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Sample records for aortic wall structure

  1. Aortic dissection simulation models for clinical support: fluid-structure interaction vs. rigid wall models.

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    Alimohammadi, Mona; Sherwood, Joseph M; Karimpour, Morad; Agu, Obiekezie; Balabani, Stavroula; Díaz-Zuccarini, Vanessa

    2015-04-15

    The management and prognosis of aortic dissection (AD) is often challenging and the use of personalised computational models is being explored as a tool to improve clinical outcome. Including vessel wall motion in such simulations can provide more realistic and potentially accurate results, but requires significant additional computational resources, as well as expertise. With clinical translation as the final aim, trade-offs between complexity, speed and accuracy are inevitable. The present study explores whether modelling wall motion is worth the additional expense in the case of AD, by carrying out fluid-structure interaction (FSI) simulations based on a sample patient case. Patient-specific anatomical details were extracted from computed tomography images to provide the fluid domain, from which the vessel wall was extrapolated. Two-way fluid-structure interaction simulations were performed, with coupled Windkessel boundary conditions and hyperelastic wall properties. The blood was modelled using the Carreau-Yasuda viscosity model and turbulence was accounted for via a shear stress transport model. A simulation without wall motion (rigid wall) was carried out for comparison purposes. The displacement of the vessel wall was comparable to reports from imaging studies in terms of intimal flap motion and contraction of the true lumen. Analysis of the haemodynamics around the proximal and distal false lumen in the FSI model showed complex flow structures caused by the expansion and contraction of the vessel wall. These flow patterns led to significantly different predictions of wall shear stress, particularly its oscillatory component, which were not captured by the rigid wall model. Through comparison with imaging data, the results of the present study indicate that the fluid-structure interaction methodology employed herein is appropriate for simulations of aortic dissection. Regions of high wall shear stress were not significantly altered by the wall motion

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

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    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

  3. Cryopreserved human aortic root allografts arterial wall: Structural changes occurring during thawing.

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    Robert Novotny

    Full Text Available The aim of our experimental work was to assess morphological changes of arterial wall that arise during different thawing protocols of a cryopreserved human aortic root allograft (CHARA arterial wall.The experiment was performed on CHARAs. Two thawing protocols were tested: 1, CHARAs were thawed at a room temperature at +23°C; 2, CHARAs were placed directly into a water bath at +37°C.After fixation, all samples were washed in distilled water for 5 min, and dehydrated in a graded ethanol series (70, 85, 95, and 100% for 5 min at each level. The tissue samples were then immersed in 100% hexamethyldisilazane for 10 minutes and air dried in an exhaust hood at room temperature. Processed samples were mounted on stainless steel stubs, coated with gold.Thawing protocol 1: All 6 (100% samples showed loss of the endothelium and damage to the subendothelial layers with randomly dispersed circular defects and micro-fractures without smooth muscle cells contractions in the tunica media. Thawing protocol 2: All 6 (100% samples showed loss of endothelium from the luminal surface, longitudinal corrugations in the direction of blood flow caused by smooth muscle cells contractions in the tunica media with frequent fractures in the subendothelial layer.All the samples thawed at the room temperature showed smaller structural damage to the CHARA arterial wall with no smooth muscle cell contraction in tunica media when compared to the samples thawed in a water bath.

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

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

    2015-09-01

    Aortic wall complications can occur in unrepaired aortic coarctation (CoA) and after surgical repair or endovascular treatment. This review summarizes the available literature and current understanding of aortic wall injury (AWI) surrounding the management of CoA, focusing specifically on acute and follow-up AWI after endovascular treatment. There have been 23 reported cases of aortic rupture after endovascular treatment for CoA, including angioplasty alone, bare metal stenting, and primary covered stent therapy. Even if these published cases represent only a minority of ruptures that have actually occurred, the incidence is substantially treatment of CoA seems to be declining in frequency with increasing experience and improving technology, it remains one of the most important potential adverse outcomes. Long-term surveillance for new AWI and monitoring of existing AWI is mandatory, with institution of appropriate treatment when necessary. A central research focus in this population should be determination of the appropriate treatment for both native and recurrent CoA across various ages with regard to limiting recurrent CoA and preventing associated aortic wall complications, in addition to determining the appropriate treatment of various AWI. Consistent definitions and reporting are necessary to truly understand the incidence of, risk factors for, and measures protective against AWI after angioplasty or stent implantation for CoA. © 2015 American Heart Association, Inc.

  5. Hyperattenuating aortic wall on postmortem computed tomography (PMCT)

    International Nuclear Information System (INIS)

    Shiotani, Seiji; Kohno, Mototsugu; Ohashi, Noriyoshi; Yamazaki, Kentaroh; Nakayama, Hidetsugu; Ito, Yoshiyuki; Kaga, Kazunori; Ebashi, Toshio; Itai, Yuji

    2002-01-01

    The purpose of this study was to quantitatively evaluate the finding of hyperattenuating aortic wall on postmortem computed tomography (PMCT) and investigate its causes. Our subjects were 50 PMCT of non-traumatic deaths and 50 CT of living persons (live CT). The ascending aorta at the level of the carina was visually assessed regarding the presence or absence of hyperattenuating aortic wall and hematocrit effect on PMCT and live CT. The diameter, thickness of the aortic wall, and CT number (HU) of the aortic wall and the lumen were also measured. Hyperattenuating aortic wall was detected in 100% of PMCT and 2% of live CT. The diameter of the aortic wall was 2.9±0.5 cm on PMCT and 3.5±0.5 cm on live CT, showing a significant difference. The thickness of the aortic wall was 2 mm on PMCT. Hematocrit effect was observed in 46% of PMCT and in none of live CT. With PMCT, there was a significant difference between the CT numbers of the upper and lower half portions of the lumen (19.6±11.7/30.9±12.9), whereas, with live CT, there was no such significant difference (37.4±7.6/38.9±6.7), with the overall value of 38.2±6.7. The CT number of the aortic wall was 49.9±10.9 on PMCT. The causes of hyperattenuating aortic wall on PMCT are considered to be increased attenuation due to contraction of the aortic wall, a lack of motion artifact, and decreased attenuation of the lumen due to dilution of blood after massive infusion at the time of cardiopulmonary resuscitation. (author)

  6. Hyperattenuating aortic wall on postmortem computed tomography (PMCT)

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    Shiotani, Seiji; Kohno, Mototsugu; Ohashi, Noriyoshi; Yamazaki, Kentaroh; Nakayama, Hidetsugu; Ito, Yoshiyuki; Kaga, Kazunori; Ebashi, Toshio [Tsukuba Medical Center Hospital, Ibaraki (Japan); Itai, Yuji [Tsukuba Univ., Ibaraki (Japan). Inst. of Clinical Medicine

    2002-08-01

    The purpose of this study was to quantitatively evaluate the finding of hyperattenuating aortic wall on postmortem computed tomography (PMCT) and investigate its causes. Our subjects were 50 PMCT of non-traumatic deaths and 50 CT of living persons (live CT). The ascending aorta at the level of the carina was visually assessed regarding the presence or absence of hyperattenuating aortic wall and hematocrit effect on PMCT and live CT. The diameter, thickness of the aortic wall, and CT number (HU) of the aortic wall and the lumen were also measured. Hyperattenuating aortic wall was detected in 100% of PMCT and 2% of live CT. The diameter of the aortic wall was 2.9{+-}0.5 cm on PMCT and 3.5{+-}0.5 cm on live CT, showing a significant difference. The thickness of the aortic wall was 2 mm on PMCT. Hematocrit effect was observed in 46% of PMCT and in none of live CT. With PMCT, there was a significant difference between the CT numbers of the upper and lower half portions of the lumen (19.6{+-}11.7/30.9{+-}12.9), whereas, with live CT, there was no such significant difference (37.4{+-}7.6/38.9{+-}6.7), with the overall value of 38.2{+-}6.7. The CT number of the aortic wall was 49.9{+-}10.9 on PMCT. The causes of hyperattenuating aortic wall on PMCT are considered to be increased attenuation due to contraction of the aortic wall, a lack of motion artifact, and decreased attenuation of the lumen due to dilution of blood after massive infusion at the time of cardiopulmonary resuscitation. (author)

  7. Enhanced delineation of degradation in aortic walls through OCT

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

    2015-03-01

    Degradation of the wall of human ascending thoracic aorta has been assessed through Optical Coherence Tomography (OCT). OCT images of the media layer of the aortic wall exhibit micro-structure degradation in case of diseased aortas from aneurysmal vessels or in aortas prone to aortic dissections. The degeneration in vessel walls appears as low-reflectivity areas due to the invasive appearance of acidic polysaccharides and mucopolysaccharides within a typical ordered microstructure of parallel lamellae of smooth muscle cells, elastin and collagen fibers. An OCT indicator of wall degradation can be generated upon the spatial quantification of the extension of degraded areas in a similar way as conventional histopathology. This proposed OCT marker offers a real-time clinical insight of the vessel status to help cardiovascular surgeons in vessel repair interventions. However, the delineation of degraded areas on the B-scan image from OCT is sometimes difficult due to presence of speckle noise, variable SNR conditions on the measurement process, etc. Degraded areas could be outlined by basic thresholding techniques taking advantage of disorders evidences in B-scan images, but this delineation is not always optimum and requires complex additional processing stages. This work proposes an optimized delineation of degraded spots in vessel walls, robust to noisy environments, based on the analysis of the second order variation of image intensity of backreflection to determine the type of local structure. Results improve the delineation of wall anomalies providing a deeper physiological perception of the vessel wall conditions. Achievements could be also transferred to other clinical scenarios: carotid arteries, aorto-iliac or ilio-femoral sections, intracranial, etc.

  8. Computed tomography of aortic wall calcifications in aortic dissection patients.

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    Pim A de Jong

    Full Text Available To investigate the frequency of aortic calcifications at the outer edge of the false lumen and the frequency of fully circular aortic calcifications in a consecutive series of patients with aortic dissection who underwent contrast-enhanced CT.The study population compromised of 69 consecutive subjects aged 60 years and older with a contrast-enhanced CT scan demonstrating an aortic dissection. All CT scans were evaluated for the frequency of aortic calcifications at the outer edge of the false lumen and the frequency of fully circular aortic calcifications by two experienced observers. Between observer reliability was evaluated by using Cohen's Kappa. Differences between groups were tested using unpaired T test and Chi-square test.Presumed media calcifications were observed in 22 (32% patients of 60 years and older and were found more frequently in chronic aortic dissection (N = 12/23, 52% than in acute aortic dissection (N = 10/46, 22%.As the intima has been torn away by the aortic dissection it is highly likely that CT scans can visualize the calcifications in the tunica media of the aorta.

  9. Ascending Aortic Wall Cohesion: Comparison of Bicuspid and Tricuspid Valves

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    Jaroslav Benedik

    2012-01-01

    Full Text Available Objectives. Bicuspid aortic valve (AV represents the most common form of congenital AV malformation, which is frequently associated with pathologies of the ascending aorta. We compared the mechanical properties of the aortic wall between patients with bicuspid and tricuspid AV using a new custom-made device mimicking transversal aortic wall shear stress. Methods. Between 03/2010 and 07/2011, 190 consecutive patients undergoing open aortic valve replacement at our institution were prospectively enrolled, presenting either with a bicuspid (group 1, n=44 or a tricuspid (group 2, n=146 AV. Aortic wall specimen were examined with the “dissectometer” resulting in nine specific aortic-wall parameters derived from tensile strength curves (TSC. Results. Patients with a bicuspid AV showed significantly more calcified valves (43.2% versus 15.8%, P<0.001, and a significantly thinner aortic wall (2.04±0.42 mm versus 2.24±0.41 mm, P=0.008. Transesophageal echocardiography diameters (annulus, aortic sinuses, and sinotubular junction were significantly larger in the bicuspid group (P=0.003, P=0.02, P=0.01. We found no difference in the aortic wall cohesion between both groups as revealed by shear stress testing (P=0.72, P=0.40, P=0.41. Conclusion. We observed no differences of TSC in patients presenting with tricuspid or bicuspid AVs. These results may allow us to assume that the morphology of the AV and the pathology of the ascending aorta are independent.

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

    DEFF Research Database (Denmark)

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

    2011-01-01

    The structural integrity of the abdominal aorta is maintained by elastin, collagen, and vascular smooth muscle cells. Changes with age in the structure can lead to develop-ment of aneurysms. This paper presents initial work to capture these changes in a finite element model (FEM) of a structural-ly-motivated...

  11. Wall Stress and Geometry of the Thoracic Aorta in Patients With Aortic Valve Disease.

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    Doyle, Barry J; Norman, Paul E; Hoskins, Peter R; Newby, David E; Dweck, Marc R

    2018-04-01

    Aortic valve disease increases velocity and changes the way blood enters the aorta. Over time, the biomechanical environment can cause aortic remodelling. We hypothesized that aortic geometry and wall stress would be different in patients with aortic valve disease compared with controls. We examined 40 patients with aortic sclerosis (n = 10) or mild (n = 10), moderate (n = 10), and severe (n = 10) aortic stenosis, and also 10 control individuals. The thoracic aorta of each individual was reconstructed into a three-dimensional model from computed tomography. We measured geometric variables and used finite element analysis to compute aortic wall stress. Statistical analyses were performed to test our hypothesis. Aortic wall stress was significantly associated with tortuosity of the descending aorta (r = 0.35, p = 0.01), arch radius (r = 0.49, p < 0.01), ascending aortic diameter (r = 0.59, p < 0.01), and aortic centerline length (r = 0.39, p < 0.01). Wall stress was highest in patients with severe stenosis (p = 0.02), although elevations in wall stress were also noted in those with mild stenosis (p = 0.02), and aortic sclerosis (p = 0.02) compared with controls. Similar trends were observed when we corrected for difference in blood pressure. Total centerline tortuosity was higher in patients with severe aortic stenosis than in controls (p = 0.04), as was descending aorta tortuosity (p = 0.04). Aortic geometry is associated with aortic wall stress. Patients with aortic valve disease have higher aortic wall stress than controls, and those with severe aortic stenosis have more tortuous aortas. However, increases in geometric measures and wall stress are not stepwise with increasing disease severity. Copyright © 2018 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  12. Clinical Implication of Aortic Wall Biopsy in Aortic Valve Disease with Bicuspid Valve Pathology

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    Yong Han Kim

    2016-12-01

    Full Text Available Background: Although unique aortic pathology related to bicuspid aortic valve (BAV has been previously reported, clinical implications of BAV to aortopathy risk have yet to be investigated. We looked for potential differences in matrix protein expressions in the aortic wall in BAV patients. Methods: Aorta specimens were obtained from 31 patients: BAV group (n=27, tricuspid aortic valve (TAV group (n=4. The BAV group was categorized into three subgroups: left coronary sinus-right coronary sinus (R+L group; n=13, 42%, right coronary sinus-non-coronary sinus (R+N group; n=8, 26%, and anteroposterior (AP group; n=6, 19%. We analyzed the expression of endothelial nitric oxide synthase (eNOS, matrix metalloproteinase (MMP-9, and tissue inhibitor of matrix metalloproteinase (TIMP-2. Results: Based on the mean value of the control group, BAV group showed decreased expression of eNOS in 72.7% of patients, increased MMP-9 in 82.3%, and decreased TIMP in 79.2%. There was a higher tendency for aortopathy in the BAV group: eNOS (BAV:TAV= 53%±7%:57%±11%, MMP-9 (BAV:TAV=48%±10%:38%±1%. The AP group showed lower expression of eNOS than the fusion (R+L, R+N group did; 48%±5% vs. 55%±7% (p=0.081. Conclusion: Not all patients with BAV had expression of aortopathy; however, for patients who had a suspicious form of bicuspid valve, aortic wall biopsy could be valuable to signify the presence of aortopathy.

  13. Distribution of Wall Stress in Abdominal Aortic Aneurysm (AAA)

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    Lasheras, Juan

    2005-11-01

    Abdominal aortic aneurysm (AAA) rupture is believed to occur when the mechanical stress acting on the wall exceeds the strength of the wall tissue. Therefore, knowledge of the AAA wall stress distribution could be useful in assessing its risk of rupture. In our research, a finite element analysis was used to determine the wall stresses both in idealized models and in a real clinical model in which the aorta was considered isotropic with nonlinear material properties and was loaded with a given pressure. In the idealized models, both maximum diameter and asymmetry were found to have substantial influence on the distribution of the wall stress. The thrombus inside the AAA was also found to help protecting the walls from high stresses. Using CT scans of the AAA, the actual geometry of the aneurysm was reconstructed and we found that wall tension increases on the flatter surface (typically corresponds to the posterior surface) and at the inflection points of the bulge. In addition to the static analysis, we also performed simulations of the effect of unsteady pressure wave propagation inside the aneurysm.

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

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    Polzer Stanislav

    2012-08-01

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

  15. Acute aortic dissection mimics acute inferoposterior wall myocardial infarction in a Marfan syndrome patient

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    Phowthongkum, Prasit

    2010-01-01

    A 30-year old man with acute chest pain was diagnosed with acute inferoposterior wall myocardial infarction following electrocardiography. After a failed coronary angiography, an echocardiogram revealed an aortic intimal flap after which acute aortic dissection was diagnosed. The patient received a successful Bentall operation without immediate complication. Retrospective examination then confirmed the diagnosis of Marfan syndrome. This case demonstrates acute aortic dissection may mimic acut...

  16. Acute aortic dissection mimics acute inferoposterior wall myocardial infarction in a Marfan syndrome patient.

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    Phowthongkum, Prasit

    2010-01-01

    A 30-year old man with acute chest pain was diagnosed with acute inferoposterior wall myocardial infarction following electrocardiography. After a failed coronary angiography, an echocardiogram revealed an aortic intimal flap after which acute aortic dissection was diagnosed. The patient received a successful Bentall operation without immediate complication. Retrospective examination then confirmed the diagnosis of Marfan syndrome. This case demonstrates acute aortic dissection may mimic acute myocardial infarction.

  17. Ferroelectricity and piezoelectricity in soft biological tissue: Porcine aortic walls revisited

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    Lenz, T.; Hummel,R.; Katsouras,I.; Groen, W.A.; Nijemeisland, M.; Ruemmler,R.; Schäfer, M.K.E.; Leeuw, D.M. de

    2017-01-01

    Recently reported piezoresponse force microscopy (PFM) measurements have proposed that porcine aortic walls are ferroelectric. This finding may have great implications for understanding biophysical properties of cardiovascular diseases such as arteriosclerosis. However, the complex anatomical

  18. Ferroelectricity and piezoelectricity in soft biological tissue : Porcine aortic walls revisited

    NARCIS (Netherlands)

    Lenz, Thomas; Hummel, Regina; Katsouras, Ilias; Groen, W.A.; Nijemeisland, M.; Ruemmler, Robert; Schäfer, Michael K.E.; de Leeuw, D.M.

    2017-01-01

    Recently reported piezoresponse force microscopy (PFM) measurements have proposed that porcine aortic walls are ferroelectric. This finding may have great implications for understanding biophysical properties of cardiovascular diseases such as arteriosclerosis. However, the complex anatomical

  19. Aortic valve replacement with simultaneous chest wall reconstruction for radiation-induced sarcoma.

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    Sachithanandan, Anand; Dandekar, Uday; Grimer, Robert; Peart, Francis; Rooney, Stephen J

    2008-01-01

    Sarcomas, a rare complication of radiotherapy for breast carcinoma, have a poor prognosis. We describe a lady with previous mantle radiotherapy exposure, who developed a radiation-induced chest wall sarcoma. She underwent simultaneous aortic valve replacement (AVR) for severe aortic stenosis and excision of the sarcoma. Chest wall reconstruction was achieved with a composite marlex cement plate and a pedicled latissimus dorsi muscle flap.

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

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    Chandra, Santanu; Seaman, Clara; Sucosky, Philippe

    2011-11-01

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

  1. Image-based biomechanical modeling of aortic wall stress and vessel deformation: response to pulsatile arterial pressure simulations

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    Hazer, Dilana; Bauer, Miriam; Unterhinninghofen, Roland; Dillmann, Rüdiger; Richter, Götz-M.

    2008-03-01

    Image-based modeling of cardiovascular biomechanics may be very helpful for patients with aortic aneurysms to predict the risk of rupture and evaluate the necessity of a surgical intervention. In order to generate a reliable support it is necessary to develop exact patient-specific models that simulate biomechanical parameters and provide individual structural analysis of the state of fatigue and characterize this to the potential of rupture of the aortic wall. The patient-specific geometry used here originates from a CT scan of an Abdominal Aortic Aneurysm (AAA). The computations are based on the Finite Element Method (FEM) and simulate the wall stress distribution and the vessel deformation. The wall transient boundary conditions are based on real time-dependent pressure simulations obtained from a previous computational fluid dynamics study. The physiological wall material properties consider a nonlinear hyperelastic constitutive model, based on realistic ex-vivo analysis of the aneurismal arterial tissue. The results showed complex deformation and stress distribution on the AAA wall. The maximum stresses occurred at the systole and are found around the aneurismal bulge in regions close to inflection points. Biomechanical modeling based on medical images and coupled with patient-specific hemodynamics allows analysing and quantifying the effects of dilatation of the arterial wall due to the pulsatile aortic pressure. It provides a physical and realistic insight into the wall mechanics and enables predictive simulations of AAA growth and assessment of rupture. Further development integrating endovascular models would help evaluating non-invasively individual treatment strategies for optimal placement and improved device design.

  2. 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

    2001-01-01

    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 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 3 to 8.70±2.98 cm 3 . The developmental rate of AWV (ΔAWV) was 0.270±0.281 cm 3 /year. ΔAWV did not have a significant correlation with any risk factor at the baseline. ΔAWV 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. ΔAWV 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)

  3. Fluid-structure interaction in abdominal aortic aneurysms: Structural and geometrical considerations

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

    2015-08-01

    Rupture of the abdominal aortic aneurysm (AAA) is the result of the relatively complex interaction of blood hemodynamics and material behavior of arterial walls. In the present study, the cumulative effects of physiological parameters such as the directional growth, arterial wall properties (isotropy and anisotropy), iliac bifurcation and arterial wall thickness on prediction of wall stress in fully coupled fluid-structure interaction (FSI) analysis of five idealized AAA models have been investigated. In particular, the numerical model considers the heterogeneity of arterial wall and the iliac bifurcation, which allows the study of the geometric asymmetry due to the growth of the aneurysm into different directions. Results demonstrate that the blood pulsatile nature is responsible for emerging a time-dependent recirculation zone inside the aneurysm, which directly affects the stress distribution in aneurismal wall. Therefore, aneurysm deviation from the arterial axis, especially, in the lateral direction increases the wall stress in a relatively nonlinear fashion. Among the models analyzed in this investigation, the anisotropic material model that considers the wall thickness variations, greatly affects the wall stress values, while the stress distributions are less affected as compared to the uniform wall thickness models. In this regard, it is confirmed that wall stress predictions are more influenced by the appropriate structural model than the geometrical considerations such as the level of asymmetry and its curvature, growth direction and its extent.

  4. Altered Aortic Upper Wall TDI Velocity Is Inversely Related with Left Ventricular Diastolic Function in Operated Tetralogy of Fallot.

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    Bassareo, Pier Paolo; Saba, Luca; Marras, Andrea R; Mercuro, Giuseppe

    2016-12-01

    Postoperative tetralogy of Fallot (TOF) patients often develop progressive aortic root dilatation due to an impairment in aortic elastic properties. (1) to assess aortic elasticity at the level of the aortic upper wall by tissue Doppler imaging (TDI); (2) to evaluate the influence of aortic elasticity on left ventricular (LV) diastolic function in TOF patients. Twenty-eight postoperative TOF patients (14 males, 14 females. Mean age: 25.7 ± 1.6 years) and 28 age- and sex-matched normal subjects were examined. Aortic distensibility and stiffness index were calculated. Aortic wall systolic and diastolic velocities, LV systolic and diastolic parameters were assessed by TDI. Aortic distensibility was significantly lower (P = .024), and aortic stiffness index significantly higher (P = .036) in TOF patients compared to controls. E/E' was significantly higher in TOF than in control group (P < .001). Aortic upper wall early diastolic velocity (AWEDV) was significantly correlated with aortic stiffness index (r: -0.42; P < .03), aortic distensibility (r = 0.54; P < .004), left atrial volume (r = -0.62; P = .0004), and E/E' ratio (r = -0.87; P < .0001). The latter relationship remained significant even when excluding the influence of age at surgery (r = -0.60; P < .0007) and of previous palliative surgery (r = -0.53; P < .02). Aortic elastic properties can be directly assessed using TDI to measure AWEDV. Aortic elasticity is significantly lower in postoperative TOF patients, exerting a negative effect also on LV diastolic function, with a potential long-term influence on clinical status. © 2016 Wiley Periodicals, Inc.

  5. Method for aortic wall strain measurement with three-dimensional ultrasound speckle tracking and fitted finite element analysis.

    Science.gov (United States)

    Karatolios, Konstantinos; Wittek, Andreas; Nwe, Thet Htar; Bihari, Peter; Shelke, Amit; Josef, Dennis; Schmitz-Rixen, Thomas; Geks, Josef; Maisch, Bernhard; Blase, Christopher; Moosdorf, Rainer; Vogt, Sebastian

    2013-11-01

    Aortic wall strains are indicators of biomechanical changes of the aorta due to aging or progressing pathologies such as aortic aneurysm. We investigated the potential of time-resolved three-dimensional ultrasonography coupled with speckle-tracking algorithms and finite element analysis as a novel method for noninvasive in vivo assessment of aortic wall strain. Three-dimensional volume datasets of 6 subjects without cardiovascular risk factors and 2 abdominal aortic aneurysms were acquired with a commercial real time three-dimensional echocardiography system. Longitudinal and circumferential strains were computed offline with high spatial resolution using a customized commercial speckle-tracking software and finite element analysis. Indices for spatial heterogeneity and systolic dyssynchrony were determined for healthy abdominal aortas and abdominal aneurysms. All examined aortic wall segments exhibited considerable heterogenous in-plane strain distributions. Higher spatial resolution of strain imaging resulted in the detection of significantly higher local peak strains (p ≤ 0.01). In comparison with healthy abdominal aortas, aneurysms showed reduced mean strains and increased spatial heterogeneity and more pronounced temporal dyssynchrony as well as delayed systole. Three-dimensional ultrasound speckle tracking enables the analysis of spatially highly resolved strain fields of the aortic wall and offers the potential to detect local aortic wall motion deformations and abnormalities. These data allow the definition of new indices by which the different biomechanical properties of healthy aortas and aortic aneurysms can be characterized. Copyright © 2013 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  6. MRI-based multiscale models for the hemodynamic and structural evaluation of surgically reconstructed aortic arches

    DEFF Research Database (Denmark)

    Pittaccio, S; Migliavacca, F; Balossino, R

    2007-01-01

    The surgical reconstruction of the aortic arch is necessary in pediatric patients suffering from different types of congenital heart malformations, in particular, coarctation of the aorta. Among the reconstruction techniques used in surgical practice end-to-end anastomosis (E/E), Gore-tex graft...... interposition (GGI) and Gore-tex patch graft aortoplasty (GPGA) are compared in this study with a control model, employing a computational fluid-structure-interaction scheme. This study analyzes the impact of introducing synthetic materials on aortic hemodynamics and wall mechanics. Three-dimensional (3D...

  7. Semiautomatic vessel wall detection and quantification of wall thickness in computed tomography images of human abdominal aortic aneurysms

    International Nuclear Information System (INIS)

    Shum, Judy; DiMartino, Elena S.; Goldhammer, Adam; Goldman, Daniel H.; Acker, Leah C.; Patel, Gopal; Ng, Julie H.; Martufi, Giampaolo; Finol, Ender A.

    2010-01-01

    Purpose: Quantitative measurements of wall thickness in human abdominal aortic aneurysms (AAAs) may lead to more accurate methods for the evaluation of their biomechanical environment. Methods: The authors describe an algorithm for estimating wall thickness in AAAs based on intensity histograms and neural networks involving segmentation of contrast enhanced abdominal computed tomography images. The algorithm was applied to ten ruptured and ten unruptured AAA image data sets. Two vascular surgeons manually segmented the lumen, inner wall, and outer wall of each data set and a reference standard was defined as the average of their segmentations. Reproducibility was determined by comparing the reference standard to lumen contours generated automatically by the algorithm and a commercially available software package. Repeatability was assessed by comparing the lumen, outer wall, and inner wall contours, as well as wall thickness, made by the two surgeons using the algorithm. Results: There was high correspondence between automatic and manual measurements for the lumen area (r=0.978 and r=0.996 for ruptured and unruptured aneurysms, respectively) and between vascular surgeons (r=0.987 and r=0.992 for ruptured and unruptured aneurysms, respectively). The authors' automatic algorithm showed better results when compared to the reference with an average lumen error of 3.69%, which is less than half the error between the commercially available application Simpleware and the reference (7.53%). Wall thickness measurements also showed good agreement between vascular surgeons with average coefficients of variation of 10.59% (ruptured aneurysms) and 13.02% (unruptured aneurysms). Ruptured aneurysms exhibit significantly thicker walls (1.78±0.39 mm) than unruptured ones (1.48±0.22 mm), p=0.044. Conclusions: While further refinement is needed to fully automate the outer wall segmentation algorithm, these preliminary results demonstrate the method's adequate reproducibility and

  8. Impact of magnesium:calcium ratio on calcification of the aortic wall.

    Science.gov (United States)

    Villa-Bellosta, Ricardo

    2017-01-01

    An inverse relationship between serum magnesium concentration and vascular calcification has been reported following observational clinical studies. Moreover, several studies have been suggesting a protective effect of magnesium on the vascular calcification. However, the exact mechanism remains elusive, and investigators have speculated among a myriad of potential actions. The effect of magnesium on calcification of the aortic wall is yet to be investigated. In the present study, the effects of magnesium and calcium on the metabolism of extracellular PPi, the main endogenous inhibitor of vascular calcification, were investigated in the rat aorta. Calcium and magnesium have antagonist effects on PPi hydrolysis in the aortic wall. Km and Ki values for PPi hydrolysis in rat aortic rings were 1.1 mmol/L magnesium and 32 μmol/L calcium, respectively, but ATP hydrolysis was not affected with calcium. Calcium deposition in the rat aortic wall dramatically increased when the magnesium concentration was increased (ratio of Mg:Ca = 1:1; 1.5 mmol/L calcium and 1.5 mmol/L magnesium) respect to low magnesium concentration (ratio Mg:Ca = 1:3, 1.5 mmol/L calcium and 0.75 mmol/L magnesium). Data from observational clinical studies showing that the serum magnesium concentration is inversely correlated with vascular calcification could be reinterpreted as a compensatory regulatory mechanism that reduces both PPi hydrolysis and vascular calcification. The impact of magnesium in vascular calcification in humans could be studied in association with calcium levels, for example, as the magnesium:calcium ratio.

  9. Mass transport properties of the rabbit aortic wall.

    Directory of Open Access Journals (Sweden)

    Emma L Bailey

    Full Text Available Uptake of circulating macromolecules by the arterial wall may be a critical step in atherogenesis. Here we investigate the age-related changes in patterns of uptake that occur in the rabbit. In immature aortas, uptake was elevated in a triangle downstream of branch ostia, a region prone to disease in immature rabbits and children. By 16-22 months, uptake was high lateral to ostia, as is lesion prevalence in mature rabbits and young adults. In older rabbits there was a more upstream pattern, similar to the disease distribution in older people. These variations were predominantly caused by the branches themselves, rather than reflecting larger patterns within which the branches happened to be situated (as may occur with patterns of haemodynamic wall shear stress. The narrow streaks of high uptake reported in some previous studies were shown to be post mortem artefacts. Finally, heparin (which interferes with the NO pathway had no effect on the difference in uptake between regions upstream and downstream of branches in immature rabbits but reversed the difference in older rabbits, as does inhibiting NO synthesis directly. Nevertheless, examination of uptake all around the branch showed that changes occurred at both ages and that they were quite subtle, potentially explaining why inhibiting NO has only minor effects on lesion patterns in mature rabbits and contradicting the earlier conclusion that mechanotransduction pathways change with age. We suggest that recently-established changes in the patterns of haemodynamic forces themselves are more likely to account for the age-dependence of uptake patterns.

  10. Relation of murine thoracic aortic structural and cellular changes with aging to passive and active mechanical properties.

    Science.gov (United States)

    Wheeler, Jason B; Mukherjee, Rupak; Stroud, Robert E; Jones, Jeffrey A; Ikonomidis, John S

    2015-02-25

    Maintenance of the structure and mechanical properties of the thoracic aorta contributes to aortic function and is dependent on the composition of the extracellular matrix and the cellular content within the aortic wall. Age-related alterations in the aorta include changes in cellular content and composition of the extracellular matrix; however, the precise roles of these age-related changes in altering aortic mechanical function are not well understood. Thoracic aortic rings from the descending segment were harvested from C57BL/6 mice aged 6 and 21 months. Thoracic aortic diameter and wall thickness were higher in the old mice. Cellular density was reduced in the medial layer of aortas from the old mice; concomitantly, collagen content was higher in old mice, but elastin content was similar between young and old mice. Stress relaxation, an index of compliance, was reduced in aortas from old mice and correlated with collagen fraction. Contractility of the aortic rings following potassium stimulation was reduced in old versus young mice. Furthermore, collagen gel contraction by aortic smooth muscle cells was reduced with age. These results demonstrate that numerous age-related structural changes occurred in the thoracic aorta and were related to alterations in mechanical properties. Aortic contractility decreased with age, likely because of a reduction in medial cell number in addition to a smooth muscle contractile deficit. Together, these unique findings provide evidence that the age-related changes in structure and mechanical function coalesce to provide an aortic substrate that may be predisposed to aortopathies. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  11. Trace elements in the wall of abdominal aortic aneurysms with and without coexisting iliac artery aneurysms.

    Science.gov (United States)

    Ziaja, Damian; Chudek, Jerzy; Sznapka, Mariola; Kita, Andrzej; Biolik, Grzegorz; Sieroń-Stołtny, Karolina; Pawlicki, Krzysztof; Domalik, Jolanta; Ziaja, Krzysztof

    2015-06-01

    Iliac artery aneurysms (IAA) and abdominal aortic aneurysms (AAA) frequently coexist. It remains unknown whether the content of trace elements in AAA walls depends on the coexistence of IAAs. The aim of this study was to compare the content of selected trace elements in AAA walls depending on the coexistence of IAAs. The content of trace elements was assessed in samples of AAA walls harvested intraoperatively in 19 consecutive patients. In the studied group, coexisting IAAs were diagnosed in 11 out of the 19 patients with AAA. The coexistence of IAAs was associated with a slightly lower content of nickel (0.28 (0.15-0.40) vs. 0.32 (0-0.85) mg/g; p = 0.09) and a significantly higher content of cadmium (0.71 (0.26-1.17) vs. 0.25 (0.20-0.31) mg/g; p = 0.04) in AAA walls. The levels of the remaining studied elements, copper, zinc, manganese, magnesium and calcium, were comparable. The elevated levels of cadmium in the walls of AAA coexisting with IAAs may suggest an impact of the accumulation of this trace element on the greater damage of the iliac artery wall.

  12. 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.

  13. Chronic high-sodium diet increases aortic wall endothelin-1 expression in a blood pressure-independent fashion in rats.

    Science.gov (United States)

    Tsai, Yu-Hwai; Ohkita, Mamoru; Gariepy, Cheryl E

    2006-06-01

    Vascular endothelin (ET)-1 is upregulated in several forms of salt-induced hypertension. It is unclear to what extent these effects are primary or secondary to endothelial damage. We hypothesized that a high-sodium diet (HNa) increases vascular ET-1 production independent of arterial blood pressure changes. We investigated the effect of chronic HNa with and without ET(A) blockade on circulating and aortic ET-1 protein levels as well as aortic expression of ET-1 and ET(A) messenger RNA (mRNA) in inbred Wistar-Kyoto (WKY) and congenic ET(B)-deficient rats. Comparing WKY rats fed a low-sodium diet (LNa) with those fed HNa for 3 weeks, aortic wall ET-1 protein is significantly increased in response to HNa (331 +/- 43 pg/g tissue for LNa vs. 557 +/- 34 pg/gm tissue for HNa). HNa also increased aortic wall ET-1 mRNA levels by 40%, as determined by quantitative reverse transcriptase polymerase chain reaction. We then compared rats chronically treated with the ET(A)-selective antagonist, ABT-627, while receiving either LNa or HNa. There were no differences in arterial blood pressure (mean arterial pressure 89 +/- 1 mm Hg for WKY on LNa; 90 +/- 3 for WKY on HNa; 91 +/- 2 for ET(B)-deficient/ABT-627-treated on HNa) or heart rate. However, aortic wall ET-1 protein levels were 4-fold higher in the HNa group. Further, HNa increased aortic wall ET-1 mRNA (approximately 1.5- to 3-fold) and ET(A) mRNA (approximately 2- to 7-fold), independent of activation of ET(B). Therefore, the expression of ET-1 mRNA by the aortic wall is increased in response to chronic high dietary sodium in WKY rats in the absence of changes in arterial blood pressure.

  14. Mechanical and geometrical determinants of wall stress in abdominal aortic aneurysms: A computational study.

    Directory of Open Access Journals (Sweden)

    Dara Azar

    Full Text Available An aortic aneurysm (AA is a focal dilatation of the aortic wall. Occurrence of AA rupture is an all too common event that is associated with high levels of patient morbidity and mortality. The decision to surgically intervene prior to AA rupture is made with recognition of significant procedural risks, and is primarily based on the maximal diameter and/or growth rate of the AA. Despite established thresholds for intervention, rupture occurs in a notable subset of patients exhibiting sub-critical maximal diameters and/or growth rates. Therefore, a pressing need remains to identify better predictors of rupture risk and ultimately integrate their measurement into clinical decision making. In this study, we use a series of finite element-based computational models that represent a range of plausible AA scenarios, and evaluate the relative sensitivity of wall stress to geometrical and mechanical properties of the aneurysmal tissue. Taken together, our findings encourage an expansion of geometrical parameters considered for rupture risk assessment, and provide perspective on the degree to which tissue mechanical properties may modulate peak stress values within aneurysmal tissue.

  15. Elevated Wall Shear Stress in Aortic Type B Dissection May Relate to Retrograde Aortic Type A Dissection: A Computational Fluid Dynamics Pilot Study.

    Science.gov (United States)

    Osswald, A; Karmonik, C; Anderson, J R; Rengier, F; Karck, M; Engelke, J; Kallenbach, K; Kotelis, D; Partovi, S; Böckler, D; Ruhparwar, A

    2017-09-01

    Retrograde aortic type A dissection (RTAD) is a known complication in patients with aortic type B dissection. The purpose of this computational fluid dynamics (CFD) study was to identify haemodynamic risk factors for the occurrence of RTAD. Computed tomographic angiography (CTA) images of 10 patients with type B dissections, who subsequently developed a RTAD, were retrospectively analysed together with patients constituting a control group (n = 10) where no further vascular events after the initial type B dissection occurred. CFD simulations were conducted based on 3D surface models of the aortic lumen derived from CTA datasets. For both groups, pressures, velocity magnitudes and wall shear stress (WSS) were compared at the site of the future RTAD entry tear and the surrounding aortic wall. WSS at the site of the future entry tear was significantly elevated compared with the surrounding wall (15.10 Pa vs. 5.15 Pa, p < .001) and was significantly higher in the RTAD group than in the control group (6.05 Pa, p < .002). Pressures and velocity magnitudes were not significantly elevated at the entry tear (3825.8 Pa, 0.63 m/s) compared with the aortic arch (3549.8 Pa, 0.50 m/s) or control group (3501.7 Pa, 0.62 m/s). Increased WSS accompanies the occurrence of RTAD. The results merit the design for a prospective study to confirm whether WSS is a risk factor for the occurrence of RTAD. Copyright © 2017 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

  16. In vivo 3-dimensional Magnetic Resonance Wall Shear Stress Estimation in Ascending Aortic Dilatation

    Science.gov (United States)

    Bieging, Erik T.; Frydrychowicz, Alex; Wentland, Andrew; Landgraf, Benjamin R.; Johnson, Kevin M.; Wieben, Oliver; François, Christopher J.

    2011-01-01

    Purpose To estimate surface-based wall shear stress (WSS) and evaluate flow patterns in ascending aortic dilatation (AscAD) using a high-resolution, time-resolved, three-dimensional (3D), three-directional velocity encoded, radially undersampled phase contrast magnetic resonance sequence (4D PC-MRI). Materials and Methods 4D PC-MRI was performed in 11 patients with AscAD (46.3±22.0 years) and 10 healthy volunteers (32.9±13.4 years) after written informed consent and IRB-approval. Following manual vessel wall segmentation of the ascending aorta (MATLAB, The Mathworks, Natick, MA), a 3D surface was created using spline interpolation. Spatial WSS variation based on surface division in 12 segments and temporal variation were evaluated in AscAD and normal aortas. Visual analysis of flow patterns was performed based on streamlines and particle traces using EnSight (v9.0, CEI, Apex, NC). Results AscAD was associated with significantly increased diastolic WSS, decreased systolic to diastolic WSS ratio, and delayed onset of peak WSS (all P wall of the ascending aorta. Vortical flow with highest velocities along the anterior wall and increased helical flow during diastole were observed in AscAD compared to controls. Conclusion Changes in WSS in the ascending aorta of AscAD correspond to observed alterations in flow patterns compared to controls. PMID:21563242

  17. Differential effects of nebivolol and metoprolol on central aortic pressure and left ventricular wall thickness.

    Science.gov (United States)

    Kampus, Priit; Serg, Martin; Kals, Jaak; Zagura, Maksim; Muda, Piibe; Karu, Külliki; Zilmer, Mihkel; Eha, Jaan

    2011-06-01

    The aim of this study was to investigate the effects of the vasodilating β-blocker nebivolol and the cardioselective β-blocker metoprolol succinate on aortic blood pressure and left ventricular wall thickness. We conducted a randomized, double-blind study on 80 hypertensive patients. The patients received either 5 mg of nebivolol or 50 to 100 mg of metoprolol succinate daily for 1 year. Their heart rate, central and brachial blood pressures, mean arterial pressure, augmentation index, carotid-femoral pulse wave velocity, and left ventricular wall thickness were measured at baseline and at the end of the study. Nebivolol and metoprolol significantly reduced heart rate, brachial blood pressure, and mean arterial pressure to the same degree. However, reductions in central systolic and diastolic blood pressures, central pulse pressure, and left ventricular wall thickness were significant only in the nebivolol group. The change in left ventricular septal wall thickness was significantly correlated with central systolic blood pressure change (r=0.41; P=0.001) and with central pulse pressure change (r=0.32; P=0.01). No significant changes in augmentation index or carotid-femoral pulse wave velocity were detected in either treatment group. This proof-of-principle study provides evidence to suggest that β-blockers with vasodilating properties may offer advantages over conventional β-blockers in antihypertensive therapy; however, this remains to be tested in a larger trial.

  18. 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.

  19. Measurements of Intra‐Aortic Balloon Wall Movement During Inflation and Deflation: Effects of Angulation

    Science.gov (United States)

    Bruti, Gianpaolo; Kolyva, Christina; Pepper, John R.

    2015-01-01

    Abstract The intra‐aortic balloon pump (IABP) is a ventricular assist device that is used with a broad range of pre‐, intra‐, and postoperative patients undergoing cardiac surgery. Although the clinical efficacy of the IABP is well documented, the question of reduced efficacy when patients are nursed in the semi‐recumbent position remains outstanding. The aim of the present work is therefore to investigate the underlying mechanics responsible for the loss of IABP performance when operated at an angle to the horizontal. Simultaneous recordings of balloon wall movement, providing an estimate of its diameter (D), and fluid pressure were taken at three sites along the intra‐aortic balloon (IAB) at 0 and 45°. Flow rate, used for the calculation of displaced volume, was also recorded distal to the tip of the balloon. An in vitro experimental setup was used, featuring physiological impedances on either side of the IAB ends. IAB inflation at an angle of 45° showed that D increases at the tip of the IAB first, presenting a resistance to the flow displaced away from the tip of the balloon. The duration of inflation decreased by 15.5%, the inflation pressure pulse decreased by 9.6%, and volume decreased by 2.5%. Similarly, changing the position of the balloon from 0 to 45°, the balloon deflation became slower by 35%, deflation pressure pulse decreased by 14.7%, and volume suctioned was decreased by 15.2%. IAB wall movement showed that operating at 45° results in slower deflation compared with 0°. Slow wall movement, and changes in inflation and deflation onsets, result in a decreased volume displacement and pressure pulse generation. Operating the balloon at an angle to the horizontal, which is the preferred nursing position in intensive care units, results in reduced IAB inflation and deflation performance, possibly compromising its clinical benefits. PMID:25959284

  20. 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

  1. 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 Sanddal; 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....

  2. Unexpected Radiation-Induced Aortic Wall Thickening Requiring Composite Graft Technique during Off-Pump Coronary Artery Bypass Grafting

    Directory of Open Access Journals (Sweden)

    Paola Redaelli

    2017-01-01

    Full Text Available Mediastinal radiation is commonly used to treat Hodgkin’s and non-Hodgkin’s lymphoma, lung and breast cancer. Cardiac complications after radiation therapy are well described, although rare. A large spectrum of injuries can occur, causing long term morbidity among survivors. We describe a case of post-actinic ascending aortic wall thickening that prevented saphenous vein proximal anastomosis and was successfully managed with aortic no-touch off-pump coronary artery bypass grafting (OPCAB, 25 years after radiation therapy for Hodgkin’s lymphoma.

  3. The composite aortic wall graft technique: an option for a short coronary artery bypass graft

    Directory of Open Access Journals (Sweden)

    João Bosco de Oliveira

    2009-01-01

    Full Text Available SUMMARY: During coronary artery bypass graft (CABG surgery, the saphenous vein is sutured through its proximal segment to the aorta. Intimal hyperplasia is one of the possible causes of graft occlusion. Notably, blood turbulence can induce wall shear stress that may also play an important role in this process. OBJECTIVE: We propose a new technique for performing proximal anastomosis to avoid CABG failure. METHOD: An 80 kg pig was subjected to open heart surgery. Four stitches were placed in the anterior ascending aorta, which formed a 2 cm by 4 cm patch. This patch was isolated through the application of a tangential clamp that was oriented parallel to the axis of the aorta. After releasing the patch, which was held to the aorta through its cranial end pedicle, the rims were sutured to each other creating a conduit with a length of 4 cm and an internal diameter of 4 mm. The rest of the aortotomy was closed by placing a direct suture between its rims. RESULT: This novel technique created an "in situ" aortic wall graft that was 4 cm long and characterized as being of uniform 4 mm caliber.

  4. Measurements of Intra-Aortic Balloon Wall Movement During Inflation and Deflation: Effects of Angulation.

    Science.gov (United States)

    Bruti, Gianpaolo; Kolyva, Christina; Pepper, John R; Khir, Ashraf W

    2015-08-01

    The intra-aortic balloon pump (IABP) is a ventricular assist device that is used with a broad range of pre-, intra-, and postoperative patients undergoing cardiac surgery. Although the clinical efficacy of the IABP is well documented, the question of reduced efficacy when patients are nursed in the semi-recumbent position remains outstanding. The aim of the present work is therefore to investigate the underlying mechanics responsible for the loss of IABP performance when operated at an angle to the horizontal. Simultaneous recordings of balloon wall movement, providing an estimate of its diameter (D), and fluid pressure were taken at three sites along the intra-aortic balloon (IAB) at 0 and 45°. Flow rate, used for the calculation of displaced volume, was also recorded distal to the tip of the balloon. An in vitro experimental setup was used, featuring physiological impedances on either side of the IAB ends. IAB inflation at an angle of 45° showed that D increases at the tip of the IAB first, presenting a resistance to the flow displaced away from the tip of the balloon. The duration of inflation decreased by 15.5%, the inflation pressure pulse decreased by 9.6%, and volume decreased by 2.5%. Similarly, changing the position of the balloon from 0 to 45°, the balloon deflation became slower by 35%, deflation pressure pulse decreased by 14.7%, and volume suctioned was decreased by 15.2%. IAB wall movement showed that operating at 45° results in slower deflation compared with 0°. Slow wall movement, and changes in inflation and deflation onsets, result in a decreased volume displacement and pressure pulse generation. Operating the balloon at an angle to the horizontal, which is the preferred nursing position in intensive care units, results in reduced IAB inflation and deflation performance, possibly compromising its clinical benefits. Copyright © 2015 The Authors. Artificial Organs published by Wiley Periodicals, Inc. on behalf of International Center for

  5. Hydraulic structures with defective sheet pile walls

    OpenAIRE

    Ahmed, Ashraf A.; Johnston, Harold T.; Oyedele, Lukumon

    2013-01-01

    A sheet pile wall driven to form a barrier wall below the floor of a hydraulic structure is frequently assumed to be watertight. Although the leakage through the interlocks of the sheet piles is usually small, damage and other factors can result in significant leakage. Consequently, this assumption is rarely, if ever, satisfied in reality. The present study used a finite-element model to investigate the effect of leaks through sheet piles driven under the floor of a hydraulic structure on see...

  6. Impact of hypertension on left ventricular structure in patients with asymptomatic aortic valve stenosis (a SEAS substudy)

    DEFF Research Database (Denmark)

    Rieck, Ashild E; Cramariuc, Dana; Staal, Eva M

    2010-01-01

    Both hypertension and aortic valve stenosis induce left ventricular hypertrophy. However, less is known about the influence of concomitant hypertension on left ventricular structure in patients with aortic valve stenosis.......Both hypertension and aortic valve stenosis induce left ventricular hypertrophy. However, less is known about the influence of concomitant hypertension on left ventricular structure in patients with aortic valve stenosis....

  7. Machine Learning Approach for Predicting Wall Shear Distribution for Abdominal Aortic Aneurysm and Carotid Bifurcation Models.

    Science.gov (United States)

    Jordanski, Milos; Radovic, Milos; Milosevic, Zarko; Filipovic, Nenad; Obradovic, Zoran

    2018-03-01

    Computer simulations based on the finite element method represent powerful tools for modeling blood flow through arteries. However, due to its computational complexity, this approach may be inappropriate when results are needed quickly. In order to reduce computational time, in this paper, we proposed an alternative machine learning based approach for calculation of wall shear stress (WSS) distribution, which may play an important role in mechanisms related to initiation and development of atherosclerosis. In order to capture relationships between geometric parameters, blood density, dynamic viscosity and velocity, and WSS distribution of geometrically parameterized abdominal aortic aneurysm (AAA) and carotid bifurcation models, we proposed multivariate linear regression, multilayer perceptron neural network and Gaussian conditional random fields (GCRF). Results obtained in this paper show that machine learning approaches can successfully predict WSS distribution at different cardiac cycle time points. Even though all proposed methods showed high potential for WSS prediction, GCRF achieved the highest coefficient of determination (0.930-0.948 for AAA model and 0.946-0.954 for carotid bifurcation model) demonstrating benefits of accounting for spatial correlation. The proposed approach can be used as an alternative method for real time calculation of WSS distribution.

  8. Structural domain walls in polar hexagonal manganites

    Science.gov (United States)

    Kumagai, Yu

    2014-03-01

    The domain structure in the multiferroic hexagonal manganites is currently intensely investigated, motivated by the observation of intriguing sixfold topological defects at their meeting points [Choi, T. et al,. Nature Mater. 9, 253 (2010).] and nanoscale electrical conductivity at the domain walls [Wu, W. et al., Phys. Rev. Lett. 108, 077203 (2012).; Meier, D. et al., Nature Mater. 11, 284 (2012).], as well as reports of coupling between ferroelectricity, magnetism and structural antiphase domains [Geng, Y. et al., Nano Lett. 12, 6055 (2012).]. The detailed structure of the domain walls, as well as the origin of such couplings, however, was previously not fully understood. In the present study, we have used first-principles density functional theory to calculate the structure and properties of the low-energy structural domain walls in the hexagonal manganites [Kumagai, Y. and Spaldin, N. A., Nature Commun. 4, 1540 (2013).]. We find that the lowest energy domain walls are atomically sharp, with {210}orientation, explaining the orientation of recently observed stripe domains and suggesting their topological protection [Chae, S. C. et al., Phys. Rev. Lett. 108, 167603 (2012).]. We also explain why ferroelectric domain walls are always simultaneously antiphase walls, propose a mechanism for ferroelectric switching through domain-wall motion, and suggest an atomistic structure for the cores of the sixfold topological defects. This work was supported by ETH Zurich, the European Research Council FP7 Advanced Grants program me (grant number 291151), the JSPS Postdoctoral Fellowships for Research Abroad, and the MEXT Elements Strategy Initiative to Form Core Research Center TIES.

  9. [18F]FDG Uptake in the Aortic Wall Smooth Muscle of Atherosclerotic Plaques in the Simian Atherosclerosis Model

    Directory of Open Access Journals (Sweden)

    Takayuki Iwaki

    2016-01-01

    Full Text Available Atherosclerosis is a self-sustaining inflammatory fibroproliferative disease that progresses in discrete stages and involves a number of cell types and effector molecules. Recently, [18F]fluoro-2-deoxy-D-glucose- ([18F]FDG- positron emission tomography (PET has been suggested as a tool to evaluate atherosclerotic plaques by detecting accumulated macrophages associated with inflammation progress. However, at the cellular level, it remains unknown whether only macrophages exhibit high uptake of [18F]FDG. To identify the cellular origin of [18F]FDG uptake in atherosclerotic plaques, we developed a simian atherosclerosis model and performed PET and ex vivo macro- and micro-autoradiography (ARG. Increased [18F]FDG uptake in the aortic wall was observed in high-cholesterol diet-treated monkeys and WHHL rabbits. Macro-ARG of [18F]FDG in aortic sections showed that [18F]FDG was accumulated in the media and intima in the simian model as similar to that in WHHL rabbits. Combined analysis of micro-ARG with immunohistochemistry in the simian atherosclerosis model revealed that most cellular [18F]FDG uptake observed in the media was derived not only from the infiltrated macrophages in atherosclerotic plaques but also from the smooth muscle cells (SMCs of the aortic wall in atherosclerotic lesions.

  10. Illinois Walls in alternative market structures

    NARCIS (Netherlands)

    Schinkel, M.P.; Tuinstra, J.

    2005-01-01

    This note extends on our paper Illinois Walls: How Barring Indirect Purchaser Suits Facilitates Collusion (Schinkel, Tuinstra and Rüggeberg, 2005, henceforth STR). It presents analyses of two alternative, more competitive, market structures to conclude that when the conditions for existence of

  11. Diuretics prevent Rho-kinase activation and expression of profibrotic/oxidative genes in the hypertensive aortic wall.

    Science.gov (United States)

    Araos, Patricio; Mondaca, David; Jalil, Jorge E; Yañez, Cristián; Novoa, Ulises; Mora, Italo; Ocaranza, María Paz

    2016-12-01

    Diuretics are current antihypertensive drugs since they reduce blood pressure and cardiovascular risk. Increased vascular tone is modulated in a relevant way by the RhoA/Rho-kinase (ROCK) pathway, by acting on vascular smooth muscle cell contraction. This pathway has also proremodeling vascular effects. There are few data on the role of diuretics on both vascular ROCK activation and on proremodeling effects. We assessed the effects of hydrochlorothiazide (HCTZ) and spironolactone (spiro) alone and in combination with the ROCK inhibitor fasudil (FAS) on ROCK activation, gene expression of proremodeling markers and on hypertrophy in the aortic wall of hypertensive rats. Deoxycorticosterone acetate (DOCA)-salt hypertensive rats (male, Sprague-Dawley) were randomized to the specific ROCK inhibitor FAS, HCTZ, spiro or the combinations of FAS/HCTZ or FAS/spiro for 3 weeks. At the end of the study, ROCK activation (by western blot), gene expression of proremodeling markers (by reverse transcription polymerase chain reaction, RT-PCR) and vascular hypertrophy (by morphometry) were determined in the aortic wall. All treatments significantly reduced blood pressure. In the DOCA rats the p-myosin phosphatase target protein-1 (MYPT1)/t-MYPT1 ratio, index of ROCK activation was higher by 2.8 fold (p diuretics alone or in combination with FAS. In the aortic wall, both HCTZ and spiro in antihypertensive doses reduce ROCK activation, subsequent expression of genes that promote vascular remodeling and hypertrophy in this experimental model of hypertension. These effects could explain some of their clinical benefits in hypertensive patients. © The Author(s), 2016.

  12. Aortic elasticity and size are associated with aortic regurgitation and left ventricular dysfunction in tetralogy of Fallot after pulmonary valve replacement

    NARCIS (Netherlands)

    Grotenhuis, H.B.; Ottenkamp, J.; de Bruijn, L.; Westenberg, J.J.M.; Vliegen, H.W.; Kroft, L.J.M.; de Roos, A.

    2009-01-01

    Background: Aortic wall pathology and concomitant aortic dilatation have been described in tetralogy of Fallot (TOF) patients, which may negatively affect aortic valve and left ventricular systolic function. Objective: To assess aortic dimensions, aortic elasticity, aortic valve competence and

  13. 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.

  14. Surgical anatomy of the aortic root: Implication for valve-sparing reimplantation and aortic valve annuloplasty

    OpenAIRE

    de Kerchove, Laurent; Jashari, Ramadan; Boodhwani, Munir; Duy, Khanh Tran; Lengelé, Benoit; Gianello, Pierre; Nezhad, Zahra Mozala; Astarci, Parla; Noirhomme, Philippe; El Khoury, Gebrine

    2015-01-01

    BACKGROUND: To enhance the reproducibility of aortic valve-sparing reimplantation and annuloplasty, we analyzed the topographic relationship between the ventriculoaortic junction (VAJ), basal ring (BR), and sinotubular junction (STJ). The root base thickness is also quantified. METHOD: Fifty-eight fresh human aortic valves were analyzed. The root was dissected to the limit where the aortic wall terminates into the cardiac structures (VAJ). Root height was measured externally from the STJ t...

  15. Enhanced caspase activity contributes to aortic wall remodeling and early aneurysm development in a murine model of Marfan syndrome.

    Science.gov (United States)

    Emrich, Fabian C; Okamura, Homare; Dalal, Alex R; Penov, Kiril; Merk, Denis R; Raaz, Uwe; Hennigs, Jan K; Chin, Jocelyn T; Miller, Miquell O; Pedroza, Albert J; Craig, Juliana K; Koyano, Tiffany K; Blankenberg, Francis G; Connolly, Andrew J; Mohr, Friedrich W; Alvira, Cristina M; Rabinovitch, Marlene; Fischbein, Michael P

    2015-01-01

    Rupture and dissection of aortic root aneurysms remain the leading causes of death in patients with the Marfan syndrome, a hereditary connective tissue disorder that affects 1 in 5000 individuals worldwide. In the present study, we use a Marfan mouse model (Fbn1(C1039G/+)) to investigate the biological importance of apoptosis during aneurysm development in Marfan syndrome. Using in vivo single-photon emission computed tomographic-imaging and ex vivo autoradiography for Tc99m-annexin, we discovered increased apoptosis in the Fbn1(C1039G/+) ascending aorta during early aneurysm development peaking at 4 weeks. Immunofluorescence colocalization studies identified smooth muscle cells (SMCs) as the apoptotic cell population. As biological proof of concept that early aortic wall apoptosis plays a role in aneurysm development in Marfan syndrome, Fbn1(C1039G/+) mice were treated daily from 2 to 6 weeks with either (1) a pan-caspase inhibitor, Q-VD-OPh (20 mg/kg), or (2) vehicle control intraperitoneally. Q-VD-OPh treatment led to a significant reduction in aneurysm size and decreased extracellular matrix degradation in the aortic wall compared with control mice. In vitro studies using Fbn1(C1039G/+) ascending SMCs showed that apoptotic SMCs have increased elastolytic potential compared with viable cells, mostly because of caspase activity. Moreover, in vitro (1) cell membrane isolation, (2) immunofluorescence staining, and (3) scanning electron microscopy studies illustrate that caspases are expressed on the exterior cell surface of apoptotic SMCs. Caspase inhibition attenuates aneurysm development in an Fbn1(C1039G/+) Marfan mouse model. Mechanistically, during apoptosis, caspases are expressed on the cell surface of SMCs and likely contribute to elastin degradation and aneurysm development in Marfan syndrome. © 2014 American Heart Association, Inc.

  16. Tamoxifen up-regulates catalase production, inhibits vessel wall neutrophil infiltration, and attenuates development of experimental abdominal aortic aneurysms.

    Science.gov (United States)

    Grigoryants, Vladimir; Hannawa, Kevin K; Pearce, Charles G; Sinha, Indranil; Roelofs, Karen J; Ailawadi, Gorav; Deatrick, Kristopher B; Woodrum, Derek T; Cho, Brenda S; Henke, Peter K; Stanley, James C; Eagleton, Matthew J; Upchurch, Gilbert R

    2005-01-01

    controls on day 7 (P = .05). Administration of the direct catalase inhibitor AT to tamoxifen-treated rats partially reversed the aneurysm inhibitory effect of tamoxifen by nearly 30% (P = .02). In contrast, catalase administration inhibited AAA formation by 44% (P = .002). The selective estrogen receptor modulator tamoxifen inhibits the development of AAAs in male rats in association with an up-regulation of catalase and inhibition of aortic wall neutrophil infiltration.

  17. Association of aortic wall thickness on contrast-enhanced chest CT with major cerebro-cardiac events.

    Science.gov (United States)

    Tresoldi, Silvia; Di Leo, Giovanni; Zoffoli, Elena; Munari, Alice; Primolevo, Alessandra; Cornalba, Gianpaolo; Sardanelli, Francesco

    2014-11-01

    There is a significant association between aortic atherosclerosis and previous major cardiovascular events. Particularly, thoracic aortic atherosclerosis is closely related to the degree of coronary and carotid artery disease. Thus, there is a rationale for screening the thoracic aorta in patients who undergo a chest computed tomography (CT) for any clinical question, in order to detect patients at increased risk of cerebro-cardiovascular (CCV) events. To estimate the association between either thoracic aortic wall thickness (AWT) or aortic total calcium score (ATCS) and CCV events. One hundred and forty-eight non-cardiac patients (78 men; 67 ± 12 years) underwent chest contrast-enhanced multidetector CT (MDCT). The AWT was measured at the level of the left atrium (AWTref) and at the maximum AWT (AWTmax). Correlation with clinical CCV patients' history was estimated. The value of AWTmax and of a semi-quantitative ATCS as a marker for CCV events was assessed using receiver-operating characteristic curve (ROC) analysis and multivariate regression analysis. Out of 148 patients, 59% reported sedentary lifestyle, 44% hypertension, 32% smoking, 23% hypercholesterolemia, 13% family history of cardiac disease, 12% diabetes, and 10% BMI ≥ 30 kg/m(2); 9% reported myocardial infarction, 8% aortic aneurism, 8% myocardial revascularization, and 2% ischemic stroke. Twenty-six percent of patients had a medium-to-high ATCS. Both AWTmax and AWTref correlated with hypertension and age (P < 0.002). At the ROC analysis, a 4.8 mm threshold was associated to a 90% specificity and an odds ratio of 6.3 (AUC = 0.735). Assuming as threshold the AWTmax median value (4.3 mm) of patients who suffered from at least one CCV event in their history, a negative predictive value of 90%, a RR of 3.6 and an OR of 6.3 were found. At the multivariate regression analysis, AWTmax was the only independent variable associated to the frequency of CCV events. Patients with increased thoracic

  18. 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.

  19. Outer Wall Segmentation of Abdominal Aortic Aneurysm by Variable Neighborhood Search Through Intensity and Gradient Spaces.

    Science.gov (United States)

    Siriapisith, Thanongchai; Kusakunniran, Worapan; Haddawy, Peter

    2018-01-19

    Aortic aneurysm segmentation remains a challenge. Manual segmentation is a time-consuming process which is not practical for routine use. To address this limitation, several automated segmentation techniques for aortic aneurysm have been developed, such as edge detection-based methods, partial differential equation methods, and graph partitioning methods. However, automatic segmentation of aortic aneurysm is difficult due to high pixel similarity to adjacent tissue and a lack of color information in the medical image, preventing previous work from being applicable to difficult cases. This paper uses uses a variable neighborhood search that alternates between intensity-based and gradient-based segmentation techniques. By alternating between intensity and gradient spaces, the search can escape from local optima of each space. The experimental results demonstrate that the proposed method outperforms the other existing segmentation methods in the literature, based on measurements of dice similarity coefficient and jaccard similarity coefficient at the pixel level. In addition, it is shown to perform well for cases that are difficult to segment.

  20. Tools to Understand Structural Property Relationships for Wood Cell Walls

    Science.gov (United States)

    Joseph E. Jakes; Daniel J. Yelle; Charles R. Frihart

    2011-01-01

    Understanding structure-property relationships for wood cell walls has been hindered by the complex polymeric structures comprising these cell walls and the difficulty in assessing meaningful mechanical property measurements of individual cell walls. To help overcome these hindrances, we have developed two experimental methods: 1) two-dimensional solution state nuclear...

  1. Thin-walled reinforcement lattice structure for hollow CMC buckets

    Science.gov (United States)

    de Diego, Peter

    2017-06-27

    A hollow ceramic matrix composite (CMC) turbine bucket with an internal reinforcement lattice structure has improved vibration properties and stiffness. The lattice structure is formed of thin-walled plies made of CMC. The wall structures are arranged and located according to high stress areas within the hollow bucket. After the melt infiltration process, the mandrels melt away, leaving the wall structure to become the internal lattice reinforcement structure of the bucket.

  2. An enzymatic approach to cell wall structure

    African Journals Online (AJOL)

    afsonderlik. Keywords: Ruminococcus a/bus, alfalfa cell walls, cellulose, hemicellulose, enzymic digestion. Introduction. The aim of the research is to provide more specific infor- mation on the chemical linkages in plant cell wall material. The procedure is (l) to determine which constituents of plant cell walls are digested by a ...

  3. Suitability of pharmacokinetic models for dynamic contrast-enhanced MRI of abdominal aortic aneurysm vessel wall: a comparison.

    Directory of Open Access Journals (Sweden)

    V Lai Nguyen

    Full Text Available PURPOSE: Increased microvascularization of the abdominal aortic aneurysm (AAA vessel wall has been related to AAA progression and rupture. The aim of this study was to compare the suitability of three pharmacokinetic models to describe AAA vessel wall enhancement using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI. MATERIALS AND METHODS: Patients with AAA underwent DCE-MRI at 1.5 Tesla. The volume transfer constant (K(trans , which reflects microvascular flow, permeability and surface area, was calculated by fitting the blood and aneurysm vessel wall gadolinium concentration curves. The relative fit errors, parameter uncertainties and parameter reproducibilities for the Patlak, Tofts and Extended Tofts model were compared to find the most suitable model. Scan-rescan reproducibility was assessed using the interclass correlation coefficient and coefficient of variation (CV. Further, the relationship between K(trans and AAA size was investigated. RESULTS: DCE-MRI examinations from thirty-nine patients (mean age±SD: 72±6 years; M/F: 35/4 with an mean AAA maximal diameter of 49±6 mm could be included for pharmacokinetic analysis. Relative fit uncertainties for K(trans based on the Patlak model (17% were significantly lower compared to the Tofts (37% and Extended Tofts model (42% (p<0.001. K(trans scan-rescan reproducibility for the Patlak model (ICC = 0.61 and CV = 22% was comparable with the Tofts (ICC = 0.61, CV = 23% and Extended Tofts model (ICC = 0.76, CV = 22%. K(trans was positively correlated with maximal AAA diameter (Spearman's ρ = 0.38, p = 0.02 using the Patlak model. CONCLUSION: Using the presented imaging protocol, the Patlak model is most suited to describe DCE-MRI data of the AAA vessel wall with good K(trans scan-rescan reproducibility.

  4. 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.

  5. Impact of post-dialysis calcium level on ex vivo rat aortic wall calcification.

    Science.gov (United States)

    Azpiazu, Daniel; González-Parra, Emilio; Ortiz, Alberto; Egido, Jesús; Villa-Bellosta, Ricardo

    2017-01-01

    Vascular calcification is a frequent complication in chronic haemodialysis patients and is associated with adverse outcomes. Serum calcium and phosphate levels and imbalances in calcification regulators are thought to contribute to the process. In this regard, the dialysate calcium concentration is a modifiable tool for modulating the risk of vascular calcification. We explored pre- and post-dialysis phosphate and calcium concentrations in stable chronic haemodialysis patients treated by dialysis with the KDIGO-suggested 1.5 mmol/L calcium dialysate to investigate the effects on ex vivo calcification of rat aortic rings. At the end of haemodialysis, mean serum calcium levels were increased in 88% of paired pre-/post-dialysis samples, while mean serum phosphate and parathyroid hormone levels were decreased. Rat aortic ring cultures grown at the same calcium and phosphate concentrations revealed that pre- and post-dialysis resulted in a similar degree of calcification. By contrast, haemodialysis with unchanged serum calcium resulted in a 5-fold reduction in calcium deposition. Dialysis with the widely prescribed 1.5 mmol/L calcium dose results in persistent high serum calcification potential in a sizable proportion of patients, driven by increased post-dialysis calcium concentration. This could potentially be mitigated by individualising dialysate calcium dosage based on pre-dialysis serum calcium levels.

  6. 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).

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

    Directory of Open Access Journals (Sweden)

    Ling Lee

    Full Text Available Marfan syndrome (MFS is an autosomal-dominant disorder of connective tissue caused by mutations in the fibrillin-1 (FBN1 gene. Mortality is often due to aortic dissection and rupture. We investigated the structural and functional properties of the heart and aorta in a [Fbn1C1039G/+] MFS mouse using high-resolution ultrasound (echo and optical coherence tomography (OCT. Echo was performed on 6- and 12-month old wild type (WT and MFS mice (n = 8. In vivo pulse wave velocity (PWV, aortic root diameter, ejection fraction, stroke volume, left ventricular (LV wall thickness, LV mass and mitral valve early and atrial velocities (E/A ratio were measured by high resolution echocardiography. OCT was performed on 12-month old WT and MFS fixed mouse hearts to measure ventricular volume and mass. The PWV was significantly increased in 6-mo MFS vs. WT (366.6 ± 19.9 vs. 205.2 ± 18.1 cm/s; p = 0.003 and 12-mo MFS vs. WT (459.5 ± 42.3 vs. 205.3 ± 30.3 cm/s; p< 0.0001. PWV increased with age in MFS mice only. We also found a significantly enlarged aortic root and decreased E/A ratio in MFS mice compared with WT for both age groups. The [Fbn1C1039G/+] mouse model of MFS replicates many of the anomalies of Marfan patients including significant aortic dilation, central aortic stiffness, LV systolic and diastolic dysfunction. This is the first demonstration of the direct measurement in vivo of pulse wave velocity non-invasively in the aortic arch of MFS mice, a robust measure of aortic stiffness and a critical clinical parameter for the assessment of pathology in the Marfan syndrome.

  8. Serum antibodies against Chlamydia pneumoniae outer membrane protein cross-react with the heavy chain of immunoglobulin in the wall of abdominal aortic aneurysms

    DEFF Research Database (Denmark)

    Lindholt, Jes Sanddal; Støvring, Jette; Østergaard, Lars

    2004-01-01

    Chlamydia pneumoniae (Cp) has been demonstrated in arteries and abdominal aortic aneurysms (AAAs). However, the validity of the methods used is questioned, and antibiotic treatment trials have thus far shown disappointing results. Nevertheless, antibodies against the Cp outer membrane proteins (O...... (OMPs) have been associated with progression of atherosclerosis and AAAs. The aim of this study was to detect Cp OMPs in the wall of AAA patients by use of purified serum antibodies directed against Cp OMP and to assess potential cross-reacting proteins in AAA walls.......Chlamydia pneumoniae (Cp) has been demonstrated in arteries and abdominal aortic aneurysms (AAAs). However, the validity of the methods used is questioned, and antibiotic treatment trials have thus far shown disappointing results. Nevertheless, antibodies against the Cp outer membrane proteins...

  9. combined spatially and temporally structured walls

    Directory of Open Access Journals (Sweden)

    D. N. Riahi

    1999-01-01

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

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

    Science.gov (United States)

    Graf, S.; Craiem, D.; Valero, M.; Alfonso, M.; Barra, J. G.; Armentano, R. L.

    2011-12-01

    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.

  11. The adventitia layer modulates the arterial wall elastic response to intra-aortic counterpulsation: in vivo studies.

    Science.gov (United States)

    Cabrera-Fischer, Edmundo I; Bia, Daniel; Zócalo, Yanina; Wray, Sandra; Armentano, Ricardo

    2013-12-01

    There is a relationship between the intra-aortic balloon pumping (IABP) benefits and the dynamic behavior of muscular arteries, which is associated with induced changes on the vessel walls through an endothelial-dependent mechanism. The arterial wall elastic behavior is influenced by adventitial function; however, no studies were performed in order to elucidate if this layer plays a role in the changes determined by IABP. Our aim was to quantify acute IABP effects on the mechanical properties of muscular arteries in induced acute heart failure (AHF), before and after adventitia removal. Pressure and diameter were recorded in the iliac arteries (IA) of sheep (n = 7), before and during 1:2 IABP: (i) in control state (CS) with intact IA, (ii) in CS after IA adventitia removal, and (iii) in de-adventitialized IA after AHF. Conduit function, compliance and arterial distensibility were calculated in each state. During CS, IABP resulted in intact IA dilatation and in an increase in conduit function, compliance and distensibility; adventitial removal determined an increase of arterial stiffness with respect to the CS, which decreased when IABP was used; the increase in arterial stiffness observed after adventitia removal was also detected in AHF state; IABP improves conduit function and arterial stiffness in de-adventitialized arteries, both before and during AHF. However, the improvement in these properties was lower than in intact arteries. Before and after AHF induction, the improvements of conduit function and arterial distensibility determined by IABP in intact IA were significantly reduced after adventitia removal. Adventitial layer integrity would be necessary to maximize IABP-related beneficial effects on arterial system properties. © 2013 Wiley Periodicals, Inc. and International Center for Artificial Organs and Transplantation.

  12. Smooth Muscle-Targeted Overexpression of Peroxisome Proliferator Activated Receptor-γ Disrupts Vascular Wall Structure and Function.

    Directory of Open Access Journals (Sweden)

    Jennifer M Kleinhenz

    Full Text Available Activation of the nuclear hormone receptor, PPARγ, with pharmacological agonists promotes a contractile vascular smooth muscle cell phenotype and reduces oxidative stress and cell proliferation, particularly under pathological conditions including vascular injury, restenosis, and atherosclerosis. However, pharmacological agonists activate both PPARγ-dependent and -independent mechanisms in multiple cell types confounding efforts to clarify the precise role of PPARγ in smooth muscle cell structure and function in vivo. We, therefore, designed and characterized a mouse model with smooth muscle cell-targeted PPARγ overexpression (smPPARγOE. Our results demonstrate that smPPARγOE attenuated contractile responses in aortic rings, increased aortic compliance, caused aortic dilatation, and reduced mean arterial pressure. Molecular characterization revealed that compared to littermate control mice, aortas from smPPARγOE mice expressed lower levels of contractile proteins and increased levels of adipocyte-specific transcripts. Morphological analysis demonstrated increased lipid deposition in the vascular media and in smooth muscle of extravascular tissues. In vitro adenoviral-mediated PPARγ overexpression in human aortic smooth muscle cells similarly increased adipocyte markers and lipid uptake. The findings demonstrate that smooth muscle PPARγ overexpression disrupts vascular wall structure and function, emphasizing that balanced PPARγ activity is essential for vascular smooth muscle homeostasis.

  13. Bichiral structure of ferroelectric domain walls driven by flexoelectricity

    Science.gov (United States)

    Yudin, P. V.; Tagantsev, A. K.; Eliseev, E. A.; Morozovska, A. N.; Setter, N.

    2012-10-01

    The influence of flexoelectric coupling on the internal structure of neutral domain walls in the tetragonal phase of perovskite ferroelectrics is studied. The effect is shown to lower the symmetry of 180∘ walls which are oblique with respect to the cubic crystallographic axes, while {100} and {110} walls stay “untouched.” Being of the Ising type in the absence of the flexoelectric interaction, the oblique domain walls acquire a new polarization component with a structure qualitatively different from the classical Bloch-wall structure. In contrast to the Bloch-type walls, where the polarization vector draws a helix on passing from one domain to the other, in the flexoeffect-affected wall, the polarization rotates in opposite directions on the two sides of the wall and passes through zero in its center. Since the resulting polarization profile is invariant upon inversion with respect to the wall center, it does not break the wall symmetry, in contrast to the classical Bloch-type walls. The flexoelectric coupling lowers the domain wall energy and gives rise to its additional anisotropy, which is comparable to that conditioned by elastic anisotropy. The atomic order-of-magnitude estimates shows that the new polarization component P2 may be comparable with spontaneous polarization Ps, thus suggesting that, in general, it is mandatory to include the flexoelectric coupling in domain wall simulations in ferroelectrics. Calculations performed for barium titanate yield the maximal value of P2, which is much smaller than that of the spontaneous polarization. This smallness is attributed to an anomalously small value of a component of the “strain-polarization” electrostrictive tensor in this material.

  14. 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.

  15. Dual-Mode Patch Filter with Metal Wall Structures

    Directory of Open Access Journals (Sweden)

    D. Kang

    2013-01-01

    Full Text Available A dual-mode patch filter with metal wall structures is presented. The proposed structure consists of substrate 1 with metal wall structures and substrate 2 with a patch resonator. Because the symmetry of the structure can be perturbed by both long and short strips of the metal wall structures, the dual mode is achieved. The inductive element is introduced to the patch resonator through vias of the metal wall structures. The capacitive element is introduced through a gap between the patch resonator and the metal strips. The measured 3 dB fractional bandwidth for the passband is 10.4%, and the measured minimum insertion loss is 1.3 dB.

  16. Seismic strengthening of RC structures with exterior shear walls

    Indian Academy of Sciences (India)

    performance of exterior RC shear walls (ESW) that are placed parallel to the building's sides. In reality, installing a shear wall to a structural system will surely ..... This study has been carried out with the financial support of State Planning Organization of Turkey with grant number BAP–08–11-DPT.2004K120760, with Middle ...

  17. Investigation of Stability Alarming for Retaining Wall Structures with Damage

    Directory of Open Access Journals (Sweden)

    Qian Xu

    2017-01-01

    Full Text Available To warn of the stability of retaining wall structures with damage, a simplified mechanical model and a finite element model of this retaining wall-soil coupling system are established. Via finite element model updating, a baseline finite element model of the wall-soil system is acquired. A damage alarming index ERSD (Energy Ratio Standard Deviation is proposed via the wavelet packet analysis of a virtual impulse response function of dynamic responses to this baseline finite element model. The internal relationships among the alarming index, earth pressure, and damage stability of the wall are analyzed. Then, a damage stability alarming method for the retaining walls is advanced. To verify the feasibility and validity of this alarming method, vibration tests on the baseline finite element model of a pile plate retaining wall are performed. The ERSD is used as an alarm for the damage stability of the wall. Analysis results show that, with an increase in the ERSD, the stability of the wall changes from a stable state to an unstable one. The wall reaches a critical stable state when the alarming index reaches its threshold value. Thus, the damage stability of this pile plate retaining wall can be alarmed via ERSD.

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

    Science.gov (United States)

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

    2017-05-01

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

  19. 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.

  20. Funnel-shaped vortical structures in wall turbulence

    International Nuclear Information System (INIS)

    Kaftori, D.; Hetsroni, G.; Banerjee, S.

    1994-01-01

    The structure of the turbulent boundary layer in a horizontal open channel was investigated experimentally by means of laser Doppler anemometry (LDA) and by flow visualization synchronized with the LDA. These experiments indicate that the dominant structures in the wall region are large scale streamwise vortices which originate at the wall and grow and expand into the outer flow region. The shape of the vortices is that of an expanding spiral, wound around a funnel which is laid sideways in the direction of flow. Most of the observations of wall turbulence phenomena made over the years, such as quasistreamwise vortices, ejections, and sweeps seem to be part of these funnel-shaped vortices

  1. Chronic inflammation, immune response, and infection in abdominal aortic aneurysms

    DEFF Research Database (Denmark)

    Lindholt, Jes Sanddal; Shi, G-P

    2006-01-01

    Abdominal aortic aneurysms (AAA) are associated with atherosclerosis, transmural degenerative processes, neovascularization, decrease in content of vascular smooth muscle cells, and a chronic infiltration, mainly located in the outer aortic wall. The chronic infiltration consists mainly of macrop......Abdominal aortic aneurysms (AAA) are associated with atherosclerosis, transmural degenerative processes, neovascularization, decrease in content of vascular smooth muscle cells, and a chronic infiltration, mainly located in the outer aortic wall. The chronic infiltration consists mainly...... matrix metalloproteases and cysteine proteases for aortic matrix remodeling. The lymphocyte activation may be mediated by microorganisms as well as autoantigens generated from vascular structural proteins, perhaps through molecular mimicry. As in autoimmune diseases, the risk of AAA is increased...

  2. Regional Mapping of Aortic Wall Stress by Using Deformable, Motion-coherent Modeling based on Electrocardiography-gated Multidetector CT Angiography: Feasibility Study.

    Science.gov (United States)

    Mileto, Achille; Heye, Tobias J; Makar, Ryan A; Hurwitz, Lynne M; Marin, Daniele; Boll, Daniel T

    2016-07-01

    Purpose To investigate the feasibility of deformable, motion-coherent modeling based on electrocardiography-gated multidetector computed tomographic (CT) angiography of the thoracic aorta and to evaluate whether quantifiable information on aortic wall stress as a function of patient-specific cardiovascular parameters can be gained. Materials and Methods For this institutional review board-approved, HIPAA-compliant study, thoracic electrocardiography-gated dual-source multidetector CT angiographic images were used from 250 prospectively enrolled patients (150 men, 100 women; mean age, 79 years). On reconstructed 50-phase CT angiographic images, aortic strain and deformation were determined at seven cardiac and aortic locations. One-way analysis of variance was used by assessing the magnitude for longitudinal and axial strain and axial deformation, as well as time-resolved peak and maxima count for longitudinal strain and axial deformation. Interdependencies between aortic strain and deformation with extracted hemodynamic parameters were evaluated. Results With increasing heart rates, there was a significant decrease in longitudinal strain (P = .009, R(2) = 0.95) and a decrease in the number of longitudinal strain peaks (P < .001, R(2) = 0.79); however, a significant increase in axial deformation (P < .001, R(2) = 0.31) and axial strain (P = .009, R(2) = 0.61) was observed. Increasing aortic blood velocity led to increased longitudinal strain (P = .018, R(2) = 0.42) and longitudinal strain peak counts (P = .011, R(2) = 0.48). Pronounced motion in the longitudinal direction limited motion in the axial plane (P < .019, R(2) = 0.29-0.31). Conclusion The results of this study render a clinical basis and provide proof of principle for the use of deformable, motion-coherent modeling to provide quantitative information on physiological motion of the aorta under various hemodynamic circumstances. (©) RSNA, 2016 Online supplemental material is available for this article.

  3. Nanodomain wall film structure and its magnetic characterization

    International Nuclear Information System (INIS)

    Hai Jiang

    2006-01-01

    In this letter, we report on a nanodomain wall thin-film structure and its fabrication. The core unit of this structure consists of a magnetic nanodot layer sandwiched between a magnetically free layer and a pinned layer. When the magnetizations of the free layer and the pinned layer are unparallel, a nanodomain wall is formed in the magnetic nanodot. Based on this concept, a nanodomain wall film structure with a Ni/Al 2 O 3 nanodot layer is prepared. Since the free and pinned layers are coupled through magnetic nanodots, a displacement of free layer M-H loop from zero field is observed. By measuring the displacement field of the free layer, the nanodomain wall energy is estimated

  4. Numerical investigation on effect of aortic root geometry on flow induced structural stresses developed in a bileaflet mechanical heart valve

    Science.gov (United States)

    Abbas, S. S.; Nasif, M. S.; Said, M. A. M.; Kadhim, S. K.

    2017-10-01

    Structural stresses developed in an artificial bileaflet mechanical heart valve (BMHV) due to pulsed blood flow may cause valve failure due to yielding. In this paper, von-Mises stresses are computed and compared for BMHV placed in two types of aortic root geometries that are aortic root with axisymmetric sinuses and with axisymmetric bulb, at different physiological blood flow rates. With BMHV placed in an aortic root with axisymmetric sinuses, the von-Mises stresses developed in the valve were found to be up to 47% higher than BMHV placed in aortic root with axisymmetric bulb under similar physiological conditions. High velocity vectors and therefore high von-Mises stresses have been observed for BMHV placed in aortic root with axisymmetric sinuses, that can lead to valve failure.

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

    CERN Document Server

    Kubiak, Tomasz

    2013-01-01

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

  6. Crystalline mesoporous zirconia catalysts having stable tetragonal pore wall structure

    Science.gov (United States)

    Sachtler, Wolfgang M. H.; Huang, Yin-Yan

    1998-01-01

    Methods for the preparation of new sulfated mesoporous zirconia materials/catalysts with crystalline pore walls of predominantly tetragonal crystal structure, characterized by nitrogen physisorption measurement, X-ray diffraction, transmission electron microscopy and catalytic tests using n-butane isomerization to iso-butane and alkylation of 1-naphthol with 4-tert-butylstyrene as probe reactions. Sulfate deposition is preferred for the transformation of a mesoporous precursor with amorphous pore walls into a material with crystalline pore walls maintaining the mesoporous characteristics.

  7. Form Follows Function: Advances in Trilayered Structure Replication for Aortic Heart Valve Tissue Engineering

    Science.gov (United States)

    Simionescu, Dan T.; Chen, Joseph; Jaeggli, Michael; Wang, Bo; Liao, Jun

    2013-01-01

    Tissue engineering the aortic heart valve is a challenging endeavor because of the particular hemodynamic and biologic conditions present in the native aortic heart valve. The backbone of an ideal valve substitute should be a scaffold that is strong enough to withstand billions of repetitive bending, flexing and stretching cycles, while also being slowly degradable to allow for remodeling. In this review we highlight three overlooked aspects that might influence the long term durability of tissue engineered valves: replication of the native valve trilayered histoarchitecture, duplication of the three-dimensional shape of the valve and cell integration efforts focused on getting the right number and type of cells to the right place within the valve structure and driving them towards homeostatic maintenance of the valve matrix. We propose that the trilayered structure in the native aortic valve that includes a middle spongiosa layer cushioning the motions of the two external fibrous layers should be our template for creation of novel scaffolds with improved mechanical durability. Furthermore, since cells adapt to micro-loads within the valve structure, we believe that interstitial cell remodeling of the valvular matrix will depend on the accurate replication of the structures and loads, resulting in successful regeneration of the valve tissue and extended durability. PMID:23355946

  8. Form Follows Function: Advances in Trilayered Structure Replication for Aortic Heart Valve Tissue Engineering

    Directory of Open Access Journals (Sweden)

    Dan T. Simionescu

    2012-01-01

    Full Text Available Tissue engineering the aortic heart valve is a challenging endeavor because of the particular hemodynamic and biologic conditions present in the native aortic heart valve. The backbone of an ideal valve substitute should be a scaffold that is strong enough to withstand billions of repetitive bending, flexing and stretching cycles, while also being slowly degradable to allow for remodeling. In this review, we highlight three overlooked aspects that might influence the long term durability of tissue engineered valves: (i replication of the native valve trilayered histoarchitecture, (ii duplication of the three-dimensional shape of the valve, (iii and cell integration efforts focused on getting the right number and type of cells to the right place within the valve structure and driving them towards homeostatic maintenance of the valve matrix. We propose that the trilayered structure in the native aortic valve that includes a middle spongiosa layer cushioning the motions of the two external fibrous layers should be our template for creation of novel scaffolds with improved mechanical durability. Furthermore, since cells adapt to micro-loads within the valve structure, we believe that interstitial cell remodeling of the valvular matrix will depend on the accurate replication of the structures and loads, resulting in successful regeneration of the valve tissue and extended durability.

  9. Structural analysis of cell wall polysaccharides using PACE

    Energy Technology Data Exchange (ETDEWEB)

    Mortimer, Jennifer C. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Joint BioEnergy Institute

    2017-01-01

    The plant cell wall is composed of many complex polysaccharides. The composition and structure of the polysaccharides affect various cell properties including cell shape, cell function and cell adhesion. Many techniques to characterize polysaccharide structure are complicated, requiring expensive equipment and specialized operators e.g. NMR, MALDI-MS. PACE (Polysaccharide Analysis using Carbohydrate gel Electrophoresis) uses a simple, rapid technique to analyze polysaccharide quantity and structure (Goubet et al. 2002). Whilst the method here describes xylan analysis, it can be applied (by use of the appropriate glycosyl hydrolase) to any cell wall polysaccharide.

  10. Factors influencing left ventricular structure and stress-corrected systolic function in men and women with asymptomatic aortic valve stenosis (a SEAS Substudy)

    DEFF Research Database (Denmark)

    Cramariuc, D.; Rieck, A.E.; Staal, E.M.

    2008-01-01

    also was a predictor of LV hypertrophy (p body mass index, heart rate, aortic valve area, LV...... mass, relative wall thickness, aortic regurgitation, hypertension, and end-systolic stress (R(2) = 0.23 and 0.59, respectively, p ... higher stress-corrected indexes of systolic function independent of LV geometry or size, wall stress, older age, or more concomitant hypertension Udgivelsesdato: 2008/2/15...

  11. The Infant with Aortic Arch Hypoplasia and Small Left Heart Structures: Echocardiographic Indices of Mitral and Aortic Hypoplasia Predicting Successful Biventricular Repair.

    Science.gov (United States)

    Plymale, Jennifer M; Frommelt, Peter C; Nugent, Melodee; Simpson, Pippa; Tweddell, James S; Shillingford, Amanda J

    2017-08-01

    In infants with aortic arch hypoplasia and small left-sided cardiac structures, successful biventricular repair is dependent on the adequacy of the left-sided structures. Defining accurate thresholds of echocardiographic indices predictive of successful biventricular repair is paramount to achieving optimal outcomes. We sought to identify pre-operative echocardiographic indices of left heart size that predict intervention-free survival in infants with small left heart structures undergoing primary aortic arch repair to establish biventricular circulation (BVC). Infants ≤2 months undergoing aortic arch repair from 1999 to 2010 with aortic and/or mitral valve hypoplasia, (Z-score ≤-2) were included. Pre-operative and follow-up echocardiograms were reviewed. Primary outcome was successful biventricular circulation (BVC), defined as freedom from death, transplant, or single ventricular conversion at 1 year. Need for catheter based or surgical re-intervention (RI), valve annular growth, and significant late aortic or mitral valve obstruction were additional outcomes. Fifty one of 73 subjects (79%) had successful BVC and were free of RI at 1 year. Seven subjects failed BVC; four of those died. The overall 1 year survival for the cohort was 95%. Fifteen subjects underwent a RI but maintained BVC. In univariate analysis, larger transverse aorta (p = 0.006) and aortic valve (p = 0.02) predicted successful BVC without RI. In CART analysis, the combination of mitral valve (MV) to tricuspid valve (TV) ratio ≤0.66 with an aortic valve (AV) annulus Z-score ≤-3 had the greatest power to predict BVC failure (sensitivity 71%, specificity 94%). In those with successful BVC, the combination of both AV and MV Z-score ≤-2.5 increased the odds of RI (OR 3.8; CI 1.3-11.4). Follow-up of non-RI subjects revealed improvement in AV and MV Z-score (median AV annulus changed over time from -2.34 to 0.04 (p indices. In this complex population, 1 year survival is high, but

  12. Partition wall structure in spent fuel storage pool and construction method for the partition wall

    International Nuclear Information System (INIS)

    Izawa, Masaaki

    1998-01-01

    A partitioning wall for forming cask pits as radiation shielding regions by partitioning inside of a spent fuel storage pool is prepared by covering both surface of a concrete body by shielding metal plates. The metal plate comprises opposed plate units integrated by welding while sandwiching a metal frame as a reinforcing material for the concrete body, the lower end of the units is connected to a floor of a pool by fastening members, and concrete is set while using the metal plate of the units as a frame to form the concrete body. The shielding metal plate has a double walled structure formed by welding a lining plate disposed on the outer surface of the partition wall and a shield plate disposed to the inner side. Then the term for construction can be shortened, and the capacity for storing spent fuels can be increased. (N.H.)

  13. Soft impact testing of a wall-floor-wall reinforced concrete structure

    Energy Technology Data Exchange (ETDEWEB)

    Vepsä, Ari, E-mail: ari.vepsa@vtt.fi; Calonius, Kim; Saarenheimo, Arja; Aatola, Seppo; Halonen, Matti

    2017-01-15

    Highlights: • A wall-floor-wall reinforced concrete structure was built. • The structure was subjected to three almost identical soft impact tests. • Response was measured with accelerometers, displacement sensors and strain gauges. • Modal tests was also carried out with the same structure in different conditions. • The results are meant to be used for validation of computational methods and models. - Abstract: Assessing the safety of the reactor building of a nuclear power plant against the crash of an airplane calls for valid computational tools such as finite element models and material constitutive models. Validation of such tools and models in turn calls for reliable and relevant experimental data. The problem is that such data is scarcely available. One of the aspects of such a crash is vibrations that are generated by the impact. These vibrations tend to propagate from the impact point to the internal parts of the building. If strong enough, these vibrations may cause malfunction of the safety-critical equipment inside the building. To enable validation of computational models for this type of behaviour, we have conducted a series of three tests with a wall-floor-wall reinforced concrete structure under soft impact loading. The response of the structure was measured with accelerometers, displacement sensors and strain gauges. In addition to impact tests, the structure was subjected to modal tests under different conditions. The tests yielded a wealth of useful data for validation of computational models and better understanding about shock induced vibration physics especially in reinforced concrete structures.

  14. Structural pounding of concrete frame structure with masonry infill wall under seismic loading

    Science.gov (United States)

    Ismail, Rozaina; Hasnan, Mohd Hafizudin; Shamsudin, Nurhanis

    2017-10-01

    Structural pounding is additional problem than the other harmful damage that may occurs due to the earthquake vibrations. A lot of study has been made by past researcher but most of them did not include the walls. The infill masonry walls are rarely involved analysis of structural systems but it does contribute to earthquake response of the structures. In this research, a comparison between adjacent building of 10-storey and 7-storey concrete frame structure without of masonry infill walls and the same dynamic properties of buildings. The diagonal strut approach is adopted for modeling masonry infill walls. This research also focused on finding critical building separation in order to prevent the adjacent structures from pounding. LUSAS FEA v14.03 software has been used for modeling analyzing the behavior of structures due to seismic loading and the displacement each floor of the building has been taken in order to determine the critical separation distance between the buildings. From the analysis that has been done, it is found that masonry infill walls do affect the structures behavior under seismic load. Structures without masonry infill walls needs more distance between the structures to prevent structural pounding due to higher displacement of the buildings when it sways under seismic load compared to structures with masonry infill walls. This shows that contribution of masonry infill walls to the analysis of structures cannot be neglected.

  15. Durability of thin-walled concrete structures

    International Nuclear Information System (INIS)

    Salomon, M.; Gallias, J.L.

    1991-01-01

    The aim of the present document is to draw up a survey of knowledge of the problems of ageing of reinforced concrete shell structure atmospheric coolers. The exposure conditions are particularly favourable to the induction and development of degradation which, because of the thinness of the reinforced concrete can compromise the stability and the durability of coolers. The study will be axed on the link between the specific characteristics of coolers from the point of view of operation, design and environment, also the durability of reinforced concrete. The set of factors exerting their influence on the reinforced concrete of the shell structure (condensates, rain water, temperature and humidity gradients, dynamic loads, weathering, etc.) is particularly complex. The principal degradation reactions involved are classified according to the chemical and physical action on concrete and on the reinforcement. Particular emphasis is placed on the analysis of degradation processes and the influence of the characteristics of the materials and of the medium. The aim is to determine the mechanisms which present the greatest risk for coolers. The interaction between the degradation to concrete and the change in mechanical characteristics is also studied [fr

  16. Unified first wall - blanket structure for plasma device applications

    Science.gov (United States)

    Gruen, D.M.

    A plasma device is described for use in controlling nuclear reactions within the plasma including a first wall and blanket formed in a one-piece structure composed of a solid solution containing copper and lithium and melting above about 500/sup 0/C.

  17. Structure of cellulose microfibrils in primary cell walls from Collenchyma

    Czech Academy of Sciences Publication Activity Database

    Thomas, L. H.; Forsyth, V. T.; Šturcová, Adriana; Kennedy, C. J.; May, R. P.; Altaner, C. M.; Apperley, D. C.; Wess, T. J.; Jarvis, M. C.

    2013-01-01

    Roč. 161, č. 1 (2013), s. 465-476 ISSN 0032-0889 R&D Projects: GA ČR GAP108/12/0703 Institutional support: RVO:61389013 Keywords : primary cell wall * cellulose microfibril structure * chain packing disorder Subject RIV: CD - Macromolecular Chemistry Impact factor: 7.394, year: 2013

  18. Anatomical changes in the cell-wall structure of Leucaena ...

    African Journals Online (AJOL)

    The structural changes in the cell wall and delignification pattern caused by Trametes versicolor and Trametes hirsuta in the sap wood of Leucaena leucocephala were examined by light and confocal laser scanning microscopy. The in vitro decay test was conducted for 12 weeks. Both species of Trametes used in this study ...

  19. Organised structures in wall turbulence as deduced from stability ...

    Indian Academy of Sciences (India)

    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 ...

  20. Structural Alterations of the Glomerular Wall And Vessels in Early ...

    African Journals Online (AJOL)

    Structural Alterations of the Glomerular Wall And Vessels in Early Stages of Diabetes Mellitus: Light and Transmission Electron Microscopic Study. ... The second group of 20 (the experimental group) was injected intraperitoneally by a single dose of streptozotocin to induce hyperglycemia. Rats were sacrificed after ten days, ...

  1. 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

  2. The stability of gabion walls for earth retaining structures

    Directory of Open Access Journals (Sweden)

    Mahyuddin Ramli

    2013-12-01

    Full Text Available The stability of earth retaining structures in flood prone areas has become a serious problem in many countries. The two most basic causes of failure arising from flooding are scouring and erosion of the foundation of the superstructure. Hence, a number of structures like bridges employ scour-arresting devices, e.g., gabions to acting on the piers and abutments during flooding. Research was therefore undertaken to improve gabion resistance against lateral movement by means of an interlocking configuration instead of the conventional stack-and-pair system. This involved simulating lateral thrusts against two dimensionally identical retaining wall systems configured according to the rectangular and hexagonal gabion type. The evolution of deformation observed suggested that the interlocking design exhibits better structural integrity than the conventional box gabion-based wall in resisting lateral movement and therefore warrants consideration for use as an appropriate scour-arresting device for earth retaining structures.

  3. Energy absorption capabilities of complex thin walled structures

    Science.gov (United States)

    Tarlochan, F.; AlKhatib, Sami

    2017-10-01

    Thin walled structures have been used in the area of energy absorption during an event of a crash. A lot of work has been done on tubular structures. Due to limitation of manufacturing process, complex geometries were dismissed as potential solutions. With the advancement in metal additive manufacturing, complex geometries can be realized. As a motivation, the objective of this study is to investigate computationally the crash performance of complex tubular structures. Five designs were considered. In was found that complex geometries have better crashworthiness performance than standard tubular structures used currently.

  4. Body wall structure in the starfish Asterias rubens.

    Science.gov (United States)

    Blowes, Liisa M; Egertová, Michaela; Liu, Yankai; Davis, Graham R; Terrill, Nick J; Gupta, Himadri S; Elphick, Maurice R

    2017-09-01

    The body wall of starfish is composed of magnesium calcite ossicles connected by collagenous tissue and muscles and it exhibits remarkable variability in stiffness, which is attributed to the mechanical mutability of the collagenous component. Using the common European starfish Asterias rubens as an experimental animal, here we have employed a variety of techniques to gain new insights into the structure of the starfish body wall. The structure and organisation of muscular and collagenous components of the body wall were analysed using trichrome staining. The muscle system comprises interossicular muscles as well as muscle strands that connect ossicles with the circular muscle layer of the coelomic lining. The collagenous tissue surrounding the ossicle network contains collagen fibres that form loop-shaped straps that wrap around calcite struts near to the surface of ossicles. The 3D architecture of the calcareous endoskeleton was visualised for the first time using X-ray microtomography, revealing the shapes and interactions of different ossicle types. Furthermore, analysis of the anatomical organisation of the ossicles indicates how changes in body shape may be achieved by local contraction/relaxation of interossicular muscles. Scanning synchrotron small-angle X-ray diffraction (SAXD) scans of the starfish aboral body wall and ambulacrum were used to study the collagenous tissue component at the fibrillar level. Collagen fibrils in aboral body wall were found to exhibit variable degrees of alignment, with high levels of alignment probably corresponding to regions where collagenous tissue is under tension. Collagen fibrils in the ambulacrum had a uniformly low degree of orientation, attributed to macrocrimp of the fibrils and the presence of slanted as well as horizontal fibrils connecting antimeric ambulacral ossicles. Body wall collagen fibril D-period lengths were similar to previously reported mammalian D-periods, but were significantly different between the

  5. Influence of Coherent Structures on the Wall Shear Stress in Axial Flow Between a Cylinder and a Plane Wall

    International Nuclear Information System (INIS)

    Khabbouchi, Imed; Guellouz, Mohamed Sadok; Tavoularis, Stavros

    2009-01-01

    Synchronised hot-film and hot-wire measurements were made in the narrower region of a rectangular channel containing a cylindrical rod. The hot-film probe was mounted flush with the channel bottom wall to measure the wall shear stress, while the hot-wire probe was placed at a fixed position, selected in order to easily detect the passage of coherent structures. Mean and rms profiles of the wall shear stress show the influence of the gap to diameter ratio on their respective distributions. The latter presented peculiarities that could only be explained by the presence of coherent structures in the flow between the rod and the wall. Evidence of this presence is seen in the velocity power spectra. The strong influence of the coherent structures on the wall shear stress spatial and temporal distributions is established through velocity-wall shear stress cross-correlations functions and through conditionally sampled measurements

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

    International Nuclear Information System (INIS)

    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

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

    Indian Academy of Sciences (India)

    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 ...

  8. Immediate Outcomes of Covered Stent Placement for Treatment or Prevention of Aortic Wall Injury Associated With Coarctation of the Aorta (COAST II).

    Science.gov (United States)

    Taggart, Nathaniel W; Minahan, Matthew; Cabalka, Allison K; Cetta, Frank; Usmani, Kudret; Ringel, Richard E

    2016-03-14

    This study aimed to describe the safety and short-term efficacy of the Covered Cheatham-Platinum stent (CCPS) in treating or preventing aortic wall injury (AWI) in patients with coarctation of the aorta (CoA). The COAST II trial (Covered Cheatham-Platinum Stents for Prevention or Treatment of Aortic Wall Injury Associated with Coarctation of the Aorta Trial) is a multicenter, single-arm trial using the CCPS for the treatment and/or prevention of AWI in patients with CoA and pre-existing AWI or increased risk of AWI. Patients were enrolled if they had a history of CoA with pre-existing AWI (Treatment group) or with increased risk of AWI (Prevention group). Pre/post-implant hemodynamics and angiography were reported. A core laboratory performed standardized review of all angiograms. One-month follow-up was reported. A total of 158 patients (male = 65%; median age 19 years) underwent placement of CCPS. Eighty-three patients had pre-existing AWI. The average ascending-to-descending aorta systolic gradient improved from 27 ± 20 mm Hg to 4 ± 6 mm Hg. Complete coverage of pre-existing AWI was achieved in 66 of 71 patients (93%) with AWI who received a single CCPS. Ultimately, complete coverage of AWI was achieved in 76 of 83 patients (92%); 7 patients had minor endoleaks that did not require repeat intervention. Four patients experienced important access site vascular injury. There were no acute AWI, repeat interventions, or deaths. The CCPS can effectively treat and potentially prevent AWI associated with CoA. Access site arterial injury is the most common important complication. Longer-term follow-up is necessary to define mid- and late-term outcomes. Copyright © 2016 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  9. 4D Flow Analysis of BAV-Related Fluid-Dynamic Alterations: Evidences of Wall Shear Stress Alterations in Absence of Clinically-Relevant Aortic Anatomical Remodeling

    Directory of Open Access Journals (Sweden)

    Filippo Piatti

    2017-06-01

    Full Text Available Bicuspid aortic valve (BAV is the most common congenital cardiac disease and is a foremost risk factor for aortopathies. Despite the genetic basis of BAV and of the associated aortopathies, BAV-related alterations in aortic fluid-dynamics, and particularly in wall shear stresses (WSSs, likely play a role in the progression of aortopathy, and may contribute to its pathogenesis. To test whether WSS may trigger aortopathy, in this study we used 4D Flow sequences of phase-contrast cardiac magnetic resonance imaging (CMR to quantitatively compare the in vivo fluid dynamics in the thoracic aorta of two groups of subjects: (i five prospectively enrolled young patients with normo-functional BAV and with no aortic dilation and (ii ten age-matched healthy volunteers. Through the semi-automated processing of 4D Flow data, the aortic bulk flow at peak systole was quantified, and WSSs acting on the endothelium of the ascending aorta were characterized throughout the systolic phase in terms of magnitude and time-dependency through a method recently developed by our group. Variables computed for each BAV patient were compared vs. the corresponding distribution of values obtained for healthy controls. In BAV patients, ascending aorta diameter was measured on cine-CMR images at baseline and at 3-year follow-up. As compared to controls, normo-functional BAV patients were characterized by minor bulk flow disturbances at peak systole. However, they were characterized by evident alterations of WSS distribution and peak values in the ascending aorta. In particular, in four BAV patients, who were characterized by right-left leaflet fusion, WSS peak values exceeded by 27–46% the 90th percentile of the distribution obtained for healthy volunteers. Only in the BAV patient with right-non-coronary leaflet fusion the same threshold was exceeded by 132%. Also, evident alterations in the time-dependency of WSS magnitude and direction were observed. Despite, these fluid

  10. Structure of wall-bounded flows at transcritical conditions

    Science.gov (United States)

    Ma, Peter C.; Yang, Xiang I. A.; Ihme, Matthias

    2018-03-01

    At transcritical conditions, the transition of a fluid from a liquidlike state to a gaslike state occurs continuously, which is associated with significant changes in fluid properties. Therefore, boiling in its conventional sense does not exist and the phase transition at transcritical conditions is known as "pseudoboiling." In this work, direct numerical simulations (DNS) of a channel flow at transcritical conditions are conducted in which the bottom and top walls are kept at temperatures below and above the pseudoboiling temperature, respectively. Over this temperature range, the density changes by a factor of 18 between both walls. Using the DNS data, the usefulness of the semilocal scaling and the Townsend attached-eddy hypothesis are examined in the context of flows at transcritical conditions—both models have received much empirical support from previous studies. It is found that while the semilocal scaling works reasonably well near the bottom cooled wall, where the fluid density changes only moderately, the same scaling has only limited success near the top wall. In addition, it is shown that the streamwise velocity structure function follows a logarithmic scaling and the streamwise energy spectrum exhibits an inverse wave-number scaling, thus providing support to the attached-eddy model at transcritical conditions.

  11. Structural constraints and dynamics of bacterial cell wall architecture

    Directory of Open Access Journals (Sweden)

    Miguel Angel De Pedro

    2015-05-01

    Full Text Available The peptidoglycan wall (PG is a unique structure which confers physical strength and defined shape to bacteria. It consists of a net-like macromolecule of peptide interlinked glycan chains overlying the cell membrane. The structure and layout of the PG dictates that the wall has to be continuously modified as bacteria go through division, morphological differentiation and adaptive responses. The PG is poorly known in structural terms. However, to understand morphogenesis a precise knowledge of glycan strand arrangement and of local effects of the different kinds of subunits is essential. The scarcity of data led to a conception of the PG as a regular, highly ordered structure which strongly influenced growth models. Here, we review the structure of the PG to define a more realistic conceptual framework. We discuss the consequences of the plasticity of murein architecture in morphogenesis and try to define a set of minimal structural constraints that must be fulfilled by any model to be compatible with present day information.

  12. SSI response of a typical shear wall structure

    International Nuclear Information System (INIS)

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

    1985-01-01

    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)

  13. Segmentation of the Aortic Valve Apparatus in 3D Echocardiographic Images: Deformable Modeling of a Branching Medial Structure.

    Science.gov (United States)

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

    2015-01-01

    3D echocardiographic (3DE) imaging is a useful tool for assessing the complex geometry of the aortic valve apparatus. Segmentation of this structure in 3DE images is a challenging task that benefits from shape-guided deformable modeling methods, which enable inter-subject statistical shape comparison. Prior work demonstrates the efficacy of using continuous medial representation (cm-rep) as a shape descriptor for valve leaflets. However, its application to the entire aortic valve apparatus is limited since the structure has a branching medial geometry that cannot be explicitly parameterized in the original cm-rep framework. In this work, we show that the aortic valve apparatus can be accurately segmented using a new branching medial modeling paradigm. The segmentation method achieves a mean boundary displacement of 0.6 ± 0.1 mm (approximately one voxel) relative to manual segmentation on 11 3DE images of normal open aortic valves. This study demonstrates a promising approach for quantitative 3DE analysis of aortic valve morphology.

  14. 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...... number of degrees of freedom. This means that the classical Vlasov thin-walled beam theory for open and closed cross sections is generalized as part of a semi-discretization process by including distortional displacement fields. A novel finite-element-based displacement approach is used in combination...... 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...

  15. 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.

  16. 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.

  17. Aortic dissection

    Science.gov (United States)

    ... made in the chest or abdomen. Endovascular aortic repair. This surgery is done without any major surgical ... needed. If the heart arteries are involved, a coronary bypass is also performed. Outlook ... aneurysm - dissecting; Chest pain - aortic dissection; Thoracic aortic aneurysm - ...

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

    Indian Academy of Sciences (India)

    Keywords. Coupled shear walls; degree of coupling; peak shear demand; concrete. ... 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.

  19. 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...

  20. 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.

  1. 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

    2016-09-02

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

  2. Lagrangian coherent structures and turbulence characteristics downstream of prosthetic aortic valves

    Science.gov (United States)

    de Tullio, Marco D.

    2015-11-01

    The flowfield through prosthetic heart valves is investigated by means of direct numerical simulations, considering the fully coupled fluid-structure interaction problem. Two different aortic valve models are modeled: a bileaflet mechanical and a biological one. In order to reveal fluid flow structures and to better understand the transport mechanics, Lagrangian coherent structures (LCS) are used. LCS are distinguished material surfaces that can be identified as boundaries to regions with dynamically distinct behavior, and are revealed as hypersurfaces that locally maximize the finite-time Lyapunov exponent (FTLE) fields. Post-processing the flow simulation data, first FTLE fields are calculated integrating dense meshes of Lagrangian particles backward in time, and then attracting LCS are extracted. A three-jet configuration is distinctive of bi-leaflet mechanical valves, with higher turbulent shear stresses immediately distal to the valve leaflets, while a jet-like flow emerges from the central orifice of bio-prosthetic valves, with high turbulent shear stresses occurring at the edge of the jet. Details of the numerical methodology along with a thorough analysis of the different flow structures developing during the cardiac cycle for the two configurations will be provided.

  3. Molecular structure of human aortic valve by μSR- FTIR microscopy

    Science.gov (United States)

    Borkowska, Anna M.; Nowakowski, Michał; Lis, Grzegorz J.; Wehbe, Katia; Cinque, Gianfelice; Kwiatek, Wojciech M.

    2017-11-01

    Aortic valve is a part of the heart most frequently affected by pathological processes in humans what constitute a very serious health problem. Therefore, studies of morphology and molecular microstructure of the AV are needed. μSR- FTIR spectroscopy and microscopy represent unique tools to study chemical composition of the tissue and to identify spectroscopic markers characteristic for structural and functional features. Normal AV reveals a multi-layered structure and the compositional and structural changes within particular layers may trigger degenerative processes within the valve. Thus, deep insight into the structure of the valve to understand pathological processes occurring in AV is needed. In order to identify differences between three layers of human AV, tissue sections of macroscopically normal AV were studied using μSR- FTIR spectroscopy in combination with histological and histochemical stainings. Tissue sections deposited onto CaF2 substrates were mapped and representative set of IR spectra collected from fibrosa, spongiosa and ventricularis were analysed by Principal Component Analysis (PCA) in the spectral range between 1850-1000 cm-1 and 3050-2750 cm-1. PCA revealed a layered molecular structure of the valve and it was possible to identify IR bands associated to different tissue parts. Spongiosa layer was well differentiated from other two layers mainly based on IR bands characteristic for the distribution of glycosaminoglycans (GAGs) in the tissue - like 1170 cm-1 (υas(C-O-S)) and 1380 cm-1 (acetyl amino group). Additionally, it was distinguished from fibrosa and ventricularis based on 1085 cm-1 and 1240 cm-1 bands characteristic for GAGs and for carbohydrates- ν(C-O) and ν(C-O-C) respectively and nucleic acids -νsym(PO2-) and νasym(PO2-) respectively, which were less specific for this layer. The use of μSR- FTIR spectroscopy demonstrated co-localization of GAGs and lipids in spongiosa layer what may indicate their contribution in the very

  4. An enzymatic approach to cell wall structure | Hungate | South ...

    African Journals Online (AJOL)

    Ruminococcus albus was incubated with isolated alfalfa cell wall material for 72 h in batch culture. Cellulose in the cell walls was digested to a somewhat greater extent (88%) than were the fermentable sugars of the hemicellulose fraction (62- 76%). The digestibility of the total insoluble alfalfa cell wall, including lignin but ...

  5. Mild aerobic exercise blocks elastin fiber fragmentation and aortic dilatation in a mouse model of Marfan syndrome associated aortic aneurysm.

    Science.gov (United States)

    Gibson, Christine; Nielsen, Cory; Alex, Ramona; Cooper, Kimbal; Farney, Michael; Gaufin, Douglas; Cui, Jason Z; van Breemen, Cornelis; Broderick, Tom L; Vallejo-Elias, Johana; Esfandiarei, Mitra

    2017-07-01

    Regular low-impact physical activity is generally allowed in patients with Marfan syndrome, a connective tissue disorder caused by heterozygous mutations in the fibrillin-1 gene. However, being above average in height encourages young adults with this syndrome to engage in high-intensity contact sports, which unfortunately increases the risk for aortic aneurysm and rupture, the leading cause of death in Marfan syndrome. In this study, we investigated the effects of voluntary (cage-wheel) or forced (treadmill) aerobic exercise at different intensities on aortic function and structure in a mouse model of Marfan syndrome. Four-week-old Marfan and wild-type mice were subjected to voluntary and forced exercise regimens or sedentary lifestyle for 5 mo. Thoracic aortic tissue was isolated and subjected to structural and functional studies. Our data showed that exercise improved aortic wall structure and function in Marfan mice and that the beneficial effect was biphasic, with an optimum at low intensity exercise (55-65% V̇o 2max ) and tapering off at a higher intensity of exercise (85% V̇o 2max ). The mechanism underlying the reduced elastin fragmentation in Marfan mice involved reduction of the expression of matrix metalloproteinases 2 and 9 within the aortic wall. These findings present the first evidence of potential beneficial effects of mild exercise on the structural integrity of the aortic wall in Marfan syndrome associated aneurysm. Our finding that moderate, but not strenuous, exercise protects aortic structure and function in a mouse model of Marfan syndrome could have important implications for the medical care of young Marfan patients. NEW & NOTEWORTHY The present study provides conclusive scientific evidence that daily exercise can improve aortic health in a mouse model of Marfan syndrome associated aortic aneurysm, and it establishes the threshold for the exercise intensity beyond which exercise may not be as protective. These findings establish a platform

  6. Wall-attached structures of streamwise velocity fluctuations in turbulent boundary layer

    Science.gov (United States)

    Hwang, Jinyul; Sung, Hyung Jin

    2017-11-01

    The wall-attached structures of streamwise velocity fluctuations (u) are explored using direct numerical simulation data of turbulent boundary layer at Reτ = 1000 . We identify the structures of u, which are extended close to the wall. Their height (ly) ranges from the near-wall region to the edge of turbulent boundary layer. They are geometrically self-similar in a sense that the length and width of the structures are proportional to the distance from the wall. The population density of the attached structures shows that the tall attached structures (290 wall. The wall-attached structures of u identified in the present work are a proper candidate for Townsend's attached eddy hypothesis and these structures exist in the low Reynolds number turbulent boundary layer. This work was supported by the Creative Research Initiatives (No. 2017-013369) program of the National Research Foundation of Korea (MSIP) and supported by the Supercomputing Center (KISTI).

  7. Risk factors for incisional hernia repair after aortic reconstructive surgery in a nationwide study

    DEFF Research Database (Denmark)

    Henriksen, Nadia A; Helgstrand, Frederik; Vogt, Katja C

    2013-01-01

    Abdominal aortic aneurysm disease has been hypothesized as associated with the development of abdominal wall hernia. We evaluated the risk factors for incisional hernia repair after open elective aortic reconstructive surgery for aortoiliac occlusive disease and abdominal aortic aneurysm....

  8. Coherent structure generation in near-wall turbulence

    Science.gov (United States)

    Schoppa, W.; Hussain, F.

    2002-02-01

    We present a new mechanism for generation of near-wall streamwise vortices which dominate turbulence phenomena in boundary layers using linear perturbation analysis and direct numerical simulations of turbulent channel flow. The base flow, consisting of the mean velocity profile and low-speed streaks (free from any initial vortices), is shown to be linearly unstable to sinuous normal modes only for relatively strong streaks, i.e. for wall inclination angles of streak vortex lines exceeding 50°. Analysis of streaks extracted from fully developed near-wall turbulence indicates that about 20% of streak regions in the buffer layer exceed the strength threshold for instability. More importantly, these unstable streaks exhibit only moderate (twofold) normal-mode amplification, the growth being arrested by self-annihilation of streak-flank normal vorticity due to viscous cross-diffusion. We present here an alternative, streak transient growth (STG) mechanism, capable of producing much larger (tenfold) linear ampliflcation of x-dependent disturbances. Note the distinction of STG responsible for perturbation growth on a streak velocity distribution U(y, z) from prior transient growth analyses of the (streakless) mean velocity U(y). We reveal that streamwise vortices are generated from the more numerous normal-mode-stable streaks, via a new STG-based scenario: (i) transient growth of perturbations leading to formation of a sheet of streamwise vorticity [omega]x (by a ‘shearing’ mechanism of vorticity generation), (ii) growth of sinuous streak waviness and hence [partial partial differential]u/[partial partial differential]x as STG reaches nonlinear amplitude, and (iii) the [omega]x sheet’s collapse via stretching by [partial partial differential]u/[partial partial differential]x (rather than rollup) into streamwise vortices. Significantly, the three-dimensional features of the (instantaneous) streamwise vortices of x-alternating sign generated by STG agree well with

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

    Directory of Open Access Journals (Sweden)

    Sebastian Zoll

    2010-03-01

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

  10. Individual domain wall resistance in submicron ferromagnetic structures.

    Science.gov (United States)

    Danneau, R; Warin, P; Attané, J P; Petej, I; Beigné, C; Fermon, C; Klein, O; Marty, A; Ott, F; Samson, Y; Viret, M

    2002-04-15

    The resistance generated by individual domain walls is measured in a FePd nanostructure. Combining transport and magnetic imaging measurements, the intrinsic domain wall resistance is quantified. It is found positive and of a magnitude consistent with that predicted by models based on spin scattering effects within the walls. This magnetoresistance at a nanometer scale allows a direct counting of the number of walls inside the nanostructure. The effect is then used to measure changes in the magnetic configuration of submicron stripes under application of a magnetic field.

  11. Structural modifications in the arterial wall during physiological aging and as a result of diabetes mellitus in a mouse model: are the changes comparable?

    Science.gov (United States)

    Prévost, G; Bulckaen, H; Gaxatte, C; Boulanger, E; Béraud, G; Creusy, C; Puisieux, F; Fontaine, P

    2011-04-01

    Vascular accelerated aging represents the major cause of morbidity and mortality in subjects with diabetes mellitus. In the present study, our aim was to compare premature functional and morphological changes in the arterial wall resulting from streptozotocin (STZ)-induced diabetes mellitus in mice over a short-term period with those that develop during physiological aging. The effect of aminoguanidine (AG) on the prevention of these alterations in the diabetic group was also analyzed. The vascular relaxation response to acetylcholine (ACh) in the mouse was tested in isolated segments of phenylephrine (Phe)-precontracted aorta at 2, 4 and 8 weeks (wk) of STZ-induced diabetes and compare to 12- and 84-wk-old mice. Aortic structural changes were investigated, and receptor for AGE (RAGE) aortic expression was quantified by western blot. Compared to the 12-wk control group (76 ± 5%), significant endothelium-dependant relaxation (EDR) impairment was found in the group of 12-wk-old mice, which underwent a 4-wk diabetes-inducing STZ treatment (12wk-4WD) (52 ± 4%; P aging preventive effect on the structural changes of the arterial wall. Our study compared EDR linked to physiological aging with that observed in the case of STZ-induced diabetes over a short-term period, and demonstrated the beneficial effect of AG. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

  12. Multiple subfailures characterize blunt aortic injury.

    Science.gov (United States)

    Stemper, Brian D; Yoganandan, Narayan; Pintar, Frank A; Brasel, Karen J

    2007-05-01

    Blunt aortic injuries result from rapid deceleration of the thorax as may occur during automotive impacts and falls from extreme heights. Pathological findings can range from failure of specific vessel layers to immediate vessel wall rupture. The purpose of this investigation was to determine the sequence of local structural events that may lead to aortic wall disruption. Fourteen porcine aorta specimens were opened to expose the intima and longitudinally distracted until rupture. Longitudinal mechanics were quantified and subfailures were identified. Histology was used to examine internal layer subfailure. Videography demonstrated that subfailures propagated into complete vessel wall rupture. Subfailures occurred before complete vessel rupture in 93% of specimens. Intimal and medial subfailures were present at 74% of the stress and 82% of the strain to rupture. Multiple subfailures were evident in 79% of specimens. Present results supported the clinical theory that nonimmediate death as a result of blunt aortic injury is commonly caused by propagation of lesser lesions, initiating on the intimal layer, into complete vessel rupture including the adventitial layer. This finding, along with histologic evidence of subfailure pathological findings, confirms the presence of an acute window during which recognition and initiation of permissive hypotension may be lifesaving.

  13. Supra-annular structure assessment for self-expanding transcatheter heart valve size selection in patients with bicuspid aortic valve.

    Science.gov (United States)

    Liu, Xianbao; He, Yuxin; Zhu, Qifeng; Gao, Feng; He, Wei; Yu, Lei; Zhou, Qijing; Kong, Minjian; Wang, Jian'an

    2018-04-01

    To explore assessment of supra-annular structure for self-expanding transcatheter heart valve (THV) size selection in patients with bicuspid aortic stenosis (AS). Annulus-based device selection from CT measurement is the standard sizing strategy for tricuspid aortic valve before transcatheter aortic valve replacement (TAVR). Because of supra-annular deformity, device selection for bicuspid AS has not been systemically studied. Twelve patients with bicuspid AS who underwent TAVR with self-expanding THVs were included in this study. To assess supra-annular structure, sequential balloon aortic valvuloplasty was performed in every 2 mm increments until waist sign occurred with less than mild regurgitation. Procedural results and 30 day follow-up outcomes were analyzed. Seven patients (58.3%) with 18 mm; three patients (25%) with sequential 18 mm, 20 mm; and only two patients (16.7%) with sequential 18 mm, 20 mm, and 22 mm balloon sizing were performed, respectively. According to the results of supra-annular assessment, a smaller device size (91.7%) was selected in all but one patient compared with annulus based sizing strategy, and the outcomes were satisfactory with 100% procedural success. No mortality and 1 minor stroke were observed at 30 d follow-up. The percentage of NYHA III/IV decreased from 83.3% (9/12) to 16.7% (2/12). No new permanent pacemaker implantation and no moderate or severe paravalvular leakage were found. A supra-annular structure based sizing strategy is feasible for TAVR in patients with bicuspid AS. © 2018 The Authors Catheterization and Cardiovascular Interventions Published by Wiley Periodicals, Inc.

  14. Development and use of a new perfusion technique to study glucose metabolism of the aortic wall in normal and alloxan-diabetic rabbits

    International Nuclear Information System (INIS)

    Brown, B.J.M.

    1985-01-01

    This study investigated (1) possible alterations in glucose uptake and utilization in the perfused, normal, and diabetic vascular wall of rabbits and (2) the effects thereon of insulin and exogenous glucose concentration. Part I involved development and characterization of an in vitro perfusion technique that closely reproduced predetermined in vivo conditions of aortic blood flow, arterial blood pressure, heart rate and pulse pressure. The responsiveness of the preparation to vasoactive agents was assessed with concentrations of norepinephrine (NE) from 10 -9 to 10 -4 M. In Part II, the effects of NE-induced tension development on glucose metabolism were determined by perfusion with oxygenated physiological salt solution (PSS) containing 7 mM glucose and tracer amounts of uniformly labeled 14 C-glucose. Aortas from 8 week-diabetic rabbits were perfused under similar conditions employing a NE infusion in the presence or absence of insulin (150 uU/ml) and variable levels of glucose. Effects of NE-induced tension development include an apparent increase (39%) in glucose uptake and a twofold increase in 14 CO 2 and lactate production. Aortas from diabetic rabbits perfused with PSS containing 7 mM glucose demonstrated marked decreases in glucose uptake (74%), 14 CO 2 (68%), lactate (30%), total tissue glycogen (75%) and labeled tissue phospholipids (70%). Insulin or elevation of exogenous glucose to 25 mM (diabetic levels) normalized glucose uptake, but had differential effects on the pattern of substrate utilization. The marked alterations of glucose metabolism in the diabetic state may contribute to the functional changes observed in diabetic blood vessels

  15. [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.

  16. Mechanism of Filling and Feeding of Thin-Walled Structures during Gravity Casting

    Directory of Open Access Journals (Sweden)

    Faguo Li

    2015-06-01

    Full Text Available The filling and feeding of thin-walled structures in metal castings pose significant difficulties in manufacturing aerospace structural materials. Samples containing 2 mm and 5 mm thin-walled structures were designed to study the kinetics of filling. The microstructural evolution of the solidification of thin-walled structures was studied with synchrotron X-radiation imaging. The formation of dendritic networks and the isotherm profiles of samples of different thickness were examined. The experimental results showed solidification microstructures of 2 mm and 5 mm thin-walled parts containing elongated equiaxed grains and normal equiaxed grains, respectively. The filling and feeding abilities of thin-walled parts were found to depend more on the wall thickness than on the pouring temperature.

  17. 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

    weight, glomerular number or volume in OHF compared with OC, but renin and Na+,K+-ATPase activity were significantly reduced in OHF compared with controls. Programmed alterations to aortic structure and function are consistent with previous observations that exposure to maternal high fat diets produces......-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...... systemic vascular changes in the offspring. Despite normal renal stereology, altered renal Na+,K+-ATPase and renin activity offers further insight into the mechanism underlying the increased blood pressure characteristic of this model....

  18. Structural Performance of Composite Shear Walls under Compression

    Directory of Open Access Journals (Sweden)

    Tingyue Hao

    2017-02-01

    Full Text Available In order to research the effect of different layout forms of steel plate on the axial compression behavior of a steel plate-concrete composite shear wall, this paper presents the experimental results and analysis of the axial compression behavior of a composite shear wall, with different layout forms of steel plate. A total of three tests were carried out, composed of two composite walls with built-in steel plate, and one composite wall with two skins of steel plate. The gross dimensions of the three specimens were 1206 mm × 2006 mm × 300 mm. Experimental results show that the composite wall with two skins of steel plate has an optimal ability of elastic-plastic deformation, and the maximum axial compressive bearing capacity among the three specimens. Using the energy method, the critical local buckling stresses of steel plate were calculated, and compared with the yield stresses. According to different confined actions of concrete, concrete constitutive models were proposed, and the axial compressive strengths of confined concrete were calculated. Considering the local buckling of steel plate and confined concrete, the calculation formula of the axial compression of the composite wall was put forward, and the calculated results were in good agreement with the test results. Therefore, the different layout forms of steel plate have a great influence on its buckling, and on the concrete inhibition effect, which can affect the axial compressive bearing capacity of the composite wall.

  19. 3D Fluid-Structure Interaction Simulation of Aortic Valves Using a Unified Continuum ALE FEM Model

    Directory of Open Access Journals (Sweden)

    Jeannette H. Spühler

    2018-04-01

    Full Text Available Due to advances in medical imaging, computational fluid dynamics algorithms and high performance computing, computer simulation is developing into an important tool for understanding the relationship between cardiovascular diseases and intraventricular blood flow. The field of cardiac flow simulation is challenging and highly interdisciplinary. We apply a computational framework for automated solutions of partial differential equations using Finite Element Methods where any mathematical description directly can be translated to code. This allows us to develop a cardiac model where specific properties of the heart such as fluid-structure interaction of the aortic valve can be added in a modular way without extensive efforts. In previous work, we simulated the blood flow in the left ventricle of the heart. In this paper, we extend this model by placing prototypes of both a native and a mechanical aortic valve in the outflow region of the left ventricle. Numerical simulation of the blood flow in the vicinity of the valve offers the possibility to improve the treatment of aortic valve diseases as aortic stenosis (narrowing of the valve opening or regurgitation (leaking and to optimize the design of prosthetic heart valves in a controlled and specific way. The fluid-structure interaction and contact problem are formulated in a unified continuum model using the conservation laws for mass and momentum and a phase function. The discretization is based on an Arbitrary Lagrangian-Eulerian space-time finite element method with streamline diffusion stabilization, and it is implemented in the open source software Unicorn which shows near optimal scaling up to thousands of cores. Computational results are presented to demonstrate the capability of our framework.

  20. Fluid-structure interaction study of transcatheter aortic valve dynamics using smoothed particle hydrodynamics

    Science.gov (United States)

    Mao, Wenbin; Li, Kewei; Sun, Wei

    2016-01-01

    Computational modeling of heart valve dynamics incorporating both fluid dynamics and valve structural responses has been challenging. In this study, we developed a novel fully-coupled fluid-structure interaction (FSI) model using smoothed particle hydrodynamics (SPH). A previously developed nonlinear finite element (FE) model of transcatheter aortic valves (TAV) was utilized to couple with SPH to simulate valve leaflet dynamics throughout the entire cardiac cycle. Comparative simulations were performed to investigate the impact of using FE-only models versus FSI models, as well as an isotropic versus an anisotropic leaflet material model in TAV simulations. From the results, substantial differences in leaflet kinematics between FE-only and FSI models were observed, and the FSI model could capture the realistic leaflet dynamic deformation due to its more accurate spatial and temporal loading conditions imposed on the leaflets. The stress and the strain distributions were similar between the FE and FSI simulations. However, the peak stresses were different due to the water hammer effect induced by the flow inertia in the FSI model during the closing phase, which led to 13%–28% lower peak stresses in the FE-only model compared to that of the FSI model. The simulation results also indicated that tissue anisotropy had a minor impact on hemodynamics of the valve. However, a lower tissue stiffness in the radial direction of the leaflets could reduce the leaflet peak stress caused by the water hammer effect. It is hoped that the developed FSI models can serve as an effective tool to better assess valve dynamics and optimize next generation TAV designs. PMID:27844463

  1. Cardiovascular Structure and Function in Children With Middle Aortic Syndrome and Renal Artery Stenosis.

    Science.gov (United States)

    Rumman, Rawan K; Slorach, Cameron; Hui, Wei; Matsuda-Abedini, Mina; Langlois, Valerie; Radhakrishnan, Seetha; Lorenzo, Armando J; Amaral, Joao; Mertens, Luc; Parekh, Rulan S

    2017-12-01

    Middle aortic syndrome (MAS) is a narrowing of the abdominal aorta, often in conjunction with renal artery stenosis (RAS). Structure and function of the cardiovascular system are not well understood. In a prospective cross-sectional study, 35 children with MAS or RAS or both (MAS/RAS) were compared with 140 age-, sex-, and body surface area-matched healthy children. Vascular assessment included carotid intima-media thickness and carotid distensibility using B-mode ultrasound and central and peripheral pulse wave velocities using applanation tonometry. Left ventricular structure and function were assessed by 2-dimensional and speckle-tracking echocardiography. Children with MAS or RAS were 12.5±3.0 years old at enrollment, and 50% were men. Carotid intima-media thickness (0.54±0.10 versus 0.44±0.05 mm; P children with disease compared with healthy children; however, after adjustment for systolic blood pressure z score, only carotid intima-media thickness remained significantly higher in the MAS/RAS group compared with the controls (β=0.07 [0.03, 0.10]). Peripheral pulse wave velocities and carotid distensibility were normal. Children with disease had significantly increased left ventricular mass and changes in diastolic function (lower E/a ratio and lower e' velocities). Systolic parameters, including ejection fraction, global longitudinal and circumferential strain, were similar to controls. Our findings demonstrate that children with MAS or RAS have evidence of carotid and left ventricular remodeling, without peripheral arterial involvement, which suggests a localized disease process. Left ventricular systolic function is preserved; however, subtle changes in diastolic function are observed. Carotid vessel changes are consistent with a 5- to 10-year aging, which underscores the importance of blood pressure control. © 2017 American Heart Association, Inc.

  2. MMP-2 Isoforms in Aortic Tissue and Serum of Patients with Ascending Aortic Aneurysms and Aortic Root Aneurysms

    Science.gov (United States)

    Tscheuschler, Anke; Meffert, Philipp; Beyersdorf, Friedhelm; Heilmann, Claudia; Kocher, Nadja; Uffelmann, Xenia; Discher, Philipp; Siepe, Matthias; Kari, Fabian A.

    2016-01-01

    Objective The need for biological markers of aortic wall stress and risk of rupture or dissection of ascending aortic aneurysms is obvious. To date, wall stress cannot be related to a certain biological marker. We analyzed aortic tissue and serum for the presence of different MMP-2 isoforms to find a connection between serum and tissue MMP-2 and to evaluate the potential of different MMP-2 isoforms as markers of high wall stress. Methods Serum and aortic tissue from n = 24 patients and serum from n = 19 healthy controls was analyzed by ELISA and gelatin zymography. 24 patients had ascending aortic aneurysms, 10 of them also had aortic root aneurysms. Three patients had normally functioning valves, 12 had regurgitation alone, eight had regurgitation and stenosis and one had only stenosis. Patients had bicuspid and tricuspid aortic valves (9/15). Serum samples were taken preoperatively, and the aortic wall specimen collected during surgical aortic repair. Results Pro-MMP-2 was identified in all serum and tissue samples. Pro-MMP-2 was detected in all tissue and serum samples from patients with ascending aortic/aortic root aneurysms, irrespective of valve morphology or other clinical parameters and in serum from healthy controls. We also identified active MMP-2 in all tissue samples from patients with ascending aortic/aortic root aneurysms. None of the analyzed serum samples revealed signals relatable to active MMP-2. No correlation between aortic tissue total MMP-2 or tissue pro-MMP-2 or tissue active MMP-2 and serum MMP-2 was found and tissue MMP-2/pro-MMP-2/active MMP-2 did not correlate with aortic diameter. This evidence shows that pro-MMP-2 is the predominant MMP-2 species in serum of patients and healthy individuals and in aneurysmatic aortic tissue, irrespective of aortic valve configuration. Active MMP-2 species are either not released into systemic circulation or not detectable in serum. There is no reliable connection between aortic tissue—and serum MMP-2

  3. Development, Implementation, and Evaluation of a Structured Reporting Web Tool for Abdominal Aortic Aneurysms

    Science.gov (United States)

    Karim, Sulafa; Fegeler, Christian; Boeckler, Dittmar; H Schwartz, Lawrence; Kauczor, Hans-Ulrich

    2013-01-01

    Background The majority of radiological reports are lacking a standard structure. Even within a specialized area of radiology, each report has its individual structure with regards to details and order, often containing too much of non-relevant information the referring physician is not interested in. For gathering relevant clinical key parameters in an efficient way or to support long-term therapy monitoring, structured reporting might be advantageous. Objective Despite of new technologies in medical information systems, medical reporting is still not dynamic. To improve the quality of communication in radiology reports, a new structured reporting system was developed for abdominal aortic aneurysms (AAA), intended to enhance professional communication by providing the pertinent clinical information in a predefined standard. Methods Actual state analysis was performed within the departments of radiology and vascular surgery by developing a Technology Acceptance Model. The SWOT (strengths, weaknesses, opportunities, and threats) analysis focused on optimization of the radiology reporting of patients with AAA. Definition of clinical parameters was achieved by interviewing experienced clinicians in radiology and vascular surgery. For evaluation, a focus group (4 radiologists) looked at the reports of 16 patients. The usability and reliability of the method was validated in a real-world test environment in the field of radiology. Results A Web-based application for radiological “structured reporting” (SR) was successfully standardized for AAA. Its organization comprises three main categories: characteristics of pathology and adjacent anatomy, measurements, and additional findings. Using different graphical widgets (eg, drop-down menus) in each category facilitate predefined data entries. Measurement parameters shown in a diagram can be defined for clinical monitoring and be adducted for quick adjudications. Figures for optional use to guide and standardize the

  4. Development, implementation, and evaluation of a structured reporting web tool for abdominal aortic aneurysms.

    Science.gov (United States)

    Karim, Sulafa; Fegeler, Christian; Boeckler, Dittmar; H Schwartz, Lawrence; Kauczor, Hans-Ulrich; von Tengg-Kobligk, Hendrik

    2013-08-16

    The majority of radiological reports are lacking a standard structure. Even within a specialized area of radiology, each report has its individual structure with regards to details and order, often containing too much of non-relevant information the referring physician is not interested in. For gathering relevant clinical key parameters in an efficient way or to support long-term therapy monitoring, structured reporting might be advantageous. Despite of new technologies in medical information systems, medical reporting is still not dynamic. To improve the quality of communication in radiology reports, a new structured reporting system was developed for abdominal aortic aneurysms (AAA), intended to enhance professional communication by providing the pertinent clinical information in a predefined standard. Actual state analysis was performed within the departments of radiology and vascular surgery by developing a Technology Acceptance Model. The SWOT (strengths, weaknesses, opportunities, and threats) analysis focused on optimization of the radiology reporting of patients with AAA. Definition of clinical parameters was achieved by interviewing experienced clinicians in radiology and vascular surgery. For evaluation, a focus group (4 radiologists) looked at the reports of 16 patients. The usability and reliability of the method was validated in a real-world test environment in the field of radiology. A Web-based application for radiological "structured reporting" (SR) was successfully standardized for AAA. Its organization comprises three main categories: characteristics of pathology and adjacent anatomy, measurements, and additional findings. Using different graphical widgets (eg, drop-down menus) in each category facilitate predefined data entries. Measurement parameters shown in a diagram can be defined for clinical monitoring and be adducted for quick adjudications. Figures for optional use to guide and standardize the reporting are embedded. Analysis of variance

  5. Assessment of structural valve deterioration of transcatheter aortic bioprosthetic balloon-expandable valves using the new European consensus definition.

    Science.gov (United States)

    Eltchaninoff, Hélène; Durand, Eric; Avinée, Guillaume; Tron, Christophe; Litzler, Pierre-Yves; Bauer, Fabrice; Dacher, Jean-Nicolas; Werhlin, Camille; Bouhzam, Najime; Bettinger, Nicolas; Candolfi, Pascal; Cribier, Alain

    2018-03-30

    Durability of transcatheter aortic bioprosthetic valves remains a major issue. Standardised definitions of deterioration and failure of bioprosthetic valves have recently been proposed. The aim of this study was to assess structural transcatheter valve deterioration (SVD) and bioprosthetic valve failure (BVF) using these new definitions. All TAVI patients implanted up to September 2012 with a minimal theoretical five-year follow-up were included. Systematic clinical and echocardiographic follow-up was performed annually. New standardised definitions were used to assess durability of transcatheter aortic bioprosthetic valves. From 2002 to 2012, 378 patients were included. Mean age and logistic EuroSCORE were 83.3±6.8 years and 22.8±13.1%. Thirty-day mortality was 13.2%. Nine patients had SVD including two severe forms and two patients had definite late BVF. The incidence of SVD and BVF at eight years was 3.2% (95% CI: 1.45-6.11) and 0.58% (95% CI: 0.15-2.75), respectively. Even though limited by the poor survival of the very high-risk/compassionate early population, our data do not demonstrate any alarm concerning transcatheter aortic valve durability. Careful prospective assessment in younger and lower-risk patients and comparison with surgical bioprosthetic valves are required for further assessment of the long-term durability of transcatheter valves.

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

    Directory of Open Access Journals (Sweden)

    LIU Jianxin

    2014-06-01

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

  7. Chest wall – underappreciated structure in sonography. Part I: Examination methodology and ultrasound anatomy

    OpenAIRE

    Smereczyński, Andrzej; Kołaczyk, Katarzyna; Bernatowicz, Elżbieta

    2017-01-01

    Chest wall ultrasound has been awarded little interest in the literature, with chest wall anatomy described only in limited extent. The objective of this study has been to discuss the methodology of chest wall ultrasound and the sonographic anatomy of the region to facilitate professional evaluation of this complex structure. The primarily used transducer is a 7–12 MHz linear one. A 3–5 MHz convex (curvilinear) transducer may also be helpful, especially in obese and very muscular patients. Do...

  8. The structure and material composition of ossified aortic valves identified using a set of scientific methods

    Science.gov (United States)

    Zeman, Antonín; Šmíd, Michal; Havelcová, Martina; Coufalová, Lucie; Kučková, Štěpánka; Velčovská, Martina; Hynek, Radovan

    2013-11-01

    Degenerative aortic stenosis has become a common and dangerous disease in recent decades. This disease leads to the mineralization of aortic valves, their gradual thickening and loss of functionality. We studied the detailed assessment of the proportion and composition of inorganic and organic components in the ossified aortic valve, using a set of analytical methods applied in science: polarized light microscopy, scanning electron microscopy, X-ray fluorescence, X-ray diffraction, gas chromatography/mass spectrometry and liquid chromatography-tandem mass spectrometry. The sample valves showed the occurrence of phosphorus and calcium in the form of phosphate and calcium carbonate, hydroxyapatite, fluorapatite and hydroxy-fluorapatite, with varying content of inorganic components from 65 to 90 wt%, and with phased development of degenerative disability. The outer layers of the plaque contained an organic component with peptide bonds, fatty acids, proteins and cholesterol. The results show a correlation between the formation of fluorapatite in aortic valves and in other parts of the human bodies, associated with the formation of bones.

  9. Seismic strengthening of RC structures with exterior shear walls

    Indian Academy of Sciences (India)

    It has been observed that the usage of exterior shear walls considerably improve the capacity and sway ... Steel bracing for RC frames has also been used to reduce drift demands. Bracing can either ..... The column and beam elements have been modelled with plastic hinges so that lumped plas- ticity behaviour would be ...

  10. Parenchyma cell wall structure in twining stem of Dioscorea balcanica

    Czech Academy of Sciences Publication Activity Database

    Radosavljević, J.S.; Pristov, J.B.; Mitrović, A.Lj.; Steinbach, Gabor; Mouille, G.; Tufegdžić, S.; Maksimović, V.; Mutavdžić, D.; Janošević, D.; Vuković, M.; Garab, G.; Radotić, K.

    2017-01-01

    Roč. 24, č. 11 (2017), s. 4653-4669 ISSN 0969-0239 R&D Projects: GA MŠk(CZ) ED2.1.00/19.0392 Institutional support: RVO:61388971 Keywords : Cell wall * Cellulose fibril order * Dioscorea balcanica Kosanin Subject RIV: EE - Microbiology, Virology OBOR OECD: Microbiology Impact factor: 3.417, year: 2016

  11. On the equilibrium configuration of the Kittel type domain structure with Bloch walls, l80deg

    International Nuclear Information System (INIS)

    Gavrila, H.

    1975-01-01

    Using a phenomenologic method for appreciating different components of the free energy, the equilibrium configuration of the Kittel-type domain structure with Bloch walls is obtained. By improving the known methods, more accurate magnetostatic energy calculations are reported. In order to determine the equilibrium structure, the total free energy is minimized with respect to two system parameters: the Bloch wall width and the structure half-period. (author)

  12. Circumferential ascending aortic strain and aortic stenosis.

    Science.gov (United States)

    Teixeira, Rogério; Moreira, Nádia; Baptista, Rui; Barbosa, António; Martins, Rui; Castro, Graça; Providência, Luís

    2013-07-01

    Two-dimensional speckle tracking (2D-ST) echocardiography for the measurement of circumferential ascending thoracic aortic strain (CAAS) in the context of aortic stenosis (AS) is not elucidated. Purpose This study assesses the thoracic ascending aortic deformation using 2D-ST echocardiography in AS patients. Population and methods Forty-five consecutive patients with an aortic valvular area (AVA) ≤0.85 cm(2)/m(2) were included. Regarding aortic deformation, the global peak CAAS was the parameter used, and an average of six segments of arterial wall deformation was calculated. The corrected CAAS was calculated as the global CAAS/pulse pressure (PP). Aortic stiffness (β2) index was assessed according to ln(Ps/Pd)/CAAS. The sample was stratified according to the stroke volume index (SVI) as: Group A (low flow, SVI ≤35 mL/m(2); n = 19) and Group B (normal flow, SVI >35 mL/m(2); n = 26). The mean age was 76.8 ± 10.3 years, 53.3% were male, the mean indexed AVA was 0.43 ± 0.15 cm(2)/m(2), and the mean CAAS was 6.3 ± 3.0%. The CAAS was predicted by SVI (β = 0.31, P < 0.01) and by valvulo-arterial impedance (Zva). The corrected CAAS was correlated with the M-mode guided aortic stiffness index (β1) (r = -0.39, P < 0.01), and was predicted by SVI, Zva, and systemic arterial compliance (β = 0.15, P < 0.01). The β2 index was significantly higher for the low-flow patients (16.1 ± 4.8 vs. 9.8 ± 5.3, P < 0.01), and was predicted by SVI (β -0.58, P < 0.01) and PP (β = 0.17, P < 0.01). Global CAAS was more accurate to predict low flow than Zva, systolic function and systemic vascular resistance. In patients with moderate-to-severe aortic stenosis, SVI and LV afterload-related variables were the most important determinants of 2S-ST global CAAS.

  13. Application of manufacturing constraints to structural optimization of thin-walled structures

    Science.gov (United States)

    Kuczek, T.

    2016-02-01

    Topology optimization can be a very useful tool for creating conceptual designs for vehicles. Structures suggested by topology optimization often turn out to be difficult to implement in manufacturing processes. Presently, rail vehicle structures are made by welding sheet metal parts. This leads to many complications and increased weight of the vehicle. This article presents a new design concept for modern rail vehicle structures made of standardized, thin-walled, closed, steel profiles that fulfil the stress and manufacturing requirements. For this purpose, standard software for topology optimization was used with a new way of preprocessing the design space. The design methodology is illustrated by an example of the topology optimization of a freight railcar. It is shown that the methodology turns out to be a useful tool for obtaining optimal structure design that fulfils the assumed manufacturing constraints.

  14. Cell Walls of Wood, Composition, Structure and a few Mechanical Properties

    OpenAIRE

    Florentina Adriana Cziple; António J. Velez Marques

    2008-01-01

    The objective of this paper was to investigate the effect between the chemical composition, molecular architecture and structure cell walls of wood and the mechanical properties of wood. Cell walls function as the major mechanical restraint that determines plant cell size and morphology.

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

    Directory of Open Access Journals (Sweden)

    S. Voß

    2016-01-01

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

  16. Characteristics of Carotid Artery Structure and Mechanical Function and Their Relationships with Aortopathy in Patients with Bicuspid Aortic Valves

    Directory of Open Access Journals (Sweden)

    Mihyun Kim

    2017-08-01

    Full Text Available Patients with a bicuspid aortic valve (BAV often have proximal aortic dilatation and systemic vascular dysfunction. We hypothesized that BAV patients would have different carotid artery structural and functional characteristics compared to tricuspid aortic valve (TAV patients. In 28 patients with surgically confirmed BAV and 27 patients with TAV, intima media thickness (IMT, number of plaques, fractional area change (FAC, global circumferential strain (GCS, and standard deviation of CS (SD-CS in both common carotid arteries were assessed using duplex ultrasound and velocity vector imaging (VVI. Patients with BAV were younger and had less co-morbidity, but showed a significantly larger ascending aorta (43.3 ± 7.5 vs. 37.0 ± 6.2 mm, p < 0.001 and a higher prevalence of aortopathy (61 vs. 30%, p = 0.021 than those with TAV. BAV patients showed a significantly lower IMT and fewer plaques. Although FAC and GCS were not significantly different between the two groups, they tended to be lower in the BAV group when each group was divided into three subgroups according to age. There was a significant age-dependent increase in IMT and decreases in FAC and GCS in the TAV group (p = 0.005, p = 0.001, p = 0.002, respectively, but this phenomenon was not evident in the BAV group (p = 0.074, p = 0.248, p = 0.394, respectively. BAV patients with aortopathy showed a higher SD-CS than those without aortopathy (p = 0.040, reflecting disordered mechanical function. In conclusion, BAV patients have different carotid artery structure and function compared with TAV patients, suggesting intrinsic vascular abnormalities that are less affected by established cardiovascular risk factors and more strongly related to the presence of aortopathy.

  17. Significance of Shear Wall in Multi-Storey Structure With Seismic Analysis

    Science.gov (United States)

    Bongilwar, Rajat; Harne, V. R.; Chopade, Aditya

    2018-03-01

    In past decades, shear walls are one of the most appropriate and important structural component in multi-storied building. Therefore, it would be very interesting to study the structural response and their systems in multi-storied structure. Shear walls contribute the stiffness and strength during earthquakes which are often neglected during design of structure and construction. This study shows the effect of shear walls which significantly affect the vulnerability of structures. In order to test this hypothesis, G+8 storey building was considered with and without shear walls and analyzed for various parameters like base shear, storey drift ratio, lateral displacement, bending moment and shear force. Significance of shear wall has been studied with the help of two models. First model is without shear wall i.e. bare frame and other another model is with shear wall considering opening also in it. For modeling and analysis of both the models, FEM based software ETABS 2016 were used. The analysis of all models was done using Equivalent static method. The comparison of results has been done based on same parameters like base shear, storey drift ratio, lateral displacement, bending moment and shear force.

  18. The structure and material composition of ossified aortic valves identified using a set of scientific methods

    Czech Academy of Sciences Publication Activity Database

    Zeman, Antonín; Šmíd, M.; Havelcová, Martina; Coufalová, L.; Kučková, S.; Velčovská, M.; Hynek, R.

    2013-01-01

    Roč. 77, November (2013), s. 311-317 ISSN 1367-9120 Grant - others:GA ČR(CZ) GA205/09/1162 Program:GA Institutional support: RVO:68378297 ; RVO:67985891 Keywords : aortic stenosis * degenerative (calcification–sclerotic) changes * hydroxyapatite * proteins * cholesterol Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.831, year: 2013 http://www.sciencedirect.com/science/journal/13679120/77

  19. Chemical composition, anatomy, lignin distribution, and cell wall structure of Malaysian plant waste fibers

    OpenAIRE

    Mohd Omar, A. K.; Siti Alwani, M.; Abdul Khalil, H. P. S.

    2006-01-01

    The chemical composition, anatomical characteristics, lignin distribution, and cell wall structure of oil palm frond (OPF), coconut (COIR), pine-apple leaf (PALF), and banana stem (BS) fibers were analyzed. The chemical composition of fiber was analyzed according to TAPPI Methods. Light microscopy (LM) and transmission electron microscopy (TEM) were used to observe and determine the cell wall structure and lignin distribution of various agro-waste fibers. The results revealed differences in a...

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

    OpenAIRE

    Luo, Ying; Wang, Jianguo; Liu, Bin; Wang, Zhouli; Yuan, Yahong; Yue, Tianli

    2015-01-01

    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 ...

  1. Perfusion computed tomography imaging of abdominal aortic aneurysms may be of value for patient specific rupture risk estimation.

    Science.gov (United States)

    Kontopodis, Nikolaos; Galanakis, Nikolaos; Tsetis, Dimitrios; Ioannou, Christos V

    2017-04-01

    Abdominal aortic aneurysm (AAA) continues to pose a significant cause of unexpected mortality in the developed countries with its incidence constantly rising. The indication of elective surgical repair is currently based on the maximum diameter and growth rate criteria which represent an oversimplification of the Law of Laplace stating that the stress exerted in a cylinder or sphere is proportional to its radius. These criteria fail to capture the complex pathophysiology of the aneurismal disease thus often leading to therapeutic inaccuracies (treating large AAAs with a very low actual rupture risk while observing smaller ones with a much greater risk). Aneurysmal disease is mainly a degenerative process leading to loss of structural integrity of the diseased aortic wall which cannot withhold the stresses due to systemic pressurization. Moreover aortic wall degeneration has been shown to be a localized phenomenon and rupture depends on the pointwise comparison of strength and stress rather than a global aortic wall weakening. Ex-vivo mechanical studies have related vessel wall hypoxia to loss of structural endurance and reduced wall strength. Therefore a module to capture in vivo variation of aortic wall blood supply and oxygenation would be of value for the evaluation of AAA rupture risk. Perfusion computed tomography (PCT) imaging represents a novel technique which has been already used to estimate tissue vascularity in several clinical conditions but not aneurismal disease. We hypothesize that PCT could be used as an adjunct tool during AAA diagnostics in order to evaluate aortic wall oxygenation in vivo, therefore providing a possible means to identify weak spots making the lesion amenable to rupture. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Stomatal cell wall composition: distinctive structural patterns associated with different phylogenetic groups.

    Science.gov (United States)

    Shtein, Ilana; Shelef, Yaniv; Marom, Ziv; Zelinger, Einat; Schwartz, Amnon; Popper, Zoë A; Bar-On, Benny; Harpaz-Saad, Smadar

    2017-04-01

    Stomatal morphology and function have remained largely conserved throughout ∼400 million years of plant evolution. However, plant cell wall composition has evolved and changed. Here stomatal cell wall composition was investigated in different vascular plant groups in attempt to understand their possible effect on stomatal function. A renewed look at stomatal cell walls was attempted utilizing digitalized polar microscopy, confocal microscopy, histology and a numerical finite-elements simulation. The six species of vascular plants chosen for this study cover a broad structural, ecophysiological and evolutionary spectrum: ferns ( Asplenium nidus and Platycerium bifurcatum ) and angiosperms ( Arabidopsis thaliana and Commelina erecta ) with kidney-shaped stomata, and grasses (angiosperms, family Poaceae) with dumbbell-shaped stomata ( Sorghum bicolor and Triticum aestivum ). Three distinct patterns of cellulose crystallinity in stomatal cell walls were observed: Type I (kidney-shaped stomata, ferns), Type II (kidney-shaped stomata, angiosperms) and Type III (dumbbell-shaped stomata, grasses). The different stomatal cell wall attributes investigated (cellulose crystallinity, pectins, lignin, phenolics) exhibited taxon-specific patterns, with reciprocal substitution of structural elements in the end-walls of kidney-shaped stomata. According to a numerical bio-mechanical model, the end walls of kidney-shaped stomata develop the highest stresses during opening. The data presented demonstrate for the first time the existence of distinct spatial patterns of varying cellulose crystallinity in guard cell walls. It is also highly intriguing that in angiosperms crystalline cellulose appears to have replaced lignin that occurs in the stomatal end-walls of ferns serving a similar wall strengthening function. Such taxon-specific spatial patterns of cell wall components could imply different biomechanical functions, which in turn could be a consequence of differences in

  3. Contact angle and droplet heat transfer during evaporation on structured and smooth surfaces of heated wall

    Science.gov (United States)

    Misyura, S. Y.

    2017-08-01

    Water evaporation in a wide range of droplet diameters and wall temperatures on the structured and smooth surfaces were studied experimentally. Linear dependence of evaporation rate (dV/dt) on a droplet radius varies when the volume is greater than 40-60 μl. The static contact angles on the structured surface vary with a droplet diameter for high wall superheating. Dependence of the contact angle on diameter for the corrugated surface is defined by a change in both potential energy barrier U and three-phase contact line tension τcl. This energy barrier for the structured wall changes with an increase in the initial droplet diameter and becomes constant for the large droplets. For high wall superheating, the power in the law of evaporation increases from 1 to 1.45 with an increase in the initial droplet diameter. Depending on the droplet radius, number of droplets and heater length, four different characters of evaporation are realized. Complete droplet evaporation time on structured surface is less than smooth wall. Heat transfer coefficient is greater for structured wall than smooth one. When simulating droplet evaporation and heat transfer, it is necessary to take into account free convection of air and vapor.

  4. Structural changes in cell wall pectins during strawberry fruit development.

    Science.gov (United States)

    Paniagua, Candelas; Santiago-Doménech, Nieves; Kirby, Andrew R; Gunning, A Patrick; Morris, Victor J; Quesada, Miguel A; Matas, Antonio J; Mercado, José A

    2017-09-01

    Strawberry (Fragaria × anannasa Duch.) is one of the most important soft fruit. Rapid loss of firmness occurs during the ripening process, resulting in a short shelf life and high economic losses. To get insight into the role of pectin matrix in the softening process, cell walls from strawberry fruit at two developmental stages, unripe-green and ripe-red, were extracted and sequentially fractionated with different solvents to obtain fractions enriched in a specific component. The yield of cell wall material as well as the per fresh weight contents of the different fractions decreased in ripe fruit. The largest reduction was observed in the pectic fractions extracted with a chelating agent (trans-1,2- diaminocyclohexane-N,N,N'N'-tetraacetic acid, CDTA fraction) and those covalently bound to the wall (extracted with Na 2 CO 3 ). Uronic acid content of these two fractions also decreased significantly during ripening, but the amount of soluble pectins extracted with phenol:acetic acid:water (PAW) and water increased in ripe fruit. Fourier transform infrared spectroscopy of the different fractions showed that the degree of esterification decreased in CDTA pectins but increased in soluble fractions at ripen stage. The chromatographic analysis of pectin fractions by gel filtration revealed that CDTA, water and, mainly PAW polyuronides were depolymerised in ripe fruit. By contrast, the size of Na 2 CO 3 pectins was not modified. The nanostructural characteristics of CDTA and Na 2 CO 3 pectins were analysed by atomic force microscopy (AFM). Isolated pectic chains present in the CDTA fractions were significantly longer and more branched in samples from green fruit than those from red fruit. No differences in contour length were observed in Na 2 CO 3 strands between samples of both stages. However, the percentage of branched chains decreased from 19.7% in unripe samples to 3.4% in ripe fruit. The number of pectin aggregates was higher in green fruit samples of both

  5. Numerical Investigation of Structural Response of Corrugated Blast Wall Depending on Blast Load Pulse Shapes

    Directory of Open Access Journals (Sweden)

    Jung Min Sohn

    Full Text Available Abstract Hydrocarbon explosions are one of most hazardous events for workers on offshore platforms. To protect structures against explosion loads, corrugated blast walls are typically installed. However, the profiles of real explosion loads are quite different depending on the congestion and confinement of Topside structures. As the level of congestion and confinement increases, the explosion load increases by up to 8 bar, and the rising time of the load decreases. This study primarily aims to investigate the structural behavior characteristics of corrugated blast walls under different types of explosion loadings. Four loading shapes were applied in the structural response analysis, which utilized a dynamic nonlinear finite element method.

  6. Wall effect on fluid–structure interactions of a tethered bluff body

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Sumant; Raghav, Vrishank, E-mail: vrishank@gatech.edu; Komerath, Narayanan, E-mail: komerath@gatech.edu; 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.

  7. Application of concrete filled steel bearing wall to inner concrete structure fro PWR nuclear power plant

    International Nuclear Information System (INIS)

    Sekimoto, Hisashi; Tanaka, Mamoru; Inoue, Kunio; Fukihara, Masaaki; Akiyama, Hiroshi.

    1992-01-01

    'Concrete filled steel bearing wall', applied to the inner concrete structure for PWR nuclear power plant, was developed for rationalization of construction procedure at site. It was concluded through preliminary studies that this new type of wall, where concrete is placed between steel plates, is best suited for the strength members of the above structure, due to the high strength and ductility of surface steel plates and the confinement effect of filled concrete. To verify the behavior from the elastic range to the inelastic range, the ultimate strength and the failure mechanism, and to clarify experimentally the structural integrity of the inner concrete structure, which was composed of a concrete filled steel bearing wall, against seismic lateral loads, horizontal loading tests using a 1/10th scale model of the inner concrete structure for PWR nuclear power plant were conducted. As a result of the tests, the inner concrete structure composed of a concrete filled steel bearing wall appeared to have a larger load carrying capacity and a higher ductility as compared with that composed of a reinforced concrete wall. (author)

  8. 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.

  9. Transmutation and activation of fusion reactor wall and structural materials

    International Nuclear Information System (INIS)

    Jarvis, O.N.

    1979-01-01

    This report details the extent of the nuclear data needed for inclusion in a data library to be used for general assessments of fusion reactor structure activation and transmutation, describes the sources of data available, reviews the literature and explores the reliability of current calculations by providing an independent assessment of the activity inventory to be expected from five structural materials in a simple blanket design for comparison with the results of other workers. An indication of the nuclear reactions which make important contributions to the activity, transmutation and gas production rates for these structural materials is also presented. (author)

  10. Development of strongly coupled FSI technology involving thin walled structures

    CSIR Research Space (South Africa)

    Suliman, Ridhwaan

    2011-01-01

    Full Text Available the most desirable results and is coupled with an in-house fluid-flow solver. The developed technology is evaluated on representative strongly coupled fluid-structure interaction test problems....

  11. Effect of Jointing Mortar on Structural Behaviour of Wall Panels ...

    African Journals Online (AJOL)

    emerging as the grand eco-material for building construction for the 21st century due to its availability, environmental/cultural appropriateness, structural adequacy, familiarity to the local people, “breathability”, amongst others. Accordingly, both ...

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

    Science.gov (United States)

    Luo, Ying; Wang, Jianguo; Liu, Bin; Wang, Zhouli; Yuan, Yahong; Yue, Tianli

    2015-01-01

    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. 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.)

  14. Chest wall – a structure underestimated in ultrasonography. Part III: Neoplastic lesions

    Directory of Open Access Journals (Sweden)

    Andrzej Smereczyński

    2017-12-01

    Full Text Available Chest wall neoplasms mainly include malignancies, metastatic in particular. Differential diagnosis should include clinical data; tumor location, extent, delineation; the degree of homogeneity; the presence of calcifications; the nature of bone destruction and the degree of vascularization. The aim of the paper is to present both the benefits and limitations of ultrasound for the diagnosis of chest wall neoplasms. The neoplastic process may be limited to the chest wall; it may spread from the chest wall into the intrathoracic structures or spread from the inside of the chest towards the chest wall. Benign tumors basically originate from vessels, nerves, bones, cartilage and soft tissues. In this paper, we briefly discuss malformations of blood and lymphatic vessels, glomus tumor as well as neurogenic tumors originating in the thoracic branches of the spinal nerves and the autonomic visceral system. Metastases, particularly lung, breast, kidney cancer, melanoma and prostate cancer, are predominant tumors of the osteocartilaginous structures of the chest wall. Plasma cell myeloma is also relatively common. The vast majority of these lesions are osteolytic, which is reflected in ultrasound as irregular cortical defects. Osteoblastic foci result only in irregular outline of the bone surface. Lipomas are the most common neoplasms of the chest wall soft tissue. Elastofibroma is another tumor with characteristic echostructure. Desmoid fibromatosis, which is considered to be a benign lesion with local aggressivity and recurrences after surgical resection, represents an interesting tumor form the clinical point of view. Ultrasonography represents an optimal tool for the monitoring of different biopsies of pathological lesions located in the chest wall. Based on our experiences and literature data, this method should be considered as a preliminary diagnosis of patients with chest wall tumors.

  15. 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.

  16. Proximal aortic stiffening in Turner patients may be present before dilation can be detected: a segmental functional MRI study.

    Science.gov (United States)

    Devos, Daniel G H; De Groote, Katya; Babin, Danilo; Demulier, Laurent; Taeymans, Yves; Westenberg, Jos J; Van Bortel, Luc; Segers, Patrick; Achten, Eric; De Schepper, Jean; Rietzschel, Ernst

    2017-02-13

    To study segmental structural and functional aortic properties in Turner syndrome (TS) patients. Aortic abnormalities contribute to increased morbidity and mortality of women with Turner syndrome. Cardiovascular magnetic resonance (CMR) allows segmental study of aortic elastic properties. We performed Pulse Wave Velocity (PWV) and distensibility measurements using CMR of the thoracic and abdominal aorta in 55 TS-patients, aged 13-59y, and in a control population (n = 38;12-58y). We investigated the contribution of TS on aortic stiffness in our entire cohort, in bicuspid (BAV) versus tricuspid (TAV) aortic valve-morphology subgroups, and in the younger and older subgroups. Differences in aortic properties were only seen at the most proximal aortic level. BAV Turner patients had significantly higher PWV, compared to TAV Turner (p = 0.014), who in turn had significantly higher PWV compared to controls (p = 0.010). BAV Turner patients had significantly larger ascending aortic (AA) luminal area and lower AA distensibility compared to both controls (all p Turner patients. TAV Turner had similar AA luminal areas and AA distensibility compared to Controls. Functional changes are present in younger and older Turner subjects, whereas ascending aortic dilation is prominent in older Turner patients. Clinically relevant dilatation (TAV and BAV) was associated with reduced distensibility. Aortic stiffening and dilation in TS affects the proximal aorta, and is more pronounced, although not exclusively, in BAV TS patients. Functional abnormalities are present at an early age, suggesting an aortic wall disease inherent to the TS. Whether this increased stiffness at young age can predict later dilatation needs to be studied longitudinally.

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

    Indian Academy of Sciences (India)

    Hong Kong, Guangzhou, pp. 28–36. Stafford Smith B and Coull A 1991 Tall building structures – analysis and design, New York: Wiley. Interscience. Stafford Smith B, Kuster M and Hoenderkamp J C D 1981 A generalized approach to the deflection analysis of braced frame, rigid frame and coupled wall structures. Can.

  18. The structure of cell wall alpha-glucan from fission yeast

    NARCIS (Netherlands)

    Grün, Christian H.; Hochstenbach, Frans; Humbel, Bruno M.; Verkleij, Arie J.; Sietsma, J. Hans; Klis, Frans M.; Kamerling, Johannis P.; Vliegenthart, Johannes F. G.

    2005-01-01

    Morphology and structural integrity of fungal cells depend on cell wall polysaccharides. The chemical structure and biosynthesis of two types of these polysaccharides, chitin and (1-->3)-beta-glucan, have been studied extensively, whereas little is known about alpha-glucan. Here we describe the

  19. The structure of cell wall alpha-glucan from fission yeast.

    NARCIS (Netherlands)

    Grün, C.H.; Hochstenbach, F.; Humbel, B.M.; Verkleij, A.J.; Sietsma, J.H.; Klis, F.M.; Kamerling, J.P.; Vliegenthart, J.F.G.

    2005-01-01

    Morphology and structural integrity of fungal cells depend on cell wall polysaccharides. The chemical structure and biosynthesis of two types of these polysaccharides, chitin and (1rarr3)-beta-glucan, have been studied extensively, whereas little is known about alpha-glucan. Here we describe the

  20. Stress state of thin – walled member of the structure with operation damages under nonuniform loading

    Directory of Open Access Journals (Sweden)

    В.В. Астанін

    2004-01-01

    Full Text Available  The publication is dedicated to determining of stress state in particular the stress concentration factors for thin – walled members of the structures subject to nonuniform tension. A structure member has obtained the operation damage generation by corrosion and other causes.

  1. The importance of structures and processes in determining outcomes for abdominal aortic aneurysm repair: an international perspective.

    Science.gov (United States)

    Bahia, Sandeep S; Ozdemir, Baris A; Oladokun, Dare; Holt, Peter J E; Loftus, Ian M; Thompson, Matt M; Karthikesalingam, Alan

    2015-11-01

    Annual procedural mortality reports have become mandatory for vascular surgery in England, reflecting a more widespread appetite for transparency and accountability across the National Health Service (NHS) [BMJ 2013;346:f854]. The outcomes of abdominal aortic aneurysm (AAA) repair, in particular, have attracted considerable commentary: from 1999 to 2006, postoperative mortality was higher in England than in many other countries (7.9 vs. 1.9-4.5%) [European Society for Vascular Surgery. 2nd Vascunet Report. 2008]. This stimulated considerable service reconfiguration (centralization), quality improvement initiatives, the uptake of endovascular technology, and the examination of institution-level mortality data [http://www.vascularsociety.org.uk/library/quality-improvement.html], which resulted in a fall in elective AAA mortality to 1.8% by 2012 [http://www.hqip.org.uk/assets/NCAPOP-Library/NCAPOP-2013-2014/Outcomes-after-Elective-Repair-of-Infra-renal-Abdominal-Aortic-Aneurysm.pdf (February 2015)]. Despite improvements at a national level, the outcomes of AAA repair vary considerably between different hospitals in the NHS [Circ Cardiovasc Qual Outcomes 2014;7:131-141], analogous to interprovider variation that has been reported across a range of emergency medical and surgical conditions [BMC Health Serv Res 2014;14:270]. This suggests that underlying institution structures and processes contribute independently to patients' outcomes. There is also considerable evidence that the outcomes of AAA repair vary in different healthcare systems, both in the elective European Society for Vascular Surgery, 2008 and emergency settings. A consideration of the role of structures and processes in influencing outcomes for AAA repair can be conducted across different institutions or even different healthcare systems. This can help identify which factors are consistently associated with the best outcomes, informing efforts to better organize and deliver services for patients

  2. 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

  3. Catheterization Laboratory: Structural Heart Disease, Devices, and Transcatheter Aortic Valve Replacement.

    Science.gov (United States)

    Fiorilli, Paul N; Anwaruddin, Saif; Zhou, Elizabeth; Shah, Ronak

    2017-12-01

    The cardiac catheterization laboratory is advancing medicine by performing procedures on patients who would usually require sternotomy and cardiopulmonary bypass. These procedures are done percutaneously, allowing them to be performed on patients considered inoperable. Patients have compromised cardiovascular function or advanced age. An anesthesiologist is essential for these procedures in case of hemodynamic compromise. Interventionalists are becoming more familiar with transcatheter aortic valve replacement and the device has become smaller, both contributing to less complications. Left atrial occlusion and the endovascular edge-to-edge mitral valve repair devices were approved. Although these devices require general anesthesia, an invasive surgery and cardiopulmonary bypass machine are not necessary for deployment. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Statistics on Near Wall Structures and Shear Stress Distribution from 3D Holographic Measurement.

    Science.gov (United States)

    Sheng, J.; Malkiel, E.; Katz, J.

    2007-11-01

    Digital Holographic Microscopy performs 3D velocity measurement in the near-wall region of a turbulent boundary layer in a square channel over a smooth wall at Reτ=1,400. Resolution of ˜1μm over a sample volume of 1.5x2x1.5mm (x^+=50, y^+=60, z^+=50) is sufficient for resolving buffer layer and lower log layer structures, and for measuring instantaneous wall shear stress distributions from velocity gradients in the viscous sublayer. Results, based on 700 instantaneous realizations, provide detailed statistics on the spatial distribution of both wall stress components along with characteristic flow structures. Conditional sampling based on maxima and minima of wall shear stresses, as well as examination of instantaneous flow structures, lead to development of a conceptual model for a characteristic flow phenomenon that seems to generating extreme stress events. This structure develops as an initially spanwise vortex element rises away from the surface, due to local disturbance, causing a local stress minimum. Due to increasing velocity with elevation, this element bends downstream, forming a pair of inclined streamwise vortices, aligned at 45^0 to freestream, with ejection-like flow between them. Entrainment of high streamwise momentum on the outer sides of this vortex pair generates streamwise shear stress maxima, 70 δν downstream, which are displaced laterally by 35 δν from the local minimum.

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

    NARCIS (Netherlands)

    den Adel, Brigit; van der Graaf, Linda M.; Strijkers, Gustav J.; Lamb, Hildo J.; Poelmann, Robert E.; van der Weerd, Louise

    2013-01-01

    High-resolution contrast-enhanced imaging of the murine atherosclerotic vessel wall is difficult due to unpredictable flow artifacts, motion of the thin artery wall and problems with flow suppression in the presence of a circulating contrast agent. We applied a 2D-FLASH retrospective-gated CINE MRI

  6. 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...

  7. A study of the native cell wall structures of the marine alga Ventricaria ventricosa (Siphonocladales, Chlorophyceae) using atomic force microscopy.

    Science.gov (United States)

    Eslick, Enid M; Beilby, Mary J; Moon, Anthony R

    2014-04-01

    A substantial proportion of the architecture of the plant cell wall remains unknown with a few cell wall models being proposed. Moreover, even less is known about the green algal cell wall. Techniques that allow direct visualization of the cell wall in as near to its native state are of importance in unravelling the spatial arrangement of cell wall structures and hence in the development of cell wall models. Atomic force microscopy (AFM) was used to image the native cell wall of living cells of Ventricaria ventricosa (V. ventricosa) at high resolution under physiological conditions. The cell wall polymers were identified mainly qualitatively via their structural appearance. The cellulose microfibrils (CMFs) were easily recognizable and the imaging results indicate that the V. ventricosa cell wall has a cross-fibrillar structure throughout. We found the native wall to be abundant in matrix polysaccharides existing in different curing states. The soft phase matrix polysaccharides susceptible by the AFM scanning tip existed as a glutinous fibrillar meshwork, possibly incorporating both the pectic- and hemicellulosic-type substances. The hard phase matrix producing clearer images, revealed coiled fibrillar structures associated with CMFs, sometimes being resolved as globular structures by the AFM tip. The coiling fibrillar structures were also seen in the images of isolated cell wall fragments. The mucilaginous component of the wall was discernible from the gelatinous cell wall matrix as it formed microstructural domains over the surface. AFM has been successful in imaging the native cell wall and revealing novel findings such as the 'coiling fibrillar structures' and cell wall components which have previously not been seen, that is, the gelatinous matrix phase.

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

    DEFF Research Database (Denmark)

    Traberg, Marie Sand; Jensen, Jørgen Arendt

    2014-01-01

    . Spectral Doppler velocity data from 3 healthy male volunteers were used to construct inlet profiles for the FSI model. Simultaneously, wall movement was tracked and used for comparison to FSI model results. Ultrasound data were acquired using a scanner equipped with a research interface. The wall...... agreement except for 1 volunteer (Male, 23 yrs.). The magnitude of the displacement in simulation, u fsi , and in vivo , u iv , is within the same order of magnitude for the young ( u iv = 1 : 48 mm, u fsi = 1 : 12 mm) and middle-aged volunteer ( u iv = 0 : 783 mm, u fsi = 1 : 31 mm). For the elderly...

  9. Comparison of ascending aortic cohesion between patients with bicuspid aortic valve stenosis and regurgitation.

    Science.gov (United States)

    Benedik, Jaroslav; Dohle, Daniel S; Wendt, Daniel; Pilarczyk, Kevin; Price, Vivien; Mourad, Fanar; Zykina, Elizaveta; Stebner, Ferdinand; Tsagakis, Konstantinos; Jakob, Heinz

    2014-12-01

    A bicuspid aortic valve (BAV) is commonly associated with aortic wall abnormalities, including dilatation of the ascending aorta and increased potential for aortic dissection. We compared the mechanical properties of the aortic wall of BAV patients with aortic valve stenosis (AS) and regurgitation (AR) using a dissectometer, a device mimicking transverse aortic wall shear stress. Between March 2010 and February 2013, 85 consecutive patients with bicuspid aortic valve undergoing open aortic valve replacement at our institution were prospectively enrolled, presenting either with stenosis (Group 1, n = 58) or regurgitation (Group 2, n = 27). Aortic wall cohesion measured by the dissectometer (Parameters P7, P8 and P9), aortic diameters measured by transoesophageal echocardiography (TOE) and thickness of the wall were compared. One patient presenting with the Marfan syndrome was excluded from the study. Patients with aortic regurgitation were significantly younger (48.2 ± 15.8 vs 64.7 ± 10.7, P group (27.3 ± 3.6 vs 25.5 ± 2.4, P = 0.008; 41.1 ± 7.7 vs 36.7 ± 8.0, P = 0.011; 37.6 ± 9.7 vs 33.8 ± 9.1, P = 0.049). The ascending aortic diameter did not differ (43.2 ± 10.6 vs 40.3 ± 9.1, P = 0.292). Patients with AR had significantly worse aortic cohesion, as measured by shear stress testing (P7: 97.2 ± 45.0 vs 145.5 ± 84.9, P = 0.015; P8: 2.00 ± 0.65 vs 3.82 ± 1.56, P cohesion, a thicker aortic wall and a larger aortic root in patients presenting with bicuspid AR compared with patients with AS. These results suggest that bicuspid AR represents a different disease process with possible involvement of the ascending aorta, as demonstrated by dissectometer examination. © The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    Drusa Marián

    2016-12-01

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

  11. 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

  12. Relevance, structure and analysis of ferulic acid in maize cell walls.

    Science.gov (United States)

    Bento-Silva, Andreia; Vaz Patto, Maria Carlota; do Rosário Bronze, Maria

    2018-04-25

    Phenolic compounds in foods have been widely studied due to their health benefits. In cereals, phenolic compounds are extensively linked to cell wall polysaccharides, mainly arabinoxylans, which cross-link with each other and with other cell wall components. In maize, ferulic acid is the phenolic acid present in the highest concentration, forming ferulic acid dehydrodimers, trimers and tetramers. The cross-linking of polysaccharides is important for the cell wall structure and growth, and may protect against pathogen invasion. In addition to the importance for maize physiology, ferulic acid has been recognized as an important chemical structure with a wide range of health benefits when consumed in a diet rich in fibre. This review paper presents the different ways ferulic acid can be present in maize, the importance of ferulic acid derivatives and the methodologies that can be used for their analysis. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Near-wall structure of a turbulent boundary layer with riblets

    Science.gov (United States)

    Choi, Kwing-So

    1989-11-01

    A detailed wind tunnel study has been carried out on the near-wall turbulence structure over smooth and riblet wall surfaces under zero pressure gradient. Time-average quantities as well as conditionally sampled profiles were obtained using hot-wire/film anemometry, along with a simultaneous flow visualization using the smoke-wire technique and a sheet of laser light. The experimental results indicated a significant change of the structure in the turbulent boundary layer near the riblet surface. The change was confined within a small volume of the flow close to the wall surface. A conceptual model for the sequence of the bursts was then proposed based on an extensive study of the flow visualization, and was supported by the results of conditionally sampled velocity fields. A possible mechanism of turbulent drag reduction by riblets is discussed.

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

    Directory of Open Access Journals (Sweden)

    Michela Zanetti

    2015-01-01

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

  15. The structure of a fluid confined by permeable walls

    Science.gov (United States)

    Margaritis, Nikolaos; Rickayzen, Gerald

    Osmosis has been studied using the methods of molecular dynamics and for several different models of a semi-permeable barrier. One of these models has also been used in theoretical and Monte Carlo investigations of the effect of such a barrier on the structure of a hard sphere fluid (Marsh, P., Rickayzen, G., and Calleja, M., 1995, Molec. Phys., 84, 799 ; Kim, S.-C., Calleja, M., and Rickayzen, G., 1995, J. Phys.: condens. Matter, 7, 8053). Results presented in these papers showed that this problem also provides a sensitive test for the validity of various density functional theories. In order to bring the theory to bear on the problem of osmosis, this earlier study is extended to the hard core Lennard-Jones fluid. At the same time a new sum rule for the density of a fluid in a periodic potential, which provides a useful check on the computations, is derived. It is again found that the agreement between the computed and the simulated density profiles is good except at the centre of the barrier and when the bulk density and pressure are close to the critical.

  16. Architecture-based multiscale computational modeling of plant cell wall mechanics to examine the hydrogen-bonding hypothesis of the cell wall network structure model.

    Science.gov (United States)

    Yi, Hojae; Puri, Virendra M

    2012-11-01

    A primary plant cell wall network was computationally modeled using the finite element approach to study the hypothesis of hemicellulose (HC) tethering with the cellulose microfibrils (CMFs) as one of the major load-bearing mechanisms of the growing cell wall. A computational primary cell wall network fragment (10 × 10 μm) comprising typical compositions and properties of CMFs and HC was modeled with well-aligned CMFs. The tethering of HC to CMFs is modeled in accordance with the strength of the hydrogen bonding by implementing a specific load-bearing connection (i.e. the joint element). The introduction of the CMF-HC interaction to the computational cell wall network model is a key to the quantitative examination of the mechanical consequences of cell wall structure models, including the tethering HC model. When the cell wall network models with and without joint elements were compared, the hydrogen bond exhibited a significant contribution to the overall stiffness of the cell wall network fragment. When the cell wall network model was stretched 1% in the transverse direction, the tethering of CMF-HC via hydrogen bonds was not strong enough to maintain its integrity. When the cell wall network model was stretched 1% in the longitudinal direction, the tethering provided comparable strength to maintain its integrity. This substantial anisotropy suggests that the HC tethering with hydrogen bonds alone does not manifest sufficient energy to maintain the integrity of the cell wall during its growth (i.e. other mechanisms are present to ensure the cell wall shape).

  17. Improving Thermal Insulation Properties for Prefabricated Wall Components Made Of Lightweight Aggregate Concrete with Open Structure

    Science.gov (United States)

    Abramski, Marcin

    2017-10-01

    Porous concrete is commonly used in civil engineering due to its good thermal insulation properties in comparison with normal concrete and high compression strength in comparison with other building materials. Reducing of the concrete density can be obviously obtained by using lightweight aggregate (e.g. pumice). The concrete density can be further minimized by using specially graded coarse aggregate and little-to-no fine aggregates. In this way a large number of air voids arise. The aggregate particles are coated by a cement paste and bonded together with it just in contact points. Such an extremely porous concrete, called ‘lightweight aggregate concrete with open structure’ (LAC), is used in some German plants to produce prefabricated wall components. They are used mainly in hall buildings, e.g. supermarkets. The need of improving thermal insulation properties was an inspiration for the prefabrication plant managers, engineers and a scientific staff of the Technical University of Kaiserslautern / Germany to realise an interesting project. Its aim was to reduce the heat transfer coefficient for the wall components. Three different wall structure types were designed and compared in full-scale laboratory tests with originally produced wall components in terms of load-carrying capacity and stiffness. The load was applied perpendicularly to the wall plane. As the components are not originally used for load-bearing walls, but for curtain walls only, the wind load is the main load for them. The wall components were tested in horizontal position and the load was applied vertically. Totally twelve wall components 8.00 × 2.00 × 0.25m (three for every series) were produced in the prefabrication plant and tested in the University of Kaiserslautern laboratory. The designed and tested components differed from each other in the amount of expanded polystyrene (EPS), which was placed in the plant inside the wall structure. The minimal amount of it was designed in the

  18. Chest wall – underappreciated structure in sonography. Part I: Examination methodology and ultrasound anatomy

    Directory of Open Access Journals (Sweden)

    Andrzej Smereczyński

    2017-09-01

    Full Text Available Chest wall ultrasound has been awarded little interest in the literature, with chest wall anatomy described only in limited extent. The objective of this study has been to discuss the methodology of chest wall ultrasound and the sonographic anatomy of the region to facilitate professional evaluation of this complex structure. The primarily used transducer is a 7–12 MHz linear one. A 3–5 MHz convex (curvilinear transducer may also be helpful, especially in obese and very muscular patients. Doppler and panoramic imaging options are essential. The indications for chest wall ultrasound include localized pain or lesions found or suspected on imaging with other modalities (conventional radiography, CT, MR or scintigraphy. The investigated pathological condition should be scanned in at least two planes. Sometimes, evaluation during deep breathing permits identification of pathological mobility (e.g. in rib or sternum fractures, slipping rib syndrome. Several structures, closely associated with each other, need to be considered in the evaluation of the chest wall. The skin, which forms a hyperechoic covering, requires a high frequency transducer (20–45 MHz. The subcutaneous fat is characterized by clusters of hypoechoic lobules. Chest muscles have a very complex structure, but their appearance on ultrasound does not differ from the images of muscles located in other anatomical regions. As far as cartilaginous and bony structures of the chest are concerned, the differences in the anatomy of the ribs, sternum, scapula and sternoclavicular joints have been discussed. The rich vascular network which is only fragmentarily accessible for ultrasound assessment has been briefly discussed. A comprehensive evaluation of the chest wall should include the axillary, supraclavicular, apical and parasternal lymph nodes. Their examination requires the use of elastography and contrast-enhanced ultrasound.

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

    Directory of Open Access Journals (Sweden)

    Hadi Taghizadeh

    2015-01-01

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

  20. Analytical and numerical calculations of resistive wall impedances for thin beam pipe structures at low frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Niedermayer, U., E-mail: u.niedermayer@gsi.de [Technische Universitaet Darmstadt, Institut fuer Theorie Elektromagnetischer Felder, Schlossgartenstrasse 8, 64289 Darmstadt (Germany); Boine-Frankenheim, O. [Technische Universitaet Darmstadt, Institut fuer Theorie Elektromagnetischer Felder, Schlossgartenstrasse 8, 64289 Darmstadt (Germany)

    2012-09-21

    The resistive wall impedance is one of the main sources for beam instabilities in synchrotrons and storage rings. The fast ramped SIS18 synchrotron at GSI and the projected SIS100 synchrotron for FAIR both employ thin (0.3 mm) stainless steel beam pipes in order to reduce eddy current effects. The lowest betatron sidebands are at about 100 kHz, which demands accurate impedance predictions in the low frequency (LF) range where the beam pipe and possibly also the structures behind the pipe are the dominating impedance sources. The longitudinal and transverse resistive wall impedances of a circular multi-layer pipe are calculated analytically using the field matching technique. We compare the impedances obtained from a radial wave model, which corresponds to the setup used in bench measurements, with the axial wave model, which corresponds to an actual beam moving with relativistic velocity. For thin beam pipes the induced wall current and the corresponding shielding properties of the pipe are important. In both models the wall current is obtained analytically. The characteristic frequencies for the onset of the wall current are calculated from equivalent lumped element circuits corresponding to the radial model. For more complex structures, like the SIS100 beam pipe, we use a numerical method, in which the impedance is obtained from the total power loss. The method is validated by the analytic expressions for circular beam pipes.

  1. Comparative Structural and functional changes in the heart and aorta of retire active and non- active endurance and bodybuilder athletes

    Directory of Open Access Journals (Sweden)

    Eskandar Rahimi

    2016-06-01

    We concluded that the BA had a greater thickness of LV posterior wall than EI and also they had a significant difference in aortic wall elasticity than BI and EI. This may be due to the Valsalva maneuver or differences in breathing of bodybuilder. We also found that the structure changes of heart in spite of detraining remain for years. Keywords: former endurance athletes, former bodybuilder athletes, Aortic elasticity, cardiac structure and function

  2. A Comparative Study of the Cell Wall Structure of Basidiomycetous and Related Yeasts

    NARCIS (Netherlands)

    Kreger-van Rij, N.J.W.; Veenhuis, M.

    1971-01-01

    The wall of basidiomycetous and related yeasts showed a lamellar structure in sections of both budding cells and hyphae fixed with potassium permanganate. The yeasts also had a typical way of bud formation and septation. These features differ from those recorded for ascomycetous yeasts. In the

  3. PRE-CAST WALL PRODUCTS MADE FROM LIGHTWEIGHT CONCRETE FOR ENCLOSING STRUCTURES OF BUILDINGS

    Directory of Open Access Journals (Sweden)

    M. R. Hadgiev

    2014-01-01

    Full Text Available The paper is devoted to the actual problem waste dismantling of buildings and structures in the form of brick waste with reception the secondary fine and coarse aggregate and concrete based on them for the manufacture of small-piece wall products. 

  4. 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.

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

    International Nuclear Information System (INIS)

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

    2008-01-01

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

  6. Research Status on Reinforcement Connection Form of Precast Concrete Shear Wall Structure

    Science.gov (United States)

    Zhang, Zhuangnan; Zhang, Yan

    2018-03-01

    With the rapid development of Chinese economy and the speeding up the process of urbanization, housing industrialization has been paid more and more attention. And the fabricated structure has been widely used in China. The key of precast concrete shear wall structure is the connection of precast components. The reinforcement connection can directly affect the entirety performance and seismic behavior of the structure. Different reinforcement connections have a great impact on the overall behavior of the structure. By studying the characteristics of the reinforcement connection forms used in the vertical connection and horizontal connection of precast concrete shear wall, it can provide reference for the research and development of the reinforcement connection forms in the future.

  7. Plant cell wall extensibility: connecting plant cell growth with cell wall structure, mechanics, and the action of wall-modifying enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Cosgrove, Daniel J.

    2015-11-25

    The advent of user-friendly instruments for measuring force/deflection curves of plant surfaces at high spatial resolution has resulted in a recent outpouring of reports of the ‘Young's modulus’ of plant cell walls. The stimulus for these mechanical measurements comes from biomechanical models of morphogenesis of meristems and other tissues, as well as single cells, in which cell wall stress feeds back to regulate microtubule organization, auxin transport, cellulose deposition, and future growth directionality. In this article I review the differences between elastic modulus and wall extensibility in the context of cell growth. Some of the inherent complexities, assumptions, and potential pitfalls in the interpretation of indentation force/deflection curves are discussed. Reported values of elastic moduli from surface indentation measurements appear to be 10- to >1000-fold smaller than realistic tensile elastic moduli in the plane of plant cell walls. Potential reasons for this disparity are discussed, but further work is needed to make sense of the huge range in reported values. The significance of wall stress relaxation for growth is reviewed and connected to recent advances and remaining enigmas in our concepts of how cellulose, hemicellulose, and pectins are assembled to make an extensible cell wall. A comparison of the loosening action of α-expansin and Cel12A endoglucanase is used to illustrate two different ways in which cell walls may be made more extensible and the divergent effects on wall mechanics.

  8. Study of the structure of ferroelectric domain walls in barium titanate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Normand, L.; Thorel, A. [Centre des Materiaux, Evry cedex (France) ; Kilaas, R. [Lawrence Berkeley Lab., CA (United States); Montardi, Y. [Rhone-Poulenc, CRA, Aubervilliers (France)

    1995-02-01

    Structure of 90{degree} ferroelectric domain boundaries in barium titanate ceramics has been studied by means of Transmission Electron Microscopy and High Resolution TEM. Tilts of specific fringes across domain walls are measured on HREM images and Selected Area Diffraction Patterns. They are in a good agreement with the twin model admitted for these domain boundaries. A computerized method has been developed to give access to quantitative information about atomic displacements across these ferroelectric domain walls. The so calculated displacement field is then compared with Landau-Ginzburg based theoretical predictions.

  9. 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.

  10. Investigation of structural and electronic properties of double walled Zn O nano tube bundle

    International Nuclear Information System (INIS)

    Moradian, R.; Amjadian, S.; Shahrokhi, M.

    2012-01-01

    We have investigated the structural and electronic properties of isolated double walled Zn O nano tube and its bundle by the first principles calculations in the framework of the density functional theory based on the full-potential augmented plane-wave within the generalized gradient approximation. Our results show that bundle nano tube is more stable than isolated nano tube. In the bundle the inter-tube interaction between each wall with its nearest neighbors causes, band splitting and reduction of semiconducting energy gap.

  11. Study of Local and Distortional Stability of Thin-Walled Structures

    Directory of Open Access Journals (Sweden)

    Imene Mahi

    2018-01-01

    Full Text Available Thin-walled structures have an increasingly large and growing field of application in the engineering sector, the goal behind using this type of structure is efficiency in terms of resistance and cost, however the stability of its components (the thin walls remains the first aspect of the behavior, and a primordial factor in the design process. The hot rolled sections are known by a consequent post-buckling reserve, cold-formed steel sections which are thin-walled elements also benefit, in this case, it seems essential to take into account the favorable effects of this reserve in to the verification procedure of the resistance with respect to the three modes of failures of this type of structure. The design method that takes into account this reserve of resistance is inevitably the effective width method. The direct strength method has been developed to improve the speed and efficiency of the design of thin-walled profiles. The latter mainly uses the buckling loads (for Local, Distortional and Global mode obtained from a numerical analysis and the resistance curves calibrated experimentally to predict the ultimate load of the profile. Among those, the behavior of a set of Cshaped profiles (highly industrialized is studied, this type of section is assumed to be very prone to modes of local and distortional instability. The outcome of this investigation revealed very relevant conclusions both scientifically and practically.

  12. 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.

  13. Pea border cell maturation and release involve complex cell wall structural dynamics

    DEFF Research Database (Denmark)

    Mravec, Jozef; Guo, Xiaoyuan; Hansen, Aleksander Riise

    2017-01-01

    of hydrolytic activities, transmission electron microscopy (TEM) and immunolocalization of cell wall components. Using this integrated glycobiology approach, we identified multiple novel modes of cell wall structural and compositional rearrangement during root cap growth and the release of border cells. Our......The adhesion of plant cells is vital for support and protection of the plant body and is maintained by a variety of molecular associations between cell wall components. In some specialized cases though, plant cells are programmed to detach and root cap-derived border cells are examples of this....... Border cells (in some species known as border-like cells) provide an expendable barrier between roots and the environment. Their maturation and release is an important but poorly characterized cell separation event. To gain a deeper insight into the complex cellular dynamics underlying this process, we...

  14. Irradiation creep lifetime analysis on first wall structure materials for CFETR

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Bing; Peng, Lei, E-mail: penglei@ustc.edu.cn; Zhang, Xiansheng; Shi, Jingyi; Zhan, Jie

    2017-05-15

    Fusion reactor first wall services on the conditions of high surface heat flux and intense neutron irradiation. For China Fusion Engineering Test Reactor (CFETR) with high duty time factor, it is important to analyze the irradiation effect on the creep lifetime of the main candidate structure materials for first wall, i.e. ferritic/martensitic steel, austenite steel and oxide dispersion strengthened steel. The allowable irradiation creep lifetime was evaluated with Larson-Miller Parameter (LMP) model and finite element method. The results show that the allowable irradiation creep lifetime decreases with increasing of surface heat flux, first wall thickness and inlet coolant temperature. For the current CFETR conceptual design, the lifetime is not limited by thermal creep or irradiation creep, which indicated the room for design parameters optimization.

  15. The electronic fine structure of 4-nitrophenyl functionalized single-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Chakraborty, Amit K; Coleman, Karl S; Dhanak, Vinod R

    2009-01-01

    Controlling the electronic structure of carbon nanotubes (CNTs) is of great importance to various CNT based applications. Herein the electronic fine structure of single-walled carbon nanotube films modified with 4-nitrophenyl groups, produced following reaction with 4-nitrobenzenediazonium tetrafluoroborate, was investigated for the first time. Various techniques such as x-ray and ultra-violet photoelectron spectroscopy, and near edge x-ray absorption fine structure studies were used to explore the electronic structure, and the results were compared with the measured electrical resistances. A reduction in number of the π electronic states in the valence band consistent with the increased resistance of the functionalized nanotube films was observed.

  16. Properties of cellulose/pectins composites: implication for structural and mechanical properties of cell wall.

    Science.gov (United States)

    Agoda-Tandjawa, G; Durand, S; Gaillard, C; Garnier, C; Doublier, J L

    2012-10-01

    The primary cell wall of dicotyledonous plants can be considered as a concentrated polymer assembly, containing in particular polysaccharides among which cellulose and pectins are known to be the major components. In order to understand and control the textural quality of plant-derived foods, it is highly important to elucidate the rheological and microstructural properties of these components, individually and in mixture, in order to define their implication for structural and mechanical properties of primary plant cell wall. In this study, the rheological and microstructural properties of model systems composed of sugar-beet microfibrillated cellulose and HM pectins from various sources, with varied degrees of methylation and containing different amounts of neutral sugar side chains, were investigated. The influence of the presence of calcium and/or sodium ions and the biopolymer concentrations on the properties of the mixed systems were also studied. The characterizations of the mixed system, considered as a simplified model of primary plant cell wall, showed that whatever the structural characteristics of the pectins, the ionic conditions of the medium and the biopolymer concentrations, the gelation of the composite was mainly controlled by cellulose. Thus, the cellulose network would be the principal component governing the mechanical properties of the cell walls. However, the neutral sugar side chains of the pectins seem to play a part in the interactions with cellulose, as shown by the interesting viscoelastic properties of cellulose/apple HM pectins systems. The rigidity of cellulose/pectins composite was strongly influenced by the structural characteristics of pectins. The particular properties of primary plant cell walls would thus result from the solid viscoelastic properties of cellulose, its interactions with pectins according to their structural characteristics (implication of the neutral sugar side chains and the specific potential calcic

  17. Aortic root replacement after previous surgical intervention on the aortic valve, aortic root, or ascending aorta.

    Science.gov (United States)

    Kirsch, E W Matthias; Radu, N Costin; Mekontso-Dessap, Armand; Hillion, Marie-Line; Loisance, Daniel

    2006-03-01

    Aortic root replacement after a previous operation on the aortic valve, aortic root, or ascending aorta remains a major challenge. Records of 56 consecutive patients (44 men; mean age, 56.4 +/- 13.6 years) undergoing reoperative aortic root replacement between June 1994 and June 2005 were reviewed retrospectively. Reoperation was performed 9.4 +/- 6.7 years after the last cardiac operation. Indications for reoperation were true aneurysm (n = 14 [25%]), false aneurysm (n = 10 [18%]), dissection or redissection (n = 9 [16%]), structural or nonstructural valve dysfunction (n = 10 [18%]), prosthetic valve-graft infection (n = 12 [21%]), and miscellaneous (n = 1 [2%]). Procedures performed were aortic root replacement (n = 47 [84%]), aortic root replacement plus mitral valve procedure (n = 5 [9%]), and aortic root replacement plus arch replacement (n = 4 [7%]). In 14 (25%) patients coronary artery bypass grafting had to be performed unexpectedly during the same procedure or immediately after the procedure to re-establish coronary perfusion. Hospital mortality reached 17.9% (n = 10). Multivariate logistic regression analysis revealed the need for unplanned perioperative coronary artery bypass grafting as the sole independent risk factor for hospital death (P = .005). Actuarial survival was 83.8% +/- 4.9% at 1 month, 73.0% +/- 6.3% at 1 year, and 65.7% +/- 9.0% at 5 years after the operation. One patient had recurrence of endocarditis 6.7 months after the operation and required repeated homograft aortic root replacement. Reoperative aortic root replacement remains associated with a high postoperative mortality. The need to perform unplanned coronary artery bypass grafting during reoperative aortic root replacement is a major risk factor for hospital death. The optimal technique for coronary reconstruction in this setting remains to be debated.

  18. Methods of Parametric Optimization of Thin-Walled Structures and Parameters which Influence on it

    Directory of Open Access Journals (Sweden)

    Kibkalo Anton

    2016-01-01

    Full Text Available The question of efficiency of thin-walled structures contains a number of contradictions. You need to select the best from all the existing structures on the criteria of optimization options. The search is conducted by varying of the parameters at parametric optimization. As a rule the aim of building structure optimization is reducing of material consumption, the labor input and cost. The costs of a particular variant of construction most full describes the given cost. There are two types of optimization parameters - immutable and varying. The result of the optimization of thin-walled beams will be a combination of parameters for each design situation in which provides the required strength and the minimum of the objective function - factory cost of production

  19. 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.

  20. Aortic Dissection

    Science.gov (United States)

    ... Follow a low-salt diet with plenty of fruits, vegetables and whole grains and exercise regularly. Wear a seat belt. This reduces the risk of traumatic injury to your chest area. Work with your doctor. If you have a family history of aortic dissection, a connective tissue disorder or ...

  1. SSI response of a typical shear wall structure. Appendix B. In-structure response spectra comparisons. Volume 2

    International Nuclear Information System (INIS)

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

    1984-04-01

    The objectives of this study were two-fold: (1) develop building response calibration factors, i.e., factors which relate best estimate or median level response to responses calculated by selected design procedures. Soil-structure interaction was the phenomenon of interest because significant simplifications are frequently introduced in its treatment; and (2) the second objective can be viewed in the context of a question: what effect does placing an identical structure on different sites and with different foundation conditions have on structure response. The structure selected for this study is a part of the Zion AFT complex. Only the auxiliary, fuel-handling, and diesel generator buildings were studied. This structure is a connected group of shear-wall buildings constructed of reinforced concrete, typical of nuclear power plant structures. The bases of comparison for this study were structure responses: peak in-structure accelerations (27 components), and peak wall forces and moments (111 components). In-structure response spectra were also considered. This appendix contains in-structure response spectra comparisons in detail

  2. Hygrothermal Modeling in the Application of Fiber-Reinforced Polymers for Structural Upgrade of Unreinforced Masonry Walls

    National Research Council Canada - National Science Library

    Feickert, Carl A; Lin, Mark W; Trovillion, Jonathan C; Abatan, Ayo O; Berman, Justin B

    2003-01-01

    .... In some instances, these aging structures fail to meet prevailing seismic engineering codes. In the United States alone, 30 percent of the Army's structures use unreinforced masonry (URM) walls...

  3. Experimental validation of tape springs to be used as thin-walled space structures

    Science.gov (United States)

    Oberst, S.; Tuttle, S. L.; Griffin, D.; Lambert, A.; Boyce, R. R.

    2018-04-01

    With the advent of standardised launch geometries and off-the-shelf payloads, space programs utilising nano-satellite platforms are growing worldwide. Thin-walled, flexible and self-deployable structures are commonly used for antennae, instrument booms or solar panels owing to their lightweight, ideal packaging characteristics and near zero energy consumption. However their behaviour in space, in particular in Low Earth Orbits with continually changing environmental conditions, raises many questions. Accurate numerical models, which are often not available due to the difficulty of experimental testing under 1g-conditions, are needed to answer these questions. In this study, we present on-earth experimental validations, as a starting point to study the response of a tape spring as a representative of thin-walled flexible structures under static and vibrational loading. Material parameters of tape springs in a singly (straight, open cylinder) and a doubly curved design, are compared to each other by combining finite element calculations, with experimental laser vibrometry within a single and multi-stage model updating approach. While the determination of the Young's modulus is unproblematic, the damping is found to be inversely proportional to deployment length. With updated material properties the buckling instability margin is calculated using different slenderness ratios. Results indicate a high sensitivity of thin-walled structures to miniscule perturbations, which makes proper experimental testing a key requirement for stability prediction on thin-elastic space structures. The doubly curved tape spring provides closer agreement with experimental results than a straight tape spring design.

  4. Arabidopsis seed coat mucilage is a specialized cell wall that can be used as a model for genetic analysis of plant cell wall structure and function

    Directory of Open Access Journals (Sweden)

    George Wentzel Haughn

    2012-04-01

    Full Text Available Arabidopsis seed coat epidermal cells produce a large quantity of mucilage that is extruded upon exposure to water. Chemical analyses and cell biological techniques suggest that this mucilage represents a specialized type of secondary cell wall composed primarily of pectin with lesser amounts of cellulose and xyloglucan. Once extruded, the mucilage capsule has a distinctive structure with an outer non-adherent layer that is easily removed by shaking in water, and an inner adherent layer that can only be removed with strong acid or base. Most of the cellulose in the mucilage is present in the inner layer and is responsible at least in part for its adherence to the seed. There are also differences in the pectin composition between the two layers that could contribute to the difference in adherence. The Arabidopsis seed coat epidermis and its mucilage are not essential for seed viability or germination. This dispensability, combined with the fact that the epidermal cells synthesize an accessible pectin-rich cell wall at a specific time in development, makes them well suited as a genetic model for studying cell wall biogenesis, function and regulation. Mutants defective in seed mucilage identified by both forward and reverse genetic analyses are proving useful in establishing connections between carbohydrate structure and cell wall properties in vivo. In the future, genetic engineering of seed coat mucilage carbohydrates should prove useful for testing hypotheses concerning cell wall structure and function.

  5. Arabidopsis Seed Coat Mucilage is a Specialized Cell Wall that Can be Used as a Model for Genetic Analysis of Plant Cell Wall Structure and Function.

    Science.gov (United States)

    Haughn, George W; Western, Tamara L

    2012-01-01

    Arabidopsis seed coat epidermal cells produce a large quantity of mucilage that is extruded upon exposure to water. Chemical analyses and cell biological techniques suggest that this mucilage represents a specialized type of secondary cell wall composed primarily of pectin with lesser amounts of cellulose and xyloglucan. Once extruded, the mucilage capsule has a distinctive structure with an outer non-adherent layer that is easily removed by shaking in water, and an inner adherent layer that can only be removed with strong acid or base. Most of the cellulose in the mucilage is present in the inner layer and is responsible at least in part for its adherence to the seed. There are also differences in the pectin composition between the two layers that could contribute to the difference in adherence. The Arabidopsis seed coat epidermis and its mucilage are not essential for seed viability or germination. This dispensability, combined with the fact that the epidermal cells synthesize an accessible pectin-rich cell wall at a specific time in development, makes them well suited as a genetic model for studying cell wall biogenesis, function, and regulation. Mutants defective in seed mucilage identified by both forward and reverse genetic analyses are proving useful in establishing connections between carbohydrate structure and cell wall properties in vivo. In the future, genetic engineering of seed coat mucilage carbohydrates should prove useful for testing hypotheses concerning cell wall structure and function.

  6. 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.

  7. Micro laser metal wire deposition for additive manufacturing of thin-walled structures

    Science.gov (United States)

    Demir, Ali Gökhan

    2018-01-01

    In this work, the micro laser metal wire deposition (μLMWD) process is studied as an additive manufacturing process for manufacturing thin walled structures with high aspect ratio. The developed μLMWD system consisted of a flash-pumped Nd:YAG laser source operating with ms-long pulses and an in-house developed wire feeding system. Processing conditions were investigated for single and multi-layer deposition in terms of geometry, microhardness and material use efficiency. Thin-walled structures with aspect ratio up to 20 were manufactured successfully, where layer width was between 700 and 800 μm. In multi-layer deposition conditions, the material use efficiency was observed to be close to 100%. The microhardness over the build direction was homogenous. The results show that the μLMWD process yields geometrical resolution close to powder-bed additive manufacturing processes, while maintaining the benefits of using wire feedstock.

  8. The bicuspid aortic valve and its relation to aortic dilation

    Directory of Open Access Journals (Sweden)

    Shi-Min Yuan

    2010-01-01

    Full Text Available BACKGROUND: A bicuspid aortic valve (BAV is a common congenital heart disease, which affects 1-2% of the population. However, the relationship between BAVs and aortic dilation has not been sufficiently elucidated. METHODS: A total of 241 BAV patients who were referred to this hospital for cardiac surgey over a 4.75-year period were included in this study. In addition to the clinical characteristics of the included patients, the morphological features of the aortic valve and aorta, the length of the left main coronary artery, and the laboratory findings (the coagulation and hematological parameters as well as the total cholesterol concentration were determined and compared with those of the tricuspid aortic valve (TAV patients. RESULTS: The BAV patients were younger than the TAV patients for a valve surgery in the last 3 months of the study period. The BAV patients were predominantly male. Most of the BAVs that were surgically treated were stenotic, regurgitant, or combined, and only 19 (7.88% were normally functioning valves. According to echocardiography or operative records, 148 (78.31% were type A, 31 (16.40% were type B, and 10 (5.29% were type C. The left main coronary artery was much shorter in the BAV patients than it was in the TAV patients. There was no significant difference between BAV and TAV patients in the total cholesterol concentrations; whereas differences were noted between patients receiving lipid-lowering therapy and those not receiving lipid-lowering therapy. The dimensions of the aortic root, sinotubular junction, and ascending aorta were beyond normal limits, while they were significantly smaller in the BAV patients than in the TAV patients. They were also much smaller in patients receiving statin therapy than those not receiving statin therapy in both groups. Moreover, the aortic dilation in the BAV group was found to be significantly associated with patient age. CONCLUSIONS: The BAV patients developed aortic wall and

  9. Two-leaf wall structures under 'soft' impact load - aircraft crash

    International Nuclear Information System (INIS)

    Eibl, J.; Block, K.

    1982-01-01

    The article describes a mechanical model with which the load conditions associated with aircraft crash on a two-leaf wall or roof structure can be analysed quite simply. The necessary assumptions for the material behaviour governing the contact of the two slabs and, in general, the maximum limit deformations of reinforced concrete slabs are more particularly dealt with. Treating the problem the authors make use, inter alia, of some of their own experimental results. (orig.)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-06-15

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

  11. Sensitivity to fuel diesel oil and cell wall structure of some Scenedesmus (Chlorococcales strains

    Directory of Open Access Journals (Sweden)

    Zbigniew Tukaj

    2014-01-01

    Full Text Available Sensitivity of three Scenedesmus strains exposed to aqueous fuel-oil extract (AFOE is strongly strain-dependent S. quadricauda is the most resistant, S. armatus moderately tolerant whereas the most sensitive appears to be S. microspina. The sensitivity of tested species increases parallel with decreasing of cell size and cell number in coenobium. The values of the cell surface/cell volumes ratios only partly explain the above relationships. Electron microscope investigations reveal that the sensitivity may depend on cell wall structure of the strains. Cell wall of all here investigated strains is built of two layers: the inner so-called cellulosic layer and the outer one showing a three-laminar structure (TLS. The latter contains an acetolysis-resistant biopolymer (ARB. These two layers are similar in thickness in the three strains tested, but the surface of Scenedesmus is covered with various epistructures that are characteristic of strains. Some of them as the tightly fitting warty layer of S. armatus and especially the loosely fitting reticulate layer of S. quadricauda may contribute to lower permeability of cell wall. The structure of the rosettes also appears to be correlated with the sensitivity of strains. Presence of invaginations of plasmalemma in areas under rosettes indicates their role in transport processes inside/outside the cells.

  12. 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".

  13. Transcatheter aortic valve replacement

    Science.gov (United States)

    ... gov/ency/article/007684.htm Transcatheter aortic valve replacement To use the sharing features on this page, please enable JavaScript. Transcatheter aortic valve replacement (TAVR) is surgery to replace the aortic valve. ...

  14. Aortic Valve Regurgitation

    Science.gov (United States)

    ... correct direction. These valves include the mitral valve, tricuspid valve, pulmonary valve and aortic valve. Each valve has ... Causes of aortic valve regurgitation include: Congenital heart valve disease. You may have been born with an aortic ...

  15. 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 parti......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...... 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...

  16. The pore wall structure of porous semi-crystalline anatase TiO2

    International Nuclear Information System (INIS)

    Kim, Man-Ho; Doh, Jeong-Mann; Han, Seong Chul; Chae, Keun Hwa; Yu, Byung-Yong; Hong, Kyung Tae; Jackson, Andrew; Maryland Univ., College Park, MD; Anovitz, Lawrence M.

    2011-01-01

    The structure of porous TiO 2 prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular in shape, were widely distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating that the interface between TiO2 and the pore was not sharp. A density gradient of around 40-60 A at the pore wall (i.e. the interface between the pore and the TiO 2 matrix) was estimated using both constant and semi-sigmoidal interface models. This gradient may be due to the presence of fluorine and carbon partially absorbed by the pore wall from the fluoride-containing electrolyte or to sorbed water molecules on the wall. The neutron contrast-matching point between the TiO 2 matrix and the pores filled with liquid H 2 O/D 2 O mixtures was 51/49%(v/v) H 2 O/D 2 O, yielding an estimated mass density of 3.32 g cm -3 . The specific surface area of the sample derived from the (U)SANS data was around 939-1003 m 2 cm -3 (283-302 m 2 g -1 ). (orig.)

  17. The pore wall structure of porous semi-crystalline anatase TiO2.

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dr Man-Ho [National Institute of Standards and Technol/University of Maryland, College Park; Doh, Dr. Jeong-Mann [Harbin Institute of Technology & Korea Institute of Science and Technology; Han, Seong Chul [Harbin Institute of Technology & Korea Institute of Science and Technology; Chae, Keun Hwa [Harbin Institute of Technology & Korea Institute of Science and Technology; Yu, Byung-Yong [Harbin Institute of Technology & Korea Institute of Science and Technology; Hong, Kyung Tea [Harbin Institute of Technology & Korea Institute of Science and Technology; Jackson, Andrew [NIST Center for Neutron Research (NCRN), Gaithersburg, MD; Anovitz, Lawrence {Larry} M [ORNL

    2011-01-01

    The structure of porous TiO2 prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular in shape, were widely distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating that the interface between TiO2 and the pore was not sharp. A density gradient of around 40 60 A at the pore wall (i.e. the interface between the pore and the TiO2 matrix) was estimated using both constant and semi-sigmoidal interface models. This gradient may be due to the presence of fluorine and carbon partially absorbed by the pore wall from the fluoride-containing electrolyte or to sorbed water molecules on the wall. The neutron contrast-matching point between the TiO2 matrix and the pores filled with liquid H2O/D2O mixtures was 51/49%(v/v) H2O/D2O, yielding an estimated mass density of 3.32 g cm3. The specific surface area of the sample derived from the (U)SANS data was around 939 1003 m2 cm3 (283 302 m2 g1).

  18. Rocket-inspired tubular catalytic microjets with grating-structured walls as guiding empennages.

    Science.gov (United States)

    Huang, Gaoshan; Wang, Jiyuan; Liu, Zhaoqian; Zhou, Dekai; Tian, Ziao; Xu, Borui; Li, Longqiu; Mei, Yongfeng

    2017-12-07

    Controllable locomotion in the micro-/nanoscale is challenging and attracts increasing research interest. Tubular microjets self-propelled by microbubbles are intensively investigated due to their high energy conversion efficiency, but the imperfection of the tubular geometry makes it harder to realize linear motion. Inspired by the macro rocket, we designed a tubular microjet with a grating-structured wall which mimics the guiding empennage of the macro rocket, and we found that the fluid can be effectively guided by the grooves. Both theoretical simulation and experimental work have been carried out, and the obtained results demonstrate that the stability margin of the grating-structured microjet can be enhanced. Compared with microjets with smooth walls, the structured microjets show an enhanced ability of moving linearly. In 10% H 2 O 2 , only 20% of the smooth microjets demonstrate linear trajectories, while 80% of the grating-structured microjets keep moving straight. The grating-structured microjet can maintain linear motion under external disturbance. We further propose to increase the stability by introducing a helical grating structure.

  19. Reoperative Aortic Root Replacement in Patients with Previous Aortic Root or Aortic Valve Procedures

    Directory of Open Access Journals (Sweden)

    Byung Kwon Chong

    2016-08-01

    Full Text Available Background: Generalization of standardized surgical techniques to treat aortic valve (AV and aortic root diseases has benefited large numbers of patients. As a consequence of the proliferation of patients receiving aortic root surgeries, surgeons are more frequently challenged by reoperative aortic root procedures. The aim of this study was to evaluate the outcomes of redo-aortic root replacement (ARR. Methods: We retrospectively reviewed 66 patients (36 male; mean age, 44.5±9.5 years who underwent redo-ARR following AV or aortic root procedures between April 1995 and June 2015. Results: Emergency surgeries comprised 43.9% (n=29. Indications for the redo-ARR were aneurysm (n=12, pseudoaneurysm (n=1, or dissection (n=6 of the residual native aortic sinus in 19 patients (28.8%, native AV dysfunction in 8 patients (12.1%, structural dysfunction of an implanted bioprosthetic AV in 19 patients (28.8%, and infection of previously replaced AV or proximal aortic grafts in 30 patients (45.5%. There were 3 early deaths (4.5%. During follow- up (median, 54.65 months; quartile 1–3, 17.93 to 95.71 months, there were 14 late deaths (21.2%, and 9 valve-related complications including reoperation of the aortic root in 1 patient, infective endocarditis in 3 patients, and hemorrhagic events in 5 patients. Overall survival and event-free survival rates at 5 years were 81.5%±5.1% and 76.4%±5.4%, respectively. Conclusion: Despite technical challenges and a high rate of emergency conditions in patients requiring redo-ARR, early and late outcomes were acceptable in these patients.

  20. Optimal Shakedown of the Thin-Wall Metal Structures Under Strength and Stiffness Constraints

    Directory of Open Access Journals (Sweden)

    Alawdin Piotr

    2017-06-01

    Full Text Available Classical optimization problems of metal structures confined mainly with 1st class cross-sections. But in practice it is common to use the cross-sections of higher classes. In this paper, a new mathematical model for described shakedown optimization problem for metal structures, which elements are designed from 1st to 4th class cross-sections, under variable quasi-static loads is presented. The features of limited plastic redistribution of forces in the structure with thin-walled elements there are taken into account. Authors assume the elastic-plastic flexural buckling in one plane without lateral torsional buckling behavior of members. Design formulae for Methods 1 and 2 for members are analyzed. Structures stiffness constrains are also incorporated in order to satisfy the limit serviceability state requirements. With the help of mathematical programming theory and extreme principles the structure optimization algorithm is developed and justified with the numerical experiment for the metal plane frames.

  1. Recent progress on the structure separation of single-wall carbon nanotubes

    Science.gov (United States)

    Cui, Jiaming; Yang, Dehua; Zeng, Xiang; Zhou, Naigen; Liu, Huaping

    2017-11-01

    The mass production of single-structure, single-wall carbon nanotubes (SWCNTs) with identical properties is critical for their basic research and technical applications in the fields of electronics, optics and optoelectronics. Great efforts have been made to control the structures of SWCNTs since their discovery. Recently, the structure separation of SWCNTs has been making great progress. Various solution-sorting methods have been developed to achieve not only the separation of metallic and semiconducting species, but also the sorting of distinct (n, m) single-chirality species and even their enantiomers. This progress would dramatically accelerate the application of SWCNTs in the next-generation electronic devices. Here, we review the recent progress in the structure sorting of SWCNTs and outline the challenges and prospects of the structure separation of SWCNTs.

  2. 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.

  3. Structural Insights into Protein-Protein Interactions Involved in Bacterial Cell Wall Biogenesis

    Directory of Open Access Journals (Sweden)

    Federica Laddomada

    2016-04-01

    Full Text Available The bacterial cell wall is essential for survival, and proteins that participate in its biosynthesis have been the targets of antibiotic development efforts for decades. The biosynthesis of its main component, the peptidoglycan, involves the coordinated action of proteins that are involved in multi-member complexes which are essential for cell division (the “divisome” and/or cell wall elongation (the “elongasome”, in the case of rod-shaped cells. Our knowledge regarding these interactions has greatly benefitted from the visualization of different aspects of the bacterial cell wall and its cytoskeleton by cryoelectron microscopy and tomography, as well as genetic and biochemical screens that have complemented information from high resolution crystal structures of protein complexes involved in divisome or elongasome formation. This review summarizes structural and functional aspects of protein complexes involved in the cytoplasmic and membrane-related steps of peptidoglycan biosynthesis, with a particular focus on protein-protein interactions whereby disruption could lead to the development of novel antibacterial strategies.

  4. Outer Hair Cell Lateral Wall Structure Constrains the Mobility of Plasma Membrane Proteins.

    Science.gov (United States)

    Yamashita, Tetsuji; Hakizimana, Pierre; Wu, Siva; Hassan, Ahmed; Jacob, Stefan; Temirov, Jamshid; Fang, Jie; Mellado-Lagarde, Marcia; Gursky, Richard; Horner, Linda; Leibiger, Barbara; Leijon, Sara; Centonze, Victoria E; Berggren, Per-Olof; Frase, Sharon; Auer, Manfred; Brownell, William E; Fridberger, Anders; Zuo, Jian

    2015-09-01

    Nature's fastest motors are the cochlear outer hair cells (OHCs). These sensory cells use a membrane protein, Slc26a5 (prestin), to generate mechanical force at high frequencies, which is essential for explaining the exquisite hearing sensitivity of mammalian ears. Previous studies suggest that Slc26a5 continuously diffuses within the membrane, but how can a freely moving motor protein effectively convey forces critical for hearing? To provide direct evidence in OHCs for freely moving Slc26a5 molecules, we created a knockin mouse where Slc26a5 is fused with YFP. These mice and four other strains expressing fluorescently labeled membrane proteins were used to examine their lateral diffusion in the OHC lateral wall. All five proteins showed minimal diffusion, but did move after pharmacological disruption of membrane-associated structures with a cholesterol-depleting agent and salicylate. Thus, our results demonstrate that OHC lateral wall structure constrains the mobility of plasma membrane proteins and that the integrity of such membrane-associated structures are critical for Slc26a5's active and structural roles. The structural constraint of membrane proteins may exemplify convergent evolution of cellular motors across species. Our findings also suggest a possible mechanism for disorders of cholesterol metabolism with hearing loss such as Niemann-Pick Type C diseases.

  5. Outer Hair Cell Lateral Wall Structure Constrains the Mobility of Plasma Membrane Proteins.

    Directory of Open Access Journals (Sweden)

    Tetsuji Yamashita

    2015-09-01

    Full Text Available Nature's fastest motors are the cochlear outer hair cells (OHCs. These sensory cells use a membrane protein, Slc26a5 (prestin, to generate mechanical force at high frequencies, which is essential for explaining the exquisite hearing sensitivity of mammalian ears. Previous studies suggest that Slc26a5 continuously diffuses within the membrane, but how can a freely moving motor protein effectively convey forces critical for hearing? To provide direct evidence in OHCs for freely moving Slc26a5 molecules, we created a knockin mouse where Slc26a5 is fused with YFP. These mice and four other strains expressing fluorescently labeled membrane proteins were used to examine their lateral diffusion in the OHC lateral wall. All five proteins showed minimal diffusion, but did move after pharmacological disruption of membrane-associated structures with a cholesterol-depleting agent and salicylate. Thus, our results demonstrate that OHC lateral wall structure constrains the mobility of plasma membrane proteins and that the integrity of such membrane-associated structures are critical for Slc26a5's active and structural roles. The structural constraint of membrane proteins may exemplify convergent evolution of cellular motors across species. Our findings also suggest a possible mechanism for disorders of cholesterol metabolism with hearing loss such as Niemann-Pick Type C diseases.

  6. The effect of functionalization on structure and electrical conductivity of multi-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Lau, Cher Hon; Cervini, Raoul; Clarke, Stephen R.; Markovic, Milena Ginic; Matisons, Janis G.; Hawkins, Stephen C.; Huynh, Chi P.; Simon, George P.

    2008-01-01

    Carbon nanotubes (CNTs) are of interest in many areas of nanotechnology and used in a number of novel applications. However effective dispersion remains a problem and one solution is to functionalize the nanotubes. Any functionalization that is undertaken must preferably not influence other key properties such as strength and electrical conductivity. In this work, multi-walled CNTs are functionalized for comparison, using a range of oxidative techniques, including thermal treatment, acid reflux, and dry UV-ozonolysis. The effects of these treatments on the multi-walled carbon nanotubes (MWCNTs) and their electrical properties were characterized using a range of surface and compositional techniques. The electrical conductivity of MWCNTs was found to increase with functionalization in all cases, and dry UV-ozonolysis was shown to be the treatment technique which best increased conductivity, whilst at the same time maintaining the structural integrity of the nanotubes, even though the level of modification was less than by the other treatment methods.

  7. Steel Plate Shear Walls: Efficient Structural Solution for Slender High-Rise in China

    International Nuclear Information System (INIS)

    Mathias, Neville; Long, Eric; Sarkisian, Mark; Huang Zhihui

    2008-01-01

    The 329.6 meter tall 74-story Jinta Tower in Tianjin, China, is expected, when complete, to be the tallest building in the world with slender steel plate shear walls used as the primary lateral load resisting system. The tower has an overall aspect ratio close to 1:8, and the main design challenge was to develop an efficient lateral system capable of resisting significant wind and seismic lateral loads, while simultaneously keeping wind induced oscillations under acceptable perception limits. This paper describes the process of selection of steel plate shear walls as the structural system, and presents the design philosophy, criteria and procedures that were arrived at by integrating the relevant requirements and recommendations of US and Chinese codes and standards, and current on-going research

  8. Thoracic Aortic Rupture and Aortopulmonary Fistulation in the Friesian Horse : Histomorphologic Characterization

    NARCIS (Netherlands)

    Ploeg, M; Saey, V; Delesalle, C; Gröne, A; Ducatelle, R; de Bruijn, M; Back, W; van Weeren, P R; van Loon, G; Chiers, K

    Aortic rupture in horses is a rare condition. Although it is relatively common in the Friesian breed, only limited histopathologic information is available. Twenty Friesian horses (1-10 years old) were diagnosed with aortic rupture by postmortem examination. Ruptured aortic walls were analyzed with

  9. Plasma levels of plasmin-antiplasmin-complexes are predictive for small abdominal aortic aneurysms expanding to operation-recommendable sizes

    DEFF Research Database (Denmark)

    Lindholt, Jes Sanddal; Jørgensen, B; Fasting, H

    2001-01-01

    Three proteolytic systems seem involved in the aneurysmal degradation of the aortic wall. Plasmin is a common activator of the systems and could thus be predictive for the progression of abdominal aortic aneurysms (AAAs).......Three proteolytic systems seem involved in the aneurysmal degradation of the aortic wall. Plasmin is a common activator of the systems and could thus be predictive for the progression of abdominal aortic aneurysms (AAAs)....

  10. Degenerated shell element for geometrically nonlinear analysis of thin-walled piezoelectric active structures

    International Nuclear Information System (INIS)

    Marinković, D; Köppe, H; Gabbert, U

    2008-01-01

    Active piezoelectric thin-walled structures, especially those with a notably higher membrane than bending stiffness, are susceptible to large rotations and transverse deflections. Recent investigations conducted by a number of researchers have shown that the predicted behavior of piezoelectric structures can be significantly influenced by the assumption of large displacements and rotations of the structure, thus demanding a geometrically nonlinear formulation in order to investigate it. This paper offers a degenerated shell element and a simplified formulation that relies on small incremental steps for the geometrically nonlinear analysis of piezoelectric composite structures. A set of purely mechanical static cases is followed by a set of piezoelectric coupled static cases, both demonstrating the applicability of the proposed formulation

  11. Study of the ruining behaviour of a structure with reinforced concrete carrying walls

    International Nuclear Information System (INIS)

    Manas, B.

    1998-06-01

    Nuclear facility buildings must be constructed with the respect of para-seismic rules. These rules are defined according to the most probable seismic risk estimated for the sites. This study concerns the ruining behaviour of a structure made of reinforced concrete walls. In a first part, a preliminary study on reinforced concrete is performed with the Castem 2000 finite elements code. This study emphasizes the non-linear phenomena that take place inside the material, such as the cracking of concrete and the plasticization of steels. In a second part, predictive calculations were performed on a U-shape structure. This structure was submitted to earthquakes of various magnitudes and the response of the structure was analyzed and interpreted. (J.S.)

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

    Directory of Open Access Journals (Sweden)

    de Gijt J.G.

    2015-12-01

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

  13. Structure of Cellulose Microfibrils in Primary Cell Walls from Collenchyma1[C][W][OA

    Science.gov (United States)

    Thomas, Lynne H.; Forsyth, V. Trevor; Šturcová, Adriana; Kennedy, Craig J.; May, Roland P.; Altaner, Clemens M.; Apperley, David C.; Wess, Timothy J.; Jarvis, Michael C.

    2013-01-01

    In the primary walls of growing plant cells, the glucose polymer cellulose is assembled into long microfibrils a few nanometers in diameter. The rigidity and orientation of these microfibrils control cell expansion; therefore, cellulose synthesis is a key factor in the growth and morphogenesis of plants. Celery (Apium graveolens) collenchyma is a useful model system for the study of primary wall microfibril structure because its microfibrils are oriented with unusual uniformity, facilitating spectroscopic and diffraction experiments. Using a combination of x-ray and neutron scattering methods with vibrational and nuclear magnetic resonance spectroscopy, we show that celery collenchyma microfibrils were 2.9 to 3.0 nm in mean diameter, with a most probable structure containing 24 chains in cross section, arranged in eight hydrogen-bonded sheets of three chains, with extensive disorder in lateral packing, conformation, and hydrogen bonding. A similar 18-chain structure, and 24-chain structures of different shape, fitted the data less well. Conformational disorder was largely restricted to the surface chains, but disorder in chain packing was not. That is, in position and orientation, the surface chains conformed to the disordered lattice constituting the core of each microfibril. There was evidence that adjacent microfibrils were noncovalently aggregated together over part of their length, suggesting that the need to disrupt these aggregates might be a constraining factor in growth and in the hydrolysis of cellulose for biofuel production. PMID:23175754

  14. 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

  15. Xyloglucan, galactomannan, glucuronoxylan, and rhamnogalacturonan I do not have identical structures in soybean root and root hair cell walls.

    Science.gov (United States)

    Muszyński, Artur; O'Neill, Malcolm A; Ramasamy, Easwaran; Pattathil, Sivakumar; Avci, Utku; Peña, Maria J; Libault, Marc; Hossain, Md Shakhawat; Brechenmacher, Laurent; York, William S; Barbosa, Rommel M; Hahn, Michael G; Stacey, Gary; Carlson, Russell W

    2015-11-01

    Chemical analyses and glycome profiling demonstrate differences in the structures of the xyloglucan, galactomannan, glucuronoxylan, and rhamnogalacturonan I isolated from soybean ( Glycine max ) roots and root hair cell walls. The root hair is a plant cell that extends only at its tip. All other root cells have the ability to grow in different directions (diffuse growth). Although both growth modes require controlled expansion of the cell wall, the types and structures of polysaccharides in the walls of diffuse and tip-growing cells from the same plant have not been determined. Soybean (Glycine max) is one of the few plants whose root hairs can be isolated in amounts sufficient for cell wall chemical characterization. Here, we describe the structural features of rhamnogalacturonan I, rhamnogalacturonan II, xyloglucan, glucomannan, and 4-O-methyl glucuronoxylan present in the cell walls of soybean root hairs and roots stripped of root hairs. Irrespective of cell type, rhamnogalacturonan II exists as a dimer that is cross-linked by a borate ester. Root hair rhamnogalacturonan I contains more neutral oligosaccharide side chains than its root counterpart. At least 90% of the glucuronic acid is 4-O-methylated in root glucuronoxylan. Only 50% of this glycose is 4-O-methylated in the root hair counterpart. Mono O-acetylated fucose-containing subunits account for at least 60% of the neutral xyloglucan from root and root hair walls. By contrast, a galacturonic acid-containing xyloglucan was detected only in root hair cell walls. Soybean homologs of the Arabidopsis xyloglucan-specific galacturonosyltransferase are highly expressed only in root hairs. A mannose-rich polysaccharide was also detected only in root hair cell walls. Our data demonstrate that the walls of tip-growing root hairs cells have structural features that distinguish them from the walls of other roots cells.

  16. Multi-wall effects on the thermal transport properties of nanotube structures

    International Nuclear Information System (INIS)

    Hata, Tomoyuki; Kawai, Hiroki; Jono, Ryota; Yamashita, Koichi

    2014-01-01

    Understanding the role of inter-layer interactions in multi-walled carbon nanotubes is one of the challenges in the design of potential materials because of their large impact on the physical properties of carbon nanotubes. We focused on the thermal properties of double-walled carbon nanotubes (DWCNTs), which are promising materials due to their high durability and thermal efficiency. We investigated the thermal conductance of DWCNTs by using the nonequilibrium Green’s function method, and found that the quadratic temperature dependence of the thermal conductance at low temperatures consisted of three regions with different tendencies. Based on analysis of the transmission coefficients and the distribution of the normal modes, the three nonuniform regions were attributed to the energy shifts of the normal modes at the low-energy region. We examined the mechanism of these energy shifts using the coupled vibration model with the parameters from our simulations, and elucidated the multi-wall effects on the thermal transport properties of the nanotube structures. The effects we found demonstrated the significance of tailoring thermal properties to obtain the desired applications. (papers)

  17. Multi-walled carbon nanotube structural instability with/without metal nanoparticles under electron beam irradiation

    Science.gov (United States)

    Khan, Imran; Huang, Shengli; Wu, Chenxu

    2017-12-01

    The structural transformation of multi-walled carbon nanotubes (MWCNT) under electron beam (e-beam) irradiation at room temperature is studied, with respect to a novel passivation effect due to gold nanoparticles (Au NPs). MWCNT structural evolution induced by energetic e-beam irradiation leads to faster shrinkage, as revealed via in situ transmission electron microscopy, while MWCNT surface modification with Au NPs (Au-MWCNT) slows down the shrinkage by impeding the structural evolution process for a prolonged time under the same irradiation conditions. The new relationship between MWCNT and Au-MWCNT shrinking radii and irradiation time illustrates that the MWCNT shrinkage rate is faster than either theoretical predictions or the same process in Au-MWCNTs. As compared with the outer surface energy (positive curvature), the inner surface energy (negative curvature) of the MWCNT contributes more to the athermal evaporation of tube wall atoms, leading to structural instability and shrinkage under e-beam irradiation. Conversely, Au NPs possess only outer surface energy (positive curvature) compared with the MWCNT. Their presence on MWCNT surfaces retards the dynamics of MWCNT structural evolution by slowing down the evaporation process of carbon atoms, thus restricting Au-MWCNT shrinkage. Au NP interaction and growth evolves athermally on MWCNT surfaces, exhibits increase in their size, and indicates the association of this mechanism with the coalescence induced by e-beam activated electronic excitations. Despite their growth, Au NPs show extreme structural stability, and remain crystalline under prolonged irradiation. It is proposed that the surface energy of MWCNTs and Au NPs, together with e-beam activated soft modes or lattice instability effects, predominantly govern all the above varieties of structural evolution.

  18. The structure of the major cell wall polysaccharide of Bacillus anthracis is species-specific.

    Science.gov (United States)

    Choudhury, Biswa; Leoff, Christine; Saile, Elke; Wilkins, Patricia; Quinn, Conrad P; Kannenberg, Elmar L; Carlson, Russell W

    2006-09-22

    In this report we describe the structure of the polysaccharide released from Bacillus anthracis vegetative cell walls by aqueous hydrogen fluoride (HF). This HF-released polysaccharide (HF-PS) was isolated and structurally characterized from the Ames, Sterne, and Pasteur strains of B. anthracis. The HF-PSs were also isolated from the closely related Bacillus cereus ATCC 10987 strain, and from the B. cereus ATCC 14579 type strain and compared with those of B. anthracis. The structure of the B. anthracis HF-PS was determined by glycosyl composition and linkage analyses, matrix-assisted laser desorption-time of flight mass spectrometry, and one- and two-dimensional nuclear magnetic resonance spectroscopy. The HF-PSs from all of the B. anthracis isolates had an identical structure consisting of an amino sugar backbone of -->6)-alpha-GlcNAc-(1-->4)-beta-ManNAc-(1-->4)-beta-GlcNAc-(1-->, in which the alpha-GlcNAc residue is substituted with alpha-Gal and beta-Gal at O-3 and O-4, respectively, and the beta-GlcNAc substituted with alpha-Gal at O-3. There is some variability in the presence of two of these three Gal substitutions. Comparison with the HF-PSs from B. cereus ATCC 10987 and B. cereus ATCC 14579 showed that the B. anthracis structure was clearly different from each of these HF-PSs and, furthermore, that the B. cereus ATCC 10987 HF-PS structure was different from that of B. cereus ATCC 14579. The presence of a B. anthracis-specific polysaccharide structure in its vegetative cell wall is discussed with regard to its relationship to those of other Bacillus species.

  19. 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). ...

  20. Bicuspid Aortic Valve

    Science.gov (United States)

    2006-08-01

    with tricuspid aortic valves matched for age, gender and grade of valvular disease . These studies suggest that the predisposition for aortic...enlargement in healthy patients with normally functioning BAV when compared to healthy subjects with normally functioning tricuspid aortic valves ...ascending aorta but also in the pulmonary arteries of patients with BAV, compared to that of patients with tricuspid aortic valves . These studies

  1. The pore wall structure of porous semi-crystalline anatase TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Man-Ho; Doh, Jeong-Mann; Han, Seong Chul; Chae, Keun Hwa; Yu, Byung-Yong; Hong, Kyung Tae [Korea Institute of Science and Technology, Seoul (Korea, Republic of); Jackson, Andrew [NIST National Institute of Standards and Technology, Gaithersburg, MD (United States). Center for Neutron Research; Maryland Univ., College Park, MD (United States). Dept. of Materials Science and Engineering; Anovitz, Lawrence M. [Oak Ridge National Laboratory, Oak Ridge, TN (United States). Chemical Sciences Div.

    2011-12-15

    The structure of porous TiO{sub 2} prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular in shape, were widely distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating that the interface between TiO2 and the pore was not sharp. A density gradient of around 40-60 A at the pore wall (i.e. the interface between the pore and the TiO{sub 2} matrix) was estimated using both constant and semi-sigmoidal interface models. This gradient may be due to the presence of fluorine and carbon partially absorbed by the pore wall from the fluoride-containing electrolyte or to sorbed water molecules on the wall. The neutron contrast-matching point between the TiO{sub 2} matrix and the pores filled with liquid H{sub 2}O/D{sub 2}O mixtures was 51/49%(v/v) H{sub 2}O/D{sub 2}O, yielding an estimated mass density of 3.32 g cm{sup -3}. The specific surface area of the sample derived from the (U)SANS data was around 939-1003 m{sup 2} cm{sup -3} (283-302 m{sup 2} g{sup -1}). (orig.)

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

    Science.gov (United States)

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

    2015-10-21

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

  3. Nucleon structure in the chiral regime with domain wall fermions on an improved staggered sea

    International Nuclear Information System (INIS)

    R.G. Edwards; G. Fleming; Ph. Hagler; J.W. Negele; K. Orginos; A.V. Pochinsky; D.B. Renner; D.G. Richards; W. Schroers

    2006-01-01

    Moments of unpolarized, helicity, and transversity distributions, electromagnetic form factors, and generalized form factors of the nucleon are presented from a preliminary analysis of lattice results using pion masses down to 359 MeV. The twist two matrix elements are calculated using a mixed action of domain wall valence quarks and asqtad staggered sea quarks and are renormalized perturbatively. Several observables are extrapolated to the physical limit using chiral perturbation theory. Results are compared with experimental moments of quark distributions and electromagnetic form factors and phenomenologically determined generalized form factors, and the implications on the transverse structure and spin content of the nucleon are discussed

  4. 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. 

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

    International Nuclear Information System (INIS)

    Majumdar, S.

    1998-01-01

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

  6. A rare case of discrete aortic coarctation in Williams-Beuren syndrome. Diagnostic and therapeutic considerations

    OpenAIRE

    Savina Mannarino; Eitan Keizman; Michele Pasotti; Alessia Claudia Codazzi; Elisabetta De Sando; Alessandro Giamberti

    2015-01-01

    Williams-Beuren syndrome (WBS) is a genetic disorder caused by elastin gene deletions, and is characterized by cardiovascular malformations, primarily including supravalvular aortic stenosis and peripheral pulmonary stenosis. We report a case of a neonate who developed severe discrete aortic coarctation, underwent multiple surgical interventions, and was subsequently diagnosed with WBS. Severe discrete aortic coarctation is a rare event in WBS newborns. An abnormally thick aortic wall is pres...

  7. Effect of personalized external aortic root support on aortic root motion and distension in Marfan syndrome patients.

    Science.gov (United States)

    Izgi, Cemil; Nyktari, Evangelia; Alpendurada, Francisco; Bruengger, Annina Studer; Pepper, John; Treasure, Tom; Mohiaddin, Raad

    2015-10-15

    Personalized external aortic root support (PEARS) is a novel surgical approach with the aim of stabilizing the aortic root size and decreasing risk of dissection in Marfan syndrome patients. A bespoke polymer mesh tailored to each patient's individual aorta shape is produced by modeling and then surgically implanted. The aim of this study is to assess the mechanical effects of PEARS on the aortic root systolic downward motion (an important determinant of aortic wall stress), aortic root distension and on the left ventricle (LV). A cohort of 27 Marfan patients had a prophylactic PEARS surgery between 2004 and 2012 with 24 having preoperative and follow-up cardiovascular magnetic resonance imaging studies. Systolic downward aortic root motion, aortic root distension, LV volumes/mass and mitral annular systolic excursion before the operation and in the latest follow-up were measured randomly and blinded. After a median follow-up of 50.5 (IQR 25.5-72) months following implantation of PEARS, systolic downward motion of aortic root was significantly decreased (12.6±3.6mm pre-operation vs 7.9±2.9mm latest follow-up, p<0.00001). There was a tendency for a decrease in systolic aortic root distension but this was not significant (median 4.5% vs 2%, p=0.35). There was no significant change in LV volumes, ejection fraction, mass and mitral annular systolic excursion in follow-up. PEARS surgery decreases systolic downward aortic root motion which is an important determinant of longitudinal aortic wall stress. Aortic wall distension and Windkessel function are not significantly impaired in the follow-up after implantation of the mesh which is also supported by the lack of deterioration of LV volumes or mass. Crown Copyright © 2015. Published by Elsevier Ireland Ltd. All rights reserved.

  8. The bicuspid aortic valve and related disorders

    Directory of Open Access Journals (Sweden)

    Shi-Min Yuan

    Full Text Available Bicuspid aortic valve (BAV is the most common congenital cardiac malformation, affecting 1-2% of the population, with strong male predominance. Individuals may have a normally functioning BAV, and may be unaware of its presence and the potential risk of complications. However, they may easily develop aortic valve disorders: either stenotic or regurgitant, or both. Today, BAV is recognized as a syndrome incorporating aortic valve disorders and aortic wall abnormalities, including aortic dilation, dissection or rupture. Congenital or hereditary diseases such as ventricular septal defect, patent ductus arteriosus, coarctation of the aorta, Turner's syndrome, Marfan's syndrome etc., may frequently be associated with BAV. Infective endocarditis and occasionally thrombus formation may develop during the lives of BAV patients. Elevated cholesterol or C-reactive protein may be seen in laboratory findings of these patients. Beta-blockers and statins are the possibilities for medical treatment, and aortic valve repair/replacement and ascending aorta replacement are indicated for patients with a severely diseased aortic valve and aorta. Rigorous follow-up throughout life is mandatory after BAV has been diagnosed. The aim of the present article was to describe the implications of BAV and its associated disorders, and to discuss diagnostic and treatment strategies.

  9. Arabidopsis Seed Coat Mucilage is a Specialized Cell Wall that Can be Used as a Model for Genetic Analysis of Plant Cell Wall Structure and Function

    OpenAIRE

    Haughn, George W.; Western, Tamara L.

    2012-01-01

    Arabidopsis seed coat epidermal cells produce a large quantity of mucilage that is extruded upon exposure to water. Chemical analyses and cell biological techniques suggest that this mucilage represents a specialized type of secondary cell wall composed primarily of pectin with lesser amounts of cellulose and xyloglucan. Once extruded, the mucilage capsule has a distinctive structure with an outer non-adherent layer that is easily removed by shaking in water, and an inner adherent layer that ...

  10. 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

  11. Thermal-structural analysis of regeneratively-cooled thrust chamber wall in reusable LOX/Methane rocket engines

    Directory of Open Access Journals (Sweden)

    Jiawen SONG

    2017-06-01

    Full Text Available To predict the thermal and structural responses of the thrust chamber wall under cyclic work, a 3-D fluid-structural coupling computational methodology is developed. The thermal and mechanical loads are determined by a validated 3-D finite volume fluid-thermal coupling computational method. With the specified loads, the nonlinear thermal-structural finite element analysis is applied to obtaining the 3-D thermal and structural responses. The Chaboche nonlinear kinematic hardening model calibrated by experimental data is adopted to predict the cyclic plastic behavior of the inner wall. The methodology is further applied to the thrust chamber of LOX/Methane rocket engines. The results show that both the maximum temperature at hot run phase and the maximum circumferential residual strain of the inner wall appear at the convergent part of the chamber. Structural analysis for multiple work cycles reveals that the failure of the inner wall may be controlled by the low-cycle fatigue when the Chaboche model parameter γ3 = 0, and the damage caused by the thermal-mechanical ratcheting of the inner wall cannot be ignored when γ3 > 0. The results of sensitivity analysis indicate that mechanical loads have a strong influence on the strains in the inner wall.

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

    Science.gov (United States)

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

    2017-11-01

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

  13. Fabrication of cylindrical superhydrophobic microchannels by replicating lotus leaf structures on internal walls

    Science.gov (United States)

    Das, Ajit; Bhaumik, Soubhik Kumar

    2018-04-01

    Cylindrical superhydrophobic microchannels are fabricated by replicating lotus leaf structures on internal walls. The fabrication process comprises of three steps: the creation of a cylindrical mold of a glass rod (125 µm) with polystyrene films bearing negative imprints of lotus leaf (superhydrophobic) structures; casting polydimethylsiloxane (PDMS, Sylgard 184) over the mold; and solvent-assisted pulling off of the glass rod to leave a positive replica on the inner wall of the PDMS cast. The last crucial step is achieved through selective dissolution of the intermediate negative replica layer in the cylindrical mold without any swelling effect. The high fidelity of the replication process is confirmed through scanning electron microscope (SEM) imaging. The attained superhydrophobicity is assessed by comparing the dynamics of the advancing meniscus in the fabricated microchannels with that over a similarly fabricated smooth microchannel. Contact angle studies of the meniscus reveal a lower capillary effect and drag force experienced by the superhydrophobic microchannel compared to smooth ones. Studies based on velocity lead to a prediction of a drag reduction of 35%. A new avenue is thus opened up for microfabrication and flow analysis of closed superhydrophobic (SH) conduits in lab on chip and microfluidic applications.

  14. Substructure hybrid testing of reinforced concrete shear wall structure using a domain overlapping technique

    Science.gov (United States)

    Zhang, Yu; Pan, Peng; Gong, Runhua; Wang, Tao; Xue, Weichen

    2017-10-01

    An online hybrid test was carried out on a 40-story 120-m high concrete shear wall structure. The structure was divided into two substructures whereby a physical model of the bottom three stories was tested in the laboratory and the upper 37 stories were simulated numerically using ABAQUS. An overlapping domain method was employed for the bottom three stories to ensure the validity of the boundary conditions of the superstructure. Mixed control was adopted in the test. Displacement control was used to apply the horizontal displacement, while two controlled force actuators were applied to simulate the overturning moment, which is very large and cannot be ignored in the substructure hybrid test of high-rise buildings. A series of tests with earthquake sources of sequentially increasing intensities were carried out. The test results indicate that the proposed hybrid test method is a solution to reproduce the seismic response of high-rise concrete shear wall buildings. The seismic performance of the tested precast high-rise building satisfies the requirements of the Chinese seismic design code.

  15. Quadricuspid Aortic Valve Combined with Moderate Ascending Aortic Dilatation

    Science.gov (United States)

    Uspenskiy, Vladimir E.; Osadchii, Alexei M.; Gordeev, Mikhail L.

    2015-01-01

    The quadricuspid aortic valve is a very uncommon malformation associated with aortic insufficiency, aortic stenosis, endocarditis, and ascending aortic dilatation. We report four cases of this aortic valve malformation. One patient with severe aortic regurgitation and moderate aortic dilatation required aortic valve replacement. Three patients had mild or moderate aortic insufficiency combined with moderate ascending aortic dilatation. These patients were referred to follow-up. The presented cases demonstrate that this aortic valve malformation may not be as rare as it appears and that attention must be paid to any quadricuspid findings during computed tomographic angiography and echocardiography. PMID:27390747

  16. 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...... by flexural loading. Numerical investigations were based on 3-D linear elastic finite element analysis. Results from the numerical investigations were compared with experimental results of small and semi-scale specimens for the validation of the design procedure. Experimental and numerical results based...

  17. Study on the influence of inner wall morphology and structure defect on the emission point of microchannel plate

    Science.gov (United States)

    Bo, Tiezhu; Shi, Xiaoxuan; Wang, Chen; Cai, Hua; Lian, Jiao; Cao, Zhenbo; Li, Qing; Liu, Chang; Liu, Hui

    2017-10-01

    The microchannel plate (MCP) as the most important component of image intensifiers and ultraviolet detectors, is avalanche two-dimensional electron multiplier device. The emission point as a pattern noise, which is characterized by a bright or a flickering point at a fixed position of the fluorescent screen, affects the visual quality and reliability of the MCP. Therefore, eliminating the emission point is an effective way to improve the performances of the MCP. In this paper, the inner wall morphology and structure defect of the channel were studied, the MCPs with different inner wall morphlogies were analyzed by SEM, and the emission point were tested by using the photoelectric imaging integrated tester. Using the above-mentioned research methods, a specific relationship between the inner wall morphology and the emission point was established. According to the field emission theory, the mechanism of the emission point was analyzed and discussed. The results show that the inner wall structure defects of the channel are the main reasons for the emission point. Furthermore, the study found that the matching of the thermal physical properties between core glass and clad glass is the main reason for the occurrence of structure defects. The structure defects of the inner wall can be effectively reduced by optimizing the composition of the glass material, make the two glasses have the suitable performance matching, avoid forming residual pores at the interface position, the inner wall of the channel will have a smooth, defect free microstructure, thereby effectively controlling the emission point of the MCP.

  18. A simulation environment for validating ultrasonic blood flow and vessel wall imaging based on fluid-structure interaction simulations: ultrasonic assessment of arterial distension and wall shear rate.

    Science.gov (United States)

    Swillens, Abigail; Degroote, Joris; Vierendeels, Jan; Lovstakken, Lasse; Segers, Patrick

    2010-08-01

    Ultrasound (US) is a commonly used vascular imaging tool when screening for patients at high cardiovascular risk. However, current blood flow and vessel wall imaging methods are hampered by several limitations. When optimizing and developing new ultrasound modalities, proper validation is required before clinical implementation. Therefore, the authors present a simulation environment integrating ultrasound and fluid-structure interaction (FSI) simulations, allowing construction of synthetic ultrasound images based on physiologically realistic behavior of an artery. To demonstrate the potential of the model for vascular ultrasound research, the authors studied clinically relevant imaging modalities of arterial function related to both vessel wall deformation and arterial hemodynamics: Arterial distension (related to arterial stiffness) and wall shear rate (related to the development of atherosclerosis) imaging. An in-house code ("TANGO") was developed to strongly couple the flow solver FLUENT and structural solver ABAQUS using an interface quasi-Newton technique. FIELD II was used to model realistic transducer and scan settings. The input to the FSI-US model is a scatterer phantom on which the US waves reflect, with the scatterer displacement derived from the FSI flow and displacement fields. The authors applied the simulation tool to a 3D straight tube, representative of the common carotid artery (length: 5 cm; and inner and outer radius: 3 and 4 mm). A mass flow inlet boundary condition, based on flow measured in a healthy subject, was applied. A downstream pressure condition, based on a noninvasively measured pressure waveform, was chosen and scaled to simulate three different degrees of arterial distension (1%, 4%, and 9%). The RF data from the FSI-US coupling were further processed for arterial wall and flow imaging. Using an available wall tracking algorithm, arterial distensibility was assessed. Using an autocorrelation estimator, blood velocity and shear

  19. The "G-Spot" Is Not a Structure Evident on Macroscopic Anatomic Dissection of the Vaginal Wall.

    Science.gov (United States)

    Hoag, Nathan; Keast, Janet R; O'Connell, Helen E

    2017-12-01

    Controversy exists in the literature regarding the presence or absence of an anatomic "G-spot." However, few studies have examined the detailed topographic or histologic anatomy of the putative G-spot location. To determine the anatomy of the anterior vaginal wall and present detailed, systematic, accessible findings from female cadaveric dissections to provide anatomic clarity with respect to this location. Systematic anatomic dissections were performed on 13 female cadavers (32-97 years old, 8 fixed and 5 fresh) to characterize the gross anatomy of the anterior vaginal wall. Digital photography was used to document dissections. Dissection preserved the anterior vaginal wall, urethra, and clitoris. In 9 cadavers, the vaginal epithelial layer was reflected to expose the underlying urethral wall and associated tissues. In 4 cadavers, the vaginal wall was left intact before preservation. Once photographed, 8 specimens were transversely sectioned for macroscopic inspection and histologic examination. The presence or absence of a macroscopic anatomic structure at detailed cadaveric pelvis dissection that corresponds to the previously described G-spot and gross anatomic description of the anterior vaginal wall. Deep to the lining epithelium of the anterior vaginal wall is the urethra. There is no macroscopic structure other than the urethra and vaginal wall lining in the location of the putative G-spot. Specifically, there is no apparent erectile or "spongy" tissue in the anterior vaginal wall, except where the urethra abuts the clitoris distally. The absence of an anatomic structure corresponding to the putative G-spot helps clarify the controversy on this subject. Limitations to this study include limited access to specimens immediately after death and potential for observational bias. In addition, age, medical history, and cause of death are not publishable for privacy reasons. However, it is one of the most thorough and complete anatomic evaluations documenting the

  20. Vascular wall proteoglycan synthesis and structure as a target for the prevention of atherosclerosis

    Directory of Open Access Journals (Sweden)

    Peter J Little

    2007-03-01

    Full Text Available Peter J Little1, 2, 3, Mandy L. Ballinger1, Narin Osman1,31Cell Biology of Diabetes Laboratory, Baker Heart Research Institute, Melbourne, Australia; Monash University, Departments of 2Medicine and 3Immunology, Central and Eastern Clinical School, Alfred Hospital, Melbourne, AustraliaAbstract: Atherosclerosis is the underlying pathology of most cardiovascular disease and it represents the major cause of premature death in modern societies. Current therapies target risk factors being hypertension, hypercholesterolemia, hypertriglyceridemia and hyperglycemia when diabetes is present however the maximum efficacy of these strategies is often 30% or less. Areas of vascular biology that may lead to the development of a complementary vascular wall directed therapy are: inflammation, oxidation, endothelial dysfunction, diabetes-specific factors —hyperglycemia and advanced glycation endproducts and lipid retention by vascular matrix specifically proteoglycans. The major structural features of proteoglycans that determine low-density lipoprotein (LDL binding are the length and sulfation pattern on the glycosaminoglycan (GAG chains. Emerging data discussed in this review indicates that these structural properties are subject to considerable regulation by vasoactive substances possibly using novel signaling pathways. For example, GAG elongation stimulated by platelet-derived growth factor is not blocked by the receptor tyrosine kinase antagonist, genistein suggesting that there may be a previously unknown signaling pathway involved in this response. Thus, modifying proteoglycan synthesis and structure may represent a prime target to prevent LDL binding and entrapment in the vessel wall and thus prevent the development and progression of atherosclerosis.Keywords: proteoglycans, signaling, lipoproteins, atherosclerosis

  1. 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.

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

    Science.gov (United States)

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

    2016-03-01

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

  3. Characterization of structural cell wall polysaccharides in cattail (Typha latifolia): Evaluation as potential biofuel feedstock.

    Science.gov (United States)

    Rebaque, Diego; Martínez-Rubio, Romina; Fornalé, Silvia; García-Angulo, Penélope; Alonso-Simón, Ana; Álvarez, Jesús M; Caparros-Ruiz, David; Acebes, José L; Encina, Antonio

    2017-11-01

    Second generation bioethanol produced from lignocellulosic biomass is attracting attention as an alternative energy source. In this study, a detailed knowledge of the composition and structure of common cattail (Typha latifolia L.) cell wall polysaccharides, obtained from stem or leaves, has been conducted using a wide set of techniques to evaluate this species as a potential bioethanol feedstock. Our results showed that common cattail cellulose content was high for plants in the order Poales and was accompanied by a small amount of cross-linked polysaccharides. A high degree of arabinose-substitution in xylans, a high syringyl/guaiacyl ratio in lignin and a low level of cell wall crystallinity could yield a good performance for lignocellulose saccharification. These results identify common cattail as a promising plant for use as potential bioethanol feedstock. To the best of our knowledge, this is the first in-depth analysis to be conducted of lignocellulosic material from common cattail. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Structural and biochemical changes in dermis of sea cucumber (Stichopus japonicus) during autolysis in response to cutting the body wall.

    Science.gov (United States)

    Liu, Yu-Xin; Zhou, Da-Yong; Liu, Zi-Qiang; Lu, Ting; Song, Liang; Li, Dong-Mei; Dong, Xiu-Ping; Qi, Hang; Zhu, Bei-Wei; Shahidi, Fereidoon

    2018-02-01

    The autolysis of sea cucumber body wall is caused by endogenous proteolysis of its structural elements. However, changes in collagen fibrils, collagen fibres and microfibrils, the major structural elements in sea cucumber body wall during autolysis are less clear. Autolysis of sea cucumber (S. japonicus) was induced by cutting the body wall, and the structural and biochemical changes in its dermis were investigated using electron microscopy, differential scanning calorimetry, infrared spectroscopy, electrophoresis, and chemical analysis. During autolysis, both collagen fibres and microfibrils gradually degraded. In contrast, damage to microfibrils was more pronounced. Upon massive autolysis, collagen fibres disaggregated into collagen fibril bundles and individual fibrils due to the fracture of interfibrillar bridges. Meanwhile, excessive unfolding of collagen fibrils occurred. However, there was only slight damage to collagen monomers. Therefore, structural damage in collagen fibres, collagen fibrils and microfibrils rather than monomeric collagen accounts for autolysis of S. japonicus dermis. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. The Disruptive Effect of Lysozyme on the Bacterial Cell Wall Explored by an "In-Silico" Structural Outlook

    Science.gov (United States)

    Primo, Emiliano D.; Otero, Lisandro H.; Ruiz, Francisco; Klinke, Sebastián; Giordano, Walter

    2018-01-01

    The bacterial cell wall, a structural unit of peptidoglycan polymer comprised of glycan strands consisting of a repeating disaccharide motif [N-acetylglucosamine (NAG) and N-acetylmuramylpentapeptide (NAM pentapeptide)], encases bacteria and provides structural integrity and protection. Lysozymes are enzymes that break down the bacterial cell wall…

  6. Chemical and enzymatic fractionation of cell walls from Fucales: insights into the structure of the extracellular matrix of brown algae.

    Science.gov (United States)

    Deniaud-Bouët, Estelle; Kervarec, Nelly; Michel, Gurvan; Tonon, Thierry; Kloareg, Bernard; Hervé, Cécile

    2014-10-01

    Brown algae are photosynthetic multicellular marine organisms evolutionarily distant from land plants, with a distinctive cell wall. They feature carbohydrates shared with plants (cellulose), animals (fucose-containing sulfated polysaccharides, FCSPs) or bacteria (alginates). How these components are organized into a three-dimensional extracellular matrix (ECM) still remains unclear. Recent molecular analysis of the corresponding biosynthetic routes points toward a complex evolutionary history that shaped the ECM structure in brown algae. Exhaustive sequential extractions and composition analyses of cell wall material from various brown algae of the order Fucales were performed. Dedicated enzymatic degradations were used to release and identify cell wall partners. This approach was complemented by systematic chromatographic analysis to study polymer interlinks further. An additional structural assessment of the sulfated fucan extracted from Himanthalia elongata was made. The data indicate that FCSPs are tightly associated with proteins and cellulose within the walls. Alginates are associated with most phenolic compounds. The sulfated fucans from H. elongata were shown to have a regular α-(1→3) backbone structure, while an alternating α-(1→3), (1→4) structure has been described in some brown algae from the order Fucales. The data provide a global snapshot of the cell wall architecture in brown algae, and contribute to the understanding of the structure-function relationships of the main cell wall components. Enzymatic cross-linking of alginates by phenols may regulate the strengthening of the wall, and sulfated polysaccharides may play a key role in the adaptation to osmotic stress. The emergence and evolution of ECM components is further discussed in relation to the evolution of multicellularity in brown algae. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please

  7. 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.

  8. 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...

  9. Analysis on spectra of hydroacoustic field in sonar cavity of the sandwich elastic wall structure

    Science.gov (United States)

    Xuetao, W.; Rui, H.; Weike, W.

    2017-09-01

    In this paper, the characteristics of the mechanical self - noise in sonar array cavity are studied by using the elastic flatbed - filled rectangular cavity parameterization model. Firstly, the analytic derivation of the vibration differential equation of the single layer, sandwich elastic wall plate structure and internal fluid coupling is carried out, and the modal method is used to solve it. Finally, the spectral characteristics of the acoustic field of rectangular cavity of different elastic wallboard materials are simulated and analyzed, which provides a theoretical reference for the prediction and control of sonar mechanical self-noise. In this paper, the sandwich board as control inside the dome background noise of a potential means were discussed, the dome background noise of qualitative prediction analysis and control has important theoretical significance.

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

    Science.gov (United States)

    Helou, S. H.; Touqan, A. R.

    2008-07-01

    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.

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

    International Nuclear Information System (INIS)

    Helou, S. H.; Touqan, A. R.

    2008-01-01

    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

  12. 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.

  13. 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.

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

    Directory of Open Access Journals (Sweden)

    G. Lombardini

    1995-06-01

    Full Text Available 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 following the earthquake of l693 (I,= XI MCS. Me 7.5 which had already been studied in depth as part of an ING research programme (1988-92. Moreover, just after recent research, this event proved to be reconstructed with a high quality standard. Photogrammetric measurements were made on several parts of the town walls to plot a numerical model aimed at ascertaining specific aspects of the earthquake damage. An estimate of the ground acceleration during the earthquake has been attempted via non-linear finite-element analyses of a building located by the main city gate. The analyses show that. in order to obtain the building vault collapse, a ground acceleration of 0.5 to 0.7 g had to be reached during the earthquake. This result, typical of a strong earthquake such as the one of 1693, proves that an approach based on finite element analysis and a sound engineering judgment Inay be systematically applied to historical earthquake sites to obtain some estimates of ground acceleration in historical earthquakes. On the whole, this work aimed at starting up the second development phase of the great event of 1693 of which the macroseismic erfects are known. In the meantime, some possibilities of tackling structural analyses in seismic archaeology are being explored.

  15. 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

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

    Directory of Open Access Journals (Sweden)

    G. M. S. ALVA

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

  17. Molecular Organization in the Native State of Wood Cell Walls: Studies of Nanoscale Structure and its Development

    Energy Technology Data Exchange (ETDEWEB)

    Atalla, R. H.

    2001-02-01

    With respect to cell wall biogenesis we have developed a theory concerning the formation of lignin in which the regulation of structure is attributed to the hemicelluloses; they are viewed as templates for the assembly of lignin. The key supporting evidence is derived from the symmetry of annual rings in trees free of reaction wood. This symmetry is interpreted to point to genetic encoding as the dominant factor in the pattern of interunit linkages in lignin. More recently, we have explored further the implications of annual ring symmetries within the contexts of systems and information theory and theories of organization of hierarchic structures. This has led us to proposed a unifying model for cell wall biogenesis that comprehends cell wall polysaccharides as well as lignin. The model is based on examining the implications of symmetries and of hierarchic relationships between different levels of structure, with respect to synchrony and coordination of the stages of formation of the individual constituents.

  18. Chemical and enzymatic fractionation of cell walls from Fucales: insights into the structure of the extracellular matrix of brown algae

    Science.gov (United States)

    Deniaud-Bouët, Estelle; Kervarec, Nelly; Michel, Gurvan; Tonon, Thierry; Kloareg, Bernard; Hervé, Cécile

    2014-01-01

    Background and Aims Brown algae are photosynthetic multicellular marine organisms evolutionarily distant from land plants, with a distinctive cell wall. They feature carbohydrates shared with plants (cellulose), animals (fucose-containing sulfated polysaccharides, FCSPs) or bacteria (alginates). How these components are organized into a three-dimensional extracellular matrix (ECM) still remains unclear. Recent molecular analysis of the corresponding biosynthetic routes points toward a complex evolutionary history that shaped the ECM structure in brown algae. Methods Exhaustive sequential extractions and composition analyses of cell wall material from various brown algae of the order Fucales were performed. Dedicated enzymatic degradations were used to release and identify cell wall partners. This approach was complemented by systematic chromatographic analysis to study polymer interlinks further. An additional structural assessment of the sulfated fucan extracted from Himanthalia elongata was made. Key Results The data indicate that FCSPs are tightly associated with proteins and cellulose within the walls. Alginates are associated with most phenolic compounds. The sulfated fucans from H. elongata were shown to have a regular α-(1→3) backbone structure, while an alternating α-(1→3), (1→4) structure has been described in some brown algae from the order Fucales. Conclusions The data provide a global snapshot of the cell wall architecture in brown algae, and contribute to the understanding of the structure–function relationships of the main cell wall components. Enzymatic cross-linking of alginates by phenols may regulate the strengthening of the wall, and sulfated polysaccharides may play a key role in the adaptation to osmotic stress. The emergence and evolution of ECM components is further discussed in relation to the evolution of multicellularity in brown algae. PMID:24875633

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

    Science.gov (United States)

    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 distinct biomass types belonging to four different subgroups (i.e. monocot grasses, woody dicots, herbaceous dicots, and softwoods) were subjected to various regimes of AFEX™ (ammonia fiber expansion) pre-treatment [AFEX is a trademark of MBI, Lansing (http://www.mbi.org]. This approach allowed detailed analysis of close to 200 cell wall glycan epitopes and their relative extractability using a high-throughput platform. In general, irrespective of the phylogenetic origin, AFEX™ pre-treatment appeared to cause loosening and improved accessibility of various xylan epitope subclasses in most plant biomass materials studied. For most biomass types analysed, such loosening was also evident for other major non-cellulosic components including subclasses of pectin and xyloglucan epitopes. The studies also demonstrate that AFEX™ pre-treatment significantly reduced cell wall recalcitrance among diverse phylogenies (except softwoods) by inducing structural modifications to polysaccharides that were not detectable by conventional gross composition analyses. It was found that monitoring changes in cell wall glycan compositions and their relative extractability for untreated and pre-treated plant biomass can provide an improved understanding of variations in structure and composition of plant cell walls and delineate the role(s) of matrix polysaccharides in cell wall recalcitrance. PMID:25911738

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

    Science.gov (United States)

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

    2015-07-01

    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 distinct biomass types belonging to four different subgroups (i.e. monocot grasses, woody dicots, herbaceous dicots, and softwoods) were subjected to various regimes of AFEX™ (ammonia fiber expansion) pre-treatment [AFEX is a trademark of MBI, Lansing (http://www.mbi.org]. This approach allowed detailed analysis of close to 200 cell wall glycan epitopes and their relative extractability using a high-throughput platform. In general, irrespective of the phylogenetic origin, AFEX™ pre-treatment appeared to cause loosening and improved accessibility of various xylan epitope subclasses in most plant biomass materials studied. For most biomass types analysed, such loosening was also evident for other major non-cellulosic components including subclasses of pectin and xyloglucan epitopes. The studies also demonstrate that AFEX™ pre-treatment significantly reduced cell wall recalcitrance among diverse phylogenies (except softwoods) by inducing structural modifications to polysaccharides that were not detectable by conventional gross composition analyses. It was found that monitoring changes in cell wall glycan compositions and their relative extractability for untreated and pre-treated plant biomass can provide an improved understanding of variations in structure and composition of plant cell walls and delineate the role(s) of matrix polysaccharides in cell wall recalcitrance. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  1. Analysis of Side-Wall Structure of Grown-in Twin-Type Octahedral Defects in Czochralski Silicon

    Science.gov (United States)

    Ueki, Takemi; Itsumi, Manabu; Takeda, Tadao

    1998-04-01

    We analyzed the side-wall structure of grown-in octahedral defects in Czochralski silicon standard wafers for large-scale integrated circuits. There are two types of twin octahedral defects: an overlapping type and an adjacent type. In the twin octahedral defects of the overlapping type, a hole is formed in the connection part. The side-wall layer in the hole part is formed continually and is the same thickness as the side-wall layers of both octahedrons. In the twin octahedral defects of the adjacent type, a partition layer is formed in the connection part. Our electron energy-loss spectroscopy analyses identified that the side-wall layer includes SiO2.

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

    International Nuclear Information System (INIS)

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

    2008-01-01

    Surface-induced dissociation (SID) of the singly protonated complex of vancomycin antibiotic with cell wall peptide analogue (N α , N # var e psilon#-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), N α , N # var e psilon#-diacetyl-L-Lys-D-Ala-D-Ala, and non-covalent complexes of VA with N-acetyl-D-Ala-D-Ala and N α , N # var e psilon#-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

  3. A case of megadolichobasilar anomaly complicated with abdominal aortic aneurysm

    International Nuclear Information System (INIS)

    Ohta, Sumio; Yamaguchi, Takenori; Ogata, Jun; Ito, Mamoru; Kikuchi, Haruhiko

    1985-01-01

    A 41 year-old hypertensive male was admitted because of progressing left hemiparesis and dysarthria. CT demonstrated hyperdense mass with partial contast enhancement, extending from the level of lower pons to that of suprasellar cistern. Reconstructed imaging of CT showed a huge mass lesion, in which a wide curvilinear hyperdensity was demonstrated by contrast enhancement. Cerebral angiography revealed markedly elongated and dilated basilar and carotid arteries. From these findings, the prepontine hyperdense mass lesion was diagnosed as megadolichobasilar anomaly with marked wall thickening. Findings of abdominal aortic angiography and abdominal CT suggested the presence of marked atherosclerosis and abdominal aortic aneurysm with mural thrombi. Six months after initial admission, neurological symptoms gradually deteriorated and CT showed dilatation of the 3rd and lateral ventricles, suggesting the development of hydrocephalus due to compression of the aqueduct by the megadolichobasilar anomaly. Magnetic resonance imaging at this time demonstrated more details of the lesion and the deformity of the brain stem, which was not detected by conventional CT. Complications of vascular anomalies other than intracranial vasculature, such as aortic aneurysm, have also been repoted. After the introduction of CT, demonstration of a long, wide, curvilinear structure with abnormal density in the prepontine region has been reported to be diagnostic for the megadolichobasilar anomaly. This patient has had hypertension for 10 years, which probably due to chronic nephritis. He had no definite findings for angitis, but had abdominal aortic aneurysm with mural thrombi. From these findings, atherosclerosis of large vessels may have played one of the roles in the pathogenesis of this anomaly in the present case. (J.P.N.)

  4. Circulating matrix metalloproteinase patterns in association with aortic dilatation in bicuspid aortic valve patients with isolated severe aortic stenosis.

    Science.gov (United States)

    Wang, Yongshi; Wu, Boting; Dong, Lili; Wang, Chunsheng; Wang, Xiaolin; Shu, Xianhong

    2016-02-01

    Bicuspid aortic valve (BAV) exhibits a clinical incline toward aortopathy, in which aberrant tensile and shear stress generated by BAV can induce differential expression of matrix metalloproteinases (MMPs) and their endogenous tissue inhibitors (TIMPs). Whether stenotic BAV, which exhibits additional eccentric high-velocity flow jet upon ascending aorta and further worsens circumferential systolic wall shear stress than BAV with echocardiographically normal aortic valve, can lead to unique plasma MMP/TIMP patterns is still unknown. According to their valvulopathy and aortic dilatation status, 93 BAV patients were included in the present study. Group A (n = 37) and B (n = 28) comprised severely stenotic patients with or without ascending aorta dilatation; Group C (n = 12) and D (n = 16) comprised echocardiographically normal BAV patients with or without ascending aorta dilatation. Plasma MMP/TIMP levels (MMP-1, -2, -3, -8, -9, -10, -13 and TIMP-1, -2, -4) were determined via a multiplex ELISA detection system in a single procedure. Among patients with isolated severe aortic stenosis, plasma levels of MMP-2 and -9 were significantly elevated when ascending aortic dilatation was present (p = 0.001 and p = 0.002, respectively). MMP-2, however, remained as the single elevated plasma component among echocardiographically normal BAV patients with dilated ascending aorta (p = 0.027). Multivariate analysis revealed that MMP-2 and MMP-9 could both serve as independent risk factor for aortic dilatation in the case of isolated severe stenosis (p = 0.003 and p = 0.001, respectively), and MMP-2 in echocardiographically normal patients (p = 0.002). In conclusion, BAV patients with isolated severe aortic stenosis demonstrated a distinct plasma MMP/TIMP pattern, which might be utilized as circulating biomarkers for early detection of aortic dilatation.

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

    Directory of Open Access Journals (Sweden)

    George Ronald Soncini da ROSA

    2002-06-01

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

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

    Science.gov (United States)

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

    2006-11-01

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

  7. Evaluation of the Mechanical Behavior of a Retaining Wall Structure on a Weathered Soil through Probabilistic Methods

    OpenAIRE

    P. V. S. Mascarenhas; B. C. P. Albuquerque; D. J. F. Campos; L. L. Almeida; V. R. Domingues; L. C. S. M. Ozelim

    2017-01-01

    Retaining slope structures are increasingly considered in geotechnical engineering projects due to extensive urban cities growth. These kinds of engineering constructions may present instabilities over the time and may require reinforcement or even rebuilding of the structure. In this context, statistical analysis is an important tool for decision making regarding retaining structures. This study approaches the failure probability of the construction of a retaining wall over the debris of an ...

  8. Ruptured Abdominal Aortic Aneurysm

    Directory of Open Access Journals (Sweden)

    Jessica Andrusaitis

    2017-07-01

    Full Text Available History of present illness: A 69-year-old male with poorly controlled hypertension presented with 1 hour of severe low back pain that radiated to his abdomen. The patient was tachycardic and had an initial blood pressure of 70/40. He had a rigid and severely tender abdomen. The patient’s history of hypertension, abnormal vital signs, severity and location of his pain were suspicious for a ruptured abdominal aortic aneurysm (AAA. Therefore, a computed tomography angiogram (CTA was ordered. Significant findings: CTA demonstrated a ruptured 7.4 cm infrarenal abdominal aortic aneurysm with a large left retroperitoneal hematoma. Discussion: True abdominal aortic aneurysm is defined as at least a 3cm dilatation of all three layers of the arterial wall of the abdominal aorta.1 An estimated 15,000 people die per year in the US of this condition.2 Risk factors for AAA include males older than 65, tobacco use, and hypertension.1,3,4 There are also congenital, mechanical, traumatic, inflammatory, and infectious causes of AAA.3 Rupture is often the first manifestation of the disease. The classic triad of abdominal pain, pulsatile mass, and hypotension is seen in only 50% of ruptured AAAs.5 Pain (abdominal, groin, or back is the most common symptom. The most common misdiagnoses of ruptured AAAs are renal colic, diverticulitis, and gastrointestinal hemorrhage.6 Bedside ultrasonography is the fastest way to detect this condition and is nearly 100% sensitive.1 One study showed that bedside ultrasounds performed by emergency physicians had a sensitivity of .94 [95% CI = .86-1.0] and specificity of 1 [95% CI = .98-1.0] for detecting AAAs.7 CTA has excellent sensitivity (approximately 100% and yields the added benefit of facilitating surgical planning and management.1 Without surgical treatment, a ruptured AAA is almost uniformly fatal, and 50% of those who undergo surgery do not survive.1 Early resuscitation and coordination with vascular surgery should be

  9. Stochastic estimation of the flow structure downstream of a separating/reattaching flow region using wall-pressure array measurements

    Science.gov (United States)

    Daoud, Mohamed Ibrahim

    This study examines the spatio-temporal characteristics of the surface-pressure fluctuations and associated flow structures in the developing flow downstream of the reattachment point of a fence-with-splitter-plate flow. The investigation focuses on understanding the wall-pressure field characteristics, and the flow sources responsible for its generation in the non-equilibrium boundary layer originating from the separating/reattaching shear layer associated with the flow over the fence, using a wall-pressure database that was simultaneously acquired with X-hotwire time series. This is motivated by guiding efforts to predict and/or control flow-induced noise and vibration in applications involving flows downstream of appendages and surface protrusions. Characterization of the wall-pressure data alone showed that the wall-pressure fluctuations were dominated by large-scale downstream-traveling disturbances that were generated upstream in the separated shear layer. Notwithstanding this dominance, the p' signature of these structures decayed with increasing downstream distance as the vortices underwent a relaxation process while the contribution of eddies, associated with the development of a "sub-boundary layer", became more significant with increasing downstream distance. In addition, wavenumber-frequency-spectrum results showed that pressure signatures of all wavenumbers and frequencies were associated with flow disturbances that travel downstream with the same convection velocity. Finally, multi-point Linear Stochastic Estimation of the flow field based on instantaneous wall-pressure information confirmed the dominance of wall-pressure generation by the passage of the outer-shear layer vortical structures and their mutual interaction. Examination of the linear source term in Poisson's equation of the pressure in conjunction with the stochastically-estimated velocity field revealed two mechanisms for p' generation associated with the quasi-periodic vortex passage

  10. Atomic structure and domain wall pinning in samarium-cobalt-based permanent magnets.

    Science.gov (United States)

    Duerrschnabel, M; Yi, M; Uestuener, K; Liesegang, M; Katter, M; Kleebe, H-J; Xu, B; Gutfleisch, O; Molina-Luna, L

    2017-07-04

    A higher saturation magnetization obtained by an increased iron content is essential for yielding larger energy products in rare-earth Sm 2 Co 17 -type pinning-controlled permanent magnets. These are of importance for high-temperature industrial applications due to their intrinsic corrosion resistance and temperature stability. Here we present model magnets with an increased iron content based on a unique nanostructure and -chemical modification route using Fe, Cu, and Zr as dopants. The iron content controls the formation of a diamond-shaped cellular structure that dominates the density and strength of the domain wall pinning sites and thus the coercivity. Using ultra-high-resolution experimental and theoretical methods, we revealed the atomic structure of the single phases present and established a direct correlation to the macroscopic magnetic properties. With further development, this knowledge can be applied to produce samarium cobalt permanent magnets with improved magnetic performance.Understanding the factors that determine the properties of permanent magnets, which play a central role in many industrial applications, can help in improving their performance. Here, the authors study how changes in the iron content affect the microstructure of samarium cobalt magnets.

  11. A structural mechanics study of single-walled carbon nanotubes generalized from atomistic simulation.

    Science.gov (United States)

    Chen, Xi; Cao, Guoxin

    2006-02-28

    A new structural mechanics model is developed to closely duplicate the atomic configuration and behaviours of single-walled carbon nanotubes (SWCNTs). The SWCNTs are effectively represented by a space frame, where primary and secondary beams are used to bridge the nearest and next-nearest carbon atoms, to mimic energies associated with bond stretching and angle variation, respectively. The elastic properties of the frame components are generalized from molecular dynamics (MD) simulation based on an accurate ab initio force field, and numerical analyses of tension, bending, and torsion are carried out on nine different SWCNTs. The space-frame model also closely duplicates the buckling behaviours of SWCNTs in torsion and bending. In addition, by repeating the same process with continuum shell and beam models, new elastic and section parameters are fitted from the MD benchmark experiments. As an application, all three models are employed to study the thermal vibration behaviours of SWCNTs, and excellent agreements with MD analyses are found. The present analysis is a systematic structural mechanics attempt to fit SWCNT properties for several basic deformation modes and applicable to a variety of SWCNTs. The continuum models and fitted parameters may be used to effectively simulate the overall deformation behaviours of SWCNTs at much larger length- and timescales than pure MD analysis.

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

    Science.gov (United States)

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

    2014-01-01

    The plant cuticle has traditionally been conceived as an independent hydrophobic layer that covers the external epidermal cell wall. Due to its complexity, the existing relationship between cuticle chemical composition and ultra-structure remains unclear to date. This study aimed to examine the link between chemical composition and structure of isolated, adaxial leaf cuticles of Eucalyptus camaldulensis and E. globulus by the gradual extraction and identification of lipid constituents (cutin and soluble lipids), coupled to spectroscopic and microscopic analyses. The soluble compounds and cutin monomers identified could not be assigned to a concrete internal cuticle ultra-structure. After cutin depolymerization, a cellulose network resembling the cell wall was observed, with different structural patterns in the regions ascribed to the cuticle proper and cuticular layer, respectively. Our results suggest that the current cuticle model should be revised, stressing the presence and major role of cell wall polysaccharides. It is concluded that the cuticle may be interpreted as a modified cell wall region which contains additional lipids. The major heterogeneity of the plant cuticle makes it difficult to establish a direct link between cuticle chemistry and structure with the existing methodologies. PMID:25278953

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

    Directory of Open Access Journals (Sweden)

    Paula eGuzmán

    2014-09-01

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

  14. 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.

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

    International Nuclear Information System (INIS)

    Economou, Nicoleta J.; Zentner, Isaac J.; Lazo, Edwin; Jakoncic, Jean; Stojanoff, Vivian; Weeks, Stephen D.; Grasty, Kimberly C.; Cocklin, Simon; Loll, Patrick J.

    2013-01-01

    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

  16. Thermomechanics of Inelastic Thin-Walled Structural Members with Piezoelectric Sensors and Actuators Under Harmonic Loading (Review)

    Science.gov (United States)

    Karnaukhov, V. G.; Kirichok, I. F.; Kozlov, V. I.

    2017-01-01

    Models, combined numerical-analytical methods, and results related to study of the forced resonance vibrations and self-heating of thin-walled inelastic structural members with piezoelectric sensors and actuators under monoharmonic mechanical and electric loading are presented. The thermomechanical behavior of passive and piezoactive materials is described using the concept of complex characteristics that are assumed to depend on temperature and invariants of the strain tensor. The classical and refined thermomechanical theories are used to model the vibrations and self-heating of thin-walled structural members with sensors and actuators. Nonlinear coupled thermoelastic problems for thin-walled structural members are solved by iteration and numerical methods. The thermal failure of structural members is considered. Methods for determining the critical electrical and mechanical monoharmonic loads and methods of postcritical analysis are described. The effect of various factors on the effectiveness of active damping of the resonance vibrations of inelastic thin-walled structural members by piezoelectric sensors and actuators is studied

  17. Functional model and general principles of structural materials selection for fusion tokamak reactor first wall and blanket

    International Nuclear Information System (INIS)

    Vinokurov, V.F.; Glukhikh, V.A.; Gorynin, I.V.; Kazantsev, A.N.; Parshin, A.M.; Saksaganskij, G.L.

    1987-01-01

    The functional mathematical model of the most energy-stressed components of the reactor (the first wall and blanket) is developed. This model is the basis for the quantitative estimate of various concepts and design options from promise view points, physical and technological requirements may be formulated in general and limiting properties may be found. In this way the first wall and blanket may be directly introduced within the framework of multi-parametric system analysis and fusion reactor optimization. The concept of base structure is suggested as a generalized representation of ''the first-wall-blanket structure'' and its functions. A set of structural, thermophysical and hydraulic parameters is introduced to describe the base structure. The calculated model is presented, permitting by variation of structural and physical parameters to determine technical and economic reactor parameters as the functions of plasma parameters and structural material properties. The mechanisms of fusion reactor destructive effects on structural materials characteristics are analyzed. Comparative estimates of promising steels and alloys of various classes and modifications are given. The effect of neutron irradiation dose and temperature on strength, plasticity and swelling of materials and their compatibility with gas and liquid metal coolants are shown. Structural, physical and technological methods to improve operating characteristics and to raise radiation material resistance are discussed. (author). 7 refs, 11 figs, 2 tabs

  18. Domain wall diffusion and domain wall softening

    International Nuclear Information System (INIS)

    Lee, W T; Salje, E K H; Bismayer, U

    2003-01-01

    A number of experimental and computational studies of materials have shown that transport rates in domain walls may significantly differ from those in the bulk. One possible explanation for enhanced transport in a domain wall is that the domain wall is elastically soft with respect to the bulk. We investigate the softening of a ferroelastic domain wall in a simple, generic model. We calculate saddle point energies of solute atoms in the bulk and domain wall, using a geometry such that variation in the saddle point energy cannot be attributed to the structural differences of the bulk and the wall, but must instead be attributed to softening of the wall. Our results show a reduction of the saddle point energy in the wall, thus indicating that, in this model at least, domain walls are elastically soft compared with the bulk. A simple analysis based on an Einstein model allows us to explain the observed softening of the wall

  19. Aortic regurgitation after valve-sparing aortic root replacement: modes of failure.

    Science.gov (United States)

    Oka, Takanori; Okita, Yutaka; Matsumori, Masamichi; Okada, Kenji; Minami, Hitoshi; Munakata, Hiroshi; Inoue, Takeshi; Tanaka, Akiko; Sakamoto, Toshihito; Omura, Atsushi; Nomura, Takuo

    2011-11-01

    Despite the positive clinical results of valve-sparing aortic root replacement, little is known about the causes of reoperations and the modes of failure. From October 1999 to June 2010, 101 patients underwent valve-sparing aortic root replacement using the David reimplantation technique. The definition of aortic root repair failure included the following: (1) intraoperative conversion to the Bentall procedure; (2) reoperation performed because of aortic regurgitation; and (3) aortic regurgitation equal to or greater than a moderate degree at the follow-up. Sixteen patients were considered to have repair failure. Three patients required intraoperative conversion to valve replacement, 3 required reoperation within 3 months, and another 8 required reoperation during postoperative follow-up. At initial surgery 5 patients had moderate to severe aortic regurgitation, 6 patients had acute aortic dissections, 3 had Marfan syndrome, 2 had status post Ross operations, 3 had bicuspid aortic valves, and 1 had aortitis. Five patients had undergone cusp repair, including Arantius plication in 3 and plication at the commissure in 2. The causes of early failure in 6 patients included cusp perforation (3), cusp prolapse (3), and severe hemolysis (1). The causes of late failure in 10 patients included cusp prolapse (4), commissure dehiscence (3), torn cusp (2), and cusp retraction (1). Patients had valve replacements at a mean of 23 ± 20.9 months after reimplantation and survived. Causes of early failure after valve-sparing root replacement included technical failure, cusp lesions, and steep learning curve. Late failure was caused by aortic root wall degeneration due to gelatin-resorcin-formalin glue, cusp degeneration, or progression of cusp prolapse. Copyright © 2011 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  20. In situ total aortic arch replacement for infected distal aortic arch aneurysms with penetrating atherosclerotic ulcer.

    Science.gov (United States)

    Okada, Kenji; Yamanaka, Katsuhiro; Sakamoto, Toshihito; Inoue, Takeshi; Matsumori, Masamichi; Kawakami, Fumi; Okita, Yutaka

    2014-11-01

    We present a series of patients who underwent in situ total aortic arch replacement for infected distal aortic arch aneurysms. Between 2002 and 2013, 9 patients with infected distal aortic arch aneurysms underwent total aortic arch replacement using antegrade selective cerebral perfusion. There were 4 male and 5 female patients with a mean age of 72.7±9.0 years. All patients had penetrating atherosclerotic ulcer in the distal aortic arch, which formed saccular aneurysms. Four patients had preoperative hoarseness. Maximum preoperative white blood cell count was 10,211±4375/μL, and mean serum C-reactive protein concentration was 12.7±7.2 mg/dL. Causative microorganisms were identified by blood culture or aortic wall culture and were as follows: Candida albicans, Pseudomonas aeruginosa, Edwardsiella tarda, Streptococcus dysgalactiae, Listeria monocytogenes, Staphylococcus aureus (2 cases), and unknown (2 cases). Radical debridement with in situ total aortic arch replacement was performed in all patients, followed by the omental flap grafting in 7 patients. All surgery was performed on an urgent or emergency basis. Average cardiopulmonary bypass time and lower body circulatory arrest time were 199.7±50.7 minutes and 66.6±13.8 minutes, respectively. There was no in-hospital mortality, but 1 patient died of asphyxia 5 months after hospital discharge. Freedom from recurrence of infection was 100%. Surgical treatment with the combination of radical debridement with in situ total aortic arch replacement using antegrade selective cerebral perfusion and omental flap grafting was a reliable procedure for the treatment of infected distal aortic arch aneurysms. Copyright © 2014. Published by Elsevier Inc.

  1. A fast vibro-acoustic response analysis method for double wall structures including a viscothermal air layer

    NARCIS (Netherlands)

    Basten, T.G.H.; Grooteman, F.P.

    2000-01-01

    The damping behaviour of a thin air layer between two flexible panels can be used to reduce sound radiation of structural excited panels. The numerical model of the double wall panels takes into account full acousto-elastic interaction and viscothermal wave propagation in the air layer. This means

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

    NARCIS (Netherlands)

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

    2013-01-01

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

  3. Initial experience with the treatment of concomitant aortic pseudoaneurysm and thoracolumbar spinal fracture: Case report

    Directory of Open Access Journals (Sweden)

    Viktor Zsolt Kovari

    2017-12-01

    Full Text Available One blunt abdominal aortic disruption (BAAD and one blunt thoracic aortic injury (BTAI case are presented. Both aortic injuries were combined with spinal fractures. In the BAAD case the aortic pseudoaneurysm manifested just above the lumbar fracture while in the BTAI case the aortic injury appeared several vertebras below the thoracal fracture site, suggesting different mechanisms in the aortic wall damage. In both cases the aortic wall first was sealed, successfully, by endovascularly-placed stents, meaning the risks of open aortic reconstructive surgery could be avoided. The adjacent crucial vessel's preservation, despite the stent covering the left subclavian artery and the left common carotid artery in one of the cases was verified by post-operative computed tomography angiography (CTA examination. In second stage those spinal fractures which were deemed unstable were stabilized by the fixateur interne (a transpedicular screw-rod system. With this treatment sequence we wanted to avoid the unnecessary risk of a possible rupture of the unsealed aortic wall during positioning for the spinal procedure and during the spinal surgery. Both patients recovered from their aortic and spinal injuries.

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

    Science.gov (United States)

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

    2017-11-01

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

  5. A GPR system for the high-resolution inspection of walls and structures

    Science.gov (United States)

    Manacorda, Guido; Simi, Alessandro; Barsacchi, Giorgio

    2014-05-01

    Nowadays GPR systems are used in a broad range of applications, including the non-destructive inspection of man-made concrete structures such as pillars and bridge decks. Concrete inspection involves several aspects including: location of reinforced bars in walls and floors, concrete condition assessment, concrete cover detection, etc. These surveys are very demanding as far as the system is concerned, because of the strict requirements in terms of resolution and accuracy. Specifically, a key GPR application concerns the condition assessment of a structure that has undergone rehabilitation (e.g. for the removal of architectural barriers or new openings); in this case, the current practice requires to re-check the stability of the entire structure that includes the identification of the number of rebars in reinforced concrete beams location of pre-tensioned cables and early detection of corrosion. This can be done by verification holes (coring) that is costly and intrusive practice or by using a pachometer, but this tool has a limited field of investigation (up to 7-8 cm from the surface). GPR can instead be a useful investigative tool especially when the surface of the beam is not accessible because it is covered by screed or floor. The need of detecting rebars with diameter in the millimeter range as well as the identification of small cavities and cracks, require the development of GPR antennas featuring linear phase and constant polarization, and capable to radiate a very short pulse (i.e. with a duration in the order of few hundreds of picosecond) with no ring-down in order to achieve a high range resolution. A novel 3 GHz center frequency antenna has been recently developed and tested; it has been found capable of providing a very clear image of the concrete internal structure that helps in locating targets and enables an early detection of damages, thus providing a fast and efficient maintenance of the structure itself. The Authors thank COST for funding COST

  6. [Effects of hypotensive treatment on structural-functional properties of the vascular wall in hypertensive patients].

    Science.gov (United States)

    Maslennikova, O M; Romanchuk, S V; Rachkova, S A; Nazarova, O A

    2008-01-01

    To study structural-functional properties of the walls of large and middle-size arteries and changes of these properties in the course of hypotensive therapy in hypertensive patients. Of 609 participants of the trial (233 males and 376 females), 377 patients with essential hypertension stage I-II (mean age 46.9 +/- 7.2 years) entered the study group, 232 healthy subjects (mean age 45.7 +/- 6.9 years)--the control group. Pulse wave velocity (PWV) for vessels of elastic and muscular type was measured in all the examinees. Circadian blood pressure monitoring, echocardiography, duplex scanning of the common carotid artery were performed in hypertensive patients. 76 hypertensive patients were reexamined 6 months after treatment with amlodipin (n = 32) or fixed combination perindopril+indapamide (n = 44). Mean PWV appeared to be higher in hypertensive patients in whom PWV correlated with left ventricular (LV) remodeling and thickness of intima-media complex (IMC). After 6 months of hypotensive therapy PWV significantly lowered for both types of vessels studied. IMC thickness reduced by 10.1%, on the average, LV myocardial mass index--by 6.3%. The link between PWV, LV hypertrophy and IMC allows PWV use as a method of detection of cardiovascular remodeling in hypertension and for follow-up of antihypertensive treatment effect on this remodeling in outpatient treatment of hypertension.

  7. X-ray irradiation-induced structural changes on Single Wall Carbon Nanotubes

    Science.gov (United States)

    Bardi, N.; Jurewicz, I.; King, A. K.; Alkhorayef, M. A.; Bradley, D.; Dalton, A. B.

    2017-11-01

    Dosimetry devices based on Carbon Nanotubes are a promising new technology. In particular using devices based on single wall Carbon Nanotubes may offer a tissue equivalent response with the possibility for device miniaturisation, high scale manufacturing and low cost. An important precursor to device fabrication requires a quantitative study of the effects of X-ray radiation on the physical and chemical properties of the individual nanotubes. In this study, we concentrate on the effects of relatively low doses, 20 cGy and 45 cGy , respectively. We use a range of characterization techniques including scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy to quantify the effects of the radiation dose on inherent properties of the nanotubes. Specifically we find that the radiation exposure results in a reduction in the sp2 nature of the nanotube bond structure. Moreover, our analysis indicates that the exposure results in nanotubes that have an increased defect density which ultimately effects the electrical properties of the nanotubes.

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

    Science.gov (United States)

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

    2012-10-01

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

  9. Hairpin packet structure of a turbulent boundary layer in inclined wall-normal/spanwise planes

    Science.gov (United States)

    Lee, Jae Hwa; Sung, Hyung Jin

    2009-11-01

    Turbulent coherent structures associated with hairpin packet motions have been scrutinized using the instantaneous flow fields obtained from the direct numerical simulation (DNS) of a turbulent boundary layer (TBL). The Reynolds number based on the momentum thickness was varied in the range Reθ=890˜2560. This study focused on the hairpin packet motions in inclined wall-normal/spanwise planes. The hairpin vortex signature associated with the hairpin leg components in the vertical inclined plane consists of a counter-rotating vortex pair, upward and downward motions and a stagnation point induced by the Q2 and Q4 events. These hairpin signatures were observed in the instantaneous flow field, in the two-point correlations and in the conditionally averaged flow fields, respectively. We considered three inclined planes (45^o, 90^o, and 135^o) to investigate the spatial characteristics of the hairpin packet motions in the log and wake regions. The statistical flow fields showed that significantly different flow patterns are induced by the intersections of the three inclined planes with the hairpin packet motions.

  10. 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

    2016-02-04

    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.

  11. An investigation on vulnerability assessment of steel structures with thin steel shear wall through development of fragility curves

    OpenAIRE

    Mohsen Gerami; Saeed Ghaffari; Amir Mahdi Heidari Tafreshi

    2017-01-01

    Fragility curves play an important role in damage assessment of buildings. Probability of damage induction to the structure against seismic events can be investigated upon generation of afore mentioned curves. In current research 360 time history analyses have been carried out on structures of 3, 10 and 20 story height and subsequently fragility curves have been adopted. The curves are developed based on two indices of inter story drifts and equivalent strip axial strains of the shear wall. T...

  12. Improving risk assessment for post-surgical low cardiac output syndrome in patients without severely reduced ejection fraction undergoing open aortic valve replacement. The role of global longitudinal strain and right ventricular free wall strain

    NARCIS (Netherlands)

    Balderas-Munoz, K.; Rodriguez-Zanella, H.; Fritche-Salazar, J. F.; Avila-Vanzzini, N.; Juarez Orozco, L. E.; Arias-Godinez, J. A.; Calvillo-Arguelles, O.; Rivera-Peralta, S.; Sauza-Sosa, J. C.; Ruiz-Esparza, M. E.; Bucio-Reta, E.; Rmero, A.; Espinola-Zavaleta, N.; Dominguez-Mendez, B.; Gaxiola-Macias, M.; Martinez-Rios, M. A.

    2017-01-01

    Low cardiac output syndrome (LCOS) after surgical aortic valve replacement (SAVR) is related to increased mortality and treatment related costs. We aimed to evaluate whether echocardiography-derived left ventricular global longitudinal strain (LV-GLS) relates to the occurrence of postoperative LCOS

  13. Nucleon structure in lattice QCD with dynamical domain-wall fermions quarks

    International Nuclear Information System (INIS)

    Huey-Wen Lin; Shigemi Ohta

    2006-01-01

    We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with about 200 gauge configurations each. The lattice cutoff is about 1.7 GeV and the spatial volume is about (1.9 fm) 3 . Despite the small volume, the ratio of the isovector vector and axial charges g A /g V and that of structure function moments u-d / Δ u-Δ d are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is about 1.6 GeV and the spatial volume is about (3.0 fm) 3 . Even with preliminary statistics of 25-30 gauge configurations, the ratios g A /g V and u-d / Δu - Δd are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d 1 , though yet to be renormalized, appears small in both sets

  14. NUCLEON STRUCTURE IN LATTICE QCD WITH DYNAMICAL DOMAIN--WALL FERMIONS QUARKS

    International Nuclear Information System (INIS)

    LIN, H.W.; OHTA, S.

    2006-01-01

    We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with 220 gauge configurations each. The lattice cutoff is a -1 ∼ 1.7GeV and the spatial volume is about (1.9fm) 3 . Despite the small volume, the ratio of the isovector vector and axial charges g A /g V and that of structure function moments u-d / Δu-Δd are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is a -1 ∼ 1.6GeV and the spatial volume is about (3.0fm) 3 . Even with preliminary statistics of 25-30 gauge configurations, the ratios g A /g V and u-d / Δu-Δd are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d 1 , though yet to be renormalized, appears small in both sets

  15. Fluid-Structure Interaction Simulation of Prosthetic Aortic Valves: Comparison between Immersed Boundary and Arbitrary Lagrangian-Eulerian Techniques for the Mesh Representation.

    Directory of Open Access Journals (Sweden)

    Alessandra M Bavo

    Full Text Available In recent years the role of FSI (fluid-structure interaction simulations in the analysis of the fluid-mechanics of heart valves is becoming more and more important, being able to capture the interaction between the blood and both the surrounding biological tissues and the valve itself. When setting up an FSI simulation, several choices have to be made to select the most suitable approach for the case of interest: in particular, to simulate flexible leaflet cardiac valves, the type of discretization of the fluid domain is crucial, which can be described with an ALE (Arbitrary Lagrangian-Eulerian or an Eulerian formulation. The majority of the reported 3D heart valve FSI simulations are performed with the Eulerian formulation, allowing for large deformations of the domains without compromising the quality of the fluid grid. Nevertheless, it is known that the ALE-FSI approach guarantees more accurate results at the interface between the solid and the fluid. The goal of this paper is to describe the same aortic valve model in the two cases, comparing the performances of an ALE-based FSI solution and an Eulerian-based FSI approach. After a first simplified 2D case, the aortic geometry was considered in a full 3D set-up. The model was kept as similar as possible in the two settings, to better compare the simulations' outcomes. Although for the 2D case the differences were unsubstantial, in our experience the performance of a full 3D ALE-FSI simulation was significantly limited by the technical problems and requirements inherent to the ALE formulation, mainly related to the mesh motion and deformation of the fluid domain. As a secondary outcome of this work, it is important to point out that the choice of the solver also influenced the reliability of the final results.

  16. Shahr-I Sokhta and its Masonry Walls from Structural and Seismicity Standpoint

    Directory of Open Access Journals (Sweden)

    Masoumi Mohammad Mehdi

    2014-12-01

    Full Text Available Shahr-I Sokhta, Burned City, located in the south of Zabol, Sistan where founded circa 3200 BCE and some part of the city was burnt. Marvelous finds such as the world's earliest known artificial eyeball, the first animation in the world, the oldest known backgammon, with its dice and so forth all in this city. Their expertise was merely not in handicrafts. In this work provided evidences which Burned City’s walls are highly resistance against seismic loads and has engineering aspects, a wall was simulated by a finite element software and seismically considerations was approve the walls minimal deformation even after circa five thousand years.

  17. Study of coherent structures of turbulence with large wall-normal gradients in thermophysical properties using direct numerical simulation

    Science.gov (United States)

    Reinink, Shawn K.; Yaras, Metin I.

    2015-06-01

    Forced-convection heat transfer in a heated working fluid at a thermodynamic state near its pseudocritical point is poorly predicted by correlations calibrated with data at subcritical temperatures and pressures. This is suggested to be primarily due to the influence of large wall-normal thermophysical property gradients that develop in proximity of the pseudocritical point on the concentration of coherent turbulence structures near the wall. The physical mechanisms dominating this influence remain poorly understood. In the present study, direct numerical simulation is used to study the development of coherent vortical structures within a turbulent spot under the influence of large wall-normal property gradients. A turbulent spot rather than a fully turbulent boundary layer is used for the study, for the coherent structures of turbulence in a spot tend to be in a more organized state which may allow for more effective identification of cause-and-effect relationships. Large wall-normal gradients in thermophysical properties are created by heating the working fluid which is near the pseudocritical thermodynamic state. It is found that during improved heat transfer, wall-normal gradients in density accelerate the growth of the Kelvin-Helmholtz instability mechanism in the shear layer enveloping low-speed streaks, causing it to roll up into hairpin vortices at a faster rate. It is suggested that this occurs by the baroclinic vorticity generation mechanism which accelerates the streamwise grouping of vorticity during shear layer roll-up. The increased roll-up frequency leads to reduced streamwise spacing between hairpin vortices in wave packets. The density gradients also promote the sinuous instability mode in low-speed streaks. The resulting oscillations in the streaks in the streamwise-spanwise plane lead to locally reduced spanwise spacing between hairpin vortices forming over adjacent low-speed streaks. The reduction in streamwise and spanwise spacing between

  18. Study of coherent structures of turbulence with large wall-normal gradients in thermophysical properties using direct numerical simulation

    Energy Technology Data Exchange (ETDEWEB)

    Reinink, Shawn K.; Yaras, Metin I., E-mail: Metin.Yaras@carleton.ca [Department of Mechanical and Aerospace Engineering, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6 (Canada)

    2015-06-15

    Forced-convection heat transfer in a heated working fluid at a thermodynamic state near its pseudocritical point is poorly predicted by correlations calibrated with data at subcritical temperatures and pressures. This is suggested to be primarily due to the influence of large wall-normal thermophysical property gradients that develop in proximity of the pseudocritical point on the concentration of coherent turbulence structures near the wall. The physical mechanisms dominating this influence remain poorly understood. In the present study, direct numerical simulation is used to study the development of coherent vortical structures within a turbulent spot under the influence of large wall-normal property gradients. A turbulent spot rather than a fully turbulent boundary layer is used for the study, for the coherent structures of turbulence in a spot tend to be in a more organized state which may allow for more effective identification of cause-and-effect relationships. Large wall-normal gradients in thermophysical properties are created by heating the working fluid which is near the pseudocritical thermodynamic state. It is found that during improved heat transfer, wall-normal gradients in density accelerate the growth of the Kelvin-Helmholtz instability mechanism in the shear layer enveloping low-speed streaks, causing it to roll up into hairpin vortices at a faster rate. It is suggested that this occurs by the baroclinic vorticity generation mechanism which accelerates the streamwise grouping of vorticity during shear layer roll-up. The increased roll-up frequency leads to reduced streamwise spacing between hairpin vortices in wave packets. The density gradients also promote the sinuous instability mode in low-speed streaks. The resulting oscillations in the streaks in the streamwise-spanwise plane lead to locally reduced spanwise spacing between hairpin vortices forming over adjacent low-speed streaks. The reduction in streamwise and spanwise spacing between

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

    Science.gov (United States)

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

    2012-02-01

    We describe our surgical technique to manage a small aortic annulus during aortic valve replacement. Starting with the posterior annular enlargement incision described by Manouguian, a stentless porcine aortic root, with excision of the left and right porcine coronary segments and conservation of the mural wall (Freestyle MS design, Medtronic, Minneapolis, MN ), was used. The Freestyle bioprosthesis enlarges the aortic annulus using a direct suture of the valve on the enlarged annulus, and the aorta is closed by a direct suture of the mural wall of the bioprosthesis. Therefore, the aortic annulus enlargement is made only using the aortic bioprosthesis, without other material. Copyright © 2012 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  20. Application of digital image processing methods on the cluster structure at the wall of a circulating fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hai-guang; Zhao, Zeng-wu; Li, Bao-wei; Wu, Wen-fei [Inner Mongolia Univ. of Science and Technology, Baotou (China). School of Environment and Energy

    2013-07-01

    This paper describes experiments to investigate the cluster structure of gas-particle flow at the wall region of a circulating fluidized bed (CFB). The setup is in a cold scale-model circulating fluidized bed with a riser that has a 0.30 m 0.28 m cross-section and is 2.9 m tall. A video camera was utilized to visualize the cluster structure through a transparent Plexiglas wall. An image processing system was used to analyze images, which were obtained under different superficial gas velocities and solid circulating rates. The results show that distinctly different cluster structures exist in the different operating conditions, which the number, shape and size of the clusters are affected by main air flow.

  1. Vortex formation and stability analysis for shear flows over combined spatially and temporally structured walls

    Directory of Open Access Journals (Sweden)

    Riahi D. N.

    1999-01-01

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

  2. Application of X-ray and neutron small angle scattering techniques to study the hierarchical structure of plant cell walls: a review.

    Science.gov (United States)

    Martínez-Sanz, Marta; Gidley, Michael J; Gilbert, Elliot P

    2015-07-10

    Plant cell walls present an extremely complex structure of hierarchically assembled cellulose microfibrils embedded in a multi-component matrix. The biosynthesis process determines the mechanism of cellulose crystallisation and assembly, as well as the interaction of cellulose with other cell wall components. Thus, a knowledge of cellulose microfibril and bundle architecture, and the structural role of matrix components, is crucial for understanding cell wall functional and technological roles. Small angle scattering techniques, combined with complementary methods, provide an efficient approach to characterise plant cell walls, covering a broad and relevant size range while minimising experimental artefacts derived from sample treatment. Given the system complexity, approaches such as component extraction and the use of plant cell wall analogues are typically employed to enable the interpretation of experimental results. This review summarises the current research status on the characterisation of the hierarchical structure of plant cell walls using small angle scattering techniques. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  3. Fully-coupled fluid-structure interaction simulation of the aortic and mitral valves in a realistic 3D left ventricle model.

    Directory of Open Access Journals (Sweden)

    Wenbin Mao

    Full Text Available In this study, we present a fully-coupled fluid-structure interaction (FSI framework that combines smoothed particle hydrodynamics (SPH and nonlinear finite element (FE method to investigate the coupled aortic and mitral valves structural response and the bulk intraventricular hemodynamics in a realistic left ventricle (LV model during the entire cardiac cycle. The FSI model incorporates valve structures that consider native asymmetric leaflet geometries, anisotropic hyperelastic material models and human material properties. Comparison of FSI results with subject-specific echocardiography data demonstrates that the SPH-FE approach is able to quantitatively predict the opening and closing times of the valves, the mitral leaflet opening and closing angles, and the large-scale intraventricular flow phenomena with a reasonable agreement. Moreover, comparison of FSI results with a LV model without valves reveals substantial differences in the flow field. Peak systolic velocities obtained from the FSI model and the LV model without valves are 2.56 m/s and 1.16 m/s, respectively, compared to the Doppler echo data of 2.17 m/s. The proposed SPH-FE FSI framework represents a further step towards modeling patient-specific coupled LV-valve dynamics, and has the potential to improve our understanding of cardiovascular physiology and to support professionals in clinical decision-making.

  4. Simulating low frequency sound transmission through walls and windows by a two-way coupled fluid structure interaction model

    Science.gov (United States)

    Løvholt, Finn; Norèn-Cosgriff, Karin; Madshus, Christian; Ellingsen, Ståle Engvik

    2017-05-01

    Aircraft, supersonic flights, blasts, and explosions emit sound with substantial energy below 100 Hz. When the low frequency sound is transmitted inside a building, it generates vibration and rattling that may lead to annoyance. Our understanding of these low frequency phenomena is presently limited. In this paper, we attempt to improve our computational capabilities related to the low frequency sound transmission. For this purpose, a finite element methodology that incorporates a two-way coupled fluid-structure interaction, has been developed. Results from a broad experimental investigation of low frequency sound transmission are compared with the numerical finite element simulations. Plain walls, and walls with windows are studied. Close agreement between the simulations and the laboratory measurement data is obtained in the frequency range investigated (10-100 Hz). It was found that structural connections were of large importance for modeling the vibration and sound transmission. The windows control the low frequency transmission from 15 to 30 Hz, whereas the walls control the sound transmission from 30 to 100 Hz. Mitigation of vibrations and rattling induced by low frequency sound therefore needs to consider both wall and window construction.

  5. 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.

  6. Acute aortic syndromes: current status.

    Science.gov (United States)

    Ridge, Carole A; Litmanovich, Diana E

    2015-05-01

    The term acute aortic syndrome comprises aortic dissection, intramural hematoma, and penetrating atherosclerotic ulcer. The most recent developments in acute aortic syndromes include (1) a change in the mindset that each entity is pathologically distinct, with a shift toward considering the acute aortic syndromes as points along a spectrum of aortic disease, (2) the optimization of aortic imaging quality and radiation dose, and (3) surgical or endovascular management. This review article focuses on how these developments pertain to thoracic radiologists.

  7. Primary metastasizing aortic endothelioma.

    Science.gov (United States)

    Schmid, E; Port, S J; Carroll, R M; Friedman, N B

    1984-10-01

    An instance of malignant endothelioma, primary in the aorta, metastasizing to intestine and bone, is reported. The aortic tumor was successfully resected. The unexpected finding of a large hepatic growth at autopsy raised the possibility that the aortic neoplasm was a metastasis. Histochemical, immunologic, and ultrastructural studies supported the diagnosis of an endothelial neoplasm. Although a number of malignant aortic and large vessel tumors have been reported, only four previous instances appear to be endotheliomatous.

  8. 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...... assigned to the 'small' aortic size subset. Effective orifice area indices were calculated for all patients to assess the geographic distribution of patient-prosthesis mismatch. Univariable and multivariable logistic regression analyses adjusting for possible confounding variables were performed. RESULTS...

  9. 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.

  10. Neonatal aortic arch obstruction due to pedunculated left ventricular foetal myxoma.

    Science.gov (United States)

    Kaulitz, Renate; Haen, Susanne; Sieverding, Ludger

    2015-10-01

    Myxoma in neonatal life are extremely rare. We report a case of a neonate with a pedunculated cardiac tumour arising from the anterolateral left ventricular wall protruding across the left ventricular outflow tract and continuously extending into the distal aortic arch. Surgical removal at 14 days of age via combined transaortic approach and apical ventriculotomy was indicated because of the risk of further compromise of aortic valve function and aortic arch obstruction. Histopathologic examination was consistent with a myxoma.

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

    Science.gov (United States)

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

    2014-07-01

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

  12. 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.

  13. Nonlinear Modeling of Autoclaved Aerated Concrete Masonry Wall Strengthened using Ferrocement Sandwich Structure

    KAUST Repository

    M., Abdel-Mooty

    2011-01-01

    Autoclaved Aerated Concrete (AAC) block are used mainly as non-load-bearing walls that provide heat insulation. This results in considerable saving in cooling energy particularly in hot desert environment with large variation of daily and seasonal temperatures. However, due to the relatively low strength there use load bearing walls is limited to single storey and low-rise construction. A system to enhance the strength of the AAC masonry wall in resisting both inplane vertical and combined vertical and lateral loads using ferrocement technology is proposed in this research. The proposed system significantly enhances the load carrying capacity and stiffness of the AAC wall without affecting its insulation characteristics. Ferrocement is made of cement mortar reinforced with closely spaced wire mesh. Full scale wall specimens with height of 2100mm and width of 1820mm were tested with different configuration of ferrocement. A finite elementmodel is developed and verified against the experimentalwork. The results of the finite element model correlates well with the experimental results.

  14. 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)

  15. Structure of the poleward wall of the trough and the inclination of the geomagnetic field above the EISCAT radar

    Directory of Open Access Journals (Sweden)

    D. G. Jones

    Full Text Available A special high-resolution routine of the EISCAT radar has been used to investigate the structure and development of the poleward wall of a deep trough in electron density. The feature was tracked by the radar during a 7-hour period under very quiet geomagnetic conditions. The field-aligned nature of the structure enabled an estimate to be made of the inclination of the geomagnetic field above EISCAT that was in good agreement with the current model. Observations of narrow field-aligned enhancements in electron temperature demonstrated that the wall of this trough is a dynamic feature, reforming regularly as the electron density responds on a time scale of tens of minutes to energy input from soft-particle precipitation.

  16. Structure of the poleward wall of the trough and the inclination of the geomagnetic field above the EISCAT radar

    Directory of Open Access Journals (Sweden)

    D. G. Jones

    1997-06-01

    Full Text Available A special high-resolution routine of the EISCAT radar has been used to investigate the structure and development of the poleward wall of a deep trough in electron density. The feature was tracked by the radar during a 7-hour period under very quiet geomagnetic conditions. The field-aligned nature of the structure enabled an estimate to be made of the inclination of the geomagnetic field above EISCAT that was in good agreement with the current model. Observations of narrow field-aligned enhancements in electron temperature demonstrated that the wall of this trough is a dynamic feature, reforming regularly as the electron density responds on a time scale of tens of minutes to energy input from soft-particle precipitation.

  17. Aortic root reconstruction by aortic valve-sparing operation (David type I reimplantation) in Marfan syndrome accompanied by annuloaortic ectasia and acute type-A aortic dissection.

    Science.gov (United States)

    Inamura, Shunichi; Furuya, Hidekazu; Yagi, Kentarou; Ikeya, Eriko; Yamaguchi, Masaomi; Fujimura, Takabumi; Kanabuchi, Kazuo

    2006-09-20

    To reconstruct the aortic root for aneurysm of the ascending aorta accompanied by aortic regurgitation, annuloaortic ectasia (AAE) and acute type-A dissection with root destruction, the Bentall operation using a prosthetic valve still is the standard procedure today. Valve-sparing procedures have actively been used for aortic root lesions, and have also been attempted in aortic root reconstruction for Marfan syndrome which may have abnormalities in the valve leaflets. We conducted a valve-sparing procedure in a female patient with Marfan syndrome who had AAE accompanied by type-A acute aortic dissection. The patient was a 37-year-old woman complaining of severe pain from the chest to the back. The limbs were long, and funnel breast was observed. Diastolic murmurs were heard. On chest computed tomography, a dissection cavity was present from the ascending aorta to the left common iliac artery, and the root dilated to 55 mm. Grade II aortic regurgitation was observed on ultrasound cardiography. Regarding her family history, her father had died suddenly at 54 years of age. She was diagnosed with type-A acute dissection concurrent with Marfan syndrome and AAE. The structure of the aortic valve was normal, and root reconstruction by a valve-sparing operation and total replacement of the aortic arch was conducted. On postoperative ultrasound cardiography, the aortic regurgitation was within the allowable range, and the shortterm postoperative results were good.

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

    CERN Document Server

    Bratt, J.D.; Engelhardt, M.; Hagler, Ph.; Lin, H.W.; Lin, M.F.; Meyer, H.B.; Musch, B.; Negele, J.W.; Orginos, K.; Pochinsky, A.V.; Procura, M.; Richards, D.G.; Schroers, W.; Syritsyn, S.N.

    2010-01-01

    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. 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.

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

    Science.gov (United States)

    Xiong, Jiang; Guo, Wei; Wei, Ren; Zuo, Shang-wei; Liu, Xiao-ping; Zhang, Tao

    2013-02-01

    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. 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. 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 Elastic fibers have been successfully overexpressed both in vitro and in a rat model of AAA by a technique

  1. Thoracic aortic aneurysm in a child due to cystic medial necrosis

    International Nuclear Information System (INIS)

    Kuribayashi, Sachio; Watabe, Tsuneya; Ohtaki, Makoto; Matsuyama, Shoya; Ogawa, Junichi

    1983-01-01

    The valuable role of computed tomography (CT) was stressed in the diagnosis of thoracic aortic aneurysm in an asymptomatic 12-year-old child. She initially presented mediastinal mass on plain chest film. A saccular thoracic aortic aneurysm was highly suspected from the CT findings, and it was confirmed on angiography. Pathological examination of the aneurysmal wall revealed cystic medial necrosis. (author)

  2. Use of chemical fractionation and proton nuclear magnetic resonance to probe the physical structure of the primary plant cell wall

    International Nuclear Information System (INIS)

    Taylor, I.E.P.; Wallace, J.C.; MacKay, A.L.; Volke, F.

    1990-01-01

    Proton magnetic resonance has been used to monitor the microscopic physical properties of etiolated hypocotyl cell walls from Phaseolus vulgaris L. at all stages in a series of chemical fractionations with ammonium oxalate and potassium hydroxide. Solid echo measurements indicate that 75% of the polymers in the intact cell wall, including the cellulose and most of the hemicelluloses, are arranged such that there is almost complete restraint of molecular motion. The chemical fractionations generally altered the physical structures of the remaining cell wall components. Digestion with 0.25% ammonium oxalate/oxalic acid solubilized the pectin and increased the mobility of the hemicellulose I component. Extraction with 4% potassium hydroxide removed the hemicellulose I component and loosened the hemicellulose II. Further extraction with 24% potassium hydroxide removed the hemicellulose II and loosened some of the cellulose. The cellulose crystallinity, as monitored by Jeener echo measurements decreased from 83% to 63% during these fractionations. We conclude that, while hemicellulose I is firmly attached to hemicellulose II, it is not in a closely packed structure. Hemicellulose II is strongly bound to cellulose and has a much more closely packed structure

  3. Impact of non-pyrethroid insecticide treated durable wall lining on age structure of malaria vectors in Muheza, Tanzania.

    Science.gov (United States)

    Emidi, Basiliana; Kisinza, William N; Mosha, Franklin W

    2017-12-19

    Malaria vectors control interventions are designed to cause immediate killing or shorten mosquito lives, therefore does not allow enough time for the development of the parasites to infective stage. The wall lining is new malaria vectors control intervention in Tanzania where its impact on age structure is not well known. Therefore this study aimed at determining the impact of non-pyrethroid durable wall lining on the age structure of malaria vectors. Higher proportions of An. gambiae sensu lato (57.1%, z = 2.66, P = 0.0077) and An. funestus (64.8%, z = 3.38, P = 0.001) were collected in the control clusters. Unexpectedly, significantly higher proportion of parous An. gambiae s. l. were collected in the intervention clusters (z = - 2.78, P = 0.0054). The wall lining intervention has demonstrated low impact on age structure of An. gambiae s. l., this call for further studies on the efficacy of the intervention.

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

    International Nuclear Information System (INIS)

    McKeon, B.J.; Sreenivasan, K.R.

    2007-05-01

    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)

  5. 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.

  6. 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.

  7. Structural and electronic properties of alkali-doped single-walled carbon nanotubes

    Science.gov (United States)

    Nemes, Norbert Marcel

    In this thesis, we study the properties of alkali doped single walled carbon nanotubes (SWNT). SWNT are crystallized into ropes, which display the one-dimensional electronic properties of the constituent nanotubes. Using x-ray diffraction, we show that the alkali atoms invade the channels in the triangular rope lattice and determine the structure of the doped ropes. We show that the diffraction profile of the doped SWNT is best described by a model where the alkali ions surround each tube in an ordered fashion by dilating the channels. Alkali doped SWNT exhibit colors similar to alkali doped graphite (GIC). We study their electronic structure with IR reflectivity; the alkali dopants donate their valence electron to the SWNT host, so the free carrier concentration increases, shifting the Drude-edge into the visible spectral range. This is accompanied by a large shift of the Fermi-level, so the characteristic transitions between the 1D van Hove singularities of the undoped SWNT diminish. The presence of the alkali ions around the SWNT breaks the translational symmetry and increases coupling between parallel tubes within ropes. We find that the momentum relaxation time shortens as the ropes become more three dimensional. We also find that alkali disorder contributes to the scattering. In p-type, HNO3 doped SWNT, the charge transfer is smaller; only the first subband of the semiconducting tubes gets depleted, shown by the disappearance of the first van Hove transition. This indicates a Fermi-level shift of ˜0.3 eV. The reflectivity has structure at low energy, which moves the Drude-peak to a sharp, intense peak at 0.1 eV in the optical conductivity, reminiscent of quasi-1D TTF-TCNQ. The DC conductivity also increases ˜80-fold during doping. The low temperature divergence of undoped SWNT disappears in alkali doped SWNT. However, we find that oxygen can modulate the low-T divergence. After outgassing, the divergence becomes ˜10 times stronger. We interpret the low

  8. Aortic valve surgery - open

    Science.gov (United States)

    ... while you are connected to this machine. This machine does the work of your heart while your heart is stopped. If your aortic valve is too damaged, you will need a new valve. This is called replacement surgery. Your surgeon will remove your aortic valve ...

  9. Imaging in aortic dissection

    International Nuclear Information System (INIS)

    Yu-Qing Liu, M.D.

    1995-01-01

    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.)

  10. Aortic arch malformations

    International Nuclear Information System (INIS)

    Kellenberger, Christian J.

    2010-01-01

    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.)

  11. [Traumatic aortic valve insufficiency].

    Science.gov (United States)

    Nascimento, J; Lemos, C; Marques, A M; Antunes, M J; Gonsalves, A

    1996-02-01

    The traumatic aortic valvular insufficiency (TAVI), through less frequent after a non-penetrating thoracic traumatism, is a serious entity with a very reserved prognosis. So it must be suspected in every patients with signs or symptoms of de novo heart failure post-traumatism. The transthoracic echocardiography and eventually transesophageal echocardiography have a fundamental role in the confirmation of the diagnosis. The clinical picture of traumatic aortic regurgitation is quickly evolutionary and the non efficacy of medical therapy has placed the valvular substitution surgery as the best succeeded treatment. With the advent of the aortic valve repairing surgery some TAVI cases has been submitted to this procedure. Nevertheless, the development of residual aortic regurgitation in these situations, usually requiring later valvular replacement surgery, make the aortic valvuloplasty a controversial surgical technique. The AA describe a recent clinical case of aortic regurgitation after a non-penetrant thoracic traumatism, discussing the aspects connected with physiopathology, diagnosis and therapy. The singularity of this case was based on the fact that the initial clinical diagnosis had been prejudiced by the context of a polytraumatism and there had been a time free of symptoms between the traumatism and the beginning of the symptomatology of left ventricular failure. Even though the identification of the problem allowed an intensive treatment of this serious situation that ended with the replacement of the aortic valve by mechanical aortic prosthesis, with the patient's total recovery.

  12. Structure and Function of the First Full-Length Murein Peptide Ligase (Mpl) Cell Wall Recycling Protein

    Science.gov (United States)

    Das, Debanu; Hervé, Mireille; Feuerhelm, Julie; Farr, Carol L.; Chiu, Hsiu-Ju; Elsliger, Marc-André; Knuth, Mark W.; Klock, Heath E.; Miller, Mitchell D.; Godzik, Adam; Lesley, Scott A.; Deacon, Ashley M.; Mengin-Lecreulx, Dominique; Wilson, Ian A.

    2011-01-01

    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. PMID:21445265

  13. Structural Health Monitoring of Above-Ground Storage Tank Floors by Ultrasonic Guided Wave Excitation on the Tank Wall

    Directory of Open Access Journals (Sweden)

    Premesh S. Lowe

    2017-11-01

    Full Text Available There is an increasing interest in using ultrasonic guided waves to assess the structural degradation of above-ground storage tank floors. This is a non-invasive and economically viable means of assessing structural degradation. Above-ground storage tank floors are ageing assets which need to be inspected periodically to avoid structural failure. At present, normal-stress type transducers are bonded to the tank annular chime to generate a force field in the thickness direction of the floor and excite fundamental symmetric and asymmetric Lamb modes. However, the majority of above-ground storage tanks in use have no annular chime due to a simplified design and/or have a degraded chime due to corrosion. This means that transducers cannot be mounted on the chime to assess structural health according to the present technology, and the market share of structural health monitoring of above-ground storage tank floors using ultrasonic guided wave is thus limited. Therefore, the present study investigates the potential of using the tank wall to bond the transducer instead of the tank annular chime. Both normal and shear type transducers were investigated numerically, and results were validated using a 4.1 m diameter above-ground storage tank. The study results show shear mode type transducers bonded to the tank wall can be used to assess the structural health of the above-ground tank floors using an ultrasonic guided wave. It is also shown that for the cases studied there is a 7.4 dB signal-to-noise ratio improvement at 45 kHz for the guided wave excitation on the tank wall using shear mode transducers.

  14. Structural Health Monitoring of Above-Ground Storage Tank Floors by Ultrasonic Guided Wave Excitation on the Tank Wall.

    Science.gov (United States)

    Lowe, Premesh S; Duan, Wenbo; Kanfoud, Jamil; Gan, Tat-Hean

    2017-11-04

    There is an increasing interest in using ultrasonic guided waves to assess the structural degradation of above-ground storage tank floors. This is a non-invasive and economically viable means of assessing structural degradation. Above-ground storage tank floors are ageing assets which need to be inspected periodically to avoid structural failure. At present, normal-stress type transducers are bonded to the tank annular chime to generate a force field in the thickness direction of the floor and excite fundamental symmetric and asymmetric Lamb modes. However, the majority of above-ground storage tanks in use have no annular chime due to a simplified design and/or have a degraded chime due to corrosion. This means that transducers cannot be mounted on the chime to assess structural health according to the present technology, and the market share of structural health monitoring of above-ground storage tank floors using ultrasonic guided wave is thus limited. Therefore, the present study investigates the potential of using the tank wall to bond the transducer instead of the tank annular chime. Both normal and shear type transducers were investigated numerically, and results were validated using a 4.1 m diameter above-ground storage tank. The study results show shear mode type transducers bonded to the tank wall can be used to assess the structural health of the above-ground tank floors using an ultrasonic guided wave. It is also shown that for the cases studied there is a 7.4 dB signal-to-noise ratio improvement at 45 kHz for the guided wave excitation on the tank wall using shear mode transducers.

  15. Role of the Candida albicans MNN1 gene family in cell wall structure and virulence

    NARCIS (Netherlands)

    Bates, S.; Hall, R.A.; Cheetham, J.; Netea, M.G.; MacCallum, D.M.; Brown, A.J.; Odds, F.C.; Gow, N.A.

    2013-01-01

    BACKGROUND: The Candida albicans cell wall is the first point of contact with the host, and its outer surface is heavily enriched in mannoproteins modified through the addition of N- and O-mannan. Previous work, using mutants with gross defects in glycosylation, has clearly identified the importance

  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. Effects of multi-wall carbon nanotubes on structural and mechanical ...

    Indian Academy of Sciences (India)

    2017-09-22

    Sep 22, 2017 ... Abstract. Poly(3-hydroxybutyrate) (PHB)/chitosan electrospun scaffold was recently prepared for cartilage tissue engineering purpose. The drawback of this scaffold was its low mechanical properties. This study was carried out to see if addition of multi-wall carbon nanotubes (MWNTs) to PHB/chitosan ...

  18. The effect of fibronectin on structural and biological properties of single walled carbon nanotube

    International Nuclear Information System (INIS)

    Mottaghitalab, Fatemeh; Farokhi, Mehdi; Atyabi, Fatemeh; Omidvar, Ramin; Shokrgozar, Mohammad Ali; Sadeghizadeh, Majid

    2015-01-01

    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

  19. 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....

  20. An investigation on vulnerability assessment of steel structures with thin steel shear wall through development of fragility curves

    Directory of Open Access Journals (Sweden)

    Mohsen Gerami

    2017-02-01

    Full Text Available Fragility curves play an important role in damage assessment of buildings. Probability of damage induction to the structure against seismic events can be investigated upon generation of afore mentioned curves. In current research 360 time history analyses have been carried out on structures of 3, 10 and 20 story height and subsequently fragility curves have been adopted. The curves are developed based on two indices of inter story drifts and equivalent strip axial strains of the shear wall. Time history analysis is carried out in Perform 3d considering 10 far field seismograms and 10 near fields. Analysis of low height structures revealed that they are more vulnerable in accelerations lower than 0.8 g in near field earthquakes because of higher mode effects. Upon the generated fragility curves it was observed that middle and high structures have more acceptable performance and lower damage levels compared to low height structures in both near and far field seismic hazards.

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

    International Nuclear Information System (INIS)

    Resasco, Daniel E.

    2010-01-01

    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.

  2. A multifunctional mannosyltransferase family in Candida albicans determines cell wall mannan structure and host-fungus interactions.

    Science.gov (United States)

    Mora-Montes, Héctor M; Bates, Steven; Netea, Mihai G; Castillo, Luis; Brand, Alexandra; Buurman, Ed T; Díaz-Jiménez, Diana F; Jan Kullberg, Bart; Brown, Alistair J P; Odds, Frank C; Gow, Neil A R

    2010-04-16

    The cell wall proteins of fungi are modified by N- and O-linked mannosylation and phosphomannosylation, resulting in changes to the physical and immunological properties of the cell. Glycosylation of cell wall proteins involves the activities of families of endoplasmic reticulum and Golgi-located glycosyl transferases whose activities are difficult to infer through bioinformatics. The Candida albicans MNT1/KRE2 mannosyl transferase family is represented by five members. We showed previously that Mnt1 and Mnt2 are involved in O-linked mannosylation and are required for virulence. Here, the role of C. albicans MNT3, MNT4, and MNT5 was determined by generating single and multiple MnTDelta null mutants and by functional complementation experiments in Saccharomyces cerevisiae. CaMnt3, CaMnt4, and CaMnt5 did not participate in O-linked mannosylation, but CaMnt3 and CaMnt5 had redundant activities in phosphomannosylation and were responsible for attachment of approximately half of the phosphomannan attached to N-linked mannans. CaMnt4 and CaMnt5 participated in N-mannan branching. Deletion of CaMNT3, CaMNT4, and CaMNT5 affected the growth rate and virulence of C. albicans, affected the recognition of the yeast by human monocytes and cytokine stimulation, and led to increased cell wall chitin content and exposure of beta-glucan at the cell wall surface. Therefore, the MNT1/KRE2 gene family participates in three types of protein mannosylation in C. albicans, and these modifications play vital roles in fungal cell wall structure and cell surface recognition by the innate immune system.

  3. Subcoronary versus supracoronary aortic stenosis. an experimental evaluation

    Directory of Open Access Journals (Sweden)

    Hasenkam J Michael

    2011-08-01

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

  4. Subcoronary versus supracoronary aortic stenosis. An experimental evaluation.

    Science.gov (United States)

    Sorensen, Mette; Hasenkam, J Michael; Jensen, Henrik; Sloth, Erik

    2011-08-22

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

  5. Spiral CT aortography: an efficient technique for the diagnosis of traumatic aortic injury

    International Nuclear Information System (INIS)

    Wicky, S.; Capasso, P.; Meuli, R.; Schnyder, P.; Fischer, A.; Segesser, L. von

    1998-01-01

    The objective of this study was to assess the efficiency of spiral CT (SCT) aortography for diagnosing acute aortic lesions in blunt thoracic trauma patients. Between October 1992 and June 1997, 487 SCT scans of the chest were performed on blunt thoracic trauma patients. To assess aortic injury, the following SCT criteria were considered: hemomediastinum, peri-aortic hematoma, irregular aspect of the aortic wall, aortic pseudodiverticulum, intimal flap and traumatic dissection. Aortic injury was diagnosed on 14 SCT examinations (2.9 %), five of the patients having had an additional digital aortography that confirmed the aortic trauma. Twelve subjects underwent surgical repair of the thoracic aorta, which in all but one case confirmed the aortic injury. Two patients died before surgery from severe brain lesions. The aortic blunt lesions were confirmed at autopsy. According to the follow-up of the other 473 patients, we are aware of no false-negative SCT examination. Our limited series shows a sensitivity of 100 % and specificity of 99.8 % of SCT aortography in the diagnosis of aortic injury. It is concluded that SCT aortagraphy is an accurate diagnostic method for the assessment of aortic injury in blunt thoracic trauma patients. (orig.)

  6. Aortic distensibility after aortic root replacement assessed with cardiovascular magnetic resonance.

    Science.gov (United States)

    Melina, Giovanni; Rajappan, Kim; Amrani, Mohamed; Khaghani, Asghar; Pennell, Dudley J; Yacoub, Magdi H

    2002-01-01

    The changes in geometry of the aortic root during the cardiac cycle are thought to be essential for optimal valve function, both in terms of leaflet stress and dynamic behavior. Using cardiac magnetic resonance (CMR), the study aim was to determine aortic root distensibility of the homograft (group H) and the Medtronic Freestyle xenograft (group F) after aortic root replacement, from a prospective randomized trial. CMR was performed in 15 patients (six homografts, nine Freestyle) at six months and one year after surgery. Percentage change in aortic radius (PCR) and pressure strain elastic modulus (PSEM) were measured as indices of distensibility, and results related to left ventricular mass (LVM). At six months after surgery, mean PCR was 12+/-2.5 in group H and 12.9+/-6.1 in group F (p = NS), and PSEM was 428.5+/-69.8 and 493.5+/-72.7 g/cm2, respectively (p = NS). PCR was reduced to 10+/-1.7% in group H, and by 8.5+/-2.8% in group F (p = NS), while PSEM was increased to 520.5+/-87.3 and 825+/-420.4, respectively (p = NS) at the one-year follow up. Regression analysis showed a correlation between PCR and LVM (r = 0.52, p = 0.08) and LVM index (r = 0.46, p = 0.14), respectively. In addition, there was a relationship between PSEM, LVM and LVM index, suggesting that the stiffer the root wall, the higher the postoperative LVM. Up to one year after aortic root replacement, the wall of both the allogenic and xenogenic valves retained near-normal distensibility. For the first time, a correlation was demonstrated between the elastic properties of the aortic root and LVM. The longer-term behavior and clinical implications of these findings require further investigation.

  7. Analysis of the response of a reinforced concrete shear wall structure during earthquakes using the transfer matrix method of multibody systems

    Directory of Open Access Journals (Sweden)

    Jianguo Ding

    2016-05-01

    Full Text Available Although reinforced concrete shear wall structures are widely used in high-rise buildings, the methods used to analyze the seismic response of such a structure during an earthquake generally have low calculation efficiencies. In this article, the transfer matrix method of multibody systems is first established as a mechanical model of a regular reinforced concrete shear wall structure with both bifurcated and closed transfer paths to analyze the seismic responses of structures. By separating the shear wall legs, establishing a state vector relationship between the two endpoints of the coupling beams, and combining all state vectors of the inputs or outputs of each shear wall leg, the total transfer between shear wall legs is realized, and the overall transfer equation and overall transfer matrix of a shear wall structure are obtained. Applying the transfer matrix method of multibody systems, a 15-story shear wall structure is used as an engineering example to analyze seismic responses for frequent and rare earthquakes using MATLAB software. The findings show that the transfer matrix method of multibody systems provides similar results to ANSYS but that the transfer matrix method of multibody systems greatly increases calculation efficiency while maintaining accuracy.

  8. 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.

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

    Science.gov (United States)

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

    2014-01-01

    Covered stents have been used for the treatment of aortic coarctation to protect the arterial wall during dilation. Early results have shown them to be safe and effective. We report two cases of infolding of the proximal edge of a covered aortic coarctation stent. Management required implantation of a second stent. Poor stent apposition to the vessel wall and/or recoil may allow conditions for these events to occur. Copyright © 2013 Wiley Periodicals, Inc.

  10. Structure of steroids and their diffusion through blood vessel walls in a counter-current system

    International Nuclear Information System (INIS)

    McCracken, J.A.; Schramm, W.; Einer-Jensen, N.

    1984-01-01

    Several substances including prostaglandin F2 alpha, progesterone and 85 krypton have been shown to be transferred from the venous side to the arterial side of the circulation in the ovarian vascular pedicle. Experiments were therefore carried out to study the transfer of three pairs of steroids (progesterone and 20 alpha-dihydroprogesterone, C-21; androstenedione and testosterone, C-19; and estrone and estradiol-17 beta, C-18) in which each member of a pair differed by one hydroxyl group. Each pair of steroids, one labeled with 3 H and the other with 14 C, were infused in sequence for 30 minutes into a side branch of an ovarian vein near the hilus of the ovary with a rest period of 90 minutes between infusions. An increase in radioactivity in ovarian arterial plasma compared to the radioactivity in an equal volume of aortic plasma sampled simultaneously was used as the index for a direct transfer of steroids from the ovarian vein to the adjacent ovarian artery. All six steroids showed such a transfer which began 3 to 6 minutes after the start of each infusion and decreased rapidly after the infusion was stopped. The results of this study also showed that a larger quantity of the less polar (ketonic) form of each steroid pair examined was transferred than its hydroxyl counterpart

  11. Structure-Processing-Property Interrelationships of Vapor Grown Carbon Nanofiber, Single-Walled Carbon Nanotube and Functionalized Single-Walled Carbon Nanotube - Polypropylene Nanocomposites

    Science.gov (United States)

    Radhakrishnan, Vinod Karumathil

    This dissertation describes the first use of a design of experiments approach to investigate the interrelationships between structure, processing, and properties of melt extruded polypropylene (PP) carbon nanomaterial composites. The effect of nanomaterial structure was evaluated by exploring the incorporation of vapor grown carbon nanofibers (VGCFs), or pristine or functionalized single-walled carbon nanotubes (SWNTs or C12SWNTs) in polypropylene, while the effect of processing was investigated by studying the influence of melt extrusion temperature, speed, and time. The nanomaterials and PP were combined by an initial mixing method prior to melt extrusion. The nanocomposite properties were characterized by a combination of morphological, rheological, and thermal methods. Preliminary investigations into the effects of the initial mixing method revealed that the distribution of nanomaterials obtained after the mixing had a considerable influence on the properties of the final melt extruded nanocomposite. Dry mixing (DM) resulted in minimal adhesion between nanomaterials and PP during initial mixing; the majority of nanomaterials descended to the bottom. Hot coagulation (HC) mixing resulted in extremely high degrees of interaction between the nanomaterials and PP chains. Rotary evaporation (RE) mixing resulted in nanomaterial distribution uniformity between that obtained from DM and HC. Employing design of experiments to investigate the effects of structure and processing conditions on melt extruded PP nanocomposite properties revealed several interesting effects. The effect of processing conditions varied depending on the degree of nanomaterial distribution in PP attained prior to melt processing. Increasing melt extrusion temperature increased the decomposition temperature (Td) of PP/C12SWNT obtained from HC mixing but decreased T d of PP/C12SWNT obtained from RE mixing. Higher melt extrusion screw speed, on the other hand, significantly improved the nanocomposite

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

    Directory of Open Access Journals (Sweden)

    Pitsis Antonis

    2009-09-01

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

  13. FOXE3 mutations predispose to thoracic aortic aneurysms and dissections

    Science.gov (United States)

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

    2016-01-01

    The ascending thoracic aorta is designed to withstand biomechanical forces from pulsatile blood. Thoracic aortic aneurysms and acute aortic dissections (TAADs) occur as a result of genetically triggered defects in aortic structure and a dysfunctional response to these forces. Here, we describe mutations in the forkhead transcription factor FOXE3 that predispose mutation-bearing individuals to TAAD. We performed exome sequencing of a large family with multiple members with TAADs and identified a rare variant in FOXE3 with an altered amino acid in the DNA-binding domain (p.Asp153His) that segregated with disease in this family. Additional pathogenic FOXE3 variants were identified in unrelated TAAD families. In mice, Foxe3 deficiency reduced smooth muscle cell (SMC) density and impaired SMC differentiation in the ascending aorta. Foxe3 expression was induced in aortic SMCs after transverse aortic constriction, and Foxe3 deficiency increased SMC apoptosis and ascending aortic rupture with increased aortic pressure. These phenotypes were rescued by inhibiting p53 activity, either by administration of a p53 inhibitor (pifithrin-α), or by crossing Foxe3–/– mice with p53–/– mice. Our data demonstrate that FOXE3 mutations lead to a reduced number of aortic SMCs during development and increased SMC apoptosis in the ascending aorta in response to increased biomechanical forces, thus defining an additional molecular pathway that leads to familial thoracic aortic disease. PMID:26854927

  14. Isolation and chemical structure of the peptidoglycan of Spirillum serpens cell walls.

    Science.gov (United States)

    Kolenbrander, P E; Ensign, J C

    1968-01-01

    The peptidoglycan layer of Spirillum serpens cell walls was isolated from intact cells after treatment with sodium dodecylsulfate and digestion with Pronase. The isolated peptidoglycan contained glucosamine, muramic acid, alanine, glutamic acid, and meso-diaminopimelic acid in the approximate molar ratio of 1:1:2:1:1. Aspartic acid and glycine were the only other amino acids found in significant quantities. N-terminal amino acid analyses of the tetrapeptide amino acids in the peptidoglycan revealed that 54% of the diaminopimelic acid molecules are involved in cross-linkage between tetrapeptides. This amount of cross-linkage is greater than that found in the peptidoglycan of previously studied cell walls of gram-negative bacteria. The polysaccharide backbone was isolated, after myxobacter AL-1 enzyme digestion of the peptidoglycan, by fractionation with ECTEOLA-cellulose and Sephadex G-100. An average length of 99 hexosamines for the polysaccharide chains was found (ratio of total hexosamines to reducing end groups).

  15. 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.

  16. Structure and Characterization of Vertically Aligned Single-Walled Carbon Nanotube Bundles

    International Nuclear Information System (INIS)

    Marquez, F.; Morant, C.; Elizalde, E.; Roque-Malherbe, R.; Lopez, V.; Zamora, F.; Domingo, C.

    2010-01-01

    Arrays of vertically aligned single-walled carbon nanotube bundles, SWCNTs, have been synthesized by simple alcohol catalytic chemical vapor deposition process, carried out at 800 degree C. The formed SWCNTs are organized in small groups perpendicularly aligned and attached to the substrate. These small bundles show a constant diameter of ca. 30 nm and are formed by the adhesion of no more than twenty individual SWCNTs perfectly aligned along their length.

  17. Studies of dust from JET with the ITER-Like Wall: Composition and internal structure

    Directory of Open Access Journals (Sweden)

    E. Fortuna-Zaleśna

    2017-08-01

    Full Text Available Results are presented for the dust survey performed at JET after the second experimental campaign with the ITER-Like Wall: 2013–2014. Samples were collected on adhesive stickers from several different positions in the divertor both on the tiles and on the divertor carrier. Brittle dust-forming deposits on test mirrors from the inner divertor wall were also studied. Comprehensive characterization accomplished by a wide range of high-resolution microscopy techniques, including focused ion beam, has led to the identification of several classes of particles: (i beryllium flakes originating either from the Be coatings from the inner wall cladding or Be-rich mixed co-deposits resulting from material migration; (ii beryllium droplets and splashes; (iii tungsten and nickel-rich (from Inconel droplets; (iv mixed material layers with a various content of small (8–200nm W-Mo and Ni-based debris. A significant content of nitrogen from plasma edge cooling has been identified in all types of co-deposits. A comparison between particles collected after the first and second experimental campaign is also presented and discussed.

  18. PIV Measurement of Wall Shear Stress and Flow Structures within an Intracranial Aneurysm Model

    Science.gov (United States)

    Chow, Ricky; Sparrow, Eph; Campbell, Gary; Divani, Afshin; Sheng, Jian

    2012-11-01

    The formation and rupture of an intracranial aneurysm (IA) is a debilitating and often lethal event. Geometric features of the aneurysm bulb and upstream artery, such as bulb size, bulb shape, and curvature of the artery, are two groups of factors that define the flow and stresses within an IA. Abnormal flow stresses are related to rupture. This presentation discusses the development of a quasi-3D PIV technique and its application in various glass models at Re = 275 and 550 to experimentally assess at a preliminary level the impact of geometry and flow rate. Some conclusions are to be drawn linking geometry of the flow domain to rupture risk. The extracted results also serve as the baseline case and as a precursor to a companion presentation by the authors discussing the impact of flow diverters, a new class of medical devices. The PIV experiments were performed in a fully index-matched flow facility, allowing for unobstructed observations over complex geometry. A reconstruction and analysis method was devised to obtain 3D mean wall stress distributions and flow fields. The quasi 3D measurements were reconstructed from orthogonal planes encompassing the entire glass model, spaced 0.4mm apart. Wall shear stresses were evaluated from the near-wall flow viscous stresses.

  19. The effect of surface roughness on the turbulence structure of a plane wall jet

    Science.gov (United States)

    Rostamy, N.; Bergstrom, D. J.; Sumner, D.; Bugg, J. D.

    2011-08-01

    In this paper, an experimental investigation of the turbulence characteristics of a plane wall jet over smooth and rough surfaces, using laser Doppler anemometry (LDA), is reported. The Reynolds number based on the slot height and exit velocity of the jet was approximately Re = 7500. A 36-grit sheet was used as the rough surface, creating a transitionally rough flow regime (44surface roughness on the Reynolds stress profiles. Comparisons between the present results and other LDA and hot-wire anemometry studies for a smooth surface indicate a similar behavior for the Reynolds stress profiles. However, the magnitudes of the peak values of the Reynolds stress were higher than in most previous studies due to the lower slot Reynolds number. The present results indicate that surface roughness does not appear to significantly modify the Reynolds stress profiles in the outer region of the jet except for a reduction in the level. In contrast, surface roughness modifies both the shape and magnitudes of the Reynolds stress profiles in the inner layer. Due to the much higher friction velocity for a rough surface, the magnitudes of both the streamwise and wall-normal Reynolds stress decrease in the inner region when normalized using inner scales compared to the smooth-wall values.

  20. Composition and structure of tuber cell walls affect in vitro digestibility of potato (Solanum tuberosum L.).

    Science.gov (United States)

    Frost, Jovyn K T; Flanagan, Bernadine M; Brummell, David A; O'Donoghue, Erin M; Mishra, Suman; Gidley, Michael J; Monro, John A

    2016-10-12

    The digestibility of starchy foods, such as potatoes, can be characterized by the proportion of starch that is rapidly digestible by in vitro hydrolysis (rapidly digestible starch, RDS). This study evaluated the RDS content in a potato germplasm collection consisting of 98 genotypes and identified three advanced lines, Crop39, Crop71 and Crop85, where cooked potato RDS content was significantly lower than that of their respective isolated starches (P starch did not differ significantly from that of five control lines with higher RDS contents. Cell wall analyses revealed that, compared with other lines tested, Crop39, Crop71 and Crop85 had at least four times the amount of rhamnogalacturonan-I (RG-I) galactan side-chains that were very firmly attached to the wall and requiring 4 M KOH for extraction. Pectin solubilization during cooking was also remarkably low (2-4%) in these three lines compared with other lines tested (7-19%). The findings suggest that possession of higher amounts of RG-I galactan that interact strongly with cellulose may provide a sturdier wall that better resists solubilization during cooking, and effectively impedes access of digestive enzymes for starch hydrolysis in an in vitro model.

  1. Shear-stress-induced structural arrangement of water molecules in nanoscale Couette flow with slipping at wall boundary

    International Nuclear Information System (INIS)

    Lin, Jau-Wen

    2014-01-01

    This study investigated the structuring of water molecules in a nanoscale Couette flow with the upper plate subjected to lateral forces with various magnitudes and water slipping against a metal wall. It was found that when the upper plate is subjected to a force, the water body deforms into a parallelepiped. Water molecules in the channel are then gradually arranged into lattice positions, creating a layered structure. The structural arrangement of water molecules is caused by the water molecules accommodating themselves to the increase in energy under the application of a lateral force on the moving plate. The ordering arrangement of water molecules increases the rotational degree of freedom, allowing the molecules to increase their Coulomb potential energy through polar rotation that accounts for the energy input through the upper plate. With a force continuously applied to the upper plate, the water molecules in contact with the upper plate move forward until slip between the water and upper plate occurs. The relation between the structural arrangement of water molecules, slip at the wall, and the shear force is studied. The relation between the slip and the locking/unlocking of water molecules to metal atoms is also studied

  2. 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

  3. Synthesis of palladium nanoparticle modified reduced graphene oxide and multi-walled carbon nanotube hybrid structures for electrochemical applications

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jie, E-mail: hujie@tyut.edu.cn [Micro and Nano System Research Center, Key Lab of Advanced Transducers and Intelligent Control System (Ministry of Education) & College of Information Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi (China); Zhao, Zhenting; Zhang, Jun; Li, Gang; Li, Pengwei; Zhang, Wendong [Micro and Nano System Research Center, Key Lab of Advanced Transducers and Intelligent Control System (Ministry of Education) & College of Information Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi (China); Lian, Kun, E-mail: liankun@tyut.edu.cn [Micro and Nano System Research Center, Key Lab of Advanced Transducers and Intelligent Control System (Ministry of Education) & College of Information Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi (China); School of Nano-Science and Nano-Engineering, Suzhou & Collaborative Innovation Center of Suzhou Nano Science and Technology, Xi' an Jiaotong University, Xi' an, 710049 (China); Center for Advanced Microstructures and Devices, Louisiana State University, LA, 70806 (United States)

    2017-02-28

    Graphical abstract: A sensitive hydrazine electrochemical sensor was fabricated by using palladium (Pd) nanoparticle functionalized reduced graphene oxide (rGO) and multi-walled carbon nanotube (MWCNTs) hybrid structures (Pd/rGO-MWCNTs). - Highlights: • rGO-MWCNTs hybrid structures and Pd nanoparticles are prepared using electrochemical methods. • rGO-MWCNTs hybrid films are used as supports and co-catalysts for Pd nanoparticles. • The Pd/rGO-MWCNTs hybrid structure based sensor shows an ultra-high sensitivity of 7.09 μA μM{sup −1} cm{sup −2} and a low detection limit of 0.15 μM. • The proposed electrochemical sensor exhibits excellent selectivity. - Abstract: In this work, palladium (Pd) nanoparticles functionalized reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) hybrid structures (Pd/rGO-MWCNTs) were successfully prepared by a combination of electrochemical reduction with electrodeposition method. The morphology, structure, and composition of the Pd/rGO-MWCNTs hybrid were characterized by scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy. The as-synthesized hybrid structures were modified on the glassy carbon electrode (GCE) and further utilized for hydrazine sensing. Electrochemical impedance spectroscopic, cyclic voltammetry and single-potential amperometry experiments were carried out on Pd/rGO-MWCNTs hybrid structures to investigate the interface properties and sensing performance. The measured results demonstrate that the fabricated Pd/rGO-MWCNTs/GCE sensor show a high sensitivity of 7.09 μA μM{sup −1} cm{sup −2} in a large concentration range of 1.0 to 1100 μM and a low detection limit of 0.15 μM. Moreover, the as-prepared sensor exhibits good selectivity and stability for the determination of hydrazine under interference conditions.

  4. Maternal educational level and blood pressure, aortic stiffness, cardiovascular structure and functioning in childhood : The generation R study

    NARCIS (Netherlands)

    S.H. Bouthoorn (Selma); F.J. van Lenthe (Frank); L.L. de Jonge (Layla); A. Hofman (Albert); L. van Osch-Gevers (Lennie); V.W.V. Jaddoe (Vincent); H. Raat (Hein)

    2014-01-01

    textabstractbackground In adults, low level of education was shown to be associated with higher blood pressure levels and alterations in cardiac structures and function. It is currently unknown whether socioeconomic inequalities in arterial and cardiac alterations originate in childhood. Therefore,

  5. 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.

  6. Structural Failure Sites in Anterior Vaginal Wall Prolapse: Identification of a Collinear Triad.

    Science.gov (United States)

    Chen, Luyun; Lisse, Sean; Larson, Kindra; Berger, Mitchell B; Ashton-Miller, James A; DeLancey, John O L

    2016-10-01

    To test the null hypothesis that six factors representing potential fascial and muscular failure sites contribute equally to the presence and size of a cystocele: two vaginal attachment factors (apical support and paravaginal defects), two vaginal wall factors (vaginal length and width), and two levator ani factors (hiatus size and levator ani defects). Thirty women with anterior-predominant prolapse (women in a case group) and 30 women in a control group underwent three-dimensional stress magnetic resonance imaging. The location of the anterior vaginal wall at maximal Valsalva was identified with the modified Pelvic Inclination Coordinate System and the six factors measured. Analysis included repeated-measure analysis of variance, logistic regression, and stepwise linear regression. We identified a collinear triad consisting of apical location, paravaginal location, and hiatus size that were not only the strongest predictors of cystocele size, but were also highly correlated with one another (r=0.84-0.89, P<.001) for the presence and size of the prolapse. Together they explain up to 83% of the variation in cystocele size. Among the less significant vaginal factors, vaginal length explained 19% of the variation in cystocele size, but no significant difference in vaginal width existed. Women in the case group were more likely to have abnormalities in collinear triad factors (up to 80%) than vaginal wall factors (up to 23.3%). Combining the strongest collinear triad with the vaginal factors, the model explained 92.5% of the variation in cystocele size. Apical location, paravaginal location, and hiatus size are highly correlated and are strong predictors of cystocele presence and size.

  7. [Long-term outcome of aortic valve sparing procedures in connective tissue disorders].

    Science.gov (United States)

    Tanaka, Hiroshi; Ogino, H; Matsuda, H; Minatoya, K; Sasaki, N

    2009-10-01

    The aim of this study is to determine the long-term outcome of aortic valve sparing procedures for patients having connective tissue disorder. Between 1993 and 2008, the aortic valve sparing surgery was performed in 94 patients having aortic root dilatation. Eighty patients of them (37.2 +/- 13.4 years, 50 male) had cystic medial necrosis in the aortic wall, which was confirmed the pathological examination. We reviewed these patients. Sixty percent (48/80) had Marfan syndrome, 5% (4/80) had Loeyz-Dietz syndrome, 2% (2/80) had bicuspid aortic valve, and 11% (9/80) had aortic dissection. Our reimplantation procedure has been refined as followed: with a tube graft in 41, a tube graft with creation of neo-sinuses in 11, and a Valsalva graft in 14. Fourteen patients underwent the remodeling procedure. The follow-up rate was 100% with the duration of 3.7+/- 3.4 years. There were no operative death but six late deaths. Seventeen (21.3%) patients required aortic valve replacement, for recurrent aortic insufficiency in 13 and infection in 4. Freedom from reoperation was 80%, 43%, and freedom from moderate or severe aortic insufficiency was 80%, 54%, at 5 and 10 years, respectively. Pathological findings of the aortic valve obtained in the reoperations showed elongation and prolapse of the aortic valve due to myxomatous degeneration and fibrous thickening caused by aortic insufficiency. Even in connective tissue disorders, aortic valve sparing operation is associated with acceptable long-term durability, although cusp degeneration resulting in recurrent aortic insufficiency might be progressive.

  8. 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...... an inflammatory response in macrophages as evidenced by the cytokine profiling and the use of image-based high-content analysis approach in contrast to non-modified CNTs. In addition, systemic administration of CNT-PL-HA into healthy C57BL/6 mice did not alter the total number of leukocytes nor increased liver...

  9. 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.

  10. Fine Structure of the Low-Frequency Raman Phonon Bands of Single-Wall Carbon Nanotubes

    Science.gov (United States)

    Iliev, M. N.; Litvinchuk, A. P.; Arepalli, S.; Nikolaev, P.; Scott, C. D.

    1999-01-01

    The Raman spectra of singled-wall carbon nanotubes (SWNT) produced by laser and are process were studied between 5 and 500 kappa. The line width vs. temperature dependence of the low-frequency Raman bands between 150 and 200/ cm deviates from that expected for phonon decay through phonon-phonon scattering mechanism. The experimental results and their analysis provided convincing evidence that each of the low-frequency Raman lines is a superposition of several narrower Raman lines corresponding to tubes of nearly the same diameter. The application of Raman spectroscopy to probe the distribution of SWNT by both diameter and chirality is discussed.

  11. Out-of-plane (SH) soil-structure interaction: a shear wall with rigid and flexible ring foundation

    Science.gov (United States)

    Le, Thang; Lee, Vincent W.; Luo, Hao

    2016-02-01

    Soil-structure interaction (SSI) of a building and shear wall above a foundation in an elastic half-space has long been an important research subject for earthquake engineers and strong-motion seismologists. Numerous papers have been published since the early 1970s; however, very few of these papers have analytic closed-form solutions available. The soil-structure interaction problem is one of the most classic problems connecting the two disciplines of earthquake engineering and civil engineering. The interaction effect represents the mechanism of energy transfer and dissipation among the elements of the dynamic system, namely the soil subgrade, foundation, and superstructure. This interaction effect is important across many structure, foundation, and subgrade types but is most pronounced when a rigid superstructure is founded on a relatively soft lower foundation and subgrade. This effect may only be ignored when the subgrade is much harder than a flexible superstructure: for instance a flexible moment frame superstructure founded on a thin compacted soil layer on top of very stiff bedrock below. This paper will study the interaction effect of the subgrade and the superstructure. The analytical solution of the interaction of a shear wall, flexible-rigid foundation, and an elastic half-space is derived for incident SH waves with various angles of incidence. It found that the flexible ring (soft layer) cannot be used as an isolation mechanism to decouple a superstructure from its substructure resting on a shaking half-space.

  12. Comparative study of the cell wall composition of broccoli, carrot, and tomato: structural characterization of the extractable pectins and hemicelluloses.

    Science.gov (United States)

    Houben, Ken; Jolie, Ruben P; Fraeye, Ilse; Van Loey, Ann M; Hendrickx, Marc E

    2011-07-01

    This study delivers a comparison of the pectic and hemicellulosic cell wall polysaccharides between the commonly used vegetables broccoli (stem and florets separately), carrot, and tomato. Alcohol-insoluble residues were prepared from the plant sources and sequentially extracted with water, cyclohexane-trans-1,2-diamine tetra-acetic acid, sodium carbonate, and potassium hydroxide solutions, to obtain individual fractions, each containing polysaccharides bound to the cell wall in a specific manner. Structural characterization of the polysaccharide fractions was conducted using colorimetric and chromatographic approaches. Sugar ratios were defined to ameliorate data interpretation. These ratios allowed gaining information concerning polysaccharide structure from sugar composition data. Structural analysis of broccoli revealed organ-specific characteristics: the pectin degree of methoxylation (DM) of stem and florets differed, the sugar composition data inferred differences in polymeric composition. On the other hand, the molar mass (MM) distribution profiles of the polysaccharide fractions were virtually identical for both organs. Carrot root displayed a different MM distribution for the polysaccharides solubilized by potassium hydroxide compared to broccoli and tomato, possibly due to the high contribution of branched pectins to this otherwise hemicellulose-enriched fraction. Tomato fruit showed the pectins with the broadest range in DM, the highest MM, the greatest overall linearity and the lowest extent of branching of rhamnogalacturonan I, pointing to particularly long, linear pectins in tomato compared with the other vegetable organs studied, suggesting possible implications toward functional behavior. Copyright © 2011 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

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

    2009-09-01

    Proteomics allows the large-scale study of protein expression either in whole organisms or in purified organelles. In particular, mass spectrometry (MS) analysis of gel-separated proteins produces data not only for protein identification, but for protein structure, location, and processing as well. An in-depth analysis was performed on MS data from etiolated hypocotyl cell wall proteomics of Arabidopsis thaliana. These analyses show that highly homologous members of multigene families can be differentiated. Two lectins presenting 93% amino acid identity were identified using peptide mass fingerprinting. Although the identification of structural proteins such as extensins or hydroxyproline/proline-rich proteins (H/PRPs) is arduous, different types of MS spectra were exploited to identify and characterize an H/PRP. Maturation events in a couple of cell wall proteins (CWPs) were analyzed using site mapping. N-glycosylation of CWPs as well as the hydroxylation or oxidation of amino acids were also explored, adding information to improve our understanding of CWP structure/function relationships. A bioinformatic tool was developed to locate by means of MS the N-terminus of mature secreted proteins and N-glycosylation.

  14. Aortic Aneurysm Statistics

    Science.gov (United States)

    ... people with inherited connective tissue disorders, such as Marfan syndrome and Ehlers-Danlos syndrome, get thoracic aortic aneurysms. ... Smoking . Some inherited connective tissue disorders, such as Marfan syndrome and Ehlers-Danlos syndrome, can also increase your ...

  15. Aortic Valve Disease

    Science.gov (United States)

    ... It is then replaced with an artificial valve (prosthesis). There are two valve options for aortic valve ... place, the catheter will be withdrawn from your body through the original access point. Because not all ...

  16. Modelling of single walled carbon nanotube cylindrical structures with finite element method simulations

    Energy Technology Data Exchange (ETDEWEB)

    Günay, E. [Gazi University, Mechanical Engineering Department, 06570, Ankara (Turkey)

    2016-04-21

    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.

  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. Modelling of single walled carbon nanotube cylindrical structures with finite element method simulations

    International Nuclear Information System (INIS)

    Günay, E.

    2016-01-01

    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.

  19. 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.

  20. Traumatic Aortic Injury

    Directory of Open Access Journals (Sweden)

    Brianna Miner

    2016-09-01

    Full Text Available History of present illness: A 48-year-old male with unknown past medical history presents as a trauma after being hit by a car traveling approximately 25 miles per hour. On initial presentation, the patient is confused, combative, and not answering questions appropriately. The patient is hypotensive with a blood pressure of 68/40 and a heart rate of 50 beats per minute, with oxygen saturation at 96% on room air. FAST scan is positive for fluid in Morrison’s pouch, splenorenal space, and pericardial space. Significant findings: The initial chest x-ray showed an abnormal superior mediastinal contour (blue line, suggestive of a possible aortic injury. The CT angiogram showed extensive circumferential irregularity and outpouching of the distal aortic arch (red arrows compatible with aortic transection. In addition, there was a circumferential intramural hematoma, which extended through the descending aorta to the proximal infrarenal abdominal aorta (green arrow. There was also an extensive surrounding mediastinal hematoma extending around the descending aorta and supraaortic branches (purple arrows. Discussion: Traumatic aortic injury is a life-threatening event. The incidence of blunt thoracic aortic injury is low, between 1 to 2 percent of those patients with blunt thoracic trauma.1 However, approximately 80% of patients with traumatic aortic injury die at the scene.2 Therefore it is imperative to diagnose traumatic aortic injury in a timely fashion. The diagnosis can be difficult due to the non-specific signs and symptoms and other distracting injuries. Clinical suspicion should be based on the mechanism of the injury and the hemodynamic status of the patient. In any patient with blunt or penetrating trauma to the chest that is hemodynamically unstable, traumatic aortic injury should be on the differential. Chest x-ray can be used as a screening tool. A normal chest x-ray has a negative predictive value of approximately 97%. CTA chest is the

  1. Thoracoabdominal Aortic Aneurysms

    Directory of Open Access Journals (Sweden)

    Ali Azizzadeh

    2008-09-01

    Full Text Available Over the last 50 years, significant progress has been made in the surgical repair of thoracoabdominal aortic aneurysms (TAAA.  Improvements in perioperative care and surgical techniques have resulted in reductions in complication and mortality rates. Adjunctive use of distal aortic perfusion and cerebrospinal fluid drainage has been especially helpful, reducing the incidence of neurological deficits to 2.4%. Current research is aimed at improving organ preservation. This review focuses on the current diagnosis and management of TAAA.

  2. Abdominal aortic aneurysms.

    Science.gov (United States)

    Lindholt, Jes Sanddal

    2010-12-01

    Although the number of elective operations for abdominal aortic aneurysms (AAA) is increasing, the sex- and age-standardised mortality rate of AAAs continues to rise, especially among men aged 65 years or more. The lethality of ruptured AAA continues to be 80-95%, compared with 5-7% by elective surgery of symptomfree AAA. In order to fulfil all WHO, European, and Danish criteria for screening, a randomised hospitalbased screening trial of 12,639 65-73 year old men in Viborg County (Denmark) was initiated in 1994. It seemed that US screening is a valid, suitable and acceptable method of screening. The acceptance rate was 77%, and 95% accept control scans. Furthermore, persons at the highest risk of having an AAA attend screening more frequently. We found that 97% of the interval cases developed from aortas that initially measured 2.5-2.9 cm - i.e. approx. only 5% attenders need re-screening at 5-year intervals. Two large RCTs have given clear indications of operation. Survivors of surgery enjoy the same quality of life as the background population, and only 2-5% of patients refuse an offer of surgery. Early detection seems relevant since the cardiovascular mortality is more than 4 times higher in AAA patients without previous hospital discharge diagnoses due to cardiovascular disease than among similar men without AAA. The absolute risk difference after 5 years was 16%. So, they will benefit from general cardiovascular preventive action as smoking cessation, statins and low-dose aspirin, which could inhibit further AAA progression. All 4 existing RCTs point in the same direction, viz. in favour of screening of men aged 65 and above. We found that screening significantly reduced AAA-related mortality by 67% within the first five years (NNT = 352). Restriction of screening to men with previous cardiovascular or pulmonary hospital discharge diagnoses would request only 27% of the relevant male population study to be invited, but would only have prevented 46.7% of the

  3. 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.

  4. Research of Customized Aortic Stent Graft Manufacture

    Science.gov (United States)

    Zhang, Lei; Chen, Xin; Liu, Muhan

    2017-03-01

    Thoracic descending aorta diseases include aortic dissection and aortic aneurysm, of which the natural mortality rate is extremely high. At present, endovascular aneurysm repair (EVAR) has been widely used as an effective means for the treatment of descending aortic disease. Most of the existing coating stents are standard design, which are unable to meet the size or structure of different patients. As a result, failure of treatment would be caused by dimensional discrepancy between stent and vessels, which could lead to internal leakage or rupture of blood vessels. Therefore, based on rapid prototyping sacrificial core - coating forming (RPSC-CF), a customized aortic stent graft manufactured technique has been proposed in this study. The aortic stent graft consists of film and metallic stent, so polyether polyurethane (PU) and nickel-titanium (NiTi) shape memory alloy with good biocompatibility were chosen. To minimum film thickness without degrading performance, effect of different dip coating conditions on the thickness of film were studied. To make the NiTi alloy exhibit super-elasticity at body temperature (37°C), influence of different heat treatment conditions on austenite transformation temperature (Af) and mechanical properties were studied. The results show that the customized stent grafts could meet the demand of personalized therapy, and have good performance in blasting pressure and radial support force, laying the foundation for further animal experiment and clinical experiment.

  5. Modelling of aortic aneurysm and aortic dissection through 3D printing.

    Science.gov (United States)

    Ho, Daniel; Squelch, Andrew; Sun, Zhonghua

    2017-03-01

    The aim of this study was to assess if the complex anatomy of aortic aneurysm and aortic dissection can be accurately reproduced from a contrast-enhanced computed tomography (CT) scan into a three-dimensional (3D) printed model. Contrast-enhanced cardiac CT scans from two patients were post-processed and produced as 3D printed thoracic aorta models of aortic aneurysm and aortic dissection. The transverse diameter was measured at five anatomical landmarks for both models, compared across three stages: the original contrast-enhanced CT images, the stereolithography (STL) format computerised model prepared for 3D printing and the contrast-enhanced CT of the 3D printed model. For the model with aortic dissection, measurements of the true and false lumen were taken and compared at two points on the descending aorta. Three-dimensional printed models were generated with strong and flexible plastic material with successful replication of anatomical details of aortic structures and pathologies. The mean difference in transverse vessel diameter between the contrast-enhanced CT images before and after 3D printing was 1.0 and 1.2 mm, for the first and second models respectively (standard deviation: 1.0 mm and 0.9 mm). Additionally, for the second model, the mean luminal diameter difference between the 3D printed model and CT images was 0.5 mm. Encouraging results were achieved with regards to reproducing 3D models depicting aortic aneurysm and aortic dissection. Variances in vessel diameter measurement outside a standard deviation of 1 mm tolerance indicate further work is required into the assessment and accuracy of 3D model reproduction. © 2017 The Authors. Journal of Medical Radiation Sciences published by John Wiley & Sons Australia, Ltd on behalf of Australian Society of Medical Imaging and Radiation Therapy and New Zealand Institute of Medical Radiation Technology.

  6. Bimodule structure of the mixed tensor product over Uq sℓ (2 | 1) and quantum walled Brauer algebra

    Science.gov (United States)

    Bulgakova, D. V.; Kiselev, A. M.; Tipunin, I. Yu.

    2018-03-01

    We study a mixed tensor product 3⊗m ⊗3 ‾ ⊗ n of the three-dimensional fundamental representations of the Hopf algebra Uq sℓ (2 | 1), whenever q is not a root of unity. Formulas for the decomposition of tensor products of any simple and projective Uq sℓ (2 | 1)-module with the generating modules 3 and 3 ‾ are obtained. The centralizer of Uq sℓ (2 | 1) on the mixed tensor product is calculated. It is shown to be the quotient Xm,n of the quantum walled Brauer algebra qw Bm,n. The structure of projective modules over Xm,n is written down explicitly. It is known that the walled Brauer algebras form an infinite tower. We have calculated the corresponding restriction functors on simple and projective modules over Xm,n. This result forms a crucial step in decomposition of the mixed tensor product as a bimodule over Xm,n ⊠Uq sℓ (2 | 1). We give an explicit bimodule structure for all m , n.

  7. NUMERICAL ANALYSIS OF THE CRITICAL STATE OF THIN-WALLED STRUCTURE WITH Z-PROFILE CROSS SECTION

    Directory of Open Access Journals (Sweden)

    Patryk Różyło

    2017-03-01

    Full Text Available The object of the study was the thin-walled profile with Z-shaped cross section made of the carbon-epoxy composite. Material model was prepared based on the implemented orthotropic properties. The purpose of study was to determine the value of the critical load at which buckling occurs, the form of buckling and operating characteristics in critical condition. In order to achieve this numerical analysis were carried out. Additionally, the effects of the modification in arrangement of layers of the laminate to the stability and strength of thin-walled composite structures was presented. Numerical studies were carried out using commercial simulation software - ABAQUS®. Within the FEM research, both forms of buckling and the associated critical load, dependent on the configuration the layers of the composite were achieved. Analysis of the obtained results, allowed the evaluation of the structure's work in relation to the level of energy consumption or rigidity estimation. In the paper only numerical simulations of the critical state were conducted.

  8. Sexithiophene encapsulated in a single-walled carbon nanotube: an in situ Raman spectroelectrochemical study of a peapod structure.

    Science.gov (United States)

    Kalbáč, Martin; Kavan, Ladislav; Gorantla, Sandeep; Gemming, Thomas; Dunsch, Lothar

    2010-10-11

    The interaction of single-walled carbon nanotubes (SWCNTs) and α-sexithiophene (6T) was studied by Raman spectroscopy and by in situ Raman spectroelectrochemistry. The encapsulation of 6T in SWCNT and its interaction causes a bleaching of its photoluminescence, and also small shifts of its Raman bands. The Raman features of the SWCNT with embedded 6T (6T-peapods) change in both intensity and frequency compared to those of pristine SWCNT, which is a consequence of a change of the resonant condition. Electrochemical doping demonstrated that the electrode potential applied to the SWCNT wall causes changes in the embedded 6T. The effects of electrochemical charging on the Raman features of pristine SWCNT and 6T@SWCNT were compared. It is shown that the interaction of SWCNT with 6T also changes the electronic structure of SWCNT in its charged state. This change of electronic structure is demonstrated both for semiconducting and metallic tubes. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Finite element elasto-plastic analysis of thin walled structures of reinforced concrete as applied to reactor facilities

    International Nuclear Information System (INIS)

    Fujita, F.; Tsuboi, Y.

    1981-01-01

    The authors developed a new program of elasto-plastic analysis of reinforced concrete shells, in which the simplest model of shell element and an orthotropic constitutive relation are adopted, and verified its validity with reference to the results of model experiments of containers and box-wall structures with various loading conditions. For the two-dimensional stress-strain relationship of concrete, an orthotropic nonlinear formula proposed by one of the authors was adopted. For concrete, the octahedral shear failure and tension cut-off criteria were also imposed. The Kirchhoff-Love's assumptions were assumed to be valid for the whole range of the analysis and the layered approach of elasto-plastic stiffness evaluation. Derivation of the shell element is outlined with examination of its accuracy in elastic range and the assumption of elasto-plastic material property and the procedure of nonlinear analysis are described. As examples, the method is applied to the analysis of a cylindrical container and a box-wall structure. Comparison of the computed results with the corresponding experimental data indicates the applicability of the proposed method. (orig./HP)

  10. A multiscale active structural model of the arterial wall accounting for smooth muscle dynamics.

    Science.gov (United States)

    Coccarelli, Alberto; Edwards, David Hughes; Aggarwal, Ankush; Nithiarasu, Perumal; Parthimos, Dimitris

    2018-02-01

    Arterial wall dynamics arise from the synergy of passive mechano-elastic properties of the vascular tissue and the active contractile behaviour of smooth muscle cells (SMCs) that form the media layer of vessels. We have developed a computational framework that incorporates both these components to account for vascular responses to mechanical and pharmacological stimuli. To validate the proposed framework and demonstrate its potential for testing hypotheses on the pathogenesis of vascular disease, we have employed a number of pharmacological probes that modulate the arterial wall contractile machinery by selectively inhibiting a range of intracellular signalling pathways. Experimental probes used on ring segments from the rabbit central ear artery are: phenylephrine, a selective α 1-adrenergic receptor agonist that induces vasoconstriction; cyclopiazonic acid (CPA), a specific inhibitor of sarcoplasmic/endoplasmic reticulum Ca 2+ -ATPase; and ryanodine, a diterpenoid that modulates Ca 2+ release from the sarcoplasmic reticulum. These interventions were able to delineate the role of membrane versus intracellular signalling, previously identified as main factors in smooth muscle contraction and the generation of vessel tone. Each SMC was modelled by a system of nonlinear differential equations that account for intracellular ionic signalling, and in particular Ca 2+ dynamics. Cytosolic Ca 2+ concentrations formed the catalytic input to a cross-bridge kinetics model. Contractile output from these cellular components forms the input to the finite-element model of the arterial rings under isometric conditions that reproduces the experimental conditions. The model does not account for the role of the endothelium, as the nitric oxide production was suppressed by the action of L-NAME, and also due to the absence of shear stress on the arterial ring, as the experimental set-up did not involve flow. Simulations generated by the integrated model closely matched experimental

  11. In vivo hypertensive arterial wall uptake of radiolabeled liposomes

    International Nuclear Information System (INIS)

    Hodis, H.N.; Amartey, J.K.; Crawford, D.W.; Wickham, E.; Blankenhorn, D.H.

    1990-01-01

    Using five sham-operated and seven aortic coarctation-induced hypertensive New Zealand White rabbits intravenously injected with neutral small unilamellar vesicles loaded with [111In]nitrilotriacetic acid, we demonstrated in vivo that the normal aortic arterial wall participates in liposome uptake and that this uptake is increased in the hypertensive aortic wall by approximately threefold (p less than or equal to 0.0001). Among the three regions examined, aortic arch, thoracic aorta, and lower abdominal aorta, the difference in uptake between the normotensive and hypertensive arterial walls was significantly different, p less than or equal to 0.05, p less than or equal to 0.0001, and p less than 0.05, respectively. The uptake by the different regions of the hypertensive arterial wall is consistent with the pathological changes present in these areas. Furthermore, the extent of liposome uptake by the aortic wall is strongly correlated with the height of the blood pressure (r = 0.85, p = 0.001, n = 11). We conclude that neutral small unilamellar liposomes can be used to carry agents into the arterial wall in vivo in the study of hypertensive vascular disease and could be especially useful for the delivery of pharmacologically or biologically active agents that would otherwise be inactivated within the circulation or are impermeable to the arterial wall

  12. Left ventricular hypertrophy in valvular aortic stenosis: mechanisms and clinical implications.

    Science.gov (United States)

    Rader, Florian; Sachdev, Esha; Arsanjani, Reza; Siegel, Robert J

    2015-04-01

    Valvular aortic stenosis is the second most prevalent adult valve disease in the United States and causes progressive pressure overload, invariably leading to life-threatening complications. Surgical aortic valve replacement and, more recently, transcatheter aortic valve replacement effectively relieve the hemodynamic burden and improve the symptoms and survival of affected individuals. However, according to current American College of Cardiology/American Heart Association guidelines on the management of valvular heart disease, the indications for aortic valve replacement, including transcatheter aortic valve replacement, are based primarily on the development of clinical symptoms, because their presence indicates a dismal prognosis. Left ventricular hypertrophy develops in a sizeable proportion of patients before the onset of symptoms, and a growing body of literature demonstrates that regression of left ventricular hypertrophy resulting from aortic stenosis is incomplete after aortic valve replacement and associated with adverse early postoperative outcomes and worse long-term outcomes. Thus, reliance on the development of symptoms alone without consideration of structural abnormalities of the myocardium for optimal timing of aortic valve replacement potentially constitutes a missed opportunity to prevent postoperative morbidity and mortality from severe aortic stenosis, especially in the face of the quickly expanding indications of lower-risk transcatheter aortic valve replacement. The purpose of this review is to discuss the mechanisms and clinical implications of left ventricular hypertrophy in severe valvular aortic stenosis, which may eventually move to center stage as an indication for aortic valve replacement in the asymptomatic patient. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Pre-deformation Analysis on Construction of Special-shaped Thin-walled Concrete Acoustic Wind Tunnel Structure

    Directory of Open Access Journals (Sweden)

    Li Boping

    2015-01-01

    Full Text Available Structural deformation of special-shaped thin-walled concrete acoustic wind tunnel under self-weight effect can not cater for requirements of high flatness and smoothness of moulding surface. Therefore pre-deformation analysis is carried out on construction of wind tunnel structure. Threshold is utilized to choose equivalent cross-section for the plane needing pre-deformation construction to do analysis. Analysis results show that design specifications of reinforced concrete is feasible for pre-deformation analysis on equivalent plane model under self-weight effect. Present construction on pre-camber wind tunnel according to deflection under self-weight effect also achieves the desired design requirements. Construction technology of arc-shaped erection template which controls mid-span pre-camber value keeps features of simple construction and high accuracy

  14. Application of the Hybrid Simulation Method for the Full-Scale Precast Reinforced Concrete Shear Wall Structure

    Directory of Open Access Journals (Sweden)

    Zaixian Chen

    2018-02-01

    Full Text Available The hybrid simulation (HS testing method combines physical test and numerical simulation, and provides a viable alternative to evaluate the structural seismic performance. Most studies focused on the accuracy, stability and reliability of the HS method in the small-scale tests. It is a challenge to evaluate the seismic performance of a twelve-story pre-cast reinforced concrete shear-wall structure using this HS method which takes the full-scale bottom three-story structural model as the physical substructure and the elastic non-linear model as the numerical substructure. This paper employs an equivalent force control (EFC method with implicit integration algorithm to deal with the numerical integration of the equation of motion (EOM and the control of the loading device. Because of the arrangement of the test model, an elastic non-linear numerical model is used to simulate the numerical substructure. And non-subdivision strategy for the displacement inflection point of numerical substructure is used to easily realize the simulation of the numerical substructure and thus reduce the measured error. The parameters of the EFC method are calculated basing on analytical and numerical studies and used to the actual full-scale HS test. Finally, the accuracy and feasibility of the EFC-based HS method is verified experimentally through the substructure HS tests of the pre-cast reinforced concrete shear-wall structure model. And the testing results of the descending stage can be conveniently obtained from the EFC-based HS method.

  15. Inhibition of early AAA formation by aortic intraluminal pentagalloyl glucose (PGG) infusion in a novel porcine AAA model

    DEFF Research Database (Denmark)

    Kloster, Brian O; Lund, Lars; Lindholt, Jes S

    2016-01-01

    and histology. CONCLUSION: In our model, intraluminal delivered PGG is able to penetrate the aortic wall from the inside and impair the early AAA development by stabilizing the elastic lamellae and preserving their integrity. The principle holds a high clinical potential if it can be translated to human...... to physiological values as seen in the control group. In the elastase group, histology revealed more or less complete resolution of the elastic lamellae in the media while they were more abundant, coherent and structurally organized in the PGG group. The control group displayed normal physiological growth...

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

    Indian Academy of Sciences (India)

    moments was also made possible (Hoenderkamp & Stafford Smith 1984) which allowed expres- sions to be derived for the shear forces in the coupling beams in MSW structures. Establishing the maximum shear force, Vb,max in the critical coupling beam and its location up the height of the structure will yield a relationship ...

  17. Effect of airway surface liquid on the forces on the pharyngeal wall: Experimental fluid-structure interaction study.

    Science.gov (United States)

    Pirnar, Jernej; Širok, Brane; Bombač, Andrej

    2017-10-03

    Obstructive sleep apnoea syndrome (OSAS) is a breathing disorder with a multifactorial etiology. The respiratory epithelium is lined with a thin layer of airway surface liquid preventing interactions between the airflow and epithelium. The effect of the liquid lining in OSAS pathogenesis remains poorly understood despite clinical research. Previous studies have shown that the physical properties of the airway surface liquid or altered stimulation of the airway mechanoreceptors could alleviate or intensify OSAS; however, these studies do not provide a clear physical interpretation. To study the forces transmitted from the airflow to the liquid-lined compliant wall and to discuss the effects of the airway surface liquid properties on the stimulation of the mechanoreceptors, a novel and simplified experimental system mimicking the upper airway fundamental characteristics (i.e., liquid-lined compliant wall and complex unsteady airflow features) was constructed. The fluctuating force on the compliant wall was reduced through a damping mechanism when the liquid film thickness and/or the viscosity were increased. Conversely, the liquid film damping was reduced when the surface tension decreased. Based on the experimental data, empirical correlations were developed to predict the damping potential of the liquid film. In the future, this will enable us to extend the existing computational fluid-structure interaction simulations of airflow in the human upper airway by incorporating the airway surface liquid effect without adopting two-phase flow interface tracking methods. Furthermore, the experimental system developed in this study could be used to investigate the fundamental principles of the complex once/twice-coupled physical phenomena. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Liquid Wall Chambers

    Energy Technology Data Exchange (ETDEWEB)

    Meier, W R

    2011-02-24

    The key feature of liquid wall chambers is the use of a renewable liquid layer to protect chamber structures from target emissions. Two primary options have been proposed and studied: wetted wall chambers and thick liquid wall (TLW) chambers. With wetted wall designs, a thin layer of liquid shields the structural first wall from short ranged target emissions (x-rays, ions and debris) but not neutrons. Various schemes have been proposed to establish and renew the liquid layer between shots including flow-guiding porous fabrics (e.g., Osiris, HIBALL), porous rigid structures (Prometheus) and thin film flows (KOYO). The thin liquid layer can be the tritium breeding material (e.g., flibe, PbLi, or Li) or another liquid metal such as Pb. TLWs use liquid jets injected by stationary or oscillating nozzles to form a neutronically thick layer (typically with an effective thickness of {approx}50 cm) of liquid between the target and first structural wall. In addition to absorbing short ranged emissions, the thick liquid layer degrades the neutron flux and energy reaching the first wall, typically by {approx}10 x x, so that steel walls can survive for the life of the plant ({approx}30-60 yrs). The thick liquid serves as the primary coolant and tritium breeding material (most recent designs use flibe, but the earliest concepts used Li). In essence, the TLW places the fusion blanket inside the first wall instead of behind the first wall.

  19. Pathogenetic Basis of Aortopathy and Aortic Valve Disease

    Science.gov (United States)

    2018-02-19

    Aortopathies; Thoracic Aortic Aneurysm; Aortic Valve Disease; Thoracic Aortic Disease; Thoracic Aortic Dissection; Thoracic Aortic Rupture; Ascending Aortic Disease; Descending Aortic Disease; Ascending Aortic Aneurysm; Descending Aortic Aneurysm; Marfan Syndrome; Loeys-Dietz Syndrome; Ehlers-Danlos Syndrome; Shprintzen-Goldberg Syndrome; Turner Syndrome; PHACE Syndrome; Autosomal Recessive Cutis Laxa; Congenital Contractural Arachnodactyly; Arterial Tortuosity Syndrome

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

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ho Jin; Lee, B. S.; Kim, K. B

    2003-09-01

    The materials for PFC's (Plasma Facing Components) in a fusion reactor are severely irradiated with fusion products in facing the high temperature plasma during the operation. The refractory materials can be maintained their excellent properties in severe operating condition by lowering surface temperature by bonding them to the high thermal conducting materials of heat sink. Hence, the joining and bonding techniques between dissimilar materials is considered to be important in case of the fusion reactor or nuclear reactor which is operated at high temperature. The first wall in the fusion reactor is heated to approximately 1000 .deg. C and irradiated severely by the plasma. In ITER, beryllium is expected as the primary armour candidate for the PFC's; other candidates including W, Mo, SiC, B4C, C/C and Si{sub 3}N{sub 4}. Since the heat affected zones in the PFC's processed by conventional welding are reported to have embrittlement and degradation in the sever operation condition, both brazing and diffusion bonding are being considered as prime candidates for the joining technique. In this report, both the materials including ceramics and the fabrication techniques including joining technique between dissimilar materials for PFC's are described. The described joining technique between the refractory materials and the dissimilar materials may be applicable for the fusion reactor and Generation-4 future nuclear reactor which are operated at high temperature and high irradiation.

  1. Electrospun single-walled carbon nanotube/polyvinyl alcohol composite nanofibers: structure-property relationships

    International Nuclear Information System (INIS)

    Naebe, Minoo; Lin Tong; Wang Xungai; Staiger, Mark P; Dai Liming

    2008-01-01

    Polyvinyl alcohol (PVA) nanofibers and single-walled carbon nanotube (SWNT)/PVA composite nanofibers have been produced by electrospinning. An apparent increase in the PVA crystallinity with a concomitant change in its main crystalline phase and a reduction in the crystalline domain size were observed in the SWNT/PVA composite nanofibers, indicating the occurrence of a SWNT-induced nucleation crystallization of the PVA phase. Both the pure PVA and SWNT/PVA composite nanofibers were subjected to the following post-electrospinning treatments: (i) soaking in methanol to increase the PVA crystallinity, and (ii) cross-linking with glutaric dialdehyde to control the PVA morphology. Effects of the PVA morphology on the tensile properties of the resultant electrospun nanofibers were examined. Dynamic mechanical thermal analyses of both pure PVA and SWNT/PVA composite electrospun nanofibers indicated that SWNT-polymer interaction facilitated the formation of crystalline domains, which can be further enhanced by soaking the nanofiber in methanol and/or cross-linking the polymer with glutaric dialdehyde

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

    International Nuclear Information System (INIS)

    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 3 N 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

  3. Poly(ethylene oxide) Crystallization in Single Walled Carbon Nanotube Based Nanocomposites: Kinetics and Structural Consequences

    Energy Technology Data Exchange (ETDEWEB)

    T Chatterjee; A Lorenzo; R Krishnamoorti

    2011-12-31

    The overall isothermal crystallization behavior of poly(ethylene oxide) (PEO) in single walled carbon nanotube (SWNT) based nanocomposites is studied with a focus on growth kinetics and morphological evolution of PEO using differential scanning calorimetry and in-situ small angle x-ray scattering measurements respectively. The characteristic time for crystallization of PEO increases due to the presence of lithium dodecyl sulfate (LDS) stabilized carbon nanotubes. Further, analysis of crystallization data using the Lauritzen-Hoffman regime theory of crystal growth shows the PEO chains stiffen in presence of LDS with an increased energy barrier associated with the nucleation and crystal growth, and the nanotubes further act as a barrier to chain transport or enhance the efficacy of the LDS action. The energy penalty and diffusional barrier to chain transport in the nanocomposites disrupt the crystalline PEO helical conformation. This destabilization leads to preferential growth of local nuclei resulting in formation of thinner crystal lamellae and suggests that the crystallization kinetics is strongly affected by the nucleation and crystal growth events. This study is particularly interesting considering the suppression of the PEO crystallinity in presence of small fraction of Lithium ion based surfactant and carbon nanotubes.

  4. Risks and Opportunities of Urbanization – Structure of Two Populations of the Balkan Wall Lizard Podarcis tauricus (Pallas, 1814) in the City of Plovdiv

    OpenAIRE

    Ivelin A. Mollov; Miglena V. Valkanova

    2009-01-01

    The current study analyzes the structure and some features of two urban metapopulations of the Balkan Wall Lizard (Podarcis tauricus (Pallas, 1814)) from Nature Monument (NM) “Mladezhki halm” and Nature Monument “Halm na osvoboditelite” in the city of Plovdiv (South Bulgaria). In both study sites, the Balkan Wall lizard inhabits exclusively the interior of the hills and prefers mainly open areas with rare grass and shrub vegetation. The recorded dominant plant species are not autochthonous fo...

  5. Morphometric Properties of the Thoracic Aorta of Warmblood and Friesian Horses with and without Aortic Rupture.

    Science.gov (United States)

    Saey, V; Ploeg, M; Delesalle, C; van Loon, G; Gröne, A; Ducatelle, R; Duchateau, L; Chiers, K

    2016-01-01

    Rupture of the aorta is much more common in Friesians compared with other breeds of horse. Rupture always occurs adjacent to the scar of the ligamentum arteriosum. Previous histological examination of ruptured aortic walls suggested the presence of an underlying connective tissue disorder. Therefore, the aim of the present study was to compare the structural characteristics of the tunica media of the mid-thoracic aorta, distant to the lesion, in warmblood and Friesian horses with and without thoracic aortic rupture. In unaffected Friesian horses, the thickness of the tunica media, as well as the percentage area comprised of collagen type I, were significantly higher compared with the warmblood horses, supporting the hypothesis of a primary collagen disorder in the Friesian horse breed. However, in the tunica media of the affected Friesian horses there was no significant wall thickening. Moreover, the percentage area comprised of elastin was significantly lower, while the percentage area comprised of smooth muscle was higher, compared with unaffected Friesian and warmblood horses. These lesions are suggestive of an additional mild elastin deficiency with compensatory smooth muscle cell hypertrophy in affected Friesians. Copyright © 2016. Published by Elsevier Ltd.

  6. Magnetic resonance imaging 4-D flow-based analysis of aortic hemodynamics in Turner syndrome.

    Science.gov (United States)

    Arnold, Raoul; Neu, Marie; Hirtler, Daniel; Gimpel, Charlotte; Markl, Michael; Geiger, Julia

    2017-04-01

    Cardiovascular surveillance is important in Turner syndrome because of the increased risk of aortic dilation and dissection with consecutively increased mortality. To compare 4-D flow MRI for the characterization of aortic 3-D flow patterns, dimensions and vessel wall parameters in pediatric patients with Turner syndrome and age-matched controls. We performed 4-D flow MRI measuring in vivo 3-D blood flow with coverage of the thoracic aorta in 25 patients with Turner syndrome and in 16 female healthy controls (age mean ± standard deviation were 16 ± 5 years and 17 ± 4 years, respectively). Blood flow was visualized by time-resolved 3-D path lines. Visual grading of aortic flow in terms of helices and vortices was performed by two independent observers. Quantitative analysis included measurement of aortic diameters, quantification of peak systolic wall shear stress, pulsatility index and oscillatory shear index at eight defined sites. Patients with Turner syndrome had significantly larger aortic diameters normalized to BSA, increased vortices in the ascending aorta and elevated helix flow in the ascending and descending aorta compared to controls (all PTurner patients compared to controls (p=0.02, p=0.002 and p=0.01 respectively). Four-dimensional flow MRI provides new insights into the altered aortic hemodynamics and wall shear stress that could have an impact on the development of aortic dissections.

  7. On the numerical investigation of sound transmission through double-walled structures with membrane-type acoustic metamaterials.

    Science.gov (United States)

    Marinova, Polina; Lippert, Stephan; von Estorff, Otto

    2017-10-01

    Acoustic metamaterials appear to be of great help in the design of reliable and effective noise reduction measures in the low frequency range. The current contribution is concerned with the modeling of a low-frequency noise shield, based on a double wall arrangement, which includes membrane-type acoustic metamaterials (MAMs), considered as the most promising approach when it comes especially to the tonal noise at frequencies below 300 Hz. MAMs consist of small-sized membranes loaded with a mass. Due to their robustness and relatively simple production, MAMs have been proven to decrease the sound transmission in frequency ranges, for which poro-elastic materials have a rather negligible effect. A simulation model of a double wall panel, whose acoustic cavity is furnished with layers of metamaterials, has been developed and the sound transmission loss (STL) through the structure was calculated, using the finite element method. In order to validate the modelling approach, the STL estimation from the finite element analysis was compared to experimental measurements. The achieved results indicate a noise-decreasing possibility in tunable narrow bands as well as a broadband noise reduction for frequencies less than 300 Hz without significantly adding to the panel mass.

  8. Effectiveness of Pocket-Wave Absorbers in Vertical-Wall, Coastal Entrance Structures

    National Research Council Canada - National Science Library

    Thompson, Edward F; Bottin, Jr., Robert R; Selegean, James P

    2004-01-01

    ... (relative to wave conditions) in vertical steel sheet-pile coastal entrance structures. The U.S. Army Corps of Engineers is responsible for dozens of harbor entrances in the Great Lakes constructed with parallel jetties...

  9. Atypical aortic dissection (intramural hematoma) of aorta: diagnosis of electron beam computer tomography

    International Nuclear Information System (INIS)

    Jin Jinglin; Dai Ruping; He Sha; Jing Baolian; Bai Hua

    2001-01-01

    Objective: To evaluate the clinical application of electron beam computer tomography (EBCT) in diagnosis of atypical aortic dissection. Methods: Between May 1994 and April 2000, 236 patients with aortic dissection were scanned by electron beam CT (EBCT) from 15000 cases. Out of which, 25 patients (female 4, male 21) were atypical dissection. All patients complained of acute chest pain. Contrast-enhanced EBCT was carried out by Imatron 150-X P system. Continues volume scanning mode (CVS) was performed to obtain 140 slice from aortic arch to iliac bifurcation with slice thickness of 3 mm. Results: The EBCT angiographic (EBCTA) direct features of atypical dissection were as follows: (1) continuous low density crescentic or circle areas along the wall of aorta (25 cases) with CT value of 50-87 HU, 5-23 mm in aortic wall thickness and 16.3 cm in length; (2) displacement of intimal calcification (5 cases); (3) the change of aortic wall thickness with follow up (6/6). The indirect features included: (1) aortic atherosclerotic ulcers (7 cases); (2) atherosclerotic plaque and calcification on the aortic wall (12 cases). According to above features, EBCT can confirm the diagnosis of atypical aortic dissection when the patient has acute chest pain. Among the 25 cases, ascending aorta (Stanford A type) and descending aorta (Stanford B type) were involved in 6 and 19, respectively. In the follow up study with EBCT, intramural hematoma was completely absent in 6 patients after 3 months to 1 year. Conclusion: For the differential diagnosis of acute chest pain, EBCT can confirm the diagnosis of atypical aortic dissection. EBCT is a noninvasive and safe method and it is useful for the follow up study

  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. [Aortic arch advancement surgery as treatment for aortic coarctation with hypoplastic aortic arch in children].

    Science.gov (United States)

    Palacios-Macedo-Quenot, Alexis; Urencio, Miguel; Ponce-De-León-Rosales, Sergio; López-Terrazas, Javier; Castañuela-Sánchez, Violeta; March-Mifsut, Almudena; López-Magallón, Alejandro; Pérez-Juárez, Fabiola; Cedillo-Rendón, Irma; Tamariz-Cruz, Orlando

    2012-01-01

    Treatment of aortic coarctation with hypoplastic aortic arch is still a surgical challenge. The aortic arch advancement surgery has shown less re-coarctation frequency. To determine the re-coarctation frequency in patients who underwent aortic arch advancement technique for aortic coarctation with hypoplastic aortic arch and analyze the results. Retrospective and observational study of 38 patients who underwent aortic arch advancement in a third level Institution from 2002 to 2010. Twenty four males and 14 females all with aortic arch Z index diameter of coarctation was O%. With the previously mentioned technique the recoarctation frequency on medium and long term basis was 0%. From the anatomical and functional point of view, we believe this technique offers the best possible results.

  12. Fractal structures of single-walled carbon nanotubes in biologically relevant conditions: role of chirality vs. media conditions.

    Science.gov (United States)

    Khan, Iftheker A; Aich, Nirupam; Afrooz, A R M Nabiul; Flora, Joseph R V; Schierz, P Ariette; Ferguson, P Lee; Sabo-Attwood, Tara; Saleh, Navid B

    2013-11-01

    Aggregate structure of covalently functionalized chiral specific semiconducting single-walled carbon nanotubes (SWNTs) was systematically studied employing static light scattering (SLS). Fractal dimensions (Df) of two specific chirality SWNTs-SG65 and SG76 with (6, 5) and (7, 6) chiral enrichments-were measured under four biological exposure media conditions, namely: Dulbecco's Modified Eagle Medium (DMEM), Minimum Essential Medium (MEM), Roswell Park Memorial Institute (RPMI) 1640 medium, and 0.9% saline solution. The SWNTs exhibited chiral dependence on Df with SG65 showing more fractal or loosely bound aggregate structures, i.e., lower Df values (range of 2.24±0.03 to 2.64±0.05), compared to the SG76 sample (range of 2.58±0.13 to 2.90±0.08). All the Df values reported are highly reproducible, measured from multiple SLS runs and estimated with 'random block-effects' statistical analysis that yielded all p values to be fractal aggregates. Moreover, presence of fetal bovine serum (FBS) and bovine serum albumin (BSA), used to mimic the in vitro cell culture condition, reduced the Df values, i.e., created more fractal structures. Steric hindrance to aggregation was identified as the key mechanism for creating the fractal structures. Also, increase in FBS concentration from 1% to 10% resulted in increasingly lower Df values. Published by Elsevier Ltd.

  13. Effects of SPORL and dilute acid pretreatment on substrate morphology, cell physical and chemical wall structures, and subsequent enzymatic hydrolysis of lodgepole pine

    Science.gov (United States)

    Xinping Li; Xiaolin Luo; Kecheng Li; J.Y. Zhu; J. Dennis Fougere; Kimberley Clarke

    2012-01-01

    The effects of pretreatment by dilute acid and sulfite pretreatment to overcome recalcitrance of lignocellulose (SPORL) on substrate morphology, cell wall physical and chemical structures, along with the subsequent enzymatic hydrolysis of lodgepole pine substrate were investigated. FE-SEM and TEM images of substrate structural morphological changes showed that SPORL...

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

    DEFF Research Database (Denmark)

    Dandolo, Corinna Ludovica Koch; Jepsen, Peter Uhd

    2016-01-01

    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...

  15. Transcatheter Aortic Valve Replacement: A Review Article

    Directory of Open Access Journals (Sweden)

    Juan A Siordia

    2016-06-01

    Full Text Available Transcatheter aortic valve replacement (TAVR is a novel therapeutic intervention for the replacement of severely stenotic aortic valves in high-risk patients for standard surgical procedures. Since the initial PARTNER trial results, use of TAVR has been on the rise each year. New delivery methods and different valves have been developed and modified in order to promote the minimally invasive procedure and reduce common complications, such as stroke. This review article focuses on the current data on the indications, risks, benefits, and future directions of TAVR. Recently, TAVR has been considered as a standard-of-care procedure. While this technique is used frequently in high-risk surgical candidates, studies have been focusing on the application of this method for younger patients with lower surgical risk. Moreover, several studies have proposed promising results regarding the use of valve-in-valve technique or the procedure in which the valve is placed within a previously implemented bioprosthetic valve. However, ischemic strokes and paravalvular leak remain a matter of debate in these surgeries. New methods and devices have been developed to reduce the incidence of post-procedural stroke. While the third generation of TAVR valves (i.e., Edwards Sapien 3 and Medtronic Evolut R addresses the issue of paravalvular leak structurally, results on their efficacy in reducing the risk of paravalvular leak are yet to be obtained. Furthermore, TAVR enters the field of hybrid methods in the treatment of cardiac issues via both surgical and catheter-based approaches. Finally, while TAVR is primarily performed on cases with aortic stenosis, new valves and methods have been proposed regarding the application of this technique in aortic regurgitation, as well as other aortic pathologies. TAVR is a suitable therapeutic approach for the treatment of aortic stenosis in high-risk patients. Considering the promising results in the current patient population

  16. Altering F-Actin Structure of C17.2 Cells using Single-Walled Carbon Nanotubes

    Science.gov (United States)

    Magers, Jay; Gillette, Nathan L. D.; Rotkin, Slava V.; Jedlicka, Sabrina; Pirbhai, Massooma; Lehigh Univesity Collaboration; Susquehanna University Collaboration

    Advancements in nanotechnology have become fundamental to the delivery of drugs to treat various diseases. One such advancement is that of carbon nanotubes and their possible implications on drug delivery. Single-walled carbon nanotubes (SWCNTs) have great potential in the biomedical field as a means to deliver materials such as drugs and genes into the human body due to their size and chemistry. However, the effects of the nanotubes on cells they interact with are still unknown. Previous studies have shown that a low dosage of SWCNTs can affect differentiation of C17.2 neural stem cells. In this experiment, we investigate how the tubes affect the structure of the cells. Specifically, we determined the impact on the cell by examining the actin filament length, protrusions along the edge of the cells, and actin distribution. Presenter/Author 1.

  17. Aortic valve-sparing operations in aortic root aneurysms: remodeling or reimplantation?

    Science.gov (United States)

    Rahnavardi, Mohammad; Yan, Tristan D; Bannon, Paul G; Wilson, Michael K

    2011-08-01

    A best evidence topic was written according to a structured protocol. The question addressed was whether the reimplantation (David) technique or the remodeling (Yacoub) technique provides the optimum event free survival in patients with an aortic root aneurysm suitable for an aortic valve-sparing operation. In total, 392 papers were found using the reported search criteria, of which 14 papers provided the best evidence to answer the clinical question. A total of 1338 patients (Yacoub technique in 606 and David technique in 732) from 13 centres were included. In most series, cardiopulmonary bypass time and aortic cross-clamp time were longer for the David technique compared to the Yacoub technique. Early mortality was comparable between the two techniques (0-6.9% for the Yacoub technique and 0-6% for the David technique). There is a tendency for a higher freedom from significant long-term aortic insufficiency in the David group than the Yacoub group, which does not necessarily result in a higher reoperation rate in the Yacoub group. In the largest series reported, freedom from a moderate-to-severe aortic insufficiency at 12 years was 82.6 ± 6.2% in the Yacoub and 91.0 ± 3.8% in the David group (P=0.035). Freedom from reoperation at the same time point was 90.4 ± 4.7% in the Yacoub group and 97.4 ± 2.2% in the David group (P=0.09). In another series, freedom from reoperation at a follow-up time of about four years was 89 ± 4% in the Yacoub group and 98 ± 2% in the David group. Although some authors merely preferred the Yacoub technique for a bicuspid aortic valve, the accumulated evidence in the current review indicates comparable results for both techniques in a bicuspid aortic valve. Current evidence is in favour of the David rather than the Yacoub technique in pathologies such as Marfan syndrome, acute type A aortic dissection, and excessive annular dilatation that may impair aortic root integrity. Careful selection of patients for each technique and

  18. Cell wall structures leading to cultivar differences in softening rates develop early during apple (Malus x domestica) fruit growth.

    Science.gov (United States)

    Ng, Jovyn K T; Schröder, Roswitha; Sutherland, Paul W; Hallett, Ian C; Hall, Miriam I; Prakash, Roneel; Smith, Bronwen G; Melton, Laurence D; Johnston, Jason W

    2013-11-19

    There is a paucity of information regarding development of fruit tissue microstructure and changes in the cell walls during fruit growth, and how these developmental processes differ between cultivars with contrasting softening behaviour. In this study we compare two apple cultivars that show different softening rates during fruit development and ripening. We investigate whether these different softening behaviours manifest themselves late during ethylene-induced softening in the ripening phase, or early during fruit expansion and maturation. 'Scifresh' (slow softening) and 'Royal Gala' (rapid softening) apples show differences in cortical microstructure and cell adhesion as early as the cell expansion phase. 'Scifresh' apples showed reduced loss of firmness and greater dry matter accumulation compared with 'Royal Gala' during early fruit development, suggesting differences in resource allocation that influence tissue structural properties. Tricellular junctions in 'Scifresh' were rich in highly-esterified pectin, contributing to stronger cell adhesion and an increased resistance to the development of large airspaces during cell expansion. Consequently, mature fruit of 'Scifresh' showed larger, more angular shaped cells than 'Royal Gala', with less airspaces and denser tissue. Stronger cell adhesion in ripe 'Scifresh' resulted in tissue fracture by cell rupture rather than by cell-to-cell-separation as seen in 'Royal Gala'. CDTA-soluble pectin differed in both cultivars during development, implicating its involvement in cell adhesion. Low pectin methylesterase activity during early stages of fruit development coupled with the lack of immuno-detectable PG was associated with increased cell adhesion in 'Scifresh'. Our results indicate that cell wall structures leading to differences in softening rates of apple fruit develop early during fruit growth and well before the induction of the ripening process.

  19. Controls on fault zone structure and brittle fracturing in the foliated hanging wall of the Alpine Fault

    Science.gov (United States)

    Williams, Jack N.; Toy, Virginia G.; Massiot, Cécile; McNamara, David D.; Smith, Steven A. F.; Mills, Steven

    2018-04-01

    Three datasets are used to quantify fracture density, orientation, and fill in the foliated hanging wall of the Alpine Fault: (1) X-ray computed tomography (CT) images of drill core collected within 25 m of its principal slip zones (PSZs) during the first phase of the Deep Fault Drilling Project that were reoriented with respect to borehole televiewer images, (2) field measurements from creek sections up to 500 m from the PSZs, and (3) CT images of oriented drill core collected during the Amethyst Hydro Project at distances of ˜ 0.7-2 km from the PSZs. Results show that within 160 m of the PSZs in foliated cataclasites and ultramylonites, gouge-filled fractures exhibit a wide range of orientations. At these distances, fractures are interpreted to have formed at relatively high confining pressures and/or in rocks that had a weak mechanical anisotropy. Conversely, at distances greater than 160 m from the PSZs, fractures are typically open and subparallel to the mylonitic or schistose foliation, implying that fracturing occurred at low confining pressures and/or in rocks that were mechanically anisotropic. Fracture density is similar across the ˜ 500 m width of the field transects. By combining our datasets with measurements of permeability and seismic velocity around the Alpine Fault, we further develop the hierarchical model for hanging-wall damage structure that was proposed by Townend et al. (2017). The wider zone of foliation-parallel fractures represents an outer damage zone that forms at shallow depths. The distinct inner damage zone. This zone is interpreted to extend towards the base of the seismogenic crust given that its width is comparable to (1) the Alpine Fault low-velocity zone detected by fault zone guided waves and (2) damage zones reported from other exhumed large-displacement faults. In summary, a narrow zone of fracturing at the base of the Alpine Fault's hanging-wall seismogenic crust is anticipated to widen at shallow depths, which is

  20. Effects of multi-wall carbon nanotubes on structural and mechanical ...

    Indian Academy of Sciences (India)

    2017-09-22

    Sep 22, 2017 ... The scaffolds provide not only a basic structure for cell growth and tissue formation, but also to determine how to transport the materials [4]. Synthetic and natural biomaterials which are used for scaffold fabrication, is chosen based on their biocompatibility, biodegradability and mechanical properties [5].

  1. Effects of multi-wall carbon nanotubes on structural and mechanical ...

    Indian Academy of Sciences (India)

    The solution components entity authenticity was approved by FTIR. The porosity assessment was illustrated by a porous structure with 81–83% porosity.Water contact angle (WCA) test showed the decrease in contact angle with the increase in MWNTs. Mechanical property results showed the strength of about 4–10 MPa for ...

  2. Reliability of sheet pile walls and the influence of corrosion. Structural reliability analysis with finite elements

    NARCIS (Netherlands)

    Schweckendiek, T.; Courage, W.M.G.; Gelder, A.J.M. van

    2007-01-01

    The Finite Element Method is well accepted in design practice nowadays. It can be used for modeling complex structures and systems. The constitutive models are improving, which enables us to make more accurate predictions ofthe real world behavior. On the other hand, especially in the field

  3. Reliability of Sheet Pile Walls And The Influence of Corrosion : Structural Reliability Analysis with Finite Elements

    NARCIS (Netherlands)

    Schweckendiek, T.; Courage, W.M.G.; Van Gelder, P.H.A.J.M.

    2007-01-01

    The Finite Element Method is well accepted in design practice nowadays. It can be used for modeling complex structures and systems. The constitutive models are improving, which enables us to make more accurate predictions of the real world behavior. On the other hand, especially in the field of

  4. Symmetry and Non-empirical Calculations of Structure and Properties of Single- and Double-Wall SrTiO3 Nanotubes

    Science.gov (United States)

    Evarestov, R. A.; Bandura, A. V.

    A large-scale first-principles simulation of the structure and stability of SrTiO3 single- and double-wall nanotubes with different chiralities has been performed for the first time using the periodic PBE0 LCAO method. The initial structures of nanotubes have been obtained by rolling up slabs consisting of two and four alternating (001) SrO and TiO2 planes. In the majority of the considered cases the inner or outer TiO2 shells of 4-layer nanotubes undergo a considerable reconstruction due to shrinkage or stretching of interatomic distances. Double-wall nanotubes constructed from 2-layer single-wall nanotubes with the intertube distance less than 4.5-5.0 Å merge to stable polyhedron-shaped tubular objects consisting of blocks with a distorted cubic perovskite structure.

  5. A Cross Structured Light Sensor and Stripe Segmentation Method for Visual Tracking of a Wall Climbing Robot

    Science.gov (United States)

    Zhang, Liguo; Sun, Jianguo; Yin, Guisheng; Zhao, Jing; Han, Qilong

    2015-01-01

    In non-destructive testing (NDT) of metal welds, weld line tracking is usually performed outdoors, where the structured light sources are always disturbed by various noises, such as sunlight, shadows, and reflections from the weld line surface. In this paper, we design a cross structured light (CSL) to detect the weld line and propose a robust laser stripe segmentation algorithm to overcome the noises in structured light images. An adaptive monochromatic space is applied to preprocess the image with ambient noises. In the monochromatic image, the laser stripe obtained is recovered as a multichannel signal by minimum entropy deconvolution. Lastly, the stripe centre points are extracted from the image. In experiments, the CSL sensor and the proposed algorithm are applied to guide a wall climbing robot inspecting the weld line of a wind power tower. The experimental results show that the CSL sensor can capture the 3D information of the welds with high accuracy, and the proposed algorithm contributes to the weld line inspection and the robot navigation. PMID:26110403

  6. Energy gaps, electronic structures, and x-ray spectroscopies of finite semiconductor single-walled carbon nanotubes.

    Science.gov (United States)

    Gao, Bin; Jiang, Jun; Wu, ZiYu; Luo, Yi

    2008-02-28

    We report hybrid density functional theory calculations for electronic structures of hydrogen-terminated finite single-walled carbon nanotubes (6,5) and (8,3) up to 100 nm in length. Gap states that are mainly arisen from the hydrogen-terminated edges have been found in (8,3) tubes, but their contributions to the density of states become invisible when the tube is longer than 10 nm. The electronic structures of (6,5) and (8,3) tubes are found to be converged around 20 nm. The calculated band-gap energies of 100 nm long nanotubes are in good agreement with experimental results. The valence band structures of (6,5), (8,3), as well as (5,5) tubes are also investigated by means of ultraviolet photoelectron spectra (UPS), x-ray emission spectroscopy (XES), and the resonant inelastic x-ray scattering (RIXS) spectra theoretically. The UPS, XES and RIXS spectra become converged already at 10 nm. The length-dependent oscillation behavior is found in the RIXS spectra of (5,5) tubes, indicating that the RIXS spectra may be used to determine the size and length of metallic nanotubes. Furthermore, the chiral dependence observed in the simulated RIXS spectra suggests that RIXS spectra could be a useful technique for the determination of chirality of carbon nanotubes.

  7. Effect of laser radiation on multi-wall carbon nanotubes: study of shell structure and immobilization process

    Energy Technology Data Exchange (ETDEWEB)

    Gyoergy, Enikoe, E-mail: egyorgy@icmab.es; Perez del Pino, Angel [Instituto de Ciencia de Materiales de Barcelona, Consejo Superior de Investigaciones Cientificas (ICMAB-CSIC) (Spain); Roqueta, Jaume; Ballesteros, Belen [Centro de Investigaciones en Nanociencia y Nanotecnologia, Consejo Superior de Investigaciones Cientificas (CIN2-CSIC) (Spain); Cabana, Laura; Tobias, Gerard [Instituto de Ciencia de Materiales de Barcelona, Consejo Superior de Investigaciones Cientificas (ICMAB-CSIC) (Spain)

    2013-08-15

    Multi-wall carbon nanotubes (MWCNTs) with diameters between 10 and 15 nm were transferred and immobilized onto SiO{sub 2} glass substrates by ultraviolet matrix assisted pulsed laser evaporation (UV-MAPLE). Toluene was chosen as solvent material for the preparation of the composite MAPLE targets. An UV KrF* ({lambda} = 248 nm, {tau}{sub FWHM} {approx_equal} 25 ns, {nu} = 10 Hz) excimer laser source was used for the irradiation experiments. The effects of incident laser fluence on the structure of the laser transferred MWCNTs was investigated by high resolution transmission electron microscopy and Raman spectroscopy. The surface morphology of the laser processed MWCNTs was investigated by field emission scanning electron microscopy and atomic force microscopy in acoustic (dynamic) configuration. Network-like structures constituted by individual nanotubes and nanotube bundles were created onto solid substrates. Changes in the nanotubes' shell structure can be induced through the tuning of the laser fluence value incident onto the composite MAPLE targets.

  8. Experimental study on semi-active control of frame-shear wall eccentric structure using MR dampers

    Science.gov (United States)

    Li, Xiu Ling, Sr.; Li, Hong Nan, Sr.

    2006-03-01

    Magnetorheological (MR) damper is a kind of intelligent actuator, which shows immense potential in the field of structural vibration control. The construction and mechanical behavior of MR damper are introduced firstly, and then a new mechanical model--double sigmoid model is proposed based on the experimental study of MR damper. The simulation system of the 3-floor frame-shear wall eccentric structure with MR dampers was built according to the coupled translation and torsion response control using MR damper, based on Matlab/Simulink software environment and hardware/software resources of dSPACE. The shaking table experiment of the structural model was implemented by using rapid control prototyping (RCP) technology. The validity of two passive control strategies and one semi-active control strategy is verified under three input earthquake excitation with different peak value. The experimental results show that the coupled translation and torsion response is significantly mitigated, and the semi-active control strategies can achieve higher performance levels as compared to those of the two passive control cases. Moreover, the location of the MR damper has an important effect on the control results.

  9. Studies of the pedestal structure and inter-ELM pedestal evolution in JET with the ITER-like wall

    Science.gov (United States)

    Maggi, C. F.; Frassinetti, L.; Horvath, L.; Lunniss, A.; Saarelma, S.; Wilson, H.; Flanagan, J.; Leyland, M.; Lupelli, I.; Pamela, S.; Urano, H.; Garzotti, L.; Lerche, E.; Nunes, I.; Rimini, F.; Contributors, JET

    2017-11-01

    The pedestal structure of type I ELMy H-modes has been analysed for JET with the ITER-like Wall (JET-ILW). The electron pressure pedestal width is independent of ρ * and increases proportionally to  √β pol,PED. Additional broadening of the width is observed, at constant β pol, PED, with increasing ν * and/or neutral gas injection and the contribution of atomic physics effects in setting the pedestal width cannot as yet be ruled out. Neutral penetration alone does not determine the shape of the edge density profile in JET-ILW. The ratio of electron density to electron temperature scale lengths in the edge transport barrier region, η e, is of order 2-3 within experimental uncertainties. Existing understanding, represented in the stationary linear peeling-ballooning mode stability and the EPED pedestal structure models, is extended to the dynamic evolution between ELM crashes in JET-ILW, in order to test the assumptions underlying these two models. The inter-ELM temporal evolution of the pedestal structure in JET-ILW is not unique, but depends on discharge conditions, such as heating power and gas injection levels. The strong reduction in p e,PED with increasing D 2 gas injection at high power is primarily due to clamping of \

  10. First-principles study of structural and work function properties for nitrogen-doped single-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Shao, Xiji; Li, Detian; Cai, Jianqiu; Luo, Haijun; Dong, Changkun

    2016-01-01

    Graphical abstract: - Highlights: • Substitutional nitrogen atom doping in capped (5, 5) SWNT is investigated. • Serious defects appear from breaks of C−N bonds with N contents of above 23.3 at.%. • Work function drops after N doping and may reach 4.1 eV. - Abstract: The structural and electronic properties of the capped (5, 5) single-walled carbon nanotube (SWNT), including the structural stability, the work function, and the charge transfer performance, are investigated for the substitutional nitrogen atom doping under different concentrations by first-principles density functional theory. The geometrical structure keeps almost intact with single or two N atom doping, while C−N bonds may break up with serious defects for N concentrations of 23.3 at.% and above. The SWNT remains metallic and the work function drops after doping due to the upward shift of Fermi level, leading to the increase of the electrical conductivity. N doping enhances the oxygen reduction activity stronger than N adsorption because of higher charge transfers.

  11. Sound insulation of lightweight partition walls with regard to structural sound transmission

    Directory of Open Access Journals (Sweden)

    Lelyuga Olga

    2018-01-01

    Full Text Available The known methods of acoustical calculation in buildings disregard the phenomenon of structural sound transmission, whereas its effect can reach from 2 to 12 dB. The purpose of this paper is to develop the calculation method for sound transmission and vibrations in connected vibroacoustic systems. Theoretical research methods were used based on the theory of statistical energy analysis (SEA and the theory of self-consistent sound fields with regard to dual nature of sound formation - resonance and inertia. Based on M. Sedov's method of sound fields consistency, a calculation method for sound insulation was developed with integration in SEA methodology. Use of the developed method allows predicting sound transmission through a double-panel partition with the account of adjacent structures.

  12. Multi-walled carbon nanotube dispersion by the adsorbed humic acids with different chemical structures.

    Science.gov (United States)

    Zhang, Di; Pan, Bo; Cook, Robert L; Xing, Baoshan

    2015-01-01

    Dissolved humic acid (disHA) is effective for suspending carbon nanotubes (CNTs), but the suspending mechanism is still unclear. This study used bleached and hydrolyzed humic acids as suspending agents to investigate effects of chemical structures on CNTs suspension. The adsorption of aromatic moieties enriched disHA to CNTs was lower than aliphatic components-enriched disHA, but the former was better at suspending CNTs. These findings led to the development of a model, in which disHA with aromatic structures results in stable suspension of CNTs due to stronger steric hindrance. Because of their flexible structures, aliphatic components-enriched disHA molecules easily conformed to CNTs leading to higher adsorption to CNTs but weaker steric hindrance between CNTs. Therefore, the bridging and less suspension of CNTs was observed. This study emphasizes that suspending CNTs by disHA is not only controlled by the adsorbed amount of disHA, but also the chemical nature of disHA.

  13. Quadricuspid Aortic Valve Combined with Moderate Ascending Aortic Dilatation: A Report of Four Cases.

    Science.gov (United States)

    Uspenskiy, Vladimir E; Osadchii, Alexei M; Gordeev, Mikhail L

    2015-12-01

    The quadricuspid aortic valve is a very uncommon malformation associated with aortic insufficiency, aortic stenosis, endocarditis, and ascending aortic dilatation. We report four cases of this aortic valve malformation. One patient with severe aortic regurgitation and moderate aortic dilatation required aortic valve replacement. Three patients had mild or moderate aortic insufficiency combined with moderate ascending aortic dilatation. These patients were referred to follow-up. The presented cases demonstrate that this aortic valve malformation may not be as rare as it appears and that attention must be paid to any quadricuspid findings during computed tomographic angiography and echocardiography.

  14. Micro-/nano-characterization of the surface structures on the divertor tiles from JET ITER-like wall

    Energy Technology Data Exchange (ETDEWEB)

    Tokitani, M., E-mail: tokitani.masayuki@LHD.nifs.ac.jp [National Institute for Fusion Science, Oroshi, Toki, Gifu 509-5292 (Japan); Miyamoto, M. [Shimane University, Matsue, Shimane 690-8504 (Japan); Masuzaki, S. [National Institute for Fusion Science, Oroshi, Toki, Gifu 509-5292 (Japan); Fujii, Y. [Shimane University, Matsue, Shimane 690-8504 (Japan); Sakamoto, R. [National Institute for Fusion Science, Oroshi, Toki, Gifu 509-5292 (Japan); Oya, Y. [Shizuoka University, Shizuoka 422-8529 (Japan); Hatano, Y. [University of Toyama, Toyama 930-8555 (Japan); Otsuka, T. [Kindai University, Higashi-Osaka, Osaka, 577-8502 (Japan); Oyaidzu, M.; Kurotaki, H.; Suzuki, T.; Hamaguchi, D.; Isobe, K.; Asakura, N. [National Institute for Quantum and Radiological Science and Technology (QST), Rokkasho Aomori 039-3212 (Japan); Widdowson, A. [EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Rubel, M. [Royal Institute of Technology (KTH), 100 44 Stockholm (Sweden)

    2017-03-15

    Highlights: • Micro-/nano-characterization of the surface structures on the divertor tiles from JET ITER-like wall were studied. • The stratified mixed-material deposition layer composed by W, C, O, Mo and Be with the thickness of ∼1.5 μm was formed on the apron of Tile 1. • The study revealed the micro- and nano-scale modification of the inner tile surface of the JET ILW. - Abstract: Micro-/nano-characterization of the surface structures on the divertor tiles used in the first campaign (2011–2012) of the JET tokamak with the ITER-like wall (JET ILW) were studied. The analyzed tiles were a single poloidal section of the tile numbers of 1, 3 and 4, i.e., upper, vertical and horizontal targets, respectively. A sample from the apron of Tile 1 was deposition-dominated. Stratified mixed-material layers composed of Be, W, Ni, O and C were deposited on the original W-coating. Their total thickness was ∼1.5 μm. By means of transmission electron microscopy, nano-size bubble-like structures with a size of more than 100 nm were identified in that layer. They could be related to deuterium retention in the layer dominated by Be. The surface microstructure of the sample from Tile 4 also showed deposition: a stratified mixed-material layer with the total thickness of 200–300 nm. The electron diffraction pattern obtained with transmission electron microscope indicated Be was included in the layer. No bubble-like structures have been identified. The surface of Tile 3, originally coated by Mo, was identified as the erosion zone. This is consistent with the fact that the strike point was often located on that tile during the plasma operation. The study revealed the micro- and nano-scale modification of the inner tile surface of the JET ILW. In particular, a complex mixed-material deposition layer could affect hydrogen isotope retention and dust formation.

  15. 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.

  16. Role of supramolecular cellulose structures in enzymatic hydrolysis of plant cell walls

    DEFF Research Database (Denmark)

    Thygesen, Lisbeth Garbrecht; Hidayat, Budi Juliman; Johansen, Katja Salomon

    2011-01-01

    The study of biomass deconstruction by enzymatic hydrolysis has hitherto not focussed on the importance of supramolecular structures of cellulose. In lignocellulose fibres, regions with a different organisation of the microfibrils are present. These regions are called dislocations or slip planes...... mixture on hydrothermally treated wheat straw, it was found that the fibres were cut into segments corresponding to the sections between the dislocations initially present, as has previously been observed for acid hydrolysis of softwood pulps. The results indicate that dislocations are important during...

  17. Fenestrated Stent Graft Repair of Abdominal Aortic Aneurysm: Hemodynamic Analysis of the Effect of Fenestrated Stents on the Renal Arteries

    International Nuclear Information System (INIS)

    Sun, Zhonghua; Chaichana, Thanapong

    2010-01-01

    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

  18. Unoperated aortic aneurysm

    DEFF Research Database (Denmark)

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

    1995-01-01

    From 1984 to 1993, 1,053 patients were admitted with aortic aneurysm (AA) and 170 (15%) were not operated on. The most frequent reason for nonoperative management was presumed technical inoperability. Survivals for patients with thoracic, thoracoabdominal, and abdominal AA were comparable. No sig...

  19. Double aortic arch

    Science.gov (United States)

    Surgery can be done to fix double aortic arch. The surgeon ties off the smaller branch and separates it from the larger branch. Then the surgeon closes the ends of the aorta with stitches. This relieves pressure on the esophagus and windpipe.

  20. Bicuspid aortic valve

    Science.gov (United States)

    ... females. A BAV often exists in babies with coarctation of the aorta (narrowing of the aorta). BAV is also seen ... to view the blood vessels of the heart Treatment ... to the heart and into the narrow opening of the aortic valve. A balloon attached to the end of ...

  1. Tissue engineered aortic valve

    OpenAIRE

    Dohmen, P M

    2012-01-01

    Several prostheses are available to replace degenerative diseased aortic valves with unique advantages and disadvantages. Bioprotheses show excellent hemodynamic behavior and low risk of thromboembolic complications, but are limited by tissue deterioration. Mechanical heart valves have extended durability, but permanent anticoagulation is mandatory. Tissue engineering created a new generation heart valve, which overcome limitations of biological and mechanical heart valves due to remodelling,...

  2. Structural investigation of cell wall polysaccharides of Lactobacillus delbrueckii subsp. bulgaricus 17.

    Science.gov (United States)

    Vinogradov, E; Sadovskaya, I; Cornelissen, A; van Sinderen, D

    2015-09-02

    Lactobacilli are valuable strains for commercial (functional) food fermentations. Their cell surface-associated polysaccharides (sPSs) possess important functional properties, such as acting as receptors for bacteriophages (bacterial viruses), influencing autolytic characteristics and providing protection against antimicrobial peptides. The current report provides an elaborate molecular description of several surface carbohydrates of Lactobacillus delbrueckii subsp. bulgaricus strain 17. The cell surface of this strain was shown to contain short chain poly(glycerophosphate) teichoic acids and at least two different sPSs, designated here as sPS1 and sPS2, whose chemical structures were examined by 2D nuclear magnetic resonance spectroscopy and methylation analysis. Neutral branched sPS1, extracted with n-butanol, was shown to be composed of hexasaccharide repeating units (-[α-d-Glcp-(1-3)-]-4-β-l-Rhap2OAc-4-β-d-Glcp-[α-d-Galp-(1-3)]-4-α-Rhap-3-α-d-Galp-), while the major component of the TCA-extracted sPS2 was demonstrated to be a linear d-galactan with the repeating unit structure being (-[Gro-3P-(1-6)-]-3-β-Galf-3-α-Galp-2-β-Galf-6-β-Galf-3-β-Galp-). Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Damage Detection on Thin-walled Structures Utilizing Laser Scanning and Standing Waves

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Se Hyeok; Jeon, Jun Young; Kim, Du Hwan; Park, Gyuhae [Chonnam Nat’l Univ., Gwangju (Korea, Republic of); Kang, To; Han, Soon Woo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-05-15

    This paper describes wavenumber filtering for damage detection using single-frequency standing wave excitation and laser scanning sensing. An embedded piezoelectric sensor generates ultrasonic standing waves, and the responses are measured using a laser Doppler vibrometer and mirror tilting device. After scanning, newly developed damage detection techniques based on wavenumber filtering are applied to the full standing wave field. To demonstrate the performance of the proposed techniques, several experiments were performed on composite plates with delamination and aluminum plates with corrosion damage. The results demonstrated that the developed techniques could be applied to various structures to localize the damage, with the potential to improve the damage detection capability at a high interrogation speed.

  4. Structural Investigation of Cell Wall Xylan Polysaccharides from the Leaves of Algerian Argania spinosa

    Directory of Open Access Journals (Sweden)

    Kadda Hachem

    2016-11-01

    Full Text Available Xylan-type polysaccharides were isolated from the leaves of Argania spinosa (L. Skeels collected in the Tindouf area (southwestern Algeria. Xylan fractions were obtained by sequential alkaline extractions and purified on Sepharose CL-4B. The xylan structure was investigated by enzymatic hydrolysis with an endo-β(1→4-xylanase followed by chromatography of the resulting fragments on Biogel P2, characterization by sugar analysis and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS . The results show that the A. spinosa xylan is composed of a β-(1→4-d-xylopyranose backbone substituted with 4-O-methyl-d-glucuronic acid and L-arabinose residues.

  5. Special structures and properties of hydrogen nanowire confined in a single walled carbon nanotube at extreme high pressure

    Directory of Open Access Journals (Sweden)

    Yueyuan Xia

    2012-06-01

    Full Text Available Extensive ab initio molecular dynamics simulations indicate that hydrogen can be confined in single walled carbon nanotubes to form high density and high pressure H2 molecular lattice, which has peculiar shell and axial structures depending on the density or pressure. The band gap of the confined H2 lattice is sensitive to the pressure. Heating the system at 2000K, the H2 lattice is firstly melted to form H2 molecular liquid, and then some of the H2 molecules dissociate accompanied by drastic molecular and atomic reactions, which have essential effect on the electronic structure of the hydrogen system. The liquid hydrogen system at 2000K is found to be a particular mixed liquid, which consists of H2 molecules, H atoms, and H-H-H trimers. The dissociated H atoms and the trimers in the liquid contribute resonance electron states at the Fermi energy to change the material properties substantially. Rapidly cooling the system from 2000K to 0.01 K, the mixed liquid is frozen to form a mixed solid melt with a clear trend of band gap closure. It indicates that this solid melt may become a superconducting nanowire when it is further compressed.

  6. Purification, structure and immunobiological activity of an arabinan-rich pectic polysaccharide from the cell walls of Prunus dulcis seeds.

    Science.gov (United States)

    Dourado, Fernando; Madureira, Pedro; Carvalho, Vera; Coelho, Ricardo; Coimbra, Manuel A; Vilanova, Manuel; Mota, Manuel; Gama, Francisco M

    2004-10-20

    The structure and bioactivity of a polysaccharide extracted and purified from a 4M KOH + H3BO3 solution from Prunus dulcis seed cell wall material was studied. Anion-exchange chromatography of the crude extract yielded two sugar-rich fractions: one neutral (A), the other acidic (E). These fractions contain a very similar monosaccharide composition: 5:2:1 for arabinose, uronic acids and xylose, respectively, rhamnose and galactose being present in smaller amounts. As estimated by size-exclusion chromatography, the acidic fraction had an apparent molecular mass of 762 kDa. Methylation analysis (from the crude and fractions A and E), suggests that the polysaccharide is an arabinan-rich pectin. In all cases, the polysaccharides bear the same type of structural Ara moieties with highly branched arabinan-rich pectic polysaccharides. The average relative proportions of the arabinosyl linkages is 3:2:1:1 for T-Araf:(1-->5)-Araf:(1-->3,5)-Araf:(1-->2,3,5)-Araf. The crude polysaccharide extract and fractions A and E induced a murine lymphocyte stimulatory effect, as evaluated by the in vitro and in vivo expression of lymphocyte activation markers and spleen mononuclear cells culture proliferation. The lymphocyte stimulatory effect was stronger on B- than on T-cells. No evidence of cytotoxic effects induced by the polysaccharide fractions was found.

  7. Sensing the Structural Differences in Cellulose from Apple and Bacterial Cell Wall Materials by Raman and FT-IR Spectroscopy

    Science.gov (United States)

    Szymańska-Chargot, Monika; Cybulska, Justyna; Zdunek, Artur

    2011-01-01

    Raman and Fourier Transform Infrared (FT-IR) spectroscopy was used for assessment of structural differences of celluloses of various origins. Investigated celluloses were: bacterial celluloses cultured in presence of pectin and/or xyloglucan, as well as commercial celluloses and cellulose extracted from apple parenchyma. FT-IR spectra were used to estimate of the Iβ content, whereas Raman spectra were used to evaluate the degree of crystallinity of the cellulose. The crystallinity index (XCRAMAN%) varied from −25% for apple cellulose to 53% for microcrystalline commercial cellulose. Considering bacterial cellulose, addition of xyloglucan has an impact on the percentage content of cellulose Iβ. However, addition of only xyloglucan or only pectins to pure bacterial cellulose both resulted in a slight decrease of crystallinity. However, culturing bacterial cellulose in the presence of mixtures of xyloglucan and pectins results in an increase of crystallinity. The results confirmed that the higher degree of crystallinity, the broader the peak around 913 cm−1. Among all bacterial celluloses the bacterial cellulose cultured in presence of xyloglucan and pectin (BCPX) has the most similar structure to those observed in natural primary cell walls. PMID:22163913

  8. Periodic density functional theory study of structural and electronic properties of single-walled zinc oxide and carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Marana, Naiara L. [Modeling and Molecular Simulations Group, São Paulo State University, UNESP, 17033-360 Bauru, SP (Brazil); Albuquerque, Anderson R. [Federal Institute of Education, Science and Technology of Sertão Pernambucano, 56400-000 Floresta, PE (Brazil); La Porta, Felipe A. [Chemistry Department, Federal Technological University of Paraná, 86036-370 Londrina, PR (Brazil); Longo, Elson [São Paulo State University, Chemistry Institute, UNESP, 14801-907 Araraquara, SP (Brazil); Sambrano, Julio R. [Modeling and Molecular Simulations Group, São Paulo State University, UNESP, 17033-360 Bauru, SP (Brazil)

    2016-05-15

    Periodic density functional theory calculations with the B3LYP hybrid functional and all-electron Gaussian basis set were performed to simulate the structural and electronic properties as well as the strain and formation energies of single-walled ZnO nanotubes (SWZnONTs) and Carbon nanotubes (SWCNTs) with different chiralities as functions of their diameters. For all SWZnONTs, the band gap, strain energy, and formation energy converge to ~4.5 eV, 0.0 eV/atom, and 0.40 eV/atom, respectively. This result suggests that the nanotubes are formed more easily from the surface than from the bulk. For SWCNTs, the strain energy is always positive, while the formation energy is negative for armchair and zigzag nanotubes, therefore suggesting that these types of nanotubes can be preferentially formed from the bulk. The electronic properties of SWCNTs depend on the chirality; all armchair nanotubes are metallic, while zigzag and chiral nanotubes can be metallic or semiconducting, depending on the n and m vectors. - Graphical abstract: DFT/B3LYP were performed to simulate the structural and electronic properties as well as the strain and formation energies of SWZnONTs and SWCNTs with different chiralities as functions of their diameters. - Highlights: • The energies of SWZnONTs converge for chirality with diameters up 20 Å. • SWCNTs electronic properties depend on the chirality. • The properties of SWZnONTs are very similar to those of monolayer surface.

  9. 14-3-3 in Thoracic Aortic Aneurysms

    Science.gov (United States)

    Chakravarti, Ritu; Gupta, Karishma; Swain, Mamuni; Willard, Belinda; Scholtz, Jaclyn; Svensson, Lars G.; Roselli, Eric E.; Pettersson, Gosta; Johnston, Douglas R.; Soltesz, Edward G.; Yamashita, Michifumi; Stuehr, Dennis; Daly, Thomas M.; Hoffman, Gary S.

    2015-01-01

    Objective Large vessel vasculitides (LVV) are a group of autoimmune diseases characterized by injury to and anatomic modifications of large vessels, including the aorta and its branch vessels. Disease etiology is unknown. This study was undertaken to identify antigen targets within affected vessel walls in aortic root, ascending aorta, and aortic arch surgical specimens from patients with LVV, including giant cell arteritis, Takayasu arteritis, and isolated focal aortitis. Methods Thoracic aortic aneurysm specimens and autologous blood were acquired from consenting patients who underwent aorta reconstruction procedures. Aorta proteins were extracted from both patients with LVV and age-, race-, and sex-matched disease controls with noninflammatory aneurysms. A total of 108 serum samples from patients with LVV, matched controls, and controls with antinuclear antibodies, different forms of vasculitis, or sepsis were tested. Results Evaluation of 108 serum samples and 22 aortic tissue specimens showed that 78% of patients with LVV produced antibodies to 14-3-3 proteins in the aortic wall (93.7% specificity), whereas controls were less likely to do so (6.7% produced antibodies). LVV patient sera contained autoantibody sufficient to immunoprecipitate 14-3-3 protein(s) from aortic lysates. Three of 7 isoforms of 14-3-3 were found to be up-regulated in aorta specimens from patients with LVV, and 2 isoforms (ε and ζ) were found to be antigenic in LVV. Conclusion This is the first study to use sterile, snap-frozen thoracic aorta biopsy specimens to identify autoantigens in LVV. Our findings indicate that 78% of patients with LVV have antibody reactivity to 14-3-3 protein(s). The precise role of these antibodies and 14-3-3 proteins in LVV pathogenesis deserves further study. PMID:25917817

  10. 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.

  11. Aortic dissection and sport: physiologic and clinical understanding provide an opportunity to save young lives.

    Science.gov (United States)

    Mayerick, C; Carré, F; Elefteriades, J

    2010-10-01

    Understanding the relationship between acute type A aortic dissection and sport is crucial to prevent sudden cardiac death in seemingly healthy young individuals. Aerobic exercise produces only a modest rise in arterial blood pressure (140-160 mmHg) except at the highest levels of exertion, at which pressures between 180-220 mmHg are reached. Weight training, on the other hand, routinely produces acute rises in blood pressure to over 300 mmHg. This presents a danger for individuals with an unknown aortic aneurysm; the deteriorated mechanical properties of the aortic wall resulting from aneurysmal enlargement increase the susceptibility to aortic rupture when the high wall coincident with exertion exceeds the tensile strength of the aortic wall. Investigations by our group into the inciting events leading up to dissection have demonstrated a causal link between extreme exertion, severe emotional stress, and acute type A aortic dissection. Since aortic enlargement is often unknown to persons participating in weight training, especially in the youth population, a ìSnapShot Echocardiogramî screening program is been proposed; such a pilot program will raise awareness of the importance of pre-participation cardiac screening and allow for early detection of aneurysms as a means of preventing this ìsilent killerî from striking. As strong supporters of the numerous benefits of weight training, we encourage this activity in individuals without aneurysm; without aneurysm, wall tension does not reach dangerous levels, even at extremes of exertion. For individuals with known aortic dilatation, we recommend a program that limits their lifting to 50% of body weight in the bench press or equivalent level of perceived exertion for other specific strength exercises.

  12. A new technique for interrupted aortic arch repair: the Neville tube.

    Science.gov (United States)

    Bergoënd, Eric; Bouissou, Antoine; Paoli, Florent; Roullet-Renoleau, Nicolas; Duchalais, Alain; Neville, Paul

    2010-10-01

    We have developed a new technique for interrupted aortic arch repair in which the pulmonary artery anterior wall is cut off and tailored so as to re-establish aortic continuity with an autologous tube. We are describing this method herein, with an 8-year follow-up of the first patient. Copyright © 2010 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  13. Aortic Compliance and Stiffness Among Severe Longstanding Hypertensive and Non-hypertensive

    OpenAIRE

    Kamberi, Lulzim Selim; Gorani, Daut Rashit; Hoxha, Teuta Faik; Zahiti, Bedri Faik

    2013-01-01

    Introduction Abnormal aortic function in hypertension is generally attributed to accelerated breakdown of elastin in the aorta, leading to dilatation of the lumen and stiffening of the wall as elastin is replaced with stiffer collagen. Aortic stiffness is an independent predictor of cardiovascular risk and all-cause and cardiovascular mortality. Vascular stiffening can activate endothelium which in turn may promote atherogenesis. Modulation of arterial stiffness has been shown to be successfu...

  14. Complete Soil-Structure Interaction (SSI) Analyses of I-walls Embedded in Level Ground During Flood Loading

    Science.gov (United States)

    2012-09-01

    75  4  Analyses of I-wall Site Founded on a Clay with Undrained Shear Strenght (Su) of 300 psf...Zero tensile strength capability is assumed along this soil-to-I-wall interface. ERDC/ITL TR-12-4 5 are discussed. A design flood depth of 9 ft1...the steel sheet-pile and the concrete I-wall section. Plate elements were used to model the concrete I-wall