the submucosa, in particular, were characterized by the thickening of the bundles of collagen fibers. A two-fold increase in the number of the cells of the fibroblast lineage was found. The number of leukocytes in the lamina propria was increased by the eldery age in the upper and lower parts of the esophagus (3.5 and 1.75 times respectively). The changes in lamina muscularis were manifested by its thinning, delamination and myocyte dissociation. Remodeling of the muscular tunic was less pronounced. The degree of changes increased distally and varied widely depending on the individual peculiarities. PMID:25282822

  6. 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.

  7. Limit load analysis of thick-walled concrete structures

    International Nuclear Information System (INIS)

    The paper illustrates the interaction of constitutive modeling and finite element solution techniques for limit load prediction of concrete structures. On the constitutive side, an engineering model of concrete fracture is developed in which the Mohr-Coulomb criterion is augmented by tension cut-off to describe incipient failure. Upon intersection with the stress path the failure surface collapses for brittle behaviour according to one of three softening rules, no-tension, no-cohesion, and no-friction. The stress transfer accompanying the energy dissipation during local failure is modelled by several fracture rules which are examined with regard to ultimate load prediction. On the numerical side the effect of finite element idealization is studied first as far as ultimate load convergence is concerned. Subsequently, incremental tangential and initial load techniques are compared together with the effect of step size. Limit load analyses of a thick-walled concrete ring and a lined concrete reactor closure conclude the paper with examples from practical engineering. (orig.)

  8. 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.

  9. [Aortic aneurysm].

    Science.gov (United States)

    Villar, Fernando; Pedro-Botet, Juan; Vila, Ramón; Lahoz, Carlos

    2013-01-01

    Aortic aneurysm is one important cause of death in our country. The prevalence of abdominal aortic aneurism (AAA) is around 5% for men older than 50 years of age. Some factors are associated with increased risk for AAA: age, hypertension, hypercholesterolemia, cardiovascular disease and, in particular, smoking. The medical management of patients with an AAA includes cardiovascular risk treatment, particularly smoking cessation. Most of major societies guidelines recommend ultrasonography screening for AAA in men aged 65 to 75 years who have ever smoked because it leads to decreased AAA-specific mortality. PMID:24238836

  10. 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.)

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Methods of first wall structural analysis with applications to the long pulse commercial tokamak reactor design

    International Nuclear Information System (INIS)

    Methods of analysis for fusion first wall design are developed. Several design limits have been evaluated and combined to present trade-offs in the form of design windows. These considerations include limits related to thermal fatigue, primary membrane strength, displacement under loading, ratcheting, radiation damage, and plasma-wall interactions. Special emphasis is placed on the investigation of thermal fatigue using a two dimensional treatment of a tubular first wall configuration. The work is motivated by the proposal of the Ultra Long Pulse Commercial Reactor (ULTR), a machine capable of delivering plasma burn pulses of up to 24 hours in length. The present work looks in detail at the impact of pertinent characteristics of the ULTR design such as pulse length, coolant pressure, first wall thickness and first wall lifetime on the structural effects considered. Computer programs are developed and consider several major structural effects on a cylindrical first wall element for both 316 stainless steel and vanadium alloy

  16. Structural ordering of multi-walled carbon nanotubes (MWCNTs) caused by gamma (γ)-ray irradiation

    International Nuclear Information System (INIS)

    Multi-walled carbon nanotubes (MWCNTs) were irradiated by Gamma (γ)-rays in air with absorbed doses of 25 and 50 kGy. As a result of γ-ray irradiation, the inter-wall distance of MWCNTs was decreased and their graphitic order was improved. The reduction in inter-wall distance and structural ordering was improved with the increasing dosage of irradiation. Experimental evidences are provided by powder XRD and micro-Raman analyses

  17. 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.

  18. 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.

  19. Seismic Behavior of Multi-story Structural Walls under Cyclic Lateral Loading: Experimental Study

    Directory of Open Access Journals (Sweden)

    Jiyang Wang

    2012-08-01

    Full Text Available The objective of this study was to investigate the seismic force resisting mechanisms of structural walls considering the interaction with the foundation beam, ground floor slabs and piles that supported the walls. Experimental tests were conducted on two 15% scale sub-assemblage specimens of the bottom three stories of a twenty-story structural wall. The structural walls were of monolithic construction for one specimen and of precast shear wall construction for the other. Cyclic lateral loads were applied with proportionally varying vertical loads to simulate loading conditions for the twenty-story prototype building. Conclusions were drawn concerning the deformation capacity and the strength deterioration after maximum strength shown by the walls. Contrary to the design, the yielding of the shear wall preceded the yielding of the foundation beam. Flexure-shear cracks of the shear wall penetrated the slabs transversely and developed to the foundation beam. At the ultimate state, the shear wall separated along these cracks involving the parts of the foundation beam, the pile, the transverse foundation beam and the slabs. These experimental phenomena clarified the monolithic action between the foundation beam and peripheral members.

  20. 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.

  1. Shaking table experimental study of recycled concrete frame-shear wall structures

    Science.gov (United States)

    Zhang, Jianwei; Cao, Wanlin; Meng, Shaobin; Yu, Cheng; Dong, Hongying

    2014-06-01

    In this study, four 1/5 scaled shaking table tests were conducted to investigate the seismic performance of recycled concrete frame-shear wall structures with different recycled aggregates replacement rates and concealed bracing detail. The four tested structures included one normal concrete model, one recycled coarse aggregate concrete model, and two recycled coarse and fine aggregate concrete models with or without concealed bracings inside the shear walls. The dynamic characteristics, dynamic response and failure mode of each model were compared and analyzed. Finite element models were also developed and nonlinear time-history response analysis was conducted. The test and analysis results show that the seismic performance of the recycled coarse aggregate concrete frame-shear wall structure is slightly worse than the normal concrete structure. The seismic resistance capacity of the recycled concrete frame-shear wall structure can be greatly improved by setting up concealed bracings inside the walls. With appropriate design, the recycled coarse aggregate concrete frame-shear wall structure and recycled concrete structure with concealed bracings inside the walls can be applied in buildings.

  2. 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.

  3. Study the Effective of Shear Wall on Behavior of Beam in Frame Structure

    Directory of Open Access Journals (Sweden)

    Dr, Hadihosseini

    2014-10-01

    Full Text Available Shear walls are a type of structural system that provides lateral resistance to a building or structure. They resist in-plane loads that are applied along its height. 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. Other important issues that must be considered in planning the structural schemes and layouts are the requirements for architectural details, building services like vertical transportation and fire safety among others. Each of the structural system will be having its own prospects and considerations. 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 reflected in the design. Lateral deflections of framed buildings should be limited to prevent damage to both structural and nonstructural elements. In the present study, the structural performance of the framed building with shear wall will be analysis. The importance of the shear wall in resist the wind and earthquake load are study, the effect of the shear walls on the conventional frame system. The improvement in the structural performance of the building with frame system by using shear wall is

  4. Structure of the cell wall of mango after application of ionizing radiation

    International Nuclear Information System (INIS)

    Cells of the mesocarp of mango cultivar Tommy Atkins were analyzed by Transmission Electron Microscope—TEM to evaluate the effects of doses of 0.5 and 1.0 kGy applied immediately after the fruit and after storage for twenty days at a temperature of 12 °C followed by 5 days of simulated marketing at a temperature of 21 °C. No alteration was found in the structure of the cell wall, middle lamella, and plasma membrane of fruits when analyzed immediately after application of doses. The mesocarp cell structure of the cell wall, middle lamella, and the plasma membrane did however undergo changes after storage. Fruits that received a dose of 0.5 kGy displayed slight changes in cell wall structure and slight disintegration of the middle lamella. Fruits that received a dose of 1.0 kGy displayed more severe changes in the structure of the cell wall, greater middle lamella degradation, and displacement of the plasma membrane. - Highlights: ► Mesocarp cells were analyzed by Transmission Electron Microscope—TEM. ► No change in cell wall structure, middle lamella and plasma membrane was found in fruits immediately after irradiation. ► Changes in cell wall structure, middle lamella and plasma membrane happened after storage. ► Fruits subjected to 0.5 kGy showed smaller cell wall change.

  5. 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.

  6. Study on electromagnetic-structural behavior of first wall/blanket structure for tokamak fusion reactor

    International Nuclear Information System (INIS)

    The electromagnetic problems related to the structural design of the first wall/blanket structure, which is a major component of Fusion Reactor, have been studied. The electromagnetic load, which is characteristic and very important of Tokamak type, is necessary for the evaluation of the structural integrity at the last item of the design process. A transient electromagnetic phenomena, which include the measurement of the eddy current obtained by the simulated plasma disruption experiment, the vibration behavior of the beam-plate by the dynamic electromagnetic load and the verification of the numerical codes, have been clarified. A static electromagnetic phenomena have been studied to evaluate the applicability of the ferromagnetic material to the first wall/blanket structure of Tokamak Power Reactor. The numerical code, which can calculate the magnetic field of the finite ferromagnetic body, has been developed and the magnetic field distortions inside and outside the materials has been studied. The deformation by the magnetic torque, which generates inside the ferromagnetic material placed in the magnetic field, has been studied. The effects of the magnetic stiffness and the saturated magnetic field to the deformation has been also clarified. (author)

  7. Introducing transapical aortic valve implantation (part 1): Effect of a structured training program on clinical outcome in a series of 500 procedures

    OpenAIRE

    Pasic, Miralem; Unbehaun, Axel; Dreysse, Stephan; Buz, Semih; Drews, Thorsten; Kukucka, Marian; Mladenow, Alexander; D'Ancona, Giuseppe; Hetzer, Roland; Seifert, Burkhardt

    2013-01-01

    OBJECTIVES: The purpose of the present study was to test whether the cumulative knowledge from the field of transapical transcatheter aortic valve implantation, when incorporated into a structured training and then gradually dispersed by internal proctoring, might eliminate the negative effect of the learning curve on the clinical outcomes. METHODS: The present study was a retrospective, single-center, observational cohort study of prospectively collected data from all 500 consecutive high-ri...

  8. Effects of magnetized walls on the particle structure and the yield stress of magnetorheological fluids

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Jianfeng, E-mail: zhoujianfeng@njtech.edu.cn [School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, Jiangsu (China); Mo, Jingwen [Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Shao, Chunlei [School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, Jiangsu (China); Li, Zhigang [Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

    2015-09-01

    In this work, we investigate the quasi-static shear deformation of magnetic particles (MPs) in a Couette flow of magnetorheological (MR) fluids through Stokesian dynamic simulations. The magnetized walls are modeled by a congregation of magnetic dipoles and their effects on the MPs are considered. The simple shear flow of the base fluid with linear velocity distribution is used to generate the shear deformation of the MP structure and the yield stresses under different shear rates are obtained. Comparing with the relatively long chains forming in base fluid without the effect of magnetized walls, the initial structure of MPs is mainly in the form of short chains due to the attractive force of walls. At the beginning of the shear deformation of the MP structure, the concentration of MPs near the walls is found. As the shear deformation develops, however, the chains concentrate at the center of the simulation domain and the MPs near wall boundaries are attracted to the center. The yield stress depends on the initial structure of MPs which is affected by the magnetized walls. It is revealed that the larger shear rate of base fluid results in the larger yield stress, and the effects of the magnetization intensity of the walls and their space distance on the yield stress are also investigated. - Highlights: • We model a Couette flow of magnetorheological fluid considering magnetized walls. • The walls are modeled by a congregation of magnetic dipoles. • Initial structure of MPs is remarkably affected by the walls, so is yield stress. • Larger base fluid shear rate causes the larger shear deformation and larger yield stress.

  9. 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.

  10. Management of Traumatic Aortic and Splenic Rupture in a Patient With Ascending Aortic Aneurysm.

    Science.gov (United States)

    Topcu, Ahmet Can; Ciloglu, Ufuk; Bolukcu, Ahmet; Dagsali, Sabri

    2016-08-01

    Traumatic aortic rupture is rupture of all or part of the aortic wall, mostly resulting from blunt trauma to the chest. The most common site of rupture is the aortic isthmus. Traumatic rupture of the ascending aorta is rare. A 62-year-old man with a family history of ascending aortic aneurysm was referred to our hospital after a motor vehicle accident. He had symptoms of cardiogenic shock. A contrast-enhanced computed tomographic scan revealed rupture of the proximal ascending aorta and an ascending aortic aneurysm with a diameter of 55 mm at the level of the sinuses of Valsalva. Transthoracic echocardiography at the bedside revealed severe aortic valvular insufficiency. We performed a successful Bentall procedure. During postoperative recovery, the patient experienced a cerebrovascular accident. Transesophageal echocardiography did not reveal thrombosis of the mechanical prosthesis. The patient's symptoms resolved in time, and he was discharged from the hospital on postoperative day 47 without any sequelae. He has been symptom free during a 6-month follow-up period. We suggest that individuals who have experienced blunt trauma to the chest and have symptoms of traumatic aortic rupture and a known medical history of ascending aortic aneurysm should be evaluated for a rupture at the ascending aorta and the aortic isthmus. PMID:27449463

  11. Endovascular resection of the native aortic valve before transcatheter aortic valve implantation: state of the art and review.

    Science.gov (United States)

    Navarra, Emiliano; Mosala Nezhad, Zahra; Bollen, Xavier; Gielen, Charles-Edouard; Mastrobuoni, Stefano; De Kerchove, Laurent; Raucent, Benoit; Astarci, Parla

    2016-09-01

    Transcatheter aortic valve implantation was introduced into clinical practice in 2002 as a rescue approach in patients presenting with symptomatic severe aortic stenosis but not eligible for conventional aortic valve replacement. This technique allows implantation of a balloon expandable bioprosthesis without resection of the native aortic valve. Several complications are described as a consequence of the residual highly calcified valve being squeezed against the aortic wall by the stent of the implant. This can result in deformation of the metal stent and paravalvular leakage, risk of occlusion of the coronary ostia, or central and peripheral embolization of valvular debris. To avoid these complications, many authors suggest the possibility to resect and remove the native aortic valve before transcatheter aortic valve implantation. In this field, different authors have described possible techniques and different sources of energy to resect the calcified valve. In this article, we review the development of these experimental techniques and discuss future prospects in this field. PMID:27032472

  12. Functional Heart Valve Scaffolds Obtained by Complete Decellularization of Porcine Aortic Roots in a Novel Differential Pressure Gradient Perfusion System.

    Science.gov (United States)

    Sierad, Leslie Neil; Shaw, Eliza Laine; Bina, Alexander; Brazile, Bryn; Rierson, Nicholas; Patnaik, Sourav S; Kennamer, Allison; Odum, Rebekah; Cotoi, Ovidiu; Terezia, Preda; Branzaniuc, Klara; Smallwood, Harrison; Deac, Radu; Egyed, Imre; Pavai, Zoltan; Szanto, Annamaria; Harceaga, Lucian; Suciu, Horatiu; Raicea, Victor; Olah, Peter; Simionescu, Agneta; Liao, Jun; Movileanu, Ionela; Harpa, Marius; Simionescu, Dan Teodor

    2015-12-01

    There is a great need for living valve replacements for patients of all ages. Such constructs could be built by tissue engineering, with perspective of the unique structure and biology of the aortic root. The aortic valve root is composed of several different tissues, and careful structural and functional consideration has to be given to each segment and component. Previous work has shown that immersion techniques are inadequate for whole-root decellularization, with the aortic wall segment being particularly resistant to decellularization. The aim of this study was to develop a differential pressure gradient perfusion system capable of being rigorous enough to decellularize the aortic root wall while gentle enough to preserve the integrity of the cusps. Fresh porcine aortic roots have been subjected to various regimens of perfusion decellularization using detergents and enzymes and results compared to immersion decellularized roots. Success criteria for evaluation of each root segment (cusp, muscle, sinus, wall) for decellularization completeness, tissue integrity, and valve functionality were defined using complementary methods of cell analysis (histology with nuclear and matrix stains and DNA analysis), biomechanics (biaxial and bending tests), and physiologic heart valve bioreactor testing (with advanced image analysis of open-close cycles and geometric orifice area measurement). Fully acellular porcine roots treated with the optimized method exhibited preserved macroscopic structures and microscopic matrix components, which translated into conserved anisotropic mechanical properties, including bending and excellent valve functionality when tested in aortic flow and pressure conditions. This study highlighted the importance of (1) adapting decellularization methods to specific target tissues, (2) combining several methods of cell analysis compared to relying solely on histology, (3) developing relevant valve-specific mechanical tests, and (4) in vitro testing

  13. 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...

  14. 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.

  15. 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...

  16. Wing walls for enhancing the seismic performance of reinforced concrete frame structures

    Science.gov (United States)

    Yang, Weisong; Guo, Xun; Xu, Weixiao; Yuan, Xin

    2016-06-01

    A building retrofitted with wing walls in the bottom story, which was damaged during the 2008 M8.0 Wenchuan earthquake in China, is introduced and a corresponding 1/4 scale wing wall-frame model was subjected to shake table motions to study the seismic behavior of this retrofitted structural system. The results show that wing walls can effectively protect columns from damage by moving areas that bear reciprocating tension and compression to the sections of the wing walls, thus achieving an extra measure of seismic fortification. A `strong column-weak beam' mechanism was realized, the flexural rigidity of the vertical member was strengthened, and a more uniform distribution of deformation among all the stories was measured. In addition, the joint between the wing walls and the beams suffered severe damage during the tests, due to an area of local stress concentration. A longer area of intensive stirrup is suggested in the end of the beams.

  17. 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

  18. 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.

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

    Science.gov (United States)

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

    2015-11-01

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

  20. Structural Insight into Cell Wall Architecture of Micanthus sinensis cv. using Correlative Microscopy Approaches.

    Science.gov (United States)

    Ma, Jianfeng; Lv, Xunli; Yang, Shumin; Tian, Genlin; Liu, Xing'e

    2015-10-01

    Structural organization of the plant cell wall is a key parameter for understanding anisotropic plant growth and mechanical behavior. Four imaging platforms were used to investigate the cell wall architecture of Miscanthus sinensis cv. internode tissue. Using transmission electron microscopy with potassium permanganate, we found a great degree of inhomogeneity in the layering structure (4-9 layers) of the sclerenchymatic fiber (Sf). However, the xylem vessel showed a single layer. Atomic force microscopy images revealed that the cellulose microfibrils (Mfs) deposited in the primary wall of the protoxylem vessel (Pxv) were disordered, while the secondary wall was composed of Mfs oriented in parallel in the cross and longitudinal section. Furthermore, Raman spectroscopy images indicated no variation in the Mf orientation of Pxv and the Mfs in Pxv were oriented more perpendicular to the cell axis than that of Sfs. Based on the integrated results, we have proposed an architectural model of Pxv composed of two layers: an outermost primary wall composed of a meshwork of Mfs and inner secondary wall containing parallel Mfs. This proposed model will support future ultrastructural analysis of plant cell walls in heterogeneous tissues, an area of increasing scientific interest particularly for liquid biofuel processing. PMID:26358178

  1. A New Rule-Based Strategy to Determine The Failure modes of Structural Walls

    International Nuclear Information System (INIS)

    Parameters affecting types of failure of reinforced concrete structural walls with arbitrary aspect ratios and cross section are investigated using data from numerous wall tests. Basically there are three known primary failure modes that covers prominent behavior of wall at the failure load. Shear failure is known by diagonal tension cracks and premature yielding of shear reinforcement that leads to abrupt none-ductile failure. To insure a ductile flexural failure, it is recommended that strength in shear be equal or grater than strength in flexure. Flexural-shear failure is another type of failure that needs to more details to identify explicitly and it is divided to two different cases namely web crushing or sliding shear failure. A new model is proposed to predict the failure modes of structural walls in terms of shear strength, nominal shear stress, shear force related to flexural capacity, the level of compression in concrete and control of sliding shear failure.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Anatomics Knowledges of Aortic Root in the Transcatheter Aortic Valve Implantation.

    OpenAIRE

    Marcelo Cerezo; Omar Bertani; Gisela Panciroli; Sebastián Duhalde; Karina Ferreira; Luciano Honaine

    2010-01-01

    The Aortic Valve is a valvular system that bears different high pressure forces. It takes part of a complex structure called Aortic Root. Nowadays, anatomic knowledge has taken a preponderant role, due to the use of the Transcatether Aortic Valve Implant (TAVI). To describe the patient´s characteristics which exclude them of the TAVI for anatomic reasons in cadaveric dissections and transthoracic echocardiograms. A descriptive retrospective analysis of 67 individuals was performed and divided...

  7. 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.

  8. 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.

  9. 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...

  10. 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.

  11. 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. PMID:26858185

  12. Effect of Yeast Cell Morphology, Cell Wall Physical Structure and Chemical Composition on Patulin Adsorption.

    Directory of Open Access Journals (Sweden)

    Ying Luo

    Full Text Available The capability of yeast to adsorb patulin in fruit juice can aid in substantially reducing the patulin toxic effect on human health. This study aimed to investigate the capability of yeast cell morphology and cell wall internal structure and composition to adsorb patulin. To compare different yeast cell morphologies, cell wall internal structure and composition, scanning electron microscope, transmission electron microscope and ion chromatography were used. The results indicated that patulin adsorption capability of yeast was influenced by cell surface areas, volume, and cell wall thickness, as well as 1,3-β-glucan content. Among these factors, cell wall thickness and 1,3-β-glucan content serve significant functions. The investigation revealed that patulin adsorption capability was mainly affected by the three-dimensional network structure of the cell wall composed of 1,3-β-glucan. Finally, patulin adsorption in commercial kiwi fruit juice was investigated, and the results indicated that yeast cells could adsorb patulin from commercial kiwi fruit juice efficiently. This study can potentially simulate in vitro cell walls to enhance patulin adsorption capability and successfully apply to fruit juice industry.

  13. 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.

  14. Wall shear stress manifolds and near wall flow topology in aneurysms

    Science.gov (United States)

    Arzani, Amirhossein; Gambaruto, Alberto M.; Chen, Guoning; Shadden, Shawn C.

    2015-11-01

    Transport of atherogenic and thrombogenic chemicals near the vessel wall highly influences atherosclerosis and thrombosis. The high Schmidt number of these species leads to a thin concentration boundary layer near the wall. The wall shear stress (WSS) vector field can be scaled to obtain the near wall velocity in this region, thus providing first order approximation to near wall transport. In this study, the complex blood flow in patient-specific abdominal aortic aneurysms was considered. Lagrangian tracking of surface-bound tracers representing near wall species was employed to identify Lagrangian coherent structures (LCS) for the WSS surface vector field. The WSS LCS matched the stable and unstable manifolds of saddle type fixed points of the time-average WSS vector field, due to the quasi-steady nature of these near wall transport processes. A WSS exposure time measure is introduced to quantify the concentration of near wall species. The effect of diffusion and normal flow on these structures is investigated. The WSS LCS highly influence the concentration of near wall species, and provide a template for near-wall transport.

  15. 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.

  16. 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.

  17. Engineering tissue constructs to mimic native aortic and pulmonary valve leaflets' structures and mechanics

    Science.gov (United States)

    Masoumi, Nafiseh

    There are several disadvantages correlated with current heart valve replacement, including anticoagulation therapy for patients with mechanical valves and the low durability of bioprosthetic valves. The non-viable nature of such devices is a critical drawback especially for pediatric cases due to the inability of the graft to grow in vivo with the patients. A tissue engineered heart valve (TEHV) with remodeling and growth ability, is conceptually appealing to use in the surgical repair and could serve as a permanent replacements when operating for pediatric valvular lesions. It is critical that scaffolds for functional heart valve tissue engineering, be capable of mimicking the native leaflet's structure and mechanical properties at the time of implantation. Meanwhile, the scaffolds should be able to support cellular proliferation and native-like tissue formation as the TEHV remodels toward a scaffold-free state. Our overall hypothesis is that an "ideal" engineered construct, designed based on native leaflet's structure and mechanics, will complement a native heart valve leaflet in providing benchmarks for use in the design of clinically-applicable TEHV. This hypothesis was addressed through several experiments conducted in the present study. To establish a functional biomimetic TEHV, we developed scaffolds capable of matching the anisotropic stiffness of native leaflet while promoting native-like cell and collagen content and supporting the ECM generation. Scaffolds with various polymer contents (e.g., poly (glycerol sebacate) (PGS) and poly (epsilon-caprolactone) (PCL)) and structural designs (e.g., microfabricated and microfibrous scaffolds), were fabricated based on native leaflet's structure and mechanics. It was found that the tri-layered scaffold, designed with assembly of microfabricated PGS and microfibrous PGS/PCL was a functional leaflet capable of promoting tissue formation. Furthermore, to investigate the effect of cyclic stress and flexure

  18. 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.

  19. 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.

  20. Experimental Investigation on Near-wall Turbulent Flow Structures over Deformable Roughness

    Science.gov (United States)

    Toloui, Mostafa; John, Nolan; Hong, Jiarong

    2015-11-01

    Wall-bounded turbulent flows over rough surfaces have been studied for almost a century. However, in most of the prior studies, little attention has been paid to the role of roughness mechanical properties, e.g. deformability, in altering the flow characteristics including both general turbulent statistics and near-wall flow structures. In this study, high resolution time-resolved digital in-line holographic PIV is employed to investigate the near-wall turbulent structures as well as turbulent statistics around and above deforming roughness structures. The rough wall samples consisting of tapered cylinders of size 0.5 mm in diameter and 3 mm in height are manufactured from transparent PDMS with similar geometrical features but various deformability levels. The experiments are conducted within an optically index-matched facility (using NaI solution) operating with different Reynolds numbers where roughness samples of different deformability are placed downstream of a 1.2 m long acrylic channel of 50 mm square cross section. The follow-up research envisions a large dataset including various Reynolds numbers and deformability to elucidate the role of roughness deformability on near-wall coherent structures and turbulent energy transport within and above the roughness sublayer. This work is supported by the startup package of Jiarong Hong and the MnDrive Fellowship of Mostafa Toloui from University of Minnesota.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. In-service inspections of thick walled concrete structures

    International Nuclear Information System (INIS)

    Ageing management and renewal of the operating license of existing NPP's are at present the main problems of nuclear energy. For the ageing management of concrete structures the OECD-Nuclear Energy Agency, Committee on the Safety on Nuclear Installations defined as the first priority ISI technigues for reinforced concrete structures having thick sections and areas not directly accessible for inspections. In this paper is described the NRI Rez research and development programme in this field. Three ISI techniques were selected: Impact-Echo ultrasound and high frequency radar or betatron 7 MeV. In the period from 2004 to 2005 the mathematical studies of efficiency of Impact-Echo method for detecting of reinforcing bars, deep surface cracks and internal voids were done. In 2005 will be manufactured the 2 × 2 × 1 m concrete specimens with reinforcing bars, crack and holes which represent possible defects. Results of the solution will be used for qualification of ISI techniques

  8. Isogeometric analysis for thin-walled composite structures

    OpenAIRE

    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 response in an isoparametric sense. Due to the tensor product property of multi-variate NURBS, it is difficult to represent complex topological shapes with a single NURBS patch. Multiple, often no...

  9. 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.

  10. 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.

  11. Influence of liquid environment and bounding wall structure on fluid flow through carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Abramyan, A.K.; Bessonov, N.M.; Mirantsev, L.V.; Reinberg, N.A., E-mail: miran@mail.ru

    2015-06-26

    Flows of different fluids through single-walled carbon nanotubes (SWCNTs) with boundary walls having the perfect and defective graphene structures have been investigated by means of molecular dynamics (MD) simulations. It has been shown that the boundary wall structure has a very strong influence on not only an average fluid flow rate but also on shapes of trajectories of individual fluid atoms (molecules) and fluid centres of mass. The fluid flows through SWCNTs surrounded by different liquid environments have been also simulated and an influence of these environments on the average fluid flow rates have been studied. It has been revealed a strong dependence of the average fluid flow rate on a molecular polarity of fluids flowing through SWCNTs and those surrounding the tubes. It has been shown that, for multi-walled carbon nanotubes (MWCNTs), an effect of liquid environment on the fluid flow can be significantly suppressed. - Highlights: • Equilibrium structures of polar and nonpolar fluids in CNTs. • Trajectories of fluid particles flowing through CNTs. • Influence of liquid environments. • Influence of defects of the walls.

  12. Seismic Performance Evaluation of Multistory Reinforced Concrete Moment Resisting Frame Structure with Shear Walls

    OpenAIRE

    Junwon Seo; Jong Wan Hu; Burte Davaajamts

    2015-01-01

    This paper is intended to evaluate the seismic performance of a twelve-story reinforced concrete moment-resisting frame structure with shear walls using 3D finite element models according to such seismic design regulations as Federal Emergency Management Agency (FEMA) guideline and seismic building codes including Los Angeles Tall Building Structural Design Council (LATBSDC) code. The structure is located in Seismic Zone 4, considered the highest-seismic-risk classification established by the...

  13. Modelling and analysis of a wall-frame structure according to EC8

    OpenAIRE

    Bašič, Sara

    2005-01-01

    In order to harmonize the standards for design of structures in Europe the family of Eurocode standards has been developed. Eurocode 8 (EC8) represents the standard for design of earthquake resistant structures. This standard has been translated and will soon be adopted as Slovenian standard SIST EN 1998-1. The application of this standard for analysis of a reinforced concrete frame-wall building was the main goal of this diploma work. We focused on chapters on structural analysis. The analys...

  14. Aortic Aneurysm Statistics

    Science.gov (United States)

    ... connective tissue disorders, such as Marfan syndrome and Ehlers-Danlos syndrome, get thoracic aortic aneurysms. Signs and symptoms of thoracic aortic aneurysm can include Sharp, sudden pain in the chest or upper back. Shortness of ...

  15. 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 ...

  16. Aortic Aneurysm Repair

    Medline Plus

    Full Text Available ... to become you to our live webcast. Today we’re going to repair an abdominal aortic aneurysm ... and together as a team of multidisciplinary physicians, we’re going to repair an abdominal aortic aneurysm ...

  17. Incidence of patients with acute aortic dissection

    OpenAIRE

    Salkovski, Safet; Panova, Gordana; Velickova, Nevenka; Panova, Blagica; Panov, Nenad; Nikolovska, Lence; Dzidrova, Violeta

    2012-01-01

    Introduction: Acute aortic dissection (AAD) e life-threatening condition that characterizes the high mortality worldwide (7-8%). When AAD is split in the wall of the aorta where the blood circulates between layers of the wall which can lead to its rupture. Early recognition of symptoms and appropriate response to the medical team is crucial to the outcome of the patient. On receipt of a patient with chest pain to bear in mind the possibility of AAD. Standard diagnostics when fasti...

  18. 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.

  19. 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)

  20. Nonlinear earthquake response analysis and energy calculation for seismic slit shear wall structures

    Institute of Scientific and Technical Information of China (English)

    蒋欢军; 吕西林

    2002-01-01

    Based on the concept of structural passive control, a new type of slit shear wall, with improved seismic performuce when compared to an ordinary solid shear wall, was proposed by the authors in 1996. The idea has been verified by a series of pseudo-static and dynamic tests. In this paper a macro numerical model is developed fior the wall element and the energy dissipation device. Then, nonlinear time history analysis is carried out for a 10-story slit shear wall model tested on a shaking table. Furthermore, the seismic input energy and the individual energy dissipated by the components are calculated by a method based on Newmark-β assumptions for this shear wall model, and the advantages of this shear wall are further demonstrated by the calculation results from the viewpoint of energy. Finally, according to the seismic damage criterion on the basis of plastic accumulative energy and maximum response, the optimal analysis is carried out to select design parameters for the energy dissipation device.

  1. X-ray and back-wall echo ultrasonic examination of wrought iron building structures

    Directory of Open Access Journals (Sweden)

    Vidovszky István

    2008-01-01

    Full Text Available The wrought iron building structures constituting part of the architectural heritage, e. g. handrails, gate hinges, columns, arch ties and wall ties represent incorporeal value, but operate as load bearing structures as well. There are few information on their mechanical properties and quality. Due to the inhomogeneity of the material of wrought iron building structures generated during the production, the known metal testing methods, as the tensile and hardness tests or metallographic examination, are not enough to survey the properties of such structures in depth. For the further and more accurate examinations, the application of X-ray and back-wall echo ultrasonic tests are essential. The goal of our paper is the presentation of the application of the examinations used extensively in the machine industry for the testing of wrought iron building structures.

  2. 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.

  3. Thermal-structural response and low-cycle fatigue damage of channel wall nozzle

    Institute of Scientific and Technical Information of China (English)

    Cheng Cheng; Wang Yibai; Liu Yu; Liu Dawei; Lu Xingyu

    2013-01-01

    To investigate the thermo-mechanical response of channel wall nozzle under cyclic work-ing loads, the finite volume fluid-thermal coupling calculation method and the finite element thermal-structural coupling analysis technique are applied. In combination with the material low-cycle fatigue behavior, the modified continuous damage model on the basics of local strain approach is adopted to analyze the fatigue damage distribution and accumulation with increasing nozzle work cycles. Simulation results have shown that the variation of the non-uniform temperature distribution of channel wall nozzle during cyclic work plays a significant role in the thermal-structural response by altering the material properties;the thermal-mechanical loads interaction results in serious defor-mation mainly in the front region of slotted liner. In particular, the maximal cyclic strains appear in the intersecting regions of liner gas side wall and symmetric planes of channel and rib, where the fatigue failure takes place initially;with the increase in nozzle work cycles, the residual plastic strain accumulates linearly, and the strain amplitude and increment in each work cycle are separately equal, but the fatigue damage grows up nonlinearly. As a result, a simplified nonlinear damage accumulation approach has been suggested to estimate the fatigue service life of channel wall nozzle. The predicted node life is obviously conservative to the Miner’s life. In addition, several workable methods have also been proposed to improve the channel wall nozzle durability.

  4. 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.

  5. Interrelation of Shape and Structure of Domain Walls with Magnetic Inhomogeneities

    Directory of Open Access Journals (Sweden)

    A.P. Kuzmenko

    2013-12-01

    Full Text Available By using atomic force microscopy (resolution of 40 nm the effect of surface roughness and internal inhomogeneities on the fine structure of domain walls of different types in thin transparent orthoferrite samples cut perpendicular to the optic axis for YFeO3 and axis [001] for DyFeO3 has been studied.

  6. 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.

  7. Structure of the cell wall of mango after application of ionizing radiation

    Science.gov (United States)

    Silva, Josenilda M.; Villar, Heldio P.; Pimentel, Rejane M. M.

    2012-11-01

    Cells of the mesocarp of mango cultivar Tommy Atkins were analyzed by Transmission Electron Microscope—TEM to evaluate the effects of doses of 0.5 and 1.0 kGy applied immediately after the fruit and after storage for twenty days at a temperature of 12 °C followed by 5 days of simulated marketing at a temperature of 21 °C. No alteration was found in the structure of the cell wall, middle lamella, and plasma membrane of fruits when analyzed immediately after application of doses. The mesocarp cell structure of the cell wall, middle lamella, and the plasma membrane did however undergo changes after storage. Fruits that received a dose of 0.5 kGy displayed slight changes in cell wall structure and slight disintegration of the middle lamella. Fruits that received a dose of 1.0 kGy displayed more severe changes in the structure of the cell wall, greater middle lamella degradation, and displacement of the plasma membrane.

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

    Science.gov (United States)

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

    2008-07-01

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

  9. 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.

  10. Vibrational behavior of adaptive aircraft wing structures modelled as composite thin-walled beams

    Science.gov (United States)

    Song, O.; Librescu, L.; Rogers, C. A.

    1992-01-01

    The vibrational behavior of cantilevered aircraft wings modeled as thin-walled beams and incorporating piezoelectric effects is studied. Based on the converse piezoelectric effect, the system of piezoelectric actuators conveniently located on the wing yield the control of its associated vertical and lateral bending eigenfrequencies. The possibility revealed by this study enabling one to increase adaptively the eigenfrequencies of thin-walled cantilevered beams could play a significant role in the control of the dynamic response and flutter of wing and rotor blade structures.

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

    International Nuclear Information System (INIS)

    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

  12. 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.

  13. Stress and lifetime calculations for first wall and blanket structural components. Pt. 1

    International Nuclear Information System (INIS)

    In this report the lifetime of first wall and blanket structures of fusion reactors is investigated. The extension of small pre-existing cracks by the cyclic operation of a fusion reactor seems to be the most important failure mode. The special application of the present investigation are tubes acting directly as parts of the first wall and affected by various radiation effects. The outer surface is asymmetrically heated and by combination of thermal extension, swelling, irradiation creep and internal pressure a complex time dependent stress distribution results. Crack growth until failure caused by cyclic operation of the reactor is computed by application of fracture mechanical methods. (orig.)

  14. 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.

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

    OpenAIRE

    Syed Khasim Mutwalli; Dr. Shaik Kamal Mohammed Azam

    2014-01-01

    This study presents the procedure for seismic performance estimation of high-rise buildings based on a concept of the capacity spectrum method. In 3D analytical model of thirty storied buildings have been generated for symmetric buildings Models and analyzed using structural analysis tool ETABS. The analytical model of the building includes all important components that influence the mass, strength, stiffness and deformability of the structure. To study the effect of concrete core wall & shea...

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Tools and procedures for structural lifetime evaluation of NET first wall design concepts

    International Nuclear Information System (INIS)

    The problems, the available technology and the needed advances on the theoretical evaluation of the NET First Wall design concepts with respect to the structural lifetime are described. Major areas are: Computational methods to determine the First Wall deformations, stresses and strains under conditions of cyclic elasto-plasticity, swelling, irradiation and thermal creep and computational fracture mechanics in situations of inelasticity and high thermal gradients; Criteria for the evaluation of the calculated thermostructural response with respect to the integrity and functional requirements; Approaches to handle very complex First Wall geometries through a combination of 2 and 3 dimensional models. Uncertainties and open questions in these lifetime analyses tools and procedures are discussed and an example of first simple localized studies is given. (author)

  2. 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.

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

    International Nuclear Information System (INIS)

    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 taking the role of the atomic spins. The coupling is, however, different. The superspins interact only by dipolar interactions as exchange coupling between individual nanoparticles may be neglected due to interparticle spacing. We observe that it is energetically favorable to introduce domain walls 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, which will always be present in realistic assemblies, pins longitudinal domain walls when the external field is reversed, and makes a gradual reversal of the magnetization by migration of longitudinal domain walls possible, in agreement with previous experimental results

  4. 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.

  5. Ag-silica composite nanotube with controlled wall structures for biomedical applications.

    Science.gov (United States)

    He, Haiyan; Wang, Juan; Gao, Qian; Chang, Mingwei; Ren, Zhaohui; Zhang, Xiwen; Li, Xiang; Weng, Wenjian; Han, Gaorong

    2013-11-01

    A range of Ag-silica composite nanotubes with tailored wall structures were successfully synthesized in situ by single-nozzle electrospinning. By increasing AgNO3 concentration, the wall structure of Ag-silica tubes changes from dense to porous, and eventually turns into a 'lace-like' structure. This is attributed to Ag ions doping into the SiOSi network of precursors, as illustrated in FTIR study. More importantly, Ag-silica composite nanotubes show robust antibacterial activity against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli microorganisms. Therefore, it is a breakthrough of the nanostructure biomaterial research for future medical applications that require strong antibacterial properties. PMID:23907057

  6. Study of the effects of corrugated wall structures due to blanket modules around ICRH antennas

    Energy Technology Data Exchange (ETDEWEB)

    Dumortier, Pierre; Louche, Fabrice; Messiaen, André; Vervier, Michel [LPP-ERM/KMS, EURATOM-Belgian State Association, TEC partner, B-1000 Brussels (Belgium)

    2014-02-12

    In future fusion reactors, and in ITER, the first wall will be covered by blanket modules. These blanket modules, whose dimensions are of the order of the ICRF wavelengths, together with the clearance gaps between them will constitute a corrugated structure which will interact with the electromagnetic waves launched by ICRF antennas. The conditions in which the grooves constituted by the clearance gaps between the blanket modules can become resonant are studied. Simple analytical models and numerical simulations show that mushroom type structures (with larger gaps at the back than at the front) can bring down the resonance frequencies, which could lead to large voltages in the gaps between the blanket modules and perturb the RF properties of the antenna if they are in the ICRF operating range. The effect on the wave propagation along the wall structure, which is acting as a spatially periodic (toroidally and poloidally) corrugated structure, and hence constitutes a slow wave structure modifying the wall boundary condition, is examined.

  7. 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

    Evidence from human and animal studies suggests that maternal nutrition can induce developmental programming of adult hypertension in offspring. We have previously described a model of maternal dietary imbalance in Sprague-Dawley rats whereby administration of a maternal diet rich in animal lard......-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...

  8. Rotation effect on near-wall turbulence statistics and flow structures

    Institute of Scientific and Technical Information of China (English)

    LIU Nansheng; LU Xiyun; ZHUANG Lixian

    2005-01-01

    Large eddy simulation (LES) of turbulent flow through an axially rotating pipe, coupled with nonlinear dynamic subgrid-scale (SGS) model, is carried out to investigate rotation effect on the near-wall turbulence characteristics and flow structures. In the rotating turbulent pipe flow, it is found that the tendency towards a relaminarized flow appears and the axial velocity fluctuation is suppressed; however, the azimuthal fluctuation is enhanced due to the presence of the pipe wall rotation. The joint probability density function (joint PDF) of the velocity fluctuations and the probability density function (PDF) of the helicity fluctuation are analyzed in detail. It is revealed that the resolved Reynolds stress and helicity fluctuation in the wall region are closely related to the correlation between the velocity and vorticity fluctuations and affected significantly by the rotation-induced azimuthal mean flow. Further, the budgets of resolved Reynolds stresses indicate that the rotation effect is responsible for the more active turbulent energy redistribution and the production of the azimuthal turbulence fluctuation. The near-wall inclined streaky structures with respect to the axial direction are ascribed to the spiral motion of the fluid induced by the rotating pipe. The turbulence characteristics revealed in this study are of great help for the understanding of physical fundamentals in the rotating turbulent flows and for the development of reliable turbulence model.

  9. Aortic Valve Sparing in Different Aortic Valve and Aortic Root Conditions.

    Science.gov (United States)

    David, Tirone E

    2016-08-01

    The development of aortic valve-sparing operations (reimplantation of the aortic valve and remodeling of the aortic root) expanded the surgical armamentarium for treating patients with aortic root dilation caused by a variety of disorders. Young adults with aortic root aneurysms associated with genetic syndromes are ideal candidates for reimplantation of the aortic valve, and the long-term results have been excellent. Incompetent bicuspid aortic valves with dilated aortic annuli are also satisfactorily treated with the same type of operation. Older patients with ascending aortic aneurysm and aortic insufficiency secondary to dilated sinotubular junction and a normal aortic annulus can be treated with remodeling of the aortic root or with reimplantation of the aortic valve. The first procedure is simpler, and both procedures are likely equally effective. As with any heart valve-preserving procedure, patient selection and surgical expertise are keys to successful and durable repairs. PMID:27491910

  10. 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

  11. 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.

  12. Minimally Invasive Aortic Valve Replacement

    Medline Plus

    Full Text Available ... opens freely when the heart contracts. On the right, we see a picture of the aortic valve ... the aortic valve because the probe is sitting right behind the aortic valve. Lots of patients on ...

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

    Science.gov (United States)

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

    2013-09-19

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

  14. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-10-28

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

  16. Manifestation of Structure of Electron Bands in Double-Resonant Raman Spectra of Single-Walled Carbon Nanotubes.

    Science.gov (United States)

    Stubrov, Yurii; Nikolenko, Andrii; Gubanov, Viktor; Strelchuk, Viktor

    2016-12-01

    Micro-Raman spectra of single-walled carbon nanotubes in the range of two-phonon 2D bands are investigated in detail. The fine structure of two-phonon 2D bands in the low-temperature Raman spectra of the mixture and individual single-walled carbon nanotubes is considered as the reflection of structure of their π-electron zones. The dispersion behavior of 2D band fine structure components in the resonant Raman spectra of single-walled carbon nanotube mixture is studied depending on the energy of excitating photons. The role of incoming and outgoing electron-phonon resonances in the formation of 2D band fine structure in Raman spectra of single-walled carbon nanotubes is analyzed. The similarity of dispersion behavior of 2D phonon bands in single-walled carbon nanotubes, one-layer graphene, and bulk graphite is discussed. PMID:26729220

  17. 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.

  18. A structural analysis in seismic archaeology: the walls of Noto and the 1693 earthquake

    OpenAIRE

    Guidoboni, E.; SGA, Storia Geofisica Ambiente, Bologna, Italy; Riva, P.; Dipartimento di Ingegneria Civile, Universitá di Brescia, Italy; Petrini, V.; Dipartimento di Ingegneria Strutturale, Politecnico di Milano, Italy; Madini Moretti, A.; ENGI.CO., Engineering & Consulting, Milano, Italy; Lombardini, G.; Facoltà di Architettura, Università di Ferrara, Italy

    1995-01-01

    A crucial problenl for seismic archeology is how to recognize seismic effects and how to date them. On an experimental basis. we proposed that the problem be reversed, and that we begin at the other end: i.e. by analyzing already known seismic effects on ancient structures, testified by written sources. to be able to .calibrate>> the types or possible observations and any subsequent elaborations. The choice of the walls of Noto was suggested by the fact that Noto was abandoned fol...

  19. Analytical Modeling of Cyclic Shear - Flexure Interaction in Reinforced Concrete Structural Walls

    OpenAIRE

    Kolozvari, Kristijan

    2013-01-01

    A study was conducted to develop a modeling approach that integrates flexure and shear interaction under cyclic loading conditions to obtain reliable predictions of inelastic responses of reinforced concrete (RC) structural walls. The proposed modeling approach incorporates cyclic RC panel constitutive behavior based on an interpretation of the fixed-strut-angle approach into a two-dimensional fiber-based macroscopic model. Coupling of axial and shear responses under cyclic loading is achieve...

  20. 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.

  1. CALCULATION OF ADAPTIVE MULTILAYERED THIN-WALLED STRUCTURES SUBJECTED TO TEMPERATURE LOADING

    OpenAIRE

    Plotnikova, S. V.; KULIKOV M.G.

    2011-01-01

    Problem statement. A number of difficult problems centre around the application of 3D isoparametric finite elements to compensate the strains and to control the shape of thin-walled structures. One of these problems is decreasing efficiency of the finite element code.Results. This paper presents a new 3D geometrically exact four-node solid-shell element based on the 7-parameter theory of thermoelectroelastic shells, which gives the possibility to use 3D constitutive equations of thermopiezoel...

  2. 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

    2016-11-30

    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. PMID:27633072

  3. 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

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

  6. Fast Ion Power Loads on ITER First Wall Structures in the Presence of NTMs and Microturbulence

    International Nuclear Information System (INIS)

    Full text: We have already studied the wall loads caused by fast ions in a variety of ITER plasmas using the 5D Monte Carlo guiding-center code ASCOT. The simulations were performed for different magnetic configurations including FIs and none or more TBMs. In earlier simulations, the fast ion transport was assumed purely neoclassical. In MHD quiescent plasmas this was believed to be true until the first NBI current drive experiments with the AUG tangential beams failed to demonstrate the predicted levels of off-axis current. The subsequent theoretical work has revealed that microturbulence can induce additional transport even for the fast ions. Furthermore, it is highly unlikely that the ITER plasmas will be MHD quiescent: the massive fast ion population consisting of the fusion alphas with energies up to 3.5 MeV drive a multitude of energetic particle modes. Furthermore, ITER is prone to NTMs with substantial island structures. All these MHD phenomena can contribute to increased transport of fast ions in the core plasma. We are incorporating non-neoclassical effects into ASCOT. Here we present the first simulation results of fast ion power loads to ITER plasma facing components where realistic 3D magnetic field and most recent 3D wall structure are used, and the fast ion redistribution due to microturbulence and NTMs is included. The simulations are carried out for ITER Scenario 2 (standard H-mode) and Scenario 4 (steady-state operation). In the neoclassical study, the wall power loads were found insignificant in Scenario 4 and much larger but still easily tolerable in Scenario 2. This is due to the different plasma profiles: in Scenario 4, thermal fusions and ionization of NBI particles occur closer to the plasma core. Thus the redistribution of fast ions due to non-neoclassical effects can be particularly treacherous in Scenario 4: drift islands and anomalous transport lead energetic ions to the edge where ripple and TBM induced transport processes rapidly take

  7. 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".

  8. CALCULATION OF ADAPTIVE MULTILAYERED THIN-WALLED STRUCTURES SUBJECTED TO TEMPERATURE LOADING

    Directory of Open Access Journals (Sweden)

    S. V. Plotnikova

    2011-04-01

    Full Text Available Problem statement. A number of difficult problems centre around the application of 3D isoparametric finite elements to compensate the strains and to control the shape of thin-walled structures. One of these problems is decreasing efficiency of the finite element code.Results. This paper presents a new 3D geometrically exact four-node solid-shell element based on the 7-parameter theory of thermoelectroelastic shells, which gives the possibility to use 3D constitutive equations of thermopiezoelectricity. As unknown functions, six tangential and transverse displacements of outer surfaces and the transverse displacement of the middle surface are chosen.Conclusions. Analytical integration used for deriving a stiffness matrix, as well as the fact that displacement vectors of outer and middle surfaces are represented in a local basis related to the reference shell surface permit one to increase the performance of a finite element code and to utilize it efficiently into controllers of adaptive thin-walled structures with segmented piezoceramic patches. Numerical examples are presented to substantiate the possibility of controlling the temperature strains in thin-walled composite structures by employing the converse piezoelectric effect.

  9. INTERACTION BETWEEN COHERENT STRUCTURES IN WALL REGION OF A TURBULENT BOUNDARY LAYER

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Using the idea of general resonant triad of the hydrodynamic stability, the theoretical models for coherent structures in the wall region of a turbulent boundary layer is proposed. The interaction between coherent structures in the wall region of a turbulent boundary layer is 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 is employed 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 are descried, respectively. The fourthorder compact schemes satisfied by the velocities and pressure in spectral space is derived. As an application,the method is implemented to the wall region of a turbulent boundary to study the interaction between coherent structures. It is found that the numerical results are satisfactory.``

  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. Selectively Structural Determination of Cellulose and Hemicellulose in Plant Cell Wall

    Science.gov (United States)

    Huang, Shih-Chun; Park, Yong; Cosgrove, Daniel; Maranas, Janna; Janna Maranas Team; Daniel Cosgrove Team

    2013-03-01

    Primary plant cell walls support the plant body, and regulate cell size, and plant growth. It contains several biopolymers that can be categorized into three groups: cellulose, hemicellulose and pectin. To determine the structure of plant cell wall, we use small angle neutron scattering in combination with selective deuteration and contrast matching method. We compare the structure between wild Arabidopsis thaliana and its xyloglucan-deficient mutant. Hemicellulose in both samples forms coil with similar radii of gyration, and weak scattering from the mutant suggests a limited amount of hemicellulose in the xyloglucan-deficient mutant. We observe good amount of hemicellulose coating on cellulose microfibrils only in wild Arabidopsis. The absence of coating in its xyloglucan-deficient mutation suggests the other polysaccharides do not have comparable interaction with cellulose. This highlights the importance of xyloglucan in plant cell wall. At larger scale, the average distance between cellulose fibril is found smaller than reported value, which directly reflects on their smaller matured plant size. U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Center for LignoCellulose Structure and Formation

  12. 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 ...

  13. Anatomical structure and ultrastructure of the endocarp cell walls of Argania spinosa (L.) Skeels (Sapotaceae).

    Science.gov (United States)

    Sebaa, H S; Harche, M Kaid

    2014-12-01

    The anatomical and histochemical study of young and adult endocarps of Argania spinosa (sampled from Tindouf; Algeria) shows a general structure that is similar to that of majority of stone fruits. These samples consist of tissues that contain lignified and cellulosic cell walls. The majority of the tissues are composed of sclerenchyma cells; with very thick lignified cell walls and conducting tissues. Coniferyl lignins are abundant in the majority of the lignified tissues. However, the coniferyl lignins appear at the primary xylem during lignification. Syringyl lignins are present in small quantities. The electron microscopy observation of the sclerenchyma cell walls of the young endocarp shows polylamellate strates and, cellular microfibrils in arced patterns. This architecture is observed in the cell walls of the adult endocarp only after the incubation of the tissue in methylamine. These configurations (arcs) are the result of a regular and complete rotation with a 180° variation in the microfibril angle; the complete and symmetrical arcs show a helicoidal mode of construction. The observation of the sclerenchyma cells revealed the capacity of helicoidal morphogenesis to adjust itself under the influence of topological constraints, such as the presence of a large number of pit canals, which maintain symplastic transport. PMID:25125280

  14. Ultrasonic delineation of aortic microstructure: The relative contribution of elastin and collagen to aortic elasticity

    Science.gov (United States)

    Marsh, Jon N.; Takiuchi, Shin; Lin, Shiow Jiuan; Lanza, Gregory M.; Wickline, Samuel A.

    2004-05-01

    Aortic elasticity is an important factor in hemodynamic health, and compromised aortic compliance affects not only arterial dynamics but also myocardial function. A variety of pathologic processes (e.g., diabetes, Marfan's syndrome, hypertension) can affect aortic elasticity by altering the microstructure and composition of the elastin and collagen fiber networks within the tunica media. Ultrasound tissue characterization techniques can be used to obtain direct measurements of the stiffness coefficients of aorta by measurement of the speed of sound in specific directions. In this study we sought to define the contributions of elastin and collagen to the mechanical properties of aortic media by measuring the magnitude and directional dependence of the speed of sound before and after selective isolation of either the collagen or elastin fiber matrix. Formalin-fixed porcine aortas were sectioned for insonification in the circumferential, longitudinal, or radial direction and examined using high-frequency (50 MHz) ultrasound microscopy. Isolation of the collagen or elastin fiber matrices was accomplished through treatment with NaOH or formic acid, respectively. The results suggest that elastin is the primary contributor to aortic medial stiffness in the unloaded state, and that there is relatively little anisotropy in the speed of sound or stiffness in the aortic wall.

  15. Abdominal Aortic Aneurysms: Treatments

    Science.gov (United States)

    ... access catheters Vertebroplasty Women and vascular disease Women's health Social Media Facebook Twitter ... Abdominal Aortic Aneurysms Interventional Radiologists Treat Abdominal Aneurysms Nonsurgically Interventional radiologists are vascular ...

  16. Analysis about the Influence of Clay Core Wall Structure towards the Slope Stability of High Embankment Dam

    Directory of Open Access Journals (Sweden)

    Li Bin

    2015-01-01

    Full Text Available As the main part of the anti-seepage system, core wall is a key point in the design of high em-bankment dam. The dam slope stability is a major factor for the type of core wall. But it is still unclear what effects the core wall structure might have on the slope stability. Based on practical projects of high embankment dam in Nuozhadu, Lianghekou and Shuangjiangkou, this paper analyzes safety factors and dangerous slip sur-faces of dam slopes of high embankment dams in both straight and slanting core wall structures and compares the influences of different core wall structures on the slope stability of high embankment dam through numerical calculations. The safety margin of the embankment dam of straight core wall is larger than that of slanting core wall in the operating condition of the reservoir water level’s drawdown. Compared with that of the straight core wall scheme, the position of the dangerous slip surface of the downstream dam slope is closer to the dam crest in the slanting core wall scheme.

  17. A Migrated Aortic Stent Graft Causing Erosive Spondylopathy

    Energy Technology Data Exchange (ETDEWEB)

    Gestrich, Christopher, E-mail: christopher.gestrich@ukb.uni-bonn.de; Probst, Chris, E-mail: chris.probst@ukb.uni-bonn.de [Universitaetsklinikum Bonn, Department of Cardiac Surgery (Germany); Wilhelm, Kai, E-mail: kai.wilhelm@ek-bonn.de [Johanniterkrankenhaus Bonn, Department of Radiology (Germany); Schiller, Wolfgang, E-mail: wolfgang.schiller@ukb.uni-bonn.de [Universitaetsklinikum Bonn, Department of Cardiac Surgery (Germany)

    2013-12-15

    We report about a patient presenting with back pain 4 months after an uneventful endovascular implantation of an aortic stent graft. Computed tomography scan revealed a migration of the stent with consecutive endoleakage, kink formation, and movement of the stent toward the spine, which caused destruction of the aortic wall as well as vertebral necrosis. Explantation of the stent and replacement of the native aorta relieved the patient of his symptoms.

  18. 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.

  19. 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.

  20. 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...

  1. 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.

  2. Mould resistance design for external wood frame wall systems : Simulation and evaluation of wall structures under varying conditions of exposure using the MRD model

    OpenAIRE

    Dahlström, Carl; Giesen, Emma

    2015-01-01

    Moisture induced damages to building envelopes can result in microbial growth possibly affecting the health and wellbeing of occupants. Recent failing structures and damaged buildings indicate a lack of tools to estimate risk of mould growth and moisture damage. In this work a so-called mould resistance design (MRD) model has been applied for mapping the risk for mould growth on a number of wood-containing wall structures. The MRD model introduces an engineering approach to moisture safety de...

  3. Local structure and shaping of ferroelectric domain walls for photonic applications

    Science.gov (United States)

    Scrymgeour, David

    Ferroelectric lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) have emerged as key technological materials for use in photonic applications, due to the high quality of crystal growth, optical transparency over a wide frequency range (240nm--4.5 mum), and their large electro-optic and nonlinear optical coefficients. Emerging fields of optical communications, optical data storage, displays, biomedical devices, sensing, and defense applications will all rely heavily on such ferroelectrics as a versatile solid-state photonic platform. Diverse functionalities can be created in these materials simply through the patterning of the ferroelectric domains. By creating specific domain features in these materials, it is possible to create new laser wavelengths from existing sources as well as active electro-optic structures that can dynamically focus, shape and steer light. However, the process of domain shaping today is mostly empirical, based on trial-and-error rather than sound, predictive science. The central focus of this thesis work is to develop a fundamental understanding of how to shape and control domain walls in ferroelectrics, specifically in lithium niobate and lithium tantalate, for photonic applications. An understanding of the domain wall phenomena is being approached at two levels: the macroscale and the nanoscale. On the macroscale, different electric field poling techniques are developed and used to create domain shapes of arbitrary orientation. A theoretical framework based on Ginzburg-Landau-Devonshire theory is developed to determine the preferred domain wall shapes. Differences in the poling characteristics and domain wall shapes between the two materials as well as differences in material composition relates to nonstoichiometric defects in the crystal. At the nanoscale, these defects influence the local electromechanical properties of the domain wall. Understanding from both of these approaches has been used to design and create photonic devices

  4. 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.

  5. 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.

  6. 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...

  7. 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.

  8. Properties of the wall structures made of autoclaved cellular concrete products on the polyurethane foam adhesive

    Directory of Open Access Journals (Sweden)

    A.S. Gorshkov

    2013-08-01

    Full Text Available The article presents information on a test experiment for the construction of masonry fragments made of autoclaved cellular concrete products (ААС blocks on the polyurethane adhesive and the ensuing structural, thermal and technological tests of this type of masonry in specialized laboratories and testing facilities. It is shown that the use of polyurethane foam adhesive to bond the concrete blocks in the masonry walls is technically and economically feasible. On the basis of the tests it was concluded that the laying of concrete blocks on the polyurethane adhesive may be used in the construction of non-load bearing interior and exterior walls of buildings, including the filling of the external frame openings of monolithic buildings with floor bearing of the masonry on load bearing monolithic floors (with appropriate justification of the settlement.

  9. 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. PMID:26471666

  10. 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.

  11. 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.

  12. 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 ...

  13. Imaging in aortic dissection

    International Nuclear Information System (INIS)

    Aortic dissection (AD) is a catastrophic aortic disease. Imaging techniques play an invaluable role in the diagnostic evaluation and management of patients with AD. Major signs of AD with different imaging modalities are described in this article with a pertinent discussion on guidelines for the optimized approach of imaging study (13 refs.)

  14. Aortic arch malformations

    Energy Technology Data Exchange (ETDEWEB)

    Kellenberger, Christian J. [University Children' s Hospital, Department of Diagnostic Imaging, Zuerich (Switzerland)

    2010-06-15

    Although anomalies of the aortic arch and its branches are relatively uncommon malformations, they are often associated with congenital heart disease. Isolated lesions may be clinically significant when the airways are compromised by a vascular ring. In this article, the development and imaging appearance of the aortic arch system and its various malformations are reviewed. (orig.)

  15. 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.

  16. 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.

  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. Quantification of abdominal aortic deformation after EVAR

    Science.gov (United States)

    Demirci, Stefanie; Manstad-Hulaas, Frode; Navab, Nassir

    2009-02-01

    Quantification of abdominal aortic deformation is an important requirement for the evaluation of endovascular stenting procedures and the further refinement of stent graft design. During endovascular aortic repair (EVAR) treatment, the aortic shape is subject to severe deformation that is imposed by medical instruments such as guide wires, catheters, and, the stent graft. This deformation can affect the flow characteristics and morphology of the aorta which have been shown to be elicitors for stent graft failures and be reason for reappearance of aneurysms. We present a method for quantifying the deformation of an aneurysmatic aorta imposed by an inserted stent graft device. The outline of the procedure includes initial rigid alignment of the two abdominal scans, segmentation of abdominal vessel trees, and automatic reduction of their centerline structures to one specified region of interest around the aorta. This is accomplished by preprocessing and remodeling of the pre- and postoperative aortic shapes before performing a non-rigid registration. We further narrow the resulting displacement fields to only include local non-rigid deformation and therefore, eliminate all remaining global rigid transformations. Finally, deformations for specified locations can be calculated from the resulting displacement fields. In order to evaluate our method, experiments for the extraction of aortic deformation fields are conducted on 15 patient datasets from endovascular aortic repair (EVAR) treatment. A visual assessment of the registration results and evaluation of the usage of deformation quantification were performed by two vascular surgeons and one interventional radiologist who are all experts in EVAR procedures.

  19. Insights into plant cell wall structure, architecture, and integrity using glycome profiling of native and AFEXTM-pre-treated biomass

    OpenAIRE

    Pattathil, Sivakumar; Hahn, Michael G.; Dale, Bruce E; Chundawat, Shishir P. S.

    2015-01-01

    Cell walls, which constitute the bulk of plant biomass, vary considerably in their structure, composition, and architecture. Studies on plant cell walls can be conducted on both native and pre-treated plant biomass samples, allowing an enhanced understanding of these structural and compositional variations. Here glycome profiling was employed to determine the relative abundance of matrix polysaccharides in several phylogenetically distinct native and pre-treated plant biomasses. Eight distinc...

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

    Science.gov (United States)

    Stylianopoulos, Triantafyllos; Barocas, Victor H

    2007-08-01

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

  1. Aluminum 2219-T87 and 5456-H116 - A comparative study of spacecraft wall materials in dual-wall structures under hypervelocity impact

    Science.gov (United States)

    Schonberg, William P.

    1992-01-01

    All earth-orbiting spacecraft are susceptible to high-speed impacts by pieces of orbital debris. To prevent mission failure and possibly loss of life, protection against perforation by high-speed orbital debris particles must be included in the spacecraft design. Although any number of materials can be used to manufacture perforation-resistant structures, aluminum is often used in such systems because of its relatively high strength-to-weight ratio. This paper presents the results of a study in which the high speed impact response characteristics of dual-wall structures made from two different aluminum alloys were analyzed to determine which alloy would be more suitable for use in a perforation-resistant dual-wall structural system that is to be exposed to the orbital debris environment. Impact response characteristics were obtained numerically and experimentally. At impact speeds below 7 km/s, it was found that the two aluminum alloys considered contributed similar levels of perforation resistance; at speeds in excess of 7 km/s, aluminum 2219-T87 was superior to aluminum 5546-H116 in preventing perforation of dual-wall structural systems.

  2. Electronic structure of single-walled carbon nanotubes inside helical DNA wraps

    Science.gov (United States)

    Snyder, Stacy; Rotkin, Slava

    2007-03-01

    Single stranded DNA can helically wrap a single-walled carbon nanotube (SWNT) leading to changes in electronic structure, which is the subject of our study. Other charged polymers may produce band gap modulation similar to that observed for DNA-SWNT complexes. For these hybrids we assume a regular helical wrap, the potential of which breaks the symmetry of the pristine SWNT. Band structure changes are modeled quantum mechanically using the tight binding method together with self-consistent electrostatics. Gap modulation and band structure symmetry-lowering effects may result in variation of the optical spectra, especially for (slightly forbidden) transverse optical transitions. The effect of environmental screening of charges is investigated. Self-consistent electrostatic calculations yield cohesion energy between a charged, regular wrap and a SWNT of the order of tenths of eV per DNA base [1]. [1] Snyder, S. E., and Rotkin, S. V., Polarization Component of Cohesion Energy in Single-Wall Carbon Nanotube-DNA Complexes, JETP Letters 84, 348 (2006).

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

    Directory of Open Access Journals (Sweden)

    Syed Khasim Mutwalli

    2014-09-01

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

  4. Current Structural Design of Side Wall in KO HCCR TBM for ITER

    Energy Technology Data Exchange (ETDEWEB)

    Shin, K. I.; Lee, D. W.; Gon, J. H.; Lee, E. H.; Kim, S. K.; Yoon, J. S. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Cho, S. [National Fusion Research Institute, Daejeon (Korea, Republic of)

    2013-10-15

    To accomplish the test and validation of the tritium self-sufficiency and a heat transfer extraction during ITER operation, the KO HCCR TBM (Korean Helium Cooled Ceramic Reflector Test Blanket Module) has been developed considering the unique concept of using a graphite reflector. The TBM consists of four sub-modules and one Back Manifold (BM), and each sub-module is composed of a First Wall (FW), Breeding Zone (BZ), Side Wall (SW), and BZ (Breeding Zone) box, which contains beryllium (Be), lithium (Li), and graphite pebbles. Among them, SW has functions as a manifold for the cooling flow distribution from FW cooling channels to BZ, and it should sustain the internal coolant pressure. In this study, the structural design of the SW was performed according to the RCC-MR design code to confirm the design requirement for ITER. To satisfy the KO HCCR TBM design requirements, structural analyses were performed for the preliminary SW design in the TBM. A design channel pressure of 10MPa was considered in the structural design progress of the SW. The stress breakdown was evaluated through PATH in SW. It was concluded that the results satisfy the design requirements in the RCC-MR codes for the ITER.

  5. 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.

  6. Lifetime predictions for the first wall and blanket structure of fusion reactors

    International Nuclear Information System (INIS)

    Lifetime analysis of the first wall including the divertor and limiter is an important subject for the design of fusion reactors. These components are exposed to severe mechanical, thermal, and irradiation effects that limit their useful structural life, and their design lifetime has a large influence on the selection of major reactor design parameters. Particular attention (at the meeting whose papers are included in this report) was given to different approaches and models for the prediction of component lifetimes. Topics covered include life-limiting mechanisms, stress analysis and lifetime evaluation, and erosion and deposition effects

  7. Crystal structure of MraY, an essential membrane enzyme for bacterial cell wall synthesis.

    Science.gov (United States)

    Chung, Ben C; Zhao, Jinshi; Gillespie, Robert A; Kwon, Do-Yeon; Guan, Ziqiang; Hong, Jiyong; Zhou, Pei; Lee, Seok-Yong

    2013-08-30

    MraY (phospho-MurNAc-pentapeptide translocase) is an integral membrane enzyme that catalyzes an essential step of bacterial cell wall biosynthesis: the transfer of the peptidoglycan precursor phospho-MurNAc-pentapeptide to the lipid carrier undecaprenyl phosphate. MraY has long been considered a promising target for the development of antibiotics, but the lack of a structure has hindered mechanistic understanding of this critical enzyme and the enzyme superfamily in general. The superfamily includes enzymes involved in bacterial lipopolysaccharide/teichoic acid formation and eukaryotic N-linked glycosylation, modifications that are central in many biological processes. We present the crystal structure of MraY from Aquifex aeolicus (MraYAA) at 3.3 Å resolution, which allows us to visualize the overall architecture, locate Mg(2+) within the active site, and provide a structural basis of catalysis for this class of enzyme. PMID:23990562

  8. Specific Properties of Single-Wall Carbon Nanohorns Due to Unique Structure

    Science.gov (United States)

    Yudasaka, M.; Nisha, J. A.; Kauya, D.; Kokai, F.; Takahashi, K.; Hirahara, K.; Iijima, S.

    2001-03-01

    Single-wall carbon nanohorns (SWNHs), 30-50 nm long and 2-3 nm thick, form aggregates that resemble dahlia flowers (DF-SWNHs) (diameter: 80 nm). CO2 laser vaporization of graphite at room temperature produced a high yield (about 75several interesting electromagnetic phenomena. The large surface area and micropores are useful for adsorbing other materials. For instance, DF-SWNHs adsorbed ethanol about three times more efficiently than conventional activated carbon. For further applications, we modified their structure by oxidation in oxygen gas. The structural change was obvious in TGA and the Raman spectrum, and TEM showed the holes that were created. This structural change varied the gas adsorption properties [3]. [1] S. Iijima et al., Chem. Phys. Lett., 309 (1999) 165. [2] J. A. Nisha et al., Chem. Phys. Lett., 328 (2000) 381. [3] K. Murata et al. this conference.

  9. Primary Response Assessment Method for Concept Design of Monotonous Thin-Walled Structures

    Directory of Open Access Journals (Sweden)

    V. Zanic

    2005-01-01

    Full Text Available A concept design methodology for monotonous, tapered thin-walled structures (wing/fuselage/ship/bridge is presented including modules for: model generation; loads; primary (longitudinal and secondary (transverse strength calculations; structural feasibility (buckling/fatigue/ultimate strength criteria; design optimization modules based on ES/GA/FFE; graphics. A method for primary strength calculation is presented in detail. It provides the dominant response field for design feasibility assessment. Bending and torsion of the structure are modelled with the accuracy required for concept design. A ‘2.5D-FEM’ model is developed by coupling a 1D-FEM model along the ‘monotonity’ axis and a 2D-FEM model(s transverse to it. The shear flow and stiffness characteristics of the cross-section for bending and pure/restrained torsion are given, based upon the warping field of the cross-section. Examples: aircraft wing and ship hull. 

  10. 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.

  11. Extraction and verification of coherent structures in near-wall turbulence

    Institute of Scientific and Technical Information of China (English)

    Hu Hai-Bao; Du Peng; Huang Su-He; Wang Ying

    2013-01-01

    According to the characteristics of coherent structures in near-wall turbulence,an accurate extraction and verification method is developed based on wavelet transform (WT) and correlation analysis in this paper.At first,the fluid field of a turbulent boundary layer is measured precisely in a gravitational low-speed water tunnel.On the basis of the distribution of the coherent structures,velocity data of three test points are selected and analyzed,whose dimensionless heights are 20.8,33.5,and 42.6.According to the frequency range of power spectrum density (PSD),coherent and incoherent structures are both extracted from the original signals using continuous and orthogonal wavelet transforms.To confirm the validity of the extracted signals,the probability density function (PDF) of each extracted signal is calculated.The result demonstrates that the incoherent structures obey the Gaussian distribution,while the coherent structures deviate from the Gaussian distribution.The PDFs of the coherent structures and the original signals are similar,which shows that the coherent structures make most contributions to the turbulence.For further verification,a correlation parameter between coherent and incoherent structures is defined,which evidently proves the validity of the extraction method in this paper.

  12. 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.

  13. 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. PMID:21219018

  14. Myocardial Infarction and Aortic Root Mycotic Aneurysm Complicating Aortic Valve Endocarditis: Utility of Cardiac CT.

    Science.gov (United States)

    Moores, Aimee E; Cahill, Michael S; Villines, Todd C

    2016-01-01

    Aortic mycotic aneurysms are a rare but life-threatening potential complication of infective endocarditis. Rapid deterioration of the vascular wall in highly focal areas makes these pseudoaneurysms particularly prone to rupture, resulting in uncontrolled aortic hemorrhage. While computed tomography angiography (CTA) is the imaging modality of choice for the evaluation of mycotic aneurysms, it is not routinely performed in patients with known or suspected infective endocarditis (IE). However, current valvular heart disease guidelines support the use of cardiac CTA in cases of IE and suspected perivalvular extension when there is inadequate or ambiguous visualization on echocardiography. Here, we describe a case of IE in which cardiac CTA was used for two purposes: to assess perivalvular complications and to define coronary anatomy in a patient with a suspected embolic myocardial infarction. Subsequent detection of an aortic root mycotic aneurysm not previously demonstrated on transthoracic or transesophageal echocardiography allowed for timely and uncomplicated surgical intervention, while avoiding invasive coronary angiography. PMID:27642299

  15. Computational Fluid Dynamics Analysis of Thoracic Aortic Dissection

    Science.gov (United States)

    Tang, Yik; Fan, Yi; Cheng, Stephen; Chow, Kwok

    2011-11-01

    Thoracic Aortic Dissection (TAD) is a cardiovascular disease with high mortality. An aortic dissection is formed when blood infiltrates the layers of the vascular wall, and a new artificial channel, the false lumen, is created. The expansion of the blood vessel due to the weakened wall enhances the risk of rupture. Computational fluid dynamics analysis is performed to study the hemodynamics of this pathological condition. Both idealized geometry and realistic patient configurations from computed tomography (CT) images are investigated. Physiological boundary conditions from in vivo measurements are employed. Flow configuration and biomechanical forces are studied. Quantitative analysis allows clinicians to assess the risk of rupture in making decision regarding surgical intervention.

  16. 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.

  17. Structure, function, and biosynthesis of plant cell walls: proceedings of the seventh annual symposium in botany

    Energy Technology Data Exchange (ETDEWEB)

    Dugger, W.M.; Bartnicki-Garcia, S. (eds.)

    1984-01-01

    Papers in the following areas were included in these symposium proceedings: (1) cell wall chemistry and biosynthesis; (2) cell wall hydrolysis and associated physiology; (3) cellular events associated with cell wall biosynthesis; and (4) interactions of plant cell walls with pathogens and related responses. Papers have been individually abstracted for the data base. (ACR)

  18. 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.

  19. 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

  20. Cell wall carbohydrates from fruit pulp of Argania spinosa: structural analysis of pectin and xyloglucan polysaccharides.

    Science.gov (United States)

    Aboughe-Angone, Sophie; Nguema-Ona, Eric; Ghosh, Partha; Lerouge, Patrice; Ishii, Tadashi; Ray, Bimalendu; Driouich, Azeddine

    2008-01-14

    Isolated cell walls of Argania spinosa fruit pulp were fractionated into their polysaccharide constituents and the resulting fractions were analysed for monosaccharide composition and chemical structure. The data reveal the presence of homogalacturonan, rhamnogalacturonan-I (RG-I) and rhamnogalacturonan-II (RG-II) in the pectic fraction. RG-I is abundant and contains high amounts of Ara and Gal, indicative of an important branching in this polysaccharide. RG-II is less abundant than RG-I and exists as a dimer. Structural characterisation of xyloglucan using enzymatic hydrolysis, gas chromatography, MALDI-TOF-MS and methylation analysis shows that XXGG, XXXG, XXLG and XLLG are the major subunit oligosaccharides in the ratio of 0.6:1:1.2:1.6. This finding demonstrates that the major neutral hemicellulosic polysaccharide is a galacto-xyloglucan. In addition, Argania fruit xyloglucan has no XUFG, a novel xyloglucan motif recently discovered in Argania leaf cell walls. Finally, the isolation and analysis of arabinogalactan-proteins showed that Argania fruit pulp is rich in these proteoglycans. PMID:18005949

  1. Helium ion beam milling to create a nano-structured domain wall magnetoresistance spin valve.

    Science.gov (United States)

    Wang, Yudong; Boden, S A; Bagnall, D M; Rutt, H N; de Groot, C H

    2012-10-01

    We have fabricated and measured single domain wall magnetoresistance devices with sub-20 nm gap widths using a novel combination of electron beam lithography and helium ion beam milling. The measurement wires and external profile of the spin valve are fabricated by electron beam lithography and lift-off. The critical bridge structure is created using helium ion beam milling, enabling the formation of a thinner gap (and so a narrower domain wall) than that which is possible with electron beam techniques alone. Four-point probe resistance measurements and scanning electron microscopy are used to characterize the milled structures and optimize the He ion dose. Successful operation of the device as a spin valve is demonstrated, with a 0.2% resistance change as the external magnetic field is cycled. The helium ion beam milling efficiency as extracted from electrical resistance measurements is 0.044 atoms/ion, about half the theoretical value. The gap in the device is limited to a maximum of 20 nm with this technique due to sub-surface swelling caused by injected ions which can induce catastrophic failure in the device. The fine patterning capabilities of the helium ion microscope milling technique indicate that sub-5 nm constriction widths could be possible. PMID:22972003

  2. 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....

  3. Seismic Performance Evaluation of Multistory Reinforced Concrete Moment Resisting Frame Structure with Shear Walls

    Directory of Open Access Journals (Sweden)

    Junwon Seo

    2015-10-01

    Full Text Available This paper is intended to evaluate the seismic performance of a twelve-story reinforced concrete moment-resisting frame structure with shear walls using 3D finite element models according to such seismic design regulations as Federal Emergency Management Agency (FEMA guideline and seismic building codes including Los Angeles Tall Building Structural Design Council (LATBSDC code. The structure is located in Seismic Zone 4, considered the highest-seismic-risk classification established by the U.S. Geological Survey. 3D finite element model was created in commercially available finite element software. As part of the seismic performance evaluation, two standard approaches for the structure seismic analysis were used; response spectrum analysis and nonlinear time-history analysis. Both approaches were used to compute inter-story drift ratios of the structure. Seismic fragility curves for each floor of the structure were generated using the ratios from the time history analysis with the FEMA guideline so as to evaluate their seismic vulnerability. The ratios from both approaches were compared to FEMA and LATBSDC limits. The findings revealed that the floor-level fragility mostly decreased for all the FEMA performance levels with an increase in height and the ratios from both approaches mostly satisfied the codified limits.

  4. Severe edge effects and simple complimentary interior solutions for thin-walled anisotropic and composite structures

    Science.gov (United States)

    Horgan, C. O.; Simmonds, J. G.

    1994-12-01

    Many useful thin-walled structures of interest to the U.S. Army, such as rifle barrels, automotive parts, rocket casings, helicopter blades, driveshafts, and containment vessels, are often constructed of layers of anisotropic, filament or fiber-reinforced materials. While many of these structures are subject to severe mechanical, inertial, or thermal loads, they often must be designed to remain elastic. This means that it is particularly important to be able to compute accurately global characteristics, such as buckling loads and natural frequencies, as well as local information such as stresses near holes or edges. Two important, complementary regions of such structures, have been studied, namely, the interior where there are no steep stress gradients, and the edge zone(s) where stress gradients are high. For both regions, simplified, cost-effective asymptotic methods have been developed. These considerations are particularly important in layered, anisotropic structures because many investigators have (1) claimed that higher-order (and hence computationally expensive) beam, plate, or shell theories are needed for such structures and (2) not paid sufficient attention to the particularly severe end effects (breakdown of Saint-Venant's principle) such structures engender.

  5. 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.

  6. 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.

  7. Tailoring polyacrylonitrile interfacial morphological structure by crystallization in the presence of single-wall carbon nanotubes.

    Science.gov (United States)

    Zhang, Yiying; Song, Kenan; Meng, Jiangsha; Minus, Marilyn L

    2013-02-01

    In order to improve stress transfer between polymer matrixes and nanofillers, controlling the structure development in the interphase region during composite processing is a necessity. For polyacrylonitrile (PAN)/single-wall carbon nanotubes (SWNT) composites, the formation of the PAN interphase in the presence of the SWNT as a function of processing conditions is studied. Under these conditions, three distinct interfacial coating morphologies of PAN are observed on SWNT. In the semidilute polymer concentration regime subjected to shearing, PAN extended-chain tubular coatings are formed on SWNT. Dilute PAN/SWNT quiescent solutions subjected to cooling yields hybrid periodic shish-kebab structures (first observation for PAN polymer), and dilute PAN/SWNT quiescent solutions subjected to rapid cooling results in the formation of an irregular PAN crystalline coating on the SWNT. PMID:23286387

  8. 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

  9. Fatal aortic pseudoaneurysm from disseminated Mycobacterium kansasii infection: case report.

    Science.gov (United States)

    Ehsani, Laleh; Reddy, Sujan C; Mosunjac, Mario; Kraft, Colleen S; Guarner, Jeannette

    2015-03-01

    Mycobacterium kansasii is a photochromogenic, slow-growing mycobacterium species that can cause pulmonary infection in patients with predisposing lung diseases, as well as extrapulmonary or disseminated disease in immunosuppressed patients. We describe a patient with a myelodysplastic syndrome, disseminated M kansasii infection, and ruptured aortic aneurysm. He had a recent diagnosis of mycobacterium cavitary lung lesions and was transferred to our facility for possible surgical intervention of an aortic aneurysm. Few hours after admission, the patient suddenly collapsed and died despite resuscitation efforts. A complete autopsy was performed and showed ruptured ascending aortic pseudoaneurysm with hemopericardium, disseminated necrotizing and nonnecrotizing granulomas with acid-fast bacilli in the aortic wall, lungs, heart, liver, spleen, and kidneys. Further genetic studies were consistent with monocytopenia and mycobacterial infection syndrome. PMID:25537975

  10. Aortic Aneurysm Repair

    Medline Plus

    Full Text Available ... as atherosclerosis, high blood pressure, smokers, or a family history of abdominal aortic aneurysms. Today’s patient is ... be screened. In fact, patients who have a family history of aneurysm, men who are smoking over ...

  11. Aortic Aneurysm Repair

    Medline Plus

    Full Text Available ... atherosclerosis, high blood pressure, smokers, or a family history of abdominal aortic aneurysms. Today’s patient is a ... screened. In fact, patients who have a family history of aneurysm, men who are smoking over the ...

  12. Nonsteroidal antiinflammatory drugs are associated with increased aortic stiffness

    Directory of Open Access Journals (Sweden)

    Martin Claridge

    2005-07-01

    Full Text Available Martin Claridge1, Simon Hobbs1, Clive Quick2, Nick Day3, Andrew Bradbury1, Teun Wilmink11Department of Vascular Surgery, University of Birmingham, Birmingham Heartlands Hospital Birmingham, UK; 2Department of Surgery, Hinchingbrooke Hospital, Huntingdon, UK; 3Department of Epidemiology and Biostatistics, University of Cambridge, Cambridge, UKObjectives: Nonsteroidal antiinflammatory drugs (NSAIDS have been shown to retard aneurysm growth in animal models. In vitro studies have shown an inhibitory effect of NSAIDS on matrix metalloproteinase-9, interleukin-1β, and IL-6 mediated arterial wall elastolysis. The aim of this study was to investigate the effects of NSAIDs on arterial stiffness, a surrogate marker of elastolysis.Methods: 447 subjects enrolled in a community-based abdominal aortic aneurysm (AAA screening program were assessed for age, blood pressure, smoking status, and drug history. Aortic diameter and stiffness were measured by M-Mode ultrasound. The concentration of the amino-terminal propeptide of type III procollagen was used as a proxy measurement of type III collagen turnover.Results: NSAID ingestion was significantly (p = 0.006 associated with increased aortic wall stiffness after adjusting for age, aortic diameter, blood pressure, and smoking status. No such effect was seen for β-blockers, calcium channel antagonists, nitrates, angiotensin-converting enzyme inhibitors, diuretics, or antiplatelet agents.Discussion: These novel data show that NSAIDS are associated with increased aortic stiffness, possibly through the effects of cytokine mediated elastolysis. This in turn may prevent aortic expansion and the development of AAA.Keywords: nonsteroidal antiinflammatory drugs, abdominal aortic aneurysm, aortic stiffness, elastolysis

  13. Endoleak Assessment Using Computational Fluid Dynamics and Image Processing Methods in Stented Abdominal Aortic Aneurysm Models

    Science.gov (United States)

    Lu, Yueh-Hsun; Mani, Karthick; Panigrahi, Bivas; Hsu, Wen-Tang

    2016-01-01

    Endovascular aortic aneurysm repair (EVAR) is a predominant surgical procedure to reduce the risk of aneurysm rupture in abdominal aortic aneurysm (AAA) patients. Endoleak formation, which eventually requires additional surgical reoperation, is a major EVAR complication. Understanding the etiology and evolution of endoleak from the hemodynamic perspective is crucial to advancing the current posttreatments for AAA patients who underwent EVAR. Therefore, a comprehensive flow assessment was performed to investigate the relationship between endoleak and its surrounding pathological flow fields through computational fluid dynamics and image processing. Six patient-specific models were reconstructed, and the associated hemodynamics in these models was quantified three-dimensionally to calculate wall stress. To provide a high degree of clinical relevance, the mechanical stress distribution calculated from the models was compared with the endoleak positions identified from the computed tomography images of patients through a series of imaging processing methods. An endoleak possibly forms in a location with high local wall stress. An improved stent graft (SG) structure is conceived accordingly by increasing the mechanical strength of the SG at peak wall stress locations. The presented analytical paradigm, as well as numerical analysis using patient-specific models, may be extended to other common human cardiovascular surgeries.

  14. Endoleak Assessment Using Computational Fluid Dynamics and Image Processing Methods in Stented Abdominal Aortic Aneurysm Models

    Directory of Open Access Journals (Sweden)

    Yueh-Hsun Lu

    2016-01-01

    Full Text Available Endovascular aortic aneurysm repair (EVAR is a predominant surgical procedure to reduce the risk of aneurysm rupture in abdominal aortic aneurysm (AAA patients. Endoleak formation, which eventually requires additional surgical reoperation, is a major EVAR complication. Understanding the etiology and evolution of endoleak from the hemodynamic perspective is crucial to advancing the current posttreatments for AAA patients who underwent EVAR. Therefore, a comprehensive flow assessment was performed to investigate the relationship between endoleak and its surrounding pathological flow fields through computational fluid dynamics and image processing. Six patient-specific models were reconstructed, and the associated hemodynamics in these models was quantified three-dimensionally to calculate wall stress. To provide a high degree of clinical relevance, the mechanical stress distribution calculated from the models was compared with the endoleak positions identified from the computed tomography images of patients through a series of imaging processing methods. An endoleak possibly forms in a location with high local wall stress. An improved stent graft (SG structure is conceived accordingly by increasing the mechanical strength of the SG at peak wall stress locations. The presented analytical paradigm, as well as numerical analysis using patient-specific models, may be extended to other common human cardiovascular surgeries.

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

    Science.gov (United States)

    Kristensen, Jan B; Thygesen, Lisbeth G; Felby, Claus; Jørgensen, Henning; Elder, Thomas

    2008-01-01

    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. PMID:18471316

  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. Infilled masonry walls contribution in mitigating progressive collapse of multistory reinforced concrete structures according to UFC guidelines

    Science.gov (United States)

    Helmy, Huda; Hadhoud, Hamed; Mourad, Sherif

    2015-09-01

    A structure is subjected to progressive collapse when an element fails, resulting in failure of adjoining structural elements which, in their turn, cause further structural failure leading eventually to partial or total collapse. The failure of a primary vertical support might occur due to extreme loadings such as bomb explosion in a terrorist attack, gas explosion and huge impact of a car in the parking area. Different guidelines such as the General Services Administration (GSA 2003) and the Unified Facilities Criteria (UFC 2009) addressed the structural progressive collapse due to the sudden loss of a main vertical support. In the current study, a progressive collapse assessment according to the UFC guidelines is carried out for a typical ten-story reinforced concrete framed structure designed according to codes [(ACI 318-08) and (ASCE 7-10)] for minimum design loads for buildings and other structures. Fully nonlinear dynamic analysis for the structure was carried out using Applied Element Method (AEM). The investigated cases included the removal of a corner column, an edge column, an edge shear wall, internal columns and internal shear wall. The numerical analysis showed that simplification of the problem into 3D bare frames would lead to uneconomical design. It was found for the studied case that, the infilled masonry walls have a valuable contribution in mitigating progressive collapse of the reinforced concrete framed structures. Neglecting these walls would lead to uneconomical design.

  19. Deuteron electromagnetic structure functions and polarization properties in soft-wall AdS/QCD

    CERN Document Server

    Gutsche, Thomas; Schmidt, Ivan

    2016-01-01

    We apply a soft-wall AdS/QCD approach to the description of deuteron structure functions and tensor polarized properties. Present work is a completion of our previous study on electromagnetic form factors. By the appropriate choice of two couplings in the effective action we are able to reproduce both the form factors and structure functions in full consistency with model-independent constraints set by perturbative QCD. Our framework is based on a five-dimensional action in AdS space formulated in terms of vector fields dual to the deuteron and the electromagnetic fields. The AdS fields depend on four Minkowski and one holographic coordinate $z$. The scale dependence of the form factors and structure functions is consistent with quark counting rules implying the $1/Q^{10}$ behavior of the charge form factor $G_C(Q^2)$, structure functions $A(Q^2)$ and $B(Q^2)$, and the $1/Q^{12}$ behavior of the magnetic $G_M(Q^2)$ and quadrupole $G_Q(Q^2)$ form factors.

  20. Anatomics Knowledges of Aortic Root in the Transcatheter Aortic Valve Implantation.

    Directory of Open Access Journals (Sweden)

    Marcelo Cerezo

    2010-12-01

    Full Text Available The Aortic Valve is a valvular system that bears different high pressure forces. It takes part of a complex structure called Aortic Root. Nowadays, anatomic knowledge has taken a preponderant role, due to the use of the Transcatether Aortic Valve Implant (TAVI. To describe the patient´s characteristics which exclude them of the TAVI for anatomic reasons in cadaveric dissections and transthoracic echocardiograms. A descriptive retrospective analysis of 67 individuals was performed and divided into two groups. Group A: Formalized cadaveric dissections with hypertrofic hearts and aortic sclerosis signs from the Chair A of Anatomy of the University of La Plata (UNLP. Group B: Transthoracic Echocardiograms realized at the San Martín Hospital of La Plata between January 2005 and December 2009. Out of 67 individuals assessed, 17 (25% had one or more contraindications for TAVI. Five on Group A (36%, and 12 on Group B (23%. The most common anatomic contraindication was the Ascending Aortic diameter less than 30mm and the aortic annulus less than 20mm, following to the RAo-TSVI Angle more than 145° (2 to Group A, and 4 to Group B and the Septal thickness more than 17mm (no one to Group A, and 3 to Group B. Only just one individual was found with a low implant left coronary artery in the Group A avoiding TAVI. According to this study, the anatomic contraindications to realize TAVI are frequent due to the diagnosis devices available at the moment. The anatomic aortic root knowledge and the aortic valve interindividual variability will allow the improvement of the manufactured devices made in the market.

  1. 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.

  2. 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.

  3. The Effect of Shear Wall Distribution on the Dynamics of Reinforced Concrete Structures

    International Nuclear Information System (INIS)

    The inclusion of a soft storey in multistory concrete buildings is a feature gaining popularity in urban areas where land is of exorbitant cost. In earthquake prone zones, this feature has been observed in post earthquake investigations. Although engineers are prepared to accept the notion that a soft storey poses a weak link in Seismic Design, yet the idea demands better understanding. The following study illustrates the importance of the judicious distribution of shear walls. The selected building is analyzed through nine numerical models which address the behavior of framed structures. The parameters discussed include, inter alias, the fundamental period of vibration, lateral displacements, axial and shear forces. It is noticed that an abrupt change in stiffness between the soft storey and the level above is responsible for increasing the strength demand on first storey columns. Extending the elevator shafts throughout the soft storey is strongly recommended

  4. 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...

  5. 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.

  6. 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.

  7. Reoperative transapical transcatheter aortic valve replacement for central aortic regurgitation.

    Science.gov (United States)

    Zhu, Yuanjia; Kapadia, Samir; Krishnaswamy, Amar; Svensson, Lars G; Mick, Stephanie

    2016-09-01

    Paravalvular leak-related aortic regurgitation after transcatheter aortic valve replacement (TAVR) is a common complication and is associated with increased short- and long-term mortality. However, the impact of isolated central aortic regurgitation is unknown. We report a case of transapical (TA) TAVR with postprocedural central aortic regurgitation, who returned after two years with progression of regurgitation. A reoperative valve-in-valve TA-TAVR was performed. PMID:27405799

  8. Aortic regurgitation after transcatheter aortic valve replacement.

    Science.gov (United States)

    Werner, Nikos; Sinning, Jan-Malte

    2014-01-01

    Paravalvular aortic regurgitation (AR) negatively affects prognosis following transcatheter aortic valve replacement (TAVR). As transcatheter heart valves (THV) are anchored using a certain degree of oversizing at the level of the aortic annulus, incomplete stent frame expansion because of heavily annular calcifications, suboptimal placement of the prosthesis, and/or annulus-prosthesis size-mismatch can contribute to paravalvular AR with subsequent increased mortality risk. Echocardiography is essential to differentiate between transvalvular and paravalvular AR and to further elucidate the etiology of AR during the procedure. However, because echocardiographic quantification of AR in TAVR patients remains challenging, especially in the implantation situation, a multimodal approach to the evaluation of AR with use of hemodynamic measurements and imaging modalities is useful to precisely quantify the severity of AR immediately after valve deployment. "Next-generation" THVs are already on the market and first results show that paravalvular AR related to design modifications (eg, paravalvular space-fillers, full repositionability) are rarely seen in these valve types.  PMID:24632758

  9. Spontaneous aortic dissecting hematoma in two dogs.

    Science.gov (United States)

    Boulineau, Theresa Marie; Andrews-Jones, Lydia; Van Alstine, William

    2005-09-01

    This report describes 2 cases of spontaneous aortic dissecting hematoma in young Border Collie and Border Collie crossbred dogs. Histology was performed in one of the cases involving an unusual splitting of the elastin present within the wall of the aorta, consistent with elastin dysplasia as described in Marfan syndrome in humans. The first case involved a young purebred Border Collie that died suddenly and the second case involved a Border Collie crossbred dog that died after a 1-month history of seizures. Gross lesions included pericardial tamponade with dissection of the ascending aorta in the former case and thoracic cavity hemorrhage, mediastinal hematoma, and aortic dissection in the latter. Histologic lesions in the case of the Border Collie crossbred dog included a dissecting hematoma of the ascending aorta with elastin dysplasia and right axillary arterial intimal proliferation. PMID:16312247

  10. Computer modeling of tasks in dynamics of viscoelastic thin-walled elements in structures of variable thickness

    Directory of Open Access Journals (Sweden)

    R.A. Abdikarimov

    2014-08-01

    Full Text Available The paper presents a numerical method and algorithm for solving tasks in dynamics of viscoelastic thin-walled elements in structures of variable thickness. The equations of motion concerning deflections are described by partial integro-differential equations (PIDE. Using Bubnov-Galerkin’s method, based on the polynomial approximation of deflections, the task is limited to the study of the system of ordinary IDEs, where the independent variable is time. The solution to the system of IDEs is obtained by the offered numerical method, which results into the algorithm of the numerical solution and the program in the Delphi algorithmic language. The study of nonlinear vibrations of thin-walled elements in structures, allowing for variable thickness in the geometrical nonlinear statement, has enabled revealing a number of mechanical effects. Depending on physico-mechanical and geometrical parameters of the considered viscoelastic thin-walled elements in structures, the authors reccommend how to use the rigidity of the system.

  11. Unique Electronic Structure in a Porous Ga-In Bimetallic Oxide Nano-Photocatalyst with Atomically Thin Pore Walls.

    Science.gov (United States)

    Chen, Hui; Yu, Guangtao; Li, Guo-Dong; Xie, Tengfeng; Sun, Yuanhui; Liu, Jingwei; Li, Hui; Huang, Xuri; Wang, Dejun; Asefa, Tewodros; Chen, Wei; Zou, Xiaoxin

    2016-09-12

    A facile synthetic route is presented that produces a porous Ga-In bimetallic oxide nanophotocatalyst with atomically thin pore walls. The material has an unprecedented electronic structure arising from its ultrathin walls. The bottom of the conduction band and the top of the valence band of the material are distributed on two opposite surfaces separated with a small electrostatic potential difference. This not only shortens the distance by which the photogenerated charges travel from the sites where they are generated to the sites where they catalyze the reactions, but also facilitates charge separations in the material. The porous structure within the walls results in a large density of exposed surface reactive/catalytic sites. Because of these optimized electronic and surface structures, the material exhibits superior photocatalytic activity toward the hydrogen evolution reaction (HER). PMID:27529769

  12. 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.

  13. 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

  14. Structures tubulaires minces en matériaux composites. Principes de calcul Thin-Walled Composite Tubular Structures. Calculation Method

    Directory of Open Access Journals (Sweden)

    Odru P.

    2006-11-01

    Full Text Available Cet article présente une méthode de calcul des structures composites fibres-résine appliquée aux cas des tubes minces. Outre l'établissement des relations contraintes - déformations généralisées des tubes à partir des caractéristiques des matériaux de base et de leur orientation, on pose les relations permettant de calculer leur comportement et leur dimensionnement sous des charges axisymétriques combinées de traction, pression et flexion. Une méthode simplifiée applicable au cas des composites microfissurés est aussi présentée. On montre ensuite, à travers quelques exemples concrets d'applications, les propriétés intéressantes ou inhabituelles que le matériau permet de conférer aux structures. This article presents a method of calculation of composite structures applied to thin-walled tubes. Starting from the characteristics and orientation of the basic materials, the generalized stress-strain equations of the tubes are determined ; then the relationship allowing the calculation of their design and behavior under combined axisymmetrical loads of tension, pressure and bending are established. A simplified method applicable to microcracked composite materials is also described. Several complete examples of applications illustrate the interesting or unusual properties that this material can impart to structures

  15. Minimally Invasive Aortic Valve Replacement

    Medline Plus

    Full Text Available ... conditions or other significant medical problems, the American College of Cardiology recommends aortic valve replacement for basically ... more likely we see aortic stenosis. Again, patient education is part of the evaluation and management of ...

  16. Minimally Invasive Aortic Valve Replacement

    Medline Plus

    Full Text Available ... North Carolina. My name is John Streitman and I'm a cardiothoracic surgeon here at the Heart ... the corrective surgery of aortic valve replacement. If I have aortic stenosis, are there any activities that ...

  17. Minimally Invasive Aortic Valve Replacement

    Medline Plus

    Full Text Available ... of that slide, that demonstrates that patients with New York Heart Association class heart failure 1 and ... right down the aortic valve and that's the new aortic valve that Dr. Streitman's placed. And you ...

  18. Minimally Invasive Aortic Valve Replacement

    Medline Plus

    Full Text Available ... to help prevent aortic stenosis? There's no prophylactic methods that anybody can take to prevent aortic stenosis ... it will be archived on the ORlive Web site and ORlive.com and, of course, a link ...

  19. 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.

  20. Assessment of thermo-mechanical behavior in CLAM steel first wall structures

    Energy Technology Data Exchange (ETDEWEB)

    Liu Fubin, E-mail: liufubin_1216@126.com [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, Liaoning (China); Yao Man, E-mail: yaoman@dlut.edu.cn [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, Liaoning (China)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer China Low Activation Martensitic steel (CLAM) as FW the structural material. Black-Right-Pointing-Pointer The thermo-mechanical behavior of the FW was analyzed under the condition of normal ITER operation combined effect of plasma heat flux and neutron heating. Black-Right-Pointing-Pointer The temperature dependence of the material physical properties of CLAM is summarized. - Abstract: The temperature and strain distributions of the mockup with distinct structural material (SS316L or China Low Activation Martensitic steel (CLAM)) in two-dimensional model were calculated and analyzed, based on a high heat flux (HHF) test recently reported with heat flux of 3.2 MW/m{sup 2}. The calculated temperature and strain results in the first wall (FW), in which SS316L is as the structural material, showed good agreement with HHF test. By substituting CLAM steel for SS316L the contrast analysis indicates that the thermo-mechanical property for CLAM steel is better than that of SS316 at the same condition. Furthermore, the thermo-mechanical behavior of the FW was analyzed under the condition of normal ITER operation combined effect of plasma heat flux and neutron heating.

  1. 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.

  2. Histopathology of aortic complications in bicuspid aortic valve versus Marfan syndrome: relevance for therapy?

    Science.gov (United States)

    Grewal, Nimrat; Franken, Romy; Mulder, Barbara J M; Goumans, Marie-José; Lindeman, Johannes H N; Jongbloed, Monique R M; DeRuiter, Marco C; Klautz, Robert J M; Bogers, Ad J J C; Poelmann, Robert E; Groot, Adriana C Gittenberger-de

    2016-05-01

    Patients with bicuspid aortic valve (BAV) and patients with Marfan syndrome (MFS) are more prone to develop aortic dilation and dissection compared to persons with a tricuspid aortic valve (TAV). To elucidate potential common and distinct pathways of clinical relevance, we compared the histopathological substrates of aortopathy. Ascending aortic wall biopsies were divided in five groups: BAV (n = 36) and TAV (n = 23) without and with dilation and non-dilated MFS (n = 8). General histologic features, apoptosis, the expression of markers for vascular smooth muscle cell (VSMC) maturation, markers predictive for ascending aortic dilation in BAV, and expression of fibrillin-1 were investigated. Both MFS and BAV showed an altered distribution and decreased fibrillin-1 expression in the aorta and a significantly lower level of differentiated VSMC markers. Interestingly, markers predictive for aortic dilation in BAV were not expressed in the MFS aorta. The aorta in MFS was similar to the aorta in dilated TAV with regard to the presence of medial degeneration and apoptosis, while other markers for degeneration and aging like inflammation and progerin expression were low in MFS, comparable to BAV. Both MFS and BAV aortas have immature VSMCs, while MFS and TAV patients have a similar increased rate of medial degeneration. However, the mechanism leading to apoptosis is expected to be different, being fibrillin-1 mutation induced increased angiotensin-receptor-pathway signaling in MFS and cardiovascular aging and increased progerin in TAV. Our findings could explain why angiotensin inhibition is successful in MFS and less effective in TAV and BAV patients. PMID:26129868

  3. 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

  4. Assessment of Analytical Prediction of JNES Seismic Wall Pressure Data for ABWR Model Structures

    International Nuclear Information System (INIS)

    Prior to the establishment of the Japan Nuclear Energy Safety Organization (JNES), the Nuclear Power Engineering Corporation (NUPEC) of Japan conducted a series of large-scale field tests for the Ministry of Economy, Trade and Industry (METI) of Japan to address various aspects of the soil-structure interaction (SSI) effect on the seismic response of nuclear power plant (NPP) structures. The experimental studies used several scaled models of advanced boiling water reactor (ABWR) structures, which were constructed at field sites typical of an actual NPP site. As part of the US-Japan collaboration effort on the soil-structure interaction (SSI) phenomenon, the U.S. Nuclear Regulatory Commission (NRC) and Brookhaven National Laboratory (BNL) performed a study to correlate the recorded earthquake induced wall pressures using commercial programs. The purpose of this study is to assess the adequacy and performance of the analytical SSI methods in predicting recorded data, and to determine the effect and breadth of the soil uncertainty on the seismic response computations to capture seismic induced passive soil pressures. The commercial programs used for the correlation study are SASSI and LS-DYNA. SASSI uses the sub-structuring method, which treats SSI responses by superimposing the finite element model of the structure with the analytical solution of wave propagation in the half-space. LS-DYNA is an explicit finite element program, and is only appropriate to treating problems which can be defined with finite boundaries. Therefore, the half-space SSI problem is approximately modeled using LS-DYNA with explicit finite elements for both structure and the surrounding soil to the extent that the scattered waves resulting from the structural vibration will not be reflected at the soil boundaries. This is further ensured by placing the Lysmer transmitting elements at the soil mesh boundaries to absorb the outgoing waves. This paper presents an overview of the NRC

  5. 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.

  6. 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.

  7. 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.

  8. Influence of structural heterogeneity of nanoporous sorbent walls on hydrogen storage

    International Nuclear Information System (INIS)

    Heterogeneity is an ubiquitous aspect of adsorption, often modifying substantially the observed behaviour of the adsorbate-adsorbent system. In this paper, the influence of heterogeneity is explicitly analyzed for the case of the adsorption of molecular hydrogen onto nanoporous carbon. Grand Canonical Monte Carlo simulations were used to study the mechanism of adsorption in the models of the adsorbate that include both energetic and structural modifications of graphene-based slit pores. In particular, a partial substitution of carbons by boron modifies both the symmetry of the energy landscape and the strength of hydrogen physisorption; which results in considerable increases of the amount of adsorbed gas without major modification of the mechanism of adsorption. Additional heterogeneity arises from structural modifications of the adsorbent by neutron irradiation of boron-doped samples, where the boron fission products generate additional surface area for adsorption. Simulations of adsorption in such pores show that hydrogen uptake is strongly dependent on the chemical nature of the modified pore walls.

  9. 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.

  10. 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.

  11. Including aortic valve morphology in computational fluid dynamics simulations: initial findings and application to aortic coarctation.

    Science.gov (United States)

    Wendell, David C; Samyn, Margaret M; Cava, Joseph R; Ellwein, Laura M; Krolikowski, Mary M; Gandy, Kimberly L; Pelech, Andrew N; Shadden, Shawn C; LaDisa, John F

    2013-06-01

    Computational fluid dynamics (CFD) simulations quantifying thoracic aortic flow patterns have not included disturbances from the aortic valve (AoV). 80% of patients with aortic coarctation (CoA) have a bicuspid aortic valve (BAV) which may cause adverse flow patterns contributing to morbidity. Our objectives were to develop a method to account for the AoV in CFD simulations, and quantify its impact on local hemodynamics. The method developed facilitates segmentation of the AoV, spatiotemporal interpolation of segments, and anatomic positioning of segments at the CFD model inlet. The AoV was included in CFD model examples of a normal (tricuspid AoV) and a post-surgical CoA patient (BAV). Velocity, turbulent kinetic energy (TKE), time-averaged wall shear stress (TAWSS), and oscillatory shear index (OSI) results were compared to equivalent simulations using a plug inlet profile. The plug inlet greatly underestimated TKE for both examples. TAWSS differences extended throughout the thoracic aorta for the CoA BAV, but were limited to the arch for the normal example. OSI differences existed mainly in the ascending aorta for both cases. The impact of AoV can now be included with CFD simulations to identify regions of deleterious hemodynamics thereby advancing simulations of the thoracic aorta one step closer to reality. PMID:22917990

  12. 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.

  13. 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.

  14. Carbon chains and the (5,5) single-walled nanotube: Structure and energetics versus length

    Science.gov (United States)

    Rodriguez, Kenneth R.; Williams, Shaun M.; Young, Matt A.; Teeters-Kennedy, Shannon; Heer, Joseph M.; Coe, James V.

    2006-11-01

    Reliable thermochemistry is computed for infinite stretches of pure-carbon materials including acetylenic and cumulenic carbon chains, graphene sheet, and single-walled carbon nanotubes (SWCNTs) by connection to the properties of finite size molecules that grow into the infinitely long systems. Using ab initio G3 theory, the infinite cumulenic chain (:CCCC:) is found to be 1.9±0.4kcal/mol per carbon less stable in free energy at room temperature than the acetylenic chain (C•C-CC•) which is 24.0kcal/mol less stable than graphite. The difference between carbon-carbon triple, double, and single bond lengths (1.257, 1.279, and 1.333Å, respectively) in infinite chains is evident but much less than with small hydrocarbon molecules. These results are used to evaluate the efficacy of similar calculations with the less rigorous PM3 semiempirical method on the (5,5) SWCNT, which is too large to be studied with high-level ab initio methods. The equilibrium electronic energy change for C(g )→C[infinite (5,5) SWCNT] is -166.7kcal/mol, while the corresponding free energy change at room temperature is -153.3kcal/mol (6.7kcal/mol less stable than graphite). A threefold alternation (6.866, 6.866, and 6.823Å) in the ring diameter of the equilibrium structure of infinitely long (5,5) SWCNT is apparent, although the stability of this structure over the constant diameter structure is small compared to the zero point energy of the nanotube. In general, different (n,m) SWCNTs have different infinite tube energetics, as well as very different energetic trends that vary significantly with length, diameter, and capping.

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

    Science.gov (United States)

    Yang, Jian-Qun; Li, Xing-Ji; Liu, Chao-Ming; Ma, Guo-Liang; Gao, Feng

    2015-11-01

    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 application 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 irradiation 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 displacements. 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 exposed

  16. 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

  17. Spectral and spatial structure of extreme ultraviolet radiation in laser plasma-wall interactions

    NARCIS (Netherlands)

    Kuznetsov, A.; Stuik, R.; Bijkerk, F.; 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 Te ~ 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 wall was i

  18. 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.

  19. 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.

  20. Mast Cells in Abdominal Aortic Aneurysms

    DEFF Research Database (Denmark)

    Shi, Guo-Ping; Lindholt, Jes Sanddal

    2013-01-01

    , outer media and adventitia inflammation, aortic wall expansion, endothelium erosion, and eventual rupture and thrombosis. Experimental animal AAA models and MC reconstitution technique allowed examination of a direct role of MCs in AAA pathogenesis, and identification of the exact role of each MC......, and two cohort studies showing the systemic level of MC specific chymase and tryptase is associated with aneurysmal growth rate, need for later aneurysmal repair and even overall mortality. These observations offer new opportunities to prevent or slow AAA growth in humans, and specific antimastcell drugs...

  1. Frequency Response of Near-Wall Coherent Structures to Localized Periodic Blowing and Suction in Turbulent Boundary Layer

    Institute of Scientific and Technical Information of China (English)

    LIU Jian-Hua; JIANG Nan

    2008-01-01

    We experimentally investigate the frequency response of near-wall coherent structures to localized periodic blowing and suction through a spanwise slot in a turbulent boundary layer by changing the frequency of periodic disturbance at similar velocities of free stream.The effects of blowing and suction disturbance on energy redistribution,turbulent intensity u'+rms over y+ and waveforms of phase-averaged velocity during sweeping process are respectively discussed under three frequencies of periodic blowing and suction in near-wall region of turbulent boundary layer,compared with those in a standard turbulent boundary layer.The most effective disturbancefrequency is figured out in this system.

  2. Manufacturing and maintenance technologies developed for a thick-wall structure of the ITER vacuum vessel

    International Nuclear Information System (INIS)

    Development of welding, cutting and non-destructive testing (NDT) techniques, and development of remotized systems have been carried out for on-site manufacturing and maintenance of the thick-wall structure of the International Thermonuclear Experimental Reactor (ITER) vacuum vessel (VV). Conventional techniques, including tungsten inert gas welding, plasma cutting, and ultrasonic inspection, have been improved and optimized for the application to thick austenitic stainless steel plates. In addition, advanced methods have been investigated, including reduced-pressure electron-beam and multi-pass neodymium-doped yttrium aluminum garnet (NdYAG) laser welding, NdYAG laser cutting, and electro-magnetic acoustic transducer inspection, to improve cost and technical performance. Two types of remotized systems with different payloads have been investigated and one of them has been fabricated and demonstrated in field joint welding, cutting, and NDT tests on test mockups and full-scale ITER VV sector models. The progress and results of this development to date provide a high level of confidence that the manufacturing and maintenance of the ITER VV is feasible

  3. Quadrilateral shell finite element for analysis of thin-walled reinforced concrete structures

    Directory of Open Access Journals (Sweden)

    S.Yu. Fialko

    2014-08-01

    Full Text Available The paper presents the quadrilateral finite element for analysis of thin-walled reinforced concrete structures. The deformation theory of plasticity, formulated in terms of residual strains, is applied for behavior simulation of the both: concrete and steel. Such an approach allows us to simulate a cyclic loading as well as a dynamic one. The stress – strain diagram, proposed by the European Committee on concrete, is used for the compressed zone of concrete. The degradation, caused by the formation of cracks in the tensile zone, is described by the descending branch of the diagram. The symmetric stress-strain diagram, or its exponential approximation, is applied for steel. The compatibility of strains for concrete and steel is adopted. Reinforcements of the given direction are considered as a layer, which works only for compression-tension in this direction. The reinforcements of each direction are presented as a separate layer. We allow for the discrete placement of rods over thickness of the cross section. The Mindlin - Reissner shell theory is used for the reduction of a 3D problem to a 2D one; and the mixed interpolation of shear tensorial components is applied to overcome a shear locking effect.

  4. Tensile Characterization of Single-Walled Carbon Nanotubes with Helical Structural Defects.

    Science.gov (United States)

    Jhon, Young I; Kim, Chulki; Seo, Minah; Cho, Woon Jo; Lee, Seok; Jhon, Young Min

    2016-01-01

    Recently, evidence was presented that certain single-walled carbon nanotubes (SWNTs) possess helical defective traces, exhibiting distinct cleaved lines, yet their mechanical characterization remains a challenge. On the basis of the spiral growth model of SWNTs, here we present atomic details of helical defects and investigate how the tensile behaviors of SWNTs change with their presence using molecular dynamics simulations. SWNTs have exhibited substantially lower tensile strength and strain than theoretical results obtained from a seamless tubular structure, whose physical origin cannot be explained either by any known SWNT defects so far. We find that this long-lasting puzzle could be explained by assuming helical defects in SWNTs, exhibiting excellent agreement with experimental observation. The mechanism of this tensile process is elucidated by analyzing atomic stress distribution and evolution, and the effects of the chirality and diameter of SWNTs on this phenomenon are examined based on linear elastic fracture mechanics. This work contributes significantly to our understanding of the growth mechanism, defect hierarchies, and mechanical properties of SWNTs. PMID:26841708

  5. 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

  6. 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

  7. Inflammatory aortic aneurysms

    DEFF Research Database (Denmark)

    Bitsch, M; Nørgaard, H H; Røder, O;

    1997-01-01

    operated on for abdominal aortic aneurysms without PF in the same period, served as reference group. RESULTS: Preoperative thickness of PF was assessed as > 1 cm in 11 and cm in 10 patients. Ureterolysis was performed in seven patients where the fibrosis caused ureteral obstruction. Postoperative CT...

  8. Aortic Aneurysm Repair

    Medline Plus

    Full Text Available ... to repair an abdominal aortic aneurysm using a technology called an “endograft,” which is sometimes called the “ ... separate area, and it’s because of this small technology that allows you to do this. Exactly. So ...

  9. Aortic Aneurysm Repair

    Medline Plus

    Full Text Available ... an abdominal aortic aneurysm. Normally this procedure takes us about 45 minutes to an hour of doctor work time, which is, I think, a fairly quick procedure to replace a major life-threatening problem in the patient’s abdomen. So you can see ...

  10. Aortic Aneurysm Repair

    Medline Plus

    Full Text Available ... the arteries, which is known as atherosclerosis, high blood pressure, smokers, or a family history of abdominal aortic ... imaging. We can integrate ultrasound imaging, the patient’s blood pressure, and so it’s a little bit like being ...

  11. Flow dynamics in anatomical models of abdominal aortic aneurysms: computational analysis of pulsatile flow.

    Science.gov (United States)

    Finol, Ender A; Amon, Cristina H

    2003-01-01

    Blood flow in human arteries is dominated by time-dependent transport phenomena. In particular, in the abdominal segment of the aorta under a patient's average resting conditions, blood exhibits laminar flow patterns that are influenced by secondary flows induced by adjacent branches and in irregular vessel geometries. The flow dynamics becomes more complex when there is a pathological condition that causes changes in the normal structural composition of the vessel wall, for example, in the presence of an aneurysm. An aneurysm is an irreversible dilation of a blood vessel accompanied by weakening of the vessel wall. This work examines the importance of hemodynamics in the characterization of pulsatile blood flow patterns in individual Abdominal Aortic Aneurysm (AAA) models. These patient-specific computational models have been developed for the numerical simulation of the momentum transport equations utilizing the Finite Element Method (FEM) for the spatial and temporal discretization. We characterize pulsatile flow dynamics in AAAs for average resting conditions by means of identifying regions of disturbed flow and quantifying the disturbance by evaluating wall pressure and wall shear stresses at the aneurysm wall. PMID:14515766

  12. The structure of a functional unit from the wall of a gastropod hemocyanin offers a possible mechanism for cooperativity.

    Science.gov (United States)

    Perbandt, Markus; Guthöhrlein, Eckhart W; Rypniewski, Wojciech; Idakieva, Krassimira; Stoeva, Stanka; Voelter, Wolfgang; Genov, Nicolay; Betzel, Christian

    2003-06-01

    Structure-function relationships in a molluscan hemocyanin have been investigated by determining the crystal structure of the Rapana thomasiana (gastropod) hemocyanin functional unit RtH2e in deoxygenated form at 3.38 A resolution. This is the first X-ray structure of an unit from the wall of the molluscan hemocyanin cylinder. The crystal structure of RtH2e demonstrates molecular self-assembly of six identical molecules forming a regular hexameric cylinder. This suggests how the functional units are ordered in the wall of the native molluscan hemocyanins. The molecular arrangement is stabilized by specific protomer-to-protomer interactions, which are probably typical for the functional units building the wall of the cylinders. A molecular mechanism for cooperative dioxygen binding in molluscan hemocyanins is proposed on the basis of the molecular interactions between the protomers. In particular, the deoxygenated RtH2e structure reveals a tunnel leading from two opposite sides of the molecule to the active site. The tunnel represents a possible entrance pathway for dioxygen molecules. No such tunnels have been observed in the crystal structure of the oxy-Odg, a functional unit from the Octopus dofleini (cephalopod) hemocyanin in oxygenated form. PMID:12767214

  13. 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

  14. The diagnosis and management of abdominal aortic aneurysms: a comparison of computed tomography, ultrasound and aortography

    International Nuclear Information System (INIS)

    It is suggested that all clinically significant abdominal aneurysms can be shown by infusion C.T. or ultrasound and routine aortography is no longer indicated. These methods give more information about wall thickness and wall thrombus but do not give detailed information about the extent of an aneurysm and its exact relationship to important aortic branches. They should complement rather than replace aortography

  15. 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.

  16. 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, ...

  17. Evolution of Endovascular Treatment for Complex Thoracic Aortic Disease

    OpenAIRE

    Roselli, Eric E.

    2008-01-01

    In a relatively short period of time, transcatheter and endovascular approaches to treat thoracic aortic and structural heart disease have exploded onto the scene. New device frontiers already being forged in the experimental stages include expanded indications and variations of fenestrated and branch stentgrafting to treat thoracoabdominal and arch disease, endovascular ascending and aortic root repair, and all of the cardiac valves. A fundamental concept to optimize durability of endovascul...

  18. Fruit wall anatomical structure of the genus Betula section Lenta (Betulaceae)

    OpenAIRE

    Olga V. Yatsenko; Igor O. Yatsenko

    2014-01-01

    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 cel...

  19. First direct aortic retrievable transcatheter aortic valve implantation in humans.

    Science.gov (United States)

    Chandrasekhar, Jaya; Glover, Chris; Labinaz, Marino; Ruel, Marc

    2014-11-01

    We describe 2 cases in which transcatheter aortic valve implantation was performed with a Portico prosthesis (St Jude Medical, St Paul, MN) through a direct aortic approach. In 1 of the cases, prosthesis retrieval was needed during the procedure and was essential to the successful outcome. This is the first report, to our knowledge, of direct aortic Portico prosthesis implantation, and it highlights the significance of the retrievable nature of this device. PMID:25442452

  20. [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.

  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. 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.

  3. Assessment and structural analysis of a PCPV with hot liner and adjustable wall temperature

    International Nuclear Information System (INIS)

    The great adaptability of the concept with elastic hot liner and adjustable wall temperature can be seen in design and assessment of the PCPV for different reactor types. The first part of the paper presents an overview of the influence and possible reactions on the main existing assumptions for this special concept. One of the most essential features - the limitation of liner stresses for elastic compression - can be attained by balancing liner and structural concrete temperatures. The temperature difference between these two components mainly influences the stress-state of the liner. Transient conditions mostly extend only to the region of liner and thermal barrier. The knowledge of material properties is a fundamental requirement of every analysis. A study demostrates how temperature and long-term behaviour of materials influence the stress and strain history of the vessel. The concept offers the possibility of vessel stabilization before operation. This method which anticipates visco-elastic deformations has particular importance for high operating temperatures. The decision whether to stabilize or not depends both on the thermal assessment and on the long-term restraints of the liner and requires an optimization of these effects. The second part of the paper deals with the analysis methods and their results used in the development of the Austrian PCPV. By means of two- and three-dimensional calculations for the reference design of a PWR with 1500 MWe some of the above mentioned aspects are explained. Stress and deformation diagrams indicate the possibility of safe operation. These extensive investigations and analyses also yielded a feeling on analytical possibilities for vessel design and their costs. (orig.)

  4. 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.

  5. Tobacco smoking and aortic aneurysm

    DEFF Research Database (Denmark)

    Sode, Birgitte F; Nordestgaard, Børge G; Grønbæk, Morten;

    2012-01-01

    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...... 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...

  6. 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.

  7. Aortic valve replacement

    DEFF Research Database (Denmark)

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

    2008-01-01

    BACKGROUND AND AIMS OF THE STUDY: Prompted by anecdotal evidence and observations by surgeons, an investigation was undertaken into the potential differences in implanted aortic valve prosthesis sizes, during aortic valve replacement (AVR) procedures, between northern and southern European...... countries. METHODS: A multi-institutional, non-randomized, retrospective analysis was conducted among 2,932 patients who underwent AVR surgery at seven tertiary cardiac surgery centers throughout Europe. Demographic and perioperative variables including valve size and type, body surface area (BSA) and early......: Prostheses with diameter valve size was also smaller in southern compared to northern European patients (21.6 +/- 2.1 mm versus 23.4 +/- 2.2 mm, p

  8. 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)

  9. Effect of end-wall boundary layer and inlet turbulence on the flow field structures in the turbine stage

    Science.gov (United States)

    Jelinek, Tomas; Straka, Petr; Uruba, Vaclav

    2016-06-01

    The article deals with the effects of the inlet flow parameters on the flow field structures in axial turbine stage. The experiment was performed on the axial turbine stage rig with an air as a working medium. The variable inlet channel produced the different inlet turbulence intensity and different inlet end-wall boundary layer thickness, resp. different inlet velocity distribution was applied. The turbulence was measured by CTA probes. The measured parameters of the inlet velocity distribution and turbulence intensity across the inlet channel height are presented. Based on the experimental inlet parameters the CFD fully turbulent calculation of the flow field was made. The differences in outlet kinetic energy loss, outlet vane angle and the turbulence distribution in the vane mid-span section are depicted. Changes of secondary flow structures with the different inlet end-wall boundary layer thickness were observed on the vane outlet parameters.

  10. Salmonella aortitis treated with endovascular aortic repair: a case report

    Directory of Open Access Journals (Sweden)

    Strahm Carol

    2012-08-01

    Full Text Available Abstract Introduction Salmonella is a typical cause of aortitis, which is associated with high morbidity and mortality. In infrarenal disease, besides open surgery, endovascular aortic repair as an alternative treatment has been reported. To the best of our knowledge, we report the first successful endovascular aortic repair documented by necropsy to date. Case presentation A 67-year-old Caucasian man presented with low back pain, fever and positive blood cultures for Salmonella Enteritidis. A computed tomography scan showed an enlargement and intramural hematoma of the infrarenal aortic wall; a Salmonella aortitis was suspected and antimicrobial therapy initiated. Because of substantial comorbidities, endovascular aortic repair was favored over open surgery; postoperatively the antibiotic treatment was continued for 12 months. Post-mortem there were neither macroscopic nor microscopic signs of aortitis or graft infection. Conclusions We could demonstrate by necropsy that endovascular aortic repair of infrarenal aortitis with prolonged pre- and postinterventional antibiotic therapy for 12 months was a minimally invasive alternative and should be considered in selected clinically stable patients with substantial co-morbidities.

  11. 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.

  12. 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.

  13. 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.

  14. 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...

  15. Capnocytophaga canimorsus endocarditis with root abscess in a patient with a bicuspid aortic valve

    OpenAIRE

    Guillaume Coutance; Olivier Lepage; Christophe Bachelet; Michèle Hamon; Damien Legallois; Arnaud Pellissier; Fabien Labombarda

    2009-01-01

    Infective endocarditis caused by a zoonotic micro organism is a rare clinical condition. Capnocytophaga canimorsus is a commensal bacterium living in the saliva of dogs and cats which produces rarely reported endocarditis whose incidence may be underestimated, considering its failure to grow on standard media. We reported the case of a 65-year-old man with bicuspid aortic valve endocarditis and multiple abscesses of the aortic wall caused by the canine bacteria C. canimorsus.

  16. Capnocytophaga canimorsus endocarditis with root abscess in a patient with a bicuspid aortic valve

    Directory of Open Access Journals (Sweden)

    Michèle Hamon

    2009-04-01

    Full Text Available Infective endocarditis caused by a zoonotic micro organism is a rare clinical condition. Capnocytophaga canimorsus is a commensal bacterium living in the saliva of dogs and cats which produces rarely reported endocarditis whose incidence may be underestimated, considering its failure to grow on standard media. We reported the case of a 65-year-old man with bicuspid aortic valve endocarditis and multiple abscesses of the aortic wall caused by the canine bacteria C. canimorsus.

  17. 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

  18. 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.

  19. Plant cell wall proteomics: mass spectrometry data, a trove for research on protein structure/function relationships.

    OpenAIRE

    Albenne, Cécile; Canut, Hervé; Boudart, Georges; Zhang, Yu; San Clemente, Hélène; Pont-Lezica, Rafael; Jamet, Elisabeth

    2009-01-01

    International audience 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 ...

  20. 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.

  1. 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.

  2. 3D Effect of Ferromagnetic Materials on Alpha Particle Power Loads on First Wall Structures and Equilibrium on ITER

    International Nuclear Information System (INIS)

    Full text: The finite number and limited toroidal extent of the TF coils cause a periodic variation of the toroidal field called the magnetic ripple. This ripple can provide a significant channel for fast particle leakage, leading to very localized fast particle loads on the walls. Ferromagnetic inserts will be embedded in the double wall structure of the vacuum vessel in order to reduce the ripple. In ITER the toroidal field deviations are locally further enhanced by the presence of discrete ferromagnetic structures, e.g. TBM. Thus, there are complex symmetry-breaking effects. It is not yet fully understood how superimposing the periodic ripple and a local perturbation affect the fast ion confinement and concerns have been voiced that the combined effect might lead to significant channelling of the alpha power. In this work, the wall power loads due to fusion-born alpha particles were restudied for a variety of cases addressing issues such as different wall configurations, proper inclusion of the TBM effect on the magnetic background, and the possible corrections to 3D equilibrium introduced by the ferromagnetic materials using the 3D equilibrium code, VMEC, since 3D corrections to the equilibrium might enhance the alpha particle loss. To properly include the TBM effect on the magnetic background, the FEMAG code was used, and the effect was calculated on the total field including the poloidal field by the plasma current as well as the vacuum field. In the VMEC analysis, it was found that the difference between a full 3D equilibrium reconstruction and 'an axisymmetric equilibrium + vacuum fields' was small. Thus, it was concluded that no 3D equilibrium reconstruction was needed and that it was sufficient to add the vacuum field perturbations onto an axisymmetric equilibrium. Under the new boundary condition, the wall load calculation was carried out by using ASCOT, DELTA5D, and F3D OFMC code. Including the plasma current contribution in the magnetic field

  3. Assessment of titanium for use in the 1st wall/blanket structure of fusion power reactors

    International Nuclear Information System (INIS)

    This report describes a portion of the work that was performed as part of a First Wall/Blanket Systems Analysis Study. The objective of this part of the study was to assess the suitability of using titanium alloys in the first wall/blanket structure of commercial controlled thermonuclear reactors (CTR). While the purpose of this study was not to recommend a specific titanium alloy, but to examine titanium alloys, in general, two near-alpha titanium alloys were selected for an indepth examination. These alloys were Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo. Using properties important to the CTR first wall/blanket structures application, these titanium alloys were compared with five other candidate structural materials (2219 aluminum, 316 stainless steel, V-20 Ti, Nb-1Zr, and Mo-0.5 Ti-0.08 Zr (TZM)). The results of this study revealed that titanium offers potential for use in a CTR from strength, minimum radioactivity, and resources standpoints and should be considered in future fusion reactor studies

  4. 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.

  5. 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.

  6. 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.

  7. The everyday used nomenclature of the aortic root components: the tower of Babel?

    Science.gov (United States)

    Sievers, Hans-Hinrich; Hemmer, Wolfgang; Beyersdorf, Friedhelm; Moritz, Anton; Moosdorf, Rainer; Lichtenberg, Artur; Misfeld, Martin; Charitos, Efstratios I

    2012-03-01

    Modern analyses of data for scientific reporting and healthcare management purposes require standardized and consistent definitions, something which also holds true for aortic root surgery, as part of the cardiovascular surgery spectrum. The aim of the present study was to investigate the currently employed nomenclature of the aortic root components. A questionnaire was constructed on the terminology of aortic root components, providing a list of common definitions including anatomical descriptions, as well as fields for custom responses. Responses were received from 534 cardiothoracic surgeons registered at www.ctsnet.org. Remarkable variations in definitions were detected. The most unanimously accepted terms were: 'aortic leaflets', the freely moving parts (52.6% of responses); 'commissures', the distal part of the leaflet attachments plus the peripheral area of the free edges of the leaflets (52.2%); 'semi-lunar leaflet attachment', the anatomic site of leaflet attachment (58%); 'annulus', the circular line defined by the nadirs of the leaflets (38%); 'interleaflet triangle', the tissue between two leaflets and annulus (23%); 'aortic valve', the three leaflets only (55%); 'aortic root' as composed of sinuses, tissue between the leaflets, sinutubular junction, leaflets and their wall attachment (63%). The remarkable variability on the everyday-used definitions of the aortic root components can potentially lead to misinterpretation of data. More stringent adoption of consistent, standardized definitions of aortic root components is necessary in the modern era of data collection and management. PMID:22345173

  8. Energy Dissipating Structures Produced by Walls in Two-Dimensional Flows at Vanishing Viscosity

    OpenAIRE

    Nguyen van yen, Romain; Farge, Marie; Schneider, Kai

    2011-01-01

    We perform numerical experiments of a dipole crashing into a wall, a generic event in two-dimensional incompressible flows with solid boundaries. The Reynolds number (Re) is varied from 985 to 7880, and no-slip boundary conditions are approximated by Navier boundary conditions with a slip length proportional to Re−1. Energy dissipation is shown to first set up within a vorticity sheet of thickness proportional to Re−1 in the neighborhood of the wall, and to continue as this sheet rolls up int...

  9. Introduction: Scaling and structure in high Reynolds number wall-bounded flows

    International Nuclear Information System (INIS)

    The papers discussed in this report are dealing with the following aspects: Fundamental scaling relations for canonical flows and asymptotic approach to infinite Reynolds numbers; large and very large scales in near-wall turbulences; the influence of roughness and finite Reynolds number effects; comparison between internal and external flows and the universality of the near-wall region; qualitative and quantitative models of the turbulent boundary layer; the neutrally stable atmospheric surface layer as a model for a canonical zero-pressure-gradient boundary layer (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    DeRenzis, A.; Kochkin, V.; Wiehagen, J.

    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.

  11. Human coronary plaque wall thickness correlated positively with flow shear stress and negatively with plaque wall stress: an IVUS-based fluid-structure interaction multi-patient study

    OpenAIRE

    Fan, Rui; Tang, Dalin; Yang, Chun; Zheng, Jie; Bach, Richard; WANG, LIANG; Muccigrosso, David; Billiar, Kristen; Zhu, Jian; Ma, Genshan; Maehara, Akiko; Mintz, Gary S

    2014-01-01

    Background Atherosclerotic plaque progression and rupture are believed to be associated with mechanical stress conditions. In this paper, patient-specific in vivo intravascular ultrasound (IVUS) coronary plaque image data were used to construct computational models with fluid-structure interaction (FSI) and cyclic bending to investigate correlations between plaque wall thickness and both flow shear stress and plaque wall stress conditions. Methods IVUS data were acquired from 10 patients afte...

  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. 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,...

  14. 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

  15. Structural characterization of pectic hairy regions isolated from apple cell walls.

    NARCIS (Netherlands)

    Schols, H.A.

    1995-01-01

    Cell wall pectic substances have a great influence on the production and quality aspects of apple juice. Apple juices were characterized by their polysaccharide content and composition. A pectic fraction, retained by ultrafiltration of a liquefaction juice, was isolated and termed MHR (modified hair

  16. 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.

  17. Controlling Structural Characteristics of Single-Walled Carbon Nanotubes (SWNT) by Tailoring Catalyst Composition and Synthesis Conditions

    International Nuclear Information System (INIS)

    This report shows the extensive research on the mechanism responsible for the formation of single walled carbon nanotubes in order to get control over their structural parameters (diameter and chirality). Catalyst formulations, pre-treatment conditions, and reaction conditions are described in detail as well as mechanisms to produce nanotubes structures of specific arrays (vertical forest, nanotube pillars). Applications of SWNT in different fields are also described in this report. In relation to this project five students have graduated (3 PhD and 2 MS) and 35 papers have been published.

  18. 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.)

  19. 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.

  20. Correlation of Near-Wall Turbulence Structures with Heat Transfer in Ribbed-Pipe Flow

    Science.gov (United States)

    Ahn, Hyungsu; Kang, Changwoo; Yang, Kyung-Soo; Park, Doohyun

    2015-11-01

    Ribbed-pipe flow is one of the most commonly used flow configurations to enhance heat transfer, albeit, at the expense of increased pressure drop. The ribs mounted on the pipe wall differently alter the flow depending on the pitch, the distance between two neighboring ribs. When the pitch is short, fluid is trapped inside grooves, resulting in a low heat-transfer rate. When the pitch is long enough, however, the ribs disturb the flow by shedding vortices, resulting in heat-transfer enhancement. We aim at elucidating the correlation of near-wall turbulence induced by the shed vortices with the increased heat-transfer rate on the ribbed-pipe wall. Our analysis is based on our LES data base obtained for Re =24,000, Pr =0.71, PR(pitch ratio) =2, 4, 6, 8, 10, 18, BR(blockage ratio) =0.0625. Here, the bulk velocity and the pipe diameter are used as the velocity and length scales, respectively. Our presentation focuses on the near-wall distributions of the higher-order turbulence statistics including but not limited to rms of temperature fluctuation, cross-correlations, rms of vorticity, and turbulent heat fluxes. Octants and JPDF are also presented in order to clarify the prevailing heat-transfer mechanism in the immediate vicinity of the ribbed-pipe wall. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2015R1A2A2A01002981).

  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. 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...... operations were completed as mini-sternotomies, 4 died later of noncardiac causes. The aortic cross-clamp and perfusion times were significantly different across all groups (P valve replacement...... 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...

  3. Doxycycline inhibition of proteases and inflammation in abdominal aortic aneurysms

    OpenAIRE

    Khawaja, Hazem Al-

    2011-01-01

    The aim of this thesis is to evaluate the effect of doxycycline on the proteolytic and inflammatory processes in abdominal aneurysms. This data is essential for the development of pharmaceutical strategies for the stabilization of an AAA. Such an approach could reduce the need for elective surgery and endovascular repair. It has repeatedly been shown that AAA progression and rupture is related to the failure of collagen in the aortic wall. Yet the exact mechanism underlying this failure remai...

  4. 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.

  5. 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. PMID:23340418

  6. 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

  7. Storage of very cold neutrons in a trap with nano-structured walls

    OpenAIRE

    E. V. Lychagin; Muzychka, A. Yu.; Nesvizhevsky, V. V.; G. Pignol; Protasov, K. V.; Strelkov, A. V.

    2008-01-01

    We report on storage of Very Cold Neutrons (VCN) in a trap with walls containing powder of diamond nanoparticles. The efficient VCN reflection is provided by multiple diffusive elastic scattering of VCN at single nanoparticles in powder. The VCN storage times are sufficiently long for accumulating large density of neutrons with complete VCN energy range of up to a few times 10(-4) eV. Methods for further improvements of VCN storage times are discussed.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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....

  13. Unoperated aortic aneurysm

    DEFF Research Database (Denmark)

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

    1995-01-01

    . No significant differences in survival for patients with dissecting and nondissecting AA were detected. In all, 132 patients (78%) died and 78 (59%) of them died of rupture. Mean time to rupture was 1,300 +/- 8 days. Cumulative 5-year hazard of rupture for the dissecting AA was twice that of the nondissecting (p......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...

  14. 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.

  15. Surface carbohydrates and cell wall structure of in vitro-induced uredospore infection structures of Uromyces riciae-fabae before and after treatment with enzymes and alkali

    OpenAIRE

    Freytag, Sibylle; Mendgen, Kurt

    1991-01-01

    Uredospores of Uromyces viciae-fabae differentiate to form germ tubes, appressoria, infection hyphae and haustorial mother cells on oil-containing collodion membranes. The cell walls of these infection structures were studied with the electron microscope and with FITC-labeled lectins before and after treatment with enzymes and inorganic solvents. Binding of the FITC-labeled lectins was measured with a microscope photometer. The enzymes pronase E, aminarinase, chitinase and lipase had differe...

  16. [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

  17. Abdominal aortic grafting for spontaneous infrarenal abdominal aortic dissection.

    Science.gov (United States)

    Iwasaki, Hiroto; Shibuya, Takashi; Shintani, Takashi; Uenaka, Hisazumi; Suehiro, Shigefumi; Satoh, Hisashi

    2010-02-01

    This case report concerns a 62-year-old woman with spontaneous infrarenal abdominal aortic dissection, which developed into claudication and rest pain in the lower extremity. Multi-row detector computed tomography showed the entry site of the abdominal aortic dissection at the second lumbar artery, while the reentry site was found intraoperatively at the median sacral artery, indicating that the false lumen had progressed and compressed the true lumen. A direct approach involving grafting appears to be an effective procedure for resolving mesenteric and lower extremity hypoperfusion due to aortic dissection with a dilated false channel, even during the acute period. PMID:19879731

  18. Experimental observation of the interaction of propagating spin waves with Néel domain walls in a Landau domain structure

    Energy Technology Data Exchange (ETDEWEB)

    Pirro, P.; Sebastian, T.; Leven, B.; Hillebrands, B. [Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern (Germany); Koyama, T. [Department of Applied Physics, Faculty of Engineering, The University of Tokyo, Bunkyo, Tokyo 113-8656 (Japan); Brächer, T. [Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern (Germany); Graduate School Materials Science in Mainz, Gottlieb-Daimler-Strasse 47, 67663 Kaiserslautern (Germany)

    2015-06-08

    The interaction of propagating dipolar spin waves with magnetic domain walls is investigated in square-shaped microstructures patterned from the Heusler compound Co{sub 2}Mn{sub 0.6}Fe{sub 0.4}Si. Using magnetic force microscopy, the reversible preparation of a Landau state with four magnetic domains separated by Néel domain walls is confirmed. A local spin-wave excitation using a microstructured antenna is realized in one of the domains. It is shown by Brillouin light scattering microscopy that the domain structure in the remanence state has a strong influence on the spin-wave excitation and propagation. The domain walls strongly reflect the spin waves and can be used as spin-wave reflectors. A comparison with micromagnetic simulations shows that the strong reflection is due to the long-range dipolar interaction which has important implications for the use of these spin waves for exerting an all-magnonic spin-transfer torque.

  19. 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.

  20. 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....

  1. Wall Painting Investigation by Means of Non-invasive Terahertz Time-Domain Imaging (THz-TDI): Inspection of Subsurface Structures Buried in Historical Plasters

    Science.gov (United States)

    Dandolo, Corinna Ludovica Koch; Jepsen, Peter Uhd

    2016-02-01

    Characterization of subsurface features of wall paintings is important in conservation and technical art history as well as in building archaeology and architecture fields. In this study, an area of the apsidal wall painting of Nebbelunde Church (Rødby, Denmark) has been investigated by means of terahertz time-domain imaging (THz-TDI). Subsurface structures have been detected at different depths inside the lime-based plaster of the wall painting until approximately 1 cm from the surface. The surface morphology of the buried structures has been 3D imaged in detail, providing a substantial contribution in their characterization.

  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. 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.

  4. 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.

  5. 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.

  6. Crystal and cryoEM structural studies of a cell wall degrading enzyme in the bacteriophage [psi]29 tail

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Ye; Morais, Marc C.; Cohen, Daniel N.; Bowman, Valorie D.; Anderson, Dwight L.; Rossmann, Michael G. (Purdue); (UMM)

    2009-08-28

    The small bacteriophage {phi}29 must penetrate the {approx}250-{angstrom} thick external peptidoglycan cell wall and cell membrane of the Gram-positive Bacillus subtilis, before ejecting its dsDNA genome through its tail into the bacterial cytoplasm. The tail of bacteriophage {phi}29 is noncontractile and {approx}380 {angstrom} long. A 1.8-{angstrom} resolution crystal structure of gene product 13 (gp13) shows that this tail protein has spatially well separated N- and C-terminal domains, whose structures resemble lysozyme-like enzymes and metallo-endopeptidases, respectively. CryoEM reconstructions of the WT bacteriophage and mutant bacteriophages missing some or most of gp13 shows that this enzyme is located at the distal end of the {phi}29 tail knob. This finding suggests that gp13 functions as a tail-associated, peptidoglycan-degrading enzyme able to cleave both the polysaccharide backbone and peptide cross-links of the peptidoglycan cell wall. Comparisons of the gp13{sup -} mutants with the {phi}29 mature and emptied phage structures suggest the sequence of events that occur during the penetration of the tail through the peptidoglycan layer.

  7. Nucleon structure from mixed action calculations using 2+1 flavors of asqtad sea and domain wall valence fermions

    International Nuclear Information System (INIS)

    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.

  8. 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.

  9. 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.

  10. 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.

  11. Structural studies of O-acetylglucuronoxylans and their modifications in plant cell walls

    OpenAIRE

    Chong, Sun-Li

    2014-01-01

    O-acetylglucuronoxylans (AcGX) are the major hemicelluloses found in the secondary cell wall of dicotyledon species. The backbone is formed by β(1→4)-linked xylopyranosyl (Xylp) residues, which are substituted by α(1→2)-linked (4-O-methyl)glucopyranosyluronic acid ((Me)GlcpA). The AcGX are also highly acetylated on the 2-O or 3-O; or both positions of Xylp units. Notably, acetylation patterns in AcGX are not well understood since they are typically destroyed during the alkaline isolatio...

  12. 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.

  13. [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.

  14. 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.

  15. 建筑结构设计中剪力墙结构设计%The Shear Wall Structure Design in the Building Structure Design

    Institute of Scientific and Technical Information of China (English)

    林涛

    2014-01-01

    This article through the analysis of the problems and solutions of the shear wall structure design in the building structure design improves the development quality of construc-tion industry in China and guarantee the rapid progress of Chi-nese social economy.%本文通过对建筑结构设计中剪力墙结构设计的问题和解决措施的分析,提升了我国建筑行业的发展质量,保证了我国社会经济的快速进步。

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. The usefulness of MRI-CT for aortic diseases

    International Nuclear Information System (INIS)

    We report here the results of our study of four recent aortic disease patients with a clinical evaluation of the efficacy of nuclear magnetic resonance imaging-computed tomography (MRI-CT). This new technique is noninvasive and particularly suited to the assessment of cardiovascular diseases. The following conclusions were obtained. 1) The MRI-CT produces a definite and clear contrast between flowing blood, mural thrombosis, and the vessel wall. A certain diagnosis can be facilitated for aortic dissection, aneurysm formation, and of atherosclerotic changes, in any of the cross-sectional, coronal, and saggital planes. 2) Repeated preoperative check-up and long-term postoperative follow-up is enabled, even at an outpatients' department. 3) MRI-CT is useful as a noninvasive method for screening of aortic abnormalities, especially so in cases of poor general conditions. We also identify the following areas where research could improve the clinical advantage of MRI-CT. 1) The physiologic effects related to an artificial valve in magnetic field must be clarified. 2) Faster and finer imaging should be developed for MRI-CT use as a choice method for cases of aortic dissection or impending aneurysm rupture. 3) Clear distinction on imaging between blood pooling, fresh thrombosis and soft tissue tumor must be developed. (author)

  2. Endovascular aortic injury repair after thoracic pedicle screw placement.

    Science.gov (United States)

    Pesenti, S; Bartoli, M A; Blondel, B; Peltier, E; Adetchessi, T; Fuentes, S

    2014-09-01

    Our objective was to describe the management and prevention of thoracic aortic injuries caused by a malposition of pedicle screws in corrective surgery of major spine deformities. Positioning pedicle screws in thoracic vertebras by posterior approach exposes to the risk of injury of the elements placed ahead of the thoracic spine, as the descending thoracic aorta. This complication can result in a cataclysmic bleeding, needing urgent vascular care, but it can also be totally asymptomatic, resulting in the long run in a pseudoaneurysm, justifying the systematic removal of the hardware. We report the case of a 76-year-old woman who underwent spinal correction surgery for thoraco-lumbar degenerative kypho-scoliosis. Immediately after the surgery, a thoracic aortic injury caused by the left T7 pedicle screw was diagnosed. The patient underwent a two-step surgery. The first step was realized by vascular surgeons and aimed to secure the aortic wall by short endovascular aortic grafting. During the second step, spine surgeons removed the responsible screw by posterior approach. The patient was discharged in a rehabilitation center 7 days after the second surgery. When such a complication occurs, a co-management by vascular and spine surgeons is necessary to avoid major complications. Endovascular management of this kind of vascular injuries permits to avoid an open surgery that have a great rate of morbi-mortality in frail patients. Nowadays, technologies exist to prevent this kind of event and may improve the security when positioning pedicle screws. PMID:25023930

  3. 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.

  4. 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.

  5. 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. PMID:27432961

  6. Minimally Invasive Aortic Valve Replacement

    Medline Plus

    Full Text Available ... see we've used the cautery to achieve access to the sternum. On the left hand side ... wound, which allows us to get more ready access to the aorta and the aortic valve. The ...

  7. 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...

  8. Minimally Invasive Aortic Valve Replacement

    Medline Plus

    Full Text Available ... No medications as such have been proven to slow that disease path life. Again, it's a progressive ... no medical therapy that has been proven to slow or reverse the process of aortic stenosis. Clearly, ...

  9. [ENDOVASCULAR ABDOMINAL AORTIC ANEURISM REPAIR].

    Science.gov (United States)

    Maĭstrenko, D N; Generalov, M I; Tarazov, P G; Zherebtsov, F K; Osovskikh, V V; Ivanov, A S; Oleshchuk, A N; Granov, D A

    2015-01-01

    The authors analyzed the single-center experience of treatment of 72 patients with abdominal aortic aneurisms and severe accompanied pathology. The aneurisms were repaired by stent-grafts. All the patients had abdominal aortic aneurisms with the diameters from 41 to 84 mm against the background of severe somatic pathology. It was a contraindication to planned open surgery. An installation of stent-graft was successful in all 72 follow-ups. It wasn't necessary to use a conversion to open surgery. The follow-up period consisted of 44,6?2,1 months. Control ultrasound and computer tomography studies hadn't revealed an increase of aneurism sack sizes or "eakages". A reduction of abdominal aortic aneurism sizes was noted in 37 patients on 4-5% during first year after operation. The stent-graft implantation extends the possibilities of abdominal aortic aneurism treatment for patients from a high surgical risk group. PMID:26234059

  10. Minimally Invasive Aortic Valve Replacement

    Medline Plus

    Full Text Available ... to minimize their symptoms, but that doesn't impact the course of the disease itself. When I' ... more likely we see aortic stenosis. Again, patient education is part of the evaluation and management of ...

  11. Minimally Invasive Aortic Valve Replacement

    Medline Plus

    Full Text Available ... for patients who would not tolerate well a traditional open operation or a less invasive operation, as ... physical reserve. So Barbara Bush recently had a traditional aortic valve replacement surgery. What makes a patient ...

  12. 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.

  13. Minimally Invasive Aortic Valve Replacement

    Medline Plus

    Full Text Available ... symptoms and ultimately surgery may be in the future. The symptoms seen primarily with aortic stenosis at ... echocardiography is? Echocardiography is the use of ultrasound technology. Ultrasound technology is a form of the same ...

  14. 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.

  15. Minimally Invasive Aortic Valve Replacement

    Medline Plus

    Full Text Available ... somebody for this operation. Again, there's no medical therapy that has been proven to slow or reverse ... to their physician. This may lead to earlier treatment and better outcomes as well. Aortic stenosis, as ...

  16. 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...

  17. beta-D-Glucose 1-phosphate. A structural unit and an immunological determinant of a glycan from streptococcal cell walls.

    Science.gov (United States)

    Pazur, J H

    1982-01-25

    Glycose 1-phosphate moieties are emerging as important structural units of macromolecular substances imparting special biological functions to these molecules. In the present study, beta-D-glucose 1-phosphate moieties are shown to be structural units and immunological determinants of a bacterial glycan. The glycan is a tetraheteroglycan from the cell wall of Streptococcus faecalis, strain N and is composed of glucose, galactose, rhamnose, N-acetylgalactosamine, and phosphate. Several lines of evidence have been obtained for the presence of beta-D-glucose 1-phosphate units in the glycan, including the liberation of glucose by mild acid hydrolysis, the inhibition of the precipitin reaction by beta-D-glucose 1-phosphate, and the formation of levoglucosan on treatment of the glycan with alkali. Work on the preparation of affinity adsorbents for isolating the new types of antibodies directed at the beta-D-glucose 1-phosphate moieties is in progress. PMID:6172422

  18. 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)

    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.

  19. Execution of high rise frame-wall reinforced concrete building using the precast structural form; PCa kozo katawaku wo mochiita koso hekishiki ramen kozo jutaku no seko

    Energy Technology Data Exchange (ETDEWEB)

    Toda, T.; Matsuura, T.; Ito, T.; Kageyama, S. [Hazama Corp., Tokyo (Japan)

    1997-10-01

    This paper introduces construction of a high-rise residential house using thin PCa members, which work also as concrete forms, in wall pillars. This building uses PCa members in wall pillars, beams and floors, and is of a wall-type rigid-frame structure using conventional construction methods for antiseismic walls. The wall pillars are common to all the stories, and use PCa-structured forms. The PCa-structured form is a rectangle with hollow cross section having a pillar width of 600 mm, pillar height of 1800 mm, and a wall thickness of 80 mm. The formwork to fabricate a PCa-structured form is made of steel, and consists of an inner form and an outer form. The inner form is constructed with checker plates to enhance integrity of the form with post-cast concrete. According to the result of a construction experiment using full-size members, no crack generation, swelling in the concrete forms, and filling voids were found. As a result of performing a bending shear experiment, the test specimen showed fracture characteristics preceded by bending yield as seen in a test specimen made by continuous concrete placement. Equivalent withstanding force and transformation performance were also discovered. 1 ref., 12 figs.

  20. 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

  1. [Completion pneumonectomy combined with graft replacement of thoracic aortic aneurysm by simple clamping].

    Science.gov (United States)

    Shimamoto, A; Takao, M; Kanemitsu, S; Fujinaga, K; Yan, G; Cruz, B P; Onoda, K; Shimono, T; Shimpo, H; Namikawa, S; Yuasa, H; Yada, I

    1999-01-01

    A 59-years-old male patient who had left upper lobe partial resection 30 years ago. He was seen at the family physician because of cough. A chest X-ray was showing an abnormal mass shadow measuring 3 x 4 cm in left lower lobe like honey comb. And squamous cell carcinoma (SCC) was detected in his sputum. He was diagnosed as primary lung cancer and introduced to our department to have operation. Chest CT-scan was showing lung tumor suspected SCC measuring 4.3 x 2.6 cm in segment 8 faced chest wall. At the same time, we detected thoracic aortic aneurysm and subcarinal lymph node, but could not see where the boundary is, so it was hard to distinguish between parietal thrombus with thoracic aortic aneurysm and swelling subcarinal lymph node. We decided it swelling subcarinal lymph node by three-dimensional treated CT-scan. Aortic angiography was showing proximal descending aortic aneurysm measuring diameter was 4.5 cm. Abdominal CT-scan was showing infrarenal abdominal aortic aneurysm measuring diameter was 5.5 cm. He was diagnosed as primary lung cancer (It. S8, SCC) (cT2N2M0, Stage IIIB), thoracic aortic aneurysm, abdominal aortic aneurysm, and idiopathic pulmonary fibrosis, and had completion pneumonectomy (R 2 b) for primary lung cancer and graft replacement with aneurysm dissection for thoracic aortic aneurysm without extracorporeal circulation. In this operation, we could find swelling subcarinal lymph node measuring 5 x 3 cm instead of parietal thrombus with thoracic aortic aneurysm. Pathological examination diagnosed middle differential SCC and no metastasis from dissected lymph node (PT2N0M0, Stage I A). PMID:10024802

  2. Properties of dust-plasma structures formed in a glow discharge above the lower wall of the discharge chamber

    Science.gov (United States)

    Dzlieva, E. S.; Ermolenko, M. A.; Karasev, V. Yu.

    2012-07-01

    The properties are studied of dusty plasma structures formed in a glow discharge in a dust trap above the lower wall of the side branch of the discharge tube, near the turn of the discharge channel. The dust structure is three-dimensional with a characteristic size of up to 3 cm and contains about 30000 dust grains. Depending on the experimental conditions, dust-acoustic, dissipative, and charge-gradient instabilities can develop in such a structure. When using highly polydisperse dust grains of arbitrary shape, the effect of selection of dust grains by the plasma with respect to their mean size and shape was discovered. This effect was studied quantitatively in two gases by using the method of gathering and extraction of the dust grains levitating in the trap. The morphology of the dust structures was determined from the pair correlation functions of the horizontal cross sections containing long-range order peaks and elements of a hexagonal lattice. Stratification of a uniform structure accompanied by convective rotation caused by the grain charge gradient was observed. Applications of the dusty plasma created in this type of device are discussed.

  3. Enhanced Aortic Macrophage Lipid Accumulation and Inflammatory Response in LDL Receptor Null Mice Fed an Atherogenic Diet

    OpenAIRE

    Wang, Shu; Wu, Dayong; Matthan, Nirupa R.; Lamon-Fava, Stefania; Lecker, Jaime L; Lichtenstein, Alice H

    2010-01-01

    The effect of an atherogenic diet on inflammatory response and elicited peritoneal macrophage (Mφ) cholesterol accumulation in relation to aortic lesion formation was assessed in LDL receptor null (LDLr−/−) mice. Mice were fed an atherogenic or control diet for 32 weeks. The atherogenic relative to control diet resulted in significantly higher plasma monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) concentrations, more aortic wall Mφ depo...

  4. Relationship between Enhanced Intensity of Contrast Enhanced Ultrasound and Microvessel Density of Aortic Atherosclerostic Plaque in Rabbit Model

    OpenAIRE

    Xiangdong You; Pintong Huang; Chao Zhang; Minghui Wang; Ying Zhang; Yurong Hong; Shumei Wei; Chunmei Liu; Zhaoxia Pu; Jianmin Zhang; Shuyuan Chen

    2014-01-01

    The aim of this study was to evaluate the relationship between enhanced intensity of contrast enhanced ultrasound and microvessel density of aortic atherosclerotic plaque in rabbit model. The abdominal aortas of thirty-six male New Zealand rabbits were damaged by balloon expansion and the animals were then fed a high fat diet for 12 weeks. Twenty-seven plaques on the near aortic wall were detected using conventional ultrasound examination. The maximum thickness of each plaque was recorded. CE...

  5. Joining and fabrication techniques for high temperature structures including the first wall in fusion reactor

    International Nuclear Information System (INIS)

    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 Si3N4. 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

  6. 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.

  7. 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.

  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. 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.

  10. 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.

  11. 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.

  12. 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

  13. The focal adhesion: a regulated component of aortic stiffness.

    Directory of Open Access Journals (Sweden)

    Robert J Saphirstein

    Full Text Available Increased aortic stiffness is an acknowledged predictor and cause of cardiovascular disease. The sources and mechanisms of vascular stiffness are not well understood, although the extracellular matrix (ECM has been assumed to be a major component. We tested here the hypothesis that the focal adhesions (FAs connecting the cortical cytoskeleton of vascular smooth muscle cells (VSMCs to the matrix in the aortic wall are a component of aortic stiffness and that this component is dynamically regulated. First, we examined a model system in which magnetic tweezers could be used to monitor cellular cortical stiffness, serum-starved A7r5 aortic smooth muscle cells. Lysophosphatidic acid (LPA, an activator of myosin that increases cell contractility, increased cortical stiffness. A small molecule inhibitor of Src-dependent FA recycling, PP2, was found to significantly inhibit LPA-induced increases in cortical stiffness, as well as tension-induced increases in FA size. To directly test the applicability of these results to force and stiffness development at the level of vascular tissue, we monitored mouse aorta ring stiffness with small sinusoidal length oscillations during agonist-induced contraction. The alpha-agonist phenylephrine, which also increases myosin activation and contractility, increased tissue stress and stiffness in a PP2- and FAK inhibitor 14-attenuated manner. Subsequent phosphotyrosine screening and follow-up with phosphosite-specific antibodies confirmed that the effects of PP2 and FAK inhibitor 14 in vascular tissue involve FA proteins, including FAK, CAS, and paxillin. Thus, in the present study we identify, for the first time, the FA of the VSMC, in particular the FAK-Src signaling complex, as a significant subcellular regulator of aortic stiffness and stress.

  14. Femtosecond laser induced submicrometer structures on the ablation crater walls of II-VI semiconductors in water

    International Nuclear Information System (INIS)

    Femtosecond laser ablations (100 fs, 800 nm, 0.2 mJ/pulse) were performed to produce craters on CdS, ZnS:Cu and ZnSe wafers in water. On the surface of the crater walls, a variety of submicrostructural formations were presented, such as the ripples and network structures for CdS, the subwavelength ripples and columnar structures for ZnS:Cu, even the regular cubic-shaped submicron rods for ZnSe. Based on the field-emission scanning electron microscope (FE-SEM) study of the different characteristic surface morphologies, the possible formation mechanisms were discussed correspondingly. For example, two distinct mechanisms are contributing to the different styles of ripples formed on CdS and ZnS:Cu. The former is the interference effects between the incoming laser beam and scattered surface wave, while the latter is the self-organization structure formation. In addition, the re-crystallization of the water-confined hot plasma would play an important role in the formation of ZnS:Cu column structures and ZnSe rods.

  15. 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.

  16. Acute aortic valve prolapse in Marfan's syndrome.

    OpenAIRE

    Carr, N J; Cullen, S. A.

    1991-01-01

    A 22 year old man with Marfan's syndrome died suddenly following acute aortic valve prolapse. Although aortic root involvement in Marfan's syndrome is common, we have found no previous description of this particular complication in the literature.

  17. 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.

  18. The application countermeasure of shear wall structure design in architectural structure design%剪力墙结构设计在建筑结构设计中的应用对策

    Institute of Scientific and Technical Information of China (English)

    黄河

    2015-01-01

    简述了剪力墙的概念及特征,依据剪力墙最大位移比例、连梁超限、楼层最小剪力系数等原则,阐述了剪力墙布置、大墙肢处理、墙体配筋应用等设计策略,以确保结构设计的科学性,提升结构设计水平。%This paper discussed the concept and characteristics of shear wall,according to the maximum displacement ratio of shear wall,cou-pling beam overrun,floor minimum shear coefficient and other principles,elaborated the shear wall arrangement,maximum wall leg treatment, wall reinforcement application and other design strategies,to ensure the scientific of structure design,lifted the structure design level.

  19. CFD Modelling of Abdominal Aortic Aneurysm on Hemodynamic Loads Using a Realistic Geometry with CT

    OpenAIRE

    Loong, T. H.; Maurizio Bordone; Uei Pua; Sriram Narayanan; Eduardo Soudah; E. Y. K. Ng

    2013-01-01

    The objective of this study is to find a correlation between the abdominal aortic aneurysm (AAA) geometric parameters, wall stress shear (WSS), abdominal flow patterns, intraluminal thrombus (ILT), and AAA arterial wall rupture using computational fluid dynamics (CFD). Real AAA 3D models were created by three-dimensional (3D) reconstruction of in vivo acquired computed tomography (CT) images from 5 patients. Based on 3D AAA models, high quality volume meshes were created using an optimal tetr...

  20. Cell Wall

    OpenAIRE

    Jamet, Elisabeth; Canut, Hervé; Boudart, Georges; Albenne, Cécile; Pont-Lezica, Rafael F

    2008-01-01

    This chapter covers our present knowledge of cell wall proteomics highlighting the distinctive features of cell walls and cell wall proteins in relation to problems encountered for protein extraction, separation and identification. It provides clues to design strategies for efficient cell wall proteomic studies. It gives an overview of the kinds of proteins that have yet been identified: the expected proteins vs the identified proteins. Finally, the new vision of the cell wall proteome, and t...