WorldWideScience

Sample records for stress wss existed

  1. Upper Bounds for the Rate Distortion Function of Finite-Length Data Blocks of Gaussian WSS Sources

    Directory of Open Access Journals (Sweden)

    Jesús Gutiérrez-Gutiérrez

    2017-10-01

    Full Text Available In this paper, we present upper bounds for the rate distortion function (RDF of finite-length data blocks of Gaussian wide sense stationary (WSS sources and we propose coding strategies to achieve such bounds. In order to obtain those bounds, we previously derive new results on the discrete Fourier transform (DFT of WSS processes.

  2. Motional Effect on Wall Shear Stresses

    DEFF Research Database (Denmark)

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

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

  3. Understanding the fluid mechanics behind transverse wall shear stress.

    Science.gov (United States)

    Mohamied, Yumnah; Sherwin, Spencer J; Weinberg, Peter D

    2017-01-04

    The patchy distribution of atherosclerosis within arteries is widely attributed to local variation in haemodynamic wall shear stress (WSS). A recently-introduced metric, the transverse wall shear stress (transWSS), which is the average over the cardiac cycle of WSS components perpendicular to the temporal mean WSS vector, correlates particularly well with the pattern of lesions around aortic branch ostia. Here we use numerical methods to investigate the nature of the arterial flows captured by transWSS and the sensitivity of transWSS to inflow waveform and aortic geometry. TransWSS developed chiefly in the acceleration, peak systolic and deceleration phases of the cardiac cycle; the reverse flow phase was too short, and WSS in diastole was too low, for these periods to have a significant influence. Most of the spatial variation in transWSS arose from variation in the angle by which instantaneous WSS vectors deviated from the mean WSS vector rather than from variation in the magnitude of the vectors. The pattern of transWSS was insensitive to inflow waveform; only unphysiologically high Womersley numbers produced substantial changes. However, transWSS was sensitive to changes in geometry. The curvature of the arch and proximal descending aorta were responsible for the principal features, the non-planar nature of the aorta produced asymmetries in the location and position of streaks of high transWSS, and taper determined the persistence of the streaks down the aorta. These results reflect the importance of the fluctuating strength of Dean vortices in generating transWSS. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Wall shear stress fixed points in blood flow

    Science.gov (United States)

    Arzani, Amirhossein; Shadden, Shawn

    2017-11-01

    Patient-specific computational fluid dynamics produces large datasets, and wall shear stress (WSS) is one of the most important parameters due to its close connection with the biological processes at the wall. While some studies have investigated WSS vectorial features, the WSS fixed points have not received much attention. In this talk, we will discuss the importance of WSS fixed points from three viewpoints. First, we will review how WSS fixed points relate to the flow physics away from the wall. Second, we will discuss how certain types of WSS fixed points lead to high biochemical surface concentration in cardiovascular mass transport problems. Finally, we will introduce a new measure to track the exposure of endothelial cells to WSS fixed points.

  5. Wall shear stress fixed points in cardiovascular fluid mechanics.

    Science.gov (United States)

    Arzani, Amirhossein; Shadden, Shawn C

    2018-05-17

    Complex blood flow in large arteries creates rich wall shear stress (WSS) vectorial features. WSS acts as a link between blood flow dynamics and the biology of various cardiovascular diseases. WSS has been of great interest in a wide range of studies and has been the most popular measure to correlate blood flow to cardiovascular disease. Recent studies have emphasized different vectorial features of WSS. However, fixed points in the WSS vector field have not received much attention. A WSS fixed point is a point on the vessel wall where the WSS vector vanishes. In this article, WSS fixed points are classified and the aspects by which they could influence cardiovascular disease are reviewed. First, the connection between WSS fixed points and the flow topology away from the vessel wall is discussed. Second, the potential role of time-averaged WSS fixed points in biochemical mass transport is demonstrated using the recent concept of Lagrangian WSS structures. Finally, simple measures are proposed to quantify the exposure of the endothelial cells to WSS fixed points. Examples from various arterial flow applications are demonstrated. Copyright © 2018 Elsevier Ltd. All rights reserved.

  6. Contrast-enhanced micro-CT imaging in murine carotid arteries: A new protocol for computing wall shear stress

    NARCIS (Netherlands)

    Xing, R. (Ruoyu); Wilde, D. (David); McCann, G. (Gayle); Y. Ridwan (Yanto); J.T.C. Schrauwen (Jelle); A.F.W. Steen (Antonius F.W.); F.J.H. Gijsen (Frank); Heiden, K. (Kim)

    2016-01-01

    textabstractBackground: Wall shear stress (WSS) is involved in the pathophysiology of atherosclerosis. The correlation between WSS and atherosclerosis can be investigated over time using a WSS-manipulated atherosclerotic mouse model. To determine WSS in vivo, detailed 3D geometry of the vessel

  7. Volumetric Arterial Wall Shear Stress Calculation Based on Cine Phase Contrast MRI

    NARCIS (Netherlands)

    Potters, Wouter V.; van Ooij, Pim; Marquering, Henk; VanBavel, Ed; Nederveen, Aart J.

    2015-01-01

    PurposeTo assess the accuracy and precision of a volumetric wall shear stress (WSS) calculation method applied to cine phase contrast magnetic resonance imaging (PC-MRI) data. Materials and MethodsVolumetric WSS vectors were calculated in software phantoms. WSS algorithm parameters were optimized

  8. Augmentation of wall shear stress inhibits neointimal hyperplasia after stent implantation - Inhibition through reduction of inflammation?

    NARCIS (Netherlands)

    Carlier, SG; van Damme, LCA; Blommerde, CP; Wentzel, JJ; van Langehove, G; Verheye, S; Kockx, MM; Knaapen, MWM; Cheng, C; Gijsen, F; Duncker, DJ; Stergiopulos, N; Slager, CJ; Serruys, PW; Krams, R

    2003-01-01

    Background - Low wall shear stress (WSS) increases neointimal hyperplasia (NH) in vein grafts and stents. We studied the causal relationship between WSS and NH formation in stents by locally increasing WSS with a flow divider (Anti-Restenotic Diffuser, Endoart SA) placed in the center of the stent.

  9. Accounting aspects of contracts for the operation of public water supply assets in WSS operators

    Directory of Open Access Journals (Sweden)

    Nedyalka Alexandrova

    2017-12-01

    Full Text Available The article investigates and analyses the nature of the Contracts for exploitation of WSS assets concluded between the Water Supply and Sewerage Associations and operators under the Water Act in order to outline the opportunities for accounting of the assets and liabilities resulting from these contracts. The contracts, as well as the WSS Associations, are new and unique for Bulgarian practice phenomena, affecting the entire water supply sector and their reporting poses considerable difficulties in practice. The article is based on an analysis of the normative requirements of the Water Act, a study of the clauses of the contracts, as well as their comparison with the concession contracts. Based on the analysis of their economic nature and under the requirements of the International Accounting Standards, a model of accounting for the assets and liabilities arising from these contracts is proposed, including their presentation and valuation in the financial statements of the operators.

  10. Wall Shear Stress Estimation of Thoracic Aortic Aneurysm Using Computational Fluid Dynamics

    Directory of Open Access Journals (Sweden)

    J. Febina

    2018-01-01

    Full Text Available An attempt has been made to evaluate the effects of wall shear stress (WSS on thoracic aortic aneurysm (TAA using Computational Fluid Dynamics (CFD. Aneurysm is an excessive localized swelling of the arterial wall due to many physiological factors and it may rupture causing shock or sudden death. The existing imaging modalities such as MRI and CT assist in the visualization of anomalies in internal organs. However, the expected dynamic behaviour of arterial bulge under stressed condition can only be effectively evaluated through mathematical modelling. In this work, a 3D aneurysm model is reconstructed from the CT scan slices and eventually the model is imported to Star CCM+ (Siemens, USA for intensive CFD analysis. The domain is discretized using polyhedral mesh with prism layers to capture the weakening boundary more accurately. When there is flow reversal in TAA as seen in the velocity vector plot, there is a chance of cell damage causing clots. This is because of the shear created in the system due to the flow pattern. It is observed from the proposed mathematical modelling that the deteriorating WSS is an indicator for possible rupture and its value oscillates over a cardiac cycle as well as over different stress conditions. In this model, the vortex formation pattern and flow reversals are also captured. The non-Newtonian model, including a pulsatile flow instead of a steady average flow, does not overpredict the WSS (15.29 Pa compared to 16 Pa for the Newtonian model. Although in a cycle the flow behaviour is laminar-turbulent-laminar (LTL, utilizing the non-Newtonian model along with LTL model also overpredicted the WSS with a value of 20.1 Pa. The numerical study presented here provides good insight of TAA using a systematic approach to numerical modelling and analysis.

  11. Pulsatility Index as a Diagnostic Parameter of Reciprocating Wall Shear Stress Parameters in Physiological Pulsating Waveforms.

    Directory of Open Access Journals (Sweden)

    Idit Avrahami

    Full Text Available Arterial wall shear stress (WSS parameters are widely used for prediction of the initiation and development of atherosclerosis and arterial pathologies. Traditional clinical evaluation of arterial condition relies on correlations of WSS parameters with average flow rate (Q and heart rate (HR measurements. We show that for pulsating flow waveforms in a straight tube with flow reversals that lead to significant reciprocating WSS, the measurements of HR and Q are not sufficient for prediction of WSS parameters. Therefore, we suggest adding a third quantity-known as the pulsatility index (PI-which is defined as the peak-to-peak flow rate amplitude normalized by Q. We examine several pulsating flow waveforms with and without flow reversals using a simulation of a Womersley model in a straight rigid tube and validate the simulations through experimental study using particle image velocimetry (PIV. The results indicate that clinically relevant WSS parameters such as the percentage of negative WSS (P[%], oscillating shear index (OSI and the ratio of minimum to maximum shear stress rates (min/max, are better predicted when the PI is used in conjunction with HR and Q. Therefore, we propose to use PI as an additional and essential diagnostic quantity for improved predictability of the reciprocating WSS.

  12. High wall shear stress and spatial gradients in vascular pathology: a review.

    Science.gov (United States)

    Dolan, Jennifer M; Kolega, John; Meng, Hui

    2013-07-01

    Cardiovascular pathologies such as intracranial aneurysms (IAs) and atherosclerosis preferentially localize to bifurcations and curvatures where hemodynamics are complex. While extensive knowledge about low wall shear stress (WSS) has been generated in the past, due to its strong relevance to atherogenesis, high WSS (typically >3 Pa) has emerged as a key regulator of vascular biology and pathology as well, receiving renewed interests. As reviewed here, chronic high WSS not only stimulates adaptive outward remodeling, but also contributes to saccular IA formation (at bifurcation apices or outer curves) and atherosclerotic plaque destabilization (in stenosed vessels). Recent advances in understanding IA pathogenesis have shed new light on the role of high WSS in pathological vascular remodeling. In complex geometries, high WSS can couple with significant spatial WSS gradient (WSSG). A combination of high WSS and positive WSSG has been shown to trigger aneurysm initiation. Since endothelial cells (ECs) are sensors of WSS, we have begun to elucidate EC responses to high WSS alone and in combination with WSSG. Understanding such responses will provide insight into not only aneurysm formation, but also plaque destabilization and other vascular pathologies and potentially lead to improved strategies for disease management and novel targets for pharmacological intervention.

  13. Real World SharePoint 2007 Indispensable Experiences From 16 MOSS and WSS MVPs

    CERN Document Server

    Hillier, Scot; Buenz, Adam; Connell, Andrew; Draper, Stacy; Solier Grinda, Luis Du; Klindt, Todd; Medero, Jason; Miller, Dustin; Perran, Shane; Poelmans, Joris; Solomon, Heather; Swan, Nick; Tielens, Jan; Walsh, Mike; Young, Shane

    2011-01-01

    Microsoft recognizes key individuals who contribute significantly to the community of technologists through the Microsoft Most Valuable Professional (MVP) award. These individuals are active authors, speakers, bloggers, and innovators. They are also skilled network engineers, developers, trainers, designers, and architects. In the SharePoint community, these MVPs are recognized for their expertise in either Windows SharePoint Services (WSS) or Microsoft Office SharePoint Server (MOSS). This book represents the efforts of 16 MVPs in the SharePoint community to present core areas of SharePoint 2

  14. Wall shear stress in portal vein of cirrhotic patients with portal hypertension.

    Science.gov (United States)

    Wei, Wei; Pu, Yan-Song; Wang, Xin-Kai; Jiang, An; Zhou, Rui; Li, Yu; Zhang, Qiu-Juan; Wei, Ya-Juan; Chen, Bin; Li, Zong-Fang

    2017-05-14

    To investigate wall shear stress (WSS) magnitude and distribution in cirrhotic patients with portal hypertension using computational fluid dynamics. Idealized portal vein (PV) system models were reconstructed with different angles of the PV-splenic vein (SV) and superior mesenteric vein (SMV)-SV. Patient-specific models were created according to enhanced computed tomography images. WSS was simulated by using a finite-element analyzer, regarding the blood as a Newtonian fluid and the vessel as a rigid wall. Analysis was carried out to compare the WSS in the portal hypertension group with that in healthy controls. For the idealized models, WSS in the portal hypertension group (0-10 dyn/cm 2 ) was significantly lower than that in the healthy controls (10-20 dyn/cm 2 ), and low WSS area (0-1 dyn/cm 2 ) only occurred in the left wall of the PV in the portal hypertension group. Different angles of PV-SV and SMV-SV had different effects on the magnitude and distribution of WSS, and low WSS area often occurred in smaller PV-SV angle and larger SMV-SV angle. In the patient-specific models, WSS in the cirrhotic patients with portal hypertension (10.13 ± 1.34 dyn/cm 2 ) was also significantly lower than that in the healthy controls ( P portal hypertension, the low WSS area extended to wider levels and the magnitude of WSS reached lower levels, thereby being more prone to disturbed flow occurrence. Cirrhotic patients with portal hypertension show dramatic hemodynamic changes with lower WSS and greater potential for disturbed flow, representing a possible causative factor of PV thrombosis.

  15. Bicuspid aortic valves are associated with increased wall and turbulence shear stress levels compared to trileaflet aortic valves.

    Science.gov (United States)

    Saikrishnan, Neelakantan; Mirabella, Lucia; Yoganathan, Ajit P

    2015-06-01

    Congenital bicuspid aortic valves (BAVs) are associated with accelerated disease progression, such as leaflet calcification and ascending aorta dilatation. Although common underlying genetic factors have been implicated in accelerated disease in BAV patients, several studies have suggested that altered hemodynamics also play a role in this disease process. The present study compares turbulence and wall shear stress (WSS) measurements between various BAV and trileaflet aortic valve (TAV) models to provide information for mechanobiological models of BAV disease. BAV and TAV models were constructed from excised porcine aortic valves to simulate parametric variations in BAV stenosis, hemodynamics and geometry. Particle image velocimetry experiments were conducted at physiological pressure conditions to characterize velocity fields in the ascending aorta. The velocity fields were post-processed to calculate turbulence, viscous and wall shear stresses in the ascending aorta. Stenosed BAV models showed the presence of eccentric systolic jets, causing increased WSS. Lower cardiac output resulted in a narrower jet, lower turbulence and lower viscous shear stress (VSS). The specific severe stenosis BAV model studied here showed reduced WSS due to reduction in non-fused leaflet mobility. Dilation of the aorta did not affect any turbulence or VSS, but reduced the WSS. In comparison with BAVs, TAVs have similar VSS values, but much smaller WSS and turbulence levels. These increased turbulence  and WSS levels in BAVs may play a key role in amplifying the biological responses of the ascending aorta wall and valvular leaflets, and support the hemodynamic underpinnings of BAV disease processes.

  16. BOF4WSS : a business-oriented framework for enhancing web services security for e-business

    OpenAIRE

    Nurse, Jason R. C.; Sinclair, Jane

    2009-01-01

    When considering Web services' (WS) use for online business-to-business (B2B) collaboration between companies, security is a complicated and very topical issue. This is especially true with regard to reaching a level of security beyond the technological layer, that is supported and trusted by all businesses involved. With appreciation of this fact, our research draws from established development methodologies to develop a new, business-oriented framework (BOF4WSS) to guide e-businesses in def...

  17. Comparison of job stress and obesity in nurses with favorable and unfavorable work schedules.

    Science.gov (United States)

    Han, Kihye; Trinkoff, Alison M; Storr, Carla L; Geiger-Brown, Jeanne; Johnson, Karen L; Park, Sungae

    2012-08-01

    To compare obesity-related factors between female nurses with favorable work schedules (WSs) and unfavorable WSs. In a cross-sectional study, 1724 female nurses were stratified by WS (favorable vs unfavorable). For each schedule type, the odds of obesity were related to health behaviors, home demands, and job stress using logistic regression models. Among nurses with unfavorable WSs, healthy behaviors (exercise, sleep) were inversely associated with obesity, whereas for those with favorable WSs, obese nurses reported significantly more unhealthy behaviors (smoking, alcohol use; odds ratio [OR], 1.19; 95% confidence interval [CI], 1.02-1.38), more physical lifting of children/dependents (OR, 1.43; 95% CI, 1.06-1.93), having more nurse input into their jobs (OR, 1.21; 95% CI, 1.02-1.44), yet less boss support at work (OR, 0.83; 95% CI, 0.68-0.99). Considering impacts of WSs on obesity and potential obesity-related health outcomes, healthful scheduling should be provided to nurses.

  18. Augmentative effect of pulsatility on the wall shear stress in tube flow.

    Science.gov (United States)

    Nakata, M; Tatsumi, E; Tsukiya, T; Taenaka, Y; Nishimura, T; Nishinaka, T; Takano, H; Masuzawa, T; Ohba, K

    1999-08-01

    Wall shear stress (WSS) has been considered to play an important role in the physiological and metabolic functions of the vascular endothelial cells. We investigated the effects of the pulse rate and the maximum flow rate on the WSS to clarify the influence of pulsatility. Water was perfused in a 1/2 inch transparent straight cylinder with a nonpulsatile centrifugal pump and a pulsatile pneumatic ventricular assist device (VAD). In nonpulsatile flow (NF), the flow rate was changed 1 to 6 L/min by 1 L/min increments to obtain standard values of WSS at each flow rate. In pulsatile flow (PF), the pulse rate was controlled at 40, 60, and 80 bpm, and the maximum flow rate was varied from 3.3 to 12.0 L/min while the mean flow rate was kept at 3 L/min. The WSS was estimated from the velocity profile at measuring points using the laser illuminated fluorescence method. In NF, the WSS was 12.0 dyne/cm2 at 3 L/min and 33.0 dyne/cm2 at 6 L/min. In PF, the pulse rate change with the same mean, and the maximum flow rate did not affect WSS. On the other hand, the increase in the maximum flow rate at the constant mean flow rate of 3 L/min augmented the mean WSS from 13.1 to 32.9 dyne/cm2. We concluded that the maximum flow rate exerted a substantial augmentative effect on WSS, and the maximum flow rate was a dominant factor of pulsatility in this effect.

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

    Directory of Open Access Journals (Sweden)

    Poulikakos Dimos

    2007-09-01

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

  20. Relation between wall shear stress and carotid artery wall thickening MRI versus CFD

    DEFF Research Database (Denmark)

    Cibis, Merih; Potters, Wouter V.; Selwaness, Mariana

    2016-01-01

    Wall shear stress (WSS), a parameter associated with endothelial function, is calculated by computational fluid dynamics (CFD) or phase-contrast (PC) MRI measurements. Although CFD is common in WSS (WSSCFD) calculations, PC-MRI-based WSS (WSSMRI) is more favorable in population studies; since...... it is straightforward and less time consuming. However, it is not clear if WSSMRI and WSSCFD show similar associations with vascular pathology. Our aim was to test the associations between wall thickness (WT) of the carotid arteries and WSSMRI and WSSCFD. The subjects (n=14) with an asymptomatic carotid plaque who...... underwent MRI scans two times within 4 years of time were selected from the Rotterdam Study. We compared WSSCFD and WSSMRI at baseline and follow-up. Baseline WSSMRI and WSSCFD values were divided into 3 categories representing low, medium and high WSS tertiles. WT of each tertile was compared by a one...

  1. Design and implementation of flexible TWDM-PON with PtP WDM overlay based on WSS for next-generation optical access networks

    Science.gov (United States)

    Wu, Bin; Yin, Hongxi; Qin, Jie; Liu, Chang; Liu, Anliang; Shao, Qi; Xu, Xiaoguang

    2016-09-01

    Aiming at the increasing demand of the diversification services and flexible bandwidth allocation of the future access networks, a flexible passive optical network (PON) scheme combining time and wavelength division multiplexing (TWDM) with point-to-point wavelength division multiplexing (PtP WDM) overlay is proposed for the next-generation optical access networks in this paper. A novel software-defined optical distribution network (ODN) structure is designed based on wavelength selective switches (WSS), which can implement wavelength and bandwidth dynamical allocations and suits for the bursty traffic. The experimental results reveal that the TWDM-PON can provide 40 Gb/s downstream and 10 Gb/s upstream data transmission, while the PtP WDM-PON can support 10 GHz point-to-point dedicated bandwidth as the overlay complement system. The wavelengths of the TWDM-PON and PtP WDM-PON are allocated dynamically based on WSS, which verifies the feasibility of the proposed structure.

  2. 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

  3. Effects of biaxial oscillatory shear stress on endothelial cell proliferation and morphology.

    Science.gov (United States)

    Chakraborty, Amlan; Chakraborty, Sutirtha; Jala, Venkatakrishna R; Haribabu, Bodduluri; Sharp, M Keith; Berson, R Eric

    2012-03-01

    Wall shear stress (WSS) on anchored cells affects their responses, including cell proliferation and morphology. In this study, the effects of the directionality of pulsatile WSS on endothelial cell proliferation and morphology were investigated for cells grown in a Petri dish orbiting on a shaker platform. Time and location dependent WSS was determined by computational fluid dynamics (CFD). At low orbital speed (50 rpm), WSS was shown to be uniform (0-1 dyne/cm(2)) across the bottom of the dish, while at higher orbital speed (100 and 150 rpm), WSS remained fairly uniform near the center and fluctuated significantly (0-9 dyne/cm(2)) near the side walls of the dish. Since WSS on the bottom of the dish is two-dimensional, a new directional oscillatory shear index (DOSI) was developed to quantify the directionality of oscillating shear. DOSI approached zero for biaxial oscillatory shear of equal magnitudes near the center and approached one for uniaxial pulsatile shear near the wall, where large tangential WSS dominated a much smaller radial component. Near the center (low DOSI), more, smaller and less elongated cells grew, whereas larger cells with greater elongation were observed in the more uniaxial oscillatory shear (high DOSI) near the periphery of the dish. Further, cells aligned with the direction of the largest component of shear but were randomly oriented in low magnitude biaxial shear. Statistical analyses of the individual and interacting effects of multiple factors (DOSI, shear magnitudes and orbital speeds) showed that DOSI significantly affected all the responses, indicating that directionality is an important determinant of cellular responses. Copyright © 2011 Wiley Periodicals, Inc.

  4. Relationship Between Endothelial Wall Shear Stress and High-Risk Atherosclerotic Plaque Characteristics for Identification of Coronary Lesions That Cause Ischemia: A Direct Comparison With Fractional Flow Reserve.

    Science.gov (United States)

    Han, Donghee; Starikov, Anna; Ó Hartaigh, Bríain; Gransar, Heidi; Kolli, Kranthi K; Lee, Ji Hyun; Rizvi, Asim; Baskaran, Lohendran; Schulman-Marcus, Joshua; Lin, Fay Y; Min, James K

    2016-12-19

    Wall shear stress (WSS) is an established predictor of coronary atherosclerosis progression. Prior studies have reported that high WSS has been associated with high-risk atherosclerotic plaque characteristics (APCs). WSS and APCs are quantifiable by coronary computed tomography angiography, but the relationship of coronary lesion ischemia-evaluated by fractional flow reserve-to WSS and APCs has not been examined. WSS measures were obtained from 100 evaluable patients who underwent coronary computed tomography angiography and invasive coronary angiography with fractional flow reserve. Patients were categorized according to tertiles of mean WSS values defined as low, intermediate, and high. Coronary ischemia was defined as fractional flow reserve ≤0.80. Stenosis severity was determined by minimal luminal diameter. APCs were defined as positive remodeling, low attenuation plaque, and spotty calcification. The likelihood of having positive remodeling and low-attenuation plaque was greater in the high WSS group compared with the low WSS group after adjusting for minimal luminal diameter (odds ratio for positive remodeling: 2.54, 95% CI 1.12-5.77; odds ratio for low-attenuation plaque: 2.68, 95% CI 1.02-7.06; both Prelationship was observed between WSS and fractional flow reserve when adjusting for either minimal luminal diameter or APCs. WSS displayed no incremental benefit above stenosis severity and APCs for detecting lesions that caused ischemia (area under the curve for stenosis and APCs: 0.87, 95% CI 0.81-0.93; area under the curve for stenosis, APCs, and WSS: 0.88, 95% CI 0.82-0.93; P=0.30 for difference). High WSS is associated with APCs independent of stenosis severity. WSS provided no added value beyond stenosis severity and APCs for detecting lesions with significant ischemia. © 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  5. Influence of the Accuracy of Angiography-Based Reconstructions on Velocity and Wall Shear Stress Computations in Coronary Bifurcations: A Phantom Study

    Science.gov (United States)

    Schrauwen, Jelle T. C.; Karanasos, Antonios; van Ditzhuijzen, Nienke S.; Aben, Jean-Paul; van der Steen, Antonius F. W.

    2015-01-01

    Introduction Wall shear stress (WSS) plays a key role in the onset and progression of atherosclerosis in human coronary arteries. Especially sites with low and oscillating WSS near bifurcations have a higher propensity to develop atherosclerosis. WSS computations in coronary bifurcations can be performed in angiography-based 3D reconstructions. It is essential to evaluate how reconstruction errors influence WSS computations in mildly-diseased coronary bifurcations. In mildly-diseased lesions WSS could potentially provide more insight in plaque progression. Materials Methods Four Plexiglas phantom models of coronary bifurcations were imaged with bi-plane angiography. The lumens were segmented by two clinically experienced readers. Based on the segmentations 3D models were generated. This resulted in three models per phantom: one gold-standard from the phantom model itself, and one from each reader. Steady-state and transient simulations were performed with computational fluid dynamics to compute the WSS. A similarity index and a noninferiority test were used to compare the WSS in the phantoms and their reconstructions. The margin for this test was based on the resolution constraints of angiography. Results The reconstruction errors were similar to previously reported data; in seven out of eight reconstructions less than 0.10 mm. WSS in the regions proximal and far distal of the stenosis showed a good agreement. However, the low WSS areas directly distal of the stenosis showed some disagreement between the phantoms and the readers. This was due to small deviations in the reconstruction of the stenosis that caused differences in the resulting jet, and consequently the size and location of the low WSS area. Discussion This study showed that WSS can accurately be computed within angiography-based 3D reconstructions of coronary arteries with early stage atherosclerosis. Qualitatively, there was a good agreement between the phantoms and the readers. Quantitatively, the

  6. Influence of the Accuracy of Angiography-Based Reconstructions on Velocity and Wall Shear Stress Computations in Coronary Bifurcations: A Phantom Study.

    Directory of Open Access Journals (Sweden)

    Jelle T C Schrauwen

    Full Text Available Wall shear stress (WSS plays a key role in the onset and progression of atherosclerosis in human coronary arteries. Especially sites with low and oscillating WSS near bifurcations have a higher propensity to develop atherosclerosis. WSS computations in coronary bifurcations can be performed in angiography-based 3D reconstructions. It is essential to evaluate how reconstruction errors influence WSS computations in mildly-diseased coronary bifurcations. In mildly-diseased lesions WSS could potentially provide more insight in plaque progression.Four Plexiglas phantom models of coronary bifurcations were imaged with bi-plane angiography. The lumens were segmented by two clinically experienced readers. Based on the segmentations 3D models were generated. This resulted in three models per phantom: one gold-standard from the phantom model itself, and one from each reader. Steady-state and transient simulations were performed with computational fluid dynamics to compute the WSS. A similarity index and a noninferiority test were used to compare the WSS in the phantoms and their reconstructions. The margin for this test was based on the resolution constraints of angiography.The reconstruction errors were similar to previously reported data; in seven out of eight reconstructions less than 0.10 mm. WSS in the regions proximal and far distal of the stenosis showed a good agreement. However, the low WSS areas directly distal of the stenosis showed some disagreement between the phantoms and the readers. This was due to small deviations in the reconstruction of the stenosis that caused differences in the resulting jet, and consequently the size and location of the low WSS area.This study showed that WSS can accurately be computed within angiography-based 3D reconstructions of coronary arteries with early stage atherosclerosis. Qualitatively, there was a good agreement between the phantoms and the readers. Quantitatively, the low WSS regions directly distal to

  7. Impact of competitive flow on wall shear stress in coronary surgery: computational fluid dynamics of a LIMA-LAD model.

    Science.gov (United States)

    Nordgaard, Håvard; Swillens, Abigail; Nordhaug, Dag; Kirkeby-Garstad, Idar; Van Loo, Denis; Vitale, Nicola; Segers, Patrick; Haaverstad, Rune; Lovstakken, Lasse

    2010-12-01

    Competitive flow from native coronary vessels is considered a major factor in the failure of coronary bypass grafts. However, the pathophysiological effects are not fully understood. Low and oscillatory wall shear stress (WSS) is known to induce endothelial dysfunction and vascular disease, like atherosclerosis and intimal hyperplasia. The aim was to investigate the impact of competitive flow on WSS in mammary artery bypass grafts. Using computational fluid dynamics, WSS was calculated in a left internal mammary artery (LIMA) graft to the left anterior descending artery in a three-dimensional in vivo porcine coronary artery bypass graft model. The following conditions were investigated: high competitive flow (non-significant coronary lesion), partial competitive flow (significant coronary lesion), and no competitive flow (totally occluded coronary vessel). Time-averaged WSS of LIMA at high, partial, and no competitive flow were 0.3-0.6, 0.6-3.0, and 0.9-3.0 Pa, respectively. Further, oscillatory WSS quantified as the oscillatory shear index (OSI) ranged from (maximum OSI = 0.5 equals zero net WSS) 0.15 to 0.35, OSI similar to the no competitive flow condition. Graft flow is highly dependent on the degree of competitive flow. High competitive flow was found to produce unfavourable WSS consistent with endothelial dysfunction and subsequent graft narrowing and failure. Partial competitive flow, however, may be better tolerated as it was found to be similar to the ideal condition of no competitive flow.

  8. Notch1 and 4 Signaling Responds to an Increasing Vascular Wall Shear Stress in a Rat Model of Arteriovenous Malformations

    Directory of Open Access Journals (Sweden)

    Jian Tu

    2014-01-01

    Full Text Available Notch signaling is suggested to promote the development and maintenance of cerebral arteriovenous malformations (AVMs, and an increasing wall shear stress (WSS contributes to AVM rupture. Little is known about whether WSS impacts Notch signaling, which is important for understanding the angiogenesis of AVMs. WSS was measured in arteriovenous fistulas (AVF surgically created in 96 rats at different time points over a period of 84 days. The expression of Notch receptors 1 and 4 and their ligands, Delta1 and 4, Jagged1, and Notch downstream gene target Hes1 was quantified in “nidus” vessels. The interaction events between Notch receptors and their ligands were quantified using proximity ligation assay. There was a positive correlation between WSS and time (r=0.97; P<0.001. The expression of Notch receptors and their ligands was upregulated following AVF formation. There was a positive correlation between time and the number of interactions between Notch receptors and their ligands aftre AVF formation (r=0.62, P<0.05 and a positive correlation between WSS and the number of interactions between Notch receptors and their ligands (r=0.87, P<0.005. In conclusion, an increasing WSS may contribute to the angiogenesis of AVMs by activation of Notch signaling.

  9. The values of wall shear stress, turbulence kinetic energy and blood pressure gradient are associated with atherosclerotic plaque erosion in rabbits.

    Science.gov (United States)

    Sameshima, Naoki; Yamashita, Atsushi; Sato, Shinya; Matsuda, Shuntaro; Matsuura, Yunosuke; Asada, Yujiro

    2014-01-01

    To clarify the contribution of hemodynamic factors to the onset of plaque erosion in smooth muscle cell (SMC)-rich atherosclerotic plaque. We developed a rabbit model of SMC-rich atherosclerotic plaque with various degree of stenosis induced by incomplete ligation and generated three-dimensional models of five rabbit femoral arteries based on 130-162 serial histological cross-sections at 100-μm intervals per artery. We performed a computational blood flow simulation using the Reynolds-averaged Navier-Stokes model and calculated the wall shear stress (WSS), turbulence kinetic energy (TKE), blood pressure (BP) and blood pressure gradients (BPG) in eight sections (the inlet, the stenotic portion and areas 1, 2 and 5mm from the stenotic portion) in each rabbit. We also investigated whether the magnitude of WSS or TKE was related to the presence or absence of erosive injury by evaluating six points (the locally highest, median and lowest of WSS or TKE) in each section. The magnitudes of WSS, TKE and BPG, but not BP, correlated significantly with the extent of histologically-defined plaque erosion (WSS, r=0.55, p<0.001; TKE, r=0.53, p<0.001; BPG, r=0.61, p<0.0001, n=40). The values for WSS and TKE were significantly larger at sites with, compared to without, erosive injury (n=107 and n=119 points, respectively; both p<0.0001). These results suggest that increased values of WSS, TKE and BPG considerably contribute to the onset of plaque erosion.

  10. Echo Particle Image Velocimetry for Estimation of Carotid Artery Wall Shear Stress: Repeatability, Reproducibility and Comparison with Phase-Contrast Magnetic Resonance Imaging.

    Science.gov (United States)

    Gurung, Arati; Gates, Phillip E; Mazzaro, Luciano; Fulford, Jonathan; Zhang, Fuxing; Barker, Alex J; Hertzberg, Jean; Aizawa, Kunihiko; Strain, William D; Elyas, Salim; Shore, Angela C; Shandas, Robin

    2017-08-01

    Measurement of hemodynamic wall shear stress (WSS) is important in investigating the role of WSS in the initiation and progression of atherosclerosis. Echo particle image velocimetry (echo PIV) is a novel ultrasound-based technique for measuring WSS in vivo that has previously been validated in vitro using the standard optical PIV technique. We evaluated the repeatability and reproducibility of echo PIV for measuring WSS in the human common carotid artery. We measured WSS in 28 healthy participants (18 males and 10 females, mean age: 56 ± 12 y). Echo PIV was highly repeatable, with an intra-observer variability of 1.0 ± 0.1 dyn/cm 2 for peak systolic (maximum), 0.9 dyn/cm 2 for mean and 0.5 dyn/cm 2 for end-diastolic (minimum) WSS measurements. Likewise, echo PIV was reproducible, with a low inter-observer variability (max: 2.0 ± 0.2 dyn/cm 2 , mean: 1.3 ± 0.1 dyn/cm 2 , end-diastolic: 0.7 dyn/cm 2 ) and more variable inter-scan (test-retest) variability (max: 7.1 ± 2.3 dyn/cm 2 , mean: 2.9 ± 0.4 dyn/cm 2 , min: 1.5 ± 0.1 dyn/cm 2 ). We compared echo PIV with the reference method, phase-contrast magnetic resonance imaging (PC-MRI); echo PIV-based WSS measurements agreed qualitatively with PC-MRI measurements (r = 0.89, p PIV vs. PC-MRI): WSS at peak systole: 21 ± 7.0 dyn/cm 2 vs. 15 ± 5.0 dyn/cm 2 ; time-averaged WSS: 8.9 ± 3.0 dyn/cm 2 vs. 7.1 ± 3.0 dyn/cm 2 (p  0.05). For the first time, we report that echo PIV can measure WSS with good repeatability and reproducibility in adult humans with a broad age range. Echo PIV is feasible in humans and offers an easy-to-use, ultrasound-based, quantitative technique for measuring WSS in vivo in humans with good repeatability and reproducibility. Copyright © 2017. Published by Elsevier Inc.

  11. Electric foot shock stress adaptation: Does it exist or not?

    Science.gov (United States)

    Bali, Anjana; Jaggi, Amteshwar Singh

    2015-06-01

    Stress adaptation is a protective phenomenon against repeated stress exposure and is characterized by a decreased responsiveness to a repeated stress stimulus. The adaptation is associated with a complex cascade of events, including the changes in behavior, neurotransmitter and gene expression levels. The non-adaptation or maladaptation to stress may underlie the affective disorders, such as anxiety, depression and post-traumatic stress disorder (PTSD). Electric foot shock is a complex stressor, which includes both physical and emotional components. Unlike immobilization, restraint and cold immersion stress, the phenomenon of stress adaptation is not very well defined in response to electric foot shock. A number of preclinical studies have reported the development of adaptation to electric foot shock stress. However, evidence also reveals the non-adaptive behavior in response to foot shocks. The distinct adaptive/non-adaptive responses may be possibly influenced by the type, intensity, and duration of the stress. The present review discusses the existence or non-existence of adaptation to electric foot shock stress along with possible mechanism. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Flow and wall shear stress characterization after endovascular aneurysm repair and endovascular aneurysm sealing in an infrarenal aneurysm model.

    Science.gov (United States)

    Boersen, Johannes T; Groot Jebbink, Erik; Versluis, Michel; Slump, Cornelis H; Ku, David N; de Vries, Jean-Paul P M; Reijnen, Michel M P J

    2017-12-01

    Endovascular aneurysm repair (EVAR) with a modular endograft has become the preferred treatment for abdominal aortic aneurysms. A novel concept is endovascular aneurysm sealing (EVAS), consisting of dual endoframes surrounded by polymer-filled endobags. This dual-lumen configuration is different from a bifurcation with a tapered trajectory of the flow lumen into the two limbs and may induce unfavorable flow conditions. These include low and oscillatory wall shear stress (WSS), linked to atherosclerosis, and high shear rates that may result in thrombosis. An in vitro study was performed to assess the impact of EVAR and EVAS on flow patterns and WSS. Four abdominal aortic aneurysm phantoms were constructed, including three stented models, to study the influence of the flow divider on flow (Endurant [Medtronic, Minneapolis, Minn], AFX [Endologix, Irvine, Calif], and Nellix [Endologix]). Experimental models were tested under physiologic resting conditions, and flow was visualized with laser particle imaging velocimetry, quantified by shear rate, WSS, and oscillatory shear index (OSI) in the suprarenal aorta, renal artery (RA), and common iliac artery. WSS and OSI were comparable for all models in the suprarenal aorta. The RA flow profile in the EVAR models was comparable to the control, but a region of lower WSS was observed on the caudal wall compared with the control. The EVAS model showed a stronger jet flow with a higher shear rate in some regions compared with the other models. Small regions of low WSS and high OSI were found near the distal end of all stents in the common iliac artery compared with the control. Maximum shear rates in each region of interest were well below the pathologic threshold for acute thrombosis. The different stent designs do not influence suprarenal flow. Lower WSS is observed in the caudal wall of the RA after EVAR and a higher shear rate after EVAS. All stented models have a small region of low WSS and high OSI near the distal outflow

  13. PEG-albumin plasma expansion increases expression of MCP-1 evidencing increased circulatory wall shear stress: an experimental study.

    Directory of Open Access Journals (Sweden)

    C Makena Hightower

    Full Text Available Treatment of blood loss with plasma expanders lowers blood viscosity, increasing cardiac output. However, increased flow velocity by conventional plasma expanders does not compensate for decreased viscosity in maintaining vessel wall shear stress (WSS, decreasing endothelial nitric oxide (NO production. A new type of plasma expander using polyethylene glycol conjugate albumin (PEG-Alb causes supra-perfusion when used in extreme hemodilution and is effective in treating hemorrhagic shock, although it is minimally viscogenic. An acute 40% hemodilution/exchange-transfusion protocol was used to compare 4% PEG-Alb to Ringer's lactate, Dextran 70 kDa and 6% Hetastarch (670 kDa in unanesthetized CD-1 mice. Serum cytokine analysis showed that PEG-Alb elevates monocyte chemotactic protein-1 (MCP-1, a member of a small inducible gene family, as well as expression of MIP-1α, and MIP-2. MCP-1 is specific to increased WSS. Given the direct link between increased WSS and production of NO, the beneficial resuscitation effects due to PEG-Alb plasma expansion appear to be due to increased WSS through increased perfusion and blood flow rather than blood viscosity.

  14. 南中国斑节对虾养殖中控制白斑综合症病的理论和策略%Theory and Strategies for Controlling White Spot Syndrome (WSS) of Cultured Penaeus monodon in South China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@ White spot syndrome virus (WSSV) is the causative agent of white spot syndrome (WSS) of cultured penaeid shrimps. WSS breaks out and prevails in cultured penaeid shrimps in many countries and regions of the world, especially in southeast Asia. WSSV is the virus most severe damaging to the cultured penaeid shrimps in the world. At the present time, the control of the outbreaks of WSSV will recover and develop the penaeid shrimp cultures in China and even in the world.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-04-15

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

  16. In vitro shear stress measurements using particle image velocimetry in a family of carotid artery models: effect of stenosis severity, plaque eccentricity, and ulceration.

    Directory of Open Access Journals (Sweden)

    Sarah Kefayati

    Full Text Available Atherosclerotic disease, and the subsequent complications of thrombosis and plaque rupture, has been associated with local shear stress. In the diseased carotid artery, local variations in shear stress are induced by various geometrical features of the stenotic plaque. Greater stenosis severity, plaque eccentricity (symmetry and plaque ulceration have been associated with increased risk of cerebrovascular events based on clinical trial studies. Using particle image velocimetry, the levels and patterns of shear stress (derived from both laminar and turbulent phases were studied for a family of eight matched-geometry models incorporating independently varied plaque features - i.e. stenosis severity up to 70%, one of two forms of plaque eccentricity, and the presence of plaque ulceration. The level of laminar (ensemble-averaged shear stress increased with increasing stenosis severity resulting in 2-16 Pa for free shear stress (FSS and approximately double (4-36 Pa for wall shear stress (WSS. Independent of stenosis severity, marked differences were found in the distribution and extent of shear stress between the concentric and eccentric plaque formations. The maximum WSS, found at the apex of the stenosis, decayed significantly steeper along the outer wall of an eccentric model compared to the concentric counterpart, with a 70% eccentric stenosis having 249% steeper decay coinciding with the large outer-wall recirculation zone. The presence of ulceration (in a 50% eccentric plaque resulted in both elevated FSS and WSS levels that were sustained longer (∼20 ms through the systolic phase compared to the non-ulcerated counterpart model, among other notable differences. Reynolds (turbulent shear stress, elevated around the point of distal jet detachment, became prominent during the systolic deceleration phase and was widely distributed over the large recirculation zone in the eccentric stenoses.

  17. Development of a system for measuring wall shear stress in blood vessels using magnetic resonance imaging and computational fluid dynamics

    International Nuclear Information System (INIS)

    Yoshida, Keita; Nagao, Taisuke; Okada, Kouji; Miyazaki, Shohei; Yang, Xiaomei; Yamazaki, Youichi; Murase, Kenya

    2008-01-01

    We developed a system for measuring the wall shear stress (WSS) in blood vessels using magnetic resonance imaging (MRI) and computational fluid dynamics (CFD). The time-dependent velocity at the center of the blood vessel was measured by phase-contrast MRI and was approximated by finite Fourier series, which was used for generating the velocity profile at the inlet for the boundary condition to the CFD method. To validate the CFD method, we compared the WSS obtained by the CFD method with the theoretical value in a straight cylinder with various radii for both steady and pulsatile flows. We also investigated the dependence of the WSS on the inlet velocity profile incorporated into the CFD method. For steady flow, there was a good agreement between the WSS obtained by the CFD method and the theoretical value. For pulsatile flow, there was a relatively good agreement between them when the radius of the cylinder was 2.5 mm and the inlet velocity profile was given by the Womersley solution for fully developed pulsatile flow in a straight circular cylinder. When the radius of the cylinder was 5 mm and/or the inlet velocity profile was assumed to be parabolic, large differences were observed between them, suggesting that the assumption of fully developed flow does not hold true in these cases. In human studies, the vortex due to the secondary blood flow in the carotid arterial sinus was clearly observed. The WSS in the bifurcation was the highest, while that in the carotid arterial sinus was the smallest. In conclusion, the system presented here appears to be useful for measuring the WSS in blood vessels and for analyzing the cause and/or extent of atherosclerosis, and our results suggest that the inlet velocity profile should be carefully considered. (author)

  18. Scan-rescan reproducibility of segmental aortic wall shear stress as assessed by phase-specific segmentation with 4D flow MRI in healthy volunteers.

    Science.gov (United States)

    van der Palen, Roel L F; Roest, Arno A W; van den Boogaard, Pieter J; de Roos, Albert; Blom, Nico A; Westenberg, Jos J M

    2018-05-26

    The aim was to investigate scan-rescan reproducibility and observer variability of segmental aortic 3D systolic wall shear stress (WSS) by phase-specific segmentation with 4D flow MRI in healthy volunteers. Ten healthy volunteers (age 26.5 ± 2.6 years) underwent aortic 4D flow MRI twice. Maximum 3D systolic WSS (WSSmax) and mean 3D systolic WSS (WSSmean) for five thoracic aortic segments over five systolic cardiac phases by phase-specific segmentations were calculated. Scan-rescan analysis and observer reproducibility analysis were performed. Scan-rescan data showed overall good reproducibility for WSSmean (coefficient of variation, COV 10-15%) with moderate-to-strong intraclass correlation coefficient (ICC 0.63-0.89). The variability in WSSmax was high (COV 16-31%) with moderate-to-good ICC (0.55-0.79) for different aortic segments. Intra- and interobserver reproducibility was good-to-excellent for regional aortic WSSmax (ICC ≥ 0.78; COV ≤ 17%) and strong-to-excellent for WSSmean (ICC ≥ 0.86; COV ≤ 11%). In general, ascending aortic segments showed more WSSmax/WSSmean variability compared to aortic arch or descending aortic segments for scan-rescan, intraobserver and interobserver comparison. Scan-rescan reproducibility was good for WSSmean and moderate for WSSmax for all thoracic aortic segments over multiple systolic phases in healthy volunteers. Intra/interobserver reproducibility for segmental WSS assessment was good-to-excellent. Variability of WSSmax is higher and should be taken into account in case of individual follow-up or in comparative rest-stress studies to avoid misinterpretation.

  19. Characterizing saccular aortic arch aneurysms from the geometry-flow dynamics relationship.

    Science.gov (United States)

    Natsume, Kayoko; Shiiya, Norihiko; Takehara, Yasuo; Sugiyama, Masataka; Satoh, Hiroshi; Yamashita, Katsushi; Washiyama, Naoki

    2017-06-01

    Low wall shear stress (WSS) has been reported to be associated with accelerated atherosclerosis, aneurysm growth, or rupture. We evaluated the geometry of aortic arch aneurysms and their relationship with WSS by using the 4-dimensional flow magnetic resonance imaging to better characterize the saccular aneurysms. We analyzed the geometry in 100 patients using multiplanar reconstruction of computed tomography. We evaluated WSS and vortex flow using 4-dimensional flow magnetic resonance imaging in 16 of them, which were compared with 8 age-matched control subjects and eight healthy young volunteers. Eighty-two patients had a saccular aneurysm, and 18 had a fusiform aneurysm. External diameter/aneurysm length ratio and sac depth/neck width ratio of the fusiform aneurysms were constant at 0.76 ± 0.18 and 0.23 ± 0.09, whereas those of saccular aneurysms, especially those involving the outer curvature, were higher and more variable. Vortex flow was always present in the aneurysms, resulting in low WSS. When the sac depth/neck width ratio was less than 0.8, peak WSS correlated inversely with luminal diameter even in the saccular aneurysms. When this ratio exceeded 0.8, which was the case only with the saccular aneurysms, such correlation no longer existed and WSS was invariably low. Fusiform aneurysms elongate as they dilate, and WSS is lower as the diameter is larger. Saccular aneurysms dilate without proportionate elongation, and they, especially those occupying the inner curvature, have higher and variable sac depth/neck width ratio. When this ratio exceeds 0.8, WSS is low regardless of diameter, which may explain their malignant clinical behavior. Copyright © 2016 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

  20. Computational and experimental assessment of influences of hemodynamic shear stress on carotid plaque.

    Science.gov (United States)

    Zhou, Hui; Meng, Long; Zhou, Wei; Xin, Lin; Xia, Xiangxiang; Li, Shuai; Zheng, Hairong; Niu, Lili

    2017-07-29

    Studies have identified hemodynamic shear stress as an important determinant of endothelial function and atherosclerosis. In this study, we assess the influences of hemodynamic shear stress on carotid plaques. Carotid stenosis phantoms with three severity (30, 50, 70%) were made from 10% polyvinyl alcohol (PVA) cryogel. The phantoms were placed in a pulsatile flow loop with the same systolic/diastolic phase (35/65) and inlet flow rate (16 L/h). Ultrasonic particle imaging velocimetry (Echo PIV) and computational fluid dynamics (CFD) were used to calculate the velocity profile and shear stress distribution in the carotid stenosis phantoms. Inlet/outlet boundary conditions used in CFD were extracted from Echo PIV experiments to make sure that the results were comparable. Echo PIV and CFD results showed that velocity was largest in 70% than those in 30 and 50% at peak systole. Echo PIV results indicated that shear stress was larger in the upper wall and the surface of plaque than in the center of vessel. CFD results demonstrated that wall shear stress in the upstream was larger than in downstream of plaque. There was no significant difference in average velocity obtained by CFD and Echo PIV in 30% (p = 0.25). Velocities measured by CFD in 50% (93.01 cm/s) and in 70% (115.07 cm/s) were larger than those by Echo PIV in 50% (60.26 ± 5.36 cm/s) and in 70% (89.11 ± 7.21 cm/s). The results suggested that Echo PIV and CFD could obtain hemodynamic shear stress on carotid plaques. Higher WSS occurred in narrower arteries, and the shoulder of plaque bore higher WSS than in bottom part.

  1. Wall Shear Stress Restoration in Dialysis Patient's Venous Stenosis: Elucidation via 3D CFD and Shape Optimization

    Science.gov (United States)

    Mahmoudzadeh Akherat, S. M. Javid; Cassel, Kevin; Hammes, Mary; Boghosian, Michael; Illinois Institute of Technology Team; University of Chicago Team

    2016-11-01

    Venous stenosis developed after the growth of excessive neointimal hyperplasia (NH) in chronic dialysis treatment is a major cause of mortality in renal failure patients. It has been hypothesized that the low wall shear stress (WSS) triggers an adaptive response in patients' venous system that through the growth of neointimal hyperplastic lesions restores WSS and transmural pressure, which also regulates the blood flow rate back to physiologically acceptable values which is violated by dialysis treatment. A strong coupling of three-dimensional CFD and shape optimization analyses were exploited to elucidate and forecast this adaptive response which correlates very well topographically with patient-specific clinical data. Based on the framework developed, a medical protocol is suggested to predict and prevent dialysis treatment failure in clinical practice. Supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health (R01 DK90769).

  2. Hemodynamic comparison of stent configurations used for aortoiliac occlusive disease.

    Science.gov (United States)

    Groot Jebbink, Erik; Mathai, Varghese; Boersen, Johannes T; Sun, Chao; Slump, Cornelis H; Goverde, Peter C J M; Versluis, Michel; Reijnen, Michel M P J

    2017-07-01

    Endovascular treatment of aortoiliac occlusive disease entails the use of multiple stents to reconstruct the aortic bifurcation. Different configurations have been applied and geometric variations exist, as quantified in previous work. Other studies concluded that specific stent geometry seems to affect patency. These variations may affect local flow patterns, resulting in different wall shear stress (WSS) and oscillating shear index (OSI). The aim of this study was to compare the effect of different stent configurations on flow perturbations (recirculation and fluid stasis), WSS, and OSI in an in vitro setup. Three different stent configurations were deployed in transparent silicone models: bare-metal kissing (BMK) stents, covered kissing (CK) stents, and the covered endovascular reconstruction of the aortic bifurcation (CERAB) configuration. Transparent covered stents were created with polyurethane to enable visualization. Models were placed in a circulation setup under physiologic flow conditions. Time-resolved laser particle image velocimetry techniques were used to quantify the flow, and WSS and OSI were calculated. The BMK configuration did not show flow disturbances at the inflow section, and WSS values were similar to the control. An area of persistent low flow was observed throughout the cardiac cycle in the area between the anatomic bifurcation and neobifurcation. The CK model showed recirculation zones near the inflow area of the stents with a resulting low average WSS value and high OSI. The proximal inflow of the CERAB configuration did not show flow disturbances, and WSS values were comparable to control. Near the inflow of the limbs, a minor zone of recirculation was observed without changes in WSS values. Flow, WSS, and OSI on the lateral wall of the proximal iliac artery were undisturbed in all models. The studied aortoiliac stent configurations have distinct locations where flow disturbances occur, and these are related to the radial mismatch

  3. 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

  4. Heat induced fracturing of rock in an existing uniaxial stress field

    International Nuclear Information System (INIS)

    Mathis, J.; Stephansson, O.; Bjarnason, B.; Hakami, H.; Herdocia, A.; Mattila, U.; Singh, U.

    1986-01-01

    This study was initiated under the premise that it may be possible to determine the state of stress in the earth's crust by heat induced fracturing of the rock surrounding a borehole. The theory involved is superficially simple, involving the superposition of the stress field around a borehole due to the existing virgin stresses and the uniform stress field of thermally loaded rock as induced by a heater. Since the heat stress field is uniform, varying only in magnitude and gradient as a function of heater input, fracturing should be controlled by the non-uniform virgin stress field. To determine if the method was, in fact, feasible, a series of laboratory test were conducted. These tests consisted of physically loading center drilled cubes of rock, 0.3 m on a side, uniaxially from 0 to 25 MPa. The blocks were then thermally loaded with a nominally rated 3.7 kW heater until failure occurred. Results from these laboratory tests were then compared to analytical studies of the problem, i.e., finite element and discrete theoretical analysis. Overall, results were such that the method is likely eliminated as a stress measurement technique. The immediate development of a thermal compressive zone on the borehole wall overlaps the tensile zone created by the uniaxial stress field, forcing the failure is thus controlled largely by the power input of the heater, being retarded by the small compressive stresses genrated by the uniaxial stress field. This small retardation effect is of such low magnitude that the retardation effect is of such low magnitude that the fracture time is relatively insensitive to the local virgin stress field. (authors)

  5. Age-related changes in aortic 3D blood flow velocities and wall shear stress: Implications for the identification of altered hemodynamics in patients with aortic valve disease

    NARCIS (Netherlands)

    van Ooij, Pim; Garcia, Julio; Potters, Wouter V.; Malaisrie, S. Chris; Collins, Jeremy D.; Carr, James C.; Markl, Michael; Barker, Alex J.

    2016-01-01

    To investigate age-related changes in peak systolic aortic 3D velocity and wall shear stress (WSS) in healthy controls and to investigate the importance of age-matching for 3D mapping of abnormal aortic hemodynamics in bicuspid aortic valve disease (BAV). 4D flow MRI (fields strengths = 1.5-3T;

  6. Conceptual model for concessioning in the Water Supply and Sanitation sector in Bulgaria

    OpenAIRE

    Todor Raychev

    2018-01-01

    The purpose of this article is to create a new conceptual model for sustainable development of the water sector in Bulgaria on the basis of concessions by statistical regions according to the NUTS-2 classification of the European Union. The essence of the proposed model includes an approach for consolidating the existing 66 WSS operators in three WSS operators – concessionaires. The approach is applied to provide WSS services for drinking and household needs of the population. WSS services fo...

  7. Analysis of blood flow dynamics in the abdominal aorta based on MR images

    International Nuclear Information System (INIS)

    Shimamura, Koumei; Tsubota, Kenichi; Ryu, Hiroshi; Sugimoto, Koichi; Haneishi, Hideaki

    2010-01-01

    Images of the abdominal aorta including peri-renal artery by PCMRA (phase contrast magnetic resonance angiography) were analyzed to calculate WSS (wall shear stress) and its OSI (oscillatory shear index) in order to visually elucidate the cause of aneurysm formation. PCMRA was conducted for acquisitions of vascular morphology in one cardiac cycle of a healthy male 30s with cardiac gating, and of blood flow rates from 3 directions. Images were median-filtered to reduce noises and regions of interest of rectangular parallelepiped were defined to involve the aorta. WSS, the parameter representing the intensity of friction stress to the vessel wall of blood flow, and OSI, the degree of oscillatory WSS change, were calculated firstly by the reported Snake model for the vessel morphology and then by applying its local information to blood flow rate information from 3 directions. Color-displayed images revealed that both WSS and OS were high at the highest incidental region of aortic aneurysm formation around the peri-renal artery. The finding was in good agreement with the result of computed bio-dynamic simulation that the strong WSS by elevated swirling of blood flow is generated at the region. Thus WSS and OS can be significant factors of aneurismal formation, which should be further confirmed from aspects of increased case number and precision. (T.T.)

  8. Validação da escala de estresse no trabalho Validation of the work stress scale

    Directory of Open Access Journals (Sweden)

    Tatiane Paschoal

    2004-04-01

    Full Text Available Este trabalho teve como objetivo construir e validar um instrumento de estresse ocupacional geral, de fácil aplicação e que pudesse ser utilizado em diversos ambientes de trabalho e para ocupações variadas. A Escala de Estresse no Trabalho (EET, inicialmente composta por 31 itens, foi aplicada a 437 trabalhadores de diferentes organizações, públicas e privadas, sendo 249 homens e 188 mulheres. A análise fatorial revelou a existência de um único fator que, após eliminação de itens com carga fatorial abaixo de 0,45, ficou composto por 23 itens e obteve um coeficiente alfa de Cronbach equivalente a 0,91. Uma versão reduzida da escala, com 13 itens e alfa de 0,85 foi proposta. Com base nos parâmetros psicométricos satisfatórios da EET, conclui-se que esta é uma alternativa para investigações empíricas e trabalhos aplicados em organizações, podendo orientar medidas que visem à qualidade de vida dos trabalhadores.The objective of this study was to develop and to validate a general instrument to evaluate occupational stress, easily administered, used in different work environments and for a variety of occupations. The Work Stress Scale (WSS initially composed of 31 items was applied to 437 workers, 249 men and 188 women, of public and private organizations. The factor analysis detected only one factor. After the elimination of the items with a factor loading below .45, the final version of the scale was composed of 23 items and had a Cronbach's coefficient of .91. A reduced version of the scale with 13 items and a Cronbach's coefficient of .85 has been proposed. Based on the satisfactory psychometric parameters of the scale, it is concluded that the WSS is useful as an alternative in empirical investigations and organizational diagnostics. The results obtained can be useful indicators for organizational decisions in relation to the life quality of the workers.

  9. Effect of tip clearance on wall shear stress of an axial LVAD

    Science.gov (United States)

    Sarath, S.; Vikas, R.

    2017-09-01

    Wall shear stress is a crucial parameter used for blood damage analysis, and typically a value of 400 Pa is set as a limit. Tip clearance is a major factor contributing to hemolysis and pump efficiency. In this study, different tip gap configurations are used to analyse the wall shear stress developed on the blade surface of a constant thickness blade design, and a varying thickness blade design using CFD analysis. It was found that, for a particular geometry, as the clearance gap reduces, flow rate over the high wall shear stress area decreases even though the high wall shear stress span is found to extend. For each design, the optimum clearance gap is iteratively attained, keeping the maximum WSS as a limiting factor. Thus a better pump designs is obtained, whose leakage flow patterns are lower than that of the initial design, hence also leading to higher pump efficiency.

  10. Osteomalacia and coxa vara. An unusual co-existence for femoral neck stress fracture

    Directory of Open Access Journals (Sweden)

    Kerim Sariyilmaz

    2015-01-01

    Conclusion: Joint and bone pain without any trauma should be investigated and bone metabolism disorders should be kept in mind. There might be co-existing factors related with stress fractures, and they must be treated simultaneously.

  11. PIV-validated numerical modeling of pulsatile flows in distal coronary end-to-side anastomoses.

    Science.gov (United States)

    Xiong, F L; Chong, C K

    2007-01-01

    This study employed particle image velocimetry (PIV) to validate a numerical model in a complementary approach to quantify hemodynamic factors in distal coronary anastomoses and to gain more insights on their relationship with anastomotic geometry. Instantaneous flow fields and wall shear stresses (WSS) were obtained from PIV measurement in a modified life-size silastic anastomosis model adapted from a conventional geometry by incorporating a smooth graft-artery transition. The results were compared with those predicted by a concurrent numerical model. The numerical method was then used to calculate cycle-averaged WSS (WSS(cyc)) and spatial wall shear stress gradient (SWSSG), two critical hemodynamic factors in the pathogenesis of intimal thickening (IT), to compare the conventional and modified geometries. Excellent qualitative agreement and satisfactory quantitative agreement with averaged normalized error in WSS between 0.8% and 8.9% were achieved between the PIV experiment and numerical model. Compared to the conventional geometry, the modified geometry produces a more uniform WSS(cyc) distribution eliminating both high and low WSS(cyc) around the toe, critical in avoiding IT. Peak SWSSG on the artery floor of the modified model is less than one-half that in the conventional case, and high SWSSG at the toe is eliminated. The validated numerical model is useful for modeling unsteady coronary anastomotic flows and elucidating the significance of geometry regulated hemodynamics. The results suggest the clinical relevance of constructing smooth graft-artery transition in distal coronary anastomoses to improve their hemodynamic performance.

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

    Science.gov (United States)

    Saho, Tatsunori; Onishi, Hideo

    2016-07-01

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

  13. The mutual influence of krypton implantation and pre-existing stress states in polycrystalline alpha titanium

    Energy Technology Data Exchange (ETDEWEB)

    Nsengiyumva, S. [Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa); Department of Physics, Kigali Institute of Education, P.O. Box 5039 Kigali (Rwanda)], E-mail: schadrack.nsengiyumva@uct.ac.za; Ntsoane, T.P. [Nuclear Energy Corporation of South Africa (NECSA), P.O. Box 582 (South Africa); Raji, A.T. [Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa); Topic, M. [iThemba LABS, Somerset West 7129 (South Africa); Kellermann, G. [Laboratorio Nacional de Luz Sincrotron (LNLS), Campinas (Brazil); Riviere, J.P. [Laboratoire de Physique des Materiaux UMR6630-CNRS, 86960 (France); Britton, D.T.; Haerting, M. [Department of Physics, University of Cape Town, Rondebosch 7701 (South Africa)

    2009-08-15

    The stress profile in polycrystalline titanium implanted with krypton ions at different fluences has been determined using synchrotron radiation diffraction. For each fluence, the krypton profile has been measured using Rutherford backscattering geometry. The results were compared to model calculations obtained from the SRIM 2008 computer code. A strong stress relaxation was found for high fluence implantation, whereas for low fluence implantation an additional source of tensile stress was introduced in the near surface region. The projected range of the implanted krypton was significantly reduced compared to the expected range. A possible cause of this discrepancy is the drift of implanted ions under the influence of the pre-existing stress gradient.

  14. The mutual influence of krypton implantation and pre-existing stress states in polycrystalline alpha titanium

    International Nuclear Information System (INIS)

    Nsengiyumva, S.; Ntsoane, T.P.; Raji, A.T.; Topic, M.; Kellermann, G.; Riviere, J.P.; Britton, D.T.; Haerting, M.

    2009-01-01

    The stress profile in polycrystalline titanium implanted with krypton ions at different fluences has been determined using synchrotron radiation diffraction. For each fluence, the krypton profile has been measured using Rutherford backscattering geometry. The results were compared to model calculations obtained from the SRIM 2008 computer code. A strong stress relaxation was found for high fluence implantation, whereas for low fluence implantation an additional source of tensile stress was introduced in the near surface region. The projected range of the implanted krypton was significantly reduced compared to the expected range. A possible cause of this discrepancy is the drift of implanted ions under the influence of the pre-existing stress gradient.

  15. Preliminary study of in vivo hemodynamic analysis of intracranial aneurysms using time-resolved three-dimensional phase-contrast MRI and in-house software [Presidential award proceedings

    International Nuclear Information System (INIS)

    Isoda, Haruo; Ohkura, Yasuhide; Seo, Taro

    2007-01-01

    We calculated in vivo wall shear stress (WSS) and streamlines of intracranial aneurysms and analyzed the relationships between the hemodynamics and WSS of the aneurysms using time-resolved three-dimensional (3D) phase-contrast magnetic resonance (MR) imaging (4D-Flow) and in-house software. We studied 10 subjects with 11 aneurysms. 4D-flow was performed using a 1.5T GE MR scanner with head coil. 3D time-of-flight (TOF) MR angiography was performed for geometric information. The software calculated the WSS based on interpolated shearing velocity using the data set obtained by 4D-flow near the wall and provided us with 3D streamlines. We acquired 3D streamlines and WSS distribution maps in arbitrary directions during the cardiac phase for all intracranial aneurysms, and each intracranial aneurysm in this study had at least one spiral flow. We noted lower WSS with lower flow velocities at the apex of the spiral flow. (author)

  16. Assessment of turbulent flow effects on the vessel wall using four-dimensional flow MRI.

    Science.gov (United States)

    Ziegler, Magnus; Lantz, Jonas; Ebbers, Tino; Dyverfeldt, Petter

    2017-06-01

    To explore the use of MR-estimated turbulence quantities for the assessment of turbulent flow effects on the vessel wall. Numerical velocity data for two patient-derived models was obtained using computational fluid dynamics (CFD) for two physiological flow rates. The four-dimensional (4D) Flow MRI measurements were simulated at three different spatial resolutions and used to investigate the estimation of turbulent wall shear stress (tWSS) using the intravoxel standard deviation (IVSD) of velocity and turbulent kinetic energy (TKE) estimated near the vessel wall. Accurate estimation of tWSS using the IVSD is limited by the spatial resolution achievable with 4D Flow MRI. TKE, estimated near the wall, has a strong linear relationship to the tWSS (mean R 2  = 0.84). Near-wall TKE estimates from MR simulations have good agreement to CFD-derived ground truth (mean R 2  = 0.90). Maps of near-wall TKE have strong visual correspondence to tWSS. Near-wall estimation of TKE permits assessment of relative maps of tWSS, but direct estimation of tWSS is challenging due to limitations in spatial resolution. Assessment of tWSS and near-wall TKE may open new avenues for analysis of different pathologies. Magn Reson Med 77:2310-2319, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  17. Hemodynamics of a Patient-Specific Aneurysm Model with Proper Orthogonal Decomposition

    Science.gov (United States)

    Han, Suyue; Chang, Gary Han; Modarres-Sadeghi, Yahya

    2017-11-01

    Wall shear stress (WSS) and oscillatory shear index (OSI) are two of the most-widely studied hemodynamic quantities in cardiovascular systems that have been shown to have the ability to elicit biological responses of the arterial wall, which could be used to predict the aneurysm development and rupture. In this study, a reduced-order model (ROM) of the hemodynamics of a patient-specific cerebral aneurysm is studied. The snapshot Proper Orthogonal Decomposition (POD) is utilized to construct the reduced-order bases of the flow using a CFD training set with known inflow parameters. It was shown that the area of low WSS and high OSI is correlated to higher POD modes. The resulting ROM can reproduce both WSS and OSI computationally for future parametric studies with significantly less computational cost. Agreement was observed between the WSS and OSI values obtained using direct CFD results and ROM results.

  18. Interaction between the Stress Phase Angle (SPA and the Oscillatory Shear Index (OSI Affects Endothelial Cell Gene Expression.

    Directory of Open Access Journals (Sweden)

    Ronny Amaya

    Full Text Available Hemodynamic forces play an important role in the non-uniform distribution of atherosclerotic lesions. Endothelial cells are exposed simultaneously to fluid wall shear stress (WSS and solid circumferential stress (CS. Due to variations in impedance (global factors and geometric complexities (local factors in the arterial circulation a time lag arises between these two forces that can be characterized by the temporal phase angle between CS and WSS (stress phase angle-SPA. Asynchronous flows (SPA close to -180° that are most prominent in coronary arteries have been associated with localization of atherosclerosis. Reversing oscillatory flows characterized by an oscillatory shear index (OSI that is great than zero are also associated with atherosclerosis localization. In this study we examined the relationship between asynchronous flows and reversing flows in altering the expression of 37 genes relevant to atherosclerosis development. In the case of reversing oscillatory flow, we observed that the asynchronous condition upregulated 8 genes compared to synchronous hemodynamics, most of them proatherogenic. Upregulation of the pro-inflammatory transcription factor NFκB p65 was confirmed by western blot, and nuclear translocation of NFκB p65 was confirmed by immunofluorescence staining. A comparative study between non-reversing flow and reversing flow found that in the case of synchronous hemodynamics, reversing flow altered the expression of 11 genes, while in the case of asynchronous hemodynamics, reversing flow altered the expression of 17 genes. Reversing flow significantly upregulated protein expression of NFκB p65 for both synchronous and asynchronous conditions. Nuclear translocation of NFκB p65 was confirmed for synchronous and asynchronous conditions in the presence of flow reversal. These data suggest that asynchronous hemodynamics and reversing flow can elicit proatherogenic responses in endothelial cells compared to synchronous

  19. Tomographic particle image velocimetry investigation of the flow in a modeled human carotid artery bifurcation

    Science.gov (United States)

    Buchmann, N. A.; Atkinson, C.; Jeremy, M. C.; Soria, J.

    2011-04-01

    Hemodynamic forces within the human carotid artery are well known to play a key role in the initiation and progression of vascular diseases such as atherosclerosis. The degree and extent of the disease largely depends on the prevailing three-dimensional flow structure and wall shear stress (WSS) distribution. This work presents tomographic PIV (Tomo-PIV) measurements of the flow structure and WSS in a physiologically accurate model of the human carotid artery bifurcation. The vascular geometry is reconstructed from patient-specific data and reproduced in a transparent flow phantom to demonstrate the feasibility of Tomo-PIV in a complex three-dimensional geometry. Tomographic reconstruction is performed with the multiplicative line-of-sight (MLOS) estimation and simultaneous multiplicative algebraic reconstruction (SMART) technique. The implemented methodology is validated by comparing the results with Stereo-PIV measurements in the same facility. Using a steady flow assumption, the measurement error and RMS uncertainty are directly inferred from the measured velocity field. It is shown that the measurement uncertainty increases for increasing light sheet thickness and increasing velocity gradients, which are largest near the vessel walls. For a typical volume depth of 6 mm (or 256 pixel), the analysis indicates that the velocity derived from 3D cross-correlation can be measured within ±2% of the maximum velocity (or ±0.2 pixel) near the center of the vessel and within ±5% (±0.6 pixel) near the vessel wall. The technique is then applied to acquire 3D-3C velocity field data at multiple axial locations within the carotid artery model, which are combined to yield the flow field and WSS in a volume of approximately 26 mm × 27 mm × 60 mm. Shear stress is computed from the velocity gradient tensor and a method for inferring the WSS distribution on the vessel wall is presented. The results indicate the presence of a complex and three-dimensional flow structure, with

  20. In vivo hemodynamic analysis of intracranial aneurysms obtained by magnetic resonance fluid dynamics (MRFD) based on time-resolved three-dimensional phase-contrast MRI

    International Nuclear Information System (INIS)

    Isoda, Haruo; Takeda, Hiroyasu; Yamashita, Shuhei; Takehara, Yasuo; Sakahara, Harumi; Ohkura, Yasuhide; Kosugi, Takashi; Hirano, Masaya; Hiramatsu, Hisaya; Namba, Hiroki; Alley, Marcus T.; Bammer, Roland; Pelc, Norbert J.

    2010-01-01

    Hemodynamics is thought to play a very important role in the initiation, growth, and rupture of intracranial aneurysms. The purpose of our study was to perform in vivo hemodynamic analysis of unruptured intracranial aneurysms of magnetic resonance fluid dynamics using time-resolved three-dimensional phase-contrast MRI (4D-Flow) at 1.5 T and to analyze relationships between hemodynamics and wall shear stress (WSS) and oscillatory shear index (OSI). This study included nine subjects with 14 unruptured aneurysms. 4D-Flow was performed by a 1.5-T magnetic resonance scanner with a head coil. We calculated in vivo streamlines, WSS, and OSI of intracranial aneurysms based on 4D-Flow with our software. We evaluated the number of spiral flows in the aneurysms and compared the differences in WSS or OSI between the vessel and aneurysm and between whole aneurysm and the apex of the spiral flow. 3D streamlines, WSS, and OSI distribution maps in arbitrary direction during the cardiac phase were obtained for all intracranial aneurysms. Twelve aneurysms had one spiral flow each, and two aneurysms had two spiral flows each. The WSS was lower and the OSI was higher in the aneurysm compared to the vessel. The apex of the spiral flow had a lower WSS and higher OSI relative to the whole aneurysm. Each intracranial aneurysm in this study had at least one spiral flow. The WSS was lower and OSI was higher at the apex of the spiral flow than the whole aneurysmal wall. (orig.)

  1. In vivo hemodynamic analysis of intracranial aneurysms obtained by magnetic resonance fluid dynamics (MRFD) based on time-resolved three-dimensional phase-contrast MRI.

    Science.gov (United States)

    Isoda, Haruo; Ohkura, Yasuhide; Kosugi, Takashi; Hirano, Masaya; Takeda, Hiroyasu; Hiramatsu, Hisaya; Yamashita, Shuhei; Takehara, Yasuo; Alley, Marcus T; Bammer, Roland; Pelc, Norbert J; Namba, Hiroki; Sakahara, Harumi

    2010-10-01

    Hemodynamics is thought to play a very important role in the initiation, growth, and rupture of intracranial aneurysms. The purpose of our study was to perform in vivo hemodynamic analysis of unruptured intracranial aneurysms of magnetic resonance fluid dynamics using time-resolved three-dimensional phase-contrast MRI (4D-Flow) at 1.5 T and to analyze relationships between hemodynamics and wall shear stress (WSS) and oscillatory shear index (OSI). This study included nine subjects with 14 unruptured aneurysms. 4D-Flow was performed by a 1.5-T magnetic resonance scanner with a head coil. We calculated in vivo streamlines, WSS, and OSI of intracranial aneurysms based on 4D-Flow with our software. We evaluated the number of spiral flows in the aneurysms and compared the differences in WSS or OSI between the vessel and aneurysm and between whole aneurysm and the apex of the spiral flow. 3D streamlines, WSS, and OSI distribution maps in arbitrary direction during the cardiac phase were obtained for all intracranial aneurysms. Twelve aneurysms had one spiral flow each, and two aneurysms had two spiral flows each. The WSS was lower and the OSI was higher in the aneurysm compared to the vessel. The apex of the spiral flow had a lower WSS and higher OSI relative to the whole aneurysm. Each intracranial aneurysm in this study had at least one spiral flow. The WSS was lower and OSI was higher at the apex of the spiral flow than the whole aneurysmal wall.

  2. Hemodynamic vascular biomarkers for initiation of paraclinoid internal carotid artery aneurysms using patient-specific computational fluid dynamic simulation based on magnetic resonance imaging.

    Science.gov (United States)

    Watanabe, Tomoya; Isoda, Haruo; Takehara, Yasuo; Terada, Masaki; Naito, Takehiro; Kosugi, Takafumi; Onishi, Yuki; Tanoi, Chiharu; Izumi, Takashi

    2018-05-01

    We performed computational fluid dynamics (CFD) for patients with and without paraclinoid internal carotid artery (ICA) aneurysms to evaluate the distribution of vascular biomarkers at the aneurysm initiation sites of the paraclinoid ICA. This study included 35 patients who were followed up for aneurysms using 3D time of flight (TOF) magnetic resonance angiography (MRA) and 3D cine phase-contrast MR imaging. Fifteen affected ICAs were included in group A with the 15 unaffected contralateral ICAs in group B. Thirty-three out of 40 paraclinoid ICAs free of aneurysms and arteriosclerotic lesions were included in group C. We deleted the aneurysms in group A based on the 3D TOF MRA dataset. We performed CFD based on MR data set and obtained wall shear stress (WSS), its derivatives, and streamlines. We qualitatively evaluated their distributions at and near the intracranial aneurysm initiation site among three groups. We also calculated and compared the normalized highest (nh-) WSS and nh-spatial WSS gradient (SWSSG) around the paraclinoid ICA among three groups. High WSS and SWSSG distribution were observed at and near the aneurysm initiation site in group A. High WSS and SWSSG were also observed at similar locations in group B and group C. However, nh-WSS and nh-SWSSG were significantly higher in group A than in group C, and nh-SWSSG was significantly higher in group A than in group B. Our findings indicated that nh-WSS and nh-SWSSG were good biomarkers for aneurysm initiation in the paraclinoid ICA.

  3. Conceptual model for concessioning in the Water Supply and Sanitation sector in Bulgaria

    Directory of Open Access Journals (Sweden)

    Todor Raychev

    2018-02-01

    Full Text Available The purpose of this article is to create a new conceptual model for sustainable development of the water sector in Bulgaria on the basis of concessions by statistical regions according to the NUTS-2 classification of the European Union. The essence of the proposed model includes an approach for consolidating the existing 66 WSS operators in three WSS operators – concessionaires. The approach is applied to provide WSS services for drinking and household needs of the population. WSS services for the sectors – Industry, Services, Agriculture, Forestry and Fisheries remain outside the scope of the study. The proposed model is based on statistical analyses of the effectiveness of the WSS operators working by statistical regions and the state of the technical infrastructure they use. Such concessioning by combining one region from the North and South Bulgaria should help to overcome the existing disproportions in the social and economical development and its harmonization in the regions of Northern and Southern Bulgaria. Its implementation should create new opportunities for introducing foreign direct investment which will contribute to the sustainable development of the water sector in the country. The practical significance of the proposed model for overall concessioning of the WSS sector is for Bulgaria as well as for other countries with low and middle incomes. The model is a part of a comprehensive study of a scientific project, according to the Ordinance No.9 of the Ministry of Education and Science of 08.08.2013, with No.NPI-130/2014, on the topic: „The concession as a factor for development of the Water Supply and Sanitation sector in the Republic of Bulgaria“.

  4. Four-dimensional flow MRI of stented versus stentless aortic valve bioprostheses

    Energy Technology Data Exchange (ETDEWEB)

    Kesteren, Floortje van [University of Amsterdam, Department of Radiology and Nuclear Medicine, Academic Medical Centre, Amsterdam (Netherlands); University of Amsterdam, Department of Cardiology, Academic Medical Centre, Amsterdam (Netherlands); Wollersheim, Laurens W.; Kaya, Abdullah; Mol, Bas A. de [University of Amsterdam, Department of Cardiothoracic Surgery, Academic Medical Centre, Amsterdam (Netherlands); Baan, Jan; Boekholdt, S.M. [University of Amsterdam, Department of Cardiology, Academic Medical Centre, Amsterdam (Netherlands); Nederveen, A.J.; Ooij, Pim van; Planken, R.N. [University of Amsterdam, Department of Radiology and Nuclear Medicine, Academic Medical Centre, Amsterdam (Netherlands)

    2018-01-15

    To evaluate aortic velocity, wall shear stress (WSS) and viscous energy loss (EL) of stented and stentless bioprostheses using 4D flow MRI 1 year after surgical aortic valve replacement. For this cross-sectional study 28 patients with stented (n = 14) or stentless (n = 14) bioprosthesis underwent non-contrast-enhanced 4D-flow MRI at 1.5 T. Analyses included a comparison of velocity, WSS and EL in the ascending aorta during peak systole for both spatially averaged values and a comparison of local differences using per-voxel analysis. No significant differences were found in peak and mean velocity (stented vs. stentless: 2.45 m/s vs. 2.11 m/s; p = 0.09 and 0.60 m/s vs. 0.62 m/s; p = 0.89), WSS (0.60 Pa vs. 0.59 Pa; p = 0.55) and EL (10.17 mW vs. 7.82 mW; p = 0.10). Per-voxel analysis revealed significantly higher central lumen velocity, and lower outer lumen velocity, WSS and EL for stentless versus stented prostheses. One year after aortic valve implantation with stented and stentless bioprostheses, velocity, WSS and EL were comparable when assessed for averaged values in the ascending aorta. However, the flow profile described with local analysis for stentless prosthesis is potentially favourable with a significantly higher central velocity profile and lower values for outer lumen velocity, WSS and EL. (orig.)

  5. Hemodynamic Modeling of Surgically Repaired Coarctation of the Aorta.

    Science.gov (United States)

    Olivieri, Laura J; de Zélicourt, Diane A; Haggerty, Christopher M; Ratnayaka, Kanishka; Cross, Russell R; Yoganathan, Ajit P

    2011-12-01

    PURPOSE: Late morbidity of surgically repaired coarctation of the aorta includes early cardiovascular and cerebrovascular disease, shortened life expectancy, abnormal vasomodulator response, hypertension and exercise-induced hypertension in the absence of recurrent coarctation. Observational studies have linked patterns of arch remodeling (Gothic, Crenel, and Romanesque) to late morbidity, with Gothic arches having the highest incidence. We evaluated flow in native and surgically repaired aortic arches to correlate respective hemodynamic indices with incidence of late morbidity. METHODS: Three dimensional reconstructions of each remodeled arch were created from an anatomic stack of magnetic resonance (MR) images. A structured mesh core with a boundary layer was generated. Computational fluid dynamic (CFD) analysis was performed assuming peak flow conditions with a uniform velocity profile and unsteady turbulent flow. Wall shear stress (WSS), pressure and velocity data were extracted. RESULTS: The region of maximum WSS was located in the mid-transverse arch for the Crenel, Romanesque and Native arches. Peak WSS was located in the isthmus of the Gothic model. Variations in descending aorta flow patterns were also observed among the models. CONCLUSION: The location of peak WSS is a primary difference among the models tested, and may have clinical relevance. Specifically, the Gothic arch had a unique location of peak WSS with flow disorganization in the descending aorta. Our results suggest that varied patterns and locations of WSS resulting from abnormal arch remodeling may exhibit a primary effect on clinical vascular dysfunction.

  6. Analysis of haemodynamic disturbance in the atherosclerotic carotid artery using computational fluid dynamics

    International Nuclear Information System (INIS)

    Birchall, Daniel; Zaman, Azfar; Hacker, Jacob; Davies, Gavin; Mendelow, David

    2006-01-01

    Computational fluid dynamics (CFD) provides a means for the quantitative analysis of haemodynamic disturbances in vivo, but most work has used phantoms or idealised geometry. Our purpose was to use CFD to analyse flow in carotid atherosclerosis using patient-specific geometry and flow data. Eight atherosclerotic carotid arteries and one healthy control artery were imaged with magnetic resonance angiography (MRA) and duplex ultrasound, and the data used to construct patient-specific computational models used for CFD and wall shear stress (WSS) analysis. There is a progressive change in three-dimensional (3-D) velocity profile and WSS profile with increasing severity of stenosis, characterised by increasing restriction of areas of low WSS, change in oscillation patterns, and progressive rise in WSS within stenoses and downstream jets. Areas of turbulent, retrograde flow and of low WSS are demonstrated in the lee of the stenoses. This study presents the largest CFD analysis of abnormal haemodynamics at the atheromatous carotid bifurcation using patient-specific data and provides the basis for further investigation of causal links between haemodynamic variables and atherogenesis and formation of unstable plaque. We propose that this provides a means for the prospective assessment of relative stroke risk in patients with carotid atherosclerosis. (orig.)

  7. Computational modeling with fluid-structure interaction of the severe m1 stenosis before and after stenting.

    Science.gov (United States)

    Park, Soonchan; Lee, Sang-Wook; Lim, Ok Kyun; Min, Inki; Nguyen, Minhtuan; Ko, Young Bae; Yoon, Kyunghwan; Suh, Dae Chul

    2013-02-01

    Image-based computational models with fluid-structure interaction (FSI) can be used to perform plaque mechanical analysis in intracranial artery stenosis. We described a process in FSI study applied to symptomatic severe intracranial (M1) stenosis before and after stenting. Reconstructed 3D angiography in STL format was transferred to Magics for smoothing of vessel surface and trimming of branch vessels and to HyperMesh for generating tetra volume mesh from triangular surface-meshed 3D angiogram. Computational analysis of blood flow in the blood vessels was performed using the commercial finite element software ADINA Ver 8.5. The distribution of wall shear stress (WSS), peak velocity and pressure was analyzed before and after intracranial stenting. The wall shear stress distributions from Computational fluid dynamics (CFD) simulation with rigid wall assumption as well as FSI simulation before and after stenting could be compared. The difference of WSS between rigid wall and compliant wall model both in pre- and post-stent case is only minor except at the stenosis region. These WSS values were greatly reduced after stenting to 15~20 Pa at systole and 3~5 Pa at end-diastole in CFD simulation, which are similar in FSI simulations. Our study revealed that FSI simulation before and after intracranial stenting was feasible despite of limited vessel wall dimension and could reveal change of WSS as well as flow velocity and wall pressure.

  8. Quantitative studies of water and sanitation utilities: a literature survey

    OpenAIRE

    Berg, Sanford V; Marques, Rui Cunha

    2010-01-01

    This paper performs a literature update of quantitative studies of water and sanitation services (WSS). There are 190 studies which use cost or production functions to evaluate the performance of WSS utilities. The studies examine (1) the scale, scope or density economies of utilities in a particular country or region, (2) the influence of ownership on efficiency, (3) the existence and power of incentives associated with different governance systems (including external regulation), and (4) pe...

  9. Level of physical activity, well-being, stress and self-rated health in persons with migraine and co-existing tension-type headache and neck pain.

    Science.gov (United States)

    Krøll, Lotte Skytte; Hammarlund, Catharina Sjödahl; Westergaard, Maria Lurenda; Nielsen, Trine; Sloth, Louise Bönsdorff; Jensen, Rigmor Højland; Gard, Gunvor

    2017-12-01

    The prevalence of migraine with co-existing tension-type headache and neck pain is high in the general population. However, there is very little literature on the characteristics of these combined conditions. The aim of this study was to investigate a) the prevalence of migraine with co-existing tension-type headache and neck pain in a clinic-based sample, b) the level of physical activity, psychological well-being, perceived stress and self-rated health in persons with migraine and co-existing tension-type headache and neck pain compared to healthy controls, c) the perceived ability of persons with migraine and co-existing tension-type headache and neck pain to perform physical activity, and d) which among the three conditions (migraine, tension-type headache or neck pain) is rated as the most burdensome condition. The study was conducted at a tertiary referral specialised headache centre where questionnaires on physical activity, psychological well-being, perceived stress and self-rated health were completed by 148 persons with migraine and 100 healthy controls matched by sex and average age. Semi-structured interviews were conducted to assess characteristics of migraine, tension-type headache and neck pain. Out of 148 persons with migraine, 100 (67%) suffered from co-existing tension-type headache and neck pain. Only 11% suffered from migraine only. Persons with migraine and co-existing tension-type headache and neck pain had lower level of physical activity and psychological well-being, higher level of perceived stress and poorer self-rated health compared to healthy controls. They reported reduced ability to perform physical activity owing to migraine (high degree), tension-type headache (moderate degree) and neck pain (low degree). The most burdensome condition was migraine, followed by tension-type headache and neck pain. Migraine with co-existing tension-type headache and neck pain was highly prevalent in a clinic-based sample. Persons with migraine and co-existing

  10. Quantitative comparison of hemodynamics in simulated and 3D angiography models of cerebral aneurysms by use of computational fluid dynamics.

    Science.gov (United States)

    Saho, Tatsunori; Onishi, Hideo

    2015-07-01

    In this study, we evaluated hemodynamics using simulated models and determined how cerebral aneurysms develop in simulated and patient-specific models based on medical images. Computational fluid dynamics (CFD) was analyzed by use of OpenFOAM software. Flow velocity, stream line, and wall shear stress (WSS) were evaluated in a simulated model aneurysm with known geometry and in a three-dimensional angiographic model. The ratio of WSS at the aneurysm compared with that at the basilar artery was 1:10 in simulated model aneurysms with a diameter of 10 mm and 1:18 in the angiographic model, indicating similar tendencies. Vortex flow occurred in both model aneurysms, and the WSS decreased in larger model aneurysms. The angiographic model provided accurate CFD information, and the tendencies of simulated and angiographic models were similar. These findings indicate that hemodynamic effects are involved in the development of aneurysms.

  11. Bibliographic citations pertinent to the Weldon Spring Site, St. Charles County, Missouri

    International Nuclear Information System (INIS)

    Owen, P.T.; Michelson, D.C.; Knox, N.P.

    1985-08-01

    This report is a compilation of 166 bibliographic references pertinent to the Weldon Spring Site (WSS), St. Charles County, Missouri. The WSS is a surplus US government facility which consists of the Weldon Spring Chemical Plant; two separate low-level radioactive waste storage properties, designated the ''raffinate pits'' and ''quarry'', and a number of potentially contaminated vicinity properties. The facility was used by the US Atomic Energy Commission from 1957 to 1966 to refine uranium. After several years the US Department of the Army acquired responsibility for the Weldon Spring Chemical Plant, performed some limited radiological decontamination, and then cancelled plans to construct a chemical process. Contamination of the facility and adjacent lands resulted from operation of the refining facility and the storage, transport, and disposal of process wastes on the property, as well as subsequent decontamination activities. All identified references to published technical documents that relate to the WSS were included in this report. In some cases citations from the reference section of existing documents were included in this report with no hardcopy to substantiate the existence of the document referenced

  12. Closure technique after carotid endarterectomy influences local hemodynamics.

    Science.gov (United States)

    Harrison, Gareth J; How, Thien V; Poole, Robert J; Brennan, John A; Naik, Jagjeeth B; Vallabhaneni, S Rao; Fisher, Robert K

    2014-08-01

    Meta-analysis supports patch angioplasty after carotid endarterectomy (CEA); however, studies indicate considerable variation in practice. The hemodynamic effect of a patch is unclear and this study attempted to elucidate this and guide patch width selection. Four groups were selected: healthy volunteers and patients undergoing CEA with primary closure, trimmed patch (5 mm), or 8-mm patch angioplasty. Computer-generated three-dimensional models of carotid bifurcations were produced from transverse ultrasound images recorded at 1-mm intervals. Rapid prototyping generated models for flow visualization studies. Computational fluid dynamic studies were performed for each model and validated by flow visualization. Mean wall shear stress (WSS) and oscillatory shear index (OSI) maps were created for each model using pulsatile inflow at 300 mL/min. WSS of OSI >0.3 were considered pathological, predisposing to accretion of intimal hyperplasia. The resultant WSS and OSI maps were compared. The four groups comprised 8 normal carotid arteries, 6 primary closures, 6 trimmed patches, and seven 8-mm patches. Flow visualization identified flow separation and recirculation at the bifurcation increased with a patch and was related to the patch width. Computational fluid dynamic identified that primary closure had the fewest areas of low WSS or elevated OSI but did have mild common carotid artery stenoses at the proximal arteriotomy that caused turbulence. Trimmed patches had more regions of abnormal WSS and OSI at the bifurcation, but 8-mm patches had the largest areas of deleteriously low WSS and high OSI. Qualitative comparison among the four groups confirmed that incorporation of a patch increased areas of low WSS and high OSI at the bifurcation and that this was related to patch width. Closure technique after CEA influences the hemodynamic profile. Patching does not appear to generate favorable flow dynamics. However, a trimmed 5-mm patch may offer hemodynamic benefits over an 8

  13. Coupled 0D-1D CFD Modeling of Right Heart and Pulmonary Artery Morphometry Tree

    Science.gov (United States)

    Dong, Melody; Yang, Weiguang; Feinstein, Jeffrey A.; Marsden, Alison

    2017-11-01

    Pulmonary arterial hypertension (PAH) is characterized by elevated pulmonary artery (PA) pressure and remodeling of the distal PAs resulting in right ventricular (RV) dysfunction and failure. It is hypothesized that patients with untreated ventricular septal defects (VSD) may develop PAH due to elevated flows and pressures in the PAs. Wall shear stress (WSS), due to elevated flows, and circumferential stress, due to elevated pressures, are known to play a role in vascular mechanobiology. Thus, simulating VSD hemodynamics and wall mechanics may facilitate our understanding of mechanical stimuli leading to PAH initiation and progression. Although 3D CFD models can capture detailed hemodynamics in the proximal PAs, they cannot easily model hemodynamics and wave propagation in the distal PAs, where remodeling occurs. To improve current PA models, we will present a new method that couples distal PA hemodynamics with RV function. Our model couples a 0D lumped parameter model of the RV to a 1D model of the PA tree, based on human PA morphometry data, to characterize RV performance and WSS changes in the PA tree. We will compare a VSD 0D-1D model and a 0D-3D model coupled to a mathematical morphometry tree model to quantify WSS in the entire PA vascular tree.

  14. Level of physical activity, well-being, stress and self-rated health in persons with migraine and co-existing tension-type headache and neck pain

    DEFF Research Database (Denmark)

    Krøll, Lotte Skytte; Hammarlund, Catharina Sjödahl; Westergaard, Maria Lurenda

    2017-01-01

    where questionnaires on physical activity, psychological well-being, perceived stress and self-rated health were completed by 148 persons with migraine and 100 healthy controls matched by sex and average age. Semi-structured interviews were conducted to assess characteristics of migraine, tension......-existing tension-type headache and neck pain in a clinic-based sample, b) the level of physical activity, psychological well-being, perceived stress and self-rated health in persons with migraine and co-existing tension-type headache and neck pain compared to healthy controls, c) the perceived ability of persons...... well-being, higher level of perceived stress and poorer self-rated health compared to healthy controls. They reported reduced ability to perform physical activity owing to migraine (high degree), tension-type headache (moderate degree) and neck pain (low degree). The most burdensome condition...

  15. Mild anastomotic stenosis in patient-specific CABG model may enhance graft patency: a new hypothesis.

    Directory of Open Access Journals (Sweden)

    Yunlong Huo

    Full Text Available It is well known that flow patterns at the anastomosis of coronary artery bypass graft (CABG are complex and may affect the long-term patency. Various attempts at optimal designs of anastomosis have not improved long-term patency. Here, we hypothesize that mild anastomotic stenosis (area stenosis of about 40-60% may be adaptive to enhance the hemodynamic conditions, which may contribute to slower progression of atherosclerosis. We further hypothesize that proximal/distal sites to the stenosis have converse changes that may be a risk factor for the diffuse expansion of atherosclerosis from the site of stenosis. Twelve (12 patient-specific models with various stenotic degrees were extracted from computed tomography images using a validated segmentation software package. A 3-D finite element model was used to compute flow patterns including wall shear stress (WSS and its spatial and temporal gradients (WSS gradient, WSSG, and oscillatory shear index, OSI. The flow simulations showed that mild anastomotic stenosis significantly increased WSS (>15 dynes · cm(-2 and decreased OSI (<0.02 to result in a more uniform distribution of hemodynamic parameters inside anastomosis albeit proximal/distal sites to the stenosis have a decrease of WSS (<4 dynes · cm(-2. These findings have significant implications for graft adaptation and long-term patency.

  16. Mild anastomotic stenosis in patient-specific CABG model may enhance graft patency: a new hypothesis.

    Science.gov (United States)

    Huo, Yunlong; Luo, Tong; Guccione, Julius M; Teague, Shawn D; Tan, Wenchang; Navia, José A; Kassab, Ghassan S

    2013-01-01

    It is well known that flow patterns at the anastomosis of coronary artery bypass graft (CABG) are complex and may affect the long-term patency. Various attempts at optimal designs of anastomosis have not improved long-term patency. Here, we hypothesize that mild anastomotic stenosis (area stenosis of about 40-60%) may be adaptive to enhance the hemodynamic conditions, which may contribute to slower progression of atherosclerosis. We further hypothesize that proximal/distal sites to the stenosis have converse changes that may be a risk factor for the diffuse expansion of atherosclerosis from the site of stenosis. Twelve (12) patient-specific models with various stenotic degrees were extracted from computed tomography images using a validated segmentation software package. A 3-D finite element model was used to compute flow patterns including wall shear stress (WSS) and its spatial and temporal gradients (WSS gradient, WSSG, and oscillatory shear index, OSI). The flow simulations showed that mild anastomotic stenosis significantly increased WSS (>15 dynes · cm(-2)) and decreased OSI (<0.02) to result in a more uniform distribution of hemodynamic parameters inside anastomosis albeit proximal/distal sites to the stenosis have a decrease of WSS (<4 dynes · cm(-2)). These findings have significant implications for graft adaptation and long-term patency.

  17. A Computational Approach to Model Vascular Adaptation During Chronic Hemodialysis: Shape Optimization as a Substitute for Growth Modeling

    Science.gov (United States)

    Mahmoudzadeh Akherat, S. M. Javid; Boghosian, Michael; Cassel, Kevin; Hammes, Mary

    2015-11-01

    End-stage-renal disease patients depend on successful long-term hemodialysis via vascular access, commonly facilitated via a Brachiocephalic Fistula (BCF). The primary cause of BCF failure is Cephalic Arch Stenosis (CAS). It is believed that low Wall Shear Stress (WSS) regions, which occur because of the high flow rates through the natural bend in the cephalic vein, create hemodynamic circumstances that trigger the onset and development of Intimal Hyperplasia (IH) and subsequent CAS. IH is hypothesized to be a natural effort to reshape the vessel, aiming to bring the WSS values back to a physiologically acceptable range. We seek to explore the correlation between regions of low WSS and subsequent IH and CAS in patient-specific geometries. By utilizing a shape optimization framework, a method is proposed to predict cardiovascular adaptation that could potentially be an alternative to vascular growth and remodeling. Based on an objective functional that seeks to alter the vessel shape in such a way as to readjust the WSS to be within the normal physiological range, CFD and shape optimization are then coupled to investigate whether the optimal shape evolution is correlated with actual patient-specific geometries thereafter. Supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health (R01 DK90769).

  18. Existence of solutions for the anti-plane stress for a new class of “strain-limiting” elastic bodies

    KAUST Repository

    Bulí ček, Miroslav; Má lek, Josef; Rajagopal, K. R.; Walton, Jay R.

    2015-01-01

    © 2015, Springer-Verlag Berlin Heidelberg. The main purpose of this study is to establish the existence of a weak solution to the anti-plane stress problem on V-notch domains for a class of recently proposed new models that could describe elastic materials in which the stress can increase unboundedly while the strain yet remains small. We shall also investigate the qualitative properties of the solution that is established. Although the equations governing the deformation that are being considered share certain similarities with the minimal surface problem, the boundary conditions and the presence of an additional model parameter that appears in the equation and its specific range makes the problem, as well as the result, different from those associated with the minimal surface problem.

  19. Existence of solutions for the anti-plane stress for a new class of “strain-limiting” elastic bodies

    KAUST Repository

    Bulíček, Miroslav

    2015-04-21

    © 2015, Springer-Verlag Berlin Heidelberg. The main purpose of this study is to establish the existence of a weak solution to the anti-plane stress problem on V-notch domains for a class of recently proposed new models that could describe elastic materials in which the stress can increase unboundedly while the strain yet remains small. We shall also investigate the qualitative properties of the solution that is established. Although the equations governing the deformation that are being considered share certain similarities with the minimal surface problem, the boundary conditions and the presence of an additional model parameter that appears in the equation and its specific range makes the problem, as well as the result, different from those associated with the minimal surface problem.

  20. A study of the hemodynamics of anterior communicating artery aneurysms

    Science.gov (United States)

    Cebral, Juan R.; Castro, Marcelo A.; Putman, Christopher M.

    2006-03-01

    In this study, the effects of unequal physiologic flow conditions in the internal carotid arteries on the intra-aneurysmal hemodynamics of anterior communicating artery aneurysms were investigated. Patient-specific vascular computational fluid dynamics models of five cerebral aneurysms were constructed from bilateral 3D rotational angiography images. The aneurysmal hemodynamics was analyzed under a range of physiologic flow conditions including the effects of unequal mean flows and phase shifts between the flow waveforms of the left and right internal carotid arteries. A total of five simulations were performed for each patient, and unsteady wall shear stress (WSS) maps were created for each flow condition. Time dependent curves of average WSS magnitude over selected regions on the aneurysms were constructed and used to analyze the influence of the inflow conditions. It was found that mean flow imbalances in the feeding vessels tend to shift the regions of elevated WSS (flow impingement region) towards the dominating inflow jet and to change the magnitude of the WSS peaks. However, the overall qualitative appearance of the WSS distribution and velocity simulations is not substantially affected. In contrast, phase differences tend to increase the temporal complexity of the hemodynamic patterns and to destabilize the intra-aneurysmal flow pattern. However, these effects are less important when the A1 confluence is less symmetric, i.e. dominated by one of the A1 segments. Conditions affecting the flow characteristics in the parent arteries of cerebral aneurysms with more than one avenue of inflow should be incorporated into flow models.

  1. Hemodynamics before and after bleb formation in cerebral aneurysms

    Science.gov (United States)

    Cebral, Juan R.; Radaelli, Alessandro; Frangi, Alejandro; Putman, Christopher M.

    2007-03-01

    We investigate whether blebs in cerebral aneurysms form in regions of low or high wall shear stress (WSS), and how the intraaneurysmal hemodynamic pattern changes after bleb formation. Seven intracranial aneurysms harboring well defined blebs were selected from our database and subject-specific computational models were constructed from 3D rotational angiography. For each patient, a second anatomical model representing the aneurysm before bleb formation was constructed by smoothing out the bleb. Computational fluid dynamics simulations were performed under pulsatile flow conditions for both models of each aneurysm. In six of the seven aneurysms, the blebs formed in a region of elevated WSS associated to the inflow jet impaction zone. In one, the bleb formed in a region of low WSS associated to the outflow zone. In this case, the inflow jet maintained a fairly concentrated structure all the way to the outflow zone, while in the other six aneurysms it dispersed after impacting the aneurysm wall. In all aneurysms, once the blebs formed, new flow recirculation regions were formed inside the blebs and the blebs progressed to a state of low WSS. Assuming that blebs form due to a focally damaged arterial wall, these results seem to indicate that the localized injury of the vessel wall may be caused by elevated WSS associated with the inflow jet. However, the final shape of the aneurysm is probably also influenced by the peri-aneurysmal environment that can provide extra structural support via contact with structures such as bone or dura matter.

  2. The effect of inlet waveforms on computational hemodynamics of patient-specific intracranial aneurysms.

    Science.gov (United States)

    Xiang, J; Siddiqui, A H; Meng, H

    2014-12-18

    Due to the lack of patient-specific inlet flow waveform measurements, most computational fluid dynamics (CFD) simulations of intracranial aneurysms usually employ waveforms that are not patient-specific as inlet boundary conditions for the computational model. The current study examined how this assumption affects the predicted hemodynamics in patient-specific aneurysm geometries. We examined wall shear stress (WSS) and oscillatory shear index (OSI), the two most widely studied hemodynamic quantities that have been shown to predict aneurysm rupture, as well as maximal WSS (MWSS), energy loss (EL) and pressure loss coefficient (PLc). Sixteen pulsatile CFD simulations were carried out on four typical saccular aneurysms using 4 different waveforms and an identical inflow rate as inlet boundary conditions. Our results demonstrated that under the same mean inflow rate, different waveforms produced almost identical WSS distributions and WSS magnitudes, similar OSI distributions but drastically different OSI magnitudes. The OSI magnitude is correlated with the pulsatility index of the waveform. Furthermore, there is a linear relationship between aneurysm-averaged OSI values calculated from one waveform and those calculated from another waveform. In addition, different waveforms produced similar MWSS, EL and PLc in each aneurysm. In conclusion, inlet waveform has minimal effects on WSS, OSI distribution, MWSS, EL and PLc and a strong effect on OSI magnitude, but aneurysm-averaged OSI from different waveforms has a strong linear correlation with each other across different aneurysms, indicating that for the same aneurysm cohort, different waveforms can consistently stratify (rank) OSI of aneurysms. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Positive Effects of a Stress Reduction Program Based on Mindfulness Meditation in Brazilian Nursing Professionals: Qualitative and Quantitative Evaluation.

    Science.gov (United States)

    dos Santos, Teresa Maria; Kozasa, Elisa Harumi; Carmagnani, Isabel Sampaio; Tanaka, Luiza Hiromi; Lacerda, Shirley Silva; Nogueira-Martins, Luiz Antonio

    2016-01-01

    Mindfulness meditation has been shown to effectively mitigate the negative effects of stress among nursing professionals, but in countries like Brazil, these practices are relatively unexplored. To evaluate the effects of a Stress Reduction Program (SRP) including mindfulness and loving kindness meditation among nursing professionals working in a Brazilian hospital setting. Pilot study with a mixed model using quantitative and qualitative methods was used to evaluate a group of participants. The quantitative data were analyzed at three different time points: pre-intervention, post-intervention, and follow-up. The qualitative data were analyzed at post-intervention. Hospital São Paulo (Brazil). Sample 13 nursing professionals, including nurses, technicians, and nursing assistants working in a hospital. Participants underwent mindfulness and loving kindness meditation during a period of six weeks. Perceived Stress Scale (PSS), Maslach Burnout Inventory (MBI), Beck Depression Inventory (BDI), State-Trait Anxiety Inventory (STAI), Satisfaction With Life Scale (SWLS), Self-Compassion Scale (SCS), WHOQOL-BREF quality of life assessment, and Work Stress Scale (WSS). Qualitative data were collected via a group interview following six weeks participation in the SRP. The quantitative analyses revealed a significant reduction (P stress, burnout, depression, and anxiety (trait). These variables showed no significant differences between post-intervention and follow-up scores. The WHOQOL-BREF revealed significant increase (P nursing activities. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Hemodynamic and morphological characteristics of unruptured posterior communicating artery aneurysms with oculomotor nerve palsy.

    Science.gov (United States)

    Lv, Nan; Yu, Ying; Xu, Jinyu; Karmonik, Christof; Liu, Jianmin; Huang, Qinghai

    2016-08-01

    OBJECT Unruptured posterior communicating artery (PCoA) aneurysms with oculomotor nerve palsy (ONP) have a very high risk of rupture. This study investigated the hemodynamic and morphological characteristics of intracranial aneurysms with high rupture risk by analyzing PCoA aneurysms with ONP. METHODS Fourteen unruptured PCoA aneurysms with ONP, 33 ruptured PCoA aneurysms, and 21 asymptomatic unruptured PCoA aneurysms were included in this study. The clinical, morphological, and hemodynamic characteristics were compared among the different groups. RESULTS The clinical characteristics did not differ among the 3 groups (p > 0.05), whereas the morphological and hemodynamic analyses showed that size, aspect ratio, size ratio, undulation index, nonsphericity index, ellipticity index, normalized wall shear stress (WSS), and percentage of low WSS area differed significantly (p PCoA aneurysms with ONP demonstrated a distinctive morphological-hemodynamic pattern that was significantly different compared with asymptomatic unruptured PCoA aneurysms and was similar to ruptured PCoA aneurysms. The larger size, more irregular shape, and lower WSS might be related to the high rupture risk of PCoA aneurysms.

  5. Investigating the influence of haemodynamic stimuli on intracranial aneurysm inception.

    Science.gov (United States)

    Chen, Haoyu; Selimovic, Alisa; Thompson, Harry; Chiarini, Alessandro; Penrose, Justin; Ventikos, Yiannis; Watton, Paul N

    2013-07-01

    We propose a novel method to reconstruct the hypothetical geometry of the healthy vasculature prior to intracranial aneurysm (IA) formation: a Frenet frame is calculated along the skeletonization of the arterial geometry; upstream and downstream boundaries of the aneurysmal segment are expressed in terms of the local Frenet frame basis vectors; the hypothetical healthy geometry is then reconstructed by propagating a closed curve along the skeleton using the local Frenet frames so that the upstream boundary is smoothly morphed into the downstream boundary. This methodology takes into account the tortuosity of the arterial vasculature and requires minimal user subjectivity. The method is applied to 22 clinical cases depicting IAs. Computational fluid dynamic simulations of the vasculature without IA are performed and the haemodynamic stimuli in the location of IA formation are examined. We observe that locally elevated wall shear stress (WSS) and gradient oscillatory number (GON) are highly correlated (20/22 for WSS and 19/22 for GON) with regions susceptible to sidewall IA formation whilst haemodynamic indices associated with the oscillation of the WSS vectors have much lower correlations.

  6. Toward translating near-infrared spectroscopy oxygen saturation data for the non-invasive prediction of spatial and temporal hemodynamics during exercise

    Science.gov (United States)

    Ellwein, Laura; Samyn, Margaret M.; Danduran, Michael; Schindler-Ivens, Sheila; Liebham, Stacy; LaDisa, John F.

    2016-01-01

    Image-based computational fluid dynamics (CFD) studies conducted at rest have shown that atherosclerotic plaque in the thoracic aorta (TA) correlates with adverse wall shear stress (WSS), but there is a paucity of such data under elevated flow conditions. We developed a pedaling exercise protocol to obtain phase contrast magnetic resonance imaging (PC-MRI) blood flow measurements in the TA and brachiocephalic arteries during three-tiered supine pedaling at 130%, 150%, and 170% of resting heart rate (HR), and relate these measurements to noninvasive tissue oxygen saturation (StO2) acquired by near-infrared spectroscopy (NIRS) while conducting the same protocol. Local quantification of WSS indices by CFD revealed low time-averaged WSS on the outer curvature of the ascending aorta and the inner curvature of the descending aorta (dAo) that progressively increased with exercise, but that remained low on the anterior surface of brachiocephalic arteries. High oscillatory WSS observed on the inner curvature of the aorta persisted during exercise as well. Results suggest locally continuous exposure to potentially deleterious indices of WSS despite benefits of exercise. Linear relationships between flow distributions and tissue oxygen extraction calculated from StO2 were found between the left common carotid versus cerebral tissue (r2=0.96) and the dAo versus leg tissue (r2=0.87). A resulting six-step procedure is presented to use NIRS data as a surrogate for exercise PC-MRI when setting boundary conditions for future CFD studies of the TA under simulated exercise conditions. Relationships and ensemble averaged PC-MRI inflow waveforms are provided in an online repository for this purpose. PMID:27376865

  7. Successful Retreatment of Recurrent Intracranial Vertebral Artery Dissecting Aneurysms After Stent-Assisted Coil Embolization: A Self-Controlled Hemodynamic Analysis.

    Science.gov (United States)

    Liu, Jian; Jing, Linkai; Zhang, Ying; Song, Ying; Wang, Yang; Li, Chuanhui; Wang, Yanmin; Mu, Shiqing; Paliwal, Nikhil; Meng, Hui; Linfante, Italo; Yang, Xinjian

    2017-01-01

    Intracranial vertebral artery dissecting aneurysms (VADAs) tend to recur despite successful stent-assisted coil embolization (SACE). Hemodynamics is useful in evaluating aneurysmal formation, growth, and rupture. Our aim was to evaluate the hemodynamic patterns of the recurrence of VADA. Between September 2009 and November 2013, all consecutive patients with recurrent VADAs after SACE in our institutions were enrolled. Recurrence was defined as recanalization and/or regrowth. We assessed the hemodynamic alterations in wall shear stress (WSS) and velocity after the initial SACE and subsequently after retreatment of the aneurysms that recurred. Five patients were included. After the initial treatment, 3 patients showed recanalization and 2 showed regrowth. In the 2 patients with regrowth, the 2 original aneurysms maintained complete occlusion; however, de novo aneurysm regrowth was confirmed near the previous site. Compared with 3 recanalized aneurysms, the completely occluded aneurysms showed high mean reductions in velocity and WSS after initial treatment (velocity, 77.6% vs. 57.7%; WSS, 74.2% vs. 52.4%); however, WSS remained high at the region near the previous lesion where the new aneurysm originated. After the second retreatment, there was no recurrence in any patient. Compared with the 3 aneurysms that recanalized, the 4 aneurysms that maintained complete occlusion showed higher reductions in velocity (62.9%) and WSS (71.1%). Our series indicated that hemodynamics might have an important role in recurrence of VADAs. After endovascular treatment, sufficient hemodynamic reduction in aneurysm dome, orifice, and parent vessel may be one of the key factors for preventing recurrence in VADAs. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. Hemodynamic effect of bypass geometry on intracranial aneurysm: A numerical investigation.

    Science.gov (United States)

    Kurşun, Burak; Uğur, Levent; Keskin, Gökhan

    2018-05-01

    Hemodynamic analyzes are used in the clinical investigation and treatment of cardiovascular diseases. In the present study, the effect of bypass geometry on intracranial aneurysm hemodynamics was investigated numerically. Pressure, wall shear stress (WSS) and velocity distribution causing the aneurysm to grow and rupture were investigated and the best conditions were tried to be determined in case of bypassing between basilar (BA) and left/right posterior arteries (LPCA/RPCA) for different values of parameters. The finite volume method was used for numerical solutions and calculations were performed with the ANSYS-Fluent software. The SIMPLE algorithm was used to solve the discretized conservation equations. Second Order Upwind method was preferred for finding intermediate point values in the computational domain. As the blood flow velocity changes with time, the blood viscosity value also changes. For this reason, the Carreu model was used in determining the viscosity depending on the velocity. Numerical study results showed that when bypassed, pressure and wall shear stresses reduced in the range of 40-70% in the aneurysm. Numerical results obtained are presented in graphs including the variation of pressure, wall shear stress and velocity streamlines in the aneurysm. Considering the numerical results for all parameter values, it is seen that the most important factors affecting the pressure and WSS values in bypassing are the bypass position on the basilar artery (L b ) and the diameter of the bypass vessel (d). Pressure and wall shear stress reduced in the range of 40-70% in the aneurysm in the case of bypass for all parameters. This demonstrates that pressure and WSS values can be greatly reduced in aneurysm treatment by bypassing in cases where clipping or coil embolization methods can not be applied. Copyright © 2018 Elsevier B.V. All rights reserved.

  9. The hemodynamics in intracranial aneurysm ruptured region with active contrast leakage during computed tomography angiography

    Science.gov (United States)

    Li, Ming-Lung; Wang, Yi-Chou; Liou, Tong-Miin; Lin, Chao-An

    2014-10-01

    Precise locations of rupture region under contrast agent leakage of five ruptured cerebral artery aneurysms during computed tomography angiography, which is to our knowledge for the first time, were successfully identified among 101 patients. These, together with numerical simulations based on the reconstructed aneurysmal models, were used to analyze hemodynamic parameters of aneurysms under different cardiac cyclic flow rates. For side wall type aneurysms, different inlet flow rates have mild influences on the shear stresses distributions. On the other hand, for branch type aneurysms, the predicted wall shear stress (WSS) correlates strongly with the increase of inlet vessel velocity. The mean and time averaged WSSes at rupture regions are found to be lower than those over the surface of the aneurysms. Also, the levels of the oscillatory shear index (OSI) are higher than the reported threshold value, supporting the assertion that high OSI correlates with rupture of the aneurysm. However, the present results also indicate that OSI level at the rupture region is relatively lower.

  10. Improved viscosity modeling in patients with type 2 diabetes mellitus by accounting for enhanced red blood cell aggregation tendency

    NARCIS (Netherlands)

    Mutsaerts, Henri J. M. M.; Out, Mattijs; Goedhart, Peter T.; Ince, Can; Hardeman, Max R.; Romijn, Johannes A.; Rabelink, Ton J.; Reiber, Johan H. C.; Box, Frieke M. A.

    2010-01-01

    Aims: Distorted wall shear stress (WSS) in patients with type 2 diabetes mellitus (T2DM) may be partly explained by an altered red blood cell aggregation tendency (RAT) on viscosity at low shear rate (SR). The present study evaluates viscosity modeling by implementation of hematocrit and RAT in

  11. Water Pipe Steam Stones: Familiarity and Use Among US Young Adults

    Science.gov (United States)

    Shensa, Ariel; Primack, Brian A.

    2015-01-01

    Introduction: Water pipe tobacco smoking (WTS) is associated with substantial toxicant exposure. Water pipe steam stones (WSS) are marketed as a healthier alternative. The purpose of this study was to determine, in a nationally representative sample, young adults’ familiarity with, perceptions regarding, and use of WSS. Methods: A survey about WTS was completed by 3,253 members of an online nonvolunteer access panel. Four items specifically addressed WSS. Results: Of the 228 individuals who had heard of WSS, 17% (n = 41) reported using them. Use was associated with ever (adjusted odds ratio [AOR] = 7.7, 95% confidence interval [CI] = 2.7–21.8) and current (AOR = 16.1, 95% CI = 5.1–51.5) WTS. Compared with those who thought that WSS had about the same harm as WTS, those who thought that WSS was “a lot less harmful” to a person’s health had substantially higher odds of having tried WSS (AOR = 6.8, 95% CI = 2.0–23.1). Conclusions: Approximately 1 in 6 young adults who have heard of WSS used them. WSS use is associated with the perception of reduced harm. PMID:25145376

  12. Existence of longitudinal waves in pre-stressed anisotropic elastic ...

    Indian Academy of Sciences (India)

    waves is truly longitudinal. Longitudinal wave in an anisotropic elastic medium is defined as the wave motion in which the particle motion (i.e., the. Keywords. General anisotropy; elastic stiffness; pre-stress; group velocity; ray direction; longitudinal waves; polarization. J. Earth Syst. Sci. 118, No. 6, December 2009, pp. 677– ...

  13. Characterization of Resistance to Cephus cinctus (Hymenoptera: Cephidae) in Barley Germplasm.

    Science.gov (United States)

    Varella, Andrea C; Talbert, Luther E; Achhami, Buddhi B; Blake, Nancy K; Hofland, Megan L; Sherman, Jamie D; Lamb, Peggy F; Reddy, Gadi V P; Weaver, David K

    2018-04-02

    Most barley cultivars have some degree of resistance to the wheat stem sawfly (WSS), Cephus cinctus Norton (Hymenoptera: Cephidae). Damage caused by WSS is currently observed in fields of barley grown in the Northern Great Plains, but the impact of WSS damage among cultivars due to genetic differences within the barley germplasm is not known. Specifically, little is known about the mechanisms underlying WSS resistance in barley. We characterized WSS resistance in a subset of the spring barley CAP (Coordinated Agricultural Project) germplasm panel containing 193 current and historically important breeding lines from six North American breeding programs. Panel lines were grown in WSS infested fields for two consecutive years. Lines were characterized for stem solidness, stem cutting, WSS infestation (antixenosis), larval mortality (antibiosis), and parasitism (indirect plant defense). Variation in resistance to WSS in barley was compared to observations made for solid-stemmed resistant and hollow-stemmed susceptible wheat lines. Results indicate that both antibiosis and antixenosis are involved in the resistance of barley to the WSS, but antibiosis seems to be more prevalent. Almost all of the barley lines had greater larval mortality than the hollow-stemmed wheat lines, and only a few barley lines had mortality as low as that observed in the solid-stemmed wheat line. Since barley lines lack solid stems, it is apparent that barley has a different form of antibiosis. Our results provide information for use of barley in rotation to control the WSS and may provide a basis for identification of new approaches for improving WSS resistance in wheat.

  14. Moving domain computational fluid dynamics to interface with an embryonic model of cardiac morphogenesis.

    Directory of Open Access Journals (Sweden)

    Juhyun Lee

    Full Text Available Peristaltic contraction of the embryonic heart tube produces time- and spatial-varying wall shear stress (WSS and pressure gradients (∇P across the atrioventricular (AV canal. Zebrafish (Danio rerio are a genetically tractable system to investigate cardiac morphogenesis. The use of Tg(fli1a:EGFP (y1 transgenic embryos allowed for delineation and two-dimensional reconstruction of the endocardium. This time-varying wall motion was then prescribed in a two-dimensional moving domain computational fluid dynamics (CFD model, providing new insights into spatial and temporal variations in WSS and ∇P during cardiac development. The CFD simulations were validated with particle image velocimetry (PIV across the atrioventricular (AV canal, revealing an increase in both velocities and heart rates, but a decrease in the duration of atrial systole from early to later stages. At 20-30 hours post fertilization (hpf, simulation results revealed bidirectional WSS across the AV canal in the heart tube in response to peristaltic motion of the wall. At 40-50 hpf, the tube structure undergoes cardiac looping, accompanied by a nearly 3-fold increase in WSS magnitude. At 110-120 hpf, distinct AV valve, atrium, ventricle, and bulbus arteriosus form, accompanied by incremental increases in both WSS magnitude and ∇P, but a decrease in bi-directional flow. Laminar flow develops across the AV canal at 20-30 hpf, and persists at 110-120 hpf. Reynolds numbers at the AV canal increase from 0.07±0.03 at 20-30 hpf to 0.23±0.07 at 110-120 hpf (p< 0.05, n=6, whereas Womersley numbers remain relatively unchanged from 0.11 to 0.13. Our moving domain simulations highlights hemodynamic changes in relation to cardiac morphogenesis; thereby, providing a 2-D quantitative approach to complement imaging analysis.

  15. Evaluation of potential substrates for restenosis and thrombosis in overlapped versus edge-to-edge juxtaposed bioabsorbable scaffolds: Insights from a computed fluid dynamic study.

    Science.gov (United States)

    Rigatelli, Gianluca; Zuin, Marco; Dell'Avvocata, Fabio; Cardaioli, Paolo; Vassiliev, Dobrin; Ferenc, Miroslaw; Nghia, Nguyen Tuan; Nguyen, Thach; Foin, Nicholas

    2018-04-01

    Multiple BRSs and specifically the Absorb scaffold (BVS) (Abbott Vascular, Santa Clara, CA USA) have been often used to treat long diffuse coronary artery lesions. We evaluate by a computational fluid dynamic(CFD) study the impact on the intravascular fluid rheology on multiple bioabsorbable scaffolds (BRS) by standard overlapping versus edge-to-edge technique. We simulated the treatment of a real long significant coronary lesion (>70% luminal narrowing) involving the left anterior descending artery (LAD) treated with a standard or edge-to-edge technique, respectively. Simulations were performed after BVS implantations in two different conditions: 1) Edge-to-edge technique, where the scaffolds are kissed but not overlapped resulting in a luminal encroachment of 0.015cm (150μm); 2) Standard overlapping, where the scaffolds are overlapped resulting in a luminal encroachment of 0.030cm (300μm). After positioning the BVS across the long lesion, the implantation procedure was performed in-silico following all the usual procedural steps. Analysis of the wall shear stress (WSS) suggested that at the vessel wall level the WSS were lower in the overlapping zones overlapping compared to the edge-to-edge zone (∆=0.061Pa, p=0.01). At the struts level the difference between the two WSS was more striking (∆=1.065e-004 p=0.01) favouring the edge-to-edge zone. Our study suggested that at both vessel wall and scaffold struts levels, there was lowering WSS when multiple BVS were implanted with the standard overlapping technique compared to the "edge-to-edge" technique. This lower WSS might represent a substrate for restenosis, early and late BVS thrombosis, potentially explaining at least in part the recent evidences of devices poor performance. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. A Novel Attempt to Standardize Results of CFD Simulations Basing on Spatial Configuration of Aortic Stent-Grafts.

    Directory of Open Access Journals (Sweden)

    Andrzej Polanczyk

    Full Text Available Currently, studies connected with Computational Fluid Dynamic (CFD techniques focus on assessing hemodynamic of blood flow in vessels in different conditions e.g. after stent-graft's placement. The paper propose a novel method of standardization of results obtained from calculations of stent-grafts' "pushing forces" (cumulative WSS--Wall Shear Stress, and describes its usefulness in diagnostic process. AngioCT data from 27 patients were used to reconstruct 3D geometries of stent-grafts which next were used to create respective reference cylinders. We made an assumption that both the side surface and the height of a stent-graft and a reference cylinder were equal. The proposed algorithm in conjunction with a stent-graft "pushing forces" on an implant wall, allowed us to determine which spatial configuration of a stent-graft predispose to the higher risk of its migration. For stent-grafts close to cylindrical shape (shape factor φ close to 1 WSS value was about 267 Pa, while for stent-grafts different from cylindrical shape (φ close to 2 WSS value was about 635 Pa. It was also noticed that deformation in the stent-graft's bifurcation part impaired blood flow hemodynamic. Concluding the proposed algorithm of standardization proved its usefulness in estimating the WSS values that may be useful in diagnostic process. Angular bends or tortuosity in bifurcations of an aortic implant should be considered in further studies of estimation of the risk of implantation failure.

  17. Application of geometric probability to the existence of faults in anisotropic media

    International Nuclear Information System (INIS)

    Cranwell, R.M.; Donath, F.A.

    1980-01-01

    Three primary aspects of faults which relate to their potential for degradation of a repository site are: the possibility of an existing but undetected fault intersecting the repository site; the potential for a new fault occurring and propagating through the repository site; the ability of any such fault to transmit groundwater. Given that a fault might be present in the region surrounding the site, the probability that it intersects the site depends primarily on its orientation and on the density of faulting in the area. Once these parameters are known, a model can be developed to determine the probability that an existing but undetected fault will intersect the repository site. Similar techniques can be used to estimate the potential for new faults occurring and intersecting site, or intersection from propagation along existing faults. However, additional data includng in situ stress measurements and records of seismic activity would be needed. One can estimate the stress level at which the strength in the surrounding media will be exceeded, and thus determine a time-dependent probability of movement along a pre-existing fault or of a new fault occurring, from a predicted rate of change in local stresses. In situ stress measurements taken at intervals of time could aid in determining the rate of stress change in the surrounding media, although measurable changes might not occur over the available period of observation. In situ stress measurements might also aid in assessing the ability of existing faults to transmit fluids

  18. Numerical investigation and identification of susceptible sites of atherosclerotic lesion formation in a complete coronary artery bypass model.

    Science.gov (United States)

    Zhang, Jun-Mei; Chua, Leok Poh; Ghista, Dhanjoo N; Yu, Simon Ching Man; Tan, Yong Seng

    2008-07-01

    As hemodynamics is widely believed to correlate with anastomotic stenosis in coronary bypass surgery, this paper investigates the flow characteristics and distributions of the hemodynamic parameters (HPs) in a coronary bypass model (which includes both proximal and distal anastomoses), under physiological flow conditions. Disturbed flows (flow separation/reattachment, vertical and secondary flows) as well as regions of high oscillatory shear index (OSI) with low wall shear stress (WSS), i.e., high-OSI-and-low-WSS and low-OSI-and-high-WSS were found in the proximal and distal anastomoses, especially at the toe and heel regions of distal anastomosis, which indicate highly suspected sites for the onset of the atherosclerotic lesions. The flow patterns found in the graft and distal anastomoses of our model at deceleration phases are different from those of the isolated distal anastomosis model. In addition, a huge significant difference in segmental averages of HPs was found between the distal and proximal anastomoses. These findings further suggest that intimal hyperplasia would be more prone to form in the distal anastomosis than in the proximal anastomosis, particularly along the suture line at the toe and heel of distal anastomosis.

  19. A Predictive Framework to Elucidate Venous Stenosis: CFD & Shape Optimization.

    Science.gov (United States)

    Javid Mahmoudzadeh Akherat, S M; Cassel, Kevin; Boghosian, Michael; Hammes, Mary; Coe, Fredric

    2017-07-01

    The surgical creation of vascular accesses for renal failure patients provides an abnormally high flow rate conduit in the patient's upper arm vasculature that facilitates the hemodialysis treatment. These vascular accesses, however, are very often associated with complications that lead to access failure and thrombotic incidents, mainly due to excessive neointimal hyperplasia (NH) and subsequently stenosis. Development of a framework to monitor and predict the evolution of the venous system post access creation can greatly contribute to maintaining access patency. Computational fluid dynamics (CFD) has been exploited to inspect the non-homeostatic wall shear stress (WSS) distribution that is speculated to trigger NH in the patient cohort under investigation. Thereafter, CFD in liaison with a gradient-free shape optimization method has been employed to analyze the deformation modes of the venous system enduring non-physiological hemodynamics. It is observed that the optimally evolved shapes and their corresponding hemodynamics strive to restore the homeostatic state of the venous system to a normal, pre-surgery condition. It is concluded that a CFD-shape optimization coupling that seeks to regulate the WSS back to a well-defined physiological WSS target range can accurately predict the mode of patient-specific access failure.

  20. In vivo measurement of hemodynamic information in stenosed rat blood vessels using X-ray PIV.

    Science.gov (United States)

    Park, Hanwook; Park, Jun Hong; Lee, Sang Joon

    2016-11-28

    Measurements of the hemodynamic information of blood flows, especially wall shear stress (WSS), in animal models with circulatory vascular diseases (CVDs) are important to understand the pathological mechanism of CVDs. In this study, X-ray particle image velocimetry (PIV) with high spatial resolution was applied to obtain velocity field information in stenosed blood vessels with high WSS. 3D clips fabricated with a 3D printer were applied to the abdominal aorta of a rat cadaver to induce artificial stenosis in the real blood vessel of an animal model. The velocity and WSS information of blood flows in the stenosed vessel were obtained and compared at various stenosis severities. In vivo measurement was also conducted by fastening a stenotic clip on a live rat model through surgical intervention to reduce the flow rate to match the limited temporal resolution of the present X-ray PIV system. Further improvement of the temporal resolution of the system might be able to provide in vivo measurements of hemodynamic information from animal disease models under physiological conditions. The present results would be helpful for understanding the relation between hemodynamic characteristics and the pathological mechanism in animal CVD models.

  1. The Relationship Between Pulsatile Flow Impingement and Intraluminal Thrombus Deposition in Abdominal Aortic Aneurysms.

    Science.gov (United States)

    Lozowy, Richard J; Kuhn, David C S; Ducas, Annie A; Boyd, April J

    2017-03-01

    Direct numerical simulations were performed on four patient-specific abdominal aortic aneurysm (AAA) geometries and the resulting pulsatile blood flow dynamics were compared to aneurysm shape and correlated with intraluminal thrombus (ILT) deposition. For three of the cases, turbulent vortex structures impinged/sheared along the anterior wall and along the posterior wall a zone of recirculating blood formed. Within the impingement region the AAA wall was devoid of ILT and remote to this region there was an accumulation of ILT. The high wall shear stress (WSS) caused by the impact of vortexes is thought to prevent the attachment of ILT. WSS from impingement is comparable to peak-systolic WSS in a normal-sized aorta and therefore may not damage the wall. Expansion occurred to a greater extent in the direction of jet impingement and the wall-normal force from the continuous impact of vortexes may contribute to expansion. It was shown that the impingement region has low oscillatory shear index (OSI) and recirculation zones can have either low or high OSI. No correlation could be identified between OSI and ILT deposition since different flow dynamics can have similar OSI values.

  2. Estimating the hemodynamic influence of variable main body-to-iliac limb length ratios in aortic endografts.

    Science.gov (United States)

    Georgakarakos, Efstratios; Xenakis, Antonios; Georgiadis, George S

    2018-02-01

    We conducted a computational study to assess the hemodynamic impact of variant main body-to-iliac limb length (L1/L2) ratios on certain hemodynamic parameters acting on the endograft (EG) either on the normal bifurcated (Bif) or the cross-limb (Cx) fashion. A customary bifurcated 3D model was computationally created and meshed using the commercially available ANSYS ICEM (Ansys Inc., Canonsburg, PA, USA) software. The total length of the EG, was kept constant, while the L1/L2 ratio ranged from 0.3 to 1.5 in the Bif and Cx reconstructed EG models. The compliance of the graft was modeled using a Fluid Structure Interaction method. Important hemodynamic parameters such as pressure drop along EG, wall shear stress (WSS) and helicity were calculated. The greatest pressure decrease across EG was calculated in the peak systolic phase. With increasing L1/L2 it was found that the Pressure Drop was increasing for the Cx configuration, while decreasing for the Bif. The greatest helicity (4.1 m/s2) was seen in peak systole of Cx with ratio of 1.5 whereas its greatest value (2 m/s2) was met in peak systole in the Bif with the shortest L1/L2 ratio (0.3). Similarly, the maximum WSS value was highest (2.74Pa) in the peak systole for the 1.5 L1/L2 of the Cx configuration, while the maximum WSS value equaled 2 Pa for all length ratios of the Bif modification (with the WSS found for L1/L2=0.3 being marginally higher). There was greater discrepancy in the WSS values for all L1/L2 ratios of the Cx bifurcation compared to Bif. Different L1/L2 rations are shown to have an impact on the pressure distribution along the entire EG while the length ratio predisposing to highest helicity or WSS values is also determined by the iliac limbs pattern of the EG. Since current custom-made EG solutions can reproduce variability in main-body/iliac limbs length ratios, further computational as well as clinical research is warranted to delineate and predict the hemodynamic and clinical effect of variable

  3. The influence of hemodynamic forces on biomarkers in the walls of elastase-induced aneurysms in rabbits

    Energy Technology Data Exchange (ETDEWEB)

    Kadirvel, Ramanathan; Ding, Yong-Hong; Dai, Daying; Danielson, Mark A.; Lewis, Debra A.; Cloft, Harry J.; Kallmes, David F. [Mayo Clinic College of Medicine, Department of Radiology, Rochester, MN (United States); Zakaria, Hasballah; Robertson, Anne M. [University of Pittsburgh, Department of Mechanical Engineering, Pittsburgh, PA (United States)

    2007-12-15

    Biological and biophysical factors have been shown to play an important role in the initiation, progression, and rupture of intracranial aneurysms. The purpose of this study was to evaluate the association between hemodynamic forces and markers of vascular remodeling in elastase-induced saccular aneurysms in rabbits. Elastase-induced aneurysms were created at the origin of the right common carotid artery in rabbits. Hemodynamic parameters were estimated using computational fluid dynamic simulations based on 3-D-reconstructed models of the vasculature. Expression of matrix metalloproteinases (MMPs), their inhibitors (TIMPs) and markers of vascular remodeling were measured in different spatial regions within the aneurysms. Altered expression of biological markers relative to controls was correlated with the locations of subnormal time-averaged wall shear stress (WSS) but not with the magnitude of pressure. In the aneurysms, WSS was low and expression of biological markers was significantly altered in a time-dependent fashion. At 2 weeks, an upregulation of active-MMP-2, downregulation of TIMP-1 and TIMP-2, and intact endothelium were found in aneurysm cavities. However, by 12 weeks, endothelial cells were absent or scattered, and levels of pro- and active-MMP-2 were not different from those in control arteries, but pro-MMP-9 and both TIMPs were upregulated. These results reveal a strong, spatially localized correlation between diminished WSS and differential expression of biological markers of vascular remodeling in elastase-induced saccular aneurysms. The ability of the wall to function and maintain a healthy endothelium in a low shear environment appears to be significantly impaired by chronic exposure to low WSS. (orig.)

  4. Unraveling the relationship between arterial flow and intra-aneurysmal hemodynamics.

    Science.gov (United States)

    Morales, Hernán G; Bonnefous, Odile

    2015-02-26

    Arterial flow rate affects intra-aneurysmal hemodynamics but it is not clear how their relationship is. This uncertainty hinders the comparison among studies, including clinical evaluations, like a pre- and post-treatment status, since arterial flow rates may differ at each time acquisition. The purposes of this work are as follows: (1) To study how intra-aneurysmal hemodynamics changes within the full physiological range of arterial flow rates. (2) To provide characteristic curves of intra-aneurysmal velocity, wall shear stress (WSS) and pressure as functions of the arterial flow rate. Fifteen image-based aneurysm models were studied using computational fluid dynamics (CFD) simulations. The full range of physiological arterial flow rates reported in the literature was covered by 11 pulsatile simulations. For each aneurysm, the spatiotemporal-averaged blood flow velocity, WSS and pressure were calculated. Spatiotemporal-averaged velocity inside the aneurysm linearly increases as a function of the mean arterial flow (minimum R(2)>0.963). Spatiotemporal-averaged WSS and pressure at the aneurysm wall can be represented by quadratic functions of the arterial flow rate (minimum R(2)>0.996). Quantitative characterizations of spatiotemporal-averaged velocity, WSS and pressure inside cerebral aneurysms can be obtained with respect to the arterial flow rate. These characteristic curves provide more information of the relationship between arterial flow and aneurysm hemodynamics since the full range of arterial flow rates is considered. Having these curves, it is possible to compare experimental studies and clinical evaluations when different flow conditions are used. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Numerical investigations of the unsteady blood flow in the end-to-side arteriovenous fistula for hemodialysis.

    Science.gov (United States)

    Jodko, Daniel; Obidowski, Damian; Reorowicz, Piotr; Jóźwik, Krzysztof

    2016-01-01

    The aim of this study was to investigate the blood flow in the end-to-side arteriovenous (a-v) fistula, taking into account its pulsating nature and the patient-specific geometry of blood vessels. Computational Fluid Dynamics (CFD) methods were used for this analysis. DICOM images of the fistula, obtained from the angio-computed tomography, were a source of the data applied to develop a 3D geometrical model of the fistula. The model was meshed, then the ANSYS CFX v. 15.0 code was used to perform simulations of the flow in the vessels under analysis. Mesh independence tests were conducted. The non-Newtonian rheological model of blood and the Shear Stress Transport model of turbulence were employed. Blood vessel walls were assumed to be rigid. Flow patterns, velocity fields, the volume flow rate, the wall shear stress (WSS) propagation on particular blood vessel walls were shown versus time. The maximal value of the blood velocity was identified in the anastomosis - the place where the artery is connected to the vein. The flow rate was calculated for all veins receiving blood. The blood flow in the geometrically complicated a-v fistula was simulated. The values and oscillations of the WSS are the largest in the anastomosis, much lower in the artery and the lowest in the cephalic vein. A strong influence of the mesh on the results concerning the maximal and area-averaged WSS was shown. The relation between simulations of the pulsating and stationary flow under time-averaged flow conditions was presented.

  6. Impact of Solid and Hollow Varieties of Winter and Spring Wheat on Severity of Wheat Stem Sawfly (Hymenoptera: Cephidae) Infestations and Yield and Quality of Grain.

    Science.gov (United States)

    Szczepaniec, Adrianna; Glover, Karl D; Berzonsky, William

    2015-10-01

    Wheat stem sawfly (WSS), Cephus cinctus Norton (Hymenoptera: Cephidae), has recently emerged as a key pest of wheat (Triticum aestivum L.) in the Great Plains and Canadian provinces. The expanding impact of WSS has caused considerable economic losses to wheat production. Solid-stem varieties of wheat remain the only effective measure of suppression of WSS, and the goal of this research was to test whether five solid- and hollow-stem varieties of winter and spring wheat reduce survival of WSS in South Dakota. We reported that solid-stem varieties had significantly lower numbers of WSS larvae, and this effect was especially evident when WSS infestation rates exceeded 15%. We also observed that the yield of solid-stem varieties was significantly lower than hollow-stem varieties when the abundance of WSS was low, but not when populations of WSS were relatively high. We did not observe consistent differences in grain quality between solid- and hollow-stem varieties, however, and in case of protein levels of grain, solid-stem wheat varieties performed better than hollow-stem wheat. We conclude that solid-stem varieties of wheat appear to effectively suppress WSS survival, and reduced yield of these varieties is less apparent when populations of C. cinctus are high enough to affect the yield of hollow-stem wheat. This is the first report to describe the effectiveness of solid-stem varieties of wheat on WSS in South Dakota. More research in the state is necessary before more robust conclusions can be drawn. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  7. Stress Prediction for Distributed Structural Health Monitoring Using Existing Measurements and Pattern Recognition.

    Science.gov (United States)

    Lu, Wei; Teng, Jun; Zhou, Qiushi; Peng, Qiexin

    2018-02-01

    The stress in structural steel members is the most useful and directly measurable physical quantity to evaluate the structural safety in structural health monitoring, which is also an important index to evaluate the stress distribution and force condition of structures during structural construction and service phases. Thus, it is common to set stress as a measure in steel structural monitoring. Considering the economy and the importance of the structural members, there are only a limited number of sensors that can be placed, which means that it is impossible to obtain the stresses of all members directly using sensors. This study aims to develop a stress response prediction method for locations where there are insufficent sensors, using measurements from a limited number of sensors and pattern recognition. The detailed improved aspects are: (1) a distributed computing process is proposed, where the same pattern is recognized by several subsets of measurements; and (2) the pattern recognition using the subset of measurements is carried out by considering the optimal number of sensors and number of fusion patterns. The validity and feasibility of the proposed method are verified using two examples: the finite-element simulation of a single-layer shell-like steel structure, and the structural health monitoring of the space steel roof of Shenzhen Bay Stadium; for the latter, the anti-noise performance of this method is verified by the stress measurements from a real-world project.

  8. Using ontology-based semantic similarity to facilitate the article screening process for systematic reviews.

    Science.gov (United States)

    Ji, Xiaonan; Ritter, Alan; Yen, Po-Yin

    2017-05-01

    Systematic Reviews (SRs) are utilized to summarize evidence from high quality studies and are considered the preferred source of evidence-based practice (EBP). However, conducting SRs can be time and labor intensive due to the high cost of article screening. In previous studies, we demonstrated utilizing established (lexical) article relationships to facilitate the identification of relevant articles in an efficient and effective manner. Here we propose to enhance article relationships with background semantic knowledge derived from Unified Medical Language System (UMLS) concepts and ontologies. We developed a pipelined semantic concepts representation process to represent articles from an SR into an optimized and enriched semantic space of UMLS concepts. Throughout the process, we leveraged concepts and concept relations encoded in biomedical ontologies (SNOMED-CT and MeSH) within the UMLS framework to prompt concept features of each article. Article relationships (similarities) were established and represented as a semantic article network, which was readily applied to assist with the article screening process. We incorporated the concept of active learning to simulate an interactive article recommendation process, and evaluated the performance on 15 completed SRs. We used work saved over sampling at 95% recall (WSS95) as the performance measure. We compared the WSS95 performance of our ontology-based semantic approach to existing lexical feature approaches and corpus-based semantic approaches, and found that we had better WSS95 in most SRs. We also had the highest average WSS95 of 43.81% and the highest total WSS95 of 657.18%. We demonstrated using ontology-based semantics to facilitate the identification of relevant articles for SRs. Effective concepts and concept relations derived from UMLS ontologies can be utilized to establish article semantic relationships. Our approach provided a promising performance and can easily apply to any SR topics in the

  9. Morphological, physiological and biochemical responses of camellia oleifera to low-temperature stress

    International Nuclear Information System (INIS)

    Hu, J.; Shu, Q.; Fu, S.; Wu, W.

    2016-01-01

    Camellia oleifera Abel originates from China and is high healthy effect food oil species. It is also a high additional plant in southern China and can help to keep some people of mountain area out of poverty. In recent years, climate change has been abnormal frequently. Abnormal low temperature in winter and late spring coldness may cause the hard hit to C. oleifera farmers. Freezing injury can be caused by sudden decreases in temperature in winter. However, C. oleifera varieties differ in their hardiness to low temperatures. The paper investigated cold-resistance mechanisms by determining and analyzing the morphological, physiological and biochemical characteristics of C. oleifera from eastern, western and southern Anhui, respectively. Sensitivity to low temperature was assessed via the number of leaves in spring shoots, leaf thickness, the activities of protective enzymes such as CAT, POD and SOD, and the inclusion contents of WSS, FPro, MDA, benzene-alcohol extracts and lignin. The results showed that C. oleifera varieties had different physiological and biochemical, and morphological responses to low winter temperatures. In different regions, the number of leaves, leaf thickness, WSS content, FPro content and MDA content varied from 5.2-7.8, 398.79 micro m-465.27 micro m, 23.41 mg/g-24.74 mg/g, 41.86 micro g/g-44.18 micro g/g and 10.08 micro mol/g-14.51 micro mol/g, respectively. The varieties from eastern Anhui, the leaf thickness were thicker. Meanwhile, the protective enzyme activities and inclusion contents were relatively higher. The protective enzyme activities and chemical components contents such as benzene-alcohol extract and lignin represented significantly difference (p<0.05) among three regions. In the future, for the abnormal low temperature in winter, a serious of cultivation measures such as improving the contents of WSS, FPro, benzene-alcohol extract and lignin, were taken to enhance the cold resistance of C. oleifera. The result broadens the

  10. Effects of walking in deep venous thrombosis: a new integrated solid and fluid mechanics model.

    Science.gov (United States)

    López, Josep M; Fortuny, Gerard; Puigjaner, Dolors; Herrero, Joan; Marimon, Francesc; Garcia-Bennett, Josep

    2017-05-01

    Deep venous thrombosis (DVT) is a common disease. Large thrombi in venous vessels cause bad blood circulation and pain; and when a blood clot detaches from a vein wall, it causes an embolism whose consequences range from mild to fatal. Walking is recommended to DVT patients as a therapeutical complement. In this study the mechanical effects of walking on a specific patient of DVT were simulated by means of an unprecedented integration of 3 elements: a real geometry, a biomechanical model of body tissues, and a computational fluid dynamics study. A set of computed tomography images of a patient's leg with a thrombus in the popliteal vein was employed to reconstruct a geometry model. Then a biomechanical model was used to compute the new deformed geometry of the vein as a function of the fiber stretch level of the semimembranosus muscle. Finally, a computational fluid dynamics study was performed to compute the blood flow and the wall shear stress (WSS) at the vein and thrombus walls. Calculations showed that either a lengthening or shortening of the semimembranosus muscle led to a decrease of WSS levels up to 10%. Notwithstanding, changes in blood viscosity properties or blood flow rate may easily have a greater impact in WSS. Copyright © 2016 John Wiley & Sons, Ltd.

  11. A computational fluid dynamics study on hemodynamics for different locations of the distal anastomosis of a bypass nearby a collateral vessel in the femoropopliteal area.

    Science.gov (United States)

    Rivera, J; van der Graaf, G B; Escudero, J R; Bellmunt, S; van de Vosse, F

    2014-11-01

    Revascularization of the femoropopliteal sector is often performed by the placement of a bypass. In this paper, we have studied the effects of hemodynamics on patency of the bypass for different positions of the distal anastomosis close to a collateral artery. Computational fluid dynamics (CFD) are used for this study. The cardiac cycle-averaged wall shear stress (WSS) and oscillation index (OSI) have been analyzed. Low WSS and high OSI may increase the risk of intimal hyperplasia (IH), which may reduce bypass patency. From the CFD simulations, spots of low WSS and high OSI are found within and near the entrance of the collateral artery, near the suture line, at the floor, toe, and heel. We regarded flow ratios of 20:80 and of 35:65. It is found that for the high flow ratio anastomosis located proximal to the collateral artery is clearly more advantageous. However for the low flow ratio anastomosis located distal to the collateral artery seems to be slightly more advantageous, the results are less conclusive. One of the studied flow geometries has been validated by in vitro experiments using a time resolved particle image velocimetry technique. Velocity fields from these experiments are in good agreement with the CFD results. Copyright © 2014 John Wiley & Sons, Ltd.

  12. Residual stresses

    International Nuclear Information System (INIS)

    Macherauch, E.

    1978-01-01

    Residual stresses are stresses which exist in a material without the influence of external powers and moments. They come into existence when the volume of a material constantly changes its form as a consequence of mechanical, thermal, and/or chemical processes and is hindered by neighbouring volumes. Bodies with residual stress are in mechanical balance. These residual stresses can be manifested by means of all mechanical interventions disturbing this balance. Acoustical, optical, radiological, and magnetical methods involving material changes caused by residual stress can also serve for determining residual stress. Residual stresses have an ambivalent character. In technical practice, they are feared and liked at the same time. They cause trouble because they can be the cause for unexpected behaviour of construction elements. They are feared since they can cause failure, in the worst case with catastrophical consequences. They are appreciated, on the other hand, because, in many cases, they can contribute to improvements of the material behaviour under certain circumstances. But they are especially liked for their giving convenient and (this is most important) mostly uncontrollable explanations. For only in very few cases we have enough knowledge and possibilities for the objective evaluation of residual stresses. (orig.) [de

  13. Composition of Web Services Using Wrappers

    Science.gov (United States)

    Haidar, Ali Nasrat; Abdallah, Ali E.

    Web services (WSs) compositions deal with specifying how to assemble a complex WS system from elementary services. These services can be provided on the Web by third parties as WSs, COTS, or bespoke components. Wrappers are becoming the norm for customising existing components in order to integrate them into larger WS systems. In many cases, using a component "as-is" is very unlikely to occur. A component has to be customized because of, for example, incompatibilities between the interfaces of components that need to communicate with one another, need for extra security features, or, blocking unneeded functionality. This paper presents an approach for modeling several wrapping techniques that can be used for composing WS application using Hoare's CSP process algebra.

  14. Interindividual differences in stress sensitivity: basal and stress-induced cortisol levels differentially predict neural vigilance processing under stress

    NARCIS (Netherlands)

    Henckens, Marloes J. A. G.; Klumpers, Floris; Everaerd, Daphne; Kooijman, Sabine C.; van Wingen, Guido A.; Fernández, Guillén

    2016-01-01

    Stress exposure is known to precipitate psychological disorders. However, large differences exist in how individuals respond to stressful situations. A major marker for stress sensitivity is hypothalamus-pituitary-adrenal (HPA)-axis function. Here, we studied how interindividual variance in both

  15. The co-existence of depression, anxiety and post-traumatic stress symptoms in the perinatal period: A systematic review.

    Science.gov (United States)

    Agius, Andee; Xuereb, Rita Borg; Carrick-Sen, Debbie; Sultana, Roberta; Rankin, Judith

    2016-05-01

    to identify and appraise the current international evidence regarding the presence and prevalence of the co-existence of depression, anxiety and post-traumatic stress symptoms in the antenatal and post partum period. using a list of keywords, Medline, CINHAL, Cochrane Library, EMBASE, PsychINFO, Web of Science and the Index of Theses and Conference Proceedings (Jan 1960 - Jan 2015) were systematically searched. Experts in the field were contacted to locate papers that were in progress or in press. Reference lists from relevant review articles were searched. Inclusion criteria included full papers published in English reporting concurrent depression, anxiety and post-traumatic stress symptoms in pregnant and post partum women. A validated data extraction review tool was used. 3424 citations were identified. Three studies met the full inclusion criteria. All reported findings in the postnatal period. No antenatal studies were identified. The prevalence of triple co-morbidity was relatively low ranging from 2% to 3%. triple co-morbidity does occur, although the prevalence appears to be low. Due to the presentation of complex symptoms, women with triple co-morbidity are likely to be difficult to identify, diagnose and treat. Clinical staff should be aware of the potential of complex symptomatology. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Blood flow and coherent vortices in the normal and aneurysmatic aortas: a fluid dynamical approach to intra-luminal thrombus formation.

    Science.gov (United States)

    Biasetti, Jacopo; Hussain, Fazle; Gasser, T Christian

    2011-10-07

    Abdominal aortic aneurysms (AAAs) are frequently characterized by the development of an intra-luminal thrombus (ILT), which is known to have multiple biochemical and biomechanical implications. Development of the ILT is not well understood, and shear-stress-triggered activation of platelets could be the first step in its evolution. Vortical structures (VSs) in the flow affect platelet dynamics, which motivated the present study of a possible correlation between VS and ILT formation in AAAs. VSs educed by the λ(2)-method using computational fluid dynamics simulations of the backward-facing step problem, normal aorta, fusiform AAA and saccular AAA were investigated. Patient-specific luminal geometries were reconstructed from computed tomography scans, and Newtonian and Carreau-Yasuda models were used to capture salient rheological features of blood flow. Particularly in complex flow domains, results depended on the constitutive model. VSs developed all along the normal aorta, showing that a clear correlation between VSs and high wall shear stress (WSS) existed, and that VSs started to break up during late systole. In contrast, in the fusiform AAA, large VSs developed at sites of tortuous geometry and high WSS, occupying the entire lumen, and lasting over the entire cardiac cycle. Downward motion of VSs in the AAA was in the range of a few centimetres per cardiac cycle, and with a VS burst at that location, the release (from VSs) of shear-stress-activated platelets and their deposition to the wall was within the lower part of the diseased artery, i.e. where the thickest ILT layer is typically observed. In the saccular AAA, only one VS was found near the healthy portion of the aorta, while in the aneurysmatic bulge, no VSs occurred. We present a fluid-dynamics-motivated mechanism for platelet activation, convection and deposition in AAAs that has the potential of improving our current understanding of the pathophysiology of fluid-driven ILT growth.

  17. The quantification of hemodynamic parameters downstream of a Gianturco Zenith stent wire using newtonian and non-newtonian analog fluids in a pulsatile flow environment.

    Science.gov (United States)

    Walker, Andrew M; Johnston, Clifton R; Rival, David E

    2012-11-01

    Although deployed in the vasculature to expand vessel diameter and improve blood flow, protruding stent struts can create complex flow environments associated with flow separation and oscillating shear gradients. Given the association between magnitude and direction of wall shear stress (WSS) and endothelial phenotype expression, accurate representation of stent-induced flow patterns is critical if we are to predict sites susceptible to intimal hyperplasia. Despite the number of stents approved for clinical use, quantification on the alteration of hemodynamic flow parameters associated with the Gianturco Z-stent is limited in the literature. In using experimental and computational models to quantify strut-induced flow, the majority of past work has assumed blood or representative analogs to behave as Newtonian fluids. However, recent studies have challenged the validity of this assumption. We present here the experimental quantification of flow through a Gianturco Z-stent wire in representative Newtonian and non-Newtonian blood analog environments using particle image velocimetry (PIV). Fluid analogs were circulated through a closed flow loop at physiologically appropriate flow rates whereupon PIV snapshots were acquired downstream of the wire housed in an acrylic tube with a diameter characteristic of the carotid artery. Hemodynamic parameters including WSS, oscillatory shear index (OSI), and Reynolds shear stresses (RSS) were measured. Our findings show that the introduction of the stent wire altered downstream hemodynamic parameters through a reduction in WSS and increases in OSI and RSS from nonstented flow. The Newtonian analog solution of glycerol and water underestimated WSS while increasing the spatial coverage of flow reversal and oscillatory shear compared to a non-Newtonian fluid of glycerol, water, and xanthan gum. Peak RSS were increased with the Newtonian fluid, although peak values were similar upon a doubling of flow rate. The introduction of the

  18. Identification of novel QTL for sawfly resistance in wheat

    Science.gov (United States)

    J. D. Sherman; D. K. Weaver; M. L. Hofland; S. E. Sing; M. Buteler; S. P. Lanning; Y. Naruoka; F. Crutcher; N. K. Blake; J. M. Martin; P. F. Lamb; G. R. Carlson; L. E. Talbert

    2010-01-01

    The wheat stem sawfly (WSS) (Cephus cinctus Nort.) is an important pest of wheat (Triticum aestivum L. em. Thell.) in the Northern Great Plains. This paper reports the genetic analysis of antixenosis for egg-laying WSS females in recombinant inbred lines (RIL) of hard red spring wheat. Female WSS preferentially choose certain wheat genotypes for egg-laying, with the...

  19. Evaluation of the Patient Effective Dose in Whole Spine Scanography Based on the Automatic Image Pasting Method for Digital Radiography

    International Nuclear Information System (INIS)

    Kim, Jung-Su; Yoon, Sang-Wook; Seo, Deok-Nam; Nam, So-Ra; Kim, Jung-Min

    2016-01-01

    Whole spine scanography (WSS) is a radiologic examination that requires whole body X-ray exposure. Consequently, the amount of patient radiation exposure is higher than the radiation dose following routine X-ray examination. Several studies have evaluated the patient effective dose (ED) following single exposure film-screen WSS. The objective of this study was to evaluate patient ED during WSS, based on the automatic image pasting method for multiple exposure digital radiography (APMDR). Further, the calculated EDs were compared with the results of previous studies involving single exposure film-screen WSS. We evaluated the ED of 50 consecutive patients (M:F = 28:22) who underwent WSS using APMDR. The anterior-posterior (AP) and lateral (LAT) projection EDs were evaluated based on the Monte Carlo simulation. Using APMDR, the mean number of exposures was 6.1 for AP and 6.5 for LAT projections. LAT projections required more exposures (6.55%) than AP projections. The mean ED was 0.6276 mSv (AP) and 0.6716 mSv (LAT). The mean ED for LAT projections was 0.6061 mSv in automatic exposure control (AEC) and 0.7694 mSv in manual mode. The relationship between dose-area-product (DAP) and ED revealed a proportional correlation (AP, R 2 = 0.943; LAT, R 2 = 0.773). Compared to prior research involving single exposure screen-film WSS, the patient ED following WSS using APMDR was lower on AP than on LAT projections. Despite multiple exposures, ED control is more effective if WSS is performed using APMDR in the AEC mode

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

    Science.gov (United States)

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

    2016-01-01

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

  1. Experimental investigation of the flow of a blood analogue fluid in a replica of a bifurcated small artery.

    Science.gov (United States)

    Anastasiou, A D; Spyrogianni, A S; Koskinas, K C; Giannoglou, G D; Paras, S V

    2012-03-01

    The scope of this work is to study the pulsatile flow of a blood mimicking fluid in a micro channel that simulates a bifurcated small artery, in which the Fahraeus-Lindqvist effect is insignificant. An aqueous glycerol solution with small amounts of xanthan gum was used for simulating viscoelastic properties of blood and in vivo flow conditions were reproduced. Local flow velocities were measured using micro Particle Image Velocimetry (μ-PIV). From the measured velocity distributions, the wall shear stress (WSS) and its variation during a pulse were estimated. The Reynolds numbers employed are relatively low, i.e. similar to those prevailing during blood flow in small arteries. Experiments both with a Newtonian and a non-Newtonian fluid (having asymptotic viscosity equal to the viscosity of the Newtonian one) proved that the common assumption that blood behaves as a Newtonian fluid is not valid for blood flow in small arteries. It was also shown that the outer wall of the bifurcation, which is exposed to a lower WSS, is more predisposed to atherosclerotic plaque formation. Moreover, this region in small vessels is shorter than the one in large arteries, as the developed secondary flow decays faster. Finally, the WSS values in small arteries were found to be lower than those in large ones. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

  2. Hemodynamic alterations after stent implantation in 15 cases of intracranial aneurysm.

    Science.gov (United States)

    Wang, Chao; Tian, Zhongbin; Liu, Jian; Jing, Linkai; Paliwal, Nikhil; Wang, Shengzhang; Zhang, Ying; Xiang, Jianping; Siddiqui, Adnan H; Meng, Hui; Yang, Xinjian

    2016-04-01

    Stent-assisted coiling technology has been widely used in the treatment of intracranial aneurysms. In the current study, we investigated the intra-aneurysmal hemodynamic alterations after stent implantation and their association with the aneurysm location. We first retrospectively studied 15 aneurysm cases [8 internal carotid artery-ophthalmic artery (ICA-OphA) aneurysms and 7 posterior communicating artery (PcoA) aneurysms] treated with Enterprise stents and coils. Then, based on the patient-specific geometries before and after stenting, we built virtual stenting computational fluid dynamics (CFD) simulation models. Before and after the stent deployment, the average wall shear stress (WSS) on the aneurysmal sac at systolic peak changed from 7.04 Pa (4.14 Pa, 15.77 Pa) to 6.04 Pa (3.86 Pa, 11.13 Pa), P = 0.001; the spatially averaged flow velocity in the perpendicular plane of the aneurysm dropped from 0.5 m/s (0.28 m/s, 0.7 m/s) to 0.33 m/s (0.25 m/s, 0.49 m/s), P = 0.001, respectively. Post stent implantation, the WSS in ICA-OphA aneurysms and PcoA aneurysms decreased by 14.4 % (P = 0.012) and 16.6 % (P = 0.018), respectively, and the flow velocity also reduced by 10.3 % (P = 0.029) and 10.5 % (P = 0.013), respectively. Changes in the WSS, flow velocity, and pressure were not significantly different between ICA-OphA and PcoA aneurysms (P > 0.05). Stent implantation did not significantly change the peak systolic pressure in either aneurysm type. After the stent implantation, both the intra-aneurysmal flow velocity and WSS decreased independently of aneurysm type (ICA-OphA and PcoA). Little change was observed in peak systolic pressure.

  3. Morphological and hemodynamic analysis of mirror posterior communicating artery aneurysms.

    Directory of Open Access Journals (Sweden)

    Jinyu Xu

    Full Text Available BACKGROUND AND PURPOSE: Hemodynamic factors are commonly believed to play an important role in the pathogenesis, progression, and rupture of cerebral aneurysms. In this study, we aimed to identify significant hemodynamic and morphological parameters that discriminate intracranial aneurysm rupture status using 3-dimensional-angiography and computational fluid dynamics technology. MATERIALS AND METHODS: 3D-DSA was performed in 8 patients with mirror posterior communicating artery aneurysms (Pcom-MANs. Each pair was divided into ruptured and unruptured groups. Five morphological and three hemodynamic parameters were evaluated for significance with respect to rupture. RESULTS: The normalized mean wall shear stress (WSS of the aneurysm sac in the ruptured group was significantly lower than that in the unruptured group (0.52±0.20 versus 0.81±0.21, P = .012. The percentage of the low WSS area in the ruptured group was higher than that in the unruptured group (4.11±4.66% versus 0.02±0.06%, P = .018. The AR was 1.04±0.21 in the ruptured group, which was significantly higher than 0.70±0.17 in the unruptured group (P = .012. By contrast, parameters that had no significant differences between the two groups were OSI (P = .674, aneurysm size (P = .327, size ratio (P = .779, vessel angle (P = 1.000 and aneurysm inclination angle (P = 1.000. CONCLUSIONS: Pcom-MANs may be a useful disease model to investigate possible causes of aneurysm rupture. The ruptured aneurysms manifested lower WSS, higher percentage of low WSS area, and higher AR, compared with the unruptured one. And hemodynamics is as important as morphology in discriminating aneurysm rupture status.

  4. Numerical analysis of the effect of turbulence transition on the hemodynamic parameters in human coronary arteries.

    Science.gov (United States)

    Mahalingam, Arun; Gawandalkar, Udhav Ulhas; Kini, Girish; Buradi, Abdulrajak; Araki, Tadashi; Ikeda, Nobutaka; Nicolaides, Andrew; Laird, John R; Saba, Luca; Suri, Jasjit S

    2016-06-01

    Local hemodynamics plays an important role in atherogenesis and the progression of coronary atherosclerosis disease (CAD). The primary biological effect due to blood turbulence is the change in wall shear stress (WSS) on the endothelial cell membrane, while the local oscillatory nature of the blood flow affects the physiological changes in the coronary artery. In coronary arteries, the blood flow Reynolds number ranges from few tens to several hundreds and hence it is generally assumed to be laminar while calculating the WSS calculations. However, the pulsatile blood flow through coronary arteries under stenotic condition could result in transition from laminar to turbulent flow condition. In the present work, the onset of turbulent transition during pulsatile flow through coronary arteries for varying degree of stenosis (i.e., 0%, 30%, 50% and 70%) is quantitatively analyzed by calculating the turbulent parameters distal to the stenosis. Also, the effect of turbulence transition on hemodynamic parameters such as WSS and oscillatory shear index (OSI) for varying degree of stenosis is quantified. The validated transitional shear stress transport (SST) k-ω model used in the present investigation is the best suited Reynolds averaged Navier-Stokes turbulence model to capture the turbulent transition. The arterial wall is assumed to be rigid and the dynamic curvature effect due to myocardial contraction on the blood flow has been neglected. Our observations shows that for stenosis 50% and above, the WSSavg, WSSmax and OSI calculated using turbulence model deviates from laminar by more than 10% and the flow disturbances seems to significantly increase only after 70% stenosis. Our model shows reliability and completely validated. Blood flow through stenosed coronary arteries seems to be turbulent in nature for area stenosis above 70% and the transition to turbulent flow begins from 50% stenosis.

  5. Annual Site Environmental Report (ASER 1999)

    Energy Technology Data Exchange (ETDEWEB)

    Holden, Gene

    2000-08-28

    In CY99, SLAC operated under the Work Smart Standards (WSS) Set, which are incorporated in SLAC's Management and Operating contract. The WSS Set includes all applicable statutory and regulatory requirements for public and worker safety and environmental protection. The WSS Set also includes a number of industry standards that were found to be necessary to control specific hazards present at SLAC.

  6. Comparative Computed Flow Dynamic Analysis of Different Optimization Techniques in Left Main Either Provisional or Culotte Stenting.

    Science.gov (United States)

    Rigatelli, Gianluca; Dell'Avvocata, Fabio; Zuin, Marco; Giatti, Sara; Duong, Khanh; Pham, Trung; Tuan, Nguyen Si; Vassiliev, Dobrin; Daggubati, Ramesh; Nguyen, Thach

    2017-12-01

    Provisional and culotte are the most commonly used techniques in left main (LM) stenting. The impact of different post-dilation techniques on fluid dynamic of LM bifurcation has not been yet investigated. The aim of this study is to evaluate, by means of computational fluid dynamic analysis (CFD), the impact of different post-dilation techniques including proximal optimization technique (POT), kissing balloon (KB), POT-Side-POT and POT-KB-POT, 2-steps Kissing (2SK) and Snuggle Kissing balloon (SKB) on flow dynamic profile after LM provisional or culotte stenting. We considered an LM-LCA-LCX bifurcation reconstructed after reviewing 100 consecutive patients (mean age 71.4 ± 9.3 years, 49 males) with LM distal disease. The diameters of LAD and LCX were modelled according to the Finnet's law as following: LM 4.5 mm, LAD 3.5 mm, LCX 2.75 mm, with bifurcation angle set up at 55°. Xience third-generation stent (Abbot Inc., USA) was reconstructed and virtually implanted in provisional/cross-over and culotte fashion. POT, KB, POT-side-POT, POT-KB-POT, 2SK and SKB were virtually applied and analyzed in terms of the wall shear stress (WSS). Analyzing the provisional stenting, the 2SK and KB techniques had a statistically significant lower impact on the WSS at the carina, while POT seemed to obtain a neutral effect. In the wall opposite to the carina, the more physiological profile has been obtained by KB and POT with higher WSS value and smaller surface area of the lower WSS. In culotte stenting, at the carina, POT-KB-POT and 2SK had a very physiological profile; while at the wall opposite to the carina, 2SK and POT-KB-POT decreased significantly the surface area of the lower WSS compared to the other techniques. From the fluid dynamic point of view in LM provisional stenting, POT, 2SK and KB showed a similar beneficial impact on the bifurcation rheology, while in LM culotte stenting, POT-KB-POT and 2SK performed slightly better than the other techniques, probably

  7. Hemodynamics in Transplant Renal Artery Stenosis and its Alteration after Stent Implantation Based on a Patient-specific Computational Fluid Dynamics Model

    Science.gov (United States)

    Wang, Hong-Yang; Liu, Long-Shan; Cao, Hai-Ming; Li, Jun; Deng, Rong-Hai; Fu, Qian; Zhang, Huan-Xi; Fei, Ji-Guang; Wang, Chang-Xi

    2017-01-01

    Background: Accumulating studies on computational fluid dynamics (CFD) support the involvement of hemodynamic factors in artery stenosis. Based on a patient-specific CFD model, the present study aimed to investigate the hemodynamic characteristics of transplant renal artery stenosis (TRAS) and its alteration after stent treatment. Methods: Computed tomography angiography (CTA) data of kidney transplant recipients in a single transplant center from April 2013 to November 2014 were reviewed. The three-dimensional geometry of transplant renal artery (TRA) was reconstructed from the qualified CTA images and categorized into three groups: the normal, stenotic, and stented groups. Hemodynamic parameters including pressure distribution, velocity, wall shear stress (WSS), and mass flow rate (MFR) were extracted. The data of hemodynamic parameters were expressed as median (interquartile range), and Mann–Whitney U-test was used for analysis. Results: Totally, 6 normal, 12 stenotic, and 6 stented TRAs were included in the analysis. TRAS presented nonuniform pressure distribution, adverse pressure gradient across stenosis throat, flow vortex, and a separation zone at downstream stenosis. Stenotic arteries had higher maximal velocity and maximal WSS (2.94 [2.14, 3.30] vs. 1.06 [0.89, 1.15] m/s, 256.5 [149.8, 349.4] vs. 41.7 [37.8, 45.3] Pa at end diastole, P = 0.001; 3.25 [2.67, 3.56] vs. 1.65 [1.18, 1.72] m/s, 281.3 [184.3, 364.7] vs. 65.8 [61.2, 71.9] Pa at peak systole, P = 0.001) and lower minimal WSS and MFRs (0.07 [0.03, 0.13] vs. 0.52 [0.45, 0.67] Pa, 1.5 [1.0, 3.0] vs. 11.0 [8.0, 11.3] g/s at end diastole, P = 0.001; 0.08 [0.03, 0.19] vs. 0.70 [0.60, 0.81] Pa, 2.0 [1.3, 3.3] vs. 16.5 [13.0, 20.3] g/s at peak systole, P = 0.001) as compared to normal arteries. Stent implantation ameliorated all the alterations of the above hemodynamic factors except low WSS. Conclusions: Hemodynamic factors were significantly changed in severe TRAS. Stent implantation can restore or

  8. Hemodynamics in Transplant Renal Artery Stenosis and its Alteration after Stent Implantation Based on a Patient-specific Computational Fluid Dynamics Model.

    Science.gov (United States)

    Wang, Hong-Yang; Liu, Long-Shan; Cao, Hai-Ming; Li, Jun; Deng, Rong-Hai; Fu, Qian; Zhang, Huan-Xi; Fei, Ji-Guang; Wang, Chang-Xi

    Accumulating studies on computational fluid dynamics (CFD) support the involvement of hemodynamic factors in artery stenosis. Based on a patient-specific CFD model, the present study aimed to investigate the hemodynamic characteristics of transplant renal artery stenosis (TRAS) and its alteration after stent treatment. Computed tomography angiography (CTA) data of kidney transplant recipients in a single transplant center from April 2013 to November 2014 were reviewed. The three-dimensional geometry of transplant renal artery (TRA) was reconstructed from the qualified CTA images and categorized into three groups: the normal, stenotic, and stented groups. Hemodynamic parameters including pressure distribution, velocity, wall shear stress (WSS), and mass flow rate (MFR) were extracted. The data of hemodynamic parameters were expressed as median (interquartile range), and Mann-Whitney U-test was used for analysis. Totally, 6 normal, 12 stenotic, and 6 stented TRAs were included in the analysis. TRAS presented nonuniform pressure distribution, adverse pressure gradient across stenosis throat, flow vortex, and a separation zone at downstream stenosis. Stenotic arteries had higher maximal velocity and maximal WSS (2.94 [2.14, 3.30] vs. 1.06 [0.89, 1.15] m/s, 256.5 [149.8, 349.4] vs. 41.7 [37.8, 45.3] Pa at end diastole, P= 0.001; 3.25 [2.67, 3.56] vs. 1.65 [1.18, 1.72] m/s, 281.3 [184.3, 364.7] vs. 65.8 [61.2, 71.9] Pa at peak systole, P= 0.001) and lower minimal WSS and MFRs (0.07 [0.03, 0.13] vs. 0.52 [0.45, 0.67] Pa, 1.5 [1.0, 3.0] vs. 11.0 [8.0, 11.3] g/s at end diastole, P= 0.001; 0.08 [0.03, 0.19] vs. 0.70 [0.60, 0.81] Pa, 2.0 [1.3, 3.3] vs. 16.5 [13.0, 20.3] g/s at peak systole, P= 0.001) as compared to normal arteries. Stent implantation ameliorated all the alterations of the above hemodynamic factors except low WSS. Hemodynamic factors were significantly changed in severe TRAS. Stent implantation can restore or ameliorate deleterious change of hemodynamic

  9. The Effect of Inlet Waveforms on Computational Hemodynamics of Patient-Specific Intracranial Aneurysms

    OpenAIRE

    Xiang, J.; Siddiqui, A.H.; Meng, H.

    2014-01-01

    Due to the lack of patient-specific inlet flow waveform measurements, most computational fluid dynamics (CFD) simulations of intracranial aneurysms usually employ waveforms that are not patient-specific as inlet boundary conditions for the computational model. The current study examined how this assumption affects the predicted hemodynamics in patient-specific aneurysm geometries. We examined wall shear stress (WSS) and oscillatory shear index (OSI), the two most widely studied hemodynamic qu...

  10. Evaluating the roles of detailed endocardial structures on right ventricular haemodynamics by means of CFD simulations.

    Science.gov (United States)

    Sacco, Federica; Paun, Bruno; Lehmkuhl, Oriol; Iles, Tinen L; Iaizzo, Paul A; Houzeaux, Guillaume; Vázquez, Mariano; Butakoff, Constantine; Aguado-Sierra, Jazmin

    2018-06-11

    Computational modelling plays an important role in right ventricular (RV) haemodynamic analysis. However, current approaches employ smoothed ventricular anatomies. The aim of this study is to characterise RV haemodynamics including detailed endocardial structures like trabeculae, moderator band and papillary muscles (PMs). Four paired detailed and smoothed RV endocardium models (two male and two female) were reconstructed from ex-vivo human hearts high-resolution magnetic resonance images (MRI). Detailed models include structures with ≥1 mm 2 cross-sectional area. Haemodynamic characterisation was done by computational fluid dynamics (CFD) simulations with steady and transient inflows, using high performance computing (HPC). The differences between the flows in smoothed and detailed models were assessed using Q-criterion for vorticity quantification, the pressure drop between inlet and outlet, and the wall shear stress (WSS). Results demonstrated that detailed endocardial structures increase the degree of intra-ventricular pressure drop, decrease the WSS and disrupt the dominant vortex creating secondary small vortices. Increasingly turbulent blood flow was observed in the detailed RVs. Female RVs were less trabeculated and presented lower pressure drops than the males. In conclusion, neglecting endocardial structures in RV haemodynamic models may lead to inaccurate conclusions about the pressures, stresses, and blood flow behaviour in the cavity. This article is protected by copyright. All rights reserved.

  11. Functional expression and characterization of five wax ester synthases in Saccharomyces cerevisiae and their utility for biodiesel production

    Directory of Open Access Journals (Sweden)

    Shi Shuobo

    2012-02-01

    Full Text Available Abstract Background Wax ester synthases (WSs can synthesize wax esters from alcohols and fatty acyl coenzyme A thioesters. The knowledge of the preferred substrates for each WS allows the use of yeast cells for the production of wax esters that are high-value materials and can be used in a variety of industrial applications. The products of WSs include fatty acid ethyl esters, which can be directly used as biodiesel. Results Here, heterologous WSs derived from five different organisms were successfully expressed and evaluated for their substrate preference in Saccharomyces cerevisiae. We investigated the potential of the different WSs for biodiesel (that is, fatty acid ethyl esters production in S. cerevisiae. All investigated WSs, from Acinetobacter baylyi ADP1, Marinobacter hydrocarbonoclasticus DSM 8798, Rhodococcus opacus PD630, Mus musculus C57BL/6 and Psychrobacter arcticus 273-4, have different substrate specificities, but they can all lead to the formation of biodiesel. The best biodiesel producing strain was found to be the one expressing WS from M. hydrocarbonoclasticus DSM 8798 that resulted in a biodiesel titer of 6.3 mg/L. To further enhance biodiesel production, acetyl coenzyme A carboxylase was up-regulated, which resulted in a 30% increase in biodiesel production. Conclusions Five WSs from different species were functionally expressed and their substrate preference characterized in S. cerevisiae, thus constructing cell factories for the production of specific kinds of wax ester. WS from M. hydrocarbonoclasticus showed the highest preference for ethanol compared to the other WSs, and could permit the engineered S. cerevisiae to produce biodiesel.

  12. Hemodynamic and Anatomic Predictors of Renovisceral Stent-Graft Occlusion Following Chimney Endovascular Repair of Juxtarenal Aortic Aneurysms.

    Science.gov (United States)

    Tricarico, Rosamaria; He, Yong; Laquian, Liza; Scali, Salvatore T; Tran-Son-Tay, Roger; Beck, Adam W; Berceli, Scott A

    2017-12-01

    To identify anatomic and hemodynamic changes associated with impending visceral chimney stent-graft occlusion after endovascular aneurysm repair (EVAR) with the chimney technique (chEVAR). A retrospective evaluation was performed of computed tomography scans from 41 patients who underwent juxtarenal chEVAR from 2008 to 2012 to identify stent-grafts demonstrating conformational changes following initial placement. Six subjects (mean age 74 years; 3 men) were selected for detailed reconstruction and computational hemodynamic analysis; 4 had at least 1 occluded chimney stent-graft. This subset of repairs was systematically analyzed to define the anatomic and hemodynamic impact of these changes and identify signature patterns associated with impending renovisceral stent-graft occlusion. Spatial and temporal analyses of cross-sectional area, centerline angle, intraluminal pressure, and wall shear stress (WSS) were performed within the superior mesenteric and renal artery chimney grafts used for repair. Conformational changes in the chimney stent-grafts and associated perturbations, in both local WSS and pressure, were responsible for the 5 occlusions in the 13 stented branches. Anatomic and hemodynamic signatures leading to occlusion were identified within 1 month postoperatively, with a lumen area 25 Pa/mm (p=0.03), and systolic WSS >45 Pa (p=0.03) associated with future chimney stent-graft occlusion. Chimney stent-grafts at increased risk for occlusion demonstrated anatomic and hemodynamic signatures within 1 month of juxtarenal chEVAR. Analysis of these parameters in the early postoperative period may be useful for identifying and remediating these high-risk stent-grafts.

  13. Hemodynamics in stented vertebral artery ostial stenosis based on computational fluid dynamics simulations.

    Science.gov (United States)

    Qiao, Aike; Dai, Xuan; Niu, Jing; Jiao, Liqun

    2016-01-01

    Hemodynamic factors may affect the potential occurrence of in-stent restenosis (ISR) after intervention procedure of vertebral artery ostial stenosis (VAOS). The purpose of the present study is to investigate the influence of stent protrusion length in implantation strategy on the local hemodynamics of the VAOS. CTA images of a 58-year-old female patient with posterior circulation transient ischemic attack were used to perform a 3D reconstruction of the vertebral artery. Five models of the vertebral artery before and after the stent implantation were established. Model 1 was without stent implantation, Model 2-5 was with stent protruding into the subclavian artery for 0, 1, 2, 3 mm, respectively. Computational fluid dynamics simulations based on finite element analysis were employed to mimic the blood flow in arteries and to assess hemodynamic conditions, particularly the blood flow velocity and wall shear stress (WSS). The WSS and the blood flow velocity at the vertebral artery ostium were reduced by 85.33 and 35.36% respectively after stents implantation. The phenomenon of helical flow disappeared. Hemodynamics comparison showed that stent struts that protruded 1 mm into the subclavian artery induced the least decrease in blood speed and WSS. The results suggest that stent implantation can improve the hemodynamics of VAOS, while stent struts that had protruded 1 mm into the subclavian artery would result in less thrombogenesis and neointimal hyperplasia and most likely decrease the risk of ISR.

  14. Concentration polarization effects on the macromolecular transport in the presence of non-uniform magnetic field: A numerical study using a lumen-wall model

    Energy Technology Data Exchange (ETDEWEB)

    Mohammadpourfard, M., E-mail: Mohammadpour@azaruniv.edu [Department of Mechanical Engineering, Azarbaijan Shahid Madani University, Tabriz 53751-71379 (Iran, Islamic Republic of); Aminfar, H., E-mail: hh_aminfar@tabrizu.ac.ir [Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of); Khajeh, K., E-mail: khajeh.k.2005@gmail.com [Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of)

    2014-04-01

    In this paper, the concentration polarization phenomena in a two dimensional tube under steady state conditions containing ferrofluid (blood and 4 vol% Fe{sub 3}O{sub 4}) is reported in the presence of non-uniform magnetic field. Lumen-wall model has been used for solving the mass transport equation. Hemodynamics parameters such as flow rate, viscosity, wall shear stress (WSS) and the macromolecules surface concentration which accumulate on the blood vessel wall, influenced the formation and progression of atherosclerosis disease. Effective parameters on the low density lipoprotein (LDL) surface concentration (LSC) such as: the wall filtration velocity, inlet Reynolds number and WSS under applied non-uniform magnetic field have been examined. Numerical solution of governing equations of the flow field have been obtained by using the single-phase model and the control volume technique. Magnetic field is generated by an electric current going through a thin and straight wire oriented perpendicular to the tube. Results show WSS in the vicinity of magnetic field source increased and LSC decreased along the wall. - Highlights: • In this paper the concentration polarization phenomena of blood flow is reported in the presence of non-uniform magnetic field. • In presence of non-uniform magnetic field LSC will decrease along the wall due to the increasing the velocity gradients near the magnetic source. • When non-uniform magnetic field intensity increases, LSC along the wall becomes lower. • Non-uniform magnetic field can affects the flow more in low Reynolds numbers.

  15. Consumers’ Preferences and Derived Willingness-to-Pay for Water Supply Safety Improvement: The Analysis of Pricing and Incentive Strategies

    Directory of Open Access Journals (Sweden)

    Jia Wang

    2018-05-01

    Full Text Available With increasing water supply accidents and higher water demand, urban water supply safety (WSS remains a crucial public policy issue in developing countries. The purpose of this paper is to investigate consumers’ willingness-to-pay (WTP and their preferences to improve WSS in China, to support governments in water regulation policy design and water providers in investment-decisions. A discrete choice experiment method with the consideration of not only attributes of WSS but also attitudinal and demographic variables have been adopted to assess consumers’ WTP and preferences for WSS improvement. The results show that Chinese urban residents are willing to pay a significantly higher price for improved WSS. Demonstrated marginal mean WTP for the change of the attributes range from 0.18 RMB/m3 (0.03 USD/m3 (1 RMB was around 0.154 USD in 2016 for decreased water supply interruption to 2.33 Yuan RMB/m3 (0.35 USD/m3 for improved drinking water quality. Investments in water processing facilities and water distribution networks should come first. Cross-subsidy concerning different developing districts is the most efficient policy instrument. The study contributes to the recent literature not only by introducing attitudinal variables in choice experiment survey in water supply field, but also by revealing the correlation of choice modeling applications in WSS improvement programs.

  16. [Complex posttraumatic stress disorder].

    Science.gov (United States)

    Green, Tamar; Kotler, Moshe

    2007-11-01

    The characteristic symptoms resulting from exposure to an extreme trauma include three clusters of symptoms: persistent experience of the traumatic event, persistent avoidance of stimuli associated with the trauma and persistent symptoms of increased arousal. Beyond the accepted clusters of symptoms for posttraumatic stress disorder exists a formation of symptoms related to exposure to extreme or prolonged stress e.g. childhood abuse, physical violence, rape, and confinement within a concentration camp. With accumulated evidence of the existence of these symptoms began a trail to classify a more complex syndrome, which included, but was not confined to the symptoms of posttraumatic stress disorder. This review addresses several subjects for study in complex posttraumatic stress disorder, which is a complicated and controversial topic. Firstly, the concept of complex posttraumatic stress disorder is presented. Secondly, the professional literature relevant to this disturbance is reviewed and finally, the authors present the polemic being conducted between the researchers of posttraumatic disturbances regarding validity, reliability and the need for separate diagnosis for these symptoms.

  17. Investigation of pulsatile flowfield in healthy thoracic aorta models.

    Science.gov (United States)

    Wen, Chih-Yung; Yang, An-Shik; Tseng, Li-Yu; Chai, Jyh-Wen

    2010-02-01

    Cardiovascular disease is the primary cause of morbidity and mortality in the western world. Complex hemodynamics plays a critical role in the development of aortic dissection and atherosclerosis, as well as many other diseases. Since fundamental fluid mechanics are important for the understanding of the blood flow in the cardiovascular circulatory system of the human body aspects, a joint experimental and numerical study was conducted in this study to determine the distributions of wall shear stress and pressure and oscillatory WSS index, and to examine their correlation with the aortic disorders, especially dissection. Experimentally, the Phase-Contrast Magnetic Resonance Imaging (PC-MRI) method was used to acquire the true geometry of a normal human thoracic aorta, which was readily converted into a transparent thoracic aorta model by the rapid prototyping (RP) technique. The thoracic aorta model was then used in the in vitro experiments and computations. Simulations were performed using the computational fluid dynamic (CFD) code ACE+((R)) to determine flow characteristics of the three-dimensional, pulsatile, incompressible, and Newtonian fluid in the thoracic aorta model. The unsteady boundary conditions at the inlet and the outlet of the aortic flow were specified from the measured flowrate and pressure results during in vitro experiments. For the code validation, the predicted axial velocity reasonably agrees with the PC-MRI experimental data in the oblique sagittal plane of the thoracic aorta model. The thorough analyses of the thoracic aorta flow, WSSs, WSS index (OSI), and wall pressures are presented. The predicted locations of the maxima of WSS and the wall pressure can be then correlated with that of the thoracic aorta dissection, and thereby may lead to a useful biological significance. The numerical results also suggest that the effects of low WSS and high OSI tend to cause wall thickening occurred along the inferior wall of the aortic arch and the

  18. Stress Assignment in Reading Italian Polysyllabic Pseudowords

    Science.gov (United States)

    Sulpizio, Simone; Arduino, Lisa S.; Paizi, Despina; Burani, Cristina

    2013-01-01

    In 4 naming experiments we investigated how Italian readers assign stress to pseudowords. We assessed whether participants assign stress following distributional information such as stress neighborhood (the proportion and number of existent words sharing orthographic ending and stress pattern) and whether such distributional information affects…

  19. Lattice Boltzmann Model of 3D Multiphase Flow in Artery Bifurcation Aneurysm Problem

    Directory of Open Access Journals (Sweden)

    Aizat Abas

    2016-01-01

    Full Text Available This paper simulates and predicts the laminar flow inside the 3D aneurysm geometry, since the hemodynamic situation in the blood vessels is difficult to determine and visualize using standard imaging techniques, for example, magnetic resonance imaging (MRI. Three different types of Lattice Boltzmann (LB models are computed, namely, single relaxation time (SRT, multiple relaxation time (MRT, and regularized BGK models. The results obtained using these different versions of the LB-based code will then be validated with ANSYS FLUENT, a commercially available finite volume- (FV- based CFD solver. The simulated flow profiles that include velocity, pressure, and wall shear stress (WSS are then compared between the two solvers. The predicted outcomes show that all the LB models are comparable and in good agreement with the FVM solver for complex blood flow simulation. The findings also show minor differences in their WSS profiles. The performance of the parallel implementation for each solver is also included and discussed in this paper. In terms of parallelization, it was shown that LBM-based code performed better in terms of the computation time required.

  20. Estimating the Reactivation Potential of Pre-Existing Fractures in Subsurface Granitoids from Outcrop Analogues and in-Situ Stress Modeling: Implications for EGS Reservoir Stimulation with an Example from Thuringia (Central Germany)

    Science.gov (United States)

    Kasch, N.; Ustaszewski, K. M.; Siegburg, M.; Navabpour, P.; Hesse, G.

    2014-12-01

    The Mid-German Crystalline Rise (MGCR) in Thuringia (central Germany) is part of the European Variscan orogen and hosts large extents of Visean granites (c. 350 Ma), locally overlain by up to 3 km of Early Permian to Mid-Triassic volcanic and sedimentary rocks. A geothermal gradient of 36°C km-1 suggests that such subsurface granites form an economically viable hot dry rock reservoir at > 4 km depth. In order to assess the likelihood of reactivating any pre-existing fractures during hydraulic reservoir stimulation, slip and dilation tendency analyses (Morris et al. 1996) were carried out. For this purpose, we determined orientations of pre-existing fractures in 14 granite exposures along the southern border fault of an MGCR basement high. Additionally, the strike of 192 Permian magmatic dikes affecting the granite was considered. This analysis revealed a prevalence of NW-SE-striking fractures (mainly joints, extension veins, dikes and subordinately brittle faults) with a maximum at 030/70 (dip azimuth/dip). Borehole data and earthquake focal mechanisms reveal a maximum horizontal stress SHmax trending N150°E and a strike-slip regime. Effective in-situ stress magnitudes at 4.5 km depth, assuming hydrostatic conditions and frictional equilibrium along pre-existing fractures with a friction coefficient of 0.85 yielded 230 and 110 MPa for SHmax and Shmin, respectively. In this stress field, fractures with the prevailing orientations show a high tendency of becoming reactivated as dextral strike-slip faults if stimulated hydraulically. To ensure that a stimulation well creates fluid connectivity on a reservoir volume as large as possible rather than dissipating fluids along existing fractures, it should follow a trajectory at the highest possible angle to the orientation of prevailing fractures, i.e. subhorizontal and NE-SW-oriented. References: Morris, A., D. A. Ferrill, and D. B. Henderson (1996), Slip-tendency analysis and fault reactivation, Geology, 24, 275-278.

  1. Surgical Stress Abrogates Pre-Existing Protective T Cell Mediated Anti-Tumor Immunity Leading to Postoperative Cancer Recurrence.

    Directory of Open Access Journals (Sweden)

    Abhirami A Ananth

    Full Text Available Anti-tumor CD8+ T cells are a key determinant for overall survival in patients following surgical resection for solid malignancies. Using a mouse model of cancer vaccination (adenovirus expressing melanoma tumor-associated antigen (TAA-dopachrome tautomerase (AdDCT and resection resulting in major surgical stress (abdominal nephrectomy, we demonstrate that surgical stress results in a reduction in the number of CD8+ T cell that produce cytokines (IFNγ, TNFα, Granzyme B in response to TAA. This effect is secondary to both reduced proliferation and impaired T cell function following antigen binding. In a prophylactic model, surgical stress completely abrogates tumor protection conferred by vaccination in the immediate postoperative period. In a clinically relevant surgical resection model, vaccinated mice undergoing a positive margin resection with surgical stress had decreased survival compared to mice with positive margin resection alone. Preoperative immunotherapy with IFNα significantly extends survival in surgically stressed mice. Importantly, myeloid derived suppressor cell (MDSC population numbers and functional impairment of TAA-specific CD8+ T cell were altered in surgically stressed mice. Our observations suggest that cancer progression may result from surgery-induced suppression of tumor-specific CD8+ T cells. Preoperative immunotherapies aimed at targeting the prometastatic effects of cancer surgery will reduce recurrence and improve survival in cancer surgery patients.

  2. Stress and Cancer

    DEFF Research Database (Denmark)

    Christoffer, Johansen,; Sørensen, Ivalu; Lim Høeg, Beverly

    2017-01-01

    The role of stress in relation to cancer remains controversial. Stress is assumed to be an emerging public health problem in modern society. Still, we argue that it is relevant to view the role of stress in cancer from a scientific point of view. A critical overview of existing evidence...... is presented through previous review studies, and the importance of methodological challenges is highlighted. We summarize the evidence on the role of stress as a cause of cancer, on the impact of stress on cancer prognosis, and on how coping mechanisms may influence stress levels in cancer patients. Finally......, we describe the evidence on interventions to relieve stress in cancer patients for the purpose of improving both well-being and cancer prognosis. Against public opinion, we critically dismiss the evidence on psychotherapy as a tool to prolong life after cancer as inconsistent and unresolved....

  3. Job-Related Stress among Mass Communication Faculty.

    Science.gov (United States)

    Endres, Fred F.; Wearden, Stanley T.

    1996-01-01

    Questions 600 full-time faculty members teaching journalism and/or mass communication about job-related stress. Finds faculty members suffer from job-related stress; differences exist in the way men and women view, experience, and cope with stress; anxiety and stress are shared by teachers at all grade levels; and times when faculty and students…

  4. No evidence for local adaptation to salt stress in the existing populations of invasive Solidago canadensis in China.

    Science.gov (United States)

    Li, Junmin; Liu, Haiyan; Yan, Ming; Du, Leshan

    2017-01-01

    Local adaptation is an important mechanism underlying the adaptation of plants to environmental heterogeneity, and the toxicity of salt results in strong selection pressure on salt tolerance in plants and different ecotypes. Solidago canadensis, which is invasive in China, has spread widely and has recently colonized alkali sandy loams with a significant salt content. A common greenhouse experiment was conducted to test the role of local adaptation in the successful invasion of S. canadensis into salty habitats. Salt treatment significantly decreased the growth of S. canadensis, including rates of increase in the number of leaves and plant height; the root, shoot, and total biomass. Furthermore, salt stress significantly reduced the net photosynthetic rate, stomatal conductance, transpiration rate and relative chlorophyll content but significantly increased peroxidase activity and the proline content of S. canadensis and the root/shoot ratio. Two-way analysis of variance showed that salt treatment had a significant effect on the physiological traits of S. canadensis, except for the intercellular CO2 concentration, whereas the population and the salt × population interaction had no significant effect on any physiological traits. Most of the variation in plasticity existed within and not among populations, excep for the root/shoot ratio. S. canadensis populations from soil with moderate/high salt levels grew similarly to S. canadensis populations from soils with low salt levels. No significant correlation between salt tolerance indices and soil salinity levels was observed. The plasticity of the proline content, intercellular CO2 concentration and chlorophyll content had significant correlations with the salt tolerance index. These findings indicate a lack of evidence for local adaption in the existing populations of invasive S. canadensis in China; instead, plasticity might be more important than local adaptation in influencing the physiological traits and salt

  5. No evidence for local adaptation to salt stress in the existing populations of invasive Solidago canadensis in China.

    Directory of Open Access Journals (Sweden)

    Junmin Li

    Full Text Available Local adaptation is an important mechanism underlying the adaptation of plants to environmental heterogeneity, and the toxicity of salt results in strong selection pressure on salt tolerance in plants and different ecotypes. Solidago canadensis, which is invasive in China, has spread widely and has recently colonized alkali sandy loams with a significant salt content. A common greenhouse experiment was conducted to test the role of local adaptation in the successful invasion of S. canadensis into salty habitats. Salt treatment significantly decreased the growth of S. canadensis, including rates of increase in the number of leaves and plant height; the root, shoot, and total biomass. Furthermore, salt stress significantly reduced the net photosynthetic rate, stomatal conductance, transpiration rate and relative chlorophyll content but significantly increased peroxidase activity and the proline content of S. canadensis and the root/shoot ratio. Two-way analysis of variance showed that salt treatment had a significant effect on the physiological traits of S. canadensis, except for the intercellular CO2 concentration, whereas the population and the salt × population interaction had no significant effect on any physiological traits. Most of the variation in plasticity existed within and not among populations, excep for the root/shoot ratio. S. canadensis populations from soil with moderate/high salt levels grew similarly to S. canadensis populations from soils with low salt levels. No significant correlation between salt tolerance indices and soil salinity levels was observed. The plasticity of the proline content, intercellular CO2 concentration and chlorophyll content had significant correlations with the salt tolerance index. These findings indicate a lack of evidence for local adaption in the existing populations of invasive S. canadensis in China; instead, plasticity might be more important than local adaptation in influencing the physiological

  6. Impact of Instructional Assessment on Elementary Children's Achievement

    Directory of Open Access Journals (Sweden)

    Samuel J. Meisels

    2003-02-01

    Full Text Available This study examined the trajectory of change in scores on the Iowa Tests of Basic Skills (ITBS of low-income, urban, third and fourth graders who had been enrolled in classrooms where the Work Sampling System (WSS, a curriculum-embedded performance assessment, was used for at least three years. The ITBS scores of children exposed to WSS were compared with those of students in a group of non-WSS contrast schools that were matched by race, income, mobility, school size, and number of parents in the home and to a comparison group of all other students in the school district.

  7. Preparation of porous carbon sphere from waste sugar solution for electric double-layer capacitor

    Science.gov (United States)

    Hao, Zhi-Qiang; Cao, Jing-Pei; Wu, Yan; Zhao, Xiao-Yan; Zhuang, Qi-Qi; Wang, Xing-Yong; Wei, Xian-Yong

    2017-09-01

    Waste sugar solution (WSS), which contains abundant 2-keto-L-gulonic acid, is harmful to the environment if discharged directly. For value-added utilization of the waste resource, a novel process is developed for preparation of porous carbon spheres by hydrothermal carbonization (HTC) of WSS followed by KOH activation. Additionally, the possible preparation mechanism of carbon spheres is proposed. The effects of hydrothermal and activation parameters on the properties of the carbon sphere are also investigated. The carbon sphere is applied to electric double-layer capacitor and its electrochemical performance is studied. These results show that the carbon sphere obtained by HTC at 180 °C for 12 h with the WSS/deionized water volume ratio of 2/3 possess the highest specific capacitance under identical activation conditions. The specific capacitance of the carbon spheres can reach 296.1 F g-1 at a current density of 40 mA g-1. Besides, excellent cycle life and good capacitance retention (89.6%) are observed at 1.5 A g-1 after 5000 cycles. This study not only provides a facile and potential method for the WSS treatment, but also achieves the high value-added recycling of WSS for the preparation of porous carbon spheres with superior electrochemical properties.

  8. Stress Managment and Health Promotion

    Directory of Open Access Journals (Sweden)

    Asghar Dadkhah

    2004-09-01

    Full Text Available Health promotion approach is utilized to address the prevention, management and early intervention for stress management and also to promote positive mental and psychological health. Stress affects everyone and must be managed effectively to reduce its chronic and deleterious effects this study consists of two sections: in first section the principals of health promotion in different human existence levels, prevention of disease related to stress, the effect of stress on human well-being, and stress management were discussed. In second section the role of rehabilitation specialists (Medical technologist, nurses, occupational therapists, physiotherapists, respiratory therapists, and social workers in stress management were counted.

  9. Projeto Vida no Vale: universal access to water and sanitation in the North East of Minas Gerais (Brazil)

    Science.gov (United States)

    Kauark-Leite, L.; Vinçon-Leite, B.; Deroubaix, J. F.; Loireau, A.; Silveira, D.; Haddad, E.

    2008-08-01

    In the rural areas of the developing countries, the access to water supply and sanitation services is still largely inadequate. Poor governance of the water sector is frequently singled out as a cause and reforms are required. Studies analyzing the great diversity of restructuring efforts currently being undertaken in the water sector have not succeeded in determining the most appropriate institutional and economic framework for such reforms. Moreover they underline the lack of documentation on actual projects and call for concrete models and tools for improving water and sanitation services (WSS) and for adapting water utility practice to real conditions. In this context, the Vida no Vale (Life in the Valley) project is aimed at bringing universal access to WSS for all inhabitants of both urban and rural areas, in the north-eastern area of the Brazilian State of Minas Gerais. The project takes sustainable development as its guiding principle, and relies on the joint implementation of an innovative technical design, a governance model involving public participation and subsidiarity, and an economic structure combining financial viability and social equity. Designed at a consistent geographical and hydrological scale, it includes the creation of a regional subsidiary of the existing state water company as a keystone element. The institutional organisation also relies on the creation of a public board consisting of the 92 municipalities of the project region and of the State of Minas Gerais. This board will be in charge of the system's governance. This paper presents the first step of the project (2006), consisting of a feasibility study and the implementation of 9 pilot sub-projects. During the feasibility study, the supply, demand and capacity to pay for water services were defined, existing infrastructure appraised, the necessary amount of investment assessed and an innovative operational model and a sustainable management system, including civil society

  10. Projeto Vida no Vale: universal access to water and sanitation in the North East of Minas Gerais (Brazil

    Directory of Open Access Journals (Sweden)

    A. Loireau

    2008-08-01

    Full Text Available In the rural areas of the developing countries, the access to water supply and sanitation services is still largely inadequate. Poor governance of the water sector is frequently singled out as a cause and reforms are required. Studies analyzing the great diversity of restructuring efforts currently being undertaken in the water sector have not succeeded in determining the most appropriate institutional and economic framework for such reforms. Moreover they underline the lack of documentation on actual projects and call for concrete models and tools for improving water and sanitation services (WSS and for adapting water utility practice to real conditions. In this context, the Vida no Vale (Life in the Valley project is aimed at bringing universal access to WSS for all inhabitants of both urban and rural areas, in the north-eastern area of the Brazilian State of Minas Gerais. The project takes sustainable development as its guiding principle, and relies on the joint implementation of an innovative technical design, a governance model involving public participation and subsidiarity, and an economic structure combining financial viability and social equity. Designed at a consistent geographical and hydrological scale, it includes the creation of a regional subsidiary of the existing state water company as a keystone element. The institutional organisation also relies on the creation of a public board consisting of the 92 municipalities of the project region and of the State of Minas Gerais. This board will be in charge of the system's governance. This paper presents the first step of the project (2006, consisting of a feasibility study and the implementation of 9 pilot sub-projects. During the feasibility study, the supply, demand and capacity to pay for water services were defined, existing infrastructure appraised, the necessary amount of investment assessed and an innovative operational model and a sustainable management system, including civil

  11. Perceived stress and anxiety among Ghanaian pregnant women ...

    African Journals Online (AJOL)

    Perceived stress and anxiety among Ghanaian pregnant women. ... Abstract. The aim of the study was to assess the prevalence of stress and anxiety, as well as the association that exists between stress/anxiety and ... from 32 Countries:.

  12. Interindividual differences in stress sensitivity: basal and stress-induced cortisol levels differentially predict neural vigilance processing under stress.

    Science.gov (United States)

    Henckens, Marloes J A G; Klumpers, Floris; Everaerd, Daphne; Kooijman, Sabine C; van Wingen, Guido A; Fernández, Guillén

    2016-04-01

    Stress exposure is known to precipitate psychological disorders. However, large differences exist in how individuals respond to stressful situations. A major marker for stress sensitivity is hypothalamus-pituitary-adrenal (HPA)-axis function. Here, we studied how interindividual variance in both basal cortisol levels and stress-induced cortisol responses predicts differences in neural vigilance processing during stress exposure. Implementing a randomized, counterbalanced, crossover design, 120 healthy male participants were exposed to a stress-induction and control procedure, followed by an emotional perception task (viewing fearful and happy faces) during fMRI scanning. Stress sensitivity was assessed using physiological (salivary cortisol levels) and psychological measures (trait questionnaires). High stress-induced cortisol responses were associated with increased stress sensitivity as assessed by psychological questionnaires, a stronger stress-induced increase in medial temporal activity and greater differential amygdala responses to fearful as opposed to happy faces under control conditions. In contrast, high basal cortisol levels were related to relative stress resilience as reflected by higher extraversion scores, a lower stress-induced increase in amygdala activity and enhanced differential processing of fearful compared with happy faces under stress. These findings seem to reflect a critical role for HPA-axis signaling in stress coping; higher basal levels indicate stress resilience, whereas higher cortisol responsivity to stress might facilitate recovery in those individuals prone to react sensitively to stress. © The Author (2015). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

  13. Surface Wave Velocity-Stress Relationship in Uniaxially Loaded Concrete

    DEFF Research Database (Denmark)

    Shokouhi, Parisa; Zoëga, Andreas; Wiggenhauser, Herbert

    2012-01-01

    The sonic surface wave (or Rayleigh wave) velocity measured on prismatic concrete specimens under uniaxial compression was found to be highly stress-dependent. At low stress levels, the acoustoelastic effect and the closure of existing microcracks results in a gradual increase in surface wave...... velocities. At higher stress levels, concrete suffers irrecoverable damage: the existing microcracks widen and coalesce and new microcracks form. This progressive damage process leads first to the flattening and eventually the drop in the velocity-stress curves. Measurements on specimens undergoing several...... loading cycles revealed that the velocities show a stress-memory effect in good agreement with the Kaiser effect. Comparing the velocities measured during loading and unloading, the effects of stress and damage on the measured velocities could be differentiated. Moreover, the stress dependency of surface...

  14. Evaluation of stress intensity factors due to welding residual stresses for circumferential cracked pipes

    International Nuclear Information System (INIS)

    Oh, Chang-Young; Kim, Yun-Jae; Oh, Young-Jin; Kim, Jong-Sung; Song, Tae-Kwang; Kim, Yong-Beum

    2013-01-01

    To investigate the applicability of existing methods to estimate stress intensity factors due to welding residual stresses, comparisons with finite element (FE) solutions are made for two types of generic welding residual stress profiles, generated by simulating repair welds. It is found that fitting residual stresses over the crack depth using third-order polynomials gives good estimates of stress intensity factors but fitting over the entire thickness can result in inaccurate estimates even with fourth-order polynomials. Noting that welding residual stresses are often determined from FE analyses, linearization of residual stresses to estimate stress intensity factors is proposed. Comparison with FE solutions shows good agreements. -- Highlights: ► Applicability of K estimation methods is investigated for welding residual stresses. ► Two types of generic residual stress profiles with repair welds are considered. ► Fitting residual stresses over the crack depth gives good estimates of K. ► A method to estimate K by linearising residual stress profiles is proposed

  15. Wind/seismic comparison for upgrading existing structures

    International Nuclear Information System (INIS)

    Giller, R.A.

    1989-01-01

    This paper depicts the analysis procedures and methods used to evaluate three existing building structures for extreme wind loads. The three structures involved in this evaluation are located at the US Department of Energy's Hanford Site near Richland, Washington. This site is characterized by open flat grassland with few surrounding obstructions and has extreme winds in lieu of tornados as a design basis accident condition. This group of buildings represents a variety of construction types, including a concrete stack, a concrete load-bearing wall structure, and a rigid steel-frame building. The three structures included in this group have recently been evaluated for response to the design basis earthquake that included non-linear time history effects. The resulting loads and stresses from the wind analyses were compared to the loads and stresses resulting from seismic analyses. This approach eliminated the need to prepare additional capacity calculations that were already contained in the seismic evaluations

  16. The water-energy relationship: energy management on water supply systems of Brazil's sanitation companies; A relacao entre agua e energia: gestao energetica nos sistemas de abastecimento de agua das companhias de saneamento basico do Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Moura, Gustavo Nikolaus Pinto de

    2010-03-15

    Energy and water resources are related in various ways, among which is the use of electric power in Water Supply Systems (WSS). This dissertation identifies actions that can be carried out under the adoption of energy management systems by sanitation companies in order to better use energy resources and, therefore, water resources. The importance of the input electric power to the WSS is presented, as well as the inefficiency of its use mainly due to losses in distribution networks, inappropriate operational routine and inadequate equipment. Two studies were conducted to evaluate the performance of possible actions for energy management in the WSS. The first action was the energy performance indicators use in hypothetical WSS, and the second, the use of EPANET 2.0 simulation software to verify the feasibility of the frequency converter equipment in the water network distribution of the Federal University of Rio de Janeiro's Environmental Sanitation Centre. (author)

  17. Optimal Allocation of Water Resources Based on Water Supply Security

    Directory of Open Access Journals (Sweden)

    Jianhua Wang

    2016-06-01

    Full Text Available Under the combined impacts of climate change and human activities, a series of water issues, such as water shortages, have arisen all over the world. According to current studies in Science and Nature, water security has become a frontier critical topic. Water supply security (WSS, which is the state of water resources and their capacity and their capacity to meet the demand of water users by water supply systems, is an important part of water security. Currently, WSS is affected by the amount of water resources, water supply projects, water quality and water management. Water shortages have also led to water supply insecurity. WSS is now evaluated based on the balance of the supply and demand under a single water resources condition without considering the dynamics of the varying conditions of water resources each year. This paper developed an optimal allocation model for water resources that can realize the optimal allocation of regional water resources and comprehensively evaluate WSS. The objective of this model is to minimize the duration of water shortages in the long term, as characterized by the Water Supply Security Index (WSSI, which is the assessment value of WSS, a larger WSSI value indicates better results. In addition, the simulation results of the model can determine the change process and dynamic evolution of the WSS. Quanzhou, a city in China with serious water shortage problems, was selected as a case study. The allocation results of the current year and target year of planning demonstrated that the level of regional comprehensive WSS was significantly influenced by the capacity of water supply projects and the conditions of the natural water resources. The varying conditions of the water resources allocation results in the same year demonstrated that the allocation results and WSSI were significantly affected by reductions in precipitation, decreases in the water yield coefficient, and changes in the underlying surface.

  18. Thyro-stress.

    Science.gov (United States)

    Kalra, Sanjay; Verma, Komal; Balhara, Yatan Pal Singh

    2017-01-01

    Our understanding of the biopsychosocial model of health, and its influence on chronic endocrine conditions, has improved over the past few decades. We can distinguish, for example, between diabetes distress and major depressive disorders in diabetes. Similar to diabetes distress, we suggest the existence of "thyrostress" in chronic thyroid disorders. Thyro-stress is defined as an emotional state, characterized by extreme apprehension, discomfort or dejection, caused by the challenges and demand of living with thyroid disorders such as hypothyroidism. This communication describes the etiology, clinical features, differential diagnosis, and management of thyro-stress.

  19. Microfocal X-ray computed tomography post-processing operations for optimizing reconstruction volumes of stented arteries during 3D computational fluid dynamics modeling.

    Science.gov (United States)

    Ladisa, John F; Olson, Lars E; Ropella, Kristina M; Molthen, Robert C; Haworth, Steven T; Kersten, Judy R; Warltier, David C; Pagel, Paul S

    2005-08-01

    Restenosis caused by neointimal hyperplasia (NH) remains an important clinical problem after stent implantation. Restenosis varies with stent geometry, and idealized computational fluid dynamics (CFD) models have indicated that geometric properties of the implanted stent may differentially influence NH. However, 3D studies capturing the in vivo flow domain within stented vessels have not been conducted at a resolution sufficient to detect subtle alterations in vascular geometry caused by the stent and the subsequent temporal development of NH. We present the details and limitations of a series of post-processing operations used in conjunction with microfocal X-ray CT imaging and reconstruction to generate geometrically accurate flow domains within the localized region of a stent several weeks after implantation. Microfocal X-ray CT reconstruction volumes were subjected to an automated program to perform arterial thresholding, spatial orientation, and surface smoothing of stented and unstented rabbit iliac arteries several weeks after antegrade implantation. A transfer function was obtained for the current post-processing methodology containing reconstructed 16 mm stents implanted into rabbit iliac arteries for up to 21 days after implantation and resolved at circumferential and axial resolutions of 32 and 50 microm, respectively. The results indicate that the techniques presented are sufficient to resolve distributions of WSS with 80% accuracy in segments containing 16 surface perturbations over a 16 mm stented region. These methods will be used to test the hypothesis that reductions in normalized wall shear stress (WSS) and increases in the spatial disparity of WSS immediately after stent implantation may spatially correlate with the temporal development of NH within the stented region.

  20. An agent-based model of leukocyte transendothelial migration during atherogenesis.

    Directory of Open Access Journals (Sweden)

    Rita Bhui

    2017-05-01

    Full Text Available A vast amount of work has been dedicated to the effects of hemodynamics and cytokines on leukocyte adhesion and trans-endothelial migration (TEM and subsequent accumulation of leukocyte-derived foam cells in the artery wall. However, a comprehensive mechanobiological model to capture these spatiotemporal events and predict the growth and remodeling of an atherosclerotic artery is still lacking. Here, we present a multiscale model of leukocyte TEM and plaque evolution in the left anterior descending (LAD coronary artery. The approach integrates cellular behaviors via agent-based modeling (ABM and hemodynamic effects via computational fluid dynamics (CFD. In this computational framework, the ABM implements the diffusion kinetics of key biological proteins, namely Low Density Lipoprotein (LDL, Tissue Necrosis Factor alpha (TNF-α, Interlukin-10 (IL-10 and Interlukin-1 beta (IL-1β, to predict chemotactic driven leukocyte migration into and within the artery wall. The ABM also considers wall shear stress (WSS dependent leukocyte TEM and compensatory arterial remodeling obeying Glagov's phenomenon. Interestingly, using fully developed steady blood flow does not result in a representative number of leukocyte TEM as compared to pulsatile flow, whereas passing WSS at peak systole of the pulsatile flow waveform does. Moreover, using the model, we have found leukocyte TEM increases monotonically with decreases in luminal volume. At critical plaque shapes the WSS changes rapidly resulting in sudden increases in leukocyte TEM suggesting lumen volumes that will give rise to rapid plaque growth rates if left untreated. Overall this multi-scale and multi-physics approach appropriately captures and integrates the spatiotemporal events occurring at the cellular level in order to predict leukocyte transmigration and plaque evolution.

  1. Workplace status: The development and validation of a scale.

    Science.gov (United States)

    Djurdjevic, Emilija; Stoverink, Adam C; Klotz, Anthony C; Koopman, Joel; da Motta Veiga, Serge P; Yam, Kai Chi; Chiang, Jack Ting-Ju

    2017-07-01

    Research suggests that employee status, and various status proxies, relate to a number of meaningful outcomes in the workplace. The advancement of the study of status in organizational settings has, however, been stymied by the lack of a validated workplace status measure. The purpose of this manuscript, therefore, is to develop and validate a measure of workplace status based on a theoretically grounded definition of status in organizations. Subject-matter experts were used to examine the content validity of the measure. Then, 2 separate samples were employed to assess the psychometric properties (i.e., factor structure, reliability, convergent and discriminant validity) and nomological network of a 5-item, self-report Workplace Status Scale (WSS). To allow for methodological flexibility, an additional 3 samples were used to extend the WSS to coworker reports of a focal employee's status, provide additional evidence for the validity and reliability of the WSS, and to demonstrate consensus among coworker ratings. Together, these studies provide evidence of the psychometric soundness of the WSS for assessing employee status using either self-reports or other-source reports. The implications of the development of the WSS for the study of status in organizations are discussed, and suggestions for future research using the new measure are offered. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  2. Stress shadows - a controversial topic

    Science.gov (United States)

    Lasocki, Stanislaw; Karakostas, Vassilis G.; Papadimitriou, Eletheria E.; Orlecka-Sikora, Beata

    2010-05-01

    The spatial correlation between the positive Coulomb stress changes and the subsequent seismic activity has been firmly confirmed in many recent studies. If, however, the static stress transfer is a consistent expression of interaction between earthquakes one should also observe a decrease of the activity in the zones of negative stress changes. Instead, the existence of stress shadows is poorly evidenced and may be questioned. We tested the influence of the static stress changes associated with the coseismic slip of the 1995 Mw6.5 Kozani-Grevena (Greece) earthquake on locations of its aftershocks. The study was based on a detailed slip model for the main shock and accurate locations and reliable fault plane solutions of an adequate number of the aftershocks. We developed a statistical testing method, which tested whether the proportions of aftershocks located inside areas determined by a selected criterion on the static stress change could be attained if there were no effect of the stress change due to the main shock on aftershock locations. The areas of stress change were determined at the focus of every aftershock. The distribution of test statistic was constructed with the use of a two-dimensional nonparametric, kernel density estimator of the reference epicenter distribution. The tests highly confidently indicated a rise in probability to locate aftershocks inside areas of positive static stress change, which supported the hypothesis on the triggering effect in these areas. Furthermore, it was evidenced that a larger stress increase caused a stronger triggering effect. The analysis, however, did not evidence the existence of stress shadows inside areas of negative stress change. Contrary to expectations, the tests indicated a significant increase of the probability of event location in the areas of a stress decrease of more than or equal to 5.0 and 10.0 bar. It turned out that for areas of larger absolute stress change this probability increased regardless of

  3. Divergence-free smoothing for MRV data on stenosed carotid artery phantom flows

    Science.gov (United States)

    Im, Chaehyuk; Ko, Seungbin; Song, Simon

    2017-11-01

    Magnetic Resonance Velocimetry (MRV) is a versatile technique for measuring flow velocity using an MRI machine. It is frequently used for visualization and analysis of blood flows. However, it is difficult to accurately estimate hemodynamics parameters like wall shear stress (WSS) and oscillatory shear index (OSI) due to its low spatial resolution and low signal-to-noise ratio. We suggest a divergence-free smoothing (DFS) method to correct the erroneous velocity vectors obtained with MRV and improve the estimation accuracy of those parameters. Unlike previous studies on DFS for a wall-free flow, we developed a house code to apply a DFS method to a wall-bounded flow. A Hagen-Poiseuille flow and stenosed carotid artery phantom flows were measured with MRV. Each of them was analyzed for validation of the DFS code and confirmation on the accuracy improvement of hemodynamic parameters. We will discuss the effects of DFS on the improvement of the estimation accuracy of velocity vectors, WSS, OSI and etc in detail This work was supported by the National Research Foundation of Korea(NRF) Grant funded by the Korea government(MSIP) (No. 2016R1A2B3009541).

  4. Real-time threat evaluation in a ground based air defence environment

    Directory of Open Access Journals (Sweden)

    JN Roux

    2008-06-01

    Full Text Available In a military environment a ground based air defence operator is required to evaluate the tactical situation in real-time and protect Defended Assets (DAs on the ground against aerial threats by assigning available Weapon Systems (WSs to engage enemy aircraft. Since this aerial environment requires rapid operational planning and decision making in stress situations, the associated responsibilities are typically divided between a number of operators and computerized systems that aid these operators during the decision making processes. One such a Decision Support System (DSS, a threat evaluation and weapon assignment system, assigns threat values to aircraft (with respect to DAs in real-time and uses these values to propose possible engagements of observed enemy aircraft by anti-aircraft WSs. In this paper a design of the threat evaluation part of such a DSS is put forward. The design follows the structured approach suggested in [Roux JN & van Vuuren JH, 2007, Threat evaluation and weapon assignment decision support: A review of the state of the art, ORiON, 23(2, pp. 151-187], phasing in a suite of increasingly complex qualitative and quantitative model components as more (reliable data become available.

  5. Thyro-stress

    Directory of Open Access Journals (Sweden)

    Sanjay Kalra

    2017-01-01

    Full Text Available Our understanding of the biopsychosocial model of health, and its influence on chronic endocrine conditions, has improved over the past few decades. We can distinguish, for example, between diabetes distress and major depressive disorders in diabetes. Similar to diabetes distress, we suggest the existence of “thyrostress” in chronic thyroid disorders. Thyro-stress is defined as an emotional state, characterized by extreme apprehension, discomfort or dejection, caused by the challenges and demand of living with thyroid disorders such as hypothyroidism. This communication describes the etiology, clinical features, differential diagnosis, and management of thyro-stress.

  6. Impact of new traumatic or stressful life events on pre-existing PTSD in traumatized refugees: results of a longitudinal study

    Directory of Open Access Journals (Sweden)

    Katrin Schock

    2016-11-01

    Full Text Available Background: A significant proportion of trauma survivors experience an additional critical life event in the aftermath. These renewed experiences of traumatic and stressful life events may lead to an increase in trauma-related mental health symptoms.Method: In a longitudinal study, the effects of renewed experiences of a trauma or stressful life event were examined. For this purpose, refugees seeking asylum in Germany were assessed for posttraumatic stress symptoms (PTS, Posttraumatic Stress Diagnostic Scale (PDS, anxiety, and depression (Hopkins Symptom Checklist [HSCL-25] before treatment start as well as after 6 and 12 months during treatment (N=46. Stressful life events and traumatic events were recorded monthly. If a new event happened, PDS and HSCL were additionally assessed directly afterwards. Mann–Whitney U-tests were performed to calculate the differences between the group that experienced an additional critical event (stressful vs. trauma during treatment (n=23 and the group that did not (n=23, as well as differences within the critical event group between the stressful life event group (n=13 and the trauma group (n=10.Results: Refugees improved significantly during the 12-month period of our study, but remained severely distressed. In a comparison of refugees with a new stressful life event or trauma, significant increases in PTS, anxiety, and depressive symptoms were found directly after the experience, compared to the group without a renewed event during the 12 months of treatment. With regard to the different critical life events (stressful vs. trauma, no significant differences were found regarding overall PTS, anxiety, and depression symptoms. Only avoidance symptoms increased significantly in the group experiencing a stressful life event.Conclusion: Although all clinicians should be aware of possible PTS symptom reactivation, especially those working with refugees and asylum seekers, who often experience new critical life

  7. Impact of new traumatic or stressful life events on pre-existing PTSD in traumatized refugees: results of a longitudinal study.

    Science.gov (United States)

    Schock, Katrin; Böttche, Maria; Rosner, Rita; Wenk-Ansohn, Mechthild; Knaevelsrud, Christine

    2016-01-01

    A significant proportion of trauma survivors experience an additional critical life event in the aftermath. These renewed experiences of traumatic and stressful life events may lead to an increase in trauma-related mental health symptoms. In a longitudinal study, the effects of renewed experiences of a trauma or stressful life event were examined. For this purpose, refugees seeking asylum in Germany were assessed for posttraumatic stress symptoms (PTS), Posttraumatic Stress Diagnostic Scale (PDS), anxiety, and depression (Hopkins Symptom Checklist [HSCL-25]) before treatment start as well as after 6 and 12 months during treatment ( N =46). Stressful life events and traumatic events were recorded monthly. If a new event happened, PDS and HSCL were additionally assessed directly afterwards. Mann-Whitney U -tests were performed to calculate the differences between the group that experienced an additional critical event (stressful vs. trauma) during treatment ( n =23) and the group that did not ( n =23), as well as differences within the critical event group between the stressful life event group ( n =13) and the trauma group ( n =10). Refugees improved significantly during the 12-month period of our study, but remained severely distressed. In a comparison of refugees with a new stressful life event or trauma, significant increases in PTS, anxiety, and depressive symptoms were found directly after the experience, compared to the group without a renewed event during the 12 months of treatment. With regard to the different critical life events (stressful vs. trauma), no significant differences were found regarding overall PTS, anxiety, and depression symptoms. Only avoidance symptoms increased significantly in the group experiencing a stressful life event. Although all clinicians should be aware of possible PTS symptom reactivation, especially those working with refugees and asylum seekers, who often experience new critical life events, should understand symptom

  8. Pre-existing high glucocorticoid receptor number predicting development of posttraumatic stress symptoms after military deployment

    NARCIS (Netherlands)

    van Zuiden, Mirjam; Geuze, Elbert; Willemen, Hanneke L. D. M.; Vermetten, Eric; Maas, Mirjam; Heijnen, Cobi J.; Kavelaars, Annemieke

    2011-01-01

    The development of posttraumatic stress disorder (PTSD) is influenced by preexisting vulnerability factors. The authors aimed at identifying a preexisting biomarker representing a vulnerability factor for the development of PTSD. To that end, they determined whether the dexamethasone binding

  9. Academic Stress and Coping Strategies among Students with ...

    African Journals Online (AJOL)

    This study examined the level of academic stress among university students with disabilities and the nature of coping strategies they used to deal with stress. It also examined if there existed significant differences in stress and coping strategies among students with different disabilities and between students with and without ...

  10. Investigations of some rock stress measuring techniques and the stress field in Norway

    Energy Technology Data Exchange (ETDEWEB)

    Hanssen, Tor Harald

    1998-12-31

    Rock stresses are important to the safe construction and operation of all man-made structures in rock, whether In mining, civil or petroleum engineering. The crucial issue is their relative magnitude and orientation. This thesis develops equipment and methods for further rock stress assessment and reevaluates existing overcoring rock stress measurements, and relates this information to the present geological setting. Both laboratory work and field work are involved. In the field, rock stresses are measured by the overcoring and the hydraulic fracturing technique. An observation technique for assessing likely high stresses is developed. The field data refer to several hydropower projects and to some offshore hydrocarbon fields. The principal sections are: (1) Tectonic setting in the western Fennoscandia, (2) Triaxial rock stress measurements by overcoring using the NTH cell (a strain gauge cell developed at the Norwegian technical university in Trondheim and based on the CSIR cell of the South African Council for Scientific and Industrial Research), (3) Laboratory testing of the NTH cell, (4) Quality ranking of stresses measured by the NTH cell, (4) Recalculated rock stresses and implications to the regional stress field, (5) Hydraulic fracturing stress measurements. 113 refs., 98 figs., 62 tabs.

  11. Investigations of some rock stress measuring techniques and the stress field in Norway

    Energy Technology Data Exchange (ETDEWEB)

    Hanssen, Tor Harald

    1997-12-31

    Rock stresses are important to the safe construction and operation of all man-made structures in rock, whether In mining, civil or petroleum engineering. The crucial issue is their relative magnitude and orientation. This thesis develops equipment and methods for further rock stress assessment and reevaluates existing overcoring rock stress measurements, and relates this information to the present geological setting. Both laboratory work and field work are involved. In the field, rock stresses are measured by the overcoring and the hydraulic fracturing technique. An observation technique for assessing likely high stresses is developed. The field data refer to several hydropower projects and to some offshore hydrocarbon fields. The principal sections are: (1) Tectonic setting in the western Fennoscandia, (2) Triaxial rock stress measurements by overcoring using the NTH cell (a strain gauge cell developed at the Norwegian technical university in Trondheim and based on the CSIR cell of the South African Council for Scientific and Industrial Research), (3) Laboratory testing of the NTH cell, (4) Quality ranking of stresses measured by the NTH cell, (4) Recalculated rock stresses and implications to the regional stress field, (5) Hydraulic fracturing stress measurements. 113 refs., 98 figs., 62 tabs.

  12. On the solid stress in a fluidized bed

    International Nuclear Information System (INIS)

    Qassim, R.Y.; Souza, R. de.

    1980-09-01

    The existence of solid stress in an incipiently gas-fluidized bed is shown by experimental measurement. This stress is shown to have two components: an isotropic pressure and an extra stress which depends on the relative velocity between fluid and solid. Both the solid pressure and the solid extra stress component are found to be of the same order of magnitude as the fluid pressure. (Author) [pt

  13. Comfort food is comforting to those most stressed: evidence of the chronic stress response network in high stress women.

    Science.gov (United States)

    Tomiyama, A Janet; Dallman, Mary F; Epel, Elissa S

    2011-11-01

    Chronically stressed rodents who are allowed to eat calorie-dense "comfort" food develop greater mesenteric fat, which in turn dampens hypothalamic-pituitary-adrenocortical (HPA) axis activity. We tested whether similar relations exist in humans, at least cross-sectionally. Fifty-nine healthy premenopausal women were exposed to a standard laboratory stressor to examine HPA response to acute stress and underwent diurnal saliva sampling for basal cortisol and response to dexamethasone administration. Based on perceived stress scores, women were divided into extreme quartiles of low versus high stress categories. We found as hypothesized that the high stress group had significantly greater BMI and sagittal diameter, and reported greater emotional eating. In response to acute lab stressor, the high stress group showed a blunted cortisol response, lower diurnal cortisol levels, and greater suppression in response to dexamethasone. These cross-sectional findings support the animal model, which suggests that long-term adaptation to chronic stress in the face of dense calories result in greater visceral fat accumulation (via ingestion of calorie-dense food), which in turn modulates HPA axis response, resulting in lower cortisol levels. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Learning During Stressful Times

    Science.gov (United States)

    Shors, Tracey J.

    2012-01-01

    Stressful life events can have profound effects on our cognitive and motor abilities, from those that could be construed as adaptive to those not so. In this review, I discuss the general notion that acute stressful experience necessarily impairs our abilities to learn and remember. The effects of stress on operant conditioning, that is, learned helplessness, as well as those on classical conditioning procedures are discussed in the context of performance and adaptation. Studies indicating sex differences in learning during stressful times are discussed, as are those attributing different responses to the existence of multiple memory systems and nonlinear relationships. The intent of this review is to highlight the apparent plasticity of the stress response, how it might have evolved to affect both performance and learning processes, and the potential problems with interpreting stress effects on learning as either good or bad. An appreciation for its plasticity may provide new avenues for investigating its underlying neuronal mechanisms. PMID:15054128

  15. Propagation of edge waves in a thinly layered laminated medium with stress couples under initial stresses

    Directory of Open Access Journals (Sweden)

    Pijush Pal Roy

    1987-01-01

    Full Text Available The propagation of edge waves in a thinly layered laminated medium with stress couples under initial stresses is examined. Based upon an approximate representation of a laminated medium by an equivalent anisotropic continuum with average initial and couple stresses, an explicit form of frequency equation is obtained to derive the phase velocity of edge waves. Edge waves exist under certain conditions. The inclusion of couple stresses increases the velocity of wave propagation. For a specific compression, the presence of couple stresses increases the velocity of wave propagation with the increase of wave number, whereas the reverse is the case when there is no couple stress. Numerical computation is performed with graphical representations. Several special cases are also examined.

  16. Environmental stresses can alleviate the average deleterious effect of mutations

    Directory of Open Access Journals (Sweden)

    Leibler Stanislas

    2003-05-01

    Full Text Available Abstract Background Fundamental questions in evolutionary genetics, including the possible advantage of sexual reproduction, depend critically on the effects of deleterious mutations on fitness. Limited existing experimental evidence suggests that, on average, such effects tend to be aggravated under environmental stresses, consistent with the perception that stress diminishes the organism's ability to tolerate deleterious mutations. Here, we ask whether there are also stresses with the opposite influence, under which the organism becomes more tolerant to mutations. Results We developed a technique, based on bioluminescence, which allows accurate automated measurements of bacterial growth rates at very low cell densities. Using this system, we measured growth rates of Escherichia coli mutants under a diverse set of environmental stresses. In contrast to the perception that stress always reduces the organism's ability to tolerate mutations, our measurements identified stresses that do the opposite – that is, despite decreasing wild-type growth, they alleviate, on average, the effect of deleterious mutations. Conclusions Our results show a qualitative difference between various environmental stresses ranging from alleviation to aggravation of the average effect of mutations. We further show how the existence of stresses that are biased towards alleviation of the effects of mutations may imply the existence of average epistatic interactions between mutations. The results thus offer a connection between the two main factors controlling the effects of deleterious mutations: environmental conditions and epistatic interactions.

  17. Investigation of blood flow rheology using second-grade viscoelastic model (Phan-Thien-Tanner) within carotid artery.

    Science.gov (United States)

    Ramiar, Abas; Larimi, Morsal Momenti; Ranjbar, Ali Akbar

    2017-01-01

    Hemodynamic factors, such as Wall Shear Stress (WSS), play a substantial role in arterial diseases. In the larger arteries, such as the carotid artery, interaction between the vessel wall and blood flow affects the distribution of hemodynamic factors. The fluid is considered to be non-Newtonian, whose flow is governed by the equation of a second-grade viscoelastic fluid and the effects of viscoelastic on blood flow in carotid artery is investigated. Pulsatile flow studies were carried out in a 3D model of carotid artery. The governing equations were solved using finite volume C++ based on open source code, OpenFOAM. To describe blood flow, conservation of mass and momentum, a constitutive relation of simplified Phan-Thien-Tanner (sPTT), and appropriate relations were used to explain shear thinning behavior. The first recirculation was observed at t = 0.2 s, in deceleration phase. In the acceleration phase from t = 0.3 s to t = 0.5 s, vortex and recirculation sizes in bulb regions in both ECA and ICA gradually increased. As is observed in the line graphs based on extracted data from ICA, at t = 0.2 s, τyy is the maximum amount of wall shear stress and τxy the minimum one. The maximum shear stress occurred in the inner side of the main branch (inner side of ICA and ECA) because the velocity of blood flow in the inner side of the bulb region was maximum due to the created recirculation zone in the opposite side in this area. The rheology of blood flow and shear stress in various important parts (the area that are in higher rates of WSS such as bifurcation region and the regions after bulb areas in both branches, Line1-4 in Fig. 7) were also analyzed. The investigation of velocity stream line, velocity profile and shear stress in various sections of carotid artery showed that the maximum shear stress occurred in acceleration phase and in the bifurcation region between ECA and ICA which is due to velocity gradients and changes in thinning behavior of blood and

  18. A Molecular Web: Endoplasmic Reticulum Stress, Inflammation and Oxidative Stress

    Directory of Open Access Journals (Sweden)

    Namrata eChaudhari

    2014-07-01

    Full Text Available Execution of fundamental cellular functions demands regulated protein folding homeostasis. Endoplasmic reticulum (ER is an active organelle existing to implement this function by folding and modifying secretory and membrane proteins. Loss of protein folding homeostasis is central to various diseases and budding evidences suggest ER stress as being a major contributor in the development or pathology of a diseased state besides other cellular stresses. The trigger for diseases may be diverse but, inflammation and/or ER stress may be basic mechanisms increasing the severity or complicating the condition of the disease. Chronic ER stress and activation of the unfolded protein response (UPR through endogenous or exogenous insults may result in impaired calcium and redox homeostasis, oxidative stress via protein overload thereby also influencing vital mitochondrial functions. Calcium released from the ER augments the production of mitochondrial Reactive Oxygen Species (ROS. Toxic accumulation of ROS within ER and mitochondria disturb fundamental organelle functions. Sustained ER stress is known to potentially elicit inflammatory responses via UPR pathways. Additionally, ROS generated through inflammation or mitochondrial dysfunction could accelerate ER malfunction. Dysfunctional UPR pathways has been associated with a wide range of diseases including several neurodegenerative diseases, stroke, metabolic disorders, cancer, inflammatory disease, diabetes mellitus, cardiovascular disease and others. In this review we have discussed the UPR signaling pathways, and networking between ER stress induced inflammatory pathways, oxidative stress and mitochondrial signaling events which further induce or exacerbate ER stress.

  19. Mean stress and the exhaustion of fatigue-damage resistance

    Science.gov (United States)

    Berkovits, Avraham

    1989-01-01

    Mean-stress effects on fatigue life are critical in isothermal and thermomechanically loaded materials and composites. Unfortunately, existing mean-stress life-prediction methods do not incorporate physical fatigue damage mechanisms. An objective is to examine the relation between mean-stress induced damage (as measured by acoustic emission) and existing life-prediction methods. Acoustic emission instrumentation has indicated that, as with static yielding, fatigue damage results from dislocation buildup and motion until dislocation saturation is reached, after which void formation and coalescence predominate. Correlation of damage processes with similar mechanisms under monotonic loading led to a reinterpretation of Goodman diagrams for 40 alloys and a modification of Morrow's formulation for life prediction under mean stresses. Further testing, using acoustic emission to monitor dislocation dynamics, can generate data for developing a more general model for fatigue under mean stress.

  20. Interfacial shear stress in stratified flow in a horizontal rectangular duct

    International Nuclear Information System (INIS)

    Lorencez, C.; Kawaji, M.; Murao, Y.

    1995-01-01

    Interfacial shear stress has been experimentally examined for both cocurrent and countercurrent stratified wavy flows in a horizontal interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress values at high gas flow rates which could be attributed to the assumptions and procedures involved in each method. The interfacial waves and secondary motions were also found to have significant effects on the accuracy of Reynolds stress and turbulence kinetic energy extrapolation methods

  1. Interfacial shear stress in stratified flow in a horizontal rectangular duct

    Energy Technology Data Exchange (ETDEWEB)

    Lorencez, C.; Kawaji, M. [Univ. of Toronto (Canada); Murao, Y. [Tokushima Univ. (Japan)] [and others

    1995-09-01

    Interfacial shear stress has been experimentally examined for both cocurrent and countercurrent stratified wavy flows in a horizontal interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress values at high gas flow rates which could be attributed to the assumptions and procedures involved in each method. The interfacial waves and secondary motions were also found to have significant effects on the accuracy of Reynolds stress and turbulence kinetic energy extrapolation methods.

  2. Preliminary Study of Hemodynamic Distribution in Patient-Specific Stenotic Carotid Bifurcation by Image-Based Computational Fluid Dynamics

    International Nuclear Information System (INIS)

    Xue, Y.J.; Gao, P.Y.; Duan, Q.; Lin, Y.; Dai, C.B.

    2008-01-01

    Background: Regions prone to atherosclerosis, such as bends and bifurcations, tend to exhibit a certain degree of non-planarity or curvature, and these geometric features are known to strongly influence local flow patterns. Recently, computational fluid dynamics (CFD) has been used as a means of enhancing understanding of the mechanisms involved in atherosclerotic plaque formation and development. Purpose: To analyze flow patterns and hemodynamic distribution in stenotic carotid bifurcation in vivo by combining CFD with magnetic resonance angiography (MRA). Material and Methods: Twenty-one patients with carotid atherosclerosis proved by digital subtraction angiography (DSA) and/or Doppler ultrasound underwent contrast-enhanced MR angiography of the carotid bifurcation by a 3.0T MR scanner. Hemodynamic variables and flow patterns of the carotid bifurcation were calculated and visualized by combining vascular imaging postprocessing with CFD. Results: In mild stenotic cases, there was much more streamlined flow in the bulbs, with reduced or disappeared areas of weakly turbulent flow. Also, the corresponding areas of low wall shear stress (WSS) were reduced or even disappeared. As the extent of stenosis increased, stronger blood jets formed at the portion of narrowing, and more prominent eddy flows and slow back flows were noted in the lee of the stenosis. Regions of elevated WSS were predicted at the portion of stenosis and in the path of the downstream jet. Areas of low WSS were predicted on the leeward side of the stenosis, corresponding with the location of slowly turbulent flows. Conclusion: CFD combined with MRA can simulate flow patterns and calculate hemodynamic variables in stenotic carotid bifurcations as well as normal ones. It provides a new method to investigate the relationship of vascular geometry and flow condition with atherosclerotic pathological changes

  3. The maximum possible stress intensity factor for a crack in an unknown residual stress field

    International Nuclear Information System (INIS)

    Coules, H.E.; Smith, D.J.

    2015-01-01

    Residual and thermal stress fields in engineering components can act on cracks and structural flaws, promoting or inhibiting fracture. However, these stresses are limited in magnitude by the ability of materials to sustain them elastically. As a consequence, the stress intensity factor which can be applied to a given defect by a self-equilibrating stress field is also limited. We propose a simple weight function method for determining the maximum stress intensity factor which can occur for a given crack or defect in a one-dimensional self-equilibrating stress field, i.e. an upper bound for the residual stress contribution to K I . This can be used for analysing structures containing defects and subject to residual stress without any information about the actual stress field which exists in the structure being analysed. A number of examples are given, including long radial cracks and fully-circumferential cracks in thick-walled hollow cylinders containing self-equilibrating stresses. - Highlights: • An upper limit to the contribution of residual stress to stress intensity factor. • The maximum K I for self-equilibrating stresses in several geometries is calculated. • A weight function method can determine this maximum for 1-dimensional stress fields. • Simple MATLAB scripts for calculating maximum K I provided as supplementary material.

  4. Fracture patterns and stresses in granite

    International Nuclear Information System (INIS)

    Price, N.J.

    1979-01-01

    If granite bodies are to be used as receptacles for toxic waste materials, the presence or absence of barren fractures and the virgin stresses in the granite are of fundamental importance. Unfortunately, very little is known regarding the incidence of fractures, or stresses, which exist at depths (of about 1 km) in granite bodies. A simple analysis is presented of a hypothetical intrusion which indicates the magnitudes of stresses and the possible fracture development which may be expected in such bodies. (auth)

  5. Water-use strategies of six co-existing Mediterranean woody species during a summer drought

    NARCIS (Netherlands)

    Quero, J.L.; Sterck, F.J.; Martínez-Vilalta, J.; Villar, R.

    2011-01-01

    Drought stress is known to limit plant performance in Mediterranean-type ecosystems. We have investigated the dynamics of the hydraulics, gas exchange and morphology of six co-existing Mediterranean woody species growing under natural field conditions during a drought that continued during the

  6. Residual stresses around Vickers indents

    International Nuclear Information System (INIS)

    Pajares, A.; Guiberteau, F.; Steinbrech, R.W.

    1995-01-01

    The residual stresses generated by Vickers indentation in brittle materials and their changes due to annealing and surface removal were studied in 4 mol% yttria partially stabilized zirconia (4Y-PSZ). Three experimental methods to gain information about the residual stress field were applied: (i) crack profile measurements based on serial sectioning, (ii) controlled crack propagation in post indentation bending tests and (iii) double indentation tests with smaller secondary indents located around a larger primary impression. Three zones of different residual stress behavior are deduced from the experiments. Beneath the impression a crack free spherical zone of high hydrostatic stresses exists. This core zone is followed by a transition regime where indentation cracks develop but still experience hydrostatic stresses. Finally, in an outward third zone, the crack contour is entirely governed by the tensile residual stress intensity (elastically deformed region). Annealing and surface removal reduce this crack driving stress intensity. The specific changes of the residual stresses due to the post indentation treatments are described and discussed in detail for the three zones

  7. Ontological Proofs of Existence and Non-Existence

    Czech Academy of Sciences Publication Activity Database

    Hájek, Petr

    2008-01-01

    Roč. 90, č. 2 (2008), s. 257-262 ISSN 0039-3215 R&D Projects: GA AV ČR IAA100300503 Institutional research plan: CEZ:AV0Z10300504 Keywords : ontological proofs * existence * non-existence * Gödel * Caramuel Subject RIV: BA - General Mathematics

  8. Assessing the reactivation potential of pre-existing fractures in the southern Karoo, South Africa: Evaluating the potential for sustainable exploration across its Critical Zone

    Science.gov (United States)

    Dhansay, Taufeeq; Navabpour, Payman; de Wit, Maarten; Ustaszewski, Kamil

    2017-10-01

    Understanding the kinematics of pre-existing fractures under the present-day stress field is an indispensable prerequisite for hydraulically increasing fracture-induced rock permeability, i.e. through hydraulic stimulation, which forms the basis of economically viable exploitation of resources such as natural gas and geothermal energy. Predicting the likelihood of reactivating pre-existing fractures in a target reservoir at particular fluid injection pressures requires detailed knowledge of the orientations and magnitudes of the prevailing stresses as well as pore fluid pressures. In the absence of actual in-situ stress measurements, e.g. derived from boreholes, as is mostly the case in previously underexplored ;frontier areas;, such predictions are often difficult. In this study, the potential of reactivating pre-existing fractures in a likely exploration region of the southern Karoo of South Africa is investigated. The orientations of the present-day in-situ stresses were assessed from surrounding earthquake focal mechanisms, implying c. NW-SE oriented maximum horizontal stress and a stress regime changing between strike-slip and normal faulting. A comparison with paleo-stress axes derived from inverted fault-slip data suggests that the stress field very likely did not experience any significant reorientation since Cretaceous times. Maximum possible in-situ stress magnitudes are estimated by assuming that these are limited by frictional strength on pre-existing planes and subsequently, slip and dilation tendency calculations were performed, assuming hydrostatic pore fluid pressures of c. 32 MPa at targeted reservoir depth. The results suggest that prevalent E-W and NW-SE oriented sub-vertical fractures are likely to be reactivated at wellhead pressures exceeding hydrostatic pore fluid pressures by as little as 2-5 MPa, while less prevalent sub-horizontal and moderately inclined fractures require higher wellhead pressures that are still technically feasible

  9. Investigation of hot- iso-static press process for tungsten target samples

    International Nuclear Information System (INIS)

    Xu Yongli; Zhang Jinquan; Li Huaqing

    2006-01-01

    Zr and stainless steel (S.S.) were selected respectively as the cladding materials of W target. The e-beam weld was used to prepare the W-Zr and W-S.S. small samples for hot iso-static press (HIP) process. The technology parameters of HIP were investigated at 1200, 1300, 1400 degree C and 180 MPa, respectively. The micro-morphology of the interface, diffusion depths and composition as well as their micro-hardness were observed and determined. The bonding of W-Zr and W-S.S. is very well under the testing conditions. There is no any pore or micro-crack in the interface, and there is no grain growth of W below 1400 degree C either. The diffusion of Zr to W at the interface of W-Zr is preferred during HIP process, and the diffusion depths under testing conditions are 6-13 μm. The diffusion of W and Fe is considerable at the interface of W-S.S. Its depth is about 13 μm, and the diffusion of Cr and Ni is mall. The hardness at the interface of W-Zr and W-S.S. shows that a diffusion layer is present for both interface. A part of stainless steel cladding was melted after HIP contained the oxygen absorber Zr at 1300 degree C and 180 MPa. Therefore, 1200 degree C and 180 MPa is suitable for W-S.S. without Zr, but 1300 or 1400 degree C and 180 MPa is better for W-Zr. (authors)

  10. On Variable Reverse Power Flow-Part I: Active-Reactive Optimal Power Flow with Reactive Power of Wind Stations

    Directory of Open Access Journals (Sweden)

    Aouss Gabash

    2016-02-01

    Full Text Available It has recently been shown that using battery storage systems (BSSs to provide reactive power provision in a medium-voltage (MV active distribution network (ADN with embedded wind stations (WSs can lead to a huge amount of reverse power to an upstream transmission network (TN. However, unity power factors (PFs of WSs were assumed in those studies to analyze the potential of BSSs. Therefore, in this paper (Part-I, we aim to further explore the pure reactive power potential of WSs (i.e., without BSSs by investigating the issue of variable reverse power flow under different limits on PFs in an electricity market model. The main contributions of this work are summarized as follows: (1 Introducing the reactive power capability of WSs in the optimization model of the active-reactive optimal power flow (A-R-OPF and highlighting the benefits/impacts under different limits on PFs. (2 Investigating the impacts of different agreements for variable reverse power flow on the operation of an ADN under different demand scenarios. (3 Derivation of the function of reactive energy losses in the grid with an equivalent-π circuit and comparing its value with active energy losses. (4 Balancing the energy curtailment of wind generation, active-reactive energy losses in the grid and active-reactive energy import-export by a meter-based method. In Part-II, the potential of the developed model is studied through analyzing an electricity market model and a 41-bus network with different locations of WSs.

  11. [Nearby nature as a moderator of stress during childhood].

    Science.gov (United States)

    Corraliza, José Antonio; Collado, Silvia

    2011-04-01

    The aim of this investigation is to study the relation between the amount of nature existing in children's daily environments and the way children deal with stressful events. Every day, children are exposed to situations that cause stress. Taking into account previous studies, it is thought that the greener the place where children spend their time, the better they cope with adversities. Thus, when comparing the stress level of children who are exposed to the same amount of adverse situations, the children who have more frequent daily contact with nature will show less stress than those who do not spend time in nature. This effect from nearby nature is called a buffering effect. The present study provides empirical evidence of the buffering effect caused by the existence of Nature in the residential and the school environment. Therefore, our results show that children who have more access to nature increase their resilience, showing a lower stress level than children whose contact with nature is less frequent.

  12. On the skew-symmetric character of the couple-stress tensor

    OpenAIRE

    Hadjesfandiari, Ali R.

    2013-01-01

    In this paper, the skew-symmetric character of the couple-stress tensor is established as the result of arguments from tensor analysis. Consequently, the couple-stress pseudo-tensor has a true vectorial character. The fundamental step in this development is that the isotropic couple-stress tensor cannot exist.

  13. Conduct disorder, war zone stress, and war-related posttraumatic stress disorder symptoms in American Indian Vietnam veterans.

    Science.gov (United States)

    Dillard, Denise; Jacobsen, Clemma; Ramsey, Scott; Manson, Spero

    2007-02-01

    This study examined whether conduct disorder (CD) was associated with war zone stress and war-related post-traumatic stress disorder (PTSD) symptoms in American Indian (AI) Vietnam veterans. Cross-sectional lay-interview data was analyzed for 591 male participants from the American Indian Vietnam Veterans Project. Logistic regression evaluated the association of CD with odds of high war zone stress and linear regression evaluated the association of CD and PTSD symptom severity. Childhood CD was not associated with increased odds of high war zone stress. Conduct disorder was associated with elevated war-related PTSD symptoms among male AI Vietnam Veterans independent of war zone stress level and other mediators. Future efforts should examine reasons for this association and if the association exists in other AI populations.

  14. 3D Centrifuge Modeling of the Effect of Twin Tunneling to an Existing Pile Group

    Directory of Open Access Journals (Sweden)

    M. A. Soomr

    2017-10-01

    Full Text Available In densely built urban areas, it is inevitable that tunnels will be constructed near existing pile groups. The bearing capacity of a pile group depends on shear stress along the soil-pile interface and normal stress underneath the pile toe while the two would be adversely affected by the unloading process of tunneling. Although extensive studies have been conducted to investigate the effects of tunnel construction on existing single piles, the influence of twin tunnel advancement on an existing pile group is merely reported in the literature. In this study, a series of three-dimensional centrifuge tests were carried out to investigate the response of an existing pile group under working load subjected to twin tunneling at various locations in dry Toyoura sand. In each twin tunneling test, the first tunnel is constructed near the mid-depth of the pile shaft, while the second tunnel is subsequently constructed either next to, below or right underneath the pile toe (Tests G_ST, G_SB and G_SU, respectively. Among the three tests, the 2nd tunnel excavated near the pile toe (Test G_ST results in the smallest settlement but the largest transverse tilting (0.2% of pile group. Significant bending moment was induced at the pile head (1.4 times of its bending moment capacity due to the 2nd tunnel T. On the contrary, tunneling right underneath the toe of pile (i.e., Test G_SU results in the smallest tilting but largest settlement of the pile group (4.6% of pile diameter and incremental mobilisation of shaft resistance (13%. Due to stress release by the twin tunneling, the axial force taken by the front piles close to tunnels was reduced and partially transferred to the rear piles. This load transfer can increase the axial force in rear piles by 24%.

  15. Hemodynamic Based Coronary Artery Aneurysm Thrombosis Risk Stratification in Kawasaki Disease Patients

    Science.gov (United States)

    Grande Gutierrez, Noelia; Mathew, M.; McCrindle, B.; Kahn, A.; Burns, J.; Marsden, A.

    2017-11-01

    Coronary artery aneurysms (CAA) as a result of Kawasaki Disease (KD) put patients at risk for thrombosis and myocardial infarction. Current AHA guidelines recommend CAA diameter >8 mm or Z-score >10 as the criterion for initiating systemic anticoagulation. Our hypothesis is that hemodynamic data derived from computational blood flow simulations is a better predictor of thrombosis than aneurysm diameter alone. Patient-specific coronary models were constructed from CMRI for a cohort of 10 KD patients (5 confirmed thrombosis cases) and simulations with fluid structure interaction were performed using the stabilized finite element Navier-Stokes solver available in SimVascular. We used a closed-loop lumped parameter network (LPN) to model the heart and vascular boundary conditions coupled numerically to the flow solver. An automated parameter estimation method was used to match LPN values to clinical data for each patient. Hemodynamic data analysis resulted in low correlation between Wall Shear Stress (WSS)/ Particle Residence Time (PRT) and CAA diameter but demonstrates the positive correlation between hemodynamics and adverse patient outcomes. Our results suggest that quantifying WSS and PRT should enable identification of regions at higher risk of thrombosis. We propose a quantitative method to non-invasively assess the abnormal flow in CAA following KD that could potentially improve clinical decision-making regarding anticoagulation therapy.

  16. A novel approach for quantifying the zero-plane displacement of rough-wall boundary layers

    Science.gov (United States)

    Ferreira, Manuel; Rodriguez-Lopez, Eduardo; Ganapathisubramani, Bharath; Aerodynamics; Flight Mechanics Team

    2017-11-01

    Indirect methods of wall shear stress (WSS) estimation are frequently used to characterise rough wall boundary-layer flows. The zero-plane displacement, hypothesised to be the vertical location where it acts, is often treated as a fitting parameter. However, it would be preferrable to measure both these quantities directly, especially for surfaces with large roughness elements where established scaling and similarity laws may not hold. In this talk we present a novel floating element balance that is able to measure not only the WSS but also the wall normal location at which it acts. While allowing compensation for mild static pressure gradients by means of a first-order analytical model. Its architecture is based on a parallel-shift linkage and it's fitted with custom built force transducers and a data acquisition system especially designed to achieve high Signal-to-Noise Ratios (SNR). The smooth-wall boundary-layer flow is used as benchmark to assess the accuracy of this balance. The values of skin friction coefficient show an agreement with hot-wire anemometry to within 2 % at a local Reynolds number Reθ = 4 ×103 up to 104. A rough surface of regularly distributed large elements is used to investigate the ability to infer the zero-plane displacement.

  17. Identification of vortex structures in a cohort of 204 intracranial aneurysms.

    Science.gov (United States)

    Varble, Nicole; Trylesinski, Gabriel; Xiang, Jianping; Snyder, Kenneth; Meng, Hui

    2017-05-01

    An intracranial aneurysm (IA) is a cerebrovascular pathology that can lead to death or disability if ruptured. Abnormal wall shear stress (WSS) has been associated with IA growth and rupture, but little is known about the underlying flow physics related to rupture-prone IAs. Previous studies, based on analysis of a few aneurysms or partial views of three-dimensional vortex structures, suggest that rupture is associated with complex vortical flow inside IAs. To further elucidate the relevance of vortical flow in aneurysm pathophysiology, we studied 204 patient IAs (56 ruptured and 148 unruptured). Using objective quantities to identify three-dimensional vortex structures, we investigated the characteristics associated with aneurysm rupture and if these features correlate with previously proposed WSS and morphological characteristics indicative of IA rupture. Based on the Q -criterion definition of a vortex, we quantified the degree of the aneurysmal region occupied by vortex structures using the volume vortex fraction ( vVF ) and the surface vortex fraction ( sVF ). Computational fluid dynamics simulations showed that the sVF , but not the vVF , discriminated ruptured from unruptured aneurysms. Furthermore, we found that the near-wall vortex structures co-localized with regions of inflow jet breakdown, and significantly correlated to previously proposed haemodynamic and morphologic characteristics of ruptured IAs. © 2017 The Author(s).

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

    Directory of Open Access Journals (Sweden)

    Eduardo Soudah

    2013-01-01

    Full Text Available The objective of this study is to find a correlation between the abdominal aortic aneurysm (AAA geometric parameters, wall stress shear (WSS, abdominal flow patterns, intraluminal thrombus (ILT, and AAA arterial wall rupture using computational fluid dynamics (CFD. Real AAA 3D models were created by three-dimensional (3D reconstruction of in vivo acquired computed tomography (CT images from 5 patients. Based on 3D AAA models, high quality volume meshes were created using an optimal tetrahedral aspect ratio for the whole domain. In order to quantify the WSS and the recirculation inside the AAA, a 3D CFD using finite elements analysis was used. The CFD computation was performed assuming that the arterial wall is rigid and the blood is considered a homogeneous Newtonian fluid with a density of 1050 kg/m3 and a kinematic viscosity of 4×10-3 Pa·s. Parallelization procedures were used in order to increase the performance of the CFD calculations. A relation between AAA geometric parameters (asymmetry index (β, saccular index (γ, deformation diameter ratio (χ, and tortuosity index (ε and hemodynamic loads was observed, and it could be used as a potential predictor of AAA arterial wall rupture and potential ILT formation.

  19. STRESS IN ORGANIZATIONS

    Directory of Open Access Journals (Sweden)

    Maria-Elena, GHEORDUNESCU

    2014-11-01

    Full Text Available Taking into account the changes that are currently taking place in our country, it is clear that these changes, which occur in almost all companies, lead to new stress factors for both employees and the organization. Occupational stress is a major problem for employees and managers, but also for the whole society. The issue of stress in organizations has given birth to many debates and studies. It is a common theme that is addressed by managers, employees and consultants from different perspectives. According to a study by the European Agency for Safety and Health at Work, in the European Union, work-related stress is the second work-related health issue after dorsal disorders. It affects 28% of EU employees. The European Parliament is fully involved in addressing issues related to the psychological support of the staff. Preventing work-related stress is one of the objectives set out in the Communique of the European Commission for Employment and Social Affairs regarding their new health and safety at work strategy. Manifestations of stress in organizations are easily observable, being manifested by behaviors such as: difficulties in adapting to the changes required to work or the dramatic drop in labor productivity. Also a double action is met: both the person who passes through the stressful situation and at the organization level on which it is reflected the existence of a stressful environment. This paper aims to address the implications of workplace stress, symptoms of stress in the workplace and strategies to eliminate and prevent stress at work This paper represents an exploratory research based on qualitative methods, being consulted various sources of information: the literature, case studies, media articles, reports of relevant organizations, etc.

  20. Stressor specificity of central neuroendocrine responses: implications for stress-related disorders.

    Science.gov (United States)

    Pacák, K; Palkovits, M

    2001-08-01

    Despite the fact that many research articles have been written about stress and stress-related diseases, no scientifically accepted definition of stress exists. Selye introduced and popularized stress as a medical and scientific idea. He did not deny the existence of stressor-specific response patterns; however, he emphasized that such responses did not constitute stress, only the shared nonspecific component. In this review we focus mainly on the similarities and differences between the neuroendocrine responses (especially the sympathoadrenal and the sympathoneuronal systems and the hypothalamo-pituitary-adrenocortical axis) among various stressors and a strategy for testing Selye's doctrine of nonspecificity. In our experiments, we used five different stressors: immobilization, hemorrhage, cold exposure, pain, or hypoglycemia. With the exception of immobilization stress, these stressors also differed in their intensities. Our results showed marked heterogeneity of neuroendocrine responses to various stressors and that each stressor has a neurochemical "signature." By examining changes of Fos immunoreactivity in various brain regions upon exposure to different stressors, we also attempted to map central stressor-specific neuroendocrine pathways. We believe the existence of stressor-specific pathways and circuits is a clear step forward in the study of the pathogenesis of stress-related disorders and their proper treatment. Finally, we define stress as a state of threatened homeostasis (physical or perceived treat to homeostasis). During stress, an adaptive compensatory specific response of the organism is activated to sustain homeostasis. The adaptive response reflects the activation of specific central circuits and is genetically and constitutionally programmed and constantly modulated by environmental factors.

  1. Managing workplace stress in community pharmacy organisations: lessons from a review of the wider stress management and prevention literature.

    Science.gov (United States)

    Jacobs, Sally; Johnson, Sheena; Hassell, Karen

    2018-02-01

    Workplace stress in community pharmacy is increasing internationally due, in part, to pharmacists' expanding roles and escalating workloads. Whilst the business case for preventing and managing workplace stress by employers is strong, there is little evidence for the effectiveness of organisational stress management interventions in community pharmacy settings. To identify and synthesise existing evidence for the effectiveness of organisational solutions to workplace stress from the wider organisational literature which may be adaptable to community pharmacies. A secondary synthesis of existing reviews. Publications were identified through keyword searches of electronic databases and the internet; inclusion and exclusion criteria were applied; data about setting, intervention, method of evaluation, effectiveness and conclusions (including factors for success) were extracted and synthesised. Eighteen reviews of the stress management and prevention literature were identified. A comprehensive list of organisational interventions to prevent or manage workplace stress, ordered by prevalence of evidence of effectiveness, was produced, together with an ordered list of the benefits both to the individual and employing organisation. An evidence-based model of best practice was derived specifying eight factors for success: top management support, context-specific interventions, combined organisational and individual interventions, a participative approach, clearly delineated tasks and responsibilities, buy-in from middle management, change agents as facilitators and change in organisational culture. This literature review provides community pharmacy organisations with evidence from which to develop effective and successful stress management strategies to support pharmacists and pharmacy staff. Well-designed trials of stress management interventions in community pharmacy organisations are still required. © 2017 Royal Pharmaceutical Society.

  2. HPA axis response to social stress is attenuated in schizophrenia but normal in depression: evidence from a meta-analysis of existing studies.

    Science.gov (United States)

    Ciufolini, Simone; Dazzan, Paola; Kempton, Matthew J; Pariante, Carmine; Mondelli, Valeria

    2014-11-01

    We conducted a meta-analysis to investigate the HPA axis response to social stress in studies that used the Trier Social Stress Test (TSST), or comparable distressing paradigms, in individuals with either depression or schizophrenia. Sample size-adjusted effect sizes (Hedge's g statistic) were calculated to estimate the HPA axis stress response to social stress. We used a meta-regression model to take into account the moderating effect of the baseline cortisol level. Participants with depression show an activation pattern to social stress similar to that of healthy controls. Despite a normal cortisol production rate, individuals with schizophrenia have lower cortisol levels than controls both in anticipation and after exposure to social stress. Participants with depression and higher cortisol levels before the task have an increased cortisol production and reached higher cortisol levels during the task. This may be explained by the presence of an impaired negative feedback. The activation pattern present in schizophrenia may explain the reduced ability to appropriately contextualize past experiences shown by individuals with psychosis in social stressful situation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. The stress shadow induced by the 1975-1984 Krafla rifting episode

    KAUST Repository

    Maccaferri, F.; Rivalta, E.; Passarelli, L.; Jonsson, Sigurjon

    2013-01-01

    of several magnitude 6–7 earthquakes. This compelling case of the existence of a stress shadow has never been studied in detail, and the implications of such a stress shadow remain an open question. According to rate-state models, intense stress shadows cause

  4. Determination of near surface in-situ stresses

    International Nuclear Information System (INIS)

    Garritty, P.; Irvin, R.

    1983-06-01

    One of the major unknowns affecting aspects of underground construction and the geohydrology of rock masses is the magnitude and direction of the geostatic principal stresses in the earth's crust. This is particularly the case in near surface rocks where there are indications that high horizontal stresses may exist. The techniques, experiences and results of a preliminary rock stress measurement programme conducted at shallow depth in the Carnmenellis Granite, Cornwall, using C.S.I.R.O. triaxial hollow inclusion cells are described. (author)

  5. Interaction between diffusion and chemical stresses

    International Nuclear Information System (INIS)

    Yang Fuqian

    2005-01-01

    The present work studies the interaction between chemical stresses and diffusion. A new relation between hydrostatic stress and concentration of solute atoms is established. For a solid free of action of body force, the Laplacian of the hydrostatic stress is proportional to the Laplacian of the concentration of solute atoms, that is, deviation of the hydrostatic stress from its local average is proportional to deviation of the local concentration of solute atoms. A general relationship among surface concentration of solute atoms, normal stress and surface deformation of a solid is then derived, in which the normal stress is dependent on the mean curvature of the undeformed surface and tangential components of the surface displacement. A closed-form solution of the steady state concentration of solute atoms in a thin plate is obtained. It turns out that linear distribution of solute atoms in the plate is non-existent due to the interaction between chemical stresses and diffusion

  6. The Methods of Stress Management and Their Classification

    Directory of Open Access Journals (Sweden)

    Honchar Mykhailo F.

    2017-12-01

    Full Text Available The article considers the content and classification of methods of stress management, which provides systematization of their varieties by the number of existing (character, time interval of application, direction of impact, period of action, way of account the interests of employees, level of formation, method of substantiation, content and the allocated new attributes (scale of changes in terms of stress management systems, level of novelty at enterprise, consistency, which allows to choose the appropriate types of such methods in overcoming undesirable deviations that have a significant negative impact on the functioning of economic entities. It has been determined that such methods are formed in the implementing of technology of stress-management; are the result of management activities of the steering subsystem of organization at each level of management; have alternative nature; form an information-management base for the adoption of managerial decisions in terms of the systems of stress administration. It has been specified that, with the assistance of certain methods in terms of stress management systems, managers can track existing and potential problems in the complex and dynamic environment of the organization, identify their relationships, identify «weak signals», adjust goals and tasks of management of critical undesirable deviations, determine indicators and criteria of stress-management, etc.

  7. Stress proteins, autoimmunity, and autoimmune disease.

    Science.gov (United States)

    Winfield, J B; Jarjour, W N

    1991-01-01

    At birth, the immune system is biased toward recognition of microbial antigens in order to protect the host from infection. Recent data suggest that an important initial line of defense in this regard involves autologous stress proteins, especially conserved peptides of hsp60, which are presented to T cells bearing gamma delta receptors by relatively nonpolymorphic class lb molecules. Natural antibodies may represent a parallel B cell mechanism. Through an evolving process of "physiological" autoreactivity and selection by immunodominant stress proteins common to all prokaryotes, B and T cell repertoires expand during life to meet the continuing challenge of infection. Because stress proteins of bacteria are homologous with stress proteins of the host, there exists in genetically susceptible individuals a constant risk of autoimmune disease due to failure of mechanisms for self-nonself discrimination. That stress proteins actually play a role in autoimmune processes is supported by a growing body of evidence which, collectively, suggests that autoreactivity in chronic inflammatory arthritis involves, at least initially, gamma delta cells which recognize epitopes of the stress protein hsp60. Alternate mechanisms for T cell stimulation by stress proteins undoubtedly also exist, e.g., molecular mimicry of the DR beta third hypervariable region susceptibility locus for rheumatoid arthritis by a DnaJ stress protein epitope in gram-negative bacteria. While there still is confusion with respect to the most relevant stress protein epitopes, a central role for stress proteins in the etiology of arthritis appears likely. Furthermore, insight derived from the work thus far in adjuvant-induced arthritis already is stimulating analyses of related phenomena in autoimmune diseases other than those involving joints. Only limited data are available in the area of humoral autoimmunity to stress proteins. Autoantibodies to a number of stress proteins have been identified in SLE and

  8. A Quantitative Examination Whether Education Mitigates Stress Levels among Law Enforcement Officers

    Science.gov (United States)

    Metts, Gary A.

    2012-01-01

    Stress is damaging if it is continual, overwhelming. and prolonged. Law enforcement officers face stressful events daily. A relationship exists between stress levels and the physical and psychological effects to the human body. Although there is a general understanding of the damage stress can do physically and psychologically, many elements that…

  9. Stress, Coping, and Internet Use of College Students

    Science.gov (United States)

    Deatherage, Scott; Servaty-Seib, Heather L.; Aksoz, Idil

    2014-01-01

    College students experience stressful life events and little research exists on the role the Internet may play in students' coping. Objective: The purpose of the present study was to examine associations among perceived stress, time spent on the Internet, underlying motives for utilizing the Internet, problematic Internet use, and traditional…

  10. Stress-affected microstructural development and creep-swelling interrelationship

    International Nuclear Information System (INIS)

    Brager, H.R.; Garner, F.A.; Gilbert, E.R.; Flinn, J.E.; Wolfer, W.G.

    1977-05-01

    Macroscopic measurement of the deformations arising from swelling and creep during neutron irradiation indicate that both processes are dependent on the magnitude and possibly the sign of the applied stress state. Current modeling efforts also indicate that a strong interaction exists between swelling and creep through the stress state. Because the macroscopic distortions arise from the integrated microscopic strains associated with specific microstructural elements, the effect of applied stress on microstructural development has been studied

  11. Patient radiation exposure dose evaluation of whole spine scanography due to exposure direction

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jung Su; Seo, Deok Nam [Dept. of Bio-convergence Engineering, Graduate School of Korea University, Seoul (Korea, Republic of); Kwon, Soon Mu [Dept. of Radiologic Technology, Daegu Health College, Daegu (Korea, Republic of); Kim, Jung Min [Dept. of Radiological Science, Korea University, Seoul (Korea, Republic of)

    2015-04-15

    Whole spine scanography (WSS) is a radiological examination that exposes the whole body of the individual being examined to x-ray radiation. WSS is often repeated during the treatment period, which results in a much greater radiation exposure than that in routine x-ray examinations. The aims of the current study were to evaluate the patient dose of WSS using computer simulation, image magnification and angulation of phantom image using different patient position. We evaluated the effective dose(ED) of 23 consecutive patients (M : F = 13:10) who underwent WSS, based on the automatic image pasting method for multiple exposure digital radiography. The Anterior-Posterior position(AP) and Posterior-Anterior position( PA) projection EDs were evaluated based on the PC based Monte Carlo simulation. We measured spine transverse process distance and angulation using DICOM measurement. For all patient, the average ED was 0.069 mSv for AP position and 0.0361 mSv for PA position. AP position calculated double exposure then PA position. For male patient, the average ED was 0.089 mSv(AP) and 0.050 mSv(PA). For female patient, the average ED was 0.0431 mSv(AP) and 0.026 mSv(PA). The transverse process of PA spine image measured 5% higher than AP but angulation of transverse process was no significant differences. In clinical practice, just by change the patient position was conformed to reduce the ED of patient. Therefore we need to redefine of protocol for digital radiography such as WSS, whole spine scanography, effective dose, patient exposure dose, exposure direction, protocol optimization.

  12. Development of a High-Sensitivity Wireless Accelerometer for Structural Health Monitoring.

    Science.gov (United States)

    Zhu, Li; Fu, Yuguang; Chow, Raymond; Spencer, Billie F; Park, Jong Woong; Mechitov, Kirill

    2018-01-17

    Structural health monitoring (SHM) is playing an increasingly important role in ensuring the safety of structures. A shift of SHM research away from traditional wired methods toward the use of wireless smart sensors (WSS) has been motivated by the attractive features of wireless smart sensor networks (WSSN). The progress achieved in Micro Electro-Mechanical System (MEMS) technologies and wireless data transmission, has extended the effectiveness and range of applicability of WSSNs. One of the most common sensors employed in SHM strategies is the accelerometer; however, most accelerometers in WSS nodes have inadequate resolution for measurement of the typical accelerations found in many SHM applications. In this study, a high-resolution and low-noise tri-axial digital MEMS accelerometer is incorporated in a next-generation WSS platform, the Xnode. In addition to meeting the acceleration sensing demands of large-scale civil infrastructure applications, this new WSS node provides powerful hardware and a robust software framework to enable edge computing that can deliver actionable information. Hardware and software integration challenges are presented, and the associate resolutions are discussed. The performance of the wireless accelerometer is demonstrated experimentally through comparison with high-sensitivity wired accelerometers. This new high-sensitivity wireless accelerometer will extend the use of WSSN to a broader class of SHM applications.

  13. Development of a High-Sensitivity Wireless Accelerometer for Structural Health Monitoring

    Science.gov (United States)

    Zhu, Li; Fu, Yuguang; Chow, Raymond; Spencer, Billie F.; Park, Jong Woong; Mechitov, Kirill

    2018-01-01

    Structural health monitoring (SHM) is playing an increasingly important role in ensuring the safety of structures. A shift of SHM research away from traditional wired methods toward the use of wireless smart sensors (WSS) has been motivated by the attractive features of wireless smart sensor networks (WSSN). The progress achieved in Micro Electro-Mechanical System (MEMS) technologies and wireless data transmission, has extended the effectiveness and range of applicability of WSSNs. One of the most common sensors employed in SHM strategies is the accelerometer; however, most accelerometers in WSS nodes have inadequate resolution for measurement of the typical accelerations found in many SHM applications. In this study, a high-resolution and low-noise tri-axial digital MEMS accelerometer is incorporated in a next-generation WSS platform, the Xnode. In addition to meeting the acceleration sensing demands of large-scale civil infrastructure applications, this new WSS node provides powerful hardware and a robust software framework to enable edge computing that can deliver actionable information. Hardware and software integration challenges are presented, and the associate resolutions are discussed. The performance of the wireless accelerometer is demonstrated experimentally through comparison with high-sensitivity wired accelerometers. This new high-sensitivity wireless accelerometer will extend the use of WSSN to a broader class of SHM applications. PMID:29342102

  14. A de novo Mutation in KMT2A (MLL) in monozygotic twins with Wiedemann-Steiner syndrome.

    Science.gov (United States)

    Dunkerton, Sophie; Field, Matthew; Cho, Vicki; Bertram, Edward; Whittle, Belinda; Groves, Alexandra; Goel, Himanshu

    2015-09-01

    Growth deficiency, psychomotor delay, and facial dysmorphism was originally described in a male patient in 1989 by Wiedemann et al. and later in 2000 by Steiner et al. Wiedemann-Steiner syndrome (WSS) has since been described only a few times in the literature, with the phenotypic spectrum both expanding and becoming more delineated with each patient reported. We report on the clinical and molecular features of monozygotic twins with a de novo mutation in KMT2A. Single nucleotide polymorphism (SNP) microarray was done on both twins and whole-exome sequencing was done using both parents and one of the affected twins. SNP microarray confirmed that they were monozygotic twins. A de novo heterozygous variant (p. Arg1083*) in the KMT2A gene was identified through whole-exome sequencing, confirming the diagnosis of WSS. In this study, we have identified a de novo mutation in KMT2A associated with psychomotor developmental delay, facial dysmorphism, short stature, hypertrichosis cubiti, and small kidneys. This finding in monozygotic twins gives specificity to the WSS. The description of more cases of WSS is needed for further delineation of this condition. Small kidneys with normal function have not been described in this condition in the medical literature before. © 2015 Wiley Periodicals, Inc.

  15. Executive summary for the Weldon Spring Site Environmental Report for calendar year 1991

    International Nuclear Information System (INIS)

    1992-07-01

    This report is the sixth in a series of annual reports produced by the Weldon Spring Site Remedial Action Project (WSSRAP) since 1986. It reports the results of a comprehensive, year-round program to monitor the impact of the Weldon Spring site (WSS) on the surrounding region's groundwater and surface waters; air quality; vegetation and wildlife; and, through these multiple pathways, the potential for exposure to receptor human populations. Information is also presented on the environmental monitoring quality assurance program, waste management activities, audits and reviews, and special environmental studies. Data are included for both the Weldon Spring Chemical Plant and raffinate pits and the Weldon Spring Quarry. Based on the consistent exercise of quality assurance in both standard operating procedures and quality control sample collection, the WSSRAP asserts that the data presented in the WSS Environmental Report for Calendar Year 1991 accurately reflect the environmental conditions monitored at the WSS. This report presents narratives, summaries, and conclusions on environmental monitoring at the WSS and surrounding vicinity properties for the entire 1991 monitoring year. During 1991 the WSSRAP also published quarterly data reports, wherein all routine monitoring data were tabulated and presented quarterly to allow the public to review the data in a timely fashion prior to issuance of the annual report

  16. Metallurgy of stress corrosion cracking

    International Nuclear Information System (INIS)

    Donovan, J.A.

    1973-01-01

    The susceptibility of metals and alloys to stress corrosion is discussed in terms of the relationship between structural characteristics (crystal structure, grains, and second phases) and defects (vacancies, dislocations, and cracks) that exist in metals and alloys. (U.S.)

  17. GASICA: Generic Automated Stress Induction and Control ApplicationDesign of an application for controlling the stress state

    Directory of Open Access Journals (Sweden)

    Benny Van Der Vijgh

    2014-12-01

    Full Text Available 1.In a multitude of research and therapy paradigms it is relevant to know, and desirably to control, the stress state of a patient or participant. Examples include research paradigms in which the stress state is the dependent or independent variable, or therapy paradigms where this state indicates the boundaries of the therapy. To our knowledge, no application currently exists that focuses specifically on the automated control of the stress state while at the same time being generic enough to be used in various therapy and research purposes. Therefore, we introduce GASICA, an application aimed at the automated control of the stress state in a multitude of therapy and research paradigms. The application consists of three components: a digital stressor game, a set of measurement devices and a feedback model. These three components form a closed loop (called a biocybernetic loop by Pope, Bogart, & Bartolome, 1995 and Fairclough, 2009 that continuously presents an acute psychological stressor, measures several physiological responses to this stressor, and adjusts the stressor intensity based on these measurements by means of the feedback model, hereby aiming to control the stress state. In this manner GASICA presents multidimensional and ecological valid stressors, whilst continuously in control of the form and intensity of the presented stressors, aiming at the automated control of the stress state. Furthermore, the application is designed as a modular open-source application to easily implement different therapy and research tasks using a high-level programming interface and configuration file, and allows for the addition of (existing measurement equipment, making it usable for various paradigms.

  18. GASICA: generic automated stress induction and control application design of an application for controlling the stress state.

    Science.gov (United States)

    van der Vijgh, Benny; Beun, Robbert J; van Rood, Maarten; Werkhoven, Peter

    2014-01-01

    In a multitude of research and therapy paradigms it is relevant to know, and desirably to control, the stress state of a patient or participant. Examples include research paradigms in which the stress state is the dependent or independent variable, or therapy paradigms where this state indicates the boundaries of the therapy. To our knowledge, no application currently exists that focuses specifically on the automated control of the stress state while at the same time being generic enough to be used in various therapy and research purposes. Therefore, we introduce GASICA, an application aimed at the automated control of the stress state in a multitude of therapy and research paradigms. The application consists of three components: a digital stressor game, a set of measurement devices, and a feedback model. These three components form a closed loop (called a biocybernetic loop by Pope et al. (1995) and Fairclough (2009) that continuously presents an acute psychological stressor, measures several physiological responses to this stressor, and adjusts the stressor intensity based on these measurements by means of the feedback model, hereby aiming to control the stress state. In this manner GASICA presents multidimensional and ecological valid stressors, whilst continuously in control of the form and intensity of the presented stressors, aiming at the automated control of the stress state. Furthermore, the application is designed as a modular open-source application to easily implement different therapy and research tasks using a high-level programming interface and configuration file, and allows for the addition of (existing) measurement equipment, making it usable for various paradigms.

  19. Post-traumatic stress disorder and beyond: an overview of rodent stress models.

    Science.gov (United States)

    Schöner, Johanna; Heinz, Andreas; Endres, Matthias; Gertz, Karen; Kronenberg, Golo

    2017-10-01

    Post-traumatic stress disorder (PTSD) is a psychiatric disorder of high prevalence and major socioeconomic impact. Patients suffering from PTSD typically present intrusion and avoidance symptoms and alterations in arousal, mood and cognition that last for more than 1 month. Animal models are an indispensable tool to investigate underlying pathophysiological pathways and, in particular, the complex interplay of neuroendocrine, genetic and environmental factors that may be responsible for PTSD induction. Since the 1960s, numerous stress paradigms in rodents have been developed, based largely on Seligman's seminal formulation of 'learned helplessness' in canines. Rodent stress models make use of physiological or psychological stressors such as foot shock, underwater trauma, social defeat, early life stress or predator-based stress. Apart from the brief exposure to an acute stressor, chronic stress models combining a succession of different stressors for a period of several weeks have also been developed. Chronic stress models in rats and mice may elicit characteristic PTSD-like symptoms alongside, more broadly, depressive-like behaviours. In this review, the major existing rodent models of PTSD are reviewed in terms of validity, advantages and limitations; moreover, significant results and implications for future research-such as the role of FKBP5, a mediator of the glucocorticoid stress response and promising target for therapeutic interventions-are discussed. © 2017 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

  20. Residual stress analysis on materials with steep stress gradient by using X-ray incidence at higher angles

    International Nuclear Information System (INIS)

    Ohya, Shin-ichi; Yoshioka, Yasuo; Maeno, Shigeki

    1996-01-01

    X-ray stress measurements for isotropic polycrystalline are materials are usually carried out by the sin 2 ψ method under the assumption of no stress gradient in X-ray penetration depth. When a steep stress gradient exists in the vicinity of surface layer, however, non-linear sin 2 ψ relation is observed and the sin 2 ψ method cannot be applied on such cases. Although several X-ray stress analyzers have been developed for materials with steep stress gradient in the surface layer, it is desirable to use diffraction data at higher incident angles of ψ 0 as possible as close on 90 degrees in order to determine the both values of surface stress and stress gradient with high accuracy. In the present study, an X-ray stress analyzer based on Ω geometry was fabricated to enable X-ray incidence at higher angle of ψ 0 . The X-ray detector was positioned on -η side against X-ray incident beam. Both of the residual surface stress and stress gradient were determined by use of the COSψ method on shot-peened steel and silicon nitride specimens. This prototype stress analyzer was found effective to perform a biaxial or triaxial stress analysis. (author)

  1. Occupational stress in the multicultural workplace.

    Science.gov (United States)

    Pasca, Romana; Wagner, Shannon L

    2011-08-01

    Occupational stress is a well researched topic leading to the development of strong, viable models of workplace stress. However, there is a gap in the literature with respect to the applicability of this research to specific cultural groups, in particular those of immigrant status. The present paper reviews the extant literature regarding occupational stress from a multicultural perspective, evaluates the usefulness for existing models in the multicultural context, and discusses current issues with respect to increasing multiculturalism in the work environment. The authors conclude that workforce diversity is emerging as a pressing issue of organizational life and consequently, that future research needs to continue investigating whether current knowledge regarding workplace stress is fitting with the multicultural diversity of the present-day working population.

  2. Teacher stress and health; examination of a model.

    Science.gov (United States)

    DeFrank, R S; Stroup, C A

    1989-01-01

    Stress in teaching derives from a variety of sources, and evidence exists linking such stress to physical and mental health concerns. Detailed examination of the linkages among personal factors, job stress, job satisfaction and symptomatology have not been done in this occupation, however, and the present study examines a model interrelating these variables. A survey of 245 predominantly female elementary school teachers in southeast Texas suggested that demographic factors and teaching background do not influence stress, satisfaction or health concerns. However, while job stress was the strongest predictor of job satisfaction, this stress had no direct relationship with health problems, an unexpected finding. Write-in responses by teachers indicated additional sources of stress, many of which were environmental or policy-based in nature. The implications of these findings for future research and stress management interventions for teachers are discussed.

  3. Effects of distance from center of a weld to fixed end on residual stress and stress intensity factor of a piping weld. Evaluation of SCC growth under residual stress field. Report 1

    International Nuclear Information System (INIS)

    Miyazaki, Katsumasa; Numata, Masanori; Saito, Koichi; Mochizuki, Masahito

    2006-01-01

    The fixed conditions of butt welds between straight pipe and valve or pump in the actual piping system are different from those of straight pipes. However, the effect of fixed condition on the residual stress and the stress intensity factor for evaluation of structural integrity of cracked piping was not clear. In this study, the finite element analyses were conducted by considering the differences in the distance from the center of weld to the fixed end L to clarify the effect of fixed condition on the residual stress and the stress intensity factor. For the 600 A piping, the axial residual stress distribution was not affected by the distance L. Furthermore, the stress intensity factor of circumferential crack under the residual stress field with fixed condition could be estimated by using the existing simplified solution for piping. (author)

  4. Thyro-stress

    OpenAIRE

    Kalra, Sanjay; Verma, Komal; Balhara, Yatan Pal Singh

    2017-01-01

    Our understanding of the biopsychosocial model of health, and its influence on chronic endocrine conditions, has improved over the past few decades. We can distinguish, for example, between diabetes distress and major depressive disorders in diabetes. Similar to diabetes distress, we suggest the existence of “thyrostress” in chronic thyroid disorders. Thyro-stress is defined as an emotional state, characterized by extreme apprehension, discomfort or dejection, caused by the challenges and dem...

  5. A physical/psychological and biological stress combine to enhance endoplasmic reticulum stress

    Energy Technology Data Exchange (ETDEWEB)

    Mondal, Tapan Kumar; Emeny, Rebecca T.; Gao, Donghong; Ault, Jeffrey G.; Kasten-Jolly, Jane; Lawrence, David A., E-mail: david.lawrence@health.ny.gov

    2015-12-01

    The generation of an immune response against infectious and other foreign agents is substantially modified by allostatic load, which is increased with chemical, physical and/or psychological stressors. The physical/psychological stress from cold-restraint (CR) inhibits host defense against Listeria monocytogenes (LM), due to early effects of the catecholamine norepinephrine (NE) from sympathetic nerves on β1-adrenoceptors (β1AR) of immune cells. Although CR activates innate immunity within 2 h, host defenses against bacterial growth are suppressed 2–3 days after infection (Cao and Lawrence 2002). CR enhances inducible nitric oxide synthase (iNOS) expression and NO production. The early innate activation leads to cellular reduction-oxidation (redox) changes of immune cells. Lymphocytes from CR-treated mice express fewer surface thiols. Splenic and hepatic immune cells also have fewer proteins with free thiols after CR and/or LM, and macrophages have less glutathione after the in vivo CR exposure or exposure to NE in vitro. The early induction of CR-induced oxidative stress elevates endoplasmic reticulum (ER) stress, which could interfere with keeping phagocytized LM within the phagosome or re-encapsuling LM by autophagy once they escape from the phagosome. ER stress-related proteins, such as glucose-regulated protein 78 (GRP78), have elevated expression with CR and LM. The results indicate that CR enhances the unfolded protein response (UPR), which interferes with host defenses against LM. Thus, it is postulated that increased stress, as exists with living conditions at low socioeconomic conditions, can lower host defenses against pathogens because of oxidative and ER stress processes. - Highlights: • Cold-restraint (physical/psychological stress) induces early oxidative stress. • The oxidative stress relates to catecholamine signaling beta-adrenoceptors. • Physical/psychological stress combines infection enhancing inflammation. • Endoplasmic reticulum

  6. Bayesian networks modelling in support to cross cutting analysis of water supply and sanitation in developing countries

    Science.gov (United States)

    Dondeynaz, C.; López Puga, J.; Carmona Moreno, C.

    2013-02-01

    Despite the efforts made towards the millennium goals targets during the last decade, access to improved water supply or basic sanitation remains still not accessible for millions of people across the world. This paper proposes a set of models that use 25 key variables from the WatSan4Dev dataset and country profiles involving Water Supply and Sanitation (Dondeynaz et al., 2012). This paper proposes the use of Bayesian Network modelling methods because adapted to the management of non-normal distribution, and integrate a qualitative approach for data analysis. They also offer the advantage to integrate preliminary knowledge into the probabilistic models. The statistical performance of the proposed models ranges between 80 and 95% which is very satisfactory taking into account the strong heterogeneity of variables. Probabilistic scenarios run from the models allow a quantification of the relationships between human development, external support, governance aspects, economic activities and Water Supply and Sanitation (WSS) access. According to models proposed in this paper, a strong poverty reduction will induce an increment of the WSS access equal to 75-76% through: (1) the organisation of on-going urbanisation process to avoid slums development; and, (2) the improvement of health care for instance for children. On one side, improving governance, such as institutional efficiency, capacities to make and apply rules or control of corruption will also have a positive impact on WSS sustainable development. The first condition for an increment of the WSS access remains of course an improvement of the economic development with an increment of household income. Moreover, a significant country environmental commitment associated with civil society freedom of expression constitutes a favourable environment for sustainable WSS services delivery. Intensive agriculture through irrigation practises also appears as a mean for sustainable WSS thanks to multi-uses and

  7. Effect of the weld joint configuration on stressed components, residual stresses and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Cevik, Bekir; Oezer, Alpay; Oezcatalbas, Yusuf [Gazi Univ., Ankara (Turkey)

    2014-03-01

    The effect of the weld joint configuration on components has been studied, which are under service loads, under repair or construction and the residual stresses as well as the mechanical properties of the joint have been determined. For this purpose, a horizontal positioned tensile testing device and a semi-automatic MIG welding machine have been used and then the weld joints of the plates were subjected to different elastic stresses. When the temperature of the joined elements decreased to room temperature, applied elastic stresses were released. By this means, the effects of the existing tensile stresses in the joined parts and the tensile stresses created by the welding processes were investigated. The tensile stresses occurring in the joined elements were determined by using the photo-elasticity analysis method and the hole-drilling method. Also, tensile-shear tests were applied in order to determine the effect of permanent tensile loads on the mechanical properties of the joint. Experimental results showed that the application of corner welded lap joints for components under tensile loading significantly decrease the shear strength and yielding capacities of the joint. (orig.)

  8. Flow Characteristics Near to Stent Strut Configurations on Femoropopliteal Artery

    Science.gov (United States)

    Paisal, Muhammad Sufyan Amir; Fadhil Syed Adnan, Syed; Taib, Ishkrizat; Ismail, Al Emran; Kamil Abdullah, Mohammad; Nordin, Normayati; Seri, Suzairin Md; Darlis, Nofrizalidris

    2017-08-01

    Femoropopiteal artery stenting is a common procedure suggested by medical expert especially for patient who is diagnosed with severe stenosis. Many researchers reported that the growth of stenosis is significantly related to the geometry of stent strut configuration. The different shapes of stent geometry are presenting the different flow pattern and re-circulation in stented femoropopliteal artery. The blood flow characteristics near to the stent geometry are predicted for the possibility of thrombosis and atherosclerosis to be formed as well as increase the growth of stenosis. Thus, this study aims to determine the flow characteristic near to stent strut configuration based on different hemodynamic parameters. Three dimensional models of stent and simplified femoropopliteal artery are modelled using computer aided design (CAD) software. Three different models of stent shapes; hexagon, circle and rectangle are simulated using computational fluid dynamic (CFD) method. Then, parametric study is implemented to predict the performance of stent due to hemodynamic differences. The hemodynamic parameters considered are pressure, velocity, low wall shear stress (WSSlow) and wall shear stress (WSS). From the observation, flow re-circulation has been formed for all simulated stent models which the proximal region shown the severe vortices. However, rectangular shape of stent strut (Type P3) shows the lowest WSSlow and the highest WSS between the range of 4 dyne/cm2 and 70 dyne/cm2. Stent Type P3 also shows the best hemodynamic stent performance as compare to others. In conclusion, Type P3 has a favourable result in hemodynamic stent performance that predicted less probability of thrombosis and atherosclerosis to be formed as well as reduces the growth of restenosis.

  9. Temperature and stress calculation for final disposal

    International Nuclear Information System (INIS)

    Tarandi, T.

    1979-02-01

    Temperature and stress distribution in and around the final storage facility has been calculated for three different arrangements of the tunnels: - 2 planes with 60 m vertical distance between them - 2 planes with 100 m distance and - 1 plane. The highest temperatures and stresses occur for the 2 plane alternative with distance 60 m between planes. The maximum compressive stress is in this case 24.0 MPa 140 years after the time of deposition, compared with 12.6 MPa in the 1 plane case. The maximum tensile stress exists at the surface and is in the 2 plane case 6.0 MPa 800 - 1,500 years after deposition, compared with 4.2 MPa for the 1 plane variant. An estimation of maximum tensile stresses between the tunnel planes yields a value of 1.5 MPa. The above-mentioned stresses are due to temperature distribution induced by the radioactive waste. To obtain the total stresses, initial stresses in the undisturbed rock, which vary according to location, are to be added to these stresses. (author)

  10. No Time to Waste: Transcriptome Study Reveals that Drought Tolerance in Barley May Be Attributed to Stressed-Like Expression Patterns that Exist before the Occurrence of Stress.

    Science.gov (United States)

    Janiak, Agnieszka; Kwasniewski, Miroslaw; Sowa, Marta; Gajek, Katarzyna; Żmuda, Katarzyna; Kościelniak, Janusz; Szarejko, Iwona

    2017-01-01

    Plant survival in adverse environmental conditions requires a substantial change in the metabolism, which is reflected by the extensive transcriptome rebuilding upon the occurrence of the stress. Therefore, transcriptomic studies offer an insight into the mechanisms of plant stress responses. Here, we present the results of global gene expression profiling of roots and leaves of two barley genotypes with contrasting ability to cope with drought stress. Our analysis suggests that drought tolerance results from a certain level of transcription of stress-influenced genes that is present even before the onset of drought. Genes that predispose the plant to better drought survival play a role in the regulatory network of gene expression, including several transcription factors, translation regulators and structural components of ribosomes. An important group of genes is involved in signaling mechanisms, with significant contribution of hormone signaling pathways and an interplay between ABA, auxin, ethylene and brassinosteroid homeostasis. Signal transduction in a drought tolerant genotype may be more efficient through the expression of genes required for environmental sensing that are active already during normal water availability and are related to actin filaments and LIM domain proteins, which may function as osmotic biosensors. Better survival of drought may also be attributed to more effective processes of energy generation and more efficient chloroplasts biogenesis. Interestingly, our data suggest that several genes involved in a photosynthesis process are required for the establishment of effective drought response not only in leaves, but also in roots of barley. Thus, we propose a hypothesis that root plastids may turn into the anti-oxidative centers protecting root macromolecules from oxidative damage during drought stress. Specific genes and their potential role in building up a drought-tolerant barley phenotype is extensively discussed with special emphasis

  11. No Time to Waste: Transcriptome Study Reveals that Drought Tolerance in Barley May Be Attributed to Stressed-Like Expression Patterns that Exist before the Occurrence of Stress

    Directory of Open Access Journals (Sweden)

    Agnieszka Janiak

    2018-01-01

    Full Text Available Plant survival in adverse environmental conditions requires a substantial change in the metabolism, which is reflected by the extensive transcriptome rebuilding upon the occurrence of the stress. Therefore, transcriptomic studies offer an insight into the mechanisms of plant stress responses. Here, we present the results of global gene expression profiling of roots and leaves of two barley genotypes with contrasting ability to cope with drought stress. Our analysis suggests that drought tolerance results from a certain level of transcription of stress-influenced genes that is present even before the onset of drought. Genes that predispose the plant to better drought survival play a role in the regulatory network of gene expression, including several transcription factors, translation regulators and structural components of ribosomes. An important group of genes is involved in signaling mechanisms, with significant contribution of hormone signaling pathways and an interplay between ABA, auxin, ethylene and brassinosteroid homeostasis. Signal transduction in a drought tolerant genotype may be more efficient through the expression of genes required for environmental sensing that are active already during normal water availability and are related to actin filaments and LIM domain proteins, which may function as osmotic biosensors. Better survival of drought may also be attributed to more effective processes of energy generation and more efficient chloroplasts biogenesis. Interestingly, our data suggest that several genes involved in a photosynthesis process are required for the establishment of effective drought response not only in leaves, but also in roots of barley. Thus, we propose a hypothesis that root plastids may turn into the anti-oxidative centers protecting root macromolecules from oxidative damage during drought stress. Specific genes and their potential role in building up a drought-tolerant barley phenotype is extensively discussed

  12. The Political Economy and Coalitions in Botswana’s Water Sector Reform 2009-13: to what extent can the process of reform be understood?

    OpenAIRE

    Colman, Anthony John

    2013-01-01

    This thesis examines the process of water sector reform in Botswana, focusing on barriers to effective delivery of clean water and improved sanitation services (WSS) to all, and water resource management (WRM), in a water insecure country, dependent for surface water on international river basin organisations. The study provides a crtitical analysis of policy change in progress. The impact of the water reforms on the poor and the process of centralising control of WSS, from both tribal and lo...

  13. Transgenerational transmission of a stress-coping phenotype programmed by early-life stress in the Japanese quail

    Science.gov (United States)

    Zimmer, Cédric; Larriva, Maria; Boogert, Neeltje J.; Spencer, Karen A.

    2017-01-01

    An interesting aspect of developmental programming is the existence of transgenerational effects that influence offspring characteristics and performance later in life. These transgenerational effects have been hypothesized to allow individuals to cope better with predictable environmental fluctuations and thus facilitate adaptation to changing environments. Here, we test for the first time how early-life stress drives developmental programming and transgenerational effects of maternal exposure to early-life stress on several phenotypic traits in their offspring in a functionally relevant context using a fully factorial design. We manipulated pre- and/or post-natal stress in both Japanese quail mothers and offspring and examined the consequences for several stress-related traits in the offspring generation. We show that pre-natal stress experienced by the mother did not simply affect offspring phenotype but resulted in the inheritance of the same stress-coping traits in the offspring across all phenotypic levels that we investigated, shaping neuroendocrine, physiological and behavioural traits. This may serve mothers to better prepare their offspring to cope with later environments where the same stressors are experienced. PMID:28387355

  14. Knowledge work and work-related stress

    DEFF Research Database (Denmark)

    Ipsen, Christine

    2006-01-01

    Work-related stress is an increasing problem in Europe. Earlier studies have stated that knowledge-work comprises working conditions which reflect a good psychosocial environment. Recent Danish studies, however, point at stress being an increasing problem in knowledge-intensive companies...... with informally, individu-ally and incidentally. It is only when problems exist that enhanced support is offered in order to help an employee to cope or recover. As most workplace initiatives work at this tertiary level, the sources of work-related and organiza-tional stress are not reduced or eliminated...... as good and stimulating, but has on the other hand sides to it which can cause frustration and stress. The implication of organisational characteristics of the knowledge-intensive companies studied is a transfer of the responsibility for ones own working-life. Consequently, issues are dealt...

  15. The Role of the Secondary Stress in Teaching the English Rhythm

    Science.gov (United States)

    Yurtbasi, Metin

    2017-01-01

    In the phonological literature in English, which is a stress-timed language, the existence of at least three levels of stress is usually taken for granted. Words, phrases, utterances or sentences have a prominent element in one of their syllables, which usually correlates with a partner in the same unit, called the secondary stress. It so happens…

  16. Mapping Tectonic Stress Using Earthquakes

    International Nuclear Information System (INIS)

    Arnold, Richard; Townend, John; Vignaux, Tony

    2005-01-01

    An earthquakes occurs when the forces acting on a fault overcome its intrinsic strength and cause it to slip abruptly. Understanding more specifically why earthquakes occur at particular locations and times is complicated because in many cases we do not know what these forces actually are, or indeed what processes ultimately trigger slip. The goal of this study is to develop, test, and implement a Bayesian method of reliably determining tectonic stresses using the most abundant stress gauges available - earthquakes themselves.Existing algorithms produce reasonable estimates of the principal stress directions, but yield unreliable error bounds as a consequence of the generally weak constraint on stress imposed by any single earthquake, observational errors, and an unavoidable ambiguity between the fault normal and the slip vector.A statistical treatment of the problem can take into account observational errors, combine data from multiple earthquakes in a consistent manner, and provide realistic error bounds on the estimated principal stress directions.We have developed a realistic physical framework for modelling multiple earthquakes and show how the strong physical and geometrical constraints present in this problem allow inference to be made about the orientation of the principal axes of stress in the earth's crust

  17. Drivers and barriers to heat stress resilience.

    Science.gov (United States)

    Hatvani-Kovacs, Gertrud; Belusko, Martin; Skinner, Natalie; Pockett, John; Boland, John

    2016-11-15

    Heatwaves are the most dangerous natural hazard to health in Australia. The frequency and intensity of heatwaves will increase due to climate change and urban heat island effects in cities, aggravating the negative impacts of heatwaves. Two approaches exist to develop population heat stress resilience. Firstly, the most vulnerable social groups can be identified and public health services can prepare for the increased morbidity. Secondly, the population level of adaptation and the heat stress resistance of the built environment can be increased. The evaluation of these measures and their efficiencies has been fragmented across research disciplines. This study explored the relationships between the elements of heat stress resilience and their potential demographic and housing drivers and barriers. The responses of a representative online survey (N=393) about heat stress resilience at home and work from Adelaide, South Australia were analysed. The empirical findings demonstrate that heat stress resistant buildings increased adaptation capacity and decreased the number of health problems. Air-conditioning increased dependence upon it, limited passive adaptation and only people living in homes with whole-house air-conditioning had less health problems during heatwaves. Tenants and respondents with pre-existing health conditions were the most vulnerable, particularly as those with health conditions were not aware of their vulnerability. The introduction of an Energy Performance Certificate is proposed and discussed as an effective incentive to increase the heat stress resistance of and the general knowledge about the built environment. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Better executive function under stress mitigates the effects of recent life stress exposure on health in young adults.

    Science.gov (United States)

    Shields, Grant S; Moons, Wesley G; Slavich, George M

    2017-01-01

    Executive function is a neuropsychological construct that enables controlled cognitive processing, which has been hypothesized to enhance individuals' resilience to stress. However, little empirical work has directly examined how executive function under different conditions mitigates the negative effects of stress exposure on health. To address this issue, we recruited 110 healthy young adults and assessed their recent life stress exposure, executive function in either a stressful or non-stressful context, and current health complaints. Based on existing research, we hypothesized that individuals exhibiting better executive function following a laboratory-based stressor (but not a control task) would demonstrate weaker associations between recent stress exposure and health because they perceived recent life stressors as being less severe. Consistent with this hypothesis, better executive function during acute stress, but not in the absence of stress, was associated with an attenuated link between participants' recent life stress exposure and their current health complaints. Moreover, this attenuating effect was mediated by lesser perceptions of stressor severity. Based on these data, we conclude that better executive function under stress is associated with fewer health complaints and that these effects may occur by reducing individuals' perceptions of stressor severity. The data thus suggest the possibility of reducing stress-related health problems by enhancing executive function.

  19. Combinatorial stresses kill pathogenic Candida species

    Science.gov (United States)

    Kaloriti, Despoina; Tillmann, Anna; Cook, Emily; Jacobsen, Mette; You, Tao; Lenardon, Megan; Ames, Lauren; Barahona, Mauricio; Chandrasekaran, Komelapriya; Coghill, George; Goodman, Daniel; Gow, Neil A. R.; Grebogi, Celso; Ho, Hsueh-Lui; Ingram, Piers; McDonagh, Andrew; De Moura, Alessandro P. S.; Pang, Wei; Puttnam, Melanie; Radmaneshfar, Elahe; Romano, Maria Carmen; Silk, Daniel; Stark, Jaroslav; Stumpf, Michael; Thiel, Marco; Thorne, Thomas; Usher, Jane; Yin, Zhikang; Haynes, Ken; Brown, Alistair J. P.

    2012-01-01

    Pathogenic microbes exist in dynamic niches and have evolved robust adaptive responses to promote survival in their hosts. The major fungal pathogens of humans, Candida albicans and Candida glabrata, are exposed to a range of environmental stresses in their hosts including osmotic, oxidative and nitrosative stresses. Significant efforts have been devoted to the characterization of the adaptive responses to each of these stresses. In the wild, cells are frequently exposed simultaneously to combinations of these stresses and yet the effects of such combinatorial stresses have not been explored. We have developed a common experimental platform to facilitate the comparison of combinatorial stress responses in C. glabrata and C. albicans. This platform is based on the growth of cells in buffered rich medium at 30°C, and was used to define relatively low, medium and high doses of osmotic (NaCl), oxidative (H 2O2) and nitrosative stresses (e.g., dipropylenetriamine (DPTA)-NONOate). The effects of combinatorial stresses were compared with the corresponding individual stresses under these growth conditions. We show for the first time that certain combinations of combinatorial stress are especially potent in terms of their ability to kill C. albicans and C. glabrata and/or inhibit their growth. This was the case for combinations of osmotic plus oxidative stress and for oxidative plus nitrosative stress. We predict that combinatorial stresses may be highly signif cant in host defences against these pathogenic yeasts. PMID:22463109

  20. Nonlinear morphoelastic plates I: Genesis of residual stress

    KAUST Repository

    McMahon, J.

    2011-04-28

    Volumetric growth of an elastic body may give rise to residual stress. Here a rigorous analysis is given of the residual strains and stresses generated by growth in the axisymmetric Kirchhoff plate. Balance equations are derived via the Global Constraint Principle, growth is incorporated via a multiplicative decomposition of the deformation gradient, and the system is closed by a response function. The particular case of a compressible neo-Hookean material is analyzed, and the existence of residually stressed states is established. © SAGE Publications 2011.

  1. Nonlinear morphoelastic plates I: Genesis of residual stress

    KAUST Repository

    McMahon, J.; Goriely, A.; Tabor, M.

    2011-01-01

    Volumetric growth of an elastic body may give rise to residual stress. Here a rigorous analysis is given of the residual strains and stresses generated by growth in the axisymmetric Kirchhoff plate. Balance equations are derived via the Global Constraint Principle, growth is incorporated via a multiplicative decomposition of the deformation gradient, and the system is closed by a response function. The particular case of a compressible neo-Hookean material is analyzed, and the existence of residually stressed states is established. © SAGE Publications 2011.

  2. Memory dynamics under stress.

    Science.gov (United States)

    Quaedflieg, Conny W E M; Schwabe, Lars

    2018-03-01

    Stressful events have a major impact on memory. They modulate memory formation in a time-dependent manner, closely linked to the temporal profile of action of major stress mediators, in particular catecholamines and glucocorticoids. Shortly after stressor onset, rapidly acting catecholamines and fast, non-genomic glucocorticoid actions direct cognitive resources to the processing and consolidation of the ongoing threat. In parallel, control of memory is biased towards rather rigid systems, promoting habitual forms of memory allowing efficient processing under stress, at the expense of "cognitive" systems supporting memory flexibility and specificity. In this review, we discuss the implications of this shift in the balance of multiple memory systems for the dynamics of the memory trace. Specifically, stress appears to hinder the incorporation of contextual details into the memory trace, to impede the integration of new information into existing knowledge structures, to impair the flexible generalisation across past experiences, and to hamper the modification of memories in light of new information. Delayed, genomic glucocorticoid actions might reverse the control of memory, thus restoring homeostasis and "cognitive" control of memory again.

  3. Comparison of dynamic changes in endogenous hormone level, water content and water-soluble sugars in camellia oleifera of different ages

    International Nuclear Information System (INIS)

    Hu, J.; Shah, F.A.; Fu, S.; Wu, W.

    2017-01-01

    The aim of this study is to investigate and understand the dynamic changes and the possible functions of hormones, water and sugar content during the development of C. oleifera. We analyzed and compared WWC, WSS and five endogenous hormones (DHZR, ZR, GA, IAA and ABA) contents between May and August in C. oleifera plants at different ages from the same orchard. The results showed that WWC, WSS, DHZR, ZR, GA, IAA and ABA contents varied from 61.64%-74.15%, 21.24mg/g-62.44mg/g, 6.237ng/g-38.342ng/g, 6.215ng/g-16.721ng/g, 5.668ng/g-18.024ng/g, 24.753ng/g-147.507ng/g and 66.541ng/g-156.212ng/g, respectively. WWC showed a decrease-increase-decrease variation pattern, while the WSS contents demonstrated a generally increasing trend with increasing tree age. The levels of ABA in leaves sampled in August was higher than that in May, but the opposite was found for the GA and IAA levels. Tree ages were negatively correlated with ZR and GA concentration at the 1% or 5% significance level. The results of this study broaden our understanding of the interrelationships between phytohormones, WWC, and WSS content in the growth and development of C. oleifera. (author)

  4. Embedding human annoyance rate models in wireless smart sensors for assessing the influence of subway train-induced ambient vibration

    Science.gov (United States)

    Sun, Ke; Zhang, Wei; Ding, Huaping; Kim, Robin E.; Spencer, Billie F., Jr.

    2016-10-01

    The operation of subway trains induces ambient vibrations, which may cause annoyance and other adverse effects on humans, eventually leading to physical, physiological, and psychological problems. In this paper, the human annoyance rate (HAR) models, used to assess the human comfort under the subway train-induced ambient vibrations, were deduced and the calibration curves for 5 typical use circumstances were addressed. An autonomous measurement system, based on the Imote2, wireless smart sensor (WSS) platform, plus the SHM-H, high-sensitivity accelerometer board, was developed for the HAR assessment. The calibration curves were digitized and embedded in the computational core of the WSS unit. Experimental validation was conducted, using the developed system on a large underground reinforced concrete frame structure adjoining the subway station. The ambient acceleration of both basement floors was measured; the embedded computation was implemented and the HAR assessment results were wirelessly transmitted to the central server, all by the WSS unit. The HAR distributions of the testing areas were identified, and the extent to which both basements will be influenced by the close-up subway-train’s operation, in term of the 5 typical use circumstances, were quantitatively assessed. The potential of the WSS-based autonomous system for the fast environment impact assessment of the subway train-induced ambient vibration was well demonstrated.

  5. Defining the Field of Existence of Shrouded Blades in High-Speed Gas Turbines

    Science.gov (United States)

    Belousov, Anatoliy I.; Nazdrachev, Sergeiy V.

    2018-01-01

    This work provides a method for determining the region of existence of banded blades of gas turbines for aircraft engines based on the analytical evaluation of tensile stresses in specific characteristic sections of the blade. This region is determined by the set of values of the parameter, which forms the law of distribution of the cross-sectional area of the cross-sections along the height of the airfoil. When seven independent parameters (gas-dynamic, structural and strength) are changed, the choice of the best option is proposed at the early design stage. As an example, the influence of the dimension of a turbine on the domain of the existence of banded blades is shown.

  6. 3D finite element analysis of stress distributions and strain energy release rates for adhesive bonded flat composite lap shear joints having pre-existing delaminations

    Energy Technology Data Exchange (ETDEWEB)

    Parida, S. K.; Pradhan, A. K. [Indian Institute of Technology, Bhubaneswar (India)

    2014-02-15

    The rate of propagation of embedded delamination in the strap adherend of lap shear joint (LSJ) made of carbon/epoxy composites has been evaluated employing three-dimensional non-linear finite elements. The delamination has been presumed to pre-exist in the thin resin layer between the first and second plies of the strap adherend. The inter-laminar peel and shear stress distributions have been studied in details and are seen to be predominantly three-dimensional in nature. The components of strain energy release rate (SERR) corresponding to the opening, sliding and cross sliding modes of delamination are significantly different at the two fronts of the embedded delamination. The sequential release of multi-point constraint (MPC) finite elements in the vicinity of the delamination fronts enables to simulate the growth of the delamination at either ends. This simulation procedure can be utilized effectively for evaluation of the status of the structural integrity of the bonded joints.

  7. Thermal stresses in long prisms by relaxation methods

    International Nuclear Information System (INIS)

    Cummins, J.D.

    1959-07-01

    A general method is presented for calculating the elastic thermal stresses in long prisms which are producing heat and are not solvable by simple analytical methods. The problem of an inverted lattice i.e. an hexagonal coolant passage surrounded by hexagonal fuel elements is considered and the temperature and principal thermal stress distributions evaluated for the particular case of 20% coolant. The maximum thermal stress for this type of fuel element is about the same as the maximum thermal stress in a cylindrical fuel element surrounded by a sea of coolant assuming the existence of the same maximum temperature drop and material properties. (author)

  8. Thermal stresses in long prisms by relaxation methods

    Energy Technology Data Exchange (ETDEWEB)

    Cummins, J D [Atomic Energy Establishment, Winfrith, Dorchester, Dorset (United Kingdom)

    1959-07-15

    A general method is presented for calculating the elastic thermal stresses in long prisms which are producing heat and are not solvable by simple analytical methods. The problem of an inverted lattice i.e. an hexagonal coolant passage surrounded by hexagonal fuel elements is considered and the temperature and principal thermal stress distributions evaluated for the particular case of 20% coolant. The maximum thermal stress for this type of fuel element is about the same as the maximum thermal stress in a cylindrical fuel element surrounded by a sea of coolant assuming the existence of the same maximum temperature drop and material properties. (author)

  9. Psychological stress and multimorbidity in general practice

    DEFF Research Database (Denmark)

    Prior, Anders

    2017-01-01

    . Additionally, stress is a common reason for contacting the general practitioner (GP), and yet no guidelines for management and treatment exist. Aims The aim of this thesis was to investigate the consequences of psychological stress on the health while taking into account mental‐physical multimorbidity, i...... found to be associated with adverse health outcomes and potentially suboptimal healthcare. The link between stress and multimorbidity could substantiate the efforts to develop management guidelines for primary care, stress‐targeted interventions, and to accommodate the healthcare system to better...... and poor prognosis of physical diseases, including increased mortality. However, little is known on the physical consequences of sub‐threshold psychological stress, which is more common than psychiatric disorders in the background population and is highly prevalent in persons with multimorbidity...

  10. occupational stress and job performance of female bankers in bank ...

    African Journals Online (AJOL)

    DGS-FUTO

    2018-06-01

    Jun 1, 2018 ... Ebonyi State University, Abakaliki ... exists between occupational stress (role boundary, distorted ... For instance, while employees in a hotel may be stressed up ..... the job performance of the female staff of UBAPlc, Abakaliki. ... as the extent of role boundary increases, there would be an inverse decrease in.

  11. Dose-stress synergism in cancer risk assessment

    International Nuclear Information System (INIS)

    Pop-Jordanova, N.; Pop-Jordanov, J.

    2001-01-01

    Our hypothesis is that the relatively low risk of cancer or leukaemia from depleted uranium, as predicted by the World Health Organization and the International Atomic Energy Agency, is a result of neglecting the synergism between physico-chemical agents and psychological stress agents (here shortly denoted as dose-stress synergism). We use the modified risk assessment model that comprises a psycho-somatic extension, originally developed by us for assessing the risks of energy sources. Our preliminary meta-analysis of animal and human studies on cancers confirmed the existence of stress effects, including the amplifying synergism. Consequently, the psychological stress can increase the probability of even small toxic chemical or ionizing radiation exposure to produce malignancy. Such dose-stress synergism might influence the health risks among military personnel and the residents in the highly stressful environment in the Balkans. Further investigation is needed to estimate the order of magnitude of these combined effects in particular circumstances. (Original)

  12. Bayesian networks modelling in support to cross-cutting analysis of water supply and sanitation in developing countries

    Directory of Open Access Journals (Sweden)

    C. Dondeynaz

    2013-09-01

    Full Text Available Despite the efforts made towards the Millennium Development Goals targets during the last decade, improved access to water supply or basic sanitation still remains unavailable for millions of people across the world. This paper proposes a set of models that use 25 key variables and country profiles from the WatSan4Dev data set involving water supply and sanitation (Dondeynaz et al., 2012. This paper suggests the use of Bayesian network modelling methods because they are more easily adapted to deal with non-normal distributions, and integrate a qualitative approach for data analysis. They also offer the advantage of integrating preliminary knowledge into the probabilistic models. The statistical performance of the proposed models ranges between 20 and 5% error rates, which are very satisfactory taking into account the strong heterogeneity of variables. Probabilistic scenarios run from the models allow an assessment of the relationships between human development, external support, governance aspects, economic activities and water supply and sanitation (WSS access. According to models proposed in this paper, gaining a strong poverty reduction will require the WSS access to reach 75–76% through: (1 the management of ongoing urbanisation processes to avoid slums development; and (2 the improvement of health care, for instance for children. Improving governance, such as institutional efficiency, capacities to make and apply rules, or control of corruption is positively associated with WSS sustainable development. The first condition for an increment of the HDP (human development and poverty remains of course an improvement of the economic conditions with higher household incomes. Moreover, a significant country commitment to the environment, associated with civil society freedom of expression constitutes a favourable setting for sustainable WSS services delivery. Intensive agriculture using irrigation practises also appears as a mean for sustainable

  13. Bayesian networks modelling in support to cross-cutting analysis of water supply and sanitation in developing countries

    Science.gov (United States)

    Dondeynaz, C.; López Puga, J.; Carmona Moreno, C.

    2013-09-01

    Despite the efforts made towards the Millennium Development Goals targets during the last decade, improved access to water supply or basic sanitation still remains unavailable for millions of people across the world. This paper proposes a set of models that use 25 key variables and country profiles from the WatSan4Dev data set involving water supply and sanitation (Dondeynaz et al., 2012). This paper suggests the use of Bayesian network modelling methods because they are more easily adapted to deal with non-normal distributions, and integrate a qualitative approach for data analysis. They also offer the advantage of integrating preliminary knowledge into the probabilistic models. The statistical performance of the proposed models ranges between 20 and 5% error rates, which are very satisfactory taking into account the strong heterogeneity of variables. Probabilistic scenarios run from the models allow an assessment of the relationships between human development, external support, governance aspects, economic activities and water supply and sanitation (WSS) access. According to models proposed in this paper, gaining a strong poverty reduction will require the WSS access to reach 75-76% through: (1) the management of ongoing urbanisation processes to avoid slums development; and (2) the improvement of health care, for instance for children. Improving governance, such as institutional efficiency, capacities to make and apply rules, or control of corruption is positively associated with WSS sustainable development. The first condition for an increment of the HDP (human development and poverty) remains of course an improvement of the economic conditions with higher household incomes. Moreover, a significant country commitment to the environment, associated with civil society freedom of expression constitutes a favourable setting for sustainable WSS services delivery. Intensive agriculture using irrigation practises also appears as a mean for sustainable WSS thanks to

  14. Pain sensitivity mediates the relationship between stress and headache intensity in chronic tension-type headache.

    Science.gov (United States)

    Cathcart, Stuart; Bhullar, Navjot; Immink, Maarten; Della Vedova, Chris; Hayball, John

    2012-01-01

    A central model for chronic tension-type headache (CTH) posits that stress contributes to headache, in part, by aggravating existing hyperalgesia in CTH sufferers. The prediction from this model that pain sensitivity mediates the relationship between stress and headache activity has not yet been examined. To determine whether pain sensitivity mediates the relationship between stress and prospective headache activity in CTH sufferers. Self-reported stress, pain sensitivity and prospective headache activity were measured in 53 CTH sufferers recruited from the general population. Pain sensitivity was modelled as a mediator between stress and headache activity, and tested using a nonparametric bootstrap analysis. Pain sensitivity significantly mediated the relationship between stress and headache intensity. The results of the present study support the central model for CTH, which posits that stress contributes to headache, in part, by aggravating existing hyperalgesia in CTH sufferers. Implications for the mechanisms and treatment of CTH are discussed.

  15. Microscopic creep models and the interpretation of stress-dip tests during creep

    International Nuclear Information System (INIS)

    Poirier, J.P.

    1976-09-01

    A critical analysis is made of the principal divergent view points concerning stress-dip tests. The raw data are examined and interpreted in the light of various creep models. The following problems are discussed: is the reverse strain anelastic or plastic; is the zero creep rate periodic due to recovery or is it spurious; can the existence or inexistence of an internal stress be deduced from stress-dip tests; can stress-dip tests allow to determine whether glide is jerky or viscous; can the internal stress be measured by stress-dip tests

  16. Sex differences in stress effects on emotional learning.

    Science.gov (United States)

    Merz, Christian J; Wolf, Oliver T

    2017-01-02

    Stress influences emotional learning and memory processes. These effects are thought to underlie stress-associated mental disorders. Sex differences in stress reactivity and in central nervous system stress sensitivity illustrate the important modulatory role of sex hormones. This Review outlines how stress hormones influence different stages of the fear conditioning process, such as fear acquisition, extinction, and retrieval. Results will be compared with findings on the impact of stress on episodic memory. The focus is on the available human data on sex differences and the impact sex hormones have on the stress effects on emotional learning and memory. It will become apparent that the menstrual cycle but also the intake of hormonal contraceptives modulates the impact of stress on brain and behavior. Additional basic research is needed for a deeper insight regarding the interplay between stress and sex hormones in emotion and cognition. In addition, new treatment options might be derived to optimize existing strategies such as exposure therapy, which relies on the principles of fear conditioning. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  17. Final Report: Characterization of Canister Mockup Weld Residual Stresses

    International Nuclear Information System (INIS)

    Enos, David; Bryan, Charles R.

    2016-01-01

    Stress corrosion cracking (SCC) of interim storage containers has been indicated as a high priority data gap by the Department of Energy (DOE) (Hanson et al., 2012), the Electric Power Research Institute (EPRI, 2011), the Nuclear Waste Technical Review Board (NWTRB, 2010a), and the Nuclear Regulatory Commission (NRC, 2012a, 2012b). Uncertainties exist in terms of the environmental conditions that prevail on the surface of the storage containers, the stress state within the container walls associated both with weldments as well as within the base metal itself, and the electrochemical properties of the storage containers themselves. The goal of the work described in this document is to determine the stress states that exists at various locations within a typical storage canister by evaluating the properties of a full-diameter cylindrical mockup of an interim storage canister. This mockup has been produced using the same manufacturing procedures as the majority of the fielded spent nuclear fuel interim storage canisters. This document describes the design and procurement of the mockup and the characterization of the stress state associated with various portions of the container. It also describes the cutting of the mockup into sections for further analyses, and a discussion of the potential impact of the results from the stress characterization effort.

  18. Final Report: Characterization of Canister Mockup Weld Residual Stresses

    Energy Technology Data Exchange (ETDEWEB)

    Enos, David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bryan, Charles R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-12-01

    Stress corrosion cracking (SCC) of interim storage containers has been indicated as a high priority data gap by the Department of Energy (DOE) (Hanson et al., 2012), the Electric Power Research Institute (EPRI, 2011), the Nuclear Waste Technical Review Board (NWTRB, 2010a), and the Nuclear Regulatory Commission (NRC, 2012a, 2012b). Uncertainties exist in terms of the environmental conditions that prevail on the surface of the storage containers, the stress state within the container walls associated both with weldments as well as within the base metal itself, and the electrochemical properties of the storage containers themselves. The goal of the work described in this document is to determine the stress states that exists at various locations within a typical storage canister by evaluating the properties of a full-diameter cylindrical mockup of an interim storage canister. This mockup has been produced using the same manufacturing procedures as the majority of the fielded spent nuclear fuel interim storage canisters. This document describes the design and procurement of the mockup and the characterization of the stress state associated with various portions of the container. It also describes the cutting of the mockup into sections for further analyses, and a discussion of the potential impact of the results from the stress characterization effort.

  19. Deployment-Related Injury and Posttraumatic Stress Disorder in US Military Personnel

    Science.gov (United States)

    2013-01-01

    stress disorder ( PTSD ), an anxiety disorder resulting from exposure to a traumatic event, is a frequent psychological...wounded Vietnam veterans. American Journal of Psychiatry 1989;146:667–9. 17. Helzer JE, Robins LN, McEvoy L. Post - traumatic stress disorder in the general...Meyer C. Post - traumatic stress disorder : the role of trauma, pre-existing psychiatric disorders , and gender. European Archives of Psychiatry

  20. Melatonin inhibits snake venom and antivenom induced oxidative stress and augments treatment efficacy.

    Science.gov (United States)

    Sharma, Rachana D; Katkar, Gajanan D; Sundaram, Mahalingam S; Swethakumar, Basavarajaiah; Girish, Kesturu S; Kemparaju, Kempaiah

    2017-05-01

    Snakebite is a neglected health hazard. Its patho-physiology has largely been focused on systemic and local toxicities; whereas, venom and antivenom induced oxidative stress has long been ignored. Antivenom therapy although neutralizes venom lethality and saves many lives, remains ineffective against oxidative stress. This prompted us to complement antivenom with an antioxidant molecule melatonin that would protect against oxidative stress and increase the efficacy of the existing snakebite therapy. Here we show that D. russelli and E. carinatus venoms induce strong oxidative stress that persists even after antivenom administration in mice model. Additionally, antivenoms also induce oxidative stress. Polyvalent antivenom induce more oxidative stress than monovalent antivenom. Strikingly, antivenom and melatonin together not only inhibit venom and antivenom induced oxidative stress but also significantly reduce the neutralizing antivenom dose. This study provides a therapeutic potential for enhancing the existing snakebite therapy. The combined treatment of antivenom+melatonin would prevent the upsurge of oxidative stress as well as minimize the antivenom load. Thus the investigation offers immense scope for physicians and toxinologists to reinvestigate, design new strategies and think beyond the conventional mode of antivenom therapy. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Correlates of housing affordability stress among older Australians.

    Science.gov (United States)

    Temple, Jeromey B

    2008-03-01

    The purpose of this study was to examine the prevalence and correlates of housing affordability stress among community-dwelling older Australians. The 2002 ABS General Social Survey was used to measure the prevalence of housing affordability stress. Rare event logistic regression was used to measure the potential correlates of housing affordability stress. Almost 5% of Australians aged 55 years and older, and 20% of those younger than 55 years, are estimated to experience housing affordability stress. Men and women living alone are more likely to experience affordability stress when compared to couples. Low-income earners, those with a consumer debt or who do not hold assets, are at a heightened risk of such stress. Home ownership, regardless of income, is the strongest buffer against housing affordability problems in old age. Although the prevalence of housing affordability stress is low among older Australians when compared to the younger population, a definite social gradient exists in those at risk.

  2. Stress corrosion crack growth in unirradiated zircaloy

    International Nuclear Information System (INIS)

    Pettersson, K.

    1978-10-01

    Experimental techniques suitable for the determination of stress corrosion crack growth rates in irradiated Zircaloy tube have been developed. The techniques have been tested on unirradiated. Zircaloy and it was found that the results were in good agreement with the results of other investigations. Some of the results were obtained at very low stress intensities and the crack growth rates observed, gave no indication of the existance of a K sub(ISCC) for iodine induced stress corrosion cracking in Zircaloy. This is of importance both for fuel rod behavior after a power ramp and for long term storage of spent Zircaloy-clad fuel. (author)

  3. Social aggravation: Understanding the complex role of social relationships on stress and health-relevant physiology.

    Science.gov (United States)

    Birmingham, Wendy C; Holt-Lunstad, Julianne

    2018-04-05

    There is a rich literature on social support and physical health, but research has focused primarily on the protective effects of social relationship. The stress buffering model asserts that relationships may be protective by being a source of support when coping with stress, thereby blunting health relevant physiological responses. Research also indicates relationships can be a source of stress, also influencing health. In other words, the social buffering influence may have a counterpart, a social aggravating influence that has an opposite or opposing effect. Drawing upon existing conceptual models, we expand these to delineate how social relationships may influence stress processes and ultimately health. This review summarizes the existing literature that points to the potential deleterious physiological effects of our relationships when they are sources of stress or exacerbate stress. Copyright © 2018 Elsevier B.V. All rights reserved.

  4. Development of New Micro Hydropower Turbine

    OpenAIRE

    Dousith, Phommachanh; Kurokawa, Junichi; Matsui, Jun; Choi, Young-Do

    2005-01-01

    There is a huge of available hydropower potential in the water supply system (WSS) that has been abandoned.Each time when we use a water faucet, the power of 10 to 80 watts is dissipated.In fact, this dissipated energy can be converted to useful energy by hydraulic turbine. Presently, there is not suitable turbine to use in WSS. Therefore, the new type turbine is needed to explore. In this study, Positive Displacement Turbine (PDT) is proposed. The main objective of this study is to develop n...

  5. Gender Specific Differences in the Perceived Antecedents of Academic Stress.

    Science.gov (United States)

    Jones, Russell W.

    This document consists of the report of a study undertaken to establish the existence of any gender specific differences in the perceived antecedents of academic stress. The definition of stress as a negative emotion strongly associated with doubt about coping is suggested to be particularly relevant to the academic arena where students…

  6. Mechanical stress and stress release channels in 10–350 nm palladium hydrogen thin films with different micro-structures

    International Nuclear Information System (INIS)

    Wagner, Stefan; Kramer, Thilo; Uchida, Helmut; Dobron, Patrik; Cizek, Jakub; Pundt, Astrid

    2016-01-01

    For thin metal films adhered to rigid substrates hydrogen uptake results in compressive stresses in the GPa range. Stresses affect the thermodynamics as well as the durability of thin films, but many films can release stress above critical stress values. Depending on the films' thickness, microstructure and adhesion to the substrate, which determine the energy available in the nano-sized system, stress release is conducted via different release mechanisms. To evaluate the different mechanisms, Palladium thin films ranging from 10 nm to 350 nm and with three different types of microstructures (nanocrystalline, multi-oriented epitaxy and three-fold epitaxy) are studied with special focus on the mechanical stress. In-situ substrate curvature measurements, XRD stress analyses and acoustic emission (AE) measurements are conducted to determine intrinsic stresses, hydrogen-induced stress changes and stress release signals. By this complementary experimental approach, different stress release mechanisms (named channels) are identified. Discrete stress relaxation (DSR) events are found already within the overall linear elastic stress-strain regime. Energies to stimulate DSRs lay well below the formation energy of dislocations, and may allow the movement of defects pre-existing in the films. For higher strain energies, all studied films can release stress by the formation of new dislocations and plastic deformation. When the adhesion to the substrate is small, an alternative release channel of film buckling opens for thick films.

  7. [Stress-induced cellular adaptive mutagenesis].

    Science.gov (United States)

    Zhu, Linjiang; Li, Qi

    2014-04-01

    The adaptive mutations exist widely in the evolution of cells, such as antibiotic resistance mutations of pathogenic bacteria, adaptive evolution of industrial strains, and cancerization of human somatic cells. However, how these adaptive mutations are generated is still controversial. Based on the mutational analysis models under the nonlethal selection conditions, stress-induced cellular adaptive mutagenesis is proposed as a new evolutionary viewpoint. The hypothetic pathway of stress-induced mutagenesis involves several intracellular physiological responses, including DNA damages caused by accumulation of intracellular toxic chemicals, limitation of DNA MMR (mismatch repair) activity, upregulation of general stress response and activation of SOS response. These responses directly affect the accuracy of DNA replication from a high-fidelity manner to an error-prone one. The state changes of cell physiology significantly increase intracellular mutation rate and recombination activity. In addition, gene transcription under stress condition increases the instability of genome in response to DNA damage, resulting in transcription-associated DNA mutagenesis. In this review, we summarize these two molecular mechanisms of stress-induced mutagenesis and transcription-associated DNA mutagenesis to help better understand the mechanisms of adaptive mutagenesis.

  8. Preventing Stress in Organizations How to Develop Positive Managers

    CERN Document Server

    Donaldson-Feilder, Emma; Yarker, Joanna

    2011-01-01

    Preventing Stress in Organizations:How to Develop Positive Managersoffers an innovative, evidence-based approach to help managers prevent and reduce workplace stress in their staff.Provides information on the critical skills managers must develop in order to prevent stress in their staff, and the key ongoing behaviours that promote a healthy work environmentShows practitioners in occupational psychology, HR, Health and Safety and related professions how positive management can be integrated into an organization???s existing practices and processesServes as an essential guide for managers thems

  9. Design and Lab Experiment of a Stress Detection Service based on Mouse Movements

    OpenAIRE

    Kowatsch, Tobias; Wahle, Fabian; Filler, Andreas

    2017-01-01

    Workplace stress can negatively affect the health condition of employees and with it, the performance of organizations. Although there exist approaches to measure work-related stress, two major limitations are the low resolution of stress data and its obtrusive measurement. The current work applies design science research with the goal to design, implement and evaluate a Stress Detection Service (SDS) that senses the degree of work-related stress solely based on mouse movements of knowledge w...

  10. Promoting Optimal Native Outcomes (PONO) by Understanding Women's Stress Experiences

    OpenAIRE

    Okihiro, May; Duke, Lisa; Goebert, Deborah; Ampolos, Lauren; Camacho, Casandra; Shanahan, Natasha; Hishinuma, Earl; Kaholokula, J. Keawe

    2017-01-01

    A growing body of evidence links stress with mental illness and chronic disease. Existing scales of women's stress fail to capture the daily stressors of low-income, rural women. We explored the psychosocial stressors of local women residing in a rural Hawaii community with a large Native Hawaiian and Other Pacific Islander population. We recruited women, aged 18?35 years, at a community health center. We convened four focus groups to elicit information about women's stress. We identified key...

  11. New developments of the Integrated Stress Determination Method and application to the Aespoe Hard Rock Laboratory, Sweden

    International Nuclear Information System (INIS)

    Ask, Daniel

    2004-04-01

    This thesis presents new developments of the Integrated Stress Determination Method (ISDM) with application to the Aespoe Hard Rock Laboratory (HRL), Oskarshamn, Sweden. The new developments involve a 12-parameter representation of the regional stress field in the rock mass. The method is applicable to data from hydraulic fracturing, hydraulic tests on pre-existing fractures (HTPF), and overcoring data from CSIR- and CSIRO-type of devices. When hydraulic fracturing/HTPF data are combined with overcoring data, the former may be used to constrain the elastic parameters, i.e. the problem involves 14 model parameters. The Swedish Nuclear Fuel and Waste Management Co. (SKB), have conducted a vast amount of rock stress measurements at the Aespoe HRL since the late 1980s. However, despite the large number of stress measurement data collected in this limited rock volume, variability in the stress field exists. Not only does the result vary depending on measuring technique, e.g. overcoring data indicated larger stress magnitudes compared to hydraulic fracturing data; the results are also affected by existing discontinuities, indicated by non-linear stress magnitudes and orientations versus depth. The objectives for this study are therefore threefold: (1) find explanations to the observed differences between existing hydraulic and overcoring stress data at the Aspo HRL; (2) explain the non-linear stress distribution indicated by existing stress data; and (3) apply the ISDM, including the new developments, based on the results obtained in step 1 and 2. To evaluate the observed differences between existing hydraulic and overcoring stress data, a detailed re-interpretation was conducted. Several measurement-related uncertainties were identified and corrected for when possible, which effectively reduced the discrepancies between the hydraulic and overcoring measuring results. Modeling studies managed by SKB have shown that the redistribution of the stresses at Aespoe HRL to a

  12. Structural transformations in Mn2NiGa due to residual stress

    International Nuclear Information System (INIS)

    Singh, Sanjay; Maniraj, M.; D'Souza, S. W.; Barman, S. R.; Ranjan, R.

    2010-01-01

    Powder x-ray diffraction study of Mn 2 NiGa ferromagnetic shape memory alloy shows the existence of a 7M monoclinic modulated structure at room temperature (RT). The structure of Mn 2 NiGa is found to be highly dependent on residual stress. For higher stress, the structure is tetragonal at RT, and for intermediate stress it is 7M monoclinic. However, only when the stress is considerably relaxed, the structure is cubic, as is expected at RT since the martensitic transition temperature is 230 K.

  13. Magneto thermal convection in a compressible couple-stress fluid

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Mahinder [Lovely School of Science, Dept. of Mathematics, Lovely Professional Univ., Phagwara (India); Kumar, Pardeep [Dept. of Mathematics, ICDEOL, H.P. Univ., Shimla (India)

    2010-03-15

    The problem of thermal instability of compressible, electrically conducting couple-stress fluids in the presence of a uniform magnetic field is considered. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For stationary convection, the compressibility, couple-stress, and magnetic field postpone the onset of convection. Graphs have been plotted by giving numerical values of the parameters to depict the stability characteristics. The principle of exchange of stabilities is found to be satisfied. The magnetic field introduces oscillatory modes in the system that were non-existent in its absence. The case of overstability is also studied wherein a sufficient condition for the non-existence of overstability is obtained. (orig.)

  14. Development of residual stress analysis procedure for fitness-for-service assessment of welded structure

    International Nuclear Information System (INIS)

    Kim, Jong Sung; Jin, Tae Eun; Dong, P.; Prager, M.

    2003-01-01

    In this study, a state of art review of existing residual stress analysis techniques and representative solutions is presented in order to develop the residual stress analysis procedure for Fitness-For-Service(FFS) assessment of welded structure. Critical issues associated with existing residual stress solutions and their treatments in performing FFS are discussed. It should be recognized that detailed residual stress evolution is an extremely complicated phenomenon that typically involves material-specific thermomechanical/metallurgical response, welding process physics, and structural interactions within a component being welded. As a result, computational procedures can vary significantly from highly complicated numerical techniques intended only to elucidate a small part of the process physics to cost-effective procedures that are deemed adequate for capturing some of the important features in a final residual stress distribution. Residual stress analysis procedure for FFS purposes belongs to the latter category. With this in mind, both residual stress analysis techniques and their adequacy for FFS are assessed based on both literature data and analyses performed in this investigation

  15. To Be or Not to Be (Stressed): The Critical Role of a Psychologically Healthy Workplace in Effective Stress Management.

    Science.gov (United States)

    Grawitch, Matthew J; Ballard, David W; Erb, Kaitlyn R

    2015-10-01

    This article explains how key practices pertaining to the psychologically healthy workplace can be used to develop a comprehensive approach to stress management in contemporary organizations. Specifically, we demonstrate the ways in which employee involvement, recognition, work-life balance, health and safety, and growth and development practices can be used to assist in the reduction of work stress and the proactive management of strain. Although many organizations strive to establish a positive environment conducive to work and well-being, identifying where to begin can often seem like a daunting task. Currently, many stress management efforts emphasize individual-level interventions that are simply implemented alongside existing organizational practices. We propose that a broader perspective allows for a better understanding of the stress process, resulting in the ability to consider a wider range of changes to organizational processes. Combining knowledge regarding psychologically healthy workplace practices, stress management intervention levels and the personal resource allocation framework, we present a comprehensive framework for approaching workplace stress management, which can be tailored to the unique needs of various organizations, departments and employees. By adopting this broader perspective, we believe organizations can more strategically address employee stress, resulting in more effective stress management and a profound impact on stress-related outcomes. Copyright © 2014 John Wiley & Sons, Ltd.

  16. Psychological stress on female mice diminishes the developmental potential of oocytes: a study using the predatory stress model.

    Directory of Open Access Journals (Sweden)

    Yu-Xiang Liu

    Full Text Available Although the predatory stress experimental protocol is considered more psychological than the restraint protocol, it has rarely been used to study the effect of psychological stress on reproduction. Few studies exist on the direct effect of psychological stress to a female on developmental competence of her oocytes, and the direct effect of predatory maternal stress on oocytes has not been reported. In this study, a predatory stress system was first established for mice with cats as predators. Beginning 24 h after injection of equine chorionic gonadotropin, female mice were subjected to predatory stress for 24 h. Evaluation of mouse responses showed that the predatory stress system that we established increased anxiety-like behaviors and plasma cortisol concentrations significantly and continuously while not affecting food and water intake of the mice. In vitro experiments showed that whereas oocyte maturation and Sr(2+ activation or fertilization were unaffected by maternal predatory stress, rate of blastocyst formation and number of cells per blastocyst decreased significantly in stressed mice compared to non-stressed controls. In vivo embryo development indicated that both the number of blastocysts recovered per donor mouse and the average number of young per recipient after embryo transfer of blastocysts with similar cell counts were significantly lower in stressed than in unstressed donor mice. It is concluded that the predatory stress system we established was both effective and durative to induce mouse stress responses. Furthermore, predatory stress applied during the oocyte pre-maturation stage significantly impaired oocyte developmental potential while exerting no measurable impact on nuclear maturation, suggesting that cytoplasmic maturation of mouse oocytes was more vulnerable to maternal stress than nuclear maturation.

  17. Effect of the critical size of initial voids on stress-induced migration

    International Nuclear Information System (INIS)

    Aoyagi, Minoru

    2004-01-01

    The stress-induced migration phenomenon is one of the problems related to the reliability of metal interconnections in semiconductor devices. This phenomenon causes voids and fractures in interconnections. The basic feature of this phenomenon is vacancy migration to minute initial voids. Expanding initial voids grow into larger voids and fractures. The purpose of this work is to theoretically clarify the effects of residual thermal stress and void surface stress on the behavior of the initial voids which exist immediately after a passivation process. Using a spherical metal sample with a spherical void under external stress, vacancy absorption or emission was investigated between the void surface and the sample surface. The behavior of vacancies and atoms was also investigated in interconnections under residual thermal stress. We show that the void or sample surface becomes a vacancy sink or source, depending on the mutual relationship between the surface stress due to the surface-free energy and the residual thermal stress. We also reveal that the initial voids, which exist immediately after a passivation process, grow into larger voids and fractures when the size of the initial voids exceeds the critical size. If the size of the initial void can be controlled to below the critical size, voids and fractures do not occur

  18. A Thermo-Hydro-Mechanical coupled Numerical modeling of Injection-induced seismicity on a pre-existing fault

    Science.gov (United States)

    Kim, Jongchan; Archer, Rosalind

    2017-04-01

    In terms of energy development (oil, gas and geothermal field) and environmental improvement (carbon dioxide sequestration), fluid injection into subsurface has been dramatically increased. As a side effect of these operations, a number of injection-induced seismic activities have also significantly risen. It is known that the main causes of induced seismicity are changes in local shear and normal stresses and pore pressure as well. This mechanism leads to increase in the probability of earthquake occurrence on permeable pre-existing fault zones predominantly. In this 2D fully coupled THM geothermal reservoir numerical simulation of injection-induced seismicity, we investigate the thermal, hydraulic and mechanical behavior of the fracture zone, considering a variety of 1) fault permeability, 2) injection rate and 3) injection temperature to identify major contributing parameters to induced seismic activity. We also calculate spatiotemporal variation of the Coulomb stress which is a combination of shear stress, normal stress and pore pressure and lastly forecast the seismicity rate on the fault zone by computing the seismic prediction model of Dieterich (1994).

  19. Oral lichen planus and stress: An appraisal

    Directory of Open Access Journals (Sweden)

    Simarpreet V Sandhu

    2014-01-01

    Full Text Available Introduction: Oral lichen planus (OLP is a chronic inflammatory disease characterized by bilateral white striations or plaques on the buccal mucosa, tongue or gingiva that has a multifactorial etiology, where the psychogenic factors seem to play an important role. Purpose: The aim of this study was to determine the existing relation between the OLP and psychological alterations of the patient, such as stress, anxiety, and depression. Materials and Methods: Hospital anxiety and depression scale was applied for psychometric analysis. Results: The study indicates a definitive relationship between a stressful life event and onset and progression of OLP. Conclusion: Stress management and bereavement counseling should be a part of management protocol of OLP.

  20. Residual stress in silicon wafer using IR polariscope

    Science.gov (United States)

    Lu, Zhijia; Wang, Pin; Asundi, Anand

    2008-09-01

    The infrared phase shift polariscope (IR-PSP) is a full-field optical technique for stress analysis in Silicon wafers. Phase shift polariscope is preferred to a conventional polariscope, as it can provide quantitative information of the normal stress difference and the shear stress in the specimen. The method is based on the principles of photoelasticity, in which stresses induces temporary birefringence in materials which can be quantitatively analyzed using a phase shift polariscope. Compared to other stress analysis techniques such as x-ray diffraction or laser scanning, infrared photoelastic stress analysis provides full-field information with high resolution and in near real time. As the semiconductor fabrication is advancing, larger wafers, thinner films and more compact packages are being manufactured. This results in a growing demand of process control. Residual stress exist in silicon during semiconductor fabrication and these stresses may make cell processing difficult or even cause the failure of the silicon. Reducing these stresses would improve manufacturability and reliability. Therefore stress analysis is essential to trace the root cause of the stresses. The polariscope images are processed using MATLAB and four-step phase shifting method to provide quantitative as well as qualitative information regarding the residual stress of the sample. The system is calibrated using four-point bend specimen and then the residual stress distribution in a MEMS sample is shown.

  1. Application of Photocurrent Model on Polymer Solar Cells Under Forward Bias Stress

    DEFF Research Database (Denmark)

    Rizzo, Antonio; Torto, Lorenzo; Wrachien, Nicola

    2017-01-01

    We performed a constant current stress at forward bias on organic heterojunction solar cells. We measured current voltage curves in both dark and light at each stress step to calculate the photocurrent. An existing model applied to photocurrent experimental data allows the estimation of several...

  2. Mini-review: Biofilm responses to oxidative stress.

    Science.gov (United States)

    Gambino, Michela; Cappitelli, Francesca

    2016-01-01

    Biofilms constitute the predominant microbial style of life in natural and engineered ecosystems. Facing harsh environmental conditions, microorganisms accumulate reactive oxygen species (ROS), potentially encountering a dangerous condition called oxidative stress. While high levels of oxidative stress are toxic, low levels act as a cue, triggering bacteria to activate effective scavenging mechanisms or to shift metabolic pathways. Although a complex and fragmentary picture results from current knowledge of the pathways activated in response to oxidative stress, three main responses are shown to be central: the existence of common regulators, the production of extracellular polymeric substances, and biofilm heterogeneity. An investigation into the mechanisms activated by biofilms in response to different oxidative stress levels could have important consequences from ecological and economic points of view, and could be exploited to propose alternative strategies to control microbial virulence and deterioration.

  3. Computational fluid dynamics (CFD) study on the fetal aortic coarctation

    Science.gov (United States)

    Zhou, Yue; Zhang, Yutao; Wang, Jingying

    2018-03-01

    Blood flows in normal and coarctate fetal aortas are simulated by the CFD technique using T-rex grids. The three-dimensional (3-D) digital model of the fetal arota is reconstructed by the computer-aided design (CAD) software based on two-dimensional (2-D) ultrasono tomographic images. Simulation results displays the development and enhancement of the secondary flow structure in the coarctate fetal arota. As the diameter narrow ratio rises greater than 45%, the pressure and wall shear stress (WSS) of the aorta arch increase exponentially, which is consistent with the conventional clinical concept. The present study also demonstrates that CFD is a very promising assistant technique to investigate human cardiovascular diseases.

  4. Resistance to early-life stress in mice: effects of genetic background and stress duration

    Directory of Open Access Journals (Sweden)

    Helene M. Savignac

    2011-04-01

    Full Text Available Early-life stress can induce marked behavioural and physiological impairments in adulthood including cognitive deficits, depression, anxiety and gastrointestinal dysfunction. Although robust rat models of early-life stress exist there are few established effective paradigms in the mouse. Genetic background and protocol parameters used are two critical variables in such model development.Thus we investigated the impact of two different early-life stress protocols in two commonly used inbred mouse strains. C57BL/6 and innately anxious BALB/c male mice were maternally deprived 3 hrs daily, either from postnatal day 1 to 14 (Protocol 1 or 6 to 10 (Protocol 2. Animals were assessed in adulthood for cognitive performance (spontaneous alternation behaviour test, anxiety (open field, light/dark box and elevated plus maze tests and depression-related behaviours (forced swim test in addition to stress-sensitive physiological changes. Overall, the results showed that early-life stressed mice from both strains displayed good cognitive ability and no elevations in anxiety. However, paradoxical changes occurred in C57BL/6 mice as the longer protocol (protocol 1 decreased anxiety in the light-dark box and increased exploration in the elevated plus maze. In BALB/c mice there were also limited effects of maternal separation with both separation protocols inducing reductions in stress-induced defecation and protocol 1 reducing the colon length. These data suggest that, independent of stress duration, mice from both strains were on the whole resilient to the maladaptive effects of early-life stress. Thus maternal-separation models of brain-gut axis dysfunction should rely on either different stressor protocols or other strains of mice.

  5. The consequences of nursing stress and need for integrated solutions.

    Science.gov (United States)

    Roberts, Rashaun K; Grubb, Paula L

    2014-01-01

    In a 2011 survey sponsored by the American Nurses Association (ANA), nurses identified the acute and chronic effects of stress and overwork as one of their two top safety and health concerns. A review of the literature was conducted to investigate the impact that job stress has on the health and safety of nursing professionals and the role that working conditions and job characteristics play in fostering job stress. Strong evidence supporting links between job stress, safety and health in general and within different types of nursing populations exists. Working conditions also contribute to the development of job stress. Combining and integrating "person-focused" strategies designed to build nurses' ability to manage stress at the individual level with "organization-focused" strategies that eliminate stressful working conditions is critical to the reduction and prevention of job stress among nursing professionals. © 2013 Association of Rehabilitation Nurses.

  6. Polyaxial stress-dependent permeability of a three-dimensional fractured rock layer

    Science.gov (United States)

    Lei, Qinghua; Wang, Xiaoguang; Xiang, Jiansheng; Latham, John-Paul

    2017-12-01

    A study about the influence of polyaxial (true-triaxial) stresses on the permeability of a three-dimensional (3D) fractured rock layer is presented. The 3D fracture system is constructed by extruding a two-dimensional (2D) outcrop pattern of a limestone bed that exhibits a ladder structure consisting of a "through-going" joint set abutted by later-stage short fractures. Geomechanical behaviour of the 3D fractured rock in response to in-situ stresses is modelled by the finite-discrete element method, which can capture the deformation of matrix blocks, variation of stress fields, reactivation of pre-existing rough fractures and propagation of new cracks. A series of numerical simulations is designed to load the fractured rock using various polyaxial in-situ stresses and the stress-dependent flow properties are further calculated. The fractured layer tends to exhibit stronger flow localisation and higher equivalent permeability as the far-field stress ratio is increased and the stress field is rotated such that fractures are preferentially oriented for shearing. The shear dilation of pre-existing fractures has dominant effects on flow localisation in the system, while the propagation of new fractures has minor impacts. The role of the overburden stress suggests that the conventional 2D analysis that neglects the effect of the out-of-plane stress (perpendicular to the bedding interface) may provide indicative approximations but not fully capture the polyaxial stress-dependent fracture network behaviour. The results of this study have important implications for understanding the heterogeneous flow of geological fluids (e.g. groundwater, petroleum) in subsurface and upscaling permeability for large-scale assessments.

  7. Anxiety and Stress--How They Affect Teachers, Teaching.

    Science.gov (United States)

    Youngs, Bettie Burres

    1978-01-01

    Principals can play an important role in the interpersonal relationships within a school building by exploring and assessing issues regarding cause and effect of the anxiety, stress, and tension that exist among personnel. (Author/MLF)

  8. [Effect of zirconia abutment angulation on stress distribution in the abutment and the bone around implant: a finite element study].

    Science.gov (United States)

    Yang, Yan-zhong; Tian, Xiao-hua; Zhou, Yan-min

    2015-08-01

    To investigate the effect of three different zirconia angular abutments on the stress distribution in bone and abutment using three-dimensional finite element analysis, and provide instruction for clinical application. Finite element analysis (FEA) was applied to analyze the stress distribution of three different zirconia/titanium angular abutments and bone around implant. The maximum Von Minses stress that existed in abutment, bolt and bone of the angular abutment model was significantly higher than that existed in the straight abutment model. The maximum Von Minses stress that existed in abutment, bolt and bone of the 20 ° angular abutment model was significantly higher than that existed in 15 ° angular abutment model. There was no significant difference between zirconia abutment model and titanium abutment model. The abutment angulation has a significant influence on the stress distribution in the abutment, bolt and bone, and exacerbates as the angulation increases, which suggest that we should take more attention to the implant orientation and use straight abutment or little angular abutment. The zirconia abutment can be used safely, and there is no noticeable difference between zirconia abutment and titanium abutment on stress distribution.

  9. Semi-integration of overcoring stress data and review of rock stress data at the Olkiluoto site

    International Nuclear Information System (INIS)

    Ask, D.

    2011-06-01

    This project involves a semi-integration of collected rock stress data at Olkiluoto. The data included in the study involves overcoring and hydraulic fracturing data reported in the 2006 Site Report, supplemented with the additional data gathered since then, measurements for the power plant construction, and measurements in ONKALO. Despite the extensive data, and although the data display a fair correspondence with respect to stress magnitudes between methods, a few discrepancies between methods exist. The discrepancies primarily concern the orientation of the horizontal stresses and the magnitude of maximum horizontal stress. The objective of the study is help answer the remaining discrepancies in the collected data using a semi-integration approach on the overcoring data, i.e. a simplified application of the Integrated Stress Determination Method. The semi-integration involves two steps: (i) a brief re-evaluation of data; and (ii) forced overcoring stress calculations based on constraints derived from the other stress measurement techniques. The overall intension was to force overcoring data, which is the method displaying the largest scatter in results at the Olkiluoto site, to be consistent with a number of constraints that were derived from other stress measurement techniques. This exercise would outline the most probable constraints and in the extension, help identifying a stress model for the site. Regrettably, the results of the semi-integration were not completely satisfactory. The most important factor of this outcome is believed to be the failure to reduce the initial scatter through a re-evaluation. The remaining scatter after re-evaluation is judged too large to represent solely in situ stress variation; hence, measurement related errors are likely still present in the re-evaluated data set. A more in-depth analysis may to some extent decrease the scatter in data, but perhaps more effectively, develop a tool that simultaneously can derive the stress

  10. Mathematical model of polyethylene pipe bending stress state

    Science.gov (United States)

    Serebrennikov, Anatoly; Serebrennikov, Daniil

    2018-03-01

    Introduction of new machines and new technologies of polyethylene pipeline installation is usually based on the polyethylene pipe flexibility. It is necessary that existing bending stresses do not lead to an irreversible polyethylene pipe deformation and to violation of its strength characteristics. Derivation of the mathematical model which allows calculating analytically the bending stress level of polyethylene pipes with consideration of nonlinear characteristics is presented below. All analytical calculations made with the mathematical model are experimentally proved and confirmed.

  11. Stress Physiology of Lactic Acid Bacteria

    Science.gov (United States)

    Papadimitriou, Konstantinos; Alegría, Ángel; Bron, Peter A.; de Angelis, Maria; Gobbetti, Marco; Kleerebezem, Michiel; Lemos, José A.; Linares, Daniel M.; Ross, Paul; Stanton, Catherine; Turroni, Francesca; van Sinderen, Douwe; Varmanen, Pekka; Ventura, Marco; Zúñiga, Manuel; Tsakalidou, Effie

    2016-01-01

    SUMMARY Lactic acid bacteria (LAB) are important starter, commensal, or pathogenic microorganisms. The stress physiology of LAB has been studied in depth for over 2 decades, fueled mostly by the technological implications of LAB robustness in the food industry. Survival of probiotic LAB in the host and the potential relatedness of LAB virulence to their stress resilience have intensified interest in the field. Thus, a wealth of information concerning stress responses exists today for strains as diverse as starter (e.g., Lactococcus lactis), probiotic (e.g., several Lactobacillus spp.), and pathogenic (e.g., Enterococcus and Streptococcus spp.) LAB. Here we present the state of the art for LAB stress behavior. We describe the multitude of stresses that LAB are confronted with, and we present the experimental context used to study the stress responses of LAB, focusing on adaptation, habituation, and cross-protection as well as on self-induced multistress resistance in stationary phase, biofilms, and dormancy. We also consider stress responses at the population and single-cell levels. Subsequently, we concentrate on the stress defense mechanisms that have been reported to date, grouping them according to their direct participation in preserving cell energy, defending macromolecules, and protecting the cell envelope. Stress-induced responses of probiotic LAB and commensal/pathogenic LAB are highlighted separately due to the complexity of the peculiar multistress conditions to which these bacteria are subjected in their hosts. Induction of prophages under environmental stresses is then discussed. Finally, we present systems-based strategies to characterize the “stressome” of LAB and to engineer new food-related and probiotic LAB with improved stress tolerance. PMID:27466284

  12. On the influence of T-Stress on photoelastic analysis under pure mode II loading

    Directory of Open Access Journals (Sweden)

    Chiara Colombo

    2008-01-01

    Full Text Available According to the classical definition for in-plane modes of crack deformation, the constant stress term T exists only in the presence of mode I. However, recent studies show that this term can exist inmode II conditions as well, and significantly affect the elastic stress field around the crack tip. These effects can be visualized using the experimental method of photoelasticity. Based on the analytical studies, presence of the T-stress in mode II cracks transforms the isochromatic fringe patterns from symmetric closed loops to asymmetric and discontinuous shapes. In this paper, presence of the T-stress in mode II cracks and its effects on the fringe patterns is experimentally investigated. The test specimens are Brazilian disks containing very sharp central cracks: experimental results indicate that these specimens contain negative values of T-stress. Experimental values are then compared to numerical results. To better understand the differences between experimental and numerical values, a thee dimensional analysis is performed with the finite element method: results show the influence of the real geometry of the crack front on the stress intensity factors.

  13. Stress distribution in two-dimensional silos

    Science.gov (United States)

    Blanco-Rodríguez, Rodolfo; Pérez-Ángel, Gabriel

    2018-01-01

    Simulations of a polydispersed two-dimensional silo were performed using molecular dynamics, with different numbers of grains reaching up to 64 000, verifying numerically the model derived by Janssen and also the main assumption that the walls carry part of the weight due to the static friction between grains with themselves and those with the silo's walls. We vary the friction coefficient, the radii dispersity, the silo width, and the size of grains. We find that the Janssen's model becomes less relevant as the the silo width increases since the behavior of the stresses becomes more hydrostatic. Likewise, we get the normal and tangential stress distribution on the walls evidencing the existence of points of maximum stress. We also obtained the stress matrix with which we observe zones of concentration of load, located always at a height around two thirds of the granular columns. Finally, we observe that the size of the grains affects the distribution of stresses, increasing the weight on the bottom and reducing the normal stress on the walls, as the grains are made smaller (for the same total mass of the granulate), giving again a more hydrostatic and therefore less Janssen-type behavior for the weight of the column.

  14. Organizational stress management interventions: Is it the singer not the song? [Editorial

    NARCIS (Netherlands)

    Kompier, M.A.J.; Aust, B.

    2016-01-01

    Good reasons exist for combating stress at work. It is a burden for individual employees and their families and costly to companies and society. Moreover preventing stress at work is a sign of good corporate citizenship as it respects modern legislation that stimulates the provision of a good

  15. Weldon Spring, Missouri: Annual environmental monitoring report, calendar year 1987

    International Nuclear Information System (INIS)

    1987-01-01

    Radiological monitoring at the WSS during 1987 measured uranium, Radium-226, and Thorium-230 concentrations in surface water, groundwater, and sediment; radon gas concentrations in air; all long-lived natural series isotopes in air particulates; and external gamma radiation exposure rates. Potential radiation doses to the public were calculated based on assumed exposure periods and the above measurements. Radon concentrations, external gamma exposure rates, and radionuclide concentrations in groundwater and surface water at the site were generally equivalent to previous years' levels. The maximum calculated annual radiation dose to a hypothetically exposed individual at the WSRP and WSCP area was 1 mrem, or 1 percent of the DOE radiation protection standard of 100 mrem. The maximum calculated annual radiation dose to a hypothetically exposed individual at the WSQ was 14 mrem, or about 14 percent of the standard. Thus the WSS currently complies with DOE Off-site Dose Standards. Chemical contamination monitoring at the WSS during 1987 measured nitroaromatics, total organic carbon and the inorganic anions chloride, nitrate, fluoride and sulfate in surface water, groundwater and sediment. 22 refs., 26 figs., 21 tabs

  16. Designing the Database of Speech Under Stress

    Directory of Open Access Journals (Sweden)

    Sabo Róbert

    2017-12-01

    Full Text Available This study describes the methodology used for designing a database of speech under real stress. Based on limits of existing stress databases, we used a communication task via a computer game to collect speech data. To validate the presence of stress, known psychophysiological indicators such as heart rate and electrodermal activity, as well as subjective self-assessment were used. This paper presents the data from first 5 speakers (3 men, 2 women who participated in initial tests of the proposed design. In 4 out of 5 speakers increases in fundamental frequency and intensity of speech were registered. Similarly, in 4 out of 5 speakers heart rate was significantly increased during the task, when compared with reference measurement from before the task. These first results show that proposed design might be appropriate for building a speech under stress database. However, there are still considerations that need to be addressed.

  17. Do uniform tangential interfacial stresses enhance adhesion?

    Science.gov (United States)

    Menga, Nicola; Carbone, Giuseppe; Dini, Daniele

    2018-03-01

    We present theoretical arguments, based on linear elasticity and thermodynamics, to show that interfacial tangential stresses in sliding adhesive soft contacts may lead to a significant increase of the effective energy of adhesion. A sizable expansion of the contact area is predicted in conditions corresponding to such scenario. These results are easily explained and are valid under the assumptions that: (i) sliding at the interface does not lead to any loss of adhesive interaction and (ii) spatial fluctuations of frictional stresses can be considered negligible. Our results are seemingly supported by existing experiments, and show that frictional stresses may lead to an increase of the effective energy of adhesion depending on which conditions are established at the interface of contacting bodies in the presence of adhesive forces.

  18. A dependent stress-strength interference model based on mixed copula function

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Jian Xiong; An, Zong Wen; Liu, Bo [School of Mechatronics Engineering, Lanzhou University of Technology, Lanzhou (China)

    2016-10-15

    In the traditional Stress-strength interference (SSI) model, stress and strength must satisfy the basic assumption of mutual independence. However, a complex dependence between stress and strength exists in practical engineering. To evaluate structural reliability under the case that stress and strength are dependent, a mixed copula function is introduced to a new dependent SSI model. This model can fully characterize the dependence between stress and strength. The residual square sum method and genetic algorithm are also used to estimate the unknown parameters of the model. Finally, the validity of the proposed model is demonstrated via a practical case. Results show that traditional SSI model ignoring the dependence between stress and strength more easily overestimates product reliability than the new dependent SSI model.

  19. Welding-induced local maximum residual stress in heat affected zone of low-carbon austenitic stainless steel with machined surface layer and its influential factors

    International Nuclear Information System (INIS)

    Okano, Shigetaka; Ihara, Ryohei; Kanamaru, Daisuke; Mochizuki, Masahito

    2015-01-01

    In this study, the effects of work-hardening and pre-existing stress in the machined surface layer of low-carbon austenitic stainless steel on the welding-induced residual stress were experimentally investigated through the use of weld specimens with three different surface layers; as-cutout, mechanically-polished and electrolytically-polished. The high tensile and compressive stresses exist in the work-hardened surface layer of the as-cutout and mechanically-polished specimens, respectively. Meanwhile, no stress and work-hardened surface layer exist in the electrolytically-polished specimen. TIG bead-on-plate welding under the same welding heat input conditions was performed to introduce the residual stress into these specimens. Using these welded specimens, the distributions of welding-induced residual stress were measured by the X-ray diffraction method. Similarly, the distributions of hardness in welds were estimated by the Vickers hardness test. And then, these distributions were compared with one another. Based on the results, the residual stress in the weld metal (WM) is completely unaffected by the machined surface layer because the work-hardened surface layer disappears through the processes of melting and solidification during welding. The local maximum longitudinal tensile residual stress in the heat affected zone (HAZ) depends on the work-hardening but not on the existing stress, regardless of whether tensile or compressive, in the machined surface layer before welding. At the base metal far from WM and HAZ, the residual stress is formed by the addition of the welding-induced residual stress to the pre-existing stress in the machined surface layer before welding. The features of the welding-induced residual stress in low-carbon austenitic stainless steel with the machined surface layer and their influential factors were thus clarified. (author)

  20. Effect of residual stress on the integrity of a branch connection

    International Nuclear Information System (INIS)

    Law, M.; Kirstein, O.; Luzin, V.

    2012-01-01

    A new connection to an existing gas pipeline was made by hot-tapping, welding directly onto a pressurised pipeline. The welds were not post-weld heat treated, causing significant residual stresses. The critical weld had residual stresses determined by neutron diffraction using ANSTO's residual stress diffractometer, Kowari. The maximum measured residual stress (290 MPa) was 60% of the yield strength. The magnitudes of errors from a number of sources were estimated. An integrity assessment of the welded branch connection was performed with the measured residual stress values and with residual stress distributions from the BS 7910 and API 579 analysis codes. Analysis using estimates of residual stress from API 579 overestimated the critical crack size. Highlights: ► Residual stresses were measured by neutron diffraction in a thick section, non post-weld heat treated ferritic weld. ► There is little published data on these welds. ► The work compares the measured residual stresses with code-based residual stress distributions.

  1. Estimation of shear stress in counter-current gas-liquid annular two-phase flow

    International Nuclear Information System (INIS)

    Abe, Yutaka; Akimoto, Hajime; Murao, Yoshio

    1991-01-01

    The accuracy of the correlations of the friction factor is important for the counter-current flow (CCF) analysis with two-fluid model. However, existing two fluid model codes use the correlations of friction factors for co-current flow or correlation developed based on the assumption of no wall shear stress. The assessment calculation for two fluid model code with those existing correlations of friction factors shows the falling water flow rate is overestimated. Analytical model is developed to calculate the shear stress distribution in water film at CCF in order to get the information on the shear stress at the interface and the wall. The analytical results with the analysis model and Bharathan's CCF data shows that the wall shear stress acting on the falling water film is almost same order as the interfacial shear stress and the correlations for co-current flow cannot be applied to the counter-current flow. Tentative correlations of the interfacial and the wall friction factors are developed based on the results of the present study. (author)

  2. Stress regimes in the northwest of Iran from stress inversion of earthquake focal mechanisms

    Science.gov (United States)

    Afra, Mahsa; Moradi, Ali; Pakzad, Mehrdad

    2017-11-01

    Northwestern Iran is one of the seismically active regions with a high seismic risk in the world. This area is a part of the complex tectonic system due to the interaction between Arabia, Anatolia and Eurasia. The purpose of this study is to deduce the stress regimes in the northwestern Iran and surrounding regions from stress inversion of earthquake focal mechanisms. We compile 92 focal mechanisms data from the Global CMT catalogue and other sources and also determine the focal mechanisms of 14 earthquakes applying the moment tensor inversion. We divide the studied region into 9 zones using similarity of the horizontal GPS velocities and existing focal mechanisms. We implement two stress inversion methods, Multiple Inverse Method and Iterative Joint Inversion Method, which provide comparable results in terms of orientations of maximum horizontal stress axes SHmax. The similar results of the two methods should make us more confident about the interpretations. We consider zones of exclusion surrounding all the earthquakes according to independent focal mechanisms hypothesis. The hypothesis says that the inversion should involve events that are far enough from each other in order that any previous event doesn't affect the stress field near the earthquake under consideration. Accordingly we deal with the matter by considering zones of exclusion around all the events. The result of exclusion is only significant for eastern Anatolia. The stress regime in this region changes from oblique to strike slip faulting because of the exclusion. In eastern Anatolia, the direction of maximum horizontal stress is nearly north-south. The direction alters to east-west in Talesh region. Errors of σ1 are lower in all zones comparing with errors of σ2 and σ3 and there is a trade-off between data resolution and covariance of the model. The results substantiate the strike-slip and thrust faulting stress regimes in the northwest of Iran.

  3. Are Non-Newtonian Effects Important in Hemodynamic Simulations of Patients With Autogenous Fistula?

    Science.gov (United States)

    Javid Mahmoudzadeh Akherat, S. M.; Cassel, Kevin; Boghosian, Michael; Dhar, Promila; Hammes, Mary

    2017-01-01

    Given the current emphasis on accurate computational fluid dynamics (CFD) modeling of cardiovascular flows, which incorporates realistic blood vessel geometries and cardiac waveforms, it is necessary to revisit the conventional wisdom regarding the influences of non-Newtonian effects. In this study, patient-specific reconstructed 3D geometries, whole blood viscosity data, and venous pulses postdialysis access surgery are used as the basis for the hemodynamic simulations of renal failure patients with native fistula access. Rheological analysis of the viscometry data initially suggested that the correct choice of constitutive relations to capture the non-Newtonian behavior of blood is important because the end-stage renal disease (ESRD) patient cohort under observation experience drastic variations in hematocrit (Hct) levels and whole blood viscosity throughout the hemodialysis treatment. For this purpose, various constitutive relations have been tested and implemented in CFD practice, namely Quemada and Casson. Because of the specific interest in neointimal hyperplasia and the onset of stenosis in this study, particular attention is placed on differences in nonhomeostatic wall shear stress (WSS) as that drives the venous adaptation process that leads to venous geometric evolution over time in ESRD patients. Surprisingly, the CFD results exhibit no major differences in the flow field and general flow characteristics of a non-Newtonian simulation and a corresponding identical Newtonian counterpart. It is found that the vein's geometric features and the dialysis-induced flow rate have far greater influence on the WSS distribution within the numerical domain. PMID:28249082

  4. Are Non-Newtonian Effects Important in Hemodynamic Simulations of Patients With Autogenous Fistula?

    Science.gov (United States)

    Javid Mahmoudzadeh Akherat, S M; Cassel, Kevin; Boghosian, Michael; Dhar, Promila; Hammes, Mary

    2017-04-01

    Given the current emphasis on accurate computational fluid dynamics (CFD) modeling of cardiovascular flows, which incorporates realistic blood vessel geometries and cardiac waveforms, it is necessary to revisit the conventional wisdom regarding the influences of non-Newtonian effects. In this study, patient-specific reconstructed 3D geometries, whole blood viscosity data, and venous pulses postdialysis access surgery are used as the basis for the hemodynamic simulations of renal failure patients with native fistula access. Rheological analysis of the viscometry data initially suggested that the correct choice of constitutive relations to capture the non-Newtonian behavior of blood is important because the end-stage renal disease (ESRD) patient cohort under observation experience drastic variations in hematocrit (Hct) levels and whole blood viscosity throughout the hemodialysis treatment. For this purpose, various constitutive relations have been tested and implemented in CFD practice, namely Quemada and Casson. Because of the specific interest in neointimal hyperplasia and the onset of stenosis in this study, particular attention is placed on differences in nonhomeostatic wall shear stress (WSS) as that drives the venous adaptation process that leads to venous geometric evolution over time in ESRD patients. Surprisingly, the CFD results exhibit no major differences in the flow field and general flow characteristics of a non-Newtonian simulation and a corresponding identical Newtonian counterpart. It is found that the vein's geometric features and the dialysis-induced flow rate have far greater influence on the WSS distribution within the numerical domain.

  5. Influence of hemodynamic factors on rupture of intracranial aneurysms: patient-specific 3D mirror aneurysms model computational fluid dynamics simulation.

    Science.gov (United States)

    Lu, G; Huang, L; Zhang, X L; Wang, S Z; Hong, Y; Hu, Z; Geng, D Y

    2011-08-01

    Hemodynamics factors play an important role in the rupture of cerebral aneurysms. The purpose of this study was to evaluate the impact of hemodynamic factors on the rupture of the MANs with 3D reconstruction model CFD simulation. RDSA was performed in 9 pairs of intracranial MANs. Each pair was divided into ruptured and unruptured groups. The hemodynamic factors of the aneurysms and their parent arteries were compared. There was a significant difference in the WSS at peak systole between the regions of the aneurysms and their parent arteries in the ruptured group (ie, 6.49 ± 3.48 Pa versus 8.78 ± 3.57 Pa, P =.015) but not in the unruptured group (ie, 9.80 ± 4.12 Pa versus 10.17 ± 7.48 Pa, P =.678). The proportion of the low WSS area to the whole area of the aneurysms was 12.20 ± 18.08% in the ruptured group and 3.96 ± 6.91% in the unruptured group; the difference between the 2 groups was statistically significant (P =.015). The OSI was 0.0879 ± 0.0764 in the ruptured group, which was significantly higher than that of the unruptured group (ie, 0.0183 ± 0.0191, P =.008). MANs may be a useful disease model to investigate possible causes linked to ruptured aneurysms. The ruptured aneurysms manifested lower WSS compared with their parent arteries, a higher proportion of the low WSS area to the whole area of aneurysm, and higher OSI compared with the unruptured aneurysms.

  6. Glyphosate sustainability in South American cropping systems.

    Science.gov (United States)

    Christoffoleti, Pedro J; Galli, Antonio J B; Carvalho, Saul J P; Moreira, Murilo S; Nicolai, Marcelo; Foloni, Luiz L; Martins, Bianca A B; Ribeiro, Daniela N

    2008-04-01

    South America represents about 12% of the global land area, and Brazil roughly corresponds to 47% of that. The major sustainable agricultural system in South America is based on a no-tillage cropping system, which is a worldwide adopted agricultural conservation system. Societal benefits of conservation systems in agriculture include greater use of conservation tillage, which reduces soil erosion and associated loading of pesticides, nutrients and sediments into the environment. However, overreliance on glyphosate and simpler cropping systems has resulted in the selection of tolerant weed species through weed shifts (WSs) and evolution of herbicide-resistant weed (HRW) biotypes to glyphosate. It is a challenge in South America to design herbicide- and non-herbicide-based strategies that effectively delay and/or manage evolution of HRWs and WSs to weeds tolerant to glyphosate in cropping systems based on recurrent glyphosate application, such as those used with glyphosate-resistant soybeans. The objectives of this paper are (i) to provide an overview of some factors that influence WSs and HRWs to glyphosate in South America, especially in Brazil, Argentina and Paraguay soybean cropped areas; (ii) to discuss the viability of using crop rotation and/or cover crops that might be integrated with forage crops in an economically and environmentally sustainable system; and (iii) to summarize the results of a survey of the perceptions of Brazilian farmers to problems with WSs and HRWs to glyphosate, and the level of adoption of good agricultural practices in order to prevent or manage it. Copyright (c) 2008 Society of Chemical Industry.

  7. Comparison of Measured Residual Stress in an Extra Thick Multi-pass Weld Using Neutron Diffraction Method and Inherent Strain Method

    International Nuclear Information System (INIS)

    Park, JeongUng; An, GyuBaek; Woo, Wan Chuck

    2015-01-01

    With the increase of large-scale containership, a large amount of high-strength steels with extra thick plates is being extensively used. The welding stress existing in the extra thick welded plates has a significant effect on the integrity of the component in terms of brittle fracture and fatigue behavior. It has been reported that welding residual stress distribution in an extra thick plate can affect the propagation path of the crack. Therefore, it is important to measure the distribution of welding residual stresses for the reliable design of the welded structures. So far various researches have been carried out for the determination of residual stresses on the surface of steels. In this paper, the total residual stresses in the 70 mm thick multipass FACW butt joint were measured by integrating initial stress into ISM. Concretely, two methods named as initial stress integrated ISM and initial inherent strain integrated ISM were employed to determine the total residual stresses. Furthermore, the distributions of residual stresses were compared with the results of the Neutron Diffraction Method(NDM). In order to measure the three dimensional residual stresses in the welded joint with initial stresses existing before welding, initial stress integrated ISM and initial inherent strain integrated ISM were developed. The residual stresses in 70 mm-thick butt joint by flux cored arc welding were carried out with a good accuracy using the two developed methods. The residual stresses in welded joint using both initial stress integrated ISM and initial inherent strain integrated ISM agreed well with the results measured by Neutron Diffraction Method. This suggests that the integrated ISM is a reliable method for residual stress measurement if initial stress existed

  8. Using the stress and adversity inventory as a teaching tool leads to significant learning gains in two courses on stress and health.

    Science.gov (United States)

    Slavich, George M; Toussaint, Loren

    2014-10-01

    The ability to measure cumulative stress exposure is important for research and teaching in stress and health, but until recently, no structured system has existed for assessing exposure to stress over the lifespan. Here, we report the results of two experimental studies that examined the pedagogical efficacy of using an automated system for assessing life stress, called the Stress and Adversity Inventory (STRAIN), for teaching courses on stress and health. In Study 1, a randomized, wait-list controlled experiment was conducted with 20 college students to test whether the STRAIN, coupled with a related lecture and discussion, promoted learning about stress and health. Results showed that this experiential lesson led to significant learning gains. To disentangle the effects of completing the STRAIN from participating in the lecture and discussion, we subsequently conducted Study 2 on 144 students using a 2 (STRAIN versus control activity) by 2 (STRAIN-specific lecture versus general stress lecture) repeated-measures design. Although the STRAIN-specific lecture was sufficient for promoting learning, completing the STRAIN also generated significant learning gains when paired with only the general stress lecture. Together, these studies suggest that the STRAIN is an effective tool for promoting experiential learning and teaching students about stress and health. Copyright © 2013 John Wiley & Sons, Ltd.

  9. Age, subjective stress, and depression after ischemic stroke.

    Science.gov (United States)

    McCarthy, Michael J; Sucharew, Heidi J; Alwell, Kathleen; Moomaw, Charles J; Woo, Daniel; Flaherty, Matthew L; Khatri, Pooja; Ferioli, Simona; Adeoye, Opeolu; Kleindorfer, Dawn O; Kissela, Brett M

    2016-02-01

    The incidence of stroke among younger adults in the United States is increasing. Few studies have investigated the prevalence of depressive symptoms after stroke among different age groups or the extent to which subjective stress at the time of stroke interacts with age to contribute to post-stroke depression. The present study examined whether there exists an age gradient in survivors' level of depressive symptoms and explored the extent to which financial, family, and health-related stress may also impact on depression. Bivariate analyses (N = 322) indicated significant differences in depression and stress by age group, as well as differences in age and stress by 3-month depression status. Linear regression analyses indicated that survivors between the ages of 25-54 and 55-64 years old had, on average, significantly higher depressive symptom scores. Those with financial, family, and health-related stress at the time of stroke, irrespective of age, also had significantly higher scores.

  10. Residual Stress Testing of Outer 3013 Containers

    International Nuclear Information System (INIS)

    Dunn, K.

    2004-01-01

    A Gas Tungsten Arc Welded (GTAW) outer 3013 container and a laser welded outer 3013 container have been tested for residual stresses according to the American Society for Testing Materials (ASTM) Standard G-36-94 [1]. This ASTM standard describes a procedure for conducting stress-corrosion cracking tests in boiling magnesium chloride (MgCl2) solution. Container sections in both the as-fabricated condition as well as the closure welded condition were evaluated. Significantly large residual stresses were observed in the bottom half of the as-fabricated container, a result of the base to can fabrication weld because through wall cracks were observed perpendicular to the weld. This observation indicates that regardless of the closure weld technique, sufficient residual stresses exist in the as-fabricated container to provide the stress necessary for stress corrosion cracking of the container, at the base fabrication weld. Additionally, sufficiently high residual stresses were observed in both the lid and the body of the GTAW as well as the laser closure welded containers. The stresses are oriented perpendicular to the closure weld in both the container lid and the container body. Although the boiling MgCl2 test is not a quantitative test, a comparison of the test results from the closure welds shows that there are noticeably more through wall cracks in the laser closure welded container than in the GTAW closure welded container

  11. FIB-based measurement of local residual stresses on microsystems

    Science.gov (United States)

    Vogel, Dietmar; Sabate, Neus; Gollhardt, Astrid; Keller, Juergen; Auersperg, Juergen; Michel, Bernd

    2006-03-01

    The paper comprises research results obtained for stress determination on micro and nanotechnology components. It meets the concern of controlling stresses introduced to sensors, MEMS and electronics devices during different micromachining processes. The method bases on deformation measurement options made available inside focused ion beam equipment. Removing locally material by ion beam milling existing stresses / residual stresses lead to deformation fields around the milled feature. Digital image correlation techniques are used to extract deformation values from micrographs captured before and after milling. In the paper, two main milling features have been analyzed - through hole and through slit milling. Analytical solutions for stress release fields of in-plane stresses have been derived and compared to respective experimental findings. Their good agreement allows to settle a method for determination of residual stress values, which is demonstrated for thin membranes manufactured by silicon micro technology. Some emphasis is made on the elimination of main error sources for stress determination, like rigid body object displacements and rotations due to drifts of experimental conditions under FIB imaging. In order to illustrate potential application areas of the method residual stress suppression by ion implantation is evaluated by the method and reported here.

  12. High-resolution stress measurements for microsystem and semiconductor applications

    Science.gov (United States)

    Vogel, Dietmar; Keller, Juergen; Michel, Bernd

    2006-04-01

    Research results obtained for local stress determination on micro and nanotechnology components are summarized. It meets the concern of controlling stresses introduced to sensors, MEMS and electronics devices during different micromachining processes. The method bases on deformation measurement options made available inside focused ion beam equipment. Removing locally material by ion beam milling existing stresses / residual stresses lead to deformation fields around the milled feature. Digital image correlation techniques are used to extract deformation values from micrographs captured before and after milling. In the paper, two main milling features have been analyzed - through hole and through slit milling. Analytical solutions for stress release fields of in-plane stresses have been derived and compared to respective experimental findings. Their good agreement allows to settle a method for determination of residual stress values, which is demonstrated for thin membranes manufactured by silicon micro technology. Some emphasis is made on the elimination of main error sources for stress determination, like rigid body object displacements and rotations due to drifts of experimental conditions under FIB imaging. In order to illustrate potential application areas of the method residual stress suppression by ion implantation is evaluated by the method and reported here.

  13. Effect study of multi-bubbles on stress distribution of fuel particle

    International Nuclear Information System (INIS)

    Zhao Yi; Wang Xiaomin; Long Chongsheng

    2015-01-01

    The finite element model was proposed to simulate the process of the UO_2 dispersion fuel particle sustaining the internal pressure of multi-bubbles, and the stress distribution of fuel particle with intra-bubbles was calculated. The results show that when the bubbles line equidistantly along x axis, the max normal stress along y axis increases with the number of bubbles, meanwhile, the increment of the normal stress gradually decreases. There is a limit that the effect of bubble's number imposes on the max normal stress in the fuel particle. When multi-column of bubbles exist, the max normal stress along x axis in the fuel particle increases, and the max normal stress along y axis decreases with the increase of the number of bubble column. The stress concentration in the fuel particle decreases with the spacing radius ratio increasing. (authors)

  14. Perceived stress and bruxism in university students.

    Science.gov (United States)

    Cavallo, Pierpaolo; Carpinelli, Luna; Savarese, Giulia

    2016-12-21

    Many studies have shown the correlation between bruxism and stress that affects the quality of life of university students. The present study highlights this correlation-for the first time-in a group of university students in Italy. We have investigated the prevalence of awake and asleep bruxism and its correlation with perceived stress in a group of 278 Italian undergraduate students (117 M). A self report questionnaire was constructed using a socio-demographic test, the Perceived Stress Scale (PSS) and the item n. 8 of the Fonseca Questionnaire for presence of bruxism. The perceived stress score using PSS-10 scale was 32.2 (SD 4.6, 95% CL 31.6-32.7) for all the subjects, with significant gender difference: M = 31.2 and F = 32.9 (P = 0.0019). The prevalence for awake bruxism was 37.9% (F = 40.8%; M = 34.2%,), while for sleep bruxism was 31.8% (F = 33.3%; M = 29.1%), both without significant gender difference. A positive correlation, with significant concordance and dependence, between stress score and awake bruxism was present for male students only. University students showed higher bruxism and stress levels compared to the general population, with higher stress for females, but, even if female students show higher stress, a correlation between stress and bruxism exists only for male gender. Further studies should be performed.

  15. Genetics of Oxidative Stress in Obesity

    Directory of Open Access Journals (Sweden)

    Azahara I. Rupérez

    2014-02-01

    Full Text Available Obesity is a multifactorial disease characterized by the excessive accumulation of fat in adipose tissue and peripheral organs. Its derived metabolic complications are mediated by the associated oxidative stress, inflammation and hypoxia. Oxidative stress is due to the excessive production of reactive oxygen species or diminished antioxidant defenses. Genetic variants, such as single nucleotide polymorphisms in antioxidant defense system genes, could alter the efficacy of these enzymes and, ultimately, the risk of obesity; thus, studies investigating the role of genetic variations in genes related to oxidative stress could be useful for better understanding the etiology of obesity and its metabolic complications. The lack of existing literature reviews in this field encouraged us to gather the findings from studies focusing on the impact of single nucleotide polymorphisms in antioxidant enzymes, oxidative stress-producing systems and transcription factor genes concerning their association with obesity risk and its phenotypes. In the future, the characterization of these single nucleotide polymorphisms (SNPs in obese patients could contribute to the development of controlled antioxidant therapies potentially beneficial for the treatment of obesity-derived metabolic complications.

  16. Genetics of oxidative stress in obesity.

    Science.gov (United States)

    Rupérez, Azahara I; Gil, Angel; Aguilera, Concepción M

    2014-02-20

    Obesity is a multifactorial disease characterized by the excessive accumulation of fat in adipose tissue and peripheral organs. Its derived metabolic complications are mediated by the associated oxidative stress, inflammation and hypoxia. Oxidative stress is due to the excessive production of reactive oxygen species or diminished antioxidant defenses. Genetic variants, such as single nucleotide polymorphisms in antioxidant defense system genes, could alter the efficacy of these enzymes and, ultimately, the risk of obesity; thus, studies investigating the role of genetic variations in genes related to oxidative stress could be useful for better understanding the etiology of obesity and its metabolic complications. The lack of existing literature reviews in this field encouraged us to gather the findings from studies focusing on the impact of single nucleotide polymorphisms in antioxidant enzymes, oxidative stress-producing systems and transcription factor genes concerning their association with obesity risk and its phenotypes. In the future, the characterization of these single nucleotide polymorphisms (SNPs) in obese patients could contribute to the development of controlled antioxidant therapies potentially beneficial for the treatment of obesity-derived metabolic complications.

  17. Brief mindfulness meditation training alters psychological and neuroendocrine responses to social evaluative stress.

    Science.gov (United States)

    Creswell, J David; Pacilio, Laura E; Lindsay, Emily K; Brown, Kirk Warren

    2014-06-01

    To test whether a brief mindfulness meditation training intervention buffers self-reported psychological and neuroendocrine responses to the Trier Social Stress Test (TSST) in young adult volunteers. A second objective evaluates whether pre-existing levels of dispositional mindfulness moderate the effects of brief mindfulness meditation training on stress reactivity. Sixty-six (N=66) participants were randomly assigned to either a brief 3-day (25-min per day) mindfulness meditation training or an analytic cognitive training control program. All participants completed a standardized laboratory social-evaluative stress challenge task (the TSST) following the third mindfulness meditation or cognitive training session. Measures of psychological (stress perceptions) and biological (salivary cortisol, blood pressure) stress reactivity were collected during the social evaluative stress-challenge session. Brief mindfulness meditation training reduced self-reported psychological stress reactivity but increased salivary cortisol reactivity to the TSST, relative to the cognitive training comparison program. Participants who were low in pre-existing levels of dispositional mindfulness and then received mindfulness meditation training had the greatest cortisol reactivity to the TSST. No significant main or interactive effects were observed for systolic or diastolic blood pressure reactivity to the TSST. The present study provides an initial indication that brief mindfulness meditation training buffers self-reported psychological stress reactivity, but also increases cortisol reactivity to social evaluative stress. This pattern may indicate that initially brief mindfulness meditation training fosters greater active coping efforts, resulting in reduced psychological stress appraisals and greater cortisol reactivity during social evaluative stressors. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Pain Sensitivity Mediates The Relationship between Stress and Headache Intensity in Chronic Tension-Type Headache

    OpenAIRE

    Stuart Cathcart; Navjot Bhullar; Maarten Immink; Chris Della Vedova; John Hayball

    2012-01-01

    BACKGROUND: A central model for chronic tension-type headache (CTH) posits that stress contributes to headache, in part, by aggravating existing hyperalgesia in CTH sufferers. The prediction from this model that pain sensitivity mediates the relationship between stress and headache activity has not yet been examined.OBJECTIVE: To determine whether pain sensitivity mediates the relationship between stress and prospective headache activity in CTH sufferers.METHOD: Self-reported stress, pain sen...

  19. AsMA Medical Guidelines for Air Travel: stresses of flight.

    Science.gov (United States)

    Thibeault, Claude; Evans, Anthony D

    2015-05-01

    Medical Guidelines for Airline Travel provide information that enables healthcare providers to properly advise patients who plan to travel by air. Modern commercial aircraft are very safe and, in most cases, reasonably comfortable. However, all flights, short or long haul, impose stresses on passengers. Preflight stresses include airport commotion on the ground such as carrying baggage, walking long distances, getting to the gate on time, and being delayed. In-flight stresses include acceleration, vibration (including turbulence), noise, lowered barometric pressure, variations of temperature and humidity, and fatigue among others. Healthy passengers normally tolerate these stresses quite well; however, there is the potential for passengers to become ill during or after the flight due to these stresses, especially for those with pre-existing medical conditions and reduced physiological reserves.

  20. The measurement of in-situ stress in near surface environments

    International Nuclear Information System (INIS)

    Garritty, P.; Irvin, R.A.

    1984-04-01

    One of the major unknowns affecting aspects of underground construction and the geohydrology of rock masses is the magnitude and direction of the geostatic principal stresses in the earth's crust. This is particularly the case in near surface rocks where there are indications that high horizontal stresses may exist. The measurement of stress in near surface environments is particularly difficult. The techniques, experience and results of a geostatic stress measurement programme using four commercially available devices at shallow depth in the Carnmenellis Granite are critically discussed and compared. This report also brings together some of the conclusions of two previous reports in the series, Garritty (1983) and Garritty and Irvin (1983), and emphasises the fundamental relationship between the state of stress in the earth's crust and the geohydrology of rock masses. (author)

  1. Prediction of residual stress distributions due to surface machining and welding and crack growth simulation under residual stress distribution

    International Nuclear Information System (INIS)

    Ihara, Ryohei; Katsuyama, JInya; Onizawa, Kunio; Hashimoto, Tadafumi; Mikami, Yoshiki; Mochizuki, Masahito

    2011-01-01

    Research highlights: → Residual stress distributions due to welding and machining are evaluated by XRD and FEM. → Residual stress due to machining shows higher tensile stress than welding near the surface. → Crack growth analysis is performed using calculated residual stress. → Crack growth result is affected machining rather than welding. → Machining is an important factor for crack growth. - Abstract: In nuclear power plants, stress corrosion cracking (SCC) has been observed near the weld zone of the core shroud and primary loop recirculation (PLR) pipes made of low-carbon austenitic stainless steel Type 316L. The joining process of pipes usually includes surface machining and welding. Both processes induce residual stresses, and residual stresses are thus important factors in the occurrence and propagation of SCC. In this study, the finite element method (FEM) was used to estimate residual stress distributions generated by butt welding and surface machining. The thermoelastic-plastic analysis was performed for the welding simulation, and the thermo-mechanical coupled analysis based on the Johnson-Cook material model was performed for the surface machining simulation. In addition, a crack growth analysis based on the stress intensity factor (SIF) calculation was performed using the calculated residual stress distributions that are generated by welding and surface machining. The surface machining analysis showed that tensile residual stress due to surface machining only exists approximately 0.2 mm from the machined surface, and the surface residual stress increases with cutting speed. The crack growth analysis showed that the crack depth is affected by both surface machining and welding, and the crack length is more affected by surface machining than by welding.

  2. Anticonvulsants to treat post-traumatic stress disorder.

    Science.gov (United States)

    Wang, Hee Ryung; Woo, Young Sup; Bahk, Won-Myong

    2014-09-01

    We reviewed the existing literature on the efficacy of anticonvulsants in treating post-traumatic stress disorder. We performed a literature search using PubMed, EMBASE and the Cochrane database on 30 September 2013. Randomized,controlled studies that investigated the efficacy of anticonvulsants for post-traumatic stress disorder were included in this review. Studies with retrospective designs, case reports and case series were excluded. A total of seven studies met the inclusion criteria for this review. Three studies used topiramate with negative findings regarding its efficacy. Two studies used divalproex, both of which failed to show superiority over placebo. One study used lamotrigine, with favourable results, and one study used tiagabine, with negative results. Future long-term studies with larger sample sizes are needed to investigate the clinical utility of anticonvulsants for posttraumatic stress disorder treatment.

  3. X-ray diffraction analysis of residual stresses in alumina-chromium composites and comparison with numerical simulations

    Energy Technology Data Exchange (ETDEWEB)

    Geandier, G.; Weisbecker, P.; Denis, S.; Mocellin, A. [L.S.G.2M., UMR, CNRS/INPL, Ecole des Mines de Nancy, Nancy (France); Hazotte, A. [L.S.G.2M., UMR, CNRS/INPL, Ecole des Mines de Nancy, Nancy (France); LETAM, UMR, CNRS/Metz Univ., ISGMP, Metz (France); Lebrun, J.L. [L.P.M.I., ENSAM Angers, Angers (France); Elkaim, E. [L.U.R.E., Centre Univ. Paris-Sud, Orsay (France)

    2002-07-01

    Residual stresses in alumina chromium composites have been determined using X ray synchrotron diffraction at LURE. Results show that non-negligible residual stresses exist in the composites. Mean residual stresses calculated by finite element show discrepancies with experimental values that are discussed in relation with experimental difficulties and calculation assumptions. (orig.)

  4. The effect of academic stress and attachment stress on stress-eaters and stress-undereaters.

    Science.gov (United States)

    Emond, Michael; Ten Eycke, Kayla; Kosmerly, Stacey; Robinson, Adele Lafrance; Stillar, Amanda; Van Blyderveen, Sherry

    2016-05-01

    It is well established that stress is related to changes in eating patterns. Some individuals are more likely to increase their overall food intake under conditions of stress, whereas others are more likely to consume less food when stressed. Attachment style has been linked to disordered eating and eating disorders; however, comparisons of eating behaviors under attachment versus other types of stress have yet to be explored. The present laboratory study examined the eating patterns in self-identified stress-undereaters and stress-eaters under various types of stress. More specifically, the study examined the effects of academic and attachment stress on calorie, carbohydrate and sugar consumption within these two groups. Under the guise of critiquing student films, university students viewed either one of two stress-inducing videos (academic stress or attachment stress, both designed to be emotionally arousing) or a control video (designed to be emotionally neutral), and their food intake was recorded. Results demonstrated that the video manipulations were effective in inducing stress. Differential patterns of eating were noted based on group and stress condition. Specifically, stress-undereaters ate fewer calories, carbohydrates and sugars than stress-eaters in the academic stress condition, but not in the attachment stress or control condition. Findings suggest that specific types of stressors may influence eating behaviors differently. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Risk factors for stress fractures.

    Science.gov (United States)

    Bennell, K; Matheson, G; Meeuwisse, W; Brukner, P

    1999-08-01

    Preventing stress fractures requires knowledge of the risk factors that predispose to this injury. The aetiology of stress fractures is multifactorial, but methodological limitations and expediency often lead to research study designs that evaluate individual risk factors. Intrinsic risk factors include mechanical factors such as bone density, skeletal alignment and body size and composition, physiological factors such as bone turnover rate, flexibility, and muscular strength and endurance, as well as hormonal and nutritional factors. Extrinsic risk factors include mechanical factors such as surface, footwear and external loading as well as physical training parameters. Psychological traits may also play a role in increasing stress fracture risk. Equally important to these types of analyses of individual risk factors is the integration of information to produce a composite picture of risk. The purpose of this paper is to critically appraise the existing literature by evaluating study design and quality, in order to provide a current synopsis of the known scientific information related to stress fracture risk factors. The literature is not fully complete with well conducted studies on this topic, but a great deal of information has accumulated over the past 20 years. Although stress fractures result from repeated loading, the exact contribution of training factors (volume, intensity, surface) has not been clearly established. From what we do know, menstrual disturbances, caloric restriction, lower bone density, muscle weakness and leg length differences are risk factors for stress fracture. Other time-honoured risk factors such as lower extremity alignment have not been shown to be causative even though anecdotal evidence indicates they are likely to play an important role in stress fracture pathogenesis.

  6. Grain orientation, deformation microstructure and flow stress

    International Nuclear Information System (INIS)

    Hansen, N.; Huang, X.; Winther, G.

    2008-01-01

    Dislocation structures in deformed metals have been analyzed quantitatively by transmission electron microscopy, high-resolution electron microscopy and Kikuchi line analysis. A general pattern for the microstructural evolution with increasing strain has been established and structural parameters have been defined and quantified. It has been found that two dislocation patterns co-exist in all grains, however, with very different characteristics dependent on grain orientation. This correlation with the grain orientation has been applied in modeling of the tensile flow stress and the flow stress anisotropy of fcc polycrystals. In conclusion some future research areas are briefly outlined

  7. Stress corrosion of alloy 600: mechanism proposition

    International Nuclear Information System (INIS)

    Magnin, T.

    1993-01-01

    A fissuring model by stress corrosion based on interactions corrosion-plasticity on the fissure top is proposed to describe the generally intergranular bursting of INCONEL 600 in the PWR. The calculation shows, and some observations check experimentally, that a pseudo intergranular cracking bound to the zigzag micro facets formation along the joints may be so that a completely intergranular bursting. This pseudo intergranular mode makes up a signature of the proposed mechanism. It may be suggested that it may exist one continuity mechanism between the trans and intergranular cracking by stress corrosion of ductile cubic centered faces materials. 2 figs

  8. Mechanical and hypoxia stress can cause chondrocytes apoptosis through over-activation of endoplasmic reticulum stress.

    Science.gov (United States)

    Huang, Ziwei; Zhou, Min; Wang, Qian; Zhu, Mengjiao; Chen, Sheng; Li, Huang

    2017-12-01

    To examine the role of mechanical force and hypoxia on chondrocytes apoptosis and osteoarthritis (OA)-liked pathological change on mandibular cartilage through over-activation of endoplasmic reticulum stress (ERS). We used two in vitro models to examine the effect of mechanical force and hypoxia on chondrocytes apoptosis separately. The mandibular condylar chondrocytes were obtained from three-week-old male Sprague-Dawley rats. Flexcell 5000T apparatus was used to produce mechanical forces (12%, 0.5Hz, 24h vs 20%, 0.5Hz, 24h) on chondrocytes. For hypoxia experiment, the concentration of O 2 was down regulated to 5% or 1%. Cell apoptosis rates were quantified by annexin V and propidium iodide (PI) double staining and FACS analysis. Quantitative real-time PCR and western blot were performed to evaluate the activation of ERS and cellular hypoxia. Then we used a mechanical stress loading rat model to verify the involvement of ERS in OA-liked mandibular cartilage pathological change. Histological changes in mandibular condylar cartilage were assessed via hematoxylin & eosin (HE) staining. Immunohistochemistry of GRP78, GRP94, HIF-1α, and HIF-2α were performed to evaluate activation of the ERS and existence of hypoxia. Apoptotic cells were detected by the TUNEL method. Tunicamycin, 20% mechanical forces and hypoxia (1% O 2 ) all significantly increased chondrocytes apoptosis rates and expression of ERS markers (GRP78, GRP94 and Caspase 12). However, 12% mechanical forces can only increase the apoptotic sensitivity of chondrocytes. Mechanical stress resulted in OA-liked pathological change on rat mandibular condylar cartilage which included thinning cartilage and bone erosion. The number of apoptotic cells increased. ERS and hypoxia markers expressions were also enhanced. Salubrinal, an ERS inhibitor, can reverse these effects in vitro and in vivo through the down-regulation of ERS markers and hypoxia markers. We confirmed that mechanical stress and local hypoxia both

  9. Stress as a one-armed bandit: Differential effects of stress paradigms on the morphology, neurochemistry and behavior in the rodent amygdala

    Directory of Open Access Journals (Sweden)

    Marlene A. Wilson

    2015-01-01

    Full Text Available Neuroplasticity may be defined as the ability of the central nervous system (CNS to respond to changes in the internal and external environment and it is well established that some stimuli have the ability to facilitate or impair neuroplasticity depending on the pre-existing milieu. A classic example of a stimulus that can both facilitate and impair neuroplasticity is stress. Indeed, the ability of CNS to respond to acute stress is often dependent upon the prior stress history of the individual. While responses to acute stress are often viewed as adaptive in nature, stress reactivity in subjects with prior chronic stress experiences are often linked to neuropsychiatric disorders, including major depressive disorder, post-traumatic stress disorder (PTSD and anxiety. In rodent studies, chronic stress exposure produces structural and functional alterations in the hippocampus and medial prefrontal cortex that are consistent across different types of stress paradigms. Conversely, the amygdala appears to exhibit differential structural and functional responses to stress that are dependent on a variety of factors, including the type of stressor performed and the duration of the stress paradigm. This is most evident in output measures including morphological analysis of amygdala neurons, measurement of glutamatergic tone in amygdalar subdivisions and the analysis of amygdala-centric behaviors. Accordingly, this review will provide an overview of the effects of stress on the structural and functional plasticity of the rodent amygdala, especially in relation to the differential effects of repeated or chronic stress paradigms on dendritic architecture, neurochemistry of the glutamatergic system and behavior.

  10. Stress as a one-armed bandit: Differential effects of stress paradigms on the morphology, neurochemistry and behavior in the rodent amygdala

    Science.gov (United States)

    Wilson, Marlene A.; Grillo, Claudia A.; Fadel, Jim R.; Reagan, Lawrence P.

    2015-01-01

    Neuroplasticity may be defined as the ability of the central nervous system (CNS) to respond to changes in the internal and external environment and it is well established that some stimuli have the ability to facilitate or impair neuroplasticity depending on the pre-existing milieu. A classic example of a stimulus that can both facilitate and impair neuroplasticity is stress. Indeed, the ability of CNS to respond to acute stress is often dependent upon the prior stress history of the individual. While responses to acute stress are often viewed as adaptive in nature, stress reactivity in subjects with prior chronic stress experiences are often linked to neuropsychiatric disorders, including major depressive disorder, post-traumatic stress disorder (PTSD) and anxiety. In rodent studies, chronic stress exposure produces structural and functional alterations in the hippocampus and medial prefrontal cortex that are consistent across different types of stress paradigms. Conversely, the amygdala appears to exhibit differential structural and functional responses to stress that are dependent on a variety of factors, including the type of stressor performed and the duration of the stress paradigm. This is most evident in output measures including morphological analysis of amygdala neurons, measurement of glutamatergic tone in amygdalar subdivisions and the analysis of amygdala-centric behaviors. Accordingly, this review will provide an overview of the effects of stress on the structural and functional plasticity of the rodent amygdala, especially in relation to the differential effects of repeated or chronic stress paradigms on dendritic architecture, neurochemistry of the glutamatergic system and behavior. PMID:26844236

  11. Prevalence and causes of self-reported work-related stress in head teachers.

    Science.gov (United States)

    Phillips, Samantha; Sen, Dil; McNamee, Roseanne

    2007-08-01

    Work-related stress (WRS) is the leading cause of occupational ill-health in the education sector in the UK. Headship is believed to be a stressful role although there is little current research into stress in head teachers. Changes in the education sector since the late 1980s have meant that the findings of many existing studies are outdated. To investigate prevalence and causes of self-reported, WRS in head teachers in West Sussex, UK. A cross-sectional study using postal questionnaire in a population of 290 head teachers and principals. The measuring instrument was a short stress evaluation tool (ASSET) plus additional questions derived from previous studies. Stress cases were defined as respondents who felt their work was 'very or extremely stressful'. Prevalence of self-reported, WRS was 43%. Using ASSET scoring, work overload and work-life imbalance were the key stressors. Females were significantly more stressed than males for a number of stressors including overload and control. Although there was some evidence that primary head teachers fared worse than their secondary counterparts, once the confounding effects of gender were included, there were few significant differences. The prevalence of self-reported stress in head teachers in West Sussex is significantly increased compared to recent studies of workers in the UK. The recurring theme in existing studies of workload as a main stressor is confirmed in the findings of this study. Gender and type of school does affect outcome and female head teachers have more reported stressors than their male colleagues.

  12. Effect of co-existing plant specie on soil microbial activity under heavy metal stress

    International Nuclear Information System (INIS)

    Nwuche, C. O.; Ugoji, E. O.

    2010-01-01

    The influence of plant primary compounds on the activity of soil microbial communities under heavy metal stress was studied in a pot-culture field experiment conducted in a green house. Amaranthus spinosus was cultivated in an agricultural soil previously amended in the laboratory with solutions of different trace elements in two separate treatment modes: singly and in combination. Culture-independent metabolism based indices such as the rate of carbon and nitrogen mineralization, microbial biomass carbon and soil basal respiration were monitored fortnightly over a period of six weeks. Result shows that plant detritus have significant modifying effect on soil microbe-metal interactions. Data on microbial and biochemical processes in the respective mesocosms did not vary from control; not even in mesocosms containing very high concentrations of copper, zinc and nickel. The soil microbial biomass carbon and the rate of carbon and nitrogen cycling were not impeded by the respective metal treatment while the respiration responses increased as a result of increase in metabolic activity of the soil microbes. The plant based substrates enabled the soil microflora to resist high metal contamination because of its tendency to absorb large amounts of inorganic cations.

  13. Stress inoculation training supported by physiology-driven adaptive virtual reality stimulation.

    Science.gov (United States)

    Popović, Sinisa; Horvat, Marko; Kukolja, Davor; Dropuljić, Branimir; Cosić, Kresimir

    2009-01-01

    Significant proportion of psychological problems related to combat stress in recent large peacekeeping operations underscores importance of effective methods for strengthening the stress resistance of military personnel. Adaptive control of virtual reality (VR) stimulation, based on estimation of the subject's emotional state from physiological signals, may enhance existing stress inoculation training (SIT). Physiology-driven adaptive VR stimulation can tailor the progress of stressful stimuli delivery to the physiological characteristics of each individual, which is indicated for improvement in stress resistance. Therefore, following an overview of SIT and its applications in the military setting, generic concept of physiology-driven adaptive VR stimulation is presented in the paper. Toward the end of the paper, closed-loop adaptive control strategy applicable to SIT is outlined.

  14. An Integrated Analysis of Changes in Water Stress in Europe

    DEFF Research Database (Denmark)

    Henrichs, T.; Lehner, B.; Alcamo, J.

    2002-01-01

    Future changes in water availability with climate change and changes in water use due to socio-economic development are to occur in parallel. In an integrated analysis we bring together these aspects of global change in a consistent manner, and analyse the water stress situation in Europe. We find...... that today high water stress exists in one-fifth of European river basin area. Under a scenario projection, increases in water use throughout Eastern Europe are accompanied by decreases in water availability in most of Southern Europe--combining these trends leads to a marked increase in water stress...

  15. Pediatric novice nurses: examining compassion fatigue as a mediator between stress exposure and compassion satisfaction, burnout, and job satisfaction.

    Science.gov (United States)

    Meyer, Rika M L; Li, Angela; Klaristenfeld, Jessica; Gold, Jeffrey I

    2015-01-01

    We investigated whether compassion fatigue mediated associations between nurse stress exposure and job satisfaction, compassion satisfaction, and burnout, controlling for pre-existing stress. The Life Events Checklist was administered to 251 novice pediatric nurses at the start of the nurse residency program (baseline) and 3 months after to assess pre-existing and current stress exposure. Compassion satisfaction, compassion fatigue, and burnout were assessed 3 months after baseline and job satisfaction 6 months after. Stress exposure significantly predicted lower compassion satisfaction and more burnout. Compassion fatigue partially mediated these associations. Results demonstrate a need for hospitals to prevent compassion fatigue in healthcare providers. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Analyses of edge effects on residual stresses in film strip/substrate systems

    International Nuclear Information System (INIS)

    Hsueh, Chun-Hway

    2000-01-01

    The residual stress distribution in a thin-film strip overlaid on a substrate is influenced by the edges of the strip. An analytical model is developed to derive a closed-form solution for the stress distribution along the film width. Because the film is much thinner than the substrate, the stress variation through the film thickness is ignored; however, the stress variation through the substrate thickness is considered in the analysis. Compared to the existing analytical models, the present model is more rigorous and the analytical results agree better with both finite element results and experimental measurements. (c) 2000 American Institute of Physics

  17. Diagnosis of Posttraumatic Stress Disorder in Preschool Children

    Science.gov (United States)

    De Young, Alexandra C.; Kenardy, Justin A.; Cobham, Vanessa E.

    2011-01-01

    This study investigated the existing diagnostic algorithms for posttraumatic stress disorder (PTSD) to determine the most developmentally sensitive and valid approach for diagnosing this disorder in preschoolers. Participants were 130 parents of unintentionally burned children (1-6 years). Diagnostic interviews were conducted with parents to…

  18. Work stress prevention needs of employees and supervisors.

    Science.gov (United States)

    Havermans, Bo M; Brouwers, Evelien P M; Hoek, Rianne J A; Anema, Johannes R; van der Beek, Allard J; Boot, Cécile R L

    2018-05-21

    Work stress prevention can reduce health risks for individuals, as well as organisational and societal costs. The success of work stress interventions depends on proper implementation. Failure to take into account the needs of employees and supervisors can hinder intervention implementation. This study aimed to explore employee and supervisor needs regarding organisational work stress prevention. Semi-structured telephone interviews were conducted with employees (n = 7) and supervisors (n = 8) from different sectors, such as the finance, health care, and services industry. The interviews focused on respondents' needs regarding the prevention of work stress within an organisational setting. Performing thematic analysis, topics and themes were extracted from the verbatim transcribed interviews using Atlas.ti. Both employees and supervisors reported a need for: 1) communication about work stress, 2) attention for determinants of work stress, 3) supportive circumstances (prerequisites) for work stress prevention, 4) involvement of various stakeholders in work stress prevention, and 5) availability of work stress prevention measures. Both employees and supervisors expressed the need for supervisors to communicate about work stress. Employees and supervisors reported similar psychosocial work factors that should be targeted for prevention (e.g., social support and autonomy). There was greater variety in the sub-themes within communication about work stress and supportive circumstances for work stress prevention in supervisor responses, and greater variety in the sub-themes within availability of work stress prevention measures in employee responses. Both employees and supervisors were explicit about who should take part in communication about work stress, what prerequisites for work stress prevention should exist, and which stakeholders should be involved. These results can inform work stress prevention practice, supporting selection and implementation of

  19. The role of implanted gas and lateral stress in blister formation mechanisms

    International Nuclear Information System (INIS)

    Evans, J.H.

    1978-01-01

    In this paper the parts played by gas and lateral stress in blister formation on metal surfaces after helium implantation are critically reviewed. Although measurements show the existence of lateral stresses in implanted surfaces, an analysis indicates that these stresses can play little part in blister formation. Conversely, there is a strong case for a gas driven model. One possible mechanism, that involving the interbubble fracture of overpressurised helium bubbles, is outlined and revised to take recent measurements into account. (Auth.)

  20. Remarks on the necessity and uniqueness of the gravitational stress-energy pseudotensor

    International Nuclear Information System (INIS)

    Noonan, T.W.

    1987-01-01

    Two uniqueness theorems are presented. The first one proves that the gravitational stress-energy pseudotensors (with upper indices) whose existence was demonstrated by Chandrasekhar are the only ones which are quadratic in the Christoffel symbols. The second theorem proves that the gravitational stress-energy tensor used recently by the writer is the only solution of its differential equation. Furthermore, arguments are presented here for the appropriateness of the differential equation which is used to define the gravitational stress-energy tensor. 7 references

  1. Occupational stress and organisational commitment of employees at higher educational institution

    Directory of Open Access Journals (Sweden)

    Simbarashe Zhuwao

    2015-12-01

    Full Text Available The objective of this study was to determine the relationship between occupational stress and organisational commitment of employees at a higher education institution. A random sample (N=30 was chosen from academic staff within the university. The study used a quantitative design. The Organisational Stress Screening Tool (ASSET and Allen and Meyer’s Organisational Commitment Tool (OCT were administered. The study revealed that a statistical significant relationship exists between occupational stress and organizational commitment of employees. The study also showed that academic staff overall experienced average levels of occupational stress and organisational commitment. Job characteristics and work relationship were found to be the major sources of occupation stress. It is recommended that higher education institutions should improve employee participation in decision making to reduce employees’ stress as a result of unmanageable workloads and overload.

  2. Emotional Diathesis, Emotional Stress, and Childhood Stuttering

    Science.gov (United States)

    Choi, Dahye; Conture, Edward G.; Walden, Tedra A.; Jones, Robin M.; Kim, Hanjoe

    2016-01-01

    Purpose: The purpose of this study was to determine (a) whether emotional reactivity and emotional stress of children who stutter (CWS) are associated with their stuttering frequency, (b) when the relationship between emotional reactivity and stuttering frequency is more likely to exist, and (c) how these associations are mediated by a 3rd…

  3. Interpretation of the Haestholmen in situ state of stress based on core damage observations

    International Nuclear Information System (INIS)

    Hakala, M.

    2000-01-01

    At the Haestholmen investigation site, direct in situ stress measurements, overcoring and hydraulic fracturing have been unsuccessful because of ring disking and horizontal hydraulic fracturing. Prior to this study, a detailed study on both core disking and ring disking was made, and based on those results an in situ state of stress interpretation method was developed. In this work this method is applied to the Haestholmen site. The interpretation is based on disk fracture type, spacing and shape. Also, the Hoek-Brown strength envelope and Poisson's ratio of intact rock are needed. The interpretation result is most reliable if both core disking and ring disking information at the same depth levels is available. A detailed core logging showed that ring disking is systematic below the -365 m level in the vertical overcoring stress measurement hole, HH-KR6. On the other hand, no representative core disking exists except for two points in two differently oriented subvertical boreholes HH-KR2 and HHKR7. Because the interpretation has to be based on ring disking only, upper and lower estimates for the vertical stress were set. These were gravitational and 67% of gravitational. Furthermore, the in situ stress state was assumed to be in horizontal and vertical planes, because the disking in vertical borehole HH-KR6 was not inclined. The interpretation resulted in a good estimate for the major horizontal stress but none of the horizontal stress rations ( 0.25, 0.5, 0.75 and 1.0 ) or vertical stress assumptions studied are clearly more probable the others. At the 500 m level the resulting maximum horizontal stress is 41 MPa. If a linear fit through the zero depth and zero stress point is applied, the maximum horizontal stress gradient is 0.0818 z MPa/m with a standard deviation between 5 and 12 per cent. The orientation of the major horizontal stress is 108 with standard deviation of 21 degrees. The interpreted major horizontal stress state also indicated that systematic

  4. Strengthening of Existing Bridge Structures for Shear and Bending with Carbon Textile-Reinforced Mortar

    Directory of Open Access Journals (Sweden)

    Martin Herbrand

    2017-09-01

    Full Text Available Increasing traffic loads and changes in code provisions lead to deficits in shear and flexural capacity of many existing highway bridges. Therefore, a large number of structures are expected to require refurbishment and strengthening in the future. This projection is based on the current condition of many older road bridges. Different strengthening methods for bridges exist to extend their service life, all having specific advantages and disadvantages. By applying a thin layer of carbon textile-reinforced mortar (CTRM to bridge deck slabs and the webs of pre-stressed concrete bridges, the fatigue and ultimate strength of these members can be increased significantly. The CTRM layer is a combination of a corrosion resistant carbon fiber reinforced polymer (CFRP fabric and an efficient mortar. In this paper, the strengthening method and the experimental results obtained at RWTH Aachen University are presented.

  5. Strengthening of Existing Bridge Structures for Shear and Bending with Carbon Textile-Reinforced Mortar.

    Science.gov (United States)

    Herbrand, Martin; Adam, Viviane; Classen, Martin; Kueres, Dominik; Hegger, Josef

    2017-09-19

    Increasing traffic loads and changes in code provisions lead to deficits in shear and flexural capacity of many existing highway bridges. Therefore, a large number of structures are expected to require refurbishment and strengthening in the future. This projection is based on the current condition of many older road bridges. Different strengthening methods for bridges exist to extend their service life, all having specific advantages and disadvantages. By applying a thin layer of carbon textile-reinforced mortar (CTRM) to bridge deck slabs and the webs of pre-stressed concrete bridges, the fatigue and ultimate strength of these members can be increased significantly. The CTRM layer is a combination of a corrosion resistant carbon fiber reinforced polymer (CFRP) fabric and an efficient mortar. In this paper, the strengthening method and the experimental results obtained at RWTH Aachen University are presented.

  6. Frustration-induced internal stresses are responsible for quasilocalized modes in structural glasses

    Science.gov (United States)

    Lerner, Edan; Bouchbinder, Eran

    2018-03-01

    It has been recently shown [E. Lerner, G. Düring, and E. Bouchbinder, Phys. Rev. Lett. 117, 035501 (2016), 10.1103/PhysRevLett.117.035501] that the nonphononic vibrational modes of structural glasses at low frequencies ω are quasilocalized and follow a universal density of states D (ω ) ˜ω4 . Here we show that the gapless nature of the observed density of states depends on the existence of internal stresses that generically emerge in glasses due to frustration, thus elucidating a basic element underlying this universal behavior. Similarly to jammed particulate packings, low-frequency modes in structural glasses emerge from a balance between a local elasticity term and an internal stress term in the dynamical matrix, where the difference between them is orders of magnitude smaller than their typical magnitude. By artificially reducing the magnitude of internal stresses in a computer glass former in three dimensions, we show that a gap is formed in the density of states below which no vibrational modes exist, thus demonstrating the crucial importance of internal stresses. Finally, we show that while better annealing the glass upon cooling from the liquid state significantly reduces its internal stresses, the self-organizational processes during cooling render the gapless D (ω ) ˜ω4 density of state unaffected.

  7. Post-traumatic stress disorder and exposure to violence among ...

    African Journals Online (AJOL)

    traumatic stress disorder (PTSD) symptoms was investigated in the second place, as well as the question whether a difference existed between the two ethnic groups in respect of this relationship. The participants were comprised of 186 Venda and ...

  8. Residual stress analysis for engineering applications by means of neutron diffraction

    International Nuclear Information System (INIS)

    Gnaeupel-Herold, T.; Brand, P.C.; Prask, H.J.

    1999-01-01

    Residual stresses originate from spatial differences in plastic deformation, temperature, or phase distribution, introduced by manufacturing processes or during service. Engineering parts and materials experience mechanical, thermal, and chemical loads during their service, and most of these loads introduce stresses that are superimposed on the already existing residual stresses. Residual stresses can therefore limit or improve life and strength of engineering parts; knowledge and understanding of these stresses is therefore critical for optimizing strength and durability. The economic and scientific importance of neutron diffraction residual stress analysis has led to an increasing number of suitable instruments worldwide. All of the major sources due in the next several years will have instruments for the sole purpose of performing residual stress and texture measurements. Recently, a dedicated, state-of-the-art diffractometer has been installed at the National Institute of Standards and Technology reactor. It has been used for a variety of measurements on basic and engineering stress problems. Among the most prominent examples that have been investigated in collaboration with industrial and academic partners are residual stresses in rails, weldments, and plasma-sprayed coatings

  9. Analysing inter-relationships among water, governance, human development variables in developing countries

    Science.gov (United States)

    Dondeynaz, C.; Carmona Moreno, C.; Céspedes Lorente, J. J.

    2012-10-01

    The "Integrated Water Resources Management" principle was formally laid down at the International Conference on Water and Sustainable development in Dublin 1992. One of the main results of this conference is that improving Water and Sanitation Services (WSS), being a complex and interdisciplinary issue, passes through collaboration and coordination of different sectors (environment, health, economic activities, governance, and international cooperation). These sectors influence or are influenced by the access to WSS. The understanding of these interrelations appears as crucial for decision makers in the water sector. In this framework, the Joint Research Centre (JRC) of the European Commission (EC) has developed a new database (WatSan4Dev database) containing 42 indicators (called variables in this paper) from environmental, socio-economic, governance and financial aid flows data in developing countries. This paper describes the development of the WatSan4Dev dataset, the statistical processes needed to improve the data quality, and finally, the analysis to verify the database coherence is presented. Based on 25 relevant variables, the relationships between variables are described and organised into five factors (HDP - Human Development against Poverty, AP - Human Activity Pressure on water resources, WR - Water Resources, ODA - Official Development Aid, CEC - Country Environmental Concern). Linear regression methods are used to identify key variables having influence on water supply and sanitation. First analysis indicates that the informal urbanisation development is an important factor negatively influencing the percentage of the population having access to WSS. Health, and in particular children's health, benefits from the improvement of WSS. Irrigation is also enhancing Water Supply service thanks to multi-purpose infrastructure. Five country profiles are also created to deeper understand and synthetize the amount of information gathered. This new

  10. Analysing inter-relationships among water, governance, human development variables in developing countries

    Directory of Open Access Journals (Sweden)

    C. Dondeynaz

    2012-10-01

    Full Text Available The "Integrated Water Resources Management" principle was formally laid down at the International Conference on Water and Sustainable development in Dublin 1992. One of the main results of this conference is that improving Water and Sanitation Services (WSS, being a complex and interdisciplinary issue, passes through collaboration and coordination of different sectors (environment, health, economic activities, governance, and international cooperation. These sectors influence or are influenced by the access to WSS. The understanding of these interrelations appears as crucial for decision makers in the water sector. In this framework, the Joint Research Centre (JRC of the European Commission (EC has developed a new database (WatSan4Dev database containing 42 indicators (called variables in this paper from environmental, socio-economic, governance and financial aid flows data in developing countries. This paper describes the development of the WatSan4Dev dataset, the statistical processes needed to improve the data quality, and finally, the analysis to verify the database coherence is presented. Based on 25 relevant variables, the relationships between variables are described and organised into five factors (HDP – Human Development against Poverty, AP – Human Activity Pressure on water resources, WR – Water Resources, ODA – Official Development Aid, CEC – Country Environmental Concern. Linear regression methods are used to identify key variables having influence on water supply and sanitation. First analysis indicates that the informal urbanisation development is an important factor negatively influencing the percentage of the population having access to WSS. Health, and in particular children's health, benefits from the improvement of WSS. Irrigation is also enhancing Water Supply service thanks to multi-purpose infrastructure. Five country profiles are also created to deeper understand and synthetize the amount of information gathered

  11. The best body spot to detect the vital capacity from the respiratory movement data obtained by the wearable strain sensor.

    Science.gov (United States)

    Liu, Haijuan; Guo, Shaopeng; Liu, Huilin; Zhang, Hao; Chen, Sujie; Kuramoto-Ahuja, Tsugumi; Sato, Tamae; Kaneko, Junichiro; Onoda, Ko; Maruyama, Hitoshi

    2018-04-01

    [Purpose] The purpose of this study is to find the best body spots on the chest and abdomen wall to obtain the correlated indicators to the vital capacity. [Subjects and Methods] Thirty healthy male staff of the center served as the participants were advised to conduct a breathing movement using spirometer and a wearable strain sensor (WSS) respectively, which was the measured at four spots on chest and abdomen wall from maximal end of inspiration to maximal end of expiration. The Pearson's correlation analysis was conducted to find the correlation of the data obtained respectively by the WSS and spirometer. [Results] The correlation of the mobility data at the four body spots to the vital capacity data were calculated for each level by means of Pearson's correlation coefficient, which showed that the values at each body spot were positive significant correlations and the highest value was at the 10th rib. [Conclusion] There was a correlation between the mobility data of the chest and abdomen obtained by the WSS and the vital capacity data obtained by the spirometer, for which, the 10th rib is the best body spot to detect the positive significant correlation.

  12. Annual site environmental report for calendar year 1990

    International Nuclear Information System (INIS)

    1991-09-01

    This report presents the results of a comprehensive, year-round program to monitor the impact of the Weldon Spring site (WSS) on the surrounding region's groundwater, surface waters, and air quality through multiple pathways as well as monitoring for potential exposure to receptor human populations. Information is also presented on the environmental monitoring quality assurance program, waste management activities, audits, and reviews, and special environmental studies. The data reported have been collected from a growing complex of monitoring stations and a routine sampling program supplemented by the following: An air monitoring network of 22 stations located within and on the perimeters of the two operable remedial units of the site, and at critical receptor locations around the WSS: Six National Pollutant Discharge Elimination System (NPDES) locations and over 25 surface water sampling locations; twenty-two locations for measuring external gamma radiation; over 100 groundwater monitoring wells and piezometers; dozens of soil and ground surface scanning locations for potential direct contact exposure; and an on-site meteorological station. Comprehensive environmental monitoring data for 1990 show that emissions of radiological contamination from the WSS continue to decrease, and contaminant migration pathways and environmental variability are better understood. 26 figs., 34 tabs

  13. Gerodermia osteodysplastica and wrinkly skin syndrome: are they the same?

    Science.gov (United States)

    Al-Gazali, L I; Sztriha, L; Skaff, F; Haas, D

    2001-07-01

    Gerodermia osteodysplastica (GO) is a connective tissue disorder characterized by premature aging, wrinkled, and lax skin with reduced elasticity which is more marked on the dorsum of the hands and feet associated with hyperextensible joints and osteoporosis. The wrinkly skin syndrome (WSS) is characterized by wrinkled skin over the dorsum of the hands, feet, and abdomen; hyperextensible joints, particularly of the hands; intrauterine growth retardation; postnatal failure to thrive; and mental and developmental delay. We report on five children from two consanguineous Arab families with features overlapping both GO and WSS. All five children had similar dysmorphic facial features consisting of broad and prominent forehead, hypotelorism with epicanthal folds, prominent bulbous nose, flat malar region, and large protruding ears. All had wrinkling of the skin more marked on the dorsum of the hands, feet, and abdomen; hyperextensibility of the joints, particularly of the hands; and aged appearance. Intrauterine growth retardation, subsequent failure to thrive, developmental delay, and variable degree of osteoporosis was also present in all of them. The older three children developed progressive prognathism. We suggest that GO and WSS could represent variable manifestation of the same disorder. Copyright 2001 Wiley-Liss, Inc.

  14. Greening Existing Tribal Buildings

    Science.gov (United States)

    Guidance about improving sustainability in existing tribal casinos and manufactured homes. Many steps can be taken to make existing buildings greener and healthier. They may also reduce utility and medical costs.

  15. Requirements for existing buildings

    DEFF Research Database (Denmark)

    Thomsen, Kirsten Engelund; Wittchen, Kim Bjarne

    This report collects energy performance requirements for existing buildings in European member states by June 2012.......This report collects energy performance requirements for existing buildings in European member states by June 2012....

  16. Re-evaluating occupational heat stress in a changing climate.

    Science.gov (United States)

    Spector, June T; Sheffield, Perry E

    2014-10-01

    The potential consequences of occupational heat stress in a changing climate on workers, workplaces, and global economies are substantial. Occupational heat stress risk is projected to become particularly high in middle- and low-income tropical and subtropical regions, where optimal controls may not be readily available. This commentary presents occupational heat stress in the context of climate change, reviews its impacts, and reflects on implications for heat stress assessment and control. Future efforts should address limitations of existing heat stress assessment methods and generate economical, practical, and universal approaches that can incorporate data of varying levels of detail, depending on resources. Validation of these methods should be performed in a wider variety of environments, and data should be collected and analyzed centrally for both local and large-scale hazard assessments and to guide heat stress adaptation planning. Heat stress standards should take into account variability in worker acclimatization, other vulnerabilities, and workplace resources. The effectiveness of controls that are feasible and acceptable should be evaluated. Exposure scientists are needed, in collaboration with experts in other areas, to effectively prevent and control occupational heat stress in a changing climate. © The Author 2014. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

  17. 13 reasons why the brain is susceptible to oxidative stress

    OpenAIRE

    James Nathan Cobley; Maria Luisa Fiorello; Damian Miles Bailey

    2018-01-01

    The human brain consumes 20% of the total basal oxygen (O2) budget to support ATP intensive neuronal activity. Without sufficient O2 to support ATP demands, neuronal activity fails, such that, even transient ischemia is neurodegenerative. While the essentiality of O2 to brain function is clear, how oxidative stress causes neurodegeneration is ambiguous. Ambiguity exists because many of the reasons why the brain is susceptible to oxidative stress remain obscure. Many are erroneously understood...

  18. X-ray stress analysis in textured polycrystalline materials

    International Nuclear Information System (INIS)

    Yokoyama, Ryouichi; Harada, Jimpei

    2010-01-01

    The relationship between stress and strain in polycrystalline materials with fibre texture is examined on the basis of the strain analysis in the constituent crystallites within the Reuss approximation. By introducing the symmetry of reciprocal lattices for the constituent crystallites, the physical meaning of taking an average of the strains observed by X-ray diffraction (XRD) is made clear. By using formulae obtained by the present treatment for the stress-strain relation in cubic specimens with fibre texture in the Laue classes m3-bar m hkl Bragg reflections with h≠k≠l split into doublets owing to the existence of crystallites with two different orientations under the stress field. This technique was confirmed by the profile analysis in XRD data observed for reflections of 222 and 420 in a cubic TiN thin film sputtered on a polyimide film. The technique of the stress analysis and its confirmation are introduced. (author)

  19. Environmental Social Stress, Paranoia and Psychosis Liability: A Virtual Reality Study.

    Science.gov (United States)

    Veling, Wim; Pot-Kolder, Roos; Counotte, Jacqueline; van Os, Jim; van der Gaag, Mark

    2016-11-01

    The impact of social environments on mental states is difficult to assess, limiting the understanding of which aspects of the social environment contribute to the onset of psychotic symptoms and how individual characteristics moderate this outcome. This study aimed to test sensitivity to environmental social stress as a mechanism of psychosis using Virtual Reality (VR) experiments. Fifty-five patients with recent onset psychotic disorder, 20 patients at ultra high risk for psychosis, 42 siblings of patients with psychosis, and 53 controls walked 5 times in a virtual bar with different levels of environmental social stress. Virtual social stressors were population density, ethnic density and hostility. Paranoia about virtual humans and subjective distress in response to virtual social stress exposures were measured with State Social Paranoia Scale (SSPS) and self-rated momentary subjective distress (SUD), respectively. Pre-existing (subclinical) symptoms were assessed with the Community Assessment of Psychic Experiences (CAPE), Green Paranoid Thoughts Scale (GPTS) and the Social Interaction Anxiety Scale (SIAS). Paranoia and subjective distress increased with degree of social stress in the environment. Psychosis liability and pre-existing symptoms, in particular negative affect, positively impacted the level of paranoia and distress in response to social stress. These results provide experimental evidence that heightened sensitivity to environmental social stress may play an important role in the onset and course of psychosis. © The Author 2016. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  20. Identification of High-Risk Plaques Destined to Cause Acute Coronary Syndrome Using Coronary Computed Tomographic Angiography and Computational Fluid Dynamics.

    Science.gov (United States)

    Lee, Joo Myung; Choi, Gilwoo; Koo, Bon-Kwon; Hwang, Doyeon; Park, Jonghanne; Zhang, Jinlong; Kim, Kyung-Jin; Tong, Yaliang; Kim, Hyun Jin; Grady, Leo; Doh, Joon-Hyung; Nam, Chang-Wook; Shin, Eun-Seok; Cho, Young-Seok; Choi, Su-Yeon; Chun, Eun Ju; Choi, Jin-Ho; Nørgaard, Bjarne L; Christiansen, Evald H; Niemen, Koen; Otake, Hiromasa; Penicka, Martin; de Bruyne, Bernard; Kubo, Takashi; Akasaka, Takashi; Narula, Jagat; Douglas, Pamela S; Taylor, Charles A; Kim, Hyo-Soo

    2018-03-14

    We investigated the utility of noninvasive hemodynamic assessment in the identification of high-risk plaques that caused subsequent acute coronary syndrome (ACS). ACS is a critical event that impacts the prognosis of patients with coronary artery disease. However, the role of hemodynamic factors in the development of ACS is not well-known. Seventy-two patients with clearly documented ACS and available coronary computed tomographic angiography (CTA) acquired between 1 month and 2 years before the development of ACS were included. In 66 culprit and 150 nonculprit lesions as a case-control design, the presence of adverse plaque characteristics (APC) was assessed and hemodynamic parameters (fractional flow reserve derived by coronary computed tomographic angiography [FFR CT ], change in FFR CT across the lesion [△FFR CT ], wall shear stress [WSS], and axial plaque stress) were analyzed using computational fluid dynamics. The best cut-off values for FFR CT , △FFR CT , WSS, and axial plaque stress were used to define the presence of adverse hemodynamic characteristics (AHC). The incremental discriminant and reclassification abilities for ACS prediction were compared among 3 models (model 1: percent diameter stenosis [%DS] and lesion length, model 2: model 1 + APC, and model 3: model 2 + AHC). The culprit lesions showed higher %DS (55.5 ± 15.4% vs. 43.1 ± 15.0%; p stress than nonculprit lesions (all p values statistic [c-index] 0.789 vs. 0.747; p = 0.014) and reclassification abilities (category-free net reclassification index 0.287; p = 0.047; relative integrated discrimination improvement 0.368; p < 0.001) than model 2. Lesions with both APC and AHC showed significantly higher risk of the culprit for subsequent ACS than those with no APC/AHC (hazard ratio: 11.75; 95% confidence interval: 2.85 to 48.51; p = 0.001) and with either APC or AHC (hazard ratio: 3.22; 95% confidence interval: 1.86 to 5.55; p < 0.001). Noninvasive hemodynamic assessment enhanced

  1. International symposium on seismic evaluation of existing nuclear facilities

    International Nuclear Information System (INIS)

    Orbovic, N.; Bouchon, M.; Vendel, J.; Gelain, T.

    2003-10-01

    Below are summarized the works of Mrs N. Orbovic and M. Bouchon; B. Stojadinovic, N. Orbovic, M.Bouchon and J.T. Wiley; M. Bouchon, N. Orbovic and B. Foure; T. Gelain, F. Gensdarmes, R. Sestier-Carlin, J. Vendel and M. Bouchon dealing respectively with: 1) seismic assessment of existing nuclear facility: a case study position of the IRSN 2) static and dynamic evaluation of an existing nuclear facility reinforced concrete frame structure 3) experimental study of cracking of low-rise reinforced concrete shear walls 4) aeraulics study of crack networks on low-rise reinforced concrete walls subject to static cycling loading. The summaries are followed: 1) The Institute for Radioprotection and Nuclear Safety (IRSN) has the task of evaluating the seismic safety of existing building inventory in French nuclear facilities. Some of the existing structures are reinforced concrete frame buildings with masonry or reinforced concrete in-fill walls built during the 1960's, 70's and 80's following different building codes and seismic input data applicable at the time of construction. The studied building is a laboratory that was built in 1962. The building is composed of three different and independent blocks. The structure is a reinforced concrete frame with masonry in-fills and few stiff concrete elements. Moreover, the building contains an independent massive concrete cell. Structurally, the building has a number of irregularities. From the detailing standpoint, well known deficiencies of low-ductile reinforced concrete structures are evident especially, a lack of transverse reinforcement in the structural joints of the frame. A number of sensitivity studies were conducted using 2D and 3D linear models to evaluate seismic demand. Ambient vibration and regional earthquake records were used to check the soil nature and the existence or not of a possible site effect around the installation as well as to characterize the dynamic behavior of the building. 3D models revealed a

  2. Three job stress models and their relationship with musculoskeletal pain in blue- and white-collar workers

    NARCIS (Netherlands)

    Herr, R.M.; Bosch, J.A.; Loerbroks, A.; van Vianen, A.E.M.; Jarczok, M.N.; Fischer, J.E.; Schmidt, B.

    2015-01-01

    Objectives: Musculoskeletal pain has been found to co-occur with psychosocial job stress. However, different conceptualizations of job stress exist, each emphasizing different aspects of the work environment, and it is unknown which of these aspects show the strongest associations with

  3. The use of high altitude remote sensing in determining existing vegetation and monitoring ecological stress

    Science.gov (United States)

    Foster, K.; Garcia, A.

    1972-01-01

    High altitude color and multispectral black and white photography was used to survey existing vegetation and soil conditions on the Empire Ranch where large scale development will soon begin. Utilizing stereo pairs of the high altitude color photography, four vegetation classifications were discernable as a function of topography and foliage characteristics. In contrast to the undeveloped Ranch, the same photography was used to detect environmental changes in the Tucson metropolitan area as a result of rapid urbanization. The most prevalent change related to development is the removal of vegetation in high density areas to allow for housing starts. Erosion then occurs where vegetation has been removed.

  4. A review of creep analysis and design under multi-axial stress states

    International Nuclear Information System (INIS)

    Yao, H.-T.; Xuan Fuzhen; Wang Zhengdong; Tu Shantung

    2007-01-01

    The existence of multi-axial states of stress cannot be avoided in elevated temperature components. It is essential to understand the associated failure mechanisms and to predict the lifetime in practice. Although metal creep has been studied for about 100 years, many problems are still unsolved, in particular for those involving multi-axial stresses. In this work, a state-of-the-art review of creep analysis and engineering design is carried out, with particular emphasis on the effect of multi-axial stresses. The existing theories and creep design approaches are grouped into three categories, i.e., the classical plastic theory (CPT) based approach, the cavity growth mechanism (CGM) based approach and the continuum damage mechanics (CDM) based approach. Following above arrangements, the constitutive equations and design criteria are addressed. In the end, challenges on the precise description of the multi-axial creep behavior and then improving the strength criteria in engineering design are presented

  5. TBHQ Alleviated Endoplasmic Reticulum Stress-Apoptosis and Oxidative Stress by PERK-Nrf2 Crosstalk in Methamphetamine-Induced Chronic Pulmonary Toxicity

    Directory of Open Access Journals (Sweden)

    Yun Wang

    2017-01-01

    Full Text Available Methamphetamine (MA leads to cardiac and pulmonary toxicity expressed as increases in inflammatory responses and oxidative stress. However, some interactions may exist between oxidative stress and endoplasmic reticulum stress (ERS. The current study is designed to investigate if both oxidative stress and ERS are involved in MA-induced chronic pulmonary toxicity and if antioxidant tertiary butylhydroquinone (TBHQ alleviated ERS-apoptosis and oxidative stress by PERK-Nrf2 crosstalk. In this study, the rats were randomly divided into control group, MA-treated group (MA, and MA plus TBHQ-treated group (MA + TBHQ. Chronic exposure to MA resulted in slower growth of weight and pulmonary toxicity of the rats by increasing the pulmonary arterial pressure, promoting the hypertrophy of right ventricle and the remodeling of pulmonary arteries. MA inhibited the Nrf2-mediated antioxidative stress by downregulation of Nrf2, GCS, and HO-1 and upregulation of SOD2. MA increased GRP78 to induce ERS. Overexpression and phosphorylation of PERK rapidly phosphorylated eIF2α, increased ATF4, CHOP, bax, caspase 3, and caspase 12, and decreased bcl-2. These changes can be reversed by antioxidant TBHQ through upregulating expression of Nrf2. The above results indicated that TBHQ can alleviate MA-induced oxidative stress which can accelerate ERS to initiate PERK-dependent apoptosis and that PERK/Nrf2 is likely to be the key crosstalk between oxidative stress and ERS in MA-induced chronic pulmonary toxicity.

  6. Residual stress measurement in 304 stainless steel weld overlay pipes

    International Nuclear Information System (INIS)

    Yen, H.J.; Lin, M.C.C.; Chen, L.J.

    1996-01-01

    Welding overlay repair (WOR) is commonly employed to rebuild piping systems suffering from intergranular stress corrosion cracking (IGSCC). To understand the effects of this repair, it is necessary to investigate the distribution of residual stresses in the welding pipe. The overlay welding technique must induce compressive residual stress at the inner surface of the welded pipe to prevent IGSCC. To understand the bulk residual stress distribution, the stress profile as a function of location within wall is examined. In this study the full destructive residual stress measurement technique -- a cutting and sectioning method -- is used to determine the residual stress distribution. The sample is type 304 stainless steel weld overlay pipe with an outside diameter of 267 mm. A pipe segment is cut from the circular pipe; then a thin layer is removed axially from the inner to the outer surfaces until further sectioning is impractical. The total residual stress is calculated by adding the stress relieved by cutting the section away to the stress relieved by axially sectioning. The axial and hoop residual stresses are compressive at the inner surface of the weld overlay pipe. Compressive stress exists not only at the surface but is also distributed over most of the pipe's cross section. On the one hand, the maximum compressive hoop residual stress appears at the pipe's inner surface. The thermal-mechanical induced crack closure from significant compressive residual stress is discussed. This crack closure can thus prevent IGSCC very effectively

  7. Testing the stress shadow hypothesis

    Science.gov (United States)

    Felzer, Karen R.; Brodsky, Emily E.

    2005-05-01

    A fundamental question in earthquake physics is whether aftershocks are predominantly triggered by static stress changes (permanent stress changes associated with fault displacement) or dynamic stresses (temporary stress changes associated with earthquake shaking). Both classes of models provide plausible explanations for earthquake triggering of aftershocks, but only the static stress model predicts stress shadows, or regions in which activity is decreased by a nearby earthquake. To test for whether a main shock has produced a stress shadow, we calculate time ratios, defined as the ratio of the time between the main shock and the first earthquake to follow it and the time between the last earthquake to precede the main shock and the first earthquake to follow it. A single value of the time ratio is calculated for each 10 × 10 km bin within 1.5 fault lengths of the main shock epicenter. Large values of the time ratio indicate a long wait for the first earthquake to follow the main shock and thus a potential stress shadow, whereas small values indicate the presence of aftershocks. Simulations indicate that the time ratio test should have sufficient sensitivity to detect stress shadows if they are produced in accordance with the rate and state friction model. We evaluate the 1989 MW 7.0 Loma Prieta, 1992 MW 7.3 Landers, 1994 MW 6.7 Northridge, and 1999 MW 7.1 Hector Mine main shocks. For each main shock, there is a pronounced concentration of small time ratios, indicating the presence of aftershocks, but the number of large time ratios is less than at other times in the catalog. This suggests that stress shadows are not present. By comparing our results to simulations we estimate that we can be at least 98% confident that the Loma Prieta and Landers main shocks did not produce stress shadows and 91% and 84% confident that stress shadows were not generated by the Hector Mine and Northridge main shocks, respectively. We also investigate the long hypothesized existence

  8. Compressible Analysis of Bénard Convection of Magneto Rotatory Couple-Stress Fluid

    Directory of Open Access Journals (Sweden)

    Mehta C.B.

    2018-02-01

    Full Text Available Thermal Instability (Benard’s Convection in the presence of uniform rotation and uniform magnetic field (separately is studied. Using the linearized stability theory and normal mode analyses the dispersion relation is obtained in each case. In the case of rotatory Benard’s stationary convection compressibility and rotation postpone the onset of convection whereas the couple-stress have duel character onset of convection depending on rotation parameter. While in the absence of rotation couple-stress always postpones the onset of convection. On the other hand, magnetic field on thermal instability problem on couple-stress fluid for stationary convection couple-stress parameter and magnetic field postpones the onset of convection. The effect of compressibility also postpones the onset of convection in both cases as rotation and magnetic field. Graphs have been plotted by giving numerical values to the parameters to depict the stationary characteristics. Further, the magnetic field and rotation are found to introduce oscillatory modes which were non-existent in their absence and then the principle of exchange of stability is valid. The sufficient conditions for non-existence of overstability are also obtained.

  9. PERSONALITY AS SUBJECT OF THE RELATION TO THE STRESS

    Directory of Open Access Journals (Sweden)

    Milena Aleksandrovna Klenova

    2015-08-01

    Full Text Available In this scientific article results of the empirical research devoted to studying of the personality as the subject of the relation to a stress are presented. The understanding of a phenomenon of a stress not only taking into account social and psychological features of the personality, but also with inclusion of such category as representations of a stress and the relation towards him for the first time is considered by authors. In empirical research it is established that there are five types of the personality, as subjects of the relation to a stress according to their social and psychological features and ideas of a stress. «Destructive persons» – differ in the reduced level of social and psychological adaptation, they are motivated on failure, and the stress is perceived by them as emotional excitement. «Constructive persons» possess the high level of social and psychological adaptation, are focused on success, for them emotional burning out isn’t characteristic, and their representations and the relation to a stress is based on acceptance of existence of eustressor. «Emotional and intense persons» differ in uneasiness, high level of emotional burning out, and their ideas of a stress are based only on negative characteristics. «Sensitive persons» are characterized by the high level of sensitivity, and their relation to a stress can be defined as «mental anguish». For «rational persons» cognitive approach to a situation of a stress and idea of it as about response of an organism to negative emotions is peculiar. Thus, this scientific article represents results of original research of the personality from a position of its relation to a stress.Purpose: to study social and psychological features of the personality with inclusion of such category as «representations and the relation to a stress».Method or methodology of research it is based on the concept of social representations of S.Moskovichi, and also on the subject

  10. Stress analysis of primary pipe rigid support of the in pile loop

    International Nuclear Information System (INIS)

    Hasibuan, Dj.

    1998-01-01

    Base on requirement of the safety analysis report and operation planning preparation on the in pile loop by using the fuel bundle in the test section, the stress analysis of primary pipe support has been done. The analysis was performed for the 3 (three) points of pipe support, which are chosen by random selection, i.e.: GU 2001, GU 2002, and GU 2331. The analysis result showed that the maximum allowable stress was greater then the actual stress. It is concluded that the existing supports fulfil the safety requirement

  11. Adaptive Finite Element-Discrete Element Analysis for Microseismic Modelling of Hydraulic Fracture Propagation of Perforation in Horizontal Well considering Pre-Existing Fractures

    Directory of Open Access Journals (Sweden)

    Yongliang Wang

    2018-01-01

    Full Text Available Hydrofracturing technology of perforated horizontal well has been widely used to stimulate the tight hydrocarbon reservoirs for gas production. To predict the hydraulic fracture propagation, the microseismicity can be used to infer hydraulic fractures state; by the effective numerical methods, microseismic events can be addressed from changes of the computed stresses. In numerical models, due to the challenges in accurately representing the complex structure of naturally fractured reservoir, the interaction between hydraulic and pre-existing fractures has not yet been considered and handled satisfactorily. To overcome these challenges, the adaptive finite element-discrete element method is used to refine mesh, effectively identify the fractures propagation, and investigate microseismic modelling. Numerical models are composed of hydraulic fractures, pre-existing fractures, and microscale pores, and the seepage analysis based on the Darcy’s law is used to determine fluid flow; then moment tensors in microseismicity are computed based on the computed stresses. Unfractured and naturally fractured models are compared to assess the influences of pre-existing fractures on hydrofracturing. The damaged and contact slip events were detected by the magnitudes, B-values, Hudson source type plots, and focal spheres.

  12. Stressful work, psychological job strain, and turnover: A 2-year prospective cohort study of truck drivers

    NARCIS (Netherlands)

    Croon, E.M.de; Sluiter, J.K.; Blonk, R.W.B.; Broersen, J.P.J.; Frings-Dresen, M.H.W.

    2004-01-01

    Based on a model that combines existing organizational stress theory and job transition theory, this 2-year longitudinal study examined antecedents and consequences of turnover among Dutch truck drivers. For this purpose, self-reported data on stressful work (job demands and control), psychological

  13. A strategy for accommodating residual stresses in the assessment of repair weldments based upon measurement of near surface stresses

    International Nuclear Information System (INIS)

    Mcdonald, E.J.; Hallam, K.R.; Flewitt, P.E.J.

    2005-01-01

    On many occasions repairs are undertaken to ferritic steel weldments on plant either during construction or to remove service induced defects. These repaired weldments are subsequently put into service with or without a post-weld heat treatment. In either case, but particularly for the latter, there is a need to accommodate the associated residual stresses in structural integrity assessments such as those based upon the R6 failure avoidance procedure. Although in some circumstances the residual macro-stresses developed within weldments of components and structures can be calculated this is not so readily achieved in the case of residual stresses introduced by repair welds. There is a range of physical and mechanical techniques available to undertake the measurement of macro-residual stresses. Of these X-ray diffraction has the advantage that it is essentially non-destructive and offers the potential for evaluating stresses, which exist in the near surface layer. Although for many structural integrity assessments both the magnitude and distribution of residual stresses have to be accommodated it is not practical to make destructive measurements on weld repaired components and structures to establish the through section distribution of stresses. An approach is to derive a description of the appropriate macro-stresses by a combination of measurement and calculation on trial ferritic steel repair weldments. Surface measurements on the plant can then be made to establish the relationship between the repaired component or structure and the trial weld and thereby improve confidence in predicted stresses and their distribution from the near-surface measured values. Hence X-ray diffraction measurements at the near-surface of the plant weldment can be used to underwrite the quality of the repair by confirming the magnitude and distribution of residual stresses used for the integrity assessment to demonstrate continued safe operation

  14. Full-field stress determination in photoelasticity with phase shifting technique

    Science.gov (United States)

    Guo, Enhai; Liu, Yonggang; Han, Yongsheng; Arola, Dwayne; Zhang, Dongsheng

    2018-04-01

    Photoelasticity is an effective method for evaluating the stress and its spatial variations within a stressed body. In the present study, a method to determine the stress distribution by means of phase shifting and a modified shear-difference is proposed. First, the orientation of the first principal stress and the retardation between the principal stresses are determined in the full-field through phase shifting. Then, through bicubic interpolation and derivation of a modified shear-difference method, the internal stress is calculated from the point with a free boundary along its normal direction. A method to reduce integration error in the shear difference scheme is proposed and compared to the existing methods; the integration error is reduced when using theoretical photoelastic parameters to calculate the stress component with the same points. Results show that when the value of Δx/Δy approaches one, the error is minimum, and although the interpolation error is inevitable, it has limited influence on the accuracy of the result. Finally, examples are presented for determining the stresses in a circular plate and ring subjected to diametric loading. Results show that the proposed approach provides a complete solution for determining the full-field stresses in photoelastic models.

  15. Honey bee (Apis mellifera) drones survive oxidative stress due to increased tolerance instead of avoidance or repair of oxidative damage

    Science.gov (United States)

    Oxidative stress can lead to premature aging symptoms and cause acute mortality at higher doses in a range of organisms. Oxidative stress resistance and longevity are mechanistically and phenotypically linked: considerable variation in oxidative stress resistance exists among and within species and ...

  16. A Discrete Fracture Network Model with Stress-Driven Nucleation and Growth

    Science.gov (United States)

    Lavoine, E.; Darcel, C.; Munier, R.; Davy, P.

    2017-12-01

    The realism of Discrete Fracture Network (DFN) models, beyond the bulk statistical properties, relies on the spatial organization of fractures, which is not issued by purely stochastic DFN models. The realism can be improved by injecting prior information in DFN from a better knowledge of the geological fracturing processes. We first develop a model using simple kinematic rules for mimicking the growth of fractures from nucleation to arrest, in order to evaluate the consequences of the DFN structure on the network connectivity and flow properties. The model generates fracture networks with power-law scaling distributions and a percentage of T-intersections that are consistent with field observations. Nevertheless, a larger complexity relying on the spatial variability of natural fractures positions cannot be explained by the random nucleation process. We propose to introduce a stress-driven nucleation in the timewise process of this kinematic model to study the correlations between nucleation, growth and existing fracture patterns. The method uses the stress field generated by existing fractures and remote stress as an input for a Monte-Carlo sampling of nuclei centers at each time step. Networks so generated are found to have correlations over a large range of scales, with a correlation dimension that varies with time and with the function that relates the nucleation probability to stress. A sensibility analysis of input parameters has been performed in 3D to quantify the influence of fractures and remote stress field orientations.

  17. Passive Vibration Control of Existing Structures by Gravity-Loaded Cables

    Science.gov (United States)

    Alvis, E.; Tsang, H. H.; Hashemi, M. J.

    2017-06-01

    Structures with high concentration of mass at or close to the top such as highway bridge piers are vulnerable in earthquakes or accidents. In this paper, a simple and convenient retrofit strategy is proposed for minimizing vibrations and damages, extending service life and preventing collapse of existing structures. The proposed system comprises of tension-only cables secured to the sides of the structure through gravity anchor blocks that are free to move in vertical shafts. The system is installed in such a way that the cables do not induce unnecessary stress on the main structure when there is no lateral motion or vibration. The effectiveness of controlling global structural responses is investigated for tension-only bilinear-elastic behaviour of cables. Results of a realistic case study for a reinforced concrete bridge pier show that response reduction is remarkably well under seismic excitation.

  18. The influence of acute stress on the regulation of conditioned fear

    Directory of Open Access Journals (Sweden)

    Candace M. Raio

    2015-01-01

    Full Text Available Fear learning and regulation is a prominent model for describing the pathogenesis of anxiety disorders and stress-related psychopathology. Fear expression can be modulated using a number of regulatory strategies, including extinction, cognitive emotion regulation, avoidance strategies and reconsolidation. In this review, we examine research investigating the effects of acute stress and stress hormones on these regulatory techniques. We focus on what is known about the impact of stress on the ability to flexibly regulate fear responses that are acquired through Pavlovian fear conditioning. Our primary aim is to explore the impact of stress on fear regulation in humans. Given this, we focus on techniques where stress has been linked to alterations of fear regulation in humans (extinction and emotion regulation, and briefly discuss other techniques (avoidance and reconsolidation where the impact of stress or stress hormones have been mainly explored in animal models. These investigations reveal that acute stress may impair the persistent inhibition of fear, presumably by altering prefrontal cortex function. Characterizing the effects of stress on fear regulation is critical for understanding the boundaries within which existing regulation strategies are viable in everyday life and can better inform treatment options for those who suffer from anxiety and stress-related psychopathology.

  19. Comparison of hemodynamics of intracranial aneurysms between MR fluid dynamics using 3D cine phase-contrast MRI and MR-based computational fluid dynamics

    International Nuclear Information System (INIS)

    Isoda, Haruo; Sakahara, Harumi; Ohkura, Yasuhide; Kosugi, Takashi; Hirano, Masaya; Alley, Marcus T.; Bammer, Roland; Pelc, Norbert J.; Namba, Hiroki

    2010-01-01

    Hemodynamics is thought to play a very important role in the initiation, growth, and rupture of intracranial aneurysms. The purpose of our study was to compare hemodynamics of intracranial aneurysms of MR fluid dynamics (MRFD) using 3D cine PC MR imaging (4D-Flow) at 1.5 T and MR-based computational fluid dynamics (CFD). 4D-Flow was performed for five intracranial aneurysms by a 1.5 T MR scanner. 3D TOF MR angiography was performed for geometric information. The blood flow in the aneurysms was modeled using CFD simulation based on the finite element method. We used MR angiographic data as the vascular models and MR flow information as boundary conditions in CFD. 3D velocity vector fields, 3D streamlines, shearing velocity maps, wall shear stress (WSS) distribution maps and oscillatory shear index (OSI) distribution maps were obtained by MRFD and CFD and were compared. There was a moderate to high degree of correlation in 3D velocity vector fields and a low to moderate degree of correlation in WSS of aneurysms between MRFD and CFD using regression analysis. The patterns of 3D streamlines were similar between MRFD and CFD. The small and rotating shearing velocities and higher OSI were observed at the top of the spiral flow in the aneurysms. The pattern and location of shearing velocity in MRFD and CFD were similar. The location of high oscillatory shear index obtained by MRFD was near to that obtained by CFD. MRFD and CFD of intracranial aneurysms correlated fairly well. (orig.)

  20. Hemodynamic Evaluation of a Biological and Mechanical Aortic Valve Prosthesis Using Patient-Specific MRI-Based CFD.

    Science.gov (United States)

    Hellmeier, Florian; Nordmeyer, Sarah; Yevtushenko, Pavlo; Bruening, Jan; Berger, Felix; Kuehne, Titus; Goubergrits, Leonid; Kelm, Marcus

    2018-01-01

    Modeling different treatment options before a procedure is performed is a promising approach for surgical decision making and patient care in heart valve disease. This study investigated the hemodynamic impact of different prostheses through patient-specific MRI-based CFD simulations. Ten time-resolved MRI data sets with and without velocity encoding were obtained to reconstruct the aorta and set hemodynamic boundary conditions for simulations. Aortic hemodynamics after virtual valve replacement with a biological and mechanical valve prosthesis were investigated. Wall shear stress (WSS), secondary flow degree (SFD), transvalvular pressure drop (TPD), turbulent kinetic energy (TKE), and normalized flow displacement (NFD) were evaluated to characterize valve-induced hemodynamics. The biological prostheses induced significantly higher WSS (medians: 9.3 vs. 8.6 Pa, P = 0.027) and SFD (means: 0.78 vs. 0.49, P = 0.002) in the ascending aorta, TPD (medians: 11.4 vs. 2.7 mm Hg, P = 0.002), TKE (means: 400 vs. 283 cm 2 /s 2 , P = 0.037), and NFD (means: 0.0994 vs. 0.0607, P = 0.020) than the mechanical prostheses. The differences between the prosthesis types showed great inter-patient variability, however. Given this variability, a patient-specific evaluation is warranted. In conclusion, MRI-based CFD offers an opportunity to assess the interactions between prosthesis and patient-specific boundary conditions, which may help in optimizing surgical decision making and providing additional guidance to clinicians. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  1. The role of social support on occupational stress among hospital nurses.

    Science.gov (United States)

    Yu, Jiegen; Ren, Xiaohua; Wang, Quanhai; He, Lianping; Wang, Jinquan; Jin, Yuelong; Chen, Yan; Wang, Linghong; Nie, Zhonghua; Guo, Daoxia; Yao, Yingshui

    2014-01-01

    Stress is a nonspecific reaction to everything the body needs. Although occupational stress exists in every occupation, it is seen with more frequency and intensity amongst those occupations related to human health. In this study, we aimed to investigate the relationship between occupational stress and social support (SS) among hospital nurses. A cross-sectional survey was conducted among 1144 hospital nurse in China. They were investigated with a self-administered questionnaire about socio-demographic characteristics, occupational stress and social support. A validated version of the revised Occupational Stress Inventory (OSI-R) was applied to evaluate occupational stress; SS was measured by nine questions. Logistic regression analysis was used to study the association between occupational stress and SS and adjusted for income, gender, marital status, working years, educational level, and profession. Of 1144 nurses, the majority age group was less than 30 years, and the mean age across participants was 31.8 years. Further correlation analysis indicated that score of ORQ and PSQ had a significant negative correlation with score of SS (Poccupational stress in hospitals nurse. We also should pay more attention to occupational stress of married and long working years nurse.

  2. A Study on Residual Stress Measurements by Using Laser Speckle Interferometry

    International Nuclear Information System (INIS)

    Rho, Kyung Wan; Kang, Young June; Hong, Seong Jin; Kang, Hyung Soo

    1999-01-01

    Residual stress is one of the causes which make defects in engineering components and materials. And interest in the measurement of residual stress exists in many industries. There are commonly used methods by which residual stresses are currently measured. But these methods have a little demerits: time consumption and other problems. Therefore we devised a new experimental technique to measure residual stress in materials with a combination of laser speckle pattern interferometry, finite element method and spot heating. The speckle pattern interferometer measures in-plane deformations while the heating provides for very localized stress relief. FEM is used for determining heat temperature and other parameters. The residual stresses are determined by the amount of strain that is measured subsequent to the heating and cool-down of the region being interrogated. A simple model is presented to provide a description of the method. In this paper, the ambiguity problem for the fringe patterns has solved by a phase shifting method

  3. Numerical Evaluation on Dynamic Response of Existing Underlying Tunnel Induced by Blasting Excavation of a Subway Tunnel

    Directory of Open Access Journals (Sweden)

    Jixue Zhou

    2017-01-01

    Full Text Available In Southwest China, most regions are mountainous, where traditional drill-and-blast method is adopted to excavate relatively harder rocks. However, blasting would cause vibration to adjacent structures and might result in damage or even failure. This paper considers a case where subway tunnel is overlying an existing railway tunnel, while the excavation requires blasting method. Vibration and stress distribution are calculated via Dynamic Finite Element Method (DFEM for both full-face excavation and CD method. Result shows that vibration induced by CD method is only 28% of that caused by full-face blasting with same distance. Peak vibration is located on the lining facing the blasting source, while peak tensile stress is on the other side of the contour due to the reflection of stress wave on strata boundary. And peak value of tensile stress induced by full-face blasting is capable of causing lining failure; thus full-face blasting is not suggested within 40 m beyond the underlying tunnel axis. However, CD method has shown much advantage, since blasting within 25 m is also considered safe to the underlying tunnel. But when the blasting source is as near as 12 m within the underlying tunnel, the CD method is no longer safe.

  4. Mercury chloride-induced oxidative stress in human erythrocytes ...

    African Journals Online (AJOL)

    ONOS

    2010-01-25

    Jan 25, 2010 ... Mercury can exist in the environment as metal, as monovalent and divalent salts and as organomercurials, one of the most important of which is mercuric chloride (HgCl2). It has been shown to induce oxidative stress in erythrocytes through the generation of free radicals and alteration of the.

  5. Residual stresses evaluation in a gas-pipeline crossing

    Energy Technology Data Exchange (ETDEWEB)

    Fonseca, Maria Cindra [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil); Almeida, Manoel Messias [COMPAGAS, Curitiba, PR (Brazil); Rebello, Joao Marcos Alcoforado [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Souza Filho, Byron Goncalves de [PETROBRAS, Rio de Janeiro, RJ (Brazil)

    2009-07-01

    The X-rays diffraction technique is a well established and effectiveness method in the determination of the residual and applied stresses in fine grained crystalline materials. It allows to characterize and to quantify the magnitude and direction of the existing surface stresses in the studied point of the material. The objective of this work is the evaluation of the surface stresses in a 10 in diameter Natural Gas Distribution Pipeline manufactured from API 5 L Gr B steel of COMPAGAS company, in a crossing with a Natural Gas Transportation Pipeline, in Araucaria-PR. This kind of evaluation is important to establish weather you have to perform a repositioning of one of the pipeline or not. The measurements had been made in two transversal sections of the pipe, the one upstream (170 mm of the external wall of the pipeline) and another one downstream (840 mm of the external wall of the pipeline). Each transversal section measurements where carried out in 3 points: 9 hours, 12 hours and 3 hours. In each measured point of the pipe surface, the longitudinal and transversal stresses had been measured. The magnitude of the surface residual stresses in the pipe varied of +180 MPa at the -210 MPa. The residual stress state on the surface of the points 12 hours region is characterized by tensile stresses and by compressive stresses in the points of 3 and 9 hours region. The surface residual stresses in gas-pipeline have been measured using X-ray diffraction method, by double exposure technique, using a portable apparatus, with Cr-K-alpha radiation. (author)

  6. Management of journalists professional stress

    Directory of Open Access Journals (Sweden)

    Rvović Jelena J.

    2014-01-01

    is therefore greater, also for reasons of its practical application. We can surely claim, as emphasised by Weldon (2011, that the most efficient activity that a HR manager can apply in work-related stress management will be prevention. It must follow immediately upon recognition that such a problem exists.

  7. CCM proteins control endothelial β1 integrin dependent response to shear stress

    Directory of Open Access Journals (Sweden)

    Zuzana Macek Jilkova

    2014-11-01

    Full Text Available Hemodynamic shear stress from blood flow on the endothelium critically regulates vascular function in many physiological and pathological situations. Endothelial cells adapt to shear stress by remodeling their cytoskeletal components and subsequently by changing their shape and orientation. We demonstrate that β1 integrin activation is critically controlled during the mechanoresponse of endothelial cells to shear stress. Indeed, we show that overexpression of the CCM complex, an inhibitor of β1 integrin activation, blocks endothelial actin rearrangement and cell reorientation in response to shear stress similarly to β1 integrin silencing. Conversely, depletion of CCM2 protein leads to an elongated “shear-stress-like” phenotype even in the absence of flow. Taken together, our findings reveal the existence of a balance between positive extracellular and negative intracellular signals, i.e. shear stress and CCM complex, for the control of β1 integrin activation and subsequent adaptation of vascular endothelial cells to mechanostimulation by fluid shear stress.

  8. ER stress proteins in autoimmune and inflammatory diseases

    Directory of Open Access Journals (Sweden)

    Daisuke eMorito

    2012-03-01

    Full Text Available Over the past two decades, heat shock proteins (HSPs have been implicated in inflammatory responses and autoimmunity. HSPs were originally believed to maintain protein quality control in the cytosol. However, they also exist extracellularly and appear to act as inflammatory factors. Recently, a growing body of evidence suggested that the other class of stress proteins such as, endoplasmic reticulum (ER stress proteins, which originally act as protein quality control factors in the secretory pathway and are induced by ER stress in inflammatory lesions, also participate in inflammation and autoimmunity. The immunoglobulin heavy-chain binding protein (Bip/glucose-regulated protein 78 (Grp78, homocysteine-induced ER protein (Herp, calnexin, calreticulin, glucose-regulated protein 94 (Grp94/gp96, oxygen-regulated protein 150 (ORP150 and heat shock protein 47 (Hsp47/Serpin H1, which are expressed not only in the ER but also occasionally at the cell surface play pathophysiological roles in autoimmune and inflammatory diseases as pro- or anti-inflammatory factors. Here we describe the accumulating evidence of the participation of ER stress proteins in autoimmunity and inflammation and discuss the critical differences between the two classes of stress proteins.

  9. NORMAL PRESSURE AND FRICTION STRESS MEASUREMENT IN ROLLING PROCESSES

    DEFF Research Database (Denmark)

    Henningsen, Poul; Arentoft, Mogens; Lagergren, Jonas

    2005-01-01

    the output from the transducer, the friction stress and normal pressure in the contact zone can be determined. The new concept differs from existing pin designs by a lower disturbance of lubricant film and material flow and limited penetration of material between transducer and roll. Aluminum, cupper...

  10. Stress transfer of a Kevlar 49 fiber pullout test studied by micro-Raman spectroscopy.

    Science.gov (United States)

    Lei, Zhenkun; Wang, Quan; Qiu, Wei

    2013-06-01

    The interfacial stress transfer behavior of a Kevlar 49 aramid fiber-epoxy matrix was studied with fiber pullout tests, the fibers of which were stretched by a homemade microloading device. Raman spectra on the embedded fiber were recorded by micro-Raman spectroscopy, under different strain levels. Then, the fiber axial stress was obtained by the relationship between the stress and Raman shift of the aramid fiber. Experimental results revealed that the fiber axial stress increased significantly with the load. The shear stress concentration occurred at the fiber entry to the epoxy resin. Thus, interfacial friction stages exist in the debonded fiber segment, and the interfacial friction shear stress is constant within one stage. The experimental results are consistent with the theoretical model predictions.

  11. Stress-Induced Premature Senescence or Stress-Induced Senescence-Like Phenotype: One In Vivo Reality, Two Possible Definitions?

    OpenAIRE

    Toussaint, Olivier; Dumont, Patrick; Remacle, Jose; Dierick, Jean-Francois; Pascal, Thierry; Frippiat, Christophe; Magalhaes, Joao Pedro; Zdanov, Stephanie; Chainiaux, Florence

    2002-01-01

    No consensus exists so far on the definition of cellular senescence. The narrowest definition of senescence is irreversible growth arrest triggered by telomere shortening counting cell generations (definition 1). Other authors gave an enlarged functional definition encompassing any kind of irreversible arrest of proliferative cell types induced by damaging agents or cell cycle deregulations after overexpression of proto-oncogenes (definition 2). As stress increases, the proportion of cells in...

  12. Biochar Ameliorate Drought and Salt Stress in Plants

    DEFF Research Database (Denmark)

    Saleem Akhtar, Saqib

    Biochar is a charcoal-like material obtained by heating any organic waste (crop residue, vegetable/ animal waste etc.) at high temperature through process of pyrolysis. It is produced with an intention to improve soil fertility, enhance crop productivity and mitigate greenhouse gas emission....... Drought and salinity are the two most crucial abiotic stresses that limit crops production worldwide. In this PhD project, it was hypothesized that biochar could be used to effectively mitigate drought and salinity stresses in crop plants due to its putative physiochemical properties. The overall...... objectives of the present PhD project were to reveal the mechanisms by which biochar addition mitigates negative effect of drought and salinity stress on plants and to test the efficacy of biochar when applied in combination with already existing drought (like DI and PRD) and salt management (inoculation...

  13. Dutch guidelines for physiotherapy in patients with stress urinary incontinence: an update

    OpenAIRE

    Bernards, Arnold T. M.; Berghmans, Bary C. M.; Slieker-ten Hove, Marijke C. Ph.; Staal, J. Bart; de Bie, Rob A.; Hendriks, Erik J. M.

    2013-01-01

    textabstractIntroduction and hypothesis: Stress urinary incontinence (SUI) is the most common form of incontinence impacting on quality of life (QOL) and is associated with high financial, social, and emotional costs. The purpose of this study was to provide an update existing Dutch evidence-based clinical practice guidelines (CPGs) for physiotherapy management of patients with stress urinary incontinence (SUI) in order to support physiotherapists in decision making and improving efficacy and...

  14. The effectiveness of stress inoculation group training (SIT on reducing job stress of employees of RAZAK pharmaceutical company in Tehran

    Directory of Open Access Journals (Sweden)

    M. Soudani

    2011-01-01

    Full Text Available Background and aims Despite the fact that work is the major part of human life and the source of satisfying the sense of idealism, innovation and the feeling of consent in the individual, but it is one of the most important factors of creating stress in today's societies. One of the most efficient methods of interfering in stress inoculation group training (SIT. The aim of the present research is the investigation of the efficacy of the stress inoculation group training (SIT on reducing career stress of employees of Razak Co.'s employees.     Methodsthis study is an intermediary study and the research method is experimental of pretest and posttest type with control group. 46 of subjects whose score in career stress test was above the average score were selected as sample, and were replaced in simple random way in two groups of test and control. 8-session test group of 1.5 hours each received team immunity training against stress. Both groups were tested and evaluated three times at the same time (pretest, posttest and follow up.   Resultsafter adjusting the posttest scores based on pretest scores, the results of one-way covariance pretest showed that stress inoculation group training (SIT had a meaningful influence on reduction of career stress on employees. Also the results of multivariable covariance analysis (Mankoa showed that this effect existed in every component of career stress, i.e. exceeding accountability, responsibility of others, very high working pressure, decision making that influences the others, and understanding of self as an individual not quite competent and qualified. In follow up studies after one month, the results showed that stress inoculation group training (SIT has a stable influence on reduction of career stress and it components.   Conclusion on the base of the obtained findings from research and effectiveness from the stress inoculation group training (SIT , it is recommended to apply this therapeutic

  15. Corrosion Behavior of the Stressed Sensitized Austenitic Stainless Steels of High Nitrogen Content in Seawater

    Directory of Open Access Journals (Sweden)

    A. Almubarak

    2013-01-01

    Full Text Available The purpose of this paper is to study the effect of high nitrogen content on corrosion behavior of austenitic stainless steels in seawater under severe conditions such as tensile stresses and existence of sensitization in the structure. A constant tensile stress has been applied to sensitized specimens types 304, 316L, 304LN, 304NH, and 316NH stainless steels. Microstructure investigation revealed various degrees of stress corrosion cracking. SCC was severe in type 304, moderate in types 316L and 304LN, and very slight in types 304NH and 316NH. The electrochemical polarization curves showed an obvious second current peak for the sensitized alloys which indicated the existence of second phase in the structure and the presence of intergranular stress corrosion cracking. EPR test provided a rapid and efficient nondestructive testing method for showing passivity, degree of sensitization and determining IGSCC for stainless steels in seawater. A significant conclusion was obtained that austenitic stainless steels of high nitrogen content corrode at a much slower rate increase pitting resistance and offer an excellent resistance to stress corrosion cracking in seawater.

  16. An analytical method on the surface residual stress for the cutting tool orientation

    Science.gov (United States)

    Li, Yueen; Zhao, Jun; Wang, Wei

    2010-03-01

    The residual stress is measured by choosing 8 kinds orientations on cutting the H13 dies steel on the HSM in the experiment of this paper. The measured data shows on that the residual stress exists periodicity for the different rake angle (β) and side rake angle (θ) parameters, further study find that the cutting tool orientations have closed relationship with the residual stresses, and for the original of the machined residual stress on the surface from the cutting force and the axial force, it can be gained the simply model of tool-workpiece force, using the model it can be deduced the residual stress model, which is feasible to calculate the size of residual stress. And for almost all the measured residual stresses are compressed stress, the compressed stress size and the direction could be confirmed by the input data for the H13 on HSM. As the result, the residual stress model is the key for optimization of rake angle (β) and side rake angle (θ) in theory, using the theory the more cutting mechanism can be expressed.

  17. Anisotropic stress as a signature of nonstandard propagation of gravitational waves.

    Science.gov (United States)

    Saltas, Ippocratis D; Sawicki, Ignacy; Amendola, Luca; Kunz, Martin

    2014-11-07

    We make precise the heretofore ambiguous statement that anisotropic stress is a sign of a modification of gravity. We show that in cosmological solutions of very general classes of models extending gravity-all scalar-tensor theories (Horndeski), Einstein-aether models, and bimetric massive gravity-a direct correspondence exists between perfect fluids apparently carrying anisotropic stress and a modification in the propagation of gravitational waves. Since the anisotropic stress can be measured in a model-independent manner, a comparison of the behavior of gravitational waves from cosmological sources with large-scale-structure formation could, in principle, lead to new constraints on the theory of gravity.

  18. X-ray study of residual stress distribution of ground ceramics

    International Nuclear Information System (INIS)

    Sakaida, Yoshihisa; Tanaka, Keisuke; Ikuhara, Yuichi; Suzuki, Kenzi.

    1997-01-01

    The residual stress distribution of ground ceramics was determined from the eigen strain existing in the ground surface. The eigen strain of ground ceramics was tensile, and exponentially decreased with the distance from the surface. The residual stress distribution is given as a superposition of an exponential function of compression and a linear function. It is found that the actual residual stress distribution can be approximated by a compressive exponential function because the magnitude of tensile residual stress is negligibly small compared to the compressive residual stress. In the experiments, the diffraction angle was measured on ground silicon nitride for a wide range of sin 2 ψ using the glancing incidence X-ray diffraction technique. A strong nonlinearity was found in the 2θ-sin 2 ψ diagram at very high ψ-angles. From the analysis of nonlinearity, the residual stress distribution was determined. The residual stress distribution of silicon nitride coincided with the distribution calculated from the eigen strain distribution. Transmission electron microscopy was used to clarify the origin of generation of the residual stress. Both strain contrasts and microcracks were observed below the ground surface ; straight dislocations were also observed within silicon nitride grains near the ground surface. (author)

  19. Critical brain circuits at the intersection between stress and learning.

    Science.gov (United States)

    Bangasser, Debra A; Shors, Tracey J

    2010-07-01

    The effects of stressful life experience on learning are pervasive and vary greatly both within and between individuals. It is therefore unlikely that any one mechanism will underlie these complicated processes. Nonetheless, without identifying the necessary and sufficient circuitry, no complete mechanism or set of mechanisms can be identified. In this review, we provide two anatomical frameworks through which stressful life experience can influence processes related to learning and memory. In the first, stressful experience releases stress hormones, primarily from the adrenals, which directly impact brain areas engaged in learning. In the second, stressful experience indirectly alters the circuits used in learning via intermediary brain regions. Importantly, these intermediary brain regions are not integral to the stress response or learning itself, but rather link the consequences of a stressful experience with circuits used to learn associations. As reviewed, the existing literature provides support for both frameworks, with somewhat more support for the first but sufficient evidence for the latter which involves intermediary structures. Once we determine the circumstances that engage each framework and identify which one is most predominant, we can begin to focus our efforts on describing the neuronal and hormonal mechanisms that operate within these circuits to influence cognitive processes after stressful life experience.

  20. Chronic stress impacts the cardiovascular system: animal models and clinical outcomes.

    Science.gov (United States)

    Golbidi, Saeid; Frisbee, Jefferson C; Laher, Ismail

    2015-06-15

    Psychological stresses are associated with cardiovascular diseases to the extent that cardiovascular diseases are among the most important group of psychosomatic diseases. The longstanding association between stress and cardiovascular disease exists despite a large ambiguity about the underlying mechanisms. An array of possibilities have been proposed including overactivity of the autonomic nervous system and humoral changes, which then converge on endothelial dysfunction that initiates unwanted cardiovascular consequences. We review some of the features of the two most important stress-activated systems, i.e., the humoral and nervous systems, and focus on alterations in endothelial function that could ensue as a result of these changes. Cardiac and hematologic consequences of stress are also addressed briefly. It is likely that activation of the inflammatory cascade in association with oxidative imbalance represents key pathophysiological components of stress-induced cardiovascular changes. We also review some of the commonly used animal models of stress and discuss the cardiovascular outcomes reported in these models of stress. The unique ability of animals for adaptation under stressful conditions lessens the extrapolation of laboratory findings to conditions of human stress. An animal model of unpredictable chronic stress, which applies various stress modules in a random fashion, might be a useful solution to this predicament. The use of stress markers as indicators of stress intensity is also discussed in various models of animal stress and in clinical studies. Copyright © 2015 the American Physiological Society.

  1. Physiology-driven adaptive virtual reality stimulation for prevention and treatment of stress related disorders.

    Science.gov (United States)

    Cosić, Kresimir; Popović, Sinisa; Kukolja, Davor; Horvat, Marko; Dropuljić, Branimir

    2010-02-01

    The significant proportion of severe psychological problems related to intensive stress in recent large peacekeeping operations underscores the importance of effective methods for strengthening the prevention and treatment of stress-related disorders. Adaptive control of virtual reality (VR) stimulation presented in this work, based on estimation of the person's emotional state from physiological signals, may enhance existing stress inoculation training (SIT). Physiology-driven adaptive VR stimulation can tailor the progress of stressful stimuli delivery to the physiological characteristics of each individual, which is indicated for improvement in stress resistance. Following an overview of physiology-driven adaptive VR stimulation, its major functional subsystems are described in more detail. A specific algorithm of stimuli delivery applicable to SIT is outlined.

  2. Fatigue crack growth behavior under cyclic thermal transient stress

    International Nuclear Information System (INIS)

    Ueda, Masahiro; Kano, Takashi; Yoshitoshi, Atsushi.

    1986-01-01

    Thermal fatigue tests were performed using straight pipe specimens subjected to cyclic thermal shocks of liquid sodium, and crack growth behaviors were estimated using striation patterns observed clearly on any crack surface. Crack growth rate under cyclic thermal strain reaches the maximum at one depth, and after that it decreases gradually with crack depth. The peak location of crack growth rate becomes deeper by superposition of constant primary stress. Parallel cracks co-existing in the neighborhood move the peak to shallower location and decrease the maximum crack growth rate. The equivalent stress intensity factor range calculated by Walker's formula is successfully applied to the case of negative stress ratio. Fatigue crack growth rate under cyclic thermal strain agreed well with that under the constant temperature equal to the maximum value in the thermal cycle. Simplified methods for calculating the stress intensity factor and the crack interference factor have been developed. Crack growth behavior under thermal fatigue could be well predicted using numerical analysis results. (author)

  3. Fatigue crack growth behavior under cyclic transient thermal stress

    International Nuclear Information System (INIS)

    Ueda, Masahiro; Kano, Takashi; Yoshitoshi, Atsushi.

    1987-01-01

    Thermal fatigue tests were performed using straight pipe specimens subjected to cyclic thermal shocks of liquid sodium, and crack growth behaviors were estimated using striation patterns observed clearly on any crack surface. Crack growth rate under cyclic thermal strain reaches the maximum at one depth, and after that it decreases gradually with crack depth. The peak location of crack growth rate becomes deeper by superposition of constant primary stress. Parallel cracks co-existing in the neighborhood move the peak to shallower location and decrease the maximum crack growth rate. The equivalent stress intensity factor range calculated by Walker's formula is successfully applied to the case of negative stress ratio. Fatigue crack growth rate under cyclic thermal strain agreed well with that under the constant temperature equal to the maximum value in the thermal cycle. Simplified methods for calculating the stress intensity factor and the crack interference factor have been developed. Crack growth behavior under thermal fatigue could be well predicted using numerical analysis results. (author)

  4. Metastability at the Yield-Stress Transition in Soft Glasses

    Directory of Open Access Journals (Sweden)

    Matteo Lulli

    2018-05-01

    Full Text Available We study the solid-to-liquid transition in a two-dimensional fully periodic soft-glassy model with an imposed spatially heterogeneous stress. The model we consider consists of droplets of a dispersed phase jammed together in a continuous phase. When the peak value of the stress gets close to the yield stress of the material, we find that the whole system intermittently tunnels to a metastable “fluidized” state, which relaxes back to a metastable “solid” state by means of an elastic-wave dissipation. This macroscopic scenario is studied through the microscopic displacement field of the droplets, whose time statistics displays a remarkable bimodality. Metastability is rooted in the existence, in a given stress range, of two distinct stable rheological branches, as well as long-range correlations (e.g., large dynamic heterogeneity developed in the system. Finally, we show that a similar behavior holds for a pressure-driven flow, thus suggesting possible experimental tests.

  5. Physical stress, mass, and energy for non-relativistic matter

    Science.gov (United States)

    Geracie, Michael; Prabhu, Kartik; Roberts, Matthew M.

    2017-06-01

    For theories of relativistic matter fields there exist two possible definitions of the stress-energy tensor, one defined by a variation of the action with the coframes at fixed connection, and the other at fixed torsion. These two stress-energy tensors do not necessarily coincide and it is the latter that corresponds to the Cauchy stress measured in the lab. In this note we discuss the corresponding issue for non-relativistic matter theories. We point out that while the physical non-relativistic stress, momentum, and mass currents are defined by a variation of the action at fixed torsion, the energy current does not admit such a description and is naturally defined at fixed connection. Any attempt to define an energy current at fixed torsion results in an ambiguity which cannot be resolved from the background spacetime data or conservation laws. We also provide computations of these quantities for some simple non-relativistic actions.

  6. Metastability at the Yield-Stress Transition in Soft Glasses

    Science.gov (United States)

    Lulli, Matteo; Benzi, Roberto; Sbragaglia, Mauro

    2018-04-01

    We study the solid-to-liquid transition in a two-dimensional fully periodic soft-glassy model with an imposed spatially heterogeneous stress. The model we consider consists of droplets of a dispersed phase jammed together in a continuous phase. When the peak value of the stress gets close to the yield stress of the material, we find that the whole system intermittently tunnels to a metastable "fluidized" state, which relaxes back to a metastable "solid" state by means of an elastic-wave dissipation. This macroscopic scenario is studied through the microscopic displacement field of the droplets, whose time statistics displays a remarkable bimodality. Metastability is rooted in the existence, in a given stress range, of two distinct stable rheological branches, as well as long-range correlations (e.g., large dynamic heterogeneity) developed in the system. Finally, we show that a similar behavior holds for a pressure-driven flow, thus suggesting possible experimental tests.

  7. Warm spells in Northern Europe in relation to atmospheric circulation

    Science.gov (United States)

    Tomczyk, Arkadiusz M.; Piotrowski, Piotr; Bednorz, Ewa

    2017-05-01

    This study describes warm spells in Northern Europe and determines the synoptic situations that cause their occurrence. In this article, a relatively warm day was defined as a day when the maximum temperature exceeded the 95th annual percentile, and a warm spell (WS) was considered to be a sequence of at least five relatively warm days. In the analysed multiannual period and within the investigated area, 24 (Kallax) to 53 (Oslo) WSs were observed. The occurrence of WSs was mainly connected with positive anomalies of sea level pressure and a 500-hPa isobaric surface, displaying the presence of high-pressure systems. This occurrence was also accompanied by positive T850 anomalies.

  8. Stress Levels of Kuwaiti Mothers of Children with SLD: Does Work and Educational Status Matter?

    Science.gov (United States)

    Alazemi, Saad S.; Hadadian, Azar; Merbler, John B.; Wang, Cen

    2015-01-01

    Existing research literature indicates that parents of children with disabilities have higher stress. The purpose of this study was to examine differences in stress levels between mothers in relation to their children with specific learning disabilities (SLD). A sub sample of 91 mothers participated in the study. The outcome of the research…

  9. A Comparison of American and Chinese Students' Perceived Stress, Coping Styles, and Health Promotion Practices

    Science.gov (United States)

    Li, Ying; Lindsey, Billie J.; Yin, Xiaoqin; Chen, William

    2012-01-01

    A cross-sectional survey utilized the Perceived Stress Scale, Brief COPE, and Health Promotion Lifestyle Profile II to ascertain similarities and differences between American (n=319) and Chinese (n=335) college students and between higher and lower stressed students in both samples. The results suggested the existence of a country difference in…

  10. Exploring the Individual Contributory Personality Factors of Stress: A Survey of Washington State Elementary Teachers

    Science.gov (United States)

    Dean, Effie J.

    2010-01-01

    Prolonged stress is shown to lead to low productivity, which is one of the leading causes of poor performance, and high absenteeism/turnover in occupational fields (Norton, 2002). The field of education is a prime example of low productivity resulting from prolonged stress (Norton, 2002). Currently, there are many existing studies on environmental…

  11. Post-traumatic Stress Disorder Post Partum

    Science.gov (United States)

    Schwab, W.; Marth, C.; Bergant, A. M.

    2012-01-01

    Traumatic birth experiences may lead to serious psychological impairment. Recent studies show that a considerable number of women can develop post-traumatic stress disorder (PTSD), in some cases in a subsyndromal form. Until now, the possibility that postpartum psychological symptoms might be a continuum of a pre-existing disorder in pregnancy has rarely been considered. This study therefore aimed to evaluate the proportion of women who develop post-traumatic stress disorder as a result of childbirth. Materials and Methods: 56 multiparous women were recruited for the study. The diagnosis of PTSD was made according to the criteria for psychological disorders in the DSM-IV (Diagnostics and Statistical Manual of Mental Disorders). The data were collected in structured interviews in the 30th to 38th week of gestation and in the 6th week post partum. Results: Of the 56 women participating, 52 (93 %) completed the survey. Uncontrolled results showed that 21.15 % of the multiparous women met the full diagnostic PTSD criteria in the 6th week post partum. After the exclusion of all cases already characterised by all criteria or a subsyndromal form of PTSD caused by previous traumatisation, the PTSD rate was below 8 % at 6 weeks postpartum (= incidence rate of PTSD post partum). Conclusions: The present study is the first prospective longitudinal study to demonstrate the occurrence of full criteria PTSD in multiparous women as a result of childbirth after having excluded pre-existing PTSD. The results of our study show a high prevalence rate of PTSD during pregnancy. A number of women report all aspects of post-traumatic stress disorder as a result of childbirth. PMID:25253905

  12. A fluid-structure interaction study using patient-specific ruptured and unruptured aneurysm: the effect of aneurysm morphology, hypertension and elasticity.

    Science.gov (United States)

    Lee, C J; Zhang, Y; Takao, H; Murayama, Y; Qian, Y

    2013-09-27

    Fluid-structure interaction (FSI) simulations using five patient-specific aneurysm geometries are carried out to investigate the difference between ruptured and unruptured aneurysms. Two different blood pressure conditions (normal and hypertension, for all cases), and two different values of elastic modulus (1 and 2MPa, for two cases) are tested. Ruptured aneurysms (RA) generally displayed larger displacement at the dome, lower area-average WSS and higher von Mises stress than unruptured aneurysms (URA) regardless of elasticity or blood pressure condition. RAs had a longitudinal expansion whereas URAs had a radial expansion, which was the key difference between the two types. The difference in expansion pattern may be one of the keys to explaining aneurysm rupture, and further analysis is required in the future to confirm this theory. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Current Status on Stress Diagnostic Kit and Detection Technology

    International Nuclear Information System (INIS)

    Park, Sang Hyun; Choi, Mi Hee; Ko, Kyong Cheol

    2008-06-01

    The accurate measurement of a stress level is one of the most important issues in a stress diagnosis and its measurement could be of great value in clinical medicine. Stress has a potent effect on the spirit and physical condition of an individual. There are various methods available for its measurement. Some of the commonly used techniques for the diagnosis of a stress level include analysis of the body fluids, questionnaire assessments, psychophysiological evaluations and by determining heart rate variability (HRV) of subjects. However, the existing diagnostic methods have several defects like, a low sensitivity, inaccuracy and long of operation time. In this report, we present a diagnostic technology to detect a stress level which is the origin of various diseases. This method can be of great help in providing an early diagnosis through a biosensor and might play a vital role in preventing diseases like hypochondria and hypertension. Majority of the human population is exposed to stress in one way or another and hence developing a convenient stress diagnosis kit will be of great use to all. This stress diagnostic kit and detection technology dose not involve simple a mechanical measurement or questionnaires, but is based on developing a detection kit with a high sensitivity, which will mean an easy use for common man. Individuals can undergo regular check ups and can personally diagnose their present situation of health by determining their stress levels, thus enabling them to diagnose the early onset of several stress disorders. This might help them take precautionary measures and thereby lead to a healthy life

  14. Current Status on Stress Diagnostic Kit and Detection Technology

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Hyun; Choi, Mi Hee; Ko, Kyong Cheol

    2008-06-15

    The accurate measurement of a stress level is one of the most important issues in a stress diagnosis and its measurement could be of great value in clinical medicine. Stress has a potent effect on the spirit and physical condition of an individual. There are various methods available for its measurement. Some of the commonly used techniques for the diagnosis of a stress level include analysis of the body fluids, questionnaire assessments, psychophysiological evaluations and by determining heart rate variability (HRV) of subjects. However, the existing diagnostic methods have several defects like, a low sensitivity, inaccuracy and long of operation time. In this report, we present a diagnostic technology to detect a stress level which is the origin of various diseases. This method can be of great help in providing an early diagnosis through a biosensor and might play a vital role in preventing diseases like hypochondria and hypertension. Majority of the human population is exposed to stress in one way or another and hence developing a convenient stress diagnosis kit will be of great use to all. This stress diagnostic kit and detection technology dose not involve simple a mechanical measurement or questionnaires, but is based on developing a detection kit with a high sensitivity, which will mean an easy use for common man. Individuals can undergo regular check ups and can personally diagnose their present situation of health by determining their stress levels, thus enabling them to diagnose the early onset of several stress disorders. This might help them take precautionary measures and thereby lead to a healthy life.

  15. Effect of geometric construction on residual stress distribution in designing a nuclear rotor joined by multipass narrow gap welding

    International Nuclear Information System (INIS)

    Tan, Long; Zhang, Linjie; Zhang, Jianxun; Zhuang, Dong

    2014-01-01

    Highlights: • The internal stress of the pipe is measured using local material removal method. • Bottom protrusion at weld seam can release the stress and mitigate stress evolution. The through-wall axial stress is bending type under the effect of the rotor discs. • The impact of geometric construction on the stress evolution begins after pass 15. - Abstract: The purpose of this study is to investigate the effect of geometric construction on the distribution of residual stresses before and after heat treatment in designing a nuclear welded rotor. The local material removal method was used to measure internal residual stress of the experimental pipe after post weld heat treatment. Three finite element models were employed as follows: a model of experimental pipe, a model with a bottom protrusion existed at the weld region, and a model of two rotor discs butt-welded with a bottom protrusion at the weld region. Investigated results showed that the bottom protrusion existed at the weld region can decrease the residual stress and mitigate the stress evolution significantly on the inner surface. Under the binding effect of the rotor discs, the axial stress of inner surface region is compressive stress; the through-wall axial stress at the weld center line can be deemed to a bending type; both the hoop stress and axial stress at the weld center line on the inner surface are compressive. The impact of geometric construction on the stress evolution at the root bead begins after pass 15 deposited

  16. Enterovirus Control of Translation and RNA Granule Stress Responses.

    Science.gov (United States)

    Lloyd, Richard E

    2016-03-30

    Enteroviruses such as poliovirus (PV) and coxsackievirus B3 (CVB3) have evolved several parallel strategies to regulate cellular gene expression and stress responses to ensure efficient expression of the viral genome. Enteroviruses utilize their encoded proteinases to take over the cellular translation apparatus and direct ribosomes to viral mRNAs. In addition, viral proteinases are used to control and repress the two main types of cytoplasmic RNA granules, stress granules (SGs) and processing bodies (P-bodies, PBs), which are stress-responsive dynamic structures involved in repression of gene expression. This review discusses these processes and the current understanding of the underlying mechanisms with respect to enterovirus infections. In addition, the review discusses accumulating data suggesting linkage exists between RNA granule formation and innate immune sensing and activation.

  17. Composite Analysis of Concrete - Creep, Relaxation and Eigenstrain/stress

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1996-01-01

    approach.The model is successfully justified comparing predicted results with recent experimental data obtained in tests made at the Danish Technological Institute and at the Technical University of Denmark on creep, relaxation, and shrinkage of very young concretes (hours) - and also with experimental...... results on creep, shrinkage, and internal stresses caused by drying shrinkage reported in the literature on the mechanical behavior of mature concretes.Shrinkage (autogeneous or drying) of mortar and concrete and associated internal stress states are examples of analysis made in this report......A composite-rheological model of concrete is presented by which consistent predictions of creep, relaxation, and internal stresses can be made from known concrete composition, age at loading, and climatic conditions. No other existing "creep prediction method" offers these possibilities in one...

  18. Stress Management: Job Stress

    Science.gov (United States)

    Healthy Lifestyle Stress management Job stress can be all-consuming — but it doesn't have to be. Address your triggers, keep perspective and ... stress triggers, it's often helpful to improve time management skills — especially if you tend to feel overwhelmed ...

  19. Vitamin D deficiency, oxidative stress and antioxidant status: only weak association seen in the absence of advanced age, obesity or pre-existing disease.

    Science.gov (United States)

    Wang, Erica W; Siu, Parco M; Pang, Marco Y; Woo, Jean; Collins, Andrew R; Benzie, Iris F F

    2017-07-01

    Vitamin D deficiency (plasma 25-hydroxycholecalciferol (25(OH)D)70 % of participants were vitamin D deficient. No significant correlations and no biomarker differences across 25(OH)D quartiles or groups were seen except for total antioxidant status. A weak direct association (r 0·252, Pstress biomarkers in the absence of advanced age, obesity and disease, though some evidence of depleted antioxidant status in those with vitamin D deficiency was seen. Poor antioxidant status may pre-date increased oxidative stress. Study of effects of correction of deficiency on antioxidant status and oxidative stress in vitamin D-deficient but otherwise healthy subjects is needed.

  20. Role of symmetry-breaking induced by Er × B shear flows on developing residual stresses and intrinsic rotation in the TEXTOR tokamak

    International Nuclear Information System (INIS)

    Xu, Y.; Shesterikov, I.; Berte, M.; Dumortier, P.; Van Schoor, M.; Vergote, M.; Hidalgo, C.; Krämer-Flecken, A.; Koslowski, R.

    2013-01-01

    Direct measurements of residual stress (force) have been executed at the edge of the TEXTOR tokamak using multitip Langmuir and Mach probes, together with counter-current NBI torque to balance the existing toroidal rotation. Substantial residual stress and force have been observed at the plasma boundary, confirming the existence of a finite residual stress as possible mechanisms to drive the intrinsic toroidal rotation. In low-density discharges, the residual stress displays a quasi-linear dependence on the local pressure gradient, consistent with theoretical predictions. At high-density shots the residual stress and torque are strongly suppressed. The results show close correlation between the residual stress and the E r × B flow shear rate, suggesting a minimum threshold of the E × B flow shear required for the k ∥ symmetry breaking. These findings provide the first experimental evidence of the role of E r × B sheared flows in the development of residual stresses and intrinsic rotation. (letter)

  1. Effects of written emotional disclosure on implicit self-esteem and body image.

    Science.gov (United States)

    O'Connor, Daryl B; Hurling, Robert; Hendrickx, Hilde; Osborne, Gabrielle; Hall, Josephine; Walklet, Elaine; Whaley, Ann; Wood, Helen

    2011-09-01

    Negative body image has a significant impact on self-esteem, disordered eating, and general health. Writing about distressing events and experiences has been found to have beneficial effects on psychological and physical health outcomes. This study investigated whether a written self-disclosure intervention, compared to a writing about body image success stories (WSS) intervention, had beneficial effects on self-esteem and body image. One hundred and fifty-eight women (aged 18-22 years) were allocated to either: written emotional disclosure (WED); WSS; or a control, non-emotional writing condition. All measures were completed at baseline and at follow-up 4 weeks later. A condition by time interaction was observed for implicit self-esteem, such that levels of self-esteem were improved 4 weeks later in the WED condition. Implicit self-esteem was also found to be greater following WED compared to the control condition, but not following WSS. This is the first study to demonstrate that WED has beneficial effects on implicit outcome measures such as self-esteem indicating that the positive effects of expressive writing may initially operate by influencing automatically activated attitudes towards the self. The impact of WED on implicit self-esteem may have implications for future health. ©2010 The British Psychological Society.

  2. Harpacticoid copepod diversity at two physically reworked sites in the deep sea

    Science.gov (United States)

    Thistle, David

    1998-01-01

    Grassle's and Jumars' theories of diversity maintenance in the quiescent deep sea view millimeter-to-meter-scale patchiness (mostly of biological origin) as crucial. In other deep-sea regions, episodes of strong near-bottom flow put the surficial sediment layers into motion, obliterating the biologically produced, millimeter-to-meter-scale patchiness. Under these theories, sites eroded so frequently that such patchiness is eliminated almost as soon as it is created should have lower diversities than sites where the time between erosive events is sufficient for this type of patchiness to be produced and exploited. I tested this prediction by comparing the diversities of harpacticoid copepods at two sites on Fieberling Guyot to determine whether Grassle's and Jumars' theories can be extended to the portion of the deep sea that experiences episodic erosive flows. At White Sand Swale (=WSS) (32°27.581'N, 127°47.839'W), strong near-bottom flows erode the surficial sediment daily. At Sea Pen Rim (=SPR) (32°27.631'N, 127°49.489'W), strong near-bottom flows erode the surficial sediment a few times annually. Contrary to expectation, the diversity of harpacticoid copepods was significantly greater at WSS than at SPR. However, the erosion regime at WSS may create small-scale patchiness that promotes harpacticoid diversity.

  3. Energy saving effect of desiccant ventilation system using Wakkanai siliceous shale

    Science.gov (United States)

    Nabeshima, Yuki; Togawa, Jun-ya; Nagano, Katsunori; Kazuyo, Tsuzuki

    2017-10-01

    The nuclear power station accident resulting from the Great East Japan Earthquake disaster has resulted in a constrained electricity supply. However, in this Asian region there is high temperature and high humidity and consequently dehumidification process requires a huge amount of energy. This is the reason for the increasing energy consumption in the residential and commercial sectors. Accordingly, a high efficiency air-conditioning system is needed to be developed. The desiccant ventilation system is effective to reduce energy consumption for the dehumidification process. This system is capable of dehumidifying without dew condensing unlike a conventional air-conditioning system. Then we focused on Wakkanai Siliceous Shale (WSS) as a desiccant material to develop a new desiccant ventilation system. This is low priced, high performance, new type of thing. The aim of this study is to develop a desiccant ventilation unit using the WSS rotor which can be regenerated with low-temperature by numerical calculation. The results of performance prediction of the desiccant unit, indicate that it is possible to regenerate the WSS rotor at low-temperature of between 35 - 45 °C. In addition, we produced an actual measurement for the desiccant unit and air-conditioning unit. This air-conditioning system was capable to reduce roughly 40 % of input energy consumption.

  4. Performance of LiCl Impregnated Mesoporous Material Coating over Corrugated Heat Exchangers in a Solid Sorption Chiller

    Directory of Open Access Journals (Sweden)

    Hongzhi Liu

    2018-06-01

    Full Text Available The composite material made by impregnating 40 wt. % lithium chloride (LiCl into the mesopores of a kind of natural porous rock (Wakkanai Siliceous Shale: WSS micropowders (short for “WSS + 40 wt. % LiCl” had been developed previously, and can be regenerated below 100 °C with a cooling coefficient of performance (COP of approximately 0.3 when adopted as a sorbent in a sorption cooler. In this study, experiments have been carried out on an intermittent solid sorption chiller with the WSS + 40 wt. % LiCl coating over two aluminum corrugated heat exchangers. Based on the experimental condition (regeneration temperature of 80 °C, condensation temperature of 30 °C in the desorption process; sorption temperature of 30 °C and evaporation temperature of 12 °C in the sorption process, the water sorption amount changes from 20 wt. % to 70 wt. % in one sorption cooling cycle. Moreover, a specific cooling power (SCP of 86 W/kg, a volumetric specific cooling power (VSCP of 42 W/dm3, and a specific sorption power of 170 W/kg can be achieved with a total sorption and desorption time of 20 min. The obtained cooling COP is approximately 0.16.

  5. Review of current research and understanding of irradiation-assisted stress corrosion cracking

    International Nuclear Information System (INIS)

    Nelson, J.L.; Andresen, P.L.

    1992-01-01

    Concerns for irradiation-assisted stress corrosion cracking (IASCC) of reactor internals are increasing, especially for components that are not readily replaceable. Both laboratory and field data show that intergranular stress corrosion cracking of stainless steels and nickel-base alloys can result from long term exposure to the high energy neutron and gamma radiation that exists in the core of light water reactors (LWR's). Radiation affects cracking susceptibility via changes in material micro-chemistry (radiation induced segregation, or RIS), water chemistry (radiolysis) and material properties/stress (e.g., radiation induced creep and hardening). Based on many common dependencies, e.g., to solution purity, corrosion potential, crevicing and stress, IASCC falls within the continuum of environmental cracking phenomenon in high temperature water

  6. On The Stress Free Deformation Of Linear FGM Interface Under Constant Temperature

    Directory of Open Access Journals (Sweden)

    Ganczarski Artur

    2015-09-01

    Full Text Available This paper demonstrates the stress free thermo-elastic problem of the FGM thick plate. Existence of such a purely thermal deformation is proved in two ways. First proof is based on application of the Iljushin thermo-elastic potential to displacement type system of equations. This reduces 3D problem to the plane stress state problem. Next it is shown that the unique solution fulfils conditions of simultaneous constant temperature and linear gradation of thermal expansion coefficient. Second proof is based directly on stress type system of equations which straightforwardly reduces to compatibility equations for purely thermal deformation. This occurs if only stress field is homogeneous in domain and at boundary. Finally an example of application to an engineering problem is presented.

  7. Hysteresis analysis of graphene transistor under repeated test and gate voltage stress

    International Nuclear Information System (INIS)

    Yang Jie; Jia Kunpeng; Su Yajuan; Zhao Chao; Chen Yang

    2014-01-01

    The current transport characteristic is studied systematically based on a back-gate graphene field effect transistor, under repeated test and gate voltage stress. The interface trapped charges caused by the gate voltage sweep process screens the gate electric field, and results in the neutral point voltage shift between the forth and back sweep direction. In the repeated test process, the neutral point voltage keeps increasing with test times in both forth and back sweeps, which indicates the existence of interface trapped electrons residual and accumulation. In gate voltage stress experiment, the relative neutral point voltage significantly decreases with the reducing of stress voltage, especially in −40 V, which illustrates the driven-out phenomenon of trapped electrons under negative voltage stress. (semiconductor devices)

  8. Existence theory in optimal control

    International Nuclear Information System (INIS)

    Olech, C.

    1976-01-01

    This paper treats the existence problem in two main cases. One case is that of linear systems when existence is based on closedness or compactness of the reachable set and the other, non-linear case refers to a situation where for the existence of optimal solutions closedness of the set of admissible solutions is needed. Some results from convex analysis are included in the paper. (author)

  9. [Reflections on stress and burnout and their relationship with nursing].

    Science.gov (United States)

    Murofuse, Neide Tiemi; Abranches, Sueli Soldati; Napoleão, Anamaria Alves

    2005-01-01

    This bibliographic review aimed to differentiate between stress and Burnout and to establish their relationship with nursing work to support the understanding of psychical suffering at work. The study was based on the analysis and interpretation of articles, thesis and dissertations produced between 1990 and 2001. Although there is a consensus among the individuals on the existence of stress and burnout, there are several controversies surrounding these terms. These theories were created in the context of capitalist production increase. Stress refers to a personal tiring that interferes in the life of the person but not necessarily in his/her relationship with the work. Burnout is a syndrome involving negative attitudes and behaviors towards users, clients, organization and work. It is a gradual process of subjective experiences that result in practical and emotional problems to workers and organizations. Nursing work facilitates stress and burnout and causes suffering and illness among workers.

  10. 10 CFR 4.127 - Existing facilities.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Existing facilities. 4.127 Section 4.127 Energy NUCLEAR... 1973, as Amended Discriminatory Practices § 4.127 Existing facilities. (a) Accessibility. A recipient... make each of its existing facilities or every part of an existing facility accessible to and usable by...

  11. Antioxidant properties of the mung bean flavonoids on alleviating heat stress.

    Directory of Open Access Journals (Sweden)

    Dongdong Cao

    Full Text Available BACKGROUND: It is a widespread belief in Asian countries that mung bean soup (MBS may afford a protective effect against heat stress. Lack of evidence supports MBS conferring a benefit in addition to water. RESULTS: Here we show that vitexin and isovitexin are the major antioxidant components in mungbean (more than 96% of them existing in the bean seed coat, and both of them could be absorbed via gavage into rat plasma. In the plasma of rats fed with mungbean coat extract before or after exposure to heat stress, the levels of malonaldehyde and activities of lactate dehydrogenase and nitric oxide synthase were remarkably reduced; the levels of total antioxidant capacity and glutathione (a quantitative assessment of oxidative stress were significantly enhanced. CONCLUSIONS: Our results demonstrate that MBS can play additional roles to prevent heat stress injury. Characterization of the mechanisms underlying mungbean beneficial effects should help in the design of diet therapy strategies to alleviate heat stress, as well as provide reference for searching natural medicines against oxidative stress induced diseases.

  12. Stresse na Profissão Docente: Um Estudo Exploratório numa Escola Secundária

    Directory of Open Access Journals (Sweden)

    Cláudia Rafaela Costa Martins

    2016-02-01

    Full Text Available Neste estudo procurou verificar-se a existência de fontes de stresse nos docentes de uma escola secundária e proporcionar uma reflexão acerca das estratégias utilizadas para prevenir ou combater situações de stresse ocupacional. Após a aplicação do Questionário Sociodemográfico, elaborado pelos autores deste estudo, e da Escala Portuguesa de Stresse Ocupacional – versão para Docência – EPSO-D, de Mota Cardoso et al., 2002, a 80 docentes, a análise dos resultados permite concluir a existência de stresse ocupacional, aproximando-se os valores obtidos aos da média da população portuguesa encontrados por Mota-Cardoso e colaboradores (2002. Consideram-se inovadores e pertinentes os resultados encontrados relativamente às variáveis „gosto pela cidade em que trabalha‟, „mudanças de local de trabalho‟ e „docência em cursos profissionais ou, simultaneamente, em cursos profissionais e científico-humanísticos‟, visto que influenciam os níveis de stresse.

  13. Continuous traumatic stress as a mental and physical health challenge: Case studies from South Africa.

    Science.gov (United States)

    Kaminer, Debra; Eagle, Gillian; Crawford-Browne, Sarah

    2018-07-01

    This article discusses the condition of continuous traumatic stress as common on the African continent and in other international settings characterised by very high levels of ongoing violence and threat of community, political or war-related origin. Through consideration of three case studies from South Africa, contexts of continuous traumatic stress are described, and the mental health and physical health effects of living in such contexts are elaborated. Cautions are raised about attempting to transpose existing posttraumatic stress models onto individuals exposed to situations of continuous traumatic stress, and guidelines for optimal interventions with such cases are proposed.

  14. Stress-induced variation in evolution: from behavioural plasticity to genetic assimilation.

    Science.gov (United States)

    Badyaev, Alexander V

    2005-05-07

    Extreme environments are closely associated with phenotypic evolution, yet the mechanisms behind this relationship are poorly understood. Several themes and approaches in recent studies significantly further our understanding of the importance that stress-induced variation plays in evolution. First, stressful environments modify (and often reduce) the integration of neuroendocrinological, morphological and behavioural regulatory systems. Second, such reduced integration and subsequent accommodation of stress-induced variation by developmental systems enables organismal 'memory' of a stressful event as well as phenotypic and genetic assimilation of the response to a stressor. Third, in complex functional systems, a stress-induced increase in phenotypic and genetic variance is often directional, channelled by existing ontogenetic pathways. This accounts for similarity among individuals in stress-induced changes and thus significantly facilitates the rate of adaptive evolution. Fourth, accumulation of phenotypically neutral genetic variation might be a common property of locally adapted and complex organismal systems, and extreme environments facilitate the phenotypic expression of this variance. Finally, stress-induced effects and stress-resistance strategies often persist for several generations through maternal, ecological and cultural inheritance. These transgenerational effects, along with both the complexity of developmental systems and stressor recurrence, might facilitate genetic assimilation of stress-induced effects. Accumulation of phenotypically neutral genetic variance by developmental systems and phenotypic accommodation of stress-induced effects, together with the inheritance of stress-induced modifications, ensure the evolutionary persistence of stress-response strategies and provide a link between individual adaptability and evolutionary adaptation.

  15. Growth responses of NaCl stressed rice (Oryza sativa L.) plants ...

    African Journals Online (AJOL)

    GREGORY

    2010-09-27

    Sep 27, 2010 ... Growth responses of NaCl stressed rice (Oryza sativa. L.) plants ... 2008), which is a real threat to human's food security. Existed situation may ..... content and composition of essential oil and minerals in black cumin. (Nigella ...

  16. Effects of stress and coping on binge eating in female college students.

    Science.gov (United States)

    Sulkowski, Michael L; Dempsey, Jack; Dempsey, Allison G

    2011-08-01

    Limited research exists on the association between stress, coping, and binge eating. To address this paucity, this study explores these associations in a sample of 147 female college students, an at-risk population for binge eating. We hypothesized that emotional and avoidant coping would be positively associated with stress and binge eating. Conversely, we expected that rational and detached coping would be negatively related to stress and binge eating. Furthermore, we expected these coping styles to mediate the relationship between stress and binge eating. As predicted, emotion-focused and avoidant coping were positively associated with stress and binge eating. Additionally, emotion-focused coping partially mediated the relationship between stress and binge eating. However, no association was found between stress, rational or detached coping, and binge eating. These results are discussed within the context of a negative reinforcement model of binge eating. Lastly, the importance of providing evidence-based treatment for individuals with binge eating symptomology is discussed in light of our findings. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. Analysis of stress sensitivity and its influence on oil productionfrom tight reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Qun; Xiong, Wei; Yuan, Cui; Wu, Yu-Shu

    2007-08-28

    This paper presents a study of the relationship betweenpermeability and effective stress in tight petroleum reservoirformations. Specifically, a quantitative method is developed to describethe correlation between permeability and effective stress, a method basedon the original in situ reservoir effective stress rather than ondecreased effective stress during development. The experimental resultsshow that the relationship between intrinsic permeability and effectivestress in reservoirs in general follows a quadratic polynomial functionalform, found to best capture how effective stress influences formationpermeability. In addition, this experimental study reveals that changesin formation permeability, caused by both elastic and plasticdeformation, are permanent and irreversible. Related pore-deformationtests using electronic microscope scanning and constant-rate mercuryinjection techniques show that while stress variation generally has smallimpact onrock porosity, the size and shape of pore throats have asignificant impact on permeability-stress sensitivity. Based on the testresults and theoretical analyses, we believe that there exists a cone ofpressure depression in the area near production within suchstress-sensitive tight reservoirs, leading to a low-permeability zone,and that well production will decrease under the influence of stresssensitivity.

  18. Inserting Stress Analysis of Combined Hexagonal Aluminum Honeycombs

    Directory of Open Access Journals (Sweden)

    Xiangcheng Li

    2016-01-01

    Full Text Available Two kinds of hexagonal aluminum honeycombs are tested to study their out-of-plane crushing behavior. In the tests, honeycomb samples, including single hexagonal aluminum honeycomb (SHAH samples and two stack-up combined hexagonal aluminum honeycombs (CHAH samples, are compressed at a fixed quasistatic loading rate. The results show that the inserting process of CHAH can erase the initial peak stress that occurred in SHAH. Meanwhile, energy-absorbing property of combined honeycomb samples is more beneficial than the one of single honeycomb sample with the same thickness if the two types of honeycomb samples are completely crushed. Then, the applicability of the existing theoretical model for single hexagonal honeycomb is discussed, and an area equivalent method is proposed to calculate the crushing stress for nearly regular hexagonal honeycombs. Furthermore, a semiempirical formula is proposed to calculate the inserting plateau stress of two stack-up CHAH, in which structural parameters and mechanics properties of base material are concerned. The results show that the predicted stresses of three kinds of two stack-up combined honeycombs are in good agreement with the experimental data. Based on this study, stress-displacement curve of aluminum honeycombs can be designed in detail, which is very beneficial to optimize the energy-absorbing structures in engineering fields.

  19. Fuel element failures caused by iodine stress corrosion

    International Nuclear Information System (INIS)

    Videm, K.; Lunde, L.

    1976-01-01

    Sections of unirradiated cladding tubes were plugged in both ends by mechanical seals and internally pressurized with argon containing iodine. The time to failure and the strain at failure as a function of stress was determined for tubing with different heat treatments. Fully annealed tubes suffer cracking at the lowest stress but exhibit the largest strains at failure. Elementary iodine is not necessary for stress corrosion: small amounts of iodides of zirconium, iron and aluminium can also give cracking. Moisture, however, was found to act as an inhibitor. A deformation threshold exists below which stress corrosion failure does not occur regardless of the exposure time. This deformation limit is lower the harder the tube. The deformation at failure is dependent on the deformation rate and has a minimum at 0.1%/hr. At higher deformation rates the failure deformation increases, but only slightly for hard tubes. Fuel was over-power tested at ramp rates varying between 0.26 to 30 W/cm min. For one series of fuel pins the failure deformations of 0.8% at high ramp rates were in good agreement with predictions based on stress corrosion experiments. For another series of experiments the failure deformation was surprisingly low, about 0.2%. (author)

  20. Improved Formula for the Stress Intensity Factor of Semi-Elliptical Surface Cracks in Welded Joints under Bending Stress

    Science.gov (United States)

    Peng, Yang; Wu, Chao; Zheng, Yifu; Dong, Jun

    2017-01-01

    Welded joints are prone to fatigue cracking with the existence of welding defects and bending stress. Fracture mechanics is a useful approach in which the fatigue life of the welded joint can be predicted. The key challenge of such predictions using fracture mechanics is how to accurately calculate the stress intensity factor (SIF). An empirical formula for calculating the SIF of welded joints under bending stress was developed by Baik, Yamada and Ishikawa based on the hybrid method. However, when calculating the SIF of a semi-elliptical crack, this study found that the accuracy of the Baik-Yamada formula was poor when comparing the benchmark results, experimental data and numerical results. The reasons for the reduced accuracy of the Baik-Yamada formula were identified and discussed in this paper. Furthermore, a new correction factor was developed and added to the Baik-Yamada formula by using theoretical analysis and numerical regression. Finally, the predictions using the modified Baik-Yamada formula were compared with the benchmark results, experimental data and numerical results. It was found that the accuracy of the modified Baik-Yamada formula was greatly improved. Therefore, it is proposed that this modified formula is used to conveniently and accurately calculate the SIF of semi-elliptical cracks in welded joints under bending stress. PMID:28772527

  1. Monitoring based maintenance utilizing actual stress sensory technology

    Science.gov (United States)

    Sumitro, Sunaryo; Kurokawa, Shoji; Shimano, Keiji; Wang, Ming L.

    2005-06-01

    In recent years, many infrastructures have been deteriorating. In order to maintain sustainability of those infrastructures which have significant influence on social lifelines, economical and rational maintenance management should be carried out to evaluate the life cycle cost (LCC). The development of structural health monitoring systems, such as deriving evaluation techniques for the field structural condition of existing structures and identification techniques for the significant engineering properties of new structures, can be considered as the first step in resolving the above problem. New innovative evaluation methods need to be devised to identify the deterioration of infrastructures, e.g. steel tendons, cables in cable-stayed bridges and strands embedded in pre- or post-tensioned concrete structures. One of the possible solutions that show 'AtoE' characteristics, i.e., (a)ccuracy, (b)enefit, (c)ompendiousness, (d)urability and (e)ase of operation, elasto-magnetic (EM) actual stress sensory technology utilizing the sensitivity of incremental magnetic permeability to stress change, has been developed. Numerous verification tests on various steel materials have been conducted. By comparing with load cell, strain gage and other sensory technology measurement results, the actual stresses of steel tendons in a pre-stressed concrete structure at the following stages have been thoroughly investigated: (i) pre-stress change due to set-loss (anchorage slippage) at the tendon fixation stage; (ii) pre-stress change due to the tendon relaxation stage; (iii) concrete creep and shrinkage at the long term pre-stressing stage; (iv) pre-stress change in the cyclic fatigue loading stage; and (v) pre-stress change due to the re-pre-stress setting stage. As the result of this testing, it is confirmed that EM sensory technology enables one to measure actual stress in steel wire, strands and steel bars precisely without destroying the polyethylene covering sheath and enables

  2. A Virtual Agent for Post-Traumatic Stress Disorder Treatment

    NARCIS (Netherlands)

    Tielman, M.L.

    2018-01-01

    Post-traumatic stress disorder (PTSD) is a mental disorder with a high impact on quality of life, and despite the existence of treatment, barriers still stop many people from receiving the care they need. An e-mental health system for home use might remove some of these barriers, as it provides a

  3. Measuring a critical stress for continuous prevention of marine biofouling accumulation with aeration.

    Science.gov (United States)

    Menesses, Mark; Belden, Jesse; Dickenson, Natasha; Bird, James

    2017-10-01

    When cleaning the hull of a ship, significant shear stresses are needed to remove established biofouling organisms. Given that there exists a link between the amount of time that fouling accumulates and the stress required to remove it, it is not surprising that more frequent grooming requires less shear stress. Yet, it is unclear if there is a minimum stress needed to prevent the growth of macrofouling in the limit of continuous grooming. This manuscript shows that single bubble stream aeration provides continuous grooming and prevents biofouling accumulation in regions where the average wall stress exceeds ~0.01 Pa. This value was found by comparing observations of biofouling growth from field studies with complementary laboratory measurements that probe the associated flow fields. These results suggest that aeration and other continuous grooming systems must exceed a wall stress of 0.01 Pa to prevent macrofouling accumulation.

  4. On residual stress prescriptions for fitness for service assessment of pipe girth welds

    International Nuclear Information System (INIS)

    Dong, Pingsha; Song, Shaopin; Zhang, Jinmiao; Kim, Myung H.

    2014-01-01

    This paper aims to provide a detailed assessment of some of the existing residual stress profiles stipulated in widely used fitness-for-service assessment codes and standards, such as BS 7910 Appendix Q and API 579 RP Annex E, by taking advantage of some comprehensive residual stress studies that have recently become available. After presenting a case study on which residual stress measurements are available for validating finite element based residual stress analysis procedure, residual stress profiles stipulated in BS 7910 for pipe girth welds are selected for detailed evaluation by comparing residual stress distribution characteristics shown in parametric finite element results. A shell theory based full-field residual stress profile estimation scheme is then presented to illustrate how an improved estimation of residual stress profiles can be achieved in light of some of the deficiencies in BS 7910 and API 579 identified in this study. - Highlights: • Critically assessed girth weld residual stress profiles in major FFS Codes and Standards. • Identified deficiencies in relating to pipe geometry, heat input, and axial distance from weld. • Presented a shell theory based scheme for prescribing full-field residual stress profiles

  5. Mean-Field Scenario for the Athermal Creep Dynamics of Yield-Stress Fluids

    Science.gov (United States)

    Liu, Chen; Martens, Kirsten; Barrat, Jean-Louis

    2018-01-01

    We develop a theoretical description based on an existent mean-field model for the transient dynamics prior to the steady flow of yielding materials. The mean-field model not only reproduces the experimentally observed nonlinear time dependence of the shear-rate response to an external stress, but also allows for the determination of the different physical processes involved in the onset of the reacceleration phase after the initial slowing down and a distinct fluidization phase. The fluidization time displays a power-law dependence on the distance of the applied stress to an age-dependent yield stress, which is not universal but strongly dependent on initial conditions.

  6. Sexual violence, post-traumatic stress disorder and dementia.

    Science.gov (United States)

    McCartney, J R; Severson, K

    1997-01-01

    Little is known of Post-Traumatic Stress Disorder (PTSD) in older people. No literature exists on this disorder in older women exposed to sexual assault. A case of apparent PTSD in a demented woman raises questions of the anatomy and phenomenology of this disorder. Difficulties in diagnosis in a demented population may cloud the issues or prevent a proper therapeutic outcome.

  7. Good stress, bad stress and oxidative stress: insights from anticipatory cortisol reactivity.

    Science.gov (United States)

    Aschbacher, Kirstin; O'Donovan, Aoife; Wolkowitz, Owen M; Dhabhar, Firdaus S; Su, Yali; Epel, Elissa

    2013-09-01

    Chronic psychological stress appears to accelerate biological aging, and oxidative damage is an important potential mediator of this process. However, the mechanisms by which psychological stress promotes oxidative damage are poorly understood. This study investigates the theory that cortisol increases in response to an acutely stressful event have the potential to either enhance or undermine psychobiological resilience to oxidative damage, depending on the body's prior exposure to chronic psychological stress. In order to achieve a range of chronic stress exposure, forty-eight post-menopausal women were recruited in a case-control design that matched women caring for spouses with dementia (a chronic stress model) with similarly aged control women whose spouses were healthy. Participants completed a questionnaire assessing perceived stress over the previous month and provided fasting blood. Three markers of oxidative damage were assessed: 8-iso-prostaglandin F(2α) (IsoP), lipid peroxidation, 8-hydroxyguanosine (8-oxoG) and 8-hydroxy-2'-deoxyguanosine (8-OHdG), reflecting oxidative damage to RNA/DNA respectively. Within approximately one week, participants completed a standardized acute laboratory stress task while salivary cortisol responses were measured. The increase from 0 to 30 min was defined as "peak" cortisol reactivity, while the increase from 0 to 15 min was defined as "anticipatory" cortisol reactivity, representing a cortisol response that began while preparing for the stress task. Women under chronic stress had higher 8-oxoG, oxidative damage to RNA (pstress and elevated oxidative stress damage, but only among women under chronic stress. Consistent with this model, bootstrapped path analysis found significant indirect paths from perceived stress to 8-oxoG and IsoP (but not 8-OHdG) via anticipatory cortisol reactivity, showing the expected relations among chronically stressed participants (p≤.01) Intriguingly, among those with low chronic stress

  8. Does student debt affect dental students' and dentists' stress levels?

    Science.gov (United States)

    Boyles, J D; Ahmed, B

    2017-10-27

    Introduction Many studies have shown financial worries and debt to induce stress in individuals, this combined with the existing stress of being a dentist raises the question of how student debt affects students' and dentists' stress levels.Objectives Determine whether student debt has had any noticeable effect on student stress levels; investigate whether student debt has any effect on dentists' career choice; investigate whether the increase in tuition fees has influenced the number of applicants to study dentistry at the University of Birmingham.Method Anonymous questionnaires were completed by 70 4th year and 38 5th year BDS and 22 Dental Core Trainees (DCTs). Participants circled the response which best fitted their situation regarding statements on their level of stress and future career path. Ethical approval granted. Application figures to study dentistry obtained from head of admissions.Results Forty-two percent of males and 63% of females strongly agreed with the statement that having no debt would reduce their stress levels. Of those with debt >£40,000, 11% strongly agreed and 42% agreed that their total amount of student debt causes them stress. Whereas, those whose debt is stress. Seventy-seven percent of participants who had parental or family financial support reported this reduced their stress levels. Student debt was found to deter females from undertaking further study more than it deters males (P stressed about their total student loan(s) (P stress (P stress; students reporting a higher level of debt also report more stress and concern about paying off their student debt. Having no student debt would reduce stress levels, although to what extent is undetermined. Applications to study dentistry have fallen since the increase in tuition fees.

  9. Secondary traumatic stress among emergency nurses: a cross-sectional study.

    Science.gov (United States)

    Duffy, Emer; Avalos, Gloria; Dowling, Maura

    2015-04-01

    Emergency department nurses are required to deal with emotional trauma issues on a daily basis, which may result in them experiencing symptoms of secondary traumatic stress, a consequence of stress experienced when helping or wanting to help a person traumatised or suffering. This study measured emergency department nurses' self-reported levels of secondary traumatic stress. Registered nurses (n = 117) working at three emergency departments in the Western geographical region of Ireland were invited to complete the secondary traumatic stress scale (STSS). A response rate of 90% (n = 105) was achieved. Most participants (n = 67/64%) met the criteria for secondary traumatic stress. A statistically significant finding was that the highest proportion (82%) of secondary traumatic stress existed in the staff nurse group (p = 0.042). Moreover, for those nurses reporting secondary traumatic stress, statistical significance was found for the variables 'change of career considered' (p = 0.017) and 'finds alcohol helpful in alleviating work-related stress' (p = 0.004), when compared with nurses not reporting secondary traumatic stress. The findings suggest the need to examine current crisis management interventions and to introduce new systems to support nurses in Irish emergency departments. Moreover, because different types of traumatic events in the ED require different types of interventions, the prevention and management of STS among emergency department nurses must be tackled using a variety of approaches. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Financial Stress, Financial Literacy, Counselling and the Risk of Homelessness

    Directory of Open Access Journals (Sweden)

    Adam Steen

    2013-09-01

    Full Text Available Poor financial literacy may lead to poor life choices. These life choices can create or contribute to financial stress with adverse consequences - not the least of which may be homelessness. These issues are relatively well understood, but there is limited research on the link between financial stress, financial literacy and counselling, and homelessness. Specifically, there has been little research on how improved financial literacy and appropriate financial counselling might help to prevent homelessness. This paper synthesises existing literature on this topic and considers these issues using the ABCX family stress model of Hill (1958 using data from an Australian program aimed at alleviating family homelessness, the Home Advice Program. We provide evidence that suggests that case management and support which incorporates financial counselling and financial literacy can assist in moderating the impact of financial stress and help those at risk of homelessness. The findings have implications for public policy in the areas of financial education, consumer finance, and social services provision.

  11. Impacts of pre-existing ocean cyclonic circulation on sea surface chlorophyll-a concentrations off northeastern Taiwan following episodic typhoon passages

    Science.gov (United States)

    Xu, Fanghua; Yao, Yuan; Oey, Leo; Lin, Yanluan

    2017-08-01

    Off northeastern Taiwan, enhancement of sea surface chlorophyll-a (Chl-a) concentration is frequently found after typhoon passages. From 1998 to 2013, 46 typhoon events are analyzed to examine the variations in Chl-a concentration from satellite ocean color data. On average, Chl-a concentration increased by 38% after a typhoon passage. Noticeably, four remarkable Chl-a increases after typhoons coincide with pre-existing oceanic cyclones in the study area. The Chl-a increase is significantly anticorrelated (p typhoons, we conduct a series of numerical experiments to simulate the oceanic response to Typhoon Kaemi (2006) with or without a pre-existing oceanic cyclone, and with or without strong typhoon winds. The results show that the experiment with a pre-existing oceanic cyclone produces the largest upwelling due to cyclone intensification, mainly induced by the positive wind stress curl dipole northeast of Taiwan.

  12. Stress and Alterations in Bones: An Interdisciplinary Perspective

    Directory of Open Access Journals (Sweden)

    Pia-Maria Wippert

    2017-05-01

    Full Text Available Decades of research have demonstrated that physical stress (PS stimulates bone remodeling and affects bone structure and function through complex mechanotransduction mechanisms. Recent research has laid ground to the hypothesis that mental stress (MS also influences bone biology, eventually leading to osteoporosis and increased bone fracture risk. These effects are likely exerted by modulation of hypothalamic–pituitary–adrenal axis activity, resulting in an altered release of growth hormones, glucocorticoids and cytokines, as demonstrated in human and animal studies. Furthermore, molecular cross talk between mental and PS is thought to exist, with either synergistic or preventative effects on bone disease progression depending on the characteristics of the applied stressor. This mini review will explain the emerging concept of MS as an important player in bone adaptation and its potential cross talk with PS by summarizing the current state of knowledge, highlighting newly evolving notions (such as intergenerational transmission of stress and its epigenetic modifications affecting bone and proposing new research directions.

  13. Thermal stresses investigation of a gas turbine blade

    Science.gov (United States)

    Gowreesh, S.; Pravin, V. K.; Rajagopal, K.; Veena, P. H.

    2012-06-01

    The analysis of structural and thermal stress values that are produced while the turbine is operating are the key factors of study while designing the next generation gas turbines. The present study examines structural, thermal, modal analysis of the first stage rotor blade of a two stage gas turbine. The design features of the turbine segment of the gas turbine have been taken from the preliminary design of a power turbine for maximization of an existing turbojet engine with optimized dump gap of the combustion chamber, since the allowable temperature on the turbine blade dependents on the hot gas temperatures from the combustion chamber. In the present paper simplified 3-D Finite Element models are developed with governing boundary conditions and solved using the commercial FEA software ANSYS. As the temperature has a significant effect on the overall stress on the rotor blades, a detail study on mechanical and thermal stresses are estimated and evaluated with the experimental values.

  14. Stress urinary incontinence in the female

    International Nuclear Information System (INIS)

    Baldelli, S.; Giovagnoni, A.; Bichi Secchi, E.; Argaglia, G.; Caraceni, E.; Muzzonigro, G.

    1988-01-01

    This work is aimed at demonstrating the validity of conventional radiological procedures, correlated with urodynamics, in the study of female urinary stress incontinence. In a study population of 110 patients with a clinical-urodynamic diagnosis of stress incontinence, radiological evaluation was performed by means of retrograde cystography, bead chain cystourethrography, and voiding cystourethrography. Radiographic findings were correlated with urodynamic data, and in particular with urethral pressure profile (fuctional lenght of the urethra, maximum closing pressure, maximum urethral pressure). In all patients the posterior urethro-vesical angle values were higher than 100 grade centigrades; moreover, a correlation was proven to exist between an increase in the angle of front urethral inclination, the lowering and mobility of the urethro-vesical junction, and the severeness of urodynamic findings. Furtheremore, in the different stages of urodynamic severeness, urethral funnelling was most frequent, and the flattening of the posterior vesical floor in voiding cystourethrography. The high reliability of the radiographic findings, although obtained by means of conventional techniques, and the variability of the morphodynamic results confirm the importance of a combined radiographic and urodynamic study in the evaluation of stress incontinence

  15. Residual stresses and critical diameter in vitreous matrix materials

    International Nuclear Information System (INIS)

    Mastelaro, Valmor R.; Zanotto, Edgar D.

    1995-01-01

    The present study was undertaken to test the validity of existing models for: i) the residual internal stresses which arise due to thermal and elastic mismatch in duplex systems, and ii) the critical particle diameter for spontaneous cracking. Partially crystallized 1,07 Na 2 O-2 Ca O-3 Si O 2 - 6% P 2 O 5 glasses were studied. The experimental residual stress was in excellent agreement with the calculated value, however, the critical particle diameter, estimated by an energy balance approach, was more than ten times smaller than the experimental value. This discrepancy indicates that the energy model is not applicable in this case. (author)

  16. Computational fluid dynamic evaluation of the side-to-side anastomosis for arteriovenous fistula.

    Science.gov (United States)

    Hull, Jeffrey E; Balakin, Boris V; Kellerman, Brad M; Wrolstad, David K

    2013-07-01

    The goal of this research was to compare side-to-side (STS) and end-to-side (ETS) anastomoses in a computer model of the arteriovenous fistula with computational fluid dynamic analysis. A matrix of 17 computer arteriovenous fistula models (SolidWorks, Dassault Systèmes, France) of artery-vein pairs (3-mm-diameter artery + 3-mm-diameter vein and 4-mm-diameter artery +6-mm-diameter vein elliptical anastomoses) in STS, 45° ETS, and 90° ETS configurations with cross-sectional areas (CSAs) of 3.5 to 18.8 mm(2) were evaluated with computational fluid dynamic software (STAR-CCM+; CD-adapco, Melville, NY) in simulations at defined flow rates from 600 to 1200 mL/min and mean arterial pressures of 50 to 140 mm Hg. Models and configurations were evaluated for pressure drop across the anastomosis, arterial inflow, venous outflow, arterial outflow, velocity vector, and wall shear stress (WSS) profile. Pressure drop across the anastomosis was inversely proportional to anastomotic CSA and to venous outflow and was proportional to arterial inflow. Pressure drop was greater in 3 + 3 models than in 4 + 6 STS models; 90° ETS configurations had the lowest pressure drops and were nearly identical, whereas 45° ETS configurations had the highest pressure drops. Venous outflow in the 4 + 6 model in STS configurations, evaluated at 100 mm Hg arterial inflow pressure, was 390, 592, 610, and 886 mL/min in anastomotic CSAs of 3.5, 5.3, 7.1, and 18.8 mm(2), respectively, and was similar in 90° ETS (609 and 908 mL/min) and lower in 45° ETS (534 and 562 mL/min) configurations at CSAs of 5.3 and 18.8 mm(2). The mean increase in venous outflow was 69 mL/min (range, -59 to 134) between 3 + 3 and 4 + 6 models at 100 mm Hg arterial inflow. The most uniform WSS profile occurs in STS anastomoses followed by 45° ETS and then 90° ETS anastomoses. The STS and 90° ETS anastomoses have high venous outflow and a tendency toward reversed arterial outflow. The 45° ETS anastomosis has reduced venous

  17. Surface stress mediated image force and torque on an edge dislocation

    Science.gov (United States)

    Raghavendra, R. M.; Divya, Iyer, Ganesh; Kumar, Arun; Subramaniam, Anandh

    2018-07-01

    The proximity of interfaces gives prominence to image forces experienced by dislocations. The presence of surface stress alters the traction-free boundary conditions existing on free-surfaces and hence is expected to alter the magnitude of the image force. In the current work, using a combined simulation of surface stress and an edge dislocation in a semi-infinite body, we evaluate the configurational effects on the system. We demonstrate that if the extra half-plane of the edge dislocation is parallel to the surface, the image force (glide) is not altered due to surface stress; however, the dislocation experiences a torque. The surface stress breaks the 'climb image force' symmetry, thus leading to non-equivalence between positive and negative climb. We discover an equilibrium position for the edge dislocation in the positive 'climb geometry', arising due to a competition between the interaction of the dislocation stress fields with the surface stress and the image dislocation. Torque in the climb configuration is not affected by surface stress (remains zero). Surface stress is computed using a recently developed two-scale model based on Shuttleworth's idea and image forces using a finite element model developed earlier. The effect of surface stress on the image force and torque experienced by the dislocation monopole is analysed using illustrative 3D models.

  18. The effects of strain induced martensite on stress corrosion cracking in AISI 304 stainless steel

    International Nuclear Information System (INIS)

    Lee, W. S.; Kwon, S. I.

    1989-01-01

    The effects of strain induced martensite on stress corrosion cracking behavior in AISI 304 stainless steel in boiling 42 wt% MgCl 2 solution were investigated using monotonic SSRT and cyclic SSRT with R=0.1 stress ratio. As the amount of pre-strain increased, the failure time of the specimens in monotonic SSRT test decreased independent of the existence of strain induced martensite. The strain induced martensite seems to promote the crack initiation but to retard the crack propagation during stress corrosion cracking

  19. Three-dimensional analysis of stresses and the development of failure mechanism in prestressed thick-walled cylinders

    International Nuclear Information System (INIS)

    Bertrand, G.; Kotulla, B.

    1984-01-01

    The new design concept for a prestressed concrete reactor vessel which integrates the complete gas cycle into the pressure vessel demands knowledge of crack zone propagation even in zones where predominantly pressure stresses exist. Analytically, the state of stresses and strains, which is dependent on the loading history, can be computed by recording the triaxial stress-strain law for concrete up to the range of critical volumetric and shear deformations. The constitutive law is derived tensorially using invariant description in the stress space. It is demonstrated that near failure loads membrane stress states develop which increase failure resistance. Collapse loads can be defined through the observation of the principal stress vector with the aid of the triaxial failure law of concrete. (author)

  20. Stress and Cognition: A Cognitive Psychological Perspective

    Science.gov (United States)

    Bourne, Lyle E., Jr.; Yaroush, Rita A.

    2003-01-01

    Research in cognitive psychology has made a significant contribution to our understanding of how acute and chronic stress affect performance. It has done so by identifying some of the factors that contribute to operator error and by suggesting how operators might be trained to respond more effectively in a variety of circumstances. The major purpose of this paper was to review the literature of cognitive psychology as it relates to these questions and issues. Based on the existence of earlier reviews (e.g., Hamilton, & Warburton, 1979; Hockey, 1983) the following investigation was limited to the last 15 years (1988-2002) and restricted to a review of the primary peer-reviewed literature. The results of this examination revealed that while cognitive psychology has contributed in a substantive way to our understanding of stress impact on various cognitive processes, it has also left many questions unanswered. Concerns about how we define and use the term stress and the gaps that remain in our knowledge about the specific effects of stressors on cognitive processes are discussed in the text.

  1. Organizational Stress for Retail Store Employees in Romania

    Directory of Open Access Journals (Sweden)

    Alina - Cerasela Aluculesei

    2015-03-01

    Full Text Available The term organizational stress appeared with people’s lifestyle and job evolution and it is used to show the direct link between the work environment and the employee’s wellbeing or health. This concept exists in all countries, and measures taken to decrease its effects are becoming increasingly more obvious. Such measures are being implemented in Romania also and, given the country’s high spa tourism potential, treatment programs in spa resorts would be the most obvious measures to decrease organizational stress and recover employee productivity. This study aims to address the main concepts related to organizational stress and to present the main benefits related to treatment of organizational stress in Romanian spa resorts. This research was carried out on 101 retail store employees of a supermarket chain. This job, due the requirements, is associated with high levels of stress. The data were processed using the Epi Info statistical software. From the analysis we conducted resulted that the employees we questioned have a low degree of personal satisfaction – in 57% of cases, declaring that their lifestyle since employment as retail store employees is less healthy, with fewer outdoor recreational activities - 65%. In regards to the presence of organizational stress, there are various associated symptoms, with correlation between headaches and increased heart rate (p value=0,003, insomnia (p value = 0,006 or back pain (p value=0,042.

  2. Short-term pre- and post-operative stress prolongs incision-induced pain hypersensitivity without changing basal pain perception

    OpenAIRE

    Cao, Jing; Wang, Po-Kai; Tiwari, Vinod; Liang, Lingli; Lutz, Brianna Marie; Shieh, Kun-Ruey; Zang, Wei-Dong; Kaufman, Andrew G.; Bekker, Alex; Gao, Xiao-Qun; Tao, Yuan-Xiang

    2015-01-01

    Background Chronic stress has been reported to increase basal pain sensitivity and/or exacerbate existing persistent pain. However, most surgical patients have normal physiological and psychological health status such as normal pain perception before surgery although they do experience short-term stress during pre- and post-operative periods. Whether or not this short-term stress affects persistent postsurgical pain is unclear. Results In this study, we showed that pre- or post-surgical expos...

  3. Pre-existing weakness is critical for the occurrence of postoperative cognitive dysfunction in mice of the same age.

    Directory of Open Access Journals (Sweden)

    Yujie Tang

    Full Text Available Occurrence of postoperative cognitive dysfunction (POCD is age-dependent and heterogenous. Factors deciding the occurrence of POCD in patients of the same age undergone same surgeries remain unclear. Here we investigated the effects of pre-existing weakness on the occurrence of POCD in mice of the same age. Pre-existing weakness of mice was induced by intraperitoneal injection of lipopolysaccharide (8mg/kg and was evaluated by physical frailty index (by open field test, neuroinflammation level (by Iba1 immunostaining and inflammatory factors TNF-α and IL-1β, and neuronal activity (by p-CREB immunostaining. POCD was induced by partial hepatolobectomy and was evaluated by puzzle box test and Morris water maze test. The brains were collected to detect the levels of neuroinflammation, synaptophysin and NMDA receptor subunits NR2A, NR2B and NR1 (by western blot, and oxidative stress (by Dihydroethidium. Compared to the normal adult mice of the same age, LPS pretreated mice had increased physical frailty index, higher levels of neuroinflammation, and lower neuronal activity. Partial hepatolobectomy induced obvious impairments in executive function, learning and memory in LPS pretreated mice after surgery, but not in normal mice of the same age. Partial hepatolobectomy also induced heightened neuroinflammation, obvious loss of NMDA receptor subunits, strong oxidative stress in LPS pretreated mice on the 1st and 3rd postoperative day. However, the POCD-associated pathological changes didn't occur in normal mice of the same age after surgery. These results suggest that pre-existing weakness is critical for the occurrence of POCD in mice of the same age.

  4. Reassessment of the role of stress in development of radiation-induced microstructure

    International Nuclear Information System (INIS)

    Garner, F.A.; Wolfer, W.G.; Brager, H.R.

    1978-10-01

    Data are now accumulating which clearly demonstrate that the stress state plays a strong role in the development of void and dislocation microstructure in metals during neutron irradiation. In these experiments the application of a tensile biaxial stress state at constant fluence and temperature has been found to lead to a progressively decreasing metal density with increasing stress. The effect of stress on the concurrent development of voids, Frank interstitial loops and dislocation networks has been studied with transmission electron microscopy. The results of these experiments clearly show that the densities of both Frank loops and voids are enhanced by a tensile stress field, with the relevant operating variable being the hydrostatic stress. More importantly it appears that any anisotropy in the stress field is reflected in a corresponding anisotropy that develops in the number of Frank loops that form on the various (111) planes. The loop density that develops on each plane exhibits a clear and direct dependence on the resolved normal stress component at each plane. Although the data from these experiments have been previously interpreted to support the existence of stress-assisted nucleation mechanisms for both loops and voids, further analysis has shown both of these explanations to be deficient in one or more respects, and both models have been replaced

  5. Direct method of design and stress analysis of rotating disks with temperature gradient

    Science.gov (United States)

    Manson, S S

    1950-01-01

    A method is presented for the determination of the contour of disks, typified by those of aircraft gas turbines, to incorporate arbitrary elastic-stress distributions resulting from either centrifugal or combined centrifugal and thermal effects. The specified stress may be radial, tangential, or any combination of the two. Use is made of the finite-difference approach in solving the stress equations, the amount of computation necessary in the evolution of a design being greatly reduced by the judicious selection of point stations by the aid of a design chart. Use of the charts and of a preselected schedule of point stations is also applied to the direct problem of finding the elastic and plastic stress distribution in disks of a given design, thereby effecting a great reduction in the amount of calculation. Illustrative examples are presented to show computational procedures in the determination of a new design and in analyzing an existing design for elastic stress and for stresses resulting from plastic flow.

  6. Thermal stresses and cyclic creep-fatigue in fusion reactor blanket

    International Nuclear Information System (INIS)

    Liu, K.C.

    1977-01-01

    Thermal stresses in the first walls of fusion reactor blankets were studied in detail. ORNL multibucket modules are emphasized. Practicality of using the bucket module rather than other blanket designs is examined. The analysis shows that applying intelligent engineering judgment in design can reduce the thermal stresses significantly. Arrangement of coolant flow and distribution of temperature are reviewed. Creep-fatigue property requirements for a first wall are discussed on the basis of existing design rules and criteria. Some major questions are pointed out and experiments needed to resolve basic uncertainties relative to key design decisions are discussed

  7. Stress free configuration of the human eye.

    Science.gov (United States)

    Elsheikh, Ahmed; Whitford, Charles; Hamarashid, Rosti; Kassem, Wael; Joda, Akram; Büchler, Philippe

    2013-02-01

    Numerical simulations of eye globes often rely on topographies that have been measured in vivo using devices such as the Pentacam or OCT. The topographies, which represent the form of the already stressed eye under the existing intraocular pressure, introduce approximations in the analysis. The accuracy of the simulations could be improved if either the stress state of the eye under the effect of intraocular pressure is determined, or the stress-free form of the eye estimated prior to conducting the analysis. This study reviews earlier attempts to address this problem and assesses the performance of an iterative technique proposed by Pandolfi and Holzapfel [1], which is both simple to implement and promises high accuracy in estimating the eye's stress-free form. A parametric study has been conducted and demonstrated reliance of the error level on the level of flexibility of the eye model, especially in the cornea region. However, in all cases considered 3-4 analysis iterations were sufficient to produce a stress-free form with average errors in node location <10(-6)mm and a maximal error <10(-4)mm. This error level, which is similar to what has been achieved with other methods and orders of magnitude lower than the accuracy of current clinical topography systems, justifies the use of the technique as a pre-processing step in ocular numerical simulations. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

  8. Memory in Posttraumatic Stress Disorder: Properties of Voluntary and Involuntary, Traumatic and Nontraumatic Autobiographical Memories in People with and without Posttraumatic Stress Disorder Symptoms

    Science.gov (United States)

    Rubin, David C.; Boals, Adriel; Berntsen, Dorthe

    2008-01-01

    One hundred fifteen undergraduates rated 15 word-cued memories and their 3 most negatively stressful, 3 most positive, and 7 most important events and completed tests of personality and depression. Eighty-nine also recorded involuntary memories online for 1 week. In the first 3-way comparisons needed to test existing theories, comparisons were…

  9. LUGS, Stress Analysis, Flexibility Factors for Rectangular Attachment on Thin Shell

    International Nuclear Information System (INIS)

    Dodge, W.G.

    1977-01-01

    1 - Description of problem or function: LUGS calculates stresses, stress indices, and flexibility factors for a rectangular attachment on a cylindrical shell. 2 - Method of solution: The program implements Bijlaard's series solution to the thin-shell equations. 3 - Restrictions on the complexity of the problem: Caution is recommended in using the code for attachments on very thin shells that have large circumferential dimension and small longitudinal dimension (GAMMA.GE.80, BETA2.LE.0.05, and BETA1.GE.0.3) as series convergence and/or numeric problems seem to exist

  10. The calm mouse: an animal model of stress reduction.

    Science.gov (United States)

    Gurfein, Blake T; Stamm, Andrew W; Bacchetti, Peter; Dallman, Mary F; Nadkarni, Nachiket A; Milush, Jeffrey M; Touma, Chadi; Palme, Rupert; Di Borgo, Charles Pozzo; Fromentin, Gilles; Lown-Hecht, Rachel; Konsman, Jan Pieter; Acree, Michael; Premenko-Lanier, Mary; Darcel, Nicolas; Hecht, Frederick M; Nixon, Douglas F

    2012-05-09

    Chronic stress is associated with negative health outcomes and is linked with neuroendocrine changes, deleterious effects on innate and adaptive immunity, and central nervous system neuropathology. Although stress management is commonly advocated clinically, there is insufficient mechanistic understanding of how decreasing stress affects disease pathogenesis. Therefore, we have developed a "calm mouse model" with caging enhancements designed to reduce murine stress. Male BALB/c mice were divided into four groups: control (Cntl), standard caging; calm (Calm), large caging to reduce animal density, a cardboard nest box for shelter, paper nesting material to promote innate nesting behavior, and a polycarbonate tube to mimic tunneling; control exercise (Cntl Ex), standard caging with a running wheel, known to reduce stress; and calm exercise (Calm Ex), calm caging with a running wheel. Calm, Cntl Ex and Calm Ex animals exhibited significantly less corticosterone production than Cntl animals. We also observed changes in spleen mass, and in vitro splenocyte studies demonstrated that Calm Ex animals had innate and adaptive immune responses that were more sensitive to acute handling stress than those in Cntl. Calm animals gained greater body mass than Cntl, although they had similar food intake, and we also observed changes in body composition, using magnetic resonance imaging. Together, our results suggest that the Calm mouse model represents a promising approach to studying the biological effects of stress reduction in the context of health and in conjunction with existing disease models.

  11. Ethnic Differences in Adolescents' Mental Distress, Social Stress, and Resources

    Science.gov (United States)

    Choi, Heeseung; Meininger, Janet C.; Roberts, Robert E.

    2006-01-01

    Limited data on ethnic group differences among young adolescents exist regarding the prevalence of mental distress, social stress, and resources. The aim of this cross-sectional study was to examine ethnic differences among African American (AA), European American (EA), Hispanic American (HA), and Asian American adolescents in mental distress,…

  12. Stabilization of the Friedmann big bang by the shear stresses

    Science.gov (United States)

    Belinski, V. A.

    2013-11-01

    The window is found in the space of the free parameters of the theory of viscoelastic matter for which the Friedmann singularity is stable. By stability we mean that in the presence of the shear stresses, a generic solution of the equations of relativistic gravity possessing an isotropic singularity exists.

  13. Type I and type II residual stress in iron meteorites determined by neutron diffraction measurements

    Science.gov (United States)

    Caporali, Stefano; Pratesi, Giovanni; Kabra, Saurabh; Grazzi, Francesco

    2018-04-01

    In this work we present a preliminary investigation by means of neutron diffraction experiment to determine the residual stress state in three different iron meteorites (Chinga, Sikhote Alin and Nantan). Because of the very peculiar microstructural characteristic of this class of samples, all the systematic effects related to the measuring procedure - such as crystallite size and composition - were taken into account and a clear differentiation in the statistical distribution of residual stress in coarse and fine grained meteorites were highlighted. Moreover, the residual stress state was statistically analysed in three orthogonal directions finding evidence of the existence of both type I and type II residual stress components. Finally, the application of von Mises approach allowed to determine the distribution of type II stress.

  14. An Empirical Analysis of the Interrelationship between Motivation and Stress in the Computing Industry

    OpenAIRE

    Ó Cuirrín, Maitiú

    2007-01-01

    Although a great body of literature exists on the concepts of motivation and stress, no such study has examined the interrelationship between them. The objectives of this thesis are thus, to investigate the factors that motivate/demotivate and cause stress among recently employed computing graduates, as well as examining the implications of these factors both individually and interdependently for both the computing graduate and their employing organisation. An empirical quantitative appro...

  15. Teacher Candidates in Context: Investigating Inquiry Learning, Self-Efficacy and Stress within Teacher Education

    OpenAIRE

    Coppersmith, Sarah A.

    2017-01-01

    Global changes since the 2008 economic collapse continue to impact teacher candidates worldwide who are facing unparalleled challenges as they prepare for service in educational systems experiencing reform. Research exists on college student stress, yet absent is data showing teacher candidates in relation to stress and self-efficacy as they engage in socio-constructivist inquiry learning. Teacher candidates hold employment while taking classes and serving in schools, yet research shows that ...

  16. Hemodynamic analysis of sequential graft from right coronary system to left coronary system.

    Science.gov (United States)

    Wang, Wenxin; Mao, Boyan; Wang, Haoran; Geng, Xueying; Zhao, Xi; Zhang, Huixia; Xie, Jinsheng; Zhao, Zhou; Lian, Bo; Liu, Youjun

    2016-12-28

    Sequential and single grafting are two surgical procedures of coronary artery bypass grafting. However, it remains unclear if the sequential graft can be used between the right and left coronary artery system. The purpose of this paper is to clarify the possibility of right coronary artery system anastomosis to left coronary system. A patient-specific 3D model was first reconstructed based on coronary computed tomography angiography (CCTA) images. Two different grafts, the normal multi-graft (Model 1) and the novel multi-graft (Model 2), were then implemented on this patient-specific model using virtual surgery techniques. In Model 1, the single graft was anastomosed to right coronary artery (RCA) and the sequential graft was adopted to anastomose left anterior descending (LAD) and left circumflex artery (LCX). While in Model 2, the single graft was anastomosed to LAD and the sequential graft was adopted to anastomose RCA and LCX. A zero-dimensional/three-dimensional (0D/3D) coupling method was used to realize the multi-scale simulation of both the pre-operative and two post-operative models. Flow rates in the coronary artery and grafts were obtained. The hemodynamic parameters were also showed, including wall shear stress (WSS) and oscillatory shear index (OSI). The area of low WSS and OSI in Model 1 was much less than that in Model 2. Model 1 shows optimistic hemodynamic modifications which may enhance the long-term patency of grafts. The anterior segments of sequential graft have better long-term patency than the posterior segments. With rational spatial position of the heart vessels, the last anastomosis of sequential graft should be connected to the main branch.

  17. Thoracic aorta 3D hemodynamics in pediatric and young adult patients with bicuspid aortic valve.

    Science.gov (United States)

    Allen, Bradley D; van Ooij, Pim; Barker, Alex J; Carr, Maria; Gabbour, Maya; Schnell, Susanne; Jarvis, Kelly B; Carr, James C; Markl, Michael; Rigsby, Cynthia; Robinson, Joshua D

    2015-10-01

    To evaluate the 3D hemodynamics in the thoracic aorta of pediatric and young adult bicuspid aortic valve (BAV) patients. 4D flow MRI was performed in 30 pediatric and young adult BAV patients (age: 13.9 ± 4.4 (range: [3.4, 20.7]) years old, M:F = 17:13) as part of this Institutional Review Board-approved study. Nomogram-based aortic root Z-scores were calculated to assess aortic dilatation and degree of aortic stenosis (AS) severity was assessed on MRI. Data analysis included calculation of time-averaged systolic 3D wall shear stress (WSSsys ) along the entire aorta wall, and regional quantification of maximum and mean WSSsys and peak systolic velocity (velsys ) in the ascending aorta (AAo), arch, and descending aorta (DAo). The 4D flow MRI AAo velsys was also compared with echocardiography peak velocity measurements. There was a positive correlation with both mean and max AAo WSSsys and peak AAo velsys (mean: r = 0.84, P max: r = 0.94, P max: rS  = 0.70, P < 0.001). AAo peak velocity was significantly higher when measured with echo compared with 4D flow MRI (2.1 ± 0.98 m/s versus 1.27 ± 0.49 m/s, P < 0.001). In pediatric and young adult patients with BAV, AS and peak ascending aorta velocity are associated with increased AAo WSS, while aortic dilation, age, and body surface area do not significantly impact AAo hemodynamics. Prospective studies are required to establish the role of WSS as a risk-stratification tool in these patients. © 2015 Wiley Periodicals, Inc.

  18. Thermoelastic stress analysis system developed for industrial applications

    DEFF Research Database (Denmark)

    Haldorsen, Lars Magne

    The thesis is divided into three parts. The first part describes an extensive evaluation of the existing thermoelastic theory. The second part describes the development and results af a reliable numerical simulation code of the thermoelastic effect and the associated heat transfer effects. Finall......, theories, methods and additional equipment are developed in order to adopt a commercial IR-imaging system to preform Termoelastic Stress Analysis (TSA)....

  19. Reality and Fiction in the Perspective of Linguistic Existence

    Directory of Open Access Journals (Sweden)

    Tomas Kačerauskas

    2011-04-01

    Full Text Available The paper deals with relation between reality and fiction. The project of phenomenology of creation is presented in this context. According to the author, reality is an environment of our becoming. We fill this environment with our objects, desires, and expectations. Reality and fiction make two poles of creative tension. Human creation, i.e. culture is developed between these two poles. The author links culture with existential creation, i.e. with creation of life story. It is stressed that life story is analogous not to a diary but to a novel where every event takes part in the existential whole. An existential novel is born in a particular spiritual environment which is renewed by its inscription into this environment. The author refers to existential events as phenomena which being inscribed into our living whole direct the stream of events. The author uses the metaphors of the theatre as a public space and the river as a reative stream. It is stated that our existence is developed as polyphonic interrelation between a part and the whole. Different modi of existential creation like realization, working, embodiment, spiritualization and their links are analysed. Working is connected with a private domestic environment the created works in which should be prooved in a public space of the city. It is discussed on an opinion that the national language is the main modus of nationality. It is stated that a multinational environment of a capitol is the best school of national existence. It is showed that a theoretical model of phenomenology of creation is useful in the interpretation of historical and cultural phenomena. 

  20. On residual stresses and fatigue of laser hardened steels

    International Nuclear Information System (INIS)

    Lin, Ru.

    1992-01-01

    This thesis deals with studies on residual stresses and fatigue properties of laser-transformation hardened steels. Two types of specimens, cylinders and fatigue specimens were used in the studies. The cylinders, made of Swedish steels SS 2244 and SS 2258 which correspond to AISI 4140 and AISI 52100 respectively, were locally hardened by a single scan of laser beam in the longitudinal direction, with various laser parameters. Residual stress distributions across the hardened tracks were measured by means of X-ray diffraction. The origins of residual stresses were investigated and discussed. For the fatigue specimens, including smooth and notched types made of Swedish steels SS 2244, SS 2225 and SS 1572 (similar to AISI 4140, AISI 4130 and AISI 1035, respectively), laser hardening was carried out in the gauge section. The residual stress field induced by the hardening process and the fatigue properties by plane bending fatigue test were studied. In order to investigate the stability of the residual stress field, stress measurements were also made on specimens being loaded near the fatigue limits for over 10 7 cycles. Further the concept of local fatigue strength was employed to correlate quantitatively the effect of hardness and residual stress field on the fatigue limits. In addition a group of smooth specimens of SS 2244 was induction hardened and the hardening results were compared with the corresponding laser hardened ones in terms of residual stress and fatigue behaviour. It has been found that compressive stresses exist in the hardened zone of all the specimens studied. The laser hardening condition, the specimen and how the hardening is carried out can significantly affect the residual stress field. Laser hardening can greatly improve the fatigue properties by inducing a hardened and compressed surface layer. (112 refs.)(au)

  1. On residual stresses and fatigue of laser hardened steels

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Ru.

    1992-01-01

    This thesis deals with studies on residual stresses and fatigue properties of laser-transformation hardened steels. Two types of specimens, cylinders and fatigue specimens were used in the studies. The cylinders, made of Swedish steels SS 2244 and SS 2258 which correspond to AISI 4140 and AISI 52100 respectively, were locally hardened by a single scan of laser beam in the longitudinal direction, with various laser parameters. Residual stress distributions across the hardened tracks were measured by means of X-ray diffraction. The origins of residual stresses were investigated and discussed. For the fatigue specimens, including smooth and notched types made of Swedish steels SS 2244, SS 2225 and SS 1572 (similar to AISI 4140, AISI 4130 and AISI 1035, respectively), laser hardening was carried out in the gauge section. The residual stress field induced by the hardening process and the fatigue properties by plane bending fatigue test were studied. In order to investigate the stability of the residual stress field, stress measurements were also made on specimens being loaded near the fatigue limits for over 10[sup 7] cycles. Further the concept of local fatigue strength was employed to correlate quantitatively the effect of hardness and residual stress field on the fatigue limits. In addition a group of smooth specimens of SS 2244 was induction hardened and the hardening results were compared with the corresponding laser hardened ones in terms of residual stress and fatigue behaviour. It has been found that compressive stresses exist in the hardened zone of all the specimens studied. The laser hardening condition, the specimen and how the hardening is carried out can significantly affect the residual stress field. Laser hardening can greatly improve the fatigue properties by inducing a hardened and compressed surface layer. (112 refs.)(au).

  2. Managing common marital stresses.

    Science.gov (United States)

    Martin, A C; Starling, B P

    1989-10-01

    Marital conflict and divorce are problems of great magnitude in our society, and nurse practitioners are frequently asked by patients to address marital problems in clinical practice. "Family life cycle theory" provides a framework for understanding the common stresses of marital life and for developing nursing strategies to improve marital satisfaction. If unaddressed, marital difficulties have serious adverse consequences for a couple's health, leading to greater dysfunction and a decline in overall wellness. This article focuses on identifying couples in crisis, assisting them to achieve pre-crisis equilibrium or an even higher level of functioning, and providing appropriate referral if complex relationship problems exist.

  3. Code-B-1 for stress/strain calculation for TRISO fuel particle (Contract research)

    International Nuclear Information System (INIS)

    Aihara, Jun; Ueta, Shohei; Shibata, Taiju; Sawa, Kazuhiro

    2011-12-01

    We have developed Code-B-1 for the prediction of the failure probabilities of the coated fuel particles for the high temperature gas-cooled reactors (HTGRs) under operation by modification of an existing code. A finite element method (FEM) is employed for the stress calculation part and Code-B-1 can treat the plastic deformation of the coating layer of the coated fuel particles which the existing code cannot treat. (author)

  4. Public Health Burden of Chronic Stress in a Transforming Society

    Directory of Open Access Journals (Sweden)

    Mária S. Kopp

    2007-12-01

    Full Text Available In this paper chronic stress is proposed as an integrating model that can be applied to the explanation of the suddenly changing patterns of premature mortality rates in transforming societies of Central-Eastern-Europe, especially in Hungary. The temporal factor in existing stress models is often neglected. Chronic stress has been shown to lead to typical pathogenetic results in animal experiments. Literature and the different models in the field of psychology, behavioural sciences, and epidemiology are reviewed in terms of the chronic stress theory. There are several conceptual bridges between psychological alterations and the risks, onset and prognosis of chronic disorders of great epidemiological significance. Depending on the field of research there are several parallel concepts which analyse practically the same phenomena. These are the stress theories in physiology, learned helplessness and control theory in psychology, depression research in psychiatry, the concept of vital exhaustion and the psychosocial risk research in sociology. Because chronic stress results in adverse health effects through biological, social and behavioural pathways, this theory might also havethe best explanatory power to understand the premature male morbidity and mortality crisis in Central and Eastern Europe in the last decades. The special features of premature mortality and morbidity crisis in Hungary might be regarded as an experimental model to understand better the human consequences of chronic stress and those processes where psychology meets physiology.

  5. International symposium on seismic evaluation of existing nuclear facilities

    Energy Technology Data Exchange (ETDEWEB)

    Orbovic, N.; Bouchon, M. [Institut de Radioprotection et de Surete Nucleaire, IRSN, 92 - Fontenay aux Roses (France); Vendel, J.; Gelain, T. [IRSN/DPEA/SERAC, 91 - Gif sur Yvette (France)

    2003-10-01

    Below are summarized the works of Mrs N. Orbovic and M. Bouchon; B. Stojadinovic, N. Orbovic, M.Bouchon and J.T. Wiley; M. Bouchon, N. Orbovic and B. Foure; T. Gelain, F. Gensdarmes, R. Sestier-Carlin, J. Vendel and M. Bouchon dealing respectively with: 1) seismic assessment of existing nuclear facility: a case study position of the IRSN 2) static and dynamic evaluation of an existing nuclear facility reinforced concrete frame structure 3) experimental study of cracking of low-rise reinforced concrete shear walls 4) aeraulics study of crack networks on low-rise reinforced concrete walls subject to static cycling loading. The summaries are followed: 1) The Institute for Radioprotection and Nuclear Safety (IRSN) has the task of evaluating the seismic safety of existing building inventory in French nuclear facilities. Some of the existing structures are reinforced concrete frame buildings with masonry or reinforced concrete in-fill walls built during the 1960's, 70's and 80's following different building codes and seismic input data applicable at the time of construction. The studied building is a laboratory that was built in 1962. The building is composed of three different and independent blocks. The structure is a reinforced concrete frame with masonry in-fills and few stiff concrete elements. Moreover, the building contains an independent massive concrete cell. Structurally, the building has a number of irregularities. From the detailing standpoint, well known deficiencies of low-ductile reinforced concrete structures are evident especially, a lack of transverse reinforcement in the structural joints of the frame. A number of sensitivity studies were conducted using 2D and 3D linear models to evaluate seismic demand. Ambient vibration and regional earthquake records were used to check the soil nature and the existence or not of a possible site effect around the installation as well as to characterize the dynamic behavior of the building. 3D models

  6. Recent progress to understand stress corrosion cracking in sodium borosilicate glasses: linking the chemical composition to structural, physical and fracture properties

    Science.gov (United States)

    Rountree, Cindy L.

    2017-08-01

    This topical review is dedicated to understanding stress corrosion cracking in oxide glasses and specifically the SiO_2{\\text-B_2O_3{\\text-}Na_2O} (SBN) ternary glass systems. Many review papers already exist on the topic of stress corrosion cracking in complex oxide glasses or overly simplified glasses (pure silica). These papers look at how systematically controlling environmental factors (pH, temperature...) alter stress corrosion cracking, while maintaining the same type of glass sample. Many questions still exist, including: What sets the environmental limit? What sets the velocity versus stress intensity factor in the slow stress corrosion regime (Region I)? Can researchers optimize these two effects to enhance a glass’ resistance to failure? To help answer these questions, this review takes a different approach. It looks at how systemically controlling the glass’ chemical composition alters the structure and physical properties. These changes are then compared and contrasted to the fracture toughness and the stress corrosion cracking properties. By taking this holistic approach, researchers can begin to understand the controlling factors in stress corrosion cracking and how to optimize glasses via the initial chemical composition.

  7. Stress

    Science.gov (United States)

    ... can be life-saving. But chronic stress can cause both physical and mental harm. There are at least three different types of stress: Routine stress related to the pressures of work, family, and other daily responsibilities Stress brought about ...

  8. Efficient production of transgenic soybean (Glycine max [L] Merrill ...

    African Journals Online (AJOL)

    Efficient production of transgenic soybean (Glycine max [L] Merrill) plants mediated via whisker-supersonic (WSS) method. MM Khalafalla, HA El-Shemy, SM Rahman, M Teraishi, H Hasegawa, T Terakawa, M Ishimoto ...

  9. Signalling fiscal stress in the euro area - a country-specific early warning system

    OpenAIRE

    Hernández de Cos, Pablo; Koester, Gerrit B.; Moral-Benito, Enrique; Nickel, Christiane

    2014-01-01

    The sovereign debt crisis in the euro area has increased the interest in early warning indicators, with the aim to indicate the build?up of fiscal stress early on and to facilitate crisis prevention by a timely counteraction of fiscal and macroeconomic policies. This paper presents possible improvements to enhance existing early warning indicators for fiscal stress, especially for the euro area. We show that a country?specific approach could strongly increase the signalling power of early war...

  10. 14 CFR 1251.301 - Existing facilities.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Existing facilities. 1251.301 Section 1251... HANDICAP Accessibility § 1251.301 Existing facilities. (a) Accessibility. A recipient shall operate each... existing facilities or every part of a facility accessible to and usable by handicapped persons. (b...

  11. 10 CFR 611.206 - Existing facilities.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Existing facilities. 611.206 Section 611.206 Energy... PROGRAM Facility/Funding Awards § 611.206 Existing facilities. The Secretary shall, in making awards to those manufacturers that have existing facilities, give priority to those facilities that are oldest or...

  12. Salivary Nerve Growth Factor Response to Intense Stress: Effect of Sex and Body Mass Index

    Science.gov (United States)

    2014-01-01

    collection and to avoid the following: brushing teeth prior to collection, using salivary stimulants (e.g., gum, lemon drops), and consuming acidic or high...individual differences in stress resilience with important prevention and therapeutic implications. A better understanding of how the stress response...existing studies of sNGF, involve mild to moderate challenges encountered in daily life. While these provide an important basis for specula- tion

  13. A new sensor for stress measurement based on blood flow fluctuations

    Science.gov (United States)

    Fine, I.; Kaminsky, A. V.; Shenkman, L.

    2016-03-01

    It is widely recognized that effective stress management could have a dramatic impact on health care and preventive medicine. In order to meet this need, efficient and seamless sensing and analytic tools for the non-invasive stress monitoring during daily life are required. The existing sensors still do not meet the needs in terms of specificity and robustness. We utilized a miniaturized dynamic light scattering sensor (mDLS) which is specially adjusted to measure skin blood flow fluctuations and provides multi- parametric capabilities. Based on the measured dynamic light scattering signal from the red blood cells flowing in skin, a new concept of hemodynamic indexes (HI) and oscillatory hemodynamic indexes (OHI) have been developed. This approach was utilized for stress level assessment for a few usecase scenario. The new stress index was generated through the HI and OHI parameters. In order to validate this new non-invasive stress index, a group of 19 healthy volunteers was studied by measuring the mDLS sensor located on the wrist. Mental stress was induced by using the cognitive dissonance test of Stroop. We found that OHIs indexes have high sensitivity to the mental stress response for most of the tested subjects. In addition, we examined the capability of using this new stress index for the individual monitoring of the diurnal stress level. We found that the new stress index exhibits similar trends as reported for to the well-known diurnal behavior of cortisol levels. Finally, we demonstrated that this new marker provides good sensitivity and specificity to the stress response to sound and musical emotional arousal.

  14. A precariedade humana e a existência estilizada Human precariousness and stylized existence

    Directory of Open Access Journals (Sweden)

    Rita Paiva

    2013-04-01

    Full Text Available Este artigo tematiza o desamparo vivenciado pela consciência ante a ausência de bases sólidas para seus anseios de felicidade e para suas representações simbólicas. Com esse propósito, toma como objeto de reflexão um dos ensaios filosóficos de Albert Camus, O mito de Sísifo, equacionando a possibilidade de uma ética que estilize a vida, sem que se minimize a dolorosa precariedade da existência humana. Posteriormente, em diálogo com alguns textos de M. Foucault, a reflexão procura estabelecer os vínculos possíveis entre a ética camusiana e a ética como uma estética da existência, tal como pensada entre os gregos antigos.This article discusses the helplessness experienced by the consciousness vis-à-vis the absence of solid bases for its longings for happiness and for its symbolic representations. For this purpose, the object of reflection of the article is one of Albert Camus' philosophical essays, The Myth of Sisyphus, and we inquire into the possibility of an ethics that stylizes life without minimizing the painful precariousness of human existence. Making reference to certain texts by Foucault, we attempt to establish possible connections between Camus' ethics and an ethics of the aesthetics of existence as found in the thinkers of ancient Greece.

  15. Promise and problems in using stress triggering models for time-dependent earthquake hazard assessment

    Science.gov (United States)

    Cocco, M.

    2001-12-01

    Earthquake stress changes can promote failures on favorably oriented faults and modify the seismicity pattern over broad regions around the causative faults. Because the induced stress perturbations modify the rate of production of earthquakes, they alter the probability of seismic events in a specified time window. Comparing the Coulomb stress changes with the seismicity rate changes and aftershock patterns can statistically test the role of stress transfer in earthquake occurrence. The interaction probability may represent a further tool to test the stress trigger or shadow model. The probability model, which incorporate stress transfer, has the main advantage to include the contributions of the induced stress perturbation (a static step in its present formulation), the loading rate and the fault constitutive properties. Because the mechanical conditions of the secondary faults at the time of application of the induced load are largely unkown, stress triggering can only be tested on fault populations and not on single earthquake pairs with a specified time delay. The interaction probability can represent the most suitable tool to test the interaction between large magnitude earthquakes. Despite these important implications and the stimulating perspectives, there exist problems in understanding earthquake interaction that should motivate future research but at the same time limit its immediate social applications. One major limitation is that we are unable to predict how and if the induced stress perturbations modify the ratio between small versus large magnitude earthquakes. In other words, we cannot distinguish between a change in this ratio in favor of small events or of large magnitude earthquakes, because the interaction probability is independent of magnitude. Another problem concerns the reconstruction of the stressing history. The interaction probability model is based on the response to a static step; however, we know that other processes contribute to

  16. Mechanical stress-controlled tunable active frequency-selective surface

    Science.gov (United States)

    Huang, Bo-Cin; Hong, Jian-Wei; Lo, Cheng-Yao

    2017-01-01

    This study proposes a tunable active frequency-selective surface (AFSS) realized by mechanically expanding or contracting a split-ring resonator (SRR) array. The proposed AFSS transfers mechanical stress from its elastic substrate to the top of the SRR, thereby achieving electromagnetic (EM) modulation without the need for an additional external power supply, meeting the requirements for the target application: the invisibility cloak. The operating mechanism of the proposed AFSS differs from those of other AFSSs, supporting modulations in arbitrary frequencies in the target range. The proposed stress-controlled or strain-induced EM modulation proves the existence of an identical and linear relationship between the strain gradient and the frequency shift, implying its suitability for other EM modulation ranges and applications.

  17. 45 CFR 1170.32 - Existing facilities.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Existing facilities. 1170.32 Section 1170.32... ASSISTED PROGRAMS OR ACTIVITIES Accessibility § 1170.32 Existing facilities. (a) Accessibility. A recipient... require a recipient to make each of its existing facilities or every part of a facility accessible to and...

  18. 45 CFR 605.22 - Existing facilities.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Existing facilities. 605.22 Section 605.22 Public... Accessibility § 605.22 Existing facilities. (a) Accessibility. A recipient shall operate each program or... existing facilities or every part of a facility accessible to and usable by qualified handicapped persons...

  19. 45 CFR 1151.22 - Existing facilities.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Existing facilities. 1151.22 Section 1151.22... Prohibited Accessibility § 1151.22 Existing facilities. (a) A recipient shall operate each program or... make each of its existing facilities or every part of a facility accessible to and usable by...

  20. Enhancement of wind stress evaluation method under storm conditions

    Science.gov (United States)

    Chen, Yingjian; Yu, Xiping

    2016-12-01

    Wind stress is an important driving force for many meteorological and oceanographical processes. However, most of the existing methods for evaluation of the wind stress, including various bulk formulas in terms of the wind speed at a given height and formulas relating the roughness height of the sea surface with wind conditions, predict an ever-increasing tendency of the wind stress coefficient as the wind speed increases, which is inconsistent with the field observations under storm conditions. The wave boundary layer model, which is based on the momentum and energy conservation, has the advantage to take into account the physical details of the air-sea interaction process, but is still invalid under storm conditions without a modification. By including the energy dissipation due to the presence of sea spray, which is speculated to be an important aspect of the air-sea interaction under storm conditions, the wave boundary layer model is improved in this study. The improved model is employed to estimate the wind stress caused by an idealized tropical cyclone motion. The computational results show that the wind stress coefficient reaches its maximal value at a wind speed of about 40 m/s and decreases as the wind speed further increases. This is in fairly good agreement with the field data.